GB1036738A - Improvements in interference film development - Google Patents

Abstract

1,036,738. Electrophotographic processes. RANK XEROX Ltd. May 1, 1963 [May 8,1962], No. 17152/63. Heading G2H. Plate 10 Fig 3 having an insulating photoconductive layer 13 e.g. of sulphur, anthracene, selenium, or zinc oxide in a binder on a support 11 is thinly coated with solution 15, Fig. 1 (not shown) by suspending in a tank 14. The solution may be a dilute solution of either a solid material or a non- volatile liquid dissolved in a volatile solvent. Examples of the solution are sucrose acetate isobutyrate, Piccolastic, Flexal and Narcoil. The thickness of the coating is controlled by varying the rate of withdrawal of the plate. The preferred coating thickness is in the range 80 to 125 millimicrons which exhibit interference between the light from its two reflecting surfaces for rendering images in the film visible. The support 11 is of metal, metal foil, metallized paper or plastic. Plate 10 is charged by passage of a corona 18, Fig. 3, connected to a high voltage supply and then exposed by projecting a light pattern on to the plate from a photographic enlarger 20, Fig. 4 (not shown) The film 13 may be softened by heat Fig 5 (not shown) or vapour Fig 6 (not shown). Due to differential electrostatic forces acting on the surface of the film after charging and exposure there are minute variations in the thickness of film 13. The images thus produced may be projected on it a screen 27, Fig. 7 (not shown) using a monochromatic light source 24, e.g. a mercury or sodium vapour lamp. The plate may be exposed to a screen pattern. When the film 13 comprises silicone resin, the application of a positive charge yields a positive image, Fig 8A (not shown), while a negative charge yields a negative image, Fig. 8B (not shown).