JPH08202174A - Transfer device - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent character dropout during transfer, toner scattering near the transfer nip, and peeling discharge. [Structure] The transfer drum 1 is composed of a drum 11, an elastic layer 12, a cloth member 13 as an electrode, a resistance layer 14, and the like. The cloth member 13 is formed by interweaving an insulating warp yarn 131 and a conductive weft yarn 132. A conductive brush 15 that applies a transfer voltage is brought into contact with a portion corresponding to the transfer nip N _1, charging only the transfer nip N _1. Since unnecessary voltage is not applied before and after the transfer nip N ₁ (upstream side and downstream side), toner scattering on the upstream side and image disturbance due to peeling discharge on the downstream side are prevented. Further, since the cloth member 13 has elasticity, the contact pressure at the transfer nip N ₁ is good, and it is possible to prevent the characters from falling out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device mounted on an image forming apparatus such as an electrophotographic copying machine and a laser beam printer.

[0002]

2. Description of the Related Art Conventionally, a non-contact corona charger has been generally used as a transfer device in an image forming apparatus such as an electrophotographic copying machine and a laser beam printer.
However, the corona charger has problems such as high voltage required and generation of ozone. In recent years, a roller transfer method using a conductive roller has been used.

In the roller transfer system, a transfer roller to which a voltage is applied is brought into pressure contact with a photosensitive drum (image carrier) on which a toner image is formed, and the transfer material is passed through the transfer nip. In the transfer nip, the toner image moves on the transfer material by the electric field generated by the charges injected from the transfer roller to the back surface of the transfer material and the transfer electric field between the transfer roller and the photosensitive drum.

Further, in a multiple transfer system in which a toner image on a photosensitive drum is transferred to a transfer drum (intermediate transfer member) in order to obtain a multicolor image, a transfer voltage is applied to a conductive substrate of the transfer drum to expose the photosensitive drum. The toner image is transferred in the transfer nip formed by the drum and the transfer drum.

In any of the methods, the toner image is transferred in a state of being in contact with the transfer material or the transfer drum with a proper pressure, so that image blurring and toner scattering during transfer are less likely to occur, and the corona charger is used. There is a high possibility that a high quality image can be obtained as compared with the case of using.

[0006]

However, as shown in FIG.
As shown in, for example, when the transfer drum 1 as the intermediate transfer member and the photosensitive drum 2 are brought into contact with each other to form the transfer nip N and rotated in the arrow R1 direction and the arrow R2 direction, respectively, these are actually On the upstream side of the transfer nip N in the rotation direction of, there is a problem that the toner flies from the surface of the photosensitive drum 2 by the electric field before entering the transfer nip N, and the toner image is disturbed. You can't take full advantage of what you do.

On the downstream side of the transfer nip N, peeling discharge is generated between the transfer drum 1 and the photosensitive drum 2 due to a sharp rise in the electric field at the time of peeling, or discharge is generated by penetrating the transfer material to cause the toner. There were problems such as disturbing the image.

The problem between the transfer drum 1 and the photosensitive drum 2 at the time of transferring the toner image is that the transfer drum 1 and the transfer roller have no transfer drum (intermediate transfer member). It also exists between the photosensitive drum 2 and the transfer roller.

These problems are caused by the fact that the surface potential of the transfer member such as the transfer drum and the transfer roller is constant at the transfer nip N, at the upstream side thereof, and at the downstream side thereof, so that the upstream side and the downstream side which are unnecessary for the transfer. This occurs because the electric field is generated up to the area.

Therefore, in order to limit the transfer electric field in the gap on the upstream side of the transfer nip N, in Japanese Patent Laid-Open No. 173434, an independent electrode subdivided in the moving direction of the surface of the transfer drum (intermediate transfer member) is used. Is provided on the surface of the transfer member, and a transfer bias is applied only to the independent electrode group existing in the transfer nip N between the photosensitive drum and the transfer drum.

In this method, an independent electrode is formed by etching and printing a metal electrode on a sheet of about 50 μm. However, in such a method, the hardness of the transfer drum is increased, the contact pressure to the toner is increased during transfer, and there is a problem in that character dropout occurs.

Further, since the electric field on the downstream side of the transfer nip N is not limited, discharge is generated by the electric field between the transfer drum and the photosensitive drum, and the surface of the transfer drum and the transferred toner layer are excessively charged. Therefore, in order to obtain the same transfer electric field as the previous color at the time of transferring the next color, an extra transfer voltage is required at the time of transferring the next color, or the secondary transfer of the toner image to the transfer material is required. At the time of transfer, there are problems such as a decrease in transfer efficiency and reverse transfer from the transfer material to the photosensitive drum.

Therefore, the present invention provides a transfer device capable of preventing defects such as voids, increase in transfer electric field, decrease in transfer efficiency, and reverse transfer by appropriately controlling the transfer electric field in the vicinity of the transfer nip. It is intended to be provided.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and electrostatically transfers a toner image formed on a first image carrier to a second image carrier. In a transfer device for transferring to at least one of the first image carrier and the second image carrier, at least one of the first image carrier and the second image carrier is electrically divided into a large number of independent electrodes in the moving direction thereof, and And a voltage applying means for applying a voltage to each of the independent electrodes arranged at a predetermined position, wherein the plurality of independent electrodes are
It is a cloth member woven by interweaving a conductive thread member and an insulating thread member.

In this case, the first image carrier may be a photoconductor and the second image carrier may be an intermediate transfer member, and the intermediate transfer member may be a transfer belt or a transfer drum. You can

In a transfer device for electrostatically transferring a toner image formed on an intermediate transfer member onto a transfer material by a transfer member, at least one of the intermediate transfer member and the transfer member has a moving direction thereof. A plurality of independent electrodes electrically subdivided into, and voltage applying means for applying a voltage to the independent electrodes arranged at a predetermined position in accordance with the movement, the plurality of independent electrodes, It is a cloth member woven by interweaving a conductive thread member and an insulating thread member.

In a transfer device for electrostatically transferring a toner image formed on a photoconductor onto a transfer material by a transfer member, the transfer member is electrically subdivided in the moving direction of the transfer member. It has a large number of independent electrodes and a voltage applying means for applying a voltage to the independent electrodes arranged at a predetermined position in accordance with the movement, and the large number of independent electrodes are electrically insulating from the conductive thread member. It is a cloth member woven by interweaving with the thread member.

In this case, the transfer member can be a transfer roller.

In any of the transfer devices described above, the resistance layer may be laminated on the cloth member, or may be formed by impregnating the cloth member with a coating agent.

Next, in a transfer device for electrostatically transferring the toner image formed on the first image carrier to the second image carrier, the first image carrier and the second image are transferred. At least one of the carriers has a conductive substrate to which a voltage can be applied, a resistance layer, a large number of independent electrodes electrically subdivided in the moving direction, and arranged at a predetermined position according to the moving. Voltage applying means for applying a voltage to each of the separated independent electrodes.

In this case, the first image carrier may be a photoconductor and the second image carrier may be an intermediate transfer member.

Next, in the transfer device for electrostatically transferring the toner image formed on the first image carrier to the second image carrier, the first image carrier and the second image are transferred. Voltage application in which at least one of the carriers applies a voltage to a large number of independent electrodes that are electrically subdivided in the moving direction and to the independent electrodes that are arranged at predetermined positions according to the movement. Means for applying a transfer voltage to an independent electrode existing in a transfer nip between the first image carrier and the second image carrier, and different from the independent electrode existing in the downstream in the moving direction. It is characterized in that a voltage is applied.

In this case, the first image bearing member may be a photoconductor and the second image bearing member may be an intermediate transfer member.

[0024]

Based on the above configuration, for example, for the photosensitive member as the first image bearing member and the intermediate transfer member as the second image bearing member, the independent electrodes subdivided in the moving direction are provided. By providing a large number of transfer biases only to the independent electrode group located in the transfer nip between the photoconductor and the intermediate transfer member, sufficient transfer efficiency can be obtained and the upstream and downstream regions of the transfer nip can be obtained. By limiting the electric field, scattering of the toner image, peeling discharge, etc. are prevented.

At this time, if the intermediate transfer member forming the transfer nip together with the photosensitive member is stiff, the contact pressure becomes high, and defects such as voids occur. Therefore, in order not to impair the elasticity of the intermediate transfer member, the independent electrode group uses, for example, an anisotropic conductive cloth member in which an insulating thread member is used for the warp threads and a conductive thread member is used for the weft threads. . As a result, it is possible to maintain a uniform transfer nip and prevent character dropout and damage to the photoconductor.

The structure of the transfer member is a laminated structure of a supporting substrate, an elastic layer formed thereon, and an independent electrode group, and voltage application to the independent electrode group is applied to the surface of the transfer member and from outside the image forming area of the transfer member. This is possible by adopting a configuration that allows the transfer voltage to be supplied to the outer periphery of the end surface of the photoconductor or its support in order to accurately apply the voltage to the independent electrode corresponding to the transfer nip member between the photoconductor and the transfer member. It is possible to provide a structure in which the electrode is provided, the independent electrode is exposed on the surface of the transfer member facing the electrode, and a voltage can be applied only to the portion where the photoconductor and the transfer member are in contact with each other.

Further, in order to limit the electric field outside the transfer nip, it is possible to directly apply a voltage different from the transfer voltage to the independent electrodes outside the transfer nip, but on the other hand, adjacent independent electrodes are adjacent to each other. Easily leaks. In the present invention, the elastic layer is used as a medium resistance and a voltage different from the Tr voltage is applied from the supporting base to limit the charges in the voids before and after the transfer without causing such a problem.

With the above-mentioned structure, it is possible to eliminate the problem caused by the electric field generated in the gap before and after the transfer nip, which has been a problem in the past.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> FIG. 2 shows a schematic configuration of a color printer as an example of an image forming apparatus equipped with a transfer device according to the present invention. In this embodiment, a drum-shaped photosensitive member (hereinafter referred to as “photosensitive drum”) 2 is used as the first image bearing member, and a drum-shaped intermediate transfer member (hereinafter referred to as “transfer drum”) is also used as the second image bearing member. I am using 1).

The photosensitive drum 2 is provided with a photosensitive layer on the surface of a cylindrical drum substrate and has a diameter of 60 mm as a whole, and a process speed (peripheral speed) of 100 mm / sec in the direction of arrow R2 by a driving means (not shown). It is driven to rotate.

Around the photosensitive drum 2, a charging roller 4,
An exposure device 3, a four-color developing device 5, a transfer drum 1, a photosensitive drum cleaning device 71, and the like are provided, and a transfer roller 6, a transfer drum cleaning device 7, and the like are provided around the transfer drum 1.

The photosensitive drum 2 is charged by the charging roller 4.
It is uniformly charged to 700 V and is image-exposed by the laser exposure device 3 to form an electrostatic latent image. Then, first, the first color developing device 5 undergoes reversal development to form a toner image. The developing method is jumping development using one-component non-magnetic toner. Development bias is -500V DC
It is a combination of a voltage and a rectangular wave of 1600 V and 1800 Hz.

The toner image formed on the photosensitive drum 2 is
Transfer nip N ₁ between the transfer drum 1 to which voltage is applied
Is transferred onto the surface of the transfer drum 1. On the other hand, the transfer residual toner remaining on the photosensitive drum 2 is cleaned by the cleaning device 71.
It is scraped off by the cleaning blade of and is used for forming an image of the next color. Such a series of image forming processes are sequentially performed for four colors of yellow Y, magenta M, cyan C, and black BK, and toner images of four colors are transferred onto the transfer drum 1 to form a full-color image.

After that, the four color toner images on the transfer drum 1 are secondarily transferred onto the transfer material P by the transfer roller 6 to which the bias is applied, and the transfer material P after the secondary transfer is fixed by not shown. After the toner image on the surface is fixed by the container, the toner image is discharged to the outside of the apparatus main body. On the other hand, after the secondary transfer, the transfer drum cleaning device 7 removes the transfer residual toner on the surface of the transfer drum 1.

Thus, the intermediate transfer member 1 such as the transfer drum
In the method using, since it is easy to perform registration (registration) of each color when performing multiple transfer and it is not necessary to adsorb the transfer material P to the transfer drum 1, It has the advantage of expanding the variety.

However, at the same time, when the intermediate transfer body 1 is used, the surface potential of the intermediate transfer body 1 is not only in the transfer nip N ₁ , but also in the rotating direction of the intermediate transfer body 1 (direction of arrow R1).
Since the gap positions with respect to the photoconductor 2 on the upstream side and the downstream side (hereinafter, appropriately referred to as “before and after the transfer nip”) are the same, toner image scattering and peeling discharge easily occur,
It has a problem that the image quality is easily deteriorated.

In the conventionally used multiple transfer device, particularly the one in which the transfer material P is adsorbed to the transfer drum 1, as shown in FIG. 3, the electric field limiting means 93 is provided in the corona discharger 91 arranged inside the transfer drum 92. However, the toner image is prevented from scattering and peeling discharge is prevented by limiting the electric field before and after the transfer nip by providing the transfer material P and conveying the transfer material P from the photosensitive drum 2 side. However, it is difficult to provide a means for limiting the electric field, and the photosensitive member 2 and the intermediate transfer member 1 are rapidly separated from _each other at the exit of the transfer nip N _1. Therefore, peeling discharge and toner image scattering are likely to occur.

In this embodiment, in order to solve this problem, the intermediate transfer member 1 having the structure shown in the perspective view of FIG. 1 was used.

First, a cylindrical drum 1 having a diameter of 150 mm
1 is a supporting substrate. In the present invention, since a voltage is directly applied to the independent electrode group on the surface of the intermediate transfer member, the support need not be conductive as in the conventional case, and a resin or the like can be used.

Next, the elastic layer 12 is provided on the drum 11. When the contact pressure between the photosensitive drum 2 and the intermediate transfer body 1 is high, the central portion of the toner image is not completely transferred, that is, a so-called hollow character occurs, and thus the intermediate transfer body 1 needs to have elasticity. is there. Therefore, in this embodiment, the elastic layer 1
As 2, a 5 mm thick insulating urethane foam was used.

An independent electrode is provided on the elastic layer 12. The characteristics required for the electrodes are that each electrode in the moving direction of the intermediate transfer member 1 is electrically independent and that the pitch between the electrodes is 1
That is, it is as narrow as 0 to 500 μm. If the pitch is too narrow, leakage easily occurs between the electrodes, and if it is too wide, the toner image corresponding to the pitch portion of the electrode is defectively transferred and unevenness occurs in the solid image.

As the structure of the electrode, it is conceivable that an electrode pattern is formed on an insulating sheet.
In 73434, a polyester sheet having a thickness of 50 μm has a width of 500 μm, a pitch of 250 to 500 μm, and a thickness of 20 μm.
There is a description that a copper electrode of m is etched and further coated with nickel.

However, as described above, the intermediate transfer body 1 needs to have appropriate elasticity, and the hardness of the intermediate transfer body 1, particularly the surface hardness, increases when a sheet subjected to etching and printing is used. That is, it is difficult to completely prevent blank characters during transfer. Further, there is a problem that it is difficult to reduce the pitch in terms of processing, and further, the structure of the sheet becomes complicated.

Therefore, in this embodiment, as shown in FIG.
As the electrode, a cloth member 13 woven by interweaving an insulating warp yarn (thread member) 131 and a conductive weft thread (thread member) 132 was used. Since the warp yarn 131 is insulative, if the cloth member 13 is arranged in a direction along which the warp yarn is parallel to the moving direction of the intermediate transfer body 1, the electrodes in the moving direction are electrically insulated from each other and in the direction orthogonal to this. Can easily obtain anisotropic conductivity which is conductive. The cloth member 13 configured in this manner has appropriate elasticity and flexibility, and the independent electrode of the present invention can be configured without increasing the hardness of the lower elastic layer 12. Further, there is an advantage that the cost is low because it is not necessary to perform etching and printing on the sheet.

In this embodiment, as the anisotropic conductive cloth member 13 as shown in FIG. 4, the warp yarn is a fiber of about 35 μm PET,
An anisotropic conductive cloth manufactured by NBC Industry Co., Ltd., which is a woven fiber of SUS having a weft of about 30 μm, was used. This corresponds to the electrode width of 35 μm, which is the width of the SUS fiber, and the pitch is actually 85 μm.

In addition to this, as the insulating thread, it is possible to use materials such as nylon, rayon, polyester and acrylic which are used as ordinary fibers, and the conductive thread is also made by drawing a metal. Made by dispersing a conductive filler such as carbon in an insulating material (for example, REC manufactured by Unitika Ltd.), and further by making the surface of the insulating thread conductive. It is possible to use those (such as Thunderon manufactured by Nippon Silkworm Co., Ltd.) and the like, and the material used in this example does not limit the gist of the invention.

In this embodiment, the cloth member 1 as this electrode layer is used.
A resistance layer 14 is provided on the surface 3. If the surface resistance of the intermediate transfer body 1 is too low, the amount of transferred charges is partially non-uniform due to abnormal discharge or a difference between the surface potential on the photosensitive drum 2 and the image after the transfer nip N _1. Disorder occurs. Further, if the surface resistance is too high, the potential on the intermediate transfer body 1 is charged up as the transfer of each color is repeated, and the transfer voltage required to obtain the same transfer electric field for each color increases. Since the dots occur, the intermediate transfer member 1
The surface resistance value of is required to be within 10 ⁵ to 10 ¹² Ω · cm.

Therefore, as the resistance layer 14, 10 ⁵ to 10 ^{12 is used.}
Ω ・ cm coated with medium resistance material. As the material having such a specific resistance, PVDF, cell roll, or the like having this value as the material specific resistance can be used, but in the present embodiment, the conductive material is dispersed in the insulating resin to obtain the resistance value. Is used in the urethane resin as the resin, and S of the metal oxide is used as the conductive material.
was used by the nO ₂ was 20% dispersion.

When the cloth member 13 is coated in this manner, the coating agent permeates between the yarns, and a resistor is provided between adjacent electrically conductive yarns which are independent electrodes.
Leakage between electrodes can be significantly reduced.

As a method of manufacturing the intermediate transfer member 1, a coating agent having a thickness of 50 μm is applied onto the anisotropically conductive cloth member 13, and the cloth member 13 after coating has the elastic layer 12 on the surface. The method of winding on the drum 11 was adopted.

By using the intermediate transfer member 1 having such a structure, the nip width of the contact portion between the photosensitive drum 2 and the intermediate transfer member 1 was 8 mm.

Next, a method of applying a transfer bias to the intermediate transfer body 1 will be described.

In the conventional intermediate transfer member 1, the support is made conductive and a voltage is applied to it, which is a very simple structure. On the other hand, however, this allows the photosensitive drum 2 and the intermediate transfer member 1 to be made conductive. An undesired electric field is formed not only at the transfer nip N ₁ but also before and after the transfer nip N ₁ , causing an adverse effect.

In order to prevent this, the electrode for applying the transfer bias is electrically divided in the moving direction of the intermediate transfer member 1, and the voltage is applied only to the electrode existing in the transfer nip N ₁ . Is effective.

However, as described above, in the intermediate transfer member 1 of the present invention, the elastic layer 12 is provided below the layer having the independent electrode group, and the voltage is individually supplied to the divided electrodes from the substrate side. Therefore, the voltage supply means is directly provided on the surface side of the intermediate transfer member 1.

Further, in the present invention, since it is necessary to apply the transfer voltage to the independent electrode in the portion corresponding to the transfer nip N ₁ with the photosensitive drum 2, the independent electrode is connected to the intermediate transfer member 1 as shown in FIG. Form up to outside the image forming area in the longitudinal direction,
The resistance layer 14 was not provided in the sliding portion with the voltage applying means. As a voltage applying means, a conductive brush,
Alternatively, a roller can be used, and the transfer nip N ₁
A voltage is applied from outside the image forming area to the independent electrode group at a position corresponding to.

In this embodiment, the conductive brush 15 is used as the voltage applying means. Since the nip width between the photosensitive drum 2 and the intermediate transfer body 1 was 8 mm, the width of the brush in the moving direction of the intermediate transfer body 1 was 7 mm.

By adopting such a configuration, conventionally,
It has become possible to prevent the scattering of toner due to the generation of an electric field outside the transfer nip N ₁ and the disturbance of an image due to peeling discharge, which are problems when the intermediate transfer member 1 is used.

An example of actually forming an image will be shown.

The photosensitive drum 2 is uniformly charged by a charging roller 4 in which a DC voltage of -700V and an AC voltage of 2000V between peaks are superposed, and then imagewise exposed by a laser light source. This is subjected to reversal development by a jumping development method using a one-component non-magnetic yellow toner. The formed yellow toner image is the intermediate transfer member 1.
Is primarily transferred is conveyed to the transfer nip N ₁ on the intermediate transfer member 1 with. At this time, the independent electrodes on the intermediate transfer member 1 are
The DC voltage of +1000 V is applied only to the electrode group existing in the transfer nip N ₁ with the photosensitive drum 2, and the other independent electrodes are in a floating state. Therefore, it is possible to prevent the generation of unnecessary electric field before and after the transfer nip N _1, the flying of the toner in the transfer nip N ₁ earlier, also enable the image disturbance due to peeling electrostatic in the transfer nip N ₁ and subsequent Can be prevented.

The circumference of the intermediate transfer member 1 is the transfer material P of A size.
Since the toner image for one screen is primarily transferred, the magenta,
In order to emphasize cyan and further image contrast, black image is appropriately formed, and multiple transfer is performed on the intermediate transfer member 1.

At this time, since the surface of the intermediate transfer body 1 is charged up as colors are superposed and the actual transfer electric field may be lowered when the same transfer bias is applied, the primary transfer bias is sequentially increased. It is also possible to do so. However, as described above, unlike the conventional intermediate transfer member 1, peeling discharge or the like after the transfer nip N ₁ is unlikely to occur, and therefore the degree of charge-up is also small.
There is also an advantage that the absolute value of the primary transfer bias finally required when the colors are overlapped can be reduced.

The full-color image thus formed on the intermediate transfer member 1 is secondarily transferred onto the transfer material P by the transfer roller 6 for secondary transfer.

Even when secondary transfer is performed, image scattering, peeling discharge to the transfer material P, and transfer charge penetration may occur due to the generation of an electric field in the gap in front of the transfer nip N _2. In order to prevent this, the secondary transfer bias was applied only to the independent electrode group existing at the position corresponding to the transfer nip N ₂ of the secondary transfer roller 6. In this embodiment, the applied bias is 2 kV, the resistance value of the secondary transfer roller 6 is 10 ⁸ Ω, and the potential of the secondary transfer roller 6 is ground.

The toner image secondarily transferred onto the transfer material P passes through a fixing device (not shown) and is discharged to the outside of the main body of the apparatus to become a final output image.

On the other hand, the transfer residual toner on the intermediate transfer body 1 during the secondary transfer is cleaned and collected by the fur brush 7.

As described above, in this embodiment, the transfer nip N that contributes to the transfer during the primary and secondary transfer of the intermediate transfer member 1
_1, N a voltage is applied only in the _2, by limiting the electric field of the transfer nip N _1, N ₂ before and after the gap causing image defects, can be conventional intermediate transfer member to improve the shortcomings had It was <Embodiment 2> In this embodiment, the intermediate transfer member 1 of Embodiment 1 is used and is formed on the same circumference as the photosensitive drum 2 or the transfer roller 6 as voltage applying means for the independent electrode group of the intermediate transfer member 1. It is characterized in that a voltage is accurately applied to the independent electrodes in the transfer nips N ₁ and N ₂ by using these electrodes and making electrical contact between these electrodes and the independent electrodes outside the image forming area.

Further, in the intermediate transfer member 1 of the present invention, unlike the conventional structure, the potential on the intermediate transfer member 1 does not need to be constant, so that a plurality of different values are formed on the intermediate transfer member 1 at the same timing. Potential can be present. Therefore, while the primary transfer is being performed between the photosensitive drum 2 and the intermediate transfer body 1, it is possible to simultaneously perform the secondary transfer in which the toner on the intermediate transfer body 1 is transferred to the transfer material P. .

The structure of this embodiment is shown in FIG.

In the first embodiment, the photosensitive drum 2 and the intermediate transfer member 1
Although a conductive brush or roller was used as a means for applying a voltage to the independent electrode group at a position corresponding to the transfer nip N ₁ with this, in such a structure, the transfer nip N ₁ and the position of the electrode are accurately aligned. Therefore, there is a possibility that the voltage may be applied to the independent electrode outside the transfer nip N ₁ .

Further, since it is necessary to separately provide the voltage applying means outside the image forming area, the longitudinal dimension of the apparatus, especially the intermediate transfer body 1 becomes long, and the photosensitive drum 2 is required to be devised to be supported. There was a problem that the configuration became complicated.

Therefore, as shown in FIG. 5, the intermediate transfer member 1
By providing the voltage applying means to the photosensitive drum 2 on the same circumference, the voltage can be accurately applied to the independent electrode group existing in the transfer nip N ₁ , and the apparatus can be further downsized. became.

The intermediate transfer member 1 is the same as that of the first embodiment shown in FIG. 1, and the elastic layer 12, the cloth member (independent electrode layer) 13, and the resistance layer 14 are provided on the drum (support) 11 and the length is increased. The resistance layer 14 is not formed at the end portions in the direction for voltage application.

The photosensitive drum 2 is OP on the aluminum cylinder.
The C photosensitive layer is applied, but as shown in FIG.
An electrode 16A for supplying a voltage to the intermediate transfer body 1 is formed on an insulating flange 17A for holding this. Specifically, a conductive ring as the electrode 16A having a width of 5 mm is provided on the circumference of the flange. The resistance layer 14 is not formed on the intermediate transfer body 1 at the position facing and contacting with this, and by contacting the electrode 16A, the transfer voltage is accurately applied only to the independent electrode existing in the transfer nip N ₁ . Can be applied.

A similar flange 17B and electrode 16B are also formed at the end of the secondary transfer roller 6 in the apparatus, even during the primary transfer between the photosensitive drum 2 and the intermediate transfer member 1. By applying another voltage to the transfer roller 6, secondary transfer can be performed and the time required for image formation can be shortened.

Here, the resistance value of the secondary transfer roller 6 is 10
It is in the range of ⁵ to 10 ⁹ Ω. If this resistance value is too low, toner scattering due to uneven distribution of transfer charges occurs, and if it is too high, transfer failure occurs.

In this embodiment, the electrode 16 of the secondary transfer roller 6 is
B is connected to the ground and +200 is applied to the secondary transfer roller 6 itself.
Secondary transfer was performed by applying a voltage of 0V.

When images were actually formed in the same sequence as in Example 1, image scattering and peeling discharge, which had occurred in the conventional apparatus using the intermediate transfer member 1, did not occur, and a good image was obtained. I was able to.

Further, by integrating the voltage applying means to the independent electrode group of the intermediate transfer body 1 into the photosensitive drum 2 and the secondary transfer roller 6, the apparatus can be downsized, and the transfer nip N ₁ , N ₂ , The transfer voltage can be applied to N ₂ easily and accurately. <Embodiment 3> In this embodiment, in order to further suppress the electric field generated in the space before and after the transfer nip N ₁ , the intermediate transfer member 1 has a laminated structure of a conductive substrate, a medium resistance elastic body, an independent electrode layer, and a resistance layer. It is characterized by doing.

In the above-described first and second embodiments, the independent electrodes outside the transfer nips N ₁ and N ₂ at the time of primary and secondary transfer are floated, so that the respective transfer nips N ₁ and N ₂ are transferred.
Suppressing the electric field before and after the gap, the transfer nip N _1, N ₂ toner flying in front, to prevent separation discharge transfer nip N _1, N ₂ later.

However, since the electric potential of the floating independent electrode group is not regulated, the electric field in the void outside the nip weakens, but there is a possibility of causing discharge.

Therefore, in this embodiment, the transfer nips N ₁ , N
This is prevented by positively applying an electric potential to the independent electrodes existing at positions other than ₁ .

FIG. 6 shows a specific structure of the intermediate transfer member 1 of this embodiment.

Unlike Examples 1 and 2, the supporting substrate 11 of the intermediate transfer member 1 is made conductive and is connected to the independent electrode group 13 via the medium resistance elastic layer 16 to apply a potential.

Specifically, since the voltage applied to the support base 11 is preferably a potential that does not cause discharge with the photosensitive drum 2, −700 V corresponding to the dark potential of the photosensitive drum 2 is used in this embodiment, but the transfer is performed. Since a value lower than the transfer voltage applied to the nips N ₁ and N ₂ is effective, it is possible to set the potential to 0V or the like.

A voltage is directly applied from the surface of the intermediate transfer member 1 to the independent electrode group in the transfer nip N ₁ , N ₂ between the intermediate transfer member 1 and the photosensitive drum 2 and the secondary transfer roller 6 without the intermediate resistance layer. Since the voltage is applied, the transfer voltage in the transfer nips N ₁ and N ₂ is maintained. This equivalent circuit is shown in FIG. The potential at point A is
The potential of + 1000V directly supplied from the power source HV1 is maintained and an electric field sufficient for transfer is formed, but the point B is a potential obtained by resistance division of the potential difference between the power source HV1 and the power source HV2 by the resistors R1 and R2. -50 in this example.
It is 0V. For this reason, toner scattering and peeling discharge do not occur.

In this embodiment, the supporting substrate of the intermediate transfer member 1 is an aluminum drum, and a medium resistance sponge layer having a volume resistance value of 10 ⁵ to 10 ¹² Ω is formed on the aluminum drum. Since the electric field distribution in the air gap before and after the transfer nips N ₁ and N ₂ can be appropriately changed by the relationship between the resistance R1 and the resistance R2 in FIG.
Although it is necessary to optimize the resistance value of the medium resistance sponge according to the apparatus configuration (nip width, process speed, photosensitive drum 2, diameter of the intermediate transfer member), in the present embodiment, a resistance value of 10 ⁹ Ω was used. An electric field distribution as shown in 8 (c) could be obtained. FIG. 8A shows the electric field distribution in the conventional intermediate transfer member having no independent electrode, and FIG. 8B shows the electric field distributions in the configurations of the first and second embodiments. It can be seen that the configuration is most effective.

As described above, in the structure of this embodiment, the electric field in the air gaps around the transfer nips N ₁ and N ₂ is regulated, so that the effect of further preventing image scattering and peeling discharge can be further improved. became. <Embodiment 4> In this embodiment, as in Embodiment 3, in order to limit the transfer electric field generated in the gap before and after the transfer nip N ₁ , in the intermediate transfer member 1 having the structure of Embodiment 1, independent electrodes are provided before and after the transfer nip. It is characterized in that a voltage is applied.

In the embodiment, the independent electrodes before and after the transfer nip N ₁ are electrically floated, and the electric field in the gap before and after the transfer nip N ₁ is smaller than that of the intermediate transfer member 1 having the conventional structure. In order to further expand this effect, in this embodiment, a potential is forcibly applied to the independent electrode group outside the transfer nip N ₁ .

When the float is used as in Example 1, a particular problem is the influence of the peeling discharge in the separation process after the transfer nip N ₁ .

In the gap before the transfer nip N ₁ , the intermediate transfer member 1
There is no electric charge in the upper independent electrode, and by setting it to the float potential, the potential of this portion does not become an extreme value that causes discharge. However, the transfer charge is moved from the photosensitive drum 2 when passing through the transfer nip N ₁ , and the surface of the intermediate transfer member 1 has a positive charge.

In the separation process after the transfer nip, the distance between the photosensitive member and the intermediate transfer member 1 increases, and as the electrostatic capacitance of this portion decreases, the potential generated by the charges charged on the surface of the intermediate transfer member 1 becomes extremely large. And may cause a discharge. Since the electrodes are floats, violent peeling discharge, which occurs in the conventional configuration, does not occur, but it is preferable to regulate the potential to a particularly low value in the gap after the transfer nip N ₁ .

Therefore, as shown in FIG. 9, in addition to the first embodiment, a voltage of another value is applied to the independent electrode groups existing in the positions before and after the transfer nip N ₁ in the feeding portion at the end of the intermediate transfer member 1. Means for applying are provided.

As the applying means, a conductive brush was used in this embodiment. In the configuration of the present embodiment, since a high voltage having a different value is applied to the adjacent and adjacent positions, there is a risk of leakage between the electrodes, and the blade shape and the roller shape can maintain the mutual position of the electrodes accurately. It is also possible to use a thing as a voltage application means.

[0095] independently electrode group in this embodiment is independently electrode group at a position corresponding to the transfer nip N ₁ to + 1000V, which corresponds to the gap portion of the transfer nip N ₁ before and after applying a 0V.

By using such means, the electric field generated in the gap around the transfer nip N ₁ can be limited in this embodiment, and the peeling discharge after the transfer nip N ₁ can be prevented in particular. <Embodiment 5> This embodiment is characterized in that an independent electrode layer is provided on the surface of the transfer roller 6 as a transfer member. In a normal electrophotographic apparatus, when the toner image on the photosensitive drum 2 is transferred onto the transfer material P such as paper by using the transfer roller 6, it is the same as the above-mentioned embodiment taking the intermediate transfer body 1 as an example. As described above, image scattering due to toner flying between the transfer material P and the photosensitive drum ₂ before the transfer nip N ₂ and the transfer nip N ₂
Disturbance image by ₂ after the separation discharge, the charge penetrates the transfer material P is positive memory of the photosensitive member by moving the photosensitive drum 2 is wrong.

In order to prevent this, conventionally, in order to reduce the electric field between the transfer material P and the photosensitive drum 2 or to shorten the flying distance of the toner, the transfer material P is placed along the photosensitive drum 2. Techniques such as penetrating the transfer nip N ₂ have been used. Further, even after the transfer nip N ₂ , the transfer material P is conveyed along the photosensitive drum 2 side to reduce the partial pressure between the photosensitive drum 2 and the transfer material P, thereby preventing peeling discharge.

However, such a means is not suitable for the transfer material P.
However, there is a problem in that the degree of freedom of the apparatus configuration is lost because the transfer path of the transfer material P is limited, and the transfer material P is transferred from the transfer nip N _{2 along the} photosensitive drum 2 so that separation is difficult. Was.

Therefore, in the present embodiment, by providing the independent electrode layer on the surface of the transfer roller 6, the transfer electric field is limited to within the transfer nip N ₂ , and these problems can be prevented.

A concrete example is shown in FIG.

The transfer roller 6 is formed as an elastic roller having a diameter of 16 mm by covering a core metal having a diameter of 6 mm with an insulating sponge. On this, the anisotropically conductive cloth member described in Example 1 was wound and further coated with a resistance layer.
As a result, the roller resistance value measured at the transfer nip N ₂ of the transfer roller 6 was 10 ⁸ Ω.

The voltage applying means forms a ring-shaped electrode on the flange of the photosensitive drum as shown in the second embodiment,
The electrode and the end of the transfer roller 6 which is not covered with the resistance layer are brought into contact with each other to apply a voltage only within the transfer nip N ₂ . The ring is supplied with power from a high-voltage power supply via a conductive brush.

As described in the third embodiment, in order to expect a further effect, the core metal of the transfer roller 6 is set to another voltage such as ground, and the elastic layer is set to the medium resistance, so that the transfer nip N ₂ outside the transfer nip N ₂ is exposed. It is possible to further limit the electric field in the air gap.

An example in which an image is actually formed by using such a transfer roller 6 will be shown. As a comparative example, an example using a single-phase roller made by coating a core metal with a sponge of medium resistance is shown.

Images were output in a low humidity environment with a relative humidity of 10% RH. In such an environment, the transfer material P dries and its resistance value rises, so that image abnormalities such as peeling discharge easily occur. The transfer material P was conveyed straight to the transfer nip N ₂ between the photosensitive drum 2 and the transfer roller 6, as shown by 10.

When +3 kV was applied to the transfer bias using the sponge roller of the comparative example, the toner flew by the electric field in the gap before the transfer nip N _2, and the image was scattered. Further, in front of the transfer nip N ₂ , the image is disturbed due to the peeling discharge, and the transfer efficiency is decreased due to the retransfer from the transfer material P to the photosensitive drum 2. Further, the transfer material P
A discharge occurred through the hole and a plus memory was formed on the photosensitive drum 2.

On the other hand, when the transfer roller 6 having the structure of the present embodiment is used, the charges in the gap around the transfer nip N ₂ can be suppressed, and therefore, even if the same bias is applied, these problems will occur. Did not occur. Further, since the anisotropic conductive cloth member is used as the independent electrode group, the hardness of the transfer roller 6 can be kept low, and image defects such as voids in the transfer do not occur.

As described above, in the present embodiment, the independent electrode group is provided on the surface of the transfer roller 6 and the transfer bias is applied only to the independent electrode in the transfer nip to overcome the problems of the conventional transfer roller 6. I was able to do it.

[0109]

As described above, according to the present invention,
For example, with respect to the photosensitive member as the first image carrier and the intermediate transfer member as the second image carrier, a large number of independent electrodes subdivided in the moving direction are provided, and the photosensitive member and the intermediate transfer member are provided. By applying the transfer bias only to the independent electrode group located in the transfer nip between the transfer nip and the transfer nip, the electric field in the upstream and downstream areas of the transfer nip is controlled while controlling the electric field of the toner. Good scattering can be performed by preventing scattering and peeling discharge. At this time, a uniform transfer nip having elasticity is formed by using the independent electrode group, for example, an anisotropic conductive cloth member using an insulating thread member for the warp thread and a conductive thread member for the weft thread. Therefore, it is possible to prevent blank characters and damage to the photoconductor.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of an intermediate transfer member according to a first embodiment.

FIG. 2 is a schematic configuration diagram of an image forming apparatus (color printer) equipped with the intermediate transfer member according to the first embodiment.

FIG. 3 is a view showing a means for limiting the electric field outside the transfer nip in the conventional transfer drum 1.

FIG. 4 is a diagram showing a configuration of an anisotropically conductive cloth member according to the first embodiment.

FIG. 5 is a perspective view showing a configuration of a transfer device according to a second embodiment.

FIG. 6 is a perspective view showing the configuration of an intermediate transfer member of Example 3.

FIG. 7 is an equivalent circuit diagram showing the potential of the intermediate transfer member before and after the transfer nip of Example 3.

FIG. 8A is a diagram showing an electric field distribution of a conventional intermediate transfer member having no independent electrode. (B) shows Example 1 and Example 2
FIG. 6 is a diagram showing the electric field distribution of the intermediate transfer member in the above configuration. (C)
FIG. 8 is a diagram showing an electric field distribution of an intermediate transfer member in Example 3.

FIG. 9 is a vertical cross-sectional view showing the configuration of a transfer device according to a fourth embodiment.

FIG. 10 is a schematic configuration diagram of an image forming apparatus in which a transfer roller according to a fifth exemplary embodiment is mounted.

FIG. 11 is a conceptual diagram showing a problem of a conventional transfer device. [Brief Description of Drawings] 1 intermediate transfer body (transfer drum) 2 first image carrier (photosensitive drum) 3 exposure device 4 charging device 5 developing device 6 transfer member (transfer roller) 7 transfer drum cleaning device 11 support substrate (Drum) 12 Elastic layer 13 Cloth member (independent electrode) 14 Resistance layer 15 Voltage applying means (conductive brush) 16A, 17A flange 16B, 17B electrode 71 Photosensitive drum cleaning device 91 Corona discharger 92 Transfer drum 93 Electric field limiting means 131 Insulating thread member 132 Conductive thread member N ₁ , N ₂ Transfer nip P Transfer material

Claims (12)

[Claims] 1. A transfer device for electrostatically transferring a toner image formed on a first image carrier onto a second image carrier, comprising: a first image carrier and a second image carrier. At least one of the bodies has a plurality of independent electrodes that are electrically subdivided in the moving direction, and a voltage applying unit that applies a voltage to each of the independent electrodes arranged at a predetermined position according to the movement. And a plurality of independent electrodes, which are cloth members woven by interweaving a conductive thread member and an insulating thread member. 2. The transfer device according to claim 1, wherein the first image bearing member is a photoconductor, and the second image bearing member is an intermediate transfer member. 3. The transfer device according to claim 2, wherein the intermediate transfer member is a transfer belt or a transfer drum. 4. A toner image formed on an intermediate transfer member,
In a transfer device for electrostatically transferring onto a transfer material by a transfer member, at least one of the intermediate transfer member and the transfer member is
A plurality of independent electrodes that are electrically subdivided in these moving directions, and a voltage applying unit that applies a voltage to each of the independent electrodes arranged at a predetermined position according to the movement, The transfer device, wherein the independent electrode is a cloth member woven by interweaving a conductive thread member and an insulating thread member. 5. A transfer device for electrostatically transferring a toner image formed on a photoconductor onto a transfer material by a transfer member, wherein the transfer member is electrically subdivided in a moving direction of the transfer member. A plurality of independent electrodes, and a voltage applying unit that applies a voltage to each of the independent electrodes arranged at a predetermined position according to the movement, wherein the plurality of independent electrodes are conductive thread members. A transfer device, which is a cloth member woven by interweaving with an insulating thread member. 6. The transfer device according to claim 4, wherein the transfer member is a transfer roller. 7. The transfer device according to claim 1, wherein a resistance layer is laminated on the cloth member. 8. The transfer device according to claim 7, wherein the resistance layer is formed by impregnating the cloth member with a coating agent. 9. A transfer device for electrostatically transferring a toner image formed on a first image bearing member onto a second image bearing member, the first image bearing member and the second image bearing member. At least one of the bodies is provided with a conductive substrate to which a voltage can be applied, a resistance layer, a large number of independent electrodes electrically subdivided in the moving direction, and arranged at a predetermined position along with the moving. And a voltage applying unit that applies a voltage to each of the independent electrodes. 10. The first image carrier is a photoconductor,
The transfer device according to claim 9, wherein the second image carrier is an intermediate transfer member. 11. A transfer device for electrostatically transferring a toner image formed on a first image bearing member to a second image bearing member, the first image bearing member and the second image bearing member. At least one of the bodies has a plurality of independent electrodes that are electrically subdivided in the moving direction, and a voltage applying unit that applies a voltage to each of the independent electrodes arranged at a predetermined position according to the movement. A transfer voltage is applied to the independent electrode existing in the transfer nip between the first image carrier and the second image carrier, and a voltage different from this is applied to the independent electrode existing downstream in the moving direction. The transfer device is characterized by applying a voltage. 12. The first image carrier is a photoconductor,
The transfer device according to claim 11, wherein the second image carrier is an intermediate transfer member.