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.”
Figure 2-4-5
Step 1 Primary charge
Figure 2-4-6
For preparation of the latent image formation, a uniform negative potential is applied to the pho-
tosensitive 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 uni-
form. The DC bias is changed with the developing DC bias.
2 - 36CHAPTER 2
0
-100
-500
Time(t)
Surfacepotential (V)
Exposedarea
Scanning
exposure
(step2)
Transfer
(step4)
Primary
charge
(step1)
Primary
charge
(step1)
Unexposed
area
Photosensitivedr um
Primarycharging roller
ACbias
DCbias