Recent progress of highly sensitive photo-polymerization initiation

Abstract

A photopolymer material has been widely used in negative-type photosensitive composition (e.g. as a radical or an acid catalyzed polymerization). A large number of photo-initiator compounds for these compositions have been developed corresponding to many industrial demands such as coatings (overcoats, adhesives), graphic materials (printing plates, inks), electronic materials (printed circuit, micro-resist, color filter), and recording materials (holography). With recent development of light source especially for IR, Visible, and UV lasers, there is a growing interest to increase their photo-sensitivity. To perform much higher sensitivity, dye sensitizers are usually utilized in both radical and cationic photo-polymerization, and are elaborately designed in combination of initiators. The dye sensitization is mainly classified into 1) electron transfer mechanism and 2) energy transfer mechanism. The dyes, therefore, are controlled and adjusted to their physical properties such as wave length, redox potential, and excited energy level according to the mechanism. In this paper, the classification of these initiators/dye sensitizers and their characteristics are shortly described. Furthermore a few recent applications are introduced as an example of high sensitive material.