Canon LBP-800 Service Manual page 99

Step 1: Primary charging
For preparation of latent image formation, a uniform negative potential is applied to the photo-
sensitive drum surface.
charges the photosensitive drum.
The primary charging roller consists of semiconductive rubber. In addition to DC bias, AC
bias is applied to the primary charging roller to keep the potential on the drum surface uniform.
The DC bias changes with the developing DC bias that changes according to the IMAGE DEN-
SITY DATA signal from the interface controller.
This direct charging method has advantages such as the lower applied voltage and almost no
ozone generation over the conventional corona charging method.
Step 2: Scanning exposure
When the laser beam scans surface of the photosensitive drum, charges on the light area are
neutralized to form an electrostatic latent image.
AC bias
Photosensitive drum
DC bias
Figure 2-4-6
This printer performs primary charge by the method that directly
Laser beam
Dark area Light area
Figure 2-4-7
Primary charging
roller
CHAPTER 2
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