Patent GB-1043981-A (GB)
Title: Electrophotographic processes
IPC: H04N5/82
Filed: 1963-05-03
Abstract: 1,043,981. Electrophotographic processes. RANK XEROX Ltd. May 3, 1963 [May 8,1962(3)], No. 17562/63. Heading G2H. An electrophotographic process utilizes a layer which is deformable by electrostatic force in the pattern of the image to be reproduced. In one embodiment, a xerographic plate 30, Fig. 1, has a support member 31 and a photoconductive coating 32. The member 31 is preferably electrically conductive, e.g. of brass, aluminium, metallized paper, or conductively coated glass. The plate 30 is electrostatically charged by movement relative to corona charging device 33 and then exposed to a light pattern, e.g. by a photographic enlarger 35, Fig. 2 (not shown). The coating 32, Fig. 1, is then softened, e.g. by a heating element 36, Fig. 3 (not shown) to enable it to flow in response to the electrostatic forces to correspond with the light pattern. The coating 32 is then rehardened e.g. by removing the source of heat or by solvent vapour. The resulting pattern may be viewed by reflected or transmitted light. The plate 30 may be re-used by again softening coating 32 to erase the image. In a modification, a xerographic plate comprises a conductive layer 37 Fig. 5 (not shown) coated with a photoconductive insulating layer 38 over which is an interlayer 39 coated with thermoplastic. Layer 37 may be brass, aluminium, conductive paper or plastic conductively coated with tin oxide, copper iodide or similarly coated glass. The photoconductive layer 38 may be anthracene, sulphur or zinc oxide. Interlayer 39 may be polyvinyl chloride, polyvinyl acetate or polyethylene terephthalate. The layer 40 is of material sufficiently insulating to support an electrostatic charge and capable of maintaining such a charge while softened by heat or vapour to permit deformation by such electrostatic charge. The layer 40 may be "Staybelite" "Piciolastic" or Nievillac. The layer 40 is charged by corona discharge 42 and then layer 39 is exposed by projection of an image 45 through an optical system 47 above Fig. 7 (not shown) or below Fig. 6 (not shown) the plate. If desired, the charging step may be repeated, after exposure, Fig. 8 (not shown) such that the charge density is increased only in the illuminated areas. The plate may be simultaneously exposed and charged Fig. 9 (not shown). The plate can be placed in a chamber 52 Fig. 10 (not shown) containing solvent vapour e.g. ethylene dichloride, carbon tetrachloride, hexane or trichloroethylene. Alternatively, the thermoplastic layer may be softened by a heat source e.g. an infra-red lamp 53 Fig. 11 (not shown) or resistance element 54 Fig. 12 (not shown). The The layer 40 may be softened during exposure Fig. 13 (not shown). In another embodiment a deformable coloured coating 59, Fig. 14, and a transparent layer are applied by dip coating and a viewable image is produced by depression of the coating 59. In this case, heating elements 60 are associated with charging device 42, and a light pattern is projected by optical system 47 onto photoconductive layer 38. The coloured coating may be dispensed with by wiping a pigmented material over the surface of the deformed plastic material, e.g. printers ink or a graphite emulsion. A photoconductive web 62, Fig. 15 (not shown), on a conductive backing is carried by rotatable cylinders 63. A thermoplastic layer 72 is coated on a heat resistant support 73. The layer 72 is fed past an erasing station 64 into contact with photoconductive web 62, the adjacent surface of the web 62 being precharged at electrostatic charging station 65. An exposure station 67 projects a pattern of light on to the web 62 while a second charging station 68 increases the variations in charge density of the photoconductive layer. A heat or vapour development station 69 produces a deformation image pattern in the thermoplastic layer 73. A bath 77 applies a liquid film, e.g. silicone oil to the web 62.