Process for preparing a coating composition

Abstract

To provide an n-type conversion technique of a single-walled carbon nanotube.SOLUTION: A method for producing a coating composition includes (A) a step of bringing a single-walled carbon nanotube into contact with an organic base type n-type doping agent in a liquid to obtain a dispersion liquid 1, and (B) a step of adding a dispersant to the dispersion liquid 1 to obtain a dispersion liquid 2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a coating composition. [Background technology]

[0002] Thermoelectric conversion, as the name suggests, is a technology that converts thermal energy directly into electrical energy, and electrical energy is obtained using a thermoelectric conversion element obtained by combining p-type thermoelectric conversion materials (p-type semiconductors) and n-type thermoelectric conversion materials (n-type semiconductors). However, the thermoelectric conversion materials currently in practical use contain expensive and toxic elements (such as Pb and Te) as their main constituent elements, which is an obstacle to the widespread use of large-scale thermoelectric power generation.

[0003] The first advantage of using carbon nanotubes as a thermoelectric conversion material is the abundance of the resource. Compared to conventional metal thermoelectric conversion materials, carbon nanotubes are easy to obtain and inexpensive, making them suitable for large-area applications (industrialization). Thermoelectric conversion materials that use carbon nanotubes also have excellent flexibility. However, carbon nanotubes are typically p-type, so they must be converted to n-type in order to be used in thermoelectric conversion elements.

[0004] Patent Document 1 describes the use of amidine compounds and guanidine compounds as n-type doping agents for nanocarbon materials. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-135933 Summary of the Invention [Problem to be solved by the invention]

[0006] In the course of research, the inventors discovered that when organic base-type n-type doping agents such as amidine compounds and guanidine compounds are used to convert single-walled carbon nanotubes to n-type, the success or failure of n-type conversion or the efficiency of n-type conversion varies significantly depending on the method used to obtain the carbon nanotube paint and coating film.

[0007] An object of the present invention is to provide a technology for converting single-walled carbon nanotubes into n-type nanotubes. [Means for solving the problem]

[0008] The present inventors have conducted extensive research in light of the above-mentioned problems and have found that the above-mentioned problems can be solved by a method for producing a coating composition, comprising the steps of (A) contacting single-walled carbon nanotubes with an organic base-type n-type doping agent in a liquid to obtain dispersion 1, and (B) adding a dispersant to dispersion 1 to obtain dispersion 2. Based on this finding, the present inventors have conducted further research and have completed the present invention. That is, the present invention encompasses the following aspects.

[0009] Item 1. (A) A step of contacting single-walled carbon nanotubes with an organic base-type n-type doping agent in a liquid to obtain a dispersion liquid 1; (B) adding a dispersant to the dispersion 1 to obtain dispersion 2; A method for producing a coating composition comprising:

[0010] Item 2. The method according to Item 1, wherein the organic base-type n-type doping agent is at least one selected from the group consisting of amidine compounds and guanidine compounds.

[0011] Item 3. The method according to Item 2, wherein the organic base-type n-type doping agent is at least one selected from the group consisting of cyclic amidine compounds and cyclic guanidine compounds.

[0012] Item 4. The method according to Item 3, wherein the organic base-type n-type doping agent is a cyclic amidine compound.

[0013] Item 5. The method according to Item 4, wherein the organic base type n-type doping agent is diazabicycloundecene or diazabicyclononene.

[0014] Item 6. The method according to any one of Items 1 to 5, wherein in the step (A), the single-walled carbon nanotubes are in contact with the organic base n-type doping agent for one hour or longer.

[0015] Item 7. The method according to any one of Items 1 to 6, wherein in step (B), the dispersant is added by adding a dispersant solution.

[0016] Item 8. The method according to any one of Items 1 to 7, wherein the amount of the organic base n-type doping agent used in step (A) is 0.001 to 0.1 mol per 1 g of the single-walled carbon nanotubes.

[0017] Item 9. The method according to any one of Items 1 to 8, wherein the coating composition is a coating composition for producing an n-type thermoelectric conversion material.

[0018] Item 10. A coating composition obtained by the method according to any one of items 1 to 9.

[0019] Item 11. A method for producing a coating film, comprising a step of applying the coating composition according to Item 10 onto a substrate.

[0020] Item 12. A coating film obtained by the method according to Item 11.

[0021] Item 13. A thermoelectric conversion element comprising an n-type thermoelectric conversion material including the coating film according to Item 12, and a p-type thermoelectric conversion material. [Effects of the Invention]

[0022] The present invention can provide a technology for n-type conversion of single-walled carbon nanotubes. Specifically, it can provide a method for producing a coating composition that can be used to prepare an n-type thermoelectric conversion material, the coating composition obtained thereby, a method for producing a coating film using the coating composition, the coating film obtained thereby, and a thermoelectric conversion element including the coating film. DETAILED DESCRIPTION OF THE INVENTION

[0023] In this specification, the expressions "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0024] In one aspect, the present invention relates to a method for producing a coating composition (sometimes referred to herein as the "coating production method of the present invention"), which comprises: (A) a step of contacting single-walled carbon nanotubes with an organic base-type n-type doping agent in a liquid to obtain dispersion 1; and (B) a step of adding a dispersant to the dispersion 1 to obtain dispersion 2.

[0025] The single-walled carbon nanotubes are not particularly limited, and for example, single-walled carbon nanotubes manufactured by arc discharge, laser evaporation, chemical vapor deposition (CVD), or the like can be used.

[0026] The length of the single-walled carbon nanotube is preferably 1 to 2000 μm, more preferably 3 to 1000 μm, and even more preferably 5 to 500 μm. The length can be determined by measuring the lengths of any number of fibers (for example, 50 fibers) using an atomic force microscope and averaging the measured lengths.

[0027] The diameter of the single-walled carbon nanotube is preferably 0.5 to 20 nm, more preferably 1 to 10 nm, and can be measured in accordance with Optical absorption: ISO / TS 10868:2017 (E).

[0028] The BET specific surface area of ​​single-walled carbon nanotubes is, for example, 100 to 5000 m 2 / g, preferably 200 to 3000 m 2 / g, more preferably 300 to 2000 m 2 / g. The specific surface area can be measured according to the BET method: ISO 9277:2010 (E).

[0029] The single-walled carbon nanotubes may be of one type alone or may be of two or more types in combination.

[0030] The organic base type n-type doping agent is an organic base that can reduce the Seebeck coefficient of the single-walled carbon nanotube or convert it to a negative value, and is not particularly limited as long as it is an organic base. Suitable examples of the organic base type n-type doping agent include amidine compounds and guanidine compounds.

[0031] The amidine compound is a cyclic or chain compound having an amidine structure, and is not particularly limited thereto. The molecular weight of the amidine compound is, for example, 50 to 1000, preferably 70 to 500, and more preferably 100 to 200. Particularly preferred examples of the amidine compound include diazabicycloundecene (1,8-diazabicyclo[5.4.0]undec-7-ene) (DBU) and diazabicyclononene (1,5-diazabicyclo[4.3.0]non-5-ene) (DBN).

[0032] The guanidine compound is a cyclic or chain compound having a guanidine structure, and is not particularly limited thereto. The molecular weight of the guanidine compound is, for example, 50 to 1000, preferably 70 to 500, and more preferably 100 to 200. Particularly preferred examples of the guanidine compound include guanidine, 1,1,3,3-tetramethylguanidine (TMG), triazabicyclodecene (1,5,7-triazabicyclo[4.4.0]dec-5-ene) (TBD), and 7-methyltriazabicyclodecene (7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene) (Me-TBD).

[0033] It is particularly preferable that the organic base-type n-type doping agent is cyclic. When it is cyclic, the steric position of the lone electron pair in the compound can be specified, and it can be used as an effective base (n-type doping reagent) for single-walled carbon nanotubes. Furthermore, by using a substance containing both π bonds and σ bonds in the molecule, the structure of the conjugate acid after electron donation to the single-walled carbon nanotube can be resonance-stabilized, and the negative charge of the n-type single-walled carbon nanotube, which is the conjugate base, can be stabilized.

[0034] The organic base type n-type doping agent may be one kind alone or two or more kinds in combination.

[0035] In step (A), single-walled carbon nanotubes and an organic base n-type doping agent are brought into contact in a liquid to obtain a dispersion (dispersion 1).

[0036] The amount of the organic base n-type doping agent used in step (A) is not particularly limited and is, for example, 0.0001 to 1.0 mol per 1 g of single-walled carbon nanotubes. From the viewpoints of efficiency of conversion to n-type, cost, etc., the amount used is preferably 0.001 to 0.1 mol, more preferably 0.002 to 0.1 mol, even more preferably 0.005 to 0.1 mol, still more preferably 0.01 to 0.1 mol, particularly preferably 0.015 to 0.1 mol, particularly more preferably 0.015 to 0.07 mol, particularly still more preferably 0.015 to 0.05 mol, and particularly preferably 0.015 to 0.03 mol.

[0037] In the coating material production method of the present invention, doping agents other than the organic base n-type doping agent may be used, but it is preferable to use a small amount of such doping agent. The amount of the organic base n-type doping agent used relative to 100% by mass of the doping agent used in the coating material production method of the present invention is, for example, 70% 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, and particularly preferably 100% by mass.

[0038] The concentration of single-walled carbon nanotubes in the liquid and dispersion 1 in step (A) is, for example, 0.1 to 5.0 mass %. From the viewpoints of efficiency of conversion to n-type, ease of handling of the liquid, etc., the concentration is preferably 0.2 to 2.0 mass %, more preferably 0.5 to 1.0 mass %.

[0039] The manner of contact in the liquid in step (A) is not particularly limited, and for example, the two can be contacted by mixing them in a solvent. In step (A), a dispersant is not used. The order of adding the two to the solvent is also not particularly limited, and the organic base type n-type doping agent can be added to the solvent first, and then the single-walled carbon nanotubes can be added, or vice versa, or both can be added simultaneously. In a preferred embodiment, the organic base type n-type doping agent can be added to the solvent first, and then the single-walled carbon nanotubes can be added.

[0040] The solvent in step (A) (solvent for the liquid at the time of contact, solvent for dispersion liquid 1) preferably contains water from the viewpoints of reducing the environmental load, making it easier to achieve the effects of the present invention, etc. In this case, the water content is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, particularly preferably 95% by mass or more, especially more preferably 99% by mass or more, and particularly preferably 100% by mass (solvent is water only), relative to 100% by mass of the solvent, from the viewpoints of the efficiency of conversion to n-type, etc.

[0041] The contact time between the single-walled carbon nanotubes and the organic base n-type doping agent in step (A) is not particularly limited, as long as it is long enough to cause the organic base n-type doping agent to adhere to the single-walled carbon nanotubes. The contact time is preferably 1 hour or more, more preferably 2 hours or more, even more preferably 4 hours or more, even more preferably 8 hours or more, particularly preferably 12 hours or more, especially more preferably 16 hours or more, and particularly preferably 20 hours or more. The upper limit of the contact time is not particularly limited, and is, for example, 100 hours, 80 hours, 60 hours, or 40 hours.

[0042] In step (A), dispersion 1 is usually obtained by stirring a liquid containing single-walled carbon nanotubes and an organic base-type n-type doping agent. The stirring method is not particularly limited, and includes methods using various dispersing / stirring machines. From the viewpoint of efficiency of conversion to n-type, ultrasonic stirring is preferred.

[0043] In step (B), a dispersant is added to dispersion 1 obtained in step (A) to obtain dispersion 2.

[0044] The dispersant is not particularly limited as long as it can improve the dispersibility of single-walled carbon nanotubes. Examples of the dispersant that can be used include polymer dispersants; anionic, cationic, nonionic, or amphoteric surfactants. In a preferred embodiment of the present invention, a polymer dispersant is used as the dispersant.

[0045] Specific examples of polymer dispersants include cellulose derivatives (cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethyl cellulose, ethylhydroxyethyl cellulose, nitrocellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, carboxymethyl cellulose, etc.), polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, and polyacrylonitrile polymers.

[0046] When selecting an anionic surfactant, its type is not particularly limited.Specific examples include, but are not limited to, fatty acid salts, polysulfonates, polystyrene sulfonates, polycarboxylates, alkyl sulfates, alkylaryl sulfonates, alkylnaphthalene sulfonates, dialkyl sulfonates, dialkyl sulfosuccinates, alkyl phosphates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl ether sulfates, naphthalene sulfonate formalin condensates, polyoxyethylene alkyl phosphate sulfonates, glycerol borate fatty acid esters, and polyoxyethylene glycerol fatty acid esters.Further examples include, but are not limited to, sodium dodecylbenzenesulfonate, sodium laurate sulfate, polyoxyethylene lauryl ether sodium sulfate, polyoxyethylene nonylphenyl ether sulfate, and the sodium salt of β-naphthalene sulfonate formalin condensates.

[0047] Cationic surfactants include alkylamine salts and quaternary ammonium salts, specifically stearylamine acetate, trimethylcoconut ammonium chloride, trimethyltallow ammonium chloride, dimethyldioleylammonium chloride, methyloleyldiethanol chloride, tetramethylammonium chloride, laurylpyridinium chloride, laurylpyridinium bromide, laurylpyridinium disulfate, cetylpyridinium bromide, 4-alkylmercaptopyridine, poly(vinylpyridine)-dodecyl bromide, and dodecylbenzyltriethylammonium chloride, but are not limited to these.

[0048] In addition, nonionic surfactants include, but are not limited to, polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and alkyl allyl ethers.Specific examples include, but are not limited to, polyoxyethylene lauryl ethers, sorbitan fatty acid esters, and polyoxyethylene octylphenyl ethers.In addition, amphoteric surfactants include, but are not limited to, aminocarboxylic acid salts.

[0049] The dispersant may be one type alone or a combination of two or more types.

[0050] The amount of the dispersant used in step (B) is preferably, for example, 50 to 2000 parts by mass, preferably 100 to 1500 parts by mass, more preferably 200 to 1000 parts by mass, even more preferably 300 to 700 parts by mass, and even more preferably 300 to 500 parts by mass, relative to 100 parts by mass of the single-walled carbon nanotubes.

[0051] The mode of adding the dispersant is not particularly limited, and examples thereof include adding a dispersant solution, adding the dispersant itself, etc. From the viewpoint of dispersion efficiency, etc., adding a dispersant solution is preferred.

[0052] The solvent in step (B) (the solvent of a dispersant solution when used, or the solvent of dispersion 2) preferably contains water. In this case, the water content is, relative to 100% by mass of the solvent, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, particularly preferably 95% by mass or more, especially more preferably 99% by mass or more, and particularly preferably 100% by mass (the solvent is water only), from the viewpoint of the efficiency of conversion to n-type.

[0053] The concentration of the single-walled carbon nanotubes in the dispersion liquid 2 in step (B) is, for example, 0.05 to 3.0 mass %, and from the viewpoints of the thermoelectric conversion performance of the coating film, the handleability of the liquid, etc., the concentration is preferably 0.10 to 1.5 mass %, more preferably 0.15 to 0.7 mass %.

[0054] In step (B), a dispersant is usually added to dispersion 1, followed by stirring to obtain dispersion 2. The stirring method is not particularly limited, and examples include methods using various dispersing / stirring machines.

[0055] The average particle size in dispersion 2 is preferably 12 μm or less, more preferably 10 μm or less, even more preferably 8 μm or less, even more preferably 6 μm or less, and particularly preferably 4 μm or less.

[0056] The dispersion 2 obtained in step (B) may be used as a coating composition as is, or may be mixed with binders, additives, etc. as needed to form a coating composition. When these are added, the coating composition is usually obtained by stirring after addition. The stirring method is not particularly limited, and may include methods using various dispersing / stirring machines.

[0057] Examples of binders include silicon compound binders; polymers or copolymers containing ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinyl pyrrolidone, or the like as constituent units; polyurethane resins, polyester resins, phenolic resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicone resins, and fluororesins; cellulose resins such as carboxymethyl cellulose; rubbers such as styrene butadiene rubber and fluororubber; and conductive resins such as polyaniline and polyacetylene.

[0058] The silicon compound binder is a colloidal dispersion, solution, or emulsion of a silicon compound, which contains a solid or liquid silicon compound in an aqueous dispersion medium. Examples of the silicon compound binder include silicates such as silicates; colloidal silica; silane and siloxane hydrolyzate emulsions; silicone resin emulsions; and emulsions of copolymers of silicone resins and other resins, such as silicone-acrylic resin copolymers and silicone-urethane resin copolymers.

[0059] The binder may be one type alone or a combination of two or more types.

[0060] When the coating composition contains a binder, the content of the binder in the coating composition is not particularly limited as long as the dispersibility of the carbon nanotubes is not significantly impaired and a coating film can be formed. The content is, for example, 50 to 2000 parts by mass, preferably 200 to 1500 parts by mass, and more preferably 400 to 1000 parts by mass relative to 100 parts by mass of the carbon nanotubes.

[0061] In one aspect, the present invention relates to a coating composition (the coating composition of the present invention) obtained by the coating production method of the present invention. A coating film can be obtained by applying the coating composition of the present invention to a substrate. Therefore, in one aspect, the present invention relates to a method for producing a coating film, which includes a step of applying the coating composition of the present invention to a substrate, and a coating film (the coating film of the present invention) obtained by the method.

[0062] The substrate is not particularly limited as long as it contains a resin (substrate resin) that can be used as a substrate for a transparent conductive film.

[0063] The substrate may contain components other than the substrate resin as long as the effects of the present invention are not significantly impaired. In such cases, the total amount of the substrate resin in the substrate is, for example, 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more, but less than 100% by mass.

[0064] The resin for the substrate is not particularly limited, and examples thereof include polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate, and modified polyester, polyolefin resins such as polyethylene (PE) resin, polypropylene (PP) resin, polystyrene resin, and cyclic olefin resin, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polyvinyl acetal resins such as polyvinyl butyral (PVB), polyether ether ketone (PEEK) resin, polysulfone (PSF) resin, polyethersulfone (PES) resin, polycarbonate (PC) resin, polyamide resin, polyimide resin, acrylic resin, triacetyl cellulose (TAC) resin, etc. Among these, from the viewpoint of transparency, etc., preferred are polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polycarbonate, etc., and more preferred is polyethylene terephthalate.

[0065] The resin for the substrate may be one type alone or a combination of two or more types.

[0066] The thickness of the substrate is not particularly limited as long as transparency and strength appropriate for the intended use are ensured, and is, for example, 2 to 500 μm, preferably 10 to 400 μm, more preferably 20 to 300 μm, even more preferably 50 to 200 μm, and still more preferably 70 to 150 μm.

[0067] The layer structure of the substrate is not particularly limited. The substrate may be composed of a single type of substrate, or may be a combination of two or more types of substrates having the same or different compositions.

[0068] The substrate may be subjected to various surface treatments, such as corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, glow discharge treatment, active plasma treatment, laser treatment, and other surface activation treatments.

[0069] The coating method is not particularly limited, and any conventionally known coating method can be used, such as bar coating, silk screen printing, gravure coating, reverse roll coating, die coating, air doctor coating, blade coating, rod coating, curtain coating, knife coating, transfer roll coating, squeeze coating, impregnation coating, kiss coating, spray coating, calendar coating, and extrusion coating.

[0070] After coating, it is preferable to dry the coating. The drying temperature is, for example, 50 to 200° C., preferably 70 to 170° C., and more preferably 90 to 150° C. The drying time may vary depending on the drying temperature, but is, for example, 30 seconds to 15 minutes, preferably 1 to 10 minutes, and more preferably 2 to 5 minutes.

[0071] The coating film of the present invention contains single-walled carbon nanotubes and an organic base-type n-type doping agent, and is obtained by the unique method of the present invention, and therefore, while containing single-walled carbon nanotubes as the main component of the thermoelectric conversion material (for example, while the content of single-walled carbon nanotubes relative to 100 mass% of the thermoelectric conversion material contained in the coating film is, for example, 70 mass% or more, preferably 80 mass% or more, more preferably 90 mass% or more, even more preferably 95 mass% or more, and particularly preferably 100 mass%), it exhibits excellent properties as an n-type thermoelectric conversion material (n-type semiconductor). Therefore, the coating composition produced by the coating production method of the present invention and the coating composition of the present invention can be a coating composition for producing an n-type thermoelectric conversion material, and the coating film of the present invention can be an n-type thermoelectric conversion material.

[0072] From the viewpoint of use as an n-type thermoelectric conversion material, the thickness of the coating film of the present invention is preferably 0.1 to 50 μm, more preferably 0.5 to 30 μm, and even more preferably 1 to 10 μm.

[0073] The amount of single-walled carbon nanotubes per unit area of ​​the coating film of the present invention is preferably 0.914 × 10 from the viewpoint of utilization as an n-type thermoelectric conversion material. -6 ~4.57×10 -4 g / cm 2 , more preferably 4.57 × 10 -6 ~2.75×10 -4 g / cm 2 , and more preferably 9.14 × 10 -6 ~0.915×10 -4 g / cm 2 is.

[0074] In one aspect, the present invention relates to a thermoelectric conversion element including an n-type thermoelectric conversion material including the coating film of the present invention, and a p-type thermoelectric conversion material.

[0075] The p-type thermoelectric conversion material is not particularly limited, but for example, a nanocarbon material, preferably a carbon nanotube, can be used.

[0076] A thermoelectric conversion element typically includes multiple thermoelectric conversion materials. More specifically, a thermoelectric conversion element is configured by electrically connecting a p-type thermoelectric conversion material and an n-type thermoelectric conversion material in series, either directly or via electrodes.

[0077] The thermoelectric conversion element may have an electrically insulating material such as an insulating heat dissipation material on the upper and lower surfaces thereof as needed. The insulating heat dissipation material can be appropriately selected depending on the application, and for example, a film or rubber containing alumina can be used.

[0078] The thermoelectric conversion element can be used as a thermoelectric cooling element, a thermoelectric power generation element, or the like. [Example]

[0079] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0080] (1) Preparation of paint and coating (Raw materials used)

[0081] [Table 1]

[0082] (Comparative Example 1) (1) 1.2 g of dispersant was dissolved in 98.5 g of ion-exchanged water. (2) 0.3 g of single-walled CNTs was added to the solution obtained in (1), and the mixture was stirred with a propeller at 1000 rpm for 5 minutes. (3) The dispersion obtained in (2) was subjected to dispersion treatment using a wet atomization device "Starburst Mini" (manufactured by Sugino Machine Co., Ltd.) to obtain a single-walled CNT dispersion. (4) To the single-walled CNT dispersion obtained in (3), binder resin and additives were added and stirred to obtain a coating material. The amount of binder (Kynar Aquatec ARC) added was 2 g, the amount of additive (leveling agent: Polyflow WS) added was 1 g, and the amount of additive (foam suppressor: SN Deformer 1340) added was 0.5 g. (5) The coating material obtained in (4) was applied to a film substrate (a 100 μm thick PET film) by silkscreen printing, and dried in a hot air dryer at 100° C. for 5 minutes to obtain a coating film.

[0083] Example 1 (1) 37.5 g of ion-exchanged water was mixed with the doping agent so that the molar ratio of the doping agent in the solution was 0.0066 mol, and 0.3 g of single-walled CNT powder was added to the solution. The molar ratio of the doping agent per 1 g of CNT was 0.022 mol. (2) The solution obtained in (1) was treated for 20 seconds with an ultrasonic disperser (manufactured by Seidensha Electronics Co., Ltd.) to obtain a dispersion. (3) The dispersion obtained in (2) was allowed to stand at room temperature for 24 hours. (4) In a separate container, 1.2 g of a dispersant was dissolved in 60 g of ion-exchanged water. (5) The dispersion obtained in (3) and the solution obtained in (4) were mixed and stirred with a propeller at 1000 rpm for 5 minutes. (6) The dispersion obtained in (5) was subjected to the same steps as in (3) to (5) of Comparative Example 1 to obtain a coating film.

[0084] Example 2 A coating film was obtained in the same manner as in Example 1, except that the amount of doping agent used was changed so that the number of moles of doping agent per 1 g of CNT was 0.005 mol.

[0085] Example 3 A coating film was obtained in the same manner as in Example 1, except that the ultrasonic dispersion in (2) was changed to propeller stirring (1000 rpm, 5 minutes).

[0086] Example 4 A coating film was obtained in the same manner as in Example 1, except that the amount of doping agent used was changed so that the number of moles of doping agent per 1 g of CNT was 0.05 mol.

[0087] (Comparative Example 2) (1) 50 g of ion-exchanged water was mixed with the doping agent so that the molar number of the doping agent in the solution was 0.0066 mol, and 0.3 g of single-walled CNT powder was added to the solution. The molar number of the doping agent per 1 g of CNT was 0.022 mol. (2) The solution obtained in (1) was treated for 20 seconds with an ultrasonic disperser (manufactured by Seidensha Electronics Co., Ltd.) to obtain a dispersion. (3) The dispersion obtained in (2) was allowed to stand at room temperature for 24 hours. (4) The dispersion obtained in (3) was filtered under suction, and the obtained solid matter was dried in a hot air dryer at 100°C for 2 hours or more to obtain doped CNT powder. (5) In a separate container, 1.2 g of a dispersant was dissolved in 98.5 g of ion-exchanged water. (6) The doped CNT powder obtained in (4) was added to the solution obtained in (5), and the mixture was stirred with a propeller at 1000 rpm for 5 minutes. (7) The dispersion obtained in (6) was subjected to the same steps as in (3) to (5) of Comparative Example 1 to obtain a coating film.

[0088] (Comparative Example 3) (1) A coating film was obtained according to (1) to (5) of Comparative Example 1. (2) The coating film obtained in (1) was cut into 10 cm squares, and the amount of CNT was calculated from the film thickness. A doping solution was then prepared so that the concentration was 0.022 mol / g of CNT. The actual amount of doping solution was 0.002 mol / L, and the total amount of solution was 20 g. The coating film was then immersed in this solution. The number of moles of doping agent per 1 g of CNT was 0.022 mol. (3) The coating film was then lifted out, the solution was lightly shaken off, and the film was dried in a hot air dryer at 100°C for 10 minutes to obtain a coating film.

[0089] Comparative Example 4 (1) A single-walled CNT dispersion was obtained according to (1) to (3) of Comparative Example 1. (2) A binder resin, an additive, and a doping agent (to give 0.022 mol per 1 g of CNT) were added to the obtained single-walled CNT dispersion and stirred to obtain a coating material. (3) The resulting coating material was subjected to the same process as in (5) of Comparative Example 1 to obtain a coating film.

[0090] (Comparative Example 5) A coating film was obtained in the same manner as in Comparative Example 1, except that the single-walled CNTs were changed to multi-walled CNTs and the coating material was applied by bar coating.

[0091] (Comparative Example 6) A coating film was obtained in the same manner as in Example 1, except that the single-walled CNTs were changed to multi-walled CNTs and the coating material was applied by bar coating.

[0092] (Comparative Example 7) A coating film was obtained in the same manner as in Example 2, except that the single-walled CNTs were changed to multi-walled CNTs and the coating material was applied by bar coating.

[0093] (Comparative Example 8) A coating film was obtained in the same manner as in Example 3, except that the single-walled CNTs were changed to multi-walled CNTs and the coating material was applied by bar coating.

[0094] (Comparative Example 9) A coating film was obtained in the same manner as in Example 4, except that the single-walled CNTs were changed to multi-walled CNTs and the coating material was applied by bar coating.

[0095] (Comparative Example 10) A coating film was obtained in the same manner as in Comparative Example 2, except that the single-walled CNTs were changed to multi-walled CNTs and the coating material was applied by bar coating.

[0096] (Comparative Example 11) A coating film was obtained in the same manner as in Comparative Example 3, except that the single-walled CNTs were changed to multi-walled CNTs and the coating material was applied by bar coating.

[0097] (Comparative Example 12) A coating film was obtained in the same manner as in Comparative Example 4, except that the single-walled CNTs were changed to multi-walled CNTs and the coating material was applied by bar coating.

[0098] (Measurement of average particle size of dispersion liquid) The average particle size of the dispersion was measured using a laser diffraction / scattering particle size distribution analyzer MT3000 II manufactured by Microtrac Bell Co., Ltd. The average particle size indicates the particle size at an integrated value of 50% in the obtained particle size distribution. The average particle size of the dispersions in Examples 1 to 4 (dispersions obtained in (5)) was 1 to 6 μm.

[0099] (film thickness) Examples 1 to 4 and Comparative Examples 1 to 4: 2 μm Comparative Examples 5 and 10 to 12: 3 μm ·Comparative Examples 6 to 9: 4μm.

[0100] (CNT amount per area (theoretical value)) Examples 1 to 4 and Comparative Examples 1 to 4: 1.83 × 10 g / cm 2 Comparative Examples 5 and 10-12: 2.74 x 10^-5 g / cm 2 ·Comparative examples 6~9: 3.65×10^-5g / cm 2 .

[0101] (2) Evaluation of thermoelectric conversion properties The laminate of the film substrate and coating was cut into a strip (2 cm x 11 cm), and Cu tape electrodes (conductive copper foil adhesive tape, Teraoka Seisakusho) were attached to both long edges of the strip to extract electricity, yielding a sample. The distance between the electrodes was 10 cm. One end of the sample was heated with a heater, and the temperatures at both ends of the sample were measured using a thermograph (FLIR i60, Nippon Barnes). The voltage between the electrodes was also measured using a digital multi-tester (PC101, Sanwa Electric Instruments). The negative terminal (black terminal) of the tester was connected to the electrode on the heated side (high temperature side), and the positive terminal (red terminal) was connected to the opposite electrode.

[0102] If the coating is a p-type thermoelectric conversion material (p-type semiconductor), a positive charge moves from the high-temperature area to the low-temperature area. This causes the low-temperature side to become positively charged, and conversely, the high-temperature side to become negatively charged. The electromotive force can be measured by using a tester on the electrode in this charged state, and by applying the negative terminal (black terminal) of the tester to the high-temperature side, a positive voltage is measured.

[0103] In contrast, in an n-type thermoelectric conversion material (n-type semiconductor), negative electrons move from the high temperature area to the low temperature area, so when the voltage is measured as described above, a negative voltage value is measured.

[0104] The evaluation index value was calculated by dividing the measured voltage (positive or negative value) by the temperature change (= measured temperature at the high temperature part (heated end) - measured temperature at the low temperature part (unheated end)).

[0105] The results are shown in Table 2. Table 3 shows an outline of the preparation methods indicated by the preparation method numbers in Table 2.

[0106] [Table 2]

[0107] [Table 3]

[0108] Coating films were obtained in the same manner as in Example 1, except that sodium hydroxide, sulfuric acid, nitric acid, or p-toluenesulfonic acid was used as the doping agent, and these were also evaluated in the same manner as above.When sodium hydroxide was used, the evaluation index value was positive, and in the other cases, the particles in the liquid were coarse (average particle diameter 30 to 50 μm), and it was determined that they could not be used as a paint.

Claims

1. (A) a step of contacting single-walled carbon nanotubes with an organic base-type n-type doping agent in a liquid to obtain a dispersion liquid 1; (B) adding a dispersant to the dispersion 1 to obtain dispersion 2; A method for producing a coating composition comprising:

2. 2. The method according to claim 1, wherein the organic base-type n-type doping agent is at least one selected from the group consisting of amidine compounds and guanidine compounds.

3. 3. The method according to claim 2, wherein the organic base-type n-type doping agent is at least one selected from the group consisting of cyclic amidine compounds and cyclic guanidine compounds.

4. The method of claim 3 , wherein the organic base-type n-type doping agent is a cyclic amidine compound.

5. 5. The method of claim 4, wherein the organic base-type n-type doping agent is diazabicycloundecene or diazabicyclononene.

6. 2. The method according to claim 1, wherein in the step (A), the contact time between the single-walled carbon nanotubes and the organic base-type n-type doping agent is 1 hour or longer.

7. 2. The method of claim 1, wherein in step (B), the addition of the dispersant is carried out by adding a dispersant solution.

8. 2. The method according to claim 1, wherein the amount of the organic base n-type doping agent used in step (A) is 0.001 to 0.1 mol per 1 g of the single-walled carbon nanotubes.

9. The method according to claim 1 , wherein the coating composition is a coating composition for producing an n-type thermoelectric conversion material.

10. A coating composition obtainable by the method according to any one of claims 1 to 9.

11. A method for producing a coating film, comprising the step of applying the coating composition according to claim 10 onto a substrate.

12. A coating film obtainable by the method of claim 11.

13. A thermoelectric conversion element comprising an n-type thermoelectric conversion material comprising the coating film according to claim 12 and a p-type thermoelectric conversion material.

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