JP6996090B2 - Transfer belt for electrophotographic equipment, image forming equipment and transfer belt unit - Google Patents

Description

The present invention relates to a transfer belt for an electrophotographic apparatus, an image forming apparatus and a transfer belt unit.

An electrophotographic image forming apparatus (also referred to as an "electrophotographic apparatus") forms an electric charge on a photoconductor, forms an electrostatic charge image of a modulated image signal with laser light or the like, and then statically uses a charged toner. The charge image is developed into a toner image. Next, the toner image is transferred to a recording medium such as paper directly or via an intermediate transfer body and fixed on the recording medium to obtain an image.

Here, an image forming apparatus adopting a method of primary transfer of a toner image on a photoconductor to an intermediate transfer body and then secondary transfer of a toner image on an intermediate transfer body to a recording medium such as paper, a so-called intermediate transfer method, is available. Are known.
Since the intermediate transfer belt (also simply referred to as “transfer belt”) used as such an intermediate transfer body is required to have mechanical strength and heat resistance, for example, a polyimide resin having both high mechanical strength and heat resistance. , Polyimideimide resin and the like are preferably used as the material.

Patent Document 1 is characterized in that "a carbon black dispersion liquid in which carbon black is uniformly dispersed in an organic polar solvent is dissolved in a substantially equal molar amount of an aromatic tetracarboxylic acid diester and an aromatic diamine. A method for producing a semi-conductive high-concentration polyimide precursor composition ”is described.
Patent Document 2 describes "endless tubular semi-conductivity, which comprises a conductive carbon black containing an aromatic polyimide and a volatile content of 10 to 25% mainly composed of a volatile acid component having a pH of 4 or less. Aromatic polyimide film "is described.
Patent Document 3 describes "a polyimide precursor composition containing a polyimide precursor containing a repeating unit represented by the general formula (1), a solvent, and acidic carbon black having a pH of 5.0 or less." There is.

Patent Document 4 states that "it is composed of a single layer of a resin layer containing a resin and a conductive agent, and the surface resistivity of the outer peripheral surface of the resin layer is higher than that of the inner peripheral surface of the resin layer, and the surface resistivity thereof is higher. A transfer belt having a common logarithmic difference of 2 digits or more. "

Japanese Unexamined Patent Publication No. 2005-247988 Japanese Unexamined Patent Publication No. 2001-047451 Japanese Unexamined Patent Publication No. 2013-181136 Japanese Unexamined Patent Publication No. 2014-222325

The conventional transfer belt is formed by using, for example, a coating liquid (resin composition) in which a polyimide resin, a polyamide-imide resin, or a precursor thereof is dissolved in N-methyl-2-pyrrolidone (NMP). Specifically, for example, by applying the above coating liquid to a mold, removing at least a part of NMP, and then heating as necessary, a transfer belt having a resin layer containing a cured product of the coating liquid can be obtained. can get. The resin layer contains a part of a solvent such as NMP used in the coating liquid.
Further, in order to impart conductivity to the transfer film, the coating liquid may further contain carbon black.
However, when a coating liquid containing NMP, a polyimide resin, a polyamide-imide resin, or a precursor thereof, and carbon black is used in the production of a transfer belt, the breaking durability of the obtained transfer belt is lowered. Was sometimes caused.

An object of the present invention is when the solvent contained in the polyimide resin layer or the polyamide-imide resin layer is only NMP, the pH of carbon black exceeds 7, or the average primary particle size of carbon black exceeds 25 nm. In comparison, it is an object of the present invention to provide a transfer belt in which a decrease in breaking durability is suppressed.

The above problem is solved by the following means.

< 1 >
At least one solvent selected from the solvent group A consisting of a urea -based solvent, an alkoxy group-containing amide-based solvent, and an ester group-containing amide-based solvent, and a pH of 7.0 or less and an average primary particle size of 25 nm or less. A transfer belt for an electrophotographic apparatus having a polyimide resin layer or a polyamide-imide resin layer containing carbon black.

< 2 >
At least one solvent selected from the solvent group A consisting of a urea -based solvent, an alkoxy group-containing amide-based solvent, and an ester group-containing amide-based solvent, at least one of a polyimide resin precursor and a polyamide-imide resin, and pH. A transfer belt for an electrophotographic apparatus having a resin layer which is a cured product of a resin composition containing carbon black having an average primary particle diameter of 25 nm or less and 7.0 or less.

< 3 >
The solvent group A is tetramethylurea, tetraethylurea, 1,3-dimethyl-2-imidazolidinone, N, N-dimethylpropylene urea, 3-methoxy-N, N-dimethylpropanamide, and 3-n. The transfer belt for an electrophotographic apparatus according to < 1 > or < 2 > , which is a solvent group consisting of butoxy-N and N-dimethylpropaneamide.

< 4 >
The transfer belt for an electrophotographic apparatus according to < 1 > or < 2 > , wherein the solvent selected from the solvent group A is 1,3-dimethyl-2-imidazolidinone.

< 5 >
An image forming apparatus including the transfer belt for an electrophotographic apparatus according to any one of < 1 > to < 4 > .

< 6 >
A transfer belt unit comprising the transfer belt for an electrophotographic apparatus according to any one of < 1 > to < 4 > , and a plurality of rolls for passing the transfer belt under tension.

According to the invention according to < 1 > , the solvent contained in the polyimide resin layer or the polyamide-imide resin layer is only NMP, the pH of carbon black exceeds 7, or the average primary particle size of carbon black is 25 nm. Provided is a transfer belt in which a decrease in breaking durability is suppressed as compared with the case where the amount exceeds.

According to the invention according to < 2 > , compared to the case where the solvent contained in the resin composition is only NMP, the pH of carbon black exceeds 7, or the average primary particle size of carbon black exceeds 25 nm. As a result, a transfer belt in which a decrease in breaking durability is suppressed is provided.

According to the invention according to < 3 > or < 4 > , there is provided a transfer belt in which a decrease in breaking durability is suppressed as compared with the case where the solvent contained in the resin composition is only NMP.

According to the invention according to < 5 > , the solvent contained in the polyimide resin layer or the polyamide-imide resin layer is only NMP, the solvent contained in the resin composition is only NMP, or the pH of carbon black is 7. An image forming apparatus is provided provided with a transfer belt in which a decrease in breaking durability is suppressed as compared with the case where the average primary particle size of carbon black exceeds 25 nm.

According to the invention according to < 6 > , the solvent contained in the polyimide resin layer or the polyamide-imide resin layer is only NMP, the solvent contained in the resin composition is only NMP, or the pH of carbon black is 7. Provided is a transfer belt unit including a transfer belt in which a decrease in breaking durability is suppressed as compared with the case where the average primary particle size of carbon black exceeds 25 nm.

It is a schematic plan view (A) and a schematic sectional view (B) which show an example of a circular electrode. It is a schematic block diagram which shows the image forming apparatus which concerns on this embodiment. It is a schematic perspective view which shows the transfer belt unit which concerns on this embodiment.

Hereinafter, embodiments that are an example of the present invention will be described in detail.

<Transfer belt for electrophotographic equipment>
The transfer belt for an electrophotographic apparatus according to the first embodiment is at least one solvent selected from the solvent group A consisting of a urea solvent, an alkoxy group-containing amide solvent, and an ester group-containing amide solvent (hereinafter, A polyimide resin layer or a polyamide imide resin containing a "specific solvent") and carbon black having a pH of 7 or less and an average primary particle size of 25 nm or less (hereinafter, also referred to as "specific carbon black"). Has a layer.
Hereinafter, the "polyimide resin layer or the polyamide-imide resin layer" is also simply referred to as a "resin layer".
The resin layer is preferably a cured product of a resin composition containing, for example, a specific solvent, at least one of a polyimide resin precursor and a polyamide-imide resin, and a specific carbon black.
When the resin composition contains a polyimide resin precursor, for example, after removing at least a part of at least one solvent selected from the solvent group A in the resin composition, the precursor is heated or the like. By forming the polyimide resin, a cured product can be obtained.
When the resin composition contains a polyamide-imide resin, for example, a cured product can be obtained by removing at least a part of at least one solvent selected from the solvent group A in the resin composition.
In any of the embodiments, the solvent in the resin layer is not completely removed, and a polyimide resin layer or a polyamide-imide resin layer containing at least one solvent selected from the solvent group A can be obtained.

The transfer belt for an electrophotographic apparatus according to the second embodiment includes at least one solvent selected from the solvent group A consisting of a urea-based solvent, an alkoxy group-containing amide-based solvent, and an ester group-containing amide-based solvent, and polyimide. It has a resin layer which is a cured product of a resin composition containing at least one of a resin precursor and a polyamide-imide resin, and carbon black having a pH of 7 or less and an average primary particle size of 25 nm or less.

According to the invention according to the first embodiment or the second embodiment, the solvent used for preparing the coating liquid is only NMP, the pH of carbon black exceeds 7, or the average of carbon black. Provided is a transfer belt in which a decrease in breaking durability is suppressed as compared with the case where the primary particle size exceeds 25 nm.
Hereinafter, the "transfer belt according to the first embodiment or the second embodiment" is also collectively referred to as "the transfer belt according to the present embodiment".
The detailed mechanism by which the above effect is obtained is unknown, but it is presumed as follows.

In the conventional transfer belt, for example, a polyimide resin, a polyamide-imide resin, or a precursor thereof is dissolved in NMP to prepare a coating liquid (resin composition), and the coating liquid is applied to a mold to obtain at least NMP. It has a resin layer containing a cured product obtained by removing a part and heating as necessary. Further, in order to impart conductivity to the transfer film, the coating liquid may further contain carbon black.
However, when a coating liquid containing NMP, a polyimide resin, a polyamide-imide resin, or a precursor thereof, and carbon black is used in the production of a transfer belt, the breaking durability of the obtained transfer belt is lowered. Was sometimes caused.
It is presumed that this is because the affinity between the resin, the carbon black, and the NMP is low, so that cracks occur at the interface between the carbon black and the resin in the obtained resin layer.
Further, when NMP is used as a solvent, carbon black may be aggregated or gelation of the coating liquid may occur due to long-term storage (for example, 120 hours, etc.) due to the low affinity described above. be.
Further, when NMP is used as the solvent, transfer failure or cleaning failure due to surface wear or scratch scratches due to contact friction between the transfer belt and the paper or other members may occur. It is presumed that this is because the resin in the resin composition, the carbon black, and the solvent are difficult to mix due to the low affinity described above, and the smoothness of the surface of the resin layer is lowered.
In addition, when NMP is used as the solvent, the transfer belt may have uneven electrical resistance due to the low affinity described above, or, for example, the electricity of the transfer belt after printing tens of thousands to hundreds of thousands of sheets. Resistance may decrease. It is presumed that this is because the resin in the resin composition, the carbon black, and the solvent are difficult to mix, and the carbon black is not dispersed in a nearly uniform state.

On the other hand, in the transfer belt according to the present embodiment, the above configuration suppresses the decrease in breaking durability, further suppresses the aggregation and gelation of the composition, and the cleaning maintainability and resistance maintainability of the transfer belt. Excellent for.
This includes at least one solvent selected from the solvent group A consisting of a urea-based solvent, an alkoxy group-containing amide-based solvent, and an ester group-containing amide-based solvent, and a pH of 7 or less and an average primary particle size of 25 nm or less. By using the above carbon black in combination, the resin, the solvent, and the carbon black have an excellent affinity, and the resin, the specific carbon black, and the specific solvent become uniform as the solvent is removed when the resin composition is cured. It is presumed that this is due to the convection in a state close to.
Since the polyimide resin precursor or the polyamide-imide resin has a polar group such as an amic acid structure, an imide group, and an amide group, it exhibits high solubility in a highly polar solvent.
Further, when the pH of the carbon black surface is set to 7 or less (increasing the acidity), the carboxy group or the sulfonyl group becomes easily polarized, an electrical bias occurs, and hydrogen bonding property occurs. In particular, when the particle size of carbon black is 25 nm or less, the surface area per unit volume becomes large, so that hydrogen bonding is likely to occur.
Furthermore, as a result of the carbon black having a particle size of 25 nm or less and hydrogen bondability being easily generated, the carbon black is in a state of being very densely dispersed in the resin, and is resistant to the discharge stress generated in the transfer process in actual use. The number of conductive points formed by CB per surface of the belt unit for reducing discharge stress can be increased, and changes in electrical characteristics such as a decrease in surface resistivity during long-term use can be suppressed.
Further, a solvent having a group containing a specific atomic group, such as a urea-based solvent, an alkoxy group-containing amide-based solvent, and an ester group-containing amide-based solvent, has high polarity and high hydrogen-bonding property.
Therefore, by using the specific carbon black in combination with the specific solvent, the affinity between the polyimide resin precursor or the polyamide-imide resin, the solvent, and the carbon black is improved, and in the resin composition and the resin layer. In each component, each component is closer to uniform than when the solvent is only NMP, the pH of carbon black exceeds 7, or the average primary particle size of carbon black exceeds 25 nm. It is considered to be dispersed.
As a result of each component being dispersed in a more uniform state, cracks are less likely to occur at the interface between the carbon black of the resin layer and the resin, so that it is considered that a transfer belt having excellent breaking durability can be obtained.
Further, as a result of each component being dispersed in a more uniform state, in the resin composition used for producing the resin layer, carbon black aggregates or a coating liquid is collected even after long-term storage (for example, 120 hours). It is considered that the gelation of the resin is suppressed.
Further, as a result of each component being dispersed in a more uniform state, the smoothness of the surface of the resin layer is improved, and it is considered that a transfer belt having excellent cleaning maintainability can be obtained.
In addition, as a result of each component being dispersed in a more uniform state, the carbon black in the resin layer is also dispersed in a nearly uniform state, and it is considered that a transfer belt having excellent resistance retention can be obtained.
Hereinafter, each component in the transfer belt for an electrophotographic apparatus according to the present embodiment will be described first.

(Resin layer)
The polyimide resin layer or the polyamide-imide resin layer of the transfer belt for an electrophotographic apparatus according to the present embodiment was selected from the solvent group A composed of a urea-based solvent, an alkoxy group-containing amide-based solvent, and an ester group-containing amide-based solvent. At least one kind of solvent (hereinafter, also referred to as “specific solvent”) and carbon black having a pH of 7 or less and an average primary particle size of 25 nm or less (hereinafter, also referred to as “specific carbon black”) are used. include.

[Specific solvent]
The specific solvent is at least one solvent selected from the solvent group A consisting of a urea-based solvent, an alkoxy group-containing amide-based solvent, and an ester group-containing amide-based solvent.
In the transfer belt according to the present embodiment, the amount of the specific solvent contained in the resin layer constituting the transfer belt is preferably 0.05% by mass or more and 2.0% by mass or less with respect to the total mass of the resin layer. , 0.1% by mass or more and 1.0% by mass or less, and more preferably 0.2% by mass or more and 0.9% by mass or less.
When a plurality of types of the specific solvent are contained, the above-mentioned content is the total amount of the specific solvent.

Here, as a method for controlling the amount of the specific solvent contained in the resin layer constituting the transfer belt according to the present embodiment within the above range, for example, in the method for producing a transfer belt described later, a coating film of the resin composition is applied. Examples thereof include a method of controlling by adjusting the conditions (heating temperature and heating time) for heating the dried film after drying.

The solvent (residual solvent) contained in the resin layer constituting the transfer belt is measured by collecting a measurement sample from the resin layer of the transfer belt to be measured and using a gas chromatograph mass spectrometer (GC-MS) or the like. Specifically, 0.40 mg of a measurement sample is accurately weighed from the resin layer of the transfer belt to be measured, and a drop-type pyrolysis device (manufactured by Frontier Lab: PY-2020D) is installed for gas chromatograph mass spectrometry. Measurement is performed under the following conditions using a meter (manufactured by Shimadzu Corporation: GCMS QP-2010).

Pyrolysis temperature: 400 ° C
Gas chromatograph introduction temperature: 280 ° C
Inject method: Split ratio 1:50
Column: Ultra ALLOY-5 0.25 μm, 0.25 μm ID, 30 m manufactured by Frontier Lab.
Gas chromatograph temperature program: 40 ° C ⇒ 20 ° C / min ⇒ 280 ° C-10 min maintenance Mass range: EI, m / z = 29-600

Hereinafter, the details of the specific solvent will be described.

-Urea solvent-
The urea-based solvent is a solvent having a urea group (NC (= O) -N). Specifically, the urea-based solvent is preferably a solvent having a "* -N (Ra ¹ ) -C (= O) -N (Ra ² )-*" structure. Here, Ra ¹ and Ra ² independently represent a hydrogen atom, an alkyl group, a phenyl group, or a phenylalkyl group. Both ends * of the two N atoms independently indicate the binding site with another atomic group. The urea-based solvent has a ring structure in which both ends * of two N atoms are linked via a linking group consisting of, for example, alkylene, -O-, -C (= O)-, or a combination thereof. May be.

The alkyl group showing Ra ¹ and Ra ² may be linear, branched or cyclic, and may have a substituent. Specific examples of the alkyl group include an alkyl group having 1 or more and 6 or less carbon atoms (preferably 1 or more and 4 or less) (for example, a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, etc.). Can be mentioned.
Examples of the substituent of the alkyl group include an alkoxy group having 1 or more and 4 or less carbon atoms, a hydroxy group, a ketone group, an ester group, an alkylcarbonyloxy group and the like.
Specific examples of the ketone group include a methylcarbonyl group (acetyl group), an ethylcarbonyl group, an n-propylcarbonyl group and the like. Specific examples of the ester group include a methoxycarbonyl group, an ethoxycarbonyl group, an n-propoxycarbonyl group, an acetoxy group and the like. Specific examples of the alkylcarbonyloxy group include a methylcarbonyloxy group (acetyloxy group), an ethylcarbonyloxy group, an n-propylcarbonyloxy group and the like.

The phenyl skeleton of the phenyl group and the phenylalkyl group showing Ra ¹ and Ra ² may have a substituent. Examples of the substituent of the phenyl skeleton include the same substituents of the above-mentioned alkyl group.

When the urea solvent has a ring structure in which both ends * of the two N atoms are connected, the number of ring members is preferably 5 or 6.

Examples of urea-based solvents include 1,3-dimethylurea, 1,3-diethylurea, 1,3-diphenylurea, 1,3-dicyclohexylurea, tetramethylurea, tetraethylurea, and 2-imidazolidinone. , Propylene, 1,3-dimethyl-2-imidazolidinone, N, N-dimethylpropyleneurea and the like.
Among these, 1,3-dimethylurea and 1,3 are examples of urea-based solvents from the viewpoints of storage stability of the resin composition and improvement of breaking durability, resistance retention and cleaning maintainability of the transfer belt. -Diethylurea, tetramethylurea, tetraethylurea, 1,3-dimethyl-2-imidazolidinone, N, N-dimethylpropyleneurea are preferable, tetramethylurea, tetraethylurea, 1,3-dimethyl-2-imidazolidione. Non-, N, N-dimethylpropylene urea is more preferable, and 1,3-dimethyl-2-imidazolidinone is further preferable.

-Alkoxy group-containing amide solvent, ester group-containing amide solvent-
The alkoxy group-containing amide solvent is a solvent having an alkoxy group and an amide group. On the other hand, the ester group-containing amide solvent is a solvent having an ester group and an amide group. Examples of the alkoxy group and the ester group include the same groups as the alkoxy group and the ester group exemplified as "substituents of the alkyl groups showing Ra ¹ and Ra ² " in the explanation of the urea-based solvent. The alkoxy group-containing amide-based solvent may have an ester group, and the ester group-containing amide-based solvent may have an alkoxy group.

Hereinafter, both the alkoxy group-containing amide-based solvent and the ester group-containing amide-based solvent will be referred to as “alkoxy group- or ester group-containing amide-based solvent”.

The alkoxy group- or ester group-containing amide-based solvent is not particularly limited, but specifically, an amide-based solvent represented by the following general formula (Am1), an amide-based solvent represented by the following general formula (Am2), and the like are preferable. Listed in.

(In the general formula (Am1), Rb ¹ , Rb ² , Rb ³ , Rb ⁴ , Rb ⁵ , and Rb ⁶ each independently represent a hydrogen atom or an alkyl group. Rb ⁷ is an alkoxy group or an ester. Shows the group.
The alkyl group indicating Rb ¹ to Rb ⁶ is synonymous with the "alkyl group indicating Ra ¹ and Ra ² " described in the description of the urea solvent.
The alkoxy group and ester group indicating Rb ⁷ are synonymous with the alkoxy group and ester group exemplified as "substituents of alkyl groups indicating Ra ¹ and Ra ² " in the description of urea-based solvents.

Hereinafter, specific examples of the amide-based solvent represented by the general formula (Am1) will be shown, but the present invention is not limited thereto.

In a specific example of the amide-based solvent represented by the general formula (Am1), Me = methyl group, Et = ethyl group, nPr = n-propyl group, nBu = n-butyl group.

( ^In the general formula (Am2), Rc ¹ , Rc ² , Rc ³ , Rc ⁴ , Rc ⁵ , Rc ⁶ , Rc ⁷ , and Rc ⁸ each independently represent a hydrogen atom or an alkyl group. , Alkyl group, or ester group.
The alkyl group indicating Rc ¹ to Rc ⁸ is synonymous with the "alkyl group indicating Ra ¹ and Ra ² " described in the description of the urea solvent.
The alkoxy group and ester group indicating Rc ⁹ are synonymous with the alkoxy group and ester group exemplified as "substituents of alkyl groups indicating Ra ¹ and Ra ² " in the description of urea-based solvents.

Hereinafter, specific examples of the amide-based solvent represented by the general formula (Am2) will be shown, but the present invention is not limited thereto.

In a specific example of the amide solvent represented by the general formula (Am2), Me = methyl group, Et = ethyl group, and nPr = n-propyl group.

Among these, 3-methoxy-N, as an amide-based solvent containing an alkoxy group or an ester group, is used from the viewpoints of storage stability of the resin composition, break durability, resistance retention and cleaning maintainability of the transfer belt. N-dimethylpropanamide (exemplified compound B-4), 3-n butoxy-N, N-dimethylpropanamide (exemplified compound B-7), 5-dimethylamino-2-methyl-5-oxo-pentanoate methyl (exemplified compound B-4). Exemplified compound C-3) is preferable, and 3-methoxy-N, N-dimethylpropanamide (exemplified compound B-4) is more preferable.

-Preferable embodiment of the specific solvent-
The solvent group A includes tetramethylurea, tetraethylurea, and 1,3-dimethyl-2-imidazolidinone from the viewpoints of storage stability of the resin composition, break durability of the transfer belt, resistance retention, and cleaning retention. , N, N-dimethylpropylene urea, 3-methoxy-N, N-dimethylpropanamide, and 3-n butoxy-N, N-dimethylpropaneamide are preferable.
These solvents have two or more nitrogen atoms, or have one nitrogen atom and an alkoxy group, and have a total of two or more methyl groups or ethyl groups bonded to the nitrogen atom. Compared to N-methyl-2-pyrrolidone, which has only one amide group nitrogen atom in one molecule, it is presumed that it easily interacts with the polyimide resin precursor or the polyamideimide resin and the affinity is improved. .. This is because the polyimide resin precursor or the polyamide imide resin has a polar group such as an amic acid structure, an imide group, and an amide group, so that the solvent and the nitrogen atom have two or more, or one nitrogen atom and an alkoxy group are used. It is presumed that this is because the methyl group or the ethyl group bonded to the nitrogen atom easily interacts with the solvent having two or more in total.
Further, from the viewpoint of breaking durability, resistance retention and cleaning maintainability of the transfer belt, the solvent selected from the solvent group A is preferably 1,3-dimethyl-2-imidazolidinone. Since 1,3-dimethylimidazolidinone has a cyclic structure and a stable conformation, it is more suitable for interaction with a resin as compared with, for example, tetraethylurea which is acyclic. Presumed to be a solvent.

-Boiling point of specific solvent-
The boiling point of the specific solvent (each solvent of the solvent group A) is, for example, preferably 100 ° C. or higher and 350 ° C. or lower, more preferably 120 ° C. or higher and 300 ° C. or lower, and further preferably 150 ° C. or higher and 250 ° C. or lower.
When the boiling point of the specific solvent is 100 ° C. or higher, the solvent contained in the resin layer is suppressed from being reduced during the use of the transfer belt.
On the other hand, when the boiling point of the specific solvent is 350 ° C. or lower (particularly 250 ° C. or lower), the amount of the specific solvent contained in the resin layer after the transfer belt is manufactured is 0.005 parts by mass with respect to 100 parts by mass of the entire resin layer. It becomes easy to control within the range of 3 parts by mass or less.

-Organic solvent other than specific solvent-
The resin layer may contain an organic solvent other than the specific solvent. The organic solvent other than the specific solvent is not particularly limited, and examples thereof include known solvents (for example, aprotonic polar solvents other than the specific solvent, ether solvents, ketone solvents, ester solvents, hydrocarbon solvents, etc.). Be done.
Specific examples of the organic solvent other than the specific solvent include N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylformamide, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide. , Dimethyl sulfoxide, hexamethylphosphortriamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, tetramethylene sulfone, dimethyltetramethylene sulfone, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate Aprotonic polar solvents other than specific solvents such as, etc .; Ketone solvents such as acetone, methylisobutylketone, diacetone alcohol, cyclopentanone, cyclohexanone; ethyl acetate, isobutylacetate, nbutyl acetate, npentyl acetate, lactic acid Ester-based solvents such as ethyl; hydrocarbon-based solvents such as hexane, benzene, and toluene can be mentioned.
When the resin layer contains an organic solvent other than the specific solvent, it is organic other than the above-mentioned specific solvent from the viewpoints of storage stability of the resin composition, break durability, resistance retention and cleaning maintainability of the obtained transfer belt. The content of the solvent is preferably 50% by mass or less, more preferably 30% by mass or less, based on the total mass of the specific solvent contained in the resin layer.

[Specific carbon black]
The resin layer in the present embodiment contains carbon black having a pH of 7 or less and an average primary particle size of 25 nm or less.

-PH-
The pH of the specific carbon black is 7 or less, preferably 6.8 or less, preferably 6.5 or less, from the viewpoint of breaking durability, resistance retention, and cleaning maintainability of the obtained transfer belt. Is more preferable.
The lower limit of the pH is not particularly limited, but is preferably 2.0 or more.
The pH of the specific carbon black in the transfer belt is measured by the following method. The transfer belt of interest is ground and mixed in chloroform to give a carbon black extract. The carbon black extract is analyzed using an NMR (nuclear magnetic resonance apparatus) to confirm the abundance of the acidic groups -COOH group (carboxy group) and -SO _3H (sulfonyl group). The pH is calculated from the abundance of the above acidic groups with respect to neutral (pH = 7) carbon.

-Average primary particle size-
The average primary particle size of the specific carbon black is 25 nm or less, and is preferably 5 nm or more and 25 nm or less, preferably 10 nm or more and 25 nm, from the viewpoint of breaking durability, resistance retention, and cleaning maintainability of the obtained transfer belt. The following is more preferable.
The average primary particle size of the specific carbon black contained in the resin layer is measured by the following method.
The transfer belt is cut by a microtome, a measurement sample having a thickness of 100 nm is taken, and this measurement sample is observed by a TEM (transmission electron microscope). Then, the diameter of a circle equal to the projected area of each of the 50 carbon black particles is defined as the particle diameter, and the average value thereof is defined as the average primary particle diameter.

The content of the specific carbon black in the resin layer according to the present embodiment with respect to the total mass of the polyimide resin or the polyamide-imide resin is 10% by mass or more and 80 from the viewpoint of making the conductivity of the transfer belt appropriate and improving the resistance retention. It is preferably 1% by mass or less, and more preferably 15% by mass or more and 60% by mass or less.

A commercially available product may be used as the specific carbon black. For example, Specific Black 4 (manufactured by Orion Engineered Carbons); "MONARCH1300", "MONARCH1100", "MONARCH1000", "MONARCH900", "MOGULL", "REGAL400R", etc. manufactured by Cabot Corporation are mentioned. Will be.
In addition, as channel black, "ColorBlackFW200", "ColorBlackFW2", "ColorBlackFW2V", "ColorBlackFW1", "ColorBlackFW18", "SpecialBlackBlack6", "ColorBlack6", "ColorBlack6", "ColorBlack" , "SpecialBlack4", "SpecialBlack4A", "PrintexU", "PrintexV", and the like.
These carbon blacks may be used alone or in combination of two or more.

When two or more types of carbon black are used, it is preferable that they have different conductivity from each other. As such carbon black, for example, those having different physical characteristics such as the degree of oxidation treatment, the amount of DBP oil absorbed, and the specific surface area by the BET method using nitrogen adsorption can be used. By containing two or more types of conductive powder, it is easy to obtain the effect of enhancing the mixability and dispersibility.
Here, when two or more kinds of conductive powders having different conductivitys are added, for example, the conductive powders exhibiting high conductivity are preferentially added, and then the conductive powders having low conductivity are added to have surface resistance. The rate may be adjusted.

In addition, the carbon black used can be refined. Purification is the removal of impurities mixed in during the manufacturing process, such as residual oxidizing agents, treatment agents or by-products, and other inorganic or organic impurities.
Examples of the purification method include high-temperature heat treatment of 500 ° C. or higher and 1000 ° C. or lower in an inert gas or vacuum, treatment with an organic solvent such as carbon disulfide or toluene, mixing (stirring) of an aqueous slurry, or an organic acid. A method of removing impurities by each treatment such as a mixing treatment in an aqueous solution can be adopted. As for the heat treatment of powder, treatment with an organic solvent or treatment mainly with water is preferable as a refining method from the viewpoint of handling points in the manufacturing process and large energy consumption. As the purification method, a treatment mainly containing water is particularly preferable. As the water used for purification, for example, ion-exchanged water, ultrapure water, distilled water, and ultra-filtered water are preferably used in order to prevent impurities from being mixed.

Further, in the transfer belt according to the present embodiment, carbon black grafted with various polymers may be used from the viewpoint of imparting semiconductivity to the polyimide resin or the polyamide-imide resin. The carbon black is preferably a carbon black grafted with a copolymer having a segment having a reactive group capable of reacting with a functional group on the surface of the carbon black and having a good affinity with the surface of the carbon black and another segment. .. Details of such grafted carbon black are described in, for example, Japanese Patent Application Laid-Open No. 10-120935. Further, from the viewpoint of mixing and dispersing carbon black in a nearly uniform state, carbon black grafted with a hydrophilic polymer is preferable. Examples of the hydrophilic polymer include poly (N-vinyl-2-pyrrolidone), poly (N, N'-diethylacrylamide), poly (N-vinylformamide), poly (N-vinylacetamide), and poly (N-vinyl). Phthalamide), poly (N-vinylsuccinamide), poly (N-vinylurea), poly (N-vinylpiperidone), poly (N-vinylcaprolactam), poly (N-vinyloxazolidone) and the like. Further, the carbon black may be one in which a segment having a good affinity with the surface of the carbon black is interposed when the hydrophilic polymer is grafted to the carbon black (block copolymer or the like).

The transfer belt of the present embodiment may contain a polymer dispersant, if necessary, in terms of improving the dispersibility of carbon black in the resin layer. As the polymer dispersant, a polymer dispersant having a nitrogen atom in the molecular structure is suitable from the viewpoint of better dispersing the conductive particles in the resin. Specific examples of the polymer dispersant include poly (N-vinyl-2-pyrrolidone), poly (N, N'-diethylacrylamide), poly (N-vinylformamide), and poly (N-vinyl). Acetamide), poly (N-vinylphthalamide), poly (N-vinylsuccinamide), poly (N-vinylurea), poly (N-vinylpiperidone), poly (N-vinylcaprolactam), poly (N-vinyloxazolidone) ), Etc., and examples thereof include poly (N-vinyl-2-pyrrolidone), poly (N, N'-diethylacrylamide), poly (N-vinylacetamide), and poly (N-vinylpiperidone). These polymer dispersants may be used alone or in combination of two or more.

The blending amount of the polymer dispersant is preferably 0.01 parts by mass or more and 3.0 parts by mass or less with respect to 10 parts by mass of the specific carbon black in terms of dispersibility of the specific carbon black and the like. It is more preferably 05 parts by mass or more and 2 parts by mass or less.

[Polyimide resin or polyamide-imide resin]
The resin layer according to this embodiment is a polyimide resin layer containing a polyimide resin or a resin layer containing a polyamide-imide resin.
Hereinafter, each resin will be described.

-Polyimide resin-
As the polyimide resin, a known polyimide resin can be used without particular limitation, but a polyamic acid resin which is a condensate of a tetracarboxylic acid dianhydride and a diamine compound is subjected to an imidization reaction (dehydration ring closure reaction). ) Is preferably mentioned.
The acid anhydride group in the tetracarboxylic acid dianhydride may be half-esterified by a reaction with an alcohol compound or the like.
Specifically, for the polyimide resin, for example, a tetracarboxylic acid dianhydride and a diamine compound are mixed at a molar ratio of 1: 1 and polymerized in an organic polar solvent, and then the polyamic acid is imidized. Examples thereof include the obtained polyimide resin.
The resin composition described later contains a polyamic acid before the imidization reaction, which is a precursor of the polyimide resin, and after the resin composition is applied to a mold or the like, the polyamic acid is imidized and the polyimide resin is subjected to the imidization reaction. To form.

-Manufacturing method of polyamic acid-
The method for producing a polyamic acid is not particularly limited. For example, a method of polymerizing a tetracarboxylic dianhydride and a diamine compound in a solvent containing a specific solvent to obtain a polyamic acid can be mentioned.

The reaction temperature during the polymerization reaction of the polyamic acid is, for example, preferably 0 ° C. or higher and 70 ° C. or lower, preferably 10 ° C. or higher and 60 ° C. or lower, and more preferably 20 ° C. or higher and 55 ° C. or lower. By setting the reaction temperature to 0 ° C. or higher, the progress of the polymerization reaction is promoted, the time required for the reaction is shortened, and the productivity is easily improved. On the other hand, when the reaction temperature is 70 ° C. or lower, the progress of the imidization reaction occurring in the molecule of the produced polyamic acid is suppressed, and the precipitation or gelation accompanying the decrease in the solubility of the polyamic acid is easily suppressed.
The time during the polymerization reaction of the polyamic acid may be in the range of 1 hour or more and 24 hours or less depending on the reaction temperature.

-Tetracarboxylic dianhydride-
The tetracarboxylic dianhydride is not particularly limited, and examples thereof include aromatic and aliphatic compounds.
Examples of the aromatic tetracarboxylic acid dianhydride include pyromellitic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4'-biphenyl. Sulfontetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 3,3', 4,4'- Biphenyl ether tetracarboxylic acid dianhydride, 3,3', 4,4'-dimethyldiphenylsilane tetracarboxylic acid dianhydride, 3,3', 4,4'-tetraphenylsilane tetracarboxylic acid dianhydride, 1 , 2,3,4-Frantetracarboxylic acid dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) diphenylsulfide dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) ) Diphenylsulfone dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) diphenylpropane dianhydride, 3,3', 4,4'-perfluoroisopropyridene diphthalic acid dianhydride, 3 , 3', 4,4'-biphenyltetracarboxylic acid dianhydride, bis (phthalic acid) phenylphosphinoxide dianhydride, p-phenylene-bis (triphenylphthalic acid) dianhydride, m-phenylene-bis ( Examples thereof include triphenylphthalic acid) dianhydride, bis (triphenylphthalic acid) -4,4'-diphenyl ether dianhydride, and bis (triphenylphthalic acid) -4,4'-diphenylmethane dianhydride.

Examples of the aliphatic tetracarboxylic acid dianhydride include butane tetracarboxylic acid dianhydride, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, and 1,3-dimethyl-1,2,3,4-cyclobutane. Tetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 2,3,5-tricarboxycyclopentylactanhydride, 3,5,6-tricarboxynorbonan-2-acetate dianhydride Anhydride, 2,3,4,5-tetracarboxylic acid dianhydride, 5- (2,5-dioxotetrahydrofuryl) -3-methyl-3-cyclohexene-1,2-dicarboxylic acid dianhydride, Bicyclo [2,2,2] -oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride or other aliphatic or alicyclic tetracarboxylic acid dianhydride; 1,3,3a, 4,5,9b-Hexahydro-2,5-dioxo-3-franyl) -naphtho [1,2-c] furan-1,3-dione, 1,3,3a,4,5,9b-hexahydro-5 -Methyl-5- (tetrahydro-2,5-dioxo-3-franyl) -naphtho [1,2-c] furan-1,3-dione, 1,3,3a,4,5,9b-hexahydro-8 -Methyl-5- (tetrahydro-2,5-dioxo-3-franyl) -naphtho [1,2-c] furan-1,3-dione and other aliphatic tetracarboxylic dianhydrides having an aromatic ring Can be mentioned.
As the tetracarboxylic acid dianhydride, aromatic tetracarboxylic acid dianhydride is desirable, and further, pyromellitic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 3, 3', 4,4'-biphenylsulfone tetracarboxylic acid dianhydride, is most desirable.
These tetracarboxylic dianhydrides are used alone or in combination of two or more.

-Diamine compound-
The diamine compound is not particularly limited as long as it is a diamine compound having two amino groups in its molecular structure.
Examples of the diamine compound include p-phenylenediamine, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylethane, 4,4'-diaminodiphenyl ether, and 4,4'-diaminodiphenyl sulfide. , 4,4'-Diaminodiphenylsulfone, 1,5-diaminonaphthalene, 3,3-dimethyl-4,4'-diaminobiphenyl, 5-amino-1- (4'-aminophenyl) -1,3,3 -Trimethylindan, 6-amino-1- (4'-aminophenyl) -1,3,3-trimethylindan, 4,4'-diaminobenzanilide, 3,5-diamino-3'-trifluoromethylbenzanilide , 3,5-Diamino-4'-trifluoromethylbenzanilide, 3,4'-diaminodiphenyl ether, 2,7-diaminofluorene, 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- (4- (4- (4- (4- (4-) Aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 1,4-bis (4-aminophenoxy) benzene, 4,4'-bis (4-amino) Phenoxy) -biphenyl, 1,3'-bis (4-aminophenoxy) benzene, 9,9-bis (4-aminophenyl) fluorene, 4,4'-(p-phenylene isopropylidene) bisaniline, 4,4' -(M-Phenylisopropyridene) bisaniline, 2,2'-bis [4- (4-amino-2-trifluoromethylphenoxy) phenyl] hexafluoropropane, 4,4'-bis [4- (4-amino) -2-Trifluoromethyl) phenoxy] -aromatic diamines such as octafluorobiphenyl; aromatics having two amino groups bonded to an aromatic ring such as diaminotetraphenylthiophene and heteroatoms other than the nitrogen atom of the amino groups. Group diamines; 1,1-methoxylylene diamine, 1,3-propanediamine, tetramethylenediamine, pentamethylenediamine, octamethylenediamine, nona Methylenediamine, 4,4-diaminoheptamethylenediamine, 1,4-diaminocyclohexane, isophoronediamine, tetrahydrodicyclopentadiene diamine, hexahydro-4,7-methanoin danirange methylenediamine, tricyclo [6,2 , 1,0 ^2.7 ] -Undecylenedimethyldiamine, aliphatic diamines such as 4,4'-methylenebis (cyclohexylamine), alicyclic diamines and the like.

As the diamine compound, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylsulfide, and 4,4'-diaminodiphenylsulfone are desirable.
These diamine compounds may be used alone or in combination of two or more.
The number average molecular weight of the polyimide resin is preferably 10,000 or more and 45,000 or less. When the number average molecular weight is 10,000 or more, the film forming property is good. Further, when it is 45,000 or less, the dispersibility of the conductive particles, the formability as a transfer belt, the thickness accuracy and the like can be improved.
The number average molecular weight of the polyimide resin is sampled at the time of resin synthesis, measured by a gel permeation chromatograph (GPC) using a calibration curve of standard polyethylene, and the synthesis is continued until the desired number average molecular weight is reached. This is controlled within the above range.

-Polyamide-imide resin-
As the polyamide-imide resin, a known polyamide-imide resin can be used without particular limitation, but as a raw material for obtaining the polyamide-imide resin, a trivalent carboxylic acid component having an acid anhydride group (tricarboxylic acid) is generally used. A condensate of the acid component) and diisocyanate or diamine is preferable. The acid anhydride group in the tricarboxylic acid component may be half-esterified by a reaction with an alcohol compound or the like.

As a raw material for obtaining a polyamide-imide resin, a trivalent carboxylic acid component (tricarboxylic acid component) having an acid anhydride group and a diisocyanate or a diamine are generally used. As the trivalent carboxylic acid component, trimellitic acid anhydride is preferable in terms of flexibility, storage stability and cost. Further, the trimellitic acid anhydride and a derivative of a trivalent carboxylic acid having an acid anhydride group that reacts with another isocyanate group or an amino group are used in combination. Preferred structures include those represented by the following formula (1).

In the formula (1), R represents hydrogen, an alkyl group having 1 or more and 10 or less carbon atoms, and a phenyl group, and X represents -CH _2- , -CO-, -SO _2- , or -O-.

In addition to these, if necessary, tetracarboxylic acid dianhydride (pyromellitic acid dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic acid dianhydride, 3,3', 4 , 4'-biphenyltetracarboxylic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 2,3,5,6-pyridinetetracarboxylic acid dianhydride, 1,4,5,5 8-naphthalenetetracarboxylic acid dianhydride, 3,4,9,10-perylenetetracarboxylic acid dianhydride, 4,4'-sulfonyldiphthalic acid dianhydride, m-terphenyl-3,3', 4 , 4'-Tetracarboxylic acid dianhydride, 4,4'-oxydiphthalic acid dianhydride, 1,1,1,3,3,3-hexafluoro-2,2-bis (2,3- or 3, 4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3- or 3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis [4- (2,3- or 3) , 4-Dicarboxyphenoxy) phenyl] propane dianhydride, 1,1,1,3,3,3-hexafluoro-2,2-bis [4- (2,3- or 3,4-dicarboxyphenoxy) ) Phenyl] Propane dianhydride, 1,3-bis (3,4-dicarboxyphenyl) -1,1,3,3-tetramethyldisiloxane dianhydride, butanetetracarboxylic acid dianhydride, bicyclo-[ 2,2,2] -Octo-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, etc.), aliphatic dicarboxylic acids (succinic acid, glutaric acid, adipic acid, azelaic acid, suberic acid, etc.) Sebasic acid, decanedioic acid, dodecanedioic acid, dimer acid, etc.), aromatic dicarboxylic acid (isophthalic acid, terephthalic acid, phthalic acid, naphthalenedicarboxylic acid, oxydibenzoic acid, etc.) are used in combination.

Examples of the diisocyanate include 3,3'-dimethylbiphenyl-4,4'-diisocyanate, 2,2'-dimethylbiphenyl-4,4'-diisocyanate, biphenyl-4,4'-diisocyanate, and biphenyl-3,3'-. Diisocyanate, Biphenyl-3,4'-diisocyanate, 3,3'-diethylbiphenyl-4,4'-diisocyanate, 2,2'-diethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxybiphenyl-4 , 4'-diisocyanate, 2,2'-dimethoxybiphenyl-4,4'-diisocyanate, naphthalene-1,5-diisocyanate, naphthalene-2,6-diisocyanate and the like can be used. Further, as the diamine, a compound having the same structure as the diisocyanate and having an amino group substituted instead of the isocyanato group is used.
It should be noted that the combined use of these plurality of diisocyanates is suitable from the viewpoint of reducing density unevenness during image formation.

As the solvent used when forming the polyamide-imide resin (performing the polymerization reaction) using the above raw materials, it is preferable to use a solvent containing a specific solvent. Examples of the solvent containing the specific solvent include a solvent containing only the specific solvent and a solvent containing the specific solvent and an organic solvent other than the specific solvent.
When an organic solvent other than the specific solvent is used, the ratio of the specific solvent to the organic solvent other than the specific solvent is not limited, but the ratio of the specific solvent is 30% by mass or more (preferably 40% by mass or more, more preferably 50). Mass% or more). By setting the ratio of the specific solvent in this range, the content of the specific solvent contained in the polyamide-imide resin layer is controlled in the range of 0.005 part by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the entire polyamide-imide resin layer. It becomes easier to do.
The details of the specific solvent and the organic solvent other than the specific solvent will be described later.

The mixing ratio of the diisocyanate or diamine and the tricarboxylic acid component is, for example, 0.6 or more and 1.4 or less (preferably) as the ratio of the total number of isocyanate groups or amino groups to the total number of carboxy groups and acid anhydride groups of the acid component. Is 0.7 or more and 1.3 or less, more preferably 0.8 or more and 1.2 or less).

Examples of the method for forming the polyamide-imide resin include the following production methods.
(1) When diisocyanate is used, a method in which a diisocyanate component and a tricarboxylic acid component are used at once and reacted to obtain a polyamide-imide resin.
(2) A method for obtaining a polyamide-imide resin by reacting an excess amount of a diisocyanate component with an acid component to synthesize an amide-imide oligomer having an isocyanate group at the terminal, and then adding a tricarboxylic acid component and reacting.
(3) An amideimide oligomer having a carboxylic acid or an acid anhydride group at the terminal is synthesized by reacting an excess amount of the tricarboxylic acid component with an isocyanate component, and then the acid component and the diisocyanate component are added and reacted to form a polyamideimide resin. How to get.

When diamine is used, it can be obtained by the same production method as when diamines shown above are used. In addition, diamine and tribasic acid anhydride monochlorolide as an acid component are reacted at a low temperature for several hours. can get.

The number average molecular weight of the polyamide-imide resin thus obtained is preferably 10,000 or more and 45,000 or less. When the number average molecular weight is 10,000 or more, the film forming property is good. Further, when it is 45,000 or less, the dispersibility of the conductive particles, the formability as a transfer belt, the thickness accuracy and the like can be improved.
The number average molecular weight of the polyamide-imide resin is sampled at the time of resin synthesis, measured by a gel permeation chromatograph (GPC) using a standard polyethylene calibration curve, and the synthesis is continued until the desired number average molecular weight is reached. By doing so, it is controlled within the above range.

[Other additives]
The polyimide resin layer constituting the transfer belt according to the present embodiment may contain various fillers and the like for the purpose of imparting various functions such as mechanical strength. Further, a catalyst for promoting the imidization reaction, a leveling material for improving the quality of film formation, and the like may be included.

Examples of the filler added for improving the mechanical strength include particulate materials such as silica powder, alumina powder, barium sulfate powder, titanium oxide powder, mica, and talc. In addition, in order to improve the water repellency and releasability of the surface of the polyimide resin layer, fluororesin powder such as polytetrafluoroethylene (PTFE) or tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (PFA) is added. May be.

(Other layers)
The transfer belt according to the present embodiment may have a layer other than the resin layer. Examples of the other layer include a functional layer such as a mold release layer (fluororesin layer, silicone resin layer, etc.). Be done.

(Resin composition)
The resin composition used for forming the resin layer in the first embodiment and the resin composition according to the second embodiment are specified as a specific solvent and at least one of a polyimide resin precursor and a polyamide-imide resin. Contains carbon black.
The resin composition preferably contains the specific solvent in an amount of 5% by mass or more and 30% by mass or less, more preferably 10% by mass or more and 20% by mass or less, based on the total mass of the resin composition.
The specific solvent, the polyimide resin precursor, the polyamide-imide resin, and the specific carbon black contained in the resin composition are the specific solvent, the polyimide resin precursor, the polyamide-imide resin, and the specific carbon black in the resin layer according to the present embodiment described above. , Which is synonymous with the specific carbon black, and the preferred embodiment is also the same.
Further, the resin composition may further contain other additives contained in the resin layer.

(Characteristics of transfer belt)
[Surface resistivity]
In general, by using a belt-shaped intermediate transfer body having a large degree of freedom in design and arranging the photoconductor and the primary transfer roll at an offset, the influence on the surface potential of the photoconductor during the primary transfer is reduced. In particular, in an image forming apparatus that performs high-speed printing, an electric field is applied for a short time, and the difference in the rise of belt resistance is emphasized, which may cause density unevenness in image quality. The electrical resistance at this time is related to the surface resistance.
In a transfer belt, the rise of the surface resistivity of the belt is reduced, that is, the difference between the common logarithmic value of the surface resistivity after 10 sec of voltage application and the common logarithmic value of the surface resistivity after 30 msec (hereinafter, "surface resistivity"). The absolute value is 1.0 (LogΩ / □) or less (preferably 0.7 (LogΩ / □) or less, more preferably 0.05 (LogΩ /)). □) It is preferable to have the following values. By setting the above range, it is possible to suppress density unevenness generated in a high-speed machine and to cope with printing speeds other than high-speed printing, so that a transfer belt having a wide range of application of the device can be obtained.
The common logarithmic difference in surface resistivity is controlled by the above-mentioned type of carbon black and the method of dispersing carbon black.

The surface resistivity of the transfer belt after 30 msec of voltage application is 9 (LogΩ / □) or more and 13 (LogΩ / □) or less (preferably 10 (LogΩ / □) or more and 12 (LogΩ) or more. / □) The following) is preferable. If the common logarithmic value of the surface resistivity after 30 msec of voltage application exceeds 13 (LogΩ / □), the recording medium and the transfer belt may be electrostatically adsorbed during the secondary transfer, and the recording medium may not be peeled off. .. On the other hand, if the common logarithmic value of the surface resistivity after 30 msec of voltage application is less than 9 (LogΩ / □), the holding power of the toner image primaryly transferred to the transfer belt is insufficient, and the graininess or image distortion of the image quality is deteriorated. It may occur. The common logarithmic value of the surface resistivity after 30 msec of the voltage application is controlled by selecting the type of carbon black described above or the amount of carbon black added.

The surface resistivity is measured according to JIS K6911 (1995) using a circular electrode (for example, "UR probe" of Hi-Lester IP manufactured by Mitsubishi Yuka Co., Ltd.). The method of measuring the surface resistivity will be described with reference to the drawings. FIG. 1 is a schematic plan view (A) and a schematic cross-sectional view (B) showing an example of a circular electrode.
The circular electrode shown in FIG. 1 includes a first voltage application electrode A and a plate-shaped insulator B. The first voltage application electrode A has a columnar electrode portion C and an inner diameter larger than the outer diameter of the columnar electrode portion C, and is a cylindrical ring-shaped electrode that surrounds the columnar electrode portion C at regular intervals. A part D is provided. The measurement target T is held between the columnar electrode portion C and the ring-shaped electrode portion D of the first voltage application electrode A and the plate-shaped insulator B, and the columnar electrode portion C and the ring shape of the first voltage application electrode A are held. The current I (A) flowing when the voltage V (V) is applied between the electrode portion D and the electrode portion D is measured, and the surface resistance ρs (Ω / □) of the measurement target T is calculated by the following equation (1). To. Here, in the following formula (1), d (mm) indicates the outer diameter of the columnar electrode portion C, and D (mm) indicates the inner diameter of the ring-shaped electrode portion D. In the present embodiment, the current I (A) is measured 10 sec after the application of the voltage V (V) and 30 msec after the application.
Equation (1) ρs = π × (D + d) / (D−d) × (V / I)

More specifically, the measurement conditions of the surface resistivity are as follows.
Electrode used: Circular electrode (manufactured by Mitsubishi Yuka Co., Ltd., UR probe of Hi-Lester IP: outer diameter Φ16 mm of columnar electrode C, inner diameter Φ30 mm, outer diameter Φ40 mm of ring-shaped electrode portion D).
Measurement environment: 22 ° C / 55% RH.
Voltage: 100V.

[Volume resistivity]
The transfer belt preferably has a volume resistivity of 8 (LogΩcm) or more and 13 (LogΩcm) or less as a common logarithmic value. If the common logarithmic value of the volume resistivity is less than 8 (LogΩcm), the electrostatic force for holding the charge of the unfixed toner image transferred from the image holder to the transfer belt may become difficult to work. Therefore, the toner may be scattered around the image due to the electrostatic repulsive force between the toners or the force of the fringe electric field near the image edge, and an image having a large noise may be formed. On the other hand, when the common logarithmic value of the volume resistivity exceeds 13 (LogΩcm), the surface of the transfer belt may be charged by the transfer electric field in the primary transfer because the charge holding force is large.
The common logarithmic value of the volume resistivity is controlled by the type of carbon black and the amount of carbon black added as described above.

In this embodiment, the volume resistivity is measured according to JIS K6911 (1995) using a circular electrode (for example, UR probe of Hi-Lester IP manufactured by Mitsubishi Yuka Co., Ltd.). The measurement is performed by the same device as the surface resistivity.
The circular electrode includes a first voltage application electrode A and a second voltage application electrode B instead of the plate-shaped insulator at the time of measuring the surface resistivity. The first voltage application electrode A includes a columnar electrode portion C. The measurement target T is held between the columnar electrode portion C of the first voltage application electrode A and the second voltage application electrode B, and the columnar electrode portion C and the second voltage application electrode B of the first voltage application electrode A The current I (A) flowing when the voltage V (V) is applied is measured, and the volume resistance ρv (Ωcm) of the measurement target T is calculated by the following equation (2). Here, in the following formula (2), t indicates the thickness of the measurement target T.
Equation (2) ρv = πd ² / 4t × (V / I)

〔Young's modulus〕
The transfer belt preferably has a Young's modulus of 1000 MPa or more, and more preferably 1500 MPa or more.

Young's modulus E is calculated from the following equation (3) by measuring the force ΔS applied to the unit cross-sectional area and the elongation Δa at the unit length.
Equation (3) E = ΔS / Δa
Here, ΔS is represented by ΔS = F / (w × t) from the load F, the film thickness t of the sample, and the sample width w, and Δa is the sample reference length L and the sample elongation ΔL when the load is applied. , Δa = ΔL / L, and is measured as follows, for example.

First, the measurement target T is cut out to 80 mm × 5 mm. The Young's modulus is measured 10 times, and the average value is used as the measurement data. As a measuring machine, a tensile tester MODEL-1605N manufactured by Aiko Engineering Co., Ltd. is used, and the measuring conditions are 22 ° C. and a tensile speed of 20 mm / min in a 55% RH environment. For the belt film thickness required for calculating the belt cross-sectional area, an average value measured five times with an eddy current type film thickness meter CTR-1500E manufactured by Sanko Electronics Co., Ltd. is used.

[Thickness]
The total thickness of the transfer belt is preferably 0.05 mm or more and 0.5 mm or less (preferably 0.06 mm or more and 0.30 mm or less, more preferably 0.06 mm or more and 0.15 mm or less). When the total thickness of the belt is in the range of 0.05 mm or more and 0.5 mm or less, the mechanical strength as a transfer belt is secured, and cracks are caused by the concentration of stress on the belt surface due to deformation at the roll bending portion. Can be suppressed.

[Surface micro hardness]
In the transfer belt, the transfer surface of the transfer belt is deformed by the pressing force of the bias roller, and the hardness of the transfer surface affects the hollow character of the line image. It is preferably 30 or less (preferably 25 or less).

The surface microhardness is determined by a method of measuring how much the indenter has penetrated into the sample. When the test load P (mN) and the indenter penetration amount (pushing depth) D (μm) into the sample, the surface microhardness DH is defined by the following formula (4).
Equation (4) DH≡αP / D ²
Here, α is a constant depending on the shape of the indenter, and α = 3.8584 (in the case of an indenter used: a triangular pyramid indenter).

The surface microhardness of the transfer belt is determined by the following method. Cut the transfer belt into 5 mm square pieces, and fix the small pieces to the glass plate with instant adhesive. The surface microhardness of the surface of this sample is measured using an ultrafine hardness tester DUH-201S (manufactured by Shimadzu Corporation).
The measurement conditions are as follows.
Measurement environment: 22 ° C, 55% RH
Indenter used: Triangular pyramid indenter Test mode: 3 (Soft material test)
Test load: 0.70 gf
Load speed: 0.0145 gf / sec
Retention time: 5 sec

The transfer belt can be applied to, for example, an image forming apparatus capable of high-speed printing. The printing speed is the transfer speed of each member used in the image forming apparatus, that is, each member involved in transferring the toner image to the image holder, the transfer belt, and the recording medium in the apparatus and performing printing. It is decided together. The transfer belt can reduce density unevenness and spot-like defects even when the transport speed of each of these members is 200 mm / sec or more. Images are well formed even when the transport speed is less than 200 mm / sec.

Also, the primary transfer from the photoconductor to the transfer belt can determine the quality of the final image. It is desirable that the transfer current value is high in terms of the transfer efficiency of the primary transfer and the suppression of image distortion at the time of transfer. When the transfer speed of the transfer belt is 200 mm / sec or more, the primary transfer current value is preferably 25 μA or more, and more preferably 30 μA or more.

The transfer belt according to the present embodiment can be used for an image forming apparatus of various aspects in addition to an image forming apparatus capable of forming a color image described later, for example, an electrophotographic copying machine, a laser printer, a facsimile, and the like. It can be used for an image forming apparatus such as these composite OA devices.

<Manufacturing method of transfer belt for electrophotographic equipment>
The method for manufacturing a transfer belt for an electrophotographic apparatus according to the present embodiment includes a step of applying the above resin composition to an object to be coated (hereinafter, also referred to as a "coating step") and a specific solvent contained in the resin composition. A step of removing at least a part of the above (hereinafter, also referred to as a “drying step”) is included.
Further, the method for manufacturing a transfer belt for an electrophotographic apparatus according to the present embodiment may further include a step of heating the resin composition after the drying step (hereinafter, also referred to as a “heating step”).

(Applying process)
[Applied material]
The object to be coated is not particularly limited, and examples thereof include a cylindrical base material. A coating film is formed by applying the resin composition to the inner surface or the outer surface of the cylindrical base material.
As the cylindrical base material, for example, a cylindrical metal base material is preferably used. Instead of metal, a base material of another material such as resin, glass, or ceramic may be used. Further, a glass coat, a ceramic coat or the like may be provided on the surface of the base material, or a silicone-based or fluorine-based release agent may be applied.

[Applying method]
As a method of applying the resin composition to the surface of the cylindrical base material, for example, the outer periphery of the cylindrical mold is moved by moving the rotating cylindrical mold in the direction of the axis of rotation while discharging the resin composition from the nozzle. Examples thereof include a method of applying the composition to the surface, a dipping annular coating method of immersing the cylindrical mold in the resin composition and pulling it up, and a method of pouring the resin composition into the inner peripheral surface of the cylindrical mold in the axial direction.

-Defoaming-
Further, in order to apply the resin composition with high accuracy, it is preferable to carry out a step of defoaming the resin composition before applying the resin composition. By defoaming the resin composition, foaming during application and generation of defects in the coating film are suppressed.
Examples of the method for defoaming the resin composition include a method of defoaming a resin composition and a method of centrifuging. However, defoaming in a defoamed state is convenient and has a large defoaming ability, and is suitable.

(Drying process)
The cylindrical base material on which the resin coating film is formed is placed in a heated or vacuum environment to dry the coating film, and a dry film is formed. In the drying step, 30% by mass or more, preferably 50% by mass or more of the contained solvent is volatilized.
The drying conditions may be set so that the content of the specific solvent can be controlled to the desired amount.

(Heating process)
After forming the dry film on the substrate, the formed dry film is heated at a higher temperature.
When the resin composition contains a polyimide precursor, the polyimide precursor is imidized by the above heating to form a molded body of the polyimide resin.
When the resin composition contains a polyimide precursor, the heating conditions include, for example, heating at 150 ° C. or higher and 400 ° C. or lower (preferably 200 ° C. or higher and 300 ° C. or lower) for 20 minutes or longer and 60 minutes or lower for an imidization reaction. Occurs, and a molded body of polyimide resin is formed. During the heating reaction, the temperature may be gradually increased gradually or at a constant rate before the final temperature of heating is reached. The temperature of imidization varies depending on, for example, the type of tetracarboxylic acid dianhydride and diamine used as raw materials, and if imidization is insufficient, the mechanical and electrical properties are inferior. Set.
When the resin composition contains a polyamide-imide precursor, by heating at a higher temperature, the solvent is further volatilized in the dried film of the polyamide-imide resin to form a resin film (molded body) containing the resin. Will be done.
As the heating conditions, for example, it is preferable to heat at a temperature higher than the glass transition temperature (Tg) of the polyamide-imide resin (preferably a temperature 10 ° C. or higher and 50 ° C. or lower higher than Tg). The heating time may be, for example, 20 minutes or more and 120 minutes or less (preferably 40 minutes or more and 90 minutes or less).
In addition, in terms of controlling the content of the specific solvent, the heating temperature may be a temperature equal to or higher than the boiling point of the specific solvent. The heating time may be set so that the content of the specific solvent can be controlled to the desired amount.

The obtained polyimide resin or the resin film containing the polyamide-imide resin is peeled off by a known method such as blowing air into the gap between the cylindrical mold and the resin film.
By going through the above steps, the transfer belt according to the present embodiment can be obtained.

<Image forming device>
Hereinafter, the image forming apparatus according to the present embodiment will be described in detail with reference to the drawings.
FIG. 2 is a schematic configuration diagram showing an image forming apparatus 100 to which the transfer belt of the present embodiment is applied. The image forming apparatus 100 shown in FIG. 2 includes four toner cartridges 1, a pair of fixing rolls 2 (an example of fixing means), a backup roll (rear roll) 3, a tension roll (tension roll) 4, and a secondary transfer roll. 5 (an example of a secondary transfer means), a paper path 6, a paper tray 7, a laser generator 8 (an example of an electrostatic charge image forming means), four photoconductors 9 (an example of an image holder), and four primary transfer rolls. 10 (example of primary transfer means), drive roll 11, intermediate transfer body cleaning device 12, four charging rolls 13 (example of charging means), photoconductor cleaning device 14, developer 15 (example of developing means), intermediate transfer A belt 16 (an example of an intermediate transfer body) and the like are included as main constituent members. In the image forming apparatus 100 shown in FIG. 2, the transfer belt according to the present embodiment is used as an intermediate transfer belt 16 that functions as a toner image superimposing means and a toner image transfer means.

Next, the configuration of the image forming apparatus 100 shown in FIG. 2 will be sequentially described. First, around the photoconductor 9, a charging roll 13, a developing device 15, a primary transfer roll 10 arranged via an intermediate transfer belt 16, and a photoconductor cleaning device 14 are arranged in a counterclockwise direction, and a set of these is arranged. The members form a developing unit corresponding to one color. Further, each developing unit is provided with a toner cartridge 1 for replenishing the developing agent in the developing unit 15, and the photoconductor 9 of each developing unit is exposed to light between the charging roll 13 and the developing device 15. A laser generator 8 capable of irradiating the surface of the body 9 with a laser beam corresponding to the image information is provided.

The four developing units corresponding to the four colors (for example, cyan, magenta, yellow, and black) are arranged in series in the horizontal direction in the image forming apparatus 100, and the photoconductor 9 of the four developing units 9 An intermediate transfer belt 16 is provided so as to pass through the nip portion between the primary transfer roll 10 and the primary transfer roll 10. The intermediate transfer belt 16 is stretched on the inner peripheral side thereof by a backup roll 3, a tension roll 4, and a drive roll 11 provided counterclockwise in the following order. The four primary transfer rolls 10 are located between the tension roll 4 and the drive roll 11. Further, an intermediate transfer body cleaning device 12 for cleaning the outer peripheral surface of the intermediate transfer belt 16 is provided on the opposite side of the drive roll 11 via the intermediate transfer belt 16 so as to be in pressure contact with the drive roll 11.

Further, a toner image formed on the outer peripheral surface of the intermediate transfer belt 16 on the surface of the recording paper conveyed from the paper tray 7 to the opposite side of the backup roll 3 via the intermediate transfer belt 16 via the paper path 6. The secondary transfer roll 5 for transferring the paper is provided so as to be in pressure contact with the backup roll 3. A static elimination roll (not shown) for statically eliminating the outer peripheral surface is provided on the outer peripheral surface of the intermediate transfer belt 16 between the backup roll 3 and the drive roll 11.

Further, a paper tray 7 for stocking recording paper is provided at the bottom of the image forming apparatus 100, and the backup roll 3 and the secondary transfer roll 5 constituting the secondary transfer unit from the paper tray 7 via the paper path 6 are provided. It is supplied so as to pass through the pressure welding portion of. The recording paper that has passed through the pressure contact portion is further conveyed by a transport means (not shown) so as to pass through the pressure contact portion of the pair of fixing rolls 2, and is finally discharged to the outside of the image forming apparatus 100.

Next, an image forming method using the image forming apparatus 100 shown in FIG. 2 will be described. The toner image is formed for each developing unit, and after the surface of the photoconductor 9 rotating in the counterclockwise direction is charged by the charging roll 13, it is latent in the surface of the photoconductor 9 charged by the laser generator 8 (exposure device). An image is formed, and then this latent image is developed with a developer supplied from the developer 15 to form a toner image, and the toner image carried to the pressure contact portion between the primary transfer roll 10 and the photoconductor 9 is formed. Transfer to the outer peripheral surface of the intermediate transfer belt 16 rotating in the X direction of the arrow. After the toner image is transferred to the photoconductor 9, the toner, dust, and the like adhering to the surface of the photoconductor 9 are cleaned by the photoconductor cleaning device 14 to prepare for the formation of the next toner image.

The toner images developed for each development unit of each color are sequentially superposed on the outer peripheral surface of the intermediate transfer belt 16 so as to correspond to the image information, and are carried to the secondary transfer unit by the secondary transfer roll 5. It is transferred from the paper tray 7 to the surface of the recording paper conveyed via the paper path 6. The recording paper on which the toner image is transferred is further fixed by being pressurized and heated when passing through the pressure contact portion of the pair of fixing rolls 2 constituting the fixing portion, and after the image is formed on the surface of the recording medium. , Is discharged to the outside of the image forming apparatus 100.

The intermediate transfer belt 16 that has passed through the secondary transfer portion further advances in the direction of arrow X, and after the outer peripheral surface is statically eliminated by a static elimination roll (not shown), the outer peripheral surface is further cleaned by the intermediate transfer member cleaning device 12, and then the next Prepare for the transfer of the toner image of.

As the photoconductor 9 (an example of an image holder), a conventionally known one can be used, and as the photosensitive layer thereof, a known one such as an organic substance or amorphous silicon is used. Organic ones are preferable from the viewpoint of image stability. When the image holder is cylindrical, it can be obtained by a known manufacturing method such as extruding aluminum or an aluminum alloy and then surface-treating it. A belt-shaped image holder is also used.

The charging roll 13 (an example of charging means) is not particularly limited, and is, for example, a contact type charger using a conductive or semi-conductive roller, a brush, a film, a rubber blade, or the like, and scorotron charging using a corona discharge. Examples thereof include chargers known per se, such as vessels and corotron chargers. Among these, the contact type charger is preferable because it is excellent in charge compensation ability. The charging means may apply a direct current to the electrophotographic photosensitive member, or may further superimpose an alternating current on the charging means.

The laser generator 8 (exposure device) (an example of the static charge image forming means) is not particularly limited, and the surface of the photoconductor 9 is, for example, a light source such as a semiconductor laser light, an LED light, or a liquid crystal shutter light, or these. Examples thereof include an optical system device capable of exposing a predetermined image from a light source of the above through a polygon mirror.

The developer 15 (an example of developing means) may be selected according to the purpose. For example, a known developer that develops by contacting or non-contacting a one-component developer or a two-component developer with a brush, a roller, or the like can be mentioned.

Examples of the primary transfer roll 10 (an example of the primary transfer means) include a contact type transfer charger using a belt, a roller, a film, a rubber blade, etc., a scorotron transfer charger using corona discharge, a corotron transfer charger, and the like. Examples thereof include transfer chargers known per se. Among these, the contact type transfer charger is preferable because it is excellent in transfer charge compensation ability. In addition to the transfer charger, a peeling charger or the like may be used in combination.

Examples of the secondary transfer roll 5 (an example of the secondary transfer means) include a contact type transfer charger, a scorotron transfer charger, a corotron transfer charger, and the like. Among these, a contact type transfer charger is preferable as in the primary transfer means. When the image is strongly pressed by a contact type transfer charger such as a transfer roll, the transfer state of the image is maintained in a good state. Further, when a contact type transfer charger such as a transfer roll is pressed at the position of a roller that guides the intermediate transfer belt 16, the action of transferring the toner image from the intermediate transfer belt 16 to the transferred object (paper) is in a good state. It is done in.

The fixing roll 2 (an example of the fixing means) is not particularly limited, and examples thereof include a fixing device known per se, such as a thermal roller fixing device and an oven fixing device.
Further, the cleaning means is not particularly limited, and a cleaning device or the like known per se may be used.

Further, it is also preferable to install an optical static elimination means. Examples of the optical static elimination means include tungsten lamps and LEDs, and examples of the light quality used in the optical static elimination process include white light such as tungsten lamps and red light such as LED light. The irradiation light intensity in the photostatic elimination process is set to be, for example, several times to 30 times the amount of light indicating the half-exposure sensitivity of the electrophotographic photosensitive member.

<Transfer belt unit>
Examples of the transfer belt unit according to the present embodiment include a transfer belt according to the present embodiment and a plurality of rolls on which the transfer belt is hung under tension.

For example, as an example of the transfer belt unit according to the present embodiment, the transfer belt unit shown in FIG. 3 may be used.
FIG. 3 is a schematic perspective view showing a transfer belt unit according to the present embodiment.
As shown in FIG. 3, the transfer belt unit 130 according to the present embodiment includes the transfer belt 30 according to the present embodiment. For example, the transfer belt 30 has a drive roll 131 and a driven roll arranged to face each other. It is hung under tension by 132.
Here, in the transfer belt unit 130 according to the present embodiment, when the transfer belt 30 is applied as an intermediate transfer body, the toner image on the surface of the photoconductor (image holder) is transferred to the transfer belt 30 as a roll supporting the transfer belt 30. A roll for primary transfer and a roll for secondary transfer of the toner image transferred on the transfer belt 30 to a recording medium may be arranged on the roll.
The number of rolls that support the transfer belt 30 is not limited, and may be arranged according to the mode of use. The transfer belt unit 130 having the above configuration is incorporated in the device and used, and rotates in a state where the transfer belt 30 is also supported as the drive roll 131 and the driven roll 132 rotate.

Examples will be described below, but the present invention is not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" are all based on mass.

<Synthesis example A>
(Preparation of Polyimide Precursor-Containing Resin Composition A-1)
A 1,3-dimethyl-2-imidazolidinone (DMI) solution of a polyamic acid consisting of 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (BPDA) and p-phenylenediamine (PDA). (Resin content, 18% by mass) and carbon black (SPECIAL BLACK4, pH3, average particle size 25 nm) manufactured by Evonik Degusa Japan Co., Ltd.) so as to be 23 parts by mass with respect to 100 parts by mass of the polyimide resin solid content. Add, use a collision-type disperser (GeneusPY manufactured by Genus), divide into two with a minimum area of 1.4 mm ² at a pressure of 200 MPa, collide, pass through the path of dividing into two again five times, mix, and carbon black. A dispersed polyamic acid solution (polyimide precursor-containing resin composition A-1) was obtained.

(Preparation of Polyimide Precursor-Containing Resin Composition A-2)
Similar to the preparation of A-1, the polyimide precursor-containing resin composition A-, except that the carbon black was changed to carbon black (Printex U, manufactured by Evonik Degussa Japan, particles 25 nm, pH 4.5). 2 was prepared.

(Preparation of Polyimide Precursor-Containing Resin Composition a-1)
The above A- The polyimide precursor-containing resin composition a-1 was prepared in the same manner as in the preparation of 1.

(Preparation of Polyimide Precursor-Containing Resin Composition a-2)
The polyimide precursor-containing resin composition a-3 was used in the same manner as in the preparation of A-1 above, except that the carbon black was changed to carbon black (PrintexXE2, manufactured by Evonik Degussa Japan, particle diameter 30 nm, pH 8.0). Prepared.

(Preparation of Polyimide Precursor-Containing Resin Composition a-3)
A polyimide precursor-containing resin composition a-3 was prepared in the same manner as in A-1 above, except that carbon black was changed to carbon black (model number REGAL330, CABOT, particle diameter 25 nm, pH 9.0). did.

(Preparation of Polyimide Precursor-Containing Resin Composition a-4)
Polyimide precursor-containing resin composition a-4, as in the preparation of A-1, except that the carbon black was changed to carbon black (Printex 150T, manufactured by Evonik Degussa Japan, particle diameter 29 nm, pH 4.0). Was prepared.

(Preparation of Polyimide Precursor-Containing Resin Composition a-5)
A polyimide precursor-containing resin composition A-2 was prepared in the same manner as in A-1 above, except that the solvent was changed from DMI to N-methyl-2-pyrrolidone.

<Synthesis example B>
(Preparation of Polyamide-imide Resin-Containing Resin Composition B-1)
A four-necked flask is charged with 192.13 parts (1.0 mol equivalent) of trimellitic acid anhydride, 250.25 parts (1.0 mol equivalent) of 4,4'-diphenylmethane diisocyanate, and DMI as a solvent. The temperature was raised to 120 ° C. under a nitrogen stream, and the reaction was carried out for about 5 hours.
The number average molecular weight of the obtained polyamide-imide resin by GPC measurement was 26,000.
Then, it was diluted with DMI to adjust the viscosity to 20 Pa · s, filtered through a stainless steel 20 μm mesh, and then defoamed under reduced pressure (0.02 MPa) for 12 hours to obtain a polyamide-imide resin-containing resin composition B. I got -1.

(Preparation of Polyimide Precursor-Containing Resin Composition B-2)
Similar to the preparation of B-1, the polyimide precursor-containing resin composition B-, except that the carbon black was changed to carbon black (Color Black FW1, manufactured by Evonik Degussa Japan, particle size 13 nm, pH 4.5). 2 was prepared.

(Preparation of Polyimide Precursor-Containing Resin Composition b-1)
Similar to the preparation of B-1, the polyimide precursor was changed from carbon black to carbon black (PrintexXE2, manufactured by Evonik Degussa Japan, particles 30 nm, pH 8.0) and the solvent was changed from DMI to NMP. The contained resin composition b-1 was prepared.

<Making seamless belts>
Aluminum cylindrical mold with a diameter of 168 mm, a thickness of 3 mm, a length of 450 mm, and a surface roughness of Ra 0.4 μm by blasting (silicone mold release agent on the outer peripheral surface (trade name: KS700, manufactured by Shin-Etsu Chemical Co., Ltd.)) The thickness is 0.5 mm while moving the dispenser and scraper from the end face of the mold to the outer peripheral surface at a speed of 150 min / min while rotating the mold that has been baked at 380 ° C for 1 hour at 100 rpm. After applying the resin composition shown in Table 1 below, the resin composition is heated at 120 ° C. for 30 minutes while rotating at 5 rpm, cooled to room temperature, and then heated to 300 ° C. for 2 hours to remove the solvent and convert to imide. Finally, after cooling to room temperature, the seamless belt was separated.
The obtained belt was cut to a predetermined length and mounted on a DC-IVC5575 manufactured by Fuji Xerox Co., Ltd. as an intermediate transfer belt, and resistance maintenance evaluation, cleaning maintainability evaluation, and breaking durability evaluation were carried out.
The results are shown below.

<Evaluation method>
(Evaluation of storage stability)
For the storage stability of the obtained resin composition, the solution was stored in a cool and dark place for 120 hours, the state of the solution was monitored, and the presence or absence of aggregation and gelation was evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1.
A: No aggregation or gelation was observed.
B: Slight aggregation and gelation were observed.
C: Aggregation and gelation were observed.

(Resistance maintenance evaluation)
Table 1 shows the number of sheets in which density unevenness was first observed in continuous printing. Examples in which no density unevenness was observed even when the number of sheets exceeded 200,000 were described as "more than 200,000" in Table 1. It can be said that the larger the number of sheets, the better the resistance retention of the transfer belt.

(Cleaning maintainability evaluation)
Table 1 shows the number of sheets for which cleaning defects were first found in continuous printing. An example in which no cleaning defect was found even if the number of sheets exceeded 200,000 was described as "more than 200,000" in Table 1. It can be said that the larger the number of sheets, the better the cleaning maintainability of the transfer belt.

(Evaluation of breaking durability)
Table 1 shows the number of sheets in which the transfer belt was first found to be broken in continuous printing. An example in which no breakage of the transfer belt was observed even if the number of sheets exceeded 200,000 was described as "more than 200,000" in Table 1. It can be said that the larger the number of sheets, the better the breaking durability of the transfer belt.

In Table 1, the name of the resin composition used is entered in the "resin composition" column, and the type of resin contained in the formed resin layer is entered in the "resin type" column of "CB-pH". The column contains the pH of the carbon black contained in the resin layer, the column "CB-particle size" contains the average primary particle size of the carbon black contained in the resin layer, and the column "solvent type" contains the pH. In the column of "Amount of solvent", the content of the solvent described in "Type of solvent" with respect to the total mass of the resin layer is described. Cut off the transfer belt, hold it at 350 ° C / 2 hours with a thermal analysis DTG (manufactured by Shimadzu Corporation), and measure the weight loss.

The abbreviations in Table 1 are as follows.
-PI: Polyimide resin-PAI: Polyamideimide resin-DMI: 1,3-dimethyl-2-imidazolidinone-NMP: N-methylpyrrolidone

1 Toner cartridge 2 Fixing roll 3 Backup roll 4 Tension roll 5 Secondary transfer roll 6 Paper path 7 Paper tray 8 Laser generator (an example of static charge image forming means)
9 Photoreceptor (example of image holder)
10 Primary transfer roll (an example of primary transfer means)
11 Drive roll 12 Intermediate transfer member cleaning device 13 Charging roll (an example of charging means)
14 Photoreceptor cleaning device 15 Developer (an example of developing means)
16 Intermediate transfer belt (an example of an intermediate transfer body)
30 Transfer belt 100 Image forming device 130 Transfer belt unit 131 Drive roll 132 Driven roll

Claims (6)

It has a polyimide resin layer or a polyamide-imide resin layer containing a solvent which is a urea-based solvent and carbon black having a pH of 7 or less and an average primary particle diameter of 25 nm or less .
The polyimide resin layer or the polyamide-imide resin layer contains a solvent which is 0.05% by mass or more and 2.0% by mass or less of the urea-based solvent with respect to the total mass of the polyimide resin layer or the polyamide-imide resin layer. ,
Transfer belt for electrophotographic equipment. A cured product of a resin composition containing a solvent which is a urea-based solvent, at least one of a polyimide resin precursor and a polyamide-imide resin, and carbon black having a pH of 7 or less and an average primary particle size of 25 nm or less. Has a resin layer that is
The resin layer contains a solvent which is the urea solvent in an amount of 0.05% by mass or more and 2.0% by mass or less with respect to the total mass of the resin layer.
Transfer belt for electrophotographic equipment. Claim that the solvent which is the urea-based solvent is at least one selected from the solvent group consisting of tetramethylurea, tetraethylurea, 1,3-dimethyl-2-imidazolidinone, and N, N-dimethylpropylene urea. 1 or the transfer belt for an electrophotographic apparatus according to claim 2. The transfer belt for an electrophotographic apparatus according to claim 1 or 2, wherein the solvent which is the urea solvent is 1,3-dimethyl-2-imidazolidinone. An image forming apparatus comprising the transfer belt for an electrophotographic apparatus according to any one of claims 1 to 4. A transfer belt unit comprising the transfer belt for an electrophotographic apparatus according to any one of claims 1 to 4, and a plurality of rolls for passing the transfer belt under tension.

Images