GB794572A - Improvements in photopolymerizable compositions and printing plates containing them - Google Patents

Abstract

Photopolymerizable compositions for use in the production of printing plates employed in offset lithography consist of an epoxy resin, obtained by reaction of epichlorhydrin with polyhydric phenols or alcohols, esterified with an unsaturated aliphatic monocarboxylic acid or a cycloaliphatic, aromatic or heterocyclic monocarboxylic acids having unsaturated side chains and a photopolymerizable catalyst. Unsaturated acids specified are cinnamic, sorbic, cyclohexanylacrylic, furyl acrylic; the corresponding acid chlorides or anhydrides may also be used; known esterification methods are employed. Suitable catalysts for the photopolymerization are quinones, e.g. tolyquinone, 2 : 6 dichlorquinone, 2 : 5-diphenyl-p-quinone, 1 : 2 and 1 : 4 naphthaquinone anthraquinones; Michler's ketone, 4,41-tetraethyldiamine; diphenyl ketone, 4 : 41-tetramethyl diamino diphenyl carbinol, 4 : 41-tetramethyl diamino benzophenone imide; cross linking may be effected by addition of dicinnamylidene vinyl ketone. Stability of the compounds is improved by adding inhibitors, e.g. hydroquinone. The materials may be applied to the plate in solution in mixtures of toluene and methyl ethyl ketone. (1) 20 Parts epoxy resin were mixed with toluene and heated under reflux and cooled. 50 Parts cinnamoyl chloride were added and the mixture refluxed at 100-110 DEG C. The mixture was diluted with toluene and the epoxy ester precipitated by addition of ethyl alcohol. A 1 per cent solution of a mixture of 200 parts of the ester and 5 parts dicinnamylidene vinyl ketone in a 95 per cent toluene-5 per cent butanol mixture was applied to an aluminium base plate and dried. The plate was exposed to ultra-violet radiation and then developed with a composition comprising an epoxy resin dissolved in a mixture of xylene and cyclohexanol, dibutyl phthalate carbon black and gum arabic.