Patent ID: 8918037

Claim:
A developing device supplying a non-magnetic one-component developer onto an image bearing member on which an electrostatic latent image is formed, comprising: an accommodating portion accommodating the developer; a supply roller holding the developer accommodated in the accommodating portion on the outer circumferential surface thereof; a development roller supplying the developer onto the image bearing member; the development roller having a roller portion receiving the developer supplied from the supply roller and holding a developer layer on the outer circumferential surface thereof, and a rotational shaft member arranged to extend along a rotational axis and having at least one magnet portion; and a plate-shaped regulating member arranged to be surface contacted onto the surface of the developer layer on the development roller and having at least part thereof configured of a magnetic member, wherein a magnetic force (m 1 ) of the at least one magnet portion is 60 [mT] or more, and wherein the magnetic force (m 1 ) of the at least one magnet portion of the rotational shaft member, a saturation magnetization (m 2 ) of the regulating member, and a distance (L) between the magnet portion and the regulating member are configured to satisfy a range of 90 to 200 of a biasing index which is calculated by a formula: (m 1 ×m 2 )/L 2 .