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Step 1 Primary charge
As preparation for latent image formation, a uniform negative potential is applied to the
photosensitive drum surface. The printer uses the charging method that directly charges the
drum for the primary charge.
The primary charging roller consists of conductive rubber. In addition to DC bias, AC bias is
applied to the primary charging roller to keep the potential on the drum surface uniform. This DC
bias is changed with the developing DC bias.
This charging method has advantages such as lower applied voltage, less ozone generation,
etc., compared with the corona charge system.
Step 2 Scanning exposure
Figure 2.10
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Laser beam
Unexposed area
Exposed area
When the laser beam scans the drum surface, it causes the charge to be neutralized in the areas
struck by the beam. Areas on the drum with no charge form the electrostatic latent image.
DC bias
AC bias
Photosensitive drum
Primary charging roller
Figure 2.9