Patent GB-843784-A (GB)
Title: Improvements in or relating to the production of photographic materials including colour photographic materials
IPC: G03C1/053
Filed: 1956-09-27
Abstract: 843,784. Photographic emulsions; colour photography. GEVAERT-PRODUCTION N.V. Sept. 27, 1956 [Oct. 1, 1955], No. 29525/56. Class 98(2) An emulsion of silver halide grains in an aqueous solution of the hydrophilic binding agent is dispersed in a solution of hydrophobic macromolecular binding agent in an organic non-watermiscible solvent and the dispersion thus obtained is dispersed in water or in an aqueous solution of a hydrophilic layer-forming binding agent. One or more layers may be formed from this or from the final dispersion in which more than one of the hydrophobic stage dispersions are dispersed, as into the last mentioned hydrophilic layer-forming binding agent solution. Such latter solution may itself constitute a silver halide emulsion. Five examples are directed to black and white procedure and five to colour, using colour couplers; thus in Example 1 a soft gelatino-silver bromide emulsion is first mixed with an aqueous solution of a styrene-maleic anhydride copolymer, then dispersed in a polyvinyl butyral solution in a chloroform/amyl alcohol/carbon tetrachloride mixture and the product is dispersed into a vigorous green sensitised silver bromide emulsion which has been diluted with aqueous gelatin and treated with "Ethofat 142/60" (a fatty acid polyethylene oxide condensate), to give a material which can be coated and dried in the ordinary way and provides soft or more vigorous gradation according to the ratio of green-light and blue-light exposure. Example 2 differs from this only in that the styrene-maleic anhydride copolymer is mixed in with the second, sensitised, emulsion instead of the first. Example 3 is for a similar multi-contrast emulsion suitable for the graphic arts. In Example 4 a gelatino-silver bromide emulsion is dispersed with a similar polyvinyl butyral solution and this is dispersed in aqueous polyvinyl alcohol containing "Ethofat 142/60" to give a friction-resistant layer after coating; and Example 5 similarly specifies polyvinyl alcohol as colloid with the silver halide and a gelatin solution for the final emulsification. Of the colour emulsions, Example 6 describes addition of a specified coupler to the first mentioned bromide-copolymer emulsion of Example 1 and dispersion of this in a chloroform solution of a vinyl chloride/vinyl acetate/maleic anhydride copolymer and the product in aqueous gelatin, for coating. exposure and colour development to a cyan image; and Examples 7-10 describe three colour procedure based on the gelatino emulsions emulsified in polyvinyl butyral solution of Example 1, thus in Example 7 two of these emulsions are green and red sensitised and provided with magenta and cyan couplers respectively, dispersed separately in aqueous gelatin, then mixed, coated, dried and overcoated with an ordinary blue-sensitive yellow coupler emulsion with intervening yellow filter if desired; in Example 8 an additional emulsion is dispersed in aqueous gelatin and the three mixed for single layer coating; in Example 9 the aqueous gelatin of Example 7 is replaced by blue sensitive-yellow coupler emulsions and in Example 10 colour couplers are added to the polyvinyl butyral solutions instead of w the silver halide emulsions directly. In all cases the emulsions include a hydrophilic inner phase containing small drops of silver halide emulsion separated from the outer phase by a thin envelope of the hydrophobic binding agent, which, however, allows passage of developer, and other manners of use of the scheme include addition of developer # to the emulsion or the envelope, and successive development of inner and outer emulsions with different developers in view of resistance of the envelope. It may be useful to evaporate the organic solvents and desirable to evaporate part of the water of the outer phase before coating. Specifications 524,154, 718,404, 750,201 and 786,274 are referred to.