Thermally conductive grease composition

Abstract

To provide a thermally conductive grease composition which has high thermal conductivity, has excellent coatability, and allows a temperature distribution to be visually recognized.SOLUTION: A thermally conductive grease composition containing a base oil, a thermally conductive filler, and a capsule pigment encapsulating a leuco dye, a developer, and a color change temperature regulator.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to thermally conductive grease compositions. [Background technology]

[0002] Among the semiconductor components used in electronic devices, there are those that generate heat during use, such as computer CPUs and power semiconductors for power supply control. To protect these semiconductor components from heat and ensure their normal function, one method is to conduct the generated heat to a heat-dissipating component such as a heat sink and dissipate it. Thermally conductive grease compositions are applied between heat-generating components, such as semiconductor components, and heat-dissipating components so as to bring them into close contact with each other, thereby enhancing heat conduction.

[0003] As a thermally conductive grease composition, for example, Patent Document 1 discloses a thermally conductive grease composition containing a base oil, a thermally conductive filler, and calcium carbonate particles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-151485 Summary of the Invention [Problem to be solved by the invention]

[0005] However, typical thermally conductive grease compositions exhibit viscosity changes with temperature, such as increasing viscosity and hardening at low temperatures, which deteriorates their applicability. It is known that the viscosity of a thermally conductive grease composition can be reduced by reducing the content of thermally conductive filler in the thermally conductive grease composition, but this also results in a problem of a decrease in the thermal conductivity of the thermally conductive grease composition. Furthermore, in order to confirm the optimum temperature for use of a thermally conductive grease composition, a measuring device such as a thermometer or a thermograph has conventionally been required. Although a thermometer is a relatively easy device to use, it can only measure the temperature value at a single contact point, and it is not easy to measure the temperature distribution throughout the entire thermally conductive grease composition.

[0006] The present disclosure has been made in view of the above, and relates to providing a thermally conductive grease composition that has high thermal conductivity, excellent applicability, and allows a temperature distribution to be visually determined. [Means for solving the problem]

[0007] The present disclosure includes the following aspects. <1> A base oil, a thermally conductive filler; an capsule pigment containing a leuco dye, a color developer, and a color change temperature adjuster; A thermally conductive grease composition comprising: <2> The total content of the capsule pigments is 0.01% by mass or more and 5.00% by mass or less based on the total amount of the thermal conductive grease composition. <1> The thermally conductive grease composition according to claim 1. <3> The capsule pigment is spherical, and the shortest axis (R min ) and the longest axis (R max ) and the ratio (R min / R max ) is between 0.7 and 1.0, <1> or <2> The thermally conductive grease composition according to claim 1. <4> The leuco dye includes at least one selected from the group consisting of triphenylmethane-based compounds, spiropyran-based compounds, fluoran-based compounds, diphenylmethane-based compounds, rhodamine lactam-based compounds, indolylphthalide-based compounds, leucoauramine-based compounds, and pyridine-based compounds. <1> ~ <3> 1. The thermally conductive grease composition according to claim 1 . <5> the developer contains at least one selected from the group consisting of diphenylacetic acid, 3,3-diphenylpropionic acid, and triphenylacetic acid; <1> ~ <4> 1. The thermally conductive grease composition according to claim 1 . <6> the discoloration temperature regulator includes at least one selected from the group consisting of alcohol-based compounds, ester-based compounds, ketone-based compounds, ether-based compounds, acid amide-based compounds, azomethine-based compounds, fatty acid-based compounds, and hydrocarbon-based compounds; <1> ~ <5> 1. The thermally conductive grease composition according to claim 1 . <7> The total content of the thermally conductive filler is 70.00% by mass or more and 98.00% by mass or less based on the total amount of the thermally conductive grease composition. <1> ~ <6> 1. The thermally conductive grease composition according to claim 1 . <8> The ratio of the total content of the thermally conductive filler to the total content of the capsule pigment is 10 or more and 10,000 or less by mass. <1> ~ <7> 1. The thermally conductive grease composition according to claim 1 . <9> The volume average particle diameter of the capsule pigment is 0.1 μm or more and 100 μm or less. <1> ~ <8> 1. The thermally conductive grease composition according to claim 1 . <10> The volume average particle diameter of the thermally conductive filler is 0.1 μm or more and 50 μm or less. <1> ~ <9> 1. The thermally conductive grease composition according to claim 1 . <11> Further, containing a dispersant, <1> ~ <10> 1. The thermally conductive grease composition according to claim 1 . <12> The thermally conductive filler contains at least one of zinc oxide and aluminum nitride. <1> ~ <11> 1. The thermally conductive grease composition according to claim 1 . <13> The base oil comprises a polyalphaolefin and an organic acid ester. <1> ~ <12> 1. The thermally conductive grease composition according to claim 1 . [Effects of the Invention]

[0008] According to the present disclosure, there is provided a thermally conductive grease composition that has high thermal conductivity, excellent applicability, and allows the temperature distribution to be visually determined. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present disclosure will be described. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the invention. In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.

[0010] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified.

[0011] In the present disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In this disclosure, "JIS" is used as an abbreviation for Japanese Industrial Standards.

[0012] <Thermal conductive grease composition> The thermally conductive grease composition of the present disclosure comprises: A base oil, a thermally conductive filler; and an encapsulated pigment containing a leuco dye, a color developer, and a color-change temperature adjuster.

[0013] The thermally conductive grease composition of the present disclosure has high thermal conductivity, excellent applicability, and allows the temperature distribution to be visually determined. Although the function of the thermally conductive grease composition of the present disclosure is not clear, it is presumed to be as follows.

[0014] The thermally conductive grease composition of the present disclosure contains a capsule pigment that encapsulates a leuco dye, a color developer, and a color change temperature regulator, so that the temperature distribution can be seen visually. Here, the leuco dye is preferably an electron-donating organic color-forming compound, the developer is preferably an electron-accepting compound, and the color-change temperature regulator is preferably a reaction medium that causes an electron-donating / accepting reaction between the electron-donating organic color-forming compound and the electron-accepting compound. That is, at temperatures below the melting point of the color-change temperature regulator, the leuco dye and developer come into close proximity, causing an electron donor / acceptor reaction between them, resulting in color development. On the other hand, at temperatures above the melting point of the color-change temperature regulator, the color-change temperature regulator melts, causing the leuco dye and developer to separate, inhibiting the electron donor / acceptor reaction between them, resulting in color loss.

[0015] By visually checking the temperature distribution of the thermally conductive grease composition, it is possible to visually confirm whether the thermally conductive grease composition is at an appropriate temperature for application when applying the thermally conductive grease composition. Furthermore, because the thermally conductive grease composition of the present disclosure has high thermal conductivity, after applying the thermally conductive grease composition, by visually checking the temperature distribution of the thermally conductive grease composition, it is also possible to visually confirm the temperature of the article to which the thermally conductive grease composition has been applied.

[0016] It is generally assumed that the inclusion of the solid capsule pigment in a thermally conductive grease composition would further increase the viscosity of the thermally conductive grease composition. However, the inclusion of the capsule pigment in the thermally conductive grease composition of the present disclosure surprisingly reduced the viscosity and improved the spreadability. This is thought to be because the rounded capsule pigment particles are interposed between the angular particles of the thermally conductive filler, increasing the fluidity of the particles in the thermally conductive grease composition and reducing the viscosity of the thermally conductive grease composition.

[0017] Furthermore, the thermally conductive grease composition of the present disclosure has high thermal conductivity because it contains a thermally conductive filler. It should be noted that the present disclosure is in no way limited to the above-mentioned presumed mechanism.

[0018] <Base oil> The thermally conductive grease composition of the present disclosure includes a base oil. The base oil is not particularly limited, and may include at least one selected from the group consisting of mineral oil, synthetic hydrocarbon oil, organic acid ester, phosphate ester, silicone oil, and fluorine oil. The base oil may be contained alone or in combination of two or more.

[0019] The total content of the base oils is preferably 2.0 mass % or more and 8.5 mass % or less, more preferably 3.0 mass % or more and 8.0 mass % or less, and even more preferably 3.5 mass % or more and 7.0 mass % or less, based on the total amount of the thermally conductive grease composition.

[0020] From the viewpoint of high thermal conductivity and applicability, the base oil has a kinematic viscosity at 40°C (also referred to as 40°C kinematic viscosity) of 10mm 2 / s or more 600mm 2 / s or less is preferable, and 20 mm 2 / s or more 450mm 2 / s or less is more preferable. The 40°C kinematic viscosity is a value measured based on the kinematic viscosity test method of JIS K 2283:2000 (corresponding international standard: ISO 3104:1994).

[0021] (mineral oil) Examples of mineral oils include those obtained by refining lubricating oil fractions of crude oil using an appropriate combination of refining methods such as solvent refining, hydrorefining, hydrocracking refining, hydrodewaxing, etc. Additionally, examples include highly refined paraffinic mineral oils obtained by subjecting hydrorefined oils, catalytic isomerized oils, etc. to treatment such as solvent dewaxing or hydrodewaxing.

[0022] (synthetic hydrocarbon oil) Examples of synthetic hydrocarbon oils include polyalphaolefins. Examples of polyalphaolefins include those obtained by polymerizing ethylene, propylene, butene, alphaolefins produced from derivatives of these, etc., either alone or in combination of two or more. The polyalphaolefin is preferably a polymer of an alphaolefin having 6 to 18 carbon atoms. The polyalphaolefin preferably contains at least one selected from the group consisting of polymers of 1-decene and polymers of 1-dodecene.

[0023] (organic acid esters) Examples of organic acid esters include monoesters, diesters, and polyol esters. Monoesters include esters of monobasic acids and alcohols. Examples of monobasic acids include fatty acids such as butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, eicosanoic acid, docosanoic acid, palmitoleic acid, oleic acid, and ricinoleic acid; acrylic acid; and methacrylic acid. Examples of alcohols used in the synthesis of monoesters include oleyl alcohol, lauryl alcohol, methanol, ethanol, pentanol, hexanol, ethylene glycol, propylene glycol, glycerol, neopentyl glycol, trimethylolmethane, trimethylolethane, trimethylolpropane, trimethylolbutane, 1,2,6-hexanetriol, pentaerythritol, and dipentaerythritol.

[0024] Diesters include esters of dibasic acids and alcohols. Examples of dibasic acids include adipic acid, azelaic acid, sebacic acid, and dodecanedioic acid. The alcohol used in the synthesis of the diester may be a monohydric alcohol or a polyhydric alcohol having two or more hydroxyl groups in one molecule. The alcohol used in the synthesis of the diester may be the same as the alcohol used in the synthesis of the monoester.

[0025] Examples of polyol esters include esters of polyols and saturated fatty acids. Examples of polyols include dihydric alcohols and polyols in which no hydrogen atom exists on the carbon atom at the β-position relative to the hydroxy group. Examples of dihydric alcohols include ethylene glycol, propylene glycol, butylene glycol, 2-butyl-2-ethylpropanediol, and 2,4-diethylpentanediol. Specific examples of polyols in which no hydrogen atom exists on the carbon at the β-position relative to the hydroxy group include neopentyl glycol, trimethylolpropane, and pentaerythritol. The saturated fatty acid is not particularly limited, and examples thereof include enanthic acid, caprylic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, stearic acid, nonadecanoic acid, arachic acid, and behenic acid.

[0026] (phosphate ester, silicone oil, fluorine oil) Examples of the phosphate ester include triethyl phosphate, tributyl phosphate, triphenyl phosphate, tricresyl phosphate, and trixylenyl phosphate. Examples of silicone oils include polysiloxanes such as dimethylpolysiloxane and methylphenylpolysiloxane; modified silicones; and the like. Examples of fluorine oils include perfluoropolyethers.

[0027] (Base oil combination) From the viewpoint of a good balance between high thermal conductivity and applicability, the base oil preferably contains at least one of polyalphaolefin and organic acid ester, more preferably polyalphaolefin and organic acid ester. Furthermore, although the use of a base oil containing low molecular weight siloxane gas may cause contact failure due to the low molecular weight siloxane gas, the use of polyalphaolefin and organic acid ester is also preferable from the viewpoint of preventing contact failure due to the low molecular weight siloxane gas.

[0028] The content of polyalphaolefin is preferably 70% by mass or more and 99% by mass or less, more preferably 80% by mass or more and 99% by mass or less, and even more preferably 85% by mass or more and 99% by mass or less, based on the total content of polyalphaolefin and organic acid ester.

[0029] <Thermal conductive filler> The thermally conductive grease composition of the present disclosure includes a thermally conductive filler. The thermally conductive filler is not particularly limited and may contain at least one of zinc oxide and aluminum nitride. From the viewpoint of achieving both excellent thermal conductivity and coatability, the thermally conductive filler preferably contains zinc oxide and aluminum nitride. From the viewpoint of achieving both excellent thermal conductivity and coatability, the content of aluminum nitride is preferably greater than the content of zinc oxide. The thermally conductive filler may be contained alone or in combination of two or more kinds.

[0030] In the present disclosure, a thermally conductive filler is a filler having a thermal conductivity of 5.0 W / (m·K) or more. The thermal conductivity of the thermally conductive filler is a value measured by the laser flash method (JIS R1611:2010 (corresponding international standard: ISO 18755:2005)).

[0031] From the viewpoints of high thermal conductivity and applicability, the total content of the thermally conductive filler is preferably 70.00 mass% or more and 98.00 mass% or less, more preferably 85.00 mass% or more and 97.00 mass% or less, even more preferably 90.00 mass% or more and 97.00 mass% or less, and even more preferably 93.00 mass% or more and 96.00 mass% or less, relative to the total amount of the thermally conductive grease composition.

[0032] Furthermore, as mentioned above, typical thermally conductive grease compositions change in viscosity with temperature, such as increasing in viscosity and becoming harder at low temperatures, which deteriorates their applicability. It is known that the viscosity of a thermally conductive grease composition can be reduced by reducing the content of thermally conductive filler in the thermally conductive grease composition, but doing so also reduces the thermal conductivity of the thermally conductive grease composition. When the thermally conductive grease composition contains an capsule pigment and the total content of the thermally conductive filler relative to the total amount of the thermally conductive grease composition is within the above range, the thermally conductive grease composition has high thermal conductivity and excellent applicability (i.e., low viscosity).

[0033] The shape of the thermally conductive filler is not particularly limited. The thermally conductive filler may be in any shape such as granular, crushed, or spherical. One embodiment of the thermally conductive filler may be spherical.

[0034] From the viewpoint of high thermal conductivity and coatability, the volume average particle size of the thermally conductive filler is preferably 0.1 μm or more and 50 μm or less, more preferably 0.15 μm or more and 45 μm or less, and even more preferably 0.15 μm or more and 40 μm or less.

[0035] In the present disclosure, the volume average particle size of the thermally conductive filler is measured by a laser diffraction / scattering method in accordance with JIS Z 8825:2013 (corresponding international standard: ISO 13320:2020). Specifically, a sample containing a thermally conductive filler is subjected to measurement of the volume distribution of the thermally conductive filler using a laser diffraction / scattering particle size analyzer. Based on the obtained measurement value (volume distribution), the volume average particle size of the thermally conductive filler contained in the sample can be calculated. As an example of the measuring device, a laser diffraction scattering type particle size measuring device, product name: Nanoparticle Size Distribution Measuring Device SALD-7500nano, manufactured by Shimadzu Corporation, can be used.

[0036] From the viewpoint of achieving both high thermal conductivity and coatability, the thermally conductive filler may contain two or more types of thermally conductive fillers having different volume average particle sizes.

[0037] From the viewpoint of achieving both high thermal conductivity and ease of application, the ratio of the total content of the thermally conductive filler to the total content of the capsule pigments described below (total content of the thermally conductive filler / total content of the capsule pigments) is, by mass, preferably 10 or more and 10,000 or less, more preferably 30 or more and 1,000 or less, even more preferably 50 or more and 500 or less, and particularly preferably 70 or more and 200 or less.

[0038] (zinc oxide) The zinc oxide is not particularly limited, and examples thereof include zinc oxides that are commonly used as thermally conductive fillers. The thermally conductive filler may contain one type of zinc oxide or two or more types of zinc oxide.

[0039] From the viewpoint of achieving both thermal conductivity and coatability, the particle size of zinc oxide is preferably a volume average particle size of 0.15 μm or more and 2.0 μm or less, more preferably 0.2 μm or more and 1.5 μm or less, and even more preferably 0.3 μm or more and 1.2 μm or less.

[0040] (aluminum nitride) The aluminum nitride is not particularly limited, and examples thereof include aluminum nitrides that are commonly used as thermally conductive fillers. The thermally conductive filler may contain one type of aluminum nitride or two or more types of aluminum nitride.

[0041] From the viewpoint of achieving both high thermal conductivity and coatability, the particle size of the aluminum nitride is preferably a volume average particle size of 5 μm or more and 40 μm or less, more preferably 6 μm or more and 30 μm or less, and even more preferably 7.5 μm or more and 25 μm or less.

[0042] Although aluminum nitride is a material with excellent thermal conductivity, when a thermally conductive grease composition contains a high content of thermally conductive filler, the spreadability of the grease composition may be significantly reduced or the composition may not turn into a grease. Here, turning into a grease refers to a state in which a composition containing a base oil and a thermally conductive filler turns into a paste-like substance that exhibits viscous deformation when subjected to an external force at room temperature (25°C).

[0043] (Other thermally conductive fillers) The thermally conductive grease composition according to the present disclosure may contain a thermally conductive filler other than zinc oxide and aluminum nitride, as long as the effects of the present disclosure are exhibited. The material of the other thermally conductive filler is not particularly limited, but examples include magnesium oxide, aluminum oxide, titanium oxide, boron nitride, carbon, silicon carbide, and silica.

[0044] The thermally conductive filler may be a thermally conductive filler that has not been surface-treated, or may be a surface-treated thermally conductive filler that can contribute to improving the affinity with other components contained in the thermally conductive filler.

[0045] The surface treatment of the thermally conductive filler is not particularly limited, and may be a physical treatment or a chemical treatment, and any known treatment capable of treating the surfaces of particles constituting the thermally conductive filler can be applied. The surface treatment is preferably a treatment using a surface treatment agent.

[0046] Examples of the surface treatment agent include a silane coupling agent, a titanium coupling agent, a carboxylic acid coupling agent, a phosphoric acid coupling agent, a fatty acid, a polymer compound, a surfactant, and an oil or fat.

[0047] From the viewpoint of dispersibility, the thermally conductive filler may be surface-treated with a silane coupling agent as a surface treatment agent.

[0048] <Capsule pigment> The thermally conductive grease composition of the present disclosure includes an encapsulated pigment, which encapsulates a leuco dye, a color developer, and a color-change temperature adjuster.

[0049] From the viewpoints of excellent application properties and easy visual observation of color development and decolorization, the total content of the capsule pigments is preferably from 0.01% by mass to 5.00% by mass, more preferably from 0.20% by mass to 3.00% by mass, and even more preferably from 0.50% by mass to 2.00% by mass, relative to the total amount of the thermal conductive grease composition.

[0050] From the viewpoints of coatability, coloring ability, color development, easy fading, and stability, the volume average particle diameter of the capsule pigment of the present disclosure is preferably 0.1 μm or more and 100 μm or less, more preferably 1 μm or more and 50 μm or less, and even more preferably 5 μm or more and 30 μm or less. Note that, in the present disclosure, the volume average particle diameter of the capsule pigment is the D50 value calculated on a volume basis using a particle size distribution analyzer HRA9320-X100 (manufactured by Nikkiso Co., Ltd.). The volume average particle size of the capsule pigment falling within the above range (0.1 μm or more and 100 μm or less) varies depending on the encapsulation method. However, when using a method such as phase separation from an aqueous solution, the capsule pigment can be prepared by appropriately combining stirring conditions when producing the capsule pigment.

[0051] The capsule pigment of the present disclosure thus configured is a thermochromic capsule pigment that has excellent color development and excellent decolorization properties due to temperature changes, and can be suitably used as a thermochromic grease composition. Furthermore, because the capsule pigment of the present disclosure contains a leuco dye, a color developer, and a color change temperature regulator encapsulated in capsules, it can exhibit the above-mentioned effects without being affected by the types of base oil, thermally conductive filler, and additives.

[0052] (leuco dye) The leuco dye is preferably an electron-donating organic color-forming compound. The leuco dye is not particularly limited as long as it functions as a color former. The leuco dye may be used alone or in combination of two or more.

[0053] From the viewpoint of excellent color development characteristics, the leuco dye preferably contains at least one selected from the group consisting of triphenylmethane-based compounds, spiropyran-based compounds, fluoran-based compounds, diphenylmethane-based compounds, rhodamine lactam-based compounds, indolylphthalide-based compounds, leucoauramine-based compounds, and pyridine-based compounds.

[0054] Specific examples of leuco dyes include 6-(dimethylamino)-3,3-bis[4-(dimethylamino)phenyl]-1(3H)-isobenzofuranone, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)- 4-Azaphthalide, 1,3-dimethyl-6-diethylaminofluoran, 2-chloro-3-methyl-6-dimethylaminofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-xylidinofluoran, 2-(2-chloroanilino)-6-dibutylaminofluoran, 3,6-dimethoxyfluoran, 3,6-di-n-butoxyfluoran Fluoran, 1,2-benz-6-diethylaminofluoran, 1,2-benz-6-dibutylaminofluoran, 1,2-benz-6-ethylisoamylaminofluoran, 2-methyl-6-(Np-tolyl-N-ethylamino)fluoran, 2-(N-phenyl-N-methylamino)-6-(Np-tolyl-N-ethylamino)fluoran, 2-(3'-trifluoromethylanilino)-6-diethylaminofluoran, 3-chloro-6-cyclohexyl fluoran, 2-methyl-6-cyclohexylaminofluoran, 3-di(n-butyl)amino-6-methoxy-7-anilinofluoran, 3,6-bis(diphenylamino)fluoran, methyl-3',6'-bisdiphenylaminofluoran, chloro-3',6'-bisdiphenylaminofluoran, 3-methoxy-4-dodecoxystyrinoquinoline, 4,4'-bis(diethylamino)benzophenone, and the like.

[0055] From the viewpoint of exhibiting color by opening the skeleton (ring), the leuco dye is preferably a compound having at least one structure selected from the group consisting of a lactone skeleton, a pyridine skeleton, a quinazoline skeleton, and a bisquinazoline skeleton. The leuco dye may be a leuco dye or a leuco pigment, and more preferably a leuco dye that changes from colored to colorless upon exposure to heat.

[0056] (developer) The color developer is preferably an electron-accepting compound. The color developer is not particularly limited as long as it has the ability to cause the leuco dye to develop color. The color developer may be used alone or in combination of two or more.

[0057] From the viewpoint of excellent color-developing and decoloring properties, the color developer preferably contains at least one selected from the group consisting of diphenylacetic acid, 3,3-diphenylpropionic acid, and triphenylacetic acid.

[0058] (Discoloration temperature regulator) The color change temperature regulator is preferably a reaction medium that causes an electron transfer reaction between the leuco dye and the color developer. The color change temperature regulator is not particularly limited as long as it controls the color change temperature during color development between the leuco dye and the color developer. The color change temperature regulator may be used alone or in combination of two or more.

[0059] From the viewpoint of making color development and decolorization due to temperature change reversible, the color change temperature regulator is preferably a reaction medium that reversibly induces an electron donor / acceptor reaction between the leuco dye and the color developer.

[0060] The discoloration temperature regulator preferably contains at least one selected from the group consisting of alcohol-based compounds, ester-based compounds, ketone-based compounds, ether-based compounds, acid amide-based compounds, azomethine-based compounds, fatty acid-based compounds, and hydrocarbon-based compounds.

[0061] Specific examples of the discoloration temperature regulator include 4,4'-(hexafluoroisopropylidene)bisphenol dicaprate, 4,4'-(hexafluoroisopropylidene)bisphenol dilaurate, 4,4'-(hexafluoroisopropylidene)bisphenol dimyristate, 4,4'-(hexafluoroisopropylidene)bisphenol dipalmiate, 4,4'-(hexafluoroisopropylidene)bisphenol diundecanoate, 4,4'-(hexafluoroisopropylidene)bisphenol ditridecanoate, 4,4'-(isopropylidene)bisphenol dicaprate, 4,4'-(isopropylidene)bisphenol dilaurate, 4,4'-(isopropylidene)bisphenol and at least one of 4,4'-methylenebisphenol dimyristate, 4,4'-(isopropylidene)bisphenol dipalmiate, 4,4'-(isopropylidene)bisphenol diundecanoate, 4,4'-(isopropylidene)bisphenol ditridecaate, 4,4'-methylenebisphenol dicaprate, 4,4'-methylenebisphenol dilaurate, 4,4'-methylenebisphenol dimyristate, 4,4'-methylenebisphenol dipalmiate, 4,4'-methylenebisphenol diundecanoate, 4,4'-methylenebisphenol ditridecanoate, 4,4'-methylenebisphenol ditridecanoate, and 4,4'-methylenebisphenol ditridecanoate.

[0062] (capsule) In the present disclosure, the leuco dye, color developer, and color change temperature regulator are encapsulated in capsules. This allows the leuco dye, color developer, and color change temperature regulator to maintain the same composition and exhibit the same effects under various usage conditions, even when they come into contact with chemically active substances such as acidic substances, basic substances, and peroxides, or other components. For example, the color-developing and color-discharging functions are not impaired, and heat resistance stability is maintained.

[0063] The capsule pigment may be contained alone or in combination of two or more kinds. When a thermally conductive grease composition contains only one type of capsule pigment, the thermally conductive grease composition develops or loses color at a certain temperature (or temperature range) depending on the types of leuco dye, color developer, and discoloration temperature regulator contained in the capsule pigment. When a thermally conductive grease composition contains a combination of two or more types of capsule pigments, the thermally conductive grease composition will develop, change, or fade at multiple temperatures (or temperature ranges) depending on the types of capsule pigments. In particular, when multiple types of capsule pigments that develop different colors when colored are used in combination, the temperature of the thermally conductive grease composition can be visually confirmed by the color change. Furthermore, by using multiple types of capsule pigments that develop or fade reversibly or irreversibly in combination, a thermally conductive grease composition can be obtained that develops, changes, or fades reversibly or irreversibly at any temperature range.

[0064] The capsule pigment may be spherical, ellipsoidal, or geometrically shaped, and from the viewpoint of improving coatability, a spherical shape (which may be either a perfect sphere or an approximately sphere) is preferred. The shortest axis (R min ) and the longest axis (R max ) and the ratio (R min / R max ) is preferably 0.7 or more and 1.0 or less, more preferably 0.8 or more and 1.0 or less, and even more preferably 0.9 or more and 1.0 or less.

[0065] The capsule pigment of the present disclosure can be produced by encapsulating at least a leuco dye, a color developer, and a discoloration temperature regulator so that the volume average particle size is 0.1 μm or more and 100 μm or less. That is, the capsule pigment is preferably a microencapsulated pigment. Examples of encapsulation methods include interfacial polymerization, interfacial polycondensation, in situ polymerization, liquid hardening coating, phase separation from an aqueous solution, phase separation from an organic solvent, melting dispersion cooling, air suspension coating, and spray drying, and can be appropriately selected depending on the application.

[0066] For example, in the phase separation method from an aqueous solution, the above-mentioned leuco dye, developer, and discoloration temperature regulator are heated and melted, then added to an emulsifier solution, and heated and stirred to disperse them into oil droplets. Next, a resin raw material or the like is used as a capsule membrane agent, and various liquids such as an amino resin solution, specifically a methylolmelamine aqueous solution, a urea solution, or a benzoguanamine solution are gradually added, and the mixture is allowed to react to prepare the desired thermochromic capsule pigment. The dispersion is then filtered, whereby the desired thermochromic capsule pigment can be produced.

[0067] The respective contents of these leuco dye, color developer, and color change temperature regulator may vary depending on the types of leuco dye, color developer, and color change temperature regulator used, the encapsulation method, etc. With respect to the total amount of the capsule pigment, the leuco dye is preferably 0.1% by mass to 20% by mass, the color developer is preferably 0.1% by mass to 20% by mass, and the color change temperature regulator is preferably 30% by mass to 80% by mass, with the remainder being the amount of the capsule membrane agent, etc. The content of the leuco dye may be appropriately selected depending on the desired color density, etc., and is adjusted within the above-mentioned specified range. If the content of the color developer is less than 0.1% by mass relative to the total amount of the encapsulated pigment, color development is poor, while if it exceeds 20% by mass, decolorization is poor. Furthermore, the content of the color change temperature regulator relative to the total amount of the encapsulated pigment may be appropriately selected depending on the desired hysteresis width and color density upon color development, and is preferably adjusted within the above-mentioned specified range.

[0068] The capsule pigment of the present disclosure can be set to a suitable temperature for each color development temperature (for example, color development at 0°C or higher) and decolorization temperature (for example, decolorization at 50°C or higher) by suitably combining the types and amounts of the leuco dye, the developer, and the discoloration temperature adjuster. Preferably, the capsule pigment changes from colored to colorless due to heat such as frictional heat.

[0069] In terms of further improving color development and storage stability, the capsule pigment of the present disclosure preferably has a wall formed of a urethane resin, a urea resin, a urethane / urea resin, an epoxy resin, or an amino resin. Examples of urethane resins include compounds of isocyanate and polyol. Examples of urea resins include compounds of isocyanate and amine. Examples of urethane / urea resins include compounds of isocyanate and polyol / amine. Examples of epoxy resins include compounds of epoxy resin and amine. Examples of amino resins include melamine resin, benzoguanamine resin, etc. The thickness of the wall of the capsule pigment is determined appropriately depending on the required strength of the wall and the density of the drawn lines.

[0070] <Additives> The thermally conductive grease composition according to the present disclosure may further contain additives in addition to the base oil, thermally conductive filler, and capsule pigment. Examples of additives include dispersants, antioxidants, calcium carbonate, rust inhibitors, corrosion inhibitors, thickeners, thickeners, and detergents, with dispersants being preferred from the viewpoint of forming a grease. The additives may be contained alone or in combination of two or more.

[0071] The total content of the additives is preferably 0.1 mass % or more and 2.0 mass % or less, more preferably 0.1 mass % or more and 1.5 mass % or less, and even more preferably 0.1 mass % or more and 1.3 mass % or less, based on the total amount of the thermal conductive grease composition.

[0072] (dispersant) As the dispersant, various dispersants can be used, and it is preferable that the dispersant is a compound having a portion that exhibits lipophilicity and a functional group that adsorbs to the thermally conductive filler. Specific examples of the dispersant include carboxylic acid compounds and polyalkylene glycol compounds.

[0073] A carboxylic acid compound is a compound having at least one carboxy group in the molecule, and examples of the carboxylic acid compound include fatty acids and polycarboxylic acids (compounds having two or more carboxy groups in one molecule).

[0074] The molecular weight of the carboxylic acid compound is preferably 100 or more and 2,000 or less, more preferably 150 or more and 1,500 or less, and even more preferably 200 or more and 1,000 or less.

[0075] When the molecular weight of the carboxylic acid compound has a molecular weight distribution, the molecular weight of the carboxylic acid compound means the weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC). The measurement conditions and apparatus are as follows: Measuring device: Shodex GPC-101 Column: Shodex GPC LF-804 (Number of columns: 3) Detector: RI (differential refractive index detector) Temperature 40℃ Mobile phase: THF (tetrahydrofuran) Flow rate: 1mL / min Sample concentration: 1.0 mass% / vol% Sample injection volume: 100 μL

[0076] Fatty acids, which are one embodiment of the carboxylic acid compound, include saturated fatty acids and unsaturated fatty acids. Examples of saturated fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, and lignoceric acid. Examples of unsaturated fatty acids include caproleic acid, linderic acid, myristoleic acid, palmitoleic acid, zomalic acid, peteroselic acid, peteroselaidic acid, oleic acid, elaidic acid, pathenic acid, codoic acid, gondoic acid, cetoleic acid, erucic acid, brassidic acid, selacholeic acid, linoleic acid, linoelaidic acid, linolenic acid, and arachidonic acid. From the viewpoints of dispersibility and heat resistance, erucic acid and oleic acid are preferred as fatty acids used as dispersants, with erucic acid being more preferred.

[0077] Other examples of carboxylic acid compounds include Hypermer KD-4 (weight average molecular weight: 1700), Hypermer KD-9 (weight average molecular weight: 760), Hypermer KD-12 (weight average molecular weight: 490), and Hypermer KD-16 (weight average molecular weight: 370), all manufactured by Croda Japan.

[0078] The polyalkylene glycol compound is a polymer compound having a repeating structure of ether bonds, and is produced, for example, by ring-opening polymerization of a cyclic ether. The polyalkylene glycol compound is preferably a polyalkylene glycol compound having a hydroxy group.

[0079] Polyalkylene glycol compounds having hydroxy groups tend to be highly adhesive, so the surface modifier adsorbed on the surface of the thermally conductive filler adheres to the adherend, improving the dispersibility of the thermally conductive filler.

[0080] Examples of the polyalkylene glycol compound having a hydroxy group include polyalkylene glycol and etherified polyalkylene glycol. Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, and polybutylene glycol.

[0081] The etherified polyalkylene glycol may be a compound in which a polyalkylene glycol and a hydrocarbon group are bonded together via an ether bond. The number of carbon atoms in the hydrocarbon group contained in the etherified polyalkylene glycol is, for example, 12 or more and 65 or less. The structure of the hydrocarbon group is not particularly limited, and may be linear, branched, or cyclic.

[0082] Specific examples of etherified polyalkylene glycols include polyoxyethylene monooleyl ether, polyoxyethylene monostearyl ether, polyoxyethylene monocetyl ether, and polyoxyethylene lanolin alcohol, with polyoxyethylene lanolin alcohol being preferred from the viewpoint of dispersibility.

[0083] The content of the dispersant is preferably 0.1% by mass or more and 1.0% by mass or less, more preferably 0.1% by mass or more and 0.7% by mass or less, and even more preferably 0.1% by mass or more and 0.5% by mass or less, based on the total amount of the thermally conductive grease composition.

[0084] The dispersant may be contained alone or in combination of two or more types. When the thermally conductive grease composition contains two or more types of dispersant, the above content refers to the total content of the dispersants.

[0085] (antioxidant) As the antioxidant, various dispersants can be used. Specific examples of antioxidants include diphenylamine compounds (for example, reaction products of N-phenylbenzenamine and 2,4,4-trimethylpentene), naphthylamine compounds, phenolic compounds, vitamin E, hindered amines, and phosphate esters.

[0086] The content of the antioxidant is preferably 0.1 mass % or more and 1.0 mass % or less, more preferably 0.1 mass % or more and 0.7 mass % or less, and even more preferably 0.1 mass % or more and 0.5 mass % or less, based on the total amount of the thermal conductive grease composition. The antioxidant may be contained alone or in combination of two or more kinds.

[0087] <Physical properties of thermally conductive grease composition> (thermal conductivity) From the viewpoint of high thermal conductivity, the thermal conductivity of the thermally conductive grease composition according to the present disclosure is preferably 4.0 W / (m·K) or more, more preferably 5.0 W / (m·K) or more, even more preferably 6.0 W / (m·K) or more, even more preferably 7.0 W / (m·K) or more, even more preferably 8.0 W / (m·K) or more, and particularly preferably 9.0 W / (m·K) or more.

[0088] The thermal conductivity is measured in accordance with ISO 22007-2. For example, a TPS2500S manufactured by Kyoto Electronics Manufacturing Co., Ltd. can be used as a thermal conductivity measuring device.

[0089] (shear viscosity) From the viewpoint of applicability, the shear viscosity of the thermally conductive grease composition according to the present disclosure, measured at a measurement temperature of 25°C and a shear rate of 10 [1 / s], is preferably 1000 Pa·s or less, more preferably 50 Pa·s or more and 800 Pa·s or less, even more preferably 100 Pa·s or more and 500 Pa·s or less, and particularly preferably 100 Pa·s or more and 300 Pa·s or less.

[0090] In the present disclosure, the shear viscosity is measured using a viscoelasticity measuring device under conditions of a measurement temperature of 25° C. and a predetermined shear rate. As the viscoelasticity measuring device, for example, a product name: MCR102e manufactured by Anton Paar can be used.

[0091] (color) The color of the thermally conductive grease composition according to the present disclosure can be any color depending on the type of capsule pigment used. The color of the thermally conductive grease composition can be confirmed visually.

[0092] <Application> The thermally conductive grease composition according to the present disclosure has high thermal conductivity and excellent spreadability, and can be applied to gaps between various heat generating elements and heat dissipating elements. Examples of heat generating bodies include power devices, peripheral parts of semiconductor elements such as transistors, and coils mounted on batteries, while examples of heat dissipating bodies include heat sinks, water-cooling pipes, and housings.

[0093] <Method for producing thermally conductive grease composition> The method for producing the thermally conductive grease composition is not particularly limited, and may be such that a dispersant is preferably added to the base oil, the thermally conductive filler, and the encapsulated pigment, and other additives are appropriately mixed as needed. The order in which the base oil, the thermally conductive filler, the encapsulated pigment, the dispersant, and other additives are mixed is not particularly limited, and each component may be mixed sequentially with the base oil. [Example]

[0094] Examples will be described below, but the thermally conductive grease composition according to the present disclosure is not limited to these examples in any way.

[0095] <Examples and Comparative Examples> The base oil, thermally conductive filler, capsule pigment, and other additives (dispersant, antioxidant) were mixed in the blending ratios (mass %) shown in Table 1 below. In addition, "-" in the composition column shown in Table 1 indicates that the corresponding component was not blended.

[0096] In Comparative Example A, Examples A1 and A2, Comparative Example B, and Examples B-1 and B-2, thermally conductive grease compositions having the formulations shown in Table 1 were prepared.

[0097] <Evaluation> The following performance evaluations were carried out using the thermally conductive grease compositions of Comparative Example A, Examples A1 and A2, Comparative Example B, and Examples B-1 and B-2 obtained as described above.

[0098] (thermal conductivity) Thermal conductivity was measured in accordance with ISO22007-2. The thermal conductivity measuring device used was a TPS2500S manufactured by Kyoto Electronics Manufacturing Co., Ltd. A thermal conductivity of 6.0 W / (m·K) or higher means that the thermally conductive grease composition has high thermal conductivity, 8.0 W / (m·K) or higher means that the thermally conductive grease composition has even higher thermal conductivity, and 9.0 W / (m·K) or higher means that the thermally conductive grease composition has even higher thermal conductivity.

[0099] (Applicability) The coatability was evaluated by measuring the shear viscosity using a viscoelasticity measuring device (product name: MCR102e, manufactured by Anton Paar) at a measurement temperature of 25°C and a shear rate of 10 [1 / s]. A shear viscosity of 500 Pa·s or less, measured under conditions of 10 [1 / s], means that the thermally conductive grease composition has excellent spreadability, and a shear viscosity of 300 Pa·s or less means that the thermally conductive grease composition has particularly excellent spreadability.

[0100] (color) A thermally conductive grease composition applied to a steel plate at a thickness of 1 mm was left for approximately 15 minutes in an environment where the temperature was less than 25°C (between 0°C and 5°C), and then transferred to an environment of 25°C or higher. The color of the thermally conductive grease composition applied to the steel plate was visually observed when the temperature was less than 25°C (i.e., immediately after being transferred to an environment of 25°C or higher) and when the temperature was 25°C or higher (i.e., after being left to stand for 15 minutes after being transferred to an environment of 25°C or higher). In Comparative Examples A and B, the color remained gray, which is the color of the thermally conductive grease composition itself, both when the temperature was below 25°C and when the temperature was 25°C or higher. On the other hand, in Examples A-1 to A-2 and Examples B-1 and B-2, when the temperature was below 25°C or immediately after being moved from an environment below 25°C to an environment of 25°C or higher, the color of the thermally conductive grease composition was blue, the color of the added capsule pigment; however, when left to stand in an environment of 25°C or higher for 15 minutes or longer, the capsule pigment faded and the color became gray, the color of the thermally conductive grease composition itself.

[0101] The results are shown in Table 1.

[0102] [Table 1]

[0103] Details of each component in Table 1 are described below.

[0104] (base oil) -Synthetic hydrocarbon oil- Polyalphaolefin 1: Product name: DURASYN-168, manufactured by INEOS Oligomeres, polyalphaolefin (polymer of 1-decene), kinematic viscosity at 40°C: 46.4 mm 2 / s Polyalphaolefin 2; Product name: DURASYIN-170INEOS, manufactured by Oligomeres, polyalphaolefin (polymer of 1-decene), kinematic viscosity at 40°C: 65.3 mm 2 / s Polyalphaolefin 3; Product name: INEOS Oligomeres, DURASYN-180R, kinematic viscosity at 40°C: 935mm 2 / s

[0105] -Organic acid esters- Lauryl methacrylate; Product name: Light Ester L, manufactured by Kyoeisha Chemical Co., Ltd., Lauryl methacrylate

[0106] (thermal conductive filler) -Zinc oxide- Zinc oxide; Product name: Zinc oxide type 1, manufactured by Sakai Chemical Industry Co., Ltd., zinc oxide particles, volume average particle diameter 0.6 μm -Aluminum nitride- Aluminum nitride; Product name: HF-20h, manufactured by Tokuyama Corporation, aluminum nitride (AlN) particles, volume average particle diameter 17.8 μm

[0107] (capsule pigment) -Capsule pigment- Capsule pigment: Product name: KT-20, manufactured by Recording Materials Research Institute, thermal color reversible type, volume average particle size 10-15μm, capsule wall: melamine resin. Contains leuco dye, color developer, and discoloration temperature adjuster. Color develops below 25°C and fades above 25°C.

[0108] (additives) -Dispersant- Dispersant 1: Product name: Hypermer KD-9, manufactured by Croda Japan, carboxylic acid compound, polycarboxylic acid, weight average molecular weight: 760 Dispersant 2: Product name: Polycol 15, manufactured by Croda Japan, polyoxyethylene lanolin alcohol

[0109] -Antioxidants- Antioxidant: BASF Japan, Irganox L57, reaction product of N-phenylbenzenamine and 2,4,4-trimethylpentene

[0110] As described above, the thermally conductive grease composition of the present disclosure is a thermally conductive grease composition that has high thermal conductivity, excellent spreadability, and allows the temperature distribution to be visually determined. Example A-1 is an example in which the base oil and additive contents (mass%) are reduced and an encapsulated pigment is incorporated, while the filling rate (mass%) of the thermally conductive filler is unchanged compared to Comparative Example A. Therefore, Example A-1 has an excellent thermal conductivity equivalent to that of Comparative Example A, and also has improved coatability compared to Comparative Example A. Furthermore, Example A-2 has a lower thermal conductivity than Example A-1, but also has further improved coatability. The same can be said for Comparative Example B, Example B-1, and Example B-2.

Claims

1. A base oil, a thermally conductive filler; an capsule pigment containing a leuco dye, a color developer, and a color change temperature adjuster; A thermally conductive grease composition comprising:

2. 2. The thermally conductive grease composition according to claim 1, wherein the total content of the capsule pigments is 0.01% by mass or more and 5.00% by mass or less, based on the total amount of the thermally conductive grease composition.

3. The capsule pigment is spherical, and the shortest axis (R min ) and the longest axis (R max ) and the ratio (R min / R max 3. The thermally conductive grease composition according to claim 1, wherein the σ is 0.7 or more and 1.0 or less.

4. 3. The thermally conductive grease composition according to claim 1, wherein the leuco dye comprises at least one selected from the group consisting of triphenylmethane-based compounds, spiropyran-based compounds, fluoran-based compounds, diphenylmethane-based compounds, rhodamine lactam-based compounds, indolylphthalide-based compounds, leucoauramine-based compounds, and pyridine-based compounds.

5. 3. The thermally conductive grease composition according to claim 1, wherein the developer comprises at least one selected from the group consisting of diphenylacetic acid, 3,3-diphenylpropionic acid, and triphenylacetic acid.

6. 3. The thermally conductive grease composition according to claim 1, wherein the discoloration temperature adjuster comprises at least one selected from the group consisting of alcohol-based compounds, ester-based compounds, ketone-based compounds, ether-based compounds, acid amide-based compounds, azomethine-based compounds, fatty acid-based compounds, and hydrocarbon-based compounds.

7. 3. The thermally conductive grease composition according to claim 1, wherein a total content of the thermally conductive filler is 70.00 mass % or more and 98.00 mass % or less, based on the total amount of the thermally conductive grease composition.

8. 3. The thermally conductive grease composition according to claim 1, wherein a ratio of a total content of the thermally conductive filler to a total content of the capsule pigments is 10 or more and 10,000 or less by mass.

9. 3. The thermally conductive grease composition according to claim 1, wherein the capsule pigment has a volume average particle size of 0.1 μm or more and 100 μm or less.

10. 3. The thermally conductive grease composition according to claim 1, wherein the thermally conductive filler has a volume average particle size of 0.1 μm or more and 50 μm or less.

11. The thermally conductive grease composition according to claim 1 or 2, further comprising a dispersant.

12. 3. The thermally conductive grease composition according to claim 1, wherein the thermally conductive filler comprises at least one of zinc oxide and aluminum nitride.

13. The thermally conductive grease composition according to claim 1 or 2, wherein the base oil comprises a polyalphaolefin and an organic acid ester.

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