| 摘要 |
A film of gelatin, glue, vegetable gums &c. for use in carrierless condition, for example in the production of photographic relief images, is formed upon thin metal foil, as of aluminium or zinc, which is readily stripped before using the film. The film material, to which may be added a sensitizer such as bichromate, or silver bromide, &c., may be cast upon the foil in sheet or band form, and the foil may be reinforced during the casting operation by a smooth rigid support such as a glass or metal sheet, a glass cylinder, or metal band, upon which the foil may be pressed as by a rubber roller. A number of foils may be attached to such a support as by pressing with a frame, or by glued-on strips, the frames or the strips serving as mould margins for the casting solution. To assist setting, the support may be cooled, or the film may be conducted through a cool indifferent liquid such as carbon tetrachloride. Thick films, e.g. 0.1 to 0.6 mm., may be so produced. Reference is made to similar casting processes in which the film either remains on the foil or is stripped therefrom; and also to the addition of materials such as lecithin in the production of thin films to prevent troublesome adherence to the usual casting supports. |
