GB530685A - Improved method of colour photography - Google Patents

Abstract

530,685. Colour photography. KODAK, Ltd. (Eastman Kodak Co.). May 10, 1939, No. 13921. [Class 98 (ii)] A colour coupler is incorporated in a gelatine silver salt emulsion which is coated upon a support while maintaining the pH of the emulsion on the acid side of neutrality during such incorporation and coating. At least one later of multi-layer material may be coated in this manner, and the pH may be below 5.5 A buffering agent may be incorporated in the emulsion as described in Specification 492,162. Processing baths not intended to bring about reaction of the colour coupler are maintained on the acid side of neutrality, and colour development is effected without immersion in an alkaline liquid, for example, by causing the layer containing the colour coupler to imbibe a colour developer of acid reaction and then treating with the alkali necessary for development and coupling without immersion in liquid, as by treatment with ammonia gas. The material may have three emulsion layers sensitized to blue, red, and green, which may or may not be separated by gelatine intermediate layers. The emulsions may be silver bromide or chloride, or some silver chloride and others bromide. The two lower layers may be silver chloride and the top silver bromide. The colour developer for the latter comprises diethyl-p-phenylenediaminehydrochloride, sodium bisulphite, and potassium bromide, while in the developer for the former the bromide is replaced by a soluble chloride. A weak sodium bisulphite bath may be used to arrest development, and the silver and silver halide removed by a bath containing a ferricyanide and hypo. The treatment with ammonia to cause development to take place may be modified by treatment with a mixture of ammonia with sulphur dioxide or carbon dioxide. The film may be processed to a positive by a first development with acid amidol or acid ferrous oxalate, followed by reexposure and treatment as before. The sound 'track may be recorded in the layer containing a colour coupler giving a minus-red colour and developed in the sound track area alone by means of a coupling developer applied by a roller before any other step in the processing. Specifications 427,472, 440,032, 458,664, 458,665, 474,353, 478,933, 478,934, 478,942, 478,983, 478,984, 478,985, 478,986, 478,989, 478,990, 478,991, 493,952, 496,245, 498,874, 499,185, 500,611, 500,717, 500,793, 500,826, 503,752, 503,814, 503,823, 503,825, 503,826, 503,827, 503,939, 503,940, and 503,941 also are referred to.