| 摘要 |
824,174. Photolithography. POLYCHROME CORPORATION. Jan. 27, 1956 [Feb. 2, 1955], No. 2777/56. Class 98(2) An image transferred to a lithographic plate is treated with an aqueous solution of a trivalent single metallic salt and a soluble organic acid which does not form a precipitate with the cation of the salt, to harden the image and make it inkreceptive. Thus a soft image comprising a silver bromide-gelatin mixture may be transferred by pressure to water-proofed paper carrying a hydrophilic layer comprising a mixture of starch carbamate and a filler and treated with a hardening solution containing water, ethylene glycol, monobasic ammonium phosphate, phosphoric acid, aluminium chloride and tannic acid of which two mixings are exemplified. Other soluble aluminium salts and soluble ferric and chromic salts and other acids such as pyrogallic and citric acids may be used but the aluminum chloridetannic-acid pair, to which a claim is directed, is preferred. A prior process of hardening a transferred image by light action and then successive treatments with pyrogallic acid and acetic acid is described. Specifications 655,274 and 732,114 are referred to. |
