Patent GB-738233-A (GB)
Title: Process for colour developing photographic images
IPC: G03C7/30
Filed: 1953-08-19
Abstract: 738,233. Colour developing photographic images. CIBA Ltd. Aug. 19, 1953 [Aug. 20, 1952], No. 22893/53. Class 98 (2). A silver image in a layer free from insoluble silver salts, produced as by normal black-andwhite photography, by the process of Specification 701,529, or by exposure and fixing of a silver halide layer without development in which case the image is in the form of nuclei only, is developed in the presence of a colour coupler and a soluble reducible silver or mercury salt with an aromatic amine suitable for colour formation. The silver image is thus toned or intensified. The metallic part of the image may be left in or bleached out to leave an image in dye only. A normal colour developed image before bleaching may be redeveloped to the same or a different tint. The process may be applied to the uppermost layer only of a multilayer colour film or to all layers simultaneously, and, as detailed below, to the introduction therein of a colour-correcting mask. In example 1 a cellulose acetate foil carrying a layer of a gelatino-silver bromide emulsion containing a red sensitizer and 1-hydroxy-2-naphthoic acid anilide is exposed to red light in contact with a stepped wedge, developed in a metol-quinone developer, fixed in hypo, washed, and then treated in a bath prepared from silver nitrate, sodium sulphite, hypo and 2-amino-5-diethylamino toluene hydrochloride, to produce an intensified silver image and corresponding bluegreen image, from which the silver may be bleached and fixed out. The image is stated to be flatter and more sensitive than that produced by material processed normally. Example 6 describes intensification by the method of example 1 of a similar but normally produced silver plus blue-green image, and states that the image so intensified loses contrast but exhibits more detail in the less exposed regions. In example 2 a silver bromide emulsion containing 1 - (21 - naphthyl) - 3 - methyl - 5 - pyrazolone is exposed, developed, fixed and treated in a solution prepared from sodium sulphite, silver nitrate and para-phenylene diamine to leave a red image after removal of silver. Example 3 describes toning and intensification of a metallic silver image with the bath of example 1 to which 1 - phenyl - 3 - methyl - 5 - pyrazolone has been added. In example 4 a red-sensitized blue-green coupler silver bromide layer with an overlying green-sensitized purple coupler silver bromide layer is exposed through green and red filters, exhaustively fixed so as to show no trace of an image, and then treated in the bath of example 1 to produce silver and coincident colour images. In example 5 a bath containing citric acid, silver nitrate, Rochelle salt and paraphenylene diamine replaces the bath of example 1 with similar result. Example 7 specifies a non-halide layer, the sensitizer being silver nitrate, citric acid and ferric ammonium citrate applied to a superficially hydrolysed cellulose triacetate film, and this is exposed, washed and developed with the solution of prior examples and coupler either in the layer or the solution. In example 8 a commercial black and white film is exposed, developed, fixed, and treated in a solution made from mercuric chloride, sodium sulphite, diethyl-para-phenylene diamine sulphate, 1 - phenyl - 3 - methyl - 5 - pyrazolone and alkali, to intensify the silver image with metallic mercury and at the same time to produce a purple dyestuff image. Example 9 describes introduction of a colour-correcting mask into a dye-destruction material, thus a two-layer differentially sensitized material with yellow and purple azo dyes in the lower and upper layers respectively is copied, developed, fixed, treated as in a thiourea-hydrobromic acid bath for dyedestruction, and then for a short time in the bath of example 1 to which aceto-acetic acid anilide has been added to produce a weak yellow reverse image in the upper layer. Example 10 describes production of an especially contrasting dye image, and states that a silver-containing image-producing solution with a low content of hypo forms a colour image in the uppermost layer of a multilayer material, while a high hypo content colours all layers simultaneously. Example 11 describes briefly the immersion of a three-layer material having silver images and colour formers in all layers into a bath prepared from diethyl-para-toluenediamine hydrochloride, silver nitrate and hypo, and then removal and suspension of the material in an atmosphere of ammonia to develop dye images in all the layers. Baths containing complex silver or mercury salts and amino developers are included in the terms of the invention.