LASER-FLASH PHOTOLYSIS IN HIGH-SPEED PHOTOPOLYMER COATING LAYERS CONTAINING CARBONYLBISCOUMARIN DYES AND OPHENYL)-4,4',5,5'-TETRAPHENYL-1,1'-BI1H-IMIDAZOLE

The sensitization mechanisms of ketocoumarin dyes with a radical-gener ating reagent (10,10'-carbonylbis[1,1,7, ,5H,11H-[1]benzopyrano[6,7,8- ij]quinolizin-11-one] (KCD-J), 3,3'-carbonyldis[7-(diethylamino)-2H-1- benzopyran-2-one] (KCD-DA)) with phenyl)-4,4',5,5'-tetraphenyl-1-1'-b i-1H-imidazole (BI) in a poly(methyl methacrylate) (PMMA) film have be en investigated by laser-flash photolysis using a total-reflection cel l. The triplet decay time of the dyes in a PMMA film was quenched by B I with a k(q)s of 1.3 and 0.60 x 10(5) mol dm(-3) s(-1) for KCD-J and KCD-DA. The fluorescence and initial absorption for KCD-DA were not qu enched by BI in a PMMA film. The fluorescence was quenched at a quench ing distance of 10.0 Angstrom, and the initial triplet absorption was not quenched for KCD-J in a PMMA film. These results show that a nonst atic sensitization from the triplet to BI is the predominant process i n a photoinitiation system containing KCD-DA, and that both static sen sitization from the singlet excited state to BI and nonstatic sensitiz ation from the triplet to BI exist in a photoinitiation system contain ing KCD-J.