GB581479A - Improvements in photographic relief images - Google Patents

Abstract

581,479. Photographic emulsions containing developing agents. KODAK, Ltd., DAVEY, E. P., and SOPER, A. K. July 28, 1944, No. 14413. [Class 98 (ii)] A relief image is formed in a silver-salt emulsion layer by incorporating in such layer the necessary developing agent and developing the exposed material by immersing in a solution of an alkali or, in the case of a waterproofed support, by using a roller to apply the alkaline solution. The method is particularly applicable in the production of templates in which the metal sheet is sensitized by transfer from another support of a layer of a gelatino-silver halide emulsion containing, for example, hydroquinone or catechol, exposed, immersed in dilute sodium carbonate or hydroxide solution, the unhardened areas washed off in warm water and the template cut to shape. Diffuse oxidation of the developing agent is avoided by making the emulsion with a pH value of between 5 and 7. A sulphite or metabisulphite may be added to the emulsion and, if desired, to the alkaline bath. A cold solution of an alkali thiocyanate may be used in place of hot water to wash away the unhardened parts of the emulsion layer. The emulsion may be of silver bromide or bromiodide or silver chloride in gelatin or other similar colloid. In an example, 5000 grams of a contrasty gelatino - silver bromide emulsion with a pH value of 6 is mixed with 50-grams of hydroquinone in alcohol and 10 grams of potassium metabisulphite in water and coated to a thickness of 5-7.5 Á on to a waterproofed paper support. After exposure, it is immersed for 10-15 seconds in a 6 per cent solution of anhydrous sodium carbonate in water,. The emulsion containing the developing agent can be transferred from a temporary support either before or after exposure, e.g. as described in Specifications 554,292, 554,298-, 554,300 and 554,301. Specification 555,949 also is referred to.