GB947168A - Improvements in or relating to the production of photographic material - Google Patents

Abstract

947,168. Photographic emulsions; colour photography. GEVAERT PHOTO-PRODUCTEN N. V. May 2, 1960 [ May 4, 1959], No. 15316/60. Heading G2C. A 'packet' emulsion comprising a disperse phase of a silver halide emulsion having a hydrophilic binder the particles of which are each surrounded by an envelope of ethyl cellulose, and a continuous phase of a hydrophilic binding agent, is prepared by emulsifying the silver halide hydrophilic emulsion in a solution of ethyl cellulose in a water-immiscible solvent, and emulsifying the product into an aqueous solution of a hydrophilic binder. The continuous phase may itself be a hydrophilic silver halide emulsion. The silver halide emulsions may comprise sensitizers and colour couplers. Multicontrast black- and-white emulsions may be prepared by mixing two packet emulsions prepared according to the invention and having different sensitivities and gradations, or by emulsifying packets prepared from one silver halide emulsion and surrounded by ethyl cellulose envelopes into the other silver halide emulsion as continuous phase. Colour emulsions are similarly prepared, wherein the disperse phase is a mixture of three different types of packets each with its own sensitizer and colour coupler, or wherein the disperse phase is a mixture of two such different types of packets containing magenta and cyan couplers emulsified in a continuous phase of blue-sensitive silver halide emulsion containing a yellow coupler. Alternatively, a mixture of two different packet emulsions prepared according to the invention, one containing a cyan coupler and the other a magenta coupler, is coated on a support and overcoated with a normal silver bromide emulsion containing a yellow coupler. The permeability of the ethyl cellulose envelope may be increased by including a methacrylic acid/methyl methacrylate copolymer therein. Specifications 718,404 and 843,784 are referred to.