JP4945308B2 - Method for producing polyamic acid solution and method for producing semiconductive polyimide belt - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a polyamic acid solution having suppressed aggregation of carbon black, excellent dispersibility of carbon black and favorable preservation stability; and to provide a manufacturing method of a semiconductive polyimide belt excellent in electric characteristics using the polyamic acid solution obtained by the method for manufacturing the polyamic acid solution, and an image forming apparatus excellent in image transferability, and the like. <P>SOLUTION: In the manufacturing method of a carbon black-dispersed polyamic acid solution, comprising a step of dissolving and polymerizing a tetracaroxylic dianhydride or its derivative and a diamine component in a dispersion liquid of carbon black in a solvent, a plurality of polyamic acid solutions having different carbon black contents are prepared; and the polyamic acid solutions are mixed. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a method for producing a carbon black-dispersed polyamic acid solution, a method for producing a semiconductive polyimide belt, and the like. A semiconductive polyimide belt using such a polyamic acid solution can be used, for example, as an intermediate transfer belt of an electrophotographic image forming apparatus such as an electrophotographic copying machine, a printer or a facsimile.

  2. Description of the Related Art Conventionally, copying machines, laser printers, video printers, facsimile machines, and their combined machines are known as electrophotographic recording apparatuses that form and record images by an electrophotographic system. For the purpose of improving the life of the apparatus and the like, the method of directly fixing the image formed on the image carrier such as the photosensitive drum or the like via the recording agent such as toner on the print sheet is avoided. An intermediate transfer method in which an image is once transferred (primary transfer) to an intermediate transfer belt and then transferred (secondary transfer) onto a printing sheet and then fixed is being studied. For the purpose of reducing the size of the apparatus, a method of using a transfer conveyance belt and causing the transfer belt to also convey a print sheet has been studied.

  As an example of a semiconductive belt used for such an intermediate transfer belt, an intermediate transfer belt in which carbon black such as furnace black or acetylene black as a conductive filler is dispersed in a polyimide resin has been proposed (Patent Literature). 1).

  In addition, a method for preparing a polyamic acid solution using two or more different types of carbon black is disclosed as a method for adjusting the electrical resistance of a polyamic acid solution in which carbon black is dispersed and a method for suppressing the aggregation of carbon black. (Patent Documents 2 to 4).

  However, when general-purpose carbon black is dispersed in polyimide resin, the variation in electrical resistance value is small with respect to environmental changes such as temperature and humidity, but it is very difficult to uniformly disperse carbon black. .

  In general, carbon black tends to cause secondary aggregation. When a polyamic acid solution is prepared in the process of forming a semiconductive belt and then stored at room temperature and normal pressure, the average particle size of the carbon black increases with time. Change. This aggregation causes a conduction path, which may lead to variations in the electric resistance value in the belt. When such a belt is used as an intermediate transfer belt of an electrophotographic recording apparatus, there is a problem that uneven transfer occurs in a toner image transferred to a printing sheet.

  The reason why the variation in the electric resistance value affects the intermediate transfer as described above is that, due to the non-uniformity of the charge suppressing ability of the semiconductive belt and the non-uniformity of the conductive suppressing ability, local peeling discharge and electric conduction This is thought to be more likely to occur.

  Therefore, in order to obtain a semiconductive belt imparted with the desired electrical resistance, a polyamic acid solution must be prepared every time the belt is molded and immediately molded into a belt, which is not suitable for production in a mass production system. It is.

  Further, not only the intermediate transfer belt and the transfer belt of the electrophotographic recording apparatus but also the charge suppressing ability and the conductivity suppressing ability required for the semiconductive polyimide belt are different depending on the use, but the more uniform the better.

JP-A-63-311263 JP 2002-148957 A JP 2003-277502 A Japanese Patent Laying-Open No. 2005-081667

  Therefore, in view of the above circumstances, the present invention provides a method for producing a polyamic acid solution in which aggregation of carbon black is suppressed, excellent dispersibility of carbon black, and good storage stability, and a polyamic acid solution obtained by the production method It is an object of the present invention to provide a method for producing a semiconductive polyimide belt excellent in electrical characteristics using a toner, an image forming apparatus excellent in image transferability, and the like.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the following polyamic acid solution production method and semiconductive polyimide belt production method, etc. The invention has been completed.

  That is, the present invention provides a method for producing a carbon black-dispersed polyamic acid solution comprising a step of dissolving and polymerizing tetracarboxylic dianhydride or a derivative thereof and a diamine component in a dispersion in which carbon black is dispersed in a solvent. A plurality of polyamic acid solutions having different carbon black contents are prepared, and these polyamic acid solutions are mixed.

  After individually preparing multiple carbon black-dispersed polyamic acid solutions from carbon black dispersions with different carbon black content ratios, mixing these together suppresses the aggregation of carbon black, provides excellent dispersibility, and provides stable storage A polyamic acid solution having excellent properties can be produced.

  In the present invention, the carbon black is the same species, and the content of the carbon black is 15 parts by weight or more and less than 23 parts by weight when the polyimide solid content is 100 parts by weight as the plurality of polyamic acid solutions. A first solution prepared and a second solution prepared by 23 parts by weight or more and less than 30 parts by weight are prepared. In preparing a plurality of dispersions, the same type of carbon black can be used, so the workability is excellent, and by preparing a dispersion in the above predetermined range, carbon black can be compared with a single dispersion. Secondary agglomeration is suppressed, a dispersibility of carbon black is excellent, and a polyamic acid solution having good storage stability can be produced. In addition, polyimide solid content means the value which deducted the weight of the water which generate | occur | produces in a polymerization reaction from the total weight of tetracarboxylic dianhydride or its derivative (tetracarboxylic acid component), and a diamine component.

  The method for producing a semiconductive polyimide belt according to the present invention includes a step of mixing and reacting a catalyst with a plurality of polyamic acid solutions. After preparing a plurality of polyamic acid solutions, the catalyst is added, mixed, and reacted, so that secondary aggregation of carbon black is suppressed and electrical resistance is reduced compared to the case where the catalyst is added when preparing the carbon black dispersion. Thus, a semiconductive polyimide belt having a small variation can be obtained.

  The present invention relates to a semiconductive polyimide belt. The semiconducting polyimide belt of the present invention has excellent electrical characteristics with reduced secondary aggregation of carbon black, small variation in electrical resistance.

  Hereinafter, embodiments of the present invention will be described in detail.

    In general, in the method for producing a carbon black-dispersed polyamic acid solution, first, a dispersion in which carbon black is dispersed is prepared. Next, it is necessary to prepare a carbon black-dispersed polyamic acid solution by dissolving and polymerizing tetracarboxylic dianhydride or a derivative thereof (tetracarboxylic acid component) and a diamine component in the prepared dispersion. In particular, in the present invention, dispersions having different carbon black contents are prepared, and the dispersion, tetracarboxylic acid component, and diamine component are dissolved and polymerized to prepare a plurality of polyamic acid solutions having different carbon black contents. A mixture of these is used as a carbon black-dispersed polyamic acid solution.

  In addition, as a method for producing the semiconductive polyimide belt of the present invention, a plurality of carbon black-dispersed polyamic acid solutions are prepared, and after mixing these, a catalyst is added and reacted, whereby a semiconductive polyimide belt is obtained. Prepare.

<Preparation of carbon black dispersion>
The preparation of a dispersion liquid in which carbon black is dispersed will be described below.

  Examples of the carbon black used in the present invention include channel black, furnace black, ketjen black, and acetylene black. These can be used alone or in combination of two or more.

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]), channel black and furnace black are particularly preferably used. Depending on the application, oxidation degradation such as oxidation treatment and graft treatment may be caused. It is preferable to use those that are prevented or that have improved dispersibility in a solvent.

  As said furnace black, Special Black 550, Special Black 350, Special Black 250, Special Black 100, Printex 35, Printex 25, Mitsubishi Chemical MA 7, MA 77, MA 77, manufactured by Degussa. 100, MA100R, MA220, MA230, manufactured by Cabot Corporation, MONARCH 1300, MONARCH 1100, MONARCH 1000, MONARCH 900, MONARCH 880, MONARCH 800, MONARCH 700, MOGUUL L, REGAL 400R, ULCAN XC-72R, and the like. Also, as channel black, Color Black FW200, Color B1ack FW2, Color Black FW2V, Color Black FW1, Color Black FW18, Special Black Black 6, 170 Black, Black Black, 170 Black Black 4A, Printex 150T, Printex U, Printex V, Printex 140U, Printex 140V, and the like.

  Further, depending on the application, it is preferable to use carbon black that has been prevented from oxidative degradation such as oxidation treatment and grafting treatment, and that has improved dispersibility in a solvent, and in particular, oxidized carbon black is used. It is preferable.

  The oxidized carbon black can be obtained by oxidizing the carbon black to give an oxygen-containing functional group (for example, carboxyl group, quinone group, lactone group, hydroxyl group, etc.) to the surface.

  The oxidation treatment is performed by an air oxidation method in which the material is brought into contact with and reacts with air in a high temperature atmosphere, a method in which nitrogen oxide or ozone is reacted at room temperature, a method in which ozone is oxidized at a low temperature after air oxidation at a high temperature, and the like. be able to. In the oxidized carbon black obtained by the above method, an excessive current flows in part and is not easily affected by oxidation due to repeated voltage application. In addition, the effect of the oxygen-containing functional group adhering to the surface provides high dispersibility in polyimide, can reduce resistance variation, reduce electric field dependency, and make it difficult for electric field concentration due to transfer voltage to occur. . As a result, the electrical resistance is prevented from lowering due to the transfer voltage, the uniformity of the electrical resistance is improved, the change in resistance due to the electric field dependency and the environment is small, and the occurrence of image quality defects such as the paper running portion being whitened is suppressed. Therefore, high image quality can be obtained.

  The content of carbon black used in the present invention is appropriately determined depending on the type of carbon black to be added according to the purpose, but as an intermediate transfer belt or transfer conveyance belt used in an image forming apparatus, the machine From the viewpoint of mechanical strength, it is preferably 3 to 40% by weight, more preferably 3 to 30% by weight, based on the polyimide solid content. When the carbon black content is less than 3% by weight, it is difficult to control the resistance value, and the variation in the belt tends to increase. On the other hand, if it exceeds 40% by weight, the mechanical strength of the belt tends to decrease.

  In addition, when the obtained polyimide solid content is 100 parts by weight as a plurality of polyamic acid solutions, the first solution prepared with a carbon black content of 15 parts by weight or more and less than 23 parts by weight, and 23 parts by weight or more It is preferable to prepare the second solution prepared to be less than 30 parts by weight, and the first solution is prepared to be 18 parts by weight or more and less than 23 parts by weight, and the second solution is prepared by 23 parts by weight or more and less than 28 parts by weight. More preferably. When the content exceeds the predetermined range, dispersion becomes difficult, aggregation and precipitation of carbon black is likely to occur, and storage stability is significantly reduced. On the other hand, when the content falls below the predetermined range, the effect of the semiconductive property cannot be exhibited.

  Although it does not restrict | limit especially as a solvent used for this invention, A polar solvent is mentioned suitably from points, such as solubility. In particular, those which can be used both for dispersing carbon black and for solvent for polymerization reaction are preferred. As the polar solvent, N, N-dialkylamides are preferable, and specific examples thereof include N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylformamide, which are low molecular weight compounds thereof. N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethyl sulfoxide, hexamethylphosphortriamide, N-methyl-2-pyrrolidone, pyridine, tetramethylenesulfone, dimethyltetramethylenesulfone and the like. These can be used singly or in combination.

  Furthermore, phenols such as cresol, phenol and xylenol, benzonitrile, dioxane, butyrolactone, xylene, cyclohexane, hexane, benzene, toluene and the like can be used alone or in combination.

  A known dispersion method can be applied to the carbon black dispersion method. For example, after carbon black is added to the solvent, a method such as nanomizer, ball mill, sand mill, basket mill, triple roll mill, planetary mixer, bead mill, homogenizer, and ultrasonic can be selected as appropriate to perform dispersion work. .

  With the aim of improving the dispersibility and affinity of carbon black, carbon black can be dispersed in the polyamic acid solution in the presence of a dispersant. 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, and 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-vinylsuccinic acid amide), poly (N-vinylurea), poly (N-vinylpiperidone), poly (N-vinylcaprolactam), poly (N-vinyloxazoline) and the like. One or more polymer dispersants can be added.

  The method for examining the dispersion state of carbon black is not particularly limited, and examples thereof include a method of visually observing with a microscope.

<Preparation of carbon black-dispersed polyamic acid solution>
Hereinafter, the carbon black-dispersed polyamic acid solution will be described.

  Examples of the tetracarboxylic acid component include pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, and 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 Anhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,2'-bis (3,4-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) sulfone And dianhydrides, perylene-3,4,9,10-tetracarboxylic dianhydrides, bis (3,4-dicarboxyphenyl) ether dianhydrides, ethylenetetracarboxylic dianhydrides, and the like.These can be used alone or in combination of two or more.

  Examples of the diamine component include 4,4′-diaminodiphenyl ether, 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′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenylpropane, 2,4-bis (β-amino-t-butyl) Toluene, bis (p-β-amino-t-butylphenyl) ether, (P-β-methyl-δ-aminophenyl) benzene, bis-p- (1,1-dimethyl-5-amino-pentyl) benzene, 1-isopropyl-2,4-m-phenylenediamine, m-xylyl Rangeamine, p-xylylenediamine, di (p-aminocyclohexyl) methane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, diaminopropyltetramethylene, 3-methylheptamethylenediamine 4,4-dimethylheptamethylenediamine, 2,11-diaminododecane, 1,2-bis-3-aminopropoxyethane, 2,2-dimethylpropylenediamine, 3-methoxyhexamethylenediamine, 2,5-dimethylhepta Methylenediamine, 3-methylhept Methylenediamine, 5-methylnonamethylenediamine, 2,11-diaminododecane, 2,17-diaminoeicosadecane, 1,4-diaminocyclohexane, 1,10-diamino-1,10-dimethyldecane, 1,12- Examples include diaminooctadecane and 2,2-bis [4- (4-aminophenoxy) phenyl] propane. These can be used alone or in combination of two or more.

  A tetracarboxylic acid component and a diamine component are dissolved and polymerized in the dispersion. Here, the polyamic acid (polyimide belt precursor) can be obtained by reacting approximately equimolar amounts of a tetracarboxylic acid component and a diamine component in an organic solvent. The monomer concentration during the polymerization reaction (the concentration of the tetracarboxylic acid component and the diamine component in the solvent) is set according to various conditions. Usually, about 5 to 30% by weight is preferable. The reaction temperature is preferably 80 ° C. or less, particularly preferably 5 to 50 ° C. The reaction time is preferably 0.5 to 10 hours. If the reaction time is less than 0.5 hours, the reaction becomes insufficient, and if the reaction time exceeds 10 hours, no further effect can be obtained.

  Although the viscosity of the carbon black-dispersed amic acid solution obtained by the above reaction increases, if the heating is performed as it is, the viscosity of the polyamic acid solution decreases. Using this phenomenon, the carbon black-dispersed amic acid solution can be adjusted to a predetermined viscosity. The heating temperature at this time is preferably 50 to 90 ° C.

<Preparation of semiconductive polyimide belt>
The semiconductive polyimide belt of the present invention is prepared by the following method.

  First, a plurality of carbon black-dispersed polyamic acid solutions having different carbon black contents are mixed. The catalyst added and mixed here is supplied into a cylindrical mold, and uniformly spread by centrifugal force on the inner peripheral surface of the mold by a rotary centrifugal molding method. At this time, the viscosity of the solution is preferably 1 to 1000 Pa · s (25 ° C.) with a B-type viscometer. In other cases, it is difficult to uniformly develop during centrifugal molding, which causes variations in the thickness of the polyimide belt. After film formation, heating is performed at 80 to 150 ° C. to remove the solvent.

  Next, the ring-closing imidization reaction (imide conversion) is advanced by heating at a high temperature of 300 to 450 ° C., and then taken out from the mold. It is necessary to perform the solvent removal and the heating during the imidization reaction evenly. If it is not uniform, agglomeration variation of the carbon black occurs during the evaporation of the solvent, and the resistance value of the polyimide belt varies. As a method of heating evenly, there are a method of heating while rotating the mold, a method of improving the circulation of hot air, and a method of charging at a low temperature to reduce the rate of temperature rise.

  In addition, the imidation reaction may use either the above-mentioned method of heating at a high temperature or the method of adding a catalyst alone or a catalyst and a dehydrating agent to a polyamic acid solution and heating at a low temperature, which meets the purpose of the present invention. If there is no particular limitation.

  Although it does not specifically limit as said catalyst, For example, an aliphatic tertiary amine, an aromatic tertiary amine, a heterocyclic tertiary amine, etc. can be mentioned. In particular, heterocyclic compounds such as imidazole, benzimidazole, isoquinoline, quinoline, diethylpyridine, and β-picoline are preferred.

  The addition amount of the catalyst is preferably 0.05 to 2.0 molar equivalents, more preferably 0.1 to 1.0 molar equivalents with respect to 1 molar equivalent of the polyamic acid in the polyamic acid solution. If the addition amount of the catalyst is less than 0.05 molar equivalent, the catalytic effect is not sufficient, and even if it exceeds 2.0 molar equivalent, the catalytic effect does not change. Further, these catalysts are effective as an imidization accelerator at a low temperature even in heat imidization without using a dehydrating agent.

  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. Of these, organic carboxylic acid anhydrides are particularly preferable.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below.

<Evaluation method>
(Viscosity of polyamic acid solution)
In evaluating the viscosity of the carbon black-dispersed polyamic acid solution, evaluation was performed at 25 ° C. using a rotational viscometer TV-10H (manufactured by Toki Sangyo Co., Ltd.).

(Surface resistivity)
Using Hiresta UP MCP-HT450 (manufactured by Mitsubishi Chemical Corporation, probe: UR), the surface resistivity (Ω / □) after 10 seconds of the applied voltage of 500 V was measured. The measurement conditions were 25 ° C. × 60% RH. In the measurement, the surface resistivity at 48 points on the belt surface was measured, and the average value was shown as a common logarithmic value.

(Storage stability)
In order to evaluate the storage stability of the carbon black-dispersed polyamic acid solution, the polyamic acid solution was prepared and stored at 25 ° C. for 120 days. 120 days later, the viscosity of the polyamic acid solution and the surface resistivity of the semiconductive polyimide belt obtained using the polyamic acid solution were evaluated.

(Section observation with a scanning microscope (SEM))
The obtained semiconductive polyimide belt was cut with a microtome, and this cross section was observed using SEM. As a result of observation, a case where the aggregated particle diameter of carbon black of 0.5 μm or more was not recognized was evaluated as “good”. Moreover, what was included was evaluated as x.

(Image / Belt drive)
The obtained semiconductive polyimide belt was incorporated into an actual copying machine as a tandem intermediate transfer belt, and a 5000 sheet image formation test was performed using plain paper. Images with good image and belt drivability were evaluated as ◯, images with some image defects or drivability defects were evaluated as Δ, and those with image defects visually recognizable or those with deficiencies in drive were evaluated as x.

  The above evaluation results are shown in Table 1.

Example 1
Polyamide acid solutions having different carbon black contents were prepared according to Production Examples 1 and 2 shown below, and a semiconductive polyimide belt was obtained using these.

Production Example 1
<Preparation of carbon black dispersion>
In 2916 g of N-methyl-2-pyrrolidone (NMP), 171.1 g of dried carbon black (Special Black 4 manufactured by Degussa) was added. Next, this solution was stirred and mixed in a ball mill at room temperature for 6 hours to obtain 5.54 wt% of carbon black dispersion 1.

<Preparation of carbon black-dispersed polyamide solution>
In the above dispersion 1, NMP, 106.8 g of p-phenylenediamine (PDA), 197.7 g of 4,4′-diaminodiphenyl ether, 581.3 g of 3,3 ′, 4,4′-biphenyltetracarboxylic acid The dianhydride (BPDA) was charged at room temperature in a nitrogen atmosphere and dissolved by stirring for 6 hours. Subsequently, the mixture was heated with stirring, heated at 75 ° C. for 10 hours, and after thickening by polymerization reaction, a 120 Pa · s carbon black-dispersed polyamic acid solution (carbon black when the polyimide solid content was 100 parts by weight) 21 parts by weight) was obtained.

Production Example 2
<Preparation of carbon black dispersion>
Except that the amount of carbon black added in Production Example 1 was changed to 207.5 g, a similar method was performed to obtain 6.64% by weight of carbon black dispersion 2.

<Preparation of carbon black-dispersed polyamide solution>
In the same manner as in Production Example 1, 108.8 g of PDA, 201.4 g of DDE, and 592.3 g of BPDA were dispersed in the above dispersion 2 in the same manner as in Production Example 1, and 110 Pa · s of carbon black was dispersed. A polyamic acid solution (25 parts by weight of carbon black when the polyimide solid content was 100 parts by weight) was obtained.

<Preparation of semiconductive polyimide belt>
Each 2000 g of the carbon black-dispersed polyamic acid solutions of Production Examples 1 and 2 were mixed, and 44.8 g of 2-phenylimidazole (0.2 molar equivalent per 1 molar equivalent of the polyamic acid solution) was further added for 1 hour. By stirring and mixing, a catalyst-added carbon black-dispersed polyamic acid solution was prepared.

  Next, the catalyst-added carbon black-dispersed polyamic acid solution was applied to the inner peripheral surface of a drum mold having an inner diameter of 300 mm and a length of 900 mm with a dispenser so as to have a final thickness of 170 μm, and rotated at 1500 rpm for 10 minutes. A uniform spreading layer was obtained. Thereafter, while rotating the drum mold at 20 rpm, hot air at 100 ° C. was applied for 30 minutes from the outside of the mold to remove the solvent. Further, the temperature was raised to 340 ° C. at a rate of 2 ° C./minute, and heating was continued for 15 minutes as it was to proceed with imidization. After cooling to room temperature, it was peeled off from the inner surface of the mold to obtain a 75 μm semiconductive polyimide belt.

(Example 2)
Example 1 except that the carbon black content was adjusted to 20 parts by weight and 26 parts by weight with respect to 100 parts by weight of the polyimide solid content in each of the carbon black-dispersed polyamic acid solutions of Production Examples 1 and 2 of Example 1. The same method as 1 was used. As a result, a 75 μm semiconductive polyimide belt was obtained.

(Comparative Example 1)

<Preparation of carbon black dispersion>
In 2889 g of NMP, 197.7 g of carbon black (Special Black 4 manufactured by Degussa) was added. Next, this solution was stirred and mixed in a ball mill at room temperature for 6 hours to obtain 6.34% by weight of carbon black dispersion 3.

<Preparation of carbon black-dispersed polyamide solution>
106.8 g of PDA, 197.7 g of DDE, 581.3 g of BPDA, and 56.9 g of 2-phenylimidazole (0.2 molar equivalent per 1 molar equivalent of polyamic acid solution) were added to dispersion 3 above. The solution was charged in an atmosphere at room temperature and dissolved by stirring for 6 hours. Subsequently, the mixture was heated with stirring, and heated at 75 ° C. for 10 hours. After thickening by polymerization reaction, a 120 Pa · s carbon black-dispersed polyamic acid solution (carbon black was added to 100 parts by weight of polyimide solids). 23 parts by weight) was obtained.

<Preparation of semiconductive polyimide belt>
The manufacturing method of the semiconductive polyimide belt is the same as that of Example 1. As a result, a 76 μm semiconductive polyimide belt was obtained.

(Comparative Example 2)
Similar to Comparative Example 1, except that catalyst addition is performed during the production of the semiconductive polyimide belt as in Example 1. As a result, a 74 μm semiconductive polyimide belt was obtained.

<Table 1> Evaluation results

  From Table 1, in the examples, in the viscosity of the mixture of two carbon black-dispersed polyamic acid solutions having different carbon black contents, no significant change was observed after 0 day and after 120 days. The surface resistivity of the conductive polyimide belt was not significantly changed, and it was confirmed that the storage stability was excellent. Moreover, when SEM cross-section observation was performed about the semiconductive polyimide belt manufactured using the said polyamic-acid solution, it was confirmed that there was almost no secondary aggregation of carbon black and was disperse | distributing uniformly. Further, in an image transferability test by a copying machine using the semiconductive polyimide belt, it was confirmed that there was no defect or image defect and that the image transferability was excellent.

On the other hand, in Comparative Example 1, a large change in the viscosity of the polyamic acid solution having a single carbon black content was observed after 0 day and after 120 days, and the surface resistivity of the semiconductive polyimide belt using these was also changed. A large change was observed, confirming poor storage stability. Moreover, when SEM cross-section observation was performed about the semiconductive polyimide belt manufactured using the said polyamic-acid solution, the secondary aggregation of carbon black was recognized and it was confirmed that it is not disperse | distributing uniformly. Further, in an image transferability test using a copying machine using the semiconductive polyimide belt, transfer unevenness was observed, and it was confirmed that the dispersion was not uniform. Similarly, in Comparative Example 2, transfer unevenness was observed, and it was confirmed that a good image was not formed due to uniform dispersion failure.

Claims (3)

In the method for producing a carbon black-dispersed polyamic acid solution comprising a step of dissolving and polymerizing tetracarboxylic dianhydride or a derivative thereof and a diamine component in a dispersion obtained by dispersing carbon black in a solvent,
A plurality of polyamic acid solutions having different carbon black contents are prepared, the polyamic acid solutions are mixed, and the carbon black is of the same type, and the resulting polyamic acid solution is 100 parts by weight of polyimide solid content. The first solution prepared to have a carbon black content of 15 parts by weight or more and less than 23 parts by weight and the second solution prepared by 23 parts by weight or more and less than 30 parts by weight. A method for producing a carbon black-dispersed polyamic acid solution. The claim 1 Symbol placement polyamic acid solution and catalyst obtained by the method of mixing method of the semiconductive polyimide belt comprising the step of reacting. A semiconductive polyimide belt obtained by the production method according to claim 2 .