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E.
Step
3
Scanning Exposure
Optical
image
Light
from the
original
is
projected onto
the
drum
surface.
Charges
in
these
light
areas on
the
drum
are neutralized
by
drum
photosensitive
effects.
F.
Step 4 Developing
Blade
Cylinder
1
Developing
Magnet
j cylinder
Figure
2-8
I
COPYING
PROCESS
Color developer
is
a
two-component
type
consisting
of iron
powder
(carrier)
and
toner
mixed
together
in
a
fixed
ratio.
The
main
component
of
the toner
is
resin.
The
toner
is
charged
to
a
positive potential
and
the
iron
powder
to
a
negative
potential
by
friction
with
the
rotating cylinder.
—
Blade
/tk_
Concentrated
Vay
-
magnetic
Magnet
Developer
Figure
2-9
A
concentrated magnetic
field
develops
between
the
magnet
and
the
edge
of
the
blade.
This
field
attracts
the
charged
developer.
The
developer
is
held
virtually
immobile by
the
magnetic
field,
forming a
curtain
along
the
edge
of
the blade.
As
the cylinder
rotates, this curtain
skims
the toner
particles
on
its
surface
to
a
thin
uniform
layer.
An
AC
bias plus
a
negative
DC
bias are
applied
simultaneously
to
the
developing
cylinder
so
that
the
waveform
of
the
developing
bias
has
a larger
negative
excursion than
positive.
Positive
excursion
Negative
excursion
DC
bias
Figure 2-10
As shown
in
Figure
2-8,
the developing
assembly
consists
of
a developing
cylinder (a
stationary
magnet
surrounded
by a
rotating
sleeve)
and
a blade
made
of
magnetic
material.
Black
toner
is
a
single
component
type
consisting
of
a
fine
powder
of
mixed
magnetite
and
resin binder.
The
toner
has
insulating properties
and
is
charged
to
a
positive potential
by
friction
with the
rotating
cylinder.
During copying toner
is
attracted to
the
drum
by
the
charges on
the
drum
surface
and
by
repulsion
due
to
the
developing
bias
(during
the
positive
excursion),
transforming
the
latent electrostatic
image
into
a
visible
image.
Excess
toner
particles
are
attracted
back
to
the
cylinder
from
the
drum due
to
the
charges on
the
drum
surface
and
the
developing
bias
(during the
negative
excursion).
The
DC
bias
affects
copy
density
and
fogging:
As
the
DC
bias
becomes
less
negative
(approaches
0V),
the density
and
degree
of
fogging both increase.
COPYRIGHT©
19)2
CANON
INC.
CANON
NW550
REV.1
SEPT. 1992
PRINTED
IN
JAPAN
(IMPRIHE
AU
JAPON)
2-3
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