Polymerizable composition

1. A polymerizable composition comprising:

(A) a monocarboxylic acid compound which causes at least one of decarboxylation and dehydration by heat;

(B) a radical initiator;

(C) a compound having at least one ethylenically unsaturated bond; and

(D) an infrared ray absorber,

wherein the compound (A) and the radical initiator (B) are separate and distinct compounds from each other, and

wherein the compound (A) is one having a group represented by the following formula:

wherein

A represents an aromatic group or a heterocyclic group,

R 1 , R 2 , R 6 , R 7 and R 8 each independently represents a hydrogen atom or a monovalent substituent, provided that R 1 and R 2 , either one of R 1 and R 2 and A, or R 8 and Z may be taken together to form a ring structure, and

Z represents a monovalent substituent.

2. The polymerizable composition according to claim 1 , wherein the compound (A) is one which causes at least one of decarboxylation and dehydration at a temperature of 100° C. to 300° C.

3. The polymerizable composition according to claim 1 , wherein the compound (A) is one having a structure capable of forming a 4 to 6-membered lactone ring, a 4 to 6-membered lactam ring or a 4 to 6-membered cyclic acid anhydride.

4. A lithographic printing plate precursor comprising a support and a recording layer containing the polymerizable composition of claim 1 .

5. A polymerizable composition comprising:

(A-1) a monocarboxylic acid compound represented by the following formula (I-2);

(B) a radical initiator;

(C) a compound having at least one ethylenically unsaturated bond; and

(D) an infrared ray absorber:

wherein

A represents an aromatic group or a heterocyclic group,

R 1 and R 2 each independently represents a hydrogen atom or a monovalent substituent, provided that R 1 and R 2 , either one of R 1 and R 2 and X 1 , either one of R 1 and R 2 and A, or A and X 1 may be taken together to form a ring structure,

X 1 represents a divalent connection group selected from —SO 2 —, —N(R 3 )—, —CH 2 —, —CH(R 4 )—, and —C(R 4 )(R 5 )—,

R 3 represents a monovalent substituent represented by one of the following formulae (i) and (ii):

wherein, R 6 , R 7 and R 8 each independently represents a hydrogen atom or a monovalent substituent, Z represents a monovalent substituent, and R 8 and Z may be taken together to form a ring structure, and

R 4 and R 5 each independently represents a hydrogen atom or a monovalent substituent.

6. The polymerizable composition according to claim 5 , wherein the umnovalent substituent represented by R 1 and R 2 is a halogen atom, a optionally substituted amino group, a alkoxycarbonyl group, a hydroxyl group, a ether group, a thiol group, a thioether group, a silyl group, a nitro group, a cyano group, a optionally substituted alkyl group, a optionally substituted alkenyl group, a optionally substituted alkynyl group, a optionally substituted aryl group, or a optionally substituted heterocyclic group.

7. A lithographic printing plate precursor comprising a support and a recording layer containing the polymerizable composition of claim 5 .