High speed electrophotographic method

Abstract

Electrophotographic medium which comprises a multilayer structure of materials for imaging radiant energy patterns at high speed comprising a transparent substrate, ohmic layer and coating of photoconductive material, which form a modulating structure for the radiant energy projected through the substrate; a dielectric layer intimately bonded to the surface of the photoconductive coating and a conductive electrode in intimate contact with the dielectric layer. The dielectric layer constitutes the storage medium for the image which is produced in electrostatic charge form and, the medium is capable of retaining latent images for a very substantial length of time. The use of the electrophotographic medium does not require initial charging; hence no means for effecting this are required. Further, the speed of the medium is so high compared with all other media that extremely low energy levels can provide sufficient contrast to produce images. The structure as described is used by connecting a d.c. voltage across the outer electrode and the ohmic layer and projecting the image onto the medium from what would be considered the bottom surface of the substrate. The charge image appears on the dielectric layer. The information represented by the latent charge image is utilized by reading the same out with an electron beam or by toning and/or fixing and transfer.