Latent Image Formation Block; Developing Block - Canon imageCLASS LBP6780dn Service Manual

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Technology > Image Formation System > Image Formation Process > Developing block

■ Latent image formation block

During the two steps that comprise this block, an invisible latent image is formed on the
photosensitivedrum.
Step 1: Primary charging
To prepare for latent image formation, the surface of the photosensitive drum is charged
with a uniform negative potential. The primary charging bias is applied to the primary
charging roller and the roller charges the drum directly.
Primary charging roller
Photosensitive drum
Step 2: Laser-beam exposure
The laser beam scans the photosensitive drum to neutralize the negative charge on
portions of the drum surface. An electrostatic latent image forms where the negative charge
was neutralized.
Unexposed area
2 Technology > Image Formation System > Image Formation Process > Developing block
Primary charging bias
F-2-5
Laser beam
Exposed area
F-2-6

■ Developing block

Toner adheres to the electrostatic latent image on the photosensitive drum, which becomes
visible.
Step 3: Developing
Toner acquires a negative charge from the friction that occurs when the developing roller
rotates against the developing blade. The negatively charged toner is attracted to the
latent image on the photosensitive drum surface because the drum surface has a higher
potential. The developing bias is applied to the developing roller.
Blade
Developing roller
Exposed area
Unexposed area
Photosensitive drum
2-6
Unexposed area
Developing bias
Exposed area
F-2-7
2-6