JP2002031965A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of obtaining a high- quality image having neither image omission nor image scattering as an image forming device using an intermediate transfer member. SOLUTION: In the electrophotographic image forming device, a toner image formed on a photoreceptor is primarily transferred to the intermediate transfer member, and transfer electric field is applied to the toner image on the intermediate transfer member, which is secondarily transferred to recording material. The image forming device is provided with a flatness correcting member securing flatness by pressing the intermediate transfer member in a width direction near the upstream side of a secondary transfer part, and the part of the flatness correcting member contacting with the intermediate transfer member is constituted of material owing to which potential by electrification obtained after the intermediate transfer member passes through the flatness correcting member does not have the same polarity as the electrifying polarity of the toner image carried on the intermediate transfer member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art A toner image is formed on a photoreceptor, and the toner image on the photoreceptor is primarily transferred onto a belt-like intermediate transfer member (intermediate transfer belt). 2. Description of the Related Art A method of forming an image by secondary-transferring a toner image from a body is known. Japanese Patent Application Laid-Open No. 1-92771 and the like disclose a device using a corotron as a secondary transfer device, and Japanese Patent Application Laid-Open No. 3-229278 discloses a device using a transfer roller as a secondary transfer device.

However, in the method using an intermediate transfer belt, undulations and wrinkles are generated on the surface of the belt, and the flatness of the belt tends to be reduced. If the intermediate transfer belt has undulations and wrinkles, the transfer paper will not adhere to the intermediate transfer belt and will enter the secondary transfer section with a gap between them,
The transfer electric field is applied to this gap, and discharge occurs in the gap between the transfer paper and the intermediate transfer belt. This discharge disturbs the toner image, or the charge generated by the discharge changes the charge polarity of the toner on the intermediate transfer belt and stops the transfer. Since the secondary transfer is performed without the belt being in close contact, there is a problem that image scattering occurs around the toner image.

Japanese Patent Application Laid-Open No. 2-50170 discloses that a secondary transfer portion is a backup roller that is one of rollers that stretches and supports an intermediate transfer belt, and faces a backup roller across the intermediate transfer belt. A secondary transfer roller disposed in contact with the intermediate transfer belt at a position, and a width direction on the back surface of the intermediate transfer belt near an upstream of a contact portion between the secondary transfer roller and the intermediate transfer belt with respect to a moving direction of the intermediate transfer belt. A transfer electric field generated between the electrode and the transfer roller by sandwiching the intermediate transfer belt and the transfer paper between the secondary transfer roller and the backup roller pair. Describes a method of performing secondary transfer. This method is considered to have the effect of preventing undulation and wrinkles of the intermediate transfer belt by the electrodes, but since the electrodes are installed upstream from the position where the transfer paper starts to contact the intermediate transfer belt, The secondary transfer electric field is already applied in a state where the intermediate transfer belt is not in contact, and the transfer is performed without the transfer paper and the intermediate transfer belt being in close contact with each other, so that image scattering occurs around the toner image. There was a problem.

In order to solve such a problem, Japanese Patent Application Laid-Open No. 9-80926 discloses a method of determining the position of the start of transfer paper contact with an intermediate transfer belt on the upstream side of a secondary transfer roll near a secondary transfer portion. There is disclosed a technique in which a flatness correcting member for preventing undulation and wrinkles of an intermediate transfer belt is placed near the upstream side on the back surface of the intermediate transfer belt (on the side where backup rollers are provided). Various examples of the material of the flatness correcting member include an insulating material, a semiconductive material, and a conductive material, but nothing is described in relation to the material of the intermediate transfer belt.

[0006]

SUMMARY OF THE INVENTION The present inventors have disclosed an image forming apparatus using a flatness correcting member for preventing undulation and wrinkles of an intermediate transfer belt as described in JP-A-9-80926. In some cases, depending on the material relationship between the flatness correcting member and the intermediate transfer belt, frictional charging occurs between the two, and the toner on the intermediate transfer belt is not charged until the toner is secondarily transferred to the transfer paper. It has been found that the toner image is diffused due to the influence of the toner image, or the secondary transfer is started in a region where the transfer paper is not sufficiently adhered to the intermediate transfer belt.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus using an intermediate transfer member that can obtain a high-quality image without image omission or image scattering.

[0008]

The above object of the present invention has been attained by the following constitutions.

1. A photoreceptor on which a latent image is formed, a developing unit for developing the latent image to form a toner image, and an intermediate transfer member for carrying the toner image by primary transfer of the toner image formed on the photoreceptor A primary transfer unit that primarily transfers a toner image on the photoconductor onto the intermediate transfer body, and a secondary transfer unit that performs a secondary transfer of the toner image carried on the intermediate transfer body to a recording material. A transfer electric field generating means for generating a transfer electric field in the secondary transfer portion; and a flatness of the intermediate transfer member in contact with the intermediate transfer member near the upstream of the secondary transfer portion in the moving direction of the intermediate transfer member. In the image forming apparatus provided with a flatness correcting member for ensuring the portion, the portion of the flatness correcting member that comes into contact with the intermediate transfer body, the charging potential of the intermediate transfer body after passing the flatness correcting member, Charging polarity of toner image carried on intermediate transfer member The image forming apparatus characterized by being composed of a material not the same polarity.

[0010] 2. The secondary transfer unit, the intermediate transfer body, a backup roller that supports the intermediate transfer body,
A secondary transfer roller disposed in contact with the intermediate transfer member at a position opposed to the backup roller with the intermediate transfer member interposed therebetween, wherein the transfer electric field generating unit is configured to control the backup roller or the secondary roller. A transfer electric field is generated in the secondary transfer section by connecting a power supply for applying a voltage to one of the transfer rollers and grounding the backup roller or the secondary transfer roller to which the power supply is not connected. 2. The image forming apparatus according to the above item 1, wherein

3. The secondary transfer unit, the intermediate transfer body, a backup roller that supports the intermediate transfer body,
A secondary transfer corotron disposed at a position facing the backup roller with the intermediate transfer member interposed therebetween, wherein the transfer electric field generating means is for applying a voltage to a discharge wire of the secondary transfer corotron. Connect the power,
2. The image forming apparatus according to claim 1, wherein the transfer roller generates a transfer electric field in the secondary transfer portion by grounding the backup roller.

4. The flatness correcting member, wherein a grounded conductive member and a semiconductive member are connected, and the semiconductive member is in contact with the intermediate transfer member. 2. The image forming apparatus according to claim 1.

5. The image forming apparatus according to claim 4, wherein the flatness correcting member is a roller in which a grounded conductive member is covered with a semiconductive member.

6. 5. The image forming apparatus according to claim 4, wherein the flatness correcting member is formed by connecting a semiconductive plate member to a grounded conductive member.

[0015] 7. A photoreceptor on which a latent image is formed, a developing unit for developing the latent image to form a toner image, and an intermediate transfer member for carrying the toner image by primary transfer of the toner image formed on the photoreceptor A primary transfer unit that primarily transfers a toner image on the photoconductor onto the intermediate transfer body, and a secondary transfer unit that performs a secondary transfer of the toner image carried on the intermediate transfer body to a recording material. A transfer electric field generating means for generating a transfer electric field in the secondary transfer portion; and a flatness of the intermediate transfer member in contact with the intermediate transfer member near the upstream of the secondary transfer portion in the moving direction of the intermediate transfer member. In the image forming apparatus provided with a flatness correction member that ensures the same, the portion of the flatness correction member that contacts the intermediate transfer member and the portion of the intermediate transfer member that contacts the flatness correction member are the same. An image characterized by being composed of a main material Forming apparatus.

[0016]

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

FIG. 1 is a schematic configuration diagram of an electrophotographic laser printer as an example of an image forming apparatus using the intermediate transfer member of the present invention.

In the drawing, reference numeral 1 denotes a charger, 2 denotes a photosensitive drum as a photosensitive member, 3 denotes a developing device as a developing unit, 4 denotes a photosensitive member cleaning blade, 5 denotes an intermediate transfer belt cleaning blade, and 6 denotes a photosensitive member cleaning blade. Primary transfer roller, 7 is a secondary transfer roller, 8 is a backup roller, 9, 10, and 11 are support rollers (including one of a belt drive roller and a tension roller), 14 is a laser exposure device, and 15 is an intermediate roller. An intermediate transfer belt as a transfer member, 20 is a flatness correction roller as a flatness correction member, 30 is a paper feed cassette for storing transfer paper P as a recording material, 31 is a pickup roller for feeding out the transfer paper P, and 32 is a resist. Rollers 33, a fixing device for thermally fixing the toner image on the transfer paper P on which the secondary transfer has been completed; and 34, a discharge tray for discharging the transfer paper P on which the image has been formed. That.

Around the photosensitive drum 2, a charger 1 for uniformly charging the surface of the photosensitive drum 2 with a charge of a predetermined polarity, and an electrostatic latent image on the photosensitive drum 2 imagewise. , A developing unit 3 for forming a toner image by attaching toner according to the electrostatic latent image, and a primary transfer for transferring the toner image on the photosensitive drum 2 to an intermediate transfer belt 15 A roller 6 (a conductive cylindrical core bar coated with a semiconductive elastic body) is provided. The photosensitive drum 2 is rotated in a direction indicated by an arrow in the figure by a drum drive motor (not shown). The charger 1 is a band electrode such as a scorotron, and can uniformly charge the photosensitive drum 2. When the photoconductor drum 2 is formed by coating a conductive substrate with a negative OPC (organic photoconductor), the photoconductor drum 2 is uniformly charged to a negative polarity. Here, the conductive substrate (aluminum cylinder) of the photosensitive drum 2 is grounded.

An image signal transmitted from an image reading unit such as a scanner (not shown) or a personal computer or the like is subjected to required processing in an image processing unit (not shown) and sent to a laser exposure unit 14. By scanning and exposing the photosensitive drum 2 with laser light corresponding to the image signal, the negative charged position of the photosensitive drum 2 is attenuated imagewise to form an electrostatic latent image.

The electrostatic latent image formed on the photosensitive drum 2 is developed in the developing unit 3 with a negatively charged toner to form a toner image. The toner image carried on the photoconductor drum 2 further rotates, reaches a primary transfer portion on which the primary transfer roller 6 is disposed, and is primarily transferred to the intermediate transfer belt 15. The intermediate transfer belt 15 is moving at substantially the same speed as the photosensitive drum 2 in the direction of the arrow in the drawing, and by applying a voltage having a polarity opposite to that of the toner to the primary transfer roller at the primary transfer portion. Intermediate transfer belt 15
Is primary-transferred.

In the case of a color printer, the process from the formation of the latent image to the primary transfer of the toner image is generally repeated for four colors of black, yellow, magenta, and cyan.
A multi-color toner image is formed on the intermediate transfer belt 15 by superimposing the multi-color toner. Until the color toner image is completed, the secondary transfer roller 7 and the intermediate transfer belt cleaning blade 5 are retracted from the intermediate transfer belt 15.
Alternatively, a so-called tandem system may be used in which a unit such as a photosensitive drum or a developing unit is provided for each color, and a toner image formed on each photosensitive member is transferred onto the intermediate transfer belt 15 in a superimposed manner. Absent.

After the toner image is primarily transferred to the intermediate transfer belt 15 at the primary transfer section, the transfer residual toner on the photosensitive drum 2 is scraped off by the cleaning blade 4 and exposed by a static eliminator (not shown). The potential on the body drum 2 is cancelled, and preparations are made for the next image formation.

On the other hand, when the primary transfer of the toner image to the intermediate transfer belt 15 is completed and the toner image reaches the secondary transfer portion where the secondary transfer roller 7 is disposed, the transfer paper P is transferred from the sheet cassette 30. It is taken out by the pickup roller 31. The picked-up transfer paper P is sent out at a timing by the registration roller 32, and is conveyed to a secondary transfer portion sandwiched between the intermediate transfer belt 15 supported by the backup roller 8 and the secondary transfer roller 7 ( (See the arrow in the figure). The secondary transfer roller 7 is connected to a power supply (not shown), a bias voltage having a polarity opposite to the charging polarity of the toner image carried on the intermediate transfer belt 15 is applied, and the backup roller 8 is grounded. (Not shown), a transfer electric field is generated in the secondary transfer portion (transfer electric field generating means). When the transfer sheet P passes through the secondary transfer section, the toner image carried on the intermediate transfer belt 15 is secondarily transferred to the transfer sheet P. At this time, whether the secondary transfer roller 7 or the backup roller 8 is connected to the power supply or grounded may be reversed. However, when the secondary transfer roller 7 is grounded, the backup roller 8 has the same polarity as the charged polarity of the toner image carried on the intermediate transfer belt 15 as described in JP-A-4-257883 and the like. A bias voltage is applied. As the transfer electric field generating means, a secondary transfer corotron is provided in place of the secondary transfer roller 7, and a power source for applying a voltage to a discharge wire of the corotron is connected to the backup roller. A method may be used in which a transfer electric field is generated in the secondary transfer portion by grounding the.

The transfer paper P on which the toner image has been secondarily transferred is further conveyed to a fixing device 33 composed of a pair of heat rollers.
The sheet is fixed by heating and pressing, and is discharged to a discharge tray 34.

On the other hand, the intermediate transfer belt 15 after the completion of the secondary transfer has the residual toner removed by the intermediate transfer belt cleaning blade 5 and is ready for the next image formation.

The above-described operations and sequence control of image formation are performed by a control unit such as a control board (not shown).

In the present embodiment, in the above-described printer, the flatness of the intermediate transfer belt 15 is ensured by contacting the intermediate transfer belt 15 near the backup roller 8 on the upstream side of the secondary transfer section. A flatness correction roller 20 is provided as a flatness correction member for performing the correction.

The flatness correcting member is in a width direction orthogonal to the moving direction (rotation direction) of the intermediate transfer belt 15, and has a length at least equal to or greater than the width of the maximum size transfer paper on which the image forming apparatus can form an image. The intermediate transfer belt 15 is pressed into contact with the intermediate transfer belt 15 to correct the plane of the intermediate transfer belt 15 to be flat, and the intermediate transfer belt surface of the secondary transfer entrance is corrected to be flat. It is brought into close contact with the entire surface, and is sent to the secondary transfer portion while maintaining this state.

In the present invention, the portion of the flatness correcting member that comes into contact with the intermediate transfer member is charged with the charge potential of the intermediate transfer member after the intermediate transfer member comes into contact with the flatness correcting member and passes therethrough. The toner image must be made of a material that does not have the same polarity as the charge polarity of the toner image carried on the intermediate transfer member. That is, when the toner image carried on the intermediate transfer member is negatively charged, after the intermediate transfer member has passed through the flattening member, the intermediate transfer member is not charged (charge potential is zero) or positively charged. It is necessary that the material be charged. To achieve this, a combination of the material of the portion of the flatness correcting member that contacts the intermediate transfer member and the material of the intermediate transfer member is appropriately selected. In this case, a combination may be selected so that the two materials are brought into frictional contact and the charge potential on the intermediate transfer body side becomes positive. One index is that when two dielectrics come into contact with each other, the dielectric having the larger dielectric constant is positively charged.
From Ehen's empirical rule (with exceptions), it can be appropriately selected according to the charging polarity of the toner image.

The flatness correcting member is formed by connecting a grounded conductive member and a semiconductive member, and is a portion where the semiconductive member comes into contact with the intermediate transfer member, and After the intermediate member has passed through the above-described property (the intermediate transfer body has come into contact with the flatness correcting member, the charging potential of the intermediate transfer body is the same as the charging polarity of the toner image carried on the intermediate transfer body). Is preferable. As a planarity correcting member in which the grounded conductive member and the semiconductive member are in contact with or connected to each other, in the present embodiment, a conductive member 21 such as a grounded metal is used as a core, and a semiconductive The flatness correction roller 20 covering the member 22 is used.

The conductive member has a volume resistivity of 10 ⁴ Ωcm.
Hereinafter, the semiconductive member has a volume resistivity of 10 ⁶ to 10 ¹² Ωc.
m is preferable.

As the semiconductive material of the flatness correcting member,
Conductive fillers such as carbon are dispersed in materials such as polycarbonate (PC), polyimide (PI), polyamide imide (PAI), polyvinylidene fluoride (PVDF), and tetrafluoroethylene-ethylene copolymer (ETFE), And a material containing an ionic conductive material.

As the material constituting the portion of the intermediate transfer member that comes into contact with the flatness correcting member (the surface layer on the back surface of the intermediate transfer belt 15), polycarbonate (PC), polyimide (P)
I), polyamide (PA), polyethylene (PE), polyethylene terephthalate (PET), polyamide imide (PAI), polyvinylidene fluoride (PVD)
F), Etrafluoroethylene-ethylene copolymer (E
TFE), EPDM, NBR, CR,
Examples thereof include those obtained by dispersing a conductive filler such as carbon in a rubber material such as polyurethane or silicone, or including an ionic conductive material. Volume resistivity is 1
0 ⁶ a to 10 ¹² [Omega] cm or so, if the thickness of the belt of a resin material 50~150μm about, in the case of rubber materials 20
It is preferably about 0 to 800 μm. The value of the above volume resistivity is the value of Mitsubishi Chemical Hiresta IP MCP-26.
0 or a value measured by using an R8340A manufactured by Advantest and applying a 500 V voltage with an HR probe manufactured by Mitsubishi Chemical Corporation. When a material having a volume resistivity lower than this is used, a phenomenon such as transfer of toner from the photosensitive drum 2 to the intermediate transfer belt 15 occurs before the photosensitive drum 2 comes into contact with the intermediate transfer belt 15. Therefore, scattering of the toner image occurs. If the volume resistivity is larger than 10 ¹² Ωcm, phenomena such as the intermediate transfer belt 15 not being self-removed or being charged only by contact with a stretching roller, etc., occur, and a destaticization device is required. Would.
Further, the thickness of the intermediate transfer belt 15 needs to be set in a region where the mechanical strength can be secured and the thickness can be made stable in manufacturing.

After the intermediate transfer member has passed the contact with the flatness correcting member, the charge potential of the intermediate transfer member is not the same as the charge potential of the toner image carried on the intermediate transfer member. As a combination, when the charging potential of the intermediate transfer member is set to be positive (when a negatively charged toner image is carried), the contact portion of the intermediate transfer member with the flatness correction member (that is, the intermediate transfer member) is used. When the back surface is mainly composed of polycarbonate (PC), polyethylene (PE), or polyethylene terephthalate (PET), the contact portion of the flatness correcting member with the intermediate transfer member is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polytetrafluoroethylene (PTF)
It is preferable to use a so-called fluororesin such as E), polyvinylidene fluoride (PVDF), or tetrafluoroethylene-ethylene copolymer (ETFE) as a main material.

The portion of the intermediate transfer member that contacts the flatness correcting member (ie, the back surface of the intermediate transfer member) is made of polyamide (P
A) When silicone rubber is used as the main material, the contact portion of the flatness correcting member with the intermediate transfer member is made of tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA) or polytetrafluoroethylene (PTF).
E), a so-called fluororesin such as polyvinylidene fluoride (PVDF), and tetrafluoroethylene-ethylene copolymer (ETFE), polycarbonate (PC), polyethylene (PE), polyethylene terephthalate (P
Preferably, ET) is the main material.

Further, the contact portion of the intermediate transfer member with the flatness correcting member (that is, the back surface of the intermediate transfer member) is made of tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), polytetrafluoroethylene (PTF).
E), when a so-called fluororesin such as polyvinylidene fluoride (PVDF) or etrafluoroethylene-ethylene copolymer (ETFE) is used as a main material, the contact portion of the flatness correcting member with the intermediate transfer member is subjected to intermediate transfer. It is preferable to use the same main material as the back of the body. By doing so, frictional charging can be suppressed. The content that the two main materials are made the same in order to suppress the triboelectric charging can be applied to all the intermediate transfer members.

Here, the "main material" means a resin material having the largest content among the materials constituting the contact portion.

The position at which the flatness correcting member contacts and presses the intermediate transfer member is about 10 to 80 mm upstream from the secondary transfer portion (nip), and the transfer paper comes into contact with the intermediate transfer belt. It is desirable that the position be downstream of the position where the flatness correcting member presses the intermediate transfer member. It is desirable to provide a guide member for introducing the transfer paper to the secondary transfer portion so that the contact position between the transfer paper and the intermediate transfer belt is as described above.

FIG. 2 is a partial schematic view of the printer shown in FIG. 1 when the flatness correcting member is a flexible plate-like member.

The same reference numerals as those in FIG.
Is a flexible plate-like member, and 24 is a tension spring. The flexible plate member 23 is a thin plate that extends in the width direction of the intermediate transfer belt 15 (at least the width of the transfer paper of the maximum size on which an image can be formed), and has linearity along the longitudinal direction. A good end is brought into contact with the intermediate transfer belt 15, and the other end with respect to the fulcrum V is pulled by a tension spring 24, so that the end is pressed against the intermediate transfer belt 15 and is slid in contact with the intermediate transfer belt 15 while being circulated. Apply tension in the width direction. The flexible plate-shaped member 23 may be a member in which a flexible sheet or a blade is connected to a sheet metal.
The extension spring 24 is made of metal (conductive) and is grounded (not shown).

The flexible plate member 23 and the flatness correction roller 2
The urging load of 0 is set to about 2 to 30N. In this range, the larger the load is, the more the flatness of the belt can be secured, so that the effect of preventing a defective image can be obtained.
Depending on the material of the flatness correction member and the material of the flatness correction member, plastic deformation may occur, and problems such as wear of the intermediate transfer belt 15 and the flatness correction member may occur. It is desirable to set the load in consideration of these. . Flexible plate member 23
The same material as the semiconductive member of the flatness correcting roller described with reference to FIG. 1 can be used.

[0043]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the printer described with reference to FIG. 1, a semiconductive member 22 of a flatness correcting roller 20 and an intermediate transfer belt 15 are provided.
The evaluation was performed by changing the material of the surface layer in contact with the semiconductive member 22 as shown in Table 1 below. Note that the toner images carried on the intermediate transfer belt 15 used in the present embodiment and the comparative example are negatively charged.
The flatness correcting roller used in the present embodiment and the comparative example uses a roller which presses the intermediate transfer belt at a load of 10N, and has a thickness of 100 μm on a grounded metal core.
A thick semiconductive member is covered. The flatness correcting roller was driven to rotate with respect to the intermediate transfer belt. The results are shown in Table 1.

With respect to the charging polarity of the intermediate transfer belt after passing through the flatness correcting roller, a single unit evaluator having the intermediate transfer belt stretched was used. The measurement was performed by contacting a metal ground roller and measuring the back surface of the metal ground roller contact portion with a non-contact surface voltmeter. A simple evaluation is also possible by rubbing the intermediate transfer belt with the flatness correction roller and then measuring the surface potential with a surface voltmeter.

Regarding the image evaluation, the unfixed toner image after the secondary transfer was visually evaluated in the image forming apparatus shown in FIG.

[0046]

[Table 1]

As is clear from the above, it can be seen that the adoption of the flatness correcting member using the semiconductive member satisfying the conditions of the present invention provides excellent image quality.

[0048]

As described above, in the image forming apparatus using the intermediate transfer member, an image forming apparatus capable of obtaining a high-quality image without image omission or image scattering can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an electrophotographic laser printer as an example of an image forming apparatus using an intermediate transfer member of the present invention.

FIG. 2 is a partial schematic view of the printer of FIG. 1 when a flatness correction member is a flexible plate-shaped member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charger 2 Photoreceptor drum 3 Developing device 4 Photoreceptor cleaning blade 5 Intermediate transfer belt cleaning blade 6 Primary transfer roller 7 Secondary transfer roller 8 Backup roller 9, 10, 11 Supporting roller 14 Laser exposure device 15 Intermediate transfer belt 20 Flat surface Sex correction roller 21 conductive member 22 semiconductive member 23 flexible plate member 24 tension spring 30 paper feed cassette 33 fixing device 34 paper discharge tray

Claims (7)

[Claims] 1. A photoconductor on which a latent image is formed, a developing unit for developing the latent image to form a toner image, and a toner image formed on the photoconductor is primarily transferred to form the toner image. An intermediate transfer member to be carried; primary transfer means for primary-transferring the toner image on the photoreceptor onto the intermediate transfer member; and a secondary transfer device for secondary-transferring the toner image carried on the intermediate transfer member to a recording material. A secondary transfer portion, a transfer electric field generating means for generating a transfer electric field in the secondary transfer portion, and the intermediate transfer member in contact with the intermediate transfer member near the upstream of the secondary transfer portion in the moving direction of the intermediate transfer member. In an image forming apparatus provided with a flatness correcting member for securing the flatness of the transfer body, a portion of the flatness correcting member that comes into contact with the intermediate transfer body is a portion of the intermediate transfer body after passing through the flatness correcting member. The charged potential of the toner carried on the intermediate transfer body is An image forming apparatus characterized by being composed of a material that has the same polarity as the charging polarity of the image. 2. The image forming apparatus according to claim 1, wherein the secondary transfer unit is configured to:
A backup roller configured to support the intermediate transfer member, and a secondary transfer roller disposed in contact with the intermediate transfer member at a position facing the backup roller with the intermediate transfer member interposed therebetween; The generating unit connects a power supply for applying a voltage to one of the backup roller and the secondary transfer roller, and grounds the backup roller or the secondary transfer roller to which the power supply is not connected. And generating a transfer electric field in the secondary transfer portion.
An image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 1, wherein the secondary transfer unit includes the intermediate transfer body,
A backup roller that supports the intermediate transfer member, and a secondary transfer corotron disposed at a position facing the backup roller with the intermediate transfer member interposed therebetween; 2. A transfer electric field is generated in the secondary transfer portion by connecting a power supply for applying a voltage to a discharge wire of the corotron and grounding the backup roller. Image forming device. 4. The flatness correcting member, wherein a grounded conductive member and a semiconductive member are connected, and the semiconductive member contacts the intermediate transfer member. The image forming apparatus according to any one of claims 1 to 3. 5. The image forming apparatus according to claim 4, wherein the flatness correcting member is a roller in which a grounded conductive member is covered with a semiconductive member. 6. The image forming apparatus according to claim 4, wherein the flatness correcting member is formed by connecting a semiconductive plate member to a grounded conductive member. 7. A photoconductor on which a latent image is formed, a developing unit for developing the latent image to form a toner image, and a toner image formed on the photoconductor is primarily transferred to form the toner image. An intermediate transfer member to be carried; primary transfer means for primary-transferring the toner image on the photoreceptor onto the intermediate transfer member; and a secondary transfer device for secondary-transferring the toner image carried on the intermediate transfer member to a recording material. A secondary transfer portion, a transfer electric field generating means for generating a transfer electric field in the secondary transfer portion, and the intermediate transfer member in contact with the intermediate transfer member near the upstream of the secondary transfer portion in the moving direction of the intermediate transfer member. In an image forming apparatus provided with a flatness correcting member for securing the flatness of a transfer body, a portion of the flatness correcting member that comes into contact with the intermediate transfer body, and a portion that contacts the flatness correcting member of the intermediate transfer body Parts are made of the same main material An image forming apparatus comprising.