Corona-Controlled Electrostatic Imaging Processes

Two electrostatic imaging processes, utilizing simultaneous corona charging and image exposure, are described. These processes have been analyzed using a mathematical model based on an equivalent circuit. It can be shown that the photoresponse is controlled by the characteristics of the corona charging device as well as the sensitivity of the photoconductor. However, the ultimate response of the photosensitive element is entirely a function of the corona device. The limiting electrostatic contrast was found to depend primarily upon the corona characteristics and the initial charge on the dielectric surface in the case of dc corona charging. For the ac corona case, the limiting contrast depends primarily upon the initial charge level.