JP2006301196A - Seamless belt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a seamless belt which has superior flexibility and rigidity and high heat conductivity enough to compensate for a thermal deficiency of a belt, excellent slidability for maintaining excellent rotation properties of the belt, and wrinkle preventive effect, and a method for manufacturing the same. <P>SOLUTION: The seamless belt made of polyimide contains a heat-conductive insulating inorganic filler and fluorine resin powder, wherein the heat-conductive insulating inorganic filler of 10 to 40 wt.% is contained in a polyimide-resin-based composition and the fluorine resin powder of 0.1 to 20 wt.% is contained in the polyimide-resin-based composition, the belt external diameter decreases from both the ends to the center part, and an external diameter difference between both the belt ends and the center part is in the rang of 0.03 to 0.5%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a seamless belt that can be used as a transfer fixing belt, a fixing belt, or the like in an electrophotographic image forming apparatus such as a copying machine, a laser beam printer, or a facsimile machine. More specifically, the present invention relates to a belt member that is excellent in preventing wrinkles and fixing defects of a conveyed sheet such as copy paper when the copying speed is increased.

  Conventionally, as an electrophotographic recording apparatus for forming and recording an image by an electrophotographic system, a copying machine, a laser beam printer, a facsimile, and a complex machine of these are known. In this type of apparatus, a fixing method using a seamless belt is employed for the purpose of speeding up image formation and saving energy. As an example of the fixing method using the belt described above, there is a system in which the toner on the recording material is heated by a heater through a film-like belt. In this fixing method, since the heater is in contact via the film-like belt, it is heated directly, so that there is an advantage that there is almost no waiting time and power consumption is reduced. As a seamless belt used in the belt fixing method as described above, a composite seamless belt (for example, see Patent Document 1) composed of a polyimide resin inner layer and a fluororesin outer layer excellent in heat resistance and mechanical strength is known. In recent years, a method of using a belt containing an inorganic filler has been proposed for the purpose of improving thermal conductivity (see, for example, Patent Document 2). Further, an anti-crown belt having a difference in circumferential length between the center and both ends is known as a countermeasure against wrinkles of the conveyed recording material. (For example, refer to Patent Document 3).

Japanese Patent Laid-Open No. 3-130145 JP-A-7-110632 Japanese Patent No. 2625021

  In recent years, this type of device has noticeably increased the size and speed of images. With conventional belts, for example, poor toner fixing due to thermal shortage of the belt, toner peeling, belt sticking to a heater, flexibility and rigidity. Various problems such as belt breakage due to lack of toner and wrinkling of recording material (transfer paper) occur. For this reason, there is a strong demand for the production of a seamless belt having characteristics that can solve these problems simultaneously. However, even if an attempt is made to obtain a belt that satisfies all of the above characteristics at the same time, a problem in the manufacturing process that makes it impossible to remove from the mold occurs.

  Therefore, the object of the present invention is excellent in flexibility and rigidity, has thermal conductivity that can compensate for the thermal shortage of the belt, and has good slidability in order to maintain good rotation of the belt. Then, it is providing the seamless belt which has a wrinkle prevention effect, and its manufacturing method.

  In order to achieve the above-mentioned object, the present inventors diligently studied about the chemical imidization of a polyimide resin, and its components and amounts, and found that the above object can be achieved by the following seamless belt and its production method. The present invention has been completed.

  That is, the seamless belt of the present invention is a polyimide resin seamless belt containing a thermally conductive insulating inorganic filler and a fluororesin powder, and the thermally conductive insulating inorganic filler is 10 to 40 in the polyimide resin composition. % By weight, containing 0.1 to 20% by weight of fluororesin powder in the polyimide resin composition, the outer diameter of the belt is reduced from both ends toward the center, and the outer diameter difference between the ends of the belt and the center Is in the range of 0.03 to 0.5%.

  Until now, even if an attempt was made to obtain a belt that satisfies all of the above characteristics at the same time, such a seamless belt could not be obtained because of a problem in the manufacturing process that prevented the mold from being removed from the mold. In the imidation of the polyamic acid which is a polyimide resin precursor, the present inventor added a predetermined amount of catalyst to the polyamic acid solution, so that when the heated imide was converted in a reverse crown-shaped mold, the reverse crown shape was changed. It was found that the mold can be easily removed from the inverted crown mold while having it.

According to the seamless belt of the present invention, since the thermal conductivity is excellent, even if the image forming apparatus is enlarged and speeded up, the heating efficiency does not decrease, and a seamless belt with good toner fixing property can be provided. . Moreover, according to the said belt, the power consumption required for a heating is also reduced and economical efficiency is also improved. Moreover, since the fluororesin powder is contained in the polyimide resin, the slidability is improved, the good rotation of the belt can be maintained, and sticking of the belt to the heater can be prevented. In addition, since the belt has excellent mechanical properties such as flexibility and rigidity, the belt of the present invention is damaged even when the belt of the present invention is set as a fixing belt in a digital multi-function peripheral and used continuously at an increased printout speed. The durability of the belt is also improved. Furthermore, since the outer diameter of the belt is a shape (reverse crown shape) that decreases from both ends of the belt toward the center, it is possible to prevent the image forming apparatus recording material (transfer paper) from being wrinkled during toner fixing.
In addition, since the belt of the present invention has a single layer structure and can exhibit the above characteristics, the belt can be manufactured easily and at a lower cost than conventional multilayer belts. Furthermore, problems peculiar to the multilayer belt, for example, peeling or dropping of the surface layer do not occur.

  The seamless belt preferably has a conductive adhesive intermediate layer on the outer peripheral surface of the seamless belt and a release outer layer on the outer peripheral surface of the conductive adhesive intermediate layer.

  According to the belt having the intermediate layer and the release outer layer, a shielding effect against charging of the inner surface of the belt and an outer surface antistatic effect can be obtained. Moreover, the seamless belt and the peeling outer layer can be firmly bonded by the bonding effect of the intermediate layer. Furthermore, the mold release property from the mold can be improved by the mold release outer layer.

  The method for producing a seamless belt of the present invention is the above-described method for producing a seamless belt, wherein 0.04 to 1.5 molar equivalents of the repeating unit of the polyamic acid in the polyamic acid solution which is a precursor of the polyimide resin is 0.04 to 1.5 molar equivalents. A catalyst is added and mixed to form a film.

  In the imidation of the polyamic acid, the present inventor has added a predetermined amount of catalyst to the polyamic acid solution, and when heated imide conversion is performed with a reverse crown-shaped mold, the reverse crown-shaped metal has a reverse crown shape. It has been found that the mold can be easily removed from the mold, and the above-described manufacturing method has all the characteristics such as thermal conductivity, toner peelability, and wrinkle prevention effect that have been difficult until now. A belt can be manufactured.

  In the above production method, the catalyst is preferably isoquinoline. Various catalysts described later can be used for imidation of the polyamic acid in the present invention, but isoquinoline is particularly effective for forming a balance between the two in terms of flexibility and rigidity which are difficult to coexist mechanically. And is suitable for the production of a polyimide resin belt having excellent mechanical properties. In addition, when isoquinoline is used as a catalyst, it is particularly easy to remove from an inverted crown mold while having an inverted crown shape.

  The seamless belt of the present invention is a seamless belt made of a polyimide resin containing a heat conductive insulating inorganic filler and a fluororesin powder, and the heat conductive insulating inorganic filler is 10 to 40% by weight in the polyimide resin composition. , Containing 0.1 to 20% by weight of fluororesin powder in the polyimide resin composition, the outer diameter of the belt is reduced from both ends toward the center, and the difference in outer diameter between the ends of the belt and the center is 0. 0.03 to 0.5% of range.

  The heat conductive insulating inorganic filler is not particularly limited as long as it is an insulating inorganic powder having a high heat conductive function, and examples thereof include boron nitride, aluminum nitride, alumina, silicon force, and silicon nitride. Among these, boron nitride is preferable because it has a high heat conduction function and is chemically safe.

  Content of the said filler needs to be set to the range of 10 to 40 weight% in a polyimide resin type composition. Especially preferably, it is the range of 20 to 35 weight%. Such a range is preferable because the thermal conductivity of the seamless belt can be kept high. In addition, it is not preferable that the content of the filler is less than 10% by weight because a sufficient effect of improving thermal conductivity cannot be obtained. On the contrary, if it exceeds 40% by weight, the mechanical strength of the belt is lowered, and cracks and cracks are likely to occur, which is not preferable.

  Furthermore, the average particle diameter of the primary particles of the filler is preferably set in the range of 0.01 to 5.0 μm. More preferably, it is the range of 0.05-2.0 micrometers. Within such a range, there is little aggregation of the particles and the particles are uniformly dispersed, so that there is no variation in thermal conductivity and strength, and the strength as a fixing belt can be maintained, which is preferable. In addition, it is not preferable that the average particle size is less than 0.01 μm because irregularities are likely to occur on the inner peripheral surface and the outer peripheral surface of the obtained seamless belt due to aggregation of the particles. On the other hand, if the thickness exceeds 5.0 μm, the particles become large, and therefore unevenness due to the particles tends to occur on the inner peripheral surface and the outer peripheral surface of the obtained seamless belt. The average particle size of the primary particles of the filler can be measured by a particle size distribution measuring instrument using a light transmission centrifugal sedimentation method using, for example, a liquid ultrasonically dispersed in an organic solvent such as ethanol.

  Examples of the fluororesin powder include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene monoperfluoroalkyl vinyl ether copolymer (PFA), and ethylene-tetrafluoro. An ethylene copolymer (ETFE) etc. are mentioned. Of these, PTFE is preferable because it has high heat resistance and a small coefficient of dynamic friction.

  Content of the said fluororesin powder needs to be set to the range of 0.1-20 weight% in a polyimide resin type composition. Especially preferably, it is the range of 0.5 to 10 weight%. If the content of the fluororesin powder is less than 0.1% by weight, the effect of reducing the friction coefficient cannot be obtained, which is not preferable. On the other hand, if it exceeds 20% by weight, the elastic modulus of the belt decreases, and buckling tends to occur during use, which is not preferable.

  Furthermore, it is preferable that the average particle diameter of the said fluororesin powder is set to the range of 0.01-5.0 micrometers. More preferably, it is the range of 0.5-5.0 micrometers. Within such a range, there is little aggregation of the particles and the particles are uniformly dispersed, so that there is no variation in thermal conductivity and strength, and the strength as a fixing belt can be maintained, which is preferable. In addition, it is not preferable that the average particle size is less than 0.01 μm because irregularities are likely to occur on the inner peripheral surface and the outer peripheral surface of the obtained seamless belt due to aggregation of the particles. On the other hand, if the thickness exceeds 5.0 μm, the particles become large, and therefore unevenness due to the particles tends to occur on the inner peripheral surface and the outer peripheral surface of the obtained seamless belt. In addition, the measuring method of the average particle diameter of the said fluororesin powder is based on the measuring method of the primary particle average particle diameter of the said heat conductive insulating inorganic filler.

  The seamless belt of the present invention has a shape in which both ends of the belt have a maximum diameter and become thinner (smaller in diameter) from the both ends of the belt toward the center, and the outer diameter difference between both ends of the belt and the center is 0. The range is 0.03 to 0.5%, preferably 0.1 to 0.3%. The above "the difference in the outer diameter between both ends and the center is in the range of 0.03 to 0.5%" is a percentage obtained by dividing the difference between the outer diameters at both ends and the center by the outer diameters at both ends. It means that the value indicated by is in the range of 0.03 to 0.5%. If the difference in outer diameter is less than 0.03%, the effect of preventing wrinkling of the recording material (transfer paper) is lost, which is not preferable. On the other hand, if it exceeds 0.5%, it is not preferable in the production process.

  Further, as described above, the seamless belt of the present invention is a polyimide resin seamless belt, and the polyimide used is not particularly limited. Polyimide resin is obtained by converting imide of polyamic acid, and the polyamic acid, which is a precursor of polyimide resin, is obtained by reacting approximately equimolar amounts of tetracarboxylic dianhydride or its derivative and diamine in an organic solvent. be able to.

  Examples of the tetracarboxylic dianhydride include those represented by the following general formula (I).

[式（Ｉ）中、Ｒは４価の有機基であり、芳香族、脂肪族、環状脂肪族、芳香族と脂肪族とを組み合わせたもの、またはそれらの置換された基である。]
そして、上記テトラカルボン酸二無水物の具体例としては、ピロメリット酸二無水物、３，３’，４，４’−ベンゾフェノンテトラカルボン酸二無水物、３，３’，４，４’−ビフェニルテトラカルボン酸二無水物、２，３，３’，４−ビフェニルテトラカルボン酸二無水物、２，３，６，７−ナフタレンテトラカルボン酸二無水物、１，２，５，６−ナフタレンテトラカルボン酸二無水物、１，４，５，８−ナフタレンテトラカルボン酸二無水物、２，２’−ビス（３，４−ジカルボキシフェニル）プロパン二無水物、ビス（３，４−ジカルボキシフェニル）スルホン酸二無水物、ペリレン−３，４，９，１０−テトラカルボン酸二無水物、ビス（３，４−ジカルボキシフェニル）エーテル二無水物、エチレンテトラカルボン酸二無水物等があげられるが、耐熱、寸法安定性の点から、特に、ビフェニルテトラカルボン酸二無水物（ＢＰＤＡ）等が好ましい。

[In the formula (I), R is a tetravalent organic group, and is an aromatic, aliphatic, cycloaliphatic, a combination of aromatic and aliphatic, or a substituted group thereof. ]
Specific examples of the tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′- Biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalene Tetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) propane dianhydride, bis (3,4-di Carboxyphenyl) sulfonic acid dianhydride, perylene-3,4,9,10-tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, ethylenetetracarboxylic dianhydride, etc. Fried That is, heat, from the viewpoint of dimensional stability, in particular, biphenyl tetracarboxylic dianhydride (BPDA) and the like are preferable.

Specific examples of diamines to be reacted with such tetracarboxylic dianhydrides include 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, and 3,3′-. Dichlorobenzidine, 4,4'-diaminodiphenyl sulfide-3,3'-diaminodiphenyl sulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine, 3,3'-dimethyl-4,4'-biphenyl Diamine, benzidine, 3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine, 4,4′-diaminophenylsulfone, 4,4′-diaminodiphenylsulfide, 4,4′-diaminodiphenylpropane, 2,4 -Bis (β-amino-tert-butyl) toluene, bis (p-β-amino-tertiary Tilphenyl) ether, bis (p-β-methyl-δ-aminophenyl) benzene, bis-p- (1,1-dimethyl-5-amino-pentyl) benzene, 1-isopropyl-2,4-m-phenylenediamine, m-xylylenediamine, p-xylylenediamine, di (p-aminocyclohexyl) methane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, diaminopropyltetramethylene, 3-methylhepta Methylenediamine, 4,4-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2-bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2,5- Dimethylhexamethyle Diamine, 2,5-dimethylheptamethylenediamine, 3-methylheptamethylenediamine, 5-methylnonamethylenediamine, 2,11-diaminododecane, 2,17-diaminoeicosadecane, 1,4-diaminocyclohexane, 1, 10-diamino-1,10-dimethyldecane, 1,12-diaminooctadecane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, piperazine, H ₂ N (CH ₂ ) ₃ O (CH ₂ ) ₂ OCH ₂ NH ₂ , H ₂ N (CH ₂ ) ₃ S (CH ₂ ) ₃ NH ₂ , H ₂ N (CH ₂ ) ₃ N (CH ₃ ) (CH ₂ ) ₃ NH _2, etc. In view of heat resistance and dimensional stability, p-phenylenediamine (PDA) is particularly preferable.

  One or more of these tetracarboxylic dianhydrides or their derivatives and diamines can be appropriately selected and reacted.

  The organic polar solvent used when the tetracarboxylic dianhydride and diamine are reacted has a dipole whose functional group does not react with tetracarboxylic dianhydride or diamine. It must be inert to the system and act as a solvent for the product polyamic acid. Moreover, it must act as a solvent for at least one of the reaction components, preferably both. As the organic polar solvent, N, N-dialkylamides are particularly useful, and examples thereof include N, N-dimethylformamide and N, N-dimethylacetamide, which have low molecular weight. They can be easily removed from the polyamic acid and the polyamic acid molded article by evaporation, displacement or diffusion.

  Other organic polar solvents include N, N-diethylformamide, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethylsulfoxide, hexamethylphosphortriamide, N-methyl-2-pyrrolidone, pyridine , Tetramethylene sulfone, dimethyltetramethylene sulfone and the like. These may be used alone or in combination.

  Furthermore, phenols such as cresol, phenol and xylenol, benzonitrile, dioxane, butyrolactone, xylene, cyclohexane, hexane, benzene, toluene and the like can be mixed alone or in combination with the organic polar solvent. However, it is preferable to avoid the use of water in order to prevent lowering the molecular weight due to hydrolysis of the produced polyamic acid.

  The seamless belt of the present invention is obtained by adding and mixing a specific amount of catalyst to the above-mentioned polyamic acid solution containing a thermally conductive insulating inorganic filler and fluororesin powder, and developing it by an appropriate method, and heating the solvent of the developing layer. It is obtained by the method of removing by drying. In this case, the amount of the catalyst added is 0.04 to 1.5 molar equivalents, preferably 0.05 to 0.00 mol, with respect to 1 molar equivalent of the polyamic acid repeating unit of the polyamic acid solution which is a polyimide resin precursor. 3 molar equivalents. When the addition amount of the catalyst is less than 0.04 molar equivalent, the effect of the catalyst is not sufficient, and even when the addition amount exceeds 1.5 molar equivalent, the improvement of the catalyst effect is not observed.

  Examples of the catalyst include trimethylamine, triethylamine, triethylenediamine, tributylamine, dimethylaniline, pyridine, α-picoline, β-picoline, γ-picoline, isoquinoline, lutidine and other tertiary amines, 1,5-diazabicyclo [4.3. Organic bases such as .0] nonene-5,1,4-diazabicyclo [2.2.2] octane, 1,8-diazabicyclo [5.4.0] undecene-7. Isoquinoline is particularly preferred from the viewpoints of releasability from the mold and flexibility and rigidity of the belt.

  The polyamic acid solution is preferably obtained by reacting the tetracarboxylic dianhydride (x) and the diamine (y) in an organic polar solvent for about 0.5 to 10 hours. That is, if it is less than 0.5 hours, the reaction becomes insufficient, and even if it exceeds 10 hours, no further effect can be obtained. The monomer concentration during the reaction [concentration of (x) + (y) in the solvent] can be set according to various factors, but is usually 5 to 30% by weight. Moreover, it is preferable to set reaction temperature to 80 degrees C or less.

  In addition, when tetracarboxylic dianhydride and diamine are reacted in an organic polar solvent in this way, the viscosity of the solution increases with the progress of the reaction. In the present invention, the logarithmic viscosity (η) is 0. It is preferable to use a polyamic acid solution having a viscosity of 5 or more. That is, when formed using a polyamic acid solution having a logarithmic viscosity (η) of 0.5 or more, the reliability against heat degradation (heat resistance) is particularly excellent compared to that having a logarithmic viscosity of less than 0.5. There are advantages. The logarithmic viscosity (η) is a value calculated by the following mathematical formula (1) by measuring the dropping time of the polyamic acid solution and the solvent using a capillary viscometer.

このようなポリアミド酸溶液は、使用する際に、粘度が高い場合には適当な溶媒で希釈して粘度を低くして用いる。例えば、ポリアミド酸溶液の粘度は、塗布厚み、シリンダーの内径、溶液温度、走行体の形状等に応じて設定されるが、通常、０．１〜１００００ポイズ（塗布作業時の温度でＢ型粘度計にて測定）に設定される。

When such a polyamic acid solution has a high viscosity, it is diluted with an appropriate solvent to lower the viscosity. For example, the viscosity of the polyamic acid solution is set according to the coating thickness, the cylinder inner diameter, the solution temperature, the shape of the traveling body, etc., but is usually 0.1 to 10,000 poise (the B-type viscosity at the temperature during the coating operation). Measured with a meter).

  The compounding of the thermally conductive insulating inorganic filler and the fluororesin powder in the polyimide resin is performed, for example, when the polyamic acid is prepared by using an appropriate dispersing machine such as a planetary mixer, a bead mill, or a three roll. The filler and the fluororesin powder can be mixed and dispersed, mixed and blended, and can be performed by an appropriate method such as a method of subjecting it to belt molding. Of course, after completion of the reaction, each may be added to the polyamic acid solution and mixed uniformly.

  As described above, a seamless belt made of polyimide resin can be obtained by appropriately developing a polyamic acid solution and forming the belt. The thickness of the belt can be appropriately determined according to the purpose of use of the polyimide resin belt. Generally, the thickness is 5 to 500 μm, especially 10 to 300 μm, especially 50 to 200 μm, depending on mechanical properties such as strength and flexibility.

  The seamless belt of the present invention preferably has a conductive adhesive intermediate layer on the outer peripheral surface of the seamless belt and a release outer layer on the outer peripheral surface of the intermediate layer.

  The material used for the conductive intermediate adhesive layer is not particularly limited as long as it is a material that can adhere the seamless belt and the release outer layer. For example, polyimide resin, polyamideimide Examples thereof include resins, polyamide-based resins, and mixtures of one or more of these resins with fluorine-based resins. Specific examples include conventionally known primers such as PR-990CL (Mitsui DuPont). be able to.

Specific examples of the conductive material contained in the conductive adhesive intermediate layer include carbon black such as ketjen black and acetylene black, inorganic compounds such as aluminum, nickel, tin oxide, and potassium titanate, polyaniline, polypyrrole, and the like. The conductive polymer represented by can be mentioned. Further, the surface resistivity of the intermediate layer is preferably 10 ⁶ Ω / □ or less.

  The material constituting the release layer is preferably a fluorine-based resin, specifically, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene. A copolymer (ETFE) etc. can be mentioned. Among these, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (FEP) is particularly preferable from the viewpoint of preventing toner contamination.

  The release outer layer may contain a conductive material in order to impart conductivity. Specific conductive materials include carbon blacks such as ketjen black and acetylene black, inorganic compounds such as aluminum, nickel, tin oxide and potassium titanate, and conductive polymers represented by polyaniline and polypyrrole. it can.

  The thicknesses of the conductive adhesive intermediate layer and the release outer layer are appropriately selected depending on the use or the design of the apparatus. Usually, the conductive adhesive intermediate layer is 0.1 to 2 μm, and the release outer layer is 5 to 50 μm. .

  The seamless belt of the present invention can be produced, for example, by the following steps.

  First, a cylindrical mold is prepared as a molding mold. A catalyst is added to and mixed with a polyamic acid solution containing a thermally conductive insulating inorganic filler and fluororesin powder, and this is applied to the inner peripheral surface of the cylindrical mold. After coating, the coating film is dried and cured until it can support at least itself, or heated until imide conversion is completed, thereby forming a seamless belt containing a thermally conductive insulating inorganic filler and fluororesin powder, The seamless belt of the present invention is obtained by peeling from the cylindrical mold. When the conductive adhesive intermediate layer and the release outer layer are formed on the belt, a resin composition (primer or the like) that forms the intermediate layer is applied to the outer peripheral surface of the belt obtained as described above. This is performed by applying a liquid containing a resin composition for forming a release outer layer on the outer peripheral surface of the intermediate layer.

  When the polyamic acid solution is used, if the solution viscosity is high, the polyamic acid solution can be used by diluting with a suitable solvent to lower the viscosity. For example, the viscosity of the polyamic acid solution is set according to the coating thickness, coating method, coating conditions, solution temperature, etc., but usually 0.1 to 10000 poise (measured with a B-type viscometer at the temperature during the coating operation) Viscosity).

  In the above manufacturing method, any cylindrical mold can be used as a molding mold as long as it has been conventionally used in the production of seamless belts. Various types such as glass, ceramics and the like are exemplified.

  As a method of applying a polyamic acid solution containing a thermally conductive inorganic filler and a fluororesin powder to a cylindrical mold, the cylindrical mold is immersed in the polyamic acid solution to form a coating film on the inner surface. After forming a film with a cylindrical die or the like, or supplying a polyamic acid solution to one end of the inner surface of the cylindrical mold, the traveling body (bullet-shaped, spherical) having a certain clearance with the cylindrical mold is caused to travel. Examples thereof include a method of rotating a cylindrical mold around an axis, supplying a polyamic acid solution to the inner surface, and forming a uniform film by centrifugal force.

  As a method of traveling the above-mentioned traveling body, in addition to the self-weight traveling method (a method in which a cylindrical mold is set up vertically and the traveling body is traveled downward by its own weight), a method using compressed air or gas explosive force, The method of pulling with a pulling wire etc. is mentioned.

  The heating temperature after the polyamic acid solution is applied to the mold can be appropriately determined. The solvent is removed by heating at a low temperature of about 80 to 200 ° C., and then the temperature is increased to about 250 to 400 ° C. It is preferable to use a multistage heating method or the like in which conversion is completed. Alternatively, the seamless belt that can be supported after low-temperature heating is peeled off to form a conductive adhesive intermediate layer or a release outer layer, and then high-temperature heating may be performed. Although the time required for heating is appropriately set according to the heating time, both the low temperature heating and the subsequent high temperature heating are usually about 20 to 60 minutes. By using such a multi-stage heating method, it is possible to prevent the generation of minute voids in the seamless belt due to the ring-closing water and solvent evaporation generated with imide conversion.

  The seamless belt thus obtained is peeled off from the cylindrical mold. Examples of a method for peeling a polyimide resin seamless belt from a cylindrical mold include a method of pressure-feeding air into a minute through-hole provided in advance on a peripheral wall surface of an end of a cylindrical mold. In addition, it is preferable to perform release treatment with a silicone resin or the like in advance on the inner peripheral surface of the cylindrical mold forming the seamless belt, which improves the peeling workability of the seamless belt.

  As a method of providing a conductive adhesive intermediate layer on the outer peripheral surface of the obtained seamless belt, it is obtained by applying a primer solution or the like, and examples thereof include methods such as roll coating, brush coating, and spray coating.

  Next, as a method of providing a release outer layer on the outer peripheral surface of the conductive adhesive intermediate layer, a method of depositing a tubular seamless belt obtained by melt extrusion on the outer surface of the conductive adhesive intermediate layer, forming a release outer layer Examples thereof include a method of coating a liquid containing the resin composition on the outer surface of the conductive adhesive intermediate layer. For example, as a method of coating a solution-like fluororesin solution, methods such as spray coating, spin coating, roll coating, brush coating, and the like are conceivable. As a procedure of application and heating, for example, after applying a fluororesin release outer layer in order to prevent generation of voids in the outer layer, after removing the solvent in the fluororesin solution, the temperature is raised above the melting point of the fluororesin. Thus, a release outer layer can be formed. At this time, the imide conversion of the base layer seamless belt may be performed simultaneously.

  In the seamless belt thus obtained, there is substantially no difference in outer diameter between the end portion and the central portion of the belt. Therefore, a seamless belt having a desired outer diameter difference is formed by the following deformation process.

The deformation process can be performed by inserting a heat-resistant core (reverse crown shape) having a required outer diameter difference, as shown in FIG. 1, into the obtained seamless belt, and heating and firing. . The material of the heat-resistant core used at this time is not particularly limited, but the linear thermal expansion coefficient is 2 × 10 ⁻⁵ cm / cm / ° C. or more in order to make it easy to pull out the core after forming the deformed seamless belt. For example, a core made of a material such as aluminum, fluorine resin, or polyimide resin is preferable. In the deformation process, it is usually preferable that the processing conditions for heating and baking are not lower than the glass transition temperature of the material forming the seamless belt and not higher than the thermal decomposition temperature. After the heat treatment, a seamless belt having a desired outer diameter difference can be obtained by cooling to room temperature and taking out from the core.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, this invention is not restrict | limited at all by this Example etc.

<Example 1>
7 g of PTFE powder (manufactured by Kitamura) and 49 g of boron nitride (manufactured by Mitsui Chemicals) are dispersed in 694 g of N-methyl-2-pyrrolidone, to which 41 g of p-phenylenediamine and 3,3 ′, 4,4′-biphenyl are dispersed. 112 g of tetracarboxylic dianhydride was dissolved (solid concentration 20 wt%) and reacted in a nitrogen atmosphere with stirring at room temperature to obtain a 3000 poise polyamic acid solution. To this solution, isoquinoline as a catalyst was added in an amount corresponding to 0.5 mol with respect to 1 mol of polyamic acid, and stirred until uniform. At this time, the boron nitride was adjusted to 35% by weight in the polyimide resin-based composition, and the fluororesin powder was adjusted to 5% by weight in the polyimide resin-based composition. After applying the above polyamic acid solution to the inner surface of a cylindrical mold having an inner diameter of 24.2 mm, the bullet-like traveling body is dropped by its own weight, then defoaming is performed to remove bubbles in the coating waist, and a uniform coating surface is obtained. Obtained. Next, the mold was heated stepwise from 150 ° C. to 200 ° C. to remove the solvent, and then peeled from the mold at room temperature to obtain a 50 μm seamless belt. A PFA dispersion (solid concentration 35%) prepared by adjusting carbon black (W311N manufactured by Lion Corporation) to 1% with respect to the fluororesin (PFA) was stirred for 12 hours to obtain a fluororesin coating solution. The seamless belt obtained as described above was coated with a conductive primer (conductive adhesive intermediate layer) by spraying, and a fluororesin (mold release outer layer) was coated thereon. The seamless belt thus obtained has a heat resistant mold having an effective length of 500 mm as shown in FIG. 1 (an opposite crown shape having an outer diameter of both ends of 24.1 mm and a central portion of 24.04 mm). ) Was fired at 400 ° C. for 20 minutes, and the ring-closing water was removed and the imide conversion completion reaction was performed to produce a seamless belt having a 10 μm fluororesin release outer layer.

  The obtained seamless belt was removable from the mold. When this was set as a fixing belt in a digital multi-function peripheral and the print speed was increased and the printout was continuously fixed, the printed material was not wrinkled and the image fixability was good. No problem occurred as a belt.

<Example 2>
1.4 g of PTFE powder (manufactured by Kitamura) and 49 g of aluminum nitride (manufactured by Mitsui Chemicals) are dispersed in 694 g of N-methyl-2-pyrrolidone, and 41 g of p-phenylenediamine and 3,3 ', 4,4' -112 g of biphenyltetracarboxylic dianhydride was dissolved (solid content concentration: 20 wt%) and reacted in a nitrogen atmosphere with stirring at room temperature to obtain a 3000 poise polyamic acid solution. At this time, the fluororesin release outer layer was formed in the same procedure as in Example 1 except that the aluminum nitride was adjusted to 35% by weight in the polyimide resin composition and the fluororesin powder was adjusted to 1% by weight in the polyimide resin composition. A seamless belt was prepared. The obtained belt was removable from the mold. When this was set as a fixing belt in a digital multi-function peripheral and the print speed was increased and the printout was continuously fixed, the fixability of the printed image was good, and no problems occurred as a belt. .

<Comparative Example 1>
When a belt was molded in the same manner as in Example 1 except that no isoquinoline was added to the polyamide solution, the belt could not be removed from the molding die, and the belt could not be obtained.

<Comparative Example 2>
A seamless belt having a 10 μm fluororesin release outer layer was obtained in the same manner as in Example 1 except that a straight mold having a diameter of 24.1 mm was used as the heat-resistant mold. When this was set as a fixing belt on a commercially available digital multi-function peripheral and printed out and fixed, wrinkles parallel to the transport direction were generated on the transfer paper.

<Comparative Example 3>
A seamless belt having a 10 μm fluororesin release outer layer was obtained in the same manner as in Example 2 except that the fluororesin powder was changed to 0.05 wt% in the polyimide resin composition. When this was set as a fixing belt on a commercially available digital multi-function peripheral and the print speed was increased to fix the printout, the belt stuck to the built-in heater, making it impossible to drive.

<Comparative example 4>
A seamless belt having a 10 μm fluororesin release outer layer was obtained in the same manner as in Example 1 except that the fluororesin powder was changed to 25 wt% in the polyimide resin composition. When this was set as a fixing belt on a commercially available digital multi-function peripheral and the printout was fixed at a higher printing speed, the belt buckled and became unable to drive.

<Comparative Example 5>
A seamless belt having a fluororesin release outer layer of 10 μm was obtained in the same manner as in Example 1 except that boron nitride was changed to 45% by weight in the polyimide resin composition. When this was set as a fixing belt on a commercially available digital multi-function peripheral and the print speed was increased to perform print-out fixing, a crack occurred at the end of the belt, and the belt was torn, making it impossible to drive.

<Comparative Example 6>
A seamless belt having a fluororesin release outer layer of 10 μm was obtained in the same manner as in Example 2 except that aluminum nitride was changed to 8% by weight in the polyimide resin composition. When this was set as a fixing belt in a commercially available digital multi-function peripheral and the print speed was increased to perform printout fixing, toner fixing failure occurred, and the toner was peeled off and dropped off.

  The results of the above examples and comparative examples are shown in Table 1.

表1に示すように、実施例にかかるシームレスベルトは、トナー転写、トナー定着性が良好で、内蔵ヒーターへの張り付きがなく、可撓性に優れ、記録材（転写紙）のシワ発生を防止できるという結果が得られた。一方、比較例にかかるシームレスベルトでは、耐熱成形型からの離型不能、シートのシワ発生、ベルトの駆動不能、トナーの定着不良等何らかの不具合が発生した。

As shown in Table 1, the seamless belt according to the example has good toner transfer and toner fixing properties, does not stick to the built-in heater, has excellent flexibility, and prevents wrinkling of the recording material (transfer paper). The result that it was possible was obtained. On the other hand, in the seamless belt according to the comparative example, some problems such as inability to release from the heat-resistant mold, generation of sheet wrinkles, inability to drive the belt, and poor toner fixing occurred.

The perspective view which shows the shape of the heat resistant core used in order to obtain the seamless belt of this invention

Claims (4)

  A seamless belt made of polyimide resin containing a heat conductive insulating inorganic filler and a fluororesin powder, wherein the heat conductive insulating inorganic filler is 10 to 40% by weight in the polyimide resin composition, and the fluororesin powder is a polyimide resin. 0.1 to 20% by weight in the system composition, the outer diameter of the belt is reduced from both ends toward the center, and the outer diameter difference between the ends of the belt and the center is 0.03 to 0.5%. A seamless belt characterized by the range.   The seamless belt according to claim 1, further comprising a conductive adhesive intermediate layer on an outer peripheral surface of the seamless belt, and a release outer layer on an outer peripheral surface of the conductive adhesive intermediate layer.   The method for producing a seamless belt according to claim 1 or 2, wherein 0.04 to 1.5 molar equivalent of a catalyst is added to 1 molar equivalent of a polyamic acid repeating unit of a polyamic acid solution which is a polyimide resin precursor. A method for producing a seamless belt, comprising mixing and forming a film.   The method for producing a seamless belt according to claim 3, wherein the catalyst is isoquinoline.

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