Alumina particles and resin composition using same

Abstract

The alumina particles have a particle diameter (D50) of more than 100 [mu] m and 200 [mu] m or less at 50% of the cumulative particle size distribution from the particle side, and a repose angle of less than 32 DEG.

Description

Technical Field

[0001] The present disclosure relates to alumina particles and a resin composition using the same. Background Art

[0002] Heat generated by energizing an electronic component is dissipated through a heat sink. A technique is known in which a heat dissipation material is filled between the electronic component and the heat sink in order to improve the heat dissipation efficiency.

[0003] As one of the heat dissipation materials, a resin composition containing a resin and inorganic particles is known, and alumina particles can be used as the inorganic particles (for example, Patent Document 1).

[0004] Patent Document 1 discloses the following method: fusing alumina is pulverized using a jet mill, and the edges of the fused alumina particles are removed, thereby obtaining circular fused alumina particles having an average particle diameter of 5 to 4000 μm.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-169090 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] In recent years, due to the miniaturization of electronic devices and the high integration of ICs, the gap between electronic components and heat sinks has become narrower. For the resin composition disposed between the electronic component and the heat sink, it is required to be able to be molded in such a narrow gap (that is, to have excellent moldability). Therefore, it is desired to suppress the viscosity of the mixture of alumina particles and a resin to a low level, and alumina particles capable of reducing the viscosity of the mixture are required.

[0010] However, regarding the alumina particles of Patent Document 1, the viscosity of the mixture of the alumina particles and the resin has not been studied.

[0011] In view of such a situation, an object of one embodiment of the present invention is to provide alumina particles that are used as a filler for a resin composition and can suppress the viscosity of the mixture to a low level when mixed with a resin. In addition, another object of the present invention is to provide a resin composition using such alumina particles.

[0012] Means for Solving the Problems

[0013] Aspect 1 of the present invention is alumina particles in which the particle diameter D50 of 50% cumulative number from the fine particle side in the cumulative particle size distribution is greater than 100 μm and 200 μm or less.

[0014] The angle of repose is less than 32°.

[0015] In Mode 2 of the present invention, the alumina particles are as described in Mode 1, wherein the ratio (L2 / L1) of the total length L2 of the boundary lines inside the alumina particles to the length L1 of the outer edge of the alumina particles is 200.0% or less.

[0016] In Mode 3 of the present invention, the alumina particles are as described in Mode 1 or 2, wherein the maximum particle size of the alumina particles with a circularity greater than 0.93 is 160 μm or more.

[0017] In Mode 4 of the present invention, the alumina particles are as described in any one of Modes 1 to 3, wherein the average circularity of the alumina particles with a particle size of 80 μm or more and less than 160 μm is greater than 0.94.

[0018] In Mode 5 of the present invention, the alumina particles are as described in any one of Modes 1 to 4, wherein the average circularity of the alumina particles with a particle size of 160 μm or more and less than 180 μm is greater than 0.86.

[0019] In Mode 6 of the present invention, the resin composition contains a resin and the alumina particles as described in any one of Modes 1 to 5.

[0020] Effects of the Invention

[0021] When the alumina particles according to one embodiment of the present invention are mixed with a resin, the viscosity of the mixture can be suppressed to be low. Since the resin composition according to another embodiment of the present invention uses the alumina particles according to one embodiment, the moldability is excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Figure 1 It is a schematic diagram showing an apparatus for carrying out a flame melting process in a method for manufacturing alumina particles. DETAILED DESCRIPTION OF THE INVENTION

[0023] [Embodiment 1: Alumina Particles]

[0024] The alumina particles according to Embodiment 1 of the present invention are used by being mixed with a resin as a filler for a resin composition. Regarding the alumina particles, the particle size D50 at which the cumulative number from the fine particle side in the cumulative particle size distribution reaches 50% is greater than 100 μm and 200 μm or less, and the angle of repose is less than 32°. The inventors of the present application have found for the first time that the alumina particles having these characteristics can suppress the viscosity of the mixture to be low when mixed with a resin, and thus completed the invention according to the present embodiment.

[0025] Regarding the characteristics of the alumina particles according to Embodiment 1, they will be described in detail below.​​

[0026] (D50, the particle size at which 50% of the cumulative number of particles from the fine particle side in the cumulative particle size distribution)

[0027] Regarding the alumina particles according to Embodiment 1 of the present invention, alumina particles with a D50 (hereinafter sometimes simply referred to as "D50") of the cumulative particle size distribution, which is the particle size at which 50% of the cumulative number of particles from the fine particle side, greater than 100 μm and 200 μm or less are targeted. The D50 of the alumina particles is preferably 115 μm or more and 195 μm or less.

[0028] Regarding the D50 of the alumina particles, based on the principle of dynamic image analysis in accordance with ISO 13322-2, the particle size distribution of the alumina particles is measured, and using the cumulative particle size distribution obtained from the measurement results, the particle size (D50) at which 50% of the cumulative number of particles from the fine particle side is obtained. As a measurement device, for example, CAMSIZER (manufactured by VERDER Scientific) is used, and the sample is sequentially introduced into the device, and the particles passing in front of the camera are measured while dispersing the agglomerated particles with dry air.

[0029] (Angle of repose)

[0030] The angle of repose is an index indicating the fluidity of the powder itself. The angle of repose of the alumina particles in Embodiment 1 of the present invention is less than 32°. Thus, the fluidity of the alumina particles is improved, and when mixed with the resin, the viscosity of the mixture can be suppressed to a low level. The angle of repose is preferably less than 29°, more preferably less than 27°. On the other hand, by making the angle of repose a specified value or more, for example, the scattering of the alumina particles can be suppressed, and the operability can be improved. The angle of repose is preferably greater than 14°, more preferably 16° or more, and particularly preferably 18° or more.

[0031] The angle of repose of the alumina particles can be adjusted by a known method. As an example, the angle of repose can be adjusted by adjusting the specific surface area of the alumina particles or by adjusting the roundness of particles with a particle size of 80 μm or more (especially 160 μm or more). In the case of alumina particles manufactured by the flame fusion method as described later, the angle of repose of the alumina particles can be adjusted by controlling the combustion amount.

[0032] The angle of repose of the alumina particles is measured in accordance with the description of JIS R 9301-2-2:1999. As the ambient atmosphere during the measurement of the angle of repose, the temperature is set to 23°C and the humidity is set to 40%.

[0033] (Ratio of the total length L2 of the boundary lines inside the particle to the length L1 of the outer edge of the alumina particle)

[0034] The fewer the grain boundaries and voids inside the alumina particles, the more uniformly the alumina particles can be dispersed in the resin when mixing the alumina particles with the resin at the stage of manufacturing a resin composition containing a resin and inorganic particles (alumina particles) for use as a heat dissipation member, for example. In addition, a decrease in the viscosity of the mixture can be expected. As a result, effects such as improved moldability of the resin composition, workability during mixing, and kneadability can be expected. There are cases where alumina particles having such characteristics have the angle of repose specified in Embodiment 1.

[0035] In addition, the fewer the grain boundaries and voids inside the alumina particles, the more it can contribute to increasing the thermal conductivity of the alumina particles. This is advantageous when using a resin composition containing a resin and inorganic particles as a heat dissipation material. It is also advantageous when disposing a resin composition containing alumina particles as a heat dissipation member near an electronic component.

[0036] Therefore, as an index of the grain boundary content inside the alumina particles, the ratio (L2 / L1) of the total length L2 of the boundary lines to the length L1 of the outer edge is introduced. L1 and L2 are obtained from the cross-sectional observation of the alumina particles.

[0037] When the length of the outer edge of one alumina particle is L1 and the total length of the boundary lines of the alumina particle is L2, alumina particles with a small L2 / L1 value can be said to have a small content of boundary lines and low dielectric loss. In particular, (L2 / L1) (%) is preferably 200.0% or less. When used as a filler for a resin composition, it can be expected to improve the heat dissipation of the resin composition and reduce the dielectric loss. (L2 / L1) is more preferably 130.0% or less, further preferably 100.0% or less, still further preferably 80.0% or less, particularly preferably 60.0% or less, preferably 5.0% or more, more preferably 15.0% or more, further preferably 35.0% or more, and particularly preferably 45.0% or more. In the case of using granulated raw material particles as polycrystalline raw material particles and manufacturing alumina particles by the flame fusion method, this L2 / L1 value particularly increases, and even through subsequent processes such as reheating, it cannot be significantly reduced.

[0038] It should be noted that the "total length L2 of the boundary lines" is the sum of the boundary lines contained inside the alumina particles and does not include the outer edge of the alumina particles. The total length L2 of the boundary lines is obtained by adding the total length L3 of the grain boundaries inside the alumina particles and the total length L4 of the inner walls of the voids (when there are voids inside the alumina particles) (that is, L2 = L3 + L4).

[0039] The measurement of L1, L2, L3, and L4 is preferably performed on alumina particles obtained from α-alumina.

[0040] (True roundness of alumina particles)

[0041] The true roundness (SPHT) of alumina particles is analyzed in accordance with ISO 9276-6. According to SPHT = 4πA / P 2 it is calculated. In the formula, A is the measured value of the area of the projected particle image, and P is the measured value of the outer perimeter of the particle projected image.

[0042] The true roundness of each alumina particle is measured by a measuring device (for example, CAMSIZER X2 (manufactured by VERDER Scientific)) based on the principle of dynamic image analysis in accordance with ISO 13322-2. The particle size distribution of alumina particles can also be measured simultaneously with the measurement of the true roundness of alumina particles.

[0043] The particle size and true roundness of the alumina particles of Embodiment 1 of the present invention preferably satisfy the following requirements (i) to (iii). When within this range, good kneadability with the resin can be achieved, and the viscosity of the mixture (composite) of the kneaded resin and alumina particles can be further reduced.

[0044] Requirement (i): The maximum particle size of alumina particles with a true roundness greater than 0.93 is 160 μm or more.

[0045] Requirement (ii): The average true roundness of alumina particles with a particle size of 80 μm or more and less than 160 μm is greater than 0.94. More preferably, it is greater than 0.95.

[0046] Requirement (iii): The average true roundness of alumina particles with a particle size of 160 μm or more and less than 180 μm is greater than 0.86. More preferably, it is 0.88 or more.

[0047] Whether the requirements (i) to (iii) are satisfied can be confirmed by analyzing using the measurement data of the true roundness and particle size distribution of alumina particles and the following method.

[0048] Requirement (i): For alumina particles with a true roundness greater than 0.93, investigate the particle size and find the value of the maximum particle size.

[0049] Requirement (ii): For alumina particles with a particle size within the range of 80 μm or more and less than 160 μm, find the average value of the true roundness (average true roundness).

[0050] Requirement (iii): For alumina particles with a particle size within the range of 160 μm or more and less than 180 μm, find the average value of the true roundness (average true roundness).

[0051] The particle size and true circularity of the alumina particles of Embodiment 1 of the present invention can satisfy the following configuration (iv). When within this range, good kneadability with the resin can be achieved, and the viscosity of the mixture (composite) of the resin and alumina particles after kneading can be further reduced.

[0052] Requirement (iv): The average true circularity of alumina particles with a particle size less than 80 μm is greater than 0.88. More preferably greater than 0.91, and particularly preferably greater than 0.93.

[0053] Whether requirement (iv) is satisfied can be confirmed by calculating the average value (average true circularity) of the true circularity of alumina particles with a particle size less than 80 μm using the measurement data of the true circularity and particle size distribution of the alumina particles.

[0054] Regarding the alumina particles of Embodiment 1 of the present invention, it is preferable that the content of alumina particles with a high true circularity is large, which can achieve good kneadability with the resin and further reduce the viscosity of the mixture (composite) of the resin and alumina particles after kneading.

[0055] The so-called "content (%) of alumina particles" refers to the volume ratio of alumina particles that satisfy specific conditions when the volume of all alumina particles is set to 100%. The content is calculated based on the cumulative distribution of the true circularity.

[0056] The content (%) of alumina particles with a true circularity greater than 0.93 is preferably 40% or more, more preferably 70% or more, and particularly preferably 75% or more.

[0057] In addition, the content (%) of alumina particles with a true circularity greater than 0.98 is preferably 20% or more, more preferably 35% or more, further preferably 45% or more, and particularly preferably 55% or more.

[0058] It should be noted that the following aspects should be noted: Since alumina particles are usually hard particles, it is difficult to obtain alumina particles with a desired angle of repose and a true circularity of 0.90 or more by simply colliding alumina particles with a low true circularity with each other or crushing alumina particles with a low true circularity. In order to improve the true circularity of alumina particles by collision and crushing, collision and crushing need to be carried out for a long time. However, in this case, a large amount of fine powder of alumina is generated, which may cause the particle size D50 of alumina particles to be excessively reduced or the desired angle of repose cannot be obtained. In addition, the new hydrophilic surface generated on the surface of alumina particles due to crushing will reduce the mixing property with the resin of alumina particles, so the viscosity of the mixture with the resin may increase.

[0059] [Manufacturing method of alumina particles]

[0060] A method for manufacturing alumina particles according to Embodiment 1 of the present invention will be described.

[0061] In the raw material of the alumina particles, alumina raw material particles mainly formed of single crystal α-alumina and having a cumulative particle size distribution with a cumulative 50% particle size D50 from the fine particle side of 100 μm or more and 250 μm or less are used. Then, alumina particles are manufactured from the alumina raw material particles by the flame fusion method.

[0062] So far, the general view has been that when the raw material particles are put into the flame, they melt and the crystal structure of the raw material particles is reset, so the crystal structure characteristics of the raw material particles do not affect the crystal structure of the particles spheroidized by the flame. However, unexpectedly, it has been found that if single crystal particles are used as the raw material particles and the formula (1) is satisfied as described later, the crystal structure characteristics of the raw material particles after spheroidization can also be inherited, and alumina particles having the desired physical properties can be obtained.

[0063] In the flame fusion process, for example, a device as Figure 1 shown is used. Through the flame fusion process, the alumina particles according to Embodiment 1 can be obtained.

[0064] In order to use single crystal alumina raw material particles, effectively utilize the crystal structure characteristics of single crystal alumina even after spheroidization, and simply manufacture alumina particles having an appropriate angle of repose, it is effective to control the particle size of the alumina raw material particles used, the supply amount of the alumina raw material particles into the flame fusion furnace of the device, the combustion amount in the flame fusion furnace, the volume of the flame fusion furnace, etc.

[0065] In order to manufacture alumina particles with a D50 of 100 μm or more and 200 μm or less, alumina raw material particles with a D50 of, for example, 100 μm or more and 250 μm or less are used. The D50 of the alumina raw material particles is preferably 110 μm or more and 240 μm or less, for example, 143.6 μm or 177.8 μm.

[0066] It should be noted that the D50 of the obtained alumina particles can also be controlled by the conditions (such as the supply amounts of the alumina raw material particles, fuel gas, and oxygen) during the flame fusion process.

[0067] It should be noted that even if the D50 of the alumina raw material particles is, for example, 100 μm or more and 250 μm or less, each alumina raw material particle may include particles with a particle size less than 100 μm and particles larger than 250 μm. Therefore, the obtained alumina particles may include polycrystalline α-alumina and / or alumina other than α-alumina. However, by making the D50 of the alumina raw material particles 100 μm or more and 250 μm or less, the content of polycrystalline α-alumina and / or alumina other than α-alumina can be suppressed to a small amount within the allowable range of the present invention.

[0068] In addition, conventionally, a method of manufacturing alumina particles using granulated raw material particles as polycrystalline raw material particles by the flame melting method has been known, but a large amount of grain boundaries and internal voids may be included inside the obtained alumina particles. In the present invention, since single crystal α-alumina itself without granulation is used as the alumina raw material particles, alumina particles with a small L2 / L1 value can be obtained.

[0069] The D50 of the alumina raw material particles can also be measured by the same method as the measurement method of the D50 of the above-mentioned alumina particles.

[0070] The case where the alumina raw material particles are single crystal α-alumina can be confirmed by the SEM-EBSD method. It is judged whether it is α-alumina or alumina other than α-alumina by PhaseMAP, and then, by Image Quality (IQ) MAP, it can be judged whether it is single crystal or polycrystalline according to the presence or absence of clear grain boundaries in the alumina particles.

[0071] The fact that α-alumina is single crystal can also be confirmed by the Debye-Scherrer method.

[0072] As the raw materials of the alumina raw material particles, sapphire and single crystal α-alumina produced by solution growth methods such as the CZ method, Verneuil method, Kyropoulos method, Bridgman method, and EFG method can be used. By crushing these raw materials and sieving them with a sieve of a desired mesh number, alumina raw material particles with a specified D50 can be prepared.

[0073] The alumina raw material particles may include a small amount (for example, about 10% by mass or less) of alumina other than α-alumina (δ-alumina, θ-alumina, etc.). In addition, a small amount (for example, about 10% by mass or less) of polycrystalline α-alumina may be included together with single crystal α-alumina, which does not hinder the purpose of the present invention.

[0074] In the flame melting process, the supply amount of alumina raw material particles, the combustion amount of fuel gas, and the internal volume of the flame melting furnace preferably satisfy the following formula (1).

[0075] 3.80×10 4 ≤C / RV (kcal / kg·m 3 )≤1.00×10 7 (1)

[0076] Among them, R is the supply amount of alumina raw material particles (kg / hour), C is the combustion amount of fuel gas in the flame melting furnace (kcal / hour), and V is the internal volume of the flame melting furnace (m 3 ).

[0077] The supply amount R (kg / hour) of alumina raw material particles is the mass (kg) of alumina raw material particles supplied into the flame melting furnace within 1 hour.

[0078] The combustion amount C (kcal / hour) of fuel gas in the flame melting furnace is obtained by multiplying the calorific value generated by every 1 m 3 of fuel gas by the volume of fuel gas (Nm 3 / hour) supplied into the flame melting furnace within 1 hour. Here, regarding the calorific value generated by every 1 m 3 of fuel gas, for example, when the fuel gas is LPG, its value is calculated as 21800 kcal / N·m 3 .

[0079] The internal volume V (m 3 ) of the flame melting furnace is calculated based on the inner diameter R (m) and length L (m) of the actually used flame melting furnace (cylindrical) according to the following formula (2).

[0080] V = π×R 2 ×L / 4

[0081] The inner diameter and length use the values described in the specification, for example.

[0082] The middle value (C / RV) of formula (1) refers to the combustion amount per 1 kg of alumina raw material particles and per 1 m 3 of the volume of the flame melting furnace, and it is an index to understand the degree of combustion amount (thermal energy) given to the alumina raw material particles. If the flame melting process is carried out under the conditions that satisfy formula (1), an appropriate thermal energy density can be given to the alumina raw material particles with D50 of 100 μm or more and 250 μm or less, and spheroidization can be carried out while effectively utilizing the crystal structure characteristics of the alumina raw material particles. For example, for alumina raw material particles with a particle size of 100 μm or more (especially 160 μm or more), the melting degree in the flame can become more appropriate.

[0083] Moreover, when the flame melting step is carried out under the conditions satisfying formula (1), alumina particles with a repose angle of less than 32° can be obtained.

[0084] The numerical range of “C / RV” is preferably 3.80×10 as shown on the left side of formula (1) 4 kcal / kg·m 3 or more, more preferably 9.60×10 4 kcal / kg·m 3 or more, particularly preferably 10.00×10 4 kcal / kg·m 3 or more.

[0085] The value of “C / RV” is preferably 1.00×10 or less as shown on the right side of formula (1) 7 kcal / kg·m 3 or less.

[0086] As the fuel gas in the present invention, for example, propane, butane, propylene, acetylene, hydrogen, etc. can be cited. Propane (for example, liquefied propane gas (LPG)) is particularly preferred.

[0087] In the flame melting step, when the molten alumina raw material particles are solidified, in order to slow down the cooling rate, they can be passed through a region of 600°C to 1500°C, preferably a region of 800°C to 1400°C, more preferably a region of 1000°C to 1300°C. By passing through such a region and solidifying the spheroidized alumina particles, the α-conversion rate can be further increased.

[0088] As a subsequent step to the above flame melting step, a step of reheating before recovering the cooled and solidified alumina particles can also be added. By reheating the cooled and solidified alumina particles, the proportion of alumina other than α-alumina can be reduced, and the α-conversion rate can be further increased. As the temperature of the reheating step, for example, it is preferably 900°C or higher, more preferably 1000°C or higher. As the reheating method, heating from the outside using a heater or the like, heating based on gas combustion again, etc. can be applied.

[0089] A plasma melting step can also be carried out instead of the flame melting step.

[0090] The plasma melting process is a process for producing alumina particles by melting and spheroidizing alumina raw material particles using the plasma melting method. In the plasma melting process, single crystal particles are also used as the raw material particles. The power and atmosphere for generating the plasma (plasma flame) are appropriately controlled so that the crystal structure characteristics of the raw material particles are also inherited after spheroidization by plasma melting. In the plasma melting process, for example, a known high-frequency thermal plasma device can be used.

[0091] In the plasma melting process, in order to obtain alumina particles with a desired particle size, the D50 of the alumina raw material particles, various conditions in the plasma melting method, etc. are also appropriately controlled. The D50 of the alumina raw material particles suitable for the plasma melting process can be set in the same range as the D50 of the alumina raw material particles suitable for the flame melting process. It should be noted that when the particle size of the alumina raw material particles is large (for example, when the D50 of the alumina raw material particles is 160 μm or more), the plasma melting process is suitable.

[0092] [Embodiment 2: Resin Composition]

[0093] By using the alumina particles according to Embodiment 1 of the present invention as a filler for a resin composition, a resin composition having excellent moldability can be obtained. The resin composition includes a resin and the alumina particles according to Embodiment 1 of the present invention.

[0094] The alumina particles according to Embodiment 1 of the present invention can improve the moldability without impairing the flexibility inherent in the resin. Therefore, the mixing ratio thereof with respect to the resin composition (composite) is preferably in the ratio of 5 to 75 vol% of the resin and 95 to 25 vol% of the alumina particles.

[0095] The alumina particles according to Embodiment 1 have the characteristic of being able to suppress the viscosity of the mixture to a low level when mixed (kneaded) with the resin. Therefore, even when the gap between the electronic component and the heat sink is narrow, the resin composition can be appropriately disposed in the narrow gap.

[0096] A method for manufacturing the resin composition will be described.

[0097] Using a known method commonly used, the alumina particles according to Embodiment 1 of the present invention are mixed with a resin, whereby a resin composition can be obtained. For example, when the resin is in a liquid state (such as a liquid epoxy resin, etc.), after mixing the liquid resin, alumina particles, and a curing agent, it can be cured by heat or ultraviolet rays, etc., whereby a resin composition can be obtained. Known curing agents and methods can be used for the curing agent, mixing method, and curing method. On the other hand, when the resin is in a solid state (such as a polyolefin resin, acrylic resin, etc.), after mixing the alumina particles with the resin, it can be kneaded by a known method such as melt kneading, whereby the target resin composition is obtained.

[0098] As the resin used in the resin composition, it can be selected from thermoplastic resins, thermoplastic elastomers, and thermosetting resins. It should be noted that the resin can be used alone as 1 type, or 2 or more types can be used in combination.

[0099] Examples of the thermoplastic resin include polyolefin resins such as polyethylene, polypropylene, ethylene-propylene copolymer, etc., polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyvinyl alcohol, polyvinyl acetal, fluoropolymers such as polyvinylidene fluoride and polytetrafluoroethylene, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polystyrene, polyacrylonitrile, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene copolymer (ABS) resin, polyphenylene ether copolymer (PPE) resin, modified PPE resin, aliphatic polyamides, aromatic polyamides, polyimide, polyamideimide, polymethacrylic acid, polymethacrylate such as polymethyl methacrylate, polyacrylic acid, polycarbonate, polyphenylene sulfide, polysulfone, polyethersulfone, polyether nitrile, polyether ketone, polyketone, liquid crystal polymer, silicone resin, ionomer, etc.

[0100] Examples of the thermoplastic elastomer include styrene-butadiene block copolymer or its hydride, styrene-isoprene block copolymer or its hydride, styrene-based thermoplastic elastomer, olefin-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, polyester-based thermoplastic elastomer, polyurethane-based thermoplastic elastomer, polyamide-based thermoplastic elastomer, etc.

[0101] Examples of the thermosetting resin include crosslinked rubber, epoxy resin, phenolic resin, polyimide resin, unsaturated polyester resin, diallyl phthalate resin, etc. Specific examples of the crosslinked rubber include natural rubber, acrylic rubber, butadiene rubber, isoprene rubber, styrene-butadiene copolymer rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, ethylene-propylene copolymer rubber, chlorinated polyethylene rubber, chlorosulfonated polyethylene rubber, butyl rubber, halogenated butyl rubber, fluororubber, polyurethane rubber, and silicone rubber.

[0102] From the viewpoints of processability and properties, it is preferable to use polyolefin resins, acrylic resins, polyimide resins, polyamide resins, polyamideimide resins, epoxy resins, phenolic resins, and silicone resins.

[0103] In addition, in these resin compositions, if necessary, known additives such as plasticizers, curing accelerators, coupling agents, fillers, pigments, flame retardants, antioxidants, surfactants, compatibilizers, weathering agents, anti-blocking agents, antistatic agents, leveling agents, and mold release agents can be appropriately blended alone or in combination of two or more within the range that does not impair the effects of the invention.

[0104] The alumina particles and the resin composition containing the same according to the present embodiment are particularly suitable for use as heat dissipation materials. Therefore, in one aspect of the present disclosure, heat dissipating alumina particles and a heat dissipating resin composition can be provided.

[0105] Examples

[0106] (1) Production of alumina particles

[0107] Raw material particles (raw material particles 1 to 4) formed of single crystal alumina were prepared. The D50 of the alumina raw material particles, the particle diameter D10 of the cumulative 10% from the fine particle side of the cumulative particle size distribution, and the particle diameter D90 of the cumulative 90% from the fine particle side of the cumulative particle size distribution were measured and summarized in Table 1. The D10, D50, and D90 of the alumina raw material particles were measured by the laser diffraction method. A laser beam was irradiated on a sample dispersed in water, and its diffraction was measured to obtain the particle size. The measuring device used was a CILAS model 1090L.

[0108] [Table 1]

[0109] Aluminum oxide raw material particles D10 (μm) D50 (μm) D90 (μm) Raw material particle 1 88.33 143.6 277.6 Raw material particle 2 114.6 177.8 266.4 Raw material particle 3 134.9 176.6 218.4 Raw material particle 4 190.0 233.1 279.9

[0110] (Alumina particles of sample numbers 1 to 2: flame fusion)

[0111] For the alumina particles of sample numbers 1 to 2, use Figure 1In a device as shown, alumina particles were prepared from alumina raw material particles. The oxygen from the oxygen supply system 10 was split, with one part (carrier oxygen 11) supplied to the feeder 30 and the other part (combustion oxygen 12) supplied to the burner 41 of the flame melting furnace 40. The alumina raw material particles supplied to the feeder 30 were transported by the carrier oxygen 11 to the burner 41 of the flame melting furnace 40. In addition, fuel gas (LPG) was supplied from the gas supply system 20 to the burner 41. In the burner 41, a high-temperature flame of 2150 °C or higher was formed by the fuel gas and the combustion oxygen 12, and the alumina raw material particles dispersed in the carrier oxygen 11 were supplied thereto. Thus, in the flame melting furnace 40, the alumina raw material particles were melted and spheroidized. Then, the spheroidized alumina particles were classified by a cyclone separator 50, and the alumina particles captured by the cyclone separator 50 were obtained.

[0112] (Alumina particles of sample numbers 4 to 5: Plasma melting)

[0113] For the alumina particles of sample numbers 4 to 5, a known high-frequency thermal plasma device was used, and in an Ar-O2 atmosphere, the alumina raw material particles were melted and spheroidized by the high-frequency thermal plasma method to manufacture alumina particles.

[0114] (Alumina particles of sample number 3: Not melted)

[0115] For sample number 3, no flame melting or plasma melting was performed.

[0116] The types of the used alumina raw material particles and the types of the melting methods are summarized in Table 2. Furthermore, for sample numbers 1 to 2 using the flame melting method, in the flame melting process, based on the supply amount R (kg / hour) of the alumina raw material particles, the combustion amount C (kcal / hour) of the fuel gas in the flame melting furnace, and the furnace volume V (m 3 ) of the flame melting furnace, the C / RV (kcal / kg·m 3 ) calculated was also summarized in Table 2.

[0117] In Table 2, when the melting method column shows "-", it means that melting itself was not performed, and when the C / RV column shows "-", it means that flame melting was not performed.

[0118] [Table 2]

[0119]

[0120] For the obtained alumina particles (sample numbers 1 to 5), various measurements were performed. It should be noted that "sample number 3" of the alumina particles is the same as the alumina raw material particles 1.

[0121] (2) Measurement of the angle of repose of alumina particles

[0122] The angle of repose of the alumina particles was measured in accordance with JIS R 9301-2-2:1999. The ambient atmosphere during the measurement of the angle of repose was set to a temperature of 23°C and a humidity of 40%.

[0123] The measurement results are shown in Table 3.

[0124] [Table 3]

[0125] Sample number Angle of repose (°) Example 1 25 Comparative example 2 32 Comparative example 3 34 Example 4 24 Example 5 24

[0126] Regarding the angle of repose, the alumina particles of sample numbers 1, 4 to 5 are within the specified numerical range in Embodiment 1, but the alumina particles of sample numbers 2 to 3 exceed the specified numerical range.

[0127] (3) Measurement of the particle size distribution and roundness of alumina particles

[0128] The particle size distribution and roundness of the alumina particles were measured.

[0129] The particle size distribution and roundness of the alumina particles were measured using a CAMSIZER X2 (manufactured by VERDER Scientific), a device based on the principle of dynamic image analysis in accordance with ISO 13322-2. The measurement was performed in a dry state. The sample was sequentially introduced into the device, and while dispersing the agglomerated particles with dry air at 50 kPa, the particles passing in front of the camera were measured. The sample for measurement was weighed at 3 g and measured once. The same measurement was repeated three times, and the particle size distribution and roundness were analyzed based on the cumulative average of these results. The particle diameter is the equivalent circular diameter. The equivalent circular diameter is the diameter of a perfect circle having the same area as the projected particle image. In addition, the reference for the particle diameter is volume.

[0130] The roundness (SPHT) was analyzed in accordance with ISO 9276-6. According to SPHT = 4πA / P 2 It was obtained. In the formula, A is the measured value of the area of the projected particle image, and P is the measured value of the outer perimeter of the particle projected image.

[0131] The D50 obtained from the particle size distribution of the alumina particles is shown in Table 4. The D50 of sample numbers 1 to 5 is all within the range of greater than 100 μm and 200 μm or less.

[0132] [Table 4]

[0133] Sample number D50 (μm) Example 1 121.5 Comparative example 2 157.5 Comparative example 3 150.0 Example 4 143.0 Example 5 193.0

[0134] Based on the measurement results of the particle size distribution and roundness of the alumina particles, the numerical values of the following requirements (i) to (iii) were obtained.

[0135] (i) Maximum particle size (μm) of alumina particles with a circularity greater than 0.93 (however, not calculated for sample No. 3)

[0136] (ii) Average circularity of alumina particles with a particle size of 80 μm or more and less than 160 μm

[0137] (iii) Average circularity of alumina particles with a particle size of 160 μm or more and less than 180 μm

[0138] Table 5 shows the measurement results. It should be noted that in the table, each requirement is abbreviated as "(i) Maximum particle size (μm)", "(ii) Average circularity of 80 - 160 μm", and "(iii) Average circularity of 160 - 180 μm".

[0139] [Table 5]

[0140]

[0141] Regarding requirements (i) to (iii), the alumina particles of sample Nos. 1, 4 to 5 are within the preferred numerical ranges specified in Embodiment 1, but the alumina particles of sample Nos. 2 to 3 are not within the specified preferred numerical ranges.

[0142] (4) Measurement of the content of alumina particles with a specific circularity

[0143] Based on the particle size distribution of alumina particles, the measurement results of circularity, and the cumulative distribution of circularity, the content of alumina particles with a specific circularity is obtained (requirements (iv), (v)).

[0144] (iv) Content (%) of alumina particles with a circularity greater than 0.93 when the mass of all alumina particles is set to 100%

[0145] (v) Content (%) of alumina particles with a circularity greater than 0.98 when the mass of all alumina particles is set to 100%

[0146] Table 6 shows the measurement results. It should be noted that in the table, each requirement is abbreviated as "(iv) Content rate (%) of circularity greater than 0.93" and "(v) Content rate (%) of circularity greater than 0.98".

[0147] [Table 6]

[0148]

[0149] Regarding requirements (iv) to (v), the alumina particles of sample Nos. 1, 4 to 5 are within the preferred numerical ranges specified in Embodiment 1, but the alumina particles of sample Nos. 2 to 3 are not within the specified preferred numerical ranges.

[0150] (5) Measurement of the total length L2 of the boundary lines inside the particles and the length L1 of the outer edge of the alumina particles

[0151] Use each alumina particle to prepare a specimen for cross-sectional observation. In the preparation of the specimen for cross-sectional observation, after embedding the alumina particles in resin, cut the resin and alumina particles using a diamond cutting machine. Then, deposit Pt on the cross-section as a protective film, prepare the cross-section using Ar ion milling, fix it to the SEM specimen stage with Cu double-sided tape, and perform SEM-EBSD measurement without deposition. Determine the observation position in such a way that two or more alumina particles completely enter the observation area (i.e., two or more alumina particles do not contact the observation area frame). The measurement is carried out on α-alumina particles.

[0152] The following equipment is used for the pretreatment of the sample and EBSD measurement.

[0153] · Equipment used

[0154] Ion milling device: IM-4000 (manufactured by Hitachi, Ltd.)

[0155] Ion sputtering device: E-1030 (manufactured by Hitachi, Ltd.)

[0156] Ultra-high resolution field emission scanning electron microscope: JSM-7800F Prime (manufactured by JEOL Ltd.)

[0157] Electron backscatter diffraction device: Digiview V (manufactured by TSL)

[0158] The conditions for EBSD measurement are as follows.

[0159] · Measurement area: 500.0 μm × 400.0 μm

[0160] · Accelerating voltage: 20.0 kV

[0161] · Magnification: ×500

[0162] · Vacuum degree: 30 Pa

[0163] In the obtained EBSD images, select two or more alumina particles that do not contact the frame of the observation region, and use the image processing software Image J (manufactured by the National Institute of Health) to calculate the average value of the length L1 of the outer edge of each alumina particle. In addition, the total length L2 of the boundary lines is also calculated. The "total length L2 of the boundary lines" is the sum of the boundary lines contained inside the alumina particles and does not include the outer edge of the alumina particles. The total length L2 of the boundary lines is obtained by adding the total length of the grain boundaries inside the alumina particles and (in the case where there are voids inside the alumina particles) the total length of the inner walls of the voids.

[0164] The ratio (L2 / L1) of the total length L2 of the boundary lines to the length L1 of the outer edge is expressed as a percentage (%). The more grain boundaries and voids there are inside the alumina particles, the larger the value of L2 / L1 (%).

[0165] The measurement results are shown in Table 7.

[0166] [Table 7]

[0167] Sample number L2 / L1 (%) Example 1 50.7 Comparative example 2 32.3 Comparative example 3 0.0 Example 4 50.4 Example 5 47.5

[0168] Regarding L2 / L1, any alumina particles of sample numbers 1 to 5 are within the preferred numerical range specified in Embodiment 1.

[0169] (6) Viscosity measurement of the mixture of alumina particles and resin

[0170] Perform shear rate-viscosity measurement on the mixture of alumina particles and epoxy resin.

[0171] Mix epoxy resin (Epoxy binder jER828 manufactured by Mitsubishi Chemical Corporation) and any one of the alumina particles of sample numbers 1 to 5 at a mixing ratio of 45:55 by volume% (equivalent to about 0.5 g of epoxy resin: about 2.0 g of alumina particles). Use a mortar to manually mix the alumina particles and epoxy resin for about 10 to 20 minutes to prepare a mixed sample for viscosity measurement.

[0172] Use HAAKE MARS III (manufactured by Thermo Fisher Scientific) to perform shear rate-viscosity measurement on the mixed sample.

[0173] The measurement conditions are as follows.

[0174] · Geometric structure: Φ20 mm parallel plate

[0175] · Shear rate: 0.001 s -1 ~100 s -1

[0176] ·Measured temperature: 23°C

[0177] ·Measured time: 4 minutes

[0178] At the measured temperature, on a stable plate, complete the sample setting within 10 minutes and start the measurement.

[0179] Shear rate 1 s -1 The measurement results of the viscosity at this time are shown in Table 8.

[0180] [Table 8]

[0181]

[0182] Regarding the alumina particles of sample numbers 1, 4 to 5 whose particle size D50 and angle of repose are within the numerical ranges specified in Embodiment 1, it can be said that the viscosity of the mixture with the resin is low and the moldability is excellent. On the other hand, regarding the alumina particles of sample numbers 2 to 3 whose angle of repose exceeds the numerical range specified in Embodiment 1, it is known that the viscosity of the mixture with the resin is significantly high and the moldability is lacking.

Claims

1. Alumina particles, wherein the particle diameter D50 at which the cumulative number from the fine particle side in the cumulative particle size distribution is 50% is greater than 100 μm and 200 μm or less, The angle of repose is less than 32°.

2. The alumina particles according to claim 1, wherein, The ratio (L2 / L1) of the total length L2 of the boundary lines inside the alumina particles to the length L1 of the outer edge of the alumina particles is 200.0% or less.

3. The alumina particles according to claim 1, wherein, The maximum particle diameter of the alumina particles with a circularity greater than 0.93 is 160 μm or more.

4. The alumina particles according to claim 1, wherein, The average circularity of the alumina particles having a particle diameter of 80 μm or more and less than 160 μm is greater than 0.

94.

5. The alumina particles according to claim 1, wherein, The average circularity of the alumina particles having a particle diameter of 160 μm or more and less than 180 μm is greater than 0.

86.

6. A resin composition comprising a resin and the alumina particles according to any one of claims 1 to 5.

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