Brother HL-1440 Service Manual page 79

The area exposed to the laser beam is the image to be printed. The surface potential of the
exposed area is reduced, forming the electrostatic image to be printed.
+870
+420
+200
Drum
Sleeve 0
2.6.3 Developing
Developing causes the toner to be attracted to the electrostatic image on the drum so as to
transform it into a visible image.
The developer consists of a non-magnetic toner. The development roller is made of
conductive rubber and the supply roller (which is also made of conductive sponge) rotate
against each other. The toner is charged and carried from the supply roller to the development
roller. The toner adheres to the development roller and is conveyed to the photosensitive drum
at an even thickness controlled by the blade. The toner is nipped between the development
roller and the drum and developed onto the latent image on the drum. The electrostatic field
between the drum and the development roller, which is DC-biased from the high-voltage power
supply, creates the electrostatic potential to attract toner particles from the development roller
to the latent image area on the drum surface.
Photosensitive drum
1 Cycle of drum
1 2 3
(a)
(b)
Time
Development roller
Corona wire
Transfer roller
Supply roller
Primary charging
1
2 Laser beam exposure and developing
(a) Unexposed area
( Non image area )
(b) Exposed area
( Image area )
3
Transfer the image to paper
Fig. 3-36
Blade
Fig. 3-37
3-29
CHAPTER 3 THEORY OF OPERATION