Canon LBP-1210 Service Manual page 124

CHAPTER 2
Step 1: Primary charging
In preparation for the latent image formation, a uniform negative potential is applied to the pho-
tosensitive drum surface. For primary charging, the printer uses the charging method which
directly charges the drum.
The primary charging roller is made of conductive rubber. In addition to DC bias, AC bias is
also applied to the primary charging roller to keep the potential on the drum surface uniform.
The DC bias changes along with the developing DC bias according to the image density infor-
mation signal sent from the interface controller.
As advantages of this method, it requires lower applying voltage and emits trance of ozone gas
as compared with the corona charging method.
Step 2: Laser beam exposure
The laser beams scan the drum surface. This causes the charges in areas struck by the laser
beams to be neutralized. These areas on the drum surface form on electrostatic latent image.
2. Developing block
Toner particles are placed onto the electrostatic latent image on the drum surface to form a vis-
ible image. This printer uses the toner projection development method with a single-component
toner.
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AC bias
DC bias
Figure 2-5-6
Laser beam
Unexposed area
Figure 2-5-7
Primary chargingroller
Photosensitive drum
Exposed area