Lithographic printing plate precursor

1 . A lithographic printing plate precursor comprising an aluminum support and at least one photosensitive layer containing a polymerization initiator, a polymerizable compound, a binder polymer, an infrared absorber and a coloring agent, wherein the photosensitive layer has a halogen ion concentration in a range of from 0 to 4×10 −5 moles/m 2 .

2 . The lithographic printing plate precursor according to claim 1 , wherein at least one of the infrared absorber and the coloring agent contains a cationic dye.

3 . The lithographic printing plate precursor according to claim 1 , wherein the polymerization initiator is a polymerization initiator which does not contain a halogen ion.

4 . The lithographic printing plate precursor according to claim 1 , wherein the photosensitive layer has a halogen ion concentration in a range of from 0 to 4×10 −6 moles/m 2 .

5 . The lithographic printing plate precursor according to claim 1 , wherein the polymerizable compound is an addition polymerizable compound containing at least one ethylenically unsaturated double bond.

6 . The lithographic printing plate precursor according to claim 1 , wherein the polymerizable compound is contained in the photosensitive layer in an amount of from 5 to 80% by weight based on solids in the photosensitive layer.

7 . The lithographic printing plate precursor according to claim 1 , wherein the binder polymer has a repeating unit represented by the following formula (i):

wherein R 1 represents a hydrogen atom or a methyl group, R 2 represents a connecting group constituted of one or more atoms selected from the group consisting of a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, and a sulfur atom, A represents an oxygen atom or —NR 3 —, R 3 represents a hydrogen atom or a monovalent hydrocarbon group having from 1 to 10 carbon atoms, and n represents an integer of from 1 to 5.

8 . The lithographic printing plate precursor according to claim 1 , wherein the photosensitive layer further contains a heat polymerization inhibitor in an amount of 0.01% by weight to 5% by weight based on a weight of non-volatile components in the photosensitive layer.

9 . The lithographic printing plate precursor according to claim 1 , further comprising a protective layer containing a water-soluble polymer, so that the aluminum support, the at least one photosensitive layer and the protective layer are in this order.

10 . The lithographic printing plate precursor according to claim 1 , wherein the polymerization initiator is an onium salt.