Aluminum nitride powder and resin composition

Abstract

The average particle diameter of the aluminum nitride powder of the present application is 5 to 50 μm, the oxygen content is 0.5 mass% or less, in a scanning electron microscope observation at a magnification of 500 times, the polyhedral particles having at least two smooth faces (a) are contained, and the average of the ratio (L / D) of the long diameter (L) to the short diameter (D) of the polyhedral particles having a long diameter (L) of 5 μm or more is in the range of 1 to 1.4. According to the present application, it is possible to provide an aluminum nitride powder which is high in thermal conductivity when filled in a resin to form a resin composition, and also good in flowability.

Description

TECHNICAL FIELD

[0001] The present application relates to an aluminum nitride powder and a resin composition containing the same. BACKGROUND

[0002] Aluminum nitride powder is widely known as a material having high thermal conductivity and also excellent electrical insulating properties, for example, for a thermal interface material or the like.

[0003] A thermal interface material refers to a material for moderating the thermal resistance of a path for escaping heat generated from a semiconductor element to a heat sink or a case or the like, and various forms such as a sheet, a gel, a grease or the like are used. As a thermal interface material, a heat dissipation material obtained by filling a thermal conductive filler such as aluminum nitride into a resin such as an epoxy resin or a silicone resin is known.

[0004] When aluminum nitride is filled in a resin, in order to improve the filling rate or to easily form a thermal path or the like, a method of combining aluminum nitrides having different average particle diameters to improve the thermal conductivity is known.

[0005] In a resin, particles having a large particle diameter easily form a thermal conduction path, but sometimes it is difficult to use for a heat dissipation material having a thin thickness, and in particular, for a spherical particle, the contact area of the particles with each other in the resin is small, and sometimes it is also difficult to form a thermal conduction path. On the other hand, particles having a small particle diameter are difficult to form a thermal conduction path in a resin, and in addition, sometimes the flowability when filled into a resin is poor. Therefore, the utilization value of an aluminum nitride powder having an average particle diameter of about 5 to 50 μm is high.

[0006] In Patent Literature 1, an invention relating to an aluminum nitride-based powder having an average particle diameter D 50 of 15 to 200 μm, a content of particles having a particle diameter of 5 μm or less is 60% or less on a number basis, an alkaline earth metal, a rare earth element, an oxygen content and a silicon content are low, and it is also described that the filling property of the aluminum nitride-based powder to a high molecular material is excellent. As a method of obtaining such an aluminum nitride-based powder, a method of pulverizing an aluminum nitride obtained by a direct nitriding method and performing a heat treatment is disclosed in the examples.

[0007] It is to be noted that the direct nitriding method is widely known as a synthesis method of ceramics such as aluminum nitride, and the exothermicity of the nitriding reaction is large, and becomes high temperature, and therefore a product as a bulk material is obtained. A pulverization treatment is required for use as a powder.

[0008] In addition, in Patent Literature 2, as an aluminum nitride powder capable of improving the thermal conductivity of a heat dissipation member, an aluminum nitride powder is disclosed, which is characterized in that the average particle diameter is 20 to 50 μm, the oxygen content is 0.6 mass% or less, and the average half-value width of the diffraction peaks of the (100), (002), and (101) planes obtained by X-ray diffraction is 0.095° or less.

[0009] Further, in Patent Literature 3, in order to improve the contact area between particles, an aluminum nitride powder containing particles having a smooth surface is proposed.

[0010] In Patent Literature 4, an aluminum nitride powder having an average particle diameter (D 50 ) of 60 μm obtained by pulverizing and classifying a crystal grain that is made large by a combustion synthesis method is described, and the filling property to a resin, the thermal conductivity, and the like are studied, and it is described that each of the properties is good.

[0011] Prior Art Documents

[0012] Patent Literature

[0013] Patent Literature 1: International Publication No. 2018 / 216591

[0014] Patent Literature 2: Japanese Patent Application Publication No. 2003-119010

[0015] Patent Literature 3: International Publication No. 2017 / 131239

[0016] Patent Literature 4: Japanese Patent Application Publication No. 2022-067865 SUMMARY

[0017] PROBLEMS TO BE SOLVED BY THE INVENTION

[0018] In the above-described prior art, the aluminum nitride powder disclosed in Patent Literature 1 and Patent Literature 4 is an aluminum nitride powder obtained by a direct nitriding method or a combustion synthesis method, and the thermal conductivity of the particles themselves is excellent because the oxygen content is low in the manufacturing method, but because the block-shaped material after the reaction is crushed or broken up, the particles constituting the powder are amorphous or firm agglomerates, and it is difficult to obtain particles having a smooth surface. In addition, the aspect ratio (the ratio (L / D) of the long diameter (L) to the short diameter (D) of the particles) of the above-described particles is high, and the flowability when filled into a resin is not sufficiently satisfied due to the influence of the properties of the above-described surface.

[0019] Furthermore, the aluminum nitride powder disclosed in Patent Document 2 improves crystallinity and achieves low oxygen content by heating the raw aluminum nitride powder. Its characteristic feature is that it heat-treats the broken powder, which restricts particle growth, to produce aluminum nitride powder with a desired particle size and low oxygen content. Therefore, the resulting aluminum nitride powder has an amorphous particle shape, and due to the presence of broken surfaces, a smooth surface is not formed.

[0020] Furthermore, although the aluminum nitride powder described in the aforementioned Patent Document 3 contains particles with smooth surfaces, which is expected to improve the flowability between particles and the thermal conductivity generated by surface contact when filled into the resin, the high oxygen concentration due to the manufacturing method used to form the smooth surface means that the thermal conductivity of the particles themselves can be improved.

[0021] As mentioned above, in the filling of resin with aluminum nitride powder, especially the conventional aluminum nitride powder used as medium-sized particles, there is room for further improvement because it cannot adequately meet the high heat dissipation requirements that have accompanied the increase in the density of power devices in recent years.

[0022] Therefore, the object of the present invention is to provide an aluminum nitride powder with high thermal conductivity and good flowability when filled in a resin to form a resin composition.

[0023] Methods for solving problems

[0024] To achieve the above objectives, the inventors conducted repeated and in-depth research. As a result, by employing the specific manufacturing method described later, they successfully developed an aluminum nitride powder with low oxygen content that affects the thermal conductivity of the particles, a smooth surface that effectively improves flowability, a small aspect ratio, and an average particle size of approximately 5–50 μm, thus completing this invention.

[0025] The main points of this invention are as follows [1] to [6].

[0026] [1] An aluminum nitride powder having an average particle size of 5 to 50 μm and an oxygen content of less than 0.5% by mass, which, when observed under a scanning electron microscope at 500x magnification, contains polyhedral particles with at least two smooth surfaces, and the average value of the ratio L / D of the major diameter L to the minor diameter D of the polyhedral particles having a major diameter L of 5 μm or more is in the range of 1.0 to 1.4.

[0027] [2] According to the aluminum nitride powder described in [1] above, the proportion of the multifaceted particles is 70% or more.

[0028] [3] According to the aluminum nitride powder described in [1] or [2] above, wherein, in a 2000x SEM image of the cross-section of the faceted particles, among any 10 selected particles, the average value M of the maximum value M corresponding to the vertical distance M between the contour line of the smooth surface and the straight line connecting the end of the contour line is... A It is below 0.15μm.

[0029] [4] The aluminum nitride powder as described in any one of [1] to [3] above is used for resin filling.

[0030] [5] A resin composition comprising aluminum nitride powder and resin as described in any one of [1] to [4] above.

[0031] [6] A method for manufacturing aluminum nitride powder, characterized in that it includes:

[0032] Step 1 involves processing particles with an average diameter of 0.5–5 μm and a specific surface area of ​​1.2–16.0 m². 2 The first aluminum nitride powder raw material has an average particle size of 3-40 μm and a specific surface area of ​​0.05-1.8 m² / g. 2 A raw material mixture is prepared by mixing 1 to 20 parts by mass of a second aluminum nitride powder raw material, wherein the ratio of the specific surface area SA2 of the second aluminum nitride powder raw material to the specific surface area SA1 of the first aluminum nitride powder raw material is SA2 / SA1 and is less than 0.8.

[0033] Step 2 involves heating the raw material mixture to 1750–2100°C under the supply of inactive gas.

[0034] Invention Effects

[0035] According to the present invention, an aluminum nitride powder with an average particle size of about 5 to 50 μm can be provided. Due to its low oxygen content, the particles themselves have high thermal conductivity. In addition, since it has two or more smooth surfaces and a small aspect ratio, it has extremely high fluidity when filled into resin. Furthermore, by increasing the contact area between the particles caused by the smooth surfaces, the resin composition filled with the aluminum nitride powder can be endowed with extremely high thermal conductivity. Attached Figure Description

[0036] [ Figure 1 [Image 1] is a SEM image of the aluminum nitride powder of the present invention.

[0037] [ Figure 2 [Image 1] is a SEM image of the aluminum nitride powder obtained in Example 26.

[0038] [ Figure 3 [ ] is an explanatory diagram defining the smooth surface of the particles constituting the aluminum nitride powder of the present invention. DETAILED DESCRIPTION

[0039] [Aluminum nitride powder]

[0040] The aluminum nitride powder of the present application has an average particle diameter of 5 to 50 μm, an oxygen content of 0.5 mass% or less, contains, in a scanning electron microscope observation at a magnification of 500 times, polyhedral particles having at least two smooth faces, and an average value of a ratio (L / D) of a long diameter (L) to a short diameter (D) with respect to the polyhedral particles having a long diameter L of 5 μm or more is in a range of 1.0 to 1.4.

[0041] [Polyhedral particle]

[0042] Figure 1 An image of the aluminum nitride powder of the present application obtained by a scanning electron microscope observation at a magnification of 500 times is shown. The aluminum nitride powder is composed of a plurality of aluminum nitride particles, and contains a plurality of polyhedral particles such as a polyhedral particle 11 and a polyhedral particle 12.

[0043] The polyhedral particle 11 is an aluminum nitride particle having a polyhedral shape with at least two smooth faces a present at random. The polyhedral particle 12 is also an aluminum nitride particle having at least two smooth faces a. In addition, in the Figure 1 , in addition to the polyhedral particle 11 and the polyhedral particle 12, a plurality of polyhedral particles are present.

[0044] The smooth face a possessed by the polyhedral particle is, as shown in Figure 1 , a smooth face in which no concave-convex structure is confirmed in-plane in a scanning electron microscope observation at a magnification of 500 times, and is a face from a crystal growth face of aluminum nitride. In addition, the smooth face a is different from a broken face formed by crushing an aluminum nitride particle. The broken face is inferior in smoothness to the smooth face, and a concave-convex structure from crushing is observed in a scanning electron microscope observation, and thus can be distinguished from the smooth face. In addition, the smoothness of the above smooth face a is described in more detail in the examples, and in a 2000 times SEM image of a cross section of a particle, in 10 arbitrarily selected particles, the maximum value of a perpendicular distance of a straight line connecting end portions of outline lines corresponding to smooth faces to a straight line connecting the end portions of the outline lines is set as M, and in M determined for the above 10 selected particles respectively, the maximum value M max is preferably 0.3 μm or less, and more preferably 0.2 μm or less. Furthermore, an average value M A of M of 10 particles is more preferably 0.15 μm or less.

[0045] Incidentally, a broken face generated by crushing a bulk of aluminum nitride, with respect to a smooth face, the above M max is not less than 0.3 μm including concave-convex and undulation, and in addition, an average value M Anot less than 0.15 μm.

[0046] The aluminum nitride powder of the present application easily increases the thermal conductivity of a resin composition when filled into a resin by containing the polyhedral particle. The reason is not certain, but it is believed that the contact area between the particles in the resin increases and a thermal conduction path is easily formed due to the presence of the polyhedral particle having a plurality of flat surfaces. In addition, the flowability of the particles is also improved due to the presence of the flat surfaces, and the improvement of the filling property when filled into a resin is also facilitated.

[0047] In the present application, the number of flat surfaces possessed by the polyhedral particle is not particularly limited as long as it is two or more, but it is preferably three or more from the viewpoint of increasing the contact area between the particles when filled into a resin, and the like. In addition, the upper limit of the number of flat surfaces possessed by the polyhedral particle is not particularly limited, and is, for example, ten. Note that the number of flat surfaces possessed by the polyhedral particle is determined based on an image obtained by observing with a scanning electron microscope (SEM) at a magnification of 500 times.

[0048] In addition, the two flat surfaces that are continuous are preferably continuous in a manner that forms a hill portion.

[0049] From the viewpoint of increasing the contact area between the particles when filled into a resin to improve the thermal conductivity, the area of each flat surface possessed by the polyhedral particle is preferably a certain degree large. From this viewpoint, the polyhedral particle preferably has at least two flat surfaces having an area of 2 to 1600 μm 2 , and more preferably has at least three flat surfaces having an area of 2 to 1600 μm 2 .

[0050] Note that the area of the flat surface is determined by an image obtained by observing with a scanning electron microscope (SEM) at a magnification of 500 times.

[0051] From the viewpoint of improving the thermal conductivity of a resin composition obtained by filling the aluminum nitride powder into a resin, the proportion of the presence of the polyhedral particle in the aluminum nitride powder of the present application is preferably 70% or more, more preferably 80% or more, and further preferably 90% or more. The proportion of the presence of the polyhedral particle is the proportion of the total area of the polyhedral particles with respect to the total area of all aluminum nitride particles determined in an image observed with a scanning electron microscope at a magnification of 500 times.

[0052] As described above, the smooth surface of the polyhedral particle is different from the broken surface on which irregularities or undulations exist. When an aluminum nitride powder having a small number of particles with broken surfaces is used, there is a tendency that the flowability of the resin composition filled in the resin improves. Therefore, the presence ratio of the particles with broken surfaces in the aluminum nitride powder of the present application is preferably 20% or less, more preferably 10% or less. The presence ratio of the particles with broken surfaces is the ratio of the total area of the particles with broken surfaces to the total area of all the aluminum nitride particles determined in the image observed by a scanning electron microscope at a magnification of 500 times.

[0053] <Aspect ratio of polyhedral particle>

[0054] The average of the ratio (L / D) of the length (L) to the short diameter (D) of the polyhedral particle having a length (L) of 5 μm or more in the aluminum nitride powder of the present application is in the range of 1.0 to 1.4. When the above ratio (L / D) exceeds 1.4, the flowability of the resin composition obtained by filling the aluminum nitride powder into the resin easily decreases, and the workability and the like deteriorate.

[0055] From the viewpoint of improving the flowability of the resin composition, the average of the ratio (L / D) of the length (L) to the short diameter (D) of the polyhedral particle having a length (L) of 5 μm or more is preferably in the range of 1.0 to 1.3, more preferably in the range of 1.0 to 1.2.

[0056] Here, the length (L) and the short diameter (D) of the polyhedral particle are determined based on the shape of the polyhedral particle observed in the scanning electron microscope observation at a magnification of 500 times.

[0057] The length (L) is defined as the maximum distance between any two points on the outer circumference of the polyhedral particle. The short diameter (D) is a line segment intersecting the length (L) perpendicularly, and is defined as a line segment passing through the midpoint of the length (L) and two points on the outer circumference of the polyhedral particle.

[0058] In addition, the average of the ratio (L / D) of the length (L) to the short diameter (D) is calculated by calculating the average of the ratio (L / D) of at least 20 or more polyhedral particles having a length (L) of 5 μm or more.

[0059] Note that the aluminum nitride powder containing the polyhedral particle of the present application can be obtained, for example, by the production method described later.

[0060] <Average particle diameter>

[0061] The average particle diameter of the aluminum nitride powder of the present application is 5 to 50 μm. Such an aluminum nitride powder having an average particle diameter of a moderate degree is easily used for filling into a resin, and thus has a high utilization value. If the average particle diameter is too large, it is sometimes difficult to use, for example, in a heat releasing material having a thin thickness, and in addition, if the average particle diameter is too small, there is a tendency that the thermal conductivity decreases. The average particle diameter of the aluminum nitride powder of the present application is preferably 5 to 40 μm, and more preferably 5 to 30 μm.

[0062] Note that, in the present specification, the average particle diameter of the aluminum nitride powder means a particle diameter (D50) at which the cumulative volume of particles is 50% in a laser diffraction particle size distribution apparatus. 50

[0063] <oxygen content>

[0064] The oxygen content of the aluminum nitride powder of the present application is 0.5 mass% or less.

[0065] Note that the oxygen content is the total oxygen amount determined by the high-temperature thermal decomposition method described in the examples.

[0066] When the above oxygen content exceeds 0.5 mass%, the thermal conductivity of the aluminum nitride powder decreases, and thus the thermal conductivity of a resin composition filled with the aluminum nitride powder also decreases. The oxygen content of the aluminum nitride powder is preferably 0.4 mass% or less, more preferably 0.3 mass% or less, and further preferably 0.2 mass% or less. Such a polyhedral particle having a low oxygen concentration is first provided by the present application, and thus the aluminum nitride powder of the present application exhibits a high thermal conductivity as shown below.

[0067] <thermal conductivity>

[0068] The thermal conductivity of the aluminum nitride powder of the present application is preferably 80 W / m-K or more, more preferably 120 W / m-K or more, and further preferably 160 W / m-K or more. Since the thermal conductivity of the aluminum nitride powder itself is so high, the thermal conductivity of a resin composition filled with the aluminum nitride powder is also high, and an excellent heat dissipation property can be exhibited. The higher the thermal conductivity of the aluminum nitride powder, the better, but it is generally 230 W / m-K or less. The thermal conductivity of the aluminum nitride powder can be adjusted by the oxygen content and the like.

[0069] Note that the measurement of the thermal conductivity of the aluminum nitride powder is based on a micro-Raman spectroscopy method, and the details are described in the examples.

[0070] [Method for producing aluminum nitride powder]

[0071] As the method for producing the aluminum nitride powder of the present application, any method that can obtain an aluminum nitride powder containing the above polyhedral particle and having the above average particle diameter and oxygen content is acceptable, and there is no particular limitation, and a method including the following process 1 and process 2 is preferable.​

[0072] Process 1 : A raw material mixture is prepared by mixing 100 parts by mass of a first aluminum nitride powder raw material having an average particle diameter of 0.5 to 5 μm and a specific surface area of 1.2 to 16.0 m 2 / g and 1 to 20 parts by mass of a second aluminum nitride powder raw material having an average particle diameter of 3 to 40 μm and a specific surface area of 0.05 to 1.8 m 2 / g, and a ratio (SA2 / SA1) of a specific surface area (SA2) of the second aluminum nitride powder raw material to a specific surface area (SA1) of the first aluminum nitride powder raw material is 0.8 or less.

[0073] Process 2: The raw material mixture is heated to 1750°C to 2100°C under supply of a non-reactive gas.

[0074] <Process 1>

[0075] Process 1 : A raw material mixture is prepared by mixing 100 parts by mass of a first aluminum nitride powder raw material having an average particle diameter of 0.5 to 5 μm and a specific surface area of 1.2 to 16.0 m 2 / g and 1 to 20 parts by mass of a second aluminum nitride powder raw material having an average particle diameter of 3 to 40 μm and a specific surface area of 0.05 to 1.8 m 2 / g, and a ratio (SA2 / SA1) of a specific surface area (SA2) of the second aluminum nitride powder raw material to a specific surface area (SA1) of the first aluminum nitride powder raw material is 0.8 or less.

[0076] The raw material mixture contains aluminum nitride having different average particle diameters in a prescribed mixing amount, and is subjected to a heating process (Process 2) described later, to obtain the aluminum nitride powder of the present application.

[0077] It is considered that, by the presence of the second aluminum nitride powder raw material having a relatively large average particle diameter in an appropriate amount, in the heating process, the first aluminum nitride powder raw material having a small average particle diameter enters the second aluminum nitride powder raw material by sublimation, and the second aluminum nitride powder raw material grows in crystal and increases in particle diameter. It is also considered that, by such crystal growth, the prescribed polyhedral particles described above are formed. Furthermore, it is considered that, since oxygen present in the first aluminum nitride powder is effectively removed by the sublimation, the aluminum nitride powder of the present application produced by the heating process has a low oxygen concentration.

[0078] On the other hand, in the case where the first and second aluminum nitride powder raw materials are not used in the prescribed mixing amount, as described above, there are phenomena such as insufficient growth of the particles or coagulation between the particles, and it is difficult to obtain the aluminum nitride powder of the present application.

[0079] The first aluminum nitride powder raw material has an average particle diameter of 0.5 to 5 μm and a specific surface area of 1.2 to 16.0 m 2 / g, preferably the average particle diameter is 0.7 to 5 μm and the specific surface area is 1.2 to 12.0 m 2 / g.

[0080] The average particle diameter of the second aluminum nitride powder raw material is 3 to 40 μm and the specific surface area is 0.05 to 1.8 m 2 The average particle diameter of the second aluminum nitride powder raw material can be appropriately selected depending on the average particle diameter of the aluminum nitride powder of the present application to be manufactured, and is preferably 3 to 20 μm, more preferably 5 to 15 μm.

[0081] The compounding amount of the second aluminum nitride powder raw material with respect to 100 parts by mass of the first aluminum nitride powder raw material in the raw material mixture is 1 to 20 parts by mass, preferably 2 to 15 parts by mass, more preferably 3 to 10 parts by mass. As described above, by appropriately adjusting the compounding amounts of the first and second aluminum nitride powder raw materials, the aluminum nitride powder of the present application can be obtained.

[0082] The ratio (SA2 / SA1) of the specific surface area (SA2) of the second aluminum nitride powder raw material to the specific surface area (SA1) of the first aluminum nitride powder raw material is 0.8 or less. In this way, by adjusting the ratio of the specific surface areas (SA2 / SA1), the aluminum nitride powder of the present application can be easily obtained. The ratio of the specific surface areas (SA2 / SA1) is preferably 0.7 or less, more preferably 0.6 or less.

[0083] In order to promote the growth of particles, an additive that promotes the growth of particles can be added in the firing. The additive is not particularly limited, and an oxide, a fluoride, a chloride, or the like of an alkali metal, an alkaline earth metal, or a rare earth element can be used.

[0084] The first and second aluminum nitride powder raw materials can be used without particular limitation as long as they have the prescribed average particle diameters, and a generally used aluminum nitride powder can be used. The aluminum nitride powder can be an aluminum nitride powder manufactured by a reduction nitriding method, or an aluminum nitride powder manufactured by a direct nitriding method such as a combustion synthesis method and adjusted to a prescribed average particle diameter through a pulverization and classification process. The aluminum nitride powder can also be an aluminum nitride powder manufactured by a manufacturing method other than these.

[0085] In addition, it is preferable to use the aluminum nitride powder of the present application manufactured by going through Process 1 and Process 2 as the second aluminum nitride powder raw material, and to carry out Process 1 and Process 2 again, thereby obtaining an aluminum nitride powder of the present application having a larger average particle diameter.

[0086] <Process 2>

[0087] Process 2 is a process of heating the raw material mixture prepared in Process 1 to 1750 to 2100°C under the supply of a non-active gas.

[0088] When the heating temperature is lower than 1750°C, the crystallization growth of the aluminum nitride particles cannot be promoted, and it is difficult to obtain an aluminum nitride powder containing aluminum nitride particles having smooth surfaces. On the other hand, when the heating temperature exceeds 2100°C, the particles are easily fused and adhered to each other. From such a viewpoint, the heating temperature is preferably 1750 to 2100°C, more preferably 1800 to 2050°C, and further preferably 1800 to 2000°C.

[0089] In addition, the heating time is not particularly limited, and is preferably 1 to 20 hours, and more preferably 2 to 15 hours. When the heating time is less than 1 hour, the crystallization growth of the aluminum nitride particles cannot sufficiently proceed, and it is difficult to form smooth surfaces. On the other hand, even when heating is performed for more than 20 hours, the particles are difficult to continue growing, and this is industrially disadvantageous.

[0090] The heating is performed under the supply of an inactive gas. That is, the most preferable mode is to supply an inactive gas into a heating device for housing the raw material mixture and to heat, but the heating can also be performed while continuously supplying an inactive gas. In addition, the raw material mixture is filled in a container for heating (hereinafter also referred to as "container") and housed in the above-mentioned heating device, and as the above-mentioned container, a carbon-made container is preferably used. Furthermore, as the inactive gas, argon, nitrogen, and the like are generally used, and among them, nitrogen is suitably used.

[0091] <Other processes>

[0092] After the process 2, a deagglomeration process can be performed as necessary. Deagglomeration is performed in order to separate the loosely bound aluminum nitride particles from each other, and is different from pulverization in which the aluminum nitride particles are partially broken. Therefore, even when the deagglomeration process is performed, the shape of the above-mentioned multifaceted particles can be maintained, and particles having broken surfaces are hardly generated.

[0093] The deagglomeration can be performed by a publicly known method, and for example, a roll-type crusher, a pin-type crusher, a vibration mill, a jet mill, a ball mill, a Masscol loider, a jaw crusher, and the like can be used.

[0094] In addition, an oxidation process can also be performed after the process 2, and the oxidation process is preferably performed after the above-mentioned deagglomeration process. By performing the oxidation process, decomposition due to contact with water or the like can be prevented.

[0095] The oxidation process can be performed by heating in an atmosphere. The heating temperature in the oxidation process is not particularly limited, and is preferably 500 to 900°C, and more preferably 600 to 800°C. The heating time is not particularly limited, and is preferably 1 to 20 hours, and more preferably 5 to 15 hours.

[0096] The oxygen content of the oxide film formed in the above oxidation step is included in the oxygen content of the aluminum nitride powder, and by performing the oxidation step in a range where the oxygen content does not exceed the oxygen content of the aluminum nitride powder, excellent thermal conductivity can be imparted to the obtained resin composition when filled into a resin.

[0097] The aluminum nitride powder of the present application can be surface-treated as needed in order to improve compatibility with a resin, water resistance, and the like. The surface treatment can be performed using a publicly known method. The surface treatment can be performed using, for example, an organic silicon compound such as silicone oil, a silylating agent, a silane coupling agent, an acid such as phosphoric acid, a phosphate, a fatty acid, a high molecular compound such as a polyamide resin, an inorganic substance such as alumina, and silica.

[0098] <USES>

[0099] The use of the aluminum nitride powder of the present application is not particularly limited, and the powder can be used as a raw material for an aluminum nitride substrate, and is preferably used for resin filling. The aluminum nitride powder of the present application is preferably filled into a resin and used as a resin composition containing a resin and the aluminum nitride powder. As described above, the aluminum nitride powder of the present application has a low oxygen content, a high thermal conductivity of the aluminum nitride powder itself, and contains a polyhedral particle having a plurality of smooth surfaces, and thus the contact area between the particles is large, and thus a thermal conduction path can be easily formed in the resin composition. Therefore, the thermal conductivity of the resin composition is improved, and the resin composition can be suitably used as a heat dissipation material.

[0100] The resin contained in the resin composition is not particularly limited, and examples include a thermosetting resin such as an epoxy resin, an epoxy resin into which a mesogen group is introduced, an unsaturated polyester resin, a polyimide resin, and a phenol resin; a thermoplastic resin such as polyethylene, polypropylene, polyamide, polycarbonate, and polyphenylene sulfide; a rubber such as ethylene propylene rubber and styrene butadiene rubber; and a silicone resin. Among these, an epoxy resin and a silicone resin are preferred.

[0101] The content of the aluminum nitride powder of the present application contained in the resin composition is not particularly limited, and is preferably 600 to 2500 parts by mass, and more preferably 1000 to 2500 parts by mass, relative to 100 parts by mass of the resin. When the content of the aluminum nitride powder is equal to or greater than the lower limit of these ranges, the thermal conductivity of the resin composition is improved, and when the content of the aluminum nitride powder is equal to or less than the upper limit of these ranges, the flowability of the resin composition is improved, and the handleability such as moldability is improved.

[0102] In a range that does not hinder the effects of the present application, other fillers other than the aluminum nitride powder of the present application can be contained in the resin composition.

[0103] As the other fillers, in addition to the aluminum nitride powder that does not satisfy the conditions of the present application, examples include alumina, zinc oxide, boron nitride, silicon nitride, silicon carbide, and graphite.

[0104] The mixing ratio of aluminum nitride powder and other fillers in this invention can be appropriately adjusted within the range of 1:99 to 99:1.

[0105] The resin composition may include additives such as plasticizers, vulcanizing agents, curing accelerators, and release agents as needed.

[0106] Resin compositions can be manufactured by mixing the components using a mixer or blender. The resulting resin composition can then be molded into heat dissipation materials of desired shapes, such as heat sinks or heat dissipation pastes, using known molding methods. Examples of molding methods include extrusion molding, compression molding, doctor blade molding, and resin impregnation. After molding, heat curing or UV curing can be performed as needed.

[0107] Example

[0108] The following embodiments are shown to illustrate the invention in more detail, but the invention is not limited to these embodiments.

[0109] [Determination Method]

[0110] The various physical properties in the examples and comparative examples were determined by the following methods.

[0111] (1) Average particle size and specific surface area

[0112] Average particle size (D) 50 The particle size distribution was determined by dispersing aluminum nitride powder in an aqueous sodium pyrophosphate solution using a homogenizer and measuring the particle size using a laser diffraction particle size distribution device (MICROTRAC HRA manufactured by Nikkiso Corporation).

[0113] The specific surface area was determined using the FlowSorb2300 automatic surface area measuring device manufactured by Shimadzu Corporation, by employing the BET method with N2 adsorption.

[0114] (2) The presence and proportion of multifaceted particles

[0115] Regarding the aluminum nitride powder, a scanning electron microscope (TM3030, manufactured by Hitachi High Technology Co., Ltd.) was used to take SEM images at a magnification of 500x (accelerating voltage 15kV, secondary electron detection). These SEM images were used to confirm the presence of particles with more than two smooth surfaces, thus determining the presence of multifaceted particles.

[0116] Furthermore, the prevalence of polyhedral particles is calculated as the ratio of the total area of ​​polyhedral particles to the total area of ​​all aluminum nitride particles obtained from the image analysis of the aforementioned SEM images. This ratio is used to determine the prevalence of polyhedral particles. The SEM images have at least 10 fields of view. Specifically, it is calculated using the following formula.

[0117] Proportion of polyhedral particles (%) = [(total area of polyhedral particles) / (total area of all aluminum nitride particles)] x 100

[0118] (3) Ratio (L / D) of long diameter (L) to short diameter (D) of polyhedral particles

[0119] From the SEM photograph obtained according to the above (2), for 20 polyhedral particles having a long diameter (L) of 5 μm or more, the ratio of the long diameter (L) to the short diameter (D) was respectively calculated, and the average value thereof was calculated as the ratio (L / D) of the long diameter (L) to the short diameter (D) of the polyhedral particles.

[0120] Note that, for the aluminum nitride powder in which no polyhedral particles were observed in the comparative example, particles having a long diameter (L) of 5 μm or more were targeted, and the ratio (L / D) was calculated in the same manner as described above.

[0121] (4) Evaluation of smoothness of flat surface

[0122] After the aluminum nitride powder was filled in an acrylic resin and cured, it was cut at an arbitrary portion, and in a 2000-fold SEM image of the cut surface, 10 particles having a flat surface were selected, and as shown in FIG. 2, a straight line L connecting an end portion PI of a contour line of the flat surface and an end portion P2 was drawn, the maximum value of the perpendicular distance from the straight line L to the contour line was set as M, and the maximum value among the values of M respectively measured in the 10 particles was set as M Figure 3 max。 In addition, the average value of the above M was represented as M A .

[0123] (5) Oxygen content

[0124] The oxygen content of the aluminum nitride powder was measured using an oxygen-nitrogen analysis device "EMGA-620W" manufactured by HORIBA, Ltd., from the amount of CO gas generated by high-temperature thermal decomposition in a graphite crucible, and the oxygen content (oxygen concentration) contained in the aluminum nitride powder.

[0125] (6) Thermal conductivity of aluminum nitride powder

[0126] The thermal conductivity of the aluminum nitride powder was measured based on the micro-Raman spectroscopy method described in Japanese Patent Application Publication No. 2021-143968. Details are as follows.

[0127] (Preparation of calibration curve)

[0128] The following S1 to S4 aluminum nitride sintered bodies were used as samples for preparing a calibration curve.

[0129] S1: commercially available product, relative density 99% or more, hexagonal system, thermal conductivity: 90 W / m·K by laser flash method ​

[0130] S2: Commercially available product, relative density over 99%, hexagonal crystal system, thermal conductivity calculated by laser flash method: 175 W / m·K

[0131] S3: Commercially available product, relative density over 99%, hexagonal crystal system, thermal conductivity calculated by laser flash method: 200 W / m·K

[0132] S4: Commercially available product, relative density over 99%, hexagonal crystal system, thermal conductivity calculated by laser flash method: 239 W / m·K

[0133] Raman spectra of commercially available aluminum nitride sintered samples S1–S4 were obtained using a micro Raman spectrometer (NRS-7100, manufactured in Japan). The settings were: excitation wavelength 532 nm, output power 10.9–11.0 mW, objective lens 100x, measurement time 30 seconds × 2 cumulative measurements, grating 3000 lines / mm, slit 10 × 1000 μm, aperture 4000 μm, and spectral resolution 0.47 cm⁻¹. -1 Measurements were taken under conditions of a 1 μm spot diameter and a 500 mm focal length spectrometer. From the obtained Raman spectrum, the E2 peak, one of the inherent peaks of aluminum nitride, was determined. H The peak of the pattern (655 cm) -1 The half-width of a peak (Half-width) is the peak width at six points near the sample. The average of these values ​​is taken as the half-width of the peak for that sample.

[0134] Next, the thermal conductivity of the aluminum nitride sintered body sample, whose peak half-width was measured, was determined by laser flash method.

[0135] The relationship between the obtained thermal conductivity and the peak half-width was plotted as a curve to confirm the results. The logarithm of the peak half-width was proportional to the logarithm of the thermal conductivity, resulting in the calibration curve shown in the following formula.

[0136] log(λ) = Alog(W) + B

[0137] In the above formula, λ is the thermal conductivity, W is the peak half-width, A is -2.25, and B is 3.50.

[0138] (Determination of thermal conductivity)

[0139] The thermal conductivity of the aluminum nitride powders obtained in each example and comparative example was measured using a micro Raman spectroscopy apparatus (NRS-7100, manufactured by Nippon Spectrophotometer Co., Ltd.). The measurement conditions were: excitation wavelength 532 nm, output power 10.9–11.0 mW, objective lens 100x, measurement time 30 seconds × 2 cumulative measurements, grating 3000 lines / mm, slit 10 × 1000 μm, aperture 4000 μm, and spectral resolution 0.47 cm⁻¹. -1The spectrometer had a spot diameter of 1 μm and a focal length of 500 mm. The measurements were performed as follows: Aluminum nitride powder samples dispersed on a glass slide by scattering were observed using an optical microscope. Particles with a diameter close to the average particle size of the powder were selected, and the focal point was aligned with their surface for Raman spectroscopy measurements.

[0140] In the obtained Raman spectrum, E2 was selected as one of the inherent peaks of aluminum nitride. H The peak of the pattern (655 cm) -1 Calculate the half-width of the peak (near the peaks). For a sample, measure the half-width of the peak for six particles and take the average as the half-width of the peak for that sample. Calculate the thermal conductivity of the aluminum nitride powder using the obtained half-widths and the calibration curve described above.

[0141] (7) Thermal conductivity of the resin composition

[0142] 100 parts by weight of aluminum nitride powder and 10 parts by weight of resin were mixed to obtain a resin composition. Epoxy resin was used as the resin. The resin composition was hot-pressed at 100°C to obtain a sheet with a thickness of 1 mm. The thermal conductivity of the obtained sheet was determined by laser flash method.

[0143] (8) Flowability of the resin composition

[0144] Regarding the resin composition obtained in (7) above, the discharge rate (g / min) was measured using a "PSY-30F" syringe manufactured by Musashi Engineering Co., Ltd.

[0145] The inner diameter of the main body of the syringe sample holder is 22 mm, and the inner diameter of the sample ejection tip is 2 mm. The ejection pressure is 0.62 Pa.

[0146] (Example 1)

[0147] With an average particle size of 0.5 μm and a specific surface area of ​​15.7 m², 2 100 parts by weight of aluminum nitride powder raw material with an average particle size of 3.2 μm and a specific surface area of ​​1.68 m² / g. 2 Mix 1 part by mass of aluminum nitride powder raw material (g / g) to prepare raw material mixture.

[0148] The raw material mixture was placed in a heating device, and nitrogen gas was supplied to create a nitrogen atmosphere. Heating was carried out at 1950°C for 4 hours under normal pressure. The resulting aluminum nitride powder was then crushed using a planetary ball mill and oxidized at 700°C for 8 hours under atmospheric pressure to obtain an average particle size of 5.0 μm and a specific surface area of ​​0.96 m². 2ALN powder (AL-1) having a specific surface area of 2.81 m2 / g. The disintegration and oxidation treatment were carried out in the same manner in all of the following examples, and thus are omitted below. The various measurement results of this ALN powder are shown in Table 1.

[0149] (Example 2)

[0150] ALN powder raw material having a specific surface area of 2.81 m2 / g, ALN powder raw material having a specific surface area of 1.79 m2 / g, and yttria as an additive were mixed to prepare a raw material mixture. 2 ALN powder raw material having a specific surface area of 2.81 m2 / g, ALN powder raw material having a specific surface area of 1.79 m2 / g, and yttria as an additive were mixed to prepare a raw material mixture. 2 ALN powder raw material having a specific surface area of 2.81 m2 / g, ALN powder raw material having a specific surface area of 1.79 m2 / g, and yttria as an additive were mixed to prepare a raw material mixture.

[0151] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and heating was carried out at 1800°C for 20 hours. The heating was carried out under normal pressure, and disintegration and oxidation treatment were further carried out to obtain ALN powder (AL-2) having an average particle diameter of 6.9 μm and a specific surface area of 0.70 m2 / g. The various measurement results of this ALN powder are shown in Table 1. 2 ALN powder raw material having a specific surface area of 2.81 m2 / g, ALN powder raw material having a specific surface area of 1.79 m2 / g, and yttria as an additive were mixed to prepare a raw material mixture.

[0152] (Example 3)

[0153] ALN powder raw material having a specific surface area of 2.81 m2 / g, ALN powder raw material having a specific surface area of 1.79 m2 / g, and yttria as an additive were mixed to prepare a raw material mixture. 2 ALN powder raw material having a specific surface area of 2.81 m2 / g, ALN powder raw material having a specific surface area of 1.79 m2 / g, and yttria as an additive were mixed to prepare a raw material mixture. 2 ALN powder raw material having a specific surface area of 2.81 m2 / g, ALN powder raw material having a specific surface area of 1.79 m2 / g, and yttria as an additive were mixed to prepare a raw material mixture.

[0154] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and heating was carried out at 1800°C for 20 hours. The heating was carried out under normal pressure, and disintegration and oxidation treatment were further carried out to obtain ALN powder (AL-2) having an average particle diameter of 6.9 μm and a specific surface area of 0.70 m2 / g. The various measurement results of this ALN powder are shown in Table 1. 2 ALN powder raw material having a specific surface area of 2.81 m2 / g, ALN powder raw material having a specific surface area of 1.79 m2 / g, and yttria as an additive were mixed to prepare a raw material mixture.

[0155] (Example 4)

[0156] ALN powder raw material having a specific surface area of 2.81 m2 / g, ALN powder raw material having a specific surface area of 1.79 m2 / g, and yttria as an additive were mixed to prepare a raw material mixture. 2 ALN powder raw material having a specific surface area of 2.81 m2 / g, ALN powder raw material having a specific surface area of 1.79 m2 / g, and yttria as an additive were mixed to prepare a raw material mixture. 2 ALN powder raw material having a specific surface area of 2.81 m2 / g, ALN powder raw material having a specific surface area of 1.79 m2 / g, and yttria as an additive were mixed to prepare a raw material mixture.

[0157] The raw material mixture was charged into a heating device, nitrogen was supplied to the device to form a nitrogen atmosphere, and the mixture was heated at 1800°C for 20 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-4) having an average particle diameter of 7.0 μm and a specific surface area of 0.69 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 1.

[0158] (Example 5)

[0159] An aluminum nitride powder raw material having an average particle diameter of 1.0 μm and a specific surface area of 2.81 m 2 / g was mixed with 100 parts by mass of an aluminum nitride powder raw material having an average particle diameter of 3.2 μm and a specific surface area of 1.68 m 2 / g, and a raw material mixture was prepared.

[0160] The raw material mixture was charged into a heating device, nitrogen was supplied to the device to form a nitrogen atmosphere, and the mixture was heated at 2100°C for 1 hour. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-5) having an average particle diameter of 7.1 μm and a specific surface area of 0.68 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 1.

[0161] (Example 6)

[0162] An aluminum nitride powder raw material having an average particle diameter of 1.0 μm and a specific surface area of 2.81 m 2 / g was mixed with 100 parts by mass of an aluminum nitride powder raw material having an average particle diameter of 3.0 μm and a specific surface area of 1.79 m 2 / g, and 0.1 parts by mass of calcium carbonate as an additive was mixed, and a raw material mixture was prepared.

[0163] The raw material mixture was charged into a heating device, nitrogen was supplied to the device to form a nitrogen atmosphere, and the mixture was heated at 1800°C for 20 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-6) having an average particle diameter of 7.1 μm and a specific surface area of 0.68 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 1.

[0164] (Example 7)

[0165] An aluminum nitride powder raw material having an average particle diameter of 1.0 μm and a specific surface area of 2.81 m 2 / g was mixed with 100 parts by mass of an aluminum nitride powder raw material having an average particle diameter of 3.0 μm and a specific surface area of 1.79 m 2 / g, and 5.0 parts by mass of sulfur as an additive was mixed, and a raw material mixture was prepared.

[0166] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and the mixture was heated at 1800°C for 20 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-7) having an average particle diameter of 7.1 μm and a specific surface area of 0.68 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 1.

[0167] (Example 8)

[0168] A raw material mixture was prepared by mixing 100 parts by mass of an aluminum nitride powder having an average particle diameter of 1.0 μm and a specific surface area of 2.81 m 2 / g, 5 parts by mass of an aluminum nitride powder having an average particle diameter of 3.0 μm and a specific surface area of 1.79 m 2 / g, and 0.1 part by mass of lanthana as an additive.

[0169] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and the mixture was heated at 1800°C for 20 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-8) having an average particle diameter of 7.2 μm and a specific surface area of 0.67 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 1.

[0170] (Example 9)

[0171] A raw material mixture was prepared by mixing 100 parts by mass of an aluminum nitride powder having an average particle diameter of 1.0 μm and a specific surface area of 2.81 m 2 / g, 5 parts by mass of an aluminum nitride powder having an average particle diameter of 3.0 μm and a specific surface area of 1.79 m 2 / g, and 0.1 part by mass of lanthana as an additive.

[0172] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and the mixture was heated at 1800°C for 20 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-9) having an average particle diameter of 7.3 μm and a specific surface area of 0.66 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 1.

[0173] (Example 10)

[0174] A raw material mixture was prepared by mixing 100 parts by mass of an aluminum nitride powder having an average particle diameter of 1.0 μm and a specific surface area of 2.81 m 2 / g, and 5 parts by mass of an aluminum nitride powder having an average particle diameter of 3.2 μm and a specific surface area of 1.68 m 2 / g.

[0175] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and the mixture was heated at 2000°C for 2 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-10) having an average particle diameter of 7.6 μm and a specific surface area of 0.63 m 2 / g. The results of various measurements of the aluminum nitride powder are shown in Table 1.

[0176] (Example 11)

[0177] A raw material of an aluminum nitride powder having an average particle diameter of 1.0 μm and a specific surface area of 2.81 m 2 / g was mixed with a raw material of an aluminum nitride powder having an average particle diameter of 5.0 μm and a specific surface area of 1.02 m 2 / g at a ratio of 100 parts by mass of the former to 5 parts by mass of the latter to prepare a raw material mixture.

[0178] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and the mixture was heated at 1950°C for 3 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-11) having an average particle diameter of 8.0 μm and a specific surface area of 0.60 m 2 / g. The results of various measurements of the aluminum nitride powder are shown in Table 2.

[0179] (Example 12)

[0180] A raw material of an aluminum nitride powder having an average particle diameter of 1.0 μm and a specific surface area of 2.81 m 2 / g was mixed with a raw material of an aluminum nitride powder having an average particle diameter of 7.8 μm and a specific surface area of 0.62 m 2 / g at a ratio of 100 parts by mass of the former to 10 parts by mass of the latter to prepare a raw material mixture.

[0181] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and the mixture was heated at 1950°C for 3 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-12) having an average particle diameter of 14.0 μm and a specific surface area of 0.27 m 2 / g. The results of various measurements of the aluminum nitride powder are shown in Table 2.

[0182] (Example 13)

[0183] A raw material of an aluminum nitride powder having an average particle diameter of 0.5 μm and a specific surface area of 15.70 m 2 / g was mixed with a raw material of an aluminum nitride powder having an average particle diameter of 7.8 μm and a specific surface area of 0.62 m 2 / g at a ratio of 100 parts by mass of the former to 5 parts by mass of the latter to prepare a raw material mixture.

[0184] The raw material mixture was charged into a heating device, nitrogen was supplied into the device to form a nitrogen atmosphere, and the mixture was heated at 1900°C for 10 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-13) having an average particle diameter of 16.2 μm and a specific surface area of 0.23 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 2.

[0185] (Example 14)

[0186] A raw material mixture was prepared by mixing 100 parts by mass of an aluminum nitride powder having an average particle diameter of 0.5 μm and a specific surface area of 15.70 m 2 / g and 10 parts by mass of an aluminum nitride powder having an average particle diameter of 7.8 μm and a specific surface area of 0.62 m 2 / g.

[0187] The raw material mixture was charged into a heating device, nitrogen was supplied into the device to form a nitrogen atmosphere, and the mixture was heated at 1950°C for 5 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-14) having an average particle diameter of 16.6 μm and a specific surface area of 0.23 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 2.

[0188] (Example 15)

[0189] A raw material mixture was prepared by mixing 100 parts by mass of an aluminum nitride powder having an average particle diameter of 0.5 μm and a specific surface area of 15.70 m 2 / g and 20 parts by mass of an aluminum nitride powder having an average particle diameter of 10.2 μm and a specific surface area of 0.47 m 2 / g.

[0190] The raw material mixture was charged into a heating device, nitrogen was supplied into the device to form a nitrogen atmosphere, and the mixture was heated at 1850°C for 20 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-15) having an average particle diameter of 17.2 μm and a specific surface area of 0.22 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 2.

[0191] (Example 16)

[0192] A raw material mixture was prepared by mixing 100 parts by mass of an aluminum nitride powder having an average particle diameter of 1.0 μm and a specific surface area of 2.81 m 2 / g and 10 parts by mass of an aluminum nitride powder having an average particle diameter of 7.8 μm and a specific surface area of 0.62 m 2 / g.

[0193] The raw material mixture was placed in a heating device, and nitrogen gas was supplied to create a nitrogen atmosphere. The mixture was heated at 1900°C for 10 hours. Heating was carried out under normal pressure, followed by crushing and oxidation treatments to obtain particles with an average diameter of 17.8 μm and a specific surface area of ​​0.21 m². 2 / g of aluminum nitride powder (AL-16). The various determination results of this aluminum nitride powder are shown in Table 2.

[0194] (Example 17)

[0195] With an average particle size of 0.5 μm and a specific surface area of ​​15.70 m², 2 100 parts by weight of aluminum nitride powder raw material with an average particle size of 10.2 μm and a specific surface area of ​​0.47 m² / g. 2 A raw material mixture is prepared by mixing 5 parts by weight of aluminum nitride powder raw material (g / g) and 0.1 parts by weight of yttrium oxide as an additive.

[0196] The raw material mixture was placed in a heating device, and nitrogen gas was supplied to create a nitrogen atmosphere. The mixture was heated at 1850°C for 10 hours. Heating was carried out under normal pressure, followed by crushing and oxidation treatments to obtain particles with an average diameter of 17.8 μm and a specific surface area of ​​0.21 m². 2 / g of aluminum nitride powder (AL-17). The various determination results of this aluminum nitride powder are shown in Table 2.

[0197] (Example 18)

[0198] With an average particle size of 0.5 μm and a specific surface area of ​​15.70 m², 2 100 parts by weight of aluminum nitride powder raw material with an average particle size of 10.2 μm and a specific surface area of ​​0.47 m² / g. 2 A raw material mixture is prepared by mixing 5 parts by weight of aluminum nitride powder (g / g) and 0.1 parts by weight of calcium fluoride as an additive.

[0199] The raw material mixture was placed in a heating device, and nitrogen gas was supplied to create a nitrogen atmosphere. The mixture was heated at 1850°C for 10 hours. Heating was carried out under normal pressure, followed by crushing and oxidation treatments to obtain particles with an average diameter of 18.1 μm and a specific surface area of ​​0.21 m². 2 / g of aluminum nitride powder (AL-18). The various determination results of this aluminum nitride powder are shown in Table 2.

[0200] (Example 19)

[0201] With an average particle size of 0.5 μm and a specific surface area of ​​15.70 m², 2 100 parts by weight of aluminum nitride powder raw material with an average particle size of 10.2 μm and a specific surface area of ​​0.47 m² / g. 2A raw material mixture is prepared by mixing 5 parts by weight of aluminum nitride powder raw material (g / g) and 5 parts by weight of calcium fluoride as an additive.

[0202] The raw material mixture was placed in a heating device, and nitrogen gas was supplied to create a nitrogen atmosphere. The mixture was heated at 1850°C for 10 hours. Heating was carried out under normal pressure, followed by crushing and oxidation treatments to obtain particles with an average diameter of 18.2 μm and a specific surface area of ​​0.21 m². 2 / g of aluminum nitride powder (AL-19). The various test results of this aluminum nitride powder are shown in Table 2.

[0203] (Example 20)

[0204] With an average particle size of 0.5 μm and a specific surface area of ​​15.70 m², 2 100 parts by weight of aluminum nitride powder raw material with an average particle size of 10.2 μm and a specific surface area of ​​0.47 m² / g. 2 A raw material mixture is prepared by mixing 5 parts by weight of aluminum nitride powder (g / g) with 0.1 parts by weight of cesium oxide as an additive.

[0205] The raw material mixture was placed in a heating device, and nitrogen gas was supplied to create a nitrogen atmosphere. The mixture was heated at 1850°C for 10 hours. Heating was carried out under normal pressure, followed by crushing and oxidation treatments to obtain particles with an average diameter of 18.3 μm and a specific surface area of ​​0.21 m². 2 / g of aluminum nitride powder (AL-20). The various test results of this aluminum nitride powder are shown in Table 2.

[0206] (Example 21)

[0207] With an average particle size of 0.5 μm and a specific surface area of ​​15.70 m², 2 100 parts by weight of aluminum nitride powder raw material with an average particle size of 10.2 μm and a specific surface area of ​​0.47 m² / g. 2 A raw material mixture is prepared by mixing 5 parts by weight of aluminum nitride powder (g / g) with 0.1 parts by weight of calcium carbonate as an additive.

[0208] The raw material mixture was placed in a heating device, and nitrogen gas was supplied to create a nitrogen atmosphere. The mixture was heated at 1850°C for 10 hours. Heating was carried out under normal pressure, followed by crushing and oxidation treatments to obtain particles with an average diameter of 18.5 μm and a specific surface area of ​​0.21 m². 2 / g of aluminum nitride powder (AL-21). The various test results of this aluminum nitride powder are shown in Table 3.

[0209] (Example 22)

[0210] With an average particle size of 0.5 μm and a specific surface area of ​​15.70 m², 2100 parts by mass of an aluminum nitride powder raw material having an average particle diameter of 10.2 μm and a specific surface area of 0.47 m 2 A raw material mixture was prepared by mixing 5 parts by mass of an aluminum nitride powder having an average particle diameter of 10.2 μm and a specific surface area of 0.47 m

[0211] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and the mixture was heated at 1850°C for 10 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-2) having an average particle diameter of 18.5 μm and a specific surface area of 0.21 m 2 / g of an aluminum nitride powder (AL-22). The various measurement results of the aluminum nitride powder are shown in Table 3.

[0212] (Example 23)

[0213] A raw material mixture was prepared by mixing 100 parts by mass of an aluminum nitride powder having an average particle diameter of 0.5 μm and a specific surface area of 15.70 m 2 / g of an aluminum nitride powder having an average particle diameter of 7.8 μm and a specific surface area of 0.62 m 2 A raw material mixture was prepared by mixing 10 parts by mass of an aluminum nitride powder having an average particle diameter of 7.8 μm and a specific surface area of 0.62 m

[0214] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and the mixture was heated at 2000°C for 5 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-23) having an average particle diameter of 18.7 μm and a specific surface area of 0.20 m 2 / g of an aluminum nitride powder (AL-23). The various measurement results of the aluminum nitride powder are shown in Table 3.

[0215] (Example 24)

[0216] A raw material mixture was prepared by mixing 100 parts by mass of an aluminum nitride powder having an average particle diameter of 0.5 μm and a specific surface area of 15.70 m 2 / g of an aluminum nitride powder having an average particle diameter of 16.2 μm and a specific surface area of 0.23 m 2 A raw material mixture was prepared by mixing 5 parts by mass of an aluminum nitride powder having an average particle diameter of 10.2 μm and a specific surface area of 0.47 m

[0217] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and the mixture was heated at 1900°C for 18 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain an aluminum nitride powder (AL-24) having an average particle diameter of 26.3 μm and a specific surface area of 0.19 m 2 / g of an aluminum nitride powder (AL-24). The various measurement results of the aluminum nitride powder are shown in Table 3.

[0218] (Example 25)

[0219] With an average particle size of 0.5 μm and a specific surface area of ​​15.70 m², 2 100 parts by weight of aluminum nitride powder raw material with an average particle size of 16.2 μm and a specific surface area of ​​0.23 m² / g. 2 A raw material mixture is prepared by mixing 5 parts by weight of aluminum nitride powder raw material (g / g) and 0.1 parts by weight of lanthanum oxide as an additive.

[0220] The raw material mixture was placed in a heating device, and nitrogen gas was supplied to create a nitrogen atmosphere. The mixture was heated at 1900°C for 18 hours. Heating was carried out under normal pressure, followed by crushing and oxidation treatments to obtain particles with an average diameter of 26.5 μm and a specific surface area of ​​0.19 m². 2 / g of aluminum nitride powder (AL-25). The various test results of this aluminum nitride powder are shown in Table 3.

[0221] (Example 26)

[0222] With an average particle size of 1.0 μm and a specific surface area of ​​2.81 m², 2 The raw material consists of 100 parts by weight of aluminum nitride powder with an average particle size of 18.7 μm and a specific surface area of ​​0.20 m² / g. 2 Mix 5 parts by weight of aluminum nitride powder raw material of / g to prepare raw material mixture.

[0223] The raw material mixture was placed in a heating device, and nitrogen gas was supplied to create a nitrogen atmosphere. The mixture was heated at 2000°C for 8 hours. Heating was carried out under normal pressure, followed by crushing and oxidation treatments to obtain particles with an average diameter of 28.8 μm and a specific surface area of ​​0.17 m². 2 / g of aluminum nitride powder (AL-26). Various measurement results for this aluminum nitride powder are shown in Table 3, and SEM observations are as follows: Figure 2 As shown.

[0224] (Example 27)

[0225] With an average particle size of 0.5 μm and a specific surface area of ​​15.70 m², 2 The raw material consists of 100 parts by weight of aluminum nitride powder with an average particle size of 18.2 μm and a specific surface area of ​​0.21 m². 2 Mix 15 parts by weight of aluminum nitride powder raw material of / g to prepare raw material mixture.

[0226] The raw material mixture was placed in a heating device, and nitrogen gas was supplied to create a nitrogen atmosphere. The mixture was heated at 1900°C for 20 hours. Heating was carried out under normal pressure, followed by crushing and oxidation treatments to obtain particles with an average diameter of 28.8 μm and a specific surface area of ​​0.17 m². 2 / g of aluminum nitride powder (AL-27). The various determination results of this aluminum nitride powder are shown in Table 3.

[0227] (Example 28)

[0228] aluminum nitride powder having an average particle diameter of 1.0 μm and a specific surface area of 2.81 m 2 / g and 100 parts by mass of aluminum nitride powder having an average particle diameter of 17.8 μm and a specific surface area of 0.21 m 2 / g were mixed to prepare a raw material mixture.

[0229] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and the device was heated at 1950°C for 10 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain aluminum nitride powder (AL-28) having an average particle diameter of 29.4 μm and a specific surface area of 0.17 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 3.

[0230] (Example 29)

[0231] aluminum nitride powder having an average particle diameter of 0.5 μm and a specific surface area of 15.70 m 2 / g and 100 parts by mass of aluminum nitride powder having an average particle diameter of 26.5 μm and a specific surface area of 0.14 m 2 / g were mixed to prepare a raw material mixture.

[0232] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and the device was heated at 1950°C for 12 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain aluminum nitride powder (AL-29) having an average particle diameter of 38.2 μm and a specific surface area of 0.11 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 3.

[0233] (Example 30)

[0234] aluminum nitride powder having an average particle diameter of 3.0 μm and a specific surface area of 1.79 m 2 / g and 100 parts by mass of aluminum nitride powder having an average particle diameter of 28.8 μm and a specific surface area of 0.13 m 2 / g were mixed to prepare a raw material mixture.

[0235] The raw material mixture was charged into a heating device, nitrogen gas was supplied into the device to form a nitrogen atmosphere, and the device was heated at 1950°C for 20 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain aluminum nitride powder (AL-30) having an average particle diameter of 39.0 μm and a specific surface area of 0.10 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 4.

[0236] (Example 31)

[0237] AlN powder having an average particle diameter of 4.7 μm and a specific surface area of 1.22 m 2 / g of aluminum nitride powder having an average particle diameter of 38.2 μm and a specific surface area of 0.10 m 2 / g of aluminum nitride powder having an average particle diameter of 38.2 μm and a specific surface area of 0.10 m

[0238] The raw material mixture was charged into a heating device, nitrogen gas was supplied to the device to form a nitrogen atmosphere, and the mixture was heated at 1950°C for 20 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain aluminum nitride powder (AL-31) having an average particle diameter of 44.0 μm and a specific surface area of 0.09 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 4.

[0239] (Example 32)

[0240] AlN powder having an average particle diameter of 1.0 μm and a specific surface area of 2.81 m 2 / g of aluminum nitride powder having an average particle diameter of 26.4 μm and a specific surface area of 0.14 m 2 / g of aluminum nitride powder having an average particle diameter of 26.4 μm and a specific surface area of 0.14 m

[0241] The raw material mixture was charged into a heating device, nitrogen gas was supplied to the device to form a nitrogen atmosphere, and the mixture was heated at 2100°C for 14 hours. The heating was performed under normal pressure, and then disintegration and oxidation treatment were performed to obtain aluminum nitride powder (AL-32) having an average particle diameter of 49.4 μm and a specific surface area of 0.05 m 2 / g. The various measurement results of the aluminum nitride powder are shown in Table 4.

[0242] (Comparative Example 1)

[0243] AlN powder having an average particle diameter of 1.0 μm and a specific surface area of 2.81 m 2 / g of aluminum nitride powder having an average particle diameter of 26.4 μm and a specific surface area of 0.14 m

[0244] The obtained aluminum nitride powder was very small particles having an average particle diameter of 2.2 μm, although there were particles having a flat surface having a relatively flat profile line at about 10%. In addition, the flat surface was evaluated for smoothness, and as a result, the smoothness was lacking. The various measurement results of the aluminum nitride powder are shown in Table 4.

[0245] (Comparative Example 2)

[0246] AlN powder having an average particle diameter of 2.0 μm and a specific surface area of 1.93 m 2and an average particle diameter of 3.0 μm and a specific surface area of 1.79 m 2 / g of aluminum nitride powder having an average particle diameter of 1.0 μm and a specific surface area of 2.8 m

[0247] The raw material mixture was charged into a heating device, nitrogen gas was supplied to the device to form a nitrogen atmosphere, and the mixture was heated at 1850°C for 10 hours. The heating was performed under normal pressure, and the resulting block was crushed and oxidized to obtain aluminum nitride powder.

[0248] The obtained aluminum nitride powder was very small particles having an average particle diameter of 3.2 μm, although about 40% of the particles had a surface having a relatively flat profile. In addition, the flat surface was evaluated for smoothness, and the result was that the surface lacked smoothness. The various measurement results of the aluminum nitride powder are shown in Table 4.

[0249] (Comparative Example 3)

[0250] Aluminum powder having an average particle diameter of 7.5 μm and aluminum nitride powder having an average particle diameter of 1.0 μm and a specific surface area of 2.8 m 2 / g of aluminum nitride powder having an average particle diameter of 3.0 μm and a specific surface area of 1.79 m 2 / g of aluminum nitride powder having an average particle diameter of 3.0 μm and a specific surface area of 1.79 m

[0251] The raw material mixture was charged into a heating device, nitrogen gas was supplied to the device to form a nitrogen atmosphere, and the mixture was heated at 1850°C for 10 hours. The heating was performed under normal pressure, and the resulting block was crushed and oxidized to obtain aluminum nitride powder.

[0252] The obtained aluminum nitride powder was very small particles having an average particle diameter of 3.7 μm, although about 50% of the particles had a surface having a relatively flat profile. In addition, the flat surface was evaluated for smoothness, and the result was that the surface lacked smoothness. The various measurement results of the aluminum nitride powder are shown in Table 4.

[0253] (Comparative Example 4)

[0254] Aluminum powder having an average particle diameter of 7.5 μm and aluminum nitride powder having an average particle diameter of 1.0 μm and a specific surface area of 2.8 m 2 / g of aluminum nitride powder having an average particle diameter of 3.0 μm and a specific surface area of 1.79 m

[0255] The average particle diameter of the obtained aluminum nitride powder was 19.2 μm, and among the particles constituting the above aluminum nitride powder, the proportion of particles having a face with a relatively flat profile line was about 20%, and the smoothness of the flat face of the above particles was evaluated, and as a result, the smoothness was lacking. Thus, in Comparative Example 4, the specified aluminum nitride powder containing the polyhedral particles having at least two smooth faces as defined in the present application was not obtained. The various measurement results of the aluminum nitride powder are shown in Table 4.

[0256]

[0257]

[0258]

[0259]

[0260] In each of the examples, an aluminum nitride powder having an average particle diameter in the range of 5 to 50 μm was obtained, the aluminum nitride powder contained polyhedral particles having at least two smooth faces and a length / short ratio in a specific range, and the oxygen concentration was also sufficiently low, and had a high thermal conductivity. Also, the resin composition obtained by filling the aluminum nitride powder of each example into a resin had a high thermal conductivity, and also had excellent flowability, and was useful as a heat dissipation material.

[0261] BRIEF DESCRIPTION OF DRAWINGS

[0262] 11, 12 Polyhedral particles

[0263] a Smooth face

Claims

1. An aluminum nitride powder having an average particle diameter of 5 to 50 μm, an oxygen content of 0.5 mass% or less, containing, in a scanning electron microscope observation at a magnification of 500 times, polyhedral particles having at least two flat surfaces, and an average value of a ratio L / D of a long diameter L to a short diameter D of the polyhedral particles having a long diameter L of 5 μm or more being in a range of 1.0 to 1.4, the polyhedral particles being present at a ratio of 70% or more.

2. The aluminum nitride powder according to claim 1, wherein In the SEM image of the cross section of the polyhedral particle at 2000 times, the average value M of the maximum value M of the perpendicular distance of the outline corresponding to the flat surface from the straight line connecting the end portions of the outline in any 10 particles selected at random A was 0.15 μm or less.

3. The aluminum nitride powder according to claim 1 or 2, which is for resin filling.

4. A resin composition containing the aluminum nitride powder according to claim 1 or 2 and a resin.

5. A method for producing an aluminum nitride powder, characterized by, including: Process 1, 100 parts by mass of a first aluminum nitride powder raw material having an average particle diameter of 0.5 to 5 μm and a specific surface area of 1.2 to 16.0 m 2 / g, and a second aluminum nitride powder raw material 1 to 20 parts by mass having an average particle diameter of 3 to 40 μm, a specific surface area of 0.05 to 1.8 m 2 / g, and a ratio SA2 / SA1 of a specific surface area SA2 of the second aluminum nitride powder raw material to a specific surface area SA1 of the first aluminum nitride powder raw material is 0.8 or less, and a raw material mixture is produced, and Process 2, heating the raw material mixture to 1750 to 2100°C under supply of a non-active gas.

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