| 摘要 |
PURPOSE:To prevent occurrence of fog and reduce consumption of magnetic toner, a carrier, by making an image carrier and developer non-contact and impressing alternating bias to a developing sleeve that carries developer. CONSTITUTION:An electrostatic latent image formed on a photosensitive drum 2 is kept in a state of non-contact with a magnetic brush of developer 13 formed on a developing sleeve 15. Alternating bias is impressed to the developing sleeve 15 by an alternating bias power source 8. Accordingly, Coulomb force acting between magnetic toner 13b and negative charge existing in the dark part of the photosensitive drum 2 is negligible, and developer flies in proportion to magnitude of electric field between the electrostatic latent image and developing sleeve. Accordingly, non-magnetic toner 13a is apt to fly to bright charge part of the photosensitive drum. On the other hand, magnetic toner 13b hardly flies as electric field to dark charge part of the photosensitive drum 2 is weak and magnetic constrained force acts to the developing sleeve 15 side. Thus, consumption of magnetic toner, a carrier, is reduced, and a high quality picture free from fog can be obtained. |
