Charge retentivity of ZnO-Resin electrophotographic coating, especially under high humidity, is remarkably improved by heating ZnO-Resin mixture.
A resin for ZnO-Resin coating behaves like an organic acid and some functional groups in a resin molecule interact with electron donative sites on ZnO surface. The interaction is promoted by heating the mixture and the charge retentivity is raised.
The sites on ZnO surface liberated through dehydration are occupied by resin or acid to interact with ZnO. It is presumed that the interaction results in a less amount of water adsorbed on ZnO surface or a good dispersion of ZnO particles and, consequently, in better dark decay characteristics of ZnO-Resin electrophotographic coating.

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