Functional Overview
Image Formation System
Developing Stage
The developing station develops the latent electrostatic image into
a visible image on the drum. The developing unit consists of a
metallic cylinder that rotates around a freed magnetic core inside
the toner cavity. Toner is a powdery substance made of black
plastic resin bound to iron particles, which is attracted to the
magnetic core of the cylinder. A rubber blade “brushes” the toner
on the developing cylinder to a uniform thickness.
The toner particles obtain a negative surface charge by rubbing
against the developing cylinder which is connected to a negative dc
supply. The negatively charged toner is attracted to the discharged
(grounded) areas of the drum exposed to laser light, and repelled
from the negatively charged (non-exposed) areas. An ac potential is
applied to the developing cylinder to decrease the attraction
between the toner and the magnetic core of the cylinder, and to
increase the repelling action of toner against the areas of the drum
not exposed to laser light. This ac potential improves density and
contrast (see Figure 5-14).
! II
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Ph
w
~ AC bias
Developing cylinder
7“
DC bias
A
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i-qure 3-14 nnage ueveloprnenl
5-29
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