Oki OKIPAGE 10e Service Manual page 39

The image drum is coated with an underlayer (UL), a carrier generation layer (CGL), and carrier transfer layer (CTL) on
aluminum base. The organic photo conductor layer (OPC), comprising CTL and CGL, is about 20 mm thick.
The image roller surface is charged to about -750 V by the contact charge of the charge roller.
When the light from the LED head irradiates the image drum surface, the light energy generates positive and negative
carriers in the CGL. The positive carriers are moved to the CTL by an electrical field acting on the image drum. Likewise,
the negative carriers flow into the aluminum layer (ground).
The positive carriers moved to the CTL combine with the negative charges on the image drum surface accumulated by
the contact charge of the charge roller, lowering the potential on the image drum surface. The resultant drop in the
potential of the irradiated portion of the image drum surface forms an electrostatic latent image on it. The irradiated
portion of the image drum surface is kept to about -100 V.