Toshiba DP1200, Service Manual

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(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 sur-
face 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 combina-
tion 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 trans-
fered onto the print paper.
Step-5: Cleaning
Residual toner on the drum surface is removed and
collected 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 sur-
face by the main charging unit. Stable potential is maintained
by means of the Scorotron charger.
Positive charges are generated in the aluminum layer.
Step-2: Exposure (laser beam, lens)
A Laser beam is generated from the semiconductor laser and
controlled by the print pattern signal. The laser writes onto the
OPC drum surface through the polygon mirrors and lens. The
resistance of the OPC layer decreases for an area exposed by
the laser beam (corresponding to the print pattern signal). The
beam neutralizes the negative charge. An electrostatic latent
image is formed on the drum surface.
Step-3: Developing (DC bias)
A bias potential is applied to the MG roller in the two com-
ponent magnetic brush developing method, and the toner is
charged negative through friction with the carrier.
Non-image area of the drum surface charged with negative
potential repel the toner, whereas the laser exposed portions
where no negative charges exist, attract the toner. As a result,
a visible image appears on the drum surface.
OPC layer
Pigment
layer
Aluminum
drum
OPC layer
Pigment
layer
Aluminum
layer
Drum surface charge
sfter the exposure
Non-image area Image area
Semiconductor laser
Exposure
(semiconductor laser)
S
N
N
: Carrier (Magnetized particle)
: Toner (Charge negative by friction)
(N) (S) :Permanent magnet
(provided in three locations)
MG roller
DC
–400V ± 8V
About
DC5.5KV
(–580V/–400V)
DP1200/1500
7 – 8