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CHAPTER 2
Reference: Toner projection development
Arlually. both unexposed and exposed areas of the drum surface have a negative potential,
but lo simplify the explanation, the drum potential is shown as positive when it is higher [less
ncgalivr) than the developing cylinder potential, and negative when it is lower (more negative)
than the developing cylinder potential.
2 - 22
Toner movmmmi and elerlrir potenlials
Description
Th? electrostatic atlraction
raused by the difference in
potential between the drum
surface and Lhe cylinder is
sufficient to overcome Lhe
altraction of the magnet, so
of loner projected depends
on
the DC bias volta@ on
I
the cylinder.
~
When the potential dif-
ference between Ihe drum
surface and the developing
i
cylinder is reduced, the
~
resulting weak electric field
,
combines with the magnelic
field to attract toner back
from the drum to the
cylinder. This removes any
excessive toner adhering to
the drum. and improves the
contrast
of
print.
The drum surface potential
is only slightly higher than
the cylinder potential, so th,
magnelic attraclion to the
I
cylinder is greater than the
electrostatic attraction to
the drum. Therefore, only a
small amount of toner is
projected toward the drum.
cylinder bias and the
I The
magnetic force now
combine to strongly allrart
the toner to the cylinder,
removing the excessive
- DC b,as IeYBI
toner from the unexposed
' Di"rn 3"TlacB
wtenw
areas of
the drum and
preventing fogging.
I
finished
the
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