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2–5
COPYING PROCESS
COPYRIGHT © 1998 CANON INC. CANON NP6621 REV.0 FEB. 1998 PRINTED IN JAPAN (IMPRIME AU JAPON)
G. Step 5 (transfer)
Figure 2-111
The transfer roller deposits negative charges
on the back of copy paper to attract toner from the
drum surface to the copy paper.
The copier uses a roller transfer method, which
requires a lower transfer voltage compared to co-
rona transfer methods and generates virtually no
ozone.
To prevent transfer failure or soiling of the back
of copy paper, the transfer guide is grounded
through a varistor.
Reference:
If the transfer guide was grounded, the charges
that should be on the back of copy paper would
escape, causing transfer failure; by the same
token, if the transfer guide is not grounded at
all, it would become charged and soiled with
deposits of toner, soiling the back of copy
paper.
An AC bias and DC bias (negative component)
are applied simultaneously* to the developing cylin-
der and the blade.
* Termed
development bias
, whose negative com-
ponent is larger than that of the positive compo-
nent.
Figure 2-110
During copying operation, the drum surface
potential and development bias (at time of positive
component) draw toner to the photosensitive drum
to turn the latent static image into a visible image.
The excess toner is drawn away from the photosen-
sitive drum by the work of the drum surface potential
and the developing bias (at time of negative compo-
nent).
The AC bias (frequency, in particular) mainly
affects gradation; a lower frequency improves the
gradation, but tends to result in fogging. The DC
bias relates to copy density and fogging; a higher
bias, that is closer to 0 V, darkens the image but in
turn could lead to fogging.
DC bias
Positive
component
0V
Negative
component
Transfer
roller
Transfer
guide plates