GB556176A - Improvements in or relating to the production of printing plates, templates and the like - Google Patents

Abstract

556,176. Photo-mechanical printing plates. ROBINSON, Ltd., E. S., & A., FOWEBAKER, T. S., and SHAW, S. T. March 25, 1942, Nos. 3961 and 8526. Drawings to Specification. [Class 98 (ii)] [Also in Group XVI] Lithographic printing plates for printing drawings on to sheets of wood, paper, artificial resin, or metal which may be converted by tooling into templates are prepared by coating a metal plate with a protective coating, e.g. a colloid capable of being hardened by the application thereto of a suitable liquid, applying the design to the coating with such liquid, and washing away the unhardened parts of the coating. The master plate thus prepared may be used to print directly or by means of an offset plate consisting of a metal plate having a coating of glycerine and gelatine, on to a number of plates from which the final prints may be made by direct or offset printing. The liquid employed may be a solution of ammonium or potassium bichromate which causes the colloid to harden by exposure to light, or may be such as to have a direct hardening action on the colloid. The design formed on the plate may be given greater relief by applying thereto a fusible powder such as bitumen or shellac. Direct printing from the plate may be effected by placing the printing plate and the plate to be printed between rubber blankets and exhausting the air from between the blankets. A plate to be formed into a template may have the design thereon rendered more legible by the application thereto of a fusible powder having a bright metal dust content. To facilitate the application of the liquid to the colloid, the design may be printed on the colloid in a coloured powder.