Patent ID: 7294447

Claim:
A heat-sensitive lithographic printing plate precursor comprising (i) a support having a hydrophilic surface or which is provided with a hydrophilic layer; and (ii) a coating provided thereon, the coating comprising an oleophilic layer which, upon image-wise exposure to heat or infrared light and subsequent immersion in an aqueous alkaline developer, dissolves in the developer at a higher dissolution rate in exposed areas than in unexposed areas, wherein the oleophilic layer comprises a polymer that is soluble in the developer and an organic dye in a amount sufficient to provide a visible color to the coating and wherein said organic dye does not reduce the dissolution rate of the unexposed areas in the developer, wherein the organic dye has a chemical structure according to the following formula: D −[( L ) x −( G ) y ] n wherein D is a chromophoric group, L is a divalent linking group, x is 0 or 1, y and n are at least 1, and G is an anionic group or a group which can be rendered anionic by immersion of the coating in the developer, wherein the organic dye is one of the following formulas: wherein i and j are independently 0 to 3; k, l and o are independently 0 to 4; m and n are independently 0 to 5; p is 0 to 3; R 1 , R 1 ′, R 1 ″, R 2 and R 2 ′ are independently selected from the group consisting of optionally substituted alkyl, optionally substituted aryl, -G, -L-G, —CN, a halogen, —NO 2 , —OR d , —CO—O—R a , —O—CO—R a , —CO—NR d R e ,—NR d R e , —NR d —CO—R a , —NR d —CO—O—R a , —NR d —CO—NR e R f , —SO 2 —O—R a , —SO 2 —NR d R e or wherein two adjacent radicals R 1 , R 1 ′, R 1 ″, R 2 or R 2 ′ together form a condensed carbocyclic or heterocyclic ring; R3, R4 and R 5 are independently selected from the group consisting of hydrogen, optionally substituted alkyl, optionally substituted aryl, —CO—R b , —CO—O—R b , —CO—NR f R g and -L-G; with R a and R b being an optionally substituted alkyl or an optionally substituted aryl group; R d , R e , R f and R g being hydrogen, an optionally substituted alkyl or an optionally substituted aryl group; wherein G is independently selected from the group consisting of —COOH, —OH, —PO 3 H 2 , —O—PO 3 H 2 , —SO 3 H, —O—SO 3 H, —SO 2 —NH 2 , —SO 2 —NH—R, —SO 2 —NH—CO—R and salts thereof, R being an optionally substituted alkyl or optionally substituted aryl group.