1. Initiator system comprising: (a) at least one compound capable of absorbing IR radiation selected from the group consisting of triarylamine dyes, thiazolium dyes, indolium dyes, oxazolium dyes, cyanine dyes, polyaniline dyes, polypyrrole dyes, polythiophene dyes and phthalocyanine pigments, (b) at least one compound capable of producing radicals wherein the at least one compound is a polyhaloalkyl-substituted compound, (c) at least one polycarboxylic acid or salt thereof wherein the polycarboxylic acid is represented by the following formula I R 4 —(CR 5 R 6 ) r —Y—CH 2 COOH   (I) wherein Y is selected from the group consisting of O, S and NR 7, each of R 4, R 5 and R 6 is independently selected from the group consisting of hydrogen, C 1 -C 4 alkyl, aryl which is optionally substituted, —COOH and NR 8 CH 2 COOH, R 7 is selected from the group consisting of hydrogen, C 1 -C 6 alkyl, —CH 2 CH 2 OH, and C 1 -C 5 alkyl substituted with —COOH, R 8 is selected from the group consisting of —CH 2 COOH, —CH 2 OH and —(CH 2 ) 2 N(CH 2 COOH) 2 and r is 0, 1, 2 or 3 and wherein at least one of R 4, R 5, R 6, R 7 and R 8 includes a —COOH group, and (d) at least one leuco dye, wherein: ox a <red b &plus;1.6 eV where ox a &equals;oxidation potential of component (a) in eV red b &equals;reduction potential of component (b) in eV