Thermally conductive composition

Abstract

Provided is a thermally conductive composition having excellent thermal conductivity and excellent workability. The present invention is a composition containing the following components: (A) 100 parts by mass of gallium and / or an alloy thereof having a melting point of-20 to 100 DEG C; and (B) 2-150 parts by mass of a metal oxide and / or a metal nitride having an average particle diameter of 0.01-200 [mu] m relative to 100 parts by mass of component (A). Wherein the total content of the component (A) and the component (B) in the composition is 95-100 mass%. The gallium alloy of the component (A) in the thermally conductive composition is one or more types selected from the group consisting of a Ga-In alloy, a Ga-Sn-Zn alloy, a Ga-In-Sn alloy, and a Ga-In-Bi-Sn alloy.

Description

Technical Field

[0001] The present invention relates to a thermally conductive composition having excellent thermal conductivity and excellent handleability. Background Art

[0002] Many heat-dissipating electronic components, such as CPUs, mounted on printed circuit boards utilize heat sinks and other heat dissipators to prevent damage and performance degradation caused by temperature increases during use. To efficiently transfer the heat generated by these components to the heat sink, a thermally conductive material is typically used between the components and the heat sink. However, as electronic components become more advanced, the amount of heat they dissipate is increasing, necessitating the development of materials and components with superior thermal conductivity.

[0003] Generally, electrical and electronic components generate heat during use. Therefore, proper operation of these components requires heat removal measures. Various heat-conductive materials for heat removal have been disclosed. These heat-conductive materials are generally classified into two forms: 1) easy-to-handle sheet form and 2) paste form.

[0004] Heat sinks can be easily attached to heat-dissipating electronic components and heat sinks. However, due to the presence of gaps at the interface with these components and heat sinks, interfacial thermal resistance increases, resulting in insufficient thermal conductivity. Meanwhile, paste-like heat dissipation materials, with their properties similar to those of liquids, are less susceptible to surface irregularities on heat-dissipating electronic components and heat sinks, allowing for close contact and reduced interfacial thermal resistance. However, this does not provide sufficient heat dissipation performance.

[0005] Therefore, for example, Patent Documents 1 to 5 disclose materials containing low-melting-point metals, metal fillers, etc. as components for imparting thermal conductivity to silicone resins. However, with the recent increase in the integration and speed of heat-dissipating electronic components, the amount of heat released has further increased, and therefore these heat-conductive materials have not been able to achieve sufficient thermal conductivity effects.

[0006] In addition, if base oils used as base materials, such as polyorganosiloxane (including silicone oil, silicone rubber, silicone resin) and hydrocarbon-based synthetic oils, are added to conventional thermally conductive compositions, the thermal conductivity of the thermally conductive compositions may decrease. Therefore, it is preferable not to include these components.

[0007] Patent Documents 6 to 8 disclose heat dissipating greases based on low-melting-point metals (including alloys of gallium, indium, and tin) and containing thermally conductive fillers. The types of fillers are tungsten, molybdenum, and metallic silicon in Patent Document 7, boron nitride, aluminum oxide, and aluminum nitride in Patent Document 6, and ceramic powder in Patent Document 8. However, Patent Documents 6 and 8 do not evaluate the appearance, operability, thermal conductivity, etc. of the compositions.

[0008] Regarding Patent Document 9, the filler is a metal fine powder, and silver powder, copper powder, etc. are used in the examples. However, the thermal conductivity is about 10 to 30 W / (m·K), which is not sufficient.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-176414

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 2005-112961

[0013] Patent Document 3: Japanese Patent Application Laid-Open No. 2003-218296

[0014] Patent Document 4: Japanese Patent Application Laid-Open No. 2004-039829

[0015] Patent Document 5: Japanese Patent Application Laid-Open No. 2007-106809

[0016] Patent Document 6: Japanese Patent Application Laid-Open No. 03-071992

[0017] Patent Document 7: Japanese Patent Application Laid-Open No. 2001-329068

[0018] Patent Document 8: Japanese Patent Application Laid-Open No. 2004-071816

[0019] Patent Document 9: Japanese Patent Application Laid-Open No. 2012-1111823 Summary of the Invention

[0020] Problems to be solved by the invention

[0021] Therefore, an object of the present invention is to provide a thermally conductive composition that is substantially free of base oils such as polyorganosiloxanes (including silicone oils, silicone rubbers, and silicone resins) and hydrocarbon-based synthetic oils, which have been used as base materials in conventional thermally conductive compositions, and that exhibits excellent thermal conductivity and handleability.

[0022] Solutions to the Problem

[0023] The present inventors have conducted intensive research to address the aforementioned issues and have developed a thermally conductive composition that, by blending gallium and / or a gallium alloy with a metal oxide and / or metal nitride of a specific particle size, reduces the fluidity of the low-melting-point metal, improves handleability in a paste-like form, and exhibits a high thermal conductivity of 30 W / m·K or higher.

[0024] The present invention was further developed based on the discovery that, similar to conventional thermally conductive greases, this thermally conductive composition can be placed so as to be sandwiched between a heat-generating electronic component and a heat-dissipating member, thereby following the irregularities on the surface of the component or member without creating any gaps. This allows the composition to be used as a thermally conductive layer with low thermal resistance. Heat generated during operation of the heat-generating electronic component is rapidly conducted to the heat-dissipating member via the thermally conductive layer containing gallium and / or its alloy, which is retained in the aforementioned structure, thereby achieving excellent heat dissipation performance.

[0025] That is, the present invention provides the following thermally conductive composition. [1]

[0027] A thermally conductive composition comprising the following components:

[0028] (A) Gallium and / or its alloy having a melting point of -20 to 100°C: 100 parts by mass; and

[0029] (B) a metal oxide and / or metal nitride having an average particle size of 0.01 μm to 200 μm: 2 to 150 parts by mass relative to 100 parts by mass of component (A);

[0030] The total content of the component (A) and the component (B) in the composition is 95 to 100% by mass. [2]

[0032] The thermally conductive composition according to [1], wherein

[0033] The total content of the component (A) and the component (B) in the composition is 98 to 100% by mass. [3]

[0035] The thermally conductive composition according to [1] or [2], wherein

[0036] The gallium alloy of the component (A) is one or more selected from the group consisting of a Ga—In alloy, a Ga—Sn—Zn alloy, a Ga—In—Sn alloy, and a Ga—In—Bi—Sn alloy.

[0037] [4] The thermally conductive composition according to any one of [1] to [3], wherein

[0038] The component (B) is one or more selected from the group consisting of zinc oxide powder, aluminum oxide powder, boron nitride powder, silicon nitride powder, aluminum nitride powder, aluminum hydroxide powder, and magnesium oxide powder.

[0039] [5] The thermally conductive composition according to any one of [1] to [4], wherein

[0040] The present invention further comprises 0.01 to 10 parts by mass of the following hydrophobic spherical silica fine particles as the component (C), based on 100 parts by mass of the component (A).

[0041] The hydrophilic spherical silica particles are obtained by hydrolyzing and condensing a tetrafunctional silane compound, a partially hydrolyzed condensation product thereof or a mixture thereof and are substantially composed of SiO2 units. 1 SiO 3 / 2 Unit (R 1 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms), and R 2 3SiO 1 / 2 Unit (each R 2 is the same or different, substituted or unsubstituted monovalent hydrocarbon group with 1 to 8 carbon atoms), the particle size is in the range of 0.005 to 1 μm, the particle size distribution D 90 / D 10 Hydrophobic spherical silica fine particles having a value of 3 or less and an average circularity of 0.8 to 1.

[0042] [6] The thermally conductive composition according to any one of [1] to [5], wherein

[0043] Furthermore, the organic silane represented by the following general formula (1) is contained as the component (D) in an amount of 0.001 to 10 parts by mass relative to 100 parts by mass of the component (A).

[0044] R 1 a R 2 b Si(OR 3 ) 4-a-b (1)

[0045] (In the formula, R 1 are independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, R 2 are each independently a substituted or unsubstituted monovalent hydrocarbon group other than an alkyl group, R 3 are identical or different monovalent hydrocarbon groups having 1 to 6 carbon atoms, a is a number from 1 to 3, b is a number from 0 to 2, and the sum of a+b is a number from 1 to 3.

[0046] Effects of the Invention

[0047] The thermally conductive composition of the present invention exhibits strong interfacial activity, sufficient wetting and spreading during stretching, excellent workability, and high thermal conductivity. Therefore, the composition of the present invention is useful for components that, when previously used alone, would form droplets due to surface tension and be difficult to handle. Furthermore, by combining components (B) with different average particle sizes, a thermally conductive composition with a high thermal conductivity of 70 W / m·K or higher and excellent workability can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a photograph showing that when the discharged composition is spread with a spatula, it becomes fully wet and spread.

[0049] Figure 2 This is a photograph showing that when the discharged composition is spread with a spatula, it fails to become fully wet and spread. DETAILED DESCRIPTION

[0050] Hereinafter, the present invention will be described in detail.

[0051] (A)Ingredients

[0052] Component (A) of the composition of the present invention is gallium or a gallium alloy, and its melting point must be in the range of -20 to 100°C. Component (A) below -20°C is difficult to produce and is therefore not economically preferred. Component (A) above 100°C does not melt quickly during the composition preparation process, sometimes resulting in poor workability or precipitation during production, leading to unevenness. Therefore, gallium or a gallium alloy with a melting point in the range of -20 to 100°C is a necessary condition for economic and operational considerations, and is also within the appropriate range. A melting point in the range of -20 to 50°C is particularly preferred.

[0053] The melting point of metallic gallium is 29.8° C. Representative gallium alloys having a melting point within the above-mentioned range include gallium-indium alloys, such as Ga-In (mass ratio = 75.4:24.6, melting point = 15.7° C.), gallium-tin alloys, gallium-tin-zinc alloys, such as Ga-Sn-Zn (mass ratio = 82:12:6, melting point = 17° C.), gallium-indium-tin alloys, such as Ga-In-Sn (mass ratio = 68.5:21.5:10, melting point = 19° C. or mass ratio = 62.0:25.0:13.0, melting point = 5.0° C. or mass ratio = 21.5:16.0:62.5, melting point = 10.7° C.), and gallium-indium-bismuth-tin alloys, such as Ga-In-Bi-Sn (mass ratio = 9.4:47.3:24.7:18.6, melting point = 48.0° C.).

[0054] (A) Component may be used alone or in combination of two or more.

[0055] Gallium and / or its alloy present in the composition of the present invention is a low melting point metal and can be used as a base material (matrix). In other words, the low melting point metal is the main component of the thermally conductive composition of the present invention.

[0056] It should be noted that if base oils used as base materials in conventional thermally conductive compositions, such as polyorganosiloxanes (including silicone oils, silicone rubbers, and silicone resins) or hydrocarbon-based synthetic oils, are added to the composition of the present invention, the thermal conductivity of the composition of the present invention may decrease. Therefore, it is preferable to exclude these components. The upper limit of the content of these components in the overall composition of the present invention is preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and particularly preferably substantially no content.

[0057] (B) Ingredients

[0058] The composition of the present invention includes a metal oxide and / or metal nitride as a thermally conductive filler. There are no particular restrictions on the type of thermally conductive filler, and powders used in conventional heat dissipation (thermal conductive) greases can be used. In particular, it can be a substance with high thermal conductivity, preferably one or more selected from zinc oxide powder, aluminum oxide powder, boron nitride powder, silicon nitride powder, aluminum nitride powder, aluminum hydroxide powder, and magnesium oxide powder. These thermally conductive fillers may also be powders whose surfaces have been hydrophobized using organic silanes, organic silazanes, organic polysiloxanes, organic fluorine compounds, or the like, as needed.

[0059] The average particle size of the thermally conductive filler is 0.01 to 200 μm, preferably 0.1 to 150 μm, and more preferably 0.5 to 120 μm. Even if the average particle size of the thermally conductive filler is less than 0.01 μm or exceeds 200 μm, the filling rate of the obtained composition cannot be improved, so it is sometimes not preferred. These thermally conductive fillers can be used alone or as a mixture of two or more types with different average particle sizes. The above average particle size is the cumulative average particle size based on volume. The average particle size can be measured using a laser diffraction scattering particle size distribution measuring device, for example, it can be measured using the MICROTRAC MT3300EX particle size analyzer manufactured by Nikkiso Co., Ltd.

[0060] The amount of the thermally conductive filler added is in the range of 2 to 150 parts by mass, preferably 2 to 100 parts by mass, more preferably 2 to 80 parts by mass, and even more preferably 5 to 60 parts by mass, relative to 100 parts by mass of component (A). If the amount of the thermally conductive filler added is less than 2 parts by mass, the composition may not have sufficient thermal conductivity. Furthermore, if the amount of the thermally conductive filler added exceeds 150 parts by mass, it may not be dispersed in the low-melting-point metal and may become powdery.

[0061] It is preferred to use two or more metal oxides and / or metal nitrides having different average particle sizes as the component (B) because the thermal conductivity of the composition is improved.

[0062] For example, the component (B) preferably contains 55% by mass or more and less than 100% by mass of a component having an average particle size of 70 to 200 μm, more preferably 57 to 90% by mass, and even more preferably 59 to 85% by mass, based on the mass of the entire component (B).

[0063] The total content of the component (A) and the component (B) in the entire composition of the present invention is 95 to 100% by mass, preferably 98 to 100% by mass, and more preferably 99 to 100% by mass.

[0064] The following components are optional components and can be added as needed.

[0065] (C) Ingredients

[0066] The component (C) of the composition of the present invention is hydrophobic spherical silica fine particles, wherein R is introduced on the surface of hydrophilic spherical silica fine particles consisting essentially of SiO2 units obtained by hydrolysis and condensation of a tetrafunctional silane compound, a partially hydrolyzed condensation product thereof, or a mixture thereof. 1 SiO 3 / 2 Unit (R 1 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms) and R 2 3SiO 1 / 2 Unit (each R 2 The particles are the same or different, substituted or unsubstituted monovalent hydrocarbon groups with 1 to 6 carbon atoms), the particle size is in the range of 0.005 to 1 μm, and the particle size distribution is D 90 / D 10 The value of is 3 or less, and the average circularity is 0.8 to 1.

[0067] The hydrophobic spherical silica particles preferably have a particle size of 0.005 to 1 μm, more preferably 0.01 to 0.3 μm, and particularly preferably 0.03 to 0.25 μm. If the particle size is less than 0.005 μm, aggregation becomes severe, while if the particle size is greater than 1 μm, the viscosity-lowering effect of the grease composition may be insufficient.

[0068] D is an indicator of the particle size distribution of the hydrophobic spherical silica fine particles. 90 / D 10 The value of is preferably 3 or less, more preferably 2.9 or less. 10 and D 90 When measuring the particle size distribution of a powder, the particle size at which 10% of the particles are accumulated from the smallest particle size is called D. 10 The particle size that accumulates to 90% from the smaller particle size side is called D 90 . Because the D 90 / D 10 Since the particle size distribution of the hydrophobic spherical silica particles in the present invention is characterized by a sharp curve, the particle size distribution is 3 or less. Such sharp and uniform particles are preferred because they are effective in reducing the viscosity of the grease composition.

[0069] In the present invention, the particle size distribution of microparticles is measured using a NANOTRAC particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., Japan, trade name: UPA-EX150) using a dynamic light scattering / laser Doppler method, with the volume-based median diameter being used as the particle size. The median diameter refers to the particle size corresponding to the cumulative 50th percentile when the particle size distribution is expressed as a cumulative distribution.

[0070] In addition, the average circularity of the above-mentioned hydrophobic spherical silica particles is preferably 0.8 to 1. Here, "spherical" includes not only true spheres but also slightly deformed spheres. Such a "spherical" shape refers to a shape whose circularity is evaluated by projecting the particles into two dimensions and is in the range of 0.8 to 1. Here, circularity means (the circumference of a circle equal to the area of ​​the particle) / (the circumference of the particle). In addition, the average circularity is the average value of the circularity of 10 silica particles. The circularity can be measured by image analysis of a particle image obtained by an electron microscope or the like.

[0071] In this specification, the phrase "hydrophilic spherical silica particles consisting essentially of SiO2 units" means that the particles are essentially composed of SiO2 units, but are not exclusively composed of these units. As is generally known, the particles possess multiple silanol groups at least on their surface. Furthermore, the phrase "hydrolyzable groups (hydrocarbyloxy groups) derived from the tetrafunctional silane compound used as a raw material and / or its partial hydrolysis-condensation products" may not be converted into silanol groups, but may remain in small amounts on the surface or within the particles.

[0072] In the composition of the present invention, when small-particle silica obtained by hydrolysis of tetraalkoxysilane (sol-gel method) is used as a silica raw material (silica before hydrophobization treatment) and is subjected to a specific surface treatment to obtain a powder (hydrophobic spherical silica fine particles), the particle size after the hydrophobization treatment retains the primary particle size of the silica raw material, thereby preventing the aggregation of the hydrophobic spherical silica fine particles.

[0073] In order to obtain silica raw materials of any particle size, the following reaction conditions can be changed: using tetraalkoxysilane with a small number of carbon atoms in the alkoxy group as the silica raw material, using alcohol with a small number of carbon atoms as the solvent, increasing the hydrolysis temperature, reducing the concentration of tetraalkoxysilane during hydrolysis, and reducing the concentration of the hydrolysis catalyst.

[0074] By subjecting the silica raw material to a specific surface treatment, the desired hydrophobic spherical silica particles can be obtained.

[0075] Hereinafter, the method for producing the hydrophobic spherical silica fine particles will be described in detail, but the method for producing the hydrophobic spherical silica fine particles is not limited thereto.

[0076] <Method for producing hydrophobic spherical silica fine particles as component (C)>

[0077] The hydrophobic spherical silica fine particles of component (C) are obtained by the following steps:

[0078] Step (C1): a step of synthesizing hydrophilic spherical silica particles;

[0079] Step (C2): Surface treatment step using a trifunctional silane compound; and

[0080] Step (C3): Surface treatment step using a monofunctional silane compound.

[0081] Hereinafter, each step will be described in order.

[0082] Step (C1): Synthesis of hydrophilic spherical silica microparticles

[0083] The general formula (I)

[0084] Si(OR 3 )4 (I)

[0085] (In the general formula, each R 3 The tetrafunctional silane compound represented by (a) is a monovalent hydrocarbon group having 1 to 6 carbon atoms, which may be the same or different. A partially hydrolyzed product thereof, or a mixture thereof, is hydrolyzed and condensed in a mixed solution of a hydrophilic organic solvent containing an alkaline substance and water to obtain a mixed solvent dispersion of hydrophilic spherical silica fine particles.

[0086] In the general formula (I), R 3 It is a monovalent hydrocarbon group having 1 to 6 carbon atoms, preferably a monovalent hydrocarbon group having 1 to 4 carbon atoms, and particularly preferably a monovalent hydrocarbon group having 1 to 2 carbon atoms. 3 Examples of the monovalent hydrocarbon group include alkyl groups such as methyl, ethyl, propyl and butyl groups, and aryl groups such as phenyl groups. Preferred examples include methyl, ethyl, propyl and butyl groups, and particularly preferred examples include methyl and ethyl groups.

[0087] Examples of the tetrafunctional silane compound represented by the general formula (I) include:

[0088] Tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane; and tetraphenoxysilane, preferably tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane, particularly preferably tetramethoxysilane and tetraethoxysilane. Examples of partial hydrolysis-condensation products of the tetrafunctional silane compound represented by general formula (I) include alkyl silicates such as methyl silicate and ethyl silicate.

[0089] The hydrophilic organic solvent is not particularly limited as long as it can dissolve the tetrafunctional silane compound represented by the general formula (I), its partial hydrolysis-condensation product, and water. Examples thereof include alcohols such as methanol, ethanol, propanol, isopropanol, and butanol; cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, and acetic cellosolve; ketones such as acetone and methyl ethyl ketone; and ethers such as dioxane and tetrahydrofuran. Alcohols and cellosolves are preferred, and alcohols are particularly preferred.

[0090] Examples of the alcohols include alcohols represented by the following general formula (VII).

[0091] R 11 OH(VII)

[0092] (In the formula, R 11It is a monovalent hydrocarbon group having 1 to 6 carbon atoms.

[0093] In the general formula (VII), R 11 A monovalent hydrocarbon group having 1 to 4 carbon atoms is preferred, and a monovalent hydrocarbon group having 1 to 2 carbon atoms is particularly preferred. 11 The monovalent hydrocarbon group represented by , for example, alkyl groups such as methyl, ethyl, propyl, isopropyl, and butyl can be exemplified, preferably methyl, ethyl, propyl, and isopropyl can be exemplified, and more preferably methyl and ethyl can be exemplified. As the alcohol represented by general formula (VII), for example, methanol, ethanol, propanol, isopropyl alcohol, butanol, etc. can be exemplified, preferably methanol and ethanol can be exemplified. If the number of carbon atoms in the alcohol increases, the particle size of the spherical silica particles sometimes generated becomes larger. Therefore, in order to obtain the target small-particle silica (silicon dioxide raw material), methanol is preferably used.

[0094] In addition, examples of the alkaline substance include ammonia, dimethylamine, and diethylamine, preferably ammonia and diethylamine, and particularly preferably ammonia. These alkaline substances are dissolved in water in a desired amount, and the resulting aqueous solution (alkaline) is mixed with the hydrophilic organic solvent.

[0095] The amount of the alkaline substance used is preferably 0.01 to 2 mol, more preferably 0.02 to 0.5 mol, and particularly preferably 0.04 to 0.12 mol per 1 mol of the total hydrocarbyloxy groups of the tetrafunctional silane compound represented by general formula (I) and / or its partial hydrolysis-condensation product. In this case, the smaller the amount of alkaline substance, the smaller the desired particle size of silica (silica raw material) can be obtained.

[0096] The amount of water used for the hydrolysis and condensation is preferably 0.5 to 5 mol, more preferably 0.6 to 2 mol, and particularly preferably 0.7 to 1 mol, per 1 mol of the total hydrocarbyloxy groups of the tetrafunctional silane compound represented by general formula (I) and / or its partial hydrolysis-condensation product. The ratio of the hydrophilic organic solvent to water (hydrophilic organic solvent:water) is preferably 0.5 to 10:1, more preferably 3 to 9:1, and particularly preferably 5 to 8:1, by mass. The greater the amount of hydrophilic organic solvent, the smaller the desired particle size of silica (silica raw material) can be obtained.

[0097] The hydrolysis and condensation of the tetrafunctional silane compound represented by the general formula (I) are carried out by a known method, namely, by adding the tetrafunctional silane compound represented by the general formula (I) to a mixture of a hydrophilic organic solvent containing a basic substance and water.

[0098] The concentration of the hydrophilic spherical silica fine particles in the mixed solvent dispersion of the silica raw material (hydrophilic spherical silica fine particles) obtained in this step (C1) is generally 3 to 15% by mass, preferably 5 to 10% by mass.

[0099] Step (C2): Surface treatment step with a trifunctional silane compound by using a silane having the general formula (II)

[0100] R 1 Si(OR 4 )3(II)

[0101] (In the general formula, R 1 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, each R 4 are the same or different monovalent hydrocarbon groups with 1 to 6 carbon atoms.

[0102] The trifunctional silane compound, its partial hydrolysis product, or a mixture thereof is added to the mixed solvent dispersion of the silica raw material (hydrophilic spherical silica fine particles) obtained in step (C1), and the surface of the hydrophilic spherical silica fine particles is treated with the same, thereby R 1 SiO 3 / 2 Unit (R 1 is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms) is introduced onto the surface of the hydrophilic spherical silica fine particles to obtain a mixed solvent dispersion of the first hydrophobic spherical silica fine particles.

[0103] This step (C2) is essential for suppressing the aggregation of silica particles in the next concentration step. If the aggregation of silica particles cannot be suppressed, the hydrophobic spherical silica particles finally obtained will not maintain their primary particle size, and thus their fluidity-imparting ability will deteriorate.

[0104] In the general formula (II), R 1 A monovalent hydrocarbon group having 1 to 3 carbon atoms is preferred, and a monovalent hydrocarbon group having 1 to 2 carbon atoms is particularly preferred. 1 The monovalent hydrocarbon group represented by alkyl groups may be, for example, methyl, ethyl, n-propyl, isopropyl, butyl, or hexyl. Preferably, methyl, ethyl, n-propyl, or isopropyl is used, and particularly preferably, methyl or ethyl is used. Furthermore, some or all of the hydrogen atoms in these monovalent hydrocarbon groups may be substituted with halogen atoms such as fluorine, chlorine, or bromine, and preferably, may be substituted with fluorine atoms.

[0105] In the general formula (II), R 4 The monovalent hydrocarbon group having 1 to 3 carbon atoms, particularly preferably 1 to 2 carbon atoms, is independently preferably a monovalent hydrocarbon group having 1 to 3 carbon atoms. 4Examples of the monovalent hydrocarbon group include alkyl groups such as methyl, ethyl, propyl, and butyl. Preferably, it is methyl, ethyl, or propyl. More preferably, it is methyl or ethyl.

[0106] Examples of the trifunctional silane compound represented by the general formula (II) include unsubstituted or halogen-substituted trialkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, hexyltrimethoxysilane, trifluoropropyltrimethoxysilane, and heptadecafluorodecyltrimethoxysilane. Preferred examples include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, and ethyltriethoxysilane. More preferred examples include methyltrimethoxysilane and methyltriethoxysilane, or partial hydrolysis-condensation products thereof.

[0107] The amount of the trifunctional silane compound represented by general formula (II) added is 0.001 to 1 mol, preferably 0.01 to 0.1 mol, and particularly preferably 0.01 to 0.05 mol, per 1 mol of Si atoms in the hydrophilic spherical silica fine particles used. If the amount added is less than 0.001 mol, the dispersibility of the resulting hydrophobic spherical silica fine particles will be poor, and the effect of imparting fluidity to the boron nitride may not be achieved. If the amount added is greater than 1 mol, aggregation of the silica fine particles may occur.

[0108] In the mixed solvent dispersion of the first hydrophobic spherical silica particles obtained in step (C2), the concentration of the first hydrophobic spherical silica particles is 3% by mass or more and less than 15% by mass, preferably 5 to 10% by mass. If the concentration is less than 3% by mass, productivity may decrease, while if it is 15% by mass or more, aggregation of the silica particles may occur.

[0109] Concentration process

[0110] From the mixed solvent dispersion of the first hydrophobic spherical silica particles thus obtained, a portion of the above-mentioned hydrophilic organic solvent and water is removed and concentrated to obtain a mixed solvent concentrated dispersion of the first hydrophobic spherical silica particles. At this time, a hydrophobic organic solvent can also be added in advance (before the concentration step) or in the concentration step. At this time, as the hydrophobic solvent used, a hydrocarbon or ketone solvent is preferably used. Specifically, as the hydrophobic solvent, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, etc. can be exemplified, preferably methyl isobutyl ketone.

[0111] Examples of methods for removing a portion of the hydrophilic organic solvent and water include distillation and vacuum distillation. The concentration of the first hydrophobic spherical silica particles in the resulting concentrated dispersion of the mixed solvent is preferably 15 to 40% by mass, more preferably 20 to 35% by mass, and particularly preferably 25 to 30% by mass. If the concentration is less than 15% by mass, the surface treatment in step (C3) described below may not proceed smoothly. If the concentration is greater than 40% by mass, aggregation of the silica particles may occur.

[0112] The concentration step is also significant in suppressing the following disadvantages: the silazane compound represented by the general formula (III) and the monofunctional silane compound represented by the general formula (IV) used as the surface treatment agent in the later-described step (C3) react with alcohol or water, resulting in insufficient surface treatment, agglomeration during subsequent drying, and the inability of the obtained silica powder to maintain its primary particle size, resulting in poor flowability.

[0113] Step (C3): Surface treatment with a monofunctional silane compound is performed by formula (III).

[0114] R 2 3SiNHSiR 2 3 (III)

[0115] (In the formula, R 2 are the same or different substituted or unsubstituted monovalent hydrocarbon groups with 1 to 8 carbon atoms.

[0116] The silazane compound shown, or the general formula (IV)

[0117] R 2 3SiX (IV)

[0118] (In the formula, R 2 are identical or different substituted or unsubstituted monovalent hydrocarbon groups having 1 to 6 carbon atoms, and X is an OH group or a hydrolyzable group.

[0119] The monofunctional silane compound shown, or a mixture thereof, is added to the concentrated dispersion of the mixed solvent obtained in the above-mentioned concentration step to treat the surface of the first hydrophobic spherical silica particles by 2 3SiO 1 / 2 Unit (R 2 By introducing the silanol groups remaining on the surface of the first hydrophobic spherical silica particles into the surface of the particles as defined by general formula (III), the second hydrophobic spherical silica particles are obtained. 2 3SiO 1 / 2 Elements are imported into this surface.

[0120] In the above general formula (III) and general formula (IV), R 2 A monovalent hydrocarbon group having 1 to 4 carbon atoms is preferred, and a monovalent hydrocarbon group having 1 to 2 carbon atoms is particularly preferred. 2 The monovalent hydrocarbon group represented by alkyl groups such as methyl, ethyl, propyl, isopropyl, and butyl can be exemplified, preferably methyl, ethyl, or propyl, and particularly preferably methyl or ethyl. Furthermore, some or all of the hydrogen atoms in the monovalent hydrocarbon group may be substituted with halogen atoms such as fluorine, chlorine, or bromine, preferably with fluorine atoms.

[0121] Examples of the hydrolyzable group represented by X include a chlorine atom, an alkoxy group, an amino group, and an acyloxy group. Preferably, an alkoxy group or an amino group is used, and particularly preferably, an alkoxy group is used.

[0122] Examples of the silazane compound represented by the general formula (III) include hexamethyldisilazane and hexaethyldisilazane, and preferably hexamethyldisilazane.

[0123] Examples of the monofunctional silane compound represented by the general formula (IV) include monosilanol compounds such as trimethylsilanol and triethylsilanol; monochlorosilanes such as trimethylchlorosilane and triethylchlorosilane; monoalkoxysilanes such as trimethylmethoxysilane and trimethylethoxysilane; monoaminosilanes such as trimethylsilyldimethylamine and trimethylsilyldiethylamine; and monoacyloxysilanes such as trimethylacetoxysilane. Preferably, trimethylsilanol, trimethylmethoxysilane or trimethylsilyldiethylamine is used, and particularly preferably, trimethylsilanol or trimethylmethoxysilane is used.

[0124] The amount of the silazane compound and / or monofunctional silane compound used is 0.1 to 0.5 mol, preferably 0.2 to 0.4 mol, and particularly preferably 0.25 to 0.35 mol per 1 mol of Si atoms in the hydrophilic spherical silica fine particles used. If the amount used is less than 0.1 mol, the dispersibility of the resulting hydrophobic spherical silica fine particles deteriorates, while if the amount used is more than 0.5 mol, it is economically disadvantageous.

[0125] The hydrophobic spherical silica fine particles are obtained as a powder by a conventional method such as drying under normal pressure or drying under reduced pressure.

[0126] The amount of component (C) added per 100 parts by mass of component (A) is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and particularly preferably 0.1 to 5 parts by mass. If the amount is less than 0.01 parts by mass, the effects of component (C), such as the effect of reducing the viscosity of the grease composition, cannot be achieved. If the amount exceeds 10 parts by mass, the viscosity of the grease composition increases, which may deteriorate the thermal conductivity and is uneconomical.

[0127] (D) Ingredients

[0128] Component (D) is added to the composition to treat the surface of the powders (components (B) and / or (C)). This not only helps achieve high powder loading but also improves the moisture resistance of component (A). Gallium and gallium alloys inherently oxidize when exposed to high humidity for extended periods, resulting in an increase in the thermal resistance of the silicone composition. However, the inclusion of component (D) prevents this increase in thermal resistance even in high humidity, maintaining performance.

[0129] The component (D) is an organosilane represented by the following general formula (1).

[0130] R 1 a R 2 b Si(OR 3 ) 4-a-b (1)

[0131] (In the formula, R 1 are independently substituted or unsubstituted alkyl groups having 1 to 20 carbon atoms, R 2 are each independently a substituted or unsubstituted monovalent hydrocarbon group other than an alkyl group, R 3 are identical or different monovalent hydrocarbon groups having 1 to 6 carbon atoms, a is a number from 1 to 3, b is a number from 0 to 2, and the sum of a+b is a number from 1 to 3.

[0132] As R in the above formula (1) 1 , for example, methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; halogen-substituted alkyl groups such as 3-chloropropyl, 3,3,3-trifluoropropyl, 2-(19fluorobutyl)ethyl, and 2-(16-fluorooctyl)ethyl. If the number of carbon atoms exceeds 20, the organosilane cures at room temperature, making it inconvenient to operate, and the low-temperature properties of the obtained composition are reduced. When a in formula (1) is 2 or 3, R 1 They may be the same group or different groups.

[0133] In addition, as R in the above formula (1),2 Examples thereof include alkenyl groups such as vinyl and allyl; aryl groups such as phenyl and tolyl; aralkyl groups such as 2-phenylethyl and 2-methyl-2-phenylethyl; and halogenated hydrocarbon groups such as p-chlorophenyl. Among them, methyl and ethyl are particularly preferred.

[0134] In addition, as R in the above formula (1) 3 Examples of the alkyl group include methyl, ethyl, propyl, butyl, pentyl, and hexyl groups. Among them, methyl and ethyl groups are particularly preferred.

[0135] Preferred specific examples of the component (D) include the following.

[0136] CH3Si(OCH3)3

[0137] C3H7Si(OCH3)3

[0138] C6H 13 Si(OCH3)3

[0139] C8H 17 Si(OCH3)3

[0140] C 10 H 21 Si(OCH3)3

[0141] C 12 H 25 Si(OCH3)3

[0142] C 16 H 33 Si(OCH3)3

[0143] C 18 H 37 Si(OCH3)3

[0144] C 20 H 41 Si(OCH3)3

[0145] C3H7Si(OC2H5)3

[0146] C6H 13 Si(OC2H5)3

[0147] C8H 17 Si(OC2H5)3

[0148] C 10 H 21 Si(OC2H5)3

[0149] C 12 H 25 Si(OC2H5)3

[0150] C 18 H 37 Si(OC2H5)3

[0151] C 10 H 21 Si(CH3)(OCH3)2

[0152] C 10 H 21 Si(C6H5)(OCH3)2

[0153] C 10 H 21 Si(CH3)(OC2H5)2

[0154] C 10 H 21 Si(CH=CH2)(OCH3)2

[0155] C 10 H 21 Si(CH2CH2CF3)(OCH3)2

[0156] (ClCH2CH2CH2)Si(OCH3)3

[0157] (ClCH2CH2CH2)Si(OC2H5)3

[0158] In addition, this (D)component may be used individually by 1 type, and may use 2 or more types in combination.

[0159] The amount of component (D) added per 100 parts by mass of component (A) is preferably 0.001 to 10 parts by mass, more preferably 0.001 to 5 parts by mass, and particularly preferably 0.001 to 2.5 parts by mass. If the amount exceeds 10 parts by mass, the effect of improving moisture resistance will not be enhanced, which is uneconomical. Furthermore, due to its volatility, the composition of the present invention may gradually harden when left in an open system.

[0160] Other ingredients

[0161] Furthermore, the thermally conductive composition of the present invention may contain conventionally known antioxidants, dyes, pigments, flame retardants, anti-settling agents, thixotropy improvers, and the like, as necessary, within the range not impairing the purpose of the present invention.

[0162] Preparation of composition

[0163] The method for producing the thermally conductive composition of the present invention can be based on a conventional method for producing a silicone grease composition, and is not particularly limited. However, conventional methods use silicone oil as a base, whereas in this production method, each component is added to a low-melting-point metal as a base. Specifically, the composition can be produced by mixing the above-mentioned components (A) and (B), and, if necessary, (C), (D), and / or other components, for 30 minutes to 4 hours using a mixer with a planetary motion (rotation or revolution) agitating blade, such as a TRI-MIX, TWIN MIX, or PLANETARY MIXER (all registered trademarks of Inoue Seisakusho Co., Ltd.), ULTRA MIXER (registered trademark of MIZUHO Kogyo Co., Ltd.), or HIVISDISPER MIX (registered trademark of Tokushiki Kagaku Kogyo Co., Ltd.) in a stirring tank. If component (A) is solid at room temperature, it is preferably preheated and melted before blending. Furthermore, if necessary, the mixture may be mixed while being heated at a temperature within the range of 50 to 150° C. Furthermore, the components may be mixed all at once or in batches.

[0164] [Thermal conductivity]

[0165] The thermal conductivity of the thermally conductive composition of the present invention is preferably 30.0 W / m·K or higher, more preferably 35.0 W / m·K or higher, and even more preferably 40.0 W / m·K or higher at 25°C. By using high-thermal-conductivity materials for both the low-melting-point metal base material and the filler, the thermally conductive composition of the present invention can achieve even higher thermal conductivity.

[0166] The thermally conductive composition of the present invention can be used as a grease. There are no particular limitations on how the composition of the present invention can be used as a grease, and it can be used in the same manner as conventional heat dissipation (thermal conductive) silicone greases. For example, it can be suitably used by sandwiching the grease between an LSI or other heat-generating component and a cooling or heat-dissipating component, thereby transferring heat from the heat-dissipating component to the cooling or heat-dissipating component. Due to its high thermal conductivity and excellent workability, the thermally conductive composition of the present invention is preferably used as a heat dissipation (thermal conductive) grease for high-quality semiconductor devices and the like.

[0167] [Example]

[0168] Hereinafter, the present invention will be specifically described using Examples and Comparative Examples, but the present invention is not limited thereto.

[0169] (A)Ingredients

[0170] (A-1) Metal Gallium [Melting Point = 29.8°C]

[0171] (A-2) Ga-In alloy [mass ratio = 75.4:24.6, melting point = 15.7°C]

[0172] (A-3) Ga-In-Sn alloy [mass ratio = 68.5:21.5:13, melting point = -19°C]

[0173] (A-4) Ga-In-Sn alloy [mass ratio = 62:25:13, melting point = 5.0°C]

[0174] (A-5) Ga-In-Zn alloy [mass ratio = 82:12:6, melting point = 17°C]

[0175] (B) Ingredients

[0176] (B-1) Aluminum nitride powder [average particle size: 100 μm]

[0177] (B-2) Aluminum nitride powder [average particle size: 70 μm]

[0178] (B-3) Aluminum nitride powder [average particle size: 60 μm]

[0179] (B-4) Aluminum nitride powder [average particle size: 20 μm]

[0180] (B-5) Aluminum nitride powder [average particle size: 5 μm]

[0181] (B-6) Aluminum nitride powder [average particle size: 1 μm]

[0182] (B-7) Zinc oxide powder [average particle size: 1 μm]

[0183] Particle size determination

[0184] The particle size of the thermally conductive filler (component (B)) was measured using a laser diffraction and scattering particle size distribution analyzer (in this example, a MICROTRAC MT3300EX particle size analyzer manufactured by Nikkiso Co., Ltd.). The measured particle size is the cumulative average diameter based on volume.

[0185] (C) Ingredient: Hydrophobic spherical silica particles

[0186] Component (C) Hydrophobic spherical silica fine particles (C-1) to (C-6) (Table 1) were prepared as follows. Note that (C-5) and (C-6) were used as comparative examples.

[0187] (D) Ingredients

[0188] (D-1) Structural formula: C10 H 21 Organosilane represented by Si(OCH3)3

[0189] (D-2) Structural formula: C 16 H 33 Organosilane represented by Si(OCH3)3

[0190] (D-3) Structural formula: Organosilane represented by (ClCH2CH2CH2)Si(OCH3)3

[0191] [Synthesis of hydrophobic spherical silica microparticles]

[0192] [Synthesis example 1]

[0193] Step (C1): Synthesis of hydrophilic spherical silica particles

[0194] In a 3-liter glass reactor equipped with a stirrer, dropping funnel, and thermometer, 989.5 g of methanol, 135.5 g of water, and 66.5 g of 28% by mass ammonia water were added and mixed. The solution was adjusted to 35°C, and 436.5 g (2.87 mol) of tetramethoxysilane was added dropwise over 6 hours while stirring. After the addition, stirring was continued for an additional 0.5 hour to allow hydrolysis to proceed, resulting in a suspension of hydrophilic spherical silica particles.

[0195] Step (C2): Surface treatment with a trifunctional silane compound

[0196] 4.4 g (0.03 mol) of methyltrimethoxysilane was added dropwise to the suspension obtained in step (C1) at room temperature over 0.5 hours. Stirring was continued for 12 hours after the addition to hydrophobize the surface of the silica particles, thereby obtaining a dispersion of hydrophobic spherical silica particles.

[0197] Concentration process

[0198] Next, an ester adapter and a cooling tube were attached to a glass reactor, and the dispersion obtained in step (C2) was heated to 60-70°C. 1021 g of a mixture of methanol and water was distilled off to obtain a mixed solvent concentrated dispersion of hydrophobic spherical silica particles. At this time, the content of the hydrophobic spherical silica particles in the concentrated dispersion was 28% by mass.

[0199] Step (C3): Surface treatment step using a monofunctional silane compound

[0200] 138.4 g (0.86 mol) of hexamethyldisilazane was added to the concentrated dispersion obtained in the concentration step at room temperature. The dispersion was then heated to 50-60°C and reacted for 9 hours to trimethylsilylate the silica particles in the dispersion. Subsequently, the solvent in the dispersion was distilled off at 130°C under reduced pressure (6650 Pa) to obtain 186 g of hydrophobic spherical silica particles (C-1).

[0201] The hydrophilic spherical silica particles obtained in step (C1) were measured using the following measurement method 1. Furthermore, the hydrophobic spherical silica particles obtained through steps (C1) to (C3) were measured using the following measurement methods 2 and 3. The results are shown in Table 1.

[0202] [Measurement methods 1-3]

[0203] 1. Particle size measurement of the hydrophilic spherical silica fine particles obtained in step (C1)

[0204] The silica particle suspension was added to methanol to a concentration of 0.5% by mass. Ultrasonic waves were then applied for 10 minutes to disperse the particles. The particle size distribution of the treated particles was measured using a dynamic light scattering / laser Doppler NANOTRAC particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., Japan, trade name: UPA-EX150), and the volume-based median diameter was used as the particle size. It should be noted that the median diameter refers to the particle size corresponding to the cumulative 50% when the particle size distribution is expressed as a cumulative distribution.

[0205] 2. Particle size measurement and particle size distribution of the hydrophobic spherical silica particles obtained in step (C3) 90 / D 10 Measurement

[0206] Silica fine particles were added to methanol to a concentration of 0.5% by mass, and the fine particles were dispersed by applying ultrasound for 10 minutes. The particle size distribution of the fine particles thus treated was measured using a dynamic light scattering / laser Doppler method NANOTRAC particle size distribution measuring device (manufactured by Nikkiso Co., Ltd., Japan, trade name: UPA-EX150), and the volume-based median diameter was used as the particle size. Particle size distribution D 90 / D 10 The particle size distribution in the particle size measurement is measured, and the particle size that accumulates to 10% from the smaller particle size side is defined as D 10 The particle size that accumulates to 90% from the small particle size side is set as D 90 , and D was calculated from the measured values 90 / D 10 .

[0207] 3. Measurement of the Shape and Circularity of Hydrophobic Spherical Silica Particles

[0208] The shape was confirmed by observation using an electron microscope (manufactured by Hitachi, Japan, trade name: S-4700, magnification: 100,000 times). "Spherical" includes not only true spheres but also slightly deformed spheres.

[0209] It should be noted that the shape of such particles is evaluated by the circularity when the particles are projected onto a two-dimensional plane. Circularity here refers to (the circumference of a circle equal to the particle area) / (the particle circumference) and is within the range of 0.8 to 1. It should also be noted that the circularity is the average of the results of measuring 10 particles.

[0210] [Synthesis example 2]

[0211] 188 g of hydrophobic spherical silica fine particles (C-2) were obtained in the same manner as in Synthesis Example 1, except that the amounts of methanol, water, and 28% by mass ammonia water in step (C1) were changed to 1045.7 g of methanol, 112.6 g of water, and 33.2 g of 28% by mass ammonia water. Using these hydrophobic spherical silica fine particles (C-2), measurements were performed in the same manner as in Synthesis Example 1. The results are shown in Table 1.

[0212] [Synthesis example 3]

[0213] Process (C1):

[0214] 623.7 g of methanol, 41.4 g of water, and 49.8 g of 28% by mass ammonia aqueous solution were added to a 3-liter glass reactor equipped with a stirrer, dropping funnel, and thermometer and mixed. The solution was adjusted to 35°C, and while stirring, 1163.7 g of tetramethoxysilane and 418.1 g of 5.4% by mass ammonia aqueous solution were added dropwise over 6 hours and 4 hours, respectively. After the addition of tetramethoxysilane, stirring was continued for 0.5 hours to allow hydrolysis, resulting in a suspension of silica fine particles.

[0215] Process (C2):

[0216] To the suspension thus obtained, 11.6 g (equivalent to a molar ratio of 0.01 to tetramethoxysilane) of methyltrimethoxysilane was added dropwise at room temperature over 0.5 hours and stirred for 12 hours to treat the surface of the silica fine particles.

[0217] An ester adapter and a cooling tube were attached to the glass reactor, 1440 g of methyl isobutyl ketone was added to the dispersion containing the surface-treated silica fine particles, and then heated to 80-110° C. to distill off methanol water over 7 hours.

[0218] Process (C3):

[0219] 357.6 g of hexamethyldisilazane was added to the dispersion obtained at room temperature, heated to 120° C., and reacted for 3 hours to trimethylsilylate the silica fine particles. The solvent was then distilled off under reduced pressure to obtain 472 g of hydrophobic spherical silica fine particles (C-3).

[0220] The hydrophobic spherical silica fine particles (C-3) obtained in this manner were subjected to the same measurements as in Synthesis Example 1. The results are shown in Table 1.

[0221] [Synthesis Example 4]

[0222] The same steps as in Synthesis Example 3 were followed, except that the hydrolysis temperature of tetramethoxysilane was adjusted from 35°C to 20°C during the synthesis of the silica microparticles, to obtain 469 g of hydrophobic spherical silica microparticles (C-4). Using these hydrophobic spherical silica microparticles (C-4), the same measurements as in Synthesis Example 1 were performed. The results are shown in Table 1.

[0223] [Comparative Synthesis Example 1]

[0224] 100 g of silica produced by the VMC method (Vaporized Metal Combustion Method) (trade name: SOC1, manufactured by Admatechs) was placed in a 0.3-liter glass reactor equipped with a stirrer and a thermometer. 1 g of pure water was added while stirring, and the reaction mixture was sealed and stirred at 60°C for 10 hours. Subsequently, after cooling to room temperature, 2 g of hexamethyldisilazane was added while stirring, and the reaction mixture was sealed and stirred for a further 24 hours. The temperature was raised to 120°C, and residual raw materials and generated ammonia were removed while nitrogen was passed through the reaction mixture, yielding 100 g of hydrophobic spherical silica fine particles (C-5).

[0225] The obtained hydrophobic spherical silica fine particles (C-5) were subjected to the same measurements as in Synthesis Example 1. The results are shown in Table 1.

[0226] [Comparative Synthesis Example 2]

[0227] 100g of silica manufactured by the VMC method (Vaporized Metal Combustion Method) (trade name: SOC1, manufactured by Admatechs) was added to a 0.3-liter glass reactor equipped with a stirrer and a thermometer, and 1g of pure water was added under stirring conditions. After sealing, the mixture was further stirred at 60°C for 10 hours. Then, after cooling to room temperature, 1g of methyltrimethoxysilane was added under stirring conditions, and after sealing, the mixture was further stirred for 24 hours. Then, 2g of hexamethyldisilazane was added under stirring conditions, and after sealing, the mixture was further stirred for 24 hours. The temperature was raised to 120°C, and the residual raw materials and the generated ammonia were removed while passing nitrogen gas, thereby obtaining 101g of hydrophobic spherical silica particles (C-6). The obtained hydrophobic spherical silica particles (C-6) were measured in the same manner as in Synthesis Example 1. The results are shown in Table 1.

[0228] [Table 1]

[0229] Synthesis example 1 Synthesis example 2 Synthesis example 3 Synthesis example 4 Comparative Synthesis Example 1 Comparative Synthesis Example 2 Hydrophobic spherical silica particles (C-1) (C-2) (C-3) (C-4) (C-5) (C-6) <![CDATA[Particle size 1) (nm)]]> 52 11 115 230 - - <![CDATA[Particle size 2) (nm)]]> 52 11 115 238 300 300 <![CDATA[Particle size distribution D 90 / D 10 > 2.21 2.40 2.23 2.80 5.40 4.80 <![CDATA[Shape 2) > spherical spherical spherical spherical spherical Amorphous Circularity 0.86 0.92 0.90 0.81 0.80 0.65

[0230] Note

[0231] 1) Particle size of the hydrophilic spherical silica fine particles in the dispersion obtained in step (C1)

[0232] 2) The particle size of the hydrophobic spherical silica particles finally obtained

[0233] [Examples 1 to 31, Comparative Examples 1 and 2]

[0234] <Preparation of Composition>

[0235] Each component was weighed at the composition ratio described in Tables 2 to 6, placed in a 1-liter planetary mixer (eg, manufactured by PRIMIX, trade name: HIVIS MIX 2P-1), and stirred at room temperature for 1 hour to prepare each composition.

[0236] In addition, (A-1) which has a melting point higher than room temperature was added by preliminarily melting the component (A-1) in an oven.

[0237] <Appearance>

[0238] The properties of the obtained compositions were visually confirmed. The results are shown in Tables 2 to 6.

[0239] <Measurement of Thermal Conductivity>

[0240] The thermal conductivity of each composition was measured at 25° C. using a thermophysical property measuring apparatus (TPS-2500S manufactured by Kyoto Electronics Co., Ltd. in this example) utilizing a hot plate method.

[0241] <Determination of operability>

[0242] After filling a disposable syringe (e.g., Terumo syringe SS-02SZ 2.5 mL center port, needleless) with approximately 1.5 mL of each composition, the plunger was pressed to discharge the composition. The discharged composition was spread with a spatula or the like. If the composition was wet and spread, it was marked as "0" (difficult to return to a droplet even after pressing), and the operability was judged to be good ( Figure 1 ). In the case where the state in which the liquid cannot be fully wetted and spread is formed, it is marked as "×" (it is easy to return to a droplet after pressing), and it is judged to be poor in operability ( Figure 2 ).

[0243] [Table 2]

[0244]

[0245] [Table 3]

[0246]

[0247] [Table 4]

[0248]

[0249] [Table 5]

[0250]

[0251] [Table 6]

[0252]

[0253] The examples demonstrate that the thermally conductive composition of the present invention exhibits excellent workability and high thermal conductivity. In particular, Examples 21 to 29 demonstrate that thermal conductivity is enhanced when a metal oxide and / or metal nitride having an average particle size of 70 to 200 μm is incorporated as component (B) in a high content, such that the content is 55% by mass or more and less than 100% by mass relative to the total content of component (B).

[0254] As can be seen from Examples 21 to 29, a preferred formulation having high thermal conductivity and excellent workability is a composition comprising the following:

[0255] Component (B) with an average particle size of 70 to 200 μm: 55% by mass or more of component (B)

[0256] Component (B) having an average particle size of 20 μm or more and less than 70 μm: 10 to 35% by mass of component (B)

[0257] Component (B) having an average particle size of less than 20 μm: occupies 30% by mass or less of component (B);

[0258] As a more preferred formulation, it is a composition comprising the following:

[0259] Component (B) with an average particle size of 70 to 200 μm: 57% by mass or more of component (B)

[0260] Component (B) having an average particle size of 20 μm or more and less than 70 μm: 12 to 30% by mass

[0261] Component (B) having an average particle size of less than 20 μm: 28% by mass or less;

[0262] As an example of a further preferred formulation, it is a composition comprising the following:

[0263] Component (B) with an average particle size of 70 to 200 μm: 59% by mass or more

[0264] Component (B) having an average particle size of 20 μm or more and less than 70 μm: 14 to 28 mass%

[0265] Component (B) having an average particle size of less than 20 μm: 26% by mass or less.

Claims

1. A thermally conductive composition comprising the following components: (A) Gallium and / or its alloy having a melting point of -20 to 100°C: 100 parts by mass; and (B) a metal oxide and / or metal nitride having an average particle size of 0.01 μm to 200 μm: 2 to 150 parts by mass relative to 100 parts by mass of component (A); in, The total content of the components (A) and (B) in the composition is 95 to 100% by mass.

2. The thermally conductive composition according to claim 1, wherein The total content of the component (A) and the component (B) in the composition is 98 to 100% by mass.

3. The thermally conductive composition according to claim 1, wherein The gallium alloy of the component (A) is one or more selected from the group consisting of a Ga—In alloy, a Ga—Sn—Zn alloy, a Ga—In—Sn alloy, and a Ga—In—Bi—Sn alloy.

4. The thermally conductive composition according to claim 1, wherein The component (B) is one or more selected from the group consisting of zinc oxide powder, aluminum oxide powder, boron nitride powder, silicon nitride powder, aluminum nitride powder, aluminum hydroxide powder, and magnesium oxide powder.

5. The thermally conductive composition according to claim 1, wherein The present invention further comprises 0.01 to 10 parts by mass of the following hydrophobic spherical silica fine particles as the component (C), based on 100 parts by mass of the component (A). The hydrophilic spherical silica particles are obtained by hydrolyzing and condensing a tetrafunctional silane compound, a partially hydrolyzed condensation product thereof or a mixture thereof and are substantially composed of SiO2 units. 1 R is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms 1 SiO 3 / 2 Unit and import each R 2 R is the same or different, substituted or unsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms 2 3SiO 1 / 2 Unit, particle size range of 0.005~1μm, particle size distribution D 90 / D 10 Hydrophobic spherical silica fine particles having a value of 3 or less and an average circularity of 0.8 to 1.

6. The thermally conductive composition according to claim 1, wherein The present invention further contains, as component (D), 0.001 to 10 parts by mass of an organosilane represented by the following general formula (1) based on 100 parts by mass of component (A), R 1 a R 2 b Si(OR 3 ) 4-a-b (1) In the formula, R 1 are independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, R 2 are each independently a substituted or unsubstituted monovalent hydrocarbon group other than an alkyl group, R 3 are identical or different monovalent hydrocarbon groups having 1 to 6 carbon atoms, a is a number from 1 to 3, b is a number from 0 to 2, and the sum of a+b is a number from 1 to 3.

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