| 摘要 |
A developer carrier in the form of a developing roller constituting a part of one of a plurality of developing units incorporated in a color developing device which is mounted on an electrophotographic image forming apparatus. Latent images electrostatically formed on a photoconductive element included in the image forming apparatus each is developed by a magnet brush formed by the developer of particular color on associated one of the developing rollers. Each developing roller has a non-magnetic conductive base, a first layer formed on the base and having an insulation resistance greater than 106 ohms, and a second layer formed on the first layer and having an insulation resistance lying in the range of 104 ohms to 109 ohms. The developing roller prevents a bias being applied thereto for development from leaking due to scratches or similar defects of the photoconductive element. While the developing device is in operation, a magnet brush is prevented from being formed on the developing rollers of those developing units which are not joining in the development.
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