Patent GB-541045-A (GB)
Title: Improvements in or relating to photographic materials comprising colloid layers
IPC: G03C1/835
Filed: 1940-05-06
Abstract: 541,045. Photographic material; colour photography. WOOSLEY, D. P., and CHILTON, L. V. May 6, 1940, Nos. 8156/40 and 3669/41. [Classes 98 (i) and 98 (ii)] [Also in Groups VIII and XL] In the production of photographic materials comprising colloid layers and embodying a lightsensitive layer, or a layer bearing a photographic image, or both, which material includes also a layer of a water-insoluble metal alginate which is soluble in an aqueous solution of ammonia or dilute sodium carbonate solution, the alginate layer is formed either (a) by applying to the surface on which it is to be carried a solution of the metal alginate in dilute sodium carbonate solution or in ammonia solution, and neutralizing or removing the sodium carbonate or ammonia, or (b) from the action on a coating of a watersoluble alginate applied to the carrying surface of a soluble salt of the metal of which the alginate is desired. Alginates of cobalt, nickel, copper, chromium, zinc, vanadium, tungsten, silver, aluminium, molybdenum, cadmium and calcium are mentioned. The alginate layer may be a protective coating over a silver halide emulsion layer, a stripping substratum, a filter layer, an antihalation layer, or a fluorescent intensifying layer 'for X-ray sensitive material. Such layers may be used as filter or stripping layers in material for colour photography, particularly multilayer sensitive material. They may be removed by the developing solution if this is alkaline, or by a separate treatment with dilute sodium carbonate or ammonia solution. In the case of multilayer material which is to remain intact on development, alginate layers insoluble in sodium carbonate solution but soluble in ammonia solution are used. The second method (b) may be performed (1) by applying to the surface in succession solutions of a water-soluble salt of the metal and of a water-soluble alginate and thereafter washing and drying, or (2) in the case of a calcium alginate layer on a gelatin layer, by merely coating the gelatin with a watersoluble alginate, the calcium alginate being formed therefrom by wandering of calcium ions normally present in gelatin, Suitable water-soluble alginates are those of the alkali metals, ammonium, magnesium, and salts' with organic bases, e.g. triethanolamine salts; and the solution used preferably contains a wetting agent such as saponin, potassium oleate, Turkey red oil, sodium lanryl sulphate, and various commercial wetting agents. For antihalation purposes, a dyed or pigmented alginate layer is coated on the back of the support or on the surface of the emulsion layer, preferably over a gelatin substratum; or a dyed gelatin layer may be coated over a plain alginate layer. Examples are given of the coating of alginate layers for protective, filter, and antihalation purposes. An example is also given of a multilayer material for colour photography formed by coating on a support in successive layers of gelatin, sodium alginate, collodion, panchromatic emulsion, sodium alginate containing a red filter dye, collodion, orthochromatic emulsion, sodium alginate containing a yellow filter dye, collodion, and a not specially coloursensitized emulsion. The alginate coatings are converted by the adjacent gelatin layers to calcium alginate. After exposure from the front in a camera, the material is treated in dilute sodium carbonate solution to separate from one another the three emulsion layers, each on its collodion support. These are'treated by a reversal process to develop in each its component colour image, and they are then reassembled in register to give a multicolour transparency or reflection positive. In another example, three colour-record positives are printed from colour-separation negatives, each on material comprising a paper support, a watersoluble gelatin substratum, and a gelatino-silverbromide emulsion layer. After developing and fixing, the three images are treated in a bleaching bath of copper chloride and potassium dichromate. The prints are washed, bathed in zinc sulphate solution, and each is squeegeed face downwards upon a sodium alginated layer coated upon a temporary support of the material known under the Registered Trade Mark " Cellophane." After soaking in water to remove the original paper supports, the silver chloride images are colour developed to dye images, which are reassembled in register, e.g. on paper, by coating this with a layer of gelatin, squeegeeing the first print thereon face downwards, removing its temporary support by immersing in ammonia solution, washing, coating again with gelatin, and repeating the transfer process with the other two prints. Specifications 11033/06, [Class 98], and 539,799 are referred to.