JP2001331047A - Transfer device and image forming device having it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stop the occurrence of an abnormal image on a photoreceptor based on the resistance unevenness of a transfer brush while suppressing the increase of a cost in an image forming device to transfer a toner image formed on the photoreceptor by feeding to the transfer belt while carrying a transfer material and making the transfer brush to which voltage is applied abut on the rear face of the transfer belt to the transfer material. SOLUTION: The transfer brush 10 abutting on the rear face of the transfer belt 9 is branched into a transfer material feeding direction upstream side part 10A and a transfer material feeding direction downstream side part 10B, so that the resistance unevenness of the transfer material feeding direction upstream side part 10A is restrained to be within a specified range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device and an image forming apparatus having the transfer device.

[0002]

2. Description of the Related Art A toner image is formed on the surface of an image carrier, and the toner image is directly transferred onto a transfer material, or the toner image formed on the image carrier is transferred onto an intermediate transfer member. Electronic copying machines, printers,
2. Description of the Related Art An image forming apparatus configured as a facsimile or a multifunction peripheral having at least two functions thereof has been conventionally known.

As an example of such an image forming apparatus, a transfer material is carried and transported on a transfer material transport member, and the transfer material is brought into contact with the surface of the image carrier, and at the opposite side of the surface of the transfer material transport member. 2. Description of the Related Art An image forming apparatus including a transfer device that transfers a toner image on the surface of an image carrier to a transfer material by applying a voltage to the transfer brush and bringing a transfer brush into contact with the back surface of a transfer material conveying member is known. ing. The transfer brush is located downstream of the contact area between the image carrier and the transfer material transport member in the transfer material transport direction.

As the transfer brush, a medium-resistance conductive brush is usually used, and a voltage is applied to the transfer brush by a power supply device under constant current control or constant voltage control. Is transferred to the transfer material. However, as a result of recent studies by the present inventors,
If a low resistance fiber is mixed in a large number of fibers constituting the transfer brush, a streak or band-shaped abnormal image is formed on the surface of the image carrier corresponding to the low resistance fiber, and this is a transfer material. It has been found that the image quality of the toner image transferred to the transfer material may be deteriorated. In order to prevent such a problem, the transfer brush may be configured so that the resistance unevenness of the entire transfer brush is kept low and the resistance values of all the fibers are equal to or more than a predetermined value. However, when the transfer brush is configured in this way, the disadvantage of increasing the cost is unavoidable.

The above problem also occurs in an image forming apparatus in which an intermediate transfer member is used in place of the transfer material conveying member and a toner image on an image carrier is formed on the intermediate transfer member.

[0006]

SUMMARY OF THE INVENTION It is a first object of the present invention to provide a transfer apparatus which eliminates the above-mentioned conventional disadvantages.

A second object of the present invention is to provide an image forming apparatus which eliminates the above-mentioned conventional disadvantages.

[0008]

In order to achieve the first object, the present invention is a transfer device for transferring a toner image formed on an image carrier to a transfer material, the transfer device supporting the transfer material. Transfer member for bringing the transfer material into contact with the image carrier on which the toner image is formed while transferring the transfer material, and transferring the transfer material to contact the back surface of the transfer material transport member on the side opposite to the side where the image carrier is located. A brush, and a power supply device for applying a voltage to the transfer brush, wherein the transfer brush is a portion of the transfer material transport member downstream of the contact area between the image carrier and the transfer material transport member in the transfer material transport direction. In the transfer device that is in contact with the back surface of the transfer material, the transfer brush in contact with the transfer material transfer member is divided into two parts: an upstream portion in the transfer material transfer direction and a downstream portion in the transfer material transfer direction. That the non-uniform resistance of the upstream part was kept within a certain Suggest transfer device according to symptoms (claim 1).

In this case, the transfer brush can be configured such that the resistance values of all the fibers constituting the brush on the upstream side in the transfer material transport direction are equal to or higher than a predetermined value.

Further, in the transfer device according to the first or second aspect, it is advantageous that the resistance unevenness at the upstream portion in the transfer material transport direction is smaller than the resistance unevenness at the downstream portion in the transfer material transport direction. ).

Furthermore, in the transfer device according to any one of the first to third aspects, it is advantageous that the fiber material of the upstream portion of the transfer brush in the transfer material transport direction is different from that of the fiber of the downstream portion in the transfer material transport direction. (Claim 4).

In order to achieve the second object, the present invention proposes an image forming apparatus including the transfer device according to any one of claims 1 to 4 (claim 5).

At this time, the image forming apparatus is replaced with a transfer material transporting member for carrying and transporting the transfer material, and an intermediate transfer in which a toner image is transferred from the image carrier while abutting on the surface of the image carrier. It may be configured to have a body (claim 6).

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings, and the principle of occurrence of the above-mentioned conventional disadvantages will be more specifically clarified with reference to the drawings.

FIG. 1 is a schematic diagram showing an image forming apparatus during an image forming operation. Reference numeral 1 denotes a drum-shaped photosensitive member as an example of an image carrier, and reference numeral 2 denotes a transfer device.
The image forming apparatus is configured as an electronic copying machine, a printer, a facsimile, or a multifunction peripheral thereof.

The photosensitive member 1 is rotatably supported by a frame of an image forming apparatus main body (not shown), and is driven to rotate clockwise (direction of arrow A) in FIG. 1 during an image forming operation. At this time, the surface of the photoreceptor is uniformly charged to a predetermined first polarity (minus polarity in the illustrated example) by the charging roller 3 which is an example of a charging device. The surface potential of the photoconductor 1 after charging is, for example, -900V. The charged surface is irradiated with light-modulated laser light LA emitted from a laser writing unit 4 which is an example of an image exposure device, whereby an electrostatic latent image corresponding to an image signal is formed on the surface of the photoconductor. . In this example, the absolute value of the surface potential of the photoreceptor portion irradiated with the laser beam LA decreases, and this constitutes an electrostatic latent image (image portion). The surface portion of the photoreceptor where the absolute value of the potential does not decrease becomes the background portion. The surface potential of the electrostatic latent image is, for example, -100 V, and the surface potential of the background remains substantially at -900 V.

The electrostatic latent image is visualized by the developing device 5 as a toner image. Developing device 5 exemplified here
Has a developing roller 6 that carries and transports a powdery toner charged to a first polarity (in this example, a negative polarity),
A bias voltage of a voltage (for example, −600 V) having a value intermediate between the electrostatic latent image on the photoconductor and the surface potential of the background portion is applied to the developing roller 6, whereby the toner on the developing roller 6 is electrostatically charged. The latent image is shifted to an electrostatic latent image, and the latent image is converted into a toner image. The electrostatic latent image is visualized by reversal development. A two-component developer having a toner and a carrier can also be used.

As described above, the toner image formed on the image carrier composed of the photoreceptor 1 is transferred by the transfer device 2 to a transfer material composed of a transfer paper or a resin sheet. The transfer device 2 shown here has an endless transfer belt 9 wound around a plurality of rollers, in the illustrated example, two rollers, a drive roller 7 and a driven roller 8, and is driven by a drive device (not shown). The driving roller 7 is rotationally driven in the counterclockwise direction in FIG. 1, whereby the transfer belt 9 is driven in the direction of arrow B. Transfer belt 9 is, for example 10 ⁴ to 10
^It is made of a medium resistor having a volume resistivity of about ⁹ Ω · cm, particularly about 10 ^{5 to} 10 ⁶ Ω · cm, and is made of a flexible material such as rubber.

On the other hand, the transfer material P sent from a paper supply unit (not shown) is transferred to the transfer belt 9 and the photosensitive member at the timing at which the toner image on the photosensitive member 1 is transferred correctly. 1 is fed in the direction shown by arrow C. In this manner, the transfer material P is carried on the transfer belt 9 while being in contact with the photoreceptor 1 on which the toner image is formed. The transfer belt 9 constitutes an example of a transfer material transporting member that makes the transfer material abut on an image carrier on which a toner image is formed while carrying and transporting the transfer material.

As shown in FIG. 2, a transfer brush 10 is in contact with the back surface of the transfer belt 9 opposite to the surface of the transfer belt 9 with which the photosensitive member 1 contacts directly or via the transfer material P. . The transfer brush 10 is in contact with the back surface of the transfer belt portion downstream of the contact area (nip portion) between the photoconductor 1 and the transfer belt 9 in the transfer material transport direction. The transfer brush 10 has a volume resistivity of, for example, 10 ^{4 to} 10
^It is composed of a medium resistor of ⁹ Ω · cm, particularly 10 ^{7 to} 10 ⁸ Ω · cm. As described above, the conductive brush 10 having a medium resistance has
The base end of the transfer belt 9 is adhered to the conductive holder 11 with, for example, a conductive adhesive. A power supply device 12 is connected to the holder 11.

As described above, when the transfer material P is transported between the photoreceptor 1 and the transfer belt 9, the power supply device 12 transfers the transfer material P to the transfer brush 10 in the opposite direction to the charge polarity of the toner image on the photoreceptor. A voltage of the second polarity (positive polarity in this example) is applied, whereby the transfer belt 9 is charged, and a current flows through the photoconductor 1 due to a potential difference between the photoconductor 1 and the transfer belt 9, and the toner on the photoconductor 1 The image is transferred onto the transfer material P. A transfer electric field is formed between the photosensitive member 1 and the transfer material P, and the toner image is electrostatically transferred to the surface of the transfer material P carried and conveyed by the transfer belt 9 by the action of the electric field. is there.

When a voltage is applied to the transfer brush 10 by the power supply device 12, a constant voltage control method of applying a constant voltage to the transfer brush 10 may be employed, or the voltage flows to the photosensitive member 1 by applying the voltage. A constant current control method for maintaining a constant current value may be employed.

As described above, the transfer device 2 of the present embodiment applies the transfer brush 10 in contact with the back surface of the transfer material conveying member on the side opposite to the side where the image carrier is located, and applies a voltage to the transfer brush 10. The transfer brush 10 has a power supply device 12, and the transfer brush 10 is in contact with the back surface of the transfer material conveying member downstream of the contact area between the image carrier and the transfer material conveying member in the transfer material conveying direction.

The transfer material P onto which the toner image has been transferred is successively carried on the surface of the transfer belt 9 and conveyed in the direction of arrow C. At this time, the charge amount of the transfer material P gradually decreases through the transfer belt 9 having a medium resistance. Be relaxed. The transfer material P, whose electrostatic force on the transfer belt 9 is weakened due to the reduction of the charge amount, reaches the portion of the transfer belt 9 wound around the peripheral surface of the drive roller 7 and is separated from the transfer belt 9 by the waist of the transfer material P. Is transported to a fixing device (not shown). In this fixing device, the toner image on the transfer material is fixed on the transfer material by the action of heat and pressure.

After transfer of the toner image to the transfer material P, the transfer residual toner adhering to the photoreceptor is removed from the surface of the photoreceptor by the cleaning device 13, and the photoreceptor then removes the light from the discharge lamp 14. Irradiation initializes the potential of the photoconductor surface.

FIG. 3 is an explanatory view schematically showing the transfer brush 10 and the photosensitive member 1 when the transfer brush 10 is viewed from above. Here, a case is considered in which the electrical resistance value of the fiber indicated by the symbol a in a large number of fibers constituting the transfer brush 10 is extremely lower than other fibers. A positive voltage is applied to the transfer brush 10 as described above. At this time, an excessive current flows through the fiber a having a low resistance, and this fiber a
The portion of the transfer belt 9 in contact with is excessively charged to the positive side. Therefore, the potential difference between the excessively charged transfer belt portion and the photosensitive member 1 becomes excessively large as compared with other portions, and the photosensitive member portion a corresponding to the transfer belt portion
An excessive current flows through the portion 1, and this portion a1 is excessively charged to the plus side. The photoreceptor portion a1 is irradiated with light from the charge removing lamp 14 in the same manner as the other portions, but the charge of the second polarity on the plus side opposite to the predetermined first polarity is removed by the charge removing lamp 14. Therefore, the charge on the positive side is left as a positive potential ripple on the photoconductor after passing through the charge removing lamp. For this reason, even if this portion receives the charging action of the charging roller 3 and receives the laser beam LA, its surface potential becomes more positive than the background portion or the potential of the electrostatic latent image, and this portion is developed by the developing device 5. Will be done. As a result, the portion a1 on the photoconductor 1 includes
A streak or band-like abnormal image appears, which is transferred to the transfer material. Such an abnormal image becomes conspicuous when halftone is copied.

As described above, in order to prevent the above-mentioned problem, the transfer brush is configured so that the electric resistance of the entire transfer brush is not uneven and the resistance of all the fibers is equal to or more than a predetermined value. do it. By doing so, the brush a having an extremely low resistance value does not exist, and the above-described problem can be prevented from occurring. However, if the unevenness of the resistance of the entire transfer brush is suppressed as described above, the cost of the transfer brush increases.

The inventor made various studies based on the above findings, and as a result, as shown in FIGS.
When the transfer brush 10 in contact with the transfer material transport direction upstream portion 10A and the transfer material transport direction downstream portion 10B are divided into two equal parts, the electrical resistance value of the transfer material transport direction upstream portion 10A is When extremely low fibers a are present, the photosensitive member 1
Although a prominent abnormal image appears on the upper side, it is apparent that no prominent abnormal image is generated on the photoreceptor 1 even when the fiber b having the same resistance as the fiber a exists in the downstream portion 10B in the transfer material transport direction. We were able to. The reason is expected as follows.

A voltage is applied to the transfer brush 10 from the power supply device 12 (FIG. 1) to the entire upstream portion 10A in the transfer material transport direction and the entire downstream portion 10B in the transfer material transport direction.
Transfer brush 1 close to contact area between photoreceptor 1 and transfer belt 9
0, a larger amount of current flows through the photoconductor 1 from the upstream portion 10A in the transfer material transport direction (arrow D in FIG. 2), and the fiber a having a small resistance value exists in the upstream portion 10A in the transfer material transport direction. Then, the above-mentioned abnormal image appears remarkably on the photoconductor.

Here, an experiment performed by the present inventor to confirm the above points will be described.

As shown in FIGS. 2 and 3, the transfer belt 9
The width of the transfer brush 10 in the transfer material transport direction that comes into contact with the transfer material is defined as L, which is divided into two equal portions of L / 2, and divided into an upstream portion 10A in the transfer material transport direction and a downstream portion 10B in the transfer material transport direction. It is assumed that low resistance fibers a and b having the same resistance value exist in each case. FIG. 4 shows an apparatus for measuring the resistance unevenness of the transfer brush 10 in the longitudinal direction. This device is
The transfer brush 10 has an electrode (probe) 15 having a width d in the longitudinal direction of 10 mm. On the other hand, the holder 11 of the transfer brush 10 is fixed on the conductive brush fixing plate 17 made of SUS304. In this state, a voltage of 2 KV is applied to the electrode 15 by the power supply 16, the electrode 15 is brought into contact with the transfer brush 10, and the electrode 15 is moved from one longitudinal end E1 to the other end E2 in the longitudinal direction. At this time, the current flowing through the brush fixing plate 17 is measured. Thereby, the current unevenness in the longitudinal direction of the transfer brush 10, that is, the resistance unevenness thereof is measured. A resistance R of 20 MΩ is inserted as a protection resistance.

Here, first, as shown in FIG.
Is brought into contact with only the upstream portion 10A of the transfer brush 10 in the transfer material transport direction, and the electrode 15 is connected to the one end E1 as described above.
When the current is measured while moving from the other end E2 to the other end E2, as shown in FIG. 7, there is a portion where the current flows excessively. This location corresponds to the fiber indicated by the symbol a in FIG. 3, and the flowing current is 20 μA.

Similarly, as shown in FIG.
When the electrode 15 is brought into contact with only the downstream portion 10B in the transfer material transport direction and the current is measured in exactly the same manner as described above, there is a portion where the current excessively flows as shown in FIG. This location corresponds to the fiber indicated by the symbol b in FIG. 3, and the flowing current is 20 μA. The other normal transfer brush part has 2KV
When the voltage is applied, almost no current flows.

Through the above-described experiment, if a fiber a through which a current of 20 μA flows exists in the upstream portion 10A in the transfer material transport direction, when the halftone image is transferred to the transfer material P,
A streak-like or band-like abnormal image is recognized on the transfer material,
It was confirmed that even if there was a fiber b in which a current of 20 μA flows in the downstream portion 10B in the transfer material transport direction, no noticeable abnormal image was generated on the photoreceptor or the transfer material. If the current flowing through the fibers in the upstream portion 10A in the transfer material transport direction was 10 μA or less, no noticeable abnormal image was generated.

In the transfer apparatus of the present embodiment, based on the above-described novel recognition, the transfer brush 10 which is in contact with the transfer material conveying member formed of the transfer belt 9 is moved to the transfer material conveying direction upstream portion 10A and the transfer material conveying direction. The configuration is such that the resistance unevenness of the upstream portion 10A in the transfer material transport direction when divided into two equal parts with the downstream portion 10B is kept within a certain range. Preferably, the transfer brush is configured so that the resistance values of all the fibers constituting the brush of the upstream portion 10A in the transfer material transport direction are equal to or higher than a predetermined value.

According to the above-described experiment, the uneven current flowing in the upstream portion 10A in the transfer material transport direction is suppressed to 10 μA or less, and the current flowing in all portions of the upstream portion 10A in the transfer material transport direction is reduced to 10 μA or less. Thus, the resistance value of the fiber is set.

According to the above configuration, it is possible to prevent a noticeable abnormal image from being generated on the photosensitive member 1, and hence on the transfer material P, and it is necessary to consider the uneven resistance in the downstream portion 10B in the transfer material transport direction. Therefore, it is possible to effectively suppress an increase in the overall cost of the transfer brush 10.

In order to ensure the above effect, the resistance unevenness of the upstream portion 10A in the transfer material transport direction may be made smaller than the resistance unevenness of the downstream portion 10B in the transfer material transport direction. Thereby, the cost of the downstream portion 10B in the transfer material transport direction can be reliably reduced, and the overall cost of the transfer brush 10 can be reduced.

In each of the above-described configurations, since the resistance unevenness of the upstream portion 10A in the transfer material transport direction is reduced, the manufacturing cost is increased, and the resistance unevenness of the downstream portion 10B in the transfer material transport direction is reduced. It is not necessary to consider it strictly as in the upstream portion 10A in the material transport direction. Therefore, the upstream portion 10A of the transfer brush 10 in the transfer material transport direction.
If the material of the fibers of the downstream portion 10B in the transfer material transport direction is made different from that of the transfer material transport direction, and the downstream portion 10B of the transfer material transport direction is made of low-cost fibers, the overall cost of the transfer brush 10 can be reliably reduced. .

The present invention can be applied to various types of image forming apparatuses other than the image forming apparatuses described above.
For example, the present invention is also applicable to an image forming apparatus that sequentially transfers toner images of different colors from a plurality of photoconductors arranged opposite to a transfer belt to a transfer material carried and carried on the transfer belt.

Further, as shown in FIG. 9, a yellow developing device 5Y, a magenta developing device 5M, a cyan developing device 5C, and a black developing device 5BK sequentially apply the respective colors on the photoreceptor 1 rotating in the direction of arrow A. The intermediate transfer belt 1 is wound around a plurality of rollers 19 and driven in the direction of arrow B1.
The toner image on the intermediate transfer belt 18 is transferred to the surface of the intermediate transfer member 8 and then the toner image on the intermediate transfer belt 18 is collectively transferred to the transfer material P by the transfer device 2A.

The transfer device 2A in this case is configured as follows. That is, the driving roller 7A and the driven roller 8
A transfer belt 9A wound around A and 8B and driven in the direction of arrow B is arranged to face the intermediate transfer belt 18, and a transfer brush 110A is brought into contact with the back surface of the transfer belt 9A. By applying a voltage to the transfer belt 9A in the same manner as in the example described above, the toner image transferred to the surface of the intermediate transfer belt 18 is transferred to the surface of the transfer material P carried and conveyed by the transfer belt 9A. I do. All of the above-described embodiments can be applied to the transfer device 2A of such an image forming apparatus. In this case, the surface is driven so as to move, and a toner image is formed on the surface. The image bearing member is constituted by an intermediate transfer belt 18, and the transfer belt 9A constitutes a transfer material carrying conveyance member.

In each of the examples described above, the transfer material conveying member is wound around a plurality of rollers and driven, and the transfer belts 9 and 9A which carry and transfer the transfer material P on the surface thereof.
However, when the transfer material conveying member is formed of a transfer sheet fixed to a drum frame and is configured to convey and transfer the transfer material on the surface of the transfer sheet, All configurations can be employed. In this case, the transfer material P is, for example, by a clamper or an electrostatic force.
The toner image formed on the surface of an image carrier, for example, a photoreceptor, is transferred onto the transfer material, which is held on a transfer sheet.

In the image forming apparatus shown in FIG. 9, the transfer brush 110B
The power supply device 12B applies a voltage thereto, and the toner image formed on the surface of the photoreceptor 1 is thereby transferred to the surface of the intermediate transfer belt 18. As described above, the image forming apparatus of the type in which the toner image formed on the image carrier made of the photoreceptor 1 is transferred to an intermediate transfer member such as the intermediate transfer belt 18 or the intermediate transfer drum also has the above-described configurations. Applicable. In this case, an intermediate transfer member is used instead of the transfer material transporting member in each of the above-described configurations. In other words, the image forming apparatus of this example uses an intermediate transfer member that transfers a toner image from the image carrier while abutting on the surface of the image carrier, instead of the transfer material transporting member that carries and transports the transfer material. The image forming apparatus is configured to transfer the toner image formed on the surface of the image carrier to the surface of the intermediate transfer body instead of transferring the toner image formed on the surface of the image carrier to a transfer material. All of the above-described configurations can be applied to the device. The other configuration of the image forming apparatus shown in FIG. 9 is well known in the related art, and thus the description thereof is omitted.

[0045]

According to the first to third aspects of the present invention, it is possible to prevent an abnormal image from being formed on the image carrier due to uneven resistance of the transfer brush, and to effectively suppress an increase in the cost of the transfer device. be able to.

According to the fourth aspect of the present invention, it is possible to more effectively reduce the cost of the transfer device.

According to the fifth and sixth aspects of the invention, it is possible to provide an image forming apparatus having the above-described effects.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating an image forming apparatus.

FIG. 2 is a partially enlarged view of FIG.

FIG. 3 is an explanatory diagram illustrating a transfer brush and a photoconductor.

FIG. 4 is a schematic view of an apparatus for measuring resistance unevenness of a transfer brush.

FIG. 5 is a diagram illustrating a state where resistance unevenness of an upstream portion of a transfer brush in a transfer material transport direction is measured.

FIG. 6 is a diagram illustrating a state where resistance unevenness of a downstream portion of a transfer brush in a transfer material conveyance direction is measured.

FIG. 7 is a graph showing a measurement result of an upstream portion of a transfer brush in a transfer material transport direction.

FIG. 8 is a graph illustrating a measurement result of a downstream portion of the transfer brush in a transfer material transport direction.

FIG. 9 is a schematic diagram illustrating another example of the image forming apparatus.

[Explanation of symbols]

 Reference Signs List 2 transfer device 2A transfer device 10 transfer brush 10A upstream portion in transfer material transport direction 10B downstream portion in transfer material transport direction 12 power supply device 12A power supply device 12B power supply device 110A transfer brush 110B transfer brush P transfer material

Claims (6)

[Claims] 1. A transfer device for transferring a toner image formed on an image carrier to a transfer material, wherein the transfer material is supported and conveyed, and the transfer material is transferred to an image carrier on which a toner image is formed. A transfer material transport member to be brought into contact with the body, a transfer brush abutting on the back surface of the transfer material transport member on the side opposite to the side where the image carrier is located, and a power supply device for applying a voltage to the transfer brush, The transfer brush is in contact with a transfer material transport member in a transfer device that is in contact with a back surface of the transfer material transport member downstream of the contact area between the image carrier and the transfer material transport member in the transfer material transport direction. A transfer method characterized in that when the transfer brush is divided into two parts, an upstream portion in the transfer material transport direction and a downstream portion in the transfer material transport direction, the uneven resistance of the upstream portion in the transfer material transport direction is suppressed within a certain range. apparatus. 2. The transfer device according to claim 1, wherein the transfer brush is configured such that the resistance values of all the fibers constituting the brush on the upstream side in the transfer material transport direction are equal to or higher than a predetermined value. 3. The transfer device according to claim 1, wherein the resistance unevenness of the upstream portion in the transfer material transport direction is smaller than the resistance unevenness of the downstream portion in the transfer material transport direction. 4. The transfer device according to claim 1, wherein a material of a fiber in an upstream portion of the transfer brush in the transfer material transport direction and a material of a fiber in a downstream portion of the transfer brush in the transfer material transport direction are different. 5. An image forming apparatus comprising the transfer device according to claim 1. 6. An image forming apparatus according to claim 5, further comprising: an intermediate transfer member for transferring the toner image from the image carrier while abutting on the surface of the image carrier, instead of the transfer material transporting member for carrying and transporting the transfer material.
An image forming apparatus according to claim 1.