GB1261445A - Method of electrophotography and photosensitive elements - Google Patents

Abstract

1,261,445. Photo-sensitive element. KATSURAGAWA DENKI K.K. 11 Feb., 1969 [14 Feb., 1968], No. 7230/69. Heading H1K. [Also in Division G2] A photo-sensitive element comprises a transparent highly insulative layer, a photo-conductive layer capable of exhibiting persistent internal polarization and a layer of screen structure, the layers being bonded together in that order. The use of a screen enables halftone images to be reproduced and also the "edge-effect" to be eliminated. The element preferably includes a transparent insulating support with a transparent conductive layer thereon and optionally an insulating layer interposed between the conductive layer and the photo-conductive layer. The screen is interposed between the transparent support and the conductive layer. In an embodiment an element is made from a glass substrate having a photographic emulsion thereon. The emulsion is exposed to a master screen having a line structure and then developed. A layer of Al is evaporated on, followed by an evaporated layer of Se-Te alloy and then a solution of polycarbonate resin. It is possible to use a coloured photographic emulsion to form the screen such that the absorption end of the emulsion is in the sensitive range of the photoconductive layer. Thus the intensity of the screening effect can be emphasized or diminished according to the wavelength of the radiation incident on the screen and hence MoirÚ effects can be eliminated when copying printed matter. The photo-conductive layer may be Se, CdS, SeAs, ZnO or CdSe whilst the transparent conductive layer may be Al, SnO 2 or Cu 2 I 2 . The transparent insulating layer may be glass. Charging of the element may be accomplished by corona discharges on both sides of the elements or removable transparent electrodes either on or a short distance from the element. The element may be cylindrical.