초록 ▼

A full-color electrophotographic apparatus of the present invention is configured such that a toner image is formed on an intermediate transfer member. The intermediate transfer member is heated to a temperature equal to or higher than the softening start temperature of resin contained in a liquid t

A full-color electrophotographic apparatus of the present invention is configured such that a toner image is formed on an intermediate transfer member. The intermediate transfer member is heated to a temperature equal to or higher than the softening start temperature of resin contained in a liquid toner and equal to or lower than the withstand temperature of a photoconductor member. A carrier-removing roller to which bias can be applied abuts the intermediate transfer member so as to remove a carrier while packing softened toner by the force of an electric field induced by bias. In a transfer section for transfer to a printing medium, a backup roller presses the printing medium against the intermediate transfer member, and the toner image is transferred from the intermediate transfer member to the printing medium. Before being pressed against the toner image on the intermediate transfer member, the printing medium is heated. Bias is applied to the backup roller such that the toner image on the intermediate transfer is attracted toward the printing medium by the action of an electric field, thereby assisting transfer. By so doing, the intermediate transfer member does not need to undergo cooling before coming into contact with the photoconductor member, thereby avoiding occurrence of thermal damage to the photoconductor member.

대표청구항 ▼

What is claimed is: 1. A full-color electrophotographic apparatus to form a full color image on a printing medium using a nonvolatile, high-viscosity, high-concentration liquid toner, comprising: an intermediate transfer member on which color toner images in a plurality of colors are sequentially

What is claimed is: 1. A full-color electrophotographic apparatus to form a full color image on a printing medium using a nonvolatile, high-viscosity, high-concentration liquid toner, comprising: an intermediate transfer member on which color toner images in a plurality of colors are sequentially superimposed so as to form the full-color image, and the full-color image being heat-melt-transferred to the printing medium; a photoconductor member to form the color toner images, the intermediate transfer member being maintained at a temperature equal to or higher than a softening start temperature of resin contained in the liquid toner and equal to or lower than a withstand temperature of the photoconductor member; a carrier-removing mechanism provided on the intermediate transfer member so as to remove a carrier when each of the color toner images is transferred to the intermediate transfer member, said carrier-removing mechanism comprising a carrier-removing roller to which a bias having a same polarity as that of particles of the toner on the intermediate transfer member and in rotary contact with the toner images on the intermediate transfer member so as to remove the carrier while packing the toner softened by a force of an electric field induced by the bias; a transfer section, comprising a backup roller, to press against the printing medium the toner images which have been formed on the intermediate transfer member and from which the carrier has been removed, to thereby transfer the toner images to the printing medium; a fixation section for fixing the transferred toner image; means for heating, before the transfer to the printing medium, the toner images formed on the intermediate transfer member to a temperature higher than a glass transition temperature of toner solids and lower than a melting point of the toner solids, wherein a bias voltage is applied in such a direction as to transfer the toner images to the printing medium at the time of toner image transfer to the printing medium, in a zone for transferring the toner images on the intermediate transfer member to the printing medium, the backup roller applying a low pressure capable of transferring the toner images on the intermediate transfer member to the printing medium, and the fixation section is configured in such a manner as not to be drivingly linked to an image formation section including the intermediate transfer member, the photoconductor member, and a development section, to apply a sufficient pressure for enhancing cohesion of the toner to the printing medium which is insufficient at the time of transfer, while being heated to a temperature higher than the melting point of the toner solids; means for setting temperature such that a temperature (T 1) of the printing medium as measured in the transfer section is higher than a softening temperature (Tg) of the resin contained in the liquid toner to be used and lower than a melting temperature (Tm) of the resin; a preheating unit for preheating the printing medium to a temperature required for transfer before the printing medium is fed to the transfer section; and means for controlling a temperature (T2) of the intermediate transfer member such that the temperature (T2) is higher than the softening temperature (Tg) and lower than the temperature (T1) of the printing medium as measured in the transfer section. 2. A full-color liquid-development electrophotographic apparatus as described in claim 1, wherein the preheating unit comprises a pair of rollers serving as heating rollers and a press member disposed so as to cause the printing medium to be wound on one of the paired rollers; and a temperature of the heating roller is set lower than the melting temperature (Tm) and higher than the temperature (T1) of the printing medium as measured in the transfer section, in consideration of cooling of the heated printing medium effected through heat radiation before the heated printing medium reaches the transfer section. 3. A full-color liquid-development electrophotographic apparatus as described in claim 2, wherein the press member is formed of a metal having high thermal conductivity. 4. A full-color liquid-development electrophotographic apparatus as described in claim 2, wherein the press member is a flexible member. 5. A full-color liquid-development electrophotographic apparatus as described in claim 4, wherein the flexible member and a surface of the heating roller are moved in the same direction; and when V1 represents a moving speed of the surface of the heating roller, and V2 represents a moving speed of the flexible member, V1 and V2 are controlled so as to establish the relation V2< V1. 6. A full-color electrophotographic apparatus to form a full color image on a printing medium using a nonvolatile, high-viscosity, high-concentration liquid toner, comprising: an intermediate transfer member on which color toner images in a plurality of colors are sequentially superimposed so as to form the full-color image, and the full-color image being heat-melt-transferred to the printing medium; a photoconductor member to form the color toner images, the intermediate transfer member being maintained at a temperature equal to or higher than a softening start temperature of resin contained in the liquid toner and equal to or lower than a withstand temperature of the photoconductor member; a carrier-removing mechanism provided on the intermediate transfer member so as to remove a carrier when each of the color toner images is transferred to the intermediate transfer member, said carrier-removing mechanism comprising a carrier-removing roller to which a bias having a same polarity as that of particles of the toner on the intermediate transfer member and in rotary contact with the toner images on the intermediate transfer member so as to remove the carrier while packing the toner softened by a force of an electric field induced by the bias; a transfer section, comprising a backup roller, to press against the printing medium the toner images which have been formed on the intermediate transfer member and from which the carrier has been removed, to thereby transfer the toner images to the printing medium; and a fixation section for fixing the transferred toner image, wherein a mixture of two types of resins of different softening temperatures is used as resin contained in the nonvolatile, high-viscosity, high-concentration liquid toner; and when Tg1 represents a softening temperature of one resin, Tg2 represents a softening temperature of the other resin, Tg3 represents a softening temperature of the mixed resin, Tm 3 represents a melting temperature of the mixed resin, and T4 represents a temperature of the image bearing member, the two types of resins are selected so as to establish the relation Tg1 <Tg3<Tg2<Tm3, and means for controlling a temperature of the intermediate transfer member is provided so as to establish the relation Tg1<T4<Tg 2<Tm 3. 7. A full-color liquid-development electrophotographic apparatus as described in claim 6, wherein, in addition to the means for controlling the temperature of the intermediate transfer member, means for controlling the temperature of the printing medium as measured at the time of transfer is provided so as to establish the relation Tg1 <T4<Tg2<Tm 3<T5, where T5 represents the temperature of the printing medium as measured at the time of transfer. 8. A full-color liquid-development electrophotographic apparatus as described in claim 6, wherein the two types of resins are prepared so as to establish the relation (T4-Tg1)<20째 C. and the relation (Tg2-T4) >10째 C. 9. A full-color liquid-development electrophotographic apparatus as described in claim 6, wherein the two types of resins are mixed such that a proportion of one resin to the other resin is 20% to 80%. 10. A full-color electrophotographic apparatus to form a full color image on a printing medium using a nonvolatile, high-viscosity, high-concentration liquid toner, comprising: an intermediate transfer member on which color toner images in a plurality of colors are sequentially superimposed so as to form the full-color image, and the full-color image being heat-melt-transferred to the printing medium; a photoconductor member to form the color toner images, the intermediate transfer member being maintained at a temperature equal to or higher than a softening start temperature of resin contained in the liquid toner and equal to or lower than a withstand temperature of the photoconductor member; a carrier-removing mechanism provided on the intermediate transfer member so as to remove a carrier when each of the color toner images is transferred to the intermediate transfer member, said carrier-removing mechanism comprising a carrier-removing roller to which a bias having a same polarity as that of particles of the toner on the intermediate transfer member and in rotary contact with the toner images on the intermediate transfer member so as to remove the carrier while packing the toner softened by a force of an electric field induced by the bias; a transfer section, comprising a backup roller, to press against the printing medium the toner images which have been formed on the intermediate transfer member and from which the carrier has been removed, to thereby transfer the toner images to the printing medium; a fixation section for fixing the transferred toner image, the fixation section being separate from the transfer section, wherein the fixation section comprises a first fixation section and a second fixation section; the first fixation section and the second fixation section are configured in such a manner as not to be drivingly linked to an image formation section including the intermediate transfer member, the photoconductor member, and a development section; and the first fixation section is configured in such a manner as to apply a sufficient pressure for enhancing toner cohesion to the printing medium which is insufficient at the time of transfer, so as to ensure fixation strength, while being heated to a temperature higher than the melting point of the toner solids; and the second fixation section is configured in such a manner as to apply pressure lower than the pressure which the first fixation section applies. 11. A full-color electrophotographic apparatus to form a full color image on a printing medium using a nonvolatile, high-viscosity, high-concentration liquid toner, comprising: an intermediate transfer member on which color toner images in a plurality of colors are sequentially superimposed so as to form the full-color image, and the full-color image being heat-melt-transferred to the printing medium; a photoconductor member to form the color toner images, the intermediate transfer member being maintained at a temperature equal to or higher than a softening start temperature of resin contained in the liquid toner and equal to or lower than a withstand temperature of the photoconductor member; a carrier-removing mechanism provided on the intermediate transfer member so as to remove a carrier when each of the color toner images is transferred to the intermediate transfer member, said carrier-removing mechanism comprising a carrier-removing roller to which a bias having a same polarity as that of particles of the toner on the intermediate transfer member and in rotary contact with the toner images on the intermediate transfer member so as to remove the carrier while packing the toner softened by a force of an electric field induced by the bias; a transfer section, comprising a backup roller, to press against the printing medium the toner images which have been formed on the intermediate transfer member and from which the carrier has been removed, to thereby transfer the toner images to the printing medium; and a fixation section for fixing the transferred toner image, wherein the fixation section comprises: heating means for heating the printing medium to which toner has been transferred, so as to melt a resin component of toner particles; and press fixation means for fixing the toner image through causing the printing medium to pass through a fixation nip zone where pressure is applied to a resin component of toner particles molten on the printing medium, and at least a toner image side of the printing medium is heat-retained, wherein the printing medium receives heat from the heating means and the pressure from the press fixation means at different times. 12. An apparatus to form a color image on a printing medium using a liquid toner containing a resin, comprising: a transfer member to receive the color image thereon; a transfer unit to transfer the color image from the transfer member to the printing medium; a temperature setting unit to set a temperature (T1) of the printing medium as measured in the transfer unit to be greater than a softening temperature (Tg) of the resin contained in the toner and lower than a melting temperature (Tm) of the resin; a preheating unit to preheat the printing medium to a temperature required for transfer of the color image before the printing medium is received by the transfer unit; and a temperature control to control a temperature (T2) of the transfer member such that the temperature (T2) is greater than the softening temperature (Tg) and lower than the temperature (T1). 13. An apparatus to form a color image on a printing medium, comprising: a transfer member to receive a liquid toner containing a mixed resin to thereby form the color image thereon; a transfer unit to transfer the color image from the transfer member to the printing medium; and a temperature controller to control a temperature T 4 of the transfer member, the mixed resin comprising a first resin having a softening temperature Tg1 and a second resin having a softening temperature Tg2 different from Tg1, so that Tg1<Tg3< Tg2<Tm3 is satisfied, wherein Tg3 represents a softening temperature of the mixed resin and Tm 3 represents a melting temperature of the mixed resin, and the temperature controller controls the temperature T 4 so that Tg1<T4< Tg2<Tm3 is satisfied. 14. An apparatus to form a color image on a printing medium using a liquid toner containing a resin, comprising: a photoconductor member to form a plurality of images of different colors thereon; a transfer member to receive the plurality of images to thereby form the color image thereon; a transfer unit to transfer the color image from the transfer member to the printing medium; and a fixation unit to fix the transferred color image, comprising: a first section to apply a first pressure to the printing medium to thereby fix the color image to the printing medium, and a second section to apply a second pressure to the printing medium which is lower than the first pressure, the first and second sections not being drivingly linked to the transfer member or the photoconductor member.