Image Forming Process Of The - Canon NP-70 Service Manual

1-8
NP -70
1.5 IMAGE FORMING PROCESS OF THE NP-70
Process
Function
Remarks
Positive charge for
sensitizing
1
With positive corona discharge, the
drum surface is positively charged.
rT~
O O O O
-~~~
Corona
Photosensive Drum Wue
Layer
Applied voltage = +6.4 kVDC
Corona wire = Gold-coated
tungsten wire, 6/ 100 mm
in diameter.
ro ~
~x
~~. b~ bo
`< w
w
* Corona discharge:
When high voltage is applied to
the corona wire, it forms an elect
tric field which causes partial
breakdown of the air and ionizes
it.
AC discharge with
simultaneous image
exposure
2
AC corona discharge and image
exposure is applied to the drum
surface at the same time.
Applied voltage = 7.0 kVAC
o n
~x
b<
~o 0
~ w
oa
* AC corona discharge:
Positive and negative corona dis-
charges occur alternately.
* Insulation coating:
Increases the efficiency of AC
corona discharge, and prevents
arc-over.
* Grid:
Stabilizes the effects of discharg-
ing.
Overall exposure
3
Fluorescent lamp (lOW x 1)
Fluorescent Lamp (lOWx 1)
Light
The surface potential after this pro-
cess is:
Dark portion: 300 ^~ SSOV
Light portion: 0~ —150V
Second Printing -June, 1974
© CANON INC.