GB769522A - Improvements in or relating to planographic printing plates - Google Patents

Abstract

769,522. Planographic printing surfaces. TICKNER, A. (Columbia Ribbon & Carbon Manufacturing Co., Inc.). Nov. 13, 1953, No. 31615/53. Class 100(2) A planographic printing plate comprises a flexible foundation sheet having an image-receptive surface, a single planographic surface coating overlying and adherent to the image receptive surface and comprising a hydrophilic colloid, the coating being not in excess of 6 pounds per ream in weight, and an ink-receptive, water repellant image on the surface of the plate permeating the coating and attaches to the image receptive surface of the foundation. The foundation sheet comprises a sheet of paper 11 which may be treated to give it wet strength properties and a waterproofing undercoat 13 which may include hardened casein, or a latex. The planographic printing coating 15 has a thickness in the'range of ¢-6 pounds per ream and preferably 4 pounds per ream. The coating 15 may be prepared by applying to the undercoating 13 an aqueous dispersion of sodium carboxymethyl cellulose including ammoniacal copper sulphate, ammonium dichromate or chromium trioxide and ferric ammonium citrate, the coating being subsequently dried to provide a water-insoluble printing surface layer upon which an image 17 is impressed. Alternatively an aqueous dispersion of aluminium carboxymethyl cellulose including ammoniacal copper sulphate, ammonium dichromate, ferric ammonium citrate and ammonium hydroxide may be employed. A filler such as clay is included in the composition, the ratio of the weight of the filler to the colloid not being in excess of the values given by Fig. 2 (not shown). Specification 769,520 is referred to.