Printing system
United States Patent 3906141
In the system of the present invention the ink used is a low concentration aqueous solution of a compound that forms a visible percipitate with a metal ion. The compound and the cooperating ion are selected to produce the desired precipitate color and for greater convenience is selected to react at room temperature. The metal ion is imparted to the printing surface either by inclusion during the manufacture of the paper stock or by treating the paper surface at some subsequent time including during the printing cycle prior to the printing operation.
US Patent References:
Manifolding sheet
Gookin et al. - March 1934 - 1950982
Ink jet nozzle
Adams et al. - October 1966 - 3281860
/3558341.html
Phillips - January 1971 - 3558341
IMAGE TRANSFER SHEET AND METHOD
Williams - January 1972 - 3632377
/3723156.html
Brockett et al. - March 1973 - 3723156
Manifolding sheet
Gookin et al. - March 1934 - 1950982
Ink jet nozzle
Adams et al. - October 1966 - 3281860
/3558341.html
Phillips - January 1971 - 3558341
IMAGE TRANSFER SHEET AND METHOD
Williams - January 1972 - 3632377
/3723156.html
Brockett et al. - March 1973 - 3723156
Inventors:
Anderson, Clifford W. (West Concord, MN)
Castrodale, Daniel O. (Rochester, MN)
Martin, Jerry T. (Plainview, MN)
Castrodale, Daniel O. (Rochester, MN)
Martin, Jerry T. (Plainview, MN)
Application Number:
05/388527
Publication Date:
09/16/1975
Filing Date:
08/15/1973
View Patent Images:
Export Citation:
Assignee:
International Business Machines Corporation (Armonk, NY)
Primary Class:
Other Classes:
346/96, 503/211, 347/101, 347/39, 503/201, 347/96, 427/145
International Classes:
B41M1/28; C09D11/00; B41M1/26; B41M5/12
Field of Search:
117/36.8,36.2,36.7,38,107 346/75
US Patent References:
Primary Examiner:
Herbert Jr., Thomas J.
Attorney, Agent or Firm:
Lahtinen, Robert W.
Claims:
We claim
1. A printing system including
2. The printing system of claim 1 wherein said ink further comprises a non-ionic surfactant that has a concentration of 0.0001% to 1.0% by weight.
3. The printing system of claim 2 wherein said non-ionic surfactant is a mono aryl ether of polyethelene glycol.
4. The printing system of claim 1 wherein said compound has a concentration in said aqueous solution between 0.5% and 3% by weight.
5. The printing system of claim 4 wherein the said metal ions in said compound will react to form a precipitate at a temperature between 60° Fahrenheit and 80° Fahrenheit.
6. The printing system of claim 1 wherein said paper stock is treated with a solution of ferrous ammonium sulfate and said ink comprises an aqueous solution containing 0.5% to 3% by weight of potassium ferricyanide.
7. The printing system of claim 1 wherein said paper stock is treated by an aqueous solution including a ferrous compound.
8. The printing system of claim 1 wherein said paper stock is treated with a solution of ferrous ammonium sulfate and said ink comprises an aqueous solution containing 0.5% to 3% by weight of 8-hydroxyquinoline.
9. The printing system of claim 1 wherein said paper stock is treated with a solution of copper sulfate and said ink comprises an aqueous solution containing 0.5% to 3% by weight of 1-nitroso-2-naphthol-3,6-disulfonic acid.
10. The printing system of claim 1 wherein said paper stock is treated with a solution of ferrous amonium sulfate and said ink comprises an aqueous solution containing 0.5% to 3% by weight of 1-nitroso-2-naphthol-3,6-disulfonic acid.
11. A printing system including
12. The printing system of claim 11 wherein said ink applied to the printing surface of said paper stock comprises an aqueous solution containing 0.5% to 3% by weight of a compound from the group consisting of a salt of a metal cyanide complex; 8-hydroxyquinoline; and 1-nitroso-2-naphthol-3,6-disulfonic acid.
13. The printing system of claim 12 wherein said paper stock is treated by an aqueous solution including a ferrous compound.
1. A printing system including
2. The printing system of claim 1 wherein said ink further comprises a non-ionic surfactant that has a concentration of 0.0001% to 1.0% by weight.
3. The printing system of claim 2 wherein said non-ionic surfactant is a mono aryl ether of polyethelene glycol.
4. The printing system of claim 1 wherein said compound has a concentration in said aqueous solution between 0.5% and 3% by weight.
5. The printing system of claim 4 wherein the said metal ions in said compound will react to form a precipitate at a temperature between 60° Fahrenheit and 80° Fahrenheit.
6. The printing system of claim 1 wherein said paper stock is treated with a solution of ferrous ammonium sulfate and said ink comprises an aqueous solution containing 0.5% to 3% by weight of potassium ferricyanide.
7. The printing system of claim 1 wherein said paper stock is treated by an aqueous solution including a ferrous compound.
8. The printing system of claim 1 wherein said paper stock is treated with a solution of ferrous ammonium sulfate and said ink comprises an aqueous solution containing 0.5% to 3% by weight of 8-hydroxyquinoline.
9. The printing system of claim 1 wherein said paper stock is treated with a solution of copper sulfate and said ink comprises an aqueous solution containing 0.5% to 3% by weight of 1-nitroso-2-naphthol-3,6-disulfonic acid.
10. The printing system of claim 1 wherein said paper stock is treated with a solution of ferrous amonium sulfate and said ink comprises an aqueous solution containing 0.5% to 3% by weight of 1-nitroso-2-naphthol-3,6-disulfonic acid.
11. A printing system including
12. The printing system of claim 11 wherein said ink applied to the printing surface of said paper stock comprises an aqueous solution containing 0.5% to 3% by weight of a compound from the group consisting of a salt of a metal cyanide complex; 8-hydroxyquinoline; and 1-nitroso-2-naphthol-3,6-disulfonic acid.
13. The printing system of claim 12 wherein said paper stock is treated by an aqueous solution including a ferrous compound.
Description:
The present invention relates to printing systems and more particularly to an improved system wherein an ink is used that resists clogging of pens and nozzles and forms visible indicia by reacting with metal ions at the document surface.
Prior inking systems particularly those dependent upon a uniform supply and flow of ink are often compromised by the tendency of ink coagulation to plug a pen or nozzle. This can occur most frequently following a few hours of non-use or overnight shutdown. Over a long period of time there has been little improvement in inking tools and technique. Recently there have been improved pens and ultrasonic pen cleaners. These solutions are efforts to aid in compensating for the inherent weakness of the ink itself.
Sludge and coagulation are the greatest problem with respect to pen type ink dispensing apparatus or the very fine ink dispensing nozzles used in drop on demand type printers such as ink jet printers. These latter particularly are designed to operate at high speed, being considered a possible solution to overcome speed limitations of impact printers. To accomplish this it is clearly necessary that a reliable, repetitive supply of ink droplets be supplied. It is necessary that not only the nozzle structure and transducer design be optimized for the application, but also that an ink be used that will not coagulate or otherwise impair the operation.
In the printing system of the present invention, the paper used is treated to impart metal ions at the printing surface. The ink used is a low concentration of a compound in an aqueous solution. The compound is selected so that the metal ion with which the paper is treated and the compound react to form a precipitate that is visible and of a desired color. In addition, the selection of metal ion and compound should be made such that the reaction forming the precipitate occurs at room temperature to preclude the necessity of an additional operation or extra equipment. Also in common with other inks, the printed characters produced by the system must withstand heat and humidity and resist ultraviolet degradation to possess desired permanence.
The ink used in the present invention is a low concentration of a solution that reacts with a metal ion to form a visible precipitate. Accordingly, pigmentation or other particle content are neither required nor used. The use of low concentration solutions assures that saturation will not be exceeded even in cases where evaporation causes an increased concentration thereby avoiding the generation of residues that would cause clogging in a similar manner to that induced by coagulated materials. Further, even very low concentrations produce adequate contrast in the resulting printed characters and in some combinations of compound and metal ion maximum contrast is generated at a very low concentration with contrast actually degraded as the concentration is increased. Although concentrations from very low values to saturation are operable, best results are obtained using concentrations of 0.5 to 3% by weight in a substantially aqueous vehicle.
The ink of the system here described uses fluids that are colorless or lightly colored and that do not require pigmentation. Standard printing colors are produced by chemical reaction which takes place when the fluid is deposited on a treated paper. This is to be contrasted with methods of printing which involve the deposition of a pigmented ink or on untreated paper. Since the chemical reaction is instantaneous the only drying time required is that associated with the evaporation of residual water. This occurs in a matter of seconds, depending on the amount of fluid applied and the absorbency of the paper. On the other hand, many pigmented inks require relatively long drying times and some inks never dry completely and are always subject to smearing.
The system of printing or writing encompassed by the present invention requires that the document be treated to provide metal ions at the printing surface. This can be accomplished by spraying, dipping or brushing a solution of the metal ion onto the paper or most economically by introducing the metal ion solution during the process of paper manufacture. To provide the treated paper with very little cost differential, the metal ion should be introduced during the paper manufacture as a water soluble solution. By using a water soluble solution it is possible to recycle waste paper back into the plant system. This presents no problem since numerous economical and suitable metal compounds are water soluble. Further, this type of compound is already being introduced during the paper making process for other purposes. For example, it is common practice to add sodium chloride to paper during manufacture to provide anti-static properties.
The metal ion in the paper stock may be iron, copper, chromium, cobalt, manganese, nickel or tin; however, the first two iron and copper are the most economical and readily available. Magnesium and aluminum have limited value as paper treatment ions since the precipitate generated are often either white or transparent. Metals such as lead, mercury or thallium are not recommended because of considerations of toxicity and numerous other metals are too costly to be economically practical for use.
The test samples of treated paper were generated from card stock of the type used for standard data cards. The materials used for metal ion treatment of the paper were copper sulfate for the copper ion and ferrous ammonium sulfate for the iron ion. These compounds were selected on the basis of being readily obtainable at low cost. The copper sulfate was applied to the paper as a 7.4% by weight solution. The ferrous ammonium sulfate was applied as an 0.1 normal solution. Both were dissolved in distilled water. The PH of the copper solution was 4.0; the PH of the iron solution was 6.0. Using a suction type paint sprayer, the metal ion solution was applied topically to paper fed from a standard roll at a constant rate. A felt pad was used against the sprayed paper to remove excess solution and to insure uniformity of application. Finally, an electric dryer was used to speed the drying before the paper was re-rolled onto a spool.
A number of examples referred to hereafter use paper treated with the iron ion. Although printing is successful, a problem of discoloration of the iron in the paper may occur several months after application. The paper turns from its normal off white or yellow white to a pale tan. Various anti-oxidants have been applied as additives to the iron solution to prevent discoloration. The two most successful have been 1% by weight stannous chloride and 1% by weight benzotriazole.
The printing operation described herein has been conducted in accordance with the following examples.
EXAMPLE 1
A document having a surface treated with an 0.1 normal solution of ferrous ammonium sulfate was printed with a drop on demand, non-impact printer using an ink consisting of a 2% solution by weight of potassium ferricyanide (a salt of the metal cyanide complex). The printed characters resulting were blue in color.
EXAMPLE 2
The printing of example 1 was repeated using a 1% solution by weight of potassium ferricyanide.
EXAMPLE 3
The printing operation of example 1 was repeated using an 0.5% concentration of potassium ferricyanide.
EXAMPLE 4
A document having a surface treated with an 0.1 normal solution of ferrous ammonium sulfate was printed using a drop on demand, non-impact printer with an ink consisting of a 2% solution by weight of 8-hydroxyquinoline (a heterocyclic) in a 95% water 5% acetic acid solvent. The color of the resulting printed characters was black,
EXAMPLE 5
The printing operation of example 4 was repeated using a 1.5% solution by weight of 8-hydroxyquinoline.
EXAMPLE 6
The printing operation of example 4 was repeated using a 1.0% solution by weight of 8-hydroxyquinoline.
EXAMPLE 7
A document surface was treated with an 0.1 normal solution of ferrous ammonium sulfate and was thereafter printed using a drop on demand, non-impact printer. The printing ink consisted of a 1% solution by weight of 2,2-bipyridine (a heterocyclic) in a 95% water, 5% ethyl alcohol solvent. The printed characters on the document were red in color.
EXAMPLE 8
The printing operation of example 7 was repeated using an 0.5% solution of 2,2-bipyridine.
EXAMPLE 9
The printing operation of example 7 was repeated using an 0.25% solution by weight of 2,2-bipyridine.
Print samples prepared in accordance with the examples 1 through 9 were tested to determine print contrasts, fading resistance and response to conditions of high humidity.
Print samples in accordance with each of the examples above were tested for print contrast in accordance with the pictorial information dissector and analyzer system (PIDAS) and in each case the print contrast exceeded standards required for optical character recognition. Of the three colors, the blue printing of examples 1 through 3 was unique in that the maximum contrast was produced by the intermediate 1% concentration rather than the highest concentration as was the case with the black ink of examples 4 through 6 and the red ink of examples 7 through 9.
The ability to resist fading was investigated using a fadometer test wherein samples were subject to ultraviolet light (Xenon 6,000 watt lamp) in a relative humidity of 50-55% until fading occurred. The red ink of examples 7 through 9 withstood 50 hours and the black ink of examples 4 through 6 withstood 100 hours. The test of the blue ink of examples 1 through 3 was terminated after 150 hours at which time no identifiable fading had occurred. In contrast to the samples of examples 1 through 9, two samples of printing with oleate dye ribbon printing inks were prepared. These latter samples were subject to fading after 10 hours exposure to the test conditions.
When subjected to humidity conditions of 100°F. and 90% relative humidity for 100 hours the red ink of examples 7 through 9 showed no change, the black ink of examples 4 through 6 showed slight fading and the blue ink of examples 1 through 3 was actually enhanced, being darker after the test. When tested for heat, exposure to 100°F. for 500 hours caused no fading or degradation of any of the samples of examples 1 through 9.
The following further examples are demonstrative of the range of colors which are available through the choice of selected combinations of metal ion and the reacting compound.
EXAMPLE 10
A document treated with a solution of 7.4% by weight copper sulfate in water was printed using a non-impact, drop on demand printer utilizing an ink consisting of a 1% by weight solution of 1-nitroso-2-naphathol-3,6-disulfonic acid (a naphthalene derivative). The resulting printed characters were of yellow color.
EXAMPLE 11
A document treated with an 0.1 normal solution of ferrous ammonium sulfate was printed using a nonimpact, drop on demand printer utilizing an ink consisting of a 1% by weight solution of 1-nitroso-2-naphathol-3,6-disulfonic acid. The printed characters on the document were a green color.
EXAMPLE 12
A document treated with a solution of 7.4% by weight copper sulfate in water was printed using a nonimpact, drop on demand printer utilizing an ink consisting of a 1% solution of weight of diphenyl carbazide (a substituted biphenyl) containing 0.1% ammonium hydroxide and 10% ethanol. This printing operation produced purple colored printed characters.
EXAMPLE 13
A document treated with a solution of 1% potassium chromate was printed using a drop on demand printer utilizing an ink consisting of a 1% solution by weight of diphenyl carbazide containing 0.1% sulfuric acid and 10% ethanol. The printed characters on the document were of purple color.
EXAMPLE 14
A document treated with an 0.1 normal solution of ferrous ammonium sulfate was printed with a drop on demand printer using an ink consisting of a 1% solution by weight of sodium diethyl dithio carbamate (a thiocarbonic acid derivative) to produce brown colored printed characters.
EXAMPLE 15
A document treated with a 10% stannous chloride solution was printed with a drop on demand printer using ink consisting of a 3% solution by weight of cacotheline (a heterocyclic) to produce purple colored printed characters.
Additionally the reaction and printing action can be enhanced by adding a surfactant to the ink solution. It will be recognized that such a surfactant must be non-ionic in nature to assure that the wetting action will enhance and not impair the reaction of the printing process. One group of such surfactants that may be used are monoarylethers of polyethylene glycol.
The ink solution should be relatively neutral or about PH 7.0, however, the reaction is somewhat more tolerant of an acid condition than an alkaline condition. The various examples have been conducted in the range of PH 4.0 to PH 8.0 without impairing the result.
While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.
Prior inking systems particularly those dependent upon a uniform supply and flow of ink are often compromised by the tendency of ink coagulation to plug a pen or nozzle. This can occur most frequently following a few hours of non-use or overnight shutdown. Over a long period of time there has been little improvement in inking tools and technique. Recently there have been improved pens and ultrasonic pen cleaners. These solutions are efforts to aid in compensating for the inherent weakness of the ink itself.
Sludge and coagulation are the greatest problem with respect to pen type ink dispensing apparatus or the very fine ink dispensing nozzles used in drop on demand type printers such as ink jet printers. These latter particularly are designed to operate at high speed, being considered a possible solution to overcome speed limitations of impact printers. To accomplish this it is clearly necessary that a reliable, repetitive supply of ink droplets be supplied. It is necessary that not only the nozzle structure and transducer design be optimized for the application, but also that an ink be used that will not coagulate or otherwise impair the operation.
In the printing system of the present invention, the paper used is treated to impart metal ions at the printing surface. The ink used is a low concentration of a compound in an aqueous solution. The compound is selected so that the metal ion with which the paper is treated and the compound react to form a precipitate that is visible and of a desired color. In addition, the selection of metal ion and compound should be made such that the reaction forming the precipitate occurs at room temperature to preclude the necessity of an additional operation or extra equipment. Also in common with other inks, the printed characters produced by the system must withstand heat and humidity and resist ultraviolet degradation to possess desired permanence.
The ink used in the present invention is a low concentration of a solution that reacts with a metal ion to form a visible precipitate. Accordingly, pigmentation or other particle content are neither required nor used. The use of low concentration solutions assures that saturation will not be exceeded even in cases where evaporation causes an increased concentration thereby avoiding the generation of residues that would cause clogging in a similar manner to that induced by coagulated materials. Further, even very low concentrations produce adequate contrast in the resulting printed characters and in some combinations of compound and metal ion maximum contrast is generated at a very low concentration with contrast actually degraded as the concentration is increased. Although concentrations from very low values to saturation are operable, best results are obtained using concentrations of 0.5 to 3% by weight in a substantially aqueous vehicle.
The ink of the system here described uses fluids that are colorless or lightly colored and that do not require pigmentation. Standard printing colors are produced by chemical reaction which takes place when the fluid is deposited on a treated paper. This is to be contrasted with methods of printing which involve the deposition of a pigmented ink or on untreated paper. Since the chemical reaction is instantaneous the only drying time required is that associated with the evaporation of residual water. This occurs in a matter of seconds, depending on the amount of fluid applied and the absorbency of the paper. On the other hand, many pigmented inks require relatively long drying times and some inks never dry completely and are always subject to smearing.
The system of printing or writing encompassed by the present invention requires that the document be treated to provide metal ions at the printing surface. This can be accomplished by spraying, dipping or brushing a solution of the metal ion onto the paper or most economically by introducing the metal ion solution during the process of paper manufacture. To provide the treated paper with very little cost differential, the metal ion should be introduced during the paper manufacture as a water soluble solution. By using a water soluble solution it is possible to recycle waste paper back into the plant system. This presents no problem since numerous economical and suitable metal compounds are water soluble. Further, this type of compound is already being introduced during the paper making process for other purposes. For example, it is common practice to add sodium chloride to paper during manufacture to provide anti-static properties.
The metal ion in the paper stock may be iron, copper, chromium, cobalt, manganese, nickel or tin; however, the first two iron and copper are the most economical and readily available. Magnesium and aluminum have limited value as paper treatment ions since the precipitate generated are often either white or transparent. Metals such as lead, mercury or thallium are not recommended because of considerations of toxicity and numerous other metals are too costly to be economically practical for use.
The test samples of treated paper were generated from card stock of the type used for standard data cards. The materials used for metal ion treatment of the paper were copper sulfate for the copper ion and ferrous ammonium sulfate for the iron ion. These compounds were selected on the basis of being readily obtainable at low cost. The copper sulfate was applied to the paper as a 7.4% by weight solution. The ferrous ammonium sulfate was applied as an 0.1 normal solution. Both were dissolved in distilled water. The PH of the copper solution was 4.0; the PH of the iron solution was 6.0. Using a suction type paint sprayer, the metal ion solution was applied topically to paper fed from a standard roll at a constant rate. A felt pad was used against the sprayed paper to remove excess solution and to insure uniformity of application. Finally, an electric dryer was used to speed the drying before the paper was re-rolled onto a spool.
A number of examples referred to hereafter use paper treated with the iron ion. Although printing is successful, a problem of discoloration of the iron in the paper may occur several months after application. The paper turns from its normal off white or yellow white to a pale tan. Various anti-oxidants have been applied as additives to the iron solution to prevent discoloration. The two most successful have been 1% by weight stannous chloride and 1% by weight benzotriazole.
The printing operation described herein has been conducted in accordance with the following examples.
EXAMPLE 1
A document having a surface treated with an 0.1 normal solution of ferrous ammonium sulfate was printed with a drop on demand, non-impact printer using an ink consisting of a 2% solution by weight of potassium ferricyanide (a salt of the metal cyanide complex). The printed characters resulting were blue in color.
EXAMPLE 2
The printing of example 1 was repeated using a 1% solution by weight of potassium ferricyanide.
EXAMPLE 3
The printing operation of example 1 was repeated using an 0.5% concentration of potassium ferricyanide.
EXAMPLE 4
A document having a surface treated with an 0.1 normal solution of ferrous ammonium sulfate was printed using a drop on demand, non-impact printer with an ink consisting of a 2% solution by weight of 8-hydroxyquinoline (a heterocyclic) in a 95% water 5% acetic acid solvent. The color of the resulting printed characters was black,
EXAMPLE 5
The printing operation of example 4 was repeated using a 1.5% solution by weight of 8-hydroxyquinoline.
EXAMPLE 6
The printing operation of example 4 was repeated using a 1.0% solution by weight of 8-hydroxyquinoline.
EXAMPLE 7
A document surface was treated with an 0.1 normal solution of ferrous ammonium sulfate and was thereafter printed using a drop on demand, non-impact printer. The printing ink consisted of a 1% solution by weight of 2,2-bipyridine (a heterocyclic) in a 95% water, 5% ethyl alcohol solvent. The printed characters on the document were red in color.
EXAMPLE 8
The printing operation of example 7 was repeated using an 0.5% solution of 2,2-bipyridine.
EXAMPLE 9
The printing operation of example 7 was repeated using an 0.25% solution by weight of 2,2-bipyridine.
Print samples prepared in accordance with the examples 1 through 9 were tested to determine print contrasts, fading resistance and response to conditions of high humidity.
Print samples in accordance with each of the examples above were tested for print contrast in accordance with the pictorial information dissector and analyzer system (PIDAS) and in each case the print contrast exceeded standards required for optical character recognition. Of the three colors, the blue printing of examples 1 through 3 was unique in that the maximum contrast was produced by the intermediate 1% concentration rather than the highest concentration as was the case with the black ink of examples 4 through 6 and the red ink of examples 7 through 9.
The ability to resist fading was investigated using a fadometer test wherein samples were subject to ultraviolet light (Xenon 6,000 watt lamp) in a relative humidity of 50-55% until fading occurred. The red ink of examples 7 through 9 withstood 50 hours and the black ink of examples 4 through 6 withstood 100 hours. The test of the blue ink of examples 1 through 3 was terminated after 150 hours at which time no identifiable fading had occurred. In contrast to the samples of examples 1 through 9, two samples of printing with oleate dye ribbon printing inks were prepared. These latter samples were subject to fading after 10 hours exposure to the test conditions.
When subjected to humidity conditions of 100°F. and 90% relative humidity for 100 hours the red ink of examples 7 through 9 showed no change, the black ink of examples 4 through 6 showed slight fading and the blue ink of examples 1 through 3 was actually enhanced, being darker after the test. When tested for heat, exposure to 100°F. for 500 hours caused no fading or degradation of any of the samples of examples 1 through 9.
The following further examples are demonstrative of the range of colors which are available through the choice of selected combinations of metal ion and the reacting compound.
EXAMPLE 10
A document treated with a solution of 7.4% by weight copper sulfate in water was printed using a non-impact, drop on demand printer utilizing an ink consisting of a 1% by weight solution of 1-nitroso-2-naphathol-3,6-disulfonic acid (a naphthalene derivative). The resulting printed characters were of yellow color.
EXAMPLE 11
A document treated with an 0.1 normal solution of ferrous ammonium sulfate was printed using a nonimpact, drop on demand printer utilizing an ink consisting of a 1% by weight solution of 1-nitroso-2-naphathol-3,6-disulfonic acid. The printed characters on the document were a green color.
EXAMPLE 12
A document treated with a solution of 7.4% by weight copper sulfate in water was printed using a nonimpact, drop on demand printer utilizing an ink consisting of a 1% solution of weight of diphenyl carbazide (a substituted biphenyl) containing 0.1% ammonium hydroxide and 10% ethanol. This printing operation produced purple colored printed characters.
EXAMPLE 13
A document treated with a solution of 1% potassium chromate was printed using a drop on demand printer utilizing an ink consisting of a 1% solution by weight of diphenyl carbazide containing 0.1% sulfuric acid and 10% ethanol. The printed characters on the document were of purple color.
EXAMPLE 14
A document treated with an 0.1 normal solution of ferrous ammonium sulfate was printed with a drop on demand printer using an ink consisting of a 1% solution by weight of sodium diethyl dithio carbamate (a thiocarbonic acid derivative) to produce brown colored printed characters.
EXAMPLE 15
A document treated with a 10% stannous chloride solution was printed with a drop on demand printer using ink consisting of a 3% solution by weight of cacotheline (a heterocyclic) to produce purple colored printed characters.
Additionally the reaction and printing action can be enhanced by adding a surfactant to the ink solution. It will be recognized that such a surfactant must be non-ionic in nature to assure that the wetting action will enhance and not impair the reaction of the printing process. One group of such surfactants that may be used are monoarylethers of polyethylene glycol.
The ink solution should be relatively neutral or about PH 7.0, however, the reaction is somewhat more tolerant of an acid condition than an alkaline condition. The various examples have been conducted in the range of PH 4.0 to PH 8.0 without impairing the result.
While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.