Patent ID: 7341828

Claim:
A photopolymerization initiator composition, comprising a thiol compound having a mercapto group-containing group that has at least one substituent on carbon atom(s) at the α- and/or β-position to the mercapto group and a photopolymerization initiator, wherein at least one of the substituents on carbon atom(s) at the α- and/or β-position to the mercapto group is an alkyl group, wherein the thiol compound is a compound comprising a mercapto group-containing group represented by formula (1) wherein R 1 and R 2 represent each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, provided that at least one of R 1 and R 2 is an alkyl group, and (m, n) is (1, 0), (1, 1), (2, 0) or (2, 1).