Process for bleach-fixing chromogenically color photographic silver halide material

#This invention relates to a process for bleach-fixing developed color photographic silver halide material, more particularly material of the kind in which dyes have been produced chromogenically by color-forming development.

#In color-forming development, a silver image is formed in addition to the dye image. However, this silver image subsequently has to be removed. It is known that bleaching baths with an oxidizing effect can be used for this purpose. So-called bleach-fixing baths which are able both to oxidize the silver and also to dissolve the oxidized silver out of the layer, have proved to be particularly suitable for this purpose. In addition to a fixing agent, which is normally sodium or ammonium thiosulfate, these bleach-fixing baths also contain a weak oxidizing agent which is able to oxidize the silver without affecting the fixing agent. Iron-III-and cobalt-III-complexes or organic amino polyacetic acids, more particularly the sodium salt of the iron-III-complex of ethylene diamine tetra acetic acid, have proved to be suitable oxidizing agents. Reference is made in connection with these bleach-fixing baths to German Pat. No. 866,605.

#Unfortunately, these bleach-fixing baths have certain disadvantages. Oxidation of the metallic silver by the weak oxidizing agent is accompanied by the formation of the corresponding iron-II- or cobalt-II-complexes, for example of the ethylene diamine tetra acetic acid.

#several strips of a standard color reversal film containing, on a transparent substrate, a red-sensitized silver halide emulsion layer with a cyan-forming coupler, above this layer a green-sensitized silver halide emulsion layer with a magenta-forming coupler then a yellow-filter layer with colloidal silver and, above this layer, a blue-sensitive silver halide layer with a yellow-forming coupler, were exposed behind a continuous wedge, sujected to an initial black-and-white development in a hydroquinone-metol developer, subsequently rinsed, subjected uniformly to a diffuse second exposure to white light and to a color development, briefly rinsed and then dried. Strip 1 was then further processed in the usual way by being successively bleached for 5 minutes in a bleaching bath of the composition shown below and rinsed for 5 minutes. Strips 2 and 3 were rinsed for 2 minutes and then bleach-fixed for 20 minutes with vigorous agitation in a bleach-fixing bath with the composition shown below, resulting in heavy reduction of the magenta and, more particularly, of the cyan dye. Strip 2 was then rinsed for 5 minutes and dried in a stream of cold air. Strip 3 was rinsed for 5 minutes, treated for 5 minutes in oxidation bath number 1, rinsed for 5 minutes and then dried cold. The colour densities set out in Table 1 were obtained.

#__________________________________________________________________________ Bath composition: __________________________________________________________________________ Bleaching bath: potassium ferricyanide 80 g potassium bromide 20 g disodium phosphate anhydrous 12 g made up with water to 1000 ml pH adjusted with glacial acetic acid to 5.2 - 5.6 Bleach-fixing bath: sodium salt of the iron-III- complex of ethylene diamine tetra-acetic acid 40 g anhydrous sodium sulfite 20 g ethylene diamine tetra- acetic acid 1.5 g potassium dihydrogen phosphate 10 g ammonium thiosulfate 80/20 200 g (commercial product consisting of 80% of ammonium thiosulfate and 20% of sodium thiosulfate) mercapto triazole 2 g made up with water to 1000 ml pH-value 6.0 Oxidation bath No.1: sodium salt of the iron-III- complex of ethylene diamine tetra-acetic acid 10 g tetra-sodium salt of ethylene diamine tetra-acetic acid commercial product with 30% active acid 10 g made up with water to 1000 ml pH-value adjusted with disodium phosphate to 8. __________________________________________________________________________ Table 1 __________________________________________________________________________ Strip No. Treatment Maximum density Yellow Magenta Cyan __________________________________________________________________________ 1 standard (with bleaching bath and fixing bath) 3.6 3.3 3.6 2 with bleach-fixing bath without oxidation bath 3.4 2.9 2.0 3 with bleach-fixing bath with oxidation bath No.1 3.4 3.2 3.4 __________________________________________________________________________

#Strip 1 shows the maximum color densities of the reversal film treated in the usual way with a postassium-ferricyanide bleaching bath. Strip 2, which was only treated with bleach-fixing bath, shows much lower color densities for magenta and cyan. The original color densities are restored by the after-treatment with the oxidation bath (strip 3).