Heat conductive sheet

Abstract

To provide a heat conductive sheet whose surface is easily deformed, which exhibits excellent heat conductivity and is excellent in tensile strength.SOLUTION: A heat conductive sheet contains a resin and a heat conductive filler (excluding a heat conductive sheet having predetermined resin layers formed on both surfaces of a predetermined base sheet), and has a heat conductivity in a thickness direction of 12 W / m K or more, a tensile strength measured according to JIS K 7113 of 0.40 MPa or more, and an indentation depth of 20 μm or more when a nanoindentation test is performed by a predetermined method.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a thermally conductive sheet. [Background technology]

[0002] In recent years, the amount of heat generated by electronic components such as plasma display panels (PDPs) and integrated circuit (IC) chips has increased as their performance has improved. As a result, electronic devices that use these components need to take measures to prevent malfunctions caused by temperature increases in the electronic components.

[0003] As a countermeasure against functional failures caused by temperature rises in electronic components, a method is generally adopted in which a heat sink, heat sink plate, heat sink fin, or other heat sink made of metal is attached to the heat generating body of the electronic component to promote heat dissipation. When using a heat sink, the heat generating body and the heat sink are closely attached with a sheet-like member with high thermal conductivity (thermal conductive sheet) in between in order to efficiently transfer heat from the heat generating body to the heat sink.

[0004] Therefore, a thermally conductive sheet that is sandwiched between a heat generating body and a heat dissipating body is required to exhibit excellent thermal conductivity.

[0005] As a method for manufacturing a thermally conductive sheet that can exhibit excellent thermal conductivity, a method is known in which a resin block consisting of a laminate of pre-thermally conductive sheets containing resin and particulate carbon material is sliced ​​using a cutting tool such as a plane to obtain a thermally conductive sheet (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2018-129377 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the above-mentioned conventional manufacturing method in which a resin block containing resin and a thermally conductive filler is sliced ​​with a cutting tool such as a plane to obtain a thermally conductive sheet, the obtained thermally conductive sheet may curl, resulting in a decrease in tensile strength and surface smoothness of the thermally conductive sheet.

[0008] To address this problem, the inventor has newly discovered that when slicing a resin block, a slicing mechanism is used that includes a single-edged cutting blade having a cutting edge formed by the intersecting angle of the clearance face and the rake face, and a guide member arranged opposite the rake face of the cutting blade, so that the portion cut out from the resin block passes between the rake face of the cutting blade and the guide member, which can prevent the thermal conductive sheet from curling.

[0009] However, after further investigation, the inventors found that when the above-mentioned slicing mechanism is used, problems may arise such as the area of ​​the resulting thermally conductive sheet being smaller than the area of ​​the sliced ​​surface of the resin block, or the surface of the thermally conductive sheet being difficult to deform.

[0010] Therefore, an object of the present invention is to provide a technique for producing a thermally conductive sheet whose surface is easily deformed while suppressing the occurrence of curling and reduction in area. [Means for solving the problem]

[0011] The present inventor conducted extensive research to achieve the above object, and discovered that by slicing a resin block using a slicing mechanism equipped with a single-edged cutting blade having a predetermined cutting edge shape and a guide member disposed opposite the rake face of the cutting blade, it is possible to manufacture a novel thermally conductive sheet having an easily deformable surface while suppressing curling and reduction in area, and thus completed the present invention.

[0012] That is, the present invention aims to advantageously solve the above problems, and the manufacturing method of the thermally conductive sheet of the present invention is a manufacturing method of the thermally conductive sheet including a step of slicing a resin block containing a resin and a thermally conductive filler with a slicing mechanism to obtain a thermally conductive sheet, the slicing mechanism is characterized in that it has a single-edged cutting blade having a flank, a scooping face, and a cutting edge formed by the intersection angle between the flank and the scooping face, and a guide member arranged opposite the scooping face, the single-edged cutting blade has a curvature radius of the cutting edge of 10.0 μm or less, and the slicing is performed so that the part cut out from the resin block passes between the scooping face and the guide member. In this way, by slicing the resin block using a slicing mechanism including a single-edged cutting blade and a guide member arranged opposite the scooping face of the single-edged cutting blade, it is possible to suppress curling of the thermally conductive sheet formed of the sliced ​​pieces of the resin block, and therefore it is possible to obtain a thermally conductive sheet that can exhibit excellent thermal conductivity and has excellent tensile strength. Furthermore, by using a cutting blade with a cutting edge radius of curvature of 10.0 μm or less, it is possible to produce a thermally conductive sheet with an easily deformable surface while suppressing the reduction in area during slicing. In the present invention, the "radius of curvature of the cutting edge" can be measured using the method described in the Examples.

[0013] Here, in the method for producing a thermally conductive sheet of the present invention, it is preferable that the static friction coefficient of the surface of the guide member facing the scooping surface is 0.4 or less. If the static friction coefficient of the surface of the guide member facing the scooping surface is 0.4 or less, the part cut out from the resin block can be smoothly passed between the scooping surface and the guide member. In the present invention, the "static friction coefficient" can be measured by the method described in the examples.

[0014] In addition, in the method for producing a thermally conductive sheet of the present invention, the length of the guide member is preferably 1 cm or more and 5 cm or less. If the length of the guide member is 1 cm or more, the thermally conductive sheet can be sufficiently prevented from curling, and a thermally conductive sheet that can exhibit excellent thermal conductivity and has excellent tensile strength can be obtained. Furthermore, if the length of the guide member is 5 cm or less, the thermally conductive sheet can be easily removed from between the scooping face and the guide member.

[0015] In the method for producing a thermal conductive sheet of the present invention, the resin block is preferably sliced ​​at a speed of 10 mm / sec to 400 mm / sec. If the slicing speed is 10 mm / sec to 400 mm / sec, the reduction in area during slicing can be effectively suppressed while the tensile strength can be sufficiently increased.

[0016] The present invention also aims to advantageously solve the above problems, and the thermally conductive sheet of the present invention is a thermally conductive sheet containing a resin and a thermally conductive filler, and is characterized in that the thermal conductivity in the thickness direction is 12 W / m·K or more, the tensile strength is 0.40 MPa or more, and the indentation depth when a nanoindentation test is performed by a specified method is 20 μm or more. Such a thermally conductive sheet has a surface that is easily deformed, can exhibit excellent thermal conductivity, and has excellent tensile strength. In the present invention, the "thermal conductivity", "tensile strength" and "indentation depth" can each be measured by the method described in the Examples.

[0017] Here, the thermally conductive sheet of the present invention preferably has an Asker C hardness of 60 or more at a temperature of 70° C. If the Asker C hardness at a temperature of 70° C. is 60 or more, the sheet can be satisfactorily used by being sandwiched between a heat generating body and a heat dissipating body. In the present invention, the "Asker C hardness" can be measured by the method described in the Examples.

[0018] In addition, the thermal conductive sheet of the present invention preferably has a thermal resistance of 0.060° C. / W or less when a pressure of 0.9 MPa is applied to it. If the thermal resistance is equal to or less than the upper limit when a pressure of 0.9 MPa is applied to it, heat can be transferred well from the heating element to the heat sink. Furthermore, the thermal conductive sheet of the present invention preferably has a thermal resistance of 0.096° C. / W or less when a pressure of 0.1 MPa is applied to it. If the thermal resistance when a pressure of 0.1 MPa is applied to it is equal to or less than the upper limit mentioned above, heat can be transferred well from the heating element to the heat sink even under low pressure. In the present invention, the "thermal resistance value" can be measured by the method described in the Examples.

[0019] In the thermal conductive sheet of the present invention, the thermal resistance value when a pressure of 0.1 MPa is applied divided by the thermal resistance value when a pressure of 0.9 MPa is applied is preferably 1.78 or less. If the thermal resistance value when a pressure of 0.1 MPa is applied divided by the thermal resistance value when a pressure of 0.9 MPa is applied is equal to or less than the above upper limit, the thermal conductive sheet can exhibit excellent thermal conductivity even when used under conditions in which the pressure applied to the thermal conductive sheet changes. Effect of the Invention

[0020] According to the present invention, it is possible to manufacture a thermally conductive sheet having an easily deformable surface while suppressing the occurrence of curling and reduction in area. Furthermore, according to the present invention, it is possible to provide a thermally conductive sheet having an easily deformable surface, capable of exhibiting excellent thermal conductivity, and having excellent tensile strength. [Brief description of the drawings]

[0021] [Figure 1] 1(a) to 1(c) are explanatory views showing a process for producing a thermally conductive sheet using an example of a method for producing a thermally conductive sheet according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of the present invention will be described in detail. Here, the method for producing a thermally conductive sheet of the present invention can be used when producing a thermally conductive sheet of the present invention. The thermally conductive sheet produced using the method for producing a thermally conductive sheet of the present invention can be used by being sandwiched between a heat generating body such as an electronic component and a heat dissipating body such as a metal heat sink, a heat dissipating plate, or a heat dissipating fin.

[0023] (Method of manufacturing thermal conductive sheet) The method for producing a thermally conductive sheet of the present invention is used for producing a thermally conductive sheet that contains a resin and a thermally conductive filler and may further contain an additive. In particular, the method for producing a thermally conductive sheet of the present invention is preferably used for producing the thermally conductive sheet of the present invention.

[0024] The method for producing a thermally conductive sheet of the present invention includes a step of slicing a resin block containing a resin and a thermally conductive filler with a slicing mechanism to obtain a thermally conductive sheet. The method for producing a thermally conductive sheet of the present invention requires the use of a slicing mechanism that includes a single-edged cutting blade having a cutting edge consisting of a flank, a rake face, and an intersection angle between the flank and the rake face, the cutting edge having a curvature radius of 10.0 μm or less, and a guide member disposed opposite the rake face of the single-edged cutting blade, and slicing the resin block so that the portion cut out from the resin block passes between the rake face and the guide member.

[0025] In this way, by using a slicing mechanism having a single-edged cutting blade and a guide member arranged opposite to the rake surface of the single-edged cutting blade, and slicing the resin block so that the cut-out portion passes between the rake surface and the guide member, it is possible to suppress curling of the thermally conductive sheet made of sliced ​​pieces of the resin block. Therefore, it is possible to suppress a decrease in tensile strength due to curling during slicing. Therefore, it is possible to obtain a thermally conductive sheet that can exhibit excellent thermal conductivity and has excellent tensile strength. In addition, by using a cutting blade with a curvature radius of 10.0 μm or less as the single-edged cutting blade of the slicing mechanism, it is possible to produce a thermally conductive sheet whose surface is easily deformed while suppressing a decrease in area during slicing.

[0026] In addition, when the content of thermally conductive filler is high, when a thermally conductive filler with a small volume average particle diameter is used, or when the thickness of the thermally conductive sheet to be produced is thin, the resulting thermally conductive sheet is usually prone to curling. However, according to the method for producing a thermally conductive sheet of the present invention, curling of the thermally conductive sheet can be sufficiently suppressed even in these cases.

[0027] <Resin block> Here, the resin block that is the material of the thermally conductive sheet contains a resin and a thermally conductive filler, and optionally further contains an additive.

[0028] [resin] Here, the resin may be at least one of a resin that is liquid at room temperature and pressure and a resin that is solid at room temperature and pressure. In this specification, "room temperature" refers to 23° C., and "room pressure" refers to 1 atm (absolute pressure).

[0029] Examples of resins that are liquid at room temperature and normal pressure include thermoplastic resins that are liquid at room temperature and normal pressure, and thermosetting resins that are liquid at room temperature and normal pressure. Examples of thermoplastic resins that are liquid at room temperature and normal pressure include acrylic resins, epoxy resins, silicone resins, and fluororesins. Furthermore, examples of thermosetting resins that are liquid at room temperature and normal pressure include natural rubber; butadiene rubber; isoprene rubber; nitrile rubber; hydrogenated nitrile rubber; chloroprene rubber; ethylene propylene rubber; chlorinated polyethylene; chlorosulfonated polyethylene; butyl rubber; halogenated butyl rubber; polyisobutylene rubber; epoxy resins; polyimide resins; bismaleimide resins; benzocyclobutene resins; phenolic resins; unsaturated polyesters; diallyl phthalate resins; polyimide silicone resins; polyurethanes; thermosetting polyphenylene ethers; and thermosetting modified polyphenylene ethers.

[0030] Examples of resins that are solid at room temperature and normal pressure include thermoplastic resins that are solid at room temperature and normal pressure, and thermosetting resins that are solid at room temperature and normal pressure. Examples of thermoplastic resins that are solid at room temperature and pressure include acrylic resins such as poly(2-ethylhexyl acrylate), a copolymer of acrylic acid and 2-ethylhexyl acrylate, polymethacrylic acid or its ester, and polyacrylic acid or its ester; silicone resins; fluororesins; polyethylene; polypropylene; ethylene-propylene copolymers; polymethylpentene; polyvinyl chloride; polyvinylidene chloride; polyvinyl acetate; ethylene-vinyl acetate copolymers; polyvinyl alcohol; polyacetal; polyethylene terephthalate; polybutylene terephthalate; polyethylene naphthalate; poly Examples of such polymers include styrene; polyacrylonitrile; styrene-acrylonitrile copolymers; acrylonitrile-butadiene-styrene copolymers (ABS resins); styrene-butadiene block copolymers or hydrogenated products thereof; styrene-isoprene block copolymers or hydrogenated products thereof; polyphenylene ether; modified polyphenylene ether; aliphatic polyamides; aromatic polyamides; polyamideimide; polycarbonate; polyphenylene sulfide; polysulfone; polyethersulfone; polyethernitrile; polyetherketone; polyketone; polyurethane; liquid crystal polymers; ionomers; and the like. Furthermore, examples of thermosetting resins that are solid at room temperature and normal pressure include natural rubber; butadiene rubber; isoprene rubber; nitrile rubber; hydrogenated nitrile rubber; chloroprene rubber; ethylene propylene rubber; chlorinated polyethylene; chlorosulfonated polyethylene; butyl rubber; halogenated butyl rubber; polyisobutylene rubber; epoxy resins; polyimide resins; bismaleimide resins; benzocyclobutene resins; phenolic resins; unsaturated polyesters; diallyl phthalate resins; polyimide silicone resins; polyurethanes; thermosetting polyphenylene ethers; and thermosetting modified polyphenylene ethers.

[0031] Among them, it is preferable to use, as the resin, a fluororesin that is liquid at room temperature and normal pressure, and a fluororesin that is solid at room temperature and normal pressure. The above-mentioned resins may be used alone or in combination of two or more kinds.

[0032] [Thermal conductive filler] The thermally conductive filler is not particularly limited, and examples thereof include particulate materials such as alumina particles, zinc oxide particles, boron nitride particles, aluminum nitride particles, silicon nitride particles, silicon carbide particles, magnesium oxide particles, and particulate carbon materials (e.g., artificial graphite, flaky graphite, exfoliated graphite, natural graphite, acid-treated graphite, expandable graphite, expanded graphite, carbon black, etc.), as well as fibrous materials such as carbon nanotubes, vapor-grown carbon fibers, carbon fibers obtained by carbonizing organic fibers, and cut products thereof. Among them, as the thermally conductive filler, it is preferable to use at least one selected from the group consisting of scaly particulate materials such as boron nitride particles, artificial graphite, scaly graphite, expandable graphite, and expanded graphite; and fibrous carbon nanomaterials such as carbon nanotubes (hereinafter sometimes referred to as "CNT"); it is more preferable to use scaly particulate materials, even more preferable to use anisotropic graphite such as scaly graphite and expanded graphite, and particularly preferable to use expanded graphite. By using these thermally conductive fillers, the thermal conductivity of the thermally conductive sheet can be further improved. The thermally conductive filler may be used alone or in combination of two or more kinds.

[0033] The volume average particle diameter of the particulate material, such as particulate carbon material, which can be used as the thermally conductive filler is preferably 10 μm or more and 150 μm or less, more preferably 30 μm or more and 80 μm or less. If the volume average particle diameter of the particulate material is equal to or less than the upper limit, the surface smoothness of the thermally conductive sheet can be further improved. If the volume average particle diameter of the particulate material is equal to or more than the lower limit, the thermal conductivity of the thermally conductive sheet can be further improved.

[0034] The content of the thermally conductive filler is not particularly limited, and is preferably 5 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 80 parts by mass or more, and preferably 150 parts by mass or less, more preferably 120 parts by mass or less, and even more preferably 100 parts by mass or less, per 100 parts by mass of the above-mentioned resin. If the content of the thermally conductive filler is equal to or more than the above lower limit, the thermal conductivity of the thermally conductive sheet can be sufficiently increased. Also, if the content of the thermally conductive filler is equal to or less than the above upper limit, curling during slicing can be suppressed, and a thermally conductive sheet with excellent tensile strength can be obtained.

[0035] [Additives] Additives that can be optionally contained in the resin block are not particularly limited, and examples thereof include flame retardants, plasticizers, toughness improvers, moisture absorbents, adhesion improvers, wettability improvers, and ion trapping agents.

[0036] [Shape and structure of resin block] The shape of the resin block is not particularly limited, and may be any shape that can provide a thermally conductive sheet of a desired shape when sliced. Specifically, for example, when a rectangular thermally conductive sheet is to be produced, the shape of the resin block is preferably a rectangular parallelepiped.

[0037] Furthermore, the structure of the resin block is not particularly limited, and may be a structure obtained by molding a resin composition containing a resin and a thermally conductive filler, and optionally further containing additives, into a desired shape using a known molding device such as a mold, or a structure obtained by molding a resin composition containing a resin and a thermally conductive filler, and optionally further containing additives, into a sheet shape and laminating, folding or rolling up the sheet. In a laminate formed by laminating sheets, the adhesive strength between the surfaces of the sheets is usually sufficient due to the pressure applied when laminating the sheets. However, when the adhesive strength is insufficient or when it is necessary to sufficiently suppress delamination of the laminate, the lamination may be performed in a state in which the surfaces of the sheets are slightly dissolved with a solvent, or in a state in which an adhesive is applied to the surfaces of the sheets or an adhesive layer is provided on the surfaces of the sheets, or the laminate formed by laminating the sheets may be further pressed in the lamination direction.

[0038] Among them, the structure of the resin block is preferably a structure in which a resin composition containing a resin and a thermally conductive filler and further containing an optional additive is pressed and molded into a sheet shape, as shown in FIG. 1(a)-(c), to obtain a sheet 11 containing a resin, a thermally conductive filler, and an optional additive, and then a plurality of the obtained sheets 11 are laminated in the thickness direction, or a structure in which the obtained sheet 11 is folded or rolled. In a sheet obtained by pressing a resin composition into a sheet shape, the filler is oriented in the in-plane direction of the sheet, so that a thermally conductive sheet having anisotropic thermal conductivity can be obtained by slicing a laminate obtained by laminating, folding, or rolling the obtained sheet. Specifically, in a sheet obtained by pressing a resin composition containing a thermally conductive filler into a sheet shape, the thermally conductive filler is oriented in the in-plane direction, and the thermal conductivity in the in-plane direction is improved. Therefore, by slicing the laminate of sheets in the stacking direction of the laminate, or in a direction perpendicular to both the stacking direction of the laminate and the sheets that make up the laminate, a thermally conductive sheet with excellent thermal conductivity in the thickness direction can be obtained. The thermally conductive sheet obtained by slicing the laminate of sheets in the lamination direction of the laminate or in a direction perpendicular to both the lamination direction of the laminate and the sheets constituting the laminate has a configuration in which slice pieces (strips containing resin and thermally conductive filler) of the sheets constituting the laminate are joined in parallel. In other words, the thermally conductive sheet has a configuration in which strips containing resin and thermally conductive filler and having a width dimension approximately equal to the thickness of the sheets constituting the laminate are joined in parallel in the width direction of the strips with the width direction of the strips perpendicular to the thickness direction of the thermally conductive sheet. Here, in particular, in a thermally conductive sheet having such a configuration, if curled during slicing, peeling easily occurs between adjacent strips, and the effect of peeling due to curling is particularly noticeable on the surface side where the flank of the cutting blade was in contact during slicing. And, if a sheet that has curled once is flattened by physical processing such as pressing, the curl itself can be eliminated, but it is difficult to rejoin the strips that have been peeled off once. However, according to the method for producing a thermally conductive sheet of the present invention, the occurrence of curling can be suppressed, peeling between the strips can be suppressed, and a thermally conductive sheet with excellent tensile strength can be obtained.

[0039] <Slice mechanism> The slicing mechanism includes a single-edged cutting blade having a cutting edge with a predetermined shape, and a guide member arranged to face the rake face of the single-edged cutting blade. Specifically, as shown in Figs. 1(a) to (c), an example of the slicing mechanism includes a single-edged cutting blade 20 having a rake face 21, a clearance face 22, and a cutting edge 23 formed by the intersection angle of the rake face 21 and the clearance face 22, and a guide member 30 arranged to face the rake face 21 of the single-edged cutting blade 20. In the illustrated example, the single-edged cutting blade 20 and the guide member 30 are connected via rod-shaped members provided at both ends in the width direction of the flat guide member 30 so that the rake face 21 and the surface 31 of the guide member 30 are parallel to each other, and as shown in Figs. 1(b) and (c), a portion 50 cut out from the resin block 10 during slicing passes through a gap 40 between the rake face 21 and the surface 31 of the guide member 30 on the rake face 21 side. In addition, the single-edged cutting blade 20 has a predetermined radius of curvature in the cross section along the blade thickness direction of the cutting edge portion. Specifically, the cutting edge 23 needs to have a radius of curvature of 10.0 μm or less, and the radius of curvature of the cutting edge 23 is preferably 0.1 μm or more, more preferably 0.5 μm or more, preferably 8.0 μm or less, and more preferably 3.0 μm or less. If the radius of curvature is equal to or greater than the lower limit, the strength of the cutting blade 20 can be sufficiently ensured and the tensile strength of the thermal conductive sheet can be sufficiently increased. If the radius of curvature is equal to or less than the upper limit, the sliced ​​surface is prevented from being crushed during slicing, and a thermal conductive sheet with a surface that is easily deformed can be manufactured while preventing a reduction in area.

[0040] Here, the static friction coefficient of the surface of the guide member facing the rake face is preferably 0.4 or less. If the static friction coefficient is equal to or less than the upper limit value, the part cut out from the resin block can be smoothly passed between the rake face and the guide member, and the occurrence of curling can be effectively suppressed.

[0041] The length of the guide member is preferably 1 cm or more, more preferably 2 cm or more, and preferably 5 cm or less. If the length of the guide member is equal to or greater than the above-mentioned lower limit, the occurrence of curling can be sufficiently suppressed. If the length of the guide member is equal to or less than the above-mentioned upper limit, the thermally conductive sheet obtained by slicing the resin block can be easily removed from between the scooping surface and the guide member.

[0042] Furthermore, the angle at which the guide member is disposed is not particularly limited as long as a sufficient distance can be secured between the guide member and the rake face. However, from the viewpoint of further effectively suppressing the occurrence of curl, it is preferable that the guide member be parallel to the rake face.

[0043] The distance between the guide member and the scooping surface is not particularly limited, but is preferably 2 to 40 times the thickness of the heat conductive sheet to be manufactured. If the distance between the guide member and the scooping surface is equal to or greater than the lower limit, the part cut out from the resin block can be smoothly passed between the scooping surface and the guide member, and curling can be effectively suppressed. If the distance between the guide member and the scooping surface is equal to or less than the upper limit, the slicing mechanism can be made compact.

[0044] The position of the lower end (the edge on the side where the cutting edge of the single-edged cutting blade is located) of the guide member in the vertical direction (the up-down direction in FIG. 1) is not particularly limited as long as the resin block can be well sliced ​​while well suppressing the occurrence of curling, but from the viewpoint of preventing the placement surface of the resin block from contacting the guide member and well slicing the resin block to the bottom surface, it is preferable that the position is the same as the cutting edge of the single-edged cutting blade or above the cutting edge. Also, from the viewpoint of well passing the part cut out from the resin block between the scooping surface and the guide member, it is preferable that the position of the lower end of the guide member in the vertical direction is lower than a position 5 mm vertically above the cutting edge of the single-edged cutting blade. Among them, it is particularly preferable that the position of the lower end of the guide member in the vertical direction is the same as the cutting edge of the single-edged cutting blade.

[0045] <Slice> The direction in which the resin block is sliced ​​using the slicing mechanism is not particularly limited, and may be a direction in which the clearance angle between the end face (slicing surface) of the sliced ​​resin block and the clearance surface of the single-edged cutting blade is 5° or less, particularly 0°. Slicing is performed so that a portion 50 cut out from the resin block 10 passes between the rake surface 21 and the guide member 30, as shown in Figs. 1(b) and (c), for example.

[0046] The slicing of the resin block using the above-mentioned slicing mechanism is not particularly limited, but is preferably performed while applying pressure to the resin block, and more preferably while applying a pressure of 0.1 MPa or more and 1.0 MPa or less.

[0047] In order to easily slice the resin block, the temperature of the resin block during slicing is preferably set to be in the range of -20°C to 30°C.

[0048] Furthermore, the slicing speed of the resin block is not particularly limited, and is preferably 10 mm / sec or more, more preferably 25 mm / sec or more, even more preferably 50 mm / sec or more, and preferably 400 mm / sec or less, more preferably 200 mm / sec or less, and even more preferably 150 mm / sec or less. If the slicing speed is set to the above lower limit value or more, it is possible to produce a heat conductive sheet whose surface is easily deformed while satisfactorily suppressing the reduction in area during slicing. Furthermore, if the slicing speed is set to the above upper limit value or less, it is possible to sufficiently increase the tensile strength of the heat conductive sheet. Furthermore, if the slicing speed is set within the above range, it is possible to obtain a heat conductive sheet in which the resin block is well sliced ​​while increasing the productivity of the heat conductive sheet and curling is sufficiently suppressed.

[0049] (Thermal Conduction Sheet) The thermally conductive sheet of the present invention can be manufactured, for example, by using the manufacturing method of the thermally conductive sheet of the present invention described above, and contains a resin and a thermally conductive filler, and may further contain an additive. The thermally conductive sheet of the present invention is required to have a thermal conductivity in the thickness direction of 12 W / m·K or more, a tensile strength of 0.40 MPa or more, and an indentation depth of 20 μm or more when a nanoindentation test is performed by a specified method. Such a thermally conductive sheet has a surface that is easily deformed, can exhibit excellent thermal conductivity, and has excellent tensile strength.

[0050] The resin, thermally conductive filler and additives for the thermally conductive sheet can be the same as those for the resin block in the method for manufacturing the thermally conductive sheet of the present invention described above, and the preferred embodiments are also the same as those for the resin block described above, so they will not be described below.

[0051] <Thermal Conduction Sheet Properties> In addition to the above-mentioned thermal conductivity, tensile strength and indentation depth, the thermally conductive sheet of the present invention preferably has the following properties.

[0052] [Thermal conductivity in the thickness direction] The thermal conductivity of the thermal conductive sheet in the thickness direction is preferably 20 W / m K or more, more preferably 25 W / m K or more, and even more preferably 30 W / m K or more. When the thermal conductivity in the thickness direction is equal to or more than the above lower limit, heat can be transferred well from the heat generating body to the heat sink.

[0053] [Tensile strength] Furthermore, the tensile strength of the thermal conductive sheet is preferably 0.45 MPa or more, more preferably 0.48 MPa or more, and is preferably 1.00 MPa or less, and more preferably 0.60 MPa or less. If the tensile strength is equal to or greater than the lower limit, sufficient strength can be ensured. Also, if the tensile strength is equal to or less than the upper limit, the thermal conductive sheet can be easily manufactured.

[0054] [Asker C hardness] Furthermore, the thermally conductive sheet preferably has an Asker C hardness of 60 or more, more preferably 65 or more, and preferably 80 or less, and more preferably 75 or less, at a temperature of 70° C. If the Asker C hardness at a temperature of 70° C. is within the above range, the sheet can be satisfactorily used by being sandwiched between a heating element and a heat sink.

[0055] [Thermal resistance value] The thermal resistance value of the thermal conductive sheet when a pressure of 0.9 MPa is applied is preferably 0.060° C. / W or less, and more preferably 0.055° C. / W or less. If the thermal resistance value when a pressure of 0.9 MPa is applied is equal to or less than the upper limit value, heat can be well transferred from the heating element to the heat sink when the sheet is sandwiched between the heating element and the heat sink. Furthermore, the thermal resistance value of the thermal conductive sheet when a pressure of 0.1 MPa is applied is preferably 0.096° C. / W or less, and more preferably 0.094° C. / W or less. If the thermal resistance value when a pressure of 0.1 MPa is applied is equal to or less than the above upper limit, heat can be well transferred from the heating element to the heat sink even if the pressure applied when sandwiched between the heating element and the heat sink is low. Furthermore, the thermal resistance value when a pressure of 0.1 MPa is applied to the thermal conductive sheet divided by the thermal resistance value when a pressure of 0.9 MPa is applied (=thermal resistance value when a pressure of 0.1 MPa is applied / thermal resistance value when a pressure of 0.9 MPa is applied) is preferably 1.78 or less, more preferably 1.75 or less. If the value obtained by dividing the thermal resistance value when a pressure of 0.1 MPa is applied by the thermal resistance value when a pressure of 0.9 MPa is applied is equal to or less than the upper limit mentioned above, the thermal conductive sheet can exhibit excellent thermal conductivity even when used under conditions in which the pressure applied to the thermal conductive sheet changes, for example, when a heat source is used in which the pressure applied to the thermal conductive sheet changes due to shrinkage caused by the influence of the surrounding temperature.

[0056] [shape] The thermal conductive sheet has a planar area of ​​3600 mm 2 It is preferable that the thickness is 10,000 mm or more. 2When the plan view area is equal to or greater than the above lower limit, productivity can be increased.

[0057] The thermally conductive sheet preferably has an average thickness of 250 μm or less, more preferably 150 μm or less, and preferably 50 μm or more, and more preferably 80 μm or more. If the average thickness is equal to or less than the upper limit, the degree of freedom of arrangement within the device when mounting the thermally conductive sheet can be increased. If the average thickness is equal to or more than the lower limit, the strength of the thermally conductive sheet can be sufficiently ensured.

[0058] The thermally conductive sheet of the present invention can be manufactured, for example, using the manufacturing method of the thermally conductive sheet of the present invention, and can have a configuration in which strips containing a resin and a thermally conductive filler are joined in parallel in the width direction of the strips, without being particularly limited thereto. EXAMPLES

[0059] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. In the examples and comparative examples, the radius of curvature of the cutting blade tip, the area maintenance rate during slicing, the static friction coefficient of the guide member, and the tensile strength, Asker C hardness, thermal conductivity, thermal resistance value, and indentation depth of the heat conduction sheet were measured using the following methods.

[0060] <Radius of curvature> The radius of curvature R of the cutting edge of the cutting blade was measured using a shape analysis laser microscope (Keyence, product name "VK-X1000"). Specifically, the cutting blade was placed on a base with the cutting edge facing up, and then the entire cutting blade was tilted 10 degrees toward the flank side. The vicinity of the cutting edge was then observed at a magnification of 50x. The radius of curvature was measured at five points at 2 mm intervals from the center of the blade, and the average value of the radius of curvature of the cutting edge at each point was taken as the radius of curvature R of the cutting edge. <Area maintenance rate> The area of ​​the sliced ​​surface of the laminate and the area of ​​the obtained sheet were each measured with a ruler, and the area retention rate at the time of slicing was calculated using the following formula (1). Area maintenance rate = area of ​​thermal conductive sheet ÷ area of ​​sliced ​​surface of laminate (1) <Static friction coefficient> The static friction coefficient was measured using a small tabletop testing machine (manufactured by Nidec-Shimpo, product name "FGS-500TV") in accordance with JIS K7125. Specifically, an aluminum plate was used as the counter material, and the average value of three measurements was taken as the static friction coefficient. <Tensile strength> The thermal conductive sheet was punched out using a dumbbell No. 2 (dumbbell type, width: 3 mm, length: 70 mm) conforming to JIS K7113 to produce a specimen. Then, using a tensile tester (manufactured by Shimadzu Corporation, product name "AG-IS20kN"), the specimen was pulled under the following conditions: load cell: 50 N, chuck distance: 35 mm, speed: 25 mm / min, temperature: 23°C, and the breaking strength (tensile strength) was measured. The sample pieces were punched out in a direction such that the long axis of the dumbbell intersected at a 90 degree angle with the strips that made up the thermal conductive sheet, and were punched out at five locations in total: the center of the sheet and its four corners (positions where part of the dumbbell was within 3 cm of the corners). The average value of the measured values ​​of the five test pieces was regarded as the tensile strength of the thermal conductive sheet. Generally, curled areas have poor tensile strength. <Asker C hardness> The Asker C hardness of the thermally conductive sheet was measured at 70°C using a hardness tester (manufactured by Kobunshi Keiki Co., Ltd., product name "ASKER CL-150LJ") in accordance with the Asker C method of the Society of Rubber Industry, Japan (SRIS). Specifically, the obtained thermally conductive sheet was cut into a size of 25 mm wide x 50 mm long x 0.1 mm thick, and 90 sheets were stacked to obtain a test piece. The obtained test piece was left to stand in a constant temperature room kept at a temperature of 70°C for 48 hours or more to obtain a thermally conductive sheet layer as a test body. Next, the damper height was adjusted so that the needle was 95 to 98, and the thermally conductive sheet layer and the damper were collided. The Asker C hardness of the thermally conductive sheet layer 60 seconds after the collision was measured twice using a hardness tester (manufactured by Kobunshi Keiki Co., Ltd., product name "ASKER CL-150LJ"), and the average of the measurement results was taken as the Asker C hardness of the thermally conductive sheet. <Thermal conductivity> For the thermal conductive sheet, the thermal diffusivity α (m 2 / s), specific heat at constant pressure Cp (J / g K) and specific gravity ρ (g / m 3 ) were measured by the following methods. [Thermal diffusivity in the thickness direction α] Measurements were performed using a thermal diffusion / thermal conductivity measuring device (manufactured by Ai-Phase Corporation, product name "Ai-Phase Mobile 1u") in accordance with the provisions of ISO 22007-3. [Specific heat at constant pressure Cp] The specific heat was measured at 25° C. under a temperature increase rate of 10° C. / min using a differential scanning calorimeter (manufactured by Rigaku, product name "DSC8230"). [Specific gravity ρ (density)] Measurements were made using an automatic specific gravity meter (manufactured by Toyo Seiki Co., Ltd., product name "DENSIMETER-H"). Then, each measured value is calculated using the following formula (I): λ = α × Cp × ρ (I) The thermal conductivity λ (W / m K) in the thickness direction of the thermal conductive sheet at 25°C was calculated by substituting <Thermal resistance value> The thermal resistance value of the thermally conductive sheet was measured using a thermal resistance tester (manufactured by Hitachi Technology and Services, Ltd., product name "Resin Material Thermal Resistance Measuring Device"). Specifically, a roughly square sample measuring 1 cm on each side was cut out from the thermally conductive sheet, and the thermal resistance (°C / W) was measured when pressures of 0.1 MPa and 0.9 MPa were applied at a sample temperature of 50°C. The smaller the thermal resistance value, the better the thermal conductivity of the thermally conductive sheet, and, for example, the better the heat dissipation characteristics when it is placed between a heat generating body and a heat sink. The thermal resistance value when a pressure of 0.1 MPa was applied was divided by the thermal resistance value when a pressure of 0.9 MPa was applied, and the rate of change in the thermal resistance value was calculated. <Indentation depth> The indentation depth of the thermal conductive sheet was measured using a nanoindentation tester (manufactured by Elionix, product name "ENT-2100") and a Berkovich indenter (No. 6382) as the indenter, by performing a nanoindentation test five times on the surface of the sheet under the following measurement conditions. Specifically, the average value of the displacement (μm) when the maximum load was reached was taken as the indentation depth. A larger indentation depth value means that the indenter has penetrated deeper, indicating that the surface of the thermal conductive sheet is more easily deformed. [Measurement conditions] Temperature: 25℃ Maximum load: 60mN Load speed: 120mN / min Hold time at maximum load: 0 seconds

[0061] Example 1 <Preparation of Composition> 70 parts of a thermoplastic fluororesin (manufactured by Daikin Industries, Ltd., trade name "Daiel G-101") that is liquid at room temperature and normal pressure, 30 parts of a thermoplastic fluororesin (manufactured by 3M Japan Ltd., trade name "Dyneon FC2211") that is solid at room temperature and normal pressure, and 90 parts of expanded graphite (manufactured by Ito Graphite Industries Co., Ltd., trade name "EC300", volume average particle size: 50 μm) as a particulate carbon material were mixed and stirred at a temperature of 150 ° C. for 20 minutes using a pressure kneader (manufactured by Nippon Spindle). Next, the resulting mixture was put into a crusher (manufactured by Osaka Chemical Co., Ltd., trade name "Wonder Crush Mill D3V-10") and crushed for 10 seconds to obtain a composition. <Formation of pre-heat conductive sheet> Next, 50 g of the obtained composition was sandwiched between a 50 μm thick protective film (PET film) that had been sandblasted, and roll-molded (primary pressing) under conditions of a roll gap of 1000 μm, a roll temperature of 50° C., a roll linear pressure of 50 kg / cm, and a roll speed of 1 m / min to obtain a pre-heat conductive sheet with a thickness of 0.8 mm. <Formation of Laminate> The resulting pre-thermal conductive sheet was then cut to a size of 150 mm length × 150 mm width × 0.8 mm thickness, and 188 sheets were stacked in the thickness direction of the pre-thermal conductive sheet. Then, the sheets were pressed (secondary pressing) in the stacking direction at a temperature of 120°C and a pressure of 0.1 MPa for 3 minutes to obtain a stack with a height of approximately 150 mm. <Formation of heat conductive sheet> Then, the laminate was placed so that the lamination direction was horizontal to the ground (the surface on which the laminate was placed), and the entire upper surface of the laminate was pressed down with a metal plate, leaving a length required for slicing at one end in the direction perpendicular to the lamination direction of the laminate, and the laminate was fixed by applying a pressure of 0.1 MPa from above. The sides and back of the laminate were not fixed. At this time, the temperature of the laminate was 25°C. Next, a slicing mechanism (spacing between the guide member and the rake face: 0.5 mm) consisting of a cutting blade A (single-edged, blade angle: 20°, maximum thickness of the blade: 3.5 mm, material: carbide, Rockwell hardness: 91.5, silicon processing of the blade surface: none, total length: 200 mm, curvature radius R of the blade tip: 1.0 μm) and a guide member (length: 50 mm, static friction coefficient: 0.4) was attached to the press part of a servo press machine (manufactured by Electrical Discharge Precision Machining Laboratory), and the laminate placed so that the lamination direction was horizontal was sliced ​​in the vertical direction (direction perpendicular to the lamination direction of the laminate) at a slicing speed of 200 mm / sec and a slice width of 100 μm to obtain a thermally conductive sheet of 150 mm length x 150 mm width x 0.10 mm thickness. The orientation of the cutting blade during slicing was such that the extension direction of the relief face was parallel to the sliced ​​surface of the laminate. The obtained thermally conductive sheet had a configuration in which slices (strips) of the pre-thermally conductive sheet were joined in parallel. The thermally conductive sheet thus obtained was subjected to various evaluations, and the results are shown in Table 1.

[0062] Example 2 A thermally conductive sheet was produced in the same manner as in Example 1, except that the slicing speed was set to 100 mm / sec. Then, various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0063] Example 3 A thermally conductive sheet was produced in the same manner as in Example 1, except that the slicing speed was set to 25 mm / sec. Then, various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0064] Example 4 A thermally conductive sheet was manufactured in the same manner as in Example 1, except that cutting blade B (single-edged, blade angle: 20°, maximum thickness of blade: 3.5 mm, material: carbide, Rockwell hardness: 91.5, silicon processing on blade surface: none, total length: 200 mm, radius of curvature R of blade tip: 0.1 μm) was used as the cutting blade of the slicing mechanism. Then, various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0065] Example 5 A thermally conductive sheet was manufactured in the same manner as in Example 1, except that cutting blade C (single-edged, blade angle: 20°, maximum thickness of blade: 3.5 mm, material: super steel, Rockwell hardness: 91.5, silicon processing on blade surface: none, total length: 200 mm, radius of curvature R of blade tip: 8.0 μm) was used as the cutting blade of the slicing mechanism. Then, various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0066] Comparative Example 1 A thermally conductive sheet was manufactured in the same manner as in Example 1, except that the thermally conductive sheet was formed as follows. Note that the thermally conductive sheet curled during slicing into a cylindrical shape with a diameter of 0.5 cm, and was stretched by hand to obtain a thermally conductive sheet. Then, various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1. <Formation of heat conductive sheet> The laminate was sliced ​​in the lamination direction using a wood slicer (Marunaka Iron Works, product name: Super Finishing Planer Super Mecha S) to obtain a thermally conductive sheet of length 150 mm x width 150 mm x thickness 0.10 mm. The slicing was performed at a sliding speed of 200 mm / sec while pressing the side of the laminate (the surface along the lamination direction) against the sliding surface of the wood slicer with a pressure of 0.3 MPa.

[0067] Comparative Example 2 A thermally conductive sheet was produced in the same manner as in Example 1, except that slicing was performed using only a cutting blade without using a guide member. Note that the thermally conductive sheet curled during slicing into a cylindrical shape with a diameter of 0.5 cm, and was stretched by hand to produce a thermally conductive sheet. Then, various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0068] Comparative Example 3 A thermally conductive sheet was manufactured in the same manner as in Example 3, except that cutting blade D (single-edged, blade angle: 20°, maximum thickness of blade: 3.5 mm, material: super steel, Rockwell hardness: 91.5, silicon processing on blade surface: none, total length: 200 mm, radius of curvature R of blade tip: 12.0 μm) was used as the cutting blade of the slicing mechanism. Then, various evaluations were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0069] [Table 1]

[0070] From Table 1, it can be seen that in Examples 1 to 5, it is possible to produce a thermally conductive sheet that is easy to deform while suppressing the occurrence of curling and reduction in area, can exhibit excellent thermal conductivity, and has excellent tensile strength. On the other hand, it can be seen that in Comparative Examples 1 and 2, in which no guide member was used, curling occurs and the tensile strength of the thermally conductive sheet decreases. Also, it can be seen that in Comparative Example 3, in which a cutting blade with a curvature radius of 12 μm was used, the area is significantly reduced during slicing, and the surface of the obtained thermally conductive sheet is less likely to deform. [Industrial Applicability]

[0071] According to the present invention, it is possible to manufacture a thermally conductive sheet having an easily deformable surface while suppressing the occurrence of curling and reduction in area. Furthermore, according to the present invention, it is possible to provide a thermally conductive sheet having an easily deformable surface, capable of exhibiting excellent thermal conductivity, and having excellent tensile strength. [Explanation of symbols]

[0072] 10 Resin Block 11 sheets 20 cutting blade 21 Scooping face 22 Flank 23 Cutting Edge 30 Guide member 31 Surface 40 Gap 50 portions

Claims

1. A thermally conductive sheet containing a resin and a thermally conductive filler (excluding a thermally conductive sheet having a base sheet in which fibers carrying a thermally conductive filler for carrying are intertwined in a planar shape and resin is filled between the fibers, and a resin layer in which a thermally conductive filler for dispersion is dispersed is formed on both sides of the base sheet), The thermal conductivity in the thickness direction is 12 W / m K or more, The tensile strength measured in accordance with JIS K7113 is 0.40 MPa or more, A thermally conductive sheet having an indentation depth of 20 μm or more when subjected to a nanoindentation test by a specified method.

2. 2. The thermal conductive sheet according to claim 1, having an Asker C hardness of 60 or more at a temperature of 70°C.

3. 3. The thermal conductive sheet according to claim 1, having a thermal resistance of 0.060° C. / W or less when a pressure of 0.9 MPa is applied.

4. 4. The thermal conductive sheet according to claim 1, wherein the thermal resistance value when a pressure of 0.1 MPa is applied is 0.096° C. / W or less.

5. 5. The thermal conductive sheet according to claim 1, wherein the thermal resistance value when a pressure of 0.1 MPa is applied divided by the thermal resistance value when a pressure of 0.9 MPa is applied is 1.78 or less.

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