JP2004184875A - Transfer device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer device for satisfactorily transferring an image, irrespective of the size of a recording medium and other conditions, as for the transfer device for secondarily transferring an image by applying a bias whose polarity is the same as that of the toner on a secondary transfer counter roller, and to provide an image forming apparatus for a copying machine, a facsimile and a printer, etc., equipped with the transfer device. <P>SOLUTION: As for the transfer device 20, the resistance of the secondary transfer counter roller 4 is made higher than the resistance of a secondary transfer roller 10, and an unfixed toner image T on an intermediate transfer body 2 is secondarily transferred to the recording medium 3 at a nip between the roller 4 and the secondary transfer roller 10 by applying the bias having the same polarity as that of the toner on the secondarily transfer counter roller 4. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is provided in an image forming apparatus such as a color electrophotographic apparatus such as a copying machine, a facsimile, and a printer, and prints an unfixed toner image formed on an image carrier such as a photosensitive drum via an intermediate transfer member on a paper. The present invention relates to a transfer device for performing secondary transfer to a recording medium such as a printer, and an image forming apparatus having the same.
[0002]
[Prior art]
Conventionally, as such a transfer device, one described in [Patent Document 1] or the like is known. Specifically, an unfixed toner image formed on an image carrier such as a photoreceptor drum is primarily transferred to a belt-shaped intermediate transfer member, and then the unfixed toner image is intermediately transferred using a secondary transfer roller. It is configured so that a desired image is formed on the recording medium by secondary transfer from the transfer body to the recording medium. In particular, in a color image forming apparatus that includes developing devices corresponding to each color of black, yellow, magenta, and cyan, and forms a full-color image by superimposing unfixed toner images of each color, each rotation of the image carrier is The unfixed toner images of the respective colors thus formed are superimposed on an intermediate transfer member, and the combined images are collectively transferred to a recording medium.
[0003]
In the conventional color image forming apparatus, since the unfixed toner image of each color is directly multiplex-transferred onto the recording medium, there are many factors such as the thickness and surface characteristics of the recording medium, and the transport characteristics of the recording medium with respect to the latent image carrier. The image quality of a color image formed on a recording medium is affected by the change. However, in such a color image forming apparatus using an intermediate transfer body, since a composite image subjected to multiple transfer has already been transferred to a recording medium, such an unstable factor can be eliminated, and a multiple This has the advantage that the occurrence of image disturbance and color shift can be effectively prevented.
[0004]
In a transfer apparatus using such an intermediate transfer member, a technique for performing good transfer even when transferring to a small-sized recording medium is disclosed in Japanese Patent Application Laid-Open No. H10-157300. ], A non-fixed toner image is formed on the secondary transfer roller by providing a resistance layer of 10 ⁷ Ω or more on the secondary transfer opposing roller provided opposite to the secondary transfer roller with the intermediate transfer member interposed therebetween. Secondary transfer is performed by applying a bias having a polarity opposite to that of the toner.
[0005]
[Patent Document 2] discloses that an intermediate transfer body has a thickness of 10 ⁶ Ω / cm to 10 ¹⁴ Ω / cm and a thickness of 0.1 mm, and a secondary transfer opposing roller has a resistance of 10 ⁷ Ω / □ on an insulating layer. The secondary transfer roller has a surface layer of 10 ⁷ Ω / cm or less, has a bias electrode member separate from the secondary transfer opposing roller, and has a surface layer of 10 ¹¹ Ω / □. A transfer device that performs a secondary transfer by applying a bias to a surface layer of a secondary transfer opposed roller is disclosed.
[0006]
[Patent Document 1]
JP-A-6-289737 [Patent Document 2]
JP-A-8-292644
[Problems to be solved by the invention]
However, Patent Literature 1 and Patent Literature 2 do not disclose a technique of applying a bias by the secondary transfer opposing roller itself. Further, as described in [Patent Document 2], the structure in which a secondary transfer is performed by applying a bias to the surface layer of the secondary transfer opposing roller from a bias electrode member separate from the secondary transfer opposing roller is complicated. It becomes.
[0008]
Therefore, the inventor of the present invention has developed a technique for applying a bias having the same polarity as the toner to the secondary transfer facing roller to perform secondary transfer. Since the current leaks through the recording medium after contributing to the formation of the transfer electric field, there is an advantage that the transfer on the recording medium having reduced resistance due to moisture absorption in a high-humidity environment is stable. It has been found that there is a problem that a leak occurs and a current that does not contribute to the formation of a transfer electric field is generated, and transfer performance is deteriorated. In addition, the problem that transfer performance is degraded due to generation of a current that does not contribute to the formation of a transfer electric field often appears when transferring to a small-sized recording medium.
[0009]
The present invention relates to a transfer device that performs secondary transfer by applying a bias having the same polarity as toner to a secondary transfer opposed roller, and that performs transfer satisfactorily regardless of the size of a recording medium and other conditions. It is an object of the present invention to provide an image forming apparatus provided with the above, such as a copying machine, a facsimile, a printer, and the like.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 provides an intermediate transfer member on which an unfixed toner image is primarily transferred from an image carrier, and secondary transfer of the unfixed toner image from the intermediate transfer member to a recording medium. And a secondary transfer opposing roller facing the secondary transfer roller with the intermediate transfer member interposed therebetween, and the secondary transfer opposing roller has the same polarity as the toner constituting the unfixed toner image. In the transfer device for applying the bias of (2) to the secondary transfer of the unfixed toner image on the intermediate transfer member to a recording medium, the resistance of the secondary transfer facing roller is higher than the resistance of the secondary transfer roller. Features.
[0011]
According to a second aspect of the present invention, in the transfer device of the first aspect, the surface resistivity of the surface of the intermediate transfer member on the side where the secondary transfer opposing roller is located is 10 ⁹ Ω / □ or more and the volume resistivity is 10 ⁹ Ω / □. rate is not more than ^{10 12 Ω} / cm, the secondary transfer opposing roller has a volume resistivity on the surface thereof has a greater than ^{10 15 Ω} / cm less than layer ^{10 11 Ω} / cm, the secondary transfer The roller is characterized in that its surface is provided with a layer having a volume resistivity of 10 ¹¹ Ω / cm or less.
[0012]
According to a third aspect of the present invention, in the transfer device according to the second aspect, the layer provided on the surface of the secondary transfer facing roller has a volume resistivity of more than 10 ¹² Ω / cm and less than 10 ¹⁴ Ω / cm. It is characterized by the following.
[0013]
According to a fourth aspect of the present invention, there is provided an image forming apparatus having the transfer device according to any one of the first to third aspects.
[0014]
【Example】
FIG. 1 schematically shows a color image forming apparatus which is a color electrophotographic copying machine to which the present invention is applied. The image forming apparatus 100 has a larger heat capacity than plain paper, such as plain paper generally used for copying, 90K paper such as OHP sheets, cards, and postcards, thick paper having a basis weight of about 100 g / m ² or more, and envelopes. Both a large so-called special sheet and a small-sized sheet can be used as a sheet-shaped recording medium for forming an image. The size of the recording medium is generally a size conforming to a general standard such as A4 size or A3 size, but may be a size outside the standard.
[0015]
In FIG. 1, reference numeral 1 denotes a photosensitive drum as an image carrier. As the photosensitive drum 1 rotates in the direction of arrow A, an electrostatic latent image corresponding to image information is formed on the surface thereof by a well-known electrophotographic process (not shown). Around the photosensitive drum 1, developing devices 5 to 8 as developing devices corresponding to respective colors of black (Bk), yellow (Y), magenta (M) and cyan (C) are arranged. The electrostatic latent image formed on the photosensitive drum 1 is developed by any one of the developing devices to form a toner image T. Therefore, if the electrostatic latent image written on the photosensitive drum 1 corresponds to the yellow image information, this electrostatic latent image is developed by the developing device 6 containing yellow (Y) toner, and On the body drum 1, a yellow toner image T is formed.
[0016]
Reference numeral 2 denotes a belt-shaped intermediate transfer member which is an intermediate transfer belt arranged so as to be in contact with the surface of the photosensitive drum 1. The intermediate transfer body 2 is stretched over a plurality of rolls and rotates in the direction of arrow B. The unfixed toner image T formed on the photoconductor drum 1 is transferred from the photoconductor drum 1 to the surface of the intermediate transfer body 2 at a primary transfer position where the photoconductor drum 1 and the intermediate transfer body 2 are in contact. At this primary transfer position, a corona discharger 9 is provided on the back surface side of the intermediate transfer body 2. By applying a voltage having a polarity opposite to the charging polarity of the toner to the corona discharger 9, The unfixed toner image T on the drum 1 is electrostatically attracted to the intermediate transfer body 2 and primary transfer is performed.
[0017]
When a single-color image is formed, the unfixed toner image T primarily transferred to the intermediate transfer body 2 is secondarily transferred to the recording medium 3 immediately, but a color image in which a plurality of color toner images are superimposed is formed. In this case, the steps of forming the toner image T on the photosensitive drum 1 and primary transferring the toner image T are repeated for the number of colors. For example, when a full-color image is formed by superimposing toner images of four colors, unfixed toner images T of black, yellow, magenta, and cyan are formed on the photoreceptor drum 1 at each rotation thereof. The image T is primarily transferred to the intermediate transfer body 2 sequentially. On the other hand, the intermediate transfer member 2 rotates at the same cycle as the photosensitive drum 1 while holding the black first-transferred unfixed toner image T. , Magenta and cyan unfixed toner images T are superimposed and transferred on black unfixed toner images T.
[0018]
On the other hand, the intermediate transfer member 2 rotates at the same cycle as the photosensitive drum 1 while holding the black first-transferred unfixed toner image T. , Magenta and cyan unfixed toner images T are superimposed and transferred on black unfixed toner images T. The unfixed toner image T primarily transferred to the intermediate transfer body 2 in this manner is conveyed to a secondary transfer position facing the conveyance path of the recording medium 3 as the intermediate transfer body 2 rotates.
[0019]
At the secondary transfer position, the secondary transfer roller 10 is in contact with the intermediate transfer member 2, and the recording medium 3 carried out of the tray 12 by the feed roller 11 at a predetermined timing is, as shown in FIG. 10 and the intermediate transfer member 2. On the back side of the intermediate transfer body 2 at the secondary transfer position, a backup roll 4 is disposed as a secondary transfer facing roller facing the secondary transfer roller 10 with the intermediate transfer body 2 interposed therebetween. When a bias having a polarity opposite to the charge polarity of the toner constituting the toner image T is applied by the backup roll 4 by the voltage application means 16 connected to the secondary transfer roller 10, the intermediate transfer member 2 is connected to the grounded secondary transfer roller 10. The unfixed toner image T carried on the recording medium 3 is electrostatically transferred to the recording medium 3 at the secondary transfer position, and the secondary transfer is performed.
[0020]
The recording medium 3 onto which the unfixed toner image has been transferred is peeled off from the intermediate transfer body 2 by the application of a bias by the separation and neutralization device 13 and the curvature of the intermediate transfer body 2 wound around the backup roll 4, and is not shown by the transport belt 14. The unfixed toner image is sent to a fixing device, which is a fixing device serving as a fixing unit, where the unfixed toner image is fixed, discharged to the outside of the image forming apparatus 100 main body, and stacked on a discharge tray (not shown).
[0021]
On the other hand, the residual toner is removed by the cleaner 15 from the intermediate transfer body 2 on which the secondary transfer of the unfixed toner image has been completed. The secondary transfer roller 10 and the cleaner 15 are disposed so as to be able to freely contact and separate from the intermediate transfer body 2. When a color image is formed, the unfixed toner image of the final color is transferred to the intermediate transfer body 2. These members are separated from the intermediate transfer member 2 until the primary transfer is performed. The transfer device 20 to which the present invention is applied has at least the intermediate transfer member 2, the secondary transfer roller 10, the backup roll 4, and the voltage applying unit 16 among the components provided in the above-described image forming apparatus 100. ing.
[0022]
When a bias having the same polarity as that of the toner is applied from the back surface of the intermediate transfer member 2, that is, from the side where the backup roll 4 is located, as in this embodiment, a transfer electric field between the intermediate transfer member 2 and the recording medium 3 is formed. After that, the current leaks along the recording medium 3, so that the transfer stability in the recording medium 3 having reduced resistance due to moisture absorption in a high humidity environment can be obtained. However, a current is generated which leaks along the rear surface of the intermediate transfer member 2 and does not contribute to the formation of the transfer electric field. It was found that the surface resistivity was required to be 10 ⁹ Ω / □ or more.
[0023]
On the other hand, when the surface resistivity of the back surface of the intermediate transfer body 2 is 10 ⁹ Ω / □ or more, if the volume resistivity is 10 ¹² Ω / cm or more, that is, if both the surface resistivity and the volume resistivity are high. In addition, the movement of the electric charges in the intermediate transfer member 2 becomes slow, and the electric charges are not successfully transferred to the secondary transfer region. Therefore, the intermediate transfer member 2 and the recording medium 3 or the recording medium 3 and the secondary An image in which a toner image is disturbed in a radial or polka dot pattern, which is considered to be an abnormal discharge occurring between the transfer rollers 10, is generated. Therefore, when the surface resistivity of the back surface of the intermediate transfer body 2 is 10 ⁹ Ω / □ or more In addition, it was found that a condition having a volume resistivity of 10 ¹² Ω / cm or less was suitable for the secondary transfer.
[0024]
When the volume resistivity of the intermediate transfer member 2 is 10 ¹¹ Ω / cm or less, the resistance is lower than that of the recording medium 3. And the resistance difference outside the paper area where the recording medium 3 is absent increases, the current easily flows out of the paper area, the current hardly flows into the paper area, and the transferability of small-size paper is not stable.
[0025]
In this case, in order to stabilize the transferability of the small-sized paper, a layer having a resistance equal to or higher than that of the recording medium 3 is provided on either the secondary transfer roller 10 or the backup roll 4, and the resistance difference depending on the presence or absence of the recording medium 3 is provided. However, if the secondary transfer roller 10 has a high resistance layer, the resistance in the volume direction of the intermediate transfer body 2 from the surface of the secondary transfer opposing roller 10, that is, the core of the secondary transfer roller 10 increases. Since the current flowing through the intermediate transfer member 2 increases, it is preferable to provide the backup roller 4 with a high resistance layer.
[0026]
However, when the high-resistance layer of the backup roll 4 has a resistance of 10 ¹⁴ Ω / cm to 10 ¹⁵ Ω / cm or more, the applied bias for flowing the current becomes high, and the internal charge transfer speed becomes slow. Was found to be too high, or abnormal discharge to surrounding members was likely to occur. Therefore, it is suitable for the backup roll 4 to provide a layer having a volume resistivity of 10 ¹⁵ Ω / cm or less, preferably 10 ¹⁴ Ω / cm or less, and a resistance equal to or higher than that of the recording medium 3 on the surface thereof. I knew it was there.
[0027]
By the way, the resistance of the recording medium 3 differs depending on the paper quality and is generally 10 ¹¹ Ω / cm to 10 ¹² Ω / cm. Then, it is 10 ⁹ Ω / cm to 10 ¹³ Ω / cm. Therefore, in order to have a resistance equal to or higher than that of the recording medium 3, it is necessary that the resistance is 10 ¹¹ Ω / cm or more.
[0028]
Here, using the image forming apparatus 100, in the following two examples and two comparative examples, transferability is compared using recording media 3 having different weighing, size, and one-sided / two-sided image forming conditions. An experiment was performed. FIG. 3 shows the results of this experiment.
[0029]
-Example 1
The intermediate transfer body 2 is made of a resin having a volume resistivity of 10 ¹⁰ Ω / cm, a surface resistivity of 10 ¹¹ Ω / □ on both the back surface and the surface, and a thickness of 0.15 mm.
The backup roll 4 is made of an elastic layer having a volume resistivity of 10 ⁷ Ω / cm, a thickness of 4 mm, and a rubber hardness of 40 degrees around a metal core, and a resin having a volume resistivity of 10 ¹³ Ω / cm and a thickness of 0.1 mm. And a surface layer.
The secondary transfer roller 10 is separated from an elastic layer having a volume resistivity of 10 ⁷ Ω / cm, a thickness of 4 mm, and a rubber hardness of 40 degrees around a metal core with a volume resistivity of 10 ¹¹ Ω / cm and a thickness of 0.02 mm. And a surface layer made of a moldable resin.
[0030]
Example 2 (only the resistance of the secondary transfer facing roller 10 differs from that of Example 1)
The intermediate transfer body 2 is made of a resin having a volume resistivity of 10 ¹⁰ Ω / cm, a surface resistivity of 10 ¹¹ Ω / □ on both the back surface and the surface, and a thickness of 0.15 mm.
The backup roll 4 is made of an elastic layer having a volume resistivity of 10 ⁷ Ω / cm, a thickness of 4 mm, and a rubber hardness of 40 degrees around a metal core, and a resin having a volume resistivity of 10 ¹² Ω / cm and a thickness of 0.1 mm. And a surface layer.
The secondary transfer roller 10 is separated from an elastic layer having a volume resistivity of 10 ⁷ Ω / cm, a thickness of 4 mm, and a rubber hardness of 40 degrees around a metal core with a volume resistivity of 10 ¹¹ Ω / cm and a thickness of 0.02 mm. And a surface layer made of a moldable resin.
[0031]
Comparative Example 1 (the secondary transfer roller 10 and the backup roll 4 of the first embodiment are replaced with each other so that the secondary transfer roller 10 has higher resistance).
The intermediate transfer body 2 is made of a resin having a volume resistivity of 10 ¹⁰ Ω / cm, a surface resistivity of 10 ¹¹ Ω / □ on both the back surface and the surface, and a thickness of 0.15 mm.
The backup roll 4 has an elastic layer having a volume resistivity of 10 ⁷ Ω / cm, a thickness of 4 mm, and a rubber hardness of 40 degrees around the core metal, and a mold release property of a volume resistivity of 10 ¹¹ Ω / cm and a thickness of 0.02 mm. And a surface layer made of a resin having a characteristic.
The secondary transfer roller 10 includes an elastic layer having a volume resistivity of 10 ⁷ Ω / cm, a thickness of 4 mm, and a rubber hardness of 40 degrees around a core metal, and a resin having a volume resistivity of 10 ¹³ Ω / cm and a thickness of 0.1 mm. And a surface layer composed of:
[0032]
Comparative Example 2 (the volume resistivity and the thickness of the surface layer of the secondary transfer roller 10 are different from those of the comparative example 1, and the secondary transfer roller 10 and the backup roll 4 have the same configuration and low resistance.)
The intermediate transfer body 2 is made of a resin having a volume resistivity of 10 ¹⁰ Ω / cm, a surface resistivity of 10 ¹¹ Ω / □ on both the back surface and the surface, and a thickness of 0.15 mm.
The backup roll 4 has an elastic layer having a volume resistivity of 10 ⁷ Ω / cm, a thickness of 4 mm, and a rubber hardness of 40 degrees around the core metal, and a mold release property of a volume resistivity of 10 ¹¹ Ω / cm and a thickness of 0.02 mm. And a surface layer made of a resin having a characteristic.
The secondary transfer roller 10 includes an elastic layer having a volume resistivity of 10 ⁷ Ω / cm, a thickness of 4 mm, and a rubber hardness of 40 degrees around a metal core, and a resin having a volume resistivity of 10 ¹¹ Ω / cm and a thickness of 0.2 mm. And a surface layer composed of:
[0033]
As a result of the experiment, the transferability was good in all of the examples and comparative examples in full width, plain paper, and surface printing. However, when the comparative example 1 was examined, the resistance of the backup roll 4 was low and the resistance of the secondary transfer roller 10 was high. The resistance of the secondary transfer roller 10 is increased from the contact point between the backup roll 4 and the intermediate transfer body 2 to the recording medium 3 side, and the fixing process is performed once to reduce the moisture content, thereby increasing the paper thickness. When the transfer is performed on both sides of the cardboard, the resistance of the recording medium 3 is high.
[0034]
Therefore, in Comparative Example 1, even though the resistance toward the recording medium 3 is high, the resistance when traveling on the back surface of the intermediate transfer body 2 does not change, so that the current leaking without contributing to the secondary transfer is reduced. As a result, the current in the secondary transfer area is reduced, and the secondary transfer electric field is reduced, so that the transferability of the back side of the thick paper is reduced. Further, in Comparative Example 2, since the resistance of the backup roll 4 and the resistance of the secondary transfer roller 10 are low, the resistance difference between the place where the recording medium 3 is provided and the place where the recording medium 3 is not provided becomes large in the case of small-size paper. 3, a current flows avoiding the place, and the transferability of small-size paper is reduced.
[0035]
On the other hand, it differs only backup roll 4 a surface layer having a volume resistivity in Examples 1 and 2, is exactly well for small size sheets in 10 ¹³ Omega / cm in Example 1, 10 ¹² Example 2 At Ω / cm, a slight decrease is observed. When the resistance of the intermediate transfer member 2 toward the recording medium 3, that is, the volume resistivity, is sufficiently high, it is considered that the same transferability as that of the embodiment can be obtained in terms of current. Experiments confirmed that only disturbed images could be obtained.
[0036]
As described above, according to the experiments, the conditions for performing good transfer are such that the resistance of the backup roll 4 is higher than the resistance of the secondary transfer roller 10, and the surface resistivity of the back surface of the intermediate transfer body 2 is 10 ⁹ Ω / □ or more. In addition, the backup roll 4 has a layer having a volume resistivity of more than 10 ¹¹ Ω / cm and less than 10 ¹⁵ Ω / cm on its surface, and the secondary transfer roller 10 has a volume resistivity of 10 ¹² Ω / cm or less. It was found that the surface had a layer having a volume resistivity of 10 ¹¹ Ω / cm or less. Also, in particular, from the comparison between Example 1 and Example 2, it is desirable that the volume resistivity of the layer provided on the surface of the backup roll 4 is larger than 10 ¹² Ω / cm and smaller than 10 ¹⁴ Ω / cm. I understood.
[0037]
As described above, the color image forming apparatus to which the present invention is applied has been described. However, the transfer apparatus according to the present invention can be applied to an image forming apparatus that forms only a single color image as long as an intermediate transfer body is used. Also, the present invention can be applied to a color image forming apparatus to a transfer apparatus in which toner images of all colors are primarily transferred onto the intermediate transfer body 1 by one rotation of the intermediate transfer body.
[0038]
【The invention's effect】
The present invention provides an intermediate transfer member on which an unfixed toner image is primarily transferred from an image carrier, a secondary transfer roller for secondary transferring the unfixed toner image from the intermediate transfer member to a recording medium, and the intermediate transfer member. And a secondary transfer opposing roller opposed to the secondary transfer roller with the intermediate transfer member interposed therebetween by applying a bias having the same polarity as the toner constituting the unfixed toner image to the secondary transfer opposing roller. In the transfer device for secondary transferring the unfixed toner image to the recording medium, the resistance of the secondary transfer facing roller is higher than the resistance of the secondary transfer roller. By performing a secondary transfer by applying a bias, transfer to a recording medium having reduced resistance due to moisture absorption in a high-humidity environment is stabilized, and an increase in current flowing through the intermediate transfer body is prevented, thereby enabling good transfer. Can do It is possible to provide a transfer device that.
[0039]
The surface of the intermediate transfer member on the side where the secondary transfer opposing roller is located has a surface resistivity of 10 ⁹ Ω / □ or more and a volume resistivity of 10 ¹² Ω / cm or less. The surface is provided with a layer having a volume resistivity of more than 10 ¹¹ Ω / cm and less than 10 ¹⁵ Ω / cm, and the secondary transfer roller is provided with a layer having a volume resistivity of 10 ¹¹ Ω / cm or less on the surface. That is, in addition to good transfer performance in a high-humidity environment, good transfer can be performed irrespective of conditions such as the size of the recording medium, other weighing, and whether one-sided or two-sided image formation is performed. It is possible to provide a transfer device that can perform the transfer.
[0040]
If the volume resistivity of the layer provided on the surface of the secondary transfer opposed roller is set to be larger than 10 ¹² Ω / cm and smaller than 10 ¹⁴ Ω / cm, particularly when transferring to a small-sized recording medium, good results can be obtained. A transfer device capable of performing transfer can be provided.
[0041]
Since the present invention resides in an image forming apparatus having the transfer device according to any one of claims 1 to 3, the above-described effects can be obtained, and excellent transfer can be achieved in various recording media and image forming conditions. By performing the above, it is possible to provide an image forming apparatus capable of performing good image formation.
[Brief description of the drawings]
FIG. 1 is a side view schematically showing a transfer device and an image forming apparatus to which the present invention is applied.
FIG. 2 is a side view illustrating a main part of the transfer device illustrated in FIG. 1;
FIG. 3 is a correlation diagram showing a correlation of transferability when an experiment is performed while changing the type, size, and image forming surface of a sheet, and the configuration of a transfer device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Image carrier 2 Intermediate transfer member 3 Recording medium 4 Secondary transfer opposing roller 10 Secondary transfer roller 20 Transfer device 100 Image forming device T Unfixed toner image

Claims (4)

An intermediate transfer member on which an unfixed toner image is primarily transferred from the image carrier, a secondary transfer roller for secondary transferring the unfixed toner image from the intermediate transfer member to a recording medium, and A secondary transfer roller facing the secondary transfer roller, and applying a bias having the same polarity as that of the toner constituting the unfixed toner image to the secondary transfer opposed roller to thereby fix the unfixed toner on the intermediate transfer member. In a transfer device for secondary transfer of a toner image to a recording medium,
A transfer device, wherein the resistance of the secondary transfer facing roller is higher than the resistance of the secondary transfer roller. The transfer device according to claim 1,
The surface resistivity of the surface of the intermediate transfer member on the side where the secondary transfer opposing roller is located is 10 ⁹ Ω / □ or more and the volume resistivity is 10 ¹² Ω / cm or less;
The secondary transfer opposing roller has a layer having a volume resistivity greater than 10 ¹¹ Ω / cm and smaller than 10 ¹⁵ Ω / cm on the surface thereof.
The transfer device, wherein the secondary transfer roller has a layer having a volume resistivity of 10 ¹¹ Ω / cm or less on a surface thereof. 3. The transfer device according to claim 2, wherein the layer provided on the surface of the secondary transfer facing roller has a volume resistivity of more than 10 ¹² Ω / cm and less than 10 ¹⁴ Ω / cm. An image forming apparatus comprising the transfer device according to claim 1.

Images