US3374094A - Lithographic plate made from an n-vinyl-amine and an organic halogen compound dispersed in an hydrophilic colloid - Google Patents

Description

United States Patent 3,374,094 LITHOGRAPHIC PLATE MADE FROM AN N-VINYL-AMINE AND AN ORGANIC HALO- GEN COMPOUND DISPERSED liN AN HY- DROPHILHI COLLOID Eugene Wainer, Shaker Heights, and Harry L. Fichter,

Jr., Lakewood, Ohio, assignors to Horizons Incorporated, a corporation of New Jersey No Drawing. Filed July 19, 1965, Ser. No. 473,238 12 Claims. (Cl. 9633) This invention relates to printing plates useful in planographic and lithographic printing and to the manufacture of such articles by a completely dry process utilizing compositions which are sensitive to light. More particularly, the invention relates to the preparation of planographic or lithographic plates in which a suitable support is impregnated or coated with a photosensitive mixture as hereinafter described, then exposed so as to produce a relief image, whereby a plate is produced in which the background is completely'hydrophilic in nature and the developed image is oleophilic and hydrophobic.

Since presently known processes for making photographs on lithographic or planographic masters requires swabbing the exposed plate with a desensitizing solution followed by swabbing with a colored lacquer to make the image visible and to provide strength for the fragile image to insure long press runsin other words, to give more impressions per plate, it will be readily apparent that a durable printing plate which does not require such swabbing would represent an advance in this art.

A number of United States patents issued to Eugene Wainer and others, describe photosensitive compositions comprising at least the following constituents:

(1) An N-vinyl amine,

(2) An organic halogen compound, and

(3) Various optional ingredients, such as a synthetic resin or other film forming material in which the two essential constituents are dispersed or supported.

These patents include the following:

United States Patent 3,042,517, issued July 3, United States Patent 3,042,518, issued July 3, United States Patent 3,042,519, issued July 3, United States Patent 3,046,125, issued July 24, 1962; United States Patent 3,056,673, issued October 2, 1962; United States Patent 3,147,117, issued September 1, 1964.

In addition various improvements thereover are described in copending United States patent applications Serial No. 445,273, filed April 2, 1965, claiming the addition of Group V aryl compounds such as triphenylstibine, -arsine, -phosphine or -bismuthine to such compositions, and Serial No. 398,097, filed September 21,

1964, claiming the use of mercaptobenzothiazole in such compositions. The disclosures in these applications are incorporated herein by reference.

As noted above, the use of N-vinyl compounds for preparing photopolymer images with halogen containing hydrocarbons as the activating source of free radicals is extensively described in the above noted patents of Eugene Wainer. These patents describe the use of compounds such as N-vinyl carbazole and carbon tetrabromide used with plastic binders dissolved in organic solvents and coated on a suitable support such as paper, glass or plastic films. The plastic binders described in the patents noted are completely hydrophobic in character and will not tolerate water in any form. With such compositions the image which is developed out by heating will accept ink-both in the background and the image areas when placed on a press. The resulting completely inked master is therefore totally unsuited to use as a planographic or lithographic master. The present invention resides in the use of hydrophilic colloidal binders for 3 ,3 74,094 Patented Mar. 19, 1968 compositions of the type already known whereby they can be coated on paper or metal supports to give uniform coatings without separation of the aqueous or the oleo phase.

When modified in this manner, i.e. by the inclusion of a hydrophilic binder in the photosensitive compositions the image formed on exposure to light followed by mild heating for development and fixing is receptive to greasy lithographic inks and repels the aqueous fountain fluid. The background material is completely hydrophilic in nature and therefore is Wetted by the aqueous fountain fluid and repels the greasy ink leaving a clean white background. The oleophilic image which picks up the ink, transfers the ink in the pattern of the image to a rubber blanket which in turn transfers it to the paper feed and repeated copies are printed by this offset procedure.

The invention provides a planogra-phic or lithographic master with a photographic image based on the photopolymerization of N-vinyl compounds using halogenated hydrocarbon activators, all active constituents being coated on paper in a hydrophilic binder. The resulting coating is exposed to visible light through a photographic negative, mask, stencil or other similar subject. The exposed print contains a latent image which is made visible by mild heating. During the course of heating the unreacted volatile activator is driven off and the print becomes fixed as development occurs. The developed and fixed print is then mounted on an off-set press as a lithographic master and copies printed from it. Both halftone and line negatives may be used in preparing these masters. The process is completely dry. No solutions are needed to produce the image or to prepare the desired printing plate.

One object of this invention therefore is to prepare lithographic masters with photographic images without any need whatever for wet processing such as desensitizing or lacquering. After exposure followed by heat development the master contains a relief image which is immediately ready for the press.

Other objects will become apparent from the description which follows in which preferred embodiments are disclosed by way of illustration which are not intended to be construed as limiting the invention.

In general the ingredients of this invention are brought together using the following technique: the N-vinyl carbazole or other suitable N-vinyl amine, and the CBr or other halogen containing activators described in the patents listed above, are dissolved in a suitable solvent such as cyclohexanone or toluene. The resulting solution is added to a water solution of the hydrophilic colloidal binder material preferably containing a suitable wetting or dispersing agent and the mixture is placed in a Waring blender and blended until a stable emulsion is formed. Emulsions made in the manner described have been found to be stable through weeks of standing without any sign of separation of the oil and water phases. In addition to the above-mentioned ingredients, the solution added to the colloidal binder should contain a sulfurcontaining organic compound such as mercaptobenzothiazole for improvement of the photographic speed of the coated emulsion. The solution should also include a triphenyl derivative of phosphorus, arsenic, antimony or bismuth. The presence of these triphenyl compounds plus suflicient heating after exposure to insure development insures a clean white 'unfogged background, but a more important reason for the incorporation of the triphenyl Group V compounds in the compositions is to provide a slight relief image after the heat treatment.

Although paper is one preferred substrate to which the photosensitive composition is applied, another and a particularly preferred plate material is aluminum having 'at least one surface anodized so that it bears a porous absorbent oxide film into which the photosensitive composition can be readily impregnated.

Having described the composition of this invention in general terms the following is a more detailed description of the specific ingredients employed and the manner in which they may be compounded. For simplicity, representative members of each group of ingredients are listed by way of illustration in the tables which follow. It will be understood that other similar materials may be used without departing from the intended scope of the invention. The hydrophilic colloids which are suitable for use in this invention may be any of the natural colloids, such as starches, gums, polysaccharides and protein material such as casein or they may be synthetic materials such as polyvinyl alcohol, methyl vinyl ether/ 'maleic anhydride copolymers, carboxymethyl cellulose and other synthetic derivative of cellulose. Table I lists the hydrophilic colloids suitable for this invention and gives a recommended range of concentration for the colloid in water.

Table I.-Hydrophilic colloids Recommended conc.

Table H.-Suitable solvents for dissolving photosensitive elements for dispersion in the protection colloid Solvent: Boiling point, C. Benzene 80.1 Cyclohexane 80 Cyclohexanone 155 Toluene 111 Xylene 144 Table III Triphenylphosphine Triphenylstibine Triphenylbismuthine Triphenylarsine Table IV Mercaptobenzothiazole (Mencaptobenzoic acid Phenylmercaptotetrazole Ethyl mercaptotetrazole Methyl mereaptotetrazole All of the materials listed in Table I were found to be useful as protective hydrophilic colloids in the practice of this invention. Some, however, gave longer and some gave shorter press runs but all exhibited the desired property necessary to this invention, that is, there was an effective rejection of ink in the non-image background and an acceptance of ink in the hydrophobic image area. The range of composition listed in the table are the extremes of a working range. Best results were observed when the concentration of colloidal binder was about midway between the extremes listed.

In order to provide a practical stability to the emulsion with the above hydrophilic colloids, it is necessary to include an emulsifying or wetting agent in the formulation. Hundreds of emulsifying agents are available commercially and many of them have been successfully employed in the preparation of emulsions for the practice of this invention, including the following wetting agents: the non-ionic agent Triton X-100, an alkyl polyether alcohol from the Rohm & Haas Company, the anionic wetting agent Tergitol No. 7 which is sodium heptadecyl sulfate from the Union Carbide Corporation or Nacconol, an alkyl aryl sodium sulfonate from the National Aniline Div. of the Allied Chemical and Dye Corporation or Nekal, a sodium alkyl naphthalene sulfonate from the General Aniline and Film Corporation.

The recommended concentration of emulsifying agent is 1 to 3 percent of the total volume of liquid in the final emulsion.

Suitable solvents for dissolving the N-vinyl carbazole and the halogen containing activators 'are listed in Table II. Boiling point of the solvent is an important consideration in its choice. If the boiling point of the solvent is too low and its volatility is too high it will flash off from the drying surface of the coating leaving an irregular surface. If on the other hand the boiling point of the solvent is too high and its volatility too low, the solvent will never evaporate from the coated mixture and a sticky, gummy layer remains on the surface. The solvents listed in the table have been found to give excellent drying conditions resulting in smooth, even, non-sticky coatings. Water may be added to the final emulsion so as to control its viscosity and make it more easily coated on the receiving sheet. This may be controlled to some extent by using a more dilute solution of the hydrophilic colloidal binder but if the viscosity of the colloidal binder is too low, the emulsion will not remain stable and separation will occur. It has been found preferable to use a higher concentration of binder and to dilute after the emulsion has been prepared.

It will be understood that all mixing, coating and drying of the photosensitive mixture is carried out under red safelight conditions.

The following examples are indicative of the method of practicing this invention, it being understood that the invention is illustrated by but not limited by the following examples:

EXAMPLE I Ten cc. of a 7% aqueous solution of polyvinyl alcohol (Elvanol grade 72-60) was added to a Waring Blendor, then one cc. of Triton X- (Rohm & Haas) and ten cc. of water were added. A solution consisting of 10 cc. of cyclohexanone, 160 mg. of mercaptobenzothiazole, 320 mg. of triphenylstibine, 6.4 grams carbontetrabromide, and 8 grams of N-vinyl carbazole was prepared and after complete solution was attained the cyclohexanone solution was added to the Elvanol solution in the Waring Blendor. The contents were blended together thoroughly for 60 seconds. The resulting emulsion was coated on gr. baryta paper at a coating thickness of .0015-inch wet. The dried coating was exposed through a photographic negative to a photoflood lamp, exposure time being 15 to 60 seconds depending on the quality of the negative and the distance from the lamp. The exposed paper Was heated carefully under an infrared lamp for a period of 30 to 90 seconds, depending upon the length of exposure to the photoflood lamp and the distance from the heating lamp. The infrared heating developed and simultaneously fixed the exposed master. After the infrared heating the sample was mounted on a press such as a Ditto or an Addressograph-Multigraph duplicating offset press and impressions made in the manner normally prescribed for the use of the particular machine. Excellent reproductions of the master were made and no sign of deterioration of the master was observed after 500 copies.

EXAMPLE II In this example the polyvinyl alcohol used in Example I was replaced with poly(methyl vinyl ether-maleic anhydride). A aqueous solution was used, and similar results were obtained.

EXAMPLE III Identical to Example I except that half of hydrophilic resin was polyvinyl alcohol and half was the poly (methyl vinyl ether-maleic anhydride). The master was similar to that obtained in Example I.

EXAMPLE IV The same as Example I except a 5% aqueous solution of polyacrylamide was used in place of polyvinyl alcohol. The polyacrylamide used was sold under the trade name Cyanamer Grade P26 by the American Cyanamid Corporation.

EXAMPLE V The same as Example I except polyvinyl pyrollidone was used in place of polyvinyl alcohol. Polyvinyl pyrollidone is a product of the General Aniline and Film Corporation; Grade K30 was used in 5% concentration.

EXAMPLE VI The same as Example I except that 2.5% aqueous solution of methyl cellulose (Methocel, Dow Chemical Company) was used in place of polyvinyl alcohol.

EXAMPLE VII The same as Example I except a 20% aqueous solution of gum arabic is used in place of polyvinyl alcohol.

The printing plates produced in Examples IV through VII were found to be suitable for planographic printing and lithographic printing.

As in the compositions described in the Wainer patents the organic halogen compound is one represented by the general formula A-C-X wherein each X is a chlorine or bromine atom and A represents either H, alkyl, haloalkyl, aroyl, aryl, substituted aryl, or bromine or chlorine atom.

The relative proportions of N-vinyl amine and organic halogen compound is between 10 and 200 parts of N-vinyl amine for each 100 parts of organic halogen compound and the amount of hydrophilic binder relative to the remainder of the composition is in the range of 10 to 100 parts of binder per 100 parts of the remainder of the composition.

The amount of Group V aryl compound necessary to produce the desired relief image is between about .625 and 6.25 parts per 100 parts by weight of N-vinylcarbazole or other N-vinyl amine.

EXAMPLE VIII The composition of this example was prepared under a red safelight as in Example 1. Again, under red safelight conditions the coated photosensitive material is calendered at high pressure in which the pressure applied by the rolls is in the range of 10,000 lbs. per square inch at the nip up to 25,000 lbs. per square inch, the rolls used being polished bright chrome plated. Under these conditions at very bright, glossy surface is obtained. Exposure time under the conditions described in Example I are reduced by a factor of 5, namely to a range of 3 to 12 seconds as against the 15 to 60 seconds presently cited in Example I. The advantage of this calendering operation other than photographic speed is to increase the life of a master with respect to high quality reproduction by at least a factor of 5 and generally up to a factor of 10.

EXAMPLE IX Paperboard stock is coated with a mixture of 100 parts of papermakers clay, 18 parts by weight of a 50 percent polyvinylacetate emulsion in water, and 2 parts of isolated soya protein which has been treated with 12 percent by weight of ammonium hydroxide, 20 parts by weight of water are added to the mixture which is then coated on paperboard stock with a doctor blade, dried at C., and then calendered on polished rolls which leaves a highly glossy surface. A solution consisting of 10 cc.s of cyclo' hexanone, 160 milligrams of mercaptobenzothiazole, 320 milligrams of triphenylstibine, 6.4 grams of carbon tetrabromide, 8 grams of N-vinylcarbazole, and 1 cc. of Triton X-l00 (Rohm & Haas) was prepared and applied to the surface of the calendered stock by roll coating yielding a wet thickness of approximately 0.002" in thickness. The photosensitive solution was prepared under red safelight conditions and the application to the base stock and subsequent drying at 50 C. also carried out under red safelight conditions. After drying the stock was again calendered and again a long-life plate was obtained Whose photographic speed was roughly 5 times that of a comparable emulsion type of coating. The amount of isolated soya protein utilized in the baseboard may be varied from 1 part to 10 parts per parts of papermakers clay and the amount of polyvinylacetate emulsion may be varied from 10 parts to 30 parts per 100 parts of papermakers clay. Casein or polyacrylamide may be substituted pound for pound for the isolated soya protein.

tion of polyacrylamide in water at 0.003" thickness, al

lowed to dry and calendered. Under darkroom safelight conditions this surface is then coated. with a solution consisting of 25 cc.s of benzene, milligrams of mercaptobenzothiazole, 320 milligrams of triphenylstibine, 6.4 grams of carbon tetrabromide, and 8 grams of N- vinylcarbazole, and 1 cc. of Triton X-lOO (Rohm & Haas), the coating being applied by dip-coating methods to achieve a wet film thickness of 0.0015". After drying under safelight conditions the composite is again calendered under equivalent safelight conditions after which the photosensitive material is ready for exposure, heat development and use as a lithographic master.

The calendering variation thus provides the possibility for combining an otherwise hydrophobic composition with a hydrophilic base so as to yield overall hydrophilic characteristics without the use of emulsion technology until the photosensitive material has been properly exposed and heat developed.

EXAMPLE XI The composition of Example I was applied to the surface of an anodized aluminum plate and a satisfactory lithographic plate resulted from the exposure and development as described in Example I.

Other substrates which can be used with the previously described emulsions include paper coated with polypropylene, a polyethylene terephthalate and polyester subbed with polyvinyl butyrate.

Example IX illustrates the use of a hydrophobic binder in this invention. Polyvinylacetate dissolved wholly in an organic solvent and dried to a film is hydrophobic in character. However, if the polyvinylacetate is prepared as a water emulsion in the presence of an emulsifying agent and further protected by means of a small amount of a protective colloid such as a soya protein or casein then the polyvinylacetate composition which develops from such an emulsion is hydrophilic in character. It appears that particles of polyvinylacetate in the emulsion are coated, in all probability, either with hydrogen ions or with hydroxyl ions which impart the hydrophilic characteristics. The difference as to whether polyvinylacetate is laid down in an organic solution or from a protected colloid type of water emulsion is quite striking.

We claim:

1. A dry photosensitive plate useful in the preparation of a photolithographic master comprising at least one of each of the following constituents:

(1) an N-vinylamine;

(2) a halogen containing compound in which at least three halogen atoms are linked to a single carbon atom, each of said halogen atoms being selected from the group consisting of Br and Cl;

(3) a triaryl compound of an element selected from the group consisting of P, Bi, Sb and As;

said constituents being dispersed in and supported by a hydrophilic binder containing a minor amount of an emulsifying agent.

2. The plate of claim 1 wherein the composition includes (4) at least one sulfur containing organic compound in which the sulfur is linked directly to a carbon atom.

3. The plate of claim 1 supported on a flexible substrate.

4. A photosensitive printing plate useful in planographic and lithographic photolithography having image and ink receptive areas comprising an N-vinylamine and a halogen containing hydrocarbon, the non-image and ink repelling areas having been rendered hydrophilic by the use of a hydrophilic binder for said N-vinylamine and said halogen containing hydrocarbon and said image areas having been rendered relieved from the surface of said plate by incorporation of a Group V triaryl compound of an element selected from the group consisting of P, Bi, Sb and As in said areas, the plate being prepared for use by imagewise exposure to light followed by heat development.

5. A dry printing plate useful in planographic and lithographic printing comprising the photochemical reaction products available from an imagewise exposure of a mixture of an N-vinylamine, a halogen containing hydrocarbon, a Group V triaryl compound, a sulphur containing organic compound in which the sulphur is linked directly to a carbon atom, dispersed through the medium of an emulsifying agent in a hydrophilic binder, in which the image and ink receptive areas are produced in relief as a consequence of exposure of the plate to light on an imagewise basis followed by blanket development with infrared light and heat, and the areas which have not been previously exposed to light are ink repellent, the distinction between image and ink receptive areas and non-image and ink repellent areas having been made permanent by the infrared and heat development step.

6. A dry printing plate useful in planographic and lithographic printing comprising the photochemical reaction products available from an imagewise exposure of a mixture of an N-vinylamine, a halogen containing hydrocarbon, a Group V triaryl compound, dispersed through the medium of an emulsifying agent in a hydrophilic binder, in which the image and ink receptive areas are produced in relief as a consequence of exposure of the plate to light on an imagewise basis followed by blanket development with infrared light and heat, and the areas which have not been previously exposed to light are ink repellent, the distinction between image and ink receptive areas and non-image and ink repellent areas having been made permanent by the infrared and heat development step.

'7. A method of preparing a photolithographic plate which comprises:

(1) applying a liquid composition to a support under darkroom conditions, said composition comprising at least one of each of the following constituents:

(a) an N-vinylamine (b) an organic halogen compound in which at least three halogen atoms are linked to a single carbon atom, each of said halogen atoms being selected from the group consisting of Br and Cl (c) a triaryl compound of an element selected from the group consisting of P, Bi, Sb and As (d) a hydrophilic film forming binder (e) a volatile liquid vehicle for said constituents and (2) drying the resulting coated article under darkroom conditions to produce a photosensitive plate.

8. The method of claim 7 including in addition the incorporation of at least one sulfur containing organic compound in which the sulfur is linked directly to a carbon atom in said composition.

9. The method of claim 7 wherein the liquid composition includes in addition a minor amount of emulsifying agent and the composition is emulsified before it is applied to the support.

10. The method of claim 9 in which the plate is calendered after the composition is dried but before imagewise exposure.

11. A method of photolithography which comprises preparing a dry photosensitive plate by the method of claim 7 and then photographically exposing said plate followed by exposing the entire surface of said plate to infrared and heat, thereby producing a relief image thereon and rendering said image permanent.

12. A method of photolithography which comprises preparing a dry photosensitive plate by the method of claim 10 and then photographically exposing said plate followed by exposing the entire surface of said plate to infrared and heat, thereby producing a relief image thereon and rendering said image permanent.

References Cited UNITED STATES PATENTS 2,882,262 4/1959 Smith et al. 96-115 X 3,046,125 7/1962 Wainer 96-35 3,065,160 11/1962 Levinos et al 96l15 NORMAN G. TORCHIN, Primary Examiner.

R. E. MARTIN, Assistant Examiner.

Claims (1)

1. 7. A METHOD OF PREPARING A PHOTOLIGHOGRAPHIC PLATE WHICH COMPRISES: (1) APPLYING A LIQUID COMPOSITION TO A SUPPORT UNDER DARKROOM CONDITIONS, SAID COMPOSITION COMPRISING AT LEAST ONE OF EACH OF THE FOLLOWING CONSTITUENTS: (A) AN N-VINYLAMINE (B)AN ORGANIC HALOGEN COMPOUND IN WHICH AT LEAST THREE HALOGEN ATOMS ARE LINKED TO A SINGEL CARBON ATOM, EACH OF SAID HALOGEN ATOMS BEING SELECTED FROM THE GROUP CONSISTING OF BR AND CL (C) A TRIARYL COMPOUND OF AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF P, BI, SB AND AS (D) A HYDROPHILIC FILM FORMING BINDER (E) A VOLATILE LIQUID FOR SAID CONSTITUTENS AND (2)DRYING THE RESULTING COATED ARTICLE UNDER DARKROOM CONDITIONS TO PRODUCE A PHOTOSENSITIVE PLATE.