Study of radical generated from coumarin dye-sensitized photo-initiator systems in high-speed photopolymer coating layers using laser flash photolysis

Radical generation from photoinitiation systems containing carbonylbiscouma rin dye with a radical-generating reagent, 3,3'-carbonylbis[7-(diethylamino )-2H-1-benzo-pyran-2-one] (KCD-DA), with 2,2'-bis(2-chlorophenyl)-4,4'5,5'- tetraphenyl-1, 1'-bi-1H-imidazole (BI) in a poly(methyl methacrylate) film has been investigated by laser flash photolysis using it total reflection c ell. Imidazolyl radical (Im) was predominantly generated from carbonylbiscoumari n triplet-sensitized decomposition of BI, the quantum yield, Phi(Im)(I). of Im at an infinite concentration of sl was measured, Phi(Im)(o) = 1.3. The high quantum yietd, Phi(Im)(o)., implies an efficient KCD-DA triplet-sensit ized photoinitiation system containing BI. (C) 1998 John Wiley & Sons, Ltd.