Patent GB-680631-A (GB)
Title: Improvements in colour photographic material
IPC: G03C1/83
Filed: 1949-08-08
Abstract: 680,631. Colour photography. GANGUIN, K. O., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. Oct. 20, 1950 [Aug. 8, 1949], No. 20579/49. Class 98 (ii). Colour photographic material comprises a support carrying at least two light-sensitive silver halide emulsion layers sensitized to different parts of the spectrum, and a coloured filter layer containing silver halide which will not be substantially affected by normal camera exposure and an azo dye of the formula RR<SP>1</SP>CH-N=N-Z or Ar-N=N-Z, wherein R and R<SP>1</SP> are organic radicals which may be joined together to form a heterocyclic ring structure, wherein Ar is an aryl radical to an aromatic nucleus of which the azo group is attached in the p-position to a hydroxy group, wherein R or R<SP>1</SP> or Ar contains at least one group conferring solubility in aqueous alkaline solutions, e.g. -COONa or -SO 3 Na, and wherein Z is an aryl radical containing one or more substituents imparting fastness to diffusion in the filter layer. The silver halide may be silver halide rendered developable by lightexposure or by the action of fogging agents such as silver or other sulphide or colloidal silver, and the filter layer is preferably formed from a fine-grain emulsion. The material, after exposure, may be developed with a substituted p-phenylenediamine, and the soluble azomethine or indophenol dye formed in the filter layer removed. Solubilizing groups such as -SO 3 H, -COOH, or -OH may be present in the substituted p - phenylenediamine. In material for reversal processing, the silver halide used in the filter layer is not developable, but may be a fine-grain silver chloride emulsion not appreciably affected by the camera exposure but rendered developable by effecting the second exposure, after a first black-andwhite development, with strong light. In an example, a melted normal gelatino-silver bromide emulsion is exposed to light while being stirred and an aqueous solution of the sodium salt of 1 - (2<SP>1</SP>: 5<SP>1</SP> - dichloro - 41- sulphophenyl) - 3 - methyl - 4 - (p - dodecylbenzeneazo) - 5 - pyrazolone added. A support is successively coated with a red-sensitized emulsion containing the cyan coupler sulphonated 1-hydroxy-2-naphthoyloleylamide (example 10 of Specification 465,823), a green-sensitized emulsion containing the magenta coupler 1 - (3<SP>1</SP>- sulphophenyl) - 3 - heptadecyl-5-pyrazolone (example 3 of Specification 502,665), a filter coating composition prepared as described, and a not specially colour sensitized emulsion containing the sodium salt of p-stearylaminobenzoylacetanilide-p<SP>1</SP>-carboxylic acid. The exposed material is colour developed in a colour developer including p-diethylaminoo-toluidine, the yellow azo dye in the filter layer being converted to a water-soluble azomethine dye dissolved away in the subsequent processing, and the film is washed, bleached, washed, fixed, washed and dried. The Provisional Specification refers also to dyes of the general formula wherein Ar is an aryl radical to an aromatic nucleus of which the azo group is attached in the ortho position to a hydroxy group, and to the use of the dyes in antihalation layers.