Oxide composite particles, method for producing the same, and resin composition

Abstract

The present invention provides oxide composite particles which are mixed with a resin so as to obtain a resin composition that has high thermal conductivity, low dielectric constant and low dielectric loss tangent. Oxide composite particles which contain silica and alumina, while comprising from 40% by mass to 85% by mass of an α-cristobalite crystal phase, from 5% by mass to 50% by mass of an α-alumina crystal phase, and 10% by mass or less of a mullite crystal phase, wherein the elemental ratio of aluminum to silicon (aluminum / silicon) is 1.5 or more as determined by X-ray photoelectron spectroscopy.

Description

[Technical Field]

[0001] The present invention relates to oxide composite particles, a method for producing the same, and a resin composition. [Background technology]

[0002] In recent years, with the increase in the volume of information communication in the communications field, the use of high frequency bands has expanded in electronic devices and communications equipment, etc., and materials used in high frequency band devices are required to have low dielectric constants and dielectric loss tangents. In addition, the miniaturization and high integration of related electronic materials and components are progressing, and further heat dissipation properties are being required.

[0003] As a high-frequency ceramic material, silica (SiO2) has a low dielectric constant (3.7) and a quality factor index Qf (the product of the reciprocal of the dielectric tangent and the measurement frequency) of approximately 120,000, making it a promising filler material with low dielectric constant and low dielectric tangent. Furthermore, to facilitate blending in resins, the closer the filler shape to a sphere, the better. Spherical silica can be easily synthesized (see, for example, Patent Document 1) and is already used in many applications. Therefore, it is expected to be widely used in high-frequency dielectric devices and other applications.

[0004] However, the spherical silica is generally amorphous and has a low thermal conductivity of about 1 W / m·K, and resin compositions filled with spherical silica may have insufficient heat dissipation properties.

[0005] In order to improve thermal conductivity, it is conceivable to crystallize spherical silica from amorphous to quartz, cristobalite, etc. For example, Patent Documents 2 and 3 propose heat-treating amorphous spherical silica to crystallize it into quartz or cristobalite. Meanwhile, Patent Document 4 discloses silica powder having a coating made of aluminum oxide ceramic formed using Aerosil. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 58-138740 [Patent Document 2] Patent No. 6207753 [Patent Document 3] International Publication No. 2018 / 186308 [Patent Document 4] Japanese Patent Application Publication No. 10-251042 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide oxide composite particles that, when mixed with a resin, give a resin composition that exhibits high thermal conductivity, low dielectric constant and dielectric loss tangent, a method for producing the same, and the resin composition. [Means for solving the problem]

[0008] The present invention includes the following embodiments.

[0009] [1] Oxide composite particles containing silica and alumina, the oxide composite particles contain 40 to 85 mass% of an α-cristobalite crystalline phase, 5 to 50 mass% of an α-alumina crystalline phase, and 10 mass% or less of a mullite crystalline phase, Oxide composite particles having an aluminum to silicon elemental ratio (aluminum / silicon) of 1.5 or greater, as detected by X-ray photoelectron spectroscopy.

[0010] [2] The oxide composite particles according to [1], wherein the content of the alumina in the oxide composite particles is 15 to 50 mass %.

[0011] [3] The oxide composite particles according to [1] or [2], wherein the average particle size of the oxide composite particles is 0.5 to 70 μm.

[0012] [4] The oxide composite particles according to any one of [1] to [3], wherein the average circularity of the oxide composite particles is 0.7 or more.

[0013] [5] A method for producing oxide composite particles according to any one of [1] to [4], Silica particles with an average particle size of 0.5 to 70 μm and an average angle of repose of 50° or more and a specific surface area of ​​50 to 170 m 2 / g of alumina particles to obtain a mixture; heating the mixture at 1300 to 1500°C for 2 to 8 hours; A method for producing oxide composite particles, comprising:

[0014] [6] A resin composition comprising the oxide composite particles according to any one of [1] to [4] and a resin.

[0015] [7] The resin composition according to [6], wherein the content of the oxide composite particles in the resin composition is 20 to 80 mass %.

[0016] [8] The resin composition according to [6] or [7], which is a resin composition for use in high-frequency substrates. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide oxide composite particles that, when mixed with a resin, produce a resin composition that exhibits high thermal conductivity, low dielectric constant and dielectric loss tangent, a method for producing the same, and the resin composition. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram showing an X-ray diffraction pattern of the oxide composite particles of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0020] [Oxide composite particles] The oxide composite particles according to this embodiment contain silica and alumina. Here, the oxide composite particles contain 40 to 85 mass% of an α-cristobalite crystalline phase, 5 to 50 mass% of an α-alumina crystalline phase, and 10 mass% or less of a mullite crystalline phase. The element ratio of aluminum to silicon (aluminum / silicon) detected by X-ray photoelectron spectroscopy (hereinafter also referred to as XPS) is 1.5 or more.

[0021] The oxide composite particles according to this embodiment contain an α-cristobalite crystalline phase, an α-alumina crystalline phase, and a mullite crystalline phase within the above-mentioned content ranges, thereby achieving high thermal conductivity, as well as low dielectric constant and dielectric loss tangent in the resin composition. In particular, the oxide composite particles according to this embodiment have an aluminum / silicon element ratio of 1.5 or more as detected by XPS, and therefore have a structure in which a large amount of alumina is present on the surface of the oxide composite particles, and at least a portion of the surface of the oxide composite particles is covered with an alumina layer. The alumina layer located on the surface of the oxide composite particles provides high thermal conductivity, and the α-cristobalite crystalline phase contained in the oxide composite particles exhibits a low dielectric constant and dielectric loss tangent, thereby achieving high thermal conductivity, as well as low dielectric constant and dielectric loss tangent overall.

[0022] The oxide composite particles contain 40 to 85 mass% of an α-cristobalite crystalline phase based on the total mass of the oxide composite particles (i.e., the total mass of the oxide composite particles is 100 mass%). If the content of the α-cristobalite crystalline phase is less than 40 mass%, the dielectric constant and dielectric loss tangent become large, making it difficult to use in high-frequency devices. On the other hand, if the content exceeds 85 mass%, the thermal conductivity of the resin composition cannot be ensured. The content can be, for example, 50 to 85 mass%, 60 to 85 mass%, 70 to 85 mass%, or 75 to 85 mass%. The crystalline phase is identified and quantified by powder X-ray diffraction / Rietveld method. The crystal assignment can be performed, for example, using an X-ray database. Specifically, analysis can be performed by the method described below.

[0023] The oxide composite particles contain 5 to 50% by mass of an α-alumina crystalline phase based on the total mass of the oxide composite particles (i.e., the total mass of the oxide composite particles is 100% by mass). If the content of the α-alumina crystalline phase is less than 5% by mass, the thermal conductivity of the resulting resin composition cannot be ensured. Furthermore, if the content exceeds 50% by mass, the dielectric constant and dielectric loss tangent become too high, making it difficult to use the resin in high-frequency devices. The content may be, for example, 10 to 50% by mass, 10 to 40% by mass, 10 to 30% by mass, 10 to 25% by mass, or 10 to 20% by mass. The crystalline phase may be identified, quantified, and assigned to the crystal structure by the same method as for the α-cristobalite crystalline phase described above. Specifically, the analysis may be performed by the method described below.

[0024] The oxide composite particles contain 10% by mass or less of a mullite crystalline phase based on the total mass of the oxide composite particles (i.e., the total mass of the oxide composite particles is 100% by mass). If the content of the mullite crystalline phase exceeds 10% by mass, the dielectric properties such as the dielectric constant and the dielectric loss tangent and the thermal conductivity performance are slightly reduced. The content of the mullite crystalline phase can be 5% by mass or less, and can also be 1% by mass or less. The lower limit of the range of the content of the mullite crystalline phase is not particularly limited, but can be, for example, 0.01% by mass or more. Note that the oxide composite particles according to this embodiment do not necessarily contain a mullite crystalline phase. The identification and quantification of the crystalline phase and the crystal assignment can be performed using the same method as for the α-cristobalite crystalline phase described above. Specifically, the analysis can be performed using the method described below.

[0025] The oxide composite particles may contain amorphous silica in an amount of 50% by mass or less, preferably 0.01 to 15% by mass, and more preferably 0.01 to 5% by mass, based on the total mass of the oxide composite particles (i.e., the total mass of the oxide composite particles is 100% by mass). By ensuring that the amorphous silica content is 50% by mass or less, the dielectric loss tangent value can be kept low. The oxide composite particles according to this embodiment do not necessarily need to contain amorphous silica. Amorphous silica can be identified and quantified by the same method as for the crystalline phase of α-cristobalite described above. Specifically, it can be analyzed by the method described below.

[0026] The oxide composite particles may further contain other crystalline phases or other amorphous phases in addition to the α-cristobalite crystalline phase, the α-alumina crystalline phase, the mullite crystalline phase, and the amorphous silica. Examples of other crystalline phases include γ-alumina, θ-alumina, and quartz. Examples of other amorphous phases include alumina. The content of the other crystalline phases may be, for example, 0 to 8% by mass, or 0 to 4% by mass, based on the total mass of the oxide composite particles (i.e., the total mass of the oxide composite particles is 100% by mass). The content of the other amorphous phases may be, for example, 0 to 8% by mass, or 0 to 4% by mass, based on the total mass of the oxide composite particles (i.e., the total mass of the oxide composite particles is 100% by mass). The oxide composite particles do not necessarily need to contain the other crystalline phases or other amorphous phases.

[0027] The alumina content in the oxide composite particles (where the mass of the entire oxide composite particles is taken as 100% by mass) is preferably 15 to 50% by mass. When the content is 15% by mass or more, the resin composition can have a certain level of heat dissipation performance. When the content is 50% by mass or less, a low dielectric constant and dielectric loss tangent that are suitable for use in high-frequency devices can be ensured. The content can be, for example, 15 to 40% by mass, or 15 to 30% by mass. Here, "alumina" refers to all alumina components, including components other than α-alumina. The alumina content is a value calculated from the amount charged during synthesis.

[0028] The silica content in the oxide composite particles (where the mass of the entire oxide composite particles is taken as 100 mass%) is preferably 50 to 90 mass%. When the content is 50 mass% or more, it is possible to ensure a low dielectric constant and dielectric loss tangent that can be used in high-frequency devices. The silica content is a value calculated from the amount charged during synthesis.

[0029] The oxide composite particles may contain other components in addition to silica and alumina, but may also consist of silica and alumina.

[0030] The oxide composite particles have an aluminum / silicon elemental ratio of 1.5 or more as detected by XPS (X-ray Photoelectron Spectroscopy). XPS can obtain information on elements present within a few nanometers of the surface of a measurement sample. Therefore, the oxide composite particles according to this embodiment, having an elemental ratio of 1.5 or more, have a structure in which a large amount of alumina is present on the surface of the oxide composite particles, and at least a portion of the surface of the oxide composite particles is coated with an alumina layer. The elemental ratio is preferably 2.0 or more, more preferably 2.3 or more. Since it is preferable that the surface of the oxide composite particles is coated with an alumina layer as much as possible, the elemental ratio is preferably high. The aluminum / silicon elemental ratio detected by XPS can be measured by the method described below.

[0031] The average particle diameter of the oxide composite particles is preferably 0.5 to 70 μm. When the average particle diameter is 0.5 μm or more, a certain level of heat dissipation characteristics can be ensured as a resin composition. Furthermore, when the average particle diameter is 70 μm or less, the particles can be used as a heat dissipation filler for high-frequency devices, filling between materials. The average particle diameter can be, for example, 5 to 70 μm, 10 to 65 μm, or 20 to 60 μm. The average particle diameter is measured using a laser diffraction particle size distribution analyzer. Specifically, it can be measured by the method described below.

[0032] The average circularity of the oxide composite particles is preferably 0.7 or more. An average circularity of 0.7 or more allows the resin composition to have a low viscosity. The average circularity is more preferably 0.8 or more, even more preferably 0.85 or more, and particularly preferably 0.9 or more. The upper limit of the range of the average circularity is not particularly limited, and a higher average circularity is preferred, and it may even be 1. As will be described later, the average circularity of the oxide composite particles can be increased by using spherical raw silica particles in the production of the oxide composite particles. The average circularity is measured by the following method. The projected area (S) and projected perimeter (L) of the oxide composite particles photographed using an electron microscope are determined, and the circularity is calculated by applying these values ​​to the following formula (1). The average circularity of all oxide composite particles contained in a circle with a certain projected area (an area containing 100 or more oxide composite particles) is then calculated, and this average value is defined as the average circularity. Specifically, the average circularity can be measured by the method described later. Circularity = 4πS / L 2 (1)

[0033] The oxide composite particles according to this embodiment can, when mixed with a resin, cause the resin composition to exhibit high thermal conductivity, as well as low dielectric constant and dielectric loss tangent. Therefore, they are useful as a filler to be filled into resin compositions that require these physical properties (e.g., resin compositions for high-frequency substrates, etc.).

[0034] [Method of manufacturing oxide composite particles] The method for producing oxide composite particles according to this embodiment includes the following steps: 2 / g of alumina particles to obtain a mixture (hereinafter also referred to as a mixture production step); and heating the mixture at 1300 to 1500°C for 2 to 8 hours (hereinafter also referred to as a heating step). According to the method of this embodiment, the oxide composite particles of this embodiment can be produced easily and efficiently.

[0035] (Mixture manufacturing process) In this process, silica particles having an average particle size of 0.5 to 70 μm and silica particles having an average angle of repose of 50° or more and a specific surface area of ​​50 to 170 m are mixed. 2 / g of alumina particles to obtain a mixture.

[0036] The silica particles used as a raw material are not particularly limited in terms of crystalline system (e.g., amorphous, quartz, cristobalite, etc.), and the method for producing the silica particles is also not particularly limited, but it is preferable to use SiO2 containing 90% by mass or more of an amorphous phase, and more preferably to use SiO2 consisting of an amorphous phase. Examples of SiO2 containing 90% by mass or more of an amorphous phase include SiO2 produced by a flame fusion method, a deflagration method, a gas-phase method, a wet method, etc.

[0037] The particle size of the oxide composite particles obtained after heating mainly reflects the particle size of the raw material silica particles. Therefore, the average particle size of the silica particles can be, for example, 0.5 to 70 μm, 3 to 65 μm, 20 to 60 μm, or 35 to 55 μm. The average particle size is measured in the same manner as the average particle size of the oxide composite particles. Furthermore, since the shape of the oxide composite particles obtained after heating mainly reflects the shape of the raw material silica particles, it is preferable to use spherical silica particles, as this can increase the average circularity of the oxide composite particles. The average circularity of the silica particles is preferably 0.60 or more, preferably 0.70 or more, and more preferably 0.80 or more. The average circularity is measured in the same manner as the average circularity of the oxide composite particles.

[0038] The alumina of the alumina particles used as a raw material is not particularly limited, but examples thereof include γ-Al2O3, θ-Al2O3, α-Al2O3, etc. These may be used alone or in combination of two or more.

[0039] The average angle of repose of the alumina particles is preferably 50° or more, more preferably 52° or more. When the average angle of repose is 50° or more, the fluidity of the alumina particles is reduced, and a sufficient amount of alumina particles adhere to the surface of the silica particles during mixing, thereby enabling the production of oxide composite particles having a structure in which the surfaces are sufficiently covered with an alumina layer. The upper limit of the average range of the angle of repose is not particularly limited, but can be, for example, 55° or less. The average angle of repose is a value measured by the method described below. When Aerosil is used as the alumina particles, the average angle of repose of Aerosil is less than 50°, so the alumina particles segregate on the surface of the silica particles, and the surfaces are not sufficiently covered with an alumina layer. Therefore, the aluminum / silicon element ratio detected by XPS is less than 1.5.

[0040] The specific surface area of ​​alumina particles is 50 to 170 m 2 / g, and 60 to 130m 2 / g is more preferable, and 70 to 100m 2 It is more preferable that the specific surface area is 50 m / g. 2 When the specific surface area is 170 m / g or more, alumina particles are easily and stably adsorbed onto the silica surface, and the degree of surface coverage by the alumina layer increases. 2 / g or less, the bulkiness of the alumina particles is suppressed to a certain level or less, making it possible to synthesize oxide composite particles by this method. The specific surface area is a value measured by the method described below.

[0041] The method for mixing the silica particles and the alumina particles may be either dry mixing or wet mixing, but dry mixing is preferred because it does not use a solvent, so there is no need to dry the solvent, and the production cost of the oxide composite particles can be reduced. Examples of mixing methods include an agate mortar, a grinder such as a ball mill or a vibration mill, and various mixers.

[0042] (Heating process) In this step, the mixture obtained in the mixture production step is heated at 1300 to 1500°C for 2 to 8 hours. The heating device for heating the mixture is not particularly limited as long as it is capable of heating at high temperatures, and examples thereof include an electric furnace, a pusher furnace, etc. The heating atmosphere is not particularly limited, and examples thereof include air, N2, Ar, and under vacuum.

[0043] The heating temperature is preferably 1300 to 1500°C, more preferably 1300 to 1450°C, and even more preferably 1300 to 1400°C. A heating temperature of 1300°C or higher increases the cristobalite content, ensuring the thermal conductivity required for a heat-dissipating filler. A heating temperature of 1500°C or lower prevents a decrease in the circularity of the oxide composite particles due to interparticle fusion during heating. The heating time is preferably 2 to 8 hours, more preferably 2 to 6 hours, and even more preferably 4 to 5 hours. A heating time of 2 hours or longer increases the cristobalite content, ensuring the thermal conductivity required for a heat-dissipating filler. A heating time of 8 hours or less prevents a decrease in the circularity of the oxide composite particles due to interparticle fusion during heating.

[0044] The oxide composite particles obtained after heating may be in the form of agglomerates in which multiple particles are aggregated. The agglomerates themselves may be used as the oxide composite particles, or, if necessary, the agglomerates may be crushed and then used as the oxide composite particles. The method for crushing the agglomerates is not particularly limited, and examples thereof include crushing methods using an agate mortar, a ball mill, a vibration mill, a jet mill, a wet jet mill, etc. Crushing may be performed in a dry manner, or in a wet manner by mixing with a liquid such as water or alcohol. In wet crushing, oxide composite particles are obtained by drying after crushing. The drying method is not particularly limited, and examples thereof include heat drying, vacuum drying, freeze drying, and supercritical carbon dioxide drying.

[0045] (Other processes) The method for producing oxide composite particles according to this embodiment may further include other steps, such as a classification step of classifying the oxide composite particles so as to obtain a desired average particle size, and a washing step of reducing impurities, in addition to the mixture production step and the heating step.

[0046] [Resin composition] The resin composition according to this embodiment contains the oxide composite particles according to this embodiment and a resin. Because the resin composition according to this embodiment contains the oxide composite particles according to this embodiment, it can exhibit high thermal conductivity, as well as low dielectric constant and dielectric loss tangent. Furthermore, the resin composition according to this embodiment has low viscosity, resulting in high fluidity and excellent moldability.

[0047] The resin is not particularly limited, but examples thereof include polyethylene, polypropylene, epoxy resin, silicone resin, phenolic resin, melamine resin, urea resin, unsaturated polyester, fluororesin, polyamide such as polyimide, polyamideimide, polyetherimide, polyester such as polybutylene terephthalate, polyethylene terephthalate, polyphenylene sulfide, wholly aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide-modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber-styrene) resin, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin, etc. These resins may be used alone or in combination of two or more.

[0048] The content of the oxide composite particles in the resin composition is appropriately selected depending on the desired physical properties such as thermal conductivity, dielectric constant, and dielectric loss tangent, but is preferably 20 to 80 mass %. This content is 11 to 67 volume % when the density of the oxide composite particles is 2.4 and the density of the resin is 1.2, and is 9 to 61 volume % when the density of the oxide composite particles is 3.1 and the density of the resin is 1.2.

[0049] The resin composition according to the present embodiment may contain components other than the oxide composite particles according to the present embodiment and the resin. Examples of the other components include a flame retardant and glass cloth. Furthermore, by further mixing other particles having different compositions, specific surface areas, average particle diameters, etc., in addition to the oxide composite particles according to the present embodiment, the thermal conductivity, dielectric constant, dielectric loss tangent, packing ratio, etc. of the resin composition can be more easily adjusted.

[0050] The thermal conductivity of the resin composition according to this embodiment is preferably 0.80 W / m K or more, and more preferably 0.85 W / m K or more. The dielectric constant of the resin composition according to this embodiment is preferably 4.0 or less, and more preferably 3.5 or less. The dielectric loss tangent of the resin composition according to this embodiment is 5.0×10 -4 Preferably, it is 4.0 x 10 or less. -4 The viscosity of the resin composition according to this embodiment is preferably 700 Pa s or less, and more preferably 500 Pa s or less. The thermal conductivity, dielectric constant, dielectric loss tangent, and viscosity of the resin composition are values ​​measured by the methods described below.

[0051] The resin composition according to this embodiment exhibits high thermal conductivity and low dielectric constant and dielectric loss tangent, and is therefore particularly useful as a resin composition for high-frequency substrates, such as fluorine substrates, PPE substrates, and ceramic substrates. [Example]

[0052] Hereinafter, the embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0053] [Example 1] Silica particles (trade name: FB40R, manufactured by Denka Co., Ltd., average particle size: 50.1 μm) were mixed with alumina particles (trade name: AKPG07, manufactured by Sumitomo Chemical Co., Ltd., average angle of repose: 52.5°, specific surface area: 80.0 m). 2 / g) was added so that the amount of alumina particles added was 15 mass %. Furthermore, the mixed particles were mixed using a vibration mixer (manufactured by Resodyn, product name: Low Frequency Resonance Acoustic Mixer Lab RAM II). 10 g of the resulting mixture was placed in an alumina crucible, heated from room temperature at a rate of 10°C / min, and heated in an electric furnace. The heating temperature was 1400°C and the heating time was 4 hours. After heating, the sample was allowed to cool naturally, and after cooling, it was crushed in an agate mortar to obtain oxide composite particles. The oxide composite particles were evaluated by the methods described below.

[0054] [Examples 2 to 6 and Comparative Examples 1 to 4] Oxide composite particles were prepared and evaluated in the same manner as in Example 1, except that the types and amounts of raw materials, heating time, and heating temperature were changed to the conditions shown in Table 1 or Table 2. In Examples 2 and 6 and Comparative Examples 2 and 4, silica particles (trade name: FB5D, manufactured by Denka Co., Ltd., average particle size: 8.0 μm) were used. In Comparative Example 4, alumina particles (trade name: TM-DA, manufactured by Taimei Chemical Industry Co., Ltd., average angle of repose: 48.0°, specific surface area: 6.6 m) were used. 2 / g) was used.

[0055] [Examples 7 and 8] Silica particles (trade name: FB40R, manufactured by Denka Co., Ltd., average particle size: 50.1 μm) or silica particles (trade name: FB5D, manufactured by Denka Co., Ltd., average particle size: 8.0 μm) were mixed with alumina particles (trade name: AKPG07, manufactured by Sumitomo Chemical Co., Ltd., average angle of repose: 52.5°, specific surface area: 80.0 m). 2 / g) was added so that the amount of alumina particles added was 15 mass %. Furthermore, the mixed particles were mixed using a vibration mixer (manufactured by Resodyn, product name: Low Frequency Resonance Acoustic Mixer Lab RAM II). 1 kg of the resulting mixture was placed in an alumina crucible, and heated in an electric furnace at a temperature increase rate of 2.5°C / min from room temperature. The heating temperature was 1400°C and the heating time was 4 hours. After heating, the sample was allowed to cool naturally, and after cooling, it was crushed in an agate mortar to obtain oxide composite particles. The oxide composite particles were evaluated by the methods described below.

[0056] The properties of the oxide composite particles prepared in each of the Examples and Comparative Examples were evaluated by the following methods. The evaluation results are shown in Tables 1 and 2.

[0057] [Identification of each crystalline phase and measurement of the content of each crystalline phase] The identification of each crystalline phase contained in the oxide composite particles and the measurement of the content of each crystalline phase were performed by powder X-ray diffraction measurement / Rietveld analysis. A horizontal sample multipurpose X-ray diffractometer (Rigaku Corporation, product name: RINT-Ultima IV) was used as the measurement device. The measurement was performed under the following conditions: X-ray source: CuKα, tube voltage: 40 kV, tube current: 40 mA, scan rate: 10.0° / min, 2θ scan range: 10° to 70°. As an example, the X-ray diffraction pattern of the oxide composite particles of Example 1 is shown in FIG. 1. Quantitative analysis of the crystalline phases was performed using Rietveld analysis software (MDI, product name: Integrated Powder X-ray Software Jade+9.6). The proportions (mass%) of each crystalline phase were calculated by Rietveld analysis after X-ray diffraction measurement of the oxide composite particle sample. In this case, the content (Rc) (mass%) of the silica component α-cristobalite in the oxide composite particle sample was calculated using the following formula (2) from the ratio of the peak area (As) of the peak derived from the α-cristobalite crystalline phase among the X-ray diffraction peaks of the sample obtained in the X-ray diffraction measurement of the oxide composite particle sample to the peak area (Ac) of the X-ray diffraction peak obtained when a cristobalite standard sample (JAWE 551) manufactured by the Japan Working Environment Measurement Association was measured. Rc=100As / Ac (2) The value of the α-cristobalite content thus obtained was compared with the proportion of the crystalline phase obtained separately by Rietveld analysis, and the contents of each crystalline phase and amorphous silica component in the oxide composite particle sample were calculated as follows. The content (mass%) of each crystalline phase determined by Rietveld analysis is assumed to be C for α-cristobalite, A for α-alumina, M for mullite, and X for other crystalline phases. In this case, the ratio Rc / C of C to the aforementioned Rc is multiplied by C, A, M, and X to obtain Rc, A×Rc / C, M×Rc / C, and X×Rc / C, which are the contents (mass%) of the α-cristobalite crystalline phase, α-alumina crystal, mullite crystal, and other crystalline phases contained in the oxide composite particles, respectively, and the remaining components are assumed to be amorphous.

[0058] [Measurement of aluminum / silicon element ratio detected by XPS] The aluminum / silicon element ratio on the surface of the oxide composite particles was measured using an X-ray photoelectron spectrometer (XPS, manufactured by Thermo Corporation, product name: K-Alpha). After introducing the oxide composite particles into the device, the measurement was performed by irradiating a 400 x 200 μm measurement area with monochromated Al-Kα radiation.

[0059] [Measuring average particle size] The average particle size was measured using a laser diffraction particle size distribution analyzer (manufactured by Beckman Coulter, product name: LS 13 320). 3 1 g of pure water and 0.1 g of the measurement sample were placed in a container and dispersed for 1 minute using an ultrasonic homogenizer (BRANSON, product name: SFX250). The dispersed dispersion of the measurement sample was added drop by drop using a dropper to a laser diffraction particle size analyzer, and measurements were taken 30 seconds after the specified amount was added. The particle size distribution was calculated from data on the light intensity distribution of diffracted / scattered light from the measurement sample detected by the sensor in the laser diffraction particle size analyzer. The average particle size was calculated by multiplying the measured particle size value by the relative particle amount (difference %) and dividing the result by the total relative particle amount (100%). Note that % here means volume %.

[0060] [Measurement of average circularity] The oxide composite particles were fixed to a sample stage with carbon tape, then coated with osmium. Images were taken with a scanning electron microscope (JEOL Ltd., product name: JSM-7001F SHL) at a magnification of 500-5000x and a resolution of 2048 x 1356 pixels and imported into a computer. The images were analyzed using an image analyzer (Nippon Roper Co., Ltd., product name: Image-Pro Premier Ver. 9.3) to calculate the projected area (S) and projected perimeter (L) of the oxide composite particles, and then the circularity was calculated using the following formula (1). The circularity of 100 oxide composite particles with a projected area equivalent circle diameter of 0.1 μm or more obtained in this way was determined, and the average value was taken as the average circularity. Circularity = 4πS / L 2 (1)

[0061] [Density measurement] The density of the oxide composite particles was measured by dry density measurement. The oxide composite particle sample, whose weight had been measured in advance, was placed in the measurement cell of a dry automatic densimeter (CurePic II1340) manufactured by Shimadzu Corporation, and the volume and density of the sample were determined by dry measurement with helium filling.

[0062] [Measurement of the average angle of repose of alumina particles] The average angle of repose of alumina particles was determined by measuring the angle of repose using a powder tester. Using a Hosokawa Micron Powder Tester (PT-X), a dispersion sieve with 1700 μm openings was used to supply the sample while vibrating it, and the alumina particle deposition formed was photographed with a CCD camera and the image was processed to measure the angle of repose.

[0063] [Measurement of the specific surface area of ​​alumina particles] The specific surface area of ​​the alumina particles was measured by gas adsorption measurement. 1 g of sample was filled into a measurement cell, and the specific surface area was measured using a Mountech Macsorb HM model-1201 fully automatic specific surface area measurement device (BET single-point method). The degassing conditions before measurement were 200°C and 10 minutes. Nitrogen was used as the adsorption gas.

[0064] [Measurement of thermal conductivity of resin composition] 25.6 parts by mass of bisphenol A liquid epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name: JER828) and 6.4 parts by mass of 4,4'-diaminophenylmethane (manufactured by Tokyo Chemical Industry Co., Ltd.) were mixed while melting at 95°C. Oxide composite particles were added to this mixture to a loading of 40% by volume, and the mixture was mixed using a planetary mixer (Thinky Corporation, product name: Awatori Rentaro AR-250, rotation speed: 2000 rpm). The resulting mixture was poured into a silicone mold (2 cm square x 6 mm thick) preheated to 80°C and press-cured using a vacuum heating press (manufactured by Imoto Machinery Co., Ltd., product name: IMC-1674-A) at 80°C for 1 hour at 3 MPa, 150°C for 1 hour at 5 MPa, and 200°C for 0.5 hours at 7 MPa, to obtain a resin composition.

[0065] The thermal conductivity of the resin composition was calculated by multiplying the thermal diffusivity, specific gravity, and specific heat. The thermal diffusivity was measured by the laser flash method using a cured sample cut into a size of 10 mm wide x 10 mm long x 1 mm thick. The measurement device used was a xenon flash analyzer (manufactured by NETZSCH, product name: LFA447 NanoFlash). The specific gravity was measured using the Archimedes method. The specific heat was measured using a differential scanning calorimeter (manufactured by TA Instruments, product name: Q2000) in a nitrogen atmosphere, heating from room temperature to 200°C at a rate of 10°C / min.

[0066] [Measurement of dielectric constant and dielectric loss tangent of resin composition] The oxide composite particles and polyethylene powder (manufactured by Sumitomo Seika Chemicals, product name: Flothane UF-20S) were weighed so that the oxide composite particle loading was 40% by volume, and mixed in a Resodyn vibration mixer (acceleration 60 g, processing time 2 minutes). The resulting mixed powder was weighed to a predetermined volume (so that the thickness was approximately 0.5 mm), placed in a metal frame with a diameter of 3 cm, and formed into a sheet using a nanoimprinting device (manufactured by SCIVAX, product name: X-300) at 140 °C for 5 minutes at 30,000 N to prepare an evaluation sample. The evaluation sample sheet was approximately 0.5 mm thick. The shape and size do not affect the evaluation results as long as they can be mounted on the measuring device, but they should be approximately 1 to 3 cm square.

[0067] The dielectric properties were measured using the following method. A 36 GHz cavity resonator (manufactured by SAMTECH) was connected to a vector network analyzer (product name: 85107, manufactured by Keysight Technologies), and an evaluation sample (1.5 cm square, 0.5 mm thick) was placed so that it covered a 10 mm diameter hole in the resonator. The resonance frequency (f0) and unloaded Q value (Qu) were measured. The evaluation sample was rotated for each measurement, and the measurement was repeated five times in the same manner. The obtained f0 and Qu values ​​were averaged and used as the measured value. The dielectric constant was calculated from f0, and the dielectric loss tangent (tan δc) was calculated from Qu using analysis software (manufactured by SAMTECH). The measurement temperature was 20°C, and the humidity was 60% RH.

[0068] [Measurement of viscosity of resin composition] The oxide composite particles were mixed with bisphenol A liquid epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name: JER828) so that the filling amount of the oxide composite particles was 40% by volume of the total, and the mixture was kneaded using a planetary mixer (Thinky Corporation, "Awatori Rentaro AR-250", rotation speed: 2000 rpm) to prepare a resin composition. The viscosity of the obtained resin composition was measured using a rheometer (Anton Paar, "MCR-302") under the following conditions. Plate shape: circular flat plate 10mmφ Sample thickness: 1 mm Temperature: 25±1℃ Shearing speed: 1s -1

[0069] [Table 1]

[0070] [Table 2]

[0071] As shown in Tables 1 and 2, the resin compositions containing the oxide composite particles of Examples 1 to 8, which are embodiments of the present invention, have high thermal conductivity (0.80 W / m K or more), low dielectric constant (4.0 or less), and low dielectric loss tangent (5.0 × 10 -4 It was found that the following

Claims

1. Oxide composite particles containing silica and alumina, the oxide composite particles contain 40 to 85 mass% of an α-cristobalite crystalline phase, 5 to 50 mass% of an α-alumina crystalline phase, and 10 mass% or less of a mullite crystalline phase, Oxide composite particles having an elemental ratio of aluminum to silicon (aluminum / silicon) of 1.5 or more as detected by X-ray photoelectron spectroscopy.

2. 2. The oxide composite particles according to claim 1, wherein the content of said alumina in said oxide composite particles is 15 to 50 mass %.

3. 3. The oxide composite particles according to claim 1, wherein the average particle size of the oxide composite particles is 0.5 to 70 μm.

4. The oxide composite particles according to any one of claims 1 to 3, wherein the average circularity of the oxide composite particles is 0.7 or more.

5. A method for producing oxide composite particles according to any one of claims 1 to 4, comprising: Silica particles with an average particle size of 0.5 to 70 μm and a specific surface area of ​​50 to 170 m ２ / g of alumina particles to obtain a mixture; heating the mixture at 1300 to 1500°C for 2 to 8 hours; A method for producing oxide composite particles, comprising:

6. A resin composition comprising the oxide composite particles according to any one of claims 1 to 4 and a resin.

7. The resin composition according to claim 6, wherein the content of the oxide composite particles in the resin composition is 20 to 80 mass%.

8. The resin composition according to claim 6 or 7, which is a resin composition for use in a high-frequency substrate.

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