Patent ID: 8385791

Claim:
A developing device comprising: a developer bearing body that bears a developer; and a developer regulating member that regulates a thickness of a layer of a developer having a degree of circularity in a range from 0.94 to 0.97 on a surface of said developer bearing body, said developer regulating member comprising a resilient plate member composed of a metal material and having a bent portion; wherein an outer surface of said bent portion contacts said surface of said developer bearing body so that a ridge line of said outer surface of said bent portion crosses a moving direction of said surface of said developer bearing body; wherein a curvature radius R (μm) of said outer surface of said bent portion and a mean crystal grain diameter D (μm) of said metal material satisfy the relationship: 60×10 −3 ×R− 11≦ D≦ 93.75×10 −3 ×R− 6.875; and wherein said developer bearing body is a roller having a resilient outer layer, and said resilient outer layer has an ASKER-C hardness in a range from 65° to 85°.