PHOTOINITIATION SYSTEMS COMPRISED OF DYES AND RADICAL PRECURSORS

Photoinitiation systems were investigated to obtain visible light sensitive photopolymerizable composition with high sensitivity to be applied to the argon laser scanning imaging systems. Each of thioxanthene dye (Dye-1), coumarin dye (Dye-2) and merocyanine dye (Dye-3) was combined with various amounts of diphenyl iodonium cloride (DPI) and/or N-phenylglycine (N-PhG) as the radical precursors to form the photoinitiation systems. A layer of the mixture of a photoinitiation system, polyfunctional acrylic monomer and acrylic polymer was applied on an aluminium plate to prepare a test plate for evaluation. In orders to eliminate inhibition of polymerization by oxygen, a poly- (vinyl alcohol) layer was applied on the top of the test plate. The sensitivity of the test plates containing initiation systems of dye/DPI/N-PhG were approximately five times as high as those containing dye/DPI or dye/N-PhG in every kind of dye. The same tendency was observed in image formation with an argon laser scanning imaging system using Dye-1-containing test plates. The minimum energy required to form gel of the Dye-1, Dye-2 and Dye- 3-containing system were 0.3, 0.2 and 1.7mJ/cm2 respectively.