Outline Of Print Process; Actual Print Process - Sharp AL-2020 Service Manual

2. Outline of print process

This printer is a non-impact printer that uses a semiconductor
laser and electrostatic print process. This printer uses an OPC
(Organic Photo Conductor) for its photoconductive material.
First, voltage from the main corona unit charges the drum surface
and a latent image is formed on the drum surface using a laser
beam. This latent image forms a visible image on the drum surface
when toner is applied. The toner image is then transferred onto the
print paper by the transfer corona and fused on the print paper in
the fusing section with a combination of heat and pressure.
Step-1: Charge
Step-2: Exposure
∗
Latent image is formed on the drum.
Step-3: Developing
Latent image formed on the drum is then changed into
visible image with toner.
Step-4: Transfer
The visible image (toner image) on the drum is transferred
onto the print paper.
Step-5: Cleaning
Residual toner on the drum surface is removed and col-
lected by the cleaning blade.
Step-6: Optical discharge
Residual charge on the drum surface is removed, by
semiconductor laser beam.

3. Actual print process

Step-1: DC charge
A uniform negative charge is applied over the OPC drum surface
by the main charging unit. Stable potential is maintained by means
of the Scorotron charger.
Positive charges are generated in the aluminum layer.
About
DC5.5KV
( 580V/ 400V)
AL-2020/2035/2040/2050/2060 COPY PROCESS 6 - 2
Step-2: Exposure (laser beam, lens)
A Laser beam is generated from the semiconductor laser and con-
trolled by the print pattern signal. The laser writes onto the OPC
drum surface through the polygon mirrors and lens. The resis-
tance of the OPC layer decreases for an area exposed by the laser
beam (corresponding to the print pattern signal). The beam neu-
tralizes the negative charge. An electrostatic latent image is
formed on the drum surface.
Semiconductor laser
Exposure
(semiconductor laser)
Drum surface charge
after the exposure
Non-image area
OPC layer
Pigment
layer
Aluminum
drum
OPC layer
Pigment
layer
Aluminum
layer
Image area