| 摘要 |
PURPOSE: To maintain the peeling effect of toner on a 2nd developing roller and to prevent an abnormal image from being formed even when the same spot of the surface of the 2nd developing roller passes through the part in contact with a 1st developing roller many times in a state that toner is not supplied from the 2nd developing roller to a photoreceptor drum. CONSTITUTION: In this developing device 2, the toner 7 on the 1st developing roller 3 regulated by a doctor blade 4 is transferred and stuck to the 2nd developing roller 5 by a potential difference generated by a DC power source 6, and the toner carried on the 2nd developing roller 5 is supplied to the photoreceptor drum 1 so as to develop an electrostatic latent image formed on the drum 1. The developer to be used for the device 2 is defined so that the content of silica is <=2wt.%, the content of zinc stearate is <=2wt.%, the surface roughness of the 1st developing roller 3 is <=Rz10μm in JIS ten-point average, and the content of coarse powder of the toner 7 whose grain size is >=12μm is <=10vol.% under the condition that the biting amount of both rollers 3 and 5 is 0.1mm to 0.5mm.
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