Heat dissipation sheet and manufacturing method thereof

Abstract

[Problem] To provide a heat-dissipating sheet having reduced hardness and increased heat conductivity, and a method for manufacturing the same.　[Solution] The present invention relates to a heat-dissipating sheet 1 and a method for manufacturing the same. The heat-dissipating sheet 1 comprises a sheet-like rubbery elastic body 10, and an elongated heat-conductive filler 20 having higher heat conductivity compared to the rubber-like elastic body 10 and embedded in the rubber-like elastic body 10 oriented obliquely with respect to a thickness direction thereof. The rubber-like elastic body 10 includes at least one hole 14 which is oriented in parallel to the thickness direction of the rubber-like elastic body 10 or obliquely with respect to the thickness direction. The heat-conductive filler 20 has both ends thereof exposed on surfaces 11, 12 of the rubber-like elastic body 10.

Description

Cross Reference

[0001] This application claims priority based on Japanese Patent Application No. 2021-149842 filed on September 15, 2021, the contents of which are incorporated herein by reference. In addition, the contents of the patents, patent applications, and literature cited in this application are incorporated herein by reference. [Technical Field]

[0002] The present invention relates to a heat dissipation sheet and a method for producing the same. [Background technology]

[0003] Control systems for automobiles, aircraft, ships, and home and commercial electronic devices are becoming more precise and complex, and as a result, the integration density of small electronic components on circuit boards is steadily increasing. As a result, there is a strong demand for solutions to the problems of electronic component failure and shortened lifespan caused by heat generation around the circuit board.

[0004] A known method for achieving rapid heat dissipation from a circuit board is to interpose a heat dissipation sheet between a heat source such as a circuit board and a cooling member such as a heat sink or a cooling fan. Widely used heat dissipation sheets are those in which a thermally conductive filler is dispersed in a rubber-like elastic material such as resin or rubber. Recently, heat dissipation sheets have become known in which carbon fibers, as a thermally conductive filler, are oriented in the thickness direction of the heat dissipation sheet (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-56299 Summary of the Invention [Problem to be solved by the invention]

[0006] Such heat-dissipating sheets require further improvements in thermal conductivity. To achieve high thermal conductivity, a common approach is to increase the filling rate of thermally conductive fillers, such as carbon fibers, contained within the heat-dissipating sheet. However, increasing the filling rate of the thermally conductive filler can result in the heat-dissipating sheet becoming too hard and losing its flexibility. A high hardness of the heat-dissipating sheet can reduce its adhesion to heat sources and cooling components, potentially resulting in reduced thermal conductivity. Furthermore, conventional heat-dissipating sheets such as those described above are manufactured by slicing a flexible sheet precursor, in which the carbon fibers are oriented in one direction within the plane, along a plane perpendicular to the orientation direction. Heat-dissipating sheets manufactured in this manner have high surface roughness at the cut surfaces, which can increase thermal resistance at the contact interface with the heat source and / or cooling component, potentially reducing the thermal conductivity of the heat-dissipating sheet through its thickness. This applies not only to circuit boards but also to other heat sources such as electronic components, electronic device bodies, and battery cells.

[0007] In order to solve the above problems, an object of the present invention is to provide a heat dissipation sheet that can achieve low hardness and high thermal conductivity, and a method for manufacturing the same. [Means for solving the problem]

[0008] (1) To achieve the above object, a heat dissipation sheet according to one embodiment comprises: a sheet-like rubber elastic body; a long thermally conductive filler having superior thermal conductivity to the rubber-like elastomer and embedded in the rubber-like elastomer so as to be oriented obliquely with respect to the thickness direction of the rubber-like elastomer; A heat dissipation sheet comprising: the rubber-like elastomer has at least one void oriented parallel to the thickness direction of the rubber-like elastomer or oriented obliquely to the thickness direction, Both ends of the thermally conductive filler are exposed on the surface of the rubber-like elastic body. (2) In another embodiment of the heat dissipation sheet, the rubber-like elastic body preferably has at least one pore oriented diagonally relative to the thickness direction of the rubber-like elastic body, and both ends of the thermally conductive filler may be exposed on the surface of the rubber-like elastic body. (3) In a heat dissipation sheet according to another embodiment, the thermally conductive filler may be embedded and oriented at an angle greater than 45° and less than 85° relative to the surface of the rubber-like elastic body. (4) In another embodiment of the heat dissipation sheet, preferably, the diameter of the two ends of the thermally conductive filler exposed on the surface of the rubber-like elastic body may be larger than the diameter of the area embedded in the rubber-like elastic body. (5) In another embodiment, the heat dissipation sheet may preferably have silicone rubber formed by hardening uncured liquid rubber between the rubber-like elastic body and the void or between the void and another void. (6) In the heat dissipation sheet according to another embodiment, the uncured liquid rubber may preferably be liquid silicone rubber. (7) In the heat dissipation sheet according to another embodiment, the rubber-like elastic body may preferably be silicone rubber. (8) In another embodiment of the heat dissipation sheet, preferably, at least one of the front and back surfaces of the rubber-like elastic body may have a coating layer of a lubricant. (9) In another embodiment of the heat dissipation sheet, the pores of the rubber-like elastic body may preferably contain a lubricant. (10) In another embodiment, the heat dissipation sheet preferably has a lubricant in the pores and may have a coating layer of the lubricant on at least one of the front and back surfaces of the rubber-like elastic body. (11) In another embodiment of the heat dissipation sheet, preferably, the voids located at the outermost periphery of the rubber-like elastic body in a planar view do not contain the lubricant, and the lubricant may be present in an area in the plane that is more inward than the voids located at the outermost periphery. (12) In the heat dissipation sheet according to another embodiment, the thermally conductive filler may preferably be carbon fiber. (13) To achieve the above object, a method for manufacturing a heat-dissipating sheet according to one embodiment is a method for manufacturing any one of the heat-dissipating sheets described above, a discharging step of discharging the curable rubber composition containing the thermally conductive filler onto a flat surface of a flat body in a plurality of rows along a first predetermined direction; a molding step of forming the curable rubber composition discharged onto the flat surface into a sheet and curing the sheet to form a filler-containing sheet in which the thermally conductive filler is oriented in the first predetermined direction and the sheet has at least one recessed portion on its surface that is aligned along a second predetermined direction; a lamination step of laminating a plurality of the filler-containing sheets in a state in which uncured liquid rubber is disposed between the filler-containing sheets, and curing the uncured liquid rubber to form a laminated block body with the thermally conductive filler aligned; a cutting step of cutting the block body into sheets in a direction oblique to the orientation direction of the thermally conductive filler; Includes. (14) In another embodiment of the method for manufacturing a heat dissipation sheet, preferably, the lamination step may involve laminating the plurality of filler-containing sheets so that the positions of the recesses of the filler-containing sheets are different in the thickness direction of the filler-containing sheets. (15) In another embodiment of the method for manufacturing a heat dissipation sheet, preferably, after the cutting step, a lubricant supplying step may be carried out in which a lubricant is supplied to at least one of the front and back surfaces of the rubber-like elastic body and / or to the inside of the pores. (16) To achieve the above object, a method for manufacturing a heat-dissipating sheet according to one embodiment is a method for manufacturing any one of the heat-dissipating sheets described above, a discharging step of discharging the curable rubber composition containing the thermally conductive filler onto a flat surface of a flat body in a plurality of rows along a first predetermined direction; a molding step of molding the curable rubber composition discharged onto the flat surface into a sheet and curing the sheet to form a filler-containing sheet in which the thermally conductive filler is oriented in the first predetermined direction; a lamination step of laminating a plurality of the filler-containing sheets in a state in which uncured liquid rubber is disposed between the filler-containing sheets, and curing the uncured liquid rubber to form a laminated block body with the thermally conductive filler aligned; a cutting step of cutting the block body into sheets in a direction oblique to the orientation direction of the thermally conductive filler; a void forming step of forming the voids in the rubber-like elastic body after the cutting step; Includes. (17) In another embodiment, in the method for producing a heat dissipation sheet, a lubricant supplying step may be carried out before or after the void forming step, in which a lubricant is supplied to at least one of the front and back surfaces of the rubber-like elastic body and / or inside the voids. (18) In the method for producing a heat dissipation sheet according to another embodiment, preferably, in the cutting step, cutting into sheets may be performed at an angle of more than 45° and less than 85° with respect to the orientation direction of the thermally conductive filler. (19) In the method for producing a heat dissipation sheet according to another embodiment, the thermally conductive filler may preferably be carbon fiber. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a heat dissipation sheet that can achieve low hardness and high thermal conductivity, and a method for producing the same. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 shows a plan view of a heat dissipation sheet according to a first embodiment of the present invention and an enlarged view of a part B thereof. [Figure 2] FIG. 2 shows a cross-sectional view of the heat dissipation sheet taken along line AA of FIG. 1, an enlarged view of a part C thereof, and an enlarged view of a part D thereof. [Figure 3] FIG. 3 shows an example of the flow of the main steps in the method for producing a heat-dissipating sheet according to the first embodiment of the present invention. [Figure 4] FIG. 4 shows the state of each step of the manufacturing method shown in FIG. 3 in plan view and cross section. [Figure 5] FIG. 5 shows cross-sectional views of the respective steps following FIG. [Figure 6] FIG. 6 shows the state of each step subsequent to FIG. 5 in plan view. [Figure 7] FIG. 7 shows cross-sectional views of the respective steps following FIG. [Figure 8] FIG. 8 is a perspective view showing the state of each step following FIG. [Figure 9] FIG. 9 shows a plan view of a heat dissipation sheet according to a second embodiment of the present invention and an enlarged view of a part B thereof. [Figure 10] FIG. 10 shows a cross-sectional view of the heat dissipation sheet taken along line AA of FIG. 9, an enlarged view of a part C thereof, and an enlarged view of a part D thereof. [Figure 11] FIG. 11 shows a plan view of a first modified example of the heat dissipation sheet of FIG. [Figure 12] FIG. 12 is a diagram showing a second modified example of the heat dissipation sheet of FIG. 9, showing a cross-sectional view similar to the cross-sectional view taken along line AA in FIG. 9 and an enlarged view of a part C thereof. [Figure 13] FIG. 13 is a diagram showing a third modified example of the heat dissipation sheet of FIG. 9, showing a cross-sectional view similar to the cross-sectional view taken along line AA in FIG. 9 and an enlarged view of a part C thereof. [Figure 14] FIG. 14 shows a cross-sectional view of the heat dissipation sheet according to the third modified example in the middle of being sandwiched between the cooling member and the heat source. [Figure 15] FIG. 15 shows a cross-sectional view of a state in which the heat dissipation sheet is completely sandwiched between the cooling member and the heat source, which is a further development from the state shown in FIG. [Figure 16] Figure 16 shows a cross-sectional view comparing an example (16A) in which a lubricant is supplied to the surface of a conventional heat dissipation sheet without pores and a heat sink, which is an example of a cooling member, is brought into contact with the heat dissipation sheet, and an example (16B) in which a lubricant is supplied to the surface of the heat dissipation sheet of Figure 9 and a heat sink is brought into contact with the heat dissipation sheet. [Figure 17] FIG. 17 shows a plan view of a heat dissipation sheet according to a fourth modified example and a cross-sectional view taken along line AA of the plan view. [Figure 18] FIG. 18 shows a plan view of a heat dissipation sheet according to a fifth embodiment and a cross-sectional view taken along line AA of the plan view. [Figure 19] FIG. 19 shows a plan view of a heat dissipation sheet according to a sixth modified example and a cross-sectional view taken along line AA of the plan view. [Figure 20] FIG. 20 shows a plan view of a heat dissipation sheet according to a seventh modification and a cross-sectional view taken along line AA of the plan view. [Figure 21] FIG. 21 shows the flow of a manufacturing method in which holes are formed after the cutting step of the block body. [Figure 22] FIG. 22 shows the flow of the manufacturing method in which a lubricant is supplied to the rubber-like elastic body after the pore forming step. [Figure 23] FIG. 23 shows a photograph of a heat dissipation sheet according to a first modified example of the second embodiment. [Figure 24] FIG. 24 shows a variation of the flow diagram of FIG. [Explanation of symbols]

[0011] 1 heat dissipation sheet, 10 rubber-like elastomer, 11, 12 surface, 14 voids, 20 carbon fiber (an example of a thermally conductive filler), 21, 22 both ends (of the carbon fiber, which is an example of a thermally conductive filler), 23 region (of the carbon fiber, which is an example of a thermally conductive filler) embedded in the rubber-like elastomer, 30 silicone rubber, 45 coating layer, 45a lubricant, 70 curable rubber composition 72, 74... Film (an example of a flat body), 76, 80, 82... Carbon-containing sheet (an example of a filler-containing sheet), 78... Recess, 85... Uncured liquid rubber, 90... Block body, Φ1... ​​Diameter of both ends of a carbon fiber which is an example of a thermally conductive filler, Φ2... Diameter of a region of a carbon fiber which is an example of a thermally conductive filler that is embedded in a rubber-like elastic body, D1... First predetermined direction, D2... Second predetermined direction. DETAILED DESCRIPTION OF THE INVENTION

[0012] Next, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below do not limit the invention according to the claims, and not all of the elements and combinations thereof described in the embodiments are necessarily essential to the solution of the present invention.

[0013] (First embodiment) 1. Heat dissipation sheet Fig. 1 shows a plan view of a heat dissipation sheet according to a first embodiment of the present invention and an enlarged view of part B. Fig. 2 shows a cross-sectional view of the heat dissipation sheet taken along line AA of Fig. 1, an enlarged view of part C, and an enlarged view of part D.

[0014] The heat dissipation sheet 1 according to this embodiment is a sheet with excellent thermal conductivity that conducts heat from a heat source to a cooling-side component, enabling heat dissipation from the heat source. The "heat dissipation sheet" may also be referred to as a "thermally conductive sheet." In this embodiment, the heat dissipation sheet 1 is a sheet that is disposed between a heat source and a cooling-side component, such that one surface 11 in the thickness direction of the rubber-like elastomer 10 contacts the heat source and the other surface 12 in the thickness direction contacts the cooling-side component. The heat dissipation sheet 1 comprises a sheet-like rubber-like elastomer 10 and carbon fibers 20 embedded and oriented obliquely relative to the thickness direction of the rubber-like elastomer 10 (the vertical direction in FIG. 2). The surfaces 11 and 12 are the widest surfaces of the rubber-like elastomer 10 and refer to the surfaces visible in a planar view of the rubber-like elastomer 10. Furthermore, the surface 11 refers to the "front surface." The surface 12 refers to the "rear surface." The carbon fibers 20 are an example of a long, thermally conductive filler. The thermally conductive filler has superior thermal conductivity to the rubber-like elastomer 10. In the following embodiments, an example using carbon fiber 20 as the thermally conductive filler will be mainly described. The rubber-like elastomer 10 has at least one void 14 oriented in a direction oblique to its thickness direction (the vertical direction in FIG. 2 ). Both ends 21, 22 of the carbon fiber 20 are exposed to the surfaces 11, 12 of the rubber-like elastomer 10. The void 14 preferably occupies more than 0% and less than 80%, and more preferably more than 20% and less than 60%, of the area of ​​the surface 11 or 12 of the rubber-like elastomer 10. This also applies to the second embodiment described below. When the void 14 is obliquely inclined, the inclination angle of the void 14 with respect to the surface 11 or 12 is preferably more than 0° and less than 80°, and more preferably more than 20° and less than 50°. This also applies to the second embodiment described below.

[0015] In this embodiment, the heat dissipation sheet 1 is a member in the form of a single sheet in plan view, formed by stacking a plurality of rubber-like elastomers 10. The heat dissipation sheet 1 preferably has silicone rubber 30, which is uncured liquid rubber cured, disposed between the plurality of rubber-like elastomers 10. The silicone rubber 30 is preferably disposed between the rubber-like elastomers 10 and the holes 14 in the thickness direction of the heat dissipation sheet 1 (the vertical direction in FIG. 2) (see the enlarged view of part C in FIG. 2). The uncured liquid rubber acts as an adhesive that bonds the rubber-like elastomers 10 together. Next, each component of the heat dissipation sheet 1 will be described.

[0016] (1) Rubber-like elastic body The rubber-like elastomer 10 is not particularly limited and can be appropriately selected depending on the performance required of the heat dissipation sheet. Examples include thermosetting resins and thermoplastic resins. Thermosetting resins include elastomeric thermosetting resins such as silicone rubber, silicone resin, polyurethane resin, and epoxy resin. Thermoplastic resins include elastomeric thermoplastic resins such as synthetic rubber, polyethylene resin, polyurethane resin, ABS resin, and soft polyvinyl chloride resin. These may be used alone or in combination. Among these, silicone rubber is particularly preferred because of its excellent moldability, weather resistance, and heat resistance, as well as its adhesion and conformability to heat sources such as electronic components. The rubber-like elastomer 10 may contain the above-mentioned resin material and a filler with higher thermal conductivity than the resin material. As a result, the rubber-like elastomer 10 has higher thermal conductivity than a material composed solely of resin material, thereby improving thermal conductivity from the heat source to the cooling side. Fillers that can be selected include particulate, fibrous, plate-like, and needle-like fillers, such as aluminum oxide (Al2O3), aluminum nitride (AlN), cubic boron nitride (cBN), hexagonal boron nitride (hBN), zinc oxide, silicon carbide, aluminum hydroxide, and diamond. Fillers with high insulating properties are preferred.

[0017] (2) Long, thermally conductive filler Carbon fibers 20, an example of a long thermally conductive filler, are preferably embedded in the rubber-like elastomer 10, oriented so that the angle θ1 relative to the surfaces 11 and 12 of the rubber-like elastomer 10 is greater than 45° and less than 85°. In the heat-dissipating sheet 1, a decrease in thermal conductivity in the thickness direction can be suppressed by making the angle θ1 greater than 45°. Furthermore, in the heat-dissipating sheet 1, an increase in hardness can be suppressed by making the angle θ1 less than 85°. However, θ1 may be greater than 0° and equal to or less than 45°. Each surface of both end portions 21 and 22 of the carbon fibers 20 is preferably flush with the surfaces 11 and 12 of the rubber-like elastomer 10, respectively, and does not significantly protrude or recess from the surfaces 11 and 12. The diameter Φ1 of the both end portions 21 and 22 exposed on the surfaces 11 and 12 of the rubber-like elastomer 10 is preferably greater than the diameter Φ2 of the region 23 embedded in the rubber-like elastomer 10. The ratio Φ1 to Φ2 is preferably 1<Φ1 / Φ2<2, more preferably 1.5<Φ1 / Φ2<2. In the heat-dissipating sheet 1, the diameter Φ1 of the two ends 21, 22 of the carbon fibers 20 is larger than the diameter Φ2 of the remaining region 23. Therefore, even if an external force is applied in the direction of pulling out the carbon fibers 20 (the orientation direction of the carbon fibers 20), the carbon fibers 20 can be prevented from being pulled out of the rubber-like elastomer 10. Furthermore, in the heat-dissipating sheet 1, the two ends 21, 22 of the carbon fibers 20, each having a diameter Φ1, come into contact with the heat source or a cooling-side component, increasing the contact area between the carbon fibers 20 and the heat source or cooling-side component, thereby increasing thermal conductivity. The orientation angle θ1 of the carbon fibers 20 is not limited to the above range, as long as the carbon fibers 20 are oriented at least obliquely relative to the thickness direction of the rubber-like elastomer 10.

[0018] The carbon fibers 20 are not particularly limited, but are preferably anisotropic pitch-based carbon fibers. However, the carbon fibers 20 are not limited to anisotropic pitch-based carbon fibers and may be other carbon fibers such as PAN-based carbon fibers, isotropic pitch-based carbon fibers, amorphous carbon fibers, carbon nanotubes, graphite nanofibers, and diamond fibers, or may be a mixture of two or more of these carbon fibers. The fiber length of the carbon fibers 20 is preferably 0.002 mm to 10 mm, more preferably 0.005 mm to 7.5 mm. The fiber diameter of the carbon fibers 20 is preferably 1 μm to 50 μm, more preferably 5 to 25 μm.

[0019] (3) Silicone rubber The silicone rubber 30 is a low-fluidity or solid silicone rubber that has been cured from an uncured liquid rubber. Uncured liquid rubber is a highly fluid rubber that can be cured by any desired method. Examples of methods for curing uncured liquid rubber include heating, light irradiation, electron beam irradiation, and curing with a catalyst or curing agent. Examples of uncured liquid rubber include liquid silicone rubber, liquid natural rubber, liquid isoprene rubber, liquid butadiene rubber, liquid styrene-butadiene rubber, liquid butyl rubber, liquid nitrile rubber, liquid ethylene-propylene rubber, liquid chloroprene rubber, liquid chlorosulfonated polyethylene rubber, liquid urethane rubber, and liquid fluororubber. Among these, liquid silicone rubber is preferred because it is less likely to undergo dimensional change or warping after curing, has small compression set, and has high heat resistance. Liquid silicone rubber may be either a condensation type or an addition type.

[0020] The heat-dissipating sheet 1 preferably has a plurality of pores 14 oriented obliquely to the thickness direction of the rubber-like elastomer 10 (the vertical direction in FIG. 2 ). The pores 14 are preferably through-holes that penetrate from one surface 11 to the other surface 12 in the thickness direction of the rubber-like elastomer 10. More preferably, the heat-dissipating sheet 1 has a plurality of pores 14 arranged at predetermined intervals on the surfaces 11 and 12. However, the number, arrangement, shape, etc. of the pores 14 are not particularly limited and are preferably designed appropriately depending on the performance required of the heat-dissipating sheet. Furthermore, the pores 14 do not have to penetrate from one surface 11 to the other surface 12. In this embodiment, the pores 14 are arranged approximately parallel to the orientation direction of the carbon fibers 20 (see the enlarged view of part C in FIG. 2 ). However, the pores 14 do not have to be arranged parallel to the orientation direction of the carbon fibers 20 as long as they are oriented obliquely to the thickness direction of the rubber-like elastomer 10. The heat dissipation sheet 1 configured in this manner can prevent the sheet from becoming too hard due to the pores 14 oriented obliquely to the thickness direction. The heat dissipation sheet 1 is compressed in the thickness direction between the heat source and the cooling-side member. Because the heat dissipation sheet 1 has pores 14, stress on the carbon fibers 20 can be reduced and damage to the carbon fibers 20 can be prevented even during deformation due to compression.

[0021] The arithmetic mean roughness Ra of surfaces 11, 12 perpendicular to the thickness direction (the vertical direction in FIG. 2) of heat-dissipating sheet 1 is preferably 1.0 μm or more and 1.8 μm or less. The ten-point mean roughness Rz of surfaces 11, 12 of heat-dissipating sheet 1 is preferably 7.7 μm or more and 18 μm or less. The arithmetic mean roughness Ra is a value measured in accordance with JIS B 0601-2001. The ten-point mean roughness Rz is a value measured in accordance with JIS B 0601-1994. By reducing the surface roughness of heat-dissipating sheet 1 in this way, surfaces 11, 12 perpendicular to the thickness direction of heat-dissipating sheet 1 become flat, thereby ensuring more reliable contact between the heat source and carbon fibers 20 and increasing thermal conductivity.

[0022] 2. Manufacturing method of heat dissipation sheet Next, a method for manufacturing the heat dissipation sheet according to the first embodiment of the present invention will be described.

[0023] The method for manufacturing the heat dissipation sheet 1 includes a discharging step of discharging a curable rubber composition containing carbon fibers 20 onto the flat surface of a planar body in multiple rows along a first predetermined direction, a shaping step of molding the curable rubber composition discharged onto the flat surface of the planar body into a sheet and curing it to form a carbon-containing sheet (an example of a filler-containing sheet) in which the carbon fibers 20 are oriented in the first predetermined direction and the surface has at least one recessed portion along a second predetermined direction, a laminating step of stacking multiple carbon-containing sheets with uncured liquid rubber disposed between them and curing the uncured liquid rubber to form a stacked block body with the orientation of the carbon fibers 20 aligned, and a cutting step of cutting the block body into sheets obliquely relative to the orientation direction of the carbon fibers 20. In the following embodiments, examples will be mainly described using carbon-containing sheets as filler-containing sheets.

[0024] FIG. 3 shows an example of a flow of the main steps of the manufacturing method of the heat dissipation sheet according to the first embodiment of the present invention. FIG. 4 shows the status of each step of the manufacturing method in FIG. 3 in plan view and cross-sectional view. FIG. 5 shows the status of each step following FIG. 4 in cross-sectional view. FIG. 6 shows the status of each step following FIG. 5 in plan view. FIG. 7 shows the status of each step following FIG. 6 in cross-sectional view. FIG. 8 shows the status of each step following FIG. 7 in perspective view. Note that in FIGS. 4 and 8, the carbon fibers 20 are exaggerated to explain the manufacturing process.

[0025] The heat dissipation sheet 1 can be manufactured through a discharge step (S100), a molding step (S110), a lamination step (S120), and a cutting step (S130). Steps S100 to S130 will be described in detail below with reference to FIGS.

[0026] (1) Discharge process (S100) In this step, a curable rubber composition 70 containing carbon fibers 20 is extruded in multiple rows along a first predetermined direction D1 (the vertical direction in FIG. 4(a)) onto a flat surface of a film (an example of a flat body) 72 (see FIG. 4). In this embodiment, in the extrusion step (S100), the curable rubber composition 70 is preferably extruded onto the film 72 while the film 72 is placed in a recess 41 (see the cross-sectional view of line E-E in FIG. 4(b)) of a lower mold 40 that constitutes a mold 60 used in the molding step (S110) described below. In the extrusion step (S100), the curable rubber composition 70 is extruded linearly along the first predetermined direction D1, and then in multiple rows aligned in a direction perpendicular to the first predetermined direction D1 (the horizontal direction in FIG. 4(a)) (see FIG. 4(a)), thereby forming a sheet-like curable rubber composition 70 on the film 72 (see FIG. 4(b)). The curable rubber composition 70 is a composition that will become a rubber-like elastomer 10 after curing. In the discharging step (S100), the curable rubber composition 70 containing the carbon fibers 20 is discharged along a first predetermined direction D1, thereby orienting the carbon fibers 20 along the first predetermined direction D1. Hereinafter, the first predetermined direction D1 will also be referred to as the carbon fiber orientation direction D1 or the discharge direction D1. The film 72 is preferably a film made of a resin. Examples of resins include polyethylene terephthalate (PET), polyethylene naphthalate, polyethylene isophthalate, polybutylene terephthalate, polyacetate, polycarbonate, polyphenylene sulfide, polyamide, polyvinyl chloride, and polyvinylidene chloride. Among these, a PET film is more preferable as the film 72.

[0027] (2) Molding process (S110) In this process, the curable rubber composition 70 dispensed onto the film 72 is molded into a sheet and cured to form a carbon-containing sheet 76 having carbon fibers 20 oriented in a first predetermined direction D1 and at least one recessed portion 78 on its surface aligned with a second predetermined direction D2 (see FIG. 5). In this embodiment, the second predetermined direction D2 is the same as the first predetermined direction D1 (the direction into the paper in FIG. 5). However, in a plan view of the carbon-containing sheet 76, the first predetermined direction may be offset from the second predetermined direction by preferably within 20 degrees, more preferably within 10 degrees, and even more preferably within 5 degrees. In this embodiment, the carbon-containing sheet 76 has a plurality of recessed portions 78 spaced at predetermined intervals in a direction perpendicular to the second predetermined direction D2 (the horizontal direction in FIG. 5). More specifically, first, the flat surface of a film (an example of a flat body) 74 is placed on the curable rubber composition 70 dispensed onto the film 72. The film 74 is preferably made of the same material as the film 72 described above. Next, the upper mold 50 that constitutes the mold 60 is prepared and placed on the side of the lower mold 40 facing the recess 41, and the lower mold 40 and the upper mold 50 are closed together (see FIGS. 5(c) and 5(d)). The upper mold 50 has a recess 51 on the surface facing the recess 41 of the lower mold 40. The recess 51 has an irregularity 52 on its inner bottom surface that can be transferred to form a recess 78. After clamping the mold 60, it is heated to mold the curable rubber composition 70 (see FIG. 5(e)). As a result, the curable rubber composition 70 cures to form a rubber-like elastomer 10 containing carbon fibers 20. The transfer of the irregularities 52 also forms the recess 78. The mold 60 is then opened, and the films 72 and 74 are peeled off to form a carbon-containing sheet 76 (see FIG. 5(f)). The carbon-containing sheet 76 is a sheet containing carbon fibers 20 oriented in a first predetermined direction D1 (the depth direction in FIG. 5(f)) in a rubber-like elastic body 10. The carbon-containing sheet 76 is also a sheet having a plurality of recesses 78 at predetermined intervals in a direction perpendicular to the second predetermined direction D2 (the left-right direction in FIG. 5) (see FIG. 6(g)).

[0028] In this embodiment, in the forming step (S110), two types of carbon-containing sheets 80 and 82 are cut out from the carbon-containing sheet 76 (see FIG. 6(g)). The carbon-containing sheet 80 and the carbon-containing sheet 82 are carbon-containing sheets in which the positions of the recesses 78 in the direction perpendicular to the second predetermined direction D2 (the left-right direction in FIG. 6) are different. The carbon-containing sheets 80 and 82 are sheets containing carbon fibers 20 oriented along the first predetermined direction D1 (the up-down direction in FIG. 6). In this embodiment, the forming step (S110) preferably involves cutting the carbon-containing sheet 76 along the second predetermined direction D2 (the up-down direction in FIG. 6) so that the positions of the recesses 78 in the direction perpendicular to the second predetermined direction D2 (the left-right direction in FIG. 6) are different, thereby forming the carbon-containing sheets 80 and 82. In this embodiment, the carbon-containing sheet 80 and the carbon-containing sheet 82 are sheets of the same size, but may be sheets of different sizes. Furthermore, the method for cutting out the carbon-containing sheets 80 and 82 from the carbon-containing sheet 76 is not particularly limited as long as the method is capable of forming the two types of carbon-containing sheets 80 and 82.

[0029] (3) Lamination process (S120) In this step, a plurality of carbon-containing sheets 80, 82 are stacked with uncured liquid rubber 85 disposed between the carbon-containing sheets 80, 82, and the uncured liquid rubber 85 is cured to form a stacked block 90 with the orientation of the carbon fibers 20 aligned (see FIG. 7). Preferably, this step is a step of stacking the plurality of carbon-containing sheets 80, 82 such that the positions of the recesses 78 of the carbon-containing sheets 80, 82 are different in the thickness direction (the vertical direction in FIG. 7) of the carbon-containing sheets 80, 82. More specifically, first, the uncured liquid rubber 85 is disposed between the carbon-containing sheets 80, 82, and then the carbon-containing sheets 82 are stacked (see FIG. 7(h)). At this time, the two carbon-containing sheets 80, 82 are stacked such that the orientation direction D1 of the carbon fibers 20 contained in the two carbon-containing sheets 80, 82 stacked with the uncured liquid rubber 80 interposed therebetween is the same. The uncured liquid rubber 85 is preferably applied to the lower surface (i.e., the surface without irregularities) of the carbon-containing sheet 82. This is because it is easier to apply the uncured liquid rubber 85 to the carbon-containing sheet 82 in a thin and uniform thickness. In addition, at this time, the two carbon-containing sheets 80, 82 are overlapped so that the positions of the recesses 78 of the two carbon-containing sheets 80, 82 overlapped with the uncured liquid rubber 80 interposed therebetween are different in the thickness direction of the carbon-containing sheets 80, 82. That is, in the laminating step (S120), the two carbon-containing sheets 80, 82 are overlapped so that the recesses 78 of the carbon-containing sheet 80 and the recesses 78 of the carbon-containing sheet 82 are not positioned on the same line along the thickness direction (the up-and-down direction in FIG. 7) (see FIGS. 7(h) and (i)). This process is repeated to alternately stack the carbon-containing sheets 80 and 82 with the uncured liquid rubber 85 interposed between them, thereby stacking a plurality of carbon-containing sheets 80, 82 (see FIG. 7(i)). The uncured liquid rubber 85 becomes silicone rubber 30 after curing, and is preferably liquid silicone rubber. In this embodiment, the uncured liquid rubber 85 also serves as an adhesive that bonds the carbon-containing sheets 80, 82 together. Then, with the plurality of carbon-containing sheets 80, 82 stacked together, the uncured liquid rubber 85 is cured to form a block 90 (see FIG. 7(j)).The block body 90 is a laminate obtained by stacking a plurality of carbon-containing sheets 80, 82 so that the orientation direction D1 of the carbon fibers 20 contained in each of the carbon-containing sheets 80, 82 is the same (see FIG. 8(k)). The uncured liquid rubber 85 preferably has a hardness equal to or less than that of the carbon-containing sheets 80, 82 after curing. This is because it is possible to prevent an increase in hardness of the block body 90 and impart flexibility. Note that the lamination step (S120) may be performed by stacking the carbon-containing sheets 82 without using the uncured liquid rubber 85, and then performing a curing treatment such as heating (or cooling).

[0030] (4) Cutting process (S130) In this step, the block body 90 is cut into sheets in a direction oblique to the orientation direction D1 of the carbon fibers 20 (see FIG. 8). More specifically, the block body 90 is cut into sheets of a predetermined thickness at an angle θ2 greater than 45° and less than 85° relative to the orientation direction D1 of the carbon fibers 20 (see FIG. 8(k)). The predetermined thickness is preferably 0.01 mm to 10 mm, and more preferably 0.05 mm to 5 mm. In the cutting step (S130), the cutting means is not particularly limited as long as it is capable of cutting to the predetermined thickness, such as a known cutter or slicer, but it is preferable to slice the carbon fibers 20 using a rotary blade as the cutting means. In the cutting step (S130), the carbon fibers 20 are pulled by the cutting means during cutting, so that the diameter Φ1 of the cut surfaces 21 and 22 can be made larger than the diameter Φ2 of the region 23 embedded in the rubber-like elastomer 10 (see FIGS. 1 and 2). In the cutting step (S130), it is preferable to cut using cutting means so that the arithmetic mean roughness Ra of the cut surfaces 11, 12 is 1.0 μm or more and 1.8 μm or less. It is also preferable to cut using cutting means so that the ten-point mean roughness Rz of the cut surfaces is 7.7 μm or more and 18 μm or less in the cutting step (S130). By cutting the block body 90 in this manner in the cutting step (S130), the heat-dissipating sheet 1 can be manufactured (see FIGS. 8(l) and (m)). Finally, it is preferable to cut the inclined end faces of the heat-dissipating sheet 1 to make them vertical end faces. Note that FIG. 8(m) shows a view from the direction of arrow F in FIG. 8(l).

[0031] The heat-dissipating sheet 1 manufactured in this manner has carbon fibers 20 and pores 14 embedded in a direction oblique to the thickness direction (the vertical direction in FIG. 8(m)) (see FIG. 8(m)). Furthermore, in the heat-dissipating sheet 1, both ends 21, 22 of the carbon fibers 20 are exposed at the cut surfaces (i.e., the surfaces 11, 12 of the rubber-like elastomer 10). The diameter Φ1 of the both ends 21, 22 exposed at the cut surfaces 11, 12 of the carbon fibers 20 is larger than the diameter Φ2 of the region 23 embedded in the rubber-like elastomer 10. Therefore, the heat-dissipating sheet 1 manufactured in this manner increases the contact area between the carbon fibers 20 and the heat source or cooling-side component, thereby increasing thermal conductivity. Furthermore, the heat-dissipating sheet 1 can prevent the carbon fibers 20 from being pulled out of the rubber-like elastomer 10, even when an external force is applied in the direction of pulling out the carbon fibers 20 (the orientation direction Do of the carbon fibers 20). Furthermore, since the heat dissipation sheet 1 is cut in the cutting step (S130) to reduce surface roughness, the cut surface is flat, allowing for more reliable contact between the heat source and the carbon fibers 20. This further increases thermal conductivity. Furthermore, as described above, the heat dissipation sheet 1 has high thermal conductivity, so there is no need to increase the packing rate of the carbon fibers 20 to increase thermal conductivity. Therefore, the heat dissipation sheet 1 can achieve low hardness and high thermal conductivity by suppressing the increase in hardness that would otherwise occur due to an increase in the packing rate of the carbon fibers 20. Furthermore, the heat dissipation sheet 1 has pores 14 oriented obliquely to its thickness direction, which suppresses the increase in hardness and reduces stress on the carbon fibers 20, even when deformed by compression in the thickness direction, thereby preventing breakage of the carbon fibers 20.

[0032] 3. Other embodiments As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited to these and can be practiced in various modifications.

[0033] The heat dissipation sheet 1 may have at least one of the surfaces 11 and 12 perpendicular to its thickness direction coated with a resin. The resin used for this coating is not particularly limited, and examples include thermosetting or thermoplastic resins similar to the material of the rubber-like elastomer 10 described above. Also, as with the rubber-like elastomer 10, the heat dissipation sheet 1 may contain the above-mentioned resin material and a filler with higher thermal conductivity than the resin material. The filler may be the same as that of the rubber-like elastomer 10. With a heat dissipation sheet 1 configured in this manner, the coating on the surfaces 11 and 12 can further prevent the carbon fibers 20 from falling off the rubber-like elastomer 10. Furthermore, by including a highly thermally conductive filler in the resin material used for the coating, the heat dissipation sheet 1 can reduce the decrease in thermal conductivity due to the coating. When the surfaces 11, 12, and 13 of the heat dissipation sheet 1, 1a, are coated with the above-mentioned resin material, the heat dissipation sheet 1 can be manufactured by coating the surfaces 11 and 12 after the cutting step (S130).

[0034] In the manufacturing method of the heat dissipation sheet 1 described above, the recesses 78 are formed in the carbon-containing sheet 76 by molding using the mold 60, but the recesses 78 may be formed by other methods such as cutting or etching. In this case, in the molding step (S110), an upper mold that does not have the irregularities 52 on the inner bottom surface of the recess 51 is used instead of the upper mold 50 to form the carbon-containing sheet 76 without the recesses 78, and then the recesses 78 are formed in the carbon-containing sheet 76 by using a method such as cutting or etching.

[0035] In the manufacturing method of the heat dissipation sheet 1 described above, the carbon-containing sheet 76 is cut out to form the two types of carbon-containing sheets 80 and 82. However, the carbon-containing sheet 80 and the carbon-containing sheet 82 may be formed separately without forming the carbon-containing sheet 76. In this case, the two types of carbon-containing sheets 80 and 82 may be formed in the molding process using a method similar to that used to form the carbon-containing sheet 76. In this case, it is preferable to use an upper mold 50 having irregularities 52 on the inner bottom surface of the recesses 51 that correspond to the arrangement of the recesses 78 in each of the two types of carbon-containing sheets 80 and 82. Alternatively, in the molding process, the carbon-containing sheets 80 and 82 without the recesses 78 may be formed using an upper mold 50 without the irregularities 52, and then the recesses 78 may be formed in the carbon-containing sheets 80 and 82 using a method such as cutting or etching.

[0036] Furthermore, in the laminating step (S120), the plurality of carbon-containing sheets 80, 82 may be laminated so that the positions of the recesses 78 of the carbon-containing sheets 80, 82 are the same in the thickness direction of the carbon-containing sheets 80, 82.

[0037] After the molding step (S110), a trimming step may be performed to trim off excess areas of the carbon-containing sheet 76.

[0038] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to the drawings. In the second embodiment, parts common to the first embodiment are given the same reference numerals, and duplicated descriptions thereof will be omitted.

[0039] Fig. 9 shows a plan view of a heat dissipation sheet according to a second embodiment of the present invention and an enlarged view of part B. Fig. 10 shows a cross-sectional view of the heat dissipation sheet of Fig. 9 taken along line AA, an enlarged view of part C, and an enlarged view of part D.

[0040] The heat dissipation sheet 1 according to this embodiment comprises a sheet-like rubber-like elastic material 10 and carbon fibers 20 embedded and oriented obliquely relative to the thickness direction of the rubber-like elastic material 10. Unlike the first embodiment, the rubber-like elastic material 10 is a single sheet in a non-laminated state. The rubber-like elastic material 10 has at least one void 14 oriented in its thickness direction. Both ends of the carbon fiber 20 are exposed on the surface of the rubber-like elastic material 10. In this embodiment, the void 14 is a through-hole connecting surfaces 11 and 12 of the rubber-like elastic material 10 in the thickness direction. The void 14 is a through-hole parallel to the thickness direction of the rubber-like elastic material 10.

[0041] On the other hand, as in the first embodiment, the carbon fibers 20 are present in the rubber-like elastomer 10 at an angle θ1 (acute angle) relative to the surface 12 of the rubber-like elastomer 10. Preferably, the diameter Φ1 of the carbon fibers 20 exposed on the surfaces 11 and 12 of the rubber-like elastomer 10 is larger than the diameter Φ2 of the carbon fibers 20 embedded in the rubber-like elastomer 10. Here, the ratio Φ1 to Φ2 satisfies the following relationship: 1 < Φ1 / Φ2 < 2, and more preferably, 1.1 < Φ1 / Φ2 < 1.5. In the heat dissipation sheet 1, the carbon fibers 20 at the portion having the diameter Φ1 come into contact with the heat source or cooling element. This increases the contact area between the carbon fibers 20 and the heat source or cooling element, thereby increasing thermal conductivity. The orientation angle θ1 of the carbon fibers 20 is not limited to the above range, as long as the carbon fibers are oriented at least obliquely relative to the thickness direction of the rubber-like elastomer 10.

[0042] The pores 14 not only facilitate deformation of the heat dissipation sheet 1, but also retain a lubricant, as will be described later. The effect of retaining a lubricant will be described in detail later.

[0043] FIG. 11 shows a plan view of a first modified example of the heat dissipation sheet of FIG.

[0044] The heat dissipation sheet 1 according to the first modification is a laminated sheet of multiple sheets, similar to the heat dissipation sheet 1 according to the first embodiment. In this heat dissipation sheet 1, preferably, silicone rubber 30, which is uncured liquid rubber cured, is disposed between multiple rubber-like elastomers 10. In other words, the silicone rubber 30 is disposed between one void 14 and another void 14. The silicone rubber 30 is preferably disposed between the rubber-like elastomer 10 and the void 14 in the thickness direction of the heat dissipation sheet 1. The uncured liquid rubber acts as an adhesive that bonds the rubber-like elastomers 10 together.

[0045] FIG. 12 is a diagram showing a second modified example of the heat dissipation sheet of FIG. 9, showing a cross-sectional view similar to the cross-sectional view taken along line AA in FIG. 9 and an enlarged view of a part C thereof.

[0046] Similar to the first embodiment, the heat dissipation sheet 1 according to the second modification has at least one pore 14 oriented obliquely relative to the thickness direction of the rubber-like elastic body 10. Here, the angle at which the pore 14 is inclined relative to the surface 12 is θ1 (acute angle), which is the same as the angle at which the carbon fiber 20 is inclined relative to the surface 12. However, the angle at which the pore 14 is inclined relative to the carbon fiber 20 may be different.

[0047] FIG. 13 is a diagram showing a third modified example of the heat dissipation sheet of FIG. 9, showing a cross-sectional view similar to the cross-sectional view taken along line AA in FIG. 9 and an enlarged view of a part C thereof.

[0048] The heat dissipation sheet 1 according to the third modification has a lubricant coating layer 45 on at least one of the surfaces 11 and 12 of the rubber-like elastomer 10. Here, the heat dissipation sheet 1 has the coating layer 45 on both surfaces 11 and 12. However, the coating layer 45 may be provided on only one of the surfaces 11 and 12. The coating layer 45 is also provided in an area of ​​the rubber-like elastomer 10 other than the pores 14. However, some of the lubricant constituting the coating layer 45 may be present in the pores 14. In this case, it is preferable that the lubricant does not fill all of the pores 14. This is because, as will be described later, it is preferable that when the coating layer 45 is compressed, there is room for the lubricant constituting the coating layer 45 to flow into the pores 14 that are not filled with lubricant. The lubricant in the coating layer 45 and the pores 14 has a high viscosity that prevents it from easily flowing from the rubber-like elastomer 10, but is softer than the rubber-like elastomer 10.

[0049] The coating layer 45 is primarily composed of grease, an example of a lubricant, and is a layer that has high viscosity and can maintain its shape. Examples of grease include those based on modified silicone, silicone oil, or ester-based oil and containing a filler with higher thermal conductivity than the base material. Examples of highly thermally conductive fillers include particulate, fibrous, plate-like, or needle-like fillers, such as aluminum oxide (Al2O3), aluminum nitride (AlN), cubic boron nitride (cBN), hexagonal boron nitride (hBN), zinc oxide, silicon carbide, aluminum hydroxide, and diamond. Fillers with high insulating properties are preferred. Alternatively, the grease may be the above-mentioned base material alone. The coating layer 45 can prevent the carbon fibers 20 from falling out of the rubber-like elastomer 10.

[0050] Fig. 14 shows a cross-sectional view of the heat dissipation sheet according to the third modification in the middle of being sandwiched between the cooling member and the heat source. Fig. 15 shows a cross-sectional view of the heat dissipation sheet after progressing further from the state shown in Fig. 14, when it has been completely sandwiched between the cooling member and the heat source.

[0051] In this application, the term "cooling member" is broadly interpreted to include not only a member that actively cools, but also a member that is at a lower temperature than a heat source and can dissipate heat from the heat source. When the heat dissipation sheet 1 according to the third modification is sandwiched between a cooling member 95 and a heat source 96, the coating layers 45 formed on both thicknesswise surfaces of the rubber-like elastic body 10 are compressed and enter the pores 14 as lubricants 45a (see arrow F). In FIG. 15, the pores 14 are filled with lubricants 45a. However, the pores 14 may not be filled with lubricants 45a, and spaces (air) may exist within the pores 14. When the lubricants 45a enter the pores 14, if the carbon fibers 20 are exposed on the inner wall surfaces of the pores 14, heat transmitted from the heat source 96 through the carbon fibers 20 can be smoothly transmitted to the cooling member 95 via the lubricants 45a.

[0052] Figure 16 shows cross-sectional views for comparison between an example (16A) in which a lubricant is supplied to the surface of a conventional heat dissipation sheet without pores and a heat sink, which is an example of a cooling member, is brought into contact with the heat dissipation sheet, and an example (16B) in which a lubricant is supplied to the surface of the heat dissipation sheet of Figure 9 and the heat sink is brought into contact with the heat dissipation sheet. Note that in Figure 16, the heat source is omitted from the surface of the heat dissipation sheet opposite the heat sink.

[0053] As shown in (16A), if lubricant 45a is supplied onto a conventional heat dissipation sheet 100 without pores, and then a heat sink 95a (an example of a cooling member 95) is placed on top of it and pressure is applied, there is a high possibility that lubricant 45a will overflow onto the outside of heat dissipation sheet 100. As a result, the outside of heat dissipation sheet 100 will be soiled with lubricant 45a.

[0054] On the other hand, as shown in (16B), when lubricant 45a is supplied onto the heat dissipation sheet 1 according to the second embodiment, and then a heat sink 95a is placed on top of it and pressure is applied, the lubricant 45a enters the holes 14 and is less likely to spill out of the heat dissipation sheet 1. This reduces the possibility of the outside of the heat dissipation sheet 1 being soiled with lubricant 45a.

[0055] FIG. 17 shows a plan view of a heat dissipation sheet according to a fourth modified example and a cross-sectional view taken along line AA of the plan view.

[0056] The heat-dissipating sheet 1 according to the fourth modification, like the heat-dissipating sheet 1 according to the third modification, has a coating layer 45 of lubricant 45a on both the front and back surfaces of the rubber-like elastomer 10, but no lubricant 45a in the pores 14. However, the number and shape of the pores 14 in plan view differ from those of the third modification. Specifically, in the heat-dissipating sheet 1 according to the fourth modification, the pores 14 are rectangular or square in plan view, with a total of 80 pores 14 arranged in 10 columns and 8 rows. When the heat-dissipating sheet 1 is sandwiched between a heat source and a cooling element in the thickness direction, pressure applied in the thickness direction compresses the rubber-like elastomer 10, and the lubricant 45a constituting the coating layer 45 enters the pores 45a. This reduces the risk of the lubricant 45a spilling out of the heat-dissipating sheet 1.

[0057] FIG. 18 shows a plan view of a heat dissipation sheet according to a fifth embodiment and a cross-sectional view taken along line AA of the plan view.

[0058] The heat-dissipating sheet 1 according to the fifth modification has the same rubber-like elastomer 10 as the heat-dissipating sheet 1 according to the fourth modification. That is, the number and shape of the pores 14 in the fifth modification are the same as those in the fourth modification. The heat-dissipating sheet 1 according to the fifth modification contains lubricant 45a in some of the pores 14. More specifically, the pores 14 located at the outermost periphery of the rubber-like elastomer 10 do not contain lubricant 45a, while the pores 14 in the region more inward than the outermost periphery contain lubricant 45a. Neither the front nor back surface of the rubber-like elastomer 10 has a coating layer 45. When this heat-dissipating sheet 1 is sandwiched between a heat source and a cooling member in the thickness direction, pressure applied in the thickness direction compresses the rubber-like elastomer 10, and some of the lubricant 45a in the pores 14 spills out of the pores 45a onto the front and back surfaces of the rubber-like elastomer 10. At this time, holes 14 located at the outermost periphery in the plane contribute to preventing lubricant 45a from spilling out of heat dissipation sheet 1. Therefore, the risk of lubricant 45a spilling out of heat dissipation sheet 1 can be further reduced.

[0059] FIG. 19 shows a plan view of a heat dissipation sheet according to a sixth modified example and a cross-sectional view taken along line AA of the plan view.

[0060] The heat dissipation sheet 1 according to the sixth modification has the same rubber-like elastomer 10 as the heat dissipation sheet 1 according to the fourth modification. That is, the number and shape of the pores 14 in the sixth modification are the same as those in the fourth modification. The heat dissipation sheet 1 according to the sixth modification contains lubricant 45a in some of the pores 14. More specifically, the pores 14 located at the outermost periphery of the surface of the rubber-like elastomer 10 do not contain lubricant 45a, but the lubricant 45a is contained in a region inward of the pores 14 located at the outermost periphery of the surface. The pores 14 in this inner region are filled with lubricant 45a. A coating layer 45 of lubricant 45a is provided on the portions of the inner region of the surface other than the pores 14, i.e., the front and back surfaces of the rubber-like elastomer 10. In this heat dissipation sheet 1, as in the fifth modification, the pores 14 located at the outermost periphery in the plane contribute to preventing the lubricant 45a from spilling out of the heat dissipation sheet 1. This further reduces the risk of the lubricant 45a spilling out of the heat dissipation sheet 1.

[0061] FIG. 20 shows a plan view of a heat dissipation sheet according to a seventh modification and a cross-sectional view taken along line AA of the plan view.

[0062] The heat dissipation sheet 1 according to the seventh modification has the same rubber-like elastic body 10 as the heat dissipation sheet 1 according to the fourth modification. That is, the number and shape of the voids 14 in the seventh modification are the same as those in the fourth modification. In the seventh modification, like the sixth modification, the voids 14 located at the outermost periphery of the rubber-like elastic body 10 do not contain lubricant 45a, but the lubricant 45a is present in a region inward of the voids 14 located at the outermost periphery. The seventh modification differs from the sixth modification in that the lubricant 45a in the voids 14 in the innermost region does not fill the entire volume of the voids 14, but only partially fills a portion of the voids 14 in the longitudinal direction. That is, in the seventh modification, a space 105 free of lubricant 45a exists along the length of the voids 14 containing lubricant 45a. This heat dissipation sheet 1 can also achieve the same effect as the sixth modification. Instead of the space 105, a wall dividing the voids 14 into two may be formed.

[0063] (Manufacturing Methods of the First and Second Embodiments) Next, a method for manufacturing the heat dissipation sheets according to the first and second embodiments will be described.

[0064] The formation of holes 14 in heat dissipation sheet 1 may be performed after S130, rather than before S120.

[0065] FIG. 21 shows the flow of a manufacturing method in which holes are formed after the cutting step of the block body.

[0066] The method for manufacturing the heat dissipation sheet shown in FIG. 21 includes the following steps: a discharge step (S100) of discharging a curable rubber composition 70 containing carbon fibers 20 onto a plane of a film (an example of a planar body) 72 in a plurality of rows along a first predetermined direction D1; a molding step (S110) of molding the curable rubber composition 70 discharged onto a flat surface into a sheet and curing it to form a carbon-containing sheet 76 in which the carbon fibers 20 are oriented in a first predetermined direction D1; a lamination step (S120) of laminating a plurality of carbon-containing sheets 76 with uncured liquid rubber 85 disposed between the carbon-containing sheets 76, and curing the uncured liquid rubber 85 to form a laminated block body 90 with the orientation of the carbon fibers 20 aligned; a cutting step (S130) of cutting the block body 90 into sheets in a direction oblique to the orientation direction of the carbon fibers 20; a void forming step (S140) of forming voids 14 in the rubber-like elastic body 10 after the cutting step; (See Figures 4 to 8).

[0067] In the cutting step (S130), the carbon fibers 20 may be cut into sheets at an angle greater than 45° and smaller than 85° with respect to the orientation direction of the carbon fibers 20.

[0068] However, unlike the molding step (S110) in the flow of Fig. 3, the molding step (S110) in Fig. 21 does not form recesses 78 during molding. That is, in the flow of Fig. 21, holes 14 are not formed by recesses 78, but are formed after the cutting step (S130) (hole forming step: S140). The manufacturing method other than not forming recesses 78 during molding and forming holes 14 after cutting has already been explained with reference to Figs. 4 to 8, so a repeated explanation will be omitted here. The flow of Fig. 21 can also be used when manufacturing the heat dissipation sheet 1 of Figs. 9 to 12.

[0069] FIG. 22 shows the flow of the manufacturing method in which a lubricant is supplied to the rubber-like elastic body after the pore forming step.

[0070] 22 shows an exemplary manufacturing method for the heat dissipation sheet 1 according to the second embodiment. In this manufacturing method, after the void formation step (S140), a lubricant supplying step (S150) is performed in which lubricant 45a is supplied to at least one of the front and back surfaces of the rubber-like elastomer 10 and / or into the voids 14. The heat dissipation sheets 1 according to the third to seventh modifications of the second embodiment can be manufactured by a manufacturing method that includes the lubricant supplying step (S150). The lubricant supplying step (S150) is broadly interpreted to include either or both of the step of filling the voids 14 with the lubricant 45a and the step of forming the coating layer 45. Furthermore, the coating layer 45 is broadly interpreted to include not only one obtained by supplying the lubricant 45a to the surfaces 11 and 12 of the rubber-like elastomer 10, but also one in which the voids 14 are filled with the lubricant 45a. Note that, before the void forming step (S140), lubricant 45a may be supplied to at least one of the front and back surfaces of rubber-like elastic body 10 and / or inside voids 14. For example, when manufacturing heat dissipation sheet 1 according to the fourth modified example of the second embodiment, the lubricant supplying step (S150) may be carried out after the cutting step (S130), and then the void forming step (S140) may be carried out to remove voids 14 and the lubricant 45a at their positions.

[0071] FIG. 23 shows a photograph of a heat dissipation sheet according to a first modified example of the second embodiment.

[0072] The two heat dissipation sheets 1 shown in Figure 23 are the same. The reason the entire sheet is black is because the sheet contains carbon fibers 20.

[0073] FIG. 24 shows a variation of the flow diagram of FIG.

[0074] The flow diagram of Fig. 24 is obtained by omitting the pore forming step (S140) from the flow diagram of Fig. 22. In this case, the pores 14 are formed in a step similar to the molding step (S110) of Fig. 3. Therefore, it is sufficient to supply the lubricant 45a to the rubber-like elastic body 10 immediately after the cutting step (S130). The heat dissipation sheets 1 according to the third to seventh modifications of the second embodiment can be manufactured by the manufacturing method of Fig. 24.

[0075] (Other embodiments) The present invention is not limited to the above-described embodiments, and various modifications are possible.

[0076] The thermally conductive filler is not limited to carbon fiber 20, and other whisker-shaped (needle-shaped) or fibrous long fillers may also be used. Examples of such long fillers include boron nitride, aluminum nitride, and alumina. Similarly, the filler-containing sheet may be a sheet containing the above-mentioned long fillers other than carbon fiber 20. The shape of the faces of pores 14 opening to surfaces 11 and 12 is not limited to a circle, ellipse, or rectangle, and may also be a triangle, a pentagon, or a polygon with more sides.

[0077] The heat dissipation sheet 1 according to the second embodiment (see FIGS. 9 and 10 ) may be manufactured by molding a single rubber-like elastic body 10 in which carbon fibers 20 are oriented in one direction, and then forming voids 14 therein. To distinguish the molding step (S110) in the flow charts of FIGS. 21 and 22 from the molding step (S110) in the flow chart of FIG. 3 , the molding step (S110) in the flow chart of FIG. 3 may be designated the first molding step (S110A), and the molding step (S110) in the flow charts of FIGS. 21 and 22 may be designated the second molding step (S110B). The components of the second embodiment and its various modified examples may also be combined. For example, the second modified example may be combined with the third modified example, and voids 14 may be formed obliquely with respect to the thickness direction of the rubber-like elastic body 10 in the third modified example. The third modified example may be combined with the fourth modified example, and voids 14 may be formed obliquely with respect to the thickness direction of the rubber-like elastic body 10 in the fourth modified example. [Industrial Applicability]

[0078] The heat dissipation sheet of the present invention can be used, for example, in various electronic devices such as automobiles, industrial robots, power generation equipment, PCs, and household electrical appliances, as well as in automobile batteries, rechargeable household batteries, and batteries for electronic devices such as PCs.

Claims

1. a sheet-like rubber elastic body; a long thermally conductive filler having superior thermal conductivity to the rubber-like elastomer and embedded in the rubber-like elastomer so as to be oriented obliquely with respect to the thickness direction of the rubber-like elastomer; A heat dissipation sheet comprising: the rubber-like elastomer has at least one void oriented parallel to the thickness direction of the rubber-like elastomer or oriented obliquely to the thickness direction, the thermally conductive filler has both ends exposed on the surface of the rubber-like elastic body, the rubber-like elastic body has at least one pore oriented in a direction oblique to the thickness direction of the rubber-like elastic body, The heat dissipation sheet is characterized in that both ends of the thermally conductive filler are exposed on the surface of the rubber-like elastic body.

2. 2. The heat dissipation sheet according to claim 1, wherein the thermally conductive filler is embedded and oriented at an angle greater than 45 degrees and less than 85 degrees relative to the surface of the rubber-like elastic body.

3. The heat dissipation sheet according to claim 1, characterized in that the diameter of the thermally conductive filler at both ends exposed on the surface of the rubber-like elastic body is larger than the diameter of the area embedded in the rubber-like elastic body.

4. 2. The heat dissipation sheet according to claim 1, wherein silicone rubber formed by hardening uncured liquid rubber is provided between the rubber-like elastic body and the void or between one void and another void.

5. 5. The heat dissipation sheet according to claim 4, wherein the uncured liquid rubber is liquid silicone rubber.

6. 2. The heat dissipation sheet according to claim 1, wherein the rubber-like elastic material is silicone rubber.

7. 2. The heat dissipation sheet according to claim 1, wherein at least one of the front and back surfaces of the rubber-like elastic body has a coating layer of a lubricant.

8. 2. The heat dissipation sheet according to claim 1, wherein the pores of the rubber-like elastic body contain a lubricant.

9. 9. The heat dissipation sheet according to claim 8, wherein the rubber-like elastic body has a coating layer of the lubricant on at least one of its front and back surfaces.

10. A heat dissipation sheet as described in claim 8, characterized in that the voids located at the outermost periphery of the rubber-like elastic body when viewed in a plane do not contain the lubricant, and the lubricant is contained in an area inward of the voids located at the outermost periphery.

11. The heat dissipation sheet according to claim 1 , wherein the thermally conductive filler is carbon fiber.

12. A sheet-like rubber-like elastic body; a long thermally conductive filler having superior thermal conductivity to the rubber-like elastomer and embedded in the rubber-like elastomer so as to be oriented obliquely with respect to the thickness direction of the rubber-like elastomer; A heat dissipation sheet comprising: the rubber-like elastomer has at least one void oriented parallel to the thickness direction of the rubber-like elastomer or oriented obliquely to the thickness direction, A method for producing a heat dissipation sheet in which both ends of the thermally conductive filler are exposed on the surface of the rubber-like elastic body, comprising: a discharging step of discharging the curable rubber composition containing the thermally conductive filler onto a flat surface of a flat body in a plurality of rows along a first predetermined direction; a molding step of forming the curable rubber composition discharged onto the flat surface into a sheet and curing the sheet to form a filler-containing sheet in which the thermally conductive filler is oriented in the first predetermined direction and the sheet has at least one recessed portion on its surface that is aligned along a second predetermined direction; a lamination step of laminating a plurality of the filler-containing sheets in a state in which uncured liquid rubber is disposed between the filler-containing sheets, and curing the uncured liquid rubber to form a laminated block body with the thermally conductive filler aligned; a cutting step of cutting the block body into sheets in a direction oblique to the orientation direction of the thermally conductive filler; A method for producing a heat dissipation sheet, comprising:

13. The method for manufacturing a heat dissipation sheet according to claim 12, characterized in that the stacking process stacks the plurality of filler-containing sheets so that the positions of the recesses of the filler-containing sheets are different in the thickness direction of the filler-containing sheets.

14. A method for manufacturing a heat dissipation sheet as described in claim 12, characterized in that after the cutting process, a lubricant supplying process is performed in which a lubricant is supplied to at least one of the front and back surfaces of the rubber-like elastic body and / or to both the insides of the holes.

15. The method for manufacturing a heat dissipation sheet according to any one of claims 12 to 14, wherein the cutting step involves cutting the sheet at an angle greater than 45° and smaller than 85° with respect to the orientation direction of the thermally conductive filler.

16. The method for manufacturing a heat dissipation sheet according to any one of claims 12 to 14, wherein the thermally conductive filler is carbon fiber.

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