Photopolymers.

Image formation by photopolymerization broadly includes light initiated reactions which increase the molecular weight of unsaturated organic components in photographic elements. The principal reactions of this type are addition polymerization, crosslinking and dimerization. The resulting increase in molecular weight changes solubility, melting point, refractivity, viscosity, electrical properties, etc.; some of these have been used to form visible or detectable images. There are several commercial products for Graphic Arts use, based on changes in solubility, i.e., relief printing plates and photo-resists for etching. Other proposed uses for images formed by photopolymerization are in copying, direct camera imaging, color photography and new methods for printing. Although photopolymerization does not now seriously challenge the commercial prospects for some of its uses are very good because photo- polymerization, more than other systems, combines many such desirable characteristics as rapid and simple processing, speed, versatility, image durability and quality.