US3907562A

US3907562A - Process for preparing waterless lithographic masters

Info

Publication number: US3907562A
Application number: US415842A
Authority: US
Inventors: Richard G Crystal
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1973-11-14
Filing date: 1973-11-14
Publication date: 1975-09-23
Anticipated expiration: 1992-09-23

Abstract

A novel method of preparing a waterless lithographic master and a method of printing therefrom are provided. To prepare the printing master, a suitable substrate which can be photoconductive or non-photoconductive is imaged with a hydrophobic particulate image pattern and the image fused to the substrate. The imaged substrate is then coated with an aqueous silicone which does not wet the hydrophobic image pattern. The silicone is then heated to selectively provide ink-receptive image areas and ink-releasing non-image areas.

Description

United States Patent 1191 Crystal Sept. 23, 1975 [54] PROCESS FOR PREPARING WATERLESS 3,632,375 1/1972 Gipe 96/33 X LITHOGRAPHIC' MASTERS 3,640,712 2/1972 Field et a1... 96/33 UX 3,677,178 7/1972 Gipe 96/33 X Inventor: Richard y as, Tex. 3,728,123 4/1973 Gipe 96/33 x i 3,772,016 11/1973 Anderson et al. 96/33 X [73] Assgnee' Cmpmamnastamfmd, 3,775,115 11/1973 Sorkin et al. 96/33 Conn.

[22] Filed: Nov. 14, 1973 Primary Examiner-Norman G. Torchin Assistant ExaminerJohn R. Miller [.21] Appl' 415842 Attorney, Agent, or Firm-James .1. Ralabate; James P. OSullivan; Donald M. MacKay [52] US. Cl 96/l.8; 96/1 R; 96/33;

101/465 [57] ABSTRACT 1 [51] Int. Cl. G03G 13/00 A novel method of preparing a waterless lithographic [58] Field of Search 96/1 R, 1.8, 33; lOl/465 master and a method of printing therefrom are vided. To prepare the printing master, a suitable sub- [561 References C'ted strate which can be photoconductive or non- UNITED STATES PATENTS photoconductive is imaged with a hydrophobic partic- 3,088,402 5/1963 Newman 96/1 R "late image Pattern and the image fused to the 3,230,081 1/1966 Tomanek et al..... 96/1 R strate. The imaged substrate is then coated with an 3,245,784 4/1966 Stricklin 96/ 1.8 aqueous silicone which does not wet the hydrophobic 3,455,240 7/1969 Martel et al- R X image pattern. The silicone is then heated to selecg tively provide ink-receptive image areas and inkoggett 3,607,255 9/1971 Back 96/1 R releasmg mage areas 3,624,227 11/1971 Hwang 96/33 12 Claims, No Drawings PROCESS FOR PREPARING WATERLESS LITHOGRAPHIC MASTERS BACKGROUND OF THE iNvENT oN Q,

It has recently been discovered that the need for a fountain solution on a printing press can be obviated if the master is coated in the nonimage areas'with a silicone elastomer which is ink releasing. A number of difficulties have been encountered in electrophotographic imaging of silicone elastomers. For example, by reason of their abhesive or nonadhesive character, it has been difficult to adhere toner particles to the silicone in order to provide an image pattern.

BRIEF DEscRiPTioNoF THE INVENTION It has now been discovered that the aforesaid defect can be obviated and printing masters having long image lives prepared. In addition. it has been found that the master can be imaged, so that the silicone elastomer does not adhere to the image, to provide inkreceptive image areas and ink releasing nonimage areas which are durable and long lasting.

More particularly the novel process comprises depositing a hydrophobic particulate image pattern on a suitable substrate, fusing said pattern to said substrate, coating said substrate with an aqueous silicone emulsion whereby the silicone does not wet the hydrophobic image pattern and heating said silicone to provide inkreceptive image areas and ink-repellent nonimage areas.

DETAILED DESCRIPTION OF THE lNVENTlOISl Substrates which can be employed to prepare the printing master are self-supporting materials to which the silicone and particulate image pattern can be adhered and which possess sufficient heat and mechanical stability to permit use under widely varying printing and handling conditions. and which are preferably ink accepting. Exemplary of suitable materials are paper; metals such as aluminum; and plastics such as polyester, polycarbonate, polysulfone, nylon and polyurethane, The substrate can be photoconductive or nonphotoconductive.

Photoconductive" as used herein means electrically photosensitive and conductive in response to activating electromagnetic radiation.

Typical photoconductive organic materials include substituted and unsubstituted organic pigments such as phthalocyanines, for example. copper phthalocyanine, beta form of metal-free phthalocyanine; tetrachlorophthalocyanine; and x-form of metal'free phthalocyanine; quinacridones, as, for example, 2,9-dimethyl quinacridone; 4,1 ldimethyl quinacridone; 3,10- dichloro-ol 3-dihydro-quinacridone; 2,9-dimethoxy- 6,13-dihydro-quinacridone and 2,4,9,l l-tetrachloroquinacridone; anthraqu inones such as l,5-bis-(betaphenylethylamino) anthraquinone: l,5-bis-( 3 methoxypropylaminoJ an thraquinone; 1.2.5 ,6-di- (Cf'-diphenyl)-thiazole-anthraquinone; HT-hydroxyphcnylmcthoxyamino) anthraquinone; triazines such as 2.4-diaminotriazine; 2,4-di( l -anthraquinonylamino-(H l "-pyrenyl)triazine; 2,4,6 tri-( l '-l ",1 pyrenyl )-triazine; azo compounds such as 2,4,6-tris (N' cthyl-paminophenylazo) phloroglucinol; l,3,5.7- tctrahydroxy-2,4,o,8-tetra (N-methyl-N-hydroxy-ethylp-amino-phenylazo) naphthalene; 1,3,5-trihydroxy- 2,4.6-tri (3 '-nitro-N-methyl-N-hydroxy-methyl-4 (ill aminophenylazo) benzene; metal salts and lakes of azo dyes such as calcium lake of 6-bromo-l (l-sulfo-2- naphthylazo)-2-naphthol; barium salt of 6-cyano-l l sulfo-Z-naphthylazo)-2-naphthol; calcium lake of l- (2-azonaphthalene-l"-sulfonic acid)-2-naphthol; calcium lake of l-(4'-ethyl-5-chloroazo-benzene-2- sulfonic acid)-2-hydroxy-3-naphthoic acid; and mixtures thereof.

Typical inorganic photoconductive compositions include cadmium sulfide, cadmium selenide, cadmium sulfo-selenide, zinc oxide, zinc sulfide, sulfur, selenium,

antimony sulfide, lead oxide, lead sulfide, arsenic sul- I fide, arsenic-selenium, and mixtures thereof.

- The photoconductive materials can be admixed with solid or liquid carriers and coated on a master substrate by the conventional methods as is well known to those skilled in the art. Typical solid carriers include sodium chloride, ammonium chloride, granular silicon, glass, silicon dioxide, steel and nickel. Typical liquid carriers include mineral oil, oleic acid,-peanut oil, kerosene, and trichloroethylene.

In addition the substrate can be a photoconductive polymer. Typical polymers include poly-N-vinyl carbazole (PVK),poly-l-vinyl pyrene (PVP), poly-9-vinyl anthracene, polyacenaphthalene, poly-9-(4-pentenyl)- carbazole, poly-9-(5-hexyl)-carbazole, polymethylene pyrene, polyl pyrenyl )-butadiene and N-substituted polymeric acrylic acid amides of pyrene. Also included are derivatives of such polymers including alkyl, nitro, amino, halogen, and hydroxy substituted polymers. Typical examples are poly-3-amino carbazole, 1,3- dibromo-poly-N-vinyl carbazole and 3,6-dibromo-poly- N-vinyl carbazole in particular derivatives of the for mula where X and Y are substituents and N is an integer. Also included are structural isomers of these polymers, typical examples include poly-N-vinyl carbazole, poly- 2-vinyl carbazole and poly-3-vinyl carbazole. Also included are co-polymers; typical examples are N-vinyl carbazole/methyl acrylate co-polymer and l-vinyl pyrene/butadiene ABA, and AB block polymers. Typical" nonpolymeric materials include carbazole, N-

ethylcarbazole, N-phenylcarbazole, pyrene, tetraphene, l-acetylpyrene, 2.3-benzochrysene, 6,7 benzopyrene, l-bromopyrene, l-ethylpyrene, l-

l,3,6,8-tetraphenylpyrene chrysene, fluorene,

rene, vinyl chloride and the like in combination with a pigment such as carbon black. Exemplary of suitable I of the silicone to print from the imaged substrate.

The particulate image pattern can be fused in the conventional manner such as in a Xerox heat or vapor fuser but preferably a vapor fuser is employed when using a catalyst which is thermally degradableorvolatile. i

The silicones which can be employed to coat the substrate are the non water curable aqueous gum emulsions, which can be thermally cured, and the aqueous silicone elastomer emulsions which coalesce upon heating, to provide ink releasing non-image areas.

Exemplary of suitable silicone gums are those having only methyl containing groups in the polymer chain such as polydimethylsiloxane; gums having both methyl and phenyl containing groups in the polymer chain as well as gums having both methyl and vinyl groups, methyl and fluorine groups, or methyl, phenyl and vinyl groups in the polymer chain.

Typical silicone gums which are of the thermally curable type suitable for use in the invention are SylGard No. 182, Syl Off No. 22 and-No. 23 manufactured by Dow Corning, Midland, Mich.; Y3557 and Y-3602 silicone gum available from Union Carbide Company,

New York, N.Y., as wellasNo. 4413 silicone and No.

4427 heat curable silicone gums available from General Electric Company, Waterford, N.Y. The Y-3557 and Y-3602 gums specifically have aminoalkane crosslinking sites in the polymer backbone which react with a diisocyanate crosslinking agent over a wide range of temperature and time to produce a durable, ink releasable elastomeric film. The aforesaid gums do not contain a catalyst.

The catalyst employed will depend on the type of gum employed as is well known to those skilled in the art. Suitable catalysts for the silicone gums of the conventional type which have been heretofore employed include the diaroyl peroxides such as dibenzoyl peroxide, di-p-chlorobenzoyl peroxide and bis-2,4.- dichlorobenzoyl peroxide can be employed. Other catalysts include the dialkyl peroxides such as di-t-butyl peroxide and 2,5-dimethyl-2,5-di-(t-butylperoxy)- hexane. Diaralkyl peroxides such as dicumyl peroxide, and alkyl aralkyl peroxides such as t-butyl cumyl peroxide can be employed, as well as blocked diisocyanates. The time and temperature relationship for crosslinking of all of these different types of gums is controlled by the chemistry of the crosslinking agent employed and a large choice of agents are available for this purpose. The present invention is therefore not intended to be limited with respect to either time or curing temperature of these materials, or the specific materials used to achieve crosslinking, although heating at temperature between about 50C'and 300C will typically cure or convert the silicone gum to an ink releasable silicone elastomer.

Other silicones which can be employed and which do not require catalysts are elastomers which coalesce upon heating to include organopolysiloxane copolymers including'diblock and triblock copolymers, multiblock copolymers'andgraft copolymers, segmented copolymers, polymer blends, and copolymer stabilized polymer blends. i v

lnk releasable copolymers comprise heterophase polymeric compositions consisting of an organopolysiloxane material and a nonsilicone polymeric material. Polymeric-materials which can be employed as a component of the heterophase polymeric composition and suitable for use in the present'invention include thermoplastic materials such as poly (a-methylstyrene), polystyrene, polyesters, polyamides, acrylic polymers, polyurethanes, and vinyl polymers.

While not limiting, preferred ink release properties of the heteroph ase polymeric compositions requires a ratio by weight of between about to 50 parts of the silicone phase to'5 to 50 parts of nonsilicone polymer, the resultant heterophase composition produces a flexible layer of good mechanical stability for printing as well as optimum ink release properties.

Particularly preferred copolymers having a silicone phase, include the diblock and multiblock copolymers of an organopolysiloxane with polystyrene and poly (o -methylstyrene). Copolymers of this type and meth ods for their preparation are described in I and EC Product Research,alul-Deve10pmemf, Volume 10, Page l0, (March, 1971) and Macromolecules, Volume 3, Page .1, (January-February, 1970), respectively. q j

The silicone gums are applied in a conventionalmanner, i.e., by solvent casting or dip coating of the substrate or similar techniques, after dissolution in organic solvents. Typical solvents include benzene, hexane, heptane,-.tetrahydrofuran, toluene .xylene, as well as other common aromatic and aliphatic solvents. Many silicones are available commercially as aqueous gum emulsions. Aqueous emulsions can be; made from the silicone elastomers by dissolving the elastomer in a suitable solvent such as one of the above, andv mixing with water and an emulsifier as exemplified by the procedure of Example I. I

Curing of the silicone should be done by heat so that the water from the emulsion is evaporated.

After the silico ne is heated to an elastomeric ink releasable condition, the master can bemounted on a lithographic printing press with the dampening system removed, whereupon during printing the particles from the particulate image pattern, may gradually be abraded or dissolved away. Thus it is preferred to employ a master with an ink accepting substrate, so that one can print from the image depressions, if the image particles are removed. Alternatively, when the substrate is ink accepting, the particulate image pattern can'be removed before mounting the master on the press by treating the master with a solvent such as acetone, benzene, toluene or other hydrocarbon in which theparticulate image material is soluble to reveal an ink accepting substrate.

Typical inks can be employed in the printing method of the invention which have been used in waterless lithographic printing from silicone masters. Typical inks include inks of the rubber or oleophilic type having the vehicle component for the ink pigments derived from various oleophilic materials such as aromatic and aliphatic hydrocarbons, drying-.oil varnishes lacquers, and solvent type resins.

The-master can be employed in the direct or offset printing-modes with the dampening system removed.

When the master is employed in the direct mode, the

substrate should be made of a resilient material such as a polyurethane.

The following examples will serve to illustrate the invention. All parts and percentages in said examples and elsewhere in the specification and claims'are by weight unless otherwise specified.

EXAMPLE I Employing a Xerox Model D Processor, a latent electrostatic test image containing line copy is formed and cascade developed with Xerox 3600 dry ink toner on a photosensitive zinc oxide coated printing master (Bruning 2000). The toner image is vapor cured by .placing the master in a Xerox vapor fuser for seven secondsemploying 'trichlorethylene. The master is then ;dipped in an aqueous emulsion to wet the nonimage areas. The emulsion is prepared by dissolving 95 parts of poly (dimethyl siloxane) gum (Dow Corning Silastic black lithographic ink and prints are made from this inked master. The ink is found to preferentially wet the toner image and good prints are obtained without the use of a dampening system.

EXAMPLE II A non-photoreceptive waterless lithographic master is prepared as follows. Employing a Xerox Model D Processor, a latent electrostatic test image containing line copy is formed and cascade developed with Xerox 3600 dry ink toner. The developed image is transferred from the photoconductive surface of the processor to a sheet of paper coated with a spray. The sheet with the developed image is contacted with a nonphotoconductive paper master stock and the developed image electrostatically transferred to the master stock. The toner image is vapor fused followed by application and curing of the silicone emulsion as in Example I. When mounted on a Davidson Printing Press with the dampening system removed. copies of good contrast are obtained employing Pope and Gray No. 2441 black lithographic ink.

Having described the present invention with reference to these specific embodiments, it is to be understood that numerous variations can be made without departing from the spirit of the invention and it isintended to include such reasonable variations and equivalents within the scope.

What is claimed is:

l. A process of preparing a waterless lithographic master comprising depositing a hydrophobic particulate image pattern on a suitable substrate, fusing said pattern to said substrate, coating said substrate. with a thermally curable but non-water curable aqueous silicone gum emulsion or an aqueous silicone elastomer emulsion and heating said silicone to selectively provide ink-receptive image areas and ink-repellent nonimage areas.

2. The process of claim 1 wherein the substrate is photoconductive.

3. The process of claim 1 wherein the substrate is non-photoconductive, the particulate image pattern is formed on a photoconductive surface and transferred to said substrate.

4. The process of claim- 1 wherein the particulate image is fused by solvent vapor.

5. The process of claim 1 wherein the particulate image pattern is fused by heat.

6. The process of claim 1 wherein the silicone is an aqueous gum emulsion.

7. The process of claim I wherein the substrate is ink accepting.

8. The process of claim 7 wherein the particulate image pattern is removed after curing of the silicone.

9. The process of claim 2 wherein the substrate is a zinc oxide coated paper.

10. The process of claim 1 wherein the substrate is selected from paper, aluminum, polyester, polycarbonate, polysulfone, nylon and polyurethane.

ll. The process of claim 1 wherein the substrate is paper.

12. A process of printing comprising depositing a hydrophobic particulate image pattern on a suitable substrate, fusing said pattern to said substrate, coating said substrate with a thermally curable but non-water curable aqueous silicone gum emulsion or an aqueous silicone elastomer emulsion and heating said silicone to selectively provide ink-repellent non-image areas and ink receptive image areas, applying ink to said inkreceptive image areas and contacting the inked master with an image-receiving surface to thereby transfer the inked image.

Claims

1. A PROCESS OF PREPARING A WATERLESS LITHOGRAPHIC MASTER COMPRISING DEPOSITING A HYDROPHOBIC PARTICULATE IMAGE PATTERN ON A SUITABLE SUBSTRATE, FUSING SAID PATTERN TO SAID SUBSTRATE, COATING SAID SUBSTRATE, WITH A THERMALLY CURABLE BUT NON-WATER CURABLE AQUEOUS SILICONE GUM EMULSION OR AN AQUEOUS SILICONE ELASTOMER EMULSION AND HEATING SAID SILICONE TO SELECTIVELY PROVIDE INK-RECEPTIVE IMAGE AREAS AND INK-REPELLENT NON-IMAGE AREAS.

2. The process of claim 1 wherein the substrate is photoconductive.

4. The process of claim 1 wherein the particulate image is fused by solvent vapor.

6. The process of claim 1 wherein the silicone is an aqueous gum emulsion.

7. The process of claim 1 wherein the substrate is ink accepting.

9. The process of claim 2 wherein the substrate is a zinc oxide coated paper.

11. The process of claim 1 wherein the substrate is paper.

12. A process of printing comprising depositing a hydrophobic particulate image pattern on a suitable substrate, fusing said pattern to said substrate, coating said substrate with a thermally curable but non-water curable aqueous silicone gum emulsion or an aqueous silicone elastomer emulsion and heating said silicone to selectively provide ink-repellent non-image areas and ink receptive image areas, applying ink to said ink-receptive image areas and contacting the inked master with an image-receiving surface to thereby transfer the inked image.