Electrophotographic process using layered element containing p-type or n-type materials, with multiple charging steps and blanket irradiation

Claim 1

An electrophotographic process for forming a latent image comprising the steps of applying a primary charge to an electrophotographic photosensitive member comprising an electrically conductive base layer, an intermediate layer superposed on said conductive base layer, a layer of photoconductive material superposed on and having a thickness greater than said intermediate layer and an insulating layer superposed on said photoconductive layer, said primary charging step being performed by applying a negative charge to said insulating layer when said photoconductive layer comprises a p-type material and by applying a positive charge to said insulating layer when said photoconductive layer comprises an n-type material so that an electrical charge from said base is bound at the interface of said photoconductive layer and said insulating layer; subjecting said photosensitive member to corona charging of a polarity opposite to that of the primary charge or to AC discharging contemporaneously with imagewise exposure; and then subjecting said photosensitive member to blanket irradiation to increase the electrostatic contrast and form an electrostatic latent image of high contrast on said insulating layer; wherein said intermediate layer has a greater p-type concentration than said photoconductive layer when said photoconductive layer comprises an p-type material, and a greater n-type concentration than said photoconductive layer when said photoconductive layer comprises an n-type material, to facilitate the injection of an electric charge from said base to said photoconductive layer.