Patent GB-595582-A (GB)
Title: Improvements in or relating to coloured colloid layers
IPC: G03C1/825
Filed: 1945-07-10
Abstract: 595,582. Colour photography. WALLER, C., DICKINSON, H. O., and ILFORD, Ltd. July 10, 1945, No. 17544. [Class 98 (ii)] Coloured colloid layers are produced by treating a substantially colourless colloid layer containing colloidal silver sulphide in such small quantity that substantially no colour is imparted thereby to the layer with a solution of a reducing agent in presence of another silver compound and a solvent therefor. When forming part of a photographic material the colloid layer may contain a silver compound such as silver halide or may be adjacent to a silver halide emulsion layer. Reduction is effected as by a photographic developer in the presence of a solvent for the silver compound such as potassium thiocyanate, the colour produced being yellow to red or brown. Layers containin gthe colloidal silver sulphide may be produced from gelatin alone (which contains sulphur compounds) heated with silver nitrate or silver halide, or a sulphur compound, such as thiourea, allyl thiourea, thiosulphates, thiosemicarbazide or allylthiosemicarbazide may be added. A multilayer material may comprise a transparent support carrying red-, green- and blue-sensitive silver halide emulsion layers with two interposed layers according to the invention, that between the green and blue sensitive layers being dyed yellow with a decolourisable dye. The material may also include subbing, antihalation and anti-abrasion layers and an ultraviolet absorbing front layer. The exposed material is developed in a developer containing a silver solvent, when the two interposed layers become coloured and the yellow dye is decolourised. The emulsion layers may be selectively processed to colour by reversal colour development with the aid of the filter layers by successive blue light exposures on eacli side of the material and by rendering the middle emulsion layer developable by exposure to bright light or X-rays or by fogging with sodium arsenite, hydrogen peroxide or guanidine thiocyanate. The first formed negative silver images may be removed, e.g. by acid dichromate or permanganate, before re-exposure, the colloidal silver sulphide being unaffected by this treatment, and the filter layers being coloured on re-development in the presence of a silver halide solvent. In example 1, material comprising a support (a), a red-sensitized silver iodobromide emulsion (b), a gelatin layer (c) containing colloidal silver sulphide and silver iodobromide, a green-sensitized silver iodobromide emulsion (d), a gelatin layer (e) as (c), but also containing 1 - (p - sulphophenyl) - 3 - methyl-4-cinnamylidene-5-pyrazolone, and a blue-sensitive silver iodobromide emulsion (f) is exposed to a coloured object, developed to silver, treated in acid dichromate solution to remove the negative silver images, and is redeveloped in a developer containing amidol and potassium thiocyanate to produce a yellow-red colour in layers (c) and (e). Layer (b) is re-exposed with violet light through the, support and is colour developed blue-greens layer (f) is re-exposed with violet light and is colour developed yellow, and layer (d) is reexposed with X-rays and is colour developed magenta. The coloured images may also be produced by dye- or chemical-toning. Example 2 describes material which contains in layer (b) the colour former 1 - hydroxy - 2 - naphthoyl - stearylamide, the processing being modified accordingly. Specification 505,099 is referred to.