The main charger is a rotating brush roller. The main charger removes residual toner from
the OPC drum by its rotating sweeping action and causes it to stick to the
brush. At the same time, a high voltage
of -950V is applied to the main charger roller to generate a discharge of
electricity between the roller and the OPC drum, generating positive and
negative charges. The negative charges are attracted to the OPC drum, and
evenly distributed on the OPC drum. (The OPC drum surface is evenly charged.)
Laser beam scanning light corresponding to the print data is
radiated on the OPC drum. Positive and
negative charges are generated in the OPC drum CGL exposed with the laser beam. Positive charges generated in the CGL are
attracted toward the OPC drum surface (negative charges), and negative charges
toward the aluminium layer (positive charges).
Therefore, the positive and negative charges neutralize each other in the
laser-exposed area of the OPC drum surface and the aluminium layer, decreasing
the potential of the OPC drum surface. The
area, which is not exposed to laser beam, has no change, and the OPC drum
surface remains negatively charged to keep a high potential. As a result,
latent electrostatic images are formed on the OPC drum.
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Development
Toner is attached to the latent electrostatic images on the
OPC drum to form visible images. Toner
is transported to the scraper area by the toner supply roller and the
developing roller. The scraper controls the quantity of toner to be transported
to the doctor section. Toner transported to the doctor section is then passed
between the developing roller and the doctor to form a thin toner layer on the
developing roller by the pressure applied by the doctor. When toner passes between the developing
roller and the doctor, it is charged negatively by friction. When an area of
OPC drum, which was exposed, to laser beam and lost its charge comes in contact
with the developing roller, toner moves from the developing roller to the OPC
drum surface. The principle of toner
movement from the developing roller to the OPC drum surface is as follows.
The bias voltage of DC-280V is applied to the developing
roller. Toner is charged negatively by the difference (electrical energy)
between the bias voltage and the OPC drum surface potential and is
attracted to the OPC drum surface which is positively charged. At that time, the potential of the area of
the OPC drum, which was exposed to the laser beam and lost its charge, is
higher than that of the developing roller.
On the other hand, when an area of OPC drum, which was not exposed
to the laser beam and did not lose its charge comes in contact with the
developing roller, any residual toner attached to the OPC drum is transferred
to the developing roller which is more positively charged. As a result, the developing unit collects
unnecessary toner on the OPC drum. The
operating principle for that case is contrary to that for transfer of toner
from the developing roller to the OPC drum surface. (The electric field energy
direction is contrary.
Visible images of toner on the OPC drum are transferred
to the paper.
The high voltage of DC+3600V plus AC760V (P-P) is applied to
the transfer roller to generate electric discharge between the roller and the OPC drum, generating positive and negative charges. Positive
charges are attracted to the OPC drum and attached to the paper transported
between the transfer roller and the OPC drum. Therefore the paper has a strong
positive charge. Negatively charged
toner on the OPC drum is attracted by the paper which is positively charged,
and the visible images of toner are transferred onto the paper.
The paper is separated from the OPC drum. There is an electrostatic force between the paper,
which is positively charged in transfer operation, and the OPC drum which is
negatively charged. The positive charge on the paper is released to the
separation electrode, which is the same potential as the aluminum layer of the
OPC drum, to reduce the potential difference between the OPC drum and the
paper, reducing the electrostatic force.
This operation facilitates separation of the paper from the OPC drum.
The drum surface is discharged to facilitate cleaning of the
drum surface. (The main charger roller easily collects the remaining toner.) The main charger is a rotating brush roller. The main charger removes residual toner from
the OPC drum by its rotating sweeping action and causes it to stick to the
brush. The main charger brush is in close contact with the mesh-type brush
cleaning plate which removes toner and paper dust from the main charger brush
mechanically.
OPC drum surface potential
Transition of OPC drums surface potential by print operation.
OPC drum surface potential and developing bias voltage
in development.
