JP2003005491A - Image forming device - Google Patents

Abstract

(57) [PROBLEMS] To prevent transfer failure during intermediate transfer (primary transfer) with a simple configuration in an image forming apparatus. An image forming apparatus includes a plurality of photoconductor units (21 to 24) provided corresponding to respective colors and configured to form a toner image by developing an electrostatic latent image formed on a photoconductor drum. ing. Then, using the conductive roller to which the voltage is applied as the primary transfer rollers 31 to 34, the intermediate transfer belt 11 is sandwiched between the primary transfer rollers, and the toner image is transferred to the intermediate transfer belt as a primary transfer image. The primary transfer image is transferred to a recording medium to form an image. At this time, when the measurement load is 4.9 N at the nip portion between the photosensitive drum and the intermediate transfer belt, the Asker C hardness on the surface of the intermediate transfer belt is set to 50 degrees or less, and the Asker C on the surface of the primary transfer roller is adjusted. C hardness is 30 degrees or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic process, and more particularly to an image forming apparatus using an intermediate transfer member.

[0002]

2. Description of the Related Art Generally, an electrophotographic image forming apparatus (image forming apparatus) using a so-called intermediate transfer member is known when a color image is formed by using an electrophotographic process. In this image forming apparatus, cyan (C), magenta (M),
A photoconductor unit including a photoconductor drum is provided for each color of yellow (Y) and black (BK). That is, it has a cyan photoconductor unit, a magenta photoconductor unit, a yellow photoconductor unit, and a black photoconductor unit. Then, the electrostatic latent images formed on the four photoconductor drums are developed using cyan toner, magenta toner, yellow toner, and black toner, respectively, to obtain toner images of respective colors. After the primary transfer of the toner images of the respective colors to the intermediate transfer body in sequence, the transfer image transferred to the intermediate transfer body is secondarily transferred and fixed on a recording medium (paper) to obtain a color image.

Each photoconductor unit is equipped with a photoconductor drum. Around the photoconductor drum, a charger (main charger), an exposure unit, a developing unit, a transfer unit (primary transfer unit), a cleaning unit, And a static elimination unit (eraser) is arranged. Then, after uniformly charging the surface of the photosensitive drum by the charger, an electrostatic latent image is formed on the surface of the photosensitive drum by the exposure unit. After that, the electrostatic latent image is developed by a developing device to form a toner image on the photosensitive drum, and the transfer device transfers the toner image on the photosensitive drum to the intermediate transfer member. Then, the residual toner remaining on the photosensitive drum is removed by the cleaning unit, and the surface of the photosensitive drum is further neutralized by the static eliminating unit.

As described above, after transferring the toner image as a primary transfer image onto the intermediate transfer member by each photoconductor unit, the primary transfer image is transferred onto the recording medium by using, for example, a secondary transfer device. A secondary transfer image is obtained. Then, the secondary transfer image on the recording medium is fixed on the recording medium by the fixing unit to obtain a color image.

In the image forming apparatus described above, an endless belt-shaped transfer member (hereinafter referred to as an intermediate transfer belt) that rotates in a predetermined direction is generally used as the intermediate transfer member, and the intermediate transfer member extends along the intermediate transfer belt. The above-mentioned photoconductor units are arranged. Further, the above-mentioned secondary transfer device is arranged on the downstream side in the rotation direction of the intermediate transfer belt.

In the above-mentioned image forming apparatus, since the toner images formed by the respective photoconductor units are sequentially transferred to the intermediate transfer belt, the toner images formed by the respective photoconductor units are accurately transferred. It is difficult to superimpose them, and image misregistration (color misregistration) and jitter are likely to occur.

In order to prevent image shift and jitter, the intermediate transfer belt is usually rotated (conveyed) while maintaining a tension of about 0.1 to 0.3 N / mm. Further, in order to prevent image shift, jitter, etc., it is necessary to reduce torque fluctuation during conveyance of the intermediate transfer belt. Therefore, it is necessary to reduce the width of the nip portion between the photosensitive drum and the intermediate transfer belt.

By the way, in the above-mentioned image forming apparatus, a conductive elastic roller is generally used as a transfer device, and the conductive elastic roller is sandwiched between the photosensitive drum and the conductive elastic roller while the conductive elastic roller is held. A voltage is applied to the roller to transfer the toner image from the photosensitive drum to the intermediate transfer belt. Thus, when the conductive elastic roller is used as the transfer device, for example, a ruled line image having a width of about 1 mm is (transferred) in parallel with the rotation direction (conveyance direction) of the intermediate transfer belt, and is primary-transferred to the intermediate transfer belt. Then, the intermediate portion (middle side) of the ruled line image may not be transferred. That is, a so-called "middle-out" state may occur. In particular, when a so-called multiple transfer image is transferred to the intermediate transfer belt, a transfer defect such as "middle gap" often occurs. For example, a yellow toner image, a magenta toner image, a cyan toner image,
When the toner image is primarily transferred to the intermediate transfer belt in the order of the black toner image and the so-called “red (R)” is transferred by the yellow toner image and the magenta toner image, the upper side on the intermediate transfer belt is used. An image defect (transfer defect) such as "middle-out" may occur in the magenta image transferred to.

On the other hand, as a method for preventing image defects, for example, the "image forming method" described in Japanese Patent Laid-Open No. 2000-75537 is known (hereinafter simply referred to as a conventional example).

In the conventional example, a developing process of developing an electrostatic latent image with toner to form a toner image on an electrostatic latent image carrier (photosensitive drum), and an intermediate transfer in which a voltage is applied to the toner image. Primary transfer step of transferring onto the body, and secondary transfer of transferring the toner image on the intermediate transfer body onto the transfer material while pressing a transfer means (for example, a secondary transfer roller) to which a voltage is applied to the transfer material. In this case, in the transmitted light spectrum in a state where the toner is made to contain a colorant and dispersed in an aqueous solution, the absorbance at wavelengths 260 nm and 400 nm when converted to a toner concentration of 1 g / liter is A And B, 0.80 ≦ A / B ≦ 1.0
I am trying to satisfy 4.

Further, in the conventional example, the surfaces of the above-mentioned intermediate transfer body and transfer means are constituted by elastic layers so that the volume resistivity value of the intermediate transfer body is lower than the volume resistivity value of the transfer means, and The surface hardness of the intermediate transfer member is JIS K-63.
When measured with 01, the range is 10 to 40 degrees, and the surface hardness of the transfer means is set to be larger than the hardness of the intermediate transfer body. Then, the transfer means is pressed against the intermediate transfer body to form a concave nip on the intermediate transfer body side, and a voltage is applied to the transfer means to transfer the toner image onto the transfer material.

[0012]

In the above-mentioned conventional example, as described above, when the absorbance at wavelengths 260 nm and 400 nm when converted to a toner concentration of 1 g / liter is A and B, 0.80 ≦ By satisfying A / B ≦ 1.04 and further defining the volume specific resistance values of the intermediate transfer body and the transfer means and the surface hardness of the intermediate transfer body and the transfer means, it is possible to prevent transfer defects such as voids. However, in the conventional example, it is only intended to prevent the transfer failure at the time of the secondary transfer from the intermediate transfer body to the transfer material (recording medium). It is difficult to prevent the transfer failure that occurs when the toner image is transferred from the drum to the intermediate transfer belt. That is, in the conventional example,
If a transfer failure occurs when the toner image is transferred from the photosensitive drum to the intermediate transfer belt, even if the transfer failure at the time of the secondary transfer from the intermediate transfer body to the transfer material (recording medium) can be prevented. However, as a result, there is a problem that an image defect occurs due to a failure of the primary transfer.

Further, in the conventional example, when the absorbances at wavelengths of 260 nm and 400 nm when converted to a toner concentration of 1 g / liter are A and B, 0.80 ≦ A / B
Since it is necessary to satisfy ≦ 1.04, the cost increases accordingly.

In any case, conventionally, there is a problem that it is difficult to prevent a transfer failure during intermediate transfer (primary transfer).

An object of the present invention is to provide an image forming apparatus capable of preventing transfer defects during intermediate transfer (primary transfer) with a simple structure.

[0016]

According to the present invention, there are provided a plurality of photoconductor units each corresponding to each color for developing an electrostatic latent image formed on an image carrier to form a toner image. Having a conductive roller to which a voltage is applied as a primary transfer roller, an intermediate transfer member is sandwiched between the primary transfer roller and the toner image to transfer to the intermediate transfer member as a primary transfer image, 3. In an image forming apparatus for forming an image by transferring the primary transfer image onto a recording medium, the Asker C hardness on the surface of the intermediate transfer body at the nip portion between the image carrier and the intermediate transfer body has a measured load of 4. The image forming apparatus is characterized in that it is 50 degrees or less when it is 9 N, and it is 30 degrees or more when the measurement load is 4.9 N on the surface of the primary transfer roller. The intermediate transfer member has, for example, an endless belt shape.

As described above, in the nip portion between the image carrier and the intermediate transfer body, the Asker C hardness on the surface of the intermediate transfer body is 50 degrees or less, and the Asker C on the surface of the primary transfer roller is further set. When the hardness is 30 degrees or more, the intermediate transfer member properly follows the unevenness formed by the toner image and the image carrier with respect to the axial nip portion between the intermediate transfer member and the image carrier. Also,
As described above, when the Asker C hardness is specified, the pressure contact force to the image carrier is appropriately maintained, the nip width does not increase, and torque increase and jitter do not occur when the intermediate transfer body is conveyed. . As a result, at the time of transfer (at the time of primary transfer), color misregistration does not occur, and voids do not occur, so that the transferability can be improved. That is, when defining the hardness of the intermediate transfer body plus the primary transfer roller in the primary transfer nip portion, the hardness when measured from the intermediate transfer surface side is defined and also the hardness of the primary transfer roller is defined. By thus defining the hardness, it is possible to improve the transferability without causing color misregistration and causing voids during transfer.

The intermediate transfer member has, for example, a plurality of layers, and the layer (outermost layer) in contact with the image carrier is an elastic layer coated with a resin film (for example, a fluororesin film). The layer (innermost layer) in contact with the primary transfer roller is a resin layer. The intermediate transfer member has a thickness of 1 m.
m or less. Further, the primary transfer roller presses the image carrier with a pressing force of 0.02 to 0.06 N / mm.

As described above, in the intermediate transfer member, when the outermost layer is an elastic layer coated with a resin film (for example, a fluororesin film), the releasability of the intermediate transfer member, the reduction of the surface friction coefficient, and The elasticity can be secured, and as a result, not only the secondary transfer property is improved, but also the cleaning property when removing the residual toner from the intermediate transfer member is improved. When the innermost layer is a resin layer, it is possible to prevent expansion and contraction during belt conveyance, which causes color misregistration and the like. In consideration of color misregistration, voids and transferability, the thickness of the intermediate transfer member is preferably 1 mm or less. Further, when the pressure contact force is in the range of 0.020 to 0.060 N / mm, the color transfer does not occur, and the hollow property does not occur, and the transferability is good.

[0020]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings. Incidentally, the dimensions of the components in the illustrated example,
Unless otherwise specified, the material, the shape, the relative arrangement, etc., are not intended to limit the scope of the present invention thereto, but are merely illustrative examples.

First, referring to FIG. 1, in the illustrated image forming apparatus, an endless belt-shaped intermediate transfer member 11 is used as an intermediate transfer member.
(Hereinafter, this intermediate transfer member is referred to as an intermediate transfer belt). A plurality of photoconductor units (toner image forming units) are arranged along the rotation direction of the intermediate transfer belt 11 (conveyance direction: indicated by solid arrows in the figure). In the illustrated example, four photoconductor units 21 to 24 are arranged along the intermediate transfer belt 11, and, for example, from the left side in the drawing, a photoconductor unit for yellow, a photoconductor unit for magenta, and a photoconductor unit for cyan. , And a black photoconductor unit in this order.

Primary transfer rollers 31 to 34 are arranged facing the photoconductor units 21 to 24, and as will be described later, an intermediate transfer belt is provided between the photoconductor drum and the primary transfer roller in each photoconductor unit. 11 is sandwiched. As shown, the intermediate transfer belt 11 includes support rollers 41 to 4
The secondary transfer roller 51 is supported by No. 3 and is conveyed in the direction of the solid line arrow in the drawing. The secondary transfer roller 51 is arranged downstream of the intermediate transfer belt 11 in the rotation direction, at the lower left of the drawing, facing the support roller 42. Then, the support roller 42 and the secondary transfer roller 5
The intermediate transfer belt 11 is nipped by 1 and the recording medium (paper) 63 is nipped, and the toner image (primary transfer image) on the intermediate transfer belt 11 is formed on the paper by the secondary transfer roller 51 as described later. 63 (secondary transfer). A fixing unit 64 is arranged downstream of the sheet 63 in the conveying direction, and the secondary transfer image transferred onto the sheet 63 is pressed against the sheet 63 and heated by the fixing unit 64 to be fixed.

The supporting roller (counter electrode roller) 43
A cleaning blade 65 is disposed so as to face to, and the residual toner remaining on the intermediate transfer belt 11 is cleaned by the cleaning blade 65. As will be described later, a fur brush may be used to clean the residual toner remaining on the intermediate transfer belt 11.

Now, referring to FIG. 2, focusing on the photoconductor unit 21, the photoconductor unit 21 is provided with a photoconductor drum (for example, an amorphous silicon photoconductor drum: an image carrier) 21a. , Photoconductor drum 21
The above-mentioned primary transfer roller 31 is arranged to face a. Further, a charger (scoroton charger) 21b, an exposure unit 21c, a developing device 21d, a cleaning unit 21e including a cleaning blade 212, and a charge eliminating unit (eraser) 21f are arranged around the photosensitive drum 21a. Then, the surface of the photoconductor drum 21a is uniformly charged by the charger 21b (for example, uniformly charged to + 250V), and then an electrostatic latent image is formed on the surface of the photoconductor drum 21a by the exposure unit 21c. . Then, the electrostatic latent image is developed by the developing device 21d to form a toner image on the photoconductor drum 21a.

Specifically, the developing device 21d is provided with a developing roll (developing sleeve) 211, and the developing roll 211 is arranged so as to face the photosensitive drum 11a. Then, for example, the developing roll 211 has an amplitude of 1.1 kV, a frequency of 3.0 Hz, and a duty ratio of 45%.
Is applied to cause the toner on the developing roller 211 to jump to the photosensitive drum 21a, and the electrostatic latent image is developed to obtain a toner image.

The toner image on the photosensitive drum 21a is transferred to the intermediate transfer belt 11 by the primary transfer roller 31. The residual toner remaining on the photoconductor drum 21a is removed by the cleaning unit 21e (cooling blade 212), and the surface of the photoconductor drum 21a is destaticized by the destaticizing unit 21f.

The photoconductor units 22 to 24 also have the same structure as the photoconductor unit 21.
The toner images formed on a to a are sequentially transferred onto the intermediate transfer belt 11 by the primary transfer rollers 32 to. That is, in each of the photoconductor units 21 to 24, the toner image is transferred to the intermediate transfer belt 11 as a primary transfer image. In this way, for example, the yellow, magenta, cyan, and black color toner images are transferred to the intermediate transfer belt 11 in such a manner that they are sequentially superposed.

In the illustrated example, the primary transfer rollers 31 to 3 are used.
A conductive elastic roller is used as 4, and a voltage is applied to the conductive elastic roller during transfer.

As the intermediate transfer belt 11, for example, an endless belt formed of a single layer sheet of polycarbonate, polyimide, fluorocarbon resin or the like is used.
Further, a multilayer type belt in which an elastic body such as urethane rubber or chloroprene rubber is arranged on the toner transfer surface of the outermost layer of the belt and the innermost layer is a resin layer is used. When the innermost layer is a resin layer, it is possible to prevent expansion and contraction during belt conveyance, which causes color misregistration, for example. In addition, a belt of a type in which the outermost layer of fluororesin is coated with urethane resin as a binder may be used. Thus, by coating the outermost layer of the fluororesin with the urethane resin as the binder, the releasability of the intermediate transfer belt, the reduction of the surface friction coefficient, and the ensuring of elasticity can be achieved, and as a result, the secondary transfer property is not only improved. Therefore, the cleaning property when removing the residual toner from the intermediate transfer belt is improved.

By the way, when the toner image on the photosensitive drum 21a is transferred to the intermediate transfer belt 11, the intermediate transfer belt 11 uses the primary transfer roller (conductive elastic roller) 31 and the photosensitive drum 21a as described above. However, as shown in FIG. 3, in the nip portion between the photoconductor drum 21a and the intermediate transfer belt 11, due to the toner, a void is generated in the portion where there is no toner image. become.

Further, as shown in FIG. 4, the intermediate transfer belt 1 is formed by a primary transfer roller (conductive elastic roller) 31.
1 is pressed upward, and as a result, at the time of transfer, the intermediate transfer belt 11 is pressed downward by the toner image on the photosensitive drum 21a, and the intermediate transfer belt 11 is present at the portion where the toner image is present.
And the primary transfer roller 31 is also slightly recessed.

Due to the above-mentioned points, the toner image developed on the photosensitive drum 21a and the unevenness of the surface of the photosensitive drum 21a in the nip portion between the intermediate transfer belt 11 and the photosensitive drum 21a, particularly in the axial direction. On the other hand, if the intermediate transfer belt 11 does not follow, a phenomenon occurs in which the intermediate transfer belt 11 is separated from the photoconductor drum 21a in a non-developed portion near the toner image. As a result,
The portion where the toner image is present becomes a conduction path for the transfer current to the intermediate transfer belt 11 and the photoconductor drum 21a, and the toner image developed on the photoconductor drum is near the primary transfer roller (conductive elastic roller) 31. , It will be charged with a polarity opposite to the polarity that it should normally have.

Further, if the nip width is unnecessarily large, the inflow time of the current also increases, so that the reverse charging of the toner is promoted. Then, in the case of a ruled line image (ruled line toner image) formed on the photoconductor drum 11a in parallel with the conveyance direction of the intermediate transfer belt 11, the current value flowing into the ruled line toner image portion becomes particularly excessive, resulting in defective transfer. Occurs. Particularly, when the ruled line is primarily transferred parallel to the conveyance direction of the intermediate transfer belt, transfer failure is likely to occur due to charging of the opposite polarity, and the toner image thickness is increased by transferring toner in multiple layers such as color images. As the value increases, the transfer failure is more likely to occur.

Here, with reference to FIG. 5, as the primary transfer roller, a conductive elastic roller formed by molding foamed EPDM into a roll shape in which carbon was impregnated to adjust the resistance value was used. As the intermediate transfer belt 11, a base material obtained by centrifugally molding urethane rubber was used. A fluorine coat (elastic layer) was applied to the outermost layer, and a PVDF layer (resin layer) was placed on the innermost layer to prevent expansion and contraction. That is, a belt having a three-layer structure was used as the intermediate transfer belt 11. Furthermore, the thickness of the intermediate transfer belt 11 is 600 μm.
m, and its surface roughness was set to a range of Rz 5 to 10 μm.
At this time, as shown in FIG. 5A, the hardness (Asker C hardness) of the surface of the intermediate transfer belt 11 on the primary transfer roller (conductive elastic roller) was measured with a measurement load of 4.9 N (hereinafter, this hardness is used). Is called hardness), and the hardness was 49 degrees. On the other hand, as shown in FIG. 5 (b), the hardness (Asker C hardness) of the primary transfer roller is measured under load 4.
When directly measured as 9 N (hereinafter, this hardness is referred to as hardness), the hardness was 36 degrees.

The pressing load for pressing the photosensitive drum via the intermediate transfer belt 11 was 0.045 N / mm, and a DC voltage of -500 to -1000 V was applied to the primary transfer roller. Similarly to the primary transfer roller, the secondary transfer roller is also formed into a roll shape of foamed EPDM in which carbon is impregnated to adjust the resistance value, and is pressed against the counter electrode with the intermediate transfer belt 11 sandwiched therebetween. 500 to-
A DC voltage of 2500 volts was applied. Further, when the intermediate transfer belt 11 is cleaned, the fur brush is brought into contact with the intermediate transfer belt 11 so that −500 to −10.
A high voltage of 00 V was applied to remove the residual toner on the intermediate transfer belt 11.

After that, the hardness of the intermediate transfer belt 11 and the hardness of each of the primary transfer rollers 31 to 34 are variously changed,
The transfer failure was observed. As shown in FIG. 5C, first,
When the hardness was 28 degrees (Asker C hardness), the hardness was measured by changing the material of the intermediate transfer belt 11 and the like, and the results shown by the symbols A to N were obtained. That is, the hardness is 3
It was 1 to 53 degrees. When the color misregistration, voids and transferability at this time were evaluated, a slight color misregistration was confirmed (indicated by Δ) when the hardness was 28 degrees. On the other hand, when the hardness is 51 degrees, hollow defects occur and the transferability is slightly deteriorated (indicated by Δ). Also, the hardness is 5
If it is twice or more, the voids will be severe and the transferability will be extremely deteriorated (indicated by x).

Next, the hardness is 31 degrees (Asker C hardness)
At this time, the hardness was measured by changing the material of the intermediate transfer belt 11 and the like, and the results shown by the symbols A to N were obtained.
That is, the hardness was 37 to 54 degrees. When the color misregistration, voids and transferability at this time were evaluated, when the hardness was 31 degrees, no color misregistration was confirmed (shown by ◯). On the other hand, when the hardness is 52 degrees, hollowing occurs and the transferability is slightly deteriorated (indicated by Δ). Further, when the hardness is 53 degrees or more, the hollow portion becomes severe and the transferability is significantly deteriorated (indicated by x).

Next, the hardness is 51 degrees (Asker C hardness).
At that time, when the hardness and the like of the intermediate transfer belt 11 were changed and the hardness was measured, the results indicated by the symbols A to H and the symbols J to N were obtained. That is, the hardness was 49 to 54 degrees. When the color misregistration, voids and transferability at this time were evaluated, when the hardness was 51 degrees, no color misregistration was confirmed (shown by ◯). On the other hand, when the hardness is 51 degrees, hollow defects occur and the transferability is slightly deteriorated (shown by Δ). Further, when the hardness is 52 degrees or more, the hollow portion becomes severe and the transferability is extremely deteriorated (indicated by x).

Thereafter, the hardness was changed variously, and the hardness was also changed variously, and the color misregistration, the hollow defects and the transferability were evaluated, and the hardness was 30 as Asker C hardness.
It was confirmed that when the hardness is not less than 100 degrees and the hardness is not more than 50 degrees in Asker C hardness, color transfer does not occur, and voids do not occur, and the transferability is good.

Further, when the thickness of the intermediate transfer belt was variously changed and the color misregistration, the hollow image and the transfer property were evaluated in the same manner, a good result was not obtained when the intermediate transfer belt was too thick. It has been found that the thickness of the transfer belt is preferably 1 mm or less. That is, as the thickness of the intermediate transfer belt becomes thicker, the hardness of the surface of the intermediate transfer belt must be lowered, and as a result, the nip width increases. Furthermore, as the thickness of the intermediate transfer belt increases,
Since the intermediate transfer belt is endless, a speed difference occurs between the inner side and the outer side (elastic portion) of the belt when the belt is conveyed (rotated), and the linear portion returns to its original state. In other words, the outermost elastic portion repeatedly expands and contracts in the transport direction, resulting in jitter and color misregistration during transfer. In order to prevent such problems, the thickness of the intermediate transfer belt should be 1
It is desirable to set it to mm or less.

Further, when the primary transfer roller was variously pressed against the photosensitive drum via the intermediate transfer belt, the pressure contact force was evaluated to evaluate the color misregistration, the void and the transfer property. In the range of 0.060 N / mm, it was confirmed that the color transfer did not occur, and the transferability was good without any hollow defects. That is, if the pressure contact force of the primary transfer roller is less than 0.020 N / mm, the intermediate transfer belt cannot follow the unevenness of the toner on the photosensitive drum, and further, the intermediate transfer belt and the photosensitive drum are Nip formation becomes unstable. On the other hand, the pressure contact force of the primary transfer roller is 0.060.
When it exceeds N / mm, the nip width increases, and accordingly, the transfer failure occurs and the belt driving torque increases. Therefore, the pressure contact force of the primary transfer roller is 0.020.
It is desirable to set the range to 0.060 N / mm.

[0042]

As described above, according to the present invention, the Asker C on the surface of the intermediate transfer member when the measurement load is 4.9 N at the nip portion between the image carrier (photosensitive drum) and the intermediate transfer member. Since the hardness is 50 degrees or more and the Asker C hardness on the surface of the primary transfer roller is 30 degrees or less, no color shift occurs during transfer (during primary transfer),
Moreover, there is an effect that it is possible to improve the transferability without causing a hollow portion, and since it is not necessary to newly add parts and the like, the configuration does not become complicated,
The cost can be reduced. That is, in the present invention,
In the primary transfer nip portion, when defining the hardness of the intermediate transfer body plus the primary transfer roller, the hardness when measured from the intermediate transfer surface side is defined, and the hardness of the primary transfer roller is also defined. By defining the hardness, there is an effect that the color transfer does not occur at the time of transfer, and the transferability can be improved without causing the void.

Further, when the layer (outermost layer) of the intermediate transfer member which is in contact with the image carrier is an elastic layer coated with a resin film (for example, a fluororesin film), the releasability of the intermediate transfer member is
The surface friction coefficient can be reduced and elasticity can be secured.
Not only the secondary transfer property is improved, but also the cleaning property when removing the residual toner from the intermediate transfer member is improved. When the innermost layer is made of a resin layer, it is possible to prevent expansion and contraction during belt conveyance, which causes color misregistration and the like.

If the thickness of the intermediate transfer member is 1 mm or less and the pressure contact force is in the range of 0.020 to 0.060 N / mm, color misregistration does not occur, and voids do not occur. Transferability can be improved.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an example of a photoconductor unit shown in FIG.

FIG. 3 is a diagram schematically showing a nip portion between a photosensitive drum and an intermediate transfer belt.

FIG. 4 is a diagram for explaining a nip portion between a photosensitive drum and an intermediate transfer belt.

FIG. 5 is a diagram for explaining transferability when the hardness (Asker C hardness) of the intermediate transfer belt and the primary transfer roller (conductive roller) is changed, and (a) is a hardness measurement of the intermediate transfer belt. FIG. 4B is a view showing hardness measurement of the primary transfer roller, and FIG. 7C is a view showing results of color misregistration and transferability observation.

[Explanation of symbols]

11 Intermediate Transfer Belts 21, 22, 23, 24 Photoreceptor Units 31, 32, 33, 34 Primary Transfer Rollers (Conductive Elastic Rollers) 41, 42, 43 Support Rollers 51 Secondary Transfer Rollers 63 Recording Media (Paper) 64 Fixing Unit 65 Cleaning blade

Continued front page    F term (reference) 2H030 AA03 AB02 BB42 BB46 BB63                 2H200 FA16 GA12 GA23 GA47 GB12                       GB25 JA02 JA25 JA27 JC04                       JC07 JC13 JC15 JC17 LA12                       LA18 LC04 MA03 MA20 MC02

Claims (5)

[Claims] 1. A plurality of photoconductor units for developing an electrostatic latent image formed on an image bearing member corresponding to each color to form a toner image, and having a voltage-applied conductivity. A roller is used as a primary transfer roller, an intermediate transfer member is sandwiched between the primary transfer roller and the toner image, the toner image is transferred to the intermediate transfer member as a primary transfer image, and the primary transfer image is transferred to a recording medium. In an image forming apparatus that forms an image by using the Asker C hardness on the surface of the intermediate transfer body at the nip portion between the image carrier and the intermediate transfer body, the measured load is 4.
An image forming apparatus having an Asker C hardness on the surface of the primary transfer roller of 30 degrees or more when the measured load is 4.9 N when the measurement load is 9N. 2. The image forming apparatus according to claim 1, wherein the intermediate transfer member has an endless belt shape. 3. The intermediate transfer member has a plurality of layers, the layer in contact with the image carrier is an elastic layer coated with a resin film, and the layer in contact with the primary transfer roller is a resin layer. The image forming apparatus according to claim 1, wherein: 4. The image forming apparatus according to claim 1, wherein the intermediate transfer member has a thickness of 1 mm or less. 5. The primary transfer roller is 0.02 to 0.
The image forming apparatus according to claim 1, wherein the image carrier is pressed with a pressing force of 06 N / mm.