Patent GB-1086197-A (GB)
Title: Electroviscous recording
IPC: G03G17/00
Filed: 1964-09-21
Abstract: 1,086,197. Printing processes. XEROX CORPORATION. Sept. 21, 1964 [Oct. 3, 1963], No. 38402/64. Heading B6C. [Also in Division G2] Particulate or colloidal liquids which gel or become grease-like in the presence of an electrostatic field are used for producing trace records or developing electrostatic or latent conductivity images, on a recording medium. A trace may be laid down on a moving paper web (21) (Fig. 2, not shown) by a recording head having two electrodes (28, 29) adapted to apply an electric field across the orifice between them. An electroviscous liquid flows through the orifice until a signal from a photoconductive cell (32) acting through a transducer (31) causes the electric field to be applied to the electrodes to interrupt the flow. In an electrophotographic application, an orifice in the form of a slit in a transparent block has one jaw provided with a transparent conductive layer (53) covered with a photoconductive insulating layer (44) of vitreous selenium (Fig. 6, not shown). An optical fibre path (51) conducts light from an original (57) to the photoconductive layer (44) and controls the emission of liquid from the slit so that a moving original (57) is reproduced on a copy sheet (21) moving at the same speed. Intermittent contact between the liquid and copy sheet is produced by a loudspeaker (46) or other means (Figs. 7 and 8, not shown). In Fig. 15, a rubber doctor blade 90 supports electroviscous liquid 26 on a conductive drum 96 having a resistive outer layer. Successive line images of an original are formed by projection on to photoconductive insulating strip 91, which is connected by a fine straight copper wire 93 to a point near the surface of drum 96. In the presence of a light image area, the corresponding part of strip 91 becomes conductive and the corresponding points near the drum 96 apply the electrical potential of the battery to thicken the liquid 26 at these points. The thickened liquid adheres to the drum and is carried past the lip of blade 90. The image thus formed on the drum is transferred to paper strip 21. By employing a separate transducer for each copper wire 93 the apparatus may be used as a facsimile receiver. In other applications, an electrostatic image is formed by projection on a photoconductive insulating surface and developed by a liquid applied by a doctor blade (Fig. 9, not shown) or by percolation through the shell of a porous ceramic or fritted glass roller (Fig. 12, not shown). Latent conductivity images may, alternatively, be developed under the influence of electrodes applying an electrostatic field which is controlled by the latent conductivity The field and liquid may be applied at the time of exposure (Fig. 10, not shown) or afterwards (Fig. 11, not shown). The liquid thickened by the field at conductive areas is retained on the photoconductive surface and transferred before re-exposure, to a final support. Electroviscous liquids are prepared by ball milling silica gel or acetamine Rubine B in heavy paraffin oil with a trace of water to form an adsorbed layer on the particles. The liquids may contain micron sized particles of pigments such as carbon black. Solutions of metal soaps in non-polar hydrocarbons, substances in the liquid crystalline state in liquid solutions, micelle forming solutions of paraffin sulphates and elongated molecules containing one or more non-polar groups are referred to.