| 摘要 |
PURPOSE:To prevent picture quality from being degraded by the scattering of a black toner so as to reproduce sharp black images in a multicolor electrophotographic device which overlays toner images of plural colors on a photoconductor to transfer the images onto paper at a time. CONSTITUTION:A black toner image is set to be formed prior to a multicolor toner image, and a magnetic toner with an electrical resistance value of 10<14>OMEGA.cm or more is used as the toner stored in a developing device for black. Also, a magnetic toner whose electrical resistance value is almost equal to that of the material of a resin binder, with colorants dispersed in the resin binder, may be used as the black toner. Therefore, a charge in a toner layer is prevented from migrating toward a photoconductor as it is attracted by a charge of the opposite polarity existing near the surface of the photoconductor, and an attracting force is generated between the charge of the toner and the charge of the opposite polarity near the surface of the photoconductor, preventing the toner from scattering. |
