Toshiba e-STUDIO350 Service Manual page 73

• Switching of developer bias polarity
With the area which has no negative charge,
background fogging is decreased by switching the
bias to the positive polarity (approx. +150 V).
• Developer material
The developer material consists of a mixture of
the toner and carrier. The toner is charged to
the negative polarity and the carrier to positive
polarity due to the friction with each other
caused by mixing.
Tone : Mainly consists of the resin and carbon.
Carrier : Consists of the ferrite and resin coating
on its surface to provide consistent fric-
tional electrification.
Note:
If the developer material is used for a long time (be-
yond its normal life span),
the toner is caked onto the carrier.
The charging performance of the carrier is lowered.
Symptom : 1.Image density is lowered.
2.Toner scattering occurs.
3.Background fogging occurs.
Solution : Replace the developer material.
• Magnetic roller
- Magnetic brush development -
The south and north poles are arranged inside
the magnetic roller as shown in the right figure.
The developer material forms a brush-like fluff
which contacts the photoconductive drum sur-
face.
This is caused by the magnetic force lines be-
tween the south and north poles.
November 2003 © TOSHIBA TEC
Carbon
(5-10%)
5-20 µm
Resin (90-95%)
[Toner]
[Carrier]
Fig.3-210
Toner
No frictional electrification
occurs on the area where the
toner is caked.
Fig.3-211
Photoconductive
drum
Magnetic roller
Fig.3-212
3 - 5 e-STUDIO350/450 COPY PROCESS
Ferrite
30-100 µm
Carrier
Magnetic force
N
line
3