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The present application is a continuation in part of U.S. application Ser. No. 11/525,857 filed 25 Sep. 2006, which is in turn a continuation of U.S. application Ser. No. 11/064,011 filed on Feb. 24, 2005, now issued as U.S. Pat. No. 717,8903 which is a continuation of U.S. application Ser. No. 10/893,380 filed on Jul. 19, 2004, now issued U.S. Pat. No. 6,938,992, which is a continuation of U.S. application Ser. No. 10/307,348 filed on Dec. 2, 2002, now issued as U.S. Pat. No. 6,764,166, which is a continuation of U.S. application Ser. No. 09/113,122 filed on Jul. 10, 1998, now issued as U.S. Pat. No. 6,557,977, the entire contents of which are herein incorporated by reference.
The following Australian provisional patent applications are hereby incorporated by reference. For the purposes of location and identification, US patents/patent applications identified by their US patent/patent application serial numbers (USSN) are listed alongside the Australian applications from which the US patents/patent applications claim the right of priority.
US PATENT/ | ||
PATENT APPLICATION | ||
CROSS-REFERENCED | (CLAIMING RIGHT | |
AUSTRALIAN | OF PRIORITY FROM | |
PROVISIONAL PATENT | AUSTRALIAN PROVISIONAL | DOCKET |
APPLICATION NO. | APPLICATION) | NO. |
PO7991 | 6,750,901 | ART01 |
PO8505 | 6,476,863 | ART02 |
PO7988 | 6,788,336 | ART03 |
PO9395 | 6,322,181 | ART04 |
PO8017 | 6,597,817 | ART06 |
PO8014 | 6,227,648 | ART07 |
PO8025 | 6,727,948 | ART08 |
PO8032 | 6,690,419 | ART09 |
PO7999 | 6,727,951 | ART10 |
PO7998 | 09/112,742 | ART11 |
PO8031 | 09/112,741 | ART12 |
PO8030 | 6,196,541 | ART13 |
PO7997 | 6,195,150 | ART15 |
PO7979 | 6,362,868 | ART16 |
PO8015 | 09/112,738 | ART17 |
PO7978 | 6831681 | ART18 |
PO7982 | 6,431,669 | ART19 |
PO7989 | 6,362,869 | ART20 |
PO8019 | 6,472,052 | ART21 |
PO7980 | 6,356,715 | ART22 |
PO8018 | 09/112,777 | ART24 |
PO7938 | 6,636,216 | ART25 |
PO8016 | 6,366,693 | ART26 |
PO8024 | 6,329,990 | ART27 |
PO7940 | 09/113,072 | ART28 |
PO7939 | 6,459,495 | ART29 |
PO8501 | 6,137,500 | ART30 |
PO8500 | 6,690,416 | ART31 |
PO7987 | 7,050,143 | ART32 |
PO8022 | 6,398,328 | ART33 |
PO8497 | 09/113,090 | ART34 |
PO8020 | 6,431,704 | ART38 |
PO8023 | 09/113,222 | ART39 |
PO8504 | 09/112,786 | ART42 |
PO8000 | 6,415,054 | ART43 |
PO7977 | 09/112,782 | ART44 |
PO7934 | 6,665,454 | ART45 |
PO7990 | 6,542,645 | ART46 |
PO8499 | 6,486,886 | ART47 |
PO8502 | 6,381,361 | ART48 |
PO7981 | 6,317,192 | ART50 |
PO7986 | 6850274 | ART51 |
PO7983 | 09/113,054 | ART52 |
PO8026 | 6,646,757 | ART53 |
PO8027 | 09/112,759 | ART54 |
PO8028 | 6,624,848 | ART56 |
PO9394 | 6,357,135 | ART57 |
PO9396 | 09/113,107 | ART58 |
PO9397 | 6,271,931 | ART59 |
PO9398 | 6,353,772 | ART60 |
PO9399 | 6,106,147 | ART61 |
PO9400 | 6,665,008 | ART62 |
PO9401 | 6,304,291 | ART63 |
PO9402 | 09/112,788 | ART64 |
PO9403 | 6,305,770 | ART65 |
PO9405 | 6,289,262 | ART66 |
PP0959 | 6,315,200 | ART68 |
PP1397 | 6,217,165 | ART69 |
PP2370 | 6,786,420 | DOT01 |
PP2371 | 09/113,052 | DOT02 |
PO8003 | 6,350,023 | Fluid01 |
PO8005 | 6,318849 | Fluid02 |
PO8066 | 6,227,652 | IJ01 |
PO8072 | 6,213,588 | IJ02 |
PO8040 | 6,213,589 | IJ03 |
PO8071 | 6,231,163 | IJ04 |
PO8047 | 6,247,795 | IJ05 |
PO8035 | 6,394,581 | IJ06 |
PO8044 | 6,244,691 | IJ07 |
PO8063 | 6,257,704 | IJ08 |
PO8057 | 6,416,168 | IJ09 |
PO8056 | 6,220,694 | IJ10 |
PO8069 | 6,257,705 | IJ11 |
PO8049 | 6,247,794 | IJ12 |
PO8036 | 6,234,610 | IJ13 |
PO8048 | 6,247,793 | IJ14 |
PO8070 | 6,264,306 | IJ15 |
PO8067 | 6,241,342 | IJ16 |
PO8001 | 6,247,792 | IJ17 |
PO8038 | 6,264,307 | IJ18 |
PO8033 | 6,254,220 | IJ19 |
PO8002 | 6,234,611 | IJ20 |
PO8068 | 6,302,528 | IJ21 |
PO8062 | 6,283.582 | IJ22 |
PO8034 | 6,239,821 | IJ23 |
PO8039 | 6,338,547 | IJ24 |
PO8041 | 6,247,796 | IJ25 |
PO8004 | 6,557,977 | IJ26 |
PO8037 | 6,390,603 | IJ27 |
PO8043 | 6,362,843 | IJ28 |
PO8042 | 6,293,653 | IJ29 |
PO8064 | 6,312,107 | IJ30 |
PO9389 | 6,227,653 | IJ31 |
PO9391 | 6,234,609 | IJ32 |
PP0888 | 6,238,040 | IJ33 |
PP0891 | 6,188,415 | IJ34 |
PP0890 | 6,227,654 | IJ35 |
PP0873 | 6,209,989 | IJ36 |
PP0993 | 6,247,791 | IJ37 |
PP0890 | 6,336,710 | IJ38 |
PP1398 | 6,217,153 | IJ39 |
PP2592 | 6,416,167 | IJ40 |
PP2593 | 6,243,113 | IJ41 |
PP3991 | 6,283,581 | IJ42 |
PP3987 | 6,247,790 | IJ43 |
PP3985 | 6,260,953 | IJ44 |
PP3983 | 6,267,469 | IJ45 |
PO7935 | 6,224,780 | IJM01 |
PO7936 | 6,235,212 | IJM02 |
PO7937 | 6,280,643 | IJM03 |
PO8061 | 6,284,147 | IJM04 |
PO8054 | 6,214,244 | IJM05 |
PO8065 | 6,071,750 | IJM06 |
PO8055 | 6,267,905 | IJM07 |
PO8053 | 6,251,298 | IJM08 |
PO8078 | 6,258,285 | IJM09 |
PO7933 | 6,225,138 | IJM10 |
PO7950 | 6,241,904 | IJM11 |
PO7949 | 6,299,786 | IJM12 |
PO8060 | 09/113,124 | IJM13 |
PO8059 | 6,231,773 | IJM14 |
PO8073 | 6,190,931 | IJM15 |
PO8076 | 6,248,249 | IJM16 |
PO8075 | 6,290,862 | IJM17 |
PO8079 | 6,241,906 | IJM18 |
PO8050 | 6,565,762 | IJM19 |
PO8052 | 6,241,905 | IJM20 |
PO7948 | 6,451,216 | IJM21 |
PO7951 | 6,231,772 | IJM22 |
PO8074 | 6,274,056 | IJM23 |
PO7941 | 6,290,861 | IJM24 |
PO8077 | 6,248,248 | IJM25 |
PO8058 | 6,306,671 | IJM26 |
PO8051 | 6,331,258 | IJM27 |
PO8045 | 6,111,754 | IJM28 |
PO7952 | 6,294,101 | IJM29 |
PO8046 | 6,416,679 | IJM30 |
PO9390 | 6,264,849 | IJM31 |
PO9392 | 6,254,793 | IJM32 |
PP0889 | 6,235,211 | IJM35 |
PP0887 | 6,491,833 | IJM36 |
PP0882 | 6,264,850 | IJM37 |
PP0874 | 6,258,284 | IJM38 |
PP1396 | 6,312,615 | IJM39 |
PP3989 | 6,228,668 | IJM40 |
PP2591 | 6,180,427 | IJM41 |
PP3990 | 6,171,875 | IJM42 |
PP3986 | 6,267,904 | IJM43 |
PP3984 | 6,245,247 | IJM44 |
PP3982 | 6,315,914 | IJM45 |
PP0895 | 6,231,148 | IR01 |
PP0870 | 09/113,106 | IR02 |
PP0869 | 6,293,658 | IR04 |
PP0887 | 6,614,560 | IR05 |
PP0885 | 6,238,033 | IR06 |
PP0884 | 6,312,070 | IR10 |
PP0886 | 6,238,111 | IR12 |
PP0871 | 09/113,086 | IR13 |
PP0876 | 09/113,094 | IR14 |
PP0877 | 6,378,970 | IR16 |
PP0878 | 6,196,739 | IR17 |
PP0879 | 09/112,774 | IR18 |
PP0883 | 6,270,182 | IR19 |
PP0880 | 6,152,619 | IR20 |
PP0881 | 09/113,092 | IR21 |
PO8006 | 6,087,638 | MEMS02 |
PO8007 | 6,340,222 | MEMS03 |
PO8008 | 09/113,062 | MEMS04 |
PO8010 | 6,041,600 | MEMS05 |
PO8011 | 6,299,300 | MEMS06 |
PO7947 | 6,067,797 | MEMS07 |
PO7944 | 6,286,935 | MEMS09 |
PO7946 | 6,044,646 | MEMS10 |
PO9393 | 09/113,065 | MEMS11 |
PP0875 | 09/113,078 | MEMS12 |
PP0894 | 6,382,769 | MEMS13 |
Not applicable.
The present invention relates to ink jet printing and in particular discloses a shape memory alloy ink jet printer.
The present invention further relates to the field of drop on demand ink jet printing.
The following applications have been filed by the Applicant simultaneously with the present application: The disclosures of these co-pending applications are incorporated herein by reference.
IJ96US | IJ97US | IJ98US | IJ99US | IJ100US | IJ101US | IJ102US |
IJ103US | IJ104US | IJ105US | IJ106US | IJ108US | IJ109US | IJ110US |
IJ111US | ||||||
The above applications have been identified by their filing docket number, which will be substituted with the corresponding application number, once assigned.
Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and inkjet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.
In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.
Many different techniques on ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).
Inkjet printers themselves come in many different types. The utilization of a continuous stream ink in inkjet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.
U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous inkjet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al)
Piezoelectric inkjet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element.
Recently, thermal inkjet printing has become an extremely popular form of inkjet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclosed inkjet printing techniques rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.
These printheads have nozzle arrays that share a common basic construction. The electrothermal actuators are fabricated on one supporting substrate and the nozzles through which the ink is ejected are formed in a separate substrate or plate. The nozzle plate and thermal actuators are then aligned and assembled. The nozzle plate and the thermal actuator substrate can be sealed together in a variety of different ways, for example, epoxy adhesive, anodic bonding or sealing glass.
Accurate registration between the thermal actuators and the nozzles can be problematic. These problems effectively restrict the size of the nozzle array in any one monolithic plate and corresponding actuator substrate. Any misalignment between the nozzles and the underlying actuators will compound as the dimensions of the array increase. Furthermore, differential thermal expansion between the nozzle plate and the actuator substrate create greater misalignments as the array sizes increase. In light of these registration issues, printhead nozzle arrays have a nozzle densities of the order of 10 to 20 nozzles per square mm and less than about 300 nozzles in any one monolithic plate and corresponding actuator substrate.
Given these limits on nozzle array size, pagewidth printheads using this two-part design are impractical. A stationary printhead extending the printing width of the media substrate would require many separate printhead arrays mounted in precise alignment with each other. The complexity of this arrangement makes such printers commercially unrealistic.
As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.
According to a first aspect, the present invention provides an inkjet printhead comprising:
an array of droplet ejectors supported on a printhead integrated circuit (IC), each of the droplet ejectors has a nozzle aperture and an actuator for ejecting a droplet of ink through the nozzle aperture and, each of the droplet ejectors has a chamber in which the actuator is positioned, the chamber having an inlet for fluid communication with an ink supply, and a filter structure in the inlet to inhibit ingress of contaminants into the chamber.
A filter structure at the inlet to each ink chamber is more likely to remove contaminants than a filter positioned further upstream in the in the ink supply flow. Contaminants, including air bubbles, can originate at all points along the ink supply line, so there is less chance of nozzle clogging or other detrimental effects if the ink flow is filtered at each of the chamber inlets.
In a particularly preferred form, the filter structure is a plurality of spaced columns. In some embodiments, the spaced columns each extend generally parallel to the droplet ejection direction.
Preferably, the printhead IC has drive circuitry for providing the actuators with power, the drive circuitry having patterned layers of metal separated by interleaved layers of dielectric material, the layers of metal being interconnected by conductive vias, wherein the drive circuitry has more than two of the metal layers and each of the metal layers are less than 2 microns thick.
Incorporating the drive circuitry and the droplet ejectors onto the same supporting substrate reduces the number of electrical connections needed on the printhead IC and the resistive losses when transmitting power to the actuators. The circuitry on the printhead IC needs to have more than just power and ground metal layers in order to provide the necessary drive FETs, shift registers and so on. However, each metal layer can be thinner and fabricated using well known and efficient techniques employed in standard semiconductor fabrication. Overall, this yields production efficiencies in time and cost.
Preferably, the metal layers are each less than 1 micron thick. In a still further preferred form, the metal layers are 0.5 microns thick. Half micron CMOS is often used in semiconductor fabrication and is thick enough to ensure that the connections at the bond pads are reliable.
Preferably, the array has a nozzle aperture density of more than 100 nozzle apertures per square millimetre. Preferably, the array has a nozzle aperture density of more than 200 nozzle apertures per square millimetre. In a further preferred form, the array has a nozzle aperture density of more than 300 nozzle apertures per square millimetre.
Forming the nozzle apertures within a layer on one side of the underlying wafer instead of laser ablating nozzles in a separated plate that is subsequently mounted to the printhead integrated circuit significantly improves the accuracy of registration between an actuator and its corresponding nozzle. With more precise registration between the nozzle aperture and the actuator, a greater nozzle density is possible. Nozzle density has a direct bearing on the print resolution and or print speeds. A high density array of nozzles can print to all the addressable locations (the grid of locations on the media substrate at which the printer can print a dot) with less passes of the printhead or ideally, a single pass.
In some embodiments, the array has more than 2000 droplet ejectors. Preferably, the array has more than 10,000 droplet ejectors. In a further preferred form, the array has more than 15,000 droplet ejectors. Increasing the number of nozzles fabricated on a printhead IC allows larger arrays, faster print speeds and ultimately pagewidth printheads.
Preferably, the printhead surface layer is less than 10 microns thick. In a further preferred form, the printhead surface layer is less than 8 microns thick. In a still further preferred form, the printhead surface layer is less than 5 microns thick. In particular embodiments, the printhead surface layer is between 1.5 microns and 3.0 microns.
Forming the nozzle apertures in a thin surface layer reduces stresses caused by differential thermal expansion. Thin surface layers mean that the ‘barrel’ of the nozzle aperture is short and has less fluidic drag on the droplets as they are ejected. This reduces the ejection energy that the actuator needs to impart to the ink which in turn reduces the energy needed to be input into the actuator. With the actuators operating at lower power, they can be placed closer together on the printhead IC because there is less cross talk between nozzles and less excess heat generated. The close spacing increases the density of droplet ejectors within the array.
Preferably, each of the droplet ejectors in the array is configured to eject droplets with a volume less than 3 pico-litres each. In a further preferred form, each of the droplet ejectors in the array is configured to eject droplets with a volume less than 2 pico-litres each. In a particularly preferred form, the droplets ejected have a volume between 1 pico-litre and 2 pico-litres.
Configuring the ejector so that it ejects small volume drops reduces the energy needed to eject drops.
Preferably, the actuator in each of the droplet ejectors is configured to generate a pressure pulse in a quantity of ink adjacent the nozzle aperture, the pressure pulse being directed towards the nozzles aperture such that the droplet of ink is ejected through the nozzle aperture, the actuator being positioned in the droplet ejector such that it is less than 30 microns from an exterior surface of the printhead surface layer. Preferably, the actuator is positioned in the droplet ejector such that it is less than 20 microns from an exterior surface of the printhead surface layer. In a further preferred form, the actuator being positioned in the droplet ejector such that it is less than 15 microns from an exterior surface of the printhead surface layer.
In some preferred embodiments, the nozzle apertures each have an area less than 600 microns squared. In a further preferred form, the nozzle apertures each have an area less than 400 microns squared. In a particularly preferred form, the nozzle apertures each have an area between 150 microns squared and 200 microns squared.
Preferably, during printing 100% coverage at full print rate, each of the actuators has an average power consumption less than 1.5 mW. In a further preferred form, the average power consumption is between 0.5 mW and 1.0 mW. In a still further preferred form, the array has more than 15,000 of the droplet ejectors and operates at less than 10 Watts during printing 100% coverage at full print rate. Configuring the actuators for low power ejection causes less cross talk between nozzles and less, if any, excess heat generation. As a result, the density of the droplet ejectors on the printhead IC can increase. Droplet ejector density has a direct bearing on the print resolution and or print speeds. A high density array of nozzles can print to all the addressable locations (the grid of locations on the media substrate at which the printer can print a dot) with less passes of the printhead or ideally, a single pass, as is the case with a pagewidth printhead.
Preferably, each of the actuators is configured to consume less than 1 Watt during activation. In a further preferred form, each of the actuators is configured to consume less than 500 mW during activation. In some embodiments, each of the actuators is configured to consume between 100 mW and 500 mW during activation.
Preferably, the array of droplet ejectors is arranged as a plurality of rows of the droplet ejectors, the inkjet printhead further comprising an ink supply channel extending parallel to the plurality of rows, and an inlet conduit extending from the supply channel to an opposing surface of the printhead IC. Preferably, the supply channel extends between at least two of the plurality of rows. Feeding ink to the rows of droplet ejectors via a parallel supply channel that has a supply conduit to the ‘back’ of the IC, reduces the number of deep anisotropic back etches. Less back etching preserves the structural integrity of the printhead IC which is more robust and less likely to be damaged by die handling equipment.
Preferably, the droplet ejectors are configured to eject ink droplets at a velocity less than 4.5 m/s. In a further preferred form, the velocity is less than 4.0 m/s. The Applicant's work has found drop ejection velocities greater than 4.5 m/s have significantly more satellite drops. Furthermore, tests show a velocity less than 4.0 m/s have negligible satellite drops.
Preferably, each of the droplet ejectors has a chamber in which the actuator is positioned, the chamber having a volume less than 30,000 microns cubed. In a further preferred form, the volume is less than 25,000 microns cubed. Low energy ejection of ink droplets generates little, if any, excess heat in the printhead. A build up of excess heat in the printhead imposes a limit on the nozzle firing frequency and thereby limits the print speed. The IJ30 printhead is self cooling (the heat generated by the thermal actuator is removed from the printhead with the ejected drop). In this case, the print speed is only limited by the rate at which the ink can be supplied to the printhead or the speed that the media substrate can be fed past the printhead. Reducing the volume of the ink chambers reduces the volume of ink in which the heat can dissipate. However, a reduced volume ink chamber has a fast refill time and relies solely on capillary action. As the actuator is configured for low energy input, the reduced volume of ink does not cause problems for heat dissipation.
Preferably, the printhead IC has a back face that is opposite said one face on which the printhead surface layer is formed, and at least one supply conduit extending from the back face to the array of droplet ejectors such that the at least one supply conduit is in fluid communication with a plurality of the droplet ejectors in the array. In a further preferred form, the printhead IC has a plurality of the supply conduits and drive circuitry for providing the actuators with power, the drive circuitry having patterned layers of metal separated by interleaved layers of dielectric material, the layers of metal being interconnected by conductive vias, wherein the drive circuitry extends between the plurality of supply conduits. Supplying the array of droplet ejectors with ink from the back face of the printhead IC instead of along the front face provides more room to the electrical contacts and drive circuitry. This in turn, provides the scope to increase the density of droplet ejectors per unit area on the printhead IC.
Preferably, the array of droplet ejectors is arranged as a plurality of rows of the droplet ejectors, the printhead IC further comprises an ink supply channel extending parallel to the plurality of rows, such that the ink supply channel connects to the plurality of supply conduits extending from the back face of the printhead IC. Preferably, the supply channel extends between at least two of the plurality of rows. In a particularly preferred form, the printhead IC has an elongate configuration with its longitudinal extent parallel to the rows of droplet ejectors, the printhead IC further comprising a series of electrical contacts along of its longitudinal sides for receiving power and print data for all the droplet ejectors in the array.
According to a second aspect, the present invention provides a method of fabricating an inkjet printhead comprising the steps of:
forming a plurality of actuators on a monolithic substrate;
covering the actuators with a sacrificial material;
covering the sacrificial material with a printhead surface layer;
defining a plurality of nozzle apertures in the printhead surface layer such that each of the actuators corresponds to one of the nozzle apertures; and,
removing at least some of the sacrificial material on each of the actuators through the nozzle aperture corresponding to each of the actuators.
By forming the nozzle apertures in a printhead surface layer that is a lithographically deposited structure on the monolithic substrate, the alignment with the actuators is within tolerances while fabrication remains cost effective. Greater precision allows the printhead to have a higher nozzle density and the array can be larger before CTE mismatch causes the nozzle to actuator alignment to exceed the required tolerances.
Preferably, the method further comprises the step of supporting the actuators on the monolithic substrate by CMOS drive circuitry positioned between the monolithic substrate and the actuators and the monolithic substrate. Preferably, the method further comprises the step of depositing a protective layer over the CMOS drive circuitry and etching the protective layer to expose areas of the CMOS drive circuitry configured to be electrical contacts for the actuators. Preferably, the protective layer is a nitride material. Silicon nitride is particularly suitable.
Preferably, the method further comprises the step of forming etchant holes in the printhead surface layer for exposing the sacrificial material beneath the printhead surface layer to etchant, the etchant holes being smaller than the nozzle apertures such that during printer operation, ink is not ejected through the etchant holes.
Preferably, the printhead surface layer is a nitride material deposited over a sacrificial layer. In a further preferred form, the printhead surface layer is silicon nitride. Preferably, the monolithic substrate has an ink ejection side providing a planar support surface for the CMOS drive circuitry and the plurality of actuators, the monolithic substrate also having an ink supply surface opposing the ink ejection side, the printhead surface layer has a roof layer extending in a plane parallel to the planar support surface, and side wall structures formed integrally with the roof layer and extending toward the planar support surface. Preferably, the printhead surface layer has a plurality of filter structures formed integrally with the roof layer and positioned to filter ink flow to each of the actuators respectively. Preferably, the method further comprises the step of etching ink supply channels from the ink supply surface of the monolithic substrate to the planar support surface of the ink ejection side. In a further preferred form, the step of removing at least some of the sacrificial material on each of the actuators through the nozzle apertures is performed after the ink supply channels are etched from the ink supply surface.
According to a third aspect, the present invention provides an inkjet printer comprising:
a printhead mounted adjacent a media feed path;
an array of droplet ejectors for ejecting ink droplets on to a media substrate, each of the droplet ejectors having an electro-thermal actuator; and,
a media feed drive for moving the media substrate relative to the array of droplet ejectors at a speed greater than 0.1 m/s.
Increasing the speed of the media substrate relative to the printhead, whether the printhead is a scanning or pagewidth type, reduces the time needed to complete printjobs.
Preferably, the media feed drive is configured for moving the media substrate relative to the array of droplet ejectors at a speed greater than 0.15 m/s.
The nozzle chamber structure may be defined by the substrate as a result of an etching process carried out on the substrate, such that one of the layers of the substrate defines the ejection port on one side of the substrate and the actuator is positioned on an opposite side of the substrate.
According to a fourth aspect of the present invention there is provided a method of ejecting ink from a chamber comprising the steps of: a) providing a cantilevered beam actuator incorporating a shape memory alloy; and b) transforming said shape memory alloy from its martensitic phase to its austenitic phase or vice versa to cause the ink to eject from said chamber. Further, the actuator comprises a conductive shape memory alloy panel in a quiescent state and which transfers to an ink ejection state upon heating thereby causing said ink ejection from the chamber. Preferably, the heating occurs by means of passing a current through the shape memory alloy. The chamber is formed from a crystallographic etch of a silicon wafer so as to have one surface of the chamber substantially formed by the actuator. Advantageously, the actuator is formed from a conductive shape memory alloy arranged in a serpentine form and is attached to one wall of the chamber opposite a nozzle port from which ink is ejected. Further, the nozzle port is formed by the back etching of a silicon wafer to the epitaxial layer and etching a nozzle port hole in the epitaxial layer. The crystallographic etch includes providing side wall slots of non-etched layers of a processed silicon wafer so as to extend the dimensions of the chamber as a result of the crystallographic etch process. Preferably, the shape memory alloy comprises nickel titanium alloy.
Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings which:
FIG. 1 is an exploded perspective view of a single ink jet nozzle as constructed in accordance with one embodiment;
FIG. 2 is a top cross sectional view of a single ink jet nozzle in its quiescent state taken along line A-A in FIG. 1;
FIG. 3 is a top cross sectional view of a single ink jet nozzle in its actuated state taken along line A-A in FIG. 1;
FIG. 4 provides a legend of the materials indicated in FIGS. 5 to 15;
FIG. 5 to FIG. 15 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle;
FIG. 16 is a schematic cross-sectional view of a single ink jet nozzle constructed in accordance with another embodiment;
FIG. 17 is a schematic cross-sectional view of a single ink jet nozzle constructed in accordance with a preferred embodiment, with the thermal actuator in its activated state;
FIG. 18 is a schematic diagram of the conductive layer utilized in the thermal actuator of the ink jet nozzle constructed in accordance with a preferred embodiment;
FIG. 19 is a close-up perspective view of portion A of FIG. 18;
FIG. 20 is a cross-sectional schematic diagram illustrating the construction of a corrugated conductive layer in accordance with a preferred embodiment of the present invention;
FIG. 21 is a schematic cross-sectional diagram illustrating the development of a resist material through a half-toned mask utilized in the fabrication of a single ink jet nozzle in accordance with a preferred embodiment;
FIG. 22 is an exploded perspective view illustrating the construction of a single ink jet nozzle in accordance with a preferred embodiment;
FIG. 23 is a perspective view of a section of an ink jet printhead configuration utilizing ink jet nozzles constructed in accordance with a preferred embodiment.
FIG. 24 provides a legend of the materials indicated in FIGS. 25 to 38; and,
FIG. 25 to FIG. 38 illustrate sectional views of the manufacturing steps in one form of construction of an ink jet printhead nozzle.
The embodiment shown in FIGS. 1 to 15 is referred to by the Applicant and within the Assignee company, as the IJ26 printhead. In this printhead, shape memory materials are utilized to construct an actuator suitable for injecting ink from the nozzle of an ink chamber.
FIG. 1 illustrates an exploded perspective view 10 of a single ink jet nozzle as constructed in accordance with the preferred embodiment. The ink jet nozzle 10 is constructed from a silicon wafer base utilizing back etching of the wafer to a boron doped epitaxial layer. Hence, the ink jet nozzle 10 comprises a lower layer 11 which is constructed from boron doped silicon. The boron doped silicon layer is also utilized a crystallographic etch stop layer. The next layer comprises the silicon layer 12 that includes a crystallographic pit 13 having side walls etched at the usual angle of 54.74 degrees. The layer 12 also includes the various required circuitry and transistors for example, CMOS layer (not shown). After this, a 0.5 micron thick thermal silicon oxide layer 15 is grown on top of the silicon wafer 12.
After this comes various layers which can comprise a two level metal CMOS process layers which provide the metal interconnect for the CMOS transistors formed within the layer 12. The various metal pathways etc. are not shown in FIG. 1 but for two metal interconnects 18, 19 which provide interconnection between a shape memory alloy layer 20 and the CMOS metal layers 16. The shape memory metal layer is next and is shaped in the form of a serpentine coil to be heated by end interconnect/via portions 21, 23. A top nitride layer 22 is provided for overall passivation and protection of lower layers in addition to providing a means of inducing tensile stress to curl upwards the shape memory alloy layer 20 in its quiescent state.
The preferred embodiment relies upon the thermal transition of a shape memory alloy 20 (SMA) from its martensitic phase to its austenitic phase. The basis of a shape memory effect is a martensitic transformation which creates a polydemane phase upon cooling. This polydemane phase accommodates finite reversible mechanical deformations without significant changes in the mechanical self energy of the system. Hence, upon re-transformation to the austenitic state the system returns to its former macroscopic state to displaying the well known mechanical memory. The thermal transition is achieved by passing an electrical current through the SMA. The actuator layer 20 is suspended at the entrance to a nozzle chamber connected via leads 18, 19 to the lower layers.
In FIG. 2, there is shown a cross-section of a single nozzle 10 when in its quiescent state, the section basically being taken through the line A-A of FIG. 1. The actuator 30 is bent away from the nozzle when in its quiescent state. In FIG. 3, there is shown a corresponding cross-section for a single nozzle 10 when in an actuated state. When energized, the actuator 30 straightens, with the corresponding result that the ink is pushed out of the nozzle. The process of energizing the actuator 30 requires supplying enough energy to raise the SMA above its transition temperature, and to provide the latent heat of transformation to the SMA 20.
Obviously, the SMA martensitic phase must be pre-stressed to achieve a different shape from the austenitic phase. For printheads with many thousands of nozzles, it is important to achieve this pre-stressing in a bulk manner. This is achieved by depositing the layer of silicon nitride 22 using Plasma Enhanced Chemical Vapour Deposition (PECVD) at around 300° C. over the SMA layer. The deposition occurs while the SMA is in the austenitic shape. After the printhead cools to room temperature the substrate under the SMA bend actuator is removed by chemical etching of a sacrificial substance. The silicon nitride layer 22 is under tensile stress, and causes the actuator to curl upwards. The weak martensitic phase of the SMA provides little resistance to this curl. When the SMA is heated to its austenitic phase, it returns to the flat shape into which it was annealed during the nitride deposition. The transformation being rapid enough to result in the ejection of ink from the nozzle chamber.
There is one SMA bend actuator 30 for each nozzle. One end 31 of the SMA bend actuator is mechanically connected to the substrate. The other end is free to move under the stresses inherent in the layers.
Returning to FIG. 1 the actuator layer is therefore composed of three layers:
1. An SiO2 lower layer 15. This layer acts as a stress ‘reference’ for the nitride tensile layer. It also protects the SMA from the crystallographic silicon etch that forms the nozzle chamber. This layer can be formed as part of the standard CMOS process for the active electronics of the printhead.
2. A SMA heater layer 20. A SMA such as nickel titanium (NiTi) alloy is deposited and etched into a serpentine form to increase the electrical resistance.
3. A silicon nitride top layer 22. This is a thin layer of high stiffness which is deposited using PECVD. The nitride stoichiometry is adjusted to achieve a layer with significant tensile stress at room temperature relative to the SiO2 lower layer. Its purpose is to bend the actuator at the low temperature martensitic phase.
As noted previously the ink jet nozzle of FIG. 1 can be constructed by utilizing a silicon wafer having a buried boron epitaxial layer. The 0.5 micron thick dioxide layer 15 is then formed having side slots 45 which are utilized in a subsequent crystallographic etch. Next, the various CMOS layers 16 are formed including drive and control circuitry (not shown). The SMA layer 20 is then created on top of layers 15/16 and being interconnected with the drive circuitry. Subsequently, a silicon nitride layer 22 is formed on top. Each of the layers 15, 16, 22 include the various slots e.g. 45 which are utilized in a subsequent crystallographic etch. The silicon wafer is subsequently thinned by means of back etching with the etch stop being the boron layer 11. Subsequent boron etching forms the nozzle hole e.g. 47 and rim 46 (FIG. 3). Subsequently, the chamber proper is formed by means of a crystallographic etch with the slots 45 defining the extent of the etch within the silicon oxide layer 12.
A large array of nozzles can be formed on the same wafer which in turn is attached to an ink chamber for filling the nozzle chambers.
One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:
1. Using a double-sided polished wafer deposit 3 microns of epitaxial silicon heavily doped with boron.
2. Deposit 10 microns of epitaxial silicon, either p-type or n-type, depending upon the CMOS process used.
3. Complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, 2 metal CMOS process. This step is shown in FIG. 5. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. FIG. 4 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.
4. Etch the CMOS oxide layers down to silicon or aluminum using Mask 1. This mask defines the nozzle chamber, and the edges of the printheads chips. This step is shown in FIG. 6.
5. Crystallographically etch the exposed silicon using, for example, KOH or EDP (ethylenediamine pyrocatechol). This etch stops on <111> crystallographic planes, and on the boron doped silicon buried layer. This step is shown in FIG. 7.
6. Deposit 12 microns of sacrificial material. Planarize down to oxide using CMP. The sacrificial material temporarily fills the nozzle cavity. This step is shown in FIG. 8.
7. Deposit 0.1 microns of high stress silicon nitride (Si3N4).
8. Etch the nitride layer using Mask 2. This mask defines the contact vias from the shape memory heater to the second-level metal contacts.
9. Deposit a seed layer.
10. Spin on 2 microns of resist, expose with Mask 3, and develop. This mask defines the shape memory wire embedded in the paddle. The resist acts as an electroplating mold. This step is shown in FIG. 9.
11. Electroplate 1 micron of Nitinol. Nitinol is a ‘shape memory’ alloy of nickel and titanium, developed at the Naval Ordnance Laboratory in the US (hence Ni—Ti-NOL). A shape memory alloy can be thermally switched between its weak martensitic state and its high stiffness austenitic state.
12. Strip the resist and etch the exposed seed layer. This step is shown in FIG. 10.
13. Wafer probe. All electrical connections are complete at this point, bond pads are accessible, and the chips are not yet separated.
14. Deposit 0.1 microns of high stress silicon nitride. High stress nitride is used so that once the sacrificial material is etched, and the paddle is released, the stress in the nitride layer will bend the relatively weak martensitic phase of the shape memory alloy. As the shape memory alloy—in its austenitic phase—is flat when it is annealed by the relatively high temperature deposition of this silicon nitride layer, it will return to this flat state when electrothermally heated.
15. Mount the wafer on a glass blank and back-etch the wafer using KOH with no mask. This etch thins the wafer and stops at the buried boron doped silicon layer. This step is shown in FIG. 11.
16. Plasma back-etch the boron doped silicon layer to a depth of 1 micron using Mask 4. This mask defines the nozzle rim. This step is shown in FIG. 12.
17. Plasma back-etch through the boron doped layer using Mask 5. This mask defines the nozzle, and the edge of the chips. At this stage, the chips are still mounted on the glass blank. This step is shown in FIG. 13.
18. Strip the adhesive layer to detach the chips from the glass blank. Etch the sacrificial layer. This process completely separates the chips. This step is shown in FIG. 14.
19. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply different colors of ink to the appropriate regions of the front surface of the wafer.
20. Connect the printheads to their interconnect systems.
21. Hydrophobize the front surface of the printheads.
22. Fill with ink and test the completed printheads. A filled nozzle is shown in FIG. 15.
Another embodiment is shown in FIGS. 16 to 38. The Assignee refers to this embodiment as the IJ30 printhead. This printhead has ink ejection nozzles actuated by means of a thermal actuator which includes a “corrugated” copper heating element encased in a polytetrafluoroethylene (PTFE) layer.
Turning now to FIG. 16, there is illustrated a cross-sectional view of a single inkjet nozzle 110 as constructed in accordance with the present embodiment. The inkjet nozzle 110 includes an ink ejection port 111 for the ejection of ink from a chamber 112 by means of actuation of a thermal paddle actuator 113. The thermal paddle actuator 113 comprises an inner copper heating portion 114 and paddle 115 which are encased in an outer PTFE layer 116. The outer PTFE layer 116 has an extremely high coefficient of thermal expansion (approximately 770×10−6, or around 380 times that of silicon). The PTFE layer 116 is also highly hydrophobic which results in an air bubble 117 being formed under the actuator 113 due to out-gassing etc. The top PTFE layer 61 is treated so as to make it hydrophilic. The heater 114 is also formed within the lower portion 60 of the actuator 113.
The heater 114 is connected at ends 120, 121 (see also FIG. 22) to a lower CMOS drive layer 118 containing drive circuitry (not shown). For the purposes of actuation of actuator 113, a current is passed through the copper heater element 114 which heats the bottom surface of actuator 113. Turning now to FIG. 17, the bottom surface of actuator 113, in contact with air bubble 117 remains heated while any top surface heating is carried away by the exposure of the top surface of actuator 113 to the ink within chamber 112. Hence, the bottom PTFE layer expands more rapidly resulting in a general rapid bending upwards of actuator 113 (as illustrated in FIG. 17) which consequentially causes the ejection of ink from ink ejection port 111. FIG. 17 also shows an air inlet channel 128 formed between two nitride layers 142, 126 such that air is free to flow 129 along channel 128 and through holes, e.g. 125, in accordance with any fluctuating pressure influences. The air flow 129 acts to reduce the vacuum on the back surface of actuator 113 during operation. As a result less energy is required for the movement of the actuator 113.
The actuator 113 can be deactivated by turning off the current to heater element 114. This will result in a return of the actuator 113 to its rest position.
The actuator 113 includes a number of significant features. In FIG. 18 there is illustrated a schematic diagram of the conductive layer of the thermal actuator 113. The conductive layer includes paddle 115, which can be constructed from the same material as heater 114, i.e. copper, and which contains a series of holes e.g. 123. The holes are provided for interconnecting layers of PTFE both above and below panel 115 so as to resist any movement of the PTFE layers past the panel 115 and thereby reducing any opportunities for the delamination of the PTFE and copper layers.
Turning to FIG. 19, there is illustrated a close up view of a portion of the panel 115 indicated as A is FIG. 18 illustrating the corrugated nature 122 of the heater element 114 within the PTFE layers of actuator 113 of FIG. 16. The corrugated nature 122 of the heater 114 allows for a more rapid heating of the portions of the bottom layer surrounding the corrugated heater. Any resistive heater which is based upon applying a current to heat an object will result in a rapid, substantially uniform elevation in temperature of the outer surface of the current carrying conductor. The surrounding PTFE volume is therefore heated by means of thermal conduction from the resistive element. This thermal conduction is known to proceed, to a first approximation, at a substantially linear rate with respect to distance from a resistive element. By utilizing a corrugated resistive element the bottom surface of actuator 113 is more rapidly heated as, on average, a greater volume of the bottom PTFE surface is closer to a portion of the resistive element. Therefore, the utilisation of a corrugated resistive element results in a more rapid heating of the bottom surface layer and therefore a more rapid actuation of the actuator 113. Further, a corrugated heater also assists in resisting any delamination of the copper and PTFE layer.
Turning now to FIG. 20, the corrugated resistive element can be formed by depositing a resist layer 150 on top of the first PTFE layer 151. The resist layer 150 is exposed utilizing a mask 152 having a half-tone pattern delineating the corrugations. After development the resist 150 contains the corrugation pattern. The resist layer 150 and the PTFE layer 151 are then etched utilizing an etchant that erodes the resist layer 150 at substantially the same rate as the PTFE layer 151. This transfers the corrugated pattern into the PTFE layer 151. Turning to FIG. 21, on top of the corrugated PTFE layer 151 is deposited the copper heater layer 114 which takes on a corrugated form in accordance with its under layer. The copper heater layer 114 is then etched in a serpentine or concertina form. Subsequently, a further PTFE layer 153 is deposited on top of layer 114 so as to form the top layer of the thermal actuator 113. Finally, the second PTFE layer 152 is planarized to form the top surface 61 of the thermal actuator 113 (FIG. 16).
Returning again now to FIG. 16, it is noted that an ink supply can be supplied through a throughway for channel 138 which can be constructed by means of deep anisotropic silicon trench etching such as that available from STS Limited (“Advanced Silicon Etching Using High Density Plasmas” by J. K. Bhardwaj, H. Ashraf, page 224 of Volume 2639 of the SPIE Proceedings in Micro Machining and Micro Fabrication Process Technology). The ink supply flows from channel 138 through a grill formed by a series of columns 140 (see also FIG. 22) into chamber 112. The grill columns 140, which can comprise silicon nitride or similar insulating material, act to remove foreign bodies from the ink flow. The grill of columns 140 also helps to pinch the PTFE actuator 113 to a base CMOS layer 118, the pinching providing an important assistance for the thermal actuator 113 so as to ensure a substantially decreased likelihood of the thermal actuator layer 113 separating from a base CMOS layer 118. It will be appreciated that a filter structure at the inlet to each ink chamber is more likely to remove contaminants than a filter positioned further upstream in the in the ink supply flow. Contaminants, including air bubbles, can originate at all points along the ink supply line, so there is less chance of nozzle clogging or other detrimental effects if the ink flow is filtered at each of the chamber inlets.
A series of sacrificial etchant holes, e.g. 119, are provided in the top wall 148 of the chamber 112 to allow sacrificial etchant to enter the chamber 112 during fabrication so as to increase the rate of etching. The small size of the holes, e.g. 119, does not affect the operation of the device 110 substantially as the surface tension across holes, e.g. 119, stops ink being ejected from these holes, whereas, the larger size hole 111 allows for the ejection of ink.
Turning now to FIG. 22, there is illustrated an exploded perspective view of a single nozzle 110. The nozzles 110 can be formed in layers starting with a silicon wafer device 141 having a CMOS layer 118 on top thereof as required. The CMOS layer 118 provides the various drive circuitry for driving the copper heater elements 114.
On top of the CMOS layer 118 a nitride layer 142 is deposited, providing primarily protection for lower layers from corrosion or etching. Next a nitride layer 126 is constructed having the aforementioned holes, e.g. 125, and posts, e.g. 127. The structure of the nitride layer 126 can be formed by first laying down a sacrificial glass layer (not shown) onto which the nitride layer 126 is deposited. The nitride layer 126 includes various features, for example, a lower ridge portion 111 in addition to vias for the subsequent material layers.
In construction of the actuator 113 (FIG. 16), the process of creating a first PTFE layer proceeds by laying down a sacrificial layer on top of layer 126 in which the air bubble underneath actuator 113 subsequently forms. On top of this is formed a first PTFE layer utilizing the relevant mask. Preferably, the PTFE layer includes vias for the subsequent copper interconnections. Next, a copper layer 143 is deposited on top of the first PTFE layer 151 and a subsequent PTFE layer is deposited on top of the copper layer 143, in each case, utilizing the required mask.
The nitride layer 146 can be formed by the utilisation of a sacrificial glass layer which is masked and etched as required to form the side walls and the grill 140. Subsequently, the top nitride layer 148 is deposited again utilizing the appropriate mask having considerable holes as required. Subsequently, the various sacrificial layers can be etched away so as to release the structure of the thermal actuator.
In FIG. 23 there is illustrated a section of an ink jet printhead configuration 190 utilizing ink jet nozzles constructed in accordance with a preferred embodiment, e.g. 191. The configuration 190 can be utilized in a three color process 1600 dpi printhead utilizing 3 sets of 2 rows of nozzle chambers, e.g. 192, 193, which are interconnected to one ink supply channel, e.g. 194, for each set. The three supply channels 194, 195, 196 are interconnected to cyan, magenta and yellow ink reservoirs respectively.
As shown in FIG. 23, nozzle rows 192 and 193 are supplied by the same supply channel 194 and offset from each other in the paper feed direction. As discussed above, the printhead resolution is 1600 dpi and hence the nozzle pitch perpendicular to the paper feed direction is one 1600th of an inch, or 15.875 microns. Accordingly, the nozzles in each row on the printhead are spaced at 31.75 micron centres such that the spacing normal to paper feed between any nozzle and its neighbour in the offset row is the required 15.875 microns.
Fabricating the printhead chips (integrated circuits) using VLSI lithographic etching and deposition techniques is fundamental to the high nozzle densities that provide the 1600 dpi nozzle arrays that extend only 0.35 mm to 0.5 mm in the paper feed direction. As discussed below, prior art printheads have about 300 nozzles formed on a single monolithic substrate. The VLSI fabrication techniques and nozzle structures developed by the Applicant provide printheads with more than 2000 nozzles on a monolithic substrate with a high nozzle density. In the case of the IJ30 printhead shown in FIG. 23, the nozzle pitch along each row e.g. 192 and 193 is 32 microns. As FIG. 23 is to scale, it can be seen that the nozzle chambers are each 72 microns long and the ink supply channel 194 between each nozzle row is 48 microns wide. The eleven nozzles shown in rows 192 and 193 occupy 33,792 square microns of the wafer. Hence the overall nozzle density for the IJ30 is about 325 nozzles per square mm.
Currently, nozzle densities on scanning printhead chips are of the order of 10 to 20 nozzles per square mm. It will be appreciated that the combination of VLSI CMOS fabrication and subsequent MEMS fabrication allow nozzle densities to easily exceed 100 nozzles per square mm and comfortably exceed 200 nozzles per square mm using lithographic techniques employed in the semiconductor industry. Design elements such as ink supply conduits extending through the wafer to the nozzles (instead along the ejection side of the wafer) can further increase the nozzle densities above 300 nozzles per square mm. The Applicant's IJ38 chip design (discussed below) is the thinnest of the 100 mm long chips at just 0.35 mm wide and has a nozzle density of about 548 nozzles per square mm.
One form of detailed manufacturing process which can be used to fabricate monolithic inkjet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:
1. Using a double sided polished wafer 141, complete drive transistors, data distribution, and timing circuits using a 0.5 micron, one poly, two metal CMOS process 118. Relevant features of the wafer at this step are shown in FIG. 25. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. FIG. 24 is a key to representations of various materials in these manufacturing diagrams, and those of other cross referenced ink jet configurations.
2. Deposit 1 micron of low stress nitride 142. This acts as a barrier to prevent ink diffusion through the silicon dioxide of the chip surface.
3. Deposit 2 microns of sacrificial material 160 (e.g. polyimide).
4. Etch the sacrificial layer to define the PTFE venting layer support pillars e.g. 127 and anchor point. This step is shown in FIG. 26.
5. Deposit 2 microns of PTFE 126.
6. Etch the PTFE using Mask 2. This mask defines the edges of the PTFE venting layer, and the holes in this layer. This step is shown in FIG. 27.
7. Deposit 3 micron of sacrificial material 161 (e.g. polyimide).
8. Etch the sacrificial layer using Mask 3. This mask defines the actuator anchor point. This step is shown in FIG. 28.
9. Deposit 1 micron of PTFE.
10. Deposit, expose and develop 1 micron of resist using Mask 4. This mask is a gray-scale mask which defines the heater vias as well as the corrugated PTFE surface 162 that the heater is subsequently deposited on.
11. Etch the PTFE and resist at substantially the same rate. The corrugated resist thickness is transferred to the PTFE, and the PTFE is completely etched in the heater via positions. In the corrugated regions, the resultant PTFE thickness nominally varies between 0.25 micron and 0.75 micron, though exact values are not critical. This step is shown in FIG. 29.
12. Deposit and pattern resist using Mask 5. This mask defines the heater.
13. Deposit 0.5 microns of gold 163 (or other heater material with a low Young's modulus) and strip the resist. Steps 12 and 13 form a lift-off process. This step is shown in FIG. 30.
14. Deposit 1.5 microns of PTFE 116.
15. Etch the PTFE down to the sacrificial layer to define the actuator paddle and the bond pads.
This step is shown in FIG. 31.
16. Wafer probe. All electrical connections are complete at this point, and the chips are not yet separated.
17. Plasma process the PTFE to make the top and side surfaces of the paddle hydrophilic. This allows the nozzle chamber to fill by capillarity.
18. Deposit 10 microns of sacrificial material 164.
19. Etch the sacrificial material down to nitride to define the nozzle chamber. This step is shown in FIG. 32.
20. Deposit 3 microns of PECVD glass 146. This step is shown in FIG. 33.
21. Etch to a depth of 1 micron to define the nozzle rim 165. This step is shown in FIG. 34.
22. Etch down to the sacrificial layer to define the nozzle and the sacrificial etch access holes e.g. 119. This step is shown in FIG. 35.
23. Back-etch completely through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems). This mask defines the ink inlets 138 which are etched through the wafer. The wafer is also diced by this etch. This step is shown in FIG. 36.
24. Back-etch the CMOS oxide layers and subsequently deposited nitride layers and sacrificial layer through to PTFE using the back-etched silicon as a mask.
25. Etch the sacrificial material. The nozzle chambers are cleared, the actuators freed, and the chips are separated by this etch. This step is shown in FIG. 37.
26. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets at the back of the wafer.
27. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper.
28. Hydrophobize the front surface of the printheads.
29. Fill the completed printheads with ink 166 and test them. A filled nozzle is shown in FIG. 38.
It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiment without departing from the spirit or scope of the invention as broadly described. Some possible variations are disclosed in the cross referenced documents listed above and incorporated herein. These disclosures provide an indication of the scope of possible and highlight that the embodiments described above are merely illustrative and in no way restrictive.
The presently disclosed ink jet printing technology is potentially suited to a wide range of printing systems including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers, high speed pagewidth printers, notebook computers with inbuilt pagewidth printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic ‘minilabs’, video printers, PHOTO CD (PHOTO CD is a registered trademark of the Eastman Kodak Company) printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.
The embodiments of the invention use an inkjet printer type device. Of course many different devices could be used. However presently popular inkjet printing technologies are unlikely to be suitable.
The most significant problem with vapor bubble forming thermal inkjet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.
The most significant problem with piezoelectric ink jet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per printhead, but is a major impediment to the fabrication of pagewidth printheads with 19,200 nozzles.
Ideally, the ink jet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new ink jet technologies have been created. The target features include:
low power (less than 10 Watts average consumption for 100% coverage printing from pagewidth printhead)
high resolution capability (1,600 dpi or more)
photographic quality output low manufacturing cost
small size (pagewidth times minimum cross section)
high speed (<2 seconds per page).
All of these features can be met or exceeded by the inkjet systems described in the tables set out below with differing levels of difficulty. Forty-five different ink jet technologies (Assignee's Docket Numbers IJ01 to IJ45) have been developed by the Assignee to give a wide range of choices for high volume manufacture. The droplet ejector mechanisms in each of IJ01 to IJ45 offer substantial advantages over existing printheads, primarily by reducing the energy required to eject a droplet of ink. As discussed in the Actuator Mechanism Table below, the IJ30 actuator uses only 15 mW to move the free end of the actuator 113 (see FIG. 16) 10 microns with a force of 180 micro-Newtons. These technologies form part of separate applications assigned to the present Assignee as set out in the table under the heading Cross References to Related Applications.
The inkjet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems.
For ease of manufacture using standard process equipment, the printhead is designed to be a monolithic 0.5 micron CMOS chip with MEMS post processing. For color photographic applications, the printhead is 100 mm long, with a width which depends upon the ink jet type. The smallest printhead designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The printheads each contain 19,200 nozzles plus data and control circuitry such that the monolithic silicon substrate supports and array of nozzles with a nozzle density of 548 nozzles per square mm. The printhead uses less than 10 Watts and so the average power consumption of each nozzle is less than 0.502 mW. It will be appreciated that this is a huge improvement over the power consumption of existing electro-thermally actuated printheads. For example, the device shown in U.S. Pat. No. 4,490,728 to Vaught et al uses about 0.3 W to 0.5 W per nozzle (given a nozzle fire rate of 10 Hz and a pulse width of 5 micro-seconds is not unreasonable for this type of printhead). Accordingly, even if the electro-thermal actuator of IJ30 were modified to eject larger droplets (say, 5 μl or 10 μl) or fabricated using material with a marginally lower CTE, the power consumption per nozzle during activation of the would be easily less than 1.5 mW, more likely less than 1.0 mW and typically in the range of 0.5 mW to 1.0 mW. It will be appreciated that these power consumption values are average values taken when the printhead is printing 100% coverage at full print rate.
The peak power consumption during activation of the IJ30 actuator is much higher than the time averaged power. However, it is still far lower than that of existing electro-thermal actuators. The Vaught et al printhead discussed above has a peak actuator power of 3 W. Using the principles of the IJ30 electro-thermal actuator, the peak power consumption is less than 100 mW even if 5 μl drops are ejected and actuator material has a CTE marginally less than PTFE. Using the IJ30 design principles and as the VLSI fabrication techniques described herein, an activation power of less than 50 mW is easily attainable. As discussed below in the Table of Actuator Types, the activation power for the IJ30 actuator is 15 mW. However, with variation of design parameters such as the droplet volume and nozzle to actuator spacing, the activation power will typically vary between 10 mW and 30 mW.
With low energy ejection of ink droplets, little, if any, excess heat is generated in the printhead. A build up of excess heat in the printhead imposes a limit on the nozzle firing frequency and thereby limits the print speed. The IJ30 printhead is self cooling (the heat generated by the thermal actuator is removed from the printhead with the ejected drop. In this case, the print speed is only limited by the rate at which the ink can be supplied to the printhead or the speed that the media substrate can be fed past the printhead. Printers using the IJ30 printhead will accommodate a media substrate feed speed relative to the printhead in excess of 0.1 m/s. Indeed, when used in a printer such as that shown in the Assignee's U.S. Pat. No. 7,011,128 (the contents of which are incorporated herein by reference), the media feed speed is greater than 0.15 m/s.
An A4 sheet printed at 1600 dpi has about 18,600 dots rows across the page. Accordingly, the IJ30 printhead in a pagewidth form prints at least 6300 rows/sec or less than 0.00016 secs per dot row. Typically, the row printing frequency is more than 9450 rows/sec or less than 0.000106 secs per dot row.
Ink is supplied to the back of the printhead by injection molded plastic ink channels. The molding requires 50 micron features, which can be created using a lithographically micro-machined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The printhead is connected to the camera circuitry by tape automated bonding.
Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee.
The following tables form the axes of an eleven dimensional table of ink jet types.
Actuator mechanism (18 types)
Basic operation mode (7 types)
Auxiliary mechanism (8 types)
Actuator amplification or modification method (17 types)
Actuator motion (19 types)
Nozzle refill method (4 types)
Method of restricting back-flow through inlet (10 types)
Nozzle clearing method (9 types)
Nozzle plate construction (9 types)
Drop ejection direction (5 types)
Ink type (7 types)
The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of ink jet nozzle. While not all of the possible combinations result in a viable ink jet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain inkjet types have been investigated in detail. These are designated IJ01 to IJ45 which match the docket numbers in the table under the heading Cross Referenced to Related Application.
Other inkjet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into ink jet printheads with characteristics superior to any currently available inkjet technology.
Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJ01 to IJ45 series are also listed in the examples column. In some cases, a print technology may be listed more than once in a table, where it shares characteristics with more than one entry.
Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.
The information associated with the aforementioned 11 dimensional matrix is set out in the following tables.
ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) | ||||
Description | Advantages | Disadvantages | Examples | |
Thermal | An electrothermal | Large force | High power | Canon Bubblejet |
bubble | heater heats the ink to | generated | Ink carrier | 1979 Endo et al GB |
above boiling point, | Simple | limited to water | patent 2,007,162 | |
transferring significant | construction | Low efficiency | Xerox heater-in- | |
heat to the aqueous | No moving parts | High | pit 1990 Hawkins et | |
ink. A bubble | Fast operation | temperatures | al U.S. Pat. No. 4,899,181 | |
nucleates and quickly | Small chip area | required | Hewlett-Packard | |
forms, expelling the | required for actuator | High mechanical | TIJ 1982 Vaught et | |
ink. | stress | al U.S. Pat. No. 4,490,728 | ||
The efficiency of the | Unusual | |||
process is low, with | materials required | |||
typically less than | Large drive | |||
0.05% of the electrical | transistors | |||
energy being | Cavitation causes | |||
transformed into | actuator failure | |||
kinetic energy of the | Kogation reduces | |||
drop. | bubble formation | |||
Large print heads | ||||
are difficult to | ||||
fabricate | ||||
Piezoelectric | A piezoelectric crystal | Low power | Very large area | Kyser et al U.S. Pat. No. |
such as lead | consumption | required for actuator | 3,946,398 | |
lanthanum zirconate | Many ink types | Difficult to | Zoltan U.S. Pat. No. | |
(PZT) is electrically | can be used | integrate with | 3,683,212 | |
activated, and either | Fast operation | electronics | 1973 Stemme | |
expands, shears, or | High efficiency | High voltage | U.S. Pat. No. 3,747,120 | |
bends to apply | drive transistors | Epson Stylus | ||
pressure to the ink, | required | Tektronix | ||
ejecting drops. | Full pagewidth | IJ04 | ||
print heads | ||||
impractical due to | ||||
actuator size | ||||
Requires | ||||
electrical poling in | ||||
high field strengths | ||||
during manufacture | ||||
Electro- | An electric field is | Low power | Low maximum | Seiko Epson, |
strictive | used to activate | consumption | strain (approx. | Usui et all JP |
electrostriction in | Many ink types | 0.01%) | 253401/96 | |
relaxor materials such | can be used | Large area | IJ04 | |
as lead lanthanum | Low thermal | required for actuator | ||
zirconate titanate | expansion | due to low strain | ||
(PLZT) or lead | Electric field | Response speed | ||
magnesium niobate | strength required | is marginal (~ 10 μs) | ||
(PMN). | (approx. 3.5 V/μm) | High voltage | ||
can be generated | drive transistors | |||
without difficulty | required | |||
Does not require | Full pagewidth | |||
electrical poling | print heads | |||
impractical due to | ||||
actuator size | ||||
Ferroelectric | An electric field is | Low power | Difficult to | IJ04 |
used to induce a phase | consumption | integrate with | ||
transition between the | Many ink types | electronics | ||
antiferroelectric (AFE) | can be used | Unusual | ||
and ferroelectric (FE) | Fast operation | materials such as | ||
phase. Perovskite | (<1 μs) | PLZSnT are | ||
materials such as tin | Relatively high | required | ||
modified lead | longitudinal strain | Actuators require | ||
lanthanum zirconate | High efficiency | a large area | ||
titanate (PLZSnT) | Electric field | |||
exhibit large strains of | strength of around 3 V/μm | |||
up to 1% associated | can be readily | |||
with the AFE to FE | provided | |||
phase transition. | ||||
Electrostatic | Conductive plates are | Low power | Difficult to | IJ02, IJ04 |
plates | separated by a | consumption | operate electrostatic | |
compressible or fluid | Many ink types | devices in an | ||
dielectric (usually air). | can be used | aqueous | ||
Upon application of a | Fast operation | environment | ||
voltage, the plates | The electrostatic | |||
attract each other and | actuator will | |||
displace ink, causing | normally need to be | |||
drop ejection. The | separated from the | |||
conductive plates may | ink | |||
be in a comb or | Very large area | |||
honeycomb structure, | required to achieve | |||
or stacked to increase | high forces | |||
the surface area and | High voltage | |||
therefore the force. | drive transistors | |||
may be required | ||||
Full pagewidth | ||||
print heads are not | ||||
competitive due to | ||||
actuator size | ||||
Electrostatic | A strong electric field | Low current | High voltage | 1989 Saito et al, |
pull | is applied to the ink, | consumption | required | U.S. Pat. No. 4,799,068 |
on ink | whereupon | Low temperature | May be damaged | 1989 Miura et al, |
electrostatic attraction | by sparks due to air | U.S. Pat. No. 4,810,954 | ||
accelerates the ink | breakdown | Tone-jet | ||
towards the print | Required field | |||
medium. | strength increases as | |||
the drop size | ||||
decreases | ||||
High voltage | ||||
drive transistors | ||||
required | ||||
Electrostatic field | ||||
attracts dust | ||||
Permanent | An electromagnet | Low power | Complex | IJ07, IJ10 |
magnet | directly attracts a | consumption | fabrication | |
electro- | permanent magnet, | Many ink types | Permanent | |
magnetic | displacing ink and | can be used | magnetic material | |
causing drop ejection. | Fast operation | such as Neodymium | ||
Rare earth magnets | High efficiency | Iron Boron (NdFeB) | ||
with a field strength | Easy extension | required. | ||
around 1 Tesla can be | from single nozzles | High local | ||
used. Examples are: | to pagewidth print | currents required | ||
Samarium Cobalt | heads | Copper | ||
(SaCo) and magnetic | metalization should | |||
materials in the | be used for long | |||
neodymium iron boron | electromigration | |||
family (NdFeB, | lifetime and low | |||
NdDyFeBNb, | resistivity | |||
NdDyFeB, etc) | Pigmented inks | |||
are usually | ||||
infeasible | ||||
Operating | ||||
temperature limited | ||||
to the Curie | ||||
temperature (around | ||||
540 K) | ||||
Soft | A solenoid induced a | Low power | Complex | IJ01, IJ05, IJ08, |
magnetic | magnetic field in a soft | consumption | fabrication | IJ10, IJ12, IJ14, |
core electro- | magnetic core or yoke | Many ink types | Materials not | IJ15, IJ17 |
magnetic | fabricated from a | can be used | usually present in a | |
ferrous material such | Fast operation | CMOS fab such as | ||
as electroplated iron | High efficiency | NiFe, CoNiFe, or | ||
alloys such as CoNiFe | Easy extension | CoFe are required | ||
[1], CoFe, or NiFe | from single nozzles | High local | ||
alloys. Typically, the | to pagewidth print | currents required | ||
soft magnetic material | heads | Copper | ||
is in two parts, which | metalization should | |||
are normally held | be used for long | |||
apart by a spring. | electromigration | |||
When the solenoid is | lifetime and low | |||
actuated, the two parts | resistivity | |||
attract, displacing the | Electroplating is | |||
ink. | required | |||
High saturation | ||||
flux density is | ||||
required (2.0-2.1 T | ||||
is achievable with | ||||
CoNiFe [1]) | ||||
Lorenz | The Lorenz force | Low power | Force acts as a | IJ06, IJ11, IJ13, |
force | acting on a current | consumption | twisting motion | IJ16 |
carrying wire in a | Many ink types | Typically, only a | ||
magnetic field is | can be used | quarter of the | ||
utilized. | Fast operation | solenoid length | ||
This allows the | High efficiency | provides force in a | ||
magnetic field to be | Easy extension | useful direction | ||
supplied externally to | from single nozzles | High local | ||
the print head, for | to pagewidth print | currents required | ||
example with rare | heads | Copper | ||
earth permanent | metalization should | |||
magnets. | be used for long | |||
Only the current | electromigration | |||
carrying wire need be | lifetime and low | |||
fabricated on the print- | resistivity | |||
head, simplifying | Pigmented inks | |||
materials | are usually | |||
requirements. | infeasible | |||
Magneto- | The actuator uses the | Many ink types | Force acts as a | Fischenbeck, |
striction | giant magnetostrictive | can be used | twisting motion | U.S. Pat. No. 4,032,929 |
effect of materials | Fast operation | Unusual | IJ25 | |
such as Terfenol-D (an | Easy extension | materials such as | ||
alloy of terbium, | from single nozzles | Terfenol-D are | ||
dysprosium and iron | to pagewidth print | required | ||
developed at the Naval | heads | High local | ||
Ordnance Laboratory, | High force is | currents required | ||
hence Ter-Fe-NOL). | available | Copper | ||
For best efficiency, the | metalization should | |||
actuator should be pre- | be used for long | |||
stressed to approx. 8 MPa. | electromigration | |||
lifetime and low | ||||
resistivity | ||||
Pre-stressing | ||||
may be required | ||||
Surface | Ink under positive | Low power | Requires | Silverbrook, EP |
tension | pressure is held in a | consumption | supplementary force | 0771 658 A2 and |
reduction | nozzle by surface | Simple | to effect drop | related patent |
tension. The surface | construction | separation | applications | |
tension of the ink is | No unusual | Requires special | ||
reduced below the | materials required in | ink surfactants | ||
bubble threshold, | fabrication | Speed may be | ||
causing the ink to | High efficiency | limited by surfactant | ||
egress from the | Easy extension | properties | ||
nozzle. | from single nozzles | |||
to pagewidth print | ||||
heads | ||||
Viscosity | The ink viscosity is | Simple | Requires | Silverbrook, EP |
reduction | locally reduced to | construction | supplementary force | 0771 658 A2 and |
select which drops are | No unusual | to effect drop | related patent | |
to be ejected. A | materials required in | separation | applications | |
viscosity reduction can | fabrication | Requires special | ||
be achieved | Easy extension | ink viscosity | ||
electrothermally with | from single nozzles | properties | ||
most inks, but special | to pagewidth print | High speed is | ||
inks can be engineered | heads | difficult to achieve | ||
for a 100:1 viscosity | Requires | |||
reduction. | oscillating ink | |||
pressure | ||||
A high | ||||
temperature | ||||
difference (typically | ||||
80 degrees) is | ||||
required | ||||
Acoustic | An acoustic wave is | Can operate | Complex drive | 1993 Hadimioglu |
generated and | without a nozzle | circuitry | et al, EUP 550,192 | |
focussed upon the | plate | Complex | 1993 Elrod et al, | |
drop ejection region. | fabrication | EUP 572,220 | ||
Low efficiency | ||||
Poor control of | ||||
drop position | ||||
Poor control of | ||||
drop volume | ||||
Thermo- | An actuator which | Low power | Efficient aqueous | IJ03, IJ09, IJ17, |
elastic bend | relies upon differential | consumption | operation requires a | IJ18, IJ19, IJ20, |
actuator | thermal expansion | Many ink types | thermal insulator on | IJ21, IJ22, IJ23, |
upon Joule heating is | can be used | the hot side | IJ24, IJ27, IJ28, | |
used. | Simple planar | Corrosion | IJ29, IJ30, IJ31, | |
fabrication | prevention can be | IJ32, IJ33, IJ34, | ||
Small chip area | difficult | IJ35, IJ36, IJ37, | ||
required for each | Pigmented inks | IJ38, IJ39, IJ40, | ||
actuator | may be infeasible, | IJ41 | ||
Fast operation | as pigment particles | |||
High efficiency | may jam the bend | |||
CMOS | actuator | |||
compatible voltages | ||||
and currents | ||||
Standard MEMS | ||||
processes can be | ||||
used | ||||
Easy extension | ||||
from single nozzles | ||||
to pagewidth print | ||||
heads | ||||
High CTE | A material with a very | High force can | Requires special | IJ09, IJ17, IJ18, |
thermo- | high coefficient of | be generated | material (e.g. PTFE) | IJ20, IJ21, IJ22, |
elastic | thermal expansion | Three methods of | Requires a PTFE | IJ23, IJ24, IJ27, |
actuator | (CTE) such as | PTFE deposition are | deposition process, | IJ28, IJ29, IJ30, |
polytetrafluoroethylene | under development: | which is not yet | IJ31, IJ42, IJ43, | |
(PTFE) is used. As | chemical vapor | standard in ULSI | IJ44 | |
high CTE materials | deposition (CVD), | fabs | ||
are usually non- | spin coating, and | PTFE deposition | ||
conductive, a heater | evaporation | cannot be followed | ||
fabricated from a | PTFE is a | with high | ||
conductive material is | candidate for low | temperature (above | ||
incorporated. A 50 μm | dielectric constant | 350° C.) processing | ||
long PTFE bend | insulation in ULSI | Pigmented inks | ||
actuator with | Very low power | may be infeasible, | ||
polysilicon heater and | consumption | as pigment particles | ||
15 mW power input | Many ink types | may jam the bend | ||
can provide 180 μN | can be used | actuator | ||
force and 10 μm | Simple planar | |||
deflection. Actuator | fabrication | |||
motions include: | Small chip area | |||
Bend | required for each | |||
Push | actuator | |||
Buckle | Fast operation | |||
Rotate | High efficiency | |||
CMOS | ||||
compatible voltages | ||||
and currents | ||||
Easy extension | ||||
from single nozzles | ||||
to pagewidth print | ||||
heads | ||||
Conductive | A polymer with a high | High force can | Requires special | IJ24 |
polymer | coefficient of thermal | be generated | materials | |
thermo- | expansion (such as | Very low power | development (High | |
elastic | PTFE) is doped with | consumption | CTE conductive | |
actuator | conducting substances | Many ink types | polymer) | |
to increase its | can be used | Requires a PTFE | ||
conductivity to about 3 | Simple planar | deposition process, | ||
orders of magnitude | fabrication | which is not yet | ||
below that of copper. | Small chip area | standard in ULSI | ||
The conducting | required for each | fabs | ||
polymer expands | actuator | PTFE deposition | ||
when resistively | Fast operation | cannot be followed | ||
heated. | High efficiency | with high | ||
Examples of | CMOS | temperature (above | ||
conducting dopants | compatible voltages | 350° C.) processing | ||
include: | and currents | Evaporation and | ||
Carbon nanotubes | Easy extension | CVD deposition | ||
Metal fibers | from single nozzles | techniques cannot | ||
Conductive polymers | to pagewidth print | be used | ||
such as doped | heads | Pigmented inks | ||
polythiophene | may be infeasible, | |||
Carbon granules | as pigment particles | |||
may jam the bend | ||||
actuator | ||||
Shape | A shape memory alloy | High force is | Fatigue limits | IJ26 |
memory | such as TiNi (also | available (stresses | maximum number | |
alloy | known as Nitinol - | of hundreds of MPa) | of cycles | |
Nickel Titanium alloy | Large strain is | Low strain (1%) | ||
developed at the Naval | available (more than | is required to extend | ||
Ordnance Laboratory) | 3%) | fatigue resistance | ||
is thermally switched | High corrosion | Cycle rate | ||
between its weak | resistance | limited by heat | ||
martensitic state and | Simple | removal | ||
its high stiffness | construction | Requires unusual | ||
austenic state. The | Easy extension | materials (TiNi) | ||
shape of the actuator | from single nozzles | The latent heat of | ||
in its martensitic state | to pagewidth print | transformation must | ||
is deformed relative to | heads | be provided | ||
the austenic shape. | Low voltage | High current | ||
The shape change | operation | operation | ||
causes ejection of a | Requires pre- | |||
drop. | stressing to distort | |||
the martensitic state | ||||
Linear | Linear magnetic | Linear Magnetic | Requires unusual | IJ12 |
Magnetic | actuators include the | actuators can be | semiconductor | |
Actuator | Linear Induction | constructed with | materials such as | |
Actuator (LIA), Linear | high thrust, long | soft magnetic alloys | ||
Permanent Magnet | travel, and high | (e.g. CoNiFe) | ||
Synchronous Actuator | efficiency using | Some varieties | ||
(LPMSA), Linear | planar | also require | ||
Reluctance | semiconductor | permanent magnetic | ||
Synchronous Actuator | fabrication | materials such as | ||
(LRSA), Linear | techniques | Neodymium iron | ||
Switched Reluctance | Long actuator | boron (NdFeB) | ||
Actuator (LSRA), and | travel is available | Requires | ||
the Linear Stepper | Medium force is | complex multi- | ||
Actuator (LSA). | available | phase drive circuitry | ||
Low voltage | High current | |||
operation | operation | |||
BASIC OPERATION MODE | ||||
Description | Advantages | Disadvantages | Examples | |
Actuator | This is the simplest | Simple operation | Drop repetition | Thermal ink jet |
directly | mode of operation: the | No external | rate is usually | Piezoelectric ink |
pushes ink | actuator directly | fields required | limited to around 10 kHz. | jet |
supplies sufficient | Satellite drops | However, this | IJ01, IJ02, IJ03, | |
kinetic energy to expel | can be avoided if | is not fundamental | IJ04, IJ05, IJ06, | |
the drop. The drop | drop velocity is less | to the method, but is | IJ07, IJ09, IJ11, | |
must have a sufficient | than 4 m/s | related to the refill | IJ12, IJ14, IJ16, | |
velocity to overcome | Can be efficient, | method normally | IJ20, IJ22, IJ23, | |
the surface tension. | depending upon the | used | IJ24, IJ25, IJ26, | |
actuator used | All of the drop | IJ27, IJ28, IJ29, | ||
kinetic energy must | IJ30, IJ31, IJ32, | |||
be provided by the | IJ33, IJ34, IJ35, | |||
actuator | IJ36, IJ37, IJ38, | |||
Satellite drops | IJ39, IJ40, IJ41, | |||
usually form if drop | IJ42, IJ43, IJ44 | |||
velocity is greater | ||||
than 4.5 m/s | ||||
Proximity | The drops to be | Very simple print | Requires close | Silverbrook, EP |
printed are selected by | head fabrication can | proximity between | 0771 658 A2 and | |
some manner (e.g. | be used | the print head and | related patent | |
thermally induced | The drop | the print media or | applications | |
surface tension | selection means | transfer roller | ||
reduction of | does not need to | May require two | ||
pressurized ink). | provide the energy | print heads printing | ||
Selected drops are | required to separate | alternate rows of the | ||
separated from the ink | the drop from the | image | ||
in the nozzle by | nozzle | Monolithic color | ||
contact with the print | print heads are | |||
medium or a transfer | difficult | |||
roller. | ||||
Electrostatic | The drops to be | Very simple print | Requires very | Silverbrook, EP |
pull | printed are selected by | head fabrication can | high electrostatic | 0771 658 A2 and |
on ink | some manner (e.g. | be used | field | related patent |
thermally induced | The drop | Electrostatic field | applications | |
surface tension | selection means | for small nozzle | Tone-Jet | |
reduction of | does not need to | sizes is above air | ||
pressurized ink). | provide the energy | breakdown | ||
Selected drops are | required to separate | Electrostatic field | ||
separated from the ink | the drop from the | may attract dust | ||
in the nozzle by a | nozzle | |||
strong electric field. | ||||
Magnetic | The drops to be | Very simple print | Requires | Silverbrook, EP |
pull on ink | printed are selected by | head fabrication can | magnetic ink | 0771 658 A2 and |
some manner (e.g. | be used | Ink colors other | related patent | |
thermally induced | The drop | than black are | applications | |
surface tension | selection means | difficult | ||
reduction of | does not need to | Requires very | ||
pressurized ink). | provide the energy | high magnetic fields | ||
Selected drops are | required to separate | |||
separated from the ink | the drop from the | |||
in the nozzle by a | nozzle | |||
strong magnetic field | ||||
acting on the magnetic | ||||
ink. | ||||
Shutter | The actuator moves a | High speed (>50 kHz) | Moving parts are | IJ13, IJ17, IJ21 |
shutter to block ink | operation can | required | ||
flow to the nozzle. The | be achieved due to | Requires ink | ||
ink pressure is pulsed | reduced refill time | pressure modulator | ||
at a multiple of the | Drop timing can | Friction and wear | ||
drop ejection | be very accurate | must be considered | ||
frequency. | The actuator | Stiction is | ||
energy can be very | possible | |||
low | ||||
Shuttered | The actuator moves a | Actuators with | Moving parts are | IJ08, IJ15, IJ18, |
grill | shutter to block ink | small travel can be | required | IJ19 |
flow through a grill to | used | Requires ink | ||
the nozzle. The shutter | Actuators with | pressure modulator | ||
movement need only | small force can be | Friction and wear | ||
be equal to the width | used | must be considered | ||
of the grill holes. | High speed (>50 kHz) | Stiction is | ||
operation can | possible | |||
be achieved | ||||
Pulsed | A pulsed magnetic | Extremely low | Requires an | IJ10 |
magnetic | field attracts an ‘ink | energy operation is | external pulsed | |
pull on ink | pusher’ at the drop | possible | magnetic field | |
pusher | ejection frequency. An | No heat | Requires special | |
actuator controls a | dissipation | materials for both | ||
catch, which prevents | problems | the actuator and the | ||
the ink pusher from | ink pusher | |||
moving when a drop is | Complex | |||
not to be ejected. | construction | |||
AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) | ||||
Description | Advantages | Disadvantages | Examples | |
None | The actuator directly | Simplicity of | Drop ejection | Most ink jets, |
fires the ink drop, and | construction | energy must be | including | |
there is no external | Simplicity of | supplied by | piezoelectric and | |
field or other | operation | individual nozzle | thermal bubble. | |
mechanism required. | Small physical | actuator | IJ01, IJ02, IJ03, | |
size | IJ04, IJ05, IJ07, | |||
IJ09, IJ11, IJ12, | ||||
IJ14, IJ20, IJ22, | ||||
IJ23, IJ24, IJ25, | ||||
IJ26, IJ27, IJ28, | ||||
IJ29, IJ30, IJ31, | ||||
IJ32, IJ33, IJ34, | ||||
IJ35, IJ36, IJ37, | ||||
IJ38, IJ39, IJ40, | ||||
IJ41, IJ42, IJ43, | ||||
IJ44 | ||||
Oscillating | The ink pressure | Oscillating ink | Requires external | Silverbrook, EP |
ink pressure | oscillates, providing | pressure can provide | ink pressure | 0771 658 A2 and |
(including | much of the drop | a refill pulse, | oscillator | related patent |
acoustic | ejection energy. The | allowing higher | Ink pressure | applications |
stimulation) | actuator selects which | operating speed | phase and amplitude | IJ08, IJ13, IJ15, |
drops are to be fired | The actuators | must be carefully | IJ17, IJ18, IJ19, | |
by selectively | may operate with | controlled | IJ21 | |
blocking or enabling | much lower energy | Acoustic | ||
nozzles. The ink | Acoustic lenses | reflections in the ink | ||
pressure oscillation | can be used to focus | chamber must be | ||
may be achieved by | the sound on the | designed for | ||
vibrating the print | nozzles | |||
head, or preferably by | ||||
an actuator in the ink | ||||
supply. | ||||
Media | The print head is | Low power | Precision | Silverbrook, EP |
proximity | placed in close | High accuracy | assembly required | 0771 658 A2 and |
proximity to the print | Simple print head | Paper fibers may | related patent | |
medium. Selected | construction | cause problems | applications | |
drops protrude from | Cannot print on | |||
the print head further | rough substrates | |||
than unselected drops, | ||||
and contact the print | ||||
medium. The drop | ||||
soaks into the medium | ||||
fast enough to cause | ||||
drop separation. | ||||
Transfer | Drops are printed to a | High accuracy | Bulky | Silverbrook, EP |
roller | transfer roller instead | Wide range of | Expensive | 0771 658 A2 and |
of straight to the print | print substrates can | Complex | related patent | |
medium. A transfer | be used | construction | applications | |
roller can also be used | Ink can be dried | Tektronix hot | ||
for proximity drop | on the transfer roller | melt piezoelectric | ||
separation. | ink jet | |||
Any of the IJ | ||||
series | ||||
Electrostatic | An electric field is | Low power | Field strength | Silverbrook, EP |
used to accelerate | Simple print head | required for | 0771 658 A2 and | |
selected drops towards | construction | separation of small | related patent | |
the print medium. | drops is near or | applications | ||
above air | Tone-Jet | |||
breakdown | ||||
Direct | A magnetic field is | Low power | Requires | Silverbrook, EP |
magnetic | used to accelerate | Simple print head | magnetic ink | 0771 658 A2 and |
field | selected drops of | construction | Requires strong | related patent |
magnetic ink towards | magnetic field | applications | ||
the print medium. | ||||
Cross | The print head is | Does not require | Requires external | IJ06, IJ16 |
magnetic | placed in a constant | magnetic materials | magnet | |
field | magnetic field. The | to be integrated in | Current densities | |
Lorenz force in a | the print head | may be high, | ||
current carrying wire | manufacturing | resulting in | ||
is used to move the | process | electromigration | ||
actuator. | problems | |||
Pulsed | A pulsed magnetic | Very low power | Complex print | IJ10 |
magnetic | field is used to | operation is possible | head construction | |
field | cyclically attract a | Small print head | Magnetic | |
paddle, which pushes | size | materials required in | ||
on the ink. A small | print head | |||
actuator moves a | ||||
catch, which | ||||
selectively prevents | ||||
the paddle from | ||||
moving. | ||||
ACTUATOR AMPLIFICATION OR MODIFICATION METHOD | ||||
Description | Advantages | Disadvantages | Examples | |
None | No actuator | Operational | Many actuator | Thermal Bubble |
mechanical | simplicity | mechanisms have | Ink jet | |
amplification is used. | insufficient travel, | IJ01, IJ02, IJ06, | ||
The actuator directly | or insufficient force, | IJ07, IJ16, IJ25, | ||
drives the drop | to efficiently drive | IJ26 | ||
ejection process. | the drop ejection | |||
process | ||||
Differential | An actuator material | Provides greater | High stresses are | Piezoelectric |
expansion | expands more on one | travel in a reduced | involved | IJ03, IJ09, IJ17, |
bend | side than on the other. | print head area | Care must be | IJ18, IJ19, IJ20, |
actuator | The expansion may be | taken that the | IJ21, IJ22, IJ23, | |
thermal, piezoelectric, | materials do not | IJ24, IJ27, IJ29, | ||
magnetostrictive, or | delaminate | IJ30, IJ31, IJ32, | ||
other mechanism. The | Residual bend | IJ33, IJ34, IJ35, | ||
bend actuator converts | resulting from high | IJ36, IJ37, IJ38, | ||
a high force low travel | temperature or high | IJ39, IJ42, IJ43, | ||
actuator mechanism to | stress during | IJ44 | ||
high travel, lower | formation | |||
force mechanism. | ||||
Transient | A trilayer bend | Very good | High stresses are | IJ40, IJ41 |
bend | actuator where the two | temperature stability | involved | |
actuator | outside layers are | High speed, as a | Care must be | |
identical. This cancels | new drop can be | taken that the | ||
bend due to ambient | fired before heat | materials do not | ||
temperature and | dissipates | delaminate | ||
residual stress. The | Cancels residual | |||
actuator only responds | stress of formation | |||
to transient heating of | ||||
one side or the other. | ||||
Reverse | The actuator loads a | Better coupling | Fabrication | IJ05, IJ11 |
spring | spring. When the | to the ink | complexity | |
actuator is turned off, | High stress in the | |||
the spring releases. | spring | |||
This can reverse the | ||||
force/distance curve of | ||||
the actuator to make it | ||||
compatible with the | ||||
force/time | ||||
requirements of the | ||||
drop ejection. | ||||
Actuator | A series of thin | Increased travel | Increased | Some |
stack | actuators are stacked. | Reduced drive | fabrication | piezoelectric ink jets |
This can be | voltage | complexity | IJ04 | |
appropriate where | Increased | |||
actuators require high | possibility of short | |||
electric field strength, | circuits due to | |||
such as electrostatic | pinholes | |||
and piezoelectric | ||||
actuators. | ||||
Multiple | Multiple smaller | Increases the | Actuator forces | IJ12, IJ13, IJ18, |
actuators | actuators are used | force available from | may not add | IJ20, IJ22, IJ28, |
simultaneously to | an actuator | linearly, reducing | IJ42, IJ43 | |
move the ink. Each | Multiple | efficiency | ||
actuator need provide | actuators can be | |||
only a portion of the | positioned to control | |||
force required. | ink flow accurately | |||
Linear | A linear spring is used | Matches low | Requires print | IJ15 |
Spring | to transform a motion | travel actuator with | head area for the | |
with small travel and | higher travel | spring | ||
high force into a | requirements | |||
longer travel, lower | Non-contact | |||
force motion. | method of motion | |||
transformation | ||||
Coiled | A bend actuator is | Increases travel | Generally | IJ17, IJ21, IJ34, |
actuator | coiled to provide | Reduces chip | restricted to planar | IJ35 |
greater travel in a | area | implementations | ||
reduced chip area. | Planar | due to extreme | ||
implementations are | fabrication difficulty | |||
relatively easy to | in other orientations. | |||
fabricate. | ||||
Flexure | A bend actuator has a | Simple means of | Care must be | IJ10, IJ19, IJ33 |
bend | small region near the | increasing travel of | taken not to exceed | |
actuator | fixture point, which | a bend actuator | the elastic limit in | |
flexes much more | the flexure area | |||
readily than the | Stress | |||
remainder of the | distribution is very | |||
actuator. The actuator | uneven | |||
flexing is effectively | Difficult to | |||
converted from an | accurately model | |||
even coiling to an | with finite element | |||
angular bend, resulting | analysis | |||
in greater travel of the | ||||
actuator tip. | ||||
Catch | The actuator controls a | Very low | Complex | IJ10 |
small catch. The catch | actuator energy | construction | ||
either enables or | Very small | Requires external | ||
disables movement of | actuator size | force | ||
an ink pusher that is | Unsuitable for | |||
controlled in a bulk | pigmented inks | |||
manner. | ||||
Gears | Gears can be used to | Low force, low | Moving parts are | IJ13 |
increase travel at the | travel actuators can | required | ||
expense of duration. | be used | Several actuator | ||
Circular gears, rack | Can be fabricated | cycles are required | ||
and pinion, ratchets, | using standard | More complex | ||
and other gearing | surface MEMS | drive electronics | ||
methods can be used. | processes | Complex | ||
construction | ||||
Friction, friction, | ||||
and wear are | ||||
possible | ||||
Buckle plate | A buckle plate can be | Very fast | Must stay within | S. Hirata et al, |
used to change a slow | movement | elastic limits of the | “An Ink-jet Head | |
actuator into a fast | achievable | materials for long | Using Diaphragm | |
motion. It can also | device life | Microactuator”, | ||
convert a high force, | High stresses | Proc. IEEE MEMS, | ||
low travel actuator | involved | February 1996, pp 418-423. | ||
into a high travel, | Generally high | IJ18, IJ27 | ||
medium force motion. | power requirement | |||
Tapered | A tapered magnetic | Linearizes the | Complex | IJ14 |
magnetic | pole can increase | magnetic | construction | |
pole | travel at the expense | force/distance curve | ||
of force. | ||||
Lever | A lever and fulcrum is | Matches low | High stress | IJ32, IJ36, IJ37 |
used to transform a | travel actuator with | around the fulcrum | ||
motion with small | higher travel | |||
travel and high force | requirements | |||
into a motion with | Fulcrum area has | |||
longer travel and | no linear movement, | |||
lower force. The lever | and can be used for | |||
can also reverse the | a fluid seal | |||
direction of travel. | ||||
Rotary | The actuator is | High mechanical | Complex | IJ28 |
impeller | connected to a rotary | advantage | construction | |
impeller. A small | The ratio of force | Unsuitable for | ||
angular deflection of | to travel of the | pigmented inks | ||
the actuator results in | actuator can be | |||
a rotation of the | matched to the | |||
impeller vanes, which | nozzle requirements | |||
push the ink against | by varying the | |||
stationary vanes and | number of impeller | |||
out of the nozzle. | vanes | |||
Acoustic | A refractive or | No moving parts | Large area | 1993 Hadimioglu |
lens | diffractive (e.g. zone | required | et al, EUP 550,192 | |
plate) acoustic lens is | Only relevant for | 1993 Elrod et al, | ||
used to concentrate | acoustic ink jets | EUP 572,220 | ||
sound waves. | ||||
Sharp | A sharp point is used | Simple | Difficult to | Tone-jet |
conductive | to concentrate an | construction | fabricate using | |
point | electrostatic field. | standard VLSI | ||
processes for a | ||||
surface ejecting ink- | ||||
jet | ||||
Only relevant for | ||||
electrostatic ink jets | ||||
ACTUATOR MOTION | ||||
Description | Advantages | Disadvantages | Examples | |
Volume | The volume of the | Simple | High energy is | Hewlett-Packard |
expansion | actuator changes, | construction in the | typically required to | Thermal Ink jet |
pushing the ink in all | case of thermal ink | achieve volume | Canon Bubblejet | |
directions. | jet | expansion. This | ||
leads to thermal | ||||
stress, cavitation, | ||||
and kogation in | ||||
thermal ink jet | ||||
implementations | ||||
Linear, | The actuator moves in | Efficient | High fabrication | IJ01, IJ02, IJ04, |
normal to | a direction normal to | coupling to ink | complexity may be | IJ07, IJ11, IJ14 |
chip surface | the print head surface. | drops ejected | required to achieve | |
The nozzle is typically | normal to the | perpendicular | ||
in the line of | surface | motion | ||
movement. | ||||
Parallel to | The actuator moves | Suitable for | Fabrication | IJ12, IJ13, IJ15, |
chip surface | parallel to the print | planar fabrication | complexity | IJ33,, IJ34, IJ35, |
head surface. Drop | Friction | IJ36 | ||
ejection may still be | Stiction | |||
normal to the surface. | ||||
Membrane | An actuator with a | The effective | Fabrication | 1982 Howkins |
push | high force but small | area of the actuator | complexity | U.S. Pat. No. 4,459,601 |
area is used to push a | becomes the | Actuator size | ||
stiff membrane that is | membrane area | Difficulty of | ||
in contact with the ink. | integration in a | |||
VLSI process | ||||
Rotary | The actuator causes | Rotary levers | Device | IJ05, IJ08, IJ13, |
the rotation of some | may be used to | complexity | IJ28 | |
element, such a grill or | increase travel | May have | ||
impeller | Small chip area | friction at a pivot | ||
requirements | point | |||
Bend | The actuator bends | A very small | Requires the | 1970 Kyser et al |
when energized. This | change in | actuator to be made | U.S. Pat. No. 3,946,398 | |
may be due to | dimensions can be | from at least two | 1973 Stemme | |
differential thermal | converted to a large | distinct layers, or to | U.S. Pat. No. 3,747,120 | |
expansion, | motion. | have a thermal | IJ03, IJ09, IJ10, | |
piezoelectric | difference across the | IJ19, IJ23, IJ24, | ||
expansion, | actuator | IJ25, IJ29, IJ30, | ||
magnetostriction, or | IJ31, IJ33, IJ34, | |||
other form of relative | IJ35 | |||
dimensional change. | ||||
Swivel | The actuator swivels | Allows operation | Inefficient | IJ06 |
around a central pivot. | where the net linear | coupling to the ink | ||
This motion is suitable | force on the paddle | motion | ||
where there are | is zero | |||
opposite forces | Small chip area | |||
applied to opposite | requirements | |||
sides of the paddle, | ||||
e.g. Lorenz force. | ||||
Straighten | The actuator is | Can be used with | Requires careful | IJ26, IJ32 |
normally bent, and | shape memory | balance of stresses | ||
straightens when | alloys where the | to ensure that the | ||
energized. | austenic phase is | quiescent bend is | ||
planar | accurate | |||
Double | The actuator bends in | One actuator can | Difficult to make | IJ36, IJ37, IJ38 |
bend | one direction when | be used to power | the drops ejected by | |
one element is | two nozzles. | both bend directions | ||
energized, and bends | Reduced chip | identical. | ||
the other way when | size. | A small | ||
another element is | Not sensitive to | efficiency loss | ||
energized. | ambient temperature | compared to | ||
equivalent single | ||||
bend actuators. | ||||
Shear | Energizing the | Can increase the | Not readily | 1985 Fishbeck |
actuator causes a shear | effective travel of | applicable to other | U.S. Pat. No. 4,584,590 | |
motion in the actuator | piezoelectric | actuator | ||
material. | actuators | mechanisms | ||
Radial constriction | The actuator squeezes | Relatively easy | High force | 1970 Zoltan U.S. Pat. No. |
an ink reservoir, | to fabricate single | required | 3,683,212 | |
forcing ink from a | nozzles from glass | Inefficient | ||
constricted nozzle. | tubing as | Difficult to | ||
macroscopic | integrate with VLSI | |||
structures | processes | |||
Coil/uncoil | A coiled actuator | Easy to fabricate | Difficult to | IJ17, IJ21, IJ34, |
uncoils or coils more | as a planar VLSI | fabricate for non- | IJ35 | |
tightly. The motion of | process | planar devices | ||
the free end of the | Small area | Poor out-of-plane | ||
actuator ejects the ink. | required, therefore | stiffness | ||
low cost | ||||
Bow | The actuator bows (or | Can increase the | Maximum travel | IJ16, IJ18, IJ27 |
buckles) in the middle | speed of travel | is constrained | ||
when energized. | Mechanically | High force | ||
rigid | required | |||
Push-Pull | Two actuators control | The structure is | Not readily | IJ18 |
a shutter. One actuator | pinned at both ends, | suitable for ink jets | ||
pulls the shutter, and | so has a high out-of- | which directly push | ||
the other pushes it. | plane rigidity | the ink | ||
Curl | A set of actuators curl | Good fluid flow | Design | IJ20, IJ42 |
inwards | inwards to reduce the | to the region behind | complexity | |
volume of ink that | the actuator | |||
they enclose. | increases efficiency | |||
Curl | A set of actuators curl | Relatively simple | Relatively large | IJ43 |
outwards | outwards, pressurizing | construction | chip area | |
ink in a chamber | ||||
surrounding the | ||||
actuators, and | ||||
expelling ink from a | ||||
nozzle in the chamber. | ||||
Iris | Multiple vanes enclose | High efficiency | High fabrication | IJ22 |
a volume of ink. These | Small chip area | complexity | ||
simultaneously rotate, | Not suitable for | |||
reducing the volume | pigmented inks | |||
between the vanes. | ||||
Acoustic | The actuator vibrates | The actuator can | Large area | 1993 Hadimioglu |
vibration | at a high frequency. | be physically distant | required for | et al, EUP 550,192 |
from the ink | efficient operation | 1993 Elrod et al, | ||
at useful frequencies | EUP 572,220 | |||
Acoustic | ||||
coupling and | ||||
crosstalk | ||||
Complex drive | ||||
circuitry | ||||
Poor control of | ||||
drop volume and | ||||
position | ||||
None | In various ink jet | No moving parts | Various other | Silverbrook, EP |
designs the actuator | tradeoffs are | 0771 658 A2 and | ||
does not move. | required to | related patent | ||
eliminate moving | applications | |||
parts | Tone-jet | |||
NOZZLE REFILL METHOD | ||||
Description | Advantages | Disadvantages | Examples | |
Surface | This is the normal way | Fabrication | Low speed | Thermal ink jet |
tension | that ink jets are | simplicity | Surface tension | Piezoelectric ink |
refilled. After the | Operational | force relatively | jet | |
actuator is energized, | simplicity | small compared to | IJ01-IJ07, IJ10-IJ14, | |
it typically returns | actuator force | IJ16, IJ20, | ||
rapidly to its normal | Long refill time | IJ22-IJ45 | ||
position. This rapid | usually dominates | |||
return sucks in air | the total repetition | |||
through the nozzle | rate | |||
opening. The ink | ||||
surface tension at the | ||||
nozzle then exerts a | ||||
small force restoring | ||||
the meniscus to a | ||||
minimum area. This | ||||
force refills the nozzle. | ||||
Shuttered | Ink to the nozzle | High speed | Requires | IJ08, IJ13, IJ15, |
oscillating | chamber is provided at | Low actuator | common ink | IJ17, IJ18, IJ19, |
ink pressure | a pressure that | energy, as the | pressure oscillator | IJ21 |
oscillates at twice the | actuator need only | May not be | ||
drop ejection | open or close the | suitable for | ||
frequency. When a | shutter, instead of | pigmented inks | ||
drop is to be ejected, | ejecting the ink drop | |||
the shutter is opened | ||||
for 3 half cycles: drop | ||||
ejection, actuator | ||||
return, and refill. The | ||||
shutter is then closed | ||||
to prevent the nozzle | ||||
chamber emptying | ||||
during the next | ||||
negative pressure | ||||
cycle. | ||||
Refill | After the main | High speed, as | Requires two | IJ09 |
actuator | actuator has ejected a | the nozzle is | independent | |
drop a second (refill) | actively refilled | actuators per nozzle | ||
actuator is energized. | ||||
The refill actuator | ||||
pushes ink into the | ||||
nozzle chamber. The | ||||
refill actuator returns | ||||
slowly, to prevent its | ||||
return from emptying | ||||
the chamber again. | ||||
Positive ink | The ink is held a slight | High refill rate, | Surface spill | Silverbrook, EP |
pressure | positive pressure. | therefore a high | must be prevented | 0771 658 A2 and |
After the ink drop is | drop repetition rate | Highly | related patent | |
ejected, the nozzle | is possible | hydrophobic print | applications | |
chamber fills quickly | head surfaces are | Alternative for:, | ||
as surface tension and | required | IJ01-IJ07, IJ10-IJ14, | ||
ink pressure both | IJ16, IJ20, IJ22-IJ45 | |||
operate to refill the | ||||
nozzle. | ||||
METHOD OF RESTRICTING BACK-FLOW THROUGH INLET | ||||
Description | Advantages | Disadvantages | Examples | |
Long inlet | The ink inlet channel | Design simplicity | Restricts refill | Thermal ink jet |
channel | to the nozzle chamber | Operational | rate | Piezoelectric ink |
is made long and | simplicity | May result in a | jet | |
relatively narrow, | Reduces | relatively large chip | IJ42, IJ43 | |
relying on viscous | crosstalk | area | ||
drag to reduce inlet | Only partially | |||
back-flow. | effective | |||
Positive ink | The ink is under a | Drop selection | Requires a | Silverbrook, EP |
pressure | positive pressure, so | and separation | method (such as a | 0771 658 A2 and |
that in the quiescent | forces can be | nozzle rim or | related patent | |
state some of the ink | reduced | effective | applications | |
drop already protrudes | Fast refill time | hydrophobizing, or | Possible | |
from the nozzle. | both) to prevent | operation of the | ||
This reduces the | flooding of the | following: IJ01-IJ07, | ||
pressure in the nozzle | ejection surface of | IJ09-IJ12, | ||
chamber which is | the print head. | IJ14, IJ16, IJ20, | ||
required to eject a | IJ22,, IJ23-IJ34, | |||
certain volume of ink. | IJ36-IJ41, IJ44 | |||
The reduction in | ||||
chamber pressure | ||||
results in a reduction | ||||
in ink pushed out | ||||
through the inlet. | ||||
Baffle | One or more baffles | The refill rate is | Design | HP Thermal Ink |
are placed in the inlet | not as restricted as | complexity | Jet | |
ink flow. When the | the long inlet | May increase | Tektronix | |
actuator is energized, | method. | fabrication | piezoelectric ink jet | |
the rapid ink | Reduces | complexity (e.g. | ||
movement creates | crosstalk | Tektronix hot melt | ||
eddies which restrict | Piezoelectric print | |||
the flow through the | heads). | |||
inlet. The slower refill | ||||
process is unrestricted, | ||||
and does not result in | ||||
eddies. | ||||
Flexible flap | In this method recently | Significantly | Not applicable to | Canon |
restricts | disclosed by Canon, | reduces back-flow | most ink jet | |
inlet | the expanding actuator | for edge-shooter | configurations | |
(bubble) pushes on a | thermal ink jet | Increased | ||
flexible flap that | devices | fabrication | ||
restricts the inlet. | complexity | |||
Inelastic | ||||
deformation of | ||||
polymer flap results | ||||
in creep over | ||||
extended use | ||||
Inlet filter | A filter is located | Additional | Restricts refill | IJ04, IJ12, IJ24, |
between the ink inlet | advantage of ink | rate | IJ27, IJ29, IJ30 | |
and the nozzle | filtration | May result in | ||
chamber. The filter | Ink filter may be | complex | ||
has a multitude of | fabricated with no | construction | ||
small holes or slots, | additional process | |||
restricting ink flow. | steps | |||
The filter also removes | ||||
particles which may | ||||
block the nozzle. | ||||
Small inlet | The ink inlet channel | Design simplicity | Restricts refill | IJ02, IJ37, IJ44 |
compared | to the nozzle chamber | rate | ||
to nozzle | has a substantially | May result in a | ||
smaller cross section | relatively large chip | |||
than that of the nozzle, | area | |||
resulting in easier ink | Only partially | |||
egress out of the | effective | |||
nozzle than out of the | ||||
inlet. | ||||
Inlet shutter | A secondary actuator | Increases speed | Requires separate | IJ09 |
controls the position of | of the ink-jet print | refill actuator and | ||
a shutter, closing off | head operation | drive circuit | ||
the ink inlet when the | ||||
main actuator is | ||||
energized. | ||||
The inlet is | The method avoids the | Back-flow | Requires careful | IJ01, IJ03, IJ05, |
located | problem of inlet back- | problem is | design to minimize | IJ06, IJ07, IJ10, |
behind the | flow by arranging the | eliminated | the negative | IJ11, IJ14, IJ16, |
ink-pushing | ink-pushing surface of | pressure behind the | IJ22, IJ23, IJ25, | |
surface | the actuator between | paddle | IJ28, IJ31, IJ32, | |
the inlet and the | IJ33, IJ34, IJ35, | |||
nozzle. | IJ36, IJ39, IJ40, | |||
IJ41 | ||||
Part of the | The actuator and a | Significant | Small increase in | IJ07, IJ20, IJ26, |
actuator | wall of the ink | reductions in back- | fabrication | IJ38 |
moves to | chamber are arranged | flow can be | complexity | |
shut off the | so that the motion of | achieved | ||
inlet | the actuator closes off | Compact designs | ||
the inlet. | possible | |||
Nozzle | In some configurations | Ink back-flow | None related to | Silverbrook, EP |
actuator | of ink jet, there is no | problem is | ink back-flow on | 0771 658 A2 and |
does not | expansion or | eliminated | actuation | related patent |
result in ink | movement of an | applications | ||
back-flow | actuator which may | Valve-jet | ||
cause ink back-flow | Tone-jet | |||
through the inlet. | ||||
NOZZLE CLEARING METHOD | ||||
Description | Advantages | Disadvantages | Examples | |
Normal | All of the nozzles are | No added | May not be | Most ink jet |
nozzle firing | fired periodically, | complexity on the | sufficient to | systems |
before the ink has a | print head | displace dried ink | IJ01, IJ02, IJ03, | |
chance to dry. When | IJ04, IJ05, IJ06, | |||
not in use the nozzles | IJ07, IJ09, IJ10, | |||
are sealed (capped) | IJ11, IJ12, IJ14, | |||
against air. | IJ16, IJ20, IJ22, | |||
The nozzle firing is | IJ23, IJ24, IJ25, | |||
usually performed | IJ26, IJ27, IJ28, | |||
during a special | IJ29, IJ30, IJ31, | |||
clearing cycle, after | IJ32, IJ33, IJ34, | |||
first moving the print | IJ36, IJ37, IJ38, | |||
head to a cleaning | IJ39, IJ40,, IJ41, | |||
station. | IJ42, IJ43, IJ44,, | |||
IJ45 | ||||
Extra | In systems which heat | Can be highly | Requires higher | Silverbrook, EP |
power to | the ink, but do not boil | effective if the | drive voltage for | 0771 658 A2 and |
ink heater | it under normal | heater is adjacent to | clearing | related patent |
situations, nozzle | the nozzle | May require | applications | |
clearing can be | larger drive | |||
achieved by over- | transistors | |||
powering the heater | ||||
and boiling ink at the | ||||
nozzle. | ||||
Rapid | The actuator is fired in | Does not require | Effectiveness | May be used |
succession | rapid succession. In | extra drive circuits | depends | with: IJ01, IJ02, |
of actuator | some configurations, | on the print head | substantially upon | IJ03, IJ04, IJ05, |
pulses | this may cause heat | Can be readily | the configuration of | IJ06, IJ07, IJ09, |
build-up at the nozzle | controlled and | the ink jet nozzle | IJ10, IJ11, IJ14, | |
which boils the ink, | initiated by digital | IJ16, IJ20, IJ22, | ||
clearing the nozzle. In | logic | IJ23, IJ24, IJ25, | ||
other situations, it may | IJ27, IJ28, IJ29, | |||
cause sufficient | IJ30, IJ31, IJ32, | |||
vibrations to dislodge | IJ33, IJ34, IJ36, | |||
clogged nozzles. | IJ37, IJ38, IJ39, | |||
IJ40, IJ41, IJ42, | ||||
IJ43, IJ44, IJ45 | ||||
Extra | Where an actuator is | A simple | Not suitable | May be used |
power to | not normally driven to | solution where | where there is a | with: IJ03, IJ09, |
ink pushing | the limit of its motion, | applicable | hard limit to | IJ16, IJ20, IJ23, |
actuator | nozzle clearing may be | actuator movement | IJ24, IJ25, IJ27, | |
assisted by providing | IJ29, IJ30, IJ31, | |||
an enhanced drive | IJ32, IJ39, IJ40, | |||
signal to the actuator. | IJ41, IJ42, IJ43, | |||
IJ44, IJ45 | ||||
Acoustic | An ultrasonic wave is | A high nozzle | High | IJ08, IJ13, IJ15, |
resonance | applied to the ink | clearing capability | implementation cost | IJ17, IJ18, IJ19, |
chamber. This wave is | can be achieved | if system does not | IJ21 | |
of an appropriate | May be | already include an | ||
amplitude and | implemented at very | acoustic actuator | ||
frequency to cause | low cost in systems | |||
sufficient force at the | which already | |||
nozzle to clear | include acoustic | |||
blockages. This is | actuators | |||
easiest to achieve if | ||||
the ultrasonic wave is | ||||
at a resonant | ||||
frequency of the ink | ||||
cavity. | ||||
Nozzle | A microfabricated | Can clear | Accurate | Silverbrook, EP |
clearing | plate is pushed against | severely clogged | mechanical | 0771 658 A2 and |
plate | the nozzles. The plate | nozzles | alignment is | related patent |
has a post for every | required | applications | ||
nozzle. A post moves | Moving parts are | |||
through each nozzle, | required | |||
displacing dried ink. | There is risk of | |||
damage to the | ||||
nozzles | ||||
Accurate | ||||
fabrication is | ||||
required | ||||
Ink | The pressure of the ink | May be effective | Requires | May be used |
pressure | is temporarily | where other | pressure pump or | with all IJ series ink |
pulse | increased so that ink | methods cannot be | other pressure | jets |
streams from all of the | used | actuator | ||
nozzles. This may be | Expensive | |||
used in conjunction | Wasteful of ink | |||
with actuator | ||||
energizing. | ||||
Print head | A flexible ‘blade’ is | Effective for | Difficult to use if | Many ink jet |
wiper | wiped across the print | planar print head | print head surface is | systems |
head surface. The | surfaces | non-planar or very | ||
blade is usually | Low cost | fragile | ||
fabricated from a | Requires | |||
flexible polymer, e.g. | mechanical parts | |||
rubber or synthetic | Blade can wear | |||
elastomer. | out in high volume | |||
print systems | ||||
Separate | A separate heater is | Can be effective | Fabrication | Can be used with |
ink boiling | provided at the nozzle | where other nozzle | complexity | many IJ series ink |
heater | although the normal | clearing methods | jets | |
drop e-ection | cannot be used | |||
mechanism does not | Can be | |||
require it. The heaters | implemented at no | |||
do not require | additional cost in | |||
individual drive | some ink jet | |||
circuits, as many | configurations | |||
nozzles can be cleared | ||||
simultaneously, and no | ||||
imaging is required. | ||||
NOZZLE PLATE CONSTRUCTION | ||||
Description | Advantages | Disadvantages | Examples | |
Electroformed | A nozzle plate is | Fabrication | High | Hewlett Packard |
nickel | separately fabricated | simplicity | temperatures and | Thermal Ink jet |
from electroformed | pressures are | |||
nickel, and bonded to | required to bond | |||
the print head chip. | nozzle plate | |||
Minimum | ||||
thickness constraints | ||||
Differential | ||||
thermal expansion | ||||
Laser | Individual nozzle | No masks | Each hole must | Canon Bubblejet |
ablated or | holes are ablated by an | required | be individually | 1988 Sercel et |
drilled | intense UV laser in a | Can be quite fast | formed | al., SPIE, Vol. 998 |
polymer | nozzle plate, which is | Some control | Special | Excimer Beam |
typically a polymer | over nozzle profile | equipment required | Applications, pp. | |
such as polyimide or | is possible | Slow where there | 76-83 | |
polysulphone | Equipment | are many thousands | 1993 Watanabe | |
required is relatively | of nozzles per print | et al., U.S. Pat. No. | ||
low cost | head | 5,208,604 | ||
May produce thin | ||||
burrs at exit holes | ||||
Silicon | A separate nozzle | High accuracy is | Two part | K. Bean, IEEE |
micromachined | plate is | attainable | construction | Transactions on |
micromachined from | High cost | Electron Devices, | ||
single crystal silicon, | Requires | Vol. ED-25, No. 10, | ||
and bonded to the | precision alignment | 1978, pp 1185-1195 | ||
print head wafer. | Nozzles may be | Xerox 1990 | ||
clogged by adhesive | Hawkins et al., U.S. Pat. No. | |||
4,899,181 | ||||
Glass | Fine glass capillaries | No expensive | Very small | 1970 Zoltan U.S. Pat. No. |
capillaries | are drawn from glass | equipment required | nozzle sizes are | 3,683,212 |
tubing. This method | Simple to make | difficult to form | ||
has been used for | single nozzles | Not suited for | ||
making individual | mass production | |||
nozzles, but is difficult | ||||
to use for bulk | ||||
manufacturing of print | ||||
heads with thousands | ||||
of nozzles. | ||||
Monolithic, | The nozzle plate is | High accuracy | Requires | Silverbrook, EP |
surface | deposited as a layer | (<1 μm) | sacrificial layer | 0771 658 A2 and |
micromachined | using standard VLSI | Monolithic | under the nozzle | related patent |
using VLSI | deposition techniques. | Low cost | plate to form the | applications |
litho- | Nozzles are etched in | Existing | nozzle chamber | IJ01, IJ02, IJ04, |
graphic | the nozzle plate using | processes can be | Surface may be | IJ11, IJ12, IJ17, |
processes | VLSI lithography and | used | fragile to the touch | IJ18, IJ20, IJ22, |
etching. | IJ24, IJ27, IJ28, | |||
IJ29, IJ30, IJ31, | ||||
IJ32, IJ33, IJ34, | ||||
IJ36, IJ37, IJ38, | ||||
IJ39, IJ40, IJ41, | ||||
IJ42, IJ43, IJ44 | ||||
Monolithic, | The nozzle plate is a | High accuracy | Requires long | IJ03, IJ05, IJ06, |
etched | buried etch stop in the | (<1 μm) | etch times | IJ07, IJ08, IJ09, |
through | wafer. Nozzle | Monolithic | Requires a | IJ10, IJ13, IJ14, |
substrate | chambers are etched in | Low cost | support wafer | IJ15, IJ16, IJ19, |
the front of the wafer, | No differential | IJ21, IJ23, IJ25, | ||
and the wafer is | expansion | IJ26 | ||
thinned from the back | ||||
side. Nozzles are then | ||||
etched in the etch stop | ||||
layer. | ||||
No nozzle | Various methods have | No nozzles to | Difficult to | Ricoh 1995 |
plate | been tried to eliminate | become clogged | control drop | Sekiya et al U.S. Pat. No. |
the nozzles entirely, to | position accurately | 5,412,413 | ||
prevent nozzle | Crosstalk | 1993 Hadimioglu | ||
clogging. These | problems | et al EUP 550,192 | ||
include thermal bubble | 1993 Elrod et al | |||
mechanisms and | EUP 572,220 | |||
acoustic lens | ||||
mechanisms | ||||
Trough | Each drop ejector has | Reduced | Drop firing | IJ35 |
a trough through | manufacturing | direction is sensitive | ||
which a paddle moves. | complexity | to wicking. | ||
There is no nozzle | Monolithic | |||
plate. | ||||
Nozzle slit | The elimination of | No nozzles to | Difficult to | 1989 Saito et al |
instead of | nozzle holes and | become clogged | control drop | U.S. Pat. No. 4,799,068 |
individual | replacement by a slit | position accurately | ||
nozzles | encompassing many | Crosstalk | ||
actuator positions | problems | |||
reduces nozzle | ||||
clogging, but increases | ||||
crosstalk due to ink | ||||
surface waves | ||||
DROP EJECTION DIRECTION | ||||
Description | Advantages | Disadvantages | Examples | |
Edge | Ink flow is along the | Simple | Nozzles limited | Canon Bubblejet |
(‘edge | surface of the chip, | construction | to edge | 1979 Endo et al GB |
shooter’) | and ink drops are | No silicon | High resolution | patent 2,007,162 |
ejected from the chip | etching required | is difficult | Xerox heater-in- | |
edge. | Good heat | Fast color | pit 1990 Hawkins et | |
sinking via substrate | printing requires | al U.S. Pat. No. 4,899,181 | ||
Mechanically | one print head per | Tone-jet | ||
strong | color | |||
Ease of chip | ||||
handing | ||||
Surface | Ink flow is along the | No bulk silicon | Maximum ink | Hewlett-Packard |
(‘roof | surface of the chip, | etching required | flow is severely | TIJ 1982 Vaught et |
shooter’) | and ink drops are | Silicon can make | restricted | al U.S. Pat. No. 4,490,728 |
ejected from the chip | an effective heat | IJ02, IJ11, IJ12, | ||
surface, normal to the | sink | IJ20, IJ22 | ||
plane of the chip. | Mechanical | |||
strength | ||||
Through | Ink flow is through the | High ink flow | Requires bulk | Silverbrook, EP |
chip, | chip, and ink drops are | Suitable for | silicon etching | 0771 658 A2 and |
forward | ejected from the front | pagewidth print | related patent | |
(‘up | surface of the chip. | heads | applications | |
shooter’) | High nozzle | IJ04, IJ17, IJ18, | ||
packing density | IJ24, IJ27-IJ45 | |||
therefore low | ||||
manufacturing cost | ||||
Through | Ink flow is through the | High ink flow | Requires wafer | IJ01, IJ03, IJ05, |
chip, | chip, and ink drops are | Suitable for | thinning | IJ06, IJ07, IJ08, |
reverse | ejected from the rear | pagewidth print | Requires special | IJ09, IJ10, IJ13, |
(‘down | surface of the chip. | heads | handling during | IJ14, IJ15, IJ16, |
shooter’) | High nozzle | manufacture | IJ19, IJ21, IJ23, | |
packing density | IJ25, IJ26 | |||
therefore low | ||||
manufacturing cost | ||||
Through | Ink flow is through the | Suitable for | Pagewidth print | Epson Stylus |
actuator | actuator, which is not | piezoelectric print | heads require | Tektronix hot |
fabricated as part of | heads | several thousand | melt piezoelectric | |
the same substrate as | connections to drive | ink jets | ||
the drive transistors. | circuits | |||
Cannot be | ||||
manufactured in | ||||
standard CMOS | ||||
fabs | ||||
Complex | ||||
assembly required | ||||
INK TYPE | ||||
Description | Advantages | Disadvantages | Examples | |
Aqueous, | Water based ink which | Environmentally | Slow drying | Most existing ink |
dye | typically contains: | friendly | Corrosive | jets |
water, dye, surfactant, | No odor | Bleeds on paper | All IJ series ink | |
humectant, and | May | jets | ||
biocide. | strikethrough | Silverbrook, EP | ||
Modern ink dyes have | Cockles paper | 0771 658 A2 and | ||
high water-fastness, | related patent | |||
light fastness | applications | |||
Aqueous, | Water based ink which | Environmentally | Slow drying | IJ02, IJ04, IJ21, |
pigment | typically contains: | friendly | Corrosive | IJ26, IJ27, IJ30 |
water, pigment, | No odor | Pigment may | Silverbrook, EP | |
surfactant, humectant, | Reduced bleed | clog nozzles | 0771 658 A2 and | |
and biocide. | Reduced wicking | Pigment may | related patent | |
Pigments have an | Reduced | clog actuator | applications | |
advantage in reduced | strikethrough | mechanisms | Piezoelectric ink- | |
bleed, wicking and | Cockles paper | jets | ||
strikethrough. | Thermal ink jets | |||
(with significant | ||||
restrictions) | ||||
Methyl | MEK is a highly | Very fast drying | Odorous | All IJ series ink |
Ethyl | volatile solvent used | Prints on various | Flammable | jets |
Ketone | for industrial printing | substrates such as | ||
(MEK) | on difficult surfaces | metals and plastics | ||
such as aluminum | ||||
cans. | ||||
Alcohol | Alcohol based inks | Fast drying | Slight odor | All IJ series ink |
(ethanol, 2- | can be used where the | Operates at sub- | Flammable | jets |
butanol, | printer must operate at | freezing | ||
and others) | temperatures below | temperatures | ||
the freezing point of | Reduced paper | |||
water. An example of | cockle | |||
this is in-camera | Low cost | |||
consumer | ||||
photographic printing. | ||||
Phase | The ink is solid at | No drying time- | High viscosity | Tektronix hot |
change | room temperature, and | ink instantly freezes | Printed ink | melt piezoelectric |
(hot melt) | is melted in the print | on the print medium | typically has a | ink jets |
head before jetting. | Almost any print | ‘waxy’ feel | 1989 Nowak | |
Hot melt inks are | medium can be used | Printed pages | U.S. Pat. No. 4,820,346 | |
usually wax based, | No paper cockle | may ‘block’ | All IJ series ink | |
with a melting point | occurs | Ink temperature | jets | |
around 80° C. After | No wicking | may be above the | ||
jetting the ink freezes | occurs | curie point of | ||
almost instantly upon | No bleed occurs | permanent magnets | ||
contacting the print | No strikethrough | Ink heaters | ||
medium or a transfer | occurs | consume power | ||
roller. | Long warm-up | |||
time | ||||
Oil | Oil based inks are | High solubility | High viscosity: | All IJ series ink |
extensively used in | medium for some | this is a significant | jets | |
offset printing. They | dyes | limitation for use in | ||
have advantages in | Does not cockle | ink jets, which | ||
improved | paper | usually require a | ||
characteristics on | Does not wick | low viscosity. Some | ||
paper (especially no | through paper | short chain and | ||
wicking or cockle). | multi-branched oils | |||
Oil soluble dies and | have a sufficiently | |||
pigments are required. | low viscosity. | |||
Slow drying | ||||
Microemulsion | A microemulsion is a | Stops ink bleed | Viscosity higher | All IJ series ink |
stable, self forming | High dye | than water | jets | |
emulsion of oil, water, | solubility | Cost is slightly | ||
and surfactant. The | Water, oil, and | higher than water | ||
characteristic drop size | amphiphilic soluble | based ink | ||
is less than 100 nm, | dies can be used | High surfactant | ||
and is determined by | Can stabilize | concentration | ||
the preferred curvature | pigment | required (around | ||
of the surfactant. | suspensions | 5%) | ||