Performance Evaluation of Rollers for Charging, Development and Transfer in Electrophotography

The performance of rollers for charging, development, and transfer processes in electrophotography depends critically on dielectric relaxation of the semi-insulating dielectric layers in these devices. In these layers, the progress of dielectric relaxation is controlled by the charge injection from bias and the charge mobility, rather than by the bulk resistance. Based on the physical principle of the processes, the shortcomings of the traditional roller characterizations by resistance measurements are explained, and a novel characterization technique that simulates more closely the actual processes is introduced. This “Electrostatic Charge-Decay” (ECD) technique is based on open-circuit measurements of dielectric relaxation, and capable of examining the transient states and spatial variations efficiently and non-destructively.