Patent GB-507211-A (GB)
Title: Coloured photographic multilayer material
IPC: G03C7/28
Filed: 1937-12-09
Abstract: 507,211. Colour photography. GASPAR, B. Dec. 9, 1937, No. 34081. [Class 98 (ii)] An additional colloid layer is mounted in front of one of several silver halide emulsion layers in a colour photographic material, and contains an acid dyestuff of appropriate colour and resistance to ordinary photographic treating solutions, and an evenly distributed substance which assists in the bleaching of the dye by dye-destroying agents e.g. finely distributed silver, colloidal silver, fogged silver halide emulsion, exposed silver halide or colour sensitized silver halide. The silver halide emulsion layer behind the colloid layer is sensitive to light which is absorbed by the colloid layer but is sensitized to light transmitted by the latter. Two adjacent layers of silver halide emulsion replace each normal single layer of a multilayer, material, one half containing dyestuff sufficient for the most intensely coloured parts of the image, the other half containing the surplus necessary for filtration and either being sensitized e.g. to infra red to allow selective exposure at a later stage, or containing finely divided silver or exposed silver halide. In a three-layer material containing a blue-sensitive front layer dyed magenta and a yellow-dyed green-sensitive layer, the surplus yellow dyestuff is in that half of the layer adjacent the blue-sensitive layer, and is sensitized and exposed to infra red light. If the third layer is a normal blue-sensitive layer, then the surplus yellow dye is on both sides of the green sensitive layer. In another example, a blue-sensitive layer in front of green- or red-sensitive layers contains the surplus yellow dye on the rear part, the emulsion in this part being exposed during the coating operation. The coating operation for each of the layers may be avoided by forming two separate strata in a single dyed emulsion layer by surface illumination. In another example a transparent support carries on one side a yellow-dyed green-sensitized emulsion, a yellow intermediate layer and a blue-sensitive magenta-coloured layer, and on the other side a yellow layer and a blue-green coloured blue-sensitive layer, the dyes used being Milling Yellow, Polar brillantrot and Direct Sky Blue, The yellow auxiliary layers may be exposed emulsions or emulsions sensitized to infra red by cryptocyanine. The auxiliary dyed layers may be used in front of light sensitive layers which are colourless or coloured with a different dyestuff, which layers may also contain colour formers. In another example, the front clement of a bipack has a blue-sensitive layer and a green-sensitive layer separated by an intermediate gelatin layer containing Milling Yellow G and an amount of exposed silver bromide emulsion. After development and fixing the element is dyed by soaking in a 1 per cent solution of Pontamine Sky Blue, and the dyestuffs in the layers are then destroyed by acid thiocarbamide solution or hydrobromic acid and the silver removed by bleaching. The intermediate layer is consequently decolourized and the gelatin is tanned by the bleaching. The film is fixed and dried, and the upper layer treated with sodium hyposulphite solution. The decolourized upper layer is then coloured at the unhardened places by a water soluble dyestuff. Specification 414,998 is referred to.