Thermally conductive composition

Abstract

Provided is a thermally conductive composition capable of suppressing an increase in viscosity even when the content of an inorganic powder filler is increased. The thermally conductive composition contains a base oil and an inorganic powder filler, and the thermally conductive composition further contains at least one of a titanate-based coupling agent and an aluminate-based coupling agent.

Description

Technical Field

[0001] This invention relates to a thermally conductive composition. Background Technology

[0002] Semiconductor components used in electronic devices include computer CPUs, Peltier devices, LEDs, power semiconductors for power control such as inverters, and other heat-generating components that generate heat during use.

[0003] To protect these heat-generating components from heat and ensure their proper functioning, methods exist to conduct and dissipate the generated heat to heat-dissipating components (cooling devices) such as heat spreaders or heat sinks. Thermally conductive grease is applied between these heat-generating and heat-dissipating components to ensure adhesion and efficiently transfer heat from the heat-generating components to the heat-dissipating components. Thermally conductive grease is a grease-like composition in which a large amount of inorganic powder filler with high thermal conductivity (such as zinc oxide, aluminum oxide, and other metal oxides; boron nitride, silicon nitride, aluminum nitride, and other inorganic nitrides; and metal powders such as aluminum and copper) is dispersed in a base oil such as liquid hydrocarbons, silicone oil, or fluorinated oil.

[0004] More specifically, thermally conductive grease is applied to the thermal contact interfaces between heat-generating components such as CPUs in computers and heat dissipation components such as heat sinks, as well as between heat-generating components such as high-output inverters in hybrid and electric vehicles and heat dissipation components such as vapor chambers. In recent years, semiconductor components in these electronic devices have become increasingly smaller and higher performance-oriented, resulting in increased heat density and heat generation, and they are increasingly being assembled close to other heat-generating components that are also semiconductor components.

[0005] For example, Patent Document 1 describes a technology involving a thermally conductive grease containing a specific antioxidant in a prescribed proportion. According to Patent Document 1, this thermally conductive grease exhibits high thermal conductivity, viscosity, and thermal stability under high-temperature conditions.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent document 1: Japanese Patent Application Publication No. 2019-081841. Summary of the Invention

[0009] The problem the invention aims to solve

[0010] Thermally conductive compositions containing inorganic powder fillers can improve thermal conductivity by increasing the content of the inorganic powder filler. On the other hand, the viscosity of the thermally conductive composition increases due to the increase in the content of the inorganic powder filler.

[0011] If the viscosity of a thermally conductive composition increases, for example, when using the thermally conductive composition as a thermally conductive grease, sometimes it is not possible to obtain sufficient coatability, and sometimes the desired properties as a thermally conductive composition cannot be obtained. Thus, in thermally conductive compositions, it is desirable to have a composition whose viscosity does not increase significantly even when the content of inorganic powder filler is increased.

[0012] The purpose of this invention is to provide a thermally conductive composition that can suppress the increase in viscosity even when the content of inorganic powder filler is increased.

[0013] means for solving problems

[0014] The inventors conducted intensive research to solve the aforementioned problems. As a result, they discovered that a thermally conductive composition containing a specific coupling agent can solve these problems, thus completing the present invention.

[0015] The first invention is a thermally conductive composition containing a base oil and an inorganic powder filler, said thermally conductive composition further containing at least one of a titanate coupling agent or an aluminate coupling agent.

[0016] The second aspect of this invention is that, in the thermally conductive composition of the first invention, the total content of the titanate coupling agent and the aluminate coupling agent is 3% by volume or more and 30% by volume or less in the total amount of the thermally conductive composition.

[0017] The third invention is that in the thermally conductive composition of the first or second invention, the inorganic powder filler is one or more selected from the group consisting of copper, aluminum, zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride, and silicon carbide.

[0018] The fourth invention is that in the thermally conductive composition of the first or second invention, the base oil is one or more selected from the group consisting of mineral oil, synthetic hydrocarbon oil, diester, polyol ester and phenyl ether.

[0019] Invention Effects

[0020] The thermally conductive composition of the present invention can effectively suppress the increase in viscosity even when the content of inorganic powder filler is increased. Detailed Implementation

[0021] The following describes in detail specific embodiments of the present invention (hereinafter referred to as "this embodiment"). It should be noted that the present invention is not limited to the following embodiment, and can be implemented with appropriate modifications within the scope of the present invention's objectives. Furthermore, in this specification, the expression "X~Y" (where X and Y are arbitrary values) means "X or more and Y or less".

[0022] 1. Thermally conductive compositions

[0023] The thermally conductive composition of this embodiment contains a base oil and an inorganic powder filler. Furthermore, this thermally conductive composition is characterized by containing at least one of a titanate coupling agent or an aluminate coupling agent.

[0024] Thus, by using a specific coupling agent, even with an increase in the content of inorganic powder filler, the increase in viscosity can be effectively suppressed.

[0025] The thermally conductive composition of this embodiment can be disposed, for example, between heat-generating components such as CPUs, Bolter elements, LEDs, and power semiconductors for power control in computer power supplies, and heat-dissipating components such as heat spreaders and heat sinks. It can be used as a thermally conductive composition for forming a thermally conductive layer, which conducts heat from the heat-generating components to the heat-dissipating components, thereby dissipating heat from the heat-generating components.

[0026] Furthermore, the thermally conductive composition of this embodiment can be used as a semi-solid or semi-fluid thermally conductive grease at room temperature. Moreover, by containing, for example, a diluent, the thermally conductive composition of this embodiment can be used as a fluid thermally conductive paste at room temperature.

[0027] Furthermore, the thermally conductive layer formed by the thermally conductive composition of this embodiment can be solid, semi-solid, or semi-fluid. Additionally, the thermally conductive composition of this embodiment can also be a phase-change type thermally conductive sheet containing, for example, a thermoplastic resin that improves fluidity at high temperatures.

[0028] The following describes the components contained in the thermally conductive composition.

[0029] (1) Inorganic powder filler

[0030] Inorganic powder fillers impart high thermal conductivity to thermally conductive compositions. The inorganic powder filler used in this embodiment is not particularly limited as long as it has higher thermal conductivity than the base oil; preferred materials include metal oxides, inorganic sulfides, inorganic nitrides, metals (including alloys), silicon compounds (silicon dioxide), and carbon materials (including carbon materials, diamond, fullerenes, etc.). One type of inorganic powder filler can be used, or a combination of two or more can be used.

[0031] For example, when electrical insulation is required for the thermally conductive composition, powders of non-conductive materials such as zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride, boron nitride, silicon carbide, silicon compounds (silicon dioxide), and diamond, or other semiconductors or ceramics, can be used more effectively. When higher thermal conductivity is required but electrical insulation is not required for the thermally conductive composition, powders of copper, silver, aluminum, and alloys containing them can be used. Additionally, combinations of metal powders and powders of non-conductive materials can also be used.

[0032] Among these inorganic powder fillers, one or more are preferably selected from the group consisting of copper, aluminum, zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride, and silicon carbide.

[0033] Furthermore, the inorganic powder filler used in the thermally conductive composition of this embodiment can be an inorganic powder filler with one average particle size, or it can be a plurality of inorganic powder fillers with different average particle sizes.

[0034] When using multiple inorganic powder fillers with different average particle sizes, although it also depends on the thickness of the intended thermally conductive layer, it is preferable to use, for example, three inorganic powder fillers with different average particle sizes, which are composed of three or more powders with different average particle sizes, and at least include a first inorganic powder filler with an average particle size in the range of 30 μm or more and 200 μm or less, a second inorganic powder filler with an average particle size in the range of 1 μm or more and 30 μm or less, and a third inorganic powder filler with an average particle size in the range of 0.1 μm or more and 1 μm or less.

[0035] By using an inorganic powder filler containing an average particle size within the range described above, turbulence of the inorganic powder filler in the thermally conductive composition can be suppressed and flowability improved, resulting in uniform expansion of the thermally conductive composition. It should be noted that the average particle size of the inorganic powder filler can be calculated as the volume average particle size of the particle size distribution determined by laser diffraction scattering (according to JIS R1629:1997).

[0036] It should be noted that, within the range that does not impede the flowability of the thermally conductive composition, an inorganic powder filler having a smaller average particle size than the third inorganic powder filler can be further added.

[0037] The content of the inorganic powder filler relative to 100% by volume of the thermally conductive composition is preferably 50% by volume or more and 90% by volume or less, more preferably 55% by volume or more and 85% by volume or less, and even more preferably 60% by volume or more and 80% by volume or less.

[0038] (2) Base oil

[0039] Base oils impart high lubricity to thermally conductive compositions. Various base oils can be used as base oils, including hydrocarbon base oils such as mineral oils and synthetic hydrocarbon oils; ester base oils such as diesters and polyol esters; ether base oils such as (poly)phenyl ethers; phosphate esters, silicone oils, and fluorinated oils. A single base oil can be used, or two or more can be used in combination.

[0040] Preferably, the base oil used contains at least one base oil selected from the group consisting of hydrocarbon base oils (mineral oil, synthetic hydrocarbon oil), ester base oils, and ether base oils. These base oils do not contain siloxanes, and by including such base oils, contact failures are avoided, and the long-term reliability of the electronic equipment is excellent.

[0041] As mineral oils, they can be obtained by purifying mineral oil-based lubricating oil fractions using appropriate combinations of solvent extraction, solvent dewaxing, hydrogenation purification, hydrogenation decomposition, wax isomerization, etc., including 150 neutral oil, 500 neutral oil, bright oil, and high viscosity index base oils. The mineral oils used in the base oils are preferably high viscosity index base oils that have undergone high hydrogenation purification.

[0042] Examples of synthetic hydrocarbon oils include those made by polymerizing α-olefins, either alone or in combination, from ethylene, propylene, butene, and their derivatives. Among the α-olefins, those with 6 or more but less than 14 carbon atoms are preferred.

[0043] Specific examples of synthetic hydrocarbon oils include poly-α-olefins (PAOs) as oligomers of 1-decene and 1-dodecene; polybutene as oligomers of 1-butene and isobutene; and co-oligomers of ethylene, propylene, and α-olefins. Additionally, alkylbenzenes and alkylnaphthalenes can also be used.

[0044] Examples of ester-based base oils include diesters and polyol esters. Examples of diesters include esters of dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and dodecanoic acid. Among the dicarboxylic acids, aliphatic dicarboxylic acids with 4 or more and 36 or fewer carbon atoms are preferred. Among the alcohol residues constituting the ester portion, monohydric alcohol residues with 4 or more and 26 or fewer carbon atoms are preferred. Among polyol esters, esters of neopentyl polyols without a hydrogen atom at the β-carbon position are examples; specifically, carboxylic acid esters such as neopentyl glycol, trimethylolpropane, and pentaerythritol are examples. Among the carboxylic acid residues constituting the ester portion, monocarboxylic acid residues with 4 or more and 26 or fewer carbon atoms are preferred.

[0045] In addition to the above, ester-based base oils can also be made from esters of aliphatic diols such as ethylene glycol, propylene glycol, butanediol, 2-butyl-2-ethylpropanediol, and 2,4-diethyl-pentanediol with straight-chain or branched saturated fatty acids. As for straight-chain or branched saturated fatty acids, mononucleotide straight-chain or branched saturated fatty acids with 4 or more but less than 30 carbon atoms are preferred.

[0046] Examples of ether-based base oils include polyglycols and (poly)phenyl ethers. Examples of polyglycols include polyethylene glycol or polypropylene glycol and their derivatives. Examples of (poly)phenyl ethers include monoalkylated diphenyl ethers, dialkylated diphenyl ethers, and other alkylated diphenyl ethers; monoalkylated tetraphenyl ethers, dialkylated tetraphenyl ethers, and other alkylated tetraphenyl ethers; pentaphenyl ethers, monoalkylated pentaphenyl ethers, dialkylated pentaphenyl ethers, and other alkylated pentaphenyl ethers. Examples of phosphate esters include triethyl phosphate, tributyl phosphate, triphenyl phosphate, tricresyl phosphate, and tri(xyl) phosphate.

[0047] Here, the thermally conductive layer formed by the thermally conductive composition of this embodiment is primarily exposed to high temperatures for extended periods due to the heat-generating components. Therefore, excellent thermal oxidative stability is desirable for the base oil contained in the thermally conductive composition. Among the aforementioned base oils, synthetic base oils are preferred, particularly synthetic hydrocarbon oils, ester base oils, and ether base oils. Among these base oils, poly-α-olefins are preferred in synthetic hydrocarbon oils, polyol esters in ester base oils, and (poly)phenyl ethers in ether base oils, as base oils exhibiting particularly excellent thermal oxidative stability.

[0048] These poly-α-olefins, (poly)phenyl ethers, and polyol esters can be used individually, but it is preferred to use them in combination of two or more.

[0049] When used in combination, particularly by combining a base oil group composed of poly-α-olefins or (poly)phenyl ethers with a polyol ester, it is possible to prepare a thermally conductive composition with a high viscosity index, high viscosity when preparing a thermally conductive composition, and excellent coatability, which is therefore preferred. In this case, the content ratio of the base oil group composed of poly-α-olefins or (poly)phenyl ethers to the polyol ester, by mass, is preferably 95:5 to 30:70, more preferably 90:10 to 50:50, and even more preferably 85:15 to 65:35.

[0050] The kinematic viscosity of the base oil is preferably 10 mm at 40°C. 2 / s or higher and 1200mm 2 / s or less. By setting the kinematic viscosity at 40°C to 10 mm. 2A viscosity of 1200 mJ / s or higher tends to suppress base oil evaporation or oil separation under high-temperature conditions, therefore it is preferred. Furthermore, the kinematic viscosity at 40°C is set to 1200 mmHg. 2 High viscosity can be easily obtained at speeds below a certain value, therefore it is preferred.

[0051] The base oil content relative to 100 vol% of the thermally conductive composition is preferably 5 vol% or more and 30 vol% or less, more preferably 7 vol% or more and 27 vol% or less, and even more preferably 8 vol% or more and 25 vol% or less.

[0052] (3) Coupling agent

[0053] Coupling agents adsorb onto the surface of inorganic powder fillers, reducing the viscosity of the thermally conductive composition. Coupling agents are compounds that chemically bond organic and inorganic materials. By adsorbing onto the surface of inorganic powder fillers, coupling agents can improve the affinity with base oils.

[0054] Here, the thermally conductive composition of this embodiment is characterized in that the coupling agent contains at least one of a titanate coupling agent or an aluminate coupling agent.

[0055] Titanate coupling agents refer to coupling agents in which titanium (Ti) is a constituent element, while aluminate coupling agents refer to coupling agents in which aluminum (Al) is a constituent element.

[0056] By incorporating this specific coupling agent, the viscosity increase of the thermally conductive composition can be suppressed. While the reason is not yet clear, it is believed that this particular coupling agent readily and densely adsorbs onto the surface of the inorganic powder filler in the thermally conductive composition, increasing the hydrophobicity of the inorganic powder filler surface and thus improving its affinity for the base oil compared to other dispersants. It should be noted that titanate-based and aluminate-based coupling agents can be used individually or in combination.

[0057] Even more surprisingly, the inventors have discovered through research that when the content of titanate-based coupling agent or aluminate-based coupling agent is increased, the viscosity of the thermally conductive composition further decreases, and the thermal conductivity of the thermally conductive layer formed by the thermally conductive composition increases.

[0058] As a titanate-based coupling agent, any known coupling agent can be used without particular limitation, but titanate-based coupling agents with hydrocarbon groups, such as alkyl titanates, can be used. Specifically, examples of titanate-based coupling agents include isopropyl-triisostearyl titanate, isopropyl tri(dioctyl pyrophosphato) titanate, tetraoctyl bis(ditridecyl phosphite) titanate, isopropyl tri(dodecyl benzene sulfonyl) titanate, bis(dioctyl pyrophosphato)oxyacetate titanate, and tetraisopropyl bis(dioctyl phosphite) titanate.

[0059] Commercially available titanate-based coupling agents include the PLENACT series manufactured by Ajinomoto Fine-Techno Co., Inc., and the ORGATIX series manufactured by Matsumoto Fine Chemical Co., Ltd.

[0060] As an aluminate coupling agent, any known aluminate coupling agent can be used without particular limitation. Examples include aluminum acetoacetate dialkylate, aluminum alkyl acetoacetate diisopropylate, and other alkyl acetoacetate esters and dialkylates; aluminum alkenyl acetoacetate esters and dialkylates; aluminum triethyl acetoacetate, aluminum diethyl acetoacetate monoacetylacetonate, aluminum triacetylacetonate, and other aluminate coupling agents.

[0061] The total content of titanate-based coupling agents and aluminate-based coupling agents in the thermally conductive composition is not particularly limited. However, the total content of these coupling agents relative to 100% by volume of the thermally conductive composition is preferably 3% by volume or more and 30% by volume or less, more preferably 7% by volume or more and 25% by volume or less, and even more preferably 12% by volume or more and 20% by volume or less. When the total content of titanate-based coupling agents and aluminate-based coupling agents is 3% by volume or more relative to 100% by volume of the thermally conductive composition, the viscosity of the thermally conductive composition can be reduced more effectively. When the total content of titanate-based coupling agents and aluminate-based coupling agents is 30% by volume or less relative to 100% by volume of the thermally conductive composition, the content of inorganic powder fillers or base oil can be relatively increased, thus imparting high thermal conductivity or lubricity to the thermally conductive composition.

[0062] Furthermore, the total content of titanate-based coupling agent and aluminate-based coupling agent in the thermally conductive composition, relative to 100 parts by volume of inorganic powder filler, is preferably 5 parts by volume or more and 35 parts by volume or less, more preferably 10 parts by volume or more and 30 parts by volume or less, and even more preferably 15 parts by volume or more and 25 parts by volume or less.

[0063] Regarding the effect of further reducing the viscosity of the thermally conductive composition by increasing the total content of this titanate-based coupling agent and aluminate-based coupling agent, this effect cannot be obtained, for example, when using coupling agents or dispersants different from these coupling agents. Because this embodiment's thermally conductive composition contains both titanate-based and aluminate-based coupling agents, the increase in viscosity can be effectively suppressed even when the content of inorganic powder filler is increased.

[0064] (4) Other additives

[0065] To improve the various properties of the thermally conductive composition, other additives may be included depending on the application. These other additives may include, for example, thickeners, antioxidants, exudation inhibitors, resins, diluents, viscosity index improvers, etc.

[0066] The thermally conductive composition of this embodiment may contain a thickener as needed. The thickener is not an essential component in the thermally conductive composition of this embodiment. For example, when the thermally conductive composition is designed as a thermally conductive grease, the presence of a thickener allows for control of the viscosity of the grease and improves the spreadability of the thermally conductive composition.

[0067] Examples of thickeners include lithium soap, lithium complex soap, calcium soap, calcium complex soap, aluminum soap, aluminum complex soap, urea compounds, sodium terephthalate, polytetrafluoroethylene, organo-modified bentonite, silica gel, petroleum wax, fluororesin, and polyethylene wax.

[0068] The thermally conductive composition of this embodiment may contain an antioxidant as needed. While the antioxidant is not an essential component in the thermally conductive composition of this embodiment, its presence helps to inhibit the oxidation of the base oil contained in the composition.

[0069] Examples of antioxidants include amine-based antioxidants and phosphorus-based antioxidants. There are no particular limitations on amine-based antioxidants; for example, aromatic amine antioxidants such as alkylated diphenylamines, alkylated phenylnaphthylamines, and phenylenediamines can be used. Examples of alkylated diphenylamines include diphenylamine, p,p'-dibutyldiphenylamine, p,p'-dipentyldiphenylamine, p,p'-dihexyldiphenylamine, p,p'-diheptyldiphenylamine, p,p'-dioctyldiphenylamine, p,p'-dinonyldiphenylamine, and mixed alkyl diphenylamines with 4 to 9 carbon atoms. As alkylated phenylnaphthylamines, N-phenyl-α-naphthylamine, N-butylphenyl-α-naphthylamine, N-pentylphenyl-α-naphthylamine, N-hexylphenyl-α-naphthylamine, N-heptylphenyl-α-naphthylamine, N-octylphenyl-α-naphthylamine, N-nonylphenyl-α-naphthylamine, etc., can be used. Furthermore, as phenylenediamines, p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, etc., can be used.

[0070] As a phosphorus-based antioxidant, a phosphite-based antioxidant is preferred, and an alkylated phenyl phosphite is more preferred. Specifically, as an alkylated phenyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, 4,4'-butylidene bis(3-methyl-6-tert-butylphenyl-di-tetrazylphosphite), or alkanol (carbon number 12-16)-4,4'-isopropylidene diphenol can be used. Triphenyl phosphite condensate, [hexaalkyl(carbon 8-18)tri(alkyl(carbon 8-9)phenyl)]1,1,3-tris(3-tert-butyl-6-methyl-4-oxyphenyl)-3-methylpropane phosphite, [trialkyl(carbon 8-18)tri(alkyl(carbon 8-9)phenyl)]1,1,3-tris(3-tert-butyl-6-methyl-4-hydroxyphenyl)-3-methylpropane phosphite, etc. Among them, [hexaalkyl(carbon number 8-18)tri(alkyl(carbon number 8-9)phenyl)]1,1,3-tris(3-tert-butyl-6-methyl-4-hydroxyphenyl)-3-methylpropane phosphite or [trialkyl(carbon number 8-18)tri(alkyl(carbon number 8-9)phenyl)]1,1,3-tris(3-tert-butyl-6-methyl-4-hydroxyphenyl)-3-methylpropane phosphite can be used.

[0071] The thermally conductive composition of this embodiment may contain an exudation inhibitor as needed. The exudation inhibitor is not an essential component in the thermally conductive composition of this embodiment, but by containing an exudation inhibitor, the exudation of the thermally conductive composition can be suppressed.

[0072] Fluorinated surfactants can be used as exudation inhibitors. Here, a fluorinated surfactant refers to a surfactant having a fluorinated group. The structure of the fluorinated group is not particularly limited, but a perfluoroalkyl or perfluoroether structure is preferred, and surfactants based on compounds having such structures are preferred. Furthermore, nonionic surfactants having both a fluorinated group and a lipophilic group are preferred.

[0073] When the thermally conductive composition of this embodiment contains a percolation inhibitor, the content of the percolation inhibitor relative to 100% by mass of the thermally conductive composition is preferably 0.001% by mass or more and 1% by mass or less, more preferably 0.1% by mass or more and 0.5% by mass or less, and even more preferably 0.1% by mass or more and 0.2% by mass or less. By making the content of the percolation inhibitor 0.001% by mass or more, the diffusion of the base oil can be effectively suppressed, thereby suppressing percolation, which is therefore preferred. On the other hand, even if the content of the base oil diffusion inhibitor exceeds 1% by mass, the properties of the base oil diffusion inhibitor will not change significantly. By making the content of the base oil diffusion inhibitor 1% by mass or less relative to 100% by mass of the thermally conductive composition, the cost can be reduced, which is therefore preferred.

[0074] The thermally conductive composition of this embodiment may contain resin as needed. When it is desired to form an elastomer from the thermally conductive composition of this embodiment at room temperature and then heat it to form a viscous body, it is preferable to contain resins such as ethylene-propylene rubber, ethylene-butene copolymer, ethylene-butene-styrene copolymer, and ethylene-propylene-styrene copolymer.

[0075] Furthermore, if it is desired that the thermally conductive composition of this embodiment has viscous properties at room temperature and can be cured by heating, it is preferable to include a thermosetting resin such as epoxy resin and a curing agent.

[0076] Furthermore, when it is desired to produce a phase change type thermally conductive sheet with improved fluidity at high temperatures from the thermally conductive composition of this embodiment, it is preferable to include a thermoplastic resin. There are no particular limitations on the thermoplastic resin; examples include ester-based resins, acrylic-based resins, rosin-based resins, and cellulose-based resins. Additionally, wax-based resins may also be used.

[0077] The thermoplastic resin contained in the thermally conductive composition of this embodiment is particularly preferably a combination of wax-based resin and rosin-based resin, which improves the shape retention of the thermally conductive composition and enhances its adhesion to heat-generating elements such as modules even when softened by heating.

[0078] Wax-based resins are organic or silicone compounds that are solid at room temperature or below, but liquefy when heated. To impart desired properties to the thermally conductive composition, the penetration or melting point can be adjusted appropriately. Additionally, different types of waxes can be added.

[0079] Rosin-based resins refer to resins whose main components are structural units derived from rosin acids (such as abietic acid, neorosinic acid, longleaf abietic acid, piratic acid, isopiratic acid, and dehydrorosinic acid). To impart desired properties to the thermally conductive composition, physical properties such as softening point, acid value, and glass transition point can be appropriately adjusted. Additionally, different types of rosin-based resins can be added.

[0080] In addition, when wax-based resins and rosin-based resins are used together, the content ratio of wax-based resins and rosin-based resins can be appropriately adjusted in order to impart the desired properties to the thermally conductive composition.

[0081] The thermally conductive composition of this embodiment may contain a diluent as needed. The diluent can reduce the viscosity of the thermally conductive composition. The diluent is not an essential component in the thermally conductive composition of this embodiment, but, for example, by using a thermally conductive composition containing a diluent, a thermally conductive sheet can be formed by conventional coating methods such as screen printing.

[0082] Examples of diluents include hydrocarbon solvents, aromatic solvents, ketone solvents, and ester solvents. In the case where the thermally conductive composition of this embodiment contains a diluent, the flash point or boiling point of the diluent can be appropriately adjusted to impart the desired properties to the thermally conductive composition.

[0083] The thermally conductive composition of this embodiment may contain a viscosity index improver if necessary. The viscosity index improver increases the viscosity of the thermally conductive composition. While the viscosity index improver is not a necessary component in the thermally conductive composition of this embodiment, its presence allows the viscosity of the thermally conductive composition to be prepared to a preferred range, for example.

[0084] Examples of viscosity index improvers include lipophilic polymers with molecular weights ranging from 10,000 to 1,500,000. At low temperatures, the cohesive energy of the polymer is greater than its affinity for the solvent. Therefore, when a viscosity index improver is present in a thermally conductive composition, it dissolves in the base oil in a contracted state. Consequently, the increased kinetic energy of the thermally conductive composition at high temperatures exceeds its cohesive energy, leading to an increased viscosity index that causes the base oil to swell and become entrained. This increases the flow resistance of the lubricant, thus preventing viscosity degradation at high temperatures.

[0085] Examples of viscosity index improvers include polymethyl methacrylate compounds, olefin copolymer compounds, and mixtures thereof. It should be noted that the larger the molecular weight, the easier it is for the main chain to be cleaved by shear forces, leading to a decrease in molecular weight, which can sometimes make it difficult to achieve the desired effect. Therefore, it is preferable to adjust the molecular weight of the viscosity index improver according to the desired viscosity.

[0086] 2. Method for manufacturing thermally conductive compositions

[0087] Regarding the manufacture of the thermally conductive composition of this embodiment, the method is not particularly limited as long as the components can be uniformly mixed. A common manufacturing method includes mixing using a planetary mixer, a rotary mixer, or similar equipment, and further uniformly mixing using a three-roll mill. It should be noted that the thermally conductive paste described later can be manufactured using the same method.

[0088] The resulting thermally conductive composition preferably has a thermal conductivity of 3.0 W / mK or higher at room temperature, more preferably 3.5 W / mK or higher, and even more preferably 3.8 W / mK or higher. By controlling the composition to achieve this thermal conductivity, heat from the heat-generating component can be transferred more effectively to the heat-dissipating component. It should be noted that the thermal conductivity of the thermally conductive composition can be measured using, for example, a rapid thermal conductivity meter QTM-500 manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0089] The shear viscosity (shear rate: 0.01 to 10 / s) of the obtained thermally conductive composition at room temperature depends on the types of components it contains, but is preferably 450 Pa·s or less, more preferably 430 Pa·s or less, and even more preferably 425 Pa·s or less. The shear viscosity of the thermally conductive composition can be measured using a rheometer (Anton Paar MC302e).

[0090] Example

[0091] The present invention will now be described in detail based on embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0092] 1. Preparation of thermally conductive compositions

[0093] Using the materials shown in (A) to (D) below, thermally conductive compositions with the compositions shown in Table 1 below were manufactured.

[0094] (A) Inorganic powder filler

[0095] Zinc oxide 1: Average particle size 5 μm

[0096] Zinc oxide 2: Average particle size 2μm

[0097] Zinc oxide 3: average particle size 0.6 μm

[0098] Alumina 1: Average particle size 5μm

[0099] Aluminum 1: Average particle size 5μm

[0100] It should be noted that the average particle size of each inorganic powder filler was determined using a particle size distribution measuring device (SALD-7000 manufactured by Shimadzu Corporation) via laser diffraction scattering.

[0101] (B) Base oil

[0102] Polyol ester oil

[0103] (C) Coupling agent

[0104] (C-1) Titanate coupling agent (isopropyl tris(dioctyl pyrophosphate) titanate)

[0105] (C-2) Aluminate coupling agent (acetylalkoxyaluminum dialkylate)

[0106] (D) Dispersant

[0107] Polyether carboxylic acid

[0108] As shown in Table 1 below, the thermally conductive compositions of Examples 1-9 and Comparative Examples 1-9 were prepared by mixing compounds (A) to (D) as described in Table 1. Specifically, the compositions were placed in a planetary mixer in the amounts shown in Table 1. Then, the mixtures were kneaded three times using a three-roll mill to produce the thermally conductive compositions.

[0109] The thermal conductivity and viscosity were evaluated using the thermally conductive compositions of Examples 1-9 and Comparative Examples 1-9 manufactured by the following method.

[0110] (1) Determination of thermal conductivity

[0111] The thermal conductivity of the obtained thermally conductive compositions was measured. Specifically, the thermal conductivity of the thermally conductive compositions of Examples 1-9 and Comparative Examples 1-9 was measured at room temperature using a rapid thermal conductivity meter QTM-500 manufactured by Kyoto Electronics Industries, Ltd., Japan.

[0112] (2) Viscosity determination

[0113] The shear viscosity of the obtained thermally conductive compositions was determined. Specifically, the thermally conductive compositions of Examples 1-9 and Comparative Examples 1-9 were measured using a rheometer (Anton Paar MC302e) capable of controlling the ambient temperature at 0.01-10 s, and evaluated at room temperature. The viscosity at 6 s was used as the viscosity value at the time of printing for comparison.

[0114]

[0115] As can be seen from the table above, if the thermally conductive composition of the embodiment contains at least one of titanate coupling agent or aluminate coupling agent, the increase in viscosity can be effectively suppressed.

[0116] Specifically, the thermally conductive compositions of Examples 2, 3, 5, 6, 8, 9, 11, and 12, in which the content of titanate-based coupling agent or aluminate-based coupling agent is 7% by volume or more of the total amount of the thermally conductive composition (or, in which the content of titanate-based coupling agent or aluminate-based coupling agent is 10% by volume or more relative to 100 parts by volume of inorganic powder filler), exhibit reduced viscosity compared to the thermally conductive compositions of Examples 1, 4, 7, and 10. Furthermore, the thermally conductive compositions of Examples 2, 3, 5, 6, 8, 9, 11, and 12 exhibit increased thermal conductivity compared to the thermally conductive compositions of Examples 1, 4, 7, and 10.

[0117] On the other hand, the thermally conductive compositions of Comparative Examples 1-9, which contain dispersants instead of coupling agents, cannot effectively suppress the increase in viscosity.

[0118] Furthermore, no increase in thermal conductivity was observed between the thermally conductive compositions of Comparative Examples 1, 4, and 7, where the dispersant content was 5% by volume in the total thermally conductive composition, and the thermally conductive compositions of Comparative Examples 2, 3, 5, 6, 8, and 9, where the dispersant content was 7% by volume or more in the total thermally conductive composition. Therefore, it can be concluded that the increase in thermal conductivity of the thermally conductive compositions of Examples 2, 3, 5, 6, 8, 9, 11, and 12 compared to the thermally conductive compositions of Examples 1, 4, 7, and 10 is due to the titanate-based or aluminate-based coupling agent.

Claims

1. A thermally conductive composition comprising a base oil and an inorganic powder filler, wherein, The thermally conductive composition further contains at least one of a titanate coupling agent or an aluminate coupling agent.

2. The thermally conductive composition according to claim 1, wherein, The total content of the titanate coupling agent and the aluminate coupling agent is 3% to 30% by volume relative to 100% by volume of the thermally conductive composition.

3. The thermally conductive composition according to claim 1 or 2, wherein, The inorganic powder filler is selected from one or more of the group consisting of copper, aluminum, zinc oxide, magnesium oxide, aluminum oxide, aluminum nitride, and silicon carbide.

4. The thermally conductive composition according to claim 1 or 2, wherein, The base oil is selected from one or more of the group consisting of mineral oil, synthetic hydrocarbon oil, diester, polyol ester and phenyl ether.

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