Image Processing Reference
In-Depth Information
|
V
h
|
V
clean
V
bias
V
dev
|
V
L
|
FIGURE 10.16
Development and cleaning voltages in a DAD system.
biased areas of the photoconductor will repel toner since the
field over these areas is
more negatively biased than the development electrode. The development and
cleaning voltages are given by (Figure 10.16)
V
dev
¼
V
bias
V
L
V
clean
¼
V
h
V
bias
(
:
)
10
29
It is important to note that the quantities V
h
and V
L
satisfy
,soin
most cases when we have negative charging, we have V
h
V
L
. This is the reason
we use absolute values in Figures 10.15 and 10.16. V
bias
j
V
h
jj
V
L
j
is typically positive
(Figure 10.12).
A typical two component developer consists of (1) toner powder that consists of
pigmented thermoplastic irregularly shaped particles between 5 and 25
m in size,
and (2) carrier beads usually circular in shape made out of magnetic core material
(e.g., ferrite) with a typical dimension of around 120
m
19] for
more details on the physics of toner electrostatic charging). A thin dielectric coating
gives the desired charging characteristics and surface properties required for the
toner particles to adhere to the carrier beads. Charge control agents are added to
the toner to adjust the magnitude of charge. Mixing toner and carrier beads will
result
m
m (see Refs. [16
-
cation. For example,
when active matrix (AMAT) photoconductors are used, during the mixing process,
toner is given positive charge and carrier beads are given negative charge. An
example of the toner particles attached to the carrier bead is shown in Figure 10.17.
in oppositely charged particles due to triboelectri
Carrier—transport toner
Toner—provide color
Additives—control
charging and flow
FIGURE 10.17
Example of toner particles attached to carrier beads.
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