Thermosetting resin composition, sheet, and metal base substrate

Abstract

To provide a resin excellent in thermal conductivity, solvent solubility and heat resistance.SOLUTION: The thermosetting resin composition comprises (A) a phenoxy resin, (B) an inorganic filler which is alumina and / or massive boron nitride, and (C) a curing agent, wherein the component (A) is a phenoxy resin obtained by reacting a compound represented by general formula (1) with a specific phenolic compound such as 2,4,4' - triglycidyloxybiphenyl. (In the formula, R1 each independently represents any of hydrogen and a C1-10 hydrocarbyl group.). ) SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermosetting resin composition, a sheet, and a metal base substrate. [Background technology]

[0002] In recent years, with the miniaturization and high performance of electronic devices, heat dissipation measures for electronic devices have become an issue, and the development of various thermally conductive materials has progressed. To improve the thermal conductivity, the type and amount of filler added have been widely investigated, and it is known that increasing the amount added is particularly effective in improving thermal conductivity. However, there is a limit to the improvement in thermal conductivity that can be achieved by adding filler, and increasing the amount of filler added deteriorates the insulation reliability of the resulting resin composition. Therefore, there is a strong demand for a resin composition that achieves both of these goals.

[0003] For example, Patent Document 1 describes a thermosetting resin composition containing a specific maleimide compound, a silicone compound having an epoxy group in its molecular structure, and a compound having a phenolic hydroxyl group, and discloses that the resin composition exhibits excellent heat resistance and low thermal expansion properties.

[0004] Patent Document 2 describes an epoxy resin composition containing an epoxy compound having a mesogenic skeleton, three types of alumina having specific D50, and a curing agent, and discloses that the resin composition has high thermal conductivity.

[0005] Patent Document 3 discloses a phenoxy resin containing a specific repeating unit. It is described as having a novel structure (mesogenic structure) with an ester bond between two benzene rings. It is disclosed that the resin has higher thermal conductivity than conventional bisphenol A-type phenoxy resins. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-149154 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-13759 [Patent Document 3] Patent Publication No. 2021-098836 Summary of the Invention [Problem to be solved by the invention]

[0007] However, although the resin composition described in Patent Document 1 has high heat resistance, its thermal conductivity and insulating reliability have not been sufficiently investigated, and it cannot be said that it has both of these properties.

[0008] Furthermore, the resin composition described in Patent Document 2 uses an amine-based curing agent when curing, which results in a problem that the resulting semi-cured sheet is prone to cracking and difficult to handle. Furthermore, detailed consideration has not been given to insulation reliability, and there is still room for improvement.

[0009] The phenoxy resin described in Patent Document 3 does not have sufficient heat resistance, and the moldability, thermal conductivity, and other properties that it will have when a filler is added have not been fully studied.

[0010] In view of the above, an object of the present invention is to provide a resin composition, a varnish, a resin sheet thereof, and a metal base substrate that combine all of thermal conductivity, insulation reliability, peel strength, and heat resistance. [Means for solving the problem]

[0011] The present inventors have found that the above problems can be solved by combining a novel phenoxy resin having a specific structure with a specific filler.

[0012] (1) A composition comprising (A) a phenoxy resin, (B) an inorganic filler which is alumina and / or block boron nitride, and (C) a curing agent; The thermosetting resin composition, wherein (A) is a phenoxy resin obtained by reacting a compound represented by the following general formula (1) with a compound represented by the following general formula (2):

[0013] [ka] (In the formula, each R1 independently represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.)

[0014] [ka] (In the formula, n and m each independently represent an integer of 1 to 3, and n+m is 3 or more and 10 or less.) (2) The thermosetting resin composition according to (1) above, wherein (B) contains at least block boron nitride having an average particle size of 10 to 80 μm and alumina having an average particle size of 25 μm or less. (3) The thermosetting resin composition according to (1) or (2) above, wherein the alumina is spherical. (4) A varnish containing the thermosetting resin composition according to any one of (1) to (3) above. (5) A resin sheet comprising a carrier material and a varnish layer, wherein the varnish layer is the varnish described in (4) above, and the varnish layer has a thickness of 30 to 200 μm in an uncured state. (6) A metal base substrate comprising the resin sheet according to (5) above as an insulating layer. [Effects of the Invention]

[0015] According to the present invention, by combining a novel phenoxy resin having a specific structure with a specific filler, it is possible to provide a resin composition that combines thermal conductivity, insulation reliability, peel strength, and heat resistance, as well as a varnish, a resin sheet thereof, and a metal base substrate. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail.

[0017] (Thermosetting resin composition) The thermosetting resin composition of the present invention contains (A) a phenoxy resin, (B) an inorganic filler which is alumina and / or block boron nitride, and (C) a curing agent.

[0018] [(A) Phenoxy resin] The (A) phenoxy resin has a structure obtained by reacting a compound represented by the following general formula (1) with a compound represented by the following general formula (2).

[0019] [ka]

[0020] In general formula (1), each R1 independently represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. Each R1 independently represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms. Examples of the hydrocarbon group include alkyl groups such as methyl, ethyl, isopropyl, and cyclohexyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; and aralkyl groups such as benzyl, phenethyl, and naphthylmethyl.

[0021] R1 may be any substituent as long as it does not significantly affect the resin composition of the present invention, its varnish, resin sheet, and metal base substrate. From the viewpoint of maintaining molecular orientation and improving thermal conductivity, a low-bulk substituent is preferred, and from the viewpoint of reducing the melt viscosity of the resulting resin, a long-chain alkyl group with high mobility is preferred. Therefore, a hydrogen atom or a hydrocarbon group having 1 to 4 carbon atoms is more preferred, a hydrogen atom or an alkyl group having 1 to 4 carbon atoms is even more preferred, and a hydrogen atom or a methyl group is particularly preferred.

[0022] [ka]

[0023] In the general formula (2), n and m each independently represent an integer of 1 to 3, and n+m is 3 or more and 10 or less.

[0024] The general formula (2) is not particularly limited, but from the viewpoint of heat resistance and handleability (solvent solubility, melting point), it is preferably a compound having at least hydroxyl groups at the 4,4'-positions, which has excellent molecular orientation, and more preferably a compound represented by the following general formula (3):

[0025] [ka]

[0026] The weight-average molecular weight (Mw) of the phenoxy resin of this embodiment is preferably 2,000 to 30,000, more preferably 2,000 to 20,000, and even more preferably 2,000 to 10,000. Mw is measured by gel permeation chromatography (GPC) and converted using a standard polystyrene calibration curve. By ensuring that Mw falls within the above range, the resulting resin composition can have excellent thermal conductivity and flowability.

[0027] The epoxy equivalent of the phenoxy resin of this embodiment is preferably 300 g / eq to 6,000 g / eq, more preferably 350 g / eq to 5,000 g / eq, and particularly preferably 400 g / eq to 4,500 g / eq. Having the epoxy equivalent within this range is preferable because the thermal conductivity and fluidity of the resulting resin composition are improved.

[0028] The melt viscosity of the phenoxy resin of this embodiment is not particularly limited, but for example, the melt viscosity at 180° C. is preferably 50 mPa s or less, and more preferably 30 mPa s or less. If it is within this range, excellent moldability can be achieved.

[0029] The thermosetting resin composition of the present invention is preferable because it contains the phenoxy resin, which has excellent flexibility, thereby improving the handleability of the resin composition, and is also preferable because it has excellent thermal conductivity when made into a resin sheet or a metal base substrate.

[0030] The phenoxy resin is preferably contained in an amount of 1 to 70% by mass, more preferably 2 to 50% by mass, and particularly preferably 3 to 45% by mass, relative to the non-volatile content (100% by mass) of the resin composition not containing the inorganic filler described below.

[0031] [Inorganic filler] In the present invention, the inorganic filler is (B) alumina and / or block boron nitride.

[0032] <Alumina> In this embodiment, "alumina" refers to aluminum oxide, and may be transition alumina of various crystalline forms such as gamma, delta, theta, and kappa, or may contain alumina hydrate in transition alumina. However, the alpha crystalline form is preferred because of its superior stability.

[0033] The alumina preferably has a spherical or polyhedral shape, and more preferably a spherical shape, which is preferable because, for example, when used in combination with boron nitride (described later), the alumina tends to fill gaps in the boron nitride, resulting in excellent thermal conductivity.

[0034] The shape of alumina can be confirmed using a scanning electron microscope (SEM). Using a JEOL JCM7000, images obtained by multiple SEM images taken from any field of view of the sample are observed. Then, from the observation results of 50 randomly selected alumina particles, the shape of 60% or more of the particles by number can be determined to be the shape possessed by the sample.

[0035] In this embodiment, the average particle size of the alumina is preferably 0.1 μm to 25 μm, more preferably 0.1 μm to 20 μm, and particularly preferably 0.1 μm to 15 μm. A particle size within this range is preferable because it provides excellent insulation reliability.

[0036] In this specification, the "average particle size" refers to a value calculated as the volume-based median diameter D50 from the volume-based cumulative particle size distribution measured using a laser diffraction / scattering particle size distribution analyzer.

[0037] The content of alumina in the resin composition of this embodiment may be 90 to 95 parts by mass, or may be 91 to 94 parts by mass, per 100 parts by mass of the total solid content of the resin composition. When boron nitride, which will be described later, is used in combination, a suitable content of alumina can be separately determined regardless of the above range.

[0038] The alumina of this embodiment may be commercially available alumina particles, or alumina particles produced by the methods described in JP 2016-028993 A and WO 2021 / 070729 A may be used.

[0039] Commercially available alumina particles include DAW45 (manufactured by Denka), CB-A20S, CB-AS30S, CB-P15 (manufactured by Resonac), AZ Series (manufactured by Nippon Steel Material & Chemical Co., Ltd.), AH40-S (manufactured by DIC Corporation), and AO-502 (manufactured by Admatechs). From the viewpoint of fluidity, CB-A20S, CB-A30S, CB-P15 (manufactured by Resonac), and AO-502 (manufactured by Admatechs) are preferred, but are not limited to these. These alumina particles may be used alone or in combination, and can be appropriately adjusted to obtain the desired thermal conductivity.

[0040] <Boron nitride> The boron nitride of this embodiment is a block boron nitride in which scale-like boron nitride is randomly oriented. The use of block boron nitride is preferable because it prevents the boron nitride from being oriented in the plane direction and improves the thermal conductivity in the thickness direction when made into a resin sheet, as described below.

[0041] The average particle size of the boron nitride is preferably 10 μm or more and 80 μm or less, more preferably 30 μm or more and 70 μm or less. Being within this range is preferable because the thermal conductivity of the resulting cured product is improved. In the present invention, the "average particle size" of the first inorganic filler refers to the particle size of the aggregated secondary particles.

[0042] The boron nitride used in this embodiment may be commercially available, such as HP-40MF, HP40-J2 (manufactured by Mizushima Ferroalloy Co., Ltd.), PTX60 (manufactured by Momentive Corp.), and Agglomerates 50 (manufactured by 3M). HP-40MF and HP40-J2 (manufactured by Mizushima Ferroalloy Co., Ltd.), which are sintered and produced in a block form without internal voids, are preferred.

[0043] The boron nitride of this embodiment can also be produced by a known method, for example, the method described in JP 2019-073409 A.

[0044] The content of boron nitride in the resin composition of this embodiment may be 55 to 85 parts by mass, and preferably 60 to 80 parts by mass, per 100 parts by mass of the total solid content of the resin composition. When the above-mentioned alumina is used in combination, a suitable content of boron nitride can be separately determined regardless of the above range.

[0045] In the thermosetting resin composition of this embodiment, when alumina and block boron nitride are used in combination, the total content thereof is preferably 60 to 95 parts by mass, and more preferably 70 to 95 parts by mass, per 100 parts by mass of the total solid content of the resin composition. By keeping the total content within this range, an increase in viscosity of the resin composition or its varnish can be suppressed, and a uniform coating film can be formed.

[0046] Any combination of alumina and massive boron nitride may be used as long as it is within the above range, but the mass ratio of alumina to massive boron nitride is preferably 15:85 to 3:97, and more preferably 10:90 to 5:95. A mass ratio within the above range is preferable because it allows for excellent levels of both thermal conductivity and insulation reliability.

[0047] The thermosetting resin composition of the present invention may contain other resins depending on the application. For example, when used as a heat dissipation and insulation material, it may contain a thermosetting resin, such as an epoxy resin, a benzoxazine resin, a phenol resin, a cyanate resin, a bismaleimide resin, or an acrylic resin. These may be used alone or in combination of two or more.

[0048] <(C) Hardener> The curing agent contained in the thermosetting resin composition is not particularly limited, and examples thereof include phenolic resin-based curing agents, amine-based curing agents, acid anhydride-based curing agents, mercaptan-based curing agents, etc. These may be used alone or in combination of two or more.

[0049] Examples of the phenolic resin-based curing agent include phenol novolac resin, cresol novolac resin, aromatic hydrocarbon formaldehyde resin-modified phenolic resin, dicyclopentadiene phenol addition type resin, phenol aralkyl resin (Zylok resin), polyhydric phenol novolac resin synthesized from a polyhydric hydroxy compound and formaldehyde, such as resorcinol novolac resin, naphthol aralkyl resin, tetraphenylolethane resin, naphthol novolac resin, naphthol-phenol co-condensed novolac resin, naphthol-cresol Examples of polyhydric phenol compounds include phenol-co-condensed novolac resins, biphenyl-modified phenolic resins (polyhydric phenol compounds in which phenol nuclei are linked via bismethylene groups), biphenyl-modified naphthol resins (polyhydric naphthol compounds in which phenol nuclei are linked via bismethylene groups), aminotriazine-modified phenolic resins (polyhydric phenol compounds in which phenol nuclei are linked via melamine, benzoguanamine, or the like), and alkoxy group-containing aromatic ring-modified novolac resins (polyhydric phenol compounds in which phenol nuclei and alkoxy group-containing aromatic rings are linked via formaldehyde).

[0050] Examples of the amine compounds include diaminodiphenylmethane, diethylenetriamine, triethylenetetramine, diaminodiphenylsulfone, isophoronediamine, imidazole, BF3-amine complex, and guanidine derivatives.

[0051] Examples of the acid anhydride compounds include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, and methylhexahydrophthalic anhydride.

[0052] Examples of the mercaptan curing agent include trimethylolpropane tris(3-mercaptobutyrate) and trimethylolethane tris(3-mercaptobutyrate).

[0053] The thermosetting resin composition may contain a curing accelerator as needed. 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, etc.

[0054] Examples of the curing accelerator include imidazoles, organic phosphorus compounds, tertiary amines, phenolic compounds, and organic acids. These may be used alone or in combination of two or more. Among these, it is preferable to use nitrogen atom-containing compounds such as imidazoles from the viewpoint of improving heat resistance.

[0055] The thermosetting resin composition may contain a silane coupling agent, which can improve the compatibility of the inorganic 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 inorganic filler.

[0056] The thermosetting resin composition may contain other components in addition to the above-mentioned components, such as an antioxidant and a leveling agent.

[0057] The thermosetting resin composition may contain low-molecular-weight components produced during the production of the phenoxy resin. The low-molecular-weight components are components having a weight-average molecular weight Mw of 1,000 or less, such as unreacted compounds represented by the general formulas (1) and (2) or their reaction products, and having a weight-average molecular weight within the range.

[0058] The lower the content of the low-molecular-weight component, the more improved the thermal conductivity and insulating reliability of the resulting resin sheet or metal base substrate can be. On the other hand, from the viewpoint of the fluidity of the resulting resin composition, a certain amount of the low-molecular-weight component may be contained.

[0059] The content of the low molecular weight components is, for example, preferably 1% by mass or more and 70% by mass or less, more preferably 2% by mass or more and 50% by mass or less, and particularly preferably 3% by mass or more and 45% by mass or less, relative to the non-volatile content (100% by mass) of the resin composition not containing inorganic fillers.

[0060] 〔varnish〕 The thermosetting resin composition of the present invention is preferably used for a varnish. The varnish can be prepared by a known method, and the resin composition can be dissolved (diluted) in an organic solvent to form a varnish.

[0061] As the solvent, for example, polar solvents such as methyl ethyl ketone, methoxypropanol, N,N-dimethylformamide, and dimethyl sulfoxide can be used, and the solvents may be used alone or in combination of two or more.

[0062] The amount of the solvent used is not particularly limited and can be determined appropriately taking into account, for example, sheet processability. Specifically, the viscosity of the resulting varnish is preferably adjusted to 3000 mPa·s to 15000 mPa·s. A viscosity of 3000 mPa·s or higher is preferred because it prevents poor appearance due to repellency during coating. A viscosity of 15000 mPa·s or lower is preferred because it prevents poor appearance due to streaks during coating.

[0063] [Resin sheet] The varnish is preferably used for a resin sheet, which is produced by applying the varnish to a carrier material and then drying it by heating. The resin sheet is formed in a semi-cured state on the surface of the carrier material. That is, the heat drying is a process of bringing the varnish to a B-stage, and by heating the varnish applied to the carrier material, the phenoxy resin in the varnish is partially reacted. Therefore, the resin sheet of this embodiment has the property of being melted once and then cured by the heat and pressure of the lamination molding.

[0064] The method for applying the varnish is not particularly limited and can be carried out by a known method. Examples include comma coating, die coating, lip coating, gravure coating, etc. Preferred methods for forming a resin sheet of a predetermined thickness include the comma coating method in which the substrate is passed through a gap, and the die coating method in which varnish is applied from a nozzle at an adjusted flow rate.

[0065] The thickness of the resin sheet formed on the carrier material is preferably 35 μm to 100 μm, more preferably 40 μm to 90 μm, and particularly preferably 40 μm to 80 μm. A thickness of 100 μm or less is preferable because thermal resistance is low. In the case of two-layer lamination, if the thickness of the resin sheet is 60 μm or less, the thermal conductivity and insulation reliability of the resulting molded product will be particularly excellent.

[0066] The carrier material preferably includes a polymer film or a metal sheet. Examples of the polymer film include polyolefins such as polyethylene, polypropylene, and polyvinyl chloride, polyesters such as polyethylene terephthalate, polycarbonate, acetyl cellulose, and tetrafluoroethylene. Examples of the metal sheet include metal foils such as copper foil, aluminum foil, and nickel foil. Further examples of the carrier material include release paper.

[0067] [Metal base substrate] The resin sheet of the present invention can be suitably laminated and used as a metal base substrate. Specifically, two or more resin sheets obtained as described above are laminated to a desired thickness, and then a metal foil is placed on one or both outermost layers to form a laminate. This laminate is then integrated by heating and pressing, such as by press molding. The metal foil can be a single, alloy, or composite metal foil of copper, aluminum, brass, nickel, or the like. The conditions for heating and pressing the laminate can be appropriately adjusted to cure the varnish of the present invention. However, if the pressure is too low, air bubbles may remain inside the resulting metal base substrate, resulting in reduced electrical properties. Therefore, it is preferable to press the laminate under conditions that satisfy moldability. For example, a metal base substrate can be integrally molded by heating and pressing at a temperature of 100 to 200°C and a pressure of 0.98 to 4.9 MPa for 10 minutes to 2 hours.

[0068] [Method for producing phenoxy resin] The phenoxy resin of the present invention can be synthesized by reacting a compound represented by the above general formula (1) with a compound represented by the above general formula (2).

[0069] <Compound of general formula (1)> Examples of the compound represented by the general formula (1) include 4,4'-bis(glycidyloxy)-1,1'-biphenyl, tetramethyl-4,4'-bis(glycidyloxy)-1,1'-biphenyl, tetraethyl-4,4'-bis(glycidyloxy)-1,1'-biphenyl, tetrabutyl-4,4'-bis(glycidyloxy)-1,1'-biphenyl, etc. Among these, 4,4'-bis(glycidyloxy)-1,1'-biphenyl and tetramethyl-4,4'-bis(glycidyloxy)-1,1'-biphenyl are more preferred from the viewpoint of maintaining molecular orientation and improving thermal conductivity.

[0070] <Compound of general formula (2)> Examples of the compound represented by the general formula (2) include 2,2',3-biphenyltriol, 2,2',4-biphenyltriol, 2,2',5-biphenyltriol, 2,2',6-biphenyltriol, 2,3',4'-biphenyltriol, 2,3',5'-biphenyltriol, 2,3,3'-biphenyltriol, 2,3',4-biphenyltriol, 2,3',5-biphenyltriol, 2,3',6-biphenyltriol, 3,3',4-biphenyltriol, 3,3',5-biphenyltriol, 2,3,4 '-biphenyltriol, 2,4,4'-biphenyltriol, 2,4',5-biphenyltriol, 2,4',6-biphenyltriol, 3,4,4'-biphenyltriol, 3,4',5-biphenyltriol, 2,2',3,4-tetrahydroxydiphenyl, 2,2',3,5-tetrahydroxydiphenyl, 2,2',3,6-tetrahydroxydiphenyl, 2,2',4,5-tetrahydroxydiphenyl, 2,2',4,6-tetrahydroxydiphenyl, 2,3',4',5'-tetrahydroxydiphenyl, 2,3, 3',4-tetrahydroxydiphenyl, 2,3,3',5-tetrahydroxydiphenyl, 2,3,3',6-tetrahydroxydiphenyl, 2,3',4,5-tetrahydroxydiphenyl, 2,3',4,6-tetrahydroxydiphenyl, 3,3',4,5-tetrahydroxydiphenyl, 2,3,4,4'-tetrahydroxydiphenyl, 2,3,4',5-tetrahydroxydiphenyl, 2,3,4',6-tetrahydroxydiphenyl, 2,4,4',5-tetrahydroxydiphenyl, 2,4,4',6-tetrahydroxydiphenyl , 3,4,4',5-tetrahydroxydiphenyl, 2,2',3,3'-tetrahydroxydiphenyl, 2,2',3,4'-tetrahydroxydiphenyl, 2,2',3,5'-tetrahydroxydiphenyl, 2,2',3,6'-tetrahydroxydiphenyl, 2,3,3',4'-tetrahydroxydiphenyl, 2,3,3',5'-tetrahydroxydiphenyl, 2,2',4,4'-tetrahydroxydiphenyl, 2,2',4,5'-tetrahydroxydiphenyl, 2,2',4,6'-tetrahydroxydiphenyl, 2,3',4,Examples of such hydroxydiphenyl include 4'-tetrahydroxydiphenyl, 2,3',4,5'-tetrahydroxydiphenyl, 2,2',5,5'-tetrahydroxydiphenyl, 2,2',5,6'-tetrahydroxydiphenyl, 2,3',4',5-tetrahydroxydiphenyl, 2,3',5,5'-tetrahydroxydiphenyl, 2,2',6,6'-tetrahydroxydiphenyl, 2,3',4',6-tetrahydroxydiphenyl, 2,3',5',6-tetrahydroxydiphenyl, 3,3',4,4'-tetrahydroxydiphenyl, 3,3',4,5'-tetrahydroxydiphenyl, and 3,3',5,5'-tetrahydroxydiphenyl. Among these, a structure with high molecular orientation is advantageous for increasing the thermal conductivity of phenoxy resins, and therefore 2,4,4'-triglycidyloxybiphenyl, 2,4,4',6-tetrahydroxydiphenyl, and 2,2',4,4'-tetrahydroxydiphenyl, which have substituents at the 4,4' positions, and 2,4',6-biphenyltriol, 3,4',5-biphenyltriol, 2,2',5,5'-tetrahydroxydiphenyl, and 3,3',5,5'-tetrahydroxydiphenyl, which have excellent molecular symmetry, are preferred.

[0071] The reaction can be carried out using the compound and a reaction catalyst in the absence or presence of a solvent.

[0072] <Reaction catalyst> The reaction catalyst is not particularly limited as long as it is a compound having catalytic activity that promotes the etherification reaction of an epoxy group and a phenolic hydroxyl group, and examples thereof include alkali metal compounds, organophosphorus compounds, tertiary amines, quaternary ammonium salts, cyclic amines, and imidazoles.

[0073] Specific examples of the alkali metal compound include alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide; alkali metal salts such as sodium carbonate, sodium bicarbonate, sodium chloride, lithium chloride, and potassium chloride; alkali metal alkoxides such as sodium methoxide and sodium ethoxide; and alkali metal salts of organic acids such as alkali metal phenoxides, sodium hydride, lithium hydride, sodium acetate, and sodium stearate.

[0074] Specific examples of the organic phosphorus compound include chain phosphines such as tri-n-propylphosphine, tri-n-butylphosphine, tricyclohexylphosphine, triphenylphosphine, and diphenylmethylphosphine; cyclic phosphines such as paramethylphosphine; bisphosphines such as 1,2-bis(dimethylphosphino)ethane and 1,4-bis(diphenylphosphino)butane; tetramethylphosphonium bromide, tetramethylphosphonium iodide, tetramethylphosphonium hydroxide, trimethylcyclohexylphosphonium chloride, trimethylcyclohexylphosphonium bromide, trimethylbenzylphosphonium chloride, trimethylbenzylphosphonium bromide, tetraphenylphosphonium bromide, triphenylmethylphosphonium bromide, triphenylmethylphosphonium iodide, triphenylethylphosphonium chloride, triphenylethylphosphonium bromide, triphenylethylphosphonium iodide, triphenylbenzylphosphonium chloride, and triphenylbenzylphosphonium bromide.

[0075] Specific examples of the tertiary amine include triethylamine, tri-n-propylamine, tri-n-butylamine, triethanolamine, benzyldimethylamine, etc. Specific examples of the quaternary ammonium salt include tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium hydroxide, triethylmethylammonium chloride, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetrapropylammonium bromide, tetrapropylammonium hydroxide, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iodide, benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, benzyltrimethylammonium hydroxide, benzyltributylammonium chloride, phenyltrimethylammonium chloride, etc.

[0076] Examples of the quaternary ammonium salt include tetramethylammonium hydroxide, benzyltributylammonium chloride, and tetrabutylammonium chloride.

[0077] Examples of the cyclic amines include 1,8-diazabicyclo(5,4,0)undecene-7, 1,5-diazabicyclo(4,3,0)nonene-5, and the like.

[0078] Specific examples of the imidazoles include 2-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenylimidazole.

[0079] These catalysts can be used in combination. Usually, the amount of catalyst used is preferably 0.001 to 3 mass %, more preferably 0.1 to 2 mass %, particularly preferably 0.5 to 1 mass %, of the reaction solid content.

[0080] Among them, chain phosphines such as triphenylphosphine and tributylphosphine are In view of ease of synthesis and storage stability, triphenylphosphine is preferred, and triphenylphosphine is more preferred.

[0081] <Solvent> In the present invention, when a solvent is used in the synthesis reaction during production, there are no particular limitations as long as it dissolves the phenoxy resin, and examples thereof include amide-based solvents, ketone-based solvents, glycol-based solvents, aromatic solvents, ester-based solvents, and other polar solvents.

[0082] Examples of the amide solvent include formamide, N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide, N,N-dimethylacetamide, N,N,N',N'-tetramethylurea, 2-pyrrolidone, N-methylpyrrolidone, and carbamic acid esters.

[0083] Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetylacetone, diisobutyl ketone, isophorone, methylcyclohexanone, and acetophenone.

[0084] Examples of the glycol solvent include ethylene glycol dialkyl ethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and ethylene glycol dibutyl ether; polyethylene glycol dialkyl ethers such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, and triethylene glycol dibutyl ether;

[0085] ethylene glycol monoalkyl ether acetates such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, and ethylene glycol monobutyl ether acetate;

[0086] Polyethylene glycol monoalkyl ether acetates such as diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, triethylene glycol monomethyl ether acetate, triethylene glycol monoethyl ether acetate, and triethylene glycol monobutyl ether acetate; propylene glycol dialkyl ethers such as propylene glycol dimethyl ether, propylene glycol diethyl ether, and propylene glycol dibutyl ether; polypropylene glycol dialkyl ethers such as dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol dibutyl ether, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, and tripropylene glycol dibutyl ether;

[0087] Examples of the propylene glycol monoalkyl ether acetates include propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and propylene glycol monobutyl ether acetate; polypropylene glycol monoalkyl ether acetates such as dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, dipropylene glycol monobutyl ether acetate, tripropylene glycol monomethyl ether acetate, tripropylene glycol monoethyl ether acetate, and tripropylene glycol monobutyl ether acetate; dialkyl ethers of copolymer polyether glycols such as low molecular weight ethylene-propylene copolymers; monoacetate monoalkyl ethers of copolymer polyether glycols; alkyl esters of copolymer polyether glycols; and monoalkyl ester monoalkyl ethers of copolymer polyether glycols.

[0088] Examples of the aromatic solvent include benzene, toluene, xylene, Solvesso 100 (manufactured by Kyoei Solvent Co., Ltd.), Solvesso 150 (manufactured by Kyoei Solvent Co., Ltd.), and the like.

[0089] Examples of the ester solvent include ethyl acetate, n-propyl acetate, isopropyl acetate, and n-butyl acetate.

[0090] Examples of the other polar solvents include dimethyl sulfoxide, sulfolane, and γ-butyrolactone.

[0091] <Synthesis conditions> The reaction temperature of the phenoxy resin is carried out within a temperature range in which the reaction catalyst does not decompose. The reaction temperature may be appropriately selected from the viewpoints of pressure conditions, the desired molecular weight, and suppression of side reactions, and is, for example, preferably 50 to 300°C, more preferably 100 to 250°C, and particularly preferably 120 to 200°C. From the viewpoint of reaction rate, a temperature of 120°C or higher is suitable, and from the viewpoint of suppressing side reactions, a temperature of 200°C or higher is suitable. When a low-boiling-point solvent is used as the solvent, the reaction temperature can be ensured by carrying out the reaction under high pressure using an autoclave.

[0092] The reaction time is not particularly limited and may be appropriately selected from the viewpoint of achieving the desired molecular weight and suppressing side reactions, and may be, for example, 2 to 10 hours.

[0093] [Application] The thermosetting resin composition of the present invention has both insulating reliability and thermal conductivity, and a resin sheet containing the composition can be suitably used for printed wiring boards such as heat dissipation substrates on which semiconductor wafers, high-brightness LEDs, power semiconductor devices, etc. are mounted. [Example]

[0094] Next, the present invention will be specifically described with reference to Examples and Comparative Examples. In the following, "parts" and "%" are based on mass unless otherwise specified. Under the conditions shown below, a phenoxy resin, a resin sheet obtained using the phenoxy resin, and a metal base substrate were prepared, and measurements or calculations were performed under the following conditions for evaluation.

[0095] <Measurement of melt viscosity> The melt viscosity at 150°C was measured using the following equipment in accordance with ASTM D4287. Equipment name: MODEL CV-1S manufactured by Codex Co., Ltd.

[0096] <Heat resistance> For the obtained resin, after measuring the exothermic peak temperature (thermosetting temperature) observed when measured using a DSC apparatus (Pyris Diamond) manufactured by PerkinElmer under a temperature increase condition of 20°C / min from room temperature, it was held at a temperature 50°C higher than that for 30 minutes. Then, the sample was cooled to room temperature under a temperature decrease condition of 20°C / min, and further heated under a temperature increase condition of 20°C / min again to measure the glass transition temperature (Tg) (°C) of the resin film (cured product). Note that as the glass transition temperature (Tg), if it is 170°C or higher, there is no practical problem, preferably 190°C or higher, more preferably 200°C or higher.

[0097] <GPC measurement (evaluation of the weight average molecular weight (Mw) of the curable resin)> Using the following measuring device and measuring conditions, a GPC chart of the curable resin obtained by the synthesis method shown below was obtained. From the results of the GPC chart, the weight average molecular weight (Mw) of the curable resin was calculated.

[0098] Measuring device: "HLC-8320 GPC" manufactured by Tosoh Corporation Column: Guard column "HXL-L" manufactured by Tosoh Corporation + "TSK-GEL G2000HXL" manufactured by Tosoh Corporation + "TSK-GEL G2000HXL" manufactured by Tosoh Corporation + "TSK-GEL G3000HXL" manufactured by Tosoh Corporation + "TSK-GEL G4000HXL" manufactured by Tosoh Corporation Detector: RI (differential refractometer) Data processing: Tosoh Corporation's "GPC Workstation EcoSEC-WorkStation" Measurement conditions: Column temperature 40°C Developing solvent: Tetrahydrofuran Flow rate 1.0ml / min Standard: The following monodisperse polystyrenes with known molecular weights were used in accordance with the measurement manual for the GPC Workstation EcoSEC-WorkStation.

[0099] (Polystyrene used) Tosoh Corporation "A-500" Tosoh Corporation "A-1000" Tosoh Corporation "A-2500" Tosoh Corporation "A-5000" "F-1" manufactured by Tosoh Corporation "F-2" manufactured by Tosoh Corporation "F-4" manufactured by Tosoh Corporation "F-10" manufactured by Tosoh Corporation "F-20" manufactured by Tosoh Corporation "F-40" manufactured by Tosoh Corporation "F-80" manufactured by Tosoh Corporation Tosoh Corporation "F-128" Sample: A tetrahydrofuran solution of 1.0 mass % of the curable resin obtained in the synthesis example (solid content equivalent) filtered through a microfilter (50 μl)

[0100] [Synthesis of phenoxy resin] [Synthesis Example 1] 14.52 parts of 3,3',5,5'-tetramethyl-4,4'-biphenol (Tokyo Chemical Industry Co., Ltd.), 80 parts of epichlorohydrin (Sigma-Aldrich), 0.65 parts of benzyltriethylammonium chloride (Tokyo Chemical Industry Co., Ltd.), and 10 parts of isopropanol were added to a reaction vessel and heated with stirring at 90°C for 6 hours. Then, 8 g of 40% sodium hydroxide solution was added dropwise and stirred for 1 hour. The resulting mixture was cooled to room temperature and then added to pure water to obtain a precipitate. The resulting precipitate was washed with water and dried to obtain 3,3',5,5'-tetraglycidyloxybiphenyl.

[0101] 59 parts of the obtained 3,3',5,5'-tetraglycidyloxybiphenyl, 35 parts of 1,1'-biphenyl-2,4,4'-triol, 0.05 parts of triphenylphosphine (TPP), and 6 parts of cyclohexanone were added to a reactor and melt-mixed at 100 to 110°C for 1 hour. The mixture was then heated to 150°C and reacted at that temperature while removing the solvent under reduced pressure. Once the target molecular weight was confirmed by GPC, the reaction was terminated to obtain phenoxy resin 1. The reaction was carried out for 16 hours. After the reaction, 100 parts of cyclohexanone were added relative to the resin to dissolve the resin, and the resin was cooled to room temperature. After cooling, the mixture was purified by reprecipitation using methanol to obtain 113 parts of phenoxy resin 1. The weight average molecular weight (Mw) of the phenoxy resin 1 was measured by GPC and was found to be 3500 in terms of standard polystyrene, and its Tg was 180°C.

[0102] [Synthesis Example 2] Except for changing 3,3',5,5'-tetramethyl-4,4'-biphenol to 4,4'-biphenol, 112 parts of phenoxy resin 2 was obtained by the same synthesis method as in Synthesis Example 1. The weight average molecular weight (Mw) of the phenoxy resin 2 measured by GPC was 4000 in terms of standard polystyrene, and the Tg was 180°C.

[0103] [Preparation of Resin Composition] [Examples 1 to 5, Comparative Examples 1 and 2] Using the phenoxy resin obtained in the above Synthesis Example and the following materials, a resin composition was prepared according to the formulation shown in Table 1. As the phenoxy resin for the comparative example, YP50 (a phenoxy resin manufactured by Nippon Steel Material & Chemical Co., Ltd.) was used.

[0104] The fillers used were as follows: HP40MF100 (lump boron nitride, JFE Mineral Co., Ltd.) DAW-15 (spherical alumina, Denka Corporation) Alumina 1 (polyhedral alumina, DIC Corporation) AO502 (spherical alumina, Admatechs Co., Ltd.)

[0105] The epoxy resins used were as follows: 850 (DIC Corporation, bisphenol A epoxy resin) NC-3000 (Phenol biphenyl aralkyl epoxy resin, manufactured by Nippon Kayaku Co., Ltd.) VG-3101 (Printec Co., Ltd., trifunctional epoxy resin)

[0106] As other components, the following curing agent, curing accelerator, dispersant, and coupling agent were used. Dicyandiamide (Nippon Carbide Corporation, hardener) 2E4MZ (Shikoku Chemicals, hardening accelerator) BYK-W903 (dispersant, manufactured by Big Chemie Japan) KBE-403 (Shin-Etsu Chemical Co., Ltd., coupling agent, γ-glycidoxypropyltriethoxysilane)

[0107] [Table 1]

[0108] [Fabrication of Metal Base Substrate] The resulting resin composition was kneaded in a planetary mixer and mixed with a specified amount of solvent (toluene) to obtain a varnish with a viscosity of 3000 mPa·s. This varnish was then applied to a 75 μm thick polyethylene terephthalate (PET) film and dried by heating at 130°C for 8 minutes, forming a 120 μm thick resin sheet in a B-stage state on one side of the carrier material.

[0109] One of the obtained resin sheets was stacked, and 18 μm of copper foil was placed on top of the coated sheet and 1 mm of aluminum plate. The resulting mixture was heated and pressurized in a vacuum at a heating temperature of 175°C and a pressure of 2.94 MPa for 30 minutes to produce a metal base substrate.

[0110] <Thermal conductivity> The resulting resin sheet was heated and pressurized in a vacuum at 175°C and 2.94 MPa for 90 minutes to obtain a 1 mm thick cured sheet. The thermal diffusivity and specific heat of the cured sheet were measured at 25°C using a thermal conductivity measuring device (LFA467 HyperFlash, manufactured by NETZSCH). The density of the heat dissipation member was then measured using the Archimedes method. The thermal conductivity of the heat dissipation member was estimated from the product of the obtained thermal diffusivity, specific heat, and density.

[0111] <90 degree peel strength evaluation> The copper foil peel strength of the obtained metal base substrate was measured in accordance with JIS C 6481. An "Autograph" manufactured by Shimadzu Corporation was used as the peel strength measuring device. The copper foil peel strength was measured for 20 test samples. The average value of the measured copper foil peel strength for the 20 test samples was taken as the 90-degree peel strength.

[0112] <Evaluation of insulation reliability> The copper foil on the obtained metal base substrate was etched to pattern the copper foil into a circle with a diameter of 2.5 cm, thereby obtaining a test sample. Using a voltage resistance tester (YST-243AT-100, manufactured by Yamayo Test Instruments Co., Ltd.), an AC voltage was applied at a temperature of 25°C so that the voltage increased in the through-layer direction at a rate of 0.5 kV / sec. The voltage at which a current of 10 mA flowed through the test sample was taken as the breakdown voltage. The breakdown voltage was normalized by dividing it by the thickness of the test sample to calculate the breakdown strength, which was then evaluated as insulation reliability.

[0113] [Table 2]

[0114] Furthermore, the resin composition of the present invention has excellent heat resistance and peel strength, making it possible to produce thin resin sheets, and as a result, it is possible to obtain a metal base substrate by laminating multiple resin sheets and making the total thickness of the resin sheets 80 to 120 μm.

[0115] [Examples 6 to 8, Comparative Example 3] The resin compositions of Examples 1, 3, and 4 and Comparative Example 1 were kneaded in a planetary mixer and mixed with a predetermined amount of solvent (toluene) to obtain a varnish with a viscosity adjusted to 3000 mPa·s. Next, this varnish was applied to a 75 μm thick polyethylene terephthalate (PET) film and dried by heating at 130°C for 8 minutes, forming a 60 μm thick resin sheet in a B-stage state on one side of the carrier material.

[0116] Two of the resin sheets were stacked, and 18 μm of copper foil was placed on the coated sheet and 1 mm of aluminum plate. The resulting mixture was heated and pressurized in a vacuum at a heating temperature of 175°C and a pressure of 2.94 MPa for 30 minutes to produce a metal base substrate.

[0117] The evaluation results are shown in Table 3. It was found that even when the same resin composition was used and the same thickness was used, the metal base substrate with two layers bonded together had further improved thermal conductivity and insulation reliability. Note that a thin resin sheet could not be produced from the resin sheet of Comparative Example 3.

[0118] [Table 3]

Claims

1. (A) a phenoxy resin; (B) an inorganic filler which is alumina and / or block boron nitride; and (C) a curing agent; The thermosetting resin composition, wherein (A) is a phenoxy resin obtained by reacting a compound represented by the following general formula (1) with a compound represented by the following general formula (2): 【Chemistry 1】 (In the formula, each R1 independently represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.) 【Chemistry 2】 (In the formula, n and m are each independently an integer of 1 to 3, and n+m is 3 or more and 10 or less.)

2. 2. The thermosetting resin composition according to claim 1, wherein (B) contains at least block boron nitride having an average particle size of 10 to 80 μm and alumina having an average particle size of 25 μm or less.

3. The thermosetting resin composition according to claim 1 or 2, wherein the alumina is spherical.

4. A varnish containing the thermosetting resin composition according to claim 1 or 2.

5. A resin sheet comprising a carrier material and a varnish layer, wherein the varnish layer is the varnish according to claim 4, and the varnish layer has a thickness of 30 to 200 μm in an uncured state.

6. A metal base substrate comprising the resin sheet according to claim 5 as an insulating layer.

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