Patent GB-512563-A (GB)
Title: Improvements in or relating to colour photography
IPC: G03C7/26
Filed: 1938-01-08
Abstract: 512,563. Colour photography. SEASE, V. B., and WEBER, J. R. Jan. 8, 1938, No. 633. [Class 98 (ii)] At least two light-sensitive emulsion layers on a single support are exposed to produce latent images in both layers, one layer being exposed' by light transmitted through the other, and thereafter the layers are differently processed, for example by re-exposure and development, a layer containing prefogged but undeveloped silver salt being interposed between the two sensitive layers to provide first a transparent layer during the initial exposure or exposures and on subsequent development an apaque barrier layer permitting differential processing of the layers. A multilayer film comprises a front bluesensitive emulsion containing the filter dye Luxol Fast Yellow T, a prefogged emulsion, a middle green sensitive emulsion, a prefogged emulsion containing the red filter dye Carmosine M, a rear red sensitive emulsion, and a support. The film after exposure is developed and washed, exposed through the support to red or white light, developed in a blue-green colour developer containing diethyl-p-phenylene diamine hydrochloride and 2: 3:4 trichlor-alpha-naphthol and washed. The blue sensitive front layer is exposed to blue or white light, developed in a yellow colour developer containing diethyl-p-phenylenediamine hydrochloride and benzoylacetone. The image in the green-sensitive middle layer is rendered developable by treatment with sodium arsenite, hydrogen peroxide, guanidine thiocyanate, X-rays, heat, or ultrasonic vibrations. The film may be treated with formaldehyde solution before the heat treatment, or may be immersed in water or other liquid which is a non-solvent for the film and subjected to ultrasonic vibration treatment. The image is then developed in a magenta colour developer containing diethyl-pphenylenediamine hydrochloride and thioindoxylcarboxylic acid. The silver is removed from all the layers by Farmer's Reducer or by treatment with potassium ferricyanide followed by treatment wth sodium thiosulphate. A modified film comprises a support, a green-sensitive emulsion, a prefogged emulsion, a red and blue sensitive emulsion insensitive to green, and a blue sensitive emulsion containing removable yellow dye. After development and washing, the film is exposed through the base with white or green light and developed in a magenta colour developer, washed, exposed from the front with orange-red light and developed iri a blue-green colour developer, washed, exposed with white light, and developed with a yellow colour developer, washed, and the silver removed with Farmer's Reducer or with cupric bromide followed by sodium thiosulphate. Three positive colour components records made from three negatives by printing or produced by the reversal process. the records being originally obtained in a camera or from a colour transparency or from a coloured print by reflection copying, may be printed on to the modified multilayer material, the blue component positive being printed by white or blue light on to, the top layer, the red component positive being printed by orange-red light on to the middle layer, and the green component positive being printed by green or white light through the support on to the bottom layer. The film is processed as described above. Specifications 354,898 and 473.993 are referred to.