Patent GB-662360-A (GB)
Title: Improvements in photographic processes and materials therefor
IPC: G03C7/30
Filed: 1949-03-11
Abstract: 662,360. Colour photography. KODAK, Ltd. March 11, 1949 [March 11, 1948], No. 6734/49. Addition to 581,772. Class 98 (ii). Colour photographic material comprises a support bearing a layer of red or green sensitive silver chloride emulsion of the surface latent image type (Type II as defined in the parent Specification), containing a colour coupler, and, over this emulsion layer, a layer of a mixture of a green or red sensitive silver chloride emulsion of the surface latent image type and a bluesensitive silver halide emulsion of the internal latent image type (Type I as defined in the parent Specification). The single emulsion layer is preferably red-sensitive, and the silver chloride emulsion of the surface latent image type in the mixture is preferably green-sensitive. The mixed emulsion layer may or may not contain a colour coupler. The exposed material may be processed by treating it with a surface colour developer to develop colour images in the red and green sensitive emulsions, and subsequently treating it with an internal colour developer containing a coupler to develop a coloured image in the blue-sensitive emulsion. If the material contains no coupler in the mixed emulsion layer, the surface colour developer contains a slowly-diffusing coupler which diffuses only into the outer layer in the time taken to develop images in both silver chloride emulsions. The blue-sensitive emulsion may be of silver bromide or bromiodide. A support, e.g. of cellulose ester, synthetic resin, or paper, may be coated with a silver chloride surface latent image type emulsion red-sensitized with 3: 3<SP>1</SP> - dimethyl - 4: 5: 4<SP>1</SP>: 5<SP>1</SP> - dibenzthiacarbocyanine iodide and containing 4: 6-dichloro-5- methyl - 2 - (2<SP>1</SP>: 4<SP>1</SP> - di - tert. - amylphenoxyacetamino)-phenol incorporated by the method described in example (1) of Specification 541,589, and is then coated with a mixture of a silver chloride surface latent image type emulsion green-sensitized with 5-[(2-ethyl-1(2)- benzoxazolylidene) - ethylidene] - 3 - n - heptyl - 1 - phenyl - 2 - thiohydantoin and an internal latent image type silver bromiodide emulsion. The blue sensitivity of the silver chloride emulsion is so low that substantially no image is formed therein during the time required to expose properly the internal latent image emulsion. After exposure, the material is treated in a formaldehyde hardening solution, washed, developed in a developer consisting of an aqueous solution of 2-amino-5-diethylaminotoluene hydrochloride, sodium sulphite, sodium carbonate, potassium chloride, sodium hexametaphosphate, 6 - nitrobenzimidazole nitrate, sodium hydroxide, and 1-phenyl-3- [m - (p - - tert. - amylphenoxy) - benzoylamino) - 5- pyrazolone, treated in a stop bath consisting of an aqueous solution of sodium sulphite, acetic acid, boric acid, and potassium alum, rinsed, treated in an aqueous solution of sodium sulphite, sodium carbonate, potassium bromide, and sodium hydroxide to remove residual coupler (this bath or the stop bath may contain resorcinol to react with residual developing agent in the material), the negative silver image areas bleached to silver chloride or allowed to remain as silver prior to the differential fixing step, the residual silver chloride is removed without affecting the silver bromiodide by treatment in a bath containing sodium sulphite, sodium carbonate, sodium hydroxide, potassium bromide, and ethylene diamine, the material is rinsed, colour developed in an internal colour developer containing 2-amino-5-diethylaminotoluene hydrochloride, sodium sulphite, sodium carbonate, sodium hydroxide, sodium hexametaphosphate, sodium thiosulphate, and #- benzoylacet - (p - - benzenesulphonamido) - anilide, rinsed, bleached, fixed, and washed. Alternatively, to avoid the differential fixing step, the film is completely exposed to yellow light after the first development, the residual silver chloride developed to completion in a surface metol-hydroquinone developer, the developed silver optionally removed with an acidammonium dichromate bath, and development effected with the internal colour developer. In a further modification, a magenta coupler is incorporated in the silver chloride emulsion of the mixed emulsion layer, the cyan and magenta images are formed by development with a surface colour developer not containing a coupler, and the yellow image is formed by colour development using a colour developing agent not coupling with the cyan and magenta couplers but coupling with a yellow coupler incorporated in the developing solution. The developing solution may contain di-iodo-paminophenol, sodium sulphite, sodium carbonate, potassium bromide, sodium hexametaphosphate, sodium thiosulphate, sodium hydroxide, and #-benzoylacetanilide. In a still further modification, the coupler incor. porated in the single emulsion layer is a magenta or yellow coupler, cyan and yellow or magenta images being formed in the mixed emulsion layer to produce false-colour material: Specification 635,841 is referred to.