JP2005247986A - Semiconducting aromatic amic acid composition and manufacturing method of semiconducting endless tubular polyimide film using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconducting polyimide film of high qualities exhibiting more excellent homogeneity of electric resistivity than conventional semiconducting polyimide films, and its manufacturing method. <P>SOLUTION: The semiconducting aromatic amic acid composition comprises an aromatic amic acid oligomer obtained by a polycondensation reaction of at least two aromatic tetracarboxylic acid components with an aromatic diamine component, conductive carbon black, and an organic polar solvent. The manufacturing method thereof is also provided. The manufacturing method of the semiconducting endless tubular polyimide film comprises subjecting the aromatic amic acid composition to rotational molding and a subsequent heat treatment at approximately 100-190°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductive aromatic amic acid composition and a method for producing a semiconductive endless tubular polyimide film using the same. Further, the semiconductive endless tubular polyimide film obtained by the production method is used as an electrophotographic intermediate transfer belt, for example.

  A tubular polyimide film obtained by mixing and dispersing conductive carbon black to impart semiconductivity is used as an intermediate transfer belt for copying machines, printers, facsimiles, and printing machines.

  As a forming raw material for the semiconductive tubular polyimide film, a polyamic acid (or polyamic acid) solution having a high molecular weight (number average molecular weight is usually about 10,000 to 30,000), which is a polyimide polymer precursor, is used.

  As a method for forming a semiconductive tubular polyimide film, a method of forming into a flat film once using the composition containing the above-mentioned forming raw material and conductive carbon black, then processing both ends of the film into a tubular shape, A method of forming an endless tubular film at once by centrifugal casting is known. A method of forming this centrifugal casting under a substantially no centrifugal force is also described, for example, in Patent Document 1 by the present applicant.

  Specific examples of the polyamic acid solution include 1,2,4,5-benzenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and 3,3. Aromatic tetracarboxylic dianhydrides that bind acid anhydride groups to point-symmetrical positions such as', 4,4'-benzophenone tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride Polycondensation reaction of an equimolar amount of the product with an aromatic diamine such as p-phenylenediamine, 4,4′-diaminodiphenyl ether, or 4,4′-diaminodiphenylmethane at a low temperature that does not imidize in an organic polar solvent Is manufactured.

  However, since the polyamic acid solution obtained by the above molding method has a pot life, there is a drawback that partial gelation tends to occur gradually upon storage. This gelation is more likely to proceed at higher temperatures, but progresses with time even at low temperatures, and even if the amount of gelation is extremely small, the physical properties of the final polyimide film will be adversely affected, and flatness may be deteriorated. I will invite you. In the film mixed with conductive carbon black, this leads to an increase in variation in electric resistance.

  In addition, the polyamic acid resin has a limit in solubility in an organic polar solvent, and has a drawback that it cannot be increased in concentration (the concentration of nonvolatile components in the solution is at most 25% by weight). With a low-concentration polyamic acid solution, it is difficult to form a thicker film at one time, and a large amount of the solvent is required and a lot of time is required for the evaporation removal.

  Incidentally, Patent Document 2 describes a molding method using a new raw material composition for the polyimide film molding from the polyamic acid solution. This is because asymmetric aromatic tetracarboxylic acid (specifically, 2,3,3 ′, 4 is used instead of point-symmetrical 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, for example. 'Aromatic tetracarboxylic acid component containing as main component (60 mol% or more)'-biphenyltetracarboxylic acid or ester thereof) and aromatic diamine component (for example, containing 4,4'-diaminodiphenyl ether as the main component), etc. This is a molding method using a solution composition mainly composed of monomers mixed with moles. Patent Document 2 discloses a method in which the solution composition is applied and cast on a glass plate and heated (stepwise temperature increase between 80 to 350 ° C.) to be used for flat film molding, silver powder, copper powder, A method of mixing carbon black or the like and providing it to a heat resistant conductive paste is disclosed.

However, the above-mentioned Patent Document 2 does not disclose any method for once converting a starting material (monomer) into an amic acid oligomer and then molding it into a polyimide film. In addition, the semiconductive polyimide film obtained by the above molding method has room for further improvement in characteristics such as electric resistance when used for an intermediate transfer belt of a toner copying machine, for which high accuracy is recently required.
JP 2000-263568 A Japanese Patent Laid-Open No. 10-182820

  An object of the present invention is to provide a high-quality semiconductive polyimide film excellent in homogeneity of electrical resistivity and a method for manufacturing the same in comparison with the conventional semiconductive polyimide film in view of the above-described problems of the prior art. There is.

  As a result of intensive studies to solve the above problems, the present inventor has heat-treated the aromatic tetracarboxylic acid component and the aromatic diamine to substantially polycondensate the aromatic amidic acid oligomer once. (Aromatic amic acid having a number average molecular weight of about 1000 to 7000), mixed with conductive carbon black, and then rotationally molded and then imidized to obtain a uniform electrical resistivity. It has been found that a semiconductive polyimide film is obtained. The present invention has been completed by further development based on this finding.

  That is, the present invention provides the following semiconductive aromatic amic acid composition, a semiconductive endless tubular polyimide film using the same, and a method for producing the same.

  Item 1. Semiconductive fragrance comprising an aromatic amic acid oligomer obtained by polycondensation reaction of approximately equimolar amounts of two or more aromatic tetracarboxylic acid components and an aromatic diamine, carbon black, and an organic polar solvent Group amic acid composition.

  Item 2. The aromatic amic acid oligomer obtained by polycondensation of approximately equimolar amounts of two or more aromatic tetracarboxylic dianhydrides and an aromatic diamine in an organic polar solvent at a temperature of about 80 ° C. or lower. Item 2. The semiconductive aromatic amic acid composition according to item 1, which is an aromatic amide acid oligomer.

  Item 3. Two or more kinds of aromatic tetracarboxylic dianhydrides are a mixture of 15 to 55 mol% of asymmetric aromatic tetracarboxylic dianhydrides and 85 to 45 mol% of symmetric aromatic tetracarboxylic dianhydrides. Item 3. The semiconductive aromatic amic acid composition according to Item 2.

  Item 4. The aromatic amic acid oligomer is an aromatic obtained by polycondensation reaction of approximately equimolar amounts of two or more aromatic tetracarboxylic acid diesters and an aromatic diamine in an organic polar solvent at a temperature of about 90 to 120 ° C. Item 2. The semiconductive aromatic amic acid composition according to item 1, which is an amic acid oligomer.

  Item 5. Item 5. The two or more kinds of aromatic tetracarboxylic acid diesters are a mixture comprising 15 to 55 mol% of asymmetric aromatic tetracarboxylic acid diesters and 85 to 45 mol% of symmetric aromatic tetracarboxylic acid diesters. Semiconductive aromatic amic acid composition.

  Item 6. Item 6. The semiconductive aromatic amic acid composition according to any one of Items 1 to 5, wherein the aromatic amic acid oligomer has a number average molecular weight of about 1000 to 7000.

  Item 7. The semiconductive aromatic amic acid according to any one of Items 1 to 6, wherein the compounding amount of carbon black is about 3 to 30 parts by weight with respect to 100 parts by weight of the total amount of the aromatic tetracarboxylic acid component and the organic diamine. Composition.

  Item 8. Item 8. A process for producing a semiconductive endless tubular polyimide film, comprising spin-molding and heat-treating the semiconductive aromatic amic acid composition according to any one of Items 1 to 7.

  Item 9. Item 10. A semiconductive endless tubular polyimide film used for an electrophotographic intermediate transfer belt manufactured by the manufacturing method according to Item 8.

  Item 10. The standard deviation of the logarithmic conversion value of the surface electrical resistivity is within 0.2, the standard deviation of the logarithmic conversion value of the volume resistivity is within 0.2, the logarithmic conversion value of the surface electrical resistivity and the logarithmic conversion of the back surface electrical resistivity Item 10. The semiconductive endless tubular aromatic polyimide film according to Item 9, wherein the difference from the value is within 0.4.

  Item 11. An aromatic amic acid oligomer (an aromatic amide having a number average molecular weight of about 1000 to 7000) is obtained by subjecting a partial condensation polymerization of approximately equimolar amounts of two or more aromatic tetracarboxylic acid components and an aromatic diamine in an organic polar solvent. Acid) solution, and this and conductive carbon black powder are uniformly mixed. A method for producing a semiconductive aromatic amic acid composition, comprising:

  The present invention is described in detail below.

The semiconductive endless tubular polyimide film of the present invention (hereinafter also referred to as “semiconductive tubular PI film”) comprises an aromatic amic acid oligomer, conductive carbon black (hereinafter also referred to as “CB”) and a polar organic solvent. The semiconductive aromatic amic acid composition is prepared by rotational molding and imidization treatment.
I. Semiconductive Aromatic Amic Acid Composition The semiconductive aromatic amic acid composition of the present invention has a substantially equimolar amount of two or more aromatic tetracarboxylic acid components and an aromatic diamine in an organic polar solvent. A partially polycondensation reaction is carried out to prepare an aromatic amic acid oligomer (aromatic amic acid having a number average molecular weight of about 1000 to 7000) solution, which is uniformly mixed with conductive carbon black powder.
(1) As the two or more aromatic tetracarboxylic acid components which are aromatic tetracarboxylic acid component forming raw materials, at least one of an asymmetric aromatic tetracarboxylic acid derivative and at least one of a symmetric aromatic tetracarboxylic acid derivative Mixtures with seeds are used.

Asymmetric aromatic tetracarboxylic acid derivative In the present invention, examples of the asymmetric aromatic tetracarboxylic acid derivative include asymmetric aromatic tetracarboxylic dianhydride or asymmetric aromatic tetracarboxylic acid diester (half ester).

Here, the asymmetric aromatic tetracarboxylic acid is a compound in which four carboxyl groups are bonded to positions that are not point targets on a monocyclic or polycyclic aromatic ring (benzene nucleus, naphthalene nucleus, biphenyl nucleus, anthracene nucleus, etc.). Or a position in which two monocyclic aromatic rings (benzene nucleus, etc.) are not point-targeted to a group in which —CO—, —CH ₂ —, —SO ₂ — or the like or a single bond is bridged The compound couple | bonded with is mentioned.

  Specific examples of the asymmetric aromatic tetracarboxylic acid include 1,2,3,4-benzenetetracarboxylic acid, 1,2,6,7-naphthalenetetracarboxylic acid, 2,3,3 ′, 4′-biphenyl. Tetracarboxylic acid, 2,3,3 ′, 4′-benzophenonetetracarboxylic acid, 2,3,3 ′, 4′-diphenyl ether tetracarboxylic acid, 2,3,3 ′, 4′-diphenylmethanetetracarboxylic acid, 2 , 3,3 ′, 4′-diphenylsulfone tetracarboxylic acid and the like.

  Examples of the asymmetric aromatic tetracarboxylic dianhydride used in the present invention include the above-mentioned asymmetric aromatic tetracarboxylic dianhydrides. Specifically, the above asymmetric aromatic tetracarboxylic dianhydride And compounds in which two acid anhydrides are formed between adjacent carboxyl groups on the aromatic ring. Of these, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, 1,2,6,7-naphthalenetetracarboxylic dianhydride and the like are preferable, and 2,3,3 ′, 4′- is particularly preferable. Biphenyltetracarboxylic dianhydride is preferably used.

  Examples of the asymmetric aromatic tetracarboxylic acid diester (half ester) used in the present invention include the above-described asymmetric aromatic tetracarboxylic acid diester (half ester). Examples include compounds in which two of the four carboxyl groups of the group tetracarboxylic acid are esterified and one of the two adjacent carboxyl groups on the aromatic ring is esterified.

Examples of the two esters in the asymmetric aromatic tetracarboxylic acid diester include di-lower alkyl esters, preferably di-C _1-3 alkyl esters (particularly dimethyl esters) such as dimethyl esters, diethyl esters, and dipropyl esters. It is done.

  Of the symmetric aromatic tetracarboxylic acid diesters, 2,3,3 ′, 4′-biphenyltetracarboxylic acid dimethyl ester and 2,3,3 ′, 4′-biphenyltetracarboxylic acid diethyl ester are preferred, 2,3,3 ′, 4′-biphenyltetracarboxylic acid dimethyl ester is preferably used.

In addition, the said symmetrical aromatic tetracarboxylic-acid diester can be manufactured commercially or by a well-known method. For example, the corresponding symmetrical aromatic tetracarboxylic dianhydride 1 is easily reacted with a corresponding alcohol (lower alcohol, preferably C _1-3 alcohol, etc.) 2 (molar ratio) by a known method. Can be manufactured. Thereby, the acid anhydride of a raw material reacts with alcohol, and a ring is opened, and the diester (half ester) which has an ester group and a carboxyl group, respectively on adjacent carbon on an aromatic ring is manufactured.

Symmetric aromatic tetracarboxylic acid derivative Examples of the symmetric aromatic tetracarboxylic acid derivative in the present invention include a symmetric aromatic tetracarboxylic dianhydride or a symmetric aromatic tetracarboxylic acid diester (half ester).

Here, the symmetric aromatic tetracarboxylic acid is a compound in which four carboxyl groups are bonded to a point-symmetrical position on a monocyclic or polycyclic aromatic ring (benzene nucleus, naphthalene nucleus, biphenyl nucleus, anthracene nucleus, etc.). Or four carboxyl groups on a compound in which two monocyclic aromatic rings (such as a benzene nucleus) are bridged by a group such as —CO—, —O—, —CH ₂ —, —SO ₂ — or the like, or a single bond. A compound bonded at a point-symmetrical position can be mentioned.

  Specific examples of the symmetric aromatic tetracarboxylic acid include 1,2,4,5-benzenetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, and 3,3 ′, 4,4′-biphenyl. Tetracarboxylic acid, 3,3 ′, 4,4′-benzophenone tetracarboxylic acid, 3,3 ′, 4,4′-diphenyl ether tetracarboxylic acid, 3,3 ′, 4,4′-diphenylmethane tetracarboxylic acid, 3 , 3 ′, 4,4′-diphenylsulfone tetracarboxylic acid and the like.

  Examples of the symmetric aromatic tetracarboxylic dianhydride used in the present invention include the above symmetric aromatic tetracarboxylic dianhydrides. Specifically, in the symmetric aromatic tetracarboxylic acid described above, The compound which forms two acid anhydrides by adjacent carboxyl groups is mentioned. Among these, 1,2,4,5-benzenetetracarboxylic dianhydride and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride are preferable, and 3,3 ′, 4,4′-biphenyltetra is particularly preferable. Carboxylic dianhydrides are preferably used. This is because it works preferably in terms of forming the strength of the obtained film.

  Examples of the symmetric aromatic tetracarboxylic acid diester (half ester) used in the present invention include the above-mentioned asymmetric aromatic tetracarboxylic acid diester (half ester). Examples include compounds in which two of the four carboxyl groups of the group tetracarboxylic acid are esterified and one of the two adjacent carboxyl groups on the aromatic ring is esterified.

Examples of the two esters in the symmetric aromatic tetracarboxylic acid diester include di-lower alkyl esters, preferably C _1-3 alkyl esters (particularly dimethyl esters) such as dimethyl esters, diethyl esters, and dipropyl esters. .

  Among the above symmetrical aromatic tetracarboxylic acid diesters, 3,3 ′, 4,4′-biphenyltetracarboxylic acid dimethyl ester, 3,3 ′, 4,4′-biphenyltetracarboxylic acid diethyl ester, 2,3, 5,6-Benzenetetracarboxylic acid dimethyl ester is preferable, and 3,3 ′, 4,4′-biphenyltetracarboxylic acid dimethyl ester is particularly preferably used.

In addition, the said symmetrical aromatic tetracarboxylic-acid diester can be manufactured commercially or by a well-known method. For example, it can be easily produced by reacting the corresponding symmetrical aromatic tetracarboxylic dianhydride 1 with the corresponding alcohol (lower alcohol, preferably C _1-3 alcohol etc.) 2 (molar ratio). . Thereby, the acid anhydride of a raw material reacts with alcohol, and a ring is opened, and the diester (half ester) which has an ester group and a carboxyl group, respectively on adjacent carbon on an aromatic ring is manufactured.

The mixing ratio of the asymmetric and symmetric aromatic tetracarboxylic acid derivative is about 15 to 55 mol% (preferably 20 to 50 mol%) of the asymmetric aromatic tetracarboxylic acid derivative. The tetracarboxylic acid derivative is specified at about 85 to 45 mol% (preferably 80 to 50 mol%). In particular, it is preferable to use about 20 to 50 mol% of the asymmetry and tetracarboxylic dianhydride and about 80 to 50 mol% of the symmetric aromatic tetracarboxylic dianhydride.

  In addition, it becomes essential to mix | blend the said symmetrical and asymmetrical aromatic tetracarboxylic acid component for the following reason. Only with a symmetric aromatic tetracarboxylic acid derivative, the polyimide film exhibits crystallinity, so that the film is pulverized during the heat treatment and cannot be formed into a film. On the other hand, an asymmetric aromatic tetracarboxylic acid derivative alone is formed into an endless tubular PI film, but the yield strength and elastic modulus of the obtained film are weak, and when used as a rotating belt, the response in driving In addition to the poor properties, there are problems such as belt elongation occurring at an early stage.

  On the other hand, when an aromatic tetracarboxylic acid derivative having the above-mentioned mixing ratio is used, a semiconductive endless tubular PI film having an extremely high film forming property (moldability) and having a high yield strength and elastic modulus. Is obtained.

  In addition, it is considered that the addition of an asymmetric aromatic tetracarboxylic acid derivative bends the polyamic acid molecule, thereby creating flexibility.

And the coexistence effect of the said symmetrical and asymmetrical aromatic tetracarboxylic acid derivative is most effectively exhibited when both have the mixing ratio shown above.
(2) Aromatic diamine As the aromatic diamine, a compound having two amino groups on one aromatic ring, or two or more aromatic rings (such as a benzene nucleus) are —O—, —S—, —CO. Examples thereof include a compound such as —, —CH ₂ —, —SO—, —SO ₂ — or the like, or a compound having two amino groups bridged by a single bond. Specifically, for example, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylthioether, 4,4′-diaminodiphenylcarbonyl, 4, Examples include 4′-diaminodiphenylmethane, 1,4-bis (4-aminophenoxy) benzene, and the like. Among these, 4,4′-diaminodiphenyl ether is particularly preferable. This is because by using these aromatic diamines, the reaction proceeds more smoothly and a tougher and higher heat-resistant film can be produced.
(3) Organic polar solvent The organic polar solvent used is preferably an aprotic organic polar solvent such as N-methyl-2-pyrrolidone (hereinafter referred to as “NMP”), N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphosphoamide, 1,3-dimethyl-2-imidazolidinone and the like are used. One or two or more of these solvents may be used. In particular, NMP is preferable. The amount of the organic polar solvent used is about 100 to 300 parts by weight (preferably about 150 to 250 parts by weight) with respect to 100 parts by weight of the total amount of the raw material aromatic tetracarboxylic acid component and aromatic diamine. Just decide. Since the produced aromatic amic acid oligomer is relatively easily dissolved in the organic polar solvent, there is an advantage that the amount of the solvent to be used can be reduced as much as possible.
(4) Preparation of aromatic amic acid oligomer solution A part of the above-mentioned two or more mixed aromatic tetracarboxylic acid components and organic diamine components are subjected to polycondensation reaction in an organic polar solvent to obtain an aromatic amic acid oligomer (number A method for preparing an average molecular weight of about 1000 to 7000) is exemplified below.

  As a method for preparing the first aromatic amic acid oligomer, a polycondensation reaction is carried out using an approximately equimolar amount of two or more aromatic tetracarboxylic dianhydrides and an aromatic diamine in an organic polar solvent at a temperature of about 80 ° C. or less. By doing so, an aromatic amic acid oligomer (number average molecular weight of about 1000 to 7000) can be produced.

  Specifically, the asymmetric aromatic tetracarboxylic dianhydride is about 15 to 55 mol% (preferably 20 to 50 mol%) and the symmetrical aromatic tetracarboxylic dianhydride is 85 to 45 mol% (preferably 80 (About 50 mol%) is subjected to a polycondensation reaction. As the organic polar solvent, those described above are employed, and NMP is particularly preferable.

  The reason for setting the reaction temperature to about 80 ° C. or less is to prevent the imidization reaction from occurring when the aromatic amic acid oligomer is formed. A more preferable reaction temperature is 30 to 70 ° C. When the reaction temperature exceeds 80 ° C., it is not preferable because polyimide is easily formed by imidization reaction. Although reaction time changes with reaction temperature etc., it is about several hours-about 72 hours normally. It should be noted that any known method may be used to adjust the molecular weight of the aromatic amic acid oligomer. For example, after polymerizing at a molar ratio of aromatic tetracarboxylic acid component / aromatic diamine of 0.5 to 0.95 to form an aromatic amic acid oligomer having a predetermined molecular weight, an aromatic tetracarboxylic acid is formed as necessary. A method of adding an aromatic tetracarboxylic acid component so that the acid component / aromatic diamine is approximately equimolar (see Japanese Examined Patent Publication No. 1-2222), or approximately equimolar aromatic tetracarboxylic acid component / aromatic diamine. The reaction can be suitably performed by a method in which a predetermined amount of a compound that suppresses high molecular weight such as water is present (see Japanese Patent Publication No. 2-3820).

  As a method for preparing the second aromatic amic acid oligomer, a polycondensation reaction is carried out using an approximately equimolar amount of two or more aromatic tetracarboxylic acid diesters and an aromatic diamine at a temperature of about 90 to 120 ° C. in an organic polar solvent. By doing so, an aromatic amic acid oligomer (number average molecular weight of about 1000 to 7000) can be produced.

  Specifically, the asymmetric aromatic tetracarboxylic acid diester is about 15 to 55 mol% (preferably 20 to 50 mol%) and the symmetrical aromatic tetracarboxylic acid diester is 85 to 45 mol% (preferably 80 to 50 mol%). ) To a polycondensation reaction. As the organic polar solvent, those described above are employed, and NMP is particularly preferable.

  In order to prepare an aromatic amic acid oligomer having a desired molecular weight, its reaction temperature and reaction time are closely related. The heating temperature is usually about 90 to 120 ° C. However, when the reaction temperature is in a high temperature range, the reaction time is shortened in order to suppress the production amount of imide (imidation rate) and high molecular weight. Is preferred. In addition, the heat treatment may be performed by gradually raising the temperature to a predetermined temperature, reacting at the predetermined temperature for about 1 to 3 hours, and then cooling. For example, the temperature may be raised to about 90 to 120 ° C. over about 1 to 4 hours, and reacted at the same temperature for about 30 minutes to 2 hours and then cooled.

  In the first and second preparation methods, the substantially equimolar amount means a reaction ratio that can prepare an aromatic amic acid of a predetermined oligomer level and thus obtain a target semiconductive tubular PI film. In addition, when dissolving both components uniformly in an organic polar solvent, you may heat (for example, about 40-70 degreeC) as needed.

  The aromatic amic acid oligomer solution is prepared by the above first and second preparation methods, and the number average molecular weight (Mn) thereof is prepared to about 1000 to 7000 (preferably about 3000 to 7000). The significance of specifying this range is that when the number average molecular weight is 1000 or less (that is, about monomer or bimer), the effect on the conductive properties cannot be obtained (for example, Comparative Example 1), and when the number average molecular weight is 7000 or more. This is because the solubility of the oligomer is extremely reduced, and the solution becomes unusable due to gelation or the like (for example, see Comparative Example 3). In addition, a number average molecular weight can be measured by the method as described in an Example, for example.

  The aromatic amic acid oligomer prepared in the present invention having a number average molecular weight (Mn) of about 1000 to 7000 usually has a ratio (Mw / Mn) of 2 or less to the weight average molecular weight (Mw).

  The main component of the aromatic amic acid oligomer solution produced by this heat treatment is an aromatic amic acid oligomer, but a part thereof may contain an imidized product in which the reaction further proceeds. However, the production rate (imidation rate) of the imide in the aromatic amic acid oligomer is 30% or less, preferably 25% or less, and particularly preferably 20% or less. In addition, the production amount (imidization rate) of the imide body by-produced can be measured by, for example, the method described in the examples.

Moreover, the non-volatile content concentration in the aromatic amic acid oligomer solution can be adjusted to a high concentration of about 30 to 45% by weight. The reason why such a high non-volatile content concentration can be prepared is that the polymer is easily dissolved in a solvent because it is an oligomer having no high molecular weight. Therefore, a film having a film thickness can be easily produced, and since the amount of the solvent used is small, the cost can be suppressed and the solvent can be easily removed by evaporation. The “nonvolatile content concentration” used in the present specification means a concentration measured by the method described in Example 1.
(5) Preparation of Semiconductive Aromatic Amide Acid Composition The aromatic amic acid oligomer solution thus obtained is uniformly mixed with the conductive CB powder to prepare a semiconductive aromatic amide composition.

  The reason why CB powder is used for imparting electrical resistance characteristics is that it is mixed and dispersible and stable with the prepared monomer mixed solution (compared to other commonly known metal and metal oxide conductive materials). This is because of excellent properties (change with time after mixing and dispersion) and no adverse effects on the polycondensation reaction.

  This CB powder has various physical properties (electrical resistance, volatile content, specific surface area, particle size, pH value) depending on its production raw materials (natural gas, acetylene gas, coal tar, etc.) and production conditions (combustion conditions). , DBP oil absorption, etc.). It is preferable to select a material that can be obtained stably and stably with the smallest possible amount of mixing and dispersion without variation in the desired electrical resistance.

  This conductive CB powder usually has an average particle size of about 15 to 65 nm. Especially when used for film for belts for intermediate transfer such as toner copying machines, color copying machines, and electrophotographic systems, the average particle size is 20 to 20 nm. A thing of about 40 nm is suitable.

  For example, channel black, oxidized furnace black, and the like can be given. Specific examples include Special Black 4 (PH3, volatile content 14%, particle size 25 nm) and Special Black 5 (PH3, volatile content 15%, particle size 20 nm) manufactured by Degussa.

  The method for mixing the CB powder into the aromatic amic acid oligomer solution is not particularly limited as long as the CB powder is uniformly mixed and dispersed in the aromatic amic acid oligomer solution. For example, a ball mill, a sand mill, an ultrasonic mill or the like is used.

  The amount of CB powder added is about 3 to 30 parts by weight (preferably 10 to 25 parts by weight with respect to 100 parts by weight of the total amount of the aromatic tetracarboxylic acid component and the organic diamine, which are raw materials for the aromatic amic acid oligomer. It is preferable to use about 1 part).

  The reason why the CB powder is used in the above range is to give the film volume resistivity (VR) and surface resistivity (SR) in the semiconductive region. The lower limit is about 3 parts by weight or more because this amount is necessary to obtain sufficient conductivity, and the upper limit is about 30 parts by weight or less for lower resistance. This is for the purpose of maintaining the moldability and preventing the physical properties of the film from being lowered.

  The non-volatile content in the semiconductive aromatic amic acid composition is about 30 to 45% by weight, and the concentration of the CB powder in the non-volatile content is about 3 to 25% by weight (preferably about 10 to 20% by weight). ), The concentration of the nonvolatile content derived from the aromatic amic acid oligomer is about 75 to 97% by weight (preferably about 80 to 90% by weight).

  It should be noted that imidazole compounds (2-methylimidazole, 1,2-dimethylimidazole, 2-methyl-4-methylimidazole, 2-ethyl-4-ethylimidazole) are contained in the composition within a range that does not adversely affect the effects of the present invention. Additives such as ethyl imidazole, 2-phenyl imidazole) and surfactants (fluorine surfactants, etc.) may be added.

Thus, a semiconductive aromatic amic acid composition for molding in which CB powder is uniformly dispersed is produced.
II. Semiconductive Endless Tubular Polyimide Film Next, a means for forming a semiconductive endless tubular polyimide film using the prepared semiconductive aromatic amic acid composition will be described.

  As this molding means, a rotational molding method using a rotary drum is adopted. First, the semiconductive aromatic amic acid composition is injected into the inner surface of the rotating drum and uniformly cast over the entire inner surface.

  The injection / casting method is performed by, for example, injecting a semiconductive aromatic amic acid composition in an amount equivalent to obtaining the final film thickness into a rotating drum that is stopped, and then gradually to a speed at which centrifugal force works. Increase the rotation speed. Cast uniformly over the entire inner surface with centrifugal force. Alternatively, injection and casting can be performed without using centrifugal force. For example, a horizontally long slit-like nozzle is arranged on the inner surface of the rotating drum, and the nozzle is rotated (at a speed higher than the rotating speed) while the drum is slowly rotated. In this method, the semiconductive aromatic amic acid composition for molding is uniformly sprayed from the nozzle toward the inner surface of the drum.

  In both methods, the inner surface of the rotating drum is mirror-finished, and barriers for preventing liquid leakage are provided around both ends. The drum is placed on a rotating roller and indirectly rotated by the rotation of the roller.

  For heating, a heat source such as a far infrared heater is disposed around the drum, and indirect heating from the outside is performed. The size of the drum is determined by the size of the desired semiconductive tubular PI film.

  In the heating, the inner surface of the drum is gradually heated to first reach about 100 to 190 ° C., preferably about 110 to 130 ° C. (first heating stage). The temperature increase rate may be about 1 to 2 ° C./min, for example. It is maintained at the above temperature for 1-2 hours, and approximately half or more of the solvent is volatilized to form a self-supporting tubular film. In order to perform imidization, it is necessary to reach a temperature of 280 ° C. or higher. However, when heated at such a high temperature from the beginning, the polyimide exhibits high crystallization, which not only affects the dispersion state of CB, but also is tough. There is a problem that a thick film is not formed. Therefore, as the first heating stage, the upper limit temperature is suppressed to about 190 ° C. at most, and the polycondensation reaction is terminated at this temperature to obtain a tough tubular PI film.

  When this stage is completed, the second stage heating is followed by heating to complete imidation, and the temperature is about 280 to 400 ° C. (preferably about 300 to 380 ° C.). Also in this case, it is preferable not to reach this temperature from the first stage heating temperature all at once, but to gradually increase the temperature to reach that temperature.

  The second stage heating may be performed while the endless tubular film is adhered to the inner surface of the rotating drum. When the first heating stage is finished, the endless tubular film is peeled off from the rotating drum, taken out, and separately imidized. For heating to 280 to 400 ° C. The time required for this imidization is usually about 2 to 3 hours. Therefore, the time required for all the steps of the first and second heating stages is usually about 4 to 7 hours.

  Thus, the semiconductive endless tubular PI film of the present invention is produced. The thickness of this film is not particularly limited, but is usually about 50 to 150 μm, preferably about 60 to 120 μm. In particular, when used as an electrophotographic intermediate transfer belt, about 75 to 100 μm is preferable.

The semiconductivity of this film is determined by coexistence of volume resistivity (Ω · cm) (hereinafter referred to as “VR”) and surface resistivity (Ω / □) (hereinafter referred to as “SR”). It is an electric resistance characteristic, and this characteristic is imparted by mixing and dispersing CB powder. The resistivity range can be freely changed basically depending on the mixing amount of the CB powder. The resistivity ranges in the film of the present invention are VR: 10 ² to 10 ¹⁴ and SR: 10 ³ to 10 ^15. Preferred ranges are VR: 10 ⁶ to 10 ¹³ , SR: 10 ⁷ to 10 ^14. Can be illustrated. These resistivity ranges can be easily achieved by adopting the blending amount of the above-mentioned CB powder. The content of CB in the film of the present invention is usually about 3 to 25% by weight, preferably about 10 to 20% by weight.

  The semiconductive PI film of the present invention has a very uniform electrical resistivity. That is, the semiconductive PI film of the present invention is characterized by small variations in logarithmically converted values of the surface resistivity SR and the volume resistivity VR, and the standard deviation of logarithmically converted values of all measurement points in the film is 0.2. Within 0.15, preferably within 0.15. Moreover, it has the characteristics that the difference of the surface resistivity (logarithm conversion value) of a film surface and a back surface is small, The difference is within 0.4, Preferably it is within 0.2. Furthermore, the value obtained by subtracting the logarithmic conversion value LogVR of the volume resistivity from the logarithmic conversion value LogSR of the surface resistivity can be maintained at a high value of 1.0 to 3.0, preferably 1.3 to 3.0.

  The PI film of the present invention has the above-mentioned excellent electrical characteristics because a semiconductive aromatic amic acid composition in which “aromatic amic acid oligomer” and CB powder are mixed in the production process of the film. This is thought to be due to the adoption of That is, in the composition, the CB powder is uniformly dispersed in the aromatic amic acid oligomer, but it can be increased in molecular weight while maintaining the uniform dispersibility in the film production process. It is considered that excellent properties were imparted to the film.

The PI film of the present invention has a wide variety of uses depending on functions such as excellent electrical resistance characteristics. For example, important applications requiring charging characteristics include color copying machines, toner copying machines, electrophotographic intermediate transfer belts, and the like. The semiconductivity (resistivity) necessary for the belt is, for example, VR10 ⁹ to 10 ¹² or SR10 ¹⁰ to 10 ¹³ , and the semiconductive endless tubular PI film of the present invention can be suitably used.

  Since the semiconductive polyimide film of the present invention uses a predetermined aromatic amic acid oligomer obtained by polycondensation of an aromatic tetracarboxylic acid component and an aromatic diamine component as a molding raw material, it has a uniform electrical resistivity. have. That is, the semiconductive polyimide film of the present invention has a small variation in surface resistivity and volume resistivity, a small difference in surface resistivity (logarithmic conversion value) between the film surface and the back surface, and a logarithmic conversion of surface resistivity. It has an excellent characteristic that the value obtained by subtracting the logarithm conversion value LogVR of the volume resistivity from the value LogSR can be maintained at a high value (1.0 to 3.0). That is, for example, when used as a transfer belt or the like, it is possible to appropriately charge and charge the charge, and to perform excellent image processing.

  The semiconductive polyimide film of the present invention thus obtained is more suitably used as an intermediate transfer belt for color copying machines.

  Next, the present invention will be described in more detail by way of examples together with comparative examples.

Example 1
2,3,3 ', 4'-biphenyltetracarboxylic acid dimethyl ester (reaction product of 1 mol of 2,3,3', 4'-biphenyltetracarboxylic acid tetracarboxylic dianhydride and 2 mol of methyl alcohol And 358.0 g (1.0 mol) and 3,3 ', 4,4'-biphenyltetracarboxylic acid dimethyl ester (1 mol of 3,3', 4,4'-biphenyltetracarboxylic acid tetracarboxylic dianhydride) And 2 mol of methyl alcohol as a diester) 358.0 (1.0 mol) and 4,4′-diaminodiphenyl ether 400 g (2 mol) mixed in 1674 g of NMP solvent at 60 ° C. and uniformly dissolved, Subsequently, the temperature was raised to 100 ° C. over 1 hour, heated at 100 ° C. for 1 hour, and then cooled. This solution was an oligomer solution having a nonvolatile content concentration of 32.9% by weight and a number average molecular weight of 2000. Hereinafter, this is referred to as “oligomer mixed solution A”.

  71.7 g of carbon black (CB) powder (PH3, particle size 23 nm) and 142.5 g of NMP were added to 1000 g of this oligomer mixed solution A, and thoroughly mixed and dispersed by a ball mill machine, and finally defoamed. This was used as a molding semiconductive oligomer solution. The non-volatile component concentration in the semiconductive oligomer solution was 33.0% by weight, and the CB concentration in the non-volatile component was 17.89% by weight.

  Then, 109 g was collected from the solution, poured into a rotating drum, and molded under the following conditions.

Rotating drum: An internal mirror finished metal drum having an inner diameter of 175 mm and a width of 540 mm was placed on two rotating rollers, and was placed in a state of rotating with the rotation of the rollers.

  Heating temperature: A far-infrared heater was disposed on the outer surface of the drum so that the inner surface m temperature of the drum was controlled at 120 ° C.

  First, 109 g of the solution was uniformly applied to the drum inner surface while rotating the rotating drum, and heating was started. Heating was performed at a rate of 2 ° C./min, reaching 120 ° C., and heated at that temperature for 90 minutes while maintaining its rotation.

  After completion of the rotation and heating, the rotating drum was removed as it was without cooling, and was left in a hot-air residence type oven to start heating for imidization. This heating also reached 320 ° C. while gradually raising the temperature. Then, after heating at this temperature for 30 minutes, it was cooled to room temperature, and the semiconductive tubular PI film formed on the inner surface of the drum was peeled off and taken out. The film thickness was 90 μm.

  The “nonvolatile content concentration” in this specification is a value calculated as follows. A sample (semiconductive oligomer solution or the like) is precisely weighed in a heat-resistant container such as a metal cup, and the weight of the sample at this time is Ag. Put the heat-resistant container containing the sample in an electric oven, heat and dry while heating up in order of 120 ℃ × 12min, 180 ℃ × 12min, 260 ℃ × 30min, and 300 ℃ × 30min. The weight of the solid content (non-volatile content weight) is Bg. The values of A and B of five samples of the same sample were measured (n = 5), and applied to the following formula (I) to determine the nonvolatile content concentration. The average value of the five samples was adopted as the nonvolatile content concentration in the present invention.

Nonvolatile content concentration = B / A x 100 (%) (I)
Comparative Example 1
Carboxylic acid dimethyl ester and diaminodiphenyl ether were mixed in the same amount ratio as in Example 1, and the solution dissolved at 60 ° C. was cooled as it was. This solution had a nonvolatile concentration of 32.9% by weight and was a substantially monomeric solution. Hereinafter, this is referred to as “monomer solution A”.

To this monomer solution A1000g, CB powder (PH3, particle size 23nm) 31.0g and NMP60.0
g was added, thoroughly mixed and dispersed with a ball mill, and finally defoamed. This was used as a semiconductive monomer solution for molding. The concentration of nonvolatile components in the semiconductive oligomer solution was 33.0% by weight, and the concentration of CB in the nonvolatile components was 8.61% by weight.

  Then, 109 g was collected from the solution, and then thermoformed in the same manner as in Example 1 to peel off and remove the semiconductive tubular PI film. The thickness of the film was 92 μm.

Example 2
2,3,3 ', 4'-biphenyltetracarboxylic acid dimethyl ester (reaction product of 1 mol of 2,3,3', 4'-biphenyltetracarboxylic acid tetracarboxylic dianhydride and 2 mol of methyl alcohol 143.2 g (0.4 mol) and 3,3 ', 4,4'-biphenyltetracarboxylic acid dimethyl ester (1 mol of 3,3', 4,4'-biphenyltetracarboxylic acid tetracarboxylic dianhydride) And 2 mol of methyl alcohol as a diester) 572.8 (1.6 mol) and 4,4′-diaminodiphenyl ether 400 g (2 mol) mixed in 1674 g of NMP solvent at 60 ° C. and uniformly dissolved, Subsequently, the temperature was raised to 110 ° C. over 1 hour, heated at 110 ° C. for 1 hour, and then cooled. This solution was an oligomer solution having a nonvolatile content concentration of 32.9% by weight and a number average molecular weight of 4000. Hereinafter, this is referred to as “oligomer mixed solution B”.

  78.9 g of CB powder (PH3, particle size 23 nm) and 157.1 g of NMP were added to 1000 g of this oligomer mixed solution B, thoroughly mixed and dispersed with a ball mill, and finally defoamed. This was used as a molding semiconductive oligomer solution. The concentration of nonvolatile components in the semiconductive oligomer solution was 33.0% by weight, and the concentration of CB in the nonvolatile components was 19.34% by weight.

  Then, 109 g was collected from the solution, poured into a rotating drum, and thereafter thermoformed in the same manner as in Example 1 to peel off and remove the semiconductive tubular PI film. The thickness of the film was 89 μm.

Comparative Example 2
Carboxylic acid dimethyl ester and diaminodiphenyl ether were mixed at the same quantitative ratio as in Example 2, dissolved at 60 ° C., then heated to 85 ° C. over 1 hr, heated at 85 ° C. for 1 hr and cooled. This solution was an oligomer solution having a nonvolatile content concentration of 32.9% by weight and a number average molecular weight of 500. Hereinafter, this is referred to as “oligomer mixed solution C”.

  To 1000 g of this oligomer solution, 31.0 g of CB powder (PH3, particle size 23 nm) and 60 g of NMP were added, thoroughly mixed and dispersed with a ball mill, and finally defoamed. This was used as a semiconductive monomer solution for molding. The concentration of nonvolatile components in the semiconductive oligomer solution was 33.0% by weight, and the concentration of CB in the nonvolatile components was 8.62% by weight.

  Then, 109 g was collected from the solution, and then thermoformed in the same manner as in Example 1 to peel off and remove the semiconductive tubular PI film. The thickness of the film was 92 μm.

Comparative Example 3
Carboxylic acid dimethyl ester and diaminodiphenyl ether were mixed at the same quantitative ratio as in Example 1, dissolved at 60 ° C., then heated to 130 ° C. over 1 hr, heated at 130 ° C. for 1 hr and cooled. However, this solution after cooling became a turbid gel-like solid and could not be used for molding.

  This gel was not redissolved even when diluted with a solvent. When the imidation rate of the obtained gel was measured, it was confirmed that the imidization reaction was progressing by about 35%. That is, it is considered that the heating temperature is high and the imidization reaction proceeds too much, so that the solubility is lowered and the resin component is precipitated.

Experimental Example Table 1 shows the film production conditions of the above Examples 1 and 2 and Comparative Examples 1 to 3, and the measurement results of the electrical resistance values of the obtained films. The surface resistivity, volume resistivity average, and standard deviation in Table 1 are all expressed in logarithmically converted values.
[Number average molecular weight]
The number average molecular weight was measured by the GPC method (solvent: NMP, converted to polyethylene oxide).
[Imidation rate]
It was calculated by the ratio of the intensity of absorption from the imide groups in an infrared spectrophotometer (1780 cm ^-1) and absorption attributable to benzene rings (1510 cm ^-1). The absorption of the benzene ring did not change either after the precursor or after imidization and was used as a control.
[Measurement of surface resistivity (SR) and volume resistivity (VR)]
The obtained tubular film was cut into a length of 400 mm as a sample, and a resistance measuring device “HIRESTA IP / UR probe” manufactured by Mitsubishi Chemical Corporation was used to make three vertical and vertical ( A total of twelve locations in the four (circumferential) directions were measured, and the average value was shown.

  The volume resistivity (VR) was measured after 10 seconds had elapsed under application of a voltage of 100 V, and the surface resistivity (SR) was measured after 10 seconds had elapsed under application of a voltage of 500 V.

表１によれば、実施例のフィルムでは、比較例に対し、表面抵抗率及び体積抵抗率の標準偏差が非常に小さい、すなわちバラツキが小さいことが分かった。

According to Table 1, in the film of an Example, it turned out that the standard deviation of surface resistivity and volume resistivity is very small with respect to a comparative example, ie, variation is small.

  Further, the film of the example has a very small difference in surface resistivity (logarithmic conversion value) between the film surface side and the back surface side as compared with the comparative example, and has preferable characteristics as an intermediate transfer belt for a color copying machine. .

  In general, if the heating rate during heating is increased, the value obtained by subtracting the logarithm converted value LogVR of the volume resistivity from the logarithm converted value LogSR of the surface resistivity (Log (SR / VR)) becomes lower. As a result, there has been a problem that the slow charge and charge of the charge cannot be performed properly, causing image defects. However, it was found that this value can be maintained at a high value (1.0 to 3.0) by using the oligomer mixed solution, and thus the productivity of the film can be further improved.

Claims (11)

Semiconductive fragrance comprising an aromatic amic acid oligomer obtained by polycondensation reaction of approximately equimolar amounts of two or more aromatic tetracarboxylic acid components and an aromatic diamine, carbon black, and an organic polar solvent Group amic acid composition. The aromatic amic acid oligomer obtained by polycondensation of approximately equimolar amounts of two or more aromatic tetracarboxylic dianhydrides and an aromatic diamine in an organic polar solvent at a temperature of about 80 ° C. or lower. The semiconductive aromatic amic acid composition according to claim 1, which is an aromatic amide acid oligomer. Two or more kinds of aromatic tetracarboxylic dianhydrides are a mixture of 15 to 55 mol% of asymmetric aromatic tetracarboxylic dianhydrides and 85 to 45 mol% of symmetric aromatic tetracarboxylic dianhydrides. The semiconductive aromatic amic acid composition according to claim 2. The aromatic amic acid oligomer is an aromatic obtained by polycondensation reaction of approximately equimolar amounts of two or more aromatic tetracarboxylic acid diesters and an aromatic diamine in an organic polar solvent at a temperature of about 90 to 120 ° C. The semiconductive aromatic amic acid composition according to claim 1, which is an amic acid oligomer. The two or more kinds of aromatic tetracarboxylic acid diesters are a mixture comprising 15 to 55 mol% of an asymmetric aromatic tetracarboxylic acid diester and 85 to 45 mol% of a symmetric aromatic tetracarboxylic acid diester. A semiconductive aromatic amic acid composition. The semiconductive aromatic amic acid composition according to any one of claims 1 to 5, wherein the aromatic amic acid oligomer has a number average molecular weight of about 1000 to 7000. The semiconductive aromatic amide according to any one of claims 1 to 6, wherein the compounding amount of the carbon black is about 3 to 30 parts by weight with respect to 100 parts by weight of the total amount of the aromatic tetracarboxylic acid component and the organic diamine. Acid composition. A method for producing a semiconductive endless tubular polyimide film, comprising subjecting the semiconductive aromatic amic acid composition according to any one of claims 1 to 7 to rotational molding and heat treatment. A semiconductive endless tubular polyimide film used for an electrophotographic intermediate transfer belt manufactured by the manufacturing method according to claim 8. The standard deviation of the logarithmic conversion value of the surface electrical resistivity is within 0.2, the standard deviation of the logarithmic conversion value of the volume resistivity is within 0.2, the logarithmic conversion value of the surface electrical resistivity and the logarithmic conversion of the back surface electrical resistivity The semiconductive endless tubular aromatic polyimide film according to claim 9, wherein a difference from the value is within 0.4. In an organic polar solvent, an approximately equimolar amount of two or more aromatic tetracarboxylic acid components and an aromatic diamine are partially subjected to a polycondensation reaction to obtain an aromatic amic acid oligomer solution, which is electrically conductive carbon black powder. A method for producing a semiconductive aromatic amic acid composition, characterized by uniformly mixing.