JP2000315020A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a transfer-scatter-free, satisfactory image by composing an intermediate transfer belt out of at least two layers, making the outermost layer higher in resistance value than other layers, providing a reinforcement layer on the external surface or/and internal surface of the peripheral edge of one or both ends of the intermediate transfer belt, and making the reinforcement layer equal to or higher in resistance value than the uppermost layer. SOLUTION: An intermediate transfer belt 20 is composed of at least two layers, and the uppermost layer 22 of the intermediate transfer belt is higher in resistance value than other layers. Also, a reinforcement layer is provided on the external surface or/and internal surface of the peripheral edge of one or both ends of the intermediate transfer belt 20, and the resistance value of the reinforcement layer is made higher than or equal to the resistance value of the uppermost layer 22. Here, it is preferable that the resistance value of the lowermost layer 21 of the intermediate transfer belt 20 be 1×108 Ω or below and the resistance value of the reinforcement layer be one hundred or more times higher than the resistance value of the uppermost layer 22 of the intermediate transfer belt 20. It is desirable to subject the intermediate transfer belt 20 to sizing by a heating process in order to increase accuracy in the length of its perimeter.

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 system, and more particularly, to an image formed by transferring a toner image formed on a first image carrier to an intermediate transfer member once and then transferring the toner image. The present invention relates to an image forming apparatus for obtaining a formed product.

[0002]

2. Description of the Related Art An image forming apparatus using an intermediate transfer member includes:
A color image forming apparatus or a multi-color image forming apparatus or a multi-color image forming apparatus that sequentially outputs a plurality of component color images of the color image information or the multi-color image information and outputs an image formed by combining and reproducing the color image or the multi-color image. It is effective as an image forming apparatus having a forming function and a multicolor image forming function.

FIG. 1 is a schematic view showing an example of an image forming apparatus using an intermediate transfer member. As the intermediate transfer member, a belt type or a drum type is mainly used.

FIG. 1 shows a color image forming apparatus (copier or laser beam printer) using an electrophotographic process. The intermediate transfer body 20 (the belt type in FIG. 1) uses a medium-resistance elastic body.

Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) which is repeatedly used as a first image carrier, and has a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow. It is driven to rotate.

[0006] The photosensitive drum 1 rotates in the primary charging device 2 during the rotation process.
Is charged uniformly to a predetermined polarity and potential, and then modulated by an image exposure means (not shown) corresponding to a color separation / imaging exposure optical system of a color original image or a time-series electric digital pixel signal of image information. Receiving an image exposure 3 by a scanning exposure system using a laser scanner that outputs a converted laser beam, thereby forming an electrostatic latent image corresponding to a first color component image (for example, a yellow color component image) of a target color image. Is done.

Next, the electrostatic latent image is developed by a first developing device (yellow developing device 41) with yellow toner Y as a first color. At this time, the developing devices of the second to fourth developing devices (the magenta developing device 42, the cyan developing device 43, and the black developing device 44) are turned off and do not act on the photosensitive drum 1, The first color yellow toner image is not affected by the second to fourth developing units.

[0008] The intermediate transfer member 20 is moved clockwise in the photosensitive drum 1.
It is driven to rotate at the same peripheral speed as.

[0009] The first type formed and supported on the photosensitive drum 1
While the yellow toner image of the color passes through the nip portion between the photosensitive drum 1 and the intermediate transfer body 20, the primary transfer roller 6
The intermediate transfer (primary transfer) is sequentially performed on the outer peripheral surface of the intermediate transfer body 20 by the electric field formed by the primary transfer bias applied to the intermediate transfer body 20 from 2.

After the transfer of the first color yellow toner image corresponding to the intermediate transfer member 20, the surface of the photosensitive drum 1 is cleaned by the cleaning device 13.

Similarly, a magenta toner image of the second color, a cyan toner image of the third color, and a black toner image of the fourth color are sequentially transferred onto the intermediate transfer member 20 in a superimposed manner to correspond to the target color image. Thus, a combined color toner image is formed.

Reference numeral 63 denotes a secondary transfer roller, which is provided in parallel with the secondary transfer opposing roller 64 so as to be supported in parallel, and is disposed on the lower surface of the intermediate transfer member 20 so as to be separated therefrom.

First transfer from the photosensitive drum 1 to the intermediate transfer member 20
The primary transfer bias for the sequential superimposed transfer of the toner images of the fourth to fourth colors has a polarity opposite to that of the toner and is applied from a bias power supply 29. The applied voltage is, for example, +100 V to +2
kV range.

The first transfer from the photosensitive drum 1 to the intermediate transfer body 20
The secondary transfer roller 63 and the cleaning charging member 7 can be separated from the intermediate transfer body 20 in the primary transfer process of the third color toner image.

The transfer of the composite color toner image transferred onto the intermediate transfer member 20 to a transfer material P, which is a second image carrier, is performed while the secondary transfer roller 63 is brought into contact with the intermediate transfer member 20 and supplied. The transfer material P is fed from the paper roller 11 to a contact nip between the intermediate transfer body 20 and the secondary transfer roller 63 at a predetermined timing, and a secondary transfer bias is applied to the secondary transfer roller 63 from the bias power supply 28. . With this secondary transfer bias, the composite color toner image is transferred (secondary transfer) from the intermediate transfer member 20 to the transfer material P as the second image carrier. The transfer material P that has received the transfer of the toner image is
And heat-fixed.

After the image transfer to the transfer material P is completed, the cleaning charging member 7 is brought into contact with the intermediate transfer body 20 and is transferred to the transfer material P by applying a bias having a polarity opposite to that of the photosensitive drum 1. Instead, a charge having a polarity opposite to that of the photosensitive drum 1 is applied to the toner (transfer residual toner) remaining on the intermediate transfer body 20.

The transfer residual toner is electrostatically transferred to the photosensitive drum 1 in a nip portion with the photosensitive drum 1 and in the vicinity thereof, thereby cleaning the intermediate transfer member.

A color electrophotographic apparatus having an image forming apparatus using the above-mentioned intermediate transfer member is pasted or attached onto a transfer drum, which is a conventional technique, and transfers an image from there onto a first image carrier. Compared with a color electrophotographic apparatus having an image forming apparatus, for example, a transfer apparatus as described in JP-A-63-301960,
Processing and control on the transfer material, which is an image carrier (for example, gripping on a gripper, adsorbing, giving a curvature, etc.)
Image can be transferred from the intermediate transfer member without the need for a thin paper (40 g) such as an envelope, a postcard or a label paper.
/ M ² paper) to thick paper (200 g / m ² paper) regardless of the width, width, length or thickness of the second image carrier. Has advantages.

Due to such advantages, a color copying machine, a color printer and the like using an intermediate transfer member are already operating in the market.

However, when the image forming apparatus using the intermediate transfer member is actually used repeatedly, it still has the following problems to be overcome.

For example, when a seamless belt made of a thermoplastic resin is used as the intermediate transfer member, the specific resistance of the uppermost layer is made larger than that of the lower layer in order to improve transfer efficiency and image quality. JP-A-8-504
In order to accurately superimpose the four color images, a position detection hole is provided for high-precision position control during driving, and the position is determined by a combination of the detection hole and the transmission type photoelectric sensor. In the case of the method, since the lower layer having low resistance is exposed at the cross section in contact with the detection hole, a current may flow when a bias is applied, and image defects such as transfer omission may occur.

Further, there is also a problem that the durability is poor due to a crack or a loss of synchronism from the end with an increase in the number of prints. This is described in, for example,
For example, as described in JP-A-63000 and 8-85645, a method of reinforcing the end portion may be used. However, in the case of a transfer member, image defects such as transfer omission due to electrical properties as described above are also expected, and therefore, other than strength. Therefore, further improvement was required.

[0023]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus having an intermediate transfer belt capable of obtaining a good image without transfer scattering.

It is a further object of the present invention to provide an image forming apparatus having an intermediate transfer belt which does not cause transfer omission due to improper flow of current.

It is a further object of the present invention to provide an image forming apparatus having an intermediate transfer belt which does not cause cracking and step-out.

It is a further object of the present invention to provide an image forming apparatus having an intermediate transfer belt whose manufacturing process can be simplified.

[0027]

That is, according to the present invention, a toner image formed on a first image carrier is transferred onto an intermediate transfer belt and then further transferred onto a second image carrier. In the image forming apparatus, the intermediate transfer belt is composed of at least two layers, the resistance value of the uppermost layer of the intermediate transfer belt is higher than the resistance values of the other layers, and one end peripheral portion of the intermediate transfer belt or An image forming apparatus having a reinforcing layer on one or both of an outer surface and an inner surface of both peripheral edges, wherein a resistance value of the reinforcing layer is equal to or more than a resistance value of the uppermost layer.

Further, according to the present invention, the resistance value of the lowermost layer of the intermediate transfer belt is 1 × 10 ⁸ Ω or less, and the resistance value of the reinforcing layer is 10 times lower than the resistance value of the uppermost layer of the intermediate transfer belt.
The image forming apparatus is at least 0 times as expensive.

Further, the present invention is the above-described image forming apparatus, wherein in the step of sizing the intermediate transfer belt by heat treatment, the reinforcing layer is thermally fused at the same time.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

In the image forming apparatus used in the present invention, the toner image formed on the first image carrier is transferred onto an intermediate transfer belt and then further transferred onto a second image carrier. Since the belt is composed of at least two layers, and the resistance value of the uppermost layer of the intermediate transfer belt is higher than the resistance values of the other layers, the uppermost layer of the intermediate transfer belt has an initial height regardless of the use environment. Since the potential is obtained and the holding time is long, the surface potential difference between the image portion and the non-image portion of the intermediate transfer belt after the transfer can be kept small, and a portion where the potential of the image portion toner is low when the intermediate transfer belt is driven. (Non-image area), and has a reinforcing layer on one or both of the outer surface and the inner surface of the peripheral edge at one end or both ends of the intermediate transfer belt, so that the intermediate transfer belt can be used during use. Crack of And step-out does not occur, shows good durability. Further, since the resistance value of the reinforcing layer is equal to or higher than the resistance value of the uppermost layer, image defects such as transfer omission do not occur.

Here, when the intermediate transfer belt is a single layer, the toner scatters violently. In particular, only a blurred image is obtained for a character image or the like, or if the initial scatter is good. Also, since the potential holding time of the uppermost layer of the intermediate transfer belt is too long, a remarkable cleaning failure occurs.

When there is no reinforcing layer, cracks occur at the ends during use, or step-out occurs. Further, when the resistance value of the reinforcing layer is less than the resistance value of the uppermost layer of the intermediate transfer belt,
During use, a current flows when a bias is applied to a lower layer having a low resistance at the contact section of the position detection hole, causing image defects such as transfer omission.

The resistance of the lowermost layer of the intermediate transfer belt used in the present invention is 1 × 10 ⁸ Ω or less, and the resistance of the reinforcing layer is one more than the resistance of the uppermost layer of the intermediate transfer belt.
When the resistance is lower than that of the lower layer having a low resistance even if there is a decrease in surface resistance due to a nitric acid product in the device or a surface deposit such as a developer itself caused by an increase in the number of prints, the resistance is lower than that of the lower layer. Since the difference is sufficiently large, current does not flow in and good image characteristics are exhibited.

Here, when the resistance value of the lowermost layer of the intermediate transfer belt exceeds 1 × 10 ⁸ Ω, or when the resistance value of the reinforcing layer is less than 100 times the resistance value of the uppermost layer of the intermediate transfer belt. In the case where the resistance value of the uppermost layer and the reinforcing layer is reduced due to surface deposits, there is no difference in resistance with the lowermost layer of the intermediate transfer belt. May occur.

The intermediate transfer belt can be produced by a method such as continuous melt extrusion molding, injection molding, blow molding, blown film molding, and the like. A belt is formed by adhesive bonding of sheets, or a coating is applied to a cylindrical film obtained by the molding method, for example, a dipping method, a roll coating method, a spray coating method, a brush coating method, or a method of bonding a resin film or the like. Method can be adopted. However, it is not limited to these.

It is desirable that the obtained intermediate transfer belt be sized by a heat treatment in order to increase the perimeter accuracy, so that the intermediate transfer belt may have a slight fold or seam due to a method other than the continuous melt extrusion molding method. Can be eliminated.

The heating temperature and time are not particularly limited, but may be appropriately determined depending on the characteristics of each material.

As a method of providing a reinforcing layer of the intermediate transfer belt used in the present invention, a method of coating a paint on the obtained intermediate transfer belt, such as a dipping method, a roll coating method, a spray coating method, a brush coating method, and the like. A method of bonding a resin sheet coated with an adhesive, a method of extruding and laminating a thermoplastic resin, a method of thermocompression bonding a resin sheet, a method of ultrasonically welding a resin sheet, and the like.
Above all, a method in which a resin sheet is thermally welded at the same time in the step of sizing the obtained intermediate transfer belt by heat treatment is preferable because the step can be simplified.

The thickness of the reinforcing layer is preferably such that no step is formed on the belt, for example, 30 to 200 μm. The width does not need to cover the image area, and is preferably a minimum necessary to cover the position detection hole, for example, 5 to 20 mm.

The thermoplastic resin used for each layer and the reinforcing layer of the intermediate transfer belt used in the present invention includes polystyrene, chloropolystyrene, poly-α-methylstyrene,
Styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-
Maleic acid copolymer, styrene-acrylate copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer And styrene-phenyl acrylate copolymer), styrene-methacrylic ester copolymers (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer and styrene-phenyl methacrylate copolymer), Styrene-based resins (mono- or copolymers containing styrene or styrene-substituted products) such as styrene-α-methyl methacrylate copolymer and styrene-acrylonitrile-acrylate copolymer, methyl methacrylate resin, methacryl Butyl resin, ethyl acrylate resin, Le butyl resins, modified acrylic resins (silicone-modified acrylic resin, vinyl chloride resin-modified acrylic resins and acrylic urethane resins), vinyl chloride resin, styrene - vinyl acetate copolymer, vinyl chloride -
Vinyl acetate copolymer, rosin-modified maleic resin, phenolic resin, epoxy resin, polyolefin resin such as polyethylene, polypropylene and polybutadiene, polyester resin such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyvinylidene chloride, Ionomer resin, polyurethane resin, silicone resin, polyvinylidene fluoride (PVd
F) Resins and fluorine resins such as ethylene tetrafluoroethylene copolymer (ETFE), ketone resins, polycarbonate resins, ethylene-ethyl acrylate copolymers, ethylene-vinyl alcohol copolymers, xylene resins, polyvinyl butyral resins, polyamides One or more kinds selected from the group consisting of resin, polyimide resin, modified polyphenylene oxide resin and the like can be used. However, it is not limited to the above materials.

A conductive agent may be added to adjust the resistance value of the intermediate transfer belt used in the present invention. The conductive agent is not particularly limited, for example, carbon,
Metal powders such as aluminum and nickel, metal oxides such as titanium oxide, quaternary ammonium salt-containing polymethyl methacrylate, polyvinylaniline, polyvinylpyrrole,
One or two or more selected from the group consisting of polydiacetylene, polyethyleneimine, boron-containing polymer compounds, and conductive polymer compounds such as polypyrrole can be used. However, it is not limited to the above conductive agent.

Known methods can be appropriately used for mixing and dispersing various additives in such various resins. When the resin component is solid, a device such as a roll mill, a kneader or a Banbury mixer is used. When the resin component is liquid, the resin component can be dispersed using a ball mill, a bead mill, a homogenizer, a paint shaker, a nanomizer or the like.

Further, in order to increase the slipperiness of the surface of the intermediate transfer belt and to improve the transferability, a lubricant may be added to the uppermost layer or each layer, if necessary, within a range not affecting the properties of the present invention. Good. The lubricant is not particularly limited as long as it improves the slipperiness, and for example, the following are used.

Fluorocarbon, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-ethylene copolymer (ETFE), and tetrafluoroethylene (PTFE) with fluorine bonded to fluororubber, fluoroelastomer, graphite, graphite, etc. Fluoroethylene-
Perfluoroalkyl vinyl ether copolymer (PF
Powders of fluorine compounds such as resins such as A), silicone resin particles, silicone powders such as silicone rubber and silicone elastomer, polyethylene (PE), polypropylene (PP), polystyrene (PS), acrylic resin, nylon Resins such as resins, phenolic resins and epoxy resins and powders of these compounds or mixtures, granular carbon such as spherical graphite, inorganic powders such as silica, alumina, titanium oxide, magnesium oxide, tin oxide and iron oxide. These may be used alone or in combination of two or more. In addition, the shape and particle size of the particles are not particularly limited, but can be used in any shape as long as lubricity is obtained, such as a spherical shape, a fibrous shape, a plate shape and an irregular shape, and the particle size is not limited, Considering dispersibility and surface properties, 0.0
A range of 2 to 20 μm is desirable. If necessary, these powders may be subjected to a surface treatment as long as lubricity is not impaired. Also, a dispersant can be used within a range that does not cause a problem in various properties.

FIG. 2 shows an example of the structure of the intermediate transfer belt used in the present invention.

In the figure, 21 is the lowermost layer, 22 is the uppermost layer, and 20 is the intermediate transfer belt.

The thickness of the intermediate transfer belt is preferably thinner as long as the intermediate transfer belt can be driven smoothly and the mechanical strength and flexibility of the intermediate transfer belt are not impaired. Specifically, 80 to 1000 μm is preferable.

The thickness of each layer is preferably from 10 to 500 μm.

The resistance of each layer other than the lowermost layer and the reinforcing layer is 1
× 10 ⁸ to 1 × 10 ¹⁵ Ω, the resistance value of the intermediate transfer member is 1 × 1
When the resistance is in the range of 0 ⁵ to 1 × 10 ¹² Ω, a high-quality image can be obtained under any environment.

In the present invention, the resistance value of the intermediate transfer belt or each layer and the reinforcing layer is a value measured by a resistance measuring device (Hiresta; manufactured by Mitsubishi Chemical Corporation, HA probe, 500 V applied).

As a method of processing the position detecting hole used in the present invention, a generally known hole processing method can be used. For example, there are a punching process, a cutting process using a laser or the like, and a melting cutting process using a heat source. However, it is not limited to these.

As for the shape of the hole, any size and shape such as a circle, an ellipse, a square and a rectangle may be used as long as they do not hinder the setting of the optical sensor.

Further, when the position is detected by the optical sensor, 700 to 15
The transmittance of light having a main wavelength at 00 nm needs to be 10% or more, preferably 20% or more. It is preferable to use a reinforcing layer that satisfies these conditions.

[0055]

The present invention will be described in detail below with reference to examples.

Example 1 An ethylene tetrafluoroethylene copolymer (ETFE) compound and a polycarbonate resin compound whose resistance was adjusted with carbon black were put into respective extruders, and a two-layer cylinder having an inner diameter of 142 mm was formed by an inflation tube molding method. A tubular tube was obtained (the top layer was ETFE, and the bottom layer was a polycarbonate resin).

This was cut into a length of 250 mm, and a hole of 5 mm square was formed at four non-image areas (equal intervals) at one end, and then covered with a metal support having an outer diameter of 140 mm. 15mm width separately prepared at the peripheral edges of both ends,
Put an ETFE tube with a thickness of 50 μm,
After heating for 0 minutes and cooling to room temperature, it was extracted from the metal support to obtain an intermediate transfer belt having an inner diameter of 140 mm having a reinforcing layer at both peripheral edges (at this time, the thickness of the uppermost layer was 70 μm,
The thickness of the lowermost layer is 130 μm).

The resistance value of the uppermost layer of the obtained intermediate transfer belt is 1.5 × 10 ¹⁰ Ω, and the resistance value of the lowermost layer is 6.2 × 10 ^6.
Ω, and the resistance value of the reinforcing layer was 1.8 × 10 ¹² Ω.

The intermediate transfer belt was heated at a temperature of 23 ° C./humidity of 6
It was mounted on the full-color electrophotographic apparatus shown in FIG. 1 in an environment of 0%, and 5000 full-color image prints were made on 80 g / m ² paper. As a result, there was no transfer scattering, no transfer omission, and no belt cracking. Was. Table 1 shows the results.

The main image forming conditions of this embodiment are as follows.

Color developer (for all four colors): non-magnetic one-component toner (negative) Primary transfer voltage: +500 V Secondary transfer current: +12 μA Process speed: 120 mm / sec

The criteria for image evaluation are as follows.

(Transfer Scattering) A scattering is not observed at all.

○ Although it can be recognized very slightly on the image,
No problem in practical use.

{Circle around (2)} Recognizable on an image.

× Recognizable on the image.

(Transfer omission) A transfer omission on the image is not observed at all.

転 写 Transfer omission on the image is slightly observed at a part of the edge, but there is no practical problem.

(4) The transfer omission on the image is observed over the entire periphery of the edge.

× Transfer omission on the image is remarkably observed over the entire periphery of the end portion.

(Crack of belt) A belt crack is not seen at all.

The belt crack is slightly seen in a part of the position detecting portion, but there is no practical problem.

(4) Fine belt cracks are found at the position detecting portion and at the end, causing drive unevenness.

C: Belt cracks are remarkably observed at the position detecting portion and the end portion, and normal driving cannot be performed at all.

(Example 2) A polyvinylidene fluoride resin (PVdF) compound and a polycarbonate resin compound whose resistance was adjusted by carbon black were put into respective extruders, and a two-layer cylindrical tube having an inner diameter of 142 mm was formed by an inflation tube molding method. (The uppermost layer was PVdF and the lowermost layer was a polycarbonate resin).

Next, this was cut into a length of 250 mm.
After drilling a 5 mm square hole at four non-image areas (equal intervals) at one end, cover the metal support having an outer diameter of 140 mm with 16 holes.
Heated at 0 ° C. for 30 minutes, cooled to room temperature, removed from the metal support, and further prepared separately at the peripheral edges of both ends with a width of 15 m.
m, and an ETFE sheet having a thickness of 50 μm was thermocompression-bonded with a heat roller to obtain an intermediate transfer belt having an inner diameter of 140 mm and a reinforcing layer at both peripheral edges (at this time, the thickness of the uppermost layer was 50 μm).
m, the thickness of the lowermost layer is 150 μm).

The resistance value of the uppermost layer of the obtained intermediate transfer belt is 2.3 × 10 ¹⁰ Ω, and the resistance value of the lowermost layer is 1.7 × 10 ^7.
Ω, and the resistance value of the reinforcing layer was 4.5 × 10 ¹² Ω.

As a result of performing 5000 full-color image prints in the same manner as in Example 1, there were no transfer scattering, no transfer omission, and no cracks in the belt. Table 1 shows the results.

(Example 3) Polyethylene terephthalate resin (PET) whose resistance was adjusted with carbon black
Compound and polybutylene terephthalate resin (P
BT) was charged into each extruder, and a two-layer cylindrical tube having an inner diameter of 142 mm was obtained by an inflation tube molding method (the uppermost layer was PET, and the lowermost layer was PBT resin).

Next, this was cut into a length of 250 mm,
After drilling a 5 mm square hole at four non-image areas (equal intervals) at one end, cover the metal support with an outer diameter of 140 mm.
Heat treatment at 0 ° C. for 15 minutes, cool to room temperature, remove from metal support, and further prepare 15 m width separately on both edges
m, a urethane resin sheet with an adhesive attached to the back surface having a thickness of 50 μm to obtain an intermediate transfer belt having an inner diameter of 140 mm having a reinforcing layer at both peripheral edges (at this time, the thickness of the uppermost layer is 80 μm, and that of the lowermost layer is The thickness is 120 μm).

The resistance value of the uppermost layer of the obtained intermediate transfer belt is 1.8 × 10 ¹⁰ Ω, and the resistance value of the lowermost layer is 4.1 × 10 ^7.
Ω, and the resistance value of the reinforcing layer was 7.2 × 10 ¹⁰ Ω.

As a result of performing 5000 full-color image prints in the same manner as in Example 1, no transfer scattering was found, and transfer omissions and cracks in the belt were slightly observed at some of the ends, but there was no practical problem. Table 1 shows the results.

(Comparative Example 1) An ethylene tetrafluoroethylene copolymer (ETFE) compound whose resistance was adjusted with carbon black was charged into an extruder, and a single-layer cylindrical tube having an inner diameter of 141 mm was obtained by an inflation tube molding method.

Next, this was cut into a length of 250 mm,
After punching a 5 mm square hole at four non-image areas (equal intervals) at one end, cover the metal support having an outer diameter of 140 mm with 20 mm.
Heat treatment was performed at 0 ° C. for 20 minutes to obtain an intermediate transfer belt having an inner diameter of 140 mm (at this time, the thickness of the single layer was 150 μm).

The resistance value of the obtained intermediate transfer belt (single layer) was 5.2 × 10 ⁸ Ω.

As a result of performing 5000 full-color image prints in the same manner as in Example 1, transfer scattering and transfer omission were remarkable, and the belt was also cracked, so that a high-definition image could not be obtained. . Table 1 shows the results.

Comparative Example 2 An intermediate transfer belt was obtained in the same manner as in Example 3 except that the reinforcing layer was made of a urethane resin and its resistance was 6.3 × 10 ⁷ Ω.

As a result of performing 5000 full-color image prints in the same manner as in Example 1, transfer scattering was not a problem, and a crack was slightly observed at a part of the end of the belt, but there was no practical problem. , A high-definition image could not be obtained. Table 1 shows the results.

[0089]

[Table 1]

[0090]

According to the present invention, an image forming apparatus having the following features can be provided by using the above-described intermediate transfer belt. (1) A good image free of transfer scattering can be obtained. (2) A good image without transfer omission can be obtained. (3) The intermediate transfer belt does not crack or lose synchronism. (4) The manufacturing process of the intermediate transfer belt can be simplified.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a color image output device using an intermediate transfer belt.

FIG. 2 is a schematic view of a part of the intermediate transfer belt of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 primary charger 3 image exposure 7 cleaning charging member 10 transfer material guide 11 paper feed roller 13 photosensitive drum cleaning device 15 fixing device 20 intermediate transfer belt 21 bottom layer 22 top layer 26 bias power supply 28 bias power supply 29 Bias power supply 41 Yellow developing device 42 Magenta developing device 43 Cyan developing device 44 Black developing device 61 Drive roller 62 Primary transfer roller 63 Secondary transfer roller 64 Secondary transfer opposing roller P Transfer material

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsunetori Ashbe 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Atsushi Tanaka 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Akihiko Nakazawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takashi Kusaba 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F-term (reference) 2H032 AA05 BA01 BA05 BA09

Claims (3)

[Claims] 1. An image forming apparatus for transferring a toner image formed on a first image carrier onto an intermediate transfer belt and further transferring the toner image onto a second image carrier, wherein the intermediate transfer belt has at least The intermediate transfer belt is formed of two layers, and the resistance value of the uppermost layer of the intermediate transfer belt is higher than the resistance value of the other layers, and one or both of the outer surface and the inner surface of the peripheral edge at one end or both ends of the intermediate transfer belt. An image forming apparatus having a reinforcing layer on both sides, wherein a resistance value of the reinforcing layer is equal to or higher than a resistance value of the uppermost layer. 2. The resistance value of the lowermost layer of the intermediate transfer belt is 1
2. The image forming apparatus according to claim 1, wherein the resistance value of the reinforcing layer is × 10 ⁸ Ω or less and the resistance value of the reinforcing layer is 100 times or more higher than the resistance value of the uppermost layer of the intermediate transfer belt. 3. The image forming apparatus according to claim 1, wherein in the step of sizing the intermediate transfer belt by a heat treatment, the reinforcing layer is simultaneously thermally fused.