Nanocarbon composite, bolometer using the same, and method for producing them

Abstract

To provide a nanocarbon composite capable of forming a low-resistance bolometer and a method for producing the same.SOLUTION: One aspect of the present disclosure relates to a nanocarbon composite including: a plurality of carbon nanotubes including semiconducting carbon nanotubes in an amount of 67 mass% or more with respect to a total amount of the plurality of carbon nanotubes; and fibrous carbon nanohorn aggregates adsorbed to the carbon nanotubes, in which the number of the fibrous carbon nanohorn aggregates is one-tenth or less of the number of the plurality of carbon nanotubes.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a nanocarbon composite, a bolometer using the same, and a method for producing the same. [Background technology]

[0002] Infrared sensors have a wide range of applications, including not only security surveillance cameras but also human body thermography, in-vehicle cameras, and inspection of structures, food, etc., and in recent years, their industrial applications have been active. In particular, there is a high expectation for the development of inexpensive, high-performance uncooled infrared sensors that can acquire biometric information in conjunction with IoT (Internet of Things). Conventional uncooled infrared sensors mainly use VO x Vanadium oxide is used, but the need for heat treatment under vacuum makes the process expensive, and the temperature coefficient of resistance (TCR) is small (approximately -2.0% / K).

[0003] To improve the TCR, a material with a large change in resistance with temperature and high conductivity is required, so it is expected that semiconducting single-walled carbon nanotubes, which have a large band gap and carrier mobility, will be used in the bolometer section. Furthermore, because carbon nanotubes are chemically stable, inexpensive device fabrication processes such as printing techniques can be applied, which may lead to the realization of low-cost, high-performance infrared sensors.

[0004] Single-walled carbon nanotubes usually contain semiconducting carbon nanotubes and metallic carbon nanotubes in a 2:1 ratio, which poses the issue of requiring separation for use in a bolometer. Patent Document 1 describes how a TCR of -2.6% / K was achieved by extracting semiconducting single-walled carbon nanotubes with uniform chirality from single-walled carbon nanotubes containing a mixture of metallic and semiconducting components using an ionic surfactant and applying them to the bolometer section. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-49207 Summary of the Invention [Problem to be solved by the invention]

[0006] However, for practical use of bolometers, it is necessary to not only improve TCR but also to reduce resistance, and further improvements are needed. To reduce the resistance of bolometers, the bonding between carbon nanotubes (CNTs) in a film formed from a carbon nanotube network is important. The inventors performed SEM observation of a carbon nanotube film (CNT film) fabricated by the drop-cast method using a CNT dispersion, revealing a network structure with many gaps, as shown in Figure 5A. Furthermore, cross-sectional TEM image analysis of the CNT film revealed that the CNT film was formed from a CNT network with many gaps, almost entirely in one layer (Figure 5B).

[0007] In view of the above problems, an object of one embodiment of the present invention is to provide a nanocarbon composite that constitutes a low-resistance bolometer and a method for producing the same. [Means for solving the problem]

[0008] One aspect of the present disclosure is a plurality of carbon nanotubes containing semiconducting carbon nanotubes in an amount of 67 mass % or more of the total amount of the carbon nanotubes; a fibrous carbon nanohorn aggregate adsorbed on the carbon nanotube; Including, The nanocarbon composite is characterized in that the number of the fibrous carbon nanohorn aggregates is 1 / 10 or less of the number of the carbon nanotubes.

[0009] One aspect of the present disclosure is A substrate; a first electrode on the substrate; a second electrode on the substrate and spaced apart from the first electrode; a nanocarbon composite film electrically connected to the first electrode and the second electrode; A bolometer comprising: The nanocarbon composite film is a plurality of carbon nanotubes containing semiconducting carbon nanotubes in an amount of 90 mass % or more of the total amount of the carbon nanotubes; a fibrous carbon nanohorn aggregate adsorbed on the carbon nanotube; Including, The present invention relates to a bolometer, wherein the number of the fibrous carbon nanohorn aggregates is 1 / 10 or less of the number of the carbon nanotubes. [Effects of the Invention]

[0010] According to one aspect of the present disclosure, it is possible to provide a nanocarbon composite capable of forming a low-resistance bolometer film, a bolometer using the same, and methods for manufacturing the same. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram (top view) illustrating a structure of a bolometer according to an embodiment of the present disclosure. [Figure 2] FIG. 1 is a diagram schematically illustrating the structure of a nanocarbon composite according to one embodiment of the present disclosure. [Figure 3] FIG. 1 is a schematic diagram showing aerosol droplets of a dispersion containing fibrous carbon nanohorn aggregates and spherical carbon nanohorn aggregates in an embodiment of the present disclosure. [Figure 4] 1 is an SEM image of a nanocarbon composite in which CNB is attached onto a CNT film produced in Example 1. [Figure 5A] This is an SEM image of carbon nanotubes in a carbon nanotube film fabricated by the drop-cast method. [Figure 5B]This is a cross-sectional TEM image of a carbon nanotube film fabricated by the drop-casting method. [Figure 6] FIG. 1 is a schematic diagram illustrating the structure of a bond between carbon nanotubes and spherical carbon nanohorn aggregates disclosed in Japanese Patent Application Laid-Open No. 2012-214342. DETAILED DESCRIPTION OF THE INVENTION

[0012] The nanocarbon composite of one embodiment of the present disclosure comprises: a plurality of carbon nanotubes containing semiconducting carbon nanotubes in an amount of 67 mass % or more of the total amount of the carbon nanotubes; a fibrous carbon nanohorn aggregate adsorbed on the carbon nanotube; Including, The number of the fibrous carbon nanohorn aggregates is 1 / 10 or less of the number of the carbon nanotubes.

[0013] The nanocarbon composite according to an embodiment of the present disclosure can be used as a resistance change material whose electrical resistance changes with temperature change, and is preferably used in a bolometer, more preferably in a bolometer for an infrared sensor. A substrate; a first electrode on the substrate; a second electrode on the substrate and spaced apart from the first electrode; a nanocarbon composite film electrically connected to the first electrode and the second electrode; A bolometer comprising: The nanocarbon composite film is A plurality of carbon nanotubes containing semiconducting carbon nanotubes in an amount of 67% by mass or more (preferably 90% by mass or more) of the total amount of the carbon nanotubes; a fibrous carbon nanohorn aggregate adsorbed on the carbon nanotube; Including, The number of the fibrous carbon nanohorn aggregates is 1 / 10 or less of the number of the carbon nanotubes.

[0014] The inventors have discovered that when a nanocarbon composite, in which fibrous carbon nanohorn aggregates are adsorbed as a conductive auxiliary material onto carbon nanotubes containing 67% by mass or more (preferably 90% by mass or more) semiconducting carbon nanotubes, is used in the resistance change film (film whose electrical resistance changes with temperature change) of a bolometer, it is possible to significantly reduce resistance while maintaining good TCR.

[0015] Although Japanese Patent No. 3453377 and Japanese Patent Laid-Open Publication No. 2012-214342 do not describe a bolometer, they do describe a composite (conjugate) of a carbon nanotube and a carbon nanohorn. For example, Figure 6 is a schematic diagram illustrating the structure of the carbon nanotube-nanohorn conjugate described in Japanese Patent Laid-Open Publication No. 2012-214342. The carbon nanotube-nanohorn conjugate 4 has a structure in which carbon nanohorn aggregates 2 are dispersed among carbon nanotubes 3. However, the conjugates described in these patent documents only include spherical carbon nanohorn aggregates (also referred to as "CNHs"). As shown in Figure 6, CNHs are zero-dimensional conductors, so the number of CNTs connected to one CNH is limited. Current flows between CNHs through hopping conduction. Therefore, the effect of providing conductivity at the junction between CNHs and CNTs is limited. Therefore, there is room for further improvement before they can be used as a bolometer.

[0016] In one embodiment of the present disclosure, the nanocarbon composite preferably forms a film, and more preferably forms an electrical resistance change film of a bolometer. In the nanocarbon composite of the present disclosure, fibrous carbon nanohorn aggregates (also referred to as "carbon nanobrushes" or "CNBs") can be present between the carbon nanotube network. The CNBs may be adsorbed on the surface of the CNT film, or may be adsorbed on the surface and inside of the CNT film.

[0017] The nanocarbon composite of this embodiment and a bolometer using the same will be described below.

[0018] <Nanocarbon composite> The nanocarbon composite of the present disclosure comprises a plurality of carbon nanotubes, including semiconducting carbon nanotubes, and fibrous carbon nanohorn aggregates (also referred to as "CNB") adsorbed on the carbon nanotubes, and preferably the number of fibrous carbon nanohorn aggregates is 1 / 10 or less of the number of carbon nanotubes.

[0019] In the present disclosure, "adsorption" is not limited to, and may be, for example, chemical adsorption or physical adsorption. Physical adsorption includes, for example, adsorption due to van der Waals forces. Chemical adsorption refers to, for example, adsorption caused by a force similar to the force that causes the formation of a compound, such as a covalent bond. In one embodiment, chemical adsorption may be preferable in terms of the strength of adsorption.

[0020] (carbon nanotubes) The nanocarbon composite of the present disclosure includes a plurality of carbon nanotubes, and the semiconducting carbon nanotubes account for 67 mass % or more of the total amount of the carbon nanotubes. In one embodiment, the carbon nanotubes preferably form a film. Although the following description will be given of the case where the carbon nanotubes form a carbon nanotube film, the present invention is not limited thereto.

[0021] The multiple carbon nanotubes constituting the nanocarbon composite film can be single-walled, double-walled, or multi-walled carbon nanotubes, but single-walled or several-walled (e.g., two-walled or three-walled) carbon nanotubes are preferred, and single-walled carbon nanotubes are more preferred. The carbon nanotubes preferably contain single-walled carbon nanotubes at 80 mass % or more, more preferably 90 mass % or more (including 100 mass %).

[0022] From the viewpoint of increasing the band gap and improving the TCR, the diameter of the carbon nanotube is preferably between 0.6 and 1.5 nm, more preferably between 0.6 and 1.2 nm, and even more preferably between 0.7 and 1.1 nm. In one embodiment, a diameter of 1 nm or less may be particularly preferable. If the diameter is 0.6 nm or more, the production of carbon nanotubes is easier. If the diameter is 1.5 nm or less, the band gap can be easily maintained within an appropriate range, and a high TCR can be obtained.

[0023] In this specification, the diameter of carbon nanotubes means that, when carbon nanotubes on a substrate are observed using an atomic force microscope (AFM) and the diameters are measured at approximately 50 locations, 60% or more, preferably 70% or more, in some cases more preferably 80% or more, and more preferably 100% of the diameters are within the range of 0.6 to 1.5 nm. Preferably, 60% or more, preferably 70% or more, in some cases more preferably 80% or more, and more preferably 100% of the diameters are within the range of 0.6 to 1.2 nm, and even more preferably 0.7 to 1.1 nm. In one embodiment, 60% or more, preferably 70% or more, in some cases more preferably 80% or more, and more preferably 100% of the diameters are within the range of 0.6 to 1 nm.

[0024] Furthermore, the length of the carbon nanotubes is preferably between 100 nm and 5 μm, as this facilitates dispersion and provides excellent coating properties. From the viewpoint of the conductivity of the carbon nanotubes, a length of 100 nm or more is also preferable. Furthermore, a length of 5 μm or less makes it easier to suppress aggregation on the substrate. The length of the carbon nanotubes is more preferably between 500 nm and 3 μm, and even more preferably between 700 nm and 1.5 μm. Furthermore, in one embodiment, the length of the carbon nanotubes is preferably 100 nm or more, more preferably 200 nm or more, and is preferably 1.5 μm or less, more preferably 1.0 μm or less, and even more preferably 500 nm or less.

[0025] In this specification, the length of carbon nanotubes means that the length distribution of carbon nanotubes is measured by observing and counting at least 50 tubes using an atomic force microscope (AFM), and that 60% or more, preferably 70% or more, in some cases more preferably 80% or more, and more preferably 100% of the tubes are in the range of 100 nm to 5 μm. Preferably, 60% or more, preferably 70% or more, in some cases more preferably 80% or more, and more preferably 100% of the tubes are in the range of 100 nm to 3 μm. More preferably, 60% or more, preferably 70% or more, in some cases more preferably 80% or more, and more preferably 100% of the tubes are in the range of 100 nm to 1.5 μm (more preferably 100 to 1 μm).

[0026] When the diameter and length of the carbon nanotube are within the above ranges, the influence of the semiconducting properties is increased and a large current value can be obtained, so that when used in a bolometer-type infrared sensor, a high TCR value is likely to be obtained.

[0027] In addition, when forming a carbon nanotube film, its thickness is not limited, but is preferably 1 nm or more, more preferably 2 nm or more, 3 nm or more, or 5 nm or more, and is preferably 10 μm or less, more preferably 1 μm or less, or 200 nm or less. In one embodiment, the thickness of the carbon nanotube film is preferably 2 nm to 1 μm, more preferably 5 nm to 200 nm.

[0028] In this embodiment, the content of semiconducting carbon nanotubes, preferably semiconducting single-walled carbon nanotubes, in the total amount of carbon nanotubes is generally more than 66% by mass, preferably 67% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more (which may be 100% by mass).

[0029] (Separation of semiconducting carbon nanotubes) Single-walled carbon nanotubes typically contain semiconducting carbon nanotubes and metallic carbon nanotubes in a ratio of about 2:1, and therefore require separation. The separation method is not limited. In one embodiment, the semiconducting carbon nanotubes constituting the nanocarbon composite film can be prepared by a method including a carbon nanotube cutting / dispersing step using a surfactant (preferably a nonionic surfactant) and a separation step.

[0030] The carbon nanotubes may be heat-treated in an inert atmosphere or in a vacuum to remove surface functional groups, impurities such as amorphous carbon, catalysts, etc. The heat treatment temperature can be appropriately selected, but is preferably 800 to 2000°C, more preferably 800 to 1200°C.

[0031] The nonionic surfactant can be selected appropriately, but it is preferable to use one or a combination of nonionic surfactants composed of a non-ionizable hydrophilic portion and a hydrophobic portion such as an alkyl chain, such as a nonionic surfactant having a polyethylene glycol structure, such as a polyoxyethylene alkyl ether, or an alkyl glucoside nonionic surfactant. As such a nonionic surfactant, a polyoxyethylene alkyl ether represented by formula (1) is preferably used. Furthermore, the alkyl portion may contain one or more unsaturated bonds.

[0032] C n H 2n+1 (OCH2CH2) m OH (1) (wherein n is preferably 12 to 18, and m is 10 to 100, preferably 20 to 100)

[0033] In particular, nonionic surfactants defined as polyoxyethylene (n) alkyl ethers (n is 20 to 100, alkyl chain length is C12 to C18), such as polyoxyethylene (23) lauryl ether, polyoxyethylene (20) cetyl ether, polyoxyethylene (20) stearyl ether, polyoxyethylene (10) oleyl ether, polyoxyethylene (10) cetyl ether, polyoxyethylene (10) stearyl ether, polyoxyethylene (20) oleyl ether, and polyoxyethylene (100) stearyl ether, are more preferred. N,N-bis[3-(D-gluconamido)propyl]deoxycholamide, n-dodecyl β-D-maltoside, octyl β-D-glucopyranoside, and digitonin can also be used.

[0034] As a nonionic surfactant, polyoxyethylene sorbitan monostearate (molecular formula: C 64 H 126 O 26 , trade name: Tween 60, manufactured by Sigma-Aldrich Co., Ltd.), polyoxyethylene sorbitan trioleate (molecular formula: C 24 H 44 O6, trade name: Tween 85, manufactured by Sigma-Aldrich Co., Ltd., etc.), octylphenol ethoxylate (molecular formula: C 14 H 22 O(C2H4O) n , n=1 to 10, product name: Triton X-100, manufactured by Sigma-Aldrich Co., Ltd., etc.), polyoxyethylene (40) isooctylphenyl ether (molecular formula: CH 17 C6H 40 (CH2CH 20 ) 40 H, product name: Triton X-405, manufactured by Sigma-Aldrich Co., Ltd., etc.), poloxamer (molecular formula: CH 10 O2, trade name: Pluronic, manufactured by Sigma-Aldrich, etc.), polyvinylpyrrolidone (molecular formula: (C6H9NO) n , n=5 to 100, manufactured by Sigma-Aldrich Co., etc.) can also be used.

[0035] In one embodiment, the molecular length of the nonionic surfactant is preferably 5 to 100 nm, more preferably 10 to 100 nm, and even more preferably 10 to 50 nm. If the molecular length is 5 nm or more, particularly 10 nm or more, after the dispersion liquid is applied to the electrodes of the bolometer (the region including the area between electrodes 1 and 2 described below), the distance between the carbon nanotubes can be appropriately maintained, and aggregation can be easily suppressed. Furthermore, if the molecular length is 100 nm or less, it is preferable from the viewpoint of building a network structure.

[0036] In one embodiment, a nonionic surfactant with a long molecular length is preferably used as the nonionic surfactant. Such a nonionic surfactant has a weak interaction with carbon nanotubes and is easily removed after the dispersion is applied to a substrate. This allows for the formation of a stable carbon nanotube conductive network and an excellent TCR value. Furthermore, because of the long molecular length of such a nonionic surfactant, the distance between carbon nanotubes increases when the dispersion is applied, making them less likely to re-aggregate during electrode fabrication. Therefore, when a carbon nanotube network is formed in an isolated, dispersed state while maintaining appropriate spacing and used in a bolometer, a large resistance change with temperature change can be achieved. For these reasons, the bolometer manufacturing method according to this embodiment may be suitable for a printing process.

[0037] The method for obtaining the dispersion solution is not particularly limited, and conventionally known methods can be used. For example, a carbon nanotube mixture (including semiconducting and metallic nanotubes), a dispersion medium, and a nonionic surfactant are mixed to prepare a solution containing carbon nanotubes, and the solution is then ultrasonicated to disperse the carbon nanotubes and prepare a carbon nanotube dispersion (micelle dispersion solution). The dispersion medium is not particularly limited as long as it is a solvent that can disperse and suspend carbon nanotubes during the separation process. For example, water, heavy water, organic solvents, ionic liquids, or mixtures thereof can be used, with water and heavy water being preferred. In addition to or instead of the ultrasonic treatment, a carbon nanotube dispersion technique using mechanical shear force may be used. Mechanical shearing may be performed in the gas phase. In a micellar dispersion of carbon nanotubes and a nonionic surfactant, the carbon nanotubes are preferably isolated. Therefore, if necessary, ultracentrifugation may be used to remove bundles, amorphous carbon, impurity catalysts, etc. The carbon nanotubes can be cut during the dispersion process, and their length can be controlled by changing the carbon nanotube crushing conditions, ultrasonic output, ultrasonic treatment time, etc. For example, untreated carbon nanotubes can be pulverized using tweezers, a ball mill, or the like to control the aggregate size. After these treatments, the length can be controlled to 100 nm to 5 μm by using an ultrasonic homogenizer at an output of 40 to 600 W, optionally 100 to 550 W, and 20 to 100 kHz for a treatment time of 1 to 5 hours, preferably up to 3 hours. If the treatment time is shorter than 1 hour, the nanotubes may not disperse well depending on the conditions, and may retain their original length. Furthermore, from the viewpoint of shortening the dispersion treatment time and reducing costs, 3 hours or less is preferable. This embodiment also has the advantage that the use of a nonionic surfactant makes it easy to adjust the cutting. Furthermore, the infrared sensor according to this embodiment, which is manufactured using carbon nanotubes prepared by a method using a nonionic surfactant, also has the advantage of not containing an ionic surfactant, which is difficult to remove.

[0038] In one embodiment, surface functional groups are generated on the surface or ends of carbon nanotubes by dispersing and cutting them. The functional groups generated include carboxyl groups, carbonyl groups, hydroxyl groups, etc. If the treatment is in a liquid phase, carboxyl groups and hydroxyl groups are generated, and if the treatment is in a gas phase, carbonyl groups are generated.

[0039] Furthermore, the surfactant concentration in the liquid containing heavy water or water and a nonionic surfactant is preferably the critical micelle concentration to 10% by mass, more preferably the critical micelle concentration to 3% by mass. A concentration below the critical micelle concentration may be undesirable because dispersion is not possible. Furthermore, a concentration of 10% by mass or less allows for the application of carbon nanotubes with a sufficient density after separation while reducing the amount of surfactant. In this specification, the critical micelle concentration (CMC) refers to the concentration at which the surface tension reaches an inflection point when the surface tension of an aqueous surfactant solution is measured at different concentrations using a surface tensiometer such as a Wilhelmy tensiometer at a constant temperature. In this specification, the "critical micelle concentration" refers to a value at atmospheric pressure and 25°C.

[0040] The concentration of carbon nanotubes in the cutting and dispersion process (weight of carbon nanotubes / (total weight of dispersion medium and surfactant) x 100) is not particularly limited, but can be, for example, 0.0003 to 10 mass%, preferably 0.001 to 3 mass%, and more preferably 0.003 to 0.3 mass%.

[0041] The dispersion obtained through the above-mentioned cutting and dispersion step may be used as is in the separation step described below, or may be subjected to a step such as concentration or dilution before the separation step.

[0042] Carbon nanotube separation can be achieved, for example, by the electric-field-induced layer formation method (ELF method: see, for example, K. Ihara et al. J. Phys. Chem. C. 2011, 115, 22827-22832 and Japanese Patent No. 5717233, which are incorporated herein by reference). An example of a separation method using the ELF method is described below. Carbon nanotubes, preferably single-walled carbon nanotubes, are dispersed in a dispersion medium using a nonionic surfactant. The resulting dispersion is placed in a vertical separation device, and a voltage is applied between electrodes arranged above and below the dispersion to separate the nanotubes by carrier-free electrophoresis. The separation mechanism can be estimated as follows: When carbon nanotubes are dispersed in a nonionic surfactant, micelles of semiconducting carbon nanotubes have a negative zeta potential, while micelles of metallic carbon nanotubes have a zeta potential of the opposite sign (positive) (although in recent years, they are believed to have a slightly negative zeta potential or to be nearly uncharged). Therefore, when an electric field is applied to the carbon nanotube dispersion, due to the effect of the difference in zeta potential, the semiconducting carbon nanotube micelles electrophoretically migrate toward the anode (+) and the metallic carbon nanotube micelles electrophoretically migrate toward the cathode (-). Ultimately, a layer of concentrated semiconducting carbon nanotubes is formed near the anode, and a layer of concentrated metallic carbon nanotubes is formed near the cathode in the separation tank. The separation voltage can be appropriately set taking into account the composition of the dispersion medium and the charge amount of the carbon nanotubes, but is preferably 1 V or more and 200 V or less, and more preferably 10 V or more and 200 V or less. From the viewpoint of shortening the separation process time, 100 V or more is preferred. Furthermore, from the viewpoint of suppressing the generation of bubbles during separation and maintaining separation efficiency, 200 V or less is preferred. Repeated separation improves purity. The dispersion after separation may be reset to its initial concentration and the same separation operation may be performed. This can further increase purity.

[0043] The above-described carbon nanotube dispersion / cutting and separation steps can yield a concentrated dispersion of semiconducting carbon nanotubes having the desired diameter and length. In this specification, a carbon nanotube dispersion in which semiconducting carbon nanotubes are concentrated may be referred to as a "semiconducting carbon nanotube dispersion." The semiconducting carbon nanotube dispersion obtained by the separation step refers to a dispersion containing semiconducting carbon nanotubes in an amount of preferably 67% by mass or more, more preferably 70% by mass or more, particularly preferably 80% by mass or more, more preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more (the upper limit may be 100% by mass) of the total amount of carbon nanotubes. The tendency for metallic and semiconducting carbon nanotubes to separate can be analyzed by microscopic Raman spectroscopy and ultraviolet-visible-near-infrared absorptiometry.

[0044] After the carbon nanotube dispersion and cutting step described above and before the separation step, the carbon nanotube dispersion may be centrifuged to remove bundles, amorphous carbon, metal impurities, and the like. The centrifugal acceleration can be adjusted as appropriate, but is preferably 10,000 x g to 500,000 x g, more preferably 50,000 x g to 300,000 x g, and in some cases may be 100,000 x g to 300,000 x g. The centrifugation time is preferably 0.5 hours to 12 hours, more preferably 1 to 3 hours. The centrifugation temperature can be adjusted as appropriate, but is preferably 4°C to room temperature, more preferably 10°C to room temperature.

[0045] In some embodiments, it may be preferable not to perform ultracentrifugation. In particular, in embodiments where the dispersion containing carbon nanotubes contains a nonionic surfactant, particularly a nonionic surfactant with a long molecular length, bundle formation can be easily suppressed, which has the advantage of reducing process steps and cost without performing ultracentrifugation.

[0046] (fibrous carbon nanohorn aggregates) The nanocarbon composite of the present disclosure contains fibrous carbon nanohorn aggregates as a conductive auxiliary material, thereby enabling the reduction of bolometer resistance. Fibrous carbon nanohorn aggregates, also known as carbon nanobrushes (CNBs), have a structure in which single-walled carbon nanohorns are radially aggregated and connected in a fibrous form. Unlike single-walled carbon nanohorn aggregates that simply appear fibrous, fibrous carbon nanohorn aggregates can maintain their fibrous shape even after centrifugal separation, ultrasonic dispersion, and other procedures. Single-walled carbon nanohorns are conical carbon structures with a diameter of 1 nm to 5 nm and a length of 30 nm to 100 nm, each of which is formed by wrapping a graphene sheet around a sharpened horn-like tip with a tip angle of approximately 20°. Here, the carbon structure refers to a structure primarily containing carbon and may also contain light elements and catalytic metals. Fibrous carbon nanohorn aggregates are fibrous carbon structures, typically with a diameter of 30 nm to 200 nm and a length of 1 μm to 100 μm, e.g., 2 μm to 30 μm. The aspect ratio (length / diameter) of the fibrous carbon nanohorn aggregate is generally 4 to 4000, for example, 5 to 3500. The surface of the fibrous carbon nanohorn aggregate has single-walled carbon nanohorn protrusions with a diameter of 1 nm to 5 nm and a length of 30 nm to 100 nm. The fibrous carbon nanohorn aggregate has high conductivity because it is characterized by a structure in which highly conductive single-walled carbon nanohorns are connected in a fibrous form and have long conductive paths. Furthermore, the fibrous carbon nanohorn aggregate also has high dispersibility, making it highly effective at imparting conductivity.

[0047] Fibrous carbon nanohorn aggregates are formed by connecting seed-type, bud-type, dahlia-type, petal-dahlia-type, and petal-type (graphene sheet structure) carbon nanohorn aggregates. In other words, one or more types of carbon nanohorn aggregates are contained within the fibrous structure. The seed-type aggregate has few or no angular protrusions on its surface, the bud-type aggregate has a few angular protrusions on its surface, the dahlia-type aggregate has many angular protrusions on its surface, and the petal-type aggregate has petal-like protrusions on its surface. The petal structure has a width of 50 nm to 200 nm, a thickness of 0.34 nm to 10 nm, and a structure of 2 to 30 graphene sheets. The petal-dahlia type is an intermediate structure between the dahlia type and the petal type. The morphology and particle size of the resulting carbon nanohorn aggregates vary depending on the type and flow rate of the gas.

[0048] Fibrous carbon nanohorn aggregates are also described in detail in WO 2016 / 147909. Transmission electron microscope photographs of fibrous carbon nanohorn aggregates are disclosed in Figures 1 and 2 of WO 2016 / 147909. In the fibrous carbon nanohorn aggregates shown in these transmission electron microscope photographs, radially assembled single-walled carbon nanohorns (carbon nanohorn aggregates) are connected in a fibrous form. The entire disclosure of WO 2016 / 147909 is incorporated herein by reference.

[0049] In one embodiment, the nanocarbon composite may contain spherical carbon nanohorn aggregates in addition to fibrous carbon nanohorn aggregates. As described below, spherical carbon nanohorn aggregates are usually produced simultaneously when fibrous carbon nanohorn aggregates are produced. In this specification, a mixture containing fibrous carbon nanohorn aggregates and spherical carbon nanohorn aggregates is also referred to as a "carbon nanohorn aggregate mixture." In one embodiment, the fibrous carbon nanohorn aggregates are produced by laser ablation of an iron-containing carbon target, and at the same time, 80 mass % or more of spherical carbon nanohorn aggregates (also referred to as "CNHs") and approximately 10 to 15 mass % of graphite and carbon fragments are also produced together. The content of fibrous carbon nanohorn aggregates in the product is approximately a few percent. In one embodiment, the carbon nanohorn aggregate mixture is a carbon mixture produced when fibrous carbon nanohorn aggregates are produced by, for example, the laser ablation method described below. Preferably, the carbon nanohorn aggregate mixture is a mixture containing, as main components, fibrous carbon nanohorn aggregates and spherical carbon nanohorn aggregates obtained by removing graphite and the like from such a carbon mixture.

[0050] The fibrous carbon nanohorn aggregates may have defects formed therein, may be modified with functional groups, or may have compounds bonded thereto.

[0051] The horn portions of fibrous and spherical carbon nanohorn aggregates contain many five- and seven-membered rings, making them highly reactive. When defects are created in these horn portions, or when functional groups or compounds with high bonding and adhesive properties to the substrate or carbon nanotubes are attached, the reactivity is further enhanced, improving the adhesiveness (bonding) to the substrate or carbon nanotubes. Compared to spherical carbon nanohorn aggregates, fibrous carbon nanohorn aggregates have a higher proportion and number of horn portions in contact with the substrate, so the introduction of defects, functional groups, compounds, etc. is more effective in improving adhesiveness. Details will be provided later in the explanations of the defect creation and functionalization processes, and cyclodextrin treatment.

[0052] (Preparation of fibrous carbon nanohorn aggregates) Fibrous carbon nanohorn aggregates can be produced by a method such as laser ablation. In the laser ablation method, catalyst-containing carbon is used as a target (referred to as a catalyst-containing carbon target), and the target is heated and evaporated by laser ablation in a nitrogen atmosphere, an inert atmosphere, hydrogen, carbon dioxide, or a mixed atmosphere while rotating in a container in which the catalyst-containing carbon target is placed. As the evaporated carbon and catalyst cool, fibrous carbon nanohorn aggregates are obtained. In addition to the laser ablation method, carbon mixtures produced by arc discharge or resistance heating can also be used as the carbon nanohorn aggregate mixture in the present invention. However, the laser ablation method is more preferable from the viewpoint of continuous production at room temperature and atmospheric pressure.

[0053] One aspect of the laser ablation method applied in the present invention is a method in which a target is irradiated with laser light in pulses or continuously, and when the irradiation intensity reaches or exceeds a threshold value, the target converts energy, resulting in the generation of a plume, and the product is deposited on a substrate located downstream of the target, or is generated in the space within the device and collected in a collection chamber.

[0054] For laser ablation, CO2 lasers, YAG lasers, excimer lasers, semiconductor lasers, etc. can be used, but CO2 lasers are the most suitable as they can be easily made high-power. CO2 lasers have a power output of 1kW / cm 2 ~1000kW / cm 2An output of 1000 kW can be used, and it can be performed by continuous irradiation or pulse irradiation. Continuous irradiation is preferable for generating fibrous carbon nanohorn aggregates. The laser light is focused using a ZnSe lens or the like and then irradiated. Continuous synthesis is also possible by rotating the target. The target rotation speed can be set as desired, but 0.1 rpm to 6 rpm is particularly preferable. If it is 0.1 rpm or higher, graphitization can be suppressed, and if it is 6 rpm or lower, the increase in amorphous carbon can be suppressed. In this case, the laser output is 15 kW / cm 2 More than 30kW / cm is preferable. 2 ~300kW / cm 2 The most effective laser power is 15 kW / cm 2 If the laser output is 300 kW / cm or more, the target vaporizes appropriately, making it easy to generate fibrous carbon nanohorn aggregates. 2 If the pressure is below this, the increase in amorphous carbon can be suppressed. The pressure inside the vessel (chamber) can be used at 13,332.2 hPa (10,000 Torr) or less, but the closer the pressure is to a vacuum, the easier it is for carbon nanotubes to be produced, and fibrous carbon nanohorn aggregates cannot be obtained. The pressure inside the vessel (chamber) is preferably 666.61 hPa (500 Torr) to 1,266.56 hPa (950 Torr), and more preferably near atmospheric pressure (1013 hPa (1 atm ≒ 760 Torr)), which is suitable for mass synthesis and low cost. The irradiation area can also be controlled by the laser output and the degree of focusing with the lens, and can be adjusted to 0.005 cm. 2 ~1cm 2 can be used.

[0055] The catalyst can be Fe, Ni, or Co, either singly or in combination. The catalyst concentration can be selected as appropriate, but is preferably 0.1% by mass to 10% by mass, and more preferably 0.5% by mass to 5% by mass, relative to carbon. A concentration of 0.1% by mass or more ensures the generation of fibrous carbon nanohorn aggregates. Furthermore, a concentration of 10% by mass or less can suppress increases in target costs.

[0056] The temperature inside the vessel can be set at any desired temperature, preferably 0°C to 100°C, and more preferably room temperature, which is suitable for mass synthesis and cost reduction.

[0057] The above atmosphere is created by introducing nitrogen gas, inert gas, hydrogen gas, CO2 gas, etc., either alone or in combination, into the reactor. From the standpoint of cost, nitrogen gas and Ar gas are preferred. These gases are circulated within the reactor, and the generated substances can be recovered from this gas flow. Any atmospheric gas flow rate can be used, but a range of 0.5 L / min to 100 L / min is preferable. The gas flow rate is controlled to a constant value during the target evaporation process.

[0058] Through the above reaction, the carbon nanohorn aggregate mixture is usually obtained as a carbon mixture of fibrous carbon nanohorn aggregates, spherical carbon nanohorn aggregates of approximately uniform size with a diameter of about 30 nm to 200 nm, graphite particles of 1 μm to several tens of μm, and carbon pieces.

[0059] ·Catalyst removal The catalytic metal contained during the production of the carbon nanohorn aggregate mixture can be removed as needed. The catalytic metal can be removed because it dissolves in nitric acid, sulfuric acid, or hydrochloric acid. From the viewpoint of ease of use, hydrochloric acid is suitable. The temperature for dissolving the catalyst can be selected as appropriate, but to thoroughly remove the catalyst, it is desirable to heat the mixture to 70°C or higher. The timing of catalyst removal is not particularly limited. For example, when using nitric acid or sulfuric acid, catalyst removal and the creation of defects (formation of openings), which will be described later, can be performed simultaneously or successively. In addition, since the catalyst may be covered with a carbon film during the production of the carbon nanohorn aggregate mixture, it is desirable to perform pretreatment to remove the carbon film. Pretreatment is desirable, with heating in air at approximately 250°C to 450°C. At temperatures above 300°C, some openings may be formed.

[0060] Graphite removal Graphite can be removed from the carbon mixture obtained by the above-mentioned laser ablation method, etc., if necessary. Specifically, the carbon mixture is dispersed in an organic solvent, and the graphite is separated by settling. When the carbon mixture is dispersed in an organic solvent, the graphite settles. On the other hand, the fibrous carbon nanohorn aggregates and spherical carbon nanohorn aggregates float due to their low density. By recovering the supernatant of the dispersion together with the floating solids, the graphite and the carbon nanohorn aggregates (fibrous carbon nanohorn aggregates and spherical carbon nanohorn aggregates) can be separated. For further processing in other steps, the solvent is preferably removed from the recovered supernatant. The method for removing the solvent is not particularly limited, and the solvent may be removed, for example, by heat.

[0061] The organic solvent preferably has a density lower than that of graphite. The density of the organic solvent is preferably less than 1 g / cm 3 less than 0.8 g / cm 3 The average density of the dispersion is less than 100%. Examples of such organic solvents include ethanol and 2-propanol. It is difficult to separate graphite from solvents with relatively high density, such as aqueous solvents. The dispersion can be prepared, for example, by ultrasonic dispersion. The obtained dispersion is allowed to stand or is centrifuged to allow only the graphite to settle, and the solid content floating in the dispersion is recovered, yielding a carbon nanohorn aggregate mixture from which the graphite has been removed.

[0062] As described above, the fibrous carbon nanohorn aggregates may have defects formed therein, may be modified with functional groups, or may have compounds bonded thereto.

[0063] A method for preparing a fibrous carbon nanohorn aggregate having defects, desired functional groups, or desired compounds that can be used in this embodiment is described below. In one embodiment, the introduction reaction of these defects, functional groups, or compounds can be carried out on a mixture of fibrous carbon nanohorn aggregates and spherical carbon nanohorn aggregates.

[0064] Defect creation and functionalization processes Since the horn portion of the fibrous carbon nanohorn aggregate contains many five-membered and seven-membered rings, slight defects can be created on the horn surface by oxidation treatment without deteriorating the conductive properties. There are no particular restrictions on the method of such oxidation treatment, and either a gas-phase process or a liquid-phase process can be used.

[0065] In the case of a gas phase process, the process is carried out in a gas atmosphere such as oxygen, air, hydrogen peroxide, carbon dioxide, or carbon monoxide. The oxidation treatment temperature in the gas atmosphere is preferably 250 to 650°C, more preferably 300 to 500°C, and even more preferably 300 to 400°C. If the temperature is too low, oxidation is difficult to occur, while if the temperature is too high, oxidation occurs too quickly and becomes difficult to control. The treatment time can be adjusted as appropriate, but is preferably within the range of about 5 to 7 hours at a temperature rise rate of 1°C / min.

[0066] In the liquid-phase process, oxidation treatment is performed in a liquid containing an oxidizing substance such as nitric acid, sulfuric acid, a sulfuric acid-nitric acid mixed solution, hydrogen peroxide, or chloric acid. Oxidation treatment using these acids is performed at approximately 0°C to 180°C (any temperature at which the aqueous solution exists as a liquid) for aqueous solutions, or at a temperature at which the solvent used exists as a liquid for organic solvents. Nitric acid and sulfuric acid are preferably used at temperatures ranging from room temperature to 120°C. Hydrogen peroxide can be used at temperatures ranging from room temperature to 100°C, with 40°C or higher being more preferred. The oxidizing power works efficiently in the temperature range of 40 to 100°C. 50 to 80°C is particularly preferred. The treatment time can be adjusted as needed, but is preferably within a range of, for example, 0.5 to 3 hours. Furthermore, the liquid-phase process is more effective when light irradiation is used in combination.

[0067] Through the above oxidation treatment, functional groups such as carbonyl groups, carboxyl groups, hydroxyl groups, nitro groups, sulfone groups, phenol groups, oxygen-containing functional groups including ether bonds or ester bonds, or imino groups can be added to the five-membered rings, seven-membered rings, and other highly reactive carbon sites at the curved graphite surfaces, such as the tips of carbon nanohorns.

[0068] In one embodiment, it is preferable to perform the oxidation treatment weakly and not excessively. This is because oxidation begins with the highly reactive five-membered and seven-membered rings present in abundance at the tips, but excessive oxidation may cause the oxidation to progress further, resulting in the disappearance of the nanohorn tips and the inability to form caps with cyclodextrin, as described below. Furthermore, the nanohorn body may also be oxidized, generating holes and changing the bulk properties of the carbon nanohorn aggregate.

[0069] The degree of oxidation in this case is preferably 1.0 × 10 oxygen to the total carbon (100 atomic %). -5 Atomic%~1.0×10 0 atomic %, more preferably 1.0 × 10 -3 Atomic%~1.0×10 0 It is preferable to include oxygen at a ratio of atomic percent. The ratio of oxygen to carbon can be estimated by various analytical methods, for example, from the intensity ratio of O1s and C1s in X-ray photoelectron spectroscopy.

[0070] Cyclodextrin treatment The adhesiveness of the fibrous carbon nanohorn aggregates to the substrate can also be further improved by bonding the fibrous carbon nanohorn aggregates with a compound that enhances the adhesiveness to the substrate, such as cyclodextrin.

[0071] By treating the carbon nanohorn assembly mixture that has undergone the above-mentioned oxidation treatment with a cyclodextrin-containing solution, it is possible to produce a hydrophilic carbon nanohorn assembly mixture in which the nanohorn tips are capped with cyclodextrin. Because oxygen-containing functional groups have been introduced into the tips of the carbon nanohorn aggregates, they interact with the OH groups of the cyclodextrin, specifically by hydrogen bonding, thereby immobilizing and stabilizing the cyclodextrin.

[0072] Cyclodextrin (hereinafter sometimes abbreviated as "CD") is a cyclic oligosaccharide, a non-reducing sugar in which glucose residues are bonded in a ring via α-1,4 bonds, and has a torus structure, also known as a bottomless bucket or crown. The interior of cyclodextrin is hydrophobic, but the numerous OH groups on the exterior make it water-soluble.

[0073] Examples of cyclodextrins include well-known cyclodextrins, such as unsubstituted cyclodextrins containing 6 to 12 glucose units, particularly α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, and / or their derivatives and / or mixtures thereof, depending on the number of glucose units constituting the cyclodextrin. α-cyclodextrin is composed of 6 glucose units, β-cyclodextrin is composed of 7 glucose units, and γ-cyclodextrin is composed of 8 glucose units, each with a different cavity size. In this embodiment, it is preferable to contain at least one cyclodextrin selected from the group consisting of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

[0074] The cyclodextrin treatment involves contacting the oxidized carbon nanohorn aggregate mixture with cyclodextrin in a solution that the cyclodextrin has been dissolved in. The dispersion medium used is water, or a dispersion medium containing, in addition to water, a surfactant, a water-soluble organic solvent, etc. as necessary.

[0075] The amount of cyclodextrin added can be selected appropriately, and is, for example, 0.1 to 50 parts by mass, and preferably 0.5 to 10 parts by mass, relative to 100 parts by mass of the carbon nanohorn aggregate mixture that has been subjected to the oxidation treatment. The treatment conditions are not particularly limited, but may be appropriately selected, for example, in the range of 0 to 100°C, preferably in the range of 10 to 70°C. In one embodiment, the temperature is preferably in the range of 15 to 60°C, which is close to room temperature. The treatment time may also be appropriately set, for example, 10 minutes or more, preferably 3 hours or more, and there is no particular upper limit, but the treatment may be carried out for, for example, 10 days or less.

[0076] As described above, the oxygen-containing functional groups at the tips of the carbon nanohorn aggregates and the hydroxyl groups of the cyclodextrin interact with each other, specifically, are fixed by hydrogen bonding, resulting in a stabilized hydrophilic carbon nanohorn aggregate mixture. The hydrophilicity obtained improves dispersibility in aqueous media.

[0077] The carbon nanohorn aggregate mixture obtained as described above, in which defects are created in the horn portion, modified with functional groups that increase adhesion to the substrate, and / or bound with compounds that increase adhesion to the substrate, is highly hydrophilic. Therefore, when preparing the carbon nanohorn aggregate mixture dispersion liquid described above, it has the advantage of being easily dispersed in an aqueous dispersion medium without the addition of a surfactant, and is easily monodispersed.

[0078] In one embodiment, the number of fibrous carbon nanohorn aggregates constituting the nanocarbon composite is preferably 1 / 10 or less, more preferably 1 / 20 or less, and is not limited to, the number of carbon nanotubes. 5 More than that, preferably 1 / 10 4 The number of fibrous carbon nanohorn aggregates and carbon nanotubes can be measured by observing a scanning electron microscope (SEM) image of the nanocarbon composite. The field of view is not limited, but is preferably approximately 1 μm to 10 μm in both length and width. In one embodiment, the mass ratio of the fibrous carbon nanohorn aggregates constituting the nanocarbon composite relative to the mass of the carbon nanotubes is, for example, preferably 1 mass% or more, more preferably 10 mass% or more, and preferably 10,000 mass% or less, more preferably 1,000 mass% or less. If the content of fibrous carbon nanohorn aggregates in the nanocarbon composite is too high, the probability of forming a conductive path consisting only of fibrous carbon nanohorn aggregates between electrodes increases, which may result in a decrease in the absolute value of TCR. If the content of fibrous carbon nanohorn aggregates in the nanocarbon composite is too low, the resistance of the nanocarbon composite may be insufficiently reduced.

[0079] <Method of manufacturing nanocarbon composite> A method for producing a nanocarbon composite will now be described. In one embodiment, a nanocarbon composite can be produced by separately preparing a first dispersion containing semiconducting carbon nanotubes and a second dispersion containing fibrous carbon nanohorn aggregates and using these (Method A). Alternatively, in one embodiment, a nanocarbon composite can be produced by using a nanocarbon mixed dispersion in which semiconducting carbon nanotubes and fibrous carbon nanohorn aggregates are dispersed in the same dispersion medium (Method B). In this specification, the "dispersion medium" may also be referred to as a "solvent."

[0080] (Method A) In one embodiment, a method for producing a nanocarbon composite includes: A step (a) of preparing a first dispersion liquid containing carbon nanotubes containing semiconducting carbon nanotubes in an amount of 67 mass % or more of the total amount of carbon nanotubes and a first dispersion medium; A step (b) of preparing a second dispersion liquid containing fibrous carbon nanohorn aggregates and a second dispersion medium; (c) applying the first dispersion and the second dispersion onto a substrate; The concentration (pieces / mL) of the fibrous carbon nanohorn aggregates in the second dispersion is preferably 1 / 10 or less of the concentration (pieces / mL) of the carbon nanotubes in the first dispersion.

[0081] In this specification, "applying" refers to "adhering" or "bringing in contact" with a target object, and includes, for example, "adhering" or "bringing in contact" by methods such as dripping, spraying, aerosol spraying, spin coating, printing by roll or inkjet or the like, dipping, brushing, etc. Furthermore, "applying a dispersion onto a substrate" may mean bringing the dispersion into direct contact with the substrate, or bringing the dispersion into contact with a coating that has previously been applied to the substrate.

[0082] (Step (a): Preparation of carbon nanotube dispersion) In one embodiment, the method for producing a nanocarbon composite includes step (a) of preparing a carbon nanotube dispersion (also referred to as "first dispersion" or "semiconducting carbon nanotube dispersion") containing a plurality of carbon nanotubes, the total amount of which is 67 mass % or more of which is semiconducting carbon nanotubes, and a first dispersion medium. In one embodiment, the first dispersion preferably further contains a surfactant, and the first dispersion medium preferably contains an aqueous solvent (preferably water or heavy water). The carbon nanotubes, surfactant (preferably a nonionic surfactant), and first dispersion medium in the first dispersion are the same as those described above in the separation of semiconducting carbon nanotubes. The first dispersion medium may be water, heavy water, an organic solvent, an ionic liquid, or a mixture thereof, but is preferably water or heavy water. In a preferred embodiment, the first dispersion may be a carbon nanotube dispersion (semiconducting carbon nanotube dispersion) in which single-walled carbon nanotubes are dispersed in a nonionic surfactant and semiconducting carbon nanotubes obtained by the ELF method or the like are concentrated, as described above, or may be a dispersion that has been further concentrated, diluted, or the like.

[0083] The zeta potential of the first dispersion is not limited, but is preferably +5 mV to -40 mV, more preferably +3 mV to -30 mV, and even more preferably +0 mV to -20 mV. A zeta potential of +5 mV or less is preferable because it indicates a low content of metallic carbon nanotubes. A zeta potential of more than -40 mV makes separation difficult in the first place. Here, the zeta potential of the semiconducting carbon nanotube dispersion refers to the zeta potential of the semiconducting carbon nanotube dispersion containing a nonionic surfactant and semiconducting carbon nanotube micelles obtained by, for example, the separation step using the ELF method. In this specification, the zeta potential of the carbon nanotube dispersion is a value measured using an ELSZ apparatus (Otsuka Electronics Co., Ltd.) for the dispersion.

[0084] In one embodiment, the concentration of carbon nanotubes in the first dispersion is not limited, but is preferably 0.1 μg / ml or more, more preferably 1 μg / ml or more, and is preferably 0.3 mg / ml or less, more preferably 0.1 mg / ml or less. The number of carbon nanotubes in the first dispersion is not limited, but is preferably 10 11 Preferably more than 10 12 More than 1000 cells / ml is preferable. 15 Preferably less than 10 14 The concentration of carbon nanotubes in the dispersion can be calculated, for example, by UV measurement and comparison with a dispersion of known concentration, and the number of tubes can be calculated from the length and diameter distribution of the CNTs applied to the substrate, measured by AFM or the like, and the dispersion concentration.

[0085] When the first dispersion contains a surfactant, the concentration of the surfactant in the first dispersion is not limited, but is preferably, for example, the critical micelle concentration to about 5% by mass, more preferably 0.001% by mass to 3% by mass, and even more preferably 0.01% by mass to 1% by mass in order to suppress re-aggregation after application.

[0086] (Step (b): Preparation of dispersion containing fibrous carbon nanohorn aggregates) In one embodiment, a dispersion containing fibrous carbon nanohorn aggregates (also referred to as "second dispersion") used in the production of a nano-carbon material composite contains fibrous carbon nanohorn aggregates and a second dispersion medium. The above description of the fibrous carbon nanohorn aggregates applies to the fibrous carbon nanohorn aggregates in the second dispersion.

[0087] The second dispersion may contain spherical carbon nanohorn aggregates, graphite, carbon pieces, etc., which are produced when the fibrous carbon nanohorn aggregates are produced. In one embodiment, the second dispersion is preferably a dispersion of carbon nanohorn aggregates containing fibrous carbon nanohorn aggregates and spherical carbon nanotubes, and is more preferably a mixture containing fibrous carbon nanohorn aggregates and spherical carbon nanohorn aggregates as main components, obtained by removing graphite, etc. from a carbon mixture (the total of CNB and CNHs in the carbon mixture is preferably 90 mass% or more, more preferably 95 mass% or more, even more preferably 99 mass% or more, and may be 100 mass%).

[0088] The second dispersion medium may be an organic solvent, an aqueous solvent, or a mixed solvent of an organic solvent and an aqueous solvent, and in one embodiment, is preferably an organic solvent.

[0089] Examples of the organic solvent include ethanol and 2-propanol. When an aqueous solvent is used, it is preferable that the second dispersion further contains a surfactant. Examples of the aqueous solvent and the surfactant include those described above in the description of the carbon nanotubes.

[0090] When fibrous carbon nanohorn aggregates are dispersed in a surfactant solution, the surfactant adheres to the periphery of the monodispersed fibrous carbon nanohorn aggregates, forming micelles. When spherical carbon nanohorn aggregates are included, the surfactant also adheres to the periphery of the spherical carbon nanohorn aggregates, forming micelles. The fibrous carbon nanohorn aggregates and spherical carbon nanohorn aggregates are dispersed in the surfactant solution, with almost no precipitation.

[0091] The surfactant may be any surfactant that spreads in the form of a film on the carbon nanohorn aggregates to prevent aggregation of the carbon nanohorn aggregates. Examples of surfactants include nonionic surfactants such as polyoxyethylene stearyl ether (Brij), and ionic surfactants such as sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfate (SDBS), sodium cholate (SC), and sodium deoxycholate (DOC). In one embodiment, the surfactant is preferably a nonionic surfactant, and for example, the nonionic surfactants that can be used to disperse the carbon nanotubes described above can be used.

[0092] The surfactant concentration can be appropriately set depending on the compound used, but is generally equal to or greater than the critical micelle concentration, preferably greater than the critical micelle concentration, and is preferably 0.001% by mass or greater, more preferably 0.01% by mass or greater, and is preferably 10% by mass or less, more preferably 5% by mass or less. In this specification, the critical micelle concentration (CMC) refers to the concentration at which the surface tension is measured at a constant temperature by varying the concentration of an aqueous surfactant solution using a surface tensiometer such as a Wilhelmy surface tensiometer. In this specification, the "critical micelle concentration" refers to the value at atmospheric pressure and 25°C.

[0093] The content of the fibrous carbon nanohorn aggregates in the second dispersion is not limited, but is preferably 0.1 μg / ml or more, more preferably 1 μg / ml or more, and is preferably 10 mg / ml or less, more preferably 1 mg / ml or less. The number of fibrous carbon nanohorn aggregates in the second dispersion is not limited, but is preferably 10 8 Preferably more than 10 9 More than 1000 cells / ml is preferable. 12 Preferably less than 10 11The concentration (number) of CNB in ​​the dispersion can be calculated from the concentration of the carbon nanohorn aggregate mixture in the dispersion and the ratio of spherical to fibrous carbon nanohorn aggregates estimated from an SEM image. In one embodiment, the total content of the spherical carbon nanohorn aggregates and fibrous carbon nanohorn aggregates in the second dispersion (content of the carbon nanohorn aggregate mixture) is not limited, but is preferably 1 μg / ml or more, more preferably 10 μg / ml or more, and is preferably 10 mg / ml or less, more preferably 1 mg / ml or less.

[0094] The second dispersion can be prepared by adding and dispersing fibrous carbon nanohorn aggregates (which may be a mixture of carbon nanohorn aggregates) in a dispersion medium. In one embodiment, ultrasonic treatment is preferably performed to improve the dispersibility of the carbon nanohorn aggregates.

[0095] (Step (c): Applying the first dispersion and the second dispersion onto a substrate) In step (c), the first dispersion liquid (semiconducting carbon nanotube dispersion liquid) prepared in step (a) above and the second dispersion liquid (fibrous carbon nanohorn aggregate dispersion liquid) prepared in step (b) above are applied onto a substrate.

[0096] The order in which the first dispersion and the second dispersion are applied is not limited; the first dispersion may be applied first and then the second dispersion, or the second dispersion may be applied first and then the first dispersion, or the first dispersion and the second dispersion may be applied simultaneously. Furthermore, a drying step (described below) may be included each time a dispersion is applied. For example, the first dispersion may be first applied to the substrate and dried, and then the first dispersion and / or the second dispersion may be applied.

[0097] In one embodiment, at least one of the steps of applying the first dispersion and applying the second dispersion may be performed multiple times. In one aspect, when applying the dispersion multiple times, it is preferable to apply the dispersion once and then dry the solvent before applying the next dispersion. When applying the dispersion multiple times, one dispersion may be repeatedly and continuously applied, or the first dispersion and the second dispersion may be applied alternately. The application method may be the same each time or may be different. When applying the dispersion multiple times, the composition of the first dispersion and / or the second dispersion may be the same each time or may be different.

[0098] The first dispersion medium and the second dispersion medium may be the same or different. In this embodiment, the first dispersion and the second dispersion are prepared separately, and one dispersion is applied, the solvent is dried and removed, and then the other dispersion is applied. Therefore, the first solvent and the second solvent may be different. When the first dispersion and the second dispersion are applied simultaneously, it is preferable that the first solvent and the second solvent are the same, both are aqueous solvents, or both are organic solvents. In one embodiment, when the first dispersion and the second dispersion are sprayed in an aerosol state (details will be described later), the droplets are small, so even if the first solvent and the second solvent are different, they may be applied simultaneously (for example, including the case where one is an aqueous solvent and the other is an organic solvent).

[0099] One embodiment of step (c) includes a step of applying a first dispersion containing an aqueous solvent onto a substrate, drying the first dispersion, and then applying a second dispersion containing an organic solvent.

[0100] The method for applying the dispersion onto the substrate is not particularly limited, and examples thereof include a dropping method, spin coating, printing, inkjet printing, spray coating, dip coating, aerosol spraying, etc. From the viewpoint of reducing the manufacturing cost of the bolometer, a printing method may be preferable.

[0101] (aerosol spray) In a preferred embodiment of step (c), the first dispersion and / or the second dispersion are sprayed onto the substrate in an aerosol state, which allows the carbon nanotubes and / or CNBs to be applied to the substrate while maintaining a dispersed state without agglomeration.

[0102] In one embodiment, spraying at least the second dispersion in an aerosol state is preferable because it allows the fibrous carbon nanohorn aggregates (CNB), which are monodispersed in the dispersion as shown in Figure 3, to be sprayed while maintaining the monodispersed state. This allows the CNB to be adsorbed in a monodispersed state on the carbon nanotube film (including the interior of the carbon nanotube film), making it easier to disperse in the carbon nanotube network. In this specification, "adsorbing the fibrous carbon nanohorn aggregates in a monodispersed state" means that the fibrous carbon nanohorn aggregates are preferably separated into individual aggregates and adhered to the carbon nanotubes (i.e., a state in which two or more fibrous carbon nanohorn aggregates are not aggregated).

[0103] The size of the aerosol droplets is not particularly limited as long as one droplet can contain one carbon nanotube or one fibrous carbon nanohorn aggregate, but the diameter of the outlet of the aerosol spray device is preferably 0.1 μm or more, and more preferably 0.5 μm or more to prevent the outlet from clogging with the dispersion. When the diameter of the outlet is 0.5 μm or more, the outlet is less likely to be clogged with the dispersion.

[0104] Furthermore, the droplet diameter of the aerosol provided on the substrate in an aerosol state is not limited, but is preferably 100 nm or more, more preferably 500 nm or more, and is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 10 μm or less. When the aerosol droplet diameter is small, the number of carbon nanohorn aggregates contained in each aerosol droplet is reduced to one or a few, so that the aerosol is provided on the substrate in a separated state. Furthermore, the solvent in the aerosol droplet dries more quickly, making aggregation on the substrate less likely to occur. The aerosol droplet diameter can be measured, for example, as D50 in the particle size distribution determined using a laser diffraction particle size distribution analyzer.

[0105] The aerosol density is not particularly limited, but the number of aerosol droplets per unit area when attached to the substrate is 10 4 pieces / mm 2 More than 10, preferably 5 pieces / mm 2 From the viewpoint of maintaining monodispersity, 8 pieces / mm 2 Below 10, preferably 7 pieces / mm 2 It is preferable to adjust the aerosol density so that:

[0106] The aerosol may be sprayed repeatedly or continuously, but it is preferable to spray next after the solvent of the aerosol droplets has dried on the substrate to avoid aggregation on the substrate. When the aerosol droplet size is small, the solvent dries quickly as described above, so the time interval between repeated sprays can be shortened.

[0107] In one embodiment, the aerosol droplets may be sprayed directly onto the substrate, or may be carried to the substrate by a constant-speed gas stream. The type of gas in the gas stream is not particularly limited, but air, nitrogen, argon, helium, or other gases that do not react with carbon nanohorn aggregates are preferred. Since the solvent in the aerosol droplets dries while they are moving in the gas stream, when the droplets reach the substrate, they can be supplied to the substrate in a state where the droplets have a smaller diameter, or as completely dried carbon nanohorn aggregates in a monodispersed state.

[0108] The orientation of the substrate when spraying the aerosol droplets, the direction in which the aerosol droplets are sprayed (spray direction), the spray angle (the spread angle of the liquid sprayed from the nozzle), and other factors are not limited. For example, the plane of the substrate may be horizontal, inclined relative to the horizontal, or vertical. The angle between the plane of the substrate and the spray direction of the droplets (e.g., the axial direction of the spray nozzle) may be any value between 90° (vertical) and 0° (horizontal). For example, the aerosol droplets may be supplied from above to below (e.g., vertically) the plane of a horizontally placed substrate. Alternatively, for example, the substrate may be set up so that its plane is vertical, and the aerosol droplets may be sprayed from the side (horizontally). The angle between the substrate and the spray direction of the aerosol droplets is not limited, and the angle between the plane of the substrate and the axial direction of the spray nozzle body may be any value between 90° (vertical) and 0° (horizontal), and can be appropriately selected. The spray angle when spraying the aerosol droplets (the angle at which the liquid sprayed from the nozzle spreads) is not limited, and may be, for example, about 30 to 160°, and preferably about 40 to 80°.

[0109] In one embodiment, both the first dispersion and the second dispersion may be sprayed onto the substrate in an aerosol state, or only one of them may be sprayed in an aerosol state. The first dispersion and the second dispersion may be sprayed alternately in an aerosol state or simultaneously. In one embodiment, it is preferable to spray the first dispersion, dry the solvent, and then spray the second dispersion.

[0110] In one embodiment, when the first dispersion and / or the second dispersion is sprayed in an aerosol state, the carbon nanotubes and CNB can be more uniformly distributed by moving the outlet of the aerosol spraying device and / or the substrate, i.e., the CNB can be more uniformly adsorbed onto the carbon nanotubes.

[0111] As mentioned above, when producing fibrous carbon nanohorn aggregates, spherical carbon nanohorns are also produced at the same time, so the second dispersion may contain spherical carbon nanohorn aggregates. In this case, the spherical carbon nanohorn aggregates have a smaller contact area with the carbon nanotubes and substrate and a weaker adhesive strength than fibrous carbon nanohorn aggregates. For this reason, the spherical carbon nanohorn aggregates may pass through the gaps in the carbon nanotube network and be shaken off during the solvent washing process described below. On the other hand, due to their shape, CNB has a large contact area with the carbon nanotubes and substrate and a strong adhesive strength, so they are more likely to be adsorbed onto the carbon nanotubes, contributing to the effect of improving conductivity.

[0112] (Additional process) Step (c) may further include additional steps such as a washing step, a drying step, a heat treatment step, and the like.

[0113] Cleaning process Step (c) may include a step of applying the dispersion onto the substrate and then washing the substrate with a solvent, such as water, ethanol, 2-propanol, or acetone.

[0114] As mentioned above, for example, the CNT dispersion liquid used to produce the CNT film may contain a surfactant to disperse the CNTs in water. In this case, it is likely that the surfactant is present at the junctions between the CNTs in the produced CNT film, which may lead to the problem of insufficient formation of conductive paths at the junctions. However, in step (c), the surfactant can be removed as described below.

[0115] In one embodiment, when the dispersion contains a surfactant, the micellar structure of the surfactant is destroyed by applying the dispersion to a substrate and then washing with an organic solvent such as ethanol or 2-propanol. The surfactant can then be removed by subsequent washing with water. Removing the surfactant facilitates direct bonding between the carbon nanotubes and the fibrous carbon nanohorn aggregates, thereby further enhancing the conductivity-imparting effect of the fibrous carbon nanohorn aggregates.

[0116] For example, when the first dispersion contains a surfactant and water as the first dispersion medium, the carbon nanotubes are covered with the surfactant and form micelles in water. After applying this first dispersion to a substrate, applying a second dispersion containing an organic solvent (ethanol, isopropanol, etc.) as the second dispersion medium causes the micellar structure around the carbon nanotubes to collapse. This facilitates direct bonding between the semiconducting carbon nanotubes and the fibrous carbon nanohorn aggregates without the intervention of the surfactant, thereby enabling better utilization of the conductivity of the fibrous carbon nanohorn aggregates. Furthermore, washing with water after applying this second dispersion further improves the effectiveness of surfactant removal. It is also preferable to move the substrate during the washing process (preferably the water washing process). Note that, by disrupting the micellar structure of the surfactant with an organic solvent in this way and removing the surfactant, the process of removing the surfactant by the heat treatment process described below can be shortened, omitted, or performed at a lower temperature, or the surfactant can be more completely removed.

[0117] ·Drying process Step (c) may include a drying step for removing the solvent from the applied dispersion. The drying step is not limited, but may involve, for example, heating the applied dispersion to, for example, about 80°C to 100°C, subjecting the applied dispersion to centrifugal force, placing the applied dispersion under reduced pressure, or leaving it in the atmosphere. In a preferred embodiment, a drying step is preferably performed after applying one dispersion and before applying another dispersion. For example, it is preferable to apply the first dispersion and then subject it to centrifugal force to remove the solvent, followed by applying the second dispersion. Both the washing step and drying step described above may be performed, and the order is not limited, but it is preferable to perform the drying step immediately after the washing step. In one embodiment, when the dispersion is applied by aerosol spraying, it is preferable to perform the washing step after the drying step.

[0118] Heat treatment process Step (c) may include a heat treatment step in which the applied dispersion is heated at a temperature higher than that of the drying step. The heat treatment step not only removes the solvent, but also removes any surfactants that the dispersion contains. The heat treatment temperature can be appropriately set to, for example, the decomposition temperature of the surfactant or higher, preferably 150 to 500°C, more preferably 160 to 500°C, even more preferably 180 to 400°C, and even more preferably 200 to 400°C. By keeping the heat treatment temperature within this range, it is easy to prevent the residue of surfactant decomposition products and also to prevent deterioration of the substrate. Furthermore, it is possible to prevent the decomposition and size change of carbon nanotubes, the release of functional groups, and the like. The heat treatment time is not limited, but can be set to, for example, 30 to 300 minutes.

[0119] In one embodiment, the crystallinity of the carbon nanohorn aggregates contained in the second dispersion can be improved by heat treating them in a non-oxidizing atmosphere such as an inert gas, hydrogen, vacuum, etc. In this case, the heat treatment temperature can be 800°C to 2000°C, and preferably 1000°C to 1500°C.

[0120] In one embodiment, if necessary, the functional groups introduced into the defects of the carbon nanohorn aggregates can be removed by heat treatment. In this case, the heat treatment temperature can be 150°C to 2000°C. To remove carboxyl groups, hydroxyl groups, etc., a temperature of 150°C to 600°C is preferable. To remove carbonyl groups, etc., a temperature of 600°C or higher is preferable.

[0121] The heat treatment step may be carried out after the application of all the dispersions onto the substrate is completed, although this is not a limitation.

[0122] (base material) The substrate used in producing the nanocarbon composite is not particularly limited, and any substrate or film can be used, for example. When the nanocarbon composite is used in a bolometer, it may be one that can be used as a substrate for the bolometer. When used as a substrate for the bolometer, at least one having an insulating or semiconducting surface on which elements are formed can be used, but one having an insulating surface on which elements are formed is particularly preferred.

[0123] The materials for the substrate and film as the base material are not particularly limited, and examples include inorganic materials such as Si, SiO2-coated Si, SiO2, SiN, glass, and metals such as silver, gold, titanium, and aluminum, as well as organic materials such as parylene, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate, acrylonitrile styrene resin, acrylonitrile butadiene styrene resin, fluororesin, methacrylic resin, and polycarbonate.

[0124] The substrate may have an intermediate layer having functional groups that enhance adhesion to the carbon nanotubes and / or fibrous carbon nanotubes.

[0125] The material for the intermediate layer is preferably a compound having both a partial structure that adheres to the substrate surface and a functional group that has high adhesiveness to carbon nanotubes or fibrous carbon nanohorn aggregates. Here, the adhesion between the fibrous carbon nanohorn aggregates and the functional group can be achieved not only by chemical bonding but also by various intermolecular interactions such as electrostatic interaction, surface adsorption, hydrophobic interaction, van der Waals force, and hydrogen bonding.

[0126] Examples of the partial structure in the intermediate layer material that adheres to the substrate surface include an alkoxysilyl group (SiOR), SiOH, a hydrophobic moiety or hydrophobic group, etc. Examples of the hydrophobic moiety or hydrophobic group include a methylene group (methylene chain) or alkyl group having 1 or more, preferably 2 or more, and preferably 20 or less, more preferably 10 or less carbon atoms.

[0127] Examples of functional groups in the intermediate layer material that have high adhesiveness to the fibrous carbon nanohorn aggregates include amino groups such as primary amino groups (-NH2), secondary amino groups (-NHR1), and tertiary amino groups (-NR1R2), ammonium groups (-NH4), carboxy groups (-COOH), hydroxy groups (-OH), carbonyl groups (-C(=O)-), imino groups (=NH), imide groups (-C(=O)-NH-C(=O)-), amide groups (-C(=O)NH-), sulfo groups (-SOH), ferrocenyl groups, epoxy groups, isocyanurate groups, isocyanate groups, ureido groups, sulfide groups, and mercapto groups.

[0128] The material for such an intermediate layer is not particularly limited, but may be, for example, a silane coupling agent. Examples of the silane coupling agent include: Silane coupling agents having an amino group and an alkoxysilyl group (aminosilane compounds), such as 3-aminopropyltrimethoxysilane, 3-aminopropylmethyltriethoxysilane, 3-aminopropylmethyltrimethoxysilane, 3-aminopropyltriethoxysilane (APTES), 3-(2-aminoethyl)aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane; silane coupling agents having an epoxy group and an alkoxysilyl group, such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyldiethoxysilane, and triethoxy(3-glycidyloxypropyl)silane; Isocyanurate-based silane coupling agents such as tris-(trimethoxysilylpropyl) isocyanurate; ureido-based silane coupling agents such as 3-ureidopropyltrialkoxysilane; mercapto-based silane coupling agents such as 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-mercaptopropyltriethoxysilane; Sulfide-based silane coupling agents such as bis(triethoxysilylpropyl)tetrasulfide; and Isocyanate-based silane coupling agents such as 3-isocyanatepropyltriethoxysilane; Examples include:

[0129] In particular, a silane coupling agent having an amino group (aminosilane compound) is preferred because of its good bonding property with the fibrous carbon nanohorn aggregates.

[0130] Other examples of materials for the intermediate layer include polymers having a partial structure that can adhere to the substrate and a partial structure that can adhere to the fibrous carbon nanohorn aggregates, such as cationic polymers and self-assembled monolayers (e.g., thiol derivatives, phosphonic acid derivatives, etc.).

[0131] Examples of such polymers include poly(N-methylvinylamine), polyvinylamine, polyallylamine, polyallyldimethylamine, polydiallylmethylamine, polydiallyldimethylammonium chloride, polydiallyldimethylammonium trifluoromethanesulfonate, polydiallyldimethylammonium nitrate, polydiallyldimethylammonium perchlorate, polyvinylpyridinium chloride, poly(2-vinylpyridine), poly(4-vinylpyridine), polyvinylimidazole, poly(4-aminomethylstyrene), poly(4-aminostyrene), polyvinyl(acrylamide-co-dimethylaminopropylacrylamide), polyvinyl(acrylamide-co-dimethylaminoethylmethyl)acrylate, polyvinyl(acrylamide-co-dimethylaminoethyl ... acrylate), polyethyleneimine (PEI), DAB-Am and polyamidoamine dendrimers, polyaminoamides, polyhexamethylene biguanide, polydimethylamine-epichlorohydrin, products of alkylation of polyethyleneimine with methyl chloride, products of alkylation of polyaminoamides with epichlorohydrin, cationic polyacrylamides with cationic monomers, formalin condensation products of dicyandiamide, dicyandiamide, polyalkylenepolyamine polycondensates, naturally-based cationic polymers (e.g., partially deacetylated chitin, chitosan, and chitosan salts), synthetic polypeptides (e.g., polyasparagine, polylysine, polyglutamine, and polyarginine).

[0132] Among these polymers, cationic polymers having an amino group and a hydrophobic group or a hydrophobic portion are preferred from the viewpoint of adhesiveness to the fibrous carbon nanohorn aggregates. An example of such a cationic polymer is polylysine.

[0133] (Method B) In one embodiment, a method for producing a nanocarbon composite includes: a step of preparing a nanocarbon mixed dispersion in which a plurality of carbon nanotubes containing semiconducting carbon nanotubes in an amount of 67 mass % or more of the total amount of carbon nanotubes and fibrous carbon nanohorn aggregates are dispersed in a dispersion medium; A step of applying the nanocarbon mixed dispersion onto a substrate; Preferably, the number of fibrous carbon nanohorn aggregates in the dispersion medium is 1 / 10 or less of the number of carbon nanotubes.

[0134] In Method B, a nanocarbon mixed dispersion is prepared in which carbon nanotubes and fibrous carbon nanohorn aggregates are dispersed in a single dispersion medium, and this is applied to a substrate. The nanocarbon mixed dispersion may be prepared by adding semiconducting carbon nanotubes and fibrous carbon nanohorn aggregates to a dispersion medium (liquid) and mixing and dispersing them using ultrasonic waves or the like. In one embodiment, the nanocarbon mixed dispersion may be prepared by adding fibrous carbon nanohorn aggregates to a semiconducting carbon nanotube dispersion containing carbon nanotubes containing semiconducting carbon nanotubes in an amount of 67 mass% or more of the total amount of carbon nanotubes, a surfactant, and water, and dispersing them using ultrasonic waves or the like.

[0135] The dispersion medium used for the nanocarbon mixed dispersion liquid is the same as that described for the first dispersion medium and the second dispersion medium in Method A above. In Method B, since carbon nanotubes and fibrous carbon nanohorn aggregates are dispersed in the same dispersion medium, it is preferable to use a dispersion medium that can disperse both of them. When an aqueous solvent is used as the dispersion medium, it is preferable to use the surfactant described above (preferably a nonionic surfactant).

[0136] In one embodiment, a nanocarbon mixed dispersion may be prepared by mixing a first dispersion and a second dispersion prepared by a method similar to Method A, and then applied to a substrate. In this case, the first dispersion medium and the second dispersion medium are preferably compatible solvents, and more preferably the same solvent.

[0137] <Bolometer, infrared sensor> One aspect of the present disclosure relates to a bolometer including a film made of the nanocarbon composite, and an infrared sensor using the same. Figure 1 is a schematic diagram of a bolometer (preferably an infrared sensor detection unit) according to one embodiment of the present invention. A first electrode 2 and a second electrode 4 are located on a substrate 1, and these electrodes are connected by a nanocarbon composite film (also referred to as a "resistance change film") 3 located therebetween. In this embodiment, the nanocarbon composite film 3 preferably includes a composite of a carbon nanomaterial including a carbon nanotube film formed of multiple carbon nanotubes forming a conductive path electrically connecting the first electrode and the second electrode, and fibrous carbon nanohorn aggregates adsorbed thereon. The carbon nanotubes constituting the carbon nanotube film are semiconducting carbon nanotubes, accounting for 67% by mass or more (preferably 90% by mass or more) of their total mass. Furthermore, the length of the CNB is preferably shorter than the distance between the first electrode 2 and the second electrode 4, so as to avoid direct connection between the electrodes via the fibrous carbon nanohorn aggregates.

[0138] The inventors of the present invention have found that by including fibrous carbon nanohorn aggregates in a resistance change film containing semiconducting carbon nanotubes in a bolometer, the resistance can be significantly reduced while maintaining a good TCR of the bolometer. This is thought to be because, as schematically shown in Figure 2, fibrous carbon nanohorn aggregates 22 exist in the nanocarbon composite film so as to connect semiconducting carbon nanotubes 21 to each other.

[0139] The nanocarbon composite film is formed from a plurality of carbon nanotubes and fibrous carbon nanohorn aggregates that form a conductive path electrically connecting a first electrode and a second electrode. The plurality of carbon nanotubes can form, for example, parallel wire, fiber, or network structures, but a network structure is preferred because it is less likely to aggregate and allows for the formation of a uniform conductive path. In this specification, the "nanocarbon composite film" may also be referred to as a "nanocarbon composite layer."

[0140] In the bolometer of the present disclosure, the distance between the electrodes is preferably 1 μm to 500 μm, and more preferably 5 to 200 μm for miniaturization. If it is 5 μm or more, degradation of the TCR characteristics can be suppressed even when a small amount of metallic carbon nanotubes is contained. Furthermore, if it is 500 μm or less, it is advantageous for application to an image sensor in a two-dimensional array.

[0141] In one embodiment, the number of carbon nanotubes between the electrodes (number density of carbon nanotubes in the nanocarbon composite layer (3)) is 1 / μm 2 ~1000 lines / μm 2 It is preferable that the number of fibers is 10 / μm. 2 ~500 lines / μm 2 More preferably, it is 50 lines / μm 2 ~300 lines / μm 2 In one embodiment, the number of fibers is 10 / μm. 2 ~100 lines / μm 2 If the number density is too low, it may be difficult to form a conductive path. 2 If the thickness is less than 1 μm, the deterioration of TCR characteristics is likely to be suppressed even if a small amount of metallic carbon nanotubes is contained. The number of carbon nanotubes can be calculated, for example, by measuring the number of carbon nanotubes per area using an AFM at 10 random points (each in an area of ​​1 μm × 1 μm) on the carbon nanotube layer and averaging the results.

[0142] The thickness of the nanocarbon composite film constituting the resistance change film of the bolometer is not limited, but may be, for example, preferably 1 nm or more, more preferably 2 nm or more, 3 nm or more, or 5 nm or more, and may be preferably 10 μm or less, more preferably 1 μm or less, or 200 nm or less. In one embodiment, the thickness of the carbon nanotube film is preferably 2 nm to 1 μm, more preferably 5 nm to 200 nm.

[0143] The bolometer in Figure 1 detects temperature by utilizing the temperature dependence of electrical resistance due to light irradiation. Therefore, it can be used in other frequency ranges as well, as long as the temperature changes due to light irradiation, for example, the terahertz range can be detected. Furthermore, changes in electrical resistance due to temperature changes can be detected not only using the structure in Figure 1, but also by amplifying the change in resistance value by providing a gate electrode to turn it into a field-effect transistor.

[0144] (Bolometer manufacturing method) One embodiment of the present disclosure relates to a method for manufacturing a bolometer (preferably a bolometer for an infrared sensor detector) having a resistance change film formed from the nanocarbon composite. As described above, one embodiment of the bolometer includes a substrate 1 on which a first electrode 2 and a second electrode 4 are disposed, and these electrodes are connected by a nanocarbon composite film 3 disposed therebetween. The nanocarbon composite film 3 is primarily composed of the nanocarbon composite. This bolometer can be manufactured, for example, as follows, but is not limited to the following. A silicon substrate coated with SiO2 is washed sequentially with acetone, isopropyl alcohol, and water, and then organic matter on the surface is removed by oxygen plasma treatment. The substrate is immersed in an aqueous solution of 3-aminopropyltriethoxysilane (APTES), washed with water, and dried. A nanocarbon composite film is manufactured on this substrate by the above-described method for manufacturing a nanocarbon composite film. For example, a first dispersion containing semiconducting carbon nanotubes, a nonionic surfactant, and water, and a second dispersion containing fibrous carbon nanohorn aggregates and isopropanol are first prepared. Next, while the substrate is being rotated by spin coating, the first dispersion is sprayed onto the substrate in an aerosol state and dried, and then the second dispersion is sprayed onto the substrate in an aerosol state and dried, followed by rinsing with water (coating process). This coating process may be repeated. Nonionic surfactants and the like may be removed by baking at 200°C in air. These operations form a thin film of nanocarbon composite on the substrate. Then, first and second electrodes are fabricated on top of the thin film of nanocarbon composite, spaced 50 μm apart by gold vapor deposition. An acrylic resin (PMMA) solution is applied to the area between the electrodes on the thin layer of carbon nanotubes formed to form a PMMA protective layer. The entire substrate is then treated with oxygen plasma to remove excess carbon nanotubes and other materials from areas other than the nanocarbon composite film 3. Excess solvent, impurities, and the like are removed by heating at 200°C in air.

[0145] The first and second electrodes on the substrate can be made using, but are not limited to, gold, platinum, or titanium, either singly or in combination. The method for making the electrodes is not particularly limited, but examples include vapor deposition, sputtering, and printing. The thickness can be adjusted as appropriate, but is preferably 10 nm to 1 mm, and more preferably 50 nm to 1 μm. The dispersion may be applied to a substrate already provided with electrodes, or the electrodes may be made after the dispersion is applied and before or after heat treatment.

[0146] A protective film may be provided on the surface of the nanocarbon composite layer, if necessary. The protective film is preferably made of a material that is highly transparent in the infrared wavelength range to be detected. Examples include acrylic resins such as PMMA and PMMA-anisole, epoxy resins, and Teflon (registered trademark).

[0147] The infrared sensor according to this embodiment may be a single element, or may be an array in which a plurality of elements are arranged two-dimensionally, as used in an image sensor. [Example]

[0148] The present invention will be illustrated in more detail below with reference to examples, but the present invention is not limited to these examples.

[0149] <Preparation Example 1: Separation of semiconducting carbon nanotubes> (Step a1) 100 mg of single-walled carbon nanotubes (Meijo Nanocarbon Co., Ltd., EC1.0 (diameter: approximately 1.1 to 1.5 nm (average diameter 1.2 nm)) were placed in a quartz boat and heat-treated in an electric furnace under vacuum. The heat treatment temperature was 900°C for 2 hours. After the heat treatment, the weight was reduced to 80 mg, indicating that surface functional groups and impurities had been removed. The obtained single-walled carbon nanotubes were crushed with tweezers, and 12 mg of them were immersed in 40 ml of a 1 wt% aqueous solution of surfactant (polyoxyethylene (100) stearyl ether) and thoroughly submerged. Then, ultrasonic dispersion treatment (BRANSON ADVANCD-DIGITAL The solution was centrifuged in a SONIFIER (output: 50 W) for 3 hours. This eliminated any carbon nanotube aggregates. The solution was then subjected to ultracentrifugation at 50,000 rpm, 10°C, and 60 minutes. This procedure removed bundles and residual catalyst, yielding a carbon nanotube dispersion. The dispersion was then applied to a SiO2 substrate, dried at 100°C, and observed with an atomic force microscope (AFM). The results showed that 70% of the single-walled carbon nanotubes were in the length range of 500 nm to 1.5 μm, with an average length of approximately 800 nm.

[0150] (Step a2) The carbon nanotube dispersion obtained in step a1 above was introduced into a double-tube separation device. Approximately 15 mL of water, approximately 70 mL of carbon nanotube dispersion, and approximately 10 mL of a 2 wt% surfactant solution were placed in the outer tube of the double-tube separation device, and approximately 20 mL of a 2 wt% surfactant solution was placed in the inner tube. The lower lid of the inner tube was then opened, creating a three-layer structure with different surfactant concentrations. A voltage of 200 V was applied, with the lower side of the inner tube acting as the anode and the upper side of the outer tube acting as the cathode. Semiconducting carbon nanotubes migrated to the anode side. Meanwhile, metallic carbon nanotubes migrated to the cathode side. Semiconducting and metallic carbon nanotubes were successfully separated approximately 80 hours after the start of separation. The separation process was carried out at room temperature (approximately 25°C). The semiconducting carbon nanotube dispersion that had migrated to the anode side was collected and analyzed by optical absorption spectroscopy, revealing that the metallic carbon nanotube components had been removed. Furthermore, the Raman spectrum showed that 99 wt% of the carbon nanotubes in the carbon nanotube dispersion that had migrated to the anode side were semiconducting carbon nanotubes. The diameter of the single-walled carbon nanotubes was approximately 1.2 nm, accounting for the majority (70% or more), and the average diameter was 1.2 nm. The optical absorption spectrum showed that the number concentration of the carbon nanotubes was approximately 5 x 10 13 It was calculated as fibers / mL.

[0151] The zeta potential of the obtained semiconducting carbon nanotube dispersion was measured using an ELSZ device (Otsuka Electronics Co., Ltd.) and was found to be approximately -10 mV.

[0152] <Preparation Example 2: Preparation of fibrous carbon nanohorn aggregates> A carbon mixture containing CNB was prepared by CO2 laser ablation of a carbon target containing iron in a nitrogen atmosphere chamber. Specifically, a graphite target containing 1 wt% iron was rotated at 1.5 rpm and continuously irradiated with a CO2 laser. The energy density of the CO2 laser was 50 kW / cm. 2The temperature inside the chamber was set to room temperature, and the flow rate of nitrogen supplied into the chamber was adjusted to 10 L / min. The pressure inside the chamber was controlled to 933.254 to 1266.559 hPa (700 to 950 Torr).

[0153] The resulting carbon mixture was subjected to thermogravimetric analysis. The fibrous carbon nanohorn aggregates and spherical carbon nanohorn aggregates burned at approximately 560°C, while the graphite burned at approximately 640°C. The thermogravimetric analysis revealed that the amount of graphite in the carbon mixture was approximately 20% by weight.

[0154] (graphite removal) The carbon mixture was ultrasonically dispersed in ethanol at a concentration of 0.1 mg / ml, the dispersion was allowed to stand for one day, and approximately 50% of the supernatant was recovered. The supernatant was dried in an oven at 150°C to obtain a solvent-free carbon mixture from which graphite had been removed. When this carbon mixture was observed under SEM, no graphite was observed, but a large number of spherical carbon nanohorn aggregates and a small number of fibrous carbon nanohorn aggregates were observed. The fibrous carbon nanohorn aggregates had diameters of approximately 30 to 100 nm and lengths of approximately 0.2 μm to 10 μm. The spherical carbon nanohorn aggregates were mostly uniform in size, with diameters ranging from approximately 30 to 200 nm. The carbon mixture obtained in this manner was used as the carbon nanohorn aggregate mixture in this example.

[0155] The supernatant was diluted to a concentration of 0.01 mg / ml and used to measure particle size distribution using dynamic light scattering. As a result, size distributions in the 100 nm to 600 nm range and the 8 μm to 10 μm range were detected. Since only spherical carbon nanohorn aggregates and fibrous carbon nanohorn aggregates were observed in this sample from the SEM photograph, it was determined that the 100 nm to 600 nm range was spherical carbon nanohorn aggregates and the 8 to 10 μm range was fibrous carbon nanohorn aggregates.

[0156] From this size distribution region, it was found that the spherical carbon nanohorn aggregates and fibrous carbon nanohorn aggregates were in a state of being almost monodispersed or dispersed as a few aggregates in ethanol.

[0157] The supernatant was dropped onto a substrate, and the dried product was observed under SEM. The ratio of fibrous carbon nanohorn aggregates to spherical carbon nanohorn aggregates (CNB / CNHs ratio) was estimated to be 0.04.

[0158] From the concentration of the supernatant and the CNB / CNHs ratio estimated from SEM observation, the number concentration of the fibrous carbon nanohorn aggregates was approximately 10 9 It was calculated as fibers / mL.

[0159] Example 1 The carbon nanotube dispersion liquid containing 99 wt % semiconducting carbon nanotubes obtained in Preparation Example 1 (the carbon nanotube dispersion liquid moved to the anode side) was used as carbon nanotube dispersion liquid A (also simply referred to as "dispersion liquid A"). The concentration of carbon nanotubes in dispersion liquid A was 30 μg / mL (3 × 10 13 The carbon nanohorn aggregate mixture dispersion B (also simply referred to as "dispersion B") was prepared by dispersing a carbon nanohorn aggregate mixture containing CNB in ​​ethanol at a concentration of 20 μg / mL (the number of CNB was 10 9 Contains at a concentration of 1000mg / mL.

[0160] (Electrode formation) After oxygen plasma treatment of a Si substrate with SiO2 formed on its surface, photoresist was applied and the electrodes were patterned so that the distance between the electrodes was 100 μm. The electrodes were formed by E-gun evaporation, with Ti 5 nm thick and Au 100 nm thick for both the first and second electrodes, and then the resist was lifted off.

[0161] (Application of dispersion liquid) The Si substrate with the electrode was washed with acetone, isopropyl alcohol, and water, treated with an oxygen plasma asher, then immersed in an aqueous solution of APTES (0.1% by volume), washed with water, and dried to form an APTES intermediate layer.

[0162] (Process (c1)) While the Si substrate with the APTES intermediate layer formed thereon was being rotated by a spin coater (condition: 500 rpm), the prepared carbon nanotube dispersion A was sprayed onto the substrate as an aerosol and dried. The D50 droplet diameter of the aerosol measured by a laser diffraction particle size distribution analyzer was 50 μm.

[0163] (Process (c2)) Next, while the Si substrate on which the coating film of Dispersion A had been formed was being rotated with a spin coater (condition: 2000 rpm), Dispersion B of fibrous carbon nanohorn aggregates was sprayed onto the coating film of carbon nanotubes formed with Dispersion A as an aerosol. After leaving it to stand for 5 seconds, 50 mL of water was dropped onto the Si substrate while rotating with the spin coater (condition: 1000 rpm) to wash the substrate and then dried. The D50 droplet diameter of the aerosol observed with a laser diffraction particle size distribution analyzer was 50 μm.

[0164] Steps (c1) and (c2) were alternately performed on the Si substrate. Specifically, the steps of applying and drying dispersion A, applying dispersion B, rinsing with water, and drying were repeated 20 times in this order, and the substrate was dried at 110°C. The substrate was heated at 200°C in the atmosphere to remove the nonionic surfactant and the like, yielding Si substrate 1 having a nanocarbon composite film.

[0165] Figure 4 shows an SEM image of the surface of the obtained Si substrate 1. As shown in Figure 4, it was observed that the CNBs were attached to the CNT network in a monodispersed state. It was also observed that 10 to 20 CNTs were connected to one CNB. From these results, it was found that by spraying the dispersion in an aerosol state, the CNBs could be spaced apart and attached to many CNTs.

[0166] (Fabrication of bolometers) A PMMA-anisole solution was applied between the electrodes on the obtained Si substrate 1 to protect the nanocarbon composite between the electrodes, and then excess carbon nanotubes and other materials near the electrodes were removed by oxygen plasma treatment. After that, it was dried at 200°C for 1 hour to obtain bolometer 1.

[0167] The TCR value (dR / RdT) of the obtained bolometer 1 was -5% / K at 300 K, and the film resistance measurement result at a voltage of 3 V was 3.5 × 10 6 It was Omega.

[0168] <Comparative Example 1> (Electrode formation) After oxygen plasma treatment of a Si substrate with SiO2 formed on its surface, photoresist was applied and the electrodes were patterned so that the distance between the electrodes was 100 μm. The electrodes were formed by E-gun evaporation, with Ti 5 nm thick and Au 100 nm thick for both the first and second electrodes, and then the resist was lifted off.

[0169] This Si substrate with electrodes was washed with acetone, isopropyl alcohol, and water, treated with an oxygen plasma asher, then immersed in an APTES aqueous solution (0.1% by volume), washed with water, and dried to form an APTES intermediate layer. 100 μL of dispersion A obtained in Preparation Example 1 was dropped onto this Si substrate and allowed to stand for 30 minutes. This was then washed with ethanol and water and dried at 110°C. It was heated at 200°C in the atmosphere to remove nonionic surfactants and the like, yielding Si substrate 2 with a carbon nanotube film (not including CNB).

[0170] A PMMA-anisole solution was applied between the electrodes on the obtained Si substrate 2 to protect the carbon nanotubes between the electrodes, and then excess carbon nanotubes near the electrodes were removed by oxygen plasma treatment. After that, it was dried at 200°C for 1 hour to obtain the bolometer 2.

[0171] The TCR value (dR / RdT) of the obtained bolometer 2 was -5% / K at 300 K, and the film resistance measurement result at a voltage of 3 V was 9.8 × 10 9 It was Omega.

[0172] The results of Example 1 and Comparative Example 1 show that the bolometer using the nanocarbon composite of the present invention has a good TCR and a low resistance.

[0173] [Note] Some or all of the above embodiments can be described as follows, but the disclosure of the present application is not limited to the following supplementary notes.

[0174] (Appendix 1) a plurality of carbon nanotubes containing semiconducting carbon nanotubes in an amount of 67 mass % or more of the total amount of the carbon nanotubes; a fibrous carbon nanohorn aggregate adsorbed on the carbon nanotube; Including, A nanocarbon composite, wherein the number of the fibrous carbon nanohorn aggregates is 1 / 10 or less of the number of the carbon nanotubes.

[0175] (Appendix 2) A substrate; a first electrode on the substrate; a second electrode on the substrate and spaced apart from the first electrode; a nanocarbon composite film electrically connected to the first electrode and the second electrode; A bolometer comprising: The nanocarbon composite film is a plurality of carbon nanotubes containing semiconducting carbon nanotubes in an amount of 90 mass % or more of the total amount of the carbon nanotubes; a fibrous carbon nanohorn aggregate adsorbed on the carbon nanotube; Including, A bolometer, wherein the number of the fibrous carbon nanohorn aggregates is 1 / 10 or less of the number of the carbon nanotubes.

[0176] (Appendix 3) 3. The bolometer according to claim 2, wherein the length of the fibrous carbon nanohorn aggregate is shorter than the inter-electrode distance between the first electrode and the second electrode.

[0177] (Appendix 4) A step (a) of preparing a first dispersion liquid containing a plurality of carbon nanotubes, the semiconducting carbon nanotubes being 67 mass % or more of the total amount of the carbon nanotubes, and a first dispersion medium; A step (b) of preparing a second dispersion liquid containing fibrous carbon nanohorn aggregates and a second dispersion medium; (c) applying the first dispersion and the second dispersion onto a substrate; Including, A method for producing a nanocarbon composite, wherein the concentration (pieces / mL) of fibrous carbon nanohorn aggregates in the second dispersion is 1 / 10 or less of the concentration (pieces / mL) of carbon nanotubes in the first dispersion.

[0178] (Appendix 5) the first dispersion medium is water or heavy water, and the first dispersion liquid further contains a surfactant; The second dispersion medium is an organic solvent. A method for producing a nanocarbon composite according to Appendix 4.

[0179] (Appendix 6) The method for producing a nanocarbon composite according to Appendix 4 or 5, wherein step (c) comprises applying a first dispersion onto a substrate and then applying a second dispersion.

[0180] (Appendix 7) 7. The method for producing a nanocarbon composite according to any one of appendix 4 to 6, wherein in the step (c), the first dispersion and the second dispersion are applied, followed by washing with water.

[0181] (Appendix 8) A method for producing a nanocarbon composite according to any one of Appendices 4 to 7, wherein step (c) includes a step of applying at least one of the steps of applying a first dispersion and applying a second dispersion multiple times.

[0182] (Appendix 9) A method for producing a nanocarbon composite according to any one of Appendices 4 to 8, wherein step (c) includes a step of applying the first dispersion and / or the second dispersion onto a substrate by spraying them in an aerosol state.

[0183] (Appendix 10) A step (a) of preparing a first dispersion liquid containing a plurality of carbon nanotubes, the carbon nanotubes comprising semiconducting carbon nanotubes in an amount of 90 mass % or more of the total amount of the carbon nanotubes, and a first dispersion medium; A step (b) of preparing a second dispersion liquid containing fibrous carbon nanohorn aggregates and a second dispersion medium; (c) applying the first dispersion and the second dispersion onto a substrate; Including, A method for producing a bolometer, wherein the concentration (pieces / mL) of the fibrous carbon nanohorn aggregates in the second dispersion is 1 / 10 or less of the concentration (pieces / mL) of the carbon nanotubes in the first dispersion.

[0184] (Appendix 11) 10. The method for producing a nanocarbon composite according to any one of appendixes 4 to 9, wherein in the step (c), a step of applying the first dispersion liquid and a step of applying the second dispersion liquid are alternately performed.

[0185] (Appendix 12) A method for producing a nanocarbon composite according to Appendix 9, wherein the substrate is moved simultaneously with or after the first dispersion and / or the second dispersion are sprayed in an aerosol state.

[0186] (Appendix 13) a step of preparing a nanocarbon mixed dispersion in which a plurality of carbon nanotubes containing semiconducting carbon nanotubes in an amount of 67 mass % or more of the total amount of carbon nanotubes and fibrous carbon nanohorn aggregates are dispersed in a dispersion medium; A step of applying the nanocarbon mixed dispersion onto a substrate; Including, A method for producing a nanocarbon composite, wherein the number of the fibrous carbon nanohorn aggregates in the dispersion medium is 1 / 10 or less of the number of the carbon nanotubes.

[0187] (Appendix 14) the dispersion medium is water, A method for producing a nanocarbon composite according to claim 13, wherein the nanocarbon mixed dispersion further contains a surfactant.

[0188] (Appendix 15) A method for producing a nanocarbon composite according to claim 13 or 14, comprising the step of providing the nanocarbon mixed dispersion on a substrate by spraying it in an aerosol state.

[0189] (Appendix 16) the first dispersion medium is water or heavy water, and the first dispersion liquid further contains a surfactant; The second dispersion medium is an organic solvent. 11. A method for manufacturing a bolometer according to claim 10.

[0190] (Appendix 17) 17. The method for manufacturing a bolometer according to claim 10 or 16, wherein step (c) comprises applying a first dispersion onto a substrate and then applying a second dispersion.

[0191] (Appendix 18) 18. The method for producing a bolometer according to claim 10, 16 or 17, wherein in step (c), the method further comprises a step of washing with water after applying the first dispersion liquid and the second dispersion liquid.

[0192] (Appendix 19) 19. The method for manufacturing a bolometer according to any one of Appendices 10 and 16 to 18, wherein step (c) includes a step of repeating at least one of a step of applying a first dispersion liquid and a step of applying a second dispersion liquid multiple times.

[0193] (Appendix 20) 20. The method for manufacturing a bolometer according to any one of Appendices 10 and 16 to 19, wherein step (c) comprises applying the first dispersion liquid and / or the second dispersion liquid onto the substrate by spraying them in an aerosol state.

[0194] (Appendix 21) 21. The method for producing a bolometer according to any one of appendixes 10 and 16 to 20, wherein in step (c), the step of applying the first dispersion liquid and the step of applying the second dispersion liquid are performed alternately.

[0195] (Appendix 22) a step of applying a semiconducting carbon nanotube dispersion liquid containing the surfactant, carbon nanotubes containing semiconducting carbon nanotubes in an amount of 90 mass % or more of the total amount of the carbon nanotubes, and a dispersion medium onto a substrate to form a carbon nanotube film; applying an organic solvent onto the carbon nanotube film; a step of applying the organic solvent and then washing with water; A method for manufacturing a bolometer, comprising: [Explanation of symbols]

[0196] 1 board 2 Electrode 1 (1st electrode) 3 Nanocarbon composite film (nanocarbon composite layer) 4 Electrode 2 (second electrode) 21 Semiconducting carbon nanotubes 22 Fibrous carbon nanohorn aggregates (CNB)

Claims

1. a plurality of carbon nanotubes containing semiconducting carbon nanotubes in an amount of 67 mass % or more of the total amount of the carbon nanotubes; a fibrous carbon nanohorn aggregate adsorbed on the carbon nanotube; Including, A nanocarbon composite, wherein the number of the fibrous carbon nanohorn aggregates is 1 / 10 or less of the number of the carbon nanotubes.

2. A substrate; a first electrode on the substrate; a second electrode on the substrate and spaced apart from the first electrode; a nanocarbon composite film electrically connected to the first electrode and the second electrode; A bolometer comprising: The nanocarbon composite film is a plurality of carbon nanotubes containing semiconducting carbon nanotubes in an amount of 90 mass % or more of the total amount of the carbon nanotubes; a fibrous carbon nanohorn aggregate adsorbed on the carbon nanotube; Including, A bolometer, wherein the number of the fibrous carbon nanohorn aggregates is 1 / 10 or less of the number of the carbon nanotubes.

3. The bolometer according to claim 2 , wherein the length of the fibrous carbon nanohorn aggregate is shorter than the inter-electrode distance between the first electrode and the second electrode.

4. A step (a) of preparing a first dispersion liquid containing a plurality of carbon nanotubes, the semiconducting carbon nanotubes being 67 mass % or more of the total amount of the carbon nanotubes, and a first dispersion medium; A step (b) of preparing a second dispersion liquid containing fibrous carbon nanohorn aggregates and a second dispersion medium; (c) applying the first dispersion and the second dispersion onto a substrate; Including, A method for producing a nanocarbon composite, wherein the concentration (pieces / mL) of fibrous carbon nanohorn aggregates in the second dispersion is 1 / 10 or less of the concentration (pieces / mL) of carbon nanotubes in the first dispersion.

5. the first dispersion medium is water or heavy water, and the first dispersion liquid further contains a surfactant; the second dispersion medium is an organic solvent; The method for producing a nanocarbon composite according to claim 4 .

6. 6. The method for producing a nanocarbon composite according to claim 4, wherein the step (c) comprises a step of applying the first dispersion onto the substrate and then applying the second dispersion onto the substrate.

7. 6. The method for producing a nanocarbon composite according to claim 4, wherein the step (c) comprises a step of washing with water after applying the first dispersion and the second dispersion.

8. 6. The method for producing a nanocarbon composite according to claim 4, wherein the step (c) includes a step of performing at least one of a step of applying the first dispersion liquid and a step of applying the second dispersion liquid multiple times.

9. 6. The method for producing a nanocarbon composite according to claim 4 or 5, wherein step (c) comprises a step of applying the first dispersion and / or the second dispersion onto the substrate by spraying them in an aerosol state.

10. A step (a) of preparing a first dispersion liquid containing a plurality of carbon nanotubes, the carbon nanotubes being semiconducting carbon nanotubes in an amount of 90 mass % or more of the total amount of the carbon nanotubes, and a first dispersion medium; A step (b) of preparing a second dispersion liquid containing fibrous carbon nanohorn aggregates and a second dispersion medium; (c) applying the first dispersion and the second dispersion onto a substrate; Including, A method for manufacturing a bolometer, wherein the concentration (pieces / mL) of the fibrous carbon nanohorn aggregates in the second dispersion is 1 / 10 or less of the concentration (pieces / mL) of the carbon nanotubes in the first dispersion.

Images