Technical information

Inthisstep,orpre-conditioningexposure,thesurface
of the drum is exposed to light from the pre-
conditioning exposure lamp. All charges remaining
on the surface of the drum from the preceding copy
cycle are eliminated in preparation for exposure by
theprimarycorona. Suchcharges, if leftastheyare,
could result in copies with uneven density.
4. Step 2 Primary corona exposure
Figure 2-6
In this step, the drum is exposed by the primaiy
corona. As a result, its surface will cometo have a
uniform layer of negative charges and maintain
primary potential.
The surface potential of the drum is determined
by the value of the grid bias’grounded by way of a
constant voltage element.
5. Step3 Image exposure
Opwal image
,l I 1
Dark_area 1 Lightarea
Figure 2-7
In this step, the optical image of the document is
projectedonthesurfaceofthedrumtoneutralizethe
charges in light areas.
COPYINGPROCESS K#ZW
6. Step 4 Development
,Blade
Developing
cylinder
Figure 2-8
As shown in Figure 2-8, the developing assembly
consists of a developing cylinder and a magnetic
blade; the developing cylinder itself is made up of a
magnet fixed in position and acylinder which rotates
around the magnet.
The black developer is a single-component
developer of magnetite and resin. The developer
has insulating properties and is charged to a positive
potential by friction with the rotating cylinder.
The color developer is a fixed-ratio mixture of
carrier (iron powder) and toner (resin).
By friction with the rotating cylinder, the iron
powder is charged to a negative potential, and the
toner to a positive potential.
Magnet Magna
Figure 2-9
Aconcentrated magneticfield develops between
the magnet and the tip ofthe blade, and the developer
is attracted to the magnetic field.
The magnetic field holds the developer it has
attracted virtually immobile and creates a collection
of developer particles hanging from the tip of the
blade. Asthecylinderrotates, thedeveloperparticles
leavethe magneticfieldtodepositthemselvesonthe
cylinder in a thin, uniform layer.
Since both thedeveloping cylinder and blade are
given AC bias and DC bias (negative component) at
the same time, the resulting waveform of the
developing bias has a larger negative component
than positive.
CANON NPZl20/2MO REY.0 MAY 1990 PAINTEO IN JAPAN [IMPRIME AU JAPONI
2-3
COPYRIGHT 0 1992 CANON INC.