Patent ID: 6960422

Claim:
A negative planographic printing plate precursor for infrared exposure comprising a support and an image recording layer formed on the support, wherein the image recording layer includes an infrared absorbing agent, a radical generator and a radical polymerizable compound, and a sensitivity ratio (S 1 /S 60 ) of a sensitivity of the image recording layer upon being developed 60 minutes after infrared laser exposure (S 60 ) and a sensitivity of the image recording layer developed one minute after exposure (S 1 ) is from 0.5 to 1.0; wherein the image recording layer includes a photosensitive composition, and the photosensitive composition includes a polymer compound which contains at least 0.1% by mol and less than 30% by mol of at least one kind of structural unit represented by the following general formulas (1), (2) and (3) and can be one of dissolved and swollen by one of water and an aqueous alkali solution: wherein each of A 1 , A 2 and A 3 independently represents an oxygen atom, a sulfur atom or —N(R 21 )—; R 21 represents a hydrogen atom or an alkyl group which may have a substituent; each of G 1 , G 2 and G3 independently represents a divalent organic group; each of X and Z independently represents an oxygen atom, a sulfur atom or —N(R 22 )—; R 22 represents an alkyl group which may have a substituent; Y represents an oxygen atom, a sulfur atom, a phenylene group which may have a substituent, or —N(R 23 )—; R 23 represents an alkyl group which may have a substituent; and each of R 1 to R 20 independently represents a hydrogen atom or monovalent organic group.