Thermally conductive particles, method for producing same, mixture, article, resin composition, and thermally conductive film

Abstract

A thermally conductive particle containing at least an aluminum raw material, a zinc raw material, and a fired product obtained by firing other raw materials than the aluminum raw material and the zinc raw material, the content of the zinc raw material being 25-70 parts by mass (inclusive) per 100 parts by mass of the aluminum raw material, and the content of the zinc raw material being 70-90 parts by mass (inclusive) per 100 parts by mass of the aluminum raw material. The other raw material contains at least one compound selected from the group consisting of a boron compound, a tungsten compound, a titanium compound, a bismuth compound and a fluorine compound, the content of the other raw material is 0.05-20 parts by mass per 100 parts by mass of the aluminum raw material, and predetermined conditions are satisfied.

Description

TECHNICAL FIELD

[0001] The present application relates to a thermally conductive particle excellent in mechanical abrasion reduction and a manufacturing method thereof. BACKGROUND

[0002] At present, as a thermally conductive material, various raw materials have been studied. With the improvement of the integration of semiconductor elements, the requirement for heat dissipation is increasingly strong, and the development of a material having a much higher thermal conductivity and insulation than ever before becomes indispensable. As a material satisfying such a requirement, a composite material (resin composition) obtained by mixing a thermally conductive filler into a resin is known.

[0003] As a filler used in a composite material, alumina is used in many cases because of excellent water resistance, acid resistance, and insulation, and because it has good thermal conductivity and is inexpensive. However, alumina powder contained in a thermally conductive composition is a very hard material, and thus becomes one of the factors that accelerate the abrasion of equipment such as a device that processes a thermally conductive composite material into a pellet or a sheet, and the like. In the case of applying a thermally conductive filler to a processed product, a thermally conductive filler having high thermal conductivity and excellent low abrasion is strongly required.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2009-249226

[0007] Patent Literature 2: International Publication No. 2015 / 137468 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] Alumina has a high Mohs hardness, and exerts a load on a blade or a shaft of an extruder, and thus it is difficult to mix into a resin composition or the like, and further, the mixing of a worn-out part into it can cause contamination. In addition, when applied to a resin, the viscosity sometimes increases, and the moldability and processability are poor. In order to solve this problem, a thermally conductive material that suppresses mechanical abrasion, and has low viscosity when mixed into a resin compared to alumina has been studied.

[0010] However, the spherical zinc oxide particle powder disclosed in Patent Literature 1 is a powder in which the surface is coated, but since the thermal conductivity of zinc oxide itself is low, it needs to be improved. In Patent Literature 2, a sinter of an alumina-based compound and a compound of a metal other than aluminum is described, but it describes only a sinter of an aluminum raw material and a zinc raw material.

[0011] The present application has been made in view of the problems of the prior art, and aims to provide a low-hardness alumina-based thermally conductive particle (hereinafter, sometimes referred to as "thermally conductive particle") and a method for producing the same, which is excellent not only in thermal conductivity but also in chemical resistance, water resistance, and electrical insulation, and which has low mechanical abrasiveness, and which enables production of a material or an article such as a resin composition, which is excellent in filling property and moldability.

[0012] To solve the above problems, the present inventors have conducted intensive studies, and as a result, have found that a mixture of an aluminum raw material, a zinc raw material, and at least one other raw material selected from the group consisting of a boron compound, a titanium compound, a tungsten compound, a bismuth compound, and a fluorine compound, other than the aluminum raw material and the zinc raw material, is fired at a prescribed temperature, the raw materials are caused to react with each other, and a compound is generated, and then the thermally conductive particle produced by pulverization can achieve both low mechanical abrasiveness and high thermal conductivity. Furthermore, it has been found that control of the shape or surface properties of the particle is effective for improving the thermal conductivity, resin kneading property, or paint suitability. It has been found that by using the thermally conductive particle, it is possible to impart high thermal conductivity to a matrix while suppressing abrasion of equipment such as a device for processing or molding a thermally conductive composite material.

[0013] The solution to the problem, that is, according to the present application, a thermally conductive particle and a method for producing the same shown below are provided.

[0014] [1] A thermally conductive particle containing at least a fired product of an aluminum raw material, a zinc raw material, and another raw material other than the aluminum raw material and the zinc raw material, wherein the content of the zinc raw material is 25 parts by mass or more and 70 parts by mass or less with respect to 100 parts by mass of the aluminum raw material, the other raw material contains at least one selected from the group consisting of a boron compound, a tungsten compound, a titanium compound, a bismuth compound, and a fluorine compound, the content of the other raw material is 0.05 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the aluminum raw material, and the following condition is satisfied:

[0015] (1) 50 g of the thermally conductive particle is mixed with 50 g of an epoxy resin having an epoxy equivalent of 200 g / eq or more and 1000 g / eq or less, and when the viscosity of the resin composition obtained by the method is measured using an E-type viscometer at a measuring temperature of 25°C, a cone (3° x R9.7), and a rotational speed of 100 s -1 -1 1000 rpm for 1 minute and 2000 rpm for 1 minute using a planetary centrifugal mixer, and the viscosity of the resin composition obtained by the method is 3000 mPa s or less when measured using an E-type viscometer at a measuring temperature of 25°C, a cone (3° x R9.7), and a rotational speed of 100 s​

[0016] (2) Place 500 parts by mass of SUS304 steel balls with a diameter of 5mm and 100 parts by mass of the thermally conductive particles into a 250mL cylindrical container with a wide mouth. Rotate the container at 80rpm for 3 hours with the central axis of the cylinder as the rotation axis. Separate the steel balls and thermally conductive particles with a sieve with a sieve hole of 1mm to obtain the thermally conductive particles after the wear test. Mix 4 parts by mass of the thermally conductive particles before and after the wear test with 8 parts by mass of lithium borate. Crush the mixture in a mortar for 5 minutes. Measure the intensity of iron element using a fluorescence X-ray analysis device. The wear degree is calculated to be below 4kcps based on the intensity of fluorescence X-rays of iron element before and after the wear test (kcps).

[0017] Wear degree = (Intensity of X-ray fluorescence of iron after wear test) - (Intensity of X-ray fluorescence of iron before wear test)

[0018] (3) For a resin composition obtained by mixing 30 parts of an epoxy resin with an epoxy equivalent of 200 g / eq or more and 1000 g / eq or less and an amine curing agent with an amine value of 100 mg KOH / g or more and 500 mg KOH / g or less in a ratio of 3:1 to 4:1 with 70 parts of thermally conductive particles, the composition is molded into a circular sheet with a diameter of 100 mm or more and a thickness of 4 mm or more, heated and cured at a set temperature of 120°C for 1 hour, and after cooling, cut into quarters in a fan shape with a central angle of 90°. The thermal conductivity measured by the hot plate method is 0.80 W / m·K or more.

[0019] [2] The thermally conductive particles according to [1], wherein the other raw materials (excluding fluorine compounds) are at least one selected from the group consisting of oxides, oxyacid salts, hydroxides, carbonates and basic carbonates.

[0020] [3] The thermally conductive particles according to [1] or [2] contain at least one element selected from the group consisting of iron, cobalt, copper, manganese, nickel and chromium and are colored. [4] A mixture obtained by mixing thermally conductive filler into the thermally conductive particles according to any one of [1] to [3].

[0021] [5] The mixture according to [4], wherein the thermally conductive filler is at least one selected from the group consisting of barium sulfate, talc, boron nitride and magnesium oxide.

[0022] [6] A method for manufacturing thermally conductive particles, wherein the method for manufacturing thermally conductive particles according to any one of [1] to [3] is a method of obtaining by firing a mixture of raw materials containing aluminum raw material, zinc raw material and other raw materials other than the aluminum raw material and zinc raw material, wherein the aluminum raw material is at least one selected from the group consisting of boehmite, aluminum hydroxide and aluminum oxide, and the zinc raw material is at least one selected from the group consisting of zinc oxide and basic carbonate.

[0023] [7] A method for manufacturing thermally conductive particles, wherein the raw material mixture described in [6] is fired at a temperature above 1000°C and below 1600°C.

[0024] [8] An article containing any one of [1] to [3] thermally conductive particles.

[0025] [9] The article according to [8] is any one of gravure ink, coating liquid, resin composition and adhesive composition.

[0026]

[10] A resin composition for forming a thermally conductive resin composition, said resin composition comprising the mixture described in [4] or [5] and a forming resin.

[0027]

[11] The resin composition according to

[10] , wherein the content of the mixture relative to the total amount of the forming resin is 5% by mass or more and 95% by mass or less.

[0028]

[12] A thermally conductive thin film formed by coating the article described in [9].

[0029]

[13] The article according to [8] is used as a heat dissipation component for any of electronic device components, electronic device housings, EV motors, and lithium batteries.

[0030] According to the present invention, thermally conductive particles and a method for manufacturing the same can be provided. These particles not only exhibit excellent thermal conductivity but also excellent chemical resistance, water resistance, and electrical insulation. Furthermore, the processing equipment experiences minimal wear, and the particles have good compatibility (filler properties) with resins. By adding coloring materials, materials and articles such as colored resin compositions with excellent moldability can be manufactured. Additionally, according to the present invention, resin compositions and articles utilizing the thermal conductivity of the aforementioned thermally conductive particles can be provided. Detailed Implementation

[0031] Thermally conductive particles

[0032] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments. The thermally conductive particles according to this embodiment are obtained by firing a mixture of raw materials containing aluminum, zinc, and other raw materials besides the aluminum and zinc. The aluminum raw material is at least one selected from the group consisting of alumina, boehmite, and aluminum hydroxide. The zinc raw material is at least one selected from the group consisting of zinc oxide and basic carbonate. The raw material mixture also contains the zinc raw material and other raw materials at least selected from the group consisting of boron compounds, titanium compounds, tungsten compounds, bismuth compounds, and fluorine compounds. The content of zinc raw material is greater than 20 parts by mass and less than 70 parts by mass relative to 100 parts by mass of the aluminum raw material. The content of other raw materials is more than 0.05 parts by mass and less than 20 parts by mass relative to 100 parts by mass of the aluminum raw material. The detailed contents of the thermally conductive particles according to this embodiment will be described below.

[0033] The thermally conductive particles involved in this embodiment are mainly composed of α-alumina and zinc aluminate with a spinel crystal structure. The volume average particle size of these thermally conductive particles is preferably 0.1 μm or more and 50 μm or less. By using a composition containing such thermally conductive particles as fillers, the composition can be endowed with high thermal conductivity while exhibiting low hardness compared to α-alumina alone, thus suppressing wear on equipment such as devices used for molding or processing the composition. The average particle size can be measured using a laser diffraction particle size distribution measuring device or a transmission electron microscope image.

[0034] The zinc content in the raw material mixture, relative to 100 parts by weight of the aluminum raw material, needs to be greater than 20 parts by weight and less than 70 parts by weight, more preferably greater than 25 parts by weight and less than 65 parts by weight. If the zinc content is less than 20 parts by weight, the improvement effect on hardness and thermal conductivity cannot be obtained. On the other hand, if the zinc content is greater than 70 parts by weight, the thermal conductivity actually decreases. By setting the aluminum and zinc raw materials to the above range, it is possible to obtain thermally conductive particles that maintain various properties while exhibiting excellent thermal conductivity, chemical resistance, water resistance, and low abrasion resistance, and good compatibility (mixability) with resins. These particles can be used to manufacture materials and articles such as resin compositions with excellent moldability.

[0035] In addition to the zinc raw material, other raw materials besides the aluminum and zinc raw materials are also mixed in. These components are used to assist the zinc composition. Oxide raw materials are added to address issues such as difficulty in α-alloying and the desire to adjust particle size distribution.

[0036] The content of other raw materials in the raw material mixture is 0.05 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the aluminum raw material, more preferably 0.1 parts by mass or more and 10 parts by mass or less, even more preferably 0.1 parts by mass or more and 8 parts by mass or less, and particularly preferably 0.5 parts by mass or more and 5 parts by mass or less. If the amount of other raw materials is less than 0.05 parts by mass relative to 100 parts by mass of the aluminum raw material, the particle size distribution is wide and the filling capacity is reduced. On the other hand, if the amount of other raw materials is greater than 20 parts by mass relative to 100 parts by mass of the aluminum raw material, the thermal conductivity is reduced. By setting the amount of other raw materials relative to 100 parts by mass of the aluminum raw material to the above range, thermally conductive particles with excellent thermal conductivity, chemical resistance, water resistance, and electrical insulation can be obtained, and thermally conductive particles that can be used to manufacture materials and articles such as resin compositions with low wear and excellent formability can be manufactured. Regarding the viscosity of the resin added to the thermally conductive particles involved in this embodiment, the value is defined as the value when 50 parts by mass are added relative to 50 parts by mass of epoxy resin. The sample used for viscosity measurement was prepared using a planetary centrifugal mixer, mixed at 1000 rpm for 1 minute and degassed at 2000 rpm for 1 minute. The viscosity was measured using an E-type viscometer at a temperature of 25°C, a conical rotor (3° × R9.7), and a rotation speed of 100 s. -1 The viscosity of the resin composition used for viscosity determination obtained by the aforementioned method was measured under the specified conditions. The viscosity of the epoxy resin composition at this time needs to be below 3000 mPa·s, preferably below 2500 mPa·s. This is because if the viscosity exceeds 3000 mPa·s, the processability is poor. There is no particular limitation on the lower limit, but if the viscosity is less than 10 mPa·s, it is sometimes difficult to form a coating film. Therefore, it is possible to produce a thermally conductive resin composition with excellent moldability or processability.

[0037] Regarding the abrasion properties of the thermally conductive particles involved in this embodiment, 500 parts by weight of SUS304 steel balls with a diameter of 5 mm and 100 parts by weight of the thermally conductive particles were placed in a 250 mL wide-mouth cylindrical container. The container was rotated at 80 rpm for 3 hours with the central axis of the cylinder as the rotation axis. The steel balls and thermally conductive particles were then separated using a sieve with 1 mm mesh, yielding the thermally conductive particles after the abrasion test. Four parts by weight of each of the thermally conductive particles before and after the abrasion test were mixed with 8 parts by weight of lithium borate, and samples were prepared by pulverizing the mixture in a mortar for 5 minutes. The intensity of iron was measured using a fluorescence X-ray analysis device. The intensity (kcps) of iron before and after the abrasion test was calculated using the following formula, and the abrasion property was evaluated based on the degree of abrasion of the steel balls.

[0038] Wear degree = (Intensity of X-ray fluorescence of iron after wear test) - (Intensity of X-ray fluorescence of iron before wear test)

[0039] Regarding the abrasion rate, it needs to be below 4 kcps. If the abrasion rate exceeds 4 kcps, the thermally conductive particles become hard, causing wear on these devices during molding and processing of the resin composition, which is therefore undesirable.

[0040] Regarding the thermal conductivity of the thermally conductive particles involved in this embodiment, the value is defined as the value when 70 parts by mass are added to a mixture of epoxy resin and amine curing agent (30 parts by mass). The sample used for thermal conductivity measurement is prepared by molding a circular sheet with a diameter of 100 mm or more and a thickness of 4 mm or more, heating and curing at a set temperature of 120°C for 1 hour, and then cooling it before cutting it into four equal parts with a central angle of 90°. The thermal conductivity is measured by the hot plate method, and the thermal conductivity of the epoxy resin composition needs to be 0.80 W / m·K or more, more preferably 0.90 W / m·K or more. If the thermal conductivity is less than 0.80 W / m·K, the performance as thermal conductivity is insufficient. Therefore, when used in electronic components, it achieves high thermal conductivity and heat dissipation performance as intended.

[0041] Regarding the epoxy resin used for determining thermal conductivity and viscosity, an epoxy equivalent of 200 g / eq or more and 1000 g / eq or less is required, more preferably 300 g / eq or more and 800 g / eq or less, and even more preferably 350 g / eq or more and 700 g / eq or less. If the epoxy equivalent is less than 200 g / eq, the curing flexibility is poor, and air bubbles cannot be removed or the resin is difficult to mold, making it difficult to perform various measurements. Conversely, if the epoxy equivalent exceeds 1000 g / eq, the viscosity decreases, the flexibility becomes excessively high, and particles settle, making it difficult to prepare uniform samples and perform various measurements.

[0042] In addition, an E-type viscometer was used at a measurement temperature of 25°C, a conical rotor (3°×R9.7), and a rotation speed of 100 s. -1 The viscosity of the epoxy resin, measured under the specified conditions, needs to be between 400 mPa·s and 900 mPa·s. A viscosity of 3000 mPa·s or less when mixing 50 g of thermally conductive particles with 50 g of epoxy resin is preferred as it provides good moldability. If the viscosity of the epoxy is less than 400 mPa·s, sedimentation occurs, making measurement difficult. If the viscosity of the epoxy exceeds 900 mPa·s, it causes a decrease in workability, such as deterioration in moldability, and measurement also becomes difficult, making it undesirable.

[0043] As an amine-based curing agent used for thermal conductivity testing, the amine value needs to be 100 mg KOH / g or higher and 500 mg KOH / g or lower, more preferably 150 mg KOH / g or higher and 450 mg KOH / g or lower. If the amine value is less than 100 mg KOH / g, the viscosity is high, making it difficult to mix uniformly and causing operational difficulties, thus it is not preferred. If the amine value exceeds 500 mg KOH / g, the cured resin becomes too hard, making it difficult to perform various tests, thus it is also not preferred.

[0044] Regarding the ratio of epoxy resin to amine curing agent in the mixture, it is set to a range of 3:1 to 4:1. If the ratio deviates from this range, sufficient curing will not be achieved, and therefore it is not preferred. As for the amine curing agent, any substance that cures the epoxy resin is sufficient can be used, and conventional materials can be employed. Examples of amine curing agents include amines, aliphatic amines, aromatic amines, and modified amines.

[0045] The thermally conductive particles described in this embodiment exhibit excellent thermal conductivity, low wear on the processing equipment, and excellent resistance to chemicals, water, and electrical insulation. Furthermore, due to their high wettability with resins and good compatibility (filler properties), they can be used to manufacture materials such as resin compositions, coatings, and adhesive compositions with excellent moldability.

[0046] The thermally conductive particles involved in this embodiment are obtained by firing a mixture of raw materials containing aluminum, zinc and other raw materials, preferably composed of α-alumina and zinc aluminate with spinel crystal structure as the main components.

[0047] (Aluminum raw materials)

[0048] Alumina, boehmite, and aluminum hydroxide can be used as aluminum raw materials. The shape and particle size of the aluminum raw material are not particularly limited, but considering factors such as the dispersibility of thermally conductive particles, particles with an average particle size of 0.1 μm or more and 50 μm or less are preferred. More specifically, spherical or amorphous shapes can be used as examples of aluminum raw material shapes.

[0049] (Raw material mixture)

[0050] The raw material mixture used with aluminum raw materials includes other raw materials besides zinc raw materials. These other raw materials are at least one selected from the group consisting of boron compounds, titanium compounds, tungsten compounds, bismuth compounds, and fluorine compounds. They contribute to improved dispersibility of thermally conductive particles, promoted α-oxidation of alumina, or adjusted particle size distribution.

[0051] (Zinc raw material)

[0052] As a zinc raw material, basic zinc carbonate, zinc hydroxide, and zinc oxide can be used.

[0053] There are no particular limitations on the shape and particle size of the raw materials, but considering the dispersibility of thermally conductive particles, particles with an average particle size of 0.1 μm or more and 50 μm or less are preferred.

[0054] (Other raw materials)

[0055] Examples of other raw materials include boron compounds such as boric acid, sodium borate, ammonium borate, magnesium borate, and lithium borate. Examples of titanium compounds include rutile or anatase titanium oxide. Examples of tungsten compounds include tungsten oxide, ammonium tungstate, and sodium tungstate. Examples of bismuth compounds include bismuth oxide, basic bismuth carbonate, and sodium bismuthate. Examples of fluorine compounds include lithium fluoride, sodium fluoride, potassium fluoride, and aluminum fluoride. Among these, the use of boric acid, sodium tungstate, titanium oxide, basic bismuth carbonate, sodium fluoride, or aluminum fluoride results in thermally conductive particles with a high filling rate, and is therefore preferred.

[0056] In addition, other raw materials (excluding fluorine compounds) are preferably selected from at least one of the group consisting of oxides, oxyacid salts, hydroxides, carbonates and basic carbonates.

[0057] (Coloring material)

[0058] Furthermore, the thermally conductive particles involved in this embodiment can be colored even without the addition of pigments or dyes, by containing at least one element selected from the group consisting of iron, cobalt, copper, manganese, and nickel.

[0059] (Surface treatment)

[0060] The thermally conductive particles of this embodiment can be surface-treated. Surface-treated thermally conductive particles exhibit improved affinity and dispersibility with resins, thus enabling the manufacture of articles such as resin compositions with excellent thermal conductivity. Examples of compounds (treatment agents) used for surface treatment include fatty acids, fatty acid esters, fatty acid metal salts, phosphate esters, phosphate ester metal salts, silane coupling agents, surfactants, polymeric flocculants, titanates, and organosilicones. These treatment agents can be used alone or in combination of two or more. The amount of the compound used for surface treatment is preferably 0.01 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the thermally conductive particles. Treatment methods include, for example, adding the treatment agent to the powder of the thermally conductive particles and mixing it, or dispersing the powder of the thermally conductive particles in water, further adding the treatment agent, and then filtering and drying.

[0061] (Use of thermally conductive particles)

[0062] In the preferred use of the thermally conductive particles involved in this embodiment, it is effective to add them to various plastics such as thermoplastic resins or thermosetting resins for the purpose of imparting thermal conductivity. As thermoplastic resins, the following can be used: polyethylene resin, polypropylene resin, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, acrylonitrile-ethylene-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylonitrile-styrene copolymer, polyvinyl chloride resin, polystyrene resin, polyacrylonitrile resin, polyamide resin, thermoplastic polyimide resin, thermoplastic urethane resin, polyaminobismaleimide resin, polyamide-imide resin, polyetherimide resin, polymethyl methacrylate resin, polyvinyl acetate resin, polycarbonate resin, polyacetal resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyphenylene ether resin, polyphenylene sulfide resin, polysulfone resin, polyethersulfone resin, polyetheretherketone resin, polyallyl sulfone resin, bismaleimide triazine resin, polymethylpentene resin, fluorinated resin, liquid crystal polymer, olefin-vinyl alcohol copolymer, ionomer resin, and polyarylate resin, etc. These thermoplastic resins can be used alone or in combination of two or more. As thermosetting resins, phenolic resins, urea resins, epoxy resins, melamine resins, silicone resins, polyurethane resins, unsaturated polyester resins, alkyd resins, polyimide resins, acrylic resins, and (modified) polyphenylene ethers can be used. These thermosetting resins can be used alone or in combination of two or more.

[0063] <Manufacturing Method of Thermally Conductive Particles>

[0064] Next, the manufacturing method of the thermally conductive particles according to this embodiment will be described. The manufacturing method of the thermally conductive particles according to this embodiment includes: a step (step (1)) of mixing aluminum raw material, zinc raw material and other raw materials other than the aluminum raw material and zinc raw material to obtain a raw material mixture; and a step (step (2)) of firing the obtained raw material mixture.

[0065] According to this manufacturing method, particles with low mechanical wear and high thermal conductivity, exhibiting lower hardness than conventional alumina, can be easily obtained. The rationale may not be clear, but the inventors speculate as follows: The thermally conductive particles contain at least α-alumina and spinel-structured zinc aluminate. Furthermore, the mixed crystals constituting the filler composition formed from this particle material contain multiple α-alumina microparticles between the spinel-structured zinc aluminate particles, thereby increasing the contact area between the particles and decreasing the interparticle thermal resistance (interfacial thermal resistance). Therefore, it exhibits higher thermal conductivity than pure spinel-structured zinc aluminate. On the other hand, although the spinel-structured zinc aluminate particles have lower thermal conductivity than α-alumina, they exhibit excellent mechanical wear resistance, thus the manufactured thermally conductive particles have lower mechanical wear than alumina. The ratio of α-alumina to spinel-structured zinc aluminate in the thermally conductive particles (α-alumina: spinel-structured zinc aluminate) is preferably in the range of 8:2 to 1:9, more preferably in the range of 6:4 to 4:6. Especially when the ratio is 5:5, the balance between thermal conductivity and hardness becomes good.

[0066] In step (1), aluminum raw materials, zinc raw materials, and other raw materials are mixed. As an apparatus for mixing aluminum raw materials, zinc raw materials, and other raw materials, a pot mill, Henschel mixer, air mixer, cone mixer, planetary ball mill, vibratory mill, ribbon mixer, and vertical mixer are used to mix the components before firing. When mixing the components, the mixing should be carried out in a manner that makes each component homogeneous. The amounts of each component in the raw material mixture are as described above.

[0067] In step (2), the raw material mixture obtained in step (1) is fired at a temperature above 1000°C and below 1600°C. Preferably, the firing temperature is above 1200°C and below 1500°C. Through firing, α-alumina and spinel crystal structure zinc aluminate formed from aluminum and zinc raw materials can be produced.

[0068] If the firing temperature is below 1000°C, it is difficult to form a crystalline structure of zinc aluminate with α-alumina and spinel crystal structure. At this temperature, unreacted zinc raw materials remain, thus reducing durability. Furthermore, since the thermal conductivity of transition alumina formed at low temperatures is lower than that of α-alumina, firing to form zinc aluminate with α-alumina and spinel crystal structure is preferred. On the other hand, even if the firing temperature exceeds 1600°C, the properties of the resulting thermally conductive particles do not change significantly, resulting in wasted energy consumption. As a method to confirm the presence of zinc aluminate with α-alumina and spinel crystal structure in thermally conductive particles, one method is to compare the peaks obtained by powder X-ray diffraction of standard substances of zinc aluminate with α-alumina and spinel crystal structure with the peaks obtained by powder X-ray diffraction of the prepared thermally conductive particles. In the case of containing zinc aluminate with α-alumina and spinel crystal structure, the peaks can be added together, and quantification can be performed by comparing the individual peak intensities. After firing, the fired material is crushed as needed, thereby obtaining the thermally conductive particles involved in this embodiment. For crushing, known methods can be used, and various conventionally used equipment such as hammer mills, roller mills, ball mills, jet mills, bead mills, or vibratory mills can be employed.

[0069] <Thermal Conductive Composition (Mixture)>

[0070] In the thermally conductive composition (mixture), in addition to the thermally conductive particles described in this embodiment, it is preferable to use it in combination with other thermally conductive fillers such as alumina, boron nitride, graphite, zinc oxide, barium sulfate, talc, and magnesium oxide. Details are described below.

[0071] Fillers are typically added to materials such as resins, rubbers, and coatings to improve strength or functionality. However, increasing the amount of thermally conductive fillers reduces the melt flowability and mechanical strength of these materials. Furthermore, carbon-based fillers are conductive, so their inclusion in resins can compromise the resin's inherent insulating properties. While ceramic fillers offer insulation, they suffer from low thermal conductivity. Examples of thermally conductive fillers include metallic fillers such as silver, copper, aluminum, and iron; inorganic fillers such as alumina, magnesium oxide, silicon dioxide, boron nitride, aluminum nitride, silicon carbide, boron carbide, and titanium carbide; and carbon-based fillers such as diamond, graphite, and graphite. In electronic devices requiring high electrical insulation, fillers such as alumina, magnesium oxide, zinc oxide, silicon dioxide, boron nitride, aluminum nitride, and diamond are preferred. However, these fillers present numerous challenges regarding water resistance, chemical resistance, hardness, and electrical insulation.

[0072] In contrast, the thermally conductive particles involved in this embodiment can improve upon the weaknesses of the various fillers described above and possess excellent properties, thus making them suitable for use as improved fillers. Furthermore, to compensate for the weaknesses of existing thermally conductive fillers, it is preferable to use them together with the various thermally conductive fillers described above. That is, in a thermally conductive composition containing the various thermally conductive fillers described above, the use of the thermally conductive particles involved in this embodiment is a preferred method based on the target properties. As for the amount of thermally conductive filler added, it is preferably 10 parts by mass or more and 150 parts by mass or less relative to 100 parts by mass of thermally conductive particles. If the amount of thermally conductive filler added is less than 10 parts by mass, it is sometimes difficult to obtain the effect of the thermally conductive filler. If the amount of thermally conductive filler added exceeds 150 parts by mass, it is sometimes difficult to obtain the effect of the thermally conductive particles.

[0073] <Items>

[0074] The articles involved in this embodiment are articles (thermally conductive articles, thermally conductive materials) containing the aforementioned thermally conductive particles, such as gravure inks, coating liquids, resin compositions, and adhesive compositions. It should be noted that, as needed, the articles involved in this embodiment preferably further contain the aforementioned various thermally conductive fillers.

[0075] (Gravure ink)

[0076] The thermally conductive particles described in this embodiment can be added to gravure inks used as top coats for battery packaging materials. The content of the thermally conductive particles in the gravure ink is preferably 5% by mass or more and 80% by mass or less relative to the total content of the gravure ink, more preferably 10% by mass or more and 50% by mass or less. Using such a gravure ink (top coat for battery packaging materials) enables the production of battery packaging materials that exhibit excellent resistance to acids and other chemicals, as well as high thermal conductivity and high thermal emissivity.

[0077] (Coating liquid)

[0078] The thermally conductive particles described in this embodiment can be added to coating liquids such as paints. The coating liquid can also be formulated as a coloring agent obtained by mixing and dispersing the thermally conductive particles with, for example, colorants, resins for film or molding, and organic solvents on a carrier. The content of thermally conductive particles in the coating liquid is preferably 5% by mass or more and 80% by mass or less relative to the total content of the coating liquid, more preferably 10% by mass or more and 70% by mass or less. Coated films and molded articles formed using the coating liquid prepared in this way exhibit excellent water resistance, chemical resistance, and insulation properties, while maintaining strength and also exhibiting excellent thermal conductivity.

[0079] Specific examples of resins that may be contained in the coating liquid include thermoplastic resins based on polyolefins, polyesters, polystyrene, acrylics, fluorine, polyamides, cellulose, polycarbonates, or polylactic acid; and thermosetting resins based on urethanes, phenols, or silicones. These resins may be emulsions.

[0080] Specific examples of liquid media that may be contained in the coating solution include water, methanol, ethanol, butanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, butyl acetate, and cyclohexane. Two or more of these liquid media may be used in combination.

[0081] The coating liquid may contain "other ingredients" as appropriate, without prejudice to the purpose of the invention, depending on the intended use. Specific examples of "other ingredients" include antioxidants, ultraviolet absorbers, light stabilizers, dispersants, antistatic agents, lubricants, and bactericides.

[0082] As a method for applying the coating liquid, conventionally known methods can be used. Specifically, methods such as spraying, brushing, electrostatic coating, curtain coating, or using a roller coater, or immersion methods, can be employed. Furthermore, as a drying method for forming a film from the coated liquid, conventionally known methods can be used. Specifically, depending on the properties of the coating liquid, methods such as natural drying or sintering can be appropriately selected.

[0083] Using a coating liquid, coated films and molded articles can be produced by coating a substrate. The substrate can be selected from various materials such as metals, glass, natural resins, synthetic resins, ceramics, wood, paper, fibers, non-woven fabrics, woven fabrics, and leather, depending on the application. It should be noted that this functional coating can be used not only in household applications but also in various industries such as industry, agriculture, mining, and fishing. Furthermore, there are no restrictions on the coating shape; sheets or films can be selected depending on the application.

[0084] (Resin Composition)

[0085] By incorporating the thermally conductive particles described in this embodiment into resins such as polyamide resins and polyolefin resins, a resin composition can be prepared. More specifically, if the thermally conductive particles are incorporating and mixing with other additives into the resin using known methods, a resin composition can be obtained. Furthermore, if the obtained resin composition is subjected to extrusion molding, a specified resin molded article can be manufactured. The content of thermally conductive particles in the resin composition is preferably 5% by mass or more and 95% by mass or less relative to the total resin composition. By setting the content of thermally conductive particles within the above range, a resin composition with superior water resistance, chemical resistance, and insulation, as well as further maintained strength and superior moldability, can be produced. If the content of thermally conductive particles exceeds 95% by mass, the strength and moldability may decrease. On the other hand, if the content of thermally conductive particles is less than 5% by mass, the thermal conductivity may be insufficient.

[0086] There are no particular limitations on the method of adding thermally conductive particles to the resin, and conventionally known methods can be used. For example, besides directly mixing the thermally conductive particles into the resin and then compounding and molding, there are methods using compositions (masterbatches) obtained by pre-dispersing the thermally conductive particles at a high concentration in the resin, lubricant, etc. Other additives include antioxidants, ultraviolet absorbers, antistatic agents, antibacterial agents, stabilizers, crosslinking agents, plasticizers, lubricants, release agents, flame retardants, and inorganic fillers such as talc, alumina, clay, and silica. Furthermore, metal soaps and polyethylene waxes can be used as dispersing aids for the thermally conductive particles. Examples of metal soaps include lithium stearate, magnesium stearate, zinc stearate, calcium stearate, magnesium palmitate, calcium oleate, and cobalt oleate. Various polyethylene waxes, such as general polymeric, decompositional, or modified types, can be used. It should be noted that various organic and inorganic pigments can also be mixed into the above-mentioned coating liquid and resin compositions as colorants. Examples of colorants include organic pigments such as phthalocyanine pigments, azo pigments, azomethyl alkali pigments, isoindolinone pigments, quinacridone pigments, anthraquinone pigments, dioxazine pigments, and perylene-perylene pigments; composite oxide pigments other than black; titanium dioxide pigments such as titanium dioxide white pigments, titanium dioxide yellow pigments, and titanium dioxide black pigments; and inorganic pigments such as carbon black, ultramarine, and iron oxide red. It should be noted that examples of phthalocyanine pigments include brominated phthalocyanine blue and phthalocyanine green pigments. Additionally, examples of azo pigments include condensation azo pigments and azomethyl alkali azo pigments.

[0087] Furthermore, for resins used in composites, resin compositions can also be obtained by melt-blending a masterbatch composite containing thermally conductive particles, various pigments, and additives using an extrusion molding machine or similar equipment. More specifically, resin compositions can be obtained by: (i) mixing thermally conductive particles and dispersing agents with a resin for composites, and adding other additives as needed, using a mixer such as a Henschel mixer; (ii) kneading the masterbatch composite using a kneader or a heated twin-roll mill, cooling it, and then pulverizing it with a pulverizer to produce a coarse powder; or (iii) feeding the masterbatch composite into an extrusion molding machine and extruding it into shapes such as beads or columns. The molding method is not particularly limited; for example, injection molding, extrusion molding, thermoforming, blow molding, blow forming, or vacuum forming can be used.

[0088] (Adhesive composition)

[0089] The thermally conductive particles described in this embodiment can be added to an adhesive and used as an adhesive composition. The type of resin contained in the adhesive is not limited; any resin with adhesive properties, such as urethane, epoxy, vinyl acetate, or acrylic resins, is acceptable. Furthermore, the bonding mechanism is not limited; it can be any of the following: chemical reaction type, solvent evaporation type, hot melt type, or hot pressing type. The content of the thermally conductive particles in the adhesive composition is preferably 5% by mass or more and 80% by mass or less relative to the total adhesive composition, more preferably 10% by mass or more and 50% by mass or less. By setting the content of the thermally conductive particles within the above range, an adhesive composition with superior thermal conductivity, adhesiveness, water resistance, chemical resistance, and insulation can be produced. If the content of the thermally conductive particles exceeds 80% by mass, the bond strength may be insufficient. On the other hand, if the content of the thermally conductive particles is less than 5% by mass, the thermal conductivity may be insufficient.

[0090] The thermally conductive particles described in this embodiment, as thermally conductive articles and materials such as gravure inks, coating liquids, resin compositions, and adhesive compositions as described above, can also be used in electronic devices that possess heat dissipation (thermal conductivity) while also exhibiting excellent chemical resistance, water resistance, and insulation. More specifically, they can be used in metal circuit boards, circuit boards, metal laminates, metal-clad laminates with inner layer circuits, battery packaging materials, sealing materials, or protective sheets. Furthermore, they can be used as adhesive sheets, heat sinks, thermal coating agents, semiconductor sealants, adhesives, thermal pads, and greases.

[0091] <Liquid Composition (Resin Composition)>

[0092] The liquid composition (resin composition) involved in this embodiment is a liquid composition for forming a thermally conductive film, which contains a thermally conductive component (mixture) including the aforementioned thermally conductive particles, a forming resin, and a liquid medium as an optional component. It should be noted that the thermally conductive component preferably also contains at least one selected from the group consisting of barium sulfate, talc, boron nitride, and magnesium oxide.

[0093] The content of thermally conductive particles in the liquid composition is preferably 5% by mass or more and 80% by mass or less relative to the total liquid composition, more preferably 10% by mass or more and 70% by mass or less. Furthermore, the content of the thermally conductive component (mixture) is preferably 20 parts by mass or more and 600 parts by mass or less relative to 100 parts by mass of the forming resin, more preferably 20 parts by mass or more and 200 parts by mass or less. The thermally conductive film formed using the liquid composition prepared in this way exhibits excellent water resistance, chemical resistance, and insulation properties, while maintaining strength and also possessing excellent thermal conductivity.

[0094] The resin used for forming is at least one solvent-soluble resin selected from the group consisting of acrylic resins, urethane resins, urea resins, epoxy resins, rubber resins, fluorinated resins, polyamide resins, polyimide resins, silicone resins, cellulose resins, and thermoplastic elastomers. Furthermore, the liquid medium is the same as that used in the aforementioned coating liquid.

[0095] <Thermoconductive thin films and components for electronic devices>

[0096] The thermally conductive film involved in this embodiment is a film formed by coating the aforementioned article or the aforementioned liquid composition (resin composition). The thickness of the thermally conductive film is preferably 20 μm or more and 1000 μm or less, more preferably 50 μm or more and 200 μm or less.

[0097] Furthermore, the thermally conductive thin film described in this embodiment can also be used in components for electronic devices. This component for electronic devices comprises a metal component and the aforementioned thermally conductive thin film disposed on the surface of the metal component.

[0098] Examples of metal components include metal circuit boards, circuit boards, metal laminates, and metal-clad laminates with inner circuitry.

[0099] The resin composition described in this embodiment, when used in housings for electronic devices, motors (e.g., EV motors), lithium batteries, etc., can efficiently release internal heat to the outside, achieving weight reduction compared to conventional metal housings. Furthermore, the article described in this embodiment can also be used as a heat dissipation component in electronic device parts.

[0100] The present invention will be specifically described below based on the embodiments, but the present invention is not limited to these embodiments. It should be noted that, unless otherwise specified, "parts" and "%" in the embodiments and comparative examples are quality standards.

[0101] <Aluminum Raw Materials>

[0102] The aluminum raw materials shown below were used.

[0103] • A-1: ​​Aluminum hydroxide (spherical, average particle size 6μm)

[0104] • A-2: Aluminum hydroxide (spherical, average particle size 1 μm)

[0105] • A-3: Boehmite (spherical, average grain size 1 μm)

[0106] • A-4: Spherical alumina (spherical shape, average particle size 3μm)

[0107] • A-5: γ-alumina (irregular shape, average particle size 0.1 μm)

[0108] Zinc Raw Materials

[0109] The zinc raw materials shown below were used.

[0110] • B-1: Basic zinc carbonate (average particle size 10 μm)

[0111] • B-2: Zinc oxide (average particle size 1 μm)

[0112] •B-3: Zinc aluminate (average particle size 10μm)

[0113] Other ingredients

[0114] The following raw materials were used.

[0115] C-1: Boric acid

[0116] C-2: Sodium tungstate dihydrate

[0117] C-3: Titanium oxide

[0118] C-4: Basic bismuth carbonate

[0119] C-5: Sodium fluoride

[0120] C-6: Aluminum fluoride

[0121] Thermally conductive filler

[0122] The packing material shown below was used.

[0123] • D-1: Barium sulfate (average particle size 0.9 μm)

[0124] • D-2: Talc (average particle size 4.3 μm)

[0125] • D-3: Boron nitride (average particle size 20 μm)

[0126] • D-4: Magnesium oxide (average particle size 20 μm)

[0127] Manufacturing of thermally conductive particles

[0128] Example 1

[0129] 100 parts of aluminum hydroxide (A-1), 27.3 parts of basic zinc carbonate (B-1), 0.5 parts of boric acid (C-1), and 0.5 parts of sodium tungstate dihydrate (C-2) were added to a small mixer and stirred to obtain a raw material mixture. The resulting raw material mixture was then calcined in air at 1250°C for 3 hours and subsequently crushed to obtain powdered thermally conductive particles. Powder X-ray diffraction confirmed the presence of α-alumina and spinel-structured zinc aluminate.

[0130] (Examples 2-22)

[0131] Except for the types and amounts of raw materials shown in Table 1, powdered thermally conductive particles were obtained in the same manner as in Example 1. It should be noted that for the thermally conductive fillers of Examples 18-22, the amounts listed in the table were added relative to 100 parts by mass of the calcined thermally conductive particles, and then the mixture was stirred using a small mixer. The presence of α-alumina and spinel-crystal zinc aluminate was confirmed by powder X-ray diffraction.

[0132] (Compare Examples 1-11 and 14)

[0133] Except for the types and amounts of raw materials shown in Table 1, powdered thermally conductive particles were obtained in the same manner as in Example 1. It should be noted that for the thermally conductive filler of Comparative Example 11, the amounts listed in the table were added relative to 100 parts by mass of the calcined thermally conductive particles, and then the mixture was stirred using a small mixer. The presence of α-alumina and spinel-crystal zinc aluminate was confirmed by powder X-ray diffraction.

[0134] Comparative Examples 12, 13 and 15–17

[0135] The raw material monomers shown in Table 1 were used as samples for Comparative Examples 12, 13 and 15-17, respectively.

[0136] (Comparative Example 18)

[0137] Using the types and amounts of raw materials shown in Table 1, the firing temperature was set to 900°C, and otherwise, thermally conductive powder particles were obtained in the same manner as in Example 1 above. Although powder X-ray diffraction was performed, the presence of α-alumina could not be confirmed.

[0138] [Table 1]

[0139]

[0140] (Determination of thermal conductivity)

[0141] A resin composition was prepared by mixing 30 parts of an epoxy resin (Mitsubishi Chemical Co., Ltd., grade 871, epoxy equivalent 390-470 g / eq, viscosity 400-900 mPa·s) and an amine curing agent (ADEKA Co., Ltd., EH-6024, amine value 370 mg KOH / g) at a ratio of 3.5:1, and then mixing this mixture with 70 parts of the obtained thermally conductive particles. The mixture was molded into circular sheets with a diameter of 100 mm or more and a thickness of 4 mm. The sheets were then cured at a set temperature of 120°C for 1 hour, cooled, and cut into quarters with a central angle of 90° to prepare test pieces. The thermal conductivity of the test pieces was measured using a hot plate thermophysical property measuring device (trade name "TPS-2500S", Kyoto Electronics Co., Ltd.). The results are shown in Table 2.

[0142] (Viscosity measurement)

[0143] 50g of the obtained thermally conductive particles were added to 50g of epoxy resin (Mitsubishi Chemical Corporation, grade 871, epoxy equivalent 390-470g / eq, viscosity 400-900mPa·s) and manually mixed. The manually mixed resin composition was then mixed using a planetary centrifugal mixer (mixing: 1000rpm, 1 minute; degassing: 2000rpm, 1 minute). The viscosity of the resin composition obtained by the above method was measured using an E-type viscometer (trade name "TV-100EH / 200", Toki Sangyo Co., Ltd.) at a temperature of 25°C, a conical rotor (3°×R9.7), and a rotation speed of 100s. -1 Viscosity was measured. Judgment was performed according to the following criteria. The results are shown in Table 2.

[0144] A: Below 3000 mPa·s

[0145] C: greater than 3000 mPa·s

[0146] (Abrasion test)

[0147] Approximately 500g of SUS304 steel balls (trade name "1-9762-02", manufactured by MISUMI) with a diameter of 5mm and approximately 100g of the resulting thermally conductive particles were placed in a 250mL I-BOY wide-mouth bottle (diameter 62mm, length 132mm, manufactured by AS ONE). The bottle was rotated at 80rpm for 3 hours around the central axis of the cylinder. The steel balls and thermally conductive particles were then separated using a 1mm mesh sieve to obtain the thermally conductive particles after the abrasion test. The degree of abrasion was determined by mixing 4g of the abrasion-tested thermally conductive particles with 8g of lithium borate and pulverizing the mixture in a mortar for 5 minutes. Similarly, the thermally conductive particles before the abrasion test were mixed and pulverized in a mortar, and the intensity of iron was measured using a fluorescence X-ray analysis device (trade name "ZSX PrimusII", manufactured by Rigaku Corporation). The difference in the intensity (kcps) of iron fluorescence X-rays before and after the abrasion test was calculated using the following formula. The results are shown in Table 2.

[0148] Wear degree = (Intensity of X-ray fluorescence of iron after wear test) - (Intensity of X-ray fluorescence of iron before wear test)

[0149] A: Wear rate is below 4kcps

[0150] B: Wear degree greater than 4kcps and less than 8kcps

[0151] C: Wear degree greater than 8kcps

[0152] (Acid resistance)

[0153] Evaluation resin molded articles formed from a resin composition containing 70 parts by weight of the thermally conductive particles prepared above were cut into pieces of 20 mm × 20 mm × 60 mm in size. The molded articles were then immersed in a hydrochloric acid solution at pH 2.0 heated to 50°C for 3 hours. Voltage resistance was measured before and after immersion, and acid resistance was determined using the obtained values ​​according to the following criteria. The results are shown in Table 2.

[0154] <Criteria for determining acid resistance>

[0155] A: The withstand voltage after impregnation decreases by less than 10% compared to the initial value before impregnation.

[0156] B: The withstand voltage after impregnation decreases by more than 10% but less than 50% compared to the initial value before impregnation.

[0157] C: The withstand voltage after impregnation is reduced by more than 50% compared to the initial value before impregnation (water resistance).

[0158] Five parts of thermally conductive granules were immersed in 100 parts of pure water, placed in a container, boiled at 100°C for 5 minutes, and then filtered. The filtrate was used as the test sample. Using the test sample prepared as described above, the conductivity was measured using a conductivity meter, and the results were judged and evaluated according to the following criteria. The results are shown in Table 2.

[0159] <Criteria for determining water resistance>

[0160] A: The conductivity after impregnation increased by less than 300 μS / cm compared to the initial value before impregnation.

[0161] B: The conductivity after impregnation increases by more than 300 μS / cm but less than 1000 μS / cm compared to the initial value before impregnation.

[0162] C: The conductivity after impregnation increases by more than 1000 μS / cm compared to the initial value before impregnation.

[0163] [Table 2]

[0164]

[0165] (Refer to Example 1)

[0166] For the thermal conductivity determination, 70 parts of the thermally conductive particles obtained in Example 1 were used to prepare test pieces. As a method for testing thermal conductivity, a resin composition obtained by mixing 30 parts of polypropylene (manufactured by Prime Polymer, MFR: 20 g / 10 min) with 70 parts of the thermally conductive particles was placed in a plasticizer and melt-blended at a set temperature of 200°C. Next, test pieces were prepared by die-pressing using a mold with dimensions of 20 mm x 20 mm x 6 mm at 175°C. The thermal conductivity of the prepared test pieces was measured using a thermophysical property measuring device (trade name "TPS-2500S", manufactured by Kyoto Electronics Industry Co., Ltd.). The thermal conductivity at this time was 1.18 W / m·K.

[0167] (Refer to Example 2)

[0168] Test pieces were prepared using 60 parts of the thermally conductive particles obtained in Example 1 and 10 parts of the thermally conductive circular disc-shaped particles described in Example 3 of Japanese Patent No. 7185798. Otherwise, the test pieces were prepared in the same manner as in Reference Example 1. The thermal conductivity was 1.19 W / m·K. Even when mixing particles of different shapes, the results were approximately the same as those obtained using only the thermally conductive particles, falling within the scope of the examples.

[0169] (Refer to Comparative Example 1)

[0170] Except for the use of 70 portions of thermally conductive particles obtained in Comparative Example 7 to prepare test pieces, test pieces were prepared in the same manner as in Reference Example 1. The thermal conductivity at this time was 0.92 W / m·K.

[0171] (Refer to Comparative Example 2)

[0172] Except for the use of 70 parts of thermally conductive particles obtained in Comparative Example 14 to prepare test pieces, test pieces were prepared in the same manner as in Reference Example 1. The thermal conductivity at this time was 1.07 W / m·K.

[0173] <Preparation and Evaluation of Adhesives>

[0174] (Application Example 1 and Comparison Application Example 1)

[0175] Thirty-five parts each of the thermally conductive particles obtained in Example 1 and Comparative Example 13 were mixed with 65 parts of polyester polyol with a viscosity of 300 mPa·s and dispersed using a disperser to prepare dispersions. Ninety-eight parts of the prepared dispersions were mixed with two parts of polyisocyanate with a viscosity of 2600 mPa·s and stirred using a dissolver to obtain a urethane resin-based chemically reactive adhesive. Each adhesive was uniformly coated onto release paper using a glass rod and placed in an oven at 100°C for 2 minutes to allow the solvent components to evaporate. Then, it was placed in an oven at 40°C for 96 hours to form a cured film of the adhesive (Application Example 1 and Comparative Application Example 1). The thermal conductivity of the cured film was measured, and the thermal conductivity of the cured film of Comparative Application Example 1, formed using α-alumina from Comparative Example 13, was 0.49 W / m·K. In contrast, it can be seen that the thermal conductivity of the cured coating of Application Example 1 formed using the thermally conductive particles of Example 1 is as high as 0.56 W / m·K.

[0176] Evaluation of thermally conductive particles

[0177] (Determination of thermal conductivity (block))

[0178] A resin composition obtained by mixing 50 parts of polypropylene (manufactured by Prime Polymer, MFR: 20 g / 10 min) and 50 parts of each thermally conductive component was placed in a plasticizer and melt-blended at a set temperature of 200°C. Next, using a mold with dimensions of 20 mm (length) × 20 mm (width) × 6 mm (height), it was molded at 175°C to obtain a test piece. The thermal conductivity of the obtained test piece was measured using the "Standard Isotropic Measurement Module" of a thermophysical property measuring device (trade name "TPS-2500S", manufactured by Kyoto Electronics Industry Co., Ltd.). The thermal conductivity formed using α-alumina from Comparative Example 13 was 0.43 W / m·K. In contrast, the thermal conductivity formed using the thermally conductive particles of Example 4 was as high as 0.59 W / m·K.

[0179] (Dielectric strength)

[0180] A resin composition obtained by mixing 30 parts of polypropylene (manufactured by Prime Polymer, MFR 20 g / 10 min) with 70 parts of thermally conductive granules was placed in a plasticizer and melt-blended at a set temperature of 200°C. Next, it was molded at 175°C to produce an evaluation molded body. The obtained evaluation molded body was cut into 100 mm × 100 mm × 1 mm thickness pieces to obtain test pieces. The obtained test pieces were immersed in oil, and the dielectric breakdown voltage was measured according to JIS K6911 and C2110-1 under AC 10 mA and a voltage increase rate of 2 kV / sec. The dielectric strength (kV / mm) obtained by dividing the measured dielectric breakdown voltage by the thickness (mm) of the test piece is shown in Table 3.

[0181] [Table 3]

[0182] Dielectric strength (kV / mm) Example 4 37 Comparative Example 13 30 Resin only 56

Claims

1. A thermally conductive particle, comprising at least a calcined product obtained by calcining aluminum raw material, zinc raw material, and other raw materials besides said aluminum and zinc raw materials, wherein, The content of zinc raw material relative to 100 parts by weight of the aluminum raw material is 25 parts by weight or more and 70 parts by weight or less. The other raw materials contain at least one selected from the group consisting of boron compounds, tungsten compounds, titanium compounds, bismuth compounds, and fluorine compounds. The content of the other raw materials relative to 100 parts by weight of the aluminum raw material is 0.05 parts by weight or more and 20 parts by weight or less, and meets the following conditions: (1) 50g of the thermally conductive particles and epoxy equivalent of 200g / eq or more and 1000g / eq or less were mixed and tested using an E-type viscometer at a measurement temperature of 25°C, a conical rotor (3°×R9.7), and a rotation speed of 100s. -1 Under the conditions described, 50g of epoxy resin with a viscosity of 400mPa·s or higher and 900mPa·s or lower was mixed and then mixed at 1000rpm for 1 minute and 2000rpm for 1 minute using a planetary centrifugal mixer. The resulting resin composition for viscosity measurement was then tested using an E-type viscometer at a measurement temperature of 25°C, a conical rotor (3°×R9.7), and a rotation speed of 100s. -1 The viscosity measured under the specified conditions was below 3000 mPa·s; (2) Place 500 parts by mass of SUS304 steel balls with a diameter of 5mm and 100 parts by mass of the thermally conductive particles into a 250mL cylindrical container with a wide mouth. Rotate the container at 80rpm for 3 hours with the central axis of the cylinder as the rotation axis. Separate the steel balls and thermally conductive particles with a sieve with a sieve hole of 1mm to obtain the thermally conductive particles after the wear test. Mix 4 parts by mass of the thermally conductive particles before and after the wear test with 8 parts by mass of lithium borate. Crush the mixture in a mortar for 5 minutes. Measure the intensity of iron element using a fluorescence X-ray analysis device. The wear degree is calculated to be below 4kcps based on the intensity of fluorescence X-rays of iron element before and after the wear test (kcps). Wear degree = (Intensity of X-ray fluorescence of iron after wear test) - (Intensity of X-ray fluorescence of iron before wear test) (3) For a resin composition obtained by mixing 30 parts of an epoxy resin with an epoxy equivalent of 200 g / eq or more and 1000 g / eq or less and an amine curing agent with an amine value of 100 mg KOH / g or more and 500 mg KOH / g or less in a ratio of 3:1 to 4:1 with 70 parts of thermally conductive particles, the composition is molded into a circular sheet with a diameter of 100 mm or more and a thickness of 4 mm or more, heated and cured at a set temperature of 120°C for 1 hour, and after cooling, cut into quarters in a fan shape with a central angle of 90°. The thermal conductivity measured by the hot plate method is 0.80 W / m·K or more.

2. The thermally conductive particles according to claim 1, wherein, The other raw materials (excluding fluorine compounds) are at least one selected from the group consisting of oxides, oxyacid salts, hydroxides, carbonates and basic carbonates.

3. The thermally conductive particles according to claim 1, wherein the particles contain at least one element selected from the group consisting of iron, cobalt, copper, manganese, nickel and chromium and are colored.

4. A mixture obtained by mixing a thermally conductive filler into thermally conductive particles according to any one of claims 1 to 3.

5. The mixture according to claim 4, wherein, The thermally conductive filler is at least one selected from the group consisting of barium sulfate, talc, boron nitride, and magnesium oxide.

6. A method for manufacturing thermally conductive particles, wherein, The method for manufacturing the thermally conductive particles according to any one of claims 1 to 3 is a method of firing a mixture of raw materials containing aluminum raw material, zinc raw material, and other raw materials besides the aluminum raw material and zinc raw material, wherein the aluminum raw material is at least one selected from the group consisting of boehmite, aluminum hydroxide and aluminum oxide, and the zinc raw material is at least one selected from the group consisting of zinc oxide and basic carbonate.

7. A method for manufacturing thermally conductive particles, wherein the raw material mixture of claim 6 is fired at a temperature above 1000°C and below 1600°C.

8. An article comprising the thermally conductive particles according to any one of claims 1 to 3.

9. The article according to claim 8, wherein it is any one of gravure ink, coating liquid, resin composition and adhesive composition.

10. A resin composition for forming a thermally conductive resin composition, said resin composition comprising the mixture of claim 4 and a forming resin.

11. The resin composition according to claim 10, wherein, The content of the mixture relative to the total amount of the forming resin is 5% by mass or more and 95% by mass or less.

12. A thermally conductive thin film formed by coating the article of claim 9.

13. The article according to claim 8, which serves as a heat dissipation component for any of electronic device components, electronic device housings, EV motors, and lithium batteries.

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