JP6574667B2 - Thermal conductive sheet, thermal conductive sheet laminate, and thermal conductive sheet molded body - Google Patents

Description

  The present invention relates to a heat conductive sheet, and a heat conductive sheet laminate and a heat conductive sheet molded body using the heat conductive sheet.

  Conventionally, a metal plate having excellent thermal conductivity has been used for a housing of an electronic device such as a mobile phone or a personal computer. In recent years, as an alternative material for such a metal plate, a heat conductive sheet having excellent heat conductivity in both the surface direction and the thickness direction has attracted attention.

  For example, Patent Document 1 below discloses a heat conductive sheet including graphite, which is a graphene laminate, and a conductive material layer. According to Patent Document 1, a conductive material layer is intercalated between graphite graphenes, thereby improving thermal conductivity in the thickness direction as well as in the in-plane direction of graphene.

JP 2012-96937 A

  However, when a heat conductive sheet or a metal plate as in Patent Document 1 is used for a housing of an electronic device, the entire housing may become hot. For this reason, there are cases where the electronic device is difficult to carry or difficult to put on the knee or the like. Moreover, the heat conductive sheet of patent document 1 was brittle, and the moldability was not enough.

  The objective of this invention is providing the heat conductive sheet which has anisotropy in heat conductivity. Moreover, the other object of this invention is to provide the heat conductive sheet laminated body and heat conductive sheet molded object which used the said heat conductive sheet.

  The heat conductive sheet which concerns on this invention is a heat conductive sheet, Comprising: The 1st synthetic resin and the several 1st resin composition layer containing the carbon material which has a graphene laminated structure, 2nd synthetic resin A plurality of second resin composition layers, wherein a content of the carbon material with respect to 100 parts by weight of the first synthetic resin is 50 parts by weight or more and 150 parts by weight or less, The resin composition layers and the second resin composition layers are alternately laminated, and in the sheet plane of the heat conductive sheet, an arbitrary direction is the x direction, and a direction orthogonal to the x direction is y. The thermal conductivity λx in the x direction, the thermal conductivity λy in the y direction, and the thermal conductivity λz in the z direction are min (λx, λy) / λz ≧ 5 is satisfied.

  In another specific aspect of the heat conductive sheet according to the present invention, the λx and the λy satisfy max (λx, λy) ≧ 2 W / (m · K).

  On the other specific situation of the heat conductive sheet which concerns on this invention, the sum total of the lamination | stacking number of the said 1st and 2nd resin composition layer is 4 layers or more and 1000 layers or less.

  In still another specific aspect of the heat conductive sheet according to the present invention, the second resin composition layer further includes a carbon material different from the carbon material having the graphene laminated structure or an inorganic filler different from the carbon material. Including.

  In still another specific aspect of the heat conductive sheet according to the present invention, the carbon material having the graphene laminated structure is graphite or exfoliated graphite.

  In still another specific aspect of the heat conductive sheet according to the present invention, the number of stacked graphene sheets of the carbon material having the graphene stacked structure is 100 or more.

  In still another specific aspect of the heat conductive sheet according to the present invention, an average particle diameter of the carbon material having the graphene laminated structure is 0.1 μm or more and 100 μm or less.

  In still another specific aspect of the heat conductive sheet according to the present invention, the carbon material having the graphene laminated structure has a thickness of 30 nm or more.

  In still another specific aspect of the heat conductive sheet according to the present invention, each of the first and second synthetic resins is a polyolefin.

  In still another specific aspect of the heat conductive sheet according to the present invention, the melt viscosity at 230 ° C. of the first synthetic resin is lower than the melt viscosity at 230 ° C. of the second synthetic resin.

  The heat conductive sheet laminated body which concerns on this invention is equipped with a foamed resin layer and the heat conductive sheet comprised according to this invention laminated | stacked on the main surface of the at least one side of the said foamed resin layer.

  The heat conductive sheet molded body according to the present invention is a molded body of a heat conductive sheet or a heat conductive sheet laminate configured according to the present invention.

  In still another specific aspect of the heat conductive sheet according to the present invention, the heat conductive sheet is used for a housing of an electronic device, an outdoor communication fixing device, or a smart meter.

  In still another specific aspect of the heat conductive sheet laminate according to the present invention, the heat conductive sheet laminate is used for a housing of an electronic device, a fixing device for outdoor communication, or a smart meter.

  In still another specific aspect of the heat conductive sheet molded body according to the present invention, the heat conductive sheet molded body is used for a housing of an electronic device, an outdoor communication fixing device, or a smart meter.

  ADVANTAGE OF THE INVENTION According to this invention, the heat conductive sheet which has anisotropy in heat conductivity can be provided.

It is typical sectional drawing which shows the heat conductive sheet which concerns on the 1st Embodiment of this invention. It is typical sectional drawing which shows the heat conductive sheet which concerns on the 2nd Embodiment of this invention. It is typical sectional drawing which shows the heat conductive sheet laminated body which concerns on one Embodiment of this invention. (A) is a schematic plan view of a pair of upper and lower container molds used for forming the heat conductive sheet laminates obtained in the examples and comparative examples, and (b) shows the AA line. It is a typical sectional view in alignment.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

[Heat conduction sheet]
FIG. 1 is a schematic cross-sectional view showing a heat conductive sheet according to the first embodiment of the present invention. As shown in FIG. 1, the heat conductive sheet 1 includes a first resin composition layer 2 and a second resin composition layer 3. The first resin composition layer 2 and the second resin composition layer 3 are alternately laminated. The first resin composition layer 2 is disposed on both sides of the heat conductive sheet 1.

  More specifically, in the heat conductive sheet 1, six first resin composition layers 2 and five second resin composition layers 3 are alternately stacked in order from the first resin composition layer 2. Has been. In the heat conductive sheet 1, the total number of laminated first and second resin composition layers 2 and 3 is 11 layers.

  The first resin composition layer 2 includes a first synthetic resin and a carbon material having a graphene laminated structure. Content of the said carbon material with respect to 100 weight part of said 1st synthetic resins is 50 to 150 weight part. The second resin composition layer 3 includes a second synthetic resin.

  Incidentally, in the heat conductive sheet 1, the heat conductivity λx in the x direction, the heat conductivity λy in the y direction, and the heat conductivity λz in the z direction satisfy min (λx, λy) / λz ≧ 5.

  In this specification, the x direction is an arbitrary direction in the sheet plane of the heat conductive sheet. The y direction is a direction orthogonal to the x direction on the sheet plane. The z direction is the thickness direction of the heat conductive sheet. Therefore, the z direction is a direction orthogonal to the x direction and the y direction.

  The thermal conductivity in each of the x direction, the y direction, and the z direction can be calculated using the following equation (1).

  Thermal conductivity (W / (m · K)) = thermal diffusivity × density × ratio (1)

  In Formula (1), the thermal diffusivity in each direction in the x direction, the y direction, and the z direction can be measured using, for example, a product name: Thermowave Analyzer, manufactured by Bethel.

  The min (λx, λy) means a value having a lower thermal conductivity among λx and λy. Therefore, min (λx, λy) / λz ≧ 5 means that the ratio of the lower thermal conductivity of λx and λy to λz is 5 or more.

  As described above, in the thermal conductive sheet 1, since λx, λy, and λz satisfy min (λx, λy) / λz ≧ 5, the thermal conductivity in the plane direction is higher than the thermal conductivity in the thickness direction. It has become. Therefore, the heat conductive sheet 1 has anisotropy in heat conductivity.

  From the viewpoint of giving further anisotropy due to thermal conductivity, λx, λy and λz preferably satisfy min (λx, λy) / λz ≧ 10, and min (λx, λy) / λz ≧ 20. Is more preferable. Note that the upper limit of min (λx, λy) is preferably as high as possible, but is preferably about 3000 because of the properties of the material.

  In the present invention, it is preferable that the λx and λy satisfy max (λx, λy) ≧ 2 W / (m · K). The max (λx, λy) means a value having a higher thermal conductivity among λx and λy. Therefore, max (λx, λy) ≧ 2W / (m · K) means that the thermal conductivity having the higher thermal conductivity of λx and λy is 2 W / (m · K) or more. Yes.

  When max (λx, λy) is in the above range, the thermal conductivity in the plane direction can be further increased, and more anisotropy can be imparted by the thermal conductivity.

  Further, the λz is preferably λz ≦ 2W / (m · K). When λz is within the above range, the thermal conductivity in the thickness direction is lowered, and it becomes possible to have more anisotropy due to the thermal conductivity.

  Moreover, in the heat conductive sheet 1, it is preferable that the tensile breaking elongation in at least one direction among the x direction and the y direction is 10% or more. In this case, the toughness of the heat conductive sheet 1 can be further enhanced and the moldability can be further enhanced. The tensile elongation at break is a value measured according to JIS K 7161.

  The tensile elongation at break is preferably 10% or more as measured in both the x direction and the y direction. In that case, the toughness of the heat conductive sheet 1 can be further enhanced, and the moldability can be further enhanced. However, in the present invention, only the value in one direction out of the x direction and the y direction out of the tensile elongation at break may be 10% or more.

  From the viewpoint of further enhancing the toughness of the heat conductive sheet 1 and further improving the moldability, the tensile breaking elongation of the heat conductive sheet 1 is preferably 15% or more, and more preferably 20% or more. . In addition, from the viewpoint of ensuring rigidity, the upper limit of the tensile elongation at break of the heat conductive sheet 1 is preferably about 40%.

  The heat conductive sheet 1 preferably has a flexural rigidity of 0.1 (N / mm) or more in at least one of the x direction and the y direction, and is 1.0 (N / mm) or more. It is more preferable. The bending rigidity means a value measured according to JIS K 7171. More specifically, the bending rigidity is a value obtained by dividing the magnitude of the inclination passing through the origin by the width of the sample in the load-displacement curve measured according to JIS K 7171.

  As described above, the heat conductive sheet according to the present invention such as the heat conductive sheet 1 has a low thermal conductivity in the thickness direction. Therefore, when used in a casing of an electronic device such as a mobile phone or a personal computer, The surface of the sheet that touches the human body is less likely to get hot. Moreover, since the thermal conductivity is excellent in the surface direction, heat can be sufficiently radiated in the surface direction. For this reason, it is difficult to cause a problem that the electronic device becomes hot and difficult to hold or difficult to put on the knee or the like. Therefore, the heat conductive sheet of this invention can be used for the housing | casing of electronic devices, such as a mobile phone and a personal computer.

  Moreover, the heat conductive sheet of the present invention has enhanced rust resistance, weather resistance and rigidity. Therefore, it can be used suitably for the outdoor communication fixing device and the housing of the smart meter. Moreover, you may aim at the further weather resistance improvement by apply | coating a plating process, heat resistance, a heat-shielding coating material, etc. to one side or both surfaces as needed.

  When used in a housing such as an outdoor communication fixing device or a smart meter, electromagnetic wave transmission may be required. Such electromagnetic wave permeability can be adjusted by the amount of carbon material having a graphene laminated structure and the degree of peeling.

  As described above, the heat conductive sheet of the present invention can diffuse the heat of the sheet surface portion heated by a heating element, direct sunlight, etc. in the horizontal direction, and can make it difficult to transfer heat to the back surface of the sheet. .

  Therefore, the heat conductive sheet of the present invention can be used in various fields such as architecture, automobiles, aviation, ships and electronic materials.

  Moreover, the elasticity modulus of a heat conductive sheet can also be adjusted according to a use. The adjustment of the elastic modulus can be performed by changing the type of carbon material having a graphene laminated structure and the blending ratio.

  Thus, in the heat conductive sheet of this invention, a physical property can be adjusted suitably according to the intended use.

  Hereinafter, the heat conductive sheet of the present invention will be described in more detail.

(First resin composition layer)
The first resin composition layer includes a first synthetic resin and a carbon material having a graphene stacked structure.

  The thickness of the first resin composition layer is not particularly limited because it can be appropriately set according to the purpose of the molded product to be used. For example, when used as a film product, it is preferably 10 μm or more, more preferably 20 μm or more, preferably 200 μm or less, more preferably 100 μm or less. Moreover, when using as a housing | casing of an outdoor communication fixing device or a smart meter, Preferably it is 2 micrometers or more, More preferably, it is 2.5 micrometers or more, Preferably it is 6 micrometers or less, More preferably, it is 4.5 micrometers or less.

A first synthetic resin;
The first synthetic resin is not particularly limited, and various known synthetic resins can be used. Preferably, a thermoplastic resin is used as the synthetic resin. When using a thermoplastic resin, the moldability of a heat conductive sheet can be improved further.

  The thermoplastic resin is not particularly limited. For example, polyethylenes such as high-density polyethylene, low-density polyethylene, and linear low-density polyethylene, polypropylenes such as homopolypropylene, block polypropylene, and random polypropylene, norbornene resin, and the like Cyclic polyolefins, polyvinyl acetates such as polyvinyl acetate and ethylene vinyl acetate, polyvinyl acetate derivatives such as polyvinyl alcohol and polyvinyl butyral, polyesters such as PET, polycarbonate and polylactic acid, polyethylene oxide, polyphenylene ether , Polyether resins such as polyetheretherketone, acrylic resins such as PMMA, sulfones such as polysulfone and polyethersulfone, fluorine such as PTFE and PVDF Resins, polyamide resins such as nylon, polyvinyl chloride, halogenated resins such as vinylidene chloride, polystyrene, polyacrylonitrile or a copolymer resin thereof such and the like. These may be used alone or in combination. Preferably, it is desirable to use a polyolefin that is inexpensive and easy to mold under heating.

A carbon material having a graphene laminated structure;
Although it does not specifically limit as a carbon material which has the said graphene laminated structure, Graphite, a carbon nanotube, exfoliated graphite, a graphene, etc. can be used. Preferably, it is graphite or exfoliated graphite. These may be used alone or in combination.

  The exfoliated graphite is obtained by exfoliating the original graphite and refers to a graphene sheet laminate that is thinner than the original graphite. The number of graphene sheets laminated in exfoliated graphite should be less than the original graphite.

  In the carbon material having the graphene stacked structure, the number of graphene sheets stacked is preferably 100 layers or more, more preferably 1000 layers or more, further preferably 1500 layers or more, and 2000 layers or more. It is particularly preferred that there be.

  When the number of stacked layers is equal to or more than the above lower limit, the cost of the carbon material having a graphene stacked structure can be suppressed. On the other hand, the upper limit of the number of graphene sheets stacked is about 3500 from the viewpoint of the rigidity reinforcing effect as a filler.

  Note that the number of graphene sheets stacked in graphite can be determined by measuring the thickness of graphite using a scanning electron microscope (SEM) and dividing the graphene by the thickness of the graphene sheet 0.33 nm / layer.

  The number of laminated graphene sheets of exfoliated graphite can be measured using a transmission electron microscope (TEM), and is an arithmetic average of the number of laminated exfoliated graphites.

  The average particle size of the carbon material having the graphene laminated structure is preferably 0.1 μm or more and 100 μm or less. If the average particle size of the carbon material is too small, the thermal conductivity in the surface direction of the heat conductive sheet may not be sufficiently increased. If the average particle size of the carbon material is too large, the heat conductive sheet may become brittle and formability may deteriorate.

  In addition, the said average particle diameter means the largest outer dimension of a surface direction. The average particle diameter can be measured using, for example, a laser diffraction particle size distribution measuring apparatus.

  The thickness of the carbon material having the graphene stacked structure is preferably 30 nm or more, more preferably 300 nm or more, further preferably 500 nm or more, and particularly preferably 660 nm or more. When the thickness of the carbon material is not less than the above lower limit, the cost of the carbon material having a graphene stacked structure can be suppressed. On the other hand, from the viewpoint of the rigidity reinforcing effect as the filler, the upper limit of the thickness of the carbon material is about 1200 nm.

  The content of the carbon material having the graphene laminated structure is preferably in the range of 50 to 150 parts by weight with respect to 100 parts by weight of the synthetic resin. When there is too little content of the said carbon material, the heat conductivity in the surface direction of a heat conductive sheet may not fully be improved. When there is too much content of the said carbon material, a heat conductive sheet will become weak and a moldability may worsen.

  The carbon material is preferably dispersed in the synthetic resin. When the said carbon material is disperse | distributed in a synthetic resin, the heat conductivity in the surface direction of a heat conductive sheet can be improved further.

  The method for dispersing the carbon material in the synthetic resin is not particularly limited, but the carbon material can be dispersed by kneading the synthetic resin and the carbon material.

  The kneading method is not particularly limited. For example, a kneading method under heating using a kneading device such as a twin screw kneader such as a plast mill, a single screw extruder, a twin screw extruder, a Banbury mixer, or a roll. Etc. Among these, the method of melt kneading using an extruder is preferable.

Other ingredients;
Various additives may be added as optional components to the first resin composition layer. Additives include, for example, antioxidants such as phenols, phosphoruss, amines, and sulfurs; ultraviolet absorbers such as benzotriazoles and hydroxyphenyltriazines; metal hazard inhibitors; hexabromobiphenyl ether, decabromo Halogenated flame retardants such as diphenyl ether; flame retardants such as ammonium polyphosphate and trimethyl phosphate; various fillers; antistatic agents; stabilizers; These may be used alone or in combination.

(Second resin composition layer)
The second resin composition layer includes a second synthetic resin. Note that the second resin composition layer preferably does not contain a carbon material having a graphene stacked structure. When the carbon material which has a graphene laminated structure is not contained in the 2nd resin composition layer, the heat conductivity of the thickness direction of a heat conductive sheet can be lowered further. Therefore, in this case, a further anisotropy can be given due to the thermal conductivity of the thermal conductive sheet.

  The thickness of the second resin composition layer is not particularly limited because it can be appropriately set according to the purpose of the molded product to be used. For example, when used as a film product, it is preferably 10 μm or more, more preferably 20 μm or more, preferably 200 μm or less, more preferably 100 μm or less. Moreover, when using as a housing | casing of an outdoor communication fixing device or a smart meter, Preferably it is 2 micrometers or more, More preferably, it is 2.5 micrometers or more, Preferably it is 6 micrometers or less, More preferably, it is 4.5 micrometers or less.

A second synthetic resin;
The second synthetic resin is not particularly limited, and various known synthetic resins can be used. Preferably, a thermoplastic resin is used as the synthetic resin. When using a thermoplastic resin, the moldability of a heat conductive sheet can be improved further.

  The thermoplastic resin is not particularly limited. For example, polyethylenes such as high-density polyethylene, low-density polyethylene, and linear low-density polyethylene, polypropylenes such as homopolypropylene, block polypropylene, and random polypropylene, norbornene resin, and the like Cyclic polyolefins, polyvinyl acetates such as polyvinyl acetate and ethylene vinyl acetate, polyvinyl acetate derivatives such as polyvinyl alcohol and polyvinyl butyral, polyesters such as PET, polycarbonate and polylactic acid, polyethylene oxide, polyphenylene ether , Polyether resins such as polyetheretherketone, acrylic resins such as PMMA, sulfones such as polysulfone and polyethersulfone, fluorine such as PTFE and PVDF Resins, polyamide resins such as nylon, polyvinyl chloride, halogenated resins such as vinylidene chloride, polystyrene, polyacrylonitrile or a copolymer resin thereof such and the like. These may be used alone or in combination. Preferably, it is desirable to use a polyolefin that is inexpensive and easy to mold under heating.

  Note that the second synthetic resin may be the same synthetic resin as the first synthetic resin, or may be another synthetic resin. However, the melt viscosity at 230 ° C. of the first synthetic resin is desirably lower than the melt viscosity at 230 ° C. of the second synthetic resin.

Other ingredients;
The second resin composition layer may further contain a carbon material different from the carbon material having the graphene stacked structure. Examples of such a carbon material include carbon fiber, carbon nanotube, and carbon nanocoil.

  The second resin composition layer may contain an inorganic filler different from the carbon material. Examples of such inorganic fillers include talc, mica, wollastonite, barium sulfate, silica, calcium carbonate, glass fiber, alumina, ceramic filler, and the like.

  Various additives may be added as optional components to the second resin composition layer. Additives include, for example, antioxidants such as phenols, phosphoruss, amines, and sulfurs; ultraviolet absorbers such as benzotriazoles and hydroxyphenyltriazines; metal hazard inhibitors; hexabromobiphenyl ether, decabromo Halogenated flame retardants such as diphenyl ether; flame retardants such as ammonium polyphosphate and trimethyl phosphate; various fillers; antistatic agents; stabilizers; These may be used alone or in combination.

(Production method)
The manufacturing method of the heat conductive sheet of this invention is not specifically limited, For example, it can manufacture with the following method.

  First, a composite material is obtained by kneading a first synthetic resin and a carbon material having a graphene stacked structure. The kneading method is not particularly limited, and for example, kneading is performed using a kneading apparatus such as a twin screw kneader such as a plast mill, a single screw extruder, a twin screw extruder, a Banbury mixer, or a roll. The method etc. are mentioned.

  Then, the obtained composite material is shape | molded by press work, an extrusion process, calendering, etc., and the 1st sheet | seat for forming a 1st resin composition layer is produced. In addition, the thermal conductivity in each direction and tensile elongation at break can be adjusted as appropriate by changing the type of carbon material having a graphene laminated structure in the first sheet, the blending ratio, and the like.

  Similarly, the second synthetic resin is molded by pressing, extruding, calendering, or the like to produce a second sheet for forming the second resin composition layer.

  Next, the plurality of first sheets and the plurality of second sheets prepared as described above are alternately stacked and fused by pressing. Then, a heat conductive sheet is obtained by pressing at normal temperature.

  For example, in the heat conductive sheet 1, eleven sheets of the produced first and second sheets are alternately laminated so that the first sheets are on the surface sides on both sides, and are fused by hot pressing. Then, the said heat conductive sheet 1 is obtained by pressing at normal temperature.

  In addition, you may obtain the heat conductive sheet of this invention with the following manufacturing methods.

  First, a first synthetic resin and a carbon material having a graphene laminated structure are kneaded under heating by the method described above to obtain a composite material.

  Next, the composite material and the second synthetic resin are coextruded to obtain a laminate of two or more layers in which the second resin composition layer is laminated on the first resin composition layer. The method for obtaining the laminate is not particularly limited, and examples thereof include a wet lamination method, a dry lamination method, an extrusion coating method, a multilayer melt extrusion method, a hot melt lamination method, and a heat lamination method.

  Preferably, as a method for obtaining the laminate, a multilayer melt extrusion method that is easy to produce can be used. Examples of the multilayer melt extrusion method include a multi-manifold method and a feed block method.

  As a manufacturing method of the said laminated body by the said feed block method, the method described below is mentioned, for example. The composite material is introduced into the first extruder, and the second synthetic resin is introduced into the second extruder. The composite material and the second synthetic resin are simultaneously extruded from the first extruder and the second extruder. The composite material and the second synthetic resin extruded from the first extruder and the second extruder are sent to a feed block. In the feed block, the composite material and the second synthetic resin extruded from the first extruder and the second extruder join together. Thereby, a laminate in which the second resin composition layer is laminated on the first resin composition layer can be obtained.

  Next, the laminate can be transferred to a multilayer forming block and multilayered in the multilayer forming block to obtain a heat conductive sheet comprising a resin composition layer having 10 or more layers. In this manufacturing method, a multilayer forming block that can be divided and stacked is attached to the downstream portion of the feed block. The laminated body is divided in the multilayer forming block, and the divided laminated body is repeatedly laminated to obtain a heat conductive sheet composed of a resin composition layer having 10 or more layers.

  The multilayer molding is not limited to the above method, and can be performed by an appropriate multilayering method and apparatus. For example, the laminated body may be folded repeatedly to obtain a heat conductive sheet composed of a resin composition layer having 10 or more layers.

(Other embodiments)
FIG. 2 is a schematic cross-sectional view showing a heat conductive sheet according to the second embodiment of the present invention. As shown in FIG. 2, in the heat conductive sheet 11, the 1st resin composition layer 12 and the 2nd resin composition layer 13 are laminated | stacked alternately. The sum total of the number of laminated first and second resin composition layers 12 and 13 is 100 layers. Like the heat conductive sheet 11, the sum total of the lamination | stacking number of the 1st and 2nd resin composition layers 12 and 13 may be 100 or more layers. Other points are the same as in the first embodiment.

  In the present invention, it is only necessary that at least two first resin composition layers and at least two second resin composition layers are alternately laminated. Therefore, the total number of the first and second resin composition layers may be at least four or more.

  The total number of the first and second resin composition layers stacked is preferably 10 layers or more, more preferably 100 layers or more, preferably 1000 layers or less, more preferably 500 or less.

  When the sum total of the number of laminated layers of the first and second resin composition layers is equal to or more than the lower limit, it is possible to give a further anisotropy to the heat conductive sheet. On the other hand, when the sum total of the number of laminated layers of the first and second resin composition layers is not more than the above upper limit, the thickness can be further reduced.

  As described above, in the present invention, it is sufficient that at least two first resin composition layers and at least two second resin composition layers are alternately laminated. The 1st and 2nd resin composition layers do not need to be laminated | stacked alternately. Moreover, layers other than the 1st and 2nd resin composition layer may be laminated | stacked.

[Heat conductive sheet laminate]
FIG. 3 is a schematic cross-sectional view showing a heat conductive sheet laminate according to an embodiment of the present invention. As shown in FIG. 3, the heat conductive sheet laminate 21 includes first and second heat conductive sheets 22 and 23 and a foamed resin layer 24.

  The foamed resin layer 24 includes a first main surface 24a and a second main surface 24b facing the first main surface 24a. A first heat conductive sheet 22 is provided on the first main surface 24 a of the foamed resin layer 24. On the other hand, a second heat conductive sheet 23 is provided on the second main surface 24 b of the foamed resin layer 24. Therefore, the foamed resin layer 24 is provided so as to be sandwiched between the first and second heat conductive sheets 22 and 23. The heat conductive sheet laminate 21 is a heat conductive sheet laminate having a three-layer structure in which the first and second heat conductive sheets 22 and 23 are provided on both surfaces of the foamed resin layer 24. In the present invention, the number of layers of each layer constituting the heat conductive sheet laminate 21 is not particularly limited.

  The first and second heat conductive sheets 22 and 23 are the above-described heat conductive sheets of the present invention.

  The foamed resin layer 24 is made of a thermoplastic resin. The foamed resin layer 24 has a plurality of bubble cells inside. The expansion ratio of the foamed resin layer 24 is preferably 3 cc / g or more and 30 cc / g or less. By setting the expansion ratio of the foamed resin layer within the above range, the heat conductive sheet laminate can be further reduced in weight and the moldability can be further enhanced.

  Although it does not specifically limit as a material which comprises the said foamed resin layer, It is preferable that it is a thermoplastic resin. The thermoplastic resin is preferably a polyolefin. Examples of the polyolefin include polyethylene which is an ethylene homopolymer, ethylene-α-olefin copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester copolymer, ethylene-vinyl acetate copolymer. Polyethylene resins such as polymers, polypropylene as propylene homopolymers, polypropylene resins such as propylene-α-olefin copolymers, butene homopolymers, homopolymers or copolymers of conjugated dienes such as butadiene and isoprene At least one selected from the group consisting of can be used. As the polyolefin, polyethylene or polypropylene is preferably used.

  Moreover, you may use various additives for the said foamed resin layer as an arbitrary component. Additives include, for example, antioxidants such as phenols, phosphoruss, amines, and sulfurs; ultraviolet absorbers such as benzotriazoles and hydroxyphenyltriazines; metal hazard inhibitors; hexabromobiphenyl ether, decabromo Halogenated flame retardants such as diphenyl ether; flame retardants such as ammonium polyphosphate and trimethyl phosphate; various fillers; antistatic agents; stabilizers; These may be used alone or in combination.

  The foamed resin layer can be formed by molding a commercially available foamed resin sheet. But you may produce by extruding foamable resin, and a manufacturing method is not specifically limited. Moreover, you may produce the said foamed resin layer by shape | molding two or more foamed resin sheets.

  It does not specifically limit about the manufacturing method of the said heat conductive sheet laminated body. For example, first, a laminate is produced by extruding and laminating a material constituting the heat conductive sheet on the surface of the foamed resin sheet. Subsequently, two sheets of the obtained laminated plate are laminated so that the foamed resin layer surfaces overlap each other, and heat-pressed to laminate the second thermal conductive sheet, the foamed resin layer, and the first thermal conductive sheet in this order. The heat conductive sheet laminated body made can be obtained.

  In the above embodiment, the laminate is a three-layered structure, but as long as the foamed resin layer and the heat conductive sheet of the present invention laminated on at least one main surface of the foamed resin layer are provided, the number of laminated layers Is not particularly limited.

[Heat conductive sheet molding]
The heat conductive sheet molded body of the present invention is obtained by molding the above-described heat conductive sheet or heat conductive sheet laminate of the present invention.

  The heat conductive sheet or the heat conductive sheet laminate can be formed by, for example, pressing, extrusion, extrusion laminating, or the like.

  As described above, the heat conductive sheet of the present invention is used in the heat conductive sheet laminate and the heat conductive sheet molded body of the present invention. Therefore, the heat conductive sheet laminate and the heat conductive sheet molded body of the present invention can be suitably used for a housing such as an electronic device, an outdoor communication fixing device, or a smart meter.

[Examples and Comparative Examples]
Hereinafter, the effects of the present invention will be clarified by giving specific examples and comparative examples of the present invention. In addition, this invention is not limited to a following example.

Example 1
95 parts by weight of polypropylene (PP, product name “E-150GK” manufactured by Prime Polymer Co., Ltd.) and 5 parts by weight of styrene-ethylene-butadiene-styrene copolymer (SEBS, product name “H1062” manufactured by Asahi Kasei Chemicals) , 100 parts by weight of graphite A (product name “CNP7”, manufactured by Ito Graphite Co., Ltd., number of layers 1300, average particle size 7 μm, thickness 420 nm) is used with a lab plast mill (product number “R100” manufactured by Toyo Seiki Co., Ltd.). Then, a composite material was obtained by melt-kneading at 200 ° C. The obtained composite material was molded into a sheet by pressing under conditions of a temperature of 200 ° C., a pressure of 20 MPa, and a time of 5 minutes, and then pressed at room temperature to obtain a resin sheet A having a thickness of 0.1 mm.

  Next, 95 parts by weight of polypropylene (PP, product name “E-150GK” manufactured by Prime Polymer Co., Ltd.) and styrene-ethylene-butadiene-styrene copolymer (SEBS, product name “H1062” manufactured by Asahi Kasei Chemicals Co., Ltd.) 5 A resin composition was obtained by melting and kneading the parts by weight at 200 ° C. using a lab plast mill (product number “R100” manufactured by Toyo Seiki Co., Ltd.) as described above. The obtained resin composition was molded into a sheet by pressing under conditions of a temperature of 200 ° C., a pressure of 20 MPa, and a time of 5 minutes, and then pressed at room temperature to obtain a resin sheet B having a thickness of 0.1 mm.

  A plurality of resin sheets A and B obtained in the same manner were alternately arranged in a total of 11 layers so that the resin sheet A would be on the outermost surface, and the temperature was 200 ° C., the pressure was 20 MPa, and the time was 5 minutes. The resin sheets A and B of the layers were heat-fused and then pressed at room temperature to obtain a heat conductive sheet having a thickness of 1.1 mm.

(Example 2)
Example 1 except that exfoliated graphite B (manufactured by xGScience, trade name “xGnPM-5”, number of layers 180 layers, average particle size 5 μm, thickness 60 nm) was used instead of graphite A in Example 1. In the same manner, a heat conductive sheet having a thickness of 1.1 mm was obtained.

(Example 3)
As materials for the first layer, 95 parts by weight of polypropylene (PP, product name “E-150GK” manufactured by Prime Polymer Co., Ltd.) and a styrene-ethylene-butadiene-styrene copolymer (SEBS, manufactured by Asahi Kasei Corporation, product name “ H1062 ”) and 5 parts by weight of graphite A (trade name“ CNP7 ”, manufactured by Ito Graphite Co., Ltd., 1300 layers, average particle diameter of 7 μm, thickness of 420 nm) were prepared.

  As a material for the second layer, 95 parts by weight of polypropylene (PP, product name “E-150GK” manufactured by Prime Polymer Co., Ltd.) and a styrene-ethylene-butadiene-styrene copolymer (SEBS, manufactured by Asahi Kasei Corporation, product name “ H1062 ") and 5 parts by weight were prepared.

  The material of the first layer and the material of the second layer were extruded by two extruders to form the first layer and the second layer. The extruded first layer and second layer were laminated in the feed block with the first layer and the second layer to produce a sheet-like laminate. Next, in a plurality of multilayer formation blocks, the laminate is divided, and the divided laminate is further laminated to form a multilayer, and the thickness is a laminate having a thickness of 2 μm per layer and 256 layers. A 0.5 mm thermal conductive sheet was obtained.

Example 4
A heat conductive sheet having a thickness of 0.5 mm was obtained in the same manner as in Example 3 except that the thickness per layer was 0.5 μm and the number of layers was 1024.

(Example 5)
When forming the resin sheet B of Example 1, a thickness of 1.1 mm was obtained in the same manner as in Example 1 except that 100 parts by weight of talc (trade name “MS-P”, manufactured by Nippon Talc Co., Ltd.) was further added. A heat conductive sheet was obtained.

(Example 6)
When forming the resin sheet A of Example 1, a heat conductive sheet having a thickness of 1.1 mm was obtained in the same manner as in Example 1 except that the number of parts of graphite A was 50 parts by weight.

(Comparative Example 1)
A heat conductive sheet having a thickness of 1.1 mm was obtained in the same manner as in Example 1 except that graphite A was not added when forming the resin sheet A of Example 1.

(Comparative Example 2)
When forming the resin sheet A of Example 1, instead of polypropylene and a styrene-ethylene-butadiene-styrene copolymer (SEBS), polypropylene (PP, manufactured by Prime Polymer Co., Ltd., trade name “E-150GK”) was used alone. ) And graphite C (product name “SG-BH8”, number of layers 15000 layers, average particle size 8 μm, thickness 5000 nm) was used in place of graphite A. A heat conductive sheet having a thickness of 1.1 mm was obtained in the same manner as in Example 1.

(Comparative Example 3)
A commercially available graphite sheet (manufactured by Panasonic Corporation, trade name “EYGS121807”) having a thickness of 70 μm was used as the heat conductive sheet.

(Evaluation)
The following evaluation was performed about the heat conductive sheet obtained by the Example and the comparative example. The results are shown in Table 1 below.

Thermal conductivity;
About the heat conductive sheet of an Example and a comparative example, the heat conductivity ((lambda) x, (lambda) y, and (lambda) z) in ax direction, y direction, and z direction was calculated | required using the following formula | equation, respectively.

  The thermal conductivity in each direction can be calculated using the following formula (1).

  Thermal conductivity (W / (m · K)) = thermal diffusivity × density × ratio (1)

  In Formula (1), the thermal diffusivity of each direction was measured using the product name: Thermowave Analyzer, manufactured by Bethel.

  Using λx, λy, and λz obtained as described above, min (λx, λy) / λz, max (λx, λy), and λz were obtained.

Tensile elongation at break;
The tensile elongation at break was performed according to the tensile test of JIS K 7161 in the direction of max (λx, λy).

Bending stiffness;
In accordance with JIS K 7171, the measurement was performed in the direction of max (λx, λy) at a test speed of 50 mm / min and a span distance of 100 mm, and bending stiffness was calculated.

  The results are shown in Table 1 below.

(Example 7)
Two sheets of PP foam (made by Sekisui Chemical Co., Ltd., trade name “Softlon SP”, foaming ratio: 15 times, thickness: 5 mm) constituting the foamed resin layer were prepared in the same manner as in Example 1. A heat conductive sheet laminate (first and second heat conductive sheets) was laminated and subjected to hot pressing to obtain a heat conductive sheet laminate having a thickness of 6 mm.

(Example 8)
Two sheets of PP foam (made by Sekisui Chemical Co., Ltd., trade name “Softlon SP”, expansion ratio: 20 times, thickness: 4 mm) constituting the foamed resin layer were prepared in the same manner as in Example 2. A heat conductive sheet laminate (first and second heat conductive sheets) was laminated and subjected to hot pressing to obtain a heat conductive sheet laminate having a thickness of 6 mm.

(Comparative Example 4)
Two heat conductive sheets of Comparative Example 2 (on the both sides of PP foam (made by Sekisui Chemical Co., Ltd., trade name “Softlon SP”, expansion ratio: 20 times, thickness: 4 mm) constituting the foamed resin layer) The first and second heat conductive sheets) were laminated and hot pressed to obtain a heat conductive sheet laminate having a thickness of 6 mm.

(Comparative Example 5)
Two sheets of Comparative Example 3 are formed on both sides of a PP-based foam constituting the foamed resin layer (manufactured by Sekisui Chemical Co., Ltd., trade name “Softlon SP”, foaming magnification: 15 times, two layers of 3 mm in thickness). The heat conductive sheets (first and second heat conductive sheets) were laminated and hot-pressed to obtain a heat conductive sheet laminate having a thickness of 6 mm.

(Evaluation)
The following evaluation was performed about the heat conductive sheet laminated body obtained in Examples 7 and 8 and Comparative Examples 4 and 5. The results are shown in Table 2 below.

Sheet top surface temperature;
A 25 mm × 25 mm heater was attached to the center of a 170 mm × 170 mm sheet-shaped sample via grease, and the heater-shaped mounting portion was on the lower side to keep the sheet-shaped sample in a horizontal state. The voltage of the heater was adjusted to 105 ° C., the temperature on the surface opposite to the heater mounting surface was observed by thermography, and the temperature of the sheet upper surface after 15 minutes was measured as “sheet upper surface temperature”. The results are shown in Table 2 below. In Table 2, the evaluation symbols are as follows.

◎ ・ ・ ・ Sheet upper surface temperature is less than 40 ℃ ○ ・ ・ ・ Sheet upper surface temperature is 40 ℃ or more, less than 60 ℃

Moldability;
About the obtained heat conductive sheet laminated body, the test piece of length 320mm x width 320mm was cut out. Subsequently, this test piece was fixed to a single molding machine (manufactured by Sanko Kiko Co., Ltd., product number: SPF-00001) and heated until the surface temperature of the test piece reached 170 ° C. After heating, it was taken out from the single molding machine and press-molded using a pair of upper and lower container molds shown in FIGS. 4 (a) and 4 (b). 4A is a schematic plan view showing a container-like upper and lower pair of molds, and FIG. 4B is a schematic cross-sectional view taken along the line AA.

  Next, the appearance quality of the test piece (molded product) after molding was evaluated. The results are shown in Table 2 below. In Table 2, the evaluation symbols are as follows.

  In addition, on the outer surface (convex surface) of the molded product, the area of the portion where wrinkles (length 2 mm or more), unevenness (height difference 0.1 mm or more), gloss unevenness, and tearing occurred was defined as a defective area.

◎ ・ ・ ・ Defect area is less than 10% of total area ○ ・ ・ ・ Defect area is 10% or more and less than 20% of total area × ・ ・ ・ Defect area is 20% or more of entire area

DESCRIPTION OF SYMBOLS 1,11 ... Thermal conductive sheet 2,12 ... 1st resin composition layer 3,13 ... 2nd resin composition layer 21 ... Thermal conductive sheet laminated body 22 ... 1st thermal conductive sheet 23 ... 2nd heat Conductive sheet 24 ... foamed resin layer 24a ... first main surface 24b ... second main surface

Claims (14)

A heat conductive sheet,
A plurality of first resin composition layers including a first synthetic resin and a carbon material having a graphene laminated structure; and a plurality of second resin composition layers including a second synthetic resin. The content of the carbon material with respect to 100 parts by weight of the first synthetic resin is 50 parts by weight or more and 150 parts by weight or less, and the number of graphene sheets stacked on the carbon material is 1000 layers or more, 1 resin composition layers and the second resin composition layers are alternately laminated, and in the sheet plane of the heat conductive sheet, an arbitrary direction is an x direction, and a direction perpendicular to the x direction is When the y direction and the thickness direction of the heat conductive sheet are the z direction, the heat conductivity λx in the x direction, the heat conductivity λy in the y direction, and the heat conductivity λz in the z direction are min (λx , Λy) / λz ≧ 5, heat transfer Sheet.   The heat conductive sheet according to claim 1, wherein the λx and the λy satisfy max (λx, λy) ≧ 2 W / (m · K).   The heat conductive sheet of Claim 1 or 2 whose sum total of the lamination | stacking number of a said 1st and 2nd resin composition layer is 4 layers or more and 1000 layers or less.   The heat according to any one of claims 1 to 3, wherein the second resin composition layer further includes a carbon material different from the carbon material having the graphene laminated structure or an inorganic filler different from the carbon material. Conductive sheet.   The heat conductive sheet of any one of Claims 1-4 whose carbon material which has the said graphene laminated structure is graphite or exfoliated graphite. The heat conductive sheet according to any one of claims 1 to 5 , wherein an average particle diameter of the carbon material having the graphene laminated structure is 0.1 µm or more and 100 µm or less. The heat conductive sheet according to any one of claims 1 to 6 , wherein a thickness of the carbon material having the graphene laminated structure is 30 nm or more. The heat conductive sheet according to any one of claims 1 to 7 , wherein each of the first and second synthetic resins is a polyolefin. The heat conductive sheet according to any one of claims 1 to 8 , wherein a melt viscosity at 230 ° C of the first synthetic resin is lower than a melt viscosity at 230 ° C of the second synthetic resin. A heat conductive sheet laminate comprising: a foamed resin layer; and the heat conductive sheet according to any one of claims 1 to 9 , which is laminated on at least one main surface of the foamed resin layer. A molded body of a heat conductive sheet laminate according to the heat conduction sheet or claim 10 according to any one of claims 1 to 9 thermally conductive sheet shaped body. Electronic device, used in the housing of the locking device or the smart meter outdoor communication, thermally conductive sheet according to any one of claims 1-9. The heat conductive sheet laminated body of Claim 10 used for the housing | casing of an electronic device, the fixing device for outdoor communications, or a smart meter. The heat conductive sheet molding according to claim 11 , which is used for a housing of an electronic device, an outdoor communication fixing device or a smart meter.

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