Polymerizable composition

1. A polymerizable composition comprising:

(A) a non-acrylic binder polymer containing a polyurethane resin and having an ethylenically unsaturated bond on a side chain;

(B) a neutrally charged hexaarylbiimidazole compound capable of generating a radical under light or heat; and

(C) a compound having an ethylenically unsaturated bond;

wherein the polyurethane resin is a reaction product of a diisocyanate compound and a diol compound, and the diol compound contains (i) at least one diol compound having an ethylenically unsaturated bond group, with at least one being a secondary alcohol, and (ii) at least one diol compound having a carboxyl group.

2. The polymerizable composition according to claim 1 , further comprising:

(D) a polymerization inhibitor.

3. The polymerizable composition according to claim 2 , wherein the polymerization inhibitor (D) contains a 1,4-benzoquinone derivative.

4. The polymerizable composition according to claim 1 , wherein the polyurethane resin has 0.3 meq/g or more of an ethylenically unsaturated bond group on a side chain, and has 0.4 meq/g or more of a carboxyl group on a side chain.

5. The polymerizable composition according to claim 1 , wherein the diol compound having an ethylenically unsaturated bond group is a compound represented by the following formula (G):

wherein R 1 , R 2 and R 3 each independently represents a hydrogen atom or a monovalent organic group, A represents a divalent organic residue, X represents an oxygen atom, a sulfur atom or —N(R 12 )—, and R 12 represents a hydrogen atom or a monovalent organic group.

6. The polymerizable composition according to claim 1 , further comprising (E′) a dye having a maximum absorption wavelength in a region of from 350 to 450 nm.

7. The polymerizable composition according to claim 1 , further comprising an infrared absorbent.

8. A lithographic printing plate precursor comprising a support and a recording layer containing the polymerizable composition according to claim 1 .

9. A polymerizable composition comprising:

(A′) a polyurethane resin having an ethylenically unsaturated bond on a side chain, which is a reaction product of an isocyanate compound and a diol compound including a diol compound represented by the following formula (G):

wherein R 1 , R 2 and R 3 each independently represents a hydrogen atom or a monovalent organic group, A represents a divalent organic residue, X represents an oxygen atom, a sulfur atom or —N(R 12 )—, and R 12 represents a hydrogen atom or a monovalent organic group;

(B) a neutrally charged hexaarylbiimidazole compound capable of generating a radical under light or heat;

(C) a compound having an ethylenically unsaturated bond;

(D′) a 1,4-benzoquinone derivative; and

(E′) a dye having a maximum absorption wavelength in a region of from 350 to 450 nm.

10. A polymerizable composition comprising:

(A) a non-acrylic binder polymer containing a polyurethane resin and having an ethylenically unsaturated bond on a side chain;

(B) a neutrally charged hexaarylbiimidazole compound capable of generating a radical under light or heat;

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

(D) a polymerization inhibitor containing a 1,4-benzoquinone derivative;

wherein the polyurethane resin is a reaction product of a diisocyanate compound and a diol compound, and the diol compound contains (i) at least one diol compound having an ethylenically unsaturated bond group, with at least one being a secondary alcohol, and (ii) at least one diol compound having a carboxyl group; and the diol compound having an ethylenically unsaturated bond group is a compound represented by the following formula (G):

wherein R 1 , R 2 and R 3 each independently represents a hydrogen atom or a monovalent organic group, A represents a divalent organic residue, X represents an oxygen atom, a sulfur atom or —N(R 12 )—, and R 12 represents a hydrogen atom or a monovalent organic group.