GB995491A - Photoconductive, thermoconductive and like dielectric recording materials - Google Patents

Abstract

A photoconductive, thermoconductive and like dielectric recording material comprises an insulating dielectric layer and, as a support therefor, a glassine-type or modified glassinetype paper defined as having a very dense surface structure, large cohesion and greaseproof character, and being very smooth and semi-transparent. The support may be a woodfree paper prepared from bleached cellulose pulp or a glassine-type tracing paper of a type as used in technical drawing offices; other glassine-type papers and baryta-coated papers are also specified. The dielectric layer may be applied directly to the glassine-type paper. The dielectric layer may comprise a polymeric material, and photoconductive material or materials, e.g. photoconductive zinc oxide, or photoconductive zinc oxide grains and one or more organic phosphorus compounds such that the dark-resistivity of the grains is substantially higher than that of a mass of grains which is identical save for the absence of such compound(s). The phosphorus compound may contain in its chemical structure at least one oxygen atom bound to a phosphorus atom and for the rest includes at least one cationic residue which comprises a hydrogen ion, an onium group, and ammonium group and/or a metal ion. A pigment layer which may contain gelatin, or ethyl cellulose, may be present between the support and the dielectric layer, or on that side of the support which is remote from the dielectric layer. A layer with a specific volume resistivity less than that of the support may be present between the support and the recording layer. Polymeric materials specified are copolymers of N-vinyl carbazole and ethyl acylrate; 4-vinyl benzyl bromide and N-ethyl carbazole; vinyl acetate and vinyl stearate; vinyl acetate, vinyl chloride and maleic anhydride; and polymers of vinyl-n-butyral, and vinyl formal. The polymeric material may be applied from an aqueous medium or from organic solvent, examples of which are given, by centrifuging, spraying, brushing, dip or vacuum-coating. The paper supports are suitable for vacuum coating with their conductive or photoconductive layers such as selenium layers. Specifications 647,479, 658,699, 856,770, 898,354, 947,479, 964,872, 964,873, 964,876, 964,879, 970,937, 980,879 and 988,228 are referred to.