Bolometer and method for manufacturing the same

Abstract

To provide a bolometer with a high TCR, a bolometer array, and manufacturing methods thereof.SOLUTION: This invention relates to a bolometer comprising a substrate and a bolometer film containing a semiconductor-type carbon nanotube and a negative thermal expansion material, wherein a positively charged adhesive layer provided on the substrate, and the negatively charged semiconductor-type carbon nanotube and the negative thermal expansion material in the bolometer film are electrostatically attracted.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a bolometer and a method for manufacturing the same, particularly a bolometer using a semiconductor-type carbon nanotube and a method for manufacturing the same.

Background Art

[0002] Uncooled infrared sensors have a very wide range of applications, not only in security surveillance cameras, but also in human thermography, in-vehicle cameras, and inspections of structures, foods, etc. Therefore, in recent years, industrial applications have been active. Conventional uncooled infrared sensors mainly use VO x (vanadium oxide) in the bolometer part, but there is a problem that the temperature coefficient of resistance (TCR: Temperature Coefficient Resistance), which is the main factor determining infrared sensitivity, is small (about -2.0% / K), and further improvement of TCR is necessary to obtain sensitivity equivalent to that of cooled sensors.

[0003] To improve TCR, a material with semiconductor properties is required. Semiconducting single-walled carbon nanotubes (CNTs) have a large bandgap, so there is a possibility of realizing a high-performance infrared sensor. When ordinary single-walled CNTs were applied to the bolometer part, the TCR was about -1% / K because metal components and semiconductor components were mixed (Patent Document 1). Also, it has been reported that more than 99% of semiconducting single-walled CNTs are extracted with a non-ionic surfactant and applied to the bolometer part, resulting in an improvement to -5% / K or more (Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

[0005] However, in order to achieve the same level of sensitivity as a cooled bolometer, there was room for improvement in TCR (Transmission Cancellation). [Means for solving the problem]

[0006] One aspect of the present invention is, circuit board and A bolometer film containing semiconductor carbon nanotubes and a negative thermal expansion material A bolometer that includes, A positively charged adhesive layer provided on a substrate is electrostatically adsorbed to negatively charged semiconductor carbon nanotubes and negative thermal expansion material in a bolometer film. Regarding.

[0007] Another aspect of the present invention is, A method for manufacturing a bolometer, A step of preparing dispersions of semiconductor carbon nanotubes and negative thermal expansion materials, comprising the steps of preparing a carbon nanotube dispersion containing semiconductor carbon nanotubes, a surfactant, and an aqueous dispersion medium, and a negative thermal expansion material dispersion containing a negative thermal expansion material and an aqueous dispersion medium, either as individual dispersions or as mixed dispersions thereof. The process involves adjusting the pH of each individual dispersion or mixed dispersion to a pH of 5 or higher and 9 or lower, thereby negatively charging the semiconductor carbon nanotubes and the negative thermal expansion material. A step of providing a pH-adjusted dispersion onto a substrate, wherein the individual dispersions or mixed dispersions are provided onto a substrate having an adhesive layer whose surface is positively charged at a pH of 5 to 9, thereby causing negatively charged semiconductor carbon nanotubes and negative thermal expansion materials to be adsorbed onto the adhesive layer by electrostatic interaction. The process of removing excess surfactant and aqueous dispersion medium from the substrate to form a bolometer film of the desired form. A method for manufacturing a bolometer, including Regarding.

[0008] Another aspect of the present invention is, A method for manufacturing a bolometer, A step of preparing dispersions of semiconductor carbon nanotubes and negative thermal expansion materials, comprising the steps of preparing a carbon nanotube dispersion containing semiconductor carbon nanotubes, a surfactant, and an aqueous dispersion medium, and a negative thermal expansion material dispersion containing a negative thermal expansion material and an aqueous dispersion medium, either as individual dispersions or as mixed dispersions thereof. A step of adjusting the pH of the negative thermal expansion material dispersion and optionally the carbon nanotube dispersion, or the mixed dispersion, to be above the isoelectric point of the negative thermal expansion material, thereby negatively charging at least the negative thermal expansion material. A step of providing a pH-adjusted dispersion onto a substrate, comprising: providing the negative thermal expansion material dispersion and / or carbon nanotube dispersion or mixed dispersion onto a substrate having an adhesive layer whose surface is positively charged at the pH of the negative thermal expansion material dispersion or mixed dispersion, thereby adsorbing the negatively charged negative thermal expansion material onto the adhesive layer by electrostatic interaction; The process of removing excess surfactant and aqueous dispersion medium from the substrate to form a bolometer film of the desired form. A method for manufacturing a bolometer, including Regarding. [Effects of the Invention]

[0009] According to the present invention, a bolometer having a high TCR and a method for manufacturing the same can be provided. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram (longitudinal section view) showing a bolometer according to one embodiment of the present invention. [Figure 2] This is a schematic diagram (top view) showing the temperature-dependent changes in the light-receiving section of a bolometer according to one embodiment of the present invention. [Figure 3] This is a schematic diagram (left: longitudinal section view, right: top view) showing a bolometer according to one embodiment of the present invention. [Figure 4]This is a schematic diagram (longitudinal cross-sectional view) illustrating a method for manufacturing a bolometer according to one embodiment of the present invention. [Figure 5] This is a schematic diagram (longitudinal cross-sectional view) showing the liquid-liquid interface in a method for manufacturing a bolometer according to one embodiment of the present invention. [Figure 6] This is a schematic diagram (longitudinal cross-sectional view) illustrating the process of manufacturing a bolometer according to one embodiment of the present invention. [Figure 7A] This is a schematic diagram (longitudinal cross-sectional view) of a bolometer manufacturing method according to one embodiment of the present invention and a bolometer manufactured thereby. [Figure 7B] This is a schematic diagram (top view) showing the light-receiving part of a bolometer manufactured by a bolometer manufacturing method according to one embodiment of the present invention, and its changes with temperature. [Figure 8] This is a SEM image of the negative thermal expansion material in the bolometer film of an infrared sensor according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] [Bolometer] The bolometer of this embodiment comprises a substrate and a bolometer film containing semiconductor carbon nanotubes and a negative thermal expansion material, wherein a positively charged adhesive layer provided on the substrate and the negatively charged semiconductor carbon nanotubes and negative thermal expansion material in the bolometer film are electrostatically adsorbed.

[0012] An example of the bolometer of this embodiment will be described with reference to the figures. Figure 1 is a schematic diagram of a bolometer according to one embodiment of the present invention, and Figure 2 is a schematic diagram of the detection unit of the bolometer. As shown in Figure 1, the bolometer of this embodiment comprises a bolometer film 4, a first electrode, and a second electrode 2 on a substrate 1, with the first electrode and the second electrode connected by the bolometer film 4. The bolometer film 4 is a carbon nanotube composite material (in this specification, such a composite material is also referred to as a "CNT nanocomposite") in which a negative thermal expansion material 5 is dispersed in a carbon nanotube aggregate formed by the aggregation of multiple semiconductor-type carbon nanotubes 6, and the carbon nanotube aggregate has a network structure of carbon nanotubes. In such a three-dimensional conductive network of carbon nanotubes, not all carbon nanotubes in the bolometer film are connected and contribute to conductivity; some carbon nanotubes do not contribute to the conductive mechanism. As shown in Figure 2, when the temperature of the bolometer film 4 rises due to incident light such as infrared radiation (T+ΔT), the negative thermal expansion material 5 inside contracts, and the volume decreases (V-ΔV). Due to the volume reduction of the negative thermal expansion material 5 as the temperature rises, semiconductor carbon nanotubes that were separated and not conducting before the temperature rise establish new conductive paths. Alternatively, the volume reduction increases the contact area between carbon nanotubes, further increasing the number of conductive paths. In other words, while the current of semiconductor carbon nanotubes normally increases exponentially with increasing temperature, in this embodiment, the increase in conductive paths due to the volume reduction of the negative thermal expansion material 5 as the temperature rises is added, allowing more current to flow. This improves the TCR value of the bolometer.

[0013] In this embodiment, as shown in Figure 3, the bolometer includes a positively charged adhesive layer 3 on the substrate 1, while the semiconductor carbon nanotubes 6 and negative thermal expansion material 5 in the bolometer film 4 are negatively charged. Therefore, the adhesive layer 3 and the semiconductor carbon nanotubes 6 and negative thermal expansion material 5 can be electrostatically attracted to each other. This increases the adhesion and amount of the semiconductor carbon nanotubes and negative thermal expansion material to the substrate, and suppresses peeling from the substrate. In particular, negative thermal expansion materials are more prone to detaching from the substrate than carbon nanotubes that form a network structure. If the negative thermal expansion material detaches from the substrate, the effect of volume reduction of the negative thermal expansion material may not be fully obtained. However, the bolometer of this embodiment can suppress the detachment of the negative thermal expansion material from the substrate, thereby achieving a high TCR improvement effect.

[0014] Furthermore, in one embodiment, as shown in Figure 3, it is preferable that at least a portion of the semiconductor carbon nanotubes in the bolometer film are oriented in a direction substantially parallel to the direction of current flow (i.e., the longitudinal direction of the carbon nanotubes is substantially perpendicular to the long side of the electrode). The orientation of multiple carbon nanotubes increases the contact area between the carbon nanotubes and increases the number of conductive paths. This is thought to enable a large change in resistance with respect to temperature changes, as well as lower resistance.

[0015] The components of the bolometer in this embodiment are described in detail below.

[0016] 1. Substrate having an adhesive layer on its surface The bolometer of this embodiment has a positively charged adhesive layer on a substrate.

[0017] (1-1) Adhesive layer The adhesive layer 3 is preferably a material that is positively charged at the pH of a mixed dispersion (or at least a dispersion of the negative thermal expansion material) containing semiconductor carbon nanotubes and a negative thermal expansion material used in the bolometer manufacturing method described later. The adhesive layer material is preferably a compound having both a substructure that bonds to or adheres to the substrate surface and a positively charged substructure. The adhesive layer functions as an intermediary to bond the substrate to the carbon nanotubes and the negatively thermally expanding material. Because the positively charged adhesive layer and the negatively charged carbon nanotubes and negatively thermally expanding material are attracted to each other by electrostatic interaction, the adhesion of the carbon nanotubes and negatively thermally expanding material to the substrate can be enhanced.

[0018] The substructures that bond to or adhere to the substrate surface in the adhesive layer material are not particularly limited, but examples include alkoxysilyl groups (SiOR), OHCl, hydrophobic moieties, or hydrophobic groups. Examples of hydrophobic moieties or hydrophobic groups include methylene groups (methylene chains) and alkyl groups, preferably having 1 or more carbon atoms, more preferably 2 or more, and preferably 20 or fewer, and more preferably 10 or fewer carbon atoms. Positively charged substructures in the adhesive layer material include, for example, amino groups such as primary amino groups (-NH2), secondary amino groups (-NHR1), and tertiary amino groups (-NR1R2), as well as ammonium groups (-NH4) and epoxy groups.

[0019] The material for such an adhesive layer is not particularly limited, but examples include silane coupling agents. Examples of silane coupling agents include: Silane coupling agents (aminosilane compounds) having an amino group and an alkoxysilyl group, 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 epoxy groups and alkoxysilyl groups, such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyldiethoxysilane, and triethoxy(3-glycidyloxypropyl)silane; These are some examples.

[0020] In particular, silane coupling agents (aminosilane compounds) having an amino group are preferred due to their good bonding properties with carbon nanotubes.

[0021] The shape of the adhesive layer is not limited; it may be formed over the entire substrate or in a desired shape to connect the electrodes.

[0022] (2-2) Circuit board The adhesive layer material described above can be appropriately selected considering the material of the substrate used. Here, the material constituting the substrate may be inorganic or organic, and any material used in the art can be used without particular limitation, but at least the element formation surface is preferably insulating and semiconducting. Examples of inorganic materials are not limited to glass, Si, Si coated with SiO2, SiO2, SiN, etc., and in this case, the silane coupling agent described above is preferred as the adhesive layer.

[0023] In this specification, the term "substrate" refers to any substrate on which a bolometer film is formed via an adhesive layer, and which supports the bolometer film and the adhesive layer. The "substrate" is not limited to a flat substrate such as a glass plate or a silicon wafer, but may have structures or a multilayer structure. Therefore, the bolometer of this embodiment is not limited to the form shown in Figure 1, but is also applicable to bolometers having a diaphragm structure or bolometers having any layer such as an insulating layer beneath the bolometer film. For example, in the case of a bolometer having a diaphragm structure, a diaphragm having gaps as an insulating structure is provided, and the adhesive layer and the bolometer film of this embodiment are provided on top of it. In this case, the entire substrate including the diaphragm can be considered as the "substrate". Also, in the case of a bolometer having an insulating layer beneath the bolometer film, the insulating layer and any other layers that may be formed on top of it as needed can be considered as the "substrate", and the adhesive layer and the bolometer film of this embodiment are provided on top of it.

[0024] 2. Bolometer film The bolometer film of this embodiment includes semiconductor carbon nanotubes and a negative thermal expansion material.

[0025] (2-1) Carbon nanotubes In this specification, the term "bolometer film" refers to a thin film composed of a plurality of carbon nanotubes and a negative thermal expansion material that forms a conductive path electrically connecting a first electrode and a second electrode. The plurality of carbon nanotubes may form structures such as parallel linear, fibrous, or network-like structures, but it is preferable that they form a three-dimensional network-like structure that is less prone to aggregation and provides a uniform conductive path. In one embodiment, it is also preferable that at least some of the carbon nanotubes are oriented.

[0026] Carbon nanotubes can be single-walled, double-walled, or multi-walled. However, when separating semiconducting carbon nanotubes, single-walled or multi-walled (e.g., two or three layers) carbon nanotubes are preferred, and single-walled carbon nanotubes are more preferred. The carbon nanotubes preferably contain 80% by mass or more of single-walled carbon nanotubes, and more preferably 90% by mass or more (including 100% by mass).

[0027] In one embodiment, it is preferable to use carbon nanotubes having a specific diameter and length. The diameter of carbon nanotubes is preferably between 0.6 and 1.5 nm, more preferably between 0.6 nm and 1.2 nm, and even more preferably between 0.7 and 1.1 nm, from the viewpoint of increasing the band gap and improving the TCR. In one embodiment, a diameter of 1 nm or less may be particularly preferable. If the diameter is 0.6 nm or greater, the production of carbon nanotubes is easier. If the diameter is 1.5 nm or less, it is easier to maintain the band gap within an appropriate range, and a high TCR can be obtained.

[0028] In this specification, the diameter of carbon nanotubes means that when the carbon nanotubes of a bolometer film are observed using an atomic force microscope (AFM) and the diameters are measured at approximately 100 locations, 60% or more, preferably 70% or more, sometimes more preferably 80% or more, and more preferably 100% are within the range of 0.6 to 1.5 nm. Preferably, 60% or more, preferably 70% or more, sometimes more preferably 80% or more, and more preferably 100% are within the range of 0.6 to 1.2 nm, and even more preferably within the range of 0.7 to 1.1 nm. In one embodiment, 60% or more, preferably 70% or more, sometimes more preferably 80% or more, and more preferably 100% are within the range of 0.6 to 1 nm. The radial breathing mode (RBM) of Raman spectroscopy can also be used to evaluate the diameter of single-walled carbon nanotubes.

[0029] Furthermore, a carbon nanotube length between 100 nm and 5 μm is more preferable because it disperses easily and has excellent coating properties. From the viewpoint of the conductivity of the carbon nanotube, a length of 100 nm or more is also preferable. Moreover, if the length is 5 μm or less, aggregation on the substrate or a predetermined substrate and / or during film formation is easily suppressed. The carbon nanotube length is more preferably 500 nm to 3 μm, and even more preferably 700 nm to 1.5 μm.

[0030] In this specification, the length of carbon nanotubes is measured by observing and counting at least 100 nanotubes using an atomic force microscope (AFM) to determine the distribution of carbon nanotube lengths, where 60% or more, preferably 70% or more, sometimes more preferably 80% or more, and more preferably 100% are in the range of 100 nm to 5 μm. Preferably, 60% or more, preferably 70% or more, sometimes more preferably 80% or more, and more preferably 100% are in the range of 500 nm to 3 μm. More preferably, 60% or more, preferably 70% or more, sometimes more preferably 80% or more, and more preferably 100% are in the range of 700 nm to 1.5 μm.

[0031] When the diameter and length of the carbon nanotube are within the above range, the effect of semiconductivity becomes greater, and a large current value can be obtained, making it easier to obtain a high TCR value when used in a bolometer.

[0032] It is preferable to use semiconductor carbon nanotubes with a large band gap and carrier mobility in the bolometer film. Therefore, the bolometer film of this embodiment contains semiconductor carbon nanotubes. The content of semiconductor carbon nanotubes, preferably semiconductor single-walled carbon nanotubes, in the carbon nanotubes is generally 67% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, particularly preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 99% by mass or more (including 100% by mass). In this specification, when the term "semiconductor-type carbon nanotubes" is used, it may also include metallic carbon nanotubes in addition to semiconductor-type carbon nanotubes, as long as the proportion of semiconductor-type carbon nanotubes is within the range described above.

[0033] Furthermore, in one embodiment, the bolometer comprises a substrate and a bolometer film containing semiconductor carbon nanotubes and a negative thermal expansion material, wherein a positively charged adhesive layer provided on the substrate and the negatively charged semiconductor carbon nanotubes and negative thermal expansion material in the bolometer film are electrostatically adsorbed, and it is also preferable that at least some of the semiconductor carbon nanotubes are oriented.

[0034] In this specification, the orientation of carbon nanotubes is defined using an image obtained by processing a two-dimensional fast Fourier transform (FFT image) of a planar scanning electron microscope (SEM) image of a carbon nanotube layer. For example, a planar FFT image is created by representing the distribution of surface irregularities in each direction as a frequency distribution by performing a two-dimensional fast Fourier transform on an SEM image of a bolometer film. In this FFT image, if the intensity of the FFT image shows a flattened ellipse with the horizontal axis as the major axis, it means that the carbon nanotubes are oriented in the vertical direction of the image, and the flatter this ellipse is, the higher the orientation. In this specification, the frequency of -1 μm is measured in one direction from the center of the FFT image. -1 From +1 μm -1 Let the sum of the amplitudes up to a certain point be the summation value f, and let the direction in which f is maximized be direction x, and the direction perpendicular to direction x be direction y. Then, in the FFT image, from the center in direction x, at a frequency of -1 μm -1 From +1 μm -1 fx is the sum of the amplitudes up to a certain point, and the frequency is -1 μm in the direction y from the center. -1 ~+1μm -1 The sum of the amplitudes up to a certain point is denoted as fy, and the degree of orientation is indicated by fx / fy. A larger value of fx / fy means a higher degree of orientation. In the FFT image, the horizontal direction corresponds to direction x. When at least a portion of the carbon nanotubes are oriented, it is preferable that fx / fy ≥ 2 in the FFT image of the bolometer film, and more preferable that fx / fy ≥ 2.4.

[0035] The SEM image that is the source of the above FFT image needs to show irregularities for calculation by Fourier transform. From the perspective of observing carbon nanotubes, the visual field range is preferably about 0.05 to 10 μm in both the vertical and horizontal directions.

[0036] The bolometer provided with the above bolometer film having high orientation shows a high TCR value and low resistance. When a plurality of carbon nanotubes are oriented in the same direction, the contact area between the nanotubes increases and the conductive paths increase. As a result, in addition to realizing a large resistance change with respect to temperature change, it is considered that the resistance becomes low.

[0037] (2-2) Negative thermal expansion material In this specification, the negative thermal expansion material means a material having a negative thermal expansion coefficient that shrinks as the temperature rises. Examples of the negative thermal expansion material include, for example, in any temperature range from -100 to +200 °C, for example, in the range from -100 to +100 °C, preferably in the temperature range of use of the bolometer, for example, at least in the range from -50 to 100 °C, the linear thermal expansion coefficient ΔL / L ((length after expansion - length before expansion) / length before expansion) per 1 K of temperature difference is preferably -1×10 -6 / K to -1×10 -3 / K, more preferably -1×10 -5 / K to -1×10 -3 / K. Examples of such materials include. The thermal expansion coefficient can be measured, for example, in accordance with JIS Z 2285 (Method for Measuring Linear Expansion Coefficient of Metallic Materials) or JIS R 1618 (Method for Measuring Thermal Expansion by Thermomechanical Analysis of Fine Ceramics).

[0038] In one embodiment, the negative thermal expansion material is preferably a material that exhibits sufficient negative thermal expansion in the use environment of the bolometer. Examples of the temperature of the use environment of the bolometer include, for example, -350 °C to 100 °C, preferably -40 °C to 80 °C, and in some cases more preferably 20 °C to 30 °C, for example, 21 °C to 30 °C. Furthermore, regarding the humidity of the bolometer's operating environment, for example, when the bolometer is used in a structure where the light-receiving part is open to the atmosphere, the ambient humidity may be used, and for example, 75% RH or less is preferred. When used in a structure where it is vacuum-packed or where an inert gas is concentrated inside the package, for example, 5% RH or less is preferred, but depending on the degree of vacuum, it may be outside the above range. However, from the viewpoint of the long-term stability of the device, lower humidity is preferable, so in all cases there is no particular lower limit, and it is 0% RH or higher, for example, greater than 0% RH.

[0039] Furthermore, the resistivity of the negative thermal expansion material is not particularly limited, but is 10 in any temperature range from -100 to +100°C, preferably at the operating temperature of the bolometer, for example, room temperature (approximately 23°C). -1 The resistance is Ωcm or greater, preferably 1.0Ωcm or greater, more preferably 10Ωcm or greater, and also 10 2 It may be preferable to set it to Ωcm or more, and also 10 8 Ωcm or less, preferably 10 7 Ωcm or less, more preferably 10 6 It may be less than Ωcm. Resistivity can be measured according to standard methods such as JIS K 7194 and JIS K 6911. In one embodiment, by using a negative thermal expansion material with higher resistance than semiconductor carbon nanotubes, conductive paths for semiconductor carbon nanotubes can be formed more efficiently.

[0040] In this specification, negative thermal expansion materials include, but are not limited to, oxides, nitrides, sulfides, or multi-element compounds containing one or more of the following elements: Li, Al, Fe, Ni, Co, Mn, Bi, La, Cu, Sn, Zn, V, Zr, Pb, Sm, Y, W, Si, P, Ru, Ti, Ge, Ca, Ga, Cr, and Cd. A mixture of two or more compounds may also be used. Examples of negative thermal expansion materials include, but are not limited to, vanadium oxide, β-eucryptite, bismuth nickel oxide, zirconium tungstate, ruthenium oxide, manganese nitride, lead titanate, samarium monosulfide, etc. (including those in which elements of these compounds are replaced with one or more of the above elements). For example, LiAlSiO4, ZrW2O8, Zr2WO4(PO4)2, BiNi 1-x Fe x O3 (0.05 ≤ x ≤ 0.5), for example, BiNi 0.85 Fe 0.15 O3, Bi 0.95 La 0.05 NiO3, Pb 0.76 La 0.04 Bi 0.20 VO3, Sm 0.78 Y 0.22 S, Cu 1.8 Zn 0.2 V2O7, Cu2V2O7, 0.4PbTiO3-0.6BiFeO3, MnCo 0.98 Cr 0.02 Ge, Ca2RuO 3.74 Mn3Ga 0.7 Ge 0.3 N 0.88 C 0.12 , Cd(CN)2·xCCl4, LaFe 10.5 Co 1.0 Si 1.5 Ca2RuO4, Mn x Sn y Zn z N(3≦x≦4, 0.1≦y≦0.5, 0.1≦z≦0.8), for example Mn 3.27 Zn 0.45 Sn 0.28 N, Mn3Ga 0.9 Sn 0.1 N 0.9 Mn3ZnN is suitable.

[0041] In one embodiment, among negative thermal expansion materials, oxides, nitrides, and sulfides are preferred from the viewpoint of ease of synthesis and availability. Furthermore, in one embodiment, the carbon nanotubes forming the bolometer film and the negative thermal expansion material can be linked by molecular chains. In particular, using an oxide as the negative thermal expansion material has the advantage of good bonding with the surface functional groups (-COOH, -OH, etc.) of the carbon nanotubes, thereby suppressing structural degradation due to temperature cycling, reducing hysteresis during temperature rise and fall of the bolometer film, and improving durability. In one embodiment, materials with high stability in the manufacturing process are preferred, such as oxides with low solubility in water.

[0042] In this specification, the size of the negative thermal expansion material can be selected as appropriate. Preferably, it is 10 nm to 100 μm, more preferably 15 nm to 10 μm, even more preferably 20 nm to 5 μm, and particularly preferably 1 μm or less. Furthermore, the form of the negative thermal expansion material is not particularly limited, but examples include spherical, needle-shaped, rod-shaped, plate-shaped, fibrous, and flaky shapes, and from the viewpoint of film formation, a spherical shape is preferred.

[0043] Furthermore, in one embodiment, the TCR value and structure can be controlled by combining the magnitude of the thermal expansion coefficient and the presence or absence of anisotropy in the negative thermal expansion material.

[0044] (2-3) Bolometer film The bolometer film of this embodiment includes the above-mentioned carbon nanotubes and negative thermal expansion material. The carbon nanotube content in the bolometer film can be appropriately selected, but preferably, 0.1% by mass or more is effective based on the total mass of the bolometer film, more preferably 1% by mass or more is effective, for example, 30% by mass, and even more preferably 50% by mass or more, and in some cases 60% by mass or more is preferable. The content of the negative thermal expansion material in the bolometer film can be selected as appropriate, but is preferably 1 to 99% by mass, more preferably 1 to 70% by mass, for example 1 to 50% by mass, and in some cases preferably 10 to 50% by mass, and may also be 40% by mass or less.

[0045] In this specification, the thickness of the bolometer film is not particularly limited, but is, for example, 1 nm or more, for example, several nm to 100 μm, preferably 10 nm to 10 μm, and more preferably 50 nm to 1 μm. In one embodiment, it is preferably in the range of 20 nm to 500 nm, and more preferably 50 nm to 200 nm. A good light absorption rate can be obtained when the thickness of the bolometer film is 1 nm or more. Furthermore, if the thickness of the bolometer film is 10 nm or more, preferably 50 nm or more, a sufficient light absorption rate can be obtained without providing a light reflection layer or light absorption structure / light absorption layer, thus simplifying the device structure. Furthermore, a thickness of 1 μm or less, preferably 500 nm or less, of the bolometer film is preferable from the viewpoint of simplifying the manufacturing method. Also, if the bolometer film is too thick, the contact electrode deposited on top may not make sufficient contact with the carbon nanotubes below the bolometer film, which may result in a higher effective resistance value. However, within the above range, the increase in resistance value can be suppressed. Furthermore, if a light-absorbing layer or the like is provided, the thickness of the bolometer film may be made thinner than the above range to further simplify the manufacturing process and improve the resistance value. Furthermore, if the thickness of the bolometer film is within the range of 10 nm to 1 μm as described above, it is preferable because the manufacturing method described later can be suitably applied as a method for manufacturing the bolometer film.

[0046] The thickness of the bolometer film can be determined as the average of the thicknesses measured at any 10 points on the bolometer film.

[0047] Furthermore, the density of the bolometer film is, for example, 0.3 g / cm³. 3 Preferably 0.8 g / cm³ 3 More preferably 1.1 g / cm³ 3 That's all. The density of the bolometer film is 0.3 g / cm³. 3 With these conditions met, a good light absorption rate can be obtained. Furthermore, the density of the bolometer film is 0.5 g / cm³. 3 The above is preferable because it allows for sufficient light absorption without the need for light-reflecting or light-absorbing layers, and simplifies the device structure. Furthermore, if a light-absorbing layer is provided, a density lower than the above may be appropriately selected as the density of the bolometer film.

[0048] The density of the bolometer film can be calculated from its weight, area, and the thickness determined above.

[0049] In addition to carbon nanotubes and negative thermal expansion materials, the bolometer film may optionally contain other components, such as ionic conductive agents (surfactants, ammonium salts, inorganic salts), resins, and binders described later. In this case, the total mass of carbon nanotubes and negative thermal expansion materials is preferably 70% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on the mass of the bolometer film.

[0050] 3. Electrode In the bolometer of this embodiment, the first and second electrodes on the substrate can be made using, for example, gold, platinum, or titanium, either individually or in combination. The thickness can be adjusted as appropriate, but is preferably 10 nm to 1 mm, and more preferably 50 nm to 1 μm. The distance between electrodes is preferably 1 μm to 500 μm, and more preferably 5 to 200 μm for miniaturization. If the distance is 5 μm or more, even if it contains a small amount of metallic carbon nanotubes, for example, the deterioration of the TCR characteristics can be suppressed. If the distance is 500 μm or less, it is advantageous for application as an image sensor using a two-dimensional array. The electrodes may be formed on the upper side of the bolometer film or on the lower side of the bolometer film.

[0051] 4. Other components In addition to the above, the bolometer of this embodiment may include any other components used in a bolometer. For example, a protective film can be provided on the surface of the bolometer film if necessary. The protective film is preferably made of a material that is highly transparent in the optical wavelength range to be detected. Examples of materials for the protective film include acrylic resins such as PMMA and PMMA anisole, epoxy resins, Teflon®, silicon nitride, and silicon oxide (SiO2). Furthermore, a light-absorbing layer may be provided on the upper side (the side into which light is incident) of the bolometer film, if necessary. Examples of light-absorbing layers provided on the protective layer include, but are not limited to, a thin film of titanium nitride, and examples of light-absorbing layers provided on the bolometer film include, but are not limited to, a coated film of polyimide.

[0052] The bolometer of this embodiment detects temperature by utilizing the temperature dependence of electrical resistance upon light irradiation. Therefore, even in other frequency ranges, if the temperature changes due to light irradiation, it can be used to detect desired electromagnetic waves. The bolometer of this embodiment, which uses a bolometer film containing carbon nanotubes and a negative thermal expansion material, is particularly suitable for detecting electromagnetic waves having wavelengths of 0.7 μm to 1 mm. Electromagnetic waves included in this wavelength range include infrared rays and terahertz waves. The bolometer of this embodiment is preferably an infrared sensor. Furthermore, detecting changes in electrical resistance due to temperature changes can be done not only with the structure shown in Figure 1, but also by amplifying the resistance change by making it a field-effect transistor by adding a gate electrode. Furthermore, the bolometer of this embodiment can be applied without particular limitation to element structures commonly used in bolometers, including not only the structure shown in Figure 1, but also elements having a diaphragm structure, elements having a desired heat insulating structure instead of a diaphragm structure, and other such elements.

[0053] The bolometer in this embodiment may be a single element, or it may be an array of multiple elements arranged in two dimensions, such as those used in image sensors.

[0054] [Method of manufacturing a bolometer] One aspect of the present invention relates to a method for manufacturing a bolometer in which a positively charged adhesive layer provided on a substrate is electrostatically bonded to negatively charged semiconductor carbon nanotubes and a negative thermal expansion material in a bolometer film.

[0055] The method for manufacturing the bolometer of this embodiment is: A step of preparing dispersions of semiconductor carbon nanotubes and negative thermal expansion materials, comprising the steps of preparing a carbon nanotube dispersion containing semiconductor carbon nanotubes, a surfactant, and an aqueous dispersion medium, and a negative thermal expansion material dispersion containing a negative thermal expansion material and an aqueous dispersion medium, either as individual dispersions or as mixed dispersions thereof. A step of adjusting the pH of the individual dispersions or mixed dispersions to a predetermined pH, thereby negatively charging the semiconductor carbon nanotubes and the negative thermal expansion material. A step of providing a pH-adjusted dispersion onto a substrate, wherein the individual dispersions or mixed dispersions are provided onto a substrate having an adhesive layer whose surface is positively charged at a pH of 5 to 9, thereby causing negatively charged semiconductor carbon nanotubes and negative thermal expansion materials to be adsorbed onto the adhesive layer by electrostatic interaction. The process of removing excess surfactant and aqueous dispersion medium from the substrate to form a bolometer film of the desired form. This relates to a method for manufacturing a bolometer, including the invention of a bolometer.

[0056] Furthermore, the method for manufacturing a bolometer according to one embodiment is: A step of preparing dispersions of semiconductor carbon nanotubes and negative thermal expansion materials, comprising the steps of preparing a carbon nanotube dispersion containing semiconductor carbon nanotubes, a surfactant, and an aqueous dispersion medium, and a negative thermal expansion material dispersion containing a negative thermal expansion material and an aqueous dispersion medium, either as individual dispersions or as mixed dispersions thereof. A step of adjusting the pH of the negative thermal expansion material dispersion and optionally the carbon nanotube dispersion, or the mixed dispersion, to be above the isoelectric point of the negative thermal expansion material, thereby negatively charging at least the negative thermal expansion material. A step of providing a pH-adjusted dispersion onto a substrate, comprising: providing the negative thermal expansion material dispersion and / or carbon nanotube dispersion or mixed dispersion onto a substrate having an adhesive layer whose surface is positively charged at the pH of the negative thermal expansion material dispersion or mixed dispersion, thereby adsorbing the negatively charged negative thermal expansion material onto the adhesive layer by electrostatic interaction; The process of removing excess surfactant and aqueous dispersion medium from the substrate to form a bolometer film of the desired form. This relates to a method for manufacturing a bolometer, including the invention of a bolometer.

[0057] The method for manufacturing a bolometer according to this embodiment is characterized by including a step of adjusting the pH of a dispersion containing semiconductor carbon nanotubes and a negative thermal expansion material used to produce a bolometer film to a pH at which the semiconductor carbon nanotubes and the negative thermal expansion material in the dispersion, or at least the negative thermal expansion material, become negatively charged. When a dispersion with the pH adjusted in this manner is applied to a substrate on which a positively charged adhesive layer has been formed on its surface, the negatively charged semiconductor carbon nanotubes and negative thermal expansion material, or at least the negative thermal expansion material, in the dispersion are electrostatically adsorbed to the positively charged adhesive layer. This increases the adhesion and amount of the semiconductor carbon nanotubes and negative thermal expansion material to the substrate, suppresses delamination from the substrate, and enables the achievement of a high TCR.

[0058] The following describes in detail an example of the manufacturing method of the bolometer according to this embodiment.

[0059] 1. Manufacturing method using a mixed dispersion containing carbon nanotubes and a negative thermal expansion material 1-1. Steps for preparing a mixed dispersion containing carbon nanotubes and a negative thermal expansion material. A mixed dispersion containing carbon nanotubes and a negative thermal expansion material is prepared. An example of the preparation method is described below. (1-1) Preparation of carbon nanotube dispersion Carbon nanotubes can be those described in the section on [Bolometer] above. Carbon nanotubes may be used that have been heat-treated in a vacuum under an inert atmosphere to remove surface functional groups, amorphous carbon, and other impurities, as well as catalysts. The heat treatment temperature can be selected as appropriate, but 800 to 2000°C is preferred, and 800 to 1200°C is more preferred.

[0060] A surfactant can be used to prepare the carbon nanotube dispersion. A nonionic surfactant is preferred. Nonionic surfactants can be selected as appropriate, but it is preferable to use one or more nonionic surfactants that consist of a non-ionizable hydrophilic part and a hydrophobic part such as an alkyl chain, such as nonionic surfactants having a polyethylene glycol structure represented by polyoxyethylene alkyl ethers or alkyl glucoside nonionic surfactants. As such a nonionic surfactant, polyoxyethylene alkyl ether represented by formula (1) is preferably used. The alkyl part may also contain one or more unsaturated bonds.

[0061] C n H 2n+1 (OCH2CH2) m OH (1) (In the formula, n is preferably 12 to 18, and m is preferably 10 to 100, and preferably 20 to 100.)

[0062] In particular, nonionic surfactants defined as polyoxyethylene(n) alkyl ethers (n is between 20 and 100, alkyl chain length is between C12 and 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. Also, N,N-bis[3-(D-gluconamido)propyl]deoxycholamide, n-dodecyl β-D-maltoside, octyl β-D-glucopyranoside, and digitonin can be used.

[0063] As a nonionic surfactant, polyoxyethylene sorbitan monostearate (molecular formula: C 64 H 126 O 26 Product name: Tween 60, manufactured by Sigma-Aldrich, etc.), polyoxyethylene sorbitan trioleate (molecular formula: C 24 H 44 O6, trade name: Tween 85, manufactured by Sigma-Aldrich, etc.), octylphenol ethoxylate (molecular formula: C 14 H 22 O(C2H4O) n n=1~10, product name: Triton X-100, manufactured by Sigma-Aldrich, etc.), polyoxyethylene (40) isooctylphenyl ether (molecular formula: C8H 17 C6H 40 (CH2CH 20 ) 40 H, product name: Triton X-405, manufactured by Sigma-Aldrich, etc.), poloxamer (molecular formula: C5H 10 O2 (product name: Pluronic, manufactured by Sigma-Aldrich, etc.), polyvinylpyrrolidone (molecular formula: (C6H9NO) n You can also use (e.g., n=5~100, manufactured by Sigma-Aldrich, etc.).

[0064] Such nonionic surfactants have weak interactions with carbon nanotubes, making them easy to remove after the dispersion is applied. Therefore, a stable carbon nanotube conductive network can be formed, and an excellent TCR value can be obtained.

[0065] Furthermore, it is also preferable to use a nonionic surfactant with a long molecular length. By using a nonionic surfactant with a long molecular length, the distance between carbon nanotubes increases when the dispersion is applied, which can suppress re-aggregation during electrode fabrication.

[0066] The method for obtaining a carbon nanotube dispersion is not particularly limited, and conventionally known methods can be applied. For example, a solution containing carbon nanotubes can be prepared by mixing a carbon nanotube mixture, a dispersion medium, and a nonionic surfactant, and the carbon nanotubes can be dispersed by sonication of this solution to 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 the carbon nanotubes during the separation process, and can be used for example, water, heavy water, organic solvents, ionic liquids, or mixtures thereof, but water and heavy water are preferred. In addition to or instead of the sonication, a carbon nanotube dispersion method using mechanical shear force may be used. Mechanical shearing may be performed in the gas phase. In the micelle dispersion aqueous solution of carbon nanotubes and a nonionic surfactant, it is preferable that the carbon nanotubes are in an isolated state. Therefore, if necessary, bundles, amorphous carbon, impurity catalysts, etc., may be removed by ultracentrifugation. During the dispersion process, the carbon nanotubes can be cut, and their length can be controlled by changing the grinding conditions of the carbon nanotubes, ultrasonic output, ultrasonic treatment time, etc. For example, untreated carbon nanotubes can be crushed with tweezers, a ball mill, etc., to control the aggregate size. After these treatments, the length can be controlled to 100 nm to 5 μm by using an ultrasonic homogenizer with an output of 40 to 600 W, sometimes 100 to 550 W, at 20 to 100 KHz, and a processing time of 1 to 5 hours, preferably up to 3 hours. If the processing time is shorter than 1 hour, under certain conditions, the nanotubes may not disperse at all and may remain almost the same length as before. Furthermore, from the viewpoint of shortening the dispersion processing time and reducing costs, 3 hours or less is preferable. This embodiment also has the advantage that the slicing can be easily adjusted by using a nonionic surfactant. In addition, the bolometer of carbon nanotubes according to this embodiment, when using a nonionic surfactant, has the advantage that it does not contain ionic surfactants, which are difficult to remove.

[0067] Dispersion and scission of carbon nanotubes generate surface functional groups on the surface or edges of the carbon nanotubes. The functional groups generated include carboxyl groups, carbonyl groups, and hydroxyl groups. In liquid-phase processing, carboxyl groups and hydroxyl groups are generated, while in gas-phase processing, carbonyl groups are generated. The presence of these surface functional groups can improve bonding with oxides when oxides are used as negative thermal expansion materials. Furthermore, it can enhance the bonding between carbon nanotubes via compounds containing amino groups, and can also exert an anchoring effect on the substrate. This can suppress structural degradation due to temperature cycling in bolometers.

[0068] Furthermore, the concentration of the surfactant in the liquid containing heavy water or water and a nonionic surfactant is preferably ~10% by mass, and more preferably ~3% by mass. A concentration below the critical micelle concentration is undesirable because dispersion is not possible. Also, if it is 10% by mass or less, carbon nanotubes of sufficient density can be coated after separation while reducing the amount of surfactant. In this specification, critical micelle concentration (CMC) refers to the concentration at which the inflection point occurs when the surface tension is measured by changing the concentration of the surfactant aqueous solution using a surface tension meter such as a Wilhelmy surface tension meter at a constant temperature. In this specification, "critical micelle concentration" is the value at atmospheric pressure and 25°C.

[0069] The concentration of carbon nanotubes in the above cutting and dispersion process (weight of carbon nanotubes / (total weight of carbon nanotubes, dispersion medium and surfactant) × 100) is not particularly limited, but can be, for example, 0.0003 to 10% by mass, preferably 0.001 to 3% by mass, and more preferably 0.003 to 0.3% by mass.

[0070] The dispersion obtained through the above-described cutting and dispersion process may be used directly in the separation process described later, or it may be subjected to processes such as concentration and dilution before the separation process.

[0071] Carbon nanotubes can be separated, for example, by field-induced layer formation (ELF method: see, for example, K. Ihara et al. J.Phys.Chem.C.2011, 115, 22827~22832, Japanese Patent No. 5717233; these documents 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 nonionic surfactant, and the dispersion is placed in a vertical separation device. By applying a voltage to electrodes positioned above and below, separation is performed by carrier-free electrophoresis. The separation mechanism can be estimated as follows: When carbon nanotubes are dispersed in a nonionic surfactant, the micelles of semiconductor-type carbon nanotubes have a negative zeta potential, while the micelles of metallic-type carbon nanotubes have a zeta potential with the opposite sign (positive) (recently, it has also been thought that they have a slightly negative zeta potential or are hardly charged at all). Therefore, when an electric field is applied to a carbon nanotube dispersion, conductive carbon nanotube micelles electrophoretically move toward the anode (+) and metallic carbon nanotube micelles electrophoretically move toward the cathode (-) due to differences in zeta potential, etc. Ultimately, a layer concentrated with semiconductor carbon nanotubes is formed near the anode, and a layer concentrated with metallic carbon nanotubes is formed near the cathode in the separation tank. The separation voltage can be appropriately set considering the composition of the dispersion medium and the charge amount of the carbon nanotubes, but 1V to 200V is preferable, and 10V to 200V is more preferable. From the viewpoint of shortening the separation process time, 100V or higher is preferable. Also, from the viewpoint of suppressing the generation of bubbles during separation and maintaining separation efficiency, 200V or lower is preferable. Purity can be improved by repeating the separation. The dispersion after separation may be reset to its initial concentration and the same separation operation may be performed. This will further increase the purity.

[0072] The above-described carbon nanotube dispersion, cleavage, and separation steps allow for the production of a dispersion containing concentrated semiconductor carbon nanotubes having a desired diameter and length. In this specification, the carbon nanotube dispersion containing concentrated semiconductor carbon nanotubes may be referred to as a "semiconductor carbon nanotube dispersion." The semiconductor carbon nanotube dispersion obtained by the separation step generally contains 67% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, particularly 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 semiconductor carbon nanotubes in the total amount of carbon nanotubes. The separation tendency of metallic and semiconductor carbon nanotubes can be analyzed by micro-Raman spectroscopy and ultraviolet-visible near-infrared spectrophotometric analysis.

[0073] After the carbon nanotube dispersion and cleavage steps described above, and before the separation steps, centrifugation may be performed to remove bundles, amorphous carbon, metal impurities, etc., from the carbon nanotube dispersion. The centrifugal acceleration can be adjusted as appropriate, but 10,000 × g to 500,000 × g is preferred, 50,000 × g to 300,000 × g is more preferred, and in some cases 100,000 × g to 300,000 × g may be used. The centrifugation time is preferably 0.5 hours to 12 hours, and more preferably 1 to 3 hours. The centrifugation temperature can be adjusted as appropriate, but 4°C to room temperature is preferred, and more preferably 10°C to room temperature.

[0074] The concentration of the surfactant in the carbon nanotube dispersion after separation can be controlled as appropriate. The concentration of the surfactant in the carbon nanotube dispersion is preferably around 5% by mass, the critical micelle concentration, more preferably 0.001% to 3% by mass, and particularly preferably 0.01% to 1% by mass to suppress re-aggregation after coating.

[0075] (1-2) Preparation of a mixed dispersion containing carbon nanotubes and a negative thermal expansion material By mixing a negative thermal expansion material with the dispersion containing semiconductor carbon nanotubes obtained through the above process, a mixed dispersion containing semiconductor carbon nanotubes and a negative thermal expansion material can be obtained. The mixing ratio of semiconductor carbon nanotubes and negative thermal expansion material in the dispersion can be appropriately selected, but preferably, based on the total mass of semiconductor carbon nanotubes and negative thermal expansion material, the semiconductor carbon nanotubes are 0.01% to 99% by mass, more preferably 0.1% to 90% by mass, and it is also preferable to have 30% or more by mass, and even more preferably 50% to 85% by mass.

[0076] When mixing the negative thermal expansion material into the semiconductor carbon nanotube dispersion obtained by the above process, binders can also be added. Adding a binder makes it easier to adjust the viscosity and makes coating easier. Furthermore, it prevents aggregation and sedimentation of the semiconductor carbon nanotubes and negative thermal expansion material after coating, making it easy to produce a uniform coated film. The type of binder can be selected as appropriate, but examples include polyvinylidene fluoride, acrylic resins, styrene-butadiene rubber, imide resins, imidoamide resins, polytetrafluoroethylene resins, polyamic acid, vinylidene fluoride-hexafluoropropylene, vinylidene fluoride-tetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamideimide, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, (meth)acrylonitrile, isoprene rubber, butadiene rubber, and fluororubber. Two or more binders may be mixed and used. When a binder is used, its content is not particularly limited, but for example, it is more than 0% by mass, preferably 0.01% by mass or more, for example 0.1% by mass or more and 30% by mass or less, preferably 10% by mass or less, and preferably 5% by mass or less, based on the total mass of the semiconductor carbon nanotubes and the negative thermal expansion material.

[0077] 1-2. Steps to adjust the pH of a mixed dispersion containing carbon nanotubes and a negative thermal expansion material. Next, the pH of the mixed dispersion containing carbon nanotubes and the negative thermal expansion material is adjusted. pH adjustment can be done by adding a pH adjusting agent to the mixed dispersion. The pH adjusting agent is not particularly limited, but examples include hydrochloric acid, sodium hydroxide, and ammonia. Alternatively, a buffer solution with adjusted pH may be used.

[0078] When a mixed dispersion containing carbon nanotubes and a negatively thermally expanding material contains a surfactant, the carbon nanotubes and the negatively thermally expanding material each form micelles. In this case, the pH of the dispersion should be adjusted so that the charge (zeta potential) on the surface of the micelles of the carbon nanotubes and the negatively thermally expanding material becomes negatively charged. When carbon nanotubes and negative thermal expansion materials become negatively charged, electrostatic adsorption occurs between them and the positively charged adhesive layer on the substrate surface, thereby improving the adhesion of carbon nanotubes and negative thermal expansion materials to the substrate. Furthermore, by charging the surfaces of carbon nanotubes and negative thermal expansion materials, aggregation of carbon nanotubes and negative thermal expansion materials can be suppressed, thereby improving their dispersibility in a mixed dispersion.

[0079] The pH of the dispersion is preferably 5.0 or higher, more preferably 6 or higher, even more preferably 7 or higher, even more preferably above 7.0, and particularly preferably 7.5 or higher. A pH of 5.0 or higher is preferable because it does not repel the adhesive layer on the substrate surface. Furthermore, the pH of the mixed dispersion is preferably 9.0 or lower, and more preferably 8.5 or lower. A pH of 9.0 or lower is preferable because it does not repel the adhesive layer on the substrate surface.

[0080] Furthermore, since negative thermal expansion materials have different isoelectric points depending on the compound, the pH of the mixed dispersion can be adjusted to a pH exceeding the isoelectric point of the negative thermal expansion material used, thereby negatively charging the negative thermal expansion material (micelles of the negative thermal expansion material and surfactant) in the mixed dispersion. This causes the positively charged adhesive layer on the substrate surface and the negatively charged negative thermal expansion material to be electrostatically attracted to each other, suppressing the detachment of the negative thermal expansion material during the manufacturing process and during use.

[0081] 1-3. Process of preparing a substrate having an adhesive layer on its surface. A substrate having the aforementioned adhesive layer on its surface is prepared as the substrate. The method for forming the adhesive layer on the substrate is not particularly limited, but for example, the substrate can be immersed in a solution of the compound used for the adhesive layer as described in the [Bolometer] section above, or the solution can be sprayed or applied to the substrate and then dried to form an adhesive layer over the entire substrate. Also, when forming the adhesive layer in the shape of a desired bolometer film, the areas other than the area where the bolometer film is to be formed may be masked in advance with tape or resist before forming the adhesive layer.

[0082] 1-4. Step of providing a mixed dispersion containing carbon nanotubes and a negative thermal expansion material onto a substrate. (4-1) In one embodiment, by applying a pH-adjusted mixed dispersion containing semiconductor carbon nanotubes and a negative thermal expansion material obtained by the above-described process onto a substrate, the negatively charged semiconductor carbon nanotubes and the negative thermal expansion material (or at least the negative thermal expansion material) can be adsorbed onto the adhesive layer by electrostatic interaction.

[0083] The method for coating a mixed dispersion containing semiconductor carbon nanotubes and a negative thermal expansion material onto a substrate is not particularly limited and includes methods such as dropping, spin coating, printing, inkjet, spray coating, and dip coating.

[0084] For example, as shown in Figure 4, a mixed dispersion 8 containing negatively charged semiconductor carbon nanotube micelles and negative thermal expansion material micelles is dropped onto a substrate 1 having a positively charged adhesive layer 3.

[0085] (4-2) In another embodiment, as shown in Figure 5, a liquid-liquid interface 10 is formed between two phases: a pH-adjusted mixed dispersion 8 containing semiconductor carbon nanotubes and a negative thermal expansion material obtained by the above-described process, and an organic solvent 9 having a higher density than the dispersion medium of the mixed dispersion and being insoluble in the dispersion medium. At this time, since the micelles of carbon nanotubes cannot be dispersed in the organic solvent phase 9, it is considered that the carbon nanotubes exist in the mixed dispersion phase 8 near the liquid-liquid interface 10 in a state approximately parallel to the interface, as shown in Figure 5. Therefore, by pulling up the substrate 1 having the adhesive layer 3 on its surface from below the liquid-liquid interface 10 (moving the substrate from the organic solvent phase to the mixed dispersion phase), the negatively charged semiconductor carbon nanotubes and negative thermal expansion material near the liquid-liquid interface in the mixed dispersion can be adsorbed onto the adhesive layer by electrostatic interaction, while orienting the semiconductor carbon nanotubes approximately parallel to the liquid-liquid interface (i.e., approximately perpendicular to the direction in which the substrate is pulled up). Methods for forming a two-phase system consisting of a pH-adjusted mixed dispersion and an organic solvent include, but are not limited to, methods such as dropping the mixed dispersion onto an organic solvent in a desired container, or injecting the organic solvent into the bottom of the mixed dispersion in a desired container.

[0086] Examples of organic solvents that have a higher density than the aqueous dispersion medium and are almost insoluble in the aqueous dispersion medium include trichloroethane, 1,1,2-trichloroethane, tetrachloromethane, and tetrachloroethylene.

[0087] The conditions for lifting the substrate with an adhesive layer on its surface from the liquid-liquid interface are not limited, but from the viewpoint of increasing the degree of orientation, the lifting speed is preferably 1 μm / sec to 100 μm / sec, and more preferably 0.01 μm / sec to 1 μm / sec. Furthermore, the angle is preferably such that the direction in which the substrate is lifted is approximately perpendicular to the liquid surface. Regarding humidity, it is preferably 60% or less, and more preferably 40% or less.

[0088] The method for lifting the substrate from below the two-phase liquid-liquid interface is not particularly limited as long as it allows the substrate to be moved at a desired angle and constant speed relative to the liquid-liquid interface. For example, as shown in Figure 6, a method using a dip coater or the like can be used.

[0089] Carbon nanotubes are adsorbed onto the adhesive layer while oriented approximately parallel to the liquid-liquid interface (i.e., approximately perpendicular to the direction in which the substrate is pulled up). Therefore, it is preferable to pull up the substrate in such a way that the direction in which the substrate is pulled up from below the liquid-liquid interface is approximately perpendicular to the direction in which the current flows. In this specification, when referring to the orientation of carbon nanotubes or the orientation of the substrate as substantially parallel or substantially perpendicular (approximately perpendicular), it includes angles of ±30° or less, preferably 20° or less, more preferably ±10° or less, for example, ±5° or less, from perfect parallelism or perpendicularity. In the case of a curve, it is preferable that the angle at the point where it deviates most significantly from perfect parallelism or perpendicularity is within the above range.

[0090] 1-5. Steps to remove dispersion medium, etc., from the substrate and deposit a bolometer film. The process involves providing a mixed dispersion containing semiconductor-type carbon nanotubes and a negative thermal expansion material onto a substrate having an adhesive layer, followed by a step to remove the aqueous dispersion medium, surfactant, organic solvent, pH adjuster, etc., from the substrate. This allows for the formation of a bolometer film on the substrate. One method of removal is heat treatment. The temperature of the heat treatment can be set appropriately above the decomposition temperature of the surfactant, but 150 to 500°C is preferred, and 180 to 500°C, for example 180 to 400°C, is more preferred. A temperature of 150°C or higher is more preferable because it makes it easier to suppress the residue of surfactant decomposition products. Furthermore, a temperature of 500°C or lower, for example 400°C or lower, is preferable because it can suppress the deterioration of the substrate and other components. In addition, it can suppress the decomposition, size change, and detachment of functional groups of carbon nanotubes. Furthermore, if impurities such as pH adjusting agents used to adjust the pH of the mixed dispersion remain, washing and drying processes may be performed after the bolometer film has been formed.

[0091] 1-6. Process for forming electrodes Electrodes are formed to connect to the bolometer film either before or after the bolometer film is formed. The method for fabricating the electrodes is not particularly limited, but examples include vapor deposition, sputtering, and printing. The electrodes may be formed on the substrate before forming the bolometer film, or they may be fabricated after the bolometer film has been formed by the above process.

[0092] After forming the bolometer film using the above process, steps such as forming a protective film on the bolometer film and removing excess carbon nanotubes from the substrate may be performed.

[0093] An example of a method for manufacturing the bolometer of this embodiment will be described with reference to Figures 7A and 7B. A silicon substrate coated with SiO2 is used as substrate 1. These substrates are sequentially washed with acetone, isopropyl alcohol, and water, and then organic matter on the surface is removed by oxygen plasma treatment. Next, the substrate is immersed in an aqueous solution of 3-aminopropyltriethoxysilane (APTES) and dried to form an adhesive layer 3. A mixed dispersion 8 is prepared by dispersing semiconductor carbon nanotubes 6 and a negative thermal expansion material (an oxide composed of bismuth, nickel, and iron) 5 in a nonionic surfactant solution of polyoxyethylene (100) stearyl ether. A pH adjuster (sodium hydroxide solution) is added to adjust the pH to 7-9. An organic solvent, trichloroethane 9, is prepared in a container, and the substrate 1 with the adhesive layer 3 formed on its surface is immersed in it. The mixed dispersion 8 is dropped onto it, forming a liquid-liquid interface 10 between the two phases, the organic solvent phase 9 and the mixed dispersion phase 8. Using a dip coater or the like, the substrate 1 is pulled up from below the liquid-liquid interface 10 at a speed of 1 μm / second so that the substrate 1 is perpendicular to the liquid-liquid interface 10 (Figure 7A). Subsequently, the substrate is dried and fired at over 180°C in air to remove nonionic surfactants, organic solvents, etc. These operations form a bolometer film 4 on the substrate 1 (Figure 7A, right). Then, by vapor deposition or coating, the first electrode and second electrode 2 are fabricated on the bolometer film 4 formed on the substrate at intervals of 50 μm, such that the orientation direction of the carbon nanotubes is approximately parallel to the direction of current flow (Figure 7B). An acrylic resin (PMMA) solution is applied to the region between the electrodes on the formed bolometer film 4 to form a PMMA protective layer. After this, the entire substrate is treated with oxygen plasma to remove excess carbon nanotubes, etc., in areas other than the bolometer film 4. Excess solvents, impurities, etc. are removed by heating at over 200°C in air.

[0094] 2. Manufacturing method using carbon nanotube dispersion and negative thermal expansion material dispersion separately. The above describes a manufacturing method using a mixed dispersion containing both carbon nanotubes and a negative thermal expansion material (hereinafter also simply referred to as "manufacturing method using a mixed dispersion"). However, a dispersion containing carbon nanotubes (carbon nanotube dispersion) and a dispersion containing a negative thermal expansion material (negative thermal expansion material dispersion) may be used as separate dispersions, and the carbon nanotubes and the negative thermal expansion material may be adsorbed separately onto the substrate. For steps not described below, the steps described in the above-mentioned manufacturing method using the mixed dispersion can be used as appropriate.

[0095] 2-1. Steps for preparing a dispersion containing carbon nanotubes and a dispersion containing a negative thermal expansion material. (1-1) Preparation of carbon nanotube dispersion A carbon nanotube dispersion can be prepared as a dispersion of carbon nanotube micelles using a desired surfactant and an aqueous dispersion medium, similar to the method described in the manufacturing method using the mixed dispersion described above.

[0096] (1-2) Preparation of a dispersion of negatively thermally expanding material The method for preparing the negative thermal expansion material dispersion is not particularly limited, but it can be prepared by mixing the negative thermal expansion material with a desired aqueous dispersion medium, such as the one used for the carbon nanotube dispersion. Furthermore, in negative thermal expansion material dispersions, it is not always necessary to micellize the negative thermal expansion material. Therefore, the negative thermal expansion material dispersion does not need to contain a surfactant, and in this case, the amount of surfactant residue on the substrate can be reduced. The concentration of the negative thermal expansion material in the negative thermal expansion material dispersion is not particularly limited, but can be, for example, 0.001 to 90% by mass, preferably 0.01 to 10% by mass, and more preferably 0.1 to 1% by mass.

[0097] 2-2. Steps to adjust the pH of the carbon nanotube dispersion and the negative thermal expansion material dispersion. Next, by adjusting the pH of the carbon nanotube dispersion and the negative thermal expansion material dispersion to a range of pH 5 to pH 9, the carbon nanotubes (micelles) and negative thermal expansion material in both dispersions are negatively charged. This improves adhesion to the positively charged adhesive layer on the substrate surface and enhances the dispersibility of the carbon nanotubes and negative thermal expansion material in the dispersion.

[0098] In another embodiment, the pH of the negative thermal expansion material dispersion may be adjusted to a pH that exceeds the isoelectric point of the negative thermal expansion material used. This makes the negative thermal expansion material negatively charged, thereby improving its adhesion to the positively charged adhesive layer on the substrate surface. Although the negative thermal expansion material is not necessarily micellized in the dispersion, charging the negative thermal expansion material causes repulsion between the negative thermal expansion materials, thereby improving the dispersibility of the negative thermal expansion material in the dispersion. In one embodiment, it is also preferable to adjust the pH of the carbon nanotube dispersion in the same manner to negatively charge the carbon nanotubes in the dispersion.

[0099] The pH of the carbon nanotube dispersion and the negative thermal expansion material dispersion can be adjusted in the same manner as described in the manufacturing method using the mixed dispersion described above.

[0100] 2-3. Process of preparing a substrate having an adhesive layer on its surface. A substrate having an adhesive layer on its surface can be the same as that described in the manufacturing method using the mixed dispersion described above.

[0101] 2-4. Steps for providing a carbon nanotube dispersion and a negative thermal expansion material dispersion onto a substrate. (4-1) In one embodiment, by applying the pH-adjusted carbon nanotube dispersion and negative thermal expansion material dispersion obtained by the above-described process onto a substrate, the negatively charged carbon nanotubes and negative thermal expansion material (or at least the negative thermal expansion material) can be adsorbed onto the adhesive layer by electrostatic interaction. In this case, a carbon nanotube dispersion may be first applied to the substrate, and if necessary, washing and drying may be performed to adsorb the carbon nanotubes onto the substrate. Then, a negative thermal expansion material dispersion may be applied to the substrate to adsorb the negative thermal expansion material. In this case, at least a portion of the negative thermal expansion material applied later will enter the network of carbon nanotubes adsorbed on the substrate, forming a composite material (CNT nanocomposite) of carbon nanotubes and negative thermal expansion material. Alternatively, a negative thermal expansion material dispersion may be applied to the substrate first, followed by washing and drying as needed to allow the negative thermal expansion material to adsorb onto the substrate. Then, a carbon nanotube dispersion may be applied to the substrate to allow the carbon nanotubes to adsorb. In this case as well, at least some of the carbon nanotubes applied later will penetrate between the negative thermal expansion materials adsorbed on the substrate, forming a composite material of carbon nanotubes and negative thermal expansion material (CNT nanocomposite).

[0102] (4-2) In another embodiment, when providing a carbon nanotube dispersion onto a substrate, a liquid-liquid interface may be formed between the pH-adjusted carbon nanotube dispersion obtained by the above-described process and an organic solvent that has a higher density than the dispersion medium and does not dissolve in the dispersion medium, in the same manner as described in the manufacturing method using the mixed dispersion above. The substrate may then be lifted from below this liquid-liquid interface. This allows negatively charged carbon nanotubes near the liquid-liquid interface in the carbon nanotube dispersion to be adsorbed onto the adhesive layer while being oriented substantially parallel to the liquid-liquid interface. Before adsorbing carbon nanotubes onto the substrate using the method described above, the negative thermal expansion material may be adsorbed onto the substrate beforehand, or the negative thermal expansion material may be adsorbed after the carbon nanotubes have been adsorbed onto the substrate. The negative thermal expansion material can be adsorbed by any method; for example, as described in (4-1), a dispersion of the negative thermal expansion material may be applied to the substrate. Alternatively, as described in (4-2), a two-phase system consisting of a dispersion of the negative thermal expansion material and an organic solvent may be formed, and the negative thermal expansion material may be adsorbed onto the substrate by pulling up the substrate from below the liquid-liquid interface between the two phases.

[0103] 2-5. Steps to remove dispersion medium, etc., from the substrate and deposit a bolometer film. After providing a carbon nanotube dispersion and a negative thermal expansion material dispersion onto a substrate having an adhesive layer, a step can be performed to remove the aqueous dispersion medium, surfactant, organic solvent, pH adjuster, etc. from the substrate. This allows a bolometer film to be formed on the substrate. These methods can be carried out in the same manner as described in the manufacturing method using the mixed dispersion described above.

[0104] 2-6. Process for forming electrodes Before or after forming the bolometer film, electrodes are formed to connect to the bolometer film. The electrodes can be formed in the same manner as described in the manufacturing method using the mixed dispersion described above.

[0105] Note Some or all of the above embodiments may also be described as follows, but are not limited to the following: (Note 1) circuit board and A bolometer film containing semiconductor carbon nanotubes and a negative thermal expansion material A bolometer that includes, A bolometer in which a positively charged adhesive layer provided on a substrate is electrostatically adsorbed to negatively charged semiconductor carbon nanotubes and negative thermal expansion material in a bolometer film. (Note 2) A bolometer as described in Appendix 1, wherein at least a portion of the semiconductor carbon nanotubes in the bolometer film are oriented. (Note 3) A bolometer as described in Appendix 1 or 2, wherein the adhesive layer is a layer of aminosilane compound. (Note 4) A bolometer according to any one of the appendices 1 to 3, wherein the negative thermal expansion material is an oxide, nitride, sulfide, multi-element compound, or mixture thereof, containing one or more elements selected from the group consisting of Fe, Ni, Co, Mn, Bi, La, Cu, Sn, Zn, V, Zr, Pb, Sm, Y, W, P, Ru, Ti, Ge, Ca, Ga, Cr, and Cd. (Note 5) A bolometer as described in any one of the appendices 1 to 4, wherein the proportion of semiconductor carbon nanotubes is 90% by mass or more of the total mass of carbon nanotubes in the bolometer film. (Note 6) The bolometer according to any one of the appendices 1 to 5, wherein the semiconductor carbon nanotube has a diameter in the range of 0.6 to 1.5 nm and a length in the range of 100 nm to 5 μm. (Note 7) A bolometer as described in any one of the appendices 1 to 6, wherein the negative thermal expansion material is an oxide. (Note 8) The linear thermal expansion ΔL / L ((length after expansion - length before expansion) / length before expansion) per 1K of a negative thermal expansion material is -1 × 10 in the temperature range of -100 to +100°C. -6 ~-1 × 10 -3 A bolometer within the range of / K, as described in any one of the appendices 1 to 7. (Note 9) The resistivity of the negative thermal expansion material is 10 in the temperature range of -100 to +100°C. -1 Ωcm~10 8 A bolometer in the range of Ωcm, as described in one of the appendices 1 to 8. (Note 10) A method for manufacturing a bolometer, A step of preparing dispersions of semiconductor carbon nanotubes and negative thermal expansion materials, comprising the steps of preparing a carbon nanotube dispersion containing semiconductor carbon nanotubes, a surfactant, and an aqueous dispersion medium, and a negative thermal expansion material dispersion containing a negative thermal expansion material and an aqueous dispersion medium, either as individual dispersions or as mixed dispersions thereof. The process involves adjusting the pH of each individual dispersion or mixed dispersion to a pH of 5 or higher and 9 or lower, thereby negatively charging the semiconductor carbon nanotubes and the negative thermal expansion material. A step of providing a pH-adjusted dispersion onto a substrate, wherein the individual dispersions or mixed dispersions are provided onto a substrate having an adhesive layer whose surface is positively charged at a pH of 5 to 9, thereby causing negatively charged semiconductor carbon nanotubes and negative thermal expansion materials to be adsorbed onto the adhesive layer by electrostatic interaction. The process of removing excess surfactant and aqueous dispersion medium from the substrate to form a bolometer film of the desired form. A method for manufacturing a bolometer, including (Note 11) The process for preparing a dispersion of semiconductor carbon nanotubes and a negative thermal expansion material includes the step of mixing semiconductor carbon nanotubes, a negative thermal expansion material, and a surfactant with an aqueous dispersion medium to prepare a mixed dispersion. The method for manufacturing a bolometer according to Appendix 10, wherein the step of providing a pH-adjusted dispersion onto a substrate includes the step of coating the mixed dispersion onto the substrate. (Note 12) The process for preparing a dispersion of semiconductor carbon nanotubes and a negative thermal expansion material includes the step of mixing semiconductor carbon nanotubes, a negative thermal expansion material, and a surfactant with an aqueous dispersion medium to prepare a mixed dispersion. The process of providing a pH-adjusted dispersion onto a substrate is - A step of forming a two-phase system consisting of the mixed dispersion and an organic solvent having a higher density than the aqueous dispersion medium and being insoluble in the aqueous dispersion medium, - A step of lifting a substrate having an adhesive layer whose surface is positively charged at a pH of 5 to 9 from below the liquid-liquid interface formed between the two phases, The method for manufacturing a bolometer as described in Appendix 10. (Note 13) The process for preparing dispersions of semiconductor-type carbon nanotubes and negative thermal expansion materials includes the process of preparing a carbon nanotube dispersion containing semiconductor-type carbon nanotubes, a surfactant, and an aqueous dispersion medium, and a negative thermal expansion material dispersion containing a negative thermal expansion material and an aqueous dispersion medium, as individual dispersions, and The process of providing a pH-adjusted dispersion onto a substrate is - A step of coating a carbon nanotube dispersion onto a substrate, - A step of applying a negative thermal expansion material dispersion onto a substrate before or after a step of applying a carbon nanotube dispersion onto a substrate, The method for manufacturing a bolometer as described in Appendix 10. (Note 14) The process for preparing dispersions of semiconductor-type carbon nanotubes and negative thermal expansion materials includes the process of preparing a carbon nanotube dispersion containing carbon nanotubes, a surfactant, and an aqueous dispersion medium, and a negative thermal expansion material dispersion containing a negative thermal expansion material and an aqueous dispersion medium, as individual dispersions, and The process of providing a pH-adjusted dispersion onto a substrate is - A step of forming a two-phase system consisting of a carbon nanotube dispersion and an organic solvent having a higher density than the aqueous dispersion medium of the carbon nanotube dispersion and being insoluble in the aqueous dispersion medium, and - A step of lifting a substrate having an adhesive layer whose surface is positively charged at a pH of 5 to 9 from below the liquid-liquid interface formed between the two phases, and - A step of providing a negative thermal expansion material dispersion onto the substrate before or after the step of lifting the substrate from below the liquid-liquid interface formed between the two phases. A method for manufacturing a bolometer as described in Appendix 10, including the method described in Appendix 10. (Note 15) A method for manufacturing a bolometer, A step of preparing dispersions of semiconductor carbon nanotubes and negative thermal expansion materials, comprising the steps of preparing a carbon nanotube dispersion containing semiconductor carbon nanotubes, a surfactant, and an aqueous dispersion medium, and a negative thermal expansion material dispersion containing a negative thermal expansion material and an aqueous dispersion medium, either as individual dispersions or as mixed dispersions thereof. A step of adjusting the pH of the negative thermal expansion material dispersion and optionally the carbon nanotube dispersion, or the mixed dispersion, to be above the isoelectric point of the negative thermal expansion material, thereby negatively charging at least the negative thermal expansion material. A step of providing a pH-adjusted dispersion onto a substrate, comprising: providing the negative thermal expansion material dispersion and / or carbon nanotube dispersion or mixed dispersion onto a substrate having an adhesive layer whose surface is positively charged at the pH of the negative thermal expansion material dispersion or mixed dispersion, thereby adsorbing the negatively charged negative thermal expansion material onto the adhesive layer by electrostatic interaction; The process of removing excess surfactant and aqueous dispersion medium from the substrate to form a bolometer film of the desired form. A method for manufacturing a bolometer, including (Note 16) The process for preparing a dispersion of semiconductor carbon nanotubes and a negative thermal expansion material includes the step of mixing semiconductor carbon nanotubes, a negative thermal expansion material, and a surfactant with an aqueous dispersion medium to prepare a mixed dispersion. The method for manufacturing a bolometer according to Appendix 15, wherein the step of providing a pH-adjusted dispersion onto a substrate includes the step of coating the mixed dispersion onto the substrate. (Note 17) The process for preparing a dispersion of semiconductor carbon nanotubes and a negative thermal expansion material includes the step of mixing semiconductor carbon nanotubes, a negative thermal expansion material, and a surfactant with an aqueous dispersion medium to prepare a mixed dispersion. The process of providing a pH-adjusted dispersion onto a substrate is - A step of forming a two-phase system consisting of the mixed dispersion and an organic solvent having a higher density than the aqueous dispersion medium and being insoluble in the aqueous dispersion medium, A method for manufacturing a bolometer according to Appendix 15, comprising the step of pulling up a substrate having an adhesive layer whose surface is positively charged at the pH of the mixed dispersion from below the liquid-liquid interface formed between the two phases. (Note 18) The process for preparing dispersions of semiconductor-type carbon nanotubes and negative thermal expansion materials includes the process of preparing a carbon nanotube dispersion containing semiconductor-type carbon nanotubes, a surfactant, and an aqueous dispersion medium, and a negative thermal expansion material dispersion containing a negative thermal expansion material and an aqueous dispersion medium, as individual dispersions, and The process of providing a pH-adjusted dispersion onto a substrate is - A step of coating a carbon nanotube dispersion onto a substrate, - A step of applying a negative thermal expansion material dispersion onto a substrate before or after a step of applying a carbon nanotube dispersion onto a substrate, The method for manufacturing a bolometer as described in Appendix 15. (Note 19) The process for preparing dispersions of semiconductor-type carbon nanotubes and negative thermal expansion materials includes the process of preparing a carbon nanotube dispersion containing carbon nanotubes, a surfactant, and an aqueous dispersion medium, and a negative thermal expansion material dispersion containing a negative thermal expansion material and an aqueous dispersion medium, as individual dispersions, and The process of providing a pH-adjusted dispersion onto a substrate is - A step of forming a two-phase system consisting of a carbon nanotube dispersion and an organic solvent having a higher density than the aqueous dispersion medium of the carbon nanotube dispersion and being insoluble in the aqueous dispersion medium, and - A step of lifting a substrate having an adhesive layer whose surface is positively charged at the pH of the negative thermal expansion material dispersion from below the liquid-liquid interface formed between the two phases, and - A step of providing a negative thermal expansion material dispersion onto the substrate before or after the step of lifting the substrate from below the liquid-liquid interface formed between the two phases. A method for manufacturing a bolometer as described in Appendix 15, including the method described in Appendix 15. (Note 20) A method for producing a bolometer according to any one of the appendices 12, 14, 17, and 19, wherein the organic solvent that does not dissolve in the aqueous dispersion medium is selected from the group consisting of trichloroethane, 1,1,2-trichloroethane, tetrachloromethane, and tetrachloroethylene. (Note 21) A method for manufacturing a bolometer according to any one of appendices 12, 14, 17, and 19, comprising pulling up a substrate having an adhesive layer whose surface is positively charged from below the liquid-liquid interface at a speed of 1 μm / second to 100 μm / second. [Examples]

[0106] The present invention will be further illustrated and described in detail below, illustrating the examples provided. Of course, the invention is not limited by these examples.

[0107] (Example 1) (Process 1) 100 mg of single-walled carbon nanotubes (Meijo Nanocarbon Co., Ltd., EC1.0 (diameter: approximately 1.1-1.5 nm (average diameter 1.2 nm)) were placed in a quartz boat and inserted into an electric furnace. The furnace was heat-treated at 900°C for 2 hours under a vacuum atmosphere. After heat treatment, the weight was 80 mg, after removal of surface functional groups and impurities. 12 mg of the obtained single-walled carbon nanotubes were immersed in 40 ml of a 1 wt% aqueous solution of a surfactant (polyoxyethylene (100) stearyl ether), and ultrasonic dispersion treatment (BRANSON ADVANCD-DIGITAL SONIFIER (output: 50W)) was performed for 3 hours. As a result, no carbon nanotube aggregates were found in the solution. The obtained solution was subjected to ultracentrifugation at 50,000 rpm, 10°C, and 60 minutes. This procedure removed bundles and residual catalysts, yielding a carbon nanotube dispersion.

[0108] (Process 2) A carbon nanotube dispersion was diluted threefold and introduced into a separation apparatus, where semiconductor-type carbon nanotubes were extracted using the ELF method. Analysis of these nanotubes using optical absorption spectroscopy revealed that the metallic-type carbon nanotube components had been removed. Furthermore, Raman spectroscopy showed that 99 wt% were semiconductor-type carbon nanotubes.

[0109] (Step 3) A negative thermal expansion material (BiNi) is added to a dispersion of semiconductor-type carbon nanotubes. 0.85 Fe 0.15O3 (thermal expansion coefficient: -180 ppm / K, resistivity: 10 Ωcm, size: 100-500 nm, shape: spherical) was mixed so that semiconductor carbon nanotubes accounted for 70% by weight. A dispersion of semiconductor carbon nanotubes and negative thermal expansion material was prepared by ultrasonic treatment. Sodium hydroxide was added to the obtained dispersion as a pH adjuster to adjust the pH of the dispersion to approximately 8.

[0110] (Step 4) A substrate was prepared by coating a silicon substrate with a 100 nm thick SiO2 film. After washing the substrate, it was immersed in a 0.1% APTES aqueous solution for 30 minutes to form an adhesive layer over the entire surface of the substrate (1.6 cm × 1.6 cm). After rinsing with water, it was dried at 105°C. 100 μl of a pH-adjusted dispersion containing semiconductor carbon nanotubes and a negative thermal expansion material was dropped onto the resulting substrate and dried at 110°C. It was heated at 200°C in air to remove nonionic surfactants, etc. Then, gold was deposited to a thickness of 50 nm at two locations on the substrate with a 100 μm gap. Next, a PMMA anisole solution was applied between the electrodes to protect the carbon nanotubes between the electrodes, and then excess carbon nanotubes near the electrodes were removed by oxygen plasma treatment. Finally, it was dried at 200°C for 1 hour to fabricate an infrared sensor. Furthermore, observations using AFM revealed that at least 70% of the carbon nanotubes had diameters ranging from 0.9 to 1.5 nm and lengths ranging from 700 nm to 1.5 μm.

[0111] (evaluation) The change in resistance of the infrared sensor fabricated in step 4 was measured when its temperature was varied from 20°C to 40°C. The result showed that the TCR value (dR / RdT) was approximately -10.9% / K at 300K. At this time, the current at 3V was approximately 10 -7 It was A.

[0112] (Example 2) A liquid-liquid interface was formed by placing trichloroethane and the semiconductor carbon nanotube / negative thermal expansion material dispersion from steps 1-3 of Example 1 into a beaker. A substrate with the adhesive layer prepared in step 4 of Example 1 was pulled up perpendicular to the liquid-liquid interface at a speed of 1 μm / second from the trichloroethane side, thereby adsorbing the semiconductor CNTs and negative thermal expansion material present near the liquid-liquid interface. It was then dried at 110°C. It was heated at 200°C in air to remove nonionic surfactants, etc. Then, gold was deposited to a thickness of 50 nm at two locations on the substrate with a spacing of 100 μm. Next, a PMMA anisole solution was applied between the electrodes to protect the carbon nanotubes between the electrodes, and then excess carbon nanotubes, etc. near the electrodes were removed by oxygen plasma treatment. It was then dried at 200°C for 1 hour to prepare an infrared sensor. When the obtained bolometer film was observed with AFM, the carbon nanotubes were more oriented than those prepared in step 4. The change in resistance was measured when the temperature of the fabricated infrared sensor was varied from 20°C to 40°C. As a result, the TCR value (dR / RdT) was approximately -11.1% / K at 300K. At this time, the current at 3V increased by 40% compared to Example 1, and the resistance decreased.

[0113] (Comparative Example 1) An infrared sensor was fabricated in the same manner as in Example 1, except that the pH of the semiconductor carbon nanotube / negative thermal expansion material dispersion was not adjusted (the pH of the dispersion was approximately 7). The TCR value was measured in the same manner as in Example 1 and was approximately -9.2% / K.

[0114] (Comparative Example 2) An infrared sensor was fabricated in the same manner as in Example 2, except that the pH of the semiconductor carbon nanotube / negative thermal expansion material dispersion was not adjusted (the pH of the dispersion was approximately 7). The TCR value was measured in the same manner as in Example 1 and was approximately -9.3% / K.

[0115] In Examples 1 and 2, adjusting the pH of the dispersion caused the carbon nanotube micelles and negative thermal expansion material micelles to become negatively charged and adsorb to the APTES adhesive layer, which is positively charged at that pH, improving the retention capacity and adsorption force of the carbon nanotubes and negative thermal expansion material. As a result, higher TCR was achieved in each case compared to Comparative Examples 1 and 2. Furthermore, as shown in Figure 8 (SEM images of infrared sensors prepared in Example 1 (pH 8) and Comparative Example 1 (pH 7)), adjusting the pH, for example from pH 7 to 8, improves the adsorption force and reduces the peeling of the negative thermal expansion material.

[0116] Furthermore, in Example 2, a lower resistance value was obtained compared to Example 1 because at least a portion of the carbon nanotubes were oriented.

[0117] Although the present invention has been described above with reference to embodiments and examples, the present invention is not limited to the above embodiments and examples. Various modifications to the configuration and details of the present invention can be understood by those skilled in the art within the scope of the present invention. [Explanation of symbols]

[0118] 1 circuit board 2 electrodes 3 Adhesive layer 4. Bolometer film 5. Materials with negative thermal expansion 6. Carbon nanotubes 7. Direction of infrared radiation incidence 8. Mixed dispersion containing carbon nanotube micelles and negative thermal expansion material micelles. 9. Insoluble organic solvents in aqueous dispersions 10 Liquid-liquid interface 11 Direction for lifting the substrate 12 Infrared detection device

Claims

1. circuit board and A bolometer film containing semiconductor carbon nanotubes and a negative thermal expansion material A bolometer that includes, A bolometer in which a positively charged adhesive layer provided on a substrate is electrostatically adsorbed to negatively charged semiconductor carbon nanotubes and negative thermal expansion material in a bolometer film.

2. The bolometer according to claim 1, wherein at least a portion of the semiconductor carbon nanotubes in the bolometer film are oriented.

3. The bolometer according to claim 1 or 2, wherein the adhesive layer is a layer of aminosilane compound.

4. A bolometer according to any one of claims 1 to 3, wherein the proportion of semiconductor carbon nanotubes is 90% by mass or more of the total mass of carbon nanotubes in the bolometer film.

5. A method for manufacturing a bolometer, A step of preparing dispersions of semiconductor carbon nanotubes and negative thermal expansion materials, comprising the steps of preparing a carbon nanotube dispersion containing semiconductor carbon nanotubes, a surfactant, and an aqueous dispersion medium, and a negative thermal expansion material dispersion containing a negative thermal expansion material and an aqueous dispersion medium, either as individual dispersions or as mixed dispersions thereof. The process involves adjusting the pH of each individual dispersion or mixed dispersion to a pH of 5 or higher and 9 or lower, thereby negatively charging the semiconductor carbon nanotubes and the negative thermal expansion material. A step of providing a pH-adjusted dispersion onto a substrate, wherein the individual dispersions or mixed dispersions are provided onto a substrate having an adhesive layer whose surface is positively charged at a pH of 5 to 9, thereby causing negatively charged semiconductor carbon nanotubes and negative thermal expansion materials to be adsorbed onto the adhesive layer by electrostatic interaction. The process of removing excess surfactant and aqueous dispersion medium from the substrate to form a bolometer film of the desired form. A method for manufacturing a bolometer, including

6. The process for preparing a dispersion of semiconductor carbon nanotubes and a negative thermal expansion material includes the step of mixing semiconductor carbon nanotubes, a negative thermal expansion material, and a surfactant with an aqueous dispersion medium to prepare a mixed dispersion. The method for manufacturing a bolometer according to claim 5, wherein the step of providing a pH-adjusted dispersion onto a substrate includes the step of coating the mixed dispersion onto the substrate.

7. The process for preparing a dispersion of semiconductor carbon nanotubes and a negative thermal expansion material includes the step of mixing semiconductor carbon nanotubes, a negative thermal expansion material, and a surfactant with an aqueous dispersion medium to prepare a mixed dispersion. The process of providing a pH-adjusted dispersion onto a substrate is - A step of forming a two phase consisting of the mixed dispersion and an organic solvent having a higher density than the aqueous dispersion medium and being insoluble in the aqueous dispersion medium, - A step of lifting a substrate having an adhesive layer whose surface is positively charged at a pH of 5 to 9 from below the liquid-liquid interface formed between the two phases, The method for manufacturing a bolometer according to claim 5.

8. A method for manufacturing a bolometer, A step of preparing dispersions of semiconductor carbon nanotubes and negative thermal expansion materials, comprising the steps of preparing a carbon nanotube dispersion containing semiconductor carbon nanotubes, a surfactant, and an aqueous dispersion medium, and a negative thermal expansion material dispersion containing a negative thermal expansion material and an aqueous dispersion medium, either as individual dispersions or as mixed dispersions thereof. A step of adjusting the pH of the negative thermal expansion material dispersion and optionally the carbon nanotube dispersion, or the mixed dispersion, to be above the isoelectric point of the negative thermal expansion material, thereby negatively charging at least the negative thermal expansion material. A step of providing a pH-adjusted dispersion onto a substrate, comprising: providing the negative thermal expansion material dispersion and / or carbon nanotube dispersion or mixed dispersion onto a substrate having an adhesive layer whose surface is positively charged at the pH of the negative thermal expansion material dispersion or mixed dispersion, thereby adsorbing the negatively charged negative thermal expansion material onto the adhesive layer by electrostatic interaction; The process of removing excess surfactant and aqueous dispersion medium from the substrate to form a bolometer film of the desired form. A method for manufacturing a bolometer, including

9. The process for preparing a dispersion of semiconductor carbon nanotubes and a negative thermal expansion material includes the step of mixing semiconductor carbon nanotubes, a negative thermal expansion material, and a surfactant with an aqueous dispersion medium to prepare a mixed dispersion. The method for manufacturing a bolometer according to claim 8, wherein the step of providing a pH-adjusted dispersion onto a substrate includes the step of coating the mixed dispersion onto the substrate.

10. The process for preparing a dispersion of semiconductor carbon nanotubes and a negative thermal expansion material includes the step of mixing semiconductor carbon nanotubes, a negative thermal expansion material, and a surfactant with an aqueous dispersion medium to prepare a mixed dispersion. The process of providing a pH-adjusted dispersion onto a substrate is - A step of forming a two phase consisting of the mixed dispersion and an organic solvent having a higher density than the aqueous dispersion medium and being insoluble in the aqueous dispersion medium, A method for manufacturing a bolometer according to claim 8, comprising the step of pulling up a substrate having an adhesive layer whose surface is positively charged at the pH of the mixed dispersion from below the liquid-liquid interface formed between the two phases.

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