PURPOSE: To obtain a photopolymerizable compsn. contg. a photopolymn. initiator having high sensitivity to visible radiation of ≥400nm wavelength, especially 488nm wavelength corresponding to the output of Ar+ laser and even to light of >500nm wavelength corresponding to the output of YAG-SHG laser or He-Ne laser.

CONSTITUTION: This photopolymerizable compsn. contains a compd. (A) having at least one addition-polymerizable ethylenically unsatd. bond, a compd. (B) represented by the formula and a compd. (C) which generates active radicals when irradiated with light under coexistence of the compd. B. In the formula, A = is optionally substd. 2(1H)-pyridylidene or 4(1H)-pyridylidene, -X- is -O-, -S-, -NR2- or CONR3-, each of R1-R3 is H, alkyl, etc., and = E is optionally substd. 1,3-dihydro-1-oxo-2H-inden-2-ylidene.