PURPOSE: To improve heat resistance, adhesion, discoloration resistance to copper, etc. by compounding 2-vinyl-4, 6-diamino-s-triazine to a compsn. contg. a photosetting resin to be cross-linked and cured by UV rays and a photopolymn. initiator.

CONSTITUTION: The intended photosetting resin comps. is obtd. by mixing (A) 100pts.wt. a photosetting resin which has ≥1 terminal unsatd. double bonds and is cross-linked and cured by UV rays (e.g.; unsatd. polyester resin, polyol acrylate), (B) about 1pt.wt. photopolymn. initiator (e.g.; benzophenone, benzoyl peroxide) and (C) about 1W20pts.wt. 2-vinyl-4,6-diamino-s-triazine expressed by the formula. The resultant photosetting resin compsn. is particularly excellent in discoloration resistance to copper and is therefore adequately used as solder resist ink for a printed wiring board, rust preventive paint for a copper material, etc.