Patent GB-524552-A (GB)
Title: Process of making natural colour photographs
IPC: G03C7/28
Filed: 1938-12-23
Abstract: 524,552. Colour photography. SCHINZEL, K., and SCHINZEL, L. Dec. 23, 1938, No. 8161/40. Convention date, Dec. 23, 1937. Divided out of 37402/38. [Class 98 (ii)] [Also in Group IV] A three-colour photograph is produced in exposed and developed material comprising three differentially colour sensitive silver halide emulsions each of which contains an insoluble compound capable of forming a dye by oxidation by removing or rehalogerizing the developed silver with simultaneous diffuse oxidation of the compounds to dyes and using the residual or rehalogerized silver halide for the production of image dyes from the diffusely formed dyes. The compounds may be insoluble leuco bases or ester-salts, azo-indigosols, substituted anthone-meso-derivatives, or hydrazo dyes or their acyl-derivatives, or their insoluble or non- diffusing salts. Residual silver chloride may be converted into silver ferrocyanide and then into an oxidizing, reducing, or catalyzing agent for the dye destruction. Residual silver chloride may also be converted into a catalyzing silver salt by ammonium molybdate, vanadate, pyrovanadate, or heteropolyvanadate, or into the complex salt with manganous thiocyanate. Analogous conversions with silver bromide require the presence of thiosinamine or like compounds. The conversion may only be superficial. Insoluble complex salts may be formed with a hydrosulphite or its aldehyde or ketone-derivatives which may contain sulphuric acid groups. A silver image may be treated with cupric bromide or chloride to give silver bromide or chloride and the insoluble cuprous salt. The residual silver bromide may be reduced with a developer not acting on the dyes and the dyes reduced image-wise by potassium cyanide, alkali sulphide, hydrosulphide, thiourea, thiosinamine, or thiosemicarbazide, or the silver is converted into a reducing, oxidizing, or catalyzing agent for dye-destruction. With unexposed residual silver bromide, the diffuse reduction of the dye requires a hydrosulphite and an accelerator such as induline scarlet or an anthraquinone sulphuric acid or a ferrous acetate or other developer. If the material is made alkaline with sodium carbonate or ammonia, the silver halide oxidizes the leuco dyes image-wise (if necessary after treatment with fogging agents or after exposure) and the residual leuco dyes are removed with caustic alkali. Agents may be precipitated in the emulsion layers in neutral conditions such that on treatment with caustic alkali they have a reducing action in the places free from silver chloride. The leuco derivatives may be added to the emulsions in the form of entirely insoluble salts with, for example, cinchonine, polycinchonine, diphenylguanidine, polyalkylamine, polyethylenediamines, polyammonium chloride, quaternary quinolinium salts, quaternary cetylammonium chloride, and the condensation product of quinine and polyalkyl chloride or polyacrylic acid chloride. Image-wise destruction or reduction of the dyes may be effected in the first developed silver areas by means of oxidizing, reducing, or catalyzing agents. The leuco dye and the silver may be oxidized with ferric chloride, the silver chloride reduced with a weak neutral developer, and the dye locally destroyed with potassium cyanide, alkali sulphide, alkali hydrosulphite, or thiourea. As oxidizers, a bichromate and hydrochloric acid, potassium ferricyanide, or cupric sulphate, a bromide, and acid may be used. The first developed silver may be removed, the residual silver halide reduced to silver and converted into lead chromate or vanadate. High-molecular sensitizers such as phthaleins with highmolecular residues or their leuco forms or leuco cyanides, or derivatives of pinaflavol, cyanines, or isocyanines having high-molecule residues combined therewith may be used. A carboxylic or sulphuric acid group may be introduced into the high-molecular residues or into the heterocyclic nucleus. Specifications 424,563, 521,833, 521,835, and 521,837 also are referred to. Amino groups in pinaflavol, isocyanine, or simple cyanine dyes may be reacted with stearyl chloride or α-bromstearic acid, or a hydroxy group therein maybe converted into a cetyl ether group. Alternatively, the quaternary ammonium salts may be formed with cetyl iodide, or p-toluene sulphonate, higher esters of bromacetic acid, or esters of α-bromstearic acid or cetyl sulphonic acid. Carboxylic or sulphonic acid groups may be introduced into the high molecular groups or into the nitrogen-containing heterocyclic nuclei.