Patent GB-656131-A (GB)
Title: Improvements in and relating to processes and material for the manufacture of colourphotographic images
IPC: G03C8/04
Filed: 1946-10-15
Abstract: 656,131. Coloured photographic images. GEVAERT PHOTO-PRODUCTEN N.V. Oct. 15, 1946, No. 30685. Convention date, Aug. 2, 1941. Addition to 614,155 and 654,630. [Class 98 (ii)] In the production of coloured photographic images by processes involving the diffusion of unreduced silver halide from an exposed and developed sensitive silver halide emulsion layer into an adjacent non-sensitive layer containing substances capable of precipitating or reducing the diffused silver halide or catalyzing the reduction of the diffused silver halide as described in the parent Specification, alone or as improved or modified according to Specification 654,630, the diffusion of the undeveloped silver halide and the formation of the secondary coloured image are effected in a single treatment. The receiving layer may contain a dye for the silver dye bleaching-out process or a colour coupler, or the latter may be incorporated in the developing solution for reducing the diffused silver halide, which solution may contain a silver halide solvent. In multi-layer material, each emulsion layer has a corresponding receiving layer, and at least one barrier layer, which separates an emulsion layer and a receiving layer not corresponding thereto, is provided. Such barrier layer may contain colloidal silver, silver sulphide, or fogged silver halide emulsion, and silver halide diffusing into the barrier layer is reduced therein. Alternatively, precipitants such as photographic stabilizing agents containing a reactive hydrogen atom in an amino or mercapto group may be incorporated in the barrier layer. Where two receiving layers are provided between two emulsion layers, no barrier layer is necessary, although the thickness of the receiving layers or the concentration of development nuclei or precipitants therein may be increased. A thin barrier layer may, however, be provided. In three-emulsion layer material in which the emulsion layers contain the " receiving " substances, barrier layers are provided between the emulsion layers. The filter or antihalation dyes may be incorporated in one or more layers. The material may be developed in an ordinary developer, washed, treated in a colour developer containing a silver salt solvent, and silver removed. Three-layer material may be used in which the receiving layer corresponding to the blue-sensitive emulsion layer contains a yellow dye for the bleach-out process, while the other receiving layers contain diffusion-fast couplers for the colour development process. In example 1, two aqueous gelatin solutions, one containing silver nitrate and the other hydroquinone, are mixed, gelled, cut up, washed, melted, mixed with water, alcohol, and formaldehyde, coated on a support, and over-coated with an unhardened silver halide emulsion. After exposure, the material is developed, washed, treated in a colour developer containing N: N-diethyl-p-phenylenediamine, sodium sulphite, sodium carbonate, sodium hydroxide, hypo, and 2: 4-dibromo-1-naphthol, the emulsion layer is removed by treatment with warm water, and the silver is removed with Farmer's Reducer. In example 2, a support is successively coated with a receiving layer containing development germs or nuclei (e.g. colloidal silver) and a diffusion-fast blue-green coupler, a red-sensitive silver halide emulsion layer, a barrier layer with development germs or nuclei, a green-sensitive silver halide emulsion layer, a receiving layer containing developments germs or nuclei and a diffusion-fast magenta coupler, a receiving layer containing yellow colloidal silver as development nuclei and a diffusion-fast yellow coupler, and a bluesensitive silver halide emulsion layer. The exposed material is developed, washed, colour developed in a bath including N: N-diethyl-pphenylenediamine and hypo, washed, and silver removed. In example 3, a support is successively coated with a red-sensitive silver halide emulsion in which is dispersed hardened gelatin grains containing development germs or nuclei and a diffusion-fast blue-green coupler, a barrier layer containing a fogged fine-grain silver chloride emulsion, a green-sensitive silver halide emulsion in which is dispersed hardened gelatin grains containing development germs or nuclei and a diffusion-fast magenta coupler, a barrier layer containing colloidal silver, and a bluesensitive silver halide emulsion layer in which is dispersed hardened gelatin grains containing development nuclei and a diffusion-fast yellow coupler. The material is processed as in example 2. Specification 654,631 also is referred to. The Specification as open to inspection under Sect, 91 comprises also the addition of the silver halide solvent to the primary developer, if a diffusion-fast coupler is incorporated in the receiving layer. In further examples, the multilayer material of example 3 is processed by incorporating hypo in the first developer, fixing, washing, rehalogenizing, washing, colour developing and removing silver, and a multilayer material having receiving layers containing dyes for the dye-destruction process is processed, after exposure, by development in a developer containing hypo, fixing, washing, treatment in an imagewise dye-destruction bath, rehalogenizing, and fixing. This subject-matter does not appear in the Specification as accepted.