Patent GB-574137-A (GB)
Title: Multilayer stripping films and methods of making them
IPC: G03C1/805
Filed: 1943-08-09
Abstract: 574,137. Photographic multilayer stripping film. KODAK, Ltd. Aug. 9, 1943, No. 12819. Convention date, Aug. 7, 1942. [Class 98 (ii)] Photographic stripping film comprises a support having on one side at least two superposed silver halide emulsion layers separated by a stripping layer of a cellulose organic acid ester which in 'an aqueous medium loses its adherence to the outermost emulsion layer. A support may have on one side three superposed silver halide emulsion layers, the outer and middle being separated by a layer of cellulose organic ester soluble or permeable in an aqueous medium and the middle and innermost by a layer of water-insoluble cellulose organic ester soluble in aqueous organic solvent media or in alkaline solution. Alternatively, the stripping layers may both be of watersoluble cellulose organic enters. In example 1, a cellulose ester support (e.g. cellulose nitrate), which may have an antihalation and antistatic layer on the rear surface, is coated successively with a red-sensitive emulsion layer, a watersoluble cellulose acetate (e.g. of 17 per cent acetyl content) from a 1 per cent solution in water (which may contain saponin), and a green-sensitive emulsion. Alternatively, the support may comprise cellulose acetate, cellulose acetate propionate, or cellulose acetate butyrate, and a subbing layer may be interposed between the support and the emulsion. The stripping layer may comprise cellulose propionate or acetate propionate of 13-19 per cent acyl content. Alternatively, the outer emulsion layer may be blue-sensitive and the inner emulsion layer red- or green-sensitive. In example 2, a cellulose nitrate or other cellulose ester support 10, Fig. 2, carrying on its rear surface with antihalation and antistatic layers is successively coated with a layer 11 of red-sensitive silver halide emulsion, a very thin layer 14 of cellulose ester (e.g. cellulose acetate of 19 per cent acetyl content) soluble in a mixture of water and alcohol (coated from a 1 per cent solution in ethyl alcohol, ethylene glycol monomethyl ether, and water, or in acetone and water), a greensensitive emulsion layer 13, a layer 12 of water-soluble cellulose organic acid ester (e.g. cellulose acetate of 17 per cent acetyl content from a 1 per cent aqueous solution), a yellow gelatin filter layer (e.g. containing a pyrrole polymethine dye with a long-chain group or an aldehyde-azo dye), and a blue-sensitive emulsion layer 16. The layer 14 may also be of cellulose propionate, acetate-propionate, or acetate-butyrate of acyl content from 19 to 33 per cent, a mixture of water-soluble and - insoluble hydrolyzed cellulose esters (e.g. cellulose acetate) or of lower and higher acyl water-insoluble cellulose esters. Layers 12 and 14 may both be of cellulose acetate propionate of different acyl contents. Treatment with water enables the blue-sensitive emulsion 16 to be stripped, and subsequent treatment with dilute alcohol solution (e.g. methyl or ethyl alcohol solution) permits stripping of the green-sensitive emulsion 13. Stripping of the green-sensitive layer may also be effected after treatment with water. In example 3, the support 10 is successively coated with a redsensitive emulsion layer 11, a layer 14 of alkali-soluble but water-insoluble cellulose ester (e.g. a cellulose dicarboxylic acid ester such as cellulose acetate phthalate of 15 per cent phthalyl content in 1 per cent methyl alcoholacetone or water-ethylene glycol monomethyl ether-acetone solution or oxidized cellulose or oxidized cellulose esters), and the remaining layers as in example 2. Both stripping layers may be of the same cellulose derivative and successive stripping effected by controlled wetting. Specifications 447,748, 479,239, 529,440, 531,283, 574,138 and 574,164 are referred to. The Specification as open to inspection under Sect. 91 also included the subject-matter of Specifications 574,138 and 574,164. This subject-matter does not appear in the Specification as accepted.