Canon LBP 2460 Service Manual - Page 82

CHAPTER 2 1. Electrostatic latent image formation stage This stage follows two steps to produce an electrostatic latent image on the photosensitive drum. At the end of the stage, negative charges remain on the unexposed "dark" areas, where the laser beam struck (exposed) the drum surface. This image of negative charges on the drum is invisible to the eye, so it is referred to as an called an "electrostatic latent image." Step 1 Primary charge Surface potential (V) 0 -100 -500 Time (t) Exposed area Primary Scanning charge exposure (step 1) (step 2) Unexposed area Transfer (step 4) Primary charge (step 1) Figure 2-4-5 Primary charging roller AC bias DC bias Photosensitive drum Figure 2-4-6 For preparation of the latent image formation, a uniform negative potential is applied to the photosensitive drum surface. For primary charge, the printer uses the charging method, which directly charges the drum. The primary charging roller is made of conductive rubber. In addition to DC bias, AC bias has been applied to the primary charging roller to keep the potential on the drum's surface uniform. The DC bias is changed with the developing DC bias. 2 - 36