Patent ID: 8588635

Claim:
A development device for causing a developer to adhere to an electrostatic latent image formed on a latent image carrier, the development device comprising: a developer container for containing the developer; a rotary cylindrical developer carrier disposed in the developer container, facing the latent image carrier; the developer carrier including multiple outer electrodes arranged in a circumferential direction of the developer carrier, an inner electrode provided on an inner circumferential side of the developer carrier from the multiple outer electrodes and electrically insulated from the multiple outer electrodes, an insulation layer disposed between the multiple outer electrodes and the inner electrode, and a surface layer overlaying an outer side of each of the multiple outer electrodes and electrically insulating the multiple outer electrodes from each other; a bias power source to generate electrical fields on a circumferential surface of the developer carrier, the electrical fields changing with time and causing the developer to hop on the developer carrier, by applying a first bias voltage and a second bias voltage to the inner electrode and the multiple outer electrodes, respectively; an electrical field adjuster to keep a state of the developer hopping on the developer carrier constant by regulating the electrical fields in accordance with a thickness of the surface layer of the developer carrier; and a controller operatively connected to the electrical field adjuster for controlling the electrical field adjuster.