| 摘要 |
PROBLEM TO BE SOLVED: To stably obtain an excellent halftone image having appropriate image density and fine smoothness in the case of performing development by making AC electric field act on a developing area where a developer carrier is opposed to an image carrier. SOLUTION: In this device; the development is performed by rotating the developer carrier 11 provided to be opposed to the image carrier 1 so that developer 2 may be carried to the developing area where the carrier 11 is opposed to the carrier 1 and alternately repeating an acting period when AC voltage is applied on the carrier 11 so as to make the AC electric field act therein and a dormant period when the AC voltage is not applied. In such a case, when it is assumed that the circumferential speed ratio of the carrier 11 to the carrier 1 isθ, an interval between the carriers 11 and 1 in the developing area is Ds (mm), the peak-to-peak value of the AC voltage is Vpp (kV), the cycle is T (ms) and the number of the dormant periods per second is N (times/s), conditions 5×10<3> <=θ×(Vpp/Ds)×T×N and 5>=Vpp/Ds are satisfied.
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