Patent ID: 6881765

Claim:
A radiation curable composition comprising: (A) a polyorganosiloxane represented by the average unit formula below: (R 1 ) m (R 2 ) n SiO (4-m-n)/2 (1) in formula 1, the R 1 groups each denote a substituted or unsubstituted monovalent hydrocarbon group having no cationic ring-opening polymerizable group, the hydrocarbon groups may be identical to or different from each other, and a part thereof may be a hydrogen atom, a hydroxyl group, or an alkoxyl group having 1 to 4 carbons; the R 2 groups each denote an alkyl group to which is bonded a cyclic ether group having cationic ring-opening polymerizability, the alkyl groups may be identical to or different from each other, and they may have an alicyclic alkyl group; n is 0.0004 to 1.0; and m is a figure such that the total of m+n is 1.2 to 2.2, the polyorganosiloxane having at least two cationic ring-opening polymerizable cyclic ether groups in the molecule, and the number of silicon atoms in the polyorganosiloxane being 10 to 1,000; (B) a monofunctional oxetane monomer represented by formula (2) below in formula 2, R 3 and R 4 denote hydrogen atoms or straight- or branched-chain alkyl groups having 1 to 4 carbons, which may have a substituent, R 5 denotes a straight- or branched-chain alkyl group having 6 to 18 carbons, R 6 denotes a hydrogen atom or an alkyl group having 1 to 4 carbons, and X denotes methylene or an oxygen atom; and (C) a cationic polymerization initiator.