JP2018159062A - Heat-conductive composite material, heat-conductive filler, and production method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite material having excellent thermal conductivity.SOLUTION: A heat-conductive composite material is provided, which is prepared by dispersing a heat-conductive filler comprising boron nitride fine particles in a matrix. At least part of the boron nitride fine particles are partial cleavage boron nitride fine particles having a partial cleavage in a boron nitride fine particle; and the composite material includes swollen boron nitride fine particles resulting from such a phenomenon that the matrix fills a cleavage void in the partial cleavage boron nitride particle to swell the particle. On a basis of a cross section of the composite material, the total area of regions corresponding to the swollen boron nitride fine particles is 1 to 50% with respect to the cross-sectional area of the composite material.SELECTED DRAWING: None

Description

  The present invention relates to a heat conductive composite material, a heat conductive filler used therefor, and a method for producing the same.

  Boron nitride is known as a highly insulating material having high thermal conductivity, and various thermally conductive composite materials in which boron nitride particles are dispersed in a matrix as a thermally conductive filler have been developed. For example, in Japanese Patent Application Laid-Open No. 2010-260225 (Patent Document 1), thermal conductivity obtained by cutting a silicone laminate containing two types of boron nitride powders having different average particle diameters as thermal conductive fillers from the lamination direction. A shaped body is disclosed.

  Further, International Publication No. 2008/042446 (Patent Document 2) includes platelet boron nitride powder material and spherical aggregate of boron nitride powder material as at least two different types of boron nitride powder materials. A polymer composition is disclosed.

  Furthermore, JP-A-2015-6985 (Patent Document 3) discloses a composition containing a filler and a resin composed of boron nitride aggregated particles in which primary particles in the boron nitride aggregated particles have a card house structure. Has been.

  However, even such a conventional heat conductive composite material has a limit in improvement of heat conductivity, and sufficient heat conductivity cannot always be achieved.

JP 2010-260225 A International Publication No. 2008/042446 JP2015-6985A

  The present invention has been made in view of the above-described problems of the prior art, and is capable of efficiently improving thermal conductivity, a method for producing the same, and thermal conductivity having excellent thermal conductivity. It is an object to provide a functional composite material and a method for producing the same.

  As a result of intensive research to achieve the above object, the present inventors have improved the thermal conductivity efficiently by jetting a fluid containing boron nitride particles from a nozzle at high pressure and performing wet collision pulverization. The present inventors have found that a heat conductive composite material having excellent heat conductivity can be obtained by using the heat conductive filler, and the present invention has been completed. .

  That is, in the method for producing a thermally conductive filler of the present invention, the partially cleaved boron nitride fine particles in which the boron nitride fine particles are partially cleaved by jetting a fluid containing boron nitride particles from a nozzle at high pressure and performing wet collision pulverization. It is a method characterized by obtaining the heat conductive filler which consists of boron nitride microparticles | fine-particles containing.

  In such a method for producing a thermally conductive filler of the present invention, it is preferable that the high pressure is 30 to 250 MPa, and the flow rate when the fluid is ejected from the nozzle is 200 to 800 m / s.

  The thermally conductive filler of the present invention comprises boron nitride fine particles containing partially cleaved boron nitride fine particles in which the boron nitride fine particles are partially cleaved, and the content of the partially cleaved boron nitride fine particles is the total amount of the boron nitride fine particles. It is characterized by being 5% by volume or more.

  In such a heat conductive filler of the present invention, the boron nitride fine particles preferably have an average particle diameter of 1 to 100 μm, and the boron nitride fine particles are hexagonal plate-like boron nitride fine particles. Is preferred.

Furthermore, the manufacturing method of the heat conductive composite material of this invention is as follows.
A step of obtaining boron nitride fine particles including partially cleaved boron nitride fine particles in which boron nitride fine particles are partially cleaved by jetting a fluid containing boron nitride particles from a nozzle at high pressure and performing wet collision pulverization;
A thermally conductive filler composed of boron nitride fine particles including the partially cleaved boron nitride fine particles is dispersed in a matrix, and the swollen boron nitride fine particles that are swollen with the matrix filled in the cleaved voids of the partially cleaved boron nitride fine particles are contained. Obtaining a thermally conductive composite material,
It is the method characterized by including.

  In such a method for producing a heat conductive composite material of the present invention, the high pressure is preferably 30 to 250 MPa, and the flow rate when the fluid is ejected from the nozzle is preferably 200 to 800 m / s. .

The thermally conductive composite material of the present invention is obtained by dispersing a thermally conductive filler composed of boron nitride fine particles in a matrix,
At least a part of the boron nitride fine particles are partially cleaved boron nitride fine particles in which the boron nitride fine particles are partially cleaved,
The composite material contains swollen boron nitride fine particles that are swollen by filling the matrix into the cleavage voids of the partially cleaved boron nitride fine particles,
The total area of the region corresponding to the swollen boron nitride fine particles is 1 to 50% with respect to the cross-sectional area of the composite material on the basis of the cross-section of the composite material.
It is characterized by this.

  In such a heat conductive composite material of the present invention, the content of the partially cleaved boron nitride fine particles is preferably 5% by volume or more based on the total amount of the boron nitride fine particles, and the heat conductive filler Is preferably 10 to 90% by volume based on the total amount of the composite material.

  Moreover, in the heat conductive composite material of this invention, in addition to the said boron nitride microparticles | fine-particles, in addition to the said boron nitride microparticles | fine-particles, the high heat conductive microparticles | fine-particles which are 20 W / mK or more are contained further. preferable.

  As described above, when the thermally conductive composite material of the present invention contains the highly thermally conductive fine particles, the content of the boron nitride fine particles is 5% by volume or more with respect to the total amount of the thermally conductive filler. Is preferred.

  Further, when the high thermal conductive fine particles are contained in the heat conductive composite material of the present invention, the boron nitride fine particles are hexagonal plate-like boron nitride fine particles, and the high thermal conductivity The fine particles are preferably at least one fine particle selected from the group consisting of cubic boron nitride, diamond, aluminum nitride, aluminum oxide, magnesium oxide, zinc oxide, silicon nitride, and silicon carbide.

  The reason why excellent thermal conductivity is obtained by the thermally conductive composite material using the thermally conductive filler of the present invention is not necessarily clear, but the present inventors infer as follows. That is, in the thermally conductive composite material of the present invention, at least a part of the boron nitride fine particles used as the thermally conductive filler is partially cleaved and has a cleavage plane that has a cleavage plane inside or at the end of the particle. Boron nitride fine particles are formed. When such partially cleaved boron nitride fine particles are dispersed in the matrix as a thermally conductive filler, the matrix enters the cleaved voids and swells. Therefore, compared with boron nitride fine particles in which partial cleavage is not formed, the boron nitride fine particles swollen in this way are easily deformed as the apparent average diameter increases, and thereby boron nitride fine particles in the composite material. The contact between the particles is easy to occur and the adhesion is improved, the network structure of the heat conduction path through which heat diffuses through the contact sites between the boron nitride particles is efficiently formed, and the interfacial thermal resistance between the particles is greatly reduced. For this reason, the present inventors speculate that the thermal conductivity of the resulting composite material is improved and excellent thermal conductivity is achieved. In addition, since the uncleaved portion inside the boron nitride fine particles retains the high thermal conductivity structure of the boron nitride particles before the cleavage, the heat transfer inside the particles can be efficiently performed, and the high thermal conductivity composite material This is advantageous.

  Further, in the method for producing a thermally conductive filler of the present invention, a fluid containing boron nitride particles is ejected from a nozzle at a high pressure, whereby the particles are refined by collision or shear flow, thereby destroying the crystal structure. While being finely pulverized while suppressing excessive miniaturization, the pressure applied to the particles suddenly disappears by rapidly decreasing the pressure from the state where the particles are sheared and compressed at high pressure in the fluid. As a result, a force that expands from the inside of the particle toward the outside acts, and along with this, the particle is pulled to the outside, so that partial cleavage occurs inside and at the end of the particle to obtain partially cleaved boron nitride fine particles. The inventors speculate.

  According to the present invention, it is possible to provide a thermally conductive filler capable of efficiently improving thermal conductivity and a method for producing the same, a thermally conductive composite material having excellent thermal conductivity, and a method for producing the same. It becomes possible.

It is a schematic diagram which shows the cylindrical composite material produced by the Example and the comparative example, and the sample for thermal conductivity measurement cut out from it. 4 is a scanning electron micrograph showing an example of a cross-sectional SEM image of the composite material obtained in Example 1. FIG. In the SEM image shown in FIG. 2, it is the scanning electron micrograph which colored the area | region other than the area | region corresponded to the swelling boron nitride fine particle by binarization by binarization. 3 is a scanning electron micrograph showing an example of a cross-sectional SEM image of the composite material obtained in Comparative Example 1. FIG. In the SEM image shown in FIG. 4, it is the scanning electron micrograph which colored the area | region corresponded to the non-swelled boron nitride particle | grains by binarization by binarization.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

  First, the thermally conductive filler of the present invention will be described. The thermally conductive filler of the present invention comprises boron nitride fine particles containing partially cleaved boron nitride fine particles in which the boron nitride fine particles are partially cleaved, and the content of the partially cleaved boron nitride fine particles is based on the total amount of the boron nitride fine particles. And 5 vol% or more.

  The thermally conductive filler of the present invention is composed of boron nitride (BN) fine particles, and boron nitride has a hexagonal atmospheric pressure phase, a cubic high pressure phase, and the like. From the viewpoint of conductivity, hexagonal plate-like boron nitride fine particles are preferable.

  The size of the boron nitride fine particles constituting the heat conductive filler of the present invention is not particularly limited, but the average particle diameter is preferably 1 to 100 μm, more preferably 2 to 50 μm, and 3 to 30 μm. It is particularly preferred that If the average particle diameter of the boron nitride fine particles is less than the lower limit, the thermal conductivity tends to decrease because the grain boundary resistance between the boron nitride fine particles and the number of grain boundaries in the composite material increase in the obtained composite material, When the upper limit is exceeded, the dispersion uniformity and filling rate of the heat conductive filler in the resulting composite material are lowered, and the heat conductivity tends to be lowered. In the present specification, “average particle diameter” means a cumulative 50% particle diameter (median diameter: D50) in a particle size distribution determined by a laser diffraction / scattering method.

  In the present invention, it is necessary that at least a part of the boron nitride fine particles are partially cleaved boron nitride fine particles in which the boron nitride fine particles are partially cleaved. Such partially cleaved boron nitride fine particles are those in which the boron nitride fine particles are partially cleaved and have a cleaved surface inside or at the end of the particle, and when dispersed in a matrix as a thermally conductive filler, The matrix enters the space between the opposing cleavage planes) and swells (swelled boron nitride fine particles).

  Such partially cleaved boron nitride fine particles are observed as swollen boron nitride fine particles in a scanning electron microscope (SEM) photograph of a cross-section of the obtained composite material, and are not cleaved without being cleaved based on brightness and shape. It can be distinguished from uncleaved boron nitride particles that remain as they are, and completely cleaved boron nitride particles that do not have a cleaved surface at the inside or at the end obtained by completely dividing the boron nitride particles by cleavage. Furthermore, it is also possible to distinguish by three-dimensional dispersion structure observation by FIB-SEM (focused ion beam-scanning electron microscope). Hereinafter, such uncleaved boron nitride particles and fully cleaved boron nitride particles are collectively referred to as “non-swelled boron nitride particles”.

  In the thermally conductive filler of the present invention, the content of the partially cleaved boron nitride fine particles is the total amount of the boron nitride fine particles (the partially cleaved boron nitride fine particles, the uncleaved boron nitride particles, and the completely cleaved boron nitride fine particles. It is necessary to be 5% by volume or more with respect to the total amount). When the content of the partially cleaved boron nitride fine particles is less than 5% by volume, a network structure of a heat conduction path in which heat is diffused through contact portions between the boron nitride fine particles is not sufficiently formed in the obtained composite material, and the resulting composite is obtained. The thermal conductivity of the material does not improve sufficiently. From the viewpoint of further improving the thermal conductivity of the obtained composite material, the content of the partially cleaved boron nitride fine particles is preferably 10% by volume or more, and 20% by volume with respect to the total amount of the boron nitride fine particles. More preferably.

The content of the partially cleaved boron nitride fine particles with respect to the total amount of the boron nitride fine particles is obtained as follows. That is, in the scanning electron micrograph (SEM image) of the cross section of the obtained composite material, based on the brightness and shape,
(I) a region corresponding to the swollen boron nitride fine particles (the partially cleaved boron nitride fine particles and the matrix incorporated in the cleaved voids thereof);
(Ii) a region corresponding to the non-swelled boron nitride fine particles (the uncleaved boron nitride particles and the completely cleaved boron nitride fine particles);
(Iii) a region of the matrix corresponding to a matrix that is not incorporated in the swollen boron nitride fine particles;
And the area of each region can be obtained by a known image analysis method such as binarization. Therefore, for the cross section of the obtained composite material, for example, 10 or more measurement regions having a width of 60 μm or more and a length of 40 μm or more are arbitrarily extracted, and in the SEM image of each measurement region, (ii) corresponds to the non-swelled boron nitride fine particles The total area of the region to be obtained is determined, and from the relationship with the total area of the region corresponding to all the boron nitride particles when all the boron nitrides in the measurement region are uncleaved boron nitride particles, The content of the partially cleaved boron nitride fine particles can be determined. Then, by calculating the average value of all the measurement regions, the content (average value) of the partially cleaved boron nitride fine particles with respect to the total amount of the boron nitride fine particles in the used thermally conductive filler is obtained.

  Thus, the thermally conductive filler of the present invention comprises the boron nitride fine particles containing a predetermined amount or more of the partially cleaved boron nitride fine particles. From the viewpoint of further improving dispersibility in the matrix, the boron nitride fine particles A functional group such as a hydroxyl group, a carboxyl group, an ester group, an amide group, an amino group, or the like may be bonded to the surface.

  The thermally conductive filler of the present invention may be composed of only the boron nitride fine particles containing a predetermined amount or more of the partially cleaved boron nitride fine particles. In addition to the boron nitride fine particles, for example, a plate-like shape Other thermally conductive particles such as graphite, plate-like aluminum nitride, plate-like alumina, aluminum flake, copper flake, diamond, silicon nitride, SiC fiber, carbon fiber, carbon nanotube, metal-plated fiber, metal fiber, etc. Other heat conductive fibers may be further contained.

  As described above, when the thermally conductive filler contains another thermally conductive material in addition to the boron nitride fine particles, the thermal conductivity is 20 W / mK or more as the other thermally conductive material. Fine particles are preferably contained, and as such high heat conductive fine particles, those having isotropic high heat conductivity are more preferable. Thus, by containing the high thermal conductive fine particles in addition to the boron nitride fine particles, the thermal conductivity in the obtained thermally conductive composite material tends to be further improved.

  When the high thermal conductivity fine particles are contained in this way, the boron nitride fine particles are hexagonal plate-like boron nitride fine particles, and the high thermal conductivity fine particles are cubic boron nitride (thermal Conductivity: 1000 to 2000 W / mK), diamond (thermal conductivity: 2000 to 3000 W / mK), aluminum nitride (thermal conductivity: 150 to 350 W / mK), aluminum oxide (thermal conductivity: 20 to 35 W / mK) , Magnesium oxide (thermal conductivity: 45-60 W / mK), zinc oxide (thermal conductivity: 20-30 W / mK), silicon nitride (thermal conductivity: 80-100 W / mK) and silicon carbide (thermal conductivity: 150-170 W / mK) is preferable. In addition, the thermal conductivity in this specification is the thermal conductivity at room temperature (20 ° C.).

  The size of the high thermal conductive fine particles is not particularly limited, but the average particle size is preferably 0.1 to 100 μm, more preferably 0.3 to 50 μm, and 0.5 to 30 μm. Particularly preferred. If the average particle size of the high thermal conductive fine particles is less than the lower limit, the thermal conductivity tends to decrease because the grain boundary resistance between the thermal conductive fillers and the number of grain boundaries in the composite material increase in the obtained composite material. On the other hand, when the above upper limit is exceeded, the dispersion uniformity and filling rate of the thermally conductive filler in the resulting composite material tend to decrease, and the thermal conductivity tends to decrease.

  Thus, when other heat conductive materials are contained, the content of the boron nitride fine particles with respect to the total amount of the heat conductive filler of the present invention is preferably 5% by volume or more, and 20% by volume or more. Is more preferable, and 60% by volume or more is particularly preferable.

  In addition, the reason why the thermal conductivity of the obtained heat conductive composite material tends to be further improved by containing the high thermal conductivity fine particles in addition to the boron nitride fine particles is not necessarily clear, The present inventors infer as follows. In other words, high thermal conductivity fine particles have the advantage of low thermal resistance in the particles, but since they are generally hard particles, the thermal resistance between the particles (interfacial thermal resistance) increases, and the conventional composite in which such particles are dispersed is used. In the material, it is difficult to sufficiently bring out the effect of improving the thermal conductivity by the high thermal conductive fine particles. On the other hand, in the present invention, partially cleaved boron nitride fine particles are contained as described above, and such partially cleaved boron nitride fine particles have not only a soft and low interface thermal resistance, but also a partially cleaved structure having a heat conduction property. The heat conduction path is efficiently formed by forming the network structure of the conductive filler. When the high thermal conductivity fine particles coexist as a part of such a thermal conductive filler, the presence of the partially cleaved boron nitride fine particles having low interfacial thermal resistance around the high thermal conductivity fine particles increases the heat The present inventors speculate that the interface between the conductive fine particles decreases and the excellent intra-particle thermal conductivity of the high thermal conductive fine particles is effectively exhibited.

Next, the thermally conductive composite material of the present invention will be described. The thermally conductive composite material of the present invention is obtained by dispersing a thermally conductive filler composed of boron nitride fine particles in a matrix,
At least a part of the boron nitride fine particles are partially cleaved boron nitride fine particles in which the boron nitride fine particles are partially cleaved,
The composite material contains swollen boron nitride fine particles that are swollen by filling the matrix into the cleavage voids of the partially cleaved boron nitride fine particles,
The total area of the region corresponding to the swollen boron nitride fine particles is 1 to 50% with respect to the cross-sectional area of the composite material on the basis of the cross-section of the composite material.
It is characterized by this.

  That is, in the thermally conductive composite material of the present invention, the thermally conductive filler of the present invention composed of the boron nitride fine particles containing the partially cleaved boron nitride fine particles is arranged dispersed in a matrix, and the partially cleaved boron nitride fine particles are arranged. The boron nitride fine particles are swollen boron nitride fine particles which are swollen by filling the matrix in the cleavage gap.

  As a matrix in such a heat conductive composite material of the present invention, an insulating resin or an insulating oil is preferably used, and specifically, although not particularly limited, examples of the resin include an epoxy resin and a phenol resin. , Thermosetting resins such as silicone resins, polystyrene, polymethyl methacrylate, polycarbonate, polyolefin (eg, polyethylene, polypropylene), polyolefin elastomer, polyethylene terephthalate, nylon, ABS resin, polyamide, polyimide, polyamideimide, ethylene-propylene- Examples thereof include thermoplastic resins such as diene rubber (EPDM), butyl rubber, natural rubber, polyisoprene and polyetherimide. Examples of the oil include silicone oil, fluoroether oil, mineral oil, animal and vegetable natural oil, and paraffin. These resins and oils may be used alone or in combination of two or more.

  In the thermally conductive composite material of the present invention, the total area of the region corresponding to the swollen boron nitride fine particles needs to be 1 to 50% with respect to the cross-sectional area of the composite material on the basis of the cross section. It is. When the ratio of the total area of the regions corresponding to the swollen boron nitride fine particles is less than 1%, a network structure of a heat conduction path through which heat diffuses through the contact portion between the boron nitride fine particles in the composite material is not sufficiently formed. The thermal conductivity of the composite material is not sufficiently improved. On the other hand, if the ratio of the total area of the regions corresponding to the swollen boron nitride fine particles exceeds 50%, the filler becomes bulky and difficult to handle when making a composite material. Further, from the viewpoint of further improving the thermal conductivity of the composite material, the ratio of the total area of the region corresponding to the swollen boron nitride fine particles is preferably 5 to 45% with respect to the cross-sectional area of the composite material. 10 to 40% is more preferable, and 15 to 35% is particularly preferable.

Note that the ratio of the total area of the regions corresponding to the swollen boron nitride fine particles (ratio to the cross-sectional area of the composite material) on the basis of the cross-section of the composite material is obtained as follows. That is, as described above, in the scanning electron micrograph (SEM image) of the cross section of the composite material, based on the brightness and shape,
(I) a region corresponding to the swollen boron nitride fine particles (the partially cleaved boron nitride fine particles and the matrix incorporated in the cleaved voids thereof);
(Ii) a region corresponding to the non-swelled boron nitride fine particles (the uncleaved boron nitride particles and the completely cleaved boron nitride fine particles);
(Iii) a region of the matrix corresponding to a matrix that is not incorporated in the swollen boron nitride fine particles;
And the area of each region can be obtained by a known image analysis method such as binarization. Therefore, with respect to the cross section of the composite material, for example, 10 or more measurement regions having a width of 60 μm or more and a length of 40 μm or more are arbitrarily extracted, and in the SEM image of each measurement region, (i) the region corresponding to the swollen boron nitride fine particles The total area can be obtained, and the ratio of the total area of the region corresponding to the swollen boron nitride fine particles in the region can be obtained as the ratio to the area of the measurement region. Then, by calculating the average value of all the measurement regions, the ratio of the total area of the regions corresponding to the swollen boron nitride fine particles (the cross section of the composite material) on the cross-sectional basis for the heat conductive composite material to be measured The ratio to the area, the average value) is obtained.

  In the heat conductive composite material of this invention, it is preferable that the content rate of the said heat conductive filler is 10-90 volume% with respect to the whole quantity of the said composite material, and it is more preferable that it is 15-80 volume%. It is especially preferable that it is 20-70 volume%. When the content of the heat conductive filler is less than the lower limit, heat is transmitted through a contact portion between the boron nitride fine particles (the boron nitride fine particles and the high heat conductive fine particles when the high heat conductive fine particles are included) in the composite material. The network structure of the diffusing heat conduction path is not sufficiently formed, and the thermal conductivity of the obtained composite material tends not to be sufficiently improved. On the other hand, if the content of the thermally conductive filler exceeds the upper limit, the matrix does not sufficiently penetrate into the swollen boron nitride fine particle region, voids are likely to be generated, and the effect of high thermal conductivity due to partial cleavage of the filler is offset. In addition, the filling rate tends to decrease due to steric interference between the particles.

  Next, the manufacturing method of the heat conductive filler of this invention and the manufacturing method of the heat conductive composite material of this invention are demonstrated.

  First, in the method for producing a thermally conductive filler of the present invention (the pre-stage step of the method for producing a thermally conductive composite material of the present invention), a fluid containing boron nitride particles is jetted from a nozzle at high pressure and wet collision pulverization is performed. Thus, a thermally conductive filler made of boron nitride fine particles including partially cleaved boron nitride fine particles in which the boron nitride fine particles are partially cleaved is obtained (wet pulverization step).

  In such a wet pulverization process according to the present invention, a fluid containing boron nitride particles as raw material particles is ejected from a nozzle at a high pressure, whereby the particles are refined by collision or shear flow, thereby forming a crystal structure. While being pulverized wet while suppressing destruction and excessive miniaturization, the pressure applied to the particles is drastically reduced by reducing the pressure rapidly from the state where the particles are sheared and compressed at high pressure in the fluid. By disappearing, a force that expands from the inside of the particle toward the outside works, and the particle is pulled outward along with it, so that partial cleavage occurs inside or at the end of the particle, and the above-mentioned partially cleaved boron nitride fine particles are formed. It will be obtained.

  The apparatus used in such a wet pulverization step is not particularly limited, and a commercially available wet pulverization apparatus (wet micronizer) based on the principle of spraying a fluid containing raw material particles from a nozzle at a high pressure and performing wet collision pulverization to make it fine. Can be used. Moreover, it is preferable to use a wet pulverizer equipped with a straight type nozzle from the viewpoint of wet pulverization while suppressing destruction of crystal structure of the boron nitride particles and excessive miniaturization.

  Further, the boron nitride particles used as the raw material particles are not particularly limited, and are commercially available nitrides having an average particle size of about 2 to 200 μm (more preferably 10 to 60 μm) depending on the average particle size of the target boron nitride fine particles. Boron powder (preferably hexagonal plate-like boron nitride powder) can be used.

  Also, the dispersion medium of the fluid ejected from the nozzle together with the boron nitride particles is not particularly limited, and for example, water; N-methyl-2-pyrrolidone, chloroform, dichloromethane, carbon tetrachloride, acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl Ketone, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, isopentyl acetate, amyl acetate, tetrahydrofuran, dimethylformaldehyde, dimethylacetamide, dimethyl sulfoxide, acetonitrile, methanol, ethanol, propanol, isopropanol, Butanol, hexanol, octanol, hexafluoroisopropanol, ethylene glycol, propylene glycol, tetramethylene glycol Tetraethylene glycol, hexamethylene glycol, diethylene glycol, benzene, toluene, xylene, chlorobenzene, dichlorobenzene, trichlorobenzene, chlorophenol, phenol, tetrahydrofuran, sulfolane, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, N -Organic solvents such as dimethylpyrrolidone, pentane, hexane, neopentane, cyclohexane, heptane, octane, isooctane, nonane, decane, diethyl ether; and oils such as silicone oil and liquid paraffin.

  Further, the concentration of the fluid (dispersion) containing the boron nitride particles is not particularly limited, but the content of the boron nitride particles is preferably 0.1 to 20% by volume, more preferably 0.5 to 10% by volume. . When the concentration of the dispersion is less than the lower limit, the yield of the cleaved boron nitride fine particles tends to be small. On the other hand, when the concentration exceeds the upper limit, the viscosity of the dispersion tends to be high and the pulverization tends to be difficult.

In addition, the conditions for the wet pulverization treatment are not particularly limited, but the following conditions are preferable from the viewpoint that the partially cleaved boron nitride fine particles can be obtained efficiently.
Pressure before injection: 30 to 250 MPa (more preferably 50 to 200 MPa)
Pressure after injection: Normal pressure Nozzle diameter: 0.1-0.5mm
Flow rate: 0.1-7.0 L / min (more preferably 0.5-1.1 L / min)
Nozzle injection flow rate: 200 to 800 m / s (more preferably 300 to 700 m / s).

  When the pre-injection pressure, flow rate, and nozzle injection flow rate in the wet pulverization treatment are less than the lower limit, the cleavage of the boron nitride particles is difficult to proceed, and the partially cleaved boron nitride fine particles tend not to be sufficiently obtained. On the other hand, when the pre-injection pressure, flow rate or nozzle injection flow rate in the wet pulverization process exceeds the upper limit, the cleavage of the boron nitride particles proceeds too much, and most of the boron nitride particles are completely divided by cleavage and the It becomes completely cleaved boron nitride fine particles, and the partially cleaved boron nitride fine particles tend not to be sufficiently obtained.

  Further, the wet pulverization treatment may be performed once on the boron nitride particles, but the boron nitride particles are repeatedly subjected to the wet pulverization treatment to obtain boron nitride fine particles including the desired amount of the partially cleaved boron nitride fine particles. You may do it. Thus, when performing the said wet grinding process repeatedly, the frequency | count (pass number) of repeating is preferably about 2-20 times (more preferably 2-10 times). If the number of times the wet pulverization process is repeated (the number of passes) exceeds the upper limit, the cleavage of the boron nitride particles proceeds excessively, and most of the boron nitride particles are completely divided by cleavage to become the completely cleaved boron nitride fine particles. The partially cleaved boron nitride fine particles tend not to be sufficiently obtained.

  In the wet pulverization step, after the wet pulverization treatment, the boron nitride fine particles containing the partially cleaved boron nitride fine particles are obtained by performing filtration, washing, and drying treatment as necessary, but such filtration, washing, and Any drying process is not particularly limited, and a known method can be appropriately employed.

  Next, in the latter step of the method for producing a heat conductive composite material of the present invention, boron nitride fine particles containing the partially cleaved boron nitride fine particles (if the high heat conductive fine particles are included, the boron nitride fine particles and the high heat conductive The thermally conductive filler comprising the finely divided fine particles) is dispersed in the matrix to obtain the thermally conductive composite material containing the swollen boron nitride fine particles that are swollen by filling the matrix into the cleaved voids of the partially cleaved boron nitride fine particles. (Composite process).

  In such a composite process according to the present invention, first, a thermally conductive filler composed of boron nitride fine particles including the partially cleaved boron nitride fine particles and a matrix are mixed. At that time, the mixing ratio of the heat conductive filler and the matrix is determined so that the content of the heat conductive filler in the obtained composite material becomes the target content. Moreover, the method in particular of mixing a heat conductive filler and a matrix is not restrict | limited, A well-known mixing method is used suitably.

  When the oil is used as such a matrix, the heat conductive composite material can be obtained by mixing the heat conductive filler and the oil into a uniform slurry. That is, in the process of mixing the thermally conductive filler and the oil in this way, the oil enters the cleaved voids of the partially cleaved boron nitride fine particles to become swollen boron nitride fine particles, and contains the swollen boron nitride fine particles. A thermally conductive composite material is obtained.

  In addition, when the resin is used as such a matrix, the heat conductive composite material can be obtained by mixing the heat conductive filler and the resin to form a uniform mixture, and molding the obtained mixture. it can. That is, in the process of mixing and molding the thermally conductive filler and the resin in this way, the resin enters into the cleaved voids of the partially cleaved boron nitride fine particles to become swollen boron nitride fine particles, and the swollen boron nitride fine particles A heat conductive composite material is obtained.

  Thus, when the heat conductive filler and the resin are mixed to form a uniform mixture, a dispersion medium may be further added to form a uniform slurry, in which case the dispersion medium is removed by a known method such as vacuum drying. After forming, it is preferable to mold. Such a dispersion medium is not particularly limited, and an organic solvent similar to the organic solvent mentioned as the dispersion medium of the fluid ejected from the nozzle together with the boron nitride particles may be appropriately used.

  Moreover, it is preferable to compress and pressurize when the said mixture is shape | molded. Such a compression method is not particularly limited, and may be uniaxial compression or biaxial compression. Moreover, you may compress isotropically by a hydrostatic pressure. Further, the pressure at the time of compression is not particularly limited, but 5 to 20 MPa is preferable. If the pressure during compression is less than the lower limit, voids tend to remain in the obtained composite material.On the other hand, if the pressure exceeds the upper limit, it becomes difficult to control the orientation of the filler in the obtained composite material, resulting in residual strain. Tend to occur.

  Furthermore, the method for solidifying the resin when molding the mixture is not particularly limited. For example, when a thermoplastic resin is used as the resin, a method by cooling such as cooling, various (heat, When a light, water) curable resin is used, an appropriate curing method can be employed. Such solidification may be performed either during molding or after molding.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
“Dencaboron nitride powder SGP” (average particle diameter: 18 μm, hexagonal plate boron nitride (BN) particles) manufactured by Denka Co., Ltd. was used as the boron nitride particles as raw material particles, and N-methyl-2-pyrrolidone (NMP) ) Was used as a dispersion medium to obtain a 5% by volume dispersion. Next, using a wet pulverizer equipped with a commercially available straight type nozzle, the pressure in the chamber before injection was set to 200 MPa, and the dispersion containing the boron nitride particles was flowed from the nozzle (nozzle diameter: 0.2 mm) at a flow rate of 1.069 L. The dispersion was subjected to the first wet pulverization treatment by injecting at a flow rate of 632 m / s at a flow rate of / min and abruptly reducing the pressure from the state of shear flow compression at high pressure to normal pressure. Further, the wet pulverization treatment in which the obtained dispersion was again sprayed from the nozzle under the same conditions was repeated a total of 10 times (the number of passes: 10 times) to obtain a dispersion containing wet-pulverized boron nitride fine particles. Then, boron nitride fine particles were filtered from the obtained dispersion, washed with methanol, and then vacuum dried to obtain wet-pulverized boron nitride fine particles. The average particle diameter of the obtained boron nitride fine particles was 5 μm.

  Next, using the obtained boron nitride fine particles as a thermally conductive filler and using a one-component thermosetting epoxy resin (“Epoxy resin EP160” manufactured by Cemedine Co.) as a matrix, a composite material was obtained as follows. That is, first, a dichloromethane solution (concentration: 6.0 vol%) of the epoxy resin and the boron nitride fine particles are mixed so that the filler (boron nitride fine particle) content in the obtained composite material is 40 vol%. The resulting slurry was stirred to evaporate dichloromethane and then vacuum dried for about 15 minutes to completely remove the dichloromethane to obtain a mixture in which the boron nitride fine particles were dispersed in the epoxy resin. Next, the obtained mixture was filled in a cylindrical container (inner diameter: 14 mmφ) preheated to 110 ° C. so that the thickness after molding was 35 mm, and compressed in a longitudinal direction of the cylindrical container at a pressure of 7.5 MPa. And maintained at 110 ° C. for 30 minutes to cure the epoxy resin to obtain a cylindrical heat conductive composite material. The porosity of the obtained composite material was 0%.

<Measurement of thermal conductivity>
As shown in FIG. 1, a sample 2 for thermal conductivity measurement (x-axis direction length: 3 mm, y-axis direction length: 10 mm, z-axis direction length: 10 mm) is cut out from the cylindrical composite material 1, The thermal diffusivity in the direction perpendicular to the compression direction (x-axis direction) was measured using a xenon flash analyzer (“LFA 447 NanoFlash” manufactured by NETZSCH) with the thickness direction (x-axis direction) of the sample as the heat flow direction.

Further, the specific heat of the sample was measured by a DSC method using a thermal vibration type differential scanning calorimeter (manufactured by TA Instruments Inc.). Furthermore, the density of the sample was determined by an underwater substitution method (Archimedes method). From these results:
Thermal conductivity (W / (m · K)) = specific heat (J / (kg · K)) × density (kg / m ³ ) × thermal diffusivity (m ² / sec)
Thus, the thermal conductivity in the direction perpendicular to the compression direction (x-axis direction) was obtained. The obtained results are shown in Table 2.

<Electron microscope observation and structural analysis of cross section>
A sample for electron microscope observation of a cross section was cut out from a cylindrical composite material, and a polishing machine (“Bulmet” manufactured by Buehler Co., Ltd.) was used for any 10 cross-section measurement regions (regions of 210 microns long and 70 microns wide in Example 1). After performing mechanical polishing using ^TM 1000 "), the cross-section was observed with an electron microscope using a scanning electron microscope (" NB-5000 "manufactured by Hitachi High-Technologies Corporation). An example of the obtained scanning electron micrograph (SEM image) is shown in FIG.

Next, in the obtained SEM image of each measurement region, based on the brightness and shape,
(I) a region corresponding to swollen boron nitride fine particles (partially cleaved boron nitride fine particles and a matrix taken into the cleaved voids);
(Ii) a region corresponding to non-swelled boron nitride fine particles (uncleaved boron nitride particles and fully cleaved boron nitride fine particles);
(Iii) a region of the matrix corresponding to a matrix that is not incorporated in the swollen boron nitride fine particles;
And (i) the total area of the region corresponding to the swollen boron nitride fine particles is obtained by binarization, and the ratio of the total area of the regions corresponding to the swollen boron nitride fine particles in the region is calculated as a ratio to the area of the measurement region. The ratio was determined. Then, by calculating the average value of all the measurement regions, the ratio of the total area of the region corresponding to the swollen boron nitride fine particles in the obtained composite material (ratio to the cross-sectional area of the composite material, average value) was obtained. . The obtained results are shown in Table 2. Also, by binarization, (i) a region other than the region corresponding to the swollen boron nitride fine particles, that is, (ii) a region corresponding to the non-swelled boron nitride fine particles and (iii) the matrix is incorporated into the swollen boron nitride fine particles. FIG. 3 shows an example of an SEM image in which the region corresponding to the existing matrix is darkly colored.

  Further, in the SEM image of each obtained measurement region, similarly, by binarization, (ii) the total area of the region corresponding to the non-swelled boron nitride fine particles (uncleaved boron nitride particles and completely cleaved boron nitride fine particles) is obtained, The total area of the regions corresponding to all boron nitride particles when all the boron nitrides in the measurement region are uncleaved boron nitride particles (corresponding to non-swelled boron nitride fine particles in the measurement region of the same area in Comparative Example 1 described later) From the relationship with the total area of the region, the content of partially cleaved boron nitride fine particles with respect to the total amount of boron nitride fine particles in the region was determined. And the content rate (average value) of the partially cleaved boron nitride fine particles with respect to the total amount of boron nitride fine particles in the filler used in the obtained composite material was calculated by calculating the average value of all the measurement regions. The obtained results are shown in Table 2.

(Comparative Example 1)
A heat conductive composite material was obtained in the same manner as in Example 1 except that the boron nitride particles used as the raw material particles in Example 1 were used as they were as the heat conductive filler without wet pulverization. And about the obtained composite material, heat conductivity measurement was performed like Example 1, and the heat conductivity of the direction (x-axis direction) perpendicular | vertical to a compression direction was calculated | required. The obtained results are shown in Table 2.

  The obtained composite material was subjected to electron microscopic observation and structural analysis of the cross section in the same manner as in Example 1, and the ratio of the total area of the region corresponding to the swollen boron nitride fine particles in the obtained composite material was used. The content of the partially cleaved boron nitride fine particles in the filler was determined. The obtained results are shown in Table 2. An example of the obtained scanning electron micrograph (SEM image) is shown in FIG. Furthermore, FIG. 5 shows an example of an SEM image in which the region corresponding to the non-swelled boron nitride particles is colored deeply by binarization.

(Comparative Example 2)
Instead of “Denkaboron Nitride Powder SGP” (average particle size: 18 μm) manufactured by Denka Co., Ltd. as the boron nitride particles, “Denkaboron Nitride Powder HGP” manufactured by Denka Co., Ltd. (average particle size: 5 μm, hexagonal plate nitriding) A thermally conductive composite material was obtained in the same manner as in Comparative Example 1 except that boron (BN) particles were used. And about the obtained composite material, heat conductivity measurement was performed like Example 1, and the heat conductivity of the direction (x-axis direction) perpendicular | vertical to a compression direction was calculated | required. The obtained results are shown in Table 2.

  The obtained composite material was subjected to electron microscopic observation and structural analysis of the cross section in the same manner as in Example 1, and the ratio of the total area of the region corresponding to the swollen boron nitride fine particles in the obtained composite material was used. The content of the partially cleaved boron nitride fine particles in the filler was determined. The obtained results are shown in Table 2.

(Example 2)
Instead of “Denkaboron Nitride Powder SGP” (average particle size: 18 μm) manufactured by Denka Co., Ltd. as the raw material particles, “Boron Nitride (BN) Powder PT110” manufactured by Momentive (average particle size: 40 μm, hexagonal) A thermally conductive composite material was obtained in the same manner as in Example 1 except that crystal plate-like boron nitride (BN) particles) were used. And about the obtained composite material, heat conductivity measurement was performed like Example 1, and the heat conductivity of the direction (x-axis direction) perpendicular | vertical to a compression direction was calculated | required. The obtained results are shown in Table 2.

  Further, the obtained composite material was subjected to electron microscopic observation and structural analysis of the cross section in the same manner as in Example 1 except that the cross-sectional measurement region was a region of 60 microns in length and 40 microns in width. The ratio of the total area of the region corresponding to the swollen boron nitride fine particles and the content of the partially cleaved boron nitride fine particles in the filler used were determined. The obtained results are shown in Table 2.

(Examples 3 to 4)
A thermally conductive composite material was obtained in the same manner as in Example 2 except that various conditions in the wet pulverization treatment were changed as shown in Table 1. And about the obtained composite material, heat conductivity measurement was performed like Example 1, and the heat conductivity of the direction (x-axis direction) perpendicular | vertical to a compression direction was calculated | required. The obtained results are shown in Table 2.

  Further, the obtained composite material was subjected to electron microscopic observation and structural analysis of the cross section in the same manner as in Example 1 except that the cross-sectional measurement region was a region of 60 microns in length and 40 microns in width. The ratio of the total area of the region corresponding to the swollen boron nitride fine particles and the content of the partially cleaved boron nitride fine particles in the filler used were determined. The obtained results are shown in Table 2.

(Comparative Example 3)
A heat conductive composite material was obtained in the same manner as in Example 2 except that the boron nitride particles used as the raw material particles in Example 2 were used as they were as the heat conductive filler without being wet pulverized. And about the obtained composite material, heat conductivity measurement was performed like Example 1, and the heat conductivity of the direction (x-axis direction) perpendicular | vertical to a compression direction was calculated | required. The obtained results are shown in Table 2.

  Further, the obtained composite material was subjected to electron microscopic observation and structural analysis of the cross section in the same manner as in Example 1 except that the cross-sectional measurement region was a region of 60 microns in length and 40 microns in width. The ratio of the total area of the region corresponding to the swollen boron nitride fine particles and the content of the partially cleaved boron nitride fine particles in the filler used were determined. The obtained results are shown in Table 2.

<Evaluation of results shown in Table 1 and Table 2>
As is clear from the results shown in Tables 1 and 2, all of the thermally conductive fillers of Examples 1 to 4 obtained by the method for producing a thermally conductive filler of the present invention contain partially cleaved boron nitride fine particles. The rate was 5% by volume or more based on the total amount of boron nitride fine particles. On the other hand, it was confirmed that none of the commercially available boron nitride particles not subjected to the wet pulverization treatment according to the present invention contains partially cleaved boron nitride fine particles.

  Furthermore, the heat conductive composite material of Examples 1-4 obtained by the manufacturing method of the heat conductive composite material of this invention using the heat conductive filler of this invention containing partially cleaved boron nitride fine particles as described above In all, the total area of the regions corresponding to the swollen boron nitride fine particles is within the range of 1 to 50% with respect to the cross-sectional area of the composite material on the basis of the cross-section of the composite material. It was confirmed that the composite material had a very high thermal conductivity as compared with the heat conductive composite materials of Comparative Examples 1 to 3 in which the presence of the swollen boron nitride fine particles was not confirmed.

(Example 5)
As the thermally conductive filler, the wet-pulverized boron nitride fine particles obtained in Example 2 and aluminum nitride fine particles (“Aluminum nitride (AlN) powder” manufactured by Sakai Kogyo Co., Ltd., average particle size: 10 μm) are used. Thermal conductivity was obtained in the same manner as in Example 2 except that the pulverized boron nitride fine particles and aluminum nitride fine particles in the obtained composite material were mixed so that the contents were 32% by volume and 8% by volume, respectively. A composite material was obtained.

  Next, a sample for thermal conductivity measurement (z-axis direction thickness: 2 mm, diameter: 14 mmφ, not shown) is cut out from the obtained cylindrical composite material 1, and the thickness direction (z-axis direction) of the sample is cut out. Using a xenon flash analyzer ("LFA 447 NanoFlash" manufactured by NETZSCH) as the heat flow direction, the thermal diffusivity in the direction parallel to the compression direction (z-axis direction) is measured, and the direction parallel to the compression direction (z-axis direction) is measured. The thermal conductivity was determined. The obtained results are shown in Table 3.

  Further, the content ratio [% by volume] of the partially cleaved boron nitride fine particles with respect to the total amount of boron nitride fine particles in the obtained composite material and the ratio [%] of the total area of the region corresponding to the swollen boron nitride fine particles to the cross-sectional area of the composite material are All were equivalent to the composite material obtained in Example 2 (the latter being proportional to the content of boron nitride fine particles).

(Comparative Example 4)
A thermally conductive composite material was prepared in the same manner as in Example 5 except that the unmilled boron nitride particles used in Comparative Example 3 were used in place of the wet-milled boron nitride fine particles obtained in Example 2. Obtained. And about the obtained composite material, heat conductivity measurement was performed like Example 5, and the heat conductivity of the direction (z-axis direction) parallel to a compression direction was calculated | required. The obtained results are shown in Table 3.

(Example 6)
Various conditions in the wet pulverization treatment were changed as shown in Table 1, and the filler (boron nitride fine particle) content in the obtained composite material was changed to 60% by volume in the same manner as in Example 2. A thermally conductive composite material was obtained. And about the obtained composite material, heat conductivity measurement was performed like Example 5, and the heat conductivity of the direction (z-axis direction) parallel to a compression direction was calculated | required. The obtained results are shown in Table 3.

  Further, the obtained composite material was subjected to electron microscopic observation and structural analysis of the cross section in the same manner as in Example 1 except that the cross-sectional measurement region was a region of 60 microns in length and 40 microns in width. When the content ratio [% by volume] of the partially cleaved boron nitride fine particles with respect to the total amount of the boron nitride fine particles and the ratio [%] of the total area of the region corresponding to the swollen boron nitride fine particles to the cross-sectional area of the composite material were determined, respectively. 1% by volume and 44.7%.

(Example 7)
As the thermally conductive filler, the wet-pulverized boron nitride fine particles obtained in Example 6 and aluminum nitride fine particles (“aluminum nitride (AlN) powder E grade” manufactured by Tokuyama Corporation, average particle diameter: 1 μm) are used. The heat conduction was conducted in the same manner as in Example 6 except that the pulverized boron nitride fine particles and aluminum nitride fine particles in the composite material were mixed so that the contents were 48% by volume and 12% by volume, respectively. A composite material was obtained. And about the obtained composite material, heat conductivity measurement was performed like Example 5, and the heat conductivity of the direction (z-axis direction) parallel to a compression direction was calculated | required. The obtained results are shown in Table 3.

  Further, the content ratio [% by volume] of the partially cleaved boron nitride fine particles with respect to the total amount of boron nitride fine particles in the obtained composite material and the ratio [%] of the total area of the region corresponding to the swollen boron nitride fine particles to the cross-sectional area of the composite material are All were equivalent to the composite material obtained in Example 6 (the latter being proportional to the content of boron nitride fine particles).

(Comparative Example 5)
Example 7 was used except that only the aluminum nitride fine particles (average particle diameter: 1 μm) were used as the heat conductive filler, and the content of the aluminum nitride fine particles in the obtained composite material was 60% by volume. Thus, a heat conductive composite material was obtained. And about the obtained composite material, heat conductivity measurement was performed like Example 5, and the heat conductivity of the direction (z-axis direction) parallel to a compression direction was calculated | required. The obtained results are shown in Table 3.

(Example 8)
As the heat conductive filler, the wet-pulverized boron nitride fine particles obtained in Example 6 and aluminum nitride fine particles ("High Thermal Conductive AlN Filler FAN-f05" manufactured by Furukawa Electronics Co., Ltd., average particle size: 5 μm) are used. The heat conduction was conducted in the same manner as in Example 6 except that the pulverized boron nitride fine particles and aluminum nitride fine particles in the composite material were mixed so that the contents were 48% by volume and 12% by volume, respectively. A composite material was obtained. And about the obtained composite material, heat conductivity measurement was performed like Example 5, and the heat conductivity of the direction (z-axis direction) parallel to a compression direction was calculated | required. The obtained results are shown in Table 3.

  Further, the content ratio [% by volume] of the partially cleaved boron nitride fine particles with respect to the total amount of boron nitride fine particles in the obtained composite material and the ratio [%] of the total area of the region corresponding to the swollen boron nitride fine particles to the cross-sectional area of the composite material are All were equivalent to the composite material obtained in Example 6 (the latter being proportional to the content of boron nitride fine particles).

(Comparative Example 6)
Example 8 was used except that only the aluminum nitride fine particles (average particle size: 5 μm) were used as the heat conductive filler, and the content of the aluminum nitride fine particles in the obtained composite material was 60% by volume. Thus, a heat conductive composite material was obtained. And about the obtained composite material, heat conductivity measurement was performed like Example 5, and the heat conductivity of the direction (z-axis direction) parallel to a compression direction was calculated | required. The obtained results are shown in Table 3.

Example 9
In the composite material obtained using the wet-pulverized boron nitride fine particles obtained in Example 6 and diamond fine particles (“Nanodiamond” manufactured by Vision Development Co., Ltd., average particle size: 5 μm) as the heat conductive filler A thermally conductive composite material was obtained in the same manner as in Example 6 except that the pulverized boron nitride fine particles and diamond fine particles were mixed and used so that the contents were 48 vol% and 12 vol%, respectively. And about the obtained composite material, heat conductivity measurement was performed like Example 5, and the heat conductivity of the direction (z-axis direction) parallel to a compression direction was calculated | required. The obtained results are shown in Table 3.

  Further, the content ratio [% by volume] of the partially cleaved boron nitride fine particles with respect to the total amount of boron nitride fine particles in the obtained composite material and the ratio [%] of the total area of the region corresponding to the swollen boron nitride fine particles to the cross-sectional area of the composite material are All were equivalent to the composite material obtained in Example 6 (the latter being proportional to the content of boron nitride fine particles).

(Comparative Example 7)
A heat conductive composite material was obtained in the same manner as in Example 9 except that only the diamond fine particles were used as the heat conductive filler, and the content of the diamond fine particles in the obtained composite material was 60% by volume. . And about the obtained composite material, heat conductivity measurement was performed like Example 5, and the heat conductivity of the direction (z-axis direction) parallel to a compression direction was calculated | required. The obtained results are shown in Table 3.

(Example 10)
As the thermally conductive filler, wet-pulverized boron nitride fine particles obtained in Example 6 and cubic boron nitride fine particles (“Cubic Boron Nitride (CBN) Powder FBN-BM” manufactured by Global Diamond Co., Ltd., average particle diameter) : 5 μm), and the mixed composite material obtained was mixed so that the content of the pulverized boron nitride fine particles and cubic boron nitride fine particles was 48% by volume and 12% by volume, respectively. In the same manner as in Example 6, a heat conductive composite material was obtained. And about the obtained composite material, heat conductivity measurement was performed like Example 5, and the heat conductivity of the direction (z-axis direction) parallel to a compression direction was calculated | required. The obtained results are shown in Table 3.

  Further, the content ratio [% by volume] of the partially cleaved boron nitride fine particles with respect to the total amount of boron nitride fine particles in the obtained composite material and the ratio [%] of the total area of the region corresponding to the swollen boron nitride fine particles to the cross-sectional area of the composite material are All were equivalent to the composite material obtained in Example 6 (the latter being proportional to the content of boron nitride fine particles).

(Comparative Example 8)
Heat conduction was carried out in the same manner as in Example 10 except that only the cubic boron nitride fine particles were used as the heat conductive filler, and the content of the cubic boron nitride fine particles in the obtained composite material was 60% by volume. A composite material was obtained. And about the obtained composite material, heat conductivity measurement was performed like Example 5, and the heat conductivity of the direction (z-axis direction) parallel to a compression direction was calculated | required. The obtained results are shown in Table 3.

(Example 11)
Example except that the wet pulverized boron nitride fine particles obtained in Example 3 were used as the thermally conductive filler, and the filler (boron nitride fine particle) content in the obtained composite material was 60% by volume. In the same manner as in No. 3, a heat conductive composite material was obtained. And about the obtained composite material, heat conductivity measurement was performed like Example 5, and the heat conductivity of the direction (z-axis direction) parallel to a compression direction was calculated | required. The obtained results are shown in Table 3.

  Further, the content ratio [% by volume] of the partially cleaved boron nitride fine particles with respect to the total amount of boron nitride fine particles in the obtained composite material and the ratio [%] of the total area of the region corresponding to the swollen boron nitride fine particles to the cross-sectional area of the composite material are All were equivalent to the composite material obtained in Example 3 (the latter being proportional to the content of boron nitride fine particles).

(Example 12)
As the thermally conductive filler, the wet-pulverized boron nitride fine particles obtained in Example 3 and alumina fine particles (“Seraph 0670” manufactured by Kinsei Matec Co., Ltd., average particle size: 0.6 μm) are used, and the resulting composite A thermally conductive composite material was obtained in the same manner as in Example 11 except that the contents of the pulverized boron nitride fine particles and alumina fine particles in the material were mixed so as to be 48% by volume and 12% by volume, respectively. It was. And about the obtained composite material, heat conductivity measurement was performed like Example 5, and the heat conductivity of the direction (z-axis direction) parallel to a compression direction was calculated | required. The obtained results are shown in Table 3.

  Further, the content ratio [% by volume] of the partially cleaved boron nitride fine particles with respect to the total amount of boron nitride fine particles in the obtained composite material and the ratio [%] of the total area of the region corresponding to the swollen boron nitride fine particles to the cross-sectional area of the composite material are All were equivalent to the composite material obtained in Example 3 (the latter being proportional to the content of boron nitride fine particles).

(Comparative Example 9)
Example 12 was used except that only the alumina fine particles (average particle size: 0.6 μm) were used as the heat conductive filler, and the content of the alumina fine particles in the obtained composite material was 60% by volume. Thus, a heat conductive composite material was obtained. And about the obtained composite material, heat conductivity measurement was performed like Example 5, and the heat conductivity of the direction (z-axis direction) parallel to a compression direction was calculated | required. The obtained results are shown in Table 3.

<Evaluation of results shown in Table 3>
As is apparent from the results shown in Table 3, the heat conductive composite material of the present invention using only wet-milled boron nitride fine particles containing partially cleaved boron nitride fine particles as the heat conductive filler also has high thermal conductivity. Although it has been achieved (Examples 6 and 11), when the thermally conductive filler further contains highly thermally conductive fine particles having a thermal conductivity of 20 W / mK or more (Examples 5, 7 to 10 and 12). It was confirmed that the thermal conductivity of the obtained composite material was further improved.

  As described above, according to the present invention, the thermal conductive filler capable of efficiently improving the thermal conductivity and the manufacturing method thereof, and the thermal conductive composite material having excellent thermal conductivity and the manufacturing method thereof. And can be provided. Therefore, since the composite material of the present invention is excellent in thermal conductivity, it is useful as, for example, a heat radiating material for automobiles and a heater material.

  In addition, since the composite material of the present invention has high thermal conductivity and is insulative, it can be used without using an insulating sheet or the like when used in combination with electrical parts or the like. Heat can be diffused and transferred only by the composite material. Therefore, the composite material of the present invention is very useful as an intermediate member (thermal interface material) for transmitting heat of heat generating electronic components such as power devices and CPUs used in power converters such as inverters and converters to heat radiating members. Useful.

1: Composite material, 2: Sample for thermal conductivity measurement.

Claims (15)

A thermally conductive composite material in which a thermally conductive filler composed of boron nitride fine particles is dispersed in a matrix,
At least a part of the boron nitride fine particles are partially cleaved boron nitride fine particles in which the boron nitride fine particles are partially cleaved,
The composite material contains swollen boron nitride fine particles that are swollen by filling the matrix into the cleavage voids of the partially cleaved boron nitride fine particles,
The total area of the region corresponding to the swollen boron nitride fine particles is 1 to 50% with respect to the cross-sectional area of the composite material on the basis of the cross-section of the composite material.
A thermally conductive composite material characterized by that.   2. The thermally conductive composite material according to claim 1, wherein the content of the partially cleaved boron nitride fine particles is 5% by volume or more based on the total amount of the boron nitride fine particles.   The thermal conductivity according to claim 1 or 2, wherein the thermal conductive filler further contains high thermal conductive fine particles having a thermal conductivity of 20 W / mK or more in addition to the boron nitride fine particles. Composite material. The boron nitride fine particles are hexagonal plate-like boron nitride fine particles, and
The high thermal conductivity fine particles are at least one fine particle selected from the group consisting of cubic boron nitride, diamond, aluminum nitride, aluminum oxide, magnesium oxide, zinc oxide, silicon nitride, and silicon carbide;
The thermally conductive composite material according to any one of claims 1 to 3, wherein   The heat conductive composite material according to any one of claims 1 to 4, wherein a content of the boron nitride fine particles is 5% by volume or more based on a total amount of the heat conductive filler.   The heat conductive composite material according to any one of claims 1 to 5, wherein a content of the heat conductive filler is 10 to 90% by volume with respect to a total amount of the composite material. . A step of obtaining boron nitride fine particles including partially cleaved boron nitride fine particles in which boron nitride fine particles are partially cleaved by jetting a fluid containing boron nitride particles from a nozzle at high pressure and performing wet collision pulverization;
A thermally conductive filler composed of boron nitride fine particles including the partially cleaved boron nitride fine particles is dispersed in a matrix, and the swollen boron nitride fine particles that are swollen with the matrix filled in the cleaved voids of the partially cleaved boron nitride fine particles are contained. Obtaining a thermally conductive composite material,
The manufacturing method of the heat conductive composite material characterized by including.   The method for producing a thermally conductive composite material according to claim 7, wherein the high pressure is a pressure of 30 to 250 MPa, and a flow rate when the fluid is ejected from the nozzle is 200 to 800 m / s.   The said heat conductive composite material is a heat conductive composite material as described in any one of Claims 1-6, The manufacture of the heat conductive composite material of Claim 7 or 8 characterized by the above-mentioned. Method.   A thermally conductive filler composed of boron nitride fine particles containing partially cleaved boron nitride fine particles in which the boron nitride fine particles are partially cleaved, wherein the content of the partially cleaved boron nitride fine particles is 5 with respect to the total amount of the boron nitride fine particles. A thermally conductive filler characterized by being at least volume%.   The heat conductive filler according to claim 10, wherein the boron nitride fine particles have an average particle diameter of 1 to 100 μm.   The thermally conductive filler according to claim 10 or 11, wherein the boron nitride fine particles are hexagonal plate-like boron nitride fine particles.   By thermally injecting a fluid containing boron nitride particles from a nozzle at high pressure and performing wet collision pulverization, a thermally conductive filler made of boron nitride fine particles including partially cleaved boron nitride fine particles in which boron nitride fine particles are partially cleaved is obtained. The manufacturing method of the heat conductive filler characterized by these.   The method for producing a thermally conductive filler according to claim 13, wherein the high pressure is a pressure of 30 to 250 MPa, and a flow rate when the fluid is ejected from the nozzle is 200 to 800 m / s.   The method for producing a thermally conductive filler according to claim 13 or 14, wherein the thermally conductive filler is the thermally conductive filler according to any one of claims 10 to 12.