Phenoxy resin

Abstract

To provide a resin excellent in thermal conductivity, solvent solubility and heat resistance.SOLUTION: The phenoxy resin is obtained by reacting a compound represented by general formula (1) with a compound represented by general formula (2).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a novel phenoxy resin. [Background technology]

[0002] In recent years, as electronic devices have become smaller and more powerful, heat dissipation measures for these devices have become an issue, and the development of various thermally conductive materials is progressing.The thermally conductive materials being developed can be broadly divided into fillers and resins, with alumina and magnesium oxide being known as fillers, and biphenyl-type epoxy resin and phenoxy resin being known as resins.

[0003] Patent Document 1 discloses an encapsulating resin composition containing an epoxy resin and an inorganic filler, which is molded using a transfer molding machine at a mold temperature of 175°C, an injection pressure of 7.4 MPa, and a curing time of 2 minutes to produce a molded product measuring 4 mm wide, 3 mm thick, and 15 mm long, and then post-cured at 175°C for 4 hours. The cured product has a glass transition temperature of 140°C to 270°C as measured by thermomechanical analysis, and a flexural modulus (E260) of 0.1 GPa to 5 GPa at 260°C. The epoxy resin is described as a biphenyl-type epoxy resin represented by general formula (1):

[0004] Patent Document 2 discloses a phenoxy resin containing a specific repeating unit. It is described as having a specific structure with a novel structure (mesogenic structure) having an ester bond between two benzene rings. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-151691 [Patent Document 2] Patent Publication No. 2021-098836 Summary of the Invention [Problem to be solved by the invention]

[0006] However, although evaluations have shown that the resin composition described in Patent Document 1 has excellent crack resistance, there is no mention whatsoever of its thermal conductivity, and there is still room for further investigation.

[0007] Furthermore, the phenoxy resin described in Patent Document 2 is insufficient in terms of heat resistance, and further improvement is required for electronic substrates and the like used in high-temperature environments. Furthermore, the solvent solubility of the resulting phenoxy resin is low, which affects processability.

[0008] In view of the above, an object of the present invention is to provide a resin that is excellent in thermal conductivity, solvent solubility, and heat resistance. [Means for solving the problem]

[0009] The present inventors have found that the above problems can be solved by using a novel phenoxy resin having a specific structure.

[0010] (1) 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):

[0011] [ka] (In the formula, each R1 independently represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.)

[0012] [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 phenoxy resin according to (1) above, wherein the general formula (2) is a compound represented by the following general formula (3):

[0013] [ka] (3) The phenoxy resin according to (1) or (2) above, wherein R1 in the general formula (1) is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. (4) The phenoxy resin according to any one of (1) to (3) above, having a weight-average molecular weight of 2,000 to 30,000. (5) The phenoxy resin according to any one of (1) to (4) above, having an epoxy equivalent of 300 g / eq to 6,000 g / eq. (6) A resin composition containing the phenoxy resin according to any one of (1) to (5) above. [Effects of the Invention]

[0014] According to the present invention, a novel phenoxy resin having high thermal conductivity, high solvent solubility and high heat resistance can be provided. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail.

[0016] [Phenoxy resin] The phenoxy resin of the present invention 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).

[0017] [ka]

[0018] In general formula (1), each R1 independently represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0019] [ka]

[0020] 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.

[0021] The hydrocarbon group having 1 to 10 carbon atoms is not particularly limited, but examples thereof include alkyl groups having 1 to 10 carbon atoms. Of these, alkyl groups having 1 to 4 carbon atoms are preferred, and methyl groups are particularly preferred. The above substituents are preferred from the viewpoint of heat resistance and discoloration resistance.

[0022] The general formula (1) is not particularly limited, but from the viewpoint of the solvent solubility of the resulting phenoxy resin, a compound represented by the following general formula (3) is more preferred.

[0023] [ka]

[0024] The weight-average molecular weight (Mw) of the phenoxy resin of the present invention 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 keeping the Mw within this range, the phenoxy resin can have excellent thermal conductivity and solvent solubility.

[0025] The epoxy equivalent of the phenoxy resin of the present invention is preferably 300 g / eq or more and 6,000 g / eq or less, more preferably 350 g / eq or more and 5,000 g / eq or less, and particularly preferably 400 g / eq or more and 4,500 g / eq or less. Having the epoxy equivalent within this range is preferable because the thermal conductivity and solvent solubility of the phenoxy resin in the resulting resin composition are improved.

[0026] 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.

[0027] [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).

[0028] <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.

[0029] <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.

[0030] The reaction can be carried out using the compound and a reaction catalyst in the absence or presence of a solvent.

[0031] <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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] Examples of the quaternary ammonium salt include tetramethylammonium hydroxide, benzyltributylammonium chloride, and tetrabutylammonium chloride.

[0036] 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.

[0037] Specific examples of the imidazoles include 2-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenylimidazole.

[0038] 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.

[0039] 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.

[0040] <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.

[0041] 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.

[0042] Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, acetylacetone, diisobutyl ketone, isophorone, methylcyclohexanone, and acetophenone.

[0043] 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;

[0044] ethylene glycol monoalkyl ether acetates such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, and ethylene glycol monobutyl ether acetate;

[0045] 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;

[0046] 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.

[0047] 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.

[0048] Examples of the ester solvent include ethyl acetate, n-propyl acetate, isopropyl acetate, and n-butyl acetate.

[0049] Examples of the other polar solvents include dimethyl sulfoxide, sulfolane, and γ-butyrolactone.

[0050] <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 achieving the desired molecular weight and suppressing 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 solvent is used as the solvent, the reaction temperature can be ensured by carrying out the reaction under high pressure using an autoclave.

[0051] 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.

[0052] The phenoxy resin of the present invention can also be synthesized by reacting a compound represented by the following general formula (4) with a compound represented by the following general formula (5).

[0053] [ka]

[0054] In the general formula (4), n and m each independently represent an integer of 1 to 3, n+m being 3 or more and 10 or less, and R represents a glycidyl ether group.

[0055] [ka]

[0056] In the general formula (5), each R1 independently represents a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms.

[0057] <Compound of general formula (4)> Examples of the compound represented by the general formula (4) include 2,3,4-triglycidyloxybiphenyl, 2,3,5-triglycidyloxybiphenyl, 2,3,6-triglycidyloxybiphenyl, 2,4,5-triglycidyloxybiphenyl, 2,4,6-triglycidyloxybiphenyl, 3,4,5-triglycidyloxybiphenyl, 2,2',3-triglycidyloxybiphenyl, 2,2',4-triglycidyloxybiphenyl, 2,2',5-triglycidyloxybiphenyl, and 2,2',6-triglycidyloxybiphenyl. , 2,3',4'-triglycidyloxybiphenyl, 2,3',5'-triglycidyloxybiphenyl, 2,3,3'-triglycidyloxybiphenyl, 2,3',4-triglycidyloxybiphenyl, 2,3',5-triglycidyloxybiphenyl, 2,3',6-triglycidyloxybiphenyl, 3,3',4-triglycidyloxybiphenyl, 3,3',5-triglycidyloxybiphenyl, 2,3,4'-triglycidyloxybiphenyl, 2,4,4'-triglycidyloxybiphenyl, 2,4',5-triglycidyloxybiphenyl Sibiphenyl, 2,4',6-triglycidyloxybiphenyl, 3,4,4'-triglycidyloxybiphenyl, 3,4',5-triglycidyloxybiphenyl, 2,3,4,5-tetraglycidyloxybiphenyl, 2,3,4,6-tetraglycidyloxybiphenyl, 2,3,5,6-tetraglycidyloxybiphenyl, 2,2',3,4-tetraglycidyloxybiphenyl, 2,2',3,5-tetraglycidyloxybiphenyl, 2,2',3,6-tetraglycidyloxybiphenyl, 2,2',4,5-tetraglycidyloxy Biphenyl, 2,2',4,6-tetraglycidyloxybiphenyl, 2,3',4',5'-tetraglycidyloxybiphenyl, 2,3,3',4-tetraglycidyloxybiphenyl, 2,3,3',5-tetraglycidyloxybiphenyl, 2,3,3',6-tetraglycidyloxybiphenyl, 2,3',4,5-tetraglycidyloxybiphenyl, 2,3',4,6-tetraglycidyloxybiphenyl, 3,3',4,5-tetraglycidyloxybiphenyl, 2,3,4,4'-tetraglycidyloxybiphenyl, 2,3,4',5-tetraglycidyloxybiphenyl, 2,3,4',6-tetraglycidyloxybiphenyl, 2,4,4',5-tetraglycidyloxybiphenyl, 2,4,4',6-tetraglycidyloxybiphenyl, 3,4,4',5-tetraglycidyloxybiphenyl, 2,2',3,3'-tetraglycidyloxybiphenyl, 2,2',3,4'-tetraglycidyloxybiphenyl, 2,2',3,5'-tetraglycidyloxybiphenyl, 2,2',3,6'-tetraglycidyloxybiphenyl, 2,3,3',4'-tetraglycidyloxybiphenyl, 2,3,3',5'-tetraglycidyloxybiphenyl, 2,2',4,4'-tetraglycidyloxybiphenyl, 2,2',4,5'-tetraglycidyloxybiphenyl, 2,2',4,6' 2,3',4,4'-tetraglycidyloxybiphenyl, 2,3',4,5'-tetraglycidyloxybiphenyl, 2,2',5,5'-tetraglycidyloxybiphenyl, 2,2',5,6'-tetraglycidyloxybiphenyl, 2,3',4',5-tetraglycidyloxybiphenyl, 2,3',5,5'-tetraglycidyloxybiphenyl, 2,2',6,6'-tetraglycidyloxybiphenyl, 2,3',4',6-tetraglycidyloxybiphenyl, 2,3',5',6-tetraglycidyloxybiphenyl, 3,3',4,4'-tetraglycidyloxybiphenyl, 3,3',4,5'-tetraglycidyloxybiphenyl, and 3,3',5,5'-tetraglycidyloxybiphenyl. Among these, since a structure with high molecular orientation is advantageous for increasing the thermal conductivity of phenoxy resins, 2,4,4'-triglycidyloxybiphenyl, 2,4,4',6-tetraglycidyloxybiphenyl, and 2,2',4,4'-tetraglycidyloxybiphenyl, which have substituents at the 4,4' positions, and 2,4',6-triglycidyloxybiphenyl, 3,4',5-triglycidyloxybiphenyl, 2,2',5,5'-tetraglycidyloxybiphenyl, and 3,3',5,5'-tetraglycidyloxybiphenyl, which have excellent molecular symmetry, are preferred.

[0058] <Compound of general formula (5)> Examples of the compound represented by the general formula (5) include biphenol, methylbiphenol, ethylbiphenol, butylbiphenol, etc. Among these, biphenol and methylbiphenol are more preferred from the viewpoint of maintaining molecular orientation and improving thermal conductivity.

[0059] [Resin composition] The resin composition of the present invention preferably contains the phenoxy resin, which is preferable because the excellent solvent solubility of the phenoxy resin improves the handleability of the resin composition, and also because the resin composition, when made into a resin sheet or a metal base substrate, has excellent thermal conductivity and heat resistance.

[0060] The phenoxy resin is more preferably 0.3% by mass or more and 30% by mass or less relative to the nonvolatile content (100% by mass) of the resin composition not including the filler described below.

[0061] The resin composition may contain a thermally conductive filler. The thermally conductive filler may contain, for example, at least one selected from alumina, aluminum nitride, boron nitride, silicon nitride, silicon carbide, and magnesium oxide. These may be used alone or in combination of two or more.

[0062] The resin composition may contain a silane coupling agent, which can improve the compatibility of the thermally conductive filler in the resin composition. The coupling agent may be added to the resin composition, or may be used by treating the surface of the thermally conductive filler.

[0063] The resin composition may contain other components in addition to the above-mentioned components, such as an antioxidant and a leveling agent.

[0064] The resin composition may contain a low-molecular-weight component produced during the production of the phenoxy resin. The low-molecular-weight component is a component having a weight-average molecular weight Mw of 1,000 or less, such as an unreacted compound represented by general formula (1) or (2) or a reaction product thereof, the weight-average molecular weight of which is within the above range.

[0065] The lower the content of the low-molecular-weight component, the more improved the thermal conductivity 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.

[0066] 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.

[0067] 〔varnish〕 The 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.

[0068] As the solvent, for example, polar solvents such as methyl ethyl ketone, methoxypropanol, N,N-dimethylformamide, dimethyl sulfoxide, etc. can be used, and the solvents may be used alone or in combination of two or more.

[0069] 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.

[0070] [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.

[0071] 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 an inorganic composite 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.

[0072] 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.

[0073] 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.

[0074] [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.

[0075] [Application] The phenoxy resin of the present invention combines thermal conductivity, solvent solubility, and heat resistance, and resin sheets and metal base substrates containing them can be suitably used for printed wiring boards such as heat dissipation substrates for mounting semiconductor wafers, high-brightness LEDs, power semiconductor devices, etc. [Example]

[0076] The present invention will now be described in detail with reference to examples and comparative examples, in which "parts" and "%" are by mass unless otherwise specified. Phenoxy resins, and resin sheets and metal base substrates obtained using the phenoxy resins were prepared under the conditions shown below, and measurements or calculations were performed and evaluations were carried out under the conditions shown below.

[0077] The present invention will now be described in detail with reference to examples and comparative examples. In the following, "parts" and "%" are by mass unless otherwise specified. Phenoxy resins and resin molded articles obtained using the phenoxy resins were prepared under the conditions shown below, and measurements or calculations were performed and evaluations were carried out under the conditions shown below.

[0078] <Heat resistance> The resulting resin was measured using a PerkinElmer DSC (Pyris Diamond) at a temperature increase of 20°C / min from room temperature to determine the exothermic peak temperature (thermosetting temperature), and then held at a temperature 50°C higher than that for 30 minutes. The sample was then cooled to room temperature at a temperature decrease rate of 20°C / min, and then heated again at a temperature increase rate of 20°C / min to measure the glass transition temperature (Tg) (°C) of the resin film (cured product). A glass transition temperature (Tg) of 170°C or higher is practically acceptable, preferably 190°C or higher, and more preferably 200°C or higher.

[0079] <Solvent solubility> 8 g of each resin from each example and comparative example and methyl ethyl ketone were added to a sample bottle to a solution concentration of 20%, and then stirred at room temperature using a shaker. After stirring, the state of the solvent in the sample bottle was visually evaluated. The evaluation was as follows: a uniform, transparent state was evaluated as "○", a state in which some solid components had precipitated was evaluated as "△", and a state in which solid components had precipitated was evaluated as "×".

[0080] (thermal conductivity) -Making resin molded products A mixture of 100 parts of phenoxy resin and 2 parts of catalyst (2-methylimidazole) The mixture was placed in a mold coated with a release agent and compression molded at 180°C for 30 minutes. After that, a resin molded product with a diameter of 10 mm and a thickness of 1 mm was obtained. The mixture was cured for 180 minutes to obtain a resin molded body (a sample for measuring thermal conductivity).

[0081] The thermal diffusivity and specific heat of the obtained resin molded body were measured at 25°C using a thermal conductivity measuring device (LFA467 HyperFlash, manufactured by NETZSCH). Next, the density of this heat dissipation member was measured by Archimedes' method. The thermal conductivity of this heat dissipation member was estimated from the product of the obtained thermal diffusivity, specific heat, and density.

[0082] <GPC Measurement (Evaluation of Weight-Average Molecular Weight (Mw) of Curable Resin)> Using the following measuring device and measurement conditions, the 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.

[0083] 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 GG2000HXL" manufactured by Tosoh Corporation + "TSK-GEL G3000HXL" manufactured by Tosoh Corporation + "TSK-GEL G4000HXL" manufactured by Tosoh Corporation Detector: RI (Differential Refractometer) Data processing: "GPC Workstation EcoSEC-WorkStation" manufactured by Tosoh Corporation Measurement conditions: Column temperature 40°C Developing solvent: Tetrahydrofuran Flow rate: 1.0 ml / min Standard: In accordance with the measurement manual of the "GPC Workstation EcoSEC-WorkStation", the following monodisperse polystyrenes with known molecular weights were used.

[0084] (Polystyrene used) "A-500" manufactured by Tosoh Corporation "A-1000" manufactured by Tosoh Corporation "A-2500" manufactured by Tosoh Corporation "A-5000" manufactured by Tosoh Corporation "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 "F-128" manufactured by Tosoh Corporation 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)

[0085] 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'-tetramethyl-4,4'-bis(glycidyloxy)-1,1'-biphenyl.

[0086] 59 parts of the obtained 3,3',5,5'-tetramethyl-4,4'-bis(glycidyloxy)-1,1'-biphenyl, 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 was 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 measured by GPC was 3500 in terms of standard polystyrene, the Tg was 180° C., and the solvent solubility was “good.” The thermal conductivity was 0.4.

[0087] Example 2 112 parts of phenoxy resin 2 were obtained by the same synthesis method as in Example 1, except that 3,3',5,5'-tetramethyl-4,4'-biphenol was replaced with 4,4'-biphenol. The weight-average molecular weight (Mw) of the phenoxy resin 2 measured by GPC was 4000 in terms of standard polystyrene, the Tg was 180°C, and the solvent solubility was "good." The thermal conductivity was 0.4.

[0088] Example 3 Phenoxy resin 3 can be obtained by the same synthesis method as in Example 1, except that 1,1'-biphenyl-2,4,4'-triol is replaced with 1,1'-biphenyl-3,4,4'-triol. The weight-average molecular weight (Mw), Tg, and solvent solubility of the phenoxy resin 3 are expected to be similar to those of Example 1, since only the substituent positions are changed. On the other hand, the thermal conductivity is expected to be less than 0.4 depending on the substituent positions.

[0089] Example 4 2,6-Diethylphenol (Merck) is dissolved in methylene chloride, Cu-TMEDA (Merck) is added, and the mixture is stirred at room temperature for 2 hours. The resulting reaction product is extracted with ethyl acetate and purified to obtain di-2,6-diethylphenol. Phenoxy resin 4 can be obtained by the same synthesis method as in Example 1, except that 3,3',5,5'-tetramethyl-4,4'-biphenol is replaced with di-2,6-diethylphenol. Based on the size of the substituent, it is expected that the Tg and thermal conductivity will be low.

[0090] Example 5 Phenoxy resin 5 can be obtained by the same synthesis method as in Example 4, except that 2,6-di-t-butylphenol (manufactured by Sigma-Aldrich) is used instead of 2,6-di-ethylphenol (manufactured by Merck). The Tg of phenoxy resin 6 is expected to be the lowest and have the lowest thermal conductivity due to the bulky substituents.

[0091] Comparative Example 1 Phenoxy resin 6 was obtained by the same synthesis method as in Example 1, except that 1,1'-biphenyl-2,4,4'-triol was replaced with 1,1'-biphenyl-4,4'-triol. The Tg of the phenoxy resin 6 was 150°C, the solvent solubility was "△", and the thermal conductivity was 0.25.

Claims

1. 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. The phenoxy resin according to claim 1, wherein the compound represented by the general formula (2) is a compound represented by the following general formula (3): 【Transformation 3】

3. The phenoxy resin according to claim 1 or 2, wherein R1 in the general formula (1) is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

4. The phenoxy resin according to claim 1 or 2, having a weight average molecular weight of 2,000 to 30,000.

5. 3. The phenoxy resin according to claim 1, wherein the epoxy equivalent is from 300 g / eq to 6,000 g / eq.

6. A resin composition comprising the phenoxy resin according to claim 1 or 2.

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