JPH11249456A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of restraining a transfer defect by charging a transfer rotating body so that the production of ozone is reduced when a toner image carrier with a toner image formed in order to form the toner image on a recording sheet and the transfer rotating body brought into contact with the toner image carrier in order to transfer the toner image on the toner image carrier are provided as an electrophotographic system. SOLUTION: As to this device A1, an electrifying belt 42, an exposing device 43, a developing device 44, a transfer belt 81 as a transfer rotating body, and a cleaning device 45 are arranged in a position facing a photoreceptor 41. The toner image formed on the photoreceptor 41 is electrostatically transferred to the recording sheet R by a charger 51 arranged in the position facing the photoreceptor 41 on the inside peripheral surface side of the belt 81. A voltage is impressed on the electrode layer of a charge sheet S1 brought into contact with the belt 81 and discharge is performed, and electrostatic charge is eliminated from the outside peripheral surface 811 of the transfer belt before transfer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an image forming apparatus for forming a toner image on a recording sheet by an electrophotographic image forming process.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, an electrostatic latent image formed on a photoreceptor is visualized by a developing device using, for example, toner. As a result, a toner image is formed on the photoconductor. The toner image is transferred to a recording sheet such as paper. In order to form a toner image of a plurality of colors (for example, four colors of yellow, magenta, cyan, and black) on a recording sheet, a so-called tandem type color image forming apparatus including a plurality of toner image forming units for forming toner images of respective colors is provided. Also in the apparatus, the toner images formed on the photoconductors by the respective toner image forming units are sequentially transferred to a recording sheet. In a so-called intermediate transfer body type color image forming apparatus, a toner image formed on a photoconductor is temporarily transferred to an intermediate transfer body such as an intermediate transfer belt, and then transferred to a recording sheet.

When a toner image is directly transferred from a photoreceptor to a recording sheet, for example, it is performed as follows. In a monochrome image forming apparatus, a tandem type image forming apparatus, or the like, when performing transfer by a transfer belt method, for example, a transfer belt made of a dielectric material is brought into contact with the photoconductor. The recording sheet is passed between the transfer belt and the photoreceptor, and the toner image on the photoreceptor is electrostatically transferred to the recording sheet by applying a charge having a polarity opposite to the toner charge to the back surface of the transfer belt by a corona charger or the like.

When transfer is performed by the transfer roller method, the transfer roller is kept in contact with the photosensitive member. The recording sheet is passed between the transfer roller and the photoconductor, and a bias voltage having a polarity opposite to that of the toner charge is applied to the transfer roller, whereby the toner image on the photoconductor is transferred to the recording sheet. In an image forming apparatus provided with an intermediate transfer member, the transfer of a toner image from a photoreceptor to an intermediate transfer member is performed, for example, as follows.

[0005] An intermediate transfer member such as an intermediate transfer belt is brought into contact with a photoreceptor, and a toner image on the photoreceptor is transferred to the intermediate transfer member by applying a charge having a polarity opposite to that of the toner to the back surface of the intermediate transfer member. You. When the toner image on the intermediate transfer member is transferred onto the recording sheet, the transfer belt method or the transfer roller method is used. In any case, the transfer rotator (transfer belt, transfer roller,
When the charged state of the surface of the intermediate transfer member is not uniform at the time of transfer, poor transfer is likely to occur. Therefore, it has been proposed to remove the charge on the surface of the transfer rotating member by a corona charger before the transfer.

When the transfer of the toner image is performed by using the transfer rotator brought into contact with the photosensitive member, the toner may adhere to the surface of the transfer rotator. This toner causes transfer failure and stains on the back surface of the recording sheet. Therefore, a cleaning device for removing toner on the surface of the transfer rotator may be provided. Since the toner is electrostatically attracted to the surface of the transfer rotator, a corona charger may be provided to remove the charge from the toner on the transfer rotator to facilitate the removal of the toner by the cleaning device.

[0007]

However, when the surface of the transfer rotator is neutralized by a corona charger in order to suppress transfer defects and stains on the back surface of the recording sheet, ozone is generated and the transfer rotator is disposed near the transfer rotator. Causes deterioration of the equipment. The same applies to the case where charge is removed from the toner on the transfer rotary member by a corona charger in order to facilitate the cleaning operation.

Accordingly, the present invention provides a toner image carrier on which a toner image is formed for forming a toner image on a recording sheet, and a toner image carrier for transferring a toner image on the toner image carrier. It is an object of the present invention to provide an electrophotographic image forming apparatus including a transfer rotating body that comes into contact with the image forming apparatus, wherein the transfer rotating body is charged with less generation of ozone, and transfer defects and recording sheet stains can be suppressed accordingly. And

[0009]

According to the present invention, there is provided an electrophotographic image forming apparatus for forming a toner image on a recording sheet, wherein an electrostatic latent image is formed on the recording sheet. A toner image carrier on which a toner image is formed by developing an electrostatic latent image; a transfer rotator that contacts the toner image carrier to transfer the toner image on the toner image carrier; A charged sheet that partially contacts the body, including an electrode layer and an insulating layer provided on the transfer rotator side of the electrode layer, supported at an upstream end in the rotation direction of the transfer rotator, There is provided an image forming apparatus comprising: a charging sheet for bringing at least a part of a downstream side of an upstream end portion into contact with the transfer rotating body; and a power supply capable of applying a voltage to the electrode layer.

The image forming apparatus of the present invention is for forming a toner image on a recording sheet such as paper, an OHP sheet, cloth, or the like by an electrophotographic image forming process. The image forming apparatus of the present invention can be used, for example, as a copier, a printer, a facsimile machine, a multifunction machine thereof, and the like. The image forming apparatus forms a toner image on a recording sheet in the following electrophotographic image forming process. First, an electrostatic latent image corresponding to the finally formed toner image is formed, and the electrostatic latent image is developed and visualized to form a toner image. Then, the toner image is directly transferred to a recording sheet. Alternatively, the toner image is temporarily transferred to an intermediate transfer member, and then the toner image on the intermediate transfer member is secondarily transferred to a recording sheet. An image forming apparatus that transfers a toner image directly to a recording sheet can be used as a monochrome image forming apparatus, an image forming apparatus of a transfer drum type, or a color image forming apparatus of a tandem type. Further, an image forming apparatus of a type in which the image is temporarily transferred to an intermediate transfer body can be used as a so-called intermediate transfer body type color image forming apparatus.

The image forming apparatus includes a toner image carrier, a transfer rotator in contact with the toner image carrier, a charged sheet partially contacting the transfer rotator, and a power supply capable of applying a voltage to an electrode layer of the charged sheet. . An electrostatic latent image is formed on the toner image carrier, and then the electrostatic latent image is developed to form a toner image. Examples of the toner image carrier include a photoconductor. Examples of the shape of the toner image carrier include a drum shape, a roller shape, and an endless belt shape.

A transfer rotating body is in contact with the toner image carrier. Examples of the shape of the transfer rotator include a roller shape, a drum shape, and an endless belt shape. The toner image on the toner image carrier may be directly transferred to the recording sheet through a recording sheet between the toner image carrier and the transfer rotating body. The toner image on the toner image carrier may be once transferred to a transfer rotating body and then transferred to a recording sheet. When the toner image is once transferred to the transfer rotator, the transfer rotator functions as a so-called intermediate transfer member.

The toner image on the toner image carrier can be transferred onto a recording sheet passing between the toner image carrier and the transfer rotary member as follows. For example, the transfer rotator may be in the form of a drum or an endless belt, and the toner image on the toner image carrier may be applied to the recording sheet by applying a charge having a polarity opposite to that of the toner charge to the inner peripheral surface side of the transfer rotator using a corona charger or the like. Can be transcribed. Further, for example, by applying a bias voltage having a polarity opposite to that of the toner charge to the transfer rotating member, the toner image on the toner image carrier can be transferred to the recording sheet.

The toner image on the toner image carrier can be transferred onto the transfer rotating member as follows. For example,
The toner image on the toner image carrier can be transferred onto the transfer rotator by providing the transfer rotator with a drum shape or an endless belt shape and applying a charge having a polarity opposite to that of the toner charge to the inner peripheral surface side of the transfer rotator. The toner image on the transfer rotator can be transferred onto the recording sheet in the same manner as when the toner image on the toner image carrier is transferred onto the recording sheet. Thus, the charged sheet is brought into contact with the transfer rotating body used for transferring the toner image. A part of the charged sheet is brought into contact with the transfer rotator. The charging sheet is a sheet having a laminated structure of two or more layers including an electrode layer and an insulating layer, and can discharge the electrode layer by applying a voltage to the electrode layer to charge the transfer rotating body. That is, the charge is removed from the transfer rotator,
The transfer rotator can be charged. It is also possible to charge toner and the like on the transfer rotating body.

The charged sheet may be formed, for example, on the outer peripheral surface of the transfer rotating body. When the charged sheet is brought into contact with the outer peripheral surface of the transfer rotator, the charge can be removed from the outer peripheral surface of the transfer rotator before the transfer. This makes the charged state of the outer peripheral surface of the transfer rotator uniform even when the toner image on the toner image carrier is directly transferred to the recording sheet and when the toner image is transferred to the transfer rotator. And good toner image transfer.

When a cleaning device for removing toner is provided in preparation for a case where toner adheres to the outer peripheral surface of the transfer rotating body, the charged sheet is placed at a position where the transfer rotating body and the toner image carrier come into contact with each other. (Transfer position) Even if the transfer rotary member is brought into contact with the outer peripheral surface of the transfer rotary member on the downstream side in the rotational direction of the transfer rotary member and on the upstream side of the cleaning device, the transfer rotation is performed on the downstream side of the cleaning device and upstream of the transfer position You may make it contact a body outer peripheral surface. When the charged sheet is brought into contact with the outer peripheral surface of the transfer rotator downstream of the transfer position and upstream of the cleaning device, static electricity can be removed from the outer peripheral surface of the transfer rotator as described above, and poor transfer can be suppressed. Electric charge can also be removed from the toner on the peripheral surface, and the electrostatic attraction of the toner to the transfer rotating body can be reduced. Thus, the toner can be easily removed by the cleaning device.

Since the transfer rotator is charged by the charging sheet, the discharge distance can be shortened and the generation of ozone can be suppressed accordingly, as will be described later, as compared with the conventional corona charger. As a result, it is possible to suppress deterioration of the transfer rotator, devices and members arranged near the transfer rotator. The transfer rotator is charged by applying a voltage to the electrode layer of the charging sheet and discharging the electrode layer as described above.

The electrode layer of the charging sheet is connected to a power supply. Examples of the power supply include a power supply to which a DC voltage can be applied, a power supply to which an alternating voltage (oscillation voltage) can be applied, and a power supply to which an alternating voltage can be superimposed and applied to the DC voltage. . Examples of the alternating voltage include a pulse voltage, a sine wave voltage, and a triangular wave voltage. In any case, the power supply
The output voltage may be variable. The voltage applied to the electrode layer may be changed according to, for example, environmental conditions such as temperature and humidity.

Hereinafter, the charging sheet will be further described. In the following description, the “rotation direction of the transfer rotator” may be simply referred to as the “rotation direction”. The “upstream side in the rotation direction of the transfer rotator” may be simply referred to as “upstream side”. The “downstream side in the rotation direction of the transfer rotating body” may be simply referred to as “downstream side”. The charging sheet is a sheet having a larger area than the thickness. The charged sheet may be a flexible sheet having self-retention and elasticity, or a thin sheet (film) having less self-retention and less elasticity.

A part (typically, a part of the surface) of the charged sheet is brought into contact with the transfer rotating body. The upstream end of the charged sheet is supported. The upstream end of the charged sheet is supported at a predetermined distance from the transfer rotator. A part (typically, part of the surface) downstream of the supported upstream end of the charged sheet is brought into contact with the transfer rotating body. The thickness of the charged sheet is preferably about several tens μm to several hundreds μm. If the thickness of the charged sheet is too large, the adhesion to the transfer rotating body is deteriorated, and the charged sheet cannot be brought into contact with the shape of the transferred rotating body. If the thickness of the charged sheet is too small, the strength becomes weak.

The charged sheet is a sheet having a laminated structure of two or more layers including an electrode layer and an insulating layer provided on the transfer rotating body side of the electrode layer. At least one insulating layer is disposed between the electrode layer and the transfer rotating body. The charged sheet may have a laminated structure of three or more layers by further providing another layer on the transfer rotating body side of the insulating layer. The charged sheet may have a laminated structure of three or more layers by further providing another layer on the side opposite to the transfer rotating body of the electrode layer.

The electrode layer may be made of a conductive material, or may be made of an electric resistance material (semiconductive material). Such conductive materials include, for example, chromium, copper,
Examples include metals such as gold, platinum, tungsten, indium, and titanium, ITO, and carbon. As such a resistance material, for example, tetrafluoroethylene resin, ethylene-tetrafluoroethylene copolymer (PETF)
E), a conductive material such as carbon dispersed in a fluororesin such as polyvinylidene fluoride (PVdF), or a conductive material dispersed in a synthetic resin such as polyimide, polyester, polyether, polyamide, polyolefin, or polycarbonate. And conductive rubber dispersed in synthetic rubber such as urethane rubber.
When the electrode layer is made of, for example, a resistance material, its volume resistance is 10 Ω · cm or more (preferably 1 Ω · cm).
0 ³ Ω · cm or more), it is possible to stably discharge from the electrode layer even in a high-humidity environment and to suppress abnormal dot discharge from the electrode layer. in this case,
The volume resistance of the resistive material should be 10 ⁸ so that the voltage applied to the electrode layer for discharging from the electrode layer does not increase significantly.
It is preferably set to Ω · cm or less (preferably, 10 ⁷ Ω · cm or less). In the electrode layer, only the portion including the discharge point may be formed of a resistive material, and the other portions may be formed of a conductive material. Also in this case, it is possible to stably discharge from the electrode layer in a high humidity environment and to suppress abnormal dot discharge from the electrode layer.

Since a part of the charged sheet is brought into contact with the transfer rotator, the downstream end of the electrode layer can be disposed close to the transfer rotator without making contact with the transfer rotator. The electrode layer can be separated from the transfer rotating body by at least the thickness of the insulating layer. Therefore, the discharge distance can be shortened accordingly, and generation of ozone can be suppressed. When the shortest distance between the electrode layer and the transfer rotator is 11 μm or more according to Paschen's rule, good discharge can be performed from the electrode layer. This allows
It is possible to suppress abnormal discharge and uneven charging of the transfer rotating body due to abnormal discharge. The shortest distance between the electrode layer and the transfer rotator is preferably 100 μm or less in order to shorten the discharge distance and suppress the generation of ozone. By reducing the generation of ozone, it is possible to suppress the deterioration of the charged sheet, the transfer rotator, and the devices and members disposed around these by the ozone. Therefore, the shortest distance between the transfer rotator and the electrode layer is preferably 11 μm to 100 μm. The shortest distance can be adjusted by the thickness of the insulating layer provided on the transfer rotating body side of the electrode layer.

In order to suppress discharge from the electrode layer to devices and members other than the transfer rotator disposed near the charged sheet, the surface portion of the electrode layer opposite to the transfer rotator is provided with a second surface.
May be covered with an insulating layer. Further, in order to prevent a discharge from a side end of the electrode layer in a direction crossing the rotation direction of the transfer rotator, the electrode layer may not be provided at a side end (ear) of the charged sheet.

When a voltage is applied to the electrode layer of the charged sheet,
The portion of the charged sheet downstream of the supported upstream end is electrostatically attracted toward the transfer rotating member. Further, the downstream portion of the charged sheet is pulled downstream by the rotation of the transfer rotator. As a result, the downstream portion of the charged sheet comes into contact with the transfer rotator while being bent or deformed according to the shape of the transfer rotator. Therefore, even if the peripheral surface of the rotating transfer rotator undulates or vibrates, the downstream portion of the charged sheet bends or deforms in response to the undulation and the like, and contacts with the transfer rotator. The contact state can be maintained. Thereby, the distance between the electrode layer of the charging sheet and the transfer rotating body is stabilized, the discharge from the electrode layer can be performed stably, and the transfer rotating body can be uniformly charged.

The charged sheet may be described in the following (A), (B) and (C). (A) The downstream end of the electrode layer may have a shape in which irregularities are arranged in a direction crossing the rotation direction of the transfer rotator (the direction of the rotation axis of the transfer rotator). The unevenness is formed by the length of each part of the electrode layer in the rotation direction.

In this case, the projection at the downstream end of the electrode layer of the charged sheet is the discharge point. When the downstream end has such a shape in which the unevenness is lined up, compared to the case where the downstream end of the electrode layer is linear, adhesion of foreign matter such as paper dust and toner, unevenness of the electrode layer surface state, and environmental change The discharge point is also stabilized by such factors, so that uniform and stable discharge can be performed from the electrode layer. If the pitch of the projections in the direction of the rotation axis of the transfer rotating body is too large, uneven charging (uneven potential) of the transfer rotating body occurs. It is no different from when it is linear. Therefore, the pitch of the convex portions is several tens μm to several tens μm.
It is preferably about 00 μm. Examples of the concavo-convex shape include a comb shape and a saw-tooth shape. (B) The downstream end of the electrode layer may protrude further downstream than another layer provided on the transfer rotating body side from the electrode layer of the charged sheet. The other layer includes the insulating layer.
When another layer is provided on the transfer rotating body side with respect to the insulating layer, the electrode layer protrudes downstream from the downstream end of the insulating layer and the other layer.

In this case, the discharge is mainly generated from the surface of the protruding end of the electrode layer protruding downstream from the insulating layer, facing the transfer rotating body. In this case, discharge from the electrode layer is facilitated, and uniform and stable discharge can be performed accordingly. In order to cause a stable discharge from the electrode layer, the amount of protrusion L [mm] of the electrode layer to the downstream side may be set so that the proximity discharge time T becomes 0.002 to 0.3 [sec]. Preferably, 0.005 to 0.1 [sec]
It is more preferable to set so that The proximity discharge time T [sec] is expressed by V [m
m / sec], it is a value (= L / V) obtained by dividing the protrusion amount L by the peripheral surface moving speed V.

The end of the electrode layer protruding downstream from the insulating layer may be warped so that the distance between the end and the transfer rotary member increases as going downstream. By doing so, abnormal discharge from the downstream end (the downstream end surface or the edge portion at the downstream end) of the protruding end of the electrode layer can be suppressed, and the surface discharge from the protruding end can be stabilized accordingly. Can be done.

The downstream end face of the protruding end of the electrode layer may be covered with an insulator. Also in this case, the abnormal discharge from the downstream end of the protruding end of the electrode layer can be suppressed, and the surface discharge from the protruding end can be stably performed accordingly. Examples of such an insulator material include a fluorine resin such as tetrafluoroethylene resin, a synthetic resin such as polyimide, polyester, and polyether, and a synthetic rubber such as urethane rubber.

In order to prevent the protruding end of the electrode layer from bending or deforming in the direction of the transfer rotator, a reinforcing layer may be provided on the surface of the electrode layer opposite to the surface facing the transfer rotator. By preventing the projecting end of the electrode layer from bending or deforming in the direction of the transfer rotating body, the distance between the projecting end having a discharge surface and the transfer rotating body can be kept constant. In other words, the discharge distance can be reduced. Can be kept constant, and a stable discharge can be performed from the electrode layer accordingly. Instead of or along with providing such a reinforcing layer, the thickness of the electrode layer itself may be increased. Further, in order to suppress discharge from the electrode layer to devices and members other than the transfer rotator disposed near the above-described charged sheet, a second electrode layer is provided on a surface portion of the electrode layer opposite to the transfer rotator. The insulating layer may have the function of the reinforcing layer. (C) The electrode layer may be divided into two or more in a direction crossing the rotation direction of the transfer rotator (direction of the rotation axis of the transfer rotator). In this case, a voltage may be independently applied to each of the divided electrode layer portions. When the electrode layer is divided into three or more in the direction of the rotation axis, the divided electrode layer portions may be divided into two or more groups so that a voltage can be independently applied to each group.

When a plurality of types of toner images having different widths in the rotation axis direction of the transfer rotator are formed on the toner image carrier, the electrode layer is divided into two or more in accordance with the width of each toner image in the rotation axis direction. I just need. With this configuration, it is possible to charge only the peripheral surface area of the transfer rotating body peripheral area facing the toner image on the toner image carrier.

The above description in (A), (B) and (C) may be a combination of two or more. Specific structural examples of the charged sheet are shown in the following (1) to (3). (1) The charged sheet is a sheet having a laminated structure of two or more layers including the electrode layer and an insulating layer provided on the transfer rotator side of the electrode layer, even if a part of the insulating layer is brought into contact with the transfer rotator. Good. For example, the charged sheet may be a sheet having a two-layer structure in which the electrode layer and an insulating layer provided on the transfer rotator side of the electrode layer are stacked.

In this case, the discharge distance can be adjusted by adjusting the thickness of the insulating layer. The charged sheet may be formed by separately forming the electrode layer and the insulating layer and then overlapping them. When the electrode layer is made of a resistance material as described above,
These electrode layer and insulating layer may be integrally formed of a resistance gradient composite material. When the electrode layer is made of a resistive material, the resistive material may be applied on the insulating layer to form the electrode layer. When the electrode layer is made of a conductive material such as a metal as described above, the electrode layer may be formed on the insulating layer by using a film forming technique such as sputtering. Further, an electrode layer having a predetermined pattern may be formed on the insulating layer by using both a film forming technique such as sputtering and an etching technique such as photoetching. The charged sheet described in (2) and (3) described later can be formed in the same manner as described above.

By providing an insulating layer on the side of the charged sheet that comes into contact with the transfer rotating body, it is possible to prevent the electrode layer from being damaged, and to perform stable discharge from the electrode layer for a long period of time. It is preferable that the insulating layer of the charged sheet that is in sliding contact with the transfer rotator be made of a material having excellent slidability and wear resistance. Examples of such an insulating layer material include fluorine resin such as tetrafluoroethylene resin, synthetic resin such as polyimide, polyester, and polyether, and synthetic rubber such as urethane rubber and silicon rubber.

As described above, the downstream end of the electrode layer may have a shape in which irregularities are arranged in the rotation axis direction of the transfer rotator. As described above, the downstream end of the electrode layer may protrude further downstream than the downstream end of the insulating layer of the charged sheet.
As described above, the electrode layer may be divided into two or more in a direction crossing the rotation direction of the transfer rotator. (2) The charging sheet includes the electrode layer (hereinafter, referred to as a “first electrode layer”), an insulating layer provided on the transfer rotator side of the first electrode layer, and a second electrode provided on the transfer rotator side of the insulating layer.
As a sheet having a laminated structure of three or more layers including an electrode layer, a part of the second electrode layer may be brought into contact with the transfer rotating body. For example, the charged sheet has a three-layer structure in which the first electrode layer, an insulating layer provided on the transfer rotator side of the first electrode layer, and a second electrode layer provided on the transfer rotator side of the insulating layer are stacked. It may be.

In this case, the discharge distance of the first electrode layer can be adjusted by adjusting the thickness of the insulating layer and the second electrode layer. The second electrode layer is also connected to a power supply capable of applying a voltage to the second electrode layer, like the first electrode layer. The second electrode layer is also similar to the first electrode layer,
It may be made of a conductive material or may be made of an electric resistance material. As a power supply capable of applying a voltage to the second electrode layer, similarly to a power supply capable of applying a voltage to the first electrode layer, for example, a power supply capable of applying a DC voltage and an alternating voltage (oscillation voltage), and an alternating voltage superimposed on the DC voltage And a power source that can apply a power source. The power supply may be a variable output voltage power supply. Similarly to the voltage applied to the first electrode layer, the voltage applied to the second electrode layer may be changed according to environmental conditions and the like.

When the charged sheet has a laminated structure of three or more layers including the first electrode layer, the insulating layer, and the second electrode layer which is brought into contact with the transfer rotating member, the charged sheet is formed by the above-described electrode layer and the transfer rotating member. Since the distance between the second electrode layer that generates electrostatic attraction and the transfer rotating body is shorter than when a laminated structure including two or more layers including an insulating layer that is in contact with the body, the charged sheet can be transferred to the transfer rotating body. Can be increased in electrostatic attraction force.

As described above, when the charged sheet has a laminated structure of three or more layers including the first electrode layer, the insulating layer, and the second electrode layer that is brought into contact with the transfer rotating member, both the first and second electrode layers are used. You may make it discharge. Alternatively, the charged sheet is electrostatically attracted to the transfer rotator by discharging only from the first electrode layer not in contact with the transfer rotator and not discharging from the second electrode layer in contact with the transfer rotator. It may be used only for.

The discharge from the first electrode layer is mainly generated from the downstream end of the first electrode layer. In addition, the discharge from the second electrode layer mainly occurs at a position slightly upstream from a portion where the second electrode layer and the transfer rotating body are in contact with each other, in other words, at a position where the second electrode layer and the transfer rotating body are close to each other. Done. Therefore, the discharge position of the second electrode layer is on the upstream side of the discharge position of the first electrode layer.

In the case where the charged sheet has a laminated structure of three or more layers including the first electrode layer, the insulating layer, and the second electrode layer which is brought into contact with the transfer rotator, for example, the transfer rotator is formed as follows. Can be charged. For example, it is possible to charge the transfer rotator by discharging from the first electrode layer after removing electricity from the transfer rotator by discharging from the second electrode layer. By doing so, the transfer rotator can be uniformly charged. Alternatively, after the transfer rotator is precharged by the discharge from the second electrode layer, the transfer rotator can be further charged by the discharge from the first electrode layer. Even in this case, the transfer rotator can be uniformly charged. Alternatively, after preliminarily discharging the transfer rotator by discharging from the second electrode layer, the transfer rotator can be further discharged by discharging from the first electrode layer. Even in this case, the charge can be uniformly removed from the transfer rotary member.

As described above, the downstream end of the first electrode layer may have a shape in which irregularities are arranged in the direction of the rotation axis of the transfer rotating member. As described above, the downstream end of the first electrode layer may protrude further downstream than the downstream ends of the insulating layer and the second electrode layer. As described above, the first electrode layer may be divided into two or more in a direction crossing the rotation direction of the transfer rotator. Similarly to the first electrode layer, the second electrode layer may be divided into two or more in the direction crossing the rotation direction of the transfer rotator (the direction of the rotation axis of the transfer rotator).

When the power supply connected to the first electrode layer of the charging sheet is a DC power supply and the power supply connected to the second electrode layer is also a DC power supply, these DC power supplies may be a common power supply. When the power supply connected to the first electrode layer and the second electrode layer is a common DC power supply, the same voltage may be applied to the first electrode layer and the second electrode layer,
Alternatively, different voltages may be applied by, for example, dividing the voltage with a resistor.

A DC voltage having the same polarity is applied between the first electrode layer of the charged sheet and the transfer rotator, and between the second electrode layer and the transfer rotator. Is discharged from the first electrode layer by the discharge from the second electrode layer before the foreign matter such as toner and paper dust on the transfer rotating body reaches the contact portion between the charged sheet and the transfer rotating body. In addition, it can be charged to the same polarity as that of the second electrode layer, or can be discharged from the foreign matter, and the electrostatic attraction of the foreign matter to the first and second electrode layers can be prevented.

When a voltage in which an alternating voltage (oscillation voltage) is superimposed on a DC voltage is applied to the second electrode layer of the charged sheet, foreign substances such as toner and paper dust are generated by the rotation of the transfer rotating member. Even if it arrives at the contact site, it is possible to suppress aggregation of foreign matter at the contact site. Therefore, such agglomerates enter between the charged sheet and the transfer rotating member, and the distance between the first electrode layer and the transfer rotating member peripheral surface and the distance between the second electrode layer and the transfer rotating member peripheral surface vary. Can be suppressed, and a stable discharge from the first electrode layer and the second electrode layer can be made accordingly. (3) The electret is a sheet having a laminated structure of three or more layers including the electrode layer, an insulating layer provided on the transfer rotator side of the electrode layer, and an electret layer provided on the transfer rotator side of the insulating layer. A part of the layer may be brought into contact with the transfer rotating body. For example, the charging sheet may be a sheet having a three-layer structure in which the electrode layer, an insulating layer provided on the transfer rotator side of the electrode layer, and an electret layer provided on the transfer rotator side of the insulating layer are stacked.

In this case, the discharge distance can be adjusted by the thickness of the insulating layer and the electret layer. The electret layer is made of an electret material and has an electric charge semipermanently, so that the charged sheet can be electrostatically attracted in the direction of the transfer rotating body without applying a voltage. Therefore,
As compared with the image forming apparatus having a three or more-layered charged sheet including the first electrode layer, the insulating layer, and the second electrode layer to be brought into contact with the transfer rotary member described in the above (2), the second electrode layer The image forming apparatus can be made compact because no power supply is required.

As described above, the downstream end of the electrode layer may have a shape in which irregularities are arranged in the direction of the rotation axis of the transfer rotator. As described above, the downstream end of the electrode layer may protrude downstream from the downstream end of the insulating layer and the electret layer. As described above, the electrode layer may be divided into two or more in the direction crossing the rotation direction of the transfer rotator (the direction of the rotation axis of the transfer rotator).

[0048]

Embodiments of the present invention will be described below with reference to the drawings. (1) FIG. 1 shows a schematic configuration diagram of an example of an image forming apparatus according to the present invention. The image forming apparatus A1 shown in FIG. 1 can form a toner image on the recording sheet R by an electrophotographic image forming process.

In this embodiment, the image forming apparatus A1 includes a photosensitive member 41 as a toner image carrier on which an electrostatic latent image is formed and then the electrostatic latent image is developed to form a toner image. The photoreceptor 41 has a drum shape, and is driven to rotate counterclockwise in the figure by a driving device (not shown). At a position facing the peripheral surface 411 of the photoconductor 41, a charging brush 42, a laser exposure device 43, a developing device 44, a transfer belt 81 as a transfer rotating body, and a cleaning device 45 are sequentially arranged.

The charging brush 42 can uniformly charge the peripheral surface 411 of the photoreceptor. The laser exposure device 43
An electrostatic latent image can be formed on the peripheral surface 411 of the photoconductor by the irradiating laser light. The developing device 44 includes a case 442 by a developing roller 441 facing the photoconductor peripheral surface 411.
The electrostatic latent image on the peripheral surface 411 can be developed and visualized by using the toner stored therein to form a toner image. In this example, a positively charged toner is used for development.

The transfer belt 81 is an endless belt wound around three rollers r1, r2 and r3. The outer peripheral surface 811 of the transfer belt 81 is
1 is in contact. The roller r1 can be rotationally driven clockwise in the figure by a driving device not shown, and the transfer belt 81 can be rotated clockwise in the figure. The cleaning device 45 uses a cleaning blade 451 that comes into contact with the photoconductor peripheral surface 411 to move the peripheral surface 41.
1 can be scraped off and collected.

The image forming apparatus A1 includes a fixing device 46 for fixing the toner image transferred onto the recording sheet R. The fixing device 46 includes two opposing fixing rollers 4.
61 and 462 are provided. A heat source (not shown) is provided for the fixing roller 461, and the fixing roller 461 is heated to a predetermined fixing temperature during fixing. Further, the fixing roller 462 is pressed toward the fixing roller 481. By passing the recording sheet R between both rollers and applying heat and pressure to the unfixed toner image,
The toner image can be fixed on the recording sheet R.

Here, the transfer belt 81 will be further described. The transfer belt 81 is made of polyvinylidene fluoride (PVDF) in this example. As a transfer belt material,
In addition, for example, a resin such as polycarbonate (PC),
Rubber such as chloroprene rubber and urethane rubber can be employed. The transfer belt 81 is an insulator having a volume resistance of 10 ¹² to 10 ¹⁶ Ω · cm in this example. The transfer belt may be semiconductive with a volume resistance of 10 ⁶ to 10 ¹² Ω · cm.

A transfer charger 51 is arranged on the inner peripheral surface side of the transfer belt 81 at a position facing the photosensitive member 41. By applying a charge to the inner peripheral surface side of the transfer belt 81 by the transfer charger 51, the toner image on the photosensitive member peripheral surface 411 is transferred onto the recording sheet R passed between the transfer belt 81 and the photosensitive member peripheral surface 411. Electrotransfer can be performed. The cleaning device 47 is disposed on the outer peripheral surface side of the transfer belt 81 at a position facing the roller r2. The cleaning device 47 has a cleaning blade 471 that comes into contact with the transfer belt 81, and can scrape and remove toner on the transfer belt 81.

On the outer peripheral surface side of the transfer belt 81, a charging device D1 is further arranged. The charging device D1 is disposed downstream of the cleaning device 47 in the rotation direction of the transfer belt 81, and upstream of a position (transfer position) where the transfer belt 81 and the photoconductor 41 are in contact with each other. In addition,
In the following description of the image forming apparatus A1, the rotation direction of the transfer belt 81 may be simply referred to as “rotation direction”. “Upstream in the rotation direction of the transfer belt 81”
May be simply described as “upstream side”. “Downstream side in the rotation direction of the transfer belt 81” may be simply referred to as “downstream side”.

The charging device D1 is provided on the outer peripheral surface 811 of the transfer belt.
Sheet S1 and power supply PS, some surfaces of which are in contact with
1 is provided. FIG. 2 shows a schematic perspective view of the charging sheet S1. FIG. 2 shows only a part of the transfer belt 81. In FIG. 2, the rotation direction of the transfer belt 81 is indicated by “α”.

The charged sheet S1 is a sheet whose area is sufficiently larger than its thickness. The charging sheet S1 is a substantially rectangular flexible sheet in this example. Charge sheet S1
Is supported by support members 71 and 72 with an upstream end thereof separated from the transfer belt 81 by a predetermined distance. The upstream end of the charging sheet S <b> 1 is not in contact with the transfer belt 81. The charging sheet S <b> 1 is bent, and a part of the surface on the downstream side is in contact with the transfer belt 81. Charge sheet S1
Is at a position facing the grounded roller r3.
Is in contact with

The charged sheet S1 is a sheet composed of two layers, the electrode layer 101 and the insulating layer 31. The insulating layer 31 is arranged on the side facing the transfer belt 81, and a part of the surface of the insulating layer 31 is in contact with the transfer belt 81. Electrode layer 101
Is made of an electric resistance material in this example. In this embodiment, the electric resistance material is obtained by dispersing carbon black in polyimide. The volume resistance of the electrode layer 101 is 10 ³ to 10 ⁷
Ω · cm.

The power supply PS1 is connected to the electrode layer 101 via a switch (not shown). The power supply PS1 is a variable output voltage DC power supply. In this embodiment, the insulating layer 31 is made of polyimide having excellent wear resistance and slidability. The thickness of the insulating layer 31 is set to 80 μm in this example.
When a voltage is applied from the power supply PS1 to the electrode layer 101 of the charging sheet S1, the electrode sheet 101 can be discharged,
The transfer belt peripheral surface 811 or the toner on the transfer belt peripheral surface 811 can be charged. Therefore, it is possible to remove the charge from the transfer belt 81 or remove the charge from the toner on the transfer belt 81. Transfer belt 81 and transfer belt 81
The amount of charge on the upper toner can be easily adjusted by adjusting the voltage applied to the electrode layer 101. Increasing the absolute value of the applied voltage can increase the amount of charge. The discharge from the electrode layer 101 is mainly caused by the electrode layer 101
Is made from the downstream end face.

The image forming apparatus A1 can form a toner image on the recording sheet R as follows. First, the photoconductor peripheral surface 411 is sequentially charged by the charging brush 42. An electrostatic latent image is sequentially formed on the charged photoconductor peripheral surface 411 by laser light from the exposure device 43, and the electrostatic latent image is developed by a developing device 44 using toner. As a result, a toner image in which the electrostatic latent image is visualized can be formed on the peripheral surface 411 of the photoconductor. The toner image is transported by a sheet transport mechanism (not shown),
The image is sequentially transferred by the transfer charger 51 onto the recording sheet R sent between the transfer belt 81 and the peripheral surface 411.

Here, before the transfer belt outer peripheral surface 811 reaches the transfer position, the charge is removed by the charging device D1.
As a result, it is possible to suppress a transfer failure caused by uneven charging state of each portion of the outer peripheral surface 811 of the transfer belt and to transfer the toner image to the recording sheet R satisfactorily. The toner remaining on the photosensitive member peripheral surface 411 without being transferred to the recording sheet R is removed by the cleaning device 45 and collected. Further, the toner adhered to the transfer belt 81 is also removed and collected by the cleaning device 47.

On the other hand, the recording sheet R on which the toner image has been transferred
Is transported to the fixing device 46, and the toner image is fixed on the recording sheet R. In the image forming apparatus A1, the charging device D1 including the charging sheet S1 removes the charge from the transfer belt 81.
Therefore, there are the following advantages. Since a part of the surface of the charged sheet S <b> 1 is brought into contact with the transfer belt 81, the electrode layer 101 can be easily arranged close to the transfer belt 81. Therefore, the discharge distance can be shortened and the generation of ozone can be suppressed accordingly, as compared with the conventional case where the charge is removed by a corona charger. This can reduce the deterioration of the charged sheet S1, the transfer belt 81, and the devices and members disposed around the charged sheet S1 and the transfer belt 81 due to ozone. Further, the arrangement space of the charged sheet S1 can be made smaller than that of the corona charger. Therefore, the entire image forming apparatus can be made compact accordingly.

Since the electrode layer 101 of the charged sheet S1 does not slide with respect to the transfer belt 81, the electrode layer 101 is not damaged and a stable discharge can be performed for a long period of time. Further, since the electrode layer 101 does not contact the transfer belt 81, foreign substances such as toner and paper dust can be prevented from adhering to the electrode layer, and stable discharge can be performed for a long period of time. Since the insulating layer 31 that slides on the transfer belt 81 is made of a material having excellent wear resistance and slidability,
The insulating layer 31 is hardly worn. Therefore, the charging device D1
Accordingly, the charge can be removed from the transfer belt 81 for a long time.

When a voltage is applied to the electrode layer 101, an electrostatic attraction force is applied to the electrode layer 101 in the direction of the transfer belt 81.
The downstream side surface of the charging sheet S1 is in close contact with the transfer belt 81. The electrostatic attraction of the charged sheet S1 in the direction of the transfer belt 81 can be easily adjusted by adjusting the voltage applied to the electrode layer 101. Increasing the absolute value of the applied voltage can increase the electrostatic attraction force. The downstream side of the charged sheet S1 is pulled to the downstream side by rotating the transfer belt 81 in a state of being electrostatically attracted to the transfer belt 81, so that the charged sheet S1 comes into contact with the transfer belt 81 without sagging or wrinkling. . Further, the charged sheet S <b> 1 contacts the transfer belt 81 according to the surface shape of the transfer belt 81. Thus, even if the transfer belt 81 undulates as the transfer belt 81 rotates, the distance between the transfer belt 81 and the downstream end face serving as the main discharge point of the electrode layer 101 can be kept constant. As a result, the discharge distance can be kept constant, a more stable discharge can be performed from the electrode layer 101, and the transfer belt 81 can be charged uniformly. Further, as described above, since the insulating layer 31 is hardly worn, the discharge distance can be kept constant for a long period of time. Therefore, stable charging can be performed by the charging sheet S1 for a long time. Furthermore, since the thickness of the insulating layer 31 is set in the range of 11 to 100 μm as described above, good discharge can be performed from the electrode layer 101 and generation of ozone can be reduced. In the charging sheet S1, the discharge distance can be easily adjusted by the thickness of the insulating layer 31.

As described above, since the electrode layer 101 is made of a resistance material having a volume resistance of 10 ³ to 10 ⁷ Ω · cm, abnormal dot discharge can be prevented, and the transfer belt 81 due to the dot discharge and the surrounding area of the transfer belt 81 can be prevented. It is possible to prevent dielectric breakdown of devices and members to be arranged. (2) FIG. 3 shows a schematic configuration diagram of another example of the image forming apparatus according to the present invention. In the drawings showing the image forming apparatus described below, devices and components having substantially the same functions and functions as those of the image forming apparatus A1 are denoted by the same reference numerals.

The image forming apparatus A2 shown in FIG. 3 is described above except that the position of the cleaning device for removing the toner on the transfer belt and the position of the charging device for removing the charge from the transfer belt are different. It is substantially the same as the image forming apparatus A1 described above. In the image forming apparatus A2, the cleaning device 47 for removing the toner on the transfer belt 81 is disposed at a position facing the roller r1. A charging device D1 for charging the transfer belt 81
Is disposed downstream of the transfer position and upstream of the cleaning device 47. Charging sheet S of charging device D1
Reference numeral 1 denotes a transfer belt 81 at a position facing the grounded roller r3.
Is in contact with

The image forming apparatus A2 can form an image in the same manner as the image forming apparatus A1.
The same effect can be obtained. In the image forming apparatus A2, the charging device D1 removes electricity from the transfer belt 81 downstream of the transfer position and upstream of the cleaning device 47. As a result, the transfer belt 81 around the transfer position
Even if the charged toner adheres to the upper portion, the charge can be removed from the toner before the toner reaches a position facing the cleaning device 47. Since the electrostatic attraction of the toner to the transfer belt 81 can be weakened, the removal of the toner by the cleaning blade 471 of the cleaning device 47 becomes easy. Since the toner can be removed from the transfer belt 81 with less wiping, the back surface stain of the recording sheet R can be suppressed accordingly. (3) FIG. 4 shows a schematic configuration diagram of still another example of the image forming apparatus according to the present invention.

In an image forming apparatus A3 shown in FIG. 4, a transfer roller 82 is used as a transfer rotating member instead of a transfer belt.
1 is in contact. The charging sheet S1 of the charging device D1 is in contact with the transfer roller 82. In the image forming apparatus A3, the toner image formed on the photoconductor 41 is transferred to the recording sheet R passed between the photoconductor 41 and the transfer roller 82 by applying a voltage from the power supply PS4 to the transfer roller 82. Is done. Also in the image forming apparatus A3, the charging device D1
As a result, the charge can be removed from the surface of the transfer roller 82 before the transfer, so that a good toner image can be transferred. (4) FIG. 5 shows a schematic configuration diagram of still another example of the image forming apparatus according to the present invention.

The image forming apparatus A4 shown in FIG. 5 can form four color toner images of yellow, magenta, cyan and black on the recording sheet R. Image forming apparatus A
Reference numeral 4 includes a photoreceptor unit for each color. That is, a photoconductor unit 4C for forming a cyan toner image, a photoconductor unit 4M for forming a magenta toner image, a photoconductor unit 4Y for forming a yellow toner image, a black toner A photoconductor unit 4Bk for forming an image is provided.

The photoreceptor unit 4C for cyan has a photoreceptor 41C, and at a position facing the photoreceptor 41C, an electrostatic latent image is formed by using a charging brush 42C, a laser exposure device 43C, and cyan toner. Developing device 44C capable of developing,
A transfer charger 51C and a cleaning device 47C are sequentially arranged. Photoconductor unit 4M for magenta color,
The same applies to the photoconductor unit 4Y for yellow and the photoconductor unit 4Bk for black.

The image forming apparatus A4 includes a transfer belt 84 as a transfer rotating body. The transfer belt 84 is an endless belt wound around rollers r7 and r8. The transfer belt 84 is in contact with the photoconductor at a position where the transfer charger of each photoconductor unit faces the photoconductor. Therefore, for example, in the cyan photoconductor unit 4C, the transfer charger 51C is arranged on the inner peripheral surface side of the transfer belt 84 at a position where the transfer belt 84 contacts the photoconductor 4C. Transfer chargers 51M, 51Y, 51 in the photoconductor unit 4M for magenta, the photoconductor unit 4Y for yellow, and the photoconductor unit 4Bk for black.
Bk is also arranged at the same position.

A cleaning device 47 for removing the toner on the transfer belt 84 is disposed on the outer peripheral surface side of the transfer belt 84 and at a position facing the roller r7. Also,
A charging device D1 for charging the transfer belt 84 is disposed on the outer peripheral surface side of the transfer belt 84 and downstream of the transfer position and upstream of the cleaning device 47. Charging device D
The first charged sheet S1 is in contact with the transfer belt 81 at a position facing the grounded roller r7.

The image forming apparatus A4 can form a color image on the recording sheet R as follows. In each photoconductor unit, cyan,
A toner image corresponding to each color of magenta, yellow, and black is formed for each color. Then, the cyan toner image, the magenta toner image, the yellow toner image, and the black toner image are sequentially transferred onto the recording sheet R. The transfer of the image of each color toner is performed by applying a charge to the back side of the transfer belt by a transfer charger similarly to the image forming apparatus A1. As a result, multiple toner images are formed on the recording sheet R. At this time, in each photoconductor unit, a toner image is formed on the photoconductor at a proper timing with respect to the conveyed recording sheet so that the position of the toner image transferred onto the recording sheet R does not shift. . Thereafter, the recording sheet R is sent to the fixing device 46, and the multi-toner image is fixed.

Also in the image forming apparatus A4, before transferring the toner images formed on the photoconductors of the photoconductor units of the respective colors to the recording sheet R, the charging device D1 applies the charge from the surface of the transfer belt 84 which comes into contact with the recording sheet R. Since the charge can be removed, a good transfer of the toner image can be performed.
Further, the charge can be removed from the toner on the transfer belt 84 before the cleaning by the charging device D1, so that the toner can be efficiently removed by the cleaning device 47. (5) FIG. 6 shows a schematic configuration diagram of still another example of the image forming apparatus according to the present invention.

The image forming apparatus A5 shown in FIG. 6 is a color image forming apparatus capable of forming four color toner images of yellow, magenta, cyan and black on a recording sheet. In the image forming apparatus A5, at a position facing the photoreceptor 41, a developing device capable of developing an electrostatic latent image on the photoreceptor peripheral surface 411 using a charging brush 42, a laser exposure device 43, and cyan toner. A developing device 44C capable of developing with magenta toner, a developing device 44Y capable of developing with yellow toner, a developing device 44Bk capable of developing with black toner, an intermediate transfer belt 83 as a transfer rotating body, The cleaning devices 45 are arranged in order.

The intermediate transfer belt 83 has rollers r4, r5
And an endless belt wound around r6. The intermediate transfer belt 83 is in contact with the photoconductor 41. At a position facing the photoconductor 41 on the inner peripheral surface side of the intermediate transfer belt 83,
The toner image formed on the photoconductor 41 is transferred to the intermediate transfer belt 8.
3 is provided with a transfer charger 51 for transfer. A roller r6 on the outer peripheral surface side of the intermediate transfer belt 83
The transfer charger 52 for transferring the toner image on the intermediate transfer belt 83 to the recording sheet R is disposed at a position facing the transfer sheet R. A cleaning device 47 and a charging device D1 are further disposed at a position on the outer peripheral surface side of the intermediate transfer belt 83 and facing the grounded roller r4.

The charged sheet S 1 of the charging device D 1 is located downstream of the primary transfer position where the transfer belt 83 contacts the photoconductor 41 and the secondary transfer position where the transfer belt 83 faces the transfer charger 52. It faces the transfer belt 83 on the upstream side. When no voltage is applied to the electrode layer 101 of the charged sheet S1, the charged sheet S1 is not in contact with the transfer belt 83.

The cleaning blade 471 of the cleaning device 47 is provided so as to be able to press and separate from the transfer belt 83. The image forming apparatus A5 can form a color image on the recording sheet R as follows.
On the photoconductor 41, toner images corresponding to each color of cyan, magenta, yellow, and black are formed for each color. Each time a toner image of one color is formed, the toner image is electrostatically transferred onto the intermediate transfer belt 83 by the transfer charger 51. The toner images of the respective colors are formed on the photoreceptor 41 at the same time so that the positions of the toner images of the respective colors on the intermediate transfer belt 83 do not shift.

Before the first color toner image is transferred onto the intermediate transfer belt 83, the charge is removed from the intermediate transfer belt 83 by the charging device D1, thereby transferring the toner image from the photosensitive member 41 to the intermediate transfer belt 83. Can be performed favorably. After the toner image is transferred onto the intermediate transfer belt 83, the charged sheet S1 is separated from the transfer belt 83 without applying a voltage to the electrode layer 101 of the charged sheet S1 so as not to disturb the toner image. . Further, the cleaning blade 471 of the cleaning device 47 is similarly separated from the transfer belt 83.

After all the toner images of each color are transferred onto the intermediate transfer belt 83, and multiple toner images are formed on the intermediate transfer belt 83, the multiple toner images are put together on the recording sheet R and are transferred by the transfer charger 52. Transcribe. After this,
The recording sheet R is sent to a fixing device 46 and fixes a multiple toner image. After the multi-toner image on the intermediate transfer belt 83 is transferred to the recording sheet R, a voltage is again applied to the electrode layer 101 of the charged sheet S1, and the charge is removed from the transfer belt 83.
Further, the static electricity is also removed from the toner on the transfer belt 83 to reduce the electrostatic attraction of the toner to the transfer belt 83. Then, the cleaning blade 47 is pressed against the transfer belt 83 to remove and collect the toner on the transfer belt 83. (6) The structure and configuration of the charging device including the charging sheet for charging the transfer rotating body such as the transfer belt, the transfer roller, and the intermediate transfer belt are limited to the structure and configuration of the charging device D1 including the above-described charging sheet S1. It is not something to be done. Hereinafter, another example of the charging device will be described.

The charging device described below will be described as a charging device for charging the transfer belt 81, instead of the charging device D1 in the image forming apparatus A1 shown in FIGS. The charging device described below includes image forming apparatuses A2 to A
5 can also be adopted. The charging sheet included in the charging device described below is supported and arranged similarly to the charging sheet S1 in the charging device D1. In the drawings showing the charging device described below, a support member for supporting the charging sheet is not shown. The rotation direction of the transfer belt is indicated by “α”.

In order to suppress discharge from the electrode layer of the charged sheet to devices and members other than the transfer rotator, for example, the surface of the electrode layer facing the transfer rotator, such as a charged sheet S2 shown in FIG. The surface on the opposite side may be covered with a second insulating layer. The charging sheet S2 includes the insulating layer 33 and the electrode layer 102.
And an insulating layer 31 in this order.
The insulating layer 31 is arranged on the side facing the transfer belt 81, and a part of the surface of the insulating layer 31 is in contact with the transfer belt 81. The insulating layer 33 is provided on the surface of the electrode layer 102 opposite to the surface facing the transfer belt 81, and covers the surface. Accordingly, it is possible to suppress discharge of the devices and members arranged near the surface of the charged sheet S2 opposite to the surface facing the transfer belt 81 from the electrode layer 102, and it is possible to suppress damage to the devices and members.

When the charged sheet has a laminated structure of two or more layers including an electrode layer and an insulating layer which is brought into contact with the transfer rotating body, the following (6-A), (6-B) and (6-B) As described in C). (6-
What is described in A), (6-B) and (6-C) may be a combination of two or more. (6-A) In order to further stabilize the discharge from the electrode layer, the length of the downstream end of the electrode layer in the rotation direction (α direction) of the transfer rotating body is changed, and the downstream end of the electrode layer is rotated by transfer. The shape may be such that irregularities are arranged in the body rotation axis direction (the direction orthogonal to the α direction). For example, a charge sheet S3 shown in FIG. 8 may be used.

The downstream end of the electrode layer 103 of the charged sheet S3 is formed in a comb shape. The protrusion 103p at the downstream end of the electrode layer 103 does not protrude downstream from the insulating layer 31. When a voltage is applied to the electrode layer 103, the electric field density of the protrusion 103p of the electrode layer 103 increases, so that the protrusion 103p becomes a discharge point. Even when environmental conditions such as temperature and humidity change, and even when used for a long period of time, the discharge point is stable, so that a more stable discharge can be performed. When the pitch of the protrusions 103p of the electrode layer 103 in the direction of the rotation axis of the transfer belt 81 is set to several tens to several hundreds of micrometers, the transfer belt 81 can be uniformly charged.

In the charged sheet S 3, the electrode layer 103 is located deeper than the insulating layer 31 in the rotation axis direction of the transfer belt 81. In other words, the electrode layer 103 is not formed on the end of the insulating layer 31 in the rotation axis direction. Thereby, discharge from the end of the electrode layer 103 in the rotation axis direction can be suppressed.

The shape of the downstream end of the electrode layer may be a sawtooth like the electrode layer 104 of the charging sheet S4 shown in FIG. 9 instead of the comb tooth. (6-B) The electrode layer may be divided into two or more in the direction of the rotation axis of the transfer rotator. For example, a charge sheet S5 shown in FIG. 10 may be used. Electrode layer 10 of charged sheet S5
Reference numeral 5 is divided into three in the rotation axis direction of the transfer belt 81. The electrode layer 105 includes three electrode layer portions 105a,
105b and 105c.

Each electrode layer portion 105a, 105b, 105
c, the width of the transfer belt 81 in the rotation axis direction is
The following settings are made in accordance with the width of the recording sheet on which the toner image formed thereon is to be transferred. In this example,
The width of the electrode layer portion 105b corresponds to the length of the short side of an A4 size recording sheet (A4 vertical sheet) conveyed in the long side direction, and the three electrode layer portions 105a, 105b and 10
The width including 5c corresponds to the long side length of the A4 size recording sheet (A4 horizontal sheet) conveyed in the short side direction.

The electrode layers 105a and 105c are connected to a DC power supply PS11. The electrode layer 105b is connected to the DC power supply PS12. When transferring the toner image to the A4 vertical sheet, discharge is performed only from the electrode layer portion 105b. Since the charge can be removed only from the transfer belt peripheral surface 81 area necessary to transfer the toner image on the photoreceptor 41 onto the A4 vertical sheet satisfactorily, the efficiency and energy saving can be improved.

When the toner image is transferred to the A4 horizontal sheet, all of the electrode layer portions 105a, 105b and 105c
From the battery. Note that between the electrode layer portion 105a and the electrode layer portion 105b, and between the electrode layer portion 105b and the electrode layer portion 1
Between 05c, an insulator may be inserted to prevent leakage between them.

The size and transport direction of the recording sheet to be used,
The division size and the number of divisions of the corresponding electrode layer are not limited to those described above. In this example, two power supplies are provided to apply a voltage to each electrode layer portion.However, one power supply and each electrode layer portion are connected via a switch, and a voltage is independently applied to each electrode layer portion. You may make it possible to apply.

As described above, even when the electrode layer is divided into two or more in the direction of the rotation axis of the transfer rotary member, the downstream end of each of the divided electrode layer portions may be a comb as shown in FIGS. Tooth-like,
It may have a sawtooth shape or the like. (6-C) The electrode layer may protrude downstream of the insulating layer in the rotation direction of the transfer rotating body. For example, a charge sheet S6 shown in FIG. 11 may be used.

The electrode layer 106 of the charged sheet S6 protrudes by a length L downstream of the insulating layer 31. Such protrusion length L
[Mm] means that the proximity discharge time T is 0.002 to 0.3 [s
ec] (preferably 0.005 to 0.1 [sec])
It is set to be. Proximity discharge time T [se
c] indicates that the projection length L is the moving speed V of the transfer belt circumferential surface 811.
(= L / V).

The electric discharge from the electrode layer 106
Mainly from the surface 106 s of the protruding end protruding downstream of the insulating layer 31 facing the transfer belt 81. When the electrode layer 106 is protruded downstream from the insulating layer 31 in this manner, discharge from the electrode layer 106 is facilitated, and uniform and stable discharge can be performed accordingly. Therefore, the transfer belt 81 can be uniformly charged.

In the case where the charged sheet has a laminated structure of two or more layers including an electrode layer and an insulating layer that is brought into contact with the transfer rotating member, and when the electrode layer is projected downstream from the insulating layer, the following (6) -C1), (6-C2) and (6-
It may be described in C3). (6-C1) In order to prevent the protruding end of the electrode layer protruding downstream from the insulating layer from bending or deforming in the direction of the transfer rotating body due to electrostatic attraction force, for example, FIG.
, A reinforcing layer may be provided.

In the charging sheet S7, the electrode layer 107 projecting downstream from the insulating layer 31 is
The reinforcing layer 61 is provided on the surface of the transfer belt 81 opposite to the transfer belt 81. The reinforcing layer 61 is made of polyester in this example. Transfer belt 81 at protruding end 107p of electrode layer 107
Since the deflection and deformation in the direction can be prevented, the discharge distance is stabilized, the stable discharge can be performed from the electrode layer 107, and the transfer belt 81 can be uniformly charged.

Note that, by increasing the thickness of the electrode layer itself, or by increasing the thickness of the electrode layer and providing a reinforcing layer, bending and deformation of the protruding end of the electrode layer may be prevented. Also,
The above-mentioned second insulating layer provided on the side opposite to the surface of the electrode layer facing the transfer rotating body may have the function of the reinforcing layer. (6-C2) In order to suppress abnormal discharge from the downstream end face and the edge portion of the downstream protruding end of the electrode layer, for example, as shown in a charged sheet S8 shown in FIGS. The downstream end face, side end face, and / or edge portion of the protruding end of the layer may be covered with an insulator.

In the charging sheet S8, the electrode layer 108
The downstream end surface 108e, both side end surfaces 108s, and the edge portion of the protruding end portion 108p are covered with the insulator 62. Thus, abnormal discharge from the downstream end surface 108e, both side end surfaces 108s, and the edge portion can be prevented, and the transfer belt 81 can be uniformly charged accordingly. (6-C3) In order to suppress abnormal discharge from the downstream end face or the edge of the downstream protruding end of the electrode layer, for example, the protruding end of the electrode layer is charged like a charged sheet S9 shown in FIG. Alternatively, the protrusion may be warped so that the distance between the protruding end portion and the transfer rotary member increases as the position moves downstream.

In the charging sheet S9, the protruding end portion 109p of the electrode layer 109 protruding downstream from the insulating layer 31 is formed.
Are warped so that the distance from the transfer belt 81 increases as going downstream. As a result, the projecting end 10
Since the distance from the transfer belt 81 to the downstream tip surface 109e and the downstream edge portion 9p is larger than the other portions, abnormal discharge from the downstream tip surface 109e and the downstream edge portion can be suppressed. The transfer belt 81 can be charged uniformly.

The above (6-C1), (6-C2) and (6
-C3) may be a combination of two or more. The charging sheet of the charging device is not limited to a laminate structure of two or more layers including an electrode layer and an insulating layer to be brought into contact with the transfer rotating body. The charging sheet is described below (7)
As described in (8) and above, a multilayer structure of three or more layers including an electrode layer may be used. Hereinafter, a charging device having such a charged sheet having a laminated structure of three or more layers will be described. In (7), a charging device having a charging sheet having a laminated structure of three or more layers including an electrode layer, an insulating layer, and a second electrode layer to be brought into contact with the transfer rotating body will be described.
In (8), a charging device having a charging sheet having a laminated structure of three or more layers including an electrode layer, an insulating layer, and an electret layer to be brought into contact with the transfer rotating body will be described. (7) FIG. 15 shows a schematic cross-sectional view of an example of a charging device provided with a charging sheet having a laminated structure of three or more layers.

The charging device D10 shown in FIG. 15 includes a charging sheet S10 and two power supplies PS1 and PS2.
The charge sheet S10 is a first electrode layer 1 made of a resistance material.
10, a three-layer sheet in which the insulating layer 32 and the second electrode layer 21 are laminated in this order. The second electrode layer 21 is arranged on the side closer to the transfer belt 81, and makes the second electrode layer 21 contact the transfer belt 81. The second electrode layer 21 is made of the same resistance material as the first electrode layer in this example.

The first electrode layer 110 is connected to a DC power supply PS1 whose output voltage is variable. The second electrode layer 21 includes
The output voltage variable DC power supply PS2 is connected. In this example, the first electrode layer 110 and the second electrode layer 21 include:
A voltage of the same polarity is applied. The insulating layer 32 is provided between the first electrode layer 110 and the second electrode layer 21 in order to maintain an electrical insulation state.

The sum of the thickness of the insulating layer 32 and the thickness of the second electrode layer 21 is set so that a satisfactory discharge is generated from the downstream end face 110 e of the first electrode layer 110 and the generation of ozone is suppressed. Is set in the range of 11 to 100 μm. In the charging device D10, both the first electrode layer 110 and the second electrode layer 21 of the charging sheet S10 are discharged, and each of the electrode layers 110 and 21 is discharged.
1 may be used for charging. Also, the first electrode layer 110
Only from the transfer belt 8 of the charged sheet S10 without discharging from the second electrode layer 21 without discharging from the second electrode layer 21.
It may be used only to generate an electrostatic attraction force in one direction. Whether to discharge from the second electrode layer 21 can be adjusted by the voltage applied to the second electrode layer 21 from the power supply PS2.

The discharge from the first electrode layer 110 is mainly generated from the downstream end face 110e. The discharge from the second electrode layer 21 is mainly performed at a position slightly upstream of a contact position with the transfer belt 81, where the second electrode layer 21 is close to the transfer belt 81. According to the charging device D <b> 10, it is possible to preliminarily remove electricity from the transfer belt 81 by discharging from the second electrode layer 21, and then further remove electricity from the transfer belt 81 by discharging from the first electrode layer 110. As a result, the transfer belt 81 can be uniformly discharged.

According to the charging device D10, even if foreign matter such as toner and paper dust arrives at a position facing the charged sheet S10 with the rotation of the transfer belt 81, the foreign matter is not charged.
Before reaching the contact portion between the transfer belt 81 and the transfer belt 81, the foreign matter can be discharged from the foreign matter by discharging from the second electrode layer 21, and the foreign matter is electrostatically attracted to the first electrode layer 110 and the second electrode layer 21. Can be suppressed. Therefore, even if the foreign matter is
Even if it is set to 1, a stable discharge can be performed from the first electrode layer 110 and the second electrode layer 21, respectively.
As a result, the transfer belt 81 can be uniformly charged.

As described above, even when the charged sheet has a laminated structure including the first electrode layer, the insulating layer, and the second electrode layer that is brought into contact with the transfer rotator, the charge sheet can be moved from the first electrode layer of the charged sheet to a member other than the transfer rotator. In order to suppress the discharge, the surface of the first electrode layer opposite to the surface facing the transfer rotating body may be covered with a second insulating layer. In this manner, the charged sheet has a laminated structure of three or more layers including the first electrode layer, the insulating layer, and the second electrode layer that is brought into contact with the transfer rotator, and has the same structure as the first electrode layer and the second electrode layer. When a polarity voltage is applied, a single power supply can be connected to these electrode layers, for example, as in a charging device D11 shown in FIG.

The charging device D11 has only the power source PS3 for applying a voltage to the first electrode layer 110 and the second electrode layer 21. The voltage from the power supply PS3 is divided by the resistors R1 and R2 and applied to the first electrode layer 110 and the second electrode layer 21. Since the number of power supplies is one less than when two power supplies are provided, the entire charging device and thus the entire image forming apparatus can be made compact and low in cost.

When the charged sheet has a laminated structure of three or more layers including the first electrode layer, the insulating layer, and the second electrode layer which is brought into contact with the transfer rotary member, for example, as in a charging device D12 shown in FIG. The alternating voltage may be applied to the second electrode layer by superimposing the alternating voltage on the DC voltage. In the charging device D12, the power supply P is provided on the second electrode layer 21 of the charging sheet S10.
S2 'is connected. The power supply PS2 'is a DC power supply P
This is a power supply in which S21 and the alternating power supply PS22 are connected in series. The alternating power supply PS22 is an AC power supply in this example.

In the charging device D12, the second electrode layer 2
By applying an AC voltage superimposed on a DC voltage and discharging the second electrode layer 21 from the second electrode layer 1, foreign matters such as toner and paper dust are brought into contact with the charged sheet S 10 and the transfer belt 81 with the rotation of the transfer belt 81. Even if it arrives at the site, it is possible to suppress the foreign matter from aggregating at the contact site. Therefore, such aggregates enter between the charged sheet S10 and the transfer belt 81, and the distance between the first electrode layer 110 and the peripheral surface 811 and the distance between the second electrode layer 21 and the peripheral surface 811 vary. Of the first electrode layer 110 and the second electrode layer 21
Stable discharge can be performed. The alternating power supply may be configured to be capable of applying a pulse-like or triangular-wave-like alternating voltage instead of a sine-wave AC voltage.

In the charging device D12, the alternating voltage is superimposed on the DC voltage and applied to the second electrode layer to suppress the aggregation of the foreign matter.
As in the case of 13, the suppression can be achieved by applying only the alternating voltage to the second electrode layer. In the charging device D13, the charging sheet S
An alternating power supply PS22 is connected to the ten second electrode layers 21. The alternating power supply PS22 is an AC power supply in this example.

When the charged sheet has a laminated structure of three or more layers including the first electrode layer, the insulating layer, and the second electrode layer which is brought into contact with the transfer rotating member, the above-mentioned (6-A), (6-
In the same manner as described in B) and (6-C), it may be further described in the following (7-A), (7-B) and (7-C). The same effect can be obtained.
What is described in (7-A), (7-B) and (7-C) may be a combination of two or more. (7-A) The length of the downstream end of the first electrode layer in the rotation direction of the transfer rotating body may be changed, and the downstream end may have a shape in which irregularities are arranged in the rotation axis direction of the transfer rotating body. (7-B) The first electrode layer is moved in the direction of the rotation axis of the transfer rotating body by 2
The above may be divided. The second electrode layer may also be divided into two or more in the rotation axis direction. 1st electrode layer, 2nd
Only one of the electrode layers may be divided into two or more in the direction, and any one of the electrode layers may be divided into two or more in the direction. (7-C) The first electrode layer may protrude downstream from the insulating layer and the second electrode layer. The first electrode layer is formed of an insulating layer and a second
When projecting downstream from the electrode layer, the above-mentioned (6-C
As described in (1), (6-C2) and (6-C3), the following (7-C1), (7-C2) and (7-C3) may be further described. The same effect can be obtained. (7-C1) A reinforcing layer for preventing the protruding end projecting downstream of the first electrode layer from bending or deforming in the direction of the transfer rotating body due to electrostatic attraction force is provided on the charged sheet. It may be provided. (7-C2) The downstream end face and / or the edge of the downstream protruding end of the first electrode layer may be covered with an insulator. (7-C3) The distance between the downstream protruding end of the first electrode layer and the transfer rotator increases as going downstream.
The first electrode layer may be warped.

The above (7-C1), (7-C2) and (7-C2)
-C3) may be a combination of two or more. (8) FIG. 19 shows a schematic cross-sectional view of another example of a charging device including a charging sheet having a laminated structure of three or more layers. The charging device D14 illustrated in FIG. 19 includes a charging sheet S11 and a power supply PS1.
It has.

The charging sheet S11 is a three-layer sheet in which the electrode layer 111, the insulating layer 32, and the electret layer 22 are laminated in this order. The electret layer 22 is disposed on the side close to the transfer belt 81, and the electret layer 2
2 is in contact with the transfer belt 81. The electret layer 22 is made of an electret material.

The electrode layer 111 is connected to a DC power supply PS1 whose output voltage is variable. The sum of the thickness of the insulating layer 32 and the thickness of the electret layer 22 is set so that good discharge is performed from the downstream end face 111 e of the electrode layer 111.
In order to suppress the generation of ozone, it is set in a range of 11 to 100 μm. According to the charging device D14, the transfer belt 81 can be charged similarly to the charging device D1.

The electret layer 22 in contact with the transfer belt 81 of the charged sheet S11 retains electric charge semipermanently, so that the charged sheet S11 exerts an electrostatic attraction force in the direction of the transfer belt 81 without applying a voltage. Can occur. Therefore, a voltage is applied to the second electrode layer as compared with a charging device having a three or more-layered charging sheet including the first electrode layer, the insulating layer, and the second electrode layer that is brought into contact with the transfer rotating body. Since no power supply is required, the entire apparatus can be made compact. By changing the voltage applied to the first electrode layer 111, the electrostatic attraction force of the charged sheet S11 toward the transfer belt 81 can be changed.

Even when the charged sheet has a laminated structure including the electrode layer, the insulating layer, and the electret layer which is brought into contact with the transfer rotator, the discharge from the electrode layer of the charge sheet to parts other than the transfer rotator can be suppressed. Alternatively, the surface of the electrode layer opposite to the surface facing the transfer rotating body may be covered with a second insulating layer. In addition, the charged sheet is thus provided with an electrode layer,
When a laminated structure of three or more layers including an insulating layer and an electret layer to be brought into contact with the transfer rotating body is used, the above (6-
A), (6-B) and (6-C) in the same manner as described in (8-A), (8-B) and (8-B).
As described in C). The same effect can be obtained. What is described in (8-A), (8-B) and (8-C) may be a combination of two or more. (8-A) The length of the downstream end of the electrode layer in the rotation direction of the transfer rotator may be changed so that the downstream end has a shape in which irregularities are arranged in the rotation axis direction of the transfer rotator. (8-B) The electrode layer may be divided into two or more in the direction of the rotation axis of the transfer rotating body. (8-C) The electrode layer may be protruded downstream from the insulating layer and the electret layer. When projecting the electrode layer downstream from the insulating layer and the electret layer, the above (6)
-C1), (6-C2) and (6-C3), as described in (8-C1), (8-C2).
And (8-C3). The same effect can be obtained. (8-C1) The protruding end protruding downstream of the electrode layer is
A reinforcing layer may be provided on the charging sheet to prevent the transfer sheet from bending or deforming due to electrostatic attraction. (8-C2) The downstream end face and / or the edge of the downstream protruding end of the electrode layer may be covered with an insulator. (8-C3) The electrode layer may be warped so that the distance between the downstream protruding end of the electrode layer and the transfer rotating body increases as going downstream.

(8-C1), (8-C2) and (8-C2)
-C3) may be a combination of two or more.

[0117]

According to the present invention, a toner image carrier on which a toner image is formed for forming a toner image on a recording sheet, and a toner image carrier for transferring the toner image on the toner image carrier are formed. Provided is an electrophotographic image forming apparatus including a transfer rotator that contacts a body, wherein the transfer rotator is charged with less generation of ozone, and accordingly, transfer failure and dirt on the back surface of a recording sheet can be suppressed accordingly. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present invention.

FIG. 2 is a schematic perspective view of a charging device provided in the image forming apparatus shown in FIG.

FIG. 3 is a schematic configuration diagram illustrating another example of the image forming apparatus according to the present invention.

FIG. 4 is a schematic configuration diagram showing still another example of the image forming apparatus according to the present invention.

FIG. 5 is a schematic configuration diagram showing still another example of the image forming apparatus according to the present invention.

FIG. 6 is a schematic configuration diagram showing still another example of the image forming apparatus according to the present invention.

FIG. 7 is a schematic sectional view showing another example of the charging device provided in the image forming apparatus according to the present invention.

FIG. 8 is a schematic perspective view showing still another example of the charging device provided in the image forming apparatus according to the present invention.

FIG. 9 is a schematic perspective view showing still another example of the charging device provided in the image forming apparatus according to the present invention.

FIG. 10 is a schematic perspective view showing still another example of the charging device provided in the image forming apparatus according to the present invention.

FIG. 11 is a schematic sectional view showing still another example of the charging device provided in the image forming apparatus according to the present invention.

FIG. 12 is a schematic sectional view showing still another example of the charging device provided in the image forming apparatus according to the present invention.

FIG. 13A is a schematic sectional view showing still another example of the charging device provided in the image forming apparatus according to the present invention, and FIG. 13B is a schematic perspective view of the charging device. .

FIG. 14 is a schematic sectional view showing still another example of the charging device provided in the image forming apparatus according to the present invention.

FIG. 15 is a schematic sectional view showing still another example of the charging device provided in the image forming apparatus according to the present invention.

FIG. 16 is a schematic sectional view showing still another example of the charging device provided in the image forming apparatus according to the present invention.

FIG. 17 is a schematic sectional view showing still another example of the charging device provided in the image forming apparatus according to the present invention.

FIG. 18 is a schematic sectional view showing still another example of the charging device provided in the image forming apparatus according to the present invention.

FIG. 19 is a schematic sectional view showing still another example of the charging device provided in the image forming apparatus according to the present invention.

[Description of Signs] A1, A2, A3, A4, A5 Image forming apparatus D1 to D14 Charging device S1 to S11 Charging sheet 101 to 111 Electrode layer 21 Second electrode layer 22 Electret layer 31, 32, 33 Insulating layer 61 Reinforcing layer 62 Insulator 41 Photoconductor (toner image carrier) 42 Charging brush 43 Exposure device 44, 41C, 41M, 41Y, 41Bk Developing device 45 Cleaning device 46 Fixing device 461, 462 Fixing roller 51, 52 Transfer charger 81, 84 Transfer belt (Transfer rotator) 82 Transfer roller (transfer rotator) 83 Intermediate transfer belt (transfer rotator) α Rotation direction of transfer rotator PS1, PS11, PS12, PS2, PS4 Power supply

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Kazuyoshi Hara 2-3-1-13 Azuchicho, Chuo-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Co., Ltd. (72) Inventor Naoki Toyoyoshi Azuchicho, Chuo-ku, Osaka 2-3-13 Osaka International Building Minolta Co., Ltd.

Claims (20)

[Claims] 1. An electrophotographic image forming apparatus for forming a toner image on a recording sheet, comprising: an electrostatic latent image formed thereon; and a toner image formed by developing the electrostatic latent image. An image carrier, a transfer rotator that contacts the toner image carrier to transfer a toner image on the toner image carrier, and a charging sheet that partially contacts the transfer rotator, And an insulating layer provided on the transfer rotator side of the electrode layer, supported at an upstream end in the rotation direction of the transfer rotator, and at least a portion downstream from the upstream end is subjected to the transfer rotation. An image forming apparatus comprising: a charging sheet to be brought into contact with a body; and a power supply capable of applying a voltage to the electrode layer. And a cleaning device for removing toner on the transfer rotating body, wherein the charged sheet is
2. The image according to claim 1, wherein the image is brought into contact with the outer peripheral surface of the transfer rotator on a downstream side in the rotation direction of the transfer rotator from a position where the transfer rotator contacts the toner image carrier and on an upstream side of the cleaning device. Forming equipment. 3. A cleaning device for removing toner on the transfer rotating body, wherein the charged sheet is
2. The image according to claim 1, wherein the image is brought into contact with the outer peripheral surface of the transfer rotator downstream of the cleaning device in the rotational direction of the transfer rotator and upstream of a position where the transfer rotator contacts the toner image carrier. Forming equipment. 4. The image forming apparatus according to claim 1, wherein said power supply is a power supply to which a DC voltage can be applied. 5. The image forming apparatus according to claim 4, wherein said power supply is a power supply having a variable output voltage. 6. The image forming apparatus according to claim 1, wherein a shortest distance between the transfer rotator and the electrode layer of the charged sheet is set to 11 μm to 100 μm. 7. The battery according to claim 1, wherein the volume resistivity of the electrode layer of the charged sheet is 10 ³ Ω · cm to 10 ⁷ Ω · cm.
The image forming apparatus according to any one of the above. 8. The downstream end of the charged sheet in the rotation direction of the electrode layer in the rotation direction of the transfer rotator is the downstream end of another layer provided on the transfer rotator side with respect to the electrode layer. The image forming apparatus according to any one of claims 1 to 7, wherein the image forming apparatus protrudes further downstream than the unit in the rotation direction. 9. The end of the charged sheet protruding downstream of the electrode rotator in the direction of rotation of the transfer rotator increases as the distance between the end and the transfer rotator decreases downstream in the direction of rotation. 9. The image forming apparatus according to claim 8, wherein the image forming apparatus is warped. 10. The image forming apparatus according to claim 8, wherein an end face of the charging layer on the downstream side in the rotation direction of the transfer rotator of the electrode layer is covered with an insulator. 11. The charging sheet according to claim 1, further comprising a reinforcing layer for preventing an end of the electrode layer protruding downstream in the rotation direction of the transfer rotator from bending toward the transfer rotator. The image forming apparatus according to claim 8, wherein the image forming apparatus is provided on a surface opposite to a surface facing the transfer rotating body. 12. The transfer sheet according to claim 1, wherein an end of the charged sheet on the downstream side in the rotation direction of the transfer rotator of the electrode layer has a shape in which irregularities are arranged in a direction crossing the rotation direction of the transfer rotator. An image forming apparatus according to any one of claims 11 to 13. 13. The image forming apparatus according to claim 1, wherein said electrode layer of said charged sheet is divided into two or more in a direction transverse to a rotation direction of said transfer rotator. 14. The charged sheet is a sheet having a laminated structure of two or more layers including the electrode layer and an insulating layer provided on the transfer rotator side of the electrode layer, and a part of the insulating layer is transferred to the transfer rotator. 14. The image forming apparatus according to claim 1, wherein the image forming apparatus is brought into contact with a body. 15. The charged sheet according to claim 1, wherein the charged sheet is an electrode layer.
A first electrode layer), an insulating layer provided on the transfer rotator side of the first electrode layer and a second electrode layer provided on the transfer rotator side of the insulating layer. 14. The sheet according to any one of claims 1 to 13, further comprising a power source that is a sheet, and that can bring a part of the second electrode layer into contact with the transfer rotator and apply a voltage to the second electrode layer. Image forming device. 16. An image forming apparatus according to claim 15, wherein said power supply capable of applying a voltage to said second electrode layer is a power supply capable of applying a DC voltage. 17. An image forming apparatus according to claim 15, wherein said power supply capable of applying a voltage to said second electrode layer is a power supply capable of applying an alternating voltage superimposed on a DC voltage. 18. An image forming apparatus according to claim 15, wherein said power supply capable of applying a voltage to said second electrode layer is a power supply having a variable output voltage. 19. The image forming apparatus according to claim 15, wherein the second electrode layer of the charged sheet is divided into two or more in a direction transverse to a rotation direction of the transfer rotating body. 20. The charged sheet has a laminated structure of three or more layers including the electrode layer, an insulating layer provided on the transfer rotator side of the electrode layer, and an electret layer provided on the transfer rotator side of the insulating layer. 2. A sheet, wherein a part of the electret layer is brought into contact with the transfer rotator.
3. The image forming apparatus according to any one of 3.