Improvements in or relating to photosensitive printing plates

1,135,082. Lithographic printing plates. ALGRAPHY Ltd. Jan.12, 1967 [Jan.12, 1966], No.1491/66. Heading G2C. A lithographic printing plate is prepared by (1) applying to the plate a coating of a composition comprising a copolymer of ethylene and maleic anhydride of formula in which n is an integer, and a lithographic sensitizer e.g. ammonium dichromate or sodium 4, 4' - diazidostilbene - 2, 2' - sulphonate; (2) exposing the plate to actinic light selectively to render insoluble areas of the coating on development; (3) removing the coating from the non- exposed areas; (4) etching or otherwise treating the bared areas to make them selectively ink receptive and (5) removing the residual coating. The plate may be of aluminium which has been grained and anodized. Other polymers such as polyvinyl alcohol, vinyl methyl ether/maleic anhydride copolymer or gum arabic may be present in the light-sensitive coating.