| 摘要 |
PROBLEM TO BE SOLVED: To restrain the occurrence of a ghost image due to reverse transfer of a developer to a photoreceptor drum. SOLUTION: A photoreceptor drum 51K for monochrome is provided upstream of a plurality of photoreceptor drums 51Y, 51M, 51C other than the photoreceptor drum for monochrome in the paper carrying direction. A control device 100 controls the absolute value of developing bias voltage applied to a developing roller corresponding to the photoreceptor drum 51K for monochrome to be smaller in monochromatic printing than in color printing, and controls a charger so that the absolute value of surface potential of the photoreceptor drum 51K for monochrome is smaller in monochromatic printing than in color printing. COPYRIGHT: (C)2011,JPO&INPIT
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