JP2016102931A - Intermediate transfer device, image forming apparatus and intermediate transfer belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermediate transfer device, an image forming apparatus and an intermediate transfer belt which regulate meandering of the intermediate transfer belt, and can suppress the occurrence of cracks in the surface layer of the intermediate transfer belt formed by coating a thermosetting resin with a dipping method or a ring coating method.SOLUTION: An intermediate transfer device includes: an intermediate transfer belt 361 having a substrate layer 361A and a surface layer 361B formed by coating a thermosetting resin on the substrate layer 361A with a dipping method or a ring coating method; a driving roller and a stretching roller 363 which stretch the intermediate transfer belt 361 in such a positional relationship that a distance of the inner periphery in a second end 361E becomes larger than a distance of the inner periphery in a first end 361D in both ends in a width direction 361C of the intermediate transfer belt 361; and a contact portion 365 which is provided on the rear face of the second end 361E in the intermediate transfer belt 361 and comes in contact with one end in the axial direction of the stretching roller 363.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus capable of forming an image by an electrophotographic method, an intermediate transfer device provided in the image forming apparatus, and an intermediate transfer belt.

  In an image forming apparatus such as a printer capable of forming an image by electrophotography, a toner image formed on an image carrier such as a photosensitive drum may be transferred to an intermediate transfer belt. The toner image transferred to the intermediate transfer belt is transferred onto a sheet by a secondary transfer roller (see, for example, Patent Document 1).

  By the way, when the intermediate transfer belt is formed of a thermosetting resin having high hardness, it is possible to improve the releasability of the toner image from the intermediate transfer belt. However, the intermediate transfer belt formed of a thermosetting resin has a problem that the material and the molding process are expensive. On the other hand, a technique is known in which an intermediate transfer belt is manufactured by coating a thermosetting resin on a substrate formed of a thermoplastic resin that is less expensive than a thermosetting resin. Here, when a dipping method or a ring coating method is employed as a method of coating the thermosetting resin on the substrate, productivity can be improved.

  On the other hand, in this type of image forming apparatus, the intermediate transfer belt sometimes runs meandering in the axial direction of a tension roller that stretches the intermediate transfer belt. On the other hand, a configuration is known in which contact portions that come into contact with both end portions in the axial direction of the stretching roller are provided on the back surfaces of both end portions in the width direction of the intermediate transfer belt to restrict meandering in the width direction of the intermediate transfer belt. ing.

JP 2003-270962 A

  By the way, when the surface layer of the intermediate transfer belt is formed by coating a thermosetting resin by the dipping method or the ring coating method, the layer thickness of the surface layer is different at both ends in the width direction of the intermediate transfer belt. For this reason, at the end of the intermediate transfer belt in the width direction where the surface layer is thicker, the surface layer is stretched at the contact position with the stretching roller, and fatigue accumulates and cracks may occur. is there. In particular, when the contact portions are provided on the back surfaces of both end portions in the width direction of the intermediate transfer belt, the load on the surface layer becomes larger at the contact position with the stretching roller, and cracks are likely to occur.

  An object of the present invention is to provide an intermediate transfer device that regulates meandering of an intermediate transfer belt and can suppress the occurrence of cracks in the surface layer of an intermediate transfer belt formed by coating a thermosetting resin by a dipping method or a ring coating method An image forming apparatus and an intermediate transfer belt are provided.

  An intermediate transfer device according to one aspect of the present invention includes an intermediate transfer belt, a plurality of stretching rollers, and a contact portion. The intermediate transfer belt has a base material layer formed of a thermoplastic resin and a surface layer formed by coating a thermosetting resin on the base material layer by a dipping method or a ring coating method, and an image is formed on the surface layer. The toner image formed on the carrier is transferred. The plurality of stretching rollers have an inner peripheral distance of the intermediate transfer belt at the second end where the thickness of the surface layer is thinner than the first end of both ends in the width direction of the intermediate transfer belt. The intermediate transfer belt is stretched in a positional relationship that is larger than the distance of the inner circumference at the end. The contact portion is provided on the back surface of the second end portion of the intermediate transfer belt and contacts one end portion in the axial direction of one or a plurality of the stretching rollers.

  An image forming apparatus according to another aspect of the present invention includes an intermediate transfer device. The intermediate transfer device includes an intermediate transfer belt, a plurality of stretching rollers, and a contact portion. The intermediate transfer belt has a base material layer formed of a thermoplastic resin and a surface layer formed by coating a thermosetting resin on the base material layer by a dipping method or a ring coating method, and an image is formed on the surface layer. The toner image formed on the carrier is transferred. The plurality of stretching rollers have an inner peripheral distance of the intermediate transfer belt at the second end where the thickness of the surface layer is thinner than the first end of both ends in the width direction of the intermediate transfer belt. The intermediate transfer belt is stretched in a positional relationship that is larger than the distance of the inner circumference at the end. The contact portion is provided on the back surface of the second end portion of the intermediate transfer belt and contacts one end portion in the axial direction of one or a plurality of the stretching rollers.

  An intermediate transfer belt according to another aspect of the present invention has a toner image formed on an image carrier transferred thereon, and includes a base material layer, a surface layer, and a contact portion. The base material layer is formed of a thermoplastic resin. The surface layer is formed by coating a thermosetting resin on the base material layer by a dipping method or a ring coating method. The contact portion is provided on the back surface of the second end portion of the intermediate transfer belt in the width direction where the thickness of the surface layer is thinner than the first end portion, and the contact portion of the intermediate transfer belt at the second end portion is provided. Contact with one end portion in the axial direction of some or all of the plurality of stretching rollers that stretch the intermediate transfer belt in a positional relationship in which the inner circumferential distance is larger than the inner circumferential distance at the first end portion. To do.

  According to the present invention, an intermediate transfer device that regulates meandering of the intermediate transfer belt and can suppress the occurrence of cracks in the surface layer of the intermediate transfer belt formed by coating a thermosetting resin by a dipping method or a ring coating method. An image forming apparatus and an intermediate transfer belt are realized.

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a system configuration of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a diagram showing the configuration of the image forming unit of the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a diagram showing the configuration of the intermediate transfer device of the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a diagram showing the configuration of the intermediate transfer device of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a diagram showing the configuration of the intermediate transfer device of the image forming apparatus according to the embodiment of the present invention. FIG. 7 is a diagram showing an experimental result using the image forming apparatus according to the embodiment of the present invention. FIG. 8 is a diagram showing an experimental result using the image forming apparatus according to the embodiment of the present invention. FIG. 9 is a diagram showing a result of an experiment using the image forming apparatus according to the embodiment of the present invention. FIG. 10 is a diagram showing experimental results using the intermediate transfer belt according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.

[Schematic Configuration of Image Forming Apparatus 10]
First, a schematic configuration of an image forming apparatus 10 according to an embodiment of the present disclosure will be described with reference to FIGS. 1 and 2. Here, FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus 10.

  As shown in FIGS. 1 and 2, the image forming apparatus 10 includes an ADF 1, an image reading unit 2, an image forming unit 3, a paper feeding unit 4, a control unit 5, and an operation display unit 6. The image forming apparatus 10 is a multifunction machine having a plurality of functions such as a scan function, a facsimile function, and a copy function, as well as a print function for forming an image based on image data. The present invention is also applicable to image forming apparatuses such as printers, facsimile machines, and copiers.

  The ADF 1 is an automatic document conveyance device that includes a document setting unit (not shown), a plurality of conveyance rollers, a document pressing unit, and a paper discharge unit, and conveys a document read by the image reading unit 2. The image reading unit 2 includes a document table (not shown), a light source, a plurality of mirrors, an optical lens, and a CCD (Charge Coupled Device), and can read image data from the document.

  The control unit 5 includes control devices such as a CPU, ROM, RAM, and EEPROM (registered trademark) (not shown). The CPU is a processor that executes various arithmetic processes. The ROM is a non-volatile storage unit in which information such as a control program for causing the CPU to execute various processes is stored in advance. The RAM is a volatile storage unit, and the EEPROM is a non-volatile storage unit. The RAM and the EEPROM are used as a temporary storage memory (working area) for various processes executed by the CPU. Then, the control unit 5 performs overall control of the image forming apparatus 10 by executing various control programs stored in advance in the ROM using the CPU. The control unit 5 may be an electronic circuit such as an integrated circuit (ASIC), and is a control unit provided separately from the main control unit that controls the image forming apparatus 10 in an integrated manner. May be.

  The operation display unit 6 is a display unit such as a liquid crystal display that displays various types of information in response to control instructions from the control unit 5, and an operation key or touch panel that inputs various types of information to the control unit 5 in response to user operations. And so on.

  Next, the image forming unit 3 will be described with reference to FIGS. 1, 3, and 4. Here, FIG. 3 is a schematic cross-sectional view showing the configuration of the image forming unit 31. FIG. 4 is a schematic cross-sectional view showing the configuration of the intermediate transfer device 36.

  The image forming unit 3 can execute an image forming process (printing process) for forming a color or monochrome image by electrophotography based on the image data read by the image reading unit 2. The image forming unit 3 can also execute the printing process based on image data input from an information processing apparatus such as an external personal computer.

  Specifically, as illustrated in FIG. 1, the image forming unit 3 includes a plurality of image forming units 31 to 34, an optical scanning device (LSU) 35, an intermediate transfer device 36, a secondary transfer roller 37, a fixing device 38, and A paper discharge tray 39 is provided. The image forming unit 31 corresponds to C (cyan), the image forming unit 32 corresponds to M (magenta), the image forming unit 33 corresponds to Y (yellow), and the image forming unit 34 corresponds to K (black). is there. The image forming units 31 to 34 are provided in the order of cyan, magenta, yellow, and black from the upstream side in the conveyance direction 36A along the toner image conveyance direction 36A by the intermediate transfer device 36.

  As shown in FIG. 3, the image forming unit 31 includes a photosensitive drum 311, a charging roller 312, a developing device 313, a primary transfer roller 314, and a drum cleaning unit 315. Each of the image forming units 32 to 34 has the same configuration as that of the image forming unit 31. Here, the photosensitive drum 311, the photosensitive drum 321, the photosensitive drum 331, and the photosensitive drum 341 (see FIG. 4) included in the image forming units 31 to 34 are examples of the image carrier in the present invention.

  In the image forming unit 3, a color image is formed on the sheet supplied from the paper feeding unit 4 according to the following procedure, and the sheet after the image formation is discharged to the paper discharge tray 39. The sheet is a sheet material such as paper, coated paper, postcard, envelope, and OHP sheet.

  First, in the image forming unit 31, the surface of the photosensitive drum 311 is uniformly charged to a predetermined potential by the charging roller 312. Next, light based on image data is irradiated onto the surface of the photosensitive drum 311 by the optical scanning device 35. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 311.

  The electrostatic latent image on the photosensitive drum 311 is developed (visualized) as a cyan toner image by the developing device 313. Specifically, toner is supplied from the developing roller 313A of the developing device 313 to the photosensitive drum 311, whereby the electrostatic latent image on the photosensitive drum 311 is developed as a toner image. In the developing device 313, the developer including toner and carrier is frictionally charged by stirring by the stirring screw 313B and sent to the magnetic roller 313C, and the toner in the developer is sent from the magnetic roller 313C to the developing roller 313A. . The developing device 313 is supplied with cyan toner from a toner container 313D (see FIG. 1) that can be attached to and detached from the image forming unit 3.

  Subsequently, the cyan toner image formed on the photosensitive drum 311 is transferred to the intermediate transfer belt 361 of the intermediate transfer device 36 by the primary transfer roller 314. On the other hand, the toner remaining on the surface of the photosensitive drum 311 is removed by the drum cleaning unit 315. For example, in the drum cleaning unit 315, the toner remaining on the surface of the photosensitive drum 311 is removed by the blade-shaped cleaning member 315A. The toner removed by the cleaning member 315A is transported to a toner storage container (not shown) by the transport screw 315B and collected.

  Next, in the image forming units 32 to 34, each of the colors of the photosensitive drum 321, the photosensitive drum 331, and the photosensitive drum 341 included in the image forming units 32 to 34 is processed in the same processing procedure as that of the image forming unit 31. A toner image is formed and transferred onto the intermediate transfer belt 361 of the intermediate transfer device 36 in the order of cyan, magenta, yellow, and black. The toner image transferred to the intermediate transfer belt 361 is transferred to a sheet supplied from the paper feeding unit 4 by the secondary transfer roller 37.

  Thereafter, the toner image is fused and fixed by the fixing device 38 on the sheet to which the toner image has been transferred, and an image is formed and discharged onto the paper discharge tray 39.

  Incidentally, when the intermediate transfer belt 361 is formed of a thermosetting resin having high hardness, it is possible to improve the releasability of the toner image from the intermediate transfer belt 361. However, the intermediate transfer belt 361 formed of a thermosetting resin has a problem that the material and the molding process are expensive. On the other hand, a technique is known in which an intermediate transfer belt 361 is manufactured by coating a thermosetting resin on a base material formed of a thermoplastic resin that is less expensive than a thermosetting resin. Here, when a dipping method or a ring coating method is employed as a method of coating the thermosetting resin on the substrate, productivity can be improved.

  On the other hand, in an image forming apparatus having the same type of configuration as the image forming apparatus 10, the intermediate transfer belt 361 may run meandering in the axial direction of a stretching roller that stretches the intermediate transfer belt 361. On the other hand, a configuration is provided in which contact portions that come into contact with both ends in the axial direction of the stretching roller are provided on the back surfaces of both ends in the width direction of the intermediate transfer belt 361 so as to restrict meandering in the width direction of the intermediate transfer belt 361. Are known.

  Here, when the surface layer of the intermediate transfer belt 361 is formed by coating a thermosetting resin with a dipping method or a ring coating method, the layer thickness of the surface layer is different at both ends in the width direction of the intermediate transfer belt 361. It becomes. Therefore, at the end of the intermediate transfer belt 361 in the width direction where the surface layer is thicker, the surface layer is stretched at the contact position with the stretching roller, and fatigue accumulates and cracks occur. There is. In particular, when the contact portions are provided on the back surfaces of both end portions in the width direction of the intermediate transfer belt 361, the load on the surface layer becomes larger at the contact position with the stretching roller, and cracks are likely to occur. On the other hand, in the image forming apparatus 10, as described below, the meandering of the intermediate transfer belt 361 is restricted, and the intermediate transfer belt 361 formed by coating a thermosetting resin by a dipping method or a ring coat method. It is possible to suppress the occurrence of cracks in the surface layer.

  Hereinafter, the intermediate transfer device 36 will be described with reference to FIGS. 4 to 6. Here, FIG. 5 is a VV arrow view in FIG. FIG. 6 is a schematic plan view showing the configuration of the intermediate transfer device 36.

  The intermediate transfer device 36 uses the intermediate transfer belt 361 to convey the toner image transferred from each of the photosensitive drums 311 to 341 to the intermediate transfer belt 361 to the transfer position to the sheet by the secondary transfer roller 37. Specifically, as shown in FIG. 4, the intermediate transfer device 36 includes an intermediate transfer belt 361, a driving roller 362, a stretching roller 363, and a belt cleaning unit 364.

  The belt cleaning unit 364 removes toner remaining on the intermediate transfer belt 361. For example, the belt cleaning unit 364 includes a blade-shaped cleaning member and cleans the surface of the intermediate transfer belt 361.

  The intermediate transfer belt 361 is an endless belt member to which a toner image formed on the photosensitive drums 311 to 341 is transferred.

  Specifically, in the image forming apparatus 10, as shown in FIG. 5, the intermediate transfer belt 361 includes a base material layer 361A formed of a thermoplastic resin, and a thermosetting resin on the base material layer 361A or a dipping method. It has a surface layer 361B formed by coating by a ring coating method. For example, the thermoplastic resin used for forming the base material layer 361A is PC (polycarbonate), PVDF (polyvinylidene fluoride), PA (nylon), PBT (polybutylene terephthalate), or the like. The thermosetting resin used for forming the surface layer 361B is PI (polyimide), PAI (polyamideimide), AC (acrylic), or the like.

The surface layer 361B of the intermediate transfer belt 361 is preferably formed of the thermosetting resin having a Martens hardness of 100 N / mm ² or more and 350 N / mm ² or less. That is, when the surface layer 361B of the intermediate transfer belt 361 is formed of the thermosetting resin having a Martens hardness of less than 100 N / mm ² , sufficient toner releasability cannot be obtained, and the surface layer 361B formed by the secondary transfer roller 37 is not obtained. The transfer efficiency of the toner image transferred to the sheet decreases. In addition, when the surface layer 361B of the intermediate transfer belt 361 is formed of the thermosetting resin having a Martens hardness of 350 N / mm ² , coating by a dipping method or a ring coating method becomes difficult.

  Here, when the surface layer 361B of the intermediate transfer belt 361 is formed by coating the thermosetting resin by the dipping method or the ring coating method, as shown in FIG. 5, the intermediate transfer belt 361 in the width direction 361C. The layer thickness of the surface layer 361B differs between the first end 361D and the second end 361E. For example, in the image forming apparatus 10, the layer thickness at the second end 361E of the intermediate transfer belt 361 is thinner than the layer thickness at the first end 361D.

  The driving roller 362 is driven to rotate by a driving force supplied from a power source (not shown) to cause the intermediate transfer belt 361 to travel along the transport direction 36A. The driving roller 362 stretches the intermediate transfer belt 361 together with the stretching roller 363.

  Here, in the image forming apparatus 10, the driving roller 362 and the stretching roller 363 are positioned such that the inner peripheral distance of the intermediate transfer belt 361 at the second end 361E is larger than the inner peripheral distance at the first end 361D. Therefore, the intermediate transfer belt 361 is stretched.

  For example, in the image forming apparatus 10, as illustrated in FIG. 6, the stretching roller 363 is disposed in a state of being inclined with respect to the axial direction of the photosensitive drum 311 (the same direction as the width direction 361 </ b> C of the intermediate transfer belt 361). In this case, the distance of the inner periphery of the intermediate transfer belt 361 at the second end 361E is larger than the distance of the inner periphery at the first end 361D. Accordingly, the tension applied to the second end 361E of the intermediate transfer belt 361 by the stretching by the driving roller 362 and the stretching roller 363 is greater than the tension applied to the first end 361D. Accordingly, in the image forming apparatus 10, the intermediate transfer belt 361 moves along the moving direction 363A from the second end 361E toward the first end 361D at the contact position between the intermediate transfer belt 361 and the stretching roller 363.

  In the image forming apparatus 10, the number of rollers that stretch the intermediate transfer belt 361 may be three or more, and the number of rollers that are arranged in an inclined state with respect to the axial direction of the photosensitive drum 311 is also two or more. It may be. In addition, the one or more rollers arranged in a state inclined with respect to the axial direction of the photosensitive drum 311 are not limited to the one that stretches the entire region in the width direction 361C of the intermediate transfer belt 361, and A part of the region in the width direction 361C may be stretched.

  On the other hand, a contact portion 365 is provided on the back surface of the second end portion 361E of the intermediate transfer belt 361 as shown in FIG. Further, as shown in FIG. 5, a contacted portion 366 is provided at one end portion of the stretching roller 363 arranged in a state inclined with respect to the axial direction of the photosensitive drum 311.

  The contact portion 365 is in contact with one end portion of the tension roller 363 in the axial direction. Specifically, the contact portion 365 is provided endlessly along the inner peripheral surface of the intermediate transfer belt 361, and has an inner peripheral surface 365A and an inner side surface 365B as shown in FIG. For example, the contact portion 365 is formed of urethane rubber.

  On the other hand, as shown in FIG. 5, the contacted portion 366 includes a first contacted surface 366A that contacts the inner peripheral surface 365A of the contact portion 365 and a second contacted surface 366B that contacts the inner side surface 365B of the contact portion 365. Have For example, the contacted part 366 is made of polyacetal. When the image forming apparatus 10 includes three or more rollers that stretch the intermediate transfer belt 361, the contacted portion 366 is disposed at one end of the roller parallel to the axial direction of the photosensitive drum 311. It may be provided.

  In the image forming apparatus 10, the inner transfer surface 365 </ b> B of the contact portion 365 is in contact with the second contacted surface 366 </ b> B of the contacted portion 366, whereby the intermediate transfer belt at the contact position between the intermediate transfer belt 361 and the stretching roller 363. Movement along the movement direction 363A of 361 is restricted. Accordingly, meandering in the width direction 361C of the intermediate transfer belt 361 is restricted.

  In the image forming apparatus 10, the contact portion 365 is provided only on the back surface of the second end portion 361E of the intermediate transfer belt 361, and is not provided on the back surface of the first end portion 361D. Therefore, the occurrence of cracks at the first end portion 361D is suppressed as compared with the configuration in which the contact portions 365 are provided at both ends in the width direction 361C of the intermediate transfer belt 361.

  Further, in the image forming apparatus 10, the inner peripheral surface 365 </ b> A of the contact portion 365 is in contact with the first contacted surface 366 </ b> A of the contacted portion 366, so that the movement along the moving direction 363 </ b> A of the intermediate transfer belt 361 is performed. The load applied to the surface layer 361B when being regulated by is distributed. Thereby, generation | occurrence | production of the crack in the 2nd end part 361E is suppressed.

[Example 1]
In the image forming apparatus 10, an experiment was conducted to investigate the relationship between the Martens hardness of the thermosetting resin used for forming the surface layer 361B of the intermediate transfer belt 361 and the transfer efficiency to the sheet by the secondary transfer roller 37. The experimental results are shown in FIG. In the experiment, a PI (polyimide) main component surface layer 361B having a Martens hardness of 200 N / mm ² or less and an AC (acrylic) main component layer 361B having a Martens hardness of 180 N / mm ^{2 to} 400 N / mm ² were used. The specifications of the image forming apparatus 10 at the time of the experiment are as follows.
Substrate layer 361A of intermediate transfer belt 361: PA (nylon) main component, Young's modulus 1500 MPa, thickness 120 μm
Drive roller 362: Aluminum three-headed tube (surface EPDM conductive rubber, layer thickness 1.0 mm), outer diameter 21 mm
Stretching roller 363: Aluminum Mitsuya tube (surface alumite treatment, layer thickness 1.0 μm to 12.0 μm), outer diameter 21 mm
Contact portion 365: formed of urethane material, thickness 0.5 mm to 1.2 mm, width 3.5 mm to 7.0 mm
Contacted portion 366: formed of polyacetal resin Tension at first end portion 361D of intermediate transfer belt 361: 5N
Tension at the second end 361E of the intermediate transfer belt 361: 7N

From the experimental results shown in FIG. 7, it is found that when the surface layer 361B is formed using the thermosetting resin having a Martens hardness of 100 N / mm ² or more, transfer efficiency to the sheet of 95% or more can be obtained. did.

[Example 2]
In the image forming apparatus 10, an experiment was conducted to investigate the minimum layer thickness required for the surface layer 361B of the intermediate transfer belt 361. The experimental results are shown in FIG. The specifications of the image forming apparatus 10 at the time of the experiment are the same as those in the first embodiment.

  From the experimental results shown in FIG. 8, it has been found that when PI (polyimide) is used as the material of the surface layer 361B of the intermediate transfer belt 361, it is necessary to ensure a layer thickness of 4.5 μm or more. Further, from the experimental results shown in FIG. 8, it was found that when AC (acrylic) is used as the material of the surface layer 361B of the intermediate transfer belt 361, it is necessary to ensure a layer thickness of 0.7 μm or more.

[Example 3]
In the image forming apparatus 10, an experiment was conducted to investigate the layer thickness at which cracks occur at the first end 361D and the second end 361E in the surface layer 361B of the intermediate transfer belt 361. The experimental results are shown in FIG. The specifications of the image forming apparatus 10 at the time of the experiment are the same as those in the first embodiment.

  From the experimental results shown in FIG. 9, when PI (polyimide) is used as the material of the surface layer 361B of the intermediate transfer belt 361, the thickness of the surface layer 361B of the intermediate transfer belt 361 is set to the second end where the contact portion 355 is provided. It has been found that the portion 361E needs to be less than 9.0 μm, and the first end portion 361D needs to be less than 12.0 μm. When AC (acrylic) is used as the material for the surface layer 361B of the intermediate transfer belt 361, the thickness of the surface layer 361B of the intermediate transfer belt 361 is set to 3.0 μm at the second end 361E where the contact portion 355 is provided. It was found that the first end 361D needs to be less than 4.0 μm.

[Example 4]
An experiment was conducted to investigate the variation in layer thickness when the surface layer 361B of the intermediate transfer belt 361 used in the image forming apparatus 10 was formed by coating by dipping or ring coating. The experimental results are shown in FIG.

  From the experimental results shown in FIG. 10, when PI (polyimide) is used as the material of the surface layer 361B of the intermediate transfer belt 361 and the layer thickness at the center is set to 7 μm, the second end 361E It was found that the layer thickness was 4.5 μm to 8.1 μm, and the layer thickness of the first end 361D was 5.5 μm to 9.9 μm. This result satisfies the condition of the minimum necessary layer thickness of 4.5 μm or more found from the experimental results in Example 2. Further, the second end 361E found from the experimental results in Example 3 satisfies the condition of less than 9.0 μm, and the first end 361D satisfies the condition of less than 12.0 μm.

  Further, from the experimental results shown in FIG. 10, when the material of the surface layer 361B of the intermediate transfer belt 361 is AC (acrylic) and the layer thickness at the center is set to 2 μm, the second end portion It was found that the layer thickness of 361E was 0.9 μm to 2.7 μm, and the layer thickness of the first end 361D was 1.1 μm to 3.3 μm. This result satisfies the condition of the minimum necessary layer thickness of 0.7 μm or more, which was found from the experimental results in Example 2. Further, the second end portion 361E found from the experimental results in Example 3 satisfies the condition of less than 3.0 μm and the first end portion 361D satisfies the condition of less than 4.0 μm.

  As described above, in the image forming apparatus 10, the distance between the inner circumferences at the second end 361E is the distance between the inner circumferences at the first end 361D among the both ends in the width direction 361C of the intermediate transfer belt 361. The intermediate transfer belt 361 is stretched between the driving roller 362 and the stretching roller 363 in a larger positional relationship. In the image forming apparatus 10, a contact portion 355 that comes into contact with one end portion in the axial direction of the stretching roller 363 is provided only on the back surface of the second end portion 361 E of the intermediate transfer belt 361. As a result, meandering in the width direction 361C of the intermediate transfer belt 361 is restricted, and cracks are generated in the surface layer 361B of the intermediate transfer belt 361 formed by coating the thermosetting resin by the dipping method or the ring coating method. It is suppressed.

1: ADF
2: Image reading unit 3: Image forming units 31 to 34: Image forming units 311 to 341: Photosensitive drum 36: Intermediate transfer device 361: Intermediate transfer belt 362: Drive roller 363: Stretching roller 364: Belt cleaning unit 365: Contact unit 366: contacted unit 37: secondary transfer roller 4: paper feeding unit 5: control unit 6: operation display unit 10: image forming apparatus

Claims (7)

A substrate layer formed of a thermoplastic resin and a surface layer formed by coating a thermosetting resin on the substrate layer by a dipping method or a ring coating method are formed on the image carrier on the surface layer. An intermediate transfer belt onto which the transferred toner image is transferred;
The distance of the inner circumference of the intermediate transfer belt at the second end where the thickness of the surface layer is thinner than the first end of the both ends in the width direction of the intermediate transfer belt is the distance of the inner circumference at the first end. A plurality of stretching rollers that stretch the intermediate transfer belt in a larger positional relationship;
A contact portion that is provided on the back surface of the second end portion of the intermediate transfer belt and contacts one end portion in the axial direction of the one or more stretching rollers;
An intermediate transfer device.   The intermediate transfer device according to claim 1, wherein the one or more stretching rollers are arranged in a state inclined with respect to the axial direction of the image carrier. The contact portion is provided endlessly along the inner peripheral surface of the intermediate transfer belt;
A contacted part having a first contacted surface in contact with an inner peripheral surface of the contact part and a second contacted surface in contact with an inner surface of the contact part at one end of one or a plurality of the stretching rollers The intermediate transfer device according to claim 1, wherein the intermediate transfer device is provided. One or a plurality of the stretching rollers are arranged in an inclined state with respect to the axial direction of the image carrier,
The intermediate transfer according to claim 3, wherein the contacted portion is provided at one end of each of the one or more stretching rollers arranged in an inclined state with respect to the axial direction of the image carrier. apparatus. The intermediate transfer device according to any one of claims 1 to 4, wherein the surface layer is formed of the thermosetting resin having a Martens hardness of 100 N / mm ² or more and 350 N / mm ² or less.   An image forming apparatus comprising the intermediate transfer device according to claim 1. An intermediate transfer belt to which a toner image formed on an image carrier is transferred,
A base material layer formed of a thermoplastic resin;
A surface layer formed by coating a thermosetting resin on the base material layer by a dipping method or a ring coating method;
Of the both ends in the width direction of the intermediate transfer belt, the surface layer is provided on the back surface of the second end where the layer thickness is thinner than the first end, and the inner peripheral distance of the intermediate transfer belt at the second end is A contact portion that comes into contact with one end portion in the axial direction of some or all of the plurality of stretching rollers that stretch the intermediate transfer belt in a positional relationship that is greater than the distance of the inner circumference at the first end portion;
An intermediate transfer belt comprising:

Images