Patent ID: 8913928

Claim:
A developing device comprising: a developer supporting member for supporting developer, said developer supporting member having a surface layer; and a developer layer regulating member arranged to abut against the surface layer for regulating a layer thickness of the developer on the surface layer, wherein said surface layer contains at least carbon black, said developer supporting member is composed so that the following equation (1) is satisfied when the surface layer has a dynamic friction coefficient μ between 0.4 and 0.9 (0.4≦μ≦0.9) and a ten-point average roughness Rz (μm) between 2 μm and 6 μm (2≦Rz≦6): 2 ≦C≦ 0.5× Rz+ 3 (1) where C is a content of the carbon black (weight parts relative to 100 weight parts of a main component of the surface layer), or said developer supporting member is composed so that the following equation (2) is satisfied when the surface layer has the dynamic friction coefficient μ and the ten-point average roughness Rz satisfy the following equation (3): 0.9≦μ≦0.05 ×Rz+ 1 (2) 10×μ−7 ≦C≦ 0.5× Rz+ 3 (3) where Rz in the equations (1)-(3) represents only a value of the ten-point average roughness Rz of the surface layer expressed in μm.