GB977904A - Xerography - Google Patents

Abstract

977,904. Electrophotographic processes. RANK-XEROX Ltd. (Haloid Co.). Jan. 10, 1961, No. 1056/61. Heading G2H. A xerographic method comprises forming a persistent conductivity image by first exposing a photosensitive member to a pattern of light and shadow, the photosensitive member having a conductive backing 11 and a photosensitive layer 12 in conductive contact with the backing 11. The photosensitive layers undergoes a persistent change in electrical conductivity upon illumination and contains as photosensitive agent a photolytic organic compound in such amount that the conductivity is preferably altered by at least two times. An electrostatic charge image is then formed by applying an electric field through the photosensitive layer, such image being developed by depositing finely divided particles of electrostatically attractable material in conformity with the image pattern. In one example an aluminium plate was coated with sensitizing lacquer prepared by adding phenol-formaldehyde to toluene, the lacquer being sensitized in the absence of illumination by adding tri-iodo methane. The lacquer coating was allowed to dry and charged. In another example, a dielectric film was prepared from a trichloroethylene solution of a copolymer hydrocarbon resin and coated on to an aluminium backing and the coated plate stored for about 5 months. A sensitizer solution was prepared by dissolving iodoform in xylene and the resulting solution applied to the coated plate. The plate was then exposed to a photographic transparency and charged. The resulting electrostatic latent image was developed by cascade development. In other examples, the following sensitizers were used:- methylene iodide, beta-gammadibromoprpylalcohol, 2, 3 di-bromopropene, methylene chloride, iodoacetic acid, 1, 3, 5-tribromobenzene, bromoacetic acid, chloroacetic acid, methylene, iodide, iodoform, benzamide, bromoform, chloral stabilized with hydroquinone, chloral hydrate, and hexachloroethane. Other sensitizers mentioned are p-bromobenzene-dichlorosulforamide, diiode of tariric acid lead tetraethyl, organic peroxides and hydroperoxides. It is also stated that a solvent for the sensitizer used in applying the photosensitive coating to the plate may react with the sensitizer to assist in dissociation of the sensitizer in the presence of light. Additional solvent may be applied prior to exposure. Examples of solvents are aromatic hydrocarbons, xylene, toluene, carbon tetrachloride, trichloroethylene, alcohol, butyl alcohol. The conductive backing 11 may be a metallic plate, web or cylinder, e.g., of iron, steel, aluminium, brass, copper or zinc or may be conductively coated or impregnated paper, plastic, resins or glass. Specifications 658,699, 679,715 and 696,515 are referred to.