JP2022010430A - Fixing belt and electrophotographic image forming apparatus - Google Patents

Abstract

To provide a fixing belt that has excellent toner releasability and fixability and has improved durability, and an electrophotographic image forming apparatus.SOLUTION: A fixing belt has an intermediate layer and an outermost surface layer in this order on a substrate layer. The substrate layer is made of a heat-resistant resin. The intermediate layer is made of a heat-resistant elastic material. In measurement of a surface quality of the outermost surface layer, when a load area rate p separating from each other a core part and a reduced peak part of a contour curved surface regulated in conformity with JIS B 0681-2 is 50%, and a load area rate q separating the core part and a reduced valley part from each other is 90%, the fixing belt has a concave part shape in which the ratio of the spatial volume Vvv of the reduced valley part to the spatial volume Vvc of the core part (Vvv/Vvc) is within a range of 0.5 to 4.0.SELECTED DRAWING: Figure 2

Description

The present invention relates to a fixing belt and an electrophotographic image forming apparatus. More specifically, the present invention relates to a fixing belt and an electrophotographic image forming apparatus having excellent toner releasability and fixing property and improved durability.

A fixing device used in an image forming apparatus such as a copying machine or a laser beam printer usually records a toner image by bringing a heated fixing belt into contact with a recording medium carrying an unfixed toner image. Fix it on the medium.
In the fixing device, for example, one of two or more rollers supporting the endless fixing belt is a heating roller for heating the fixing belt.
Since the heat capacity of the fixing belt is relatively small, the fixing device is excellent in fixing property, and is advantageous for speeding up image formation, for example.

The fixing device has a fixing belt having a three-layer structure of a base material, an elastic layer and a surface layer, and is on the outlet side (downstream side in the transport direction of the recording medium) of the nip portion composed of the upper pressure roller and the fixing belt. The fixing belt is made of a fluororesin such as perfluoroalkoxy alkane (PFA), which is a material having a non-adhesive surface layer and a large curvature. A technique for modifying the surface property is known (see, for example, Patent Document 1).
However, there is a trade-off between the outlet curvature and the speeding up (larger size) of the copying machine.

Further, the modification of the surface property, for example, the improvement of the releasability, is usually how many fluorine atoms (F groups) can be arranged on the surface of the surface layer, whereby the non-adhesiveness (high contact angle, low contact angle) of the surface layer is obtained. Surface energy) is determined.
However, in the surface layer made of fluororesin, fluorine atoms are likely to be unevenly distributed on the surface, and there are almost no F group that can be introduced into the surface and other substituents that should replace the F group.
Therefore, it is difficult to improve the non-adhesiveness by modifying PFA.

As described above, in the present situation where high-speed image formation is required, there is still room for consideration in achieving both separability and fixing property of the fixing belt having a surface layer made of fluororesin.

On the other hand, a technique aimed at improving the separability by combining the roughness of the surface roughness in the depth direction (see, for example, Patent Document 2) and improving the separability by imparting periodicity to the roughness. The targeted technology (see, for example, Patent Document 3) and the like are disclosed.
However, there was room for examination in the durability of these due to the decrease in separability due to the adhesion of toner to the roughened portion.

Japanese Unexamined Patent Publication No. 2012-108545 Japanese Unexamined Patent Publication No. 2018-169530 Japanese Unexamined Patent Publication No. 2019-70771

The present invention has been made in view of the above problems and situations, and the problems to be solved thereof are a fixing belt having excellent toner releasability and fixing property, and excellent durability, and electrophotographic image formation. To provide the device.

As a result of examining the cause of the above problem in order to solve the above-mentioned problems, the present inventor has a ratio (Vvv / Vvc) of the space volume Vvv of the protruding valley portion and the space volume Vvc of the core portion of the outermost layer of the fixing belt. ) Has been found to be able to solve the above problem by having at least one concave shape in the range of 0.5 to 4.0, and has reached the present invention.
That is, the above-mentioned problem according to the present invention is solved by the following means.

1. 1. A fixing belt having an intermediate layer and an outermost layer on the base material layer in this order.
The base material layer is made of heat-resistant resin and is made of heat-resistant resin.
The intermediate layer is made of a heat-resistant elastic material and
In the measurement of the surface texture of the outermost layer,
The load area ratio p that separates the core portion and the protruding peak portion of the contour curved surface defined in accordance with JIS B 061-2 is 50%, and the load area ratio q that separates the core portion and the protruding valley portion is 90%. When
A fixing belt having a concave shape in which the ratio (Vvv / Vvc) of the space volume Vvv of the protruding valley portion to the space volume Vvc of the core portion is in the range of 0.5 to 4.0.

2. 2. The fixing belt according to item 1, wherein the ratio (Vvv / Vvc) is in the range of 0.8 to 2.0.

3. 3. The inner diameter of the concave shape is within the range of 5 to 30 μm, and the inner diameter is within the range of 5 to 30 μm.
The fixing belt according to item 1 or 2, wherein the height of the protruding valley portion of the concave shape is within the range of 10 to 80% of the thickness of the outermost layer.

4. The fixing belt according to any one of the items 1 to 3, wherein the thickness of the outermost layer is in the range of 40 to 150 μm.

5. The base material layer is made of polyimide.
The intermediate layer is made of silicone rubber and
The fixing belt according to any one of items 1 to 4, wherein the outermost layer contains a fluororesin.

6. Item 6. The fixing belt according to Item 5, wherein the fluororesin is a perfluoroalkoxyalkano resin.

7. The electrophotographic image forming apparatus using the fixing belt according to any one of the items 1 to 6.
The endless fixing belt and
Two or more rollers that pivotally support the fixing belt, and
A fixing member including a heating device for heating the fixing belt, and
It has a pressure roller arranged to be urged relative to one of the rollers via the fixing belt, and has.
An electrophotographic image forming apparatus, wherein the roller diameter of the roller urged by the pressure roller among the rollers is 50 mm or more.

8. The fixing belt is axially supported by two or more rollers, and
The electrophotographic image forming apparatus according to Item 7, wherein the tension is adjusted to be 45 N or less.

9. The electrophotographic image forming apparatus according to Item 7 or 8, wherein an unfixed toner image formed on a recording medium by an electrophotographic method is fixed on the recording medium by heating and pressurizing.

By the above means of the present invention, it is possible to provide a fixing belt having excellent toner releasability and fixing property and excellent durability, and an electrophotographic image forming apparatus.
Although the mechanism of expression or mechanism of action of the effect of the present invention has not been clarified, it is inferred as follows.

Toner and paper are fixed by sandwiching them between a pressure roller and a high-temperature fixing belt.
The image is separated from the pressure roller and the anchoring belt at the nip outlet.
Conventionally, as a means for modifying the surface of the fixing belt, there has been a technique of forming the surface shape of the fixing belt by containing a fluororesin in the surface layer (for example, the shape as shown in FIG. 1). Although the separability of the toner is improved, the durability may cause the toner to accumulate in the recesses and the separation performance may be deteriorated.
In order to maintain the toner separation performance even after durability, it is necessary to suppress toner adhesion, and for that purpose, it is effective to give a special uneven shape to the outermost layer of the fixing belt.

On the other hand, in the present invention, a vertical hole-shaped recess is formed on the outermost layer of the fixing belt so that the wall surface is substantially vertical (for example, the shape as shown in FIG. 2).
From the above, the toner is less likely to be deposited on the outermost layer of the fixing belt, and the toner separation performance is maintained even after the durability.

(A) A view of the image in the observation field viewed from a direction perpendicular to the image surface (conventional surface shape of the fixing belt) (b) A view of the image in the observation field viewed from a horizontal direction with respect to the image surface. Figure (surface shape of conventional fixing belt) (A) A view of the image in the observation field viewed from a direction perpendicular to the image surface (surface shape of the fixing belt of the present invention) (b) A view of the image in the observation field viewed from a horizontal direction with respect to the image surface. Figure (surface shape of the fixing belt of the present invention) Diagram showing the relationship between the load area ratio and the load curve The figure which shows the relationship between Vvv and Vvc when the load area ratio p = 50% and q = 90%. The figure which shows an example of the fixing device schematically. The figure which shows an example of the image forming apparatus schematically. Schematic diagram for explaining the evaluation method of the fixing belt (test image consisting of vertical strip-shaped solid images with 10% coverage)

The fixing belt of the present invention is a fixing belt having an intermediate layer and an outermost layer in this order on a base material layer, the base material layer is made of a heat-resistant resin, and the intermediate layer is heat-resistant. In the measurement of the surface texture of the outermost layer, which is made of an elastic material, the load area ratio p that separates the core part and the protruding mountain part of the contour curved surface defined in accordance with JIS B 0681-2 is set to 50%. When the load area ratio q for separating the core portion and the protruding valley portion is 90%, the ratio (Vvv / Vvc) of the space volume Vvv of the protruding valley portion and the space volume Vvc of the core portion is 0. It is characterized by having a concave shape within the range of 5 to 4.0.
This feature is a technical feature common to or corresponding to each of the following embodiments (forms).

In an embodiment of the present invention, the toner releasability is such that the ratio (Vvv / Vvc) of the space volume of the protruding valley portion to the space volume of the core portion is in the range of 0.8 to 2.0. It is preferable from the viewpoint of.

Further, the inner diameter of the concave shape is within the range of 5 to 30 μm, and the height of the protruding valley portion of the concave shape is within the range of 10 to 80% of the thickness of the outermost layer. , Preferable from the viewpoint of toner releasability.

It is preferable that the thickness of the outermost layer is in the range of 40 to 150 μm from the viewpoint of heat transfer, follow-up to deformation of the intermediate layer, and development of releasability.

It is preferable that the base material layer is made of polyimide from the viewpoint of heat resistance.
It is preferable that the intermediate layer is made of silicone rubber from the viewpoint of suppressing nip pressure stress concentration.
Further, it is preferable that the outermost layer contains a fluororesin from the viewpoint of toner releasability.

It is preferable that the fluororesin is a perfluoroalkoxy fluororesin from the viewpoint of toner releasability.

The fixing belt of the present invention comprises an endless fixing belt, two or more rollers for pivotally supporting the fixing belt, a fixing member including a heating device for heating the fixing belt, and the fixing belt via the fixing belt. It has a pressure roller arranged to be urged relative to one of the rollers, and the roller diameter of the roller urged to the pressure roller among the rollers. However, it is preferable that the thickness is 50 mm or more from the viewpoint of securing the heat capacity of the roller, which can increase the printing speed.

From the viewpoint of preventing damage to the rollers, the fixing belt of the electrophotographic image forming apparatus is pivotally supported by two or more rollers and the tension is adjusted to be 45 N or less. preferable.

In the electrophotographic image forming apparatus of the present invention, it is preferable to fix an unfixed toner image formed on a recording medium by an electrophotographic method on the recording medium by heating and pressurizing from the viewpoint of exhibiting the effect.

Hereinafter, the present invention, its constituent elements, and modes and embodiments for carrying out the present invention will be described in detail. In addition, in this application, "-" is used in the meaning which includes the numerical values described before and after it as the lower limit value and the upper limit value.

[Fixing belt]
The fixing belt of the present invention is a fixing belt having an intermediate layer and an outermost layer in this order on a base material layer, the base material layer is made of a heat-resistant resin, and the intermediate layer is heat-resistant. In the measurement of the surface texture of the outermost layer, which is made of an elastic material, the load area ratio p that separates the core part and the protruding mountain part of the contour curved surface defined in accordance with JIS B 0681-2 is set to 50%. When the load area ratio q that separates the core portion and the protruding valley portion is 90%, the ratio (Vvv / Vvc) of the space volume Vvv of the protruding valley portion and the space volume Vvc of the core portion is 0.5. It is characterized by having a concave shape within the range of about 4.0.

In addition, terms such as contour curved surface, core part, protruding mountain part, load area ratio p, protruding valley part, load area ratio q, space volume Vvv of protruding valley part, space volume Vvc of core part, etc. are JIS B 0681-2. : 2018 (Corresponding international standard: ISO 25178-2: 2012) It is a term defined in "Geometric characteristic specifications of products (GPS) -Surface texture-Part 2: Terms, definitions and surface texture parameters". Definitions of each term will be described later as appropriate below.

1. 1. Outermost surface layer The outermost surface layer (hereinafter, also referred to as “release layer”) is a layer having a mold releasability that contributes to improving the separability of the molten toner layer on the recording medium from the surface of the fixing belt in the fixing nip portion. Yes, it has an appropriate releasability with respect to the toner component.
It also constitutes the outer surface of the fixing belt that comes into contact with the recording medium during fixing.

(1.1) Surface Shape In the fixing belt of the present invention, a vertical hole-shaped recess is formed in the outermost layer so that the wall surface is substantially vertical (for example, the shape as shown in FIG. 2).
From the above, the toner is less likely to be deposited on the outermost layer of the fixing belt, and the toner separation performance is maintained even after the durability.

(Surface shape forming method)
Fixing the fixing belt in a direct pressure type manual blasting device (5-501 specification; Fuji Seisakusho) Fly zirconia beads (Φ5-100μm) toward the outermost layer, make unevenness, and fix it to the fixing device as shown in FIG. By attaching a belt, increasing the fixing pressure by 1.2 times, and flowing 100 sheets of A4 blank paper, at least one vertical hole-shaped recess is formed on the outermost surface layer so that the wall surface is substantially vertical.

(1.2) Measurement and evaluation of surface texture The measurement and observation of the surface texture of the outermost layer according to the present invention shall be in accordance with JIS B 0681-6: 2014 (corresponding international standard: ISO 25178-6: 2010). This was done by a method of measuring three-dimensional surface irregularities. The details of the measurement method will be described later.
In the following, various evaluation elements of surface texture obtained by the measurement will be described with reference to FIGS. 3 and 4.

In the graphs shown in FIGS. 3 and 4, the vertical axis indicates the height of the surface unevenness.
The horizontal axis shows the area ratio of the total area of the area equal to or higher than the height of the horizontal plane when the surface unevenness is cut by the horizontal plane at each height, that is, the load area ratio.
Hereinafter, terms and the like used in the present invention will be described.

(1.2.1) Load area ratio and load curve The "load area ratio" refers to the area ratio of the region at the cutting level (certain height) c with respect to the evaluation region of the contour curved surface (surface textured curved surface).
For example, the load area ratio at height c is expressed as Smr (c) (see FIG. 3).
The "load curve" refers to a curve representing the area ratio of a region above a certain height of a surface, that is, the height at which the load area ratio is 0% to 100% (see FIG. 3).
The "contour curved surface" is a general term for point cloud data representing surface texture, and is also referred to as a surface texture curved surface.

(1.2.2) Space volume Vvv of the protruding valley part, space volume Vvc of the core part, and height of the protruding valley part (core part, protruding valley part, protruding mountain part)
The "core portion" of the contour curved surface means a curved portion in which the high protruding peak portion and the deep protruding valley portion, which will be described later, are removed from the contour curved surface.
More specifically, the secant line of the load curve drawn from the load area ratio of 0% with the difference of the load area ratio set to 40% along the load curve is moved from the load area ratio of 0%, and the slope of the score line is the most. The position where it becomes loose is called the central part of the load curve.
The straight line that minimizes the sum of squares of the deviations in the vertical axis direction with respect to this central portion is called an equivalent straight line.
The portion included in the height range of the load area ratio of the equivalent straight line from 0% to 100% is called the core portion.

The “load area ratio Smr1 of the core portion” refers to the load area ratio in percent units at the point where the straight line separating the protruding peak portion of the evaluation region and the core portion of the contour curved surface intersects the load curve.
The “load area ratio Smr2 of the core portion” refers to the load area ratio in percent units at the point where the straight line separating the protruding valley portion of the evaluation region and the core portion of the contour curved surface intersects the load curve.

The "protruding valley portion" is a portion recessed downward from the core portion and corresponds to a portion corresponding to the range of the load area ratio Smr2 to 100% of the load curve.
The “protruding mountain portion” is a portion protruding upward from the core portion and corresponds to a portion corresponding to the range of the load area ratio of 0 to Smr1 (%) of the load curve.

(Space volume Vvv in the protruding valley, space volume Vvc in the core)
The "space volume Vvv of the protruding valley portion" means the volume of the valley in the load area ratio p.
The "space volume Vvc of the core portion" means the difference in the space volume between the load area ratios p and q.
Here, the "load area ratio p" refers to the load area ratio that separates the core portion and the protruding mountain portion of the contour curved surface, and is set to 50% in the present invention.
Further, the "load area ratio q" means a load area ratio that separates the core portion and the protruding valley portion, and is 90% in the present invention.

When using the volume parameters of the space volume Vvv of the protruding valley and the space volume Vvc of the core, the load area ratio p (%) that separates the core and the protruding peak and the core and the protruding valley are separated. It is necessary to determine the load area ratio q (%) to be applied, and in the present invention, p = 50 and q = 90.
FIG. 4 shows the relationship between the space volume Vvv of the protruding valley portion and the space volume Vvc of the core portion in the present invention.

In the fixing belt of the present invention, in the measurement of the surface shape of the outermost layer, the load area ratio p that separates the core portion and the protruding peak portion is 50%, and the load area ratio q that separates the core portion and the protruding valley portion is 90. %, The ratio (Vvv / Vvc) of the space volume Vvv of the protruding valley portion to the space volume Vvc of the core portion is characterized by having a concave shape in the range of 0.5 to 4.0. do.

In an embodiment of the present invention, the toner releasability is such that the ratio (Vvv / Vvc) of the space volume of the protruding valley portion to the space volume of the core portion is in the range of 0.8 to 2.0. It is preferable from the viewpoint of.

Further, the inner diameter of the concave shape is within the range of 5 to 30 μm, and the height of the protruding valley portion of the concave shape is within the range of 10 to 80% of the thickness of the outermost layer. , Preferable from the viewpoint of toner releasability.

(Height of protruding peaks and height of protruding valleys)
By determining the load area ratio p (%) that separates the core portion and the protruding peak portion and the load area ratio q (%) that separates the core portion and the protruding valley portion, the core portion included in a certain height is determined. , The height of the protruding mountain part and the height of the protruding valley part are determined.

(12.3) Method for measuring and observing the surface texture of the fixing belt The space volume Vvv of the protruding valley portion, the space volume Vvc of the core portion, and the height of the protruding valley portion are measured by the following methods. In addition, the inner diameter of the concave shape, which will be described later, is also measured at the same time.
First, using a laser microscope (VK-X250, manufactured by KEYENCE), a surface image of the fixing belt was taken with a 50x objective lens, and three-dimensional height data with an area of 216 μm in width × 288 μm in length was acquired to obtain three-dimensional height data on the surface. Automatic correction was performed for the curvature.
Other conditions are as follows.

(Other conditions)
Optical zoom: 1x Double scan: Always Measurement size (number of pixels): Standard (1024 x 768)
Measurement quality: High-precision image processing: Surface tilt correction (flat surface), with reference surface correction Digitization area (ROI): Whole area filter: Not applicable

Then, using a multi-file analysis application manufactured by KEYENCE compliant with ISO25178, the space volume Vvv of the protruding valley portion, the space volume Vvc of the core portion, and the height of the protruding valley portion were obtained.

(1.3) Resin type The release layer is preferably made of fluororesin. "Made of fluororesin" means that the main material constituting the release layer is fluororesin.
Examples of the fluororesin include perfluoroalkoxy alkane resin (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP) and tetrafluoroethylene-ethylene copolymer (ETFE).
Of these, it is preferable to use perfluoroalkoxy alkane (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) (Perfluoroalkoxy alkane: PFA) from the viewpoint of exhibiting the effect.

(1.4) Outermost layer thickness The outermost layer thickness is preferably in the range of 15 to 150 μm from the viewpoint of heat transfer, follow-up to deformation of the intermediate layer, and development of releasability, for example. ..

2. 2. Base material layer The base material layer is made of a heat-resistant resin. "Made of heat-resistant resin" means that the main material constituting the base material layer is heat-resistant resin, and "heat resistance" means that the toner image is recorded on a recording medium in electrophotographic image formation. It means that it is sufficiently stable at the temperature (for example, 150 to 220 ° C.) when the fixing belt is used for fixing and exhibits the desired physical properties.

The heat-resistant resin is appropriately selected from resins that do not substantially modify or deform at the above-mentioned operating temperature of the fixing belt, and may be one kind or more.
Examples of the heat-resistant resin include polyphenylene sulfide, polyallylate, polysulfone, polyethersulfone, polyetherimide, polyimide, polyamideimide and polyetheretherketone.
Of these, polyimide is preferable from the viewpoint of heat resistance.

The polyimide can be obtained by advancing the dehydration and cyclization (imidization) reaction of the precursor polyamic acid by heating at 200 ° C. or higher or by using a catalyst.
The polyamic acid may be produced by dissolving a tetracarboxylic acid dianhydride and a diamine compound in a solvent and performing a polycondensation reaction by mixing and heating, or a commercially available product may be used.
Examples of the diamine compound and the tetracarboxylic dianhydride include the compounds described in paragraphs 0123 to 0130 of JP2013-25120A.

The content of the heat-resistant resin in the base material layer may be an amount sufficient to form the base material layer, for example, preferably 50% by mass or more, and is in the range of 60 to 75% by mass. It is more preferable that the amount is in the range of 76 to 90% by mass.

The base material layer may further contain components other than the heat-resistant resin as long as the effects of the present embodiment can be obtained.
For example, the base material layer may further contain a filler.
The filler is a component that contributes to, for example, improving at least one of the hardness, heat transferability, and conductivity of the base material layer.
The filler may be one or more, and examples of the material include carbon black, ketjen black, nanocarbon and graphite.

If the content of the filler in the base material layer is too large, the toughness of the base material layer may be low and the fixability and separability of the fixing belt may be low, and if it is too low, for example, appropriate conductivity. The desired effect of the filler, such as the addition of, may be insufficient.
From such a viewpoint, the content of the filler in the base material layer is preferably 3% by mass or more, more preferably 4% by mass or more, and further preferably 5% by mass or more.
From the above viewpoint, the content of the filler in the base material layer is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 10% by mass or less. ..

3. 3. Intermediate layer The intermediate layer is a layer having elasticity that contributes to improving the contactability between the surface of the fixing belt in the fixing nip portion and the recording medium carrying the unfixed toner image, and is made of an elastic material.
"Made of elastic material" means that the main material constituting the intermediate layer is an elastic material, and "elasticity" means fixing of a toner image to a recording medium in electrophotographic image formation. It means that the fixing belt is deformed so as to be sufficiently in contact with the surface of the recording medium having the unfixed toner image.

The elastic material may be one kind or more, and is, for example, a material having a loss tangent tan δ (ratio of loss elastic modulus to storage elastic modulus) at 20 Hz of 0.1 or less.
Examples of such elastic materials include elastic resin materials, examples of which include silicone rubber, thermoplastic elastomers and rubber materials.
Above all, the elastic material is preferably silicone rubber from the viewpoint of heat resistance in addition to the desired elasticity.

The silicone rubber may be one kind or more.
Examples of the silicone rubber include polyorganosiloxane or a heat-cured product thereof, and an addition reaction type silicone rubber described in JP-A-2009-122317.
Examples of the polyorganosiloxane include dimethylpolysiloxane described in JP-A-2008-255283, in which both ends are sealed with a trimethylsiloxane group and the side chain has a vinyl group.

The thickness of the intermediate layer is preferably in the range of 5 to 300 μm, more preferably in the range of 50 to 250 μm, and more preferably in the range of 100 to 200 μm, for example, from the viewpoint of sufficiently exhibiting heat transferability and elasticity. It is more preferable to be inside.

The intermediate layer may further contain components other than the elastic resin material as long as the effects of the present embodiment can be obtained.
For example, the elastic material may further contain a heat-conducting filler for enhancing the heat-conducting property of the intermediate layer.
Examples of the material of the filler include silica, metallic silica, alumina, zinc, aluminum nitride, boron nitride, silicon nitride, silicon carbide, carbon and graphite.
The form of the filler is not limited, and is, for example, a spherical powder, an amorphous powder, a flat powder or a fiber.

The content of the elastic resin material in the elastic material is preferably in the range of, for example, 60 to 100% by volume, and is in the range of 75 to 100% by volume, from the viewpoint of achieving both heat transferability and elasticity. Is more preferable, and more preferably in the range of 80 to 100% by volume.

[Fixing device]
The fixing device according to the present embodiment is relative to one of the above-mentioned endless fixing belt, two or more rollers that pivotally support the fixing belt, and the above-mentioned roller via the above-mentioned fixing belt. It has a pressure roller, which is arranged to be urged to.
The fixing device can be configured in the same manner as a known so-called biaxial belt type fixing device except that it has the above-mentioned fixing belt.

The number of rollers that pivotally support the fixing belt is two or more, and includes a heating roller for heating the fixing belt.
The heating roller has, for example, a heat-conducting sleeve made of aluminum or the like, and a heating source such as a halogen heater arranged inside the sleeve.
The outer peripheral surface of the sleeve may be covered with a layer made of a fluororesin such as polytetrafluoroethylene (PTFE).

The number of rollers other than the heating rollers that pivotally support the fixing belt may be one or more, and can be appropriately configured according to other desired functions.

The tension of the fixing belt pivotally supported by the two or more rollers is preferably 46 N or less, and more preferably 43 N or less, from the viewpoint of being applied to higher-speed image formation.
The tension is determined by, for example, the elastic force (urging force) of an elastic member such as a spring that urges the roller in a direction of increasing the distance between the axes of the roller, the distance between the axes of the roller that supports the fixing belt, and the like. It is possible to adjust.

The pressure roller constitutes a contact portion (fixing nip portion) with the fixing belt at the time of fixing.
Examples of the pressure roller include a roller having elasticity on the outer peripheral surface and a roller whose rotation axis can approach and separate from the fixing belt.

Among the above rollers, the roller diameter of the roller urged by the pressure roller is preferably 45 mm or more, and more preferably 60 mm or more, from the viewpoint of applying to higher speed image formation.
The upper limit of the roller diameter of the roller can be appropriately determined, for example, depending on the allowable size of the fixing device.

Further, in the fixing device, the separation angle of the recording medium used for fixing is preferably in the range of 67 to 85 ° from the viewpoint of applying to higher speed image formation.
The separation angle is a straight line parallel to the straight line connecting the axes of the two rollers constituting the fixing nip portion (L1 in FIG. 5) at the downstream end of the fixing nip portion in the transport direction of the recording medium. It is an angle (θ in FIG. 5) formed by the tangent line (L2 in FIG. 5) of the fixing belt.

In general, a large separation angle tends to be advantageous for speeding up image formation and disadvantageous from the viewpoint of the separability of the recording medium with respect to the fixing belt.
However, the above-mentioned fixing belt satisfies the above-mentioned condition of tan δ.
Therefore, even at a relatively large separation angle, which has been considered to be disadvantageous for speeding up image formation, sufficient separation is exhibited.
From the viewpoint of achieving both high-speed image formation and the above-mentioned separability, the separation angle is more preferably in the range of 70 to 81 °, and further preferably in the range of 73 to 77 °.

The separation angle can be adjusted, for example, by the roller diameter of the roller constituting the fixing nip portion, the image forming speed, the urging force (nip pressure) of the pressure roller, and the like.

The fixing device may further have a configuration other than the above as long as the effect of the present embodiment can be obtained.
Examples of the other configuration include a first temperature sensor for detecting the temperature of the fixing belt heated by the heating roller, a shaft moving mechanism of the pressure roller, and a second temperature sensor arranged in the pressure roller. The heater, the second temperature sensor for detecting the temperature of the pressurizing roller, the airflow separation device for generating an airflow in the direction in which the recording medium is peeled off from the fixing belt in the fixing nip portion, and the fixing nip for the recording medium. A guide member for guiding the portion or from the fixing nip portion is included.
For these other configurations, known members and the like used in known fixing devices can be adopted.
Hereinafter, an example of the fixing device will be described in more detail.

As shown in FIG. 5, for example, the fixing device 70 includes a fixing belt 10, a heating roller 71, a first pressure roller 72, a second pressure roller 73, heaters 74, 75, a first temperature sensor 76, and a second temperature. It has a sensor 77, an air flow separating device 78, a guide plate 79, and a guide roller 80.

The fixing belt 10 is the fixing belt according to the present embodiment described above. The fixing belt 10 is pivotally supported and stretched by a heating roller 71 and a first pressure roller 72. The tension of the fixing belt 10 is, for example, 43N.

The heating roller 71 has a rotatable aluminum sleeve and a heater 74 arranged therein. The first pressure roller 72 has, for example, a rotatable core metal and an intermediate layer arranged on the outer peripheral surface thereof.

The second pressure roller 73 is arranged to face the first pressure roller 72 via the fixing belt 10.
The second pressure roller 73 has, for example, a rotatable aluminum sleeve and a heater 75 arranged in the sleeve.
The second pressure roller 72 is arranged so as to be able to approach and separate from the first pressure roller 72, and when the second pressure roller 72 approaches the first pressure roller 72, the first pressure roller 72 is applied via the fixing belt 10. The intermediate layer of the pressure roller 71 is pressed to form a fixing nip portion that is a contact portion with the fixing belt 10.

The first temperature sensor 76 is a device for detecting the temperature of the fixing belt 10 heated by the heating roller 71, and the second temperature sensor 77 is for detecting the temperature of the outer peripheral surface of the second pressurizing roller 73. It is a device of.

The air flow separation device 78 is a device for generating an air flow from the upstream side in the moving direction of the fixing belt 10 toward the fixing nip portion to promote the separation of the recording medium from the fixing belt 10.

The guide plate 79 is a member for guiding a recording medium having an unfixed toner image to the fixing nip portion, and the guide roller 80 is an image forming apparatus for guiding the recording medium on which the toner image is fixed from the fixing nip portion. It is a member for guiding to the outside.

In the fixing device 70, the roller diameter of the first pressure roller 72 is, for example, 60 mm, the rotational movement speed of the fixing belt 10 is 315 m / sec, and the separation angle θ is 73 °.
The rotational movement speed of the fixing belt 10 is 60 sheets / minute when converted into an image forming speed (“fixing speed” or “printing speed”) on an A4 plate recording medium.

In FIG. 5, the separation angle θ is a fixing nip portion in the transport direction of the recording medium with respect to a straight line L1 parallel to a straight line connecting the rotation axis of the first pressure roller 72 and the rotation axis of the second pressure roller 73. Of the angles formed by the tangents of the fixing belt 10 at the downstream end of the above, it is the angle on the second pressure roller 73 side.
The separation angle can be adjusted by the roller diameter of the second pressure roller 73 or the like.

For example, assuming that the separation angle when the roller diameter of the second pressure roller 73 is 50 mm is θ ₅₀ (for example, 79 °), when the roller diameter of the second pressure roller 73 is 40 mm, the separation angle at that time is set. The separation angle θ ₄₀ is (θ ₅₀ -4) °.
Further, for example, when the roller diameter of the second pressure roller 73 is 60 mm, the separation angle θ ₆₀ at that time is (θ ₅₀ + 4) °.

The fixing belt 10 is rotationally driven at the above speed, and is heated to a desired temperature (for example, 190 ° C.) by the heater 74, for example, by feedback control by the first temperature sensor 76.
The second pressurizing roller 73 is heated to a desired temperature (for example, 180 ° C.) by the heater 75, for example, by feedback control by the second temperature sensor 77.
Then, the second pressure roller 73 urges the outer peripheral surface of the first pressure roller 72 via the fixing belt 10 in accordance with the arrival of the recording medium to form the fixing nip portion.

On the other hand, the recording medium carrying the unfixed toner image is guided to the nip portion while being guided by the guide plate 79. Since the fixing belt 10 satisfies the above-mentioned condition of tan δ, it sufficiently adheres to the recording medium. Therefore, the unfixed toner image is quickly fixed to the recording medium by the sufficiently heated fixing belt 10.

At the downstream end of the fixing nip portion, a force that adheres to the fixing belt 10 and a force that tends to move in the tangential direction of the fixing belt 10 are applied to the recording medium on which the toner image is fixed.
As described above, the fixing belt 10 satisfying the above-mentioned tan δ condition is considered to exhibit an appropriate repulsive force against the recording medium at the downstream end of the fixing nip portion, and as a result, the recording medium is the fixing belt. It moves away from 10 in the tangential direction of the fixing belt 10.

Further, the recording medium receives the airflow from the airflow separating device 78 at the downstream end of the fixing nip portion. Therefore, the separation of the recording medium from the fixing belt 10 is promoted.

The recording medium separated from the fixing belt 10 is guided to the outside of the image forming apparatus by the guide roller 80.

The fixing nip portion may be formed by denting the peripheral surface of the first pressure roller 72 and the fixing belt 10 as described above, or the peripheral surface of the second pressure roller 73 may be dented. May be formed by.

As described above, the fixing device is suitably adopted as a fixing device of an electrophotographic image forming device, and particularly, when adopted in a high-speed image forming device, a remarkable effect is exhibited.

[Electrophotograph image forming apparatus]
The electrophotographic image forming apparatus of the present invention (hereinafter, also simply referred to as “image forming apparatus”) is an electrophotographic image forming apparatus using the fixing belt of the present invention, and is the endless fixing belt and the above. Two or more rollers that pivotally support the fixing belt, a fixing member including a heating device for heating the fixing belt, and one of the rollers being relatively urged via the fixing belt. It has a pressure roller arranged so as to be such, and the roller diameter of the roller urged by the pressure roller among the rollers is 50 mm or more.

It is preferable that the fixing belt is pivotally supported by two or more rollers and the tension is adjusted to be 45 N or less. Further, it is preferable that the unfixed toner image formed on the recording medium by the electrophotographic method is fixed on the recording medium by heating and pressurizing.

The image forming apparatus according to the present embodiment has the above-mentioned fixing device for fixing an unfixed toner image formed on a recording medium by an electrophotographic method to the recording medium by heating and pressurizing.
The image forming apparatus may be configured in the same manner as a known image forming apparatus except that the fixing belt is adopted in the fixing device. Hereinafter, an example of the image forming apparatus according to the present embodiment will be described with reference to FIG.

As shown in FIG. 6, the image forming apparatus 50 includes an image forming unit, an intermediate transfer unit, a fixing device 70, an image reading unit, and a recording medium conveying unit.

The image forming unit includes four image forming units corresponding to each color of, for example, yellow, magenta, cyan and black.
As shown in FIG. 6, the image forming unit is an exposure device that forms an electrostatic latent image by irradiating a photoconductor drum 51, a charging device 52 for charging the photoconductor drum 51, and a charged photoconductor drum 51 with light. 53, a developing device 54 that supplies toner to a photoconductor drum 51 on which an electrostatic latent image is formed to form a toner image corresponding to the electrostatic latent image, and a cleaning device 55 that removes residual toner from the photoconductor drum 51. Has.

The photoconductor drum 51 is, for example, a negatively charged organic photoconductor having photoconductivity.
The charging device 52 is, for example, a corona charging device.
The charging device 52 may be a contact charging device in which a contact charging member such as a charging roller, a charging brush, or a charging blade is brought into contact with the photoconductor drum 51 to be charged.
The exposure apparatus 53 is composed of, for example, a semiconductor laser.
The developing device 54 is, for example, a known developing device in an electrophotographic image forming device.
The "toner image" means a state in which toner is collected in an image shape.

The intermediate transfer unit includes a primary transfer unit and a secondary transfer unit.
The primary transfer unit includes an intermediate transfer belt 61, a primary transfer roller 62, a backup roller 63, a plurality of support rollers 64, and a cleaning device 65.
The intermediate transfer belt 61 is an endless belt.
The intermediate transfer belt 61 is stretched in a loop by the backup roller 63 and the support roller 64.
By rotationally driving at least one of the backup roller 63 and the support roller 64, the intermediate transfer belt 61 travels on the endless track at a constant speed in one direction.

The secondary transfer unit has a secondary transfer belt 66, a secondary transfer roller 67, and a plurality of support rollers 68.
The secondary transfer belt 66 is also an endless belt.
The secondary transfer belt 66 is stretched in a loop by the secondary transfer roller 67 and the support roller 68.

The fixing device 70 is, for example, the fixing device 70 shown in FIG.
Paper S corresponds to a recording medium.

The image reading unit includes a paper feeding device 81, a scanner 82, a CCD sensor 83, and an image processing unit 84.
The recording medium transport unit has three paper tray units 91 and a plurality of resist roller pairs 92.
Paper S (standard paper, special paper) identified based on the basis weight, size, and the like is stored in the paper feed tray unit 91 for each preset type.
The resist roller pair 92 is arranged so as to form a desired transport path.

[Image formation method]
The image forming method according to the present embodiment includes a step of fixing an unfixed toner image formed on a recording medium by an electrophotographic method to a recording medium by heating and pressurizing using the above-mentioned fixing device.
The image forming method can be performed by the image forming apparatus 50.
As an example of the image forming method, the formation of an image by the image forming apparatus 50 will be described below.

The scanner 82 optically scans and reads the document D on the contact glass sent from the paper feed device 81.
The reflected light from the document D is read by the CCD sensor 83 and becomes input image data.
The input image data is subjected to predetermined image processing in the image processing unit 84 and sent to the exposure apparatus 53.

On the other hand, the photoconductor drum 51 rotates at a constant peripheral speed corresponding to a printing speed of 60 sheets / minute or more on an A4 size recording medium.

The charging device 52 uniformly charges the surface of the photoconductor drum 51 to a negative electrode property.
The exposure apparatus 53 irradiates the photoconductor drum 51 with a laser beam corresponding to the input image data of each color component.
In this way, an electrostatic latent image is formed on the surface of the photoconductor drum 51.
The developing device 54 visualizes the electrostatic latent image by adhering toner to the surface of the photoconductor drum 51.
In this way, a toner image corresponding to the electrostatic latent image is formed on the surface of the photoconductor drum 51.
The toner image on the surface of the photoconductor drum 51 is transferred to the intermediate transfer belt 61.
The transfer residual toner of the photoconductor drum 51 is removed by the cleaning device 55.
Toner images of each color formed by each photoconductor drum 51 are sequentially transferred to the intermediate transfer belt 61 so as to be overlapped with each other.

On the other hand, the secondary transfer roller 67 presses the secondary transfer belt 66 toward the backup roller 63 and presses it against the intermediate transfer belt 61.
As a result, a secondary transfer nip portion is formed.
On the other hand, the paper S is conveyed from the paper feed tray unit 91 to the secondary transfer nip portion via the resist roller pair 92.
The resist roller pair 92 corrects the inclination of the paper S and adjusts the transfer timing.

When the paper S is conveyed to the secondary transfer nip, a transfer voltage is applied to the secondary transfer roller 67, and the toner image on the intermediate transfer belt 61 is transferred to the paper S.
The paper S on which the toner image is transferred is conveyed to the fixing device 70 by the secondary transfer belt 66.
The transfer residual toner on the intermediate transfer belt 61 is removed by the cleaning device 65.

In the fixing device 70, the fixing belt 10 rotates at a constant speed corresponding to a printing speed of 60 sheets / minute or more on an A4 size recording medium, and when the paper S is conveyed, the second pressure roller 74 is described above. Form the fixing belt 10 and the fixing nip portion.
The paper S is heated and pressurized at the fixing nip portion, and is guided to the outside of the image forming apparatus 50 by the repulsive force of the fixing belt 10 as described above, and is discharged.
In this way, the toner image on the paper S is formed, and the paper S is discharged to the outside of the machine.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Although the display of "parts" or "%" is used in the examples, it represents "parts by mass" or "% by mass" unless otherwise specified.

[Manufacturing of fixing belt 1]
(Formation of base material layer)
A varnish containing polyamic acid and 8% by mass of carbon black was rotationally applied to the outside of the cylindrical mold, then dried at 300-450 ° C. and imidized to have an inner diameter of 99 mm and a length of 360 mm. A cylindrical polyimide tubular material (polyimide base material layer) having a thickness of 70 μm was formed.
The polyamic acid is a polymer obtained by dehydration condensation of 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride and p-phenylenediamine.

(Formation of the outermost layer)
Next, a stainless steel cylindrical core metal having an outer diameter of 99 mm is brought into close contact with the inside of the base material layer, and a PFA tube having a thickness of 30 μm is held on the inner peripheral surface outside the base material layer. It was covered with a mold to form the outermost layer.

(Formation of intermediate layer)
In this way, the core metal and the cylindrical mold were held coaxially, and a cavity was formed between them.
Next, a silicone rubber material was injected into the cavity and cured by heating to form an intermediate layer made of silicone rubber having a thickness of 200 μm on the base material layer.

The rubber hardness (type A) of the silicone rubber is 30 °, the tensile strength is 1.5 MPa, the thermal conductivity is 0.7 W / (m · K), and the elongation is 250%.

The rubber hardness of the silicone rubber is measured by a durometer A according to JIS K6301 using a rubber sheet for measurement having a thickness of 10.0 mm. The rubber sheet is manufactured under the same conditions as those for manufacturing the intermediate layer.

The tensile strength of the silicone rubber is measured by a Tensilon universal tensile tester (manufactured by A & D Co., Ltd.) using the rubber sheet in the same manner as that of the base material layer.
The elongation of the silicone rubber is measured by a Tensilon universal tensile tester (manufactured by A & D Co., Ltd.) using the rubber sheet.
The thermal conductivity of the silicone rubber is measured by a QTM rapid thermal conductivity meter (manufactured by Kyoto Electronics Manufacturing Co., Ltd.) using the rubber sheet.

(Surface shape formation of the outermost layer 1; Example)
Fix the fixing belt in a direct pressure type manual blasting device (5-501 specification; Fuji Seisakusho). Fly zirconia beads (Φ5-100μm) toward the outermost layer to make unevenness, and attach the fixing belt to the image forming device in FIG. The fixing belt 1 was obtained by mounting, increasing the fixing pressure by 1.2 times, flowing 100 sheets of A4 blank paper, and forming a surface shape.

Each value related to the fixing belt 1 is measured, and the ratio of the space volume of the protruding valley portion to the space volume of the core portion (Vvv / Vvc), the inner diameter of the recess, the ratio of the height of the protruding valley portion to the thickness of the outermost layer, and the maximum. When the thickness of the surface layer was calculated, the result of Table I was obtained.
The surface texture of the fixing belt was measured according to the above method. The following fixing belts were also subjected to the same method.

[Manufacturing of fixing belts 2 to 12]
The resin type of the outermost layer of the fixing belt, the thickness of the outermost layer, the inner diameter of the recess, the ratio of the height of the protruding valley to the thickness of the outermost layer, and the ratio of the space volume of the protruding valley to the space volume of the core ( The fixing belts 2 to 12 were manufactured in the same manner as the fixing belt 1 except that Vvv / Vvc) was changed as shown in Table I.

[Manufacturing of fixing belt 13]
(Formation of base material layer)
A varnish containing polyamic acid and 8% by mass of carbon black was rotationally applied to the outside of the cylindrical mold, then dried at 300-450 ° C. and imidized to have an inner diameter of 99 mm and a length of 360 mm. A cylindrical polyimide tubular material (polyimide base material layer) having a thickness of 70 μm was formed.
The polyamic acid is a polymer obtained by dehydration condensation of 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride and p-phenylenediamine.

(Formation of the outermost layer)
Next, a stainless steel cylindrical core metal having an outer diameter of 99 mm is brought into close contact with the inside of the base material layer, and a PFA tube having a thickness of 30 μm is held on the inner peripheral surface outside the base material layer. It was covered with a mold to form the outermost layer.

(Formation of intermediate layer)
In this way, the core metal and the cylindrical mold were held coaxially, and a cavity was formed between them.
Next, a silicone rubber material was injected into the cavity and cured by heating to form an intermediate layer made of silicone rubber having a thickness of 200 μm on the base material layer.

The rubber hardness (type A) of the silicone rubber is 30 °, the tensile strength is 1.5 MPa, the thermal conductivity is 0.7 W / (m · K), and the elongation is 250%.

The rubber hardness of the silicone rubber is measured by a durometer A according to JIS K6301 using a rubber sheet for measurement having a thickness of 10.0 mm. The rubber sheet is manufactured under the same conditions as those for manufacturing the intermediate layer.

The tensile strength of the silicone rubber is measured by a Tensilon universal tensile tester (manufactured by A & D Co., Ltd.) using the rubber sheet in the same manner as that of the base material layer.
The elongation of the silicone rubber is measured by a Tensilon universal tensile tester (manufactured by A & D Co., Ltd.) using the rubber sheet.
The thermal conductivity of the silicone rubber is measured by a QTM rapid thermal conductivity meter (manufactured by Kyoto Electronics Manufacturing Co., Ltd.) using the rubber sheet.

(Formation of surface shape of outermost layer 2; Comparative Example 1)
The obtained laminated belt was fixed in a direct pressure type manual blasting device (FD-5-501 type, manufactured by Fuji Seisakusho Co., Ltd.) with the PFA layer on the outside, and almost spherical glass beads (media) as a projection material (media). (Representative particle size: 5 μm) was blown toward the PFA layer (50 μm) to form a relatively large first uneven shape on the surface of the PFA layer.
Next, the medium was replaced with substantially spherical zirconia beads (representative particle size: 0.5 μm), and the surface of the PFA layer was further blasted so that the entire surface of the PFA layer having the first uneven shape was relatively covered. A small second uneven shape was formed.

In this way, on an endless fixing belt having a substrate layer made of polyimide, an intermediate layer made of silicone rubber, and an outermost layer made of PFA in this order and having a surface shape including first and second uneven shapes. The fixing belt 13 was obtained by further forming a new surface shape.

[Manufacturing of fixing belt 14]
The fixing belt 14 was manufactured by repeating the same blasting process as the belt 13 twice and changing the thickness of the outermost layer, the inner diameter of the recess, and the ratio of the protruding valley portion to the thickness of the outermost layer as shown in Table I. ..

[Examples 1 to 12]
The fixing belts 1 to 12 created in the above-mentioned image forming apparatus are incorporated, and as shown in FIG. 7, a vertical strip-shaped solid image having a coverage rate of 10% for each YMCK of A4 is continuously printed 40,000 sheets in A4 horizontal feed, and then the following. The separability and fixability of the fixing belts 1 to 12 were evaluated according to the evaluation criteria of.
The evaluation results are shown in Table I.

[Comparative Examples 1 and 2]
The fixing belts 13 and 14 created in the above-mentioned image forming apparatus are incorporated, and as shown in FIG. 7, a vertical strip-shaped solid image having a coverage rate of 10% for each YMCK of A4 is continuously printed 40,000 sheets in A4 horizontal feed, and then described below. The separability and fixability of the fixing belts 13 and 14 were evaluated by the evaluation method and the evaluation standard.
The evaluation results are shown in Table I.

(Evaluation method of fixability)
At a printing speed of 60 sheets / minute, a solid black strip-shaped image with a width of 5 cm and a coverage of 10% each in the direction perpendicular to the transport direction is formed on A4 size plain paper, and the obtained image is visually observed. Then, the fixability was judged according to the following evaluation criteria.

(Evaluation criteria)
⊚: No defects due to poor fixing are seen in the solid image ○: Defects due to poor fixing may be slightly seen in the solid image △: Small defects are seen but there is no problem

(Evaluation method of toner releasability)
The surface temperature of each fixing belt was set to 180 ° C., and the A4 size copy paper having the above solid image was conveyed in the vertical direction at a speed of 60 sheets / minute using a “color copy” basis weight 90 g / m ² manufactured by Mondi. ..
The separability between each fixing belt and the copy paper on the image side at this time was determined as the releasability of the toner by the following evaluation criteria.
The portion of the blank sheet from the tip of the solid image to the beginning of the image is called a margin, and if there is a margin, the separability is improved.

(Evaluation criteria)
◎: Separation without margin ○: Paper does not curl △: Paper curls a little, but there is no problem ×: Does not separate

As is clear from Table I, it can be seen that the electrophotographic image forming apparatus provided with the fixing member of the present invention exhibits sufficient performance in both fixing property and toner releasability.

10 Fixing belt 12 Base material 16 Outermost layer 50 Image forming device 51 Photoconductor drum 52 Charging device 53 Exposure device 54 Developing device 55, 65 Cleaning device 61 Intermediate transfer belt 62 Primary transfer roller 63 Backup roller 64, 68 Support roller 66 Secondary Transfer belt 67 Secondary transfer roller 70 Fixing device 71 Heating roller 72 First pressurizing roller 73 Second pressurizing roller 74, 75 Heater 76 First temperature sensor 77 Second temperature sensor 78 Air flow separation device 79 Guide plate 80 Guide roller 81 Feeding device 82 Scanner 83 CCD sensor 84 Image processing unit 91 Feeding tray unit 92 Resist roller vs. D Manuscript S Paper L1 Straight line parallel to the axis connecting the axes of the two rollers that make up the fixing nip part L2 Recording at the fixing nip part The tangent line θ separation angle of the fixing belt at the downstream end in the transport direction of the medium.

Claims (9)

A fixing belt having an intermediate layer and an outermost layer on the base material layer in this order.
The base material layer is made of heat-resistant resin and is made of heat-resistant resin.
The intermediate layer is made of a heat-resistant elastic material and
In the measurement of the surface texture of the outermost layer,
The load area ratio p that separates the core portion and the protruding peak portion of the contour curved surface defined in accordance with JIS B 061-2 is 50%, and the load area ratio q that separates the core portion and the protruding valley portion is 90%. When
A fixing belt having a concave shape in which the ratio (Vvv / Vvc) of the space volume Vvv of the protruding valley portion to the space volume Vvc of the core portion is in the range of 0.5 to 4.0. The fixing belt according to claim 1, wherein the ratio (Vvv / Vvc) is in the range of 0.8 to 2.0. The inner diameter of the concave shape is within the range of 5 to 30 μm, and the inner diameter is within the range of 5 to 30 μm.
The fixing belt according to claim 1 or 2, wherein the height of the protruding valley portion of the concave shape is within the range of 10 to 80% of the thickness of the outermost surface layer. The fixing belt according to any one of claims 1 to 3, wherein the thickness of the outermost layer is in the range of 40 to 150 μm. The base material layer is made of polyimide.
The intermediate layer is made of silicone rubber and
The fixing belt according to any one of claims 1 to 4, wherein the outermost surface layer contains a fluororesin. The fixing belt according to claim 5, wherein the fluororesin is a perfluoroalkoxyalkano resin. An electrophotographic image forming apparatus using the fixing belt according to any one of claims 1 to 6.
The endless fixing belt and
Two or more rollers that pivotally support the fixing belt, and
A fixing member including a heating device for heating the fixing belt, and
It has a pressure roller arranged to be urged relative to one of the rollers via the fixing belt, and has.
An electrophotographic image forming apparatus, wherein the roller diameter of the roller urged by the pressure roller among the rollers is 50 mm or more. The fixing belt is axially supported by two or more rollers, and
The electrophotographic image forming apparatus according to claim 7, wherein the tension is adjusted to be 45 N or less. The electrophotographic image forming apparatus according to claim 7 or 8, wherein an unfixed toner image formed on a recording medium by an electrophotographic method is fixed on the recording medium by heating and pressurizing.

Images