Patent GB-564976-A (GB)
Title: Improvements in or relating to multi-layer photographic material and to methods of using the same
IPC: G03C1/805
Filed: 1943-10-08
Abstract: 564,976. Photographic multilayer material. AUSTIN, A. ST. J., and COOTE, J. H. Oct. 8, 1943, No. 16494. [Class 98 (ii)] Multilayer material having two or more superposed silver halide emulsion layers on a common support comprises interposed between adjacent emulsion layers a thin intermediate layer of regenerated cellulose united at its outer surface to the emulsion layer superposed thereon by means of a bond permeable to aqueous liquids without substantial reduction in the adhesive power of the bond, and united at its inner surface to the underlying emulsion layer in such manner that when the latter is permeated by an aqueous liquid the union is so weakened as to enable the intermediate layer to be separated from the underlying emulsion layer. The regenerated cellulose layer may be united to the superposed emulsion layer by means of gelatin hardened with chrome alum, or a hardener for the gelatin or other colloid binder of the emulsion may be interposed between the two layers. The regenerated cellulose layer may be applied directly to the underlying emulsion layer after being wetted, e.g. with water or alcohol and water with or without wetting agents. The adhesive or hardener may be applied to the outer surface of the regenerated cellulose before or after it is applied to the underlying emulsion layer. The hardener solution (e.g. chrome alum solution) is preferably applied when the regenerated cellulose layer is dry and in the form of a fine spray. The material may be a three-layer material or a bipack having two emulsion layers on one support and another emulsion layer on a second support. One of the layers may be sensitized to infra-red. The intermediate layers may be coloured to act as filter layers, or one or more of the emulsion layers may contain filter dyes. The green and red sensitizers may be sufficiently selective to obviate the use of filters, apart from a yellow filter dye in the blue sensitive layer. After exposure of the material, the latent image recorded in an upper emulsion layer may be developed and printed with light to which the associated emulsion layer or layers is or are not sensitive, and the developed emulsion layer and the associated intermediate layer removed from the underlying emulsion layer. In a three-layer material, the middle emulsion layer may then likewise be developed, printed from, and removed. Alternatively, the emulsion layer or layers may be stripped after development and transferred each to a separate support for further treatment, e.g. fixing. In example 1, to a celluloid or other transparent flexible support are successively applied a greensensitized emulsion, a thin sheet of regenerated cellulose, an aqueous gelatin solution containing chrome alum (by spraying), a red-sensitized emulsion, a second thin sheet of regenerated cellulose, the gelatin-chrome alum solution, and finally a blue-sensitive emulsion containing a yellow filter dye. After exposure, the top layer only is developed and the material immersed in an acetic acid stop bath. The developed image, preferably without fixing, is copied on to infra-red sensitized material with infra-red rays, and the intermediate layer carrying the top emulsion layer is peeled off. The operation is repeated with the red-sensitized emulsion, and then the bottom green-sensitized emulsion is developed, fixed, and dried. In example 2, to a glass or celluloid support are successively applied a blue-sensitive emulsion containing a yellow filter dye, an intermediate regenerated cellulose layer, a green-sensitized emulsion layer, an intermediate regenerated cellulose layer, and a red-sensitized emulsion layer. The material is exposed through the support and the top layer is developed, immersed in a stop bath, stripped with its associated regenerated cellulose layer, and transferred to an alcohol-water bath. The middle layer is likewise treated. The bottom layer is developed and fixed. The stripped layers are transferred to glass, nitrocellulose, or cellulose acetate supports coated on one side with gelatin and chrome alum, and are fixed and washed. The three negatives are used for printing positive prints.