Polymerizable composition, photopolymerizing method and process for producing lithographic printing plate using the polymerizable composition

A polymerizable composition comprising an ethylenic monomer, a photopolymerization initiator and a benzotriazole compound represented by the following formula (II) or (III):

• wherein X′ represents O, S or NZ′, Z and Z′ each independently represents a straight-chain, branched-chain or cyclic alkyl group containing from 1 to 20 carbon atoms, a straight-chain, branched-chain or cyclic alkenyl group containing from 2 to 20 carbon atoms, an alkynyl group containing from 2 to 20 carbon atoms, an aryl group containing from 6 to 20 carbon atoms, an acyloxy group containing from 1 to 20 carbon atoms, a carbamoyloxy group containing from 1 to 20 carbon atoms, an alkoxy group containing from 1 to 20 carbon atoms, an aryloxy group containing from 6 to 20 carbon atoms, an alkylsulfonyl group containing from 1 to 20 carbon atoms, an arylsulfonyl group containing from 6 to 20 carbon atoms, an amino group containing from 0 to 20 carbon atoms, an imino group containing from 1 to 20 carbon atoms, a sulfo group, an alkylthio group containing from 1 to 20 carbon atoms, an arylthio group containing from 6 to 20 carbon atoms, a ureido group containing from 1 to 20 carbon atoms, a hetero ring group containing from 2 to 20 carbon atoms, an acyl group containing from 1 to 20 carbon atoms, a halogen atom, a silyl group containing from 2 to 20 carbon atoms, provided that each of the recited groups may further have a substituent, Y represents a straight-chain, branched-chain or cyclic alkyl group containing from 1 to 20 carbon atoms, an alkoxy group containing from 1 to 20 carbon atoms, an aryl group containing from 6 to 20 carbon atoms, a halogen atom, a ureido group containing from 1 to 20 carbon atoms, a hetero ring group containing from 2 to 20 carbon atoms, a cyano group or a hydrogen atom, n represents an integer of from 1 to 4 provided that, when n represents 2 or more, the plural Y's may be the same or different from each other, or may be combined with each other to form a ring structure, W represents —C(═O)— or —S(═O)2—, and m represents an integer of from 0 to 3.