Developing device and image forming apparatus having developer layer regulating member

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.