Toner is attracted over the shadowed area because of the
developing bias.
Step-4: Transfer
The visible image on the drum surface is transferred onto the
print paper by applying a positive charge from the transfer
corona to the backside of the print paper.
Step-5: Separation
Since the print paper is charged positively by the transfer
corona, it is discharged by the separation corona. The separa-
tion corona is connected to ground.
Step-6: Cleaning
Toner remaining on the drum is removed and collected by the
cleaning blade. It is transported to the waste toner collecting
section in the cleaning unit by the waste toner transport roller.
Step-7: Optical discharge (Semiconductor laser)
Before the drum rotation is stopped, the semiconductor laser is
radiated onto the drum to reduce the electrical resistance in the
OPC layer and elimate residual charge, providing a uniform
state to the drum surface for the next page to be printed.
When the electrical resistance is reduced, positive charges on
the aluminum layer are moved and neutralized with negative
charges on the OPC layer.
Charge by the Scorotron charger
Function
The Scorotron charger functions to maintain the surface poten-
tial of the drum even at all times which. It is used to control the
surface potential regardless of the charge characteristics of the
photoconductor.
Basic function
A screen grid is placed between the saw tooth and the
photoconductor. A stable voltage is added to the screen grid to
maintain the corona current on the photoconductor.
As the photoconductor is charged by the saw tooth from the
main corona unit, the surface potential increases. This in-
creases the current flowing through the screen grid. When the
photoconductor potential nears the grid potential, the current
turns to flow to the grid so that the photoconductor potential can
be maintained at a stable level.
Process controlling
Function
The print pattern signal is converted into an invisible image by
the semiconductor laser using negative to positive (reversible)
developing method. Therefore, if the developing bias is added
before the drum is charged, toner is attracted onto the drum. If
the developing bias is not added when the drum is charged, the
carrier is attracted to the drum because of the strong electros-
tatic force of the drum.
To avoid this, the process is controlled by adjusting the drum
potential and the grid potential of the Scorotron charger.
Basic function
Voltage added to the screen grid can be selected, high and low.
To make it easily understood, the figure below shows voltage
transition at the developer unit.
-600
0
Toner attract
potential
D
rum su
rfa
c
e
po
te
n
tia
l
Non-image area
Developing bias
Image area
Residual potential (-50 to -100V)
Charge
Exposure
Developing
Transfer
Discharge
Charge
Time
-400
Semiconductor laser
0
START
STOP
Print potentioal
Toner attract
potential
2)
3)
1)
Low
4)
High
Drum potential
Developing bias
Time
About DC 5.2kV
AL-1000/1010
6-3
