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 carbonylbiscoumarin dye with a radical-generating reagent, 3,3′-carbonylbis[7-(diethylamino)-2H-1-benzopyran-2-one] (KCD-DA), with 2,2′-bis(2-chloro-phenyl)-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 a total reflection cell. Imidazolyl radical (Im·) was predominantly generated from carbonylbiscoumarin triplet-sensi-­tized decomposition of BI, the quantum yield, Φ^o_Im· of Im· at an infinite concentration of BI was measured, Φ^o_Im· = 1.3. The high quantum yield, Φ^o_Im·, implies an efficient KCD-DA triplet-sensitized photoinitiation system containing BI. Copyright © 1998 John Wiley & Sons, Ltd.