Thermally conductive adhesive, cured product, and structure

Abstract

To provide a thermally conductive adhesive which allows easy mixing between a polyol composition and a polyisocyanate composition, and which has excellent dispersion stability, thermal conductivity, rapid hardenability at room temperature, adhesiveness to aluminum substrates, and long-term moist heat resistance; a cured product made using the adhesive; and a structure.SOLUTION: The foregoing problem is solved by a thermally conductive adhesive comprising: a polyol composition containing a polyol (A), a phosphoric acid compound (B), a dispersant (C), and a thermally conductive filler (D1); and a polyisocyanate composition containing a polyisocyanate (E), a trifunctional or higher epoxy compound (F), and a thermally conductive filler (D2).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a thermally conductive adhesive having good miscibility between a polyol composition and a polyisocyanate composition, excellent in dispersion stability, thermal conductivity, room-temperature rapid curability, adhesiveness to an aluminum substrate, and long-term moisture and heat resistance, a cured product using the adhesive, and a structure.

Background Art

[0002] In recent years, with the miniaturization and high integration of electronic components, excessive heat generation and malfunction due to it have become problems. In order to operate electronic components normally, a member that efficiently dissipates the generated heat is required. In particular, when it is necessary to fix a component that generates heat to a structure, a thermally conductive adhesive imparted with thermal conductivity by blending a thermally conductive filler into an adhesive resin is useful. When materials are adhered using such a thermally conductive adhesive, there is a problem that a high stress is applied to the adhesive layer due to the difference in expansion rate between the materials caused by temperature changes in the manufacturing process or the use temperature environment, and the destruction or deterioration of the adhesive layer is promoted. Therefore, urethane-based thermally conductive adhesives having excellent stress relaxation properties have attracted attention.

[0003] On the other hand, from the viewpoints of productivity and energy saving, a performance (hereinafter referred to as room-temperature rapid curability) that exhibits sufficient initial adhesive strength under room-temperature short-time curing conditions is required, but conventional urethane-based thermally conductive adhesives have a problem that the urethanization reaction is slow. In addition, conventional urethane-based thermally conductive adhesives have a problem that sufficient adhesive strength cannot be obtained without providing a primer. Furthermore, in order to obtain a high thermal conductivity, it is necessary to fill the adhesive resin with a thermally conductive filler at a high concentration, but such a heat-dissipating adhesive has an adverse effect on the mechanical properties of the cured coating film and the adhesive strength decreases.

[0004] For example, Patent Document 1 discloses a urethane-based thermally conductive adhesive having excellent mechanical properties, which contains a polyol component and a polyisocyanate component blended by combining different filler materials having different thermal conductivities.

[0005] Patent Document 2 discloses a urethane-based thermally conductive adhesive comprising an isocyanate composition containing metal oxide particles having a predetermined average particle size surface-treated with a polyisocyanate and an alkoxysilane, and a polyol composition containing a specific thermally conductive filler, which is described as having a low viscosity during mixing and a high thermal conductivity during curing.

[0006] Patent Document 3 discloses a curable composition comprising a polyol containing 50% by weight or more of a polyalkylene glycol having a chemical formula weight or number average molecular weight of 1,000 or less, a polyisocyanate, an inorganic filler, and a specific dispersant, which is described as being excellent in thermal conductivity and flexibility, capable of following / adhering to the shape of a heating element, and having excellent heat dissipation efficiency.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, the adhesive described in Patent Document 1 does not contain a phosphoric acid compound or a dispersant in the polyol component, and does not contain a filler or an epoxy compound in the polyisocyanate component. When no primer is provided, the adhesive strength to an aluminum substrate is low, and there are problems with long-term resistance to wet heat. In addition, since only the polyol component contains a filler, there is a problem that the viscosity difference between the polyol component and the polyisocyanate component is large, and mixing failure is likely to occur. The adhesive described in Patent Document 2 contains spherical metal oxide particles having an average particle size of 20 μm or more, but does not use a dispersant, and has a problem of poor dispersion stability. Since the composition described in Patent Document 3 does not contain an epoxy compound in the polyisocyanate component and the urethanization reaction is slow, there is a problem that the room-temperature rapid curability is insufficient.

[0009] Therefore, an object of the present invention is to provide a thermally conductive adhesive having excellent miscibility between a polyol composition and a polyisocyanate composition, excellent dispersion stability, thermal conductivity, room-temperature rapid curability, adhesiveness to an aluminum substrate, and long-term heat and humidity resistance, a cured product using the adhesive, and a structure. [Means for Solving the Problems]

[0010] As a result of intensive studies, the present inventors have found that the above problems can be solved. [1] The present disclosure relates to a thermally conductive adhesive including a polyol composition containing a polyol (A), a phosphoric acid-based compound (B), a dispersant (C), and a thermally conductive filler (D1), and a polyisocyanate composition containing a polyisocyanate (E), a trifunctional or higher-functional epoxy compound (F), and a thermally conductive filler (D2).

[0011] [2] The present disclosure relates to the thermally conductive adhesive according to [1], wherein the thermally conductive filler (D1) and the thermally conductive filler (D2) each independently contain at least one filler selected from the group consisting of metal oxides and metal nitrides.

[0012] [3] The present disclosure relates to the thermally conductive adhesive according to [1] or [2], wherein the thermally conductive filler (D1) and the thermally conductive filler (D2) are each independently surface-treated with a silane coupling agent.

[0013] [4] The present disclosure relates to the thermally conductive adhesive according to any one of [1] to [3], wherein the total amount of the thermally conductive filler (D1) and the thermally conductive filler (D2) is 60% by mass or more based on the mass of the thermally conductive adhesive.

[0014] [5] The present disclosure relates to the thermally conductive adhesive according to any one of [1] to [4], wherein the polyol (A) contains 50% by mass or more of a polyol (A1) having a number average molecular weight of 2,000 or less.

[0015] [6] The present disclosure relates to the thermally conductive adhesive according to any one of [1] to [5], wherein the content of the phosphoric acid compound (B) is 0.1 to 5% by mass based on the mass of the polyol (A).

[0016] [7] The present disclosure relates to the viscosity (V OH ) of the polyol composition with respect to the viscosity (V NCO ) of the polyisocyanate composition, and the ratio (V NCO / V OH ) is 0.1 to 10, and relates to the thermally conductive adhesive according to any one of [1] to [6].

[0017] [8] The present disclosure relates to a cured product of the thermally conductive adhesive according to any one of [1] to [7].

[0018] [9] The present disclosure relates to a structure having an adhesive layer between a first substrate and a second substrate, wherein the adhesive layer is the cured product according to [8].

Advantages of the Invention

[0019] According to the present invention, it is possible to provide a thermally conductive adhesive having easy miscibility between a polyol composition and a polyisocyanate composition, excellent in dispersion stability, thermal conductivity, room temperature rapid curability, adhesiveness to an aluminum substrate, and long-term moisture and heat resistance, a cured product using the adhesive, and a structure.

Embodiments for Carrying Out the Invention

[0020] The thermally conductive adhesive of the present invention contains a polyol composition and a polyisocyanate composition. The polyol composition contains a polyol (A), a phosphoric acid compound (B), a dispersant (C), and a thermally conductive filler (D1). The polyol composition is characterized by containing a polyisocyanate (E), a trifunctional or higher epoxy compound (F), and a thermally conductive filler (D2). With the above configuration, sedimentation of the filler is suppressed, and the miscibility is improved, and the miscibility of the polyol composition and the polyisocyanate composition is improved. In addition, excellent thermal conductivity, room temperature rapid curability, adhesiveness to an aluminum substrate, and long-term heat and humidity resistance can be exhibited. Hereinafter, the present invention will be described in detail. As long as it conforms to the gist of the present invention, other embodiments are also included in the scope of the present invention. In this specification, the numerical range specified using "~" shall include the numerical values described before and after "~" as the range of the lower limit value and the upper limit value.

[0021] <<Polyol composition>> The polyol composition contains a polyol (A), a phosphoric acid compound (B), a dispersant (C), and a thermally conductive filler (D1).

[0022] <Polyol (A)> The polyol (A) may be any compound having two or more hydroxyl groups in the molecule and is not particularly limited. When the polyol (A) is a resin, the hydroxyl group may be at any of the terminals, side chains, or side groups of the resin. Examples of such polyol (A) include polyester polyol, polyether polyol, polyurethane polyol, polyester amide polyol, acrylic polyol, polycarbonate polyol, polycaprolactone polyol, polyvalerolactone polyol, polybutadiene polyol, polyolefin polyol, polyhydroxyalkane, castor oil, or a mixture thereof. As the polyol (A), for example, glycols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-5-pentanediol, 1,6-hexanediol, neopentyl glycol, methylpentaneglycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, bishydroxyethoxybenzene, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, triethylene glycol; polyalkylene glycols with a number average molecular weight of 200 to 3,000; trifunctional or tetrafunctional aliphatic alcohols such as glycerin, trimethylolpropane, pentaerythritol; polyols obtained by adding the above glycol or polyol to the above trifunctional or tetrafunctional aliphatic alcohol can be used. Among them, polyether polyol, polyurethane polyol, acrylic polyol, polycarbonate polyol, and polybutadiene polyol are preferable from the viewpoint of long-term heat and humidity resistance. These polyols (A) may be used alone or in combination of two or more.

[0023] The polyol (A) preferably contains 50% by mass or more of a polyol (A1) having a number average molecular weight of 2,000 or less based on the total mass of the polyol (A). This is preferable because the fluidity of the polyol composition is not impaired even when a thermal conductivity filler is blended. More preferably, it is 60% by mass or more. Also preferably, it is 70% by mass or more, more preferably 80% by mass or more. The number average molecular weight of the polyol (A1) is preferably 1,000 or less, more preferably 500 or less. In this specification, the number average molecular weight is a conversion value based on standard polystyrene measured by GPC (gel permeation chromatography).

[0024] The polyol (A) may have a primary hydroxyl group at its terminal. If it has a primary hydroxyl group at its terminal, it is excellent in initial adhesion strength at room temperature, suppression of foam generation in the coating film, and strength after curing. Further, the polyol (A) may be a polyol having a urethane bond in the molecule (hereinafter also referred to as urethane polyol). By containing such a urethane polyol, sagging of the adhesive during vertical application is suppressed and the stretchability of the cured coating film is excellent. That is, preferably, the polyol (A) includes a urethane polyol having a primary hydroxyl group at its terminal and a urethane bond in the molecule.

[0025] The method for producing the above urethane polyol is not particularly limited, and for example, a reaction product of a polyol and a polyisocyanate can be preferably used. As the polyol, for example, the compounds exemplified in the section of <Polyol (A)> described above can be used.

[0026] Examples of the polyisocyanate include aromatic, aliphatic, or alicyclic diisocyanates (hereinafter also referred to as polyisocyanate monomers); dimers, trimers, biurets, allophanates derived from polyisocyanate monomers; polyisocyanates having a 2,4,6-oxadiazinetrione ring obtained from carbon dioxide gas and the above polyisocyanate monomers. These may be used alone or in combination of two or more.

[0027] Examples of aromatic diisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, m-tetramethylxylylene diisocyanate, p-tetramethylxylylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate.

[0028] Examples of aliphatic diisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, lysine ester triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate tetramethylene diisocyanate, pentamethylene diisocyanate, trimethylhexamethylene diisocyanate.

[0029] Examples of the alicyclic diisocyanate include isophorone diisocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,4-bis(isocyanatomethyl)cyclohexane, hydrogenated xylylene diisocyanate, dimer acid diisocyanate, and norbornene diisocyanate.

[0030] The number average molecular weight of the urethane polyol is not particularly limited, but is preferably from 3,000 to 100,000. When the number average molecular weight is 3,000 or more, the cured product has excellent extensibility, and when it is 100,000 or less, the cured product has excellent adhesion at room temperature curing.

[0031] The urethane polyol may further have a urea bond in the molecule. By having a urea bond in the molecule, the heat resistance durability and the adhesive strength are improved. Examples of the urethane polyol having such a urea bond include a compound obtained by reacting an isocyanate group of a urethane polymer having an isocyanate group at the terminal, which is a reaction product of a polyol and a polyisocyanate, with an amino group of a monoamine compound having a hydroxyl group in the molecule and having a molecular weight of less than 200. A compound using such a low molecular weight monoamine can increase the cohesive force of the resin without excessive increase in molecular weight, and is preferable from the viewpoints of suppressing sagging of the adhesive and adhesive strength.

[0032] <Phosphoric acid compound (B)> The polyol composition contains a phosphoric acid compound (B). The phosphoric acid compound (B) can promote the curing of the adhesive, improve the initial strength at good room temperature curing and the adhesion to metal, and exhibit excellent adhesion to aluminum without using a primer. The phosphoric acid compound (B) may be any compound having at least one free oxyacid. For example, phosphoric acids such as hypophosphorous acid, phosphorous acid, orthophosphoric acid, and metaphosphoric acid; condensed phosphoric acids such as metaphosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, polyphosphoric acid, and ultraphosphoric acid; phosphonic acids; etc. can be mentioned. As the phosphoric acid compound (B), derivatives of phosphoric acid compounds may also be used. Examples of such derivatives include those partially esterified with an alcohol while leaving at least one free oxyacid among the above-mentioned oxyacids of phosphorus, and phosphonic acid esters. Examples of the alcohol include aliphatic alcohols such as methanol, ethanol, ethylene glycol, and glycerin; aromatic alcohols such as phenol, xylenol, hydroquinone, catechol, and phloroglucinol; etc. The phosphoric acid compound (B) may be used alone or in combination of two or more.

[0033] From the viewpoints of curing acceleration and adhesion to metals, the compounding amount of the phosphoric acid compound (B) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, still more preferably 0.6% by mass or more, still more preferably 0.7% by mass or more, based on the mass of the polyol (A). Also, from the viewpoint of the pot life after compounding, it is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less. The compounding amount of the phosphoric acid compound (B) may be, for example, 0.1 to 5% by mass based on the mass of the polyol (A).

[0034] <Dispersant (C)> The polyol composition contains a dispersant (C). As the dispersant (C), it can be appropriately selected from those conventionally used as dispersants for fillers and used. The dispersant (C) can uniformly disperse the thermally conductive filler (D1) in the polyol composition and achieve reduction in viscosity and suppression of aggregation. As the dispersant (C), for example, surfactants such as anionic, cationic, nonionic, and amphoteric surfactants can be used. An anionic dispersant is one in which a hydrophilic group ionizes to produce an anion when dissolved in water. Examples of anionic dispersants include phosphate ester type, sulfate ester type, sulfonic acid type, and carboxylic acid type. A cationic dispersant is one in which a hydrophilic group ionizes to produce a cation when dissolved in water. Examples of cationic dispersants include alkylamine salt type and alkylammonium salt type. A nonionic dispersant is one in which the hydrophilic group does not have ionic dissociability. Examples of nonionic dispersants include polyoxyalkylene type and ester type. An amphoteric dispersant is one that has both the above-mentioned anionic and cationic groups. The dispersant (C) may be used alone or in combination of two or more. Among surfactants, a polymer surfactant (polymer dispersant) is preferable from the viewpoint of being able to disperse uniformly and finely, and more preferably a polymer dispersant having an acidic group. Examples of the acidic group include carboxy group, phosphate group and its salts, sulfonic acid group and its salts, etc. Examples of commercially available products of polymer dispersants having an acidic group include DISPERBYK-103, DISPERBYK-111, DISPERBYK-118, Ajisper PN411, Ajisper PA111, etc.

[0035] From the viewpoint of dispersibility, the compounding amount of the dispersant (C) is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, and still more preferably 0.5% by mass or more based on the mass of the heat conductive filler (D1) described later. Also, from the viewpoint of adhesiveness, it is preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 2% by mass or less.

[0036] <Heat conductive filler (D1)> The polyol composition contains a heat conductive filler (D1). Examples of the heat conductive filler (D1) include silicon dioxide; metal oxides such as alumina, magnesium oxide, titanium oxide, and silica; metal carbonates such as calcium carbonate and magnesium carbonate; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, and calcium hydroxide; metal nitrides such as aluminum nitride, boron nitride, and silicon nitride; metal carbides such as silicon carbide and boron carbide; and particles such as silver, copper, aluminum, and alloys containing these. Among them, the heat conductive filler (D1) preferably contains at least one filler selected from the group consisting of metal oxides and metal nitrides from the viewpoints of electrical insulation and thermal conductivity. The thermal conductivity of the heat conductive filler (D1) is preferably 5 W / m·K or more, more preferably 10 W / m·K or more, and still more preferably 20 W / m·K or more.

[0037] The heat conductive filler (D1) may be surface-treated with a silane coupling agent. The surface treatment with the silane coupling agent improves the wettability to the resin and suppresses the reaction with functional groups and moisture in the polyol composition. Thereby, the handleability and the strength of the cured film of the adhesive are improved. Silane coupling agents include, for example, trialkoxysilanes having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane; trialkoxysilanes having an amino group such as 3-aminopropyltriethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; trialkoxysilanes having a glycidyl group such as 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane; alkoxysilane compounds having an isocyanate group such as 3-isocyanatopropyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane; trialkoxysilanes having a mercapto group such as 3-mercaptopropyltrimethoxysilane; trialkoxysilane compounds such as methyltrimethoxysilane, methyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, and phenyltrimethoxysilane; dialkoxysilane compounds such as dimethyldimethoxysilane, dimethyldiethoxysilane, and dimethoxydiphenylsilane; alkoxysilane compounds having a (meth)acrylic group such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropyltripropoxysilane, 3-(meth)acryloxypropyltributoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane. These may be used alone or in combination of two or more.

[0038] The content of the thermally conductive filler (D1) is preferably 60% by mass or more, more preferably 80% by mass or more, based on the mass of the polyol composition. It is also preferably 97% by mass or less, more preferably 93% by mass or less. The total amount of the heat conductive filler (D1) and the heat conductive filler (D2) described below is preferably 60% by mass or more, more preferably 80% by mass or more, based on the mass of the heat conductive adhesive. Also, it is preferably 97% by mass or less, more preferably 93% by mass or less. The heat conductive filler (D1) and the heat conductive filler (D2) described below may be the same or different.

[0039] <<Polyisocyanate Composition>> The polyisocyanate curing agent contains a polyisocyanate (E), a trifunctional or higher epoxy compound (F), and a heat conductive filler (D2).

[0040] <Polyisocyanate (E)> The polyisocyanate (E) may be a compound having two or more isocyanate groups in the molecule. Examples of the polyisocyanate (E) include aromatic, aliphatic, or alicyclic diisocyanates (hereinafter also referred to as polyisocyanate monomers); dimers, trimers, biurets, allophanates derived from polyisocyanate monomers; polyisocyanates having a 2,4,6-oxadiazinetrione ring obtained from carbon dioxide gas and the above polyisocyanate monomers. These may be used alone or in combination of two or more.

[0041] Examples of the aromatic diisocyanate include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, m-tetramethylxylylene diisocyanate, p-tetramethylxylylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate.

[0042] Examples of the aliphatic diisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, lysine ester triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate tetramethylene diisocyanate, pentamethylene diisocyanate, trimethylhexamethylene diisocyanate.

[0043] Examples of the alicyclic diisocyanate include isophorone diisocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,4-bis(isocyanatomethyl)cyclohexane, hydrogenated xylylene diisocyanate, dimer acid diisocyanate, and norbornene diisocyanate.

[0044] The polyisocyanate (E) may be a polyisocyanate having a urethane bond, which is a reaction product of the above-mentioned polyisocyanate and polyol. By including such a polyisocyanate having a urethane bond, the cured film of the adhesive is preferably excellent in flexibility. As the polyol, for example, the compounds exemplified in the section of <Polyol (A)> described above can be used.

[0045] As the polyisocyanate for forming the polyisocyanate having the urethane bond, from the viewpoint of the initial adhesive strength, an aromatic diisocyanate is preferably used, and more preferably diphenylmethane diisocyanate. That is, as the polyisocyanate (E), from the viewpoints of the flexibility of the cured film and the initial adhesive strength, a reaction product of an aromatic diisocyanate and a polyol is preferable, and more preferably a reaction product of diphenylmethane diisocyanate and a polyol. The ratio (NCO / OH) of the number of isocyanate groups of diphenylmethane diisocyanate to the number of hydroxyl groups of the polyol in the reaction may be 1 or more, preferably 1.5 or more. Polyisocyanate (E) may be used in combination with another polyisocyanate according to the required physical properties and viscosity. Examples of polyisocyanates used in combination with polyisocyanates having urethane bonds include polymeric MDI (hereinafter also referred to as crude MDI) and liquid MDI (a mixture of 2,4'-diphenylmethane diisocyanate and 4,4'-diphenylmethane diisocyanate), which can be preferably used.

[0046] <Epoxy compound (F) having 3 or more functional groups> The polyisocyanate curing agent contains an epoxy compound (F) having 3 or more functional groups. By containing a compound (F) having 3 or more epoxy groups in one molecule, the adhesive strength after the wet heat resistance test of the adhesive can be maintained. Examples of such epoxy compound (F) include epoxy compounds derived from polyvinylphenol, polyisopropenylphenol, 1,1-bis-(4-hydroxyphenyl)-1-phenylethane, 1,1-bis-(4-hydroxyphenyl)-1,1-dimethylmethane, etc.; novolak resins derived from phenol novolak, brominated phenol novolak, cresol novolak, brominated cresol novolak, resorcinol novolak, brominated resorcinol novolak, etc.; polyhydric phenol-based epoxy resins derived from resorcinol, hydroquinone, methylresorcinol, etc.; amine-based epoxy resins derived from aniline, p-aminophenol, m-aminophenol, p-amino-m-cresol, 4,4'-diaminodiphenylmethane, etc.; glycidyl ester-based compounds derived from aromatic carboxylic acids such as p-oxybenzoic acid, m-oxybenzoic acid, terephthalic acid, isophthalic acid, etc.; hydantoin-based epoxy resins derived from 5,5'-dimethylhydantoin, etc.; polymers of alicyclic epoxies such as vinylcyclohexene oxide, etc.; polyglycidyl ethers of polyfunctional polyols such as trimethylolpropane, sorbitol, etc.; and others, for example, triglycidyl isocyanurate, 2,4,6-triglycidoxy-5-triazine, epoxidized polybutadiene, epoxidized vegetable oil, etc. Further, modified products thereof such as dimer acid-modified epoxy resin, urethane-modified epoxy resin, etc. may be used. These epoxy compounds (F) may be used alone or in combination of two or more kinds.

[0047] From the viewpoint of the solution stability of the polyisocyanate curing agent, the epoxy compound (F) is preferably a polymer of alicyclic epoxies such as epoxidized butadiene, epoxidized SEBS, epoxidized vegetable oil, vinylcyclohexene oxide, etc., which are formed by adding oxygen to double bonds.

[0048] <Thermally conductive filler (D2)> The polyisocyanate curing agent contains a thermally conductive filler (D2). As the thermally conductive filler (D2), the description in the section of <Thermally conductive filler (D1)> described above can be cited. The content of the heat conductive filler (D2) is preferably 60% by mass or more, more preferably 70% by mass or more, based on the mass of the polyisocyanate curing agent. It is also preferably 97% by mass or less, more preferably 93% by mass or less. Similar to the heat conductive filler (D1), the heat conductive filler (D2) may be surface-treated with a silane coupling agent. By surface treatment with a silane coupling agent, the wettability to the resin is improved, and the reaction with functional groups and moisture in the polyisocyanate composition is suppressed. Thereby, the handleability and the strength of the cured film of the adhesive are improved.

[0049] <<Adjustment of Heat Conductive Adhesive>> The heat conductive adhesive of the present invention can be obtained by mixing at least a polyol composition and a polyisocyanate composition by a known method. The ratio [NCO / OH] of the number of hydroxyl groups in the polyol composition to the number of isocyanate groups in the polyisocyanate composition is preferably 0.9 to 1.3, more preferably 1.0 to 1.2. The adhesive of the present invention may be either a solvent type or a solvent-free type, but is preferably a solvent-free type in that a drying step is not required in the curing process. However, the solvent-free type may contain a small amount of solvent such as the solvent contained in the defoaming agent or the diluting solvent used when adding a solid additive.

[0050] From the viewpoint of coatability, the viscosity of the polyol composition is preferably 1 Pa·s to 500 Pa·s, more preferably 10 Pa·s to 300 Pa·s, and the viscosity of the polyisocyanate composition is preferably 1 Pa·s to 500 Pa·s, more preferably 10 Pa·s to 300 Pa·s. Also, the ratio (V OH ) of the viscosity (V NCO ) of the polyisocyanate composition to the viscosity (V NCO / V OH ) is preferably 0.1 to 10, more preferably 0.2 to 5, from the viewpoint of the stability of the adhesive strength. The viscosity is a value measured using a rheometer MCR302 (manufactured by Anton Paar) under the conditions of a temperature of 25°C and a shear rate of 10 / s.

[0051] <Additive> The adhesive of the present invention may further contain known additives such as epoxy compounds, reaction accelerators, silane coupling agents, leveling agents or defoaming agents, fillers, propellants, plasticizers, superplasticizers, wetting agents, flame retardants, viscosity modifiers, preservatives, stabilizers, and colorants. Such additives may be used alone or in combination of two or more.

[0052] Examples of epoxy compounds include epoxy compounds derived from polyvinylphenol, polyisopropenylphenol, 1,1-bis-(4-hydroxyphenyl)-1-phenylethane, 1,1-bis-(4-hydroxyphenyl)-1,1-dimethylmethane, etc.; novolak resins derived from phenol novolak, brominated phenol novolak, cresol novolak, brominated cresol novolak, resorcinol novolak, brominated resorcinol novolak, etc.; polyhydric phenol-based epoxy resins derived from resorcinol, hydroquinone, methylresorcinol, etc.; amine-based epoxy resins derived from aniline, p-aminophenol, m-aminophenol, p-amino-m-cresol, 4,4'-diaminodiphenylmethane, etc.; glycidyl ester-based compounds derived from aromatic carboxylic acids such as p-oxybenzoic acid, m-oxybenzoic acid, terephthalic acid, isophthalic acid, etc.; hydantoin-based epoxy resins derived from 5,5'-dimethylhydantoin, etc.; polymers of alicyclic epoxies such as vinylcyclohexene oxide; polyglycidyl ethers of polyfunctional polyols such as trimethylolpropane, sorbitol, etc.; and others, such as triglycidyl isocyanurate, 2,4,6-triglycidoxy-5-triazine, epoxidized polybutadiene, epoxidized vegetable oil, etc. Further, modified products thereof such as dimer acid-modified epoxy resins, urethane-modified epoxy resins, etc. can be mentioned. From the viewpoints of adhesiveness and wet heat resistance, the compounding amount of the epoxy compound is preferably 1 to 20% by mass based on the total mass of the polyol (A).

[0053] Examples of the reaction accelerator include metal catalysts such as dibutyltin diacetate, dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin dimaleate. The compounding amount of the reaction accelerator is preferably 0.005 to 1% by mass based on the total mass of the polyol (A).

[0054] Examples of the silane coupling agent include trialkoxysilanes having a vinyl group such as vinyltrimethoxysilane and vinyltriethoxysilane; trialkoxysilanes having an amino group such as 3-aminopropyltriethoxysilane and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; trialkoxysilanes having a glycidyl group such as 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 3-glycidoxypropyltriethoxysilane; trialkoxysilanes having an isocyanato group such as 3-isocyanatopropyltriethoxysilane; and trialkoxysilanes having a mercapto group such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane. The compounding amount of the silane coupling agent is preferably 0.05 to 10% by mass based on the total mass of the adhesive.

[0055] Examples of the leveling agent include polyether-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, aralkyl-modified polymethylalkylsiloxane, polyester-modified hydroxyl group-containing polydimethylsiloxane, polyether-ester-modified hydroxyl group-containing polydimethylsiloxane, acrylic copolymer, methacrylic copolymer, polyether-modified polymethylalkylsiloxane, alkyl acrylate copolymer, alkyl methacrylate copolymer, and lecithin.

[0056] Examples of the defoaming agent include known ones such as silicone resin, silicone solution, and copolymer of alkyl vinyl ether, alkyl acrylate, and alkyl methacrylate.

[0057] <<Laminate, cured product>> The cured product of the present invention can be obtained by curing the thermally conductive adhesive of the present invention by a known method. Further, the structure of the present invention is characterized in that it includes an adhesive layer between a first base material and a second base material, and the adhesive layer is the above-mentioned cured product. The manufacturing method of the structure is not particularly limited. For example, an adhesive is applied to one surface of the first base material, and then the second base material is overlaid on the uncured adhesive surface, and a curing reaction is carried out at about 20 to 40 ° C to cure the adhesive, thereby obtaining a structure. The thickness of the adhesive layer after curing is preferably 0.1 μm to 300 mm.

[0058] <First base material, second base material> The adhesive of the present invention can be used for adhesion between various base materials. Examples of suitable base materials that can be used as the first and second base materials include metals such as aluminum, thermoplastic polymers such as polyethylene, polypropylene, polyurethane, polyacrylate, polycarbonate and their copolymers, thermosetting polymers such as vulcanized rubber, urea-formaldehyde foam, melamine resin, wood, carbon fiber reinforced plastic, glass fiber reinforced plastic and other fiber reinforced plastics. The first base material and the second base material may be the same base material or different base materials.

[0059] The adhesive of the present invention has good miscibility between the polyol composition and the polyisocyanate composition, and is excellent in dispersion stability, thermal conductivity, room temperature rapid curing property, adhesiveness to an aluminum base material, and long-term heat and humidity resistance. The structure using the adhesive is useful for cooling applications of heat generating members such as semiconductor elements, LED backlights, batteries, and electric circuits equipped with these.

Examples

[0060] Hereinafter, the present invention will be further specifically described by way of examples. However, the following examples do not limit the scope of rights of the present invention in any way. Unless otherwise specified, "parts" and "%" in the examples represent "parts by mass" and "mass%".

[0061] <Number average molecular weight (Mn)> The number average molecular weight (Mn) and mass average molecular weight (Mw) of the resin were determined as conversion values based on standard polystyrene by GPC (gel permeation chromatography). The measurement was carried out using GPC-8020 (manufactured by Tosoh Corporation) as the GPC apparatus, tetrahydrofuran as the eluent, and three TSKgel Super HM-M (manufactured by Tosoh Corporation) columns connected in series under the conditions of a flow rate of 0.6 ml / min, an injection volume of 10 μl, and a column temperature of 40°C.

[0062] The abbreviations of the compounds in this specification are shown below. <Polyol> · P-400; difunctional polypropylene glycol, number average molecular weight 400, hydroxyl value 280 mg KOH / g, manufactured by ADEKA · P-1000; difunctional polypropylene glycol, number average molecular weight 1,000, hydroxyl value 112 mg KOH / g, manufactured by ADEKA · P-2000; difunctional polypropylene glycol, number average molecular weight 2,000, hydroxyl value 56 mg KOH / g, manufactured by ADEKA · T-400: trifunctional polypropylene glycol, number average molecular weight 400, hydroxyl value 410 mg KOH / g, manufactured by Mitsui Chemicals · T5650E; difunctional polycarbonate polyol, number average molecular weight 500, hydroxyl value 220 mg KOH / g, trade name "Duranol T5650E", manufactured by Asahi Kasei · T5651; difunctional polycarbonate polyol, number average molecular weight 1,000, hydroxyl value 110 mg KOH / g, trade name "Duranol T5651", manufactured by Asahi Kasei · TMP: trimethylolpropane · GI-1000: polybutadiene polyol, number average molecular weight 1,400, hydroxyl value 69 mg KOH / g, manufactured by Nippon Soda Co., Ltd.

[0063] <Polyisocyanate> · IPDI: isophorone diisocyanate · TDI: tolylene diisocyanate · 4,4’-MDI: 4,4’-diphenylmethane diisocyanate · Liquid MDI: Millionate MN, manufactured by Tosoh Corporation · Crude MDI: PM-200, manufactured by Wanhua Chemical Group Co., Ltd. · HDI-nurate: Nurate form of hexamethylene diisocyanate, Basonat HI-100, manufactured by BASF SE

[0064] <Epoxy compound> · JP-100: Epoxidized polybutadiene, manufactured by Nippon Soda Co., Ltd. · ED-505: Trimethylolpropane triglycidyl ether, manufactured by ADEKA Corporation · jER-828: Bisphenol A type epoxy resin, manufactured by Mitsubishi Chemical Corporation

[0065] <Dispersant> · BYK-111: Phosphate ester compound (corresponding to a polymer dispersant having an acidic group), trade name "DISPERBYK-111", manufactured by BYK-Chemie Japan Co., Ltd., acid value 129 mg KOH / g, non-volatile content 95.0%.

[0066] <Thermally conductive filler> · DAW-45: Alumina, average particle size 46 μm, thermal conductivity 27 W / m·K, manufactured by Denka Company Limited · DAW-20: Alumina, average particle size 23 μm, thermal conductivity 27 W / m·K, manufactured by Denka Company Limited · DAW-05: Alumina, average particle size 6 μm, thermal conductivity 27 W / m·K, manufactured by Denka Company Limited · DAW-01: Alumina, average particle size 2 μm, thermal conductivity 27 W / m·K, manufactured by Denka Company Limited · HFS-80: Aluminum nitride, average particle size 80 μm, thermal conductivity 170 W / m·K, manufactured by Tokuyama Corporation · SP-3: Boron nitride, average particle size 4 μm, thermal conductivity 60 W / m·K, manufactured by Denka Company Limited

[0067] <Filler> · MS-KY: Talc, average particle size 21 μm, manufactured by Nippon Talc Co., Ltd.

[0068] <Synthesis of polyol> · (Polyol a1) Into a reaction vessel equipped with a nitrogen gas inlet tube, a stirrer, a thermometer, and a reflux condenser, 100 parts of T5651 and 13.7 parts of tolylene diisocyanate were charged. After uniformly stirring, the mixture was reacted at 110 °C for 5 hours under a nitrogen atmosphere to obtain a urethanized polyol (a1) having a number average molecular weight of 5,000.

[0069] (Polyol a2) Into a reaction vessel equipped with a nitrogen gas inlet tube, a stirrer, a thermometer, and a reflux condenser, 100 parts of T5651 and 30.5 parts of isophorone diisocyanate were charged. After uniformly stirring, the mixture was reacted at 90 °C for 5 hours under a nitrogen atmosphere to obtain a urethanized prepolymer. Next, the mixture was cooled to 80 °C, 4.8 parts of ethanolamine was added, and the mixture was reacted at 75 °C for 2 hours to obtain a polyurethane urea polyol (a2) having a number average molecular weight of 6,000.

[0070] (Polyol a3) Into a reaction vessel equipped with a nitrogen gas inlet tube, a stirrer, a thermometer, and a reflux condenser, 100 parts of P-1000 and 13.9 parts of tolylene diisocyanate were charged. After reacting at 110 °C for 5 hours under a nitrogen atmosphere, a urethanized polyol (a3) having a number average molecular weight of 5,000 was obtained.

[0071]

Table 1

[0072] (Synthesis of Polyisocyanate) (Polyisocyanate e1) Into a reaction vessel equipped with a nitrogen gas inlet tube, a stirrer, a thermometer, and a reflux condenser, 25 parts of P-400 and 45 parts of 4,4'-diphenylmethane diisocyanate were charged. After reacting at 90 °C for 3 hours under a nitrogen atmosphere, a urethanization reaction was carried out. Then, the mixture was cooled to 50 °C, 30 parts of crude MDI was added, and the mixture was stirred for 15 minutes to obtain a polyisocyanate (e1).

[0073] (Polyisocyanate e2) A reaction vessel equipped with a nitrogen gas inlet tube, a stirring device, a thermometer, and a reflux condenser was charged with 12 parts of P-400, 12 parts of P-2000, and 1.6 parts of T-400. After stirring uniformly, 32.4 parts of 4,4'-MDI was charged, and the reaction was carried out at 90 °C for 3 hours under a nitrogen atmosphere to perform a urethanization reaction. Then, it was cooled to 50 °C, 30 parts of crude MDI and 12 parts of liquid MDI were added, and it was stirred for 15 minutes to obtain polyisocyanate (e2).

[0074] (Polyisocyanate e3) 35 parts of liquid MDI was charged into a reaction vessel equipped with a nitrogen gas inlet tube, a stirring device, a thermometer, and a reflux condenser. A premixed mixture of 39.6 parts of GI-1000 and 0.4 parts of TMP was charged little by little. After stirring uniformly, the reaction was carried out at 90 °C for 3 hours under a nitrogen atmosphere to perform a urethanization reaction. Then, it was cooled to 50 °C, 25 parts of liquid MDI was added and stirred to obtain polyisocyanate (e3).

[0075]

Table 2

[0076] <Adjustment of Thermal Conductive Filler> (Thermal Conductive Filler d1) 60 parts of DAW-45, 25 parts of DAW-20, and 15 parts of DAW-01 were charged into a reaction vessel equipped with a stirring device and a thermometer. After stirring uniformly, 1 part of decyltrimethoxysilane was charged and stirred at 60 °C for 30 minutes. Then, it was dried at 150 °C for 3 hours to obtain a thermal conductive filler (d1).

[0077] (Thermal Conductive Filler d2) 30 parts of DAW-45, 50 parts of DAW-20, and 20 parts of DAW-01 were charged into a reaction vessel equipped with a stirring device and a thermometer. After stirring uniformly, 1 part of decyltrimethoxysilane was charged and stirred at 60 °C for 30 minutes. Then, it was dried at 150 °C for 3 hours to obtain a thermal conductive filler (d2).

[0078] (Thermal Conductive Filler d3) 60 parts of HFS-80, 25 parts of DAW-05, and 15 parts of DAW-01 were charged into a reaction vessel equipped with a stirring device and a thermometer, and after stirring uniformly, 1 part of decyltrimethoxysilane was charged and stirred at 60 °C for 30 minutes. Then, it was dried at 150 °C for 3 hours to obtain a thermal conductivity filler (d3).

[0079] (Thermal conductivity filler d4) 12 parts of DAW-45, 5 parts of DAW-05, 3 parts of DAW-01, and 40 parts of SP-3 were charged into a reaction vessel equipped with a stirring device and a thermometer, and after stirring uniformly, 1 part of decyltrimethoxysilane was charged and stirred at 60 °C for 30 minutes. Then, it was dried at 150 °C for 3 hours to obtain a thermal conductivity filler (d4).

[0080] (Thermal conductivity filler d5) 60 parts of HFS-80, 25 parts of DAW-20, and 15 parts of SP-3 were charged into a reaction vessel equipped with a stirring device and a thermometer, and after stirring uniformly, 1 part of decyltrimethoxysilane was charged and reacted and stirred at 60 °C for 30 minutes. Then, it was dried at 150 °C for 3 hours to obtain a thermal conductivity filler (d5).

[0081] (Thermal conductivity filler d6) 60 parts of DAW-45, 25 parts of DAW-20, and 15 parts of DAW-01 were charged into a reaction vessel equipped with a stirring device and a thermometer and stirred uniformly to obtain a thermal conductivity filler (d6).

[0082]

Table 3

[0083] <Production of dispersant> (Dispersant (c1)) Into a reaction vessel equipped with a nitrogen gas inlet tube, a stirrer, a thermometer, and a reflux condenser, 62.6 parts of 1-dodecanol, 287.4 parts of ε-caprolactone, and 0.1 part of monobutyltin(IV) oxide as a catalyst were charged, and the mixture was heated and stirred at 120 °C for 4 hours under a nitrogen atmosphere. After confirming by solid content measurement that 98% had reacted, 36.6 parts of pyromellitic dianhydride were charged into the above reaction product, and the mixture was reacted at 100 °C for 5 hours to obtain a dispersant (c1) which is a polymer dispersant having an acidic group.

[0084] <Production of Polyol Composition> (Polyol Composition 1) 10 parts of polyol (a1), 90 parts of T5650E, 1.00 part of polyphosphoric acid, 1.45 parts of dispersant (c1), and 580 parts of heat conductive filler (d1) were mixed, and the mixture was stirred and defoamed with a planetary mixer (Bubble Kneading Tarō, manufactured by Shin-Kee Co., Ltd.) to obtain Polyol Composition 1.

[0085] (Polyol Compositions 2 to 23) Except that the blending composition ratio of each component was changed to the content shown in Table 4, the components were mixed in the same manner as Polyol Composition 1 to obtain Polyol Compositions 2 to 23.

[0086] For the obtained polyol compositions, the viscosity was measured at a temperature of 25 °C and a shear rate of 10 / s using a rheometer MCR302 (manufactured by Anton Paar). The results are shown in Table 4.

[0087]

Table 4

[0088] <Production of Polyisocyanate Composition> (Polyisocyanate Composition 1) 100 parts of polyisocyanate (e1), 10 parts of JP-100, and 625 parts of heat conductive filler (d1) were added, and the mixture was stirred and defoamed with a planetary mixer (Bubble Kneading Tarō, manufactured by Shin-Kee Co., Ltd.) to obtain Polyisocyanate Composition 1.

[0089] (Polyisocyanate Compositions 2 to 17) The polyisocyanate compositions 2 to 17 were obtained by mixing in the same manner as polyisocyanate composition 1, except that the compounding ratio of each component was changed to the content shown in Table 5.

[0090] The viscosity of the obtained polyisocyanate compositions was measured under the same conditions as the polyol compositions. The results are shown in Table 5.

[0091] [Table 5]

[0092] [Adjustment of Thermally Conductive Adhesive] [Examples 1 to 23, Comparative Examples 1 to 6] After storing the polyol composition and the polyisocyanate composition in an environment at 40°C for one month, they were returned to room temperature, and two types of adhesives with different stirring and mixing times were prepared. Specifically, the thermally conductive adhesive (X) was prepared by stirring and mixing uniformly at 50 rpm for 60 seconds with the compounding ratio described in Table 6 until it became uniform. Similarly, the thermally conductive adhesive (Y) was prepared by stirring and mixing for a short time at 50 rpm for 10 seconds. Note that since polyol composition 20 did not contain a dispersant, the filler precipitated and it could not be evaluated as an adhesive (Comparative Example 1).

[0093] [Evaluation of Thermally Conductive Adhesive] The following evaluations were performed using the obtained adhesives (X) and (Y). The results are shown in Table 6. [Thermal Conductivity] The obtained adhesive (X) was applied to the untreated surface of a CPP film to a thickness of 1 mm and cured in an environment at 23°C for 3 days to obtain a cured film. The obtained cured film was removed from the CPP film, and the thermal conductivity was measured using TRIDENT (manufactured by C-THERM). Based on the value of the thermal conductivity, the following criteria were used for evaluation. A: 2.0 W / m·K or more (extremely good) B: 1.5 W / m·K or more and less than 2.0 W / m·K (good) C: Above 1.0 W / m·K and less than 1.5 W / m·K (usable) D: Less than 1.0 W / m·K (not usable)

[0094] [Room temperature rapid hardening] The obtained adhesive (X) was applied onto the first aluminum substrate (length 100 mm, width 25 mm, thickness 2 mm) to have a width of 25 mm, a length of 10 mm, and a thickness of 0.3 mm, bonded to the same second aluminum substrate, and cured was started in an environment at 23°C while maintaining a thickness of 0.3 mm under pressure. Every 10 minutes after the start of curing, the shear adhesion strength was measured using a tensile testing machine under the conditions of 23°C and a tensile speed of 50 mm / min. Based on the time until the shear strength reached 0.4 MPa or more, evaluation was performed according to the following criteria. A: Within 20 minutes (extremely good) B: Exceeding 20 minutes and within 30 minutes (good) C: Exceeding 30 minutes and within 60 minutes (usable) D: Exceeding 60 minutes (not usable)

[0095] [Adhesion to AL substrate] The test piece prepared in the same manner as the above-mentioned [Room temperature rapid hardening] using the adhesive (X) was cured for 3 days in an environment at 23°C, and then the shear adhesion strength was measured using a tensile testing machine under the conditions of 23°C and a tensile speed of 50 mm / min. Based on the value of the shear adhesion strength, evaluation was performed according to the following criteria. A: 10 MPa or more (extremely good) B: 7 MPa or more and less than 10 MPa (good) C: 5 MPa or more and less than 7 MPa (usable) D: Less than 5 MPa (not usable)

[0096] [Long-term resistance to humidity and heat] The test pieces prepared in the same manner as the above-mentioned [room temperature rapid curability] using the adhesive (X) were cured for 3 days in an environment of 23°C and then stored for 1000 hours in an environment of 85°C and 85% relative humidity. For the test pieces before and after storage, the shear strength was measured using a tensile testing machine at a tensile speed of 50 mm / min under the condition of 23°C. The ratio of the value of the shear strength after storage to the value of the shear strength before storage was calculated from the following formula and evaluated according to the following criteria. Formula) Ratio (%) of the value of the shear strength after storage to the value of the shear strength before storage =[(Value of the shear strength after storage) / (Value of the shear strength before storage)] × 100 A: 85% or more (extremely good) B: 75% or more and less than 85% (good) C: 50% or more and less than 75% (usable) D: Less than 50% (unusable)

[0097] [Adhesion strength stability] Except for using the adhesive (Y) with a short mixing time instead of the adhesive (X), test pieces were prepared in the same manner as the above-mentioned [AL substrate adhesiveness], cured for 3 days in an environment of 23°C, and then the shear adhesion strength was measured using a tensile testing machine at a tensile speed of 50 mm / min under the condition of 23°C. The ratio of the value of the shear strength when using the adhesive (Y) to the value of the shear strength when using the adhesive (X) (= the value of the shear strength of the above-mentioned [AL substrate adhesiveness]) was calculated from the following formula and evaluated according to the following criteria. Formula) Ratio (%) of the value of the shear strength when using the adhesive (Y) to the value of the shear strength when using the adhesive (X) =[(Value of the shear strength when using the adhesive (Y)) / (Value of the shear strength when using the adhesive (X))] × 100 A: 85% or more (extremely good) B: 75% or more and less than 85% (good) C: 50% or more and less than 75% (usable) D: Less than 50% (unusable)

[0098]

Table 6

[0099] According to Table 6, a thermally conductive adhesive comprising a polyol composition containing a polyol, a phosphoric acid-based compound, a dispersant, and a thermally conductive filler, and a polyisocyanate composition containing a polyisocyanate, a trifunctional or higher epoxy compound, and a thermally conductive filler has excellent dispersion stability, hardly causes sedimentation of the filler, has a high thermal conductivity, exhibits good initial adhesive strength at room temperature in a short time, and furthermore, is excellent in adhesion to an aluminum substrate, long-term heat and humidity resistance, and adhesive strength stability in short-time mixing.

Claims

1. A polyol composition comprising a polyol (A), a phosphoric acid compound (B), a dispersant (C), and a thermal conductivity filler (D1), and a polyisocyanate composition comprising a polyisocyanate (E), a trifunctional or higher epoxy compound (F), and a thermal conductivity filler (D2), A thermally conductive adhesive comprising the same.

2. The thermally conductive adhesive according to Claim 1, wherein the thermal conductivity filler (D1) and the thermal conductivity filler (D2) each independently contain at least one filler selected from the group consisting of metal oxides and metal nitrides.

3. The thermally conductive adhesive according to Claim 1, wherein the thermal conductivity filler (D1) and the thermal conductivity filler (D2) are each independently surface-treated with a silane coupling agent.

4. The thermally conductive adhesive according to Claim 1, wherein the total amount of the thermal conductivity filler (D1) and the thermal conductivity filler (D2) is 60% by mass or more based on the mass of the thermally conductive adhesive.

5. The thermally conductive adhesive according to Claim 1, wherein the polyol (A) contains 50% by mass or more of a polyol (A1) having a number average molecular weight of 2,000 or less.

6. The thermally conductive adhesive according to Claim 1, wherein the content of the phosphoric acid compound (B) is 0.1 to 5% by mass based on the mass of the polyol (A).

7. The viscosity (V ＯＨ of the polyol composition with respect to the viscosity (V ＮＣＯ of the polyisocyanate composition) of the ratio (V ＮＣＯ / V ＯＨ ) is from 0.1 to 10, the thermally conductive adhesive according to claim 1.

8. A cured product of the thermally conductive adhesive according to Claim 1.

9. A structure having an adhesive layer between a first substrate and a second substrate, wherein the adhesive layer is the cured product according to Claim 8.

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