GB755566A - Improvements in or relating to recording blanks for electric recording in facsimile telegraphy - Google Patents

Abstract

755,566. Copying-telegraphy. CREED & CO., Ltd. May 21, 1954 [May 26, 1953], No. 15076/54. Class 40 (3). [Also in Groups VIII, XVI and XIX] An electro-sensitive recording blank for copying-telegraphy comprises a non-conductive base sheet carrying an adherent electrically-conducting coating of finely-divided carbon dispersed in a water-soluble binder, the coating being such as to have a high resistance surface stratum consisting mainly of a surface concentration of a varnish or lacquer resin having intermingled therewith some of the water-soluble binder and carbon, the stratum having thereon a thin adherent surface coating of substance of a character to be disintegrated in elemental areas in response to electrical marking currents. The high resistance surface stratum is due to the surface concentration of the resin phase of a resin solution emulsified in an aqueous solution of the binder in which the carbon is dispersed. The base sheet 70 of a suitable paper is coated with a layer of a mixture of an emulsified resin solution and a carbon dispersion in a watersoluble binder, preferably comprising casein, the water being absorbed by the paper sheet 70 and partially evaporated at the outer surface of the coating to form a layer 71 including the conductive carbon and a layer 72 containing mainly the resin, but including a small amount of carbon. The surface coating 73 of relatively high electrical resistance may comprise cuprous or lead thiocyanate, zinc sulphide, lead thiosulphate or an oxide of lead, titanium or zinc. The water-soluble binder may comprise polyvinyl alcohol, starch, or glue, and the resin may be an air-drying styrenated alkyd resin dissolved in toluol. Other resins include vinyls, modified resin esters, ethyl cellulose, dammar or rosin, and examples of the emulsifying agent are the oleate or stearate of ammonia or the oleate of morpholine. If the blank is to be used for lithographic off-set printing, the carbon layer may be made water-repellent and ink-receptive by adding to the mixture a small amount of water-soluble silicone, such as sodium methyl siliconate. Specification 660,029 is referred to.