WO2023157829A1

WO2023157829A1 - Heat dissipation sheet manufacturing method and heat dissipation sheet

Info

Publication number: WO2023157829A1
Application number: PCT/JP2023/004938
Authority: WO
Inventors: 太陽山浦; 基田中; 光祐和田; 将太渡邉; 昌樹松本
Original assignee: デンカ株式会社; 株式会社U-Map
Priority date: 2022-02-16
Filing date: 2023-02-14
Publication date: 2023-08-24
Also published as: TW202344581A; JPWO2023157829A1; JP7399359B1

Abstract

This heat dissipation sheet manufacturing method includes: a slurry preparation step for preparing a slurry containing a fibrous filler, a dispersant, a solvent, and a resin; a shaping step for applying the slurry in a sheet to obtain a sheet-like shaped body; and a pressing step for pressing the sheet-like shaped body. This heat dissipation sheet is obtained by shaping a thermally conductive resin composition containing the fibrous filler and the resin, said fibrous filler being oriented in the in-plane direction of the heat dissipation sheet. With the present invention, it is possible to provide a heat dissipation sheet manufacturing method with which it is possible to improve the relative density of a heat dissipation sheet containing a fibrous filler as an inorganic filler. It is also possible to provide a heat dissipation sheet manufactured using said manufacturing method.

Description

Method for manufacturing heat-dissipating sheet and heat-dissipating sheet

The present invention relates to a heat dissipation sheet containing fibrous fillers and a method for producing the same.

In recent years, electronic devices have become smaller and more sophisticated. Accompanying this, electronic components are becoming higher in output and higher in density. Therefore, it is an important issue to improve the thermal conductivity of insulating materials used in electronic devices. Insulating materials with improved thermal conductivity include, for example, composite materials containing inorganic fillers and resins. In order to increase the thermal conductivity of composite materials, it is important to efficiently conduct heat between inorganic fillers. As a method for efficiently conducting heat between inorganic fillers, for example, a method using a fibrous filler as the inorganic filler can be mentioned. By using a fibrous filler as the inorganic filler, a network structure serving as a heat transfer path is formed by the fibrous filler in the composite material, thereby allowing heat to be efficiently conducted in the composite material.

Examples of composite materials using fibrous fillers as inorganic fillers include resin compositions containing AlN whiskers (see, for example, Patent Document 1). In the resin composition described in Patent Document 1, heat dissipation paths are efficiently formed by AlN whiskers with high thermal conductivity, so the thermal conductivity of the resin composition is improved.

JP 2014-073951 A

However, many fibrous fillers such as AlN whiskers and fibrous carbon have low adhesion to resins. Therefore, when a composite material is produced by mixing a fibrous filler and a resin, voids are formed between the resin and the fibrous filler, and the relative density of the composite material is sometimes lowered. In addition, the thermal conductivity of the voids, which causes a decrease in the relative density of the composite material, is not high. Therefore, the thermal conductivity of the composite material with the lowered relative density was not as high as expected.

Therefore, an object of the present invention is to provide a method for manufacturing a heat-dissipating sheet that can improve the relative density of a heat-dissipating sheet containing a fibrous filler as an inorganic filler, and a heat-dissipating sheet manufactured by the method.

As a result of intensive research, the present inventors found that a heat-dissipating sheet with a high relative density can be produced by adding a dispersant to the slurry used for manufacturing the heat-dissipating sheet, and completed the present invention. . The gist of the present invention is as follows.
[1] A slurry preparation step of preparing a slurry containing a fibrous filler, a dispersant, a solvent, and a resin, a forming step of applying the slurry into a sheet to obtain a sheet-like molded body, and the sheet A method for producing a heat-dissipating sheet, comprising a pressing step of pressing the shaped body.
[2] The method for producing a heat-dissipating sheet according to [1] above, further including a surface treatment step of surface-treating the fibrous filler using a silane coupling agent before the slurry preparation step.
[3] The silane coupling agent is methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, dimethoxydiphenylsilane, n-propyltrimethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, 1,6-bis from (trimethoxysilyl)hexane, trifluoropropyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltriethoxysilane, hexyltriethoxysilane and octyltriethoxysilane The method for producing a heat-dissipating sheet according to [2] above, wherein the at least one alkoxysilane is selected from the group consisting of:
[4] Further includes a sieving step of sieving the fibrous filler using a sieve with an opening of 30 to 500 mesh, and the fibrous filler used in the slurry adjustment step is sieved in the sieving step. The method for producing a heat-dissipating sheet according to any one of [1] to [3] above, wherein the fibrous filler is a sieve.
[5] In the slurry adjustment step, after obtaining a mixture by mixing the fibrous filler, the dispersant, and the solvent, the slurry is adjusted by mixing the mixture and the resin. [1] A method for producing a heat-dissipating sheet according to any one of [4].
[6] The method for producing a heat-dissipating sheet according to [5], wherein the fibrous filler, the dispersant, and the solvent are mixed in the slurry adjustment step for a mixing time of 0.5 to 30 minutes.
[7] The dispersant used in the slurry adjustment step is at least one dispersant selected from the group consisting of anionic surfactants, nonionic surfactants and alkoxysilanes [1] to [6] The method for producing a heat-dissipating sheet according to any one of [6].
[8] The heat-dissipating sheet according to [7] above, wherein the dispersant is at least one dispersant selected from the group consisting of polyoxyalkylene alkyl ether phosphate, sorbitan fatty acid ester, and dimethyldimethoxysilane. Production method.
[9] The method for producing a heat-dissipating sheet according to any one of [1] to [8] above, wherein the resin used in the slurry adjustment step is a silicone resin.
[10] The method for producing a heat-dissipating sheet according to any one of [1] to [9] above, wherein the molding step dries the slurry applied in the form of a sheet for a drying time of 3 to 60 minutes.
[11] Any one of the above [1] to [10], wherein the pressing pressure is 0.5 to 30 MPa and the pressing time is 5 to 60 minutes when pressing the sheet-shaped compact in the pressing step. 3. The method for manufacturing the heat-dissipating sheet according to 1.
[12] A heat dissipation sheet formed by molding a thermally conductive resin composition containing a fibrous filler and a resin, wherein the fibrous filler is oriented in the in-plane direction of the heat dissipation sheet.
[13] The heat dissipation sheet according to [12] above, wherein the resin is a silicone resin.

According to the present invention, it is possible to provide a method for manufacturing a heat-dissipating sheet that can improve the relative density of a heat-dissipating sheet containing a fibrous filler as an inorganic filler, and a heat-dissipating sheet manufactured by the method.

[Manufacturing method of heat dissipation sheet]
The method for producing a heat-dissipating sheet of the present invention includes a slurry preparation step of preparing a slurry containing a fibrous filler, a dispersant, a solvent, and a resin, and a sheet-like molding obtained by coating the slurry into a sheet. It includes a molding step and a pressing step for pressing the sheet-like formed body. Thereby, the relative density of the heat dissipation sheet containing the fibrous filler as the inorganic filler can be improved. Each step will be described in detail below.

(Slurry preparation step)
In the slurry preparation step, a slurry containing a fibrous filler, a dispersant, a solvent, and a resin is prepared.
<Fibrous filler>
Examples of fibrous fillers used in the slurry preparation process include AlN whiskers, alumina fibers, titania fibers, zirconia fibers, and other ceramic fibers. These fibrous fillers can be used singly or in combination of two or more. Among these fibrous fillers, AlN whiskers are preferable from the viewpoint of thermal conductivity and insulation.

The average fiber length of the fibrous filler is preferably 25-500 μm. When the average fiber length of the fibrous filler is 25 μm or more, the thermal conductivity of the heat dissipation sheet can be further increased. When the average fiber length of the fibrous filler is 500 µm or less, the dispersibility of the fibrous filler in the heat dissipation sheet can be improved. In addition, it is possible to further improve the handleability of the fibrous filler. From this point of view, the average fiber length of the fibrous filler is more preferably 35-400 μm, still more preferably 40-300 μm. The average fiber length of the fibrous filler can be measured by the method described in Examples below.

The average fiber diameter of the fibrous filler is preferably 0.1-20 μm. When the average fiber diameter of the fibrous filler is 0.1 μm or more, the strength of the fibrous filler can be improved, so that the handleability of the fibrous filler can be further improved. When the average fiber diameter of the fibrous filler is 20 μm or less, gaps between the fibrous fillers are less likely to occur in the heat dissipation sheet, facilitating the formation of heat conduction paths. From this point of view, the average fiber diameter of the fibrous filler is more preferably 0.5 to 15 μm, still more preferably 1 to 10 μm. The average fiber diameter of the fibrous filler can be measured by the method described in Examples below.

The ratio of the average fiber length to the average fiber diameter of the fibrous filler (average fiber length/average fiber diameter) (hereinafter referred to as aspect ratio) is preferably 10 or more. When the fibrous filler has an aspect ratio of 10 or more, heat dissipation paths are efficiently formed in the heat dissipation sheet, and a heat dissipation sheet with high thermal conductivity can be obtained. From such a viewpoint, the aspect ratio of the fibrous filler is more preferably 15 or more, still more preferably 20 or more, and even more preferably 30 or more. The upper limit of the aspect ratio range of the fibrous filler is not particularly limited, but is usually 1000 or less.

<Resin>
Examples of resins used in the slurry preparation process include epoxy resins, silicone resins, silicone rubbers, acrylic resins, phenolic resins, melamine resins, urea resins, unsaturated polyesters, fluorine resins, polyimides, polyamideimides, polyetherimides, poly Butylene terephthalate, polyethylene terephthalate, polyphenylene ether, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide modified resin, ABS (acrylonitrile-butadiene-styrene) resin, AAS (acrylonitrile-acrylic rubber/styrene) ) resin, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin, and the like. These resins can be used individually by 1 type or in combination of 2 or more types. Among these resins, silicone resins are preferred.

<Solvent>
The solvent used in the slurry preparation process is not particularly limited as long as it can dissolve the resin and dispersant used in the slurry preparation process and can be easily removed by heating. For example, when the resin is a silicone resin, the solvent used in the slurry preparation step is preferably a non-polar solvent with a small solubility parameter (SP value). When the resin is a silicone resin, solvents used in the slurry preparation process include, for example, benzene, toluene, xylene, acetone, hexane, isopropyl alcohol, ligroin, mineral spirits, chlorinated hydrocarbons, and the like. These solvents can be used singly or in combination of two or more.

<Dispersant>
From the viewpoint of improving the wettability of the fibrous filler to the solvent and suppressing the aggregation of the fibrous filler, the dispersant used in the slurry preparation step is preferably a surfactant and a silane coupling agent, more preferably It is a surfactant. Surfactants include, for example, cationic surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, and the like. These surfactants can be used singly or in combination of two or more. Among these surfactants, anionic surfactants and nonionic surfactants are preferable from the viewpoint of improving the wettability of the fibrous filler to the solvent and suppressing aggregation of the fibrous filler.

Examples of anionic surfactants include alkyl sulfates, polyoxyethylene alkyl sulfates, alkylbenzene sulfonates, alkylnaphthalenesulfonates, fatty acid salts, naphthalenesulfonic acid formalin condensate salts, and polycarboxylic acid type surfactants. Polymeric surfactants, alkenyl succinates, alkanesulfonates, polyoxyalkylene alkyl ether phosphates and salts thereof, polyoxyalkylene alkyl aryl ether phosphates and salts thereof, and the like can be mentioned. These anionic surfactants can be used singly or in combination of two or more. Among these anionic surfactants, phosphate esters of polyoxyalkylene alkyl ethers are preferred from the viewpoint of improving the wettability of fibrous fillers to solvents and suppressing aggregation of fibrous fillers. Ethylene alkyl ether phosphate is more preferable, polyoxyethylene tridecyl ether phosphate is more preferable, and polyoxyethylene tridecyl ether phosphate represented by the following formula (1) is even more preferable.

In the formula, R ₁ represents an alkyl group having 1 to 20 carbon atoms or an alkylaryl group having 7 to 25 carbon atoms, R ₂ represents a hydrogen atom or —(CH ₂ CH ₂ O) _n R ₃ , and R ₃ represents an alkyl group having 1 to 20 carbon atoms or an alkylaryl group having 7 to 25 carbon atoms, and n is an integer of 1 to 20 representing the number of ethylene oxide additions.

Nonionic surfactants include, for example, polyoxyethylene alkyl ethers, polyoxyalkylene alkyl ethers, polyoxyethylene derivatives, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, Polyoxyethylene fatty acid esters, polyoxyethylene hydrogenated castor oil, polyoxyethylene alkylamines, polyoxyalkylenealkylamines, alkylalkanolamides, and the like. These nonionic surfactants can be used singly or in combination of two or more. Among these nonionic surfactants, sorbitan fatty acid esters are preferred, and sorbitan toluoleate is more preferred, from the viewpoint of improving the wettability of the fibrous filler to the solvent and suppressing aggregation of the fibrous filler.

Among the silane coupling agents, alkoxysilanes are preferable from the viewpoint of improving the wettability of the fibrous filler to the solvent and suppressing the aggregation of the fibrous filler. Alkoxysilanes used as dispersants include, for example, methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, phenyltrimethoxysilane, dimethoxydiphenylsilane, n-propyltrimethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane. , 1,6-bis(trimethoxysilyl)hexane, trifluoropropyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltriethoxysilane, hexyltriethoxysilane , octyltriethoxysilane and the like. These alkoxysilanes can be used singly or in combination of two or more. Among these alkoxysilanes, selected from the group consisting of methyltrimethoxysilane, dimethyldimethoxysilane and trimethylmethoxysilane, from the viewpoint of improving the wettability of the fibrous filler to the solvent and suppressing the aggregation of the fibrous filler. is preferred, and dimethyldimethoxysilane is more preferred.

<Combination amount>
From the viewpoint of the thermal conductivity of the heat-dissipating sheet and the suppression of voids in the heat-dissipating sheet, the amount of the fibrous filler is preferably 5 to 60 parts by volume with respect to the total 100 parts by volume of the fibrous filler and the resin, More preferably 10 to 50 parts by volume, still more preferably 15 to 40 parts by volume.
From the viewpoint of the slurry coatability, the amount of the solvent is preferably 10 to 80 parts by mass, more preferably 20 to 70 parts by mass, with respect to the total 100 parts by mass of the fibrous filler and the resin, More preferably, it is 30 to 60 parts by mass.
From the viewpoint of suppressing the aggregation of the fibrous filler and the thermal conductivity of the heat dissipation sheet, the amount of the dispersant compounded is preferably 0.01 to 10 parts by mass, more preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of the fibrous filler. is 0.05 to 5 parts by mass, more preferably 0.1 to 3 parts by mass.

<Mixed>
A device for mixing the fibrous filler, the dispersant, the solvent and the resin is not particularly limited as long as it can mix while suppressing pulverization of the fibrous filler. For example, fibrous fillers, dispersants, solvents and resins can be mixed using a stirring mixer. The stirring kneader is equipped with rotating stirring blades, and the fibrous filler, dispersant, solvent and resin are mixed by the stirring blades. The fibrous filler, dispersant, solvent and resin can also be mixed using a high speed agitator (dissolver). In high-speed agitators, rotating turbine-like blades create convection currents in the ingredients in a vessel, thereby mixing the ingredients.

In the slurry adjustment step, it is preferable to prepare a slurry by mixing a fibrous filler, a dispersant, and a solvent to obtain a mixture, and then mixing the mixture with a resin. Thereby, the dispersion of the fibrous filler in the slurry can be further improved, and as a result, the relative density of the heat dissipation sheet can be further improved.

The mixing time for mixing the fibrous filler, dispersant, solvent and resin is preferably 0.5 to 30 minutes. The fibrous filler in a dry state is often agglomerated, but if the mixing time is 0.5 minutes or longer, the agglomeration of the fibrous filler can be further sufficiently disentangled, and the fibrous filler in the slurry can be disaggregated. Dispersion can be further improved. As a result, the relative density of the heat dissipation sheet can be further improved. If the mixing time is 30 minutes or less, it is possible to suppress pulverization of the fibrous filler during mixing. From this point of view, the mixing time is more preferably 1.0 to 15 minutes, more preferably 1.2 to 10 minutes.

(Molding process)
In the forming step, the slurry is applied in the form of a sheet to obtain a sheet-like formed body. For example, the slurry can be formed into a sheet by a doctor blade method. The doctor blade method is a method of thinly spreading a slurry on a carrier film to obtain a compact. The thickness of the sheet-like compact can be adjusted by adjusting the distance between the blade for thinly spreading the slurry and the carrier film and the speed at which the carrier film is drawn.

The slurry applied in sheet form is dried to form a sheet-like molded body. The drying time of the slurry applied in sheet form is preferably 3 to 60 minutes. When the drying time is 3 minutes or longer, the solvent in the slurry can be sufficiently removed. When the drying time is 60 minutes or less, the sheet-like molding is not too hardened, so that it is possible to suppress the formation of gaps between the fibrous filler and the resin in the later-described pressing step. From this point of view, the drying time is more preferably 5 to 30 minutes, still more preferably 10 to 20 minutes.

The drying temperature of the slurry applied in sheet form is preferably 50 to 150°C. When the drying temperature is 50°C or higher, the solvent in the slurry can be sufficiently removed. When the drying temperature is 150° C. or less, the sheet-like molding is not too hardened, so that it is possible to suppress the formation of gaps between the fibrous filler and the resin in the later-described pressing step. From such a point of view, the drying temperature is more preferably 60 to 120°C, more preferably 70 to 100°C.

(Pressing process)
In the pressing step, the sheet-like compact is pressed. The press pressure when pressing the sheet-shaped compact is preferably 0.5 to 30 MPa. When the pressing pressure is 0.5 MPa or more, the relative density of the sheet-shaped molding can be further improved by pressing. When the pressing pressure is 30 MPa or less, deformation of the sheet-like molding caused by pressing can be suppressed. If the deformation of the sheet-like molding caused by pressing is large, gaps are likely to occur between the fibrous filler and the resin. From such a point of view, the press pressure when pressing the sheet-shaped compact is more preferably 1.0 to 20 MPa, and still more preferably 1.5 to 7 MPa.

The pressing time for pressing the sheet-shaped compact is preferably 5 to 60 minutes. When the pressing time is 5 minutes or more, the relative density of the sheet-like compact can be further improved by pressing. When the pressing time is 60 minutes or less, the deformation of the sheet-like molding caused by pressing can be suppressed. If the deformation of the sheet-like molding caused by pressing becomes large, a gap is likely to occur between the fibrous filler and the resin. From such a point of view, the press pressure when pressing the sheet-shaped compact is more preferably 5 to 50 minutes, and even more preferably 5 to 45 minutes.

The press temperature when pressing the sheet-shaped compact is preferably room temperature (15 to 30°C). By pressing the sheet-like molded article at room temperature, deformation of the sheet-like molded article caused by pressing can be suppressed while further orienting the fibrous filler in the sheet-shaped molded article in the plane direction.

(Surface treatment process)
The method for producing a heat-dissipating sheet of the present invention may further include a surface treatment step before the slurry preparation step. In the surface treatment step, the fibrous filler is surface treated using a silane coupling agent.

<Silane coupling agent>
From the viewpoint of improving the affinity between the fibrous filler and the resin and improving the relative density of the heat-dissipating sheet, the silane coupling agent used in the surface treatment step is preferably alkoxysilane. Alkoxysilanes used in the surface treatment step include, for example, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, dimethoxydiphenylsilane, n-propyltrimethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, 1, 6-bis(trimethoxysilyl)hexane, trifluoropropyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltriethoxysilane, hexyltriethoxysilane, octyltri ethoxysilane and the like. These alkoxysilanes can be used singly or in combination of two or more. Among these alkoxysilanes, dimethyldimethoxysilane is preferred from the viewpoint of improving the affinity between the fibrous filler and the resin and improving the relative density of the heat-dissipating sheet.

<Surface treatment method>
Examples of surface treatment methods for surface treatment of fibrous fillers using a silane coupling agent include dry methods and wet methods. The dry method is a method in which a fibrous filler and a silane coupling agent are stirred and mixed using a high-speed agitator such as a Henschel mixer or a blender, and the surface of the fibrous filler is modified with the silane coupling agent. An organic solvent containing the silane coupling agent obtained by diluting the silane coupling agent to a concentration of approximately 1% by mass or an aqueous solution containing the silane coupling agent is sprayed onto the fibrous filler by a sprayer or the like to uniformly coat the surface of the fibrous filler. It is preferable to add the silane coupling agent to the fibrous filler so that it is dispersed in the Organic solvents for diluting the silane coupling agent include, for example, methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, toluene, and xylene. The wet method is a method in which a fibrous filler and a silane coupling agent are reacted in a slurry or solution to modify the surface of the fibrous filler with the silane coupling agent. Examples of the solution for reacting the fibrous filler with the silane coupling agent include water, methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, toluene, and xylene. After reaction, the fibrous filler is separated from the solution by methods such as filtration, centrifugation, decantation, and dried. Also, fibrous fillers may be used in a state of being contained in a solution. In the dry method, the fibrous filler may be pulverized during the surface treatment, so the wet method is preferred.

The temperature at which the fibrous filler is surface-treated with the silane coupling agent is preferably 0 to 50°C, more preferably 10 to 35°C. The treatment time for surface treatment of the fibrous filler with the silane coupling agent is preferably 0.1 to 5 hours, more preferably 0.2 to 2 hours. The amount of the silane coupling agent used when surface-treating the fibrous filler with the silane coupling agent is preferably 0.05 to 10 parts by mass, more preferably 0.05 to 10 parts by mass, with respect to 100 parts by mass of the fibrous filler. 0.1 to 5 parts by mass.

(Sieving process)
The method for producing a heat-dissipating sheet of the present invention may further include a sieving step of sieving the fibrous filler surface-treated in the surface treatment step using a sieve with an opening of 30 to 500 mesh. The fibrous filler used in the slurry adjusting step may be the fibrous filler on the sieve sieved in the sieving step. As a result, short fibrous fillers that do not contribute much to the formation of a network structure that serves as a heat transfer path can be removed from the fibrous fillers used in the slurry adjustment step. As a result, it is possible to obtain a heat dissipating sheet having a higher thermal conductivity in the surface direction.

The average fiber length of the fibrous filler after the sieving step is preferably 50-500 μm. When the average fiber length of the fibrous filler is 50 µm or more, the thermal conductivity of the heat dissipation sheet can be further increased. When the average fiber length of the fibrous filler is 500 µm or less, the dispersibility of the fibrous filler in the heat dissipation sheet can be improved. In addition, it is possible to further improve the handleability of the fibrous filler. From this point of view, the average fiber length of the fibrous filler is more preferably 100-400 μm, still more preferably 150-300 μm. The average fiber length of the fibrous filler can be measured by the method described in Examples below.

The average fiber diameter of the fibrous filler after the sieving step is preferably 0.1 to 20 μm. When the average fiber diameter of the fibrous filler is 0.1 μm or more, the strength of the fibrous filler can be improved, so that the handleability of the fibrous filler can be further improved. When the average fiber diameter of the fibrous filler is 20 μm or less, gaps between the fibrous fillers are less likely to occur in the heat dissipation sheet, facilitating the formation of heat conduction paths. From this point of view, the average fiber diameter of the fibrous filler is more preferably 0.5 to 15 μm, still more preferably 1.0 to 10 μm. The average fiber diameter of the fibrous filler can be measured by the method described in Examples below.

The ratio of the average fiber length to the average fiber diameter of the fibrous filler after the sieving process (average fiber length/average fiber diameter) (hereinafter referred to as aspect ratio) is preferably 10 or more. When the fibrous filler has an aspect ratio of 10 or more, heat dissipation paths are efficiently formed in the heat dissipation sheet, and a heat dissipation sheet with high thermal conductivity can be obtained. From such a viewpoint, the aspect ratio of the fibrous filler is more preferably 15 or more, and still more preferably 20 or more. The upper limit of the aspect ratio range of the fibrous filler is not particularly limited, but is usually 200 or less.

The fibrous filler surface-treated by the wet method in the surface treatment step may be dried after the sieving step without drying. In the surface treatment step, the fibrous filler that has been surface-treated by a wet method and dried may be sieved in the sieving step.

[Heat release sheet]
The heat dissipating sheet of the present invention is formed by molding a thermally conductive resin composition containing a fibrous filler and a resin, and the fibrous filler is oriented in the in-plane direction of the heat dissipating sheet. This makes it possible to obtain a heat-dissipating sheet with high thermal conductivity in the surface direction. The heat-dissipating sheet of the present invention can be manufactured, for example, by the method for manufacturing a heat-dissipating sheet of the present invention. In the method for producing a heat-dissipating sheet of the present invention, a dispersing agent is blended in a slurry (thermally conductive resin composition) containing a fibrous filler, a resin, and a solvent. As a result, the fibrous filler is sufficiently deagglomerated in the slurry, and the dispersibility of the fibrous filler in the slurry is improved. When the slurry is applied in a sheet form, the fibrous filler is easily oriented in the coating direction, so a heat dissipation sheet in which the fibrous filler is oriented in the in-plane direction of the heat dissipation sheet can be easily produced. .

(thickness)
The thickness of the heat-dissipating sheet of the present invention is preferably 100-5000 μm. When the thickness of the heat-dissipating sheet is 100 µm or more, the insulation of the heat-dissipating sheet can be improved. When the thickness of the heat-dissipating sheet is 5000 μm or less, the heat conductivity in the thickness direction of the heat-dissipating sheet can be improved. From this point of view, the thickness of the heat dissipation sheet of the present invention is more preferably 150 to 2000 μm, still more preferably 200 to 1000 μm. In the heat-dissipating sheet of the present invention, since the fibrous filler is oriented in the in-plane direction of the heat-dissipating sheet, the thickness of the heat-dissipating sheet of the present invention can be easily reduced to 1000 μm or less.

(Thermal conductivity in surface direction)
The thermal conductivity in the surface direction of the heat dissipation sheet of the present invention is preferably 3 W/m·K or more. When the thermal conductivity in the surface direction of the heat-dissipating sheet is 3 W/m·K or more, heat generated by heating a part of the heat-dissipating sheet can be easily conducted to the entire heat-dissipating sheet. As a result, heat generated by heating a part of the heat dissipation sheet is radiated from the entire heat dissipation sheet, so that the heat generated by heating a part of the heat dissipation sheet can be easily dissipated. From this point of view, the thermal conductivity in the plane direction of the heat dissipation sheet of the present invention is more preferably 4 W/m·K or more, and still more preferably 5 W/m·K or more. Although the upper limit of the range of thermal conductivity in the surface direction of the heat dissipation sheet of the present invention is not particularly limited, it is usually 15 W/m·K or less. Further, the thermal conductivity in the surface direction of the heat-dissipating sheet can be measured by the method described in Examples below.

(Thermal conductivity ratio of the thermal conductivity in the plane direction to the thermal conductivity in the thickness direction (plane direction/thickness direction))
The thermal conductivity ratio (surface direction/thickness direction) of the thermal conductivity in the plane direction to the thermal conductivity in the thickness direction of the heat dissipation sheet of the present invention is preferably 3.5 or more. When the thermal conductivity ratio (plane direction/thickness direction) is 3.5 or more, the thermal conductivity of the heat dissipation sheet can be concentrated in the plane direction, so that the heat conductivity in the plane direction of the heat dissipation sheet is further improved. be able to. From such a viewpoint, the thermal conductivity ratio (surface direction/thickness direction) of the heat dissipation sheet of the present invention is more preferably 5 or more, still more preferably 6 or more, and even more preferably 7 or more. , more preferably 8 or more, and particularly preferably 9 or more. Although the thermal conductivity in the thickness direction of the heat dissipation sheet is low, the heat conductivity in the thickness direction of the heat dissipation sheet is improved by making the heat dissipation sheet thinner. The upper limit of the thermal conductivity ratio (surface direction/thickness direction) of the heat-dissipating sheet of the present invention is not particularly limited, but is usually 15 or less. The heat conductivity in the thickness direction and the heat conductivity in the plane direction of the heat dissipation sheet can be measured by the method described in Examples below.

(relative density)
The relative density of the heat dissipation sheet of the present invention is preferably 90% or more. When the relative density of the heat-dissipating sheet of the present invention is 90% or more, the thermal conductivity of the heat-dissipating sheet can be further improved. From this point of view, the relative density of the heat dissipation sheet is more preferably 93% or higher, more preferably 95% or higher. The upper limit of the relative density range of the heat-dissipating sheet is 100%. The relative density can be calculated by dividing the density of the heat-dissipating sheet by the theoretical density of the heat-dissipating sheet. The density of the heat-dissipating sheet can be measured by the method described in Examples below. The theoretical density of the heat-dissipating sheet can be calculated from the density of the resin forming the heat-dissipating sheet, the density of the fibrous filler forming the heat-dissipating sheet, and the volume ratio of the resin to the fibrous filler in the heat-dissipating sheet.

(resin and fibrous filler)
The resin and fibrous filler constituting the heat-dissipating sheet of the present invention are the same as the resin and fibrous filler used in the method for manufacturing the heat-dissipating sheet of the present invention. is omitted.

(Proportion of fibrous filler)
From the viewpoint of the thermal conductivity of the heat-dissipating sheet and the suppression of voids in the heat-dissipating sheet, the ratio of the fibrous filler in the heat-dissipating sheet of the present invention is preferably 5 to 50% with respect to the total 100% by volume of the fibrous filler and the resin. % by volume, more preferably 10 to 45% by volume, and even more preferably 15 to 35% by volume. Even if the ratio of the fibrous filler in the heat-dissipating sheet is small, the network structure of the fibrous filler that serves as a heat transfer path can be formed inside the heat-dissipating sheet. Therefore, even if the proportion of the fibrous filler in the heat dissipation sheet is small, the thermal conductivity of the heat dissipation sheet can be increased.

EXAMPLES The present invention will be described in detail below with reference to examples. In addition, the present invention is not limited to the following examples.
[Evaluation of fibrous filler]
(Average fiber length, average fiber diameter, average aspect ratio of fibrous filler)
The average fiber length, average fiber diameter, and average aspect ratio of the fibrous filler were obtained by selecting 50 or more fibers from an SEM (scanning electron microscope, JEOL Ltd., JMS-7001F) and calculating the volume average according to the following formula. .
(Average fiber length) = Σ (V _n ×l _n )/ΣV _n
(Average fiber diameter) = Σ (V _n ×d _n )/ΣV _n
(average aspect ratio) = Σ(V _n ×(l _n /d _n ))/ΣV _n
l _n : Fiber length of n-th fiber d _n : Fiber diameter of n-th fiber V _n : Volume of n-th fiber = (d _n /2) ² × l _n × π

[Evaluation of Heat Dissipating Sheet]
(relative density)
The relative density of the heat-dissipating sheet was calculated by measuring the actual specific gravity of the heat-dissipating sheet by the Archimedes method and dividing the measured value by the theoretical specific gravity.
Specifically, using a specific gravity measurement kit (manufactured by A&D, trade name "AD-1653"), the weight of the heat dissipation sheet in the air and the weight in water are measured, and the measurement results and The measured specific gravity of the heat-dissipating sheet was calculated from the density of water.
Next, the theoretical specific gravity of the heat-dissipating sheet was calculated from the specific gravity of each material constituting the solid content of the slurry and the composition ratio thereof.
Then, the relative density (%) of the heat dissipation sheet was calculated from the following formula.
Relative density (%) of heat-dissipating sheet = (measured specific gravity/theoretical specific gravity) x 100

(surface thermal conductivity)
The in-plane thermal diffusivity of the heat-dissipating sheet was measured by the In-Plane method using a thermal diffusivity measuring device (manufactured by Netzsch, trade name "LFA447 Nanoflash"). The specific heat of the heat-dissipating sheet was calculated from the specific heat of each material constituting the solid content of the slurry and its composition ratio. The measured specific gravity of the heat-dissipating sheet was measured in the same manner as the relative density measurement method described above. Then, the in-plane thermal conductivity of the heat dissipation sheet was calculated from the following formula.
In-plane thermal conductivity of heat-dissipating sheet = In-plane thermal diffusivity x Specific heat x Measured specific gravity

(thickness direction thermal conductivity)
The thermal diffusivity in the thickness direction of the heat-dissipating sheet was measured by a laser flash method using a thermal diffusivity measuring device (manufactured by Netzsch, trade name "LFA447 Nanoflash"). The specific heat and measured specific gravity of the heat-dissipating sheet were measured in the same manner as the method for measuring the in-plane thermal diffusivity of the heat-dissipating sheet. Then, the thermal conductivity in the thickness direction of the heat dissipation sheet was calculated from the following formula.
Thermal conductivity in the thickness direction of the heat dissipation sheet = thermal diffusivity in the thickness direction x specific heat x measured specific gravity

[Production of heat dissipation sheet]
(Preparation of Heat Dissipating Sheet 1)
<Surface treatment process>
AlN whisker 1 (manufactured by U-MAP Co., Ltd., trade name "Thermalnite (registered trademark) short fiber crushing type (fine powder removal)") 100 parts by mass, 1 part by mass of a silane coupling agent (Dow Toray Industries, Inc. manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name "DOWSIL Z-6329 Silane", dimethyldimethoxysilane) and 100 parts by mass of toluene, 400 parts by mass of methanol and 5 parts by mass of a dispersant (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name "Plysurf 215C") was added and mixed for 40 minutes before passing through a 750 μm (24 mesh) sieve to obtain surface treated AlN whiskers.

<Slurry adjustment process>
The obtained surface-treated AlN whisker, 5 parts by mass of a dispersant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name "Plysurf 215C", polyoxyethylene tridecyl ether phosphate ester per 100 parts by mass of the surface-treated AlN whisker ), and 50 parts by mass of toluene with respect to a total of 100 parts by mass of the surface-treated AlN whisker and the silicone resin described later was added to 7. using a stirrer (manufactured by Thinky Co., Ltd., trade name "Awatori Mixer ARE-310"). Mix for 5 minutes. After that, 70 parts by volume of silicone resin (manufactured by Asahi Kasei Corporation, trade name "ELASTOSIL LR3303/20", dimethyl silicone) was added to a total of 100 parts by volume of the surface-treated AlN whisker and silicone resin using the above stirrer. A slurry (thermal conductive resin composition) was prepared by mixing for 5 minutes.

<Molding process>
By the doctor blade method, a carrier film (manufactured by Nitto Denko Corporation, trade name “NITOFLON Films 920UL”, thickness 0.1 μm, Teflon (registered trademark) film) with a thickness of 0.6 mm was applied in the slurry adjustment process. The prepared slurry was applied and dried at 80° C. for 15 minutes to prepare a sheet-shaped compact.

<Press process>
Using a flat plate press (manufactured by Yanase Seisakusho Co., Ltd.), the sheet-like molded body was heat-pressed for 40 minutes at 150 ° C. and a pressure of 15 MPa to prepare a heat dissipation sheet 1 with a thickness of 0.33 mm. . When the cross section of the heat dissipation sheet 1 was observed with a scanning electron microscope (SEM), the AlN whiskers were oriented in the in-plane direction of the heat dissipation sheet.

(Heat dissipation sheet 2)
A heat-dissipating sheet 2 was produced in the same manner as the heat-dissipating sheet 1, except that the surface treatment was not performed. When the cross section of the heat dissipation sheet 2 was observed with a scanning electron microscope (SEM), the AlN whiskers were oriented in the in-plane direction of the heat dissipation sheet.

(Heat-dissipating sheet 3)
<Slurry adjustment process>
AlN whisker 1 (manufactured by U-MAP Co., Ltd., trade name “Thermalnite (registered trademark) short fiber crushing type (fine powder removal)”), 5 parts by mass of dispersant (Daiichi Kogyo Seiyaku Co., Ltd.) per 100 parts by mass of AlN whisker 50 parts by mass of toluene is added to a total of 100 parts by mass of a total of 100 parts by mass of surface-treated AlN whiskers and a silicone resin described later. The mixture was mixed for 7.5 minutes using a product name “Awatori Mixer ARE-310” manufactured by Thinky Corporation. After that, 70 parts by volume of silicone resin (manufactured by Asahi Kasei Corporation, trade name "ELASTOSIL LR3303/20", dimethyl silicone) was added to a total of 100 parts by volume of the surface-treated AlN whisker and silicone resin using the above stirrer. A slurry (thermal conductive resin composition) was prepared by mixing for 5 minutes.

<Press process>
Using a flat press machine (manufactured by Yanase Seisakusho Co., Ltd.), the sheet-like molded body was heat-pressed for 40 minutes at 150 ° C. and a pressure of 15 MPa to prepare a heat dissipation sheet 3 with a thickness of 0.25 mm. . When the cross section of the heat dissipation sheet 3 was observed with a scanning electron microscope (SEM), the AlN whiskers were oriented in the in-plane direction of the heat dissipation sheet.

(Heat radiation sheet 4)
Heat-dissipating sheet 4 was prepared in the same manner as heat-dissipating sheet 3, except that sorbitan trioleate (manufactured by Kao Corporation, trade name "Rheodol SP-O30V") was used as a dispersant. When the cross section of the heat dissipation sheet 4 was observed with a scanning electron microscope (SEM), the AlN whiskers were oriented in the in-plane direction of the heat dissipation sheet.

(Heat dissipation sheet 5)
Heat-dissipating sheet 5 was prepared in the same manner as heat-dissipating sheet 3, except that dimethyldimethoxysilane (manufactured by Dow Toray Industries, Inc., trade name: "DOWSIL Z-6329 Silane") was used as a dispersant. When the cross section of the heat dissipation sheet 5 was observed with a scanning electron microscope (SEM), the AlN whiskers were oriented in the in-plane direction of the heat dissipation sheet.

(Heat dissipation sheet 6)
An attempt was made to produce heat-dissipating sheet 6 in the same manner as heat-dissipating sheet 3, except that no dispersant was used. However, the AlN whiskers formed agglomerates during mixing in the slurry preparation process, and a coatable slurry could not be produced. Therefore, the heat dissipation sheet 6 could not be produced.

(Heat dissipation sheet 7)
<Slurry adjustment process>
AlN whisker 2 (manufactured by U-MAP Co., Ltd., trade name "Thermalnite (registered trademark) short fiber crushing type") (no fine powder removal), 5 parts by mass of dispersant (Daiichi Kogyo Pharmaceutical Co., Ltd., trade name "Plysurf 215C", polyoxyethylene tridecyl ether phosphate), surface-treated AlN whiskers and silicone resin described later Add 50 parts by mass of toluene to a total of 100 parts by mass The mixture was mixed for 7.5 minutes using a product name “Awatori Mixer ARE-310” manufactured by Thinky Co., Ltd. After that, 70 parts by volume of silicone resin (manufactured by Asahi Kasei Corporation, trade name "ELASTOSIL LR3303/20", dimethyl silicone) was added to a total of 100 parts by volume of the surface-treated AlN whisker and silicone resin using the above stirrer. A slurry (thermal conductive resin composition) was prepared by mixing for 5 minutes.

<Molding process>
A carrier film (manufactured by Nitto Denko Corporation, trade name “NITOFLON Films 920UL”, thickness 0.1 μm, Teflon (registered trademark) film) with a thickness of 0.6 mm is prepared by a slurry adjustment process by a doctor blade method. The resulting slurry was applied and dried at 80° C. for 15 minutes to prepare a sheet-like molding.

<Press process>
Using a flat press machine (manufactured by Yanase Seisakusho Co., Ltd.), the sheet-like molded body was heat-pressed for 40 minutes at 150 ° C. and a pressure of 15 MPa to prepare a heat dissipation sheet 7 with a thickness of 0.33 mm. . When the cross section of the heat dissipation sheet 7 was observed with a scanning electron microscope (SEM), the AlN whiskers were oriented in the in-plane direction of the heat dissipation sheet.

(Heat dissipation sheet 8)
A heat-dissipating sheet 8 was produced in the same manner as the heat-dissipating sheet 7, except that the slurry preparation process was changed as follows. When the cross section of the heat dissipation sheet 8 was observed with a scanning electron microscope (SEM), the AlN whiskers were oriented in the in-plane direction of the heat dissipation sheet.
<Slurry adjustment process>
AlN whisker 2 (manufactured by U-MAP Co., Ltd., trade name "Thermalnite (registered trademark) short fiber crushing type") (no fine powder removal), 5 parts by mass of dispersant (Daiichi Kogyo Pharmaceutical Co., Ltd., trade name "Plysurf 215C", polyoxyethylene tridecyl ether phosphate), surface-treated AlN whiskers and silicone resin, 50 parts by weight of toluene per 100 parts by weight in total, and surface-treated AlN 70 parts by volume of silicone resin (manufactured by Asahi Kasei Corporation, product name "ELASTOSIL LR3303/20", dimethyl silicone) was added to a total of 100 parts by volume of whiskers and silicone resin with a stirrer (manufactured by Thinky Co., Ltd., product name "Awatori Kneading"). Taro ARE-310") was mixed for 7.5 minutes to prepare a slurry (thermal conductive resin composition).

(Heat dissipation sheet 9)
<Slurry adjustment process>
AlN whisker 1 (manufactured by U-MAP Co., Ltd., trade name “Thermalnite (registered trademark) short fiber crushing type (fine powder removal)”), 5 parts by mass of dispersant (Daiichi Kogyo Seiyaku Co., Ltd.) per 100 parts by mass of AlN whisker 50 parts by mass of toluene is added to a total of 100 parts by mass of a total of 100 parts by mass of surface-treated AlN whiskers and a silicone resin described later. The mixture was mixed for 7.5 minutes using a product name “Awatori Mixer ARE-310” manufactured by Thinky Corporation. After that, 70 parts by volume of silicone resin (manufactured by Asahi Kasei Corporation, trade name "ELASTOSIL LR3303/20", dimethyl silicone) per 100 parts by volume in total of surface-treated AlN whiskers and silicone resin was added to the stirrer, and A slurry (thermal conductive resin composition) was prepared by mixing for 5 minutes.

<Molding process>
By the doctor blade method, a carrier film (manufactured by Nitto Denko Corporation, trade name “NITOFLON Films 920UL”, thickness 0.1 μm, Teflon (registered trademark) film) with a thickness of 0.6 mm was applied in the slurry adjustment process. The prepared slurry was applied and dried at 80° C. for 5 minutes to prepare a sheet-shaped compact.

(Heat dissipation sheet 10)
Heat-dissipating sheet 10 was produced in the same manner as heat-dissipating sheet 9 except that the drying time in the molding process was changed from 5 minutes to 10 minutes. When the cross section of the heat dissipation sheet 10 was observed with a scanning electron microscope (SEM), the AlN whiskers were oriented in the in-plane direction of the heat dissipation sheet.

(Heat dissipation sheet 11)
Heat-dissipating sheet 11 was produced in the same manner as heat-dissipating sheet 9 except that the drying time in the molding process was changed from 5 minutes to 15 minutes. When the cross section of the heat dissipation sheet 11 was observed with a scanning electron microscope (SEM), the AlN whiskers were oriented in the in-plane direction of the heat dissipation sheet.

(Heat dissipation sheet 12)
Heat-dissipating sheet 12 was produced in the same manner as heat-dissipating sheet 9 except that the drying time in the molding process was changed from 5 minutes to 20 minutes. When the cross section of the heat dissipation sheet 12 was observed with a scanning electron microscope (SEM), the AlN whiskers were oriented in the in-plane direction of the heat dissipation sheet.

(Heat dissipation sheet 13)
Heat-dissipating sheet 13 was produced in the same manner as heat-dissipating sheet 9 except that the drying time in the molding process was changed from 5 minutes to 30 minutes. When the cross section of the heat dissipation sheet 13 was observed with a scanning electron microscope (SEM), the AlN whiskers were oriented in the in-plane direction of the heat dissipation sheet.

(Heat dissipation sheet 14)
<Surface treatment process>
1 part by mass of a silane coupling agent (manufactured by , trade name “DOWSIL Z-6329 Silane”, dimethyldimethoxysilane) and 100 parts by mass of toluene, 400 parts by mass of methanol and 5 parts by mass of a dispersant (Daiichi Kogyo Seiyaku Co., Ltd., trade name “Plysurf 215C ”), mixed for 40 minutes, passed through a 45 μm (325 mesh) sieve, and collected on the sieve to obtain a surface-treated AlN whisker.

<Press process>
Using a flat plate press (manufactured by Yanase Seisakusho Co., Ltd.), the sheet-shaped molded body is heat-pressed for 40 minutes at room temperature (25 ° C.) and a pressure of 2 MPa to form a heat dissipation sheet 14 with a thickness of 0.3 mm. was made. When the cross section of the heat dissipation sheet 14 was observed with a scanning electron microscope (SEM), the AlN whiskers were oriented in the in-plane direction of the heat dissipation sheet.

(Heat dissipation sheet 15)
A heat-dissipating sheet 15 was produced in the same manner as the heat-dissipating sheet 14 except that the pressing temperature in the pressing process was changed from room temperature to 150° C. and the pressing pressure was changed from 2 MPa to 15 MPa. When the cross section of the heat dissipation sheet 15 was observed with a scanning electron microscope (SEM), the AlN whiskers were oriented in the in-plane direction of the heat dissipation sheet.

The evaluation results are shown in Tables 1-6.

From the above examples and comparative examples, it was found that by adding a dispersant to the slurry containing AlN whiskers, resin, and solvent, the relative density of the heat dissipation sheet can be increased even when AlN whiskers are used.

Claims

A slurry preparation step of preparing a slurry containing a fibrous filler, a dispersant, a solvent, and a resin;
A forming step of applying the slurry into a sheet to obtain a sheet-like molded body;
and a pressing step of pressing the sheet-like formed body.
The method for producing a heat-dissipating sheet according to claim 1, further comprising a surface treatment step of surface-treating the fibrous filler using a silane coupling agent before the slurry preparation step.
The silane coupling agent is methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, dimethoxydiphenylsilane, n-propyltrimethoxysilane, hexyltrimethoxysilane, decyltrimethoxysilane, 1,6-bis(trimethoxysilane). silyl)hexane, trifluoropropyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltriethoxysilane, hexyltriethoxysilane and octyltriethoxysilane 3. The method for producing a heat-dissipating sheet according to claim 2, wherein at least one alkoxysilane is selected.
Further comprising a sieving step of sieving the fibrous filler using a sieve with an opening of 30 to 500 mesh,
3. The method for producing a heat-dissipating sheet according to claim 1, wherein the fibrous filler used in the slurry adjusting step is a sieved fibrous filler sieved in the sieving step.
1 or 2, wherein in the slurry adjustment step, the slurry is adjusted by mixing the fibrous filler, the dispersant, and the solvent to obtain a mixture, and then mixing the mixture with the resin. 3. The method for manufacturing the heat-dissipating sheet according to 2.
The method for producing a heat-dissipating sheet according to claim 5, wherein the fibrous filler, the dispersant, and the solvent are mixed in the slurry adjusting step for a mixing time of 0.5 to 30 minutes.
3. The dispersant according to claim 1 or 2, wherein the dispersant used in the slurry preparation step is at least one dispersant selected from the group consisting of anionic surfactants, nonionic surfactants and alkoxysilanes. A method for manufacturing a heat dissipation sheet.
The method for producing a heat-dissipating sheet according to claim 7, wherein the dispersant is at least one dispersant selected from the group consisting of polyoxyalkylene alkyl ether phosphate, sorbitan fatty acid ester, and dimethyldimethoxysilane.
The method for manufacturing a heat-dissipating sheet according to claim 1 or 2, wherein the resin used in the slurry adjustment step is a silicone resin.
The method for producing a heat-dissipating sheet according to claim 1 or 2, wherein the forming step dries the slurry coated in a sheet form for a drying time of 3 to 60 minutes.
The method for producing a heat-dissipating sheet according to claim 1 or 2, wherein the press pressure is 0.5 to 30 MPa and the press time is 5 to 60 minutes when pressing the sheet-like formed body in the pressing step.
A heat dissipating sheet formed by molding a thermally conductive resin composition containing a fibrous filler and a resin,
A heat-dissipating sheet in which the fibrous filler is oriented in an in-plane direction of the heat-dissipating sheet.
13. The heat dissipation sheet according to claim 12, wherein the resin is a silicone resin.