JP2001284859A - Heat-conductive sheet and application thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-conductive sheet to meet heat-radiation and heat- transfer requirements for various electric apparatus, electronic apparatus, power generator and the like. SOLUTION: The heat conductive sheet comprises binder, magnetic body, and carbon fiber. The magnetic body and the carbon fiber are oriented in thickness direction of the heat-conductive sheet within the binder. Related to a heat- radiation structure, a high temperature part is jointed to a heat radiation part through the heat conductive sheet. Further, the heat conductive sheet stays on the surface of the high temperature part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat conductive sheet and its use.

[0002]

2. Description of the Related Art In recent years, as home appliances and office electrical appliances, electronic appliances, power generation appliances, etc. have become highly integrated, have large capacities, and have high performance, semiconductor devices or heat generation vibrations of various appliances have been developed. In many cases, the amount of heat generated from a heating element such as a body tends to increase, and furthermore, due to demands for downsizing and thinning of equipment, effective heat radiation from the heating element can be used for such electric equipment, electronic equipment, This is an important issue for power generation equipment and the like. For example, IC, LS of electric and electronic equipment
I, or a semiconductor package part including these, a rotating machine part of a generator, a voice coil part of a speaker of an audio device, etc., can efficiently radiate heat generated from a heating element of each of these devices. This is an important issue from the viewpoint of maintaining the performance of the equipment and improving the durability.

For this reason, conventionally, a high-temperature portion such as a heating element and a radiating portion such as a radiating fin are joined without any gap to improve the heat radiation effect. Attempts have been made to join through highly conductive sheets. However, for example, IC, LSI
A conventional resin sheet interposed between a high heat portion such as a semiconductor element such as a semiconductor device and a heat radiator or a heat radiating portion such as a printed circuit board has a thermal conductivity of at most about 5 to 6 W / mK, which may be good. It was about 8 W / m · K, which was insufficient to exhibit sufficient heat radiation to cope with an increase in the amount of heat generated due to high integration of semiconductor elements.

On the other hand, while there is a demand for improving the heat radiation performance in a form in which a heat radiating member is mounted on such a high heat portion, a strong mounting load such as a heat radiating fin is applied to a semiconductor package with the increase in integration of electronic components. In some cases, a sheet-like heat dissipating member having extremely excellent thermal conductivity has been demanded. On the other hand, electrical equipment other than semiconductor-related parts, also in the field of machinery, for example, generators,
For high-voltage rotating machines such as electric motors, increase the capacity of a single machine,
Due to demands for higher voltage, smaller size and lighter weight, the permissible heat generated by the rotating machine itself tends to increase,
In particular, the further improvement of the thermal conductivity of the heat conductive sheet used between the coil and the iron core of the high-voltage rotating electric machine has been an important issue. In addition, for example, in order to radiate heat accumulated in a magnetic circuit of a speaker unit of an audio device, further improvement in thermal conductivity of a radiating material has been required.

Further, since the output of a UV lamp or the like is also increased, the lamp housing or the like is extremely heated, which causes problems such as shortening the life of the lamp and accelerating thermal deterioration of peripheral materials and elements. Therefore, a further improvement in thermal conductivity of the heat dissipation material has been required. The present inventors have conducted intensive studies to satisfy the above requirements, and have a heat dissipation structure using a heat conductive sheet in which a magnetic material and carbon fibers are oriented in a thickness direction of a resin sheet in a binder. Or the heat dissipation member,
The inventors have found that the requirements as a heat radiation material in various electric equipment, electronic equipment, power generation equipment, and the like are satisfied, and have completed the present invention.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems associated with the prior art as described above, and to provide a heat dissipation structure or a heat dissipation structure which satisfies the demand for high thermal conductivity required for electric and electronic products. It is intended to provide a heat dissipating material.

[0007]

SUMMARY OF THE INVENTION A heat conductive sheet according to the present invention is a heat conductive sheet containing a binder, a magnetic material and carbon fibers, wherein the magnetic material and the carbon fibers contain the heat conductive sheet in the binder. It is characterized by being oriented in the thickness direction of the sheet. The heat dissipation structure according to the present invention is characterized in that the high heat portion and the heat dissipation portion are joined via the heat conductive sheet. The heat dissipation structure according to the present invention is characterized in that the heat conductive sheet exists on the surface of the high heat portion. It is preferable that the high heat portion has a heat dissipation structure that is a heating element. The high heat portion of the heat radiation structure in which the high heat portion and the heat radiation portion are joined via the heat conductive sheet includes a semiconductor element, a semiconductor package, a power transistor, and a PTC (Positive Temperature Coe).
fficient: positive temperature coefficient) element, thyristor, heating coil of high-pressure rotating machine, coil of voice coil, Plasma Displa
Preferably, it is y, EL panel, LD or LED. The high-temperature portion of the heat dissipation structure in which the heat conductive sheet is provided on the surface of the high heat portion includes a semiconductor element, a semiconductor package,
It is preferably a light emitter such as a power transistor, a PTC element, a thyristor, a printed circuit board, a heater for an image forming apparatus, a high-temperature fluid, or a light bulb.

[0008]

DETAILED DESCRIPTION OF THE INVENTION [Composition for heat conductive sheet ] The heat conductive sheet according to the present invention comprises a binder, a magnetic material and carbon fibers, wherein the magnetic material and the carbon fibers are contained in the binder. It is oriented in the thickness direction of the heat conductive sheet.

The heat conductive sheet according to the present invention is obtained by curing or semi-curing the composition for a heat conductive sheet containing the binder, the magnetic substance and the carbon fiber.
It can be obtained by orienting the magnetic body and the carbon fibers in the thickness direction of the heat conductive sheet. <Binder> As the binder for the heat conductive sheet of the present invention, any of a thermoplastic or thermosetting rubbery polymer or a resinous polymer can be used, and if necessary, an unsaturated double bond may be used. May be added.

Specific examples of such a rubbery polymer include polybutadiene, natural rubber, polyisoprene, and S
Conjugated diene rubbers such as BR and NBR and hydrogenated products thereof, block copolymers such as styrene butadiene diene block copolymer, styrene isoprene block copolymer and hydrogenated products thereof, chloroprene,
Examples include urethane rubber, polyester rubber, epichlorohydrin rubber, silicone rubber, ethylene propylene copolymer, and ethylene propylene diene copolymer. 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 or a hydroxyl group.

As the resinous polymer according to the present invention, specifically, an epoxy resin, a phenol resin, a melamine resin, an unsaturated polyester resin and 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 resins, alicyclic epoxy resins, polyglycidyl (meth) acrylate, copolymers of glycidyl (meth) acrylate with other copolymerized monomers, and the like can be used.

Examples of the reactive monomer having an unsaturated double bond include aromatic vinyl compounds such as hydroxystyrene, isopropenylphenol, styrene, α-methylstyrene, p-methylstyrene, chlorostyrene, and p-methoxystyrene; Hetero atom-containing alicyclic vinyl compounds such as pyrrolidone and vinyl caprolactam, and cyano group-containing vinyl compounds such as acrylonitrile and methacrylonitrile.

As the reactive monomer having an unsaturated double bond, (meth) acrylamide compounds and (meth) acrylic esters can also be used.
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. Ethylene 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 2,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, glycerol di (meth) acrylate, bisphenol A Bifunctional (meth) acrylates such as lenoxide, diacrylate of propylene oxide adduct, bisphenol A-diepoxy-acrylic acid adduct, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, glycerin tri (meth) And (3) trifunctional (meth) acrylates such as acrylate.

Of these, diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate
Di (meth) acrylates such as acrylate and glycerol di (meth) acrylate are preferably used. These may be used alone or as a mixture.

The heat conductive sheet according to the present invention can be prepared, for example, by selecting (a) a non-adhesive or weakly adhesive sheet (hereinafter referred to as a sheet) by selecting the type of the compound used for the binder according to the use of the heat conductive sheet. (Bad) adhesive sheet (hereinafter sometimes referred to as "adhesive sheet"), (c) Initially in a semi-cured state and then further cured Thus, it can be formed into various forms such as a fixed type sheet (hereinafter sometimes referred to as a “fixed type sheet”).
For example, when obtaining the non-adhesive sheet (a), it is preferable to use a cured sheet obtained by curing silicone rubber or the epoxy resin among the above. Also,
When obtaining the adhesive sheet (b), it is preferable to form the sheet using the (meth) acrylic compound. Furthermore, when obtaining the fixed type sheet (c), if it is desired to obtain a fixed type thermally conductive sheet to be used by curing the semi-cured sheet at the time of use, for example, a photocurable component as a binder, It is preferable that a thermosetting composition comprising a thermosetting component is first semi-cured by light, and then, when used, cured and bonded by heat and thermocompression bonding.

Among them, the fixed sheet (c) will be described in more detail. Fixable sheet (c) (Photo-curable component) The photo-curable component contained in the heat conductive sheet composition for the fixable sheet includes photo-radical polymerizable and photo-cationic polymerizable by ultraviolet rays, electron beams and the like. Monomers, oligomers, prepolymers or polymers that are reactive, coordinated photopolymerizable, photopolyaddition reactive.
Examples of such photocurable monomers, oligomers, prepolymers or polymers include the cyano group-containing vinyl compounds, (meth) acrylamide compounds and (meth) acrylamide compounds.
(Meth) acrylic compounds such as acrylates, photo-radical polymerizable compounds such as vinyl ether-maleic acid copolymers, and photopolyaddition-reactive compounds such as thiol-ene compounds are preferable. A system compound is 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.

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 and (meth) acrylic acid ester include those described above, and these can be used alone or in combination. (Thermosetting component) Examples of the thermosetting component include monomers, oligomers, prepolymers, and polymers having a functional group which does not cure under the photocuring conditions according to the present invention and is cured by heat.

Examples of such a functional group include an epoxy group, a hydroxyl group, a carboxyl group, an amino group, an isocyanate group and the like, and an epoxy group is preferred from the viewpoint of reactivity.
Examples of such a monomer, oligomer, prepolymer or polymer having a functional group include an epoxy compound and a urethane compound. Among them, it is preferable to use an epoxy compound from the viewpoint of excellent adhesiveness and shortening of the thermosetting time, and it is desirable that the epoxy compound has two or more epoxy groups in a molecule.

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. In addition, as a component of the binder related to the use of the fixing sheet (c) according to the present invention, a compound containing, in one molecule, a photocurable functional group and a thermosetting functional group that is not cured under photocuring conditions. Using,
Both components can be combined. 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.

The mixing ratio of the photo-curable component and the thermo-curable component (photo-curable component / thermo-curable component) contained in the binder when used in the application (c) of the present invention is preferably 80/20 to 20/80% by weight, more preferably 70/30 to 30/70% by weight, particularly preferably 4%
It is desirable that the content be 0/60 to 40/60% by weight. When the photocurable component and the thermosetting component are in such a range, the orientation of the magnetic material and carbon fibers in the semi-cured heat conductive sheet in the thickness direction of the sheet is sufficiently performed. Thus, a sheet obtained by curing the semi-cured heat conductive sheet having excellent adhesiveness can be obtained. In addition, in this specification, "weight%" shows the ratio of weight.

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.

The binder according to the present invention contains, in addition to the photocurable component and the thermosetting component, other binder components as long as the formation of the semi-cured heat conductive sheet by curing the photocurable component is not impaired. It may be. Such other binder components include, for example, the thermoplastic or thermosetting rubbery polymer, the resinous polymer or the unsaturated double bond other than the photocurable component and the thermosetting component. The compound of. (Photoinitiator) Depending on the type of radiation used for the photocuring, for example, in the case of ultraviolet curing, a photoinitiator can be mixed.

Such a photoinitiator cures the photocurable component contained in the composition for a heat conductive sheet and cures the thermosetting component under the photocuring conditions according to the present invention. If not, 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- Benzophenones such as diethylthioxanthone, thioxanthone-4-sulfonic acid, benzophenone, 4,4 (-bis (dimethylamino) benzophenone, and 4,4′-bis (diethylamino) benzophenone; acetophenone, p-dimethylaminoacetophenone, α, α '-Dimethoxyacetoxybenzophenone, 2,2'-dimethoxy-2-phenylacetophenone, p-methoxyacetophenone,
-Methyl [4- (methylthio) phenyl] -2-morpholino-1-propanone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butane-
Acetophenones such as 1-one; anthraquinone, 1,
Quinones such as 4-naphthoquinone; halogen compounds such as phenacyl chloride, tribromomethylphenylsulfone, and tris (trichloromethyl) -s-triazine;
Peroxides such as di-t-butyl peroxide;
Acylphosphine oxides such as 6-trimethylbenzoyldiphenylphosphine oxide; As commercially available products, Irgacure 184,
651,500,907, CG1369, CG24-6
1, Darocur 1116, 1173 (manufactured by Ciba Specialty Chemicals Co., Ltd.), Lucirin LR8728,
Examples include TPO (manufactured by BASF) and Jubecryl P36 (manufactured by UCB).

Of these, when the photocurable component contained in the composition for a heat conductive sheet is a (meth) acrylic compound and the thermosetting component is an epoxy compound, Irgacure 651 having a high curing speed, Lucirin A photoinitiator such as TPO 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 contained in the binder,
It is particularly preferred that it is contained in a proportion of 30 parts by weight. When the amount is less than 1 part by weight, the sensitivity is easily reduced by oxygen,
If the amount is more than 50 parts by weight, the compatibility becomes poor or the storage stability decreases.

A photoinitiator can 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 composition for the fixed-type heat conductive sheet 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 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 and the like.

The amount of the thermosetting agent used is preferably an appropriate amount in consideration of the balance between the actual curing speed and the pot life, but specifically, the thermosetting agent is preferably a thermosetting agent. The binder is preferably contained in the binder at a ratio of 1 to 50% by weight, particularly preferably 1 to 30% 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. . <Magnetic Material and Carbon Fiber> The magnetic material and carbon fiber contained in the heat conductive sheet according to the present invention are magnetic particles and carbon fiber, or carbon fiber having a magnetic material attached to the surface of carbon fiber. Is preferred. Hereinafter, the magnetic material, the carbon fiber, and the carbon fiber having the magnetic material adhered to the surface will be described. <Magnetic Body> Examples of the material used for the magnetic body according to the present invention include a ferromagnetic metal such as iron, cobalt, and nickel or an alloy made of such a metal. An intermetallic compound containing a metal exhibiting ferromagnetism or a metal compound such as a metal oxide of the metal may be used.

It is preferable that such a magnetic substance is a magnetic substance in the form of particles or a magnetic substance adhered to the surface of a carbon fiber. Magnetic Particles The magnetic particles used as a preferred form of the magnetic material according to the present invention are not particularly limited as long as they exhibit a degree of magnetism that can be oriented in the direction of a magnetic field when a magnetic field is applied by a method described below.

Such magnetic particles are metal particles obtained by converting the above-mentioned magnetic particles into particles. Such magnetic particles,
Particles of metal such as iron, nickel, cobalt, etc. are used as core particles, and the surface of the core particles is plated with another metal, for example, a metal having high thermal conductivity, or an inorganic substance such as non-magnetic metal particles or glass beads. Particles or polymer particles as core particles, the surface of the core particles, iron, nickel,
Examples include particles that have been plated with at least a ferromagnetic metal such as cobalt. The method of coating the surface of the core particles with a metal is not particularly limited, but may be, for example, chemical plating, electroless plating, or the like.

The coating amount of the magnetic substance is preferably 0.5 to 50% by weight based on the core particles, more preferably 1 to 3% by weight.
0% by weight, more preferably 2 to 25% by weight, particularly preferably 4 to 20% by weight. The particle diameter of the magnetic particles according to the present invention is preferably 1 to 1000 μm,
More preferably 2-500 μm, even more preferably 5-
It is 300 μm, particularly preferably 10 to 200 μm.

The shape of the magnetic particles is not particularly limited, but may be spherical, star-shaped, or agglomerated secondary particles formed by aggregation of these, or elongated rod-shaped. In this specification,
"Orientation" means that the particles are aligned in a substantially constant direction,
Alternatively, this means a case where rod-like carbon fibers or the like are oriented in a substantially constant direction.

The water content of the magnetic particles is preferably at most 5%, more preferably at most 3%, further preferably at most 2%, particularly preferably at most 1%.
By using the magnetic particles satisfying such conditions, in the manufacturing method described below, when the heat conductive sheet composition is semi-cured to obtain a semi-cured heat conductive sheet, the semi-cured heat conductive sheet is used. The generation of bubbles in the conductive sheet is prevented or suppressed.

It is preferable that such magnetic particles are used at a volume fraction of 10 to 50% by volume, preferably 15 to 40% by volume, based on the composition for a heat conductive sheet. If the ratio is less than 10% by volume, it may be difficult to orient the carbon fibers in the semi-cured heat conductive sheet together with the magnetic particles in the direction of the magnetic field. On the other hand, if this ratio exceeds 50% by volume, the obtained semi-cured heat conductive sheet and the heat conductive sheet cured therefrom tend to be brittle, and the elasticity required as a high heat conductive sheet cannot be obtained. There is.

The magnetic particles and the carbon fibers are preferably contained in a total amount of 20 to 80% by volume in the total volume of the composition for a heat conductive sheet, and more preferably 3% by volume.
Desirably, it is contained in an amount of 0 to 60% by volume. Also,
A magnetic particle whose surface has been treated with a coupling agent such as a silane coupling agent can also be used as appropriate.

Carbon Fiber The carbon fiber used in the present invention is not particularly limited as long as it has higher thermal conductivity than the binder. Such a carbon fiber can be selected, for example, from cellulosic, PAN, and pitch-based carbon fibers depending on the type of raw material. In the present invention, from the viewpoint of 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.

The carbon fiber according to the present invention can be prepared by a generally known method, and a commercially available carbon fiber can be used. The diameter of such carbon fibers is preferably 5 to 500 μm, more preferably 1 to 500 μm.
0 to 200 μm. Further, the length of the carbon fiber used in the present invention is not particularly limited, but is oriented in the thickness direction in the semi-cured heat conductive sheet and the cured heat conductive sheet, and the heat conductivity of the cured heat conductive sheet is reduced. Preferably, the length is such that it can be increased.

The aspect ratio of such a carbon fiber is 2
To 100, more preferably 5 to 100.
100, particularly preferably 10 to 50. Such a carbon fiber has a volume fraction of 10 to 70%, preferably 15 to 50%, based on the composition for a heat conductive sheet.
% Is preferably used. If this ratio is less than 10%, the heat conductivity of the cured heat conductive sheet may not be sufficiently enhanced, while
If this proportion exceeds 70%, the resulting heat conductive sheet tends to be brittle, and the elasticity required for the heat conductive sheet may not be obtained.

The carbon fiber and the magnetic particles according to the present invention are:
As described above, the total amount contained in the total volume of the composition for a thermally conductive sheet is preferably contained in a total amount of 20 to 80% by volume in the total volume of the composition for a thermally conductive sheet, More preferably, the amount is 30 to 60% by volume. Carbon fiber having a magnetic substance adhered to its surface "Carbon fiber having a magnetic substance adhered to its surface" according to the present invention
Is a carbon fiber in which the magnetic substance is attached to the surface of the carbon fiber.

The magnetic substance attached to the surface of the carbon fiber according to the present invention has a magnetic property such that it can be oriented in the direction of the magnetic field when a magnetic field is applied by the method described later. It may be attached in a layered manner or may be attached to a part of the carbon fiber surface without forming a layer, and the material and thickness of the magnetic material are not particularly limited. Further, the magnetic substance attached to the carbon fiber preferably has higher thermal conductivity than the binder.

The method of attaching the magnetic substance to the surface of the carbon fiber can be performed by, for example, electroless plating such as chemical plating. Such a "carbon fiber having a magnetic substance adhered to the surface" according to the present invention, the total amount contained in the total volume of the heat conductive sheet composition is the total volume of the heat conductive sheet composition. It is preferably contained in a total amount of 2 to 70% by volume, and more preferably 10 to 60% by volume.

If this proportion is less than 2% by volume, the thermal conductivity of the cured heat conductive sheet may not be sufficiently increased, while if this proportion exceeds 70% by volume, it is obtained. The heat conductive sheet tends to be fragile, and the elasticity required for the heat conductive sheet may not be obtained. In addition, a carbon fiber having a surface to which a magnetic substance is adhered, the surface of which has been further treated with a coupling agent such as a silane coupling agent can be used as appropriate. <Other Additives> In the present invention, the composition for a heat conductive sheet may contain an inorganic filler such as ordinary silica powder, colloidal silica, airgel silica, and alumina, if necessary. By including such an inorganic filler, the thixotropy at the time of uncuring is secured, the viscosity is increased, and the dispersion stability of the carbon fiber having the magnetic substance adhered to the surface is improved. In addition, the strength of the high heat conductive sheet after curing or semi-curing can be improved.

The amount of the inorganic filler used is not particularly limited. However, if the inorganic filler is used in an excessively large amount, the orientation of the magnetic particles and the carbon fibers or the carbon fibers having the magnetic substance adhered to the surface by the magnetic field can be sufficiently improved. It is not preferable because it becomes impossible to achieve the above. Further, the composition for a thermally conductive sheet of the present invention,
A silane coupling agent and a titanium coupling agent may be contained.

Further, the composition for a heat conductive sheet according to the present invention may contain other additives as required. Examples of such additives include an ultraviolet absorber, a thermal polymerization stabilizer, an antioxidant, a heat stabilizer, an antistatic agent, a flame retardant, an adhesion improver, and a fungicide. <Composition for heat conductive sheet> As a method for preparing the composition for heat conductive sheet according to the present invention, any of the conventionally known methods can be adopted, for example, a photo-curable component and a thermo-curable component. And a method of mixing and kneading a binder, a magnetic material, a carbon fiber, and, if necessary, a photoinitiator, a thermosetting agent, or an inorganic filler.

The viscosity of the composition for a heat conductive sheet of the present invention is 10,000 to 1,000,000 cp at a temperature of 25 ° C.
Is preferably within the range. [Thermal Conductive Sheet] The composition for a thermal conductive sheet of the present invention is preferably in the form of a paste. For example, the composition is formed into a sheet and a magnetic field is applied in the thickness direction of the sheet composition. Along with orienting the magnetic material and carbon fibers, the sheet composition is cured or semi-cured by light irradiation or heating, and the non-adhesive sheet (a), the adhesive sheet (b) or the fixed sheet (c) Can be formed according to the application.

When used, the surface of the coated material is coated by a method such as application, and a magnetic field is applied in the thickness direction of the applied sheet-like composition to orient the magnetic material and the carbon fibers. The sheet composition can be cured or semi-cured by light irradiation or heating to form a heat conductive sheet. Such orientation of the magnetic material and carbon fiber and curing or semi-curing of the sheet-like composition may be performed simultaneously, or after the orientation, curing or semi-curing may be performed.

The composition ratio of the binder, the magnetic material and the carbon fibers in the thus obtained heat conductive sheet is the same as that of the above-mentioned composition for heat conductive sheet. The thickness of such a heat conductive sheet varies depending on the application to be used and is not particularly limited, but is usually preferably about 50 μm to 1000 μm. Hereinafter, the method for forming a heat conductive sheet according to the present invention will be described in more detail.

FIGS. 1 and 2 show specific examples of the obtained heat conductive sheet. For example, as shown in FIG. 1, in the heat conductive sheet 1 according to the present invention, the magnetic particles 3 and the carbon fibers 4 are oriented in the direction of the thickness of the heat conductive sheet in the binder 2. I have. Also,
As shown in FIG. 2, the heat conductive sheet 1 according to the present invention
In the binder 2, carbon fibers 5 having a magnetic material adhered to the surface are oriented in the direction of the thickness of the heat conductive sheet. 1 and 2 are schematic drawings of the heat conductive sheet of the present invention.

In order to form the composition for a heat conductive sheet according to the present invention into a sheet shape, a conventionally known method can be employed, but a roll rolling method, a casting method, a coating method or the like can be employed. The thickness of such a sheet-like composition is not particularly limited, although it depends on the use of a molded article obtained by further curing a semi-cured heat-conductive sheet obtained from the final sheet-like composition, but is usually 50 μm to 1000 μm. It is about.

The magnetic material and carbon fiber in the sheet-like composition obtained by applying the composition for a heat-conductive sheet according to the present invention to a sheet or the sheet-like composition coated on the surface of a coating material,
The strength of the magnetic field applied for orientation in the thickness direction of the sheet composition is preferably about 500 to 50,000 gauss, more preferably about 2,000 to 20,000 gauss, and the magnetic field application time is preferably one to one. It is about 120 minutes, more preferably about 5 to 30 minutes. The application of a magnetic field may be performed at room temperature or may be cured by heating if necessary, but the formation of the non-adhesive sheet, the adhesive sheet and the fixed sheet required according to the application is performed. It is preferable to carry out at a temperature suitable for.

The method for curing or semi-curing the composition for a thermally conductive sheet 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 non-adhesive sheet (a) is preferably made of, for example, 80 to 1 using the epoxy resin as a binder component.
It can be obtained by heating and curing at 80 ° C, more preferably in the range of 100 to 160 ° C. Such a heating method is not particularly limited, and a known method can be used. The sheet-shaped composition of the composition for a thermally conductive sheet may be cured using a usual heater or the like. The heating time is not particularly limited, and is preferably in a range of about 5 to 120 minutes.

Further, for example, the pressure-sensitive adhesive sheet (b) is preferably formed by using the (meth) acrylic compound as a binder component, preferably at 60 to 120 ° C., more preferably at 80 to 120 ° C.
In the range of 0 ° C., preferably by heating and curing for preferably 5 to 120 minutes, more preferably 10 to 60 minutes,
Obtainable. When the (meth) acrylic resin is used as a binder component, visible light, ultraviolet light, infrared light, far ultraviolet light, electron beam,
The adhesive heat conductive sheet (b) can also be obtained by selectively irradiating light such as X-rays. The method of light irradiation is not particularly limited, and a known method can be used.
What is necessary is just to irradiate the said heat conductive sheet with ultraviolet rays etc. of a specific wavelength using a normal 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 about 10 to 20 seconds, and the irradiation distance is about 7 to 20 cm. Preferably, there is.

Further, for example, the fixing type sheet (c) is used as a binder component and as the photo-curable component (meth)
It can be obtained from a sheet composition containing an acrylic compound and an epoxy compound as the thermosetting component. Specifically, such a sheet-shaped composition is selectively irradiated with light such as visible light, ultraviolet light, infrared light, far ultraviolet light, electron beam, and X-ray to supply energy required for curing. Thereby, the photocurable component contained in the sheet composition is polymerized and cured to obtain a semi-cured heat conductive sheet, and then, when used, the semi-cured heat conductive sheet, It can be obtained by thermocompression bonding between a semiconductor element and a heat radiating member and curing.

The method of light irradiation is not particularly limited, and a known method can be used. For example, the heat conductive sheet is irradiated with ultraviolet rays having a specific wavelength using a usual photopolymerization apparatus. Just do it. The light source for the light irradiation is not particularly limited, but in the case of the ultraviolet irradiation, an ultraviolet fluorescent lamp or a high-pressure mercury lamp can be preferably used as the ultraviolet light source. In the case of an ultraviolet fluorescent lamp, the irradiation time is 2 to
It is about 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 preferably 10 to 20 seconds, and the irradiation distance is preferably about 7 to 20 cm.

A procedure for obtaining a semi-cured thermally conductive sheet by performing photopolymerization while applying a magnetic field to the uncured sheet-like composition to orient the magnetic material and the carbon fibers in the thickness direction of the sheet. Is not particularly limited, and light irradiation may be performed simultaneously with the application of a magnetic field, or after the magnetic material and the carbon fibers are oriented in the thickness direction of the sheet by the application of the magnetic field, the light may be irradiated on the sheet-shaped composition to make it semi-conductive. It may be cured. From the viewpoint of sufficiently orienting the magnetic material and the carbon fibers, it is preferable that after applying a magnetic field to orient them, the sheet composition is semi-cured by light irradiation. The temperature at which such a semi-cured heat conductive sheet is obtained is not particularly limited as long as the thermosetting component contained in the sheet-like composition is not cured, but may be usually performed at about room temperature, and is preferably performed. It is desirable to be 20 to 100 ° C, more preferably 20 to 60 ° C.

Such a semi-cured heat conductive sheet according to the present invention can be formed simply and in a short time.
In order to form the fixed type sheet by joining the high heat portion and the heat radiating portion via the heat conductive sheet obtained by curing the obtained semi-cured heat conductive sheet, the semi-cured sheet is cut into a predetermined shape. The heat conductive sheet is sandwiched between two members, for example, a high heat part and a heat radiating part, and the thermosetting component in the semi-cured heat conductive sheet is thermoset by thermocompression bonding. be able to. The conditions of such thermocompression bonding differ depending on the member used and are not limited.
For example, in the case of the heat dissipation structure according to the semiconductor package, the high heat portion according to the heat dissipation structure, the heat dissipation portion, the wiring in the heat dissipation structure,
It is desirable that bumps and other parts be deformed, damaged, or melted by the temperature and pressure associated with thermocompression bonding.Temporary bonding is performed at room temperature or under pressure while heating to the extent that the curing reaction does not proceed sufficiently. Thereafter, a method of heating to complete the curing reaction or a method of heating sufficiently at the time of pressure bonding to simultaneously perform adhesion and curing can be appropriately selected as necessary. For example, the thermocompression bonding temperature is preferably 80 to 180 ° C., more preferably 10 to 180 ° C.
It is desirable to carry out in the range of 0 to 160 ° C, particularly preferably 120 to 150 ° C. When the temperature is lower than 80 ° C., the heat curing is not performed smoothly, and a long reaction time may be required. When the temperature is higher than 180 ° C., the solder or the like attached to the heating element or the like may be dissolved. . The pressure for thermocompression bonding is preferably in the range of 0.1 to 5 kg / cm ² , particularly preferably 0.5 to ² kg / cm ² . If the pressure is less than 0.1 kg / cm ² , the adhesive between the high-temperature part and the heat radiating part may be insufficient, and if the pressure exceeds 5 kg / cm ² , the semiconductor element, etc., which is the high-temperature part, may be damaged. is there. The time for such thermocompression bonding is usually preferably 1 minute to 120 minutes.
Minutes, more preferably about 20 to 60 minutes.

[ Use of Thermal Conductive Sheet ] In the thermal conductive sheet according to the present invention, the magnetic material and the carbon fibers are oriented in the thickness direction of the thermal conductive sheet in the binder. It has high thermal conductivity in the thickness direction of the conductive sheet. Specifically, the heat conductive sheet according to the present invention has an anisotropic heat conductivity in the thickness direction of the sheet of 15 to 20 comparable to SUS.
It has thermal conductivity of about W / m · K. For this reason, the heat conductive sheet according to the present invention is useful in a wide range of fields as a sheet relating to a heat dissipation structure of electric machines, electronics, power generation components and the like.

The heat radiation structure using the heat conductive sheet according to the present invention, specifically, as shown in FIG. And a heat dissipation structure 10 in which a heat conductive sheet is present on the surface of the high heat portion 9 as shown in FIG. In forming such a heat dissipation structure, the shape of the heat conductive sheet according to the present invention depends on the application and is not particularly limited, and the sheet may be any one of a planar shape, a curved surface shape, and a tubular shape.

In the present specification, the high heat portion in the heat dissipation structure 8 means that the temperature is higher than that of the heating element or the heat dissipation portion. In the heat radiation structure 10, the high heat portion means a heating element or a solid or fluid (gas, liquid or gel) on a high temperature side via a heat conductive sheet. Hereinafter, the heat dissipation structure according to the present invention will be described. (I) The high heat portion and the heat radiating portion are interposed via the heat conductive sheet.
The heat dissipating structure (I) in which the heat conductive sheet according to the present invention is sandwiched between the high heat portion and the heat dissipating portion is, for example, various heat dissipating structures related to a semiconductor package. As such a heat radiation structure, specifically, a high heat portion is a semiconductor element such as an IC or an LSI, a semiconductor package, a power transistor, a thyristor, a PTC (Pos
Heat dissipation structure in which the heat radiating portion is a heat radiating member such as a heat radiating plate or radiating fin. The high heat portion is a semiconductor device such as IC or LSI, a semiconductor package, a power transistor, a thyristor, or a PTC device. There is a heat radiation structure where the heat radiation part is a printed circuit board, a flexible printed circuit board, a circuit board, etc.
A heat radiating structure in which a heat radiating portion is a heat radiating member such as a heat radiating plate or a heat radiating fin is a circuit board or the like.

When the heat conductive sheet according to the present invention is used for such purposes, it is preferable that the heat conductive sheet is the above-mentioned adhesive sheet (b) or fixed sheet (c). When used in the form of the fixed type sheet, it is preferable to use the heat conductive sheet in a semi-cured state by thermocompression bonding at the time of manufacturing a semiconductor package or the like.

When the heat conductive sheet according to the present invention is used in such a structure, since the heat conductive sheet according to the present invention has a high heat conductivity in the thickness direction of the sheet, the heat conductive sheet moves from the high temperature portion to the heat radiating portion. Can have a heat dissipation structure that is extremely excellent in thermal conductivity. In addition, since the heat conductive sheet according to the present invention contains a conductive material such as carbon fiber and has an antistatic property, static electricity generated in a semiconductor package or the like, or generated at the time of thermocompression bonding between a high temperature part and a heat radiating part. It can also reduce static electricity. Further, the heat conductive sheet according to the present invention is rich in elasticity, has a large cushioning property, and is excellent in vibration damping property, so that damage of the semiconductor package due to vibration and impact given to the semiconductor package can be prevented. (Ii) Another example of the heat dissipation structure (I) according to the present invention includes the following. The high heat part is the external heater for heating and pressing, and the heat radiation part is Pl
Heat dissipating structure that is a member to be compressed such as asma Display, EL panel, LD, LED or printed circuit board. The heat conductive sheet according to the present invention can be used as a flexible printed circuit board, such as a Plasma Display, EL panel, LD, LED or printed circuit board. In the case of thermocompression-bonding with a member to be press-bonded, the heat from the heater can be transferred effectively if it is used as an auxiliary sheet for thermocompression bonding between an external heater for thermocompression bonding and these press-bonded bodies. This has the advantage that thermocompression bonding can be performed reliably and in a short time. A rotating electric machine in which the high-temperature portion is a coil of a high-voltage rotating machine and the heat-radiating portion is an iron core.The heat conductive sheet according to the present invention can also be used for heat radiation of a coil that generates heat in a high-voltage rotating machine such as a generator or an electric motor. it can. For example, the present invention can be applied to a high-pressure rotating machine in which a heat conductive sheet according to the present invention is sandwiched in a gap between a heating coil of a high-pressure rotating machine and an iron core having a slot, and the coil and the iron core coil are joined. With this configuration, the iron core and the coil are integrated, and heat conduction between the coil and the iron core can be performed efficiently, so that the cooling performance of the high-pressure rotating machine can be improved. When the heat conductive sheet according to the present invention is used for such a heat radiation structure, it is preferable to use the semi-curable heat conductive sheet and heat and cure the heat conductive sheet at the time of use. A speaker in which the high heat portion is a voice coil and the heat radiating portion is a coil portion or auxiliary paper. The heat conductive sheet according to the present invention is used as a means for radiating heat from the bobbin of the voice coil for heat radiation from the voice coil of the speaker. be able to. For example, by wrapping the heat conductive sheet according to the present invention around the voice coil and further wrapping the coil therearound, a speaker excellent in heat dissipation from the voice coil can be obtained. Examples of the heat conductive sheet according to the present invention, which is preferably used for such a heat dissipation structure, include the above-mentioned pressure-sensitive adhesive sheet or a fixed sheet which is heated and cured at the time of use using a semi-curable heat conductive sheet. (II) The heat conductive sheet according to the present invention is provided on the surface of the high heat portion.
The existing heat dissipation structure (i) The heat dissipation structure (II) in which the heat conductive sheet according to the present invention is present on the surface of the high heat portion can be used, for example, in various heat dissipation structures related to a semiconductor package. Specific examples of such a heat dissipation structure include the following heat dissipation structures. Heat dissipation structure in which the heat dissipation portion is a semiconductor element such as an IC or an LSI, a semiconductor package, a power transistor, a PTC, or a thyristor. Such a heat dissipation structure has a thermal conductivity according to the present invention on an electronic component such as a semiconductor element or a semiconductor package. The sheets are joined by thermocompression bonding or the like, and heat radiation from a semiconductor element or a semiconductor package or the like is efficiently performed via the heat conductive sheet. Further, the heat conductive sheet according to the present invention also has a function as a protective sheet for a semiconductor package. When used in such applications, the heat conductive sheet according to the present invention is preferably a pressure-sensitive adhesive sheet or a fixed sheet which is heated and cured at the time of use using a semi-curable heat conductive sheet.

In addition, the heat dissipation structure is characterized in that the heat conductive sheet according to the present invention is used as a circuit board material and a semiconductor element,
A heat dissipation structure provided with a semiconductor package can also be used. When the high thermal conductive sheet of the present invention is used as such a substrate material, it is preferable to use it as a non-adhesive sheet. Heat dissipation structure in which the heat dissipation portion is a flexible printed board A printed circuit board in which the heat dissipation portion is coated on a printed board such as a flexible board and the heat conductive sheet according to the present invention has excellent heat dissipation from the printed board itself. It will be. Further, by making the heat conductive sheet according to the present invention sticky, it is also possible to easily temporarily fix the electronic component when the electronic component or the like is mounted on the printed circuit board. The method for coating the heat conductive sheet according to the present invention on a printed board such as a flexible printed board is, for example, a method of coating the surface of a printed board by a method such as coating, and the thickness of the applied sheet-shaped composition. A magnetic field acts in the direction to orient the magnetic material and carbon fibers, and the applied sheet-like composition is cured or semi-cured by light irradiation or heating to form a printed board covered with a heat conductive sheet. be able to. (Ii) Another example of the heat dissipation structure (II) according to the present invention is as follows. Heat dissipation structure in which a high heat part is a heater of a heat fixing part of an image forming apparatus The heat conductive sheet according to the present invention is used for a fixing roll or a fixing belt of a heat fixing part in an image forming apparatus such as a copying machine, a laser beam printer, and a facsimile. It can also be used. For example, the heat conductive sheet according to the present invention,
By using the heat fixing roll heated by the heat fixing heater, the heat conductivity can be improved, and thus the fixing speed can be increased. When used in such applications, it is preferable that the binder is a component that gives a cured product having excellent heat resistance and mechanical strength (such as Young's modulus) such as silicone rubber. When used for such applications, it is preferable to use it as a non-adhesive sheet. Heat-dissipating structure in which a high-temperature part is a high-temperature fluid The heat conductive sheet according to the present invention can also be used as a material for a low-temperature part exhaust gas heat recovery device of a large-sized combustion device such as a boiler. For example, the heat conductive sheet according to the present invention,
Since the thermal conductivity in the thickness direction is similar to that of SUS, heat recovery is performed through the heat conductive sheet according to the present invention when the high heat portion is exhaust gas of about 150 ° C. or less, and the high heat portion is formed through the heat conductive sheet. By conducting heat to the medium on the opposite side, heat can be efficiently recovered from exhaust gas.

The tubular heat conductive sheet according to the present invention can be used as a heat exchange heat transfer tube for a heat exchanger. That is, heat exchange with the medium outside the cylinder from the medium, which is a high-temperature portion existing inside the cylinder formed by the heat conductive sheet according to the present invention, via the cylindrical heat conductive sheet according to the present invention. And can be used as a heat transfer tube for a heat exchanger having excellent heat conductivity. When used in such applications, it is preferable to use a component that gives a cured product having excellent heat resistance such as silicone rubber as the binder, and such a sheet is preferably a non-adhesive sheet. .

In this specification, the high-temperature fluid is a high-temperature portion of gas or liquid, and has a higher temperature than a solid or fluid (gas, liquid or gel) on the opposite side via a heat conductive sheet. It means there is. The heat dissipation structure in which the high heat portion is a luminous body such as a light bulb The heat conductive sheet according to the present invention can be used for the exterior and radiating portion of a luminous body such as a light bulb such as a UV lamp, and radiates heat generated due to the high output of the lamp. Can be performed efficiently. Heat radiating structure in which the high heat portion is a motor that requires high-speed rotation such as a CD-ROM drive, CD-R / RW drive, DVD drive, hard disk drive, etc. The heat conductive sheet according to the present invention includes a CD-ROM drive, a CD-R / RW drive, DVD drive, hard disk drive, etc., can be provided on the surface of a motor bearing portion and a casing portion of a drive, and heat can be efficiently radiated from these rotating portions. The heat dissipating structure in which the high heat part is a bearing part, a casing part, and a gear part of the rotating part of the electric drill. The heat conductive sheet according to the present invention can be provided on the outer surface of the motor or gear part of the electric drill. Can efficiently dissipate heat. Heat dissipating structure in which the high heat portion is the outer casing of the battery The heat conductive sheet according to the present invention can be provided on the surface of the outer portion of the battery, and can efficiently dissipate heat from the battery.

[0067]

In the heat conductive sheet according to the present invention, since the magnetic material and the carbon fibers are oriented in the thickness direction of the heat conductive sheet, the heat conductivity in the thickness direction of the heat conductive cured layer is reduced. Excellent. Further, the heat conductive sheet according to the present invention satisfies the requirements related to heat dissipation and heat conduction required for various electric devices, electronic devices, power generation devices, and the like.

[Brief description of the drawings]

FIG. 1 is a schematic view of a cross section of a semi-cured heat conductive sheet containing magnetic particles and carbon fibers.

FIG. 2 is a schematic view of a cross section of a semi-cured heat conductive sheet containing a carbon fiber having a magnetic substance adhered to the surface.

FIG. 3 is a schematic diagram of a cross section of a heat dissipation structure.

FIG. 4 is a schematic view of a cross section of the heat dissipation structure.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 heat conductive sheet 2 binder 3 magnetic particles 4 carbon fiber 5 carbon fiber having magnetic material adhered to surface 6 high heat section 7 heat radiating section 8 heat radiating structure 9 high heat section 10 heat radiating structure

Continued on the front page (72) Inventor Ryoji Setaka 2-11-24 Tsukiji, Chuo-ku, Tokyo Inside JSR Corporation (72) Inventor Hozumi Sato 2-11-24 Tsukiji 2-chome, Chuo-ku, Tokyo J F-term in SR Inc. (Reference) 4F071 AA01 AA33 AA67 AB03 AD01 AE14 AE17 AF44 AH12 AH13 BC01 5E322 AA01 FA04 5F036 AA01 BB21 BD11 BD21

Claims (6)

[Claims] 1. A thermally conductive sheet containing a binder, a magnetic substance and carbon fibers, wherein the binder comprises:
The heat conductive sheet, wherein the magnetic material and the carbon fibers are oriented in a thickness direction of the heat conductive sheet. 2. A heat dissipating structure, wherein a high heat portion and a heat dissipating portion are joined via the heat conductive sheet according to claim 1. 3. A heat dissipation structure, wherein the heat conductive sheet according to claim 1 is present on a surface of a high heat portion. 4. The heat radiating structure according to claim 2, wherein the high heat portion is a heating element. 5. The semiconductor device, a semiconductor package, a power transistor, a PTC device, a thyristor,
Heating coil of high voltage rotating machine, coil of voice coil, Plas
The heat dissipation structure according to claim 2, wherein the heat dissipation structure is a ma display, an EL panel, an LD, or an LED. 6. The high-heat portion includes a semiconductor element, a semiconductor package, a power transistor, a PTC element, a thyristor,
The heat dissipation structure according to claim 3, wherein the heat dissipation structure is a light emitting body such as a printed board, a heater of an image forming apparatus, a high-temperature fluid, or a light bulb.