GB934406A - Image development of electrostatic charge patterns - Google Patents

Abstract

934,406. Developing electrostatic latent images. RANK-XEROX Ltd. (Haloid Co.). July 17, 1959, No. 24683/59. Drawings to Specification. Class 98 (2). To avoid the halo effect which results on developing large areas of charge by cascade methods there is added to the usual developer, comprising a granular carrier and a pigmented toner powder, conductive filamentary elements triboelectrically similar to the granular carrier. The carrier may be of glass, sand, steel beads, or polymethyl methacrylate of 20 to 300 mesh; the toner may be pigmenting or colouring materials, e.g. carbon, encased in an insulating material such as a rosin-modified phenolformaldehyde resin or asphaltum to give particles of not more than 20 Á diameter and the conductive filaments may be of steel, aluminium, copper, brass, nickel, the alloy sold under the Registered Trade Mark " Nichrome," or copper or nickel-coated copper strands which have been exposed to hot sulphur fumes and of length from 1/ 16 to ¥ inch and diameter 1 to 20 mils. The ratio of carrier : toner in the developer may be 20 to 200 : 1 and to 100 parts of this developer mixture there may be added 20 to 100 parts of conductive filaments, a preferred percentage ratio of carrier: toner developer being 49: 2: 49. The Specification mentions considerations affecting the choice of a particular set of ratios and size of conductive filament depending inter alia on the size of the individual charged regions. Reference is made to a developer in which the separate granular carrier is omitted but raking of the developed image occurs if too large a proportion of conductive filament is used or if long filaments are used. Reference has been directed by the Comptroller to Specification 679,715.