Light emitted by the LED head irradiates the image drum surface with a negative charge. The surface potential of the irradiated portion of the image drum drops,

forming an electrostatic latent image associated with the image signal.

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 a CTL and a CGL, is about 20 m m thick.

The image drum 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.

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