JPH11282283A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of forming an excellent image being free from the transfer unevenness. SOLUTION: This image forming device, an intermediate transfer body 20 is provided with a conductive layer 21, a resistance layer 22 formed on the conductive layer, and an electrode part 23 exposed on the surface of an end part of the intermediate transfer body for feeding transfer voltage to the conductive layer, and an annular and rib-shaped gap member 25 for forming the gap G between the electrode 23 and a photoreceptor 10, is disposed on the position except an edge part 23a of the electrode 23 in the intermediate transfer body end part. The gap member 25 is composed of material provided with resistance value higher than the resistive layer on the intermediate transfer medium, preferably the insulating material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus such as a printer, a facsimile, a copying machine, etc. for forming an image by using an electrophotographic technique. In particular, it relates to the intermediate transfer member.

[0002]

2. Description of the Related Art In general, an image forming apparatus using an electrophotographic technique includes a photosensitive member having a photosensitive layer on an outer peripheral surface of a conductive layer, a charging means for uniformly charging the photosensitive layer of the photosensitive member, and a charging device. Exposure means for selectively exposing the photosensitive layer uniformly charged by the means to form an electrostatic latent image, and applying a toner as a developer to the electrostatic latent image formed by the exposure means The image forming apparatus includes a developing unit that forms a visible image (toner image), and a transfer device that transfers the toner image developed by the developing unit to a recording medium such as paper.

Conventionally, as a transfer device for transferring a toner image developed on a photoconductor to a recording medium such as paper, a toner image formed on the photoconductor is transferred (primary transfer).
There is known an image forming apparatus including an intermediate transfer member for further transferring (secondarily transferring) the toner image to a recording medium.

FIG. 5 is a diagram showing an example of an image forming apparatus provided with such an intermediate transfer member, wherein (a) is a schematic perspective view,
(B) is a bb partial cross-sectional view in FIG.

In FIG. 1, reference numeral 1 denotes a photosensitive member, and a conductive layer 1
a and a photosensitive layer 1b formed on the conductive layer 1a. The conductive layer 1a is grounded.

Reference numeral 2 denotes an intermediate transfer member, which is composed of, for example, a dielectric material (medium resistance layer) having a resistance value of about 10 ⁷ to 10 ¹⁴ Ωcm. Such an intermediate transfer body 2 can be prepared by kneading conductive carbon into a synthetic resin or the like.

The intermediate transfer member 2 contacts the photosensitive member 1 at least during image formation, and the contact portion T1 forms a transfer portion (in this case, a primary transfer portion). In the primary transfer section T1, a primary transfer roller 3 is arranged from inside the intermediate transfer body 2, and a primary transfer voltage is applied to the intermediate transfer medium 2 by the primary transfer roller 3.

Further, a secondary transfer roller 4 for applying a secondary transfer voltage is pressed against the intermediate transfer member 2, and the pressed portion forms a secondary transfer portion T2. In the secondary transfer portion T2, a backup roller 5 is disposed from inside the intermediate transfer member 2.

At the time of image formation, first, the photosensitive member 1 and the intermediate transfer member 2 are driven to rotate, and the photosensitive layer 1b of the photosensitive member 1 is uniformly charged by a charging unit (not shown), and then exposed to light (see FIG. (Not shown) to form an electrostatic latent image. Next, toner as a developer is applied to the electrostatic latent image by a developing unit (not shown) to form a visible image (toner image), and this toner image is transferred onto the intermediate transfer body 2 in the primary transfer unit T1. Then, in the secondary transfer portion T2,
The image is transferred to a recording medium such as a sheet supplied to the secondary transfer unit T2.

The recording medium onto which the toner image has been transferred passes through a fixing device (not shown), where the toner image is fixed.

[0011]

The intermediate transfer member 2 in the above-described conventional image forming apparatus has a single-layer structure formed by kneading conductive particles such as conductive carbon into synthetic resin or the like. In addition, since the conductive particles are difficult to uniformly disperse in the resin, the resistance value tends to be uneven.

Therefore, there is a problem that the electric field in the transfer portion is likely to be uneven, and consequently the transfer unevenness is easily generated.

In addition, local protrusions on the surface of the intermediate transfer member are easily caused by a gelling component in the resin or agglomerates of the conductive particles. At the contact portion with the roller disposed on the back surface, the contact is locally unstable, and there is a problem that transfer unevenness is likely to occur.

An object of the present invention is to provide an image forming apparatus which solves the above-mentioned problems, hardly causes transfer unevenness, and can form a good image.

[0015]

According to another aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive member having an image formed on a surface of a photosensitive layer formed on a conductive layer; An image forming apparatus, comprising: a transfer portion formed between the transfer portion and the surface; and an intermediate transfer member on which the image is transferred at the transfer portion, wherein the intermediate transfer member includes a conductive layer and a conductive layer on the conductive layer. A resistive layer to be formed and to which the image is transferred, and an electrode portion exposed on the surface of an end portion of the intermediate transfer member for supplying a transfer voltage to the conductive layer, and the electrode portion and the photoconductor An annular rib-shaped gap member forming an interval between the intermediate transfer member and the end portion of the intermediate transfer member is provided at a position avoiding the edge of the electrode portion.

According to a second aspect of the present invention, there is provided an image forming apparatus according to the first aspect.
In the above image forming apparatus, the gap member is made of a material having a higher resistance value than a resistance layer of the intermediate transfer medium.

According to the third aspect of the present invention, there is provided the image forming apparatus according to the second aspect.
In the above image forming apparatus, the gap member is made of an insulating material.

According to a fourth aspect of the present invention, in the image forming apparatus of the first, second, or third aspect, the sectional shape of the gap member is trapezoidal.

[0019]

According to the image forming apparatus of the first aspect, the following effects can be obtained.

(A) A transfer portion is formed between a photosensitive member on which an image is formed on the surface of the photosensitive layer formed on the conductive layer and the photosensitive member surface, and the image is transferred at the transfer portion. The image formed on the surface of the photoreceptor is transferred to the intermediate transfer body at the transfer section.

The intermediate transfer member has a multilayer structure having a conductive layer and a resistive layer formed on the conductive layer and onto which the image is transferred. It can be formed by applying, curing, and drying a resin solution in which particles are dispersed. Thus, when the conductive particles are dispersed in the resin solution in which the resin is dissolved in the solvent, the dispersibility of the conductive particles becomes better than in the case where the conductive particles are kneaded in the hot-melted resin. . Therefore, resistance unevenness of the resistance layer itself can be suppressed. Also, since the dispersibility of the conductive particles becomes good,
Local projections on the surface of the resistive layer can be almost completely eliminated, and the contact with the photoreceptor or the like can be stabilized to prevent poor transfer.

Further, since the resistive layer is formed integrally on the conductive layer, when a transfer voltage is supplied to the conductive layer by the electrode portion, the potential on the back side of the resistive layer becomes substantially uniform, and the entire surface of the transfer region becomes uniform. As a result, a substantially uniform transfer electric field is formed.

Therefore, according to the image forming apparatus of the first aspect, unevenness of the electric field in the transfer portion is less likely to occur, and as a result, a good image with less transfer unevenness can be formed.

Moreover, since the electrode portion for supplying the transfer voltage to the conductive layer is exposed on the surface of the end portion of the intermediate transfer member, the transfer voltage can be easily supplied to the conductive layer.

By the way, the intermediate transfer member has the above-mentioned structure, that is, the resistance layer is formed on the conductive layer, and the electrode portion for supplying the transfer voltage to the conductive layer is provided at the end surface of the intermediate transfer member. It has been found that the following problem occurs when the configuration is exposed to the light.

As shown in FIG. 6A, a pinhole 1c may be present in the photosensitive layer 1b of the photoreceptor 1, and this pinhole 1c exists at an end of the photoreceptor 1 as shown. May be.

In such a situation, as shown in FIG. 6B, the structure of the intermediate transfer member 20 is such that the resistance layer 22 is formed on the conductive layer 21 and the transfer voltage V1 is supplied to the conductive layer 21. Of the photosensitive member 1 through the pinhole 1c from the electrode portion 23 if no measures are taken if the electrode portion 23 is exposed on the surface of the end portion of the intermediate transfer body 10 for this purpose. 1a is generated, and the transfer voltage V
1 was not properly applied, and it was found that transfer failure occurred.

On the other hand, according to the image forming apparatus of the first aspect, the annular rib-shaped gap member for forming a space between the electrode portion of the intermediate transfer member and the photosensitive member is provided in the intermediate transfer member. Since the gap member is provided at the body end, it is possible to form an appropriate gap between the surface of the conductive layer of the photosensitive member and the surface of the electrode portion of the intermediate transfer member in the transfer portion by the gap member.

Accordingly, even if the intermediate transfer member has the above-described structure, even if there is a pinhole at the end of the photoreceptor, the discharge current does not occur, so that transfer failure does not occur.

When the intermediate transfer member has a conventional single-layer structure, as described above, even if there is a pinhole 1c at the end of the photosensitive member 1, as shown in FIG. No problem.

(B) Since the gap member is provided in an annular rib shape at a position avoiding the edge of the electrode portion in the intermediate transfer member, it functions as a partition, and the toner on the resistance layer is removed. , At least to the edge of the electrode portion.

Therefore, it is possible to prevent a power supply failure that may occur when the toner on the resistance layer moves to the entire surface of the electrode portion and adheres to the surface of the electrode portion.

(C) Since the gap member is formed in the shape of a rib, a gap member having substantially the same width as the above-mentioned electrode portion is provided at the end of the photosensitive member, or a sliding contact having substantially the same width as the above-mentioned electrode portion. The contact area between the gap member and the photoreceptor or the intermediate transfer member is reduced as compared with the case where the member is interposed between the photoreceptor and the intermediate transfer member so as to be able to slidably contact them.
Therefore, an increase in the rotational load, twisting, and meandering (deviation) due to the application of a force to a part of the photosensitive member and the intermediate transfer member in the width direction (axial direction) are reduced.

According to the image forming apparatus of the second aspect, in the image forming apparatus of the first aspect, the gap member is made of a material having a higher resistance value than a resistance layer of the intermediate transfer medium. Therefore, generation of the discharge current described above is more reliably prevented, and transfer failure is reliably prevented.

According to the image forming apparatus of the third aspect, in the image forming apparatus of the second aspect, since the gap member is made of an insulating material, the generation of the discharge current described above is further ensured. Thus, the transfer failure is more reliably prevented.

According to the image forming apparatus of the fourth aspect, in the image forming apparatus of the first, second, or third aspect, since the cross-sectional shape of the gap member is trapezoidal, the strength of the gap member is improved. Will be done.

[0037]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIGS. 1A and 1B show a first embodiment of an image forming apparatus according to the present invention, wherein FIG. 1A is a schematic perspective view, and FIG. It is a bb partial sectional view in ().

In the figure, reference numeral 10 denotes a photosensitive member, and a conductive layer 10a and a photosensitive layer 10 formed on the conductive layer 10a.
b. The conductive layer 10a is grounded.

Reference numeral 20 denotes an intermediate transfer member, and a conductive layer 21
A resistive layer 22 formed on the conductive layer 21 and a transfer voltage V applied to the conductive layer 21 exposed at the end surface of the intermediate transfer member.
1 for supplying power to the power supply 1. In this embodiment, the conductive layer 21 is formed on an insulating substrate 24 made of a synthetic resin, and the resistance layer 22 is formed on the conductive layer 21. The conductive layer 21 is exposed in a strip shape because the resistance layer 22 is removed in a strip shape at one side edge portion of the intermediate transfer body 20 or is not formed in a strip shape in advance, and the electrode portion 23 is formed in this exposed portion. . Note that the electrode portion can be formed by the strip-shaped exposed portion itself of the conductive layer 21.

The intermediate transfer member 20 comes into contact with the photosensitive member 10 at least at the time of image formation, and the contact portion T1 forms a transfer portion (in this case, a primary transfer portion). In the primary transfer portion T1,
The primary transfer roller 15 made of an elastic material such as rubber is arranged from the inside of the intermediate transfer body 20. However, the primary transfer roller 15 may not be necessarily provided.

As shown in FIG. 3A, an electrode roller 37 is disposed in contact with the electrode portion 23 of the intermediate transfer member 20. The primary transfer voltage V1 is applied to the reference numeral 21.

Further, a secondary transfer roller 38 for applying a secondary transfer voltage V2 is pressed against the intermediate transfer member 20, and the pressed portion forms a secondary transfer portion T2. The secondary transfer portion T2 includes a backup roller 33 from inside the intermediate transfer member 20.
Is arranged.

At least one of the photoreceptor 10 and the intermediate transfer member 20 is formed in a flexible thin cylindrical shape or belt shape.

At the time of image formation, first, the photosensitive member 10 and the intermediate transfer member 20 are driven to rotate, and the photosensitive layer 1 of the photosensitive member 10 is rotated.
After 0b is uniformly charged by a charging unit (not shown), it is selectively exposed by an exposure unit (not shown) to form an electrostatic latent image. Next, a toner as a developer is applied to the electrostatic latent image by a developing unit (not shown) to form a visible image (toner image), and this toner image is transferred onto the intermediate transfer body 20 in the primary transfer unit T1. After that, the secondary transfer portion T2
Is transferred to a recording medium such as a sheet supplied to the secondary transfer section T2.

The recording medium onto which the toner image has been transferred passes through a fixing device (not shown), where the toner image is fixed.

By the way, as described above, the pinhole 10c may exist in the photosensitive layer 10b of the photoconductor 10, and this pinhole 10c exists at the end of the photoconductor 10 as shown in FIG. May be.

In such a situation, the intermediate transfer member 20
Is formed on the conductive layer 21 as described above.
2 is formed, and the electrode portion 23 for supplying the transfer voltage V1 to the conductive layer 21 is exposed on the surface of the end portion of the intermediate transfer body 10, if no measures are taken.
As described above, a discharge current flows from the electrode portion 23 to the conductive layer 10a of the photoreceptor 10 via the pinhole 10c, and the transfer voltage V1 is not properly applied, resulting in a transfer failure.

Therefore, in this embodiment, the electrode portion 23
An annular rib-shaped gap member 25 that forms a space between the intermediate transfer member 20 and the photosensitive member 10 is provided at a position avoiding the edge 23 a of the electrode portion 23 at the end of the intermediate transfer member 20. The cross-sectional shape can be configured as a trapezoid as shown by a virtual line 25 '. The gap member 25 is provided so as not to cover the entire surface of the electrode portion 23 of the intermediate transfer body 20.

The gap member 25 is formed of a material having a higher resistance value than the resistance layer 22 of the intermediate transfer medium 20, more preferably, an insulating material.

In this embodiment, since the annular rib-shaped gap member 25 is provided on the electrode portion 23, the electrode roller 37 extends over the gap member 25. In order to be able to contact the surface of the gap member, the groove member 25 has a concave groove into which the gap member 25 enters, or an elastic roller is used. Preferably, it is constituted by an elastic roller having the above-mentioned concave groove.

According to the image forming apparatus as described above, the following operation and effect can be obtained.

(A) A transfer portion T1 is formed between the photosensitive member 10 on which an image is formed on the surface of the photosensitive layer 10b formed on the conductive layer 10a and the surface of the photosensitive member.
And the intermediate transfer body 20 to which the image is transferred, the image formed on the surface of the photoconductor 10 is transferred to the intermediate transfer body at the transfer portion T1.

Then, the intermediate transfer member 20 is
And a resistance layer 22 formed on the conductive layer 21 and onto which the image is transferred, so that the resistance layer 22 is coated with, for example, a resin solution in which conductive particles are dispersed. Then, it can be formed by curing and drying. Thus, when the conductive particles are dispersed in the resin solution in which the resin is dissolved in the solvent, the dispersibility of the conductive particles becomes better than in the case where the conductive particles are kneaded in the hot-melted resin. . Therefore, resistance unevenness of the resistance layer 22 itself can be suppressed. In addition, since the dispersibility of the conductive particles is improved, local protrusions on the surface of the resistance layer 22 can be substantially prevented from occurring, and the contact with the photoconductor 10 and the like can be stabilized to prevent poor transfer. Becomes possible.

Since the resistance layer 22 is formed integrally on the conductive layer 21, the conductive layer 21 is
When a transfer voltage is supplied to the transfer region, the potential on the back side of the resistance layer 22 becomes substantially uniform, and a substantially uniform transfer electric field is formed over the entire transfer region.

Therefore, according to the image forming apparatus of this embodiment, unevenness of the electric field in the transfer portion T1 is less likely to occur, and as a result, a good image with less transfer unevenness can be formed.

Moreover, since the electrode portion 23 for supplying the transfer voltage V1 to the conductive layer 21 is exposed on the surface of the end portion of the intermediate transfer member 20, for example, the electrode roller 3 as shown in FIG.
7, the transfer voltage V1 can be easily supplied to the conductive layer 21.

(B) Since an annular rib-shaped gap member 25 for forming a space between the electrode portion 23 of the intermediate transfer member 20 and the photosensitive member 10 is provided at the end of the intermediate transfer member 20. The gap member 25 makes it possible to form an appropriate gap G between the surface of the conductive layer 10a of the photoconductor 10 in the transfer portion T1 and the surface of the electrode portion 23 of the intermediate transfer member 20.

Therefore, despite the intermediate transfer member 20 having the above structure, the pinhole 1
Even if 0c is present, the occurrence of the discharge current can be prevented, and the occurrence of transfer failure can be prevented. In addition, it is desirable that the interval G is set to be 20 μm or more. It has been confirmed by experiments by the present inventor that if the interval G is 20 μm or more, the discharge current does not occur at the transfer voltage adopted in this type of image forming apparatus.

Further, even if there is a partly thin portion in the photosensitive layer 10b opposite to the electrode portion 23, generation of a new pinhole due to the discharge phenomenon is prevented.

(C) The gap member 25 is the intermediate transfer member 2
0 is provided in an annular rib shape at a position avoiding the edge portion 23a of the electrode portion 23, so that it serves as a partition wall, and the toner on the resistance layer 22
3 is prevented from moving to the edge 23a.

In particular, a cleaning member for collecting waste toner remaining on the resistance layer 22 is generally disposed on the resistance layer 22 of the intermediate transfer member 20. Waste toner may spill out or not be completely recovered.

On the other hand, according to this embodiment, the gap member 25 functions as a partition wall for the toner, so that the waste toner is prevented from moving over the entire surface of the electrode portion 23. It will be.

Therefore, the toner on the resistance layer 22 moves to the entire surface of the electrode portion 23 (to the edge portion 23a) and
It is possible to prevent a power supply failure that may occur due to attachment to the three surfaces.

(D) Since the gap member 25 is formed in a rib shape, a gap member having substantially the same width as that of the electrode portion 23 is provided at the end of the photosensitive member, or a gap member having substantially the same width as the electrode portion. The contact area between the gap member 25 and the photoconductor 10 or the intermediate transfer body 20 is reduced as compared with the case where the sliding contact member is interposed between the photoconductor and the intermediate transfer body so as to be able to slide therebetween. It will be. Therefore, the increase in the rotational load, the twist, and the meandering (deviation) due to the application of a force to a part of the photoconductor 10 and the intermediate transfer body 20 in the width direction (axial direction) are reduced.

(E) Since the gap member 25 is made of a material having a higher resistance value than the resistance layer 22 of the intermediate transfer medium 20, the above-described generation of the discharge current is more reliably prevented. . When the gap member 25 is made of an insulating material, the generation of the discharge current described above is more reliably prevented.

(F) The gap member 25 is used as the intermediate transfer member 20
Since it is provided on the electrode portion 23, an effect that a relatively thin and weak electrode portion is reinforced is obtained. further,
When the cross-sectional shape of the gap member 25 is configured to be trapezoidal as indicated by a virtual line 25 ', the strength of the gap member 25 itself is also improved.

<Second Embodiment> FIG. 2 is a view showing a second embodiment of the image forming apparatus according to the present invention.
It is a figure corresponding to the bb partial sectional view in (a).
In this figure, the same or corresponding parts as in the first embodiment described above are denoted by the same reference numerals.

The second embodiment differs from the first embodiment in that a gap member 25 is provided at an end of the resistance layer 22 of the intermediate transfer member 20.

The resistance layer 22 of the intermediate transfer member 20 has a structure in which a conductive agent is dispersed in a binder resin.
It is desirable that the same material as the binder resin be formed integrally with the resistance layer 22.

According to the second embodiment, the same functions and effects as those (a) to (e) of the first embodiment can be obtained.

When the resistance layer 22 of the intermediate transfer body 20 is formed by dispersing a conductive agent in a binder resin, and the gap member 25 is formed integrally with the resistance layer 22 using the same material as the binder resin. In this case, the bonding force between the gap member 25 and the resistance layer 22 is increased, and as a result, the strength of the gap member 25 is improved.

<Third Embodiment> FIG. 3 is a view showing a third embodiment of the image forming apparatus according to the present invention.
It is a figure corresponding to the bb partial sectional view in (a).
In the figure, the same or corresponding parts as in the first embodiment described above are denoted by the same reference numerals.

The third embodiment differs from the first embodiment in that the gap member 25 is provided at the boundary between the resistance layer 22 and the electrode portion 23.

The resistance layer 22 of the intermediate transfer member 20 has a structure in which a conductive agent is dispersed in a binder resin.
Is formed integrally with the resistance layer 22 and the electrode portion 23 using the same material as the binder resin.

According to the third embodiment, the same functions and effects as those (a) to (f) of the first embodiment can be obtained.

Further, the gap member 25 is connected to the resistance layer 22.
Because it is provided at the boundary between the electrode and the electrode portion 23, a relatively weak boundary made of a different material is reinforced. The resistance layer 22 of the intermediate transfer member 20 is formed by dispersing a conductive agent in a binder resin.
However, since it is formed integrally with the resistance layer 22 using the same material as the binder resin, the bonding force between the gap member 25 and the resistance layer 22 increases, and as a result, the strength of the gap member 25 improves. Become.

[0078]

FIG. 4 is a schematic diagram showing an example of an image forming apparatus to which the first, second, or third embodiment can be applied. In FIG. 4, the same or corresponding parts as those in the above-described embodiment are denoted by the same reference numerals.

This image forming apparatus is applicable to yellow, cyan,
This is an apparatus that can form a full-color image using a developing device using magenta and black toners.

In FIG. 4, reference numeral 10 denotes a photosensitive member, which can be rotationally driven in a direction indicated by an arrow by an appropriate driving means (not shown).

Around the photoreceptor 10, along the rotation direction thereof, a charging roller 11 as a charging unit, a developing roller 17 (Y, M, C, K) as a developing unit, an intermediate transfer device 30, and a cleaning unit Means 12 are arranged.

The photosensitive member 10 has a cylindrical conductive substrate 10a.
And a photosensitive layer 10b formed on the surface thereof.

The charging roller 11 can contact the outer peripheral surface of the photoconductor 10 to uniformly charge the photosensitive layer 10b (for example, it can be charged to about -600 V). The outer peripheral surface of the uniformly charged photoreceptor 10 is selectively exposed to light L in accordance with desired image information by an exposure unit (not shown).
An electrostatic latent image is formed thereon. The potential of the exposed portion, that is, the portion where the electrostatic latent image is formed can be set to, for example, about -100V.

This electrostatic latent image is developed by the developing roller 17
The toner charged to “−” is applied and developed.

The developing rollers 17Y for yellow, the developing roller 17C for cyan, the developing roller 17M for magenta, and the developing roller 1 for black.
7K is provided. These developing rollers 17Y, 17
C, 17M, and 17K can selectively come into contact with the photoconductor 10, and when they come into contact, any one of yellow, cyan, magenta, and black is applied to the surface of the photoconductor 10. Then, the electrostatic latent image on the photoconductor 10 is developed.

The developed toner image is transferred onto an intermediate transfer belt 20 as an intermediate transfer member described later.

After the transfer, the cleaning means 12
A cleaner blade 13 for scraping off the toner remaining on and adhering to the outer peripheral surface of the photoreceptor 10, and a receiving unit 14 for receiving the toner scraped off by the cleaner blade 13
And

The intermediate transfer device 30 includes a driving roller 31 and
It has four driven rollers 32, 33, 34, 35 and an intermediate transfer belt 20 stretched around these rollers.

The drive roller 31 rotates at substantially the same peripheral speed as the photosensitive member 10 because a gear (not shown) fixed to an end of the drive roller 31 meshes with a drive gear (not shown) of the photosensitive member 10. Driven and therefore the intermediate transfer belt 2
0 can be circulated at substantially the same peripheral speed as the photoconductor 10 in the direction of the arrow shown in the figure.

The driven roller 35 is disposed at a position where the intermediate transfer belt 20 is pressed against the photosensitive member 10 by its own tension between the driven roller 35 and the driven roller 31.
Primary transfer portion T at the pressure contact portion between
1 is formed. Therefore, the primary transfer roller 15
Is not provided. The driven roller 35 is disposed near the primary transfer portion T1 on the upstream side in the circulation direction of the intermediate transfer belt 20.

The driving roller 31 includes the intermediate transfer belt 20
The electrode roller 37 is disposed via the intermediate transfer belt 2 via the electrode roller 37 as described above.
A transfer voltage (primary transfer voltage, for example, a voltage of about +500 V) V1 having a polarity opposite to the charging polarity of the photoconductor 10 can be applied to the 0 conductive layer 21.

The driven roller 32 is a tension roller, and urges the intermediate transfer belt 20 in the tension direction by an urging means (not shown).

The driven roller 33 is a backup roller that forms the secondary transfer portion T2. A secondary transfer roller 38 is opposed to the backup roller 33 via the intermediate transfer belt 20. The secondary transfer roller 38
It can be moved toward and away from the intermediate transfer belt 20 by an unillustrated contact and separation mechanism. The secondary transfer roller 38 applies a secondary transfer voltage V2 (a voltage higher than the primary transfer voltage, for example, +1
(Approximately 000 V).

The driven roller 34 is a backup roller for the belt cleaner 39. Belt cleaner 39
Is a cleaner blade 39 which comes into contact with the intermediate transfer belt 20 and scrapes off the toner remaining and adhering to the outer peripheral surface thereof.
a, and a receiving portion 39b for receiving the toner scraped off by the cleaner blade 39a. The belt cleaner 39 can be moved toward and away from the intermediate transfer belt 20 by a contact / separation mechanism (not shown).

The intermediate transfer belt 20 in this embodiment
Comprises an insulating substrate 24 made of sheet-shaped transparent PET, and AL is deposited thereon to form a conductive layer 21, on which urethane is used as a base (binder resin) and fine fluorine particles and a conductive agent are formed. Paint with SnO dispersed as
Both ends of the belt coated with the thickness of about 100 μm to form the resistance layer 22 are welded by ultrasonic fusion to have an endless shape. The surface resistance of the resistance layer 22 is 10 ⁸ to 10 ¹⁵ Ω / □.
And the volume resistivity is about 10 ⁷ to 10 ¹⁴ Ωcm.
The resistance value of the conductive layer 21 is preferably set to 10 6 Ωcm or less. The coating is applied while leaving one side edge portion of the belt in a band shape to expose the conductive layer 21 in a band shape, and the electrode portion 23 is formed in the exposed portion or the electrode portion 23 is formed in the exposed portion. And the electrode roller 3
7 is brought into contact. The gap member 25 is
It is formed of urethane. The gap member 25 is formed by silk printing or attaching a tape.
When formed by silk printing, a patterned formation with no variation in height is possible. In the case where the intermediate transfer member 20 is formed by attaching a tape, there is no need to perform a treatment such as heating during manufacturing, and therefore, there is no possibility that the intermediate transfer member 20 is deteriorated.

The electrode roller 37 is constituted by an elastic roller made of a single foam having conductivity.

While the intermediate transfer belt 20 is being driven to circulate, the toner image on the photoreceptor 10 is transferred onto the intermediate transfer belt 20 in the primary transfer section T1.
In the secondary transfer section T2, the toner image transferred onto the recording medium S is transferred to a recording medium S such as paper supplied between the secondary transfer roller 38 and the toner image. The recording medium S is fed from a sheet feeding device (not shown), and is supplied to the secondary transfer unit T2 at a predetermined timing by the gate roller pair 40.

The basic operation of the entire image forming apparatus as described above is as follows.

(I) When a print command signal (image forming signal) from a not-shown host computer or the like (a personal computer or the like) is input to the control unit of the image forming apparatus,
Photoconductor 10, developing roller 17, and intermediate transfer belt 2
0 is rotationally driven.

(Ii) The outer peripheral surface of the photoconductor 10 is uniformly charged by the charging roller 11.

(Iii) The outer peripheral surface of the uniformly charged photoreceptor 10 is subjected to selective exposure L in accordance with the image information of the first color (for example, yellow) by an exposure unit (not shown). A latent image is formed.

(Iv) Only the developing roller 17Y for the first color (for example, yellow) comes into contact with the photoconductor 10, whereby the electrostatic latent image is developed, and the toner image for the first color (for example, yellow) is formed. Is formed on the photoconductor 10.

(V) A primary transfer voltage V1 having a polarity opposite to the polarity of the toner is applied to the intermediate transfer belt 20, and the toner image formed on the photoconductor 10 is transferred to the primary transfer section, The image is transferred onto the intermediate transfer belt 20 at a pressure contact portion T1 with the intermediate transfer belt 20. At this time,
The secondary transfer roller 38 and the belt cleaner 39 are separated from the intermediate transfer belt 20.

(Vi) After the toner remaining on the photoreceptor 10 is removed by the cleaning means 12, the photoreceptor 10 is neutralized by static elimination light from a static elimination means (not shown).

(Vii) The above operations (ii) to (vi) are repeated as necessary. That is, the second color, the third color, the fourth color,
Is repeated on the intermediate transfer belt 20 to form a toner image corresponding to the content of the print command signal.

(Viii) The recording medium S is supplied at a predetermined timing, and immediately before or after the leading end of the recording medium S reaches the second transfer portion T2 (in short, at the desired position on the recording medium S, the intermediate transfer is performed). At the timing when the toner image on the belt 20 is transferred, the secondary transfer roller 38 is pressed against the intermediate transfer belt 20 and the secondary transfer voltage V2 is applied, so that the toner image on the intermediate transfer belt 20 (basically, (A full-color image) is transferred onto the recording medium S. Also,
The belt cleaner 39 comes into contact with the intermediate transfer belt 20, and the toner remaining on the intermediate transfer belt 20 after the secondary transfer is removed.

(Ix) The toner image is fixed on the recording medium S by passing the recording medium S through a fixing device (not shown), and then the recording medium S is discharged out of the apparatus.

According to the above-described image forming apparatus, the intermediate transfer belt 20 is applied to the photosensitive member 10 by the rollers 31 and 3.
5, the intermediate transfer belt 20 is pressed against the photoreceptor 10 by its own tension in the pressed portion (primary transfer portion) T1.

Therefore, without providing a pressing roller (primary transfer roller) for pressing the intermediate transfer belt 20 against the photosensitive member 10 at the pressing portion T1, the photosensitive member 10
The upper visible image can be transferred onto the intermediate transfer belt 20.

Further, the intermediate transfer belt 20 is formed on the conductive layer 21.
And a multilayer belt having a resistance layer 22 formed on the conductive layer 21 and pressed against the photoconductor 10, so that a pressure-contact portion (that is, a primary contact) between the photoconductor 10 and the intermediate transfer belt 20 is formed. The potential on the back side of the resistance layer 22 of the intermediate transfer belt 20 becomes substantially uniform over the entire area of the transfer portion (T1). As a result, transfer with less toner scattering is obtained.

In addition, the photosensitive member 10 and the intermediate transfer belt 20
Since the potential on the back side of the resistance layer 21 of the intermediate transfer belt 20 is substantially uniform over the entire area of the pressure contact portion (i.e., the primary transfer portion) T1, the transfer with the minimum necessary voltage is possible. .

Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments and examples, and can be appropriately modified and implemented within the scope of the present invention. It is.

[0113]

According to any one of the image forming apparatuses of the first to fourth aspects, transfer failure and unevenness of the electric field in the transfer portion are less likely to occur, and as a result, a good image with less transfer unevenness can be formed. It becomes possible. In addition, the transfer voltage can be easily and reliably supplied, and transfer failure does not occur.

Further, according to the image forming apparatus of the second aspect, transfer failure can be more reliably prevented.

According to the image forming apparatus of the third aspect, transfer defects can be more reliably prevented.

According to the image forming apparatus of the fourth aspect, the strength of the gap member is improved.

[0117]

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing a first embodiment of an image forming apparatus according to the present invention, wherein FIG. 1A is a schematic perspective view, and FIG. 1B is a partial cross-sectional view taken along line bb in FIG.

FIG. 2 is a view showing a second embodiment of the image forming apparatus according to the present invention, and is a view corresponding to a bb partial cross-sectional view in FIG.

FIG. 3 is a view showing a third embodiment of the image forming apparatus according to the present invention, and is a view corresponding to a bb partial cross-sectional view in FIG.

FIG. 4 is a schematic diagram showing an example of an image forming apparatus to which the first, second, or third embodiment is applied.

FIG. 5 is a diagram illustrating an example of a conventional image forming apparatus, and FIG.
Is a schematic perspective view, and (b) is a bb partial cross-sectional view in FIG.

6A and 6B are cross-sectional views for explaining a problem.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Photoconductor 10a Conductive layer 10b Photosensitive layer T1 Primary transfer part T1 (transfer part) 20 Intermediate transfer body 21 Conductive layer 22 Resistance layer 23 Electrode part G interval 25 Gap member

Claims (4)

[Claims] 1. A transfer section is formed between a photosensitive member on which an image is formed on a surface of a photosensitive layer formed on a conductive layer and a surface of the photosensitive member, and the image is transferred at the transfer section. An image forming apparatus having an intermediate transfer member, wherein the intermediate transfer member has a conductive layer, a resistive layer formed on the conductive layer to which the image is transferred, and a surface of an end portion of the intermediate transfer member. An electrode portion for supplying a transfer voltage to the conductive layer that is exposed, and an annular rib-shaped gap member that forms a gap between the electrode portion and the photoreceptor; An image forming apparatus, wherein the image forming apparatus is provided at a position avoiding an edge of an electrode portion at a body end. 2. The image forming apparatus according to claim 1, wherein the gap member is made of a material having a higher resistance value than a resistance layer of the intermediate transfer medium. 3. The image forming apparatus according to claim 2, wherein said gap member is made of an insulating material. 4. The image forming apparatus according to claim 1, wherein the gap member has a trapezoidal cross section.