We claim:

1. A process for producing a lithographic printing plate, comprising subjecting a lithographic printing plate precursor to image-wise exposure and then removing the photosensitive layer from an unexposed portion in the presence of a developer having a pH from 2 to 10,

wherein the lithographic printing plate precursor comprising at least a photosensitive layer on a support and employing a system of removing a photosensitive layer from an unexposed portion in a presence of a developer having a pH from 2 to 10, wherein the photosensitive layer comprises the following components (A), (B), and (C):

(A) a copolymer having a repeating unit represented by the formula (1) and at least either one of a repeating unit represented by the formula (2) and a repeating unit represented by the formula (3):

in the formulae (1), (2), and (3), each of A and B independently represents a hetero atom, each of R and R1 to R9 represents a monovalent substituent, L represents a divalent linking group, X represents a hydroxyl group, a monovalent group containing an acid group, an alkyleneoxy group, an amide group, or an ether group, an amino group, an ammonium group, or a salt obtained by neutralizing an acid group, L0 represents a single bond or a divalent hydrocarbon group, with the proviso that R2 and R in the formula (1), R5 and L in the formula (2), and R8 and Lo in the formula (3) may be coupled to each other to form a ring;

(B) a compound having an ethylenically unsaturated bond; and

(C) a polymerization initiator.

2. The process for producing a lithographic printing plate according to claim 1, wherein X in the formula (2) or (3) in the component (A) is selected from an amino group, a sulfonic acid group, a carboxylic acid group, a phosphonic acid group, a group obtained by neutralizing a carboxylic acid, a group obtained by neutralizing a sulfonic acid, and a group obtained by neutralizing a phosphonic acid.

3. The process for producing a lithographic printing plate according to claim 1 or 2, wherein the photosensitive layer further comprises (D) a sensitizing dye.

4. The process for producing a lithographic printing plate according to any one of claims 1 to 3, wherein the copolymer (A) contains the repeating unit represented by the formula (2) or (3) in which X represents a carboxylic acid or a carboxylate and further contains a repeating unit represented by the following formula (I):

in the formula (I), each of two A's independently represents a hetero atom and each of R1 to R3 and R10 independently represents a monovalent substituent, with the proviso that any two of Rx to R3 may be the same or different.

5. The process for producing a lithographic printing plate according to claim 4, wherein the copolymer (A) contains 70 mol% or greater but not greater than 95 mol% of the repeating unit represented by the formula (I).

6. The process for producing a lithographic printing plate according to claim 4 or 5, wherein the copolymer (A) contains the repeating unit represented by the formula (2) or formula (3) in which X represents a carboxylic acid or a carboxylate; contains a repeating unit represented by the formula (II) which is a repeating units represented by the formula (3); and contains, in the copolymer, 30 mol% or greater but not greater than 80 mol% of the repeating unit represented by the formula (II):

7. The process for producing a lithographic printing plate according to any one of claims 4 to 6, wherein the copolymer (A) has a mass average molecular weight (Mw) of from 10,000 to 40,000.

8. The process for producing a lithographic printing plate according to any one of claims 4 to 7, wherein the copolymer (A) contains the repeating unit represented by the formula (2) or the formula (3) in which X represents a carboxylic acid or a carboxylate; and the number of the carboxylic acid or carboxylate contained in one repeating unit is one.

9. The process for producing a lithographic printing plate according to any one of claims 4 to 8, wherein the copolymer (A) contains the repeating unit represented by the formula (2) or the formula (3) in which X represents a carboxylic acid or a carboxylate and L or Lo represents an aliphatic linking group which may have a substituent.

10. The process for producing a lithographic printing plate according to any one of claims 4 to 9, wherein the copolymer (A) has at least one ethylenically unsaturated double bond group.

11. The process for producing a lithographic printing plate according to any one of claims 4 to 10, wherein the copolymer (A) contains the repeating unit represented by the formula (2) or the formula (3) in which X represents a carboxylate having a metal salt as a counter cation.

12. The process for producing a lithographic printing plate according to any one of claims 4 to 11, wherein the photosensitive layer further contains an acrylic resin.

13. The process for producing a lithographic printing plate according to claim 1, wherein the developer contains a surfactant.

14. The process for producing a lithographic printing plate according to claim 13, wherein the surfactant is a surfactant selected from the group consisting of nonionic surfactants and amphoteric surfactants, and combinations thereof.

15. The process for producing a lithographic printing plate according to claim 1, wherein the developer contains an organic amine compound.

16. The process for producing a lithographic printing plate according to any one of claims 1 to 15, wherein removal of the protective layer, development, and gumming are carried out at the same time.