Laminate

Abstract

A purpose of the present invention is to provide a laminate which has high heat transport capacity, high strength, and small specific gravity, and which an be applied to an electronic apparatus. The present invention provides a laminate (1) including a plurality of first layers (2) formed from a carbon fiber composite material and a plurality of second layers (3) formed from a graphite sheet, the first layers (2) and the second layers (3) being laminated, and the laminate (1) having a region in which the first layers (2) are connected to each other.

Description

Laminate

[0001] The present invention relates to a laminate.

[0002] In recent years, as electronic devices and systems incorporating electronic devices become smaller and more powerful, heat countermeasures have become increasingly important. Some of the reasons why heat countermeasures are necessary in electronic devices and systems include the following: Reduction in heat dissipation area and heat dissipation paths due to high-density packaging of electronic devices. Increase in thermal resistance due to miniaturization of components with the same performance. Increase in heat generation due to faster processing speeds of semiconductor elements. Increase in heat generation due to miniaturization (increased integration) of semiconductor integrated circuits.

[0003] Heat dissipation measures for electronic devices and systems include radiators, heat sinks, cooling fans, and heat pipes. To efficiently diffuse and release heat from the heat source, it is necessary to construct a heat dissipation mechanism using materials with heat transport capabilities. However, in the latest electronic devices, which are densely packed with high-heat-generating elements, heat dissipation mechanisms made from conventional materials tend to be large and heavy. This often places a strain on the electronic device. Therefore, to make heat dissipation mechanisms smaller and lighter, materials with low specific gravity, high heat transport capabilities, and strength and rigidity are needed.

[0004] An example of a material having heat transport capacity is a graphite sheet. Although a graphite sheet has a high thermal conductivity of 1000 W / m / K or more, its thickness is small (generally several tens of μm), resulting in low heat transport capacity. Furthermore, since the graphite sheet has low strength (less than 10 MPa), the graphite sheet itself cannot support the structure of an electronic device. Although graphite sheets with improved heat transport capacity have been commercialized, the strength of these graphite sheets remains low.

[0005] Examples of materials that form the structure of electronic devices include aluminum (alloys), copper (alloys), magnesium (alloys), ZA-based new alloys (see, for example, Non-Patent Document 1), rubber composite materials (see, for example, Non-Patent Document 2), and pitch-based high-thermal-conductivity carbon fiber reinforced plastics (see, for example, Patent Document 1). Aluminum (alloys) have a thermal conductivity of 150 to 200 W / m / K and a specific gravity of 2.7. Copper (alloys) have a thermal conductivity of 391 W / m / K and a specific gravity of 8.9. Magnesium (alloys) have a thermal conductivity of 40 W / m / K and a specific gravity of 1.83. ZA-based new alloys have a thermal conductivity of 131 W / m / K and a specific gravity of 1.76. Rubber composite materials have a thermal conductivity of 14 W / m / K and a specific gravity of approximately 1.5. Pitch-based high-thermal-conductivity carbon fiber reinforced plastics have a thermal conductivity of 360 W / m / K and a specific gravity of 1.72.

[0006] Patent No. 3031197

[0007] National Institute of Advanced Industrial Science and Technology (AIST) website, "Newly developed 'ZA-based new magnesium alloy rolled material' with excellent room-temperature formability, strength, and high thermal conductivity" (https: / / www.aist.go.jp / aist_j / press_release / pr2021 / pr20211020 / pr20211020.html) National Institute of Advanced Industrial Science and Technology (AIST) website, "Development of rubber composite material with thermal conductivity comparable to that of metal" (https: / / www.aist.go.jp / aist_j / press_release / pr2020 / pr20200217 / pr20200217.html)

[0008] Conventional materials used in electronic devices can be classified into three types: (1) high thermal conductivity and high strength, but high specific gravity; (2) high strength and low specific gravity, but not very high thermal conductivity; and (3) high thermal conductivity and low specific gravity, but low strength. As such, conventional materials do not meet the three conditions of high heat transport capacity, high strength, and low specific gravity, and therefore, when taking measures to prevent heat from entering a device or system, it is necessary to sacrifice either heat transport capacity, strength, or specific gravity.

[0009] The present invention has been made in view of the above circumstances, and has an object to provide a laminate that has high heat transport capacity, high strength, and a small specific gravity, and that can be applied to electronic devices.

[0010] The present invention has the following aspects: [1] A laminate comprising: a plurality of first layers made of a carbon fiber composite material; and a plurality of second layers made of a graphite sheet, wherein the plurality of first layers and the plurality of second layers are stacked together, the plurality of first layers have a region where they contact each other, and the graphite sheet has a product of the thickness a (μm) and the thermal conductivity b (W / (mK)) in a direction along the sheet surface of the graphite sheet of 75,000 or more. [2] A laminate comprising: a plurality of first layers made of a carbon fiber composite material; and a plurality of second layers made of graphite sheets, wherein the plurality of first layers and the plurality of second layers are stacked together, wherein the plurality of first layers have a region where they contact each other, and when the shortest distance between two opposing surfaces is defined as the thickness, the longest distance is defined as the length, and the distance in a direction perpendicular to the thickness direction and the length direction is defined as the width, both ends of the plurality of second layers in the width direction are positioned so as to contact the inner surface of a layer that forms the surface of the laminate. [3] The laminate according to [1] or [2], wherein the first layer has a region that surrounds the second layer. [4] The laminate according to [1] or [2], wherein the second layer extends parallel to one direction of the outermost surface in the thickness direction of the laminate. [5] The laminate according to [4], wherein at least one of the second layers extends parallel to the outermost surface in the thickness direction of the laminate and in a direction perpendicular to the one direction. [6] The laminate according to [1] or [2], wherein the carbon fiber composite material is a pitch-based carbon fiber composite material. [7] The laminate according to [1] or [2], wherein the graphite sheet has a product of the thickness a (μm) and the thermal conductivity b (W / (mK)) in a direction along one main surface of the graphite sheet of 100,000 or more. [8] The laminate according to [1] or [2], wherein the first layer has a region that is connected to the other outermost surface in the thickness direction of the laminate. [9] The laminate according to [1] or [2], wherein two or more graphite sheets are in contact with each other to form the second layer.

[10] The laminate according to [1] or [2], wherein three or more of the second layers are present in the width direction or thickness direction of the laminate.

[11] The laminate according to [1] or [2], wherein the thickness of the laminate is 3.1 to 20 mm.

[12] The laminate according to [1] or [2], wherein the carbon fibers of the carbon fiber composite material are continuous carbon fibers.

[13] The laminate according to [1] or [2], wherein the graphite sheet has a thickness a of 50 μm or more.

[0011] According to the present invention, it is possible to provide a laminate that has high heat transport capacity, high strength, and low specific gravity, and is applicable to electronic devices.

[0012] Fig. 1 is a cross-sectional view showing a laminate according to a first embodiment of the present invention. Fig. 2 is a cross-sectional view showing a laminate according to a second embodiment of the present invention. Fig. 3 is a cross-sectional view showing a laminate according to a third embodiment of the present invention. Fig. 4 is a cross-sectional view showing a laminate according to a fourth embodiment of the present invention. Fig. 5 is a cross-sectional view showing a laminate according to a fifth embodiment of the present invention. Fig. 6 is a diagram showing the relationship between the thickness of the laminate or aluminum plate and the temperature rise in Examples and Comparative Examples.

[0013] [Laminate] A laminate according to one embodiment of the present invention will be described below with reference to the drawings. Note that this embodiment is specifically described to provide a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. Furthermore, in this specification, the shortest distance between two opposing surfaces is referred to as the thickness, and the longest distance is referred to as the length. Furthermore, the distance perpendicular to the thickness direction and the length direction is referred to as the width. In other words, in a laminate, the distance between the upper end surface and the lower end surface in the stacking direction is referred to as the thickness. Furthermore, in this specification, the upward direction in the Y-axis direction in Figures 1 to 5 is referred to as the up direction, and the opposite direction is referred to as the down direction.

[0014] (First Embodiment) Fig. 1 is a cross-sectional view showing a laminate according to a first embodiment of the present invention. As shown in Fig. 1, the laminate 1 of this embodiment includes a plurality of first layers 2 and a plurality of second layers 3. The laminate 1 of this embodiment is a laminate in which a plurality of first layers 2 and a plurality of second layers 3 are stacked. An upper surface (outermost surface) 1a in the thickness direction of the laminate 1 is formed by the first layer 2 and the second layer 3, and the upper surface (outermost surface) of the first layer 2 and the upper surface (outermost surface) of the second layer 3 form the same plane. A lower surface (outermost surface) 1b in the thickness direction of the laminate 1 is formed by the first layer 2 and the second layer 3, and the lower surface (outermost surface) of the first layer 2 and the lower surface (outermost surface) of the second layer 3 form the same plane.

[0015] The laminate 1 has a region where the first layers 2 contact each other. Specifically, as shown in FIG. 1 , the laminate 1 has a region where an edge 2a of the first layer 2A located on the upper side in the thickness direction of the laminate 1 contacts an edge 2a of the first layer 2B located in contact with the lower surface of the first layer 2A in the thickness direction of the laminate 1. More specifically, the laminate 1 has a region where an edge 2a of the first layer 2B located on the upper side in the thickness direction of the laminate 1 contacts an edge 2a of the first layer 2C located in contact with the lower surface of the first layer 2B in the thickness direction of the laminate 1. This connects the multiple first layers 2, and the laminate 1 has a region where the first layer 2 surrounds the second layer 3. Specifically, the laminate 1 has a region where the first layer 2A, the first layer 2B, and the first layer 2C surround the second layer 3. The laminate 1 has a plurality of regions in which the first layer 2 surrounds the second layer 3 .

[0016] A first layer 2 and a second layer 3 extend in one direction with their longitudinal directions aligned so as to form an upper surface 1 a of the laminate 1 .

[0017] The first layer 2 is made of a carbon fiber composite material. Examples of carbon fiber composite materials include pitch-based carbon fiber composite materials and PAN-based carbon fiber composite materials. Among these, pitch-based carbon fiber composite materials are preferred from the viewpoint of high thermal conductivity.

[0018] Pitch-based carbon fiber composite materials are composite materials made of pitch-based carbon fibers, which are produced by graphitizing a by-product (pitch) of coal, petroleum, or coal tar at high temperatures, and resins, such as epoxy resins and cyanate ester resins.

[0019] The carbon fiber content relative to the total mass (100 mass%) of the carbon fiber composite material is preferably 40 mass% or more and 75 mass% or less, more preferably 50 mass% or more and 70 mass% or less, and even more preferably 55 mass% or more and 65 mass% or less. If the carbon fiber content is less than the lower limit, the strength and thermal conductivity of the composite material are low. If the carbon fiber content exceeds the upper limit, voids are more likely to occur during molding. The carbon fiber includes pitch-based carbon fiber.

[0020] The thickness of the first layer 2 is preferably 50 μm or more and 500 μm or less, and more preferably 100 μm or more and 250 μm or less. If the thickness of the first layer 2 is less than the lower limit, the mechanical properties (strength, rigidity) cannot be exhibited. If the thickness of the first layer 2 exceeds the upper limit, the relative proportion of the second layer 3 in the laminate 1 decreases, resulting in poor thermal conductivity. The thickness of the first layer 2 is the distance between two opposing surfaces on the Y axis in FIG. 1.

[0021] The second layer 3 is made of a graphite sheet. The thickness of the second layer 3 is also the distance between two opposing surfaces along the Y axis in FIG.

[0022] The thickness of the graphite sheet (hereinafter sometimes referred to as "thickness a") is preferably 50 μm or more, more preferably 100 μm or more, and even more preferably 150 μm or more. If the thickness of the graphite sheet is less than the lower limit, the heat transport capacity will be reduced. The upper limit of the thickness of the graphite sheet is not particularly limited, but may be 400 μm or less, 200 μm or less, or 160 μm or less.

[0023] The thickness of the graphite sheet was measured using a standard outside micrometer and was determined by averaging thicknesses measured at five randomly selected points.

[0024] The graphite sheet preferably has a thermal conductivity in a direction along the sheet surface (hereinafter sometimes referred to as "thermal conductivity b") of 1000 W / (mK) or more, more preferably 1500 W / (mK) or more, and even more preferably 2000 W / (mK) or more. When the thermal conductivity in a direction along one main surface of the graphite sheet is equal to or greater than the above-mentioned lower limit, the heat transport capacity is high.

[0025] The thermal diffusivity of the graphite sheet in the direction along the sheet surface was measured in an environment of 23°C using a Thermowave Analyzer TA33 manufactured by BETHER Co., Ltd., using the cyclic heating method (distance heating method) in accordance with JIS R 7240 (2018). Five measurement frequencies were used: 60 Hz, 70 Hz, 75 Hz, 80 Hz, and 90 Hz. The average of the thermal diffusivities measured at each of the five frequencies was used as the thermal diffusivity of the graphite sheet in the direction along the sheet surface. For the measurement, the sample size was 4 cm to 10 cm in the measurement direction and 1.5 cm to 10 cm in the direction perpendicular to the measurement direction of the sheet surface. The thickness of the cut sample was measured. The thermal conductivity of the graphite sheet in the direction along the sheet surface was calculated according to the following formula: b = α × d × c, where the symbols in this formula have the following meanings. b: Thermal conductivity of the graphite sheet in the direction along the sheet surface (W / (mK)); α: Thermal diffusivity of the graphite sheet in the direction along the sheet surface (mm ２ / s) d: density of graphite sheet (g / cm ３ ) c: specific heat of graphite (0.85 J / gK)

[0026] The product of the thickness a and the thermal conductivity b is preferably 75,000 or more, more preferably 100,000 or more, and even more preferably 200,000. When the product of the thickness a and the thermal conductivity b is equal to or greater than the lower limit, the heat transport capacity is high. The upper limit of the product of the thickness a and the thermal conductivity b is not particularly limited, but may be 800,000 or less, 600,000 or less, or 300,000 or less.

[0027] The density of the graphite sheet is 1.7 g / cm ３ It is preferable that the density is 1.8 g / cm or more. ３ More preferably, it is 1.9 g / cm or more. ３ It is more preferable that the density of the graphite sheet is equal to or greater than the lower limit. If the density of the graphite sheet is less than the lower limit, the thermal conductivity of the graphite sheet is low. The density d of the graphite sheet was determined by measuring the mass of the graphite sheet in air and in ethanol and using the following formula: d = ρs × Wa / (Wa - Ws) where each symbol in this formula has the following meaning: d: density of the graphite sheet (g / cm ３ ) ρs: density of ethanol (g / cm ３ Wa: Mass of graphite sheet in air (g) Wa: Mass of graphite sheet in ethanol (g)

[0028] The graphite sheet may have a single layer structure or a multi-layer structure in which a plurality of layers are stacked on top of each other.

[0029] When a carbon fiber composite material and a graphite sheet are simply combined (compositely laminated), the resulting laminate has a heat transport capacity that corresponds to the lamination ratio of the carbon fiber composite material and the graphite sheet. However, the structural performance (strength, rigidity) of the resulting laminate is the same as that of the graphite sheet, and the laminate cannot be used as a structural material. In contrast, the laminate 1 of this embodiment is a laminate in which multiple first layers 2 and multiple second layers 3 are laminated. The first layers 2 have regions where they are in contact with each other, which connects the first layers 2 to each other, allowing the structural performance of the carbon fiber composite material to be exhibited in the laminate and increasing the strength of the laminate. Furthermore, the laminate 1 of this embodiment has a region where the first layer 2 surrounds the second layer 3, allowing the structural performance of the carbon fiber composite material to be exhibited in the laminate. Preferably, there are three or more second layers in the width direction or thickness direction of the laminate. The wide distribution of the second layer (graphite sheet) in the laminate increases the heat transport efficiency, and the presence of the first layer between the second layers makes it easier for the structural performance of the carbon fiber composite material to be expressed in the laminate.

[0030] Second Embodiment Fig. 2 is a cross-sectional view showing a laminate according to a second embodiment of the present invention. As shown in Fig. 2, the laminate 10 of this embodiment includes a plurality of first layers 11 and a plurality of second layers 12. The laminate 10 of this embodiment is a laminate in which a plurality of first layers 11 and a plurality of second layers 12 are stacked. An upper surface (outermost surface) 10a in the thickness direction of the laminate 10 is formed by a first layer 11A. A lower surface (outermost surface) 10b in the thickness direction of the laminate 10 is formed by the first layer 11 and the second layer 12, and the lower surface (outermost surface) of the first layer 11 and the lower surface (outermost surface) of the second layer 12 form the same plane.

[0031] The first layer 11 has a first layer 11A extending in the X-axis so as to form an upper surface 10a in the thickness direction of the laminate 10, a first layer 11B that contacts the lower surface of the first layer 11A in the thickness direction (Y direction) of the laminate 10 and extends along the Z-axis intersecting the extension direction (X-axis) of the first layer 11A, and a first layer 11C that contacts the lower surface of the first layer 11B and is arranged so as to overlap at least partially with the first layer 11B along the Z-axis, preferably so as to overlap along the Z-axis.

[0032] The second layer 12 is composed of a second layer 12 (12A) and a second layer 12 (12B). Specifically, the second layer 12 is parallel to the upper surface 10a of the laminate 10, contacts the lower surface of the first layer 11A in the thickness direction of the laminate 10, and extends (extends along the Z axis) intersecting the direction in which the first layer 11A extends (X axis). The second layer 12 is in contact with the lower surface of the second layer 12 (12A) and is at least partially overlapping the second layer 12 (12A) along the Z axis, preferably arranged so as to overlap along the Z axis. The second layer 12 (12A) and the second layer 12 (12B) are stacked along the thickness direction of the laminate 10.

[0033] The laminate 10 has a region where the first layers 11 are connected to each other. Specifically, as shown in FIG. 2 , the laminate 10 has a region where the first layer 11A constituting the upper surface 10a contacts the first layer 11B that contacts the lower surface of the first layer 11A in the thickness direction of the laminate 10. The laminate 10 also has a region where the first layer 11B contacts the first layer 11C that contacts the lower surface of the first layer 11B in the thickness direction of the laminate 10. Furthermore, the laminate 10 has a region where the first layer 11C contacts the first layer 11A located below the first layer 11C in the thickness direction of the laminate 10. As a result, the laminate 10 has a region where the first layer 11 surrounds the second layer 12. Specifically, first layer 11A, first layer 11B, and first layer 11C have an area surrounding second layer 12A and second layer 12B. Laminate 10 has a plurality of such areas where first layer 11 surrounds second layer 12. It is preferable that the first layers are connected to each other from the outermost surface to the other outermost surface in the thickness direction of the laminate, because this allows the structural performance of the carbon fiber composite material to be better exhibited in the laminate.

[0034] The first layer 11 has the same structure as the first layer 2 described above.

[0035] The second layer 12 has the same structure as the second layer 3 described above.

[0036] The laminate 10 of this embodiment is a laminate in which a plurality of first layers 11 and a plurality of second layers 12 are stacked, and the first layers 11 have regions where they contact each other, which connects the first layers 11, allowing the structural performance of the carbon fiber composite material contained in the first layers to be exerted in the laminate, thereby increasing the strength of the laminate. Furthermore, the laminate 10 of this embodiment has a region in which the first layers 11 surround the second layers 12, allowing the structural performance of the carbon fiber composite material to be exerted in the composite structure. Furthermore, in the laminate 10 of this embodiment, the second layer 12 is composed of a second layer 12 (12A) and a second layer 12 (12B). Specifically, the second layer 12 (12A) is parallel to the upper surface 10a of the laminate 10 and extends (along the Z-axis) intersecting the direction in which the first layer 11A extends (X-axis) so as to be in contact with the underside of the first layer 11A, and the second layer 12 (12B) is positioned so as to overlap at least a portion of the underside of the second layer 12 (12A) along the Z-axis, preferably so as to overlap along the Z-axis. This allows the structural performance of the carbon fiber composite material to be better exhibited in the laminate and increases the heat transport capacity. In this embodiment, the second layer 12A and the second layer 12B may be the same or different. In addition, although the second layer is described as having two layers (two graphite sheets) composed of graphite sheet 12A and graphite sheet 12B, the second layer is not limited to this, and may be composed of only one layer (one graphite sheet) or three or more layers (three or more graphite sheets). Two or more graphite sheets are preferable because they increase the heat transport efficiency.

[0037] Third Embodiment Fig. 3 is a cross-sectional view showing a laminate according to a second embodiment of the present invention. As shown in Fig. 3, the laminate 20 of this embodiment includes two laminates 10 stacked so as to face each other with the first layer 11 interposed therebetween. Specifically, the two laminates 10 are stacked so that the first layer 11C of one laminate 10A faces the first layer 11C of the other laminate 10B with the first layer 11D interposed therebetween, and the second layer 12B of one laminate 10A faces the second layer 12B of the other laminate 10B with the first layer 11D interposed therebetween. That is, the laminate 20 of this embodiment includes a plurality of first layers 11 and a plurality of second layers 12. The laminate 10 is the laminate 10 of the second embodiment described above.

[0038] The first layers 11D extend in the Z-axis direction and are arranged intermittently at a predetermined interval between the two laminated bodies 10. That is, a gap 21 is provided between two adjacent first layers 11D.

[0039] The laminate 20 of this embodiment is a laminate in which a plurality of first layers 11 and a plurality of second layers 12 are stacked, and by having regions where the first layers 11 contact each other, the first layers 11 are connected to each other, allowing the structural performance of the carbon fiber composite material to be exhibited in the laminate and increasing the strength of the laminate. Furthermore, by having regions where the first layers 11 surround the second layers 12, the laminate 20 of this embodiment can further exhibit the structural performance of the carbon fiber composite material. Furthermore, in the laminate 20 of this embodiment, the second layer 12 is composed of a second layer 12 (12A) and a second layer 12 (12B). Specifically, the second layer 12 includes a second layer 12 (12A) that is parallel to the upper surface 10a of the laminate 10 and extends (along the Z-axis) transversely to the direction in which the first layer 11A extends (X-axis) so as to be in contact with the underside of the first layer 11A, and a second layer 12 (12B) that at least partially overlaps the underside of the second layer 12 (12A) along the Z-axis, preferably along the Z-axis. This allows the structural performance of the carbon fiber composite material to be better exhibited in the laminate and improves heat transport capacity. In this embodiment, the second layer 12 (12A) and the second layer 12 (12B) may be the same or different. While the second layer 12 is described as being two layers, consisting of layers 12A and 12B, the second layer may be a single layer or three or more layers.

[0040] (Fourth Embodiment) Fig. 4 is a cross-sectional view showing a laminate according to a fourth embodiment of the present invention. As shown in Fig. 4, the laminate 30 according to this embodiment includes a plurality of first layers 31 and a plurality of second layers 32. The laminate 30 according to this embodiment is a laminate in which a plurality of first layers 31 and a plurality of second layers 32 are stacked. An upper surface (outermost surface) 30a in the thickness direction of the laminate 30 is formed by the first layer 31. A lower surface (outermost surface) 30b in the thickness direction of the laminate 30 is also formed by the first layer 31. In this example, the thickness of the laminate 30 is the distance between two opposing surfaces along the Y axis in Fig. 4.

[0041] The first layer 31 includes a plurality of first layers 31A and a plurality of second layers 31B. The first layer 31A includes first layers 31A, 31A extending along the X-axis to form the upper surface 30a and the lower surface 30b of the laminate 30, and a plurality of first layers 31B extending along the Z-axis so that both ends in the width direction (Y-axis direction) of the first layer 31A contact the lower surface of the upper surface 30a and the upper surface of the lower surface 30b. The first layers 31B are arranged at a predetermined interval via the second layer 32. Note that the plurality of first layers 31B may be arranged in contact with each other. The thickness direction of the first layers 31A, 31A is the Y-axis direction in FIG. 4, and the thickness is the distance between the two opposing surfaces along the Y-axis. The thickness direction of the first layer 31B is the X-axis direction in FIG. 4. The thickness is the distance between the two opposing surfaces along the X-axis.

[0042] The second layer 32 is composed of a second layer 32 (32A) and a second layer 32 (32B). Specifically, the second layer 32 has second layers 32A and 32B extending along the Z direction so that both ends of the second layer 32 in the width direction (Y-axis direction) are in contact with the lower surface of the upper surface 30a and the upper surface of the lower surface 30b. In other words, the second layers 32A, 32B, and first layers 31B are arranged so that both ends of the second layer 32A, 32B, and first layer 31B are in contact with the inner surfaces of the first layers 31A and 31A, which form the surface of the laminate, and are also in contact with each other. The width direction of the second layer 32 is the X-axis direction in FIG. 4. The thickness is the distance between the two opposing surfaces along the X-axis.

[0043] The laminate 30 has regions where the first layers 31 contact each other. Specifically, as shown in FIG. 4 , the laminate 30 has regions where the first layer 31A forming the upper surface 30a, the first layer 31A forming the lower surface 30b, and the first layer 31B disposed between the two first layers 31A contact each other. The first layers 31A, 31A, and 31B are connected. As a result, the laminate 30 has regions where the first layer 31 surrounds the second layer 32. Specifically, the first layer 31A and the first layer 31B surround the second layer 32A and the second layer 32B. The laminate 30 has a plurality of such regions where the first layer 31 surrounds the second layer 32.

[0044] The first layer 31 has the same configuration as the above-described first layer 2. Note that the thickness of the first layer 31 (31A and 31B) in this embodiment is the distance between two opposing surfaces on the Y axis in FIG.

[0045] The second layer 32 has the same configuration as the above-described second layer 3. In this embodiment, the thickness of the second layer 32 is the distance between two opposing surfaces along the X axis in Fig. 4. The width of the second layer 32 is the distance between two opposing surfaces along the Y axis in Fig. 1.

[0046] The laminate 30 of this embodiment is a laminate in which a plurality of first layers 31 and a plurality of second layers 32 are stacked, and the first layers 31 are connected by having regions where they contact each other. This allows the structural performance of the carbon fiber composite material contained in the first layers 31 to be exerted in the laminate, and the strength of the laminate can be increased. Furthermore, the laminate 30 of this embodiment has a region in which the first layers 31 surround the second layers 32, so that the structural performance of the carbon fiber composite material can be further exerted in the laminate. Furthermore, in the laminate 30 of this embodiment, the second layer 32 is composed of a second layer 32 (32A) and a second layer 32 (32B). Specifically, the second layer 12 has second layers 32A and 32B extending along the Z direction such that both ends of the second layer 32 in its width (Y-axis direction) contact the lower surface of the upper surface 30a and the upper surface of the lower surface 30b. This allows the structural performance of the carbon fiber composite material to be fully realized in the laminate, and increases the heat transport capacity of the laminate in the thickness direction (Y direction). In this embodiment, the second layers 32A and 32B may be the same or different. While the second layer 12 is described as being two layers, consisting of 32A and 32B, the present invention is not limited to this configuration and may include only one second layer or three or more second layers.

[0047] Fifth Embodiment Fig. 5 is a cross-sectional view showing a laminate according to a fifth embodiment of the present invention. As shown in Fig. 5, the laminate 40 according to this embodiment includes a plurality of first layers 41 and a plurality of second layers 42. The laminate 40 according to this embodiment is a laminate in which the plurality of first layers 41 and the plurality of second layers 42 are stacked. An upper surface (outermost surface) 40a in the thickness direction of the laminate 40 is formed by the first layer 41. A lower surface (outermost surface) 40b in the thickness direction of the laminate 40 is also formed by the first layer 41. In this example, the thickness of the laminate 40 is the distance between two opposing surfaces along the Y axis in Fig. 5.

[0048] The first layer 41 includes a plurality of first layers 41A extending along the Z axis to form the upper surface 40a and the lower surface 40b of the laminate 40, and a plurality of first layers 41B extending along the Z direction so that both ends in the width direction (Y axis direction) of the first layers 41A contact the lower surface of the upper surface 40a and the upper surface of the lower surface 40b. The first layers 41A, 41A extend in the Z axis direction and are arranged intermittently at a predetermined interval. That is, a gap 43 is provided between two first layers 41A. Alternatively, the plurality of first layers 41B may be arranged in contact with each other.

[0049] The second layer 42 is composed of a second layer 42 (42A) and a second layer 42 (42B). Specifically, the second layer 42 has the second layer 42 (42A) and the second layer 42 (42B) extending along the Z direction so that both ends in the width direction (Y-axis direction) of the second layer 42 contact the lower surface of the upper surface 40a and the upper surface of the lower surface 40b. The thickness of the second layer 42 is the distance between the two opposing surfaces on the X-axis in FIG. 5. Note that multiple first layers 41B may be arranged in contact with each other.

[0050] The laminate 40 has regions where the first layers 41 contact each other. Specifically, as shown in FIG. 5 , the laminate 40 has regions where the first layer 41A forming the upper surface 40a, the first layer 41A forming the lower surface 40b, and the first layer 41B disposed between the two first layers 41A contact each other. The first layers 41A, 41A, and 41B are connected. As a result, the laminate 40 has regions where the first layer 41 surrounds the second layer 42. Specifically, the first layer 41A and the first layer 41B surround the second layer 42A and the second layer 42B. The laminate 40 has a plurality of such regions where the first layer 41 surrounds the second layer 42.

[0051] The first layer 41 has the same structure as the first layer 2 described above.

[0052] The second layer 42 has the same structure as the second layer 3 described above.

[0053] The laminate 40 of this embodiment is a laminate in which a plurality of first layers 41 and a plurality of second layers 42 are stacked, and the first layers 41 are connected by having regions where they contact each other. This allows the structural performance of the carbon fiber composite material contained in the first layers 41 to be exerted in the laminate. Furthermore, the laminate 40 of this embodiment has a region in which the first layers 41 surround the second layers 42, allowing the structural performance of the carbon fiber composite material to be exerted in the laminate. Furthermore, in the laminate 40 of this embodiment, the second layer 42 is composed of a second layer 42 (42A) and a second layer 42 (42B). Specifically, the second layer 42 has second layers 42A and 42B extending along the Z direction so that both ends of the second layer 42 in the width direction (Y-axis direction) contact the lower surface of the upper surface 40a and the upper surface of the lower surface 40b, thereby enabling the laminate to better exhibit the structural performance of the carbon fiber composite material. In this embodiment, the second layers 42A and 42B may be the same or different. While the second layer 42A and 42B are two layers in the above description, the present invention is not limited to this configuration and may include only one second layer or three or more second layers.

[0054] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0055] Examples 1 to 5 A laminate 20 was fabricated by stacking a plurality of laminates 10 having the structure shown in FIG. 3 . A pitch-based carbon fiber composite material was used as the carbon fiber composite material constituting the first layer. A graphite sheet was used as the second layer, having a thickness (a) of 120 μm, a thermal conductivity b of 2000 (W / (mK)) in the direction along the sheet surface of the graphite sheet, and a product of the thickness (a) and the thermal conductivity b of 240,000. The number of layers of the laminate 10 was adjusted to fabricate laminates 20 with thicknesses of 3 mm, 6 mm, 9 mm, 12 mm, and 15 mm.

[0056] [Comparative Examples 1 to 5] The same graphite sheet as in the Examples was used, and pitch-based carbon fiber composite materials were laminated on both main surfaces of the graphite sheet to produce laminates for the Comparative Examples. The pitch-based carbon fiber composite materials and graphite sheets used were the same as in the Examples. Laminates with thicknesses of 3 mm, 6 mm, 9 mm, 12 mm, and 15 mm were produced.

[0057] Reference Examples 1 to 5 As reference examples, aluminum plates having thicknesses of 3 mm, 6 mm, 9 mm, 12 mm, and 15 mm were used.

[0058] [Evaluation of Changes in Temperature Rise] Changes in temperature rise were observed for the laminate of the Example, the laminate of the Comparative Example, and the aluminum plate of the Reference Example. A heat load of 140 W was applied to the center of a heat conduction plate 300 mm long and 180 mm wide by a sheet heater, and the temperature rise relative to the heat sink temperature of the heater part in a steady state was evaluated in a heat transfer system with heat sinks at both ends. The results are shown in Figure 6. From the results shown in Figure 6, it can be seen that the temperature of the laminate of the Example did not change significantly even when the thickness changed. On the other hand, the temperature of the laminate of the Comparative Example tended to change significantly when the thickness changed. Furthermore, the temperature of the aluminum plate of the Reference Example changed significantly when the thickness changed.

[0059] [Examples 6 to 8] Laminates were produced in the same manner as in Examples 1 to 5, except that the thickness of the laminate was changed to 1.2 mm. [Comparative Examples 6 to 8] Laminates were produced in the same manner as in Comparative Examples 1 to 5, except that the thickness of the laminate was changed to 1.2 mm. [Measurement of Interlaminar Shear Strength] The interlaminar shear strength (τ) was measured for the laminates of the Examples and the laminates of the Comparative Examples. The interlaminar shear strength was measured in accordance with JIS K7078. Three specimens were prepared for each of the laminates of the Examples and the laminates of the Comparative Examples, and the interlaminar shear strength of each specimen was measured. The results are shown in Table 1.

[0060]

[0061] The results shown in Table 1 indicate that the laminates of Examples 6 to 8 have about twice the interlaminar shear strength of the laminates of Comparative Examples 6 to 8.

[0062] Examples 9 to 11: Laminates having a length (L) of 80 mm, a width (b) of 15 mm, and a thickness (h) of 1.5 mm were prepared in the same manner as in Examples 1 to 5. [Measurement of Flexural Strength] The flexural strength (σ) of the laminates of Examples 9 to 11 was measured. The flexural strength was measured in accordance with JIS K7078. Three specimens were prepared for the laminates of the examples, and the flexural strength of each specimen was measured. The results are shown in Table 2.

[0063]

[0064] From the results shown in Table 2, the bending test results showed that the laminates of Examples 8 to 10 had strength and rigidity equivalent to that of an aluminum plate (elastic modulus 70 GPa, bending strength 200 MPa). The laminates of the Examples had a specific gravity of 1.74 and a calculated thermal conductivity of 600 to 1400 W / m / K. The thermal conductivity of the laminates of the Examples was 1.2 times that of copper, and the heat transport capacity was achieved with 1 / 5 the mass of copper. In other words, it was found that the heat transport capacity per mass of the laminates of Examples 8 to 10 was 6.6 times that of copper.

[0065] From the above results, it can be seen that the laminate of the embodiment solves all of the conventional heat countermeasures (high heat transport capacity, lightweight, compact) that have previously required either compromising on the heat transport capacity of aluminum or using copper at the expense of mass, or adding a heat pipe, which is a heat transport device, at the expense of mass and space (complicating the structure and reducing reliability).

[0066] The laminate of the present invention can be used to dissipate heat generated from IC chips while supplementing the mechanical strength of the substrate in devices that mount a large number of heat-generating elements (IC chips) densely in a planar array antenna, such as an electronically scanned planar array antenna. Furthermore, the laminate of the present invention provides thermal management in environments with strict mass requirements, such as satellite-mounted equipment, with performance equivalent to that of aluminum at less than half the mass. The laminate of the present invention can contribute to weight reduction of mounted equipment and simplification of thermal management within a satellite casing by controlling the direction of heat conduction.

[0067] 1, 10, 20, 30, 40 Laminate 2, 11, 31, 41 First layer 3, 12, 32, 42 Second layer 21, 43 Air gap

Claims

1. A laminate comprising: a plurality of first layers made of a carbon fiber composite material; and a plurality of second layers made of a graphite sheet, wherein the plurality of first layers and the plurality of second layers are stacked together, wherein the plurality of first layers have an area where they contact each other, and the graphite sheet has a product of the thickness a (μm) and the thermal conductivity b (W / (mK)) in a direction along the sheet surface of the graphite sheet of 75,000 or more.

2. A laminate comprising a plurality of first layers made of a carbon fiber composite material and a plurality of second layers made of graphite sheets, wherein the plurality of first layers and the plurality of second layers are stacked together, wherein the plurality of first layers have an area where they contact each other, and when the shortest distance between two opposing surfaces is defined as the thickness, the longest distance is defined as the length, and the distance in a direction perpendicular to the thickness direction and the length direction is defined as the width, both ends in the width direction of the plurality of second layers are positioned so as to contact the inner surface of the layer that forms the surface of the laminate.

3. The laminate according to claim 1 or 2, wherein the first layer has an area surrounding the second layer.

4. A laminate according to claim 1 or 2, wherein the second layer extends parallel to one direction of the outermost surface in the thickness direction of the laminate.

5. The laminate according to claim 4, wherein at least one of said second layers extends parallel to the outermost surface in the thickness direction of said laminate and in a direction perpendicular to said one direction.

6. The laminate according to claim 1 or 2, wherein the carbon fiber composite material is a pitch-based carbon fiber composite material.

7. The laminate according to claim 1 or 2, wherein the product of the thickness a (μm) and the thermal conductivity b (W / (mK)) in a direction along one main surface of the graphite sheet is 100,000 or more.

8. A laminate according to claim 1 or 2, wherein the first layer has a region that is connected to the other outermost surface from the outermost surface in the thickness direction of the laminate.

9. The laminate according to claim 1 or 2, wherein two or more of the graphite sheets are in contact with each other to form the second layer.

10. The laminate according to claim 1 or 2, wherein three or more of the second layers are present in the width direction or thickness direction of the laminate.

11. The laminate according to claim 1 or 2, wherein the thickness of the laminate is 3.1 to 20 mm.

12. The laminate according to claim 1 or 2, wherein the carbon fibers of the carbon fiber composite material are continuous carbon fibers.

13. The laminate according to claim 1 or 2, wherein the graphite sheet has a thickness a of 50 μm or more.

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