Patent GB-1165409-A (GB)
Title: Electrophotography
IPC: G03G15/045
Filed: 1966-07-12
Abstract: 1,165,409. Electro-photographic materials. CANON CAMERA CO. Inc. 12 July, 1966 [1 Sept., 1965; 28 Oct., 1965; 1 Dec., 1965; 24 Dec., 1965; 23 Feb., 1966], No. 17413/69. Divided out of 1,165,405. Heading H1K. An electro-photographic member consists of first and second insulating layers between which a photo-conductive layer is located, at least one of the insulating layers being translucent for exposing the member and the member being such that, upon application to the surfaces of the first and second insulating layers of a positive and a negative charge respectively, layers of negative and positive charge are formed respectively in the regions of the interfaces between the photo-conductive layer and the first and second insulating layers and said layers of charge are bound in said regions. It is preferable to expose the member to uniform radiation during the application of the said charges. After this, in use, the member is simultaneously imagewise exposed and reverse charged and then (preferably) is uniformly exposed to increase the contrast. A double corona charger may be used during the process or alternatively the member may be placed on a grounded conductive plate and a single corona charger used. This conductive plate may form part of the member itself. Suitable photo-conductors are cadmium sulphide, cadmium selenide each of which may be doped with copper), zinc oxide (which may be doped with lithium) both amorphous and metallic forms of selenium, titania, selenium telluride (SeTe), lead monoxide, sulphur, anthracene, and carbazole. A binder may be present. Binders useful with cadmium sulphide are a copolymer of vinyl chloride and vinyl acetate, polyvinyl acetate, and acrylic resins. Binders useful with zinc oxide are silicone resins, and mixtures of chlorinated rubber and copolymers of styrene and butadiene. The insulating layers may consist of fluoroethylene resin, polycarbonate resin, polyethylene, cellulose acetate, and polyester resins. The thickness of the photoconductive layer is preferably in the range of 50-200 microns, and the thickness of at least that insulating layer upon which an image is to be developed is preferably 10-50 microns. A member possessing at the same time high resolution and high sensitivity may have a divided photo-conductive layer; that sub-layer nearest the insulating layer on which the final image is to be developed contains finely divided photoconductor and that nearest the conductive layer contains coarse photo-conductive granules. So that the final image may be developed on either side, the photo-conductive layer may have two fine particle sublayers sandwiching a coarse particle sublayer. Specific embodiments of the member are:-(1) a layer of cadmium sulphide doped with copper in an acrylic binder and between polyester films; (2) an insulating layer bearing a resin bound layer of coarse cadmium sulphide particles then a resin bound layer of fine zinc oxide particles and an insulating layer; (3) two polyester layers sandwiching a structure consisting of a coarse particle cadmium sulphide layer surrounded by two fine particle cadmium sulphide layers. The electrographic members of this invention are used in the apparatuses claimed in co-pending Specifications 1,165,408 and 1,165,410.