Fixer compositions used in planographic printing containing onium compounds
AssigneeAgfa-Gevaert
InventorsUrbain Leopold Laridon, Rene Alois Van Brandt, Albert Lucien Poot
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Abstract
A method for the preparation of a planographic printing plate wherein a sheet material comprising an outer hardenable hydrophilic colloid layer on whose surface is concentrated a visible silver image that has been formed thereon from silver halide complexes according to the silver complex diffusion transfer process, is treated with an aqueous lithographic fixer having a pH in the range of 1.0 to 6.5 and containing 1. an iron(III) salt of a polyaminopolycarboxylic acid as oxidizing agent for the silver image, 2. a compound yielding in dissolved state iodide ions as precipitating agent for silver ions, and 3. an organic onium compound.
Claims11
A method for the preparation of a planographic printing plate wherein a sheet material comprising an outer hardenable hydrophilic colloid layer on whose surface is concentrated a visible silver image that has been formed thereon from silver halide complexes according to the silver complex diffusion transfer process, is treated with an aqueous lithographic fixer having a pH in the range of 1.0 to 6.5 and containing
- 1. an iron (III) salt of a polyaminopolycarboxylic acid as oxidizing agent for the silver image,
- 2. a compound yielding in dissolved state iodide ions as precipitating agent for silver ions, and
- 3. an organic onium compound, which liquid imparts a stronger ink-receptivity to the silver image areas for a lithographic ink as defined hereinafter than the same liquid which is free from ingredient (3), the type and concentration of said organic onium compound in said liquid being such that said liquid is capable of making a silver image, which is obtained through said silver halide complex diffusion transfer process on an image-receiving layer as described hereinafter, by treating it for 8 s at 22.degree. C sufficiently ink-receptive for said lithographic ink to form on a lithographic press in printing position with said lithographic ink an ink deposit on paper used in lithographic printing of an optical density at least 0.5 higher than obtained with the same liquid being free from ingredient (3), the image-receiving layer being coated at 20 g per sq.m from:
- ______________________________________ water 890 ml 12.5 % by weight aqueous solution of saponin 10 ml aqueous dispersion of colloidal nickel sulphide comprising 0.2 g of nickel sulphide and 10 g of gelatin 100 ml ______________________________________
- onto a supported gelatino-silver chlorobromide (1.5 mole % Br) emulsion layer having a silver halide content equivalent with 1 g of silver nitrate per sq.m and wherein the ratio by weight of gelatin to silver halide (expressed as silver nitrate) is 10 to 3;
- and said lithographic ink having the following composition:
- ______________________________________ parts by weight Lake Red C (C.I. 15,585) 80 styrenated linseed-tung oil alkyd of 60 percent oil length and 10 percent styrene content 100 aliphatic petroleum having a boiling range of 260-290.degree. C 50 lead naphthenate 1 cobalt naphthenate 0.12 ______________________________________
Dependencies are inferred from the claim text.