| 摘要 |
PROBLEM TO BE SOLVED: To solve the problem that the desired image density is not obtained even though the same transfer bias is applied, when a bias whose polarity is opposite to that of the toner is simply applied on a contact roller arranged upstream a transfer nip, as for an image forming apparatus using an intermediate transfer belt, having a secondary transfer process, and wherein, a secondary transfer bias is applied from behind the belt. SOLUTION: When a toner image has a negative polarity, a power source 16 for applying a counter roller current as a negative polarity transfer bias on a transfer counter roller 7d, and a power source 17 for applying a contact roller current as a positive polarity electric field on the contact roller 7r are prepared as constant current power sources, and a transfer roller 11 and also a transfer entrance guide plate 19 are grounded. By setting the value of the sum of the counter roller current value and the contact roller current value including the polarity to be a fixed value equal to or exceeding a certain value capable of obtaining the desired image density, the image of satisfactory density is obtained. COPYRIGHT: (C)2004,JPO
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