Patent GB-1026704-A (GB)
Title: Improvements in xerographic development
IPC: G03G15/08
Filed: 1963-09-20
Abstract: 1,026,704. Electro photographic processes. RANK XEROX Ltd. Sept. 20, 1963 [Oct. 1,1962], No. 37067/63. Heading G2H. A drum 10, Fig. 3, is driven in a counter clockwise direction by a motor Ml. The drum has a photoconductive layer 8 on a conductive backing 9. A corona discharge device 11 applies a sensitizing charge to the layer 8 before a projector 12 projects a light image of an original on to the charged surface. A latent electrostatic image thus formed on the layer 8 is developed at developing station 14. The developing apparatus comprises an endless donor web 37. The web 37 is continuously driven around rollers 38, 39,40, and 41 by a motor M2. The web is uniformly charged by a corona discharge device 42 and then passes upwardly into loading mechanism 43. A two component developer 44 comprising toner 46 and carrier is cascaded over the web 37. Toner is added to replace that used in controlled quantities by a gate 48 from a dispenser 47. A lamp LMP-1 at discharge station 15 discharges residual charges in non-image areas. The developed image on the layer 8 is transferred to a web 20 at station 16 by a corona generating device 21, the image being fused by apparatus 27. The web 20 is rewound on a driven roll 25 or cut into severed lengths. The drum passes through a cleaning station 26 having a brush 30 driven by a motor M4 and is then illuminated by a lamp LMP-2 which removes any remaining electro static charges. The donor web 37, Fig. 5, has a conductive layer 54 a layer 55 of poorly insulating, light insensitive material, and a pattern of posts 56 of electrically insulating light insensitive material. The posts 56 remain electro statically charged after passing charging device 42 at least until passing through mechanism 43. The toner 44 becomes tribo electrically charged to the same polarity as the posts 56 and is thereby repelled by the posts into the recessed spaces between the posts. In one example, the donor web is formed by coating an aluminium plate with an alkyl resin film, drying the layer and coating with photo resist. The plate is then exposed to a screen image using ultra-violet light and the unexposed photoresist removed with developer. In another example, a contact printing paper is coated with photo resist and dried. The coated paper is then exposed to a screen image using ultra-violet light and the photo resist was removed with developer. In another example, the donor is formed by an aluminium base with an epoxy coating thinned with Cellosolve (Trade Mark). A screen pattern is formed with photo resist as in the previous examples or by applying a thin sheet of brass in contact with the expoxy coating before polymerization. The brass was then photo chemically etched and polystyrene used to fill the holes. Ferric chloride is then applied to remove the brass. In another embodiment of donor, an insulating coating 60, Fig 6 (not shown) applied to a conductive layer 61 and a metal screen 62 placed on coating 60 either by applying a coating of copper and selectively etching to give a screen pattern or by placing a metallic screen on the coating 60 and flash evaporating a layer of chromium and then copper. In another embodiment of donor, an insulating film 70 of polyethylene tetraphthalate or polystyrene, Fig.7 (Not shown) is in contact with a screen pattern 71 overlying a conductive support 72 of aluminium. After electrostatic charging, the film areas in contact with the screen repels like-charged toner particles. In another embodiment, a conductive base 80, Fig. 8 (not shown) has an insulating layer 81, a screen 82, and an insulating layer 84. A potential is applied by battery 85 to the screen 82 of opposite polarity to a sensitizing charge applied to layer 84. Toner particles of polarity opposite to the polarity of sensitizing charge deposit on areas not overlying the screen 82. The donor web may be loaded by powder cloud, brush, liquid immersion besides the cascade method described with reference to Fig 3. Donor webs for use with different colour developers may be arranged for sequential development in registration.