PURPOSE: To form a developer layer on a carrier thinnly, uniformly, and stably for a long period by forming a specifying member of two-layered structure of an electrode layer and an insulating layer arranged on the carrier side, and applying an alternating current to the electrode layer and oscillating the specifying member.
CONSTITUTION: The specifying member 15 has the two-layered structure of the electrode layer 18 and insulating layer 19 arranged on the side of a roll 11, and an alternating voltage is applied to the electrode layer 18 by an AC power source 20. Consequently, an electric field is produced between the specifying member 15 and roll 11 and the specifying member 15 oscillates at the same time, so even when the press-contacting force of the roll 11 to the specifying member 15 is reduced, the thin and uniform toner layer which is electrostatically charged negatively is formed on the surface of the roll 11. Then the toner layer sticks to an electrostatic latent image 23 which is charged positively on the photosensitive layer 23 on a drum 21 to develop the image. Thus, the toner layer is formed on the carrier thinnly, uniformly, and stably to form a developed image with uniform density on the photosensitive layer.
HOSOYA MASAHIRO
UEHARA TSUTOMU
