Patent GB-407830-A (GB)
Title: Photographic process for producing written characters or representations or a surface coloration, on aluminium and aluminium alloys
IPC: G03C1/77
Filed: 1933-03-29
Abstract: 407,830. Electrolytic surface treatment of aluminium and its alloys. SIEMENS & HALSKE AKT.-GES., Siemensstadt, Berlin. March 29, 1933, Nos. 9455, 9456, 9457, 9458, and 9460. Convention dates, June 30, 1932, Nov. 19, 1932, Nov. 19, 1932, Nov. 19, 1932, and Feb. 9, 1933. [Class 41.] A photographic process for producing written characters or pictures or a surface colouration on aluminium or aluminium alloys comprises modifying the surface by electrolytic means to form a carrier layer capable of adsorbing light-sensitive material, impregnating the layer so formed with light-sensitive material, exposing to light and thereafter treating it in photographic baths. The layer may comprise an oxidic, fluorine-containing, or phosphate layer or a combination thereof. In examples, (1) a sheet of aluminium is coated with a oxygencontaining layer in an oxalic acid bath under direct or alternating current and, after washing and drying, the coating is impregnated with a silver chloride solution, dried, exposed under a negative and thereafter fixed, toned if necessary, washed and dried ; (2) a sheet of alloy known under the Registered Trade Mark " Duralumin," coated with an oxygen-containing layer by means of a chromic acid bath and an alternating current, is treated in like manner; (3) an aluminium sheet coated as in Example (1), is impregnated with a solution of ironchloride and tartaric acid, exposed under a diapositive, and the yellow image is developed in a weak solution of gallic and oxalic acids ; a layer, produced as in Example (1), is impregnated with silver bromide by successive treatment with solutions of potassium bromide and silver nitrate, rinsed to remove excess silver nitrate, dried, exposed and treated with a usual developer; (5) an aluminium sheet provided with an oxide layer is immersed in a solution of sodium-chloride and ammonium iodide, treated with silver nitrate, exposed and developed with an acid iron solution. The layers may be colour-sensitized and may be subjected to reversal, toning or dye-toning treatment. Examples are given of the production of red and violet heat resisting surface colourings by toning a silver image with gold, and heating. Oxidic layers may be produced in alkaline baths, e.g. soda or water-glass, with or without the application of an electric current. A fluorine-containing layer is obtained by the use of a molten fluoride bath, e.g. acid potassium fluoride with 20 per cent sodium fluoride at 220‹ C., with direct or alternating current. For a phosphate layer, a 3 per cent solution of phosphoric acid is employed with direct current of 110 volts. A combined oxygen, fluorine and phosphorus containing layer is formed by successive electrolytic treatment in baths of chromic or oxalic acid, fused fluorides, and aqueous phosphoric acid. The process is suitable for exposure in the ultra violet part of the spectrum ; and for the production of passports, signs, instrument scales, imitations of wood, marble &c. graining, &c. Specification 378,521 is referred to.