JP2008076518A - Semiconductive polyimide resin belt and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductive belt having superior electrical characteristics such that a resistance change due to transfer voltage is prevented and high-quality transferred images can be obtained stably over a long period of time, and also having superior physical characteristics of cracks and breakages due to the load applied in the width direction of the belt hardly occur and stable use is possible, even after a long-term running because of superior durability. <P>SOLUTION: The semiconductive belt comprises 70-80 wt.% of a polyimide resin and 30-20 wt.% of a carbon black, having a volatile matter content of 2-6% manufactured by an oil furnace method and has a surface resistivity of 1×10<SP>8</SP>-1×10<SP>14</SP>Ω/square, wherein the polyimide resin is a copolymer obtained by imidating substantially equimolar amounts of a biphenyltetracarboxylic acid component comprising 15-50 mol% of an asymmetric biphenyltetracarboxylic acid component and 80-50 mol% of a symmetric 3,3',4,4'-biphenyltetracarboxylic acid component, and an aromatic diamine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a semiconductive polyimide belt used as an intermediate transfer belt for an electrophotographic copying machine, a printer, a facsimile, a composite machine thereof, and a digital printing machine equipped with a color image forming apparatus, and a method for manufacturing the same.

  In an image forming apparatus using an electrophotographic system, first, a uniform charge is formed on a latent image carrier made of an inorganic or organic photoconductive photosensitive member, and electrostatic is generated by a laser or light emitting diode light that modulates an image signal. After the latent image is formed, the electrostatic latent image is developed with charged toner to obtain a visualized toner image. The toner image is electrostatically primary transferred onto an intermediate transfer belt, and the toner image on the intermediate transfer belt is electrostatically secondary transferred onto a recording sheet, and fixed by heating or pressurizing the toner image. There is known an intermediate transfer method for obtaining a required reproduced image by performing the above.

  Patent Document 1 exemplifies a conductive polyimide seamless belt in which conductive carbon black having a relatively small powder resistance, such as acetylene black and ketjen black, which are conductive carbon blacks, is dispersed in a polyimide resin. However, the intermediate transfer belt filled with conductive carbon black cannot eliminate the problem that unevenness occurs in the formed image even when the value of electrical resistivity is set within a predetermined range. It is considered that when conductive carbon black is dispersed in a polyimide resin, the structure formation due to primary aggregation or the conductive chain due to secondary aggregation significantly affects the image.

  And in patent document 2, the semiconductive belt using the conductive carbon black containing 10-25% of volatile components which mainly have a volatile acid component is disclosed. Further, it is described that when the volatile content of carbon black is less than 10%, the dispersibility of carbon black is poor, and as a result, the electric resistance value cannot be satisfied.

  Next, as an intermediate transfer body with little variation in electrical resistivity over time in a long-term durability test, Patent Document 3 contains a plurality of types of carbon black having different conductivity in polyimide resin, and at least one of them is oxidized. The use of treated carbon black is described. Patent Document 4 describes that 10 to 30% by weight of carbon black oxidized on a polyimide resin is contained. These Patent Documents 3 and 4 disclose that the fluctuation range of the surface resistivity is 1.0 (logΩ / □) or less in the common logarithmic value even after the transfer is continuously repeated 10,000 times.

  However, the polyimide resin used in these patent documents passes through a high molecular weight polyamic acid solution obtained by reacting 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine. This is a rigid polyimide resin. A semiconductive belt containing carbon black in such a rigid polyimide resin up to about 20% by weight is very fragile and loses the inherent toughness of the polyimide resin. When used as an intermediate transfer belt, it is caused by a load applied in the width direction. There was a problem that cracks and cracks occurred.

  Further, as toughening of polyimide resin, in Patent Document 5 and Patent Document 6, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, p-phenylenediamine and 4,4′-diaminodiphenyl ether are used. A copolymer belt is disclosed. However, even with these copolymer belts, the semiconductive belt containing 20% by weight or more of carbon black in the polyimide resin has a problem that the belt is damaged when the belt is run for a long time. One reason for this is that since the polyimide resin has a crystal structure, non-uniform distribution of stress, that is, stress concentration, is caused, and this stress concentration causes local breakage of the molecular chain of the polyimide resin.

  The polyimide film (belt) generally uses a high molecular weight solution having a weight average molecular weight of 20000 or more of a polyamic acid solution which is a precursor thereof. When the weight average molecular weight is less than 20000, the film becomes mechanically fragile due to a decrease in molecular weight due to depolymerization during the drying process at 120 to 200 ° C., and as a result, reaction shrinkage in the in-plane direction of the film during thermal imidization. This is because the film cannot be tolerated and cracks occur, making it very difficult to produce the film.

In Patent Documents 7 to 10, the carbon black of the oil furnace method is modified to provide an oxygen functional group on the surface for the purpose of producing carbon black suitable for liquid toner, ink, paint, and the like. Various oxidation methods have been reported.
JP-A-5-77252 JP 2001-47451 A JP 2002-148951 A JP 2002-148957 A JP 2002-341673 A JP 2003-266454 A JP-A-11-181326 JP 2000-7937 A JP 2000-290529 A JP 2001-40240 A

  The present invention can realize accurate transfer in a color image forming apparatus, prevents resistance change due to a transfer voltage, and has excellent electrical characteristics such as being able to obtain a high-quality transfer image stably over a long period of time. In addition, the semiconductive belt has excellent mechanical properties such as being resistant to cracking and cracking due to the load applied in the width direction of the belt, excellent durability, and stable use even if it is run for a long period of time. Is to provide.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor is an intermediate transfer belt matrix in order to obtain an intermediate transfer belt that is excellent in durability and can realize precise semiconductivity control. We focused on the composition of the polyimide resin and the dispersibility of the carbon black in the polyimide resin.

  In said patent documents 4-6, since polyimide resin has a crystal structure, it becomes rigid and brings about non-uniform distribution of stress, ie, stress concentration. Therefore, it was considered important to provide flexibility by lowering the crystallinity of the polyimide resin.

  In addition, in order to obtain a semiconductive polyimide belt having tough mechanical properties, it was considered that there was room for studying a method for preparing a polyamic acid solution as a precursor solution thereof.

  Furthermore, in order to improve the dispersibility of the carbon black contained in the polyimide resin, attention was paid to its physical properties.

  For example, in the conductive model of carbon black in the resin shown in FIG. 1, there are three types: a partially continuous (A), a discontinuous (B), and a continuous (C). From the equivalent circuit shown on the right, it can be understood that the conductivity of the polyimide belt is manifested by a combination of a chain effect (R: resistor) and a tunnel effect (C: capacitor) due to carbon black. FIG. 2 is a photomicrograph reproducing the states (A) to (C). In (A), carbon black aggregates to cause resistance variation at the micro level, resulting in image defects. In (B), semiconductivity can be controlled by uniform dispersion, but the resistivity changes due to mechanical or electrical stress. In (C), stable conductivity is expressed, and the conductivity is almost determined by the powder resistance of carbon black.

  Therefore, as shown in FIG. 1, it is necessary that the carbon black is not dispersed partially continuously or discontinuously in the resin, but it is necessary to uniformly disperse it as continuously as possible. It was considered important to make the carbon black highly filled, that is, to increase the carbon black concentration in the solid content in the carbon black-dispersed polyimide precursor solution composition.

  Therefore, the present inventor has developed a polyimide resin obtained by copolymerizing a biphenyltetracarboxylic component containing an asymmetrical biphenyltetracarboxylic acid component and an aromatic diamine with a volatile content of 2-6% produced by an oil furnace method. It has been found that a semiconductive belt in which carbon black is dispersed has excellent mechanical properties and a high-quality transfer image can be obtained. Based on this knowledge, further studies have been made and the present invention has been completed.

  That is, this invention provides the following semiconductive polyimide resin belt and its manufacturing method.

Item 1. The surface resistivity is 1 × 10 ⁸ to 1 × 10 ¹⁴ Ω / □ including 70 to 80% by weight of polyimide resin and 30 to 20% by weight of carbon black having a volatile content of 2 to 6% manufactured by the oil furnace method. A semiconductive belt, in which the polyimide resin has an asymmetric biphenyltetracarboxylic acid component of 15 to 50 mol% and a symmetrical 3,3 ′, 4,4′-biphenyltetracarboxylic acid component of 85 to 50 mol. A semiconductive belt which is a copolymer obtained by imidizing a substantially equimolar amount of a biphenyltetracarboxylic acid component consisting of 1% and an aromatic diamine.

  Item 2. Item 2. The asymmetric biphenyltetracarboxylic acid component is 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride or 2,3,3 ′, 4′-biphenyltetracarboxylic acid diester. Semi-conductive belt.

  Item 3. Item 3. The semiconductive belt according to Item 1 or 2, wherein the aromatic diamine is 4,4'-diaminodiphenyl ether.

Item 4. Item 1-3, wherein the carbon black produced by the oil furnace method has a pH of 2 to 4, a nitrogen adsorption specific surface area of 60 to 150 m ² / g, and a DBP absorption of 40 to 120 ml / 100 g. The semiconductive belt according to any one of the above.

  Item 5. Item 5. An intermediate transfer belt of an electrophotographic apparatus comprising the semiconductive belt according to any one of Items 1 to 4.

Item 6. Biphenyltetracarboxylic dianhydride comprising 15-50 mol% asymmetric biphenyltetracarboxylic dianhydride and 85-50 mol% symmetrical 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride And an approximately equimolar amount of the aromatic diamine are reacted in an organic polar solvent to produce a polyamic acid solution having a weight average molecular weight of 20000 or less, and the volatilization produced by the oil furnace method is added to the polyamic acid solution. A polyimide precursor solution composition is prepared by uniformly dispersing 2 to 6% of carbon black, and the carbon black-dispersed polyimide precursor solution composition is formed into a tubular product by a rotational molding method. A method for producing a semiconductive belt that is imidized by heat treatment,
(1) A step of coating the carbon black-dispersed polyimide precursor solution composition with a uniform thickness on the inner peripheral surface of a cylindrical mold rotating at a centrifugal acceleration of about 0.5 to 10 times the gravitational acceleration.
(2) A process of forming a self-supporting film by heating the cylindrical mold at a temperature of about 100 to 140 ° C. while rotating at a centrifugal acceleration of about 0.5 to 10 times the gravitational acceleration, and ( 3) A step of imidizing by heating at a temperature of about 300 ° C. or higher while the film is attached to the inner peripheral surface of the cylindrical mold,
The manufacturing method characterized by including.

Item 7. A biphenyl tetracarboxylic acid diester comprising 15 to 50 mol% of an asymmetric biphenyl tetracarboxylic acid diester and 85 to 50 mol% of a symmetrical 3,3 ′, 4,4′-biphenyl tetracarboxylic acid diester, an aromatic diamine, and Is dissolved in an organic polar solvent to prepare a nylon salt type monomer solution, and carbon black having a volatile content of 2 to 6% produced by the oil furnace method is uniformly added to the nylon salt type monomer solution. A semiconductive belt in which a polyimide precursor solution composition is prepared by dispersion, the carbon black-dispersed polyimide precursor solution composition is formed into a tubular product by a rotational molding method, and the molded body is heated to imidize. A manufacturing method of
(1) A step of coating the carbon black-dispersed polyimide precursor solution composition with a uniform thickness on the inner peripheral surface of a cylindrical mold rotating at a centrifugal acceleration of about 0.5 to 10 times the gravitational acceleration.
(2) A process of forming a self-supporting film by heating the cylindrical mold at a temperature of about 100 to 140 ° C. while rotating at a centrifugal acceleration of about 0.5 to 10 times the gravitational acceleration, and ( 3) A step of imidizing by heating at a temperature of about 300 ° C. or higher while the film is attached to the inner peripheral surface of the cylindrical mold,
The manufacturing method characterized by including.

  Item 8. Item 8. A semiconductive belt manufactured by the manufacturing method according to Item 6 or 7.

  Hereinafter, the present invention will be described in detail.

The semiconductive polyimide belt of the present invention contains 70 to 80% by weight of a polyimide resin and 30 to 20% by weight of carbon black having a volatile content of 2 to 6% manufactured by an oil furnace method, and its surface resistivity is 1 × 10 ⁸ to 1 × 10 ¹⁴ Ω / □, and the polyimide resin contains 15 to 50 mol% of asymmetric biphenyltetracarboxylic acid component and symmetric 3,3 ′, 4,4′-biphenyltetracarboxylic acid. It is a copolymer obtained by imidizing a substantially equimolar amount of a biphenyltetracarboxylic acid component consisting of 85 to 50 mol% of an acid component and an aromatic diamine.

This semiconductive polyimide belt is capable of obtaining a stable and high-quality transfer image and is excellent in durability.
1. Carbon black having a volatile content of 2 to 6% The carbon black used in the present invention is a carbon black produced by an oil furnace method, and further prepared by oxidizing to a volatile content of 2 to 6%. is there.

  The production method of carbon black by the oil furnace method is currently mainstream of carbon black because it has better yield and productivity than the channel method and does not pollute the environment during production. However, since channel black contains a large amount of volatile matter (usually 10.0% or more), it is familiar with the polyimide precursor solution and has excellent dispersibility, whereas oil furnace carbon black is more volatile than channel black. Since the content is extremely small (usually 1.5% or less), the dispersibility in the polyimide precursor solution is poor and carbon black aggregates during storage. This is because carbon black of the oil furnace method is manufactured by pyrolyzing hydrocarbons in a reducing atmosphere in a high-temperature gas combusted with fuel, so it has significantly less volatile content than channel black made at low temperature in the air. It is to become.

  In the present invention, carbon black of the oil furnace method is modified (oxidation treatment) to increase the volatile content to a range of 2 to 6%.

  In the oxidation treatment, the kind of the oxidant used for the oxidation is particularly important, and as the oxidant, an oxidant such as nitrogen oxide containing nitric acid, ozone, hypochlorous acid, sulfuric acid gas or the like can be used. In particular, an oxidizing agent containing ozone, particularly ozone, is preferably used because the raw material oxidizing agent remains little in the treated carbon black and the undecomposed raw material hydrocarbon (PAH) is decomposed. The undecomposed raw material hydrocarbon (PAH) should be as small as possible, specifically 10 ppm or less.

  It is important that the volatile content of the carbon black by the oil furnace method is in the range of 2 to 6% by the oxidation treatment, preferably about 2.5 to 5%.

  Since the surface of carbon black having a volatile content of 2 to 6% contains oxygen functional groups (particularly carboxyl groups) such as phenolic hydroxyl groups, carbonyl groups, and carboxyl groups, it has fluidity and dispersion stability in a polyamic acid solution. And the affinity to the polyimide resin is also improved.

  If carbon black is produced by the oil furnace method and has the same specific surface area and dibutyl phthalate adsorption amount (DBP absorption amount), the volatile content and the powder resistance are in a substantially proportional relationship. Since the oxygen functional group, which is a volatile component on the surface of the carbon black, acts as an insulator that inhibits the flow of π electrons, the powder resistance is higher than that of the carbon black produced by the oil furnace method that has not been oxidized. By setting to this range, the powder resistance of carbon black can be controlled at a high value of about 3 to 30 Ω · cm.

Therefore, when the surface resistivity of the polyimide resin belt is set to a desired range (10 ⁸ to 10 ¹⁴ Ω / □), the carbon black is highly filled into the polyimide resin (the carbon black concentration in the polyimide resin is 20 to 30). % By weight). Thereby, the electroconductivity by the chain | linkage of carbon black is provided and the polyimide resin belt which has the stable electrical property which is hard to be influenced by an external environment and an applied voltage can be obtained. In other words, the carbon black concentration in the solid content in the carbon black-dispersed polyimide precursor solution composition can be controlled to a high concentration of 20 to 30% by weight.

  Carbon black with a volatile content of less than 2% (for example, Mitsubishi Carbon Black “MA11” “MA100” manufactured by Mitsubishi Chemical, “Printex 95” “Printex L6” manufactured by Dexa, etc.) has an affinity problem with the polyimide precursor solution. , Secondary dispersion tends to be easily formed by van der Waals force after dispersion.

Carbon blacks with a volatile content exceeding 6% (for example, Dexa Color Black FW200, Special Black 5, Special Black 4 and Printex 150T) are mostly channel method carbon black, and hydrogen. In addition to oxygen and oxygen, there are many impurities such as sulfur and undecomposed raw material hydrocarbons (PAH), which degrade the original mechanical properties of binder resins such as polyimide resins. In addition, when it is an oil furnace carbon black that is oxidized at a volatile content exceeding 6%, the powder resistance will be significantly higher (because it becomes insulating carbon black), so the surface required as an intermediate transfer belt. Resistivity of 10 ⁹ to 10 ¹⁴ Ω / □ cannot be realized.

The carbon black used in the present invention preferably has a nitrogen adsorption specific surface area (JIS K6217) of 60 to 150 m ² / g, more preferably 80 to 130 m ² / g. Generally, when carbon black is oxidized by various methods, more oxygen functional groups are imparted as the specific surface area increases. However, the powder resistance of carbon black and the physical properties when blended with various materials correlate with the number of oxygen functional groups imparted to the unit surface, not the absolute amount of oxygen functional groups.

When the specific surface area is smaller than 60 m ² / g, affinity with the polyimide precursor solution cannot be obtained, and the powder resistance does not have a sufficiently high value. In addition, when it exceeds 150 m ² / g, carbon black with a high specific surface area, that is, carbon black with primary particles being small or having pores even at the same particle diameter, and even if oxygen functional groups are added, as a result The powder resistance of carbon black does not increase. Therefore, a semiconductive polyimide resin belt having a high carbon black concentration in the solid content (for example, filled at a high concentration of 20% by weight or more) cannot be obtained. That is, only a semiconductive polyimide resin belt having a low carbon black filling amount can be obtained.

  The carbon black used in the present invention has a pH of 2 to 4, preferably 2 to 3.

The carbon black used in the present invention preferably has a dibutyl phthalate absorption amount (DBP absorption amount) of 40 to 120 ml / 100 g, more preferably 50 to 90 ml / 100 g. When the DBP absorption exceeds 120 ml / 100 g, the powder resistance of carbon black does not increase even when oxidation treatment is performed. Therefore, a semiconductive polyimide resin belt filled with a carbon black concentration of 20% by weight or more in the solid content cannot be obtained. When the DBP absorption amount is less than 40 ml / 100 g, the powder resistance becomes too high. Therefore, unless the carbon black concentration in the solid content exceeds 30% by weight, a semiconductive polyimide resin belt cannot be obtained.
2. Carbon Black Dispersed Polyimide Precursor Solution Composition The semiconductive polyimide belt of the present invention is a rotationally molded carbon black dispersed polyimide precursor solution composition (hereinafter also referred to as “CB dispersed PI precursor solution composition”). To manufacture. This CB-dispersed PI precursor solution composition is a volatilization produced by an oil furnace method into a polyimide precursor solution containing an organic polar solvent and a polyimide resin raw material as a solid content (hereinafter also referred to as “PI precursor solution”). Carbon black having a content of 2 to 6% is uniformly dispersed.

  The PI precursor solution comprises a biphenyl tetracarboxylic acid component comprising 15 to 50 mol% of an asymmetric biphenyl tetracarboxylic acid component and 85 to 50 mol% of a symmetrical 3,3 ′, 4,4′-biphenyl tetracarboxylic acid component. And an approximately equimolar amount of aromatic diamine. Specifically, a polyamic acid solution having a weight average molecular weight of 20000 or less or a nylon salt monomer solution shown below can be used.

  In addition, as a biphenyltetracarboxylic acid component, biphenyltetracarboxylic dianhydride or biphenyltetracarboxylic acid diester is mentioned as mentioned below.

Polyamic acid solution having a weight average molecular weight of 20000 or less This polyamic acid solution having a weight average molecular weight of 20000 or less is composed of 15 to 50 mol% of asymmetric biphenyltetracarboxylic dianhydride and a symmetrical 3,3 ′, 4,4. It is produced by reacting biphenyltetracarboxylic dianhydride consisting of 85 to 50 mol% of '-biphenyltetracarboxylic dianhydride with an approximately equimolar amount of aromatic diamine in an organic polar solvent.

  A typical example of an asymmetric biphenyltetracarboxylic dianhydride is 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride (a-BPDA). The asymmetric biphenyltetracarboxylic dianhydride is 15 to 50 mol%, preferably 20 to 40 mol%, more preferably 20 to 30 mol% in the biphenyltetracarboxylic dianhydride.

  The symmetrical 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride is 85 to 50 mol%, preferably 80 to 60 mol%, more preferably 80 in biphenyltetracarboxylic dianhydride. -70 mol%.

  When the amount of the asymmetric biphenyltetracarboxylic dianhydride is 50 mol% or less, the yield strength and elastic modulus of the obtained belt are good, and when used as an intermediate transfer belt, the drive response is excellent.

  On the other hand, when the amount is less than 15 mol%, a highly crystalline and rigid polyimide is produced. Therefore, a semiconductive belt containing carbon black up to about 20% by weight is very brittle and loses toughness. In addition, when the weight average molecular weight of the polyamic acid is less than 20000, the film is cracked in the drying process at 120 to 200 ° C., and as a result, the film cannot withstand the reaction shrinkage in the film in-plane direction at the time of thermal imidization and crack. This makes it difficult to produce a belt.

As an 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—, —CH ₂ —. , —SO—, —SO ₂ — and 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. Of 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.

  The organic polar solvent is preferably an aprotic organic polar solvent. For example, N-methyl-2-pyrrolidone (hereinafter referred to as “NMP”), N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, 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.

  Any known method may be used to adjust the molecular weight of the polyamic acid. For example, after forming a polyamic acid having a predetermined molecular weight by polymerizing a biphenyltetracarboxylic dianhydride / aromatic diamine molar ratio of 0.5 to 0.95, a biphenyltetracarboxylic dianhydride is formed as necessary. Biphenyltetracarboxylic acid is added so that the product / aromatic diamine is approximately equimolar (see, for example, Japanese Patent Publication No. 1-2290), and biphenyltetracarboxylic dianhydride / aromatic diamine is approximately equimolar. The reaction can be suitably carried out by a method in which a predetermined amount of a compound that suppresses high molecular weight such as water coexists (for example, see Japanese Patent Publication No. 2-3820).

  In general, it is known that the tensile properties (tensile strength, elongation at break, elastic modulus) of a polyimide film (belt) having a symmetric structure greatly depend on the weight average molecular weight of the polyamic acid in the polyamic acid solution. The tensile properties show a substantially constant value when the weight average molecular weight is 30000 or more, but rapidly decrease when the weight property is 20000 or less. Therefore, a polyamic acid having a weight average molecular weight of 30000 or more is used for the polyamic acid having a symmetric structure.

  In contrast, in a solution containing a polyamic acid having an asymmetric structure containing 15 mol% or more of an asymmetric biphenyltetracarboxylic dianhydride, the tensile properties of the polyimide film do not depend on the weight average molecular weight of the polyamic acid, Even if the average molecular weight is 20000 or less, a tough film can be formed. Therefore, even if the polyimide precursor composition as described later is a nylon salt monomer solution (weight average molecular weight around 5000), it is possible to produce a high-strength and tough polyimide belt.

  Furthermore, in the case of a polyamic acid solution containing 15 mol% or more of an asymmetric biphenyltetracarboxylic dianhydride, the solubility of the polyamic acid in an organic polar solvent can be increased, and the solidity of the polyamic acid solution composition can be increased. The partial concentration can be adjusted to a high concentration of 20% by weight or more, especially 30-50% by weight. The reason why such a high solid content concentration can be prepared is that the polyamic acid is not high in molecular weight and is therefore easily dissolved in a solvent. Therefore, a belt having a film thickness of 100 μm or more can be easily manufactured, and since the amount of the solvent used is small, the cost can be suppressed and the solvent can be easily removed by evaporation.

  In addition, if there are many solvents to evaporate, the buoyancy and surface tension that causes temperature convection and evaporation convection in the drying process, viscosity changes due to solvent evaporation, density changes, etc. are large, and the dispersion state of carbon black occurs unevenly. Phenomenon ". However, since the amount of the solvent is small in the polyamic acid solution composition used in the present invention, such a problem can be suppressed as much as possible.

  In addition, when a predetermined amount of asymmetric biphenyltetracarboxylic dianhydride is mixed with an aromatic diamine, the molecular structure of the polyimide resin is bent, and flexibility is produced in the polyimide resin belt.

  The coexistence effect of symmetric and asymmetric biphenyltetracarboxylic dianhydride is most effectively exhibited when 15 to 50 mol% of asymmetric biphenyltetracarboxylic dianhydride is blended. The yield strength, breaking strength, and breaking strain in the tensile test of the polyimide resin belt are greatly improved. As a result, even when the polyimide resin contains carbon black at a high concentration of 20% by weight or more, a tough semiconductive belt is obtained.

  In general, when a polyimide is produced from symmetrical biphenyltetracarboxylic dianhydride (s-BPDA), a crystal structure is easily formed due to its high symmetry. However, copolymerization with addition of 15 mol% or more of asymmetric biphenyltetracarboxylic dianhydride (a-BPDA) inhibits the regularity of the molecular chain, so that the formation of crystals is suppressed and the amorphous structure is reduced. Become dominant. Therefore, the affinity with carbon black having a volatile content of 2 to 6% is increased, and the carbon black concentration in the polyimide resin can be increased. The carbon black concentration can be adjusted to a high concentration of, for example, 20 to 30% by weight (particularly 25 to 30% by weight).

Nylon salt type monomer solution Nylon salt type monomer solution is composed of 15-50 mol% of asymmetric biphenyltetracarboxylic acid diester and 85-50 mol% of symmetric 3,3 ′, 4,4′-biphenyltetracarboxylic acid diester. A biphenyltetracarboxylic acid diester and an approximately equimolar amount of an aromatic diamine are dissolved in an organic polar solvent.

  Typical examples of the asymmetric biphenyltetracarboxylic acid diester include 2,3,3 ', 4'-biphenyltetracarboxylic acid diester. The asymmetric biphenyltetracarboxylic acid diester is 15 to 50 mol%, preferably 20 to 40 mol%, more preferably 20 to 30 mol% in the biphenyltetracarboxylic acid diester.

  The symmetrical 3,3 ′, 4,4′-biphenyltetracarboxylic acid diester is 85 to 50 mol%, preferably 80 to 60 mol%, more preferably 80 to 70 mol% in the biphenyl tetracarboxylic acid diester. It is.

  In the symmetric or asymmetric biphenyltetracarboxylic acid diester, two carboxyl groups out of four carboxyl groups of biphenyltetracarboxylic acid are esterified, and two adjacent benzene rings are adjacent to each other. One of the carboxyl groups is an esterified compound.

Examples of the two esters in the biphenyltetracarboxylic 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.

The symmetric or asymmetric biphenyltetracarboxylic acid diester is commercially available or can be produced by a known method. For example, it can be easily produced by a known method such as reacting 1 mol of the corresponding biphenyltetracarboxylic dianhydride with 2 mol of the corresponding alcohol (lower alcohol, preferably C _1-3 alcohol). . As a result, the raw acid anhydride reacts with the alcohol to open the ring to produce diesters each having an ester group and a carboxyl group on adjacent carbons on the two benzene rings.

  When the amount of the asymmetric biphenyltetracarboxylic acid diester exceeds 50 mol%, the yield strength and elastic modulus of the obtained belt are weak, and when used as an intermediate transfer belt, not only the drive response is poor, but also the initial There are problems such as belt elongation at the stage.

  On the other hand, when the amount is less than 15 mol%, a highly crystalline and rigid polyimide is produced. Therefore, a semiconductive belt containing carbon black up to about 20% by weight is very brittle and loses toughness.

As an 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—, —CH ₂ —. , —SO—, —SO ₂ — and 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. Of 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.

  The organic polar solvent is preferably an aprotic organic polar solvent. For example, N-methyl-2-pyrrolidone (hereinafter referred to as “NMP”), N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, 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 nylon salt monomer solution is produced by dissolving approximately equimolar amounts of biphenyltetracarboxylic acid diester and aromatic diamine in an organic polar solvent. It is considered that the ion pair of the carboxylate ion of biphenyltetracarboxylic acid diester and the ammonium ion of aromatic diamine is in a substantial monomer state in an organic polar solvent.

  In the nylon salt type monomer solution, for example, an ion pair of a carboxylate ion of a biphenyltetracarboxylic acid diester and an ammonium ion of an aromatic diamine in an organic polar solvent is considered to have a substantial monomer state (for example, the following formula See). Moreover, since it is in a substantially monomer state, it is extremely easy to dissolve in the above-mentioned organic polar solvent, and there is an advantage that the amount of the solvent to be used can be reduced as much as possible.

(In the formula, Ar is a tetravalent residue obtained by removing two carboxyl groups and two ester groups from a biphenyltetracarboxylic acid diester, Ar ′ is a divalent residue obtained by removing two amino groups from an aromatic diamine, R represents an alkyl group.)
Therefore, the solid content concentration of the nylon salt monomer solution can be adjusted to a high concentration of 20% by weight or more, particularly 30 to 50% by weight. As a result, a belt having a film thickness of 100 μm or more can be easily manufactured. Since the amount of the solvent used is small, the cost can be suppressed and the solvent can be easily removed by evaporation.

  In addition, if there are many solvents to evaporate, the buoyancy and surface tension that causes temperature convection and evaporation convection in the drying process, viscosity changes due to solvent evaporation, density changes, etc. are large, and the dispersion state of carbon black occurs unevenly. Phenomenon ". However, since the nylon salt monomer solution (PI precursor solution) of the present invention has a small amount of solvent, such a problem can be suppressed as much as possible.

  Further, by copolymerizing a predetermined amount of asymmetric biphenyltetracarboxylic acid diester with an aromatic diamine, the molecular structure of the polyimide resin is bent, and the polyimide resin belt is made flexible.

  The coexistence effect of the symmetric and asymmetric biphenyltetracarboxylic acid diester is most effectively exhibited when 15 to 50 mol% of the asymmetrical biphenyltetracarboxylic acid diester is blended. The yield strength, breaking strength, and breaking strain in the tensile test of the polyimide resin belt are greatly improved. As a result, even when the polyimide resin contains carbon black at a high concentration of 20% by weight or more, a tough semiconductive belt is obtained.

  In general, when a polyimide is produced from a symmetrical biphenyltetracarboxylic acid diester, a crystal structure is easily formed due to the high symmetry. However, when 15 mol% or more of asymmetric biphenyltetracarboxylic acid diester is added and copolymerized, the regularity of the molecular chain is inhibited, so that the formation of crystals is suppressed and the amorphous structure becomes dominant. Therefore, the affinity with carbon black having a volatile content of 2 to 6% is increased, and the carbon black concentration in the polyimide resin can be increased. The carbon black concentration can be adjusted to a high concentration of, for example, 20 to 30% by weight (particularly 25 to 30% by weight).

Preparation of carbon black-dispersed polyimide precursor solution composition The CB-dispersed PI precursor solution composition uniformly disperses carbon black having a volatile content of 2 to 6% produced by an oil furnace method in the PI precursor solution. Prepare.

  The method of mixing the carbon black into the PI precursor solution is not particularly limited as long as the carbon black is uniformly mixed and dispersed in the PI precursor solution. For example, a method using a sand mill, a bead mill, an ultrasonic mill, a three roll or the like is used. The average particle size of the carbon black after mixing and dispersion is usually about 0.1 to 0.5 μm, preferably about 0.2 to 0.4 μm.

  The amount of carbon black added to the PI precursor solution is determined to be 20 to 30% by weight in the solid content of the PI precursor solution composition. The lower limit is 20% by weight or more because, for example, when used as an intermediate transfer belt of a color image forming apparatus, it is possible to appropriately perform charge stability and slow charge of the charge, and to stably provide high quality over a long period of time. 30% by weight or less is necessary for obtaining a transfer image in order to maintain the strength as an intermediate transfer belt and prevent problems such as breakage of the intermediate transfer member even during long-term use. It is.

  It should be noted that an imidazole compound (2-methylimidazole, 1,2-dimethylimidazole, 2-methyl-4-methylimidazole, 2-ethyl-4-methyl) is contained in the composition as long as the effect of the present invention is not adversely affected. Additives such as ethyl imidazole, 2-phenylimidazole) and surfactants (fluorine surfactants, etc.) may be added.

  Thus, a PI precursor solution composition in which carbon black is uniformly dispersed in a solid content in the range of 20 to 30% by weight is produced.

If the viscosity of the carbon black dispersion PI precursor solution composition is, for example, 0.5 to 50 Pa · s, and preferably 1 to 10 Pa · s, the dispersion deterioration of the carbon black can be controlled to a minimum. The average particle size of carbon black in the solution is preferably in the range of 0.1 to 0.5 μm, and the maximum particle size is preferably 1 μm or less.
3. Method for Producing Semiconductive Polyimide Belt The semiconductive polyimide belt of the present invention is obtained by molding the carbon black-dispersed polyimide precursor solution composition (CB-dispersed PI precursor solution composition) into a tubular material by a rotational molding method. This is manufactured by heat treatment.

  In particular, (1) a step of applying the CB-dispersed PI precursor solution composition at a uniform thickness on the inner peripheral surface of a cylindrical mold rotating at a centrifugal acceleration of about 0.5 to 10 times the gravitational acceleration; (2 ) The cylindrical mold is heated at a temperature of about 100 to 140 ° C. while rotating at a centrifugal acceleration of about 0.5 to 10 times the gravitational acceleration to form a self-supporting film (the film does not flow). A step of forming, and (3) a step of imidizing by heating at a temperature of about 300 ° C. or higher while the film is attached to the inner peripheral surface of the cylindrical mold.

  Hereinafter, a means for forming a semiconductive belt using a CB-dispersed PI precursor solution composition (hereinafter simply referred to as “liquid raw material”) will be described.

  The liquid material is applied with a uniform thickness on the inner peripheral surface of a cylindrical mold that rotates at a low speed with a centrifugal acceleration of 0.5 to 10 times the acceleration of gravity. In other words, the shear force applied in the rotational direction is low when the liquid raw material is supplied at a low-speed rotation of 0.5-10 times the gravitational acceleration, and the orientation of molecular chains and the structure orientation of fillers such as carbon black are reduced. Can be suppressed. If the centrifugal acceleration is less than 0.5 times the gravitational acceleration, there is a risk that the supplied liquid raw material may flow down (sag) without being in close contact with the inner peripheral surface of the cylindrical mold. On the other hand, if the acceleration is greater than 10 times the gravitational acceleration, not only the orientation of the molecular chain due to the shearing force in the rotational direction and the structure orientation of the filler such as carbon black, but also the flow of the liquid material due to the centrifugal force occurs. is there.

  The centrifugal acceleration (G) used in the present invention is derived from the following equation.

G (m / s ² ) = r · ω ² = r · (2 · π · n) ²
Here, r is the radius (m) of the cylindrical mold, ω is the angular velocity (rad / s), and n is the number of rotations per second (the number of rotations during 60 s is rpm). The gravitational acceleration (g) to be compared is 9.8 (m / s ² ).

  Here, the spray method is preferred as a method for supplying the liquid raw material. The effect applied by the spray method is that the liquid raw material is atomized so that the flow at the time of supply is as small as possible and can be instantaneously adhered to the inner peripheral surface of the rotating cylindrical mold. The material can be supplied at the same rotational speed without being greatly affected by the viscosity of the liquid material. A thin coating film can be easily obtained, and the non-volatile concentration of the liquid raw material can be set high.

  The liquid source supply means applies the liquid source to the inner peripheral surface of the cylindrical mold with a uniform thickness by moving the liquid source in the direction of the axis of rotation of the cylindrical mold rotating while being discharged by the nozzle method or the spray method. The shape of the coating head is not particularly limited, and can be used as appropriate, such as a circle or a rectangle. Also, the size is not particularly limited, and it can be designed to have an appropriate discharge pressure depending on the combination with the viscosity of the liquid material to be discharged. The distance between the spray head and the cylindrical mold may be arbitrary, and is preferably about 5 mm to 200 mm. There is no particular limitation on the discharge pressure method, but a compressed air or a high viscosity liquid-compatible MONO pump, gear pump, or the like is used.

  When the liquid material is applied to the inner peripheral surface of the cylindrical mold with a uniform thickness in this way, it is necessary to make the film thickness uniform by flowing the liquid raw material by high-speed rotation of the cylindrical mold, that is, centrifugal force. There is no. Generally, in rotational molding using centrifugal force, after supplying the raw material, the liquid raw material is uniformly cast on the inner surface of the cylindrical mold by centrifugal force, so that the carbon black particles are structured in the flow direction by the flow caused by the centrifugal force. Lined up as if molded. This may adversely affect the electrical characteristics of the polyimide intermediate transfer belt. On the other hand, according to the method of the present invention which does not rotate at high speed, such a problem hardly occurs.

  It is preferable to apply a release agent to the inner peripheral surface of the cylindrical mold so that the polyimide resin does not adhere. There is no limitation on the type of release agent, but there is no particular limitation as long as it is not affected by the solvent of the liquid raw material or the water vapor generated from the resin during the heating reaction.

  In the liquid resin film forming step, the solvent is evaporated at a temperature of 100 to 140 ° C. while rotating at a low speed with a centrifugal acceleration of 0.5 to 10 times the weight acceleration to make the solid content concentration 40% by weight or more. This can be achieved by forming a self-supporting film on the inner peripheral surface of the cylindrical mold.

  In the polyimide resin film forming step, the temperature rises to about 250 ° C. in 60 to 120 minutes while remaining attached to the inner peripheral surface of the cylindrical mold, although it varies depending on the type of polyimide resin. Next, the polyimide resin film can be formed by heating the film at a temperature at which the polyimide is completely converted, for example, at 300 to 350 ° C. for 30 to 90 minutes. By performing the film formation while adhering to the inner peripheral surface of the cylindrical mold, it is possible to suppress the shrinkage caused by the imidization reaction or solvent volatilization and to uniformly align the polymer chains in the in-plane direction with the stress.

  The semiconductive belt containing 70 to 80% by weight of the polyimide resin and 30 to 20% by weight of carbon black thus manufactured can achieve accurate transfer in a color image forming apparatus, and changes in resistance due to transfer voltage. And a high-quality transfer image can be obtained stably over a long period of time. Further, cracks and cracks due to the load applied in the width direction of the belt are unlikely to occur, and even when the belt is run for a long time, it has excellent durability and can be used stably. Further, when the asymmetrical 2,3,3 ', 4'-biphenyltetracarboxylic acid component increases, the glass transition point shifts to the high temperature side. Therefore, it is also effective to use the transfer and fixing belt system as a belt base material in which transfer and fixing are performed simultaneously with a single belt.

  The average film thickness of the obtained semiconductive polyimide belt is usually adjusted to about 50 to 150 μm, preferably about 60 to 120 μm.

The surface resistivity is usually adjusted to be about 10 ⁹ to 10 ¹⁴ Ω / □, preferably about 10 ¹⁰ to 10 ¹³ Ω / □.

  The semiconductive polyimide belt manufactured as described above can appropriately perform charge charging stability and slow charge when used as an intermediate transfer belt of a color image forming apparatus of an electrophotographic apparatus, and for a long time. It becomes possible to stably obtain a high-quality transfer image.

  The color image forming apparatus is an electrophotographic image forming apparatus comprising at least one intermediate transfer member made of the polyimide resin of the present invention. By providing the intermediate transfer member made of the polyimide resin of the present invention as an intermediate transfer belt, a direct transfer belt, or a transfer and fixing belt, a high-quality transfer image can be obtained. When used as a transfer and fixing belt, it is effective to form a non-adhesive resin film on the surface in order to improve the releasability of the toner adhering to the surface. Examples of the non-adhesive resin film material include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and tetrafluoroethylene-hexafluoropropylene copolymer (FEP). A fluorine-based resin or the like is preferable. Further, an elastic silicone resin, a fluororubber resin, an elastic fluorosilicone resin, an elastic polysiloxane, or the like may be used.

  The polyimide resin belt of the present invention can achieve accurate transfer in a color image forming apparatus, can prevent resistance change due to transfer voltage, and can stably obtain a high-quality transfer image for a long period of time. In addition to its excellent electrical characteristics, it also has excellent physical characteristics such as being resistant to cracking and cracking due to the load applied in the width direction of the belt, excellent durability, and stable use even after running for a long period of time. Yes. Therefore, it is effective as a belt base material for an intermediate transfer belt and a transfer / fixing belt in which a single belt has both transfer and fixing.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example with a comparative example, this invention is not limited to these Examples.

Measurement of each physical property value described in this specification was performed as follows.
(1) Nitrogen adsorption surface area The nitrogen adsorption surface area was measured according to JIS K6217 (low temperature nitrogen adsorption method). Alternatively, reference was made to characteristic data of commercially available carbon.
(2) DBP absorption
DBP absorption was measured according to JIS K6217. Alternatively, reference was made to characteristic data of commercially available carbon.
(3) Volatile content of carbon black In accordance with JIS K6221, the volatile matter was measured for weight loss when the carbon black was heated at 950 ° C for 7 minutes, and the weight loss relative to the weight of carbon black before heating was displayed as a percentage (weight) %)did.
(4) pH of carbon black
The pH value was a value obtained by measuring a mixed solution of carbon black and distilled water with a glass electrode meter.
(5) Particle size of carbon black in solution The particle size of carbon black in the solution is a value measured using a LA-920 laser diffraction / scattering particle size distribution analyzer manufactured by HORIBA.
(6) Solid content and concentration in polyimide precursor solution composition The solid content concentration of the carbon black-dispersed polyimide precursor solution composition is a value calculated as follows. The sample is precisely weighed in a heat-resistant container such as a metal cup, and the weight of the sample at this time is defined as A (g). Put the heat-resistant container containing the sample in an electric oven, heat and dry while heating up in order of 120 ℃ × 15min, 180 ℃ × 15min, 260 ℃ × 30min, and 300 ℃ × 30min. The weight of the solid content (solid content weight) is defined as B (g). The values of A and B of five samples for the same sample were measured (n = 5) and applied to the following equation to determine the solid content concentration. The average value of the five samples was adopted as the solid content concentration.

Solid content concentration = B / A x 100 (%)
(7) Weight average molecular weight of polyamic acid The weight average molecular weight in this specification is a value measured by GPC method (solvent: NMP, converted to polyethylene oxide).
(8) Surface resistivity of semiconductive belt The surface resistivity (SR) is measured by using a sample obtained by cutting the obtained semiconductive belt into a length of 400 mm, and using a resistance measuring instrument “Mitsubishi Chemical Corporation” Using a Hiresta IP / UR probe, measurements were made at a total of 12 locations, 3 locations at equal pitches in the width direction and 4 locations in the longitudinal (circumferential) direction, and the average values were shown. The surface resistivity (SR) was measured after 10 seconds had elapsed while applying a voltage of 500V.
(9) Evaluation of mechanical properties The belt obtained in each example was cut into a width of 5 mm and a length of 100 mm, and this was used as a test piece with a uniaxial tensile tester (manufactured by Shimadzu Corporation, Autograph) with a tensile span of 40 mm, Measurement was performed at a strain rate of 200 mm / min. The yield strength and breaking strength were read from the recorded SS curve. As an indicator of toughness, the breaking strength must be greater than the yield strength, which contributes to the life (toughness) of belt rotation. As a guideline, at least (breaking strength) / (yield strength) = 1.10 or more is required.

Trouser tear strength was measured according to JIS K7128 at a strain rate of 200 mm / min.
(10) High voltage application test and idling durability test The evaluation was carried out with an energization system shown in FIG. 3 in an environment of 20 ° C. and 55% RH. The applied voltage was 4.0 kV (energization current of about 60 μA), and the surface resistivity was measured after the operation for 50 hours. Thereafter, idling durability evaluation was performed at a running speed of 280 mm / s without applying voltage, and durability was cleared for 300 consecutive hours.

Example 1
A carbon black produced by an oil furnace method in which a high temperature atmosphere of 1400 ° C. or higher is formed is subjected to a gas phase oxidation reaction using a jet stream containing ozone, and a nitrogen adsorption specific surface area of 120 (m ² / g) and a volatile content of 3. The carbon black was 52 (%) and had a pH value of 2.4.

  After dissolving 100 mol% of 4,4′-diaminodiphenyl ether in an N-methyl-2-pyrrolidone (NMP) solution, 2,3,3′4′-biphenyltetracarboxylic dianhydride: 20 mol% and 3 , 3 ′, 4,4′-biphenyltetracarboxylic dianhydride: Polyamic acid solution (weight average molecular weight 15000) synthesized in accordance with Japanese Patent Publication No. 2-3820 by adding 80 mol% and adding water thereto. 5 kg was prepared. This solution had a viscosity of 6.5 Pa · s and a solid content concentration of 30.0% by weight.

  To this solution, 510 g of the above carbon black and 1000 g of NMP were added, and the carbon black was uniformly dispersed by a bead mill. This carbon black-dispersed polyamic acid solution had a solid content concentration of 30.88 wt% and a carbon black concentration in the solid content of 25.37 wt%. The average particle size of carbon black in the solution was 0.28 μm, and the maximum particle size was 0.51 μm.

  While rotating a cylindrical mold having an outer diameter of 324 mm, an inner diameter of 300 mm, and a length of 500 mm at a centrifugal acceleration 4.0 times the gravitational acceleration, spray the carbon black-dispersed polyamic acid solution on the inner peripheral surface of the cylindrical mold. The coating was uniformly performed at 480 mm by the method. The coating thickness was calculated from the solid content concentration and determined so that the thickness of the intermediate transfer member was 100 μm. Thereafter, while rotating at a centrifugal acceleration of 4.0 times the gravitational acceleration, the temperature was raised to 120 ° C. in 60 minutes, and then heated at 120 ° C. for 60 minutes to form a self-supporting film.

  Next, this film was put in a high-temperature heating furnace while adhering to the inner peripheral surface of the cylindrical mold, heated to 320 ° C. in 120 minutes, and heated at 320 ° C. for 60 minutes to complete the polyimide conversion. Then, it cooled to normal temperature and took out the semiconductive belt from the metal mold | die. The characteristics of the semiconductive belt are shown in Table 1.

  The semiconductive belt was cut to a length of 350 mm and the surface resistivity was measured.

Example 2
A carbon black produced by an oil furnace method in which a high temperature atmosphere of 1400 ° C. or higher is formed is subjected to a gas phase oxidation reaction by a jet stream containing ozone, and has a nitrogen adsorption specific surface area of 115 (m ² / g) and a volatile content of 5.5 ( %) And carbon black having a pH value of 2.2.

  In a mixed solvent of NMP solution and methanol, 2,3,3'4'-biphenyltetracarboxylic dianhydride: 50 mol% and 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride: 50 mol% Then, the acid anhydride reacts with the alcohol to open the ring to synthesize a diester having an ester group and a carboxyl group on adjacent carbons on the aromatic ring, respectively, and then 4,4′-diamino is added to this solution. Diphenyl ether: 100 mol% was added and stirred at 50 ° C. for 3 hours, and then excess methanol was removed at 60 ° C. over 1 hour to prepare 5 kg of a nylon salt monomer solution. This solution had a viscosity of 0.3 Pa · s and a solid content concentration of 40.0% by weight.

  750 g of the above carbon black and 1200 g of NMP were added to this nylon salt monomer solution, and the carbon black was uniformly dispersed by a bead mill. This carbon black-dispersed polyimide precursor solution had a solid content concentration of 39.57% by weight and a carbon black concentration in the solid content of 27.27% by weight. The average particle size of carbon black in the solution was 0.23 μm, and the maximum particle size was 0.65 μm.

  The semiconductive belt was produced under the same conditions as in Example 1, and the characteristics are shown in Table 1.

Example 3
A carbon black produced by an oil furnace method in which a high temperature atmosphere of 1400 ° C. or higher is formed is subjected to a gas phase oxidation reaction by a jet stream containing ozone, and has a nitrogen adsorption specific surface area of 120 (m ² / g) and a volatile content of 2.5 ( %) And carbon black having a pH value of 2.8.

  After 100 mol% of 4,4′-diaminodiphenyl ether was dissolved in the NMP solution, 2,3,3′4′-biphenyltetracarboxylic dianhydride: 30 mol% and 3,3 ′, 4,4′- Biphenyltetracarboxylic dianhydride: 5 kg of a polyamic acid solution (weight average molecular weight 30000) synthesized by adding 70 mol% was prepared. This solution had a viscosity of 6.5 Pa · s and a solid content concentration of 20.0% by weight.

  260 g of the above carbon black and NMP: 1000 g were added to this solution, and the carbon black was uniformly dispersed by a bead mill. This carbon black-dispersed polyamic acid solution had a solid content concentration of 20.13 wt% and a carbon black concentration in the solid content of 20.63 wt%. The average particle size of carbon black in the solution was 0.23 μm, and the maximum particle size was 0.45 μm.

  The semiconductive belt was produced under the same conditions as in Example 1, and the characteristics are shown in Table 1.

Comparative Example 1
5 kg of a polyamic acid solution (weight average molecular weight 32000) prepared by synthesizing 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine in an NMP solution was prepared. This solution had a viscosity of 5.0 Pa · s and a solid content concentration of 18.0% by weight.

Denka black manufactured by Denki Kagaku Kogyo manufactured from acetylene gas in this solution (acetylene method); nitrogen adsorption specific surface area 70 (m ² / g), volatile content 0.1 (%), pH value 7.7 and 70 g NMP: 1800 g was added, and carbon black was uniformly dispersed by a bead mill. Here, the amount of NMP added was 1800 g because the solution viscosity was high and it was difficult to disperse the carbon black. This carbon black-dispersed polyamic acid solution had a solid concentration of 14.12% by weight and a carbon black concentration in the solid content of 7.22% by weight. The average particle size of carbon black in the solution was 1.13 μm, and the maximum particle size was 11.56 μm.

  While rotating a cylindrical mold having an outer diameter of 324 mm, an inner diameter of 300 mm, and a length of 500 mm at a centrifugal acceleration 4.0 times the gravitational acceleration, spray the carbon black-dispersed polyamic acid solution on the inner peripheral surface of the cylindrical mold. The coating was uniformly performed at 480 mm by the method. The coating thickness was calculated from the solid content concentration and determined so that the thickness of the intermediate transfer member was 100 μm. Thereafter, while rotating at a centrifugal acceleration of 4.0 times the gravitational acceleration, the temperature was raised to 120 ° C. in 60 minutes, and then heated at 120 ° C. for 60 minutes to form a self-supporting film.

  Next, the molded belt was removed from the inner peripheral surface of the cylindrical mold, and an aluminum cylindrical mold having an outer diameter of 290 mm and a length of 420 mm was inserted into the removed belt. Thereafter, the temperature was raised to 400 ° C. over 180 minutes, and the polyimide conversion was completed by heating at 400 ° C. for 60 minutes at a high temperature. The reason why it was once removed from the cylindrical mold for molding was that the belt was peeled off or damaged from the inner peripheral surface of the cylindrical mold due to reaction shrinkage in the in-plane direction accompanying imide conversion at 150 to 250 ° C. is there.

Comparative Example 2
5 kg of a polyamic acid solution (weight average molecular weight 32000) prepared by synthesizing 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine in an NMP solution was prepared. This solution had a viscosity of 5.0 Pa · s and a solid content concentration of 18.0% by weight.

Degussa “Special Black 4” produced by the channel method in this solution; nitrogen adsorption specific surface area 180 (m ² / g), volatile content 14.0 (%), pH value 3.0 225 g and NMP: 1600 g In addition, carbon black was dispersed with a bead mill. This carbon black-dispersed polyamic acid solution had a solid content concentration of 16.48% by weight and a carbon black concentration in the solid content of 20.00% by weight. The average particle size of carbon black in the solution was 0.31 μm, and the maximum particle size was 0.77 μm.

  The semiconductive belt was produced under the same conditions as in Comparative Example 1, and the characteristics are shown in Table 1.

Comparative Example 3
3 kg of a polyamic acid solution (weight average molecular weight 32000) obtained by synthesizing 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine in an NMP solution, and 3,3 ′, 4 2, 4'-biphenyltetracarboxylic dianhydride and 4,4'-diaminodiphenyl ether were prepared in 2 kg of a polyamic acid solution (weight average molecular weight 32000) synthesized in an NMP solution.

The two types of polyamic acid solutions were blended and stirred for 24 hours. This solution had a viscosity of 5.0 Pa · s and a solid content concentration of 18.0% by weight. “MA100” manufactured by Mitsubishi Chemical Co., Ltd. manufactured by the oil furnace method; nitrogen adsorption specific surface area 110 (m ² / g), volatile matter 1.5 (%), pH value 3.5 225 g and NMP: 1600 g In addition, carbon black was dispersed with a bead mill. This carbon black-dispersed polyamic acid solution had a solid content concentration of 16.48% by weight and a carbon black concentration in the solid content of 20.00% by weight. The average particle size of carbon black in the solution was 0.41 μm, and the maximum particle size was 1.42 μm.

  The semiconductive belt was produced under the same conditions as in Comparative Example 1, and the characteristics are shown in Table 1.

Comparative Example 4
5 kg of a polyamic acid solution (weight average molecular weight 32000) prepared by synthesizing 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and p-phenylenediamine in an NMP solution was prepared. This solution had a viscosity of 5.0 Pa · s and a solid content concentration of 18.0% by weight.

“MA100” manufactured by Mitsubishi Chemical Co., Ltd. manufactured by the oil furnace method; nitrogen adsorption specific surface area 110 (m ² / g), volatile matter 1.5 (%), pH value 3.5 140 g and NMP: 1200 g In addition, carbon black was dispersed with a bead mill. This carbon black-dispersed polyamic acid solution had a solid content concentration of 16.40% by weight and a carbon black concentration in the solid content of 13.46% by weight. The average particle size of carbon black in the solution was 0.40 μm, and the maximum particle size was 1.12 μm.

  The semiconductive belt was produced under the same conditions as in Comparative Example 1, and the characteristics are shown in Table 1.

Test example 1
The semiconductive belts produced in Examples 1 to 3 and Comparative Examples 1 to 4 were evaluated for mechanical properties (yield strength, breaking strength and trouser tear strength). The results are shown in Table 2.

  The yield strength and breaking strength obtained from the stress-strain curve, and the ratio of the breaking strength to the yield strength are shown. The magnitude of the ratio of the breaking strength to the yield strength is proportional to the toughness of the belt, and the breaking strength needs to be at least larger than the yield strength, and contributes to the life resistance (toughness) of the belt rotation. In many materials, plastic deformation due to yielding takes precedence and so-called ductile deformation occurs. However, when stress concentration occurs depending on the high filling of carbon black or its dispersion state, the deformation mode becomes brittle. The higher the ratio of the breaking strength to the yield strength, the more the material can be deformed. As a guideline, if this ratio is 1.10 or more, brittle fracture can be avoided.

  The trouser tear strength is used as an evaluation of sensitivity to stress concentration. As the trouser tear strength increases, cracks and cracks due to the load applied in the width direction of the belt are less likely to occur.

  According to Table 2, it can be seen that Examples 1 to 3 all have good mechanical properties.

Test example 2
About the semiconductive belt manufactured in Examples 1-3 and Comparative Examples 1-4, the high voltage application test and the idling durability test were done. The results are shown in Table 3.

  From Table 3, the belts of Examples 1 to 3 had no change (decrease) in surface resistivity even in the high voltage application test. This is considered to be because the dispersion state is as continuous as possible by increasing the filling of carbon black.

  Furthermore, the belt was not damaged even after 300 hours of continuous running in the idling durability evaluation. These results show that, for example, when used as an intermediate transfer belt, even if an excessive current is repeatedly applied, the surface resistivity does not change and a high-quality transfer image is obtained, and it is not damaged even after long-term use. Means.

The conductive model of carbon black in resin is shown. It is the microscope picture which reproduced the state of (A)-(C) in FIG. It is a schematic diagram of the electricity supply system used for the high voltage application test and the idling durability test (under 20 degreeC and 55% RH environment) in the example 2 of a test.

Claims (8)

The surface resistivity is 1 × 10 ⁸ to 1 × 10 ¹⁴ Ω / □ including 70 to 80% by weight of polyimide resin and 30 to 20% by weight of carbon black having a volatile content of 2 to 6% manufactured by the oil furnace method. A semiconductive belt, in which the polyimide resin has an asymmetric biphenyltetracarboxylic acid component of 15 to 50 mol% and a symmetrical 3,3 ′, 4,4′-biphenyltetracarboxylic acid component of 85 to 50 mol. A semiconductive belt which is a copolymer obtained by imidizing a substantially equimolar amount of a biphenyltetracarboxylic acid component consisting of 1% and an aromatic diamine.   The asymmetric biphenyltetracarboxylic acid component is 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride or 2,3,3', 4'-biphenyltetracarboxylic acid diester. The semiconductive belt as described.   The semiconductive belt according to claim 1 or 2, wherein the aromatic diamine is 4,4'-diaminodiphenyl ether. The carbon black produced by the oil furnace method has a pH of 2 to 4, a nitrogen adsorption specific surface area of 60 to 150 m ² / g, and a DBP absorption of 40 to 120 ml / 100 g. The semiconductive belt according to any one of 3 above.   An intermediate transfer belt for an electrophotographic apparatus, comprising the semiconductive belt according to claim 1. Biphenyltetracarboxylic dianhydride comprising 15-50 mol% asymmetric biphenyltetracarboxylic dianhydride and 85-50 mol% symmetrical 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride And an approximately equimolar amount of the aromatic diamine were reacted in an organic polar solvent to produce a polyamic acid solution having a weight average molecular weight of 20000 or less, and the polyamic acid solution was produced by an oil furnace method. A polyimide precursor solution composition is prepared by uniformly dispersing carbon black having a volatile content of 2 to 6%, and the carbon black-dispersed polyimide precursor solution composition is formed into a tubular product by a rotational molding method. A process for producing a semiconductive belt by imidizing by heat treatment,
(1) A step of coating the carbon black-dispersed polyimide precursor solution composition with a uniform thickness on the inner peripheral surface of a cylindrical mold rotating at a centrifugal acceleration of about 0.5 to 10 times the gravitational acceleration.
(2) A process of forming a self-supporting film by heating the cylindrical mold at a temperature of about 100 to 140 ° C. while rotating at a centrifugal acceleration of about 0.5 to 10 times the gravitational acceleration, and ( 3) A step of imidizing by heating at a temperature of about 300 ° C. or higher while the film is attached to the inner peripheral surface of the cylindrical mold,
The manufacturing method characterized by including. A biphenyl tetracarboxylic acid diester comprising 15 to 50 mol% of an asymmetric biphenyl tetracarboxylic acid diester and 85 to 50 mol% of a symmetrical 3,3 ′, 4,4′-biphenyl tetracarboxylic acid diester, an aromatic diamine, and Is dissolved in an organic polar solvent to prepare a nylon salt type monomer solution, and carbon black having a volatile content of 2 to 6% produced by the oil furnace method is uniformly added to the nylon salt type monomer solution. A semiconductive belt in which a polyimide precursor solution composition is prepared by dispersion, the carbon black-dispersed polyimide precursor solution composition is formed into a tubular product by a rotational molding method, and the molded body is heated to imidize. A manufacturing method of
(1) A step of coating the carbon black-dispersed polyimide precursor solution composition with a uniform thickness on the inner peripheral surface of a cylindrical mold rotating at a centrifugal acceleration of about 0.5 to 10 times the gravitational acceleration.
(2) A process of forming a self-supporting film by heating the cylindrical mold at a temperature of about 100 to 140 ° C. while rotating at a centrifugal acceleration of about 0.5 to 10 times the gravitational acceleration, and ( 3) A step of imidizing by heating at a temperature of about 300 ° C. or higher while the film is attached to the inner peripheral surface of the cylindrical mold,
The manufacturing method characterized by including.   A semiconductive belt manufactured by the manufacturing method according to claim 6.

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