Patent ID: 8221959

Claim:
A lithographic printing plate precursor comprising: an aluminum support having a hydrophilic surface; and a photosensitive layer comprising a binder polymer having an acid value of 0.3 meq/g or less, wherein the photosensitive layer comprises a pigment dispersed with a pigment dispersant which is free from a —COOH group, a —PO 3 H 2 group and a —OPO 3 H 2 group, and is a compound comprising (a) a unit having a functional group adsorbing to the pigment, the functional group being selected from groups represented by the following formulae, and (b) a unit having a functional group imparting dispersibility in an organic solvent: wherein R 1 to R 36 each independently represents an alkyl group which may have a substituent, an aryl group which may have a substituent, an alkenyl group which may have a substituent, an alkynyl group which may have a substituent, —OR, —NRR′, —SR, —COR, —COOR, —CONRR′, —OCOR, —OCONRR′, —OCOOR, —NRCOR′, —NRCOOR′, —NRCONR′R″, —N═R, —SO 2 R, —SO 3 R, —SO 2 NRR′, a hydrogen atom, a halogen atom, a cyano group, a nitro group, a hydroxy group or a mercapto group, in which R, R′ and R″each represents an alkyl group, an aryl group, an alkenyl group, an alkynyl group or a hydrogen atom or may be connected with each other to form a ring, provided that a —COOH group is not formed, or R 1 to R 36 may be connected with each other to form a ring, L represents a divalent connecting group for connecting to a compound skeleton and comprising one or more atoms selected from a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom, a phosphorus atom, a silicon atom, a halogen atom and a boron atom, X represents an oxygen atom, a sulfur atom, a selenium atom or NR 37 in which R 37 has the same meaning as R 1 , Y represents a covalent bond, an oxygen atom, a sulfur atom, NR 38 in which R 38 has the same meaning as R 1 , CO or SO 2 , and M represents an alkali metal; wherein the pigment dispersant has a weight average molecular weight of from 1,000 to 1,000,000; wherein the functional group imparting dispersibility in an organic solvent included in the unit (b) comprises a hydrocarbon group having 6 or more carbon atoms; wherein the lithographic printing plate precursor further comprises an undercoat layer between the aluminum support and the photosensitive layer, the undercoat layer comprising a compound having a polymerizable group, and wherein the undercoat layer does not comprise a pigment dispersed with the pigment dispersant.