Space charge limited discharge from microscopic electrical defects in xerographic photoreceptors

Microscopic electrical defects in the photoreceptor termed charge deficient spots (CDS) can give rise to objectionable print defects in xerographic systems such as laser printers. Experimental measurements of the current voltage characteristics of individual defects exhibit a space charge limited behavior (current proportional to the square of the voltage) consistent with the defects representing injection spots (emitters) from the ground plane of the photoreceptor. Previous theoretical and numerical studies have explored the relationship between the emitter size and the current in various geometries, where the emitter is on the ground electrode while the other electrode is biased at a constant potential. In this paper, the authors explore the problem of practical interest in xerography, i.e. how a photoreceptor is discharged by these microscopic defects. A photoreceptor with uniform surface charge is discharged by space charge limited injection from a finite sized defect at the ground plane. The authors explore the surface charge distribution as function of time.