Patent GB-701551-A (GB)
Title: Colour photography
IPC: G03C8/04
Filed: 1951-10-22
Abstract: 701,551. Colour photography. GENERAL ANILINE & FILM CORPORATION. Oct. 22, 1951 [Dec. 30, 1950], No. 24595/51. Drawings to Specification. Class 98(2) A process of preparing tricolour separations from an exposed multilayer colour film comprising a support bearing superimposed silver halide emulsion layers sensitized respectively to the blue, green, and red regions of the spectrum, the blue sensitive layer being outermost and being devoid of colour former, and the green and red sensitive layers each containing a colour former fast to diffusion and capable of reacting with the oxidation products of an aromatic primary amino developing agent to yield dyestuff images adaptable for colour separation by printing with coloured light, comprises contacting the outermost layer of said exposed film with an auxiliary film comprising an impermeable support -bearing a colloidal layer containing an alkali sulphide, stannous chloride, colloidal silver, colloidal silver sulphide or colloidal gold sulphide, while forcing the colloidal layer of said auxiliary film firmly against the surface of the blue sensitive layer of the multilayer film in the presence of a developer-fixer solution for a sufficient length of time to cause the developer-fixer solution to develop the negative image in said blue sensitive layer, to dissolve the residual silver halide of said layer and transfer it to the colloidal layer of the auxiliary film and effect reduction of said transferred silver halide in said colloidal layer, stripping off and washing the auxiliary film which now contains the blue record, processing the multilayer film by colour forming development, bleaching and fixing it to produce a negative containing the red and green records respectively, and printing said records with sharp cutting filters on to separate sensitized films. To facilitate this printing the colour formers in the green and red sensitive layers of the multilayer film may be such as to produce yellow and green images respectively. Colour correction may be effected by use of a coloured colour former in the red sensitive layer as described in Specification 637,852, or by production of azo dye masks from residual colourless colour former by treatment with a diazonium salt solution as described in Specification 701,039. The colloidal layer of the auxiliary film may contain also a compound such as mercaptobenzothiazole, mercaptophenyltetrazole or mercaptobenzimidazole to provide an image therein of increased blackness. In example I, 3-(pstearoylaminobenzoylacetamido)-isophthalic acid and 1-hydroxy-2-naphthoyl-4<SP>1</SP>-laurylamino-7<SP>1</SP>-sulphonaphthalide are used as yellow and cyan colour formers in the green and red sensitive layers respectively, and the uppermost, blue sensitive, layer of the multilayer film after exposure is coated with developer-fixer solution comprising metol, hydroquinone, sodium sulphite, sodium hydroxide, sodium thiosulphate, sodium carboxymethyl cellulose, potassium bromide and water, contacted with the auxiliary film by pressure rollers for about a minute to obtain therein a positive record from the blue sensitive layer, and, after stripping off the auxiliary film, the multilayer film is subjected to conventional colour development and bleaching procedure. The green record so produced may be printed on to blue sensitive film using Wratten 49-B and the red record on to panchromatic film using Wratten 29. The word " Wratten " is a Registered Trade Mark Examples II and III outline the procedure of example I as adapted to produce colour corrected records by the methods of the above mentioned Specifications. Innumerable additional colour formers are quoted. Specifications 614,155, 652,953, 654,630 and 665,657 also are referred to.