JP5910223B2 - Polyamic acid composition, endless belt, method for producing the same, and image forming apparatus - Google Patents

Description

  The present embodiment relates to a polyamic acid composition, an endless belt, a manufacturing method thereof, and an image forming apparatus.

  In an image forming apparatus using an electrophotographic method, conventionally, an electrostatic latent image is formed on an image carrier such as an electrophotographic photosensitive member, the electrostatic latent image is developed with toner, and the obtained toner image is transferred to an endless belt. 2. Description of the Related Art Image forming apparatuses are known that form an image after electrostatically transferring (primary transfer process) onto an intermediate transfer belt, and then transferring again to a transfer medium such as transfer paper (secondary transfer process). . In particular, an intermediate transfer belt is preferably used in an image forming apparatus of a system (tandem system) that obtains a full color image by superimposing different color toner images. In this type of image forming apparatus, a conductive intermediate transfer belt having conductivity has been widely used.

As such a belt, an endless belt made of polyimide resin is used because of its mechanical strength, elasticity, creep resistance, and the like.
For example, Patent Document 1 discloses that a polyamic acid composition in which carbon black having a pH of less than 7 is dispersed in a solution containing a polyamic acid having an amino group at a molecular end and a solvent is used as a polyimide precursor. Has been.
Further, for example, Patent Document 2 includes at least two layers of an inner layer and an outer layer laminated on the outer peripheral surface side of the inner layer, which are used in an electrophotographic image forming apparatus. Discloses an annular body in which the content of carbon black contained per unit volume is less than the content of carbon black contained per unit volume in the inner layer.
Furthermore, for example, Patent Document 3 has at least two layers of an outer layer and an inner layer including a resin and conductive particles, and the inner layer is more conductive than other regions in the thickness direction. A tubular body having a high area is disclosed.

JP 2009-237157 A JP 2009-258699 A JP 2010-241123 A

  An object of the present invention is to provide a polyamic acid composition having high dispersibility of carbon black having a pH of less than 7.

The above problems are solved by the present invention described below. That is,
The invention according to claim 1 is a polyamic acid in which all terminals are amino groups, and is a terminal amino group not sealed with a carboxylic acid monoanhydride and a terminal amino group sealed with a carboxylic acid monoanhydride ratio Z / X of the total molar amount of the total molar amount of terminal amino groups which have been sealed with Luke carboxylic acid monoanhydride that against the (X) (Z) is, 0.05 ≦ Z / X ≦ 0.1 Is a polyamic acid composition, a carbon black having a pH of 10% to 80% by mass and less than pH 7 with respect to the total solid content, and a solvent.

The invention according to claim 2 is a polyamic acid which is a polymer of a carboxylic acid dianhydride and a diamine compound and which is not end-capped with a carboxylic acid monoanhydride, and has a terminal amino group and a terminal carboxy group The polyamic acid in which the ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the compound is 0.05 ≦ Y / X <0.4;
10% by mass or more and 80% by mass or less of carbon black having a pH of less than 7 based on the total solid content,
A solvent,
Is a polyamic acid composition.

The invention according to claim 3 is the polyamic acid composition according to claim 2 , wherein the ratio Y / X is 0.1 ≦ Y / X <0.4.

The invention according to claim 4, a first layer formed by using a polyamic acid composition according to any one of claims 1 to 3 on the first layer, provided adjacent to the first layer And an endless belt having a second layer containing polyimide.

The invention which concerns on Claim 5 apply | coats the 1st polyimide precursor solution containing the polyamic acid composition of any one of Claims 1-3 on the surface of a core body, and applies a 1st coating film. A first coating step to be formed;
A first drying step of removing the solvent so that the amount of residual solvent in the first coating film is 10% by mass or more and 50% by mass or less;
A second polyimide precursor solution is applied to the first coating film having a residual solvent amount of 10% by mass or more and 50% by mass or less to form a second coating film adjacent to the first coating film. A second coating step,
A second drying step for removing the solvent of the second coating film;
The first coating film and the second coating film are heated, the polyimide precursor in the first coating film and the polyimide precursor in the second coating film are imidized, and the first layer And a heating step in which the second layer forms an adjacent endless belt;
Extracting the endless belt from the core;
It is a manufacturing method of the endless belt which has.

An invention according to claim 6 is an image holding body,
Charging means for charging the surface of the image carrier;
Latent image forming means for forming a latent image on the surface of the image carrier;
Developing means for developing a latent image on the surface of the image carrier with toner to form a toner image;
An intermediate transfer member to which the toner image formed on the surface of the image carrier is transferred;
Primary transfer means for primarily transferring the toner image formed on the surface of the image carrier to the surface of the intermediate transfer member;
Secondary transfer means for secondary transfer of the toner image transferred to the surface of the intermediate transfer member to a transfer medium;
Fixing means for fixing the toner image transferred to the recording medium;
With
5. The image forming apparatus according to claim 4 , wherein the intermediate transfer member is an endless belt.

According to the invention described in claim 1, when the polyamic acid whose all terminals are amino groups, carbon black having a pH of 10 to 80% by mass and less than pH 7 with respect to the total solid content, and a solvent, sealed with Luke carboxylic acid monoanhydride that against the total molar amount of terminal amino groups which have been sealed with the terminal amino group and a carboxylic acid monoanhydride not sealed with a carboxylic acid monoanhydride of the polyamic acid (X) Compared with the case where the ratio Z / X of the total molar amount (Z) of terminal amino groups stopped is not 0 ≦ Y / X <0.4, the dispersibility of carbon black having a pH of less than 7 is high .

According to invention of Claim 2 , when polyamic acid, 10 mass% or more and 80 mass% or less carbon black of pH <7 are included with respect to the total solid, and a solvent, the terminal amino group of polyamic acid and Dispersibility of carbon black having a pH of less than 7 compared to the case where the ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal carboxy group is not 0 ≦ Y / X <0.4 Is expensive.
According to the invention of claim 3 , the pot life of the polyamic acid composition is longer than that in the case where the ratio Y / X is 0 ≦ Y / X <0.1.

According to the invention described in claim 4, the first layer is provided adjacent to the second layer comprising a polyimide, not formed by using a polyamic acid composition according to any one of claims 1 to 3 when compared to, that to suppress unevenness of the back surface resistance of the endless belt.

According to the invention described in claim 5, in the first coating film formed by coating a first polyimide precursor solution containing a polyamic acid composition according to any one of claims 1 to 3 The solvent is dried so that the residual solvent amount is 10% by mass or more and 50% by mass or less, and the second polyimide precursor solution is applied to the first coating film having the residual solvent amount of 10% by mass or more and 50% by mass or less. As compared with the case where the second coating film adjacent to the first coating film is not formed, unevenness of the back surface resistance of the endless belt is suppressed, and adhesion between the first layer and the second layer is suppressed. To produce an endless belt with high height.

According to the invention described in claim 6 , on the first layer formed using the polyamic acid composition according to any one of claims 1 to 3 as an intermediate transfer member, Image density unevenness is suppressed as compared with a case where an endless belt having a second layer including polyimide and provided adjacent to the first layer is not used.

It is the schematic plan view (A) and schematic sectional drawing (B) which show an example of the circular electrode used for the measurement of a back surface resistivity and volume resistivity. It is a schematic diagram for demonstrating the spin coating method. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to an exemplary embodiment.

Hereinafter, embodiments of the present invention will be described.
<Polyamic acid composition of the first embodiment>
In the polyamic acid composition of the first embodiment, the ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group and terminal carboxy group (hereinafter referred to as total mol of terminal amino group) The ratio of the total molar amount (Y) of the terminal carboxy group to the amount (X) (also referred to as Y / X) is 0 ≦ Y / X <0.4, and 10% by mass with respect to the total solid content It is comprised including 80% by mass or less of carbon black having a pH of less than 7 and a solvent. However, the polyamic acid in the first embodiment is a polymer of a carboxylic acid dianhydride and a diamine compound, and is a polyamic acid that is not end-capped with a carboxylic acid monoanhydride. Further, the ratio Y / X in the first embodiment is 0.05 ≦ Y / X <0.4.
Hereinafter, carbon black having a pH of less than 7 is also referred to as “acidic carbon black”.
Dispersibility of acidic carbon black in the polyamic acid composition can be enhanced by setting the polyamic acid composition of the first embodiment to the above configuration. The reason is considered to be as follows.

Since carbon black and polyamic acid are in a relationship between an inorganic compound and a polymer that is an organic compound and generally are not compatible with each other, they are separated into an inorganic layer and a polymer layer even if they are added to a solvent. There is a tendency.
By the way, the end of the molecular chain of the polyamic acid molecule is mainly an amino group or a carboxy group, and the polyamic acid is a molecule in which both ends are amino groups, a molecule in which both ends are carboxy groups, or one end is It has an amino group and a chemical structure in which the other end is a carboxy group. Here, the ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group of the polyamic acid contained in the polyamic acid composition of the first embodiment is 0 ≦ Y / When X <0.4, that is, when the polyamic acid contained in the polyamic acid composition is a molecule having amino groups at both ends (0 = Y / X), and a polyamic acid having a carboxy group Even so, when the proportion of the terminal amino group is large (0 <Y / X <0.4), the polyamic acid is considered to have an excess of amino groups.

It is considered that the amino group of the polyamic acid that exceeds the amount of the terminal carboxy group by connecting the terminal group of the polyamic acid with more amino groups than the carboxy group forms a hydrogen bond with the acidic carbon black. It is considered that the dispersibility in the solvent of the acidic carbon black is enhanced by linking hydrogen bonds between the amino group of the polyamic acid and the acidic carbon black.
On the other hand, when the content of acidic carbon black in the polyamic acid composition exceeds 80% by mass with respect to the total solid content of the composition, the acidic carbon black aggregates regardless of the presence of the polyamic acid having a terminal amino group. Tend to. Therefore, the content of acidic carbon black needs to be 80% by mass or less, and when the content of acidic carbon black is 10% by mass to 80% by mass with respect to the total solid content in the polyamic acid composition, To increase the polyamic acid, it is considered that more amino groups are required in excess.
Therefore, in a system containing 10% by mass or more and 80% by mass or less of acidic carbon black and a solvent, the ratio Y of the total molar amount (Y) of terminal carboxy groups to the total molar amount (X) of terminal amino groups of polyamic acid Y It is considered that dispersibility of acidic carbon black in the polyamic acid composition is enhanced by setting / X to 0 ≦ Y / X <0.4.

  However, if the polyamic acid has too many amino groups, the functional group of acidic carbon black and the amino group of the polyamic acid are considered to form a stronger structure over time, and the viscosity of the polyamic acid composition tends to increase over time. Therefore, the ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group of the polyamic acid is preferably 0.1 ≦ Y / X <0.4. . Thereby, the pot life of a polyamic acid composition becomes long.

  Hereinafter, the components of the polyamic acid composition of the first embodiment will be described.

[Polyamic acid]
In the polyamic acid composition of the first embodiment, the ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group is 0 ≦ Y / X <0.4. Contains polyamic acid. The “terminal carboxy group” includes a terminal anhydrous carboxy group obtained by dehydrating two carboxy groups.
Polyamic acid is a precursor of polyimide, and is a polymer compound having an amide bond (—NH—CO—) and a carboxy group in the same repeating unit.
The polyamic acid according to the first embodiment only needs to have an amino group at the end of the molecular chain (main chain) containing at least one repeating unit having an amide bond and a carboxy group, and the polyamic acid. If the ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group in all the polyamic acids in the composition is within a range where 0 ≦ Y / X <0.4. For example, you may have a carboxy group in the terminal of the molecular chain (main chain) containing the repeating unit which has an amide bond and a carboxy group. Moreover, the main chain part of polyamic acid will not be restrict | limited especially if it is a structure containing the repeating unit in which an amide bond and a carboxy group coexist.

  As described above, the polyamic acid is mainly composed of a polyamic acid having both amino groups at both ends (hereinafter also referred to as “DA”) and a polyamic acid having both ends having a carboxy group (hereinafter also referred to as “DC”). It is divided into polyamic acid (hereinafter also referred to as “AC”) in which one terminal is an amino group and the other terminal is a carboxy group.

Here, the total molar amount (X) of terminal amino groups in all the polyamic acids in the polyamic acid composition is when all types of polyamic acids of DA, DC, and AC are contained in the polyamic acid composition , And the total molar amount of the terminal amino group present at both ends of DA and the terminal amino group present at one end of AC. That is, the total molar amount (X) of the terminal amino group refers to the total terminal amino group amount (molar amount) of the polyamic acid having a terminal amino group in the polyamic acid composition.
The total molar amount (X) of the terminal amino group is measured by neutralizing and titrating the polyamic acid composition with an acid (for example, hydrochloric acid or the like).

The same applies to the total molar amount (Y) of terminal carboxy groups in all polyamic acids in the polyamic acid composition.
The total molar amount (Y) of the terminal carboxy group is the terminal carboxy group present at both ends of the DC when the polyamic acid composition contains all kinds of DA, DC, and AC polyamic acids, and , Refers to the total molar amount of terminal carboxy groups present at one end of AC. That is, the total molar amount (Y) of the terminal carboxy group refers to the total terminal carboxy group amount (molar amount) of the polyamic acid having the terminal carboxy group in the polyamic acid composition.
The total molar amount (Y) of the terminal carboxy group is measured by neutralizing and titrating the polyamic acid composition with a base (for example, sodium hydroxide).

The ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group is the ratio of X and Y obtained from the above two neutralization titrations.
Y / X is preferably 0 ≦ Y / X <0.4, and more preferably 0 ≦ Y / X ≦ 0.3, from the viewpoint of dispersibility of the acidic carbon black. On the other hand, Y / X is preferably 0.1 ≦ Y / X <0.4, more preferably 0.2 ≦ Y / X <0.4, from the viewpoint of the pot life of the polyamic acid composition.
Moreover, content of the total polyamic acid in a polyamic acid composition shall be 10 mass% or more and 80 mass% or less with respect to the total solid content of a polyamic acid composition from a dispersible viewpoint with acidic carbon black. Is preferable, and it is more preferable that it is 20 mass% or more and 40 mass% or less.

  The range of the preferred weight average molecular weight (Mw) of the polyamic acid varies depending on the use of the polyimide obtained by heating and dehydrating condensation of the polyamic acid, and is generally from 27,000 to 39,000. For example, the polyamic acid composition Is used for the production of an endless belt used for an intermediate transfer member or the like of an image forming apparatus, it is preferably 33,000 or less, and more preferably 30,000 or less.

In general, polyamic acid is synthesized by polymerizing equimolar amounts of tetracarboxylic dianhydride or its derivative and a diamine compound, so that polyamic acid (DA) whose both ends are amino groups and both ends are A polyamic acid (DC) that is a carboxy group and a polyamic acid (AC) that is an amino group at one end and a carboxy group at the other end are DA: DC: AC = 2: 2: 1 (molar basis). It is obtained with.
As the tetracarboxylic dianhydride and diamine compound that can be used for the synthesis of polyamic acid, for example, the following may be used.

-Tetracarboxylic dianhydride-
The tetracarboxylic dianhydride is not particularly limited as long as it is a compound having two structures derived from carboxylic anhydride (—CO—O—CO—) in the molecular structure, and is aromatic or aliphatic. Any compound in the system may be used.
For example, what is shown by the following general formula (I) is mentioned.

(In the general formula (I), R is a tetravalent organic group, which is aromatic, aliphatic, cycloaliphatic, a combination of aromatic and aliphatic, or a substituted group thereof.)

  Examples of the aromatic tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-benzoenone tetracarboxylic dianhydride, 3,3 ′, 4,4. '-Biphenylsulfonetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3', 4 4′-biphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-dimethyldiphenylsilane tetracarboxylic dianhydride, 3,3 ′, 4,4′-tetraphenylsilane tetracarboxylic dianhydride , 1,2,3,4-furantetracarboxylic dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenyl sulfide dianhydride, 4,4′-bis (3,4) Dicarboxyl Noxi) diphenylsulfone dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenylpropane dianhydride, 3,3 ′, 4,4′-perfluoroisopropylidenediphthalic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, bis (phthalic acid) phenylphosphine oxide dianhydride, p-phenylene-bis (triphenylphthalic acid) dianhydride, m-phenylene-bis (Triphenylphthalic acid) dianhydride, bis (triphenylphthalic acid) -4,4′-diphenyl ether dianhydride, bis (triphenylphthalic acid) -4,4′-diphenylmethane dianhydride, and the like.

  Examples of the aliphatic tetracarboxylic dianhydride include butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4- Cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 3,5,6-tricarboxynorbonane-2-acetic acid Dianhydride, 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 5- (2,5-dioxotetrahydrofural) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride Aliphatic or cycloaliphatic tetracarboxylic dianhydrides such as bicyclo [2,2,2] -oct-7-ene-2,3,5,6-tetracarboxylic dianhydride; , , 5,9b-Hexahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro-5 Methyl-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione, 1,3,3a, 4,5,9b-hexahydro-8- Examples include aliphatic tetracarboxylic dianhydrides having an aromatic ring such as methyl-5- (tetrahydro-2,5-dioxo-3-furanyl) -naphtho [1,2-c] furan-1,3-dione. It is done.

The tetracarboxylic dianhydride is preferably an aromatic tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3, 3 ′, 4,4′-biphenylsulfonetetracarboxylic dianhydride is more preferred.
These tetracarboxylic dianhydrides may be 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 the molecular structure.
Examples of the diamine compound include p-phenylenediamine, m-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylethane, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfide. 4,4′-diaminodiphenylsulfone, 1,5-diaminonaphthalene, 3,3-dimethyl-4,4′-diaminobiphenyl, 5-amino-1- (4′-aminophenyl) -1,3,3 -Trimethylindane, 6-amino-1- (4'-aminophenyl) -1,3,3-trimethylindane, 4,4'-diaminobenzanilide, 3,5-diamino-3'-trifluoromethylbenzanilide 3,5-diamino-4′-trifluoromethylbenzanilide, 3,4′-diaminodiphenyl ether, 2 7-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-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) -biphenyl, 1,3′-bis (4-aminophenoxy) benzene, 9,9-bis 4-aminophenyl) fluorene, 4,4 ′-(p-phenyleneisopropylidene) bisaniline, 4,4 ′-(m-phenyleneisopropylidene) bisaniline, 2,2′-bis [4- (4-amino-2 -Trifluoromethylphenoxy) phenyl] hexafluoropropane, aromatic diamines such as 4,4′-bis [4- (4-amino-2-trifluoromethyl) phenoxy] -octafluorobiphenyl; diaminotetraphenylthiophene, etc. An aromatic diamine having two amino groups bonded to an aromatic ring and a hetero atom other than the nitrogen atom of the amino group; 1,1-metaxylylenediamine, 1,3-propanediamine, tetramethylenediamine, pentamethylene Diamine, Octamethylenediamine, Nonamethylenediamine, 4,4-Diaminohept Methylenediamine, 1,4-diaminocyclohexane, isophoronediamine, tetrahydrodicyclopentadienylenediamine, hexahydro-4,7-methanoindanylene methylenediamine, tricyclo [6,2,1,02.7] -undecylene Examples thereof include aliphatic diamines such as dimethyldiamine and 4,4′-methylenebis (cyclohexylamine), and alicyclic diamines.

  As the diamine compound, p-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, and 4,4'-diaminodiphenyl sulfone are preferable. These diamine compounds may be used alone or in combination of two or more.

-Combination of tetracarboxylic dianhydride and diamine compound-
The preferred combination of tetracarboxylic dianhydride and diamine compound used for the synthesis of polyamic acid is preferably a combination of aromatic tetracarboxylic dianhydride and aromatic diamine.

The solid content concentration of the polymerization system when synthesizing (polymerizing) the polyamic acid is not particularly specified, but is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 30% by mass or less.
The polymerization temperature when synthesizing the polyamic acid is preferably in the range of 0 ° C. or higher and 80 ° C. or lower.

〔solvent〕
The polyamic acid composition of the first embodiment contains at least one solvent.
The solvent also serves as a dispersion medium in which acidic carbon black is dispersed in the polyamic acid composition.
Examples of such solvents include organic polar solvents, and specifically, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide; N , N-dimethylacetamide, N, N-diethylacetamide and other acetamide solvents; N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone and other pyrrolidone solvents; phenol, o-, m-, or p- Phenolic solvents such as cresol, xylenol, halogenated phenol and catechol; ether solvents such as tetrahydrofuran, dioxane and dioxolane; alcohol solvents such as methanol, ethanol and butanol; cellosolve such as butyl cellosolve; and hexamethylphos Ruamido, and the like and γ- butyrolactone.
Among these, pyrrolidone solvents are preferable, and N-methyl-2-pyrrolidone (hereinafter also referred to as “NMP”) is more preferable.

  The solvent contained in the polyamic acid composition may be used alone or in combination of two or more. In addition, the content of the solvent in the polyamic acid composition is preferably 70% by mass or more and 80% by mass or less, and 76% by mass or more and 78% by mass with respect to the total amount of the polyamic acid composition, from the viewpoint of dispersibility of the acidic carbon black. It is more preferable that the amount is not more than mass%.

  In addition, the said organic polar solvent is used also as a polymerization solvent used when making tetracarboxylic dianhydride and a diamine compound react, and synthesize | combining a polyamic acid, The said organic polar solvent is used individually or in mixture. Is preferred. As the polymerization solvent, aromatic hydrocarbons such as xylene and toluene may be further used. The polymerization solvent for the polyamic acid is not particularly limited as long as it dissolves the polyamic acid.

[Acid carbon black]
The polyamic acid composition of the first embodiment contains carbon black (acidic carbon black) having a pH of 10 to 80% by mass and less than pH 7.
Acidic carbon black is produced by subjecting carbon black to oxidation treatment to give a carboxyl group, a quinone group, a lactone group, a hydroxyl group or the like to the surface. This oxidation treatment is an air oxidation method in which contact is made with air in a high temperature (eg, 300 ° C. or higher and 800 ° C. or lower) atmosphere, and a reaction with nitrogen oxides or ozone at room temperature (eg, 25 ° C., the same applies hereinafter). The method is performed by air oxidation at a high temperature (for example, 300 ° C. or more and 800 ° C. or less) and then by ozone oxidation at a low temperature (for example, 20 ° C. or more and 200 ° C. or less).

Specifically, acidic carbon black is produced by, for example, a contact method. Examples of the contact method include a channel method and a gas black method. Acidic carbon black can be produced by a furnace black method using gas or oil as a raw material. Further, if necessary, after performing these treatments, a liquid phase oxidation treatment with nitric acid or the like may be performed.
Acidic carbon black can be manufactured by a contact method, but is generally manufactured by a closed furnace method. In the furnace method, only carbon black having a high pH and a low volatile content is usually produced. However, the pH may be adjusted by performing the above-described liquid acid treatment. For this reason, carbon black obtained by manufacturing by the furnace method and adjusted to have a pH of less than 7 by a post-process treatment can also be applied.

The pH value of acidic carbon black is less than 7, but is preferably 4.4 or less, more preferably 4.0 or less.
Here, pH of acidic carbon black is calculated | required by adjusting the aqueous suspension of carbon black and measuring with a glass electrode. In addition, the pH of the acidic carbon black is adjusted by conditions such as the treatment temperature and treatment time in the oxidation treatment step.

  For example, the acidic carbon black preferably has a volatile component content of 1% by mass to 25% by mass, more preferably 2% by mass to 20% by mass, and more preferably 3.5% to 15%. More preferably.

  Specific examples of the acidic carbon black include “Printex 150T” (pH 4.5, volatile content 10.0%) and “Special Black 350” (pH 3.5, volatile content 2.2) manufactured by Degussa. %), “Special Black 100” (pH 3.3, volatile content 2.2%), “Special Black 250” (pH 3.1, volatile content 2.0%), “Special Black 5” (pH 3. 0, volatile content 15.0%), "Special Black 4" (pH 3.0, volatile content 14.0%), "Special Black 4A" (pH 3.0, volatile content 14.0%), " "Special Black 550" (pH 2.8, volatile content 2.5%), "Special Black 6" (pH 2.5, volatile content 18.0%), "Color Black FW200" (pH 2.5, volatile content 20) . %), “Color Black FW2” (pH 2.5, volatile content 16.5%), “Color Black FW2V” (pH 2.5, volatile content 16.5%), “MONARCH1000” (pH 2. 5, volatile content 9.5%), “MONARCH 1300” (pH 2.5, volatile content 9.5%) manufactured by Cabot, “MONARCH 1400” (pH 2.5, volatile content 9.0%) manufactured by Cabot, “ MOGUL-L "(pH 2.5, volatile matter 5.0%)," REGAL400R "(pH 4.0, volatile matter 3.5%) and the like.

  The content of the acidic carbon black in the polyamic acid composition is 10% by mass or more and 80% by mass or less, and preferably 20% by mass or more and 40% by mass or less, based on the total solid content of the composition. 22 mass% or more and 29 mass% or less is more preferable.

[Dispersant etc.]
As described above, acidic carbon black is considered to increase dispersibility by linking hydrogen bonds with terminal amino groups of polyamic acid as an excess existing in the polyamic acid composition, but further enhance dispersibility. Therefore, the polyamic acid composition may further contain a dispersant.
The dispersant that can be used for dispersing acidic carbon black may be low molecular weight or high molecular weight, and any type of dispersant selected from cationic, anionic, and nonionic types may be used. It is preferable to use a nonionic polymer as the dispersant.

-Nonionic polymer-
Nonionic polymers include poly (N-vinyl-2-pyrrolidone), poly (N, N′-diethylacrylazide), poly (N-vinylformamide), poly (N-vinylacetamide), poly (N -Vinylphthalamide), poly (N-vinylsuccinamide), poly (N-vinylurea), poly (N-vinylpiperidone), poly (N-vinylcaprolactam), poly (N-vinyloxazoline) and the like.
These nonionic polymers may be used alone or in combination of two or more. Of these, poly (N-vinyl-2-pyrrolidone) is preferable.
The compounding amount of the nonionic polymer in the polyamic acid composition is preferably 0.2 parts by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the polyamic acid.

[Method for Preparing Polyamic Acid Composition of First Embodiment]
What is necessary is just to prepare the polyamic acid composition of 1st Embodiment as follows.
First, a tetracarboxylic dianhydride and a diamine compound are polymerized in a solvent to obtain a polyamic acid solution that is a precursor of a polyimide resin. Such a polyamic acid solution is added to a poor solvent such as methanol, and once purified, the polyamic acid is precipitated in the poor solvent and reprecipitated. After the precipitated polyamic acid is filtered off, it is redissolved in a solvent in which polyamic acid such as γ-butyrolactone is dissolved to obtain a polyamic acid solution.
Next, acidic carbon black may be added to the obtained polyamic acid solution in a range of, for example, 20 parts by mass or more and 50 parts by mass or less in total with respect to 100 parts by mass of the dry mass of the polyamic acid resin.

  Furthermore, in order to improve the dispersibility of acidic carbon black, you may mix the component in a polyamic acid solution using physical methods, such as stirring with a mixer and a stirring element, a parallel roll, and ultrasonic dispersion. Furthermore, as a technique for enhancing the dispersibility of acidic carbon black, a chemical technique such as introduction of a dispersant into the polyamic acid solution is exemplified, but it is not limited thereto.

<Polyamic acid of the second embodiment>
The polyamic acid composition of the second embodiment is a polyamic acid having all amino groups as amino groups, and is sealed with a terminal amino group and a carboxylic acid monoanhydride that are not sealed with a carboxylic acid monoanhydride. the total molar amount of terminal amino groups to the total molar amount of terminal amino groups which have been sealed with Luke carboxylic acid monoanhydride that against the (X) (Z) ratio Z / X (hereinafter, sealed with a carboxylic acid monoanhydride (The ratio Z / X of the total molar amount (Z) of the terminal amino group sealed with carboxylic acid monoanhydride with respect to the total molar amount (X) of the terminal amino group not blocked) is also 0 ≦. A polyamic acid with Z / X <0.4, a carbon black of 10% by mass or more and 80% by mass or less and less than pH 7 with respect to the total solid content, and a solvent.
However, 0.05 ≦ Z / X ≦ 0.1 is applied to the ratio Z / X in the second embodiment.
By setting the polyamic acid composition to the above configuration, the dispersibility of acidic carbon black in the polyamic acid composition can be enhanced. The reason is considered to be as follows.

  The total moles of terminal amino groups that are capped with carboxylic acid monoanhydrides relative to the total molar amount (X) of terminal amino groups that are not capped with carboxylic acid monoanhydrides in a polyamic acid in which all ends are amino groups In the case where the ratio Z / X of the amount (Z) is 0 ≦ Z / X <0.4, that is, in the polyamic acid in which all the terminals contained in the polyamic acid composition are amino groups, the terminal amino group When all are not sealed with carboxylic acid monoanhydride (0 = Y / X), and even when some of the terminal amino groups are sealed with carboxylic acid monoanhydride, they are sealed with carboxylic acid monoanhydride. When the proportion of terminal amino groups that are not stopped is large (0 <Z / X <0.4), the polyamic acid is considered to be excessive in amino groups.

  Therefore, even in the polyamic acid composition of the second embodiment, for the same reason as the polyamic acid composition of the first embodiment, in the system containing 10% by mass to 80% by mass of acidic carbon black and a solvent, The ratio Z / X of the total molar amount (Z) of the terminal amino group sealed with carboxylic acid monoanhydride to the total molar amount (X) of the terminal amino group not sealed with acid monoanhydride, By setting 0 ≦ Z / X <0.4, it is considered that the dispersibility of the acidic carbon black in the polyamic acid composition is enhanced.

  However, even in the polyamic acid composition of the second embodiment, if the amino group is excessive, the polyamic acid composition is liable to increase in viscosity over time. Therefore, the polyamic acid is sealed with a carboxylic acid monoanhydride. The ratio Z / X of the total molar amount (Z) of the terminal amino group sealed with carboxylic acid monoanhydride to the total molar amount (X) of no terminal amino group is 0.1 ≦ Z / X <0. .4 is recommended. Thereby, the pot life of the polyamic acid composition of 2nd Embodiment becomes long.

Here, the polyamic acid is a polyamic acid obtained by synthesizing a polyamic acid and, if necessary, sealing with a carboxylic acid monoanhydride as in the following scheme as an example.
First, for example, tetracarboxylic dianhydride or a derivative thereof and a diamine compound are reacted in excess of the diamine compound to synthesize an all amine-terminated polyamic acid. Next, the carboxylic acid monoanhydride is reacted with the terminal amine group to seal the terminal amine group. In this way, the terminal amine group of the carboxylic acid monoanhydride is capped.

And the total molar amount (X) of the terminal amino group which is not sealed with the carboxylic acid monoanhydride in all the polyamic acids in the polyamic acid composition is both ends of the polyamic acid (DA) whose both ends are amino groups. Among the terminal amino groups present in the carboxylic acid monoanhydride, the total molar amount of terminal amino groups that have not reacted with the carboxyl group.
The total molar amount (X) of the terminal amino group is measured by neutralizing and titrating the polyamic acid composition with an acid (for example, hydrochloric acid or the like).

On the other hand, the total molar amount (Z) of the terminals in which the terminal amino groups in all the polyamic acids in the polyamic acid composition are sealed with carboxylic acid monoanhydrides is the same for both polyamic acids (DA) in which both terminals are amino groups. Of the terminal amino groups present at the terminal, the total molar amount of the terminal reacted with the carboxyl group of the carboxylic acid monoanhydride.
The total molar amount (Z) of terminals in all polyamic acids in the polyamic acid composition is measured by neutralization titration with an acid (for example, hydrochloric acid or the like).

That is, in a polyamic acid having all amino groups at the ends, the terminal amino groups are sealed with carboxylic acid monoanhydrides with respect to the total molar amount (X) of the terminal amino groups not sealed with carboxylic acid monoanhydrides. The ratio Z / X of the total molar amount (Z) is the ratio of X and Z obtained from the above measurement method.
Z / X is preferably 0 ≦ Z / X <0.4, more preferably 0 ≦ Z / X ≦ 0.3, from the viewpoint of dispersibility of acidic carbon black. On the other hand, Z / X is preferably 0.1 ≦ Z / X <0.4, more preferably 0.2 ≦ Z / X <0.4, from the viewpoint of the pot life of the polyamic acid composition.

  Here, the polyamic acid whose both ends are amino groups can be obtained by synthesizing tetracarboxylic dianhydride or its derivative and a diamine compound by polymerizing them in excess of the diamine compound.

In addition, in polyamic acid having both amino groups at both ends, the carboxylic acid monoanhydride that seals the terminal amino group has two carboxyl groups, and the two carboxy groups have undergone an intramolecular dehydration condensation reaction. Of carboxylic acid anhydride.
Specific examples of the carboxylic acid monoanhydride include phthalic anhydride, maleic anhydride, 2,3-benzophenone dicarboxylic acid anhydride, 3,4-benzophenone dicarboxylic acid anhydride, and 2,3-dicarboxyphenyl phenyl ether. Anhydride, 3,4-dicarboxyphenyl phenyl ether anhydride, 2,3-biphenyl dicarboxylic acid anhydride, 3,4-biphenyl dicarboxylic acid anhydride, 2,3-dicarboxyphenyl phenyl sulfone anhydride, 3, 4-dicarboxyphenyl phenyl sulfone anhydride, 2,3-dicarboxyphenyl phenyl sulfide anhydride, 3,4-dicarboxyphenyl phenyl sulfide anhydride, 1,2-naphthalenedicarboxylic anhydride, 2,3-naphthalenedicarboxylic Acid anhydride, 1,8-naphthalenedicarboxylic acid anhydride 1,2-anthracene dicarboxylic acid anhydride, 2,3-anthracene dicarboxylic acid anhydride, 1,9-anthracene dicarboxylic acid anhydride and the like. Among these, phthalic anhydride, it is maleic anhydride.
In addition, the usage-amount (sealing amount) of carboxylic acid anhydride is adjusted in the range from which said Z / X becomes the said range.

  Since the polyamic acid of the second embodiment described above is the same as the polyamic acid composition of the first embodiment except for the above, the description thereof is omitted.

<Endless belt>
An endless belt according to this embodiment includes a first layer formed using the polyamic acid composition according to the first or second embodiment (hereinafter referred to as this embodiment), a first layer on the first layer, It is a laminated body of at least two-layer structure provided adjacently and having a second layer containing polyimide. The endless belt may be a laminate of three or more layers in which one or more layers are further laminated in addition to the adjacent first layer and second layer.
In an endless belt having a multilayer configuration of at least two layers, the lower layer (first layer) is a layer formed using the polyamic acid composition according to this embodiment, and the upper layer (second layer) containing polyimide is the lower layer. By adopting the adjacent configuration, unevenness of the back surface resistance of the endless belt is suppressed.
The endless belt preferably has a configuration in which the first layer is the inner layer side of the endless belt and the second layer is the outer layer side of the endless belt, and the surface of the first layer opposite to the second layer side is the endless belt. It is called the back side.
The reason why the endless belt has the above-described configuration to suppress unevenness of the back surface resistance of the endless belt is not clear, but is considered to be due to the following reason.

  The polyamic acid composition that has been conventionally used for the production of laminated endless belts has a low dispersibility of carbon black in the polyamic acid composition, and makes a laminate of two or more layers using such a conventional polyamic acid composition. And carbon black sometimes agglomerated. Therefore, the carbon black aggregate layer is formed on the surface side (adjacent layer side) in the lower layer, and the polyamic acid polymer layer tends to be formed on the carbon black aggregate layer. At this time, a polymer layer of polyamic acid is present at the interface between the lower layer and the upper layer, and the carbon black is covered with the polymer layer. Therefore, it is considered that the electric resistance is uneven.

On the other hand, the polyamic acid composition according to the present embodiment is excellent in dispersibility of acidic carbon black because the terminal amino group of the polyamic acid having a terminal amino group and an acidic carbon black form a hydrogen bond. Therefore, the first layer (lower layer) formed using the polyamic acid composition according to the present embodiment is not separated into the aggregated layer of acidic carbon black and the polymer layer of polyamic acid, and the acidic carbon black is the first layer. It is thought that it is dispersed without being unevenly distributed in a part of the layer.
Therefore, it is considered that the acidic carbon black is dispersed in the first layer, the electric resistance in the layer is not uneven, and the back surface resistance unevenness of the endless belt is suppressed.
In particular, resistance unevenness in the circumferential direction of the endless belt is suppressed.
Hereinafter, the configuration of the endless belt will be described.

  The endless belt includes a first layer formed using the polyamic acid composition according to the present embodiment, and a second layer that is provided on the first layer adjacent to the first layer and includes polyimide. It is a configuration.

[First layer]
The first layer only needs to be formed using the polyamic acid composition according to the present embodiment. For example, the polyamic acid composition according to the present embodiment is applied to the core to form a coating film, and then heated and dried. Thus, any polyamic acid layer may be used. Therefore, the first layer of the endless belt is configured to contain the polyimide derived from the polyamic acid composition according to this embodiment. In the polyamic acid composition according to the present embodiment, the acidic carbon black is dispersed in the composition without being unevenly distributed. Therefore, the acidic carbon black contained in the first layer is not unevenly distributed in the first layer. Is distributed.
The preferable aspect of the polyamic acid composition according to this embodiment used for forming the first layer of the endless belt is as described above.

[Second layer]
The second layer that the endless belt has is adjacent to the first layer, as long as it contains at least polyimide, and may further contain conductive particles such as carbon black.

-Polyimide-
As the polyimide that can be contained in the second layer, one obtained from a reaction between tetracarboxylic dianhydride or a derivative thereof and a diamine compound is used.
Examples of the tetracarboxylic dianhydride or derivative thereof and the diamine compound include the compounds mentioned as compounds that can be used for the preparation of the polyamic acid composition according to this embodiment. Preferred examples and preferred combinations of tetracarboxylic dianhydride and diamine compound are the same as those used for the polyamic acid composition according to this embodiment, but polyamic that can be used to obtain the polyimide contained in the second layer. The end group species of the acid is not particularly limited.

  The second layer may further contain other polymers such as polyamide, polyamideimide, polyether ether ester, polyarylate, polyester, polyester obtained by adding a reinforcing material (so-called fiber reinforced resin).

-Conductive particles-
As the conductive particles, conductive or semiconductive powder can be used, and there is no limitation on the conductivity if a specific electric resistance can be stably obtained as a belt. For example, Ketchen black, acetylene black, Examples thereof include carbon black such as acidic carbon black, metals such as aluminum and nickel, metal oxide compounds such as tin oxide, and potassium titanate. These may be used alone or in combination, but carbon black which is advantageous in terms of price is desirable.
Here, “conductive” means that the volume resistivity is less than 10 ⁷ Ωcm. “Semiconductive” means that the volume resistivity is 10 ⁷ or more and 10 ¹³ Ωcm or less. Others are the same.

In the present embodiment, it is preferable that the surface resistance is smaller on the back surface of the endless belt, that is, the first layer side than the second layer side, and the volume resistance is larger on the first layer side than the second layer side.
From this point of view, the content of the conductive particles in the second layer is preferably smaller than the content of the conductive particles contained in the first layer. Specifically, the conductive particles in the first layer It is preferable that it is 99 mass% or less of content.

Next, the characteristics of the endless belt according to the present embodiment will be described.
−Surface resistivity−
In the endless belt according to the present embodiment, the surface resistivity of the back surface (inner peripheral surface) is preferably 9 (LogΩ / □) or more and 13 (LogΩ / □) or less as a common logarithmic value, and 10 (LogΩ / □). ) Or more and 12 (LogΩ / □) or less. When an endless belt is used as an intermediate transfer belt of an image forming apparatus, if the common logarithmic value of the surface resistivity after 10 seconds of voltage application exceeds 13 (Log Ω / □), the primary transfer member and the intermediate transfer belt are in contact with each other during primary transfer. There is a case where an image quality defect occurs due to discharge between the two. On the other hand, if the common logarithmic value of the surface resistivity after 10 seconds of voltage application is less than 9 (LogΩ / □), the retention power of the toner image primarily transferred to the intermediate transfer belt is insufficient, and the image quality graininess and image disturbance May occur.

Here, the surface resistivity is measured as follows.
The measurement was performed according to JIS K6911 using a circular electrode (for example, “UR-100 probe” of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd.). A method for 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-like insulator B. The first voltage application electrode A has a cylindrical electrode portion C and a cylindrical ring electrode having an inner diameter larger than the outer diameter of the cylindrical electrode portion C and surrounding the cylindrical electrode portion C at a constant interval. Part D is provided. A belt T is sandwiched between the cylindrical electrode portion C and ring electrode portion D in the first voltage application electrode A and the plate insulator B, and the cylindrical electrode portion C and ring electrode in the first voltage application electrode A are sandwiched between them. The current I (A) that flows when the voltage V (V) is applied between the portion D and the surface D is measured, and the surface resistivity ρs (Ω / □) of the transfer surface of the belt T is calculated by the following equation. Here, in the following formula, d (mm) indicates the outer diameter of the cylindrical electrode portion C, and D (mm) indicates the inner diameter of the ring-shaped electrode portion D.
Formula: ρs = π × (D + d) / (D−d) × (V / I)
The surface resistivity is a circular electrode (UR probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd .: outer diameter Φ16 mm of the cylindrical electrode portion C, inner diameter Φ30 mm, outer diameter Φ40 mm of the ring-shaped electrode portion D), Under a 22 ° C./55% RH environment, a voltage value of 500 V and a current value after application for 10 seconds are calculated.

-Volume resistivity-
The endless belt according to this embodiment preferably has an overall volume resistivity of 8 (Log Ωcm) or more and 13 (Log Ωcm) or less as a common logarithmic value. When an endless belt is used as an intermediate transfer belt, if the common logarithmic value of the volume resistivity is less than 8 (Log Ωcm), the electrostatic charge that holds the charge of the unfixed toner image transferred from the image carrier to the intermediate transfer belt Therefore, the toner is scattered around the image due to electrostatic repulsive force between the toners and the fringe electric field at the image edge, and an image with a large noise may be formed. On the other hand, if the common logarithmic value of the volume resistivity exceeds 13 (Log Ωcm), the charge holding power is large, so that the surface of the transfer belt is charged by the transfer electric field in the primary transfer, and thus a static elimination mechanism is required. There is a case. The common logarithmic value of the volume resistivity is controlled by the type of conductive agent and the amount of conductive agent added, which will be described later.

Here, the volume resistivity is measured as follows.
The measurement is performed according to JIS K6911 using a circular electrode (for example, UR-100 probe of Hiresta IP manufactured by Mitsubishi Yuka Co., Ltd.). A method for measuring the volume resistivity will be described with reference to the drawings. The measurement is performed with the same device as the surface resistivity. However, the circular electrode shown in FIG. 1 includes a second voltage application electrode B ′ instead of the plate-like insulator B at the time of measuring the surface resistivity. Then, the belt T is sandwiched between the cylindrical electrode portion C and the ring-shaped electrode portion D in the first voltage application electrode A and the second voltage application electrode B ′, and the cylindrical electrode portion C in the first voltage application electrode A. The current I (A) that flows when the voltage V (V) is applied between the second voltage application electrode B and the second voltage application electrode B is measured, and the volume resistivity ρv (Ωcm) of the belt T is calculated by the following equation. Here, in the following formula, t represents the thickness of the belt T.
Formula ρv = 19.6 × (V / I) × t
In addition, volume resistivity uses a circular electrode (UR probe of Hiresta IP manufactured by Mitsubishi Oil Chemical Co., Ltd .: outer diameter Φ16 mm of the cylindrical electrode portion C, inner diameter Φ30 mm of the ring-shaped electrode portion D, outer diameter Φ40 mm), Under a 22 ° C./55% RH environment, a voltage value of 500 V and a current value after application for 10 seconds are calculated.

Moreover, 19.6 shown by the said formula is an electrode coefficient for converting into a resistivity, and it is (pi) d < ² > / 4t from the outer diameter d (mm) of a cylindrical electrode part, and the thickness t (cm) of a sample. Is calculated as The thickness of the belt T is measured using an eddy current film thickness meter CTR-1500E manufactured by Sanko Electronics.

The endless belt according to the present embodiment has the above-described configuration, thereby suppressing uneven resistance on the back surface of the endless belt.
Here, the resistance unevenness of the back surface of the endless belt means that the surface resistivity of the back surface of the endless belt having a diameter of 366 mm and a width of 369 mm is measured 24 points in total, 3 points in the width direction and 8 points in the circumferential direction. In this case, the difference between the maximum value and the minimum value exceeds 0.5. That is, the endless belt according to the present embodiment has the above-described configuration, so that the maximum-minimum difference in surface resistivity on the back surface of the endless belt is 0.2 or less.

[Evaluation Method for Acidic Carbon Black Dispersibility in First Layer]
The dispersibility of acidic carbon black in the first layer of the endless belt is determined by cutting the interface between the first layer and the second layer of the endless belt with a focused ion beam (FIB), and then using a transmission electron microscope. There are a method of directly observing particles and a method of observing the presence or absence of particles from height information of an atomic force microscope (AFM) by preparing a cross section by a microtome.
For example, the interface between the first layer and the second layer of the endless belt is a layer containing no carbon black (CB) (referred to as a non-CB layer) or a layer in which carbon black is aggregated (referred to as a CB aggregated layer). These are compared by a method in which a cross section is prepared by a microtome and conducting AFM observation in a conducting mode.

Specific conditions in this method are as follows.
AFM apparatus: D3000 and Nanoscope III manufactured by Digital Instruments
・ Measurement mode: Contact mode ・ Cantilever: Au-coated conductive cantilever ・ Spring constant: 0.2 N / m
・ Applied voltage: -10V

Under the above conditions, the maximum value of the current value in each region when the sample is observed at 10 μm square is defined as the conductivity in that region. A sample is prepared by embedding a cross-sectional sample by a microtome, and a silver paste electrode is bonded in parallel to the sample depth direction to form a counter electrode of the cantilever. This sample is observed at 10 μm square to obtain conductivity and height information.
However, the above conditions and measurement methods are examples, and are not limited to the same conditions. Depending on the sample, the measurement range, applied voltage, spring constant, etc. may be changed.
The conductivity is compared based on the current image obtained by the above method and the maximum value of the current value.

<Method for producing endless belt>
In the method of manufacturing an endless belt according to this embodiment, the first layer is formed using the polyamic acid composition according to this embodiment, the second layer is formed adjacent to the first layer, and polyimide. If it is a method which can form the lamination | stacking endless belt of 2 or more layers used as the structure containing this, it will not restrict | limit.
For example, the following production methods [1] to [3] can be mentioned.
[1 (1a)] A polyamic acid composition according to this embodiment containing a polyamic acid, which is a polyimide precursor, is applied to a core and dried to form a first layer, and a polyimide precursor is formed on the first layer. A method of forming a second layer by applying a solution containing a body and drying.
[2] An endless belt for a first layer formed by applying the polyamic acid composition according to the present embodiment to a core and drying, and an endless belt that becomes a second layer containing polyimide separately prepared by the same method Are bonded to form a laminate.
[3] An endless belt to be coated with a solution containing a polyamide precursor on a core and dried to prepare a second layer, and the polyamic acid according to the present embodiment is formed on the inner peripheral surface of the endless belt. A method in which the composition is applied to a core and dried to form the first layer.

Among these, the method [1a] has good production efficiency.
Furthermore, it is preferable to manufacture an endless belt by the following method [1b] from the viewpoints of suppressing back surface resistance unevenness of the belt and adhesion between the first layer and the second layer.

That is, the manufacturing method of the endless belt according to the present embodiment is as follows:
[1b] a first coating step of applying a first polyimide precursor solution containing the polyamic acid composition according to the present embodiment to the surface of the core to form a first coating film;
A first drying step of removing the solvent so that the amount of residual solvent in the first coating film is 10% by mass or more and 50% by mass or less;
A second polyimide precursor solution is applied to the first coating film having a residual solvent amount of 10% by mass or more and 50% by mass or less to form a second coating film adjacent to the first coating film. A second coating step,
A second drying step for removing the solvent of the second coating film;
The first coating film and the second coating film are heated, the polyimide precursor in the first coating film and the polyimide precursor in the second coating film are imidized, and the first layer And a heating step in which the second layer forms an adjacent endless belt;
Extracting the endless belt from the core;
It is comprised.

  In this embodiment, in the process of manufacturing an endless belt, a film formed by applying a polyimide precursor solution, which is not completed with polyimide conversion of the polyimide precursor, is referred to as “coating film”. The “coating film” is dried and heated to complete the conversion of the polyimide precursor to polyimide, and is referred to as “layer”.

  By making the manufacturing method of the endless belt into the method shown in [1b] above, unevenness of the back surface resistance of the endless belt is suppressed, and further, an endless belt excellent in adhesiveness between the first layer and the second layer is obtained. Can be manufactured. The reason for this is not clear, but is presumed to be due to the following reason.

In the method shown in [1b], after the first coating step, the solvent is dried in the first drying step so that the residual solvent amount in the first coating film is 10% by mass or more and 50% by mass or less. Then, after the removal, the second polyimide precursor solution is applied in a state where at least 10% by mass or more of the solvent remains in at least the first coating film, and the second polyimide film adjacent to the first coating film is applied. The coating film is formed.
When the second coating film is formed, if it is dried so that the residual solvent amount in the first coating film is less than 10% by mass, a belt surface defect occurs due to overdrying. If the conductive particles in the first coating film serving as the first layer of the endless belt are aggregated, the back surface resistivity and unevenness of the endless belt are likely to occur. The conductive particles in the first coating film are aggregated because the solvent in the second polyimide precursor solution penetrates into the dried first coating film when the second coating film is formed. It is considered that a region where the conductive agent is dense is formed because the poramic acid moves in the second layer direction when the second layer is dried. When the residual solvent amount in the first coating film is 50% by mass or more, the application of the second film is affected, resulting in film thickness unevenness and belt surface property deterioration and volume resistivity unevenness. Also, the adhesion between the first layer and the second layer is poor.

  On the other hand, in the endless belt manufacturing method according to the present embodiment (the method shown in [1b]), at least the first coating film forming the first layer contains the polyamic acid composition according to the present embodiment. Formed by the containing solution. If the polyamic acid composition according to the present embodiment is used, since the polyamic acid and the acidic carbon black are bonded by hydrogen bonding, the surface of the first coating film is temporarily assumed by the solvent of the second polyimide precursor solution. Even if redissolves, it is considered that the surface of the first coating film is difficult to separate into a polymer layer and an aggregated layer of carbon black.

Furthermore, when the polyimide precursor solution for forming the second coating film is applied to the first coating film that has been dried so that the residual solvent amount in the coating film is less than 10% by mass, the first layer is overdried. Therefore, belt surface defects occur due to overdrying.
In the endless belt according to this embodiment, the first coating film forming the first layer is formed by a solution containing the polyamic acid composition according to this embodiment. If the polyamic acid composition according to the present embodiment is used, since the polyamic acid and the acidic carbon black are bonded by hydrogen bonding, the surface of the first coating film is temporarily assumed by the solvent of the second polyimide precursor solution. Even if redissolves, it is considered that the surface of the first coating film is difficult to separate into a polymer layer and an aggregated layer of carbon black.

  Therefore, it is considered that the back surface resistance unevenness of the entire endless belt that suppresses the aggregation of the first layer of carbon black and suppresses the resistance unevenness of the first layer can be suppressed.

Further, when the second coating film is formed, the residual solvent amount in the first coating film is 10% by mass or more and 50% by mass or less, so that the residual solvent amount in the first coating film is 10% by mass. Compared with the case of less than%, the adhesion between the layers is strong, and a belt having no belt surface defects can be obtained. This is presumably because entanglement of resin molecular chains is formed between the layers.
Hereinafter, the manufacturing method of the endless belt according to the present embodiment (method shown in [1b]) will be described in more detail.

-First application step-
First, a first coating film is formed by applying the first polyimide precursor solution containing the polyamic acid composition according to the present embodiment to the surface of the core (first coating step).
Details and preferred aspects of the polyamic acid composition according to this embodiment are as described above. In order to use the polyamic acid composition according to the present embodiment as the first polyimide precursor solution, the polyamic acid composition according to the present embodiment is used as it is, or the polyamic acid composition according to the present embodiment is used as the main solution. What is necessary is just to further dilute with the solvent (for example, NMP etc.) contained in the polyamic acid composition which concerns on embodiment.

Since the polyimide precursor solution in which carbon black is dispersed is a highly viscous solution, the air bubbles mixed during production do not escape naturally, and defects such as belt protrusions, dents and holes due to the air bubbles are generated by application. To do. For this reason, defoaming is desirable. It is desirable to defoam as much as possible just before application.
As the core, a cylindrical core whose inside is not hollow or a cylindrical core whose inside is hollow is used.

  The coating method of the first polyimide precursor solution on the core is not particularly limited. For example, the first polyimide precursor solution is immersed in the outer peripheral surface of the cylindrical core or the cylindrical core. The first coating film is formed endlessly using a method such as spin coating on the outer peripheral surface of the body. The method of spin coating on the inner peripheral surface of a cylindrical core can also be used. However, when forming a belt by the method described later, the method of applying a coating on the outer peripheral surface of a cylindrical core to create a coating film Since the inner circumference and the outer circumference are reversed, a method of immersing in the outer circumferential surface or a method of coating the outer circumferential surface of the cylindrical core body to form a coating film is preferable. In forming the belt, the core body is preferably subjected to mold release treatment.

  As a specific example of a method for applying the first polyimide precursor solution onto the core, a spin coating method will be described. In the spin coating method, as shown in FIG. 2, for example, a cylindrical core 11 having an outer diameter corresponding to the length of the endless belt is prepared. A nozzle 15 for discharging the first polyimide precursor solution 16 onto the outer peripheral surface of the cylindrical core body 11 is disposed at a position along the outer peripheral surface of the cylindrical core body 11. The precursor solution container 14 is connected to the precursor solution container 14, and the polyimide precursor solution container 14 is connected to the pressurizing device 17 through a pipe. A blade 18 for leveling the discharged first polyimide precursor solution 16 on the outer peripheral surface of the cylindrical core 11 is disposed below the nozzle 15.

  The cylindrical core body 11 is rotated in the direction of the rotation direction of the cylindrical core body (arrow D), and the first polyimide precursor solution 16 (inner layer coating solution) is supplied from the nozzle 15 onto the outer peripheral surface of the cylindrical core body 11. And leveled on the outer peripheral surface of the cylindrical core body 11 by the blade 18. The nozzle 15 and the blade 18 move at a constant speed in the nozzle and blade movement direction (arrow E), and the coating liquid 16 is applied on the outer peripheral surface of the cylindrical core body 11 with a constant thickness. The first polyimide precursor solution 16 is adjusted so that a predetermined amount is discharged from the nozzle 15 by the pressurizing device 17. Thus, a coating film (first coating film) of the first polyimide precursor solution 16 is formed on the outer peripheral surface of the cylindrical core body 11.

-First drying step-
Next, the first coating film applied to the cylindrical core 11 is dried (first drying step). In the main drying, the residual solvent amount of the first coating film is preferably 50% by mass or less, particularly 40% by mass or less, and desirably 36% by mass or less. When the residual solvent amount of the first coating film exceeds 50% by mass, it becomes difficult to apply the second polyimide precursor solution on the first coating film. On the other hand, the lower the amount of residual solvent, the easier it is to cause uneven distribution (increase in density) of conductive particles described later. By controlling the residual solvent amount of the first coating film, that is, the dry state of the first coating film, the degree of uneven distribution (concentration) of conductive particles described later is controlled.

  Here, the residual solvent amount indicates the ratio of the solvent mass present in the first polyimide precursor solution to the solid content (mass of solid content of resin material + mass of acidic carbon black). The method for obtaining the residual solvent amount is as follows.

  For example, when the mass of the solid content of the resin material (dry mass of the resin material) and the mass of acidic carbon black are known as the solid content, the total mass of the coating film before drying is accurately weighed, and the coating film The mass of the solvent contained in the total mass of is calculated. Thereafter, the total mass of the coating film after drying is accurately weighed, and the mass of the solvent lost before the drying is subtracted from the mass of the solvent calculated before drying as the mass of the solvent that has lost the decrease. Find the mass. From this, the mass of residual solvent / (mass of acidic carbon black + part mass of resin solid + mass of residual solvent) is calculated, and the amount of residual solvent is obtained.

  Further, the residual solvent amount may be obtained using a heat extraction gas chromatogram mass spectrometer. An example of this measurement is shown below. For example, a sample is obtained by cutting out from about 2 mg to 3 mg from the dried coating film, and the sample is weighed and then placed in a heat extraction device (PY2020D: manufactured by Frontier Laboratories) and heated to 400 ° C. Volatile components are injected into a gas chromatogram mass spectrometer (GCMS-QP2010: manufactured by Shimadzu Corporation) through an interface at 320 ° C. and quantified. That is, using helium gas as a carrier gas, 1/51 of the amount volatilized from the sample (split ratio 50: 1) is a linear velocity of 153.8 cm / second (carrier gas flow rate at a column temperature of 50 ° C., 1.50 ml / min, pressure) 50 kPa), and is injected into a column (frontier lab capillary column UA-5) having an inner diameter of 0.25 μmφ × 30 m. Subsequently, after maintaining at 50 ° C. for 3 minutes, the column was heated to 400 ° C. at a rate of 8 ° C. per minute and held at the same temperature for 10 minutes to desorb volatile components. Further, a volatile component is injected into the mass spectrometer at an interface temperature of 320 ° C., and a peak area corresponding to the solvent is obtained. The quantification was performed by preparing a calibration curve in advance with a known amount of the same solvent. The solvent mass calculated | required from this is divided by the sample mass after the said drying, and a residual solvent amount is calculated | required. However, the above measurement example is an example, and the measurement conditions may be changed depending on the decomposition or changing temperature of the resin used or the boiling point of the solvent.

-Second coating process-
Next, the 2nd polyimide precursor solution containing electroconductive particle is apply | coated on the 1st coating film dried with the amount of residual solvent as stated above, and the coating film (2nd polyimide precursor solution ( A second coating film) is formed (second coating step).
The coating method of the second polyimide precursor solution on the first coating film formed and dried on the cylindrical core body 11 is the same as that for the inner layer coating solution.

The second polyimide precursor solution is a composition containing a polyimide precursor and dissolved in a solvent to form a solution.
Here, an example of preparing a polyamic acid solution in which carbon black (conductive particles) is dispersed is illustrated as a polyimide precursor solution. First, purified carbon black is prepared and dispersed in an organic polar solvent to prepare a carbon black dispersion. As a dispersion method, a method of dispersing by a disperser or a homogenizer after preliminary stirring is desirable. As with the carbon black purification method, the mixing of fine media reduces the carbon black purification effect. Therefore, a media-free dispersion method that does not use media is desirable, especially jets that suppress dispersion of high-viscosity solutions and disperse them. A mill is preferred.

  A polyamic acid solution in which carbon black is dispersed is prepared by dissolving and polymerizing a diamine component and an acid dianhydride component in the obtained carbon black dispersion.

  In this case, the monomer concentration (concentration of the diamine component and the acid anhydride component in the solvent) is set according to various conditions, but is preferably 5% by mass or more and 30% by mass or less. The reaction temperature is preferably set to 80 ° C. or less, particularly preferably 5 ° C. to 50 ° C., and the reaction time is 5 hours to 10 hours.

  From the viewpoint of adhesion between the first coating film and the second coating film, the second polyimide precursor solution preferably has the same component composition as the first polyimide precursor solution.

-Second drying step-
Next, the second coating film applied to the surface of the first coating film is dried (second drying step). In the main drying, for example, the residual solvent amount is preferably 40% by mass or less. The amount of residual solvent is determined from the type of resin material used, the intended use of the resulting endless belt, the strength and maintainability of the obtained endless belt, and the like.
When the second coating film is thicker than the first coating film, the total energy applied to the second coating film is preferably larger than the total energy applied to the first coating film. Specifically, for example, if the drying temperature is the same, the drying time of the second coating film is preferably longer than that of the first coating film. Thereby, since the solvent of the first coating film is dried through the second coating film, the drying is performed simultaneously with the first coating film and the second coating film.

-Heating process-
After drying the first coating film and the second coating film, the first coating film and the second coating film are heated and baked (heating process), whereby an endless belt is manufactured. In order to perform this baking, that is, to convert the polyamic acid into an imide, a high temperature treatment of 200 ° C. or more is generally used. Sufficient imide conversion cannot be obtained at 200 ° C. or lower. On the other hand, high-temperature treatment is advantageous for imide conversion, and stable characteristics can be obtained.However, since heat energy is used, the thermal efficiency is low and the cost is high, so the heat treatment temperature is set in consideration of the characteristics and productivity of the transfer belt. It is necessary to decide.
By baking the first coating film and the second coating film, the polyimide precursor is converted into polyimide, and becomes a first layer containing polyimide and a second layer containing polyimide, respectively.

  By pulling out the obtained endless belt from the cylindrical core body 11, an endless belt is obtained.

  Through the above steps, the endless belt according to this embodiment is manufactured.

<Image forming apparatus>
The image forming apparatus according to the present embodiment includes an image carrier, a charging unit that charges the surface of the image carrier, a latent image forming unit that forms a latent image on the surface of the image carrier, and a surface of the image carrier. Developing means for developing a latent image with toner to form a toner image, an intermediate transfer member to which the toner image formed on the surface of the image carrier is transferred, and the toner image formed on the surface of the image carrier Primary transfer means for primarily transferring the toner image onto the surface of the intermediate transfer body, secondary transfer means for secondary transfer of the toner image transferred onto the surface of the intermediate transfer body onto the transfer medium, and the toner transferred onto the recording medium A fixing unit that fixes the image, and the intermediate transfer member is configured as the endless belt according to the present embodiment.
Details of the image forming apparatus according to the present embodiment will be described with reference to FIG. FIG. 3 is a schematic configuration diagram illustrating the image forming apparatus according to the present embodiment.

  The image forming apparatus 100 according to the present embodiment is a so-called tandem system, and is an embodiment in which the endless belt according to the present embodiment is applied as an intermediate transfer belt.

  As shown in FIG. 3, the image forming apparatus 100 according to the present embodiment sequentially includes charging devices 102 a to 102 d around the four image holding bodies 101 a to 101 d made of an electrophotographic photosensitive member in the rotation direction. Exposure devices 114a to 114d, developing devices 103a to 103d, primary transfer devices (primary transfer rolls) 105a to 105d, and image carrier cleaning devices 104a to 104d are arranged. Note that a static eliminator may be provided in order to remove residual potential remaining on the surfaces of the image carriers 101a to 101d after transfer.

  Further, an intermediate transfer belt 107 is stretched around tension rolls 106a to 106d, a drive roll 111, and a backup roll 108 to constitute a transfer unit. By these tension rolls 106a to 106d, the drive roll 111, and the backup roll 108, the intermediate transfer belt 107 is in contact with the surfaces of the image carriers 101a to 101d, and the image carriers 101a to 101d and the primary transfer rolls 105a to 105a. It can move in the direction of arrow A between 105d. A portion where the primary transfer rolls 105a to 105d come into contact with the image carriers 101a to 101d via the intermediate transfer belt 107 becomes a primary transfer portion, and a contact portion between the image carriers 101a to 101d and the primary transfer rollers 105a to 105d. A primary transfer voltage is applied to.

  Further, as a secondary transfer device, a backup roll 108 and a secondary transfer roll 109 are arranged to face each other with an intermediate transfer belt 107 interposed therebetween. The transfer medium 115 such as paper moves in the direction of arrow B between the intermediate transfer belt 107 and the secondary transfer roll 109 while contacting the surface of the intermediate transfer belt 107, and then passes through the fixing device 110. A portion where the secondary transfer roll 109 comes into contact with the backup roll 108 via the intermediate transfer belt 107 becomes a secondary transfer portion, and a secondary transfer voltage is applied to a contact portion between the secondary transfer roll 109 and the backup roll 108. . Further, intermediate transfer belt cleaning devices 112 and 113 are arranged so as to come into contact with the intermediate transfer belt 107 after transfer.

  In the full-color image forming apparatus 100 having this configuration, the image carrier 101a rotates in the direction of the arrow C and the surface thereof is uniformly charged by the charging device 102a, and then the first color is applied by the exposure device 114a such as laser light. Electrostatic latent image is formed. The formed electrostatic latent image is developed (visualized) with toner by a developing device 103a containing toner corresponding to the color to form a toner image. The developing devices 103a to 103d contain toners (for example, yellow, magenta, cyan, and black) corresponding to the electrostatic latent images of the respective colors.

  The toner image formed on the image carrier 101a is electrostatically transferred (primary transfer) onto the intermediate transfer belt 107 by the primary transfer roll 105a when passing through the primary transfer portion. Thereafter, the primary transfer rollers 105b to 105d perform primary transfer so that the second color, third color, and fourth color toner images are sequentially superimposed on the intermediate transfer belt 107 that holds the first color toner image. Finally, a full color multiple toner image is obtained.

  The multiple toner images formed on the intermediate transfer belt 107 are electrostatically collectively transferred to the transfer medium 115 when passing through the secondary transfer portion. The transfer medium 115 onto which the toner image has been transferred is conveyed to the fixing device 110, subjected to a fixing process by heating and / or pressing, and then discharged outside the apparatus.

  Residual toner is removed from the image carriers 101a to 101d after the primary transfer by the image carrier cleaning devices 104a to 104d. On the other hand, the residual toner is removed from the intermediate transfer belt 107 after the secondary transfer by the intermediate transfer belt cleaning devices 112 and 113 to prepare for the next image forming process.

(Image carrier)
As the image carriers 101a to 101d, known electrophotographic photosensitive members can be widely applied. As the electrophotographic photoreceptor, an inorganic photoreceptor having a photosensitive layer made of an inorganic material, an organic photoreceptor having a photosensitive layer made of an organic material, or the like can be used. In the organic photoconductor, a function-separated type organic photoconductor in which a charge generation layer that generates charges upon exposure and a charge transport layer that transports charges are stacked, and a function that generates charges and a function that transports charges are the same. A single layer type organic photoreceptor fulfilled by the layer is preferably used. In addition, as the inorganic photoconductor, a photoconductive layer composed of amorphous silicon is preferably used.

  The shape of the image carrier is not particularly limited, and a known shape such as a cylindrical drum shape, a sheet shape, or a plate shape is employed.

[Charging device]
The charging devices 102a to 102d are not particularly limited, and are, for example, conductive (here, “conductive” means, for example, a volume resistivity of less than 10 ⁷ Ω · cm. In this specification, special mention is made. The same is true unless otherwise specified.) Or semiconductive (here, “semiconductive” means, for example, a volume resistivity of 10 ⁷ to 10 ¹³ Ωcm. In this specification, the same applies unless otherwise specified. .) Can be widely applied to a contact charger using a roller, brush, film, rubber blade, or the like, a scorotron charger using a corona discharge, or a corotron charger. Among these, a contact charger that generates less ozone and can perform efficient charging is preferable.

  The charging devices 102a to 102d normally apply a direct current to the image carriers 101a to 101d, but an alternating current may be further superimposed and applied.

[Exposure equipment]
The exposure devices 114a to 114d are not particularly limited, and for example, on the surfaces of the image carriers 101a to 101d, light sources such as semiconductor laser light, LED light, or liquid crystal shutter light, or from these light sources through a polygon mirror. A known exposure apparatus such as an optical system apparatus that can perform exposure in a desired image manner can be widely applied.

[Development equipment]
The developing devices 103a to 103d can be selected according to the purpose. For example, a known developing device that develops a one-component developer or a two-component developer in contact or non-contact with a brush, a roller, or the like can be used.

  The toner (developer) used in the image forming apparatus 100 of the present embodiment is not particularly limited, and includes, for example, a binder resin and a colorant.

[Primary transfer roll]
The primary transfer rolls 105a to 105d may be either a single layer or a multilayer. For example, in the case of a single layer structure, it is composed of a roll in which an appropriate amount of conductive particles such as carbon black is blended in foamed or non-foamed silicone rubber, urethane rubber, ethylene-propylene-diene rubber (EPDM), or the like. The resistance value is preferably in the range of 10 ⁵ Ω to 10 ¹⁰ Ω. A voltage of 1.0 kV to 5.5 kV is applied to the primary transfer rolls 105a to 105d, and the toner is transferred by an electric field generated between the image carriers 101a to 101d.

[Image carrier cleaning device]
The image carrier cleaning devices 104a to 104d are for removing residual toner adhering to the surfaces of the image carriers 101a to 101d after the primary transfer process. In addition to the cleaning blade, brush cleaning, roll cleaning, or the like Can be used. Among these, it is preferable to use a cleaning blade. Examples of the material for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber.

[Secondary transfer roll]
The layer structure of the secondary transfer roll 109 is not particularly limited. For example, in the case of a three-layer structure, the layer structure includes a core layer, an intermediate layer, and a coating layer covering the surface. The core layer is a foamed material such as silicone rubber, urethane rubber or EPDM in which conductive particles are dispersed, and the intermediate layer is composed of these non-foamed materials. Examples of the material for the coating layer include tetrafluoroethylene-hexafluoropropylene copolymer and perfluoroalkoxy resin. The volume resistivity of the secondary transfer roll 109 is preferably 10 ⁷ Ωcm or less. A two-layer structure excluding the intermediate layer is also possible.

[Backup roll]
The backup roll 108 forms a counter electrode of the secondary transfer roll 109. The layer structure of the backup roll 108 may be either a single layer or a multilayer. For example, in the case of a single layer structure, it is composed of a roll in which a suitable amount of conductive particles such as carbon black is blended in silicone rubber, urethane rubber, EPDM or the like. In the case of a two-layer structure, it is composed of a roll in which the outer peripheral surface of the elastic layer composed of the rubber material as described above is covered with a high resistance layer. The surface resistivity of the backup roll 108 is preferably in the range of 10 ⁷ Ω / □ to 10 ¹¹ Ω / □.

  A voltage of 1 kV to 6 kV is normally applied between the shafts of the backup roll 108 and the secondary transfer roll 109. Further, instead of applying a voltage to the shaft of the backup roll 108, a voltage can be applied between the electrically conductive electrode member brought into contact with the backup roll 108 and the secondary transfer roll 109. Examples of the electrode member include a metal roll, a conductive rubber roll, a conductive brush, a metal plate, or a conductive resin plate.

[Fixing device]
As the fixing device 110, for example, a known fixing device such as a heat roller fixing device, a pressure roller fixing device, or a flash fixing device can be widely applied.

[Intermediate transfer belt cleaning device]
As the intermediate transfer belt cleaning devices 112 and 113, in addition to a cleaning blade, brush cleaning, roll cleaning, and the like can be used. Among these, it is preferable to use a cleaning blade. Examples of the material for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber.

  In the above-described embodiment, a so-called tandem image forming apparatus including a plurality of image carriers has been described. However, the present invention is not limited to this. For example, one image carrier is used and intermediate transfer is performed for the number of colors. A well-known apparatus such as a so-called multi-cycle type (for example, four-cycle type) image forming apparatus in which the belt rotates and forms an image can be applied.

  Hereinafter, although this embodiment is described using an example, this embodiment is not limited at all by these examples.

[[Example A]]
In Example A shown below, Example A2, Example A4, and Example A6 are shown as reference examples for the present invention.
<1. Preparation and Evaluation of Polyamic Acid Composition>
(Synthesis of polyamic acid)
Polyamic acid DA-A1 was synthesized as a polyamic acid in which both ends of the molecular chain are amino groups, and polyamic acid DC-A1 was synthesized as a polyamic acid in which both ends of the molecular chain were carboxy groups.

-Synthesis of polyamic acid DA-A1-
In 800 g of NMP, 83.48 g (416.9 mmol) of 4,4′-diaminodiphenyl ether (hereinafter abbreviated as “ODA”) was added as a diamine compound and dissolved while stirring at room temperature (25 ° C.). Next, 116.52 g (396.0 mmol) of 3,3 ′, 4,4′biphenyltetracarboxylic dianhydride (hereinafter abbreviated as “BPDA”) was gradually added as tetracarboxylic dianhydride. After addition and dissolution of tetracarboxylic dianhydride, the temperature of the reaction solution is heated to 60 ° C., and then the polymerization reaction is performed for 20 hours while maintaining the reaction solution temperature, and the reaction solution containing polyamic acid DA-A1 and NMP Got. The obtained reaction solution was filtered using a # 800 stainless mesh, cooled to room temperature (25 ° C.), and solution viscosity at 25 ° C. was 2.0 Pa · s (Eki rotational viscometer, manufactured by Toki Sangyo Co., Ltd.). , Using a TV-20H, with a standard rotor (1 ° 34 "× R24), measurement temperature: 25 ° C, rotation speed: 0.5 rpm (100 Pa · s or more), 1 rpm (less than 100 Pa · s) The same is true for the following synthesis example) to obtain a polyamic acid solution DA-A1.
The composition of the obtained polyamic acid DA-A1 was BPDA / ODA = 95/100 (mol / mol).

-Synthesis of polyamic acid DC-A1-
Viscosity of solution containing polyamic acid DC-A1 and NMP 6.0 Pa, as in Synthesis Example 1, except that 79.57 g (397.4 mmol) of ODA and 120.43 g (409.3 mmol) of BPDA were used. -The polyamic acid solution DC-A1 of s was obtained. The composition of the obtained polyamic acid DC-A1 was BPDA / ODA = 103/100 (mol / mol), and had the following structure.

[Preparation of polyamic acid composition A1]
-Polyamic acid solution DA-A1 containing polyamic acid DA-A1 700 g
-Polyamic acid solution DC-A1 containing polyamic acid DC-A1 300 g
・ Acid carbon black (dry state; conductive agent)
[SPECIAL BLACK4: manufactured by Degussa, pH 4.0, volatile content: 14.0% (hereinafter abbreviated as “SB-4”)] 55.6 g

  The polyamic acid solution DA-A1 and the polyamic acid solution DC-A1 having the above composition are mixed, and the acidic carbon black SB-4 is dispersed in a mixed solution of the polyamic acid solution by dispersion treatment at 30 ° C. for 12 hours in a pole mill. did. Thereafter, the mixed solution in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition A1 having the following composition.

The composition of the polyamic acid composition A1 is: polyamic acid solid content (total of polyamic acid DA-A1 and DC-A1) /NMP/SB-4=185.4/814.6/55.6 (mass ratio) there were.
The ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group in all the polyamic acids in the polyamic acid composition A1 was 0.3.
Moreover, the composition when the polyamic acid composition A1 is imide-converted, that is, the composition of the polyimide film in which the acidic carbon black produced using the polyamic acid composition A1 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Preparation of polyamic acid composition A2]
-Polyamic acid solution DA-A1 containing polyamic acid DA-A1 1000 g
・ Acid carbon black (dry state; conductive agent) [SB-4] 55.6 g

  Acidic carbon black SB-4 was added to the polyamic acid solution DA-A1 having the above composition, followed by dispersion treatment at 30 ° C. for 12 hours using a pole mill. Thereafter, the polyamic acid solution DA-A1 in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition A2 having the following composition.

The composition of the polyamic acid composition A2 was: polyamic acid (polyamic acid DA-A1) /NMP/SB-4=185.4/814.6/55.6 (mass ratio).
The ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group in all the polyamic acids in the polyamic acid composition A2 was 0.
Moreover, the composition when the polyamic acid composition A2 is imide-converted, that is, the composition of the polyimide film in which the acidic carbon black produced using the polyamic acid composition A2 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Preparation of polyamic acid composition A3]
-Polyamic acid solution DA-A1 containing polyamic acid DA-A1 800 g
-Polyamic acid solution DC-A1 200g containing polyamic acid DC-A1
・ Acid carbon black (dry state; conductive agent)
[SPECIAL BLACK4: manufactured by Degussa, pH 4.0, volatile content: 14.0% (hereinafter abbreviated as “SB-4”)] 55.6 g

  The polyamic acid solution DA-A1 and the polyamic acid solution DC-A1 having the above composition are mixed, and the acidic carbon black SB-4 is dispersed in a mixed solution of the polyamic acid solution by dispersion treatment at 30 ° C. for 12 hours in a pole mill. did. Thereafter, the mixed solution in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition A3 having the following composition.

The composition of the polyamic acid composition A3 is: polyamic acid solid content (total of polyamic acid DA-A1 and DC-A1) /NMP/SB-4=185.4/814.6/55.6 (mass ratio) there were.
The ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group in all the polyamic acids in the polyamic acid composition A3 was 0.2.
Moreover, the composition when polyamic acid composition A3 is imide converted, that is, the composition of the polyimide film in which acidic carbon black produced using polyamic acid composition A3 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Preparation of polyamic acid composition A4]
950 g of polyamic acid solution DA-A1 containing polyamic acid DA-A1
-Polyamic acid solution DC-A1 containing polyamic acid DC-A1 50 g
・ Acid carbon black (dry state; conductive agent)
[SPECIAL BLACK4: manufactured by Degussa, pH 4.0, volatile content: 14.0% (hereinafter abbreviated as “SB-4”)] 55.6 g

  The polyamic acid solution DA-A1 and the polyamic acid solution DC-A1 having the above composition are mixed, and the acidic carbon black SB-4 is dispersed in a mixed solution of the polyamic acid solution by dispersion treatment at 30 ° C. for 12 hours in a pole mill. did. Thereafter, the mixed solution in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition A4 having the following composition.

The composition of the polyamic acid composition A4 is: polyamic acid solid content (total of polyamic acid DA-A1 and DC-A1) /NMP/SB-4=185.4/814.6/55.6 (mass ratio) there were.
The ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group in all the polyamic acids in the polyamic acid composition A4 was 0.05.
Moreover, the composition when polyamic acid composition A4 is imide converted, that is, the composition of the polyimide film in which acidic carbon black produced using polyamic acid composition A4 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Preparation of polyamic acid composition A101]
-Polyamic acid solution DA-A1 400g containing polyamic acid DA-A1
-Polyamic acid solution DC-A1 600g containing polyamic acid DC-A1
・ Acid carbon black (dry state; conductive agent) [SB-4] 55.6 g

  The polyamic acid solution DA-A1 and the polyamic acid solution DC-A1 having the above composition are mixed, and the acidic carbon black SB-4 is dispersed in a mixed solution of the polyamic acid solution by dispersion treatment at 30 ° C. for 12 hours in a pole mill. did. Thereafter, the mixed solution in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition A101 having the following composition.

The composition of the polyamic acid composition A101 was: polyamic acid (total of polyamic acid DA-A1 and DC-A1) /NMP/SB-4=185.4/614.6/55.6 (mass ratio). .
The ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group in all the polyamic acids in the polyamic acid composition 101 was 0.6.
Moreover, the composition when polyamic acid composition A101 is imide converted, that is, the composition of the polyimide film in which acidic carbon black produced using polyamic acid composition A101 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Preparation of polyamic acid composition A102]
-600 g of polyamic acid solution DA-A1 containing polyamic acid DA-A1
-Polyamic acid solution DC-A1 400g containing polyamic acid DC-A1
・ Acid carbon black (dry state; conductive agent) [SB-4] 55.6 g

  The polyamic acid solution DA-A1 and the polyamic acid solution DC-A1 having the above composition are mixed, and the acidic carbon black SB-4 is dispersed in a mixed solution of the polyamic acid solution by dispersion treatment at 30 ° C. for 12 hours in a pole mill. did. Thereafter, the mixed solution in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition A102 having the following composition.

The composition of the polyamic acid composition A102 was: polyamic acid (total of polyamic acid DA-A1 and DC-A1) /NMP/SB-4=185.4/814.6/55.6 (mass ratio) .
The ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group in all the polyamic acids in the polyamic acid composition A102 was 0.4.
Moreover, the composition when polyamic acid composition A102 is imide converted, that is, the composition of the polyimide film in which acidic carbon black produced using polyamic acid composition A102 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Preparation of polyamic acid composition A103]
・ Polyamic acid solution DC-A1 containing polyamic acid DC-A1 1000 g
・ Acid carbon black (dry state; conductive agent) [SB-4] 55.6 g

  Acidic carbon black SB-4 was added to the polyamic acid solution DC-A1 having the above composition, followed by dispersion treatment at 30 ° C. for 12 hours using a pole mill. Thereafter, the mixed solution in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition 103 having the following composition.

The composition of the polyamic acid composition A103 was: polyamic acid (polyamic acid DC-A1) /NMP/SB-4=185.4/814.6/55.6 (mass ratio).
The ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group in all the polyamic acids in the polyamic acid composition A103 was ∞ (X = 0).
Moreover, the composition when polyamic acid composition A103 is imide-converted, that is, the composition of the polyimide film in which acidic carbon black produced using polyamic acid composition A103 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Evaluation of Dispersibility of Acidic Carbon Black in Polyamic Acid Composition]
About obtained polyamic acid composition A1, A2, A3, A4, A101, A102, and A103, viscoelasticity was measured and the dispersibility of acidic carbon black was evaluated. The pot life was also evaluated.

(Dispersibility evaluation method)
The storage viscoelastic modulus G ′ of each polyamic acid composition was measured using the MARSII manufactured by HAKKE under the following conditions. Further, the storage viscoelastic modulus G0 ′ of each polyamic acid solution before carbon black dispersion was measured. G ′ / G0 ′ at a frequency of 0.1 Hz was calculated, and the dispersibility of the acidic carbon black was evaluated. It shows that the dispersibility of acidic carbon black is so high that G '/ G0' is large. The results are shown in Table 1.

-Measurement conditions-
・ Measurement temperature: 23 ℃
・ Frequency range: 0.1-100Hz
・ Shear stress: 1Pa
Probe: C35 / 1 L07 041

(Pot life evaluation method)
The pot life was evaluated by measuring the liquid viscosity of each polyamic acid composition up to 240 h every 24 h with an E-type viscometer. Details of the E-type viscometer are as follows.
・ E type viscometer: (Toki Sangyo TV-22 type or TV-25 type), circulating thermostat ・ Rotor: 3 ° × R14
・ Rotor speed: 50rpm
・ Measurement temperature: 22 ± 0.5 ℃

The pot life evaluation criteria are as follows.
A: Viscosity difference between 0h and 240h is within 3% B: Viscosity difference between 0h and 240h is within 10% C: Viscosity difference between 0h and 240h is within 15% D: Viscosity difference between 0h and 240h is 15 Exceed

  As is clear from Table 1, the polyamic acid compositions of the examples were superior in dispersibility of acidic carbon black as compared to the polyamic acid compositions of the comparative examples.

<2. Manufacturing and evaluation of endless belts>
-Preparation of polyimide precursor solution-
1) 1st polyimide precursor solution The polyamic acid composition A1, the polyamic acid composition A2, the polyamic acid composition A3, the polyamic acid composition A4 obtained in “<1. Preparation and Evaluation of Polyamic Acid Composition>” The polyamic acid composition A101 and the polyamic acid composition A102 are respectively converted into a first polyimide precursor solution A1, a first polyimide precursor solution A2, a first polyimide precursor solution A101, and a first polyimide precursor. Used as body solution A102.

2) Second polyimide precursor solution The second polyimide precursor solution was prepared in the same manner as in the preparation of the polyamic acid composition A1, except that the amount of SB-4, which was acidic carbon black, was changed from 55.6 g to 40 g. A polyamic acid composition to be the body solution A1 was prepared.
The composition of the second polyimide precursor solution A1 was: polyamic acid (total of polyamic acid DA-A1 and DC-A1) /NMP/SB-4=185.4/614.6/40 (mass ratio). It was.
The ratio Y / X of the total molar amount (Y) of the terminal carboxy group to the total molar amount (X) of the terminal amino group in all the polyamic acids in the polyamic acid composition A1 was 0.3.
Moreover, the composition when the polyamic acid composition 1 is imide converted, that is, the composition of the polyimide film in which the acidic carbon black produced using the polyamic acid composition 1 is dispersed is polyimide / SB-4 = 185.4 / 40 ( Mass ratio). Therefore, carbon black / polyimide is 22/100 (mass ratio).

[Production of polyimide endless belt A1]
A cylindrical mold made of SUS material having an outer diameter of 90 mm and a length of 450 mm was prepared, and a silicone release agent was applied to the outer surface and subjected to a drying treatment (release agent treatment).
The first polyimide precursor solution 1 is discharged from a 1.0 mm diameter dispenser from the end of the cylindrical mold while rotating the cylindrical mold subjected to the release agent treatment in the circumferential direction at a speed of 10 rpm. The coating was carried out by pressing with a metal blade placed above at a uniform pressure. The first polyimide precursor solution 1 was spirally applied onto the cylindrical mold by moving the dispenser unit in the axial direction of the cylindrical mold at a speed of 100 mm / min. After the application of the first polyimide precursor solution 1, the blade was released and the cylindrical mold was continuously rotated for 2 minutes for leveling.

Thereafter, the mold and the coating material were dried in a drying furnace for 30 minutes while rotating at 10 rpm in an air atmosphere at 145 ° C.
The residual solvent amount of the first coating film after the drying treatment is measured, and after confirming that the residual solvent amount is 10% by mass or more and 50% by mass or less, the first polyimide precursor solution A1 is used as the second polyimide By changing to the precursor solution A1, the formation of the second coating film was started in the same manner as the application of the first polyimide precursor solution A1.
The residual solvent amount of the first coating film after the drying treatment is shown in Table 2.

After the application of the second polyimide precursor solution A1, the blade was released and the cylindrical mold was continuously rotated for 2 minutes for leveling.
Thereafter, the mold and the coating material were dried in a drying furnace for 30 minutes while rotating at 10 rpm in an air atmosphere at 145 ° C.
After drying, the solvent was volatilized from the coated material, so that the coated material changed to a polyamic acid resin molded product (endless belt body) having self-supporting properties.

  After the drying treatment, a calcination treatment was then performed in a clean oven at 300 ° C. for 2 hours to advance the imidization reaction. Thereafter, the mold was set to 25 ° C., the resin was removed from the mold, and the target polyimide endless belt A1 was obtained.

[Production of polyimide endless belts A2 to A4 and polyimide endless belts A101 to A104]
In the manufacture of the polyimide endless belt A1, for the first polyimide precursor solution, the first polyimide precursor solution A1 is changed to the solution shown in “application process”, “application liquid type” and “first” in Table 2, respectively. In the same manner, polyimide endless belts A2 to A4 and polyimide endless belts A101 to A104 were produced in the same manner.

[Evaluation of polyimide endless belt]
The following evaluation was performed for the polyimide endless belts A1 to A4 and the polyimide endless belts A101 to A104. The results are shown in Table 2.

(Measurement of back surface resistivity, volume resistivity, back surface resistance unevenness of endless belt)
The back surface resistivity [LogΩ / □], the volume resistivity [Ω · cm], and the back surface resistance unevenness [LogΩ / □] of the endless belt were measured by the methods described above, and the results are shown in Table 2.

(Evaluation of dispersibility of acidic carbon black in the first layer)
Using an atomic force microscope (AFM), the interface between the first layer and the second layer of the endless belt is a layer that does not contain carbon black (CB) (referred to as a non-CB layer), or carbon black aggregates It was confirmed whether it was a layer (referred to as a CB aggregated layer), and the dispersibility of acidic carbon black in the first layer was evaluated.

-Measurement conditions-
AFM apparatus: D3000 and Nanoscope III manufactured by Digital Instruments
・ Measurement mode: Contact mode ・ Cantilever: Au-coated conductive cantilever ・ Spring constant: 0.2 N / m
・ Applied voltage: -10V

Each of the polyimide endless belts A1 to A4 and the polyimide endless belts A101 to A104 was cut into 10 μm squares and used as samples.
Under the above conditions, the maximum value of the current value in each region when the sample was observed by AFM was measured. After embedding the sample, the sample was cut with a microtome to produce a cross-section, and a silver paste electrode was bonded in parallel to the sample depth direction to form a cantilever counter electrode. This sample was observed in a 10 μm square to obtain conductivity and height information.
Table 2 shows the AFM current amount [A] of the non-CB layer and the AFM current amount [A] of the CB aggregated layer. Further, the knowledge obtained from the AFM current image is shown in the “AFM current image” column.

  As is clear from Table 2, the endless belts of the examples were excellent in the dispersibility of the acidic carbon black in the first layer, and the back surface resistance unevenness was small. Moreover, it was excellent also in the adhesiveness of a 1st layer and a 2nd layer.

<3. Manufacturing and evaluation of image forming apparatus>
The polyimide endless belt A1 obtained in “<2. Production and Evaluation of Endless Belt>” is mounted on an image forming apparatus obtained by modifying a full color printer (DocuPrint C5450: manufactured by Fuji Xerox Co., Ltd.) having the basic configuration shown in FIG. The image forming apparatus A1 was obtained.
Using this image quality evaluation machine, a black halftone image (image density 45%) is output on A3 paper (C2 paper manufactured by Fuji Xerox Co., Ltd.) in a general environment (22 ° C., 50% RH). Image density unevenness was evaluated. The evaluation results are shown in Table 3.

The evaluation criteria for image density unevenness are as follows.
A: There is no occurrence of uneven image density, and there is no problem in use in a high-quality area. O: There is a slight occurrence of uneven image density, but there is no problem in actual use. , The problem is confirmed ×: Image density unevenness occurs throughout and cannot be used in actual use

  Further, in the manufacture of the image forming apparatus A1, the image forming apparatus A2 and the image forming apparatus are similarly provided except that the polyimide endless belts A2 to A4 or the polyimide endless belts A101 to A104 are mounted instead of the polyimide endless belt A1. A101 to A104 were produced. The obtained image forming apparatuses A2 to A4 and image forming apparatuses A101 to A104 were evaluated for image density unevenness in the same manner as the image forming apparatus A1. The evaluation results are shown in Table 3.

[[Example B]]
In Example B shown below, Example B1, Example B2, Example B2-2, Example B3, Example B4, Example B4-1, Example B5, Example B6, and Example B6-1 are These are shown as reference examples for the present invention.
<1. Preparation and Evaluation of Polyamic Acid Composition>
(Synthesis of polyamic acid)
Polyamic acid DA-B1 as a polyamic acid in which both ends of the molecular chain are amino groups, and polyamic acid DC-B1 as a polyamic acid in which all of the amino groups at both ends of the molecular chain are sealed with carboxylic acid monoanhydride Was synthesized.

-Synthesis of polyamic acid DA-B1-
In 800 g of NMP, 83.48 g (416.9 mmol) of 4,4′-diaminodiphenyl ether (hereinafter abbreviated as “ODA”) was added as a diamine compound and dissolved while stirring at room temperature (25 ° C.). Next, 116.52 g (396.0 mmol) of 3,3 ′, 4,4′biphenyltetracarboxylic dianhydride (hereinafter abbreviated as “BPDA”) was gradually added as tetracarboxylic dianhydride. After addition and dissolution of tetracarboxylic dianhydride, the temperature of the reaction solution is heated to 60 ° C., and then the polymerization reaction is carried out for 20 hours while maintaining the reaction solution temperature, and the reaction solution containing polyamic acid DA-B1 and NMP Got. The obtained reaction solution was filtered using a # 800 stainless mesh, cooled to room temperature (25 ° C.), and solution viscosity at 25 ° C. was 2.0 Pa · s (Eki rotational viscometer, manufactured by Toki Sangyo Co., Ltd.). , Using a TV-20H, with a standard rotor (1 ° 34 "× R24), measurement temperature: 25 ° C, rotation speed: 0.5 rpm (100 Pa · s or more), 1 rpm (less than 100 Pa · s) The same is true for the following synthesis example) to obtain a polyamic acid solution DA-B1.
The composition of the obtained polyamic acid DA-B1 was BPDA / ODA = 95/100 (mol / mol).

-Synthesis of polyamic acid DC-B1-
Both terminal amino groups of polyamic acid DA-B1 in which both ends of the molecular chain are amino groups were sealed with carboxylic acid monoanhydride.
Specifically, according to the blending method described in paragraph 0064 of JP 2010-77300 publication was polymerized by mixing DA-B1 41.8 mmol of phthalic anhydride.
Thus, polyamic acid DC-B1 was obtained.

[Preparation of polyamic acid composition B1]
-Polyamic acid solution DA-B1 700g containing polyamic acid DA-B1
-Polyamic acid solution DC-B1 300g containing polyamic acid DC-B1
・ Acid carbon black (dry state; conductive agent)
[SPECIAL BLACK4: manufactured by Degussa, pH 4.0, volatile content: 14.0% (hereinafter abbreviated as “SB-4”)] 55.6 g

  The polyamic acid solution DA-B1 and the polyamic acid solution DC-B1 having the above composition are mixed, and the acidic carbon black SB-4 is dispersed in a mixed solution of the polyamic acid solution by dispersion treatment at 30 ° C. for 12 hours in a pole mill. did. Thereafter, the mixed solution in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition B1 having the following composition.

The composition of the polyamic acid composition B1 is: polyamic acid solid content (total of polyamic acid DA-B1 and DC-B1) /NMP/SB-4=185.4/814.6/55.6 (mass ratio) there were.
The total number of terminal amino groups sealed with carboxylic acid monoanhydrides relative to the total molar amount (X) of terminal amino groups not sealed with carboxylic acid monoanhydrides in all the polyamic acids in polyamic acid composition B1 The ratio Z / X of molar amount (Z) was 0.3.
Moreover, the composition when the polyamic acid composition B1 is imide converted, that is, the composition of the polyimide film in which the acidic carbon black prepared using the polyamic acid composition B1 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Preparation of polyamic acid composition B2]
-Polyamic acid solution DA-B1 containing polyamic acid DA-B1 1000 g
・ Acid carbon black (dry state; conductive agent) [SB-4] 55.6 g

  Acidic carbon black SB-4 was added to the polyamic acid solution DA-B1 having the above composition, followed by dispersion treatment at 30 ° C. for 12 hours using a pole mill. Thereafter, the polyamic acid solution DA-B1 in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition B2 having the following composition.

The composition of the polyamic acid composition B2 was: polyamic acid (polyamic acid DA-B1) /NMP/SB-4=185.4/814.6/55.6 (mass ratio).
The total number of terminal amino groups sealed with carboxylic acid monoanhydrides relative to the total molar amount (X) of terminal amino groups not sealed with carboxylic acid monoanhydrides in all the polyamic acids in polyamic acid composition B2 The ratio Z / X of the molar amount (Z) was 0.
Moreover, the composition when polyamic acid composition B2 is imide converted, that is, the composition of the polyimide film in which acidic carbon black produced using polyamic acid composition B2 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Preparation of polyamic acid composition B3]
-Polyamic acid solution DA-B1 containing polyamic acid DA-B1 800 g
-Polyamic acid solution DC-B1 200g containing polyamic acid DC-B1
・ Acid carbon black (dry state; conductive agent)
[SPECIAL BLACK4: manufactured by Degussa, pH 4.0, volatile content: 14.0% (hereinafter abbreviated as “SB-4”)] 55.6 g

  The polyamic acid solution DA-B1 and the polyamic acid solution DC-B1 having the above composition are mixed, and the acidic carbon black SB-4 is dispersed in a mixed solution of the polyamic acid solution by dispersion treatment at 30 ° C. for 12 hours in a pole mill. did. Thereafter, the mixed solution in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition B3 having the following composition.

The composition of the polyamic acid composition B3 is: polyamic acid solid content (total of polyamic acid DA-B1 and DC-B1) /NMP/SB-4=185.4/814.6/55.6 (mass ratio) there were.
The total number of terminal amino groups sealed with carboxylic acid monoanhydrides relative to the total molar amount (X) of terminal amino groups not sealed with carboxylic acid monoanhydrides in all polyamic acids in polyamic acid composition B3 The ratio Z / X of the molar amount (Z) was 0.2.
Moreover, the composition when polyamic acid composition B3 is imide converted, that is, the composition of the polyimide film in which acidic carbon black produced using polyamic acid composition B3 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Preparation of polyamic acid composition B4]
-950 g of polyamic acid solution DA-B1 containing polyamic acid DA-B1
・ Polyamic acid solution DC-B1 containing polyamic acid DC-B1 50 g
・ Acid carbon black (dry state; conductive agent)
[SPECIAL BLACK4: manufactured by Degussa, pH 4.0, volatile content: 14.0% (hereinafter abbreviated as “SB-4”)] 55.6 g

  The polyamic acid solution DA-B1 and the polyamic acid solution DC-B1 having the above composition are mixed, and the acidic carbon black SB-4 is dispersed in a mixed solution of the polyamic acid solution by dispersion treatment at 30 ° C. for 12 hours in a pole mill. did. Thereafter, the mixed solution in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition B4 having the following composition.

The composition of the polyamic acid composition B4 is: polyamic acid solid content (total of polyamic acid DA-B1 and DC-B1) /NMP/SB-4=185.4/814.6/55.6 (mass ratio) there were.
The total number of terminal amino groups sealed with carboxylic acid monoanhydrides with respect to the total molar amount (X) of terminal amino groups not sealed with carboxylic acid monoanhydrides in all the polyamic acids in polyamic acid composition B4 The molar ratio (Z) ratio Z / X was 0.05.
Moreover, the composition when polyamic acid composition B4 is imide converted, that is, the composition of the polyimide film in which acidic carbon black prepared using polyamic acid composition B4 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Preparation of polyamic acid composition B101]
-Polyamic acid solution DA-B1 400g containing polyamic acid DA-B1
-Polyamic acid solution DC-B1 600g containing polyamic acid DC-B1
・ Acid carbon black (dry state; conductive agent) [SB-4] 55.6 g

  The polyamic acid solution DA-B1 and the polyamic acid solution DC-B1 having the above composition are mixed, and the acidic carbon black SB-4 is dispersed in a mixed solution of the polyamic acid solution by dispersion treatment at 30 ° C. for 12 hours in a pole mill. did. Thereafter, the mixed solution in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition B101 having the following composition.

The composition of the polyamic acid composition B101 was: polyamic acid (total of polyamic acid DA-B1 and DC-B1) /NMP/SB-4=185.4/614.6/55.6 (mass ratio). .
The total number of terminal amino groups sealed with carboxylic acid monoanhydrides relative to the total molar amount (X) of terminal amino groups not sealed with carboxylic acid monoanhydrides in all polyamic acids in polyamic acid composition 101 The ratio Z / X of the molar amount (Z) was 0.6.
Moreover, the composition when polyamic acid composition B101 is imide-converted, that is, the composition of a polyimide film in which acidic carbon black prepared using polyamic acid composition B101 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Preparation of polyamic acid composition B102]
-Polyamic acid solution DA-B1 600g containing polyamic acid DA-B1
-Polyamic acid solution DC-B1 400g containing polyamic acid DC-B1
・ Acid carbon black (dry state; conductive agent) [SB-4] 55.6 g

  The polyamic acid solution DA-B1 and the polyamic acid solution DC-B1 having the above composition are mixed, and the acidic carbon black SB-4 is dispersed in a mixed solution of the polyamic acid solution by dispersion treatment at 30 ° C. for 12 hours in a pole mill. did. Thereafter, the mixed solution in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition B102 having the following composition.

The composition of the polyamic acid composition B102 was: polyamic acid (total of polyamic acids DA-B1 and DC-B1) /NMP/SB-4=185.4/814.6/55.6 (mass ratio). .
The total number of terminal amino groups whose terminal amino groups are sealed with carboxylic acid monoanhydrides with respect to the total molar amount (X) of terminal amino groups that are not blocked with carboxylic acid monoanhydrides in all the polyamic acids in polyamic acid composition B102 The ratio Z / X of the molar amount (Z) was 0.4.
Moreover, the composition when polyamic acid composition B102 is imide-converted, that is, the composition of the polyimide film in which acidic carbon black produced using polyamic acid composition B102 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Preparation of polyamic acid composition B103]
-Polyamic acid solution DC-B1 containing polyamic acid DC-B1 1000 g
・ Acid carbon black (dry state; conductive agent) [SB-4] 55.6 g

  Acidic carbon black SB-4 was added to the polyamic acid solution DC-B1 having the above composition, followed by dispersion treatment at 30 ° C. for 12 hours using a pole mill. Thereafter, the mixed solution in which SB-4 was dispersed was filtered through a # 400 stainless steel mesh to obtain a polyamic acid composition 103 having the following composition.

The composition of the polyamic acid composition B103 was polyamic acid (polyamic acid DC-B1) /NMP/SB-4=185.4/814.6/55.6 (mass ratio).
The total of terminal amino groups whose terminal amino groups are sealed with carboxylic acid monoanhydrides with respect to the total molar amount (X) of terminal amino groups not sealed with carboxylic acid monoanhydrides in all the polyamic acids in polyamic acid composition B103 The ratio Z / X of the molar amount (Z) was ∞ (X = 0).
Moreover, the composition when polyamic acid composition B103 is imide-converted, that is, the composition of the polyimide film in which acidic carbon black produced using polyamic acid composition B103 is dispersed is polyimide / SB-4 = 185.4 / 55. 6 (mass ratio). Therefore, carbon black / polyimide is 30.0 / 100 (mass ratio).

[Evaluation of Dispersibility of Acidic Carbon Black in Polyamic Acid Composition]
The resulting polyamic acid compositions B1, B2, B3, B4, B101, B102, and B103 were measured for viscoelasticity and evaluated for dispersibility of acidic carbon black. The pot life was also evaluated. The results are shown in Table 4.
The evaluation of dispersibility and pot life of acidic carbon black was performed in the same manner as in Example A.

  As is clear from Table 4, the polyamic acid compositions of the examples were superior in dispersibility of acidic carbon black compared to the polyamic acid compositions of the comparative examples.

<2. Manufacturing and evaluation of endless belts>
-Preparation of polyimide precursor solution-
1) 1st polyimide precursor solution The polyamic acid composition B1, the polyamic acid composition B2, the polyamic acid composition B3, the polyamic acid composition B4 obtained in “<1. Preparation and Evaluation of Polyamic Acid Composition>” The polyamic acid composition B101 and the polyamic acid composition B102 are respectively converted into a first polyimide precursor solution B1, a first polyimide precursor solution B2, a first polyimide precursor solution B101, and a first polyimide precursor. Used as body solution B102.

2) Second polyimide precursor solution The second polyimide precursor solution was prepared in the same manner as in the preparation of the polyamic acid composition B1, except that the amount of SB-4, which is acidic carbon black, was changed from 55.6 g to 40 g. A polyamic acid composition B1 to be a body solution B1 was prepared.
The composition of the second polyimide precursor solution B1 was: polyamic acid (total of polyamic acid DB-B1 and DC-B1) /NMP/SB-4=185.4/614.6/40 (mass ratio). It was.
The total number of terminal amino groups sealed with carboxylic acid monoanhydrides relative to the total molar amount (X) of terminal amino groups not sealed with carboxylic acid monoanhydrides in all the polyamic acids in polyamic acid composition B1 The ratio Z / X of molar amount (Z) was 0.3.
Moreover, the composition when the polyamic acid composition 1 is imide converted, that is, the composition of the polyimide film in which the acidic carbon black produced using the polyamic acid composition 1 is dispersed is polyimide / SB-4 = 185.4 / 40 ( Mass ratio). Therefore, carbon black / polyimide is 22/100 (mass ratio).

[Manufacture of polyimide endless belts B1 to B4 and polyimide endless belts B101 to B104]
In the manufacture of the polyimide endless belt A1 of Example A, for the first polyimide precursor solution, the first polyimide precursor solution A1 is changed to “application step”, “application liquid type” and “first” in Table 5, respectively. The polyimide endless belts B1 to B4 and the polyimide endless belts B101 to B104 are changed in the same manner except that the second polyimide precursor solution A1 is changed to the second polyimide precursor solution B1. Manufactured.

[Evaluation of polyimide endless belt]
Evaluation similar to Example A was performed for the polyimide endless belts B1 to B4 and the polyimide endless belts B101 to B104. The results are shown in Table 5.

  As is apparent from Table 5, the endless belts of the examples were excellent in dispersibility of the acidic carbon black in the first layer, and the back surface resistance unevenness was small. Moreover, it was excellent also in the adhesiveness of a 1st layer and a 2nd layer.

<3. Manufacturing and evaluation of image forming apparatus>
The polyimide endless belt B1 obtained in “<2. Production and Evaluation of Endless Belt>” is mounted on an image forming apparatus obtained by remodeling a full color printer (DocuPrint C5450: manufactured by Fuji Xerox Co., Ltd.) having the basic configuration shown in FIG. The image forming apparatus B1 was obtained.
Evaluation was performed in the same manner as in Example A using this image quality evaluator. The evaluation results are shown in Table 6.

  Further, in the manufacture of the image forming apparatus B1, the image forming apparatus B2 and the image forming apparatus are similarly provided except that the polyimide endless belts B2 to B4 or the polyimide endless belts B101 to B104 are mounted instead of the polyimide endless belt B1. B101 to B104 were produced. The obtained image forming apparatuses B2 to B4 and the image forming apparatuses B101 to B104 were evaluated for image density unevenness in the same manner as the image forming apparatus B1. The evaluation results are shown in Table 6.

100 Image forming apparatus 101Y, 101M, 101C, 101BK Photosensitive drum 102 Intermediate transfer belt 105 to 108 Developer 200 Image forming apparatus 200Y, 200M, 200C, 200Bk Image forming unit 206 Transfer conveyance belt

Claims (6)

A polyamic acid having amino groups at all ends, the total molar amount (X) of terminal amino groups not sealed with carboxylic acid monoanhydrides and terminal amino groups sealed with carboxylic acid monoanhydrides. ratio Z / X of the total molar amount (Z) of the terminal amino groups which have been sealed with Luke carboxylic acid mono anhydride against comprises a polyamic acid which is 0.05 ≦ Z / X ≦ 0.1, total solid A polyamic acid composition comprising 10% by mass or more and 80% by mass or less of carbon black having a pH of less than 7 and a solvent. A polyamic acid which is a polymer of a carboxylic acid dianhydride and a diamine compound and which is not end-capped with a carboxylic acid monoanhydride, with respect to the total molar amount (X) of the terminal amino group and terminal carboxy group A polyamic acid in which the ratio Y / X of the total molar amount (Y) of the terminal carboxy group is 0.05 ≦ Y / X <0.4;
10% by mass or more and 80% by mass or less of carbon black having a pH of less than 7 based on the total solid content,
A solvent,
A polyamic acid composition comprising: The polyamic acid composition according to claim 2 , wherein the ratio Y / X is 0.1 ≦ Y / X <0.4. The 1st layer formed using the polyamic acid composition of any one of Claims 1-3 , The 2nd layer provided adjacent to the 1st layer on the 1st layer, and containing a polyimide And having an endless belt. A first coating step of applying a first polyimide precursor solution containing the polyamic acid composition according to any one of claims 1 to 3 on the surface of the core body to form a first coating film; ,
A first drying step of removing the solvent so that the amount of residual solvent in the first coating film is 10% by mass or more and 50% by mass or less;
A second polyimide precursor solution is applied to the first coating film having a residual solvent amount of 10% by mass or more and 50% by mass or less to form a second coating film adjacent to the first coating film. A second coating step,
A second drying step for removing the solvent of the second coating film;
The first coating film and the second coating film are heated, the polyimide precursor in the first coating film and the polyimide precursor in the second coating film are imidized, and the first layer And a heating step in which the second layer forms an adjacent endless belt;
Extracting the endless belt from the core;
A process for producing an endless belt having An image carrier,
Charging means for charging the surface of the image carrier;
Latent image forming means for forming a latent image on the surface of the image carrier;
Developing means for developing a latent image on the surface of the image carrier with toner to form a toner image;
An intermediate transfer member to which the toner image formed on the surface of the image carrier is transferred;
Primary transfer means for primarily transferring the toner image formed on the surface of the image carrier to the surface of the intermediate transfer member;
Secondary transfer means for secondary transfer of the toner image transferred to the surface of the intermediate transfer member to a transfer medium;
Fixing means for fixing the toner image transferred to the recording medium;
With
The image forming apparatus according to claim 4 , wherein the intermediate transfer member is an endless belt.