| 摘要 |
PURPOSE:To acquire two kinds of favourable image qualities with one device by carrying out development respectively suitable for a letter image and a photographic image by way of changing a development bias over to an alternating current bias where direct current components are superimposed and to a direct current bias without alternating current components. CONSTITUTION:Development is carried out with a black developing machine 105 by way of applying a development bias where alternating current components are superimposed to direct current components and making rotational circumferential speed ratio against a sensitizing body 102 of a developing sleeve 201 about 1.8 times against the developing sleeve 201 arranged with a gap from the sensitizing body 102. In this way, it is possible to acquire a developing characteristic suitable for a character image with less edge effect by applying alternating current voltage to which the direct current components are superimposed. Consequently, it is possible to acquire favourable images by way of applying the direct current bias without the alternating current components in the case when the developing bias is changed over and an image formation mode is a character image formation mode, and applying the alternating current bias where the direct current components are superimposed in the case of a photographic image formation mode. Accordingly, it is possible to acquire favourable quality for either of the images of 'character' and 'photograph'. |
