JP6950148B2 - Aluminum Nitride-Boron Nitride Composite Agglomerated Particles and Their Manufacturing Methods - Google Patents

Description

The present invention relates to aluminum nitride-boron nitride composite agglomerated particles (hereinafter referred to as "AlN-BN composite agglomerated particles") and a method for producing the particles, and more specifically, it is referred to as aluminum nitride primary particles (hereinafter referred to as "AlN primary particles"). ) And boron nitride primary particles (hereinafter referred to as “BN primary particles”) are aggregated to form AlN-BN composite agglomerated particles and a method for producing the same.

Boron nitride (hereinafter referred to as "BN") is an insulating substance, and has various types such as c-BN having a diamond structure, h-BN having a graphite structure, α-BN having a multi-layer structure, and β-BN. Crystal type is known.
Among these, h-BN has the same layered structure as graphite, is relatively easy to synthesize, and has the characteristics of being excellent in thermal conductivity, solid lubricity, chemical stability, and heat resistance. Therefore, it is widely used in the fields of electrical and electronic materials.

In recent years, especially in the fields of electricity and electronics, heat generation due to high density of integrated circuits has become a big problem, and how to dissipate heat has become an urgent issue. Although h-BN is insulating, it is attracting attention as such a heat conductive filler for a heat radiating member by taking advantage of its feature of having high heat conductivity.

h-BN is a plate-like crystal, and although it exhibits high thermal conductivity in the plate surface direction (in the ab plane or (002) plane) (usually, the thermal conductivity is about 400 W / mK), it is in the plate thickness direction. (C-axis direction) shows only low thermal conductivity (usually, the thermal conductivity is about 2 to 3 W / mK). In general, when a composite composition is prepared by blending a plate-shaped crystal as a filler with a resin or the like, the plate surface of the plate-shaped crystal is oriented in a specific direction in a process such as raw material mixing, press molding, or injection molding. Phenomenon occurs. That is, when a composite material composition is prepared by blending h-BN plate crystals with a resin, a large thermal conduction anisotropy occurs in the composite composition due to the orientation of the h-BN plate crystals. For example, when a plate-shaped molded product is produced by press molding, the plate surface of the h-BN plate-shaped crystal is oriented parallel to the plate surface of the molded product. As a result, there arises a problem that the thermal conductivity of the obtained plate-shaped molded body is high in the plate surface direction and low in the thickness direction.

Therefore, in order to improve the thermal conductivity anisotropy that such h-BN plate-like crystals give to the composite composition, h-BN agglomerated particles having a shape other than the scaly shape in which orientation is unlikely to occur as described above. Has been considered. Examples of such h-BN agglomerated particles include h-BN agglomerated particles granulated by spray drying or the like, and h-BN agglomerated particles produced by sintering h-BN and crushing a sintered body. (Patent Documents 1 and 2). Further, h-BN agglomerated particles produced from a mixture of boric acid and melamine, which are pine-shaped h-BN agglomerated particles in which the primary particles are agglomerated without being oriented, have also been proposed (Patent Document 3).

Since the thermal conductivity anisotropy of the h-BN plate-like crystal is very large (usually, the thermal conductivity is about 400 W / mK in the ab plane and about 2 to 3 W / mK in the c-axis direction), h-BN The thermal conductivity of the heat conduction path formed between the h-BN primary particles varies greatly depending on how the h-BN primary particles come into contact with each other inside and outside the agglomerated particles. Specifically, the heat conduction path formed so as to pass through the ab plane (hereinafter referred to as "ab in-plane pass") has high thermal conductivity, and the heat conduction path formed in the c-axis direction (hereinafter referred to as "" The "c-axis direction path") has a low thermal conductivity. Therefore, if the heat conduction path formed by the h-BN primary particles inside and outside the h-BN agglomerated particles is an ab in-plane path at a high ratio, high heat conductivity is exhibited in the composite composition.

Therefore, h-BN agglomerated particles that form ab in-plane paths at a high rate are produced by a simple method suitable for mass production called spray drying, and such h-BN agglomerated particles are provided to the composite composition. It was confirmed that the thermal conductivity was dramatically increased (Patent Document 2).

When trying to further increase the thermal conductivity given to the composite composition by such h-BN agglomerated particles, the ratio of ab in-plane paths formed by the h-BN primary particles inside and outside the h-BN agglomerated particles is further increased. It is necessary to increase or further decrease the proportion of c-axis paths. However, in such h-BN agglomerated particles, since the arrangement of the h-BN primary particles is determined by self-organization, it is difficult to significantly change the arrangement of the h-BN primary particles. That is, it has been difficult to increase the ratio of ab in-plane paths or decrease the ratio of c-axis direction paths more than ever.

Japanese Unexamined Patent Publication No. 2006-257392 Japanese Patent Application Laid-Open No. 2008-510878 Japanese Unexamined Patent Publication No. 9-202663

In the h-BN agglomerated particles, if the heat conduction path formed by the h-BN primary particles inside and outside the h-BN agglomerated particles is an ab in-plane path at a high ratio, the heat conduction is high in the composite composition. The rate develops. Conventionally, h-BN agglomerated particles that form ab in-plane paths at a high rate have been produced by a simple method suitable for mass production called spray drying (Patent Document 2). However, since the arrangement of the h-BN primary particles in such h-BN agglomerated particles is determined by self-organization, the ratio of the ab in-plane path is increased more than ever, or the c-axis direction path is increased. It was difficult to reduce the proportion of. That is, it has been difficult to further increase the thermal conductivity given to the composite composition by such h-BN agglomerated particles.

An object of the present invention is to solve the above-mentioned conventional problems and to obtain h-BN agglomerated particles that give a composite material composition a larger thermal conductivity than the conventional ones.

As a result of diligent studies, the present inventors have found that the AlN-BN composite agglomerated particles in which the AlN primary particles are arranged in the heat conduction path created by the BN primary particles have dramatically higher thermal conductivity with respect to the composite material composition. Found to give a rate. Aluminum nitride (hereinafter referred to as "AlN") is similar to h-BN in that it is insulating and exhibits high thermal conductivity (usually, thermal conductivity is about 300 W / mK). doing. However, it is significantly different from h-BN in that the crystal shape is granular and that it does not have thermal conduction anisotropy. Therefore, when AlN agglomerated particles composed of only AlN are produced, most of the heat conduction paths formed inside and outside the AlN agglomerated particles are considered to have high heat conduction as in the ab in-plane path in h-BN. .. However, since the AlN primary particles are granular and inferior in deformability to the plate-shaped h-BN primary particles, the contact area between the AlN primary particles and the AlN agglomerated particles is small, and therefore, between the AlN primary particles and between the AlN primary particles and It is considered that the density of the heat conduction path formed between the AlN agglomerated particles is smaller than that in the case of h-BN. From the above, by combining the AlN primary particles and the h-BN primary particles to form AlN-BN composite agglomerated particles, it is possible to increase the proportion of high thermal conductive paths while maintaining the density of the thermal conductive paths. it is conceivable that.
The present invention has been achieved based on such findings, and the gist of the present invention is as follows.

(1) Aluminum nitride-boron nitride composite agglomerated particles formed by agglomerating aluminum nitride primary particles and boron nitride primary particles having a major axis of the particles of 0.1 μm or more.
(2) The composite agglomerated particles according to (1), wherein the boron nitride primary particles form a card house structure.
(3) The composite agglomerated particles according to (1) or (2), which contain at least a component consisting of boron, carbon, nitrogen, and oxygen.
(4) A method for producing aluminum nitride-boron nitride composite agglomerated particles, which is formed by aggregating aluminum nitride primary particles and boron nitride primary particles, and includes a step of reducing and nitriding aluminum oxide.
(5) The production method according to (4), wherein the reduction nitriding step is performed in the presence of carbon black and in a non-oxidizing gas or reducing gas atmosphere.
A composite composition composed of the composite agglomerated particles according to any one of claims 1 to 3 and a resin. (6) A composite composition composed of any of the composite agglomerated particles according to (1) to (3) and a resin. (7) A sheet or substrate obtained by molding the composite composition according to (6).
(8) The sheet or substrate according to (7), which is a heat radiating member.

INDUSTRIAL APPLICABILITY The present invention provides AlN-BN composite agglomerated particles in which AlN primary particles are arranged in a heat conduction path created by BN primary particles. The composite composition in which the AlN-BN composite aggregated particles of the present invention are blended in a matrix such as a resin exhibits high thermal conductivity. That is, AlN-BN composite agglomerated particles useful as a heat conductive filler for a heat radiating member are provided.

It is an XRD pattern of the heat-treated particles which concerns on Comparative Examples 1 and 2. 3 is an SEM image of the heat-treated particles according to Comparative Examples 1 and 2. It is a thermal conductivity graph of the composite material composition which concerns on Comparative Examples 1, 2, and Examples 1, 2, and 3. 5 is an XRD pattern of heat-treated particles according to Examples 1, 2 and 3. 3 is an SEM image of the heat-treated particles according to Examples 1, 2 and 3. 5 is an XRD pattern of high-purity reduced nitrided particles according to Examples 1, 2 and 3. 5 is an XRD pattern of high-purity reduced nitriding particles and heat-treated particles according to Examples 1, 2 and 3. 3 is an SEM image of high-purity reduced nitriding particles according to Examples 1, 2 and 3. It is the SEM-EDX analysis result of the high-purity reduced nitriding particle which concerns on Examples 1, 2 and 3. It is an XRD pattern of the heat-treated particles which concerns on Comparative Example 3. 6 is an SEM image of the heat-treated particles according to Comparative Example 3. It is a thermal conductivity graph of the composite material composition which concerns on Comparative Examples 1, 2, 3 and 4.

Hereinafter, the present invention will be described in detail, but the scope of the present invention is not limited to specific embodiments.
[AlN-BN composite aggregate particles]
The AlN-BN composite agglomerated particles of the present invention are formed by aggregating AlN primary particles and BN primary particles, and are other than the AlN primary particles or the BN primary particles as long as the effects of the present invention are not impaired. Ingredients may be included. Examples of the components other than the AlN primary particles or the BN primary particles include a binder, a surfactant, and a solvent-derived component that may be added to the slurry, which will be described later in [Method for producing BN agglomerated particles].

The form of the AlN-BN composite agglomerated particles of the present invention is not particularly limited, but preferably has a spherical shape. Further, the morphology of the AlN-BN composite aggregated particles can be confirmed by SEM. Here, "spherical" means that the aspect ratio (ratio of major axis to minor axis) is 1 or more and 2 or less, preferably 1 or more and 1.5 or less. The aspect ratio of the AlN-BN composite agglomerated particles of the present invention is obtained by arbitrarily selecting 200 or more particles from the image taken by SEM, calculating the ratio of the major axis and the minor axis of each, and calculating the average value. decide.

Further, the AlN-BN composite agglomerated particles are BN-like morphologies in which the crystals of the BN primary particles of the AlN-BN composite agglomerated particles grow radially from the center side to the surface side of the AlN-BN composite agglomerated particles. It is preferable that the primary particles are small plates and have a uni-like spherical shape in which they are sintered and aggregated. Further, the AlN-BN composite agglomerated particles preferably have a card house structure. The card house structure is, for example, ceramics 43 No. It is described in 2 (published by the Japan Ceramics Association in 2008), and has a structure in which plate-like particles are intricately laminated without being oriented. More specifically, the AlN-BN composite agglomerated particles having a cardhouse structure are aggregates of AlN primary particles and BN primary particles, and have a structure in which the plane portion and the end face portion of the BN primary particles are in contact with each other. AlN-BN composite agglomerated particles containing AlN primary particles, preferably spherical. Further, the card house structure is preferably the same structure inside the particles. The aggregated morphology and internal structure of these AlN-BN composite aggregated particles can be confirmed by a scanning electron microscope (SEM).

Further, in the AlN-BN composite agglomerated particles, it is preferable that a component (compound) composed of boron, carbon, nitrogen and oxygen is present on the surface of the AlN primary particles or the BN primary particles constituting the AlN-BN composite agglomerated particles. In AlN crystals and BN crystals, oxygen atoms dissolved in the crystals reduce the thermal conductivity. Therefore, by retaining oxygen as a compound on the crystal surface, it is possible to prevent such a decrease in thermal conductivity. The presence of a compound consisting of boron, carbon, nitrogen, and oxygen is measured by X-ray diffraction measurement (XRD) if the compound is crystalline, or by energy dispersive X-ray analysis (EDX) if it is amorphous. It can be confirmed by elemental analysis such as.

In the AlN-BN composite agglomerated particles of the present invention, the AlN primary particles and the BN primary particles constituting the AlN-BN composite agglomerated particles have specific physical properties. This will be described in detail below. The sample (powder) to be used for the physical property measurement specified in the present specification may be an AlN-BN composite agglomerated particle powder before being molded into a molded body, or may be a molded body containing AlN-BN composite agglomerated particles. May be AlN-BN composite agglomerated particles taken out from the molded body. It is preferably an AlN-BN composite agglomerated particle powder before being molded into a molded product.

(Characteristics of AlN-BN composite aggregated particles)
-Size of primary particles The major axis of the BN primary particles constituting the AlN-BN composite agglomerated particles is usually 0.1 μm or more, preferably 0.3 μm or more, more preferably 0.5 μm or more, still more preferably 0.7 μm. As mentioned above, it is particularly preferably 1.0 μm or more. Further, it is usually 10 μm or less, preferably 7 μm or less, and more preferably 5 μm or less. The major axis is the maximum length of the BN primary particles that can be observed on the image for the BN primary particles that make up one BN agglomerated particle by enlarging one BN agglomerated particle obtained by SEM measurement. It is an average value.
The major axis of the AlN primary particles constituting the AlN-BN composite agglomerated particles is usually 0.1 μm or more, preferably 0.5 μm or more, more preferably 1.0 μm or more, still more preferably 2.0 μm or more, and particularly preferably 3. It is 0.0 μm or more. Further, it is usually 20 μm or less, preferably 15 μm or less, and more preferably 10 μm or less. The major axis is an AlN primary particle that can be observed on an image by enlarging one AlN-BN composite agglomerated particle obtained by SEM measurement and constituting one AlN-BN composite agglomerated particle. It is a value obtained by averaging the maximum lengths of primary particles.

-Crystal structure of primary particles The crystal structure of BN primary particles is not particularly limited, but those containing hexagonal h-BN as a main component are preferable in terms of ease of synthesis and thermal conductivity. When an inorganic component other than BN is contained as the binder, they crystallize in the process of heat treatment, but BN may be contained as the main component. The crystal structure of the BN primary particles can be confirmed by XRD measurement.

-Average particle size of AlN-BN composite agglomerated particles (D ₅₀ )
The average particle size (D ₅₀ ) of the AlN-BN composite agglomerated particles is usually 1.0 μm or more, preferably 5.0 μm or more, more preferably 10 μm or more, still more preferably 20 μm or more, and particularly preferably 30 μm or more. Most preferably, it is 40 μm or more, 50 μm or more is preferable, and 60 μm or more is preferable. Further, it is usually 200 μm or less, preferably 150 μm or less, and more preferably 100 μm or less. If it is too large, the smoothness of the surface of the molded product will be poor, the gaps between the AlN-BN composite agglomerated particles will increase, and the thermal conductivity will not be improved. If it is too small, the contact resistance between the AlN-BN composite agglomerated particles will increase when the molded product is formed, and the thermal conductivity of the AlN-BN composite agglomerated particles themselves will tend to decrease.

Note that D ₅₀ means the particle size when the cumulative volume is exactly 50% when the cumulative volume is drawn with the volume of the powder used for measurement as 100%, and the measurement method is a wet measurement method. Can be measured using a laser diffraction / scattering particle size distribution measuring device or the like on a sample in which BN agglomerated particles are dispersed in a pure water medium containing sodium hexametaphosphate as a dispersion stabilizer. As a method, it can be measured using "Morgrafi" manufactured by Malvern.

-AlN: BN ratio in AlN-BN composite agglomerated particles The composition ratio of AlN and BN in AlN-BN composite agglomerated particles is not particularly limited, but the AlN: BN ratio (mass ratio) is usually 3: 97 to 85 :. It is 15, preferably 10:90 to 80:20, and more preferably 20:80 to 55:45. Within the above range, a card house structure made of BN primary particles is formed, which is preferable.

[Method for Producing AlN-BN Composite Agglomerated Particles]
{Preparation of slurry}
<Raw material BN powder>
Types of Raw Material BN Powder Examples of the raw material BN powder used in the present invention include commercially available h-BN, commercially available α and β-BN, BN produced by the reduction nitride method of boron compounds and ammonia, and boron compounds and melamine. Any BN synthesized from a nitrogen-containing compound can be used without limitation, but h-BN is particularly preferably used because it exerts the effect of the present invention more.

Crystalline of Raw Material BN Powder As the form of the raw material BN powder used in the present invention, powdery BN particles having a wide half-value width of the peak obtained by XRD measurement and low crystallinity are preferable. As a measure of crystallinity, the peak half-value width of the (002) plane obtained from the XRD measurement is usually 0.4 ° or more, preferably 0.45 ° or more, more preferably 0.5 ° or more at an angle of 2θ. be. Further, it is usually 2.0 ° or less, preferably 1.5 ° or less, and more preferably 1 ° or less. If it is larger than the above upper limit, the crystallites do not become sufficiently large, and it takes a long time to make them large, so that the productivity tends to deteriorate. If it is less than the above lower limit, the crystallinity is too high, sufficient crystal growth cannot be expected, and the dispersion stability during slurry preparation tends to deteriorate.

-Oxygen Atom Concentration in Raw Material BN Powder From the viewpoint of BN crystal growth, it is preferable that some oxygen atoms are present in the raw material BN powder, and in the present invention, the total oxygen concentration in the raw material BN powder is usually 1% by mass. As mentioned above, it is preferably 2% by mass or more, more preferably 3% by mass or more, and further preferably 4% by mass or more. Further, it is usually 20% by mass or less, more preferably 10% by mass or less. If it is larger than the above upper limit, oxygen tends to remain even after the heat treatment, so that the effect of improving the thermal conductivity tends to be small. If it is less than the above lower limit, the crystallinity is too high, crystal growth cannot be expected, and the peak intensity ratio that can be confirmed from the XRD measurement tends to deviate from the desired range.

As a method of adjusting the total oxygen concentration of the raw material BN powder within the above range, for example, a method of performing the synthesis temperature at the time of BN synthesis at a low temperature of 1500 ° C. or lower, or a method of performing the raw material BN in a low temperature oxidizing atmosphere of 500 ° C. to 900 ° C. Examples thereof include a method of heat-treating the powder.
The total oxygen concentration of the raw material BN powder can be measured by an inert gas melting-infrared absorption method using an oxygen / nitrogen analyzer manufactured by HORIBA, Ltd.

<Raw material Al ₂ O ₃ powder>
- The material _Al 2 _{O 3} powder used in the raw material _Al 2 _{O 3} powder types present invention, commercially available alpha, gamma, [delta] and _θ-Al 2 _{O 3,} any such amorphous _Al 2 _{O 3} can be used without limitation.
The particle size of the raw material Al ₂ O ₃ powder is not particularly limited, but is usually 0.005 μm to 10 μm, preferably 0.01 μm to 5 μm, and more preferably 0.1 μm to 1 μm. Within the above range, it becomes difficult for the raw material BN powder and the raw material Al ₂ O ₃ powder to separate in the slurry, and the slurry does not become too viscous.

<Carbon black powder>
-Types of carbon black As the carbon black powder used in the present invention, any commercially available carbon black or the like can be used without limitation.
As the carbon black, carbon black such as the furnace method and the channel method, acetylene black and the like can be used. The particle size of these carbon blacks is arbitrary, but preferably 0.01 to 20 μm. As an alternative to carbon black, graphite or a carbon precursor that can be a carbon source at high temperatures can also be used. Examples of the carbon precursor include synthetic resin condensates such as phenol resin, melamine resin, epoxy resin and furanphenol resin, hydrocarbon compounds such as pitch and tar, and organic compounds such as cellulose, sucrose, polyvinylidene chloride and polyphenylene. Be done. In particular, those having few metal impurities such as phenol resin, cellulose, and polyphenylene are preferable.

<Medium>
The _{medium used for preparing the Al 2} O _3- BN slurry is not particularly limited, and water and / or various organic solvents can be used, but water can be used from the viewpoint of ease of spray drying and simplification of the apparatus. Is preferable, and pure water is more preferable.

<Binder>
The Al ₂ O _3- BN slurry may contain a binder in order to effectively granulate the raw material Al ₂ O _{3 powder and the raw material BN powder into particles.} The binder acts to firmly bind the primary particles to each other and stabilize the granulated particles.
The _{binder used in the Al 2} O _3- BN slurry may be any binder capable of enhancing the adhesiveness between the primary particles, but in the present invention, the granulated particles are heat-treated after being granulated. Those having heat resistance to high temperature conditions in the heat treatment step are preferable.

As such a binder, metal oxides such as aluminum oxide, magnesium oxide, yttrium oxide, calcium oxide, silicon oxide, boron oxide, cerium oxide, zirconium oxide and titanium oxide are preferably used. Among these, aluminum oxide and yttrium oxide are preferable from the viewpoints of thermal conductivity and heat resistance as oxides and a bonding force for binding primary particles to each other. As the binder, a liquid binder such as alumina sol may be used, or a binder that reacts during the heat treatment and is converted into other inorganic components may be used. One of these binders may be used alone, or two or more of these binders may be mixed and used.

(If a liquid binder, as the amount of solids) binders usage, Al the raw material powder total amount of 2 _O 3 _-BN slurry is usually less than 30 wt% or more 0 wt%, preferably It is 0% by mass or more and 20% by mass or less, more preferably 0% by mass or more and 15% by mass or less. When the above upper limit is exceeded, _{the contents of the raw material Al 2} O ₃ powder and the raw material BN powder in the granulated particles decrease, which not only affects the crystal growth but also has the effect of improving the thermal conductivity when used as a thermally conductive filler. It becomes smaller.

<Slurry preparation method>
The slurry preparation method is _{not particularly limited as long as the raw material Al 2} O ₃ powder, the raw material BN powder, and if necessary, the medium, the binder, and the surfactant are uniformly dispersed and prepared in a desired viscosity range, but the raw material BN is not particularly limited. When a powder, a raw material Al ₂ O ₃ powder and a medium, and if necessary, a binder and a surfactant are used, the preparation is preferably as follows.

The raw material Al ₂ O ₃ powder and the raw material BN powder are weighed in a predetermined amount in a container, and then a predetermined amount of a binder is added. Further, after adding a predetermined amount of the surfactant, the mixture is stirred with a hand mixer until it becomes uniform.
The order of addition is not particularly limited, but when a large amount of raw material Al ₂ O ₃ powder and raw material BN powder are slurried, agglomerates such as lumps are likely to be formed. After producing the above, a predetermined amount of the raw material Al ₂ O ₃ powder and the raw material BN powder may be added little by little, and this may be stirred using a household hand mixer to form a slurry.

In addition to the hand mixer, a dispersion device such as a pot mill, a bead mill, or a planetary mixer may be used for dispersion. At the time of slurrying, the temperature of the slurry is 10 ° C. or higher and 60 ° C. or lower. If it is lower than the lower limit, the viscosity of the slurry increases and tends to deviate from the desired viscosity range, and if it is higher than the upper limit, the raw material BN powder is easily decomposed into ammonia in the aqueous solution. Usually, it is 10 ° C. or higher and 60 ° C. or lower, preferably 15 ° C. or higher and 50 ° C. or lower, more preferably 15 ° C. or higher and 40 ° C. or lower, and further preferably 15 ° C. or higher and 35 ° C. or lower.
The content ratio of the raw material Al ₂ O ₃ powder and the raw material BN powder is not particularly limited, but the raw material Al ₂ O ₃ powder: raw material BN powder ratio (mass ratio) is usually 1:99 to 90:10, preferably 2: It is 98 to 85:15, more preferably 13:87 to 60:40. Within the above range, a card house structure made of BN primary particles is formed, which is preferable.

{Granulation}
In _{order to obtain granulated particles from the Al 2} O _3- BN composite slurry, general granulation methods such as a spray-drying method, a rolling method, a fluidized bed method, and a stirring method can be used, and among these, spray-drying can be used. The method is preferred.
In the spray-drying method, granulated particles of a desired size are produced by the concentration of the slurry as a raw material, the amount of liquid to be introduced into the apparatus per unit time, and the compressed air pressure and the amount of compressed air when spraying the supplied slurry. It is also possible to obtain spherical granulated particles.

_{The average particle size of the Al 2} O _3- BN composite granulated particles obtained by granulation is preferably 5 μm or more and 150 μm or less in the volume-based average particle size range of the AlN-BN composite agglomerated particles of the present invention. The average particle size D ₅₀ on a volume basis is usually 1.0 μm or more, preferably 5.0 μm or more, more preferably 10 μm or more, still more preferably 20 μm or more, particularly preferably 30 μm or more, and most preferably. It is 40 μm or more, preferably 50 μm or more, and preferably 60 μm or more. Further, it is usually 200 μm or less, preferably 150 μm or less, and more preferably 100 μm or less. Here, the average particle size D _{50 based on} the volume of the granulated particles can be measured by, for example, "LA920" manufactured by HORIBA, Ltd. for the wet type and "Morphorogi" manufactured by Malvern for the dry type.

{Temporary heat treatment}
By further heat-treating the above-mentioned Al ₂ O _3- BN composite granulated particles in an oxidizing atmosphere, Al ₂ O _3- BN composite temporary heat-treated particles can be produced.
Here, the oxidizing atmosphere is an oxidizing gas atmosphere containing oxygen gas and the like. Depending on the type of acid gas used here, the amount of removal of organic components in the _{Al 2} O _{3-BN composite granulated particles by combustion differs.}
The tentative heat treatment temperature is usually 500 ° C. or higher and 900 ° C. or lower, but is preferably 700 ° C. or higher, and preferably 800 ° C. or lower. If the tentative heat treatment temperature is too low, the removal of organic components by combustion becomes insufficient, and toxic gas containing nitrogen and carbon may be generated in the heat treatment step described later. If the temporary heat treatment temperature is too high, the BN may be oxidized.

The heat treatment time of the temporary heat treatment is usually 1 hour or more, preferably 2 hours or more, and usually 12 hours or less, preferably 5 hours or less. If the heat treatment time of the temporary heat treatment is less than the above lower limit, the removal of the organic component by combustion becomes insufficient, and if it exceeds the above upper limit, BN may be partially oxidized.

As the firing furnace used for the heat treatment of the temporary heat treatment, a batch type furnace such as a muffle furnace, a tubular furnace, and an atmosphere furnace, and a continuous furnace such as a rotary kiln, a screw conveyor furnace, a tunnel furnace, a belt furnace, a pusher furnace, and a vertical continuous furnace are used. Can be used according to the purpose.

{Heat treatment}
By further heat-treating the above-mentioned Al ₂ O _3- BN composite temporary heat-treated particles in a non-oxidizing gas atmosphere, Al ₂ O _3- BN composite heat-treated particles can be produced.
Here, the non-oxidizing gas atmosphere is an atmosphere of nitrogen gas, helium gas, argon gas, ammonia gas, hydrogen gas, methane gas, propane gas, carbon monoxide gas and the like. _{The crystallization rate of Al 2} O ₃ particles or BN particles differs depending on the type of atmospheric gas used here, and in order to carry out crystallization in a short time, nitrogen gas or a mixture of nitrogen gas and another gas is particularly used. Gas is preferably used.
The heat treatment temperature is usually 1500 ° C. or higher and 2000 ° C. or lower, preferably 1600 ° C. or higher, and preferably 1900 ° C. or lower. If the heat treatment temperature is too low, the growth of the average crystallites of BN may be insufficient, and the thermal conductivity of the BN agglomerated particles and the molded product may be reduced. If the heat treatment temperature is too high _{, decomposition of Al 2} O ₃ or BN may occur.

The heat treatment time is usually 1 hour or more, preferably 5 hours or more, more preferably 12 hours or more, and usually 72 hours or less, preferably 48 hours or less. If the heat treatment time is less than the above lower limit, the crystal growth becomes insufficient, and if it exceeds the above upper limit, Al ₂ O ₃ or BN may be partially decomposed.

Since the heat treatment is performed in a non-oxidizing gas atmosphere, preferably, the inside of the firing furnace is usually exhausted by using a vacuum pump, and then heated to a desired temperature while introducing the non-oxidizing gas to raise the temperature. Although it is heated, if the inside of the firing furnace can be sufficiently replaced with a non-oxidizing gas, the temperature may be raised by heating while introducing the non-oxidizing gas under normal pressure. Examples of the firing furnace include batch type furnaces such as muffle furnaces, tubular furnaces, and atmospheric furnaces, and continuous furnaces such as rotary kilns, screw conveyor furnaces, tunnel furnaces, belt furnaces, pusher furnaces, and vertical continuous furnaces, depending on the purpose. It can be used properly.

{Reduction nitriding treatment}
By reducing and nitriding the above Al ₂ O _3- BN composite heat-treated particles, AlN-BN composite aggregated particles can be produced.
Here, the reduction nitriding treatment is to _{heat-treat a mixture of Al 2} O _3- BN composite heat-treated particles and carbon black in a non-oxidizing gas atmosphere or a reducing gas atmosphere.
Here, the non-oxidizing gas atmosphere is an atmosphere of nitrogen gas, helium gas, argon gas, ammonia gas, hydrogen gas, methane gas, propane gas, carbon monoxide gas and the like. Further, here, the reducing gas atmosphere is an atmosphere containing ammonia gas, hydrogen gas, carbon monoxide gas, and the like.
The heat treatment temperature is usually 1000 ° C. or higher and 2000 ° C. or lower, preferably 1600 ° C. or higher, and preferably 1900 ° C. or lower. If the heat treatment temperature is too low, reductive nitriding may be insufficient, and the thermal conductivity of the AlN-BN composite agglomerated particles and the molded product may be reduced. If the heat treatment temperature is too high _{, decomposition of Al 2} O ₃ , Al N, or BN may occur.
The content of carbon black in the reduction nitriding is not otherwise _limited, Al ₂ O 3 -BN composite heat treatment to _Al 2 _O 3 100 parts by weight of the particles generally 30 parts by weight or more, preferably 35 parts by mass or more, Further, it is usually 75 parts by mass or less, preferably 55 parts by mass or less.

The heat treatment time in the reduction nitriding treatment is usually 1 hour or more, preferably 5 hours or more, more preferably 12 hours or more, and usually 72 hours or less, preferably 48 hours or less. If the heat treatment time is less than the above lower limit, the reduction nitriding becomes insufficient, and if the heat treatment time exceeds the above upper limit, Al ₂ O ₃ , Al N, or BN may be partially decomposed.

Since the reduction nitriding treatment is performed in a non-oxidizing gas atmosphere or a reducing gas atmosphere, it is preferable that the inside of the firing furnace is usually exhausted by using a vacuum pump, and then the non-oxidizing gas or the reducing gas is blown into the furnace. While introducing the gas, it is heated to a desired temperature to raise the temperature. If the inside of the firing furnace can be sufficiently replaced with a non-oxidizing gas or a reducing gas, the temperature may be raised by heating while introducing the non-oxidizing gas or the reducing gas under normal pressure. Examples of the firing furnace include batch type furnaces such as muffle furnaces, tubular furnaces, and atmospheric furnaces, and continuous furnaces such as rotary kilns, screw conveyor furnaces, tunnel furnaces, belt furnaces, pusher furnaces, and vertical continuous furnaces, depending on the purpose. It can be used properly.

{Carbon black removal treatment}
High-purity AlN-BN composite agglomerated particles can be produced by further heat-treating the above AlN-BN composite agglomerated particles in an oxidizing atmosphere.
Here, the oxidizing atmosphere is an oxidizing gas atmosphere containing oxygen gas and the like. Depending on the type of acid gas used here, the amount of excess carbon black remaining in the AlN-BN composite agglomerated particles will be removed by combustion.
The carbon black removal treatment temperature is usually 500 ° C. or higher and 900 ° C. or lower, but is preferably 700 ° C. or higher, and preferably 800 ° C. or lower. If the carbon black removal treatment temperature is too low, the removal of carbon black by combustion may be insufficient, and the insulating property of the AlN-BN composite agglomerated particles may be lowered. If the carbon black removal treatment temperature is too high, the BN may be oxidized.

The heat treatment time in the carbon black removal treatment is usually 1 hour or more, preferably 2 hours or more, and usually 12 hours or less, preferably 5 hours or less. If the heat treatment time is less than the above lower limit, the removal of carbon black by combustion becomes insufficient, and if it exceeds the above upper limit, BN may be partially oxidized.

Examples of the firing furnace used for heat treatment include batch type furnaces such as muffle furnaces, tubular furnaces, and atmospheric furnaces, and continuous furnaces such as rotary kilns, screw conveyor furnaces, tunnel furnaces, belt furnaces, pusher furnaces, and vertical continuous furnaces. It can be used properly according to the purpose.

The method for producing AlN-BN composite agglomerated particles described above is another embodiment of the present invention.
It is a production method of aluminum nitride-boron nitride composite aggregated particles formed by agglomerating aluminum nitride primary particles and boron nitride primary particles, and is a production method including a reduction nitride step of aluminum oxide.
The reduction nitriding step is preferably carried out in the presence of carbon black and in a non-oxidizing gas or reducing gas atmosphere.

<Composite composition>
Another embodiment of the present invention is a composite composition obtained by blending the above AlN-BN composite agglomerated particles into a matrix.
The matrix used preferably has high thermal conductivity, and the thermal conductivity of the matrix is preferably 0.2 W / mK or more, and particularly preferably 0.22 W / mK or more.
As a method for measuring the thermal conductivity of the matrix, the thermal diffusivity, the specific gravity, and the specific heat are measured using the following devices, and the thermal conductivity is obtained by multiplying these three measured values.
(1) Thermal diffusivity: "Eye Phase Mobile 1u" manufactured by Eye Phase
(2) Specific gravity: "Balance XS-204" manufactured by METTLER TOLEDO (using solid density measurement kit)
(3) Specific heat: Seiko Instruments Inc. "DSC320 / 6200"

A resin is usually used as the matrix, and either a curable resin or a thermoplastic resin can be used without limitation. The curable resin may be any crosslinkable resin such as thermosetting, photocurable, and electron beam curable, but a thermosetting resin is preferable in terms of heat resistance, water absorption, dimensional stability, and the like. Used.
As the thermosetting resin and the thermosetting resin, for example, those exemplified in WO2013 / 081061 can be used. Of these, it is preferable to use a thermosetting resin, and it is particularly preferable to use an epoxy resin.
As the epoxy resin, a phenoxy resin having at least one skeleton selected from the group consisting of a naphthalene skeleton, a fluorene skeleton, a biphenyl skeleton, an anthracene skeleton, a pyrene skeleton, a xanthene skeleton, an adamantane skeleton and a dicyclopentadiene skeleton is preferable. Among them, a phenoxy resin having a fluorene skeleton and / or a biphenyl skeleton is particularly preferable because heat resistance is further enhanced, and in particular, it has at least one or more skeletons of a bilphenol A skeleton, a bisphenol F skeleton and a biphenyl skeleton. It is preferably a phenoxy resin.

The content of the matrix in the composite composition is usually 2 wt% or more, preferably 5 wt% or more, more preferably 7 wt% or more, usually 70 wt% or less, preferably 60 wt% or less, more preferably 40 wt% or less. be.
The content of the (high-purity) AlN-BN composite agglomerated particles in the composite composition is usually 30 wt% or more, preferably 40 wt% or more, more preferably 50 wt% or more, and usually 99 wt% or less, preferably 99 wt% or less. It is 98 wt% or less, more preferably 95 wt% or less.

An organic solvent can be used to prepare the composite composition. Examples of the organic solvent include alcohol-based solvents, aromatic solvents, amide-based solvents, alkane-based solvents, ethylene glycol ethers and ether / ester-based easy agents, propylene glycol ethers and ether-ester-based solvents, ketone-based solvents, and ester-based solvents. From the above, it can be suitably selected and used in consideration of the solubility of the resin and the like.
As a specific example of the organic solvent, those exemplified in WO2013 / 081061 can be used.
As the organic solvent, one type may be used alone, or two or more types may be used in combination in any combination and ratio.

The composite composition may contain a curing agent, if necessary.
The curing agent refers to a substance that contributes to the cross-linking reaction between the cross-linking groups of the matrix, such as the epoxy group of the epoxy resin.
In the epoxy resin, a curing agent and a curing accelerator for the epoxy resin are used together, if necessary.
Examples of the curing agent include an acid anhydride-based curing agent and an amine-based curing agent. Examples of the acid anhydride-based curing agent include tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, and benzophenone tetracarboxylic acid anhydride. Examples of the amine-based curing agent include aliphatic polyamines such as ethylenediamine, diethylenetriamine and triethylenetetramine, aromatic polyamines such as diaminodiphenylsulfone, diaminodiphenylmethane, diaminodiphenyl ether and m-phenylenediamine, and dicyandiamide. One of these may be used alone, or two or more thereof may be mixed and used.

Further, for the purpose of further improving the functionality, various additives (other additives) may be contained as long as the effects of the present invention are not impaired. Examples of other additives include functional resins having functionality added to the matrix, such as liquid crystal epoxy resins, nitride particles such as aluminum nitride, silicon nitride, and fibrous boron nitride, alumina, and fibrous alumina. , Insulating metal oxides such as zinc oxide, magnesium oxide, beryllium oxide and titanium oxide, insulating carbon components such as diamond and fullerene, resin curing agents, resin curing accelerators, viscosity modifiers and dispersion stabilizers.

Further, as other additives, as an additive component for improving the adhesiveness between the matrix and the (high-purity) AlN-BN composite agglomerated particles, a coupling agent such as a silane coupling agent or a titanate coupling agent, and storage. Examples thereof include UV inhibitors, antioxidants, plasticizers, flame retardants, colorants, dispersants, fluidity improvers and the like for improving stability.

In addition, a surfactant, an emulsifier, a low elasticity agent, a diluent, an antifoaming agent, an ion trapping agent, etc., which improve the dispersibility of each component in the composition, can be added.
One of these may be used alone, or two or more thereof may be mixed and used in any combination and ratio.
As a specific example of the additive, those exemplified in WO2013 / 081061 can be used, and the amount of the additive can also be within the range described in WO2013 / 081061.

The composition of the composite material is prepared by a paint shaker, a bead mill, a planetary mixer, a stirring type disperser for the purpose of dispersing and mixing (high-purity) AlN-BN composite aggregated particles, a matrix, a solvent and other additives. , It is preferable to mix using a general kneading device such as a self-revolving stirring mixer, a three-roll, kneader, a single-screw or twin-screw kneader.
The mixing order of each compounding component of the composite material composition is also arbitrary as long as there are no particular problems such as reaction or precipitation, and any two components or three or more components of the composition are mixed in advance. Then the remaining ingredients may be mixed or all at once.

By forming the composite material composition into a molded body, it can be a heat radiating member such as a sheet or a substrate.
As a method for molding this molded product, a method generally used for molding a resin composition can be used.
The substrate referred to here means a board in which a plate made of metal or ceramics is bonded to one side or both sides of a sheet.
For example, it can be molded by curing the coating liquid for a heat radiating sheet in a desired shape, for example, in a state of being filled in a mold. As a method for producing such a molded product, an injection molding method, an injection compression molding method, an extrusion molding method, and a compression molding method can be used.
When the composite composition contains a thermosetting resin composition such as an epoxy resin or a silicone resin, the molded product can be molded, that is, cured under curing temperature conditions according to the respective compositions.
The sheet / substrate obtained by molding the composite composition according to the present embodiment has high heat dissipation because the composite agglomerated particles contained therein are excellent in thermal conductivity, and dissipate heat from the heat dissipation sheet and the heat dissipation substrate for power device applications. It is suitably used as a member.

When the composite material composition contains the thermoplastic resin composition, the molded product can be molded under the conditions of a temperature equal to or higher than the melting temperature of the thermoplastic resin and a predetermined molding speed and pressure. Further, a molded product can also be obtained by cutting the composite material composition into a desired shape from a solid material that has been molded and cured.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded. The values of various conditions and evaluation results in the following examples indicate the preferable range of the present invention as well as the preferable range in the embodiment of the present invention, and the preferable range of the present invention is the preferred range in the above-described embodiment. It can be determined in consideration of the preferable range and the range indicated by the combination of the values of the following examples or the values of the examples.

{Measurement condition}
The characteristics in the present invention were measured by the methods described below.
-Average particle size (D ₅₀ ):
The average particle size was measured _{D 50 (μm)} using a HORIBA Ltd. "LA-300".
-XRD pattern For XRD measurement, an X-ray diffractometer "X'Pert Pro MPD" manufactured by PANalytical Co., Ltd. was used. The X-ray source is CuKα.
-Particle shape The particle shape was observed using SEM (Zeiss Ultra55).
-Elemental analysis For elemental analysis, an energy dispersive X-ray analysis (SEM-EDX) device "QUANTAX 200" manufactured by BRUKER AXS was used.
-Thermal conductivity in the thickness direction of the molded body The thermal diffusivity in the thickness direction of the molded body was measured using a thermal diffusivity measuring device "ai-Phase Mobile 1u" manufactured by iPhase Co., Ltd., and was determined as follows.
Thermal conductivity in the thickness direction of the molded body = Thermal diffusivity in the thickness direction of the molded body × Specific gravity of the molded body × Specific heat of the molded body

(Comparative Example 1)
The thermal conductivity given to the composite composition by the agglomerated particles consisting only of BN was evaluated and used as a comparison target with the AlN-BN composite agglomerated particles.
<Preparation of aggregated particles>
[Preparation of slurry]
A binder (“Taxerum M160L” manufactured by Taki Chemical Co., Ltd., solid content concentration 21% by mass) was weighed in a container, and raw material h-BN powder (oxygen concentration 7.5% by mass) was weighed therein. The amount of binder was 1.15 times the amount of raw material h-BN powder. The blending amount of each substance is shown in Table 1. This was stirred with a hand mixer until uniform.

[Preparation of granulated particles]
Granulation from the slurry was carried out using a micro mist spray dryer (MDL-050M) Labo manufactured by Fujisaki Electric Co., Ltd. to obtain spherical granulated particles. _D of the granulated particles ₅₀ are shown in Table 1.

[Preparation of temporary heat-treated particles]
The granulated particles were heated to 700 ° C. at 700 ° C./hour in the atmosphere, held as they were for 2 hours after reaching 700 ° C., and then cooled to room temperature to obtain temporary heat-treated particles.

[Preparation of heat-treated particles]
After vacuuming the tentative heat-treated particles at room temperature, nitrogen gas is introduced to repressurize the particles, and the temperature is raised to 1600 ° C. at 230 ° C./hour while introducing nitrogen gas at 0.5 L / min as it is, and the temperature is raised to 1600 ° C. After reaching, it was held for 24 hours while introducing nitrogen gas as it was. Then, it cooled to room temperature, and spherical heat-treated particles having a card house structure were obtained.

<Evaluation of aggregated particles>
[Composition of heat-treated particles]
The XRD pattern of the heat-treated particles is as shown in FIG. Peaks were assigned to h-BN (circled) and Al ₅ BO ₉ (unmarked). Since _{the peak intensity of Al 5} BO ₉ is weak, its content is considered to be extremely small. Further, it is considered that this Al ₅ BO ₉ was formed by the reaction of the binder-derived aluminum oxide and the boron oxide in h-BN.
The amount of AlN in the heat-treated particles defined by (raw material AlN powder amount) × 100 / (raw material AlN powder amount + raw material BN powder amount), (raw material BN powder amount) × 100 / (raw material AlN powder amount + raw material BN powder amount) The amount of BN in the heat-treated particles defined in Table 1 is as shown in Table 1.
[Structure of heat-treated particles]
The SEM image of the heat-treated particles is as shown in FIG. The formation of a card house structure by plate-shaped h-BN primary particles was confirmed.

<Preparation of composite composition>
[Preparation of composite composition]
(material)
The obtained heat-treated particles, an epoxy resin "LX-01" manufactured by Daiso, a dispersant "BYK-2155" manufactured by BYK, and a curing agent "C11Z-CN" manufactured by Shikoku Kasei Co., Ltd. were used.
(Preparation of composite composition)
The obtained heat-treated particles, epoxy resin, and dispersant were weighed in a container with a lid and mixed using a self-revolving stirrer (Sinky, ARV-310). Then, the curing agent was weighed there and mixed using a self-revolving stirrer. The amount of the dispersant was 0.02 times the amount of the reduced nitride particles, and the amount of the curing agent was 0.06 times the amount of the epoxy resin. The blending amount of each substance is shown in Table 2. The obtained mixture was sandwiched between a glass plate subjected to a shape-removing treatment together with a 500 μm gap made of silicone rubber, and heat-cured at 160 ° C. for 4 hours to obtain a composite material composition for evaluation of thermal conductivity.

<Evaluation of composite composition>
The thermal conductivity in the thickness direction of the composite composition was measured. The measurement results are shown in Table 2. Moreover, when the thermal conductivity was plotted with respect to the content rate of agglomerated particles, it was as shown in FIG.

(Comparative Example 2)
The thermal conductivity given to the composite composition by the agglomerated particles composed only of AlN was evaluated and used as a comparison target with the AlN-BN composite agglomerated particles.
<Preparation of aggregated particles>
The same procedure as in Comparative Example 1 was carried out except that the raw material h-BN powder was changed to the raw material AlN powder (Toyo Aluminum Co., Ltd. Toyalnite JC).

<Evaluation of aggregated particles>
[Composition of heat-treated particles]
The XRD pattern of the heat-treated particles is as shown in FIG. Peaks were assigned to AlN (stars), and CaAl ₁₂ O _19. Since _{the peak intensity of CaAl 12} O ₁₉ is weak, its content is considered to be extremely small. Further, _{it is considered that this CaAl 12} O ₁₉ was formed by the reaction of AlN with the calcium compound contained as a trace impurity in the binder.
[Structure of heat-treated particles]
The SEM image of the heat-treated particles is as shown in FIG. Granular AlN primary particles were confirmed.

<Preparation of composite composition>
This was done in the same manner as in Comparative Example 1.

<Evaluation of composite composition>
This was done in the same manner as in Comparative Example 1. The measurement results are shown in Table 2. Moreover, when the thermal conductivity was plotted with respect to the content rate of agglomerated particles, it was as shown in FIG. That is, it was confirmed that the thermal conductivity given to the composite composition by the agglomerated particles composed only of AlN is equivalent to that of the agglomerated particles composed only of BN.

(Examples 1, 2, 3)
The thermal conductivity of the AlN-BN composite agglomerated particles on the composite composition was evaluated, and the effect of converting the AlN primary particles and the BN primary particles into composite agglomerated particles was confirmed on the thermal conductivity.
<Preparation of aggregated particles>
[Preparation of slurry]
A binder ("Taxerum M160L" manufactured by Taki Chemical Co., Ltd., solid content concentration 21% by mass) is weighed in a container, and the raw material Al ₂ O ₃ powder ("Sumicolund AA03" manufactured by Sumitomo Chemical Co., Ltd.) and raw materials are placed therein. The h-BN powder (oxygen concentration 7.5% by mass, primary particle diameter 0.05 μm) was weighed. The amount of the binder was _{1.15 times the total amount of the raw material Al 2} O ₃ powder and the raw material h-BN powder. The blending amount of each substance is shown in Table 3. This was stirred with a hand mixer until uniform.

[Preparation of granulated particles]
Granulation from the slurry was carried out using a micro mist spray dryer (MDL-050M) Labo manufactured by Fujisaki Electric Co., Ltd. to obtain spherical granulated particles. _D of the granulated particles ₅₀ are shown in Table 3.

[Preparation of temporary heat-treated particles]
The granulated particles were heated to 700 ° C. at 700 ° C./hour in the atmosphere, held as they were for 2 hours after reaching 700 ° C., and then cooled to room temperature to obtain temporary heat-treated particles.

[Preparation of heat-treated particles]
After vacuuming the tentative heat-treated particles at room temperature, nitrogen gas is introduced to repressurize the particles, and the temperature is raised to 1600 ° C. at 230 ° C./hour while introducing nitrogen gas at 0.5 L / min as it is, and the temperature is raised to 1600 ° C. After reaching, it was held for 24 hours while introducing nitrogen gas as it was. Then, it cooled to room temperature, and spherical heat-treated particles having a card house structure were obtained.

[Preparation of reduced nitrided particles]
The heat-treated particles and carbon black were weighed in a predetermined amount in a container and covered. The blending amount of each substance is shown in Table 3. This was shaken by hand for 5 minutes to mix to give a carbon black mixture. After vacuuming the carbon black mixture at room temperature, nitrogen gas is introduced to repressurize, and the temperature is raised to 1600 ° C. at 230 ° C./hour while introducing nitrogen gas at 0.5 L / min as it is, reaching 1600 ° C. After that, it was held for 24 hours while introducing nitrogen gas as it was. Then, it cooled to room temperature. The particles were heated to 700 ° C. at 700 ° C./hour in the atmosphere, and after reaching 700 ° C., they were kept as they were for 5 hours. Then, it cooled to room temperature, and spherical reduced nitriding particles were obtained.

[Preparation of high-purity reduced nitrided particles]
High-purity reduced nitriding particles were obtained by raising the temperature of the reduced nitriding particles to 700 ° C. at 700 ° C./hour in the atmosphere, holding the reduced nitriding particles as they were for 5 hours after reaching 700 ° C., and then cooling to room temperature.

<Evaluation of aggregated particles>
[Composition of heat-treated particles]
The XRD pattern of the heat-treated particles is as shown in FIG. Peaks were _{assigned to Al 2} O ₃ (triangular), h-BN (circle), and Al ₅ BO ₉ (unmarked). Since the peak intensity of _{Al 5} BO ₉ is weak, it is considered that the _{Al 5} BO _{9 content is small.} Further, it is considered that this Al ₅ BO ₉ was formed by the reaction of the binder-derived aluminum oxide and the boron oxide in h-BN.
(Raw material Al ₂ O ₃ powder amount) x 100 / (Raw material Al ₂ O ₃ powder amount + Raw material BN powder amount) Al ₂ O ₃ amount in the heat-treated particles, (Raw material BN powder amount) x 100 / (Raw material) The _{amount of BN in the heat-treated particles defined by (Al 2} O ₃ powder amount + raw material BN powder amount) is as shown in Table 3.

[Structure of heat-treated particles]
The SEM image of the heat-treated particles is as shown in FIG. A cardhouse structure consisting of granular Al ₂ O ₃ primary particles and plate-shaped h-BN primary particles was confirmed. From FIG. 5, the length of the major axis of the h-BN primary particles was about 1.29 μm in Example 1, about 0.72 μm in Example 2, and about 0.65 μm in Example 3.

[Composition of high-purity reduced nitrided particles]
The XRD pattern of the high-purity reduced nitride particles is as shown in FIG. Peaks were assigned to AlN (stars) and h-BN (circles). Further, when the XRD patterns of the heat-treated particles and the high-purity reduced nitride particles were superimposed and plotted, the results were as shown in FIG. 7 (former: thin line, latter: thick line). The h-BN peak shape was exactly the same in both cases. Therefore, it is considered that h-BN primary particles having exactly the same plate shape and crystallinity as those found in the heat-treated particles are also present in the reduced nitride particles. Assuming that the weight of AlN obtained by nitriding the entire amount of the raw material Al ₂ O ₃ powder is α, the amount of AlN in the reduced nitride particles defined by α × 100 / (α + the amount of the raw material BN powder) and the amount of the raw material BN powder × 100. The amount of BN in the reduced nitride particles defined by / (α + amount of raw material BN powder) is as shown in Table 3.

[Structure of high-purity reduced nitrided particles]
The SEM image of the high-purity reduced nitride particles is as shown in FIG. It was found that the particle surface was covered with amorphous material. The SEM-EDX analysis results of the high-purity reduced nitride particles produced in exactly the same manner as in Example 2 except that the raw material Al ₂ O _{3 powder was changed to TM-DA manufactured by Taimei Chemicals Co., Ltd. are as shown in FIG.} Became. In addition, EDX point analysis was performed at the arrow portion in the SEM image. This amorphous material was found to consist of boron, carbon, nitrogen, and oxygen.

<Preparation of composite composition>
[Preparation of composite composition]
(material)
The obtained high-purity reduced nitride particles, an epoxy resin "LX-01" manufactured by Daiso, a dispersant "BYK-2155" manufactured by BYK, and a curing agent "C11Z-CN" manufactured by Shikoku Kasei Co., Ltd. were used.
(Preparation of composite composition)
The obtained high-purity reduced nitride particles, epoxy resin, and dispersant were weighed in a container with a lid and mixed using a self-revolving stirrer (manufactured by Shinky Co., Ltd., ARV-310). Then, the curing agent was weighed there and mixed using a self-revolving stirrer. The amount of the dispersant was 0.02 times the amount of high-purity reduced nitrided particles, and the amount of the curing agent was 0.06 times the amount of the epoxy resin. The blending amount of each substance is shown in Table 4. The obtained mixture was sandwiched between a glass plate subjected to a shape-removing treatment together with a 300 μm gap made of silicone rubber, and heat-cured at 160 ° C. for 4 hours to obtain a composite material composition for evaluation of thermal conductivity.

<Evaluation of composite composition>
The thermal conductivity in the thickness direction of the composite composition was measured. The measurement results are shown in Table 4. Moreover, when the thermal conductivity was plotted with respect to the content rate of agglomerated particles, it was as shown in FIG. Looking at FIG. 3, it can be seen that the thermal conductivity of Examples 1, 2 and 3 is higher than that of Comparative Example 1 or 2. That is, it was shown that the composite of the AlN primary particles and the h-BN primary particles to form the AlN-BN composite agglomerated particles greatly increases the thermal conductivity given to the composite material composition by the agglomerated particles.

(Comparative Example 3)
AlN-BN composite agglomerated particles were prepared using the raw material AlN powder instead of the raw material Al ₂ O ₃ powder, the thermal conductivity of the composite material composition using the particles was evaluated, and the raw material Al ₂ O ₃ powder was used. It was used as a comparison target with the case.

<Preparation of aggregated particles>
[Preparation of slurry]
A binder (“Taxerum M160L” manufactured by Taki Chemical Co., Ltd., solid content concentration 21% by mass) is weighed in a container, and the raw material h-BN powder (oxygen concentration 7.5% by mass) and the raw material AlN powder (Toyo Aluminum) are placed therein. "Toyal Night JC" manufactured by Co., Ltd.) was weighed. The amount of the binder was 1.15 times the total amount of the raw material h-BN powder and the raw material AlN powder. Table 5 shows the blending amount of each substance.
Shown in. This was stirred with a hand mixer until uniform.

[Preparation of granulated particles]
Granulation from the slurry was carried out using a micro mist spray dryer (MDL-050M) Labo manufactured by Fujisaki Electric Co., Ltd. to obtain spherical granulated particles.

[Preparation of temporary heat-treated particles]
The granulated particles were heated to 700 ° C. at 700 ° C./hour in the atmosphere, held as they were for 2 hours after reaching 700 ° C., and then cooled to room temperature to obtain temporary heat-treated particles.

[Preparation of heat-treated particles]
After vacuuming the tentative heat-treated particles at room temperature, nitrogen gas is introduced to repressurize the particles, and the temperature is raised to 1600 ° C. at 230 ° C./hour while introducing nitrogen gas at 0.5 L / min as it is, and the temperature is raised to 1600 ° C. After reaching, it was held for 24 hours while introducing nitrogen gas as it was. Then, it cooled to room temperature, and spherical heat-treated particles having a granular structure were obtained.

<Evaluation of aggregated particles>
[Composition of heat-treated particles]
The XRD pattern of the heat-treated particles is as shown in FIG. Peaks were assigned to h-BN (circles), AlN (stars), and CaAl ₁₂ O ₁₉ (unmarked). Since _{the peak intensity of CaAl 12} O ₁₉ is weak, its content is considered to be extremely small. Further, _{it is considered that this CaAl 12} O ₁₉ was formed by the reaction of AlN with the calcium compound contained as a trace impurity in the binder. The half width of the h-BN peak was larger than that of Examples 1, 2, and 3, suggesting that the plate-shaped h-BN primary particles did not grow sufficiently.

[Structure of heat-treated particles]
The SEM image of the heat-treated particles is as shown in FIG. The major axis of the h-BN primary particles is about 50 nm, and it can be seen that the plate-shaped h-BN primary particles did not grow sufficiently (less than 0.1 μm).

<Preparation of composite composition>
[Preparation of composite composition]
(material)
The obtained heat-treated particles, an epoxy resin "LX-01" manufactured by Daiso, a dispersant "BYK-2155" manufactured by BYK, and a curing agent "C11Z-CN" manufactured by Shikoku Kasei Co., Ltd. were used.
(Preparation of composite composition)
The obtained heat-treated particles, epoxy resin, and dispersant were weighed in a container with a lid and mixed using a self-revolving stirrer (Sinky, ARV-310). Then, the curing agent was weighed there and mixed using a self-revolving stirrer. The amount of the dispersant was 0.02 times the amount of the reduced nitride particles, and the amount of the curing agent was 0.06 times the amount of the epoxy resin. The blending amount of each substance is shown in Table 6. The obtained mixture was sandwiched between a glass plate subjected to a shape-removing treatment together with a 500 μm gap made of silicone rubber, and heat-cured at 160 ° C. for 4 hours to obtain a composite material composition for evaluation of thermal conductivity.

<Evaluation of composite composition>
The thermal conductivity in the thickness direction of the composite composition was measured. The measurement results are shown in Table 6. Moreover, when the thermal conductivity was plotted with respect to the content rate of agglomerated particles, it was as shown in FIG. For comparison, the results of Comparative Examples 1 and 2 are also plotted. Then, it can be seen that the thermal conductivity given to the complex composition by the agglomerated particles of Comparative Example 3 is about the same as or less than that of Comparative Examples 1 and 2. As described above, it was found that the presence of AlN in the heat treatment stage inhibits the plate-like growth of the h-BN primary particles. Moreover, it was shown that the thermal conductivity given to the composite composition by such agglomerated particles is low.

(Comparative Example 4)
The heat conduction of Al ₂ O ₃ is isotropic like Al N, but its size is much smaller than that of Al N (usually, the thermal conductivity is about 40 W / mK). The thermal conductivity of the composite composition using the Al ₂ O _3- BN composite agglomerated particles was evaluated and used as a comparison target with the AlN-BN composite agglomerated particles.
<Preparation of aggregated particles>
As the agglomerated particles, the heat-treated particles obtained in Example 2 were used.
<Evaluation of aggregated particles>
It is the same as the heat-treated particles of Example 2.

<Preparation of composite composition>
This was done in the same manner as in Comparative Example 3.

<Evaluation of composite composition>
This was done in the same manner as in Comparative Example 3. The measurement results are shown in Table 6. Moreover, when the thermal conductivity was plotted with respect to the content rate of agglomerated particles, it was as shown in FIG. For comparison, the results of Comparative Examples 1 and 2 are also plotted. Then, it can be seen that the thermal conductivity given to the complex composition by the agglomerated particles of Comparative Example 4 is about the same as or less than that of Comparative Examples 1 and 2. That is, even if the substance does not have thermal conductivity anisotropy, if its thermal conductivity is small, even if it is composited with h-BN primary particles to form BN composite aggregated particles, the thermal conductivity given to the composite material composition by the aggregated particles. The rate was shown to be low.

Claims (5)

A method for producing aluminum nitride-boron nitride composite agglomerated particles, which is formed by aggregating aluminum nitride primary particles and boron nitride primary particles .
Acid aluminum - obtaining a boron nitride composite granulated particles, the aluminum oxide - reduction step of cooling the boron nitride composite granulated particles after heat treatment, and heat treatment particles obtained in the step of cooling after the heating nitriding reduction nitriding step in the process is aluminum oxide, include, and,
Before SL aluminum nitride - boron nitride composite agglomerated particles,
Aluminum nitride primary particles and boron nitride primary particles having a major axis of 0.1 μm or more and 5 μm or less are aggregated.
The total oxygen concentration in the raw material boron nitride powder of the boron nitride primary particles is 3% by mass or more and 10% by mass or less.
A method for producing composite agglomerated particles, wherein the mass ratio of aluminum nitride to boron nitride in the aluminum nitride-boron nitride composite agglomerated particles is 3: 97 to 85:15. The production method according to claim 1 , wherein the reduction nitriding step is performed in the presence of carbon black and in a non-oxidizing gas or a reducing gas atmosphere. The production method according to claim 1 or 2 , wherein the heat treatment temperature in the heat treatment is 1500 ° C. or higher and 2000 ° C. or lower. The production method according to any one of claims 1 to 3, wherein the boron nitride primary particles form a card house structure. The production method according to any one of claims 1 to 4, wherein the aluminum nitride-boron nitride composite aggregate particles contain at least a component consisting of boron, carbon, nitrogen, and oxygen.

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