GB447032A - Process for the production of coloured photographic pictures - Google Patents

Abstract

447,032. Photographic imbibition printing processes ; colour photography. 1. G. FARBENINDUSTRIE AKT.-GES., Frankforton-Main, Germany. Aug. 8, 1934, No. 22950. Void [Abridged as open to inspection under Sect. 91 of the Acts, Feb. 9, 1935]. [Class 98 (ii)] In an imbibition process, the printing-surfaces are produced by exposing to light a thin gelatino-silver emulsion layer, developing it, and treating it with an agent such as hydrogen peroxide, or ammonium persulphate, which removes the gelatin containing the silver image and leaves the remaining gelatin relief absorbent. The emulsion may contain a finely-dispersed, "photographically-indifferent," coloured pigment in order to improve gradation. The dye to be imprinted is applied to the relief in aqueous alcoholic or aqueous-acetone solution, and the prints may be made on gelatincoated paper, which should contain a mordant in the case of basic dyestuffs. Printing may alternatively be performed with a substance which produces a colouring-matter only in co-operation with another substance, which may be present in the print surface before printing or may be applied subsequently. Pairs of substances which may be so used are diazo bodies and their coupling-components, silver nitrate and sodium sulphide, or indigosol and hydrogen peroxide. In one example, a blue-black print is produced in a gelatin layer by using the acid dyestuff Brilliant Black B. In another example, tricolour components are printed in succession with basic dyestuffs in a gelatin layer containing a copper-silver thiocyanate mordant, the dyes used being Para-fuchsine for the red, Auramine G for the yellow, and Turkish Blue G for the blue, and registration being effected by pins.