Ir - sensitive composition and on the press developable ir - sensitive printing plates

摘要

The present invention relates to IR-sensitive compositions suitable for the manufacture of printing plates developable on-press. The IR-sensitive compositions comprise:(a) a first polymeric binder which does not comprise acidic groups having a pKa value less than or equal to 8;(b) a second polymeric binder comprising polyether groups(c) an initiator system comprising(i) at least one compound capable of absorbing IR radiation selected from triarylamine dyes, thiazolium dyes, indolium dyes, oxazolium dyes, cyanine dyes, polyanifne dyes, polypyrrole dyes, polythiophene dyes and phthalocyanine pigments;(ii) at least one compound capable of producing radicals selected from polyhaloalkyl-substituted compounds; and(iii) at least one polycarboxylic acid represented by the following formula IR4-(CR5R6)r - Y - CH2COOH (I) wherein Y is selected from the group consisting of O, S and NR7,each of R4, R5 and R6 is independently selected from the group consisting of hydrogen, C1-C4 alkyl, substituted or unsubstituted aryl, -COOH and NR8CH2COOH,R7 is selected from the group consisting of hydrogen, C1-C6 alkyl, -CH2CH2OH, and C1-C5 alkyl substituted with -COOH,R8 is selected from the group consisting of -CH2COOH, -CH2OH and -(CH2)2N(CH2COOH)2 and r is 0, l, 2 or 3, with the proviso that at least one of R4, R5, R6, R7 and R8 comprises a -COOH group or salts thereof, and(d) a free radical polymerizable system comprising at least one member selected from unsaturated free radical polymerizable monomers, oligomers which are free radical polymerizable and polymers containing C=C bonds in the back bone and/or in the side chain groups,wherein the following inequality is met:oxi redii + 1.6 eVwith oxi = oxidation potential of component (i) in eVredii = reduction potential of component (ii) in eV.