OKIDATA DOC-IT3000, Service Manual

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Service Guide DOC-IT3000/4000
Chapter 2 Principles of Operation
Exposure
Light emitted from the LED head is radiated to the image drum surface charged with negative
charges. The surface potential falls on the irradiated part of the image drum surface, thereby
forming a latent image associated with the image signal.
The image drum is coated with an underlayer (UL), a carrier generation layer (CGL), and a carrier
transfer layer (CTL) on the aluminum base. The image drum layer, comprising a CTL and a CGL,
is about 20um thick.
The corona discharge around the charge wire charges the image drum surface to about -700V.
When light from the LED is radiated to the image drum surface, the light energy generates positive
and negative carriers in the CGL, with the positive carrier being moved to the CTL by means of an
electrical field acting on the image drum.
Likewise, the negative carrier flows into the aluminum layer (ground).
The positive carrier moved to the CTL combines with the negative charges on the image drum
surface accumulated by corona discharge, lowering the potential on the image drum surface. The