Specifications

2.3 Xerographic Process
2.3.1 Primary Charging Process
Primary Charge 
Roller
AC
Bias
DC
Bias
OPC
The ac and dc biases on the primary
charge roller distributes an even charge
across the Organic photoconductor
(OPC) drum. The ac bias is applied to
keep the primary charge even across the
surface of the print drum.
Density can be adjust to obtain a darker print by concurrently changing both
the primary and development dc bias. The development dc bias is described in
Section 2.3.3.
The primary charging roller is made of a conductive foam rubber-like compound
and is part of the EP-ED cartridge. The foam roller charging system requires
less high-voltage bias and produces less ozone then corona type charging
systems used on other printers.
As the OPC drum turns, the primary charge is subjected to the exposure
process.
2.3.2 Exposure Process
Unexposed
Area
Exposed
Area
Laser Beam
– – –


+ + +
Time (t)
Surface Potential (V)
0
-100



-500
Exposed
Area
Primary
Charge
Scanning
Process
Transfer Primary
Charge
The data modulated scanning laser
beam paints a latent image on the
rotating OPC drum. Where the laser
exposes the drum, the existing primary
charge is neutralized. The primary
charge remains in the unexposed areas.
This exposure system is commonly
referred to as a write black system.
The areas exposed to the laser light
correspond to the black areas of the
printed image. The unexposed areas
retain the primary charge, failing to
attract toner to the drum during the
development process.
2–16 Technical Description