Resin sheets and metal base substrates

Abstract

To provide a resin sheet that is excellent in insulation durability, and a metal base substrate including the resin sheet.SOLUTION: The resin sheet of the present invention is obtained by curing a thermosetting resin composition including a thermosetting resin (A), a phenoxy resin (B) having mesogenic structure in the molecule, and a thermally conductive particle (C), the thermal conductivity and the moisture absorptivity of the resin sheet satisfy the following formula. Formula: thermal conductivity≥0.77×moisture absorptivity+17, 18.0≤thermal conductivity (W / m-K)≤25.0, and 0.28≤moisture absorptivity (%)≤0.40.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin sheet and a metal-based substrate containing the resin sheet. [Background technology]

[0002] Insulating materials used in electrical and electronic equipment are required to have good heat dissipation properties. Various developments have been undertaken to improve the heat dissipation of insulating materials.

[0003] As an example of this type of technology, the technology described in Patent Document 1 is known. Patent Document 1 describes a thermosetting resin composition using a bisphenol A type epoxy resin as the thermosetting resin and flaky or spherical boron nitride particles as the thermally conductive particles. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-193504 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, in the conventional technology described in Patent Document 1, the insulation durability sometimes deteriorated. [Means for solving the problem]

[0006] The inventors have discovered that a thermosetting resin composition containing predetermined components, having a thermal conductivity and moisture absorption rate that are not satisfied by conventional resin sheets, and both being within predetermined ranges with an excellent balance between these, exhibits superior insulation durability. According to the present invention, [1] (A) Thermosetting resin and (B) A phenoxy resin having a mesogenic structure within the molecule, (C) A thermally conductive particle and, A resin sheet obtained by curing a thermosetting resin composition containing The resin sheet has a thermal conductivity and a moisture absorption rate that satisfy the following formula. Formula: Thermal conductivity ≥ 0.77 × Moisture absorption rate + 17 18.0 ≤ Thermal conductivity (W / m·K) ≤ 25.0 0.28 ≤ Moisture absorption rate (%) ≤ 0.40 Further, according to the present invention, the following resin sheet is provided. [2] The thermosetting resin (A) contains at least one selected from an epoxy resin, a cyanate resin, a maleimide resin, a phenol resin, and a benzoxazine resin, and the resin sheet according to [1]. [3] The epoxy resin contains an epoxy resin having a mesogenic structure, and the resin sheet according to [2]. [4] The phenoxy resin (B) contains a structural unit derived from a phenol compound and a structural unit derived from an epoxy compound, and the resin sheet according to any one of [1] to [3]. [5] The thermally conductive particle (C) contains at least one selected from silica, alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide, and magnesium oxide, and the resin sheet according to any one of [1] to [4]. [6] The thermally conductive particle (C) contains the boron nitride, The boron nitride contains monodisperse particles, granular particles, aggregated particles, or a mixture thereof of flaky boron nitride, and the resin sheet according to [5]. [7] Furthermore, it contains an organosiloxane compound (D), and the resin sheet according to any one of [1] to [6]. [8] Furthermore, it contains a curing accelerator (E), and the resin sheet according to any one of [1] to [7]. According to the present invention, [9] A first metal substrate, and An insulating layer made of the resin sheet according to any one of [1] to [8], and a second metal layer, are provided in this order, a metal base substrate is provided.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a resin sheet excellent in insulation durability and a metal base substrate including the resin sheet.

Brief Description of the Drawings

[0008] [Figure 1] It is a schematic cross-sectional view showing the configuration of the metal base substrate according to the present embodiment.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and the description will be omitted as appropriate. Further, "~" represents "above" to "below" unless otherwise specified.

[0010] The resin sheet of the present embodiment is formed by curing a thermosetting resin composition containing (A) a thermosetting resin, (B) a phenoxy resin having a mesogenic structure in the molecule, and (C) thermally conductive particles, and the thermal conductivity and the moisture absorption rate satisfy the following formula. Formula: Thermal conductivity ≧ 0.77 × Moisture absorption rate + 17 18.0 ≦ Thermal conductivity (W / m·K) ≦ 25.0 0.28 ≦ Moisture absorption rate (%) ≦ 0.40 The resin sheet of the present embodiment is made of a thermosetting resin composition containing predetermined components, and the thermal conductivity and the moisture absorption rate are in a predetermined range, and since these satisfy the above formula, it is excellent in insulation durability.

[0011] The insulating layer (resin sheet) that constitutes the metal base substrate contains various components such as resin, and even if the moisture absorption rate of each of these components is improved, there are limits to the improvement in the moisture absorption rate of the composite material as a whole. Since the moisture absorption rate affects the insulating properties, reducing the moisture absorption rate is an important issue. On the other hand, the insulating layer (resin sheet) contains thermally conductive particles to provide heat dissipation, and the inventors have discovered that the moisture absorption rate increases at the interface between these thermally conductive particles and the resin. However, since the thermally conductive particles are an essential component, there is a trade-off relationship between improving thermal conductivity and moisture absorption rate, and there was room for improvement in long-term insulating durability. The inventors of the present invention conducted diligent research to simultaneously achieve improvements in thermal conductivity and moisture absorption, and found that in a thermosetting resin composition comprising (A) a thermosetting resin, (B) a phenoxy resin having a mesogenic structure in its molecule, and (C) thermally conductive particles, by setting the thermal conductivity and moisture absorption within a specific range and further satisfying the aforementioned formula, the thermal conductivity and moisture absorption are improved, and the insulation durability over a long period of time is also excellent, thus completing the present invention.

[0012] [Thermosetting resin (A)] The thermosetting resin composition constituting the resin sheet of this embodiment includes a thermosetting resin (A). The thermosetting resin (A) does not contain a phenoxy resin (B).

[0013] Examples of thermosetting resins (A) include thermosetting compounds that contain a mesogenic structure (mesogenic skeleton) within the molecule, and thermosetting compounds that do not contain a mesogenic structure within the molecule.

[0014] Examples of thermosetting resins (A) include epoxy resins, cyanate resins, maleimide resins, phenol resins, benzoxazine resins, polyimide resins, unsaturated polyester resins, melamine resins, silicone resins, acrylic resins, and phenol derivatives and their derivatives, and may contain at least one of these.

[0015] In this embodiment, the thermosetting resin (A) preferably contains at least one selected from epoxy resin, cyanate resin, bismaleimide resin, phenol resin, and benzoxazine resin, and more preferably contains at least one or both of epoxy resin and cyanate resin.

[0016] These thermosetting resins can utilize monomers, oligomers, and polymers in general that have two or more reactive functional groups in a single molecule, and their molecular weight and molecular structure are not particularly limited.

[0017] (Epoxy resin) As the epoxy resin, any known epoxy resin can be used within the range that achieves the effects of the present invention. For example, glycidyl ethers such as bisphenol A, F, S, and AD types, hydrogenated bisphenol A type glycidyl ether, phenol novolac type glycidyl ether, cresol novolac type glycidyl ether, bisphenol A type novolac type glycidyl ether, naphthalene type glycidyl ether, biphenol type glycidyl ether, dihydroxypentadiene type glycidyl ether, triphenylmethane type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, hydroquinone type glycidyl ether, etc., and at least one of these can be used.

[0018] From the viewpoint of the effects of the present invention, it is preferable that the epoxy resin contains at least one selected from naphthalene-type glycidyl ether, biphenol-type glycidyl ether, dihydroxypentadiene-type glycidyl ether, and hydroquinone-type glycidyl ether. The epoxy resin may preferably include an epoxy resin containing a mesogenic skeleton. This further enhances the thermal conductivity (heat dissipation) during curing.

[0019] It is believed that during the curing of epoxy resins containing a mesogenic skeleton, a higher-order structure (liquid crystal phase or crystalline phase) is formed by the mesogenic skeleton. Furthermore, it is thought that heat is transferred through this higher-order structure, further enhancing thermal conductivity (heat dissipation). The presence of this higher-order structure in the cured material can be investigated by observation using a polarizing microscope.

[0020] Mesogenic skeletons can refer to any skeleton that facilitates the development of liquid crystalline or crystallinity through intermolecular interactions. Mesogenic skeletons preferably include conjugated structures. Specific examples of mesogenic skeletons include biphenyl skeletons, phenylbenzoate skeletons, azobenzene skeletons, stilbene skeletons, naphthalene skeletons, anthracene skeletons, and phenanthrene skeletons. The epoxy resin particularly preferably contains a condensed polycyclic aromatic hydrocarbon skeleton, and especially preferably contains a naphthalene skeleton.

[0021] For example, in the biphenyl skeleton (-C6H4-C6H4-), the central carbon-carbon single bond in the structure may "rotate" due to thermal motion at high temperatures, potentially reducing its liquid crystalline properties. Similarly, in the phenylbenzoate skeleton (-C6H4-COO-C6H4-), the ester bond may rotate at high temperatures. However, in the case of condensed polycyclic aromatic hydrocarbon skeletons such as the naphthalene skeleton, such a decrease in liquid crystalline properties due to rotation does not occur in principle. In other words, epoxy resins containing condensed polycyclic aromatic hydrocarbon skeletons can more easily improve heat dissipation in high-temperature environments.

[0022] Furthermore, by specifically adopting a naphthalene skeleton as the polycyclic aromatic hydrocarbon skeleton, it is possible to obtain the aforementioned advantages while suppressing the epoxy resin from becoming too rigid. This is because the naphthalene skeleton is relatively small as a mesogenic skeleton. The fact that the epoxy resin does not become too rigid is preferable in that it allows for easier relaxation of stress during curing of the thermosetting resin composition of this embodiment, thereby suppressing cracks and other issues.

[0023] The epoxy resin preferably contains two or more functional epoxy resins. That is, it is preferable that each molecule of epoxy resin contains two or more epoxy groups. The number of functional groups in the epoxy resin is preferably 2 to 6, more preferably 2 to 4. From the viewpoint of the effects of the present invention, the epoxy resin in this embodiment preferably contains one or more resins selected from those represented by the following formula.

[0024] [ka]

[0025] The epoxy equivalent of the epoxy resin is, for example, 100 to 200 g / eq, preferably 105 to 190 g / eq, and more preferably 110 to 180 g / eq. By using an epoxy resin with an appropriate epoxy equivalent, it is possible to control the curing properties and optimize the physical properties of the cured product.

[0026] In one embodiment, the epoxy resin preferably further comprises another epoxy resin that is liquid or semi-solid at room temperature (23°C). Specifically, it is preferable that part or all of the epoxy resin is liquid or semi-solid at 23°C. Using liquid or semi-solid epoxy resins is preferable in terms of ease of forming cured products of the desired shape. The thermosetting resin composition of this embodiment may contain only one type of epoxy resin, or it may contain two or more types.

[0027] In this embodiment, the epoxy resin is, for example, 5% to 40% by mass, preferably 7% to 35% by mass, and more preferably 10% to 30% by mass, relative to the resin component (100% by mass) of the thermosetting resin composition that does not contain thermal conductive particles (D). This makes it possible to obtain a resin sheet that satisfies predetermined conditions for thermal conductivity and moisture absorption rate, and has superior insulation durability.

[0028] (Cyanate resin) As the cyanate resin, any known resin can be used within the range that achieves the effects of the present invention. The cyanate resin may include, for example, one or more selected from novolac-type cyanate resins; bisphenol-type cyanate resins such as bisphenol A-type cyanate resins, bisphenol E-type cyanate resins, and tetramethylbisphenol F-type cyanate resins; naphthol aralkyl-type cyanate resins obtained by the reaction of naphthol aralkyl-type phenol resins with cyanide halides; dicyclopentadiene-type cyanate resins; and biphenylene skeleton-containing phenol aralkyl-type cyanate resins. Among these, from the viewpoint of the effects of the present invention, it is more preferable to include at least one of novolac-type cyanate resins and naphthol aralkyl-type cyanate resins, and particularly preferable to include novolac-type cyanate resins. As a novolac-type cyanate resin, for example, one represented by the following general formula (I) can be used.

[0029] [ka]

[0030] The average repeating unit n of the novolac-type cyanate resin represented by general formula (I) is any integer. The average repeating unit n is not particularly limited, but is preferably 1 or greater, and more preferably 2 or greater. When the average repeating unit n is greater than or equal to the lower limit, the heat resistance of the novolac-type cyanate resin is improved, and the desorption and volatilization of low-molecules during heating can be further suppressed. Furthermore, the average repeating unit n is not particularly limited, but is preferably 10 or less, and more preferably 7 or less. When n is less than or equal to the upper limit, the increase in melt viscosity can be suppressed, and the moldability of the resin sheet can be improved.

[0031] Furthermore, naphthol aralkyl type cyanate resins represented by the following general formula (II) are also suitably used as cyanate resins. Naphthol aralkyl type cyanate resins represented by the following general formula (II) are obtained, for example, by condensing a naphthol aralkyl type phenol resin obtained by the reaction of naphthols such as α-naphthol or β-naphthol with p-xylylene glycol, α,α'-dimethoxy-p-xylene, 1,4-di(2-hydroxy-2-propyl)benzene, etc., with a cyanide halide. The repeating unit n in general formula (II) is preferably an integer of 10 or less. When the repeating unit n is 10 or less, a more uniform resin sheet can be obtained. In addition, intramolecular polymerization is less likely to occur during synthesis, liquid-liquid separation during washing with water is improved, and a decrease in yield tends to be prevented.

[0032] [ka]

[0033] In the above general formula (II), R independently represents either a hydrogen atom or a methyl group, and n represents an integer between 1 and 10.

[0034] The cyanate resin content is, for example, 10% to 70% by mass, preferably 20% to 60% by mass, relative to the resin component (100% by mass) of the thermosetting resin composition that does not contain thermally conductive particles (C). This makes it possible to obtain a resin sheet that satisfies predetermined conditions for thermal conductivity and moisture absorption rate, and has superior insulation durability.

[0035] (Maleimide resin) The maleimide resin is preferably one having, for example, at least two maleimide groups in its molecule.

[0036] Examples of maleimide resins having at least two maleimide groups in their molecule include 4,4'-diphenylmethanebismaleimide, m-phenylenebismaleimide, p-phenylenebismaleimide, 2,2-bis[4-(4-maleimoidphenoxy)phenyl]propane, bis-(3-ethyl-5-methyl-4-maleimoidphenyl)methane, 4-methyl-1,3-phenylenebismaleimide, N,N'-ethylenedimaleimide, N,N'-hexamethylenedimaleimide, bis(4-maleimoidphenyl)ether, bis(4-maleimoidphenyl)sulfone, 3,3-dimethyl-5,5-diethyl-4,4-diphenylmethanebismaleimide, bisphenol A diphenyl ether bismaleimide, and other resins having two maleimide groups in their molecule, as well as biphenylaralkyl type maleimides and polyphenylmethanemaleimides, and other resins having three or more maleimide groups in their molecule.

[0037] (Phenolic resin) Examples of phenolic resins include novolac-type phenolic resins such as phenol novolac resin, cresol novolac resin, and bisphenol A novolac resin, as well as resol-type phenolic resins. One of these may be used alone, or two or more may be used in combination. Among phenolic resins, phenol novolac resins are preferred.

[0038] (Benzoxazine resin) Benzooxazine resins include, specifically, o-cresolaniline type benzooxazine resin, m-cresolaniline type benzooxazine resin, p-cresolaniline type benzooxazine resin, phenol-aniline type benzooxazine resin, phenol-methylamine type benzooxazine resin, phenol-cyclohexylamine type benzooxazine resin, phenol-m-toluidine type benzooxazine resin, phenol-3,5-dimethylaniline type benzooxazine resin, bisphenol A-aniline type benzooxazine resin, bisphenol A-amine type benzooxazine resin, and bisphenol F-amine type benzooxazine resin. Examples include diline-type benzoxazine resins, bisphenol S-aniline-type benzoxazine resins, dihydroxydiphenylsulfone-aniline-type benzoxazine resins, dihydroxydiphenylether-aniline-type benzoxazine resins, benzophenone-type benzoxazine resins, biphenyl-type benzoxazine resins, bisphenol AF-aniline-type benzoxazine resins, bisphenol A-methylaniline-type benzoxazine resins, phenol-diaminodiphenylmethane-type benzoxazine resins, triphenylmethane-type benzoxazine resins, and phenolphthalein-type benzoxazine resins.

[0039] From the viewpoint of the effects of the present invention, the content of the thermosetting resin (A) is preferably, for example, 0.1% to 70% by mass, more preferably 0.5% to 65% by mass, and even more preferably 1% to 60% by mass, relative to the resin component (100% by mass) of the thermosetting resin composition that does not contain thermally conductive particles (D).

[0040] [Phenoxy resin (B)] The thermosetting resin composition constituting the resin sheet of this embodiment includes a phenoxy resin (B) having a mesogenic structure within its molecule.

[0041] An example of the mesogenic structure-containing phenoxy resin is a compound that contains structural units derived from phenol compounds and structural units derived from epoxy compounds within the molecule, and at least one of these structural units has a mesogenic structure. Another example of the mesogenic structure-containing phenoxy resin is one that contains structural units derived from mesogenic structure-containing phenol compounds within the molecule.

[0042] An example of the mesogenic structure-containing phenoxy resin can be produced by known methods, for example, by reacting a polyfunctional phenol compound having two or more hydroxyl groups in its molecule with a polyfunctional epoxy compound having two or more epoxy groups in its molecule.

[0043] In other words, the phenoxy resin may contain a reaction compound of a polyfunctional phenol compound and a polyfunctional epoxy compound. Either one or both of these polyfunctional phenol compounds and polyfunctional epoxy compounds have a mesogenic structure.

[0044] Other examples of the mesogenic structure-containing phenoxy resin can be produced by known methods, for example, by an addition polymerization reaction of a mesogenic structure-containing phenol compound having two or more phenol groups in its molecule into epichlorohydrin. In other words, the phenoxy resin may contain an addition polymer of a mesogenic structure-containing phenol compound.

[0045] The phenoxy resin can be produced without a solvent or in the presence of a reaction solvent. Suitable reaction solvents include aprotic organic solvents such as methyl ethyl ketone, dioxane, tetrahydrofuran, acetophenone, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide, sulfolane, and cyclohexanone. After the reaction is complete, the resin can be obtained dissolved in a suitable solvent by solvent replacement or other methods. Furthermore, the phenoxy resin obtained by the solvent reaction can be converted into a solvent-free solid resin by desolvent treatment using an evaporator or the like.

[0046] As reaction catalysts that can be used in the production of the phenoxy resin, alkali metal hydroxides, tertiary amine compounds, quaternary ammonium compounds, tertiary phosphine compounds, and quaternary phosphonium compounds and imidazole compounds are conventionally known polymerization catalysts that are preferably used.

[0047] The weight-average molecular weight (Mw) of the phenoxy resin is typically 500 to 200,000. Preferably, it is 1,000 to 100,000, and more preferably 2,000 to 50,000. Mw is measured by gel permeation chromatography and the value shown is converted using a standard polystyrene calibration curve.

[0048] In this embodiment, the mesogenic structure has, for example, a structure represented by the following general formula (1) or general formula (2). -A1-x-A2- ··(1) -x-A1-x- ··(2)

[0049] In the above general formulas (1) and (2), A1 and A2 each independently represent an aromatic group, a condensed aromatic group, an alicyclic group, or an alicyclic heterocyclic group, and x each independently represents a direct bond or a divalent bond group selected from the group consisting of -O-, -C=C-, -C≡C-, -CO-, -CO-O-, -CO-NH-, -CH=N-, -CH=NN=CH-, -N=N-, and -N(O)=N-.

[0050] Here, A1 and A2 are preferably independently selected from a hydrocarbon group having 6 to 12 carbon atoms and a benzene ring, a hydrocarbon group having 10 to 20 carbon atoms and a naphthalene ring, a hydrocarbon group having 12 to 24 carbon atoms and a biphenyl structure, a hydrocarbon group having 3 or more benzene rings and a hydrocarbon group having 12 to 36 carbon atoms, a hydrocarbon group having 12 to 36 carbon atoms and a condensed aromatic group, and an alicyclic heterocyclic group having 4 to 36 carbon atoms. A1 and A2 may be unsubstituted or derivatives having substituents.

[0051] Specific examples of A1 and A2 in the mesogenic structure include, for example, phenylene, biphenylene, naphthylene, anthracenylene, cyclohexyl, pyridyl, pyrimidyl, and thiophenylene. These may be unsubstituted, or derivatives having substituents such as aliphatic hydrocarbon groups, halogen groups, cyano groups, and nitro groups.

[0052] The x corresponding to the bonding group (linking group) in the mesogen structure is preferably, for example, a direct bond or a divalent substituent selected from the group -C=C-, -C≡C-, -CO-O-, -CO-NH-, -CH=N-, -CH=NN=CH-, -N=N-, or -N(O)=N-.

[0053] Here, direct bonding means a single bond, or the linkage of A1 and A2 in the mesogenic structure to form a ring structure. For example, the structure represented by the general formula (1) may include a naphthalene structure.

[0054] As the aforementioned polyfunctional phenol compound, for example, a mesogenic structure-containing compound represented by the following general formula (A) can be used. These may be used individually or in combination of two or more.

[0055] [ka]

[0056] In the above general formula (A), R 1 and R 3 Each of these independently represents a hydroxyl group, and R 2 and R 4 Each of the following independently represents a hydrogen atom, a chain or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, and a halogen atom, where a and c are integers from 1 to 3, and b and d are integers from 0 to 2. However, a+b and c+d are each one of 1 to 3. a+c may be 3 or greater.

[0057] As the polyfunctional epoxy compound, for example, a compound containing a mesogenic structure represented by the following general formula (B) can be used. These may be used alone or in combination of two or more kinds.

[0058]

Chemical formula

[0059] In the general formula (B), R 5 and R 7 each independently represent a glycidyl ether group, and R 6 and R 8 each independently represent one selected from a hydrogen atom, a linear or cyclic alkyl group having 1 to 6 carbon atoms, a phenyl group, and a halogen atom, e and g are each an integer of 1 to 3, and f and h are each an integer of 0 to 2. However, e + f and g + h are each either 1 to 3.

[0060] Also, R in the general formula (A) and the general formula (B) each represents the above -A1-x-A2-, -x-A1-x-, or -x-. In addition, the two benzene rings in the general formula (A) may be connected to each other to form a condensed ring.

[0061] Specific examples of the R 2 , R 4 , R 6 and R 8 include, for example, a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, a chlorine atom, a bromine atom, etc., respectively. Among these, particularly, a hydrogen atom and a methyl group are preferable.

[0062] As the polyfunctional epoxy compound containing the mesogenic structure, for example, an addition polymer of the compound represented by the above general formula (B) may be used. These may be used alone or in combination of two or more kinds.

[0063] Among the aforementioned polyfunctional phenol compounds and polyfunctional epoxy compounds, polyfunctional phenol compounds having three or more hydroxyl groups in the molecule and polyfunctional epoxy compounds having two or more epoxy groups in the molecule may be used.

[0064] In other words, the phenoxy resin may contain a branched reaction compound of a polyfunctional phenol compound having three or more hydroxyl groups in its molecule and a polyfunctional epoxy compound having two or more epoxy groups in its molecule. Examples of polyfunctional phenol compounds having three or more hydroxyl groups in their molecule include polyphenols or polyphenol derivatives.

[0065] The polyphenol is a compound containing three or more phenolic hydroxyl groups within its molecule. Furthermore, it is preferable that the polyphenol has the aforementioned mesogenic structure within its molecule. For example, the mesogenic structure can be a biphenyl skeleton, a phenylbenzoate skeleton, an azobenzene skeleton, a stilbene skeleton, or the like.

[0066] Furthermore, polyphenol derivatives include compounds in which a polyphenol compound having three or more phenolic hydroxyl groups and a mesogenic structure is modified by changing the substituents at the substituted positions of the compound.

[0067] In this embodiment, the branched reaction compound can be obtained using one or more of the polyfunctional phenol compounds, each containing at least three hydroxyl groups in its molecule, and one or more of the polyfunctional epoxy resins.

[0068] For example, a combination of a trifunctional phenol compound and a difunctional epoxy compound, or a combination of a trifunctional phenol compound, a difunctional phenol compound, and a difunctional epoxy compound may be used. As the aforementioned trifunctional phenol compound, for example, resveratrol represented by the following chemical formula can be used.

[0069] [ka]

[0070] For example, the R 1 and R 3 A compound can be used in which the hydroxyl group is bonded to the para position of each benzene ring.

[0071] Furthermore, as the bifunctional epoxy compound, the R 5 and R 7 A glycidyl ether group can be used in which the glycidyl ether group is bonded to the para position of each benzene ring.

[0072] Furthermore, if the difunctional phenol compound includes a naphthalene ring as a condensed ring, the R 1 and R 3 A compound can be used in which the hydroxyl group is bonded to any of the following positions on the naphthalene ring: position 1 and position 4, position 1 and position 5, position 1 and position 6, position 2 and position 3, position 2 and position 6, or position 2 and position 7. Furthermore, if the difunctional epoxy compound includes a naphthalene ring as a fused ring, the R 5 and R 7 A glycidyl ether group can be used in which it is bonded to any of the following positions on the naphthalene ring: position 1 and position 4, position 1 and position 5, position 1 and position 6, position 2 and position 3, position 2 and position 6, or position 2 and position 7.

[0073] The aforementioned combinations of trifunctional phenol compounds and difunctional epoxy compounds, or combinations of trifunctional phenol compounds, difunctional phenol compounds, and difunctional epoxy compounds, can yield the aforementioned branched reaction compounds (branched phenoxy resins).

[0074] On the other hand, among the polyfunctional phenol compounds and polyfunctional epoxy compounds, difunctional phenol compounds and difunctional epoxy compounds may also be used. These may be used individually or in combination of two or more.

[0075] In other words, the phenoxy resin may contain a linear reaction compound of a difunctional phenol compound having two hydroxyl groups in its molecule and a difunctional epoxy compound having two epoxy groups in its molecule.

[0076] As the aforementioned difunctional phenol compound, R 1 and R 3 A compound in which the hydroxyl group is bonded to the para position of each benzene ring can be used. In addition, as the bifunctional epoxy compound, the R 5 and R 7 A glycidyl ether group can be used in which the glycidyl ether group is bonded to the para position of each benzene ring.

[0077] Furthermore, if the difunctional phenol compound includes a naphthalene ring as a condensed ring, the R 1 and R 3 A compound can be used in which the hydroxyl group is bonded to any of the following positions on the naphthalene ring: position 1 and position 4, position 1 and position 5, position 1 and position 6, position 2 and position 3, position 2 and position 6, or position 2 and position 7. Furthermore, if the difunctional epoxy compound includes a naphthalene ring as a fused ring, the R 5 and R 7 A glycidyl ether group can be used in which it is bonded to any of the following positions on the naphthalene ring: position 1 and position 4, position 1 and position 5, position 1 and position 6, position 2 and position 3, position 2 and position 6, or position 2 and position 7. By using such a difunctional phenol compound and a difunctional epoxy compound in combination, the aforementioned linear reaction compound (linear phenoxy resin) can be obtained.

[0078] The branched phenoxy resin and linear phenoxy resin may have epoxy or hydroxyl groups at the molecular ends and epoxy or hydroxyl groups within the molecule. Having epoxy groups at the ends or within the molecule allows for crosslinking reactions, thereby improving heat resistance. Furthermore, by having rigid, electron-conjugated linear structural units, heat dissipation characteristics can be improved.

[0079] The phenoxy resin (B) is, for example, 5% to 60% by mass, preferably 10% to 50% by mass, and more preferably 15% to 40% by mass, relative to the resin component (100% by mass) of the thermosetting resin composition that does not contain thermal conductive particles (D). This makes it possible to obtain a resin sheet that satisfies predetermined conditions for thermal conductivity and moisture absorption and has superior insulation durability.

[0080] [Thermal conductive particles (C)] The thermosetting resin composition constituting the resin sheet of this embodiment contains thermally conductive particles (C). The thermally conductive particles (C) may include, for example, highly thermally conductive inorganic particles having a thermal conductivity of 20 W / m·K or higher. Examples of highly thermally conductive inorganic particles include at least one selected from silica, alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide, and magnesium oxide. These may be used individually or in combination of two or more.

[0081] The boron nitride may include monodisperse particles, aggregated particles, or mixtures thereof of flaky boron nitride. The flaky boron nitride may be granulated. By using aggregated particles of flaky boron nitride, the thermal conductivity can be further enhanced. The aggregated particles may be sintered particles or unsintered particles.

[0082] The content of thermally conductive particles (C) is 100% to 400% by mass, preferably 150% to 350% by mass, and more preferably 200% to 300% by mass, relative to the resin component (100% by mass) of the thermosetting resin composition. Setting it above the lower limit can improve thermal conductivity. Setting it below the upper limit can suppress a decrease in processability.

[0083] [Organosiloxane compound (D)] The thermosetting resin composition constituting the resin sheet of this embodiment may optionally contain an organosiloxane compound (D).

[0084] The organosiloxane compound (D) is an aliphatic hydrocarbon compound having a Si-OQ bond (where Q is an alkyl group) at one end of its molecular chain. More preferably, the organosiloxane compound (D) has at least one functional group selected from epoxy, glycidyl ether, amino, isocyanate, phenyl, carboxyl, hydroxyl, alkyl, vinyl, and mercapto groups at the other end. This makes it possible to obtain a resin sheet with lower moisture absorption and better insulation durability. The organosiloxane compound (D) may include a compound represented by the following general formula (1).

[0085] [ka]

[0086] In general formula (1), each R independently represents an alkoxy group having 1 to 3 carbon atoms or an alkyl group having 1 to 3 carbon atoms, and at least two of the Rs are alkoxy groups having 1 to 3 carbon atoms. Preferably, all of the Rs are alkoxy groups having 1 to 3 carbon atoms, and more preferably, all of the Rs are alkoxy groups having 1 to 2 carbon atoms. L represents a linear or branched alkylene group having 2 to 12 carbon atoms.

[0087] X represents an epoxy group, a glycidyl ether group, an amino group, an isocyanate group, a phenyl group, a carboxyl group, a hydroxyl group, an alkyl group, a vinyl group, or a mercapto group. From the viewpoint of the effects of the present invention, X is preferably an epoxy group, a glycidyl ether group, an amino group, an isocyanate group, an alkyl group having 1 to 3 carbon atoms, a phenyl group, or a mercapto group, and from the viewpoint of the pot life of the thermosetting resin composition, an epoxy group, a phenyl group, a glycidyl ether group, or a methyl group is more preferably.

[0088] Examples of compounds represented by general formula (1) include 3-aminopropyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-mercaptopropyltriethoxysilane, 3-isocyanatetopropyltriethoxysilane, glycidoxyoctyltriethoxysilane, decyltriethoxysilane, and phenyltriethoxysilane.

[0089] The thermosetting resin composition of this embodiment may contain an organosiloxane compound (D) in an amount of 0.01 to 0.5 parts by mass, preferably 0.02 to 0.3 parts by mass, and more preferably 0.03 to 0.2 parts by mass, per 100 parts by mass of thermally conductive particles (C). This makes it possible to obtain a resin sheet that satisfies predetermined conditions for thermal conductivity and moisture absorption, and has superior insulation durability.

[0090] (Curing accelerator (E)) The thermosetting resin composition constituting the resin sheet of this embodiment may optionally contain a curing accelerator (E). The type and amount of curing accelerator (E) are not particularly limited, but an appropriate one can be selected from the viewpoint of reaction rate, reaction temperature, and storage properties.

[0091] Examples of curing accelerators (E) include imidazoles, organophosphorus compounds, tertiary amines, phenolic compounds, and organic acids. These may be used individually or in combination of two or more. Among these, nitrogen atom-containing compounds such as imidazoles are preferred from the viewpoint of improving heat resistance.

[0092] Examples of the imidazoles include 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenyl-4-methylimidazole, 2,4-diethylimidazole, 2-phenyl-4-methyl-5-hydroxyimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 1-cyanoethyl-2-phenylimidazole, and 1-cyanoethyl-2-phenylimidazolium trimellitate.

[0093] Examples of the aforementioned tertiary amines include triethylamine, tributylamine, 1,4-diazabicyclo[2.2.2]octane, and 1,8-diazabicyclo(5,4,0)undecene-7.

[0094] Examples of the phenolic compounds include phenolic resins, bisphenol A, nonylphenol, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, and allylphenol. Examples of the aforementioned organic acids include acetic acid, benzoic acid, salicylic acid, and p-toluenesulfonic acid.

[0095] The content of the curing accelerator (E) may be 0.01% to 10% by mass, 0.02% to 5% by mass, or 0.05% to 1.5% by mass, based on 100% by mass of the total thermosetting resin.

[0096] The thermosetting resin composition of this embodiment may contain other components besides those described above. Examples of these other components include antioxidants and leveling agents. For example, the following method can be used to produce the thermosetting resin composition of this embodiment.

[0097] A resin varnish (a varnish-like thermosetting resin composition) can be prepared by dissolving, mixing, and stirring each of the above components in a solvent. Various mixing machines can be used for this mixing, including ultrasonic dispersion, high-pressure impact dispersion, high-speed rotation dispersion, bead mill, high-speed shear dispersion, and rotational dispersion.

[0098] The above solvents are not particularly limited, but examples include acetone, methyl isobutyl ketone, toluene, ethyl acetate, cyclohexane, heptane, cyclohexanone, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, ethylene glycol, cellosorb-based solvents, carbitol-based solvents, anisole, and N-methylpyrrolidone.

[0099] [Resin sheet] The resin sheet of this embodiment is obtained by curing the thermosetting resin composition, and its thermal conductivity and moisture absorption rate satisfy the following formulas. Formula: Thermal conductivity ≥ 0.77 × Moisture absorption rate + 17 18.0 ≤ Thermal conductivity (W / m·K) ≤ 25.0 0.28≦Moisture absorption rate (%)≦0.40

[0100] The resin sheet of this embodiment is made of a thermosetting resin composition with the composition described above, and its thermal conductivity and moisture absorption rate are in a relationship that conventional resin sheets cannot satisfy, and both are within a predetermined range, and have an excellent balance between them, resulting in excellent insulation durability. In other words, by optimizing the trade-off relationship between thermal conductivity and moisture absorption rate, the insulation durability of the resin sheet can be improved.

[0101] The specific form of the resin sheet comprises a carrier substrate and a resin layer provided on the carrier substrate, the resin layer being made of the thermosetting resin composition of this embodiment. The above-mentioned resin sheet can be obtained, for example, by applying a varnish-like thermosetting resin composition onto a carrier substrate to a coated film (resin layer), and then performing a solvent removal treatment on that film. The solvent content in the above-mentioned resin sheet can be 10% by mass or less relative to the entire thermosetting resin composition. For example, the solvent removal treatment can be performed under conditions of 80°C to 200°C for 1 to 30 minutes.

[0102] Furthermore, in this embodiment, the carrier substrate can be, for example, a polymer film or a metal foil. The polymer film is not particularly limited, but examples include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate, release paper such as silicone sheets, thermoplastic resin sheets with heat resistance such as fluororesins and polyimide resins. The metal foil is not particularly limited, but examples include copper and / or copper alloys, aluminum and / or aluminum alloys, iron and / or iron alloys, silver and / or silver alloys, gold and gold alloys, zinc and zinc alloys, nickel and nickel alloys, tin and tin alloys.

[0103] The resin substrate of this embodiment comprises an insulating layer made of a cured product of the thermosetting resin composition described above. This resin substrate can be used as a material for printed circuit boards for mounting electronic components such as LEDs and power modules.

[0104] (Metal-based substrate) The metal base substrate 100 of this embodiment will be described with reference to Figure 1. Figure 1 is a schematic cross-sectional view showing an example of the configuration of the metal base substrate 100.

[0105] As shown in Figure 1, the metal base substrate 100 may comprise a metal substrate 101, an insulating layer 102 provided on the metal substrate 101, and a metal layer 103 provided on the insulating layer 102. The insulating layer 102 can be composed of one selected from the group consisting of a resin layer made of the thermosetting resin composition, a cured product of the thermosetting resin composition, and a laminate. Each of these resin layers and laminates may be composed of a thermosetting resin composition in a B-stage state before circuit processing of the metal layer 103, and may be a cured product obtained by curing it after circuit processing.

[0106] The metal layer 103 is provided on the insulating layer 102 and subjected to circuit processing. Examples of metals constituting the metal layer 103 include one or more selected from copper, copper alloys, aluminum, aluminum alloys, nickel, iron, tin, etc. Among these, the metal layer 103 is preferably a copper layer or an aluminum layer, and particularly preferably a copper layer. Using copper or aluminum improves the circuit processability of the metal layer 103. The metal layer 103 may be made of metal foil available in sheet form or metal foil available in roll form. The lower limit of the thickness of the metal layer 103 is, for example, 0.01 mm or more, and preferably 0.035 mm or more, so that it can be applied to applications requiring high current.

[0107] Furthermore, the upper limit of the thickness of the metal layer 103 is, for example, 10.0 mm or less, preferably 5 mm or less. Keeping the thickness below this value improves circuit processability and allows for a thinner overall substrate.

[0108] The metal substrate 101 has the role of dissipating heat accumulated in the metal base substrate 100. The metal substrate 101 is not particularly limited as long as it is a heat-dissipating metal substrate, but for example, it may be a copper substrate, a copper alloy substrate, an aluminum substrate, or an aluminum alloy substrate, with a copper substrate or an aluminum substrate being preferred, and a copper substrate being more preferred. By using a copper substrate or an aluminum substrate, the heat dissipation performance of the metal substrate 101 can be improved. The thickness of the metal substrate 101 can be set as appropriate, as long as the objective of the present invention is not impaired.

[0109] The upper limit of the thickness of the metal substrate 101 is, for example, 20.0 mm or less, preferably 5.0 mm or less. This improves the processability of the metal substrate 100 in processes such as shaping and cutting.

[0110] Furthermore, the lower limit of the thickness of the metal substrate 101 is, for example, 0.01 mm or more, and preferably 0.6 mm or more. By using a metal substrate 101 with a thickness of this value or greater, the heat dissipation performance of the metal base substrate 100 as a whole can be improved.

[0111] In this embodiment, the metal base substrate 100 can be used for various substrate applications, but because it has excellent thermal conductivity and heat resistance, it can be used as a printed circuit board for LEDs and power modules.

[0112] The metal base substrate 100 may have a metal layer 103 that has been processed with a circuit by etching or the like. In this metal base substrate 100, a solder resist (not shown) may be formed on the outermost layer, and connection electrode portions may be exposed so that electronic components can be mounted by exposure and development.

[0113] Although embodiments of the present invention have been described above, these are merely examples, and various other configurations can be adopted as long as they do not impair the effects of the present invention. [Examples]

[0114] The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto.

[0115] <Manufacturing of thermosetting resin composition (varnish)> A varnish-like thermosetting resin composition was obtained by stirring each component and solvent according to the mixing ratios shown in Table 1. In Table 1, the content of thermally conductive particles is expressed as a volume % relative to the resin component of a thermosetting resin composition that does not contain thermally conductive fillers.

[0116] The details of each component in Table 1 are as follows. Note that the unit of measurement for each component in Table 1 is parts by mass.

[0117] (Epoxy resin) • Epoxy resin 1: Manufactured by DIC Corporation, epoxy resin represented by the following structural formula, product number "EPICLON HP-4700"

[0118] [ka]

[0119] • Epoxy resin 2: Manufactured by Mitsubishi Chemical Corporation, tetramethylbiphenyl type epoxy resin represented by the following structural formula, product number "YX4000"

[0120] [ka]

[0121] • Epoxy resin 3: Manufactured by DIC Corporation, dicyclopentadiene type epoxy resin represented by the following structural formula, product number "HP-7200"

[0122] [ka]

[0123] • Epoxy resin 4: Manufactured by DIC Corporation, epoxy resin represented by the following structural formula, product number "EPICLON 830"

[0124] [ka]

[0125] (Cyanate resin) • Cyanate resin 1: Primaset "PT-30" manufactured by Lonza.

[0126] (Phenoxy resin containing a mesogenic structure within the molecule) • Phenoxy resin 1: A phenoxy resin having a mesogenic structure within the molecule, obtained by the following synthesis procedure. 23.5 parts by mass of epoxy resin (with mesogenic structure, 4,4'-dihydroxybiphenyl diglycidyl ether), 72.5 parts by mass of bisphenol compound (with mesogenic structure, a difunctional phenol with the following structure, manufactured by Ueno Pharmaceutical Co., Ltd., HQPOB), 0.04 parts by mass of triphenylphosphine (TPP), and 3.9 parts by mass of solvent (methyl ethyl ketone) were added to a reactor. The reaction was carried out at a temperature of 120-150°C while removing the solvent. The reaction was stopped after confirming that the desired molecular weight was reached by GPC. A phenoxy resin with a molecular weight of 4500 was obtained.

[0127] [ka]

[0128] (Curing accelerator) • Curing accelerator 1: Novolac-type phenol compound (PR-51470, manufactured by Sumitomo Bakelite Co., Ltd.)

[0129] (Organosiloxane compounds) Organosiloxane 1: 3-Glycidoxypropyltriethoxysilane Organosiloxane 2: 3-Isocyanatetopropyltriethoxysilane • Organosiloxane 3: Glycidoxyoctyltriethoxysilane • Organosiloxane 4: Decyltriethoxysilane

[0130] (Thermal conductive particles) • Thermally conductive particles 1: Granular boron nitride prepared using the following procedure was used. [procedure] Commercially available boron carbide powder was placed in a carbon crucible and nitrided under a nitrogen atmosphere at 2000°C for 10 hours. Next, commercially available diboron trioxide powder was added to the nitrided boron nitride powder and mixed in a blender for 1 hour (boron nitride:diboron trioxide = 7:3 (mass ratio)). The resulting mixture was placed in a carbon crucible and calcined under a nitrogen atmosphere at 2000°C for 10 hours. Granular boron nitride was obtained using the above method.

[0131] <Measurement of physical properties of resin molded articles of thermosetting resin compositions> (Thermal conductivity) • Fabrication of resin molded products

[0132] Using the thermosetting resin composition containing the obtained thermally conductive filler, it was sandwiched between 0.018 μm copper foil and compression molded at 10 MPa, 180°C, and 90 min to obtain a resin molded body (Sample 1 for thermal conductivity measurement). The copper foil is removed by etching. A sample with a diameter of 10 mm was cut out for thermal diffusivity measurement and used for the measurement.

[0133] Specific gravity measurements were performed in accordance with JIS K 6911 (General Test Methods for Thermosetting Plastics). Test specimens were taken from the above-mentioned resin molded products. The copper foil is removed by etching. A piece cut to 2cm x 2cm x 2mm thick was used. The unit of specific gravity (SP) is g / cm 3 Let's assume that.

[0134] • Specific heat of resin molded body Regarding the resin molded product obtained above, The copper foil is removed by etching. The specific heat (Cp) was measured using the DSC method.

[0135] • Measurement of the thermal conductivity of a resin molded product From the obtained resin molded body, The copper foil is removed by etching. For thickness measurement, a specimen cut to a diameter of 10 mm was used. Next, the thermal diffusivity (α) in the thickness direction of the plate-shaped specimen was measured using the transient method with a ULVAC Xe flash analyzer TD-1RTV. The measurement was performed under atmospheric conditions at 25°C. For the resin molded product, the thermal conductivity was calculated from the obtained measured values ​​of thermal diffusivity (α), specific heat (Cp), and specific gravity (SP) based on the following formula. Thermal conductivity [W / m K]=α[m 2 / s] × Cp[J / kg·K] × Sp[g / cm 3 ] In Table 1, the thermal conductivity of the resin molded article is referred to as "thermal conductivity".

[0136] (Volume resistivity) Measurements were taken in accordance with JIS C 2139. Specifically, a hardened sample processed to an appropriate size was placed in an oven at 30°C, and its volume resistivity was measured when it reached the target temperature (i.e., 30°C).

[0137] (moisture absorption rate) The copper foil was removed from the obtained resin molded body by etching, and the moisture absorption rate (%) was calculated from the weight change before and after treatment when left at 30°C / 90%RH conditions for 48 hours.

[0138] (insulation durability) Specifically, a resin molded body was fabricated with a 25mmφ ring electrode on one side and copper foil on the other. The ring electrode side was used as the anode and the copper foil side as the cathode. The body was left standing under 85°C / 85%RH conditions, and the time taken for conductivity to be achieved when a DC voltage of 2kV was applied was measured. The following criteria were used for evaluation: (Evaluation Criteria) ○: No continuity was established even after more than 100 hours. ×: Conduction occurred in less than 100 hours.

[0139] [Table 1] [Explanation of Symbols]

[0140] 100 Metal base substrate 101 Metal substrate 102 Insulating layer 103 Metal layer

Claims

1. Thermosetting resin (A) and, A phenoxy resin (B) having a mesogenic structure within the molecule, Thermally conductive particles (C) and, A resin sheet obtained by curing a thermosetting resin composition containing, Thermal conductivity and moisture absorption rate satisfy the following equations: The aforementioned moisture absorption rate was calculated from the weight change before and after treatment when left for 48 hours under 30°C / 90%RH conditions. Thermosetting resin (A) comprises epoxy resin and cyanate resin. The epoxy resin is a resin sheet containing a condensed polycyclic aromatic hydrocarbon skeleton. Formula: Thermal conductivity ≥ 0.77 × moisture absorption rate + 17 18.0 ≤ Thermal conductivity (W / m·K) ≤ 25.0 0.28≦Moisture absorption rate (%)≦0.40

2. The resin sheet according to claim 1, wherein the epoxy resin comprises an epoxy resin having a mesogenic structure.

3. The resin sheet according to claim 1 or 2, wherein the phenoxy resin (B) comprises structural units derived from a phenol compound and structural units derived from an epoxy compound.

4. The resin sheet according to claim 1, wherein the thermally conductive particles (C) include at least one selected from silica, alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide, and magnesium oxide.

5. The thermally conductive particles (C) contain the boron nitride, The resin sheet according to claim 4, wherein the boron nitride comprises monodisperse particles, granular particles, aggregated particles, or mixtures thereof of flaky boron nitride.

6. Furthermore, the resin sheet according to any one of claims 1 to 5, further comprising an organosiloxane compound (D).

7. The resin sheet according to any one of claims 1 to 6, further comprising a curing accelerator (E).

8. First metal substrate and An insulating layer made of the resin sheet according to any one of claims 1 to 7, A metal-based substrate comprising a second metal layer and the following in this order.

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