JP5879782B2 - HEAT CONDUCTIVE COMPOSITE SHEET, PROCESS FOR PRODUCING THE SAME, AND HEAT DISSULATING DEVICE - Google Patents

Description

  The present invention relates to a heat conductive composite sheet, a manufacturing method thereof, and a heat dissipation device using the heat conductive composite sheet.

Conventionally, in electronic devices and optical devices such as semiconductor packages, displays, personal computers, light emitting diodes (LEDs), etc., in order to prevent malfunctions and deterioration of characteristics due to heat from heat-generating components during operation, Thermal conductive sheets have been developed.
This heat conductive sheet is required to have a higher thermal conductivity as the amount of heat generated by the heat generating component increases. Up to now, as one of the methods to dramatically improve the thermal conductivity, boron nitride, which has a particularly high thermal conductivity, is used as a thermal conductive filler (thermal conductive filler) for the polymer compound constituting the sheet-like body. Various heat conductive sheets have been proposed in which an inorganic powder is selected and oriented perpendicularly to the sheet surface (see, for example, Patent Document 1).

In the lighting field, as the density of LEDs increases in recent years, the resin layer that covers the LED bulbs deteriorates due to the heat released from the LED bulbs, and the phenomenon that causes a decrease in the light convergence is increasingly problematic. It has become.
On the other hand, in an electronic device such as a liquid crystal module, a heat conductive sheet or heat conductive grease is sandwiched between an LED board (heat generating element) on which an LED is mounted and a heat radiator made of aluminum, copper, or the like. A heat dissipating device that dissipates heat is used by screwing with a strong torque.

In such a heat radiating device, the heat conductive sheet is generally used more easily than the heat conductive grease because the heat conductive sheet is superior in workability when assembling the device.
However, when the heat conductive sheet is used, there is a drawback that when the heat conductive sheet is tightened with a strong torque as described above, the heat conductive sheet is destroyed and sufficient heat dissipation characteristics cannot be secured.

  In addition, a technique using a glass fiber cloth that has been sealed with a cured product of a siloxane-containing ethylene propylene diene rubber composition containing an inorganic filler as an intermediate material of a heat conductive sheet is known. Thereby, in order to be able to endure the use in a high-temperature, high-humidity atmosphere, improvement of chemical resistance, insulation, and plasma gas resistance is achieved (for example, refer patent document 2).

Japanese Patent Laid-Open No. 2002-26202 JP 7-125137 A

  However, since the tearing strength of the sheet is weakened when the thermal conductive filler is oriented perpendicularly to the sheet surface as in the thermal conductive sheet described in Patent Document 1, it is difficult to reduce the thickness 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, in particular when the film is thinned, sufficient adhesion cannot be obtained, and it may be difficult to sufficiently reduce the thermal resistance.

In addition, in the heat conductive sheet disclosed in Patent Document 2, a slurry-like raw material is impregnated and coated on a glass fiber cloth, and a heat conductive filler is uniformly dispersed to form a sheet, thereby ensuring heat conductivity. However, sufficient thermal conductivity is not obtained.
Then, this invention makes it a subject to provide the heat conductive composite sheet which has the outstanding heat conductivity, and was equipped with high mechanical strength, and its manufacturing method. Another object of the present invention is to provide a highly reliable heat dissipating device having a high heat dissipating capability.

  As a result of intensive studies to solve the above problems, the present inventors have provided a porous reinforcing material, preferably a reinforcing material having a plurality of through holes penetrating in the thickness direction, between the two heat conductive layers. By arranging and forming a composite body having a heat conductive layer / reinforcing material / heat conductive layer laminate structure, a highly functional heat conductive composite sheet having excellent thermal conductivity and high mechanical strength can be obtained. I found out that

That is, the present invention relates to the following.
<1> a first heat conductive layer containing scale, sphere or rod-shaped hexagonal boron nitride particles and a poly (meth) acrylate polymer compound having a glass transition temperature of 50 ° C. or lower;
A sheet-like porous reinforcing material,
A second heat conductive layer containing scales, Ryukyu or rod-shaped hexagonal boron nitride particles and a poly (meth) acrylate polymer compound having a glass transition temperature of 50 ° C. or lower is laminated in this order. And
At least part of the pores of the porous reinforcing material is filled with at least one of the poly (meth) acrylic acid ester polymer compound and the hexagonal boron nitride particles,
The hexagonal boron nitride particles contained in the first heat conductive layer and the second heat conductive layer have a (0001) crystal plane of the scale direction, the long axis direction of the Ryukyu, or the long axis direction of the rod shape. And the surface direction of the scale, the major axis direction of the Ryukyu or the major axis direction of the rod are oriented in the thickness direction of the first heat conductive layer, the reinforcing material and the second heat conductive layer. It is a heat conductive composite sheet.
Such a heat conductive composite sheet can be suitably used for heat dissipation of a heat-generating component having high mechanical strength and high calorific value as well as excellent heat conductivity.

<2> The porous reinforcing material has a plurality of through holes penetrating in the thickness direction, and the plurality of through holes are filled with the poly (meth) acrylate polymer compound, and the plurality The heat conductive composite sheet according to <1>, wherein at least a part of the hexagonal boron nitride particles is inserted into at least a part of the through holes.
Thereby, it has higher mechanical strength.
<3> The heat conductive composite sheet according to <1> or <2>, wherein the porous reinforcing material is a woven fabric.
Thereby, the further outstanding mechanical strength can be provided.
<4> The heat conductive composite sheet according to <3>, wherein the woven fabric is made of glass fiber.
Thereby, the mechanical strength in the thin film can be dramatically improved.

<5> The heat conductive composite sheet according to <3> or <4>, wherein the woven fabric is a mesh-like body, and the mesh diameter is 0.38 mm or more.
Thereby, in addition to the effects of the inventions <1> to <4>, excellent thermal conductivity can be ensured while maintaining higher mechanical strength.
<6> The heat conductive composite sheet according to any one of <3> to <5>, wherein a fiber diameter of the woven fabric is 0.6 mm or less.
Thereby, higher thermal conductivity can be secured.

<7> The heat conductive composite sheet according to any one of <3> to <6>, wherein the woven fabric is a biaxial woven fabric or a plain woven fabric.
Thereby, it becomes possible to control the tensile strength and the thermal resistance.
<8> The first heat conductive layer and the second heat conductive layer further contain a flame retardant, and the flame retardant in the total volume of the first heat conductive layer and the second heat conductive layer. It is a heat conductive composite sheet as described in any one of said <1>-<7> whose content rate is the range of 5 volume%-50 volume%.
Thereby, the heat conductive composite sheet excellent in a flame retardance can be comprised.
<9> Said <1>-wherein the content ratio of said hexagonal boron nitride particles in the total volume of said first heat conductive layer and said second heat conductive layer is in the range of 25 vol% to 80 vol% It is a heat conductive composite sheet as described in any one of <8>.
Thereby, in addition to the effect of the above-mentioned invention, the further outstanding heat conductivity can be achieved.

<10> hexagonal boron nitride particles that are flaky, elliptical, or rod-shaped, and the (0001) crystal plane is oriented in the plane direction of the flaky, the major axis of the ellipse, or the major axis of the rod; Containing a poly (meth) acrylate polymer compound having a glass transition temperature of 50 ° C. or less, and a scale direction of the hexagonal boron nitride particles, a major axis direction of an ellipse, or a major axis direction of a rod A step of preparing two composition layers oriented in the thickness direction, one of the composition layers, the sheet-like porous reinforcing material penetrating in the thickness direction, and the other of the composition layers are laminated in this order and heated. And a step of applying pressure.
Thereby, the heat conductive composite sheet provided with the outstanding heat conductivity and high mechanical strength can be manufactured advantageously and reliably in terms of productivity, cost and energy efficiency.

<11> Any one of <1> to <9>, disposed between the heating element, the radiator, and between the heating element and the radiator so as to be in contact with both the heating element and the radiator. And a heat conducting composite sheet according to claim 1.
As a result, a highly reliable heat dissipating device having a high heat dissipating capability over a long period of time can be configured.

ADVANTAGE OF THE INVENTION According to this invention, it can provide the heat conductive composite sheet which has the outstanding heat conductivity, and was equipped with high mechanical strength, and its manufacturing method.
In addition, according to the present invention, it is possible to provide a heat dissipation device having high heat dissipation capability and high reliability.

  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, a numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. Further, when referring to the amount of each component in the composition in the present specification, when there are a plurality of substances corresponding to each component in the composition, the plurality of the components present in the composition unless otherwise specified. It means the total amount of substance.

<Heat conduction composite sheet>
The heat conductive composite sheet of the present invention is a first heat containing scale, Ryukyu or rod-shaped hexagonal boron nitride particles and a poly (meth) acrylate polymer compound having a glass transition temperature of 50 ° C. or lower. A conductive layer, a sheet-like porous reinforcing material (hereinafter sometimes simply referred to as “reinforcing material”), preferably a sheet-like reinforcing material having a plurality of through-holes penetrating in the thickness direction; Spherical or rod-shaped hexagonal boron nitride particles and a second heat conductive layer containing a poly (meth) acrylate polymer compound having a glass transition temperature of 50 ° C. or lower are laminated in this order.
At least a part of the pores of the reinforcing material is filled with at least one of the poly (meth) acrylate polymer compound and the hexagonal boron nitride particles. Preferably, the plurality of through holes of the sheet-like reinforcing material having a plurality of through holes penetrating in the thickness direction are filled with the poly (meth) acrylate polymer compound, and further, the plurality of through holes are formed. At least a portion of the hexagonal boron nitride particles is inserted into at least some of the through holes.
The hexagonal boron nitride particles contained in the first heat conductive layer and the second heat conductive layer have a (0001) crystal plane in the scale direction, the major axis direction of the Ryukyu, or the rod-like major axis. And the surface direction of the scale, the major axis direction of the Ryukyu or the major axis direction of the rod are oriented in the thickness direction of the first heat conduction layer, the reinforcing material and the second heat conduction layer. Yes.

  That is, in the heat conductive composite sheet of the present invention, at least the poly (meth) acrylate polymer compound and the hexagonal boron nitride particles contained in the first heat conductive layer and the second heat conductive layer. A part of one enters the hole of the reinforcing material. In particular, the reinforcing material is a sheet-like reinforcing material having a plurality of through holes penetrating in the thickness direction, and the first heat conductive layer and the second heat conductive layer are poly (meta) through the through holes. It is preferable that the polymer is filled and integrated with an acrylate polymer compound. Further, at least a part of the hexagonal boron nitride particles contained in the first heat conductive layer and the second heat conductive layer is inserted into at least some of the through holes, and the surface of the scale It is preferable that the direction, the long axis direction of the Ryukyu or the long axis direction of the rod are oriented in the thickness direction of the first heat conductive layer and the second heat conductive layer. Therefore, when viewed as a whole sheet in which the first heat conductive layer, the reinforcing material, and the second heat conductive layer are combined, the hexagonal boron nitride particles are almost continuously present in a state oriented in a specific direction. doing. Such a structure can be confirmed by, for example, observing a cross section SEM of the heat conducting composite sheet.

At least a part of the pores of the reinforcing material is filled with at least one of the poly (meth) acrylate polymer compound and the hexagonal boron nitride particles. When at least a part of the pores is filled with one of a poly (meth) acrylate polymer compound and the hexagonal boron nitride particles, the thermal conductivity is improved. Further, when both the poly (meth) acrylic acid ester polymer compound and the hexagonal boron nitride particles are filled, a further excellent thermal conductivity can be obtained. Here, the hexagonal boron nitride particles are not limited to a state in which the entire particles are inserted into the holes, but may be in a state in which at least a portion is inserted.
It is preferable that the poly (meth) acrylate polymer compound and the hexagonal boron nitride particles are surely filled in the pores, but even if voids are generated in the pores as long as the effects are not impaired. Good. As the number of voids in the hole is smaller, the increase in thermal resistance is suppressed. The porosity in the through hole is, for example, preferably 50% by volume or less, and more preferably 20% by volume or less. Thereby, excellent thermal conductivity can be realized. Here, the void ratio in the through hole means the ratio of the total volume of the void portion in the total volume of the plurality of through holes. The porosity in the through hole can be calculated from SEM observation of the cross section of the heat conductive composite sheet.

  The heat conductive composite sheet having such a configuration has both excellent thermal conductivity and high mechanical strength that could not be obtained with a conventional heat conductive sheet. This heat conductive composite sheet, for example, exhibits excellent strength even in a usage method in which the heat conductive composite sheet is tightened with a strong torque, so that sufficient heat dissipation characteristics can be realized without causing breakage. This can be considered as follows, for example.

In the heat conductive composite sheet of the present invention, the entire sheet has a laminated structure in which a sheet-like porous reinforcing material is sandwiched between the first heat conductive layer and the second heat conductive layer (each heat conductive layer). The strength of the is secured.
Further, at least one of the poly (meth) acrylic acid ester polymer compound forming each thermal conductive layer and the hexagonal boron nitride particles contained in each thermal conductive layer enters the pores of the reinforcing material, The (0001) crystal plane of hexagonal boron nitride particles is oriented in the plane direction of the scale, the long axis direction of the Ryukyu, or the long axis direction of the rod, and the plane direction of the scale, the long axis direction of the ellipsoid, or the rod Since the major axis direction is oriented in the thickness direction of each heat conductive layer and the reinforcing material, excellent heat conductivity can be obtained.

That is, in the heat conduction composite sheet, the orientation of the hexagonal boron nitride particles is preferably such that excellent heat conductivity can be exhibited, and in the first heat conduction layer, in the holes of the reinforcing material, and in the second heat conduction. Arranged continuously in the layer. Thereby, even if it contains the reinforcing material which is hard to say that heat conductivity is enough, heat conductivity can fully be ensured and the heat conductivity outstanding as the whole sheet | seat can be implement | achieved.
Therefore, by setting it as such a laminated structure, it becomes possible to provide the highly functional heat conductive composite sheet which has the outstanding heat conductivity and high mechanical strength.

  In the heat conductive composite sheet of the present invention, the scale direction of the hexagonal boron nitride particles, the long axis direction of the ellipsoid or the long axis direction of the rod are oriented in the thickness direction of the heat conductive composite sheet. If there is no orientation in this direction, sufficient thermal conductivity may not be obtained.

  In the present invention, “orientation in the thickness direction of the heat conduction composite sheet” means that a cross section in the thickness direction of the heat conduction composite sheet is observed using an SEM (scanning electron microscope), and any 50 hexagonal nitridings are observed. The angle with respect to the surface of the heat conductive composite sheet in the major axis direction is measured from the direction in which the boron particles are visible (in the case of 90 degrees or more, a complementary angle is adopted), and the average value is in the range of 60 degrees to 90 degrees The state which becomes.

[First Thermal Conductive Layer and Second Thermal Conductive Layer]
The first heat conductive layer and the second heat conductive layer are composed of at least one kind of scale, sphere or rod-shaped hexagonal boron nitride particles (hereinafter simply referred to as “hexagonal boron nitride particles”) and a glass transition. Each containing at least one poly (meth) acrylate polymer compound (hereinafter, simply referred to as “poly (meth) acrylate polymer compound”) having a temperature of 50 ° C. or less, as necessary. And other components (hereinafter also referred to as “resin composition”).

The hexagonal boron nitride particles contained in the first heat conductive layer and the hexagonal boron nitride particles contained in the second heat conductive layer may be the same or different, but the same It is preferable that
In addition, the poly (meth) acrylate polymer compound contained in the first heat conduction layer and the poly (meth) acrylate polymer compound contained in the second heat conduction layer are the same. Even if it exists, it may differ, but it is preferable that it is the same.

(Hexagonal boron nitride particles)
The first heat conductive layer and the second heat conductive layer are at least one selected from hexagonal boron nitride particles having a scale shape, an elliptical shape, or a rod shape, and a (0001) crystal plane is the scale surface. It includes at least one kind of hexagonal boron nitride particles oriented in the plane direction, the major axis direction of the ellipsoid or the major axis direction of the rod.

By including hexagonal boron nitride particles having such a specific crystal structure, the heat conductive composite sheet of the present invention can achieve excellent heat conductivity.
The hexagonal boron nitride particles have a scaly shape, an oval shape, or a rod shape, with a scaly shape being preferred. When the hexagonal boron nitride particles have a scaly shape, an elliptical shape, or a rod shape, a heat conductive composite sheet excellent in heat conductivity and moldability can be configured.
On the other hand, when the hexagonal boron nitride particles have a spherical or irregular shape, the thermal conductivity may be inferior, and when the shape is fibrous, it may be difficult to form into a sheet and the productivity may be inferior.

  The hexagonal boron nitride particles used in the present invention have a hexagonal crystal shape. The hexagonal boron nitride particles have a hexagonal plane in which a six-membered ring is formed (hereinafter also referred to as “six-membered ring plane”), that is, a (0001) crystal plane is oriented in a specific direction in the grain. Yes. Specifically, when the hexagonal boron nitride particles are scale-like, the (0001) crystal plane is oriented in the plane direction of the scale. When the hexagonal boron nitride particles are elliptical, the (0001) crystal plane is oriented in the major axis direction of the elliptical. Furthermore, when the hexagonal boron nitride particles are rod-shaped, the (0001) crystal plane is oriented in the major axis direction of the rod. Since the hexagonal boron nitride particles have such a specific crystal structure, the thermal conductivity is excellent.

  Here, when the shape of the hexagonal boron nitride particles is elliptical or rod-shaped, the major axis means that the hexagonal boron nitride particles are observed using an SEM (scanning electron microscope, magnification of about 20 to 200 times). When hexagonal boron nitride particles are sandwiched between two parallel planes, it means the axis that passes through the two contact points between the plane and the hexagonal boron nitride particles that are selected to maximize the distance between the planes. To do.

The orientation of the (0001) crystal plane of the hexagonal boron nitride particles can be confirmed by X-ray diffraction measurement. Specifically, it can be confirmed as follows.
First, a sample sheet for measurement in which the surface direction of the hexagonal boron nitride particles, the major axis direction of the ellipsoid, or the major axis direction of the rod is oriented substantially parallel to the surface direction of the sheet or film is prepared. To do.

  As a specific method for preparing the measurement sample sheet, for example, a mixture of hexagonal boron nitride particles and resin of 10% by volume or more is formed into a sheet. As the resin, a material corresponding to a poly (meth) acrylic acid ester-based polymer compound can be used, but is not limited thereto. For example, a material that can form a material or a shape that does not show a peak that hinders X-ray diffraction, such as an amorphous resin, can be used even if it is not a resin.

The sheet of the mixture is preferably pressed to 1/10 or less of the original thickness. Next, the operation of laminating the pressed sheets and further crushing the obtained laminate to 1/10 or less is repeated three or more times. By this operation, in the prepared measurement sample sheet, the scale direction of the hexagonal boron nitride particles, the major axis direction of the ellipse, or the major axis direction of the rod are substantially the same as the plane direction of the measurement sample sheet. It is in a state of being oriented in parallel with.
When the X-ray diffraction measurement is performed on the surface of the measurement sample sheet prepared as described above, the height of the peak corresponding to the (110) plane of hexagonal boron nitride particles appearing in the vicinity of 2θ = 77 °, The value divided by the height of the peak corresponding to the (002) plane of hexagonal boron nitride particles appearing in the vicinity of 2θ = 27 ° is 0 to 0.02.

  Therefore, in the present invention, “the (0001) crystal plane in the crystal is oriented in the plane direction of the scale, the major axis direction of the ellipse or the major axis direction of the rod” means that the hexagonal boron nitride particles And the surface of the resin composition containing the poly (meth) acrylic acid ester polymer compound or the like is subjected to X-ray diffraction measurement, and hexagonal boron nitride particles (110) around 2θ = 77 °. ) When the peak height corresponding to the plane is divided by the peak height corresponding to the (002) plane of hexagonal boron nitride particles appearing in the vicinity of 2θ = 27 ° is 0 to 0.02. I understand that there is.

Examples of the hexagonal boron nitride particles include plate-like boron nitride powder, scaly boron nitride powder, and the like, which can be appropriately selected from commercially available hexagonal boron nitride particles.
The hexagonal boron nitride particles are preferably those that easily become scale-like hexagonal boron nitride particles when mixed with a poly (meth) acrylate polymer compound. Specifically, a scaly boron nitride powder is preferable. As a result, the hexagonal boron nitride particles can be easily oriented in a desired state, the interparticle contact can be easily maintained, and high thermal conductivity can be achieved.

  The size of the hexagonal boron nitride particles is not particularly limited, but from the viewpoint of improving thermal conductivity, the average value of the major axis is each film thickness of the first thermal conductive layer or the second thermal conductive layer × 0. .8 or more is preferable. With such a size, the hexagonal boron nitride particles almost penetrate in the thickness direction of the first heat conductive layer or the second heat conductive layer, and excellent heat conductivity can be achieved. In addition, the theoretical maximum value is a case where all the numbers penetrate, and is film thickness × 1. The average value of the major axis of the hexagonal boron nitride particles is preferably 0.03 mm to 2.0 mm, more preferably 0.1 mm to 1.0 mm, and particularly preferably 0.2 mm to 0.5 mm.

Here, the “average value of the major axis” means that the cross section in the thickness direction of the heat conducting composite sheet is observed using a SEM (scanning electron microscope, magnification of about 20 to 200 times), and any 50 hexagonal nitridings The major axis is measured from the direction in which the boron particles are visible, and the average value is obtained.
Further, the major axis of the hexagonal boron nitride particles is a length that maximizes the distance between the two surfaces when the observed hexagonal boron nitride particles are sandwiched between two parallel surfaces.

Further, the weight average particle diameter of the hexagonal boron nitride particles is not particularly limited. From the viewpoint of thermal conductivity and flexibility, the thickness is preferably 20 μm to 1000 μm, and more preferably 40 μm to 500 μm.
The weight average particle diameter of the hexagonal boron nitride particles is a value obtained by measuring the particle diameter of the raw hexagonal boron particles, and is usually classified with a JIS sieve, and the weight of each particle size component is measured with an electronic balance. Weighing and obtaining a cumulative weight distribution curve means a diameter at which the cumulative mass reaches 50%.

  The preferred range of the weight average particle diameter varies depending on the thickness of each heat conductive layer, but is preferably in the range of 1/100 to 10 times the thickness of each heat conductive layer, more preferably 1/10 to 7 times. Double to 4 times is more preferable. When the weight average particle diameter is not less than the above range, the interface between hexagonal boron particles affecting the heat transfer path becomes good, and excellent thermal conductivity can be obtained. On the other hand, if it is below the said range, it can slice efficiently and a sheet | seat of uniform thickness can be produced.

  The content of the hexagonal boron nitride particles in the heat conductive composite sheet is not particularly limited, and can be appropriately selected depending on the shape and type of the hexagonal boron nitride particles. Especially, it is preferable that it is 25 volume%-80 volume% in the said resin composition total volume, and it is more preferable that it is 30 volume%-70 volume%. When the content of the hexagonal boron nitride particles is 25% by volume or more, the thermal conductivity tends to be further improved. Moreover, the softness | flexibility of a heat conductive composite sheet improves that it is 80 mass% or less, and there exists a tendency for adhesiveness to improve, and the heat conductive composite sheet of a favorable three-layer structure can be produced.

In addition, the content rate (volume%) of the hexagonal boron nitride particles in the present specification is a value obtained by the following formula (1).

Hexagonal boron nitride particle content (volume%) =
(Aw / Ad) / ((Aw / Ad) + (Bw / Bd) + (Cw / Cd)) × 100 (1)

Here, in the formula (1), Aw is a mass composition (mass%) of hexagonal boron nitride particles, and Bw is a mass composition (mass%) of a poly (meth) acrylate polymer compound described later. , Cw is the mass composition (mass%) of other optional components such as phosphate ester flame retardant, Ad is the specific gravity of hexagonal boron nitride particles (In the present invention, Ad is hexagonal boron nitride particles 2.3, and Bd represents the specific gravity of the poly (meth) acrylate polymer compound, and Cd represents the specific gravity of other optional components (such as phosphate ester flame retardant).

(Poly (meth) acrylate polymer compound)
Said 1st heat conductive layer and said 2nd heat conductive layer contain at least 1 sort (s) of the poly (meth) acrylic-ester type | system | group polymer compound whose glass transition temperature is 50 degrees C or less.

The poly (meth) acrylate polymer compound has a glass transition temperature Tg of 50 ° C. or lower, preferably −70 ° C. to 20 ° C., more preferably −60 ° C. to 0 ° C. When glass transition temperature Tg exceeds 50 degreeC, a softness | flexibility will become inadequate and the adhesiveness with respect to a heat generating body and a heat radiator may fall.
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 contains at least one (meth) acrylic acid ester and, if necessary, a monomer composition containing another monomer copolymerizable with the (meth) acrylic acid ester. Can be obtained by polymerizing.
Here, (meth) acrylic acid means at least one of acrylic acid and methacrylic acid.

The (meth) acrylic acid ester constituting the monomer composition is 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 composite sheet. Preferably, it is a (meth) acrylic acid alkyl ester having an alkyl group having 2 to 8 carbon atoms.
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 of (meth) acrylate ester in the poly (meth) acrylate polymer compound is preferably 70% by mass or more from the viewpoint of thermal conductivity and flexibility of the thermal conductive composite sheet, 85 More preferably, it is at least mass%.

Other monomers copolymerizable with this (meth) acrylic acid ester include, for example, 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 is not particularly limited. From the viewpoint of thermal conductivity and flexibility of the heat conductive composite sheet, it is preferably 30% by mass or less, and more preferably 15% by mass or less.

The poly (meth) acrylate polymer compound is derived from (meth) acrylic acid alkyl ester having 2 to 8 carbon atoms and (meth) acrylic acid from the viewpoint of strength and stress relaxation. A copolymer having a weight average molecular weight of 100,000 to 1,000,000 is preferred. From the viewpoint of thermal conductivity and flexibility, the structural unit is derived from a (meth) acrylic acid alkyl ester having an alkyl group having 2 to 8 carbon atoms, and the content is 85% by mass or more in the copolymer. And a copolymer having a weight average molecular weight of 300,000 to 900,000, which is derived from (meth) acrylic acid and contains 15 % by mass or less of the structural unit in the copolymer. . Furthermore, a reactive functional group may be appropriately introduced into this copolymer.
The weight average molecular weight of the poly (meth) acrylic acid ester polymer compound can be measured by a usual method using GPC.

  The content of the poly (meth) acrylate polymer compound is not particularly limited, but is preferably 10% by volume to 70% by volume, and 20% by volume to 50% by volume in the total volume of the resin composition. It is more preferable that There exists a tendency which can suppress that a sheet | seat becomes weak because it is 10 volume% or more in the total volume of the said resin composition, and there exists a tendency which heat conductivity and intensity | strength improve more by being 70 volume% or less. is there.

  The poly (meth) acrylic acid ester polymer compound may further contain a curing agent such as a polyfunctional epoxy resin as a curing agent. In particular, butyl acrylate and 2-ethylhexyl acrylate include 70 to 99% by mass of structural units in the copolymer component and (meth) acrylic acid 1 to 10% by mass of structural units. A crosslinked cured product obtained by adding a polyfunctional epoxy resin as a curing agent to the copolymer is more preferable in terms of an appropriate reaction rate during production and a balance between flexibility and strength of the obtained sheet. In this cross-linked cured product, if there are many copolymer components such as butyl acrylate and 2-ethylhexyl acrylate, the glass transition temperature tends to decrease. Therefore, it is preferable that the amount of these copolymerization components is appropriately adjusted so that the glass transition temperature of the crosslinked cured product is 50 ° C. or lower.

  As the curing agent, any conventionally known ones can be used, and specific examples include polyfunctional epoxy resins, polyfunctional isocyanates, polyfunctional amines, imidazoles, compounds having a plurality of phenolic hydroxyl groups, and the like. Can be mentioned.

(Other optional ingredients)
Moreover, in the said resin composition, other arbitrary components, such as a flame retardant, may be added as needed.
The flame retardant is not particularly limited, and examples thereof include red phosphorus flame retardants and phosphate ester flame retardants.
Examples of red phosphorus flame retardants include pure red phosphorus powder, various coatings for the purpose of improving safety and stability, and master batches. Novared, Nova Excel, Nova Quel, Nova pellets (all trade names) etc. manufactured by Rin Chemical Industry Co., Ltd.) can be used.

  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-2, Aromatic phosphate esters such as 6-xylenyl phosphate, tris (t-butylated phenyl) phosphate, tris (isopropylated phenyl) phosphate, triaryl isopropylate, resorcinol bisdiphenyl phosphate, bisphenol A bis (diphenyl) Phosphate), and aromatic condensed phosphoric acid esters such as resorcinol bis-dixylenyl phosphate. These may be used alone or in combination of two or more. Among them, a liquid phosphate ester flame retardant is preferable because it contributes to the flexibility of the heat conductive composite sheet.

  Although the content rate of the said flame retardant is not restrict | limited in particular, Preferably it is 5 volume%-50 volume% in the said resin composition total volume, More preferably, it is 10 volume%-40 volume%. If the content rate of the said flame retardant is the said range, since sufficient flame retardance will be expressed and it will become advantageous in a softness | flexibility point, it is preferable. When the content of the flame retardant is 5% by volume or more, sufficient flame retardancy is obtained, and when it is 50% by volume or less, high mechanical strength can be secured.

  When the resin composition contains a hexagonal boron nitride particle, a poly (meth) acrylic acid ester polymer compound, and a flame retardant such as a phosphoric acid ester, the content of each component is hexagonal boron nitride. The content of the elementary particles is 5% by mass or more and 25% by mass or less in the total mass, and the content of the poly (meth) acrylate polymer compound is 40% by mass or more and 75% by mass or less in the total mass. The content of the phosphate ester flame retardant is preferably 10% by mass or more and 40% by mass or less based on the total mass. When the content of each component is in the above range, it constitutes a heat conductive composite 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. it can.

Examples of the other optional components include tackifiers such as liquid polybutene and liquid phosphate. By adding a tackifier such as polybutene to the resin composition, the resin composition oozes out to the surface and easily exhibits the effect of tackiness.
When polybutene is added, the content is not particularly limited, but is preferably 5 vol% to 40 vol% of the total volume of the resin composition. When it is 5% by volume or more, sufficient tackiness is obtained, and when it is 40% or less, the strength of the sheet can be sufficiently secured. A more preferred range is 10% to 30% by volume.

[Reinforcing material]
The reinforcing material is a porous sheet-like body having holes on at least one surface. The hole may penetrate in the thickness direction of the heat conducting composite sheet or may not penetrate. Among these, a through hole is preferable. The hole is filled with the resin composition forming the first heat conductive layer and the second heat conductive layer. Thereby, the fall of the heat conductivity of the heat conductive composite sheet by interposing a reinforcing material is suppressed.

The reinforcing material is not particularly limited as long as it is in the form of a porous sheet having the holes. For example, a woven fabric, a nonwoven fabric, etc. can be mentioned. A woven fabric or a nonwoven fabric is preferable, and a woven fabric is more preferable because the resin composition is filled without forming voids in the pores, and a decrease in thermal conductivity due to the presence of the voids is suppressed.
Examples of the material of the reinforcing material include synthetic fibers such as polyester, nylon, and acrylic resin, and inorganic fibers such as glass.
When the reinforcing material is a woven fabric, the knitting method is not particularly limited. For example, plain weaving, biaxial weaving and the like can be mentioned. From the viewpoint of tensile strength, biaxial weaving is preferable, and from the viewpoint of thermal resistance, plain weaving is preferable.

The shape of the hole may be any of a lattice shape, a dot shape, an indefinite shape, and the like.
When the hole is a through hole, the size of the hole is preferably large as long as sufficient strength can be imparted to the heat conductive composite sheet. The larger the hole diameter, the more disadvantageous in terms of strength, but the filling rate of the resin composition into the through-hole can be increased, and excellent thermal conductivity can be obtained. Specifically, from the viewpoint of strength and thermal conductivity, the thickness is preferably 0.1 mm or more, more preferably 0.2 mm or more, and still more preferably 0.3 mm or more.
The shape and size of the through hole may be appropriately selected depending on the type and material of the reinforcing material so that the filling rate of the resin composition into the through hole is increased.

The reinforcing material is preferably a woven fabric (glass cloth) made of glass fiber from the viewpoint of strength. The glass cloth is not particularly limited, and can be appropriately selected from commercially available glass cloths, for example.
When the reinforcing material is a glass cloth, a mesh-like body is preferable from the viewpoint of thermal conductivity, and the mesh diameter is preferably 0.1 mm or more, more preferably 0.2 mm or more, Furthermore, it is more preferable that it is 0.38 mm or more, and it is especially preferable that it is 2.5 mm or less.
The fiber diameter of the woven fabric is preferably 2 mm or less, more preferably 1 mm or less, still more preferably 0.6 mm or less, and further preferably 0.3 mm or more from the viewpoint of thermal conductivity. It is particularly preferred that
The thickness of the reinforcing material is preferably in the range of 100 μm to 500 μm from the viewpoint of strength and thermal conductivity, and more preferably in the range of 130 μm to 250 μm in controlling the thickness of the heat conductive composite sheet.

[Protective film]
Moreover, in order to protect the surface of the 1st heat conductive layer and the 2nd heat conductive layer of the heat conductive composite sheet of this invention, you may cover the surface of each heat conductive layer with the 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.
The thickness of the protective film is not particularly limited, but it is 50 μm to 200 μm from the viewpoint of the relationship between the depth of cut into the protective film and the strength when pre-cutting the heat conductive composite sheet into a desired shape, the handleability of the sheet, etc. The range is preferable, and the range of 75 μm to 150 μm is more preferable.

<The manufacturing method of a heat conductive composite sheet>
The manufacturing method of the heat conductive composite sheet of this invention contains the following process (1) and (2), and may include the other process as needed. Accordingly, the hexagonal boron nitride particles having a specific crystal structure and a poly (meth) acrylate polymer compound having a glass transition temperature of 50 ° C. or lower are contained, and the hexagonal boron nitride particles are scaled. Excellent thermal conductivity and high machine having a laminated structure in which a reinforcing material is disposed between two composition layers in a state in which the plane direction of the ellipse, the major axis direction of the ellipsoid or the major axis direction of the rod is oriented in the thickness direction It is possible to manufacture a heat conductive composite sheet having sufficient strength.
(1) Hexagonal boron nitride particles that are scale-like, elliptical, or rod-shaped, and that have a (0001) crystal plane oriented in the plane direction of the scale, the major axis direction of the ellipse, or the major axis direction of the rod; Containing a poly (meth) acrylate polymer compound having a glass transition temperature of 50 ° C. or less, and a scale direction of the hexagonal boron nitride particles, a major axis direction of an ellipse, or a major axis direction of a rod Preparing two composition layers oriented in the thickness direction.
(2) One of the composition layers, a sheet-like porous reinforcing material, preferably a sheet-like reinforcing material having a plurality of through holes penetrating in the thickness direction, and the other of the composition layers are laminated in this order. The process of heating and pressing.

Hereinafter, each process (1) and (2) is demonstrated.
(1) Step of preparing two composition layers The step of preparing two composition layers preferably includes the following steps (a) to (c), for example.
Hereinafter, each process (a)-(c) is demonstrated.
(A) Primary sheet production process First, a resin composition for a primary sheet containing hexagonal boron nitride particles and a poly (meth) acrylate polymer compound is obtained. Although the resin composition for primary sheets is obtained by mixing these, the mixing method is not specifically limited. For example, a poly (meth) acrylate polymer compound is dissolved in a solvent, hexagonal boron nitride particles and other components are added thereto as needed, and stirred, or the hexagonal nitriding A method of roll-kneading boron particles and the poly (meth) acrylic acid ester polymer compound or a method of mixing with a kneader, a brabender, an extruder, or the like can be used.

  Subsequently, the obtained resin composition for a primary sheet is rolled, press-molded, extruded or coated to a thickness of 20 times or less the weight average particle diameter of hexagonal boron nitride particles, and the hexagonal boron nitride particles A primary sheet in which the surface direction of the scale, the major axis direction of the ellipse or the major axis direction of the rod is oriented in the thickness direction is produced. Here, the orientation directions of the hexagonal boron nitride particles do not need to be completely aligned in the thickness direction, but may be approximately aligned.

  The primary sheet resin composition is rolled, press-molded, extruded or coated so that the surface direction of the scale of hexagonal boron nitride particles, the major axis direction of the ellipsoid, or the major axis direction of the rod is thick. A primary sheet oriented in the direction is produced. Roll forming or press forming is preferable because it facilitates the orientation of hexagonal boron nitride particles.

  The hexagonal boron nitride particle scale surface direction, the major axis direction of the ellipsoid or the major axis direction of the rod is oriented in the thickness direction means the scale direction of the hexagonal boron nitride particle scale, A state in which the major axis direction or the major axis direction of the rod is oriented so as to be oriented substantially parallel to the surface direction of the sheet. The orientation of the hexagonal boron nitride particles in the sheet plane is controlled by adjusting the flowing direction of the primary sheet resin composition when the primary sheet resin composition is molded. That is, the direction in which the resin composition for primary sheet is passed through a rolling roll, the direction in which the resin composition for primary sheet is extruded, the direction in which the resin composition for primary sheet is applied, and the resin composition for primary sheet are pressed The direction of the hexagonal boron nitride particles is controlled by adjusting the direction in which they are performed. Since the hexagonal boron nitride particles are basically anisotropic particles, the hexagonal nitriding is usually performed by rolling, pressing, extrusion or coating the resin composition for the primary sheet. The orientation of the boron particles is aligned.

  Further, when the primary sheet is produced, the resin composition for the primary sheet containing hexagonal boron nitride particles and the poly (meth) acrylate polymer compound is a lump shape before molding. In some cases, roll forming, press forming or extrusion forming is performed such that the thickness (dp) of the primary sheet after forming is dp / d0 <0.15 with respect to the thickness (d0) of the lump, or the exit of the extruder It is preferable to perform extrusion molding so that the thickness (dp ′) is dp ′ / W <0.15 with respect to the lateral width (W) of the primary sheet by shape adjustment corresponding to the primary sheet cross-sectional shape. By shaping so that dp / d0 <0.15 or dp ′ / W <0.15, the scale direction of the hexagonal boron nitride particles, the major axis direction of the ellipsoid, or the major axis direction of the rod It becomes easy to orient in the thickness direction.

(B) The process of obtaining a molded object Then, the said primary sheet is laminated | stacked and a molded object is obtained. The method of laminating the primary sheets is not particularly limited, and examples thereof include a method of laminating a plurality of primary sheets and a method of folding the primary sheets. When laminating, the orientation directions of hexagonal boron nitride particles are aligned in the sheet plane. The shape of the primary sheet when laminating is not particularly limited. For example, when a rectangular primary sheet is laminated, a prismatic shaped body is obtained, and when a circular primary sheet is laminated, a cylindrical shaped body is obtained. can get.

  Instead of the method of laminating a plurality of primary sheets and the method of folding the primary sheet, it is possible to obtain a molded body by winding the primary sheet. A method for winding the primary sheet is not particularly limited, and the primary sheet may be wound around the orientation direction of the hexagonal boron nitride particles as an axis. The shape of the winding is not particularly limited, and may be, for example, a cylindrical shape or a rectangular tube shape.

  The pressure when laminating the primary sheet is a sufficient laminating surface or winding without collapsing the sliced surface for the convenience of slicing at an angle of 0 to 30 degrees with respect to the normal line coming out from the primary sheet surface in the subsequent process. It is adjusted to be weak enough to secure the area of the surface and strong enough to bond the sheets sufficiently. Usually, this adjustment can provide a sufficient adhesive force between the laminated surfaces or the wound surfaces. However, if insufficient, lamination may be performed after thinly applying a solvent or an adhesive to the primary sheet. Moreover, you may perform lamination | stacking under a heating suitably.

(C) Slicing step Next, the molded body is sliced at an angle of 0 degrees to 30 degrees, preferably an angle of 0 degrees to 15 degrees with respect to the normal line coming out from the primary sheet surface, and a predetermined thickness is obtained. A thick composition layer is obtained. When the slicing angle exceeds 30 degrees, the thermal conductivity tends to decrease.
When the molded body is a laminated body, it may be sliced so as to be perpendicular or substantially perpendicular to the lamination direction of the primary sheet. Further, when the molded body is a wound body, it may be sliced so as to be perpendicular or almost perpendicular to the winding axis. Further, in the case of a cylindrical molded body in which circular primary sheets are laminated, the molded body may be sliced like a wig within the range of the angle.

  The slicing method is not particularly limited, and examples thereof include a multi-blade method, a laser processing method, a water jet method, and a knife processing method. However, the knife processing method is easy to keep the thickness of the heat conductive composite sheet uniform. preferable. The cutting tool for slicing is not particularly limited, but it is difficult to disturb the orientation of the hexagonal boron nitride particles in the vicinity of the surface of the obtained heat conducting composite sheet, such as a slicer, a kanna, or the like with a sharp blade, and A thin sheet is also preferable because it is easy to produce.

  The slicing is preferably performed in the temperature range of Tg (glass transition temperature) + 5 ° C. to Tg (glass transition temperature) + 50 ° C. of the poly (meth) acrylate polymer compound, and Tg (glass transition temperature) + 10 ° C. It is more preferable to carry out in a temperature range of ~ Tg (glass transition temperature) + 40 ° C. When the slicing temperature is Tg (glass transition temperature) + 50 ° C. or less of the poly (meth) acrylate polymer compound, the molded article has good flexibility (hardness) and is easily sliced. Also, the orientation of hexagonal boron nitride particles is easy to control. When it is Tg (glass transition temperature) + 5 ° C. or higher, the molded product has flexibility, tends to be sliced, and the sheet tends to hardly break immediately after slicing.

  The thickness of the composition layer is appropriately set depending on the application and the like, but is preferably 0.05 mm to 3 mm, more preferably 0.1 mm to 1 mm, and still more preferably 0.15 mm to 0.3 mm. It is. The thinner the composition layer, the better the thermal resistance characteristics. However, in consideration of handling during production, a range of 150 μm to 300 μm is more preferable. When the thickness of the composition layer is 0.05 mm or more, it is excellent in handleability as a sheet and can be easily combined. In the case of 3 mm or less, a sufficient heat dissipation effect is obtained.

(2) Step of Laminating Two Composition Layers and Reinforcing Material In the method for producing a heat conductive composite sheet of the present invention, after the step of preparing two of the composition layers, one of the composition layers is in the form of a sheet. The other of the porous reinforcing material and the composition layer is laminated in this order and heated and pressed.
This step can be performed as follows.

  First, a sheet-like porous reinforcing material is overlaid on one side of one composition layer prepared as described above, and the other side of the other composition layer is overlaid so as to sandwich this reinforcing material. Thereby, the laminated body by which one side of the said composition layer, the reinforcing material, and the other of the said composition layer were laminated | stacked in this order is formed.

Then, it heat-presses in the state which clamped this laminated body. As a result, the poly (meth) acrylate polymer compound that forms the composition layer (not heated and pressurized) is plastically deformed by heat and pressure, and the poly (meth) acrylate polymer is Each composition layer formed by the compound is closely attached in such a manner as to sandwich the reinforcing material, and the first heat conductive layer composed of one composition layer, the second heat conductive layer composed of the reinforcing material and the other composition layer. Are laminated in this order (the first heat conduction layer and the second heat conduction layer are constituent members of the heat conduction composite sheet, and indicate those heated and pressurized). Is obtained. At this time, the hole of the reinforcing material is filled with a part of the plastically deformed poly (meth) acrylate polymer compound, and at least a part of the hexagonal boron nitride particles is inserted into the hole. Thereby, each heat conductive layer and a reinforcing material are integrated through a hole. Furthermore, the hexagonal boron nitride particles are continuously present in a specific direction throughout the sheet.
Therefore, according to the manufacturing method of such a heat conductive composite sheet, it is possible to provide a highly functional heat conductive composite sheet having high heat conductivity while ensuring excellent strength.

As a method of laminating the composition layer and the reinforcing material and heating and pressing, any conventionally known method can be used, and examples thereof include a hot roll and a hot press.
The conditions at the time of heating and pressing are preferably set as appropriate according to the configuration and thickness of the composition layer. For example, when a hot roll is used, it is preferable that the moving speed is 0.1 m / min to 1.5 m / min at a roll temperature of 50 ° C. to 90 ° C. under a pressure condition of 1 MPa to 20 MPa.
Moreover, the thickness of a heat conductive composite sheet changes with the thickness of the composition layer to prepare. For example, when preparing a heat conductive composite sheet having a thickness of 0.3 mm, after preparing two composition layers having a thickness of 0.15 mm, sandwiching a reinforcing material and pressing with a hot roll or the like, heat conduction of 0.3 mm is obtained. A composite sheet can be obtained.
In addition, you may laminate | stack the said protective film further in order to protect the said composition layer surface.

<Heat dissipation device>
The heat dissipating device of the present invention is obtained by arranging the heat conductive composite sheet of the present invention described above or the heat conductive composite sheet obtained by the manufacturing method of the present invention between the heat generator and the heat radiator.
The heat conductive composite sheet of the present invention is suitable for a heating element whose surface temperature does not exceed 200 ° C.
The temperature range in which the heat conductive composite sheet of the present invention or the heat conductive composite sheet manufactured by the manufacturing method of the present invention can be used particularly preferably is −10 ° C. to 120 ° C., and LED, semiconductor package, display, lamp, etc. Examples of suitable heating elements are mentioned.

  Examples of the radiator include a heat sink using aluminum, copper fins and plates, an aluminum or copper block connected to a heat pipe, and an aluminum or copper block in which cooling liquid is circulated by a pump. A typical Peltier element and an aluminum or copper block having the Peltier element can be used.

  The heat dissipation device of the present invention is established by bringing each surface of the heat conductive composite sheet of the present invention or the heat conductive composite sheet obtained by the manufacturing method of the present invention into contact with the heat generator and the heat dissipator. As long as the heating element, the heat conductive composite sheet and the radiator can be fixed in a sufficiently intimately fixed manner, the contacting method is not limited, but a method of screwing through a spring from the viewpoint of maintaining the adhesion, clip A contact method in which the pressing force is sustained, such as a method of pinching with a pin, is preferable.

  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
First, as hexagonal boron nitride particles, 3700 g of flaky hexagonal boron nitride particles (Momentive Co., Ltd., trade name: HGF-L, weight average particle size 10 μm), poly (meth) acrylic acid ester type As a polymer compound, butyl acrylate / ethyl acrylate / acrylic acid copolymer (butyl acrylate: ethyl acrylate: acrylic acid = 19: 76: 5 (mass ratio), manufactured by Nagase ChemteX Corporation, weight average molecular weight 700 g of 600000, Tg; -41 ° C), 14 g of liquid BPA type / BPF type high purity epoxy resin (manufactured by Nippon Steel Chemical Co., Ltd., trade name: YDF-8170C) as a curing agent and bisphenol A bis (diphenyl) as a flame retardant 6) Phosphate (phosphate ester flame retardant, manufactured by Daihachi Chemical Industry Co., Ltd., trade name: CR-741) 0g were prepared respectively, to prepare a primary sheet resin composition are premixed.
The compounding ratio of each component was calculated from the specific gravity of each component with respect to the total volume of the resin composition for the primary sheet. As a result, about 60% by volume of hexagonal boron nitride particles, about 23 poly (meth) acrylate polymer compound 0.2% by volume, about 0.2% by volume curing agent, and about 16.6% by volume flame retardant.

The primary sheet resin composition was kneaded using a pressure kneader (trade name: LABOLATRY MILL (8 × 20 T roll) manufactured by Moriyama Co., Ltd.) set at a temperature of 80 ° C. to obtain a kneaded product.
A part of the kneaded product was rounded into a spherical shape having a diameter of 1 cm and formed into a sheet having a thickness of 0.5 mm with a small press. This was cut into 20 sheets and laminated again and pressed in the same manner.
After repeating this operation one more time, the surface of the obtained kneaded sheet was analyzed by X-ray diffraction. As a result, a peak corresponding to the (110) plane of hexagonal boron nitride particles was confirmed around 2θ = 77 °. It was not possible to confirm that the hexagonal boron nitride particles used had “the (0001) crystal plane in the crystal was oriented in the plane direction of the scale”.

  The obtained kneaded sheet was cut into a size of about 2 mm to 3 mm square to form a pellet. This was extruded into a sheet having a width of 60 mm and a thickness of 1 mm at 100 ° C. using a lab plast mill (product name: MODEL20C200, manufactured by Toyo Seiki Kogyo Co., Ltd.) to obtain a primary sheet.

This primary sheet is cut into a size of 4cm x 20cm with a cutter, laminated 40 sheets, lightly pressed by hand to adhere between the sheets, and further loaded with 3kg of weight, and then treated with a hot air dryer at 70 ° C for 1 hour Thus, the sheets were sufficiently bonded to obtain a molded body having a thickness of 4 cm.
Next, after cooling this molded body to −20 ° C. with dry ice, a laminated section of 4 cm × 20 cm was formed into a super-finished canna board (manufactured by Marunaka Co., Ltd., trade name; (Protruding length of the portion: 0.19 mm)) (sliced at an angle of 0 degrees with respect to the normal line coming out of the primary sheet surface), and a composition layer of 4 cm long × 20 cm wide × 0.15 mm thick Obtained.

  Then, on the composition layer, a plain-woven glass cloth (i) (manufactured by Nittobo, trade name: KS5210, length 4 cm × width 20 cm × 0.180 mm) and the composition layer are overlapped by hand in this order. A PET sheet (thickness 75 μm) of 5 cm long and 30 cm wide that has been released so as to be in contact with the surface of the composition layer is sandwiched so that the composition layer does not protrude, and heated at 80 ° C. with a hot roll. Pressure bonding was performed at a moving speed of 0.3 m / min at a temperature to obtain a heat conductive composite sheet (I) having a thickness of 0.30 mm.

  The cross section of the obtained heat conducting composite sheet (I) was observed using an SEM (scanning electron microscope), and from the direction in which any 50 hexagonal boron nitride particles were seen, the heat in the surface direction of the scales When the angle and major axis with respect to the surface of the conductive composite sheet were measured and the average value was obtained, the angle was 90 degrees, and the plane direction of the scale of the hexagonal boron nitride particles was oriented in the thickness direction of the heat conductive composite sheet. It was recognized that Moreover, the average value of the major axis was 0.18 mm. Furthermore, the through hole of the glass cloth (i) is filled with the poly (meth) acrylate polymer compound contained in the composition layer, and the scale direction of the hexagonal boron nitride particles Was inserted in a state oriented in the thickness direction of the heat conductive composite sheet (I), and it was confirmed that the porosity was 10% by volume or less.

A heat-conductive composite sheet (I) punched into a 2 cm square is laminated until it reaches a height of 5 mm or more, and when measured with an Asker hardness meter C type at 25 ° C., a flexible rubber sheet with an Asker C hardness of 60 It was confirmed that.
Next, the thermal resistance used as an index of the thermal conductivity of this thermal conductive composite sheet (I) was determined by the following method.

A 1.0 cm square heat conductive composite sheet was sandwiched between a transistor (2SC2233) and a water-cooled copper heat sink, and current was passed through the transistor while pressing it. Then, the temperature T1 (° C.) of the transistor and the temperature T2 (° C.) of the copper heat sink are measured, and the thermal resistance X (° C. · cm ² ) is calculated from the measured value and the applied power W1 (W) according to the following equation (2). / W) was calculated.
X = (T1-T2) / W1 (2)

  As a result, when the thermal conductivity of the heat conductive composite sheet (I) was measured, it showed a good value of 10 W / mK. Moreover, the adhesiveness with respect to the transistor and copper heat sink at the time of measurement of heat conductive composite sheet (I) was also favorable.

Moreover, the tensile strength of this heat conductive composite sheet (I) was measured.
That is, using a heat conductive composite sheet punched out to 1 cm × 5 cm as a sample, using a measuring machine (trade name: STROGRAP ES) manufactured by Toyo Seiki Seisakusho Co., Ltd., a temperature of 25 ° C. and a tensile speed of 5 mm / min or less. When the tensile strength was measured below, it became clear that the material had a sufficient handling property of 7 MPa.

(Example 2, Example 3)
As shown in Table 1 below, the glass cloth (i) used in Example 1 was replaced with various glass cloths (ii) and glass cloths (iii) having different fiber diameters and mesh diameters, and the others were the same as described above. Thus, a heat conductive composite sheet (II) and a heat conductive composite sheet (III) were prepared, and these were designated as Example 2 and Example 3.

  For each cross section of the obtained heat conductive composite sheets (II) and (III), the same SEM observation as in Example 1 was performed, and the surface direction of the scale of the hexagonal boron nitride particles was the thickness of the heat conductive composite sheet. Orientation was observed in the direction. Moreover, the average value of the major axis was 0.18 mm.

Using such heat conducting composite sheets (II) and (III), the Asker C hardness was examined in the same manner as in Example 1. As a result, it was confirmed that the Asker C hardness was 60 and the rubber sheet was flexible.
Moreover, the thermal conductivity and the tensile strength were measured as described above.
The results are shown in Table 1 below.

As shown in Table 1, the thermal conductivity was 5.1 W / mK, which was a good value, and the adhesion between the transistor and the copper heat sink was also good.
As for the tensile strength, it was revealed that the material has a sufficient handling property of 7 MPa.

(Example 4, Example 5)
The hexagonal boron nitride particles used in Example 1 were replaced with 2000 g of flaky hexagonal boron nitride particles (product name: PT-110A, weight average particle size 10 μm, manufactured by Momentive Inc.), and a flame retardant. As shown in Table 1 above, the glass cloth is replaced with various biaxially woven glass cloth (iv) and glass cloth (v), and otherwise the same as above, the heat conductive composite sheet (IV) And a heat conductive composite sheet (V) were produced, and these were designated as Example 4 and Example 5.

  When each SEM observation similar to Example 1 was performed about each cross section of obtained heat conductive composite sheet (IV) and (V), the surface direction of the scale of a hexagonal boron nitride particle is the thickness of a heat conductive composite sheet. Orientation was observed in the direction. Moreover, the average value of the major axis was 0.18 mm.

Using such heat conducting composite sheets (IV) and (V), the Asker C hardness was examined in the same manner as in Example 1. As a result, it was confirmed that the Asker C hardness was 60 and the rubber sheet was flexible.
Moreover, the thermal conductivity and the tensile strength were measured as described above. The results are also shown in Table 1.
As a result, when biaxially woven glass cloths (iv) and (v) were used, an excellent handling property of 20 MPa was exhibited while maintaining excellent thermal conductivity.

(Comparative Example 1)
In the resin composition for a primary sheet prepared in Example 1, a heat conductive sheet (VI) having a thickness of 0.3 mm was obtained without using a glass cloth.

Hereafter, it evaluated similarly to Example 1 and calculated | required the property of heat conductive sheet (VI).
SEM observation of the cross section of the heat conductive sheet (VI), from the direction seen about any 50 hexagonal boron nitride particles, the angle and the major axis of the surface direction of the scale to the heat conductive composite sheet surface, When the average value was obtained, the angle was 89 degrees, and it was recognized that the surface direction of the scale of the hexagonal boron nitride particles was oriented in the thickness direction of the composition layer. Moreover, the average value of the major axis was 0.18 mm.
It was confirmed that the Asker C hardness was 65 and the rubber sheet was flexible.

  When the heat conductivity of this heat conductive sheet (VI) was measured, it showed a good value of 10 W / mK. Moreover, the adhesiveness with respect to the transistor of a heat conductive sheet (VI) and a copper heat sink was also favorable.

  When the tensile strength of this heat conductive composite sheet (VI) was measured, it was 0.3 MPa, a value that was insufficient for handling.

  From the above, in the heat conductive composite sheet according to the present invention, both have excellent thermal conductivity equivalent to the conventional heat conductive sheet that does not use glass cloth, and at the same time exhibit high mechanical strength. I understood.

Next, the influence which the shape of the various glass cloth used in Examples 1-5 has on the characteristic of a heat conductive composite sheet was examined.
As a result, as shown in Table 1, when a glass cloth (i) used in Example 1 having a relatively large mesh diameter is used, extremely excellent thermal conductivity can be realized. It became clear.

Moreover, compared with Example 2, 3, Example 1, 4, 5 using the glass cloth (i) with a comparatively thin fiber diameter showed the outstanding heat conductivity.
Therefore, it was found that appropriately selecting the shape such as the mesh diameter and the fiber diameter as a reinforcing material contributes to the improvement of the thermal conductivity so that a sufficient conductive area can be secured.

Claims (11)

A first heat-conducting layer containing scales, Ryukyu or rod-shaped hexagonal boron nitride particles and a poly (meth) acrylate polymer compound having a glass transition temperature of 50 ° C. or lower;
A sheet-like porous reinforcing material,
A second heat conductive layer containing scales, Ryukyu or rod-shaped hexagonal boron nitride particles and a poly (meth) acrylate polymer compound having a glass transition temperature of 50 ° C. or lower is laminated in this order. And at least a part of the pores of the porous reinforcing material is filled with at least one of the poly (meth) acrylate polymer compound and the hexagonal boron nitride particles,
The hexagonal boron nitride particles contained in the first heat conductive layer and the second heat conductive layer have a (0001) crystal plane of the scale direction, the long axis direction of the Ryukyu, or the long axis direction of the rod shape. And the surface direction of the scale, the major axis direction of the Ryukyu or the major axis direction of the rod are oriented in the thickness direction of the first heat conductive layer, the reinforcing material and the second heat conductive layer. Heat conduction composite sheet.   The porous reinforcing material has a plurality of through holes penetrating in the thickness direction, the plurality of through holes are filled with the poly (meth) acrylate polymer compound, and the plurality of through holes The heat conductive composite sheet according to claim 1, wherein at least a part of the hexagonal boron nitride particles is inserted into at least a part of the through holes.   The heat conductive composite sheet according to claim 1, wherein the porous reinforcing material is a woven fabric. The heat conductive composite sheet according to claim 3 , wherein the woven fabric is made of glass fiber.   The heat conductive composite sheet according to claim 3 or 4, wherein the woven fabric is a mesh-like body, and the mesh diameter is 0.38 mm or more.   The heat conductive composite sheet according to any one of claims 3 to 5, wherein a fiber diameter of the woven fabric is 0.6 mm or less.   The heat conductive composite sheet according to any one of claims 3 to 6, wherein the woven fabric is a biaxial woven fabric or a plain woven fabric.   The first heat conduction layer and the second heat conduction layer further contain a flame retardant, and the content ratio of the flame retardant in the total volume of the first heat conduction layer and the second heat conduction layer is It is the range of 5 volume%-50 volume%, The heat conductive composite sheet as described in any one of Claims 1-7.   The content of the hexagonal boron nitride particles in the total volume of the first heat conductive layer and the second heat conductive layer is in the range of 25 vol% to 80 vol%. The heat conductive composite sheet as described in any one of the above. Hexagonal boron nitride particles that are scale-like, elliptical, or rod-shaped, and whose (0001) crystal plane is oriented in the plane direction of the scale, the major axis of the ellipse, or the major axis of the rod, and the glass transition temperature Is a poly (meth) acrylic acid ester-based polymer compound having a temperature of 50 ° C. or less, and the surface direction of the scale of the hexagonal boron nitride particles, the major axis direction of the ellipsoid, or the major axis direction of the rod is the thickness direction. Preparing two composition layers oriented to
Laminating one of the composition layers, the sheet-like porous reinforcing material and the other of the composition layers in this order, and heating and pressing;
The manufacturing method of the heat conductive composite sheet which has this. A heating element;
A radiator,
The heat conductive composite sheet according to any one of claims 1 to 9, 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.