JP2006243082A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of stabilizing primary transfer by keeping the potential of an intermediate transfer body proper. <P>SOLUTION: The image forming apparatus of the present invention has a transfer device which transfers a toner image, developed on a developer carrier coated with a liquid developer formed as a thin layer on an image carrier where an electrostatic latent image is formed, by using a liquid developer and formed on the image carrier, to an intermediate transfer body, and further transfers it to a recording body. Then the image forming apparatus of the present invention includes a 1st bias application member which abuts against the reverse surface of the intermediate transfer body to apply a bias and a 2nd bias application member which abuts against the top surface to a width larger than the lengthwise width of the intermediate transfer body to apply a bias, the 2nd bias application member is arranged abutting against the top surface of the intermediate body during primary transfer from downstream from secondary transfer of the intermediate transfer body, and the 1st bias application member and 2nd bias application member are loaded with voltages equal in potential. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly to an improvement capable of stabilizing primary transfer in an image forming apparatus such as a copying machine, a facsimile machine, or a printer.

In this type of image forming apparatus, particularly a full-color image forming apparatus, an image carrier and an intermediate transfer member are brought into contact with each other, and a toner image formed on the image carrier by a transfer electric field formed by a charge applying unit is transferred to the intermediate transfer member. It is known that an image is formed through a primary transfer process for transferring the toner image to a toner image and a secondary transfer process for transferring the toner image onto a transfer material. As an intermediate transfer member in such an image forming apparatus, an intermediate transfer belt, an intermediate transfer drum, or the like is used. In such an intermediate transfer body, for example, an intermediate transfer belt, a medium resistance having a volume resistivity of 10 ⁸ to 10 ¹¹ Ωcm is often used. Such an intermediate-resistance intermediate transfer belt does not normally require a neutralizing means for neutralizing the surface of the intermediate transfer belt, and can reduce costs.

  When such an intermediate resistance intermediate transfer member is used, the surface of the intermediate transfer member is charged by a transfer bias applied at the time of primary transfer and retains the charged potential. However, as time elapses, the charge forming the potential flows out from the back surface of the intermediate transfer member to a member or the like that comes into contact, and the charge potential of the intermediate transfer member becomes approximately 0V. As a result, the potential difference between the charging potential of the intermediate transfer member and the charging potential of the toner image primarily transferred onto the intermediate transfer member becomes large. As a result, a part of the toner, particularly the upper toner when a plurality of color toner images are superposed, is attracted to the surface of the intermediate transfer member. In other words, the transfer dust in which the toner is scattered on the intermediate transfer member has a great influence on image formation. This is particularly noticeable when a full-color image is formed, and background smudges, blurring of characters, etc. occur, leading to a decrease in image quality.

As a conventional example, in Patent Document 1, a high-resistance intermediate transfer member having a volume resistivity of about 10 ¹³ Ωcm is used in order to eliminate such problems. In such a high-resistance intermediate transfer member, the charging potential on the surface thereof is increased by peeling discharge that occurs when peeling off from the image carrier after completion of primary transfer. Since the intermediate transfer member has high resistance, the charge on the front surface does not flow out to the member in contact with the back surface. Therefore, the difference in charging potential between the surface of the intermediate transfer member and the toner adsorbed thereon can be reduced. In this way, the above-mentioned transfer dust is suppressed and deterioration of image quality is prevented.

However, when such a high-resistance intermediate transfer member is used, or at least when an intermediate transfer member having a volume resistivity of 10 ¹¹ Ωcm or more is used, it is charged at the time of primary transfer unlike the above-described medium-resistance one. The residual charge remaining on the surface is retained until the next primary transfer. For this reason, in the next primary transfer step, a desired transfer electric field, that is, at least the same transfer electric field as the previous time cannot be formed. Accordingly, when such a high resistance intermediate transfer member is used, it is necessary to provide a charge eliminating means for eliminating residual charges.

In addition, when a jam occurs, the toner image formed on the intermediate transfer member passes through the secondary transfer region without being transferred to the transfer material. Such a toner image must be removed before the next toner image is formed on the intermediate transfer member. Therefore, the toner image is generally removed by a cleaning member such as a cleaning blade.
JP 2000-231286 A

  However, an image forming apparatus using an intermediate transfer body is usually used as a full-color image forming apparatus, and forms an image by superposing a plurality of colors of toner on the intermediate transfer body. Such a full-color image forming apparatus has an extremely large amount of toner used for one-time image formation as compared with a black and white (single color) image forming apparatus, and cannot be completely removed by a conventional cleaning member.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of stabilizing primary transfer by maintaining an appropriate potential of an intermediate transfer member.

  In order to solve the above problems, the image forming apparatus of the present invention uses a liquid developer, and a development in which a thin liquid developer layer is applied to an image carrier on which an electrostatic latent image is formed. And a transfer device that visualizes the toner image on the developer carrying member, transfers the toner image formed on the developer carrying member to the intermediate transfer member, and further transfers the toner image to the recording member. In the image forming apparatus of the present invention, the first bias applying member that abuts on the back surface of the intermediate transfer member and applies a bias and the surface that has a width equal to or larger than the width in the longitudinal direction of the intermediate transfer member applies the bias. The second bias applying member is disposed so as to contact the surface of the intermediate transfer member between the primary transfer from the downstream side of the secondary transfer of the intermediate transfer member. A characteristic is that an equipotential voltage is applied to the bias applying member and the second bias applying member. Therefore, by using a bias applying member on the surface of the intermediate transfer member after the secondary transfer, good primary transfer and secondary transfer can be performed without being affected by the electrical properties of the intermediate transfer member.

Further, since the volume resistivity of the second bias applying member is 10 ³ Ωcm or less, it can be applied to the bias applying member without an applied voltage drop.

  Further, since the second bias applying member is configured in a plate shape, the entire surface of the intermediate transfer member can be set to the same potential as the first bias applying member.

  The second bias applying member is a cleaning blade of a cleaning device that cleans the intermediate transfer member. Therefore, it is not necessary to provide a special device, and the apparatus can be simplified.

  Further, the second bias applying member is configured to be rotatable in a columnar shape, and by contacting the intermediate transfer member, residual toner does not accumulate at a portion where the bias applying member and the intermediate transfer member are in contact with each other. Thus, a desired bias can be applied to the intermediate transfer member by contacting the intermediate transfer member.

  The second bias applying member is downstream of the secondary transfer and contacts the intermediate transfer member in the cleaning device. Therefore, since the second bias applying member contacts the intermediate transfer member and becomes dirty with the residual toner after the secondary transfer, the cleaning device has a mechanism for collecting the residual toner, so there is no need to provide it specially. The device can be simplified.

  Further, by changing the surface speed so that the surface speeds of the second bias applying member and the intermediate transfer member are different, the cleaning property of the intermediate transfer member can be improved, and a desired bias is applied to the intermediate transfer member. be able to.

  Further, since the second bias applying member is a cleaning roller provided in the cleaning device, residual toner on the intermediate transfer member can be removed, and a desired bias can be applied to the intermediate transfer member.

  Further, the cleaning roller is made of a porous material having elasticity. Therefore, residual toner on the intermediate transfer member can be trapped and removed in the pores of the porous member, so that the cleaning property is improved and a desired bias can be applied to the intermediate transfer member.

  In addition, a non-contact corona charger as a second bias applying member is disposed at a position facing the intermediate transfer member before the primary transfer, so that the surface potential is the same as the voltage applied to the intermediate transfer member. To control. Therefore, since it is non-contact, there is no need for cleaning, and the surface potential of the intermediate transfer member can be controlled.

  According to the image forming apparatus of the present invention, a good primary transfer and secondary transfer can be performed without being affected by the electrical properties of the intermediate transfer member by using a bias applying member on the surface of the intermediate transfer member after the secondary transfer. It can be performed.

  FIG. 1 is a schematic sectional view showing the structure of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus of the present embodiment shown in the figure includes a photoreceptor 1 as an image carrier, and around the photoreceptor 1, a charger 2, an exposure device 3, a developing device 4, and excess toner removal. An image forming means comprising an apparatus 5, a static eliminator 6, a photoreceptor cleaning device 7, and an intermediate transfer body 8 is disposed. As a material of the photoreceptor 1, a-Si, OPC, or the like can be used. The charger 2 can be in the form of a roller or a charger. Further, as the exposure device 3, an LED, a laser scanning optical system, or the like can be used.

  Next, a case where an image is formed by reversal development using the image forming apparatus of the present embodiment having the configuration shown in FIG. 1 will be described. In FIG. 1, a photosensitive member 1 is rotationally driven in a direction indicated by an arrow at a constant speed during image formation by a driving unit such as a motor (not shown). The surface of the photoconductor 1 is uniformly charged in the dark by the charger 2. Next, an original light image is irradiated and formed on the surface of the photoreceptor 1 by the exposure device 3. As a result, an electrostatic latent image is formed on the surface of the photoreceptor 1. Thereafter, when the electrostatic latent image passes through the development region, the electrostatic latent image is visualized (developed) by the developing device 4, and a toner image is formed on the surface of the photoreceptor 1. Next, the toner image visualized on the photosensitive member 1 is brought into contact with the sweep roller 51 of the excess toner removing device 5 in order to remove excess developer. A bias is applied to the sweep roller 51 so that an electric field for removing the non-image area toner and an electric field for compressing the image area toner on the photosensitive member are generated. Moreover, you may add a sweep roller as needed. The toner image is primarily transferred onto the intermediate transfer member 8 by a transfer bias applied through the intermediate transfer member 8 in the transfer region. Although the primary transfer bias varies depending on the image portion potential before transfer, in the present embodiment, −200 V is illustrated on the rotating shaft of the intermediate transfer body so that −200 V can be directly applied to the substrate drum on the back surface of the intermediate transfer body 8 at a constant voltage. The contact is not applied. The toner image primarily transferred onto the intermediate transfer member 8 faces the packing roller 91. Further, the packing roller 91 applies an electric field that does not peel off the toner image on the intermediate transfer member 8, removes excess developer, and applies an electric charge to the toner image on the intermediate transfer member 8. It is in contact. The packing roller 91 is controlled with a constant current, and is controlled with about 0.5 mA to 2 mA. Further, in the secondary transfer region, the secondary transfer roller 10 performs secondary transfer onto a transfer material such as copy paper or an OHP sheet. The transfer material onto which the toner image has been secondarily transferred is fixed to the toner image by a fixing device (not shown) and then discharged out of the machine as a printed matter. The secondary transfer roller 10 is controlled by a constant current, and is controlled by about 0.1 mA to 1 mA.

  Here, electric discharge occurs near the contact surface between the packing roller 91 and the surface of the intermediate transfer member 8, and charges the toner. A corona charger 13 may be provided as a charge applying device in front of the packing roller 91 to charge the toner and perform packing. The polarity may be either, but the same polarity as the toner is more advantageous. In addition, since the toner layer has a large amount of carrier liquid, the fixing property is deteriorated, and it is uneconomical to take the carrier liquid out of the apparatus. And separate. In this manner, the carrier liquid is separated from the toner by using discharge and bias at various places, thereby preventing the carrier liquid from being taken out onto the transfer paper.

  On the other hand, the residual potential remaining on the photoreceptor 1 after the primary transfer is removed by the static eliminator 6. Residual toner remaining on the photoreceptor 1 after the primary transfer is removed by the photoreceptor cleaning device 7 to prepare for the next image formation. As the fixing device, for example, a thermal transfer method, solvent fixing, UV fixing, pressure fixing, or the like can be used.

  In the image forming apparatus according to the present embodiment, as a developer for developing the electrostatic latent image on the photoreceptor 1, a low-viscosity (isopar (registered trademark)) that has been conventionally commercially available and used as a carrier ( A liquid developer having a high viscosity and a high concentration is used instead of a liquid developer having a low concentration (about 1%). As the viscosity and concentration range of the developer, for example, it is preferable to use a developer having a viscosity of 50 to 10,000 mPa · S and a concentration of 5% to 40%. As the carrier liquid, a highly insulating material such as silicone oil, normal paraffin, Isopar M (registered trademark), vegetable oil, mineral oil or the like can be used. Moreover, as a liquid developer, a volatile thing or a non-volatile thing can be selected and used according to the objective. Furthermore, the particle diameter of the toner of the liquid developer can be selected from submicron to about 6 μm according to the purpose.

Next, the developing device in the image forming apparatus of this embodiment will be described.
As shown in FIG. 1, the developing device 4 is provided with a coating roller 43 that is rotatably disposed in a developer storage tank that stores a liquid developer 41 therein, and is further rotatably disposed in a casing. An intermediate roller 45 and a developing roller 47 are provided. Further, the developing device 4 includes a coating device for applying the liquid developer 41 to the developing roller 47 as a member to be coated. The coating apparatus includes a coating roller 43 having a uniform pattern engraved on the surface as a coating member, an intermediate roller 45 as an intermediate coating member that applies the liquid developer 41 to the developing roller 47, and stirring of the liquid developer 41. -It is mainly comprised by the stirring / conveyance screw 42 etc. as a conveyance means.

  Further, the intermediate roller 45 of the developing device 4 and the sweep roller 51 of the surplus toner removing device 5 are respectively provided with cleaning blades 46 and 52 made of metal blades or rubber blades. The cleaning blades 46 and 52 may be roller type instead of blade type.

  Further, in the coating device, the intermediate roller 45 contacts the surface of the coating roller 43 to remove excess liquid developer on the surface, and the doctor roller that regulates the amount of developer carried on the surface of the coating roller 43. As a role. Then, the liquid developer which is applied to the application roller 43 and measured by the doctor blade 44 as an application amount regulating member is transferred onto the surface of the intermediate roller 45.

  Further, as shown in FIG. 2, the intermediate roller 45 is provided with an elastic layer 45-2 made of an elastic body on the outer peripheral surface of the core metal 45-1, and further on the outer peripheral surface of the elastic layer 45-2. -3 is provided. As a material of the elastic layer 45-2 of the intermediate roller 45, urethane rubber can be used. The material of the elastic layer 45-2 is not limited to urethane rubber, and may be any material that does not swell or dissolve with the carrier liquid / developer.

  Further, an intermediate transfer member 8 is disposed so as to abut on the photosensitive member 1 of the image forming apparatus, and a bias voltage is applied to the intermediate transfer member 8 so that an electric field that generates a potential difference with the potential of the image portion on the photosensitive drum 1 is generated. Apply. In this embodiment, by applying −200 V to the intermediate transfer member 8, the image can be primary transferred onto the intermediate transfer member 8 satisfactorily. The intermediate transfer member 8 will be described as an intermediate transfer drum in this embodiment.

  Conventionally, when a belt is assumed as an intermediate transfer member, it is an endless belt of a low resistance conductive member having a predetermined thickness. For example, the thickness is 30 to 150 μm, and polyimide, PET (polyethylene terephthalate), PVDF resin, etc. A material in which a conductive substance (carbon, metal powder, etc.) is mixed in a certain ratio has been used. However, when the transfer paper P is secondarily transferred to a paper having a relatively large concave portion on its surface, such as plain paper, by the intermediate transfer belt made of the conventional material, the following problems occur. That is, as described above, since the surface of the intermediate transfer belt is hard, it cannot follow the concave portion on the surface of plain paper or the like, resulting in density unevenness due to transfer failure. Therefore, the intermediate transfer drum according to the present embodiment is mainly composed of an elastic body so as to follow the concave portion on the surface of plain paper or the like so that transfer defects do not occur.

FIG. 3 is a partial cross-sectional view showing the structure of the intermediate transfer member in the image forming apparatus of this embodiment. The intermediate transfer member 8 shown in FIG. 1 includes an elastic conductor 81, a drum 82 in which the elastic conductor 81 is bonded to a metallic drum, and a surface coat layer 83. The elastic conductor 81 can be made of polyurethane rubber in which carbon is dispersed, for example. If the elastic conductor 81 has a thickness of 2 to 10 mm, a volume resistivity of 10 ³ to 10 ¹² Ωcm, and a hardness of 15 to 80 degrees (Hs) by JISA, a predetermined effect can be obtained. The surface coat layer is for improving the releasability of toner particles to improve the secondary transfer property and improving the separation property of the transfer paper P after the secondary transfer. For example, it is formed by coating a coating layer containing a fluororesin to a thickness of 5 to 60 μm.

Further, the surface resistance of the surface coat layer 83 of the intermediate transfer member 8 is 10 ¹⁰ Ωcm or more, and if it is less than that, it leaks to the coat layer of the intermediate transfer member due to the surface potential of the photoreceptor during primary transfer. The next transfer electric field cannot be maintained. Therefore, the electrical resistance value of the surface coat layer 83 is preferably 10 ¹⁰ Ωcm or more. Further, even if the intermediate transfer body 8 has a high surface resistance, the toner is transferred by an electric field with the transfer body with a bias applied from the back surface. Becomes important. Therefore, the volume resistivity of the intermediate transfer member 8 including the base material and the elastic layer needs to be 10 ⁶ Ωcm or more and 10 ¹² Ωcm or less.

  Further, most of the variation in the electric resistance value of the intermediate transfer member 8 is large in the elastic layer. When the electrical resistance value of the elastic layer is lowered in order to suppress the resistance variation of the elastic layer, the volume resistivity of the intermediate transfer member is secured by the coating thickness of the surface layer. In this case, the volume resistivity of the intermediate transfer member is controlled by the thickness of the surface coat layer. However, if the volume resistivity of the surface coat layer 83 becomes too high, an electrical history may remain on the intermediate transfer member 8.

  The intermediate transfer member 8 includes elements that destabilize the primary transfer bias, such as the secondary transfer roller 10, the packing roller 91, and the corona charger 13 of the charge applying device. The value also affects.

  As described above, various bias applying means are brought into contact with the intermediate transfer body 8, and whether the primary transfer bias is properly applied at the time of the primary transfer depends on the electric resistance value of the base material of the intermediate transfer body 8, the surface coating. It depends on the electrical resistance of the layer. It also depends on the time constant of the resistance value. Further, when the process speed is high, it is difficult for the intermediate transfer body 8 that has passed through the corona charger 13 of the charge applying device, the packing roller 91, and the secondary transfer roller 10 to maintain an appropriate primary transfer electric field in the primary transfer area. It is.

  However, by using a bias applying member on the surface of the intermediate transfer body after the secondary transfer, good primary transfer and secondary transfer can be performed without being affected by the electrical properties of the intermediate transfer body.

  As described in the apparatus configuration, the intermediate transfer body 8 is in contact with the packing roller 91 and the secondary transfer roller 10, and a bias is applied to each roller. The packing roller 91 may raise the surface potential of the intermediate transfer member, but the secondary transfer bias can cancel the potential increase. However, the potential of the intermediate transfer body, which has dropped below the primary transfer potential by the potential of the secondary transfer roller 10, cannot be recovered until a voltage is supplied from the back surface due to the time constant. Therefore, according to the present invention, the primary transfer bias is supplied from the surface of the intermediate transfer member 8 after the secondary transfer.

  First, after the secondary transfer, the bias applying member 12 shown in FIGS. 4 and 5 was arranged, and the same potential as the primary transfer bias was applied to the bias applying member 12. The bias applying member 12 used was a plate-like metal member bonded with a conductive resin 12-1 on the contact surface with the intermediate transfer member. As the pressure biasing member 12-2, a stainless plate having a thickness of about 100 μm that can be bent so as to follow a slight rotational shake of the intermediate transfer member 8 was used. Further, since the bias applying member 12 is made of an elastic body, the intermediate transfer member 8 has a high possibility of scratching the surface when a metal member is used without bonding the resin. Therefore, it is preferable to select a resin material having elasticity for the bias applying member 12. When using a resin material, conductive particles and ionic conductive material are dispersed in the resin and shaped into a desired shape as shown.

In order to prevent the electric resistance value unevenness of the bias applying member 12, it is preferable to set the volume resistivity of the bias applying member 12 to 10 ³ Ωcm or less. The bias applying member 12 is configured as a plate-like member having a width equal to or larger than the axial width of the intermediate transfer member 8. Since the bias applying member 12 is in contact with the intermediate transfer member 8, there may be residual toner even after the secondary transfer, and the toner may be soiled with toner. Therefore, the bias applying member 12 may be provided in the cleaning device. The toner adhering to the bias applying member 12 is deposited in the cleaning device. Since the mechanism for collecting the residual toner is provided in the cleaning device, the load on the cleaning device can be reduced. Further, as shown in FIG. 6, a bias applying member can be used as the cleaning blade 113. That is, the cleaning blade 113 is made of a conductive resin and a bias is applied. In this way, by applying a bias to the cleaning blade 113, the intended effect can be obtained, so that it is not necessary to provide a special bias application member, and the apparatus can be simplified. In this case, it is necessary to insulate from other parts so that a bias can be applied.

  Further, when the plate-like bias applying member 12 is used, the secondary transfer residual toner may adhere, and therefore, the residual toner is deposited on the contact portion with the intermediate transfer body 8 and needs to be removed. Accordingly, as shown in FIGS. 7 and 8, a bias applying roller 114 having a width equal to or larger than the axial width of the intermediate transfer member 8 and configured to be rotatable in a roller shape is disposed as a bias applying member. Since the bias applying roller 114 has a cylindrical rotatable roller shape, unlike the plate-like bias applying member 12, the toner removing member 115 can be provided to remove the toner attached to the bias applying roller 114. By providing the toner removing member 115, the remaining toner does not accumulate at the portion where the bias applying roller 114 and the intermediate transfer body 8 are in contact with each other, and can always come into contact with the intermediate transfer body 8 with a desired bias. Can be applied to the intermediate transfer member 8. At this time, if the bias applying roller 114 is disposed in the cleaning device, the toner removed by the toner removing member 115 can be collected by the removed toner collecting mechanism provided in the cleaning device 11.

  In order to apply a bias to the bias applying roller 114, a contact is provided on the core of the bias applying roller 114, and the bias is directly applied to the rotation shaft of the bias applying roller 114. The intermediate transfer body 8 and the bias application roller 114 of the bias application member may be contacted by spring pressure or contact by the distance between the axes, and any one may be used if they are in contact.

  Furthermore, by making the surface movement direction of the bias application roller 114 reverse to the surface movement direction of the intermediate transfer body 8, the intermediate transfer body 8 can be cleaned by the bias application roller 114. The cleaning property can also be improved by changing the surface speed. Although not shown, the toner image adhering to the intermediate transfer member 8 is removed by changing the surface movement direction of the bias applying roller 114 to the same direction as the surface movement direction of the intermediate transfer member 8 and changing the peripheral speed. It may be. As described above, the bias applying roller 114 can also be used as the cleaning roller 111. As a result, it is not necessary to provide a separate cleaning roller, and the apparatus can be simplified. However, the bias applying roller 114 can remove most of the developer on the intermediate transfer body 8 depending on the rotation direction and speed, but the carrier liquid cannot be completely removed. Therefore, the liquid removing blade 113 is provided downstream. Is preferable. Hereinafter, the bias application roller 114 will be described by replacing it with the cleaning roller 111.

  The cleaning roller 111 of the bias applying member may be a metal roller. However, in consideration of the rotational vibration of the intermediate transfer member 8, it is preferable that the cleaning roller 111 is made of a resin-made conductive and elastic member. Further, since the intermediate transfer body 8 is an elastic body, the surface runout accuracy is inferior to that of a rigid body. Therefore, in order to make a stable contact, the cleaning roller 111 of the bias applying member needs to be formed of an elastic body and a stable nip must be formed. There is. In addition, the secondary transfer residual toner of the intermediate transfer member 8 may have a cleaning effect. Further, as shown in FIG. 9, the cleaning roller 111 of the bias applying member is formed of a foam having no continuous pores, that is, a single foam. The cleaning roller 111 has a sufficient length so as to include the liquid ring contact area at the end in the width direction, and the liquid ring is absorbed by the surface cell of the sponge of the cleaning roller 111 and conveyed. Since the foam of a single foam does not have continuous pores, liquid impregnation to the inside of the foam is small. Therefore, the liquid can be discharged by absorbing and squeezing the liquid in cell units.

  The elastic body of the cleaning roller 111 has the effect of releasing the compressed toner particles in the foamed (single bubble) body having independent pores, but it sucks and discharges the liquid, but cannot sufficiently perform the cleaning. The circumferential liquid ring cannot be removed sufficiently. Therefore, the cleaning roller 111 is composed of a foam having a uniform porosity in the width direction and continuous pores, that is, a foam having continuous bubbles. Furthermore, by constituting with conductivity and with a porous body, the residual toner on the intermediate transfer body can be trapped in the pores of the porous body and removed. Further, by applying a bias, the potential on the surface of the intermediate transfer member can be kept at the primary transfer potential. By constructing the cleaning roller 111 with a foam having a uniform porosity in the width direction and having continuous pores, that is, a foamed body of continuous bubbles, the liquid ring is sucked and discharged, and the throttle member is sucked. Can remove the liquid developer. For the foam, it is necessary to select a material that does not swell in the liquid developer. The foam material used in the present embodiment was a foamed urethane resin. Further, the remaining toner adhering can be efficiently removed by bringing the squeeze roller 112 into contact with the cleaning roller 111 of the bias applying member and reversing the surface moving direction. By using a foam having continuous pores, it is possible to provide a means for impregnating the porous body with the carrier liquid in advance and remove the transfer residual toner having a very high solid content while washing it off. Therefore, by configuring the cleaning roller 111 of the bias applying member on the porous body having elasticity, the cleaning property is improved and a desired bias can be applied to the intermediate transfer body 8.

  Note that the roller and blade bias applying members as described above cannot be disposed after cleaning because they always contact the intermediate transfer member. Therefore, as shown in FIG. 10, in order to make the surface potential of the intermediate transfer member 8 equal to the primary transfer potential, a corona charger 13 is disposed at a position facing the intermediate transfer member 8. The bias applied to the corona wire is controlled by a constant current. When the positive polarity toner is used, the secondary transfer bias needs to be a value shifted more to the minus side than the primary transfer bias of the intermediate transfer body 8. Therefore, the surface potential of the intermediate transfer member 8 temporarily becomes lower than the primary transfer potential, that is, shifts more negatively. Therefore, the discharge to the corona charger 13 in FIG. 10 is a positive discharge, and it is necessary to remove the charge and adjust the potential. The discharge amount can also be adjusted by the charger applied current, but fine adjustment may be controlled by adjusting the potential of the charger case and the discharge efficiency to the intermediate transfer member. The bias applying means that comes in contact with the bias applying means needs to be cleaned, so the layout is very limited. However, when the corona charger 13 is used as shown in FIG. 10, since it is non-contact, there is no need for cleaning, layout can be performed relatively freely, and the surface potential of the intermediate transfer member can be controlled.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications and substitutions are possible as long as they are described within the scope of the claims.

1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which shows the structure of the intermediate roller of FIG. FIG. 3 is a partial cross-sectional view illustrating the structure of an intermediate transfer member in the image forming apparatus according to the present embodiment. It is a schematic sectional drawing which shows the structure of a bias application member. It is a perspective view which shows the example of arrangement | positioning of a bias application member. It is a schematic sectional drawing which shows the example which used the bias application member as a cleaning blade. It is a schematic sectional drawing which shows the structure of a roller-shaped bias application member. It is a perspective view which shows the example of arrangement | positioning of a roller-shaped bias application member. It is a fragmentary sectional view of a single bubble roller. FIG. 3 is a schematic cross-sectional view showing a configuration of an intermediate transfer member peripheral device to which a non-contact corona charger is added.

Explanation of symbols

1; photoreceptor, 2; charger, 3; exposure device, 4; developing device,
5; excess toner removing device, 6; static eliminator,
7; photoconductor cleaning device, 8; intermediate transfer member,
10; secondary transfer roller, 11; cleaning device,
12; bias applying member; 13; corona charger.

Claims (10)

In an image forming apparatus having a transfer device that uses a liquid developer to primarily transfer a toner image formed on an image bearing member to an intermediate transfer member and then secondary transfer to a recording member, and a cleaning device that removes toner ,
A first bias applying member that abuts on the back surface of the intermediate transfer member and applies a bias and a second bias applying member that abuts on the surface and applies a bias with a width equal to or greater than the longitudinal width of the intermediate transfer member are disposed. And the second bias applying member is disposed so as to come into contact with the surface of the intermediate transfer member between the primary transfer from the downstream of the secondary transfer of the intermediate transfer member,
An image forming apparatus, wherein an equipotential voltage is applied to the first bias applying member and the second bias applying member. The image forming apparatus according to claim 1, wherein a volume resistivity of the second bias applying member is 10 ³ Ωcm or less.   The image forming apparatus according to claim 1, wherein the second bias applying member is configured in a plate shape.   The image forming apparatus according to claim 1, wherein the second bias applying member is a cleaning blade of the cleaning device that cleans the intermediate transfer member.   The image forming apparatus according to claim 1, wherein the second bias applying member is configured to be rotatable in a columnar shape and abuts on the intermediate transfer member.   The image forming apparatus according to claim 1, wherein the second bias applying member is downstream of the secondary transfer and contacts the intermediate transfer member in the cleaning device.   The image forming apparatus according to claim 5, wherein surface speeds of the second bias applying member and the intermediate transfer member are different.   The image forming apparatus according to claim 1, wherein the second bias applying member is a cleaning roller provided in the cleaning device.   The image forming apparatus according to claim 8, wherein the cleaning roller is made of an elastic porous material.   A non-contact corona charger as the second bias applying member is disposed at a position facing the intermediate transfer member before the primary transfer, and the surface is the same as the voltage applied to the intermediate transfer member. The image forming apparatus according to claim 1, wherein the potential is controlled.

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