GB952609A - Improved image development - Google Patents

Abstract

952,609. Printing processes. RANK-XEROX Ltd. May 3, 1960 [May 7, 1959], No. 15524/60. Heading B6C. A method of producing a powder image on an insulating transfer surface comprises forming a substantially uniform layer of charged conductive particles on the surface of a layer of photoconductive material supported on a conductive base, exposing the photoconductive layer to a pattern of activating energy to selectively vary the conductivity through the photoconductive layer, and placing the transfer surface in contact with the powder layer with an electrostatic bias applied behind and across the transfer surface to effect selective transfer from the powder layer to form an image on the transfer surface. The photoconductive layer may be sprayed with powder particles less than 20 microns in diameter in aerosol form. Charging may be by a corona discharge electrode mounted on a sleeve which traverses a screw drive shaft. Exposure may be to light through a transparent conductive backing, or to X-rays or other radiation through a backing which need not be transparent, or through the particle layer. Image transfer may take place during or after exposure, by bringing against the particle layer a transfer member comprising an insulating layer with a charged conductive backing, or by rolling a transfer sheet against the particle layer by means of a charged or grounded roller. The transfer member may be polyethylene, or polyethylene-coated paper. In one form, the photoconductive layer 131 is supported on half the periphery of a rotatable drum 130. Powder is applied to the layer 131 by a brush 62 controlled by a cam to contact the drum when the layer 131 is passing. The powder layer is charged at a station 54. An original 142 is fed against the drum 130, where the layer 131 is not present, by a cam-controlled roller 136, and light from fluorescent tubes 133 is reflected from the original on to the back of the layer 131, which at the same time as the exposure, passes a transfer station 144, where a transfer sheet or web 147 is fed against the layer 131 by a camcontrolled, conductive and electrostatically biased roller 145 having a conductive layer 146 of sponge rubber. The image is fixed at a station 64. The remaining charge is removed by a fluorescent tube 58. By controlling the potential applied across the transfer zone, either the powder on that part of the photoconductive layer which has been exposed to radiation, or the powder on the unexposed part, can be transferred.