Composite and method for producing composite

Abstract

A composite which includes a base material and a carbon nanotube forest, wherein the carbon nanotube forest is provided on the base material without interposing any of a catalyst layer and an adhesive layer therebetween.

Description

Composite and Method for Producing the Composite Cross - Reference to Related Applications

[0001] This application claims priority based on Japanese Patent Application No. 2024 - 227678 filed on December 24, 2024, and incorporates by reference all the descriptions set forth in the Japanese application.

[0002] This disclosure relates to a composite and a method for producing the composite.

[0003] For example, by chemical vapor deposition (CVD method), a carbon nanotube forest can be grown on a catalyst substrate. Also, it is known that a carbon nanotube forest can be transferred from a catalyst substrate onto a support having adhesiveness (for example, Patent Document 1).

[0004] Japanese Patent Publication No. 2018 - 524255

[0005] An object of this disclosure is to provide a novel composite including a base material and a carbon nanotube forest and a method for producing the same.

[0006] One aspect of the composite of this disclosure includes a base material and a carbon nanotube forest, and the carbon nanotube forest is provided on the base material without any intervening catalyst layer and adhesive layer. One aspect of the method for producing the composite of this disclosure includes a first step of preparing a base material, a catalyst substrate, and a CNT growth substrate provided with a carbon nanotube (CNT) forest on the catalyst substrate, and a second step of transferring the CNT forest onto the base material by pressure to form a composite in which the CNT forest is provided on the base material without any intervening catalyst layer and adhesive layer.

[0007] According to this disclosure, a novel composite including a base material and a carbon nanotube forest and a method for producing the same can be provided.

[0008] FIG. 1A is a schematic diagram for explaining a method for producing a composite. FIG. 1B is a schematic diagram for explaining a method for producing a composite. FIG. 1C is a schematic diagram for explaining a method for producing a composite.

[0009] An example of an embodiment of this disclosure will be described in detail below with reference to the drawings. Note that, for convenience, the drawings used in the following description may show enlarged versions of key features to make the features of this disclosure easier to understand. Therefore, the dimensional ratios of each component may differ from those of the actual components.

[0010] In this specification, the numerical range A to B means A or greater and B or less. In this specification, if the units of the numbers before and after the "~" indicating a numerical range are the same, the unit of the number before the "~" may be omitted. Throughout this specification, singular expressions should be understood to include the concept of their plural form unless otherwise specified. Therefore, singular articles (for example, "a," "an," and "the" in English) should be understood to include the concept of their plural form unless otherwise specified. Furthermore, terms used in this specification should be understood to be used in the sense commonly used in the field unless otherwise specified. The upper and / or lower limits of numerical ranges described in this specification can be arbitrarily combined to define a preferred range. For example, the upper and lower limits of numerical ranges can be arbitrarily combined to define a preferred range, the upper limits of numerical ranges can be arbitrarily combined to define a preferred range, and the lower limits of numerical ranges can be arbitrarily combined to define a preferred range.

[0011] In the following description, the terms "film" and "sheet" are not clearly distinguished, and the term "film" includes "sheet," and vice versa. In this specification, "parallel" includes not only strictly parallel but also approximately parallel. For parallel lines, the angle between them may be, for example, 30° or less, 20° or less, 10° or less, or 5° or less. In this specification, "perpendicular" includes not only strictly perpendicular but also approximately perpendicular. For perpendicular lines, the angle between them may be, for example, 60° or more and 90° or less, 70° or more and 90° or less, 80° or more and 90° or less, or 85° or more and 90° or less.

[0012] Hereafter, carbon nanotubes will also be referred to as "CNT," fibers composed of carbon nanotubes will also be referred to as "CNT fibers," a web of carbon nanotubes will also be referred to as "CNT web," and a film of carbon nanotubes will also be referred to as "CNT film."

[0013] [Composite] The composite of the present disclosure comprises a substrate and a carbon nanotube forest (CNT forest).

[0014] <Substrate> The composite of the present disclosure comprises a substrate. Examples of the substrate's shape include a plate, a polyhedron, a polygonal prism, a polygonal pyramidal shape, and a frustoconical shape. Examples of the polyhedron shape include a cube and a rectangular parallelepiped. Examples of the polygonal prism shape include a triangular prism and a square prism. Examples of the polygonal pyramidal shape include a triangular pyramidal shape and a square pyramidal shape. Examples of the frustoconical shape include a square frustoconical shape.

[0015] The base material may have a flat portion, or it may have both a flat portion and a curved portion. Examples of base material shapes having both a flat portion and a curved portion include conical and cylindrical shapes.

[0016] In the composite manufacturing method described later, the substrate is preferably in the form of a plate or polyhedron, and more preferably a plate, from the viewpoint of being able to uniformly pressurize the planar portion of the substrate. Examples of plate-shaped substrates include solid substrates, specifically semiconductor substrates, metal substrates, ceramic substrates, resin substrates, carbon substrates, paper substrates, diamond substrates, and glass substrates.

[0017] Examples of semiconductor materials used in semiconductor substrates include silicon, gallium nitride, and silicon carbide. Examples of metallic materials used in metal substrates include copper, aluminum, magnesium, titanium, nickel, iron, molybdenum, tungsten, and alloys thereof. Examples of ceramic materials used in ceramic substrates include metal oxides. Examples of metal oxides include magnesium oxide, zinc oxide, alumina, titania, and zirconia. Other ceramic materials include silicon carbide, silicon nitride, boron nitride, aluminum nitride, and barium titanate.

[0018] The surface of the metal substrate may be oxidized. On an oxidized surface, the metallic material exists as a metal oxide.

[0019] Examples of resin materials used in resin substrates include epoxy resins, phenolic resins, polyamide resins, polyimide resins, polyolefin resins, polystyrene resins, polycarbonate resins, polymethyl methacrylate resins, polyethylene terephthalate resins, polyethersulfone resins, cellulose ester resins, benzocyclobutene resins, vinyl chloride resins, and acrylic resins. Examples of carbon materials used in carbon substrates include graphene and graphite.

[0020] Examples of glass used for glass substrates include quartz glass, barium borosilicate glass, aluminoborosilicate glass, and soda-lime glass.

[0021] The solid substrate may have its surface coated with a coating material. Examples of coating materials include semiconductors, metals, resins, carbon, glass, and ceramics. Examples of semiconductors, metals, resins, carbon, glass, and ceramics include those similar to those used for semiconductor substrates, metal substrates, resin substrates, carbon substrates, glass substrates, and ceramic substrates. The coating material and the material used for the substrate coated with the coating material may be the same or different.

[0022] The substrate is preferably a solid substrate, such as a semiconductor substrate, metal substrate, ceramic substrate, carbon substrate, or resin substrate, from the viewpoint of being able to uniformly transfer the CNT forest to the substrate and having pressure resistance. Furthermore, when the composite is used for heat dissipation purposes, it is preferable that the solid substrate be a carbon substrate. Using a carbon substrate tends to achieve higher thermal conductivity. The semiconductor substrate is preferably a silicon substrate. The metal substrate is preferably a copper substrate or a stainless steel substrate. The resin substrate is preferably an epoxy resin substrate. The substrate may be made of one material or two or more materials.

[0023] The substrate may be, for example, a film or a sheet. The substrate may or may not be flexible. From the viewpoint of uniformly transferring the CNT forest to the substrate, the substrate is preferably not flexible.

[0024] There are no particular restrictions on the thickness of the substrate, but for example, it may be 1 μm to 100 mm, 10 μm to 50 mm, or 100 μm to 10 mm. There are no particular restrictions on the width and length of the substrate, but for example, it may be 1 mm to 100 m, 1 cm to 100 cm, or 10 cm to 50 cm.

[0025] The substrate may consist of two or more solid substrates stacked on top of each other, or two or more solid substrates arranged on the same plane.

[0026] The surface of the substrate that is in contact with the CNT forest is preferably smooth, from the viewpoint of enabling uniform transfer of the CNT forest to the substrate. For example, the ten-point average roughness Rz of the substrate surface in contact with the CNT forest, measured in accordance with JIS B0601 (1976), is preferably 0.1 to 200 μm, more preferably 0.5 to 150 μm, and even more preferably 1 to 100 μm.

[0027] The ten-point average roughness Rz can be calculated, for example, by measuring the surface roughness of a substrate using a surface roughness and shape measuring instrument, Surfcom 1400D, manufactured by Tokyo Seimitsu Co., Ltd., under the conditions of measurement length: 12.5 mm, measurement speed: 0.15 mm / s, and cutoff wavelength: 0.8 mm.

[0028] The above composite does not have an adhesive layer on the surface of the substrate facing the CNT forest. Examples of adhesive layers include layers formed with adhesives such as rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, and polyvinyl ether-based adhesives.

[0029] The composite may comprise two or more substrates; for example, it may comprise two substrates so as to sandwich the CNT forest described later. If the composite comprises two or more substrates, it is sufficient that the CNT forest is provided on at least one substrate (it is sufficient that the CNT forest is directly fixed by at least one substrate), and the CNT forest may or may not be directly fixed by the other substrates.

[0030] <Carbon Nanotube Forest> The composite of the present disclosure comprises a CNT forest. The composite is obtained, for example, by transferring a CNT forest provided on a catalyst substrate (described later) onto the substrate, particularly onto a planar portion of the substrate. A CNT forest refers to an aggregate of multiple CNTs oriented in one direction. In the composite, the CNT forest is provided on the substrate, particularly on a planar portion of the substrate. The multiple CNTs constituting the CNT forest are oriented perpendicular to the surface of the substrate and stand in a forest-like manner on the substrate. In the above composite, the CNT forest is provided on the substrate without the interposition of either a catalyst layer or an adhesive layer. That is, the above composite does not have either a catalyst layer or an adhesive layer between the substrate and the CNT forest. The CNT forest is provided, for example, on one surface of the substrate. Being provided on the substrate means that it is in contact with the substrate surface and fixed to the substrate surface. In other words, being provided on the substrate means that it is in contact with the substrate surface and adheres to the substrate surface without the interposition of an adhesive layer.

[0031] The CNT forest provided on the catalyst substrate, as described later, is adhered to the support via a catalyst layer (and buffer layer), whereas the CNT forest in the composite described above is adhered to the substrate without the catalyst layer (and buffer layer). Because the CNT forest maintains the high surface energy of the CNTs, it can adhere to the substrate without an adhesive layer. The method for manufacturing the CNT forest will be described later.

[0032] In the composite described above, the CNT forest may have catalyst particles at positions other than between the CNT forest and the substrate, such as on the side opposite to the side facing the substrate.

[0033] The average length of the CNTs in the CNT forest is preferably 10 to 1000 μm, more preferably 30 to 800 μm, and even more preferably 50 to 500 μm. The average length of the CNTs can be adjusted, for example, by adjusting the time spent performing the CVD method described later, i.e., the CNT growth time. The average diameter of the CNTs in the CNT forest is preferably 1 to 50 nm, more preferably 3 to 30 nm, and even more preferably 5 to 15 nm. The average diameter of the CNTs can be adjusted, for example, by adjusting the thickness of the catalyst layer and the type of catalyst described later.

[0034] The average length and average diameter of a carbon nanotube (CNT) are measured using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). Specifically, ten images of the CNT are obtained using an SEM or TEM. Ten length measurement points are arbitrarily selected from each of the ten images and measured, for a total of 100 lengths. The average length of the CNT is then calculated by arithmetic mean of these 100 length measurements. Similarly, ten diameter measurement points are arbitrarily selected from each of the ten images and measured, for a total of 100 diameter measurements. The average diameter of the CNT is then calculated by arithmetic mean of these 100 diameter measurements.

[0035] The carbon purity of the CNTs constituting the CNT forest is preferably 95.0 to 99.999%. The lower limit of the carbon purity of the CNTs is preferably 96.0%, more preferably 97.0%, even more preferably 98.0%, even more preferably 99.0%, and particularly preferably 99.8%. The upper limit of the carbon purity of the CNTs may be, for example, 99.99% or 99.9%. The carbon purity of the CNTs can be determined, for example, by elemental analysis using X-ray fluorescence.

[0036] The crystallinity of the carbon nanotubes (CNTs) that make up a CNT forest can be evaluated, for example, using Raman spectroscopy. In evaluating crystallinity using Raman spectroscopy, the D / G ratio is used as an indicator. The D / G ratio is the value at 1580 cm⁻¹ in the Raman spectrum measured by Raman spectroscopy. -1 1360 cm⁻¹ relative to the peak intensity of the G-band appearing in the vicinity -1 This is the ratio of the peak intensities of the D-band appearing in the vicinity. A smaller D / G ratio indicates higher crystallinity of the carbon nanotube. The D / G ratio of CNTs is preferably 0.5 to 1.0, more preferably 0.6 to 0.8.

[0037] The carbon purity and crystallinity of the CNTs can be adjusted, for example, by adjusting the thickness of the buffer layer in the catalyst substrate, the type of material used for the buffer layer, the thickness of the catalyst layer, the type of catalyst, the type and flow rate of the raw material gas in the CVD method, and the temperature and pressure in the reaction chamber, as described later.

[0038] The CNTs may be single-walled carbon nanotubes or multi-walled carbon nanotubes with two or more layers. Preferably, the CNTs are multi-walled carbon nanotubes. The number of layers in the multi-walled carbon nanotubes is not particularly limited, but is preferably 2 to 20.

[0039] [Method for Manufacturing the Composite] The above composite can be manufactured, for example, by a method comprising: a first step of preparing a substrate, a catalyst substrate, and a CNT growth substrate comprising a carbon nanotube (CNT) forest provided on the catalyst substrate; and a second step of transferring the CNT forest onto the substrate by pressure to form a composite in which the CNT forest is provided on the substrate without the need for a catalyst layer or an adhesive layer.

[0040] The CNT growth substrate, particularly the CNT forest, to be prepared in the first step can be manufactured by, for example, the following method. In the first step, the CNT growth substrate may be prepared by manufacturing it by the following method, or a CNT growth substrate that has already been manufactured may be prepared.

[0041] A CNT forest can be obtained, for example, by performing chemical vapor deposition (CVD) using a catalyst substrate comprising a support and a catalyst layer provided on the support. The CVD method involves placing the catalyst substrate in a reaction chamber, supplying a raw material gas to the reaction chamber, and growing CNTs on the surface of the catalyst layer. Thermal CVD is preferred as the CVD method.

[0042] Examples of support materials for the catalyst substrate include silicon substrates, alumina substrates, magnesium oxide substrates, glass substrates, sapphire substrates, and stainless steel substrates.

[0043] The catalyst layer can be formed, for example, by attaching catalyst particles to a support by sputtering. Examples of catalysts include metals, specifically iron (Fe), nickel (Ni), cobalt (Co), molybdenum (Mo), gold (Au), and alloys containing at least one metal selected from the group consisting of these. Examples of alloys include iron alloys, nickel alloys, and cobalt alloys. The catalyst may also be a metal precursor, such as a metal oxide or metal compound. Examples of metal oxides include iron oxide, nickel oxide, and cobalt oxide. An example of a metal compound is iron chloride. When using a precursor, it is necessary to convert the precursor to a metal before performing the CVD method, for example, by heating it.

[0044] The catalyst substrate may further include a buffer layer between the support and the catalyst layer. Examples of materials used for the buffer layer include silica (SiO2), alumina (Al2O3), silicon nitride (SiN), zinc oxide (ZnO), copper oxide (Cu2O), and nickel oxide (NiO). The buffer layer can be formed, for example, by sputtering.

[0045] The sputtering for forming the catalyst layer and the sputtering for forming the buffer layer can be carried out using known apparatuses and conditions according to the sputtering target. The pressure condition for sputtering is preferably 0.01 to 10 Pa, more preferably about 0.1 to 1 Pa.

[0046] As the source gas, a source gas containing carbon can be used. Examples include hydrocarbons, sulfur-containing organic gases, phosphorus-containing organic gases, carbon monoxide, and alcohols. Examples of hydrocarbons include alkane compounds such as methane and ethane, alkene compounds such as ethylene and butadiene, alkyne compounds such as acetylene, aryl hydrocarbon compounds such as benzene, toluene, and styrene, aromatic hydrocarbons having condensed rings such as indene, naphthalene, and phenanthrene, cycloalkane compounds such as cyclopropane and cyclohexane, cycloolefin compounds such as cyclopentene, and alicyclic hydrocarbon compounds having condensed rings such as steroids. Examples of alcohols include methanol and ethanol. The source gas is preferably a hydrocarbon from the viewpoint of the carbon purity of the obtained CNT.

[0047] A carrier gas, which is a gas for transporting the source gas, may be supplied to the reaction chamber together with the source gas. Examples of the carrier gas include helium, neon, argon, nitrogen, and hydrogen.

[0048] In the CVD process, the temperature inside the reaction chamber is preferably 600 to 850°C, more preferably 650 to 800°C, from the viewpoint of the growth rate of CNTs and the carbon purity of the resulting CNTs. The pressure inside the reaction chamber in the CVD process is preferably atmospheric pressure, from the viewpoint of the growth rate of CNTs and the carbon purity. Depending on other conditions when carrying out the CVD process, the pressure inside the reaction chamber may be reduced or increased from atmospheric pressure.

[0049] In a CNT growth substrate, the catalyst substrate comprises a catalyst layer. In this specification, embodiments in which a large number of catalyst particles are arranged in layers on the surface of a support or a buffer layer are also included in the term "catalyst layer." The catalyst layer is located between the CNT forest and the support. The CNT growth substrate may also have catalyst particles at locations other than between the CNT forest and the support. When catalyst particles are present at such locations, they are few in number compared to the catalyst particles contained in the catalyst layer.

[0050] The manufacturing method of the composite will be described below with reference to the drawings. Figure 1 is a diagram illustrating a manufacturing method of the composite 50 using a substrate 40, a catalyst substrate 10, and a CNT growth substrate 30 equipped with a CNT forest 20 provided on the catalyst substrate 10.

[0051] In the first step, as shown in Figure 1A, a substrate 40, a catalyst substrate 10, and a CNT growth substrate 30 comprising a CNT forest 20 provided on the catalyst substrate 10 are prepared. The catalyst substrate 10 in Figure 1A comprises a catalyst layer (not shown).

[0052] In the second step, the CNT forest is transferred onto the substrate by pressure to form a composite in which the CNT forest is provided on the substrate without the need for a catalyst layer or adhesive layer. One method of transferring by pressure is to stack the substrate and the CNT growth substrate so that the substrate and the CNT forest are in contact, apply pressure to obtain a laminate, and then remove the catalyst substrate from the laminate. The second step will be described below with reference to the drawings.

[0053] First, as shown in Figure 1B, the substrate 40 and the CNT growth substrate 30 are placed on top of each other so that the substrate 40 and the CNT forest 20 are in contact. If the substrate 40 has a flat portion and a curved portion, the substrate 40 and the CNT growth substrate 30 are placed on top of each other so that the flat portion and the CNT forest 20 are in contact.

[0054] Before stacking the substrate 40 and the CNT growth substrate 30, the CNT forest 20 may or may not undergo surface activation treatment. From the viewpoint of manufacturing costs and productivity, it is preferable not to perform surface activation treatment. Examples of surface activation treatments include corona discharge treatment, flame treatment, ultraviolet irradiation treatment, high-frequency treatment, glow discharge treatment, activated plasma irradiation treatment, laser irradiation treatment, and fast atomic beam (FAB) irradiation treatment.

[0055] Next, pressure is applied from either the substrate 40 side or the catalyst substrate 10 side to obtain a laminate. Then, the catalyst substrate 10 is removed from the laminate to transfer the CNT forest 20 onto the substrate 40. As a result, a composite 50 is formed in which the CNT forest 20 is provided on the substrate 40 without the need for a catalyst layer or adhesive layer. In the second step, pressure may be applied from either the substrate 40 side or the catalyst substrate 10 side, or from both sides.

[0056] Pressurization may be performed by pressing the laminate with a hand or pressure roller, or by using a pressurizing device. The pressure applied during pressurization is, for example, 0.05 to 500 MPa, preferably 0.1 to 500 MPa, more preferably 0.45 to 300 MPa, even more preferably 0.55 to 200 MPa, and particularly preferably 1 to 100 MPa, from the viewpoint of uniformly transferring the CNT forest 20 to the substrate 40 and minimizing damage to the substrate 40 and catalyst substrate 10.

[0057] To uniformly transfer the CNT forest 20 to the substrate 40, it is preferable to uniformly pressurize the surface of the substrate 40 or the catalyst substrate 10. Furthermore, to prevent the CNTs constituting the CNT forest from adhering to each other, it is preferable to apply pressure perpendicularly to the surfaces of the substrate 40 and the catalyst substrate 10.

[0058] The pressurizing time may be, for example, 1 second to 1 minute, 3 seconds to 45 seconds, or 5 seconds to 30 seconds. Removing the catalyst substrate 10 in the laminate means, for example, peeling the catalyst substrate 10 from the CNT forest 20 in the laminate.

[0059] It is presumed that the bond between the substrate 40 and the CNT forest 20, based on the high surface energy of the CNTs, is stronger than the bond between the catalyst substrate 10 and the CNT forest 20, particularly the bond between the catalyst layer and the CNT forest 20, and that the CNT forest 20 can be transferred onto the substrate 40 by the above operation.

[0060] In one embodiment, in the method for manufacturing the composite, the area of ​​the substrate in contact with the CNT forest before pressurization and the area to which the CNT forest adheres after transfer are approximately the same. That is, the CNT forest is transferred to almost the entire portion of the substrate surface that was in contact with the CNT forest before pressurization. Therefore, the CNT forest can be transferred efficiently. When manufacturing a composite having a carbon substrate as a solid substrate, a carbon substrate may be used as the substrate in the first step. Alternatively, a resin substrate formed from a resin material such as polyimide resin may be used as the substrate in the first step, and the resin may be carbonized after the second step to obtain a composite having a carbon substrate.

[0061] [Applications of the composite] Since CNTs have high thermal conductivity in the longitudinal direction (growth direction, i.e., perpendicular to the surface of the substrate or catalyst substrate), the CNT forest has high thermal conductivity perpendicular to the surface of the substrate. Therefore, the composite can be used, for example, in heat dissipation applications that require high thermal conductivity. In addition, the CNT forest is resistant to damage even when high pressure is applied in the longitudinal direction of the CNTs and has excellent pressure resistance. Therefore, the composite is suitably used, for example, in TIM (Thermal Interface Material).

[0062] The above composite material can be used as a thermal conductive material (TIM1) placed between a semiconductor chip, which is a heat-generating element, and a heat spreader, which is a heat sink, or as a thermal conductive material (TIM2) placed between a semiconductor package, which is a heat-generating element and includes a heat spreader, and a heat sink, which is a heat sink. The composite material is preferably used as TIM1.

[0063] When using the above composite in TIM1, for example, the substrate in the composite may be a semiconductor substrate (semiconductor chip), and an IHS (Integrated Heat Spreader) may be placed on top of the composite so that the side opposite to the side facing the substrate in the CNT forest is in contact with it. Alternatively, the substrate in the composite may be an IHS, and a semiconductor substrate (semiconductor chip) may be placed on top of the composite so that the side opposite to the side facing the substrate in the CNT forest is in contact with it.

[0064] From the above composite, a CNT forest can also be transferred to a substrate other than the substrate provided by the composite. Hereinafter, the substrate provided by the composite will be referred to as the first substrate, and the other substrate will be referred to as the second substrate. As a method for transferring a CNT forest from the above composite to the second substrate, for example, the second substrate and the composite are stacked so that the second substrate and the CNT forest are in contact, pressure is applied to obtain a laminate, and then the first substrate is removed from the laminate. As the second substrate, for example, a substrate similar to the substrate provided by the composite (the first substrate) can be used.

[0065] In the above composite, powdered CNTs can be produced by scraping the CNTs off the substrate using a scraper or the like. Furthermore, carbon nanotube webs (CNT webs) or carbon nanotube fibers (CNT fibers) can also be produced from the above composite by the method described later. Powdered CNTs, CNT fibers, CNT webs, and carbon nanotube films (CNT films) described later can be used, for example, in sports and leisure applications such as shoes, fishing rods, golf shafts, and tennis rackets; in electrical and electronic equipment applications such as secondary batteries, heat dissipation materials, electrode sheets, electromagnetic shields, electromagnetic wave absorbing sheets, antistatic sheets, battery components, electronic components, and casings for notebook computers, tablets, and smartphones; in building applications such as building materials; in transportation machinery applications such as automobiles, motorcycles, bicycles, railways, drones, rockets, aircraft, and ships; in energy applications such as hydroelectric generators and wind turbines; and in fashion applications such as clothing and bags.

[0066] A CNT web can be manufactured, for example, by extracting multiple CNTs from a CNT forest, specifically by extracting multiple CNTs in a sheet-like manner. More specifically, a CNT web can be manufactured, for example, by using a gripping tool such as tweezers to extract CNTs located at the ends of the CNT forest so that they move away from the CNT forest in a direction parallel to the surface of the substrate on which the CNT forest is provided. When CNTs located at the ends of the CNT forest are extracted, the CNTs adjacent to the extracted CNTs are sequentially extracted by van der Waals forces. The extracted CNTs are oriented so that their longitudinal direction aligns with the direction from which they were extracted. Therefore, the multiple CNTs constituting the CNT fiber are oriented in one direction. The multiple CNTs constituting the CNT fiber are bonded to each other by van der Waals forces. As a result, a CNT web is obtained, which is composed of multiple CNT fibers extending in the direction from which the CNTs were extracted.

[0067] A CNT film containing CNT fibers can be manufactured, for example, by producing multiple sheets of CNT webs obtained by extracting multiple CNTs from a CNT forest, and then laminating each CNT web, or by manufacturing a roll by winding multiple CNT webs obtained by extracting multiple CNTs from a CNT forest around the circumferential surface of a roller, and then cutting open the roll along the rotation axis of the roller.

[0068] In the composite of the present disclosure, the substrate and the CNT forest are in direct contact. Therefore, the composite maintains the thermal conductivity of the CNTs.

[0069] This disclosure relates, for example, to the following [1] to [7]: [1] A composite comprising a substrate and a carbon nanotube forest, wherein the carbon nanotube forest is provided on the substrate without interposing either a catalyst layer or an adhesive layer.

[0070] [2] The composite according to [1], wherein the substrate is a solid substrate.

[0071] [3] The composite according to [2], wherein the solid substrate is a semiconductor substrate, a metal substrate, a ceramic substrate, a carbon substrate, or a resin substrate.

[0072] [4] A method for producing a composite, comprising: a first step of preparing a substrate, a catalyst substrate, and a CNT growth substrate having a carbon nanotube (CNT) forest provided on the catalyst substrate; and a second step of transferring the CNT forest onto the substrate by pressure to form a composite in which the CNT forest is provided on the substrate without the interposition of either a catalyst layer or an adhesive layer.

[0073] [5] The method for producing the composite according to [4], wherein the pressure used when applying the pressurization is 0.05 to 500 MPa.

[0074] [6] The method for manufacturing the composite according to [4] or [5], wherein the substrate is a solid substrate.

[0075] [7] The method for manufacturing a composite according to [6], wherein the solid substrate is a semiconductor substrate, a metal substrate, a ceramic substrate, a carbon substrate, or a resin substrate.

[0076] The composites of the present disclosure will be described in more detail below based on examples, but the composites of the present disclosure are not limited to the examples.

[0077] [Transfer Evaluation] In the following examples, after transferring the CNT forest to the substrate, the ratio of the CNT forest coverage area to the substrate area (coverage rate) was calculated. A coverage rate of 100% was evaluated as a complete transfer.

[0078] [Manufacturing Example 1] (Manufacturing of CNT growth substrate) A wafer (4-inch disc-shaped wafer) coated with a catalyst for CNT growth was prepared as a catalyst substrate, and vertically oriented CNTs were grown from the catalyst by chemical vapor deposition to create a vertically oriented CNT forest oriented perpendicular to the wafer. This resulted in obtaining a CNT growth substrate comprising a catalyst substrate and a CNT forest provided on the catalyst substrate. The CNTs constituting the CNT forest were multi-walled carbon nanotubes, with an average length of 250 μm per tube, an average diameter of 6 to 10 nm, a carbon purity of 99.8% or higher, and a crystallinity (D / G ratio) of 0.6 to 0.8.

[0079] [Example 1] As a base material, a stainless steel substrate with a length of 2 cm and a width of 1 cm was prepared by cutting a reference surface portion of a comparative surface roughness standard piece (manufactured by Nippon Kinzoku Densetsu Co., Ltd., in accordance with JIS B0659-1:2002 Annex 1) where the processing method was surface grinding and Rz was 1.6 μm using a diamond cutter.

[0080] The stainless steel substrate and the CNT growth substrate were stacked so that the above-mentioned reference surface was in contact with the CNT forest. Then, pressure was applied by hand from the stainless steel substrate side to obtain a laminate. In the laminate, the catalyst substrate was peeled off from the CNT forest, thereby transferring the CNT forest to the stainless steel substrate. The pressure was applied for 10 seconds. The transfer was performed a total of five times in the same manner as described above.

[0081] The same procedure as described above was followed for each of the three types of stainless steel substrates with different surface roughness. The only difference was that the processing method was surface grinding, and the stainless steel substrates obtained by cutting the reference surface portion with an Rz of 6.3 μm or 25 μm were used. A total of five transfers were performed for each of the three Rz stainless steel substrates. Of the five transfers performed for each substrate, four were complete transfers. The complete transfer rate was 80%.

[0082] [Example 2] The process was the same as in Example 1, except that pressure was applied using a pressurizing device to apply a force of 0.1 t. A total of 15 transfers were performed, five times on each stainless steel substrate. The pressure applied was 4.9 MPa. Of the 15 transfers performed, all 15 were complete transfers. The complete transfer rate was 100%.

[0083] [Example 3] The process was the same as in Example 1, except that pressure was applied using a pressurizing device to apply a force of 0.5 t. A total of 15 transfers were performed, five times on each stainless steel substrate. The pressure applied was 24.5 MPa. Of the 15 transfers performed, all 15 were complete transfers. The complete transfer rate was 100%.

[0084] [Example 4] The process was the same as in Example 1, except that pressure was applied using a pressurizing device to apply a force of 1 ton. Each stainless steel substrate was transferred 5 times for a total of 15 times. The pressure applied was 49 MPa. Of the 15 transfers performed, 15 were complete transfers. The complete transfer rate was 100%.

[0085] [Example 5] An epoxy resin substrate measuring 2 cm in length and 1 cm in width was prepared as the base material. The epoxy resin substrate and the CNT growth substrate were stacked so that the epoxy resin substrate and the CNT forest were in contact. Then, pressure was applied from the epoxy resin substrate side using a pressure device to obtain a laminate, and the catalyst substrate was peeled from the CNT forest in the laminate to transfer the CNT forest to the epoxy resin substrate. The pressure was 49 MPa and the pressurizing time was 10 seconds. The transfer was performed a total of 5 times in the same manner as above. Of the 5 transfers performed, 5 were complete transfers. The rate of complete transfer was 100%.

[0086] [Example 6] The transfer was performed a total of five times in the same manner as in Example 5, except that a copper substrate was used as the base material. Of the five transfers performed, five were complete transfers. The rate of complete transfer was 100%.

[0087] [Example 7] The transfer was carried out a total of five times in the same manner as in Example 5, except that a ceramic substrate was used as the base material. Of the five transfers carried out, five were complete transfers. The rate of complete transfer was 100%.

[0088] [Example 8] The transfer was performed a total of five times in the same manner as in Example 5, except that a silicon substrate was used as the base material. Of the five transfers performed, five were complete transfers. The rate of complete transfer was 100%.

[0089] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various omissions, substitutions, modifications, and changes are possible within the scope of the gist of the present invention as described in the claims. These embodiments and their variations are included in the scope and gist of the invention, as well as in the scope of the invention and its equivalents as described in the claims.

[0090] 10... Catalyst substrate 20... CNT forest 30... CNT growth substrate 40... Substrate 50... Composite

Claims

1. A composite comprising a substrate and a carbon nanotube forest, wherein the carbon nanotube forest is provided on the substrate without interposing either a catalyst layer or an adhesive layer.

2. The composite according to claim 1, wherein the substrate is a solid substrate.

3. The composite according to claim 2, wherein the solid substrate is a semiconductor substrate, a metal substrate, a ceramic substrate, a carbon substrate, or a resin substrate.

4. A method for producing a composite, comprising: a first step of preparing a substrate, a catalyst substrate, and a CNT growth substrate comprising a carbon nanotube (CNT) forest provided on the catalyst substrate; and a second step of transferring the CNT forest onto the substrate by pressure to form a composite in which the CNT forest is provided on the substrate without the interposition of either a catalyst layer or an adhesive layer.

5. The method for manufacturing the composite according to claim 4, wherein the pressure used when applying the pressurization is 0.05 to 500 MPa.

6. The method for manufacturing a composite according to claim 4, wherein the substrate is a solid substrate.

7. The method for manufacturing a composite according to claim 6, wherein the solid substrate is a semiconductor substrate, a metal substrate, a ceramic substrate, a carbon substrate, or a resin substrate.

Images