Method for producing silicon-containing oxide-coated aluminum nitride particles, and silicon-containing oxide-coated aluminum nitride particles

Abstract

Provided is a method for producing silicon-containing oxide-coated aluminum nitride particles comprising aluminum nitride particles and a silicon-containing oxide film covering the surfaces of the aluminum nitride particles, the method comprising: a first step for crushing agglomerates contained in raw aluminum nitride particles to obtain crushed aluminum nitride particles; a second step for covering the surfaces of the crushed aluminum nitride particles with an organosilicon compound having a specific structure to obtain organosilicon compound-coated aluminum nitride particles; and a third step for heating the organosilicon compound-coated aluminum nitride particles at a heating temperature of 300°C or higher and lower than 1000°C, wherein the reduction rate of the loose bulk density of the crushed aluminum nitride particles relative to the loose bulk density of the raw aluminum nitride particles is at least 10%.

Description

Technical Field

[0001] The present invention relates to a method for producing silicon-containing oxide-coated aluminum nitride particles and to silicon-containing oxide-coated aluminum nitride particles.

Background Art

[0002] Aluminum nitride has high thermal conductivity and excellent electrical insulation properties. Therefore, aluminum nitride is promising as a filler for resin compositions used in products such as heat dissipation sheets and encapsulants for electronic components. However, aluminum nitride causes hydrolysis by reaction with moisture and is denatured into aluminum hydroxide with low thermal conductivity. At the same time, aluminum nitride also generates ammonia, which has corrosiveness during hydrolysis.

[0003] The hydrolysis of aluminum nitride also proceeds due to moisture in the air. Therefore, products containing aluminum nitride not only cause a decrease in moisture resistance and thermal conductivity under high-temperature and high-humidity conditions, but also raise concerns about performance degradation such as corrosion caused by ammonia generated by the hydrolysis of aluminum nitride.

[0004] As a technique for improving the moisture resistance of aluminum nitride, for example, there has been proposed a method for producing silicon-containing oxide-coated aluminum nitride particles including aluminum nitride particles and a silicon-containing oxide film covering the surface of the aluminum nitride particles, the method including a first step of covering the surface of the aluminum nitride particles with a silicone compound including a specific structure, and a second step of heating the aluminum nitride particles covered with the organic silicone compound at a specific temperature (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the production methods described in Patent Documents 1 and 2, the obtained silicon-containing oxide-coated aluminum nitride particles may aggregate, and when the silicon-containing oxide-coated aluminum nitride particles aggregate, there is a problem that the filling property into various materials decreases. Further, when the aggregated silicon-containing oxide-coated aluminum nitride particles are crushed during the preparation of the composition, there is a problem that the silicon-containing oxide film covering the surface of the aluminum nitride particles peels off, and the moisture resistance of the composition decreases.

[0007] The present invention has been made in view of such circumstances, and an object thereof is to provide a method for producing silicon-containing oxide-coated aluminum nitride particles that can maintain the high thermal conductivity of aluminum nitride particles, have excellent moisture resistance, and suppress aggregation, and to provide the silicon-containing oxide-coated aluminum nitride particles.

Means for Solving the Problems

[0008] As a result of intensive studies by the present inventors, it has been found that the above problems can be solved by crushing the agglomerated particles contained in the raw material aluminum nitride particles to obtain crushed aluminum nitride particles, and coating the crushed aluminum nitride particles with a specific organosilicon compound, and the present invention has been completed. That is, the present invention has the following configuration.

[0009] [1] A method for producing silicon-containing oxide-coated aluminum nitride particles comprising aluminum nitride particles and a silicon-containing oxide film covering the surface of the aluminum nitride particles, a first step of crushing agglomerated particles contained in raw material aluminum nitride particles to obtain crushed aluminum nitride particles, A second step of coating the surface of the crushed aluminum nitride particles with an organosilicon compound containing a structure represented by the following formula (1) to obtain organosilicon compound-coated aluminum nitride particles; A third step of heating the organosilicon compound-coated aluminum nitride particles at a heating temperature of 300°C or higher and lower than 1000°C; and A method for producing silicon-containing oxide-coated aluminum nitride particles, wherein the reduction rate of the loose bulk density of the crushed aluminum nitride particles with respect to the loose bulk density of the raw material aluminum nitride particles is 10% or more.

Chemical formula

Chemical formula

Chemical formula

[0010] According to the present invention, there can be provided a method for producing silicon-containing oxide-coated aluminum nitride particles capable of producing silicon-containing oxide-coated aluminum nitride particles that maintain high thermal conductivity of aluminum nitride particles, are excellent in moisture resistance, and have suppressed aggregation, and the silicon-containing oxide-coated aluminum nitride particles. [Embodiments for Carrying Out the Invention]

[0011] Hereinafter, the present invention will be described in detail. Aspects arbitrarily selected from the matters described in this specification or aspects arbitrarily combined thereof are also included in the present invention. In this specification, the provisions defined as preferable can be arbitrarily selected, and combinations of the provisions defined as preferable can be said to be more preferable. In this specification, the description of "XX to YY" means "XX or more and YY or less". In this specification, for preferable numerical ranges (for example, ranges such as content), the lower limit value and the upper limit value described stepwise can be combined independently. For example, from the description of "preferably 10 to 90, more preferably 30 to 60", it is also possible to combine the "preferred lower limit value (10)" and the "more preferred upper limit value (60)" to obtain "10 to 60".

[0012] In this specification, the "90% cumulative volume particle size (D190 and D290)" refers to the particle size at which the cumulative volume integration value for a certain particle size distribution is 90%. The "50% cumulative volume particle size (D150 and D250)" refers to the particle size at which the cumulative volume integration value for a certain particle size distribution is 50%. The "10% cumulative volume particle size (D110 and D210)" refers to the particle size at which the cumulative volume integration value for a certain particle size distribution is 10%. D190, D290, D150, D250, D110, and D210 are all determined from the particle size distribution by the laser diffraction scattering method. Specifically, it can be measured by using a laser diffraction / scattering type particle size distribution measuring device (manufactured by Microtrac Bell Corporation, trade name: Microtrac MT3300EX2).

[0013] <Method for Producing Silicon-Containing Oxide-Coated Aluminum Nitride Particles> The method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention is for producing silicon-containing oxide-coated aluminum nitride particles comprising aluminum nitride particles and a silicon-containing oxide film covering the surface of the aluminum nitride particles. The aluminum nitride particles included in the silicon-containing oxide-coated aluminum nitride particles are made from raw material aluminum nitride particles. Also, examples of the "silicon-containing oxide" of the silicon-containing oxide film and the silicon-containing oxide-coated aluminum nitride particles include silica and composite oxides of silicon element and aluminum element, which will be described in detail later. In this specification, oxides include oxynitrides, oxycarbynitrides, and the like. And the method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention comprises: a first step of crushing agglomerated particles contained in raw material aluminum nitride particles to obtain crushed aluminum nitride particles; a second step of coating the surface of the crushed aluminum nitride particles with an organosilicon compound having a structure represented by the following formula (1) to obtain organosilicon compound-coated aluminum nitride particles; and a third step of heating the organosilicon compound-coated aluminum nitride particles at a heating temperature of 300°C or higher and lower than 1000°C. The reduction rate (hereinafter, also simply referred to as "reduction rate") of the loose bulk density of the crushed aluminum nitride particles with respect to the loose bulk density of the raw material aluminum nitride particles is 10% or more.

[0014]

Chemical formula

[0015] (In formula (1), R is an alkyl group having 1 to 4 carbon atoms.)

[0016] From the viewpoint of producing silicon-containing oxide-coated aluminum nitride particles with more suppressed aggregation and excellent fillability, the reduction rate of the loose bulk density of the crushed aluminum nitride particles with respect to the loose bulk density of the raw material aluminum nitride particles is preferably 12% or more, more preferably 14% or more, and still more preferably 16% or more. This reduction rate tends to increase by increasing the crushing strength, increasing the crushing frequency, or lengthening the crushing time. The upper limit value of the reduction rate of the loose bulk density of the crushed aluminum nitride particles with respect to the loose bulk density of the raw material aluminum nitride particles is not particularly limited, and may be 35% or less, may be 30% or less, or may be 25% or less.

[0017] 〔First step〕 In this step, the agglomerated particles contained in the raw material aluminum nitride particles are crushed to obtain crushed aluminum nitride particles. The method of pulverization is not particularly limited, and general pulverizers such as grinders (mortar-type pulverizers), high-pressure homogenizers, ultra-high-pressure homogenizers, high-pressure impact pulverizers, ball mills, bead mills, disk refiners, conical refiners, twin-screw kneaders, vibration mills, homomixers under high-speed rotation, ultrasonic dispersers, beaters, roll crushers, etc. can be used for pulverization. Among these, from the viewpoint of producing silicon-containing oxide-coated aluminum nitride particles with more suppressed aggregation and excellent packing properties, it is preferable to use a grinder for pulverization.

[0018] The pulverization of the agglomerated particles contained in the raw material aluminum nitride particles in the first step may be carried out two or more times as necessary.

[0019] <Raw material aluminum nitride particles> In the method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention, as the raw material aluminum nitride particles used as the raw material, known ones such as commercially available products can be used. The production method of the raw material aluminum nitride particles is not particularly limited. For example, there are a direct nitridation method in which metallic aluminum powder is directly reacted with nitrogen or ammonia, and a reduction nitridation method in which alumina is heated in a nitrogen or ammonia atmosphere while being carbon-reduced and simultaneously a nitridation reaction is carried out.

[0020] Further, as the raw material aluminum nitride particles, particles obtained by granulating an aggregate of aluminum nitride particles by sintering can be used. For example, sintered granules made of high-purity aluminum nitride particles as the raw material can be preferably used.

[0021] Here, high-purity aluminum nitride particles refer to particles with a low oxygen content and few metal impurities. Specifically, for example, high-purity aluminum nitride particles with an oxygen content of 1% by mass or less and a total content of metal impurities (that is, metal atoms other than aluminum) of 1000 ppm by mass or less are suitable for obtaining higher thermal conductivity of the aluminum nitride particles contained in the silicon-containing oxide-coated aluminum nitride particles. The raw material aluminum nitride particles can be used alone or in combination of two or more kinds.

[0022] In addition, the oxygen content described above can be measured by an inorganic analyzer or the like equipped with an infrared detector for oxygen detection. Specifically, the oxygen content can be measured by using an oxygen, nitrogen, hydrogen analyzer (ONH836: manufactured by LECO Japan Co., Ltd.).

[0023] Also, the total content of metal atoms other than aluminum can be measured by an ICP (Inductively Coupled Plasma) mass spectrometer or the like. Specifically, the total content of metal atoms other than aluminum can be measured by using an ICP mass spectrometer (ICPMS - 2030: manufactured by Shimadzu Corporation).

[0024] The cumulative volume 50% particle size (D150) of the raw material aluminum nitride particles used in the present invention is not particularly limited, but is preferably 0.01 μm or more and 100 μm or less, more preferably 0.1 μm or more and 20 μm or less, and still more preferably 0.5 μm or more and 5 μm or less.

[0025] When the D150 of the raw material aluminum nitride particles is within the above - described range, even when a resin composition containing silicon - containing oxide - coated aluminum nitride particles is used for a heat - dissipating material on which power - system electronic components are mounted, it is possible to supply a heat - dissipating material with a minimum thickness and, for some reason, the coating can easily cover the surface of the aluminum nitride particles uniformly, so that the moisture resistance of the silicon - containing oxide - coated aluminum nitride particles is further improved.

[0026] The loose bulk density of the raw material aluminum nitride particles used in the present invention is not particularly limited, but may be 0.3 g / cm 3 or more, preferably 1.5 g / cm 3 or less, more preferably 1.2 g / cm 3 or less, and still more preferably 0.8 g / cm 3 or less.

[0027] When the bulk density of the raw material aluminum nitride particles is within the above-described range, even when a resin composition containing silicon-containing oxide-coated aluminum nitride particles is used as a heat dissipation material on which power system electronic components are mounted, it is possible to supply a heat dissipation material with a minimum thickness and a thin film, and since the film easily coats the surface of the aluminum nitride particles uniformly, the moisture resistance of the silicon-containing oxide-coated aluminum nitride particles is further improved.

[0028] From the viewpoint of producing silicon-containing oxide-coated aluminum nitride particles that maintain the high thermal conductivity of the aluminum nitride particles, have excellent moisture resistance, and are suppressed in aggregation, the BET specific surface area of the raw material aluminum nitride particles is preferably 0.01 to 100.0 m 2 / g, more preferably 0.05 to 10.0 m 2 / g, and still more preferably 1.0 to 5.0 m 2 / g. The BET specific surface area of the raw material aluminum nitride particles can be measured by the nitrogen adsorption BET one-point method by the gas flow method, and specifically, it can be measured by the method described in the examples.

[0029] From the viewpoint of producing silicon-containing oxide-coated aluminum nitride particles that maintain the high thermal conductivity of the aluminum nitride particles, have excellent moisture resistance, and are suppressed in aggregation, the sieve passing rate of the raw material aluminum nitride particles with a mesh opening of 45 μm is preferably 65.0% by mass or more, more preferably 70.0% by mass or more, still more preferably 75.0% by mass or more, and may be 99.5% by mass or less from the viewpoint of productivity. That is, the sieve passing rate of the silicon-containing oxide-coated aluminum nitride particles with a mesh opening of 45 μm is preferably 65.0 to 99.5% by mass, more preferably 70.0 to 99.0% by mass, still more preferably 75.0 to 98.7% by mass. The sieve passing rate of the raw material aluminum particles with a mesh opening of 45 μm can be specifically calculated by the method described in the examples.

[0030] <Crushed Aluminum Nitride Particles> The crushed aluminum nitride particles of the present invention are obtained by crushing raw material aluminum nitride particles.

[0031] The shape of the crushed aluminum nitride particles of the present invention is not particularly limited, and examples thereof include amorphous (crushed shape), spherical, elliptical, plate-like (scaly), and the like. Further, when silicon-containing oxide-coated aluminum nitride particles are dispersed and contained in a resin composition as a filler, as the crushed aluminum nitride particles, only the same kind of crushed aluminum nitride particles (single substance) having the same shape and structure may be used, but two or more different kinds of crushed aluminum nitride particles having different shapes and structures may be used in the form of a mixture of crushed aluminum nitride particles mixed at various ratios.

[0032] When silicon-containing oxide-coated aluminum nitride particles are dispersed and contained in a resin composition, the higher the volume ratio (filling amount) of the aluminum nitride particles constituting the silicon-containing oxide-coated aluminum nitride particles to the resin composition, the higher the thermal conductivity of the resin composition. Therefore, the shape of the crushed aluminum nitride particles is preferably close to a spherical shape in which the volume ratio of the aluminum nitride particles is likely to be large and the viscosity increase of the resin composition due to the addition of the silicon-containing oxide-coated aluminum nitride particles is small.

[0033] The integrated volume 50% particle size of the crushed aluminum nitride particles used in the present invention is not particularly limited, but is preferably 0.01 μm or more and 100 μm or less, more preferably 0.1 μm or more and 20 μm or less, and still more preferably 0.5 μm or more and 5 μm or less.

[0034] The loose bulk density of the crushed aluminum nitride particles used in the present invention is not particularly limited, but may be 0.3 g / cm 3 or more, preferably 1.2 g / cm 3 or less, more preferably 0.9 g / cm 3 or less, and still more preferably 0.6 g / cm 3 or less.

[0035] 〔Second Step〕 In this step, the surface of the crushed aluminum nitride particles obtained in the first step is coated with an organosilicon compound containing the structure represented by the following formula (1) to obtain organosilicon compound-coated aluminum nitride particles. The second step is preferably carried out within 3 days, more preferably within 2 days, and even more preferably within 1 day after the first step.

[0036] <Organosilicon Compound Used for Coating> In the method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention, the organosilicon compound used as a raw material for the silicon-containing oxide film constituting the silicon-containing oxide-coated aluminum nitride particles can be used without particular limitation as long as it is an organosilicon compound containing the structure represented by the above formula (1), regardless of whether it is in a linear, cyclic or branched form. The structure represented by formula (1) is a hydrogen siloxane unit in which hydrogen is directly bonded to a silicon atom.

[0037] In the above formula (1), as R which is an alkyl group having 1 to 4 carbon atoms, a methyl group, an ethyl group, a propyl group, a t-butyl group, etc. are preferable from the viewpoint of efficiently volatilizing the silicone compound and covering the surface of the aluminum nitride particles, and a methyl group is particularly preferable. In the method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention, the organosilicon compound used as a raw material is, for example, an oligomer or polymer containing the structure represented by formula (1).

[0038] As the organosilicon compound, at least one of the compound represented by the following formula (2) and the compound represented by the following formula (3) is preferable.

[0039]

Chemical Formula

[0040] (In formula (2), R1 and R2 are each independently a hydrogen atom or a methyl group, at least one of R1 and R2 is a hydrogen atom, and m is an integer from 0 to 10.)

[0041]

Chemical formula

[0042] (In formula (3), n is an integer from 3 to 6.)

[0043] In particular, the cyclic hydrogen siloxane oligomer in which n is 4 in the formula (3) is excellent in that it can form a uniform film on the surface of the aluminum nitride particles. The weight average molecular weight of the organosilicon compound containing the structure represented by the formula (1) is preferably 100 or more and 2000 or less, more preferably 150 or more and 1000 or less, and still more preferably 180 or more and 500 or less. By using the organosilicon compound containing the structure represented by the formula (1) having a weight average molecular weight within this range, it is presumed that a thin and uniform film can be easily formed on the surface of the aluminum nitride particles. In the formula (2), m is preferably 1.

[0044] In this specification, the weight average molecular weight is the polystyrene-equivalent weight average molecular weight measured using gel permeation chromatography (GPC). Specifically, it can be measured using a combination of a column (Shodex (registered trademark) LF-804: manufactured by Resonac Co., Ltd.) and a differential refractive index detector (Shodex (registered trademark) RI-71S: manufactured by Resonac Co., Ltd.).

[0045] In the second step, the surface of the crushed aluminum nitride particles is coated with an organosilicon compound having a structure represented by formula (1). The coating method is not particularly limited, but from the viewpoint of producing silicon-containing oxide-coated aluminum nitride particles that maintain the high thermal conductivity of the aluminum nitride particles, are excellent in moisture resistance, and have suppressed aggregation, it is preferably carried out by vapor deposition. The vapor deposition may be carried out, for example, by a gas-phase adsorption method in which a vapor of an organosilicon compound having a structure represented by formula (1) alone or a mixed gas with an inert gas such as nitrogen gas is deposited on the surface of the stationary aluminum nitride particles. Also, in a state where the aluminum nitride particles are stirred using a stirring blade, a fluidized bed, etc., a vapor of an organosilicon compound having a structure represented by formula (1) alone or a mixed gas with an inert gas such as nitrogen gas may be adsorbed on the particle surface.

[0046] The treatment temperature is not particularly limited because it also depends on the boiling point and vapor pressure of the silicone compound having the structure represented by formula (1), but the preferred temperature is 30°C or higher and 200°C or lower, more preferably 35°C or higher and 150°C or lower, and even more preferably 35°C or higher and 100°C or lower. Also, the treatment time is not particularly limited, but it is preferably 1 to 12 hours, more preferably 2 to 10 hours, and even more preferably 3 to 8 hours.

[0047] Furthermore, if necessary, the inside of the system can be pressurized or depressurized. As the apparatus that can be used in this case, an apparatus that is a closed system and can easily replace the gas inside the system is preferable. For example, a glass container, a desiccator, a CVD apparatus, etc. can be used.

[0048] The timing of introducing the organosilicon compound having the structure represented by formula (1) may be at any stage before the temperature of the treatment system is raised as long as the reaction amount of the organosilicon compound is maintained.

[0049] 〔Third step〕 In this process, the aluminum nitride particles coated with the organosilicon compound obtained in the second process are heated at a heating temperature of 300°C or higher and less than 1000°C, preferably 300°C or higher and 900°C or lower, more preferably 300°C or higher and 850°C or lower, and even more preferably 300°C or higher and 800°C or lower. Thereby, a silicon-containing oxide film can be formed on the surface of the aluminum nitride particles. When the heating in this third process is at a low temperature, a silica film is formed on the surface of the aluminum nitride particles, and silica-coated aluminum nitride particles can be produced. That is, the silicon-containing oxide film is formed as a silica film. When the heating in this third process is at a high temperature, a film of a composite oxide of silicon element and aluminum element is formed on the surface of the aluminum nitride particles, and aluminum nitride particles coated with a composite oxide of silicon element and aluminum element can be produced. That is, the silicon-containing oxide film is formed as a film of a composite oxide of silicon element and aluminum element. When the temperature in the third process increases, it is presumed that aluminum constituting the aluminum nitride particles comes out to the surface of the aluminum nitride particles, forms a composite oxide with silicon derived from the organosilicon compound, and a film of a composite oxide of silicon element and aluminum element is formed. From the viewpoint of producing silicon-containing oxide-coated aluminum nitride particles that maintain high thermal conductivity of the aluminum nitride particles, are excellent in moisture resistance, and have suppressed aggregation, it is preferable that the silicon-containing oxide film is a silica film.

[0050] In the third process, if the aluminum nitride particles coated with the organosilicon compound obtained in the second process can be heated at a temperature of 300°C or higher and less than 1000°C, preferably 300°C or higher and 950°C or lower, more preferably 400°C or higher and 900°C or lower, and even more preferably 500°C or higher and 880°C or lower, that is, if the aluminum nitride particles coated with the organosilicon compound obtained in the second process can be maintained in a temperature range of 300°C or higher and less than 1000°C, preferably 300°C or higher and 950°C or lower, more preferably 400°C or higher and 900°C or lower, and even more preferably 500°C or higher and 880°C or lower, a general heating furnace can be used.

[0051] Note that silica coating means being coated with a thin film mainly composed of silica. However, since there may be a plurality of inorganic composites at the interface between the coated silica and the aluminum nitride particles, when analyzed by ToF-SIMS (Time of Flight Secondary Ion Mass Spectrometry, manufactured by ION-TOF, TOF.SIMS5), recombination of secondary ions and decomposition during ionization overlap, and segments such as AlSiO4 ions and SiNO ions may be simultaneously detected as secondary components. The composite segments analyzed by this ToF-SIMS analysis can also be defined as partial detection products when aluminum nitride is silicified. As a guideline, if the secondary electron amount of silica is larger than other fractions, silica can be regarded as the main component.

[0052] Furthermore, as an experiment to increase the accuracy and confirm the purity of silica, when the surface of a sample with a silica film formed in the same manner on a polycrystalline aluminum nitride substrate was measured with a photoelectron spectroscopy device (XPS: X-ray Photoelectron Spectroscopy, manufactured by ULVAC-PHI, Quantera II), since the kinetic energy of the photoelectrons derived from Si detected was almost the same as the standard peak of silica at 103.7 eV, it is presumed that most of them have an SiO2 structure. Depending on the heating temperature, there may be cases where organic components remain. As long as the effects of the present invention are not impaired, it is quite possible that an organosiloxane component is mixed.

[0053] The content of carbon atoms can be measured with a carbon and sulfur analyzer or the like using the non-dispersive infrared absorption method by the tubular electric furnace method. Specifically, it can be measured by using a carbon and sulfur analyzer (Carbon Anlyzer EMIA-821, manufactured by Horiba, Ltd.).

[0054] The heating temperature (heat treatment temperature) in the third step is 300°C or higher and less than 1000°C, preferably 300°C or higher and 950°C or lower, more preferably 400°C or higher and 900°C or lower, and even more preferably 500°C or higher and 880°C or lower. By performing within this temperature range, a silicon-containing oxide film with good moisture resistance and thermal conductivity is formed. Specifically, when heated at 300°C or higher, the silicon-containing oxide film becomes densified and it becomes difficult for moisture to permeate, and thus the moisture resistance of the silicon-containing oxide-coated aluminum nitride particles improves. Also, when heated at less than 1000°C, preferably 950°C or lower, more preferably 900°C or lower, and even more preferably 880°C or lower, the thermal conductivity of the silicon-containing oxide-coated aluminum nitride particles improves. On the other hand, when it is 1000°C or higher, the moisture resistance of the silicon-containing oxide-coated aluminum nitride particles deteriorates. Also, if the heating temperature is 300°C or higher and less than 1000°C, preferably 300°C or higher and 950°C or lower, more preferably 400°C or higher and 900°C or lower, and even more preferably 500°C or higher and 880°C or lower, a silicon-containing oxide film is uniformly formed on the surface of the aluminum nitride particles. Also, if the heating temperature is 300°C or higher, the silicon-containing oxide film becomes excellent in insulating properties, and if it is less than 1000°C, preferably 950°C or lower, more preferably 900°C or lower, and even more preferably 880°C or lower, it is also effective in terms of energy cost. The heating temperature is preferably 500°C or higher.

[0055] The heating time is preferably 30 minutes or longer and 12 hours or shorter, more preferably 1 hour or longer and 10 hours or shorter, and even more preferably 2 hours or longer and 8 hours or shorter. If the heat treatment time is 30 minutes or longer, there is no remaining decomposition product of the organic group (alkyl group having 4 or less carbon atoms) of the organosilicon compound, and it is preferable in that a silicon-containing oxide film with a very low carbon atom content can be obtained on the surface of the aluminum nitride particles. Also, setting the heating time to 12 hours or shorter is preferable in that the silicon-containing oxide-coated aluminum nitride particles can be produced with high production efficiency.

[0056] The atmosphere of the heat treatment in the third step is not particularly limited. For example, it may be an inert gas atmosphere such as N2, Ar, He, etc., an atmosphere containing a reducing gas such as H2, CO, CH4, etc., or an atmosphere containing oxygen gas, for example, in the atmosphere (in the air).

[0057] In addition, in order to further enhance the moisture resistance, after the heat treatment in the third step, the second step and the third step may be further performed in sequence. That is, the steps of performing the second step and the third step in sequence may be repeatedly executed.

[0058] The coating method of covering the surface of aluminum nitride particles with an organosilicon compound by the gas-phase adsorption method in the second step can form a uniform and thin silicon-containing oxide film compared with the coating method performed by liquid treatment. Therefore, even if the steps of performing the second step and the third step in sequence are repeated a plurality of times, for example, about 2 to 5 times, good thermal conductivity of the aluminum nitride particles can be exhibited.

[0059] On the other hand, regarding the moisture resistance, a positive correlation is recognized between the number of times of performing the steps of the second step and the third step in sequence and the moisture resistance. Therefore, according to the level of moisture resistance required in the actual application, the number of times of performing the steps of the second step and the third step in sequence can be freely selected.

[0060] The silicon-containing oxide-coated aluminum nitride particles obtained by the method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention have a particle size distribution change rate of the particle size distribution width (P2) of the silicon-containing oxide-coated aluminum nitride particles with respect to the particle size distribution width (P1) of the raw material aluminum nitride particles calculated from the following formula (I), preferably 0% or less, more preferably -0.5% or less, and still more preferably -1% or less. By sufficiently performing the crushing in the aforementioned first step, the change rate can be reduced. Particle size distribution width change rate (%) = [(P2 / P1) - 1] × 100 (I) Particle size distribution width (P1) of the raw material aluminum nitride particles = (D190 - D110) / D150 (I-1) Particle size distribution width (P2) of silicon-containing oxide-coated aluminum nitride particles = (D290 - D210) / D250 (I-2) (In the formula, D190 is the cumulative volume 90% particle size of the raw material aluminum nitride particles, D150 is the cumulative volume 50% particle size of the raw material aluminum nitride particles, D110 is the cumulative volume 10% particle size of the raw material aluminum nitride particles, D290 is the cumulative volume 90% particle size of the silicon-containing oxide-coated aluminum nitride particles, D250 is the cumulative volume 50% particle size of the silicon-containing oxide-coated aluminum nitride particles, and D210 is the cumulative volume 10% particle size of the silicon-containing oxide-coated aluminum nitride particles.)

[0061] The change rate of the particle size distribution width calculated from the above formula (I) is an index indicating the degree of aggregation of the silicon-containing oxide-coated aluminum nitride particles in the first to third steps. The smaller the change rate, the more the aggregation of the silicon-containing oxide-coated aluminum nitride particles is suppressed. When the change rate is 0% or less, the silicon-containing oxide-coated aluminum nitride particles are micronized, and it becomes easy to control the filling property into various materials by precise particle size blending. Also, when aggregation is suppressed and micronization is achieved, there is no need to crush the aggregated particles during the preparation of the composition, so the high thermal conductivity of the aluminum nitride particles is maintained, and silicon-containing oxide-coated aluminum nitride particles with excellent moisture resistance are obtained.

[0062] The silicon-containing oxide-coated aluminum nitride particles obtained by the method for producing silicon-containing oxide-coated aluminum nitride particles of the present invention maintain the original high thermal conductivity of the aluminum nitride particles and are also excellent in moisture resistance, so they can be widely applied as fillers for heat dissipation material applications used in the electric and electronic fields and the like.

[0063] <Silicon-containing oxide-coated aluminum nitride particles> The silicon-containing oxide-coated aluminum nitride particles of the present invention include aluminum nitride particles and a silicon-containing oxide film covering the surface of the aluminum nitride particles, and have a loose bulk density of less than 0.58 g / cm 3 and the ammonia concentration measured under the following measurement conditions is less than 10 mg / L. Measurement conditions: A mixed solution is prepared by adding 3 g of the silica-coated aluminum nitride particles to 17 g of a hydrochloric acid aqueous solution with a pH of 4, and the mixture is heated at 134 °C for 2 hours and then left to stand at room temperature (25 °C) for 1 hour to prepare a measurement sample. The ammonia concentration at 25 °C in the measurement sample is measured using an ammonia electrode. The silicon-containing oxide-coated aluminum nitride particles of the present invention maintain the high thermal conductivity of the aluminum nitride particles, are excellent in moisture resistance, have suppressed aggregation, and have good filling properties into various materials. The silicon-containing oxide-coated aluminum nitride particles of the present invention can be obtained by the method for producing the silicon-containing oxide-coated aluminum nitride particles of the present invention. The "silicon-containing oxide" of the silicon-containing oxide film and the silicon-containing oxide-coated aluminum nitride particles includes the silica and the composite oxide of a silicon element and an aluminum element. The oxide also includes oxynitride, oxycarbynitride, etc.

[0064] The loose bulk density of the silicon-containing oxide-coated aluminum nitride particles is preferably 0.57 g / cm from the viewpoint of obtaining silicon-containing oxide-coated aluminum nitride particles with more suppressed aggregation and excellent filling properties. 3 More preferably, it is 0.56 g / cm or less. 3 From the viewpoint of productivity, it is preferably 0.3 g / cm or more. 3 More preferably, it is 0.35 g / cm or more. 3 Even more preferably, it is 0.4 g / cm or more. 3 That is, the loose bulk density of the silicon-containing oxide-coated aluminum nitride particles is preferably 0.3 g / cm or more. 3 and less than 0.58 g / cm. 3 More preferably, it is 0.35 to 0.57 g / cm. 3 Even more preferably, it is 0.4 to 0.57 g / cm. 3 That is.

[0065] The ammonia concentration measured under the above measurement conditions for the silicon-containing oxide-coated aluminum nitride particles of the present invention is less than 10 mg / L. The measurement of the ammonia concentration is carried out by exposing the silicon-containing oxide-coated aluminum nitride particles to an aqueous hydrochloric acid solution, which is an acidic solution adjusted to pH 4. In the acidic solution, the hydrolysis reaction of the silicon-containing oxide-coated aluminum nitride particles is promoted more than in air, hydrolysis occurs, and ammonia is generated. Therefore, the measurement of the ammonia concentration under the above measurement conditions is an accelerated test for moisture resistance. Further, the ammonia concentration is an index of moisture resistance, and it can be said that the silicon-containing oxide-coated aluminum nitride particles with an ammonia concentration of less than 10 mg / L under the above measurement conditions are excellent in moisture resistance. In addition, by using an aqueous hydrochloric acid solution with a pH of 4, the chemical resistance can also be compared.

[0066] The concentration of the ammonia is preferably 8 mg / L or less, more preferably 6 mg / L or less, still more preferably 5 mg / L or less, particularly preferably 1.5 mg / L or less, and may be 0 mg / L.

[0067] From the viewpoint of the filling property to various materials, the BET specific surface area of the silicon-containing oxide-coated aluminum nitride particles is preferably 0.1 to 20.0 m 2 / g, more preferably 0.5 to 10.0 m 2 / g, still more preferably 1.0 to 5.0 m 2 / g. The BET specific surface area of the silicon-containing oxide-coated aluminum nitride particles can be measured by the nitrogen adsorption BET one-point method by the gas flow method, and specifically, it can be measured by the method described in the examples.

[0068] From the viewpoint of the filling property to various materials, the sieve passing rate of the silicon-containing oxide-coated aluminum nitride particles with a mesh opening of 45 μm is preferably 70% or more, more preferably 75% or more, still more preferably 80% or more, and may be 99.5% or less from the viewpoint of productivity. The sieve passing rate of the silicon-containing oxide-coated aluminum nitride particles with a mesh opening of 45 μm can be specifically calculated by the method described in the examples.

[0069] From the viewpoint of moisture resistance, the lower the carbon atom content in the silicon-containing oxide-coated aluminum nitride particles, the more preferable. Since the silicon-containing oxide-coated aluminum nitride particles of the present invention use an organosilicon compound having a structure represented by the formula (1) as a raw material, they often contain carbon atoms. For example, they may contain 50 mass ppm or more in terms of carbon atoms, and further may contain 60 mass ppm or more in terms of carbon atoms, and may contain 100 mass ppm or less in terms of carbon atoms.

[0070] The content of silicon atoms (ΔSi amount) in the silicon-containing oxide film of the silicon-containing oxide-coated aluminum nitride particles is preferably 20 to 2000 mass ppm, more preferably 30 to 1950 mass ppm, and still more preferably 40 to 1900 mass ppm from the viewpoint of achieving better moisture resistance. The ΔSi amount can be measured by the ICP method, specifically, it can be measured by the method described in the examples.

[0071] <Method for producing resin composition> A resin composition can be produced using the silicon-containing oxide-coated aluminum nitride particles of the present invention. That is, the method for producing a resin composition in the present invention includes a production step of producing silicon-containing oxide-coated aluminum nitride particles by the method for producing the silicon-containing oxide-coated aluminum nitride particles, and a mixing step of mixing the silicon-containing oxide-coated aluminum nitride particles and a resin. Examples of the "silicon-containing oxide" of the silicon-containing oxide film and the silicon-containing oxide-coated aluminum nitride particles include the above-mentioned silica and composite oxides of silicon element and aluminum element. Oxides also include oxynitrides, oxycarbynitrides, etc. Since the silicon-containing oxide-coated aluminum nitride particles of the present invention have suppressed aggregation and good filling properties into the resin composition, the resin composition can be easily produced. In addition, the silicon-containing oxide-coated aluminum nitride particles maintain the high thermal conductivity of the aluminum nitride particles and improve the moisture resistance. Therefore, the resin composition obtained by the method for producing the resin composition has excellent moisture resistance and thermal conductivity.

[0072] In the mixing step, silicon-containing oxide-coated aluminum nitride particles produced by the method for producing silicon-containing oxide-coated aluminum nitride particles are mixed with a resin.

[0073] The resin to be mixed in the mixing step is not particularly limited, but it is preferable that the resin be a thermosetting resin, a thermoplastic resin, or a mixture of a thermosetting resin and a thermoplastic resin in terms of the heat resistance of the resulting resin composition. Examples of the thermosetting resin include silicone resins such as polydimethylsiloxane, epoxy resins, phenol resins, bismaleimide resins, cyanate resins, urethane resins, (meth)acrylic resins, vinyl ester resins, unsaturated polyester resins, polyvinyl alcohol acetal resins, etc., and they can be used alone or in combination of two or more. Further, a mixture obtained by adding a curing agent and a curing accelerator to the thermosetting resin may be used. In particular, an epoxy resin is preferable in terms of good heat resistance, adhesiveness, and electrical properties after curing, and a silicone resin is preferable for applications that emphasize flexible adhesiveness.

[0074] Note that silicone resins include addition reaction-curing silicone resins, condensation reaction-curing silicone resins, organic peroxide-curing silicone resins, etc., and they can be used alone or in combination of two or more types with different viscosities. In particular, when used in applications that emphasize soft adhesion, examples of silicone resins include addition reaction-curing liquid silicone resins that do not produce by-products that can cause substances such as bubbles. A silicone resin cured product can be obtained by reacting an organopolysiloxane having an alkenyl group as a base polymer and an organopolysiloxane having an Si-H group as a cross-linking agent in the presence of a curing agent at room temperature or by heating. Specific examples of the organopolysiloxane as the base polymer include those having a vinyl group, an allyl group, a propenyl group, a hexenyl group, etc. as the alkenyl group. In particular, the vinyl group is preferable as the organopolysiloxane. Also, as the curing catalyst, for example, a platinum metal-based curing catalyst can be used, and the addition amount can be adjusted and used to achieve the hardness of the desired resin cured product.

[0075] Examples of epoxy resins include bifunctional glycidyl ether type epoxy resins such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, and biphenyl type epoxy resin; glycidyl ester type epoxy resins such as glycidyl hexahydrophthalate and glycidyl dimer acid; linear aliphatic epoxy resins such as epoxidized polybutadiene and epoxidized soybean oil; heterocyclic epoxy resins such as triglycidyl isocyanurate; glycidyl amine type epoxy resins such as N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-1,3-benzenedimethanamine, 4-(glycidyloxy)-N,N-diglycidylaniline, and 3-(glycidyloxy)-N,N-diglycidylaniline; polyfunctional glycidyl ether type epoxy resins such as phenol novolac type epoxy resin, cresol novolac type epoxy resin, biphenyl aralkyl type epoxy resin, naphthalene aralkyl type epoxy resin, tetrafunctional naphthalene type epoxy resin, and triphenylmethane type epoxy resin; and the like. The above-mentioned epoxy resins can be used alone or in admixture of two or more.

[0076] When using the above-mentioned epoxy resin, a curing agent, a curing accelerator, etc. may be blended. Examples of the curing agent include alicyclic acid anhydrides such as methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and himic anhydride; aliphatic acid anhydrides such as dodecenyl succinic anhydride; aromatic acid anhydrides such as phthalic anhydride and trimellitic anhydride; bisphenols such as bisphenol A, bisphenol F, and bisphenol S; phenolic resins such as phenol-formaldehyde resin, phenol-aralkyl resin, naphthol-aralkyl resin, and phenol-dicyclopentadiene copolymer resin; organic dihydrazides such as dicyandiamide and adipic dihydrazide; etc. Examples of the curing catalyst include amines such as tris(dimethylaminomethyl)phenol, dimethylbenzylamine, 1,8-diazabicyclo(5,4,0)undecene, and its derivatives; imidazoles such as 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, and its derivatives; etc. These can be used alone or in combination of two or more kinds.

[0077] In the mixing step, fillers such as boron nitride, alumina, silica, zinc oxide, etc., which are usually used in addition to the silicon-containing oxide-coated aluminum nitride particles, may be used in combination.

[0078] In the mixing step, furthermore, if necessary, flexibility-imparting agents such as silicone, urethane acrylate, butyral resin, acrylic rubber, diene rubber and its copolymer, silane coupling agents, titanium coupling agents, inorganic ion scavengers, pigments, dyes, diluents, solvents, etc. can be appropriately added.

[0079] The mixing method in the mixing step is not particularly limited. For example, a method of mixing, dissolving, and kneading silicon-containing oxide-coated aluminum nitride particles, resin, other additives, etc., all at once or in portions, using a dispersion and dissolution device such as a kneader, a planetary mixer, a rotating and revolving mixer, a kneader, a roll mill, etc., alone or in appropriate combination, and heating if necessary, can be mentioned.

[0080] In addition, the obtained resin composition can be formed into a sheet shape and, if necessary, reacted to obtain a heat dissipation sheet. The above-described resin composition and heat dissipation sheet can be suitably used for adhesive applications such as semiconductor power devices and power modules.

[0081] Examples of the method for manufacturing the heat dissipation sheet include a method of forming the resin composition by compression pressing or the like with a base film sandwiching both sides, and a method of applying the resin composition on the base film using an apparatus such as a bar coater, screen printer, blade coater, die coater, comma coater, etc. Further, for the heat dissipation sheet after forming and coating, a step of removing the solvent, a treatment step such as B-staging or complete curing by heating, etc. can be added. As described above, heat dissipation sheets in various forms can be obtained depending on the process, and it becomes possible to widely correspond to the target application fields and usage methods.

[0082] When applying or forming the resin composition on the base film, a solvent can be used to improve workability. The solvent is not particularly limited, but examples include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone; ether solvents such as 1,4-dioxane, tetrahydrofuran, diglyme; glycol ether solvents such as methyl cellosolve, ethyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, diethylene glycol methyl ethyl ether; other benzyl alcohol; N-methylpyrrolidone; γ-butyrolactone; ethyl acetate; N,N-dimethylformamide; etc., which can be used alone or in a mixture of two or more.

[0083] In order to form the resin composition into a sheet shape, sheet formability to maintain the sheet shape is required. In order to obtain sheet formability, a high molecular weight component can be added to the resin composition. Examples of the high molecular weight component include phenoxy resin, polyimide resin, polyamide resin, polycarbodiimide resin, cyanate ester resin, (meth)acrylic resin, polyester resin, polyethylene resin, polyethersulfone resin, polyetherimide resin, polyvinyl acetal resin, urethane resin, acrylic rubber, etc. Among them, from the viewpoint of excellent heat resistance and film formability, phenoxy resin, polyimide resin, (meth)acrylic resin, acrylic rubber, cyanate ester resin, and polycarbodiimide resin are preferred, and phenoxy resin, polyimide resin, (meth)acrylic resin, and acrylic rubber are more preferred. They can be used alone or as a mixture or copolymer of two or more kinds.

[0084] The weight average molecular weight of the high molecular weight component is preferably 10,000 or more and 100,000 or less, more preferably 20,000 or more and 50,000 or less.

[0085] In addition, a good sheet shape with good handleability can be maintained by adding a high molecular weight component within the above-mentioned range.

[0086] The addition amount of the high molecular weight component is not particularly limited, but in order to maintain the sheet properties, it is preferably 0.1% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, and still more preferably 2% by mass or more and 10% by mass or less with respect to the resin composition. In addition, with an addition amount of 0.1% by mass or more and 20% by mass or less, good handleability can be achieved, and good sheets and films can be formed.

[0087] The base film used in the production of the heat dissipation sheet is not particularly limited as long as it can withstand the process conditions such as heating and drying during production. For example, films made of polyesters having an aromatic ring such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polypropylene films, polyimide films, polyetherimide films, etc. can be mentioned. The above-mentioned films may be multilayer films combined with two or more types, or those with a surface treated with a release agent such as a silicone-based one. In addition, the thickness of the base film is preferably 10 μm or more and 100 μm or less.

[0088] The thickness of the heat dissipation sheet formed on the base film is preferably 20 μm or more and 500 μm or less, and more preferably 50 μm or more and 200 μm or less. When the thickness of the heat dissipation sheet is 20 μm or more, a heat dissipation sheet with a uniform composition can be obtained, and when it is 500 μm or less, good heat dissipation performance can be obtained.

[0089] <Resin composition> The resin composition of the present invention contains the silicon-containing oxide-coated aluminum nitride particles. Since the silicon-containing oxide-coated aluminum nitride particles maintain the high thermal conductivity of the aluminum nitride particles and improve the moisture resistance, the resin composition of the present invention is excellent in moisture resistance and thermal conductivity.

[0090] The resin contained in the resin composition of the present invention is not particularly limited, but it is preferable that it is a thermosetting resin, a thermoplastic resin, or a mixture of a thermosetting resin and a thermoplastic resin described in the <Method for producing resin composition> in terms of the obtained resin composition being excellent in heat resistance.

[0091] The resin composition may contain fillers such as boron nitride, alumina, silica, zinc oxide, etc. that are usually used in addition to the silicon-containing oxide-coated aluminum nitride particles.

[0092] The total content of the silicon-containing oxide-coated aluminum nitride particles and fillers other than the silicon-containing oxide-coated aluminum nitride particles in the resulting resin composition is not particularly limited as long as it is an amount that results in a desired resin composition, but is preferably 50% by mass or more and 99% by mass or less, more preferably 60% by mass or more and 97% by mass or less, and even more preferably 70% by mass or more and 95% by mass or less. When the total content is 50% by mass or more, good heat dissipation performance can be exhibited, and when it is 99% by mass or less, good workability can be obtained when using the resin composition.

[0093] Also, the content of the silicon-containing oxide-coated aluminum nitride particles in the resulting resin composition is preferably 30% by mass or more and 100% by mass or less, more preferably 40% by mass or more and 100% by mass or less, and even more preferably 50% by mass or more and 100% by mass or less of the total content of the silicon-containing oxide-coated aluminum nitride particles and fillers other than the silicon-containing oxide-coated aluminum nitride particles. When the total content is 30% by mass or more, good heat dissipation performance can be exhibited.

[0094] The resin composition of the present invention may further contain, if necessary, flexibility-imparting agents such as silicone, urethane acrylate, butyral resin, acrylic rubber, diene rubber and its copolymers, silane coupling agents, titanium coupling agents, inorganic ion scavengers, pigments, dyes, diluents, solvents, and the like.

[0095] The resin composition of the present invention can be obtained by the method for producing the resin composition of the present invention.

Examples

[0096] Next, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples.

[0097] <Method for Measuring and Calculating Physical Properties> [Integrated Volume 50% Particle Size (D150 and D250)] The cumulative volume 50% particle sizes (D150 and D250) were determined from the particle sizes at which the cumulative volume was 50% in the particle size distribution measured using a laser diffraction / scattering particle size distribution analyzer (manufactured by Microtrac Bell Corporation, trade name: Microtrac MT3300EX2).

[0098] [Particle size distribution width] In the same manner as the measurement of the above cumulative volume 50% particle sizes (D150 and D250), the cumulative volume 90% particle sizes (D190 and D290) and the cumulative volume 10% particle sizes (D110 and D210) were determined using a laser diffraction / scattering particle size distribution analyzer (manufactured by Microtrac Bell Corporation, trade name: Microtrac MT3300EX2). Using the obtained cumulative volume 10% particle sizes, cumulative volume 50% particle sizes, and cumulative volume 90% particle sizes, the particle size distribution widths (P1) of the raw material aluminum nitride particles and the particle size distribution widths (P2) of the silicon-containing oxide-coated aluminum nitride particles were calculated from the following formulas. Particle size distribution width (P1) of raw material aluminum nitride particles = (D190 - D110) / D150 (I-1) Particle size distribution width (P2) of silicon-containing oxide-coated aluminum nitride particles = (D290 - D210) / D250 (I-2)

[0099] [Change rate of particle size distribution width] From P1 and P2 obtained in the above [Particle size distribution width], the change rate of the particle size distribution width (P2) of the silicon-containing oxide-coated aluminum nitride particles with respect to the particle size distribution width (P1) of the raw material aluminum nitride particles was calculated from the following formula (I). Change rate of particle size distribution width (%) = [(P2 / P1) - 1] × 100 (I)

[0100] [BET specific surface area] Measurement was carried out by the BET one-point method by nitrogen adsorption using a specific surface area analyzer (manufactured by Mountech Co., Ltd., trade name: Macsorb HM model-1210). As the adsorption gas, a mixed gas of 70 vol% He and 30 vol% N2 was used.

[0101] [Sieve passing rate of 45 μm mesh opening] The sieve passing rate (mass %) with a mesh opening of 45 μm was calculated by the following procedure. (1) 5 g of the particles to be measured (raw material aluminum nitride or silicon-containing oxide-coated aluminum nitride particles) and 50 mL of distilled water were placed in a 100 mL container, stirred 30 times with a stirring rod, and poured onto a sieve with a mesh opening of 45 μm. (2) The particles were rinsed with water at a flow rate of 10 L / min for 5 minutes, and the finer particles were washed away through the sieve. (3) The particles remaining on the sieve were collected using filter paper (qualitative filter paper JIS standard No. 5 A), and the collected particles together with the filter paper were heated at 110 °C for 1 hour. (4) The particles after heating were left to cool in a desiccator for 1 hour. (5) The particles after cooling were weighed, and the ratio passing through the sieve was calculated from the obtained results and taken as the sieve passing rate with a mesh opening of 45 μm.

[0102] [Sieve passing rate ratio with a mesh opening of 45 μm] The sieve passing rate ratio with a mesh opening of 45 μm was calculated by dividing the sieve passing rate of the silicon-containing oxide-coated aluminum nitride particles obtained by the above [sieve passing rate with a mesh opening of 45 μm] by the sieve passing rate of the raw material aluminum nitride particles obtained by the above [sieve passing rate with a mesh opening of 45 μm].

[0103] [Loose bulk density] The loose bulk density was measured in accordance with JIS R 9301-2-3:1999 "Alumina powder - Methods for measuring physical properties - 3". Specifically, a 200 mL cylinder was filled with silicon-containing oxide-coated aluminum nitride, leveled off along the upper surface of the cylinder, and then the filled mass was measured. The value obtained by dividing by the cylinder volume was taken as the loose bulk density. Also, the raw material aluminum nitride particles and the crushed aluminum nitride particles were measured in the same manner. In addition, the reduction rate of the loose bulk density of the crushed aluminum nitride particles with respect to the loose bulk density of the raw material aluminum nitride particles was calculated.

[0104] [Ammonia concentration] The ammonia concentration in a specific solution, which serves as an index of the moisture resistance of the particles, was calculated by the following procedure. (1) A 50 mL Teflon container was charged with 17 g of an aqueous hydrochloric acid solution at pH 4 and 3 g of particles (raw material aluminum nitride or silicon-containing oxide-coated aluminum nitride particles), and then sealed. (2) The entire Teflon container was placed into a stainless steel pressure-resistant container, heated at 134 °C for 2 hours, and then left standing at room temperature (25 °C) for 1 hour to prepare a measurement sample. (3) The ammonia concentration in the supernatant of the obtained measurement sample was measured at a temperature of 25 °C using an ammonia electrode (ammonia electrode 5002A: manufactured by Horiba, Ltd.). The measurement results were recorded in the "Ammonia Concentration" column in the table.

[0105] [Silicon atom content (Si content) in silicon-containing oxide-coated aluminum nitride particles] The silicon atom content (Si content) of the silicon-containing oxide-coated aluminum nitride particles was calculated by the following procedure. (1) A 20 mL Teflon container was charged with 10 mL of a solution obtained by mixing 97 mass% sulfuric acid (ultra special grade, manufactured by Wako Pure Chemical Industries, Ltd.) and ion-exchanged water at a volume ratio of 1:2, and 0.5 g of silicon-containing oxide-coated aluminum nitride particles. (2) The entire Teflon container was placed into a stainless steel pressure-resistant container, heated at 230 °C for 15 hours to dissolve the charged silicon-containing oxide-coated aluminum nitride particles. (3) The solution in which the silicon-containing oxide-coated aluminum nitride particles were dissolved was taken out, and the concentration of silicon atoms was measured using ICP (ICPS-7510, manufactured by Shimadzu Corporation). From the measured concentration of silicon atoms, the silicon atom content (Si content) (unit: mass ppm) of the silicon-containing oxide-coated aluminum nitride particles was calculated.

[0106] [Calculation method for silicon atom content (ΔSi content) in the silicon-containing oxide film of silicon-containing oxide-coated aluminum nitride particles] By subtracting the silicon content (Si content) of the crushed aluminum nitride alone, calculated by the above calculation method, from the silicon atom content (Si amount) of the silicon-containing oxide-coated aluminum nitride particles calculated by the same method, the silicon atom content (ΔSi amount) (unit: mass ppm) in the silicon-containing oxide film of the silicon-containing oxide-coated aluminum nitride particles was calculated.

[0107] [Thermal conductivity of resin molded body] Using a hot disk method with a thermal property measuring device (manufactured by Kyoto Electronics Industry Co., Ltd., trade name TPS 2500 S), in accordance with ISO22007-2:2015, the thermal conductivity (unit: W / m·K) of the resin molded body test pieces prepared in each example and comparative example was measured.

[0108] [Each material] The materials used in the examples and comparative examples are as follows. · Raw material aluminum nitride particles A: Trade name "N01P", manufactured by Toyo Aluminum Co., Ltd., D50 = 1.3 μm · Raw material aluminum nitride particles B: Trade name "JM", manufactured by Toyo Aluminum Co., Ltd., D50 = 2.8 μm · AKP-30: High-purity alumina: Trade name "AKP-30", manufactured by Sumitomo Chemical Co., Ltd., D50 = 0.3 μm) · EG-3100(A): Polydimethylsiloxane gel (Trade name: DOWSIL TM EG-3100, manufactured by Dow Corning Toray Co., Ltd., viscosity 420 mPa·s, a mixture of vinyl oil and platinum catalyst) · EG-3100(B): Polydimethylsiloxane gel (Trade name: DOWSIL TM EG-3100, manufactured by Dow Corning Toray Co., Ltd., viscosity 320 mPa·s, a mixture of vinyl oil and crosslinking agent)

[0109] [Example 1] (Manufacture of silicon-containing oxide-coated aluminum nitride particles) The raw material aluminum nitride particles A were continuously crushed using a mortar crusher (“Super Mass Colloid Mill MKCA6-5J”, manufactured by Masuko Sangyo Co., Ltd.) at a rotational speed of 2000 rpm, a clearance of 50 μm, and a particle feed rate of 20 kg / h to obtain crushed aluminum nitride particles A. The obtained crushed aluminum nitride particles A were stored in a desiccator, and the second step was carried out within 24 hours after the crushing treatment. The raw material aluminum nitride particles B were also crushed in the same manner as above to obtain crushed aluminum nitride particles B, which were stored in a desiccator, and the second step was carried out within 24 hours after the crushing treatment. In the second step, a reaction apparatus based on a large oven with a reaction tank volume of 250 L was used to perform surface coating of the crushed aluminum nitride particles. In the reaction tank, 50 g of crushed aluminum nitride particles A and 50 g of crushed aluminum nitride particles B were evenly spread on separate stainless steel trays and left standing. Next, 52 g of an organosilicon compound A (product name “2,4,6,8-tetramethylcyclotetrasiloxane”, manufactured by Tokyo Chemical Industry Co., Ltd.) with n = 4 in formula (3) was placed in a glass petri dish, left standing in the reaction tank, and the reaction tank was closed. Since hydrogen gas is generated by the reaction, the inside of the reaction tank was evacuated in advance until the oxygen concentration became 8% by volume or less, which is the explosion limit, and then nitrogen gas was introduced into the reaction tank to return the internal pressure to normal pressure (0.1 MPa). Thereafter, the reaction tank was heated at 80 °C for 7.5 hours to vaporize the organosilicon compound A, and organosilicon compound-coated aluminum nitride particles A and organosilicon compound-coated aluminum nitride particles B were obtained. After the completion of the second step, the organosilicon compound-coated aluminum nitride particles A and the organosilicon compound-coated aluminum nitride particles B were each placed in an alumina crucible and heated in the atmosphere at 700 °C for 3 hours in the third step to obtain silicon-containing oxide-coated aluminum nitride particles 1-A and 1-B, which are silica-coated aluminum nitride particles. The measurement and calculation results of the physical properties of the silicon-containing oxide-coated aluminum nitride particles 1-A and 1-B are shown in Table 1.

[0110] (Manufacture of resin molded body) EG-3100(A) (polydimethylsiloxane gel, trade name: DOWSIL TM EG-3100, manufactured by Dow Corning Toray Co., Ltd.) 50 parts by mass, EG-3100(B) 50 parts by mass, silicon-containing oxide-coated aluminum nitride particles 1-A 500 parts by mass, and AKP-30 225 parts by mass were stirred and mixed at 1000 rpm for 30 seconds while depressurizing using a rotating and revolving mixer (manufactured by Shinki Co., Ltd., trade name: ARV-310P) to obtain a resin composition. After cooling the obtained resin composition to room temperature (25°C), the resin composition was sandwiched between two PET substrates to form a laminate, and the laminate was stretched to a thickness of 2 mm using a rolling roll and then heat-treated at 100°C for 15 minutes to cure it, obtaining a resin composition molded body test piece 1-A. In the above, except that silicon-containing oxide-coated aluminum nitride particles 1-B were used instead of silicon-containing oxide-coated aluminum nitride particles 1-A, a resin composition molded body test piece 1-B was obtained in the same manner. The measurement and calculation results of the physical properties of the resin composition molded body test pieces 1-A and 1-B are shown in Table 1.

[0111] [Example 2] (Manufacture of silicon-containing oxide-coated aluminum nitride particles) In Example 1, except that the amount of the organosilicon compound A used in the second step was 10 g, silicon-containing oxide-coated aluminum nitride particles 2-A (obtained by coating crushed aluminum nitride particles A with the organosilicon compound A and then performing the heating in the third step) and 2-B (obtained by coating crushed aluminum nitride particles B with the organosilicon compound A and then performing the heating in the third step), which are silica-coated aluminum nitride particles, were obtained. The measurement and calculation results of the physical properties of the silicon-containing oxide-coated aluminum nitride particles 2-A and 2-B are shown in Table 1. (Manufacture of resin molded body) In Example 1, a resin composition molded body test piece 2-A was obtained in the same manner except that silicon-containing oxide-coated aluminum nitride particles 2-A were used instead of the silicon-containing oxide-coated aluminum nitride particles 1-A. Further, in Example 1, a resin composition molded body test piece 2-B was obtained in the same manner except that silicon-containing oxide-coated aluminum nitride particles 2-B were used instead of the silicon-containing oxide-coated aluminum nitride particles 1-A. The measurement and calculation results of the physical properties of the resin composition molded body test pieces 2-A and 2-B are shown in Table 1.

[0112] [Example 3] (Production of silicon-containing oxide-coated aluminum nitride particles) In Example 1, in the same manner except that the amount of the organosilicon compound A used in the second step was 340 g, silicon-containing oxide-coated aluminum nitride particles 3-A (obtained by coating crushed aluminum nitride particles A with the organosilicon compound A and then performing the heating in the third step) and 3-B (obtained by coating crushed aluminum nitride particles B with the organosilicon compound A and then performing the heating in the third step), which are silica-coated aluminum nitride particles, were obtained. The measurement and calculation results of the physical properties of the silicon-containing oxide-coated aluminum nitride particles 3-A and 3-B are shown in Table 1. (Production of resin molded body) In Example 1, a resin composition molded body test piece 3-A was obtained in the same manner except that the silicon-containing oxide-coated aluminum nitride particles 3-A were used instead of the silicon-containing oxide-coated aluminum nitride particles 1-A. Further, in Example 1, a resin composition molded body test piece 3-B was obtained in the same manner except that the silicon-containing oxide-coated aluminum nitride particles 3-B were used instead of the silicon-containing oxide-coated aluminum nitride particles 1-A. The measurement and calculation results of the physical properties of the resin composition molded body test pieces 3-A and 3-B are shown in Table 1.

[0113] [Comparative Example 1] (Production of silicon-containing oxide-coated aluminum nitride particles) In Example 3, in the same manner except that the first step was not carried out, silicon-containing oxide-coated aluminum nitride particles 4-A (obtained by coating raw material aluminum nitride particles A with an organosilicon compound A and then performing the heating in the third step) and 4-B (obtained by coating raw material aluminum nitride particles B with an organosilicon compound A and then performing the heating in the third step), which are silica-coated aluminum nitride particles, were obtained. The measurement and calculation results of the physical properties of the silicon-containing oxide-coated aluminum nitride particles 4-A and 4-B are shown in Table 1. (Manufacture of resin molded body) In Example 3, in the same manner except that the silicon-containing oxide-coated aluminum nitride particles 4-A were used instead of the silicon-containing oxide-coated aluminum nitride particles 3-A, a resin composition molded body test piece 4-A was obtained. Further, in Example 3, in the same manner except that the silicon-containing oxide-coated aluminum nitride particles 4-B were used instead of the silicon-containing oxide-coated aluminum nitride particles 3-A, a resin composition molded body test piece 4-B was obtained. The measurement and calculation results of the physical properties of the resin composition molded body test pieces 4-A and 4-B are shown in Table 1.

[0114] [Comparative Example 2] (Manufacture of silicon-containing oxide-coated aluminum nitride particles) In Example 1, in the same manner except that the first step was not carried out, silicon-containing oxide-coated aluminum nitride particles 5-A (obtained by coating raw material aluminum nitride particles A with an organosilicon compound A and then performing the heating in the third step) and 5-B (obtained by coating raw material aluminum nitride particles B with an organosilicon compound A and then performing the heating in the third step), which are silica-coated aluminum nitride particles, were obtained. The measurement and calculation results of the physical properties of the silicon-containing oxide-coated aluminum nitride particles 5-A and 5-B are shown in Table 1. (Manufacture of resin molded body) In Example 1, a resin composition molded body test piece 5-A was obtained in the same manner except that silicon-containing oxide-coated aluminum nitride particles 5-A were used instead of the silicon-containing oxide-coated aluminum nitride particles 1-A. Further, in Example 1, a resin composition molded body test piece 5-B was obtained in the same manner except that silicon-containing oxide-coated aluminum nitride particles 5-B were used instead of the silicon-containing oxide-coated aluminum nitride particles 1-A. The measurement and calculation results of the physical properties of the resin composition molded body test pieces 5-A and 5-B are shown in Table 1.

[0115] [Comparative Example 3] (Production of silicon-containing oxide-coated aluminum nitride particles) In the same manner as in Comparative Example 2, after obtaining silicon-containing oxide-coated aluminum nitride particles 5-A and 5-B, which are silica-coated aluminum nitride particles, the silicon-containing oxide-coated aluminum nitride particles 5-A and 5-B were continuously crushed using a mortar type grinder (“Super Mass Colloid MKCA6-5J”, manufactured by Masuda Sangyo Co., Ltd.) at a rotation speed of 2000 rpm, a clearance of 50 μm, and a particle feed amount of 20 kg / h to obtain silicon-containing oxide-coated aluminum nitride particles 6-A and 6-B. The measurement and calculation results of the physical properties of the silicon-containing oxide-coated aluminum nitride particles 6-A and 6-B are shown in Table 1. (Production of resin molded body) In Example 1, a resin composition molded body test piece 6-A was obtained in the same manner except that silicon-containing oxide-coated aluminum nitride particles 6-A were used instead of the silicon-containing oxide-coated aluminum nitride particles 1-A. Further, in Example 1, a resin composition molded body test piece 6-B was obtained in the same manner except that silicon-containing oxide-coated aluminum nitride particles 6-B were used instead of the silicon-containing oxide-coated aluminum nitride particles 1-A. The measurement and calculation results of the physical properties of the resin composition molded body test pieces 6-A and 6-B are shown in Table 1.

[0116] [Reference Example 1] Using raw material aluminum nitride A and raw material aluminum nitride B, the ammonia concentrations measured under the above measurement conditions are shown in Table 2. In addition, in Example 1, a resin composition molded body test piece obtained in the same manner except that raw material aluminum nitride A was used instead of the silicon-containing oxide-coated aluminum nitride particles 1-A, and in Example 1, a resin composition molded body test piece obtained in the same manner except that raw material aluminum nitride B was used instead of the silicon-containing oxide-coated aluminum nitride particles 1-A, the measurement and calculation results of the physical properties are shown in Table 2.

[0117]

Table 1-1

[0118]

Table 1-2

[0119]

Table 2

[0120] In Examples 1 to 3, in the first step of the method for producing silicon-containing oxide-coated aluminum nitride particles, by crushing the agglomerated particles contained in the raw material aluminum nitride, it can be seen that the bulk density decreases and silicon-containing oxide-coated aluminum nitride particles with suppressed aggregation are obtained. Also, it can be seen that the silicon-containing oxide-coated aluminum nitride particles of Examples 1 to 3 have high thermal conductivity and excellent moisture resistance. On the other hand, it can be seen that the silicon-containing oxide-coated aluminum nitride particles obtained in Comparative Examples 1 and 2 that did not go through the first step have a large bulk density and aggregation is not suppressed. Also, it can be seen that the silicon-containing oxide-coated aluminum nitride particles obtained in Comparative Example 3 that did not go through the first step and were crushed after the third step have a high ammonia concentration measured under the above measurement conditions and low moisture resistance.

Claims

1. A method for producing aluminum nitride particles coated with silicon-containing oxide, comprising: aluminum nitride particles; and a silicon-containing oxide coating covering the surfaces of the aluminum nitride particles, the method comprising the steps of: A first step of crushing agglomerates contained in raw aluminum nitride particles to obtain crushed aluminum nitride particles; A second step of covering the surfaces of the crushed aluminum nitride particles with an organosilicon compound having a structure represented by the following formula (1) to obtain organosilicon compound-coated aluminum nitride particles; A third step of heating the organosilicon compound-coated aluminum nitride particles at a heating temperature of 300° C. or more and less than 1000° C., A method for producing aluminum nitride particles coated with a silicon-containing oxide, wherein a reduction rate of the loose bulk density of the crushed aluminum nitride particles relative to the loose bulk density of the raw material aluminum nitride particles is 10% or more. 【Chemistry 1】 (In formula (1), R is an alkyl group having 1 to 4 carbon atoms.)

2. 2. The method for producing aluminum nitride particles coated with silicon-containing oxide according to claim 1, wherein the heating temperature in the third step is 300° C. or more and 850° C. or less.

3. 3. The method for producing aluminum nitride particles coated with silicon-containing oxide according to claim 1, wherein the silicon-containing oxide coating is a silica coating.

4. 3. The method for producing aluminum nitride particles coated with silicon-containing oxide according to claim 1, wherein the second step is carried out by a gas phase adsorption method.

5. The method for producing aluminum nitride particles coated with silicon-containing oxide according to claim 4, wherein the second step is carried out under a temperature condition of 30 to 200°C.

6. 3. The method for producing aluminum nitride particles coated with silicon-containing oxide according to claim 1 or 2, wherein the organosilicon compound having a structure represented by formula (1) comprises at least one of a compound represented by the following formula (2) and a compound represented by the following formula (3): 【Chemistry 2】 (In formula (2), R1 and R2 each independently represent a hydrogen atom or a methyl group, at least one of R1 and R2 represents a hydrogen atom, and m represents an integer of 0 to 10.) 【Chemistry 3】 (In formula (3), n is an integer from 3 to 6.)

7. The particle size distribution width (P １ ) relative to the particle size distribution width (P ２ 3. The method for producing aluminum nitride particles coated with silicon-containing oxide according to claim 1, wherein the rate of change in particle size distribution width of the silicon-containing oxide-coated aluminum nitride particles is 0% or less. Particle size distribution width change rate (%) = [(P ２ / P １ )-1]×100 (I) The particle size distribution of the raw material aluminum nitride particles (P １ ) = (D １ 90-D １ 10) / D １ 50 (I-1) The particle size distribution width of the silicon-containing oxide-coated aluminum nitride particles (P ２ ) = (D ２ 90-D ２ 10) / D ２ 50 (I-2) (In the formula, D １ 90 is the cumulative volume 90% particle diameter of the raw material aluminum nitride particles, and D １ D50 is the cumulative volume 50% particle diameter of the raw material aluminum nitride particles, １ D10 is the cumulative volume 10% particle diameter of the raw material aluminum nitride particles, ２ D90 is the cumulative volume 90% particle diameter of the silicon-containing oxide-coated aluminum nitride particles, ２ D50 is the particle size of the silicon-containing oxide-coated aluminum nitride particles at 50% of their cumulative volume, ２ 10 is the particle size of the silicon-containing oxide-coated aluminum nitride particles at 10% of their cumulative volume.)

8. A silicon-containing oxide-coated aluminum nitride particle comprising an aluminum nitride particle and a silicon-containing oxide coating covering a surface of the aluminum nitride particle, The lightly packed bulk density is less than 0.58; The silicon-containing oxide-coated aluminum nitride particles have an ammonia concentration of less than 10 mg / L measured under the following measurement conditions: Measurement conditions: 3 g of the silicon-containing oxide-coated aluminum nitride particles are added to 17 g of a hydrochloric acid aqueous solution having a pH of 4, and the resulting mixed solution is heated at 134° C. for 2 hours and then allowed to stand at room temperature (25° C.) for 1 hour to prepare a measurement sample. The ammonia concentration in the measurement sample at 25° C. is measured using an ammonia electrode.

9. A resin composition comprising the silicon-containing oxide-coated aluminum nitride particles according to claim 8.

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