Toshiba e-STUDIO350, Service Manual, Page: 70 / 286

e-STUDIO350/450 COPY PROCESS 3 - 2 November 2003 © TOSHIBA TEC
3
3.2 Details of Copying Process
(1) Photoconductive drum
The photoconductive drum consists of two lay-
ers. The outer layer is a photoconductive layer
made of an organic photoconductive carrier
(OPC), and the inner layer is an aluminum
conductive base in a cylindrical form.
The photoconductor has the following prop-
erty: when it is exposed to light, the electrical
resistance it possesses increases or de-
creases according to the strength of the light.
Example:
· Strong lightn
Resistance is decreased (works as a conductor.)
· Weak lightn
Resistance is increased (works as an insulator.)
[Formation of electrostatic latent image]
In the processes of charging, data reading,
data writing, discharging described later, nega-
tive potential of the areas on the drum corre-
sponding to black areas of the original are
eliminated, while the areas on the drum corre-
sponding to white areas retains the negative
charge.
As this image on the drum formed by the nega-
tive potential is not visible, it is called an “elec-
trostatic latent image.”
(2) Charging
Charging is the process to apply charge
evenly on the drum surface.
The charger wire produces negative corona
discharge is controlled by the grid, allowing
the drum surface to be evenly charged with
the negative potential.
The surface potential on the drum is deter-
mined by the grid potential and is controlled to
a certain value by the grid control circuit.
Photoconductive layer
Base
Structure of the photoconductive drum
(Example of OPC)
Main charger
Drum rotation
Grid control circuit High-voltage
transformer
Fig.3-201
Fig.3-203
0
– 500
– 1000
Time (t)
Black area of original
White area of original
Surface potential (V)
Discharge
process Charging
process
Electric potential of the photoconductive drum
Fig.3-202