Lithographic printing plate precursor

1. A lithographic printing plate precursor comprising a support and a photosensitive layer, said lithographic printing plate precursor further comprising a subbing layer between said photosensitive layer and said support,

said subbing layer containing a maleamic acid (co)polymer, in which at least one hydrogen atom on a nitrogen atom is substituted with an onium group, wherein said maleamic acid (co)polymer contains a recurring unit of the following formula Chemical Formula 1:

wherein Y 1 represents an onium group having the following Chemical Formula 2:

wherein:

R 1 and R 2 each independently represents a C 1 -C 4 alkyl group;

R 3 represents a hydrogen atom or a C 1 -C 4 alkyl group;

X − represents a counter anion; and

Z represents a divalent organic group), and

Y 2 represents a hydrogen atom or an onium group as defined above.

2. The lithographic printing plate precursor of claim 1 wherein said onium group comprises a positive nitrogen, phosphorus, or sulfur atom.

3. The lithographic printing plate precursor of claim 1 wherein said maleamic acid (co)polymer comprises a carboxyl group and a carbamoyl group bonded to two adjacent carbon atoms in the main chain.

4. The lithographic printing plate precursor of claim 1 , wherein said maleamic acid (co)polymer is obtained by a first step of reacting a maleic anhydride (co)polymer with an N,N-dialkylamino group-containing amine to obtain a maleamic acid (co)polymer, and a second step of reacting the resulting maleamic acid (co)polymer with an alkyl halide, an alkyl sulfonate ester, or an acid compound.

5. The lithographic printing plate precursor of claim 4 , wherein said N,N-dialkylamino group-containing amine is N,N-di C 1 -C 4 alkylamino C 1 -C 4 alkylamine.

6. The lithographic printing plate precursor of claim 4 , wherein the first and second steps are conducted successively or simultaneously.

7. The lithographic printing plate precursor of claim 4 , wherein said maleic anhydride (co)polymer is a copolymer obtained by copolymerizing maleic anhydride with at least one vinyl-based monomer selected from the group consisting of ethylene, propylene, styrene, α-methylstyrene, and acrylonitrile.

8. The lithographic printing plate precursor of claim 1 wherein said maleic anhydride (co)polymer is present in said subbing layer in an amount of 50% by mass or more.

9. The lithographic printing plate precursor of claim 1 wherein said maleic anhydride (co)polymer is present in said subbing layer in an amount of from 70% to 100% by mass.

10. The lithographic printing plate precursor of claim 1 wherein said photosensitive layer is a positive type photosensitive layer.

11. The lithographic printing plate precursor of claim 1 wherein said photosensitive layer is a negative type photosensitive layer.

12. The lithographic printing plate precursor of claim 1 further comprising a photothermal conversional material.

13. The lithographic printing plate precursor of claim 11 wherein said photothermal conversional material is a pigment or dye having a sensitivity to infrared radiation.

14. The lithographic printing plate precursor of claim 1 that is developable on a printing press.

15. A method of forming an image comprising:

A) imagewise exposing the lithographic printing plate precursor of claim 1 to provide an imagewise exposed element, and

B) developing said imagewise exposed element.

16. The method of claim 15 wherein imagewise exposure is carried out using an infrared radiation laser.

17. The method of claim 15 wherein said developing is carried out using water or a developer.

18. The method of claim 15 wherein said developing is carried out on a printing press using dampening water.