GB1252091A - - Google Patents

Abstract

1,252,091. Printing plates. RICOH K.K. 10 April 1969 [13 April 1968], No. 18502/69. Heading B6C. The non-image areas of a lithographic printing plate are rendered hydrophilic before using theplate in a printing press by treating the plate in a solution comprising an aqueous solution con taining dissolved therein at least one iron-cyanocomplex, at least one heteropoly-acid and at least one phosphate. The solution may also comprise acacia, sodium alginate, ester of alginic acid-propylene glycol, carboxymethyl cellulose, dextrin, polyacrylic acid or glycerine. The iron-cyano-complex may be selected from sodium ferrocyanide, sodium ferricyanide, potassium ferrocyanide, potassium ferricyanide, ammonium ferricyanide and ammonium ferrocyanide. The heteropoly-acid may be selected from phosphorus, silicon, hydrogen, titanium and aluminium molybdates, wolframates and vanadates, ammonium salts of the said acids and alkali metal salts of the said acids. The phosphate may be selected from disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, diammonium hydrogen phosphate and ammonium dihydrogen phosphate. A printing plate is made by coating a paper support having water resisting properties with an aqueous solution of sodium carboxymethyl cellulose, colloidal silica, clay and glycerine. The coating layer is made insoluble by treatment with an aqueous solution consisting of copper sulphate and aluminium sulphate. After imaging with a typewriter or oily pencil a treating solution comprising hydrogen phosphorous wolframate, potassium hydrogen phosphate, sodium ferrocyanide, carboxymethyl cellulose and glycerine was applied.