JP2006301255A - Conductive polyimide belt and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive polyimide belt excellent in electrical and mechanical properties and useful as an intermediate transfer belt for an image, a transfer conveyance belt for an image recording sheet, a fixing belt or the like in an electrophotographic recording apparatus, and a method for manufacturing the conductive polyimide belt. <P>SOLUTION: The conductive polyimide belt contains a conductive agent, wherein positron lifetime (τ<SB>2</SB>) at 50°C measured by a positron annihilation method is ≤0.324 ns. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive belt, and is particularly useful for an intermediate transfer belt for an image in an electrophotographic recording apparatus or the like, a transfer conveyance belt or a fixing belt for a recording sheet of the image, and the like.

In devices such as copying machines, laser printers, video printers, facsimiles and their combined machines that form and record images using electrophotographic methods, recording toner etc. on an image carrier such as a photosensitive drum for the purpose of improving the life of the device. Avoiding the method of directly fixing the image formed through the agent on the recording sheet, and transferring the image on the image carrier to the intermediate transfer belt and fixing it on the recording sheet. In addition, a transfer system that transfers the image to a recording sheet and also serves to convey the sheet has been studied.
Accordingly, if the intermediate transfer belt, the transfer conveyance belt, and the fixing belt cannot withstand the tension load caused by continuous driving, the belt is deformed and the transfer image is disturbed. In fixing, it leads to buckling and end damage. Therefore, high strength and high elasticity are required for the intermediate transfer belt, transfer conveyance belt, and fixing belt.

In addition, in order to obtain a high-quality transfer image, the electric resistance value of the intermediate transfer member is controlled within a predetermined range, and the in-plane variation (maximum resistance value and minimum resistance value) of the intermediate transfer member is small. In fixing, a surface resistance of 5 [logΩ / □] or less is required for static elimination purposes. In order to achieve these, a polyimide ring having a composition in which a semiconductive filler is added to a polyimide resin has been proposed. (For example, see Patent Document 1).
Japanese Patent Laid-Open No. 2003-213014 JP 2002-296919 A

  However, the belt has a relatively stable surface resistivity and is effective against bending fatigue when driven in a stretched state between rolls. However, when stress is applied to the belt end, It was easy to bend and tear.

  In addition, an inorganic powder-containing polyimide belt in which a tertiary amine is added to a polyimide precursor (see, for example, Patent Document 2) is improved in tear propagation strength to 3000 N / m or more, but is easy to stretch and lacks elasticity. , Buckling was easy to occur.

  On the other hand, conventionally, after dispersing a conductive agent in an organic polar solvent such as N-methyl-2-pyrrolidone, a tetracarboxylic dianhydride and a diamine component are added and reacted to form a polyamic acid solution, which is converted into an imide. And manufactured a belt. However, it has been found that in this manufacturing method, a minute gap is formed between the resin and the conductive agent, which causes electrical trapping and deteriorates the electrical characteristics and mechanical characteristics of the belt. Specifically, problems such as an increase in the electric dependency of the belt and a decrease in tear strength have occurred.

  Accordingly, an object of the present invention is to provide a conductive polyimide belt excellent in an intermediate transfer belt for an image, a transfer conveyance belt for a recording sheet of the image, a fixing belt, and the like in an electrophotographic recording apparatus having excellent electrical characteristics and mechanical characteristics, and production thereof. It is to provide a method.

In order to solve the above problems, the present inventors have conducted extensive research on the analysis and structural control of nano-order minute voids. It was found that a minute void can be controlled between the _two, and the size of the void can be specified based on the correlation between the void and the annihilation lifetime (τ ₂ ) of the positron, and the present invention has been completed.

That is, the conductive polyimide belt of the present invention is a conductive polyimide belt containing a conductive agent, and the positron annihilation lifetime (τ ₂ ) at 50 ° C. measured by the positron annihilation method is 0.324 ns or less. Features.

The belt of the present invention has a small local gap between the polyimide resin and the conductive agent, has good electrical characteristics and mechanical characteristics, and ensures a good image by long-term stable driving and stable electrical characteristics of the belt in a mounted state. Can be achieved. The annihilation lifetime (τ ₂ ) of the positron is a value measured by the method shown in the examples.

  In the belt, the common logarithmic value of the surface resistivity of the belt is in the range of 1 to 14 [log Ω / □], and the difference between the common logarithmic values of the surface resistivity at an applied voltage of 100 V and 1000 V is 0.5 [ logΩ / □] or less. The belt having the electrical characteristics can prevent the occurrence of whitening and transfer dust. Further, since the voltage dependency is low, for example, a decrease in electric resistance value and an overcurrent are less likely to occur during use of the apparatus, and a reduction in belt life can be prevented. The surface resistivity is a value measured by the method shown in the examples.

  In the belt, the tear strength is preferably 6 N / mm or more. Since the belt of the present invention has good tear strength, even when stress is applied to the belt end portion, it is difficult for seating and tearing to occur. The tear strength is a value measured by the method shown in the examples.

  In the method for producing a conductive polyimide belt of the present invention, a conductive agent is dispersed in a polyamic acid diluted solution having a solid content concentration of 0.1 to 5 wt%, and then equimolar amounts of tetracarboxylic dianhydride or its derivative and a diamine component are mixed. It includes a step of adding and reacting.

  According to the production method of the present invention, the coverage of the polyamic acid on the surface of each conductive agent particle can be increased, and the generation of voids at the interface between the polyimide and the conductive agent after imide conversion can be reduced or prevented. . As a result, a belt having good electrical and mechanical properties can be manufactured.

  In the manufacturing method, the conductive agent is preferably dispersed by ultrasonic treatment at a frequency of 25 to 100 kHz. By the ultrasonic treatment, the dispersibility of the conductive agent and the coverage of the polyamic acid on the conductive agent particles can be increased, and the electrical characteristics and mechanical characteristics of the belt can be further enhanced.

  The conductive polyimide belt of the present invention has a small local gap between the polyimide resin and the conductive agent, and does not easily trap electricity when the belt is charged. For this reason, potential dependence is small, and favorable electrical characteristics can be expressed. Further, since the local gap is small, even when stress is applied to the belt end, buckling and tearing are unlikely to occur. As a result, it is possible to achieve good image securing by long-term stable driving of the belt in the mounted state and stable electrical characteristics. In the method for producing a conductive polyimide belt of the present invention, the polyamic acid coverage on the surface of the conductive agent particles can be increased by dispersing the conductive agent in the polyamic acid diluent, and in the polyimide resin and in the polyimide resin and the conductive agent. It is possible to reduce the generation of local voids between them or the size of local voids.

  Hereinafter, the present invention will be described in detail.

  In the conductive polyimide belt of the present invention, the polyimide used is not particularly limited. Polyimide resin is obtained by converting polyamic acid into an imide, and polyamic acid, which is a precursor of polyimide resin, can be obtained by reacting tetracarboxylic dianhydride or its derivative with approximately equimolar amount of diamine in an organic solvent. it can.

  Specific examples of the tetracarboxylic dianhydride forming the polyamic acid include pyromellitic dianhydride (PMDA), 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) propane dianhydride Bis (3,4-dicarboxyphenyl) sulfone dianhydride, berylene-3,4,9,10-tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, Examples include ethylene tetracarboxylic dianhydride.

  Examples of the diamine include 4,4′-diaminodiphenyl ether (DDE), 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, 3,3′-dichlorobenzidine, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenylsulfone, 1,5-diaminonaphthalene, m-phenylenediamine, p-phenylenediamine (PDA), 3,3′-dimethyl-4,4′-biphenyldiamine, benzidine, 3,3 ′ -Dimethylbenzidine, 3,3'-dimethoxybenzidine, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylpropane, 2,4-bis (β-amino-tert-butyl) toluene, bis (p- β-amino-tert-butylphenyl) ether, bis (p-β-methyl-6-amino) Phenyl) 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-methylheptamethylenediamine, 4,4-dimethylheptamethylesidiamine, 2,11-diaminododecane, 1,2-bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2,5-dimethylhexamethylenediamine, 2,5-dimethylheptamethylene Diamine, 3 Methylheptamethylenediamine, 5-methylnonamethylenediamine, 2,17-diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10-dimethyldecane, 1,12-diaminooctadecane, 2, 2-bis [4- (4-aminophenoxy) phenyl] propane and the like can be mentioned.

  In addition, as a solvent for polymerizing and diluting the above tetracarboxylic dianhydride and diamine, an appropriate solvent can be used, but a polar solvent is preferable from the viewpoint of solubility, dispersibility of carbon black, and the like. Can be used. N, N-dialkylamides are useful as examples of the polar solvent, and examples thereof include N, N-dimethylformamide and N, N-dimethylacetamide, which have low molecular weight.

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

  The conductive polyimide belt of the present invention contains a conductive agent in order to obtain conductivity. In this case, the common logarithmic value of the surface resistivity of the belt is preferably in the range of 1 to 14 [log Ω / □], and more preferably in the range of 10 to 12 [log Ω / □]. For example, when used as an intermediate transfer belt, white spots occur when the surface resistivity is too smaller than the above range, and transfer dust tends to occur when the surface resistivity is too large. Further, the difference (voltage dependency) between the common logarithm values of the surface resistivity at an applied voltage of 100 V and 1000 V is preferably 0.5 [logΩ / □] or less, and more preferably 0.4 [logΩ / □] or less. If the difference between the common logarithmic values exceeds 0.5 [log Ω / □], for example, a decrease in electrical resistance or an overcurrent may occur during use of the apparatus, leading to a reduction in belt life.

  Specific examples of the conductive agent include inorganic compounds such as carbon black, aluminum, nickel, tin oxide, and potassium titanate, and conductive polymers represented by polyaniline, polypyrrole, etc. From this viewpoint, carbon black is preferable.

Examples of the carbon black used in the present invention include channel black, furnace black, ketjen black, acetylene black, and the like. These can be used alone or a plurality of types of carbon blacks can be used in combination. The type of these carbon blacks can be appropriately selected depending on the intended conductivity, and can be selected from medium resistance to high resistance range (surface resistivity 10 ⁸ to 10 ¹⁴ [Ω / □], such as an intermediate transfer belt and a transfer conveyance belt. , Volume resistivity 10 ⁸ to 10 ¹⁴ [Ω · cm]), when channel resistance is required, channel black or furnace black is particularly preferably used. Depending on the application, oxidation such as oxidation treatment or graft treatment may be used. It is preferable to use one that prevents deterioration or one that has improved dispersibility in a solvent.

  The carbon black content is appropriately determined depending on the purpose and the type of carbon black to be added. As a functional belt for an image forming apparatus, from the viewpoint of mechanical strength, the polyimide resin solid content 3 to 40% by weight, and more preferably 3 to 30% by weight.

  Specifically, as the furnace black, “Special Black 550”, “Special Black 350”, “Special Black 250”, “Special Black 100”, “Printex 35”, “Print Mitsubishi” manufactured by Degussa Huls, Inc. “MA 7”, “MA 77”, “MA 8”, “MA 11”, “MA 100”, “MA 100R”, “MA 220”, “MA 230”, manufactured by Cabot Corporation, “MONARCH” 1300 "," MONARCH 1100 "," MONARCH 1000 "," MONARCH 900 "," MONARCH 880 "," MONARCH 800 "," MONARCH 700 "," MOGUL 1 "," REGAL 400R "," VULCAN XC-72R "and the like, and" Color Black FW200 "," Color Black FW2 "," Color Black FW2V "," Color Black FW1 "," Color Black " “Special Black 6”, “Color Black S170”, “Color Black S160”, “Special Black 5”, “Special Black 4”, “Special Black 4A”, “Printex 150T”, “Printex P” "Printex 140U", "Printex 140V", etc. are mentioned.

The conductive polyimide belt of the present invention has a positron annihilation lifetime (τ ₂ ) at 50 ° C. measured by a positron annihilation method of 0.324 ns or less, preferably 0.317 to 0.323 ns. If the annihilation lifetime (τ ₂ ) of the positron in the belt exceeds 0.324 ns, the mechanical and electrical characteristics of the belt become unstable.

Here, the positron annihilation method measures the time (positron annihilation lifetime) from positron (e ⁺ ) incidence to annihilation (positron annihilation lifetime), and the size and density of vacancies and local voids existing in the material. Is a method of measuring. A positron is an antiparticle of an electron, and is an elementary particle having the same mass as an electron and a positive charge. It is known that when a positron encounters an electron in a molecular crystal or an amorphous solid, an electron-positron pair may be formed by Coulomb force and then disappear (for example, Doyama et al., Materia, 35, No. 2, pp 91-173 (1996), The TRC NEWS No. 80 (Jul. 2002)).

This positron-electron pair exhibits a particle-like behavior, which is called positronium. There are two types of positronium: para-positronium (p-Ps), in which the spins of a pair of electrons and positrons are parallel, and ortho-positronium (o-Ps), which are antiparallel. When a positron is injected into the polymer, the positron (e ⁺ ) may combine with one of the electrons ejected in the polymer to form o-Ps. e ⁺ and o-Ps are trapped in a portion having a low electron density in the polymer material, that is, a local void in the polymer, and overlap with the electron cloud emitted from the void wall and disappear. When e ⁺ or o-Ps is present in a void in the polymer, the size of the void and the extinction lifetime of e ⁺ or o-Ps are in an inversely proportional relationship. That is, when the void is small, the overlap between e ⁺ and o-Ps and surrounding electrons becomes large, and the positron annihilation lifetime becomes short. On the other hand, if the gap is large, the probability that e ⁺ or o-Ps overlaps with other electrons that ooze out from the gap wall and disappears becomes lower, and the annihilation lifetime of e ⁺ and o-Ps becomes longer. Therefore, the size of the local voids in the polymer resin can be evaluated by measuring the extinction lifetime of e ⁺ and o-Ps.

For the measurement of positron annihilation lifetime used radioactive isotopes ^{22 Na} well as positron source. ²² Na emits positrons and 1.28 MeV gamma rays simultaneously when β ⁺ decays to ²² Ne. The positron incident on the polymer emits 511 keV gamma rays through an annihilation process. Therefore, the annihilation lifetime of the positron can be obtained by measuring the time difference between the 1.28 MeV γ ray and the 511 kev γ ray as the end signal.

  In the present invention, the tear strength of the belt is preferably 6 N / mm or more, and more preferably 6.2 N / mm or more. When the tear strength is less than 6 N / mm, the end portion is likely to tear when the belt is driven.

  In this invention, it is preferable that a tensile elasticity modulus is 4000 Mpa or more, More preferably, it is 4800 Mpa or more. When the tensile elastic modulus is less than 4000 MPa, the elongation percentage of the belt becomes high and the dimensional stability becomes poor. When the tensile elastic modulus is incorporated and operated in the image forming apparatus, the belt gradually expands and image unevenness occurs.

  Next, the manufacturing method of the electroconductive polyimide belt of this invention is demonstrated. In the present invention, the belt is preferably a seamless type, but is not limited thereto.

  In the conductive polyimide belt of the present invention, a conductive agent is dispersed in a polyamic acid diluted solution, and then an equimolar amount of tetracarboxylic dianhydride or a derivative thereof and a diamine component are added to the polyamic acid diluted solution to cause a reaction. It can be obtained by imide conversion.

  The polyamic acid diluted solution is not particularly limited as long as it is polymerized from tetracarboxylic dianhydride or the like or diamine, but the solid content concentration is preferably 0.1 to 5 wt%, more preferably 0.8. It is 3 to 3 wt%. If the solid content concentration is less than 0.1 wt%, the coverage of the polyamic acid on the surface of each conductive agent is reduced, and voids are likely to be generated at the interface between the polyimide and the conductive additive after imide conversion. Properties and mechanical properties are degraded. On the other hand, if it exceeds 5 wt%, the solution viscosity also becomes high, the mechanical dispersion means does not work effectively, processing unevenness of the polyamic acid with respect to all the conductive agents occurs, and as a result, the coverage decreases.

  Before dispersing the conductive agent such as carbon black used in the present invention in the dilute polyamic acid solution, a dispersant can be added for the purpose of improving the dispersibility and improving the affinity with the conductive agent. The dispersant is not particularly limited as long as it meets the object of the present invention. For example, a dispersion stabilizer such as a polymer dispersant, a surfactant, or an inorganic salt can be used.

  Examples of the polymer dispersant include poly (N-vinyl-2-pyrrolidone), poly (N, N′-diethylacrylazide), poly (N-vinylformamide), poly (N-vinylacetamide), poly (N— Vinylphthalamide), poly (N-vinylsuccinamide), poly (N-vinylurea), poly (N-vinylpiperidone), poly (N-vinylcaprolactam), poly (N-vinyloxazoline), etc. Alternatively, a plurality of polymer dispersants can be added.

  Surfactants include carboxylic acid type, sulfate type, sulfonic acid type anionic surfactants, quaternary ammonium types, aliphatic amine types, imidazolinium type cationic surfactants, ether amine oxide types. Glycine type, betaine type amphoteric surfactants, ether type, ester type, amino ether type, ether ester type, alkanolamide type nonionic surfactants.

  Examples of the mechanical dispersion method of the conductive agent such as carbon black include ultrasonic waves, a ball mill, a sand mill, a basket mill, a three roll mill, a planetary mixer, a bead mill, and a homogenizer.

  Among these, it is particularly preferable to disperse by ultrasonic waves. Since the conductive agent does not take a share, it is preferable that the shape change is small and the particle size distribution variation is small. Moreover, the permeability and adsorbability of the diluted polyamic acid solution to the surface of the conductive agent are also good. The frequency is preferably 25 kHz to 100 kHz. More preferably, it is 39 to 41 kHz. If it is less than 25 kHz, the process varies, and if it exceeds 100 kHz, it is difficult to obtain a cavitation effect, so that the coverage with the polyamic acid decreases.

  The polyamic acid solution, which is a polyimide precursor solution, can be obtained by adding approximately equimolar amounts of tetracarboxylic dianhydride or its derivative and a diamine component to the polyamic acid diluted solution and allowing them to react. The monomer concentration (concentration of acid dianhydride and diamine in the solvent) in the polyamic acid solution is appropriately set according to various conditions, but is preferably 5 to 30% by weight. Moreover, it is preferable to set reaction temperature to 80 degrees C or less, Especially preferably, it is 5-50 degreeC. The polymer component of the polyamic acid solution may be copolymerized or blended with the above acid dianhydride and diamine component as long as the object of the present invention can be achieved.

  The conductive polyimide belt of the present invention can be obtained by removing the solvent of the polyamic acid solution by heating, removing dehydrated ring-closing water, and completing the imide conversion reaction.

  For the imide conversion, either a high temperature heating method or a low temperature heating method in which a dehydrating agent and a reagent showing a catalytic function are added to the polyamic acid solution may be used. Examples of the heating method include a method of passing through a heating furnace and a method of blowing heating air, but the method is not particularly limited, and examples of the heating furnace include a radial type and a circulating air type. Examples of the formation include a hot air fan, a heating roll, and a far infrared heater. Moreover, the method of winding a coil around a metal mold | die and heating a metal mold | die directly by induction heating is also mentioned.

  Examples of the dehydrating agent include organic carboxylic acid anhydrides, N, N′-dialkylcarbodiimides, lower fatty acid halides, halogenated lower fatty acid anhydrides, arylphosphonic acid dihalides, and thionyl halides. Among these, An organic carboxylic acid anhydride is particularly preferable.

  The organic carboxylic acid anhydride includes acetic anhydride, propionic acid anhydride, butyric acid anhydride, valeric acid anhydride, and a mixture of these intermolecular anhydrides and organic carboxylic acid anhydrides. Also, aromatic monocarboxylic acids such as anhydrides such as benzoic acid and naphthoic acid, mixtures thereof and organic carboxylic acid anhydrides, and carbonic acid, formic acid and aliphatic ketene anhydrides, mixtures thereof and organic carboxylic acids. Examples of the acid anhydride include acetic anhydride.

  Examples of the reagent that exhibits a catalytic function for the dehydration reaction include imidazole, secondary amine, and tertiary amine, and those having a pKb of 10 or less are particularly preferable. Specific examples of the catalyst include 1,4-diazabicyclo [2.2.2] octane, 2-phenylimidazole, imidazole, isoquinoline, etc. Among these, 2-phenylimidazole has a high boiling point. Is preferable. The addition amount of the catalyst is preferably 0.01 to 5 molar equivalents, more preferably 0.1 to 1 molar equivalents relative to 1 molar equivalent of the polyamic acid in the polyamic acid solution. Further, these catalysts are effective as an imidization accelerator at a low temperature even in heat imidization without using a dehydrating agent.

  Examples that specifically illustrate the structure and effects of the present invention will be described below. The test / evaluation items in Examples and the like were measured as follows.

<Evaluation test method>
1. Surface resistivity For surface resistivity of 0 to 6th power, a four-probe probe (MCP-TP03P) connected to Loresta-GP (Mitsubishi Chemical) was pressed against the belt surface for measurement. For the surface resistivity of 6 to 15th, a ring probe (UR) connected to HYSTA-UP (Mitsubishi Chemical) was pressed against the belt surface for measurement. After 10 seconds of applied voltage of 100 V or 1000 V, the surface resistivity was measured under measurement conditions of 20 ± 5 ° C. and 65 ± 20% RH, and the surface resistivity was shown as a common logarithmic value.
2. Tensile modulus According to JIS K 7127, the measurement was performed using an Orientec UTM1000 Tensilon (manufactured by Orientec) at a chuck interval of 30 mm and a tensile speed of 100 mm / min. As a test piece, a punched piece with a JIS K 6301 No. 3 dumbbell was used. The tensile modulus was calculated from the slope of the maximum tangent line of the stress-strain curve.
3. Tear strength The tear strength was determined according to the JIS K 7128-1 trouser tear method. A test piece having a length of 150 mm and a width of 75 mm with a slit of 75 ± 1 mm was measured with an Orientec UTM1000 Tensilon (manufactured by Orientec) at a tensile speed of 20 mm / min. The value obtained by dividing (maximum stress + minimum stress) / 2 (N) by the polyimide thickness (mm) was taken as the tear strength.
4). Positron annihilation lifetime by the positron annihilation method The positron lifetime was measured in a fast-fast coincidence system using the PATFIT and MELT programs. One gamma ray detector measures 1.28 MeV gamma rays emitted simultaneously with positron emission, and uses this as a start signal, and the other gamma ray detector measures 511 keV annihilation gamma rays and outputs this as an end signal. It was. The measurement was performed under the following conditions.
Positron beam source: ²² NaCl (intensity 0.6 MBq)
Gamma ray detector: barium fluoride scintillator and photomultiplier tube Measurement temperature: normal temperature (298K), in vacuum Count: 1,000,000
Sample size: Two pieces of belt pieces of 1.2cm x 1.2cm x 1mm are used (measured in a vacuum vessel with a positron beam source sandwiched between them)
The obtained time spectrum is represented by the following formula (1) assuming the presence of three exponential function components.

によって解析し、消滅寿命の短いものからτ_１、τ_２、τ_３、それに応じた強度をＩ_１、Ｉ_２、Ｉ_３（Ｉ_１+Ｉ_２+Ｉ₃＝１００％）として、τ_２を算出した。前述の陽電子消滅寿命の機構を考慮すると、τ₁、τ₂およびτ_３は、それぞれｐ−Ｐｓ、ｅ⁺およびｏ−Ｐｓの消滅寿命を反映していると考えられる。

Were analyzed by _one from those short annihilation lifetime τ, τ _2, τ _3, the intensity as the _{I 1, I 2, I 3} (I 1 + I 2 + I 3 = 100%) corresponding thereto, the tau ₂ Calculated. Considering the mechanism of the positron annihilation lifetime described above, it is considered that τ ₁ , τ _2, and τ ₃ reflect the annihilation lifetimes of p-Ps, e ^+, and o-Ps, respectively.

<Example 1>
N-methyl-2-pyrrolidone (NMP) 23.4 g is added to 9 g of a polyamic acid solution (solid content 18 wt%, U-varnish-S (manufactured by Ube)), and a polyamic acid diluted solution with a solid content concentration of 0.5 wt% is added. It was prepared, 16 g of Vulcan (XC-72, manufactured by Cabot) was added thereto, and sonication was performed at a frequency of 40 kHz for 1 hour. Subsequently, 0.2 mol of p-phenylenediamine and approximately equimolar amount of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride were added. After thickening, 0.06 mol of 2-phenylimidazole was added, and the mixture was heated with stirring. Carbon black 18 wt% (carbon black solid content weight / (carbon black solid content weight + polyimide solid content weight) × 100), solid A conductive polyamic acid solution having a content of 20 wt% ((carbon black solid content weight + polyimide solid content weight) / total weight × 100) was obtained. The conductive polyamic acid solution was applied to the inner surface of a cylindrical mold having an inner diameter of 60 mm and a length of 850 mm with a dispenser, and then rotated at 1500 rpm for 10 minutes to obtain a uniform coating surface. Thereafter, the film was formed by heating at 130 ° C. for 20 minutes and at 220 ° C. for 20 minutes while rotating at 40 rpm. A cylindrical film was taken out from the mold, replaced with a pipe, and further heated at 360 ° C. for 30 minutes for imide conversion to obtain a conductive polyimide belt. When this belt was evaluated, the annihilation lifetime (τ ₂ ) of the positron measured by the positron annihilation method was 0.320 to 0.322 ns (see FIG. 1) under the condition of 20 to 120 ° C., and the tear strength was 7.5 N / mm, and the tensile modulus of elasticity was 5600 MPa. The common logarithm of the surface resistivity was 3.2 [logΩ / □].

<Example 2>
N-methyl-2-pyrrolidone (NMP) 23.4 g is added to 9 g of a polyamic acid solution (solid content 18 wt%, U-varnish-S (Ube)), and a polyamic acid diluted solution with a solid content concentration of 0.5 wt% is added. After that, 18 g of channel black (Special Black 4 (manufactured by Degussa)) was added, and sonication was performed at a frequency of 40 kHz for 1 hour. Next, 0.2 mol of a mixture of p-phenylenediamine and 4,4′-diaminodiphenyl ether (molar ratio 5: 5) is added as an amine component, followed by 3,3 ′, 4,4′-biphenyltetracarboxylic acid. Acid dianhydride was added to make approximately equimolar. After thickening, the mixture was heated with stirring, and when the viscosity decreased to 2000 p, 0.04 mol of 2-phenylimidazole was added, and the mixture was cooled with stirring to obtain carbon black 18 wt% (carbon black solid weight / (carbon black solid content). Weight + polyimide solid content weight) × 100) and a solid content of 20 wt% ((carbon black solid content weight + polyimide solid content weight) / total weight × 100) were obtained. The conductive polyamic acid solution was applied to the inner surface of a cylindrical mold having an inner diameter of 320 mm and a length of 850 mm with a dispenser, and then rotated at 800 rpm for 10 minutes to obtain a uniform coating surface. Thereafter, a film was formed by heating at 130 ° C. for 20 minutes while rotating at 40 rpm, followed by heating at 360 ° C. for 30 minutes for imide conversion to obtain a conductive polyimide belt. When this belt was evaluated, the tear strength was 6.4 N / mm, and the tensile modulus was 4300 Mpa. The common logarithm of the surface resistivity was 12.8 [logΩ / □] at 100 V, 12.5 [logΩ / □] at 1000 V, and the difference was 0.3 [logΩ / □].

<Comparative Example 1>
Example 1 was repeated except that the polyamic acid diluted solution was omitted. When this belt was evaluated, the annihilation lifetime (τ ₂ ) of positrons measured by the positron annihilation method was 0.325 to 0.327 ns (see FIG. 1) under the condition of 20 to 120 ° C., and the tear strength was 5.4 N / mm, and the tensile modulus was 4600 MPa. The common logarithm of the surface resistivity was 3.2 [logΩ / □].

<Comparative Example 2>
Example 2 was repeated except that the polyamic acid diluted solution was omitted. When this belt was evaluated, the tear strength was 5.8 N / mm and the tensile modulus was 4200 Mpa. The common logarithm of the surface resistivity was 12.8 [logΩ / □] at 100 V, 12.1 [logΩ / □] at 1000 V, and the difference was 0.7 [logΩ / □].

<Comparative Example 3>
The same procedure as in Example 1 was conducted except that the concentration of the polyamic acid diluted solution was changed to 7 wt%. When this belt was evaluated, the tear strength was 5.8 N / mm and the tensile modulus was 5300 Mpa. The common logarithm of the surface resistivity was 3.2 [logΩ / □].

FIG. 1 shows the relationship between the annihilation lifetime (τ ₂ ) of the positron and the measurement temperature. In the figure, (◯) represents the result of measurement in Comparative Example 1, and (□) represents the result of measurement in Example 1. As is clear from FIG. 1, in Example 1 in which carbon black was dispersed with a polyamic acid diluent, the positron annihilation lifetime (τ ₂ ) in the belt was higher than that in Comparative Example 1 in which the polyamic acid diluent was not used. It becomes shorter within the range, and it can be seen that the size of the local gap in the belt is reduced.

表１の結果が示すように、ポリアミド酸希釈液によりカーボンブラックを分散させた実施例１および２のベルトは、比較例１〜３のベルトに比べ、引裂強度に優れ、電位依存性も小さい。

As shown in the results of Table 1, the belts of Examples 1 and 2 in which carbon black is dispersed with a polyamic acid diluent are superior in tear strength and have less potential dependence than the belts of Comparative Examples 1 to 3.

The graph which shows the relationship between the annihilation lifetime ((tau) ₂ ) of the positron in a belt when measured by the positron annihilation method, and measurement temperature.

Claims (5)

A conductive polyimide belt containing a conductive agent, wherein a positron annihilation lifetime (τ ₂ ) at 50 ° C. measured by a positron annihilation method is 0.324 ns or less.   The common logarithmic value of the surface resistivity of the belt is in the range of 1 to 14 [logΩ / □], and the difference between the common logarithm values of the surface resistivity at an applied voltage of 100 V and 1000 V is 0.5 [logΩ / □]. The conductive polyimide belt according to claim 1, wherein:   The conductive polyimide belt according to claim 2, wherein the tear strength is 6 N / mm or more.   A step of dispersing a conductive agent in a polyamic acid diluted solution having a solid content concentration of 0.1 to 5 wt%, and then adding a tetracarboxylic dianhydride or a derivative thereof and a diamine component to react with each other. A method for manufacturing a conductive polyimide belt.   The method for producing a conductive polyimide belt according to claim 4, wherein the conductive agent is dispersed by ultrasonic treatment at a frequency of 25 to 100 kHz.

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