JP2003270973A - Image forming device - Google Patents

Abstract

An object of the present invention is to solve the problem that a current for forming a secondary transfer electric field leaks to other electrodes and members through an intermediate transfer member. A voltage applied to the back electrode for secondary transfer is applied to an electrode which is close to at least one of upstream and downstream of the back electrode for secondary transfer and electrically connected to an intermediate transfer body. Is applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer and a facsimile having an intermediate transfer member.

[0002]

2. Description of the Related Art Image forming apparatuses include a color image forming apparatus having an intermediate transfer member such as an intermediate transfer belt and an intermediate transfer drum. In this color image forming apparatus, a toner image is formed on the image carrier, and the toner image on the image carrier is primarily transferred to the surface of the intermediate transfer member. A back electrode for secondary transfer is provided so as to face the secondary transfer member and is electrically joined (electrically connected) to the back surface of the intermediate transfer member, and the voltage subjected to constant current control is the back surface for secondary transfer. The secondary transfer member is applied from the electrodes to the back surface of the intermediate transfer member, and the secondary transfer member is grounded to form a secondary transfer electric field between the intermediate transfer member and the secondary transfer member. The toner image on the intermediate transfer body is secondarily transferred onto a recording medium such as a transfer paper passing through the space.

Another electrode electrically connected to the back surface of the intermediate transfer member is provided near the back electrode for secondary transfer. As the other electrode, there is a back electrode for cleaning which is provided so as to face the cleaning member and is electrically joined to the back surface of the intermediate transfer member, and a voltage is applied between the cleaning member and the back electrode for cleaning. As a result, the toner remaining on the intermediate transfer body after the secondary transfer is removed from the intermediate transfer body by the cleaning member with an electric field.

The other electrode is provided opposite to the residual toner charging member for reversing the polarity of the toner remaining on the intermediate transfer body after the secondary transfer, and is electrically connected to the back surface of the intermediate transfer body. There is a back electrode for charging the residual toner, and by applying a voltage between the residual toner charging member and the back electrode for charging the residual toner, the charging polarity of the toner remaining on the intermediate transfer member in the secondary transfer is reversed. And the toner 1
There is a residual toner charging back electrode which is transferred to the image carrier at the next transfer portion. A tension roller is provided near the back electrode for secondary transfer as a member that contacts the back surface of the intermediate transfer member, and the tension roller is held by the housing.

In Japanese Patent Laid-Open No. 10-49019, by applying a voltage having the same polarity as toner to the back surface of the intermediate transfer drum,
An image forming apparatus is described in which the charge polarity of the toner remaining on the intermediate transfer drum is reversed in the next transfer and the toner whose polarity is reversed is transferred to the photoconductor in the first transfer.

[0006]

In the above color image forming apparatus, a constant current controlled voltage is applied to the back surface of the intermediate transfer member from the back electrode for secondary transfer, and the secondary transfer member is grounded to form an intermediate image. By forming the secondary transfer electric field between the transfer body and the secondary transfer body, even if there is a current flowing through the recording medium, or if there is a resistance fluctuation of the intermediate transfer body or the secondary transfer body, The secondary transfer electric field does not change significantly, and therefore a stable image can be always formed on the recording medium.

However, when there are electrodes such as a cleaning rear electrode and a residual toner charging rear electrode near the secondary transfer rear electrode, if the other electrodes are grounded, then 2
The current supplied from the secondary transfer back electrode to the intermediate transfer body side to form the secondary transfer electric field leaks to the electrodes such as the cleaning back electrode and the residual toner charging back electrode through the intermediate transfer body to the recording medium. Shortage occurs. Also, when a tension roller that comes into contact with the back surface of the intermediate transfer member is provided near the back electrode for secondary transfer,
The current supplied from the back electrode for secondary transfer to the intermediate transfer body side to form the secondary transfer electric field leaks from the tension roller to the housing through the intermediate transfer body, and the current to the recording medium may be insufficient.

According to the present invention, the current for forming the secondary transfer electric field can be prevented from leaking to the electrode or member near the back electrode for secondary transfer through the intermediate transfer member, and the current to the recording medium is insufficient. An object of the present invention is to provide an image forming apparatus capable of preventing the above.

[0009]

In order to achieve the above object, the invention according to claim 1 provides an image carrier on which a toner image having a predetermined polarity is formed, and a toner image formed on the image carrier. Is primarily transferred, and a voltage electrically connected to the back surface of the intermediate transfer body and having the same polarity as the regular charging polarity of the toner is applied to the back surface of the intermediate transfer body.
An image forming apparatus having a secondary transfer back electrode for secondary transfer of a toner image transferred to the intermediate transfer member by a secondary transfer onto a recording medium, at least one of upstream and downstream of the secondary transfer back electrode. A voltage having the same polarity as that of the voltage applied to the back electrode for secondary transfer is applied to the electrode that is in close proximity and electrically connected to the intermediate transfer member.

According to a second aspect of the invention, an image carrier on which a toner image of a predetermined polarity is formed, an intermediate transfer member on which the toner image formed on the image carrier is primarily transferred, and an intermediate transfer member A toner image transferred to the intermediate transfer member by primary transfer is recorded by applying a voltage having the same polarity as the regular charging polarity of the toner to the back surface of the transfer member by the primary transfer. A back electrode for secondary transfer for secondary transfer to the medium,
A cleaning member that removes the toner remaining on the intermediate transfer member by secondary transfer from the intermediate transfer member, and the cleaning member that is provided so as to face the cleaning member and is electrically bonded to the back surface of the intermediate transfer member. An image forming apparatus having a cleaning back electrode for transferring the toner remaining on the intermediate transfer member by secondary transfer to the cleaning member by applying a voltage to the back surface of the same, the same toner as the toner is applied to the cleaning back electrode. A voltage of polarity is applied.

According to a third aspect of the present invention, an image carrier on which a toner image of a predetermined polarity is formed, an intermediate transfer member on which the toner image formed on the image carrier is primarily transferred, and an intermediate member between them. A toner image transferred to the intermediate transfer member by primary transfer is recorded by applying a voltage having the same polarity as the regular charging polarity of the toner to the back surface of the transfer member by the primary transfer. A back electrode for secondary transfer for secondary transfer to the medium,
By electrically bonding to the back surface of the intermediate transfer member and applying a voltage to the back surface of the intermediate transfer member, the charge polarity of the toner remaining on the intermediate transfer member in the secondary transfer is reversed to make the toner primary. In an image forming apparatus having a back electrode for charging residual toner, which is transferred to the image carrier at a transfer portion, a voltage having the same polarity as that of toner is applied to the back electrode for charging residual toner.

According to a fourth aspect of the present invention, an image carrier on which a toner image having a predetermined polarity is formed, an intermediate transfer member on which the toner image formed on the image carrier is primarily transferred, and an intermediate member A toner image transferred to the intermediate transfer member by primary transfer is recorded by applying a voltage having the same polarity as the regular charging polarity of the toner to the back surface of the transfer member by the primary transfer. In an image forming apparatus having a secondary transfer back electrode s that is secondarily transferred to a medium, it is held by a housing and comes into contact with the intermediate transfer member in proximity to at least one of upstream and downstream of the secondary transfer back electrode. The part of the member that contacts the intermediate transfer member and the case are insulated.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the voltage applied to the back surface of the intermediate transfer member by the back electrode for secondary transfer is a constant current. The voltage is controlled.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the intermediate transfer is close to at least one of the upstream and the downstream of the secondary transfer back electrode. To the electrode electrically connected to the back of the body,
A voltage having the same polarity and the same magnitude as the voltage applied to the intermediate transfer member is applied.

[0015]

1 shows an embodiment of the present invention. This embodiment is one form of a color image forming apparatus. FIG. 1 shows the polarity of toner that enters and leaves the intermediate transfer belt as an intermediate transfer member and a power supply device that applies a voltage to each electrode. Shows the polarity of. Figure 1
Indicates that the toner amount is not proportional to the actual amount, but qualitatively indicates the size of the toner amount.

On the drum-shaped photosensitive member 1 as an image bearing member, a toner image of a negative polarity which is a regular charging polarity is formed by a well-known image forming means (not shown). That is, the photoconductor 1 is rotationally driven by the rotary drive unit and uniformly charged by the charging unit, and is exposed by the exposure unit according to image signals of a plurality of colors, for example, yellow, magenta, cyan, and black, and each color is exposed. Electrostatic latent images corresponding to the image signals of are sequentially formed. The electrostatic latent image corresponding to the image signal of each color on the photoconductor 1 is developed with the toner of each color of yellow, magenta, cyan, and black by the developing unit of each color, and the toner of each color of yellow, magenta, cyan, and black is developed. It becomes image 2.

The intermediate transfer belt 3 as an intermediate transfer member is
The drive roller 4, the secondary transfer back roller 5 as the secondary transfer back electrode, the cleaning back roller 6 as the cleaning back electrode, and the tension roller 7 are bridged to form a photoreceptor at the primary transfer portion. 1, and the driving roller 4 is rotationally driven by a driving source (not shown), so that the driving roller 4 is rotationally driven at the same peripheral speed as the photoconductor 1. The tension roller 7 is elastically pressed against the back surface (inner peripheral surface) of the intermediate transfer belt 3 by a spring 8 to apply tension to the intermediate transfer belt 3.

The primary transfer roller 9 as a back electrode for primary transfer is formed by forming an elastic body of low resistance or medium resistance around a core metal, and is electrically joined to the back surface of the intermediate transfer belt 3. A primary transfer electric field is formed between the core metal and the conductive base layer of the photoconductor 1 by applying a positive polarity voltage controlled by the power source device 10 to a predetermined current value. Due to the direction of the primary transfer electric field, the toner images of the respective colors of the negative polarity on the photoconductor 1 are sequentially superposed and transferred onto the intermediate transfer belt 3 to form a full-color toner image. After the toner image is primarily transferred, the photoconductor 1 is cleaned by a cleaning device (not shown) to prepare for the next toner image formation.

The cleaning roller 11 as a cleaning member is separated from the intermediate transfer belt 3 during the formation of a full-color image by a contact / separation mechanism (not shown), and contacts the surface of the intermediate transfer belt 3 after the secondary transfer of the full-color toner image. Then, the intermediate transfer belt 3 is cleaned. The positive polarity toner 12 remaining on the intermediate transfer belt 3 even after cleaning is reversely transferred to the photoconductor 1 at the primary transfer portion.

The back roller 5 for secondary transfer is made of only metal and is electrically joined to the back surface of the intermediate transfer belt 3, and a negative polarity voltage controlled by the power supply 13 to a predetermined current value is applied. Is applied. 2 as a secondary transfer body
The next transfer roller 14 has an elastic body 14b having a low resistance or a medium resistance formed around a core metal 14a, is electrically joined to the back surface of the intermediate transfer belt 3, and the core metal 14a is grounded.

A transfer paper 16 as a recording medium is fed between the intermediate transfer belt 3 and the secondary transfer roller 14 from a paper feeding device (not shown). A negative polarity voltage, which is constant current controlled to a predetermined current value, is applied to the back surface of the intermediate transfer belt 3 from the power supply device 13 via the back surface roller 5 for secondary transfer, whereby the back surface roller 5 for secondary transfer is formed. A secondary transfer electric field is formed between the secondary transfer roller 14 and the cored bar 14a, and the negative polarity toner image 17 on the intermediate transfer belt 3 is transferred to the transfer paper 16 in the direction of the secondary transfer electric field. .
An AC voltage is applied from the AC power supply 22 to the separation charge-eliminating needle 21 to charge the transfer paper 16 and separate it from the intermediate transfer belt 3. After the transfer paper 16 is separated from the intermediate transfer belt 3, the toner image 23 is fixed by a fixing device (not shown) and discharged to the outside.

The secondary transfer electric field induces a positive charge from the cored bar 14a of the grounded secondary transfer roller 14 to inject charges into the toner of the toner image during the secondary transfer operation. . Therefore, 2 on the intermediate transfer belt 3
The next transfer residual toner 18 contains both positive and negative polar toners.

The back roller 6 for cleaning is made of only metal, and a negative polarity voltage having the same magnitude as the voltage applied to the back roller 5 for secondary transfer is applied from the power supply device 19. The power supply device 19 detects the output voltage of the power supply device 15 based on the output signal of the voltage detector 24.
Is a power supply device that outputs a negative polarity voltage having the same magnitude as the output voltage. It is also possible to branch from the same power supply device 15 and apply a negative polarity voltage of the same magnitude to the secondary transfer rear roller 5 and the cleaning rear roller 6.

The cleaning roller 11 comprises an elastic body 11b having a low resistance or a medium resistance formed around a core metal 11a, and the core metal 11a is grounded. By applying a voltage from the power supply device 19 to the cleaning back roller 6,
Cleaning back roller 6 and cleaning roller 11
A cleaning electric field is formed between the core metal 11a and the core metal 11a.
Due to the direction of the cleaning electric field, the negative polarity toner of the toner 18 remaining on the intermediate transfer belt 3 after the secondary transfer is transferred to the cleaning roller 11. The cleaning blade 20 removes the toner on the cleaning roller 11.

Here, the cleaning electric field induces positive charges from the cored bar 11a of the cleaning roller 11 which is grounded, and charges are injected into the toner during the cleaning action, so that the negative polarity toner has its charged polarity reversed. As a result, the toner has a positive polarity. Therefore, the cleaning roller 11 also functions as a residual toner charging member that reverses the charging polarity of the residual toner, and the cleaning back roller 6 also functions as a residual toner charging back electrode.

The secondary transfer and the cleaning are performed twice,
The negatively charged toner is transferred and left, and is subjected to the charge injection action twice, so that only the positive polarity toner remains on the intermediate transfer belt 3 after cleaning. Then, the positive polarity toner remaining on the intermediate transfer belt 3 after cleaning is reversely transferred to the photoconductor 1 by the primary transfer electric field.

A tension roller 7 is arranged between the secondary transfer back roller 5 and the cleaning back roller 6.
The tension roller 7 is a member that is closest to the secondary transfer back roller 5 and is in contact with the intermediate transfer belt 3. However, the tension roller 7 has a cored bar covered with an insulating resin such as polycarbonate, and the insulating resin insulates the intermediate transfer belt 3 from the casing. No current leaks from the tension roller 7 through the intermediate transfer belt 3 and does not affect the secondary transfer. The drive roller 4 is a back roller 5 for secondary transfer.
The current flowing away from the driving roller 4 through the intermediate transfer belt 3 is small, and its influence can be ignored.

According to this embodiment, two electrodes 6 are provided in the vicinity of the secondary transfer back roller 5 as the secondary transfer back electrode.
Since a voltage having the same polarity as the applied voltage of the rear transfer back roller 5 is applied, it is possible to reduce the leakage of the current for forming the secondary transfer electric field to other electrodes 5 through the intermediate transfer belt 3 as an intermediate transfer member. A constant-current-controlled voltage is applied to the back surface of the intermediate transfer belt 3 from the back electrode 5 for secondary transfer, and the secondary transfer is performed between the intermediate transfer belt 3 and the secondary transfer roller 14 as a secondary transfer member. Due to the formation of the electric field, the secondary transfer electric field changes greatly even if there is a current flowing through the transfer paper 16 as a recording medium or if the resistance of the intermediate transfer belt 3 or the secondary transfer roller 14 changes. Without doing so, it is possible to prevent the current flowing to the transfer paper 16 from becoming insufficient, and it is possible to always form a stable image on the transfer paper 16.

Further, according to this embodiment, since the cleaning back electrode 6 is applied with the same polarity as the voltage applied to the secondary transfer back electrode 5, that is, the voltage having the opposite polarity to the regular charging polarity of the toner, the cleaning is performed. Even if the cleaning roller 11 as a member is grounded, a cleaning electric field for transferring the toner remaining on the intermediate transfer belt 3 after the secondary transfer to the cleaning roller 11 can be formed, and the back electrode 6 for cleaning and the secondary transfer are formed. By reducing the potential difference from the back electrode 5 for cleaning, it is possible to reduce leakage of the current supplied from the back electrode 5 for secondary transfer to the back electrode 6 for cleaning through the intermediate transfer belt 3.

Further, according to this embodiment, since a voltage having the same polarity as that of the secondary transfer back electrode 5, that is, a polarity opposite to that of the toner, is applied to the cleaning back roller 6 as the back electrode for charging the residual toner, the residual toner is left. Even if the cleaning roller 11 as a toner charging member is grounded, a charge having a polarity opposite to that of the toner is induced in the cleaning roller 11 and injected into the toner, thereby reversing the charge polarity of the residual toner. It is possible to reversely transfer the reversed toner to the photoconductor 1 by the primary transfer electric field. Moreover, by applying a voltage having the same polarity as that of the secondary transfer back electrode 5 to the cleaning back roller 6, the potential difference between the cleaning back roller 6 and the secondary transfer back electrode 5 is reduced, and the secondary transfer back electrode 5 is reduced. It is possible to reduce leakage of current supplied from the back electrode 5 to the back roller 6 for cleaning through the intermediate transfer belt 3.

Further, according to this embodiment, since the contact portion between the tension roller 7 as a member contacting the intermediate transfer belt 3 and the intermediate transfer belt 3 and the housing are electrically insulated, the intermediate transfer is performed. It is possible to eliminate the electric current leaking from the tension roller 7 through the belt 3.

Further, according to this embodiment, since the back electrode 5 for secondary transfer and the other back electrode 6 adjacent thereto are made to have the same polarity and the same voltage, the current for forming the secondary transfer electric field is generated by the intermediate transfer belt. The leakage current to the other electrode 6 through 3 is completely eliminated, and a constant-current-controlled voltage is applied to the back surface of the intermediate transfer belt 3 from the back electrode 5 for secondary transfer, and the intermediate transfer belt 3 and the secondary transfer roller 14 A secondary transfer electric field is formed between the secondary transfer electric field and the transfer paper 16 even if there is a current flowing through the transfer paper 16 or the resistance of the intermediate transfer belt 3 or the secondary transfer roller 14 changes. Does not change significantly, it is possible to prevent a shortage of the current flowing to the transfer paper 16, and it is possible to always form a stable image on the transfer paper 16.

The present invention is not limited to the above embodiment, and for example, the cleaning member and the cleaning back electrode and the residual toner charging member and the residual toner charging back electrode may be separately configured. In addition, a separate photoconductor is provided for each color, and the toner images of the respective colors are superposed on the intermediate transfer member from the respective photoconductors and primary transfer is performed, whereby the color is superposed on the intermediate transfer member, and the toner of the color superposition is obtained. The present invention may be similarly applied to an image forming apparatus that collectively transfers an image onto a recording medium by secondary transfer.

[0034]

As described above, according to the present invention, the current for forming the secondary transfer electric field can be prevented from leaking to the electrode or member near the back electrode for secondary transfer through the intermediate transfer member, and recording It is possible to prevent the current flowing to the medium from becoming insufficient, and it is possible to always form a stable image on the recording medium. Further, it is possible to reduce the leakage of the current for forming the secondary transfer electric field to the cleaning back electrode through the intermediate transfer member.

Further, it is possible to prevent the current for forming the secondary transfer electric field from leaking to the residual toner charging rear electrode through the intermediate transfer member. In addition, the current for forming the secondary transfer electric field leaks out from a member that is held by the housing through the intermediate transfer member and is close to at least one of the upstream side and the downstream side of the back electrode for secondary transfer and that contacts the intermediate transfer body. Can be eliminated. Further, the current for forming the secondary transfer electric field can be completely prevented from leaking to other electrodes through the intermediate transfer member.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

[Explanation of symbols]

1 photoconductor 3 Intermediate transfer belt 4 drive roller 5 Back roller for secondary transfer 6 Rear roller for cleaning 7 Tension roller 9 Primary transfer roller 10, 13, 15, 19 Power supply 11 Cleaning roller 14 Secondary transfer roller 16 Transfer paper

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shin Chihara             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh (72) Inventor Ryuichi Tambe             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh (72) Inventor Yuji Sawai             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh (72) Inventor Mitsuru Takahashi             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh (72) Inventor Satoshi Uchida             1-3-3 Nakamagome, Ota-ku, Tokyo, stock             Company Ricoh F term (reference) 2H200 GA47 HA03 HB12 HB22 JA02                       JA28 JB10 JC04 JC12 JC13                       JC18 JC19 KA03 KA07 KA28                       LA24 LB03 LB15 LB35 LB38                       NA02 NA03 NA16 PA30

Claims (6)

[Claims] 1. An image carrier on which a toner image of a predetermined polarity is formed, an intermediate transfer member on which the toner image formed on the image carrier is primarily transferred, and an electric charge is formed on the back surface of the intermediate transfer member. The toner image transferred to the intermediate transfer member by the primary transfer is secondarily transferred to a recording medium by applying a voltage having the same polarity as the regular charging polarity of the toner, which is bonded to the intermediate transfer member, to the back surface of the intermediate transfer member. In an image forming apparatus having a back electrode for secondary transfer, the electrode for secondary transfer is provided to an electrode that is adjacent to at least one of upstream and downstream of the back electrode for secondary transfer and electrically joined to the intermediate transfer member. An image forming apparatus characterized in that a voltage having the same polarity as the applied voltage of the back electrode is applied. 2. An image carrier on which a toner image of a predetermined polarity is formed, an intermediate transfer member on which the toner image formed on the image carrier is primarily transferred, and an electric charge is formed on the back surface of the intermediate transfer member. The toner image transferred to the intermediate transfer member by the primary transfer is secondarily transferred to a recording medium by applying a voltage having the same polarity as the regular charging polarity of the toner, which is bonded to the intermediate transfer member, to the back surface of the intermediate transfer member. A secondary electrode for secondary transfer, a cleaning member for removing the toner remaining on the intermediate transfer member by secondary transfer from the intermediate transfer member, and an electric member provided on the rear surface of the intermediate transfer member so as to face the cleaning member. An image forming apparatus having a cleaning back electrode for transferring the toner remaining on the intermediate transfer member by secondary transfer to the cleaning member by applying a voltage to the back surface of the intermediate transfer member, An image forming apparatus comprising applying a toner of the same polarity of the voltage to the back electrode for the cleaning. 3. An image carrier on which a toner image having a predetermined polarity is formed, an intermediate transfer member on which the toner image formed on the image carrier is primarily transferred, and an electric charge is formed on the back surface of the intermediate transfer member. The toner image transferred to the intermediate transfer member by the primary transfer is secondarily transferred to a recording medium by applying a voltage having the same polarity as the regular charging polarity of the toner, which is bonded to the intermediate transfer member, to the back surface of the intermediate transfer member. By electrically bonding the back electrode for secondary transfer and the back surface of the intermediate transfer member and applying a voltage to the back surface of the intermediate transfer member, the charge polarity of the toner remaining on the intermediate transfer member in the secondary transfer is changed. In an image forming apparatus having a back electrode for charging residual toner, which reverses and transfers the toner to the image carrier at a primary transfer portion, applying a voltage having the same polarity as the toner to the back electrode for charging residual toner. An image forming apparatus characterized by. 4. An image carrier on which a toner image of a predetermined polarity is formed, an intermediate transfer member on which the toner image formed on the image carrier is primarily transferred, and an electric charge is formed on the back surface of the intermediate transfer member. The toner image transferred to the intermediate transfer member by the primary transfer is secondarily transferred to a recording medium by applying a voltage having the same polarity as the regular charging polarity of the toner, which is bonded to the intermediate transfer member, to the back surface of the intermediate transfer member. In an image forming apparatus having a secondary transfer back electrode, the intermediate transfer member, which is a member that is held by a casing and is in contact with the intermediate transfer member in proximity to at least one of upstream and downstream of the secondary transfer back electrode. The image forming apparatus is characterized in that a contact portion of the device is insulated from the casing. 5. The image forming apparatus according to claim 1, wherein the voltage applied to the back surface of the intermediate transfer member by the back electrode for secondary transfer is constant current controlled. An image forming apparatus comprising: 6. The image forming apparatus according to claim 1, wherein an electric field is formed on the back surface of the intermediate transfer member in the vicinity of at least one of the upstream side and the downstream side of the secondary transfer back surface electrode. An image forming apparatus characterized in that a voltage having the same polarity and the same magnitude as the voltage applied to the intermediate transfer member is applied to the electrode bonded to.