Title:
XEROGRAPHIC IMAGERY USING A LONG PERSISTENCE PHOSPHOR INTERMEDIATE
United States Patent 3619049


Abstract:
Apparatus for placing an image on a photoreceptor by exciting a phosphorescent intermediate which then contacts the photoreceptor causing an image in the pattern of the excited phosphors on the intermediate. Apparatus may be added for viewing the image formed on the intermediate. By use of a long persistence phosphor, the intermediate is capable of several exposures on the photoreceptor though it is excited only once.



Inventors:
Starkweather, Gary K. (Rochester, NY)
Bobbe, Richard M. (Rochester, NY)
Application Number:
05/019587
Publication Date:
11/09/1971
Filing Date:
03/16/1970
Assignee:
XEROX CORP.
Primary Class:
Other Classes:
250/315.3, 358/300, 399/159, 430/139
International Classes:
G03G15/04; (IPC1-7): G03G15/08
Field of Search:
355/5,11,12,16,3 250
View Patent Images:
US Patent References:
3519344IMAGE PROJECTION1970-07-07Clark et al.
3278302Phosphorescent screen reflex1966-10-11Gundlach
3273477Random events camera and method1966-09-20De Hart
3254998Induction image formation1966-06-07Schwertz
3212417Reflex exposure system1965-10-19Gundlach



Primary Examiner:
Matthews, Samuel S.
Assistant Examiner:
Braun, Fred L.
Parent Case Data:


This is a division of application Ser. No. 663,805, filed Aug. 28, 1967, now abandoned.
Claims:
What is claimed is

1. An electrostatic printing machine of the type employing a photoconductive member, means for developing an electrostatic latent image upon the member and means for moving the member along a path between an exposure station and a developing station, including

Description:
This invention relates to xerography and particularly to xerographic imaging using a phosphorescent intermediate.

It has been difficult in the past to make photographic or xerographic copies directly from electron emitters such as cathode ray tubes or the like without the use of complex apparatus and electrical circuitry to achieve the desired result. Elaborate equipment for image character generation has been designed employing elaborate electronic apparatus and a linotron tube in order to form image characters of electronic input. Such apparatus is described in an article by J. K. Moore and J. F. Cavanaugh in the Apr. 3, 1967 issue of Electronics Magazine.

Aside from the difficulty encountered in forming suitable character images from electronic input, another stumbling block in the reproduction of objects has been the lack of ability to make multiple copies from a single exposure input. Methods have been developed for xerographic duplication from a single exposure. See for example U.S. Pat. No. 2,951,443 issued to J. F. Bryne and Pat. No. 3,045,587 issued to F. A. Schwertz and Pat. No. 3,084,061 issued to R. H. Hall. However, all of these apparatus and methods provide for induction or removal of charge from the xerographic member.

It is an object of this invention to provide improved methods and apparatus for copying images from a CRT input.

Another object of this invention is to provide improved methods and apparatus for making multiple copies from a single illumination exposure of the input.

Still another object of this invention is to permit viewing of an image generated by a CRT while making copies of that image.

Still a further object of this invention is to form an image intermediate between an input and a photoreceptor for exposing the photoreceptor.

A further object is to reduce the size of a copier while maintaining a 1:1 copy magnification ratio with the input.

Another object is to improve copying machines by eliminating lenses in the exposure step.

These and other objects of this invention are accomplished by methods and means of providing a phosphorescent intermediate between the input and the photoreceptor, the intermediate being provided with a viewing screen and a phosphor quenching device, and having suitable input exposed thereto for exposing a prepared photoreceptor and then recycling either with or without a subsequent exposure from the input to be copied.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention as well as other objects and features thereof, reference is had to the following detailed description of the invention to be read in conjunction with the accompanying drawings:

Fig. 1 is a schematic embodiment of the invention within a xerographic system having a CRT input;

Fig. 2 is a schematic embodiment of the invention within a xerographic system providing for transparency copying; and

Fig. 3 is a schematic embodiment providing for copying opaque input.

DESCRIPTION OF THE PREFERRED EMBODIMENT

There is shown schematically in FIG. 1 a xerographic copying apparatus comprising a xerographic member 20 formed in the shape of a drum which is mounted on a shaft 22 suitably journaled to rotate in the direction indicated by the arrow to cause the drum surface sequentially to pass a plurality of xerographic-processing stations. For the purpose of the present disclosure, the several xerographic-processing stations in the path of movement of the drum surface may be described functionally as follows:

A charging station A at which a uniform electrostatic charge is deposited on the photoconductive layer of the drum 20; an exposure station located preferably as shown by reference character B at which a light or radiation pattern of copy to be reproduced and supplied by a phosphorescent support material 24 is exposed onto the drum surface to dissipate the drum charge in the exposed portions thereof forming a latent electrostatic image of the pattern found on the phosphorescent support 24; a developing station C whereat the latent electrostatic image is developed by cascading an electrostatic powder over the drum forming a powder image corresponding to the latent electrostatic image on the drum; an image transfer station D where the powder image is electrostatically transferred from the drum surface to a transfer material; and a cleaning station E where the drum is cleaned of residual powder and is discharged in order to prepare the drum surface for the next cycle. The support material may then pass through the fusing station F where heat is applied to the material in a sufficient quantity to melt the electrostatic powder image thereon forming a bond between the powder and the support material to which it is adhered.

It should be noted here that the embodiment shown in FIGS. 2 and 3 function xerographically in the same manner as that of FIG. 1.

The exposure station of the embodiment shown in FIG. 1 is comprised of an original radiation emitting source such as the cathode ray tube 28 which is capable of generating characters at its tube face 30 which nearly contacts the phosphorescent surface of support 24. The support 24 is journaled for rotation about shaft 32 which is coupled to shaft 22 of the xerographic drum such that the phosphorescent support 24 rotates in the direction indicated by the arrow at a speed sufficient to permit synchronized rolling contact between the support 24 and the photoreceptive surface of the xerographic drum 20. Located adjacent the support positioned in the path of motion intermediate between the excitation of the support 24 by the radiation generated through the CRT 28 at its tube front 30 and the xerographic drum 20 is a viewing station 34 provided with a lens 36 and a translucent viewing screen 38 permitting a viewer to observe the excited phosphors on support 24 as they pass beyond the tube face 30 of the CRT 28.

At a position intermediate the photoreceptive surface of drum 20 and the original exposure surface of the tube face 30 of the CRT is a quenching mechanism 40 which may be an infrared source or any suitable radiation or technique for deexciting the phosphors within the support 24.

In operation the phosphorescent support and the xerographic drum would be in motion while the CRT presents a radiation pattern to the surface of support 24. This radiation would excite the phosphors at that surface in a mirror image pattern to the radiation emitted by the CRT 28. As the support rotates about its axis 32, the image generated appears in the area 34 for viewing at viewing screen 38 through the lens 36. A transparent screen can be used with a single mirror to view the image on support 24 without lenses. A right reading image is in both cases presented to a person viewing screen 38. As the support drum 24 rotates, it contacts the previously uniformly charged xerographic drum 20 and dissipates the charge on said member in accordance with the emittance of the phosphors in the image orientation in which they are excited on the support 24. The support continues to rotate as does the xerographic member, the latter being developed at station C and transferred at station D and cleaned and prepared at station E for a further uniform charging at station A. It is noted, of course, that reference here is to a line of exposure across the surface of both the support 24 and xerographic member 20 and that while the apparatus is in operation, all stations simultaneously act upon either the support 24 or plate 20. Each step can be accomplished sequentially and by hand using a flat xerographic plate and phosphorescent sheet.

The area of the support 24 that exposed the xerographic member 20 moves passed the quenching device 40 which may or may not be activated. If not activated the support continues in its rotation until it once again contacts the exposure station B of the xerographic member where it once again exposes the plate without the necessity of a second exposure on the phosphorescent support 24 by the CRT 28.

Since the apparatus shown here has the capability of multiple copy making from a single original exposure input, it is preferable to impregnate the support material 24 which may be a transparent, translucent or opaque belt or drum with a high persistence phosphor. Phosphors such as P2, P10, P12, P19, P21 and P25 as classified by the Joint Electron Tube Engineering Council Committee 6 on Cathode Ray Tubes could be used on support 24. The choice would depend on the color sensitivity of the photoreceptor and the length of persistance desired.

The persistence of the P2 phosphor, for example, would enable sufficient radiation for exposure of a typical xerographic photoreceptor for approximately two seconds if the phosphor is initially irradiated to nearly its maximum potential as by a mercury arc lamp or the like. If the lineal velocity at the contact between the xerographic drum 20 and the support 24 is approximately two inches per second with the diameter of the phosphor support 24 being approximately three inches, the phosphor support could rotate three revolutions before becoming too weak to sufficiently discharge the xerographic photoconductor; therefore, as many as three copies could be made with one initial exposure using the P2 phosphor for the support 24. Other material dimensions and speeds would give other results but are contemplated within the scope of this invention and the above is only one example of a combination of factors. Others listed would give a longer persistence if illuminated with proper exciting light.

If the number of copies desired from this apparatus is less than the total achievable by the long persistence of the phosphor, then it becomes essential to quench the phosphor by the use of a quenching means 40 which may be infrared or some other generally known method of depleting the phosphor of its radiant energy such as, for example, ultrasonics. The phosphor elements in the phosphorescent support glow because the electrons therein once activated wander and continue to wander from atom to atom or molecule to molecule. They oscillate at an optical frequency. By disturbing the latice of atoms or molecules in which these electrons are distributed, the electrons get back from their excited state more rapidly than they would otherwise. The molecules and atoms are oscillated at radio frequencies and in the infrared zone of the spectrum. Thereby, by causing an oscillation at the radio and infrared frequencies thereby disturbing the lattice, the electrons more rapidly get back to their stable state and the glow of the phosphorescent support is discontinued.

If, instead of quenching the phosphor, a longer run of copies is desired than is obtainable during the normal persistence cycle of the phosphor, the phosphor can from time to time be re-energized by the CRT 28 in timed relation to the original image previously placed on the support 24. This reinforcement of the image would require less energy to maintain a radiance level on the support material 24 sufficient to expose the photoreceptor than would be required for an initial radiance of the phosphors within the support material.

It should be noted of this and the other embodiments shown herein that exposure of the phosphorescent support and the photoreceptor is accomplished without lenses in a 1:1 magnification system. This permits a significantly more efficient system than might otherwise exist if lenses were required. Although contact between the support 24 and the photoreceptor 20 is desirable and preferable it is not necessarily essential.

Another embodiment of the invention is shown in FIGS. 2 and 3. In FIG. 2 a xerographic belt 26 is rotated through drive roller 42 and around idler rollers 44 and 46. A support material belt 48, impregnated with phosphors, is rotated by drive roller 50 and around idler roller 52 at a timed sequence so that there is a rolling contact between the support 48 and the xerographic belt 26 along the contacting surfaces thereof. Both the xerographic belt and the support material belt can rotate around two or more rollers without affecting their relation with the invention hereof. It is possible also to employ a support drum such as drum 24 of FIG. 1 with the xerographic belt 26 of FIG. 2 and likewise a support belt such as belt 48 may be combined with a xerographic drum such as drum 20 of FIG. 1.

The initial radiating source for the embodiment shown in FIG. 2 is a lamp 54 for exposing transparencies or single sided translucent objects such as, for example, sheet 56 to the phosphorescent support belt 48. The transparencies or single sided translucent objects are caused to move passed the light source in contact or nearly contacting the phosphorescent support 48 while rolling with the support so that there is no slippage between the moving transparency and the phosphorescent support. The support belt 48 then continues to rotate passed the xerographic belt 26 exposing it in a manner similar to that described in FIG. 1. The xerographic belt may then be processed as described above for the xerographic drum. A reflex system for copying from opaque documents may also be used with standard optical design to focus the image at the phosphor support. (See FIG. 3.)

The optical apparatus shown in FIG. 3 employs a scan system which reflects light from light source 60 off an opaque document 62 placed on a moving platen 64. The platen, support surface 24 and the xerographic belt 26 move at the same surface speeds. The object light rays are reflected through a lens 66 to a slit 68 at the phosphor support surface where a flowing image of the moving object is placed on the support for subsequent imaging on the xerographic member 26. The platen moves past the aperture 68 in the optical path of the system and located within the light baffle 70 by any means such as a gearing set 72 run by a motor drive 74 and returns by a biasing spring 76. This, of course, is a schematic representation of a scan system which may take the form, for example, of those shown in Pat. No. 3,221,622 issued on Dec. 7, 1965 or Pat. No. 3,062,095 issued on Nov. 6, 1962.

At the viewing station 34, which is located in the path of travel of the support after the imaging of the xerographic member is a viewing hood 80. The image on the support is viewed directly without any lenses, mirrors or back-lighted screens.

While the invention has been described with reference to the structures disclosed herein, it is not confined to the specific details set forth, and this application is intended to cover such modifications or changes as may come within the purposes or scope of the following claims.