Method for producing CNT product

Abstract

To inhibit a non-uniform residue of a CNT on a basal plate when removing or pulling out the CNT having grown on the basal plate from the basal plate.SOLUTION: A method for producing a CNT product includes a CNT synthetic process using a chemical vapor deposition method including: a growth process of supplying a raw material gas to a reaction chamber including a basal plate and making a CNT grow on the basal plate under a growth temperature and a growth pressure; a discharge process of discharging the raw material gas and reducing a pressure of the raw material gas to a reduction pressure being 5% to 95% of the growth pressure; and a holding process of holding the pressure of the raw material gas within a range of the reduction pressure for a prescribed duration.SELECTED DRAWING: Figure 4A

Description

[Technical Field]

[0001] The present disclosure relates to methods for manufacturing CNT products. [Background technology]

[0002] Carbon nanotubes (hereinafter sometimes referred to as "CNTs") are expected to be used in a variety of applications in a wide range of fields due to their excellent thermal conductivity, electrical conductivity, mechanical strength, etc.

[0003] Examples of CNT synthesis processes include arc discharge, laser evaporation, and chemical vapor deposition (hereinafter sometimes referred to as "CVD"). Of these, CVD is primarily used industrially because it is suitable for mass production. CNT production using CVD involves reacting a gas containing carbon atoms as a raw material in the presence of a catalyst to grow CNTs. Patent Document 1 discloses a CNT synthesis process in which a raw material gas is supplied at a first temperature and a raw material gas at a second temperature 50 to 200°C higher than the first temperature is supplied, thereby producing CNTs with a sufficiently thick amorphous layer and suppressing aggregation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-231446 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have found that when using a CVD CNT synthesis process, depending on the adhesiveness between the substrate and the CNTs grown on the substrate, the CNTs may remain unevenly on the substrate after being peeled off or pulled out (as a CNT web). Such uneven CNT residue is problematic from the perspective of CNT productivity. Furthermore, uneven CNT residue can impair the uniformity and continuity of the CNTs obtained by peeling or pulling out, as well as the density of the peeled CNT surfaces, which can also be problematic from the perspective of CNT properties (e.g., reliability, thermal conductivity, electrical conductivity, etc.). [Means for solving the problem]

[0006] The present disclosure has been made in light of the above circumstances. Rather than addressing the above by simply extending the conventional technology, the present inventors attempted to achieve the above object by addressing the problem in a new direction, and discovered that the above main object could be achieved, leading to the present disclosure. One preferred embodiment of the present disclosure is as follows: [Section 1] a growth step of supplying a source gas into a reaction chamber containing a substrate and growing CNTs on the substrate at a growth temperature and a growth pressure; an exhaust step of exhausting the source gas to reduce the source gas pressure to a reduced pressure that is 5% to 95% of the growth pressure; a maintaining step of maintaining the source gas pressure within the reduced pressure range for a predetermined time; A method for producing a CNT product, comprising a CNT synthesis process using chemical vapor deposition, comprising: [Section 2] Item 2. The method for producing a CNT product according to Item 1, wherein the growth temperature is maintained in the maintaining step. [Section 3] Item 3. A method for producing a CNT product according to item 1 or 2, wherein a halide of a transition metal element is used as a reaction catalyst. [Section 4] Item 4. The method for producing a CNT product according to any one of Items 1 to 3, wherein at least one second gas selected from the group consisting of hydrocarbons having oxygen atoms and hydrogen is supplied simultaneously with the supply of the raw material gas. [Section 5] Item 5. The method for producing a CNT product according to any one of items 1 to 4, wherein in the growth step, the growth temperature is 500° C. or higher and the source gas pressure is 1 Torr or higher. [Section 6] Item 6. The method for producing a CNT product according to any one of Items 1 to 5, wherein the reduced pressure is 30% to 80% of the growth pressure. [Section 7] Item 7. The method for producing a CNT product according to any one of items 1 to 6, further comprising, after the maintaining step, a temperature lowering step of lowering the ambient temperature of the reaction chamber. [Section 8] Item 8. The method for producing a CNT product according to any one of items 1 to 7, further comprising a second discharge step of discharging the source gas to a source gas pressure of 0.1 Torr or less after the holding step. [Section 9] Item 9. The method for producing a CNT product according to any one of items 1 to 8, wherein the second discharging step is carried out simultaneously with the temperature lowering step. [Section 10] Item 10. A method for producing a CNT product according to any one of items 1 to 9, comprising a CNT array production process including a peeling step of peeling off the CNTs grown on the substrate from the substrate. [Section 11] Item 10. A method for producing a CNT product according to any one of items 1 to 9, comprising a CNT fiber product production process including a pulling-out step of pulling out the CNTs grown on the substrate from the substrate as a CNT web. [Section 12] Item 12. The method for producing a CNT product according to any one of items 1 to 11, wherein CNTs are grown on both sides of the substrate. [Section 13] Item 13. The method for producing a CNT product according to any one of Items 1 to 12, wherein a double-side polished substrate is used as the substrate. [Section 14] Item 14. The method for producing a CNT product according to any one of items 1 to 13, wherein the reaction chamber includes a plurality of the substrates, and the distance between the plurality of substrates is minimized within a range where the CNTs grown from each substrate do not come into contact with each other. [Section 15] A CNT product that is an aggregate of CNTs, wherein the ends of multiple CNTs among the CNTs form a tapered structure in which the ratio (D1 / D2) of the average diameter D1 at 10 nm to 100 nm from the end point to the average diameter D2 at 1000 nm to 2000 nm from each end point is 0.75 or less. [Section 16] Item 16. The CNT product according to item 15, wherein the CNT product is a CNT array that is an aligned aggregate of CNTs, and a plurality of CNT ends on one surface form a tapered structure in which the ratio (D1 / D2) of the average diameter D1 at 10 nm to 100 nm from each end point to the average diameter D2 at 1000 nm to 2000 nm from each end point is 0.75 or less. [Section 17] The CNT product is a CNT fiber product containing CNTs as fibers, and a plurality of CNT ends are Item 17. The CNT product according to item 15 or 16, wherein the ratio (D1 / D2) of the average diameter D1 at 10 nm to 100 nm from each end point to the average diameter D2 at 1000 nm to 2000 nm from each end point is 0.75 or less. [Section 18] Item 18. The CNT product according to item 17, which is a CNT web, a CNT yarn, a CNT sheet, a CNT sheet, a CNT woven or knitted fabric, or a CNT nonwoven fabric. [Section 19] Item 19. The CNT product according to any one of items 15 to 18, wherein a plurality of CNT ends among the CNTs form a repeatedly uneven surface in the length direction of the CNT. [Section 20] 20. The CNT product according to any one of items 15 to 19, wherein a plurality of CNT ends have a crimped shape. [Section 21] Item 21. The CNT product according to any one of Items 15 to 20, wherein a plurality of CNT ends form an entangled structure together with neighboring CNT ends. [Section 22] 22. A CNT-resin composite obtained by impregnating the CNT product according to any one of items 15 to 21 with a resin. [Section 23] Item 22. An article comprising the CNT product according to any one of items 15 to 21 or the CNT resin composite according to item 22. [Item 24] The article according to Item 23 selected from the group consisting of a heat dissipation material, a heater, and an electromagnetic wave absorption sheet.

Effect of the Invention

[0007] According to the present disclosure, the peelability and drawability of CNTs grown on a substrate from the substrate can be improved, and non-uniform residual CNTs on the substrate after peeling or drawing the CNTs from the substrate can be suppressed. Thereby, the productivity of CNT products can be improved. Further, thereby, the characteristics of CNTs (for example, reliability, thermal conductivity, electrical conductivity, etc.) can be improved.

Brief Description of the Drawings

[0008] [Figure 1] A schematic diagram of the manufacturing process of a CNT array is shown. [Figure 2] A schematic diagram of the manufacturing process of a CNT sheet is shown. [Figure 3A] An SEM photograph of the end of the CNT obtained in CNT array production example 1 is shown. [Figure 3B] An SEM photograph of the end of the CNT obtained in comparative CNT array production example 1 is shown. [Figure 4A] An SEM photograph of the substrate surface after peeling the CNT obtained in CNT array production example 1 is shown. [Figure 4B] An SEM photograph of the substrate surface after peeling the CNT obtained in comparative CNT array production example 1 is shown. [Figure 5] The characteristics, etc. of the CNT resin composites obtained in CNT resin composite production examples 1 to 4 are shown.

Modes for Carrying Out the Invention

[0010] [CVD method] The CNT synthesis process in this disclosure uses the CVD method. CVD is a type of deposition method, so named because it uses a chemical reaction during the deposition process. CVD methods include thermal CVD, which uses heat to decompose raw materials by increasing the temperature; photo-CVD, which uses light to promote chemical reactions; and plasma CVD, which excites gas into a plasma state. However, thermal CVD is typically preferred for the CNT synthesis process in this disclosure. Examples of thermal CVD methods include the DIPS method, CoMoCAT method, HiPCO method, super-growth CVD method, solid-phase catalytic method, and gas-phase catalytic method.

[0011] [CVD equipment] In the CNT synthesis process of the present disclosure, a CVD apparatus is used. The CVD apparatus in the present disclosure is not particularly limited, but may be one that heats the entire reaction chamber (hot wall type) or one that heats only the substrate table and cools the reaction chamber (cold wall type), may be horizontal or vertical (excellent in temperature distribution, response speed, gas flow control, etc.), and may be a batch processing type (processing multiple substrates simultaneously), a single wafer type (processing one substrate at a time), or a continuous processing type (conveyor type). From the viewpoint of suitability for mass production, a continuous processing type is preferable.

[0012] The CVD apparatus may have a reaction chamber containing a substrate, a gas inlet means for introducing gas (source gas or carrier gas) into the reaction chamber, an exhaust means for exhausting gas (unreacted source gas, source decomposition product gas, or carrier gas) from the reaction chamber, and a heater.

[0013] [Substrate and catalyst] The substrate serves as a base for growing CNTs. The substrate has a melting point equal to or higher than the growth temperature. The substrate can be a semiconductor substrate such as a silicon substrate, an insulating substrate such as an alumina (sapphire) substrate, an MgO substrate, or a glass substrate, or a metal substrate. These substrates may also have a thin film formed on them. For example, a silicon substrate can have an oxide film (e.g., a silicon oxide film) with a thickness of about 10 nm to 1000 nm (e.g., 100 nm to 500 nm) formed thereon.

[0014] The reaction chamber may contain multiple substrates. The number of substrates contained in the reaction chamber may be 5 or more, 10 or more, or 30 or more. The number of substrates contained in the reaction chamber may be 500 or less, 250 or less, or 50 or less. When multiple substrates are contained in the reaction chamber, it is preferable that the distance between the multiple substrates is minimized so that the CNTs grown from each substrate do not come into contact with each other. This eliminates excess space in the reaction chamber, making it possible to place the maximum number of substrates in the reaction chamber, which can improve CNT productivity.

[0015] Although CNTs may be grown on one side of the substrate, it is preferable to grow CNTs on both sides of the substrate from the viewpoint of improving CNT productivity.

[0016] A polished substrate may be used as the substrate. By using a polished substrate, the growth potential of CNTs can be improved. Although only one side of the substrate may be polished, it is preferable to polish both sides of the substrate from the viewpoint of improving productivity of CNTs.

[0017] The substrate is a catalyst support, and is made up of Mo, Ti, Hf, Zr, Nb, V, TaN, and TiSi. x (e.g. x=1-2), Al, Al2O3, TiO x (e.g., x=1 to 2), Ta, W, Cu, Au, Pt, Pd, TiN, or a support containing at least one of these. The support may have a thickness of 0.1 nm or more, 0.5 nm or more, or 1 nm or more, and may be 10 nm or less, 7.5 nm or less, or 5 nm or less. The support layer and catalyst layer may form a laminated structure, or the catalyst may be dispersed on the support.

[0018] The substrate preferably has a catalytic layer on its surface. The catalytic layer can be formed by depositing catalytic particles, for example, by sputtering. From the perspective of CNT growth, it is preferable to alternately form areas where catalytic particles are deposited and areas where they are not. Such island-shaped catalytic layers can be produced, for example, by placing a mesh on the substrate and depositing catalytic particles in a specific pattern on top of it by sputtering, or by controlling the size of the catalytic particles in advance using a differential electrostatic classifier. The thickness of the catalytic layer may be 0.1 nm or more, 0.5 nm or more, or 1 nm or more, and 10 nm or less, 7.5 nm or less, or 5 nm or less. The diameter of the island-shaped catalytic layer may be 0.1 nm or more, 0.5 nm or more, 1 nm or more, or 3 nm or more, and 15 nm or less, 10 nm or less, 7.5 nm or less, or 5 nm or less.

[0019] The catalyst used in the CNT growth reaction is not limited to a specific type, but preferably contains a transition metal element from Groups 3 to 12, such as V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, W, Ag, Au, or Pt. The catalyst may be a halide (e.g., fluoride, chloride, bromide, or iodide) or oxide of these elements. From the viewpoint of growth rate, the catalyst may be a halide, and iron halide is particularly preferred. More specific examples of halides include iron fluoride, cobalt fluoride, nickel fluoride, iron chloride, cobalt chloride, nickel chloride, iron bromide, cobalt bromide, nickel bromide, iron iodide, cobalt iodide, and nickel iodide. Here, the halide may be divalent, trivalent, or polyvalent, such as iron(II) chloride or iron(III) chloride.

[0020] A sublimable catalyst (e.g., iron chloride) may be present in the reaction chamber as a gas-phase catalyst. The method for introducing the gas-phase catalyst into the reaction chamber is not limited. Alternatively, a material (catalyst source) in a physical state other than the gas phase (typically a solid state) that provides the gas-phase catalyst may be placed inside the reaction chamber, and the gas-phase catalyst may be generated from the catalyst source by heating and / or applying a negative pressure to the inside of the reaction chamber. Alternatively, the catalyst generation reaction may occur within the reaction chamber. For example, in the case of iron chloride, the gas-phase catalyst may be generated by heating an iron-group element-containing material, such as iron in the form of a lump, plate, steel wool, or powder, in the reaction chamber at a predetermined temperature and then supplying a halogen-containing substance to react with the iron-group element-containing material in the reaction chamber. As a specific example of generating a gas-phase catalyst using a catalyst source, anhydrous iron (II) chloride is placed inside a reaction chamber as a catalyst source, and the inside of the reaction chamber is heated and negative pressure is applied to sublimate the anhydrous iron (II) chloride, thereby creating a gas-phase catalyst consisting of iron (II) chloride vapor inside the reaction chamber.

[0021] [Each step in the CNT synthesis process] The method for producing a CNT product according to the present disclosure includes a CNT synthesis process. The CNT synthesis process includes a growth step, a discharge step, and a holding step. The CNT synthesis process according to the present disclosure may further include a temperature-lowering step, a second discharge step, and other steps.

[0022] (growth process) The synthesis process in the present disclosure includes a growth step. The growth step involves supplying a source gas to a reaction chamber containing a substrate and growing CNTs on the substrate at a growth temperature and a growth pressure. Before heating the substrate to the growth temperature, the atmosphere in the reaction chamber may be evacuated or replaced with a carrier gas. When the source gas is supplied into the reaction chamber, the atmosphere in the reaction chamber may be heated to a predetermined temperature (growth temperature). Here, the "growth temperature" refers to the reaction chamber ambient temperature at which the CNT growth reaction can proceed, and the "growth pressure" refers to the reaction chamber pressure of the source gas at which the CNT growth reaction can proceed.

[0023] The source gas is a gaseous compound that serves as a carbon source for CNTs. The number of carbon atoms in the source gas may be 1 or more, 2 or more, or 3 or more, and may be 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less, preferably 3 or less. The source gas may be a hydrocarbon. Examples of source gases include aliphatic saturated hydrocarbons such as methane, ethane, propane, butane, and hexane; aliphatic unsaturated hydrocarbons such as ethylene, propylene, butene, isobutene, and acetylene; aromatic hydrocarbons such as benzene, toluene, xylene, and naphthalene; alcohols such as methanol and ethanol; and mixtures thereof, with acetylene being a typical example.

[0024] A second gas may be supplied into the reaction chamber simultaneously with the source gas. The second gas is a gas different from the source gas and is at least one gas selected from the group consisting of a hydrocarbon having an oxygen atom, hydrogen, and carbon monoxide. The second gas may have an etching effect on the catalyst. The second gas may also be a reducing substance.

[0025] The hydrocarbon having an oxygen atom may be a hydrocarbon having an alcohol oxygen, a hydrocarbon having a carbonyl oxygen, or a hydrocarbon having an ether oxygen, preferably a hydrocarbon having an alcohol oxygen or a hydrocarbon having a carbonyl oxygen, particularly a hydrocarbon having a carbonyl oxygen. The number of carbon atoms in the hydrocarbon having an oxygen atom may be 1 or more, 2 or more, or 3 or more, and may be 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, or 1 or less, preferably 3 or less.

[0026] Specific examples of the second gas include carbon monoxide, acetone, ethanol, methanol, and hydrogen, and preferred examples include carbon monoxide, acetone, and hydrogen, particularly carbon monoxide and acetone.

[0027] Supplying the second gas simultaneously with the source gas can have the effect of increasing the growth rate of CNTs and further improving the spinnability of the produced CNTs. It can also have the effect of reducing the activation energy of the reaction involved in the growth of the CNT array, increasing the growth rate and stability of the CNT array, extending the life of the gas-phase catalyst by removing amorphous carbon, which is the cause of deactivation, and improving the uniformity of the growth length.

[0028] In order to supply the second gas, in addition to or instead of supplying the second gas itself, a raw material capable of forming the second gas can be supplied. For example, in order to supply carbon monoxide as the second gas, in addition to or instead of supplying the carbon monoxide itself, a raw material capable of forming carbon monoxide can be supplied. Examples of raw materials capable of forming carbon monoxide include carbon dioxide and carbonyl complexes. These raw materials can form (generate) carbon monoxide in the reaction chamber, thereby achieving the same effect as when carbon monoxide is supplied.

[0029] The source gas pressure in the growth step may be 1 Torr or more, 3 Torr or more, 5 Torr or more, 10 Torr or more, 25 Torr or more, or 50 Torr or more, preferably 1 Torr or more.The source gas pressure in the growth step may be 300 Torr or less, 200 Torr or less, 150 Torr or less, 100 Torr or less, 50 Torr or less, 25 Torr or less, or 12.5 Torr or less, preferably 100 Torr or less.

[0030] The ratio of the second gas pressure to the source gas pressure in the growth step (second gas pressure / source gas pressure) may be 0.1% or more, 1% or more, 2% or more, 3% or more, 5% or more, 10% or more, or 20% or more, and is preferably 1% or more. The ratio of the second gas pressure to the source gas pressure in the growth step (second gas pressure / source gas pressure) may be 500% or less, 300% or less, 100% or less, 50% or less, 30% or less, 20% or less, 10% or less, or 5% or less, and is preferably 30% or less.

[0031] A carrier gas may be supplied into the reaction chamber simultaneously with the source gas. Examples of the carrier gas include rare gases such as argon, helium, and neon, and nitrogen. The amount of the carrier gas may be determined appropriately, and may be, for example, 100% to 10,000% of the source gas pressure. In addition, other gases such as hydrogen and water vapor may be supplied into the reaction chamber as needed, provided that the effects of the present invention are not impaired.

[0032] The growth temperature may be any temperature at which the source gas reacts to grow CNTs on the substrate, and may be, for example, 500° C. or higher, 550° C. or higher, 600° C. or higher, 650° C. or higher, 700° C. or higher, 750° C. or higher, 800° C. or higher, or 850° C. or higher, preferably 600° C. or higher. The growth temperature may be 1100° C. or lower, 1050° C. or lower, 1000° C. or lower, 950° C. or lower, 900° C. or lower, or 850° C. or lower, preferably 1000° C. or lower.

[0033] The time for the growth step may be determined based on the desired length of the CNTs; if short CNTs are required, the time for the growth step may be shortened, and if long CNTs are required, the time for the growth step may be lengthened.

[0034] (discharge process) The synthesis process according to the present disclosure further includes an exhaust step, which includes stopping the supply of the source gas and exhausting the source gas to reduce the source gas pressure to a reduced pressure that is 5% to 95% of the growth pressure.

[0035] The reduced pressure may be 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, or 60% or more of the source gas pressure in the growth step, preferably 30% or more or 50% or more. The reduced pressure may be 95% or less, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, or 40% or less of the source gas pressure in the growth step, preferably 80% or less.

[0036] The duration of the discharge step may be 0.01 seconds or more, 0.1 seconds or more, 1 second or more, or 10 seconds or more. The duration of the discharge step may be 300 seconds or less, 200 seconds or less, 100 seconds or less, 60 seconds or less, or 30 seconds or less, for example, 25 seconds or less, 20 seconds or less, 15 seconds or less, 10 seconds or less, or 5 seconds or less.

[0037] (holding process) The synthesis process according to the present disclosure further includes a holding step, in which the source gas pressure is maintained within the reduced pressure range for a predetermined period of time. During the holding step, the source gas pressure is preferably maintained constant. To maintain the pressure during the holding step, gas supply into the reaction chamber and gas discharge from the reaction chamber may be blocked.

[0038] The duration of the holding step may be a predetermined time, for example, 5 seconds or more, 10 seconds or more, 20 seconds or more, 30 seconds or more, 40 seconds or more, 50 seconds or more, or 60 seconds or more, or 300 seconds or less, 250 seconds or less, 200 seconds or less, 150 seconds or less, 100 seconds or less, or 50 seconds or less.

[0039] In the holding step, the reaction chamber ambient temperature may be held within a certain range, and preferably the reaction chamber ambient temperature is held at the growth temperature. During the holding step, the reaction chamber ambient temperature may be held constant.

[0040] (Temperature cooling process) The synthesis process of the present disclosure may further include a temperature-reducing step, which is carried out after the holding step and includes lowering the ambient temperature of the reaction chamber.

[0041] The rate of decrease in the reaction chamber ambient temperature may be 3° C. / min or more, 5° C. / min or more, 7° C. / min or more, 9° C. / min or more, or 12° C. / min or more. The rate of decrease in the reaction chamber ambient temperature may be 50° C. / min or less, 40° C. / min or less, 30° C. / min or less, or 20° C. / min or less.

[0042] The temperature-lowering step may be carried out until the reaction chamber atmosphere temperature reaches a temperature at which the CNTs are not oxidized by oxygen in the air, for example, less than 500° C., 400° C. or less, or 300° C. or less. Once the reaction chamber atmosphere temperature reaches a temperature at which the CNTs are not oxidized by oxygen in the air, the substrate may be released to atmospheric pressure.

[0043] (Second discharge process) The synthesis process of the present disclosure may further include a second discharging step, which is carried out after the holding step, in which the source gas is discharged to further reduce the source gas pressure from the reduced pressure.

[0044] The source gas pressure after the second evacuation step is not particularly limited, but may be 0 Torr or more, 0.0001 Torr or more, 0.001% or more of the reduced pressure, or 0.01% or more of the reduced pressure. The source gas pressure after the second evacuation step may be 0.1 Torr or less, 0.08 Torr or less, 0.05 Torr or less, 0.03 Torr or less, or 0.01 Torr or less, preferably 0.05 Torr or less. The source gas pressure after the second evacuation step may be 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, or 1% or less of the reduced pressure, preferably 10% or less.

[0045] The lower limit of the time for the second discharge step is not particularly limited, and may be 0.01 seconds or more, 0.1 seconds or more, 1 second or more, or 10 seconds or more. The time for the second discharge step may be 300 seconds or less, 200 seconds or less, 100 seconds or less, 60 seconds or less, or 30 seconds or less, for example, 25 seconds or less, 20 seconds or less, 15 seconds or less, 10 seconds or less, or 5 seconds or less.

[0046] The second discharge step may be carried out simultaneously with the temperature-lowering step. Note that, if the desired source gas pressure has been reached but the desired reaction chamber ambient temperature has not yet been reached, the temperature-lowering step may be continued even after the second discharge step is completed.

[0047] [CNT structure] The CNTs obtained by the synthesis process of the present disclosure may be single-walled or multi-walled, but are preferably multi-walled. The diameter of the CNTs may be 0.5 nm or more, 3 nm or more, 5 nm or more, 10 nm or more, 30 nm or more, 50 nm or more, or 100 nm or more, preferably 5 nm or more, more preferably 10 nm or more. The diameter of the CNTs may be 500 nm or less, 300 nm or less, 100 nm or less, 80 nm or less, 60 nm or less, 40 nm or less, or 20 nm or less, preferably 100 nm or less. The number of walls of the CNTs may be 1 or more, 2 or more, 3 or more, 5 or more, 7 or more, 10 or more, or 20 or more, preferably 2 or more. The number of walls of the CNTs may be 55 or less, 45 or less, 35 or less, 25 or less, 15 or less, or 5 or less. The diameter and number of walls of the CNTs can be determined by the type of catalyst, the size of the catalyst particles, etc.

[0048] The CNTs obtained by the synthesis process of the present disclosure are preferably relatively long. The average length of the CNTs may be 0.05 mm or more, 0.1 mm or more, 0.2 mm or more, 0.4 mm or more, 0.6 mm or more, 1.0 mm or more, 3.0 mm or more, 5 mm or more, or 10 mm or more, preferably 0.1 mm or more, and more preferably 0.4 mm or more. The average length of the CNTs may be 200 mm or less, 150 mm or less, 100 mm or less, 50 mm or less, 25 mm or less, 10 mm or less, or 5.0 mm or less, preferably 25 mm or less. The length of the CNTs is determined by the time of the growth process; if short CNTs are required, the time of the growth process can be shortened, and if long CNTs are required, the time of the growth process can be extended. The average length of the CNTs can be determined, for example, from SEM images.

[0049] The G / D ratio of the CNTs obtained by the synthesis process of the present disclosure may be 1 or more, 1.5 or more, 2 or more, or 2.5 or more, and is preferably 2 or more. The G / D ratio of the CNTs obtained by the synthesis process of the present disclosure may be 10 or less, 8 or less, 6 or less, or 4 or less. The G / D ratio is an index of the crystallinity of carbon nanotubes determined by Raman spectroscopy.

[0050] The purity of the CNTs obtained by the synthesis process of the present disclosure may be 80% or more, 85% or more, 90% or more, 95% or more, 98% or more, or 99% or more, and is preferably 95% or more. The purity of the CNTs can be determined, for example, by elemental analysis using fluorescent X-rays.

[0051] The CNTs obtained by the synthesis process of the present disclosure have a specific structure at the ends of the CNTs on one surface (the side surface of the substrate).

[0052] In this specification, the term "CNT end" may refer to a distance of 10,000 nm or less, 9,000 nm or less, 8,000 nm or less, 7,000 nm or less, 6,000 nm or less, 5,000 nm or less, 4,000 nm or less, 3,000 nm or less, 2,000 nm or less, 1,000 nm or less, or 750 nm or less from the terminal point (endmost point) of the CNT.

[0053] [CNT array manufacturing process] In this specification, the term "CNT array" refers to an aligned aggregate of CNTs (also called a CNT forest) grown on a substrate and then separated from the substrate. Due to the synthesis process described above, the CNT array in this disclosure has a unique structure at the ends of multiple CNTs on one side (the side of the substrate (the side that was attached to the substrate before the CNTs were peeled off)).

[0054] The manufacturing process for a CNT array in the present disclosure further includes a peeling step after the above-mentioned CNT synthesis process. In the peeling step, CNTs grown on a substrate are peeled from the substrate to obtain a CNT array. The CNTs grown on the substrate here are a CNT aggregate vertically aligned on the substrate (a so-called CNT forest). In this specification, the vertically aligned CNT aggregate isolated by peeling is referred to as a CNT array. Figure 1 shows a schematic diagram of the manufacturing process for a CNT array.

[0055] The method for peeling the CNTs from the substrate in the peeling step may be a physical, chemical, or mechanical peeling method. Specific examples include peeling methods using an electric field, a magnetic field, centrifugal force, surface tension, etc., mechanical peeling methods from the substrate, and methods using pressure or heat. It is also possible to use a vacuum pump to suck the CNTs and peel them off the substrate. Examples of mechanical peeling methods include a method in which the CNTs are directly picked up with tweezers and peeled off from the substrate, and a method in which the CNTs are peeled off from the substrate using a thin blade such as a plastic spatula or cutter blade with a sharp part.

[0056] (Structure of CNT ends in CNT arrays) In the CNT array, the CNT ends preferably have a structure in which the ratio (D1 / D2) of the average diameter D1 within 10 nm to 100 nm from each end to the average diameter D2 within 1000 nm to 2000 nm from each end is 0.75 or less.

[0057] In the CNT array, the CNT ends having a structure in which D1 / D2 is 0.75 or less may be 25% or more of the CNT ends on one surface, for example, 30% or more, 35% or more, 40% or more, 45% or more, or 50% or more. In the CNT array, the CNT ends having a structure in which D1 / D2 is 0.75 or less may be 75% or less, 50% or less, or 25% or less of the CNT ends on one surface.

[0058] In the CNT array, D1 / D2 may be 0.75 or less, 0.6 or less, 0.45 or less, or 0.30 or less. In the CNT array, D1 / D2 may be 0.10 or more, 0.20 or less, 0.30 or more, 0.35 or more, or 0.40 or more.

[0059] It is preferable that the ends of the multiple CNTs in the CNT array form a repeated uneven surface in the length direction of the CNTs. The repeated uneven surface is also called a wavy surface, an undulating surface, or a zigzag surface. The repeated uneven surface occurs because the CNT array forms a structure called a dumpling structure, a node structure, a bellows structure, or a twisted structure.

[0060] The CNT ends forming the repeating uneven surface in the CNT array may be 25% or more of the CNT ends on one side, for example, 30% or more, 35% or more, 40% or more, 45% or more, or 50% or more. The CNT ends forming the repeating uneven surface in the CNT array may be 75% or less, 50% or less, or 25% or less of the CNT ends on one side. Here, the CNT ends may refer to those that are 1000 nm or less, 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, 600 nm or less, 500 nm or less, 400 nm or less, or 300 nm or less from the end points of the CNTs.

[0061] The number of projections and recesses on the repeating uneven surface of the CNT ends in the CNT array may be 5 or more per μm, 10 or more per μm, 20 or more per μm, 30 or more per μm, 40 or more per μm, 50 or more per μm, or 60 or more per μm along the length of the CNT. The number of projections and recesses on the repeating uneven surface in the CNT array may be 100 or less per μm, 80 or less per μm, 60 or less per μm, 40 or less per μm, 30 or less, or 20 or less per μm along the length of the CNT.

[0062] Preferably, multiple CNT ends in the CNT array have a crimped shape. Crimping is also called curling. The type of crimp is not particularly limited, but may be, for example, zigzag, wavy / omega, or spiral. By crimping, these CNTs may form an entangled structure with neighboring CNT ends. Here, the CNT end may refer to a distance of 1000 nm or less, 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, 600 nm or less, 500 nm or less, 400 nm or less, or 300 nm or less from the end point of the CNT.

[0063] The crimped CNT ends in the CNT array may be 25% or more of the CNT ends on one surface, for example, 30% or more, 35% or more, 40% or more, 45% or more, or 50% or more. The crimped CNT ends in the CNT array may be 75% or less, 50% or less, or 25% or less of the CNT ends on one surface.

[0064] In the CNT array, the number of crimps (the number of peaks per unit length) at the CNT ends may be 1 peak / μm or more, 2 peaks / μm or more, 3 peaks / μm or more, 4 peaks / μm or more, 5 peaks / μm or more, or 6 peaks / μm or more. In the CNT array, the number of crimps (the number of peaks per unit length) may be 20 peaks / μm or less, 15 peaks / μm or less, 10 peaks / μm or less, 7 peaks / μm or less, or 5 peaks / μm or less.

[0065] [CNT fiber product manufacturing process] In this disclosure, a "CNT fiber product" refers to a fiber product containing CNTs as fibers. The CNT fiber product in this disclosure contains CNTs obtained by the synthesis process described above. Specific examples of CNT fiber products include CNT webs, CNT yarns, CNT sheets, CNT woven or knitted fabrics, and CNT nonwoven fabrics. Because they have undergone the synthesis process described above, the CNT ends of the CNTs contained as fibers in the CNT fiber product in this disclosure have a specific structure.

[0066] The manufacturing process for CNT fiber products preferably includes a drawing step in which the CNTs grown on the substrate are drawn from the substrate as a CNT web to obtain a CNT fiber product. The drawing step may utilize the dry spinning phenomenon of CNTs. The "dry spinning phenomenon of CNTs" refers to the phenomenon in which a vertically aligned CNT aggregate (a so-called CNT forest) on a substrate is pinched by its end and drawn along the substrate surface, forming a CNT web in which CNTs spontaneously bond with each other through van der Waals forces. This dry spinning phenomenon of CNTs can transform a CNT aggregate growing three-dimensionally on a substrate into an aggregate forming a two-dimensional network. This morphological change is similar to the action of spinning thread from a silkworm cocoon. However, because the CNTs are bonded by strong van der Waals forces, spinning is possible without twisting the CNT web, unlike conventional spinning. CNT webs can be twisted to form CNT yarn, and stacking CNT webs can form a CNT sheet. The manufacturing process of CNT fiber products using the dry spinning phenomenon is well known, and reference can be made, for example, to Y. Inoue, K. Kakihata, Y. Hirono, T. Horie, A. Ishida & H. Mimura: Appl. Phys. Lett., 92, 21 (2008), 213113; Y. Inoue, Y. Suzuki, Y. Minami, J. Muramatsu, Y. Shimamura, K. Suzuki, A. Ghemes, M. Okada, S. Sakakibara, H. Mimura & K. Naito: Carbon, 49, 7 (2011), 2437-2443. CNT woven fabrics and CNT knitted fabrics can be obtained by weaving or knitting CNTs or CNT yarns as fibers. CNT nonwoven fabrics can be obtained, for example, by dispersing CNTs in a dry or wet process and then bonding them.

[0067] (CNT sheet) The CNT fiber product may be a CNT sheet, which is a laminate of CNT webs. CNT sheets have anisotropic thermal conductivity and are therefore suitable as heat dissipation materials. CNT sheets can be obtained by laminating CNT webs from CNTs synthesized on a substrate using the dry spinning phenomenon. The CNT webs can be laminated using a take-up roll. Figure 2 shows a schematic diagram of the CNT sheet manufacturing process.

[0068] The number of layers in the CNT sheet may be 5 or more, 10 or more, 20 or more, 30 or more, 50 or more, 70 or more, or 100 or more, and the greater the number of layers, the better the thermal conductivity. The number of layers in the CNT sheet may be 10,000 or less, 1,000 or less, or 100 or less. During drawing, CNTs are detached (a type of peeling) from the substrate, but the CNTs obtained by the synthesis process of the present disclosure have excellent detachability from the substrate, and therefore, according to the present disclosure, it is possible to suppress CNTs from remaining on the substrate.

[0069] (Structure of CNT ends in CNT fiber products) In a CNT fiber product, the CNT ends preferably have a structure in which the ratio (D1 / D2) of the average diameter D1 within 10 nm to 100 nm from each end to the average diameter D2 within 1000 nm to 2000 nm from each end is 0.75 or less.

[0070] In a CNT fiber product, CNT ends having a structure in which D1 / D2 is 0.75 or less may account for 12.5% ​​or more of the CNT ends, for example, 15% or more, 17.5% or more, 20% or more, 22.5% or more, or 25% or more. In a CNT fiber product, CNT ends having a structure in which D1 / D2 is 0.75 or less may account for 40% or less, 30% or less, or 15% or less of the CNT ends.

[0071] In the CNT fiber product, D1 / D2 may be 0.75 or less, 0.6 or less, 0.45 or less, or 0.30 or less. In the CNT fiber product, D1 / D2 may be 0.10 or more, 0.20 or more, 0.30 or more, 0.35 or more, or 0.40 or more.

[0072] It is preferable that the CNT ends in the CNT fiber product repeatedly form an uneven surface in the length direction of the CNT. The repeated uneven surface is also called a wavy surface, an undulating surface, or a zigzag surface. The repeated uneven surface occurs because the CNT fiber product forms a structure called a ball-like structure, a knot-like structure, a bellows structure, or a twisted structure.

[0073] The CNT ends forming the repeated uneven surface in a CNT fiber product may be 12.5% ​​or more of the CNT ends, for example, 15% or more, 17.5% or more, 20% or more, 22.5% or more, or 25% or more. The CNT ends forming the repeated uneven surface in a CNT fiber product may be 40% or less, 30% or less, or 15% or less of the CNT ends. Here, the CNT ends may refer to those 1000 nm or less, 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, 600 nm or less, 500 nm or less, 400 nm or less, or 300 nm or less from the end points of the CNTs.

[0074] The number of irregularities on the repeated irregular surface of the CNT ends in the CNT fiber product may be 5 / μm or more, 10 / μm or more, 20 / μm or more, 30 / μm or more, 40 / μm or more, 50 / μm or more, or 60 / μm or more in the length direction of the CNT. The number of irregularities on the repeated irregular surface of the CNT fiber product may be 100 / μm or less, 80 / μm or less, 60 / μm or less, 40 / μm or less, 30 or less, or 20 / μm or less in the length direction of the CNT.

[0075] It is preferable that a plurality of CNT ends in the CNT fiber product have a crimped (curled) shape. Crimping (curling) is also referred to as curling. The type of crimp is not particularly limited, and for example, it may be a zigzag type, a waveform / omega type, or a spiral type. By crimping, these CNTs may form an entangled structure together with adjacent CNT ends. Here, the CNT end may refer to a distance of 1000 nm or less, 900 nm or less, 800 nm or less, 700 nm or less, 600 nm or less, 500 nm or less, 400 nm or less, or 300 nm or less from the end point of the CNT.

[0076] The CNT ends having a crimped shape in the CNT fiber product may be 12.5% or more of the CNT ends, and for example, may be 15% or more, 17.5% or more, 20% or more, 22.5% or more, or 25% or more. The CNTs having a crimped shape in the CNT fiber product may be 40% or less, 30% or less, or 15% or less of the CNT ends.

[0077] In the CNT fiber product, the number of crimps (number of peaks per unit length) at the CNT end may be 1 peak / μm or more, 2 peaks / μm or more, 3 peaks / μm or more, 4 peaks / μm or more, 5 peaks / μm or more, or 6 peaks / μm or more. In the CNT fiber product, the number of crimps (number of peaks per unit length) may be 20 peaks / μm or less, 15 peaks / μm or less, 10 peaks / μm or less, 7 peaks / μm or less, or 5 peaks / μm or less.

[0078] <CNT resin composite> The CNT resin composite in the present disclosure is obtained by impregnating the above-described CNT product with a resin. The CNT resin composite may be obtained by impregnating a CNT orientation aggregate with a resin and then curing the resin. Conventionally, a heat dissipation material in which a metal or a carbon filler is compounded with a resin has been known, but its thermal conductivity has not been sufficient. Also, if a metal is used as a heat dissipation material, the thermal conductivity increases and heat dissipation becomes easy, but molding is difficult and it is difficult to use for applications where insulation is required. By using the CNT resin composite in the present disclosure, such problems can be solved.

[0079] Examples of manufacturing methods for CNT-resin composites in the present disclosure include impregnating a CNT product with a heated and melted resin and then cooling and hardening it, or impregnating a CNT with a liquid resin (e.g., a monomer or prepolymer) and then hardening it (heat hardening, photo-hardening, etc.). Figures 1 and 2 show schematic diagrams of a process for obtaining a CNT-resin composite by combining a CNT array with a resin and a process for obtaining a CNT-resin composite by combining a CNT sheet with a resin, respectively. The CNT product contained in the CNT-resin composite may be an aligned CNT aggregate. By including an aligned CNT aggregate, the CNT-resin composite can have anisotropic thermal conductivity, exhibiting greater thermal conductivity in the length direction (growth direction) of the CNTs than in the diameter direction (perpendicular to the growth direction). Furthermore, the thermal conductivity of the CNT-resin composite is significantly greater than that of the resin alone (1 W / mK or less). The unique thermal conductivity of this CNT-resin composite makes it suitable as a heat dissipation material. Furthermore, the use of resin improves moldability, making it easier to use in applications where insulation is required.

[0080] [Components of CNT-resin composite] (CNT component) The CNT-resin composite includes the above-mentioned CNT product (for example, an aligned CNT aggregate such as a CNT array or a CNT sheet).

[0081] (resin component) The CNT-resin composite contains a resin. The resin may be a thermosetting resin or a thermoplastic resin. Examples of thermosetting resins include epoxy resins, phenolic resins, melamine resins, urea resins, unsaturated polyester resins, alkyd resins, urethane resins, thermosetting polyimides, and thermosetting acrylic resins. Examples of thermoplastic resins include polyolefins, polyhalogenated olefins, polystyrene, polyvinyl acetate, polyurethane, Teflon (registered trademark), ABS resins, AS resins, acrylic resins, polyamides, polyacetals, polycarbonates, polyethers, polyesters, thermoplastic polyimides, polyamide resins, polyamide-imide resins, polyester resins, non-curable acrylic resins, and mixtures thereof.

[0082] The CNT content (amount occupied by CNT products) in the CNT-resin composite depends on the type of CNT products to be composited, but may be 5% by weight or more, 20% by weight or more, 40% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, or 85% by weight or more, and preferably 40% by weight or more, 60% by weight or more, or 80% by weight or more. The CNT content in the CNT-resin composite may be 99% by weight or less, 95% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, or 50% by weight or less. The higher the CNT content, the more excellent the thermal conductivity of the CNT-resin composite.

[0083] (Other ingredients) The CNT-resin composite may contain other components to the extent that the effects of the present invention are not impaired. Examples of other components include colorants such as organic dyes and organic pigments, organic fillers such as organic particles and organic fibers, antioxidants / antioxidants, UV absorbers, and light stabilizers.

[0084] [Structure of CNT-resin composite] The CNT-resin composite may be in the form of a sheet, a film, a rectangular parallelepiped, a cylinder, or the like.

[0085] The size of the CNT-resin composite depends on the type of CNT product to be compounded, but the amount of resin component can be adjusted to achieve a size similar to that of the compounded CNT product. Alternatively, it is possible to design the composite with a smaller amount of resin component so that the CNT product is exposed from the surface, or a larger amount so that the CNT product is not exposed from the surface. For example, the end points of a portion of the CNTs (e.g., 1% or more, 5% or more, 10% or more, or 25% or more, and 75% or less, 50% or less, 25% or less, 10% or less, or 5% or less) may be within ±1.0 mm, ±0.5 mm, ±0.3 mm, ±0.2 mm, ±0.1 mm, or ±0.05 mm of the outer surface of the resin.

[0086] When the CNT product to be composited is an aligned CNT aggregate, the orientation direction of the aligned CNT aggregate (the growth direction of the CNTs) may be along the plane direction of the CNT resin composite, or may be inclined from the plane direction of the CNT resin composite (for example, the inclination angle is 1° or more, 3° or more, 10° or more, 15° or more, or 30° or more, and 45° or less, 30° or less, or 15° or less).

[0087] [Physical properties of CNT-resin composites] The thermal conductivity of the CNT resin composite in the length direction of the CNTs may be 1 W / mK or more, 3 W / mK or more, 5 W / mK or more, 10 W / mK or more, or 15 W / mK or more. The thermal conductivity of the CNT resin composite in the length direction of the CNTs may be 100,000 W / mK or less, 10,000 W / mK or less, 1,000 W / mK or less, or 1,000 W / mK or less.

[0088] The thermal conductivity of the CNT resin composite in the diameter direction of the CNTs may be 0.3 W / mK or more, 1 W / mK or more, 2 W / mK or more, 3 W / mK or more, or 5 W / mK or more. The thermal conductivity of the CNT resin composite in the diameter direction may be 50,000 W / mK or less, 5,000 W / mK or less, or 500 W / mK or less.

[0089] The thermal conductivity of the CNTs in the length direction of the CNTs in the CNT-resin composite may be 1.2 times or more, 1.5 times or more, 2.0 times or more, 2.5 times or more, 3.0 times or more, 3.5 times or more, or 4.0 times or more, and preferably 2 times or more, of the thermal conductivity of the CNTs in the diameter direction of the CNTs in the CNT-resin composite. The thermal conductivity of the CNTs in the length direction of the CNTs in the CNT-resin composite may be 50 times or less, 25 times or less, or 10 times or less of the thermal conductivity of the CNTs in the diameter direction of the CNTs in the CNT-resin composite.

[0090] <Goods> The articles of the present disclosure include the above-described CNT products or CNT-resin composites. CNT products and CNT-resin composites can be applied to a variety of articles by taking advantage of their thermal conductivity, electrical conductivity, insulating properties, mechanical properties, and the like. There are a wide variety of articles that include CNT products and CNT-resin composites, including heat dissipation materials, heaters, stretchable sheet-like strain sensors, electrode sheets, battery components, electronic components, automobiles, aircraft, building materials, and electromagnetic wave absorbing sheets. [Example]

[0091] The present invention will be explained in more detail below by showing examples and comparative examples, but the present invention is not limited to these examples.

[0092] [CNT synthesis example 1] A thermal CVD system was used, which included a reaction chamber (volume 38 L) containing a substrate, a gas inlet, and a gas outlet. A 4-inch diameter Si substrate with a thermal oxide film was used as the substrate. Iron (II) chloride was heated above its sublimation temperature as a catalyst, and iron (II) chloride particles were deposited on the substrate. The resulting substrate was placed in the reaction chamber of the CVD system. CNTs were grown on the substrate for 10 to 30 minutes under the following conditions: temperature (approximately 800°C), acetylene gas flow rate (approximately 10 L / min), carbon monoxide flow rate (1 L / min or less), and reaction chamber gas pressure (approximately 5 Torr). After 10 to 30 minutes, the reaction chamber gas pressure was reduced by approximately 2 Torr from the pressure during growth and maintained at the growth temperature for approximately 40 seconds. The reaction chamber gas pressure was then reduced to approximately 0 Torr over approximately 20 seconds, and the temperature was lowered to below 300°C at a rate of 15 to 20°C / min, after which the system was opened to the atmosphere. This resulted in CNTs (multi-layered, approximately 0.5 to 1.5 mm long, approximately 40 to 60 nm in diameter, G / D ratio of approximately 2.5 to 3, purity of 99% or more) growing almost perpendicular to the substrate surface. The length and diameter were determined from SEM photographs. The G / D ratio was determined by Raman analysis. The purity was determined by thermogravimetric analysis.

[0093] [Comparative CNT synthesis example 1] After 10 to 30 minutes of CNT growth, the gas was discharged to reduce the gas pressure in the reaction chamber to approximately 0 Torr, and the temperature was lowered to 300°C or less at a rate of 15 to 20°C / min, and the chamber was opened to the atmosphere. Except for this, CNTs were synthesized in the same manner as in CNT Synthesis Example 1. As a result, CNTs grown almost perpendicular to the substrate surface were obtained.

[0094] [CNT array manufacturing example 1] CNTs grown from the substrate after synthesis in CNT Synthesis Example 1 were peeled off using a resin spatula with a sharp tip to obtain a CNT array. Figure 3A shows an SEM image of the CNT ends on the substrate side of the obtained CNT array. Figure 4A shows an SEM image of the substrate after CNT peeling. After peeling, relatively long CNTs were barely visible remaining on the substrate, and they were uniform. The SEM image shows that a tapered structure is formed at the CNT ends on the substrate side. The SEM image also shows that a surface with repeated irregularities is formed along the length of the CNTs at the CNT ends on the substrate side, that a crimped shape is formed, and that an entangled structure is formed.

[0095] [Comparative CNT array manufacturing example 1] The CNTs grown from the substrate after synthesis in Comparative CNT Synthesis Example 1 were peeled off in the same manner as in CNT Array Production Example 1 to obtain a CNT array. Figure 3B shows an SEM image of the CNT ends on the substrate side of the obtained comparative CNT array. Figure 4B also shows an SEM image of the substrate after the CNTs were peeled off. After peeling, relatively long CNTs remained on the substrate and were uneven. The SEM image shows that the CNT ends on the substrate side were straight and did not have a specific structure.

[0096] [CNT sheet manufacturing examples 1-3] After synthesis, the ends of the CNTs grown from the substrate were pinched and pulled out, and then wound up using a take-up roll to obtain CNT sheets with stacking numbers of 10, 40, and 80, respectively.

[0097] [CNT resin composite production examples 1-4] The CNT array and CNT sheets obtained in CNT Array Production Example 1 and CNT Sheet Production Examples 1 to 3 were impregnated with epoxy resin (ADEKA EP-4100) and then heat-cured to obtain CNT Resin Composite Production Examples 1 to 4. The physical properties of the resulting CNT resin composites were measured, and the results are shown in Figure 5. The physical properties were measured using the following equipment and conditions. Thermal diffusivity can be calculated from thermal conductivity and specific heat. Thermal conductivity measurement: Bethel Thermowave Analyzer TA (periodic heating radiation thermometer, room temperature) Specific heat measurement: Hitachi High-Tech DSC7020 (heat flow rate differential scanning calorimetry, room temperature)

[0098] Although the embodiments have been described above, it will be understood that various changes in form and details can be made without departing from the spirit and scope of the claims. [Industrial Applicability]

[0099] The method for producing a CNT product according to the present disclosure can be used to produce various articles containing CNTs (for example, heat dissipation materials).

Claims

1. A CNT product that is an aggregate of CNTs, wherein a plurality of CNT ends among the CNTs form a tapered structure in which the ratio (D1 / D2) of the average diameter D1 at 10 nm to 100 nm from the end point to the average diameter D2 at 1000 nm to 2000 nm from each end point is 0.75 or less.

2. 2. The CNT product according to claim 1, wherein the CNT product is a CNT array that is an aligned aggregate of CNTs, and a plurality of CNT ends on one surface form a tapered structure in which the ratio (D1 / D2) of the average diameter D1 at 10 nm to 100 nm from each end point to the average diameter D2 at 1000 nm to 2000 nm from each end point is 0.75 or less.

3. 3. The CNT product according to claim 1 or 2, wherein the CNT product is a CNT fiber product containing CNTs as fibers, and wherein a plurality of CNT ends form a tapered structure in which the ratio (D1 / D2) of the average diameter D1 at 10 nm to 100 nm from each end point to the average diameter D2 at 1000 nm to 2000 nm from each end point is 0.75 or less.

4. 4. The CNT product of claim 3, which is a CNT web, a CNT yarn, a CNT sheet, a CNT woven or knitted fabric, or a CNT nonwoven fabric.

5. 5. The CNT product according to claim 1, wherein a plurality of CNT ends among the CNTs form an uneven surface repeatedly in the length direction of the CNT.

6. The CNT product according to any one of claims 1 to 5, wherein a plurality of CNT ends have a crimped shape.

7. 7. The CNT product according to claim 1, wherein a plurality of CNT ends form an entangled structure with neighboring CNT ends.

8. A CNT-resin composite obtained by impregnating the CNT product according to any one of claims 1 to 7 with a resin.

9. An article comprising the CNT product according to any one of claims 1 to 7 or the CNT-resin composite according to claim 8.

10. The article according to claim 9, which is selected from the group consisting of a heat dissipating material, a heater, and an electromagnetic wave absorbing sheet.

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