Patent GB-1178238-A (GB)
Title: Improvements in Photocharge Recording
IPC: G03G5/026
Filed: 1966-12-28
Abstract: 1,178,238. Electrophotographic materials. GENERAL ELECTRIC CO. 28 Dec., 1966 [29 Dec., 1965], No. 57969/66. Addition to 1,069,426. Heading H1K. [Also in Division G2] An optical recording method utilizes a material which when in or brought to a plastic or liquid state is selectively deformable under the influence of an internal electric charge pattern generated solely in response to exposure to a pattern of activating radiation. The recording layer may consist solely of a photosensitive substance such as a polymer of N- vinyl-p-phenylazoaniline or of p-phenylazo-4- vinyldiphenylamine, but the examples have a recording layer of polystyrene in which are dissolved or dispersed one or more photosensitive substances (which may be synergystic in action) and possibly a sensitizer, or have a layer of polystyrene containing two or more materials which together are photosensitive. It is suggested that other vinyl resins, acetal resins, acrylic resins, polyester resins, silicone resins, a combination of polystyrene, copoly-(butadiene-styrene) and mterphenyl, or a combination of polydiphenylsiloxane and poly-(2 : 6-dimethyl-1 4-phenylene)ether may replace polystyrene as the carrier, or that the carrier may be normally liquid so that with suitable materials a continuously changing display is possible. Suitable photosensitive materials are halogenated hydrocarbons having at most two hydrogen atoms on the halogen-bearing carbon atom (examples of these occur in the parent Specification), benzoquinones, nitrophenylamines, and arylazoaryl compounds. Carbon tetrabromide and trichloromethyl sulphonyl chloride are not intrinsically photo-sensitive but may be activated by materials such as diphenylamine, triphenylamine, 2: 4: 6 - tris - (dimethylamino - methyl)phenol, dimethylaniline, 1: 1- diphenyl - 2 - picryl - hydrazine, and 3- methylindole. The recording layer may be on a rigid or flexible supporting layer such as one of glass, of aromatic polyester (polyethylene glycol terephthalate) or polyamide, of an acetal polymer, of silicone resin, or of a polycarbonate resin. A conductive layer of sufficient resistivity to allow I<SP>2</SP>R or inductive heating for. development of the deformation image may be provided between the supporting and recording. layers. Such a layer may be of cuprous iodide, iron, chromium, nickel, or indium oxide. Infra-red or dielectric heating may be used for development when no conductive layer is present. A developed image may be read by the use of transmissive or reflective Schlieren systems or by light scattering techniques. In the examples, visible or U.V. light is used for exposure but X-ray or γ-ray exposure is also envisaged. Certain of the recording members show prominent memory effects (particularly when over exposed) and though the deformation image may be removed by heating the layer with a higher energy pulse than that used in development the internal charge image remains and the deformation image may be subsequently redeveloped without further exposure. A further exposure enables superimposition. The internal image (and the deformation image) may be removed by extended heating or by flooding the layer with radiation and then heating it.