JP2007226219A - Intermediate transfer member and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an intermediate transfer member which ensures a small variation in electric resistance under environmental changes in temperature and humidity and a small variation in electric resistance due to a change in applied voltage. <P>SOLUTION: The intermediate transfer member contains a conductive agent and a resin and satisfies all of the following conditions (1)-(3); (1) common logarithm of surface resistivity in voltage application of 100 V in an environment at 22°C and 55% RH is 9-13 (logΩ/square), (2) difference between common logarithms of volume resistivities in voltage application of 10 V and 100 V in an environment at 22°C and 55% RH is ≤0.5 (logΩ cm), (3) difference between common logarithms of surface resistivities in voltage application of 100 V in an environment at 28°C and 85% RH and in an environment at 10°C and 15% RH is ≤1.0 (logΩ/square). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an intermediate transfer member and an image forming apparatus.

  Conventionally, a conductive film or sheet is produced by adding a conductive agent such as carbon black into a thermoplastic resin or a thermosetting resin, and dispersing and molding it under a wet or dry method. However, depending on the characteristics of the conductive agent and resin used, there may be a large variation due to environmental temperature and humidity, or a large variation due to the voltage used.

  For example, a resin composition to which a conductive agent such as a quaternary ammonium salt or a surfactant is added exhibits conductivity due to adsorbed water molecules, so that the conductive effect is reduced in winter at low temperature and low humidity. Occurs.

  Further, in the electrophotographic field, since the image forming method is performed by charge transfer, a component having a small fluctuation due to the environment and the operating voltage is desired.

  Patent Document 1 proposes a resin composition obtained by adding titanium oxide and alumina to polyimide, and an electrophotographic tubular product.

  In an electrophotographic apparatus, an electric charge is uniformly formed on a photosensitive member made of a conductive material, an electrostatic latent image is formed with a modulated image signal using a laser beam or the like, and then the electrostatic latent image is developed with charged toner. Thus, a toner image is obtained. 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, image formation employing a so-called intermediate transfer method The intermediate transfer belt used in the apparatus is, for example, a conductive belt in which a conductive agent such as carbon black is dispersed in a thermoplastic resin such as polyvinylidene fluoride, polycarbonate, or a blend of an ethylene-tetrafluoroethylene copolymer and polycarbonate. Proposed.

  In the following Patent Documents 2, 3 and the like, an intermediate transfer body in which carbon black is dispersed as a conductive fine powder in a polyimide resin is proposed. Normally, when carbon black is dispersed in polyimide as a conductive powder, the electrical resistance value varies little with respect to environmental changes in temperature and humidity, but it is difficult to uniformly disperse carbon black. In-plane variation tends to increase. Furthermore, since the voltage dependency of the resistance value is as large as 2.0 or more, it is difficult to use it in the image forming apparatus. In addition, there is a problem that voltage concentration applied in the transfer portion occurs, and the electric resistance value is lowered by the transfer voltage over time.

On the other hand, as a method for imparting conductivity to a molded product of polyimide, a method using a conductive polymer such as polyaniline as a conductive material is known. A conductive polymer such as polyaniline easily dissolves or disperses uniformly in a polyimide varnish, making it easy to adjust a molded product to a predetermined resistance value, and having a uniform resistance value with in-plane variation in dispersion. There is an advantage that it can be obtained. Thus, the method of providing electroconductivity by adding polyaniline as a electrically-conductive material in a polyimide is disclosed by the cited documents 4-6, for example.
JP 2003-113305 A Japanese Patent No. 2560727 JP-A-5-77252 JP-A-8-259709 Japanese Patent Laid-Open No. 9-176329 JP 2000-226765 A

  However, as in the above cited references 4 to 6, when using a conductive polymer (polyaniline), a large amount of dopant must be added, and as a result, it is easily affected by humidity in the air. The quality of the molded product obtained using this as a coating liquid, for example, the difference between the common logarithm of the surface resistivity under high temperature and high humidity and the surface resistivity under low temperature and low humidity is as large as 1.0 or more, Variations in image quality could occur depending on the environment.

Therefore, the present invention aims to solve the conventional problems and achieve the following object. That is,
SUMMARY OF THE INVENTION An object of the present invention is to provide an intermediate transfer member in which both a change in electrical resistance value with respect to environmental changes in temperature and humidity and a change in electrical resistance value due to changes in applied voltage are small.
Another object of the present invention is to provide an image forming apparatus comprising the intermediate transfer member and capable of obtaining a high-quality transfer image.

Means for solving the above-mentioned problems are as follows. That is,
<1> An intermediate transfer member comprising a conductive agent and a resin and satisfying all of the following conditions (1) to (3).
(1) The common logarithm of the surface resistivity when a voltage of 100 V is applied in an environment of 22 ° C. and 55% RH is 9 to 13 (logΩ / □).
(2) In an environment of 22 ° C. and 55% RH, the difference in common logarithm of volume resistivity when a voltage of 10 V and 100 V is applied is 0.5 (log Ω · cm) or less.
(3) The difference in the common logarithm of the surface resistivity when a voltage of 100 V is applied in an environment of 28 ° C. and 85% RH and 10 ° C. and 15% RH is 1.0 (logΩ / □) or less It is.

<2> The intermediate transfer member according to <1>, wherein the resin is polyimide.

<3> The intermediate transfer member according to <1> or <2>, wherein the conductive agent is made of a conductive polymer.

<4> The intermediate transfer member according to <3>, wherein the conductive polymer is polyaniline.

<5> an image carrier;
Charging means for charging the surface of the image carrier;
Latent image forming means for forming a latent image on the surface of the charged image carrier;
Developing means for developing the latent image with toner to form a toner image;
Transfer means for transferring the toner image onto a recording medium;
Fixing means for fixing the toner image on a recording medium;
In an image forming apparatus having
In the image forming apparatus, the transfer unit includes the intermediate transfer member according to any one of <1> to <4>.

According to the present invention, it is possible to provide an intermediate transfer member in which both the fluctuation of the electric resistance value with respect to the environmental change of temperature and humidity and the fluctuation of the electric resistance value due to the change of applied voltage are small.
Furthermore, by providing the intermediate transfer member of the present invention, it is possible to provide an image forming apparatus capable of obtaining a high-quality transfer image.

<Intermediate transfer member>
Next, the intermediate transfer member of the present invention will be described.
The intermediate transfer member of the present invention contains a conductive agent and a resin, and satisfies all of the following conditions (1) to (3).
(1) The common logarithm of the surface resistivity when a voltage of 100 V is applied in an environment of 22 ° C. and 55% RH is 9 to 13 (logΩ / □).
(2) In an environment of 22 ° C. and 55% RH, the difference in common logarithm of volume resistivity when a voltage of 10 V and 100 V is applied is 0.5 (log Ω · cm) or less.
(3) The difference in the common logarithm of the surface resistivity when a voltage of 100 V is applied in an environment of 28 ° C. and 85% RH and 10 ° C. and 15% RH is 1.0 (logΩ / □) or less It is.
Hereinafter, the intermediate transfer member and the image forming apparatus of the present invention will be described in detail.

  As described above, the intermediate transfer member of the present invention satisfies all of the above conditions (1) to (3). By satisfying these conditions, fluctuations in the electrical resistance value with respect to environmental changes in temperature and humidity, It indicates that the intermediate transfer member has a small variation in electric resistance value due to a change in applied voltage.

Condition (1) defines a common logarithm of surface resistivity when a voltage of 100 V is applied in an environment of 22 ° C. and 55% RH, and the common logarithm of the surface resistivity is 9 to 14 ( logΩ / □), preferably 10 to 13 (logΩ / □), more preferably 11 to 13 (logΩ / □).
When the common logarithmic value of the surface resistivity is less than 9 (log Ω / □), 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. For this reason, the electrostatic repulsive force between toners or the force of a fringe electric field in the vicinity of the image edge may cause the toner to scatter around the image (blur), resulting in the formation of a noisy image. On the other hand, when the common logarithmic value of the surface resistivity is higher than 14 (log Ω / □), since the charge holding power is large, the surface of the intermediate transfer member is charged by the transfer electric field in the primary transfer, and thus the static elimination mechanism. May be required. Therefore, by setting the surface resistivity within the above range, it is possible to solve the problem of toner scattering and the need for a static elimination mechanism.

Condition (2) defines the difference in common logarithm of volume resistivity when different voltages (10 V and 100 V) are applied under the same temperature and humidity environment as in condition (1). The difference in resistance of the volume resistivity is 0.5 (logΩ · cm) or less, preferably 0.4 (logΩ · cm) or less, more preferably 0.3 (log Ω · cm) or less.
Condition (3) is a common logarithm of the surface resistivity when a voltage of 100 V is applied when the temperature and humidity conditions are different (under an environment of 28 ° C. and 85% RH and under an environment of 10 ° C. and 15% RH). The difference in electrical resistance value with respect to environmental changes in temperature and humidity is small, and the difference in common logarithm of the surface resistivity is 1.0 (log Ω / □) or less, Preferably it is 0.7 (logΩ / □) or less, more preferably 0.5 (logΩ / □) or less.

  The intermediate transfer member of the present invention is preferably used in an electrophotographic apparatus such as an electrophotographic copying machine, a laser beam printer, a facsimile, or a composite apparatus thereof. More specifically, the intermediate transfer member is preferably applied as an endless belt, such as a transfer belt, a conveyance belt, and an intermediate transfer belt in an electrophotographic apparatus using an intermediate transfer method.

If the difference between the maximum thickness and the minimum thickness when the intermediate transfer member of the present invention is used as a belt is too large, it causes wrinkles. When the belt is used in an electrophotographic apparatus, 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, the difference between the maximum thickness and the minimum thickness of the intermediate transfer belt is preferably 20% or less of the average of the belt thickness, more preferably 15% or less, and further preferably 10% or less. preferable. 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, if the thickness of the belt is too thick, it is not preferable from the viewpoint of thermal conductivity, resistance value, etc., and if it is too thin, its toughness is too small. Therefore, considering the use of the belt, the thickness is preferably 10 μm or more and 1000 μm or less, and more preferably 30 μm or more and 150 μm or less.

As described above, the intermediate transfer member of the present invention contains a conductive agent and a resin. As the conductive agent, a conductive polymer is preferable, and polyaniline, polypyrrole, and polythiophene are particularly preferable. Examples of the resin include polyimide, polyamideimide, and polycarbonate. Among them, polyimide obtained by polycondensation from biphenyltetracarboxylic dianhydride and oxydianiline is preferable.
The intermediate transfer member containing polyaniline as a conductive agent and polyimide as a resin will be described below. The intermediate transfer member can be prepared by preparing a polyamic acid composition, applying the composition to a mold such as a cylindrical base material, and causing imide conversion.

[Polyamic acid composition]
The polyamic acid composition used in the present invention is characterized by containing a polyamic acid, a conductive polymer, a dopant for making the conductive polymer conductive, and a solvent.

[Conductive polymer]
Examples of the conductive polymer include those described above, and polyaniline is preferable. As described above, the polyaniline in the present invention is used as a conductive material, and the synthesis and structure of the polyaniline are described in detail in JP-A-3-28229.
The polyaniline in the present invention can be easily produced from aniline or an aniline derivative by oxidative polymerization. As shown below, polyaniline is known to have the structure of leucoemeraldine (or leucoemeraldine), emeraldine (emeraldine) and pernigraniline depending on its oxidation state. ing.

  Of these, polyaniline having an emeraldine structure is most useful because it has the highest electrical conductivity during doping and is stable in air. Since polyaniline is usually easily oxidized, it is preferable that there is less perniguraniline structure in order to improve and stabilize conductivity, and it can be efficiently doped by doping from a reduced state. In the present invention, a polyamic acid composition capable of forming the intermediate transfer member of the present invention is obtained by performing a reduction treatment using a reducing agent described later, dissolving in a solvent, and performing a doping treatment.

  In the synthesis of polyaniline, as described in detail in JP-A-3-28229, the temperature of aniline is maintained at 5 ° C. or lower, preferably 0 ° C. or lower in a solvent in the presence of a protonic acid. Meanwhile, an oxidant polymerization is performed by causing an oxidant to act to produce an oxidized polymer of aniline doped with a protonic acid (to be described later) (hereinafter referred to as doped polyaniline). This doped polyaniline can then be obtained by undoping with a basic material.

  The addition amount (use amount) of polyaniline in the polyamic acid composition is appropriately adjusted depending on the conductivity to be expressed. Generally, the polyaniline to be added is preferably 5 to 40 parts by mass, more preferably 10 to 30 parts by mass with respect to 100 parts by mass of the polyamic acid resin content in the polyamic acid composition. If the amount of polyaniline added is less than 5 parts by mass, the predetermined electrical conductivity cannot be expressed, and if it exceeds 40 parts by mass, the flexibility of the polyimide molded product using the polyamic acid composition is lost. This is because, for example, when a polyimide endless belt is molded, it does not have a function as a belt.

[Reducing agent]
As the reducing agent, hydrazine compounds such as phenylhydrazine, hydrazine, hydrazine hydrate, hydrazine sulfate and hydrazine hydrochloride, and reducing metal hydrides such as lithium aluminum hydride and lithium borohydride are preferably used.

[Polyamic acid]
The polyamic acid in the present invention is obtained by polycondensation of a tetracarboxylic dianhydride and a diamine compound. For example, the polyamic acid is obtained by polymerizing a substantially equimolar amount of the amphoteric component in an organic polar solvent. It is what In addition, the polyamic acid may be partially imidized.
Hereinafter, the tetracarboxylic dianhydride and the diamine compound will be described.

(Tetracarboxylic dianhydride)
There is no restriction | limiting in particular as tetracarboxylic dianhydride which can be 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 butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic 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, Aliphatic or alicyclic tetracarboxylic dianhydrides 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.

The tetracarboxylic dianhydride used in the present invention is preferably an aromatic tetracarboxylic dianhydride, and more preferably 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.

(Diamine compound)
Next, the diamine compound that can be used for the production of the polyamic acid is not particularly limited as long as it is a diamine compound having two amino groups in the molecular structure.
Specifically, 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-dia Nofluorene, 2,2-bis (4-aminophenyl) hexafluoropropane, 4,4'-methylene-bis (2-chloroaniline), 2,2 ', 5,5'-tetrachloro-4,4'- Diaminobiphenyl, 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-a Nophenyl) fluorene, 4,4 ′-(p-phenyleneisopropylidene) bisaniline, 4,4 ′-(m-phenyleneisopropylidene) bisaniline, 2,2′-bis [4- (4-amino-2-trifluoro) Aromatic diamines such as methylphenoxy) phenyl] hexafluoropropane, 4,4′-bis [4- (4-amino-2-trifluoromethyl) phenoxy] -octafluorobiphenyl; aromatic rings such as diaminotetraphenylthiophene An aromatic diamine having two bonded amino groups and a hetero atom other than the nitrogen atom of the amino group; 1,1-metaxylylenediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, octa Methylenediamine, nonamethylenediamine, 4,4-diaminoheptamethyle Diamine, 1,4-diaminocyclohexane, isophorone diamine, tetrahydrodicyclopentadienylenediamine, hexahydro-4,7-methanoindanylene methylene diamine, tricyclo [6,2,1,02.7] -undecylenedimethyl Examples include diamines, aliphatic diamines such as 4,4′-methylenebis (cyclohexylamine), 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, 4,4′-diaminodiphenylsulfone, Is preferred.
These diamine compounds can be used alone or in combination of two or more.

(Preferable combination of tetracarboxylic dianhydride and diamine compound)
As a polyamic acid in this invention, Preferably, what consists of aromatic tetracarboxylic dianhydride and aromatic diamine from a viewpoint of the intensity | strength of a molded object is preferable. Furthermore, what consists of biphenyltetracarboxylic dianhydride and oxydianiline is preferable.

(Synthetic solvent)
Examples of the organic polar solvent used in the 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 and catechol, ether solvents such as tetrahydrofuran, dioxane and dioxolane, alcohol solvents such as methanol, ethanol and butanol, cellosolve such as butyl cellosolve and hexamethyl. Phosphoramides, .gamma.-butyrolactone, etc. can be mentioned, but it is desirable to use them alone or as a mixture, further, xylene, aromatic hydrocarbons such as toluene can be used.

(Solid content concentration during polyamic acid polymerization)
Although the solid content concentration in the reaction solution at the time of polyamic acid polymerization is not particularly defined, it is preferably 5 to 50% by mass. Furthermore, 10-30 mass% is especially 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.

(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 0 ° C. or lower, the viscosity of the solution increases and the reaction system cannot be sufficiently stirred. Further, when the reaction temperature is higher than 80 ° C., there is a problem in terms of reaction control because a part of imidization reaction occurs in parallel with the polymerization of polyamic acid.

[Dopant]
In the present invention, as a dopant for doping polyaniline to make it conductive, it is preferable to use a protonic acid having an acid dissociation constant pKa of 5 or less, and a protonic acid having a pKa in the range of 1 to 4 is particularly preferably used. . As the form of the protonic acid, any form of acid such as monobasic acid, dibasic acid, tribasic acid, and polybasic acid can be used. For example, in the case of phosphoric acid which is a tribasic acid, the pKa of three protons contained in phosphoric acid is: pKa1 = 2.1, pKa2 = 7.2, pKa3 = 12.3, and two protons In the present invention, phosphoric acid is added in a controlled manner so that only one proton is used as an effective proton acid for the structural unit of polyaniline. In the present invention, for example, sulfonic acid compounds, carboxylic acid compounds, and phosphonic acid compounds are preferably used as the type of protonic acid.

  Examples of the sulfonic acid compound include aminonaphthol sulfonic acid, metanilic acid, sulfanilic acid, allyl sulfonic acid, lauryl sulfuric acid, xylene sulfonic acid, chlorobenzene sulfonic acid, methane sulfonic acid, ethane sulfonic acid, 1-propane sulfonic acid, 1- Butanesulfonic acid, 1-hexanesulfonic acid, 1-heptanesulfonic acid, 1-octanesulfonic acid, 1-nonanesulfonic acid, 1-decanesulfonic acid, 1-dodecanesulfonic acid, benzenesulfonic acid, styrenesulfonic acid, p- Toluenesulfonic acid, naphthalenesulfonic acid, ethylbenzenesulfonic acid, propylbenzenesulfonic acid, butylbenzenesulfonic acid, pentylbenzenesulfonic acid, hexylbenzenesulfonic acid, heptylbenzenesulfonic acid, octylbenzenesulfonic acid Nonylbenzenesulfonic acid, decylbenzenesulfonic acid, undecylbenzenesulfonic acid, dodecylbenzenesulfonic acid, pentadecylbenzenesulfonic acid, octadecylbenzenesulfonic acid, diethylbenzenesulfonic acid, dipropylbenzenesulfonic acid, dibutylbenzenesulfonic acid, methylnaphthalenesulfone Acid, ethyl naphthalene sulfonic acid, propyl naphthalene sulfonic acid, butyl naphthalene sulfonic acid, pentyl naphthalene sulfonic acid, hexyl naphthalene sulfonic acid, heptyl naphthalene sulfonic acid, octyl naphthalene sulfonic acid, nonyl naphthalene sulfonic acid, decyl naphthalene sulfonic acid, undecyl naphthalene Sulfonic acid, dodecylnaphthalenesulfonic acid, pentadecylnaphthalenesulfonic acid, octadecylnaphtha Sulfonic acid, dimethylnaphthalenesulfonic acid, diethylnaphthalenesulfonic acid, dipropylnaphthalenesulfonic acid, dibutylnaphthalenesulfonic acid, dipentylnaphthalenesulfonic acid, dihexylnaphthalenesulfonic acid, diheptylnaphthalenesulfonic acid, dioctylnaphthalenesulfonic acid, dinonylnaphthalenesulfonic acid , Trimethylnaphthalenesulfonic acid, triethylnaphthalenesulfonic acid, tripropylnaphthalenesulfonic acid, tributylnaphthalenesulfonic acid, camphorsulfonic acid, acrylamide-t-butylsulfonic acid, and the like. Among these, phenolsulfonic acid is preferably used.

  Specific examples of organic carboxylic acid compounds include benzoic acid, m-bromobenzoic acid, p-chlorobenzoic acid, m-chlorobenzoic acid, p-chlorobenzoic acid, o-nitrobenzoic acid, 2,4-dinitrobenzoic acid. Acid, 3,5-dinitrobenzoic acid, picric acid, o-chlorobenzoic acid, p-nitrobenzoic acid, m-nitrobenzoic acid, trimethylbenzoic acid, p-cyanobenzoic acid, m-cyanobenzoic acid, thymol blue, And salicylic acid, 5-aminosalicylic acid, o-methoxybenzoic acid, 1,6-dinitro-4-chlorophenol, 2,6-dinitrophenol, 2,4-dinitrophenol, p-oxybenzoic acid, and the like. .

Furthermore, as the polybasic acid used as a dopant in the present invention, for example, polyvinyl sulfonic acid, polyvinyl sulfuric acid, polystyrene sulfonic acid, sulfonated styrene-butadiene copolymer, polyallyl sulfonic acid, polymethallyl sulfonic acid, poly -2-acrylamido-2-methylpropanesulfonic acid, polyisoprenesulfonic acid, and the like.
Of these dopants, dodecylbenzenesulfonic acid, phenolsulfonic acid, and phenylphosphonic acid are particularly preferable.

  These dopants are added in the range of 0.1 to 0.75 mol, more preferably 0.2 to 0.40 mol, per 1 mol of the polyaniline repeating unit represented by the following formula (1). . If the amount is less than 0.1 mol, conductivity may not be exhibited and the intermediate transfer member may not be used. If the amount exceeds 0.75 mol, environmental fluctuation of the intermediate transfer member is increased, which is not preferable.

  Conventionally, 1.0 to 1.2 equivalents of a dopant are added to a structural unit of polyaniline in which different oxidation states are mixed. However, in the present invention, polyaniline is doped after reduction treatment. Thus, even when added in an amount of 0.1 to 0.75 mol with respect to the repeating unit represented by the above formula (1), it can be made conductive efficiently. The smaller the amount of dopant added in this range, the smaller the environmental fluctuation of the surface resistivity and the electric field fluctuation of the volume resistivity can be reduced.

[solvent]
The solvent of the polyamic acid composition is not particularly limited as long as it dissolves the polyamic acid. Specifically, for example, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, N, Formamide solvents such as N-diethylformamide, N, N-dimethylacetamide, acetamide solvents such as N, N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, Phenolic solvents such as phenol, o-, m-, or p-cresol, xylenol, halogenated phenol, catechol, ether solvents such as tetrahydrofuran, dioxane, dioxolane, alcohol solvents such as methanol, ethanol, butanol, butyl Examples include cellosolve such as rosolve, hexamethylphosphoramide, γ-butyrolactone, etc., and these are preferably used alone or as a mixture, but aromatic hydrocarbons such as xylene and toluene can also be used. It is.

This solvent may be used in preparing the polyamic acid composition. Moreover, this solvent may be used from the above-mentioned polyamic acid polymerization or may be replaced with a predetermined solvent after the polyamic acid polymerization. For solvent replacement, a method in which a predetermined amount of solvent is added to the polyamic acid polymerization solution for dilution, a method in which the polyimide polymer is reprecipitated and then re-dissolved in the predetermined solvent, and the solvent is gradually distilled off. Any of the methods for adjusting the composition by adding a predetermined solvent may be used.
The concentration of the polyamic acid in the polyamic acid composition is preferably adjusted in the range of 10 to 50 parts by mass.

  This solvent may also be used when preparing a polyaniline solution. In that case, the content of polyaniline in the polyaniline liquid is preferably adjusted in the range of 0.1 to 30% by mass.

[Additive]
Moreover, carbon black etc. are mentioned as an arbitrary component (additive) which can be added to a polyamic acid composition.

(Carbon black)
Carbon black as an optional component is used, for example, for the purpose of adjusting the resistance value of a molded product obtained using a polyamic acid composition.
For example, when using a polyamic acid composition to obtain a polyimide endless belt applied to an electrophotographic image forming apparatus, the amount of carbon black added is 100 parts by mass of the polyamic acid in the polyamic acid composition. It is preferably 0 to 20 parts by mass, and more preferably 5 to 10 parts by mass. When the added amount of carbon black exceeds 20 parts by mass, it becomes difficult to obtain a desired resistance value. Furthermore, by containing 5 to 10 parts by mass of carbon black, the effect can be maximized, and the in-plane unevenness of the surface resistivity and the electric field dependency can be remarkably improved.

[Preparation of polyamic acid composition]
The polyamic acid composition is prepared by the following procedure.
(A) A polyaniline solution obtained by dissolving polyaniline and a polyamic acid solution obtained by dissolving polyamic acid are prepared. A dopant is added to the prepared polyaniline solution to make the polyaniline conductive, and then a polyamic acid solution is gradually added to this mixed solution, followed by stirring and mixing to obtain a polyamic acid composition.
(B) A polyaniline solution obtained by dissolving polyaniline and a polyamic acid solution obtained by dissolving polyamic acid are prepared. A polyamic acid composition is obtained by gradually adding a polyaniline liquid to a mixed liquid obtained by adding a dopant to the prepared polyamic acid solution, and stirring and mixing.
In addition, preparation of a polyamic acid composition may include the process of adding arbitrary components, such as the above-mentioned carbon black, and stirring and disperse | distributing as needed.

In the polyamic acid composition thus obtained, the viscosity ratio V2 / V0 between the viscosity V0 immediately after adjustment and the viscosity V2 after 2 days in a room temperature environment is 0.8 or more and 1.2 or less. Preferably, it is 0.9 or more and 1.15 or less. When V2 / V0 is less than 0.8, sagging or the like may occur during coating due to a decrease in viscosity, resulting in a defective part of the molded product. On the other hand, when it exceeds 1.2, a polyaniline gel is generated, The viscosity of the polyamic acid composition is a viscosity at a liquid temperature of 25 ° C. and measured using a constant velocity viscometer PK100 manufactured by HAKKE Co., Ltd. It is the value.

  The polyamic acid composition has been described above, but the present invention is not limited only to these embodiments, and various improvements, changes, and modifications can be made based on the knowledge of those skilled in the art without departing from the spirit of the present invention. It can implement in the aspect which added.

As an intermediate transfer member of the present invention, a polyimide endless belt is a step of applying the above polyamic acid composition onto a cylindrical substrate, and heating to heat the polyamic acid composition applied onto the cylindrical substrate. It is preferable to manufacture by going through a treatment step.
The polyimide endless belt thus obtained is mainly composed of a polyimide molded body.

An example of a method for producing a polyimide endless belt will be specifically described.
First, the above-mentioned polyamic acid composition is applied to the inner surface or outer surface of a mold that is a cylindrical substrate. In addition, instead of the mold, cylindrical molds made of various known materials such as resin, glass, and ceramic can be used. It is also possible to appropriately select to provide a glass coat or ceramic coat on the surface of the cylindrical mold or cylindrical mold, and to use a silicone-based or fluorine-based release agent.
Also, by moving the film thickness control mold with the clearance adjusted to the cylindrical mold through the cylindrical mold in parallel, the excess solution is eliminated and the thickness of the solution on the cylindrical mold is made uniform. You may apply the method to do. If the uniform thickness control of the solution is performed at the stage of applying the solution onto the cylindrical mold, it is not necessary to use a film thickness control mold.

Next, the cylindrical mold to which the polyamic acid composition is applied is placed in a heating environment, and drying is performed to volatilize 30% by mass or more, preferably 50% by mass or more of the contained solvent. At this time, the drying temperature is preferably in the range of 50 to 200 ° C.
Furthermore, this cylindrical mold is heated at a temperature of 150 ° C. to 300 ° C. to sufficiently advance the imide conversion reaction. The temperature of the imide conversion reaction varies depending on the types of tetracarboxylic dianhydride and diamine used as raw materials, but insufficient imidization results in inferior mechanical and electrical properties. Must be set to a temperature that completes.
Thereafter, the polyimide is removed from the cylindrical mold, and a belt-like polyimide (polyimide endless belt) can be obtained.

As described above, the polyimide endless belt obtained in this way has both small fluctuations in electrical resistance values due to changes in temperature and humidity, and fluctuations in electrical resistance values due to changes in applied voltage, and is applicable to image forming apparatuses. In this case, it contributes to the improvement of image quality.
The polyimide endless belt has been described above, but the present invention is not limited only to these embodiments, and various improvements, changes, and modifications can be made based on the knowledge of those skilled in the art without departing from the spirit of the invention. It can implement in the aspect which added.

<Image forming apparatus>
The image forming apparatus of the present invention may have any configuration as long as it includes the above-described intermediate transfer member of the present invention. Specifically, for example, a monocolor electrophotographic apparatus having only a single color (usually black) in the apparatus, a color electrophotographic apparatus that repeats primary transfer of a toner image carried on a photoreceptor to an intermediate transfer belt sequentially, Any of the tandem color electrophotographic apparatuses in which a plurality of latent image carriers having developing units for respective colors are arranged in series on an intermediate transfer belt may be used. Further, it may be an intermediate transfer system using an intermediate transfer belt, and / or an image forming apparatus having a mechanism for directly or indirectly heating the belt.
In these image forming apparatuses, the above-described intermediate transfer member of the present invention can be used not only for intermediate transfer and fixing, but also as an intermediate transfer belt, a conveyance belt, and a fixing belt. The intermediate transfer and fixing belt is a belt that performs an intermediate transfer process and a fixing process on the same belt.
As described above, the intermediate transfer member of the present invention has uniform resistance and excellent mechanical properties and surface properties. By applying this to an image forming apparatus, a high-quality transfer image can be stabilized. Can be obtained.

  Hereinafter, a configuration example of an image forming apparatus of the present invention having a polyimide endless belt as an intermediate transfer member of the present invention will be described in detail with reference to the drawings. Here, FIG. 1 shows a schematic configuration diagram of a color electrophotographic copying machine 100 as an example of the image forming apparatus of the present invention using the above-described polyimide endless belt of the present invention as an intermediate transfer belt.

  In FIG. 1, reference numerals 101BK, 101Y, 101M, and 101C denote photosensitive drums (image carriers), and the surface thereof is converted into image information by a known electrophotographic process (not shown) as it rotates in the direction of arrow A. A corresponding electrostatic latent image is formed.

  Further, around the photosensitive drums 101BK, 101Y, 101M, and 101C, developing units 105 to 108 corresponding to black (BK), yellow (Y), magenta (M), and cyan (C), respectively, and Corona discharge devices 109 to 112 are arranged, and electrostatic latent images formed on the photosensitive drums 101BK, 101Y, 101M, and 101C by charging of the corona discharge devices 109 to 112 are respectively developed by the developing devices 105 to 108. A toner image is formed by development. 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-like intermediate transfer belt disposed so as to be in contact with the surfaces of the photosensitive drums 101BK, 101Y, 101M, and 101C. The belt-shaped intermediate transfer belt is stretched around the plurality of belt support rolls 117 to 119 and the heating transfer roll 120. And rotate in the direction of arrow B.

  Since the polyimide endless belt of the present invention described above is used for the intermediate transfer member 102, defects due to non-uniform film thickness, non-uniform conductivity, etc. of the conventional endless belt can be reduced. As a result, the quality of the transferred image obtained by this image forming apparatus is excellent.

  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 and transferred onto the surface of the intermediate transfer body 102 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 preferably has a surface coated with a fluororesin, and may include a heating source in the same manner as the heating 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 in contact with and away from the intermediate transfer body 102, and these members are separated from the intermediate transfer body 102 until the secondary transfer is performed.

  Since the above-described image forming apparatus includes the above-described intermediate transfer body of the present invention, both the fluctuation of the electric resistance value due to the environmental change of temperature and humidity and the fluctuation of the electric resistance value due to the change of the applied voltage are both small. Transfer images with low image quality can be obtained.

  A plurality of examples corresponding to the present invention and comparative examples for these examples will be described below. These examples are all illustrative, and the scope of the present invention is not limited by this description.

[Example B1]
<Preparation of polyamic acid solution (a)>
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 (NMP) 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 dropwise addition of the diamine solution, stirring and polymerization were performed 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 separated by filtration and dried, and then redissolved in N-methyl-2-pyrrolidone to obtain a 20% by mass polyamic acid solution (a).

<Synthesis of polyaniline>
In a 10 L-separable flask, 6000 g of ion-exchanged water, 400 ml of 35% hydrochloric acid, and 400 g (4.295 mol) of aniline were charged and stirred to dissolve aniline. While cooling with ice water in a beaker container, 434 g (4.295 mol) of 98% concentrated sulfuric acid was added to and mixed with 1493 g of ion-exchanged water to prepare an aqueous sulfuric acid solution. This sulfuric acid aqueous solution was gradually added to the aniline solution while cooling with ice.

Next, an aqueous oxidizing agent solution in which 980 g (4.295 mol) of ammonium peroxodisulfate was dissolved in 2300 g of ion exchange was gradually added dropwise to the aniline solution while cooling with ice. After the dropping, the colorless and transparent solution changed from greenish blue to blackish green as the polymerization proceeded, and then a blackish green powder precipitated. And stirring was further continued for 1 hour after dripping ammonium peroxodisulfate aqueous solution.
The obtained powder was filtered off, washed with water, washed with acetone, and vacuum dried at room temperature to obtain 430 g of conductive polyaniline doped with sulfuric acid as a black-green powder.
Subsequently, 350 g of doped conductive polyaniline powder was added to 4 liters of 2N aqueous ammonia, and the mixture was stirred for 5 hours at a rotation speed of 5000 rpm with a homomixer. The mixture changed from black-green to blue-violet. The powder was filtered off, washed with ion-exchanged water / acetone, and vacuum-dried at room temperature for 10 hours to obtain 280 g of black-brown dedope polyaniline powder.

<Preparation of polyaniline solution>
After reducing 18.22 g (0.10 mol) of the polyaniline powder (undoped state) obtained by the above method using hydrazine, it is dissolved in 180 g of N-methyl-2-pyrrolidone (NMP) to obtain polyaniline. A liquid was obtained.

<Preparation of polyamic acid composition>
To the polyaniline solution prepared by the above method, 17.42 g (0.10 mol) of phenolsulfonic acid was added as a dopant. This was gradually added to 500 g of the 20% by mass polyamic acid solution (a) obtained by the above method while stirring. Then, the aggregate was removed with a 50 μm pore metal mesh to obtain a polyamic acid composition.

The composition of the polyamic acid composition thus obtained is as follows.
-Composition of polyamic acid composition-
・ Polyamic acid; 100g
・ Polyaniline; 18.22g
(0.05 mol; 18.22 parts by mass with respect to 100 parts by mass of polyamic acid)
・ Dopant; 17.42g
(0.1 mole; 1 mole equivalent per mole of polyaniline constituent unit)
・ Solvent: 580 g

[Evaluation]
In the obtained polyamic acid composition, the viscosity ratio V2 / V0 between the viscosity V0 immediately after adjustment and the viscosity V2 after 2 days in a room temperature environment was evaluated as follows.
(Viscosity ratio)
After adjusting the obtained polyamic acid composition to a liquid temperature of 25 ° C., the average value of the viscosity measured three times using a constant velocity viscometer PK100 manufactured by HAKKE was used as the viscosity V0. Moreover, after holding the obtained polyamic acid composition in a room temperature environment for 2 days, the liquid temperature was adjusted to 25 ° C., and the viscosity measured three times using a constant velocity viscometer PK100 manufactured by HAKKE Co., Ltd. The average value was designated as viscosity V2. The viscosity ratio V2 / V0 was determined from the obtained value. The results are shown in Table 1.

<Manufacture of polyimide endless belt>
The obtained polyamic acid composition 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 is preliminarily coated with a fluorine-based release agent to improve the peelability after belt molding. Thereafter, a drying process was performed for 30 minutes at a temperature of 120 ° C. while rotating the cylindrical mold. After the drying treatment, the cylindrical mold was placed in an oven and baked at 280 ° C. for about 30 minutes to advance the imide conversion reaction. Subsequently, the cylindrical 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 had a circumferential length of 283 mm and a width of 400 mm.

[Examples B2 to B4, Comparative Examples B1 to B4]
A polyimide endless belt was produced in the same manner as in Example 1 except that the formulation of the polyamic acid composition was changed as shown in Table 1 below.

In Table 1, “PI” represents polyimide, “PAI” represents polyamideimide, and “CB” represents carbon black.
The acid dissociation constant pKa of the dopant is shown below.
phOH-SO ₃ H: 1.1
phOH: 9.99
The dopant amount is the number of moles relative to 1 mole of the repeating unit represented by the formula (1).

[Evaluation]
The thickness, electrical properties (surface resistivity, environmental variation of surface resistivity, electric field variation of volume resistivity) of the resulting polyimide endless belt, and the quality of the transferred image when mounted on an electrophotographic apparatus were evaluated as follows. did.

(Thickness)
Ten pieces of 20 mm × 200 mm test pieces were randomly cut out from the obtained polyimide endless belt, and measured using a film thickness meter (constant pressure thickness measuring instrument PG-02 type (TECLOCK)). Was the thickness of the polyimide endless belt. Further, the maximum value was the maximum thickness of the polyimide endless belt, the minimum value was the minimum thickness, and the difference between the maximum thickness and the minimum thickness of the polyimide endless belt was also determined, and the difference in thickness of the polyimide endless belt was taken. The measurement results are shown in Table 1.

"Evaluation of electrical characteristics"
(Measurement of surface resistivity)
The surface resistivity is a numerical value obtained by dividing the potential gradient in the direction parallel to the current flowing along the surface of the belt by the current per unit width of the surface. This numerical value is equal to the surface resistance between two electrodes each having an opposite side of a square of 1 cm on each side as an electrode. The unit of surface resistivity is formally (Ω), but is generally written as (Ω / □) to distinguish it from simple resistance. Therefore, in this application, (Ω / □) and (Ω / cm ² ) are equivalent units.
The surface resistivity of the obtained polyimide endless belt was measured using an R8340A digital ultra-high resistance / microammeter (manufactured by Advantest Co., Ltd.) and a double ring electrode structure UR probe MCP- whose connection was modified for R8340A. Using HTP12 and register table UFL MCP-ST03 (both manufactured by Dia Instruments Co., Ltd.), the test was performed in accordance with JIS K6911 (1995).
In addition, the belt piece manufactured in the Example and the comparative example was used for the test piece in the case of a measurement.

  On the register table UFL MCP-ST03 (using a fluororesin surface), the test surface was placed with the measurement surface facing up, and the double electrode of the UR probe MCP-HTP12 was applied so as to contact the measurement surface. A weight of 2.00 kg ± 0.10 kg (19.6 N ± 1.0 N) was attached to the top of the UR probe MCP-HTP 12 so that a uniform load was applied to the test piece.

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 test piece 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), According to the “Rate meter series” catalog, since RCF (S) = 10.00, the following equation (1) is obtained.
That is, formula (1): ρs [Ω / □] = R × RCF (S) = R × 10.00.

(Measurement of volume resistivity)
The volume resistivity is a numerical value obtained by dividing the potential gradient in the direction parallel to the current flowing through the belt by the current density. This value is equal to the volume resistance between two electrodes having two opposing surfaces of a cube of 1 cm on each side as electrodes.
For measuring the volume resistivity of the intermediate transfer belt, an R8340A digital ultra-high resistance / microammeter (manufactured by Advantest Co., Ltd.), a UR probe MCP-HTP12 having a double ring electrode structure in which the connection portion is modified for R8340A, and The registration table UFL MCP-ST03 (both manufactured by Dia Instruments Co., Ltd.) was used in accordance with JIS K6911 (1995).
In addition, the belt piece manufactured by the Example and the comparative example was used for the test piece in the case of a measurement.

  A test piece was placed on the register UFL MCP-ST03 (the metal surface was used as the lower electrode), and the double electrode part of the UR probe MCP-HTP12 was applied as the upper electrode. A weight of 2.00 kg ± 0.10 kg (19.6 N ± 1.0 N) was attached to the top of the UR probe MCP-HTP 12 so that a uniform load was applied to the test piece.

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, the volume resistivity of the test piece 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 coefficient of the UR probe MCP-HTP12 is When RCF (V) is used, according to the Mitsubishi Chemical "Resistivity Meter Series" catalog, RCF (V) = 2.011, so the following equation (2) is obtained.
That is, Formula (2): ρv [Ω · cm] = R × RCF (V) × (10000 / t) = R × 2.011 × (10000 / t).

  According to the above measurement method, the common logarithm of the surface resistivity (logΩ / □) when a voltage of 100 V is applied under the condition of 22 ° C. and 55% RH, and the voltages of 10 V and 100 V under the condition of 22 ° C. and 55% RH Difference in common logarithm of volume resistivity when applied (log Ωcm) and difference in common logarithm of surface resistivity when voltage of 100V is applied under conditions of 28 ° C 85% RH and 10 ° C15% RH (LogΩ / □) was determined. The results are shown in Table 1.

"Evaluation of the quality of transferred images"
The obtained polyimide endless belt was incorporated in an electrophotographic apparatus (DocuCenterColor400CP) manufactured by Fuji Xerox Co., Ltd. as an intermediate transfer belt, and the image quality of the initial transferred image was evaluated. As an evaluation item for the image quality of the transferred image, the presence or absence of print density unevenness was evaluated.
The presence or absence of print density unevenness is measured with an X-Rite densitometer (manufactured by X-Rite). When the variation is 5% or less, ○ is 10% or less, △ is 15% or less. did.

As is clear from the above, the polyimide endless belt, which is the intermediate transfer member of the present invention, uses polyimide or polyamideimide as the resin, uses polyaniline as the conductive agent, and lists the dopant and the amount of the polyaniline as shown in Table 1. In each of Examples B1 to B4, the environmental fluctuation of the surface resistivity and the electric field dependence of the volume resistivity both showed good results. On the other hand, Comparative Examples B1 to B4 in which the conductive agent, the dopant type, or the amount of the dopant are different from those in the examples are not satisfactory values in the surface resistivity and the volume resistivity, and in the image quality evaluation. It became bad.
It can also be seen that when such a polyimide endless belt of the present invention is mounted on an image forming apparatus, the quality of the transferred image is excellent.

1 is a schematic explanatory diagram illustrating a configuration of an image forming apparatus of the present invention.

Explanation of symbols

100 color electrophotographic copying machine (image forming device)
101BK to Y photoconductor drum 102 intermediate transfer belt 103 recording medium 105 to 108 developing device 109 to 112 corona discharge device 113 tray 114 peeling claw 115 transport belt 116 cleaning device 117 to 119 belt support roll 120 heating transfer roll 121 to 124 transfer baffle 125 Pressure roll 126 Feed roller

Claims (5)

An intermediate transfer member comprising a conductive agent and a resin and satisfying all of the following conditions (1) to (3):
(1) The common logarithm of the surface resistivity when a voltage of 100 V is applied in an environment of 22 ° C. and 55% RH is 9 to 13 (logΩ / □).
(2) In an environment of 22 ° C. and 55% RH, the difference in common logarithm of volume resistivity when a voltage of 10 V and 100 V is applied is 0.5 (log Ω · cm) or less.
(3) The difference in the common logarithm of the surface resistivity when a voltage of 100 V is applied in an environment of 28 ° C. and 85% RH and 10 ° C. and 15% RH is 1.0 (logΩ / □) or less It is.   The intermediate transfer member according to claim 1, wherein the resin is polyimide.   The intermediate transfer member according to claim 1, wherein the conductive agent is made of a conductive polymer.   The intermediate transfer member according to claim 3, wherein the conductive polymer is polyaniline. An image carrier;
Charging means for charging the surface of the image carrier;
Latent image forming means for forming a latent image on the surface of the charged image carrier;
Developing means for developing the latent image with toner to form a toner image;
Transfer means for transferring the toner image onto a recording medium;
Fixing means for fixing the toner image on a recording medium;
In an image forming apparatus having
An image forming apparatus comprising: an intermediate transfer member that includes a conductive agent and a resin and satisfies all of the following conditions (1) to (3):
(1) The common logarithm of the surface resistivity when a voltage of 100 V is applied in an environment of 22 ° C. and 55% RH is 9 to 13 (logΩ / □).
(2) In an environment of 22 ° C. and 55% RH, the difference in common logarithm of volume resistivity when a voltage of 10 V and 100 V is applied is 0.5 (log Ω · cm) or less.
(3) The difference in the common logarithm of the surface resistivity when a voltage of 100 V is applied in an environment of 28 ° C. and 85% RH and 10 ° C. and 15% RH is 1.0 (logΩ / □) or less It is.

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