US3455240A - Imaging system - Google Patents

Description

y 15, 1969 R. w. MARTEL ETAL 3,455,240

IMAGING SYSTEM Filed Sept. 15, 1965 INVENTOR. ROBERT w. MARTEL JOHN W. WEIGL OSEPH MAMMINO United States Patent US. Cl. 101450 3 Claims ABSTRACT OF THE DISCLOSURE The subject matter of this patent application pertains to a method of preparing a lithographic master. An electrostatic latent image is formed on a conventional xerographic plate. An aqueous based, polarity insensitive developer is applied to the surface of the plate retaining the latent image the developer adhering thereto to the charged portions of the plate in an imagewise configuration. The imaged surface of the plate is then placed in face-to-face contact with a suitable substrate and pressure applied to effect transfer of the image from the Xerographic plate to the surface of the substrate. The substrate master may then be used in lithographic printing mode.

This invention relates to an imaging system and more specifically to a method of making a lithographic plate.

Lithographic printing is a well-known and established art. In general, the process involves printing from a fiat plate, depending upon different properties of the image and nonimage areas for printability. In conventional lithography the non-image area is hydrophilic while the image area is hydrophobic. In the lithographic printing process, a conversion solution is applied to the plate surface which wets all portions of the surface not covered by the hydrophobic image. This solution keeps the plate moist and prevents it from scumming up. An oil based printing ink is applied to the image surface depositing the lithographic ink only on the image area, the hydrophilic non-image area repelling the ink. The ink image may then be transferred directly to a paper sheet or other receptive surface, but generally it is transferred to a rubber off-set blanket which in turn transfers the print to the final paper sheet. Hence, for each print made during a run, the lithographic plate is first dampened with an aqueous conversion solution and then inked with a lithographic ink and finally printed.

It has been known that lithographic plates can be made in a photoconductive system by utilizing the conventional developed Xerographic plate as a lithographic printing plate. The general process of utilizing a Xerographic plate in a lithographic system is described in US. Patents 3,107,169 and 3,001,872. In these systems, usually a zinc oxide-type plate is charged by conventional means, exposed to the image to be reproduced, and developed with conventional xerographic toner. The toner used is generally hydrophobic in nature as isthe background of the conventional inorganic binder-type xerographic plate. In order that the developed Xerographic plate be useful as a lithographic master, a differential must be established between the toned image and the background of the plate. Since both are hydrophobic in nature, it has heretofore been required that the background of the xerographic plate betreated, by the use of a conversion solution, to make it hydrophilic in nature. After the conversion of the background, the plate is then wetted with a non-aqueous or oil based ink whereby the toner will accept the ink and the now hydrophilic background will repel the ink.

3,455,240 Patented July 15, 1969 While basically this system has been found useful for lithographic purposes, there are inherent disadvantages to its use. One disadvantage, for example, is the fact that it is required that a conversion solution be used to convert the initially hydrophobic background to hydrophilic so that it will not accept the oil based ink in the inking step. A second disadvantage to this system is that the Xerographic plate, when developed, has thereon fused toner, fixed to the surface of the plate and inherently non-reusable. A further disadvantage is that the imaging toner is sensitive to polarity and therefore it is necessary to restrict the photoconductive plate used to one which will accept a charge compatible with the toner.

It is therefore an object of this invention to provide a lithographic imaging system which will overcome the above noted disadvantages.

It is a further object of this invention to provide a novel method for the preparation of a lithographic master plate.

Another object of this invention is to provide an imaging system utilizing a master prepared by a one-step process.

Still a further object of this invention is to provide a method of making a lithographic plate utilizing xerography whereby the xerographic plate can be reused.

Yet still a further object of this invention is to provide a method of making a lithographic plate wherein the materials used to make the master are not limited by the steps of the process, such as the type of charging required.

The foregoing objects and others are accomplished in accordance with this invention, generally speaking, by providing a method for making a lithographic plate wherein the conventional xerographic imaging process is used for the formation of electrostatic latent image on a Xerographic plate. After the latent image is formed, an aqueous based, polarity-insensitive developer is applied to the surface of the plate retaining the latent image. The developer is thereby held in an imagewise configuration to the charged portion of the plate. The imaged surface of the plate is then placed in face-to-face contact with a substrate and contact pressure applied to the back of the Xerographic plate sufficient to effect transfer of the developed image from the Xerographic plate to the surface of the substrate. The substrate master can then be used in a one-step process to continuously make prints whereby an aqueous based ink is applied to the master, the ink adhering only to the aqueous developer of the lmage.

The invention is illustrated in the accompanying drawings in which;

FIG. 1 is a diagrammatic perspective view of a Xerographic plate bearing an electrostatic latent image;

FIG. 2 is a frontal view of a latent image bearing xerographic plate partially developed with a water soluble, polarity-insensitive developer;

FIG. 3 is a frontal view of a developed xerographic plate in contact with a base substrate;

FIG. 4 is a diagrammatic perspective view of a xerographic plate with the image bearing susbtrate partially removed therefrom;

FIG. 5 is a diagrammatic perspective view of a substrate base lithographic master with a partially inked image.

In the present process for preparing a lithographic master, a xerographic plate 1 illustrated in FIG. 1 comprising a backing material 2 and a photoconductive insulating layer 3 is uniformly charged and this charge selectively dissipated by exposure to a line-copy image whereupon there results an electrostatic charge pattern 4 corresponding to the charge pattern of the image.

FIG. 2 illustrates the development technique whereby an aqueous based, polarity-insensitive developer 5 is applied by means of a roller 6 to the imaged surface of the xerographic plate 1. The developer 5 is thereby held in imagewise configuration 5a to the charged portion of the plate 4. The imaged surface of the plate is then placed in face-to-face contact with a receiving substrate 7, as illustrated in FIG. 3, and contact pressure applied to the back of the xerographic plate 1 sufficient to effect transfer of the developed image 5a from the xerographic plate 1 to the surface of the receiving substrate 7. If a hydrophilic type substrate is used as the receiving substrate then after placing the Xerographic plate bearing the developed image in contact with the receiving substrate the backside of the substrate is coated with a hydrophobic material 8. This material penetrates the fibers of the substrate and renders them hydrophobic. The same coating procedure may be used to render presently existing oil resistant substrate more hydrophobic.

FIG. 4 illustrates the separation phase of the process whereby the receiving substrate 7 is turned back from the xerographic plate 1. The developed image 5a adheres to the surface of the substrate 7 in a mirror image configuration.

FIG. 5 illustrates the finished master plate 9 comprising a receiving substrate 7 bearing a developed image 5a. The master plate is prepared for printing by applying an aqueous based ink 10 to the surface of the plate by means of an ink applicator 11, the aqueous based ink being retaiend by the imaged area 12 and repelled by the nonimaged, hydrophobic background area 13.

While it is preferred to use a xerographic plate which has a photoconductive layer that forms a high contact angle with the aqueous based developer of this invention to achieve good image retention any other suitable photoconductive insulating material may be used, if desired. Typical inorganic photoconductive materials are sulfur, selenium (vitreous, amorphous alpha monoclinic), zinc sulfide, zinc oxide, zinc cadmium sulfide, zinc magnesium oxide, cadmium selenide, zinc silicate, calcium-strontium sulfide, cadmium sulfide, mercuric iodide, mercuric oxide, mercuric sulfide, indium trisulfide, gallium triselenide, arsenic disulfide, arsenic trisulfide, arsenic triselenide, antimony trisulfide, cadmium sulfo-selenide, doped chalcogenides of zinc and cadmium, aluminum oxide, bismuth oxide, molybdenum oxide, lead oxide, molybdenum iodide, molybdenum selenide, molybdenum sulfide, molybdenum telluride, aluminum iodide, aluminum selenide, aluminum sulfide, aluminum telluride, bismuth iodide, bismuth selenide, bismuth sulfide, bismuth telluride, cadmium telluride, mercuric selenide, mercuric telluride, lead oxide, lead selenide, lead sulfide, lead telluride, cadmium arsenide, lead chromate, gallium sulfide, gallium telluride, indium sulfide, indium selenide, induim telluride, red lead and mixtures thereof. Typical organic photoconductors that may be used in the present invention are triphenyl amine;

2,4-bis(4,4-diethy1-amino-pehnyl)-1,3 ,4-oxadiazol;

N-isopropyl carbozole;

triphenylpyrol;

4,S-diphenylimidazolidinone;

4,5-diphenylimidazolidinethione;

4,5-bis-(4'-amino-pheny1)-imidazolidinone;

1,5-cyanonaphthalene;

1,4-dicyanonaphthalene;

aminophthalo dinitrile;

nitrophthalidinitrile;

1,2,5 ,6-tetraazacyclooctatetraene- 2,4,6,8

3 ,4-di- 4-methoxy-phenyl 7,8-diphenyl-1,2,5,6-tetraaza-cyclooctatetraene-(2,4,6,8

3,4-di-(4'-phenoxyphenyl)-7,8-diphenyl-1,2,5,6-tetraaza-cyclooctatetraene- 2,4,6,8)

3,4,7,8-tetramethoxy-1,2,5,6-tetraaza-cyclooctatetraene-(2,4,6,8

Z-mercapto-benzth iazole 2-phenyl-4-alpha-naphthylidene-oxazolone;

2-phenyl-4-diphenylide-oxazolone;

2-phenyl-4-p-meth0xybenzylideneoxazolone;

6-hydroxy-2-phenyl-3- p-dimethylamino phenyl benzofurane;

6-hydroxy-2,3-di(p-methoxyphenyl) benzofurane;

2,3 ,5,6-tetra (p-methoxyphenyl -furo- 3 ,2

benzofurane;

4-dimethylaminobenzylidene-benzhydrazide;

4-dimehylamin0benzylidene-isonicotinic acid hydrazide;

furfurylidene- 2 -4'-dimethylaminobenzhydrazide;

S-benzilidene-aminoacenaphthene;

3 -benzylidene-amino-carbazole;

(4-N,N-dimethyl aminob enzylidene) -p-N,N-dimethylaminoaniline;

( 2-nitro-benzylidene -p-bromo-aniline;

N,N-dimethyl-N- (2-nitro-4-cyano-benzylidene) -pphenylene-diamine;

2,3-diphenyl-quinazoline;

2- 4-amino-phenyl) -4-phenyl-quinazoline;

2-phenyl-4- 4'-di-methyl-amino-phenyl -7-methoxyquinazoline;

1,3-diphenyl-tetrahydroimidazole;

1,3-di- (4-chlorophenyl -tetrahydroimidazole;

1,3-diphenyl-2,4'-dimethylamino phenyl -tetrahydroimidazole;

1,3 -di- (p-tolyl -2-quinolyl- 2'- -tetrahydroimidazole;

3 (4'-dimethylamino-phenyl -5- 4-meth0xy phenyl-)-6-phenyl-1,2,4,triazine;

3-pyridyl- 4 -5- (4-dimethylamino-phenyl -6- phenyl-1,2,4-triazine;

3 -(4-amino-phenyl)-5,6-diphenyl-1,2,4-triazine;

2,5 -bis [4'-aminophenyl-( 1 1 ,3,4-triazole;

2,5 -bis [4'-N-ethyl-N-acetylamino -phenyl-( 1 1,3 ,4-triazole;

1,5 -diphenyl-3 -methyl-pyrazoline 1,3,4,S-tetraphenyl-pyrazoline;

1-phenyl-3 (p-rnethoxystyryl -5- (p-methoxyphenyl) -pyrazoline;

1-methyl-2-( 3 ,4'-dihydroxy-methylene-phenyl) benzimidazole;

2-(4-dimethylamino phenyl)-benzoxazole;

2- (4-methoxyphenyl -benzthiazole;

2,5 -bis- [p-aminophenyl 1 1,3 ,4-oxadiazole;

4,5-diphenyl-imidazolone 3 -aminocarb azole;

and mixtures thereof. Generally, when used in this process, the organic photoconductive layer will accept a positive charge. In addition, other typical photoconductors are charge-transfer type photoconductors such as disclosed in copending applicatons Ser. Nos. 426,409; 426,- 423; 426,431; 426,428; and 426,396. As above mentioned, the photoconductive insulating surface preferred is one which maintains a high contact angle with the aqueous developer solution used, the most effective results being achieved when the contact angle is greater than The contact angle as herein used is defined as being the angle through the liquid which lies between the horizontal solid surface and the tangent to the drop of developer at the point at which the surface of the drop intersects the horizontal surface. The tangent will be in a plane perpendicular to the horizontal surface which also passes through the center of the drop. Examples of some of the photoconductive insulating materials which exhibit this property are zinc oxide, zinc sulfide, zinc cadmium sulfide,, cadmium selenide, cadmium sulfide, cadmium sulfoselenide, mercuric oxide, mercuric sulfide, gallium triselenide, arsenic disulfide, arsenic trisulfide, arsenic triselenide, antimony trisulfide, triphenyl amine, polyvinyl carbazole, 4,5 diphenyl-imidazolidinone, 1,4 dicyanonaphthalene, and nitrophthalidinitrile, among others.

When desirable, any suitable binder material may be incorporated into the photoconductive layer of the xerographic plate used in the course of this invention. Typical binders and photoconductive layers are similar to those disclosed in US. Patents 3,121,006 and 3,121,007. Preferred binder materials for the practice of this invention are polystyrene, styrenated alkyd resins, phthalic alkyd resins, polyvinyl ester resins and melamine formaldehyde resins, inasmuch as the preferred contact angle could be readily obtained.

Any suitable backing material for the xerographic plate may be used in the course of this invention. Generally, the preferred barking material should have an electrical resistance less than the photoconductive layer so that it -will act as a ground when the electrostatically charged coating is exposed to light. Typical such materials are aluminum, brass, glass, aluminum coated glass, stainless steel, nickel, steel, bronze, copper, engravers copper, engravers zinc, grained lithographic zinc, and both conductive and non-conductive paper. Other materials having electrical resistances similar :to the aforementioned can also be used as backing material to receive the photoconductive layer thereon. Other non-conductive materials such as thermoplastics may be used as the backing of the xerographic plate. When used, however, it is necessary to charge both sides of the xerographic plate according to the process set out in US. Patent 2,922,883.

Any suitable aqueous based, polarity-insensitive dcveloper may be used in the process of this invention, said developers having viscosities ranging from one to onehundred thousand centipoises, preferably five thousand to twenty thousand centipoises inasmuch as the optimum results are obtained within this preferred range. Typical developer components are vinyl resins such as carboxy vinyl polymers for example carboxy polymethylene, polyvinylpyrrolidones, poly(methylvinyl-ether maleic anhydride) interpolymers, polyvinyl alcohols, cellulosics such as sodium carboxymethyl cellulose, hydroxypropylmethyl cellulose, hydroxyethyl cellulose, and methyl cellulose, cellulose derivatives such as esters and ether, water, starch, alkali soluble proteins, casein, gelatin, acrylate salts such as ammonium polyacrylate and sodium polyacrylate, polyacrylic acid, polymethacrylic acid and copolymers thereof and the alkali and ammonia salts of alginic acid and mixtures thereof. For purposes of this invention, optimum results were obtained with the vinyl resins inasmuch as the preferred viscosity levels could be readily reached at low concentrations. By the expression aqueous based developer is meant a developer comprising a major proportion of water and a minor proportion of another solvent, such as alcohol.

Any conventional and/or suitable aqueous based ink may be used in the process of this invention. This includes both the inks containing water soluble dye substances and the pigmented inks. Typical dye substances are Methylene Blue, available from Eastman Kodak Co., Brilliant Yellow, available from Harlaco Chemical Co., potassium permanganate, ferric chloride, cobaltous chloride, available from Dayco Laboratories and Methylene Violet, Rose Bengal, and Quinoline Yellow, the latter three all available from Allied Chemical Co.

It is also possible to use simple compounds or colored water-soluble complexes, such as those which are formed by a certain number of transition elements, principally of the first long period of the periodic table, for example the known cuprous tetramine complex, the chromium salts such as chromium sulfate, chorme and potassium alum, potassium chromate, the aquoand acido-complexes of trivalent chromium, certain ferric compounds such as ferric thiocyanate and the thio-cyanato-ferrates, the prusside compounds of iron, the acetatoferric salts, iron-ammonium citrate, the thiocyanate and the thiocyanocobaltates of bivalent cobalt, cobalt sulfate and chloride, the great number of cobaltic complexes, for example the amine, the aquo-and acido-complexes which exist in as great an abundance as the chromium complexes, the chlorides and sulfates of bivalent nickel, the copper tartrate complex, copper-glycine, the soluble compounds between iron and gallic acid or tannin, the complexes of ferrous salts with alphapicolinic acid or analagous compounds which contain one atom of nitrogen cyclically combined in the alpha position in relation to a carboxyl group, iron or bivalent cobalt complexes with the alphadioximes, such as dimethyl-glyoxime, the ferric complexes with salicyclic acid, compounds between titanium or iron salts and pyrocathechine or chromotropic acid.

Typical pigments that are suitable for the present invention are carbon black, titanium dioxide, white lead, zinc oxide, zinc sulfide, iron oxide, chromium oxide, lead chromate, zinc chromate, cadmium yellow, cadmium red, red lead, antimony dioxide, magnesium silicate, calcium carbonate, calcium silicate, phthalocyanines, benzidines, dinitranilines, naphthols and toluidines. The pigmented links are preferred in the present invention inasmuch as the final reproduced prints are longer lasting and possess optimum optical density characteristics. Specifically preferred among the pigments is carbon black because it is more suitable for most printing operations.

Any suitable material may be used as the substrate to which the developed image is transferred in order to form the lithographic master. Typical types of substrate are zinc, aluminum, polyethylene, polypropylene and ordinary bond paper. If the substrate is a metallic material it will be such that its impurity content renders it oleophilic in nature. If the substrate is hydrophilic in nature by coating the backside of the substrate with a hydrophobic material, such as an isoparafiinic aliphatic hydrocarbon, until the coating penetrates the substrate, it can be made to be hydrophobic in nature. For purposes of this invention polyethylene, polypropylene and ordinary bond papers are preferred as substrates due to their flexibili ty.

To further define the specifics of the present invention the following examples are intended to illustrate and not limit the particulars of the present system. Parts and percentages are by weight unless otherwise indicated. The examples are also to illustrate various preferred embodiments of the present invention.

EXAMPLE I A sheet of commercial zinc oxide paper available from Charles Brunning Co., is charged to 350-400 volts by means of a laboratory corotron unit powered by a high voltage power sup-ply. The charging current is 0.1 of a. milliamp at 7,500 volts. A transparent positive USAF test chart is placed on the charged zinc oxide paper and exposed with a 75 Watt photoflood lamp. An exposure of about 20-foot-candle seconds is required for the zinc oxide paper. The electrostatic latent image produced is then developed with a one percent aqueous solution of an ammonium salt of oarboxy polymethylene, Carbopol 961, available from B. F. Goodrich Chemical Co., by applying said solution by means of a doctored gravure roll. A piece of ordinary bond paper is then placed in direct contact with the surface of the zinc oxide paper bearing the developed image. The back side of the bond paper is then coated with a fine spray of a water-immiscible hydrocarbon such as an isoparaffinic aliphatic hydrocarbon. Contact pressure is applied to the back of the zinc oxide paper to transfer the developed image to the surface of the bond paper. The sheets are then separated and the bond paper with the clear transferred image on the surface thereof represents the lithographic master plate. The image on the bond paper master sheet is then inked with a water based Sheaffer Skrip washable blue ink by means of a rubber blade and the final print made by contacting the master plate with a final copy sheet. Images of good optical density and resolution are obtained.

EXAMPLE II The procedure of Example I is repeated excepting a xerographic plate comprising a film of amorphous selenium on an aluminum substrate is substituted for the zinc oxide paper. The printed images obtained are of better quality than those obtained in Example inasmuch as the resolution of the images is more definite.

EXAMPLE III The procedure of Example I is repeated excepting a xerographic plate comprising a zinc sulfide photoconductive binder layer on an aluminum substrate is substituted for the zinc oxide paper. The resolution of the images obtained is not as definite as in Example I.

EXAMPLE IV The procedure of Example I is repeated excepting a xerographic plate comprising a zinc cadmium sulfide photoconductive binder layer on an aluminum substrate is substituted for the zinc oxide paper. The resolution of the images obtained is comparable to that obtained in Example III.

EXAMPLE V The procedure of Example I is repeated excepting a xerographic plate comprising a cadmium selenide photoconductive-binder layer on an aluminum substrate is substituted for the Zinc oxide paper. The results obtained are comparable to those in Example II.

EXAMPLE VI The procedure of Example I is repeated excepting a xerographic plate comprising a cadmium sulfide photoconductive binder layer on an aluminum substrate is substituted for the zinc oxide paper. The results obtained are comparable to those of Example III.

EXAMPLE VII The procedure of Example I is repeated excepting a xerographic plate comprising a polyvinyl carbazole photo conductive layer on an aluminum substrate is substituted for the zinc oxide paper. The quality of the images obtained are comparable to those of Example II.

EXAMPLE VIII The procedure in Example I is repeated except that the developed latent image is transferred to a polyethylene sheet instead of bond paper. During this procedure the coating of the master with a hydrophobic hydrocarbon as in Example I is eliminated. The quality of the images obtained when using a polyethylene material as the master substrate are comparable to those obtained in Example 1. However, it apppears that the life of the image is longer when applied to a paper substrate.

EXAMPLE IX The procedure of Example I is repeated except that the developed latent image is transferred to a polypropylene sheet instead of bond paper. During this procedure the coating of the master with a hydrophobic hydrocarbon as in Example I is eliminated. Again, as in Example 8, the image appears to be more permanent when transferred to a paper substrate.

EXAMPLE X EXAMPLE XI The procedure of Example I is repeated excepting a xerographic plate comprising a film of amorphous selenium on an aluminum substrate is substituted for the zinc oxide paper. Also, the developed latent image is transferred to a polypropylene sheet instead of the bond paper.

During this procedure a coating of the master with a hydrophobic hydrocarbon as in Example I is eliminated. As in Example X, a resultant image is obtained which is of a high quality as explained in Example II. However, the life of the image on the polypropylene is not as long as that of the image on the bond paper.

EXAMPLE XII The procedure of Example I is repeated excepting a xerographic plate comprising a polyvinyl carbazole photoconductive layer on an aluminum substrate is substituted for the zinc oxide paper. Also, the developed latent image is transferred to a polyethylene sheet instead of bond paper. During this procedure a coating of the master with a hydrophobic hydrocarbon as in Example I is eliminated. Results obtained are similar to those obtained in Example X.

EXAMPLE XIII Procedure of Example I is repeated excepting a xerographic plate comprising a polyvinyl carbazole photoconductive layer on an aluminum substrate is substituted for the zinc oxide paper. Also, the developed latent image is transferred to a polypropylene sheet instead of the bond paper. During this procedure the coating of the master with a hydrophobic hydrocarbon as in Example I is eliminated. Results obtained are similar to those obtained in Example XI.

Although the present examples are very specific in terms of conditions and materials used, any of the above listed typical materials may be substituted when suitable in the above examples with similar results. In addition to the steps used to prepare the lithographic master of the present invention, other steps or modifications may be used if desirable. In addition, other materials may be incorporated in the developer, inks, paper, or xerographic plate which will enhance, synergize or otherwise desirably afiect the properties of these materials for the present use. For example, in the cases where it is expedient to have a particularly high mechanical resistance of the image, the development solution can contain thickening or adhesive agents such as gum arabic, gum tragacanth, gum karaya, gum guar, agar-agar, and dextrines without disadvantages as regards to the quality of the developed image. The properties of the aqueous developer can be modified by addition of alcohols such as glycols and glycerols, or polyethylene oxides.

Anyone skilled in the art will have other other modifications occur to him based on the teaching of the present invention. These modifications are intended to be encompassed within the scope of this invention.

What is claimed is:

1. A process for preparing a lithographic master from a xerographic plate, said process comprising charging said xerographic plate, selectively exposing said charged plate to a light source so as to produce threon an electrostatic latent image, applying to said exposed surface an aqueous solution of a hydrophilic, polarity, insensitive developer in such a manner that said electrostatic latent image retains said developer, placing the imaged surface of said xerographic plate in face-to-face contact with a hydrophilic base, coating the back of said base with a liquid, water immisible hydrocarbon until said base is hydrophobic, applying pressure to the back of said xerographic plate suflicient to effect transfer of the developed image from said xerographic plate to said base said trafisferred image being hydrophilic and the non-imaged background hydrophobic, and separating said base from said xerographic plate to form said lithographic master.

2. The process as described in claim 1 wherein said xerographic plate comprises zinc oxide, and said polarity insensitive developer comprises an ammonium salt of a carboxy polymethylene.

3. A method of making multiple copies from a Xerographic image which comprises:

(a) forming an electrostatic latent image on the surface of a xerographic plate;

(b) applying to said surface a hydrophilic, aqueous, polarity insensitive developer in such a manner that the developer is distributed thereon conforming to said latent image in an imagewise configuration;

(c) placing the imaged surface of said xerographic plate in face-to-face contact with a hydrophilic base;

((1) coating the back of said base with a liquid, Water emissible hydrocarbon until said base is hydrophobic;

(e) applying contact pressure to the back of said xerographic plate sufficient to effect transfer of the developed image from said xerographic plate to said base, said transfer image being hydrophilic and the non-image background areas hydrophobic;

(f) separating said base from said Xerographic plate to form a lithographic master;

(g) contacting the image surface of said lithographic master with a water based ink said ink conforming to said transferred image;

(h) contacting said inked surface with a copy sheet 10 in such a manner that the ink image is transferred to said copy sheet to produce a final print; (i) repeating steps (g) and (h) until the desired copies are produced.

References Cited UNITED STATES PATENTS 1,669,416 5/1928 Huebner 101149.2 2,297,691 10/1942 Carlson 10l-149.2 XR 3,037,861 6/1962 Hoeql et al.

3,096,260 7/1963 Nail 10ll49.2 X 3,104,169 7/1963 Metcalf et al. 101-1492 X 3,245,381 4/1966 Brenneisen et al.

3,285,741 11/1966 Gesierich et al. 961

DAVID KLEIN, Primary Examiner U.S. C1. X.R.

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