PURPOSE: To form a dry film resist or a solder mask or to enable development with a diluted soln. of a base by mixing a specified photopolymerizable oligomer, compd. and photoinitiator.

CONSTITUTION: This compsn. is prepared by mixing at least one kind of polymerizable olefin unsatd. oligomer, at least one kind of material having at least one reactive group with at least one carboxyl group, and a photopolymn. initiator which initiates the polymn. of aromatic groups/aldehyde oligomers. The polymerizable olefin unsatd. oligomer has at least one in-chain residue of -Ar1-CHR1-, wherein Ar1 is an aromatic or substd. aromatic group and R1 is a hydrogen atom or hydrocarbyl group, at least one pendant and/or end carboxyl group, and one pendant and/or end acyloxy methyl group the acyl group of which is derived from an olefin unsatd. carboxylic acid. With the obtd. compsn., a dry film resist or a solder mask can be formed and development with a diluted soln. of a base can be performed.