Patent ES-290429-A1 (ES)
Title: Electrostatic printing method and element
IPC: G03G5/147
Filed: 1963-07-30
Abstract: A recording member comprises a resinous photoconductive insulating heat-deformable layer and adherent to this layer a film of up to 500 thick constituted by a material insoluble in the heat-deformable material. In operation an electrostatic charge image is placed on the material which is then heated to cause it to deform and break-up the film in the areas of high change density which then show a frosted-glass appearance. The image may be viewed by transmitted light or slanting illumination. The material may be uniformly corona-charged and provided with a charge image electrophotographically or it may be charged using a corona source and a stencil which prevents charge from being deposited in selected areas. It may also be charged by direct charge deposition from selectively energized pin electrodes, or by electron beam scanning. Heat deformable materials identified are polystyrene, chlorinated paraffins, polyvinyl chloride, copolymers of vinyl chloride, copolymers of styrene with butadiene, hydrocarbon resins, acrylate polymers and copolymers, epoxy resins, and thermoplastic hydrocarbon terpene resins. Combinations of these materials may be used and materials such as plasticizers may be added. Polystyrene is itself photoconductive but its sensitivity is enhanced and the photoconductivity of the other resins enhanced or assured by the inclusion of dye intermediates which to some extent react with the resin. Many intermediates are listed. They are all di- or tri-phenyl methanes or derivatives of Michler's ketone. The thin surface film may be of polyvinyl alcohol, gelatin, or of other water soluble resinous materials. Highly cross-linked polymers are also suitable, for example a layer of cross-linked polystyrene may be applied by a vacuum vapour deposition process using a glow discharge. Very thin metal or metal oxide films are also suitable, for example those of gold or of aluminium oxide having an average thickness of about 0.4 . The recording materials preferably have a supporting layer under the heat-deformable layer. Suitable supports are metal plates, conductive glass, glass slides coated with conductive tin, oxide, high melting films coated with copper or aluminium, and high-melting conductive plastics. A specific complete material consists of superimposed polystyrene and polyvinyl alcohol layers on a tin oxide coated lantern slide. After a charge image has been placed on the material it may be developed by heating for a few seconds at e.g. 140-215 C. If an image is developed on such a material having a polystyrene layer of less than about 11Á an interference pattern is formed. With a layer about 1 Á thick the deformations produced by development scatter light predominantly blue in colour while slightly thicker layers result in scattering of green and red light. Viewing of the developed slides may be carried out using an ordinary slide projection or a schlieren projection system. Several other specific complete materials having similar supports are described. Another specific material has a heat-deformable layer of a mixture of polystyrene, a chlorinated paraffin, and a dye intermediate, the layer being carried by a slide first coated with conductive tin oxide and then with nickel or gold for use as a lantern slide. Silver paint electrodes are applied to the edges of the nickel or gold layer. The film is a very thin layer of gold or aluminium oxide. After providing a uniform corona charge and exposing with a tungsten source the image is developed with heat produced by passing current through the nickel film.