Abstract: A fixing device in an image formation apparatus has a heating roller and a backup roller. These rollers are each coated with single silicone rubber layers around the respective peripheries of their core bars. This silicone rubber has a volume resistance value of 1013 &OHgr;·cm or more. The heating roller is charged with electricity of the same polarity as the polarity of toner particles due to frictional electrification caused at the time of feeding of a recording medium. The heating and the backup roller are polarized reverse to the polarity of the recording medium. A quantity of charged electricity on the backup roller is made larger than that on the heating roller. This permits the image formation apparatus to prevent offset from occurring at the time of fixing a toner image onto the recording medium to cope with various types of recording media.

Abstract: An electrograph apparatus includes a photoconductor, a charging device for uniformly charging the surface of the photoconductor, a developing device, a charge extinguishing device functioning so that a sheet of printed paper can be easily released, and a fixing device in which denatured silicone oil having a mercapto-group as a functional group is used as a releasing agent, for fixing a toner image copied on a printing paper, in which the fixing device is provided above the charging device and the charge extinguishing device.

Abstract: A developing magnet roller is provided on a developing frame, and a developing agent accommodating cartridge and a toner accommodating cartridge member are fitted detachably into the developing frame. The toner accommodating cartridge member is fitted detachably into the developing agent accommodating cartridge. A developing agent is recovered in the developing agent accommodating cartridge. The developing agent and the developing agent accommodating cartridge are exchanged together from a developing apparatus. The new developing agent accommodated in the exchanged new developing agent accommodating cartridge is circulated by the developing magnet roller. The exchange for the developing agent in the developing apparatus can be realized without the lowering of the developing performance.

Abstract: A developing magnet roller is provided on a developing frame and a developing agent accommodating cartridge is fitted detachably into the developing frame. A toner accommodating cartridge unit is fitted detachably in the developing agent accommodating cartridge. A developing agent is recovered in the developing agent accommodating cartridge. The developing agent and the developing agent accommodating cartridge are exchanged together from a developing apparatus. The new developing agent accommodated in the exchanged new developing agent accommodating cartridge is circulated by the developing magnet roller. The exchange for the developing agent in the developing apparatus can be realized without the lowering of the developing performance.

Abstract: A electrophotographic image fixing device fixes a toner image on a substrate. The substrate is passed between two pressing rollers disposed in opposition to each other to fix toner images on the substrate. The pressing rollers includes a surface constructed from an elastic material layer such that the elastic material layer can be deformed approximately 0.5-1.5% in terms of thickness. The pressing force against the toner applied side of the substrate is adjusted to 0.3-1 kg/cm.sup.2. As a result, an image with excellent toner fixing strength can be formed on a substrate such as an envelope without wrinkling the substrate during the fixing operation.