2–5COPYING PROCESSCOPYRIGHT © 1998 CANON INC. CANON NP6621 REV.0 FEB. 1998 PRINTED IN JAPAN (IMPRIME AU JAPON)G. Step 5 (transfer)Figure 2-111The transfer roller deposits negative chargeson the back of copy paper to attract toner from thedrum surface to the copy paper.The copier uses a roller transfer method, whichrequires a lower transfer voltage compared to co-rona transfer methods and generates virtually noozone.To prevent transfer failure or soiling of the backof copy paper, the transfer guide is groundedthrough a varistor.Reference:If the transfer guide was grounded, the chargesthat should be on the back of copy paper wouldescape, causing transfer failure; by the sametoken, if the transfer guide is not grounded atall, it would become charged and soiled withdeposits of toner, soiling the back of copypaper.An AC bias and DC bias (negative component)are applied simultaneously* to the developing cylin-der and the blade.* Termeddevelopment bias, whose negative com-ponent is larger than that of the positive compo-nent.Figure 2-110During copying operation, the drum surfacepotential and development bias (at time of positivecomponent) draw toner to the photosensitive drumto turn the latent static image into a visible image.The excess toner is drawn away from the photosen-sitive drum by the work of the drum surface potentialand the developing bias (at time of negative compo-nent).The AC bias (frequency, in particular) mainlyaffects gradation; a lower frequency improves thegradation, but tends to result in fogging. The DCbias relates to copy density and fogging; a higherbias, that is closer to 0 V, darkens the image but inturn could lead to fogging.DC biasPositivecomponent0VNegativecomponentTransferrollerTransferguide plates
