| 摘要 |
1323563 Photographic colour transfer material INTERNATIONAL POLAROID CORP 31 July 1970 [31 July 1969] 37181/70 Addition to 1220474 Heading G2C A colour transfer film unit yielding on exposure and development a colour print consisting of a positive colour image over a negative image and separated therefrom by a light opacifying layer, comprises a first support, a silver halide layer containing a dye-image-forming compound e. g. a dye-developer, a polymeric dye-image receiving layer, a second, transparent support, and a light opacifying layer of light opacifying material e. g TiO 2 between the silver halide and image-receiving layers or, when an aqueous alkaline processing composition is positioned to be spread between the said layers, then the light opacifying material may be suspended in the processing composition, and which film unit also contains a dispersion of particulate acidic material in at least one layer, the acidic material being protected from immediate contact with alkaline processing composition by a polymeric coating that is permeable to the processing composition at a rate sufficient to permit reduction in pH to a pH at which the dye-imageforming material is substantially non-diffusable only after substantial conclusion of image formation. In preferred film units, the processing composition is in a rupturable container positioned to be spread between the silver halide and image-receiving layers, the first support being transparent when an opacifying layer is situated between the said layers or opaque when the opacifying material is in the processing composition. The dispersion of particulate acidic material may comprise acids such as citric, succinic, oxalic, phosphoric and polyphosphoric acids, acidic polymers such as sulphonated polystyrene or acid precursors such as esters, anhydrides or lactones such as ethylene/ maleic anhydride copolymer, and may be protected from processing composition by being embedded in or encapsulated by polymers such as cyanoethyl polyvinyl alcohol, polyvinyl acetal, cellulose esters and hydroxypropyl cellulose for example. Preferred acidic dispersions include citric acid in cellulose acetate, and are present in each permeable layer of the film unit. |
