Photopolymerizable compositions containing nitroso dimers to selectively inhibit thermal polymerization

Claim 1

A thermally stable photopolymerizable composition comprising: (i) at least one nongaseous, ethylenically unsaturated compound capable of polymerization by free-radical initiated chain propagation; (ii) 20 parts per million to 10% by weight, based on the total weight of the photopolymerizable composition, of a nitroso dimer containing a dinitroso group of the structure ##STR8## which is a noninhibitor of free-radical polymerization but thermally dissociates to nitroso monomer which is an inhibitor of free-radical polymerization, and is characterized by (a) a dissociation constant of 10 -2 --10 -10 in solution at 25° C., and (b) a rate of dissociation having a half-life of at least 30 seconds in solution at 25° C.; and (iii) 0.001-5 parts by weight, per part of unsaturated compound, of an organic, radiation-sensitive free-radical generating system activatable by actinic radiation that does not dissociate the nitroso dimer to nitroso monomer.