GB935621A - Method of producing and developing electrostatic latent images - Google Patents

Abstract

935,621. Electrophotographic processes and apparatus. COMMONWEALTH OF AUSTRALIA. March 4, 1960 [March 5, 1959], No. 7783/60. Classes 98 (1) and 98 (2). A method of producing and developing electrostatic latent images comprises subjecting a solid surface, which has previously been stored in a cool dark place, without the use of an applied charge, to a light or heat pattern and developing with a developer comprising an electrically insulating liquid having pigment particles suspended therein of a size below half a micron. The solid surface may comprise a photoconductive material such as zinc oxide in a suitable insulating base coated, for example, on paper, or may comprise an ordinary metal surface such as lead foil, or tin or aluminium foil or plates. The developer comprises, for example, Kromal Blue, Monastral Blue, or Organic Red, in an insulating liquid such as toluene, an aliphatic hydrocarbon solvent or lighting kerosine. The pigment may be ground in a ball mill to obtain the desired small grain size. Triggered developers may be used as disclosed in British Specification 879,464 and control and fixing agents may be added to the developer as disclosed in British Specification 835,044. No fixing agent is required, however, with a rough zinc oxide surface. Apparatus for carrying out the above method, as shown, comprises a table 1, a resilient pad 2, a sheet 3 (having said solid surface), a transparency 4, a glass plate 5 which is doubly hinged at 7 and 9 to the table 1, a support column 13 for a source of intense radiation-e.g. mercury lamps, or an electric radiator-and a dish 15 containing the fine grain developer 16.