Epoxy resin composition and mold sealing material

Abstract

To provide an epoxy resin composition capable of forming a cured product having a high glass transition temperature after curing, relaxed in residual stress by heat treatment, and suppressed in deterioration of heat resistance, and to provide a mold sealing material.SOLUTION: The epoxy resin composition contains an epoxy resin (A), an acid anhydride curing agent (B) and a transesterification reaction catalyst (C), wherein the content of the acid anhydride curing agent (B) is more than 0.3 equivalent and less than 1.0 equivalent based on 1 equivalent of the epoxy group of the epoxy resin (A). The transesterification reaction catalyst (C) contains a metal compound (C-1) and a basic catalyst (C-2), and a total content of the metal compound (C-1) and the basic catalyst (C-2) is more than 2 parts by mass and less than 9 parts by mass with respect to 100 parts by mass of the epoxy resin (A), A content of the basic catalyst (C-2) with respect to a total content of the metal compound (C-1) and the basic catalyst (C-2) is 25% by mass or more and 75% by mass or less, a stress when a cured product of the epoxy resin composition is pulled by 3% with respect to an initial length under a temperature atmosphere of at least one temperature equal to or higher than a glass transition temperature of the cured product is σ 1, and the cured product is pulled by 3% with respect to the initial length and held under the temperature atmosphere, when a stress when the stress does not change is σ 2, a ratio of the σ 2 to the σ 1 is 85% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to epoxy resin compositions and mold encapsulants. [Background technology]

[0002] Epoxy resins, which are thermosetting resins, are resins that cure when exposed to external stimuli such as heat or light. Epoxy resins have high mechanical strength as well as excellent heat and chemical resistance. Utilizing these properties, thermosetting resins are used in a variety of applications, including encapsulants, structural components, adhesives, coatings, and composite matrix materials.

[0003] One application of epoxy resin is carbon fiber reinforced plastics (CFRP), a composite of carbon fiber and epoxy resin. CFRP is a lightweight, rust-proof, highly rigid and strong material, and its applications are expanding from industrial to aircraft and automotive applications.

[0004] In recent years, there has been a demand for the reuse and remolding of CFRP from the perspectives of cost reduction and SDGs. However, because the curing reaction of general epoxy resins is irreversible, processing of cured epoxy resins is limited to mechanical processing. Therefore, there is a demand for epoxy resin compositions that can be remolded after curing.

[0005] Other uses of epoxy resins include as encapsulants for rotating machines such as motors, or for power devices used in power electronics equipment. Using epoxy resins as encapsulants can provide benefits such as electrical insulation, improved heat dissipation during operation, absorption of humming noise caused by electrical vibrations, and adhesion of component materials.

[0006] In applications where the resin is used as an encapsulant for power devices, metals such as copper, aluminum, and iron, or chips (ceramics), are embedded in the encapsulant. Stress is generated due to the difference in thermal expansion coefficient between these embedded materials and the encapsulant, and if the stress increases, interfacial peeling or cracking may occur, potentially reducing reliability. Therefore, there is a demand for tough epoxy resin compositions with excellent crack resistance, as well as low-stress epoxy resin compositions that suppress the stress that is generated.

[0007] The epoxy resins described above form a three-dimensional network structure in which polymer chains are cross-linked by irreversible covalent bonds. While epoxy resins with cross-linked structures offer high heat resistance and strength, they do not melt when heated because the molecules do not flow, and they are insoluble in solvents, making them impossible to reshape or reprocess. However, in recent years, research has focused on dynamic covalent bonds, which, despite being covalent bonds, exhibit dissociation and recombination behavior in response to external stimuli such as heat or light. Materials with dynamic covalent bonds introduced at cross-linking points exhibit sufficient strength under normal operating conditions, where the dissociation and recombination behavior is frozen. However, because the cross-linking bonds are exchanged under external stimuli, they are attracting attention as materials that can be reshaped, recycle, and repaired.

[0008] Epoxy resins incorporating dynamic covalent bonds can be used as a stress relief technique. Specifically, when the ester bond moieties formed in the encapsulant are heated above the glass transition temperature (Tg), they recombine with molecular chains containing hydroxyl groups, reconnecting the molecular chains and reconstructing the crosslinked structure (transesterification), thereby reducing stress during the curing reaction. In recent years, epoxy resin compositions using dynamic covalent bonds activated by external stimuli such as heat and light have been proposed (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Special Publication No. 2014-503670 [Patent Document 2] Japanese Patent Publication No. 2022-76623 Summary of the Invention [Problem to be solved by the invention]

[0010] Patent Documents 1 and 2 describe suitable transesterification catalysts containing metal salts such as zinc acetylacetonate and manganese acetylacetonate. However, when using transesterification catalysts containing such metal salts, the rate of bond recombination is slow, resulting in a long time for stress relaxation (stress relaxation time) when stress is applied. Therefore, it is necessary to add a large amount of these catalysts to promote the transesterification reaction. Furthermore, the Tg after curing is also low.

[0011] In addition, basic catalysts such as tertiary amines and imidazoles are effective as catalysts for transesterification reactions, and while they increase the Tg after curing, they also promote thermal decomposition, which can cause thermal decomposition during heat treatment and lead to a decrease in Tg.

[0012] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide an epoxy resin composition and a mold encapsulant that are capable of forming a cured product that has a high glass transition temperature after curing, in which residual stress is reduced by heat treatment, and in which deterioration in heat resistance is suppressed. [Means for solving the problem]

[0013] The epoxy resin composition according to the present disclosure comprises: The composition comprises an epoxy resin (A), an acid anhydride curing agent (B), and a transesterification catalyst (C), the content of the acid anhydride curing agent (B) is more than 0.3 equivalents and less than 1.0 equivalent relative to 1 equivalent of the epoxy group of the epoxy resin (A); the transesterification catalyst (C) comprises a metal compound (C-1) and a basic catalyst (C-2), the total content of the metal compound (C-1) and the basic catalyst (C-2) is more than 2 parts by mass and less than 9 parts by mass per 100 parts by mass of the epoxy resin (A), the content of the basic catalyst (C-2) relative to the total content of the metal compound (C-1) and the basic catalyst (C-2) is 25% by mass or more and 75% by mass or less, When the stress when a cured product of the epoxy resin composition is stretched by 3% of its initial length in at least one temperature atmosphere equal to or higher than the glass transition temperature of the cured product is defined as σ1, and the stress when the cured product is stretched by 3% of its initial length in the same temperature atmosphere and maintained at that temperature atmosphere and the stress no longer changes is defined as σ2, the ratio of σ2 to σ1 is 85% or less.

[0014] The mold encapsulant according to the present disclosure comprises the above-described epoxy resin composition. [Effects of the Invention]

[0015] According to the present disclosure, it is possible to provide an epoxy resin composition and a mold encapsulant which are capable of forming a cured product that has a high glass transition temperature after curing, in which residual stress is reduced by heat treatment, and in which deterioration in heat resistance is suppressed. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present disclosure will be described.

[0017] Embodiment 1 <Epoxy resin composition> The epoxy resin composition of this embodiment contains an epoxy resin (A), an acid anhydride curing agent (B), and a transesterification catalyst (C). The content of the acid anhydride curing agent (B) is more than 0.3 equivalents and less than 1.0 equivalent relative to 1 equivalent of the epoxy groups in the epoxy resin (A). The transesterification catalyst (C) contains a metal compound (C-1) and a basic catalyst (C-2). The total content of the metal compound (C-1) and the basic catalyst (C-2) is more than 2 parts by mass and less than 9 parts by mass per 100 parts by mass of the epoxy resin (A). The content of the basic catalyst (C-2) relative to the total content of the metal compound (C-1) and the basic catalyst (C-2) is 25% by mass or more and 75% by mass or less. When the stress (initial stress) when a cured product of an epoxy resin composition is stretched by 3% of its initial length in at least one temperature atmosphere equal to or higher than the glass transition temperature of the cured product is defined as σ1, and the stress (saturated residual stress) when the cured product is stretched by 3% of its initial length in the same temperature atmosphere and maintained at that temperature atmosphere and the stress no longer changes is defined as σ2, the ratio of the saturated residual stress σ2 to the initial stress σ1 (hereinafter also referred to as the "residual stress ratio") is 85% or less.

[0018] (Epoxy resin (A)) The epoxy resin (A) contained in the epoxy resin composition of this embodiment is a compound having two or more oxirane rings (epoxy groups) per molecule. Examples of such epoxy resins (A) include bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, bisphenol E epoxy resins, biphenyl epoxy resins, novolac epoxy resins, alicyclic epoxy resins, linear aliphatic epoxy resins, and glycidylamine epoxy resins. Among these epoxy resins (A), bisphenol A epoxy resins and bisphenol F epoxy resins are preferred from the viewpoints of workability and heat resistance. Furthermore, when high heat resistance is required, multifunctional epoxy resins are preferred.

[0019] The epoxy resin (A) may be used alone or in combination of two or more thereof. When two or more thereof are used in combination, the combination is not particularly limited.

[0020] (Acid anhydride curing agent (B)) The epoxy resin composition of the present embodiment contains an acid anhydride curing agent (B). The acid anhydride curing agent (B) is not particularly limited as long as it can cure the epoxy resin (A), and known acid anhydride curing agents can be used. Examples of the acid anhydride curing agent (B) include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, 3-dodecenylsuccinic anhydride, octenylsuccinic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, dodecylsuccinic anhydride, chlorendic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, ethylene glycol bis(anhydrotrimate), methylcyclohexene tetracarboxylic anhydride, trimellitic anhydride, polyazelaic anhydride, and ethylene glycol bisanhydrotrimellitate.

[0021] The acid anhydride curing agent (B) may be used alone or in combination of two or more thereof. When two or more thereof are used in combination, the combination is not particularly limited.

[0022] The content of the acid anhydride curing agent (B) is more than 0.3 equivalents and less than 1.0 equivalent relative to 1 equivalent of the epoxy group in the epoxy resin (A). If the content of the acid anhydride curing agent (B) is outside the above range, poor curing is likely to occur, properties such as heat resistance may not be fully exhibited, and the stress relaxation effect due to heat treatment may be insufficient. The content of the acid anhydride curing agent (B) is preferably 0.4 equivalents or more and 0.8 equivalents or less relative to 1 equivalent of the epoxy group in the epoxy resin (A).

[0023] (Transesterification catalyst (C)) The epoxy resin composition of this embodiment contains a transesterification catalyst (C). The transesterification catalyst (C) contains a metal compound (C-1) and a basic catalyst (C-2). By containing the metal compound (C-1) and the basic catalyst (C-2), the epoxy resin composition has a higher Tg after curing and exhibits a faster reduction in residual stress upon heat treatment than when the epoxy resin composition contains only the metal compound (C-1) or only the basic catalyst (C-2), or neither. The transesterification catalyst (C) may consist of the metal compound (C-1) and the basic catalyst (C-2).

[0024] The metal compound (C-1) is not particularly limited as long as it can promote the transesterification reaction, and known metal compounds can be used. Examples of the metal compound (C-1) include zinc acetate (II), zinc (II) acetylacetonate, zinc naphthenate (II), acetylacetonate iron (III), acetylacetonate cobalt (II), acetylacetonate cobalt (III), aluminum isopropoxide, titanium isopropoxide, methoxide (triphenylphosphine) copper (I) complex, ethoxide (triphenylphosphine) copper (I) complex, propoxide (triphenylphosphine) copper (I) complex, isopropoxide (triphenylphosphine), Examples of suitable metal compounds (C-1) include zinc acetylacetonate (Zn(II)), ...

[0025] The metal compound (C-1) may be used alone or in combination of two or more kinds. When two or more kinds are used in combination, the combination is not particularly limited.

[0026] The content of the metal compound (C-1) is preferably 0.5 parts by mass or more and 7 parts by mass or less per 100 parts by mass of the epoxy resin (A). If the content of the metal compound (C-1) is less than 0.5 parts by mass, the stress relaxation effect due to heat treatment may be insufficient. If the content of the metal compound (C-1) is more than 7 parts by mass, the heat resistance may be reduced during heat treatment. The content of the metal compound (C-1) is more preferably 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of the epoxy resin (A).

[0027] The basic catalyst (C-2) is not particularly limited as long as it can promote the transesterification reaction, and a known basic catalyst can be used. Examples of the basic catalyst (C-2) include N,N-dimethyl-4-aminopyridine, diazabicycloundecene (1,8-diazabicyclo[5.4.0]-7-undecene, DBU (registered trademark)), diazabicyclononene (1,5-diazabicyclo[4.3.0]-5-nonene, DBN), triazabicyclodecene (1,5,7-triazabicyclo[4.4.0]dec-5-ene, TBD), 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, and 1-cyanoethyl-2-phenylimidazole. Among these basic catalysts (C-2), DBU (registered trademark), DBN and TBD are preferred, and DBU (registered trademark) is more preferred, from the viewpoint of rapidly promoting the curing reaction of the epoxy resin (A) with the acid anhydride curing agent (B) and the transesterification reaction of the cured product.

[0028] The basic catalyst (C-2) may be used alone or in combination of two or more. When two or more types are used in combination, the combination is not particularly limited.

[0029] The content of the basic catalyst (C-2) is preferably 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of the epoxy resin (A). If the content of the basic catalyst (C-2) is less than 1 part by mass, the curing reaction of the epoxy resin (A) with the acid anhydride curing agent (B) may be insufficient. If the content of the basic catalyst (C-2) is more than 5 parts by mass, the heat resistance may decrease during heat treatment. The content of the basic catalyst (C-2) is more preferably 2 parts by mass or more and 4 parts by mass or less per 100 parts by mass of the epoxy resin (A).

[0030] The total content of the metal compound (C-1) and the basic catalyst (C-2) is more than 2 parts by mass and less than 9 parts by mass per 100 parts by mass of the epoxy resin (A). If the total content of the metal compound (C-1) and the basic catalyst (C-2) is 2 parts by mass or less, the curing reaction of the epoxy resin (A) by the acid anhydride curing agent (B) and the stress relaxation effect by heat treatment may be insufficient. If the total content of the metal compound (C-1) and the basic catalyst (C-2) is 9 parts by mass or more, the curing reaction of the epoxy resin (A) by the acid anhydride curing agent (B) may be accelerated, resulting in reduced workability and reduced heat resistance during curing and heat treatment. The total content of the metal compound (C-1) and the basic catalyst (C-2) is more preferably 3 parts by mass or more and 7 parts by mass or less.

[0031] The content of the basic catalyst (C-2) relative to the total content of the metal compound (C-1) and the basic catalyst (C-2) (basic catalyst (C-2) content / (metal compound (C-1) content + basic catalyst (C-2) content) × 100) is 25% by mass or more and 75% by mass or less. If the content of the basic catalyst (C-2) relative to the total content of the metal compound (C-1) and the basic catalyst (C-2) is less than 25% by mass, the curing reaction of the epoxy resin (A) by the acid anhydride curing agent (B) and the stress relaxation effect by heat treatment may be insufficient. If the content of the basic catalyst (C-2) relative to the total content of the metal compound (C-1) and the basic catalyst (C-2) is more than 75% by mass, the curing reaction of the epoxy resin (A) by the acid anhydride curing agent (B) may be accelerated, resulting in reduced workability and reduced heat resistance during curing and heat treatment. The content of the basic catalyst (C-2) relative to the total content of the metal compound (C-1) and the basic catalyst (C-2) is preferably 30% by mass or more and 70% by mass or less, and more preferably 40% by mass or more and 67% by mass or less.

[0032] (Inorganic filler) The epoxy resin composition of the present embodiment may further contain an inorganic filler. The inorganic filler is not particularly limited, but examples thereof include metal oxide particles such as aluminum oxide (alumina), zinc oxide, indium tin oxide (ITO), magnesium oxide, beryllium oxide, and titanium oxide; metal nitride particles such as boron nitride, silicon nitride, and aluminum nitride; carbon compound particles such as silicon carbide, graphite, diamond, amorphous carbon, carbon black, and carbon fiber; and silica compound powders such as quartz and quartz glass. These may be used alone or in combination of two or more. Among these, aluminum oxide (alumina), zinc oxide, magnesium oxide, beryllium oxide, titanium oxide, boron nitride, silicon nitride, aluminum nitride, diamond, quartz, and quartz glass are preferred from the viewpoint of insulating properties.

[0033] The average particle size of the inorganic filler is preferably 0.1 to 100 μm, more preferably 1 to 80 μm. If the average particle size of the inorganic filler is less than 0.1 μm, the viscosity of the epoxy resin composition may increase, which may impair workability and moldability. If the average particle size of the inorganic filler is more than 100 μm, the strength of the cured product of the epoxy resin composition may decrease and the inorganic filler may settle during storage of the epoxy resin composition.

[0034] The content of the inorganic filler is preferably 40 to 95% by mass, more preferably 70 to 85% by mass, based on the total weight of the epoxy resin composition. If the content of the inorganic filler is less than 40% by mass, it may be difficult to obtain a cured product of the epoxy resin composition having the desired mechanical strength and thermal expansion coefficient. If the content of the inorganic filler is more than 95% by weight, the viscosity of the epoxy resin composition may increase, which may impair workability and moldability.

[0035] (coupling agent) The inorganic filler may be subjected to a coupling treatment with a coupling agent for the purposes of improving the wettability of the inorganic filler with the epoxy resin composition, reinforcing the interface between the inorganic filler and the epoxy resin composition, improving the dispersibility of the inorganic filler, etc. Examples of such coupling agents include γ-glycidoxypropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, etc. These may be used alone or in combination of two or more types.

[0036] The content of the coupling agent may be appropriately set depending on the types of epoxy resin (A) and inorganic filler, and is, for example, 0.01 to 5 parts by mass per 100 parts by mass of epoxy resin (A).

[0037] (residual stress rate) In a cured product of the epoxy resin composition of this embodiment, when the stress when the cured product is stretched 3% of its initial length in an atmosphere of at least one temperature equal to or higher than the Tg is defined as initial stress σ1, and when the stress when the cured product is stretched 3% of its initial length and held at that temperature and no longer changes is defined as saturated residual stress σ2, the ratio of saturated residual stress σ2 to initial stress σ1 (residual stress rate) is 85% or less. Because the residual stress of the cured product is reduced by heat treatment, it is less likely to develop interfacial peeling or cracks, and has excellent reliability.

[0038] Here, the cured product of the epoxy resin composition of the present embodiment contains ester bonds, hydroxyl groups, and a transesterification catalyst inside. When the cured product is heated, the ester bonds and molecular chains having hydroxyl groups bond together, and the molecular chains are reconnected, resulting in the reconstruction of the crosslinked structure (transesterification), which reduces the residual stress during the curing reaction.

[0039] In this embodiment, the residual stress rate is measured by a creep test. For example, an epoxy resin composition is poured into a plate-shaped mold with a thickness of 1 mm and heated at 100°C for 3 hours and at 160°C for 3 hours to obtain a test piece of the cured product. The Tg of the resulting cured product is measured. The method for measuring Tg will be described later. The resulting test piece is placed in a tensile tester, and the initial stress σ1 and saturated residual stress σ2 are measured in a temperature atmosphere at least at one point equal to or higher than the Tg of the cured product. The initial stress σ1 is the stress obtained when the test piece is stretched to a tensile elongation of 3% of its initial length. The saturated residual stress σ2 is the stress obtained when the test piece is stretched to a tensile elongation of 3% of its length and held there, and a certain time has passed until the stress no longer changes. The temperature atmosphere may be, for example, 180°C or 200°C. Note that the cured product formed from the epoxy resin composition of this embodiment is not limited to the cured product obtained under the above-mentioned curing conditions. Details of the curing conditions for the epoxy resin composition of this embodiment will be described later.

[0040] Based on the initial stress σ1 and the saturated residual stress σ2, the residual stress rate (%) is calculated using the following formula (1). Residual stress rate (%) = (saturated residual stress σ2 / initial stress σ1) × 100 Equation (1)

[0041] A smaller value of the residual stress rate indicates a greater reduction in residual stress. In this embodiment, a residual stress rate of 85% or less is determined to be a reduction in residual stress. The residual stress rate is preferably 70% or less, more preferably 60% or less, even more preferably 50% or less, and particularly preferably 40% or less.

[0042] Since the cured product of the epoxy resin composition of this embodiment has reduced residual stress, cracks that occur in the cured product can be repaired by thermal deformation by applying an appropriate temperature and mechanical restraint to the cured product. In other words, the epoxy resin composition of this embodiment can be remolded after curing.

[0043] In order to make the epoxy resin composition of this embodiment suitable for industrial application, it is necessary to make it possible to deform within a predetermined time. To achieve this, it is necessary to heat treat the epoxy resin composition at a temperature equal to or higher than the Tg of the material that constitutes the cured product (molded article) of the epoxy resin composition. The temperature is preferably set at a temperature 10 to 100°C higher than the Tg of the cured product, and more preferably set at a temperature 20 to 50°C higher than the Tg of the cured product.

[0044] The Tg of the cured product of the epoxy resin composition of the present embodiment is, for example, preferably 100° C. or higher, and more preferably 120° C. or higher, which allows the reheating temperature required for remolding the cured product to be lowered.

[0045] Tg can be measured, for example, by the following procedure. Specifically, an epoxy resin composition is heated under the same conditions as in the measurement of the residual stress rate described above to obtain a test piece of the cured product. The obtained test piece is placed in a dynamic mechanical analysis (DMA) device. After placement, measurement is performed under the following test conditions, and the peak top temperature of the loss tangent (tan δ) is taken as Tg. [Test conditions] Deformation mode: tension mode Measurement temperature: 25~300℃ Heating rate: 2°C / min Frequency: 1Hz

[0046] <Method of producing epoxy resin composition> The method for producing the epoxy resin composition of this embodiment is not particularly limited. For example, the epoxy resin (A) and the metal compound (C-1) are heated and mixed to obtain a mixture. The heating temperature is, for example, in the range of 40 to 180°C. After cooling the mixture, the acid anhydride curing agent (B) and the basic catalyst (C-2) are added and mixed to obtain the epoxy resin composition. The cooling temperature is, for example, room temperature.

[0047] A solvent may be used when mixing the epoxy resin (A) and the metal compound (C-1). The solvent is not particularly limited, but examples thereof include toluene and methyl ethyl ketone.

[0048] The curing conditions for the epoxy resin composition are not particularly limited, but for example, the heating temperature is in the range of 40 to 180° C., and the heating time is in the range of 1 minute to 100 hours.

[0049] When an inorganic filler is used, the mixing method is not particularly limited, but for example, the inorganic filler may be mixed in the process of heating and mixing the epoxy resin (A) and the metal compound (C-1) to obtain a mixture. For example, the inorganic filler may be mixed in the process of adding the acid anhydride curing agent (B) and the basic catalyst (C-2) to the mixture. For example, the mixture obtained by heating and mixing the epoxy resin (A) and the metal compound (C-1) to obtain a mixture with the inorganic filler mixed in may be combined with the mixture obtained by adding the acid anhydride curing agent (B) and the basic catalyst (C-2) to obtain a mixture with the inorganic filler mixed in the process of mixing the acid anhydride curing agent (B) and the basic catalyst (C-2).

[0050] The coupling treatment of the inorganic filler with a coupling agent may be carried out using a conventionally known method when the inorganic filler is mixed, or may be carried out before the inorganic filler is mixed.

[0051] Embodiment 2 The mold sealing material of embodiment 2 is a mold sealing material made from the epoxy resin composition of embodiment 1. The mold sealing material of this embodiment is made from the epoxy resin composition of embodiment 1, in which residual stress is reduced by reheating. Therefore, the mold sealing material of this embodiment also has residual stress reduced by reheating.

[0052] The mold encapsulant of the present embodiment can be applied to, for example, encapsulants for motors and power devices. The mold encapsulant can suppress the occurrence of cracks, thereby improving the reliability of the devices. [Example]

[0053] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to these examples.

[0054] Example 1 Components (A) to (C) were prepared in the amounts shown in Table 1. Component (A-1) and component (C-1-1) were heated to 120°C and mixed uniformly to obtain a mixture. After cooling the mixture to room temperature, components (B-1) and (C-2-1) were added and mixed uniformly to obtain the epoxy resin composition of Example 1. The obtained epoxy resin composition was poured into a 1 mm-thick plate-shaped mold and heated at 100°C for 3 hours and at 160°C for 3 hours, respectively, to obtain a cured product of the epoxy resin composition of Example 1.

[0055] <Examples 2 to 19> An epoxy resin composition and a cured product thereof were obtained in the same manner as in Example 1, except that the amounts of the components (A) to (C) were changed to those shown in Table 1.

[0056] <Comparative Examples 1, 4 to 6> Epoxy resin compositions and cured products thereof were obtained in the same manner as in Example 1, except that the amounts of components (A), (B), and (C-2) were changed to those shown in Table 1 and that component (C-1) was not added.

[0057] <Comparative Examples 2 and 3> Epoxy resin compositions and cured products thereof were obtained in the same manner as in Example 1, except that the amounts of components (A), (B), and (C-1) were changed to those shown in Table 1 and that component (C-2) was not added.

[0058] <Comparative Examples 7 to 13> An epoxy resin composition and a cured product thereof were obtained in the same manner as in Example 1, except that the amounts of the components (A) to (C) were changed to those shown in Table 1.

[0059] The components shown in Table 1 (each component symbolized) are as follows:

[0060] [Epoxy resin: component A] (A-1) Bisphenol A epoxy resin (Mitsubishi Chemical Corporation, jER828US) ​​(liquid at room temperature) (A-2) Alicyclic epoxy resin (Daicel Corporation, Celloxide 2021P)

[0061] [Acid anhydride hardener: Component B] (B-1) Methyltetrahydrophthalic anhydride (Resonac Corporation, HN2000) (B-2) Methyl nadic anhydride (MHAC-P, manufactured by Resonac Corporation)

[0062] [Metal compound: C-1 component] (C-1-1) Zinc(II) acetylacetonate (Tokyo Chemical Industry Co., Ltd.)

[0063] [Basic catalyst: component C-2] (C-2-1) Diazabicycloundecene (DBU (registered trademark)) (Tokyo Chemical Industry Co., Ltd.) (C-2-2) Diazabicyclononene (DBN) (C-2-3) Triazabicyclodecene (TBD)

[0064] <Evaluation method> The evaluation was carried out by the following method.

[0065] (1) Glass transition temperature of the cured product A DMA device (RDA-II, manufactured by Rheometrics) was prepared. Measurements were performed under the following test conditions using the cured products of each Example and Comparative Example. The peak top temperature of tan δ in this measurement was taken as Tg. The results are shown in "Tg (after curing)" in Tables 1 to 3. A Tg of 150°C or higher is considered to be good for the cured product. [Test conditions] Deformation mode: tension mode Measurement temperature: 25~300℃ Heating rate: 2°C / min Frequency: 1Hz

[0066] (2) Residual stress rate The cured products (length 10 mm x width 3 mm x thickness 1 mm) of each Example and Comparative Example were placed in a tensile testing machine (TMA7100, manufactured by Hitachi High-Tech Science Corporation), and the initial stress σ1 was measured when the cured products were stretched to a tensile elongation of 3% of their length in an atmosphere of 180°C. The cured products were also stretched to a tensile elongation of 3% of their length in an atmosphere of 180°C, and the saturated residual stress σ2 was measured when the stress reached a constant value and no longer changed. After the measurements, the residual stress ratio was calculated using the above formula (1). The results are shown in the "Residual Stress Ratio" column in Tables 1 to 3.

[0067] (3) Glass transition temperature of the cured product after heat treatment The cured products of each Example and Comparative Example were reheated at 180°C for 3 hours. The Tg of each cured product after reheating was measured under the test conditions described above. The results are shown in "Tg (after reheating)" in Tables 1 to 3. The Tg of the cured product after heat treatment was considered good if it was not lower than the Tg of the cured product ("Tg (after curing)" in Tables 1 to 3) by 10°C or more.

[0068] [Table 1]

[0069] [Table 2]

[0070] [Table 3]

[0071] <Result> The epoxy resin compositions of Examples 1 to 19 had residual stress rates of 85% or less. Furthermore, the Tg of the cured product was 150°C or higher, and the Tg of the cured product after heat treatment was higher than that before heat treatment, or at most lower by about 1 to 4°C. These results confirmed that the epoxy resin compositions of the present disclosure had high Tg after curing, that residual stress was alleviated by heat treatment, and that a decrease in heat resistance was suppressed.

[0072] Comparative Example 1 had a high residual stress rate because it contained a large amount of the acid anhydride curing agent (B) and did not contain the metal compound (C-1).

[0073] Comparative Example 2 did not contain the basic catalyst (C-2), and therefore had a high residual stress rate and a low Tg after curing. Comparative Example 3 contained a larger amount of metal compound (C-1) than Comparative Example 2, and therefore had a lower residual stress rate but a low Tg after curing.

[0074] Comparative Example 4 did not contain the metal compound (C-1) and therefore had a high residual stress rate. Comparative Example 5 contained a higher content of basic catalyst (C-2) than Comparative Example 4, which resulted in a lower residual stress rate, but the Tg of the cured product after heat treatment was lower by 10°C or more compared to before heat treatment. Comparative Example 6 contained an even higher content of basic catalyst (C-2) than Comparative Example 5, which resulted in a further lower residual stress rate, but the Tg of the cured product was lower, and the Tg of the cured product after heat treatment was lower by 10°C or more compared to before heat treatment.

[0075] Comparative Examples 7 and 8 contained a metal compound (C-1) and a basic catalyst (C-2), but had a high content of acid anhydride curing agent (B), resulting in a high residual stress rate. This is thought to be because the epoxy groups in the epoxy resin (A) reacted with the acid anhydride groups in the acid anhydride curing agent in equivalent amounts, resulting in fewer hydroxyl groups in the cured epoxy resin composition, making it less likely for transesterification to occur.

[0076] Comparative Examples 9 and 10 contained a metal compound (C-1) and a basic catalyst (C-2), but because the total content of the metal compound (C-1) and the basic catalyst (C-2) was high, the Tg of the cured product after heat treatment was lowered by 10°C or more compared to before heat treatment.

[0077] Comparative Example 11 contained a metal compound (C-1) and a basic catalyst (C-2), but because the total content of the metal compound (C-1) and the basic catalyst (C-2) was low, the residual stress rate was high and the Tg after curing was also low.

[0078] Comparative Example 12 contained a metal compound (C-1) and a basic catalyst (C-2), but because the content of the basic catalyst (C-2) relative to the total content of the metal compound (C-1) and the basic catalyst (C-2) was low, the residual stress rate was high and the Tg after curing was also low.

[0079] Comparative Example 13 contained a metal compound (C-1) and a basic catalyst (C-2), but the content of the acid anhydride curing agent (B) was low, so the residual stress rate was high and the Tg after curing was low.

[0080] The embodiments and examples disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

Claims

1. An epoxy resin composition comprising an epoxy resin (A), an acid anhydride curing agent (B), and a transesterification catalyst (C), the content of the acid anhydride curing agent (B) is more than 0.3 equivalents and less than 1.0 equivalent relative to 1 equivalent of the epoxy group of the epoxy resin (A); The transesterification catalyst (C) contains a metal compound (C-1) and a basic catalyst (C-2), the total content of the metal compound (C-1) and the basic catalyst (C-2) is more than 2 parts by mass and less than 9 parts by mass per 100 parts by mass of the epoxy resin (A), the content of the basic catalyst (C-2) relative to the total content of the metal compound (C-1) and the basic catalyst (C-2) is 25% by mass or more and 75% by mass or less, an epoxy resin composition, wherein σ1 is the stress when a cured product of the epoxy resin composition is stretched by 3% of its initial length in at least one temperature atmosphere equal to or higher than the glass transition temperature of the cured product, and σ2 is the stress when the cured product is stretched by 3% of its initial length in the same temperature atmosphere and maintained at that temperature atmosphere and the stress no longer changes, and the ratio of σ2 to σ1 is 85% or less.

2. the content of the metal compound (C-1) is 0.5 parts by mass or more and 7 parts by mass or less relative to 100 parts by mass of the epoxy resin (A), 2. The epoxy resin composition according to claim 1, wherein the content of the basic catalyst (C-2) is 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of the epoxy resin (A).

3. 2. The epoxy resin composition according to claim 1, wherein the metal compound (C-1) is zinc acetylacetonate.

4. 2. The epoxy resin composition according to claim 1, wherein the basic catalyst (C-2) is at least one selected from the group consisting of diazabicycloundecene, diazabicyclononene, and triazabicyclodecene.

5. A mold encapsulant comprising the epoxy resin composition according to any one of claims 1 to 4.

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