Patent GB-595356-A (GB)
Title: Improvements in sensitive photographic materials
IPC: G03C1/74
Filed: 1944-03-01
Abstract: 595,356. Photographic dry-stripping material. KODAK, Ltd., SOPER, A. K., and BERRIMAN, R. W. March 1, 1944, No. 3856. [Class 98 (ii)] Dry-stripping material comprises a sensitive silver salt emulsion layer united to a temporary support by a dry-stripping layer, the emulsion binder being composed of at least 75 per cent by weight of one or more polyvinyl substances insoluble in water at 20‹ C., but permeable to water at that temperature. The emulsion may have no overcoating layer, or a dyed or pigmented overcoating layer (e.g. of cellulose nitrate) may be provided. The processing solutions may contain softening agents. Material with a wax dry-stripping layer may be formed by coating the wax-coated temporary support coming from the usual drying chamber with emulsion and again passing through the heated chamber, without an intermediate cooling step. The polyvinyl substance may be a partially hydrolysed organic ester (acetate, e.g. water-insoluble acetates containing 59 to 85 per cent of acetate calculated as vinyl acetate, propionate, or butyrate), or an acetal or ester-acetal containing free hydroxyl groups (e.g. acetaldehyde, propionaldehyde or butyraldehyde acetals). The polyvinyl substance may be dispersed through a concentrated emulsion made with a small quantity of another binder. The permanent support is coated.with lacquer (e.g. comprising cellulose nitrate, tricresyl phosphate, triphenyl phosphate, acetone and butyl acetate), which is dried and softened with a softening liquid (e.g. a mixture of methylated spirits with butyl alcohol), the emulsion side of the dry-stripping material pressed into contact therewith, and the temporary support (e.g. paper) stripped off. The lacquer may contain titanium dioxide and the emulsion may contain a white or other pigment. The temporary support or dry-stripping layer may be dyed or pigmented or may serve as a filter if the emulsion is exposed by the reflex copying process while still on the temporary support. The emulsion may be transferred before or after exposure or before or after development. The material may be used to apply a pattern to ceramic material, the binder being burned away on firing. In example 1, aqueous ethyl alcoholic solutions of silver nitrate and of ammonium bromide and potassium iodide are added to an aqueous ethyl alcoholic solution of polyvinyl acetate containing 70 per cent of acetate calculated as vinyl acetate, ethyl alcoholic polyvinyl acetate solution is added, the emulsion is poured into water and washed, and is dissolved in ethyl alcohol for coating on paper previously coated with a trichlorethylene solution of beeswax and dried. The material may be applied to a surface lacquered with cellulose nitrate. After development, the emulsion may be fixed with ammonium thiocyanate or iodized in an aqueous solution of potassium iodide and sodium metabisulphite. In example 2, the polyvinyl acetate used contains 85 per cent acetate calculated as vinyl acetate and sufficient ammonia is added to the silver nitrate solution to dissolve the first-formed precipitate. The developer used comprises hydroquinone, caustic soda, sodium sulphite and potassium bromide. Specifications 529,041, 542,703, 542,704, 543,854, 543,855, 554,292, 554,298, 554,300, 554,301, 559,843, 564,267 and 595,361 are referred to.