Aqueous developable lithographic printing plates containing an admixture of diazonium salts and polymers and composition therefor

Claim 1

A photosensitive composition which comprises in admixture: a polyvinyl acetate resin having an average molecular weight in the range of from about 100,000 to less than about 800,000; a styrene end-capped co-polymer of the formula ##STR7## wherein R is a lower aliphatic alcohol residue having from 1 to about 5 carbon atoms and wherein said polymer has an average molecular weight of not more than about 50,000; at least one light sensitive, negative working diazonium salt Diazo 1 which is a light sensitive, substantially linear polymeric diazonium reaction compound comprising repeating units of the condensation product of each of the general types E + X - and Q, in which E + X - is a radical of the compound of the general formula: ##STR8## wherein: --K-- is selected from the group consisting of ##STR9## --S--, --O--, and --CH 2 --, or is absent; R' is selected from the group consisting of phenyl and C 1 to C 4 alkyl substituted phenyl; P and P 1 are selected from the group consisting of C 1 to C 4 alkyl, methoxy, ethoxy, butoxy, or H; P 1 may be the same as P or different; and X - is an anion; and Q is a radical of an oligomer having the structure: ##STR10## wherein: R is selected from the group consisting of ##STR11## n is an integer from 0 to 3; M is an aromatic radical selected from the group consisting of aromatic hydrocarbons, diaryl ethers, diaryl sulfides, diaryl sulfones, diaryl amines, diaryl ketones and diaryl diketones; m is 1 to 6; Y is selected from the group consisting of --CH 2 -- or --CH 2 --O--CH 2 --bridge; and T is the same as R when Y=--CH 2 -- and H-- when Y=--CH 2 --0--CH 2 -- wherein said diazonium compound is prepared by a two-step process consisting essentially of forming a precondensed oligomer component Q and reacting said component Q with radical E + X - such that the ratio of M to E + X - is at least 2:1; and at least one light sensitive, negative working diazonium salt Diazo 2 which is a light sensitive diazonium compound prepared by reacting in the absence of added paraformaldehyde at least one A--N 2 X compound and at least one B 1 compound of the formula E(--CHR.sub.a --OR.sub.b).sub.m in which A--N 2 X is a radical of a compound selected from the group consisting of a compound of the formula ##STR12## wherein R 1 is a phenyl or naphthyl group R' 1 is a phenylene or naphthylene group R 2 is a phenylene group R 3 is a single bond or one of the groups --(CH 2 ) q --NR 4 -- --O--(CH 2 ) r --NR 4 -- --S--(CH 2 ) r --NR 4 -- --S--CH 2 --CO--NR 4 -- --O--R 5 --O-- --O-- --S-- or --CO--NR 4 -- the left-hand free valence of the specified groups is attached to R 1 and the right-hand free valence is attached to R 2 , wherein q is a number from 0 to 5 r is a number from 2 to 5 R 4 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, R 5 is an arylene group having 6 to 12 carbon atoms Y is one of the groups --NH--, and --O-- 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 group selected from the group consisting of aromatic amines, phenols, thiophenols, phenyl ethers, aromatic thioethers, aromatic heterocyclic compounds, aromatic hydrocarbons and organic acid amides, R a is selected from the group consisting of hydrogen and phenyl, R b is selected from the group consisting of hydrogen, alkyl, ##STR13## wherein n is from 0 to 3 and a phenyl group, and m is an integer from 1 to 10 in a strongly acidic condensation medium and under condensation conditions sufficient to produce a polycondensation product of an aromatic diazonium compound containing, on the average, about 0.1 to 50 B 1 units per unit of A--N 2 X, wherein the total amount of the diazonium compounds ranges from about 20% to about 50% by weight of the composition, and the ratio of Diazo 1 to Diazo 2 is in the range of 1 to about 0.95-1.45; and wherein the polyvinyl acetate resin is present in the amount of from about 8% to about 33%; and wherein the styrene/maleic acid half ester copolymer is present in an amount of from about 25% to about 55% by weight of said composition.