GB1070748A - Electrophotographic developer - Google Patents

Abstract

1,070,748. Xerography; development processes. COMMONWEALTH OF AUSTRALIA, DEPARTMENT OF SUPPLY. July 7, 1964 [July 11, 1963], No.28028/64. Heading G2H. A developer for use in chargeless developing of xerographic surfaces containing an electrical image, comprises an insulating carrier liquid in which a pigment is suspended, a dispersing agent for the pigment to create a finer suspension, and also comprises a further dispersion to said carrier liquid of a medium of charge polarity opposite to that of the said pigment, this medium having less electric charge than the pigment whereby the pigment develops a maximum image density and the second developer, as well as driving down more pigment, forms a background shield during development to lessen contamination of the background by pigment particles. In this xerographic system no corona charging is used, but the zinc oxide or other photo-conductive surface is darkrested for some days and acquires an attraction for positively charged toner particles. Positively charged areas are formed where light falls and the toner is there repelled; direct image reproduction is therefore possible. The developer components are:- (a) Carrier liquid; an insulating hydrocarbon. (b) Pigment of opposite polarity to the area to be developed; Carbon Blacks, Peerless Blacks, Monolite Trade Mark Blacks (ICI), Irgalit Fast Blue (Geigy). (c) Control coating to make the pigment of (b) have an opposite charge to the area being developed or increase its charge; vegetable oils may be linseed oil, Sunflower seed oil, Tung oil, etc.; mineral oils may be B. P. "Viscostatic" (Trade Mark) Motor oil, polybutyl methacrylate, Bitumen. (d) Dispersing agent; long oil alkyd resins such as Super Beckosol Trade Mark +1352- (Reickold Corp.), Rhodene resin, +PC2/70 (Polymer Corp). (e) Dispersion of opposite charge polarity to the combination of (b) and (c), or a control agent at opposite polarity effect to the one of (c) placed on the pigment; for use when (b) plus (c) is negative the mineral oil agents of (c), alcohols, low concentrations of strongly positive pigments, bitumen; for use when (b) plus (c) is positive, the vegetable oils of (c), low concentration of any long oil alkyd of (d) with negative pigments.