Canography (Canon NP process) in electrophotography

A new system of electrophotography--the Canon NP process--is discussed. A photosensitive member comprising an insulating layer, a photoconductive layer, and a conductive layer is used in this process. The procedure for the formation of latent images consists of three steps: 1) primary charging, 2) image exposure with ac corona discharging, and 3) blanket exposure. The principle of image formation can be explained by a simple RC equivalent circuit representing the insulating layer, the photoconductive layer, and the air gap, etc. The influence of the thickness of the insulating layer on image quality can be represented by the response function of the NP plate. Sharpness and resolution calculated from the response function agree with the measured values. The NP plate has higher sensitivity than the conventional plate. This is explained by the fact that the electrostatic contrast required for development is obtained by a smaller amount of charge and that photoconductive layers of low resistance can be used. Since the NP process utilizes the injecting and rectifying properties of the photoreceptor, CdS or Se-Te alloys that are well known as one carrier photoreceptors can be used.