GB893011A - Improvements in and relating to photographic and like reproduction methods and apparatus and materials for carrying such methods into effect - Google Patents

Abstract

893,011. Printing processes. OZALID CO. Ltd., and FERMINGER, A. R. Feb. 24, 1959 [Feb. 27, 1958], No. 6343/58. Class 100(2) [Also in Group XX] In apparatus for electrophotographic copying, the original is placed against an electrostatically charged transparent layer of photo-conductive insulating material, and illuminated from behind the said layer, so that the light passes through the layer first and is then reflected back therethrough from the original so as to form an electrostatic latent image of the original therein, the light then being reflected back again into the layer at least once more; the latent image is then rendered visible by applying powder to the layer, or transferred therefrom on to a transfer surface and fixed on the latter. In the form shown, a glass drum 10 has a transparent aluminium coating 11, on which is a further transparent coating 12 of a photoconductive insulating material such as zinc oxide disposed in a resinous binder; this last may be protected by a hard lacquer coating. The drum 10 can alternatively be of conductive glass or synthetic resin having a partially reflecting surface. The original to be copied is passed against a portion of the photo-conductive surface by a roller feed 15, and illuminated by a light source 13 within the drum, the light being constrained to fall only on the sector required by a shield 14. The surface of the drum is charged by a corona discharge device 19, and after the latent electrostatic image is formed, it is passed through a developing unit 20. The developed image is transferred on to a band of receiving paper 24 by means of a second corona discharge device 28, and fixed by a fusing unit 29. Residual powder on surface 12 is removed by a cleaning device 30. Fig. 2 (not shown) is a simpler non-rotating form of the apparatus.