Epoxy resin composition and cured product

Abstract

To provide an epoxy resin composition which has excellent moldability, high thermal conductivity when combined with an inorganic filler, and gives a molded article low thermal expansion property, excellent heat resistance, moisture resistance and flame retardancy, and to provide a cured molded article using the epoxy resin composition.SOLUTION: There is provided an epoxy resin composition containing an epoxy resin and a curing agent, or an additional inorganic filler as main components, in which the epoxy resin composition is obtained by using an epoxy resin having a benzonitrile structure as the epoxy resin component in an amount of 50 wt.% or more in the epoxy resin component, and a bifunctional phenolic compound as a curing agent component in an amount of 50 wt.% or more in the curing agent component.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an epoxy resin composition useful as an insulating material for electrical and electronic materials such as semiconductor encapsulation, laminates, and heat dissipation substrates with excellent reliability, and a cured product using the same.

Background Art

[0002] Conventionally, as a method for encapsulating electrical and electronic components such as diodes, transistors, and integrated circuits, and semiconductor devices, for example, an encapsulation method using an epoxy resin or a silicon resin, or a hermetic sealing method using glass, metal, ceramic, etc. has been adopted. In recent years, resin encapsulation by transfer molding, which enables mass production with improved reliability and has cost advantages, has become the mainstream.

[0003] In the resin composition used for resin encapsulation by transfer molding, an encapsulation material composed of an epoxy resin and a resin composition mainly composed of a phenolic resin as a curing agent is generally used.

[0004] The epoxy resin composition used for the purpose of protecting elements such as power devices is filled with an inorganic filler such as crystalline silica at a high density in order to cope with a large amount of heat released by the elements.

[0005] Power devices include those composed of a one-chip incorporating IC technology and those that are modularized, and further improvement in heat dissipation, heat resistance, and thermal expansion of the encapsulation material is desired.

[0006] In order to meet these requirements, attempts have been made to contain inorganic fillers such as crystalline silica, silicon nitride, aluminum nitride, and spherical alumina powder having high thermal conductivity in order to improve the thermal conductivity (Patent Documents 1 and 2). However, when the content of the inorganic filler is increased, the fluidity decreases along with the increase in viscosity during molding, and there is a problem that the moldability is impaired. Therefore, there is a limit to the method of simply increasing the content of the inorganic filler.

[0007] From the above background, methods for improving the thermal conductivity of the composition by increasing the thermal conductivity of the matrix resin itself have also been studied. For example, Patent Documents 3, 4, and 5 propose liquid crystalline epoxy resins having a rigid mesogenic group and epoxy resin compositions using the same. However, as the curing agent used in these epoxy resin compositions, an aromatic diamine compound is used, and there are limitations in increasing the filling rate of the inorganic filler, and there are also problems in terms of electrical insulation. In addition, when an aromatic diamine compound is used, although the liquid crystallinity of the cured product can be confirmed, the crystallinity of the cured product is low, and it is not sufficient in terms of high thermal conductivity, low thermal expansion, low moisture absorption, etc. Furthermore, in order to develop liquid crystallinity, it is necessary to apply a strong magnetic field to orient the molecules, and there are significant equipment constraints for widespread industrial use. In addition, in the blending system with the inorganic filler, the thermal conductivity of the inorganic filler is overwhelmingly larger than that of the matrix resin, and even if the thermal conductivity of the matrix resin itself is increased, it does not significantly contribute to the improvement of the thermal conductivity of the composite material, and a sufficient thermal conductivity improvement effect has not been obtained.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0009] Accordingly, an object of the present invention is to solve the above problems, provide an epoxy resin composition that has excellent moldability, high thermal conductivity when compounded with an inorganic filler, and is excellent in low thermal expansion, heat resistance, moisture resistance, and further flame retardancy, and further provide a molded article using the same.

Means for Solving the Problems

[0010] The present inventors have found that when an epoxy resin having a benzonitrile structure is combined with a specific bifunctional curing agent in which the reaction proceeds two-dimensionally, physical properties such as thermal conductivity, heat resistance, and low thermal expansion are specifically improved, and the present invention has been achieved. Regarding this, in conventional resins, when a rigid structure typified by a biphenyl skeleton is introduced, physical properties such as thermal conductivity and heat resistance are improved, but there are handling problems such as an increase in the melting point of the resin, a decrease in compatibility with a curing agent, etc., and a decrease in solvent solubility. Therefore, in the present invention, attention is paid to the fact that by adopting a benzonitrile structure in which a highly polar nitrile group is introduced, even when a rigid structure is introduced, the increase in melting point is suppressed, and compatibility with a curing agent, solvent solubility, etc. can be ensured. Furthermore, it is also noted that the nitrile group does not significantly inhibit the molecular packing sterically and does not impair the improvement effects of thermal conductivity, heat resistance, etc. derived from the rigid structure.

[0011] The present invention relates to an epoxy resin composition mainly composed of an epoxy resin and a curing agent, or these and an inorganic filler, wherein 50 mass (wt)% or more of the epoxy resin has an epoxy resin having a benzonitrile structure, and 50 wt% or more of the curing agent is a bifunctional phenolic compound.

[0012] The epoxy resin having the above benzonitrile structure is represented by the following formula (1).

Chemical formula

[0013] As the above bifunctional phenolic compound, preferably, at least one bifunctional phenolic compound selected from the group consisting of hydroquinone, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenyl sulfone, dihydroxydiphenylmethanes, and naphthalenediols is preferably mentioned.

[0014] The epoxy resin composition of the present invention can contain an inorganic filler, and in this case, it is preferable to contain 50 to 96 wt% of the inorganic filler in the epoxy resin composition. Further, as the inorganic filler, spherical alumina is preferably mentioned, and the usage amount thereof is preferably 50 wt% or more of the inorganic filler.

[0015] The epoxy resin composition of the present invention is suitable as an epoxy resin composition for electronic materials, particularly for encapsulants or insulating substrates.

[0016] Furthermore, the present invention is a cured molded article (hereinafter, sometimes simply referred to as "cured product") characterized by being obtained by reacting and molding and curing the above epoxy resin composition.

[0017] The above cured molded article preferably has a thermal conductivity of 4 W / m·K or more. Furthermore, for this cured molded article, the melting point peak in differential scanning calorimetry is preferably in the range of 120°C to 280°C, and the endothermic amount in terms of resin components in the thermal analysis is preferably 5 J / g or more.

Advantages of the Invention

[0018] The epoxy resin composition of the present invention is excellent in moldability and reliability, and provides a cured molded product excellent in high thermal conductivity, low water absorption, low thermal expansion, high heat resistance, and flame retardancy. It is suitably applied as an insulating material for electrical and electronic materials such as semiconductor encapsulation, laminates, and heat dissipation substrates, and exhibits excellent high heat dissipation, high heat resistance, flame retardancy, and high dimensional stability. The reason for such specific effects is presumed to be that the rigid structure of the benzonitrile structure and the use of a phenolic compound, particularly a bifunctional phenolic compound, as the curing agent improved the orientation of the resin skeleton.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, the present invention will be described in detail.

[0020] The epoxy resin used in the epoxy resin composition of the present invention contains 50 wt% or more of an epoxy resin having a benzonitrile structure represented by the following formula (1).

Chemical formula

[0021] In formula (1), m independently represents a number from 1 to 3. Preferred structures within the parentheses include a 1,4-phenylene group, a 4,4'-biphenylene group, a 4,4''-p-terphenylen group, and a 4,4''-m-terphenylen group. Particularly preferred are a 1,4-phenylene group or a 4,4'-biphenylene group. A mixture of these structures may also be used.

[0022] n represents a number from 0 to 50, but the preferred value of n varies depending on the application. For example, in the application of semiconductor encapsulants that require a high filling rate of the filler, those with low viscosity are desirable. The value of n is 0 to 5, preferably 0.1 to 2, and more preferably, those with n = 0 account for 50 wt% or more. When the epoxy resin of the present invention is a mixture with different values of n, the number average value of n is 0 to 5, preferably 0.1 to 2, and more preferably, those with n = 0 account for 50 wt% or more, and the number average value of n is 0.1 to 1. These low molecular weight epoxy resins may be crystallized in some cases and used as solids at room temperature. Also, for applications such as printed wiring boards, high molecular weight epoxy resins are preferably used. In this case, the value of n is 5 to 50, preferably 10 to 40, and more preferably 20 to 40. When it is a mixture with different values of n, the number average value of n is also preferably in the above range. In this case, if the number average value is 50 or less, molecules with an integer value of n of 50 or more may be included.

[0023] The production method of the epoxy resin used in the present invention is not particularly limited, but it can be produced by reacting a phenolic compound having a benzonitrile structure of the following formula (2) with epichlorohydrin. This reaction can be carried out in the same manner as a normal epoxidation reaction.

Chemical formula

[0024] In the general formula (2), m is the same as m in the general formula (1). When used as a raw material for the epoxy resin, it may be a single compound or a mixture of multimers of compounds with different values of m.

[0025] Here, regarding the phenolic compound represented by this formula (2), although not limited, for example, with respect to benzonitrile compounds such as 2,4-dichlorobenzonitrile, 2,5-dichlorobenzonitrile, 2,6-dichlorobenzonitrile, 3,5-dichlorobenzonitrile, 2,4-dibromobenzonitrile, 2,5-dibromobenzonitrile, 2,6-dibromobenzonitrile, 3,5-dibromobenzonitrile, etc., it can be obtained by a method of reacting a dihydroxy compound such as hydroquinone, 4,4'-dihydroxybiphenyl, 4,4''-dihydroxyp-terphenyl, 4,4''-dihydroxy-m-terphenyl, etc. in the presence of a basic catalyst.

[0026] The reaction between the phenolic compound of formula (2) and epichlorohydrin is, for example, after dissolving the phenolic compound in an excess of epichlorohydrin, in the presence of an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide, reacting at 50 to 150 °C, preferably in the range of 60 to 100 °C for 1 to 10 hours. The amount of the alkali metal hydroxide used at this time is in the range of 0.8 to 2.0 moles, preferably 0.9 to 1.5 moles, per 1 mole of the hydroxyl group in the dihydroxy form. Epichlorohydrin is used in an excess amount relative to the hydroxyl group in the phenolic compound, and usually, it is 1.5 to 15 moles per 1 mole of the hydroxyl group in the phenolic compound. After the reaction is completed, the excess epichlorohydrin is distilled off, the residue is dissolved in a solvent such as toluene or methyl isobutyl ketone, filtered, washed with water to remove inorganic salts, and then the solvent is distilled off to obtain the target epoxy resin.

[0027] The epoxy resin used in the epoxy resin composition of the present invention can also be synthesized using a mixture of a phenolic compound having a benzonitrile structure and another phenolic compound not having a benzonitrile structure. The mixing ratio of the phenolic compound having a benzonitrile structure in this case is 50 wt% or more. Also, there are no particular restrictions on the other phenolic compound, and it is selected from those having two or more hydroxyl groups in one molecule.

[0028] The epoxy equivalent of the epoxy resin used in the epoxy resin composition of the present invention is usually in the range of 200 to 600. However, from the viewpoints of increasing the filling ratio of the inorganic filler and improving the fluidity, those having low viscosity are preferable, and those having an epoxy equivalent in the range of 200 to 400 are more preferable.

[0029] The epoxy resin having this benzonitrile structure is usually preferably used in a crystalline form at normal temperature. The preferable melting point range is 70°C to 250°C, more preferably 100°C to 200°C. If it is lower than this, blocking etc. is likely to occur and the handleability as a solid may be inferior. If it is higher than this, the compatibility with a curing agent etc. and the solubility in a solvent etc. may decrease.

[0030] The purity of the epoxy resin having this benzonitrile structure, particularly the amount of hydrolyzable chlorine, is preferably less from the viewpoint of improving the reliability of the electronic components to be applied. Although not particularly limited, it is preferably 1000 ppm or less, more preferably 500 ppm or less. The hydrolyzable chlorine referred to in the present invention means a value measured by the following method. That is, after dissolving 0.5 g of the sample in 30 ml of dioxane, 10 ml of 1N-KOH is added and boiled under reflux for 30 minutes, then cooled to room temperature, and further 100 ml of 80% acetone water is added, and it is the value obtained by performing potentiometric titration with a 0.002N-AgNO3 aqueous solution.

[0031] In the epoxy resin composition of the present invention, in addition to the epoxy resin having a benzonitrile structure of formula (1) used as an essential component, other epoxy resins having two or more epoxy groups in the molecule may be used in combination as the epoxy resin component. For example, divalent phenols such as bisphenol A, bisphenol F, 3,3',5,5'-tetramethyl-4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfide, fluorene bisphenol, 2,2'-biphenol, resorcinol, catechol, t-butylcatechol, t-butylhydroquinone, allylated bisphenol A, allylated bisphenol F, allylated phenol novolak, or trivalent or higher phenols such as phenol novolak, bisphenol A novolak, o-cresol novolak, m-cresol novolak, p-cresol novolak, xylenol novolak, poly-p-hydroxystyrene, tris-(4-hydroxyphenyl)methane, 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane, fluoroglycinol, pyrogallol, t-butylpyrogallol, allylated pyrogallol, polyallylated pyrogallol, 1,2,4-benzenetriol, 2,3,4-trihydroxybenzophenone, phenol aralkyl resin, naphthol aralkyl resin, dicyclopentadiene-based resin, or glycidyl ether compounds derived from halogenated bisphenols such as tetrabromobisphenol A. These epoxy resins can be used alone or in combination of two or more. Also, for epoxy resins having a mesogenic group, one or more can be used.

[0032] The compounding ratio of the epoxy resin having a benzonitrile structure of the formula (1) used in the epoxy resin composition of the present invention is 50 wt% or more of the total epoxy resin, preferably 70 wt% or more, more preferably 90 wt% or more. Further, it is desirable that the total amount of the bifunctional epoxy resin is 90 wt% or more, preferably 95 wt% or more. If it is less than this, the effect of improving physical properties such as thermal conductivity when formed into a cured product may be reduced. This is because the higher the content of the epoxy resin having a benzonitrile structure and the higher the content of the bifunctional epoxy resin, the higher the degree of orientation as a molded product.

[0033] As other epoxy resins other than the epoxy resin having a benzonitrile structure of the formula (1), a bisphenol-based epoxy resin represented by the following general formula (3) is preferable.

Chemical formula

[0034] These other epoxy resins can be synthesized, for example, by using hydroquinone, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfide as raw materials and performing a normal epoxidation reaction. These epoxy resins may be synthesized using a mixture with a dihydroxy compound having a mesogenic group at the raw material stage.

[0035] The bifunctional phenolic compound used as a curing agent has two phenolic hydroxyl groups in one molecule and is not particularly limited. For example, bisphenol A, bisphenol F, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl ether, 1,4-bis(4-hydroxyphenoxy)benzene, 1,3-bis(4-hydroxyphenoxy)benzene, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxybiphenyl, 2,2'-dihydroxybiphenyl, 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phosphaphenanthrene-10-oxide, hydroquinone, resorcinol, t-butylhydroquinone, 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 1,8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, and further, bisphenol compounds having a benzonitrile structure of the above formula (2) can be mentioned. Two or more of these may be used.

[0036] As the bifunctional phenolic compound used as a curing agent, those having a mesogenic group are preferably used. Specifically, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ketone, 1,5-naphthalenediol, 2,6-naphthalenediol, 2,7-naphthalenediol, and further, bisphenol compounds having a benzonitrile structure of the above formula (2) can be exemplified. Also, those without a mesogenic group and preferred bifunctional phenolic compounds include hydroquinone, resorcinol, 4,4'-dihydroxydiphenylmethane, 4,4'-dihydroxydiphenyl ether, 1,4-bis(4-hydroxyphenoxy)benzene, and 4,4'-dihydroxydiphenyl sulfide.

[0037] The amount of the bifunctional phenolic compound used as a curing agent is 50 wt% or more, preferably 70 wt% or more, more preferably 80 wt% or more of the total curing agent. If it is less than this, the effect of improving physical properties such as the thermal conductivity of the cured product is small. This is because the higher the content of the bifunctional phenolic compound, the higher the degree of orientation as a molded product.

[0038] As the curing agent used in the epoxy resin composition of the present invention, in addition to the above-mentioned bifunctional phenolic compound, other curing agents generally known as curing agents can be used in combination. For example, amine-based curing agents, acid anhydride-based curing agents, phenol-based curing agents, polymercaptan-based curing agents, polyaminoamide-based curing agents, isocyanate-based curing agents, blocked isocyanate-based curing agents, etc. can be mentioned. The blending amount of these other curing agents may be appropriately set in consideration of the type of the curing agent to be blended and the physical properties of the resulting thermally conductive epoxy resin molded body. However, it does not exceed 50 wt% of the total curing agent.

[0039] In the epoxy resin composition of the present invention, the blending ratio of the epoxy resin and the curing agent is preferably in the range of 0.8 to 1.5 in terms of the equivalent ratio of the epoxy group and the functional group in the curing agent. Outside this range, unreacted epoxy groups or functional groups in the curing agent may remain even after curing, and the reliability regarding the insulating material for electronic parts may decrease.

[0040] In the epoxy resin composition of the present invention, it is preferable to incorporate an inorganic filler. In this case, the addition amount of the inorganic filler is usually 50 to 98 wt% based on the epoxy resin composition, preferably 75 to 96 wt%, and more preferably 85 to 96 wt%. If it is less than this, the effects such as high thermal conductivity, low thermal expansion, and high heat resistance may not be fully exhibited. These effects improve as the addition amount of the inorganic filler increases, but they do not improve in accordance with the volume fraction, and they improve dramatically when the addition amount exceeds a specific amount. These physical properties are due to the effect of controlling the higher-order structure in the polymer state, and since this higher-order structure is mainly achieved on the surface of the inorganic filler, it is considered that a specific amount of inorganic filler is required. On the other hand, if the addition amount of the inorganic filler is more than this, the viscosity may increase and the moldability may deteriorate.

[0041] The inorganic filler is preferably spherical, and is not particularly limited as long as it is spherical including those with an elliptical cross-section, but from the viewpoint of improving fluidity, it is particularly preferable that it is as close to a true sphere as possible. Thereby, it is easy to take a closest packing structure such as a face-centered cubic structure or a hexagonal close-packed structure, and a sufficient packing amount can be obtained. If it is not spherical, when the packing amount increases, the friction between the fillers increases, and the fluidity extremely decreases and the viscosity increases before reaching the above upper limit, and the moldability may deteriorate. Therefore, it should be appropriately selected and adjusted for use according to the applicable applications and the like.

[0042] From the viewpoint of improving the thermal conductivity, it is preferable that 50 wt% or more, preferably 80 wt% or more of the inorganic filler has a thermal conductivity of 5 W / m·K or more. As such an inorganic filler, alumina, aluminum nitride, crystalline silica, etc. are suitable. Among these, spherical alumina is excellent. In addition, amorphous inorganic fillers such as fused silica and crystalline silica may be used in combination as necessary regardless of the shape.

[0043] Also, the average particle size of the inorganic filler is preferably 30 μm or less. If the average particle size is larger than this, the fluidity of the epoxy resin composition may be impaired and the strength may also decrease.

[0044] In the epoxy resin composition of the present invention, conventionally known curing accelerators can be used. For example, there are amines, imidazoles, organic phosphines, Lewis acids, etc. Specifically, 1,8-diazabicyclo(5,4,0)undecene-7, triethylenediamine, benzyldimethyamine, triethanolamine, dimethylaminoethanol, tertiary amines such as tris(dimethylaminomethyl)phenol, imidazoles such as 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecylimidazole, organic phosphines such as tributylphosphine, methyldiphenylphosphine, triphenylphosphine, diphenylphosphine, phenylphosphine, tetrasubstituted phosphonium·tetrasubstituted borate such as tetraphenylphosphonium·tetraphenylborate, tetraphenylphosphonium·ethyltriphenylborate, tetrabutylphosphonium·tetrabutylborate, and tetraphenylboron salts such as 2-ethyl-4-methylimidazole·tetraphenylporate, N-methylmorpholine·tetraphenylporate, etc.

[0045] The addition amount of the above curing accelerator is preferably 0.1 to 10.0 wt% based on the total of the epoxy resin and the curing agent. If it is less than 0.1 wt%, the gelation time becomes slow, resulting in a decrease in workability due to a decrease in rigidity during the heating reaction. Conversely, if it exceeds 10.0 wt%, the reaction proceeds during molding, and unfilling is likely to occur. Therefore, when using, it is desirable to be within the above range.

[0046] In the epoxy resin composition of the present invention, in addition to the above components, a release agent, a coupling agent, thermoplastic oligomers, and other components generally usable in epoxy resin compositions can be appropriately blended and used. For example, a phosphorus-based flame retardant, a flame retardant such as a bromine compound or antimony trioxide, and a colorant such as carbon black or an organic dye can be used.

[0047] As the release agent, wax can be used. As the wax, for example, stearic acid, montanic acid, montanic acid ester, phosphate ester, etc. can be used.

[0048] As the coupling agent, for example, epoxy silane can be used. The addition amount of the coupling agent is preferably 0.1 to 2.0 wt% based on the epoxy resin composition. If it is less than 0.1 wt%, the effect of addition cannot be expected, and conversely, if it exceeds 2.0 wt%, there is a possibility of molding product fouling in continuous moldability. The coupling agent is used to improve the adhesive force between the inorganic filler and the resin component.

[0049] Examples of the thermoplastic oligomers include C5-based and C9-based petroleum resins, styrene resins, indene resins, indene-styrene copolymer resins, indene-styrene-phenol copolymer resins, indene-coumarone copolymer resins, indene-benzothiophene copolymer resins, etc. The addition amount is usually in the range of 2 to 30 parts by weight based on 100 parts by weight of the epoxy resin. The thermoplastic oligomers are used to improve the fluidity during the molding of the epoxy resin composition and to improve the adhesion to substrates such as lead frames.

[0050] The epoxy resin composition of the present invention contains the epoxy resin of formula (1) and a curing agent as essential components, and if necessary, components such as inorganic fillers (excluding the coupling agent) are uniformly mixed by a mixer or the like, and then, if necessary, a coupling agent is added and kneaded by a heating roll, a kneader, etc. to produce it. There is no particular limitation on the mixing order of these components except for the coupling agent. Further, after kneading, it is also possible to pulverize the melt-kneaded product to make it into powder or tablet form.

[0051] Since the epoxy resin composition of the present invention is particularly excellent for encapsulating electronic components and for heat dissipation substrates, it is suitable as an epoxy resin composition for electronic materials.

[0052] The epoxy resin composition of the present invention can be combined with a fibrous substrate such as glass fiber to form a composite material. For example, a solution of an epoxy resin composition mainly composed of the epoxy resin of formula (1) and a curing agent in an organic solvent is impregnated into a sheet-like fiber substrate and dried by heating to partially react the epoxy resin to obtain a prepreg.

[0053] In order to obtain a cured molded article using the epoxy resin composition of the present invention, for example, heat molding methods such as transfer molding, press molding, casting molding, injection molding, and extrusion molding are applicable. From the viewpoint of mass productivity, transfer molding is preferred.

[0054] Even when the epoxy resin composition of the present invention is composed only of bifunctional epoxy resin and curing agent, when heated and reacted, since a part of the hydroxyl groups generated by the reaction of the epoxy resin and the curing agent further reacts with the epoxy groups in the epoxy resin, it usually gives a three-dimensional cured product. However, by controlling the heating reaction conditions such as the use of an organic solvent, the selection of a curing accelerator type, and the reaction temperature, it can be made into a thermoplastic molded article substantially composed only of a two-dimensional polymer.

[0055] The cured molded article of the present invention preferably has crystallinity from the viewpoints of high heat resistance, low thermal expansion, and high thermal conductivity. The expression of crystallinity of the molded article can be confirmed by observing, as the melting point, the endothermic peak accompanying the melting of the crystal by differential scanning calorimetry. The preferred melting point is in the range of 120°C to 280°C, more preferably in the range of 150°C to 250°C. Also, the preferred thermal conductivity of the cured molded article is 4 W / m·K or more, particularly preferably 6 W / m·K or more.

[0056] Here, the effect of crystalline expression will be briefly explained. Generally, in a cured epoxy resin, the glass transition point is used as an index of heat resistance. This is because a normal cured epoxy resin is an amorphous (glass-like) molded product without crystallinity, and the physical properties change greatly with the glass transition point as the boundary. Therefore, in order to increase the heat resistance of a cured epoxy resin, that is, to increase the glass transition point, it is necessary to increase the crosslinking density, but conversely, there is a drawback that the flexibility decreases and it becomes brittle. On the other hand, the cured molded product of the present invention is characterized in that it develops crystallinity, but since the physical properties change little up to the melting point, the melting point can be used as an index of heat resistance. Since the melting point of a polymer substance is at a higher temperature than the glass transition point, the cured molded product of the present invention can ensure high heat resistance while maintaining high flexibility with a low crosslinking density. Further, the expression of crystallinity means that a high cohesive force acts between molecules, which suppresses the movement of molecules, achieves low thermal expansibility, and exhibits a high thermal diffusivity and improved thermal conductivity. Furthermore, the high cohesive force between molecules greatly suppresses the diffusion of water, and can reduce the water vapor permeability and water absorption rate.

[0057] Therefore, the higher the crystallinity of the cured molded product of the present invention, the better. Here, the degree of crystallization can be evaluated from the endothermic amount accompanying the melting of crystals in differential scanning calorimetry. The preferable endothermic amount is 5 J / g or more per unit weight of the resin component excluding the filler. More preferably, it is 10 J / g or more, and particularly preferably, it is 15 J / g or more. If it is smaller than this, the effects of improving the heat resistance, low thermal expansibility, and thermal conductivity of the molded product are small. The endothermic amount referred to here means the endothermic amount obtained by measuring with a differential scanning calorimeter using a sample precisely weighed to about 10 mg under a nitrogen stream at a heating rate of 10 °C / min. In addition, the crystallized cured molded product of the present invention can also be observed as a distinct peak in wide-angle X-ray diffraction. In this case, the crystallinity can be obtained by dividing the area obtained by subtracting the peak of the non-crystallized amorphous resin from the total peak area by the total peak area. The desirable crystallinity obtained in this way is 10% or more, more desirably 20% or more, and particularly desirably 30% or more.

[0058] The cured molded article of the present invention can be obtained by heating and reacting by the above molding method. Usually, the molding temperature is 80°C to 250°C. However, in order to increase the crystallinity of the molded article, it is desirable to react at a temperature lower than the melting point of the molded article. The preferred molding temperature is in the range of 100°C to 200°C, more preferably 130°C to 180°C. Also, the preferred molding time is 30 seconds to 1 hour, more preferably 1 minute to 30 minutes. Further, after molding, the crystallinity can be further increased by post-curing. Usually, the post-curing temperature is 130°C to 250°C and the time is in the range of 1 hour to 20 hours. However, it is desirable to perform post-curing at a temperature 5°C to 40°C lower than the endothermic peak temperature in differential thermal analysis over 1 hour to 24 hours.

Examples

[0059] The present invention will be described more specifically with reference to the following examples.

[0060] Reference Example 1 (Production of Hydroxy Resin A) 115.7 g of 4,4'-dihydroxybiphenyl was dissolved in 700 g of NMP in a 2 L four-necked separable flask, and then 56.7 g of potassium carbonate was added. The temperature was raised to 120°C while stirring under a nitrogen stream. Then, 35.6 g of 2,6-dichlorobenzonitrile was added, and the temperature was raised to 145°C and reacted for 6 hours. 49.2 g of acetic acid was added to the reaction solution for neutralization, and then NMP was distilled off under reduced pressure. 500 mL of MIBK was added to the reaction solution to dissolve the product, and then the resulting salt was removed by washing with water. Then, MIBK was removed by distillation under reduced pressure to obtain 129 g of a hydroxy resin (hydroxy resin A). The hydroxyl equivalent of the obtained hydroxy resin A was 170 g / eq., and the melting point was 272°C.

[0061] Reference Example 2 (Production of Epoxy Resin A) 50.0 g of hydroxy resin A obtained in Reference Example 1, 380 g of epichlorohydrin, and 96 g of diethylene glycol dimethyl ether (diglyme) were charged. Under reduced pressure (about 130 Torr), 27.5 g of a 48.6% aqueous sodium hydroxide solution was added dropwise at 65°C over 3 hours. During this time, the water generated was removed from the system by azeotropy with epichlorohydrin, and the distilled epichlorohydrin was returned to the system. After completion of the dropwise addition, the reaction was continued for another 1 hour for dehydration. Then, epichlorohydrin and diglyme were distilled off under reduced pressure. After dissolving in 200 mL of methyl isobutyl ketone, the salt formed was removed by filtration. Then, 0.4 g of a 48% aqueous sodium hydroxide solution was added, and the mixture was reacted at 80°C for 2 hours. After the reaction, filtration and washing with water were carried out, and then the solvent methyl isobutyl ketone was distilled off under reduced pressure to obtain 43 g of an epoxy resin in the form of a solid at room temperature (epoxy resin A). The melting point of the obtained epoxy resin A was 139°C, the epoxy equivalent was 226 g / eq., and the hydrolyzable chlorine was 80 ppm. Here, the hydrolyzable chlorine was determined by dissolving 0.5 g of the resin sample in 30 ml of 1,4-dioxane, adding 10 ml of 1N-KOH, boiling under reflux for 30 minutes, cooling to room temperature, further adding 100 ml of 80% acetone water, and performing potentiometric titration with a 0.002N-AgNO3 aqueous solution.

[0062] Reference Example 3 (Production of Hydroxy Resin B) 128.1 g of hydroquinone was dissolved in 700 g of N-methylpyrrolidone (NMP) in a 2 L four-necked separable flask, and then 139.3 g of potassium carbonate was added. The temperature was raised to 120°C with stirring under a nitrogen stream. Then, 50.0 g of 2,6-dichlorobenzonitrile was added, and the temperature was raised to 150°C and reacted for 6 hours. After adding 121.1 g of acetic acid to the reaction solution for neutralization, NMP was distilled off under reduced pressure. After adding 500 mL of methyl isobutyl ketone (MIBK) to the reaction solution to dissolve the product, the formed salt and unreacted hydroquinone were removed by washing with water. Then, MIBK was removed by distillation under reduced pressure to obtain 71 g of a yellow powdery polyhydroxy resin (hydroxy resin B). The hydroxyl equivalent of the obtained hydroxy resin B was 162 g / eq., and the melting point was 255°C.

[0063] Reference Example 4 (Production of Epoxy Resin B) 15 g of the hydroxy resin B obtained in Reference Example 3 was dissolved in 130 g of epichlorohydrin and 33 g of diglyme, and 7.8 g of a 48% aqueous sodium hydroxide solution was added dropwise thereto at 60°C under reduced pressure (about 100 mmHg) over 4 hours. During this time, the water generated was removed from the system by azeotropy with epichlorohydrin, and the distilled epichlorohydrin was returned to the system. After completion of the dropwise addition, the reaction was continued for another 1 hour. Thereafter, epichlorohydrin and diglyme were distilled off under reduced pressure, and after dissolving in 120 mL of methyl isobutyl ketone, the salt formed was removed by filtration. Thereafter, 0.4 g of a 48% aqueous sodium hydroxide solution was added, and the mixture was reacted at 80°C for 2 hours. After the reaction, filtration and washing with water were performed, and then the solvent, methyl isobutyl ketone, was distilled off under reduced pressure to obtain 16 g of a yellow powdery epoxy resin (Epoxy Resin B). The melting point of the obtained Epoxy Resin B was 147.3°C, the epoxy equivalent was 230 g / eq., and the hydrolyzable chlorine was 340 ppm.

[0064] Examples 1 to 4, Comparative Examples 1 to 5 As the epoxy resin, the epoxy resin obtained in Reference Example 2 (Epoxy Resin A), the epoxy resin obtained in Reference Example 4 (Epoxy Resin B), and a biphenyl-based epoxy resin (Epoxy Resin C: manufactured by Japan Epoxy Resins, YX-4000H, epoxy equivalent 193, melting point 105°C) were used. As the curing agent, 4,4'-dihydroxydiphenyl ether (Curing Agent A), 4,4'-dihydroxybiphenyl (Curing Agent B), and phenol novolak (Curing Agent C: manufactured by Aica Kogyo, BRG-557, OH equivalent 105 g / eq., softening point 82°C) were used. As the curing accelerator, triphenylphosphine was used, and as the inorganic filler, spherical alumina (manufactured by Denka, DAW-10, average particle diameter 12.2 μm) was used.

[0065] The components shown in Table 1 were blended and thoroughly mixed with a mixer. After that, the mixture was kneaded with a heating roll for about 5 minutes, cooled, and pulverized to obtain the epoxy resin compositions of Examples 1 to 4 and Comparative Examples 1 to 5, respectively. Using this epoxy resin composition, after molding under the conditions of 170 °C for 5 minutes, post-curing was carried out at 170 °C for 12 hours to obtain a cured molded product, and its physical properties were evaluated. The results are summarized in Table 1. Note that the numbers of each component in Table 1 represent parts by weight.

[0066] [Evaluation] (1) Thermal conductivity The thermal conductivity was measured by the transient hot-wire method using a NETZSCH LFA447 type thermal conductivity meter. (2) Measurement of melting point and heat of fusion (DSC method) Using a Hitachi High-Tech Science TG / DTA7300 type differential scanning calorimeter, about 10 mg of accurately weighed sample was used for measurement under a nitrogen stream at a heating rate of 10 °C / min. When a cured product containing an inorganic filler was used as the sample, the heat of fusion was converted only to the resin component. (3) Coefficient of linear expansion and glass transition temperature The coefficient of linear expansion and the glass transition temperature were measured using a Hitachi High-Tech Science TMA7100 type thermomechanical measuring device at a heating rate of 10 °C / min. (4) Water absorption A disk with a diameter of 50 mm and a thickness of 3 mm was molded. After post-curing, the weight change rate was measured after absorbing moisture for 100 hours under the conditions of 85 °C and 85% relative humidity. (5) Heat distortion temperature Measurement was carried out in accordance with JIS K 7191-1 using a Toyo Seiki 533 type HDT test device.

[0067]

Table 1

Claims

1. In an epoxy resin composition containing an epoxy resin and a curing agent, 50 wt% or more of the epoxy resin is an epoxy resin having a benzonitrile structure represented by the following formula (1), and 50 wt% or more of the curing agent is a bifunctional phenolic compound (however, excluding the case where the bifunctional phenolic compound is a polyhydroxy resin represented by the following general formula (4)). 【Chemical 1】 (However, m represents a number from 1 to 3, and n represents a number from 0 to 50.) [Chemical 2] (However, in formula (4), A represents a divalent aromatic group. Also, n represents a number from 1 to 10.)

2. The epoxy resin composition according to claim 1, wherein the bifunctional phenolic compound is at least one phenolic compound selected from the group consisting of hydroquinone, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenyl sulfone, dihydroxydiphenylmethanes, and naphthalenediols.

3. The epoxy resin composition according to any one of claims 1 or 2, characterized in that it contains 50 to 96 wt% of an inorganic filler.

4. The epoxy resin composition according to any one of claims 1 to 3, characterized in that it is an epoxy resin composition for electronic materials.

5. A cured product obtained by curing the epoxy resin composition according to any one of claims 1 to 4.

6. The cured product according to claim 5, having a thermal conductivity of 4 W / m·K or more.

7. The cured product according to claim 5 or 6, wherein the peak of the melting point in the differential scanning calorimetry is in the range of 120°C to 280°C.

8. The cured product according to any one of claims 5 to 7, wherein the endothermic amount in terms of the resin component in the differential scanning calorimetry is 5 J / g or more.

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