Patent GB-602881-A (GB)
Title: Colour correction of multicolour negative film by integral masking images
IPC: G03C7/30
Filed: 1945-06-08
Abstract: 602,881. Colour photography. GENERAL ANILINE & FILM CORPORATION. June 8, 1945, No. 14565. Convention date, May 3, 1944. Drawings to Specification. [Class 98 (ii)] A colour correcting positive azo dye image of low colour density is formed in the cyan layer or the magenta layer or both of multilayer sensitive material processed to colour by colour development by dyeing the layer with the azo dye, either during manufacture or processing, and producing the positive azo dye image by utilizing the negative silver image produced in the colour development in a dye destruction process. The multilayer material may comprise a support coated successively with a redsensitive layer (1) containing a cyan coupler, a green-sensitive layer (2) containing a magenta coupler, a yellow filter layer (3) consisting either of gelatin containing yellow colloidal silver or of a fogged emulsion containing a yellow azo dye which can be destroyed in presence of silver in a dye-destruction bath, and a blue-sensitive layer (4) containing a yellow coupler. Suitable couplers are specified. A yellow or red azo dye may be incorporated in the layer (1) and a yellow azo dye in the layer (2) during manufacture or may be introduced during processing. The dyes may be capable of precipitation with calcium lactate, diphenyl guanidine, or #-naphthylbiguanide. Suitable dyes are specified. Exposed material having the azo dyes incorporated may be colour developed, fixed and washed, and is treated in a dye-destruction bath comprising acidified thiourea or potassium thiocyanate (or rhodanine, thiohydantoin, thiourazole, thiotetrazoline, or thioureadioxide) to produce a red positive azo dye image in layer (1) and a yellow positive azo dye image in layer (2). The filter dye is removed in the bath. The colour densities of the negative colour developed images may be restored, if necessary, by treatment with dilute sodium carbonate solution. Residual silver may be removed by bleaching with ferricyanide and fixing. The film, originally without azo dye, may be treated after colour development with dye precipitant, which is then removed from the layer (4) only by washing with aqueous isopropyl alcohol. On dyeing with a yellow azo dye and washing, the dye is confined to layers .(1), (2) and (3). The film is further treated as above to produce yellow positive correcting images in layers (1) and (2) only. In example (1), layer (1) contains the cyan coupler sodium 1 - N -stearyl-4-N- (1<1> - hydroxy - 2<1> - naphthoyl - phenylenediaminesulphonate and Brilliant Purpurine 10B, layer (2) contains the magenta coupler, the condensation product of m-aminophenyl-methyl-pyrazolone and the mixed polymer of vinyl chloride and maleic anhydride, and layer (4) contains the yellow coupler terephthaloylbisacetic acid anilide-p<1>-carboxylic acid. The Brilliant Purpurine 10B may be replaced by Congo Red, Cotton Red 4B, or Benzo Fast Yellow RL. The material is colour developed, fixed and treated by the dyedestruction process. In example (2), layers (1) and (4) contain the couplers of example (1) and layer (2) contains the magenta coupler 1- (myristylamino - 2 -sulpho) -phenyl- 3 -methyl-5- pyrazolone and Milling Yellow. The material is treated as in example (1). In example (3), layer (1) contains the cyan coupler of example (1) and Congo Red, layer (2) contains the magenta coupler of example (2) and Benzo Fast Yellow RL, and layer (4) contains the yellow coupler of example (1). The material is treated as in example (1) to give a cyan negative image and a weak masking positive red image in layer (1), a magenta negative image and a weak masking positive yellow image in layer (2), and a negative yellow image in layer (4). Specifications 471,520 and 18697/47 (as open to inspection under Sect. 91) are referred to.