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Abstract
Photopolymers play an important role in technical imaging systems. Several basic principles of photopolymer crosslinking and photoinduced radical polymerization systems will be reviewed.
Photopolymers are amorphous solids and the photo crosslinking reaction (e.g. increase in molecular weight) takes place in the glassy state. Their ultimate photographic speed may be calculated from basic physical properties of the irradiated areas. A continuous decrease of quantum yield during irradiation is characteristic for the photoreaction. The response to light is made possible by built in or added chromophores that can undergo different reactions depending upon their nature.
In a photoinduced polymerization the photo initiator decays into a radical pair when exposed to radiation. The photochemical reaction is amplified by a subsequent polymerization with multi functional reactive monomers to form an insoluble network. The photographic speed is governed by several factors including the quantum yield of cleavage and the rates of initiator decay, propagation and termination of the growing chain. The extent of conversion is diffusion controlled and therefore temperature dependent.