US3474719A - Offset printing plates - Google Patents

Description

United States Patent 3,474,719 OFFSET PRINTING PLATES Steven Levinos, Vestal, N.Y., assignor to GAF Corporation, New York, N.Y., a corporation of Delaware No Drawing. Continuation-impart of application Ser. No. 542,757, Apr. 15, 1966. This application July 5, 1966, Ser. No. 562,513

Int. Cl. G03c 1/52; G03f 7/10 US. Cl. 96-75 7 Claims ABSTRACT OF THE DISCLOSURE Light-sensitive material having on a metal base an anchoring layer of a thermoplastic alkali-soluble filmforming acrylic esteracrylic acid copolymer resin containing 1-20 mol percent acrylic acid and 8099 mol percent acrylic ester units, and an overlying light-sensitive layer containing a water-insoluble alkali resistant resin and a light-sensitive water-insoluble diazo oxide; and a process for making offset printing plates therewith by image-wise exposure to light and development with a liquid polyhydroxy compound or mixture of the latter with an alkaline compound whereby the light struck areas of the diazo oxide layer and the overlying anchoring layer are removed.

This application is a continuation-in-part of copending U.S. application Ser. No. 542,727 filed Apr. 15, 1966 (S. Levinos).

The present invention relates to pre-sensitized positive or negative working, offset printing plates derived from a metallic plate having a hydrophobic resinous layer sensitized with a diazonium compound, said resinous layer being capable of being rendered hydrophilic, after exposure of the plate, at the light-struck portions of the same and wherein said printing plate is provided with an adhesive intermediate, i.e., anchoring layer which serves to provide improved adhesion between the sensitized resinous layer and the metallic support and to the preparation and processing of such plates.

A vast amount of duplication and reproduction is required in modern business and industrial practice. In those applications which require the production of fewer than 30 copies from a single original, the diazotype process is ideal. This process, as is understood, involves the sensitization of a base with a light-sensitive diazonium compound, the exposure of the sensitive element under a pattern, and the treatment of the element with a base in the presence of a coupling component to produce an azodye in those portions where the sensitized element has not been struck by light. To a large degree, the success of this system can be attributed to the variety of originals capable of duplication without special preparations.

An increasing number of business systems and methods which require the production of several copies from a single original are based upon the diazotype process. The common denominator of these diazotype systems is the so-called translucent paper original which serves as the photoprinting master for the production of additional copies. Since these masters differ from ordinary printed,

3,474,719 Patented Oct. 28, 1969 typed, or written originals only in the higher translucency of the paper base stock, it is clear that, in addition to being highly economical to prepare, they are unexcelled in their over-all versatility and convenience with special reference to ease of adding, deleting, or changing information on the master. As a matter of fact, matter appearing on paper of relatively high opacity is successfully reproduced by diazotype since the contrast of the diazo process is so high.

Reproduction based on the photocopying of translucent originals by the diazotype process has thus proved to be a most convenient and economical solution to duplicating problems, provided the number of copies required is not too great. However, in a considerable proportion of the originals encountered, more than 30 copies are required and the reproduction processes requiring the production of a special master, in spite of their many disadvantages, become attractive because they are capable of producing copies at much greater speeds than with diazotype, once the special master has been prepared.

The offset printing method is especially interesting since the copies prepared using the offset press possess several advantages over competitive processes. Thus, the image produced by the offset press is composed of a permanent carbon or other pigment in a suitable carrier material while the image in a diazotype or spirit reproduction is composed of dye which in time may fade. In a diazotype print, the non-image areas contain photo-decomposition products which are prone to cause a yellow discoloration, especially if the print be exposed to strong light. In addition, stability against premature color formation in diazotype papers is brought about through the use of a heavy load of acid in the sensitive layer and some loss of strength of the paper may occur on aging. Finally, the quality of the printing produced by the offset press is outstanding. On the other hand, the use of the offset press has heretofore involved either the manual recopying of an original onto a so-called direct image master plate or the use of expensive, light-sensitive master plates either negative-working or positive-working. In the type of duplicating application in which the dizaotype process has proved so useful, the preparation of master plates using a negative-working photosensitive ofiset plate involves several time-consuming operations and expensive photographic equipment which have rendered the use of these plates in conjunction with the offset press impractical and decidedly overly expensive for the duplicating field. Hence, much effort has been directed toward the development of a direct-positive, photo-offset plate which would allow the translucent original of the diazotype process to also serve as the original in applications requiring more copies than the diazotype process can economically produce.

Recently introduced, positive-working metal offset plates have proved to be of considerable interest in the socalled legitimate graphic arts field, where the requirements of exceptionally high printing quality, absolute dimensional stability and long runs justify the use of a necessarily expensive metal base olfset plate. However, the relatively low photographic contrast of these plates and the consequent critical nature of the exposure step make it difficult to obtain acceptable copy from the average translucent original of the type discussed above. Due basically to their inadequate contrast and their high cost, these metal based plates have failed to fill the need for a lowcost, positive-working, offset plate with working properties suited to the needs of the duplicating field.

The problems associated with the provision of metal base printing plates capable of yielding high quality reproduction -at a minimum of cost trace their origin to a plurality of factors. Perhaps the paramount source of difficulty relates to the fact that the adhesion of the sensitized coating to the surface of the metal plate, whether pre-treated or untreated is most unsatisfactory. Thus, in many cases with printing plates of the positive-working type, the unexposed areas of the sensitized coating do not possess the requisite adhesion to the metal plate surface and tend to separate therefrom, such a tendency becoming particularly manifest during the development operations, i.e., those instances wherein the plate is subjected to continued and prolonged immersion in the solvent media. In other cases, considerable difficulty is encountered in removing the exposed areas of the sensitized coating during the wash-out operation.

In an attempt to overcome or otherwise mitigate the aforementioned and related problems, the art has resorted to a wide variety of remedial techniques which, in the main, are based upon the utilization of anchor layers, i.e., adhesion layers, situated intermediate the metal base plate and the sensitized overcoating. Although such techniques have met with some degree of success, there nevertheless remains considerable room for improvement. For example, the adhesive layers heretofore promulgated in this regard are usually of such a nature as to require added solvent treating operations in order to assure their removal from the metal base, In addition, the degree of adhesion provided by such adhesive inter-layers has been found to substantially weaken under the effects of the solvent treatments. As is well known, the production of printing plates based upon the use of light-sensitive diazo oxides has enjoyed a considerable measure of commercial exploitation. Such methods are extensively described in the literature both patent and otherwise. The industrial importance of diazo oxide printing plates has quite naturally made resolution of the foregoing problems particularly critical in this area.

In accordance with the discovery forming the basis of the present invention, it has been ascertained that these disadvantages can be overcome and pro-sensitized coatings based upon the use of light-sensitive diazo oxides having excellent stability and adhesion to metal plates may be obtained by the use of a sensitized layer comprising a light-sensitive water-insoluble diazo oxide dispersed in a water-insoluble alkali-resistant binder resin and by anchoring such a sensitized layer to the surface of the metal base by means of a thermoplastic, filmforming acrylic resin soluble in alkaline media.

The preparation of metal offset printing plates utilizing these features constitutes the purposes and objectives of the present invention.

The base plate is preferably aluminum over which is electroplated a thin layer of copper (Lithengrave plate developed by the Lithographic Technical Foundation), or it may carry an additional surface of metal by electrodeposition of chromium on the copper layer. Such plates, after pre-treatment are coated with a resin layer designed to tenaciously anchor the resin matrix containing the alkali-resistant resin and diazo oxide to the surface of the metal and to relax adhesion of the unexposed areas during processing so that they may be removed during the washing step. An aluminum plate coated with copper will eventually lead to a positive plate. A plate which carries an additional chromium layer will eventually produce a negative plate.

The film-forming alkaline soluble resin materials contemplated for use in accordance with the present invention are preferably derived from the polymerization of one or more monomers of the alpha, beta-monoethylenically unsaturated carboxylic acid series including their esters and salts. Suitable monomers include for example, acrylic acid, methacrylic acid, methylacrylate, ethylacrylate, butylacrylate, etc., methylmethacrylate, ethylmethacrylate, butylmethacrylate and the like.

Resins of this type are readily available commercially such as the product Carboset from the B. F. Goodrich Chemical Co., e.g., Carboset 525, Although beneficial results may be obtained with the use of alkaline soluble resins of the general type encompassed by the aforestated definition, it has nevertheless been determined that optimum realization of the improvements made possible by the present invention are obtained with those polymeric materials containing within their skeletal structure, on a mole basis, from about to about 99% of units of the following structural formula:

wherein R represents hydrocarbon, e.g., alkyl, aralkyl, aryl and alkaryl and preferably lower alkyl of 1 to 4 carbon atoms, e.g., methyl, ethyl, butyl, etc. and wherein R represents lower alkyl; and from about 1% to about 20% of units of the following structural formula:

wherein R has the above defined significance.

As will be recognized, the presence of the carboxyl pendent groups may result from the fact that a corresponding proportion of acrylic acid type monomers was present in the initial polymerizable monomer mixture or alternatively, such carboxy groups may be introduced into the polymer skeletal chain by subjecting an acrylate polymer, i.e., one containing no free acid group, to a suitable hydrolysis after treatment. The manner in which the polymer is prepared is not a particularly critical factor in the practice of the present invention so long as the relative proportions of the carboxy solubilizing substituents in the polymer chain are maintained within the above defined limitations. Furthermore, the acrylate monomers may be employed in admixtures of 2, 3. or more. Thus, methyl acrylate; ethyl acrylate; butyl acrylate monomer systems have been found to provide polymers eminently suited to the purposes of the present invention. The resin is applied in the form of an 0.5 to 1% solution in isopropyl alcohol, although other solvents such as methanol, ethanol, acetone, diacetone alcohol, methyl cellosolve, dioxane, cyclohexanol, ethyl acetate and the like may be used. The addition of a small quantity of oleic acid and a surface-active agent such as Alkaterge A (Commercial Solvents Corporation) is advantageous in promoting uniform wetting when the resin is applied to the metal surface. The molecular weight of the resinous material is likewise not of critical miport so long as it be capable of depositing continuous films from solvent media. Thus, the molecular weight may range from 5,000 to 10,000 up to several million. As a general proposition, however, resin materials having a molecular weight of from about 500,000 to 1,000,- 000 are preferred.

In general, the resin is applied in the form of an 0.5 to 1% solution in isopropyl alcohol, although other solvents such as methanol, ethanol, acetone, diacetone, alcohol, methyl cellosolve, dioxane, cyclohexanol, ethyl acetate, and the like may be used. The addition of a small quantity of oleic acid and a surface-active agent such as Alkaterge A (Commercial Solvents Corporation) is adyantageous in promoting uniform wetting when the resin is applied to the metal surface. If desired, a small quantity of a suitable shade dye may be added to this solution to enhance the contrast of the coating on the metal surface. Alkaterge A is a substituted oxazoline of the following general formula:

wherein R is a long chain alkyl group such as pentadecyl or heptadecyl, While R and R are lower alkyl groups, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl and the like. In its preferred form, R is heptadecyl and R and R are methyl or ethyl.

The adhesive interlayer comprising the alkaline soluble, thermoplastic, film-forming acrylic resin following application, e.g., flow coating to the metal plate is thereafter directly overcoated with the sensitized layer comprising the light-sensitive diazo oxide and alkali-resistant resin. The diazo oxide compounds found to be eminently suitable for use herein can be characterized as being waterinsoluble but which display solubility to the extent of at least 1% in a solvent which is a liquid and is an aliphatic ester, an aliphatic ketone or an aliphatic alcohol, i.e., alcohols in which the OH group is aliphatically linked. Examples of such solvents are ethylacetate, butylacetate, amylacetate and the like, acetone, diethylketone, methylpropylketone, methylisobutylketone, dipropylketone, methylethylketone, methylbutylketone and the like, ethyl alcohol, 'isopropyl alcohol, butyl alcohol, diacetone alcohol, benzyl alcohol, and the like. Many diazo oxides of extremely high molecular weight and complex structure are of such a mixed, polar-non-polar character that they are only soluble in such powerful solvents as dimethylformamide, dimethylacetarnide, dioxane or methyl cellosolve. Since the solubilizing effects of the latter mentioned solvents would, in all likelihood, deleteriously affect the adhesive interlayer, it is preferred that such diazo oxides be employed which possess the solubility characteristics mentioned hereinbefore.

Diazo oxides within the broad class which have been found to be particularly suitable are those derived by amidation or esterification of 2 diazo 1 naphthol 5- sulfonyl chlorides or Z-naphthol-l-diazo-S-sulfonyl chlorides with comparatively simple amines or alcohols or with more complex compounds which possess a saturated, unconjugated, non-polar molecule such as rosin amines, rosin alcohols and their derivatives.

The above diazo oxides may be formulistically represented as follows:

SOzR

and

wherein R is alkoxy, i.e., methoxy, ethoxy, propoxy, aryloxy such as phenoxy, naphthoxy and the like, amino such as primary amino, alkyl amino, i.e., methylamino, dimethylamino, ethylamino, diethylamino, propylamino, dipropylamino, butylamino, dibutylamino, arylamino such as phenylamino, naphthylamino and the like, aralkylamino such as benzylamino, dehydroabietylamino, didehydroabietylamino, and the like, carbalkoxyalkylamino such as carbmethoxymethylamino, carbethoxymethylamino, carbethoxyethylamino and the like. Specific examples of such diazo oxides embraced by these formulae are:

(1) Z-diazo-1 naphtho1-5-su1furic acid ethyl ester (2) 2-diazo-l-naphthol-S-sulfuric acid methyl ester (3) 2-diazo-l-naphthol-S-sulfuric acid phenyl ester (4) 2-diazo-l-naphthol-S-sulfuric acid naphthyl ester (5) Z-diazo-l-naphthol-S-sulfuric acid butyl ester (6) Z-diazo-l-naphthol-S-sulfuric acid benzyl ester (7) 1-diazo-2-naphthol-5-sulfuric acid ethyl ester (8) 1diazo2-naphthol-5-sulfuric acid phenyl ester (9) 2-diazo-l-naphthol-S-sulfonamide (10) 2-diazo-l-naphthol-SN-methyl-sulfonamide l 1) 2-diazo-1-naphthol-5-N-(carbemethoxymethyl)- sulfonamide 12) 2-diazo-1-naphthol-5-N- (carbethoxymethyl) sulfonamide 13) Z-diazolnaphthol-SN-dimethylsulfonamide (14) 2-diazo-lnaphthol-S-N-butylsulfonamide (l5 2-diazo-1naphthol-S-N-dibutylsulfonamide (16) N-dehydroabietyl-6-diazo-5(6)-0x0 l-naphthalenesulfonamide (17 N-dehydroabietyl-N-2-hydroxyethyl-6-diazo-5 (6 0x0-l-naphthalenesulfonamide (18) N,N-didehydroabietyl-N,N'-ethylene bis[6-diazo- 5(6)-oxolnaphthalensulfonamide] The aforementioned diazo oxides, excepting for those containing the rosin amine structure, are known compounds and are prepared by a simple esterification or amidation of the sulfonyl chloride in the presence of an acid binding agent such as pyridine. The rosin derivatives, on the other hand, are prepared according to the method described in US. Patent 2,797,213 issued June 25, 1957.

The light-sensitive diazo oxide as noted is laid down with an alkali-resistant adhesive resin preferably lipophilic in order to ensure adequate adhesion to the acrylic resin interlayer. As such resin there may be employed any water-insoluble, alkali-resistant resinous material which is soluble in any of the aforementioned limited classes of solvents for the diazo oxide, at least to an extent of 1% by weight. In addition, the resin must be resistant to or impervious to the action of the solutions utilized in the processing of the raw plate to the finished offset printing plate. The resin should thus withstand a contact time of one-half minute or longer with such reagents and resist removal from the anchorage layer during such period of contact in the absence of the photodecomposition products. It is advantageous but not essential that the resin be of low or moderate molecular weight since such resins have improved adhesive character and are more readily removed in the presence of the photodecomposition products.

Many resins available on the open market manifestly fit these requirements and in this connection, reference is made to polyvinyl resins such as phenol modified coumarone-indene resins, polyvinyl acetate, polymethylacrylate, polymethylmethacrylate, cellulose derivatives such as ethyl cellulose, cellulose acetate, cellulose propionate, mixed esters and the like. Here again, it is a very simple test, the solvents being identified, to determine a suitable resin having adhesive characteristics which may be utilized for application with the light-sensitive diazo compound.

Without intending to be bound by any theory, it has nevertheless been postulated that the photodecomposition products of the diazo oxide are soluble or sWellable in liquid aliphatic polyhydroxy compounds, thus permitting the selective removal of the photodecomposition products and the adhesive resin commingled therewith.

The phenomenon permitting the achievement of this result has been studied and it is believed to be attributable to the following circumstances.

It has been conclusively demonstrated that the action of actinic light on compounds containing the grouping causes the loss of nitrogen accompanied by a rearrangement to form a ketene intermediate. It is well known that ketenes may react with compounds containing an active hydrogen. In the case of hydroxyl-containing compounds esters are formed. Apparently, the liquid polyhydroxy compounds react with the diazo oxide photodecomposition product to form an ester derivative of the polyhydroxy reagent, only a portion of the hydroxyls being so converted. The resulting compound bears Sufficient resemblance to the polyhydroxy solvent to promote tendency toward mutual solubility. The generality of the solubility behavior is thus explicable.

It is to 'be recognized that this is a theory of operation which is offered in explanation of the changes which ensue in the removal of the photodecomposition prodnets and the adhesive resin. Despite the accuracy of this theory, it is a fact that the diazo photodecomposition products play a crucial role in creating permeability to the various polyhydroxy compounds.

The polyhydroxy compound utilized for removal of the decomposition products and the adhesive resin is any liquid aliphatic polyhydroxy compound such as the various alkyl glycols, i.e., ethylene glycol, propylene glycol, diethylene glycol, 1-3-butylene gyco, 2-3 butyene glycol, dipropylene glycol, hexylene glycol, trihydric alcohols such as glycerin and the like. Such polyhydroxy compounds may be used alone or in admixture with suitable mixtures including for example, ethylene glycol with glycerin, hexylene glycol with glycerin, 2,3-butylene glycol with glycerin, propylene glycol with ethylene glycol and the like. It has been found that the solubility or swellability of the diazo oxide photodecornposition products in liquid aliphatic polyhydroxy compounds is a general phenomenon and, hence, any such solvent is suitable for use.

One of the outstanding features of the present invention results from the fact that the alkaline-soluble acrylic resin utilized as the adhesive interlayer is soluble in alkaline media. Thus, by including a suitable alkaline reagent in the solution containing the above-described polyhydroxy compound, there is accomplished a simultaneous removal of both the exposed areas of the diazo oxide layer and those portions of the acrylic resin adhesive layer lying directly therebeneath. As will be recognized, this represents a particularly desirable feature since it makes possible the elimination of the added steps which would otherwise be necessary. Thus, in those applications involving the preparation of an offset printing plate of the etch type, the metal surface is laid bare by a single solvent treatment being thus available directly for treatment with the metal etching medium.

This can perhaps be better explained by particular reference to the preparation of a positive-working bimetallic printing plate. In such a case, the plate structure would comprise, for example, a copper-coated aluminum base, the copper surface being directly coated with the alkaline-soluble acrylic resin adhesive interlayer the latter in turn being directly overcoated with the light-sensitive diazo oxide layer. Following exposure, the light struck areas of the diazo oxide layer as well as the corresponding portion of the subjacent surface layer are removed by the employment of a single solvent solution comprising for example, diethanolamine and ethylene glycol. The copper portion of the bimetallic plate laid bare by the foregoing solvent treatment can then be readily etched out by the use of a suitable etching solution, e.g., ferric chloride, in order to expose the aluminum surfaced disposed therebeneath. The remaining portions of the diazo oxide layer, i.e., those unaffected by the exposure radiation are then removed by treatment with an organic solvent for the resin, e.g.,

acetone, methyl, ethyl ketone, methyl isobutyl ketone, etc. while the remaining portions of the resinous interlayer can be removed by alkaline treatment as more fully described hereinbefore.

The present invention can likewise be applied to distinct advantage in the preparation of printing plates of the type described in US. Patent 2,772,972 (C. E. Herrick, Jr., et a1.) i.e., in which the raised portions of the diazo oxide layer which remain following the post-exposure wash-out operation comprise the grease receptive printing areas. According to the process described in the patent, those portions of the sub-stratum layer laid bare by wash-out of the diazo oxide layer must be rendered hydrophilic by a solvent treatment distinct from the wash-out operation unless hydrophilic character be imparted to such sub-stratum layer simultaneously with the wash-out operation by replacing a part of the polyhydroxy compound with a substantially equivalent amount of alkylola-mine.

In contradistinction, the present invention obviates the necessity of resorting to a separate treatment as regards imparting hydrophilic character to the sub-stratum layer since the resin materials described herein for such purposes inherently possess the required degree of hydrophilicity. It will be understood, of course, that the pro duction of such a printing plate would require omitting any alkaline reagent from the solution employed in the Wash-out of the diazo oxide layer in order to exclude any possibility of removing the alkaline-soluble acrylic resin comprising the adhesive interlayer.

It will further be understood that the present invention may be implemented with equal success to the production of both positive and negative-working printing plates. Production of a negative-working plate could be readily effected by employing as the metal support a copper-coated aluminum sheet further provided on the copper surface with a layer of chromium. As Will be appreciated, by employing a chromium etch in the processing of the exposed plate, the printing areas of the plate will correspond to the exposed areas of the diazo oxide layer, the copper being exposed in such portions as a result of the chromium etch.

The present invention will be further illustrated by the following examples but it is to be understood that the invention is not restricted thereto.

EXAMPLE I A copper surfaced aluminum plate in rinsed with warm water to remove the protective gum layer. It is then flushed with nitric acid (2 ounces per gallon of water) for about 30 seconds. It is rinsed thoroughly again with water, followed by an acetone rinse. After drying, the plate is coated with the following compositron:

Parts Carboset 525, 0.75% in isopropyl alcohol 98.0 Alkaterge A, 1% in isopropyl alcohol 1.0 Oleic acid, 2% in isopropyl alcohol 1.0

Molecular weight approximately 800,000 as determined by light scattering.

This solution is filtered and then applied to the copper surface by flow coating, using 5 cc. per square foot of area to be coated. The coating is allowed to dry for a period of 15 to 20 minutes and then overcoated in subdued light with a mixture of the following composition:

by swabbing the plate with a solution of the following composition:

Parts Diethanolamine 10 Ethylene glycol 67 Glycerin 23 The plate is then rinsed with water and dried for minutes with a warm air blast.

A ferric chloride etch solution, of the type described on page 214 of Offset Platemaking (Lithographic Technical Foundation, 1955) is now spread evenly over the entire plate. entire plate. This solution has the following composition:

Iron perchloride, crystals g 4,800 Water c 1,000

EXAMPLE II The procedure is the same as in Example I excepting that the diazo oxide layer is prepared utilizing the following composition:

Polyvinyl acetate 100 Polyvinyl acetate 2 Methyl isobutyl ketone 100 N,N didehydroabietyl-N,N'-ethylene bis[6-diazo-5 (6)-oxo-1-naphthalenesulfonamide) 2 EXAMPLE III This example illustrates the manner in which a negative-working offset printing plate can be produced in accordance with the present invention.

An ungummed trimetallic chromium-copper-aluminum plate is coated on its chromium surface with the Carboset and diazo oxide compositions described in Example I. Following exposure through a photographic positive, followed by washout, drying and removal of the undercoating as described in Example I, the plate was dried for 5 minutes with a warm air blast. A chromium etch solution of the type described on page 182 of Offset Platemaking (Lithographic Technical Foundation, 1955 is then used to etch away the chromium in the exposed image areas. This solution has the following composition:

Aluminum chloride solution, 32 B. cc 750 Zinc chloride g 630 Phosphoric acid, 85% cc 40 EXAMPLE IV The procedure is the same as in Example III excepting that the diazo oxide layer is prepared utilizing the composition of Example II.

EXAMPLE V An ungummed aluminum plate is coated as described in Example I. Following exposure, the diazo oxide layer was swabbed with a pad moistened with the following solution:

Ethylene glycol Glycerin The sensitizing layer is thus rapidly removed in the regions of the plate which were unprotected during the exposure by opaque portions of the orginal. The completeness of this removal can be conveniently followed by the presence of color on the exposed surface since the exposed sensitizing layer is brownish in hue. Since no alkaline material is present in the washout solution, the resinous adhesive layer remains intact and the plate is directly available for inking, the raised portions of the diazo oxide layer serving as the grease-receptive printing areas. Since the adhesive interlayer possesses the requisite hydrophilicity to repel greasy inks, further solution treatments are totally unnecessary.

EXAMPLES VI THRU X Examples 1 through V are repeated utilizing as the resin component in the anchoring layer composition a polymer containing on a mole basis 90.4% of a mixture of methyl acrylate, ethyl acrylate and butyl acrylate polymer units and 19.6% acrylic acid polymer units.

The offset printing plates produced according to the foregoing examples exhibit excellent structural stability throughout the entire processing as evidenced by the fact that the various layer strata display no tendency to peel or otherwise separate from the element. Moreover, such plates provided offset prints characterized by excellent reproduction quality.

Results similar to those described in the foregoing examples are obtained for example, when the ethanolamine component of the washout solution is replaced by an aqueous solution of ammonia, trisodium phosphate, etc. The nature of the alkaline material employed for simultaneous removal of the diazo oxide and adhesive layers is not particularly critical, the primary requirement being that it be present in amounts sufficient to yield a pH on the order of 7.5 to 8.0 or higher.

The present invention has been disclosed with respect to certain preferred embodiments thereof, and there will become obvious to persons skilled in the art various modifications, equivalents or variations thereof which are intended to be included within the spirit and scope of this invention.

What is claimed is:

1. A light-sensitive material comprising a unitary metallic base carrying on one side thereof a thermoplastic, alkaline-soluble, film-forming acrylic resin as an anchoring layer, said resin containing on a mole basis from about to 99% of acrylate units of the structural formula:

oH,o

wherein R is an alkyl, arakyl, aryl or alkaryl group and R is a lower alkyl group and from about 1 to about 20% of acrylic acid units, said anchoring layer being overcoated with a light-sensitive layer comprising 150% by weight of a water-insoluble alkali-resistant resin and a light-sensitive water-insoluble diazo oxide.

2. A light-sensitive material according to claim 1 wherein said metallic base comprises aluminum.

3. A light-sensitive material according to claim 1 wherein said unitary metallic base comprises aluminum having an outer metallic surface layer selected from the group consisting of copper and chromium said outer metallic sucface serving as the support for said anchoring and light-sensitive diazo oxide layers.

4. A light-sensitive material according to claim 1 wherein said alkaline-soluble, film-forming acrylic resin comprises an interpolymer of methyl acrylate, ethyl acrylate, butyl acrylate and acrylic acid.

5. A light-sensitive material according to claim 4 wherein said water insoluble alkali-resistant resin comprises polyvinyl acetate.

6. A light-sensitive material according to claim 1 Disclaimer 3,474,719.Steven Levinos, Vestal, N.Y. OFFSET PRINTING PLATES. Patent dated Oct. 28, 1969. Disclaimer filed Sept. 30, 1982, by the assignee, Eastman Kodak Co.

Hereby enters this disclaimer to all claims of said patent.

[Official Gazette March I, 1983.]