WO2019235478A1 - ダイヤモンド粒子、ダイヤモンド含有組成物、及びダイヤモンド粒子の製造方法 - Google Patents
ダイヤモンド粒子、ダイヤモンド含有組成物、及びダイヤモンド粒子の製造方法 Download PDFInfo
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- WO2019235478A1 WO2019235478A1 PCT/JP2019/022178 JP2019022178W WO2019235478A1 WO 2019235478 A1 WO2019235478 A1 WO 2019235478A1 JP 2019022178 W JP2019022178 W JP 2019022178W WO 2019235478 A1 WO2019235478 A1 WO 2019235478A1
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/25—Diamond
- C01B32/28—After-treatment, e.g. purification, irradiation, separation or recovery
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K9/00—Use of pretreated ingredients
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L101/00—Compositions of unspecified macromolecular compounds
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L83/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon only; Compositions of derivatives of such polymers
- C08L83/04—Polysiloxanes
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- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09C—TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES ; PREPARATION OF CARBON BLACK ; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS
- C09C1/00—Treatment of specific inorganic materials other than fibrous fillers; Preparation of carbon black
- C09C1/44—Carbon
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/30—Particle morphology extending in three dimensions
- C01P2004/32—Spheres
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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- C01P2006/32—Thermal properties
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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- C01P2006/40—Electric properties
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
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- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
- C08G77/04—Polysiloxanes
- C08G77/12—Polysiloxanes containing silicon bound to hydrogen
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G77/00—Macromolecular compounds obtained by reactions forming a linkage containing silicon with or without sulfur, nitrogen, oxygen or carbon in the main chain of the macromolecule
- C08G77/04—Polysiloxanes
- C08G77/20—Polysiloxanes containing silicon bound to unsaturated aliphatic groups
Definitions
- the present invention relates to diamond particles, a diamond-containing composition containing diamond particles, and a method for producing diamond particles, which are used for, for example, a heat dissipation member.
- a heat radiating member may be provided to radiate heat generated from the electronic component to the outside of the device.
- the heat radiating member is disposed, for example, between an electronic component and a housing or a heat sink.
- the heat radiating member is generally formed from a resin composition in which a heat conductive filler is blended with a resin or an elastomer.
- Patent Document 1 a silicone resin composition having a silicone resin, diamond, zinc oxide, and a dispersant is known. Since diamond has higher thermal conductivity than alumina, magnesium oxide, boron nitride and the like that are generally used as a thermally conductive filler, the silicone resin composition of Patent Document 1 has good heat dissipation. Further, diamond has a low electrical conductivity, and easily imparts electrical insulation to the heat dissipation member. In Patent Document 1, silicone oil and silicone gel are used as the silicone resin.
- the composition for forming the heat dissipating member it is desirable to cure the composition for forming the heat dissipating member from the viewpoint of improving the handleability.
- a composition containing diamond diamond-containing composition
- the curability is lowered and sufficient. This causes problems such as not being cured. If the diamond-containing composition is not sufficiently cured, liquid dripping or the like may occur, contaminating the electronic device, and causing problems such as failure to hold the heat dissipation member in a certain shape.
- the diamond-containing composition is stored for a long period of time, the polymer matrix may deteriorate and the curability may decrease.
- an object of the present invention is to provide diamond particles capable of appropriately curing a diamond-containing composition and a diamond-containing composition.
- the inventors of the present invention have studied the cause of the decrease in curability in a diamond-containing composition containing diamond particles and a polymer matrix, and as a result, ionic impurities attached to the diamond particles inhibit the curing, It was found that the molecular matrix was degraded. And it discovered that the said subject could be solved by reducing the amount of the ionic impurity, and completed the following this invention. That is, the present invention provides the following [1] to [11].
- a method for producing diamond particles [6] A diamond-containing composition containing the diamond particles according to the above [1] and a polymer matrix. [7] In a diamond-containing composition containing diamond particles and a polymer matrix, The complex elastic modulus after 5 minutes when cured by heating at 70 ° C. is A2, and the complex elastic modulus after 30 minutes when cured by heating at 70 ° C. is A4.
- a diamond-containing composition having a rate of change at the start of curing represented by ((A2-A1) / (A4-A1)) ⁇ 100 of 50% or more, where A1 is a complex elastic modulus.
- A1 is a complex elastic modulus.
- the diamond-containing composition according to [10] wherein a filling rate of the diamond particles is 10% by volume or more and 90% by volume or less.
- diamond particles capable of improving the curability of the diamond-containing composition and the diamond-containing composition can be provided.
- the diamond particles of the present invention are represented by the following formula, where Ds is the ionic conductivity of an aqueous solution obtained by elution by PCT performed according to IEC68-2-66, and Dw is the ionic conductivity of distilled water.
- the ionic conductivity Di is 0.8 mS / m or less.
- Di Ds ⁇ Dw PCT is an abbreviation for pressure cooker test, and diamond particles are exposed to high temperature and high humidity by PCT, so that almost all ionic impurities attached to the surface of diamond particles are removed from the particles.
- the amount of ionic impurities adhering to the surface of the diamond particles can be detected by measuring the above-described ion conductivity Di.
- the ionic conductivity Di exceeds 0.8 mS / m
- the amount of ionic impurities adhering to the surface of the diamond particles increases, and the diamond-containing composition containing the diamond particles and the polymer matrix is cured. It becomes difficult. Therefore, it becomes difficult to increase the curing rate of the diamond-containing composition.
- ionic impurities adhering to the surface of the diamond particles may deteriorate the polymer matrix, resulting in a decrease in curability after long-term storage.
- the ionic conductivity Di of the diamond particles is preferably 0.7 mS / m or less, more preferably 0.55 mS / m or less, and further preferably 0.52 mS / m or less.
- the ionic conductivity Di is not more than these upper limit values, the curability of the diamond-containing composition becomes excellent, and the curing rate can be sufficiently increased.
- the diamond-containing composition can be appropriately cured even after long-term storage, and the curability after long-term storage is improved.
- the ionic conductivity Di of the diamond particles is preferably as low as possible, but is preferably 0.05 mS / m or more, and preferably 0.10 mS / m or more from the viewpoint of preventing the amount of impurities from being reduced more than necessary and improving productivity. Is more preferable, and 0.15 mS / m or more is more preferable.
- the diamond particles of the present invention are typically synthetic diamond.
- Synthetic diamond usually has a minute amount of components derived from a compound such as a metal catalyst and an acid component used in the production process as ionic impurities on the surface of diamond particles (raw material diamond particles).
- the ionic conductivity Di of the diamond particles can be lowered as described above by removing ionic impurities adhering to the raw material diamond particles in a small amount by a cleaning process described later.
- the impurities attached to the surface of the raw material diamond particles are not particularly limited, and are, for example, compounds containing at least one of a metal atom, a sulfur atom, a phosphorus atom, a silicon atom, a halogen atom, a nitrogen atom and the like.
- metal atoms often inhibit the curing reaction.
- a diamond-containing composition is cured by a curing catalyst such as a platinum-based catalyst, such as in the case of an addition reaction type silicone resin, the curing catalyst is used. Is deactivated to make it difficult to cure the diamond-containing composition.
- the metal atom is attached to the surface of the diamond particle in a metal salt state, for example.
- the metal atom is usually derived from a metal catalyst used at the time of diamond production, and specifically includes iron, chromium and the like.
- Sulfur atoms are attached to the surface of the diamond particles in the form of a salt such as sulfate.
- a sulfur atom originates in the acid used for acid cleaning, for example. Impurities containing sulfur atoms such as sulfates often deteriorate the polymer matrix, and for example, the silicone compound may be cut to lower the molecular weight.
- the ion conductivity Di By setting the value to a predetermined value or less, the content of these atoms is also reduced. Therefore, deterioration of the polymer matrix can be prevented, and further, the curing reaction can be appropriately advanced to increase the curing rate.
- the impurities attached to the surface of the diamond particles include those derived from iron atoms and chromium atoms, as described above, and these easily deteriorate the polymer matrix. Therefore, in another aspect of the present invention, it is a feature that the content of these impurities is reduced in the diamond particles.
- the chromium element content and the iron element content in the diamond particles may be 0.5 mass ppm or less. These contents are all preferably 0.3 mass ppm or less, more preferably 0.2 mass ppm or less. When the contents of chromium element and iron element are both below these upper limit values, deterioration of the polymer matrix is appropriately prevented. Furthermore, it is possible to appropriately proceed without inhibiting the curing reaction and increase the curing rate.
- the content of the chromium element and the iron element in the diamond particles should be as small as possible, but from the viewpoint of improving productivity by preventing these contents from being lowered more than necessary, preferably 0.001.
- the mass ppm or more more preferably 0.01 mass ppm or more.
- chromium element and the iron element is, for example, chromium sulfate (CrSO 4), is estimated to be attached to the diamond particles as an iron sulfate (FeO 4), they are particularly susceptible to inhibit the curing reaction.
- the sphericity of the diamond particles of the present invention is, for example, 0.5 or more, preferably 0.55 or more, more preferably 0.6 or more. As the sphericity is closer to 1, it becomes an index indicating that it is closer to a sphere. By increasing the sphericity, the diamond particles can be easily dispersed in the polymer matrix, and the filling rate can be further increased.
- the upper limit of the sphericity is not particularly limited and is 1.
- the sphericity of the diamond particles can be obtained by confirming an electron micrograph and calculating (the diameter of a circle equal to the projected area of the particle / the diameter of the smallest circle circumscribing the projected image of the particle).
- the sphericity means an average value of the plurality of diamond particles.
- the average value of diamond particles may be the average value of the sphericity of 300 particles measured as described above, but when there are not 300 diamond particles, it means the average value of all diamond particles.
- the specific shape of the diamond particles is not particularly limited, and may be, for example, a spherical shape, a crushed shape, or other shapes.
- the spherical shape means a spherical shape or a shape that approximates a spherical shape.
- a spherical shape having a sphericity of 0.8 or more is defined as a spherical shape.
- the crushing shape means a shape refined by crushing, and generally has a square shape.
- the crushing shape has, for example, a sphericity of 0.5 or more and less than 0.8, preferably 0.55 or more and less than 0.8, more preferably 0.6 or more and less than 0.8.
- the particle diameter of the diamond particles is, for example, not less than 0.1 ⁇ m and not more than 250 ⁇ m.
- the particle size of the tiremond particles By setting the particle size of the tiremond particles to 0.1 ⁇ m or more, the thermal conductivity is easily increased in the diamond-containing composition described later. Further, when the diamond particles are 250 ⁇ m or less, they can be appropriately dispersed in the polymer matrix and can be blended in the diamond-containing composition with a high filling rate. From these viewpoints, the particle diameter of the diamond particles is preferably 0.5 ⁇ m or more and 200 ⁇ m or less, more preferably 1 ⁇ m or more and 150 ⁇ m or less, and further preferably 10 ⁇ m or more and 100 ⁇ m or less.
- the particle size means an average value (average particle size) of the plurality of diamond particles.
- the average particle diameter is an average particle diameter obtained by averaging the particle diameters on a volume basis, and can be measured using, for example, a “laser diffraction particle size distribution analyzer” manufactured by Horiba, Ltd. About the calculation method of an average particle diameter, what is necessary is just to let the particle diameter (d50) when an accumulation volume is 50% be an average particle diameter.
- the diamond particles contained in the diamond-containing composition may include two or more kinds of diamonds having different average particle diameters.
- the diamond particles having the smaller average particle diameter enter between the diamonds having the larger average particle diameter, and appropriately disperse the diamond particles in the polymer matrix. It is easy to increase the filling rate of diamond.
- a diamond containing composition contains 2 or more types of diamonds from which an average particle diameter differs by two or more peaks appearing in the particle size distribution of a diamond particle. The same applies to other thermally conductive fillers to be described later.
- the diamond particles are, for example, diamond having an average particle diameter of 10 ⁇ m or more and 250 ⁇ m or less (hereinafter also referred to as “large-diameter diamond”), and an average particle diameter of 0.2 ⁇ m.
- large-diameter diamond diamond having an average particle diameter of 10 ⁇ m or more and 250 ⁇ m or less
- small-diameter diamond A mixture of diamonds having a diameter of 1 ⁇ m or more and less than 10 ⁇ m (hereinafter also referred to as “small-diameter diamond”) is preferable.
- the volume ratio of the large particle size diamond to the small particle size diamond is, for example, 0.1 or more and 10 or less , Preferably 0.2 or more and 8 or less, more preferably more than 0.3 and 6 or less.
- the average particle diameter of the large-diameter diamond is more preferably 15 ⁇ m or more and 200 ⁇ m or less, and further preferably 18 ⁇ m or more and 150 ⁇ m or less.
- the large-diameter diamond may be used in combination with two types of diamonds having different average particle diameters.
- the average particle size of the small-diameter diamond is more preferably 0.2 ⁇ m or more and 8 ⁇ m or less, and further preferably 0.5 ⁇ m or more and 7 ⁇ m or less.
- the small-diameter diamond two kinds of diamonds having different average particle diameters may be used in combination.
- the diamond particles need not include both small-diameter diamonds and large-diameter diamonds, for example, two or more kinds of small particles having different average particle diameters. Only two or more kinds of diamonds having a particle diameter may be used, or two or more kinds of large-diameter diamonds having different average particle diameters may be used.
- Two or more kinds of diamond particles having different average particle diameters may have the same or different sphericity, but the sphericity is preferably within the above range.
- the diamond particles of the present invention may be subjected to a surface treatment as long as the ion conductivity Di, the amount of impurities, and the like are within the predetermined ranges described above.
- a surface treatment agent such as a silane compound, an organic titanium compound, an organoaluminum compound, and a phosphoric acid compound, and are preferably surface-treated with a silane compound.
- the silane compound include known silane coupling agents.
- the diamond particles of the present invention can be produced, for example, by the production methods of the following first and second embodiments.
- the method for producing diamond particles according to the first embodiment of the present invention includes a washing step of washing generally available diamond particles (hereinafter also referred to as “raw material diamond particles”) with a polar solvent.
- raw material diamond particles generally available diamond particles
- the amount of various ionic impurities adhering to the surface of the diamond particles can be reduced, and the ionic conductivity Di can be lowered as described above.
- the content of various impurities including chromium atoms and iron atoms can be set to a predetermined value or less as described above.
- the method for producing diamond particles according to the second embodiment of the present invention includes a step of cleaning the raw diamond particles with a cleaning liquid obtained by adding a cleaning agent to a polar solvent.
- a cleaning liquid obtained by adding a cleaning agent to a polar solvent.
- the amount of various ionic impurities adhering to the surface of the diamond particles can be reduced, and the ionic conductivity Di as described above. Can be lowered.
- the content of various impurities including chromium atoms and iron atoms can be set to a predetermined value or less as described above.
- the cleaning liquid used in the second embodiment includes a cleaning agent and a polar solvent, and is obtained by adding the cleaning agent to the polar solvent by a known method.
- the cleaning agent include organic acids and inorganic bases.
- Organic acids having 2 to 6 carbon atoms in the molecule such as acetic acid, citric acid, malonic acid, maleic acid, fumaric acid, oxalic acid, propionic acid, lactic acid, malic acid, tartaric acid, succinic acid, glycolic acid Is mentioned.
- the inorganic base include alkali metal bases such as sodium hydroxide and potassium hydroxide.
- organic acids having 2 to 6 carbon atoms in the molecule are preferred, acetic acid and citric acid are more preferred, and citric acid is particularly preferred.
- organic acid By using an organic acid, the ionic impurities adhering to the diamond particle surface can be effectively removed without adhering the ionic impurities derived from the cleaning agent to the diamond particle surface.
- the cleaning liquid used in the second embodiment becomes acidic or alkaline depending on the type of the cleaning agent by adding the cleaning agent to a polar solvent such as water.
- a polar solvent such as water.
- an acidic cleaning agent such as an organic acid becomes acidic
- the pH of the specific cleaning liquid is, for example, 1 or more and 5.5 or less, preferably 1.5 or more and 5 or less.
- the cleaning liquid used in the second embodiment becomes acidic when a basic cleaning agent such as an inorganic base is added.
- the pH of the specific cleaning liquid is, for example, 9 or more and 13 or less, preferably 10 or more. 12 or less.
- the concentration of the cleaning agent in the cleaning liquid is not particularly limited, but may be, for example, about 0.1 mmol / L to 1 mol / L, preferably 0.5 mmol / L to 500 mmol / L.
- Examples of the raw material diamond particles used in the production methods of the first and second embodiments include synthetic diamond produced by a conventionally known method.
- the manufacturing method is not particularly limited, it can be synthesized by crystallizing a carbon raw material such as graphite in the presence of a metal catalyst such as iron or chromium under high temperature and high pressure.
- the diamond particles synthesized in this way are subjected to acid cleaning or the like in order to remove graphite, impurities, etc. as impurities. For this reason, as described above, a minute amount of a metal catalyst-derived component, an acid-derived component, or the like is attached to the surface of the diamond particle as an ionic impurity.
- the raw diamond particles may be commercially available products.
- Commercially available products include TMS series, AGD series, CMM series, MD series, IMS series manufactured by Tomei Dia Co., Ltd., MB grade, MBP grade, MBP2 grade, MBMC grade, MBA grade, MBE grade, MRB made by Saint-Gobain Co., Ltd. Grade and so on.
- Further examples include GMM diamond, MBG diamond manufactured by Hyperion, MDA manufactured by Element Six, and IMPM manufactured by Iljin.
- the solvent used in the first and second embodiments of the present invention is a polar solvent. If it is not a polar solvent, in the first embodiment, the ionic impurities attached to the surface of the diamond particles cannot be sufficiently removed, and it may be difficult to adjust the ionic conductivity Di within the above range. Further, when the pH is lowered, a large amount of ionic components are contained in the polar solvent, and the ionic components may adhere to the surface of the diamond particles, which may increase the ionic conductivity Di. From the viewpoint of reducing the ionic component in the polar solvent, the polar solvent preferably has a neutral or near-neutral property. Specifically, the pH of the polar solvent is preferably 5 or more.
- the pH of the polar solvent can be measured using an electronic pH meter.
- the polar solvent in each embodiment include water and alcohol, and water is more preferable in order to lower the ion conductivity Di and the amount of impurities attached to the diamond particles.
- the alcohol include alcohols having 1 to 4 carbon atoms. Specific examples include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, isobutyl alcohol, t-butyl alcohol, and ethylene glycol. In these, methanol and ethanol are preferable and ethanol is more preferable.
- water Distilled water, ion-exchange water, a pure water etc. can be used conveniently, However, You may use a tap water, industrial water, etc.
- the polar solvent preferably contains substantially no ionic component. Therefore, the content of the ionic component in the polar solvent is 100 mass ppm or less, more preferably 0.1 mass ppm or more and 50 mass ppm or less. The content of the ionic component can be measured by ion chromatography.
- the cleaning with the polar solvent or the cleaning liquid in each of the above embodiments includes, for example, adding diamond particles in the polar solvent or the cleaning liquid, stirring the polar solvent or the cleaning liquid containing the diamond particles, and then the diamond particles being the polar solvent or the cleaning liquid. This is done by separating from Stirring may be performed, for example, with a vibration stirrer or stirring using a stirring blade. Separation of the diamond particles from the polar solvent or the washing liquid may be performed by filtration, decantation, or centrifugation, and filtration is particularly preferable.
- the cleaning with the polar solvent or the cleaning liquid is completed, the diamond particles are appropriately dried and the polar solvent attached to the surfaces of the diamond particles is removed.
- the amount of the polar solvent or cleaning liquid used is preferably 1 to 10 times, more preferably 1.5 to 8 times, based on the mass of the diamond particles.
- the temperature of the polar solvent or the cleaning liquid may be from the melting point to the boiling point of the polar solvent, for example, 5 ° C. or more and 100 ° C. or less.
- stirring time is 1 minute or more and 10 hours or less, for example.
- the temperature of the polar solvent (that is, water) or the cleaning liquid in the cleaning step is preferably relatively high, specifically 50 ° C. or higher. 60 ° C. or higher is more preferable, and 65 ° C. or higher is more preferable.
- impurities adhering to the surface of the diamond particles are removed by elution in the solvent and by washing off by stirring, etc., but when water is used as the polar solvent, the impurities are removed in the solvent. It is presumed that it is dominant to be eluted and removed.
- the temperature of the polar solvent or cleaning liquid is increased to some extent as described above to increase the amount of impurities that dissolve in the water, thereby removing impurities by cleaning. Efficiency can be improved. Further, as in the second embodiment, by using a cleaning liquid in which a cleaning agent is added to a polar solvent, it is possible to further improve the efficiency of removing impurities by cleaning.
- the temperature of the polar solvent or the cleaning liquid may be 100 ° C. or less, but is preferably 90 ° C. or less, more preferably 80 ° C. or less from the viewpoint of productivity. Further, the stirring of the polar solvent or the cleaning liquid to which the diamond particles are added may be performed under atmospheric pressure.
- the stirring time is preferably increased, preferably 1.5 hours or more, more preferably 2.5 hours or more, 5 More preferable is an hour or more.
- the stirring time is preferably short from the viewpoint of productivity, and is preferably 10 hours or less, more preferably 8 hours or less.
- the temperature of the polar solvent or the cleaning liquid is not particularly limited, and may be, for example, 5 ° C. or more and 100 ° C. or less. More preferably, it is not higher than ° C. It is presumed that impurities adhering to the surface of the diamond particles are dominantly removed by washing by stirring when alcohol is used as a polar solvent. Therefore, even if the temperature of the polar solvent or the cleaning liquid is relatively low as 50 ° C. or less, impurities can be removed appropriately. Further, by adjusting the temperature of the polar solvent or the cleaning liquid within the above range, the temperature of the polar solvent or the cleaning liquid is hardly adjusted, so that the productivity is improved.
- the stirring time is preferably 1 minute or more and 1 hour or less, more preferably 2 minutes or more and 30 minutes or less, and further preferably 3 minutes or more and 20 minutes or less.
- the polar solvent is alcohol, it is possible to remove impurities without inferiority even when the stirring time in the washing step is shortened or longer. Moreover, productivity is improved by shortening the stirring time.
- the cleaning with the polar solvent or the cleaning liquid may be repeated a plurality of times. That is, the washing process may be performed again by adding the diamond particles washed and separated from the polar solvent or washing liquid as described above to the newly prepared polar solvent or washing liquid.
- the cleaning may be performed once or more, but when it is performed a plurality of times, it is preferably performed twice or more. By performing the cleaning a plurality of times, more impurities can be removed, and the ionic conductivity Di can be further reduced.
- the number of times of washing is not particularly limited, but is preferably 10 times or less, more preferably 5 times or less, and further preferably 3 times or less from the viewpoint of productivity.
- a part of the plurality of cleanings may be performed with a cleaning liquid to which a cleaning agent is added, and the rest may be performed with a polar solvent.
- the order of the cleaning with the cleaning liquid to which the cleaning agent is added and the cleaning with the polar solvent are not particularly limited, but after the cleaning with the cleaning liquid is performed once or a plurality of times, the cleaning with the polar solvent is performed once or It is preferable to carry out several times. This prevents the cleaning agent from adhering to the resulting diamond particles, and makes it easier to lower the ionic conductivity described above.
- the diamond-containing composition of the present invention contains diamond particles and a polymer matrix.
- the diamond-containing composition contains diamond particles having a low volume resistivity and a high thermal conductivity, so that both the insulating properties and the thermal conductivity are excellent.
- the diamond particles described above may be used as the diamond particles used in the diamond-containing composition of the present invention, and the details thereof are as described above.
- the ionic conductivity Di of the diamond particles is lowered as described above, or the content of ionic impurities having chromium atoms, iron atoms, etc. is lowered, whereby the curability is improved and the diamond content is increased.
- the curing rate of the composition is increased. Further, even when stored for a long period of time, it is possible to prevent the polymer matrix from being deteriorated and the curability from being lowered.
- the filling rate of diamond particles in the diamond-containing composition is preferably 10% by volume to 90% by volume, more preferably 20% by volume to 85% by volume, and 25% by volume to 80% by volume. Further preferred.
- the thermal conductivity of a diamond containing composition can be made high by making the filling rate of a diamond particle more than these lower limits. Moreover, even if the filling rate of diamond particles is relatively high, the use of diamond particles having a low elution ion conductivity can improve the curability of the diamond-containing composition. Furthermore, by setting the upper limit value or less, diamond particles can be appropriately dispersed in the polymer matrix.
- the filling rate of diamond particles is relatively high.
- the filling rate of diamond particles is preferably 20% by volume to 90% by volume, more preferably 30% by volume to 85% by volume, and more preferably 40% by volume to 80% by volume. A volume% or less is more preferable.
- the filling rate of diamond particles need not be so high.
- the filling rate of diamond particles is preferably 10% by volume to 80% by volume, more preferably 20% by volume to 75% by volume, and further preferably 25% by volume to 60% by volume.
- the “filling rate” means volume% with respect to the total volume of the diamond-containing composition.
- the filling rate of diamond particles occupies the diamond particles with respect to the total volume of the diamond-containing composition.
- polymer matrix examples of the polymer matrix in the present invention include resins and liquid polymer components.
- the resin examples include curable resins such as silicone resin, epoxy resin, urethane resin, phenol resin, unsaturated polyester resin, and polyimide resin.
- the curable resin may be any of a moisture curable type, a thermosetting type, and a photocurable type, but a thermosetting type is preferable.
- Polyolefin resin such as polypropylene resin, polyethylene resin, poly (1-) butene resin, and polypentene resin, polyester resin such as polyethylene terephthalate, polystyrene resin, acrylonitrile-butadiene-styrene (ABS) resin, ethylene vinyl acetate copolymer
- Thermoplastic resins such as (EVA), (meth) acrylic resin, polyamide resin, and polyvinyl chloride resin (PVC) may be used.
- elastomer resins such as acrylonitrile butadiene rubber, ethylene-propylene-diene rubber, ethylene-propylene rubber, natural rubber, polybutadiene rubber, and polyisoprene rubber can be used. These elastomer resins may be liquid elastomers that are liquid at room temperature (23 ° C.) and normal pressure (1 atm), may be solid, or may be a mixture thereof. Further, as the elastomer resin, thermoplastic elastomers such as polyester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, and styrene-based thermoplastic elastomers can also be used.
- the polymer matrix may use silicone oil or the like as the liquid polymer component.
- These liquid polymer components may be used alone or in combination with a resin.
- the silicone oil include methylphenyl silicone oil, dimethyl silicone oil, and modified silicone oil.
- the viscosity of the silicone oil at 25 ° C. is preferably 5 mPa ⁇ s or more and 1000 mPa ⁇ s or less, more preferably 30 mPa ⁇ s or more and 700 mPa ⁇ s or less, and further preferably 150 mPa ⁇ s or more and 600 mPa ⁇ s or less.
- the liquid polymer component is liquid at room temperature and normal pressure at the time of blending, and is also a liquid or gel-like component at the time of use. That is, the liquid polymer component is not cured by a curing agent or the like, and even if it is cured, it becomes a liquid or gel after curing. Therefore, when the liquid polymer component is used alone or in a relatively high blending ratio, the heat dissipating member formed from the diamond-containing composition can be made into a paste.
- the polymer matrix preferably has curability in the above.
- the curable polymer matrix is preferably the curable resin described above, and more preferably a thermosetting resin.
- the polymer matrix is preferably a silicone such as silicone oil or silicone resin, but is preferably a silicone resin such as a condensation curable silicone resin or an addition reaction curable silicone resin, with an addition reaction curable silicone resin being particularly preferred.
- Silicone may be deteriorated by molecular chains being broken by sulfur atoms contained in impurities attached to the surface of diamond particles. In the present invention, the amount of such impurities is reduced. Therefore, deterioration of the silicone is suppressed, and a decrease in curability after long-term storage is suppressed.
- the addition reaction curable silicone resin is preferably composed of a silicone compound as a main agent and a curing agent for curing the main agent.
- the silicone compound used as the main agent is preferably an organopolysiloxane having an alkenyl group, specifically, vinyl end-terminated polydimethylsiloxane, vinyl end-terminated polyphenylmethylsiloxane, vinyl end-terminated dimethylsiloxane-diphenylsiloxane copolymer, vinyl Examples thereof include vinyl end-terminated organopolysiloxanes such as a both-end dimethylsiloxane-phenylmethylsiloxane copolymer and a vinyl end-end dimethylsiloxane-diethylsiloxane copolymer.
- the silicone compound used as the main agent has a viscosity at 25 ° C. of preferably 5 mPa ⁇ s or more and 1000 mPa ⁇ s or less, more preferably 30 mPa ⁇ s or more and 700 mPa ⁇ s or less, and further preferably 150 mPa ⁇ s or more and 600 mPa ⁇ s or less. is there.
- the viscosity is measured using a viscometer (BROOKFIELD rotational viscometer DV-E) with spindle No. It is good to measure using a rotor of 14 at a rotation speed of 5 rpm and a measurement temperature of 25 ° C.
- the curing agent used for the addition reaction curable silicone resin is not particularly limited as long as it can cure the silicone compound as the main component, but is an organopolysiloxane having two or more hydrosilyl groups (SiH). Organohydrogenpolysiloxane is preferred.
- the ratio (molar ratio) of the hydrosilyl group to the vinyl group of the silicone compound is preferably 0.3 or more and 5 or less, more preferably 0.4 or more and 4 or less, and further preferably 0.6 or more and 4 or less.
- the reaction between the main agent and the curing agent may not proceed due to the diamond particles. However, when the molar ratio is 0.6 or more, the reaction proceeds and the curability is improved. It becomes good.
- organohydrogenpolysiloxane examples include methylhydrosiloxane-dimethylsiloxane copolymer, polymethylhydrosiloxane, polyethylhydrosiloxane, methylhydrosiloxane-phenylmethylsiloxane copolymer, and the like. These may contain a hydrosilyl group at the terminal, but may not contain it. The viscosity of the curing agent at 25 ° C.
- the diamond-containing composition is preferably 5 mPa ⁇ s to 1000 mPa ⁇ s, more preferably 30 mPa ⁇ s to 700 mPa ⁇ s, and further preferably 150 mPa ⁇ s to 600 mPa ⁇ s.
- the viscosity range of the main agent and curing agent described above is within the above range, the diamond-containing composition can be maintained in a certain shape, for example, in a paste form, and thus can be easily placed on an electronic component or the like. Moreover, it becomes easy to mix
- a curing catalyst is usually added to the diamond-containing composition.
- the curing catalyst include a platinum-based catalyst, a palladium-based catalyst, and a rhodium-based catalyst, and among these, a platinum-based catalyst is preferable.
- the curing catalyst is a catalyst for curing a silicone compound that is a raw material for the silicone resin and a curing agent.
- the blending amount of the curing catalyst is usually 0.1 to 200 ppm, preferably 0.5 to 100 ppm, based on the total mass of the silicone compound and the curing agent.
- a curing catalyst such as a platinum-based catalyst is caused by impurities such as metal atoms. Is prevented from being inactivated. Therefore, even when an addition reaction type silicone resin is used as the polymer matrix, the curability is excellent and the curing rate can be increased.
- the thermosetting resin may be either a one-component curable type or a two-component curable type, but is preferably a two-component curable type.
- the two-component curable type it is preferable to prepare a diamond-containing composition by mixing one component containing the main agent and two components containing a curing agent.
- the diamond particles may be blended in one of the first and second solutions, or may be blended in both. The same applies to other thermally conductive fillers described later.
- the volume ratio of the polymer matrix is preferably 8% by volume to 70% by volume, more preferably 10% by volume to 60% by volume, and still more preferably 12% by volume to 48% by volume with respect to the total amount of the diamond-containing composition. It is as follows. When the volume ratio of the polymer matrix is above these lower limits, the thermally conductive filler such as tiremond particles dispersed in the polymer matrix can be retained by the polymer matrix, and the diamond-containing composition maintains a certain shape. become able to. Moreover, by setting it as these upper limits or less, thermal conductive fillers, such as a tiremond particle
- the diamond-containing composition of the present invention may further contain a heat conductive filler other than diamond particles (hereinafter also referred to as “other heat conductive filler”) as a heat conductive filler.
- a heat conductive filler other than diamond particles hereinafter also referred to as “other heat conductive filler”
- other heat conductive fillers materials having low electrical conductivity are used from the viewpoint of insulation, and examples thereof include carbon-based materials other than carbides, nitrides, oxides, hydroxides, and diamonds.
- the carbide include silicon carbide, boron carbide, aluminum carbide, titanium carbide, and tungsten carbide.
- Examples of the nitride include silicon nitride, boron nitride, aluminum nitride, gallium nitride, chromium nitride, tungsten nitride, magnesium nitride, molybdenum nitride, and lithium nitride.
- Examples of the oxide include aluminum oxide such as iron oxide, silicon oxide (silica), alumina, boehmite, magnesium oxide, titanium oxide, cerium oxide, and zirconium oxide.
- Examples of the hydroxide include aluminum hydroxide, calcium hydroxide, and magnesium hydroxide.
- Examples of the carbon-based material include carbon black, graphite, graphene, fullerene, carbon nanotube, and carbon nanofiber.
- thermal conductivity of the other thermally conductive filler is preferably 8 W / m ⁇ K or more, more preferably 20 W / m ⁇ K or more, from the viewpoint of improving the thermal conductivity.
- the other thermally conductive filler is preferably at least one selected from aluminum oxide, magnesium oxide, boron nitride, talc, aluminum nitride, and graphene from the viewpoints of thermal conductivity and insulation, such as aluminum oxide, magnesium oxide, and One or more selected from aluminum nitride is more preferable, and one or more selected from aluminum oxide and magnesium oxide is more preferable.
- Other heat conductive fillers may be surface-treated.
- Other heat conductive fillers are easily surface-treated so that they can be easily adapted to the polymer matrix, and are easily dispersed uniformly together with a large amount of diamond particles in the polymer matrix.
- the other thermally conductive filler is surface-treated with a surface treatment agent such as a silane compound, an organic titanium compound, an organoaluminum compound, or a phosphoric acid compound, and is preferably surface-treated with a silane compound.
- a surface treatment agent such as a silane compound, an organic titanium compound, an organoaluminum compound, or a phosphoric acid compound, and is preferably surface-treated with a silane compound.
- Examples of the silane compound include known silane coupling agents.
- the other thermally conductive filler has a sphericity of, for example, 0.5 or more, preferably 0.55 or more, and more preferably 0.6 or more.
- the upper limit of the sphericity is not particularly limited and is 1.
- the total filling amount of diamond particles and other heat conductive fillers can be easily increased by increasing the sphericity of the diamond particles as described above.
- the shape of the other thermally conductive filler is not particularly limited, and may be any of a plate shape, a scale shape, a needle shape, a fiber shape, a tube shape, a spherical shape, a crushed shape, etc., but either a spherical shape or a crushed shape is preferable.
- the spherical shape means a spherical shape or a shape approximating a spherical shape as described above, and the sphericity is 0.8 or more.
- the crushing shape has, for example, a sphericity of 0.5 or more and less than 0.8, preferably 0.55 or more and less than 0.8, more preferably 0.6 or more and less than 0.8. .
- the average particle size of the other thermally conductive filler is, for example, 0.1 ⁇ m or more and 250 ⁇ m or less. When it is 0.1 ⁇ m or more, thermal conductivity is easily improved by using it together with diamond particles. Moreover, by setting it as 250 micrometers or less, it becomes difficult to produce malfunctions, such as a filler not being disperse
- the filling rate of other thermally conductive fillers may be appropriately adjusted so that the total filler filling rate falls within the range described below, but is preferably 75% by volume or less, more preferably 70% by volume or less. By setting it as these upper limit values or less, since a certain amount or more of diamond particles can be blended with the diamond-containing composition, it becomes easy to improve the thermal conductivity. Further, the filling rate of the other thermally conductive filler is preferably 2% by volume or more, more preferably 10% by volume or more. If it is above these lower limit values, it becomes easy to exert the effect of blending other heat conductive fillers.
- the filling rate of other thermally conductive fillers is preferably 0.1 or more and 5 or less, more preferably 0.2 or more and 4 or less, with respect to the filling rate of diamond particles, from the viewpoints of insulation and thermal conductivity. From the viewpoint of further improving the insulating properties, 0.3 or more and 2 or less are more preferable.
- the other thermally conductive filler may be, for example, a thermally conductive filler having an average particle size of 10 ⁇ m or more and 250 ⁇ m or less (hereinafter also referred to as “large particle size thermally conductive filler”), and the average particle size is 0. .1 ⁇ m or more and less than 10 ⁇ m of heat conductive filler (hereinafter also referred to as “small particle size heat conductive filler”).
- Other heat conductive fillers include large particle size heat conductive fillers and Both small particle size thermally conductive fillers may be used.
- the large particle size thermally conductive filler preferably has an average particle size of 15 ⁇ m or more and 200 ⁇ m or less, more preferably 18 ⁇ m or more and 150 ⁇ m or less, and further preferably 20 ⁇ m or more and 125 ⁇ m or less.
- One type of large particle size thermally conductive filler may be used alone, or two or more types having different average particle sizes may be used in combination.
- the average particle size of the small particle size thermally conductive filler is more preferably 0.2 ⁇ m or more and 8 ⁇ m or less, and further preferably 0.4 ⁇ m or more and 7 ⁇ m or less.
- the small particle size thermally conductive filler may be used alone or in combination of two or more different average particle sizes.
- the other thermally conductive filler is preferably contained in a complementary combination with the diamond particles.
- heat conductive fillers tiremond particles and other heat conductive fillers
- a large particle size filler and a small particle size filler in order to increase the heat conductivity. It is preferable to add a filler having a diameter and a small particle diameter in a predetermined amount or more. Therefore, when the diamond particles do not contain large-diameter diamond or when it is contained in a small amount, at least a large-diameter thermally conductive filler may be blended as the other thermally conductive filler.
- the thermally conductive fillers are also small-diameter thermally conductive fillers and large-diameter thermally conductive fillers. Both of these may be blended appropriately.
- the total filling rate of the heat conductive filler (that is, the sum of the filling rate of diamond particles and the filling rate of other heat conductive fillers) is preferably 30% by volume or more and 92% by volume or less, more preferably 40% by volume. It is 90 volume% or less, More preferably, it is 50 volume% or more and 85 volume% or less. Heat conductivity can be made favorable by setting it as these minimum values or more. Moreover, it becomes possible to disperse
- the diamond-containing composition of the present invention contains additives generally used for heat radiating members such as a dispersant, an antioxidant, a heat stabilizer, a colorant, a flame retardant, and an antistatic agent, if necessary. Also good. Further, when a thermosetting resin is used in the diamond-containing composition, a reaction retarder may be contained.
- the diamond-containing composition of the present invention contains diamond particles and a polymer matrix and has the following curing characteristics. That is, the diamond-containing composition of the present invention has a complex elastic modulus after 5 minutes when cured at 70 ° C. and cured at 70 ° C. A2 and a complex elastic modulus after 30 minutes when cured at 70 ° C. Is A4, and the complex elastic modulus at the start of heating at 70 ° C. (that is, after 0 minutes) is A1, the rate of change at the start of curing represented by ((A2 ⁇ A1) / (A4 ⁇ A1)) ⁇ 100 is 50 % Or more.
- the change rate at the start of curing of the diamond-containing composition is preferably 55% or more, and more preferably 60% or more.
- the rate of change at the start of curing is not less than these lower limit values, the curing rate becomes even faster and the curability of the diamond-containing composition becomes excellent. Therefore, problems such as liquid sag are less likely to occur. Further, the higher the rate of change at the start of curing, the better, but it is, for example, 100% or less.
- the ratio of the complex elastic modulus A3 after 25 minutes to the complex elastic modulus A4 after 30 minutes when cured at 70 ° C. (A3 / A4 ⁇ 100) (hereinafter, “25 minutes / 30 minutes curing”
- the ratio is also preferably 50% or more.
- the 25/30 minute curing rate is 50% or more, the curing rate of the diamond-containing composition is increased, and the diamond-containing composition can be cured in a short time. Therefore, dripping or the like caused by poor curing is less likely to occur.
- the 25-minute / 30-minute curing rate of the diamond-containing composition is preferably 65% or more and 100% or less, and 80% or more and 100%. The following is more preferable.
- the diamond-containing composition of the present invention can maintain high curability even after long-term storage, and the curability change rate after the accelerated deterioration test is small.
- the curable change rate is the ratio of the complex elastic modulus A4 after curing at 70 ° C. for 30 minutes before the deterioration to the complex elastic modulus B4 after curing at 70 ° C. for 30 minutes (A4 / B4 ⁇ 100). It is represented by In the two-component curable type, the complex elastic modulus A4 is a complex elastic modulus when the first and second liquids before thermal acceleration deterioration are mixed and heated at 70 ° C. for 30 minutes to be cured.
- the complex elastic modulus B4 is the complex elasticity when each of the liquid 1 and liquid 2 is heated at 70 ° C. for 1 week for thermal acceleration and then mixed and heated at 70 ° C. for 30 minutes for curing. Rate.
- the rate of change in sclerosis after the accelerated deterioration test is preferably 75% or more and 125% or less.
- the rate of change in curability after the accelerated deterioration test is preferably 85% or more and 115% or less, and more preferably 95% or more and 105% or less.
- the diamond particles described above may be used as the diamond particles.
- the above-described polymer matrix may be used as described above.
- the polymer matrix only needs to have curability as described above, and preferably a heat-resistant matrix.
- a curable resin such as a curable resin, among which a silicone resin is more preferable, and an addition reaction curable silicone resin is particularly preferable. Details of these polymer matrices are as described above.
- the above-mentioned rate of change at the start of curing and 25/30 minute curing rate are measured using a rheometer as shown below.
- the diamond-containing composition is set in the rheometer, and it takes 500 seconds from 30 ° C. to 70 ° C. Temperature.
- the heating is started (0 minutes), and the complex elastic modulus at that time is measured as the complex elastic modulus A1.
- the diamond-containing composition was maintained at 70 ° C., and after 5 minutes, 25 minutes, and 30 minutes, the complex elastic modulus was measured as complex elastic modulus A2, complex elastic modulus A3, and complex elastic modulus A4, respectively. To do. Using the measured complex elastic modulus A1 to A4, the rate of change at the start of curing and the rate of curing for 25 minutes / 30 minutes can be determined according to the above formula. The details of the measurement conditions of the rheometer are as described in the examples.
- the rate of change in sclerosis after the accelerated deterioration test was determined by heating and heating the diamond-containing composition before heat deterioration and after heat deterioration at 70 ° C. for 1 week under the same conditions as described above.
- the complex elastic modulus is measured after 30 minutes have passed since the temperature is reached, and the complex elastic modulus is designated as A4 and the complex elastic modulus B4, respectively.
- the curable change rate after the accelerated deterioration test can be obtained according to the above-described calculation formula.
- the diamond-containing composition is cured at 70 ° C. as described above for the measurement of curing characteristics. However, the diamond-containing composition does not need to be cured at 70 ° C. in actual use. It may be cured in the vicinity.
- the diamond-containing composition of the present invention may be prepared by mixing a polymer matrix and diamond particles, and other heat conductive fillers and additives such as a dispersant added as necessary.
- the method of mixing these components is not particularly limited.
- diamond particles, and other thermally conductive fillers and additives that are blended as necessary are added to the polymer matrix, followed by stirring or kneading. It is good to adjust by doing.
- a two-component curable thermosetting resin as described above, it may be prepared by mixing a first solution prepared in advance and a second solution.
- various components constituting each of the 1st liquid and the 2nd liquid may be mixed and prepared.
- the heat dissipating member of the present invention is formed from the above-described diamond-containing composition.
- the heat dissipating member is formed into a predetermined shape by making the diamond-containing composition into a predetermined shape and then curing it by heating or the like as appropriate. Can be obtained.
- the polymer matrix is thermosetting
- the diamond-containing composition may be heated and cured, or may not be cured without being heated.
- a two-component curable thermosetting resin can be sufficiently cured near normal temperature (for example, about 10 ° C. or more and 40 ° C. or less) without being heated.
- the diamond-containing composition may be formed into a predetermined shape to form a heat radiating member.
- the method of making the diamond-containing composition into a predetermined shape is not particularly limited, and may be a thin film shape, a sheet shape, a block shape, an indefinite shape, or the like by coating, casting, potting, extrusion molding or the like.
- the heat dissipating member of the present invention is used, for example, inside an electric device. Since the heat radiating member of the present invention is excellent in insulating properties and heat radiating properties, high heat radiating properties can be secured without causing abnormal operation even when used inside an electric device. More specifically, the heat dissipating member is disposed on the electronic component and used to dissipate heat generated by the electronic component, and preferably disposed on the uneven surface of the electronic component having unevenness on the surface. used. By disposing on the uneven surface, the heat dissipating member may have uneven thickness in some parts different from other parts, but the heat dissipating member of the present invention uses diamond particles and is thermally conductive. Is excellent and heat dissipation is excellent, so that heat spots caused by thickness unevenness can be suppressed.
- the heat dissipating member of the present invention is arranged and used so as to fill a gap between two opposing members.
- one of the two opposing members may be an electronic component and the other may be any one of a heat sink for releasing heat from the electronic component, a housing of the electronic device, a substrate, and the like.
- two opposing members it is preferable that either one of the mutually opposing surfaces has unevenness. If any of the surfaces facing each other has unevenness, the heat dissipation member may have uneven thickness according to the unevenness, but the heat dissipation member of the present invention is excellent in heat dissipation by using diamond particles. Therefore, heat spots caused by thickness unevenness can be suppressed.
- the heat-dissipating member is compressed when sandwiched between two members and used, but the diamond-containing composition of the present invention is less likely to sag even when compressed, so that it can be used for such applications. It can be particularly preferably used.
- the measurement method and evaluation method of various physical properties of the present invention are as follows.
- [Ionic conductivity Di] In accordance with IEC68-2-66, the autoclave was subjected to a PCT (pressure cooker test) for 12 hours using 10 g of distilled water with respect to 5 g of diamond particles at a temperature of 120 ° C. and a relative humidity of 100 RH%.
- the adhering substance was eluted in distilled water to obtain an aqueous solution.
- the ionic conductivity of the aqueous solution was measured with a portable ion conductivity meter (trade name “LAQUAact”, manufactured by HORIBA, Ltd.) manufactured by HORIBA, Ltd. to obtain the ionic conductivity Ds of the eluate.
- the complex elastic moduli A1 to A4 are as follows. Complex elastic modulus A1: Complex elastic modulus of the diamond-containing composition when it reaches 70 ° C. (0 minutes) Complex elastic modulus A2: Complex elastic modulus of the diamond-containing composition after reaching 70 ° C. and then 5 minutes later Complex modulus of elasticity A3: Diamond-containing composition after reaching 30 ° C., and after 30 minutes, the complex modulus of the diamond-containing composition A4: reaching the complex modulus of elasticity A4: 70 ° C. Complex elastic modulus of objects
- each of the first and second liquids constituting the diamond-containing composition was left to stand in a thermostatic bath maintained at 70 ° C. and a humidity of 50 RH% for 7 days to cause thermal accelerated deterioration. Then, using a diamond-containing composition that has been thermally accelerated and deteriorated, the temperature is raised and heated under the same conditions as described above to reach 70 ° C., and then the complex elastic modulus B4 is measured after 30 minutes at 70 ° C. did. From the complex elastic modulus B4 and the complex elastic modulus A4 measured above, the curable change rate [A4 / B4 ⁇ 100] after the accelerated deterioration test was calculated.
- the 25 minute / 30 minute curing rate obtained above and the curability change rate after the accelerated deterioration test were evaluated according to the following evaluation criteria.
- C 25 minutes / 30 minutes The curing rate is 50% or more and less than 65%, the curability is good, and the diamond-containing composition can be cured in a time without any practical problems.
- Curability change rate after accelerated deterioration test is 100 ⁇ 5%, curability is hardly changed by accelerated deterioration, and excellent storage stability is obtained.
- the diamond-containing composition obtained by mixing the first and second solutions prepared in each Example and Comparative Example was coated on a glass plate of 10 cm ⁇ 10 cm ⁇ thickness 1 cm with an initial coating area of 5 cm ⁇ 5 cm. The coating was applied so that the film thickness was 5 mm. Then, a 10 cm ⁇ 10 cm ⁇ 1 cm thick glass plate is overlaid on the coating film made of the diamond-containing composition, and the environment of 23 ° C. and 50% RH in a state where the thickness direction of the coating film is the vertical direction. Left under for 12 hours.
- the dripping evaluation was evaluated according to the following evaluation criteria based on the increase rate of the occupied area of the coating film after standing for 12 hours with respect to the initial application area.
- A The area increase rate of the coating film is 5% or less, and dripping does not substantially occur.
- B The area increase rate of the coating film is more than 5% and 10% or less, and only a small amount of liquid dripping occurs.
- C The area increase rate of the coating film is more than 10% and 15% or less, and dripping occurs only at a level where there is no practical problem.
- D The area increase rate of the coating film exceeds 15%, and dripping occurs remarkably.
- the raw material diamond particles used in Examples and Comparative Examples are as follows. ⁇ Raw material diamond particles> Diamond particle (1): manufactured by Tomei Diamond Co., Ltd., trade name “CMM grade”, average particle size 40 ⁇ m, sphericity 0.6, crushed diamond particles (2): manufactured by Tomei Dia Co., Ltd., trade name “TMS grade”, average Particle diameter 70 ⁇ m, sphericity 0.9, spherical diamond particle (3): manufactured by Hyperion, trade name “GMM diamond”, average particle diameter 40 ⁇ m, sphericity 0.6, crushed diamond particle (4): Element Six Product name “MDA”, average particle size 40 ⁇ m, sphericity 0.6, crushed diamond particles (5): manufactured by Saint-Gobain Co., Ltd., product name “MBE grade”, average particle size 20 ⁇ m, sphericity 0.6 , Crushed diamond particles (6): manufactured by Hyperion, trade name “MBG”, average particle diameter 70 ⁇ m, spheri
- the Cr element was 0.1 mass ppm and the Fe element was 0.1 mass ppm.
- Example 2 The same procedure as in Example 1 was performed except that the stirring time in the washing step was changed to 6 hours.
- Example 3 The diamond particles obtained in Example 2 were carried out in the same manner as in Example 2 except that the same washing process was repeated to make the number of washings twice.
- Example 5 The diamond particles obtained in Example 4 were carried out in the same manner as in Example 4 except that the same washing process was repeated and the number of washings was two.
- Examples 6 to 10 were respectively carried out in the same manner as Examples 1 to 5 except that the raw material diamond particles used were changed to diamond particles (2).
- Examples 11 to 41 The same procedure as in Example 3 was performed by changing the type of cleaning liquid for cleaning the raw diamond particles, the type of raw diamond particles, or both as shown in Tables 1 to 4.
- an acetic acid aqueous solution having a pH of 4 was used, and an aqueous sodium hydroxide solution having a pH of 11 was used.
- the aqueous citric acid solution used was 0.26 mol / L (pH 2) in which 5 g of citric acid was dissolved in 100 g of water.
- Comparative Example 1 The diamond particles (1) that were not subjected to the washing step were used as the diamond particles of Comparative Example 1.
- the Cr element was 1 mass ppm and the Fe element was 3 mass ppm.
- a diamond-containing composition was prepared and evaluated in the same manner as in Example 1 except that the diamond particles of Comparative Example 1 were used.
- the diamond particles of the above examples were washed under specific conditions, so that the ionic conductivity Di was low, and impurities having chromium atoms, iron atoms, etc. could be reduced. Therefore, the diamond-containing composition in each example had good curing characteristics and substantially no dripping or the like occurred. On the other hand, since the diamond particles of the comparative example were not subjected to predetermined cleaning, the ionic conductivity Di could not be lowered and impurities could not be sufficiently removed. Therefore, the diamond-containing composition in each comparative example has poor curability and liquid dripping.
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Abstract
Description
[1]IEC68-2-66に準拠して行うプレッシャークッカー試験により溶出させて得た水溶液のイオン伝導度をDs、蒸留水のイオン伝導度をDwとすると、以下の式で表されるイオン伝導度Diが0.8mS/m以下であるダイヤモンド粒子。
Di=Ds-Dw
[2]極性溶媒で原料ダイヤモンド粒子を洗浄する工程を含む、ダイヤモンド粒子の製造方法。
[3]前記極性溶媒が、アルコール及び水の少なくとも一つである上記[2]に記載のダイヤモンド粒子の製造方法。
[4]前記極性溶媒が、50℃以上の水である上記[2]に記載のダイヤモンド粒子の製造方法。
[5]分子中の炭素数が2~6の有機酸と前記極性溶媒とを含む液体で原料ダイヤモンド粒子を洗浄する工程を含む、上記[2]~[4]のいずれか1項に記載のダイヤモンド粒子の製造方法。
[6]上記[1]に記載のダイヤモンド粒子と、高分子マトリクスとを含有するダイヤモンド含有組成物。
[7]ダイヤモンド粒子と、高分子マトリクスとを含有するダイヤモンド含有組成物において、
70℃で加熱して硬化させたときの5分後の複素弾性率をA2とし、70℃で加熱して硬化させたときの30分後の複素弾性率をA4とし、70℃加熱開始時の複素弾性率をA1とすると、((A2-A1)/(A4-A1))×100で表される硬化開始時変化率が、50%以上である、ダイヤモンド含有組成物。
[8]前記ダイヤモンド粒子の充填率が、10体積%以上90体積%以下である上記[6]又は[7]に記載のダイヤモンド含有組成物。
[9]クロム元素及び鉄元素の含有量が、いずれも0.5質量ppm以下である、ダイヤモンド粒子。
[10]上記[9]に記載のダイヤモンド粒子と、高分子マトリクスとを含有するダイヤモンド含有組成物。
[11]前記ダイヤモンド粒子の充填率が、10体積%以上90体積%以下である上記[10]に記載のダイヤモンド含有組成物。
[ダイヤモンド粒子]
本発明のダイヤモンド粒子は、IEC68-2-66に準拠して行うPCTにより溶出させて得た水溶液のイオン伝導度をDs、蒸留水のイオン伝導度をDwとすると、以下の式で表されるイオン伝導度Diが0.8mS/m以下となるものである。
Di=Ds-Dw
PCTとは、プレッシャークッカー試験の略であり、ダイヤモンド粒子は、PCTにより高温、高湿環境下にさらされることで、ダイヤモンド粒子の表面に付着されるイオン性の不純物が、殆ど全て粒子から取り除かれて水溶液に流出される。したがって、上記したイオン伝導度Diを測定することで、ダイヤモンド粒子の表面に付着されるイオン性の不純物量を検出できる。
ダイヤモンド粒子のイオン伝導度Diは、低ければ低いほどよいが、不純物量を必要以上に減らすことを防止し生産性を向上させる観点から、0.05mS/m以上が好ましく、0.10mS/m以上がより好ましく、0.15mS/m以上がさらに好ましい。
これらのうち、金属原子は、硬化反応を阻害することが多く、例えば、付加反応型シリコーン樹脂の場合など、白金系触媒などの硬化触媒によりダイヤモンド含有組成物を硬化させる場合には、その硬化触媒を不活性化して、ダイヤモンド含有組成物を硬化させにくくする。金属原子は、例えば、金属塩の状態でダイヤモンド粒子の表面に付着される。また、金属原子は、通常、ダイヤモンド製造時に使用される金属触媒由来のものであり、具体的には、鉄、クロムなどが挙げられる。
また、硫黄原子は、硫酸塩などの塩の状態でダイヤモンド粒子の表面に付着される。硫黄原子は、例えば、酸洗浄に使用される酸に由来するものである。硫酸塩などの硫黄原子を含む不純物は、高分子マトリクスを劣化させることが多く、例えば、シリコーン化合物を切断して低分子化させることがある。
具体的には、ダイヤモンド粒子におけるクロム元素及び鉄元素の含有量が、いずれも0.5質量ppm以下とするとよい。これら含有量は、いずれも好ましくは0.3質量ppm以下、より好ましくは0.2質量ppm以下である。クロム元素及び鉄元素の含有量がいずれもこれら上限値以下となると、高分子マトリクスの劣化が適切に防止される。さらに、硬化反応を阻害することなく適切に進行させ、硬化速度を速くすることも可能になる。
ダイヤモンド粒子におけるクロム元素及び鉄元素の含有量は、いずれも少なければ少ないほうがよいが、これらの含有量を必要以上に低くすることを防止して生産性を向上させる観点から、好ましくは0.001質量ppm以上、より好ましくは0.01質量ppm以上である。なお、クロム元素及び鉄元素は、例えば、硫酸クロム(CrSO4)、硫酸鉄(FeO4)としてダイヤモンド粒子に付着されると推定され、これらは特に硬化反応を阻害しやすい。
本発明のダイヤモンド粒子は、その球形度が例えば0.5以上、好ましくは0.55以上、さらに好ましくは0.6以上である。球形度は1に近いほど球形に近いことを示す指標となるものであり、球形度を高くすることで、ダイヤモンド粒子を高分子マトリクスに分散させやすくなり、さらに充填率も高めやすくなる。球形度の上限は、特に限定されず、1である。
ダイヤモンド粒子の球形度は、電子顕微鏡写真を確認して、(粒子の投影面積に等しい円の直径/粒子の投影像に外接する最小円の直径)を算出することで得ることができる。
また、ダイヤモンド粒子は、通常、複数個使用するので、上記球形度は、複数個のダイヤモンド粒子の平均値を意味する。ダイヤモンド粒子の平均値は、上記のように測定した300個の粒子の球形度の平均値でよいが、ダイヤモンド粒子が300個ない場合には、全てのダイヤモンド粒子の平均値を意味する。
ダイヤモンド粒子の粒子径は、例えば、0.1μm以上250μm以下である。タイヤモンド粒子は、粒子径を0.1μm以上とすることで、後述するダイヤモンド含有組成物において、熱伝導性を高くしやすくなる。また、ダイヤモンド粒子は、250μm以下とすることで、高分子マトリクスに適切に分散させることが可能であり、高い充填率でダイヤモンド含有組成物に配合することが可能になる。これら観点から、ダイヤモンド粒子の粒子径は、好ましくは、0.5μm以上200μm以下、より好ましくは1μm以上150μm以下、さらに好ましくは10μm以上100μm以下である。
なお、ダイヤモンド粒子は、通常、複数個使用されるので、上記粒子径は、複数個のダイヤモンド粒子の平均値(平均粒子径)を意味する。平均粒子径は、体積基準での粒子径を平均した平均粒子径であり、例えば、堀場製作所社製「レーザー回折式粒度分布測定装置」を用いて測定することができる。平均粒子径の算出方法については、累積体積が50%であるときの粒子径(d50)を平均粒子径とすればよい。
ダイヤモンド粒子が小粒径ダイヤモンド及び大粒径ダイヤモンドの両方を含有する場合、小粒径ダイヤモンドに対する大粒径ダイヤモンドの体積比(大粒径/小粒径)は、例えば、0.1以上10以下、好ましくは0.2以上8以下、より好ましくは0.3より大きく6以下である。
大粒径ダイヤモンドは、その平均粒子径が15μm以上200μm以下であることより好ましく、18μm以上150μm以下であることがさらに好ましい。
また、上記大粒径ダイヤモンドは、さらに互いに平均粒子径が異なる2種のダイヤモンドが併用されてもよい。
なお、平均粒子径が異なる2種以上のダイヤモンド粒子を含む場合、ダイヤモンド粒子は、小粒径ダイヤモンド及び大粒径ダイヤモンドの両方を含む必要はなく、例えば、平均粒子径が異なる2種以上の小粒径ダイヤモンドのみ2種類以上であってもよいし、平均粒子径が異なる2種以上の大粒径ダイヤモンドのみ2種類以上であってもよい。
また、平均粒子径が異なる2種以上のダイヤモンド粒子は、その球形度が互いに同一であってもよいし、異なってもよいが、球形度はいずれも上記範囲内であることが好ましい。
ダイヤモンド粒子は、シラン化合物、有機チタン化合物、有機アルミニウム化合物、リン酸化合物などの表面処理剤などで表面処理され、好ましくはシラン化合物により表面処理される。シラン化合物は、公知のシランカップリング剤などが挙げられる。
本発明のダイヤモンド粒子は、例えば以下の第1及び第2の実施形態の製造方法で製造できる。
本発明の第1の実施形態のダイヤモンド粒子の製造方法は、一般的に入手されるダイヤモンド粒子(以下、「原料ダイヤモンド粒子」ともいう)を極性溶媒で洗浄する洗浄工程を含む。
本発明においては、このような洗浄工程を行うことで、ダイヤモンド粒子の表面に付着される各種のイオン性不純物の量を低減でき、上記したようにイオン伝導度Diを低くできる。また、例えば、クロム原子及び鉄原子などを有する各種不純物の含有量を、上記したように所定値以下にすることもできる。
本発明においては、このような洗浄工程を含む製造方法でダイヤモンド粒子を製造しても、ダイヤモンド粒子の表面に付着される各種のイオン性不純物の量を低減でき、上記したようにイオン伝導度Diを低くできる。また、例えば、クロム原子及び鉄原子などを有する各種不純物の含有量を、上記したように所定値以下にすることもできる。
有機酸としては酢酸、クエン酸、マロン酸、マレイン酸、フマル酸、シュウ酸、プロピオン酸、乳酸、リンゴ酸、酒石酸、コハク酸、グリコール酸などの分子中の炭素数が2~6の有機酸が挙げられる。また、無機塩基としては、水酸化ナトリウム、水酸化カリウムなどのアルカリ金属塩基などが挙げられる。これら洗浄剤を使用することで、ダイヤモンド粒子表面に付着するイオン性不純物を有効に除去できる。
また、上記した中では、分子中の炭素数が2~6の有機酸が好ましく、酢酸、クエン酸がより好ましく、特にクエン酸が好ましい。有機酸を使用することで洗浄剤に由来するイオン性不純物をダイヤモンド粒子表面に付着させることなく、ダイヤモンド粒子表面に付着するイオン性不純物を有効に除去できる。
第2の実施形態で使用する洗浄液体は、無機塩基などの塩基性の洗浄剤が加えられることで酸性となるが、具体的な洗浄液体のpHは、例えば9以上13以下、好ましくは10以上12以下である。
また、洗浄液体における洗浄剤の濃度は、特に限定されないが、例えば0.1mmol/L以上1mol/L以下程度、好ましくは0.5mmol/L以上500mmol/L以下であればよい。
第1及び第2の実施形態の製造方法で使用する原料ダイヤモンド粒子としては、従来公知の方法で製造される合成ダイヤモンドが挙げられる。その製造方法は、特に限定されないが、グラファイトなどの炭素原料を、鉄、クロムなどの金属触媒存在下、高温高圧下で結晶化して合成できる。このように合成したダイヤモンド粒子は、不純物としてのグラファイトや、金属触媒などを除去するために酸洗浄などが行われる。そのため、ダイヤモンド粒子の表面には、上記したように、金属触媒由来の成分や、酸由来成分などがイオン性不純物として微少量付着される。
本発明の上記第1及び第2の実施形態で使用する溶媒は、極性溶媒である。極性溶媒でないと、第1の実施形態では、ダイヤモンド粒子の表面に付着されるイオン性不純物を十分に除去できずに、イオン伝導度Diを上記した範囲内に調整しにくくなることがある。
また、pHが低くとなると、極性溶媒中にイオン性成分が多く含有され、そのイオン性成分がダイヤモンド粒子の表面に付着して、イオン伝導度Diを向上させる要因になることもある。極性溶媒は、極性溶媒中のイオン性成分を少なくする観点から、中性又は中性に近い性質を有することが好ましく、具体的には、極性溶媒のpHは5以上が好ましく、極性溶媒のpHは5.5以上9以下が好ましく、6以上8以下がさらに好ましく、6.5以上7.5以下がよりさらに好ましく、6.8以上7.2以下であることが最も好ましい。
なお、極性溶媒のpHは、電子型pHメータを使用して測定することができる。
アルコールとしては、炭素数1~4のアルコールが挙げられる。具体的にはメタノール、エタノール、n-プロパノール、イソプロパノール、n-ブタノール、2-ブタノール、イソブチルアルコール、t-ブチルアルコール、エチレングリコール等が挙げられる。これらの中では、メタノール、エタノールが好ましく、エタノールがより好ましい。
水としては、特に限定されないが、蒸留水、イオン交換水、純水などを好適に使用可能であるが、水道水、工業用水などを使用してもよい。
極性溶媒又は洗浄液体による洗浄が終わると、ダイヤモンド粒子は、適宜乾燥などされて、ダイヤモンド粒子の表面に付着された極性溶媒が除去される。
極性溶媒又は洗浄液体の使用量は、ダイヤモンド粒子に対して、質量基準で1倍以上10倍以下であることが好ましく、1.5倍以上8倍以下がより好ましい。
また、極性溶媒又は洗浄液体の温度は、極性溶媒の融点以上沸点以下であればよく、例えば、5℃以上100℃以下である。また、攪拌時間は、例えば、1分以上10時間以下である。
上記洗浄工程においては、ダイヤモンド粒子の表面に付着した不純物は、溶媒中に溶出させることで、また、攪拌によって洗い落とすことなどで取り除かれるが、極性溶媒として水を使用する場合、不純物は、溶媒中に溶出させて取り除かれることが支配的であると推定される。したがって、極性溶媒として水を使用する場合には、極性溶媒又は洗浄液体の温度を上記のようにある程度高くすることで、水中に溶け出す不純物の量を増加させ、それにより、洗浄による不純物の除去効率を向上させることが可能になる。また、第2の実施形態のように、極性溶剤に洗浄剤を添加した洗浄液体を使用することで、洗浄による不純物の除去効率をより向上させることも可能である。
なお、極性溶媒が水である場合、極性溶媒又は洗浄液体の温度は、100℃以下であればよいが、生産性の観点から90℃以下が好ましく、80℃以下がより好ましい。また、ダイヤモンド粒子が加えられた極性溶媒又は洗浄液体の攪拌は、大気圧下で行うとよい。
洗浄は、1回以上であればよいが、複数回行う場合、2回以上行うことが好ましい。洗浄を複数回行うことで、不純物をより多く取り除くことができ、イオン伝導度Diをさらに低くしやすくなる。洗浄の回数は、特に限定されないが、生産性の観点から、10回以下が好ましく、5回以下がより好ましく、3回以下がさらに好ましい。
また、洗浄を複数回行う場合、その複数回の洗浄の一部を、洗浄剤が加えられた洗浄液体で行い、残りを極性溶媒で行ってもよい。この場合、洗浄剤が加えられた洗浄液体による洗浄と、極性溶媒による洗浄の順番は、特に限定されないが、洗浄液体による洗浄を1回又は複数回行った後に、極性溶媒による洗浄を1回又は複数回行うことが好ましい。これにより、得られるダイヤモンド粒子に洗浄剤が付着することを防止して、上記したイオン伝導度をより低くしやすくなる。
本発明のダイヤモンド含有組成物は、ダイヤモンド粒子と、高分子マトリクスとを含有する。ダイヤモンド含有組成物は、体積抵抗値が低く熱伝導率が高いダイヤモンド粒子を含有することで、絶縁性と熱伝導性がいずれも優れたものになる。
一方で、ダイヤモンド粒子を、後述するダイヤモンド粒子以外の熱伝導性フィラーと併用する場合、ダイヤモンド粒子の充填率はそれほど高くする必要はない。したがって、そのような場合、ダイヤモンド粒子の充填率は、10体積%以上80体積%以下が好ましく、20体積%以上75体積%以下がより好ましく、25体積%以上60体積%以下がさらに好ましい。
なお、本明細書において「充填率」とは、ダイヤモンド含有組成物の全体積に対する、体積%を意味し、例えば、ダイヤモンド粒子の充填率は、ダイヤモンド含有組成物の全体積に対する、ダイヤモンド粒子が占める体積%を意味する。各成分の体積は、各成分の重量と、比重により算出可能である。
本発明における高分子マトリクスは、樹脂、液状高分子成分などが挙げられる。
樹脂としては、シリコーン樹脂、エポキシ樹脂、ウレタン樹脂、フェノール樹脂、不飽和ポリエステル樹脂、ポリイミド樹脂等の硬化性樹脂が挙げられる。硬化性樹脂は、湿気硬化型、熱硬化型、光硬化型のいずれでもよいが、熱硬化型が好ましい。
また、ポリプロピレン樹脂、ポリエチレン樹脂、ポリ(1-)ブテン樹脂、及びポリペンテン樹脂等のポリオレフィン樹脂、ポリエチレンテレフタレート等のポリエステル樹脂、ポリスチレン樹脂、アクリロニトリル-ブタジエン-スチレン(ABS)樹脂、エチレン酢酸ビニル共重合体(EVA)、(メタ)アクリル系樹脂、ポリアミド樹脂、ポリ塩化ビニル樹脂(PVC)等の熱可塑性樹脂などでもよい。
また、エラストマー樹脂としては、ポリエステル系熱可塑性エラストマー、ポリウレタン系熱可塑性エラストマー、スチレン系熱可塑性エラストマーなどの熱可塑性エラストマーも使用できる。
シリコーンオイルとしては、メチルフェニルシリコーンオイル、ジメチルシリコーンオイル、変性シリコーンオイルなどが挙げられる。シリコーンオイルは、例えば25℃における粘度が、好ましくは5mPa・s以上1000mPa・s以下、より好ましくは30mPa・s以上700mPa・s以下、さらに好ましくは150mPa・s以上600mPa・s以下である。
液状高分子成分は、配合時に室温かつ常圧下に液状であり、かつ使用時においても液状ないしゲル状の成分である。すなわち、液状高分子成分は、硬化剤などにより硬化されず、また、硬化されても硬化後も液状ないしゲル状となるものである。したがって、液状高分子成分を単独で、又は比較的高い配合割合で使用すると、ダイヤモンド含有組成物から形成される放熱部材をペースト状にできる。
また、高分子マトリクスは、シリコーンオイル、シリコーン樹脂などのシリコーンが好ましいが、縮合硬化型シリコーン樹脂、付加反応硬化型シリコーン樹脂などのシリコーン樹脂が好ましく、中でも付加反応硬化型シリコーン樹脂が好ましい。シリコーンは、ダイヤモンド粒子の表面に付着された不純物に含まれる硫黄原子などによって分子鎖が切断されて劣化することがあるが、本発明では、そのような不純物量が低減されている。したがて、シリコーンの劣化が抑えられ、長期保管後の硬化性の低下が抑えられる。
主剤として使用されるシリコーン化合物は、25℃における粘度が、好ましくは5mPa・s以上1000mPa・s以下、より好ましくは30mPa・s以上700mPa・s以下、さらに好ましくは150mPa・s以上600mPa・s以下である。
なお、本明細書において粘度は、粘度計(BROOKFIELD回転粘度計DV-E)でスピンドルNo.14の回転子を用い、回転速度5rpm、測定温度25℃で測定するとよい。
硬化剤の25℃における粘度は、好ましくは5mPa・s以上1000mPa・s以下、より好ましくは30mPa・s以上700mPa・s以下、さらに好ましくは150mPa・s以上600mPa・s以下である。
上記した主剤や硬化剤の粘度範囲を上記範囲内とすると、ダイヤモンド含有組成物を例えばペースト状で一定の形状に保つことができるため、電子部品などの上に容易に配置できるようになる。また、ダイヤモンドなどの熱伝導性フィラーを適切に分散させたうえで多量に配合しやすくなる。
本発明では、イオン伝導度Diが所定の値より低くなり、ダイヤモンド粒子に付着される金属原子などのイオン性の不純物の量が少なくなるため、金属原子などの不純物によって白金系触媒などの硬化触媒が不活性化されることが防止される。そのため、高分子マトリクスとして付加反応型シリコーン樹脂を使用しても、硬化性が優れたものとなり、硬化速度を速くすることが可能になる。
なお、2液硬化型の場合、ダイヤモンド粒子は、1液及び2液の一方に配合されていてもよいし、両方に配合されていてもよい。後述するその他の熱伝導性フィラーも同様である。
本発明のダイヤモンド含有組成物は、熱伝導性フィラーとして、ダイヤモンド粒子以外の熱伝導性フィラー(以下、「その他の熱伝導性フィラー」ともいう)をさらに含有してもよい。その他の熱伝導性フィラーを含有することで、熱伝導性フィラー全体の充填率を向上させて、熱伝導性を向上させることが可能になる。
その他の熱伝導性フィラーとしては、絶縁性の観点から電気伝導率の低い材料が使用され、例えば、炭化物、窒化物、酸化物、水酸化物、ダイヤモンド以外の炭素系材料などが挙げられる。
炭化物としては、例えば、炭化ケイ素、炭化ホウ素、炭化アルミニウム、炭化チタン、炭化タングステンなどが挙げられる。窒化物としては、例えば、窒化ケイ素、窒化ホウ素、窒化アルミニウム、窒化ガリウム、窒化クロム、窒化タングステン、窒化マグネシウム、窒化モリブデン、窒化リチウムなどが挙げられる。酸化物としては、例えば、酸化鉄、酸化ケイ素(シリカ)、アルミナ、ベーマイトなどの酸化アルミニウム、酸化マグネシウム、酸化チタン、酸化セリウム、酸化ジルコニウムなどが挙げられる。水酸化物としては、例えば、水酸化アルミニウム、水酸化カルシウム、水酸化マグネシウムなどが挙げられる。炭素系材料としては、例えば、カーボンブラック、黒鉛、グラフェン、フラーレン、カーボンナノチューブ、カーボンナノファイバーなどが挙げられる。また、ケイ酸塩鉱物であるタルクなども使用できる。
これらその他の熱伝導性フィラーは、単独で使用してもよいが、2種類以上併用してもよい。
その他の熱伝導性フィラーの熱伝導率は、熱伝導性を向上させる観点から、好ましくは8W/m・K以上であり、より好ましくは20W/m・K以上である。
その他の熱伝導性フィラーは、シラン化合物、有機チタン化合物、有機アルミニウム化合物、リン酸化合物などの表面処理剤で表面処理され、好ましくはシラン化合物により表面処理される。シラン化合物は、公知のシランカップリング剤などが挙げられる。
また、本発明では、その他の熱伝導性フィラーに加えて、上記したようにダイヤモンド粒子の球形度も高くすることで、ダイヤモンド粒子及びその他の熱伝導性フィラーの合計充填量を高めやすくなる。
また、その他の熱伝導性フィラーの充填率は、絶縁性及び熱伝導性の観点から、ダイヤモンド粒子の充填率に対して、0.1以上5以下が好ましく、0.2以上4以下がより好ましく、絶縁性をさらに高める観点から0.3以上2以下がさらに好ましい。
小粒径熱伝導性フィラーは、その平均粒子径が0.2μm以上8μm以下であることより好ましく、0.4μm以上7μm以下であることがさらに好ましい。
小粒径熱伝導性フィラーは、1種を単独で使用してもよいが、互いに平均粒子径が異なる2種以上を併用してもよい。
したがって、ダイヤモンド粒子が大粒径ダイヤモンドを含有しない場合や、含有しても少ない場合には、その他の熱伝導性フィラーとして少なくとも大粒径熱伝導性フィラーを配合すればよい。
同様に、ダイヤモンド粒子が小粒径ダイヤモンドを含有しない場合や、含有しても少ない場合には、熱伝導性フィラーとして少なくとも小粒径のその他の熱伝導性フィラーを配合すればよい。
また、ダイヤモンド粒子が、大粒径ダイヤモンドと、小粒径ダイヤモンドの両方をそれぞれ適度な量含有する場合には、熱伝導性フィラーも、小粒径熱伝導性フィラー及び大粒径熱伝導性フィラーの両方をそれぞれ適度に配合するとよい。
本発明のダイヤモンド含有組成物は、必要に応じて、分散剤、酸化防止剤、熱安定剤、着色剤、難燃剤、帯電防止剤等の放熱部材に一般的に使用する添加剤を含有してもよい。また、ダイヤモンド含有組成物に、熱硬化性樹脂を使用する場合には、反応遅延剤を含有させてもよい。
(硬化開始時変化率、及び25分/30分硬化率)
本発明のダイヤモンド含有組成物は、ダイヤモンド粒子と、高分子マトリクスとを含有し、以下の硬化特性を有するものである。
すなわち、本発明のダイヤモンド含有組成物は、70℃で加熱して硬化させたときの5分後の複素弾性率をA2、70℃で加熱して硬化させたときの30分後の複素弾性率をA4、70℃加熱開始時(すなわち0分後)の複素弾性率をA1とすると、((A2-A1)/(A4-A1))×100で表される硬化開始時変化率が、50%以上となる。
硬化開始時変化率が50%未満となると、ダイヤモンド含有組成物の硬化速度が遅くなり、実使用においてダイヤモンド含有組成物の硬化不良などが生じやすくなる。そのため、液ダレなどが生じて、電子機器を汚染したり、放熱部材を一定の形状に保持できないなどの不具合が生じたりする。
ダイヤモンド含有組成物の硬化開始時変化率は、55%以上が好ましく、60%以上がより好ましい。硬化開始時変化率がこれら下限値以上であると、硬化速度はより一層速くなり、ダイヤモンド含有組成物の硬化性を優れたものとなる。そのため、液ダレなどの不具合が生じにくくなる。また、硬化開始時変化率は、高ければ高いほどよいが、例えば、100%以下である。
硬化速度を速くして、ダイヤモンド含有組成物をより短期間で硬化させるためには、ダイヤモンド含有組成物の25分/30分硬化率は、65%以上100%以下が好ましく、80%以上100%以下がより好ましい。
また、本発明のダイヤモンド含有組成物は、長期保管後でも、高い硬化性を維持できるものであり、加速劣化試験後の硬化性変化率が小さくなるものである。
ここで、硬化性変化率は、劣化後の70℃、30分間硬化時の複素弾性率B4に対する、劣化前の70℃、30分間硬化時の複素弾性率A4の割合(A4/B4×100)で表される。
なお、2液硬化型においては、複素弾性率A4は、熱加速劣化前の1液及び2液を混合して70℃で30分間加熱して硬化したときの複素弾性率である。また、複素弾性率B4は、1液及び2液それぞれを70℃で1週間加熱して熱加速劣化させた後、これらを混合して70℃で30分間加熱して硬化させたときの複素弾性率である。
まず、1液硬化型であればそのまま、2液硬化型であれば1液と2液とを混合して直ちに、ダイヤモンド含有組成物をレオメータにセットして、30℃から70℃に500秒掛けて昇温する。ダイヤモンド含有組成物が70℃に到達した時点を加熱開始(0分)として、そのときの複素弾性率を複素弾性率A1として測定する。
その後、ダイヤモンド含有組成物を70℃に維持し、5分経過後、25分経過後、30分経過後の複素弾性率をそれぞれ、複素弾性率A2、複素弾性率A3、複素弾性率A4として測定する。測定された複素弾性率A1~A4を用いて、上記した計算式に従って、硬化開始時変化率、及び25分/30分硬化率が求めることができる。
なお、レオメータの測定条件の詳細は、実施例に記載されるとおりである。
なお、ダイヤモンド含有組成物は、硬化特性の測定のために、上記のように70℃で硬化されるが、ダイヤモンド含有組成物は、実使用においては70℃で硬化される必要はなく、例えば常温付近で硬化してもよい。
本発明のダイヤモンド含有組成物は、高分子マトリクス及びダイヤモンド粒子、さらには、必要に応じて配合されるその他の熱伝導性フィラー、分散剤などの添加剤などを混合して調製するとよい。これら成分を混合する方法は、特に限定されないが、例えば、高分子マトリクスに、ダイヤモンド粒子、さらには、必要に応じて配合されるその他の熱伝導性フィラー、添加剤など添加し、その後攪拌ないし混練などすることで調整するとよい。また、2液硬化型の熱硬化性樹脂の場合には、上記したように、予め用意した1液と、2液とを混合することで調製するとよい。1液、2液それぞれを用意する際も同様に、1液及び2液それぞれを構成する各種成分を混合して調製するとよい。
本発明の放熱部材は、上記したダイヤモンド含有組成物により形成されるものである。放熱部材は、例えば、高分子マトリクスが硬化性樹脂を含む場合には、上記ダイヤモンド含有組成物を所定の形状にした後、適宜加熱などして硬化させることで所定の形状に成形された放熱部材を得ることが可能になる。なお、高分子マトリクスが熱硬化性である場合、ダイヤモンド含有組成物は、加熱され硬化されてもよいし、加熱されずに硬化されなくてもよい。例えば、2液硬化型の熱硬化性樹脂は、加熱されなくても常温付近(例えば、10℃以上40℃以下程度)で十分に硬化可能である。
また、高分子マトリクスが硬化性樹脂を含む場合以外でも、ダイヤモンド含有組成物を所定の形状にして、放熱部材とすればよい。ダイヤモンド含有組成物を所定の形状にする方法としては、特に限定されず、塗布、キャスティング、ポッティング、押出成形などにより、薄膜状、シート状、ブロック状、不定形状などの形状とすればよい。
より具体的には、放熱部材は、電子部品の上に配置されて、電子部品で発生した熱を放熱するために使用され、好ましくは表面に凹凸を有する電子部品の凹凸面上に配置されて使用される。凹凸面上に配置されることで、放熱部材は、一部の厚さが他の部分と異なる厚みムラが生じることがあるが、本発明の放熱部材は、ダイヤモンド粒子を使用し、熱伝導性が良好で放熱性に優れることから、厚みムラによって生じるヒートスポットを抑制できる。
[イオン伝導度Di]
IEC68-2-66に準拠し、オートクレープにおいて、ダイヤモンド粒子5gに対して蒸留水10gを用い、温度120℃、相対湿度100RH%の条件で12時間PCT(プレッシャークッカー試験)を行い、ダイヤモンド粒子に付着する物質を蒸留水中に溶出させて水溶液を得た。その水溶液のイオン伝導度を、株式会社堀場製作所製のポータブル型イオン伝導度率メーター(商品名「LAQUAact」、株式会社堀場製作所製)により測定して、溶出液のイオン伝導度Dsを得た。また、蒸留水のイオン伝導度を上記ポータブル型イオン伝導度率メーターにより測定し、蒸留水のイオン伝導度Dwを得た。得られたイオン伝導度Ds,Dwより、ダイヤモンド粒子由来のイオン伝導度Diを以下の式で求めた。なお、各イオン伝導度の測定は23℃で行った。
Di=Ds-Dw
ICP分析により、ダイヤモンド粒子の表面に付着される不純物の種類、及びダイヤモンド粒子に対する含有量を測定した。
ダイヤモンド含有組成物の硬化開始時変化率及び25分/30分硬化率は、レオメータ(ARES、TAインスツルメント社製)を用いて測定した。具体的には、1液硬化型であればそのまま、2液硬化型であれば1液と2液とを混合して得たダイヤモンド含有組成物を直ちに、レオメータにセットした。
次いで、歪みが1%、周波数6.28Hz、回転プレート直径8mm、厚みが1mmの条件下、30℃から70℃に500秒掛けて昇温した後、70℃で30分間維持し、明細書記載の方法に従って、複素弾性率A1~A4を測定した。複素弾性率A1~A4から、硬化開始時変化率[(A2-A1)/(A4-A1)×100]、及び25分/30分硬化率[A3/A4×100]を求めた。
複素弾性率A1:70℃に到達した時点(0分)におけるダイヤモンド含有組成物の複素弾性率
複素弾性率A2:70℃に到達し、その後、5分経過した後のダイヤモンド含有組成物の複素弾性率
複素弾性率A3:70℃に到達し、その後、25分経過した後のダイヤモンド含有組成物の複素弾性率
複素弾性率A4:70℃に到達し、その後、30分経過した後のダイヤモンド含有組成物の複素弾性率
また、ダイヤモンド含有組成物を構成する1液、2液それぞれを、70℃、湿度50RH%に維持される恒温槽に7日間放置して、熱加速劣化させた。その後、熱加速劣化されたダイヤモンド含有組成物を用いて、上記と同様の条件で昇温及び加熱して、70℃に到達し、その後70℃で30分経過した後の複素弾性率B4を測定した。その複素弾性率B4と、上記で測定した複素弾性率A4から、加速劣化試験後の硬化性変化率[A4/B4×100]を算出した。
(25分/30分硬化率)
A:25分/30分硬化率が80%以上となり、硬化性が優れており、ダイヤモンド含有組成物を短期間で硬化することができる。
B:25分/30分硬化率が65%以上80%未満であり、硬化性が高く、ダイヤモンド含有組成物を比較的短期間で硬化することができる。
C:25分/30分硬化率が50%以上65%未満であり、硬化性が良好であり、ダイヤモンド含有組成物を実用上問題ない時間で硬化することができる。
D:25分/30分硬化率が50%未満であり、硬化性が不十分であり、ダイヤモンド含有組成物を長時間かけて硬化しても硬化不良が生じる。
A:加速劣化試験後の硬化性変化率が100±5%であり、加速劣化によって硬化性は殆ど変化せず、優れた保管安定性を有する。
B:加速劣化試験後の硬化性変化率が100±5%の範囲外であるが、100±15%の範囲内であり、加速劣化による硬化性の変化は少なく、高い保管安定性を有する。
C:加速劣化試験後の硬化性変化率が100±15%の範囲外であるが、100±25%の範囲内であり、実用上問題ないレベルの保管安定性を有する。
D:加速劣化試験後の硬化性変化率が100±25%の範囲外であり、加速劣化により硬化性が大きく変化して保管安定性が低い。
各実施例、比較例で調製した1液及び2液を混合して得たダイヤモンド含有組成物を、10cm×10cm×厚さ1cmのガラス板の上に、初期の塗布面積が5cm×5cm、塗膜厚さが5mmとなるように塗布した。その後、ダイヤモンド含有組成物からなる塗膜の上に10cm×10cm×厚さ1cmのガラス板を重ね合わせて、塗膜の厚さ方向が鉛直方向となる状態で、23℃、50%RHの環境下で12時間放置した。
液ダレ評価は、12時間放置後の塗膜の占有面積の、上記初期の塗布面積に対する増加率により、以下の評価基準により評価した。
A:塗膜の面積増加率が5%以下となり、液ダレが実質的に生じない。
B:塗膜の面積増加率が5%超10%以下となり、少量の液ダレしか生じない。
C:塗膜の面積増加率が10%超15%以下となり、液ダレは実用上問題ないレベルでしか生じない。
D:塗膜の面積増加率が15%超となり、液ダレが顕著に生じる。
<原料ダイヤモンド粒子>
ダイヤモンド粒子(1):トーメイダイヤ社製、商品名「CMMグレード」、平均粒子径40μm、球形度0.6、破砕品
ダイヤモンド粒子(2):トーメイダイヤ社製、商品名「TMSグレード」、平均粒子径70μm、球形度0.9、球状品
ダイヤモンド粒子(3):ハイペリオン社製、商品名「GMMダイヤモンド」、平均粒子径40μm、球形度0.6、破砕品
ダイヤモンド粒子(4):エレメントシックス社製、商品名「MDA」、平均粒子径40μm、球形度0.6、破砕品
ダイヤモンド粒子(5):サンゴバン株式会社製、商品名「MBEグレード」、平均粒子径20μm、球形度0.6、破砕品
ダイヤモンド粒子(6):ハイペリオン社製、商品名「MBG」、平均粒子径70μm、球形度0.9、球状品
ダイヤモンド粒子(7):トーメイダイヤ社製、商品名「IMS」、平均粒子径70μm、球形度0.9、球状品
ダイヤモンド粒子(8):イルジン社製、商品名「IMPM」、平均粒子径40μm、球形度0.6、破砕品
ダイヤモンド粒子(9):トーメイダイヤ社製、商品名「CMMグレード」、平均粒子径4μm、球形度0.6、破砕品
(洗浄工程)
洗浄液として70℃に維持された蒸留水(pH=7)50gが入れられたビーカーに、原料ダイヤモンド粒子として、ダイヤモンド粒子(1)10gを加え、その後、攪拌装置「スリーワンモーター」の羽根着きセパラを用いて攪拌条件500rpmsで3時間攪拌した。攪拌終了後、濾過によりダイヤモンド粒子を分離し、かつ乾燥させ、実施例1のダイヤモンド粒子を得た。実施例1において、ダイヤモンド粒子の表面をICPにより分析したところ、Cr元素が0.1質量ppm、Fe元素が0.1質量ppmであった。
高分子マトリクスとして、付加反応型シリコーン樹脂の主剤を構成するビニル両末端オルガノポリシロキサン(25℃での粘度が300mPa・s)2質量部に対して、上記で得られたダイヤモンド粒子を8質量部加え、さらに反応遅延剤0.01質量部、白金触媒を触媒量添加して、ダイヤモンド含有組成物の1液を調製した。
また、付加反応型シリコーン樹脂の硬化剤を構成するオルガノハイドロジェンポリシロキサン(25℃での粘度が400mPa・s)2質量部に対して、上記で得られたダイヤモンド粒子を8質量部加え、ダイヤモンド含有組成物の2液を調製した。
1液と、2液を質量比(1液/2液)1:1で混合して、ダイヤモンド含有組成物を作製して評価した。その結果を表1に示す。なお、ダイヤモンド含有組成物におけるダイヤモンド粒子の充填率は、53体積%、高分子マトリクスは47体積%であった。
洗浄工程における攪拌時間を6時間に変更した点を除いて実施例1と同様に実施した。
実施例2で得られたダイヤモンド粒子に対して、同様の洗浄工程を繰り返して、洗浄回数を2回にした点を除いて実施例2と同様に実施した。
25℃に維持されたエタノール(pH=7)50gが入れられたビーカーに、原料ダイヤモンド粒子として、ダイヤモンド粒子(1)を10g加え、その後、攪拌条件500rpmsで5分間攪拌した。攪拌終了後、濾過によりダイヤモンド粒子を分離し、かつ乾燥させ、実施例4のダイヤモンド粒子を得た。その後、実施例1と同様にダイヤモンド含有組成物を調製して評価した。
実施例4で得られたダイヤモンド粒子に対して、同様の洗浄工程を繰り返して、洗浄回数を2回にした点を除いて実施例4と同様に実施した。
実施例6~10はそれぞれ、使用する原料ダイヤモンド粒子をダイヤモンド粒子(2)に変更した点を除いて実施例1~5それぞれと同様に実施した。
原料ダイヤモンド粒子を洗浄するための洗浄液の種類、原料ダイヤモンド粒子の種類、又はこれらの両方を表1~4に示すとおりに変更して、実施例3と同様に実施した。
なお、各実施例において、酢酸水溶液には、pH4のものを使用し、水酸化ナトリウム水溶液にはpH11のものを使用した。クエン酸水溶液には、水100gに対して、クエン酸5gを溶解した0.26モル/L(pH2)のものを使用した。
洗浄工程を行わないダイヤモンド粒子(1)を比較例1のダイヤモンド粒子とした。比較例1のダイヤモンド粒子では、ダイヤモンド粒子の表面をICPにより分析したところ、Cr元素が1質量ppm、Fe元素が3質量ppmであった。比較例1のダイヤモンド粒子を用いた点以外は実施例1と同様に、ダイヤモンド含有組成物を調製して評価した。
洗浄工程を行わないダイヤモンド粒子(2)~(9)それぞれを比較例2~9のダイヤモンド粒子とした。比較例2~9のダイヤモンド粒子を用いた点以外は実施例1と同様に、ダイヤモンド含有組成物を調製して評価した。
それに対して、比較例のダイヤモンド粒子は、所定の洗浄を行わなかったため、イオン伝導度Diを低くすることができず、不純物を十分に取り除くことができなかった。そのため、各比較例におけるダイヤモンド含有組成物は、硬化性が悪く、液ダレも発生した。
Claims (8)
- IEC68-2-66に準拠して行うプレッシャークッカー試験により溶出させて得た水溶液のイオン伝導度をDs、蒸留水のイオン伝導度をDwとすると、以下の式で表されるイオン伝導度Diが0.8mS/m以下であるダイヤモンド粒子。
Di=Ds-Dw - 極性溶媒で原料ダイヤモンド粒子を洗浄する工程を含む、ダイヤモンド粒子の製造方法。
- 前記極性溶媒が、アルコール及び水の少なくとも一つである請求項2に記載のダイヤモンド粒子の製造方法。
- 前記極性溶媒が、50℃以上の水である請求項2に記載のダイヤモンド粒子の製造方法。
- 分子中の炭素数が2~6の有機酸と前記極性溶媒とを含む液体で原料ダイヤモンド粒子を洗浄する工程を含む、請求項2~4のいずれか1項に記載のダイヤモンド粒子の製造方法。
- 請求項1に記載のダイヤモンド粒子と、高分子マトリクスとを含有するダイヤモンド含有組成物。
- ダイヤモンド粒子と、高分子マトリクスとを含有するダイヤモンド含有組成物において、
70℃で加熱して硬化させたときの5分後の複素弾性率をA2とし、70℃で加熱して硬化させたときの30分後の複素弾性率をA4とし、70℃加熱開始時の複素弾性率をA1とすると、((A2-A1)/(A4-A1))×100で表される硬化開始時変化率が、50%以上である、ダイヤモンド含有組成物。 - 前記ダイヤモンド粒子の充填率が、10体積%以上90体積%以下である請求項6又は7に記載のダイヤモンド含有組成物。
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