Patent GB-706921-A (GB)
Title: Improvements in or relating to process of forming positive photographic images in colour
Inventor: LAND EDWIN HERBERT
IPC: G03C8/08
Filed: 1951-03-20
Abstract: 706,921. Process and element for coloured photographic positives. INTERNATIONAL POLAROID CORPORATION. March 20, 1951, No. 6641/51. Class 98(2) Single-, and by superimposition, multi-coloured positives are made by absorbing an aqueous alkaline liquid provided with a colour forming developing agent into a silver halide emulsion layer containing a latent negative image dissolving coupler material in the liquid so absorbed to react with oxidized developer to form a dye image in situ with the developed silver image, transferring from the emulsion layer by imbibition at least part of the imagewise distribution of unreacted developer and unreacted coupling material to a superposed image carrying layer, and oxidizing the transferred materials to form a positive dye image in the imagecarrying layer. The aqueous alkaline liquid may, initially be spread between the exposed emulsion layer and the image carrying layer and the liquid may be only a solvent for developing agent contained as in a permeable layer provided for that purpose, such permeable layer being, if desired, arranged so that the liquid first permeates the emulsion layer, then contacts developing agent, and lastly before the imbibition transfer contacts coupler material which may be contained in a further permeable layer. Alternatively coupler material may be introduced into the liquid before the developer is introduced. After imbibition the image-carrying layer is separated from the emulsion layer and oxidation as by air or by an oxidizing agent provided in the image-carrying layer or elsewhere produces a positive dye image. The light sensitive element, also part of the invention, always embodies a collapsible container for the liquid processing agent, and consists as shown in Fig. 1 of a unit 10 comprising a silver halide emulsion layer 11 on a base 12 united at 15 to image-carrying layer 14 which latter carries containers 16 of processing agent so spaced apart that an area of layer 11 may be exposed as indicated by use of a camera with lens 17 and bellows 18. After exposure the element may be drawn through pressure rollers 19 to crush a container and spread the contained agent between the layers to effect processing. In this element coupler may be incorporated in the photosensitive layer 11, the image-carrying layer 14 may contain an oxidizing agent, and the developer may be in the liquid in the container. In Fig. 2 a support 22 carries silver halide layer 21 in which coupler is incorporated and which carries, in turn, a hydrophilic layer 27 provided with developing agent; container 26 lies on layer 27; and 24 is the image carrying layer, the whole being designated 20. Element 30, Fig. 3, has image-carrying layer 34, container 36 in photosensitive layer 31 and layer 37 containing developing agent lying on a support 32. A preferred unit 57, Fig. 4, has photosensitive element 40 comprising a support 41 carrying permeable layer 42 containing developing agent, emulsion layer 44, permeable layer 45 with colour coupler, and container 49; and image receiving element 46 with base layer 47 containing an oxidizing agent and permeable layer 48; rollers 43 to crush the container are shown. To avoid wandering of developing agent or coupler from one layer to another during casting of the layers or drying them a further modification, Fig. 5, has negative material 50 comprising support 51, a layer 52 of water insoluble alkali soluble material such as cellulose acetate hydrogen phthalate, shellac or Japan wax containing developing agent and which layer 51 is cast in a non-aqueous solvent gelatin layer 53, layer 55 similar to layer 53 but containing colour coupler and emulsion 54 with container 59; the image carrying portion 56 comprises a base 57 carrying a gelatin layer 58 with oxidizing agent therein. The light sensitive elements and particularly the collapsable containers therein are made generally by the methods and of the materials described in Specifications 684,592, 684,641 and 706,901 and may be used for direct daylight production of positive images in the camera apparatus of Specifications 684,591 and 685,685. Preferably the aqueous alkaline liquid in the containers includes a viscosity-increasing film-forming material to assist in the spreading of the liquid after crushing the container and hydroxyethyl cellulose or sodium carboxymethyl cellulose may be used for this purpose. The developing agent may be p-phenylenediamine or alkyl substituted derivative thereof to be used with a conventional coupler material, of which a list is provided, to produce an azomethine, indaniline or indophenol dye, or a selfcoupling developing agent such as 1, 5-dihydroxynaphthalene, 4-chloro-2-methyl-aminophenol or 4- amino-pyrazolone may be used. As oxidizing agents, when such are used, salts of polyvalent heavy metals such as copper, antimony, uranium, manganese and iron in their higher valent form are preferred and other oxidizing agents are listed. Of 19 examples, Example 1, described in relation to Fig. 1, uses a silver chlorobromide emulsion on a conventional support treated with the coupler p-nitrophenylacetonitrile as emulsion layer 11, a baryta paper sheet surface treated with sodium perborate as image carrying layer 14, and aqueous sodium carboxymethyl cellulose, sodium carbonate with 2-amino-5-diethylaminotoluene hydrochloride as coupling developer in the container 16; exposure of the emulsion and passage of the assembly through the pressure rollers 19 to spread the liquid produces, after about 5 minutes for development, imbibition transfer, oxidation of developer and coupling thereof, a positive magenta dye image in layer 14 which layer may then be separated from the emulsion 11. In Example 3 the sodium perborate treatment of the image-carrying layer 14 is omitted and the imbibed developer is oxidized by air. Other examples describe the production of cyan and yellow positive images, and, by use of mixed couplers, black images. Tripack type film, each layer prepared with appropriate coupler and developing agent and each layer pressed, with the liquid, on to individual image-carrying layers which are assembled in register after production of the positive colour images, or pressed successively in register on to the same image carrying layer, with if desired, re-treatment of the latter with oxidizing agent, be used for three-colour reproduction.