Patent ID: 7771916

Claim:
A negative planographic printing plate precursor, comprising a substrate, a recording layer and a protective layer on the recording layer; wherein the recording layer contains a polymerizable composition comprising (A) a compound represented by the following formula (I), of which a value of log P defined by the following numerical formula is 2.00 or more, (B) an infrared absorbent, and (C) a compound having at least one addition-polymerizable ethylenically unsaturated bond: wherein R 1 represents an optionally substituted alkyl group having 6 to 20 carbon atoms, and R 2 , R 3 , R 4 , R 5 , and R 6 each independently represent a hydrogen atom or a monovalent organic group which may have one or more substituents; and X − represents an acid anion selected from the group consisting of halide anions, BF 4 − , BCl 4 − , ZnCl 4 − , SbCl 6 − , FeCl 4 − , GaCl 4 − , GaBr 4 − , AlI 4 − , AlCl 4 − , SbF 6 − , CF 3 SO 3 − , PF 6 − , a p-toluenesulfonate anion, anions of fused polycyclic sulfonic acids and sulfonate group-containing dyes; log P=log(Coil/Cwater); Coil: a molar concentration in an organic phase at an equilibrium state; Cwater: a molar concentration in an aqueous phase at an equilibrium state; Oil: 1-octanol.