JP2001331049A - Fixing belt - Google Patents

Abstract

(57) [Summary] [Problem] A release layer on a belt surface has a wear resistance of 20 ppm.
The present invention provides a fixing belt which has a sufficient releasability, which is sufficient for high-speed paper passing exceeding, and which does not easily cause offset even for anchored toner. SOLUTION: In a fixing belt having a heat-resistant endless belt layer and a release layer provided on the surface, the release layer is made of a fluororesin and a heat distortion temperature (ASTM: D64).
8, 1.82 MPa) is a binder resin having a temperature of 200 ° C. or higher and 327 ° C. or lower as an essential resin component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for fixing an image forming apparatus such as a copying machine, a facsimile, and a printer.
The present invention relates to a fixing belt having a release layer on the surface.

[0002]

2. Description of the Related Art A heat roller fixing method is known as a method of fixing an image on transfer paper in an image forming apparatus. This heat roller fixing method is a method in which a heat roller and a press roller are arranged to face each other, and the transfer paper is fed between the two rollers. The toner temporarily attached to the transfer paper by the heat generated by a heater built in the heat roller is used. The fixing is carried out by fusing and pressing by a press roller to strengthen the fixing, thereby forming an image with toner on the transfer paper. In the case of such a heat roller fixing method, since the contact area is small, the pressure load must be increased in order to fuse and fix the toner on the transfer paper. Further, as in recent years, the paper passing speed is 10 pp.
If m exceeds m, the pressure load between the rollers must also be increased, which causes a problem that the toner release layer on the roller surface is severely worn and offset occurs in a short life.

In order to solve these problems of the heat roller fixing method, a belt fixing method has been proposed. In this method, a roller and a belt are arranged to face each other, and toner is fixed by feeding a transfer sheet between them. In this case, the basic functions of pressurizing, heating, driving, and releasing are necessary as in the heat roller fixing method, but these functions may be provided on the roller side or on the belt side. By using one side of the belt with good followability, the contact area can be increased and the pressure load can be reduced. But,
Also in this belt fixing method, when the sheet passing speed exceeds 20 ppm, the pressure load is further increased, so that the wear resistance of the release layer is required.

Various types of release layers have been proposed for the purpose of improving the wear resistance of the release layer of the fixing roller or the fixing belt. For example, JP-A-10-142990
In the publication, a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA, particle size 1 to 15) is disclosed.
A release layer composed of 20 to 97 wt% (μm, molecular weight 300,000 or more) and 3 to 80 wt% of polytetrafluoroethylene (PTFE, particle diameter 1 μm or less, molecular weight 1,000,000 or more) has been proposed.

JP-A-10-186923 discloses PFA (particle size of 5 μm or more, molecular weight of 650,000 or more) or PFA (particle size of 5 μm or more, molecular weight of 650,000 or more).
There has been proposed a release layer comprising 80 to 20% by weight and 80 to 20% by weight of PFA (particle size: 1 μm or less).

[0006]

However, even in a release layer composed of PFA having a defined molecular weight or a mixture of PFA and PTFE, sufficient release resistance can be obtained under the high stress of the system due to paper passing exceeding 20 ppm. No abrasion was obtained.

On the other hand, for the release layer of the fixing belt, the required surface energy (in other words, the releasability) varies depending on the type and state of the toner.

For example, the melting point of toners has been reduced along with the development of full color printing. However, when these toners are transferred directly to paper and fixed directly, the belt surface is made of pure PFA or PTFE having low surface energy, or a composite of these. If it is not the body, offset tends to occur. However, when the toner is previously melted and fixed on the back surface of the transfer paper to which new toner is fixed, such as when performing double-sided copying, and the paper anchored on the paper is passed, the back surface of the transfer paper is The surface energy of the fixing belt pressed against the (fixing surface) need not be so low.

Heretofore, there has been a conductive primer layer containing a thermoplastic resin having a relatively low heat distortion temperature and a fluororesin, but the release resistance of the release layer provided on the surface thereof is high. It is unlikely to contribute to improvement.

The present invention has been made in view of such circumstances, and is sufficient for high-speed paper passing where the abrasion resistance of the release layer on the belt surface exceeds 20 ppm. An object of the present invention is to provide a fixing belt having an appropriate releasability in which an offset hardly occurs.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the material and forming method of the release layer on the belt surface in order to achieve the above-mentioned object. It has been found that by using a binder resin having a heat distortion temperature as an essential resin component, the abrasion resistance can be significantly improved, and the present invention has been completed.

That is, the fixing belt of the present invention is a fixing belt having a heat-resistant endless belt layer and a release layer provided on the surface, wherein the release layer is made of a fluorine resin and a heat distortion temperature (ASTM: D648). 1.82 MPa) is 20
A binder resin having a temperature of 0 ° C. or more and 327 ° C. or less is used as an essential resin component.

In the above, it is preferable that the binder resin is contained in an amount of 5 to 75% by weight based on the fluororesin.

It is preferable that the release layer is formed by heating the mixture of the fluororesin and the binder resin to a temperature equal to or higher than the melting point of both, and then cooling and solidifying the mixture.

Further, the fixing belt of the present invention is preferably used as a fixing belt which is pressed against a non-fixing side surface of a recording material on which toner is fixed.

[Effects] According to the fixing belt of the present invention, the release layer contains a fluororesin and a binder resin having a specific heat distortion temperature as essential resin components. Wear resistance can be significantly improved while maintaining excellent mold releasability. Although the details of the reason are not clear, it is considered that the binder resin having a specific heat deformation temperature has a good abrasion resistance of itself and a structure in which a fluorine resin is suitably bonded can be obtained.

When the binder resin is contained in an amount of 5 to 75 wt% with respect to the fluororesin, the fluororesin can be suitably bonded, and the releasability of the fluororesin can be suitably exhibited.

In the case where the release layer is formed by heating the mixture of the fluororesin and the binder resin to a temperature higher than their melting points and then cooling and solidifying the mixture, the two resins are melted. In this state, the abrasion resistance can be further improved by dissolving or micro-dispersing.

When the fixing belt of the present invention is used as a fixing belt pressed against a non-fixing side surface of a recording material on which a toner is fixed, the excellent abrasion resistance as described above causes a problem.
The abrasion resistance of the release layer on the belt surface is sufficient even for high-speed paper passing exceeding ppm. Further, since the toner has an appropriate release property, an offset hardly occurs even for the toner anchored on the non-fixed side surface of the recording material.

[0020]

Embodiments of the present invention will be described below.

Although the fixing belt of the present invention has a heat-resistant endless belt layer and a release layer provided on the surface, a release layer may be provided directly on the surface of the heat-resistant endless belt layer. A primer layer for improving the binding force and an elastic layer for further increasing the contact area may be provided between the layers.

The thickness of each layer of the fixing belt can be arbitrarily set, but the thickness of the heat-resistant endless belt layer is 5-20.
It is preferable to set the range to 0 μm. If it is less than 5 μm, buckling is likely to occur, and if it exceeds 200 μm, the separation angle for feeding the paper tends to be small, and the toner releasability tends to decrease. Further, the thickness of the primer layer is preferably in the range of 0.5 to 10 μm. If the thickness is less than 0.5 μm, the binding force is low.
If it exceeds 0 μm, it tends to become brittle. The thickness of the elastic layer is preferably 50 to 1000 μm. If the thickness is less than 50 μm, it is difficult to uniformly fuse the toner, and if it exceeds 1000 μm, the thermal conductivity, electric conductivity, and mechanical properties of the entire belt tend to decrease. The release layer is preferably from 5 to 100 μm,
More preferably, it is set to 50 μm. If it is less than 5 μm, the life in which offset occurs when paper is passed becomes short, and if it exceeds 100 μm, cracks tend to occur.

The material of the heat-resistant endless belt layer may have a heat resistance higher than the temperature used in the fixing section.
Preferably, a resin having a continuous use temperature of 200 ° C. or more and a flexible metal are used. Specifically, examples thereof include heat-resistant resins such as polyimide, polyamideimide, polyetheretherketone, polyphenylene sulfide, and polybenzimidazole, and metals such as aluminum, iron, nickel, and alloys thereof.

Among them, a polyimide resin having excellent mechanical properties, heat resistance and flexibility is most suitable. The polyimide resin is, for example, tetracarboxylic dianhydride as an acid component and a substantially equimolar amount of a diamine as an amine component dissolved in a suitable solvent and reacted to prepare a polyamic acid solution. To obtain a polymer (imide conversion).

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

The fluororesin of the release layer is not particularly limited as long as it contains a fluorine atom in the molecule. Specifically, polytetrafluoroethylene (PT
FE) and its modified products, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), tetrafluoroethylene-ethylene copolymer (ETF)
E), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-vinylidene fluoride copolymer (TFE / VdF), tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinyl ether copolymer (EPA) ), Polychlorotrifluoroethylene (PCTFE), chlorotrifluoroethylene-ethylene copolymer (ECTF)
E), chlorotrifluoroethylene-vinylidene fluoride copolymer (CTFE / VdF), polyvinylidene fluoride (PVdF), polyvinyl fluoride (PVF) and the like.

Heat deformation temperature (ASTM: D648, 1.8)
Examples of the binder resin having a pressure of 2 MPa) of 200 ° C. to 327 ° C. include polyamide imide, polyether sulfone, polyether imide, polyether ether ketone, polyether ketone, and the like. These may be used in combination. Among the above, the heat deformation temperature is 25
Polyamide imide, polyetheretherketone and polyetherketone at 0 ° C. or higher are preferred. In addition, a resin having a heat deformation temperature exceeding 327 ° C. is not preferable because it generally has poor compatibility with a fluororesin, makes the surface brittle, and lowers abrasion resistance. Conversely, polycarbonate and polyacetal whose heat distortion temperature is around 130 ° C. have a fixing temperature of 200 ° C.
Under an atmosphere of ° C., wear is undesirably fast.

The release layer in the present invention contains a fluororesin and a binder resin as essential resin components, and preferably contains the binder resin in an amount of 5 to 75% by weight, more preferably 20 to 50% by weight, based on the fluororesin. Is more preferred.
When the amount of the binder resin is less than 5% by weight, the binding by the binder resin becomes insufficient, and the effect of improving the wear resistance tends to be insufficient. If it exceeds 75 wt%, the releasability of the fluororesin tends to be insufficient.

The release layer may be formed by, for example, binding unmelted fluororesin particles with a binder resin. However, a mixture of the fluororesin and the binder resin was heated to a temperature higher than the melting point of both. Thereafter, it is preferable to form by cooling and solidifying. Further, such a method by fusion can be carried out simultaneously with curing (imide conversion, etc.) of the heat-resistant endless belt layer, and at this time, a release layer is fused (adhered) to the heat-resistant endless belt layer or the like. be able to. In particular, by using a binder resin having good compatibility with the heat-resistant endless belt layer, both layers can be firmly bonded without a primer layer.

For example, when a polyimide resin is used for the heat-resistant endless belt layer, by using polyamideimide or polyether sulfone as the binder resin, both layers can be suitably bonded.

The application or coating of the material for forming the release layer can be carried out by using a powder mixture, a solvent-based or aqueous dispersion, an enamel, or the like, by an electrostatic method, a spray method, a dipping method, or the like. Various coating solutions in which the above binder resin is dissolved and dispersed in a fluororesin dispersion are commercially available, and these can be used.

In the present invention, a filler such as heat conductive particles or electric conductive particles may be further added for the purpose of imparting heat conductivity or electric conductivity to the release layer. In that case, 10 ^-3 c
It is preferable that a filler having a thermal conductivity of al / s · cm · ° C. or higher is contained in the fluororesin in an amount of 1 to 50 wt%, and the total amount of the filler and the binder resin is 5 to 75 wt%. Further, it is preferable that a filler having a resistance of 10 ¹⁰ Ω · cm or less is contained in the fluororesin in an amount of 1 to 50 wt% and a total amount of 5 to 75 wt% with the binder resin.

Specifically, examples of the thermally conductive particles include diamond, silver, copper, aluminum, marble, glass, and the like. Practically, silica, alumina, magnesium oxide, boron nitride, and beryllium oxide are mentioned. Can be

Examples of the electrically conductive particles include conductive polymers such as polyacetylene, polypyrrole, and polythiophene; carbon such as ketchin black and acetylene black; metals such as graphite, silver, nickel, and copper; alloys thereof; and mica, carbon, and glass. And a metal oxide such as tin oxide and indium oxide, an anion, a cation, a nonion, and an amphoteric surfactant.

Also for the elastic layer, a material that can withstand the fixing temperature is preferable, and examples thereof include heat-resistant rubbers such as fluorine rubber and silicone rubber. The softness of these rubbers can be controlled by crosslinking and foaming, but is preferably 80 or less in Shore D. It is not preferable because the toner exceeding 80 cannot be uniformly fused, the glossiness of the printed matter on paper is reduced, or the transparency of the printed matter on the OHP is lost, resulting in blurred images. Also, heat conductive particles and electric conductive particles may be dispersed in the elastic layer.

As the primer layer, various commercially available primers for improving the adhesion between the heat-resistant endless belt layer and the release layer or the elastic layer can be used. For example, a polyimide resin is used for the heat-resistant endless belt layer. A system primer, a fluorine system primer, and a mixture of these primers are preferably used.

The Vickers hardness of the release layer on the surface of the fixing belt of the present invention is preferably from 50 to 300 Hv from the viewpoint of abrasion resistance. Further, the surface roughness (Ra) is preferably 0.05 to 0.8 μm from the viewpoint of image characteristics.

The fixing belt of the present invention can be used in a fixing section of an image forming apparatus such as a copying machine, a facsimile, a printer, etc., but any fixing section employing a 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. However, the fixing belt is preferably used as a fixing belt pressed against the non-fixing side surface of the recording material to which the toner is fixed, and is particularly useful for fixing by high-speed paper passing exceeding 20 ppm. As such a fixing method, a nip portion is formed in which a recording material is passed through the outer surface of the fixing belt by pressing the fixing belt against a heating drive roll with a pressing member disposed inside the tubular fixing belt. A fixing method may be used.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and the like specifically showing the configuration and effects of the present invention will be described below. The physical properties and the like in the examples and comparative examples were measured as follows.

The Vickers hardness is measured by a Vickers hardness tester (M
H-400, manufactured by NEC), and the indenter is
The indentation depth was 0.5 μm and the indentation speed was 21 nm / sec. Surface roughness (R
a) was measured using a roughness meter (Surfcom 554A, manufactured by Tokyo Seimitsu) with a cutoff of 0.32 mm and a measurement length of 2.5.
mm, drive speed 0.12 mm / sec, stylus load 4
It was measured as 00 mg. The amount of abrasion was measured by performing a Matsubara abrasion test under the conditions of a speed of 500 mm / sec and a load of 5 kg, and the tensile modulus was measured according to ASTM (D885).

Example 1 As an acid component, 3,3′4
4'-biphenyltetracarboxylic dianhydride is dissolved as an amine component in N-methyl-2-pyrrolidone (NMP) in approximately equimolar amount of p-phenylenediamine (monomer concentration: 20% by weight), and the mixture is dissolved at 20 ° C. for 6 hours. Reaction and rotational viscosity 3
A polyamic acid solution having a 3,000 poise (measured with a B-type viscometer at a temperature of 20 ° C.) and a logarithmic viscosity of 2.6 was prepared. Then
The temperature of the polyamic acid solution was adjusted to 1500 poise by heating to 70 ° C.

The polyamic acid solution was applied to an inner diameter of 30.61 m.
m, and passed through a pig having an outer diameter of 29 mm, and was heated to 150 ° C. for 10 minutes to solidify.
Further, the temperature of the mold was raised from 150 ° C. at 1.5 ° C./min to 220 ° C., and was lowered at 2 ° C./min.
Returned to room temperature. After releasing the polyimide belt from the mold, the polyimide belt is inserted into an aluminum pipe having an outer diameter of 29.8 mm, and the polyamide imide (heat deformation temperature 280)
C) spray-coated a solvent-based fluorine coating solution (TC7100, Daikin Co., Ltd.) containing 10 wt% and 20 wt% of PTFE, and heated at 380 ° C for 30 min to imidize the polyimide belt and melt the polyamideimide and PTFE, Polyimide, PTFE, and polyamideimide were simultaneously bound.

The belt obtained here was a polyimide layer having a tensile elasticity of 8130 N / mm ² and a thickness of 80 μm in order from the inside, and a release layer 4 of PTFE in which polyamideimide was compatible.
It was composed of 0 μm. The surface of the release layer had a Vickers hardness of 110 Hv and Ra of 0.8 μm. The amount of wear by Matsubara formula was 0.1 mg / h.

A support having a sliding sheet was placed inside the belt, and a heating roller having silicone rubber applied to an aluminum roller was pressed in parallel with the belt to fix the toner. On the belt side, the anchored toner, which has been previously fixed on the silicone rubber surface, passed at a speed of 20 ppm. The target life of 100,000 sheets was passed, but no offset was found.

Example 2 A solvent-based fluorine coating solution for forming a release layer in Example 1 was prepared by mixing 10 wt% of polyether sulfone (heat deformation temperature: 210 ° C.) with PTFE2.
0 wt% fluorine coating solution (TCW-880 from Daikin)
A fixing belt was produced in the same manner as in Example 1 except that the fixing belt was changed to 0). The release layer of 40 μm has a Vickers hardness of 60
Hv, Ra = 1.2 μm. The wear amount is 0.3
mg / h.

A support having a sliding sheet was placed inside the belt, and a heating roller having silicone rubber applied on an aluminum roller was pressed in parallel with the belt to fix the toner. On the belt side, the anchored toner, which has been previously fixed on the silicone rubber surface, passed at a speed of 20 ppm. The target life of 100,000 sheets was passed, but no offset was found.

Comparative Example 1 A 0.5 μm thick polyimide-based primer (Mitsui DuPont, K001-02) and a 40 μm thick PTF were placed on the polyimide belt of Example 1.
A belt was produced in the same manner as in Example 1 except that an E release layer (Mitsui DuPont, 056-1) was applied. The release layer had a Vickers hardness of 10 Hv and Ra of 1.6 μm. The wear amount was 29 mg / h. When the release layer is formed of PFA and PTFE, as in the prior art,
The amount of wear was 7 mg / h.

A support having a sliding sheet was placed inside the belt, and a heating roller having silicone rubber applied on an aluminum roller was pressed in parallel with the belt to fix the toner. . On the belt side, the anchored toner, which has been previously fixed on the silicone rubber surface, passed at a speed of 20 ppm. Offset is 1
Occurred in 10,000 sheets.

Claims (4)

[Claims] In a fixing belt having a heat-resistant endless belt layer and a release layer provided on the surface, the release layer is made of a fluororesin and a heat distortion temperature (ASTM: D64).
8. A fixing belt characterized in that a binder resin having a temperature of 200 ° C. or more and 327 ° C. or less is used as an essential resin component. 2. The fixing belt according to claim 1, wherein the binder resin is contained in an amount of 5 to 75 wt% based on the fluororesin. 3. The release layer according to claim 1, wherein the release layer is formed by heating the mixture of the fluororesin and the binder resin to a temperature higher than their melting points and then cooling and solidifying the mixture. Fixing belt. 4. The fixing belt according to claim 1, wherein the fixing belt is pressed against a non-fixing side surface of the recording material to which the toner is fixed.
The fixing belt according to any one of the above.