Canon LBP 2460 - B/W Laser Printer Service Manual page 82

CHAPTER 2
1. Electrostatic latent image formation stage
This stage follows two steps to produce an electrostatic latent image on the photosensitive drum.
At the end of the stage, negative charges remain on the unexposed "dark" areas, where the
laser beam struck (exposed) the drum surface.
This image of negative charges on the drum is invisible to the eye, so it is referred to as an
called an "electrostatic latent image."
Step 1 Primary charge
For preparation of the latent image formation, a uniform negative potential is applied to the
photosensitive drum surface. For primary charge, 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 has
been applied to the primary charging roller to keep the potential on the drum's surface uniform.
The DC bias is changed with the developing DC bias.
2 - 36
0
-100
Exposed area
-500
Primary Scanning
charge exposure
(step 1) (step 2)
Figure 2-4-5
Primary charging roller
AC bias
Photosensitive drum
DC bias
Figure 2-4-6
Time (t)
Unexposed
area
Transfer Primary
(step 4) charge
(step 1)