Electrophotographic process capable of image overlay and apparatus therefor

A process for forming an overlay latent image, comprising the steps of:

• (a) charging, with a predetermined polarity, the surface of an insulating layer of a photosensitive member essentially composed of a conductive substrate, a photoconductive layer having a property of rejecting the injection thereinto of charge of a polarity opposite to the predetermined polarity in the dark, and said insulating layer;
• (b) providing said photosensitive member with a first image-forming irradiation actinic to said photoconductive layer substantially simultaneous with or subsequent to said charging, so that the charge of said opposite polarity is substantially injected into the photoconductive layer at a light area of the first image, but the charge is not injected at a dark area of the first image;
• (c) providing the surface of the insulating layer of said photosensitive member, after said irradiation, with a corona discharge having a component of corona ions opposite in polarity to the polarity of charging applied on the insulating surface during said charging step, and further providing a second image-forming irradiation actinic to said photoconductive layer substantially simultaneous with said corona discharge, wherein said first and second images are different;
• and
• (d) providing the entire surface of said photosensitive member with a uniform irradiation actinic to said photoconductive layer of said member, thereby forming an overlay latent image of said first and second images on the surface of said insulating layer.