Patent GB-591123-A (GB)
Title: Improvements in photographic elements and colour photography
IPC: G03C1/825
Filed: 1945-05-15
Abstract: 591,123. Colour photography. COLLINS, R. B., FLANNERY, F. E., ROBINSON, R. R., and ILFORD, Ltd. May 15, 1945, No. 12174. [Class 98 (ii)] Multilayer material comprises differentially sensitized photographic silver halide emulsion layers and at least one layer containing a substantially colourless surface active compound which enables this layer to absorb substantively from aqueous solution a dye which is not absorbedsubstantively by the other layers, the compound being unaffected by developing solutions. The exposed element may be developed, treated with an aqueous dye solution to form a coloured filter layer or layers, selectively re-exposed with the aid of the filters, the re-exposed layers processed to colour, and the silver, silver salts and filter dye removed. The method of forming the coloured layer or layers is described in Specification 591,124 and the method of decolourising the layers in Specification 591,122. Preferably the surface active compound is unaffected by oxidising agents for developed silver, and the negative silver images are removed before the dye treatment ; alternatively one of the filter layers may be resistant to oxidation and another not resistant, so that a second filter layer may be introduced after removal of the silver. The multi-layer material may consist. of a support carrying red, green and blue sensitive emulsions with a layer of surface active compound between the green and the blue and optionally a second such layer between the red and the green. Other constructions are indicated. An example describes material of layers : (a) support ; (b) gelatino silver iodo bromide emulsion red sensitized by means of 2 : 2<1> : 8-triethyl-4 : 4<1>-dichloro thiacarbocyanine bromide ; (c) gelatin layer containing " Teepol X " (Registered Trade Mark) ; (d) gelatino silver iodobromide emulsion green sensitized by means of 2 : 2<1>-diethyI pseudocyanine iodide ; (e) gelatin layer containing Auramine . and Teepol X; (f) gelatino silver iodobromide emulsion ; on exposure and treatment with a metol-hydroquinone developer silver colour records are produced in layers (b), (d) and (f), and the silver, and also the Auramine is then removed by acid permanganate solution. A yellow colour is formed in layers (c) and (e) by bathing in AuraminÞ solution, followed by washing. The material is exposed to violet light through the support and a cyan image colour developed in (b). After washing layer (f) is re-exposed by violet light and a yellow image colour developed therein with 2-chloroacetoacetanilide as colour former. The colour in layers (e) and (e) is removed by bathing in a solution of " Lissolamine A " (Registered Trade Mark) and then washing. The layer (d) is re-exposed with white or blue light from either side and colour developed to magenta. The material is then bathed in Farmers Reducer. In a modification the layer (d) may be rendered developable by fogging with thiourea and the frier step of colour removal from layers (c) and (e) omitted. A decolourisable anti-halation layer and a plain gelatin or ultra-violet absorbing supercoat layer may be provided. Specifications 461,006 and 500,793 are also referred to.