Patent GB-1016693-A (GB)
Title: Recording process and recording material for use with the said process
IPC: G03G17/02
Filed: 1961-06-27
Abstract: Silver sulphide is produced at the platinum cathode on electrolysis of an aqueous solution of sodium silver thiosulphate.ALSO:Crystals of sodium silver thiosulphate are obtained by dissolving silver bromide in an aqueous solution of sodium thiosulphate and adding alcohol to form a precipitate, washing the precipitate with alcohol, and drying it.ALSO:An electrolytic recording material, e.g. for use in a facsimile copying telegraphy system employing a recording scanning electrode, comprises a conductive support bearing a layer containing as an initiator for record formation a heavy metal of atomic weight greater than 60 or an oxide or sulphide of such metal, or a substance, other than a light-sensitive compound capable of producing a visible or latent record by the action of light only, which yields such metal, oxide or sulphide on the passage of current through it. The electrolytic action may either form an imagewise distribution of the initiator or it may remove the initiator imagewise.  Typically a platinum plate or tin oxide-coated glass plate coated with a gelatin solution of sodium silver thiosulphate crystals is wetted and subjected to a small current through a scanning platinum cathode and a fixed backing electrode.  The latent silver sulphide image so formed is then developed with a hydroquinone photographic developer containing also 1-phenyl-3-pyrazolidone, sodium sulphite, sodium thiosulphate, citric acid and sodium hydroxide and thickened with sodium carboxymethyl cellulose.  A colour coupler may be included in the sodium silver thiosulphate layer or in an adjacent layer, e.g. aceto-aceta-2-chloroanilide, p-nitrophenylaceto-nitrile, or 2 : 4-dichloro1-naphthol which yield yellow, magenta or cyan dyes respectively together with silver when developed with a photographic colour developer of the p-phenylenediamine type.  The backing electrode may be affixed to the colour-changeable reagent layer as a thin vapour-deposited or sputtered liquid-permeable film.  To facilitate penetration of the developer the sodium silver thiosulphate may be mixed as a powder with silica gel and dispersed in an oil-soluble resin such as polyvinylbutyral, or polyvinylmethylether or sodium carboxymethyl-cellulose to provide the film-forming coating.  Unreduced silver salt remaining after imagewise reduction to silver may be used to form records in receiving sheets bearing a layer containing silica gel, sodium sulphide, and one or more of cadmium or lead acetate or zinc nitrate by placing the silver image layer and receiving sheet wet with developer in contact in a manner analogous to the silver halide diffusion transfer process.  With coloured transfer records, e.g. formed by dyes, only part of the dyeforming components need be in the recording material, the remainder being in the receiving sheet or the components in non-reactive form in the recording material may be caused to react to form a dye by an oxidizing agent such as copper sulphate in the receiving sheet. As an alternative to forming the initiator imagewise by electrolysis, a tin oxide-coated glass support may be coated with silver, and covered with a completely saponified water-insoluble polyvinyl alcohol film and subjected to electrolysis using sodium nitrate as electrolyte to dissolve away silver imagewise as soluble silber nitrate which is washed away.  The resulting silver initiator image covered with the water-insoluble film is then covered with a gelatin film containing sodium silver thiosulphate and developed as above, the developed image being darkest where least current is passed.  Reference is also made to the use as initiators of salts of Cu, Hg or Pb, of the product of heating at above 500 DEG C. a glass plate spray-coated with an aqueous solution of tin chloride, antimony chloride, hydrochloric acid and ammonium fluoride, or a metal compound of a pyrazole, triazole, imidazole, thiazole, or thiazolidine.  If multicolour records are to be produced a film is used including a mosaic colour filter layer and similar to that disclosed in Specification 983,488 (see Division H1), but omitting the photo-current layer and including an initiator in or adjacent the mosaic colour-changeable reagent layer.