JP2003114585A - Durable fixing belt and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing belt that has sufficient wear resistance even in high speed paper passage at 20 ppm or higher and has as a release layer a fluorocarbon resin that is excellent in releasability which is free of offset even in the use of color toner and to provide a method for the production of the fixing belt. SOLUTION: In the fixing belt having at least a heat-resistant endless belt and a releasing layer formed on the surface of the belt, the releasing layer is a fluorocarbon resin layer with a fusion heat quantity of 28 mJ/mg or less. The method for producing the fixing belt includes the step of applying a fluorocarbon resin to the surface of the heat-resistant belt, heating it at temperatures higher than the fusing point of the fluorocarbon resin, and then cooling it to the fusing point at a cooling speed of 10 deg.C/min or higher, thereby forming the releasing layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endless belt used for fixing an image forming apparatus such as a copying machine, a facsimile and a printer, and a manufacturing method thereof.

[0002]

2. Description of the Related Art A heat roller fixing method is known as an image fixing method for a transfer sheet in an image processing apparatus. In this heat roller fixing method, a heat roller and a press roller are arranged so as to face each other, and the transfer paper is sent between both rollers, and the toner temporarily attached to the transfer paper is melted by the heat generated by the heater built in the heat roller. The image is formed by toner on the transfer paper by fixing and fixing by pressing with a press roller. In the case of such a heat roller fixing method, since the contact area is small, it is necessary to increase the pressure load in order to melt and fix the toner on the transfer paper. Further, in recent years, when the sheet passing speed exceeds 10 ppm, the pressure load between the rollers has to be increased, and therefore the toner release layer on the roller surface is greatly worn, and there is a problem that offset occurs in a short life. It was

To solve the above problems, a belt fixing method has been proposed. In this method, a roller and a belt are arranged so as to face each other, and the transfer paper is fed between them to fix the toner. In this case, pressurization, heating,
Although the basic functions of driving and releasing are required as in the heat roller fixing method, these functions may be provided on the roller side or the belt side. By using a belt having good followability on one side, the contact area can be increased and the pressure load can be reduced. However, even in this belt fixing method, when the sheet passing speed exceeds 20 ppm, the pressure load is further increased, so that the abrasion resistance of the release layer is important.

By the way, as an abrasion-resistant release layer of a fixing roller that has been conventionally proposed, in JP-A-4-6849, a tetrafluoroethylene-ethylene copolymer having a crystallinity of 45% or less (ETFE, Melting point 270 ° C, decomposition 390 ° C) and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA, melting point 310)
Inorganic filler 10 to 100 parts of fluororesin)
25 parts and 0 to 20 parts of an ethylenically unsaturated crosslinking aid enhance wear resistance and flexibility. In addition, JP-A-10
In Japanese Patent Laid-Open No. 142990/1992, in the structure of roller / rubber / fluororesin, the fluororesin is tetrafluoroethylene-
Perfluoroalkyl vinyl ether copolymer (PF
A, average particle size 1 to 15 μm, molecular weight of 300,000 or more) 20
~ 97 wt% and polytetrafluoroethylene (PTF
E, average particle diameter 1 μm or less, molecular weight 1,000,000 or more) 3 to
A fixing roller having a layer of 80% by weight is known. In JP-A-10-186923, PFA (average particle diameter of 5 μm or more, molecular weight of 650,000 or more) or PFA (average particle diameter of 5 μm or more, molecular weight of 650,000 or more) is known. ) A fixing roller or belt having a fluorine resin layer of 20 to 80% by weight and PFA (average particle size of 1 μm or less) of 80 to 20% by weight is known.

However, when these components, the molecular weight and the average particle size are combined, it is not only difficult to maintain a uniform composition in the release layer, but also when a filler is added to the fluororesin or a combination of fluororesins having different compositions is used. ,
A sufficient wear resistant film could not be obtained. On the other hand, in the case of high molecular weight PFA, the abrasion resistance of the resin itself is improved, but it is not well compatible with the heat-resistant resin that is the base material, and even if an adhesive treatment such as a primer is applied, sufficient binding force is obtained. There was a problem that it was difficult to obtain. Therefore, under the condition of high stress load associated with high-speed paper passing, the surface hardness is rather high, so that the fluororesin peels off easily, which is remarkable when the paper passing speed exceeds 10 ppm. In addition to the fact that sufficient durability is not obtained, there is a problem that surface roughness and pinholes occur due to a decrease in non-adhesiveness due to the addition of a filler and an increase in melt viscosity due to the high molecular weight of PFA.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and has sufficient abrasion resistance even for high-speed paper passing of 20 ppm or more, and for color toners. An object of the present invention is to provide a fixing belt having a release layer that is a fluororesin layer having excellent releasability that does not cause offset even when it is used, and a method for manufacturing the fixing belt.

[0007]

[Means for Solving the Problems] The inventors of the present invention have made earnest studies on the step of forming a release layer in order to achieve the above-mentioned object. As a result, the heating temperature of the fluororesin and the cooling rate after heating are controlled. Finding that the above objectives can be achieved,
The present invention has been completed.

That is, the fixing belt of the present invention is a fixing belt having at least a heat-resistant endless belt and a release layer provided on the surface, wherein the release layer is a fluororesin layer having a heat of fusion of 28 mJ / mg or less. It is characterized by The measuring method of each physical property value defined in this specification is as described in the examples.

The heat of fusion is preferably 27 mJ / mg or less.

When the heat resistant endless belt is a polyimide belt, the tensile elastic modulus of the polyimide belt is 60.
It is preferably 00 N / mm ² or more.

The method of manufacturing the fixing belt of the present invention is
Fluorine resin is applied to the surface of the heat-resistant endless belt and heated at a temperature exceeding the melting point of the fluorine resin, and then 10 ° C.
The method is characterized by including a step of forming a release layer for cooling to the melting point at a cooling rate of not less than / min.

The release layer preferably contains 1.5 to 2.3% by weight of carbon black based on the solid content of the fluororesin.

When the heat resistant endless belt is a polyimide belt, in the forming step, after heating at a temperature exceeding the glass transition temperature of the polyimide, 10 ° C./min.
It is preferable to cool to the glass transition temperature at the above cooling rate.

[Operation and Effect] According to the fixing belt of the present invention, the heat of fusion of the fluororesin constituting the release layer is 28 mJ.
/ Mg or less, preferably 27 mJ / mg or less, the film is hard to crystallize and becomes a comparatively hard film, and the abrasion resistance and the releasability during high-speed paper passing are improved, and the offset hardly occurs.

When a polyimide belt is used as the heat-resistant endless belt of the fixing belt of the present invention, the polyimide belt has a tensile elastic modulus of 6000 N / mm ² or more, further improving the durability in high-speed paper passing.

Further, according to the method of manufacturing the fixing belt of the present invention, the resin is melted by heating at a temperature exceeding the melting point of the applied fluororesin and then rapidly cooling to the melting point at a cooling rate of 10 ° C./min or more. It is possible to form a release layer having a heat amount equal to or less than the above value, abrasion resistance at high speed paper passing,
The fixing belt can have improved releasability.

The release layer has a ratio of 1.
When a fixing belt containing 5 to 2.3% by weight of carbon black is produced, a fixing belt having high heat resistance and desired conductivity can be provided.

When the heat-resistant endless belt is a polyimide belt, it is heated at a temperature exceeding the glass transition temperature of the polyimide in the forming step, and then 10 ° C./min.
By cooling to the glass transition temperature at the above cooling rate, the tensile elastic modulus of the polyimide belt is 6000 N /
Since it is more than mm ² , the durability at high speed paper passing is further improved,
It is possible to provide a fixing belt in which the adhesiveness between the polyimide layer and the fluororesin layer is enhanced and the abrasion resistance and the releasability of the fluororesin layer, which is the release layer, are improved.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

The fixing belt of the present invention has at least a heat-resistant endless belt and a release layer provided on the surface thereof. The binding force is improved between the heat-resistant endless belt and the release layer. You may provide the primer layer for this.

The thickness of each layer of the fixing belt can be set arbitrarily, but the thickness of the heat resistant endless belt is 5 to 200.
It is preferable to set in the range of μm. Below 5 μm,
Buckling is likely to occur, and if it exceeds 200 μm, the separation angle from the fed paper becomes small, and the releasability of the toner tends to deteriorate.

Between the heat-resistant endless belt and the release layer, a primer layer may be formed by subjecting it to an adhesive treatment such as a primer as described above. At this time, the thickness of the primer layer is preferably in the range of 0.5 to 10 μm. 0.5 μm
If it is less than 10 μm, the binding strength tends to be low, and if it exceeds 10 μm, it tends to be brittle.

The fluororesin layer constituting the release layer on the surface of the belt is set to 5 to 100 μm, preferably 10 to 50 μm. If it is less than 5 μm, the life until offset occurs when the paper is passed,
If it exceeds m, cracks are likely to occur in the fluororesin layer.

Heat resistance The heat resistance of the endless belt varies from the temperature used in the fixing section to the heat distortion temperature (ASTM: D64
8) A resin or metal that does not decompose at 340 to 430 ° C., which is a temperature for heating and melting the fluororesin at 200 ° C. (1.8 MPa) or more, and a material having excellent bending resistance is preferable. For example, heat-resistant resin such as polyimide, polyamide-imide, polyether ether ketone, polyphenylene sulfide, polybenzimidazole, aluminum,
Metals such as iron, nickel, and alloys thereof can be used.

Of these, a polyimide resin having excellent mechanical properties, heat resistance and flexibility is most suitable. The polyimide resin is, for example, tetracarboxylic dianhydride which is an acid component, and approximately equimolar amounts of a diamine which is an amine component are dissolved and reacted in a suitable solvent to prepare a polyamic acid solution, and the solvent is further dried at a higher temperature. It can be obtained by polymerizing (imide conversion).

When a polyimide resin is used as a material for the heat resistant endless belt, it is preferable to form the primer layer and / or the release layer at the stage of the polyimide precursor, and heat the release layer and perform imide conversion at the same time.

The heat-resistant resin and the metal may be laminated to form a multilayer, or the heat-resistant resin may contain an organic or inorganic filler to control thermal characteristics, electrical characteristics, and the like. However, the metal may be a pure metal having a single composition or an alloy having a plurality of compositions.

As the primer layer, various commercially available primers that enhance the adhesiveness between the heat resistant endless belt and the release layer can be used. For the heat resistant endless belt of polyimide resin, the polyimide-based primer is preferably used. It

The fixing belt of the present invention is characterized in that the releasing layer is a fluororesin layer having a heat of fusion of 28 mJ / mg or less. The heat of fusion is preferably 27 mJ / mg or less, more preferably 24 to 26 mJ / mg. If the amount of heat of fusion exceeds 28 mJ / mg, the fluororesin tends to crystallize to form a relatively soft layer, and the abrasion resistance during paper passing tends to decrease.

The release layer as described above is manufactured by the method of the present invention, that is, the surface of the heat-resistant endless belt is coated with a fluororesin and heated at a temperature exceeding the melting point of the fluororesin, and then 10 ° C./min or more. It can be preferably obtained by the step of forming the release layer which is cooled to the melting point at the cooling rate of.

Examples of usable fluororesins include, for example,
Polytetrafluoroethylene (PTFE) or a modified product thereof, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-ethylene copolymer (ETFE), tetrafluoroethylene-hexafluoropropylene copolymer ( F
EP), tetrafluoroethylene-vinylidene fluoride copolymer (TFE / VdF), tetrafluoroethylene-
Hexafluoropropylene-perfluoroalkyl vinyl ether copolymer (EPA), polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTFE), chlorotrifluoroethylene-vinylidene fluoride copolymer (CTFE) /
VdF), polyvinylidene fluoride (PVdF), polyvinyl fluoride (PVF) and the like. Above all, P
FA is preferably used.

The melt flow rate of the fluororesin is 1 to
30 g / 10 min is preferable, more preferably 1.5
~ 5g / 10min. If it is less than 1 g / 10 min, it is difficult to melt even if it is heated at 340 ° C. or higher after coating, resulting in a brittle and rough film, and if it exceeds 30 g / 10 min, it is easily melted at the time of heating so that a smooth surface can be obtained. Abrasion resistance tends to be poor.

When PFA is used as the fluororesin, P
The average particle diameter of FA is preferably 0.1 μm or more and less than 5 μm. If the average particle size is less than 0.1 μm, the particles are likely to aggregate, and the particle size distribution becomes nonuniform. If the average particle size is 5 μm or more, the surface of the coating formed by applying and heating this tends to become rough.

The fluororesin layer in the present invention preferably contains carbon black. The content of carbon black is preferably 1.5 to 2.3% by weight based on the solid content of the fluororesin. If it is less than 1.5% by weight, the surface resistivity tends to be large, and if it exceeds 2.3% by weight, the surface roughness tends to be large.

As the carbon black, in order to maintain the smoothness of the surface of the fluororesin layer, a carbon black having a surface resistivity of 10 ⁸ Ω / □ or less is preferable even if it is added in a small amount. From this viewpoint, the average particle diameter is 100 to 500 nm.
Carbon black is preferable, and the dibutyl phthalate (DBP) oil absorption is 300 to 500 cc / 100 g.
Are preferred. Here, the DBP oil absorption is JIS
It is measured according to the A method of K 6221. Examples of such carbon black include Ketjen black, acetylene black, graphite and the like.

The fluororesin may be applied by applying the fluororesin particles or a dispersion thereof or a dispersion containing carbon black thereof by an electrostatic method, a spray method, a dipping method or the like. Note that a tube-shaped material formed in advance by the coating method or the like may be covered, and then heat-treated to shrink.

The heating temperature of the fluororesin depends on the melt flow rate of the fluororesin, but may be any temperature above the melting point, preferably 340 to 430 ° C. The heating method is a known method such as a dryer using a heater as a heat source. If the temperature is lower than 340 ° C, the fluororesin particles are insufficiently melted during coating, so that not only a smooth film having a high binding strength with the heat-resistant base belt cannot be obtained, but also pinholes easily occur. If it exceeds 430 ° C, the decomposition of the fluororesin tends to proceed. The heating time depends on the heating temperature and the average particle size of the fluororesin, but it is preferably 10 minutes or more.

With respect to cooling after heating and melting, the material is cooled to the melting point at a rate of 10 ° C./min or more, preferably 40 ° C./min or more. Examples of the cooling method include air cooling with a spot cooler and water cooling with immersion in a water tank.

When cooled at less than 10 ° C./min, the heat of fusion exceeds 28 mJ / mg, and crystallization is likely to occur, resulting in a relatively soft fluororesin layer. The use of such a belt tends to reduce the resistance to anomalous properties during paper passing.

The binding force of the release layer formed is 3 in terms of pencil hardness.
It is preferably H or more.

When a polyimide resin is used for the heat-resistant endless belt, the heating condition of the fluororesin may be not less than the glass transition temperature of polyimide, but is preferably 340 to 430 ° C. If the temperature is lower than 340 ° C., the solvent contained in the polyimide precursor is likely to remain and the shrinkage with time tends to occur. If it exceeds 430 ° C, the polyimide resin tends to deteriorate and tear strength tends to decrease. The heating time is usually about 5 to 60 minutes. Regarding cooling after heating and imidization, the glass transition temperature is 10 ° C.
/ Min or more, preferably 40 ° C./min or more. When cooled at less than 10 ° C./min, the polyimide has a tensile elastic modulus of 6000 N / mm ² or less, and durability tends to decrease.

The fixing belt made of the polyimide belt thus obtained has a polyimide tensile elastic modulus of 60.
00N / mm ² or more, preferably 6500 to 70
It is 00 N / mm ² .

The fixing belt of the present invention can be used in the fixing portion of an image forming apparatus such as a copying machine, a facsimile, a printer, etc., but any type of fixing portion adopting the belt fixing method can be used. For example, it can be used in a system in which a fixing belt is stretched between rolls, a system in which a tubular fixing belt is supported by an appropriate stay, or the like. The present invention is particularly useful for fixing by high-speed paper passing exceeding 20 ppm, but high durability can be expected even in the case of high-speed paper passing.
Further, due to the excellent releasability, it is possible to sufficiently deal with full-color image formation.

[0044]

EXAMPLES Examples and the like specifically showing the constitution and effects of the present invention will be described below. The physical properties in the examples and the like were evaluated as follows.

[Amount of heat of fusion] PFA on the surface of the belt was sampled with a trimming knife and then placed in an aluminum container.
The sealed one was used as a measurement sample for a differential scanning calorimeter (DSC).

DSC: EXSTAR 6000 (Seiko Instruments Inc.) Temperature rise: 10 ° C./min The heat of fusion was calculated from the DSC curve of the endothermic peak associated with crystal melting.

[Melt Flow Rate] ASTM (D33
07).

[Matsubara Abrasion Test] A load was 5 kg, a rotation speed was 500 mm / sec, and the mating material was plain paper.

[Tensile Strength] Samples were punched into a No. 3 dumbbell (JIS K 6301) shape in the longitudinal direction of the belt. Using Orientec UTM1000 Tensilon, pulling speed 100mm / min, chuck distance 30
It was measured under the condition of mm.

[Pencil hardness] Using a pencil hardness meter (Yasuda Seiki Seisakusho) based on JIS K5400, a load of 500
It was measured under the conditions of g and angle of 60 °.

Example 1 As acid components 3, 3 ', 4,
Dissolving 4'-biphenyltetracarboxylic dianhydride in N-methyl-2-pyrrolidone (NMP) in an approximately equimolar amount of p-phenylenediamine as an amine component (monomer concentration 20% by weight), and then at 20 ° C. for 6 hours Rotational viscosity 3 by reaction
A polyamic acid solution having 3000 poise (temperature: 20 ° C., measured by B-type viscometer) and logarithmic viscosity of 2.6 was prepared. Then
The viscosity of the polyamic acid solution was adjusted to 1500 poise by heating to 70 ° C.

This polyamic acid solution was treated with an inner diameter of 30.61 m.
After being applied to a m-shaped mold, a pig having an outer diameter of 29 mm was passed through, and hot air at 150 ° C. was applied for 10 minutes to make a solid state.
Further, this mold was heated from 150 ° C. at a rate of 1.5 ° C./min until it reached 220 ° C., then cooled at a rate of 2 ° C./min and returned to room temperature. The formed polyimide precursor belt is removed from the mold, inserted into an aluminum pipe having an outer diameter of 29.8 mm, and a polyimide primer (Mitsui DuPont, K001-02) is heated on the surface of the polyimide precursor belt while being heated to 100 ° C. It was spray coated on. Next, the average particle size is 0.3 μm, and the melt flow rate is 1.7 g / 10.
35% dispersion liquid (Mitsui DuPont, 510CL) in which PFA of min was dispersed in water was spray-coated,
By heating at 400 ° C. for 30 minutes, imidization of the polyimide precursor, melting of PFA, and binding of polyimide and PFA were simultaneously performed.

Thereafter, cooling was carried out at 40 ° C./min to 310 ° C., which is the melting point of PFA.

The fixing belt thus obtained has a tensile elastic modulus of 657.
It is composed of 0 N / mm ² 80 μm thick polyimide, 1 μm thick primer and 30 μm PFA.
A heat of fusion of 24.6 mJ / mg, pencil hardness of PFA 4
It became H (23 ° C). Further, in the Matsubara-type wear test, the amount of wear was 1.9 mg / h.

A support having a sliding sheet was installed inside the belt, and a heating roller made of silicon rubber on an aluminum roller was pressed in parallel with the belt,
The toner was fixed. No offset was observed when 100,000 sheets were passed at a speed of 20 ppm.

Example 2 A fixing belt was obtained in the same manner as in Example 1 except that PFA (Mitsui DuPont, 500CL) having a melt flow rate of 17 g / 10 min was used.

The obtained fixing belt has a tensile elastic modulus of 657.
It is composed of 0 N / mm ² 80 μm thick polyimide, 1 μm thick primer and 30 μm PFA.
A heat of fusion of 25.9 mJ / mg, pencil hardness of PFA 4
It became H (23 ° C). Furthermore, in the Matsubara-type wear test, the amount of wear was 3.1 mg / h.

When toner was fixed using the fixing belt thus obtained in the same manner as in Example 1, no offset was observed.

Example 3 A fixing belt was obtained in the same manner as in Example 1 except that the PFA cooling rate was 12 ° C./min.

The belt obtained has a tensile modulus of elasticity of 6250 N.
It is composed of 80 μm thick polyimide / mm ² and 1 μm thick primer and 30 μm PFA. The heat of fusion of PFA is 27.3 mJ / mg, and the pencil hardness of PFA is 4H.
(23 ° C). Furthermore, in the Matsubara wear test,
The amount of wear was 4.2 mg / h.

When the toner was fixed using the obtained fixing belt in the same manner as in Example 1, no offset was observed.

[Example 4] In Example 1, the primer was changed to a mixed system primer of PFA and polyimide (Mitsui DuPont, PR-902YL), and PFA was carbon black (Lion, W-311N) 1.7% by weight. A fixing belt was obtained in the same manner as in Example 1 except that the dispersion liquid in which was dispersed was used.

The belt obtained has a tensile elastic modulus of 6570 N.
It is composed of polyimide having a thickness of 80 μm / mm ² , a primer having a thickness of 1 μm, and PFA containing carbon black of 30 μm. The heat of fusion of PFA is 29.4 mJ / mg, P
The pencil hardness of FA was 3H (23 ° C). Furthermore, in the Matsubara wear test, the amount of wear was 6.4 mg / h.

When the toner was fixed using the obtained fixing belt in the same manner as in Example 1, no offset was observed.

Comparative Example 1 A fixing belt was obtained in the same manner as in Example 1 except that the cooling rate after heating and melting PFA was changed to 3 ° C./min.

The obtained fixing belt has a tensile elastic modulus of 556.
It is composed of 0 N / mm ² 80 μm thick polyimide, 1 μm thick primer and 30 μm PFA.
A heat of fusion of 28.7 mJ / mg, pencil hardness of PFA 2
It became H (23 ° C). Furthermore, in the Matsubara-type wear test, the amount of wear was 5.4 mg / h.

When the fixing belt thus obtained was used to fix the toner in the same manner as in Example 1, an offset was observed after 100,000 sheets or less.

[Comparative Example 2] A fixing belt was obtained in the same manner as in Example 2 except that the cooling rate after heating and melting the PFA was changed to 6 ° C / min.

The obtained fixing belt has a tensile elastic modulus of 580.
It is composed of 0 N / mm ² 80 μm thick polyimide, 1 μm thick primer and 30 μm PFA.
A heat of fusion of 28.3 mJ / mg, pencil hardness of PFA 4
It became H (23 ° C). Furthermore, in the Matsubara-type wear test, the amount of wear was 5 mg / h.

When the toner was fixed using the obtained fixing belt in the same manner as in Example 1, an offset was observed after 100,000 sheets or less.

[Comparative Example 3] A fixing belt was obtained in the same manner as in Example 4, except that the cooling rate after heating and melting the PFA was changed to 6 ° C / min.

The fixing belt thus obtained has a tensile elastic modulus of 580.
It is composed of polyimide of 0 N / mm ² and thickness of 80 μm, primer of 1 μm and PFA containing carbon black of 30 μm, and the heat of fusion of PFA is 34.3 mJ / m.
g, pencil hardness of PFA was 3H (23 ° C.). Further, in the Matsubara-type wear test, the amount of wear was 7.1 mg / h.

When the toner was fixed using the obtained fixing belt in the same manner as in Example 1, an offset was observed after 100,000 sheets.

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Claims (6)

[Claims] 1. A fixing belt having at least a heat-resistant endless belt and a release layer provided on the surface,
A fixing belt, wherein the release layer is a fluororesin layer having a heat of fusion of 28 mJ / mg or less. 2. The fixing belt according to claim 1, wherein the heat of fusion is 27 mJ / mg or less. 3. The heat-resistant endless belt is a polyimide belt, and the polyimide belt has a tensile elastic modulus of 60.
The fixing belt according to claim 1 or 2, having a density of 00 N / mm ² or more. 4. A step of forming a release layer in which a fluororesin is applied to the surface of a heat-resistant endless belt, heated at a temperature exceeding the melting point of the fluororesin, and then cooled to the melting point at a cooling rate of 10 ° C./min or more. A method for manufacturing a fixing belt, including: 5. The release layer contains carbon black in an amount of 1.5 to 2.3% by weight based on the solid content of fluororesin.
The manufacturing method according to claim 4. 6. The heat-resistant endless belt is a polyimide belt, and after the forming step is heated at a temperature exceeding the glass transition temperature of the polyimide, 10 ° C./min.
The manufacturing method according to claim 4, wherein the glass transition temperature is cooled at the above cooling rate.