CA1276048C - Polyvinyl acetal resin and photosensitive composition containing same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A resin comprising units of each of the general types A, B and C, in an ordered or random sequence, wherein A is present in an amount of from 5 % to 20 % by weight and is a unit of the formula B is present in an amount of from 4 % to 30 % by weight and is a unit of the formula and C is present in an amount of from 50 % to 91 % by weight and comprises units of each of the formulae C I, C II and C III
(C I), (C II), (C III) where R is lower alkyl or hydrogen, and wherein said units C I are present in an amount of from 75 % to 85 %;
units C II are present in an amount of from 3 % to 5 %;
and units C III are present in an amount of from 10 % to 22 %, based on the total weight of the units C. Resins of this type may be used in the production of a photosensitive composition.

Description

6~

sACKGROUND OF THE INVENTION
The present invention relates to a resin which may be used in the production of photosensitive elements and which renders such photosensitive elements developable by aqueous developers. The invention further relates to a radiation-sensitive composition which may be employed to produce an improved photographic element such as a lithographic printing plate. Such plates show an increase of stability and press run life and can be developed without organic solvents. The composition can be readily formed into adherent coatings useful in the graphic arts especially in the production of lithographic printing plates.
Although there are many resins known which may be used in the production of photosensitive elements in general, the majority of them are severely limited by the need to develop the photosensitive elements with solutions containing substantial amounts of organic solvents. Such developing solutions are undesirable in that their effluent is toxic and environmentally harmful and the solvents are costly.
It is known to prepare interpolymers for the stabilization of formaldehyde solutions wherein the interpolymer is composed of vinyl acetate, vinyl acetal and vinyl alcohol, as shown in IJnited States Patent 4,085,079. Similar polymers are also disclosed in United States Patent 2,179,051. Each of these resins, though, when used in photosensitive elements, must be developed with developers which contain organic solvents.
What is desired, therefore, is a resin which may be used to produce a photosensitive element which is developable with a solution which does not necessarily contain organic ~76~

solvents and need only contain minor amounts of salts and surfactants. Such resin should allow the photosensitive element to develop in a dissolving fashion, thereby substantially eliminating the presence of particles which may be re-deposited onto the element surface and in-terfere with the operation of the element. Such resin should also allow the production of a photosensitive element having superior sensitivity, image resolution, run length, and post-exposure and post development image contrast, and which is compatible with commonly used printing plate and press processing solutions.

SUMMARY OF THE INVENTION
.
This invention relates to a resin which may be used in the production of a photosensitive element. More particularly, this invention relates to a resin comprising units of each of the general types A, s and C, in an ordered or random sequence, wherein A is present in an amount of from 5% to 20% by weight and is a unit of the formula -CH -CH-C = O

B is present in an amount of from 4% to 30% by weight and is a unit of the formula OH

~ Z~$~

and C is present in an amount of from 50% to 91~ by weight and comprises ~nits of each of the formulae C I, C II and C III

/C~2\
-CH OEI- -CH C~ CH-O O (C I), 1 O (C II), O (C III) ~ / \/ I
CH CH H-C-R

R R

-CH-where R is lower alkyl or hydrogen, and wherein said un:its C I
are present in an amount of from 7S~ to 85%; units C II are present in an amount of from 3~ to 5%; and units C III are present in an amount of from 10% to 22%, based on the total weight of the units C.
ccording to another aspect, the invention relates to a photosensitive composition which comprises, as a binder, a resin as defined above and a photosensitive diazonium salt condensation product.
DETAILED DESCRIPTION OF THE INVENTION
As used in describing the resin of this invention, the term "lower alkyl" refers to a straight or branched chain hydrocarbon having from 1 to 8 carbon atoms and containing no unsaturation.
The vinyl alcohol/vinyl acetate copolymers useful as a starting material for the production of the resin of this invention are those having from about 75~ to about 80~

hydrolization by weight and, preferably, an average molecular weight (AMW) of from about 5,000 to about 100,000. As used in ~ ~t7~ 4~

this application hydrolization is on a weight basis and not a mole basis. Such copolymers are easily synthesized by methods known to those skilled in the art, or are commercially available.
Suitable copolymers include Vinol* 523 (AMW - 70,000) and Vinol 205 (AMW = 26,000) available from Air products Co. of Allentown, Pennsylvania; Elvanol* 52-22 (A~W - 72,000) available from DuPont of Wilmington, Delaware; and Gelvatol* 20-30 (AMW - 10,000), Gelvatol 20-60 (AMW - 60,000), and Gelvatol 2~-90 ~AMW - 90,000) available from Monsanto Co. of St. Louis, Missouri.
The particular copolymer chosen as the starting material depends upon the end use desired for the resin. For instance, if the resin is to be used in the production of a lithographic printing plate, the copolymers are preferably those having higher molecular weights (i.e. about 50,000 to about 100,000). If the resin is to be used in the production of screens for screen printing applications, the copolymers are preferably those having lower molecular weights (i.e. about 5,000 to about 30,000).
Although these ranges are generally preferred, they are not critical.
In forming the resin of this invention, the copolymer is first dissolved in a solvent mixture of water and a hydroxyl group containing solvent. The hydroxyl group-containing solvent must be miscible with water, it must be a solvent for the copolymer, and it must be a solvent for the final resin product. Preferably, the hydroxyl group containing solven~ is an aliphatic alcohol.
Most preferably, the alcohol is one having from about 1 to 4 carbon atoms such as ethanol. In order to ensure that the copolymer * Trade Mark - 4 -7~r~

molecules of the starting material are not so intertwined with each other nor having tertiary or quaternary structure to the extent that the reaction is interfered with to a substantial degree.
The invention provides a method of preparing the foregoing resin. The process steps include first dissolving the vinyl alcohol/vinyl acetate copolymer in a solvent mixture of water and a hydroxyl-group containing solvent to form a reaction solution. This is usually conducted for at least about 12 hours at a temperature of from about 20C to the boiling point of the solution depending on the molecular weight of the copolymer. The solution is then adjusted to at least about 50C while adding a catalytic amount, preferably from about 1.0% to about 1.5% by weight of an acid. ~his is insufficient to cause hydrolization.
Titrated into the acidified mixture is an aliphatic aldehyde over a period of several hours. The aldehyde is added in an amount sufficient to produce a degree of acetal formation of from about 50% to about 91% by weight. Preferably one vigorously mixes said reaction mixture throughout the foregoing steps.
Preferably the acid is then removed from the mixture by evaporation or the mixture is neutralized.
The preferred aldehyde is acetaldehyde or propionalde-hyde. The particular aldehyde chosen may also be related to the end use intended for the resin of this invention. E'or use in the production of a lithographic printing plate, propionaldehyde is preferred; for use in the production of a screen printing screen, acetaldehyde is preferred, The amount of aldehyde titrated into the reaction mixture is preferably from about 25%

to about 100~ by weight of the copolymer. More preferably the amount of the aldeh~de is from about 28% to about 67~ by weight of the copolymer.
As the acetal groups are formed at the expense of the hydroxyl content of the copolymer, the water solubility is reduced. In order to prevent premature precipitation of the product formed, additional amounts of the hydroxyl group containing solvent used in the solvent mixture are added simultaneously with the aldehyde to accommodate the product's reduced water solubility and increasing solvent solubility.
In order to properly form the acetal groups, a catalytic amount of an acid is required to be present during the titrations. Preferably the acid used is an inorganic mineral acid or an organic sul~onic acid. Suitable mineral inorganic acids include hydrochloric acid, sulfuric acid and phosphoric acid. Suitable organic sulfonic acids include p-toluene sulfonic acid and stilbene disulfonic acid. Most preferably, the acid catalyst is hydrochloric acid.
After the titrations are completed, the reaction mixture preferably is neutralized with an alkaline salt in order to quench the reaction mixture so as to prevent the deacetaliz-ation which may otherwise occur. The neutralization shouldadjust the pEI of the reaction mixture to about 6.5 to about 7.5, and should preferably be 7Ø Suitable alkaline salts for the neutralization include sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide, with sodium carbonate being the most preferred.
After neutralization, the reaction mixture is preferably, although not necessarily, cooled to room temperature (about 22 to ~.276~?4(~

25C) and then slowly mixed with water or other suitable compositions such as acetone or methyl ethyl ketone with continued vigorous agita-tion to effect precipitation. The resulting precipitates is water washed to remove all remaining acid, aldehyde and unreacted copolymer, and is then warm air dried so as to have not more than 1% water residue.
The resultant resin, when used to form a photosensitive element, is found to be developable with a solution which does not necessarily contain organic solvents and need only contain a minor amount, if any, of salts and surfactants; it allows the photosensitive element to develop in a dissolving fashion, thereby substantially eliminating the presence of particles which may be re-deposited and interfe~e with the operation of the element; allows the production of a photosensitive element having superior sensitivity, image resolution, run length and post-exposure and post-development image contrast; and is compatible with commonly used plate and press processing solutions.
A photosensitive composition which may be prepared using the resin of this invention comprises, for example, an admixture of a diazonium salt, and, if desired, a photo-polymerizable monomer and a photoinitiator; and the resin of this invention. The mixture is usually prepared in a solvent composition which is compatible with all the composition ingredients. Suitahle solvents for this purpose include water, tetrahydrofuran, butyrolactone, glycol ethers such as propylene glycol monomethyl ether and methyl cellosolve, alcohols such as ethanol and n-propanol, and ketones such as methyl ethyl ketone, or mixtures thereof. Preferably, the solvent comprises a mixture of tetrahydrofuran, propylene glycol monomethyl ether and butyrolacetone. The composition is then coated on the substrate and the solvent removed by drying.
The composition may also contain other art recognized ingredients such as colorants, acid stabilizers, plasticizers and exposure indicators in amounts easily determined by those ski]led in the art.
Specific examples of light sensitive diazonium materials useful as aforementioned include any suitable light sensitive diazonium polymeric or monomeric compound which are well known to the skilled artisan, although the polymeric diazonium compounds are preferred. Suitable diazonium compounds include those condensed with formaldehyde such as disclosed in United States 2,063,631 and 2,667,415, the polycondensation products such as disclosed in United States 3,849,392 and 3,867,147, and the high photo-speed and co-condens~d diazos such as disclose~ in United States 4,436,804 and United States 4,533,620.
Preferably, the polymeric binder is present in the photosensitive composition at a percent solids level of from about 20% to about 75P~ by weight. A more preferred range is from about 30% to about 65% by weight and, most preferably, the polymeric binder is present at a percent solids level of -from about 35% to about 50% by weight. A preferred light sensitive diazonium salt condensation product is prepared by reacting at least one A-N2X compound and at least one Bl compound of the formula E( C a b)m in which A is a radical of a compound of the formula (Rl-R3-) pR2 N2X
wherein Rl is an optionally substituted phenyl or naphthyl group, R2 is an optionally substituted phenylene group r R3 is a single bond or one of the groups 2 q 4 -O- (CH2) r-NR4--S- (CH2) r-NR4-, -S-CHz-CO-NR4-~

--O--, -S- or wherein q is a number from 0 to 5, r is a number from 2 to 5, R4 is selected from the group consisting of hydrogen~
alkyl with 1 to 5 carbon atoms, aralkyl with 7 to 12 carbon atoms, and aryl with 6 to 12 carbon atoms, R5 is an arylene group having 6 to 12 carbon atoms, X is an anion p is a number from 1 to 3, E is a radical obtained by splitting off of m H atoms from a compound free of diazonium groups selected from the group consisting of aromatic amines, ~ ~:'7~

phenols, thiophenols, phenyl ethers, aromatic thioethers, aromatic heterocyclic compounds, aromatic hydrocarbons and organic acid amides, Ra is selected from the group consisting of hydrogen and phenyl, Rb is selected from the group consisting of hydrogen, alkyl, lower acyl and phenyl, and m is an integer from 1 to 10 in a strongly acidic condensation medium under condensation conditions sufficient to produce a polycondensation product of an aromatic diazonium compound containing, on the average, about 0.] to 50 Bl units per unit of A-N2X.
Preferably, this diazonium salt embodiment comprises the 1:1 polycondensation product of 3-methoxy-4-diazo-diphenyl amine sulfate and 4,4'-bis-methoxy-methyl-diphenyl ether, precipitated as the mesitylene sulfonate, such as is taught in United States 3,849,392.
The diazonium salt is preferably present in the composition of the subject invention at a percent solids level of from about 3% to about 20% by weight. More preferably it is present at about 5% to about 18% by weight and most preferably the diaæonium salt is present at a percent solids level of from about10% to about 15% by weight.
A particular photosensitive composition further includes an acrylic monomer. When a photopolymerizable composition such as this is being employed, a suitable photo-initiator is usually also present. Suitable photoinitiators which may be used in this invention are preferably those free-.276Q~8 radical photoinitiators having a maximum absorption range of fromabout 320 to about 400 nm. Examples include the acetophenones, benzophenones, triazines, benzoins, benzoin ethers, xanthones, thioxanthones, acridenes and benæoquinones. More preferred of these are the 2-aryl-4,6-bis-trichloromethyl-triazines.
The most preferred photoinitiator is 2-stilbenyl 4,6-di(trichloromethyl)triazine.
The photoinitiator is preferably present in the composition at a percent solids level of about 1.5% to about 8.0% or more by weight, more preferably about 2.0~ to about 6.0% ~y weight and is most preferably present at a percent solids level of from about 3.0~ to about 4. 06 by weight~
According to a particular embodiment, the photopoly-merizable mixture of the subject invention comprises a polyfunctional acrylic monomer which has two or more unsaturated groups and a urethane oligomer which is hereinafter described.
The polyfunctional monomer is capable of reacting with the urethane oligomer upon exposure to imaging radiation. The monomer is characterized as having the unsaturated groups being acrylic or methacrylic acid esters. The preferred monomer is either a solid or liquid having a viscosity of greater than about 700 cps at 25C, preferably greater than about 2000 cps at 25C.
Most preferably, the monomer has a viscosity of greater than about 4000 cps at 25C. A preferred polyfunctional monomer is an ethylenically unsaturated compound having from 2 to 6 acrylic or methacrylic acid ester groups.
Examples of compounds which are suitable for use as the monomer of this invention include trimethylol propane tri(meth)-acrylate and the ethoxylated or propoxylated analogs thereof, pentaerythritol triacrylate, pentaerythritol trimethacrylate, dipentaerythritol monohydroxy penta(meth)acrylate, dipentaery-thritol hexaacrylate, dipentaerythritol hexamethacrylate, pentaerythritol tetracrylate and pentaerythritol tetramethacryl-ate. Preferably, the monomer is dipentaerythritol monohydroxy pentaacrylate, although a combination of suitable JnOnOmerS is also advantageous.
The monomer is present at a percent solids level which is preEerably in the range of from about 10% to about 35~ by weight. More preferably, the monomer is present at a percent solids level of from about 15~ to about 30~ by weight and most preferably from about 1~ to about 25% by weight. The oligomeric component of the photopolymerizable mixture of the composition of the subject inven~ion is a photocurable oligomer or polymer which i5 prepared by reacting one molar equivalent of a substantially linear polymeric compound having an active hydrogen group at each end thereof with at least two molar equivalents of a diisocyanate compound so as to form a prepolymer having an isocyanate group at each end thereof; and subsequently reacting said prepolymer with at least two equivalents of an ethylenically unsaturated compound having an active hydrogen group to provide said prepolymer with unsaturation at each end thereof. The preferred oligomer is one having a polyester backbone prepared from an aliphatic dicarboxy-lic acid and an aliphatic diol. The preferred dicarboxylic acid is linear and has from about 2 -to 8 carbon atoms. The polyester is prepared in such a way that the compound is symmetrical and hydroxy-terminated. A procedure for doing so would be known to ~;~7~

the skilled artisan, for example as shown in Sandler and Karo, POlymer Synthesis, Vol. 2, Academic Press 1977, pp 140-167. The polyester polyol is in turn reacted with preferably an aliphatic diisocyanate having from 2 to 15 carbon atoms, more preferably withacycloaliphatic diisocyanate. The diisocyanate is reacted with the polyester polyol so that one of the two isocyanate groups is reacted with the terminal hydroxy group on the end of the polyester backbone. The remaining isocyanate group is subsequently reacted with a hydroxy~containing acrylate or methacrylate. For example, 1,6-hexane diol is reacted with adipic acid in a mole ratio of greater than 1:1 (adipic acid/1,6-hexane diol) to form a polyester and then reacted with dicyclohexyl-methane-4,4' bis diisocyanate in a 2:1 mole ratio (diisocyanate/polyester). The product is reacted with 2-hydroxy ethyl acrylate in a 2:1 mole ratio (acrylate/diisocyanate-polyester product) to form an oligomer useful in this invention.
The oligomer may be characterized as follows:
U-D-R -D-U
wherein:
Rl is the radical of an essentially linear polymeric compound having two end groups with active hydrogen functionality, D is the radical of a diisocyanate compound, and U is the radical of a compound having ethylenic unsaturation and a group with an active hydrogen.
Examples o~ compounds which can be used as the Rl group are polyesters obtained by reacting a dicarboxylic acid with a diol in such a fashion that the mole ratio of diol to dicarboxylic acid is greater than 1:1 so as to have a symmetrical ~ 2~7~

hydroxyl terminated polymer; polyethers obtained by reacting a diol with an alkylene oxide in such a fashion that the mole ratio of diol to alkylene oxide is greater than 1:1 so as to have a symmetrical hydroxyl terminated polymer; and epoxies obtained by reacting a symmetrical diglycidyl compound with a diol in such a fashion that the mole ratio of diol to diglycidyl compound is greater than 1:1 so as to have a symmetrical hydroxyl terminated polymer.
More specifically, Rl groups which are polyesters are prepared from dicarboxylic acids such as oxalic, malonic, succinic, glutaric, adipic, pimelic, suberic, azelaic and sebacic acids, and from diols such as ethylene glycol, diethylene glycol, neopentyl glycol, propylene glycol, dipropylene glycol, 1,3-butane diol, 1,4-butane diol, 1,6-hexanediol and 2-ethyl-1, 6-hexane diol.
Rl groups which are polyethers are prepared from diols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butane diol, 1,4-butane diol, 1,6-hexane diol and 2-ethyl-1,6-hexane diol, and alkylene oxides such as ethylene oxide, propylene oxide and tetrahydrofuran.
Rl groups which are epoxies are prepared ~rom diols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butane diol, 1,4-butane diol, 1,6-hexane diol and 2-ethyl-1,6-hexane diol, and diglycidyls such as diglycidyl isophthalate, diglycidyl terephthalate, diglycidyl phthalate and bisphenol-A diglycidyl ether.
Examples of compounds which can be used as the D group are ethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate, dicyclohexyl-methane-4,4'-diisocyanate, hexamethy-lene diisocyanate, l-methyl-2,3-diisocyanatocyclohexane, l-methyl-2,6-diisocyanatocyclohexane, lysine diisocyanate, 4,4'-ethylene-bis-(cyclohexyl isocyanate) and isophorone diisocyanate.
Example of compounds which may be used as the U group include hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, hydro~yethyl methacrylate, 1,3-butane diol acrylate, 1,3-butane diol methacrylate, 2,4-butane diol acrylate, 1,4-butane diol methacrylate, neopentyl glycol acrylate, neopentyl glycol methacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate and the mono acrylate and ~ethacrylate of polyethylene glycol, polypropylene glycol and polycopolymers of ethylene glycol and propylene glycol.
Useful oligomers in the practice of this invention include those oligomers preferably having a molecular weight of from about 1500 to about 4000, more preferably from about 2000 to about 3500 and, most preferably, the oligomer has a molecular weight of about 3000. It is desirable that the oligomer be in solid form or semi-solid form, i.e. having a viscosity of greater than about 480,000 cps at 25C. The composition preferably contains the oligomer at a percent solids level of from about 10~ to about 35% by weight. ~ore preferably the oligomer is present in the radiation polymerizable composition of this invention in an amount of from about 15% to about 30%
by weight and it is most preferably present at a percent solids level of from about 15% to about 25% by weight. A fuller description of such oligomers appears in EP-A 184725 ~.~7~ 8 One o~ the significant aspects of this em~odiment of the invention is the fact ~hat the unique combination of photo~
initiator, diazonium salt and photopolymerizable mixture eliminates the need for use of an oxygen barrier layer or the necessity for processing in a nitrogen barrier environment, although the e~act mechanism for this is unclear. Among the advantages derived is elimination of 1) the inconvenience of applying a second coating, 2) the concern over the refractive index and solubility of the oxygen barrier layer, 3) the concern over bllnding on a printing press due to residue from the oxygen barrier layer, and 4) the concern over potential image gain due to the oxygen barrier layer.
~ he photoacti~ator which may be included in the composition of this invention should be an amine-containing photoactivator which combines synexgistically with the free-radical photoinitiator in order to extend the effective half-life of the photoinitiator, which is normally in the approximate range of about 10 9 to 10 15 seconds. Suitable photoactivators include 2-(N-butoxy) ethyl-4-dimethylamino benzoate, 2-(dimethylamino) amino benzoate and acrylated amines. Preferably the photo-activator is ethyl-4-dimethylamino benzoate. The photoacti~ator is preerably present in the composi~ion of this invention in an amount of from about 1.0% to about ~.0% by weight, although the skilled artisan may use more ox less as desired.
Accordin~ to another particular embodiment, the photopolymerizable mixture of the subject invention comprises a polyfunctional acrylic monomer which has two or more ~ 27~

unsaturated groups and a monofunctional acrylic monomer which has 1 unsaturated group.
The polyfunctional acrylic monomer is described above.
The monofunctional monomer is an ethylenically unsaturated compound having one unsaturated group. The mono-functional monomer is characterized as having the unsaturated group being an acrylic or methacrylic acid ester. Preferably, ; the monofunctional monomer is a liquid having a viscosity in the range of from about 1 to about 25 cps at 25C.
Examples of compounds which are suitable for use as the monofunctional monomer of this invention include tri-methylol propane mono(meth)acrylate and the ethoxylated or propoxylated analogs t~ereof, pentaerythritol(meth)acrylate, tetrahydro furfuryl(meth)acrylate, cyclohexyl acrylate, cyclo~
hexyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, glycidyl acrylate and glycidyl methacrylate. Preferably, the monomer is pentaerythritol acrylate, although a combination of suitable monomers is also advantageous.
In the photopolymerizable mixture of these two mono-mers the polyfunctional monomer should be present in an amount of more than about 50% and, more preferably, should be present in an amount of from about 65% to about 99%, most preferably from about ~0% to about 97.5~. The monofunctional monomer should comprise the balance of the photopolymerizable mixture.
The photopo]ymerizable mi~ture is present at a percent solids level which is preferably in -the range of from about 20~ to about 70~ by weight. More preferably, the ~1.27~i~?4,~3 photopolymerizable mixture is present at a percent solids level of from about 30~ to about 60% by weight and most preferably about 30% to about 50% by weight.
One of the significant aspects of this embodiment of the invention is that the 3-dimensional structure provided by the polyfunctional monomer provides good matrix integrity allowing for a tough image and the linear propagation provided by the mono-functional monomer provides good photospeed.
This embodiment, too, reduces the need for use of an oxygen barrier layer or the necessity for processing in a nitrogen barrier environment.
One of the significant aspects of this invention is that the photosensitive composition produced thereby may be developed with a composition which does not necessarily con-tain any organic solvents and which need only contain a minor amount o salts and surfactants. There is a great advantage in the elimination of organic solvents in the developer composition due to the fact that such solvents are expensive and their effluents are toxic.
Other components which may be included in the photosensitive composition of this invention include acid stabilizers, exposure indicators, plasticizers, photoactivator5 and colorants.
Suitable acid stabilizers useful within the context of this invention include phosphoric, citric, benzoic, m-nitro benzoic, p(p-anilino phenylazo) benzene sulfonic acid, ~,~'-dinitro-2,2'-stilbene disul~onic, itaconic, tartaric and p-toluene sulfonic acid, and mixtures thereof. Preferably, the acid stabilizer is phosphoric acid. When used, the acid stabilizer is preferably present in the radiation-polymerizable composition in the amount ~1 27~ 8 of from about 0.3% to about 2.0%, and most preferably from about0.75% to about 1.5%, although the skilled artisan may use more or less as desired.
Exposure indicators (or photoimagers) which may be useful in conjunction with the present invention include 4-phenylaæodiphenylamine, eosin, azobenzene/ Calcozine Fuchine dyes and Crystal Violet and Methylene Blue dyes. Preferably, the exposure indicator is 4-phenylazodiphenylamine. The e~posure indicator, when one is used, is preferably present in the composition in an amount of from about 0.001% to about 0.0035~
by weight. ~ more preferred range is from about 0.002% to about 0.030~ and, most preferably, the exposure indicator is present in an amount of from about 0.005~ to about 0.20~; although the skilled artisan may u~e more or less as desired.
A plasticizer may also be included in the composition of this invention to prevent coating brittleness and to keep the composition pliable if desired. Suitable plasticizers include dibutylphthalate, triarylphosphate and substituted analogs thereof and, preferably, dioctylphthalate. The plasticizer is preferably present in the composition of this invention in an amount of from about 0.5~ to about 1.25~ by weiyht, although the skilled artisan may use more or less as desired.
Colorants useful herein include dyes such as Rhodamine, Calcozine, Victoria Blue and Methyl violet, and such pigments as the anthraquinone and phthalocyanine types. Generally, the colorant is present in the form of a pigment dispersion which may comprise a mixture of one or more pigments and/or one or more dyes dispersed in a suitable solvent or mixture of solvents.

When a colorant is used, it is preferably present in the composition of this invention in an amount of from about 1.5% to about 4.0% by weight, more preferably from about 1.75~ to about 3.0% and most preferably from about 2.0% to about 2.75%, although the skilled artisan may use more or less as desired.
The composition of this invention may be dispersed or dissolved in a solvent to facilitate application of the composition to the substrate. Suitable solvents for this purpose include water, tetrahydrofuran, butyrolactone, glycol ethers such as propylene glycol monomethyl ekher and methyl cellosolve, alcohols such as ethanol and n-propanol, and ketones such as methyl ethyl ketone, or mixtures thereof. Preferably, the solvent comprises a mixture of tetrahydrofuran, propylene glycol monomethyl ether and butyrolactone. In general, the solvent system is evaporated from the coating composition once it is applied to an appropriate substrate, however, some insignificant amount of solvent may remain as residue.
Substrates useful for coating with the composition of this invention to form a lithographic printing plate include sheets o~
transparent films such as polyester, aluminum and its alloys and other metals, silicon and similar materials which are well known in the art. Preferably, the substrate comprises aluminum. The substrate may irst be pretreated by standard graining and/or etching and/or anodizing techniques as are well known in the art, and also may or ma~ not have been treated with a composition such as polyvinyl phosphonic acid, sodium silicate or the like suitable for use as a hydrophilizing agent.
In the production of photographic elements such as lithogra-phic printing plates, an aluminum substrate is first preferably ~ ~2'76a~

grained by art recognized methods such as by means of a wire brush, a slurry of particulates or by chemical or electrochemical means, for example in an electrolyte solution comprising hydrochloric acid~ The grained plate is preferably then anodized for example in sulfuric or phosphoric acid in a manner well known in the art. The grained and optionally anodized surface is preferably then rendered hydrophilic, for example, by treatment with polyvinyl phosphonic acid, sodium silicate or the like by means which are also known to the skilled artisan. The thusly prepared plate is then coated with the composition of the present invention, preferably at a coating weight of from about 0.6g/m2 to about 2~5g/m2, more preferabl~ from about 0.8g/m~
to about 2.0g/m2 and most preferably from about 1.2g/m2 to about 1 5g/m2, although these coating wei~hts are not critical to the practice of this invention, and dried.
Preferably the thusly prepared lithographic printing plate is exposed to actinic radiation through a negative. The exposed plate is then developed with a suitable aqueous developer composition such as an aqueous developer comprising one or more 0 o~ the following groups:
a) a sodium, potassium or lithium salt of octyl, decyl or dodecyl monosulfate;
b) a sodium, lithium, potassium or ammonium metasilicate salt; and c) a lithium, potassium, sodium or ammonium borate salt;and d) an aliphatic dicarboxylic acid, or sodium, potassium or ammonium salt thereof having from 2 to 6 carbon atoms;
and e) mono,di-, or tri-sodium or -potassium phosphate.

Other suitable developers include water, benzoic acid or sodium, lithium and potassium benzoates and the hydroxy substitutea analogs thereof as well as those developers described in United States Patent 4,43G,807.
In conventional use, the developed plate is finished with a subtractive finisher such as a hydrophilic polymer. Examples include cold water soluble dextrin and/or polyvinyl pyrrolidone, a nonionic surfactant, a humectant, an inorganic salt and water, as taught by United States 4,213,887.
For the purpose of improving the press performance of a plate prepared as described above, it is known that baking of the exposed and developed plate can result in an increase in the number of quality impressions over that otherwise obtainable. To properly bake the plate, it is first treated with a solution desig-nated to prevent loss of hydrophilicity of the background during baking. An example of an effective solution is disclosed in United States 4,355,096. The thusly prepared plate is then heat treated by baking at a temperature of from about 180C up to the annealing temperature of the substrate, most preferably about 240C. The effective baking time is inversely proportional to the temperature and averages in the range of from about 2 to about 15 minutes. At 240C the time is about 7 minutes.
Example 1 75.0 g of Vinol 523, a vinyl alcohol/vinyl acetate copo-lymer which has from about 75~ to 80~ hydroxyl groups by weight and an average molecular weight of about 70,000, is dissolved in a ~ 2~

solution comprising 225.0 g of water and 200.0 g of ethanol for 16 hours at 70C after which 10.13 g of hydrochloric acid (37%) is added and the temperature adjusted to 60C while mixing vigorously. 37.66 g of propionaldehyde is slowly titrated into the reaction mixture. Simultaneously, 250.0 g of ethanol is likewise titrated into the reaction mixture. The mixture i~ then neutralized to a pH of 7.0 with a sodium carbonate/sodium hydroxide (50/50) mixture. The product is isolated in granular form by precipitation with water. It is then dried so as to have a moisture residue of not greater than 1.0%. A yield of 107 g or about 96% is obtained. The average molecular weight is about 90, ono.
Using stanaard analytical techniques the product is found to consist of 13.6% acetate, 9.8% hydroxyl and 76.6~ aceta~
groups. Of the acetal groups, 80% are found to be six-membered cyclic acetal, 4% are five-membered cyclic acetal, and 16% are intermolecular acetals.
Example 2 40.0 g of Gelvatol 20-30, a vinyl alcohol/vinyl acetate copolymer which has from about 75% to 80% hydroxyl groups by weight and an average molecular weight of about 10,000, is dissolved in a solution comprising 120.0 g of water and 120.0 g of ethanol for 16 hours at 70C after which 10.13 g of hydrochloric acid (37%) are added and the temperature is adjusted to 60C while mixing vigorously. 12.06 g of acetaldehyde is slowly titrated into the reaction mixture. Simultaneously, 120.0 g of ethanol is likewise titrated into the reaction mixture.
The mixture is then neutrali~ed to a pH of 7.0 with a sodium carbonate/sodium hydroxide (50/50) mixture. The product is isolated in granular form by precipitation with water. It is then dried so as to have a moisture residue of not greater than 1.0%. A yield of 49.5 g or about 95% is obtained. The average molecular weight is about 10,500.
Using standard analytical techniques the product is found to consist of 17.0% acetate, 28.0% hydroxyl and 55.0% acetal groups. Of the acetal groups, 80% are found to be six-memberecl cyclic acetal, 4% are five-membered cyclic acetal, and 16% are intermolecular acetals.
Example 3 40.0 g of Gelvatol 20-30, is dissolved in a solution comprising 120.0 g of water and 120.0 g of ethanol for 16 hours at 70C after which 10.13 g of hydrochloric a-id (37%) are added and the temperature is adjusted to 60C while mixing vigorously.
27.41 g of hexanal is slowly titrated into the reaction mixture.
Simultaneously, 120.0 g of ethanol is likewise titrated into the reaction mi~ture. The mixture is then neutralized to a pH
of 7.0 with a sodium carbonate/sodium hydroxide (50/50) mixture.
The product is isolated in granular form by precipitation with water. It is then dried so as to have a moisture residue of not greater than 1.0~. A yield of 64.9 g or about 95% is obtained-Using standard analytical techniques the product is foundto consist o~ 17.0% acetate,9.0~ hydroxyl and 74.0% acetal groups.
Of the acetal groups, 80% are Eound to be six-membered cyclic acetal, 4% are ~ive-membered cyclic aceta~, and 16% are intermolecular acetals.

~ ~7~

Example 4 40.0 g of Gelvatol 20-30, is dissolved in a solution comprising 120.0 g of water and 120.0 g of ethanol ~or 16 hours at 70C after which 10.13 g of hydrochloric acid (37%) are added and the temperature is adjusted to 60C while mixing vigorously.
35.98 g of octanal is slowly titrated into the reaction mixture.
Simultan~ously, 120.0 g of ethanol is likewise titrated into the reaction mixture. The mixture is then neutralized to a pH of 7.0 with a sodium carbonate/sodium hydroxide (50/50) mixture.
~he product is isolated in granular form by precipitation with water. It is then dried so as to have a moisture residue of not greater than 1.0%. A yield of 72.5 g or about 95% is obtained. The average molecular weight is about 11,200.
Using standard analytical techniques the product is found to consist of 17.0% acetate, 10.0% hydroxyl and 73.0% acetal groups. Of the acetal groups, 80% are found to be six membered cyclic acetal, 4% are five-membered cyclic acetal, and 16% are intermolecular acetals.
Example 5 (Comparison~
A sample of Formvar 12/85, a polyvinyl acetal resin obtained from Monsanto Corporation of St. Louis, Missouri which has been prepared according to United States Patent 2,179,~51 is analyzed using standard analytical techniques whereby the product is found to have an average molecular weight of 32,000 and to consist of 23.5~ acetate, 5.7~ hydroxyl and 70.8% acetal groups. Of the acetal groups, 90-95% are found to be six-membered cyclic acetals, 0% are five-membered cyclic acetals and 5-10~ are intermolecular acetals.

, ~ ~

~ 2~

Example 6 (Comparison) A sample of Butvar B-90, a polyvinyl butyral resin obtained from Monsan-to Corporation of St. Louis, Missouri which has been prepared according to United States Patent 2,915,58~ is analyzed using s-tandard analytical -techniques whereby the product is Pound to have an average molecular weight of 41,000 and to consist of 1~ acetate, 19~ hydroxyl and 80~ acetal groups. Of the acetal groups, 90-95% are fo~nd to be six-membered cyclic acetals, 0 are five-membered cyclic acetals and 5-10~ are intermolecular acetals.
Example 7 Various properties o~ a resin prepared as in Example 1 are compared with those ofFormYar*12/85, as described in Example 5 and Butvar B-90, as described in Example 6. The results are tabulated in Table I. The procedures employed are standard ASTM ana}ytical techniques as shown, unless indicated.

Table I
ASTM Inventive Formvar Butvar Units Method Resin 12/85 ~-90 Tensile 3 Strength 10 psi D638-58T 12.5-16.36.5-7.5 7.0-8.0 Elon~ation % D638-58T 85 30 75 Glass Temperature C D1043-51(1) 57-71 92-100 62-68 Dielectric 103 ohm D150-59T 2.7 3.1 3.0 Constant 106 ohm D150-59T 2.5 2.9 2.8 Viscosity cps (2) 2~00-3000500-600 ~,000-18,000 Speci~ic Gravity - D792-50 1.227 1.219 1.100 . 26 -*Trade Mark (1) The glass transition temperatur~ was determined by ASTM
D1043~Sl and by Differential Scanning Calorimetry. Results by Differential Scanning Calorimeter run 5 to 8C higher than ASTM method.
t2) Viscosity was determined in 15~ by weight solutions in toluene: ethanol (60:40) at 25C using a Brookfield ~iscometer.
It can be readily seen that the resin of this invention shows substantially increased tensile strength and elongation while maintaining similar glass transition temperature, dielectric constant and specific gravity. Viscosity variations are not significant since they are essentially a function of molecular weight.
Example 8 40O0 g of Gelvatal 20-~0, a vinyl alcohol/vinyl acetate copolymer which has from about 75% to 80% hydroxyl groups by weight and an average molecular weight of about 60,000 is dissolved in a solution comprising 120.0 g of water and 120~0 g of ethanol for 16 hours at 70C after which 10.13 g of hydrochloric acid (37%) are added and the temperature is adjusted to 60C while mixing vigorously with 27.41 g of hexanal.
Using standard analytical techniques the product is found to consist of 1502% acetate, 7.6% hydroxyl and 77.2~
acetal groups. Of the acetal groups, ~0% are found to be six-membered cyclic acetal, 4% are five-membered cyclic acetal, and 16% are intermolecular acetals.
Example 9 75.0 g of Elvanol 52-22, a vinyl alcohol/vinyl acetate copolymer which has from about 75% to 80% hydroxyl groups by weight and an average molecular weight of about 90,000, is 7~

dissolved in a solution comprising 225.0 g of water and 200.0 g of ethanol for 16 hours at 70C after which 10.13 g of hydrochloric acid (37%) is added and the temperature adjusted to 60C while mixing vigorously with 28.62 g of acetaldehyde.
Using standard analytical teehniques the product is found to consist of 17O2% aeetate, 13.6% hydroxyl and 69.2%
aeetal groups. Of the aeetal groups~ 80% are found to be six-membered eyclic acetal, 4% are five-membered cyclie aeetal, and 16% are intermoleeular aeetals.
Example 10 40.0 g of Vinol 205, a vinyl alcohol/vinyl acetate copolymer which has from about 75% to 80% hydroxyl groups and an average molecular weight of about 26,000, is dissolved in a solution comprising 120.0 g of water and 120.0 g of ethanol for 16 hours at 70C after which 10.13 g of hydrochloric acid (37%) are added and the temperature is adjusted to 60C while mixing ;~ vigorously with 20.09 g of propionaldehyde.
Using standard analytical techniques the produet is found to eonsist of 13.6% acetate, 9.8% hydroxyl and 76.6%
aeetal groups. Of the acetal groups, 80% are found to be six-membered eyelic aeetal, 4~ are five-membered eyclic acetal, and 16% are intermoleeular aeetals.
Example 11 An 8" x 25" seetion of lithographie grade 1100 aluminum alloy is degreased with an aqueous alkaline degreasing solution and eleetroehemieally grained using 900 coulombs of alternating current in a medium of nitric aeid and aluminum nitrate. The grained plate is well rinsed and anodized in a sulfuric acid bath. Sufficient eurrent and voltage is used to ~ 2~ -~v27~ gL8 produce an oxide layer of 2.8g/m2. The anodized plate is well rinsed and hydrophilized by immexsin~ the plate into a solution of polyvinyl phosphonic acid. The plate is well rinsed and dried.
The thusly prepared plate is whirler coated with a solution having the following composition:

~ w/w Binder Resin as described in Example l4.36 Polycondensation product of 3-methoxy-diphenyl amine-4-diazonium sulfate and 4,4-bis-methoxy methyl diphenyl ether, isolated as the mesitylene sulfonate 4.59 Phosphoric Acid 0.23 4-Phenylazodiphenylamine 0.09 Pigment Dispersion 6.57 Propylene glycol monomethyl ether 74.08 Butyrolactone 10.08 The coated and dried plate is exposed to actinic radiation through a negative exposure flat so as to yield a solid seven on a 21 step Stouffer step wedge. The plate is developed using the following composition at a pH o 7.3:
% w/w sodium benzoate 6.9 sodium octyl sulfate 3~0 trisodium phosphate 2.8 monosodium phosphate 1.5 2 Balance and finished with the following composition:
% w/w Dextrin*** 5.52 sodium octyl sulfate 1.61 Triton X-100**** 1.00 ~R~P~ RJ~

~.27~

% W/W
G.ivgaurd DXN***** 0.05 H3PO~ 2.37 H2O Balance ________ *** hydrolyzed tapioca dextrin **** isooctyl phenol polyoxyethylene ethanol; 4.5 moles ethylene oxide ***** 1,4-dimethyl-6-acetoxy-dioxane and run on a Solna sheet fed press using abrasive ink, over-packing, and a Dahlgren dampening system until image breakdown is achieved. Under these conditions the plate provides 103,000 acceptable impressions.
Example 12 An aluminum plate selected and pretreated as in Example 11 is whirler coated with a solution having the following composition: % w/w Binder Resin as described i.n Example 8 3.72 Polycond.ensation product as in Example 11 3.72 Phosphoric Acid 0.37 Dye 0.19 Propylene glycol monomethyl ether76.60 Butyrolactone 18.40 The coated and dried plate is exposed to actinic radiation throuyh a negative exposure flat so as to yield a solid seven on a 21 step Stou~fer step wedge. The plate is developed and finished as described in Example 11.

Under the conditions of Example ll the plate provides llO,000 acceptable impressions.
Example 13 An aluminum plate prepared as in Example 11 is whirler coated with a solution having the following composition:

% w/w Binder Resin as described in Example 94.19 Polycondensation product as in Example 11 4.41 Phosphoric Acid 0.51 Pigment Dispersion 4.42 4-Phenylazodiphenylamine 0.013 Solvent System 90.00 where.in the solvent system is comprised of 95% of a mixture of n-propanol and water (72:28) and 5% of butyrolactone.
The coated and dried plate is exposed to actinic radiation through a negative exposure flat so as to yield a solid seven on a 21 step Stouffer step wedge~ The plate is developed and finished as described in Example 11.
Under the conditions of Example 11 the plate provides 125,000 acceptabl.e impressions.
Example 14 An aluminum plate prepared as in Example 11 is whirler coated with a solution ha~ing the following composition:
% w/w Binder Resin as described in Example 10 8.0 Polycondensation product as in Example ll 10.0 Phosphoric Acid 2.0 4-Phenylazodiphenylamine 0.05 Pigment Dispersion 9.0 4~

% W/W
Propylene glycol monomethyl ether 35.48 Butyrolactone 35.48 The coated and dried plate is exposed to actinic radiation through a negative exposure flat so as to yield a solid seven on a 21 step Stouffer step wedge. The plate is developed and finished as described in Example 11.
Under the conditions of Example 11 the plate provides 70,000 acceptable impressions.
Example 15 An aluminum plate prepared as in Example 11 is whirler coated with a solution having the following composi-tion:

~_ w/w Binder Resin as described in Example 2 5.48 Co-condensation product of diphenyl amine-4-diazonium sulfate and 2,5-dimethoxy-4-(tolyl mercapto)benzene diazonium tetrachlorozincate with paraformaldehyde 3.47 Phosphoric Acid 0.23 4-Phenylazodiphenylamine 0.09 Pigment Dispersion 6.57 Propylene glycol monomethvl ether74.08 Butyrolactone 10.08 The coated and dried plate is exposed to actinic radiation through a negative exposure flat so as to yield a solid seven on a Stouffer Step Wedge.

~.2~ 463 The pla~e is de~eloped with tap water and is found to be fully developed and fully desensitized~ It is then ~inished with ~he composition stated in ~xample 11.
Under the conditions of Example 11 the plate provides 95,000 acceptable impressions.
It can be readily observed that plates prepared according to -this invention show substantially increased press runs yet may be developed with compositions that do not necessarily contain organic solvents and need only contain a minor amount of salts and surfactants.
An aluminum plate as described in Example 11 is whirler coated with a solution having the following composition:

w/w Binder resin as described in Example 1 4.54 Dipentaerythritol monohydroxy pentaacrylate 2.01 Diacrylated urethane oligomer formed by reacting 1,6-hexane diol with adipic acid in a mole ratio o~ greater than 1:1 (adipic acid/1,6-hexane diol) to form a polyester 20and then reacting with dicyclohexyl-methane-41~'-bis diisocyanate in a 2:1 mole ratio (diisocyanate/polyester). The product is then reacted with 2-hydroxy ethyl acrylate in a 2:1 mole ratio (acrylate/diiso-cyanate polyester product) 2.01 Polycondensation product as in Example 11 1.22 2-Stilbenyl-4,6-dl(trichloromethyl)triazine 0.32 .s' ~,~, .

% w/w Methyl cellosolve 89.90 The coated and dried plate is exposed to actinic radiation through a neqative exposure flat so as to yield a solid seven on a 21 s-tep Stouffer step wedge. ~he plate is developed and finished as described in ~xample 11.
Under the conditions of Example 11 the plate provides 595,000 acceptable impreqsions, Example 17 A lithographic printing plate is prepared and processed as described in Example 16 excep~ that the diacrylated ~rethane oligomer i5 omitted. Under these conditions the plate providas only 315,000 acceptable impressions.
Example~
A lithographic printing plate is prepared and processed as described in Example 16 except that the dipentaerythritol monohydroxy pentaacrylate is omitted. Under these conditions the pla-te provides only 340,000 acceptable impressions.
Example 19 A lithographic printing plate is prepared and processed as descri~ed in Example 16 except that the diazo composition is omitted. Under these conditions the plate provides only 220,000 acceptable impressions.
Example 20 A }ithographic printing plate is prepared and processed as described in Example 16 except that the 2-stilbenyl-4,6-di-(trichloromethyl)triazine is omitted. Under these conditions the plate provide~ only 335,000 acceptable impressions.

- - \

It can be readily observed that plates prepared according to this invention IExample 16) show substantially increased press runs and may be developed with compositions which do not contain organic solvents.
Example 21 An aluminum plate as described in Example 11 is whirler c~a-ted with a solution having the following composition:

% w/w Binder resin as described in Example 9 4.54 10 Pentaerythritol tetraacrylate2.01 Diacrylated urethane oligomer as in Example 16 2.01 Polyconaensa~ion product as in Example 11 1.22 2-Stilbenyl-~,6-di(trichloromethyl~triazine 0.32 Methyl cellosolve 89.90 The coated and dried plate is exposed to actinic radiation through a negative exposure flat so as to yield a solid seven on a 21 step Stouffer step wedge. The plate is developed and finished as described in Example 11.
Under the conditions of Example 11 the plate provides 605,000 acceptable impressions.
Example 22 A~ aluminum plate as in Example 11 is whirler coated with a soluti.on havin~ the following composition:

w/w ~inder resin as descr~.bed in Example 84.54 Pentaerythritol tetraacrylate 2.01 Diacrylated urethane oligomer as described in Example 16 2.01 ~ 35 -~ w/w Polycondensation product as described in Example 11 1.22 2-Stilbenyl-4,6-di(trichloromethyl)triazine 0.32 Methyl cellosolve _ _ The coated ana dried plate is exposed to actinic radiation through a negative exposure flat so as to yield seven on a 21 s-tep Stouffer step wedge. The plate is de~eloped and finished as described in Example 11.
Under the conditions of Example 11 ~he plate provides 10 515, 000 acceptable impressions.
Exam~le ?3 ~Comparison) An aluminum plate as in Example 11 is whirler coated ; with a solution having the followin~ composition:

% w~w Binder resin Formvar 12/85,(see Example 6J 4.54 Pentaerythritol~tetraacrylate 2.01 ; Diacrylated urethane oligomer as described in Example 16 2.01 Polycondensation product as in Example 11 1.22 20 2-Stilbenyl-4,6-di(trichloromethyl)triazine0.32 Methyl cellosolve The coated and dried plate is exposed to actinic radiation through a negative exposure flat so as to yield a solid seven on a 21 step Stouffer step wedge. The plate is attempted to be developed with the developer described in Example 11.

!~

\
~.2~

It is found that ~he plate cannot be de~eloped. No indication of coating removal or de~ensitiza-tion is detected.
Example 24 An alumlnum plate as in Example 11 i9 whirler coated with a solut~on ha~ing the following composition:
~ w~w Binder resln as de~cribed in Example 1 4.54 Pentaerythritol tetraacrylate 2.85 Pentaerythritol triacrylate 0.86 10 Pentaerythritol diacrylate 0.19 Pentaerythritol acrylate 0.12 Polycondensation product as in Example 11 1.22 2-Stilbenyl-4,6-di(trichloromethyl)triazine 0.32 Methyl cellosolve Balance The coated and dried plate i5 exposed to actinic radiation through a ne~ative exposure flat so as to yield a solid seven on a 21 step Stouffer step wedge. The plate is developed and finished as described in Example 11.
Under the c~nditions of Example 11 the plate provides 540,000 acceptable impressions.
Example_25 A lithographic printing plate ~s prepared and processed as described in Example 24 except that the pentaerythritol acrylate is omitted. Under these conditlons the plake provides only 315,~00 acceptable impressions.

? ~
, .:

Example 26 A lithographic printinq plate is prepared and processed as described in Example 2~ except that the 2~stilben~yl-4,6-di-(trichloromethyl)triazine is om:itted. Vnder ~hese conditions the plate provides only 335,000 acceptable impressions.
~xa~ple 27 An aluminu~ plate as described i.n Example 11 is whirler coa-ted with a solution havinq the following composition:

1 0 ~ w/w ~inder resin as described in Example 8 4.54 Pentaerythrito1 tetraacrylate 2.~5 Pentaerykhritol triacrylate 0.86 Pentaerythritol diacrylate D.l9 Pentaerythritol acrylate 0.12 Polycondensation product as in Example 11 1.22 2-Stilbenyl 4,6-di(trichloromethyl)triazine 0.32 Methyl cellosolve Balance The coated and dried pla e is exposed to actinic radiation through a negative expos~lre ~lat so as to yield a solid seven on a 21 step Stouf~er step wedge. The plate is developed and ~inished as described in Example 11.
Under the conditio~s of Example 11 the plate provides 510,000 acceptable impressions.
Example 28 An aluminum plate as in ~xample 11 is whirler coated with a solution having the following composition:

% w/w Binder resin as described in Example ~ 4.54 Pentaerythritol tetraacrylate 2.85 Pentaerythritol triacrylate 0.86 Pentaerythritol diacrylate 0.19 Pentaerythritol acrylate ~.12 Polycondensation product as described in Example 11 1.22 2-Stilbenyl-4,6-di(trichloromethyl)triazine 0.32 Methyl cellosolve Balance i~ The coated and dried plate is exposed to actinic radiation through a negati~e exposure flat so as to yield a solid seven on a 21 step Stouffer step wedge. The plate is developed and finished as described in Example 11.
Under the conditions of Example 11 the plate provides 575,000 acceptable impressions.

Claims (19)

1. A resin comprising units of each of the general types A, B and C, in an ordered or random sequence, wherein A is present in an amount of from 5 % to 20 % by weight and is a unit of the formula B is present in an amount of from 4 % to 30 % by weight and is a unit of the formula and C is present in an amount of from 50 % to 91 % by weight and comprises units of each of the formulae C I, C II and C III

(C I), (C II), (C III) where R is lower alkyl or hydrogen, and wherein said units C I
are present in an amount of from 75 % to 85 %; units C II are present in an amount of from 3 % to 5 %; and units C III are pres-ent in an amount of from 10 % to 22 %, based on the total weight of the units C.

2. The resin of claim 1 wherein R is an alkyl group having from 1 to 8 carbon atoms.

3. The resin of claim 1 which has a molecular weight of from 5,000 to 100,000.

4. A method of preparing the resin of claim 1 which comprises a) dissolving a vinyl alcohol/vinyl acetate copolymer having from 75 % to 80 % hydrolization by weight in a solvent mixture of water and a hydroxyl-group containing organic solvent, b) heating the solution at a temperature of from about 50° C to the boiling point of the solution; and adding a catalytic amount of an acid selected from the group consisting of organic sulfonic acids and mineral acids to said reaction solution; and c) adding an aliphatic aldehyde having the formula R-CHO, wherein R is hydrogen or lower alkyl, to said solution in an amount sufficient to produce a degree of acetal formation of from about 50 % to about 91 % by weight.

5. The method of claim 4 which further comprises either removing said acid from the reaction solution or neutralizing the reaction solution to a pH of from 6.5 to 7.5.

6. The method of claim 4 wherein the amount of said aldehyde is from 25 % to 100 % by weight of said copolymer.

7. A photosensitive composition comprising a binder resin as claimed in claim 1 and a diazonium salt polycondensation product.

8. A photosensitive composition according to claim 7, wherein said diazonium salt polycondensation product is prepared by reacting at least one A-N2X compound and at least one B1 com-pound of the formula E(-CHRa-ORb)m in which A is a radical of a compound of the formula (R1-R3-)pR2-N2X
wherein R1 is an optionally substituted phenol or naphthyl group R2 is an optionally substituted phenylene group, R3 is a single bond or one of the groups -(CH2)q-NR4-, -O-(CH2)r-NR4-, -S-(CH2)r-NR4-, -S-CH2-CO-NR4-, -O-R5-O-, - O -, - S - or wherein q is a number from 0 to 5, r is a number from 2 to S, R4 is selected from the group consisting of hydrogen, alkyl with 1 to 5 carbon atoms, aralkyl with 7 to 12 carbon atoms, and aryl with 6 to 12 carbon atoms, R5 is an arylene group having 6 to 12 carbon atoms, X is an anion, p is a number from 1 to 3, E is a radical obtained by splitting off of m H atoms from a compound free of diazonium groups selected from the group consisting of aromatic amines, phenols, thiophenols, phenyl ethers, aromatic thioethers, aromatic heterocyclic compounds, aromatic hydro-carbons and organic acid amides, Ra is selected from the group consisting of hydrogen and phenyl, Rb is selected from the group consisting of hydrogen, alkyl, lower acyl and phenyl, and m is an integer from 1 to 10 in a strongly acidic condensation medium under conden-sation conditions sufficient to produce a polycondensa-tion product of an aromatic diazonium compound contain-ing, on the average, about 0.1 to 50 B1 units per unit of A-N2X.

9. A photosensitive composition according to claim 7 which further comprises a photointiator and an acrylic monomer.

10. A photosensitive composition according to claim 8 where-in said monomer is a photopolymerizable mixture of a) an acrylic monomer having two or more unsaturated groups; and b) an oligomer which is prepared by reacting one molar equivalent of a substantially linear polymeric com-pound having an active hydrogen group at each end thereof with at least two molar equivalents of a diisocyanate compound so as to form a prepolymer having an isocyanate group at each end thereof and subsequently reacting said prepolymer with at least two equivalents of an ethylenically unsaturated compound having an active hydrogen group.

11. A photosensitive composition according to claim 9 wherein said acrylic monomer is an ethylenically unsaturated compound having two or more acrylic or methacrylic acid ester groups.

12. A photosensitive composition according to claim 9 or 10 wherein said monomer is present in said composition in an amount of from about 10 % to about 35 % by weight.

13. A photosensitive composition according to claim 10 wherein said oligomer is present in said composition in an amount of from about 10 % to about 35 % by weight.

14. A photosensitive composition according to claim 9 wherein said monomer is a photopolymerizable mixture of a) a polyfunctional acrylic monomer having two or more unsaturated groups; and b) a monofunctional acrylic monomer having one unsat-urated group.

15. A composition according to claim 14 wherein said polyfunctional monomer is an ethylenically unsaturated compound having from 2 to 6 acrylic or methacrylic acid ester groups.

16. A composition according to claim 14 wherein said mono-functional monomer is an acrylic or methacrylic acid ester.

17. A composition according to claim 14 wherein said photopolymerizable mixture is present in said composition in an amount of from 20 % to 70 % by weight.

18. A composition according to claim 14 wherein said polyfunctional monomer is present in said photopolymerizable mixture in an amount of more than 50 % by weight.

19. A composition according to claim 18 wherein said poly-functional monomer is present in said photopolymerizable mixture in an amount of from 65 % to 99 % by weight.