DEVELOPING DEVICE AND IMAGE FORMING APPARATUS INCLUDING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a developing device that can give an image with good graininess while suppressing occurrence of base contamination, and an image forming apparatus including the developing device.SOLUTION: A developing device 4 includes a developing roller 42A as a developer carrier that travels and carries a two-component developer comprising a toner and a carrier on its travelling surface and that is disposed to oppose to a photoreceptor 2 as a latent image carrier. The developing device includes a picture quality improving roller 42B as a downstream counter member that is disposed to oppose to the photoreceptor 2 at a downstream side along a surface traveling direction of the photoreceptor 2 with respect to the developing region where the developing roller 42A opposes to the photoreceptor 2, and that travels and carries a two-component developer having sufficiently low toner concentration compared to the two-component developer carried on the surface of the developing roller 42A or carries only a carrier on its travelling surface. The developing device also includes a power supply unit as AC voltage application means to apply a voltage including an AC component such as an alternating voltage to the picture quality improving roller 42B.