PURPOSE: To obtain a visible photosensitizer which provides photopolymerizable composition useful in photoresists, holograms, etc., when mixed with hexaarylbisimidazole, chain-transfer agent and ethylenically unsaturated monomer.

CONSTITUTION: (A) The visible photosensitizer is selected from the group consisting of compounds of formula I (wherein R1, R2 are each a 1-4C alkyl; R3, R4 are each H, a 1-6C alkyl, 1-6C alkoxy; R5 is H, methyl; R7 is a 1-6C alkyl, etc.; R6 is H, methyl; R8 is a 1-6C alkyl, etc.), and a compound of formula II [wherein X is, O, S, NR14, CR15R16 (wherein R14, R15 and R16 are each a 1-6C alkyl, etc.); R9 is a 1-7C alkyl, etc.; R10-R13 are each H, a 1-6C alkyl, alkoxy, etc.]. (B) The photopolymerizable composition comprisies B1: an ethylenically unsaturated monomer, which is capable of undergoing an addition polymerization initiated with a free radical and B2: an active-radiation-activated photoinitiator system comprising hexaarylbisimidazole, chain-transfer agent (e.g. 2-mercaptobenzimidazole) and the visible photosensitizer of A.