WO2024204162A1

WO2024204162A1 - Method for manufacturing conductive pigment paste and method for manufacturing mixture paste

Info

Publication number: WO2024204162A1
Application number: PCT/JP2024/011891
Authority: WO
Inventors: 耕吾木下; 心次郎後藤
Original assignee: 関西ペイント株式会社
Priority date: 2023-03-27
Filing date: 2024-03-26
Publication date: 2024-10-03
Also published as: JP7565474B1

Abstract

The present invention addresses the problem of providing: a conductive pigment paste and a mixture paste having excellent pigment dispersibility and storage stability even in a high pigment concentration; and an electrode layer for a lithium ion secondary battery, the electrode layer having excellent performance in various aspects (such as conductivity and battery performance). Provided as a solution for the problem is a method for manufacturing a conductive pigment paste containing a pigment dispersion resin (A), a conductive pigment (B), a solvent (C), and an optional fluorine resin (D), the method being characterized by sequentially carrying out step 1 for pulverizing a conductive pigment composition having a pigment concentration of 50% by mass or more of the conductive pigment (B) in a pulverizer and step 2 for mixing and dispersing a component containing the pigment dispersion resin (A), the solvent (C) and the optional fluorine resin (D) in the conductive pigment composition obtained in the step 1.

Description

Method for producing conductive pigment paste and method for producing composite paste

The present invention relates to a method for producing a conductive pigment paste and a composite paste that have excellent conductivity, pigment dispersibility, and storage stability even at high pigment concentrations, and a method for producing a battery electrode layer that has excellent battery performance.

　Traditionally, paste-like pigment dispersions, in which pigments are dispersed in a mixture of pigment dispersion resins and solvents, have been widely used in fields such as paints, battery electrodes, coating materials, electromagnetic shielding, display panels, touch screen panels, colored films, colored sheets, decorative materials, protective materials, magnet modifiers, printing inks, device components, electronic equipment components, printed wiring boards, solar cells, functional rubber components, and resin molding films. Furthermore, conductive pigments and conductive polymers are added to these materials to impart functions such as electrostatic paintability, conductivity, electromagnetic shielding, and antistatic properties.

In these fields, there is an increasing demand for improved pigment dispersibility, storage stability, electrical conductivity, coatability, finish, and other performance features. As a result, pigment dispersion resins and pigment pastes are being developed that have excellent pigment dispersion capabilities and excellent pigment dispersion stability that prevents re-agglomeration of pigment particles in the formed pigment dispersion.

When designing a pigment paste, it is important to create a highly concentrated, uniformly dispersed pigment paste using a small amount of pigment dispersion resin so that the pigment dispersion resin does not adversely affect the conductive properties of the final product itself, such as the coating film, and from the perspective of reducing the amount of solvent and pigment dispersion resin used and reducing the energy used during drying.

For example, Patent Document 1 discloses a method for manufacturing an electrode for a nonaqueous electrolyte battery, which comprises a step of kneading a carbon-based conductive agent and a dispersion solvent, and then dispersing the carbon-based conductive agent using a medium-type disperser, a step of adding an active material and a binder to the paste obtained in the above step and kneading them to form an active material paste, and a step of applying the active material paste to an electrode substrate.
However, in the case of pastes having high pigment concentrations and/or high viscosities, these inventions sometimes fail to achieve uniform dispersion and have poor storage stability.

Japanese Patent Application Publication No. 10-144302

The object of the present invention is to provide a method for producing a conductive pigment paste and a method for producing a composite paste that are excellent in pigment dispersibility and storage stability even in pastes with high pigment concentrations and/or high viscosity, and further to provide a method for producing a coating film (electrode layer for batteries) that is excellent in finish quality and conductivity, etc.

As a result of intensive research into solving the above problems, the present inventors have discovered a method for producing a conductive pigment paste containing a pigment dispersing resin (A), a conductive pigment (B), a solvent (C), and a fluororesin (D) which may be included as necessary, comprising the steps of:
Step 1: A step of pulverizing a conductive pigment composition having a pigment concentration of 50 mass% or more of the conductive pigment (B) by a pulverizer; and
Step 2: A step of mixing and dispersing the conductive pigment composition obtained in step 1 with components including a pigment dispersing resin (A), a solvent (C), and a fluororesin (D) which may be included as needed;
The present inventors have found that the above-mentioned problems can be solved by a method for producing a conductive pigment paste, the method including the steps of:

That is, the present invention provides the following method for producing a conductive pigment paste, method for producing a composite paste, and method for producing an electrode layer for a battery.
Item 1.
A method for producing a conductive pigment paste containing a pigment dispersing resin (A), a conductive pigment (B), a solvent (C), and a fluororesin (D) which may be included as necessary, comprising the steps of:
Step 1: A step of pulverizing a conductive pigment composition having a pigment concentration of 50 mass% or more of the conductive pigment (B) by a pulverizer; and
Step 2: A step of mixing and dispersing the conductive pigment composition obtained in step 1 with components including a pigment dispersing resin (A), a solvent (C), and a fluororesin (D) which may be included as needed;
A method for producing a conductive pigment paste, comprising the steps of:
Item 2.
2. The method for producing a conductive pigment paste according to item 1, wherein the conductive pigment (B) contains carbon nanotubes (B1).
Item 3.
In the carbon nanotubes (B1) before and after the pulverization in step 1, the following (1) and (2) are
(1) The G/D ratio of the carbon nanotubes (B1) before pulverization is 0.1 or more and 5.0 or less, where G is the maximum peak intensity in the range of 1560 cm ^-1 to 1600 cm ^- ¹ and D is the maximum peak intensity in the range of 1310 cm-1 to 1350 cm ^-1 .
(2) When the G/D ratio of the carbon nanotubes (B1) before pulverization is α and the G/D ratio of the carbon nanotubes (B1) after pulverization is β, β/α<1.00;
Item 3. The method for producing a conductive pigment paste according to Item 2, which satisfies the above.
Item 4.
4. The method for producing a conductive pigment paste according to any one of items 1 to 3, wherein the pigment dispersing resin (A) has at least one alkyl group having 12 or more carbon atoms.
Item 5.
5. The method for producing a conductive pigment paste according to any one of items 1 to 4, wherein the pigment dispersion resin (A) has at least one polar functional group selected from the group consisting of an amide group, an imide group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphate group, a silanol group, a cyano group, a pyrrolidone group, and an amino group, and the concentration of the polar functional group in the pigment dispersion resin (A) is 0.3 mmol/g to 23 mmol/g.
Item 6.
6. The method for producing a conductive pigment paste according to any one of Items 1 to 5, wherein the conductive pigment paste contains a fluororesin (D), and the step of mixing the fluororesin (D) includes a step of mixing and dissolving the fluororesin (D) in a solvent having a liquid temperature of 40° C. or higher in advance, or a step of mixing the fluororesin (D) with a solvent and then heating the resulting mixture to a temperature of 40° C. or higher.
Item 7.
7. The method for producing a conductive pigment paste according to any one of items 1 to 6, wherein the solvent (C) is N-methyl-2-pyrrolidone.
Item 8.
The step 2 is
Step 2-1: adding components containing a conductive pigment composition in an amount of 70 mass% or less based on 100 mass% of the total amount of the conductive pigment composition contained in the conductive pigment paste obtained after dispersion into a disperser and performing a dispersion treatment; and Step 2-2: adding the conductive pigment composition into the disperser until a desired concentration is reached, and performing a dispersion treatment.
8. The method according to any one of items 1 to 7, comprising the steps of:
Item 9.
Item 10. The conductive pigment paste obtained by the method for producing a conductive pigment paste according to any one of Items 1 to 8, further comprising step 3: mixing at least one electrode active material (F);
A method for producing a composite paste for a lithium ion secondary battery, comprising:
Item 10.
Item 10. A method for producing an electrode layer for a lithium ion secondary battery, comprising a step of applying the lithium ion secondary battery composite paste obtained by the production method of item 9 to a current collector.
Item 11.
Item 11. A method for producing an electrode for a lithium ion secondary battery, comprising the step of applying an electrode insulating part to an end or an upper layer of the electrode layer obtained by the method for producing an electrode layer for a lithium ion secondary battery according to item 10.

The method for producing a conductive pigment paste and the method for producing a composite paste of the present invention are excellent in pigment dispersibility and storage stability even at high pigment concentrations and/or high viscosities, and can sufficiently reduce the viscosity of the paste with a relatively small amount of dispersion resin. In addition, the coating film (battery electrode layer) is excellent in finish, conductivity, battery performance, etc.

The following provides a detailed explanation of how to implement the present invention.

It should be understood that the present invention is not limited to the following embodiments, but includes various modified examples that are implemented within the scope that does not deviate from the gist of the present invention.
In the present invention, a composition containing the conductive pigment (B) in a pigment concentration of 50 mass % or more and obtained by pulverizing the pigment with a pulverizer is referred to as a "conductive pigment composition".
A paste prepared by further blending the conductive pigment composition with at least one pigment dispersing resin (A), a solvent (C), a fluororesin (D) which may be included as necessary, and optionally other various components is referred to as a "conductive pigment paste."
The term "conductive pigment paste" refers to a paste containing a conductive pigment, but does not mean that the paste itself is conductive.
It can be said that the conductive pigment paste is a paste that does not substantially contain an electrode active material.
The conductive pigment paste is prepared by further mixing at least one electrode active material and, optionally, other various components, and the resulting paste is called a "composite paste." The composite paste that is applied to a substrate and dried is called a "coating film" or a "composite layer."
When the coating film is used as an electrode for a battery, it can also be called an "electrode layer."
Carbon nanotubes can also be abbreviated as "CNT."

[Method of manufacturing conductive pigment paste]
The present invention is a method for producing a conductive pigment paste containing a pigment dispersing resin (A), a conductive pigment (B), a solvent (C), and a fluororesin (D) that can be included as necessary, the method comprising: first, a step of grinding the conductive pigment (B) with a grinder at a pigment concentration of 50 mass% or more to obtain a conductive pigment composition (step 1: grinding step); and a step of mixing and dispersing components including the pigment dispersing resin (A), the solvent (C), and the fluororesin (D) that can be included as necessary into the conductive pigment composition obtained in step 1 (step 2: dispersing step). This method has a conductive pigment paste having a conductive pigment (B) in a well-dispersed state.
The present invention may include another step between step 1 and step 2 or before or after step 2.

Step 1 (Crushing step)
Step 1 is a step of pulverizing (including disintegration) the conductive pigment (B) with a pulverizer to obtain a conductive pigment composition, and the pigment concentration of the conductive pigment (B) is usually 50 mass% or more, preferably 80 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, particularly preferably 99 mass% or more, and even more particularly preferably 100 mass% based on 100 mass% of the conductive pigment composition. Note that the above "pigment concentration of the conductive pigment (B)" refers to the pigment concentration of the conductive pigment (B) contained in the conductive pigment composition, and does not include pigments or solids other than the conductive pigment (B).
As the components other than the conductive pigment (B) in the conductive pigment composition, the below-mentioned solvent, resin, and pigment other than the conductive pigment (B) can be suitably used.
The solid content concentration of the conductive pigment composition is usually 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, particularly preferably 99% by mass or more, and even more particularly preferably 100% by mass, based on 100% by mass of the conductive pigment composition. The "solid content concentration" refers to the proportion (mass%) of solids when 1 g of a sample is dried by heating at 130°C for 3 hours.

Furthermore, the conductive pigment composition obtained in step 1 may contain components other than the conductive pigment (B) as long as they have the above-mentioned pigment concentration and solid content concentration. For example, the conductive pigment composition may contain a pigment dispersion resin (A), a pigment other than the conductive pigment (B), a solvent (C), and a fluororesin (D) that can be contained as necessary, which will be described later. However, it is preferable for the conductive pigment composition to contain substantially only the conductive pigment (B), and it is particularly preferable for the conductive pigment composition to contain substantially only the carbon nanotubes (B1).
Furthermore, when the conductive pigment paste is used for an electrode layer, it is preferable that the paste does not substantially contain an electrode active material, which will be described later, since the electrode active material is mixed in a later step (step 3).

Conductive pigment (B)
The conductive pigment (B) is a conductive pigment, and any conductive pigment known per se can be used, but it is preferable that the conductive pigment (B) contains carbon nanotubes (B1). The conductive pigment (B) may further contain a conductive pigment (B2) other than the carbon nanotubes (B1).

The content of carbon nanotubes (B1) in the conductive pigment (B) is, for example, 50% by mass or more, preferably 75% by mass or more, more preferably 95% by mass or more, particularly preferably 99% by mass or more, and even more particularly preferably 100% by mass, based on 100% by mass of the conductive pigment (B).

Carbon nanotubes (B1)
As the carbon nanotubes (B1), single-walled carbon nanotubes or multi-walled carbon nanotubes can be used alone or in combination. In particular, in terms of viscosity, electrical conductivity, and cost, it is preferable to use multi-walled carbon nanotubes.

When carbon nanotubes (B1) are used, the content thereof is, for example, 0.5 mass% or more, preferably 1 mass% or more, and more preferably 2 mass% or more, based on 100 mass% of the total amount of the conductive pigment paste, and is, for example, 10 mass% or less, preferably 7 mass% or less, and more preferably 6 mass% or less.
Furthermore, based on 100 mass% of the total solid content of the conductive pigment paste, the content is, for example, 5 mass% or more, preferably 10 mass% or more, and more preferably 20 mass% or more, and for example, 90 mass% or less, preferably 70 mass% or less, and more preferably 50 mass% or less.

The average outer diameter of the carbon nanotubes (B1) is, for example, 1 nm or more, preferably 3 nm or more, more preferably 5 nm or more, and is, for example, 30 nm or less, preferably 28 nm or less, more preferably 25 nm or less.

The average length of the carbon nanotubes (B1) is, for example, 0.1 μm or more, preferably 1 μm or more, more preferably 5 μm or more, and is, for example, 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less.

The BET specific surface area of the carbon nanotubes (B1) is, in consideration of the relationship between viscosity and electrical conductivity, usually 100 m ² /g or more, preferably 130 m ² /g or more, more preferably 160 m ² /g or more, and usually 800 m ² /g or less, preferably 600 m ² /g or less, more preferably 400 m ² /g or less.
The BET specific surface area of the present invention can be calculated by the BET method using nitrogen adsorption measurement. Specifically, for example, the BET specific surface area (m ² /g) can be measured using a specific surface area measuring device (BERSORP-MAX (Microtrac-Bell Co., Ltd.)) in accordance with JIS Z8830:2013.

The amount of acidic groups in the carbon nanotubes (B1) is usually 0.01 mmol/g or more, preferably 0.01 mmol/g or more, and usually 1.0 mmol/g or less, preferably 0.5 mmol/g or less, more preferably 0.2 mmol/g or less, and even more preferably 0.1 mmol/g or less, from the viewpoints of dispersibility and storage property. If the amount of acidic groups is 0.01 mmol/g or more, the dispersibility will be good, and if it is 1.0 mmol/g or less, the storage property will be good.

The above acidic groups can be imparted to carbon nanotubes by acid treatment as described below.

(Acid Treatment Method)
The acid treatment method is not particularly limited as long as it can bring the carbon nanotubes into contact with the acid, but a method of immersing the carbon nanotubes in an acid treatment solution (aqueous solution of acid) is preferred. The acid contained in the acid treatment solution is not particularly limited, but examples thereof include nitric acid, sulfuric acid, and hydrochloric acid. These can be used alone or in combination of two or more. Among these, nitric acid and sulfuric acid are preferred.
The amount of acidic groups in the carbon nanotubes can be adjusted by the concentration of the acid treatment solution, the temperature, the treatment time, and the like.

After the acid treatment, the excess acid component adhering to the surface is removed by a washing method described below, thereby obtaining acid-treated carbon nanotubes.
The method for washing the acid-treated carbon nanotubes is not particularly limited, but washing with water is preferred. For example, the carbon nanotubes are collected from the acid-treated carbon nanotubes by a known method such as filtration, and then washed with water. After the above washing, the water adhering to the surface can be removed by drying, etc., as necessary, to obtain the acid-treated carbon nanotubes.

The volume-equivalent median diameter (D50) of the carbon nanotubes (B1) is usually 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and usually 250 μm or less, preferably 200 μm or less, more preferably 150 μm or less, when measured by the method described in the examples below. Here, the median diameter (D50) can be obtained by irradiating a carbon nanotube particle with a laser beam and converting the diameter of the carbon nanotube into a sphere from the scattered light. The larger the median diameter (D50), the more carbon nanotube agglomerates there are, which means that the dispersibility is poor. If the median diameter (D50) is larger than 250 μm, there is a high possibility that carbon nanotube agglomerates exist in the electrode, and the conductivity of the entire electrode becomes non-uniform. On the other hand, if the median diameter (D50) is smaller than 10 μm, the fiber length is short, so the conductive path is insufficient, and the conductivity decreases. When the median diameter (D50) is within the range of 10 μm or more and 250 μm or less, the carbon nanotubes can be uniformly dispersed within the electrode while maintaining their electrical conductivity.

In the Raman spectrum of the carbon nanotube (B1), the G/D ratio, where G is the maximum peak intensity in the range of 1560 cm ^-1 to 1600 cm ^-1 and D is the maximum peak intensity in the range of 1310 cm ^-1 to 1350 cm ^-1 , is usually 0.1 or more, preferably 0.4 or more, more preferably 0.6 or more, and is usually 5.0 or less, preferably 3.0 or less, more preferably 1.0 or less.

Here, a G/D ratio in the range of 0.1 to 5.0 is preferable because it tends to have high conductivity due to fewer defects and crystal interfaces on the carbon surface.

In addition, when carbon nanotubes (B1) are used as the conductive pigment (B), it is preferable that the carbon nanotubes (B1) before and after the pulverization in the step 1 satisfy the following (1) and (2).
(1) The G/D ratio of the carbon nanotubes (B1) before pulverization is 0.1 or more ^and 5.0 or ^less , where G is the maximum peak intensity in the range of 1560 cm ⁻¹ to 1600 cm ⁻¹ and D is the maximum peak intensity in the range of 1310 cm −1 to 1350 cm −1.
(2) When the G/D ratio of the carbon nanotubes (B1) before pulverization is α and the G/D ratio of the carbon nanotubes (B1) after pulverization is β, β/α<1.00.
Furthermore, the value of the above β/α decreases as the pulverization progresses, and is usually β/α<1.00, preferably 0.50<β/α<1.00, more preferably 0.70<β/α<0.98, and even more preferably 0.90<β/α<0.96.
When β/α is within the above range, the ground surface is suitably activated in a relatively short grinding time, and good dispersibility and storage stability can be obtained in the dispersion step of step 2 described below, and the coating film can have excellent conductivity and finish.

Other conductive pigments (B2)
Examples of the conductive pigment (B2) other than the carbon nanotubes (B1) include at least one conductive carbon selected from the group consisting of acetylene black, ketjen black, furnace black, thermal black, graphene, and graphite. Preferably, it is at least one selected from the group consisting of acetylene black, ketjen black, furnace black, and thermal black, more preferably at least one selected from the group consisting of acetylene black and ketjen black, and even more preferably it is acetylene black.

The average primary particle diameter of the other conductive pigment (B2) is, for example, 10 nm or more, preferably 20 nm or more, and more preferably, for example, 80 nm or less, and more preferably, 70 nm or less. Here, the average primary particle diameter refers to the average particle diameter of primary particles obtained by observing the conductive pigment (B2) under an electron microscope, calculating the projected area of each of 100 particles, calculating the diameter of a circle assuming an area equal to that area, and then averaging the diameters of the 100 particles. Note that if the pigment is in an aggregated state, the calculation is performed using the primary particles that make up the aggregated particles.

The BET specific surface area of the other conductive pigment (B2) is not particularly limited and is, for example, 1 m ² /g or more, preferably 10 m ² /g or more, more preferably 20 m ² /g or more, and is, for example, 500 m ² /g or less, preferably 250 m ² /g or less, more preferably 200 m ² /g or less, depending on the relationship between viscosity and conductivity.

The dibutyl phthalate (DBP) oil absorption of the other conductive pigment (B2) is not particularly limited. In relation to pigment dispersibility and conductivity, it is, for example, 60 ml/100 g or more, preferably 150 ml/100 g or more, and, for example, 1,000 ml/100 g or less, preferably 800 ml/100 g or less.

Grinding method and grinding machine The conductive pigment (B) is ground (including disintegration) by a grinding machine. In the present invention, it is particularly preferable that the conductive pigment (B) contains carbon nanotubes.
In the pulverization step of step 1, pulverization is performed using a pulverizer incorporating pulverization media such as glass beads, zirconia beads, steel balls, etc. The pulverization is performed by utilizing the pulverizing or destructive force caused by the collision of the pulverization media with each other and/or the collision of the pulverizer with the pulverization media. Known pulverization devices such as a high-speed rotation impact mill, jet mill, roll mill, attritor, ball mill, vibration mill, and bead mill can be used as the pulverization device.

In addition, various types of steam or gas can be blown into the grinder during grinding to further activate the surface of the conductive pigment (B) or adjust the activity. As the steam, acidic or basic compounds are suitable, and as the gas, oxygen, nitrogen, etc. are suitable.

The above-mentioned pulverization is preferably carried out by so-called dry dispersion. Here, "dry dispersion" means pulverizing the pigment without substantially containing any liquid components, and since energy can be applied directly to the pigment, highly efficient and powerful pulverization (disintegration) is possible. In addition, since the pulverized surface is activated and interacts with the surrounding substances, good dispersibility and storage stability can be obtained in the dispersion step of step 2 described below, and the coating film can have excellent conductivity and finish.

The outer diameter of the grinding media is preferably 0.1 to 5 mm, and more preferably 0.5 to 3 mm. Within the above range, the desired grinding force can be obtained, and when the conductive pigment (B) is carbon nanotubes, the pigment can be efficiently ground and disintegrated without excessively destroying the fiber shape.

Step 2 (dispersion step)
Step 2 is a step of mixing and dispersing a component containing a pigment dispersing resin (A), a solvent (C), and a fluororesin (D) which may be included as necessary, into the conductive pigment composition obtained in step 1, and a liquid conductive pigment paste can be obtained by step 2.

The upper limit of the solids concentration of the conductive pigment paste is usually less than 80% by mass, preferably less than 50% by mass, more preferably less than 20% by mass, and even more preferably less than 10% by mass. The lower limit is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more.

The conductive pigment paste is a conductive pigment paste containing a pigment dispersion resin (A), a conductive pigment (B), a solvent (C), and a fluororesin (D) which may be included as necessary, and it is preferable that the pigment dispersion resin (A) has at least one polar functional group selected from the group consisting of an amide group, an imide group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphate group, a silanol group, a cyano group, a pyrrolidone group, and an amino group, and that the concentration of the polar functional group in the pigment dispersion resin (A) is 0.3 mmol/g or more and 23 mmol/g or less.
It is also preferred that the composition further contains a highly polar, low molecular weight component (E) as required.

In the dispersing step of step 2, the above-mentioned components can be uniformly mixed and dispersed using a conventionally known dispersing machine such as a paint shaker, a sand mill, a ball mill, a pebble mill, an LMZ mill, a DCP pearl mill, a planetary ball mill, a homogenizer, a twin-screw kneader, or a thin film swirling high-speed mixer (manufactured by Filmix, product name "Clearmix", etc.).
The order in which the components are mixed is not particularly limited.

Pigment dispersing resin (A)
The pigment dispersion resin (A) preferably has at least one alkyl group having 12 or more carbon atoms. As the alkyl group having 12 or more carbon atoms, any known alkyl group (hydrocarbon group) can be used without any particular limitation, and a linear or branched alkyl group is preferable, and a linear alkyl group is more preferable.
The alkyl group having 12 or more carbon atoms is preferably an alkyl group having 12 or more and less than 30 carbon atoms, more preferably an alkyl group having 15 or more and less than 26 carbon atoms, and even more preferably an alkyl group having 19 or more and less than 24 carbon atoms.
The alkyl group having 12 or more carbon atoms can be introduced into the resin, for example, by (co)polymerizing a polymerizable monomer containing an alkyl group having 12 or more carbon atoms.
Examples of polymerizable monomers containing an alkyl group having 12 or more carbon atoms include lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, lauryl (meth)acrylamide, stearyl (meth)acrylamide, behenyl (meth)acrylamide, etc. These may be used alone or in combination of two or more.
It is believed that when the pigment dispersing resin (A) has a relatively bulky side chain of an alkyl group having 12 or more carbon atoms, the pigment dispersibility and storage stability are improved due to steric repulsion.

The pigment dispersion resin (A) preferably has at least one polar functional group selected from the group consisting of an amide group, an imide group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphoric acid group, a silanol group, a cyano group, a pyrrolidone group, and an amino group. When the pigment dispersion resin (A) has a polar functional group, the polar functional group concentration is preferably 0.3 mmol/g or more and 23 mmol/g or less. The acid group may be in the form of a salt.
Among them, as the polar functional group, it is preferable to use at least an amide group, a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphoric acid group, and an amino group, and it is more preferable to use at least a hydroxyl group, a carboxyl group, and an amino group.

The type of resin is not particularly limited as long as it is a resin other than the fluororesin (D) described below. Examples include acrylic resin, polyester resin, epoxy resin, polyether resin, alkyd resin, urethane resin, polyvinyl alcohol, polyvinyl acetal, polyvinylpyrrolidone, polyvinyl acetate, silicone resin, polycarbonate resin, chlorine-based resin, and composite resins thereof. These resins can be used alone or in combination of two or more.

Among these, from the viewpoints of pigment dispersibility, storage stability, finish quality, and the like, the pigment dispersing resin (A) preferably contains a vinyl (co)polymer (A1) obtained by polymerizing or copolymerizing a monomer containing a polymerizable unsaturated group-containing monomer of the following formula (1), and in particular, an acrylic resin obtained by (co)polymerizing at least one polymerizable unsaturated group-containing monomer that contains a (meth)acryloyl group is preferred.
Incidentally, the "(co)polymer" of the present invention includes both a polymer obtained by polymerizing one type of monomer and a copolymer obtained by copolymerizing two or more types of monomers.

C(-R) ₂ =C(-R) ₂ ...Formula (1)
[In the above formula, R may be the same or different and is a hydrogen atom or an organic group.]
Examples of the vinyl (co)polymer (A1) include hydroxyl group-containing vinyl (co)polymers, carboxyl group-containing vinyl (co)polymers, amide group-containing vinyl (co)polymers, sulfonic acid group-containing vinyl (co)polymers, and the like. Examples of such (co)polymers include vinyl (co)polymers containing phosphoric acid groups, vinyl (co)polymers containing pyrrolidone groups, and vinyl (co)polymers containing amino groups. They can be used alone or in combination of two or more.

Examples of hydroxyl group-containing vinyl (co)polymers include polyhydroxyethyl (meth)acrylate, polyvinyl alcohol, vinyl alcohol-fatty acid vinyl copolymer, vinyl alcohol-ethylene copolymer, vinyl alcohol-(N-vinylformamide) copolymer, and copolymers of hydroxyethyl (meth)acrylate and other polymerizable unsaturated monomers. The vinyl alcohol units in the (co)polymer may be obtained by (co)polymerizing fatty acid vinyl units and then hydrolyzing them.

Examples of carboxyl group-containing vinyl (co)polymers include polymers of (meth)acrylic acid, and copolymers of poly(meth)acrylic acid and other polymerizable unsaturated monomers.

Examples of amide group-containing vinyl (co)polymers include (meth)acrylamide polymers and copolymers of (meth)acrylamide and other polymerizable unsaturated monomers.

Examples of sulfonic acid group-containing vinyl (co)polymers include polymers of allylsulfonic acid or styrenesulfonic acid, copolymers of allylsulfonic acid and/or styrenesulfonic acid with other polymerizable unsaturated monomers, etc.

Examples of phosphate group-containing vinyl (co)polymers include polymers of (meth)acryloyloxyalkyl acid phosphate, and copolymers of (meth)acryloyloxyalkyl acid phosphate with other polymerizable unsaturated monomers.

Examples of amino group-containing vinyl (co)polymers include N,N-dimethylaminoethyl (meth)acrylate and copolymers of N,N-diethylaminoethyl (meth)acrylate with other polymerizable unsaturated monomers.

Other copolymerizable unsaturated monomers include, for example, vinyl formate, vinyl acetate, vinyl propionate, isopropenyl acetate, vinyl valerate, vinyl caprylate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl versatate, and vinyl pivalate; olefins such as ethylene, propylene, and butylene; aromatic vinyls such as styrene and α-methylstyrene; methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. ethylenically unsaturated carboxylic acid alkyl ester monomers such as dimethyl fumarate, dimethyl maleate, diethyl maleate, and diisopropyl itaconate; vinyl ether monomers such as methyl vinyl ether, n-propyl vinyl ether, isobutyl vinyl ether, and dodecyl vinyl ether; halogenated vinyl monomers or vinylidene monomers such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; allyl compounds such as allyl acetate and allyl chloride; and quaternary ammonium group-containing monomers such as 3-(meth)acrylamidopropyltrimethylammonium chloride. These monomers can be used alone or in combination of two or more.

From the viewpoints of pigment dispersibility, storage stability, and compatibility with the solvent, the polar functional group concentration of the pigment dispersing resin (A) is usually 0.3 mmol/g to 23 mmol/g, preferably 0.3 mmol/g to 12 mmol/g, more preferably 0.4 mmol/g to 8.0 mmol/g, even more preferably 0.4 mmol/g to 6.0 mmol/g, and even more preferably 0.4 mmol/g to 2.0 mmol/g.

The vinyl (co)polymer (A1) can be produced by a polymerization method known per se. For example, it is preferable to use solution polymerization, but this is not limiting, and bulk polymerization, emulsion polymerization, suspension polymerization, etc. may also be used. When solution polymerization is performed, continuous polymerization or batch polymerization may be used, and the monomers may be charged all at once or in portions, or may be added continuously or intermittently.

The polymerization initiator used in the solution polymerization is not particularly limited, but specific examples include azo compounds such as azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), azobis-2,4-dimethylparabennitrile, and azobis(4-methoxy-2,4-dimethylparabennitrile); acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, and 2,4,4-trimethylpentyl-2,4-dimethylparabennitrile. -Peroxides such as peroxyphenoxyacetate; percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; perester compounds such as t-butyl peroxyneodecanate, α-cumyl peroxyneodecanate, and t-butyl peroxyneodecanate; and known radical polymerization initiators such as azobisdimethylvaleronitrile and azobismethoxyvaleronitrile can be used.

The polymerization reaction temperature is not particularly limited, but can usually be set in the range of 30°C or higher and 200°C or lower.

The vinyl (co)polymer (A1) obtainable as described above has a degree of polymerization of, for example, 100 or more, preferably 150 or more, and, for example, 4,000 or less, preferably 3,000 or less, more preferably 700 or less.

The weight average molecular weight is, for example, 1,000 or more, preferably 2,000 or more, more preferably 7,000 or more, and, for example, 2,000,000 or less, preferably 1,000,000 or less, more preferably 500,000 or less.

In this specification, unless otherwise specified, the weight average molecular weight is a value obtained by converting the retention time (retention volume) measured using a gel permeation chromatograph (GPC) into the molecular weight of polystyrene using the retention time (retention volume) of a standard polystyrene of known molecular weight measured under the same conditions. Specifically, the gel permeation chromatograph is "HLC8120GPC" (product name, manufactured by Tosoh Corporation), and the four columns are "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL" and "TSKgel G-2000HXL" (all product names, manufactured by Tosoh Corporation), and the measurements can be performed under the following conditions: mobile phase tetrahydrofuran, measurement temperature 40°C, flow rate 1mL/min, and detector RI.

After completion of the synthesis, the vinyl (co)polymer (A1) can be converted into a solid or into a resin solution in which any solvent has been replaced by removing the solvent and/or replacing the solvent.

The method of desolvation may be by heating at normal pressure or under reduced pressure. The method of solvent replacement may be to add a replacement solvent at any stage before, during, or after desolvation.

In addition, the content of the alkyl group having 12 or more carbon atoms in the dispersion resin (A), in the case of the vinyl (co)polymer (A1), is preferably 1 to 100 mass%, more preferably 10 to 90 mass%, even more preferably 20 to 80 mass%, and particularly preferably 30 to 60 mass%, expressed as the mass ratio of the monomer when all monomers are taken as 100 mass%.
Incidentally, the content of the alkyl group having 12 or more carbon atoms is calculated based on the mass proportion of a compound having a reactive alkyl group having 12 or more carbon atoms added to the resin later.

When the pigment dispersion resin (A) is converted from a solid state into a resin solution, it is preferable that the pigment dispersion resin (A) is first mixed and dissolved in a solvent having a liquid temperature of 60° C. or higher (preferably 80° C. or higher) (the upper limit is 200° C. or lower, preferably 100° C. or lower) to convert it into a resin solution, and then mixed with other components [components (B), (C), (D), etc.], from the viewpoint of solubility in the solvent.
The "liquid temperature" refers to the temperature of the solvent or resin solution at the time of dissolution.
The solid pigment dispersion resin (A) may be mixed and dissolved in a solvent at 60° C. or higher in advance, or the solid pigment dispersion resin (A) may be mixed with a solvent and then heated to a temperature of 60° C. or higher.
Furthermore, the ink may contain components other than the pigment dispersing resin (A) and the solvent.
The solvent to be used may be one type alone or two or more types in combination. As the type, those exemplified as the solvent (C) described later can be suitably used.

The solid content of the pigment dispersion resin (A) is, based on 100% by mass of the total solid content of the conductive pigment paste, for example, 0.1% by mass or more, preferably 1% by mass or more, and more preferably 3% by mass or more, and for example, 40% by mass or less, preferably 30% by mass or less, and more preferably 20% by mass or less.

The solid content of the pigment dispersion resin (A) is, based on 100% by mass of the total amount of the conductive pigment paste, for example, 0.1% by mass or more, preferably 0.4% by mass or more, and more preferably 0.7% by mass or more, and for example, 10% by mass or less, preferably 5% by mass or less, and more preferably 2% by mass or less.

The solid content of the pigment dispersion resin (A) is, based on the content of the conductive pigment (B) of 100% by mass, for example, 0.1% by mass or more, preferably 1% by mass or more, more preferably 5% by mass or more, and for example, 150% by mass or less, preferably 120% by mass or less, more preferably 80% by mass or less.

Solvent (C)
As the solvent (C), water or various organic solvents can be suitably used.
Specific examples of the solvent include hydrocarbon solvents such as n-butane, n-hexane, n-heptane, n-octane, cyclopentane, cyclohexane, and cyclobutane; aromatic solvents such as toluene and xylene; ketone solvents such as methyl isobutyl ketone; ether solvents such as n-butyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and diethylene glycol; ethyl acetate, n-butyl acetate, isobutyl acetate, and ethylene glycol monomethyl ether. Examples of the solvent include ester-based solvents such as ethyl ether acetate and butyl carbitol acetate; ketone-based solvents such as methyl ethyl ketone, methyl isobutyl ketone and diisobutyl ketone; alcohol-based solvents such as ethanol, isopropanol, n-butanol, sec-butanol and isobutanol; and amide-based solvents such as Equamide (an amide-based solvent, product name, manufactured by Idemitsu Kosan Co., Ltd.), N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformamide, N-methylacetamide, N-methylpropioamide and N-methyl-2-pyrrolidone.

Among these, amide-based solvents are preferred, and N-methyl-2-pyrrolidone is more preferred. These solvents can be used alone or in combination of two or more.

From the viewpoint of pigment dispersibility of the conductive pigment paste and preventing deterioration or hydrolysis of the resin component, it is preferable that the conductive pigment paste is substantially free of water. Here, "substantially free of water" means that the water content is usually 1 mass % or less, preferably 0.5 mass % or less, and particularly preferably 0.1 mass % or less, based on 100 mass % of the total amount of the conductive pigment paste.
In the present invention, the water content of the conductive pigment paste can be measured by Karl Fischer coulometric titration. Specifically, the water content can be measured using a Karl Fischer moisture meter (manufactured by Kyoto Electronics Manufacturing Co., Ltd., product name "MKC-610") with the moisture vaporizer (manufactured by Kyoto Electronics Co., Ltd., product name "ADP-611") attached to the device set at a temperature of 130°C.

When using amide compounds (solvents) such as N-methyl-2-pyrrolidone, amine components may be included as impurities, and in the conductive pigment paste of the present invention, the viscosity or tendency to thicken may vary from lot to lot depending on the amine components that are impurities.

In addition, when the conductive pigment paste of the present invention is made into an electrode layer by the method described below, the solvent and the like volatilize and do not remain, but it is preferable to recover and reuse the volatilized solvent in order to reduce waste, be environmentally friendly, and/or reduce raw material costs. In other words, it is preferable to use a recycled product as the solvent (C). This recycled solvent (recycled product) will also contain the amine compound (E1) that is originally contained in the conductive pigment paste of the present invention, and similarly the viscosity or thickening tendency of the conductive pigment paste will differ from lot to lot. Furthermore, amine compounds often have a strong odor.

Therefore, it is preferable to control and adjust the amine compound content in the recycled solvent (C) to a certain amount or less, and the amine compound content is usually 1 mass% or less, preferably 0.5 mass% or less, and particularly preferably 0.1 mass% or less.

The amount of amine compounds contained can be quantified using common analyses such as ion chromatography-mass spectrometry (IC-MS). The amount can be quantified by creating a calibration curve for the peaks of amine species that are expected to be present.

The above phrase "using recycled products as the solvent (C)" means that the solvent (C) used in the conductive pigment paste of the present invention contains 10% by mass or more (preferably 20% by mass or more) of recycled products.

The content of the solvent (C) in the conductive pigment paste is, based on 100 mass% of the total amount of the conductive pigment paste, for example, 40 mass% or more, preferably 60 mass% or more, and more preferably 80 mass% or more, and for example, 99 mass% or less, preferably 98 mass% or less, and more preferably 97 mass% or less.
The solid content of the conductive pigment paste is, for example, 1 mass % or more, preferably 2 mass % or more, and more preferably 3 mass % or more, based on 100 mass % of the total amount of the conductive pigment paste, and is, for example, 60 mass % or less, preferably 40 mass % or less, and more preferably 20 mass % or less.

Fluorine resin (D)
The fluororesin (D) is a resin intended for forming a film of an electrode layer, and may be contained in the conductive pigment paste as necessary, and is preferably contained therein.
It is also an essential component of the composite paste described below.

As the fluororesin (D), polyvinylidene fluoride (PVDF) is particularly preferred, and one type may be used alone or two or more types may be used in combination. Furthermore, polyvinylidene fluoride may be modified in various ways, and from the viewpoint of adhesion to the substrate, it is preferable that it has a polar functional group.

The fluororesin (D) may be contained when the pigment is dispersed, or may be added after the pigment is dispersed, or may be contained during the production of a composite paste, which will be described later.
The weight average molecular weight of the fluororesin (D) is, from the viewpoints of adhesion to the substrate, reinforcement of the film properties, and solvent resistance, for example, 100,000 or more, preferably 500,000 or more, more preferably 650,000 or more, and for example, 3,000,000 or less, preferably 2,000,000 or less.

When fluororesin (D) is included, the content is, based on 100% by mass of the solid content of the conductive pigment paste, for example, 10.0% by mass or more, preferably 30.0% by mass or more, more preferably 40.0% by mass or more, and for example, 99.0% by mass or less, preferably 80.0% by mass or less, more preferably 60.0% by mass or less. Also, based on 100% by mass of the total amount of the conductive pigment paste, the content is, for example, 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 1% by mass or more, and for example, 10% by mass or less, preferably 7% by mass or less, more preferably 5% by mass or less.

When the fluororesin (D) is made into a resin solution from a solid state, from the viewpoint of solubility in the solvent, it is preferred that the fluororesin (D) is first mixed and dissolved in a solvent at a liquid temperature of 40° C. or higher (preferably 60° C. or higher, more preferably 80° C. or higher) (the upper limit is 200° C. or lower, preferably 100° C. or lower) to make a resin solution, and then the fluororesin (D) is further mixed and dispersed with the conductive pigment composition.
The "liquid temperature" refers to the temperature of the solvent or resin solution at the time of dissolution.
The solid fluororesin (D) may be mixed and dissolved in a solvent at 40° C. or higher in advance, or the solid fluororesin (D) may be mixed with a solvent and then heated to a temperature of 40° C. or higher.
Furthermore, the composition may contain components other than the fluororesin (D) and the solvent.
When the above-mentioned hot dissolution is carried out, the fluororesin (D) is preferably polyvinylidene fluoride (or a modified product thereof).
The solvent to be used may be one type alone or two or more types in combination, and as the type, those exemplified as the solvent (C) above can be suitably used.
In addition, it is preferable to cool the resin solution that has been hot dissolved as described above to a predetermined temperature of 10° C. or more and less than 40° C., and the cooling step is carried out by reacting the resin solution with ... by the following reaction:
From the viewpoint of preventing precipitation, it is preferable that the cooling rate, defined as cooling rate=(solution temperature at the start of cooling−solution temperature at the end of cooling)/cooling time, is 0.5° C./min or more (preferably 1° C./min or more).

High polar low molecular weight component (E)
The highly polar, low-molecular-weight component (E) is a component that increases the wettability and/or storage stability of the conductive pigment. Examples of the highly polar, low-molecular-weight component (E) include basic components and acidic components known per se. Among these, amine compounds ( It is preferred that the compound contains a cyclic alkyl group.

The content of the amine compound (E1) in the highly polar, low molecular weight component (E) is, for example, 50% by mass or more, preferably 75% by mass or more, and more preferably 95% by mass or more, based on 100% by mass of the highly polar, low molecular weight component (E).

Examples of the amine compound (E1) include ammonia, primary amines, secondary amines, and tertiary amines.

Primary amines include, for example, ethylamine, n-propylamine, sec-propylamine, n-butylamine, sec-butylamine, i-butylamine, tert-butylamine, pentylamine, hexylamine, heptylamine, octylamine, decylamine, laurylamine, myristyrylamine, 1,2-dimethylhexylamine, 3-pentylamine, 2-ethylhexylamine, allylamine, aminoethanol, 1-aminopropanol, 2-aminopropanol, aminobutanol, aminopentanol, aminohexanol, 3-ethoxypropylamine, 3-propoxypropylamine, 3-isopropoxypropylamine, 3-butoxypropylamine, 3-isobutoxypropylamine, 3-(2-ethylhexyloxy)propylamine, aminocyclopentane, aminocyclohexane, aminonorbornene, aminomethylcyclohexane, aminobenzene, benzylamine, phenethylamine, α-furan, primary monoamines such as phenylethylamine, naphthylamine, and furfurylamine; ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,2-diaminobutane, 1,3-diaminobutane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, dimethylaminopropylamine, diethylaminopropylamine, bis-(3-aminopropyl)ether, 1,2- Bis-(3-aminopropoxy)ethane, 1,3-bis-(3-aminopropoxy)-2,2'-dimethylpropane, aminoethylethanolamine, 1,2-bisaminocyclohexane, 1,3-bisaminocyclohexane, 1,4-bisaminocyclohexane, 1,3-bisaminomethylcyclohexane, 1,4-bisaminomethylcyclohexane, 1,3-bisaminoethylcyclohexane, 1,4-bisaminoethylcyclohexane, 1,3-bisaminopropylcyclohexane, 1,4-bisaminopropylcyclohexane, hydrogenated 4,4'-diaminodiphenylmethane, 2-aminopiperidine, 4-aminopiperidine, 2-aminomethylpiperidine, 4-aminomethylpiperidine, 2-aminoethylpiperidine, 4-aminoethylpiperidine, N-aminoethylpiperidine, N-aminopropylpiperidine, N-aminoethylmorpholine, N-aminopropylmorpholine, isophoronediamine, menthanediamine, 1,4-bisa Aminopropylpiperazine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 2,4-tolylenediamine, 2,6-tolylenediamine, 2,4-toluenediamine, m-aminobenzylamine, 4-chloro-o-phenylenediamine, tetrachloro-p-xylylenediamine, 4-methoxy-6-methyl-m-phenylenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-naphthalenediamine, 2,6-naphthalenediamine Benzidine, 4,4'-bis(o-toluidine), dianisidine, 4,4'-diaminodiphenylmethane, 2,2-(4,4'-diaminodiphenyl)propane, 4,4'-diaminodiphenyl ether, 4,4'-thiodianiline, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminoditolyl sulfone, methylenebis(o-chloroaniline), 3,9-bis(3-aminopropyl)2,4,8,10-tetraoxaspiro[5,5]undecane, diethylene Examples of primary polyamines include bis(hexamethylene)triamine, iminobispropylamine, methyliminobispropylamine, bis(hexamethylene)triamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, N-aminoethylpiperazine, N-aminopropylpiperazine, 1,4-bis(aminoethylpiperazine), 1,4-bis(aminopropylpiperazine), 2,6-diaminopyridine, and bis(3,4-diaminophenyl)sulfone.

Secondary amines include, for example, diethylamine, dipropylamine, di-n-butylamine, di-sec-butylamine, diisobutylamine, di-n-pentylamine, di-3-pentylamine, dihexylamine, dioctylamine, di(2-ethylhexyl)amine, methylhexylamine, diallylamine, pyrrolidine, piperidine, 2,4-leupetidine, 2,6-leupetidine, 3,5-leupetidine, diphenylamine, secondary monoamines such as N,N'-dimethylethylenediamine, N,N'-dimethyl-1,2-diaminopropane, N,N'-dimethyl-1,3-diaminopropane, N,N'-dimethyl-1,2-diaminobutane, N,N'-dimethyl-1,3 ... '-Dimethyl-1,4-diaminobutane, N,N'-dimethyl-1,5-diaminopentane, N,N'-dimethyl-1,6-diaminohexane, N,N'-dimethyl-1,7-diaminoheptane, N,N'-diethylethylenediamine, N,N'-diethyl-1,2-diaminopropane, N,N'-diethyl-1,3-diaminopropane, N,N'-diethyl-1,2-diaminobutane, N,N'-diethyl-1,3-diaminobutane Examples of secondary polyamines include hexane, N,N'-diethyl-1,4-diaminobutane, N,N'-diethyl-1,6-diaminohexane, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2,6-dimethylpiperazine, homopiperazine, 1,1-di-(4-piperidyl)methane, 1,2-di-(4-piperidyl)ethane, 1,3-di-(4-piperidyl)propane, and 1,4-di-(4-piperidyl)butane.

Examples of tertiary amines include trimethylamine, triethylamine, tri-n-propylamine, tri-iso-propylamine, tri-1,2-dimethylpropylamine, tri-3-methoxypropylamine, tri-n-butylamine, tri-iso-butylamine, tri-sec-butylamine, tri-pentylamine, tri-3-pentylamine, tri-n-hexylamine, tri-n-octylamine, tri-2-ethylhexylamine, tri-dodecylamine, tri-laurylamine, dicyclohexylethylamine, cyclohexyldiethylamine, tri-cyclohexylamine, N,N-dimethylhexylamine, N-methyldihexylamine, N,N-dimethylcyclohexylamine, N-methyldicyclohexylamine, N,N-diethylethanolamine, N,N-dimethylethanolamine, N-ethyldiethanolamine, triethanolamine, tribenzylamine, N,N-dimethylbenzylamine, diethylbenzylamine, tertiary monoamines such as diphenylamine, triphenylamine, N,N-dimethylamino-p-cresol, N,N-dimethylaminomethylphenol, 2-(N,N-dimethylaminomethyl)phenol, N,N-dimethylaniline, N,N-diethylaniline, pyridine, quinoline, N-methylmorpholine, N-methylpiperidine, 2-(2-dimethylaminoethoxy)-4-methyl-1,3,2-dioxabornane, and 2-, 3-, and 4-picoline; tetramethylethylenediamine, Examples of tertiary polyamines include pyrazine, N,N'-dimethylpiperazine, N,N'-bis((2-hydroxy)propyl)piperazine, hexamethylenetetramine, N,N,N',N'-tetramethyl-1,3-butanamine, 2-dimethylamino-2-hydroxypropane, diethylaminoethanol, N,N,N-tris(3-dimethylaminopropyl)amine, 2,4,6-tris(N,N-dimethylaminomethyl)phenol, and heptamethylisobiguanide.

These can be used alone or in combination of two or more types.

Among these, primary amine compounds are preferred, and monovalent amine compounds (monoamines) are more preferred.

The above amine compound (E1) may be an alkanolamine, an aliphatic amine, an alicyclic amine, an aromatic amine, etc., any of which may be suitably used, but aromatic amines are preferred.

Since it is preferable that no amine compound remains in the electrode layer after drying, the weight average molecular weight of the amine compound (E1) is preferably less than 1,000, more preferably 800 or less, even more preferably 500 or less, particularly preferably 350 or less, and even more particularly preferably 250 or less.
For the same reason, the boiling point of the amine compound is preferably 400° C. or lower, more preferably 300° C. or lower, and even more preferably 200° C. or lower.
Furthermore, if the boiling point is low, there is a possibility that the liquid will volatilize during production or storage, and furthermore, from the viewpoint of odor, the lower limit is preferably 50° C. or higher, and more preferably 100° C. or higher.
The amine value of the amine compound (E1) is usually 5 mgKOH/g or more, preferably 50 mgKOH/g or more, more preferably 105 mgKOH/g or more, and is usually within the range of 1,000 mgKOH/g or less.

As the other highly polar, low molecular weight component, for example, an acidic highly polar, low molecular weight component selected from organic acids and inorganic acids can be used alone or in combination with two or more of them in combination with the amine compound (E1). Also, a basic highly polar, low molecular weight component selected from organic bases and inorganic bases can be used alone or in combination with two or more of them in combination.
Examples of the organic acid include organic carboxylic acids (formic acid, acetic acid, propionic acid, benzoic acid, phthalic acid, etc.), organic sulfonic acids (benzenesulfonic acid, etc.), and examples of the inorganic acid include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and the like. Acid anhydrides of these acids can also be used.

Examples of organic bases include base components other than amine compounds, and examples of inorganic bases include metal hydroxides (sodium hydroxide, potassium hydroxide, etc.).

The content of the highly polar, low molecular weight component (E) is, for example, 1% by mass or more, preferably 1.5% by mass or more, and more preferably 2% by mass or more, based on 100% by mass of the solid content of the conductive pigment paste, and is, for example, 600% by mass or less, preferably 300% by mass or less, and more preferably 50% by mass or less.

Based on 100% by mass of the solid content of the conductive pigment (B), the lower limit is, for example, 1% by mass or more, preferably 2% by mass or more, and more preferably 5% by mass or more, and the upper limit is, for example, 1,000% by mass or less, preferably 500% by mass or less, and more preferably 50% by mass or less.
Based on 100% by mass of the total amount of the conductive pigment paste, the lower limit is, for example, 0.01% by mass or more, preferably 0.05% by mass or more, and more preferably 0.1% by mass or more, and the upper limit is, for example, 10% by mass or less, preferably 5% by mass or less, and more preferably 1% by mass or less.

Many highly polar, low molecular weight components (E) [especially amine compounds (E1)] have a strong odor, which can lead to poor working conditions during mixing and drying. In addition, they are generally expensive, which can lead to increased costs. Therefore, it is necessary to keep the content at the minimum necessary.

The content ratio of the solvent (C) to the highly polar, low molecular weight component (E) is usually within the range of 100/0.01 to 100/10, preferably within the range of 100/0.02 to 100/7, more preferably within the range of 100/0.05 to 100/5, and more preferably within the range of 100/0.1 to 100/4, in terms of the mass ratio of the solvent (C) to the highly polar, low molecular weight component (E).

Other Components The conductive pigment paste may further contain other components in addition to the above-mentioned components (A), (B), and (C), and the components (D) and (E) which may be included as necessary.

Other components include, for example, resins other than the pigment dispersion resin (A) and the fluororesin (D), neutralizing agents, defoamers, preservatives, rust inhibitors, plasticizers, pigments other than the conductive pigment (B), etc.

Pigments other than the conductive pigment (B) include, for example, white pigments such as titanium white and zinc oxide; blue pigments such as cyanine blue and indanthrene blue; green pigments such as cyanine green and verdigris; organic red pigments such as azo and quinacridone, red pigments such as red iron oxide; organic yellow pigments such as benzimidazolone, isoindolinone, isoindoline and quinophthalone, and yellow pigments such as titanium yellow and yellow lead. These pigments can be used alone or in combination of two or more. These pigments other than the conductive pigment (B) can be used for purposes such as color adjustment and reinforcement of the physical properties of the film within a range that does not significantly impair the conductivity, and may be dispersed simultaneously with the pigment dispersion resin (A) and the conductive pigment (B), or may be mixed as a pigment or pigment paste after dispersing the pigment dispersion resin (A) and the conductive pigment (B) to prepare a paste.

The content of pigments other than the conductive pigment (B) is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, based on 100% by mass of all pigments in the conductive pigment paste, and it is particularly preferable that they are substantially not contained.

From the viewpoints of pigment dispersibility, storage stability, and the like, the viscosity of the conductive pigment paste at a shear rate of 2 s ⁻¹ is, for example, less than 5,000 mPa·s, preferably less than 2,500 mPa·s, and more preferably less than 1,000 mPa·s, and is, for example, 10 mPa·s or more, preferably 50 mPa·s or more, and more preferably 100 mPa·s or more.

The viscosity can be measured, for example, using a cone and plate viscometer (manufactured by HAAKE, product name "Mars2", diameter 35 mm, cone and plate inclined at 2°).

[Method of manufacturing composite paste (for lithium ion secondary batteries)]
Step 3 (electrode active material mixing step)
In the production method of the present invention, first, a conductive pigment paste containing a conductive pigment is prepared by the above-mentioned steps 1 and 2. Furthermore, in step 3 (electrode active material mixing step), the conductive pigment paste and at least one kind of electrode active material (F) are mixed to produce a composite paste for a lithium ion secondary battery.

The solid content of the electrode active material (F) is usually 10% by mass or more, preferably 20% by mass or more, based on 100% by mass of the total amount of the composite paste, and is usually 99% by mass or less, preferably 95% by mass or less, which is suitable in terms of battery performance.
The fluororesin (D), which was an optional component in the conductive pigment paste, is an essential component in the composite paste and is always contained therein.
The solid content of the fluororesin (D) is usually 0.05 mass % or more, preferably 0.1 mass % or more, based on 100 mass % of the total amount of the composite paste, and is usually 10 mass % or less, preferably 2 mass % or less, which is suitable in terms of battery performance, paste viscosity, etc.

In the mixing step of step 3, the composite paste can be mixed uniformly using a conventional mixer and disperser.

The solid content of the pigment dispersion resin (A) in the solid content of the composite paste is usually 0.01% by mass or more, preferably 0.05% by mass or more, based on 100% by mass of the total amount of the composite paste, and is usually 10% by mass or less, preferably 1% by mass or less, which is suitable in terms of battery performance, paste viscosity, etc.

In the composite paste of the present invention, from the viewpoint of storage stability (suppression of thickening) in the composite paste, it contains a highly polar, low molecular weight component (E), and it is preferable that the highly polar, low molecular weight component (E) contains at least one type of amine compound (E1).
From the viewpoint of alleviating aggregation between the conductive pigment (B) and the electrode active material (F) by contacting (wetting) the highly polar, low molecular weight component (E) with the conductive pigment (B) and then mixing the electrode active material (F), it is preferable to include a sequence of first mixing the conductive pigment (B) and the highly polar, low molecular weight component (E).

The solid content of the conductive pigment (B) in the composite paste solids of the present invention is typically 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, based on 100% by mass of the total composite paste, and is typically 30% by mass or less, preferably 10% by mass or less, more preferably 5% by mass or less, which is preferred in terms of battery performance. The content of the solvent (C) in the composite paste of the present invention is typically 1% by mass or more, preferably 4% by mass or more, more preferably 7% by mass or more, based on 100% by mass of the total composite paste, and is typically 90% by mass or less, preferably 70% by mass or less, more preferably 50% by mass or less, which is preferred in terms of electrode drying efficiency and paste viscosity.

The above composite paste is suitable for use as a positive or negative electrode for lithium ion secondary batteries, and is preferably used as a positive electrode.

Electrode active material (F)
Examples of the electrode active material (F) include lithium composite oxides such as lithium nickel oxide (LiNiO ₂ ), lithium manganate (LiMn ₂ O ₄ ), lithium cobalt oxide (LiCoO ₂ ), and LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ; lithium iron phosphate (LiFePO ₄ ); sodium composite oxide; and potassium composite oxide. These electrode active materials (F) can be used alone or in combination of two or more. The electrode active material containing lithium iron phosphate is inexpensive and has relatively good cycle characteristics and energy density, and can therefore be used preferably.

The particle size of the electrode active material is usually 0.5 μm or more, preferably 10.5 μm or more, and usually 30 μm or less, preferably 20 μm or less.

The solid content of the electrode active material (F) in the 100% by mass solids of the composite paste for lithium ion secondary battery electrodes of the present invention is usually 50% by mass or more, preferably 60% by mass or more, and is preferably less than 100% by mass in terms of battery capacity, battery resistance, etc.

When the composite paste contains the electrode active material (F), it may thicken during storage. The reason for this is that the electrode active material (F) has alkali metal hydroxides (e.g., LiOH, KOH, NaOH, etc.) derived from the raw materials on the particle surface, and is thought to aggregate (thicken) due to the conductive pigment (B) having an acidic surface. Therefore, by containing a certain amount or more of the highly polar low molecular weight component (E) [particularly the amine compound (E1)], it is possible to suppress the thickening of the composite paste during storage.

As the electrode active material (F) of the present invention, an electrode active material composite (F-1) having at least a part of its surface covered with carbon nanotubes can be suitably used.
The composite (F-1) can be obtained in advance by mixing the electrode active material (F), the carbon nanotubes, and, if necessary, other components (e.g., a solvent or a dispersion resin). If necessary, a drying step can be added after mixing, so that the carbon nanotubes can be more uniformly adsorbed and/or fixed to the electrode active material (F).
Furthermore, the electrode active material composite (F-1) produced as described above can form a uniform conductive network around the electrode active material by adsorbing and/or fixing the carbon nanotubes to the surface of the electrode active material.
As the carbon nanotubes that can be used in the electrode active material composite (F-1), any known carbon nanotubes can be used without any particular limitation, but the carbon nanotubes exemplified as the carbon nanotubes (B1) can be preferably used.

[Lithium-ion secondary battery electrodes]
As described above, an electrode layer for a lithium ion secondary battery (also referred to as an electrode mixture layer or a mixture layer) can be produced by applying a mixture paste for a lithium ion secondary battery to a core surface (current collector) of a positive electrode or a negative electrode and drying the applied paste, and is particularly preferably used for a positive electrode.

Furthermore, the conductive pigment paste obtained by the production method of the present invention can be used not only as a paste for a composite layer (electrode layer) but also as a primer layer (also called a functional layer or adhesive layer) between an electrode core material and a composite layer (electrode layer).
The method of applying the composite paste for lithium ion secondary batteries can be carried out by a method known per se using a die coater or the like. The amount of application of the composite paste for lithium ion secondary batteries is not particularly limited, but can be set so that the thickness of the composite layer after drying is, for example, 0.04 mm or more, preferably 0.06 mm or more, and, for example, 0.30 mm or less, preferably 0.24 mm or less. The temperature of the drying step can be appropriately set, for example, 80° C. or more, preferably 100° C. or more, and, for example, 250° C. or less, preferably 200° C. or less. The time of the drying step can be appropriately set, for example, 5 seconds or more, and, for example, 120 minutes or less, preferably 60 minutes or less.

In the drying step, all or part of the solvent (C) and the highly polar, low molecular weight component (E) that may be contained as needed volatilize. As mentioned above, however, in order to reduce waste, be environmentally friendly, and/or reduce costs, it is preferable to recover and reuse the volatilized components (C) and (E).

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these specific embodiments. In each example, "parts" refers to parts by mass and "%" refers to % by mass.

[Production of Dispersion Resin]
Production Example 1
A reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, and a water separator was charged with 75 parts of N-methyl-2-pyrrolidone (note 1) and heated to 120°C in a nitrogen stream. When the temperature reached 120°C, a mixture of the monomer species (total 100 parts) shown in Table 1 below and 2 parts of 2,2'-azobis(2-methylbutyronitrile) was added dropwise over 3 hours. After the addition was completed, the mixture was aged at 120°C for 30 minutes, and a mixture of 1 part of 2,2'-azobis(2-methylbutyronitrile) and 20 parts of N-methyl-2-pyrrolidone (note 1) was added dropwise over 1 hour. After further aging at 120°C for 1 hour, the mixture was cooled, and N-methyl-2-pyrrolidone (note 1) was added to obtain an acrylic resin (A1) with a solid content of 50%. The polar functional group concentration was 1.3 mmol/g.

(Note 1) N-methyl-2-pyrrolidone: water content 500 ppm (Note 2), amine content 500 ppm (Note 2), recycled product (Note 2) The water content and amine content were measured using a Karl Fischer moisture meter (Kyoto Electronics Manufacturing Co., Ltd., product name "MKC-610") and ion chromatography (Shimadzu Corporation, product name "prominence HIC-NS").

Production Example 2
An acrylic resin (A2) having a solids content of 50% was obtained in the same manner as in Production Example 1, except that the monomer types shown in Table 1 below were used.
The weight average molecular weights of the resins obtained are shown in Table 1. In the table, "resin A1" means acrylic resin (A1), and "resin A2" means acrylic resin (A2).

The abbreviations for the monomer species in Table 1 above are as follows.
SLMA: Lauryl methacrylate (having a hydrocarbon group with 12 carbon atoms)
BEMA: Behenyl methacrylate (having a hydrocarbon group with 22 carbon atoms)
St: styrene DMAEMA: N,N-dimethylaminoethyl methacrylate.

[Crushing of Carbon Nanotubes (CNT)]
Production Example 3
Using a continuous dry bead mill "Drystar SDA1" (manufactured by Ashizawa Finetech Co., Ltd.), carbon nanotubes (CNT1 (Table 2 below)) were pulverized for 1 hour at a supply rate of 0.5 kg/hr with zirconia beads (diameter 3.0 mm), a filling rate of 70%, and a mill peripheral speed of 5.0 m/s, to obtain a pulverized carbon nanotube product (C1-1).
When the G/D ratio of the carbon nanotubes before pulverization is α and the G/D ratio after pulverization is β, β/α was 0.97. The G/D ratio was measured by the method described below.

Production Example 4
Using a continuous dry bead mill "Drystar SDA1" (manufactured by Ashizawa Finetech Co., Ltd.), carbon nanotubes (CNT1 (Table 2 below)) were pulverized for 2 hours at a supply rate of 0.5 kg/hr with zirconia beads (diameter 3.0 mm), a filling rate of 70%, and a mill peripheral speed of 5.0 m/s, to obtain a pulverized carbon nanotube product (C1-2).
When the G/D ratio of the carbon nanotubes before pulverization is α and the G/D ratio after pulverization is β, β/α was 0.95. The G/D ratio was measured by the method described below.

Production Example 5
Using a continuous dry bead mill "Drystar SDA1" (manufactured by Ashizawa Finetech Co., Ltd.), carbon nanotubes (CNT2 (Table 2 below)) were pulverized for 2 hours at a supply rate of 0.5 kg/hr with zirconia beads (diameter 3.0 mm), a filling rate of 70%, and a mill peripheral speed of 5.0 m/s, to obtain a pulverized carbon nanotube product (C2-2).
When the G/D ratio of the carbon nanotubes before pulverization is α and the G/D ratio after pulverization is β, β/α was 0.95. The G/D ratio was measured by the method described below.

Production Example 6
Using a continuous dry bead mill "Drystar SDA1" (manufactured by Ashizawa Finetech Co., Ltd.), carbon nanotubes (CNT3 (Table 2 below)) were pulverized for 1 hour at a supply rate of 0.5 kg/hr with zirconia beads (diameter 3.0 mm), a filling rate of 70%, and a mill peripheral speed of 5.0 m/s, to obtain a pulverized carbon nanotube product (C3-1).
When the G/D ratio of the carbon nanotubes before pulverization is α and the G/D ratio after pulverization is β, β/α was 0.97. The G/D ratio was measured by the method described below.

The above carbon nanotubes are all multi-walled carbon nanotubes.
The median diameter (D50), G/D ratio, specific surface area (BET specific surface area), and amount of acidic groups in Table 2 were measured by the methods described below.

[Production of conductive pigment paste and composite paste]
Example 1A
In a container, 5,000 parts of N-methyl-2-pyrrolidone (Note 1), 200 parts of crushed carbon nanotubes (C1-2), 80 parts of polyvinylpyrrolidone (40 parts solids) (Note 3) as a dispersion resin, 1,800 parts of KF Polymer W#7300 (manufactured by Kureha Corporation, trade name, polyvinylidene fluoride, weight average molecular weight 1,000,000) resin solution (180 parts solids) (Note 4), and 25 parts of benzylamine as an amine were mixed while stirring, and finally N-methyl-2-pyrrolidone (Note 1) was used to adjust the total mass to 10,000 parts. Then, the mixture was dispersed in a ball mill for 4 hours to produce a conductive pigment paste (A-1).
(Note 3) Polyvinylpyrrolidone: weight average molecular weight (Mw) 12,000, polar functional group concentration 9.0 (mmol/g)
(Note 4) The polyvinylidene fluoride resin solution was prepared by mixing and dissolving polyvinylidene fluoride and N-methyl-2-pyrrolidone (Note 1) at a temperature of 80°C, and then cooling the mixture to 30°C over 40 minutes to obtain a resin solution.

Examples 2A to 10A, Comparative Examples 1A to 2A
Conductive pigment pastes (A-2) to (A-12) were obtained in the same manner as in Example 1A, except that the dispersion resin, carbon nanotubes (CNT), and amine were mixed as shown in Table 3 below.
In the comparative example, carbon nanotubes [CNT1 (C1-0)] that were not pulverized (dry dispersed) were used.
The results of the evaluation test of the conductive pigment paste described below are shown in Table 3 below.

The blending amounts of the dispersing resin in Table 3 above are values based on solid content.
The compositions of the dispersing resins in Table 3 above are as follows:
Polyvinyl butyral: average degree of polymerization 600, amount of hydroxyl groups 12 mol%, amount of butyral groups 87 mol%, amount of acetyl groups 1 mol%, concentration of polar functional groups 1.0 (mmol/g)
Polymethyl methacrylate: weight average molecular weight 20,000, homopolymer of methyl methacrylate, polar functional group concentration 0 (mmol/g).
The boiling points and molecular weights of the amines in Table 3 above are as follows:
Benzylamine: boiling point 185°C, molecular weight 107
Aminomethylpropanol: boiling point 166°C, molecular weight 89.

Example 1B
100 parts of the conductive pigment paste (A-1) was mixed with 900 parts of electrode active material particles ₍ lithium nickel manganese oxide particles having a spinel structure represented by _the composition formula _{LiNi0.5Mn1.5O4} , average particle diameter 6 μm, BET specific surface area 0.7 ^m2 /g) using a disper to produce a composite paste (B-1).

Examples 2B to 10B, Comparative Examples 1B to 2B
Composite pastes (B-2) to (B-12) were obtained in the same manner as in Example 1B except that the compositions were as shown in Table 4 below.
The results of the evaluation test of the composite paste, which will be described later, are shown in Table 3 above.

<Median diameter (D50)>
The median diameter (D50) was measured using a laser diffraction/scattering type particle size distribution measuring device "LA-960" (trade name, manufactured by HORIBA Co., Ltd.) according to the following procedure.

[Preparation of aqueous dispersion medium]
0.10 g of F10MC (trade name, carboxymethylcellulose sodium (hereinafter also referred to as CMCNa), manufactured by Nippon Paper Industries Co., Ltd.) was added to 100 mL of distilled water and dissolved by stirring at room temperature for 24 hours or more to prepare an aqueous dispersion medium containing 0.1% by mass of CMCNa.

[Preparation of CMCNa aqueous solution]
2.0 g of F10MC (trade name, sodium carboxymethylcellulose, manufactured by Nippon Paper Industries Co., Ltd.) was added to 100 mL of distilled water and dissolved by stirring at room temperature for 24 hours or more to prepare an aqueous solution of 2.0 mass % CMCNa.

[Pre-measurement processing]
6.0 mg of carbon nanotubes were weighed into a vial, and 6.0 g of the aqueous dispersion medium was added. An ultrasonic homogenizer (Microtec Nithion, "SmurtNR-50") was used for pre-measurement treatment. The tip was confirmed to be free of deterioration, and was adjusted so that the tip was immersed 10 mm or more below the surface of the sample to be treated. The time set (irradiation time) was 40 seconds, the power set was 50%, the start power was 50% (output 50%), and the carbon nanotube aqueous dispersion was homogenized by ultrasonic irradiation using auto power operation with a constant output power.

[measurement]
Using the carbon nanotube aqueous dispersion, the proportion of dispersed carbon nanotube particles having a size of 1 μm or less and the median diameter (D50) were measured according to the following methods.
The optical model of the LS 13 320 universal liquid module is set to a refractive index of 1.520 for carbon nanotubes and 1.333 for water, and after the module has been washed, it is filled with approximately 1.0 mL of a CMCNa aqueous solution.
After performing offset measurement, optical axis adjustment, and background measurement under the condition of 50% pump speed, the prepared carbon nanotube aqueous dispersion was added to the particle size distribution meter so that the relative concentration, which indicates the percentage of light scattered outside the beam by the particles, was 8-12%, or the PIDS was 40-55%, and ultrasonic irradiation was performed for 2 minutes at 78 W using the particle size distribution meter attachment (measurement pretreatment), and after circulating for 30 seconds to remove air bubbles, the particle size distribution was measured. A graph of particle size (particle diameter) versus volume % was obtained, and the presence ratio and median diameter (D50) of dispersed particles of 1 μm or less were determined.
For each carbon nanotube sample, three measurement samples were taken from different locations and particle size distribution was measured. The proportion of dispersed particles of 1 μm or less and the median diameter (D50) were calculated as the average value.

<G/D ratio of carbon nanotubes>
The Raman spectrum of the carbon nanotube was measured by placing the carbon nanotube in a Raman microscope (manufactured by Horiba, Ltd., product name "XploRA") and using a laser wavelength of 532 nm. The G/D ratio of the carbon nanotube was determined by taking the maximum peak intensity G within the range of 1560 cm ^-1 to 1600 cm ^-1 in the spectrum and the maximum peak intensity D within the range of 1310 cm ^-1 to 1350 cm ^-1 .

<Specific surface area (BET specific surface area)>
The BET specific surface area of the carbon nanotubes was measured as a BET specific surface area (m ² /g) in accordance with JIS Z8830:2013 using a specific surface area measuring device (BERSORP-MAX (Microtrac-Bell Corporation)).

<Amount of Acidic Groups in Carbon Nanotubes (CNTs)>
2 g of CNT was weighed out, immersed in 50 ml of 0.01 M benzylamine/n-methylpyrrolidone solution, and dispersed for 1 hour using an ultrasonic irradiator. Then, the mixture was centrifuged and the supernatant was filtered through a filter. The benzylamine remaining in the obtained filtrate was quantitatively analyzed by potentiometric titration with 0.1 M hydrochloric acid, and the amount of acidic groups (mmol/g) per 1 g of the obtained CNT was identified.

Evaluation Tests Evaluation tests were carried out on the conductive pigment pastes and composite pastes obtained in the above Examples and Comparative Examples. If there was even one unacceptable evaluation result, the evaluation was deemed to be unacceptable.

<Dispersibility>
The conductive pigment paste thus obtained was subjected to the dispersion test of JIS K-5600-2-5, and the dispersibility was evaluated using a grain gauge according to the following criteria. C and D are failures.
A: The pigment is dispersed at a particle size of less than 10 μm. The dispersibility is very good.
B: The pigment is dispersed at a size of 10 μm or more and less than 20 μm. The dispersibility is somewhat good.
C: The pigment is dispersed at a particle size of 20 μm or more, but no aggregates are visible. Dispersibility is somewhat poor.
D: Aggregates are visually observed. Dispersibility is very poor.

<Volume resistivity (conductivity)>
The volume resistivity of the obtained conductive pigment paste was further measured. In the measurement of the volume resistivity, a 5 mass % solution of polyvinylidene fluoride (manufactured by Kureha Corporation, product name "KF Polymer W#7300", solvent: N-methyl-2-pyrrolidone) was used as a binder.
The conductive pigment paste and the KF Polymer W#7300 solution were weighed out so that the ratio of the mass of the conductive pigment (B) in the obtained conductive pigment paste to the total mass of the solid content of the pigment dispersion resin (A) and the solid content of the KF Polymer W#7300 in the conductive pigment paste was 5:100, and mixed for 2 minutes with an ultrasonic homogenizer to obtain a measurement sample.
A sample for measurement was applied to a glass plate (2 mm x 100 mm x 150 mm) by the doctor blade method, and the plate was dried by heating at 80 ° C. for 60 minutes to form a coating film on the glass plate. After measuring the film thickness of the coating film obtained, the resistance value was measured with an ASP probe (manufactured by Mitsubishi Chemical Analytech Co., Ltd., product name "MCP-TP03P") and a resistivity meter (manufactured by Mitsubishi Chemical Analytech Co., Ltd., product name "Loresta-GP MCP-T610"), and the obtained resistance value was multiplied by a resistivity correction factor (RCF) of 4.532 and the film thickness of the coating film to calculate the volume resistivity. The volume resistivity was evaluated according to the following criteria. D is a failure.
A: The volume resistivity is less than 7 Ω·cm and the electrical conductivity is good.
B: The volume resistivity is 7 Ω·cm or more and less than 15 Ω·cm, and the electrical conductivity is normal.
D: The volume resistivity is 15 Ω·cm or more, and the electrical conductivity is poor.

<Initial viscosity>
The viscosity of the obtained composite paste was measured at a shear rate of 2.0 sec ^-1 using a cone and plate viscometer (manufactured by HAAKE, product name "Mars2", diameter 35 mm, cone and plate inclined at 2°) and evaluated according to the following criteria. D is failure.
A: The viscosity is less than 10 Pa·s.
B: Viscosity is 10 Pa·s or more and less than 20 Pa·s.
C: Viscosity is 20 Pa·s or more and less than 50 Pa·s.
D: Viscosity is 50 Pa·s or more.

[Production of battery electrode layer]
Application Examples 1C to 10C
The composite pastes obtained in Examples 1B to 10B were applied in strip form by roller coating to both sides of a long aluminum foil (positive electrode current collector) having an average thickness of 15 μm so that the basis weight per side was 10 mg/cm ² (based on solid content), and then dried (drying temperature 180° C., 10 minutes) to form a positive electrode layer. The positive electrode active material layer (positive electrode layer) supported on this positive electrode current collector was rolled with a roll press machine to adjust the properties.
The resulting electrode layer had a residual solvent amount of less than 1% and was an electrode layer with good finish and other properties.

Claims

A method for producing a conductive pigment paste containing a pigment dispersing resin (A), a conductive pigment (B), a solvent (C), and a fluororesin (D) which may be included as necessary, comprising the steps of:
Step 1: A step of pulverizing a conductive pigment composition having a pigment concentration of 50 mass% or more of the conductive pigment (B) by a pulverizer; and
Step 2: A step of mixing and dispersing the conductive pigment composition obtained in step 1 with components including a pigment dispersing resin (A), a solvent (C), and a fluororesin (D) which may be included as needed;
A method for producing a conductive pigment paste, comprising the steps of:
The method for producing a conductive pigment paste according to claim 1, characterized in that the conductive pigment (B) contains carbon nanotubes (B1).
In the carbon nanotubes (B1) before and after the pulverization in step 1, the following (1) and (2) are
(1) The G/D ratio of the carbon nanotubes (B1) before pulverization is 0.1 or more and 5.0 or less, where G is the maximum peak intensity in the range of 1560 cm -1 to 1600 cm - 1 and D is the maximum peak intensity in the range of 1310 cm-1 to 1350 cm -1 .
(2) When the G/D ratio of the carbon nanotubes (B1) before pulverization is α and the G/D ratio of the carbon nanotubes (B1) after pulverization is β, β/α<1.00;
The method for producing a conductive pigment paste according to claim 2 , which satisfies the above.
The method for producing a conductive pigment paste according to claim 1, characterized in that the pigment dispersion resin (A) has at least one alkyl group having 12 or more carbon atoms.
The method for producing a conductive pigment paste according to claim 1, characterized in that the pigment dispersion resin (A) has at least one polar functional group selected from the group consisting of amide groups, imide groups, hydroxyl groups, carboxyl groups, sulfonic acid groups, phosphate groups, silanol groups, cyano groups, pyrrolidone groups, and amino groups, and the concentration of the polar functional groups in the pigment dispersion resin (A) is 0.3 mmol/g to 23 mmol/g.
The method for producing a conductive pigment paste according to claim 1, characterized in that the conductive pigment paste contains a fluororesin (D), and the step of mixing the fluororesin (D) includes a step of mixing and dissolving the fluororesin with a solvent having a liquid temperature of 40°C or higher in advance, or a step of mixing the fluororesin (D) with a solvent and then heating the mixture to a temperature of 40°C or higher.
The method for producing a conductive pigment paste according to claim 1, characterized in that the solvent (C) is N-methyl-2-pyrrolidone.
The step 2 is
Step 2-1: adding components containing a conductive pigment composition in an amount of 70 mass% or less based on 100 mass% of the total amount of the conductive pigment composition contained in the conductive pigment paste obtained after dispersion into a disperser and performing a dispersion treatment; and Step 2-2: adding the conductive pigment composition into the disperser until a desired concentration is reached, and performing a dispersion treatment.
2. The method according to claim 1, further comprising the steps of:
The conductive pigment paste obtained by the method for producing a conductive pigment paste according to any one of claims 1 to 8 further comprises step 3: mixing at least one electrode active material (F);
A method for producing a composite paste for a lithium ion secondary battery, comprising:
A method for producing an electrode layer for a lithium ion secondary battery, comprising a step of applying a composite paste for a lithium ion secondary battery obtained by the method of claim 9 to a current collector.
A method for producing an electrode for a lithium ion secondary battery, comprising the step of applying an electrode insulating portion to an end portion or an upper layer of the electrode layer obtained by the method for producing an electrode layer for a lithium ion secondary battery according to claim 10.