| 摘要 |
PURPOSE: To form an excellent image high in gradation by cyclically fluctuating a distance between an electrostatic latent image carrier and the surface of a developer holding means. CONSTITUTION: A developing roller 36 which is the developer holding means arranged to be opposed to a photoreceptor drum 12 being the electrostatic latent image carrier and imparting toner 34 to the drum 12 so as to make an electrostatic latent image a visible image and has recessed and projected parts 36a on the surface of a conductive urethane rubber layer formed around a metallic shaft 36c is arranged in a housing 35 of a developing device 16 storing the toner 34. When it is assumed that the cycle of the recessed part and the projected part is T, the surface moving speed ratio of the developing roller 36 to the drum 12 is (v), and contact width between the drum 12 and the roller 36 is (d), (v-1)×d/T>5 is set to be satisfied. Since the distance between the drum 12 and the roller 36 is distributively set because of the recessed and projected parts 36a formed on the surface of the roller 36, electric field applied to the toner is distributively set and the inclination of developing characteristic is made gentle. |
