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COPY PROCESS
3 - 3
3.3 Details of Copying Process
1) Photoconductive drum
The photoconductive drum consists of two layers.
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 photoconductive carrier has a special property: when it is exposed to light, the electrical resis-
tance it possesses increases or decreases with the strength of the light.
Example:
- Strong incident light
→
Decreases resistance (works as a conductor.)
- Weak incident light
→
Increases resistance (works as an insulator.)
Fig. 3-4
[Formation of electrostatic latent images]
In the processes of charging, data reading, data writing, and discharging described below, the areas
on the drum corresponding to colored areas on the original are deprived of negative charge, while
the areas on the drum corresponding to white areas retain the negative charge. Thus it forms a neg-
ative charge image on the drum surface.
As this negative charge image on the drum is not visible to the human eye, it is called an “electro-
static latent image.”
Fig. 3-5
Photoconductive layer
Base
Structure of the photoconductive drum
(Example of OPC)
0
Time (t)
Colored area of original
White area of original
Surface potential
( V
)
Discharge
process Charging
process
Electric potential of the photoconductive drum
-500
-1000