Photopolymerizable composition containing group Va aromatic onium salts

Cationically polymerizable compositions consisting essentially of

• A. a monomeric or prepolymeric cationically polymerizable organic material free of oxirane oxygen selected from vinyl organic monomers, vinyl organic prepolymers, vinyl organic esters, cyclic organic amines, cyclic organo sulfides, organosilicon cyclics, and cyclic amines, and
• B. from 0.1% to 15% by weight based on the weight of polymerizable composition of a photodecomposable aromatic onium salt of a Group Va element capable of effecting the cationic polymerization of (A) when exposed to radiant energy having the formula,
• [(R).sub.a (R.sup.1).sub.b (R.sup.2).sub.c X] .sub.d .sup.+ [MQ.sub.e ] .sup.-(e-f),
• where R is a monovalent aromatic organic radical selected from carbocyclic radicals and heterocyclic radicals, R.sup.1 is a monovalent organic aliphatic radical selected from alkyl, cycloalkyl and substituted derivatives thereof, R.sup.2 is a polyvalent organic radical forming an aromatic heterocyclic or fused ring structure with X, X is a Group Va element selected from N, P, As, Sb and Bi, M is a metal or metalloid, Q is a halogen radical, a is a whole number equal to 0 to 4 inclusive, b is a whole number equal to 0 to 2 inclusive, c is a whole number equal to 0 to 2 inclusive, and the sum of a + b + c is a value equal to 4 or the valence of X,
• d.dbd.e-f
• f=valence of M and is an integer equal to from 2 to 7 inclusive
• 3 is >f and is an integer having a value up to 8.