Curable composition, cured product, and production method for cured product

Abstract

The present invention provides a curable composition and a cured product of the curable composition. The curable composition contains a thermally conductive filler, a monomer that has a (meth)acryloyl group, a polymerization initiator, a dispersant, and a plasticizer, the monomer content being at least 73 mass% relative to the total amount of the liquid components of the curable composition, and the dispersant being oleic acid.

Description

Curable composition, cured product, and method for producing the cured product

[0001] The present disclosure relates to a curable composition, a cured product, and a method for producing the cured product.

[0002] In recent years, the performance of electronic devices such as personal computers, mobile phones, and personal digital assistants (PDAs), as well as lighting and display devices such as light emitting diodes (LEDs) and electronic luminescent devices (ELs), has improved significantly. This is due to the significant performance improvements in computing elements and light emitting elements. As the performance of computing elements and light emitting elements improves, the amount of heat generated also increases significantly, making heat dissipation in electronic devices, lighting, and display devices an important issue. To address this issue, thermal interface materials (TIMs) are often placed between the heat generating element and the heat sink to transfer heat generated by the computing element or light emitting element to the heat sink without loss and dissipate it through the heat sink. Commonly used TIMs include heat dissipation sheets, thermally conductive greases, and gap fillers. However, gap fillers, which are initially in a paste form and harden into a solid after application, have attracted attention.

[0003] As a gap filler excellent in flexibility, shape stability, and thermal conductivity, for example, Patent Document 1 discloses a curable composition containing a compound (A) having one (meth)acrylate group in one molecule, a compound (B) having two or more (meth)acrylate groups in one molecule, a polymerization initiator (C), a dispersant (D), and a thermally conductive filler (E) containing zinc oxide.

[0004] Patent Document 1: International Publication No. 2020 / 149193

[0005] Methods for curing the gap filler include irradiation with active energy rays, heating, etc. In the case of a curing method using heat, the heating time is often relatively long, at 30 minutes or more, and although the heating time can be shortened by increasing the heating temperature, increasing the heating temperature may result in the generation of voids in the cured product.

[0006] An object of one embodiment of the present disclosure is to provide a curable composition that is less likely to generate voids even when cured at a relatively high heating temperature (e.g., above 100°C), a cured product, and a method for producing the cured product.

[0007] The present disclosure includes the following aspects. <1> A curable composition comprising a thermally conductive filler, a monomer having a (meth)acryloyl group, a polymerization initiator, a dispersant, and a plasticizer, wherein the content of the monomer is 73 mass% or more based on the total amount of liquid components of the curable composition, and the dispersant is oleic acid. <2> The curable composition according to <1>, wherein the monomer comprises an alkyl methacrylate, and the alkyl methacrylate has 12 to 18 carbon atoms. <3> The curable composition according to <1> or <2>, wherein the monomer comprises 2-decyltetradecyl methacrylate. <4> The curable composition according to any one of <1> to <3>, wherein the monomer comprises 79 mass% or more based on the total amount of liquid components of the curable composition. <5> The curable composition according to any one of <1> to <4>, wherein the polymerization initiator is an organic peroxide having a one-minute half-life temperature of 150°C to 170°C. <6> The curable composition according to any one of <1> to <5>, wherein the plasticizer is a trimellitic acid ester. <7> A cured product of the curable composition according to any one of <1> to <6>. <8> A method for producing a cured product, comprising curing the curable composition according to any one of <1> to <6> at a temperature of 100°C or higher.

[0008] According to one embodiment of the present disclosure, there are provided a curable composition, a cured product, and a method for producing a cured product that are less likely to produce voids even when cured at a relatively high heating temperature (e.g., above 100°C).

[0009] The curable composition, cured product, and method for producing the cured product according to the present disclosure are described in detail below. In this disclosure, the symbol "to" used to denote a numerical range indicates a range that includes the numerical values ​​recited as the upper and lower limits. Furthermore, when a unit is used only for the upper limit of a numerical range represented by "to," the same unit is used for the lower limit. In this disclosure, when multiple substances corresponding to each component are present in the composition, the content or amount of each component refers to the total content or amount of the multiple substances present in the composition, unless otherwise specified. In the numerical ranges described in stages in this disclosure, the upper or lower limit of a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages. In the numerical ranges described in this disclosure, the upper or lower limit of a certain numerical range may be replaced with a value shown in the examples.

[0010] In the present disclosure, "(meth)acrylic" is a term used as a concept encompassing both acrylic and methacrylic, and "(meth)acryloyl" is a term used as a concept encompassing both acryloyl and methacryloyl. In the present disclosure, when a plurality of components are present in the composition, each component in the composition refers to the total amount of the corresponding plurality of substances present in the composition, unless otherwise specified. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, "JIS" is used as an abbreviation for Japanese Industrial Standards.

[0011] (Curable Composition) The curable composition according to the present disclosure contains a thermally conductive filler, a monomer having a (meth)acryloyl group, a polymerization initiator, a dispersant, and a plasticizer, the content of the monomer being 73 mass% or more based on the total amount of liquid components of the curable composition, and the dispersant being oleic acid.

[0012] When the curable composition according to the present disclosure has the above-described configuration, it is possible to obtain a curable composition that is less likely to generate voids even when cured at a relatively high heating temperature for a short period of time.

[0013] Gap fillers are heat dissipation materials that harden through a chemical reaction after application. Types that harden through heat are easy to work with because the timing of hardening can be easily controlled. However, the chemical reaction during hardening is a polymer reaction, and the heating time is often relatively long, at 30 minutes or more, which hinders the improvement of production speed when mass-producing products. On the other hand, increasing the heating temperature to shorten the heating time can sometimes cause voids to form in the hardened product. These voids in the hardened product can lead to a significant increase in thermal resistance, which can cause problems with its function as a gap filler.

[0014] Therefore, the present inventors focused on the proportion of monomer in the liquid component of the curable composition, and discovered that by increasing the proportion of monomer in the binder, which is also called the liquid component of the curable composition, it is possible to make it possible to reduce the occurrence of voids in the cured product by heating at a high temperature (e.g., above 100°C), and by making the proportion of monomer in the binder relatively high, the monomer, which is the liquid component, can react before evaporating.

[0015] Hereinafter, each component of the curable composition according to the present disclosure will be described. The curable composition according to the present disclosure is a thermosetting composition.

[0016] The monomer content is 73% by mass or more, preferably 77% by mass or more, more preferably 78% by mass or more, and even more preferably 79% by mass or more, based on the total amount of liquid components of the curable composition. A monomer content of 73% by mass or more allows the curable composition to cure quickly when heated at a high temperature (e.g., above 100°C), thereby making it less likely for voids to form in the cured product. The high temperature in the high-temperature heating is preferably 120°C or more, more preferably 150°C or more, and even more preferably 200°C or more. The liquid components of the curable composition include a monomer, a dispersant, a polymerization initiator, and a plasticizer.

[0017] When the curable composition according to the present disclosure is cured at a high temperature of 100°C or higher, it can be cured in a short time. The short time is preferably 15 minutes or less, more preferably 10 minutes or less, and even more preferably 5 minutes or less. The curable composition according to the present disclosure can shorten the curing time compared to conventional curable compositions, which can contribute to improving production speed.

[0018] Furthermore, the curable composition according to the present disclosure cures in a short time and is less likely to produce voids in the cured product. Therefore, when the curable composition according to the present disclosure is cured during baking of an IC substrate (e.g., at 125°C for 24 hours) or during a solder reflow process (e.g., at a peak temperature of 250°C), the cured product is formed in a short time, and therefore these processes can be used in common as the curing process of the curable composition.

[0019] <Thermally conductive filler> The curable composition according to the present disclosure contains a thermally conductive filler. The material of the thermally conductive filler is not particularly limited, and examples thereof include zinc oxide, magnesium oxide, aluminum oxide, boron nitride, aluminum nitride, and carbon. From the viewpoints of insulation, high thermal conductivity, and a track record of use as a thermally conductive filler, the thermally conductive filler preferably contains at least one selected from aluminum nitride, zinc oxide, magnesium oxide, and aluminum oxide, and more preferably is aluminum nitride or zinc oxide.

[0020] The thermally conductive filler may be a surface-treated thermally conductive filler, which can improve the affinity with other components contained in the composition other than the thermally conductive filler, thereby contributing to lowering the viscosity and improving the thermal conductivity.

[0021] 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.

[0022] 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.

[0023] From the viewpoint of dispersibility, the thermally conductive filler is preferably surface-treated using a silane coupling agent as a surface treatment agent.

[0024] - Content - The content of the thermally conductive filler is preferably 87% by mass or more, more preferably 90% to 98% by mass, and even more preferably 92% to 96% by mass, relative to the total mass of the composition. Furthermore, the content of the thermally conductive filler is preferably 40% by volume or more, more preferably 47% to 80% by volume, and even more preferably 60% to 80% by volume, relative to the total volume of the composition. By ensuring that the content of the thermally conductive filler is within the above range, high thermal conductivity can be obtained.

[0025] <Monomer Having a (Meth)Acryloyl Group> The curable composition according to the present disclosure contains a monomer having a (meth)acryloyl group. The monomer having a (meth)acryloyl group may be a monomer having one (meth)acrylate group in one molecule, or may be a monomer having two or more (meth)acrylate groups in one molecule. The monomer having one (meth)acrylate group in one molecule is not particularly limited, and examples thereof include linear, branched, or cyclic alkyl (meth)acrylate, acrylic acid, and the like. From the viewpoint of achieving both heat resistance and flexibility, the monomer having one (meth)acrylate group in one molecule is preferably a linear or branched alkyl (meth)acrylate, and more preferably contains a compound represented by the following formula (1):

[0026]

[0027] In formula (1), R １ represents an alkyl group having 1 to 50 carbon atoms, and R ２ represents a hydrogen atom or a methyl group.

[0028] In formula (1), R１ The alkyl group in may be linear or branched. The alkyl group may have a substituent. Examples of the substituent include a carboxy group, a hydroxy group, an amino group, an aryl group, and a heterocyclic group. A carboxy group or a hydroxy group is preferred, and a hydroxy group is more preferred.

[0029] From the viewpoint of achieving both heat resistance and flexibility, R １ The number of carbon atoms in the alkyl group is preferably 2 to 30, more preferably 5 to 25, still more preferably 10 to 25, and particularly preferably 12 to 18. Here, when the alkyl group has a substituent containing a carbon atom, the number of carbon atoms means the total number of carbon atoms including the number of carbon atoms in the substituent.

[0030] From the viewpoint of achieving both heat resistance and flexibility, R １ is preferably a linear or branched alkyl group or a substituted alkyl group having 2 to 30 carbon atoms (i.e., the total number of carbon atoms), more preferably a linear or branched alkyl group or a hydroxyl group-containing alkyl group having 2 to 25 carbon atoms, and is preferably a linear or branched unsubstituted alkyl group having 12 to 18 carbon atoms.

[0031] From the viewpoint of preventing the formation of voids in the cured product due to heating at a relatively high temperature, the monomer having a (meth)acryloyl group is preferably an alkyl methacrylate.

[0032] Examples of monomers having one (meth)acrylate group per molecule include lauryl (meth)acrylate, isostearyl (meth)acrylate, tetradecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 2-decyltetradecyl (meth)acrylate. Of these, 2-decyltetradecyl (meth)acrylate is preferred as a monomer having one (meth)acrylate group per molecule, and 2-decyltetradecyl methacrylate is more preferred.

[0033] R ２ is a hydrogen atom or a methyl group, and is preferably a methyl group.

[0034] Examples of monomers having two or more (meth)acrylate groups in one molecule include hexanediol di(meth)acrylate, butanediol di(meth)acrylate (1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate), ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and trimethylolpropane tri(meth)acrylate.

[0035] From the viewpoint of achieving both heat resistance and flexibility, the monomer having two or more (meth)acrylate groups in one molecule is preferably a compound having two and / or three (meth)acrylate groups in one molecule, more preferably a compound having two (meth)acrylate groups in one molecule, and even more preferably a compound represented by the following formula (2):

[0036]

[0037] In formula (2), R Ｂ１ represents an alkylene group having 1 to 5 carbon atoms, and R Ｂ２ and R Ｂ３ R each independently represents a hydrogen atom or a methyl group, and n represents an integer of 4 or more. Ｂ１ The alkylene group having 1 to 5 carbon atoms represented by the formula (I) may be linear or branched. Ｂ１ The alkylene group represented by R is preferably a branched alkylene group having 2 to 5 carbon atoms, more preferably a linear or branched alkylene group having 2 to 4 carbon atoms, and even more preferably a branched alkylene group having 3 or 4 carbon atoms. Ｂ２ and R Ｂ３ are each independently preferably a methyl group. n is preferably 4 to 25, more preferably 4 to 10, and even more preferably 3 to 8.

[0038] From the viewpoint of flexibility and shape stability, R Ｂ１ is preferably a branched alkylene group having 2 to 5 carbon atoms, more preferably a linear or branched alkylene group having 2 to 4 carbon atoms, and even more preferably a branched alkylene group having 3 or 4 carbon atoms. Ｂ２ and R Ｂ３ is preferably a methyl group. n is preferably 4 to 25, more preferably 4 to 10, and even more preferably 3 to 8.

[0039] As described above, the content of the monomer having a (meth)acryloyl group is 73% by mass or more based on the total amount of liquid components of the curable composition. Furthermore, the content of the monomer having a (meth)acryloyl group is preferably 1% by mass to 10% by mass, and more preferably 2% by mass to 8% by mass, relative to the total mass of the curable composition. The monomer having a (meth)acryloyl group may be contained in the composition alone, or two or more types may be contained.

[0040] In one embodiment, the monomer having a (meth)acryloyl group preferably includes at least one selected from monomers having one (meth)acrylate group in one molecule and at least one selected from monomers having two or more (meth)acrylate groups in one molecule.

[0041] The content ratio (A:B; by mass) of the content A of the monomer having one (meth)acrylate group in one molecule to the content B of the monomer having two or more (meth)acrylate groups in one molecule is preferably from 99.5:0.5 to 95:5, and more preferably from 99:1 to 97:3, from the viewpoints of the hardness and curing rate of the cured product.

[0042] The monomer having a (meth)acryloyl group is preferably a monomer having a molecular weight of less than 1,000. In this disclosure, a monomer refers to a polymerizable compound having a molecular weight of less than 1,000, and a polymerizable polymer refers to a polymerizable compound having a weight average molecular weight (Mw) of 1,000 or more. The concept of "polymerizable polymer" in this disclosure also includes so-called oligomers.

[0043] <Polymerization initiator> The curable composition according to the present disclosure contains a polymerization initiator. The polymerization initiator is a compound that generates a polymerization initiating species such as a radical or a cation by the energy of light, heat, or both, and can be appropriately selected from known thermal polymerization initiators, known photopolymerization initiators, etc. From the viewpoint of the reactivity of the monomer having a (meth)acryloyl group, the polymerization initiator is preferably a radical polymerization initiator, more preferably a peroxide that generates a free radical by heat, and even more preferably an organic peroxide that generates a free radical by heat.

[0044] Examples of organic peroxides include isobutyl peroxide, α,α'-bis(neodecanoylperoxy)diisopropylbenzene, cumyl peroxyneodecanoate, di-n-propyl peroxydicarbonate, di-s-butyl peroxydicarbonate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, bis(4-t-butylcyclohexyl)peroxydicarbonate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, di-2-ethoxyethyl peroxydicarbonate, and di(ethylhexyl)peroxide. Dicarbonate, t-hexyl peroxyneodecanoate, dimethoxybutyl peroxydicarbonate, di(3-methyl-3-methoxybutyl) peroxydicarbonate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, succinic peroxide, 2,5-dimethyl-2,5-di (2-ethylhexanoyl)hexane, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylhexanoate, 4-methylbenzoyl peroxide, t-butylperoxy-2-ethylhexanoate, m-toluoylbenzoyl peroxide, benzoyl peroxide, t-butylperoxyisobutyrate, 1,1-bis(t-butylperoxy)2-methylcyclohexane, 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1 -bis(t-hexylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexanone, 2,2-bis(4,4-dibutylperoxycyclohexyl)propane, 1,1-bis(t-butylperoxy)cyclododecane, t-hexylperoxyisopropyl monocarbonate, t-butylperoxymaleic acid, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, 2,5-dimethyl-2,5-di(m-toluoylperoxy)hexane, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl carbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, t-butylperoxyacetate, 2,2-bis(t-butylperoxy)butane, t-butylperoxybenzoate, n-butyl-4,4-bis(t-butylperoxy)valerate, di-t-butylperoxyisophthalate, α,α'-bis(t-butylperoxy)diisopropylbenzene, dicumylperoxy Examples of organic peroxides include 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-butyl peroxide, p-menthane hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne, diisopropylbenzene hydroperoxide, t-butyltrimethylsilyl peroxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroperoxide, t-butyl hydroperoxide, benzoyl peroxide, and lauroyl peroxide. Among these, from the viewpoint of reactivity, the organic peroxide is preferably at least one compound selected from the group consisting of benzoyl peroxide, t-butylperoxy-2-ethylhexyl monocarbonate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, and cumene hydroperoxide.

[0045] The polymerization initiator is preferably an organic peroxide having a one-minute half-life temperature of 120°C to 170°C. By using an organic peroxide having a one-minute half-life temperature of 120°C to 170°C as the polymerization initiator, it is possible to obtain a curable composition that is less likely to generate voids even when cured at a relatively high heating temperature (for example, above 100°C). The one-minute half-life temperature of the organic peroxide is more preferably 150°C to 170°C. By using an organic peroxide having a one-minute half-life temperature of 150°C to 170°C as the polymerization initiator, it is possible to obtain a curable composition that is less likely to generate voids even when cured at an even higher heating temperature (for example, above 180°C).

[0046] Here, the one-minute half-life temperature means the temperature at which the amount of active oxygen is reduced to half in one minute, i.e., the temperature at which the organic peroxide decomposes and reduces to half the initial amount of active oxygen in one minute. The measurement method is not particularly limited, but it can be determined, for example, by determining the half-life of an organic peroxide at a peroxide concentration of 0.10 mol / L in a solvent relatively inert to radicals (such as benzene) at multiple temperatures and plotting the data.

[0047] Specifically, examples of organic peroxides having a one-minute half-life temperature of 120°C to 170°C include t-butylperoxy-2-ethylhexyl monocarbonate, which has a one-minute half-life temperature of 124°C, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, which has a one-minute half-life temperature of 161°C, and 1,1-bis(3,3-dimethylbutylperoxy)cyclohexane (trade name: Perhexa HC, manufactured by NOF Corporation) which has a one-minute half-life temperature of 149.2°C. Furthermore, examples of organic peroxides having a one-minute half-life temperature of 150°C to 170°C include 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, which has a one-minute half-life temperature of 161°C.

[0048] -Content- The content of the polymerization initiator is preferably 0.5 parts by mass or more and 10 parts by mass or less, and more preferably 0.5 parts by mass or more and 4 parts by mass or less, per 100 parts by mass of the monomer having a (meth)acryloyl group.

[0049] <Dispersant> The curable composition according to the present disclosure includes a dispersant, and the dispersant includes oleic acid. The dispersant may be oleic acid. In an embodiment, the dispersant preferably consists solely of oleic acid. By using oleic acid as the dispersant, the curable composition can be one in which voids are less likely to occur in the cured product, even when cured at a relatively high heating temperature (e.g., above 100°C).

[0050] -Content- The content of the dispersant is preferably 0.1 parts by mass or more and 1.0 parts by mass or less, more preferably 0.1 parts by mass or more and 0.8 parts by mass or less, and even more preferably 0.1 parts by mass or more and 0.5 parts by mass or less, relative to 100 parts by mass of the thermally conductive filler.

[0051] <Plasticizer> The curable composition according to the present disclosure contains a plasticizer. The plasticizer is not particularly limited as long as it is a compound that does not form a crosslinked structure with a monomer or the like. Examples include polymers that can be used as plasticizers, fatty acid ester compounds having an unsaturated hydrocarbon group, aromatic carboxylic acid ester compounds, and oils containing fatty acids and aromatic carboxylic acids having an unsaturated hydrocarbon group. In the present disclosure, the term "polymer" refers to a compound having a weight-average molecular weight (Mw) of 1,000 or more. In the present disclosure, the concept of "polymer" also includes so-called oligomers.

[0052] Examples of the polymer include acrylic polymers, polyester polymers, polyurethane polymers, and silicone polymers, and from the viewpoint of the heat resistance and flexibility of the resulting cured product, acrylic polymers are preferred.

[0053] Examples of polymers used as plasticizers include acrylic polymers, polyester polymers, polyurethane polymers, and silicone polymers, with acrylic polymers being preferred from the standpoints of heat resistance and flexibility.

[0054] From the viewpoint of heat resistance, the acrylic polymer preferably contains a structural unit formed from an acrylic acid ester. The (meth)acrylic ester is preferably an alkyl (meth)acrylate. Examples of the meth)acrylic ester include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and isobutyl (meth)acrylate. The alkyl acrylate may be a non-functional alkyl acrylate or an alkyl acrylate having a functional group such as a carboxy group or a hydroxy group (hydroxyl group). The functional group of the alkyl acrylate is preferably a hydroxy group.

[0055] The acrylic polymer is represented by the following formula (P ＡＣ The polymer may be a polymer having a structure represented by the formula:

[0056]

[0057] Formula (P ＡＣ ) Medium, R ｐ represents a hydrogen atom or an alkyl group. ＡＣ In the above, the alkyl group may have a substituent. Examples of the substituent include a carboxy group, a hydroxyl group, and an amino group. The substituent is preferably a carboxy group or a hydroxy group, and more preferably a hydroxy group. The alkyl group is preferably a saturated alkyl group, and examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, and a hexyl group. Of these, an alkyl group having 1 to 4 carbon atoms is more preferred.

[0058] When the plasticizer contained in the curable composition according to the present disclosure is a polymer, from the viewpoint of the heat resistance and flexibility of the resulting cured product, it is preferably a polymer having a glass transition temperature of -20°C or lower, and more preferably an acrylic polymer having a glass transition temperature of -20°C or lower. When the plasticizer contained in the curable composition according to the present disclosure is a polymer, from the viewpoint of the heat resistance and flexibility of the resulting cured product, it is preferably a polymer having a glass transition temperature of -90°C or higher and -20°C or lower, and more preferably an acrylic polymer having a glass transition temperature of -90°C or higher and -20°C or lower. The glass transition temperature (Tg) of the polymer can be determined by examining the inflection point of a DSC curve measured using a differential scanning calorimeter (DSC).

[0059] When the plasticizer contained in the curable composition according to the present disclosure is a compound other than a polymer, from the viewpoint of the heat resistance and flexibility of the resulting cured product, the plasticizer is preferably a compound having a softening temperature of −20° C. or lower, and more preferably a compound having a softening temperature of −25° C. or lower. The softening temperature of the compound other than a polymer can be determined by examining the inflection point of a DSC curve measured using a differential scanning calorimeter (DSC).

[0060] Examples of fatty acid ester compounds having an unsaturated hydrocarbon group include ester compounds of palmitoleic acid, oleic acid, linoleic acid, linolenic acid, etc. Examples of aromatic carboxylic acid ester compounds include ester compounds of phthalic acid, terephthalic acid, benzoic acid, trimellitic acid, etc.

[0061] When the curable composition according to the present disclosure contains a plasticizer, from the viewpoint of high-temperature stability, the plasticizer preferably contains an aromatic carboxylic acid ester compound, and more preferably contains a trimellitic acid ester.

[0062] The plasticizer may be contained alone or in combination of two or more kinds.

[0063] -Content- The content of the plasticizer is preferably 0.1 parts by mass or more and 3 parts by mass or less, more preferably 0.1 parts by mass or more and 2.5 parts by mass or less, and particularly preferably 0.5 parts by mass or more and 2.0 parts by mass or less, relative to 100 parts by mass of the thermally conductive filler.

[0064] <Other Additives> The curable composition according to the present disclosure may contain components other than the thermally conductive filler, the compound having a (meth)acryloyl group, the polymerization initiator, the dispersant, and the plasticizer (hereinafter also referred to as "other additives"). Examples of other additives that may be appropriately blended include reducing agents, antioxidants, corrosion inhibitors, rust inhibitors, and rheology control agents (viscosity modifiers). The above-mentioned additives may be used alone or in combination of two or more.

[0065] <Reducing Agent> The curable composition according to the present disclosure may contain a reducing agent, if necessary. When the curable composition according to the present disclosure is applied to a two-component curable composition described below, it is preferable that one of the compositions contains a reducing agent. Addition of a reducing agent facilitates the decomposition of a polymerization initiator (e.g., a peroxide), making it easier for the polymerization reaction to proceed even under low-temperature conditions.

[0066] The reducing agent is not particularly limited as long as it can promote the decomposition of the polymerization initiator, and examples thereof include known reducing agents that are used in combination with polymerization initiators. From the viewpoint of promoting the decomposition of the polymerization initiator, a metal compound-based reducing agent is preferred.

[0067] Examples of metal compound reducing agents include stannous oxide, dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin diacetate, zinc naphthenate, antimony trichloride, potassium oleate, sodium O-phenylphenate, bismuth nitrate, ferric chloride, tetra-n-butyltin, tetra(2-ethylhexyl) titanate, cobalt 2-ethylhexoate, and iron 2-ethylhexoate.

[0068] When the curable composition according to the present disclosure contains a reducing agent, from the viewpoint of curing rate, the content of the reducing agent is preferably 0.5 parts by mass or more and 10 parts by mass or less, and more preferably 2 parts by mass or more and 9 parts by mass or less, relative to 100 parts by mass of the monomer having a (meth)acryloyl group. The reducing agent may be used alone, or two or more types may be used in combination.

[0069] <Antioxidant> Examples of the antioxidant include phenol-based antioxidants, amine-based antioxidants, and phosphite-based antioxidants.

[0070] <Corrosion Inhibitor> Examples of the corrosion inhibitor include benzotriazole, tolyltriazole, thiadiazole, and benzimidazole.

[0071] <Rust Inhibitor> Examples of the rust inhibitor include sulfonic acid metal salt compounds and sorbitan compounds.

[0072] <Rheology Control Agent> In the present disclosure, a rheology control agent refers to an agent that imparts non-Newtonian properties with respect to changes in shear rate, and is an additive that imparts flow characteristics such that the shear viscosity is high in the low shear rate range while the shear viscosity is low in the high shear rate range.

[0073] The rheology control agent may be an inorganic compound-based rheology control agent or an organic compound-based rheology control agent. Examples of inorganic compound-based rheology control agents include fumed silica, bentonite, mica, and kaolin. Examples of organic compound-based rheology control agents include urea-modified polymers, urethane-modified polymers, castor oil wax, polyethylene wax, polyamide wax, and fatty acid amide wax. Among these, inorganic compound-based rheology control agents are preferred, with fumed silica or bentonite being more preferred, and bentonite being even more preferred. When using fumed silica, it is preferable to use silica whose surface has been rendered hydrophobic with a silane coupling agent or other surface modifier. When using bentonite, it is preferable to use organo-bentonite, which has been organically modified with a quaternary ammonium salt or other organic modifier.

[0074] The content of the rheology control agent is not particularly limited and can be set appropriately.

[0075] [Form of Curable Composition] The curable composition according to the present disclosure is preferably a one-component curable composition in which one type of curable composition is used when applying it to a substrate, a heating element, etc. The curable composition according to the present disclosure may also be a two-component curable composition in which two types of curable compositions are mixed and used.

[0076] [Method for Producing Curable Composition] The method for producing the curable composition according to the present disclosure is not particularly limited and is not particularly limited. The curable composition according to the present disclosure can be produced, for example, by the following method. In an embodiment, the curable composition according to the present disclosure is obtained by adding a thermally conductive filler, a polymerization initiator, a dispersant, a plasticizer, and other additives to a stirring vessel, and stirring and mixing them. Note that a known stirrer or the like can be used for stirring and mixing.

[0077] In the method for producing a curable composition, when other additives are added, they may be stirred for a period of time sufficient for the other additives to dissolve or disperse, and may be added to a stirring vessel together with components other than the other additives, or may be added after mixing of components other than the other additives.

[0078] (Cured product and method for producing the cured product) The cured product according to the present disclosure is a cured product of the curable composition according to the present disclosure. The method for curing the curable composition is not limited and can be appropriately selected from commonly used methods. Examples of the curing method include irradiation with active energy rays and heating, and a curing method by heating is preferred.

[0079] The method for producing a cured product according to the present disclosure is a method for producing a cured product by curing the above-described curable composition at a temperature of 100° C. or higher. The heating temperature is preferably 120° C. or higher, more preferably 150° C. or higher, even more preferably 180° C. or higher, and particularly preferably 200° C. or higher. When the heating temperature is within the above range, the curable composition according to the present disclosure can be cured in a short period of time.

[0080] When the heating time is short to obtain a cured product, the heating time is preferably 3 to 20 minutes, more preferably 5 to 15 minutes. When curing within a short time is not required, the heating temperature is preferably 60°C or higher, more preferably 70°C or higher, and the heating time is preferably 1 to 120 minutes.

[0081] Specifically, the heating time can be determined depending on the heating temperature. For example, when the heating temperature is 120°C, the heating time can be 10 to 20 minutes, when the heating temperature is 150°C or higher, the heating time can be 5 to 10 minutes, and when the heating temperature is 200°C, the heating time can be 3 to 5 minutes. When the curable composition according to the present disclosure is heated under the above conditions, crosslinking of the monomer is almost completed, and a cured product can be obtained even in a relatively short time.

[0082] The curable composition may be cured by reacting with moisture in the air, or may be cured at room temperature.

[0083] The thermal conductivity of the cured product according to the present disclosure is preferably 0.5 (W·m / K) to 50 (W·m / K), more preferably 1 (W·m / K) to 20 (W·m / K), and even more preferably 3 (W·m / K) to 20 (W·m / K), from the viewpoints of flexibility, shape stability, and suppression of changes in thermal conductivity.

[0084] Regarding the softness of the cured product according to the present disclosure, from the viewpoint of stress relaxation to peripheral parts of the cured product, the Asker C hardness is preferably 95 or less, more preferably 90 or less, and even more preferably 85 or less. The lower limit is preferably 30 or more, more preferably 40 or more, and even more preferably 50 or more, from the viewpoint of preventing pump-out. Similarly, regarding the softness of the cured product according to the present disclosure, from the viewpoint of stress relaxation to peripheral parts of the cured product, the Shore OO hardness is preferably 98 or less, and even more preferably 95 or less. The lower limit is preferably 30 or more, more preferably 40 or more, and even more preferably 50 or more, from the viewpoint of preventing pump-out.

[0085] Regarding the softness of the cured product according to the present disclosure, Asker C is determined in accordance with JIS K 7312: 1996. Furthermore, Shore OO hardness is a value measured using a spring-type hardness tester such as Durometer (registered trademark), and is a value measured immediately after pressing the hardness tester against the object to be measured.

[0086] <Applications> The curable composition according to the present disclosure can be suitably used, for example, as a TIM to be filled in recesses (gaps between a heating element and a heat sink) formed on a substrate. A cured product obtained from the curable composition according to the present disclosure has excellent flexibility, shape stability, and thermal conductivity, and therefore excellent conformability to coated surfaces such as recesses formed on a substrate. Therefore, even when components of different heights are present on the substrate, heat can be efficiently dissipated. Furthermore, the curable composition according to the present disclosure can conform to microscopic unevenness of materials on a substrate, allowing for efficient heat dissipation. Furthermore, because of its excellent conformability to coated surfaces that change with temperature, it can be suitably used as a gap filler.

[0087] The curable composition according to the present disclosure can be preferably cured at a relatively high temperature in a short time, and therefore is preferably used, particularly when the composition is heated together with other heating processes, because this improves productivity. Specifically, the curing step of the curable composition according to the present disclosure can be incorporated into a baking process for IC substrates or a solder reflow process. The curable composition according to the present disclosure can be cured at a relatively high temperature in a short time, and the cured product has heat resistance after curing, so it can be applied without problems, for example, to 24-hour heating in a baking process. In this way, when the curing step of the curable composition according to the present disclosure can be incorporated into other heating processes, a reduction in labor and time can be expected, and therefore the curable composition according to the present disclosure can be preferably used.

[0088] Next, the curable composition and cured product according to the present disclosure will be specifically described using examples, but the curable composition and cured product according to the present disclosure are not limited to these examples in any way.

[0089] (Examples 1 to 5 and Comparative Examples 1 to 9) Each raw material was blended in the amount shown in Table 1, and mixed at 2,000 rpm (revolutions per minute) for 2 minutes under atmospheric pressure using a planetary centrifugal mixer (Thinky Corporation, product name: Awatori Rentaro ARV-310) to prepare a curable composition.

[0090] Details of each raw material listed in Table 1 are as follows: 1. Monomer having a (meth)acryloyl group 2-decyltetradecyl methacrylate: ITEC (manufactured by Shin-Nakamura Chemical Co., Ltd.) Lauryl methacrylate: Light Ester L (manufactured by Adeka Corporation) Polypropylene dimethacrylate: 9PG (manufactured by Shin-Nakamura Chemical Co., Ltd.) 2. Dispersant Oleic acid: oleic acid (manufactured by NOF Corporation) Phosphate ester: Crodafos 03A (manufactured by Croda Japan) 3. Polymerization initiator 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate: Perocta O (manufactured by NOF Corporation) t-butyl peroxy-2-ethylhexyl monocarbonate: Perbutyl E (manufactured by NOF Corporation) 4. Plasticizer Trimellitic acid mixed linear alkyl ester: C-880 NB (manufactured by Adeka Corporation)

[0091] 5. Viscoelasticity adjuster: Organically modified bentonite: CLAYTONE-40 (manufactured by BYK Corporation) 6. Color pigment: Copper phthalocyanine: Cyanine Blue 4920 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.)

[0092] 7. Thermally conductive filler Calcined zinc white: K-485 (0.6 μm) (manufactured by Hakusui Tech Co., Ltd.) Calcined zinc white: Calcined zinc white DW-4 (4 μm) (manufactured by Hakusui Tech Co., Ltd.) Calcined zinc white: K-036 (10 μm) (manufactured by Hakusui Tech Co., Ltd.) Calcined zinc white: surface-treated calcined zinc white (12 μm) (manufactured by Hakusui Tech Co., Ltd.) Magnesium oxide: DMG-60 (manufactured by Maruwa Corporation) Aluminum nitride: HF-01Dh (manufactured by Tokuyama Corporation) Aluminum nitride: HF-20 (manufactured by Tokuyama Corporation)

[0093] The following evaluations were performed using the curable compositions prepared in Examples 1 to 5, each having the composition shown in Table 1, and the curable compositions prepared in Comparative Examples 1 to 9, each having the composition shown in Table 3. In Tables 1 and 3, "binder" refers to the liquid component in the curable composition, which contains a monomer having a (meth)acryloyl group, a dispersant, a polymerization initiator, and a plasticizer. The "binder amount" refers to the total mass of the monomer having a (meth)acryloyl group, the dispersant, the polymerization initiator, and the plasticizer. The "monomer ratio in binder" refers to the ratio of the mass of the monomer to the binder amount. The "filling ratio by mass %" refers to the ratio of the mass of the thermally conductive filler to the total amount of the curable composition, and the "filling ratio by volume %" refers to the ratio of the volume of the thermally conductive filler to the total volume of the curable composition. In the tables, blank spaces indicate that the target compound is not included or is not applicable.

[0094] - Evaluation - <Viscosity> The shear viscosity η [Pa s] of the curable compositions prepared above was measured at 25°C using a dynamic viscoelasticity measuring device (rheometer, manufactured by Anton Paar, product name: MCR 101). A PP25 parallel plate (diameter 25 mm, manufactured by Anton Paar) was used as a jig for the curable composition to be measured. The measurement was performed by measuring the shear viscosity η [Pa s] at a shear rate of 10 [1 / s]. The measurement results are shown in Table 2 or Table 4.

[0095] <Minimum Film Thickness> The film thickness of each of the curable compositions prepared above was measured using an eddy current film thickness meter when a load of 0.3 MPa was applied to the curable composition. The measurement results are shown in Table 2 or Table 4.

[0096] <Presence or absence of cracks upon heating at 120°C> A test specimen was prepared by sandwiching the curable composition prepared above between two glass plates and using spacers to form a film with a thickness of 2 mm. The prepared test specimen was heated in a thermostatic oven at 120°C for 15 minutes to heat-cure the curable composition, thereby obtaining a cured product. Each cured product was visually evaluated for the presence or absence of cracks that penetrated the film thickness, and this was used as an index for evaluating the occurrence of voids. The evaluation criteria were as follows: Pass: No cracks were observed Fail: Cracks were observed The evaluation results are shown in Table 2 or Table 4.

[0097] <Presence or absence of cracks upon heating at 200°C> The curable composition of Example 5 was heated at 200°C for 5 minutes using a thermostatic bath in the same manner as in the case of heating at 120°C, and the curable composition was heat-cured to obtain a cured product. The cured product was visually evaluated for the presence or absence of cracks that penetrated the film thickness, and this was used as an index for evaluating the occurrence of voids. The evaluation criteria were as follows: Pass: No cracks were observed Fail: Cracks were observed The evaluation results are shown in Table 5.

[0098] <Thermal Conductivity> The thermal conductivity was measured by the Hot Disk method in accordance with ASTM D5470. The curable composition was molded to a size of 10 mm x 10 mm x 1 mm in length, width, and height (thickness), and sandwiched between 10 mm x 10 mm copper plates on the top and bottom. The composition was cured in an N2 purged atmosphere at 80°C for 30 minutes, and the thermal resistance (unit: K cm) was measured using a thermal resistance measuring device (manufactured by Tsukubarika Seiki Co., Ltd., product name: Thermal Resistance Measuring Device). ２ / W) was measured and converted into thermal conductivity. In this evaluation, a thermal conductivity of 2.8 W / (m·K) or more can be evaluated as excellent thermal conductivity. The evaluation results are shown in Table 2 or Table 4.

[0099] <Hardness: Flexibility> - Softness after curing: Asker C hardness (sample thickness: 6 mm) - The softness of the cured product of the curable composition was measured in accordance with JIS K 7312:1996. The curable composition was molded into a size of 50 mm x 20 mm x 6 mm (6 mm thick) and cured in an N2 purged atmosphere at 80°C for 30 minutes, after which the Asker C hardness was measured using an Asker Rubber Hardness Tester Type C (manufactured by Kobunshi Keiki Co., Ltd.). From the viewpoint of flexibility of the cured product, it is preferable that the Asker C hardness be 95 or less. The measurement results are shown in Table 2 or Table 4.

[0100] - Softness after curing: Shore OO hardness - The softness of the cured product of the curable composition after curing under the conditions of 80°C and 30 minutes was measured using a durometer (manufactured by Teclock Corporation) in accordance with ASTM D 2240. From the viewpoint of flexibility of the cured product, the Shore OO hardness is preferably 95 or less. The measurement results are shown in Table 2 or Table 4.

[0101]

[0102]

[0103]

[0104]

[0105]

[0106] The results shown in Tables 1 to 4 indicate that the curable compositions of the Examples did not develop cracks in the cured products cured for a short time at a relatively high heating temperature of 120°C or higher. In contrast, the curable compositions of the Comparative Examples developed cracks in all of the cured products cured for a short time at a relatively high heating temperature of 120°C or higher. Therefore, the curable compositions and cured products of the Examples were curable compositions and cured products that were less likely to develop voids, even when cured for a short time at a relatively high heating temperature of 120°C or higher. The results shown in Table 5 indicate that the curable composition of Example 5 did not develop cracks in the cured product cured for a short time at a relatively high heating temperature of 200°C or higher.

[0107] The disclosure of Japanese Patent Application No. 2024-058103, filed on March 29, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A curable composition comprising: a thermally conductive filler; a monomer having a (meth)acryloyl group; a polymerization initiator; a dispersant; and a plasticizer, wherein the content of the monomer is 73 mass% or more based on the total amount of liquid components of the curable composition; and the dispersant is oleic acid.

2. The curable composition according to claim 1, wherein the monomer comprises an alkyl methacrylate, and the alkyl methacrylate has an alkyl group having 12 to 18 carbon atoms.

3. The curable composition of claim 1, wherein said monomer comprises 2-decyltetradecyl methacrylate.

4. The curable composition according to claim 1, wherein the monomer accounts for 79% by mass or more of the total amount of liquid components of the curable composition.

5. The curable composition according to claim 1, wherein the polymerization initiator is an organic peroxide having a one-minute half-life temperature of 120°C to 170°C.

6. The curable composition of claim 1, wherein the plasticizer is a trimellitic acid ester.

7. A cured product of the curable composition according to any one of claims 1 to 6.

8. A method for producing a cured product, comprising curing the curable composition according to any one of claims 1 to 6 at a temperature of 100°C or higher.

Images