JP2001322139A - Method for producing composite sheet and composite sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composite sheet which has a high degree of orientation of a fibrous filler in the thickness direction of the sheet even when the content of the filler is high, or the filler has a high aspect ratio and is high in anisotropic thermal or electric conductivity in the thickness direction of the sheet and excellent in heat resistance, durability. mechanical strength, and adhesion to a heating element. SOLUTION: In a method for producing the composite sheet. while a composition for the sheet comprising the magnetic fibrous filler (A) and a binder (B) which can be cured by heat and/or light is rolled into a sheet. and the filler is oriented in the thickness direction of the sheet by applying a magnetic field to the sheet in the thickness direction of the sheet. the sheet is cured or semi- cured by heat and/or light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a composite sheet and a composite sheet produced by the method.

[0002]

2. Description of the Related Art The number of electrodes of a semiconductor device is increasing with the further improvement of the performance of electric devices or electronic devices, and the semiconductor device tends to consume higher power. It is important to dissipate heat well. Conventionally, in order to efficiently dissipate heat from a semiconductor package or a semiconductor, an attempt has been made to dissipate heat by providing a heat dissipation mechanism in a semiconductor package or the like, or to dissipate heat from a wiring board on which a semiconductor element is mounted. For example, heat dissipation of a semiconductor package is generally performed by natural convection from the body surface of the heating element or forced convection by a fan provided in the unit. However, in this method, the amount of heat generated is increased as the function of the semiconductor package is improved. When the number increases, the heat radiation effect becomes insufficient, and there is a problem that the performance degradation of the semiconductor package cannot be reliably prevented. There is also provided a method in which a heat radiator is pressed against the surface of the semiconductor package to improve heat dissipation by convection. However, in this method, the contact area of the pressure contact surface between the semiconductor package and the heat radiator is reduced due to the generation of a gap. ,
There was a problem in exhibiting the heat radiation effect as designed. For this reason, for example, when a heat radiator is joined to a semiconductor package, heat dissipation is effectively performed while a heat conductive resin sheet or the like is interposed between the semiconductor package and the heat radiator so that the semiconductor package and the heat radiator are in close contact with each other. What is done is done. In addition, for example, in bonding a semiconductor element and a heat spreader that comes into contact with the semiconductor element, heat is radiated from the semiconductor element while maintaining the adhesion between the semiconductor element and the heat spreader with an adhesive having high thermal conductivity interposed therebetween. Has been done.

[0003] As such a resin composition or the like for increasing thermal conductivity interposed between a semiconductor element or a semiconductor package and a radiator, for example, Japanese Patent Application Laid-Open No. 5-32691 is disclosed.
In Japanese Patent Application Laid-Open No. 6-26, a clay-like thermosetting adhesive type silicone rubber sheet is used. However, this silicone rubber sheet is not sufficient in terms of thermal conductivity to cope with high power consumption of a semiconductor element. There was a point. In order to increase the thermal conductivity, metal particles having a high thermal conductivity are randomly dispersed in a resin sheet such as silicone rubber.In order to further improve the thermal conductivity, the metal particles are dispersed in the resin sheet. Attempts have been made to achieve high dispersion and high filling. However, even if the metal particles are highly dispersed and filled, the heat is diffused in a random direction, so that the thermal conductivity between the semiconductor element and the heat radiator is not sufficiently improved. However, there is a problem that the tensile strength and elasticity of the resin sheet are reduced due to the high filling of the resin sheet, and the moldability is also reduced.

[0004] From such a viewpoint, the present inventors have proposed that, for example, carbon fibers having a magnetic substance adhered to the surface thereof in a binder, or magnetic particles and carbon fibers are oriented in the thickness direction of the resin sheet. It has been found that the use of a high thermal conductive sheet greatly improves the anisotropic thermal conductivity in the thickness direction of the sheet (Japanese Patent Application Nos. 11-325757 and 2000-02).
7738).

[0005] These heat conductive sheets provide high heat conductivity. However, in order to further enhance the heat conductivity, when the filling amount of magnetic fibers such as carbon fibers is increased, or fibers having a large aspect are used. When used, the orientation tends to be insufficient, and it may be difficult to obtain stable performance. The present inventors have studied the above causes,
In order to orient the fibrous filler such as carbon fibers randomly dispersed in the binder in a certain direction at a high rate, it is necessary to have a freely movable space in which interference with other fibers is suppressed. When the fiber filling amount increases, the fibers tend to interfere with each other, and when the aspect ratio of the fibers increases, the fibers that are oriented in the thickness direction become difficult to orient the fibers that are oriented in the direction perpendicular to the sheet thickness and direction. It was found that the degree of orientation was greatly restricted by the amount of fiber, aspect ratio, and the like.

[0006] In order to solve the above-mentioned problems, the present inventors applied a composition comprising a fibrous filler having magnetic properties and a binder which is cured by heat or light in advance, and then applied the composition in the thickness direction. If a roll is applied while a magnetic field is applied, the fibrous filler has a space for free movement, so the amount of fibrous filler increases,
Alternatively, even when the aspect ratio of the fibrous filler is increased, the orientation of the fibrous filler is significantly improved as compared with the conventional method of manufacturing a non-rolled sheet, for example, anisotropic heat conduction in the thickness direction of the obtained sheet. It has been found that the performance is greatly improved. Further, the sheet thus obtained was found to be excellent in heat resistance, durability and mechanical strength, and also excellent in adhesion to semiconductor elements and the like, and completed the present invention.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to solve the problems associated with the prior art as described above. Even if a sheet contains a fibrous filler having a high filling amount or a high aspect ratio, The fibrous filler has excellent orientation in the thickness direction of the sheet, and has high anisotropic thermal conductivity or anisotropic conductivity in the thickness direction of the sheet, and has heat resistance, durability, mechanical strength, and close contact with the heating element. It is an object of the present invention to provide a method for producing a composite sheet having excellent properties.

[0008]

SUMMARY OF THE INVENTION A method for producing a composite sheet according to the present invention comprises:
While rolling a sheet composition comprising a magnetic fibrous filler (A) and a binder curable by heat and / or light (B) into a sheet, a magnetic field is applied in the thickness direction of the sheet, While orienting the magnetic fibrous filler in the thickness direction of the sheet, the sheet is heated and / or heated.
Alternatively, it is characterized by being cured by light. Further, in the heat conductive composite sheet according to the present invention, the heat conductivity in the fiber direction of the magnetic fibrous filler (A) is 100 (W).
m ^-1 · K ^-1 ) or more. The conductive composite sheet according to the present invention is a fibrous filler having magnetism (A)
Is preferably a conductive filler having a noble metal adhered to the surface.

In the method for producing a composite sheet, a magnetic field is applied in the thickness direction of the sheet while the sheet composition is rolled into a sheet, and the fibrous filler (A) having magnetism is reduced in the sheet thickness. In orienting in the direction, the average thickness (D ₁ ) of the magnetic fibrous filler at the start of the orientation is at least 1.3 times the average thickness (D ₂ ) of the obtained thermally conductive sheet. Is preferred. The average thickness (D ₂ ) of the heat conductive sheet and the average length (L) of the magnetic fibrous filler (A) are 0.8 ≦ D
It is preferable that _{2 /} L ≦ 1.5.

The aspect ratio of the magnetic fibrous filler (A) is preferably 5 or more. It is preferable that the magnetic fibrous filler (A) is contained in the sheet composition in an amount of 2 to 60% by volume.
The fibrous filler (A) having magnetism is preferably a metal fiber having magnetism or a fiber having a magnetic susceptibility different in a fiber axis direction and a fiber circumferential direction. The fibers having different magnetic susceptibilities in the fiber axis direction and the fiber circumferential direction are preferably carbon fibers. The fibrous filler (A) having magnetism is preferably composed of fibers having a ferromagnetic material attached to the surface.

The magnetic fibrous filler (A)
May be exposed on the surface of the composite sheet or may be exposed on the heat conductive sheet. The composite sheet according to the present invention is characterized in that the magnetic fibrous filler (A) produced by the production method is oriented in the thickness direction of the sheet.

[0012]

DETAILED DESCRIPTION OF THE INVENTION <Composite sheet> The composite sheet according to the present invention is a sheet in which a magnetic fibrous filler in a binder is oriented in the thickness direction. It is a sheet having conductivity.

The method for producing a composite sheet according to the present invention is characterized in that a sheet composition comprising a fibrous filler having magnetism and a binder which is cured by heat and / or light is rolled into a sheet while the thickness of the sheet is reduced. Applying a magnetic field in the direction to orientate the magnetic fibrous filler in the thickness direction of the sheet and curing or semi-curing the sheet by heat and / or light. However, in the case where the fiber having high thermal conductivity in the fiber direction (having a thermal conductivity of 100 Wm ^-1 · K ^-1 or more), an effective method for producing a heat conductive sheet is provided. When the filler in the form has a high conductivity, an effective method for producing an anisotropic conductive sheet is provided.

In this specification, the term "orientation" means that the fibrous filler is oriented in a substantially constant direction. <Composition for sheet> Fibrous filler having magnetism (A) As the `` fibrous filler having magnetism (A) '' according to the present invention, when a magnetic field is applied to the sheet composition according to the present invention, The fiber has a strength with a certain diameter that can be oriented substantially parallel to the direction of the magnetic field without refraction or breakage, and
It is a fibrous filler having a certain preferred aspect ratio, having resistance to heat applied as needed when forming or using the sheet according to the present invention (for example, having a melting point of 100 ° C. or more).

The fibrous filler having such magnetic properties
(A) includes metal fibers or fibers having different magnetic susceptibilities in the fiber axis direction and the fiber circumferential direction. As such a metal fiber, by being processed into a fibrous shape, it has a magnetic property such as a metal such as Fe, Co, and Ni that shows magnetic anisotropy derived from the shape, an alloy thereof, or an oxide thereof. Fiber.

The fiber having different magnetic susceptibility in the fiber axial direction and the fiber circumferential direction has a structure in which aromatic rings such as carbon fiber, aramid fiber, and polyparabenzazole fiber are arranged in parallel in the fiber direction. Fibers which are easy and exhibit essentially magnetic anisotropy. Among such fibers, as the carbon fiber, for example, depending on the type of the raw material, it can be selected from cellulose-based, PAN-based, and pitch-based carbon fibers, and from the viewpoint of adding good thermal conductivity. It is preferable to use pitch-based carbon fibers. Among pitch-based carbon fibers, any of anisotropic carbon fibers and isotropic carbon fibers can be used as long as they exhibit high thermal conductivity.

Examples of the aramid fiber include poly-p-phenylene terephthalamide and poly-m-phenylene isophthalamide. Of these, poly-p-phenylene terephthalamide fiber is preferable. Examples of the fibers of polyparabenzazoles include poly-p-phenylene benzobisoxazole and poly-p-phenylene benzobisthiazole, and among them, poly-p-phenylene benzobisoxazole is preferable.

Further, a ferromagnetic material such as Fe, Co, or Ni is adhered to a fiber having a different magnetic susceptibility in a fiber axial direction and a fiber circumferential direction, such as the carbon fiber and the aramid fiber, or other fibers. Fibers can also be used as the fibrous filler (A) according to the present invention. Examples of fibers other than fibers such as carbon fibers and aramid fibers include known recycled fibers and synthetic fibers. For example, recycled fibers made of rayon or the like, aliphatic polyamides such as nylon 6, nylon 66, and polyester ( PET), polyacrylonitrile (PAN), polyvinyl alcohol (PVA),
Synthetic fibers such as polypropylene (PP), polyvinyl chloride (PVC) and polyethylene (PE); so-called high heat-resistant polymers such as polyphenylene sulfide (PPS), ultra-high molecular weight polyethylene (UHMWPE) and polyoxymethylene (POM) And high-modulus, high-strength polymers such as aromatic polyesters and polyimides, glass fibers, and the like.

Among them, from the viewpoints of heat resistance, strength and the like, for example, wholly aromatic polyesters, polyimides, heterocyclic polymers and glass fibers are preferable. Further, heterocyclic polymers, polyimides and wholly aromatic polyamides are preferable. It can be particularly preferably used. Such as carbon fiber,
Fibers having different magnetic susceptibilities in the fiber axis direction and the fiber circumferential direction, such as aramid fibers, or as a ferromagnetic substance to be attached to other fibers, are oriented in the magnetic field direction when a magnetic field is applied by a method described later. If it shows a certain degree of magnetism, it may adhere to the entire surface of the fiber in a layered manner or may partially adhere to the fiber surface without forming a layer.

As such a ferromagnetic material, for example,
Metals such as iron, cobalt and nickel or alloys composed of such metals are mentioned. Further, an intermetallic compound containing a ferromagnetic metal such as iron, cobalt and nickel or a metal compound such as a metal oxide of the metal is used. No.
The rate of adhesion of these ferromagnetic materials to the fibrous filler (the area ratio of adhesion) is not particularly limited, and as described above, by the method described below, the magnetism is such that it can be oriented in the direction of the magnetic field when a magnetic field is applied. It is not particularly limited if shown, for example,
It is preferable that the magnetic substance adhesion ratio (adhesion area ratio) on the surface of the fibrous filler is 30% or more, more preferably 50% or more, and particularly preferably 80% or more. The film thickness when the ferromagnetic material is deposited on the surface of the fibrous filler is, for example, 0.01 to 10 μm.
m, preferably 0.1-5 μm, particularly preferably 0.2
It is desirably about 1 μm.

The magnetic substance can be attached to the fiber surface by, for example, electroless plating such as chemical plating. In the present invention, while rolling the sheet composition into a sheet, a magnetic field is applied in the thickness direction of the sheet to orient the fibrous filler having magnetism in the sheet thickness direction. Even with a fiber having a high aspect ratio, a fiber having a high orientation can be obtained. The aspect ratio of such fibers is between 5 and
It is preferably 100, and more preferably 10
100, particularly preferably 10 to 50. The shape of the magnetic fibrous filler (A) according to the present invention is preferably cylindrical. The diameter of the fiber according to the present invention is preferably 5 to 500 μm.
m, more preferably 10 to 200 μm. The average length (L) of the magnetic fibrous filler according to the present invention and the average thickness (D ₂ ) of the obtained heat conductive sheet are preferably 0.8 ≦ D ₂ / L ≦ 1.5,
More preferably, the relationship of 0.9 ≦ D ₂ /L≦1.3 is preferable.

Such a “filamentous filler having magnetism”
(A) "is contained in the total volume of the sheet composition in a total volume of 2 to 60% by volume in the total volume of the sheet composition.
And more preferably 10 to 5
The amount is preferably 0% by volume, particularly preferably 20 to 40% by volume. In the present invention, while rolling the sheet composition into a sheet, a magnetic field acts in the thickness direction of the sheet to orient the fibrous filler having magnetism in the thickness direction of the sheet. Even if the content of the fibrous filler (A) having a content of, for example, 20% by volume or more, a sheet having high orientation can be obtained.

If the proportion is less than 2% by volume, the heat conductivity or conductivity in the thickness direction of the sheet obtained by curing the sheet composition may not be sufficiently increased,
On the other hand, if this ratio exceeds 60% by volume, the resulting composite sheet may have insufficient insulation in the direction perpendicular to the thickness direction of the sheet and may be fragile. (Thermal Conductive Composite Sheet, Conductive Composite Sheet) When the magnetic fibrous filler (A) according to the present invention has a high thermal conductivity in the fiber direction, the resulting composite sheet is a thermally conductive composite sheet. When the fibrous filler (A) having magnetism has high conductivity in the fiber direction, a composite sheet having anisotropic conductivity can be obtained.

When a thermally conductive composite sheet is obtained, the above-mentioned magnetically conductive fibrous filler (A) has a thermal conductivity (W m ^-1 K ^-1 ) in the fiber direction of 100 or more, preferably 500 or more, particularly preferably 500 or more. Preferably, it is 1200 or more. As the fibrous filler for the heat conductive sheet among the fibrous fillers, carbon fibers, aramid fibers, fibers of polyparabenzazoles, and those obtained by attaching a magnetic substance to these fibers are preferable. Further, metal fibers made of Fe, Co, and Ni can also be preferably used.

In the case of obtaining a conductive composite sheet, the fibrous filler (A) having magnetism may be any one of those exemplified above.
A metal that imparts conductivity may be attached to a metal fiber or a fiber having a different magnetic susceptibility in the fiber axis direction and the fiber circumferential direction. As such a material, a noble metal which is hardly oxidized in air and has high conductivity is preferable, and examples of such a noble metal include gold, silver, ruthenium, palladium, rhodium, osmium, iridium, and platinum. And preferably gold and silver. Such a noble metal may be attached to the entire fiber surface in a film form or not to the entire surface as long as the anisotropic conductive sheet is attached to the fiber surface so as to have conductivity. The noble metal can be attached to the fiber surface by, for example, electroless plating such as chemical plating. Further, since such a noble metal has an antioxidant effect, it is preferable to attach the noble metal to the outermost side. As the fiber having the magnetic substance and the noble metal adhered to the surface, for example, nickel is adhered to the carbon fiber surface as a magnetic substance,
Fibers having a noble metal such as gold or silver adhered to the surface thereof may be used.

The adhesion rate (adhesion area ratio) of the noble metal to the fibrous filler is preferably 30% or more, more preferably 50% or more, and particularly preferably 80% or more. In addition, as a film thickness when the noble metal is deposited on the surface of the fibrous filler, for example, 0.01 to 2 μm,
Preferably 0.02 to 1 μm, particularly preferably 0.05
It is desirable that the thickness be 0.5 μm. As such a magnetic fibrous filler (A) according to the present invention, those having a surface further treated with a coupling agent such as a silane coupling agent can be used as appropriate. When the surface of the magnetic fibrous filler is further treated with a coupling agent, the adhesiveness between the fibrous filler and the binder is increased, and as a result, the obtained heat conductive composite sheet or conductive composite sheet is , High durability.

Binder (B) In the sheet composition for forming the composite sheet of the present invention, either a rubbery polymer or a resinous polymer can be used as the binder, and the binder may be used in a state before curing or semi-curing. A liquid binder can be preferably used.
Further, a photo-curable component and / or a thermo-curable component can be added to the binder, and the rubber-like polymer or the resin-like polymer as the binder component can be added to the photo-curable component and / or the thermo-curable component. It can also serve as a component.

The rubbery polymer, resinous polymer, photo-curable component and thermo-curable component used in the present invention will be described below. (Rubber-like polymer) Specific examples of the rubber-like polymer used in the present invention include conjugated diene-based rubbers such as polybutadiene, natural rubber, polyisoprene, SBR and NBR, hydrogenated products thereof, and styrene-butadiene block. Copolymers, block copolymers such as styrene isoprene block copolymers and their hydrogenated products, chloroprene, urethane rubber, polyester rubber, epichlorohydrin rubber, silicone rubber, ethylene propylene copolymer, ethylene propylene diene copolymer And the like. Among these, silicone rubber is particularly preferred from the viewpoint of moldability, weather resistance, heat resistance and the like.

Here, the silicone rubber will be described in more detail. It is preferable to use liquid silicone rubber as the silicone rubber. Liquid silicone rubber is
Any of a condensation type and an addition type may be used. Specific examples include dimethylsilicone raw rubber, methylphenylvinylsilicone raw rubber, and those containing a functional group such as a vinyl group, a hydroxyl group, a hydrosilyl group, a phenyl group, or a fluoro group. (Resinous polymer) As the resinous polymer according to the present invention,
Specifically, an epoxy resin, a phenol resin, a melamine resin, an unsaturated polyester resin, or the like can be used.
Of these, it is preferable to use an epoxy resin.

As the epoxy resin, those having two or more epoxy groups in one molecule are preferable. For example, phenol novolak type epoxy resin, cresol novolak type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, Bisphenol AD type epoxy resin, alicyclic epoxy resin, or polyglycidyl (meth) acrylate, a copolymer of glycidyl (meth) acrylate and another copolymer monomer, and the like can be given. (Photo-curable component) As the photo-curable component contained in the binder according to the present invention, there are photo-radical polymerizable, photo-cationic polymerizable, coordinating photo-polymerizable, which is cured by ultraviolet light, electron beam,
Examples include monomers, oligomers, prepolymers or polymers that are photopolyaddition reactive. Such photocurable monomers, oligomers, prepolymers or polymers include (meth) acrylic compounds, vinyl ether-
Photo-radical polymerizable polymer such as maleic acid copolymer, thiol-
Preferred are photopolyaddition-reactive compounds such as ene-based compounds, and among them, (meth) acrylic-based compounds are particularly preferred. As the photocurable component according to the present invention, a monomer of a (meth) acrylic compound, which requires a short time for photocuring, is preferably used.

Specific examples of such photopolymerizable monomers, oligomers, prepolymers or monomers of (meth) acrylic compounds include monomers which can be derived from cyano group-containing vinyl compounds such as acrylonitrile and methacrylonitrile. , (Meth) acrylamide compounds and (meth) acrylic esters. Examples of the (meth) acrylamide compound include acrylamide, methacrylamide, N, N-dimethylacrylamide and the like, and these may be used alone or as a mixture.

The (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hydroxyethyl (meth) acrylate, and phenyl (meth) acrylate. ) Monofunctional (meth) acrylates such as acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and tricyclodecanyl (meth) acrylate; Used alone or as a mixture.

Examples of the polyfunctional (meth) acrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene glycol. Di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, neopentyl glycol di (meth)
Acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, glycerol di (meth) acrylate, ethylene oxide of bisphenol A Bifunctional (meth) acrylates such as diacrylate of propylene oxide adduct, bisphenol A-diepoxy-acrylic acid adduct, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate,
Examples include trifunctional (meth) acrylates such as glycerin tri (meth) acrylate. Of these, particularly preferred are di (meth) acrylates such as diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and glycerol di (meth) acrylate.

These may be used alone or as a mixture. (Thermosetting component) Examples of the thermosetting component that can be preferably used as the binder according to the present invention include monomers, oligomers, prepolymers and polymers having a functional group that is cured by heat.

As such functional groups, epoxy groups, hydroxyl groups, carboxyl groups, amino groups, isocyanate groups,
Examples thereof include a vinyl group and a hydrosilyl group, and an epoxy group, a vinyl group, and a hydrosilyl group are preferable from the viewpoint of reactivity. Monomers, oligomers having such functional groups,
Examples of the prepolymer or polymer include an epoxy compound, a urethane compound, and a silicone compound. Among these, it is preferable to use an epoxy compound and a silicone compound from the viewpoint of shortening the heat curing time. Further, the epoxy compound or the silicone compound has two or more epoxy groups, vinyl groups or hydrosilyl groups in the molecule. It is desirable to have.

The molecular weight of such an epoxy compound is not particularly limited, but is usually from 70 to 20,000.
Preferably, it is 300 to 5000, and specifically, various epoxy resins having a certain molecular weight or more, such as oligomers, prepolymers, or polymers of the epoxy compound, are preferably used. Specific examples of such an epoxy compound include, for example, the above-mentioned phenol novolak type epoxy resin, cresol novolak type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol AD type epoxy resin, alicyclic ring Examples include a formula epoxy resin, a polyglycidyl (meth) acrylate, and a copolymer of glycidyl (meth) acrylate with another copolymerized monomer.

When these phenol novolak type epoxy resins and the like are used as thermosetting components, they can also serve as resinous polymer components at the same time. Examples of the silicone-based compound include the above-described vinyl-containing silicone rubber, and a vinyl-containing silicone type is preferred as a silicone-based compound because of its reactivity with a hydrosilyl-containing compound used as a curing agent. When these silicone compounds are used as thermosetting components, they can also serve as rubbery polymer components at the same time.

A commercially available silicone compound which can also serve as a rubber-like polymer component is a room temperature-curable two-part addition type thermosetting liquid silicone rubber containing a hydrosilyl compound as a curing agent. Can be mentioned. These resins are used alone or as a mixture. (Combined Use of Photocurable Component and Thermosetting Component) As the binder according to the present invention, the photocurable component and the thermosetting component can be used in combination. In such a combined system, it is preferable that the thermosetting component does not cure under light curing conditions. As described above, when the photo-curable component and the thermo-curable component are used in combination as the binder according to the present invention, the mixing ratio (photo-curable component / thermo-curable component) is preferably from 80/20 to 20/20. /
80% by weight, more preferably 70/30 to 30/70
% By weight, particularly preferably 40/60 to 40/60% by weight
It is desirable that When the photocurable component and the thermosetting component are in such a range, the orientation of the fibrous filler in the composite sheet in a semi-cured state in the thickness direction of the sheet is sufficiently achieved, and When the sheet is cured, a composite sheet having excellent adhesiveness can be obtained.

As such a photo-curable component and a thermo-curable component according to the present invention, the combination of the (meth) acrylic compound and the epoxy-based compound can be used to shorten the molding time of the semi-cured heat conductive sheet. It is preferable from the viewpoint of shortening and excellent adhesiveness. The method of mixing the photocurable component and the thermosetting component is not particularly limited.For example, when the acrylic compound monomer is used as the photocurable component and the epoxy resin is used as the thermosetting component, acrylic The epoxy resin can be dissolved and mixed with the system compound monomer.

As a component of the binder according to the present invention, a compound containing, in one molecule, a photocurable functional group and a thermosetting functional group that does not cure under photocuring conditions is used, and both components are used. You can also double. Examples of the compound containing such a photocurable functional group include the (meth) acrylic compound, and the thermosetting functional group include the epoxy group. Specific examples of the compound that can serve as both components include: Epoxy (meth) acrylamide such as glycidyl (meth) acrylamide, epoxy (meth) acrylate such as glycidyl (meth) acrylate, and 3,4-epoxycyclohexyl (meth) acrylate are exemplified.

Also, a reactive monomer having an unsaturated double bond can be contained as a binder component. Examples of such a reactive monomer include hydroxystyrene, isopropenylphenol, styrene, α-
Aromatic vinyl compounds such as methylstyrene, p-methylstyrene, chlorostyrene, p-methoxystyrene,
Hetero atom-containing alicyclic vinyl compounds such as vinylpyrrolidone and vinylcaprolactam. (Photoinitiator) In the composition for a composite sheet according to the present invention, depending on the type of radiation used for curing the photocurable component,
For example, in the case of ultraviolet curing, a photoinitiator and the like can be mixed.

Such a photoinitiator may be any as long as it cures the photocurable component contained in the sheet composition under the photocuring conditions according to the present invention. When a thermosetting component is used in combination, the photocurable component is cured and the thermosetting component is not cured, and a known photoinitiator can be used. Examples of such a photoinitiator include α-diketones such as benzyl and diacetyl; acyloins such as benzoin; acyloin ethers such as benzoin methyl ether, benzoin ethyl ether and benzoin isopropyl ether; thioxanthon, 2,4- Diethylthioxanthone, thioxanthone-4-sulfonic acid, benzophenone, 4,4
(-Bis (dimethylamino) benzophenone, 4,4 '
Benzophenones such as -bis (diethylamino) benzophenone; acetophenone, p-dimethylaminoacetophenone, α, α′-dimethoxyacetoxybenzophenone, 2,2′-dimethoxy-2-phenylacetophenone, p-methoxyacetophenone, 2-methyl [4 −
(Methylthio) phenyl] -2-morpholino-1-propanone, 2-benzyl-2-dimethylamino-1-
Acetophenones such as (4-morpholinophenyl) -butan-1-one; quinones such as anthraquinone and 1,4-naphthoquinone; phenacyl chloride, tribromomethylphenylsulfone, and tris (trichloromethyl)
Halogen compounds such as -s-triazine; peroxides such as di-t-butyl peroxide; acylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide. Also,
Commercial products include Irgacure 184, 651, 50
0,907, CG1369, CG24-61, Darocur 1116, 1173 (manufactured by Ciba Specialty Chemicals Co., Ltd.), Lucirin LR8728, TPO (BA
SF) and Ubecryl P36 (UCB).

When the photocurable component and the thermosetting component are used together as a binder, the photocurable component contained in the sheet composition is a (meth) acrylic compound,
When the thermosetting component is an epoxy compound, a photoinitiator such as Irgacure 651 or Lucirin TPO, which has a high curing rate, can be preferably used. The amount of the photoinitiator used is preferably an appropriate amount in consideration of the actual curing speed, the balance with the pot life, and the like. Specifically, based on 100 parts by weight of the photocurable component, , 1 to 50 parts by weight, preferably in the binder.
It is particularly preferred that it is contained in a proportion of up to 30 parts by weight. 1
If the amount is less than 10 parts by weight, the sensitivity is easily reduced by oxygen. If the amount is more than 50 parts by weight, the compatibility is deteriorated or the storage stability is deteriorated.

A photoinitiator may be used in combination with such a photoinitiator. When a photoinitiator is used in combination, the initiation reaction is promoted as compared with the use of the photoinitiator alone,
The curing reaction can be performed efficiently. As such a photo-initiating aid, a commonly used photo-initiating aid can be used. Such photoinitiating aids include, for example, triethanolamine, methyldiethanolamine, triisopropanolamine, n-butylamine, N-
Aliphatic amines such as methyldiethanolamine and diethylaminoethyl (meth) acrylate, Michler's ketone, 4,4′-diethylaminophenone, ethyl 4-dimethylaminobenzoate, ethyl 4-dimethylaminobenzoate,
Isoamyl dimethylaminobenzoate and the like. (Thermosetting agent) A thermosetting agent may be mixed with the sheet composition according to the present invention in order to promote the thermosetting of the thermosetting component. As such a thermosetting agent according to the present invention, a known thermosetting agent can be used. Examples of such a thermosetting agent include amines, dicyandiamide, dibasic dihydrazide, imidazoles, hydrosilyl compounds, vinylsilyl compounds, and the like.

Specifically, polymethylenediamine, diethylenetriamine, dimethylaminopropylamine, bishexamethylenetriamine, diethylaminopropylamine, polyetherdiamine, 1,3-diaminocyclohexane, diaminodiphenylmethane, diaminodiphenylsulfone, 4,4 ′ -Bis (o-toluidine), m-phenylenediamine, 2-phenyl-4-methyl-5-hydroxymethylimidazole, block imidazole, polydimethylsiloxane containing both ends hydrosilyl group, polydimethylsiloxane containing both ends vinyl group, etc. Can be

It is preferable to use an appropriate amount of such a thermosetting agent in consideration of the balance between the actual curing speed and the pot life, but specifically, the thermosetting agent is a thermosetting agent. The binder is preferably contained in a proportion of 1 to 50 parts by weight, particularly preferably 1 to 30 parts by weight, based on 100 parts by weight of the active ingredient. The method of adding the photoinitiator and the thermosetting agent is not particularly limited, but it is preferable that the photoinitiator and the thermosetting agent are preliminarily mixed with a binder from the viewpoint of storage stability, prevention of uneven distribution of the catalyst when mixing the components, and the like. .

Other Additives In the present invention, the sheet composition may contain, if necessary, an inorganic filler such as ordinary silica powder, colloidal silica, airgel silica, and alumina. By including such an inorganic filler,
The thixotropic property at the time of uncuring is ensured, the viscosity is increased, and the dispersion stability in the composition of the fibrous filler (A) having magnetism is improved, and the strength of the sheet after curing or semi-curing is improved. Can be done.

The amount of the inorganic filler is not particularly limited. However, if the amount is too large, the orientation of the magnetic fibrous filler by the magnetic field may not be sufficiently achieved. Preparation of Sheet Composition Preparation of the sheet composition according to the present invention can employ any conventionally known methods, for example, a binder, a fibrous filler having magnetism, or if necessary, a photoinitiator And a method in which a thermosetting agent or an inorganic filler is mixed and kneaded.

The viscosity of the sheet composition of the present invention is preferably in the range of 10,000 to 1,000,000 cp at a temperature of 25 ° C., and such a sheet composition is preferably in the form of a paste. Is preferred. In order to form the sheet composition according to the present invention into a sheet shape, a conventionally known method can be employed, but a coating method, a roll rolling method, a casting method, or the like can be employed. <Method for Producing Composite Sheet> As shown in FIG. 1, a composite sheet 1 according to the present invention has a magnetic fibrous filler 2 in a binder 3 which is cured by heat and / or light, in the thickness direction of the sheet. An oriented sheet, and while a sheet composition comprising the magnetic fibrous filler and the binder is rolled into a sheet, a magnetic field is applied in the thickness direction of the sheet to produce the magnetic fibrous filler. The sheet is cured or semi-cured while orienting the filler in the thickness direction of the sheet. If the thermal conductivity in the fiber direction of the fibrous filler (A) having magnetism is 100 (Wm ^-1 · K ^-1 ) or more, the anisotropic thermal conductivity or the anisotropic conductive property in the thickness direction of the sheet. A composite sheet having excellent properties can be obtained. In such rolling of the sheet composition, the thickness (D ₁ ) of the sheet at the start of the orientation of the magnetic fibrous filler is determined by the thickness of the sheet at the end of the orientation of the magnetic fibrous filler. (D ₂ ) is preferably at least 1.3 times, more preferably 2 to 4 times, particularly preferably 2 to 3 times.

As described above, after a composition comprising a magnetic fibrous filler and a binder curable by heat and / or light is applied in advance to a relatively large thickness, it is rolled while applying a magnetic field in the thickness direction. Since the fibrous filler has a space in which it can move freely, especially when the amount of the fibrous filler is increased, or even when the aspect ratio of the fibrous filler is increased, the conventional method of manufacturing a non-rolled sheet The orientation of the fibrous filler is greatly improved as compared with the above, and the anisotropic thermal conductivity or anisotropic conductivity in the thickness direction of the obtained sheet can be greatly improved.

The method of such rolling is not particularly limited. For example, as shown in FIG. 2, a film 4 such as polyethylene terephthalate (PET) is 1.3 times as thick as the desired sheet as described above. The sheet composition 5 containing the magnetic fibrous filler 2 in the binder 3 is applied so as to have the above thickness, and the upper surface thereof is PET.
After coating with the film 6, while applying a magnetic field 7 under conditions such as strength described below, the PET film is pressed uniformly by applying a pressure 8 until the desired thickness is reached, and the light or heat is applied. For example, the composition can be cured or semi-cured to obtain the sheet 1 according to the present invention.

The sheet-like composition is rolled to form a sheet having a thickness of 1.3 times or more the thickness of the desired sheet while applying a magnetic field to the sheet-like composition. A method of curing or semi-curing the composition by sheet light or heat while pressing may be employed. The strength of the magnetic field applied to orient the fibrous filler having magnetism in the sheet composition obtained by forming the sheet composition according to the present invention into a sheet, in the direction of the thickness of the sheet composition, Preferably about 500 to 50,000 Gauss, more preferably about 2000 to 20000 Gauss, magnetic field application time is preferably about 1 to 120 minutes,
More preferably, it is about 5 to 30 minutes. The application of the magnetic field may be performed at room temperature or may be performed by heating as needed.

The method for curing the sheet composition according to the present invention depends on the kind of the binder used and the required sheet performance and is not limited. For example, the epoxy resin is preferably used as a binder component, preferably from 80 to 1%.
The sheet composition can be cured by heating at 80 ° C, more preferably at 100 to 160 ° C. The method of such heating is not particularly limited,
A known method can be used, and the sheet composition may be cured using an ordinary heater or the like. The heating time is
There is no particular limitation, and a range of about 5 to 120 minutes is preferable.

When, for example, the (meth) acrylic resin is used as a binder component, light such as visible light, ultraviolet light, infrared light, far ultraviolet light, electron beam, X-ray, etc. is emitted in the presence of a photoinitiator. The adhesive composite sheet can be obtained by selective irradiation. The method of light irradiation is not particularly limited, and a known method can be used. For example, the light irradiation may be performed by irradiating the sheet with ultraviolet light having a specific wavelength using a general photopolymerization apparatus. In the case of an ultraviolet fluorescent lamp, the irradiation time is about 2 to 3 minutes, the irradiation distance is about 5 to 10 cm, and in the case of a high pressure mercury lamp, the irradiation time is 10 to 20 minutes.
It is preferable that the irradiation distance in seconds is about 7 to 20 cm.

When the photocurable component and the thermosetting component are used in combination as the binder component, for example, a sheet in which the photocurable component is semi-cured is first formed by photocuring, and the sheet is heated at the time of use. What is necessary is just to thermoset the thermosetting component by pressure bonding etc. The composite sheet according to the present invention obtained by such a production method, the fibrous filler (A)
May be exposed or exposed to the surface of the composite sheet. Further, such a fibrous filler (A)
May be exposed on the surface of the composite sheet when the composite sheet is compressed in its thickness direction. In this specification, the fibrous filler is “exposed” on the surface of the composite sheet.
Means that the end of the fibrous filler exists on the surface of the sheet,
For example, when the surface of the composite sheet is joined to the surface of another member, it means that the mating member and the fibrous filler are in contact with each other.

The method of compressing the composite sheet can be selected according to the use of the sheet and the like, and is not particularly limited. For example, a constant weight is applied in the thickness direction of the sheet or a constant distortion is applied to the sheet thickness. It can be done by giving from outside. Further, the sheet to be formed can be compressed by utilizing the curing shrinkage caused by curing the composition capable of forming the sheet according to the present invention from an uncured liquid state. Further, the sheet in a semi-cured state can be compressed by thermocompression bonding to cure the sheet under pressure.

[0057]

According to the production method of the present invention, even if the sheet contains a fibrous filler having a high filling amount or a high aspect ratio, excellent orientation of the fibrous filler in the thickness direction of the sheet can be obtained. A composite sheet having a heat conductive sheet having high anisotropic heat conductivity or anisotropic conductivity in the thickness direction of the sheet, and having excellent heat resistance, durability, mechanical strength, and adhesion to a heating element is obtained. Obtainable.

[0058]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by these Examples.

[0059]

[Example 1] [Production of heat conductive composite sheet] Two-pack type addition type thermosetting liquid silicone rubber (containing dimethylsilicone rubber containing vinyl group, dimethylpolysilicon containing hydrosilyl group and platinum as a catalyst, viscosity 10)
P), pitch-based carbon fibers having an average diameter of 10 μm and an average length of 120 μm (electrothermal conductivity of 1400 W / m · K in the fiber axis direction) obtained by electrolessly plating nickel metal on the surface so as to have an average thickness of 0.7 μm. ) Was added thereto and mixed in a vacuum for 30 minutes to obtain a composition for a heat conductive sheet. After hanging this composition on a PET film (50 μm thick) so that the thickness of the composition in the form of a sheet becomes about 0.3 mm, another PET film is lightly placed on the upper surface and stacked. Place it on the lower plate of the press installed on the electromagnet (magnetic field strength of about 4000 gauss) through which the magnetic field lines pass in the thickness direction of the molded product, and slowly push the upper plate, and the gap between the upper plate and the lower plate 0.25mm (sheet thickness 0.
Roll the paste until it reaches 15mm) and make it 0.15mm thick
A sheet-shaped molded product was obtained. Next, the upper plate and the lower plate of the press were each heated to 100 ° C. to obtain a cured sheet whose both surfaces were protected by a PET film. The thermally conductive composite sheet having a thickness of 0.15 mm was obtained by peeling off the PET films on both sides. The thermal conductivity of the obtained heat conductive composite sheet was evaluated by the following method. <Thermal Conductivity Test> FIG. 3 shows a method for evaluating the thermal diffusivity of a thermally conductive composite sheet by a thermal alternating current method. The thermal diffusivity (α) is calculated based on the relationship shown in Expression 2, and the thermal conductivity in the thickness direction of the heat conductive composite sheet is calculated from the values of the heat capacity and density separately obtained by a conventional method based on Expression 1 below. (Λ) can be obtained.

As shown in FIG. 3, the system for measuring the phase difference (△ θ) of the temperature change by the thermal AC method comprises a function generator 12, a lock-in amplifier 13, a personal computer 14, a sample 9, electrodes 10, 11. . One surface of the sample 9 is heated by sandwiching both surfaces of the sample 9 between electrodes 10 and 11 (a metal thin film provided on a glass plate by sputtering), and applying an AC voltage to one electrode 10 to heat the other surface of the sample 9. The temperature change was detected from the resistance change, and the phase difference (Δθ) of the temperature change (ΔT) was measured from the response delay as shown in FIG. The thermal diffusivity (α) was determined based on Equation 2, and the conductivity (λ) was determined based on Equation 1. In addition, under normal conditions, the measurement was performed under the condition that the sample was not compressed as much as possible.

[0061]

(Equation 1)

[0062]

(Equation 2)

[0063]

Example 2 A photoinitiator was added to a mixture of 60 parts of polyethylene glycol dimethacrylate (PDE400, manufactured by Kyoeisha Co., Ltd.) and 40 parts of a bisphenol A type epoxy resin (EP1001, manufactured by Yuka Shell Epoxy Co., Ltd.). 3% by weight of Irgacure 651, Ciba-Geigy Co., Ltd. based on methacrylate, imidazole-based curing agent (2P4M
HZ-PW, manufactured by Shikoku Kasei Co., Ltd.)
Pitch-based carbon fiber having an average diameter of 7 μm and an average length of 120 μm (thermal conductivity in the fiber axis direction of 1400 W / m · K ) Is added to 25 volume fraction (%),
The mixture was mixed in a vacuum for 30 minutes to obtain a curable composition for a heat conductive composite sheet.

This composition was treated with a PET film (50 μm thick)
After hanging down, another PET film was laid lightly from the top and stacked, and a roll (gap: 0. 0) set on an electromagnet (magnetic field strength of about 4000 gauss) through which magnetic lines of force passed in the thickness direction of the molded product. 3 mm) and a thickness of 0.
A 2 mm sheet-like molded product was obtained. Next, ultraviolet light is irradiated from above the sheet on the electromagnet through which magnetic lines of force pass in the thickness direction of the molded product by an ultraviolet irradiation device for 1 minute, and both sides are protected by a PET film.
A 2 mm sheet was obtained.

The heat conductivity was measured by sandwiching both surfaces of a semi-cured heat conductive composite sheet obtained by peeling the protective films on both surfaces between electrodes (a metal thin film provided on a glass plate by sputtering), and measuring 0.15 mm. After pressing down to the spacer thickness of
After the electrode and the sample were completely bonded by heating at 120 ° C. for 30 minutes, the thermal conductivity was evaluated by the thermal alternating current method in the same manner as in Example 1.

[0066]

COMPARATIVE EXAMPLE 1 The composition for a thermally conductive composite sheet obtained in the same manner as in the above-mentioned Example 1 was placed in parallel on two PET films (50 each) via a 0.15 mm-thick spacer.
μm thickness), formed into a sheet, and heated to 100 ° C. on an electromagnet (magnetic field strength of about 4000 gauss). A 0.15 mm cured sheet was obtained. The thermal conductivity of the obtained sheet was measured in the same manner as in Example 1.

[0067]

Comparative Example 2 The composition for a heat conductive sheet obtained in the same manner as in Example 2 was placed on two PET films (50 μm each) placed in parallel via a 0.2 mm thick spacer.
Thickness), molded into a sheet, and then irradiated with ultraviolet light for 1 minute from above the sheet with an ultraviolet irradiator on an electromagnet through which magnetic lines of force pass in the thickness direction.
A 0.2 mm thick sheet in a semi-cured state protected by a T film was obtained. The thermal conductivity of the obtained sheet was measured in the same manner as in Example 2.

[0068]

Comparative Example 3 The composition for a thermally conductive composite sheet obtained in the same manner as in Example 1 was placed on two PET films (50 each) placed in parallel with a 0.15 mm thick spacer interposed therebetween.
μm thickness), molded into a sheet, and heated in an oven to 100 ° C without applying a magnetic field.
A 0.15 mm thick cured sheet protected by a T film was obtained. The thermal conductivity of the obtained sheet was measured in the same manner as in Example 1.

The thermal conductivity of the sheets of Examples 1 and 2 and Comparative Examples 1 to 3 was evaluated as x when the thermal conductivity of the sheet obtained in Comparative Example 3 was less than 5 times. A sample of 5 times or more and less than 20 times was evaluated as Δ, and a sample of 20 times or more was evaluated as ○.
Table 1 shows the results.

[0070]

[Table 1]

[Brief description of the drawings]

FIG. 1 is a schematic view of a cross section of a composite sheet in which magnetic fibrous fillers are oriented in a thickness direction of the sheet.

FIG. 2 is a schematic diagram showing a magnetic field application and rolling of a sheet-shaped composition.

FIG. 3 is a diagram showing a method of measuring thermal conductivity by a thermal alternating current method.

FIG. 4 is a diagram showing a phase difference of a temperature change in a method of measuring thermal conductivity by a thermal alternating current method.

[Explanation of symbols]

 Reference Signs List 1 composite sheet 2 magnetic fibrous filler 3 binder curable by heat and / or light 4 protective film 5 composition for sheet 6 protective film 7 magnetic field 8 pressure 9 sample 10 electrode 11 electrode 12 function generator 13 lock-in amplifier 14 personal computer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 101/00 C08L 101/00 H01B 5/00 H01B 5/00 CNH 5/16 5/16 13 / 00 501 13/00 501P H01L 23/373 B29K 101: 10 // B29K 101: 10 105: 18 105: 18 B29L 7:00 B29L 7:00 H01L 23/36 M (72) Inventor Hozumi Sato Tokyo 2-11-24 Tsukiji, Chuo-ku JSR Co., Ltd. FF06 FQ40 4J002 AA02W CD05W CH05W CL06X CM02X CN06X CP03W DA016 DA066 DA086 DC006 DE096 DE116 DL006 FA04X FA046 FB076 FD01X FD010 FD016 FD11X FD116 FD140 FD150 GG01 GQ05 5F036 AA0 1 BA23 BB21 BC01 BC23 BD21 5G307 AA02 HA02 HB03 HC01

Claims (12)

[Claims] 1. A sheet composition comprising a magnetic fibrous filler (A) and a binder (B) curable by heat and / or light is rolled into a sheet, and a magnetic field is applied in the thickness direction of the sheet. And curing the sheet by heat and / or light while orienting the magnetic fibrous filler in the thickness direction of the sheet. 2. The thermal conductivity according to claim 1, wherein the thermal conductivity of the magnetic fibrous filler (A) in the fiber direction is 100 (Wm ⁻¹ · K ⁻¹ ) or more. A method for producing a composite sheet. 3. The method for producing a conductive composite sheet according to claim 1, wherein the magnetic fibrous filler (A) is a conductive filler having a noble metal adhered to its surface. 4. Rolling the sheet composition into a sheet while applying a magnetic field in the thickness direction of the sheet to orient the magnetic fibrous filler (A) in the sheet thickness direction. The average thickness (D ₁ ) of the sheet at the start of the orientation of the magnetic fibrous filler is at least 1.3 times the average thickness (D ₂ ) of the obtained thermally conductive sheet. Item 4. The method for producing a composite sheet according to any one of Items 1 to 3. 5. An average thickness (D ₂ ) of the heat conductive sheet.
The average length (L) of the magnetic fibrous filler (A) has a relationship of 0.8 ≦ D ₂ /L≦1.5. A method for producing a composite sheet according to any one of the above. 6. The magnetic fibrous filler (A)
The method for producing a composite sheet according to claim 1, wherein the aspect ratio of the composite sheet is 5 or more. 7. The magnetic fibrous filler (A)
Is contained in the composition for a sheet in an amount of 2 to 60% by volume. The method for producing a composite sheet according to any one of claims 1 to 6, wherein 8. The magnetic fibrous filler (A)
Is a metal fiber having magnetism, or a fiber having a different magnetic susceptibility in a fiber axial direction and a fiber circumferential direction, the composite sheet manufacturing method according to claim 1. 9. The method according to claim 8, wherein the fibers having different magnetic susceptibilities in the fiber axis direction and the fiber circumferential direction are carbon fibers. 10. A fibrous filler having magnetic properties.
The method for producing a composite sheet according to any one of claims 1 to 9, wherein (A) comprises a fiber having a ferromagnetic substance adhered to a surface thereof. 11. A fibrous filler having magnetic properties.
The production of a composite sheet according to any one of claims 1 to 10, wherein (A) is exposed on the surface of the composite sheet or is present so as to be exposed in the thermally conductive sheet. Method. 12. A composite sheet produced by the method according to claim 1, wherein the fibrous filler (A) having magnetic properties is oriented in the thickness direction of the sheet.