Novel diaryliodonium salts for cationic photopolymerization

Abstract

Novel diaryliodonium hexafluorophosphate salts (NDAI) as cationic photoinitiators were synthesized. The substituent groups of two aromatic rings were investigated to lower the toxicity and to improve the solubility of diaryliodonium salts. NDAIs were negative in the mutagenicity tests and soluble well in common organic solvents and representative cationic polymerizable resins. The photocuring ability of NDAI was evaluated by the real-time FT-IR measurement. NDAI exerted high photoactivity in the presence of appropriate photosensitizers, e.g. naphthalene derivatives, carbazole derivatives and anthracene derivatives. Especially, in the pigmented system containing titanium dioxide, the combination of NDAI and 2-ethyl-9,10-dimethoxyanthracene showed higher photocuring ability than naphtyl-type sulfonium salt. The organic solvent resistance of cured film and the thick film curing were also examined. NDAIs are highly efficient cationic photopolymerization initiators having various features and possible to be employed in the wide applications.