PURPOSE: To prepare a light-sensitive mixture useful as a photopolymerization initiator incorporating a specific bis-trichloromethyl-s-triazine, which can be prepared by an easy process and exert sensitivity to radiation in Ultra Violet range as well as visible spectral range.

CONSTITUTION: A light sensitive mixture incorporating a compound of formula I (R1, R2 are each H or an alkyl; R3, R4 are each H or 4,6-bis-trichloromethyl-s- triazin-2-yl; R5, R6 are each H, a halogen, an alkyl, an alkenyl or the like; Ar is an aromatic) and a specific polymerizable compound. The specific polymerizable compound is such as an ethylenic unsaturated compound which polymerizes by a free radical, a compound having C-O-C- bond decomposable by an acid or a compound which carries out a cation-polymerizaiton induced by an acid or the like. Ary-bis-trichloromethyl-s-triazine used here is obtained easily by allowing an arylcarbonic acid nitrile of formula II (R10, R11 are not identical to each other and are each H, CN) and trichloroacetonitrile to form a trimer in the presence of a hydrogen halide.