Patent GB-700502-A (GB)
Title: Improved method and materials for making a permanent record
IPC: G01D15/14
Filed: 1949-04-26
Abstract: 700,502. Producing photographic records electrically. OFFICE NATIONAL D'ETUDES ET DE RECHERCHES AERONAUTIQUES. April 26, 1949 [April 30, 1948], No. 11062/49. Class 98(2) A method of permanently recording in graphical form variable phenomena consists in submitting a strip comprising a photo-conducting material to the substantially simultaneous actions of electromagnetic radiations and an electric field, said field being produced between electrodes between or adjacent which the strip passes freely, and one of said actions having an effect on said strip in relation to the phenomena being recorded, whereby the strip undergoes a visible permanent change due to the passage of current under the action of the electric field in those zones which are rendered conductive by the said radiation. In a modification, the strip is irradiated uniformly and thereafter is subjected just prior to the action of the electric field to the action of a pencil of infra-red rays in proportion to the said variable phenomena so as to quench the conductivity of the strip locally and produce the trace as the unchanged portions of the strip. As shown, scanning light beams 30 ... 32 from mirrors 27 ... 29 expose a marginally perforated conducting strip 10 bearing or incorporating a photo-conducting material with or without a further material which is permanently changed by passage of an electric current, and this sheet is fed from a supply spool 11 to a driven take-up spool 12 by a driven sprocket 15, the exposed material being developed to yield records 35 ... 37 by passage through the electric field between electrodes 33, 34. If the recording strip comprises a photo-conducting material on an insulating support strip the electrodes may be disposed on the same side of the strip and separated by an insulating screen. The photo-conducting material may be phosphorescent. Numerous photo-conducting bodies, including metal sulphides, fluorescein, calcium fluoride, calcite, salicylic acid, unacyl acetate, anthracene, selenium, and thallium oxysulphide are specified. Current-reactive bodies include cobalt hexamethylene tetramine bromide and thiocyanate, and chromium hexammino pyrophosphate. Binders such as natural or synthetic resins, starches, or casein may be used, and colouring matters may be added. In examples, the recording material may be (1) a thin aluminium sheet, paper containing carbon or metal powder, or semi-conducting paper may be successively coated with urea-formaldehyde resin and a mixture of cadmium and zinc sulphides with a copper activator, optionally with cobalt hexamethylene tetramine thiocyanate, or (2) a thin sodium sulphate pulp paper loaded with carbon bound by means of starch and painted with zinc silicate containing a manganese activator. Specifications 478,140 and 506,201 are referred to. In the Specification as open to inspection under Sect. 91, the photo-conducting material comprises a phosphorescent paint containing a radio-active material such as radio-active barium sulphate, mesothorium, or radio-thorium. Under the action of current, the material is explosively disintegrated and the effect of the current on the reactive body may result in variation of optical anisotropy detectable by examination with polarized light. This subject-matter does not appear in the Specification as accepted.