Patent GB-298979-A (GB)
Title: Process of producing pictures consisting of dyes in photographic manner
IPC: G03C7/26
Filed: 1928-08-20
Abstract: 298,979. Lierg, F. Oct. 18, 1927, [Convention date]. Photographic dye images; colour photography. -Dye images are produced by embodying in a silver emulsion layer the dye-components necessary for forming the image, these components being in a water-insoluble condition, and such as have no action on the silver emulsion and are not affected by the reagents to be used for developing the silver image; and, after producing the silver image, developing directly or indirectly on top of it the dye image from the dye-components. As insoluble dye-components may be used (1) components which couple to form a dyestuff when treated with an oxidizing bath such as chromic acid &c. e.g. p-aminodimethylaniline and p-toluidine, which on oxidation yield a red-violet dyestuff; or (2) a basic component capable of being diazotized, such as benzidine used in the form of a uric acid, fatty acid, resin acid or other insoluble salt, and an azo coupling component such as a naphthol, e.g.#-naphthol in the form of an insoluble metal compound, or an acid, e.g. a sulphonic acid rendered insoluble by esterification or formation of the anilide, such as anthranilic acid ester, or the anilide of hydroxynaphthoic acid. Development of the dye image is effected by oxidation or diazotization. For producing colour-record component images, the silver halide layers may contain, as dye components, (a) for the blue, the phospho-tungstic acid salt of benzidine, and the aluminium salt of 1-amino-8-naphthol-3.6-disulphonic acid; (b) for the yellow, the abietic acid salt of benzidine and salicyclic acid ester, which yield chrysamine G; and for the red, anthranilic acid ester, and aluminium-#-naphthoxide, which yield lake red D. A coloured negative image may be produced by exposing the silver-halide layer under a negative, developing and fixing the silver image and treating it in a bleaching bath which tans the gelatine in presence of the silver image, and then treating it in an oxidizing or diazotizing bath, which develops the dye only at the untanned parts of the gelatine. Alternatively, there may be included in the emulsion layer, in addition to azo dye components, a water-insoluble substance which yields nitrous acid by treatment with acids, acid vapours, &c., such as the double salts of luteo cobaltic chloride with potassium diammine-cobaltinitrite or with sodium cobaltinitrite. By treatment with a neutral salt, this substance is destroyed by oxidation at the parts occupied by the silver image when this has been developed and fixed with neutral baths, leaving the nitrite body unchanged at the parts free from silver. For example, the silver may be converted into vanadyl ferrocyanide, and then treated in a solution of potassium chlorate; this reacts with the vanadyl compound to form potassium hypochlorite, which destroys the nitrite combination only where silver is present. A dye image may then be developed at the silver-free parts by treating the layer with a weak acid bath. In another modification, the silver of the developed image may be converted by neutral solutions into an insoluble nitrite body, by first converting it into silver ferrocyanide and then bathing it successively in solutions of luteo cobalt chloride and either ammonium tetranitritodiammine cobaltiate or cobalt nitrite, whereafter the dye image is developed at the silver-containing parts by treatment with acids &c. The Specification as open to inspection under Sect. 91 (3) (a) states also that (1) instead of employing luteo bodies for the conversion, inorganic bodies such as thallium salts in conjunction with sodium cobalt nitrite may be used, and that (2) for tricolour work, three colour-sensitive silver emulsions, containing water-insoluble dye-components which will yield the required partial colours, are coated in succession on a support, whereafter the compound layer is exposed, and developed by treatment in a single bath, for example containing acidified alum. This subjectmatter does not appear in the Specification as accepted.