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

Abstract

The present invention addresses the problem of providing a conductive pigment paste and composite paste that exhibit excellent pigment dispersibility and storage stability even at high pigment concentrations, and furthermore, an electrode layer for a lithium-ion secondary battery that exhibits excellent performance (such as conductivity and battery performance). The solution provided 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 may be included as needed, the method comprising the following steps in sequence: Step 1: pulverizing a conductive pigment composition having a pigment concentration of the conductive pigment (B) of 50 mass % or more using a pulverizer; and Step 2: mixing and dispersing components containing the pigment dispersing resin (A), the solvent (C), and the fluororesin (D) that may be included as needed with the conductive pigment composition obtained in Step 1.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a conductive pigment paste and a composite paste that are excellent in conductivity, pigment dispersibility, and storage stability even at a high pigment concentration, and to a method for producing a battery electrode layer that has excellent battery performance. [Background technology]

[0002] Paste-like pigment dispersions in which a pigment is dispersed in a mixture of a pigment dispersing resin, a solvent, and the like have conventionally been widely used in fields such as paints, battery electrodes, coating materials, coating materials, electromagnetic wave shields, display panels, touch screen panels, colored films, colored sheets, decorative materials, protective materials, magnet modifiers, printing inks, device members, electronic device members, printed wiring boards, solar cells, functional rubber members, and resin molded films. Furthermore, conductive pigments, conductive polymers, and the like are incorporated into these materials to impart functions such as electrostatic coating properties, conductivity, electromagnetic wave shielding properties, and antistatic properties.

[0003] In these fields, there is an increasing demand for improvements in performance such as pigment dispersibility, storage stability, conductivity, coatability, and finish. To this end, pigment dispersing resins and pigment pastes are being developed that have excellent pigment dispersing ability and excellent pigment dispersion stability that prevents reagglomeration of pigment particles in the formed pigment dispersion.

[0004] When designing a pigment paste, it is important to prepare a highly concentrated and uniformly dispersed pigment paste using a small amount of pigment dispersing resin, in order to prevent the pigment dispersing resin from adversely affecting the conductive properties of the final product itself, such as the coating film, and from the perspective of reducing the amounts of solvent and pigment dispersing resin used and reducing the energy used during drying.

[0005] For example, Patent Document 1 discloses a method for producing an electrode for a non-aqueous electrolyte battery, which comprises the steps of kneading a carbon-based conductive agent and a dispersion solvent, and then dispersing the carbon-based conductive agent using a medium-type disperser; 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 applying the active material paste to an electrode substrate. However, in these inventions, when the paste has a high pigment concentration and / or a high viscosity, uniform dispersion cannot be achieved and storage stability is poor. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 10-144302 Summary of the Invention [Problem to be solved by the invention]

[0007] An 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 (battery electrode layer) that is excellent in finish quality, conductivity, etc. [Means for solving the problem]

[0008] As a result of intensive research into solving the above-mentioned 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) that can be contained as needed, the method comprising: Step 1: A step of pulverizing a conductive pigment composition having a pigment concentration of the conductive pigment (B) of 50 mass % or more using a pulverizer; and Step 2: A step of mixing and dispersing components including a pigment dispersing resin (A), a solvent (C), and a fluororesin (D) which may be included as needed, into the conductive pigment composition obtained in Step 1; The present inventors have found that the above-mentioned problems can be solved by a method for producing a conductive pigment paste including the steps of sequentially carrying out the above, and have thus completed the present invention.

[0009] 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. Section 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) that may be included as needed, comprising: Step 1: A step of pulverizing a conductive pigment composition having a pigment concentration of the conductive pigment (B) of 50 mass % or more using a pulverizer; and Step 2: A step of mixing and dispersing components including a pigment dispersing resin (A), a solvent (C), and a fluororesin (D) which may be included as needed, into the conductive pigment composition obtained in Step 1; A method for producing a conductive pigment paste, comprising the steps of: Section 2. Item 2. The method for producing a conductive pigment paste according to Item 1, wherein the conductive pigment (B) contains carbon nanotubes (B1). Section 3. In the carbon nanotubes (B1) before and after the pulverization in step 1, the following (1) and (2) are used: (1) 1560cm -1 More than 1600cm -1 The maximum peak intensity within the following range is G, 1310 cm -1 More than 1350cm -1 The G / D ratio of the carbon nanotubes (B1) before pulverization is 0.1 or more and 5.0 or less, where D is the maximum peak intensity within the following range: (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, wherein the above conditions are satisfied. Section 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. Section 5. 5. The method for producing a conductive pigment paste according to any one of Items 1 to 4, wherein the pigment dispersing 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 dispersing resin (A) is 0.3 mmol / g to 23 mmol / g. Section 6. Item 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 at 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. Section 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. Section 8. The step 2 Step 2-1: Adding components containing a conductive pigment composition in an amount of 70% by mass or less, based on 100% by 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; Step 2-2: A step of adding a conductive pigment composition to a disperser to perform a dispersion treatment until the conductive pigment composition reaches a desired concentration; 8. The method according to any one of items 1 to 7, comprising the steps of: Section 9. 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: Section 10. Item 10. A method for producing an electrode layer for a lithium ion secondary battery, comprising the step of applying the lithium ion secondary battery composite paste obtained by the production method of Item 9 to a current collector. Section 11. Item 11. A method for producing an electrode for a lithium ion secondary battery, comprising the step of applying an electrode insulating portion 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. [Effects of the Invention]

[0010] 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 dispersing resin. Furthermore, the resulting coating film (battery electrode layer) is excellent in finish, conductivity, battery performance, etc. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail.

[0012] It should be understood that the present invention is not limited to the following embodiments, but also includes various modifications that are implemented within the scope of the present invention. In the present invention, a composition containing the conductive pigment (B) at a pigment concentration of 50 mass % or more and obtained by pulverizing it 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) that may be included as needed, and optionally other various components is called 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 blending at least one electrode active material and, optionally, other various components to be applied, and the resulting paste is called a "composite paste." The composite paste that is applied to an object to be coated and dried is called a "coated film" or a "composite layer." When the coating film is used as a battery electrode, it can also be called an "electrode layer." Carbon nanotubes can also be abbreviated as "CNT."

[0013] [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 needed, comprising the steps of: first, pulverizing the conductive pigment (B) in a pulverizer at a pigment concentration of 50 mass % or more to obtain a conductive pigment composition (step 1: pulverizing step); and second, mixing and dispersing components including the pigment dispersing resin (A), the solvent (C), and the fluororesin (D) that can be included as needed with the conductive pigment composition obtained in step 1 (step 2: dispersing step), thereby producing a conductive pigment paste having the 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.

[0014] Process 1 (Crushing process) Step 1 is a step of pulverizing (including disintegration) the conductive pigment (B) using a pulverizer to obtain a conductive pigment composition, and the pigment concentration of the conductive pigment (B) 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 particularly preferably 100% by mass, based on 100% by mass of the conductive pigment composition. Note that the above-mentioned "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 components other than the conductive pigment (B) in the conductive pigment composition, solvents, resins, pigments other than the conductive pigment (B), and the like, which will be described later, 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 particularly preferably 100% by mass, based on 100% by mass of the conductive pigment composition. The "solid content concentration" mentioned above is the proportion (% by mass) of solids when 1 g of a sample is dried by heating at 130°C for 3 hours.

[0015] Furthermore, the conductive pigment composition obtained in step 1 may contain components other than the conductive pigment (B) as long as the pigment concentration and solid content concentration are as described above. For example, the conductive pigment composition may contain a pigment dispersing resin (A), a pigment other than the conductive pigment (B), a solvent (C), and a fluororesin (D) that can be contained as needed, as described below. 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 will be mixed in a later step (step 3).

[0016] Conductive pigment (B) The conductive pigment (B) is a conductive pigment, and any known conductive pigment 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).

[0017] The content of the 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).

[0018] 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, from the viewpoints of viscosity, conductivity, and cost, it is preferable to use multi-walled carbon nanotubes.

[0019] When carbon nanotubes (B1) are used, the content thereof is, for example, 0.5% by mass or more, preferably 1% by mass or more, and more preferably 2% by mass or more, based on 100% by mass of the total amount of the conductive pigment paste, and is for example, 10% by mass or less, preferably 7% by mass or less, and more preferably 6% by mass or less. Furthermore, based on 100% by mass of the total solid content of the conductive pigment paste, the content is, for example, 5% by mass or more, preferably 10% by mass or more, and more preferably 20% by mass or more, and for example, 90% by mass or less, preferably 70% by mass or less, and more preferably 50% by mass or less.

[0020] 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 for example, 30 nm or less, preferably 28 nm or less, more preferably 25 nm or less.

[0021] 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 for example, 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less.

[0022] The BET specific surface area of ​​carbon nanotubes (B1) is usually 100 m due to the relationship between viscosity and conductivity. 2 / g or more, preferably 130m 2 / g or more, more preferably 160m 2 / g or more, usually 800m 2 / g or less, preferably 600m 2 / g or less, more preferably 400m 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, in accordance with JIS Z8830:2013, the BET specific surface area (m 2 / g) can be measured.

[0023] From the viewpoint of dispersibility and storage stability, 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. If the amount of acidic groups is 0.01 mmol / g or more, dispersibility will be good, and if it is 1.0 mmol / g or less, storage stability will be good.

[0024] The acidic groups can be imparted to the carbon nanotubes by the acid treatment described below.

[0025] (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 acid solution) is preferred. The acid contained in the acid treatment solution is not particularly limited, but examples 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 adjusting the concentration, temperature, treatment time, etc. of the acid treatment solution.

[0026] After the acid treatment, excess acid components adhering to the surface are 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 recovered from the acid-treated carbon nanotubes by a known method such as filtration, and then washed with water. After the washing, if necessary, water adhering to the surface can be removed by drying, or the like, to obtain the acid-treated carbon nanotubes.

[0027] The volume-equivalent median diameter (D50) of the carbon nanotubes (B1), as measured by the method described in the Examples below, is typically 10 μm or more, preferably 15 μm or more, and more preferably 20 μm or more, and typically 250 μm or less, preferably 200 μm or less, and more preferably 150 μm or less. The median diameter (D50) can be determined by irradiating carbon nanotube particles with laser light and converting the diameter of the carbon nanotubes into a spherical equivalent based on the scattered light. A larger median diameter (D50) indicates more carbon nanotube aggregates and poor dispersibility. A median diameter (D50) greater than 250 μm increases the likelihood of carbon nanotube aggregates being present in the electrode, resulting in non-uniform conductivity throughout the electrode. On the other hand, a median diameter (D50) smaller than 10 μm results in insufficient conductive paths due to the short fiber length, resulting in reduced conductivity. 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 in the electrode while maintaining their electrical conductivity.

[0028] In addition, in the Raman spectrum of the carbon nanotube (B1), -1 More than 1600cm -1 The maximum peak intensity within the following range is G, 1310 cm -1 More than 1350cm -1 When the maximum peak intensity within the following range is defined as D, the G / D ratio 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.

[0029] Here, it is preferable that the G / D ratio is in the range of 0.1 to 5.0, since there are fewer defects and crystal interfaces on the carbon surface and the conductivity is likely to be high.

[0030] When carbon nanotubes (B1) are used as the conductive pigment (B), the carbon nanotubes (B1) before and after the pulverization in the step 1 preferably satisfy the following (1) and (2). (1) 1560cm -1 More than 1600cm -1 The maximum peak intensity within the following range is G, 1310 cm -1 More than 1350cm -1 When the maximum peak intensity within the following range is defined as D, the G / D ratio of the carbon nanotubes (B1) before pulverization is 0.1 or more and 5.0 or less. (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 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 ground time, and good dispersibility and storage stability are obtained in the dispersion step of Step 2 described below, and the coating film obtained thereby has excellent conductivity and finish.

[0031] 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 acetylene black.

[0032] 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, 80 nm or less, 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) with an electron microscope, determining the projected area of ​​each of 100 particles, calculating the diameter of a circle equivalent to that area, and then simply averaging the diameters of the 100 particles. Note that if the pigment is in an aggregated state, the calculation is based on the primary particles that make up the aggregated particles.

[0033] The BET specific surface area of ​​the other conductive pigment (B2) is not particularly limited. 2 / g or more, preferably 10m 2 / g or more, more preferably 20m 2 / g or more, for example, 500m 2 / g or less, preferably 250m 2 / g or less, more preferably 200m 2 / g or less.

[0034] The dibutyl phthalate (DBP) oil absorption of the other conductive pigment (B2) is not particularly limited, and is, in view of the relationship between pigment dispersibility and conductivity, 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.

[0035] Crushing method and crusher The conductive pigment (B) is pulverized (including disintegration) by a pulverizer. 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 carried out using a pulverizer equipped with pulverizing media such as glass beads, zirconia beads, steel balls, etc. The pulverization is carried out by utilizing the crushing or destructive force generated by collisions between the pulverizing media and / or between the pulverizer and the pulverizer. Known pulverizing devices such as high-speed impact mills, jet mills, roll mills, attritors, ball mills, vibration mills, and bead mills can be used.

[0036] During pulverization, various vapors or gases can be blown into the pulverizer to further activate the surface of the conductive pigment (B) or adjust the activity. Suitable vapors include acidic or basic compounds, and suitable gases include oxygen and nitrogen.

[0037] The above-mentioned pulverization is preferably carried out by so-called dry dispersion. Here, "dry dispersion" refers to pulverizing a 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 surrounding substances, good dispersibility and storage stability can be obtained in the dispersion step (Step 2) described below, and the resulting coating film can have excellent conductivity and finish.

[0038] The outer diameter of the grinding media is preferably 0.1 to 5 mm, more preferably 0.5 to 3 mm. Within the above range, a 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.

[0039] Process 2 (dispersion process) Step 2 is a step of mixing and dispersing components containing a pigment dispersing resin (A), a solvent (C), and a fluororesin (D) that can be included as needed into the conductive pigment composition obtained in Step 1, and Step 2 allows a liquid conductive pigment paste to be obtained.

[0040] 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.

[0041] The conductive pigment paste is a conductive pigment paste containing a pigment dispersing resin (A), a conductive pigment (B), a solvent (C), and a fluororesin (D) that may be included as needed, and it is preferable that the pigment dispersing 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 dispersing resin (A) is 0.3 mmol / g or more and 23 mmol / g or less. Furthermore, it is preferable that the composition further contains a highly polar, low-molecular-weight component (E) as required.

[0042] 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, sand mill, ball mill, pebble mill, LMZ mill, DCP pearl mill, planetary ball mill, homogenizer, twin-screw kneader, or thin film swirling high-speed mixer (manufactured by Filmix, trade name "Clearmix," etc.). The order in which the components are mixed is not particularly limited.

[0043] Pigment dispersing resin (A) The pigment dispersing resin (A) preferably has at least one alkyl group having 12 or more carbon atoms. Any known alkyl group (hydrocarbon group) can be used as the alkyl group having 12 or more carbon atoms without any particular limitation, and is preferably a linear or branched alkyl group, more preferably a linear alkyl group. 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 by, for example, (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.

[0044] The pigment dispersing 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 phosphate group, a silanol group, a cyano group, a pyrrolidone group, and an amino group. When the pigment dispersing resin (A) has a polar functional group, the concentration of the polar functional group 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 these, 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 as the polar functional group, and it is more preferable to use at least a hydroxyl group, a carboxyl group, and an amino group.

[0045] 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 resins, polyester resins, epoxy resins, polyether resins, alkyd resins, urethane resins, polyvinyl alcohol, polyvinyl acetal, polyvinylpyrrolidone, polyvinyl acetate, silicone resins, polycarbonate resins, chlorine-based resins, and composite resins thereof. These resins can be used alone or in combination of two or more.

[0046] Among these, from the viewpoints of pigment dispersibility, storage stability, finish quality, and the like, it is preferable that the pigment dispersing resin (A) 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 containing a (meth)acryloyl group is preferred. The term "(co)polymer" in 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.

[0047] C(-R)2=C(-R)2...Equation (1) [In the above formula, each 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, phosphate group-containing vinyl (co)polymers, pyrrolidone group-containing vinyl (co)polymers, amino group-containing (co)polymers, etc. These (co)polymers can be used alone or in combination of two or more.

[0048] 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, copolymers of hydroxyethyl (meth)acrylate with other polymerizable unsaturated monomers, etc. The vinyl alcohol units in the (co)polymer may be obtained by (co)polymerizing fatty acid vinyl units and then hydrolyzing them.

[0049] Examples of the carboxyl group-containing vinyl (co)polymer include a polymer of (meth)acrylic acid, and a copolymer of poly(meth)acrylic acid and other polymerizable unsaturated monomers.

[0050] Examples of the amide group-containing vinyl (co)polymer include a polymer of (meth)acrylamide, and a copolymer of (meth)acrylamide and other polymerizable unsaturated monomers.

[0051] Examples of sulfonic acid group-containing vinyl (co)polymers include polymers of allylsulfonic acid or styrenesulfonic acid, and copolymers of allylsulfonic acid and / or styrenesulfonic acid with other polymerizable unsaturated monomers.

[0052] Examples of the phosphoric acid group-containing vinyl (co)polymer include a polymer of (meth)acryloyloxyalkyl acid phosphate, and a copolymer of (meth)acryloyloxyalkyl acid phosphate with other polymerizable unsaturated monomers.

[0053] Examples of amino group-containing vinyl (co)polymers include copolymers of N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate and other polymerizable unsaturated monomers.

[0054] Other copolymerizable unsaturated monomers include, for example, vinyl carboxylate ester monomers such as 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; Examples of the monomer include 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.

[0055] 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 particularly preferably 0.4 mmol / g to 2.0 mmol / g.

[0056] The vinyl (co)polymer (A1) can be produced by a polymerization method known per se, and for example, solution polymerization is preferably used, but is not limited thereto, and bulk polymerization, emulsion polymerization, suspension polymerization, etc. When solution polymerization is carried out, it may be continuous polymerization or batch polymerization, and the monomers may be charged all at once or in portions, or may be added continuously or intermittently.

[0057] The polymerization initiator used in the solution polymerization is not particularly limited, but specific examples thereof include azo compounds such as azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), azobis-2,4-dimethylpaleronitrile, and azobis(4-methoxy-2,4-dimethylpaleronitrile); acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, and 2,4,4-trimethylpentyl-2 peroxides such as α-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.

[0058] The polymerization reaction temperature is not particularly limited, but can usually be set in the range of about 30°C or higher and 200°C or lower.

[0059] 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.

[0060] 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.

[0061] Unless otherwise specified, the weight-average molecular weight in this specification 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 weight-average molecular weight can be measured using a gel permeation chromatograph "HLC8120GPC" (manufactured by Tosoh Corporation, trade name) and four columns "TSKgel G-4000HXL," "TSKgel G-3000HXL," "TSKgel G-2500HXL," and "TSKgel G-2000HXL" (all manufactured by Tosoh Corporation, trade name) under the conditions of a mobile phase of tetrahydrofuran, a measurement temperature of 40°C, a flow rate of 1 mL / min, and a detector RI.

[0062] After completion of the synthesis, the vinyl (co)polymer (A1) can be converted into a solid or a resin solution in which any solvent has been substituted by removing the solvent and / or replacing the solvent.

[0063] The solvent may be removed by heating at normal pressure or under reduced pressure. The solvent replacement method may involve adding a replacement solvent at any stage before, during, or after the solvent removal.

[0064] Furthermore, in the case of a vinyl (co)polymer (A1), the content of alkyl groups having 12 or more carbon atoms in the dispersing resin (A) 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%. In addition, when a compound having a reactive alkyl group with 12 or more carbon atoms is added to the resin later, the content of the alkyl group with 12 or more carbon atoms is calculated based on the mass proportion of the compound.

[0065] When the pigment dispersion resin (A) is converted from a solid state into a resin solution, it is preferable that, from the viewpoint of solubility in the solvent, the pigment dispersion resin (A) is first mixed and dissolved in a solvent at 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 form a resin solution, and then further mixed with other components [components (B), (C), (D), etc.]. 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 may be used alone or in combination of two or more kinds, and the types that can be suitably used are those listed as solvent (C) described below.

[0066] 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.

[0067] 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.

[0068] The solid content of the pigment dispersion resin (A) is, based on 100% by mass of the content of the conductive pigment (B), 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.

[0069] Solvent (C) As the solvent (C), water or various organic solvents can be suitably used. Specific examples of the solvents 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, ethylene glycol monomethyl ether, and diethylene glycol; Examples of suitable solvents 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, manufactured by Idemitsu Kosan Co., Ltd., trade name), N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformamide, N-methylacetamide, N-methylpropioamide and N-methyl-2-pyrrolidone.

[0070] Among these, amide solvents are preferred, and N-methyl-2-pyrrolidone is more preferred. These solvents can be used alone or in combination of two or more.

[0071] Furthermore, from the viewpoint of pigment dispersibility in 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% by mass or less, preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less, based on 100% by 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 measurement can be performed using a Karl Fischer moisture meter (manufactured by Kyoto Electronics Manufacturing Co., Ltd., product name "MKC-610") with the temperature of the moisture vaporizer (manufactured by Kyoto Electronics Manufacturing Co., Ltd., product name "ADP-611") attached to the meter set to 130°C.

[0072] When an amide compound (solvent) such as N-methyl-2-pyrrolidone is used, an amine component may be contained as an impurity. 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 component as an impurity.

[0073] Furthermore, when the conductive pigment paste of the present invention is used to form an electrode layer by the method described below, the solvent and other components volatilize and do not remain. However, it is preferable to recover and reuse the volatilized solvent to reduce waste, be environmentally friendly, and / or reduce raw material costs. That is, it is preferable to use a recycled product as the solvent (C). This recycled solvent (recycled product) will also contain the amine compound (E1) originally contained in the conductive pigment paste of the present invention, which will also result in differences in the viscosity or thickening tendency of the conductive pigment paste from lot to lot. Furthermore, amine compounds often have a strong odor.

[0074] Therefore, it is preferable to control and adjust the content of amine compounds in the recycled solvent (C) to a certain amount or less, and the content of amine compounds is usually 1% by mass or less, preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less.

[0075] The content of amine compounds can be quantified by common analytical methods such as ion chromatography-mass spectrometry (IC-MS). The content can be quantified by preparing a calibration curve in advance for the peaks of amine species that are expected to be present.

[0076] The above phrase "using a recycled product 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 a recycled product.

[0077] The content of the solvent (C) in the conductive pigment paste is, based on 100% by mass of the total amount of the conductive pigment paste, for example, 40% by mass or more, preferably 60% by mass or more, and more preferably 80% by mass or more, and for example, 99% by mass or less, preferably 98% by mass or less, and more preferably 97% by mass or less. The solid content of the conductive pigment paste is, based on 100% by mass of the total amount of the conductive pigment paste, for example, 1% by mass or more, preferably 2% by mass or more, and more preferably 3% by mass or more, and for example, 60% by mass or less, preferably 40% by mass or less, and more preferably 20% by mass or less.

[0078] Fluorine resin (D) The fluororesin (D) is a resin intended for forming a film of the electrode layer, and can be, and preferably is, contained in the conductive pigment paste as needed. It is also an essential component of the composite paste described below.

[0079] 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. The polyvinylidene fluoride may be variously modified, and from the viewpoint of adhesion to the substrate, it is preferred that it has a polar functional group.

[0080] The fluororesin (D) may be contained when the pigment is dispersed, or may be added after the pigment is dispersed, or may be contained when the composite paste described below is produced. 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.

[0081] When the fluororesin (D) is contained, the content thereof 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 thereof 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.

[0082] When the fluororesin (D) is converted from a solid state into a resin solution, it is preferred, from the viewpoint of solubility in the solvent, 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 form a resin solution, and then the resin solution 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 the types that can be suitably used are those listed above as solvent (C). Furthermore, it is preferable to cool the resin solution that has been hot dissolved as described above to a predetermined temperature of 10°C or higher but lower than 40°C, and the cooling step is carried out by reacting the resin solution with the resin solution with the resin solution that has been hot dissolved as described above to a predetermined temperature of 10°C or higher but lower than 40°C. Cooling rate = (solution temperature at the start of cooling - solution temperature at the end of cooling) / cooling time From the viewpoint of preventing precipitation, it is preferable that the cooling rate defined by is 0.5°C / min or more (preferably 1°C / min or more).

[0083] Highly 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, and examples thereof include known basic components and acidic components. Among these, it is preferable that the component (E) contains an amine compound (E1).

[0084] 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).

[0085] Examples of the amine compound (E1) include ammonia, primary amines, secondary amines, and tertiary amines.

[0086] Examples of primary amines include 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-phenylethylamine, naphthylamine, Primary monoamines such as 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-bisaminopropylpiperazine, 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, diethylenetriamine, Examples of the primary polyamines include 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.

[0087] Examples of secondary amines include secondary monoamines such as 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-lupetidine, 2,6-lupetidine, 3,5-lupetidine, diphenylamine, N-methylaniline, N-ethylaniline, dibenzylamine, methylbenzylamine, dinaphthylamine, pyrrole, indoline, indole, and morpholine; 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-diaminobutane, N,N' -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 and secondary polyamines such as 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.

[0088] 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, tripentylamine, 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 , tertiary polyamines such as 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.

[0089] These may be used alone or in combination of two or more.

[0090] Of these, primary amine compounds are preferred, and monovalent amine compounds (monoamines) are more preferred.

[0091] Examples of the amine compound (E1) include alkanolamines, aliphatic amines, alicyclic amines, and aromatic amines, and any of these can be suitably used, with aromatic amines being preferred.

[0092] 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 solvent 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.

[0093] As other highly polar, low-molecular-weight components, for example, acidic highly polar, low-molecular-weight components selected from organic acids and inorganic acids can be used alone or in combination with two or more thereof in combination with the amine compound (E1), and basic highly polar, low-molecular-weight components selected from organic bases and inorganic bases can be used alone or in combination with two or more thereof. Examples of organic acids include organic carboxylic acids (formic acid, acetic acid, propionic acid, benzoic acid, phthalic acid, etc.) and organic sulfonic acids (benzenesulfonic acid, etc.), and examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc., and their acid anhydrides can also be used.

[0094] Examples of organic bases include basic components other than amine compounds, and examples of inorganic bases include metal hydroxides (sodium hydroxide, potassium hydroxide, etc.).

[0095] 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.

[0096] 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. Furthermore, 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.

[0097] The highly polar, low-molecular-weight component (E) [especially the amine compound (E1)] often has a strong odor, which can worsen the working environment during blending and drying. Furthermore, they are generally expensive, which can increase costs. Therefore, it is necessary to keep the content to the minimum necessary.

[0098] The content ratio of the solvent (C) to the highly polar, low-molecular-weight component (E) is typically 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 even 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).

[0099] Other ingredients The conductive pigment paste may further contain other components in addition to the above-described components (A), (B), and (C), and optionally the components (D) and (E).

[0100] Examples of other components include resins other than the pigment dispersing resin (A) and the fluororesin (D), neutralizing agents, antifoaming agents, preservatives, rust inhibitors, plasticizers, pigments other than the conductive pigment (B), and the like.

[0101] Examples of pigments other than the conductive pigment (B) include 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-based and quinacridone-based pigments, red pigments such as red iron oxide; organic yellow pigments such as benzimidazolone-based, isoindolinone-based, isoindoline-based, and quinophthalone-based pigments; 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 film property reinforcement, as long as they do not significantly impair conductivity. They can be dispersed simultaneously with the pigment dispersing resin (A) and the conductive pigment (B), or they can be dispersed in the pigment dispersing resin (A) and the conductive pigment (B) to form a paste and then mixed as a pigment or pigment paste.

[0102] The content of pigments other than the conductive pigment (B) is preferably 10 mass% or less, more preferably 5 mass% or less, and even more preferably 1 mass% or less, based on 100 mass% of all pigments in the conductive pigment paste, and it is particularly preferable that no pigments are substantially contained.

[0103] The viscosity of the conductive pigment paste is determined based on a shear rate of 2 s from the viewpoint of pigment dispersibility and storage stability. -1 The viscosity at 1000 kJ / min is, for example, less than 5,000 mPa·s, preferably less than 2,500 mPa·s, more preferably less than 1,000 mPa·s, and is, for example, 10 mPa·s or more, preferably 50 mPa·s or more, more preferably 100 mPa·s or more.

[0104] The viscosity can be measured, for example, using a cone and plate viscometer (manufactured by HAAKE, trade name "Mars2", diameter 35 mm, cone and plate tilted at 2°).

[0105] [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 steps 1 and 2. Then, in step 3 (electrode active material mixing step), the conductive pigment paste and at least one electrode active material (F) are mixed to produce a composite paste for a lithium ion secondary battery.

[0106] The solid content of the electrode active material (F) is generally 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 generally 99% by mass or less, preferably 95% by mass or less, which is suitable from the standpoint 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. The solid content of the fluororesin (D) is generally 0.05% by mass or more, preferably 0.1% by mass or more, based on 100% by mass of the total amount of the composite paste, and is generally 10% by mass or less, preferably 2% by mass or less, which is suitable from the viewpoints of battery performance, paste viscosity, etc.

[0107] In the mixing step of step 3, the composite paste can be mixed uniformly using a conventionally known mixer and disperser.

[0108] The solid content of the pigment dispersion resin (A) in the solid content of the composite paste is generally 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 generally 10% by mass or less, preferably 1% by mass or less, which is suitable from the viewpoints of battery performance, paste viscosity, etc.

[0109] In the composite paste of the present invention, from the viewpoint of storage stability (suppression of thickening) of 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 amine compound (E1). From the viewpoint that the aggregation of the conductive pigment (B) and the electrode active material (F) is alleviated by bringing the highly polar, low-molecular-weight component (E) into contact with (wetting) 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).

[0110] 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 suitable from the viewpoint 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 suitable from the viewpoint of electrode drying efficiency and paste viscosity.

[0111] The composite paste is suitable for use as a positive or negative electrode for a lithium ion secondary battery, and is preferably used as a positive electrode.

[0112] Electrode active material (F) Examples of the electrode active material (F) include lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4), lithium cobalt oxide (LiCoO2), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3Examples of the electrode active material (F) include lithium composite oxides such as O2; lithium iron phosphate (LiFePO4); sodium composite oxides; and potassium composite oxides. These electrode active materials (F) can be used singly 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 therefore can be used preferably.

[0113] 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.

[0114] The solid content of the electrode active material (F) in 100% by mass of the solid content 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 from the viewpoints of battery capacity, battery resistance, etc.

[0115] When the electrode active material (F) is contained in the composite paste, the paste may thicken during storage. This is because the electrode active material (F) contains alkali metal hydroxides (e.g., LiOH, KOH, NaOH, etc.) derived from the raw materials on the particle surface, which is thought to cause aggregation (thickening) due to the conductive pigment (B) having an acidic surface. Therefore, by including a certain amount or more of the highly polar, low-molecular-weight component (E) [particularly the amine compound (E1)], the thickening of the composite paste during storage can be suppressed.

[0116] Furthermore, the electrode active material (F) of the present invention can suitably be an electrode active material composite (F-1) in which at least a part of the surface is covered with carbon nanotubes. The composite (F-1) can be obtained by previously 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 carried out after mixing, which allows the carbon nanotubes to 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 restrictions, but the carbon nanotubes listed as the carbon nanotubes (B1) can be preferably used.

[0117] [Lithium-ion secondary battery electrodes] Manufacturing method for electrode layer for lithium-ion secondary battery As described above, an electrode layer for a lithium ion secondary battery (also referred to as an electrode composite layer or composite layer) can be produced by applying a composite paste for a lithium ion secondary battery to the surface of a core material (current collector) of a positive electrode or a negative electrode and drying the paste, and is particularly preferably used for a positive electrode.

[0118] 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 referred to as a functional layer or adhesive layer) between an electrode core material and a composite layer (electrode layer). The lithium ion secondary battery composite paste can be applied by a known method using a die coater or the like. The amount of the lithium ion secondary battery composite paste to be applied 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 within a range of, for example, 80°C or more, preferably 100°C or more, and, for example, 250°C or less, preferably 200°C or less. The drying step time can be appropriately set within a range of, for example, 5 seconds or more, and, for example, 120 minutes or less, preferably 60 minutes or less.

[0119] 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 described above, it is preferable to recover and reuse the volatilized components (C) and (E) in order to reduce waste, be environmentally friendly, and / or reduce costs. [Example]

[0120] 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" means parts by mass and "%" means % by mass.

[0121] [Manufacturing of dispersion resin] Manufacturing Example 1 A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, and water separator was charged with 75 parts of N-methyl-2-pyrrolidone (Note 1) and heated to 120°C under a nitrogen stream. Once the temperature reached 120°C, a mixture of the monomer species shown in Table 1 below (100 parts total) and 2 parts of 2,2'-azobis(2-methylbutyronitrile) was added dropwise over 3 hours. After the addition was complete, the mixture was aged at 120°C for 30 minutes, and then 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 solids content of 50%. The polar functional group concentration was 1.3 mmol / g.

[0122] (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").

[0123] Manufacturing Example 2 An acrylic resin (A2) with a solid 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 weight values ​​of the obtained resins are shown in the following Table 1. In the table, "resin A1" means acrylic resin (A1), and "resin A2" means acrylic resin (A2).

[0124] [Table 1]

[0125] 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.

[0126] [Carbon nanotube (CNT) crushing] Manufacturing Example 3 Using a continuous dry bead mill "Drystar SDA1" (manufactured by Ashizawa Finetech Co., Ltd.), carbon nanotubes (CNT1 (Table 2 below)) were milled for 1 hour at a feed rate of 0.5 kg / hr using zirconia beads (diameter 3.0 mm), a filling rate of 70%, and a mill peripheral speed of 5.0 m / s, to obtain a milled 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.

[0127] Manufacturing Example 4 Using a continuous dry bead mill "Drystar SDA1" (manufactured by Ashizawa Finetech Co., Ltd.), carbon nanotubes (CNT1 (Table 2 below)) were milled for 2 hours at a feed rate of 0.5 kg / hr using zirconia beads (diameter 3.0 mm), a filling rate of 70%, and a mill peripheral speed of 5.0 m / s, to obtain milled carbon nanotubes (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.

[0128] Production Example 5 Using a continuous dry bead mill "Drystar SDA1" (manufactured by Ashizawa Finetech Co., Ltd.), carbon nanotubes (CNT2 (Table 2 below)) were milled for 2 hours at a feed rate of 0.5 kg / hr using zirconia beads (diameter 3.0 mm), a filling rate of 70%, and a mill peripheral speed of 5.0 m / s, to obtain a milled 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.

[0129] Manufacturing Example 6 Using a continuous dry bead mill "Drystar SDA1" (manufactured by Ashizawa Finetech Co., Ltd.), carbon nanotubes (CNT3 (Table 2 below)) were milled for 1 hour at a feed rate of 0.5 kg / hr using zirconia beads (diameter 3.0 mm), a filling rate of 70%, and a mill peripheral speed of 5.0 m / s, to obtain a milled 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.

[0130] [Table 2]

[0131] All of the above carbon nanotubes are 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 above were measured by the methods described below.

[0132] [Manufacturing of conductive pigment paste and composite paste] Example 1A A container was charged with 5,000 parts of N-methyl-2-pyrrolidone (Note 1), 200 parts of crushed carbon nanotubes (C1-2), 80 parts of polyvinylpyrrolidone (solids: 40 parts) (Note 3) as a dispersing resin, 1,800 parts of a resin solution of KF Polymer W#7300 (Kureha Corporation, product name, polyvinylidene fluoride, weight-average molecular weight: 1,000,000) (solids: 180 parts) (Note 4), and 25 parts of benzylamine as an amine, all of which were mixed with stirring. Finally, N-methyl-2-pyrrolidone (Note 1) was added to bring the total mass to 10,000 parts. The mixture was then 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 the resin solution.

[0133] 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 dispersing resin, carbon nanotubes (CNTs), and amine were mixed in the proportions 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, which will be described later, are shown in Table 3 below.

[0134] [Table 3]

[0135] The blending amounts of the dispersing resin in Table 3 above are values ​​based on the solid content. The compositions of the dispersing resins in Table 3 above are as follows: Polyvinyl butyral: average degree of polymerization 600, hydroxyl group content 12 mol%, butyral group content 87 mol%, acetyl group content 1 mol%, polar functional group concentration 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.

[0136] Example 1B For 100 parts of the conductive pigment paste (A-1), electrode active material particles (composition formula LiNi 0.5 Mn 1.5 Lithium nickel manganese oxide particles with a spinel structure represented by O4, an average particle size of 6 μm, and a BET specific surface area of ​​0.7 m 2 900 parts of the mixture (1 / g) was mixed in a disperser to prepare a composite paste (B-1).

[0137] 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 shown in Table 4 below were used. The results of the evaluation test of the composite paste, which will be described later, are shown in Table 3 above.

[0138] [Table 4]

[0139] <Median diameter (D50)> The median diameter (D50) was measured using a laser diffraction / scattering particle size distribution analyzer "LA-960" (trade name, manufactured by HORIBA Corporation) according to the following procedure.

[0140] [Preparation of aqueous dispersion medium] 0.10 g of F10MC (trade name, manufactured by Nippon Paper Industries Co., Ltd., carboxymethylcellulose sodium (hereinafter also referred to as CMCNa)) 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.

[0141] [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.

[0142] [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 (Microtech Nichion, "SmurtNR-50") was used for pre-measurement. After confirming that the tip was not deteriorating, the tip was adjusted so that it was immersed at least 10 mm below the surface of the sample being treated. A carbon nanotube aqueous dispersion was prepared by homogenizing the sample with ultrasonic irradiation using auto-power operation with a constant output power, with a time set (irradiation time) of 40 seconds, a power set of 50%, and a start power set of 50% (50% output).

[0143] [measurement] Using the carbon nanotube aqueous dispersion, the proportion of dispersed particles of carbon nanotubes with 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, approximately 1.0 mL of CMCNa aqueous solution is filled. After performing offset measurement, optical axis adjustment, and background measurement at a pump speed of 50%, the prepared carbon nanotube aqueous dispersion was added to the particle size distribution analyzer 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%. The particle size distribution analyzer accessory was used to irradiate the dispersion with ultrasound at 78 W for 2 minutes (pre-measurement), circulate for 30 seconds to remove air bubbles, and then measure the particle size distribution. A graph of particle size (particle diameter) versus volume % was obtained, and the proportion of dispersed particles below 1 μm and the median diameter (D50) were determined. For each carbon nanotube sample, three measurement samples were collected 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.

[0144] <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. -1 More than ~1600cm -1 The maximum peak intensity within the range of G, 1310 cm -1 More than ~1350cm -1 The G / D ratio of the carbon nanotube was determined by setting the maximum peak intensity within the following range as D.

[0145] <Specific surface area (BET specific surface area)> The BET specific surface area of ​​carbon nanotubes was measured in accordance with JIS Z8830:2013 using a specific surface area measuring device (BERSORP-MAX (Microtrac BEL Co., Ltd.)). 2 / g) was measured.

[0146] <Amount of acidic groups in carbon nanotubes (CNTs)> 2 g of CNT was weighed out and immersed in 50 ml of a 0.01 M benzylamine / n-methylpyrrolidone solution, then dispersed for 1 hour using an ultrasonicator. The solution was then centrifuged and the supernatant was filtered. The benzylamine remaining in the 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 resulting CNT was determined.

[0147] Evaluation Test The conductive pigment pastes and composite pastes obtained in the above Examples and Comparative Examples were subjected to evaluation tests. If even one evaluation result was unacceptable, the evaluation was deemed unacceptable.

[0148] <Dispersibility> The resulting conductive pigment paste was evaluated for dispersibility using a particle gauge according to the dispersibility test of JIS K-5600-2-5, with the following criteria: C and D are failures. A: The pigment is dispersed at a particle size of less than 10 μm. Dispersibility is very good. B: The pigment is dispersed at a size of 10 μm or more and less than 20 μm. Dispersibility is fairly good. C: The pigment is dispersed at a particle size of 20 μm or more, but no aggregates are visible to the naked eye. Dispersibility is somewhat poor. D: Aggregates are visually observed. Dispersibility is very poor.

[0149] <Volume resistivity (conductivity)> The volume resistivity of the resulting conductive pigment paste was also measured using a 5% by mass solution of polyvinylidene fluoride (manufactured by Kureha Corporation, trade name "KF Polymer W#7300", solvent: N-methyl-2-pyrrolidone) as the 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 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 measurement sample was applied to a glass plate (2 mm × 100 mm × 150 mm) using a doctor blade method and dried by heating at 80°C for 60 minutes to form a coating film on the glass plate. The film thickness of the resulting coating film was measured, and then the resistance value was measured with a resistivity meter (Mitsubishi Chemical Analytech Co., Ltd., product name "MCP-TP03P") using an ASP probe (manufactured by Mitsubishi Chemical Analytech Co., Ltd., product name "Loresta-GP MCP-T610"). The volume resistivity was calculated by multiplying the obtained resistance value by a resistivity correction factor (RCF) of 4.532 and the film thickness of the coating film. The volume resistivity was evaluated according to the following criteria: D indicates failure. A: The volume resistivity is less than 7 Ω·cm and the conductivity is good. B: The volume resistivity is 7 Ω·cm or more and less than 15 Ω·cm, and the conductivity is normal. D: The volume resistivity is 15 Ω·cm or more, and the conductivity is poor.

[0150] <Initial viscosity> The obtained composite paste was measured using a cone and plate viscometer (manufactured by HAAKE, product name "Mars2", diameter 35 mm, cone and plate tilted at 2°) at a shear rate of 2.0 sec -1 The viscosity was measured and evaluated according to the following criteria: D is unacceptable. 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.

[0151] [Manufacturing of electrode layers for batteries] Application examples 1C~10C The composite pastes obtained in Examples 1B to 10B were applied to both sides of a long piece of aluminum foil (positive electrode current collector) having an average thickness of 15 μm in a weight per side of 10 mg / cm. 2 The positive electrode layer was formed by applying the positive electrode active material layer (positive electrode layer) supported on the positive electrode current collector in a strip shape by a roller coating method so that the solid content was 100% (based on the solid content) and drying (drying temperature: 180°C, 10 minutes). The positive electrode active material layer (positive electrode layer) supported on the positive electrode current collector was rolled using a roll press 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.

Claims

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 the conductive pigment (B) of 50 mass% or more 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 process includes the steps of: 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; Fulfilling Method for producing conductive pigment paste.

2. 2. The method for producing a conductive pigment paste according to claim 1, wherein the pigment dispersing resin (A) has at least one alkyl group having 12 or more carbon atoms.

3. 2. The method for producing a conductive pigment paste according to claim 1, 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.

4. A method for producing a conductive pigment paste comprising a pigment dispersion resin (A), a conductive pigment (B), a solvent (C), and a fluororesin (D), comprising: Step 1: A step of pulverizing a conductive pigment composition having a pigment concentration of the conductive pigment (B) of 50 mass% or more by a pulverizer; and Step 2: mixing and dispersing the conductive pigment composition obtained in step 1 with a component including a pigment dispersing resin (A), a solvent (C), and a fluororesin (D); The process includes the steps of: the step of mixing a component containing 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 includes a step of mixing the fluororesin (D) with a solvent and then heating the mixture to a temperature of 40°C or higher.

5. 2. The method for producing a conductive pigment paste according to claim 1, wherein the solvent (C) is N-methyl-2-pyrrolidone.

6. The step 2 is Step 2-1: A step of adding components containing a conductive pigment composition in an amount of 70% by mass or less based on 100% by 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; Step 2-2: A step of adding a conductive pigment composition to a disperser until a desired concentration is reached, and performing a dispersion treatment; 2. The method for producing a conductive pigment paste according to claim 1, further comprising the steps of:

7. The conductive pigment paste obtained by the method for producing a conductive pigment paste according to any one of claims 1 to 6 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:

8. A method for producing an electrode layer for a lithium ion secondary battery, comprising the step of applying to a current collector a composite paste for a lithium ion secondary battery obtained by the method for producing a composite paste for a lithium ion secondary battery according to claim 7.

9. 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 8.