JP2016006467A - Method of manufacturing intermediate transfer belt, intermediate transfer belt, and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an intermediate transfer belt that has small voltage dependency of volume resistivity and high folding resistance.SOLUTION: There is provided a method of manufacturing an intermediate transfer belt that includes a process of forming an inner peripheral surface layer by applying and heating a coating liquid (inner) for inner peripheral surface layer formation to and on an outer surface of a cylindrical metal mold and a process of forming an outer peripheral surface layer by applying and heating a coating liquid (outer) for outer peripheral surface layer formation to and on an inner peripheral surface of the cylindrical metal mold, wherein carbon black in a carbon dispersion liquid (inner) for coating liquid (outer) preparation and carbon black in a carbon dispersion liquid (outer) for coating liquid (outer) preparation are the same material, a volume average particle size (Mv outer) of the carbon black in the carbon dispersion liquid (outer) is 0.25 μm or less while a volume average particle size (Mv inner) of the carbon black in the carbon dispersion liquid (inner) is larger than the volume average particle size (Mv outer) of the carbon black in the carbon dispersion liquid (outer), and an occupation mass ratio of the carbon black to the total amount of a solid in the coating liquid (inner) is smaller than that of the carbon black to the total amount of a solid in the coating liquid (outer).

Description

  The present invention relates to an intermediate transfer belt manufacturing method used in an image forming apparatus, an intermediate transfer belt, and an image forming apparatus using the intermediate transfer belt.

In electrophotographic apparatuses, seamless belt members are used for various purposes in the apparatus.
For example, a fixing belt, a transfer belt, a paper conveyance belt, and the like can be given.
Among them, in a full-color electrophotographic apparatus, a four-color toner image formed on a photoreceptor is temporarily transferred to an intermediate transfer belt to form a full-color image on the intermediate transfer belt, and then a transfer medium such as paper There is an intermediate transfer belt in a batch transfer system.
The demand for intermediate transfer belts has been increasing rapidly as full-color copying machines have been developed.
As the intermediate transfer belt, materials such as thermoplastic resin, thermosetting resin, rubber, and elastomer are used.

However, in the intermediate transfer system, in order to obtain high speed, a system called a tandem system in which color developing devices for respective colors facing the intermediate transfer belt are arranged in series is the mainstream.
The intermediate transfer belt used in the tandem system is required to have high strength that can withstand repeated use without causing color misregistration due to deformation during running, and also requires flame retardancy.
For this reason, a polyimide resin or a polyamideimide resin is preferably used as a material for the intermediate transfer belt. In particular, a polyimide resin is particularly preferably used in terms of creep deformability and durability.

The intermediate transfer belt used in the electrophotographic apparatus needs to be controlled in resistance value in order to transfer the toner image to the toner image by the action of an electric field. Further, the intermediate transfer belt needs to transfer the toner image to a transfer material such as paper while maintaining a high quality image without disturbing the toner image.
Various proposals have been made that define appropriate electrical characteristics as an intermediate transfer belt using a polyimide resin.
Patent Documents 1, 2, and 3 propose to reduce the electric field dependence of surface resistance, and Patent Documents 4, 5, and 6 propose to specify the voltage dependence of the surface resistance value and the volume resistance value. Has been made.
Especially the thing of patent document 6 has suppressed the generation | occurrence | production of the white spot by local leak generation | occurrence | production by prescribing | regulating the voltage dependence of volume resistivity.

However, in order to produce an intermediate transfer belt having a small voltage dependency of resistance with a polyimide resin in which carbon is dispersed, it is necessary to finely disperse carbon particles in the polyimide resin, and a large amount of carbon is not added. And the resistance cannot be adjusted.
On the other hand, when the amount of carbon added in the belt is large, the molded film is brittle and easily broken from the viewpoint of mechanical strength, and there is a problem that the folding resistance of the belt is lowered. In a polyimide resin belt in which carbon is dispersed, there is a problem of achieving both “reduction in voltage dependency of resistance” and “belt folding resistance”.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing an intermediate transfer belt made of polyimide resin in which carbon particles are dispersed and having low voltage dependency of resistance and high folding resistance.

As a result of studies by the inventor in order to solve the above problems, the volume average particle diameter of carbon black in a coating liquid for coating and molding the outer peripheral surface layer (hereinafter referred to as “coating liquid (outside)”) is expressed as “ When the volume average particle size of carbon black in the coating liquid for coating and molding the belt inner peripheral surface layer (hereinafter referred to as “coating liquid (inside)”) is “inside Mv”, ”Is 0.25 μm or less, within Mv <Mv outside, and the mass ratio of carbon black to the total solid content in the coating liquid (inside) accounts for the total solid content in the coating liquid (outside). The present invention has been completed by finding that the above problem can be solved by making the ratio smaller than the mass ratio.
That is, the present invention is as described in the following (1).

(1) An electrophotographic intermediate transfer belt having a seamless two-layer structure is formed by coating and molding a coating solution prepared by mixing a polyimide resin precursor in a carbon dispersion obtained by dispersing carbon black in at least a solvent. A method of manufacturing comprising:
Coating a coating liquid (inner) for forming the belt inner peripheral surface layer on the outer surface of the cylindrical mold, and heating to form the belt inner peripheral surface layer;
Applying a coating liquid (outside) for forming a belt outer peripheral surface layer on the belt inner peripheral surface layer, and heating to form a belt outer peripheral layer;
Having at least
The carbon black in the carbon dispersion liquid (inner) for preparing the coating liquid (inner) and the carbon black in the carbon dispersion liquid (outer) for preparing the coating liquid (outer) are the same material. And
The volume average particle size (outside of Mv) of carbon black in the carbon dispersion (outside) for preparing the coating liquid (outside) is 0.25 μm or less,
The volume average particle size (inside Mv) of carbon black in the carbon dispersion (inside) for preparing the coating liquid (inside) is the carbon dispersion (outside) for preparing the coating liquid (outside). ) Larger than the volume average particle size (outside Mv) of carbon black in
Intermediate transfer characterized in that the mass ratio of carbon black to the total solid content in the coating liquid (inside) is smaller than the mass ratio of carbon black to the total solid content in the coating liquid (outside). A method for manufacturing a belt.

  According to the manufacturing method of the present invention, it is possible to obtain an intermediate transfer belt in which the volume resistivity of the intermediate transfer belt is small in voltage dependency and the belt has high folding resistance.

1 is a diagram showing an outline of an image forming apparatus using an intermediate transfer belt of the present invention.

The belt manufactured by the intermediate transfer belt manufacturing method of the present invention is a volume resistance formed by laminating two layers of an outer peripheral surface layer (outer peripheral surface layer) and an inner peripheral surface layer (inner peripheral surface layer). It is a belt with a small voltage dependency of the rate.
The present invention also includes an intermediate transfer belt manufactured by the manufacturing method and an image forming apparatus equipped with the intermediate transfer belt as embodiments.

<Outline of Manufacturing Method of Intermediate Transfer Belt of the Present Invention>
In a two-layer belt comprising an inner peripheral surface layer and an outer peripheral surface layer manufactured by the intermediate transfer belt manufacturing method of the present invention, the outer peripheral surface layer forms the base of the belt.
The outer peripheral surface layer is prepared by dispersing carbon black having a volume average particle size of 0.25 μm or less in order to reduce the voltage dependency of the volume resistivity. If the outer peripheral surface layer is made of a carbon dispersion having a small particle size of carbon black, the resistance is unlikely to decrease with respect to the amount of carbon added, so that the amount of carbon added increases and the film becomes brittle.

In the intermediate transfer belt of the present invention, the carbon black contained in the carbon dispersion liquid for preparing a coating liquid used for coating molding of the belt outer peripheral surface layer and the inner peripheral surface layer is the same material.
In the present invention, the carbon black in the carbon dispersion (outside) and the carbon black in the carbon dispersion (inside) are “the same material”, for example, as carbon black in the carbon dispersion (inside) If “channel black” is used, it means that “channel black” is used as the carbon black in the carbon dispersion (outside).
Further, it is preferable to use the same product type as carbon black, that is, the same model number (same manufacturer, same grade) as carbon black.

  Therefore, in the present invention, in order to solve the fragility of the outer peripheral surface layer, the fragility is eliminated by providing an inner peripheral surface layer in which the amount of carbon added is smaller than that of the outer peripheral surface layer. Here, when the inner peripheral surface layer is made of the same carbon dispersion as that of the outer peripheral surface layer, the inner peripheral surface layer is increased in resistance, and the desired resistance cannot be controlled. In the present invention, the carbon dispersion used for the inner peripheral surface layer is a dispersion having a larger particle size than the outer peripheral surface layer, so that the outer peripheral surface can be added even if the amount of carbon added is smaller than that of the outer peripheral surface layer. It can be adjusted to the same resistance as the layer.

<About each process of intermediate transfer belt production>
The intermediate transfer belt manufacturing method of the present invention includes at least the following steps.
A step of uniformly dispersing carbon black in a solvent to prepare a carbon dispersion. A step of mixing and adjusting the dispersion and a polyimide resin precursor for producing a polyimide resin so that a predetermined amount of carbon black is added. Step of coating the coating liquid on the outer surface of the cylindrical mold and heating to form a belt inner peripheral surface layer. Coating the coating liquid on the belt inner peripheral surface layer, heating the belt outer peripheral surface Step of forming face layer Each of the above steps will be described below.
Hereinafter, the polyimide resin precursor may be referred to as a polyimide resin.

<Process for dispersing carbon black>
Carbon black is added to the solvent, and pulverized and finely dispersed in a disperser such as a ball mill, a bead mill, a pent shaker, or a high-pressure jet mill.
At this time, a preferable combination can be selected depending on the combination of the solvent and the carbon black material, but the type of the solvent is often limited by the solubility of the binder resin.
For this reason, many methods for dispersing carbon black are used.
As the method, there is a method of using carbon black subjected to surface treatment with a reactive compound such as carbon black subjected to oxidation treatment or a coupling agent as carbon black.

Examples of carbon black include channel black, furnace black, channel black, acetylene black, graphite, and carbon nanotube.
Also in the oxidation treatment, manufacturers producing these carbon blacks have different varieties of oxidation treatment grades for various uses.

As the surface treatment, there is a method of controlling basicity or acidity by adding a compound such as a coupling agent having a functional group that reacts with a functional group on the surface of carbon black.
However, this method has a drawback that it is difficult to produce a dispersion of carbon black having a fine particle size, and it is difficult to increase the concentration of carbon black in the dispersion, which is expensive.

In general, a method of adding a dispersant to a solution is often used.
Examples of the dispersant include ionic and nonionic surfactants, organic compounds and polymer compounds having an acid or base functional group at the terminal, and appropriate dispersants that are appropriately selected from commercially available dispersants. Can be selected.
As the solvent used for the carbon dispersion liquid, an organic polar solvent used for the polymerization reaction of polyamic acid can be preferably used.

  In this dispersion step, the volume average particle diameter (outside Mv) of carbon black in the carbon dispersion (outside) used in the coating liquid (outside) for forming the outer peripheral surface layer is set to 0.25 μm or less. In addition, the volume average particle diameter (in Mv) of carbon black in the carbon dispersion liquid (inner) used for the inner peripheral surface layer forming coating liquid (inner) is the outer peripheral surface layer forming coating liquid (inner). Larger than the volume average particle size (outside Mv) of carbon black in the carbon dispersion used in the above.

The outer peripheral surface layer is a layer that forms the base of the belt. When the volume average particle size (outside Mv) of carbon black in the carbon dispersion (outside) is larger than 0.25 μm, the voltage dependency of resistance increases. On the other hand, the inner peripheral surface layer is a layer for eliminating the brittleness of the belt, and the inner peripheral surface layer forming carbon containing carbon black having a larger particle size than the carbon dispersion liquid (outer) for forming the outer peripheral surface layer. Prepared by a coating liquid (inner) using a dispersion liquid (inner).
By using such a dispersion, it is possible to control the resistance to be the same as that of the outer peripheral layer even if the amount of carbon added to the inner peripheral layer is reduced.

More preferably, the volume average particle size of the carbon black in the carbon dispersion (outside) used in the coating liquid (outside) for forming the outer peripheral surface layer is Mv outside, and the coating liquid for forming the inner peripheral surface layer ( When the volume average particle diameter of carbon black in the carbon dispersion liquid (inner) used in (inner) is Mv, it is preferable that the inside / outside Mv is 1.200 to 1.700.
When the inside / outside Mv is 1.200 or more, sufficient folding resistance of the belt can be obtained, and when inside / outside Mv is 1.700 or less, the voltage dependency of the resistance is reduced. Can do.
In order to obtain such a particle size, it can be obtained by appropriately controlling the conditions of an appropriate disperser, the kind and amount of a dispersant, the amount of a binder resin, and the like.
The concentration of carbon black contained in the dispersion is preferably 5 to 15% by mass.

  In addition, two types of carbon dispersions used in the present invention are prepared for the belt outer peripheral surface layer and the belt inner peripheral surface layer. These dispersions are produced with the same carbon blank, but the volume average particle size of carbon black in the carbon dispersion is controlled by changing the dispersion conditions. For example, to reduce the particle size of the carbon dispersion liquid, it is possible to control the dispersion conditions such as increasing the dispersion time and reducing the media diameter to be used.

Further, a polyimide resin precursor having the same composition as that of the polyimide resin precursor of the coating liquid and having a molecular weight equal to or less than 10 parts by mass of carbon black is previously contained in the carbon dispersion. Also good.
Carbon black when the polyimide resin precursor is mixed with the carbon dispersion by preliminarily containing in the carbon dispersion a polyimide resin precursor having the same composition as that of the polyimide resin precursor in the coating liquid. Re-aggregation can be prevented, and fluctuations in the particle size during the preparation of the coating liquid in the subsequent step can be suppressed, whereby a uniform belt with uniform electric resistance can be obtained.

The molecular weight preferable as the polyimide resin precursor is 10,000 to 50,000 in number average molecular weight. Moreover, as a molecular weight of the polyimide resin precursor previously contained in a carbon dispersion liquid, 30,000 or less is preferable.
The molecular weight of the polyimide resin precursor and the polyimide resin precursor previously contained in the carbon dispersion may be the same.
In addition, the same composition as the polyimide resin precursor of the coating liquid means a composition made of the same monomer as that constituting the polyimide resin precursor of the coating liquid.

<Coating liquid preparation process>
Next, a process of preparing a coating liquid by mixing a polyimide resin precursor with the dispersion liquid will be described.
As a method of mixing the dispersion and the polyimide resin precursor, mixing is performed by stirring with a commonly used stirrer.
In the present invention, polyamic acid is particularly preferably used as the polyimide resin precursor.
In this case, since the viscosity of the solution is a high viscosity solution of about 1 to 100 Pa · s, a stirrer suitable for high viscosity stirring such as a self-revolving centrifugal stirrer or a triaxial planetary stirrer should be used. Is desirable.
Further, since many bubbles are generated in the solution at the time of stirring, it is preferable to remove bubbles after the stirring to remove bubbles in the liquid.

The mixing amount for mixing the carbon dispersion is adjusted so as to obtain a desired resistance value.
This required amount varies depending on the type of carbon black and the dispersed particle size, but cannot be generally stated. Preferably, the carbon black ratio is added at about 10 to 30% by mass with respect to the total solid content of the coating liquid. It is preferable to do.
If it is 10% by mass or less, the resistance tends to vary, and if it is 30% by mass or more, the film becomes unfavorable.

The mass ratio of carbon black to the total solid content of the coating liquid is the ratio of the mass ratio of carbon black in the coating liquid of the inner peripheral surface layer to the coating liquid of the inner peripheral surface layer and the coating liquid of the outer peripheral surface layer. Less.
Folding resistance is improved by reducing the mass ratio of carbon black in the inner peripheral surface layer.
In order to obtain sufficient durability, the mass ratio (mass%) of carbon black to the total solid content in the coating liquid (inner) is defined as “mass ratio (inner)”. When the mass ratio (mass%) of the carbon black to the solid content is “mass ratio (outside)”, the mass ratio (inside) is 25% by mass or less, and the “mass ratio (inside)” and “mass ratio” (Outside) ", it is preferable that the absolute value of the difference between the two satisfies the following relationship.
| Mass ratio (inside)-Mass ratio (outside) | ≧ 3

  In addition to the dispersant, the leveling agent, antioxidant, heat stabilizer, ultraviolet absorber, lubricant, colorant, conductive agent other than carbon black, etc. One or more known additives may be added.

The polyamic acid which is a binder resin preferably used in the present invention will be described.
A polyamic acid is a precursor of a polyimide resin obtained by polymerizing an acid anhydride compound and a diamine compound in a polar solvent.
Hereinafter, polyimide will be described.
The polyimide used in the present invention is obtained via a polyamic acid (polyimide precursor) by a reaction of a generally known aromatic polycarboxylic acid anhydride or derivative thereof with an aromatic diamine.
That is, polyimide is insoluble in solvents and the like due to its rigid main chain structure and has an infusible property. Therefore, a polyimide precursor that is soluble in an organic solvent from an acid anhydride and an aromatic diamine ( Polyamic acid or polyamic acid) is synthesized, and at this stage, molding is performed by various methods, and then the polyamic acid is subjected to dehydration reaction by heating or a chemical method to be cyclized (imidized) to obtain polyimide.
The outline of the reaction is shown in the following chemical reaction formula (I).

（式中、Ａｒ１は少なくとも１つの炭素６員環を含む４価の芳香族残基を示し、Ａｒ２は少なくとも１つの炭素６員環を含む２価の芳香族残基を示す。）

(In the formula, Ar1 represents a tetravalent aromatic residue containing at least one carbon 6-membered ring, and Ar2 represents a divalent aromatic residue containing at least one carbon 6-membered ring.)

Specific examples of the aromatic polyvalent carboxylic acid anhydride include, for example, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3 '-Benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 2,2- Bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis ( 3,4-dicarbo Silphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid Dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride Products, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, and the like.
These may be used alone or in combination of two or more.

Next, specific examples of the aromatic diamine to be reacted with the aromatic polycarboxylic acid anhydride include, for example, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, and p-aminobenzyl. Amine, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, bis (3-aminophenyl) sulfide, (3-aminophenyl) (4-aminophenyl) sulfide, bis (4-aminophenyl) sulfide, bis (3-aminophenyl) sulfide, (3-aminophenyl) (4-aminophenyl) sulfoxide, bis (3-aminophenyl) sulfone, (3-aminophenyl) (4-amino Phenyl) sulfone, bis (4-aminophenyl) sulfur 3,3′-diaminobenzophenone, 3,4′-diaminobenzophenone, 4,4′-diaminobenzophenone, 3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, Bis [4- (3-aminophenoxy) phenyl] methane, bis [4- (4-aminophenoxy) phenyl] methane, 1,1-bis [4- (3-aminophenoxy) phenyl] ethane, 1,1- Bis [4- (4-aminophenoxy) phenyl] -ethane, 1,2-bis [4- (3-aminophenoxy) phenyl] ethane, 1,2-bis [4- (4-aminophenoxy) phenyl] ethane 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl Propane, 2,2-bis [4- (3-aminophenoxy) phenyl] butane, 2,2-bis [3- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexa Fluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 1,3-bis (3-aminophenoxy) benzene, 1 , 3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (3-aminophenoxy) Biphenyl, 4,4′-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [ -(3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfoxide, bis [4- (4-aminophenoxy) phenyl Sulfoxide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- ( 4-aminophenoxy) phenyl] ether, 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 4,4′- Bis [3- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4′-bis [3- (3-a Minophenoxy) benzoyl] diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α- Dimethylbenzyl) phenoxy] diphenylsulfone, bis [4- {4- (4-aminophenoxy) phenoxy} phenyl] sulfone, 1,4-bis [4- (4-aminophenoxy) phenoxy] -α, α-dimethylbenzyl Benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene and the like.
These are used individually or in mixture of 2 or more types.

A polyimide precursor (polyamic acid) can be obtained by carrying out a polymerization reaction in an organic polar solvent using substantially equimolar amounts of the aromatic polycarboxylic anhydride component and the diamine component.
Below, the manufacturing method of a polyamic acid is demonstrated concretely.
Examples of the organic polar solvent used in the polymerization reaction of polyamic acid include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide, N , N-dimethylacetamide, N, N-diethylacetamide and other acetamide solvents, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone and other pyrrolidone solvents, phenol, o-, m-, or p- Phenolic solvents such as cresol, xylenol, halogenated phenol, catechol, ether solvents such as tetrahydrofuran, dioxane, dioxolane, alcohol solvents such as methanol, ethanol, butanol, cellosolve such as butyl cellosolve or hex Methyl phosphoramide, .gamma.-butyrolactone, etc. may be mentioned, it is desirable to use them alone or as a mixed solvent.
The solvent is not particularly limited as long as it dissolves polyamic acid, but N, N-dimethylacetamide and N-methyl-2-pyrrolidone are particularly preferable.

As an example for producing a polyimide precursor, first, one or a plurality of diamines are dissolved in the above organic solvent or diffused in a slurry state in an inert gas atmosphere such as argon or nitrogen.
When at least one aromatic polycarboxylic acid anhydride or derivative thereof is added to this solution (either in a solid state, in a solution state dissolved in an organic solvent, or in a slurry state), it generates heat. A ring-opening polyaddition reaction occurs, and the viscosity of the solution rapidly increases, and a high molecular weight polyamic acid solution is obtained.
The reaction temperature at this time is preferably controlled to −20 ° C. to 100 ° C., desirably 60 ° C. or less. The reaction time is about 30 minutes to 12 hours.
By controlling the reaction temperature and reaction time, a product having a predetermined molecular weight can be produced.

The above is an example. Contrary to the addition procedure in the reaction, the aromatic polycarboxylic acid anhydride or derivative thereof is first dissolved or diffused in an organic solvent, and the diamine may be added to this solution. Good.
The diamine may be added in a solid state, in a solution state dissolved in an organic solvent, or in a slurry state.
That is, the mixing order of the aromatic polycarboxylic anhydride component and the diamine component is not limited.
Further, the aromatic polyvalent carboxylic acid anhydride and the aromatic diamine may be simultaneously added to the organic polar solvent for reaction.
As described above, the polyamic acid composition is dissolved in the organic polar solvent by polymerizing the aromatic polyvalent carboxylic acid anhydride or derivative thereof and the aromatic diamine component in about an equimolar amount of the organic polar solvent. A polyimide precursor solution is obtained in a uniformly dissolved state.

As the polyimide precursor solution (polyamic acid solution) in the present invention, the one synthesized as described above can be used, but the so-called polyamic acid composition is simply dissolved in an organic solvent. What is marketed as a polyimide varnish can also be obtained and used.
Examples of this include Trenys (manufactured by Toray Industries, Inc.), U-Varnish (manufactured by Ube Industries, Ltd.), Rika Coat (manufactured by Nippon Nippon Chemical Co., Ltd.), Optmer (manufactured by JSR), SE812 (manufactured by Nissan Chemical Industries), CRC8000 ( Sumitomo Bakelite Co., Ltd.) is a typical example.

The coating liquid is prepared by mixing the synthesized or obtained polyamic acid solution and the carbon dispersion.
The coating liquid is applied to a support (molding mold) as described later, and then subjected to a treatment such as heating, whereby conversion (imidation) from polyamic acid, which is a polyimide precursor, to polyimide is performed.

That is, the polyamic acid can be imidized by a heating method (1) or a chemical method (2).
The heating method (1) is a method of converting polyamic acid to polyimide by heat treatment at 200 to 350 ° C., and is a simple and practical method for obtaining polyimide (polyimide resin).
On the other hand, the chemical method (2) is a method in which a polyamic acid is reacted with a dehydrating cyclization reagent (such as a mixture of a carboxylic acid anhydride and a tertiary amine) and then heat-treated to completely imidize, (1 The method (1) is often used because the method is more complicated and costly than the method of heating.
In order to exhibit the intrinsic performance of polyimide, it is necessary to complete imidization by heating to a temperature above the glass transition temperature of the corresponding polyimide.

The progress of imidization (degree of imidization) can be evaluated by a commonly performed method for measuring the imidization rate.
As a method for measuring such an imidization rate, for example, nuclear magnetic resonance spectroscopy calculated from an integration ratio of 1H attributed to an amide group in the vicinity of 9 to 11 ppm and 1H attributed to an aromatic ring in the vicinity of 6 to 9 ppm. Various methods are used such as a method (NMR method), Fourier transform infrared spectroscopy (FT-IR method), a method for quantifying moisture accompanying imide ring closure, and a carboxylic acid neutralization titration method. Outer spectroscopy (FT-IR method) is the most common method.

In Fourier transform infrared spectroscopy (FT-IR method), the imidization rate is defined as follows, for example.
That is, assuming that (A) is the number of moles of imide groups at the firing stage (imidation treatment stage) and (B) is the number of moles of imide groups when 100% imidized (theoretical), Is done.
Imidation rate = [(A)) / (B))] × 100
The number of moles of the imide group in this definition can be determined from the absorbance ratio of the characteristic absorption of the imide group measured by the FT-IR method.

For example, as a typical characteristic absorption, the imidization ratio can be evaluated using the following absorbance ratio.
(1) Absorbance ratio between 725 cm ⁻¹ (immobilization vibration band of imide ring C═O group), which is one of characteristic absorptions of imide, and 1,015 cm ⁻¹ of characteristic absorption of benzene ring (2) Characteristics of imide Absorbance ratio between 1,380 cm ⁻¹ (inflection band of imide ring C—N group) which is one of absorption and characteristic absorption 1,500 cm ^{−1 of} benzene ring (3) One of characteristic absorption of imide Absorbance ratio between 1,720 cm ⁻¹ (an oscillating band of imide ring C═O group) and 1,500 cm ⁻¹ characteristic absorption of benzene ring (4) 1, which is one of characteristic absorption of imide Absorbance ratio between 720 cm ⁻¹ and amide group characteristic absorption 1,670 cm ^{−1 (} interaction between amide group N—H bending vibration and CN stretching vibration) and amide group over 3000 to 3300 cm ⁻¹ Confirmed the disappearance of multiple absorption bands This further increases the reliability of imidization completion.

<Seamless belt manufacturing method>
Next, a method for producing a seamless belt using the coating liquid containing the polyimide precursor will be described.
In the seamless belt manufacturing method of the present invention, the coating liquid is applied to the outer surface of the cylindrical mold. Since it is a method of coating on the outer surface of the mold, first, coating is performed from the coating liquid for the belt inner peripheral surface layer.
While slowly rotating the cylindrical metal mold, the coating liquid is applied and cast (forms a coating) so as to be uniform over the entire outer surface of the cylinder by a liquid supply device such as a nozzle or dispenser. Thereafter, the rotation speed is increased to a predetermined speed, and when the predetermined speed is reached, the rotation speed is maintained at a constant speed and the rotation is continued for a desired time. And it is preferable to evaporate the solvent in a coating film at the temperature of about 80-150 degreeC, heating to 200-260 degreeC preferably further, heating up gradually and raising it. In this process, it is preferable to efficiently circulate and remove atmospheric vapor (such as a volatilized solvent). When a self-supporting film is formed, cooling is performed.

  Next, the belt outer peripheral surface layer is applied. While slowly rotating the cylindrical metal mold on which the belt inner peripheral surface layer is formed, the coating liquid for the belt outer peripheral surface is uniformly applied to the entire outer surface of the cylinder by a liquid supply device such as a nozzle or a dispenser. Apply and cast (form a coating film). Thereafter, the rotation speed is increased to a predetermined speed, and when the predetermined speed is reached, the rotation speed is maintained at a constant speed and the rotation is continued for a desired time. And the solvent in a coating film is evaporated at the temperature of about 80-150 degreeC, heating up gradually while rotating. In this process, it is preferable to efficiently circulate and remove atmospheric vapor (such as a volatilized solvent). When a self-supporting film is formed, the mold is transferred to a heating furnace (firing furnace) capable of high-temperature processing, and the temperature is raised stepwise, and finally high-temperature heat processing (firing is performed at about 250 ° C. to 450 ° C. And fully imidize the polyimide resin precursor. After imidation is completed, slow cooling is performed, and the mold is removed from the mold to obtain a seamless belt having a two-layer structure.

Regarding the volume resistivity, when the volume resistivity of the intermediate transfer belt when 10 V is applied is ρv10 (Ω · cm) and the volume resistivity of the intermediate transfer belt when 100 V is applied is ρv100, the logarithmic value (Log) of ρv10 is used. The difference between (ρv10)) and the common logarithm of ρv100 (Log (ρv10)) is preferably 1.5 or less, and more preferably 1.3 or less.
By reducing the voltage dependency of the volume resistivity, the occurrence of white spots due to local leaks can be suppressed.

<Regarding Image Forming Apparatus of the Present Invention>
An example of the image forming apparatus of the present invention is shown in FIG.
The image forming apparatus of the present invention is preferably an image forming apparatus in which a plurality of photosensitive drums are arranged side by side along one intermediate transfer belt formed of a seamless belt so that high-speed printing can be performed even during color image printing. FIG. 1 shows a configuration of a four-drum digital color printer including four photosensitive drums 21BK, 21Y, 21M, and 21C for forming toner images of four different colors (black, yellow, magenta, and cyan). An example is shown.

  In FIG. 1, the printer main body 10 includes an image writing unit 12, an image forming unit 13, and a paper feeding unit 14 for performing color image formation by electrophotography. Based on the image signal, the image processing unit converts the image into black (BK), magenta (M), yellow (Y), and cyan (C) color signals for image formation and transmits them to the image writing unit 12. To do. The image writing unit 12 is a laser scanning optical system including, for example, a laser light source, a deflector such as a rotary polygon mirror, a scanning imaging optical system, and a mirror group. Image writing corresponding to each color signal is performed on image carriers (photoconductors) 21BK, 21M, 21Y, and 21C that have a writing optical path and are provided for each color of the image forming unit 13.

  The image forming unit 13 includes photoconductors 21BK, 21M, 21Y, and 21C that are image carriers for black (BK), magenta (M), yellow (Y), and cyan (C). As each photoconductor for each color, an OPC photoconductor is usually used. Around the photoreceptors 21BK, 21M, 21Y, and 21C, there are a charging device, an exposure unit for laser light from the writing unit 12, and developing devices 20BK, 20M, 20Y for black, magenta, yellow, and cyan, respectively. 20C, primary transfer bias rollers 23BK, 23M, 23Y, and 23C as primary transfer means, a cleaning device (not shown), and a photosensitive member static elimination device (not shown) are arranged. The developing devices 20BK, 20M, 20Y, and 20C use a two-component magnetic brush developing system. The intermediate transfer belt 22, which is a belt component, is interposed between the photosensitive members 21BK, 21M, 21Y, and 21C and the primary transfer bias rollers 23BK, 23M, 23Y, and 23C, and is formed on the photosensitive members. The toner images of each color are sequentially superimposed and transferred.

  On the other hand, the transfer paper P is fed from the paper feed unit 14 and then carried by the transfer conveyance belt 50, which is a belt component, via the registration roller 16. When the intermediate transfer belt 22 and the transfer conveyance belt 50 come into contact, the toner image transferred onto the intermediate transfer belt 22 is subjected to secondary transfer (collective transfer) by a secondary transfer bias roller 60 as a secondary transfer unit. ) As a result, a color image is formed on the transfer paper P. The transfer paper P on which the color image is formed is conveyed to the fixing device 15 by the transfer conveying belt 50, and after the image transferred by the fixing device 15 is fixed, it is discharged out of the printer main body.

  The residual toner that is not transferred during the secondary transfer and remains on the intermediate transfer belt 22 is removed from the intermediate transfer belt 22 by the belt cleaning member 25. A lubricant application device 27 is disposed on the downstream side of the belt cleaning member 25. The lubricant application device 27 includes a solid lubricant and a conductive brush that rubs the intermediate transfer belt 22 to apply the solid lubricant. The conductive brush is always in contact with the intermediate transfer belt 22 and applies a solid lubricant to the intermediate transfer belt 22.

  The solid lubricant has an effect of improving the cleaning property of the intermediate transfer belt 22, preventing the occurrence of filming, and improving the durability. In particular, a small-diameter toner or a toner with a high degree of circularity has poor cleaning properties, so it is desirable to apply a lubricant. As the solid lubricant, conventionally known lubricants can be used, and particularly good cleaning properties can be obtained with zinc stearate.

The present invention relates to the following method (1) for producing an intermediate transfer belt, and includes the intermediate transfer belt and the image forming apparatus described in the following (2) to (6) as embodiments.
(1) An electrophotographic intermediate transfer belt having a seamless two-layer structure is formed by coating and molding a coating solution prepared by mixing a polyimide resin precursor in a carbon dispersion obtained by dispersing carbon black in at least a solvent. A method of manufacturing comprising:
Coating a coating liquid (inner) for forming the belt inner peripheral surface layer on the outer surface of the cylindrical mold, and heating to form the belt inner peripheral surface layer;
Applying a coating liquid (outside) for forming a belt outer peripheral surface layer on the belt inner peripheral surface layer, and heating to form a belt outer peripheral layer;
Having at least
The carbon black in the carbon dispersion liquid (inner) for preparing the coating liquid (inner) and the carbon black in the carbon dispersion liquid (outer) for preparing the coating liquid (outer) are the same material. And
The volume average particle size (outside of Mv) of carbon black in the carbon dispersion (outside) for preparing the coating liquid (outside) is 0.25 μm or less,
The volume average particle size (inside Mv) of carbon black in the carbon dispersion (inside) for preparing the coating liquid (inside) is the carbon dispersion (outside) for preparing the coating liquid (outside). ) Larger than the volume average particle size (outside Mv) of carbon black in
Intermediate transfer characterized in that the mass ratio of carbon black to the total solid content in the coating liquid (inside) is smaller than the mass ratio of carbon black to the total solid content in the coating liquid (outside). A method for manufacturing a belt.
(2) Volume average particle size (inside Mv) of carbon black in the carbon dispersion (inside) for preparing the coating liquid (inside) and carbon dispersion for preparing the coating liquid (outside) The method for producing an intermediate transfer belt as described in (1) above, wherein the volume average particle size (outside Mv) of carbon black in the liquid (outside) satisfies the following relationship.
1.200 ≦ (within Mv) / (outside Mv) ≦ 1.700
(3) An intermediate transfer belt manufactured by the method for manufacturing an intermediate transfer belt according to (1) or (2).
(4) Electrons for performing primary transfer by sequentially superimposing a plurality of color toner developed images sequentially formed on an image carrier on an intermediate transfer belt, and performing secondary transfer of the primary transfer image collectively to a recording medium. The intermediate transfer belt as described in (3) above, which is used in a photographic apparatus.
(5) When the volume resistivity of the intermediate transfer belt when 10 V is applied is ρv10 (Ω · cm) and the volume resistivity of the intermediate transfer belt when 100 V is applied is ρv100, the common logarithm of ρv10 (Log (ρv10)) ) And the common logarithmic value of ρv100 (Log (ρv10)) satisfy the following relationship, and the number of folding resistances by the MIT test according to JIS P8115 is 10,000 or more (3) Or the intermediate transfer belt as described in (4).
Log (ρv10) −Log (ρv100) ≦ 1.5
(6) The intermediate transfer belt according to (5), wherein a difference between Log (ρv10) and Log (ρv10) satisfies the following relationship.
Log (ρv10) −Log (ρv100) ≦ 1.3

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by these examples without departing from the gist thereof.
Further, in the following description, unless otherwise specified, parts indicate parts by mass and% indicates mass%.

[Example 1]
[Preparation of intermediate transfer belt]
<Adjustment of carbon dispersion>
−Preparation of carbon dispersion for belt inner surface layer−
N-methyl-2-pyrrolidone solution of polyamic acid having a number average molecular weight of 15,000 consisting of biphenyl-3,4,3 ′, 4′-tetracarboxylic anhydride and 4,4′-diaminodiphenyl ether (solid content 20% ) 10 parts by weight of carbon black (Degussa Special Black 4) and 80 parts by weight of N-methyl-2-pyrrolidone were mixed and dispersed in a bead mill, and the volume average particle size (within Mv) was 0. 1982 μm of [Carbon dispersion A] was obtained.

In addition, the volume average particle diameter was measured with the following apparatus and conditions.
Device: Nano Track UPA150 (Nikkiso Co., Ltd.)
Measurement parameters;
Particle refractive index: 1.82
Particle density: 1.86 g / cm ³
Solvent refractive index: 1.47
Solvent viscosity: 1.63 mPa · s
Measurement conditions: The sample solution was diluted 200 times with a solvent and measured at a measurement time of 240 sec.

-Preparation of carbon dispersion for belt outer peripheral surface layer-
A dispersion was prepared in the same manner as the carbon dispersion for the inner peripheral surface except that the dispersion time was extended to obtain [Carbon dispersion B] having a volume average particle size (outside of Mv) of 0.1730 μm.

<Preparation of coating liquid>
―Preparation of coating solution for inner surface of belt―
[Carbon Dispersion A] is a polyamic acid N-methyl-2 having a number average molecular weight of 40,000 consisting of biphenyl-3,4,3 ′, 4′-tetracarboxylic anhydride and 4,4′-diaminodiphenyl ether. -The pyrrolidone solution (solid content 18%) was uniformly mixed with a triaxial planetary stirrer to obtain [Coating Solution A] having an addition amount of carbon black of 25.0% based on the entire solid content.
―Preparation of belt outer peripheral coating solution―
[Carbon Dispersion B] is a polyamic acid N-methyl-2 having a number average molecular weight of 40,000 consisting of biphenyl-3,4,3 ′, 4′-tetracarboxylic anhydride and 4,4′-diaminodiphenyl ether. -The pyrrolidone solution (solid content 18%) was uniformly mixed with a triaxial planetary stirrer to obtain [Coating fluid B] having an added amount of carbon black of 28.1% based on the entire solid content.

<Coating of belt inner surface layer>
Next, a cylindrical mold having an outer diameter of 310 mm and a length of 380 mm roughened by blasting is used, and while rotating the cylinder at 50 rpm (times / minute), the above-mentioned [coating liquid A] was applied with a dispenser so as to be uniformly cast on the outer surface of the cylinder, and after the predetermined amount was completely poured, the coating film was spread evenly to form a coating film of the polyimide resin precursor solution.

<Heating the belt inner surface layer>
The rotational speed of the mold is increased to 100 rpm, introduced into a hot air circulating drier that has been heated to 50 ° C., heated to 110 ° C. at a rate of temperature increase of 3 ° C./min, and heated at 110 ° C. for 60 minutes. Then, the coating film of the polyimide resin precursor solution was dried, and further heated from there to 240 ° C. at a temperature rising rate of 3 ° C./min, and kept at 240 ° C. for 60 minutes. After cooling, it was taken out, and the mold on which the belt inner peripheral surface layer was formed was taken out.

<Coating of belt outer peripheral surface layer>
The mold on which the belt inner peripheral surface layer is formed is coated with a dispenser so as to be uniformly cast on the belt inner peripheral surface layer while rotating at 50 rpm (times / minute). The film was spread evenly to form a coating film of the polyimide precursor solution on the belt outer peripheral surface layer.

<Heating of belt outer peripheral surface layer>
The rotational speed of the mold is increased to 100 rpm, introduced into a hot air circulating drier that has been heated to 50 ° C., heated to 110 ° C. at a rate of temperature increase of 3 ° C./min, and heated at 110 ° C. for 60 minutes. Then, the coating film of the polyimide resin precursor solution was dried, and further heated to 340 ° C. at a temperature rising rate of 3 ° C./min, and held at 340 ° C. for 60 minutes. After cooling, the sheet was taken out and demolded to obtain an intermediate transfer belt A having a two-layer structure.
The obtained belt had a film thickness of 81.0 μm. When the cross-section was observed, the layer on the belt inner peripheral surface side had a thickness of 20.8 μm, and the layer on the belt outer peripheral surface side had a thickness of 60.2 μm.

[Physical property measurement]
<Volume resistivity>
The measurement was performed using a URS probe with a Hirester (Mitsubishi Chemical).
The volume resistivity at the time of applying 10 V / 10 seconds and at the time of applying 100 V / 10 seconds was measured. Measurements were taken at three locations in the belt circumferential direction, three locations in the belt width direction (center and both ends), and a total of nine locations in the circumferential x width direction, and the average value was adopted. Measurement was performed on the outer peripheral surface and inner peripheral surface of the belt.

<Voltage resistivity voltage dependency>
Evaluation was made by subtracting the common logarithm of the volume resistivity ρv100 (Ω · cm) applied at 100 V / 10 seconds from the common logarithm of the volume resistivity ρv10 (Ω · cm) when 10 V / 10 seconds was applied.

<Surface resistivity measurement>
The measurement was performed using a URS probe with a Hirester (Mitsubishi Chemical).
The surface resistance value at the time of applying 500 V / 10 seconds was measured. Measurements were taken at three locations in the belt circumferential direction, three locations in the belt width direction (center and both ends), and a total of nine locations in the circumferential x width direction, and the average value was adopted. Measurement was performed on the outer peripheral surface and inner peripheral surface of the belt.

<Belt folding resistance evaluation>
The folding resistance was evaluated by the MIT test. Evaluation was performed under the following conditions in accordance with JIS P8115.
Evaluation equipment: MIT fatigue resistance tester DA (Toyo Seiki)
Bending angle: 135 °
Bending speed: 175 cpm
Load: 1kgf
Sample size: width 15mm, length 100mm
The belt production conditions and the results of the belt physical properties are summarized in Table 1.

[Example 2]
<Adjustment of carbon dispersion>
−Preparation of carbon dispersion for belt inner surface layer−
Except for shortening the dispersion time, dispersion was performed with a bead mill in the same manner as the carbon dispersion A prepared in Example 1 to obtain [Carbon dispersion C] having a volume average particle size (within Mv) of 0.2171 μm.
-Preparation of carbon dispersion for belt outer peripheral surface layer-
The same [Carbon dispersion B] as the carbon dispersion for the belt outer peripheral surface layer of Example 1 was used.

<Preparation of coating liquid>
−Preparation of coating liquid for belt inner surface layer−
[Carbon Dispersion C] is a polyamic acid N-methyl-2 having a number average molecular weight of 40,000 consisting of biphenyl-3,4,3 ′, 4′-tetracarboxylic anhydride and 4,4′-diaminodiphenyl ether. -The pyrrolidone solution (solid content 18%) was uniformly mixed with a triaxial planetary stirrer to obtain [Coating Solution C] having an addition amount of carbon black of 23.5% based on the entire solid content.
-Preparation of coating liquid for belt outer peripheral surface layer [Coating liquid B] same as the coating liquid for outer peripheral surface layer of Example 1 was used.

<Seamless belt manufacturing method>
A seamless belt was prepared in the same manner as in Example 1 except that the coating liquid for the belt inner peripheral surface layer was changed to [Coating liquid C], and an [intermediate transfer belt] having an inner peripheral length of 973 mm, a width of 320 mm, and a thickness of 80.8 μm. B] was obtained.
When the belt cross section was observed, the inner peripheral layer was 20.1 μm and the outer peripheral layer was 60.7 μm.

[Physical property measurement]
About the obtained [Intermediate transfer belt B], volume resistivity, surface resistivity, and folding resistance were evaluated in the same manner as in Example 1.

[Example 3]
<Preparation of carbon dispersion>
−Preparation of carbon dispersion for belt inner surface layer−
Except for shortening the dispersion time, dispersion was performed with a bead mill in the same manner as the carbon dispersion A prepared in Example 1 to obtain [Carbon dispersion D] having a volume average particle size (within Mv) of 0.2512 μm.
-Preparation of carbon dispersion for belt outer peripheral surface layer-
The same [Carbon dispersion B] as the carbon dispersion for the belt outer peripheral surface layer of Example 1 was used.

<Preparation of coating liquid>
−Preparation of coating liquid for belt inner surface layer−
The carbon dispersion A was converted to N-methyl-2-pyrrolidone of polyamic acid having a number average molecular weight of 40,000 consisting of biphenyl-3,4,3 ′, 4′-tetracarboxylic anhydride and 4,4′-diaminodiphenyl ether. The solution (solid content 18%) was uniformly mixed with a triaxial planetary stirrer to obtain [Coating Liquid D] having an addition amount of carbon black of 16.8% based on the entire solid content.
−Preparation of coating liquid for belt outer peripheral surface layer−
[Coating liquid B], which is the same as the coating liquid for the outer peripheral surface layer of Example 1, was used.

<Preparation of seamless belt>
A seamless belt was prepared in the same manner as in Example 1 except that the coating liquid for the belt inner peripheral surface layer was changed to [Coating liquid D], and an [intermediate transfer belt] having an inner peripheral length of 973 mm, a width of 320 mm, and a thickness of 80.6 μm. C] was obtained.
When the belt cross section was observed, the inner peripheral layer was 19.8 μm and the outer peripheral layer was 60.8 μm.

[Physical property measurement]
About the obtained [Intermediate transfer belt C], volume resistivity, surface resistivity, and folding resistance were evaluated in the same manner as in Example 1.

[Example 4]
<Adjustment of carbon dispersion>
−Preparation of carbon dispersion for belt inner surface layer−
Except for shortening the dispersion time, dispersion was performed with a bead mill in the same manner as in the carbon dispersion A prepared in Example 1 to obtain [Carbon dispersion E] having a volume average particle size (within Mv) of 0.2661 μm.
-Preparation of carbon dispersion for belt outer peripheral surface layer-
The same [Carbon dispersion B] as the carbon dispersion for the belt outer peripheral surface layer of Example 1 was used.

<Preparation of coating liquid>
−Preparation of coating liquid for belt inner surface layer−
The carbon dispersion A was converted to N-methyl-2-pyrrolidone of polyamic acid having a number average molecular weight of 40,000 consisting of biphenyl-3,4,3 ′, 4′-tetracarboxylic anhydride and 4,4′-diaminodiphenyl ether. The solution (solid content 18%) was uniformly mixed with a triaxial planetary stirrer to obtain [Coating Solution E] having an addition amount of carbon black of 11.1% based on the entire solid content.
−Preparation of coating liquid for belt outer peripheral surface layer−
The same [Coating liquid B] as the coating liquid for the outer peripheral surface layer of Example 1 was used.

<Preparation of seamless belt>
A seamless belt was prepared in the same manner as in Example 1 except that the coating liquid for the belt inner peripheral surface layer was changed to the coating liquid E, and [intermediate transfer belt D] having an inner peripheral length of 973 mm, a width of 320 mm, and a thickness of 80.3 μm. Got.
When the belt cross section was observed, the inner peripheral layer was 20.7 μm and the outer peripheral layer was 59.6 μm.

[Physical property measurement]
About the obtained [Intermediate transfer belt D], volume resistivity, surface resistivity, and folding resistance were evaluated in the same manner as in Example 1.

[Example 5]
<Adjustment of carbon dispersion>
−Preparation of carbon dispersion for belt inner surface layer−
Except for shortening the dispersion time, dispersion was performed with a bead mill in the same manner as [Carbon dispersion A] prepared in Example 1, and [Carbon dispersion F] having a volume average particle size (within Mv) of 0.2864 μm.
Got.
-Preparation of carbon dispersion for belt outer peripheral surface layer-
The same [Carbon dispersion B] as the carbon dispersion for the belt outer peripheral surface layer of Example 1 was used.

<Preparation of coating liquid>
−Preparation of coating liquid for belt inner surface layer−
The carbon dispersion A was converted to N-methyl-2-pyrrolidone of polyamic acid having a number average molecular weight of 40,000 consisting of biphenyl-3,4,3 ′, 4′-tetracarboxylic anhydride and 4,4′-diaminodiphenyl ether. The solution (solid content 18%) was uniformly mixed with a triaxial planetary stirrer to obtain [Coating Solution F] having an addition amount of carbon black of 10.4% based on the entire solid content.
−Preparation of coating liquid for belt outer peripheral surface layer−
The same [Coating liquid B] as the outer peripheral surface layer coating liquid of Example 1 was used.

<Preparation of seamless belt>
A seamless belt was prepared in the same manner as in Example 1 except that the coating liquid for the belt inner peripheral surface layer was changed to [Coating liquid F], and an [intermediate transfer belt] having an inner peripheral length of 973 mm, a width of 320 mm, and a thickness of 80.4 μm. E] was obtained.
When the belt cross section was observed, the inner peripheral layer was 20.2 μm and the outer peripheral layer was 60.2 μm.

[Physical property measurement]
About the obtained [Intermediate transfer belt E], volume resistivity, surface resistivity, and folding resistance were evaluated in the same manner as in Example 1.

[Example 6]
<Adjustment of carbon dispersion>
−Preparation of carbon dispersion for belt inner surface layer−
Except for shortening the dispersion time, dispersion was performed with a bead mill in the same manner as [Carbon dispersion A] prepared in Example 1 to obtain [Carbon dispersion G] having a volume average particle size (within Mv) of 0.2988 μm. It was.
-Preparation of carbon dispersion for belt outer peripheral surface layer-
The same [Carbon dispersion B] as the carbon dispersion for the belt outer peripheral surface layer of Example 1 was used.

<Preparation of coating liquid>
−Preparation of coating liquid for belt inner surface layer−
[Carbon Dispersion G] is a polyamic acid N-methyl-2 having a number average molecular weight of 40,000 consisting of biphenyl-3,4,3 ′, 4′-tetracarboxylic anhydride and 4,4′-diaminodiphenyl ether. -The pyrrolidone solution (solid content 18%) was uniformly mixed with a triaxial planetary stirrer to obtain [Coating Solution G] having an addition amount of carbon black of 9.1% based on the entire solid content.
−Preparation of coating liquid for belt outer peripheral surface layer−
The same [Coating liquid B] as the outer peripheral surface layer coating liquid of Example 1 was used.

<Preparation of seamless belt>
A seamless belt was prepared in the same manner as in Example 1 except that the coating liquid for the belt inner peripheral surface layer was changed to [Coating liquid G], and an [intermediate transfer belt] having an inner peripheral length of 973 mm, a width of 320 mm, and a thickness of 79.9 μm. F] was obtained.
When the belt cross section was observed, the inner peripheral layer was 19.9 μm and the outer peripheral layer was 60 μm.

[Physical property measurement]
About the obtained [Intermediate transfer belt F], volume resistivity, surface resistivity, and folding resistance were evaluated in the same manner as in Example 1.

[Example 7]
<Adjustment of carbon dispersion>
−Preparation of carbon dispersion for belt inner surface layer−
The same [carbon dispersion E] as the carbon dispersion for the inner peripheral surface layer of Example 4 was used.
The same [carbon dispersion C] as the carbon dispersion for the belt inner peripheral surface layer of Example 2 was used.

<Preparation of coating liquid>
−Preparation of coating liquid for belt inner surface layer−
The same [Coating fluid E] as the inner peripheral surface layer coating solution of Example 4 was used.
−Preparation of coating liquid for belt outer peripheral surface layer−
The same [Coating fluid C] as the coating solution for the belt inner peripheral surface layer of Example 2 was used.

<Preparation of seamless belt>
A seamless belt was prepared in the same manner as in Example 1 except that the coating liquid for the belt inner peripheral surface layer was changed to [Coating liquid E] and the coating liquid for the belt outer surface layer was changed to [Coating liquid C]. [Intermediate transfer belt G] having a circumferential length of 973 mm, a width of 320 mm, and a thickness of 80.1 μm was obtained.
When the belt cross section was observed, the inner peripheral layer was 20.1 μm and the outer peripheral layer was 60 μm.

[Physical property measurement]
About the obtained [Intermediate transfer belt G], volume resistivity, surface resistivity, and folding resistance were evaluated in the same manner as in Example 1.

[Comparative Example 1]
In Example 5, except that the coating liquid used for the outer peripheral surface layer was changed to [Coating liquid F], it was prepared in the same manner as in Example 5, and the inner peripheral length was 973 mm, the width was 320 mm, and the thickness was 80.6 μm. [Intermediate transfer belt H] having a layer structure was obtained [Physical property measurement]
About the obtained [Intermediate transfer belt H], volume resistivity, surface resistivity, and folding resistance were evaluated in the same manner as in Example 1.

[Comparative Example 2]
In Example 3, except that the coating liquid used for the outer peripheral surface was changed to [Coating liquid D], it was prepared in the same manner as in Example 3, and two layers having an inner peripheral length of 973 mm, a width of 320 mm, and a thickness of 80.8 μm were prepared. [Intermediate transfer belt I] having a structure was obtained, and various evaluations were performed. [Measurement of physical properties]
About the obtained [Intermediate transfer belt I], volume resistivity, surface resistivity, and folding resistance were evaluated in the same manner as in Example 1.

[Comparative Example 3]
In Example 1, except that the coating liquid used for the inner peripheral surface was changed to [Coating liquid B], it was prepared in the same manner as in Example 1, and the inner peripheral length was 973 mm, the width was 320 mm, and the thickness was 80.4 μm. [Intermediate transfer belt J] having a layer structure was obtained, and various evaluations were performed. [Measurement of physical properties]
About the obtained [Intermediate transfer belt J], volume resistivity, surface resistivity, and folding resistance were evaluated in the same manner as in Example 1.

  Table 1 summarizes the production conditions and physical property measurement results of the intermediate transfer belts produced in Examples 1 to 7 and Comparative Examples 1 to 3.

JP 2002-148951 A JP 2006-103140 A JP 2007-41214 A JP 2007-226219 A JP 2007-224279 A JP 2010-256390 A

Claims (6)

A method for producing a seamless two-layer electrophotographic intermediate transfer belt by coating and molding a coating solution prepared by mixing a polyimide resin precursor in a carbon dispersion obtained by dispersing carbon black in at least a solvent Because
Coating a coating liquid (inner) for forming the belt inner peripheral surface layer on the outer surface of the cylindrical mold, and heating to form the belt inner peripheral surface layer;
Applying a coating liquid (outside) for forming a belt outer peripheral surface layer on the belt inner peripheral surface layer, and heating to form a belt outer peripheral layer;
Having at least
The carbon black in the carbon dispersion liquid (inner) for preparing the coating liquid (inner) and the carbon black in the carbon dispersion liquid (outer) for preparing the coating liquid (outer) are the same material. And
The volume average particle size (outside of Mv) of carbon black in the carbon dispersion (outside) for preparing the coating liquid (outside) is 0.25 μm or less,
The volume average particle size (inside Mv) of carbon black in the carbon dispersion (inside) for preparing the coating liquid (inside) is the carbon dispersion (outside) for preparing the coating liquid (outside). ) Larger than the volume average particle size (outside Mv) of carbon black in
Intermediate transfer characterized in that the mass ratio of carbon black to the total solid content in the coating liquid (inside) is smaller than the mass ratio of carbon black to the total solid content in the coating liquid (outside). A method for manufacturing a belt. Volume average particle size (inside Mv) of carbon black in the carbon dispersion (inside) for preparing the coating liquid (inside) and carbon dispersion (outside) for preparing the coating liquid (outside) 2) satisfies the following relationship with the volume average particle size (outside Mv) of the carbon black in (2).
1.200 ≦ (within Mv) / (outside Mv) ≦ 1.700   An intermediate transfer belt manufactured by the method for manufacturing an intermediate transfer belt according to claim 1.   An electrophotographic apparatus in which a plurality of color toner developed images sequentially formed on an image carrier are sequentially superimposed on an intermediate transfer belt to perform primary transfer, and the primary transfer images are collectively transferred to a recording medium. The intermediate transfer belt according to claim 3, wherein the intermediate transfer belt is used. When the volume resistivity of the intermediate transfer belt when 10 V is applied is ρv10 (Ω · cm) and the volume resistivity of the intermediate transfer belt when 100 V is applied is ρv100, the common logarithmic value (Log (ρv10)) of ρv10 and ρv100 The difference from the common logarithmic value (Log (ρv10)) of the above satisfies the following relationship, and the folding endurance by the MIT test based on JIS P8115 is 10,000 or more: 5 or 5 Intermediate transfer belt.
Log (ρv10) −Log (ρv100) ≦ 1.5 The intermediate transfer belt according to claim 5, wherein a difference between the Log (ρv10) and the Log (ρv10) satisfies the following relationship.
Log (ρv10) −Log (ρv100) ≦ 1.3

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