JP7707699B2 - Thermosetting resin composition, resin sheet, metal base substrate, and electronic device - Google Patents

Description

The present invention relates to a thermosetting resin composition, a resin sheet made of the thermosetting resin composition, an electronic device having a cured product of the resin sheet as a thermally conductive sheet, a metal-based substrate having a cured product of the resin sheet, and an electronic device having the metal-based substrate.

As semiconductors become more highly integrated and the processing power of electronic devices rapidly improves, electronic components with high processing power generate a lot of heat. For this reason, heat countermeasures that effectively dissipate heat from electronic components to the outside have become a very important issue. As a countermeasure for such heat dissipation, thermally conductive members made of heat dissipating materials such as metals, ceramics, and polymer compositions are used for heat dissipation components such as printed wiring boards, semiconductor packages, housings, heat pipes, heat sinks, and heat diffusion plates.

Among these heat dissipation components, thermally conductive epoxy resin molded products made from epoxy resin compositions have excellent electrical insulation, mechanical properties, heat resistance, chemical resistance, adhesive properties, etc., and are therefore widely used primarily in the electrical and electronics fields as castings, laminates, sealing materials, thermally conductive sheets, adhesives, etc.

For example, Patent Document 1 proposes a thermally conductive epoxy resin composition and a molded product thereof, in which bisphenol A epoxy resin is used as the epoxy resin and scaly or spherical boron nitride particles are used as the thermally conductive particles. It has also been proposed to improve the thermal conductivity and heat resistance of the epoxy resin itself (for example, Patent Document 2). In Patent Document 2, an insulating composition with improved thermal conductivity is obtained by polymerizing a liquid crystal epoxy resin having a mesogenic group.

JP 2015-193504 A Patent Application No. 2004-331811

However, as a result of the inventor's investigations, it was found that there is room for further improvement in terms of thermal conductivity of conventional resin compositions.

The present invention was made in consideration of the above problems, and the inventors discovered that a new phenoxy resin with a specific structure has high thermal conductivity, leading to the completion of the present invention.

According to the present invention,
(A) an epoxy resin;
(B) a thermosetting resin (excluding the epoxy resin (A));
(C) a phenoxy resin;
(D) a thermally conductive filler,
The phenoxy resin (C) is
A bifunctional epoxy compound (c1) having two epoxy groups;
A phenoxy resin obtained by reacting a polyfunctional phenol compound (c2) having at least two phenolic hydroxyl groups with
The bifunctional epoxy compound (c1) includes a compound represented by the formula (d-EP):

In the formula (d-EP), X represents a divalent group having a mesogenic skeleton,
The polyfunctional phenol compound (c2) is at least one selected from the compounds represented by formulas (p1) to (p8),

In the formulas (p1) to (p8), R ¹¹ and R ¹² independently represent a hydrogen atom, an alkoxy group having 1 to 4 carbon atoms, or a linear or branched alkyl group having 1 to 4 carbon atoms.

The present invention also provides a resin sheet made of the above-mentioned thermosetting resin composition.

Further, according to the present invention,
A heat generating member;
A heat dissipation member;
a thermally conductive sheet provided between the heat generating component and the heat dissipating component,
The thermally conductive sheet is made of a cured product of the resin sheet, and an electronic device is provided.

Further, according to the present invention,
A metal substrate;
A thermally conductive sheet;
A metal base substrate comprising, in this order,
The thermally conductive sheet is a metal base substrate made of the cured product of the resin sheet.

The present invention also provides an electronic device having the above-mentioned metal base substrate.

The present invention provides a thermosetting resin composition that can be used to produce a thermally conductive sheet with high thermal conductivity.

1 is a schematic cross-sectional view showing a structure of a metal base substrate according to an embodiment of the present invention. 1 is a schematic cross-sectional view showing a configuration of an electronic device using a metal base substrate according to an embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings. In all drawings, similar components are given similar reference symbols and descriptions will be omitted where appropriate. In addition, "~" indicates "above" to "below" unless otherwise specified.

[Thermosetting resin composition]
The thermosetting resin composition of the present embodiment contains the following components (A) to (D).
(A) an epoxy resin;
(B) a thermosetting resin (excluding the epoxy resin (A));
(C) a phenoxy resin;
(D) Thermally conductive filler.
Since the thermosetting resin composition of the present embodiment has the above composition, it has high thermal conductivity and can be suitably used, for example, as a thermally conductive sheet for electronic devices.

The components used in the thermosetting resin composition of this embodiment are described below.

(Epoxy resin (A))
The thermosetting resin composition of the present embodiment includes an epoxy resin (A). Examples of the epoxy resin (A) include glycidyl ethers such as bisphenol A type, F type, S type, and AD type, 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, and hydroquinone type glycidyl ether, and at least one of them can be used.
From the viewpoint of the effects of the present invention, the epoxy resin (A) preferably contains at least one selected from naphthalene-type glycidyl ethers, biphenol-type glycidyl ethers, dihydroxypentadiene-type glycidyl ethers, and hydroquinone-type glycidyl ethers.

The epoxy resin (A) may preferably contain an epoxy resin containing a mesogenic skeleton, which can further enhance the thermal conductivity (heat dissipation) of the cured resin.
It is believed that when epoxy resins containing a mesogenic skeleton are cured, a higher-order structure (liquid crystal phase or crystalline phase) is formed by the mesogenic skeleton. It is believed that the thermal conductivity (heat dissipation) is further increased by the transfer of heat through the higher-order structure. The presence of the higher-order structure in the cured product can be confirmed by observation with a polarizing microscope.

The mesogenic skeleton may be any skeleton that facilitates the expression of liquid crystallinity or crystallinity through intermolecular interactions. The mesogenic skeleton preferably includes a conjugated structure. Specific examples of the mesogenic skeleton include a biphenyl skeleton, a phenylbenzoate skeleton, an azobenzene skeleton, a stilbene skeleton, a naphthalene skeleton, an anthracene skeleton, a chalcone skeleton, and a phenanthrene skeleton.

Epoxy resin (A) particularly preferably contains a condensed polycyclic aromatic hydrocarbon skeleton, and particularly preferably contains a naphthalene skeleton.

Here, for example, in the case of a biphenyl skeleton (-C ₆ H ₄ -C ₆ H ₄ -), the central carbon-carbon single bond of the structure may "rotate" due to thermal motion at high temperatures, which may result in a decrease in liquid crystallinity. Similarly, in the case of a phenylbenzoate skeleton (-C ₆ H ₄ -COO-C ₆ H ₄ -), the ester bond may rotate at high temperatures. However, in the case of a condensed polycyclic aromatic hydrocarbon skeleton such as a naphthalene skeleton, in principle, there is no decrease in liquid crystallinity due to such rotation. In other words, by including a condensed polycyclic aromatic hydrocarbon skeleton in an epoxy resin, the heat dissipation properties of the resulting cured resin in a high-temperature environment can be further improved.

In addition, by employing a naphthalene skeleton as the polycyclic aromatic hydrocarbon skeleton, the above-mentioned advantages can be obtained while preventing the epoxy resin from becoming too rigid. This is because the naphthalene skeleton is relatively small as a mesogen skeleton. The fact that the epoxy resin does not become too rigid is preferable in terms of preventing cracks and the like caused by the stress being more easily relaxed during curing of the thermosetting resin composition of this embodiment.

The epoxy resin (A) preferably contains a bifunctional or higher functional epoxy resin. In other words, it is preferable that one molecule of the epoxy resin contains two or more epoxy groups. The number of functional groups of the epoxy resin is preferably 2 to 6, and more preferably 2 to 4.
From the viewpoint of the effects of the present invention, the epoxy resin (A) in the present embodiment preferably contains at least one epoxy resin selected from compounds represented by the following formula:

The epoxy equivalent of the epoxy resin (A) 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 property and optimize the physical properties of the cured product.

In one embodiment, the epoxy resin (A) preferably further contains another epoxy resin that is liquid or semi-solid at room temperature (23° C.). Specifically, it is preferable that a part or all of the epoxy resin is liquid or semi-solid at 23° C.
By using a liquid or semi-solid epoxy resin, it becomes easier to form a cured product in a desired shape.

In one embodiment, the epoxy resin (A) preferably contains a combination of an epoxy resin that is liquid at room temperature and an epoxy resin that is semi-solid or solid at room temperature. This improves the moldability of the resulting thermosetting resin composition.

The epoxy resin (A) is, for example, 5% by mass to 40% by mass, preferably 7% by mass to 35% by mass, and more preferably 10% by mass to 30% by mass, relative to the resin component (100% by mass) of the thermosetting resin composition not including the thermally conductive particles (D). This ensures sufficient curability, and allows a resin sheet with excellent thermal conductivity and insulation to be obtained.

(Thermosetting resin (B))
The thermosetting resin composition of the present embodiment contains a thermosetting resin (B). Here, the thermosetting resin (B) does not contain the above-mentioned epoxy resin (A).
The thermosetting resin (B) may be a thermosetting compound containing a mesogenic structure (mesogenic skeleton) in the molecule, or a thermosetting compound not containing a mesogenic structure in the molecule.

Thermosetting resin (B) may contain at least one of, for example, cyanate resin, maleimide resin, phenol resin, benzoxazine resin, polyimide resin, unsaturated polyester resin, melamine resin, silicone resin, acrylic resin, and phenol derivatives or derivatives thereof.

In the present embodiment, the thermosetting resin (B) preferably contains at least one selected from a cyanate resin, a bismaleimide resin, a phenol resin, and a benzoxazine resin, and more preferably contains a cyanate resin.
As these thermosetting resins, any monomer, oligomer or polymer having two or more reactive functional groups in one molecule can be used, and there are no particular limitations on the molecular weight or molecular structure.

<Cyanate resin>
As the cyanate resin, known ones can be used within the scope of the effects of the present invention. The cyanate resin can include one or more selected from, for example, novolac type cyanate resin; bisphenol type cyanate resin such as bisphenol A type cyanate resin, bisphenol E type cyanate resin, tetramethylbisphenol F type cyanate resin; naphthol aralkyl type cyanate resin obtained by reacting naphthol aralkyl type phenol resin with cyanogen halide; dicyclopentadiene type cyanate resin; and biphenylene skeleton-containing phenol aralkyl type cyanate resin. 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 resin and naphthol aralkyl type cyanate resin, and it is particularly preferable to include novolac type cyanate resin.

As the novolac-type cyanate resin, for example, one represented by the following general formula (I) can be used.

The average repeating unit n of the novolac cyanate resin represented by general formula (I) is any integer. The average repeating unit n is not particularly limited, but is preferably 1 or more, and more preferably 2 or more. When the average repeating unit n is equal to or more than the above lower limit, the heat resistance of the novolac cyanate resin is improved, and the elimination and volatilization of low molecular weight compounds during heating can be further suppressed. In addition, the average repeating unit n is not particularly limited, but is preferably 10 or less, and more preferably 7 or less. When n is equal to or less than the above upper limit, the melt viscosity can be suppressed from increasing, and the moldability of the resin sheet can be improved.

As the cyanate resin, naphthol aralkyl type cyanate resin represented by the following general formula (II) is also preferably used. The naphthol aralkyl type cyanate resin represented by the following general formula (II) is obtained by condensing a naphthol aralkyl type phenol resin obtained by reacting 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 cyanogen 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, and separation during washing with water is improved, which tends to prevent a decrease in yield.

In the above general formula (II), each R independently represents a hydrogen atom or a methyl group, and n represents an integer of 1 to 10.

The cyanate resin is, for example, 10% by mass to 70% by mass, preferably 15% by mass to 60% by mass, and more preferably 20% by mass to 50% by mass, relative to the resin component (100% by mass) of the thermosetting resin composition not including the thermally conductive particles (D). This ensures sufficient curability, and allows the production of a resin sheet with excellent thermal conductivity and insulation.

<Maleimide resin>
The maleimide resin is preferably, for example, a maleimide resin having at least two maleimide groups in the molecule.

Examples of maleimide resins having at least two maleimide groups in the molecule include 4,4'-diphenylmethane bismaleimide, m-phenylene bismaleimide, p-phenylene bismaleimide, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, bis-(3-ethyl-5-methyl-4-maleimidophenyl)methane, 4-methyl-1,3-phenylene bismaleimide, N,N'-ethylene dimaleimide, N,N'-hexamethylene dimaleimide, bis(4-maleimidophenyl)ether, bis(4-maleimidophenyl)sulfone, 3,3-dimethyl-5,5-diethyl-4,4-diphenylmethane bismaleimide, bisphenol A diphenyl ether bismaleimide, and other resins having two maleimide groups in the molecule, as well as biphenyl aralkyl maleimide and polyphenylmethane maleimide, and other resins having three or more maleimide groups in the molecule.

<Phenol resin>
Examples of the phenolic resin include novolac-type phenolic resins such as phenol novolac resin, cresol novolac resin, and bisphenol A novolac resin, and resol-type phenolic resin. One of these may be used alone, or two or more may be used in combination. Among the phenolic resins, it is preferable to use phenol novolac resin.

<Benzoxazine resin>
Specific examples of the benzoxazine resin include o-cresolaniline type benzoxazine resin, m-cresolaniline type benzoxazine resin, p-cresolaniline type benzoxazine resin, phenol-aniline type benzoxazine resin, phenol-methylamine type benzoxazine resin, phenol-cyclohexylamine type benzoxazine resin, phenol-m-toluidine type benzoxazine resin, phenol-3,5-dimethylaniline type benzoxazine resin, bisphenol A-aniline type benzoxazine resin, bisphenol A-amine type benzoxazine resin, bisphenol F-aniline ... Examples of the benzoxazine resin include aniline type benzoxazine resin, bisphenol S-aniline type benzoxazine resin, dihydroxydiphenylsulfone-aniline type benzoxazine resin, dihydroxydiphenylether-aniline type benzoxazine resin, benzophenone type benzoxazine resin, biphenyl type benzoxazine resin, bisphenol AF-aniline type benzoxazine resin, bisphenol A-methylaniline type benzoxazine resin, phenol-diaminodiphenylmethane type benzoxazine resin, triphenylmethane type benzoxazine resin, and phenolphthalein type benzoxazine resin.

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

(Phenoxy resin (C))
The thermosetting resin composition of the present embodiment contains a phenoxy resin (C). The phenoxy resin (C) is
A bifunctional epoxy compound (c1) having two epoxy groups, represented by the formula (d-EP),
and a polyfunctional phenol compound (c2) having at least two phenolic hydroxyl groups.
More specifically, the phenoxy resin (C) is a polymer obtained by reacting an epoxy group of the bifunctional epoxy compound (c1) with a phenolic hydroxyl group of the polyfunctional phenol compound (c2) to generate a crosslinked structure. That is, the phenoxy resin (C) used in this embodiment is a phenoxy resin containing a structural unit derived from the bifunctional epoxy compound (c1) and a structural unit derived from the polyfunctional phenol compound (c2).

The bifunctional epoxy compound (c1) constituting the phenoxy resin (C) used in this embodiment includes a compound represented by the formula (d-EP).

In formula (d-EP), X is a divalent group having a mesogenic skeleton.
The phenoxy resin (C) used in the thermosetting resin composition of the present embodiment contains a structural unit derived from the epoxy compound (c1) having a mesogenic skeleton, and thus the cured product thereof has high thermal conductivity and high heat resistance.

The mesogenic skeleton of the X group in formula (d-EP) includes a biphenyl skeleton, a naphthalene skeleton, a phenylbenzoate skeleton, an azobenzene skeleton, a stilbene skeleton, a cyclohexylbenzene skeleton, and derivatives thereof. When the X group has the above-mentioned mesogenic skeleton, the phenoxy resin (C) can have high thermal conductivity.

In one embodiment, at least one of the X groups in formula (d-EP) is a group represented by formula (2). By including a structure having a mesogenic skeleton represented by formula (2), the phenoxy resin (C) has high thermal conductivity and excellent heat resistance, and therefore the thermosetting resin of this embodiment containing this can have high thermal conductivity.

In one embodiment, the group represented by formula (2) is preferably a group in which R ₁ , R ₄ , R ₅ , and R ₈ are alkyl groups having 1 to 4 carbon atoms, and R ₂ , R ₃ , R ₆ , and R ₇ are hydrogen atoms. Among these, a group in which R ₁ , R ₄ , R ₅ , and R ₈ are alkyl groups having 1 carbon atom, and R ₂ , R ₃ , R ₆ , and R ₇ are hydrogen atoms in formula (2) (referred to as a "tetramethylbiphenyl group") is preferred in that the thermal conductivity and heat resistance of the resulting phenoxy resin (C) can be simultaneously achieved in an excellent balance.

In one embodiment, the group represented by formula (2) may be a group in which R ₁ , R ₄ , R ₅ , and R ₈ are alkyl groups having one carbon atom, and R ₂ , R ₃ , R ₆ , and R ₇ are hydrogen atoms (referred to as a "biphenyl group"). By having such a group, the phenoxy resin (C) has excellent thermal conductivity and heat resistance.

In one embodiment, the formula (d-EP) preferably contains a tetramethylbiphenyl group and a biphenyl group as the X group. The phenoxy resin (C) containing a combination of these groups can have an excellent balance of thermal conductivity and heat resistance.

The polyfunctional phenol compound (c2) constituting the crosslinked structure of the phenoxy resin (C) used in this embodiment is a phenol compound having at least two phenolic hydroxyl groups, preferably a bifunctional phenol compound having two phenolic hydroxyl groups, or a trifunctional phenol compound having three phenolic hydroxyl groups, and specifically, at least one selected from the compounds represented by formulas (p1) to (p8).

In the formulas (p1) to (p8), R ¹¹ and R ¹² each independently represent a hydrogen atom, an alkoxy group having 1 to 4 carbon atoms, or a linear or branched alkyl group having 1 to 4 carbon atoms.
Since the phenoxy resin (C) contains structural units derived from the compounds represented by formulas (p1) to (p8), a thermosetting resin composition containing it can have high thermal conductivity.
In this embodiment, the polyfunctional phenol compounds having a flavanone skeleton represented by formulae (P3), (p4), (p7) and (p8) include stereoisomers. Specifically, the isoflavanone compounds of formulae (p3) and (p7) include stereoisomers in which the C2 carbon is an asymmetric carbon atom, and the isoflavanone compounds of formulae (p4) and (p8) include stereoisomers in which the C3 atom is an asymmetric carbon atom.

In one embodiment, all of R ¹¹ and R ¹² in the compounds represented by formulae (p1) to (p8) are hydrogen atoms. The phenoxy resin (C) having a structural unit derived from the polyfunctional phenol compound (c2) having such a structure can have high thermal conductivity and heat resistance, and as a result, the cured product obtained from the thermosetting resin composition containing the phenoxy resin (C) has high thermal conductivity.

The phenoxy resin (C) used in this embodiment may contain structural units derived from other components (c3) in addition to the bifunctional epoxy compound (c1) and polyfunctional phenol compound (c2) described above, as long as the properties of the phenoxy resin are not affected. Examples of component (c3) include, but are not limited to, glycidyl ester type epoxy compounds, glycidyl amine type epoxy compounds, alicyclic epoxy compounds, Bis-A type epoxy compounds, Bis-E type epoxy compounds, Bis-F type epoxy compounds, Bis-S type epoxy compounds, and bisphenol compounds that are precursors of these. When the phenoxy resin (C) contains structural units derived from component (c3), the content thereof is, for example, 10 mol% or less, preferably 5 mol% or less, based on the total structural units constituting the phenoxy resin (C).

In one embodiment, the phenoxy resin (C) is a resin having a structure represented by the following (1) obtained by reacting a bifunctional epoxy compound represented by the above formula (d-EP) with at least one selected from the bifunctional phenol compounds represented by the above formulas (p1) to (p4).

In formula (1),
n is a number representing a repeating unit, and represents an integer of 2 to 50, preferably an integer of 5 to 40, more preferably an integer of 6 to 30, and even more preferably an integer of 8 to 20;
X has the same meaning as X in formula (d-EP).
Y is independently at least one divalent group selected from the following formulas (y1) to (y4):

In formulae (y1) to (y4), R ¹¹ and R ¹² each independently represent a hydrogen atom, an alkoxy group having 1 to 4 carbon atoms, or a linear or branched alkyl group having 1 to 4 carbon atoms, and * represents a linking position. The groups of formulae (y1) to (y4) are groups derived from polyfunctional phenol compounds (c2) of formulae (p1) to (p4), respectively.

The phenoxy resin (C) having a structure represented by formula (1) of this embodiment has in its structure a divalent organic group having a mesogen skeleton represented by "X" in formula (1) and at least one divalent group selected from formula (y1) having an isoflavonoid skeleton, formula (y2) having a flavonoid skeleton, formula (y3) having a flavanone skeleton, and formula (y4) represented by "Y" in formula (1). By having such a structure, the cured product of the thermosetting resin composition containing the phenoxy resin (C) has high thermal conductivity.

The phenoxy resin (C) represented by formula (1) may contain, in addition to the above-mentioned X and Y groups, other groups as long as they do not affect the properties of the phenoxy resin.

The weight average molecular weight (Mw) of the phenoxy resin (C) used in this embodiment is, for example, 1,000 to 10,000, preferably 2,000 to 8,000, more preferably 3,000 to 7,000, and even more preferably 3,500 to 6,500. Mw is a value measured by gel permeation chromatography and converted using a standard polystyrene calibration curve. By setting Mw in the above range, the thermal conductivity of the phenoxy resin (C) can be further improved.

In this embodiment, the weight average molecular weight (Mw) of the phenoxy resin (C) can be measured by obtaining a molecular weight distribution curve using GPC (Gel Permeation Chromatography). The weight average molecular weight (Mw), number average molecular weight (Mn), and polydispersity (PDI: Mw/Mn) of the phenoxy resin are calculated using polystyrene equivalent values obtained from the calibration curve of standard polystyrene (PS) obtained by GPC measurement.

The measurement conditions for GPC are, for example, as follows.
Gel permeation chromatography device HLC-8320GPC manufactured by Tosoh Corporation
Column: TSK-GEL GMH, G2000H, Super HM-M manufactured by Tosoh Corporation
Detector: RI detector for liquid chromatography Measurement temperature: 40°C
Solvent: THF
Sample concentration: 2.0 mg/ml

The dispersity (Mw/Mn) of the phenoxy resin (C) is, for example, 1.00 to 7.00, preferably 2.00 to 6.00, and more preferably 3.50 to 5.50. By setting the dispersity within the above range, the thermal conductivity and fluidity of the phenoxy resin (C) can be further improved.

The phenoxy resin (C) may contain a low molecular weight phenoxy resin having a weight average molecular weight (Mw) of 1000 or less. When the phenoxy resin contains a low molecular weight phenoxy resin, the low molecular weight phenoxy resin is, for example, 5% to 60% and preferably 5% to 50% in terms of the ratio of the total area of components corresponding to a weight average molecular weight Mw of 1,000 or less to the total area 100% of the entire molecular weight distribution obtained by GPC measurement. A phenoxy resin containing a low molecular weight phenoxy resin in an amount within the above range has improved fluidity and excellent handleability. Therefore, for example, the processing stability is improved when the resin composition of this embodiment is processed into the form of a sheet or film.

From the viewpoint of the effects of the present invention, the epoxy equivalent of the phenoxy resin (C) is, for example, 300 to 6,000 g/eq, preferably 350 to 5,000 g/eq, and more preferably 400 to 4,500 g/eq.

The phenoxy resin (C) can improve the thermal conductivity of its cured product by having the specific configuration described above. The thermal conductivity of the cured product of the phenoxy resin (C) is, for example, 0.3 W/(m·K) or more, preferably 0.35 W/(m·K) or more, and more preferably 0.4 W/(m·K) or more. Since the phenoxy resin (C) itself has high thermal conductivity, the cured product of the thermosetting resin composition containing it can also have high thermal conductivity.

The phenoxy resin (C) has the specific structure described above, and thus the cured product has a high 1% weight loss temperature. The 1% weight loss temperature of the cured product of the phenoxy resin (C) is 300°C or higher, preferably 310°C or higher, more preferably 320°C or higher, and even more preferably 330°C or higher. The upper limit of the 1% weight loss temperature of the cured product of the phenoxy resin (C) is, for example, 400°C or lower.

(Production of phenoxy resin (C))
The phenoxy resin (C) used in this embodiment can be synthesized by reacting the bifunctional epoxy compound (c1) represented by the above formula (d-EP) with at least one of the polyfunctional phenol compounds (c2) represented by the above formulas (p1) to (p8). The phenoxy resin (C) may be synthesized using the above-mentioned component (c3) in addition to the bifunctional epoxy compound (c1) and the polyfunctional phenol compound (c2) within a range that does not impair the effects of the present invention.

The above reaction can be carried out without a solvent or in the presence of a reaction solvent using a reaction catalyst.

Suitable reaction solvents include aprotic organic solvents such as methyl ethyl ketone, dioxane, tetrahydrofuran, acetophenone, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylacetamide, sulfolane, propylene glycol monomethyl ether, and cyclohexanone. The use of a reaction solvent can reduce the initial viscosity and improve the reactivity of the monomer.

As the reaction catalyst, a conventionally known polymerization catalyst can be used, and alkali metal hydroxides, tertiary amine compounds, quaternary ammonium compounds, tertiary phosphine compounds, quaternary phosphonium compounds, and imidazole compounds are preferably used.

Specifically, a bifunctional epoxy compound (c1), a polyfunctional phenol compound (c2), a reaction catalyst, and, if necessary, a reaction solvent are added and melt-mixed under stirring. The heating temperature during melt-mixing is about 90 to 120°C, the mixing time is about 30 minutes to 2 hours, and the reaction pressure is normal pressure. After melt-mixing, the mixed solution is heated and a polymerization reaction is carried out at a predetermined reaction temperature under reduced pressure or normal pressure. The reaction temperature is about 140 to 180°C, the reaction time is about 2 to 10 hours, and the reaction pressure is about 1 to 760 Torr.

After the reaction is complete, it is possible to obtain the resin dissolved in a suitable solvent by performing solvent replacement or the like. In addition, the phenoxy resin (C) obtained by the solvent reaction can also be obtained as a solvent-free solid resin by performing a solvent removal process using an evaporator or the like.

In the above synthesis method, a phenoxy resin having the desired weight average molecular weight can be obtained by appropriately selecting reaction conditions such as the amount of starting material used, reaction temperature, and reaction time to adjust the degree of polymerization.

The bifunctional epoxy compound (c1) used in the synthesis of the phenoxy resin (C) may be 4,4'-diglycidylbiphenyl or 4,4'-diglycidyl-3,3',5,5'-tetramethylbiphenyl.

Examples of the polyfunctional phenolic compound (c2) used in the synthesis of the phenoxy resin (C) include flavones such as luteolin, apigenin, baicalein, scutellarein, tricetin, diosmetin, and nobiletin; isoflavonoids such as daidzein and genistein; and flavanones such as naringenin, butin, eriodictyol, hesperetin, homoeriodictyol, isosakuranetin, pinocembrin, sakuranetin, and sterubin. Among these, it is preferable to use daidzein, genistein, and naringenin, since they are easy to handle and the resulting phenoxy resin has high thermal conductivity.

(Thermal Conductive Filler (D))
The thermosetting resin composition of the present embodiment contains thermally conductive particles (D).
The thermally conductive particles (D) may include, for example, highly thermally conductive inorganic particles having a thermal conductivity of 20 W/m·K or more. The highly thermally conductive inorganic particles may include, for example, at least one selected from silica, alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide, and magnesium oxide. These may be used alone or in combination of two or more.

The boron nitride may include monodisperse particles, agglomerated particles, or a mixture thereof, of scaly boron nitride. The scaly boron nitride may be granulated. By using agglomerated particles of scaly boron nitride, the thermal conductivity can be further increased. The agglomerated particles may be sintered or non-sintered.

Thermally conductive particles (D) (100% by mass) can contain 60% by mass or more of the boron nitride, preferably 65% by mass or more, and more preferably 70% by mass or more. The upper limit is not particularly limited, but can be 100% by mass or less, preferably 95% by mass or less, and more preferably 90% by mass or less.

The content of the thermally conductive particles (D) is 100% by mass to 400% by mass, preferably 150% by mass to 350% by mass, and more preferably 200% by mass to 330% by mass, relative to the resin component (100% by mass) of the thermosetting resin composition. By making the content equal to or greater than the lower limit, it is possible to improve thermal conductivity. By making the content equal to or less than the upper limit, it is possible to suppress deterioration of processability.

(Cure Accelerator)
The thermosetting resin composition of the present embodiment may contain a curing accelerator as necessary.
The type and amount of the curing accelerator are not particularly limited, but an appropriate one can be selected from the viewpoints of reaction rate, reaction temperature, storage properties, and the like.

Examples of hardening accelerators include imidazoles, organic phosphorus compounds, tertiary amines, phenolic compounds, organic acids, etc. These may be used alone or in combination of two or more. Among these, from the viewpoint of improving heat resistance, it is preferable to use nitrogen atom-containing compounds such as imidazoles.

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.

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

Examples of the phenol compound include phenol resin, bisphenol A, nonylphenol, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, and allylphenol.
Examples of the organic acid include acetic acid, benzoic acid, salicylic acid, and p-toluenesulfonic acid.

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

(Silane coupling agent)
The thermosetting resin composition may contain a silane coupling agent. This can improve the compatibility of the thermally conductive filler in the thermosetting resin composition. The coupling agent may be added to the thermosetting resin composition, or may be used by treating the surface of the thermally conductive filler.

(Other additives)
The thermosetting resin composition of the present embodiment may contain other components in addition to the above-mentioned components. Examples of the other components include an antioxidant and a leveling agent.

[Method for producing thermosetting resin composition]
The thermosetting resin composition of the present embodiment can be prepared into a resin varnish (a varnish-like thermosetting resin composition) by dissolving, mixing, and stirring the above-mentioned components other than the thermally conductive filler in a solvent. This mixing can be performed using various mixers such as an ultrasonic dispersion type, a high-pressure collision type dispersion type, a high-speed rotation dispersion type, a bead mill type, a high-speed shear dispersion type, and a rotation-revolution type dispersion type.

The above solvents are not particularly limited, but include acetone, methyl isobutyl ketone, toluene, ethyl acetate, cyclohexane, heptane, cyclohexanone, tetrahydrofuran, dimethylformamide, dimethylacetamide, dimethylsulfoxide, ethylene glycol, cellosolve-based solvents, carbitol-based solvents, anisole, and N-methylpyrrolidone.

A thermosetting resin composition in a B-stage state can be obtained by adding a thermally conductive filler to the resin varnish and kneading the mixture using a three-roll mill or the like. By adding the filler during kneading, it is possible to disperse the inorganic filler more uniformly in the thermosetting resin, but this is not limited to the above. The thermally conductive filler may be added during kneading, or may be added when the resin varnish is mixed. From the viewpoint of dispersibility, it is preferable to add the nanoparticles dispersed in a specific solvent (nanoparticle dispersion) to the resin varnish. After kneading, the mixture may be cooled and solidified, and processed into granules, tablets, or sheets.

[Resin sheet]
The resin sheet of the present embodiment is obtained by curing the thermosetting resin composition. A specific form of the resin sheet includes a carrier substrate and a resin layer formed on the carrier substrate and made of the thermosetting resin composition of the present embodiment.

The resin sheet can be obtained, for example, by applying a varnish-like thermosetting resin composition onto a carrier substrate to obtain a coating film (resin layer) and then carrying out a solvent removal process. The solvent content in the resin sheet can be 10 mass% or less based on the entire thermosetting resin composition. For example, the solvent removal process can be carried out under conditions of 80°C to 200°C and 1 minute to 30 minutes.

The resin sheet (resin layer) of this embodiment is in a B-stage state, and the thermosetting resin composition that does not contain the thermally conductive particles (D) that serve as a binder preferably has the following curing behavior.
Specifically, a thermosetting resin composition not containing thermally conductive particles (D) is pre-dried at 115° C. for 12 minutes to prepare a sheet in a B-stage state, and the curing torque of the sheet in the B-stage state is measured over time using a cone-plate rheometer at a measurement temperature of 180° C. When the time T max required from the start of measurement to reach the maximum torque is taken as T _max , the ratio of this time T ₅₀ required from the start of measurement to a value that is 50% of the maximum torque value (T ₅₀ /T _max ) is preferably 0.1 to 1.0, more preferably 0.2 to 0.8, and even more preferably 0.25 to 0.75.

As the cone-plate rheometer, for example, a rheometer "MCR-301" manufactured by Anton Paar Inc. can be used. The measurement frequency can be 1 Hz and the oscillation angle can be 1%.
When the curing behavior (ratio ( _T50 / _Tmax )) of the filler-free thermosetting resin composition of this embodiment is in the above-mentioned range, the cycle time during pressing can be kept within an appropriate range, and the occurrence of molding defects such as voids can be suppressed, thereby improving the productivity of metal base substrates and the like, which will be described later.

In this embodiment, the carrier substrate may be, for example, a polymer film or a metal foil. Examples of the polymer film include, but are not limited to, polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polycarbonates, release papers such as silicone sheets, and heat-resistant thermoplastic resin sheets such as fluorine-based resins and polyimide resins. Examples of the metal foil include, but are not limited to, copper and/or copper-based alloys, aluminum and/or aluminum-based alloys, iron and/or iron-based alloys, silver and/or silver-based alloys, gold and gold-based alloys, zinc and zinc-based alloys, nickel and nickel-based alloys, and tin and tin-based alloys.

The resin substrate of this embodiment has an insulating layer made of the cured product of the above-mentioned thermosetting resin composition. This resin substrate can be used as a material for a printed circuit board on which electronic components such as LEDs and power modules are mounted.

[Electronic device]
The cured resin sheet is used as a thermally conductive sheet interposed between a heat generating body and a heat dissipating body.

Examples of the heating element include a semiconductor element, an LED element, a substrate on which a semiconductor element or an LED element is mounted, a Central Processing Unit (CPU), a power semiconductor, a lithium ion battery, and a fuel cell.
Examples of the heat dissipator include a heat sink, a heat spreader, and a heat dissipation (cooling) fin.
The heat dissipation insulating member may be partially composed of the thermosetting resin composition of this embodiment, and specifically, it may be a heat dissipation sheet obtained by curing the thermosetting resin composition, or a laminate in which the heat dissipation sheet and a substrate are laminated (for example, the metal base substrate 100 in FIG. 1). The substrate is not particularly limited as long as it is a heat dissipation metal substrate, and may be, for example, 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 properties of the heat dissipation insulating member can be improved.
The heat dissipating and insulating member is partially composed of the thermosetting resin composition of this embodiment, and has a thermal conductivity of preferably 12 W/m·K or more, and more preferably 15 W/m·K or more.
The heat dissipating insulation member and the heat sink may be formed on one side or both sides of the heating element. In addition, various base materials or layers may be provided between the heating element and the heat dissipating insulation member, or between the heat dissipating insulation member and the heat sink, as long as they do not affect the heat dissipation properties.

In this embodiment, the heat generating element, the heat dissipation insulating member, and the heat dissipating element can be appropriately combined from those described above to obtain a laminated structure. The laminated structure can be used for various applications requiring heat dissipation and insulation, such as semiconductor devices, smartphones, LED light bulbs and lights, power modules, lithium ion batteries, fuel cells, wireless base stations, and uninterruptible power supplies.
Hereinafter, the components contained in the thermosetting resin composition of the present embodiment will be described.

[Metal base substrate]
A metal base substrate (heat dissipating resin member) 100 of this embodiment will be described with reference to FIG.
FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a metal base substrate 100. As shown in FIG.

As shown in FIG. 1, the metal base substrate 100 can include 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 made of one selected from the group consisting of a resin layer made of the above-mentioned thermosetting resin composition, a cured product of the thermosetting resin composition, and a laminate. Each of these resin layers and laminates may be made of a thermosetting resin composition (resin sheet) in a B-stage state before the circuit processing of the metal layer 103, and may be a cured product obtained by curing the resin composition after the circuit processing.

The metal layer 103 is provided on the insulating layer 102 and is processed into a circuit. Examples of metals constituting the metal layer 103 include one or more selected from copper, copper alloys, aluminum, aluminum alloys, nickel, iron, tin, and the like. Among these, the metal layer 103 is preferably a copper layer or an aluminum layer, and is particularly preferably a copper layer. By using copper or aluminum, the circuit processability of the metal layer 103 can be improved. The metal layer 103 may be a metal foil available in a plate form, or a metal foil available in a 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 the metal layer 103 can be applied to applications requiring a high current.
The upper limit of the thickness of the metal layer 103 is, for example, 10.0 mm or less, and preferably 5 mm or less. If the thickness is less than this value, the circuit processability can be improved, and the substrate as a whole can be made thinner.

The metal substrate 101 has a 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 may be, for example, 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 properties of the metal substrate 101 can be improved.
The thickness of the metal substrate 101 can be appropriately set as long as the object of the present invention is not impaired.

The upper limit of the thickness of the metal substrate 101 is, for example, 20.0 mm or less, and preferably 5.0 mm or less. When the thickness is less than this value, the workability of the metal base substrate 100 can be improved in the external processing, cutting processing, etc.

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 more, the heat dissipation properties of the metal base substrate 100 as a whole can be improved.

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 that uses LEDs and power modules.

The metal base substrate 100 can have a metal layer 103 that has been circuitized by etching or the like into a pattern. In this metal base substrate 100, a solder resist (not shown) may be formed on the outermost layer, and connection electrodes may be exposed so that electronic components can be mounted by exposure and development.

[Semiconductor device]
The metal base substrate (heat dissipation and insulation member) 100 of the embodiment can be used in various applications requiring heat dissipation and insulation properties, for example, in electronic devices such as semiconductor devices.
FIG. 2 is a schematic cross-sectional view showing an example of a semiconductor device using the metal base substrate 100. As shown in FIG.
A semiconductor element 201 is mounted on a metal layer 103 of a metal base substrate 100 via an adhesive layer 202 (die attach material). The semiconductor element 201 is connected to a connection electrode portion formed on the metal base substrate 100 via a bonding wire 203, and is mounted on the metal base substrate 100.
The semiconductor element 201 is encapsulated on the metal base substrate 100 by an encapsulation resin layer 205 .

A heat sink 207 is provided on the metal substrate 101 side of the metal base substrate 100 via a thermally conductive layer 206 (thermal interface material (TIM)). The heat sink 207 is made of a material with excellent thermal conductivity, such as aluminum, iron, or copper.

Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various configurations other than those described above can also be adopted.
Examples of embodiments are given below.
1. (A) an epoxy resin;
(B) a thermosetting resin (excluding the epoxy resin (A));
(C) a phenoxy resin;
(D) a thermally conductive filler,
The phenoxy resin (C) is
A bifunctional epoxy compound (c1) having two epoxy groups;
A phenoxy resin obtained by reacting a polyfunctional phenol compound (c2) having at least two phenolic hydroxyl groups with
The bifunctional epoxy compound (c1) includes a compound represented by the formula (d-EP):
In the formula (d-EP), X represents a divalent group having a mesogenic skeleton,
The polyfunctional phenol compound (c2) is at least one selected from the compounds represented by formulas (p1) to (p8),
In the formulas (p1) to (p8), R ¹¹ and R ¹² each independently represent a hydrogen atom, an alkoxy group having 1 to 4 carbon atoms, or a linear or branched alkyl group having 1 to 4 carbon atoms.
Thermosetting resin composition.
2. The thermosetting resin composition according to 1. , wherein in the polyfunctional phenol compound (c2) represented by the formulas (p1) to (p8), all of R ¹¹ and R ¹² are hydrogen atoms.
3. The thermosetting resin composition according to 1. or 2., wherein X in the formula (d-EP) contains a divalent group represented by formula (2):
In formula (2), R ¹ to R ⁸ independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, and * represents a linking position.
4. The thermosetting resin composition according to 3., wherein in the group represented by formula (2), R ¹ , R ⁴ , R ⁵ and R ⁸ are alkyl groups having 1 to 4 carbon atoms, and R ² , R ³ , R ⁶ and R ⁷ are hydrogen atoms.
5. The thermosetting resin composition according to 3., wherein in the group represented by formula (2), R ¹ , R ⁴ , R ⁵ , and R ⁸ are methyl groups, and R ² , R ³ , R ⁶ , and R ⁷ are hydrogen atoms.
6. The thermosetting resin composition according to 3., wherein in the group represented by formula (2), all of R ¹ to R ⁸ are hydrogen atoms.
7. At least one of X in the formula (d-EP) is a divalent group represented by the formula (2) in which R ¹ , R ⁴ , R ⁵ , and R ⁸ are methyl groups, and R ² , R ³ , R ⁶ , and R ⁷ are hydrogen atoms; and
3. The thermosetting resin composition according to 3., wherein at least one of X in the formula (d-EP) is a divalent group represented by the formula (2) in which all of R ¹ to R ⁸ are hydrogen atoms.
8. The polyfunctional phenol compound (c2) is at least one selected from the compounds represented by formulas (p1) to (p4),
The thermosetting resin composition according to any one of 1. to 7., wherein the phenoxy resin has a structure represented by formula (1):
In formula (1),
n is a number representing a repeating unit and is an integer of 2 to 50;
X has the same meaning as X in formula (d-EP).
Y is independently at least one divalent group selected from the following formulas (y1) to (y4):
In formulae (y1) to (y4), R ¹¹ and R ¹² independently represent a hydrogen atom, an alkoxy group having 1 to 4 carbon atoms, or a linear or branched alkyl group having 1 to 4 carbon atoms, and * represents a linking position.
9. The thermosetting resin composition according to any one of 1. to 8., wherein the phenoxy resin (C) has a weight average molecular weight of 1,000 or more and 10,000 or less.
10. The thermosetting resin composition according to any one of 1. to 9., wherein the thermal conductivity of a cured product of the phenoxy resin (C) is 0.3 W/(m·K) or more.
11. The thermosetting resin composition according to any one of 1. to 10., wherein the 1% weight loss temperature of the cured product of the phenoxy resin (C) is 300° C. or higher.
12. The thermosetting resin composition according to any one of 1. to 11., further comprising an organic solvent (E).
13. The thermosetting resin composition according to any one of 1. to 12., wherein the epoxy resin (A) includes an epoxy resin that is liquid at room temperature.
14. The thermosetting resin composition according to 13., wherein the epoxy resin (A) further contains an epoxy resin that is solid at room temperature.
15. The thermosetting resin composition according to any one of 1. to 14., wherein the content of the thermally conductive filler (D) is 60 mass% or more and 98 mass% or less, based on the total solid content of the thermosetting resin composition.
16. The thermosetting resin composition according to any one of 1. to 15., wherein the thermally conductive filler (D) includes at least one selected from silica, alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide, and magnesium oxide.
17. The thermosetting resin composition according to any one of 1. to 16., wherein the thermally conductive filler (D) contains boron nitride.
18. The thermosetting resin composition according to 16. or 17., wherein the boron nitride is in the form of monodisperse particles, granular particles, agglomerated particles, or a mixture thereof, of scaly boron nitride.
19. The thermosetting resin composition according to any one of 1. to 18., wherein the thermosetting resin (B) includes at least one selected from the group consisting of a cyanate resin, a maleimide resin, a phenol resin, and a benzoxazine resin.
20. The thermosetting resin composition according to any one of 1. to 19., wherein the thermosetting resin (B) contains a cyanate resin.
21. The thermosetting resin composition according to any one of 1. to 20., further comprising a curing accelerator.
22. A resin sheet comprising the thermosetting resin composition according to any one of 1. to 21.
23. The resin sheet according to 22., which is in a B-stage state.
24. Heat generating member, and
A heat dissipation member;
a thermally conductive sheet provided between the heat generating component and the heat dissipating component,
24. An electronic device, wherein the thermally conductive sheet is made of a cured product of the resin sheet according to 22. or 23.
25. The electronic device according to 24., wherein the thermal conductivity of the thermally conductive sheet is 12 W/m·K or more.
26. A metal substrate;
A thermally conductive sheet;
A metal base substrate comprising, in this order,
24. The metal base substrate, wherein the thermally conductive sheet is made of a cured product of the resin sheet according to 22. or 23.
27. The metal base board according to 26., wherein the thermal conductivity of the thermally conductive sheet is 12 W/m·K or more.
28. An electronic device comprising the metal base substrate according to 26. or 27.

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these.

<Examples 1 to 3 and Comparative Example 1 (Production of Thermosetting Resin Composition (Varnish-like))>
A varnish-like thermosetting resin composition was obtained by stirring each component and the solvent according to the blending ratio shown in Table 1. In Table 1, the content of the thermally conductive particles is expressed as a volume % relative to the resin component of the thermosetting resin composition not including the thermally conductive filler.
Details of each component in Table 1 are as follows. The amount of each component in Table 1 is expressed in parts by mass.

(Epoxy resin)
Epoxy resin 1: Epoxy resin having the following structure (manufactured by DIC Corporation, HP-4032D, liquid at room temperature)

Epoxy resin 2: dicyclopentadiene type epoxy resin (DIC Corporation, EPICLON HP-7200L, solid at room temperature)
Epoxy resin 3: Biphenyl type epoxy resin (manufactured by Mitsubishi Chemical Corporation, YX-4000K, solid at room temperature)

(Cyanate resin)
Cyanate resin 1: Primaset "PT-30S" manufactured by Lonza

(Phenol resin)
Phenolic resin 1: Allyl group-containing phenol novolac resin (manufactured by Meiwa Kasei Co., Ltd., product name "MEH-8000H")

(Phenoxy resin)
Phenoxy resin 1: A phenoxy resin obtained by the following procedure.
62 parts by weight of epoxy compound 1, 31 parts by weight of phenol compound 1, 0.05 parts by weight of triphenylphosphine (TPP), and 7 parts by weight of a solvent (cyclohexanone) were added to a reactor and melt-mixed at 100°C to 110°C for 1 hour. The mixture was then heated to 180°C and reacted at that temperature while removing the solvent under reduced pressure. It was confirmed by GPC that the desired molecular weight was reached, and the reaction was stopped to obtain a phenoxy resin represented by the following formula (1-1). The reaction was carried out for 6 hours. After the reaction, 100 parts by weight of dimethylformamide was added to the resin to dissolve the resin, and the resin was cooled to room temperature. After cooling, the mixture was purified by a reprecipitation method using methanol to obtain 100 parts by weight of a phenoxy resin represented by the following formula (1-1). (The average value of the number of repeating units n in formula (1-1) is 11, X is a structural unit derived from epoxy compound 1 of formula (3), Y is a structural unit derived from daidzein which is phenol compound 1, the weight average molecular weight Mw measured by GPC is 4236, and the dispersity (weight average molecular weight Mw)/(number average molecular weight Mn) is 4.28.)

Phenoxy resin 2: A phenoxy resin obtained by the following procedure.
62 parts by weight of epoxy compound 2, 31 parts by weight of phenol compound 1, 0.05 parts by weight of triphenylphosphine (TPP), and 7 parts by weight of a solvent (cyclohexanone) were added to a reactor and melt-mixed at 100°C to 110°C for 1 hour. The mixture was then heated to 180°C and reacted at that temperature while removing the solvent under reduced pressure. It was confirmed by GPC that the desired molecular weight was reached, and the reaction was stopped to obtain a phenoxy resin represented by the following formula (1-2). The reaction was carried out for 6 hours. After the reaction, 100 parts by weight of dimethylformamide was added to the resin to dissolve the resin, and the resin was cooled to room temperature. After cooling, the mixture was purified by a reprecipitation method using methanol to obtain 100 parts by weight of a phenoxy resin represented by the following formula (1-2), in which the average value of the number of repeating units n in formula (1-2) is 11, X is a structural unit derived from an epoxy compound of formula (3) and a structural unit derived from an epoxy compound of formula (4), Y is a structural unit derived from daidzein which is phenol compound 1, the weight average molecular weight Mw measured by GPC is 5422, and the dispersity (weight average molecular weight Mw)/(number average molecular weight Mn) is 4.49.

The raw material compounds used in the synthesis of the above-mentioned phenoxy resin 1 and phenoxy resin 2 are as follows.
(Epoxy compound (c1))
Epoxy compound 1: a tetramethylbiphenyl type epoxy resin represented by the following formula (3) ("YX4000" manufactured by Mitsubishi Chemical Corporation)

Epoxy compound 2: a 1:1 mixture of a tetramethylbiphenyl type epoxy resin represented by the following formula (3) and a biphenyl type epoxy resin represented by the following formula (4) ("YL-6121" manufactured by Mitsubishi Chemical Corporation)

(Phenol compound (c2))
Phenolic compound 1: daidzein (a bifunctional phenolic compound represented by the following formula (5))

Phenolic compound 2: Naringenin (a trifunctional phenolic compound represented by the following formula (6))

Phenoxy resin 3: Bisphenol A type phenoxy resin represented by the following formula (7) (no mesogen structure, manufactured by Mitsubishi Chemical Corporation, YP-55)

(Thermal Conductive Particles)
Thermally conductive particle 1: Agglomerated boron nitride (HP40, manufactured by Mizushima Ferroalloy Co., Ltd.)

<Measurement of physical properties of resin molded product of thermosetting resin composition>
The cured product (resin molded product) of the thermosetting resin composition was measured for the following physical properties. The results are shown in Table 1.

(Thermal Conductivity)
- Preparation of resin molded body The obtained thermosetting resin composition containing the thermally conductive filler was sandwiched between 0.018 mm copper foil and compression molded at 10 MPa, 180 ° C. for 90 minutes to obtain a resin molded body (thermal conductivity measurement sample 1). A sample for thermal diffusivity measurement with a diameter of 10 mm was cut out from the obtained molded body and used for thermal diffusivity measurement.

- Density (specific gravity) of resin molded body
The density (specific gravity) measurement was performed in accordance with JIS K 6911 (general test method for thermosetting plastics). Test pieces were cut out from the above resin molded body to a size of 2 cm length x 2 cm width. The unit of density (specific gravity) (ρ) is g/ ^cm3 .

Specific Heat of Resin Molded Article The specific heat (Cp) of the above-obtained resin molded article was measured by a DSC method.

Measurement of thermal conductivity of resin molded body A test piece with a diameter of 10 mm was cut out from the obtained resin molded body for measurement in the thickness direction. Next, the thermal diffusion coefficient (α) in the thickness direction of the plate-shaped test piece was measured by a non-steady method using a Xe flash analyzer TD-1RTV manufactured by ULVAC. The measurement was performed under the condition of air atmosphere and 25°C.
The thermal conductivity of the resin molded body was calculated from the measured values of the thermal diffusion coefficient (α), specific heat (Cp), and density (ρ) according to the following formula. The results are shown in Table 1.
Thermal conductivity [W/m・K] = α [m ² /s] × Cp [J/kg・K] × ρ [g/cm ³ ]
In Table 1, the thermal conductivity of the resin molded body is indicated as "thermal conductivity."

(moisture absorption rate)
The copper foil was removed from the obtained resin molded product by etching, and the product was left to stand for 48 hours under conditions of 30° C./90% RH, and the moisture absorption rate (%) was calculated from the change in weight before and after the treatment.

(solder heat resistance)
The obtained resin molded body was cut into 50 mm x 50 mm with a grinder saw, and then etched to prepare a sample with only half of the copper foil remaining, which was evaluated in accordance with JIS C 6481. The evaluation was performed by immersing the sample in a solder bath at 300°C for 5 minutes and then checking for the presence or absence of abnormalities in appearance. The evaluation criteria were as follows.
<Evaluation criteria>
○: No abnormality ×: Abnormality (bulging in all areas)

(Moisture absorption and solder heat resistance)
The obtained resin molded body was cut into 50 mm x 50 mm with a grinder saw, and then half-surface etching was performed according to JIS C 6481 to prepare a sample. After leaving it for 2 days in an environment of 40°C temperature and 90% humidity, it was floated with the copper foil side down in a solder bath at 297°C, and the presence or absence of appearance abnormality was checked after 1 minute. The evaluation criteria are as follows. The results are shown in Table 1.
<Evaluation criteria>
○: No abnormality ×: Swelling (there are swollen areas all over the product)

REFERENCE SIGNS LIST 100 Metal base substrate 101 Metal substrate 102 Insulating layer 103 Metal layer 200 Semiconductor device 201 Semiconductor element 202 Adhesive layer 203 Bonding wire 205 Sealing resin layer 206 Thermally conductive layer 207 Heat sink

Claims (26)

(A) an epoxy resin;
(B) a thermosetting resin (excluding the epoxy resin (A));
(C) a phenoxy resin;
(D) a thermally conductive filler,
The phenoxy resin (C) is
A bifunctional epoxy compound (c1) having two epoxy groups;
A phenoxy resin obtained by reacting a polyfunctional phenol compound (c2) having at least two phenolic hydroxyl groups with
The bifunctional epoxy compound (c1) includes a compound represented by the formula (d-EP):
In the formula (d-EP), X represents a divalent group having a mesogenic skeleton,
The polyfunctional phenol compound (c2) is at least one selected from the compounds represented by formulas (p1) to (p8),
In the formulas (p1) to (p8), R ¹¹ and R ¹² each independently represent a hydrogen atom, an alkoxy group having 1 to 4 carbon atoms, or a linear or branched alkyl group having 1 to 4 carbon atoms.
Thermosetting resin composition. The thermosetting resin composition according to claim 1, wherein in the polyfunctional phenol compound (c2) represented by the formulas (p1) to (p8), all of R ¹¹ and R ¹² are hydrogen atoms. The thermosetting resin composition according to claim 1 or 2, wherein X in the formula (d-EP) contains a divalent group represented by formula (2):
In formula (2), R ¹ to R ⁸ independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, and * represents a linking position. The thermosetting resin composition according to claim 3, wherein in the group represented by formula (2), R ¹ , R ⁴ , R ⁵ , and R ⁸ are alkyl groups having 1 to 4 carbon atoms, and R ² , R ³ , R ⁶ , and R ⁷ are hydrogen atoms. The thermosetting resin composition according to claim 3, wherein in the group represented by formula (2), R ¹ , R ⁴ , R ⁵ , and R ⁸ are methyl groups, and R ² , R ³ , R ⁶ , and R ⁷ are hydrogen atoms. 4. The thermosetting resin composition according to claim 3, wherein in the group represented by formula (2), all of R ¹ to R ⁸ are hydrogen atoms. The thermosetting resin composition according to claim 3, wherein at least one of X in formula (d-EP) is a divalent group represented by formula (2) in which R ¹ , R ⁴ , R ⁵ , and R ⁸ are methyl groups, and R ² , R ³ , R ⁶ , and R ⁷ are hydrogen atoms, and at least one of X in formula (d-EP) is a divalent group represented by formula ( 2 ) in which R ¹ to R ⁸ are all hydrogen atoms. The polyfunctional phenol compound (c 2 ) is at least one selected from the compounds represented by the formulas (p1) to (p4),
The thermosetting resin composition according to any one of claims 1 to 7, wherein the phenoxy resin has a structure represented by formula (1):
In formula (1),
n is a number representing a repeating unit and is an integer of 2 to 50;
X has the same meaning as X in formula (d-EP).
Y is independently at least one divalent group selected from the following formulas (y1) to (y4):
In formulae (y1) to (y4), R ¹¹ and R ¹² independently represent a hydrogen atom, an alkoxy group having 1 to 4 carbon atoms, or a linear or branched alkyl group having 1 to 4 carbon atoms, and * represents a linking position. The thermosetting resin composition according to any one of claims 1 to 8, wherein the weight average molecular weight of the phenoxy resin (C) is 1,000 or more and 10,000 or less. The thermosetting resin composition according to claim 1 , further comprising an organic solvent (E). The thermosetting resin composition according to claim 1 , wherein the epoxy resin (A) comprises an epoxy resin that is liquid at room temperature. The thermosetting resin composition according to claim 11 , wherein the epoxy resin (A) further comprises an epoxy resin that is solid at room temperature. The thermosetting resin composition according to claim 1 , wherein a content of the thermally conductive filler (D) is 60 mass% or more and 98 mass% or less with respect to a total solid content of the thermosetting resin composition. The thermosetting resin composition according to any one of claims 1 to 13 , wherein the thermally conductive filler (D) comprises at least one selected from the group consisting of silica, alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide, and magnesium oxide. The thermosetting resin composition according to claim 1 , wherein the thermally conductive filler (D) comprises boron nitride. The thermosetting resin composition according to claim 14 or 15 , wherein the boron nitride is in the form of monodisperse particles, granular particles, agglomerated particles, or a mixture thereof, of scaly boron nitride. The thermosetting resin composition according to claim 1 , wherein the thermosetting resin (B) comprises at least one selected from the group consisting of a cyanate resin, a maleimide resin, a phenolic resin, and a benzoxazine resin. The thermosetting resin composition according to claim 1 , wherein the thermosetting resin (B) comprises a cyanate resin. The thermosetting resin composition according to claim 1 , further comprising a curing accelerator. A resin sheet comprising the thermosetting resin composition according to any one of claims 1 to 19 . The resin sheet according to claim 20 , which is in a B-stage state. A heat generating member;
A heat dissipation member;
a thermally conductive sheet provided between the heat generating component and the heat dissipating component,
22. An electronic device, wherein the thermally conductive sheet is made of a cured product of the resin sheet according to claim 20 . The electronic device according to claim 22 , wherein the thermal conductivity of the thermally conductive sheet is 12 W/m·K or more. A metal substrate;
A thermally conductive sheet;
A metal base substrate comprising, in this order,
The thermally conductive sheet is a metal base substrate comprising a cured product of the resin sheet according to claim 20 or 21 . 25. The metal base substrate according to claim 24 , wherein the thermal conductivity of the thermally conductive sheet is 12 W/m·K or more. 26. An electronic device comprising the metal base substrate according to claim 24 or 25 .