TREATMENT OF IMAGE-BEARING LITHOGRAPHIC PRINTING PLATES AND COATED PLATE

摘要

1495895 Printing plate treatments; developers for photo-sensitive materials DOW CHEMICAL CO 7 April 1976 [7 April 1975 (4) 12 June 1975 (2)] 14092/76 Headings G2C and G2M Aqueous solutions for treating printing plates include an active polymer component selected from:- (a) a polyacrylamide-based polymer wherein 3-70% of the carbaryl sites are - COOM (M being H, alkali metal or NH 4 +), and the balance amide; (b) a physical blend of 97-30 wt. per cent of polyacrylamide (containing at least 98% of the carbaryl sites as amide) and 3-70 wt. per cent polyacrylic acid or an alkali metal or ammonium salt thereof; (c) a physical blend of polyacrylamide or polyacrylic acid or an alkali metal or ammonium salt thereof and at least one polyacrylamide-based polymer as in (a); the polymer being in such proportion that 3-70% of the carbaryl sites are -COOM (M = H, alkali metal or NH 4 +) and the balance amide; (d) a mixture of any two or more of (a)-(c); the average molecular weight of each of the polyacrylamide-based polymer, polyacrylamide and polyacrylic acid or salt being 5,000- 1,000,000; or (e) a mixture of one or more of (a)-(d) with up to 30 wt. per cent of a hydroxypropyl methyl cellulose which gives a 2% aqueous solution having a viscosity of 1-100cl as measured by ASTM method D2363-72. This solution may form the aqueous phase of a photographic developer, may be used as a gum solution of pH 3-9 preferably incorporating alkali metal or ammonium phosphate; may be a gum etch solution of pH1-3 and incorporate phosphoric acid or of pH 9-12À5 and incorporates an alkali metal or ammonium phosphate; may be used as fountain solutions incorporating phosphoric acid, alkali metal or ammonium phosphate, a metal nitrate, a source of chromium acids and/or alcohol; may be used as part of an asphaltum gum emulsion, wherein the solution, optionally containing phosphoric acid, is used as the aqueous phase. Concentrated solutions may be provided which provide the above solutions when diluted. When used as the aqueous phase of a developer, the non-aqueous phase includes a solvent for the exposed or unexposed portions of a photo-sensitive coating. The photo-sensitive coating comprises a diazo compound or polyvinyl cinnamate.