| 摘要 |
PROBLEM TO BE SOLVED: To improve the non-uniformity of potential by electrification by forming an electric field between a supply means and an image carrier so that more quantity of conductive grains per unit area is supplied to the region of the image carrier where a toner image is formed than the region where the toner image is not formed. SOLUTION: Positive DC bias being identical polarity to the triboelectrifying polarity of electrification promoting grains is applied to the core bar 32a of a coating roller 32 as the coating bias. For example, it is +700 V. The triboelectrifying polarity of the electrification promoting grains is positive and the coating bias V1 is set between the coating bias V1 and the image carrier V2 of a region which is developed by toner so that potential difference V2-V1 becomes reverse polarity to the triboelectrifying polarity of the grains. Therefore, the bias V1 is made to be larger than +700 V. By applying the lager bias than the potential obtained after image exposure (light-part potential) to the core bar 32a of the roller 32, a large grain supply electric field is formed in the region where the toner image is formed and the electrification promoting grains are supplied.
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