| 摘要 |
PROBLEM TO BE SOLVED: To prevent image density from being thinned because of a primary transfer bias control technique and to simplify a primary transfer bias controller. SOLUTION: This image forming device is constituted so that a multiple toner image by plural transfer actions is formed on an intermediate transfer belt 1 by repeatedly executing such a process that a toner image formed on a photoreceptor drum 11 on the belt 1 in an area where the drum 11 is brought into contact with the belt 1 by applying bias to the belt 1 plural times from the single drum 11, for example. Then, developing units 14a-14d are provided with a function recovering toner on the drum 11 after the toner image is transferred to the belt 1 from the drum 11. Besides, the belt 1 is provided with such a characteristic that the relation ofπ<=T is established when the electrifying relaxation time of the belt 1 is defined asπ(s) and time till one part of the surface of the intermediate transfer belt is passed through the contact area with the photoreceptor drum and it arrives at the contact area with the photoreceptor drum next in the transfer process of the toner image executed to the belt 1 from the drum 11 plural times is defined T(s).
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