Patent GB-651059-A (GB)
Title: Colour photography
IPC: G03C7/18
Filed: 1948-09-15
Abstract: 651,059. Colour photography. GANGUIN, K. O., HADDOCK, N. H., MACDONALD, E., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. Sept. 15, 1948, No. 24229. [Class 98 (ii)] A subtractively coloured multilayer photographic element comprising a base with three superimposed layers containing respectively, cyan, magenta and yellow dye images is characterized in that the layer containing the magenta image contains also a complementary yellow styryl dye masking image to correct for undesired absorption of blue light by the magenta dye. This masking image is made by use of a magenta colour former which contains in its molecular structure a reactive methylene group and cyan and yellow colour formers which do not react with aldehydes to give coloured compounds ; and, subsequent to colour development, treating the element with an aromatic aldehyde of the benzene or naphthalene series which contains at least one auxochromic group, or with a functional derivative thereof. Suitable magenta colour formers are pyrazolones such as 1-(41-phenoxy-31- sulphophenyl) - 3 - heptadecyl - 5 - pyrazolone, oxindoles including N-amyl oxindole, rhodanines for example N-ethyl rhodanine, diketopyrazolidines such as 1 : 2-diphenyl- or 1 : 2- di - (p - chlorophenyl) - 3 : 5 - diketopyrazolidene, coumaranones, thioindexyls, cyanoacetyl compounds such as the mono-p-(omega-cyanaceto) anilide of octadecenylsuccinic acid, cyanoacetylurea and its N-substituted derivatives and imidazolones. Of the yellow and cyan colour formers which give no dyestuff with the aromatic aldehydes used for forming the masking image, yellow colour formers of the acylacetylarylamide series such as pstearyl - amino - benzoylacetanilide - p<SP>1</SP>- carboxylic acid ; and cyan colour formers of the 1-naphthol series such as the product obtained by condensing 1-hydroxy-2-naphthoyl chloride with oleylamine and sulphonating, are preferred. As aromatic aldehyde there may be used 2 : 4-dimethoxybenzaldehyde or an aldehyde of the formula RNH-C<SP>6</SP>H<SP>4</SP>-CHO or R 1 R 2 N-C<SP>6</SP>H<SP>4</SP>-CHO where R, R 1  and R 2  are alkyl, aryl, aralkyl, hydroxyalkyl, halogenoalkyl, cyanoalkyl, nitroalkyl, carboxyalkyl or sulphoalkyl, or where R 1  and R 2 , together with the nitrogen atom form part of a 5- or 6- membered ring, and where the benzene nucleus may carry substituents such as nitro, alkyl, halogen, sulphonic acid or carboxylic acid groups ; but preferably a functional derivative of an aldehyde is used instead of the aldehyde itself as a more rapid reaction occurs with the residual magenta colour formers to form the yellow styryl dye, and as examples of such functional derivatives there are mentioned the anils, acetals and arylhydrazones, preferably those with solubilizing groups such as anils obtained by condensing p-N : N-diethylaminobenzaldehyde with aniline o-, m- or p-sulphonic acid or with aniline 2 : 5-disulphonic acid. To decrease overall fog of masking image due to unused magenta colour former a minimum quantity of this should be used, or by treatment in a tanning bleaching bath the image areas should be hardened to prevent reaction between the colour former and the aldehyde. Eight examples describe the procedure, covering direct and reversal colour development and the tanning-bleaching bath feature. Specifications 465,823 and 486,848 are referred to.