31 October 1995COPY PROCESSES AROUND THE DRUM
1. DRUM CHARGE
In the dark, the charge corona unit gives a uniform negative charge to the organic
photoconductive (OPC) drum. The charge remains on the surface of the drum because the
OPC drum has a high electrical resistance in the dark.
2. EXPOSURE
An image of the original is reflected to the drum surface via the optics assembly. The charge
on the drum surface is dissipated in direct proportion to the intensity of the reflected light,
thus producing an electrical latent image on the drum surface.
3. ERASE
The erase lamp illuminates the areas of the charged drum surface that will not be used for
the latent image. The resistance of the drum in the illuminated areas drops and the charge on
those areas dissipates.
4. DEVELOPMENT
Positively charged toner is attracted to the negatively charged areas of the drum, thus
developing the latent image. (The positive triboelectric charge is caused by friction between
the carrier and toner particles.)
5. IMAGE TRANSFER
Paper is fed to the drum surface at the proper time so as to align the copy paper and the
developed image on the drum surface. Then, a strong negative charge is applied to the back
side of the copy paper, producing an electrical force which pulls the toner particles from the
drum surface to the copy paper. At the same time, the copy paper is electrically attracted to
the drum surface.
6. PAPER SEPARATION
A strong ac corona discharge is applied to the back side of the copy paper, reducing the
negative charge on the copy paper and breaking the electrical attraction between the paper
and the drum. Then, the stiffness of the copy paper causes it to separate from the drum
surface. The pick-off pawls help to separate paper.
7. CLEANING
The cleaning blade scrapes the loosened toner off the drum.
8. QUENCHING
Light from the quenching lamp electrically neutralizes the surface of the drum.
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