| 摘要 |
PURPOSE:To prevent the degradation of an electrostatic image and obtain a high-density copy image even if the electrostatic image formed once is developed and transferred repeatedly, by making the width of a magnet for development in the circumferential direction wider than conventional one. CONSTITUTION:A magnetic pole M1 for development and plural magnetic poles M2-M5 for carrying are provided fixedly to a magnet roll 6 a prescribed length apart from a photosensitive drum 2, and a nonmagnetic sleeve 7 is provided on the outside circumferential face of the magnet roll 6 rotatably in the direction of an arrow (b). A magnetic two-component developer 3 on sleeve 7 is smoothed with a prescribed thickness by a doctor blade 8 and crests in the position of the magnetic pole M1 and is brought into contact with the photosensitive drum 2 and is slided there to develop an electrostatic latent image. As the result of the experiment where a width (d) of the magnetic pole M1 for development in the circumferential direction is set to 7-12mm., desirably, 8-10mm., the degradation of the electrostatic image is suppressed considerably in case of generation of plural copies due to repeated development and transfer, and high-density copies are obtained. |
