GB652953A - Colour photography - Google Patents

Abstract

652,953. Colour photography. GANQUIN, K. O., HADDOCK, N. H., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. Aug. 20, 1948, No. 22000. [Class 98 (ii)] A colour corrected multicolour record is made by colour developing an exposed multilayer film comprising a base and superimposed thereon three differently sensitized gelatinosilver halide emulsion layers containing respectively a cyan colour former, a magenta colour former, and a yellow colour former which contains in its molecular structure the grouping -CO-CH 2 -CO- as part of an open chain of atoms, treating the film before, during or after the removal of silver with a gelatin hardening agent, and treating the film with a solution of a diazonium compound after the treatment with a gelatin hardening agent. The hardening treatment prevents residual yellow colour former from reacting with the diazonium compound, but the residual cyan and magenta colour formers do so react to form correcting masks of azo dyestuff. Suitable yellow colour formers are p-stearoylaminobenzoylacetanilidep-carboxylic acid, p-methoxybenzoylaceto-(2-N- octadecyl - N - methylamino) - 5 - carboxyanilide and p - stearoylaminobenzoylacetanilide - 3: 5- dicarboxylic acid. Potassium or chrome alum or image-wise tanning agents as used in the " carbon " and similar processes may be used as hardening agents. The diazonium compounds may be made by diazotizing the parent bases, or may be prepared from any available form of stabilized or passive diazonium compound. Positive or negative multicolour pictures, developed if desired by reversal, may be produced, particularly coloured negatives suitable for printing. Five examples illustrate the process using known couplers and other substances; example 1 describing direct colour development of the exposed film, treatment of this in a combined tanning and bleaching bath of aqueous potassium-ferricyanide, -bromide, - dichromate, -alum, and acetic acid, and then in the zinc chloride double salt of p-nitrobenzene diazonium chloride, followed by fixing, to produce a negative. Example 2 describes exposure of a film to a colour negative or positive transparency which may be colour corrected or not, development to black and white, bleaching with ferrocyanide and sodium chloride to convert developed silver to silver chloride, removal of this with sodium sulphite, re-exposure of residual silver bromide, colour development, and treatment with a diazo compound such as that derived from 4-nitro-6- methoxy-aniline to produce a negative or positive. Examples 3 and 4 describe application of the method to films containing reduced amounts of the cyan and magenta colour formers to avoid undesired reaction of such with the diazo compound used, and example 5 describes another direct colour development process of the nature of example 1, but using separate tanning and bleaching baths followed by mask production with the zinc chloride double salt of 2-nitro-4-methoxy-benzene diazonium chloride and fixing. Specifications 465,823, 502,665 and 602,881 are referred to.