Abstract
Aqueous coating method was applied for preparing layered photoreceptors. Electrophotographic measurements of a layered photoreceptor, consisting of a charge generation layer (CGL) of ε-type copper phthalocyanine (ε-CuPc) and a hole transport layer of hydrazone derivative, showed a fast dark decay rate, suggesting increased injection of holes from the aluminum substrate into the CGL. Measurements of work function(φ) of substrate aluminum revealed that deposition of CGL was accompanied by an increase in φ of the substrate during the processes and that the enhanced φ value was nearly equal to the ionization potential of ε-CuPc (5.16 eV). This resulted in the increase in dark decay rate.
An approach for retarding dark decay rate was made by forming carrier-injection barriers between the substrate and CGL. Use of some improved photoreceptors led to lowering of dark decay rate without decrease in photo-sensitivity. One of them was an electron-transport type receptor in which an sufficient injection barrier was developed between ε-CuPc and Al. Another was a hole-transport type receptor that employed a pelylene pigment that possesses a high ionization potential.
