JP2006016592A - Polyamic acid composition, polyimide endless belt and method for producing the same, and image formation equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyamic acid capable of its imidization reaction at low baking temperatures, to provide an endless belt excellent in productivity, film thickness uniformity and mechanical properties by using the polyamic acid composition, and to provide a method for producing the endless belt, and also to provide image formation equipment capable of reducing defects caused by endless belt film thickness nonuniformity, etc. <P>SOLUTION: The polyamic acid composition comprises (A) a polyamic acid of the general formula (1) (wherein, R1 is a tetravalent organic group; and R2 is a bivalent organic group), (B) either one of an aromatic carboxylic acid compound having either one or more of hydroxy, amino and sulfonyl groups and a phenolic compound having either one or more of amino and sulfonyl groups and (C) an electrically conductive agent. The polyimide endless belt produced by coating a mold with the polyamic acid composition followed by undergoing drying treatment, etc., is provided. The image formation equipment furnished with the polyimide endless belt as intermediate transferred element and/or fixed element is also provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyimide endless belt used in an electrophotographic apparatus such as an electrophotographic copying machine, a laser beam printer, a facsimile, and a composite apparatus thereof, a method for producing the same, and a polyamic acid composition that is optimal for the production of the polyimide endless belt. The present invention also relates to an image forming apparatus including the polyimide endless belt.

In an electrophotographic apparatus, first, a charge is uniformly formed on a photosensitive member made of a conductive material, a modulated image signal is formed as an electrostatic latent image with laser light or the like, and then the electrostatic latent image is formed with charged toner. To develop a toner image. Next, the toner image is transferred to a recording medium such as paper directly or via an intermediate transfer member to obtain an image.
Here, a method of primary transfer of a toner image on a photosensitive member to an intermediate transfer member and then secondary transfer of the toner image on the intermediate transfer member to a recording medium such as paper, an image forming apparatus adopting a so-called intermediate transfer method. Examples of the intermediate transfer belt used include polyvinylidene fluoride (see, for example, Patent Document 1), polycarbonate (see, for example, Patent Document 2), and a blend of an ethylene-tetrafluoroethylene copolymer and polycarbonate (for example, Patent Document 3). A conductive endless belt has been proposed in which a conductive agent such as carbon black is dispersed in a thermoplastic resin.

  Furthermore, in recent years, a method for fixing a toner image on a recording medium by heating the intermediate transfer member, that is, an intermediate transfer / fixing method has been disclosed (for example, see Patent Document 4). In the intermediate transfer / fixing method, after the toner image is secondarily transferred to the recording medium via the intermediate transfer member, the intermediate transfer member is directly or indirectly heated to contact the intermediate transfer member. This is a method for fixing a toner image on a recording medium, and has an advantage that the apparatus can be reduced in size and cost compared with a conventional apparatus in which the intermediate transfer mechanism and the fixing mechanism are separated.

  Here, the belt material used in the intermediate transfer / fixing system is required to have a mechanical strength that can withstand the stress during driving, and at the same time be able to withstand the heat of about 200 ° C. that is applied during fixing. From this requirement, a polyimide resin having both high mechanical strength and heat resistance is suitable for the material used for the intermediate transfer / fixing belt.

  As an intermediate transfer body using the polyimide resin, an intermediate transfer body in which carbon black is dispersed in a polyimide resin (see, for example, Patent Document 5), or a layer having polyimide as a main constituent material is included. In addition, an intermediate transfer member is proposed in which the polyimide layer contains polyaniline and a dopant capable of making the polyaniline conductive (see, for example, Patent Documents 6 to 8). Further, an intermediate transfer member is proposed in which a filler is added as a reinforcing material for reducing expansion during moisture absorption (see, for example, Patent Document 9).

  Since the polyimide resin is generally insoluble, it is used as a polyimide by applying a solution of a polyamic acid that is a precursor thereof, heating after drying, and performing a dehydration imidization reaction of an amic acid group. The imidization reaction generally requires a high temperature of 250 ° C. to 350 ° C., which causes a problem in terms of energy consumption.

  For example, when polydoped polyaniline and a dopant for conducting the polyaniline are used as the polymer conductive agent, the polyaniline has a high firing temperature of 250 ° C. to 400 ° C. during the dehydration imidation reaction of the polyimide resin. Oxidation has progressed excessively, and some have become insulating, resulting in a problem that the material use efficiency of polyaniline is lowered. For this reason, in order to obtain the target surface resistivity and volume resistivity, it is necessary to add extra polyaniline and a dopant for making the polyaniline conductive in anticipation of excessive oxidation. Furthermore, generally, since the dopant is an acid, when a polyamic acid, polyaniline in an undoped state, and a dopant solution for conducting polyaniline are applied to a metal belt or a mold, the metal belt or the mold is rusted. There was a problem of generating and hurting.

  In addition, due to the dehydration of polyamic acid, the film surface and the voids in the coating film are generated, the film thickness is not uniform due to the stress generated by the volume shrinkage accompanying the dehydration reaction, and the resistance value varies. There was also a problem in terms of film quality.

For this problem, the use of a solvent-soluble polyimide material has been proposed. Soluble polyimide imparts solubility in a solvent by introducing a flexible structure in the molecule, despite having a rigid imide structure. Therefore, the soluble polyimide material can form the polyimide film only by applying to the base material and drying the solvent, so that the above problems can be solved.
However, soluble polyimides are generally unsuitable for use as a belt due to their molecular structure, generally low in strength, prone to elongation and breakage.

  Moreover, in order to promote the imidation of a polyamic acid, the method of heating by coexisting tertiary amine etc. is disclosed (for example, refer patent documents 10-12). However, such tertiary amines generally have an unpleasant odor and adverse health effects on the human body. When handling polyamic acid compositions containing tertiary amines, the safety of workers becomes a problem. Moreover, since such tertiary amine volatilizes in the drying process and the baking process, there is a problem from the point of environmental load.

  By the way, the liquid crystal aligning film use is mentioned as an example which mixed oxycarboxylic acid in the polyimide varnish (for example, refer patent document 13). The liquid crystal aligning agent is a polyimide film formed on a glass substrate, and its function is aimed at aligning liquid crystal molecules, and the strength of the polyimide film itself exhibiting self-supporting properties is not required.

Moreover, various examples are mentioned as a laminated film use which forms a polyimide film | membrane on the thermoplastic resin surface (for example, refer patent documents 14-16). However, in these examples, since the polyimide film is intended to impart flame retardancy, the polyimide film thickness is preferably 5% or less of the total film thickness, and the film strength is the heat of the crosslinked base material. Since it is held by a plastic resin, the strength of the polyimide material is hardly expected. The amount of oxycarboxylic acids used is as high as 10% or more relative to the polyimide material, which is essentially different from the present invention requiring the strength and self-supporting property of the polyimide molded product.
Japanese Patent Laid-Open No. 5-200904 JP-A-6-228335 Japanese Patent Laid-Open No. 6-149083 JP-A-6-258960 JP 63-11263 A JP-A-8-259709 JP 2000-226765 A JP 2000-122435 A JP 2001-109277 A Japanese Patent Laid-Open No. 6-207014 JP 2002-127165 A JP 2002-283366 A JP 7-138479 A Japanese Patent Laid-Open No. 2003-200545 JP 2003-080651 A JP 2002-192673 A

The object of the present invention is to solve the above-described conventional problems. That is, an object of the present invention is to provide a polyamic acid composition capable of performing an imidization reaction at a lower firing temperature than a conventional polyamic acid composition.
It is another object of the present invention to provide an endless belt excellent in productivity and film thickness uniformity and having good mechanical properties and a method for manufacturing the same.
It is another object of the present invention to provide an image forming apparatus that can reduce defects caused by non-uniform film thickness of a conventional endless belt by using the endless belt.

  As a result of intensive studies to solve the above problems, the present inventors have found that at least "aromatic carboxylic acid compound having any one or more of a hydroxyl group, an amino group and a sulfonyl group in the molecule" or "molecule By using a polyamic acid composition containing a phenol compound having at least one of an amino group and a sulfonyl group in the inside, it becomes possible to realize a reduction in firing temperature and a reduction in firing time for imidization. The inventors have found that an endless belt having good mechanical properties such as sufficient strength can be obtained by preventing the deterioration of film quality (film thickness uniformity, etc.) due to the imidization reaction, and the present invention has been completed. .

  That is, the present invention provides (A) a polyamic acid represented by the following general formula (1) (polyamic acid containing a repeating unit represented by the following general formula (1)), (B) a hydroxyl group, an amino group, and a sulfonyl group. Any one or more of an aromatic carboxylic acid compound having any one or more of groups and a phenol compound having any one or more of an amino group and a sulfonyl group, and (C) a conductive agent. It is a polyamic acid composition characterized by these.

It is preferable that at least 1 aspect is applied to the polyamic acid composition of this invention among the following 1st-6th aspects.
[1] The first aspect is an aspect in which the polyamic acid includes a polyimide represented by the following general formula (2) (including a repeating unit represented by the following general formula (2)).

[2] A second aspect is an aspect in which the aromatic carboxylic acid compound is represented by any one of the following general formulas (3) to (5).

[3] A third aspect is an aspect in which the phenol compound is represented by any one of the following general formulas (6) to (8).

[4] In a fourth aspect, the aromatic carboxylic acid compound or the phenol compound is added in an amount of 0.01 to 20 parts by mass with respect to 100 parts by mass of the polyamic acid.

[5] A fifth aspect is an aspect in which the conductive agent is carbon black.
[6] A sixth aspect is an aspect in which, when the conductive agent is carbon black, the carbon black is oxidized carbon black.
[7] A seventh aspect is an aspect in which the conductive agent is a polymer conductive agent.
[8] In an eighth aspect, when the conductive agent is a polymer conductive agent, the polymer conductive agent is polyaniline.

The present invention also provides (A) a polyamic acid represented by the above general formula (1) (polyamic acid containing a repeating unit represented by the above general formula (1)), (B) a hydroxyl group, an amino group, and a sulfonyl group. A polyamic acid composition containing any one or more of an aromatic carboxylic acid compound having any one or more of a group and a phenol compound having any one or more of an amino group and a sulfonyl group as a mold A polyimide endless belt produced by applying a drying process and a baking process after coating.
The polyamic acid composition preferably further contains a conductive agent (for example, the above-described carbon black or polymer conductive agent).

Furthermore, the present invention provides (A) a polyamic acid represented by the above general formula (1), (B) an aromatic carboxylic acid compound having any one or more of a hydroxyl group, an amino group and a sulfonyl group, and an amino group. And a polyamic acid composition containing any one or more of phenol compounds having any one or more of sulfonyl groups, and then applying a drying treatment and a baking treatment to the mold, followed by a polyimide endless It is a manufacturing method of a belt.
The polyamic acid composition preferably further contains a conductive agent (for example, the above-described carbon black or polymer conductive agent).

  The present invention also provides an image forming apparatus comprising the above-described polyimide endless belt as an intermediate transfer member and / or a fixing member.

  The polyimide endless belt of the present invention produced using the polyamic acid composition of the present invention is suppressed in the generation of voids in the coating film, which has been a problem with conventional belts, and the film thickness non-uniformity due to volume shrinkage, Further, variation in resistance value is reduced, and film quality is improved. In addition, they succeeded in achieving both mechanical properties such as tensile strength and electrical properties such as volume resistivity, which could not be achieved with a conventional endless belt manufactured with low energy.

  When a polyimide is produced by applying high energy to polyamic acid as in the prior art, target values can be achieved for mechanical properties and electrical properties. However, the belt is inferior in film quality due to excessive load. On the other hand, when film quality is emphasized and polyimide is produced with low energy, the generation of voids and the like can be suppressed, but the mechanical strength and the like are weak and it cannot be used as a belt.

In the present invention, these contradictory performances are compatible, and the polyimide endless belt of the present invention has film quality, mechanical performance, and electrical performance.
In other words, the belt obtained by the present invention is completely different from the conventional belt, and is an excellent belt that can achieve all of film quality, mechanical characteristics, and electrical characteristics.

When the polyamic acid composition of the present invention is used, an imidization reaction can be performed at a lower firing temperature as compared with conventional polyamic acid compositions. As a result, the polyimide endless belt produced from the polyimide composition of the present invention can be produced with low energy at the time of firing, and can greatly contribute to reduction of energy consumption and suppression of environmental load. That is, a highly productive polyimide endless belt can be obtained. Moreover, the polyimide endless belt according to the present invention has few defects such as generation of voids observed during thermal imidization, and can prevent film thickness non-uniformity due to in-plane variation of imidization reaction.
In particular, by using oxidized carbon black, it is possible to manufacture a polyimide endless belt having uniform semiconductivity without deterioration of belt characteristics due to aggregation of the conductive agent.
Furthermore, by using the endless belt, it is possible to provide an image forming apparatus that can reduce defects caused by non-uniform film thickness of the endless belt.

[Polyamic acid composition]
The polyamic acid composition of the present invention is (A) a polyamic acid represented by the following general formula (1) (a polyamic acid containing a repeating unit represented by the following general formula (1): hereinafter referred to as “polyamic acid”. And (B) an aromatic carboxylic acid compound having one or more of a hydroxyl group, an amino group and a sulfonyl group (hereinafter sometimes referred to as “aromatic carboxylic acid compound”), and an amino group and a sulfonyl group Any one or more of phenol compounds (hereinafter sometimes referred to as “phenol compounds”), and (C) a conductive agent. In addition, as a polyamic acid, Preferably, what consists of aromatic tetracarboxylic dianhydride and aromatic diamine from a viewpoint of the intensity | strength of a molded object is preferable.

  In addition, “R1” in the following general formula (1) is a tetravalent organic group. Specifically, a residue obtained by removing four carboxyl groups from a tetracarboxylic acid (dianhydride) exemplified later. Groups. Moreover, “R2” in the following general formula (1) is a divalent organic group, and specific examples thereof include a residue obtained by removing two amino groups from a diamine compound exemplified later. In addition, “R3” and “R4” in the general formula (2) described later are also the same as “R1” and “R2”, respectively.

  The aromatic carboxylic acid compound and the phenol compound do not volatilize at the temperature at which the imidization reaction is performed. Accordingly, it is possible to reduce the firing temperature and the firing time for imidization with a smaller amount than the conventional imidization catalyst. As a result, the endless belt produced using the polyamic acid composition of the present invention is prevented from being deteriorated in film quality (such as film thickness uniformity) due to imidation reaction as compared with the conventional one, and has satisfactory strength. It will have good mechanical properties. In addition, since the effect can be exhibited with a small amount of addition, the dispersibility of the conductive agent is not affected, and thus the function of the conductive agent can be efficiently expressed.

The polyamic acid composition of the present invention can be produced by various methods according to the conditions such as the following constituents. For example, it can be prepared by dispersing a conductive agent in a polyamic acid solution and then mixing an aromatic carboxylic acid compound or a phenol compound. Moreover, when using the polyimide-polyamic acid copolymer mentioned later as a polyamic acid, after imidating a polyamic acid partially and dispersing a electrically conductive agent, it mixes with an aromatic carboxylic acid compound or a phenol compound. can do. Moreover, you may produce in the order as described in an Example.
Hereinafter, each component etc. are demonstrated in detail.

(Polyamic acid)
The polyamic acid described above can be obtained by polymerizing a tetracarboxylic dianhydride and a diamine compound in a substantially equimolar amount in an organic polar solvent.
Moreover, it is preferable that a polyamic acid contains the polyimide represented by following General formula (2) (The repeating unit represented by following General formula (2) is included). That is, it is preferable that a part of the polyamic acid is imidized to form a polyimide-polyamic acid copolymer. By partially imidizing after polyamic acid polymerization, the reaction rate of imidization can be further increased and the energy can be further reduced.

(1) Tetracarboxylic dianhydride:
There is no restriction | limiting in particular as tetracarboxylic dianhydride used for manufacture of a polyamic acid, Either an aromatic type or an aliphatic type compound can be used.
Examples of the aromatic tetracarboxylic acid include pyromellitic dianhydride, 3,3 ′, 4,4′-benzoenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyl sulfone. Tetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyl Ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-dimethyldiphenylsilane tetracarboxylic dianhydride, 3,3 ′, 4,4′-tetraphenylsilane tetracarboxylic dianhydride, 1, 2,3,4-furantetracarboxylic dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) Diphenylsulfo Dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) diphenylpropane dianhydride, 3,3 ', 4,4'-perfluoroisopropylidenediphthalic dianhydride, 3,3' , 4,4'-biphenyltetracarboxylic dianhydride, bis (phthalic acid) phenylphosphine oxide dianhydride, p-phenylene-bis (triphenylphthalic acid) dianhydride, m-phenylene-bis (triphenylphthal Acid) dianhydride, bis (triphenylphthalic acid) -4,4′-diphenyl ether dianhydride, bis (triphenylphthalic acid) -4,4′-diphenylmethane dianhydride, and the like.

  Aliphatic tetracarboxylic dianhydrides include butane tetracarboxylic dianhydride, 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutane. Tetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 3,5,6-tricarboxynorbonane-2-acetic acid dianhydride Anhydride, 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 5- (2,5-dioxotetrahydrofural) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, An aliphatic or alicyclic tetracarboxylic dianhydride such as bicyclo [2,2,2] -oct-7-ene-2,3,5,6-tetracarboxylic dianhydride; 4 5,9b-Hexahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro-5-methyl -5- (Tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro-8-methyl Examples include aliphatic tetracarboxylic dianhydrides having an aromatic ring such as -5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione. Can do.

As the tetracarboxylic dianhydride used in the present invention, an aromatic tetracarboxylic dianhydride is preferable, and pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid. The dianhydride, 3,3 ′, 4,4′-biphenylsulfone tetracarboxylic dianhydride, is optimally used.
These tetracarboxylic dianhydrides can be used alone or in combination of two or more.

(2) Diamine compound:
Next, the diamine compound that can be used for producing the polyamic acid is not particularly limited as long as it is a diamine compound having two amino groups in the molecular structure.
For example, p-phenylenediamine, m-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylethane, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfide, 4,4 ′ -Diaminodiphenylsulfone, 1,5-diaminonaphthalene, 3,3-dimethyl-4,4'-diaminobiphenyl, 5-amino-1- (4'-aminophenyl) -1,3,3-trimethylindane, 6 -Amino-1- (4'-aminophenyl) -1,3,3-trimethylindane, 4,4'-diaminobenzanilide, 3,5-diamino-3'-trifluoromethylbenzanilide, 3,5- Diamino-4′-trifluoromethylbenzanilide, 3,4′-diaminodiphenyl ether, 2,7-diaminofluore 2,2-bis (4-aminophenyl) hexafluoropropane, 4,4′-methylene-bis (2-chloroaniline), 2,2 ′, 5,5′-tetrachloro-4,4′-diamino Biphenyl, 2,2′-dichloro-4,4′-diamino-5,5′-dimethoxybiphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 4,4′-diamino-2,2 ′ -Bis (trifluoromethyl) biphenyl, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane,

1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) -biphenyl, 1,3′-bis (4-aminophenoxy) benzene, 9,9-bis (4- Aminophenyl) fluorene, 4,4 ′-(p-phenyleneisopropylidene) bisaniline, 4,4 ′-(m-phenyleneisopropylidene) bisaniline, 2,2′-bis [4- (4-amino-2-tri Fluoromethylphenoxy) phenyl] hexafluoropropane, aromatic diamines such as 4,4′-bis [4- (4-amino-2-trifluoromethyl) phenoxy] -octafluorobiphenyl; aromatic rings such as diaminotetraphenylthiophene An aromatic diamine having two amino groups bonded to and a hetero atom other than the nitrogen atom of the amino group; 1,1-metaxy Range amine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, octamethylenediamine, nonamethylenediamine, 4,4-diaminoheptamethylenediamine, 1,4-diaminocyclohexane, isophoronediamine, tetrahydrodicyclopenta Aliphatic diamines such as dienylenediamine, hexahydro-4,7-methanoindanylene methylene diamine, tricyclo [6,2,1,02.7] -undecylenedimethyl diamine, 4,4'-methylene bis (cyclohexyl amine) And alicyclic diamines.
Examples of the diamine compound used in the present invention include p-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfide, and 4,4′-diaminodiphenylsulfone. preferable.
These diamine compounds can be used alone or in combination of two or more.

(3) Synthesis solvent (organic polar solvent):
Examples of the organic polar solvent used in this polyamic acid production reaction include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide; N, Acetamide solvents such as N-dimethylacetamide and N, N-diethylacetamide; Pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; Phenol, o-, m-, or p-cresol , Phenol solvents such as xylenol, halogenated phenol, catechol; ether solvents such as tetrahydrofuran, dioxane, dioxolane; or hexamethylphosphoramide, γ-butyrolactone, and the like. Although it is desirable to use Te, further xylene, aromatic hydrocarbons such as toluene can be used. The solvent is not particularly limited as long as it dissolves polyamic acid and polyamic acid-polyimide copolymer.

(4) Solid content concentration during polyamic acid polymerization:
The solid content concentration of the polyamic acid solution is not particularly limited, but is preferably 5 to 50% by mass. Furthermore, 10 to 30% by mass is particularly suitable. When the solid content concentration is less than 5% by mass, the degree of polymerization of the polyamic acid is low, and the strength of the molded product finally obtained is lowered. Moreover, when the solid content concentration at the time of polymerization is higher than 50% by mass, an insoluble part of the raw material monomer is generated and the reaction does not proceed.

(5) Polyamic acid polymerization temperature:
As reaction temperature at the time of polyamic acid polymerization, it is carried out in the range of 0 ° C to 80 ° C. This is because when the reaction temperature is less than 0 ° C., the viscosity of the solution increases and the reaction system cannot be sufficiently stirred. Moreover, when reaction temperature becomes higher than 80 degreeC, since imidation reaction occurs partially in parallel with the polymerization of polyamic acid, there is a problem in terms of reaction control.

(6) Imidization reaction:
The polyamic acid-polyimide copolymer used in the present invention is obtained by subjecting the polyamic acid to imidization by heat treatment, or a chemical imidization method in which a dehydrating agent and / or a catalyst is allowed to act. It is obtained by converting a part of the amic acid group to an imide group by a dehydration ring-closing reaction.
The heating temperature in the heating method is usually 60 ° C. or higher and 200 ° C. or lower, preferably 100 ° C. or higher and 170 ° C. or lower. When the heating temperature is less than 60 ° C., dehydration ring closure does not proceed sufficiently, and when the heating temperature exceeds 200 ° C., the molecular weight of the polymer obtained is small.

On the other hand, in the method of adding a dehydrating agent and a cyclization catalyst to the polyamic acid solution, the dehydrating agent is not particularly limited as long as it is a monovalent carboxylic acid anhydride. For example, acid anhydrides such as acetic anhydride, propionic anhydride, and trifluoroacetic anhydride can be used. The amount of the dehydrating agent used is preferably 0.01 mol or more and 2 mol or less with respect to 1 mol of the polyamic acid repeating unit.
Examples of the catalyst include tertiary amines such as pyridine, picoline, collidine, lutidine, quinoline, isoquinoline, and triethylamine, but are not limited thereto. The amount of the cyclization catalyst used is preferably 0.01 mol or more and 2 mol or less with respect to 1 mol of the dehydrating agent to be used.
This dehydration ring closure is performed by adding a dehydrating agent and a cyclization catalyst to the polyamic acid solution and heating as necessary. The reaction temperature for dehydration and ring closure is usually 0 ° C. or higher and 180 ° C. or lower, preferably 60 ° C. or higher and 150 ° C. or lower.

  Although the dehydrating agent / dehydrating agent and catalyst that acted on the polyamic acid-polyimide copolymer do not have to be removed, they may be removed by the following method in order to improve the stability of the solution viscosity over time. As a method for removing the dehydrating agent / dehydrating agent and the catalyst that have been acted on, heating under reduced pressure or a reprecipitation method can be used. The reduced pressure heating is performed at a temperature of 80 ° C. or higher and 120 ° C. or lower under vacuum to distill off the tertiary amine, unreacted dehydrating agent and hydrolyzed carboxylic acid used as a catalyst. The reprecipitation method uses a poor solvent that dissolves the tertiary amine used as a catalyst, unreacted dehydrating agent and hydrolyzed carboxylic acid, and does not dissolve the polyamic acid-polyimide copolymer. It is carried out by adding the reaction solution in a large excess of a poor solvent. The poor solvent is not particularly limited, and water, alcohol solvents such as methanol and ethanol, ketone solvents such as acetone and methyl ethyl ketone, hydrocarbon solvents such as hexane, and the like can be used. The polyamic acid-polyimide copolymer to be precipitated is dissolved again in a solvent such as NMP after filtration and drying.

The imide fraction of the polyamic acid-polyimide copolymer is not particularly limited, but the composition ratio between the imidized structure and the unreacted amic acid structure ("imided structure" / "unreacted amic acid The “structure”) is preferably 1/99 (mol / mol) to 80/20 (mol / mol). When the composition ratio between the imide group and the amic acid group exceeds 80/20 (mol / mol), the polyamic acid-polyimide copolymer may be insolubilized.
Further, in the composition according to the present invention, a polyamic acid and a polyamic acid-polyimide copolymer may be individually synthesized and then blended as appropriate.

(Aromatic carboxylic acid compounds, phenol compounds)
Examples of the aromatic carboxylic acid compound having one or more of a hydroxyl group, an amino group and a sulfonyl group in the molecule include compounds represented by the following general formulas (3) to (5).
By adding such a compound to the polyamic acid composition, the compound acts to accelerate the polyamic acid dehydration ring-closing reaction during the drying / firing step. As a result, it is possible to obtain an effect that the imidization reaction can be performed at a lower temperature and a shorter time during the polyimide molding process. These aromatic carboxylic acid compounds may be used alone or in combination of two or more. Moreover, you may use together with the phenolic compound mentioned later.

  Of these, 3-hydroxybenzoic acid, 4-hydroxybenzoic acid, 3-aminobenzoic acid, 4-aminobenzoic acid, 4-sulfonylbenzoic acid, 3-hydroxy-1-naphthoic acid, 4-hydroxynaphthoic acid, 5- Hydroxynaphthoic acid, 4-aminonaphthoic acid, 4-sulfonylnaphthoic acid, etc. are preferably used.

Moreover, the compound shown by following formula (6)-(8) is illustrated by the phenol compound which has any one or more of an amino group and a sulfonyl group in a molecule | numerator.
By adding such a compound to the polyamic acid composition, the compound acts to accelerate the polyamic acid dehydration ring-closing reaction during the drying / firing step. As a result, it is possible to obtain an effect that the imidization reaction can be performed at a lower temperature and a shorter time during the polyimide molding process. These phenol compounds may be used alone or in combination of two or more. Moreover, you may use together with the above-mentioned aromatic carboxylic acid compound.

Of these, 3-aminophenol, 4-aminophenol, 3-hydroxysulfonic acid, 4-hydroxysulfonic acid and the like are preferably used. These may be used alone or in combination of two or more weeks. These are used by dissolving in a solvent of the polyamic acid composition.
The addition amount of an aromatic carboxylic acid compound having any one or more of a hydroxyl group, an amino group and a sulfonyl group in the molecule or a phenol compound having any one or more of an amino group and a sulfonyl group in the molecule is relative to the polyamic acid polymer. It is preferable that it is 0.01-20 mass%. More preferably, it is 0.1-10 mass%, More preferably, it is 0.1-5 mass%. If the addition amount exceeds 20% by mass, it may be deposited as a foreign matter after firing, and the belt quality will deteriorate. On the other hand, when the addition amount is less than 0.01% by mass, a predetermined effect cannot be exhibited.

(8) Coating solvent:
The coating solvent is not particularly limited as long as it dissolves a polyamic acid and a polyamic acid-polyimide copolymer as shown in the aforementioned synthesis solvent. In addition, in order to improve the leveling property during coating and to adjust the drying speed, it is a poor solvent for polyamic acid and polyamic acid-polyimide copolymer, such as alcohol solvents such as methanol, ethanol, butanol or butyl cellosolve. A cellosolve solvent can be used by mixing with the aforementioned solvent. By mixing these poor solvents, the contact angle of the polyamic acid composition with respect to the substrate can be lowered, so that a smooth coating film can be obtained, and there is also an effect of filling the micropores of the substrate. it can.

  Even if it is used from the time of the previous polyamic acid synthesis, it may be substituted with a predetermined solvent after the polyamic acid polymerization or after the imidization reaction. For solvent replacement, a method of diluting a polyamic acid solution or a polyamic acid-polyimide copolymer solution by adding a solvent in various steps, a method of re-precipitating a polymer and then re-dissolving it in a predetermined solvent, a solvent gradually Any of the methods of adjusting the composition by adding a predetermined solvent while distilling off may be used.

(Conductive agent)
As the conductive agent, conductive or semiconductive fine powder can be used, and there is no particular limitation as long as the desired electric resistance can be stably obtained. However, carbon black such as Ketchen Black and Acetylene Black, aluminum and the like Examples thereof include metals such as nickel, metal oxide compounds such as yttrium oxide and tin oxide, and potassium titanate.
Further, an ion conductive material such as LiCl, or a conductive polymer material such as polyacetylene, polypyrrole, polyaniline, polythiophene, poly-p-phenylene, polysulfone, or the like can be added. These may be used alone or in combination.

  These conductive agents are appropriately selected depending on the purpose of use. In the present invention, since the dispersibility in the resin is good, good dispersion stability can be obtained, the resistance variation of the polyimide belt can be reduced, the electric field dependency is also reduced, and the electric field concentration due to the transfer voltage is increased. Oxidized carbon black having a pH of 5 or less is preferably added from the viewpoint of the stability over time of the electric resistance that tends to shift. Further, from the viewpoint of imparting electrical durability to the polyimide belt, it is preferable to add a polymer conductive agent (for example, polyaniline).

(1) Oxidized carbon black:
Oxidized carbon black can be produced by oxidizing carbon black to impart a carboxyl group, a quinone group, a lactone group, a hydroxyl group, or the like to the surface. This oxidation treatment is an air oxidation method in which contact is made with air in a high-temperature atmosphere to react, a method of reacting with nitrogen oxides or ozone at room temperature, and air oxidation at high temperature, followed by ozone oxidation at a low temperature. It can be performed by a method or the like.

  Specifically, the oxidized carbon black can be produced by a contact method. Examples of the contact method include a channel method and a gas black method. Oxidized carbon black can also be produced by a furnace black method using gas or oil as a raw material. If necessary, after these treatments, a liquid phase oxidation treatment with nitric acid or the like may be performed. Acidic carbon black can be produced by a contact method, but is usually produced by a closed furnace method. In the furnace method, only carbon black having a high pH and a low volatile content is usually produced, but the pH can be adjusted by subjecting it to the above-mentioned liquid phase acid treatment. For this reason, carbon black obtained by furnace method production and adjusted to have a pH of 5 or less by post-processing is also considered to be included in the above-described oxidized carbon black.

The pH value of the oxidized carbon black of the present invention is preferably pH 5.0 or less, more preferably pH 4.5 or less, and further preferably pH 4.0 or less.
Oxidized carbon having a pH of 5.0 or less has an oxygen-containing functional group such as a carboxyl group, a hydroxyl group, a quinone group, and a lactone group on the surface, so that it has good dispersibility in the resin, and thus good dispersion stability is obtained. The resistance variation of the polyimide endless belt can be reduced, the electric field dependency is also reduced, and the electric field concentration due to the transfer voltage is less likely to occur.

It is obtained by adjusting an aqueous suspension of carbon black and measuring with a glass electrode. Moreover, pH of acidic carbon black can be adjusted with conditions, such as processing temperature in an oxidation treatment process, and processing time.
The oxidation-treated carbon black preferably contains 1 to 25%, preferably 2 to 20%, more preferably 3.5 to 15% of a volatile component. When the volatile content is less than 1%, the effect of the oxygen-containing functional group attached to the surface is lost, and the dispersibility in the binder resin may be reduced. On the other hand, when the content is higher than 25%, the appearance of the molded product obtained may be decomposed when dispersed in the binder resin or the amount of water adsorbed on the oxygen-containing functional group on the surface increases. May cause problems such as worsening. Therefore, the dispersion | distribution in binder resin can be made more favorable by making a volatile content into the said range. This volatile content can be determined from the ratio of organic volatile components (carboxyl group, hydroxyl group, quinone group, lactone group, etc.) that come out when carbon black is heated at 950 ° C. for 7 minutes.

  Specific examples of the oxidation-treated carbon black include “Printex 150T” (pH 4.5, volatile content 10.0%) and “Special Black 350” (pH 3.5, volatile content 2.2%) manufactured by Degussa. ), "Special Black 100" (pH 3.3, volatile matter 2.2%), "Special Black 250" (pH 3.1, volatile matter 2.0%), "Special Black 5" (pH 3.0) Volatile content 15.0%), "Special Black 4" (pH 3.0, volatile content 14.0%), "Special Black 4A" (pH 3.0, volatile content 14.0%), "Special" "Black 550" (pH 2.8, volatile content 2.5%), "Special Black 6" (pH 2.5, volatile content 18.0%), "Color Black FW200" (pH 2.5, volatile content 20. 0% "Color Black FW2" (pH 2.5, volatile content 16.5%), "Color Black FW2V" (pH 2.5, volatile content 16.5%), "MONARCH1000" (pH 2.5, manufactured by Cabot Corporation) Volatile content 9.5%), Cabot “MONARCH 1300” (pH 2.5, volatile content 9.5%), Cabot “MONARCH 1400” (pH 2.5, volatile content 9.0%), “MOGUL- L ”(pH 2.5, volatile matter 5.0%),“ REGAL400R ”(pH 4.0, volatile matter 3.5%) and the like.

(2) Addition amount of oxidized carbon black:
Oxidized carbon black as described above has better dispersibility in the resin composition due to the effect of the oxygen-containing functional group present on the surface as described above, compared to general carbon black. It is preferable to increase the amount added as. Thereby, since the amount of carbon black in the polyimide endless belt increases, the effect of using the oxidized carbon black that can suppress the in-plane variation of the electric resistance value can be maximized.

The oxidized carbon black is preferably contained in an amount of 10 to 30% by mass with respect to 100 parts by mass of the polyamic acid composition or the polyamic acid-polyimide copolymer. The effect of oxidation-treated carbon black is exhibited, such as suppressing in-plane variation in surface resistivity of the polyimide endless belt. When the content is less than 10% by mass, the uniformity of electrical resistance is lowered, and the in-plane unevenness and electric field dependency of the surface resistivity are increased. On the other hand, when it exceeds 30 mass%, it becomes difficult to obtain a desired resistance value. Further, by containing 18 to 30% by mass of oxidized carbon black, the effect can be exhibited to the maximum, and the in-plane unevenness of the surface resistivity and the electric field dependency can be remarkably improved.
In addition, it is preferable that content of another electrically conductive agent is also made into the said range.

(3) Polymer conductive agent:
Examples of the polymer conductive agent contained in the polyamic acid include polyacetylene, polypyrrole, polyaniline, polythiophene, poly-p-phenylene, and polysulfone. For example, a doped polyaniline filler can be used as the polymer conductive agent. Specifically, the trade name “Panipol F” doped with emeraldine base of Panipol is suitable.

  In addition, a polyaniline in a dedope state is prepared, and a doped polyaniline filler may be prepared by performing a doping treatment with a known dopant, for example, dodecylbenzenesulfonic acid, which is a thermally stable organic sulfonic acid. Also, an additive is added that stabilizes the doped polyaniline, prevents detachment of the protonic acid from the polyaniline, and prevents the detached protonic acid from moving to the surface of the conductive resin composition. You can also Specific examples include metal compounds such as zinc, copper, aluminum, titanium, iron, zirconium, magnesium, and barium, and organic bases such as alkylamines.

  When adjusting the particle size (major axis) of the polyaniline filler, it is necessary to pulverize beforehand using a physical method such as a pulverizer. The major axis of the polyaniline filler is preferably 2 μm or less, and more preferably 1.5 μm or less.

  The doped polyaniline filler is preferably contained in an amount of 5 to 25% by mass based on 100 parts by mass of the polyamic acid composition or the polyamic acid-polyimide copolymer depending on the desired surface resistivity and volume resistivity. When this content is less than 5% by mass or exceeds 25% by mass, it is difficult to obtain desired surface resistivity and volume resistivity.

  The polymer conductive agent as described above is not limited only to these embodiments, and various improvements, changes, and modifications are made based on the knowledge of those skilled in the art without departing from the spirit of the polymer conductive agent. Can be implemented.

  For example, a filler (filler) can be added to the polyamic acid composition. As the inorganic filler as the inorganic filler, insulating fillers such as silica, alumina, mica, talc, whisker, barium sulfate; tin oxide, antimony-doped tin oxide, indium-doped tin oxide, antimony-doped titanium oxide, Conductive / semiconductive fillers such as carbon black can be used. When the conductive / semiconductive filler is used, it can be used in the same manner as the insulating filler by setting the addition amount to be equal to or less than the percolation threshold.

  In this case, the particle size of the inorganic filler (filler) is preferably 0.1 μm or more. When the particle size is 0.1 μm or more, a good reinforcing effect can be exhibited. When the particle size is less than 0.1 μm, the reinforcing effect may not be sufficiently exhibited, which is not preferable. Moreover, it is preferable that the filling amount is 0.1 to 10% in volume fraction. When the volume fraction is less than 0.1%, the reinforcing effect may not be sufficiently exerted, and when it exceeds 10%, the strength of the molded product may be lowered and the toughness is inferior.

  Examples of the method for dispersing the filler and crushing the aggregates include physical methods such as stirring with a mixer and a stirrer, parallel rolls, ultrasonic dispersion, and chemical methods such as introduction of a dispersing agent. However, it is not limited to these.

  Although the polyamic acid composition according to the present invention has been described above, the present invention is not limited only to these embodiments, and various improvements can be made based on the knowledge of those skilled in the art without departing from the spirit of the present invention. The present invention can be implemented in a mode in which changes, modifications are made.

[Polyimide endless belt and manufacturing method thereof]
The polyimide endless belt of the present invention comprises (A) a polyamic acid represented by the general formula (1) described above and (B) an aromatic carboxylic acid compound having any one or more of a hydroxyl group, an amino group and a sulfonyl group, And a polyamic acid composition containing any one or more of a phenolic compound having at least one of an amino group and a sulfonyl group, and applied to a mold, followed by drying treatment and firing treatment. This is an endless belt. In particular, when the endless belt is used as an intermediate transfer member, it is preferable that the polyamic acid composition further contains a conductive agent, specifically, the polyamic acid composition of the present invention described above. Is preferably used as the polyamic acid composition.

  The polyimide endless belt of the present invention can be used in an electrophotographic apparatus such as an electrophotographic copying machine, a laser beam printer, a facsimile, and a composite apparatus thereof. Specifically, the polyimide endless belt of the present invention is preferably incorporated as long as the transfer system is an intermediate transfer belt system and / or has a mechanism for directly or indirectly heating the endless belt. The apparatus is not particularly limited.

  For example, a monocolor electrophotographic apparatus having only a single color (usually black) in the apparatus; a color electrophotographic apparatus that sequentially repeats primary transfer of a toner image carried on a photoreceptor onto an intermediate transfer belt; and a developing device for each color A tandem color electrophotographic apparatus in which a plurality of latent image carriers provided is arranged in series on an intermediate transfer belt may be used. Therefore, the polyimide endless belt of the present invention can be used not only for intermediate transfer and fixing, but also as an intermediate transfer belt and fixing belt. The “intermediate transfer and fixing belt” described above is a belt that performs an intermediate transfer process and a fixing process on the same belt.

  This polyimide belt has the shape of an endless belt. The polyimide endless belt of the present invention is mainly composed of the polyamic acid composition of the present invention described above.

If the difference between the maximum thickness and the minimum thickness of the polyimide endless belt is too large, it will cause wrinkles. It is necessary to reduce the wrinkle of the belt as much as possible because it induces a decrease in image quality when transferring or fixing. From this point, it is desirable that the difference between the maximum thickness and the minimum thickness of the polyimide endless belt is 20% or less of the average thickness of the polyimide endless belt.
The “belt thickness” refers to a thickness that can be measured with a thickness meter that measures the distance between flat plates in contact with the belt at an area of 5 mm ² or more, and has a width of 50 μm or less that exists specifically on the belt surface. The height of the protrusion is ignored.
Moreover, when the thickness of a polyimide endless belt is too thick, it is unpreferable from viewpoints, such as thermal conductivity and resistance value, and when too thin, its toughness is too small, and is not preferable. Therefore, considering the use of the belt, the thickness of the belt is preferably 10 μm or more and 1000 μm or less, and preferably 30 μm or more and 150 μm or less.

When the conductive agent is included, the volume resistivity of the polyimide endless belt is preferably 10 ⁶ Ω · cm or more and 10 ¹² Ω · cm or less. More preferably, it is 10 ⁹ Ω · cm or more and 10 ¹² Ω · cm or less. When this volume resistivity is less than 1 × 10 ⁶ ΩCm, the electrostatic force that holds the charge of the unfixed toner image transferred from the image carrier to the intermediate transfer member becomes difficult to work. Due to the electrostatic repulsive force and the force of the fringe electric field in the vicinity of the image edge, the toner may be scattered around the image (blur), and an image having a large noise may be formed. On the other hand, if the volume resistivity is higher than 1 × 10 ¹² [Omega] cm, in order retention of charge is large, it is necessary to neutralizing mechanism for the intermediate transfer member surface by the transfer electric field at the primary transfer is charged Sometimes. Therefore, by setting the volume resistivity within the above range, it is possible to solve toner scattering and problems that require a charge removal mechanism.

Next, an example is shown about the specific method of shape | molding a polyimide endless belt.
In a polyamic acid solution, which is a precursor of a polyimide resin obtained by polymerizing a tetracarboxylic dianhydride component and a diamine component in an organic solvent, 0.01 mol or more 2 per mol of the polyamic acid repeating unit. 1 mol or less, 0.5 mol to 2 mol of a monovalent carboxylic acid anhydride and 0.01 mol or more and 2 mol or less of a tertiary amine are mixed with respect to the monovalent carboxylic acid anhydride. After the dehydration ring-closing reaction is performed at a temperature from room temperature to 200 ° C., the partially imidized polyamic acid is precipitated by adding the reaction solution to a poor solvent such as methanol. The precipitated partially imidized polyamic acid is filtered and then dissolved in a solvent such as N-methyl-2-pyrrolidone to obtain a partially imidized polyamic acid solution.

  Next, the solution may contain a total of 5 to 60 parts by mass of one or more inorganic powders per 100 parts by mass of the dry weight of the polyamic acid resin. Examples of the inorganic powder include insulating compounds such as silica, mica, talc, whisker, and barium sulfate. These inorganic powders function as a reinforcing material and can increase the mechanical strength of the resulting polyimide endless belt.

Examples of methods for dispersing inorganic powder and disrupting the aggregates include physical methods such as stirring with a mixer or stirrer, parallel rolls, ultrasonic dispersion, and chemical methods such as introduction of a dispersant. However, it is not limited to these.
Thereafter, a predetermined amount of the above-mentioned aromatic carboxylic acid compound or phenol compound is added to prepare a coating liquid for producing an endless belt.

  Next, this coating solution is applied to the inner or outer surface of the mold. As the mold, a cylindrical mold is preferable, and instead of the mold, molds made of various known materials such as resin, glass, and ceramic work well as the mold according to the present invention. obtain. It is also possible to appropriately select to provide a glass coat, a ceramic coat or the like on the surface of the mold, and to use a silicone-based or fluorine-based release agent. Further, the film thickness control mold with the clearance adjusted to the cylindrical mold is moved in parallel through the cylindrical mold, so that the excess solution is eliminated and the thickness of the solution on the cylindrical mold is made uniform. If uniform thickness control of the coating liquid is performed at the stage of applying the coating liquid onto the cylindrical mold, it is not particularly necessary to use a film thickness control mold.

  Next, this cylindrical mold coated with the coating liquid (polyimide resin precursor solution) is placed in a heated or vacuum environment, and drying is performed to volatilize 30% by mass or more, preferably 50% by mass or more of the contained solvent. (Drying process).

Further, this mold is heated at 200 ° C. to 450 ° C. to advance the imide conversion reaction (baking treatment). The imidization temperature varies depending on the types of the raw material tetracarboxylic dianhydride and diamine, but must be set to a temperature at which imidization is completed. Insufficient imidization results in poor mechanical and electrical properties. When the imidized polyamic acid that is not imidized is compared with the case where the partially imidized polyamic acid-polyimide copolymer is imidized, it varies depending on the partial imidization ratio, etc. If the same type is used, imidization can be completed at a low temperature of about 50 ° C. to 200 ° C.
Thereafter, the imidized resin is removed from the mold, and the target polyimide endless belt can be obtained.

  As mentioned above, although the manufacturing method of the polyimide endless belt of this invention was demonstrated, this invention is not limited only to these embodiment, Based on the knowledge of those skilled in the art within the range which does not deviate from the meaning, The present invention can be implemented in a mode with improvements, changes and modifications. That is, of course, by using the polyamic acid composition of the present invention, it is possible to produce not only polyimide endless belts but also molded articles such as polyimide sheets and films.

[Image forming apparatus]
The image forming apparatus of the present invention includes the above-described polyimide endless belt of the present invention as an intermediate transfer member and / or a fixing member.
FIG. 1 shows a schematic configuration diagram of a color electrophotographic copying machine 100 which is an example of an image forming apparatus of the present invention using the above-described polyimide endless belt of the present invention as an intermediate transfer member.
Reference numerals 101BK, 101Y, 101M, and 101C denote photosensitive drums (image carriers), and electrostatic charges corresponding to image information are formed on the surface of the photosensitive drums according to a known electrophotographic process (not shown) along with the rotation in the arrow A direction. A latent image is formed.
Further, around the photosensitive drums 101BK, 101Y, 101M, and 101C, developing units 105 to 108 corresponding to the respective colors of black (BK), yellow (Y), magenta (M), and cyan (C) are disposed. The electrostatic latent images formed on the photosensitive drums 101BK, 101Y, 101M, and 101C are developed by the developing units 105 to 108 to form toner images T. Therefore, for example, the electrostatic latent image written on the photosensitive drum 101Y corresponds to yellow image information, and this electrostatic latent image is developed by the developer 106 containing yellow (Y) toner, A yellow toner image is formed on the photosensitive drum 101Y.

Reference numeral 102 denotes a belt-shaped intermediate transfer member disposed so as to be in contact with the surfaces of the photosensitive drums 101BK, 101Y, 101M, and 101C. The belt-shaped intermediate transfer member is stretched around a plurality of rolls 117 to 120 and rotated in the arrow B direction. Move.
Since the intermediate transfer member 102 uses the polyimide endless belt of the present invention described above, defects due to film thickness non-uniformity of the conventional endless belt can be reduced.

  The unfixed toner images formed on the photosensitive drums 101BK, 101Y, 101M, and 101C are sequentially exposed at respective primary transfer positions where the photosensitive drums 101BK, 101Y, 101M, and 101C are in contact with the intermediate transfer member 102. Each color is superimposed on the surface of the intermediate transfer body 102 and transferred from the body drums 101BK, 101Y, 101M, and 101C. At the primary transfer position, corona dischargers 109 to 112 that prevent the transfer prenip from being charged by transfer baffles 121 to 124 are disposed on the back side of the intermediate transfer member 102. The corona dischargers 109 to 112 are disposed. By applying a voltage having the opposite polarity to the toner charging polarity, the unfixed toner images on the photosensitive drums 101BK, 101Y, 101M, and 101C are electrostatically attracted to the intermediate transfer member 102. The primary transfer means is not limited to a corona discharger as long as it uses an electrostatic force, and may be a conductive roll or a conductive brush to which a voltage is applied. The reason for using such an electrostatic force is that if the adhesive force of toner due to heat or pressure is used for primary transfer, the photoreceptor is easily damaged.

  The unfixed toner image primarily transferred to the intermediate transfer member 102 in this way is conveyed to a secondary transfer position facing the conveyance path of the recording medium 103 as the intermediate transfer member 102 rotates. At the secondary transfer position, a heating transfer roll 120 incorporating a heating source such as a ceramic heater or a halogen lamp is in contact with the back side of the intermediate transfer member 102. In addition, a pressure roll 125 is disposed facing the heating transfer roll 120 at the secondary transfer position. The pressure roll 125 is preferably coated with a fluororesin on the surface, and a heat source may be built in like the heat transfer roll 120. The recording medium 103 carried out from the tray 113 at a predetermined timing by the feed roller 126 is inserted between the pressure roll 125 and the intermediate transfer member 102. At this time, a voltage may be applied between the heat transfer roll 120 and the pressure roll 125. The unfixed toner image carried on the intermediate transfer member 102 is heat-melted and transferred to the recording medium 103 at the secondary transfer position. Since the toner image is melted and transferred by heating and pressure means, even if an intermediate transfer member 102 without charge attenuation is used, a discharge occurs between the intermediate transfer member 102 and the recording medium 103 and the toner scatters. It does not cause the problem of image quality defects.

Then, the recording medium 103 on which the unfixed toner image is transferred is peeled off from the intermediate transfer body 102 by the peeling claw 114, and sent to a fixing device (not shown) by the conveying belt 115 to fix the unfixed toner image. The At this time, the secondary transfer device (the heat transfer roll 120 and the pressure roll 125) may serve as fixing, but in order to obtain sufficient color fixing properties, it is preferable to make the fixing process independent as described above. .
The pressure roll 125, the peeling claw 114, and the cleaning device 116 are disposed so as to be able to come into contact with and separate from the intermediate transfer member 102, and these members are separated from the intermediate transfer member 102 until the secondary transfer is performed.

  When the polyimide endless belt is semiconductive, it is preferably used as an intermediate transfer belt or a fixing belt. However, a conductive agent (a metal oxide is preferable because conductivity can be easily increased) is used. When added to form a conductive belt, it can also be used as a transport belt for transporting paper.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

<Example 1>
[Polyamic acid composition]
(Synthesis Example 1 Preparation of polyamic acid solution)
Into a flask equipped with a stirrer, a thermometer and a dropping funnel, nitrogen gas dried with phosphorus pentoxide was passed through 29.42 g (0.1 mol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride. ) And 117.68 g of N-methyl-2-pyrrolidone were injected. After sufficiently stirring and dissolving, a solution prepared by dissolving 20.02 g (0.1 mol) of 4,4′-diaminodiphenyl ether in 80.08 g of N-methyl-2-pyrrolidone was gradually put in a flask maintained at 10 ° C. It was dripped. After dropping the solution, stirring and polymerization were carried out at 10 to 15 ° C. The reaction solution was poured into a large amount of methanol, and reprecipitation purification was performed. The precipitated white polymer was filtered off and dried, and then redissolved in N-methyl-2-pyrrolidone to obtain a 20% by mass polyamic acid (PAA) solution.

(Synthesis Example 2 Preparation of Polyamic Acid-Polyimide Copolymer Composition)
After polymerizing the polyamic acid in the flask in the same manner as in Synthesis Example 1, 7.91 g (0.1 mol) of pyridine and 10.21 g (0.1 mol) of acetic anhydride were sequentially added. Reaction was performed at 60 degreeC for 2 hours. The reaction solution was poured into methanol for reprecipitation purification. The precipitated polyamic acid-polyimide copolymer was filtered off. After drying, it was redissolved in N-methyl-2-pyrrolidone to obtain a 20% by mass polyamic acid-polyimide copolymer (PAA-PI) composition solution.
A 20% by mass polyamic acid-polyimide copolymer (PAA-PI) composition solution was diluted to 1% by mass and spin-coated on a silicon wafer at 3000 rpm for 60 seconds to form a thin film. After drying in a vacuum dryer at 80 ° C. and 1 mmHg, an infrared absorption spectrum was measured with a microscopic FT-IR spectrometer FT-530 manufactured by Horiba. The imidation ratio was calculated from the absorbance of the imide group at 1780 cm ⁻¹ with reference to the absorption of the phenyl group at 1500 cm ⁻¹ . As a result, the imidation ratio of the polyamic acid-polyimide copolymer was 20%.

(Preparation Example 1 Preparation of Polyamic Acid Composition (A))
In 200 g of the polyamic acid solution, 0.8 g of 4-hydroxybenzoic acid as an additive (2 parts by mass with respect to 100 parts by mass of the polyamic acid) was added and dissolved to obtain a polyamic acid composition (A).

(Preparation Example 2 Preparation of carbon black-dispersed polyamic acid composition liquid (a))
In 200 g of polyamic acid solution, 0.8 g of 4-hydroxybenzoic acid as an additive (2 parts by mass with respect to 100 parts by mass of polyamic acid) was added and dissolved, and then oxidized carbon black as a dried conductive agent. (SPECIAL BLACK4 (manufactured by Degussa, pH 4.0, volatile content: 14.0%) 8.0 g was added and treated in a ball mill for 6 hours to obtain a carbon black-dispersed polyamic acid composition (a). It was.

(Preparation Examples 3 to 16 Preparation of polyamic acid compositions (B) to (O))
Polyamic acid compositions (B) to (O) were obtained in the same manner as in Preparation Example 1, except that the polymer (polyamic acid or polyamic acid-polyimide copolymer) and additives were changed to Table 1 below.

(Preparation Examples 17 to 30 Preparation of carbon black-dispersed polyamic acid compositions (b) to (o))
Carbon black-dispersed polyamic acid compositions (b) to (o) were prepared in the same manner as in Preparation Example 2 except that the polymer (polyamic acid or polyamic acid-polyimide copolymer) and additives were changed to the following Table 1. Obtained. In addition, the Example of a polyamic acid composition is equivalent to the preparation example 2 and the preparation examples 17-30.

[Polyimide endless belt]
(Production Example 1 of polyimide endless belt)
The obtained polyamic acid composition (A) was uniformly applied to the surface of a cylindrical SUS mold having an inner diameter of 90 mm and a length of 450 mm.
In addition, the release property after belt molding was improved by previously applying a fluorine-based mold release agent to the surface of the cylindrical mold.
Next, a drying process was performed for 30 minutes at a temperature of 120 ° C. while rotating the mold. After the drying treatment, the mold was placed in an oven and baked at 220 ° C. for about 30 minutes to advance the imidization reaction. Thereafter, the mold was allowed to cool at room temperature, the resin was removed from the mold, and the target polyimide endless belt was obtained.

  The obtained polyimide endless belt was subjected to mechanical properties such as imidization ratio, thickness measurement, volume resistance measurement, and tensile strength as follows. The results are shown in Table 2 below.

(Imidation rate)
A test piece was cut out from the obtained polyimide endless belt and measured with an FT-IR (microscopic FT-IR spectrometer FT-530 manufactured by Horiba, Ltd.). The 400 ° C. calcined product as 100% imidization ratio was determined by the ratio of the vibration peaks of the aromatic ring of the stretch peak and 1500 cm ^-1 of the carbonyl group derived from the imide groups of the 1776 cm ^-1.

(Belt thickness measurement)
Ten pieces of 10 cm square test pieces were randomly cut out from the obtained polyimide endless belt, and 5 points at the center and at the four corners for each sample using a film thickness meter (manufactured by TECLOCK CORPORATION: constant pressure thickness measuring instrument PG-02). The thickness was measured, and the variation from the average thickness was evaluated.

(Tensile strength and elongation)
The tensile strength was measured with a tensile tester (1605N manufactured by Aiko Engineering Co., Ltd.). Using a punch molding machine, a test piece having a length of 100 mm and a width of 5 mm was prepared, and a tensile test was performed with a length of 40 mm. The elongation percentage was calculated by comparing the original length of the test piece with the length at the time of tensile fracture.

(Belt appearance)
The appearance of the obtained belt was visually observed and evaluated as follows.
“◯”: No voids are observed, and the film has excellent uniformity.
“◯ △”: Some voids are observed, but there is no problem in practical use.
“Δ”: Generation of voids is observed, and there is a slight hindrance to practical use.
“×”: Voids frequently occur and cannot be used practically.

  From the results in Table 2, the imidization ratio of the obtained polyimide endless belt was about 100% and the thickness was 70 ± 5 μm, and the film thickness unevenness seen in the progress of the imidization reaction was suppressed and uniform. Moreover, since the imidation reaction has substantially progressed, the belt has high film strength. It showed characteristics suitable as a fixing belt.

(Production Examples 2-45 of polyimide endless belt)
Using the polyamic acid compositions (A) to (O) prepared in Preparation Examples 1 and 3 to 16, the endless polyimide was obtained in the same manner as in Production Example 1 except that the firing temperature was changed as shown in Table 2 above. A belt was produced. The characteristics of the obtained polyimide belt are shown in Table 2 above.
It was confirmed that the belt obtained under any conditions had suitable characteristics similar to Example 1.

(Production Examples 46 to 90 of polyimide endless belt)
Using the polyamic acid compositions (a) to (o) in which carbon black prepared in Preparation Examples 2 and 17 to 30 was dispersed, Production Example 1 and Except that the firing temperature was changed as shown in Table 3 below Similarly, a polyimide endless belt was produced. The obtained endless belt was evaluated in the same manner as in Production Example 1. Further, when the volume resistance and electrophotographic machine mounting test were measured under the following conditions, the volume resistance value of any belt showed 1 × 10 ¹⁰ Ωcm, and as a result of the electrophotographic machine mounting test, it was suitable as an intermediate transfer belt. It was confirmed that it had characteristics.

(Measurement of volume resistance)
For measuring the volume resistivity of the intermediate transfer member (belt) as a polyimide endless belt, a 10 × 10 cm ² test piece was cut out from the polyimide endless belt, and R8340A digital ultrahigh resistance / microammeter (manufactured by Advantest Co., Ltd.) ) And a double ring electrode structure UR probe MCP-HTP12 and a register UFL MCP-ST03 (both manufactured by Dia Instruments Co., Ltd.) whose connection portions were modified for R8340A.

  A film (D) sample was placed on the register UFL MCP-ST03 (using the metal surface as the lower electrode), and the double electrode portion of the UR probe MCP-HTP12 was applied as the upper electrode. A weight of 19.6N ± 1N was attached to the upper part of the UR probe MCP-HTP12 so that a uniform load was applied to the film (D) sample.

  The measurement conditions of the R8340A digital ultrahigh resistance / microammeter were a charge time of 30 sec, a discharge time of 1 sec, and an applied voltage of 100V.

  At this time, the volume resistivity of the film (D) is ρv, the thickness t (μm) of the intermediate transfer member, the R8340A digital ultrahigh resistance / microammeter reading is R, and the volume resistivity correction of the UR probe MCP-HTP12 is performed. If the coefficient is RCF (V), according to the Mitsubishi Chemical “Resistivity Meter Series” catalog, since RCF (V) = 2.01, the following equation (B) is obtained.

Formula (B): ρv [Ω · cm] = R × RCF (V) × (10000 / t) = R × 2.111 × (10000 / t)

(Electronic camera mounting test)
The polyimide endless belts obtained in Production Examples 46 to 90 were incorporated as an intermediate transfer belt in an electrophotographic apparatus (DocuCentreColor400CP) manufactured by Fuji Xerox Co., Ltd., and the initial copy image quality was evaluated. As evaluation items for copy image quality, the presence / absence of printing deviation, the presence / absence of uneven printing density, the presence / absence of ghost, etc. were evaluated. The image quality after the 50,000 sheet passing test was similarly evaluated. The belt length before and after the paper passing test was measured, and the belt durability when using the actual machine was evaluated and compared. The evaluation results are shown in Table 4. It should be noted that the ratio of the belt length after passing through to before passing (after passing / before passing) is preferably in the range of 1.000 ± 0.008.

<Comparative Example 1>
(Preparation Example Preparation of polyamic acid composition (X))
A polyamic acid was synthesized in the same manner as in Synthesis Example 1. Then, after precipitating in methanol, it was dissolved in a single solvent of N-methyl-2-pyrrolidone to obtain a 20% by mass polyamic acid composition (X).

(Preparation Example Preparation of Polyamic Acid-Polyimide Copolymer Composition (Y))
A polyamic acid-polyimide copolymer was synthesized in the same manner as in Synthesis Example 2. Then, after precipitating in methanol, it was made to melt | dissolve in the N-methyl-2-pyrrolidone single solvent, and the 20 mass% polyamic acid-polyimide copolymer composition (Y) was obtained.

(Preparation Example Preparation of carbon black-dispersed polyamic acid composition liquids (x) and (y))
Carbon black (SPECIAL BLACK4 (manufactured by Degussa, pH 4.0, volatile content: 14.0%) is added and dispersed in each of the polyamic acid composition (X) and the polyamic acid-polyimide copolymer composition (Y). Thus, carbon black-dispersed polyamic acid compositions (x) and (y) were obtained, respectively.
Carbon black was 22 parts by mass with respect to 100 parts by mass of the polyamic acid composition (X) and the polyamic acid-polyimide copolymer composition (Y).

(Production Examples 91-102 of polyimide endless belt)
Polyimide endless belt using the polyamic acid compositions (X) and (Y) and the carbon black-dispersed polyamic acid composition liquids (x) and (y) in the same manner as in Production Example 1 at the firing temperature shown in Table 5 below. Manufactured.
Table 5 below shows the characteristics of the manufactured belt. In addition, the polyimide endless belt made of the polyamic acid composition containing carbon black produced in Production Examples 97 to 102 shown in Table 6 below was evaluated by being incorporated into an electrophotographic apparatus as an intermediate transfer member in the same manner as in Production Example 46. . The results are shown in Table 6 below.

It was confirmed that the polyamic acid composition of the present invention can undergo an imidization reaction at a low firing temperature.
Moreover, from the above results, the polyimide endless belt that improved the film quality while improving the mechanical characteristics and electrical characteristics was only the one according to the present invention.
Furthermore, in the image forming apparatus using such an endless belt, defects due to the film thickness non-uniformity of the conventional endless belt hardly occurred.

<Example 2>
[Polyamic acid composition]
(A: Preparation of polyamic acid solution)
Into a flask equipped with a stirrer, a thermometer and a dropping funnel, nitrogen gas dried with phosphorus pentoxide was passed through 29.42 g (0.1 mol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride. ) And 117.68 g of N-methyl-2-pyrrolidone were injected. After sufficiently stirring and dissolving, a solution prepared by dissolving 20.02 g (0.1 mol) of 4,4′-diaminodiphenyl ether in 80.08 g of N-methyl-2-pyrrolidone was gradually put in a flask maintained at 10 ° C. It was dripped. After dropping the solution, stirring and polymerization were carried out at 10 to 15 ° C. The reaction solution was poured into a large amount of methanol, and reprecipitation purification was performed. The precipitated white polymer was filtered off and dried, and then redissolved in N-methyl-2-pyrrolidone to obtain a 20% by mass polyamic acid (PAA) solution.

(B: Preparation of polyaniline filler)
Product name: Panipol F / Panipol was used. The addition amount was added at a ratio to the mass corresponding to the solid content of the polyamic acid.

(C: Preparation of imidization accelerator)
4-Hydroxybenzoic acid or 3-aminobenzoic acid was used. The addition amount was added at a ratio to the mass corresponding to the solid content of the polyamic acid (see Table 7 below for details).

  As mentioned above, after combining A, B, and C, the mixture was stirred for 2 hours with a mixer to prepare a polyamic acid composition.

[Polyimide endless belt]
(Production Examples 103 to 106 of polyimide endless belt)
The obtained film forming solution was uniformly applied to the surface of a cylindrical SUS mold having an inner diameter of 90 mm and a length of 450 mm. The cylindrical mold was previously coated with a fluorine release agent on the surface to improve the peelability after belt molding.

  Next, a drying process was performed while rotating the mold. After the drying treatment, the mold was placed in an oven and baked to advance the imidization reaction. Thereafter, the mold was allowed to cool at room temperature, the resin was removed from the mold, and the target polyimide endless belt (polyimide endless belt according to Production Examples 103 to 106 in Table 7 below) was obtained. In addition, the used drying furnace / baking furnace consists of a continuous two-chamber structure, and if each processing time is set, it will be conveyed automatically.

<Comparative example 2>
Polyimide endless according to Production Examples 107 to 109 in the same manner as in Example 2 except that neither 4-hydroxybenzoic acid nor 3-aminobenzoic acid was used and the composition and drying / firing conditions in Table 8 below were used. I got a belt.

  The obtained polyimide endless belt (polyimide endless belt according to Production Examples 103 to 109) was subjected to mechanical properties such as imidization ratio, thickness measurement, volume resistance measurement, and tensile strength as follows.

(Measurement of imidization rate)
A test piece was cut out from the obtained polyimide endless belt and measured by FT-IR (microscopic FT-IR spectrometer FT-530 manufactured by Horiba, Ltd.). The 400 ° C. calcined product as 100% imidization ratio was determined by the ratio of the vibration peaks of the aromatic ring of the stretch peak and 1500 cm ^-1 of the carbonyl group derived from the imide groups of the 1776 cm ^-1.

(Measurement of tensile strength and tensile modulus)
The obtained polyimide endless belt was cut into 10 mm width × 200 mm length to prepare a sample. At this time, the length of 200 mm was adjusted in the circumferential direction of the belt. Measurement was performed with a tensile tester (1605N manufactured by Aiko Engineering Co., Ltd.) according to JIS K7127, with a distance between marked lines of 100 mm and a tensile speed of 10 mm / min, and a tensile strength and a tensile elastic modulus were calculated.

(Measurement of surface resistivity)
For measuring the surface resistivity of the intermediate transfer member (belt) as a polyimide endless belt, a 10 × 10 cm ² test piece was cut out from the polyimide endless belt, and R8340A digital ultrahigh resistance / microammeter (manufactured by Advantest Co., Ltd.) And a UR probe MCP-HTP12 and a register UFL MCP-ST03 (both manufactured by Dia Instruments Co., Ltd.) having a double ring electrode structure modified for R8340A.

  Place the sample of the film (D) on the register UFL MCP-ST03 (using a fluororesin surface) with the measurement surface (the surface layer on the transfer surface side in the case of a multi-layer configuration) facing up, and touch the measurement surface A double electrode of UR probe MCP-HTP12 was applied. A weight of 19.6N ± 1N was attached to the upper part of the UR probe MCP-HTP12 so that a uniform load was applied to the film (D) sample.

  The measurement conditions of the R8340A digital ultra-high resistance / microammeter were a charge time of 30 sec, a discharge time of 1 sec, and an applied voltage of 100V.

  At this time, assuming that the surface resistivity of the film (D) is ρs, the reading value of the R8340A digital ultrahigh resistance / microammeter is R, and the surface resistivity correction coefficient of the UR probe MCP-HTP12 is RCF (S), Mitsubishi Chemical According to the “Resistivity Meter Series” catalog, since RCF (S) = 10.00, the following equation (A) is obtained.

Formula (A): ρs [Ω / □] = R × RCF (S) = R × 10

(Measurement of volume resistivity)
The volume resistivity of the intermediate transfer member (belt) as a polyimide endless belt was measured in the same manner as described above.

(Electronic camera mounting test)
The polyimide endless belts obtained in Example 2 and Comparative Example 2 were incorporated as an intermediate transfer belt in an electrophotographic apparatus (DocuCenter Color 400CP) manufactured by Fuji Xerox Co., Ltd., and the initial copy image quality was evaluated. As evaluation items for copy image quality, the presence / absence of printing deviation, the presence / absence of uneven printing density, the presence / absence of ghost, etc. were evaluated.

  The results of Example 2 are summarized in Table 7 below. In addition, the results of Comparative Example 2 are summarized in Table 8 below. As evaluation indexes in Tables 7 and 8, “◯” indicates a level that does not cause a problem in practical use, “Δ” indicates a degree of difficulty in practical use, and “×” indicates a level that is not practical.

  The polyamic acid composition of Example 2 was confirmed to be capable of performing an imidization reaction at a low firing temperature. By combining an imidization accelerator that accelerates the imidization reaction of the polyimide and a polymer conductive agent, the polyimide can be fired at a lower temperature than in the past, and polyaniline due to excessive oxidation as in the conventional high temperature firing. It was possible to reduce the amount of polyaniline added to obtain the desired surface resistivity and volume resistivity.

1 is a schematic view showing a color electrophotographic copying machine which is an example of an image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100: Color electrophotographic copying machine 102: Intermediate transfer body 103: Recording medium 105-108: Developing device 109-112: Transfer corotron 116: Cleaning device 117, 118: Cooling roll 120: Heating transfer roll 121-124: Transfer baffle 125 : Backup role

Claims (9)

(A) A polyamic acid represented by the following general formula (1), (B) an aromatic carboxylic acid compound having any one or more of a hydroxyl group, an amino group and a sulfonyl group, and any of an amino group and a sulfonyl group One or more types of the phenolic compound which has 1 or more, and (C) conductive agent, The polyamic acid composition characterized by the above-mentioned.

The polyamic acid composition according to claim 1, wherein the polyamic acid contains a polyimide represented by the following general formula (2).

The polyamic acid composition according to claim 1 or 2, wherein the aromatic carboxylic acid compound is represented by any one of the following general formulas (3) to (5).

The polyamic acid composition according to claim 1, wherein the phenol compound is represented by any one of the following general formulas (6) to (8).

  The addition amount of the said aromatic carboxylic acid compound or the said phenol compound is 0.01-20 mass parts with respect to 100 mass parts of said polyamic acids, The any one of Claims 1-4 characterized by the above-mentioned. A polyamic acid composition. (A) A polyamic acid represented by the following general formula (1), (B) an aromatic carboxylic acid compound having any one or more of a hydroxyl group, an amino group and a sulfonyl group, and any of an amino group and a sulfonyl group A polyimide endless belt produced by applying a polyamic acid composition containing any one or more of phenol compounds having one or more to a mold, followed by drying treatment and firing treatment.

  The polyimide endless belt according to claim 6, wherein a conductive agent is further contained in the polyamic acid composition. (A) A polyamic acid represented by the following general formula (1), (B) an aromatic carboxylic acid compound having any one or more of a hydroxyl group, an amino group and a sulfonyl group, and any of an amino group and a sulfonyl group A method for producing a polyimide endless belt, comprising applying a polyamic acid composition containing any one or more of phenol compounds having one or more to a mold, followed by drying treatment and firing treatment.

  An image forming apparatus comprising the polyimide endless belt according to claim 6 as an intermediate transfer member and / or a fixing member.

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