Polyimide pipe

Abstract

The present invention addresses the problem of providing a fixing belt which has excellent thermal conductivity, is not susceptible to breakage due to paper pullout when a paper jam occurs, and can be applied to a fixing belt or the like. The polyimide tube according to the present invention contains a polyimide resin, the polyimide resin contains carbon nanotubes, the thermal conductivity of the polyimide tube is 1.00 W / mK or more, and the thermal conductivity in the longitudinal direction / the thermal conductivity in the circumferential direction of the polyimide tube is 1.05 or more. The product of the tensile modulus of elasticity in the longitudinal direction of the polyimide tube and the tensile load at the time of fracture in a tensile test is 4000 kgf2 / mm2 or more.

Description

TECHNICAL FIELD

[0001] The present application relates to a polyimide tube which can be suitably used for a fixing belt or the like mounted on an image forming apparatus or the like. BACKGROUND

[0002] In an image forming apparatus such as a copier, printer or the like using an electrophotographic method, an unfixed toner image formed on a recording medium such as a recording paper is fixed by a fixing device. In this method, a transfer paper temporarily provided with a heat-sensitive ink on one surface of a fixing belt is fed between the fixing belt provided with a heater on the back side and a pressure roller, whereby the heat-sensitive ink is fused and fixed on the transfer paper while the fixing is made firm by pressing the heat-sensitive ink on the transfer paper.

[0003] In order to achieve a reduction in the waiting time after power-on, a reduction in power consumption, a high speed of fixing, and the like while improving the heat conductivity of the fixing belt and enhancing the fixing property of the heat-sensitive ink to the transfer paper, a method in which a filler having excellent heat conductivity (high-heat-conductivity filler) is contained in the base material layer of the fixing belt is widely known.

[0004] As a fixing belt to which the above method is applied, a "resin-made tubular article which is a resin-made tubular article using a heat-resistant resin as a base material, characterized by incorporating 1 to 25 parts by volume of a filler having a thermal conductivity of greater than 60 W / mk" has been proposed in the past (for example, see Japanese Patent Application Publication No. 2006-330405 and the like). PRIOR ART DOCUMENTS PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-330405 SUMMARY PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] However, when paper jamming (so-called jam) occurs in the image forming apparatus, the user needs to remove the fixing device, pull out the jammed paper from the paper conveying path, and thereby release the jam. At this time, if the paper is forcibly pulled out, a load is applied to the fixing belt, which can cause breakage of the end portion of the fixing belt. In order to solve such a problem, a polyimide tube which can produce a fixing belt which is not easily broken by paper pulling out while maintaining heat conductivity when jam occurs is required.

[0007] An object of the present application is to provide a polyimide tube which is not easily broken by paper pulling out while maintaining excellent heat conductivity when jam occurs, and which can be suitably used for a fixing belt or the like. MEANS OF SOLVING THE PROBLEMS

[0008] The polyimide tube of the present invention is a polyimide tube containing polyimide resin, wherein carbon nanotubes are contained in the polyimide resin. Furthermore, this polyimide tube can be formed with polyimide resin as the main component. Alternatively, this polyimide tube can be composed of polyimide resin and carbon nanotubes. Moreover, the thermal conductivity in the thickness direction of this polyimide tube is 1.00 W / mK or higher. Furthermore, the ratio of the thermal conductivity in the length direction to the thermal conductivity in the circumferential direction (i.e., the ratio of the thermal conductivity in the length direction to the thermal conductivity in the circumferential direction of the polyimide tube) is 1.05 or higher. Furthermore, the product of the tensile modulus of elasticity in the length direction and the tensile load at fracture in a tensile test is 4000.0 kgf. 2 / mm 2 above.

[0009] Furthermore, the thermal conductivity in the thickness direction of the aforementioned polyimide tube is preferably 3.2 W / mK or less, more preferably 2.5 W / mK or less. Additionally, the ratio of the thermal conductivity in the length direction to the thermal conductivity in the circumferential direction of the polyimide tube is preferably 1.60 or less, more preferably 1.30 or less, and even more preferably 1.10 or less. Furthermore, in this polyimide tube, the product of the tensile modulus of elasticity in the length direction and the tensile load at fracture during a tensile test is preferably 13000 kgf. 2 / mm 2 The following is more preferably 11000 kgf 2 / mm 2 The following is a further preferred value: 8000 kgf 2 / mm 2 the following.

[0010] Furthermore, the aforementioned polyimide resin is preferably a blend of a first polyimide resin and a second polyimide resin, wherein the first polyimide resin comprises units from 3,3',4,4'-biphenyltetracarboxylic dianhydride and units from p-phenylenediamine, and the second polyimide resin comprises units from pyromellitictetracarboxylic dianhydride and units from 4,4'-diaminodiphenyl ether. Moreover, the mass ratio of the first polyimide resin to the second polyimide resin is preferably in the range of 70:30 or more and 100:0 or less.

[0011] Furthermore, the tensile modulus of elasticity in the longitudinal direction of the aforementioned polyimide tube is preferably 700 kgf / mm². 2 That's all. Furthermore, the tensile modulus of elasticity along the length of the polyimide tube is preferably 1200 kgf / mm². 2 The preferred value is 1100 kgf / mm. 2 the following. Beneficial effects

[0012] By using the polyimide tube of the present application, a fixing belt which is not easily broken by paper pull-out when paper jam occurs in a fixing device while maintaining excellent heat conductivity can be produced. DETAILED DESCRIPTION

[0013] The polyimide tube of the embodiment of the present application is a polyimide tube containing a polyimide resin, and contains carbon nanotubes (hereinafter referred to as "CNTs") in the polyimide resin. Hereinafter, such a polyimide tube will be referred to as a "CNT-containing polyimide tube". In addition, the polyimide tube can be formed with the polyimide resin as a main component. The "main component" described herein means a component having a content of more than 50% by mass. Furthermore, the CNTs are preferably contained in a range of 15 parts by volume or more and 35 parts by volume or less, more preferably in a range of 15 parts by volume or more and 32 parts by volume or less, and further preferably in a range of 15 parts by volume or more and 30 parts by volume or less, with respect to the volume of the CNT-containing polyimide resin (i.e., the total volume of the polyimide resin and the CNTs). Furthermore, the fiber diameter of the CNTs is preferably in a range of 100 nm or more and 200 nm or less, more preferably in a range of 120 nm or more and 180 nm or less, and further preferably in a range of 140 nm or more and 160 nm or less. Furthermore, the fiber length of the CNTs is preferably in a range of 1 μm or more and 10 μm or less, and preferably in a range of 3 μm or more and 7 μm or less. Furthermore, the polyimide tube can be composed of the polyimide resin and the CNTs.

[0014] The thermal conductivity in the film thickness direction of the polyimide tube is 1.00 W / mK or more. In addition, the thermal conductivity in the film thickness direction of the polyimide tube is preferably 1.05 W / mK or more, and more preferably 1.10 W / mK or more. Furthermore, the higher the thermal conductivity in the film thickness direction of the polyimide tube is, the more preferable it is, but the upper limit thereof is preferably 3.2 W / mK, and more preferably 2.5 W / mK, in consideration of the amount of CNTs that can be added to the polyimide resin, and the like.

[0015] Furthermore, the (thermal conductivity in the length direction) / (thermal conductivity in the circumferential direction) of the polyimide tube (i.e., the ratio of the thermal conductivity in the length direction of the polyimide tube to the thermal conductivity in the circumferential direction of the polyimide tube) is 1.05 or more. In addition, the "length direction" described herein indicates the axial direction of the polyimide tube, or the direction perpendicular to the circumferential direction of the polyimide tube. In addition, the higher the (thermal conductivity in the length direction) / (thermal conductivity in the circumferential direction) of the polyimide tube is, the more preferable it is, but the upper limit thereof is preferably 1.60, more preferably 1.30, further preferably 1.20, and particularly preferably 1.15, in consideration of the amount of CNTs that can be added to the polyimide resin, the limit of controllability of the orientation of the CNTs, and the like.

[0016] Further, in the polyimide tube of the present embodiment, the (thermal conductivity in the length direction) / (thermal conductivity in the circumferential direction) is 1.05 or more. That is, in the polyimide tube, the thermal conductivity in the length direction is higher than the thermal conductivity in the circumferential direction (it is presumed that this is because the CNTs are oriented along the length direction of the polyimide tube in the length direction). Therefore, in the case where the polyimide tube is used as a base layer of a fixing belt or the like, it is possible to suppress excessive temperature rise of the end portion of the fixing belt or the like due to passage of paper or the like between the fixing belt and a pressure roller. Further, it is presumed that this is because the thermal conductivity in the length direction of the polyimide tube becomes high, and thus temperature unevenness in the length direction of the fixing belt due to passage of paper is suppressed.

[0017] Further, the product of the tensile elastic modulus in the length direction of the polyimide tube and the tensile load at the time of breakage in the tensile test is 4000.0 kgf 2 / mm 2 or more. Further, the "tensile load at the time of breakage" described herein refers to the tensile load at the time of breakage observed when the tensile test is performed according to the method prescribed in JIS P8113. Further, the higher the product of the tensile elastic modulus in the length direction of the polyimide tube and the tensile load at the time of breakage in the tensile test, the more preferable it is, but considering the limit of control of the amount of CNTs that can be added to the polyimide resin, the limit of orientation of the CNTs, and the like, the upper limit thereof is preferably 13000 kgf 2 / mm 2 , more preferably 11000 kgf 2 / mm 2 , and further preferably 8000 kgf 2 / mm 2 .

[0018] Further, in the polyimide tube of the present embodiment, the product of the tensile elastic modulus in the length direction and the tensile load at the time of breakage in the tensile test is 4000.0 kgf 2 / mm 2 or more. Therefore, it is considered that breakage of the polyimide tube that can occur due to forcible paper extraction or the like when paper jam occurs in the fixing device is suppressed. Further, it is presumed that the reason why breakage of the end portion of the polyimide tube occurs when paper is forcibly extracted when paper jam occurs in the fixing device is that a load in the length direction of the polyimide tube is applied when paper is forcibly extracted when paper jam occurs in the fixing device, and thus the end portion of the fixing belt is deformed. That is, it is considered that, in the polyimide tube, breakage is less likely to occur because deformation thereof is suppressed.

[0019] The polyimide tube of the present embodiment is suitable for use as a base layer of a fixing belt installed in an image forming device. Further, the polyimide tube of the present embodiment has the physical properties described above, and thus is less likely to break due to paper extraction when paper jam occurs while maintaining excellent thermal conductivity.

[0020] Further, the tensile elastic modulus in the length direction of the polyimide tube of the present embodiment is preferably 700 kgf / mm 2 More preferably, it is 710 kgf / mm 2 Further, the tensile elastic modulus in the length direction of the polyimide tube is more preferably higher, but due to the characteristics of the polyimide resin, the upper limit is preferably 1200 kgf / mm 2 More preferably, it is 1100 kgf / mm 2 .

[0021] Regarding the thickness of the polyimide tube of the present embodiment, from the viewpoint of maintaining the minimum mechanical properties, it is preferably in the range of 30 μm or more and 100 μm or less, and from the viewpoint of the flexibility required when used as a base layer of a fixing belt or the like, it is preferably in the range of 50 μm or more and 80 μm or less.

[0022] Next, as the polyimide resin used in the present embodiment, for example, an imide of a polyamic acid (polyamide acid, polyamic acid) which is a polymer of a tetracarboxylic dianhydride and a diamine compound is exemplified. As the polyimide resin, a polyimide resin obtained by subjecting equimolar amounts of a tetracarboxylic dianhydride and a diamine compound to a polymerization reaction in a solvent to obtain a solution of a polyamic acid, and then subjecting the polyamic acid to imidization is specifically exemplified.

[0023] As the tetracarboxylic dianhydride, specifically mentioned are aromatic tetracarboxylic dianhydrides such as pyromellitic dianhydride (PMDA), 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 2,2',3,3'-biphenyl tetracarboxylic dianhydride, 2,3,3',4'-biphenyl tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 2,3,3',4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 1.05-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1.05-bis(3,4-dicarboxyphenyl)ethane dianhydride, 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, oxydiphthalic anhydride (ODPA), bis(3,4-dicarboxyphenyl)sulfone dianhydride, bis(3,4-dicarboxyphenyl)sulfoxide dianhydride, thiodiphthalic dianhydride, 3,4,9,10-perylene tetracarboxylic dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 1,2,7,8-phenanthrene tetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, and 9,9-bis[4-(3,4'-dicarboxyphenoxy)phenyl]fluorene dianhydride; cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride, 2,3,4,5-tetrahydrofuran tetracarboxylic dianhydride, 1,2,4,5-cyclohexane tetracarboxylic dianhydride, 3,4-dicarboxy-1-cyclohexyl succinic dianhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride. In addition, two or more of these tetracarboxylic dianhydrides can be mixed and used. Among these tetracarboxylic dianhydrides, specifically preferred are pyromellitic dianhydride (PMDA), 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 2,2-bis[3,4-(dicarboxyphenoxy)phenyl]propane dianhydride (BPADA), and oxydiphthalic anhydride (ODPA).

[0024] As the diamine compound, specifically mentioned are p-phenylenediamine (PPD), m-phenylenediamine (MPDA), 2,5-diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 2,2-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane (MDA), 2,2-bis-(4-aminophenyl)propane, 3,3'-diaminodiphenylsulfone (33DDS), 4,4'-diaminodiphenylsulfone (44DDS), 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether (34ODA), 4,4'-diaminodiphenyl ether (ODA), 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 1,3-bis(3-aminophenoxy)benzene (133APB), 1,3-bis(4-aminophenoxy)benzene (134APB), 1,4-bis(4-aminophenoxy)benzene, bis[4-(3-aminophenoxy)phenyl]sulfone (BAPSM), bis[4-(4-aminophenoxy)phenyl]sulfone (BAPS), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2-bis(3-aminophenyl)1.05,1,3,3,3-hexafluoropropane, 2,2-bis(4-aminophenyl)1.05,1,3,3,3-hexafluoropropane, 9,9-bis(4-aminophenyl)fluorene, and the like aromatic diamines.

[0025] Among the polyimide resins, from the viewpoints of durability, thermal conductivity, and bending durability, etc., a polyimide resin composed of 3,3',4,4'-biphenyltetracarboxylic dianhydride and p-phenylenediamine (BPDA-PPD), or a polyimide resin composed of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether (BPDA-ODA), or a polyimide resin composed of pyromellitic dianhydride and 4,4'-diaminodiphenyl ether (PMDA-ODA) are preferably selected. These polyimide resins can be used in combination (i.e., can be copolymerized or blended).

[0026] Further, as the organic polar solvent in which the monomer tetracarboxylic dianhydride and diamine compound used for preparing the above polyamic acid is dissolved, for example, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-methylcaprolactam, hexamethylphosphoric triamide, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and the like are exemplified. Among these diamines, N,N-dimethylacetamide (DMAC), N-methyl-2-pyrrolidone (NMP) are particularly preferable. Further, these organic polar solvents can be used alone or in combination. Furthermore, an aromatic hydrocarbon such as toluene, xylene, or the like can also be mixed in the organic polar solvent.

[0027] For the polyimide resin of the embodiment of the present application, other thermally conductive particles or the like can be added to the extent that the strength and thermal conductivity of the polyimide tube are not impaired.

[0028] Next, the manufacturing method of the fixing belt using the polyimide tube of the embodiment of the present application as the base layer will be described in detail. The fixing belt of the embodiment of the present application is manufactured mainly through a CNT-containing polyamic acid solution preparation step, a base layer forming step, a primer layer forming step, a release layer forming step, a firing step, and a demolding step. Further, here, the base layer forming step corresponds to the forming step of the polyimide tube of the embodiment of the present application. The fixing belt of the present embodiment can also have an elastic layer provided between the base layer and the release layer. In this case, an elastic layer forming step is inserted between the primer layer forming step and the release layer forming step. The elastic layer forming step will be described last.

[0029] (1) CNT-containing polyamic acid solution preparation step In the CNT-containing polyamic acid solution preparation step, the CNT-containing polyamic acid solution is obtained by adding the above CNT to the polyimide precursor solution prepared as follows. Further, the method of adding the CNT to the polyamic acid solution is not particularly limited, and can naturally be a method of directly adding the CNT to the polyamic acid solution or a method of adding the CNT during the preparation of the polyamic acid solution.

[0030] Further, as the organic polar solvent in which the above-mentioned polyamic acid solution can be prepared, for example, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-methylcaprolactam, hexamethylphosphoric triamide, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and the like are exemplified. Among these diamines, N,N-dimethylacetamide (DMAC), N-methyl-2-pyrrolidone (NMP) are particularly preferable. Further, these organic polar solvents can be used alone or in combination. Furthermore, toluene, xylene, and the like aromatic hydrocarbons, and the like can also be mixed in the organic polar solvent.

[0031] In the present embodiment, it is preferable to use 4,4'-diaminodiphenyl ether as the diamine and pyromellitic dianhydride as the tetracarboxylic dianhydride to prepare the polyamic acid solution, and it is particularly preferable to use p-phenylenediamine as the diamine and 3,3',4,4'-biphenyltetracarboxylic dianhydride as the tetracarboxylic dianhydride to prepare the polyamic acid solution. This is because the polyimide resin obtained by imidizing the polyamic acid prepared from these monomers has excellent mechanical properties and is strong and tough, and even if the temperature of the fixing belt rises, it does not soften or melt like a thermoplastic resin, and exhibits excellent heat resistance. Furthermore, by blending the above-mentioned two kinds of polyamic acid, a polyimide resin having excellent mechanical properties such as flexibility can be obtained, and thus can be suitably used. As such a blend, for example, a blend of a first polyimide resin containing units derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride and units derived from p-phenylenediamine and a second polyimide resin containing units derived from pyromellitic dianhydride and units derived from 4,4'-diaminodiphenyl ether, and the like are exemplified. Further, the mass ratio of the first polyimide resin to the second polyimide resin is preferably in the range of 70:30 or more and 100:0 or less, more preferably in the range of 80:20 or more and 100:0 or less, and further preferably in the range of 80:20 or more and 97.5:2.5 or less.

[0032] Further, other resins such as a polyamide-imide, a polyether sulfone, and the like can be added to the polyamic acid solution as necessary without impairing the gist of the present application.

[0033] Further, known additives such as a dispersant, a solid lubricant, an anti-settling agent, a leveling agent, a surface modifier, a moisture absorbent, an anti-gelling agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a plasticizer, an anti-skinning agent, a surfactant, an anti-static agent, an antifoaming agent, an antibacterial agent, a mildew preventive, a preservative, a thickening agent, and the like can be added to the polyamic acid solution without impairing the properties of the present application. Further, a dehydrating agent and an imidization catalyst in an amount of one or more moles can be added to the polyamic acid solution.

[0034] Further, regarding the polyamic acid solution, it is preferable to perform a preliminary treatment such as filtration, defoaming, and the like before use.

[0035] (2) Base layer forming step The base layer can be formed using, for example, a coating device. As one example, the coating device is provided with a slit head and a moving mechanism that moves at least one of the slit head and the core body upward or downward at a certain speed. In the coating device, the core body moves relatively upward or downward while maintaining a prescribed gap on the inner side of the slit head. At this time, in the coating device, the CNT-containing polyamic acid solution is ejected from the slit head to the outer surface of the core body from the outside at a prescribed ejection speed, and the CNT-containing polyamic acid solution is cast formed on the outer surface of the core body at a prescribed film thickness, thereby forming a coating film of the CNT-containing polyamic acid solution. The coating film is dried and heated until a state is reached in which at least the strength as a base layer can be maintained, and then the core body and the base layer are separated to obtain the base layer.

[0036] In addition, the base layer can also be formed by a method in which, after the CNT-containing polyamic acid solution is applied to the outer surface of the core body, a mold is caused to fall by its own weight at a speed of 100 mm / s or more on the outside of the core body, thereby orienting the CNTs in the length direction of the base layer.

[0037] (3) Primer layer forming step In the primer layer forming step, the core body on which the base layer is formed is dipped in a primer liquid and then lifted, thereby uniformly applying the primer liquid to the outer peripheral surface of the base layer, and then the primer liquid is heat-dried to form the primer layer, wherein the primer liquid contains a dispersion medium of a fluorine-containing resin and a water-soluble heat-resistant resin or the like. In addition, the heating temperature at this time is preferably a temperature at which the solvent volatilizes but the polyimide precursor in the CNT-containing polyamic acid solution before the volatilization does not undergo imidization, and is preferably, for example, a temperature of 320°C or lower. The primer layer is composed of a fluorine resin, an adhesive resin such as an acrylic resin, a water-soluble polyamide-imide resin, a water-soluble polyimide resin, and the like, and functions to bond the base layer and the release layer (in the case where an elastic layer is provided, functions to bond the base layer and the elastic layer).

[0038] (4) Release layer forming step In the release layer forming step, after the fluororesin dispersion liquid is applied, the coating film is dried, whereby the coating film of the fluororesin dispersion liquid is formed on the primer layer. As the fluororesin, for example, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP) are cited, which can be used alone or in combination. In addition, an electrically conductive material or the like can be contained to the extent that the performance as a release layer is not impaired.

[0039] (5) Firing step In the firing step, the substance obtained in the release layer forming step is subjected to a firing treatment, whereby the fixing belt is obtained. The firing temperature at this time is preferably in the range of 300°C or higher and 450°C or lower. In addition, the treatment time is preferably in the range of 30 minutes or more and 2 hours or less. This is because the completion of the imidization of the base layer and the firing of the fluororesin of the release layer are performed simultaneously, not only the manufacturing time of the fixing belt can be shortened and the thermal efficiency can be improved, but also the adhesion of each layer can be improved.

[0040] (6) Demolding step In the demolding step, the fixing belt is pulled out from the core. (7) Elastic layer forming step As described above, when the fixing belt is provided with the elastic layer between the base layer and the release layer, the elastic layer forming step is implemented between the primer layer forming step and the release layer forming step, and the primer layer forming step is again implemented between the elastic layer forming step and the release layer forming step. In the elastic layer forming step, after the dope of the silicone rubber is applied on the primer layer, the coating film is heat-cured, whereby the elastic layer is formed on the primer layer. In the subsequent primer layer forming step, after the core on which the elastic layer is formed is dipped in the primer liquid and then pulled up, the primer liquid is uniformly applied to the outer peripheral surface of the elastic layer, and then the primer liquid is heat-dried, whereby the primer layer is formed.

[0041] <Features of the fixing belt of the embodiment of the present application> In an image forming apparatus using a general fixing belt, a heater provided inside the fixing belt melts and fixes toner on a recording medium such as paper via the fixing belt. Therefore, not only the recording medium but also the fixing belt is heated by the heater. Also, when the recording medium such as paper passes between the fixing belt and a pressure roller, the heat of the fixing belt is taken away by the recording medium. Therefore, in the fixing belt, a temperature difference is generated between a passing portion and a non-passing portion of the recording medium, and the non-passing portion is easily overheated. However, the fixing belt of the embodiment of the present application can more uniformly maintain the temperature by increasing the thermal conductivity in the length direction due to the orientation of the CNTs in the length direction, and can further suppress the overheating of itself. In addition, by orienting the CNTs in the length direction, even in the case where the end portion of the fixing belt is deformed due to the forcible pulling out of the recording medium when paper jam occurs, the breakage of the fixing belt can be suppressed.

[0042] <Examples and Comparative Examples> Examples and comparative examples will be shown below to explain the fixing belt of the present embodiment in more detail. In addition, the present application is not limited by these examples and comparative examples. Example 1

[0043] 1. Production of fixing belt First, a mold having an outer diameter of 18 mm and a length of 500 mm on which a release treatment was performed on the surface was prepared.

[0044] Next, in a polyamide acid solution (polyamide acid being polyamide acid A of 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA) / p-phenylenediamine (PPD) and polyamide acid B of pyromellitic dianhydride (PMDA) / 4,4'-diamino diphenyl ether (ODA) blended at a mass ratio of polyamide acid A:polyamide acid B = 97.5:2.5, solid content 18.8 parts by mass), carbon nanotubes (VGCF-H (fiber diameter 150 nm, fiber length 4 μm) manufactured by Showa Denko K.K., hereinafter referred to as "CNT") were added at 17.0 parts by volume relative to the total volume of the solid content (i.e., polyimide resin) and CNT of the polyamide acid solution, and the polyamide acid solution was stirred until the CNT became uniform, thereby obtaining a CNT-containing polyamide acid solution having a viscosity of 900 poise.

[0045] Next, the CNT-containing polyamic acid solution was ejected from the outer side of the slit nozzle of the device equipped with a ring-shaped slit nozzle at a certain ejection speed to the outer surface of the mold moving at a speed of 100 mm / s, so that the CNT-containing polyamic acid solution was applied to the outer surface of the mold, wherein the ring-shaped slit nozzle was opposed to the outer diameter of the passing mold with a prescribed gap. After that, the mold with the applied film was put into an oven at 120°C and dried for 30 minutes, and then the temperature was raised to 200°C in 20 minutes, and then kept at the temperature for 20 minutes, and then cooled to room temperature, so that the base layer was produced.

[0046] Next, the base coat liquid was applied to the surface of the base layer and the applied film was dried at 150°C for 10 minutes, so that the base coat layer was produced.

[0047] Next, the PFA dispersion was applied to the base coat layer and dried, so that a PFA applied film was formed on the base coat layer. Then, the PFA applied film was dried at room temperature for 30 minutes, and then gradually heated to 350°C, and then baked at 350°C for 30 minutes, so that the fixing tape of the target base layer having a thickness of 60 μm was obtained.

[0048] 2. Physical property evaluation (1) Measurement of thermal conductivity of the base layer Here, the base layer obtained before the base coat liquid and the PFA dispersion were applied was used as the measurement object.

[0049] First, the base layer was cut into a 2 cm x 2 cm piece only, and a transistor was provided on one side of the base layer through a heat-conducting lubricant, and a heat sink (aluminum) was provided on the opposite side through a heat-conducting lubricant, with reference to JIS R2616. Next, the temperature of the transistor was raised to 60°C by applying a current, and the base layer was heated at 60°C for 3 minutes. Next, the temperature A of the surface of the transistor and the temperature B of the surface of the base layer on which the heat sink was provided were measured using a thermocouple, and the power consumption was also measured. The temperature of each surface and the power consumption were substituted into the following equation to calculate the thermal resistance.

[0050] Thermal resistance = (temperature A of the surface of the transistor - temperature B of the surface of the base layer) / power consumption

[0051] The film thickness of the base layer, the cross-sectional area of the transistor, and the thermal resistance calculated by the above equation were substituted into the following equation to calculate the thermal conductivity.

[0052] Thermal conductivity = film thickness of the base layer / (cross-sectional area of the transistor x thermal resistance)

[0053] As a result, the thermal conductivity of the base layer was 1.10 W / mK.

[0054] Next, the thermal conductivity in the length direction and the circumferential direction of the base layer was measured. The measurement method was as follows.

[0055] First, the base layer was cut into 1.5 cm x 1.5 cm squares to prepare base layer sheets, and the base layer sheets were stacked in a lengthwise and circumferential direction alignment manner to 5 mm, thereby producing a test sheet. Next, an aluminum square bar (hereinafter referred to as "aluminum bar") of 15 mm in width x 5 mm in thickness x 60 mm in length was placed on a hot plate set at 180°C. Next, the test sheet was placed on the aluminum bar so that the lengthwise direction of the test sheet (in the case of measuring the thermal conductivity in the lengthwise direction) or the circumferential direction (in the case of measuring the thermal conductivity in the circumferential direction) was parallel to the thickness direction of the aluminum bar, and the periphery of the aluminum bar and the test sheet was covered with heat insulating material. Next, a fan for cooling was installed on the test sheet. Finally, the temperatures of the upper and lower surfaces of the test sheet and the temperatures of the upper and lower surfaces of the aluminum plate required for calculating the thermal conductivity of the test sheet were measured with thermocouples.

[0056] The measured results were substituted into the following equation to calculate the thermal conductivity. λf = ((λa x ΔTa / La) x (Lf / ΔTf) λf: thermal conductivity of the test sheet, λa: thermal conductivity of the aluminum bar, ΔTf: temperature difference between the upper and lower surfaces of the test sheet, ΔTa: temperature difference between the upper and lower surfaces of the aluminum bar, Lf: thickness of the test sheet, La: thickness of the aluminum bar

[0057] The above results confirmed that the lengthwise direction thermal conductivity / circumferential direction thermal conductivity of the test sheet (i.e., the base layer) was 1.05. From this result, it was considered that the CNTs were oriented in the lengthwise direction.

[0058] (2) Measurement of Tensile Elastic Modulus and Tensile Load at Break of Base Layer After the base layer was cut, the cut base layer was punched in the lengthwise direction of the base layer in the up and down direction of a JIS No. 3 dumbbell (JIS K6301), thereby producing a dumbbell-shaped test sheet. The dumbbell-shaped test sheet was mounted on an Autograph AGS-50A (manufactured by Shimadzu Corporation) with a chuck-to-chuck distance set to 30 mm, and the dumbbell-shaped test sheet was stretched at a stretching speed of 50 mm / min in accordance with a conventional method, and the tensile elastic modulus and the tensile load at break were measured in accordance with the method prescribed in JIS P8113. As a result, the tensile elastic modulus was 982 kgf / mm 2 , the tensile load at break was 7.2 kgf, and the product of the tensile elastic modulus and the tensile load at break was 7070.4 kgf 2 / mm 2 .

[0059] (3) Paper Pulling Test at Jamming The fixing belt was assembled into the fixing unit, and the fixing unit was repeatedly jammed to confirm that the fixing belt was not easily damaged even if the paper was forcibly pulled out. Example 2

[0060] Except as described below, the fixing tape was obtained using the same method as in Example 1: CNTs were added to a polyamic acid solution such that the total volume of the solid components (i.e., polyimide resin) and CNTs relative to the polyamic acid solution was 21.0 parts by volume, and the CNT-containing polyamic acid solution was further coated onto the outer surface of the mold to make the base layer thickness 60 μm. Additionally, the following was obtained.

[0061] The thermal conductivity of the base layer of the resulting fixing tape is 1.45 W / mK, the ratio of its longitudinal thermal conductivity to its circumferential thermal conductivity is 1.05, and its tensile modulus of elasticity is 976 kgf / mm². 2 The tensile load at fracture of the substrate is 6.6 kgf, and the product of the tensile modulus of elasticity and the tensile load at fracture is 6441.6 kgf. 2 / mm 2 In addition, the fixing belt was assembled into the fixing unit, and the fixing unit was repeatedly subjected to paper jams to confirm that the fixing belt was not easily damaged even if the paper was forcibly pulled out. Example 3

[0062] Except as described below, the fixing tape was obtained in the same manner as in Example 1: the polyamic acid solution was replaced with the following polyamic acid solution (the polyamic acid is polyamic acid A of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) / p-phenylenediamine (PPD) and polyamic acid B of pyromellitic tetracarboxylic dianhydride (PMDA) / 4,4'-diaminodiphenyl ether (ODA) in a mass ratio of polyamic acid A: polyamic acid B = 80:20, with a solid content of 17.0 parts by mass), CNTs were added to the polyamic acid solution so that the total volume of the solid content (i.e., polyimide resin) and CNTs relative to the polyamic acid solution was 26.0 parts by volume, and the CNT-containing polyamic acid solution was further coated on the outer surface of the mold to make the thickness of the base layer 70 μm.

[0063] The thermal conductivity of the base layer of the resulting fixing tape is 1.85 W / mK, the ratio of its longitudinal thermal conductivity to its circumferential thermal conductivity is 1.06, and its tensile modulus of elasticity is 932 kgf / mm². 2 The tensile load at fracture of the substrate is 5.6 kgf, and the product of the tensile modulus of elasticity and the tensile load at fracture is 5219.2 kgf. 2 / mm 2 In addition, the fixing belt was assembled into the fixing unit, and the fixing unit was repeatedly subjected to paper jams to confirm that the fixing belt was not easily damaged even if the paper was forcibly pulled out. Example 4

[0064] A fixing belt was obtained in the same manner as in Example 3, except that the CNT was added to the polyamide acid solution so as to be 30.0 parts by volume relative to the total volume of the solid content (i.e., the polyimide resin) of the polyamide acid solution and the CNT, and further the CNT-containing polyamide acid solution was applied to the outer surface of the mold so that the thickness of the base layer was 70 μm.

[0065] The thermal conductivity of the base layer of the obtained fixing belt was 2.20 W / mK, the length direction thermal conductivity / circumferential direction thermal conductivity of the base layer was 1.07, the tensile elastic modulus of the base layer was 923 kgf / mm 2 , the tensile load at the time of breakage of the base layer was 5.4 kgf, and the product of the tensile elastic modulus and the tensile load at the time of breakage of the base layer was 4984.2 kgf 2 / mm 2 . Further, the fixing belt was assembled into a fixing device, and the fixing device was repeatedly subjected to paper jam, and it was confirmed that even if the paper was forcibly pulled out, the fixing belt was not easily broken. Example 5

[0066] A fixing belt was obtained in the same manner as in Example 1, except that the polyamide acid solution was replaced with the following polyamide acid solution (polyamide acid was only 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) / p-phenylenediamine (PPD) polyamide acid, solid content 18.8 parts by mass), the CNT was added to the polyamide acid solution so as to be 15.5 parts by volume relative to the total volume of the solid content (i.e., the polyimide resin) of the polyamide acid solution and the CNT, and further the CNT-containing polyamide acid solution was applied to the outer surface of the mold so that the thickness of the base layer was 80 μm.

[0067] The thermal conductivity of the base layer of the obtained fixing belt was 1.00 W / mK, the length direction thermal conductivity / circumferential direction thermal conductivity of the base layer was 1.06, the tensile elastic modulus of the base layer was 1013 kgf / mm 2 , the tensile load at the time of breakage of the base layer was 10.2 kgf, and the product of the tensile elastic modulus and the tensile load at the time of breakage of the base layer was 10332.6 kgf 2 / mm 2 . Further, the fixing belt was assembled into a fixing device, and the fixing device was repeatedly subjected to paper jam, and it was confirmed that even if the paper was forcibly pulled out, the fixing belt was not easily broken. Example 6

[0068] A fixing belt was obtained in the same manner as in Example 1, except that the polyamic acid solution was replaced with a polyamic acid solution (polyamic acid being a polyamic acid in which polyamic acid A of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) / p-phenylenediamine (PPD) and polyamic acid B of pyromellitic dianhydride (PMDA) / 4,4'-diaminodiphenyl ether (ODA) were blended at a mass ratio of polyamic acid A:polyamic acid B = 70:30, solid content 17.0 parts by mass) to which CNT was added so as to be 32.0 parts by volume relative to the total volume of the solid content (i.e., the polyimide resin) of the polyamic acid solution and the CNT, and the polyamic acid solution containing the CNT was further applied to the outer surface of the mold so that the base layer had a thickness of 70 μm.

[0069] The base layer of the resulting fixing belt had a thermal conductivity of 2.55 W / mK, a lengthwise thermal conductivity / circumferential thermal conductivity of 1.08, a tensile elastic modulus of 903 kgf / mm 2 , a tensile load at break of 4.6 kgf, and a product of the tensile elastic modulus and the tensile load at break of 4153.8 kgf 2 / mm 2 . Further, the fixing belt was assembled into a fixing device, and the fixing device was repeatedly subjected to paper jamming, and it was confirmed that even if the paper was forcibly pulled out, the fixing belt was not easily damaged.

[0070] (Comparative Example 1) A fixing belt was obtained in the same manner as in Example 1, except that the polyamic acid was replaced with a polyamic acid solution (polyamic acid being a polyamic acid in which polyamic acid A of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) / p-phenylenediamine (PPD) and polyamic acid B of pyromellitic dianhydride (PMDA) / 4,4'-diaminodiphenyl ether (ODA) were blended at a mass ratio of polyamic acid A:polyamic acid B = 80:20, solid content 18.8 parts by mass), the CNT was replaced with boron nitride (MBN-010T manufactured by Mitsui Chemicals, Inc.), and the boron nitride was added to the polyamic acid solution so as to be 40.0 parts by volume relative to the total volume of the solid content (i.e., the polyimide resin) of the polyamic acid solution and the boron nitride, and the polyamic acid solution was stirred until the boron nitride became uniform, and the polyamic acid solution containing the boron nitride was further applied to the outer surface of the mold so that the base layer had a thickness of 60 μm.

[0071] The base layer of the resulting fixing belt had a thermal conductivity of 1.05 W / mK, a lengthwise thermal conductivity / circumferential thermal conductivity of 1.00, a tensile elastic modulus of 915 kgf / mm 2The tensile load at break of the base layer is 4.0 kgf, and the product of the tensile elastic modulus of the base layer and the tensile load at break is 3660.0 kgf 2 / mm 2 In addition, when the fixing belt is assembled into the fixing device, the fixing device repeatedly occurs paper jam, forcibly pulls out the paper, and the fixing belt is damaged.

Claims

1. A polyimide tube, wherein, the polyimide tube is a polyimide tube containing a polyimide resin, the polyimide resin contains a carbon nanotube, the thermal conductivity in the film thickness direction of the polyimide tube is 1.00 W / mK or more, the thermal conductivity in the length direction of the polyimide tube / the thermal conductivity in the circumferential direction is 1.05 or more, The product of the tensile elastic modulus in the length direction of the polyimide tube and the tensile load at the time of breaking in the tensile test is 4000.0 kgf 2 / mm 2 The above.

2. The polyimide tube according to claim 1, wherein, the thermal conductivity in the film thickness direction of the polyimide tube is 3.20 W / mK or less.

3. The polyimide tube according to claim 1, wherein, the thermal conductivity in the length direction of the polyimide tube / the thermal conductivity in the circumferential direction is 1.60 or less.

4. The polyimide tube according to claim 1, wherein, The product of the tensile elastic modulus in the length direction of the polyimide tube and the tensile load at the time of breaking in the tensile test is 13000 kgf 2 / mm 2 Below.

5. The polyimide tube according to claim 1, wherein, the polyimide resin is a blend of a first polyimide resin containing units derived from 3,3',4,4'-diphenyltetracarboxylic dianhydride and units derived from p-phenylenediamine and a second polyimide resin containing units derived from pyromellitic dianhydride and units derived from 4,4'-diaminodiphenyl ether, the mass ratio of the first polyimide resin to the second polyimide resin is in the range of 70:30 or more and 100:0 or less.

6. The polyimide tube according to any one of claims 1 to 4, wherein, The tensile elastic modulus in the length direction of the polyimide tube is 700 kgf / mm 2 The above.

7. The polyimide tube according to claim 5, wherein, The tensile elastic modulus in the length direction of the polyimide tube is 1200 kgf / mm 2 The following.

8. A fixing belt using the polyimide tube according to claim 1 as a base layer.