OKIDATA OF1050, Service Manual

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Page: 134
Service Guide OF1050/2350/2450
Chapter 3 Board Description/Printer Operation
3.16.03 Exposure
Light emitted from the LED head irradiates the EP (image) drum surface with negative charges. The
surface potential of the irradiated part of the EP drum drops, thereby forming an electrostatic latent image
associated with the image signal.
The EP (image) drum is coated with an underlayer (UL), a carrier generation layer (CGL), and carrier
transfer layer (CTL) on the aluminum base. The organic photo conductor layer (OPC), comprising a CTL
and a CGL, is about 20 mm thick.
The EP (image) drum surface is charged to about -750 V by the contact charge of the charge roller.
When light from the LED head irradiates the EP (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 EP (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 EP (image) drum
surface accumulated by the contact charge of the charge roller, lowering the potential on the EP (image)
drum surface. The resultant drop in the potential of the irradiated part of the EP (image) drum surface
forms an electrostatic latent image on it. The irradiated part of the EP (image) drum surface is kept at
about -100 V.