User manual

95.08.23.11.29
Color LaserWriter 12/600 PS Basics & Theory 1–49
Step 1:
Primary
Charging
As a preliminary step in forming the latent image, the surface of the
photosensitive drum is uniformly charged with negative potential. The
primary charging is done by directly imparting charges onto the photo-
sensitive drum.
In order to keep uniform the surface potential charged on the surface of
the photosensitive drum, AC bias is superimposed on the primary
charging roller in addition to the DC bias.
The AC bias (current value) varies according to the values sensed for
temperature and humidity to prevent toner from adhering to the
charging roller.
Step 2:
Scanning
Exposure
When the laser beam is scanned across the photosensitive drum surface,
the charge in the irradiated area is neutralized and becomes an electro-
static latent image. This is known as “write-black” laser imaging.
Primary Charging Roller
AC
Bias
DC
Bias
Photosensitive Drum
Laser beam
Irradiated
Area
Nonirradiated
Area