SUMMARY In electrophotography, corona charges on photoconductive layers are preferable to show slow decay in the dark and quick decay by the exposure of image light. It is important, therefore, to clarify the theory and mechanism of dark and light decay for the improvement, of electrophotographic paper and equipment.
In this paper, some theoretical analyses and experimental verifications are given on the mechanism of dark decay of corona charges on ZnO-resin type photoconductive layers. The surface charged ZnO-resin layer is composed of electrode capacitance charge Qe and bulk capacitance Charge Qb. The dark decay curve is consisted of three ranges; avalanche-, electrode capacitance- and space charge capacitance-discharging ranges.
At the beginning of dark decay, the surface charge Qe is discharged by the leakage of avalance current. A linear relation between 1/(
V-
Vn) and decay time
t is expected theoretically in this range, where
Vn is the avalanche breakdown potential of the layer. After the avalanche range, the surface charge Qe is discharged by the ohmic leakage current. A linear relation between log(
V-
Vm)and decay time
t is expected in this range, where
Vm is the value of surface potential at the end of this range. In the final range, the sureface charge Qb is discharged also by the ohmic leakage current. A linear relation between log
V and decay time
t is expected in this range. The above three relations between
V and
t were proved to hold in experimental results.
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