JP2012158695A - Heat conductive sheet and heat dissipation plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat conductive sheet having excellent thermal conductivity and handleability.SOLUTION: The heat conductive sheet includes: a thermoplastic poly(meth)acrylic acid ester high molecular compound (A) having a glass transition temperature of ≤50°C; inorganic particles (B) which are at least one selected from graphite particles and hexagonal boron nitride particles having a scale-like shape, an elliptical spherical shape or a rod-like shape, and in which the (0001) crystal surface is oriented in the plane direction of the scale, in the long axis direction of the elliptical sphere or in the long axis direction of the rod; and a phenolic high molecular compound (C). In the heat conductive sheet, the plane direction of the scale, the long axis direction of the elliptical sphere or the long axis direction of the rod of the inorganic particles (B) is oriented in the thickness direction.

Description

  The present invention relates to a heat conductive sheet and a heat dissipation device.

  In recent years, the density of wiring on multilayer wiring boards and semiconductor packages has increased, the mounting density of electronic components has increased, and the amount of heat generated per unit area has increased due to the increased integration of semiconductor elements. It has become desirable to improve.

  2. Description of the Related Art Generally, a heat radiating device that dissipates heat by using a heat conductive grease or a heat conductive sheet and sandwiching it between a heat generating body such as a semiconductor package and a heat radiating body such as aluminum or copper is used. In general, a thermal conductive sheet is superior in workability when assembling a heat dissipation device compared to a thermal conductive grease.

  Examples of a method for sandwiching a thermal conductive grease or a thermal conductive sheet between the heat generating body and the heat radiating body include a method of applying pressure using a spring at room temperature, a method of thermocompression bonding, and the like. The former has the advantage of being easy and easy to have reworkability, but it is difficult to obtain sufficient adhesion because it is not heated. On the other hand, the method of thermocompression bonding at a high temperature has an advantage that it is easy to achieve both the strength at room temperature and the flexibility necessary for adhesion at the time of crimping. In the contact method, the latter method is used.

  In recent years, CPU chips have a tendency to increase in area due to multi-core and multi-chip, and the pressure for pressure bonding tends to be reduced, and further flexibility in pressure bonding is required.

  Generally, metallic indium or thermal grease is used between the CPU and the spreader of the desktop PC. Since the thermal conductivity of the thermal grease is low, the thermal resistance cannot be reduced unless the film is thinned, and the reliability is lowered when the film is thinned. On the other hand, indium metal requires heating at about 150 ° C. or more when fused, and since it is necessary to perform surface treatment on the chip and spreader to make a firm bond, the process becomes complicated. In addition, metal indium is a rare metal, so the amount of resources is limited.

  In general, the heat conductive sheet is often in the form of a resin sheet filled with a heat conductive filler. So-called silicone gel sheets filled with an inorganic filler such as alumina in a crosslinked silicone gel, paraffin, EVA, or the like. A so-called phase change sheet or the like in which an inorganic filler such as alumina is filled in a resin liquefied by heat at the time of operation of a semiconductor is generally used. However, these materials do not have such a high thermal conductivity that they can be used between a CPU and a spreader such as a desktop PC or server that generate a large amount of heat.

As one of the methods to dramatically improve the thermal conductivity of the resin sheet filled with the thermal conductive filler, an inorganic powder with particularly high thermal conductivity is selected as the thermal conductive filler, and it is further perpendicular to the sheet surface. Various oriented thermal conductive sheets have been proposed.
For example, a heat conductive sheet (for example, refer to Patent Document 1) in which a heat conductive filler (boron nitride) is oriented in a direction substantially perpendicular to the sheet surface, or a carbon fiber dispersed in a gel material is perpendicular to the sheet surface. A thermally conductive sheet having an oriented structure (see, for example, Patent Document 2) has been proposed.

Japanese Patent Laid-Open No. 2002-26202 JP 2005-82721 A

  However, if the thermal conductive filler is oriented perpendicularly to the sheet surface as in the thermal conductive sheets described in Patent Documents 1 and 2, the tearing strength of the sheet becomes weak, so it is difficult to reduce the film thickness in order to maintain the handling strength. As a result, it may be difficult to sufficiently reduce the thermal resistance. When the resin is cross-linked to maintain strength, the deformability of the sheet is restricted. As a result, particularly when the film is thinned, sufficient adhesion cannot be obtained, and the thermal resistance tends to be difficult to sufficiently reduce.

  This invention makes it a subject to provide the heat conductive sheet excellent in heat conductivity and a handleability. Another object of the present invention is to provide a heat dissipation device having a high heat dissipation capability.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have a glass transition temperature of 50 ° C. or lower and a thermoplastic poly (meth) acrylate ester-based polymer having a high glass transition temperature. Molecular compound (A) and graphite having a scaly shape, an elliptical shape, or a rod shape, and the (0001) crystal plane in the crystal is oriented in the surface direction of the scaly, the major axis direction of the ellipsoid, or the major axis direction of the rod Particles and an inorganic particle (B) which is at least one selected from hexagonal boron nitride particles and a phenolic polymer compound (C), and the surface direction of the scale of the inorganic particles (B), elliptical It has been found that a heat conductive sheet excellent in heat conductivity and handleability can be obtained by orienting the long axis direction of the sphere or the long axis direction of the rod in the thickness direction of the heat conductive sheet.

That is, the present invention is as follows.
<1> Glass transition temperature of 50 ° C. or lower, thermoplastic poly (meth) acrylate polymer compound (A), scaly, oval or rod-like graphite particles and hexagonal boron nitride An inorganic particle (B) that is at least one selected from particles, and whose (0001) crystal plane is oriented in the plane direction of the scale, the long axis direction of the ellipsoid, or the long axis direction of the rod; and phenol A high molecular compound (C), and the surface direction of the scale of the inorganic particles (B), the major axis direction of the ellipse, or the major axis direction of the rod is oriented in the thickness direction. It is a conductive sheet.
Such a heat conductive sheet has high heat conductivity, has handleability at room temperature, and has a strength capable of being handled with a free film, and can be suitably used for heat dissipation.

<2> The heat conductive sheet according to <1>, wherein the phenolic polymer compound (C) has a softening temperature of 50 ° C. or higher and 200 ° C. or lower.
Thereby, the strength at normal temperature and the adhesiveness at the time of thermocompression bonding can be achieved at a high level.

<3> The content of the inorganic particles (B) is 40% by mass to 75% by mass in the total mass, and the content of the phenolic polymer compound (C) is from the total mass to the inorganic particles (B). It is a heat conductive sheet as described in said <1> or <2> which is 10 mass% or more and 75 mass% or less in the mass except this.
Thereby, high thermal conductivity and high adhesion in a thin film can be achieved.

<4> The poly (meth) acrylate polymer compound (A) includes a structural unit derived from at least one of n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate, and has a weight average. It is a heat conductive sheet of any one of said <1>-<3> whose molecular weight is 200,000 or more and 600,000 or less.
Thereby, the heat conductive sheet which is further excellent in compatibility of strength and stress relaxation property can be constituted.

<5> The phenolic polymer compound (C) is the heat conductive sheet according to any one of <1> to <4>, which is a terpene phenol resin.
Thereby, the heat conductive sheet which is further excellent in compatibility of strength and stress relaxation property can be constituted.

<6> The heat conductive sheet according to any one of <1> to <5>, further including a phosphate ester-based flame retardant (D).
Thereby, the heat conductive sheet excellent in a flame retardance can be comprised.

<7> The content of the poly (meth) acrylate polymer compound (A) is 5% by mass to 25% by mass in the total mass, and the content of the inorganic particles (B) is in the total mass. 40 mass% or more and 75 mass% or less, and the content of the phenolic polymer (C) is 5 mass% or more and 40 mass% or less in the total mass, and the phosphate ester flame retardant (D) Is a heat conductive sheet according to the above <6>, wherein the content is 10 mass% or more and 40 mass% or less in the total mass.
Thereby, the heat conductive sheet which is excellent in any of the intensity | strength in normal temperature, heat conductivity, the adhesiveness at the time of thermocompression bonding, the high adhesiveness in a thin film, and a flame retardance can be comprised.

<8> Any one of <1> to <7>, disposed between the heat generator, the heat radiator, and the heat generator and the heat radiator so as to contact both the heat generator and the heat radiator. It is a heat radiating device which has a heat conductive sheet given in any 1 paragraph.
Thereby, the thermal radiation apparatus which has high thermal radiation capability can be comprised.

  ADVANTAGE OF THE INVENTION According to this invention, the heat conductive sheet excellent in heat conductivity and a handleability can be provided. Moreover, according to this invention, the thermal radiation apparatus which has high thermal radiation capability can be provided.

In this specification, the term “process” is not limited to an independent process, and is included in the term if the intended action of the process is achieved even when it cannot be clearly distinguished from other processes. .
In the present specification, numerical ranges indicated using “to” indicate ranges including the numerical values described before and after “to” as the minimum value and the maximum value, respectively.

<Heat conduction sheet>
The heat conductive sheet of the present invention has a glass transition temperature of 50 ° C. or less, a thermoplastic poly (meth) acrylate polymer compound (A), graphite particles having a scale shape, an oval shape or a rod shape, and Inorganic particles (B) which are at least one kind of hexagonal boron nitride particles, and whose (0001) crystal plane is oriented in the plane direction of the scale, the long axis direction of the ellipsoid or the long axis direction of the rod And a phenolic polymer compound (C), and the surface direction of the scale of the inorganic particles (B), the major axis direction of the ellipse or the major axis direction of the rod are oriented in the thickness direction. It is characterized by that.
The heat conductive sheet having such a configuration has excellent heat conductivity and handleability. In particular, it has a strength capable of handling with a free film at room temperature, and further has high adhesion with a thin film, so it is suitable for heat dissipation applications.

(A) Poly (meth) acrylic acid ester polymer compound The poly (meth) acrylic acid ester polymer compound (A) has a glass transition temperature (Tg) of 50 ° C. or lower, preferably from −70 ° C. It is 20 ° C, more preferably -60 ° C to 0 ° C.
When glass transition temperature (Tg) exceeds 50 degreeC, it is inferior to a softness | flexibility and the adhesiveness with respect to a heat generating body and a heat radiator may become inadequate.
The glass transition temperature (Tg) is measured under normal conditions by a differential scanning calorimeter (DSC).
Moreover, a glass transition temperature can be made into a desired range by selecting suitably the kind and content rate of the monomer which comprise a poly (meth) acrylic-ester type polymer compound.

The poly (meth) acrylic acid ester polymer compound (A) has thermoplasticity. Here, the term “thermoplastic” means that the shape can be arbitrarily changed by heating.
Specifically, for example, a non-crosslinked poly (meth) acrylate polymer compound, or a poly (meth) acrylate capable of reversibly cleaving and re-bonding pseudo-crosslinks due to hydrogen bonding or the like by heating. -Based polymer compounds and the like.
On the other hand, the poly (meth) acrylate polymer compound having a three-dimensional network structure due to cross-linking by chemical bonding is difficult to arbitrarily change its shape by heating, and therefore the thermoplastic poly (meth) referred to in the present specification. It does not correspond to the acrylic ester polymer compound (A).

The poly (meth) acrylate polymer compound (A) contains at least one (meth) acrylate ester, and optionally contains other monomers copolymerizable with the (meth) acrylate ester. It can be obtained by polymerizing the composition.
Here, (meth) acrylic acid means at least one of acrylic acid and methacrylic acid.

The (meth) acrylic acid ester constituting the monomer composition is preferably a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms from the viewpoint of thermal conductivity and flexibility of the heat conductive sheet. More preferably, it is a (meth) acrylic acid alkyl ester having a C 2-8 alkyl group.
The alkyl group in the (meth) acrylic acid alkyl ester may be cyclic, linear, or branched, but is preferably linear or branched. The alkyl group may have a substituent. Examples of the substituent include a hydroxy group, a glycidyl group, a dialkylamino group, and the like.

Specific examples of the (meth) acrylate ester include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and (meth) acrylate n- Butyl, i-butyl (meth) acrylate, sec-butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, etc. (Meth) acrylic acid ester having a substituent such as (meth) acrylic acid ester, (meth) acrylic acid hydroxyethyl ester, (meth) acrylic acid glycidyl ester, (meth) acrylic acid dimethylaminoethyl, etc. Can be mentioned.
These may be used alone or in combination of two or more.

  The content rate of the structural unit derived from the (meth) acrylate ester in the poly (meth) acrylate polymer compound (A) is not particularly limited. From the viewpoint of thermal conductivity and flexibility of the heat conductive sheet, it is preferably 70% by mass or more, and more preferably 85% by mass or more.

Examples of monomers other than the (meth) acrylic acid ester constituting the monomer composition include carboxy group-containing monomers such as (meth) acrylic acid and maleic acid, nitrile group-containing monomers such as (meth) acrylonitrile, (meth) acrylamide Amide group-containing monomers such as styrene, and styrene monomers such as styrene.
These may be used alone or in combination of two or more.

  The content rate of the structural unit derived from monomers other than (meth) acrylate ester in the poly (meth) acrylate polymer compound (A) is not particularly limited. From the viewpoint of thermal conductivity and flexibility of the heat conductive sheet, it is preferably 30% by mass or less, and more preferably 15% by mass or less.

The weight average molecular weight of the poly (meth) acrylate polymer compound (A) is not particularly limited. From the viewpoint of thermal conductivity and flexibility of the heat conductive sheet, it is preferably 100,000 or more and 1,000,000 or less, more preferably 200,000 or more and 600,000 or less.
The weight average molecular weight of the poly (meth) acrylic acid ester polymer compound can be measured by a usual method using GPC.

  The poly (meth) acrylate polymer compound (A) is selected from n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and ethyl acrylate from the viewpoint of strength and stress relaxation. A structural unit derived from at least one of butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate, preferably having a weight average molecular weight of 100,000 to 1,000,000. It is more preferable that the weight average molecular weight is 200,000 or more and 600,000 or less including the unit.

  The poly (meth) acrylate polymer compound (A) includes a structural unit derived from a (meth) acrylate having an alkyl group having 1 to 12 carbon atoms, a carboxy group-containing monomer, and a nitrile group-containing monomer. It is preferable that the weight average molecular weight is 100,000 or more and 1,000,000 or less, and is derived from a (meth) acrylic acid ester having an alkyl group having 2 to 8 carbon atoms. And a structure having a content of 2% by mass to 30% by mass derived from at least one selected from a structural unit having a content of 70% by mass to 98% by mass and a carboxy group-containing monomer and a nitrile group-containing monomer. More preferably, the weight average molecular weight is 200,000 or more and 600,000 or less.

  The poly (meth) acrylate polymer compound (A) is composed of a structural unit derived from a (meth) acrylate ester having an unsubstituted alkyl group having 1 to 12 carbon atoms, a hydroxy group, and a glycidyl group. It is also preferable to include a structural unit derived from a (meth) acrylic acid ester having an alkyl group having a selected substituent, and derived from a (meth) acrylic acid ester having an unsubstituted alkyl group having 2 to 8 carbon atoms. The content is derived from a (meth) acrylic acid ester having a structural unit having a content of 70% by mass to 98% by mass and an alkyl group having a substituent selected from a hydroxy group and a glycidyl group, and the content is 2% by mass. It is more preferable to contain a structural unit of ˜30% by mass.

  Furthermore, the poly (meth) acrylate polymer compound (A) is a structural unit derived from a (meth) acrylate ester having an unsubstituted alkyl group having 1 to 12 carbon atoms, a hydroxy group, and a glycidyl group. And a structural unit derived from a (meth) acrylic acid ester having an alkyl group having a substituent selected from the group consisting of a weight average molecular weight of 100,000 or more and 1,000,000 or less, preferably 2 to 8 carbon atoms. It is derived from a (meth) acrylic acid ester having a substituted alkyl group and has a structural unit having a content of 70% by mass to 98% by mass and an alkyl group having a substituent selected from a hydroxy group and a glycidyl group (meta ) Derived from acrylic acid ester and containing 2 to 30% by mass of a structural unit, and having a weight average molecular weight of 200,000 or more and 600,000 or less More preferably.

The content of the thermoplastic poly (meth) acrylate polymer compound (A) is preferably 3 to 30% by mass, and 5 to 25% by mass in the total mass of the heat conductive sheet. Is more preferable.
There exists a tendency which can suppress that a sheet | seat becomes weak because it is 3 mass% or more, and there exists a tendency for thermal conductivity and intensity | strength to improve more because it is 30 mass% or less.

(B) Inorganic particles The heat conduction sheet is at least one selected from graphite particles and hexagonal boron nitride particles that are flaky, oval or rod-shaped, and the (0001) crystal plane is the surface direction of the flaky particles, It contains at least one kind of inorganic particles oriented in the major axis direction of the ellipsoid or the major axis direction of the rod.
By including inorganic particles having such a specific structure, excellent thermal conductivity can be achieved.

The shape of the inorganic particles is scaly, oval or rod-like, and of these, scaly is preferable. When the shape of the inorganic particles is a scale shape, an oval shape or a rod shape, a heat conductive sheet excellent in heat conductivity and moldability can be configured.
On the other hand, when the shape of the inorganic particles is spherical or indeterminate, the thermal conductivity may be inferior, and when it is fibrous, it may be difficult to form a sheet and the productivity may be inferior.

The inorganic particles are at least one selected from graphite particles and hexagonal boron nitride particles. Therefore, the crystals of the inorganic particles take a hexagonal form. In the inorganic particles, a plane in which a six-membered ring is formed in a hexagonal crystal form (hereinafter also referred to as “six-membered ring plane”), that is, a (0001) crystal plane is oriented in a specific direction in the particle. Specifically, when the shape of the inorganic particles is scaly, the (0001) crystal plane is oriented in the plane direction of the scaly. Further, when the shape of the inorganic particles is the ellipsoid, the (0001) crystal plane is oriented in the major axis direction of the ellipse. Furthermore, when the shape of the inorganic particles is rod-like, the (0001) crystal plane is oriented in the major axis direction of the rod. Since the inorganic particles have such a specific crystal structure, the thermal conductivity is excellent.
Here, the long axis in the case where the shape of the inorganic particles is elliptical or rod-shaped means that the inorganic particles are observed with an SEM (scanning electron microscope, magnification of about 20 to 200 times) and are observed in two parallel planes. This means an axis that passes through two contact points between the plane and the inorganic particles that are selected so that the distance between the planes is maximum.

The orientation of the (0001) crystal plane in such inorganic particles can be confirmed by X-ray diffraction measurement. Specifically, it can be confirmed as follows.
First, a measurement sample sheet in which the surface direction of the scale of the inorganic particles (B), the long axis direction of the ellipsoid, or the long axis direction of the rod is oriented substantially parallel to the surface direction of the sheet or film is prepared. . As a specific method for preparing a sample sheet for measurement, a mixture with a resin containing 10% by volume or more of graphite particles or hexagonal boron nitride particles is formed into a sheet. As the “resin” used here, a resin corresponding to a thermoplastic poly (meth) acrylate polymer compound (A) can be used. Any material that does not show a peak that hinders X-ray diffraction, such as an amorphous resin, or a material that can be shaped can be used even if it is not a resin.

  A sheet of this mixture is pressed to 1/10 or less of the original thickness. Subsequently, the operation of crushing the pressed sheets and further crushing the laminated body to 1/10 or less is repeated three or more times. By this operation, in the prepared measurement sample sheet, the surface direction of the scale of the inorganic particles (B), the major axis direction of the ellipse, or the major axis direction of the rod is substantially the surface direction of the measurement sample sheet. It will be in the state of parallel orientation.

When X-ray diffraction measurement is performed on the surface of the sample sheet for measurement prepared as described above in both cases of graphite particles and hexagonal boron nitride particles, graphite particles or hexagonal crystals appearing around 2θ = 77 °. The value obtained by dividing the height of the peak corresponding to the (110) plane of boron particles by the height of the peak corresponding to the (002) plane of graphite or hexagonal boron nitride particles appearing near 2θ = 27 ° is 0. ~ 0.02.
From the above, “the (0001) crystal plane in the crystal is oriented in the plane direction of the scale, the long axis direction of the ellipsoid or the long axis direction of the rod” means that the inorganic particles (B) and thermoplastic are used. An X-ray diffraction measurement is performed on the surface of a sheet of a composition containing a poly (meth) acrylic acid ester polymer compound (A) and the like, and both graphite particles and hexagonal boron nitride particles are used. The height of the peak corresponding to the (110) plane of graphite particles or hexagonal boron nitride particles appearing near 2θ = 77 ° is set to (002) of the graphite particles or hexagonal boron nitride particles appearing near 2θ = 27 °. ) It can be seen that the value divided by the height of the peak corresponding to the plane is 0 to 0.02.

As the graphite particles, for example, flaky graphite powder, artificial graphite powder, exfoliated graphite powder, acid-treated graphite powder, expanded graphite powder, carbon fiber flakes and other scaly, oval or rod-like graphite particles may be used. it can.
Examples of the hexagonal boron nitride particles include plate-like boron nitride powder and scaly boron nitride powder.
These can be appropriately selected from commercially available graphite particles or hexagonal boron nitride particles.

  The inorganic particles are preferably those that easily become scaly graphite particles when mixed with the thermoplastic poly (meth) acrylate polymer compound (A). Specifically, flake graphite particles of exfoliated graphite powder and expanded graphite powder are preferable. Thereby, it is easy to orient the graphite particles in a desired state, and it is easy to maintain contact between the particles, and high thermal conductivity can be achieved.

The size of the inorganic particles (B) is not particularly limited, but from the viewpoint of improving thermal conductivity, the average value of the major axis is preferably not less than the film thickness of the thermal conductive sheet × 0.8. With such a size, the inorganic particles almost penetrate the heat conductive sheet in the thickness direction, and excellent heat conductivity can be achieved. Note that the theoretical maximum value is the case of all penetrations, and is film thickness × 1.
Here, the “average value of the major axis” means that a cross section in the thickness direction of the heat conductive sheet is observed using a SEM (scanning electron microscope, magnification of about 20 to 200 times), and about 50 arbitrary inorganic particles are visible. The major axis is measured from the direction in which it is located, and the average value is obtained.
The major axis of the inorganic particles is a length that maximizes the distance between the two surfaces when the observed inorganic particles are sandwiched between two parallel surfaces.

The weight average particle diameter of the inorganic particles (B) is not particularly limited, but is preferably 20 μm to 1000 μm and more preferably 40 μm to 500 μm from the viewpoint of thermal conductivity and flexibility.
The weight average particle size of the inorganic particles (B) is usually measured by classifying with a JIS sieve, weighing each particle size component with an electronic balance, and obtaining a weight distribution curve.

The content of the inorganic particles (B) in the heat conductive sheet is not particularly limited and can be appropriately selected depending on the shape and type of the inorganic particles. Especially, it is preferable that it is 40 mass%-80 mass% in the mass of the whole heat conductive sheet, and it is more preferable that it is 50 mass%-75 mass%.
There exists a tendency for thermal conductivity to improve that the content rate of an inorganic particle is 40 mass% or more. Moreover, the softness | flexibility of a heat conductive sheet improves that it is 80 mass% or less, and there exists a tendency for adhesiveness to improve.

(C) Phenol polymer compound The heat conductive sheet contains at least one phenol polymer compound. By including the phenolic polymer compound, the mechanical strength of the heat conductive sheet is improved, and the heat conductive sheet itself (hereinafter also referred to as “free film”) having no protective film or the like is excellent.
Specific examples of the phenolic polymer compound include cresol novolac resin, phenol novolac resin, dicyclopentadiene ring type phenol resin, phenol aralkyl resin, naphthol resin, rosin-modified phenol resin, terpene phenol resin and the like.
These phenol polymer compounds can be appropriately selected from commercially available phenol polymer compounds.

Among these, at least one selected from terpene phenol resins and phenol novolac resins is preferable, and at least one selected from terpene phenol resins is more preferable.
These phenolic polymer compounds are highly stable and have excellent compatibility with the poly (meth) acrylic acid ester polymer compound (A). Conductivity and flexibility can be achieved.

The terpene phenol resin is obtained by modifying a natural resin extract component with a phenol resin, and examples thereof include YS Polystar and Mighty Ace manufactured by Yashara Chemical, Tamanol manufactured by Arakawa Chemical, and TP series of Kaisai Xiamen (Xiamen) Chemical Co., Ltd. .
The phenol novolac resin includes monofunctional phenols such as phenol, o-cresol, m-cresol, p-cresol, bifunctional phenols such as catechol, resorcinol, hydroquinone, bisphenol A, bisphenol F, bisphenol S, and 1 Phenol novolac resin in which trifunctional phenols such as 1,2,3-trihydroxybenzene, 1,2,4-trihydroxybenzene, 1,3,5-trihydroxybenzene and the like are connected by a methylene chain, monofunctional or polyfunctional A phenol novolac resin in which a functional phenol and a xylylene glycol dialkyl ether or the like are connected by a methylene chain or the like can be exemplified. Specific examples include phenol / p-xylene glycol dimethyl ether polycondensate.

Although the softening temperature of the phenolic polymer compound is not particularly limited, it is preferably 50 ° C. or more and 200 ° C. or less, and 80 ° C. or more and 160 ° C. or less from the viewpoint of the strength of the heat conductive sheet and the adhesiveness during thermocompression bonding. More preferably.
When the softening temperature of the phenolic polymer compound is 50 ° C. or higher, the strength at normal temperature tends to be further improved and the handleability tends to be further improved. Moreover, there exists a tendency which the adhesiveness at the time of thermocompression bonding improves more, and the mixing property at the time of manufacture improves more that it is 200 degrees C or less.
The softening temperature is measured by the ring and ball method (JIS-K2207).
Moreover, the softening temperature can be made into a desired range by selecting appropriately the kind of monomer which comprises a phenol type high molecular compound, content rate, a polymerization degree, etc.

The weight average molecular weight of the phenolic polymer compound is not particularly limited. From the viewpoint of the strength and flexibility of the heat conductive sheet, it is preferably 200 or more and 10,000 or less, and more preferably 500 or more and 2000 or less.
In addition, the weight average molecular weight of a phenol-type high molecular compound can be measured by the normal method using GPC.

The content of the phenolic polymer compound (C) in the heat conductive sheet is not particularly limited, but is 10% by mass to 75% by mass in the mass excluding the inorganic particles (B) from the total mass of the heat conductive sheet. Is preferable, and it is more preferable that it is 12 mass% or more and 60 mass% or less.
The intensity | strength in normal temperature improves more that a content rate is 10 mass% or more. Moreover, it can suppress that a sheet | seat becomes brittle as it is 75 mass% or less. Moreover, it is suppressed that it is compressed too much at the time of thermocompression bonding, the orientation in the thickness direction of the inorganic particles (B) can be maintained in a desired state, and there is a tendency that excellent thermal conductivity can be achieved.

  From the viewpoint of thermal conductivity, strength, and flexibility, the thermal conductive sheet contains at least one phenolic polymer compound (C) selected from terpene phenol resin and phenol novolac resin, and inorganic particles from the total mass of the thermal conductive sheet. It is preferable to contain 10% by mass to 75% by mass in the mass excluding (B), and a phenolic polymer compound selected from terpene phenol resin and phenol novolac resin and having a softening temperature of 50 ° C. or more and 200 ° C. or less. It is more preferable that 12 mass% or more and 60 mass% or less are included in the mass excluding the inorganic particles (B) from the total mass of the heat conductive sheet.

  The content ratio of the poly (meth) acrylate polymer compound (A) and the phenol polymer compound (C) in the heat conductive sheet is not particularly limited, but from the viewpoint of strength, stress relaxation and flexibility, poly (meth) The content ratio ((C) / (A)) of the phenolic polymer compound (C) to the (meth) acrylate polymer compound (A) is preferably 0.3 to 3, and preferably 0.6 to 2 It is more preferable that

  Furthermore, the heat conductive sheet is at least selected from n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate from the viewpoint of strength, stress relaxation and flexibility. A phenol compound selected from a (meth) acrylic acid ester polymer compound (A) having a structural unit derived from one species and having a weight average molecular weight of 100,000 to 1,000,000, and a terpene phenol resin and a phenol novolac resin It is more preferable that the polymer compound (B) is included, including a structural unit derived from at least one of n-butyl acrylate and 2-ethylhexyl acrylate, and having a weight average molecular weight of 200,000 to 600,000. (Meth) acrylic acid ester polymer compound (A) and phenolic terpene phenol resin More preferably contains a molecular compound (B).

(D) Flame retardant The heat conductive sheet can contain at least one flame retardant. It does not specifically limit as a flame retardant, For example, it can select and use suitably from a red phosphorus flame retardant, a phosphate ester flame retardant, etc.
In the present invention, it is preferably at least one phosphoric acid ester flame retardant. Phosphoric ester-based flame retardants are highly safe and have an excellent effect of improving adhesion by a plastic effect.

  Examples of red phosphorus flame retardants include pure red phosphorus powder, various coatings for the purpose of improving safety and stability, and master batches. Specific examples include trade names: NOVA RED, NOVA EXCEL, NOVA QUEEL, NOVA pellets, etc., manufactured by Rin Chemical Industry Co., Ltd.

Examples of the phosphate ester flame retardant include aliphatic phosphate esters such as trimethyl phosphate, triethyl phosphate, tributyl phosphate; triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, trixylenyl phosphate, cresyl- Aromatic phosphate esters such as 2,6-xylenyl phosphate, tris (t-butylated phenyl) phosphate, tris (isopropylated phenyl) phosphate, triaryl isopropylate; resorcinol bisdiphenyl phosphate, bisphenol A bis ( And aromatic condensed phosphoric acid esters such as diphenyl phosphate) and resorcinol bis-dixylenyl phosphate.
These may be used alone or in combination of two or more.

  Although the content rate of the flame retardant (D) in the heat conductive sheet is not particularly limited, it is preferably 10% by mass or more and 40% by mass or less in the heat conductive sheet from the viewpoint of flame retardancy and adhesion, and 20% by mass. More preferably, it is 35 mass% or less.

When the heat conductive sheet contains a phosphoric acid ester-based flame retardant (D) in addition to the poly (meth) acrylic acid ester-based polymer compound (A), the inorganic particles (B) and the phenolic polymer compound, each component The content of the poly (meth) acrylate polymer compound (A) is 5% by mass or more and 25% by mass or less in the total mass, and the content of the inorganic particles (B) is in the total mass. Of the phenolic polymer compound (C) is 5% by mass or more and 40% by mass or less of the total mass of the phosphoric ester-based flame retardant (D). The content is preferably 10% by mass or more and 40% by mass or less in the total mass.
When the content of each component is within the above range, it is possible to constitute a heat conductive sheet that is excellent in any of strength at normal temperature, thermal conductivity, adhesion during thermocompression bonding, high adhesion in a thin film, and flame retardancy. .

In the heat conductive sheet of the present invention, the inorganic particles (B) are oriented in a specific direction. Specifically, when the shape of the inorganic particles is scaly, the surface direction of the scaly is oriented in the thickness direction of the heat conductive sheet. When the shape of the inorganic particles is an ellipsoid, the major axis direction of the ellipse is oriented in the thickness direction of the heat conductive sheet. Furthermore, when the shape of the inorganic particles is rod-shaped, the long axis direction of the rod is oriented in the thickness direction of the heat conductive sheet.
Excellent thermal conductivity can be achieved because the inorganic particles are oriented in this way.

  In the present invention, “orientation in the thickness direction of the heat conductive sheet” means a direction in which a cross section in the thickness direction of the heat conductive sheet is observed using an SEM (scanning electron microscope) and any 50 inorganic particles are visible. Then, an angle with respect to the surface of the inorganic particles or the surface of the heat conductive sheet in the long axis direction (a complementary angle is adopted when 90 degrees or more) is measured, and the average value is in a range of 60 to 90 degrees.

As a method for orienting the inorganic particles in the specific direction as described above, for example, a method for producing a heat conductive sheet as follows can be mentioned.
That is, a sheet-like composition comprising a poly (meth) acrylate polymer compound (A), inorganic particles (B), and a phenol polymer compound, the surface or long axis of the inorganic particles being the surface of the sheet A sheet-like composition substantially parallel to is prepared as described above.
A predetermined number of the produced sheet-like compositions are laminated to form a laminate. The obtained laminated body is sliced to a desired thickness in a plane parallel to the lamination direction to produce a heat conduction sheet, so that the surface or long axis of the inorganic particles is oriented in the thickness direction of the heat conduction sheet. Can be obtained.

Moreover, in the heat conductive sheet of this invention, in order to protect an adhesive surface, you may cover the adhesive surface of the heat conductive sheet before use with a protective film.
Examples of the material for the protective film include resins such as polyethylene, polyester, polypropylene, polyethylene terephthalate, polyimide, polyetherimide, polyether naphthalate, and methylpentene film, and metals such as coated paper, coated cloth, and aluminum.
Two or more kinds of these protective films may be combined to form a multilayer film, and the protective film whose surface is treated with a release agent such as silicone or silica is preferably used.

<Heat dissipation device>
The heat dissipating device of the present invention has a heat generating body, a heat dissipating body, and the heat conductive sheet, and is disposed between the heat generating body and the heat dissipating body so as to be in contact with both the heat generating body and the heat dissipating body. can get.
Since the heat conductive sheet is interposed between the heat generating body and the heat radiating body, the heat from the heat generating body can be efficiently conducted to the heat radiating body.

As a heat generating body, that whose surface temperature does not exceed 200 degreeC is preferable. When the surface temperature of the heating element does not exceed 200 ° C., a decrease in flexibility of the heat conductive sheet is suppressed, and a decrease in heat conductivity can be suppressed.
The temperature range in which the heat conductive sheet of the present invention can be used particularly preferably is −10 ° C. to 120 ° C., and examples of suitable heating elements include semiconductor packages, displays, LEDs, and electric lamps.

  On the other hand, as a heat sink, for example, a heat sink using aluminum, copper fins, plates, etc., an aluminum or copper block connected to a heat pipe, an aluminum or copper that circulates cooling liquid with a pump inside A typical example is a block, a Peltier element, and an aluminum or copper block having the same.

  The heat dissipating device of the present invention is one in which each surface of the heat conductive sheet of the present invention is placed in contact with a heat generating body and a heat dissipating body. There is no limitation on the contact method as long as the heating element, the heat conductive sheet, and the heat dissipation element can be fixed in a sufficiently adhered state, but the heating method is heated to 50 ° C to 170 ° C and applied to about 0.1 MPa to 2 MPa. It is preferably assembled with a heated thermocompression bonding step, and more preferably assembled with a thermocompression bonding step heated to 70 ° C. to 150 ° C. and pressurized to about 0.15 MPa to 1 MPa.

When the heating temperature is 50 ° C. or higher, or the applied pressure is 0.1 MPa or higher, sufficient adhesion tends to be obtained. Further, when the heating temperature is 170 ° C. or lower, or the pressing pressure is 2 MPa or lower, the sheet is suppressed from being compressed, so that the orientation state of the inorganic particles is suppressed and the increase in thermal resistance is suppressed. There is a tendency to be able to.
In addition, in the heat radiating device, it is preferable that the heat generating body and the heat radiating body are separately fixed by means such as screws, springs, and other adhesives in order to maintain the close contact.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, “%” is based on mass.

Example 1
Poly (meth) acrylate polymer compound (A), butyl acrylate / ethyl acrylate / acrylonitrile / acrylic acid copolymer (manufactured by Nagase ChemteX Corporation, trade name: HTR-280 modified 2DR, copolymer Mass ratio: 82/10/3/5, Tg: -39 ° C., weight average molecular weight: 530,000: 444 g, scale-like expanded graphite powder (trade name, manufactured by Hitachi Chemical Co., Ltd.) as inorganic particles (B) : HGF-L, mass average diameter: 270 μm, it was confirmed by the method using X-ray diffraction measurement described above that the six-membered ring plane in the crystal was oriented in the plane direction of the scales.): 2156 g, As the phenolic polymer compound (C), terpene phenol resin (manufactured by Yasuhara Chemical Co., Ltd., trade name YS Polystar T145, softening temperature 145 ° C.): 333 g, phosphoric acid ester As a tellurium flame retardant (D), 1067 g of bisphenol A bis (diphenyl phosphate) (phosphate ester flame retardant, manufactured by Daihachi Chemical Industry Co., Ltd., trade name: CR-741) was charged into a 4 L pressure kneader. The mixture was kneaded at a temperature of 156 ° C. to obtain a composition.
The content rate of a phenol type high molecular compound (C) is 18 mass% with respect to the component except an inorganic particle (B), and it contains with respect to the whole of (A), (B), (C), (D). The rates (unit: mass%) were 11.1, 53.9, 8.3, and 26.7, respectively, in this order.

  This composition was put into an extruder and extruded into a flat plate shape having a width of 20 cm and a thickness of 1.5 mm to 1.6 mm to obtain a primary sheet.

  The obtained primary sheet was press-punched using a 40 mm × 150 mm die blade, and 56 sheets of the punched sheets were laminated, and pressure was applied at 80 ° C. for 2 minutes in the laminating direction so that the thickness became 80 mm. Got the body.

  Next, an 80 mm × 150 mm laminated section (surface parallel to the lamination direction) of this molded body was sliced using a woodworking slicer to obtain a heat conductive sheet (I) 80 mm long × 150 mm wide × 0.15 mm thick. It was.

<Evaluation>
(Orientation of inorganic particles)
The cross section of this heat conductive sheet (I) is observed by SEM, and the angle of the scale in the long axis direction (plane direction) to the heat conductive sheet surface is measured from the direction seen for any 50 graphite particles (B). As a result, the average value of the angles was 90 degrees, and it was confirmed that the surface direction of the scale of the graphite particles (B) was oriented in the thickness direction of the heat conductive sheet.

(Measurement of thermal resistance)
A heat conductive sheet was sandwiched between copper plates having a thickness of 1 mm and a diameter of 13.75 mm, and was stopped with two clips (CP-107SI made by PLUS, scissor force 12N to 14N) (pressure conversion value 0.16 to 0.18 MPa). The sample was pressure-bonded at 120 ° C./30 minutes in the state, and after cooling at room temperature, the clip was removed to prepare a sample for evaluation.
Subsequently, the thermal conductivity of this evaluation sample at 25 ° C. was measured using a thermal diffusivity measuring device (manufactured by NETZCH, device name: LFA447). The thermal conductivity of the copper plate was measured in advance, and the thermal conductivity λ (W / mK) of the thermal conductive sheet portion was determined by the three-layer method of the apparatus. The thermal resistance Rth (K · cm ² / W) was obtained from this value and the film thickness t (mm) by the following equation. The film thickness t (mm) is a value obtained by subtracting the thickness of the upper and lower copper plates measured in advance from the thickness of the pressure-bonded sample, and was measured with a micrometer.
Rth = 10 × t / λ (Formula)

The thermal resistance of the heat conductive sheet (I) was a good value of 0.036 (K · cm ² / W).

(Measurement of tensile strength)
Tensile strength was measured with the following apparatus and conditions using a heat conductive sheet punched out to 1 cm × 5 cm.
Equipment used: STROGRAPH ES made by Toyo Seiki
Temperature: 25 ° C
Tensile speed: 10 mm / min In addition, if a numerical value is 0.10 Mpa or more, it is enough for the handling with a free film.

  The tensile strength of the heat conductive sheet (I) was 0.13 (MPa), which was a value sufficient for handling with a free film.

(Example 2)
In Example 1, operation was carried out in the same manner as in Example 1 except that terpene phenol resin (trade name YS Polystar T130, softening temperature 130 ° C.): 333 g was used as the phenolic polymer compound (C). Thus, a heat conductive sheet (II) having a length of 80 mm × width of 150 mm × thickness of 0.15 mm was obtained.
The content rate of a phenol type high molecular compound (C) is 18 mass% with respect to the component except an inorganic particle (B), and it contains with respect to the whole of (A), (B), (C), (D). The rates (unit: mass%) were 11.1, 53.9, 8.3, and 26.7, respectively, in this order.

  The cross section of this heat conductive sheet (II) is observed with an SEM, and the angle of the scale in the long axis direction (plane direction) to the heat conductive sheet surface is measured from the direction seen for any 50 graphite particles (B). As a result, the average value of the angles was 88 degrees, and it was recognized that the surface direction of the scale of the graphite particles (B) was oriented in the thickness direction of the heat conductive sheet.

The thermal resistance of the heat conductive sheet (II) was a good value of 0.035 (K · cm ² / W).
Further, the tensile strength of the heat conductive sheet (II) was 0.12 (MPa), which was a value sufficient for handling with a free film.

(Example 3)
Poly (meth) acrylate polymer compound (A), butyl acrylate / ethyl acrylate / acrylonitrile / acrylic acid copolymer (manufactured by Nagase ChemteX Corporation, trade name: HTR-280 modified 2DR, copolymer Mass ratio: 82/10/3/5, Tg: −39 ° C., weight average molecular weight: 530,000): 35 g, scale-like expanded graphite powder (trade name, manufactured by Hitachi Chemical Co., Ltd.) as inorganic particles (B) : HGF-L, mass average diameter: 270 μm, the method using the above-mentioned X-ray diffraction measurement confirmed that the six-membered ring surface in the crystal was oriented in the plane direction of the scale.): 194 g, As the phenolic polymer compound (C), terpene phenol resin (manufactured by Yasuhara Chemical Co., Ltd., trade name YS Polyster T115, softening temperature 115 ° C.): 35 g, phosphate ester As a flame retardant (D), bisphenol A bis (diphenyl phosphate) (phosphate ester flame retardant, manufactured by Daihachi Chemical Industry Co., Ltd., trade name: CR-741): 96 g in a polyethylene bag was premixed. It knead | mixed (100 degreeC) with the axial roll (made by Kansai roll company), and obtained the composition in the form of the kneading | mixing sheet | seat.
The content rate of a phenol type high molecular compound (C) is 21 mass% with respect to the component except an inorganic particle (B), and content with respect to the whole of (A), (B), (C), (D) The rate (unit: mass%) was 9.7, 53.9, 9.7, and 26.7, respectively, in this order.

  The kneaded sheet is sandwiched between release-treated PET films and pressed using a roll forming machine (manufactured by Hitachi Machine Engineering Co., Ltd., apparatus name: V2S-SR type sheeting hot roll machine), and a primary sheet having a thickness of about 1 mm is obtained. Obtained.

  The obtained primary sheet is press-punched using a 30 mm × 90 mm mold blade, 60 sheets of the punched sheets are stacked, and pressure is applied at 80 ° C. for 2 minutes in the stacking direction so that the thickness becomes 50 mm, and molding is performed. Got the body.

  Next, a 50 mm × 90 mm laminated section of this molded body was sliced using a woodworking slicer to obtain a heat conductive sheet (III) having a length of 50 mm × width of 90 mm × thickness of 0.15 mm.

  The cross section of this heat conductive sheet (III) is observed with SEM, and the angle of the scale in the long axis direction (plane direction) to the heat conductive sheet surface is measured from the direction seen for any 50 graphite particles (B). As a result, the average value of the angle was 89 degrees, and it was recognized that the surface direction of the scale of the graphite particles (B) was oriented in the thickness direction of the heat conductive sheet.

The heat resistance of the heat conductive sheet (III) was 0.038 (K · cm ² / W), which was a good value.
Further, the tensile strength of the heat conductive sheet (III) was 0.11 (MPa), which was a value sufficient for handling with a free film.

Example 4
Poly (meth) acrylate polymer compound (A), butyl acrylate / ethyl acrylate / acrylonitrile / acrylic acid copolymer (manufactured by Nagase ChemteX Corporation, trade name: HTR-280 modified 2DR, copolymer Mass ratio: 82/10/3/5, Tg: −39 ° C., weight average molecular weight: 530,000): 30 g, scale-like expanded graphite powder (trade name, manufactured by Hitachi Chemical Co., Ltd.) as inorganic particles (B) : HGF-L, mass average diameter: 270 μm, the method using the above-mentioned X-ray diffraction measurement confirmed that the six-membered ring surface in the crystal was oriented in the plane direction of the scale.): 194 g, As the phenolic polymer compound (C), phenol / p-xylene glycol dimethyl ether polycondensate (phenol novolac resin: manufactured by Mitsui Chemicals, trade name: Millex X C-LL, softening temperature 77 ° C.): 40 g, as phosphate ester flame retardant (D), bisphenol A bis (diphenyl phosphate) (phosphate ester flame retardant, manufactured by Daihachi Chemical Industry Co., Ltd., trade name: CR -741): Using 96 g, a heat conductive sheet (IV) having a length of 50 mm, a width of 90 mm, and a thickness of 0.15 mm was obtained in the same manner as in Example 3 below.
The content rate of a phenol type high molecular compound (C) is 24 mass% with respect to the component except an inorganic particle (B), and content with respect to the whole of (A), (B), (C), (D) The rate (unit: mass%) was 8.3, 53.9, 11.1, 26.7 in this order, respectively.

  The cross section of this heat conductive sheet (IV) is observed with an SEM, and the angle of the scale in the long axis direction (plane direction) with respect to the surface of the heat conductive sheet is measured from the direction seen for any 50 graphite particles (B). As a result, the average value of the angles was 88 degrees, and it was recognized that the surface direction of the scale of the graphite particles (B) was oriented in the thickness direction of the heat conductive sheet.

The heat resistance of this heat conductive sheet (IV) was 0.040 (K · cm ² / W), which was a good value.
Further, the tensile strength of the heat conductive sheet (IV) was 0.11 (MPa), which was a value sufficient for handling with a free film.

(Example 5)
Poly (meth) acrylic ester polymer compound (A), butyl acrylate / ethyl acrylate / hydroxyethyl acrylate copolymer (manufactured by Nagase ChemteX Corporation, trade name: HTR-811DR, copolymer mass ratio) : 76/19/5, Tg: −43 ° C., weight average molecular weight: 420,000): 363 g, as inorganic particles (B), scaly hexagonal boron nitride (manufactured by Momentive Co., Ltd., trade name: PT-110) The mass average diameter: 35 to 60 μm, and the method using the above-described X-ray diffraction measurement confirmed that the six-membered ring plane in the crystal was oriented in the plane direction of the scale.): 3710 g, phenolic As polymer compound (C), terpene phenol resin (manufactured by Yasuhara Chemical, trade name YS Polystar T130, softening temperature 130 ° C.): 363 g, phosphate ester type As a flame retardant (D), bisphenol A bis (diphenyl phosphate) (phosphate ester flame retardant, manufactured by Daihachi Chemical Industry Co., Ltd., trade name: CR-741): 564 g was charged into a 4 L pressure kneader, and an ultimate temperature of 150 It knead | mixed on the conditions of (degreeC) and obtained the composition.
The content rate of a phenol type high molecular compound (C) is 28 mass% with respect to the component except an inorganic particle (B), and content with respect to the whole of (A), (B), (C), (D) The rate (unit: mass%) was 7.3, 74.2, 7.3, and 11.3, respectively, in this order.
Thereafter, the same operation as in Example 1 was performed to obtain a heat conductive sheet (V) having a length of 80 mm × width of 150 mm × thickness of 0.25 mm.

  The cross section of this heat conductive sheet (V) is observed with an SEM, and the angle of the scale in the long axis direction (plane direction) with respect to the surface of the heat conductive sheet is measured from the direction seen for any 50 graphite particles (B) As a result, the average value of the angles was 90 degrees, and it was confirmed that the surface direction of the scale of the graphite particles (B) was oriented in the thickness direction of the heat conductive sheet.

The heat resistance of the heat conductive sheet (V) was 0.150 (K · cm ² / W), which was a non-conductive and 0.25 mm thick heat conductive sheet.
Further, the tensile strength of the heat conductive sheet (V) was 0.14 (MPa), which was a value sufficient for handling with a free film.

  The contents of the above examples are summarized in Table 1.

(Comparative Example 1)
Poly (meth) acrylate polymer compound (A), butyl acrylate / ethyl acrylate / acrylonitrile / acrylic acid copolymer (manufactured by Nagase ChemteX Corporation, trade name: HTR-280 modified 2DR, copolymer Mass ratio: 82/10/3/5, Tg: −39 ° C., weight average molecular weight: 530,000): 70 g, except that the resin corresponding to the phenolic polymer compound (C) was not blended, A heat conductive sheet (VI) was obtained by the same operation as in Example 3.
The content rate of a phenol type polymer compound (C) is 0 mass% with respect to the component except an inorganic particle (B), and content with respect to the whole of (A), (B), (C), (D) The rate (unit: mass%) was 19.4, 53.9, 0, and 26.7, respectively, in this order.

  The cross section of this heat conductive sheet (VI) is observed with an SEM, and the angle of the scale in the long axis direction (plane direction) to the surface of the heat conductive sheet is measured from the direction seen for any 50 graphite particles (B). As a result, the average value of the angles was 88 degrees, and it was recognized that the surface direction of the scale of the graphite particles (B) was oriented in the thickness direction of the heat conductive sheet.

The thermal resistance of the heat conductive sheet (VI) was inferior at 0.064 (K · cm ² / W).
The tensile strength of the heat conductive sheet (VI) was 0.06 (MPa), which was insufficient for handling with a free film.

(Comparative Example 2)
The terpene phenol resin used as the phenolic polymer compound (C) in the blending composition of Example 3 (manufactured by Yasuhara Chemical Co., Ltd., trade name YS Polystar T115, softening temperature 115 ° C.): instead of 35 g, the phenolic polymer compound Polybutene resin not corresponding to (C) (manufactured by NOF Corporation, polybutene 200N): A heat conductive sheet (VII) was obtained in the same manner as in Example 3 except that 35 g was used. The content rate of a phenol type polymer compound (C) is 0 mass% with respect to the component except an inorganic particle (B), and content with respect to the whole of (A), (B), (C), (D) The rate (unit: mass%) was 9.7, 53.9, 0, and 26.7, respectively, in this order.

  Observe the cross section of this thermal conductive sheet (VII) with SEM, and measure the angle of the scale in the long axis direction (plane direction) to the thermal conductive sheet surface from the direction seen for any 50 graphite particles (B). As a result, the average value of the angle was 89 degrees, and it was recognized that the surface direction of the scale of the graphite particles (B) was oriented in the thickness direction of the heat conductive sheet.

The thermal resistance of the heat conductive sheet (VII) was inferior at 0.055 (K · cm ² / W).
Moreover, the tensile strength of this heat conductive sheet (VII) was 0.05 (MPa), showing an insufficient value for handling with a free film.

(Comparative Example 3)
The terpene phenol resin used as the phenolic polymer compound (C) in the blending composition of Example 3 (manufactured by Yasuhara Chemical Co., Ltd., trade name YS Polystar T115, softening temperature 115 ° C.): instead of 35 g, the phenolic polymer compound Aliphatic saturated hydrocarbon resin (Arakawa Chemical Co., Ltd., Alcon P-140) not corresponding to (C): The same operation as in Example 3 was performed except that 35 g was used, but the kneaded sheet was separated. Step of sandwiching between mold-treated PET films and pressing using a roll forming machine (manufactured by Hitachi Machine Engineering Co., Ltd., device name: V2S-SR type sheeting hot roll machine) to obtain a primary sheet having a thickness of about 1 mm However, the cohesive force was insufficient and the primary sheet could not be produced.

(Comparative Example 4)
Poly (meth) acrylate polymer compound (A), butyl acrylate / ethyl acrylate / acrylonitrile / acrylic acid copolymer (manufactured by Nagase ChemteX Corporation, trade name: HTR-280 modified 2DR, copolymer Mass ratio: 82/10/3/5, Tg: −39 ° C., weight average molecular weight: 530,000): 726 g, except that the resin corresponding to the phenolic polymer compound (C) was not blended, A heat conductive sheet (VIII) was obtained by the same operation as in (Example 5). The content of the phenolic polymer or copolymer (C) is 0% by mass with respect to the components excluding the inorganic particles (B), and the content of (A), (B), (C), and (D) The rate (unit: mass%) was 14.6, 74.2, 0, and 11.3, respectively, in this order.

  The cross section of this heat conductive sheet (VIII) is observed with an SEM, and the angle of the scale in the long axis direction (plane direction) to the heat conductive sheet surface is measured from the direction seen for any 50 graphite particles (B). As a result, the average value of the angles was 90 degrees, and it was confirmed that the surface direction of the scale of the graphite particles (B) was oriented in the thickness direction of the heat conductive sheet.

The heat resistance of the heat conductive sheet (VIII) was 0.240 (K · cm ² / W), which was non-conductive and inferior as a heat conductive sheet having a thickness of 0.25 mm.
Further, the tensile strength of the heat conductive sheet (VIII) was 0.10 (MPa), which was a value sufficient for handling with a free film.
The above results are shown in Table 2 below.

  As mentioned above, it turns out that the heat conductive sheet of this invention has the outstanding heat conductivity. Moreover, it turns out that it is excellent in tensile strength and is easy to handle.

Claims (8)

A glass transition temperature of 50 ° C. or lower and a thermoplastic poly (meth) acrylate polymer compound (A);
It is at least one selected from graphite particles and hexagonal boron nitride particles that are flaky, oval or rod-like, and the (0001) crystal plane is the surface direction of the flaky, the major axis direction of the oval sphere, or the rod Inorganic particles (B) oriented in the major axis direction of
A phenolic polymer compound (C),
The heat conductive sheet in which the surface direction of the scale of the inorganic particles (B), the major axis direction of the ellipsoid, or the major axis direction of the rod is oriented in the thickness direction.   The heat conductive sheet of Claim 1 whose softening temperature of the said phenol type high molecular compound (C) is 50 to 200 degreeC.   The content of the inorganic particles (B) is 40% by mass to 75% by mass in the total mass, and the content of the phenolic polymer compound (C) is the total mass excluding the inorganic particles (B). The heat conductive sheet according to claim 1 or 2 which is 10 mass% or more and 75 mass% or less in mass.   The poly (meth) acrylate polymer compound (A) includes a structural unit derived from at least one of n-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate, and has a weight average molecular weight of 20. The heat conductive sheet according to any one of claims 1 to 3, which is from 10,000 to 600,000.   The heat conductive sheet according to any one of claims 1 to 4, wherein the phenolic polymer compound (C) is a terpene phenol resin.   The heat conductive sheet according to any one of claims 1 to 5, further comprising a phosphate ester-based flame retardant (D). The content of the poly (meth) acrylate polymer compound (A) is 5% by mass or more and 25% by mass or less in the total mass,
The content of the inorganic particles (B) is 40% by mass to 75% by mass in the total mass,
The content of the phenolic polymer compound (C) is 5% by mass or more and 40% by mass or less in the total mass,
The heat conductive sheet of Claim 6 whose content rate of the said phosphate ester type flame retardant (D) is 10 mass% or more and 40 mass% or less in a gross mass. A heating element;
A radiator,
The heat conductive sheet according to any one of claims 1 to 7, which is disposed between the heat generating body and the heat radiating body so as to be in contact with both the heat generating body and the heat radiating body. A heat dissipation device.