Predicting Print Quality in Electrophotography Using Electrostatic Charge Decay Measurements on Development Rollers

The quality of the printed output from an electrophotographic printer or copier is determined by the performance of, and the interactions among, the major components in the system: namely, the photoreceptor, the charging subsystem, the exposure subsystem, and the development subsystem. The existence of the many variables which affect component interactions make prediction of print quality quite difficult. However, if we confine our attention to any one of the subsystems, or a single component of a subsystem, we can correlate print quality with the characteristics of the component(s) involved. In this paper, the electrostatic charge decay (ECD) technique is used to evaluate the development roller (or mag roller) employed in popular low speed electrophotographic printers and copiers. This technique measures the conductivity of the surface coating on the development roller non-contactly and nondestructively. Using these measurements, the propensity for ghosting and drop-off in print density can be predicted. The principle underlying this technique and the design considerations for a practical measurement system suitable for product development and manufacturing quality control will be discussed.