Aromatic lactone-containing resin, method for producing same, and curable resin composition

Abstract

The present invention provides an aromatic lactone-containing resin represented by general formula (1).　In the formula, R1, R2, and R3 each independently represent an alkyl group having 1-8 carbon atoms, X represents -CH2-, or a hydrocarbon group having 8-24 carbon atoms and having an aromatic ring and an alkylene group; a hydrogen atom of the hydrocarbon group may be substituted with a hydroxy group; a represents an integer of 0-3; b represents an integer of 0-2; c represents an integer of 0-3; and n represents an integer of 0-10.

Description

Aromatic lactone-containing resin, method for producing same, and curable resin composition

[0001] The present invention relates to an aromatic lactone-containing resin, a curable resin composition containing the same, and a method for producing the aromatic lactone-containing resin.

[0002] For semiconductor device encapsulants, a need has traditionally existed for reliability and excellent heat resistance under the temperature environment in which they are used. Traditionally, Si-based materials have been the mainstream for semiconductor device materials, and cured products of resin compositions containing epoxy resins as their primary component have been used. In recent years, SiC and GaN have attracted attention and their use has increased. Accordingly, the required operating temperature for semiconductor encapsulants has risen significantly from approximately 200°C or less to 250°C or higher. However, encapsulants for semiconductor devices manufactured using Si-based materials do not meet the heat resistance requirements for encapsulants used in semiconductor devices manufactured using SiC or GaN. Therefore, research and development of resin compositions that can yield encapsulants with high heat resistance has been underway. For example, Patent Document 1 discloses an encapsulating resin composition containing a maleimide resin having a specific chemical structure, a benzoxazine resin, and an inorganic filler as an encapsulant for use in high-temperature environments using SiC or GaN. It is believed that the benzoxazine resin functions as a curing agent in this encapsulating resin composition. The document describes that by using a benzoxazine resin, it is possible to improve the mechanical properties of the encapsulant without reducing its heat resistance, and to provide an encapsulant with excellent temperature cycle reliability.

[0003] Furthermore, in terms of reliability, encapsulants for semiconductor devices have traditionally been required to have excellent insulating properties and water resistance. For example, Patent Document 2 describes that a curable resin composition described therein, which contains a phenolic resin and melamine cyanurate, has excellent tracking resistance.

[0004] Patent Document 3 discloses an epoxy resin composition containing an epoxy resin, a six-membered lactone condensed with an aromatic or heteroaromatic skeleton, and a curing accelerator. The document states that the epoxy resin composition described therein can provide an epoxy resin cured product with small cure shrinkage and high elastic modulus.

[0005] JP 2018-115233 A JP 2021-105168 A JP 2013-032510 A

[0006] Resin compositions containing benzoxazine resins, such as those described in Patent Document 1, have the disadvantage that their curing mechanism results in a matrix with a high crosslink density, making the cured product hard and brittle. As a result, encapsulants produced using the encapsulating resin compositions described in Patent Document 1 have a certain level of high heat resistance, but are insufficient in terms of toughness. Furthermore, as described in Patent Document 2, in order to improve the tracking resistance of phenolic resins, special methods such as the addition of melamine cyanurate may be required.

[0007] On the other hand, Patent Document 3 does not consider at all a cured product having both high heat resistance and toughness, or a cured product having excellent tracking resistance and water resistance.

[0008]

[0009] Therefore, an object of the present invention is to provide a compound that is reactive with epoxy resins and that can give a cured product that has excellent toughness in addition to high heat resistance, or a cured product that has high tracking resistance and high water resistance. Another object of the present invention is to provide a curable resin composition that can give a cured product that has excellent toughness in addition to high heat resistance, or a cured product that has high tracking resistance and high water resistance. A further object of the present invention is to provide a method for producing the aromatic lactone-containing resin, which can produce the aromatic lactone-containing resin in an industrially advantageous manner.

[0009] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by using an aromatic lactone-containing resin having a specific chemical structure, and have thus completed the present invention.

[0010] That is, the present invention provides the following items [1] to [9]: [1] An aromatic lactone-containing resin represented by the following general formula (1):

[0011]

[0012] In the formula, R １ , R ２ and R ３ each independently represents an alkyl group having 1 to 8 carbon atoms, and X is —CH ２ - or a hydrocarbon group having 8 to 24 carbon atoms containing an aromatic ring and an alkylene group, wherein a hydrogen atom of the hydrocarbon group may be substituted with a hydroxyl group, a represents an integer of 0 to 3, b represents an integer of 0 to 2, c represents an integer of 0 to 3, and n represents an integer of 0 to 10. [2] The aromatic lactone-containing resin according to [1], represented by the following formula (2):

[0013]

[0014] In the formula, n represents an integer of 0 to 10.

[0015] [3] A curable resin composition comprising the aromatic lactone-containing resin according to [1] or [2], an epoxy resin, and a curing accelerator.

[0016] [4] The curable resin composition according to [3], further comprising a maleimide compound containing at least two maleimide groups in one molecule.

[0017] [5] The curable resin composition according to [3] or [4], further comprising an inorganic filler.

[0018] [6] A semiconductor encapsulant comprising the curable resin composition according to any one of [3] to [5].

[0019] [7] A cured product obtained by heat-curing the curable resin composition according to any one of [3] to [5].

[0020] [8] A semiconductor device having the cured product according to [7].

[0021] [9] A method for producing the aromatic lactone-containing resin according to [1] or [2], comprising a step of reacting an aromatic lactone monomer represented by the following general formula (3) with a crosslinking agent in the presence of an acid catalyst:

[0022]

[0023] In the formula, R represents an alkyl group having 1 to 8 carbon atoms, and d represents an integer of 0 to 3.

[0024] As described above, the aromatic lactone-containing resin of the present invention can provide a curable resin composition that can give a cured product having excellent heat resistance and toughness, as well as excellent temperature cycle reliability and durability, or a cured product having excellent tracking resistance and water resistance.

[0025] When the aromatic lactone-containing resin of the present invention reacts with an epoxy resin, the lactone ring opens, resulting in the formation of an alkylene chain (e.g., ethylene chain) and an ether group, which are generated by the ring opening. The cured product is therefore likely to have flexibility. Furthermore, the aromatic lactone-containing resin of the present invention is likely to undergo anionic copolymerization with an epoxy resin to produce a cured product with high crosslink density, thereby improving heat resistance. In particular, the reaction between the epoxy resin and a maleimide compound is likely to improve heat resistance. For these reasons, the use of the aromatic lactone-containing resin of the present invention facilitates the achievement of both toughness and heat resistance. In this specification, "excellent toughness" encompasses the cured product having high flexibility or excellent flexural strength. In this specification, examples of "excellent heat resistance" include a high glass transition temperature and a low coefficient of linear expansion at high temperatures (e.g., 260 to 280°C). The aromatic lactone-containing resin disclosed herein can provide a cured product that exhibits excellent heat resistance and low elasticity at high temperatures, in addition to excellent heat resistance and toughness. Such cured products also exhibit excellent temperature cycle reliability.

[0026] Furthermore, the aromatic lactone-containing resin of the present invention exhibits improved tracking resistance because the chain structure containing an ether group and an alkylene chain generated by ring-opening during reaction with an epoxy resin easily blocks carbonization pathways. Furthermore, the aromatic lactone-containing resin of the present invention more easily produces a cured product with excellent water resistance than a phenolic resin. This is because, while a phenolic resin produces a cured product with secondary hydroxyl groups when reacted with an epoxy group, the aromatic lactone-containing resin of the present invention theoretically does not produce hydroxyl groups when reacted with an epoxy group. For these reasons, the aromatic lactone-containing resin of the present invention is more likely to achieve both tracking resistance and water resistance in the cured product obtained by reacting it with an epoxy resin.

[0027] In addition, the aromatic lactone-containing resin of the present invention is likely to achieve both tracking resistance and flame retardancy. More specifically, the aromatic lactone-containing resin of the present invention is likely to improve tracking resistance as described above, while the open ring structure of the aromatic lactone-containing resin has an aromatic ring, making it easy to ensure the carbon residue rate required for flame retardancy. In particular, in the present invention, when X has an aromatic group, particularly a biphenyl structure, flame retardancy is particularly likely to be improved.

[0028] Although the mechanisms assumed in the present invention have been described above, the present invention is not limited to these mechanisms.

[0029] (Aromatic Lactone-Containing Resin) First, the aromatic lactone-containing resin of the present invention will be described. The aromatic lactone-containing resin of the present invention has a structure represented by the following general formula (1).

[0030]

[0031] In the formula, R １ , R ２ and R ３ each independently represents an alkyl group having 1 to 8 carbon atoms, and X is —CH ２-, or a hydrocarbon group having 8 to 24 carbon atoms containing an aromatic ring and an alkylene group, wherein a hydrogen atom of the hydrocarbon group may be substituted with a hydroxyl group; a represents an integer of 0 to 3; b represents an integer of 0 to 2; c represents an integer of 0 to 3; and n represents an integer of 0 to 10.

[0032] R in general formula (1) １ , R ２ and R ３ The alkyl group having 1 to 8 carbon atoms represented by the formula (I) may be linear or branched. Examples of linear alkyl groups include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group. Examples of branched alkyl groups include an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group, a tert-pentyl group, an isooctyl group, a 2-ethylhexyl group, and a tert-octyl group.

[0033] In the present invention, examples of hydrocarbon groups having 8 to 24 carbon atoms, which contain an aromatic ring and an alkylene group, represented by X, include those represented by the following formula (a), where the number of carbon atoms, 8 to 24, includes the number of carbon atoms in both the alkylene group and the aromatic ring.

[0034] -B-A-B- (a) In the formula, A represents an arylene group or a phenylalkylene group. B represents a direct bond or an alkylene group having 1 to 4 carbon atoms, and two Bs may be the same or different. However, when A is an arylene group, B represents an alkylene group having 1 to 4 carbon atoms.

[0035] The alkylene group having 1 to 4 carbon atoms represented by B in general formula (a) may be linear or branched. Examples of linear alkylene groups include methylene, ethylene, propylene, and butylene. Examples of branched alkylene groups include isopropylene, isobutylene, sec-butylene, and tert-butylene.

[0036] The arylene group represented by A in general formula (a) may contain an aromatic ring of a monocyclic structure, or may contain an aromatic ring of a condensed ring structure. Examples of the arylene group containing an aromatic ring of a monocyclic structure include a phenylene group; a biphenylene group; and bisphenylene groups such as a methylene bisphenylene group, an ethylene bisphenylene group, a propylene bisphenylene group, a monomethyl methylene bisphenylene group, and a dimethyl methylene bisphenylene group. Examples of the arylene group containing an aromatic ring of a condensed ring structure include a naphthylene group, a binaphthylene group, an anthracenylene group, and a phenanthrylene group.

[0037] Examples of the phenylalkylene group include a phenylmethylene group (such as a 1-phenylmethane-1,1-diyl group), a phenylethylene group (such as a 1-phenylethane-1,1-diyl group), a phenylpropylene group (such as a 1-phenylpropane-1,1-diyl group), and a phenylbutylene group (such as a 1-phenylbutane-1,1-diyl group).

[0038] X substitutes for a hydrogen atom on the benzene ring in each dihydrocoumarin structure in formula (1) and bonds to the benzene ring. １ When b is 2 or more, a plurality of R ２ may be the same or different. When c is 2 or more, a plurality of R ３ may be the same or different.

[0039] In the present invention, from the viewpoint of the polymerizability of the aromatic lactone-containing resin, a and c in general formula (1) are each independently preferably an integer of 0 to 2, more preferably an integer of 0 to 1, and most preferably 0.

[0040] In the present invention, from the viewpoint of the polymerizability of the aromatic lactone-containing resin, b in general formula (1) is preferably an integer of 0 to 1, and more preferably 0.

[0041] From the viewpoint of steric hindrance during polymerization of an aromatic lactone-containing resin, polymerization of an epoxy resin using an aromatic lactone-containing resin, or polymerization of an epoxy resin with a maleimide compound, R １ , R ２ and R ３ are each independently preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and particularly preferably an alkyl group having 1 or 2 carbon atoms. Needless to say, in this specification, the expression "during polymerization of an epoxy resin or an epoxy resin and a maleimide compound" allows the addition of other curable components to the "epoxy resin or an epoxy resin and a maleimide compound."

[0042] When the group represented by X in general formula (1) is a hydrocarbon group having 8 to 24 carbon atoms containing an aromatic ring and an alkylene group, B in general formula (a) is preferably a direct bond or a linear alkylene group having 1 to 4 carbon atoms, and more preferably a direct bond or a methylene group, from the viewpoints of material availability, curability, heat resistance of the cured product, low elasticity at heat, low water absorption, etc. From the same viewpoint, the arylene group represented by A in general formula (a) is preferably one containing an aromatic ring with a monocyclic structure, and more preferably a phenylene group, biphenylene group, or phenylalkylene group.

[0043] Specific examples of the hydrocarbon group having 8 to 24 carbon atoms containing an aromatic ring and an alkylene group represented by X in general formula (1) include groups represented by any of the following formulas (α) to (γ):

[0044] In the formula, R １１ , R １２ , R １３ and R １５ R each independently represents a hydroxyl group or an alkyl group having 1 to 5 carbon atoms. １４ represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. n11, n12, and n13 each independently represent an integer of 0 to 4. n15 represents an integer of 0 to 5. Each L independently represents an alkylene group having 1 to 4 carbon atoms.

[0045] From the viewpoint of the availability of materials and the polymerizability of the aromatic lactone-containing resin, n11, n12, n13, and n15 are each preferably independently an integer of 0 to 2, and particularly preferably 0. １１ , R １２ , R １３ , R １４ and R １５ The alkyl group represented by the formula (1) is R １ In view of steric hindrance during polymerization of an aromatic lactone-containing resin, polymerization of an epoxy resin using an aromatic lactone-containing resin, or polymerization of an epoxy resin with a maleimide compound, R １１ , R １２ , R １３ , R １５ are each independently preferably an alkyl group having 1 to 2 carbon atoms, and particularly preferably a methyl group. １４ is preferably a hydrogen atom or a methyl group, and particularly preferably a hydrogen atom. In (α), the methylene groups are preferably bonded to each other at the para-position, and in (β), they are preferably bonded to the 4,4'-positions of the biphenyl. Examples of L and their preferred values ​​are the same as those of B above.

[0046] From the viewpoint of availability of materials and polymerizability of the aromatic lactone-containing resin, preferred examples of the group represented by X include the groups represented by the following (i) to (v).

[0047]

[0048] X is -CH ２ The formula (i) is preferable in terms of heat resistance and the like, since the crosslink density of the cured product obtained by curing the epoxy resin or the composition of the epoxy resin and the maleimide compound is high.

[0049] Furthermore, it is preferable that X is a hydrocarbon group having 8 to 24 carbon atoms containing an aromatic ring and an alkylene group from the viewpoints of heat resistance, low water absorption, low elastic modulus at heat, etc. When X is a hydrocarbon group containing an aromatic ring and an alkylene group, it is preferable that X is a group represented by any of (α) to (γ), and among these, from the viewpoints of heat resistance, low water absorption, low elastic modulus at heat, and being able to achieve both flame retardancy and tracking resistance / water resistance, it is preferable that X is a group represented by (β), and in particular, the above-mentioned groups represented by (ii) or (iii) are most preferable.

[0050] In particular, a particularly preferred embodiment of the aromatic lactone-containing resin of the present invention is, for example, one represented by the following general formula (2).

[0051]

[0052] In the formula, n represents an integer of 0 to 10.

[0053] The aromatic lactone-containing resin of the present invention preferably has a softening point of 50° C. or higher, more preferably 55° C. or higher, and even more preferably 60° C. or higher, from the viewpoint of handleability due to blocking when the aromatic lactone-containing resin itself or when made into a curable resin composition such as an epoxy resin composition or a maleimide composition. Furthermore, the aromatic lactone-containing resin preferably has a softening point of 130° C. or lower, more preferably 120° C. or lower, and even more preferably 110° C. or lower, from the viewpoint of handleability when kneading with an inorganic filler or the like when made into a curable resin composition such as an epoxy resin composition or a maleimide composition. The softening point of the aromatic lactone-containing resin can be measured by the method described in the Examples below.

[0054] From the viewpoint of the fluidity of curable resin compositions such as epoxy resin compositions and maleimide compositions, the aromatic lactone-containing resin of the present invention preferably has a melt viscosity at 150°C of 2.0 Pa·s or less, more preferably 1.7 Pa·s or less, and particularly preferably 1.5 Pa·s or less. Furthermore, from the viewpoint of preventing the aromatic lactone-containing resin from overflowing from a mold during molding of the composition, the melt viscosity at 150°C is preferably 0.01 Pa·s or more, and more preferably 0.02 Pa·s or more. The melt viscosity of the aromatic lactone-containing resin can be measured by the method described in the examples below.

[0055] In the present invention, it is preferable to contain a component in which n is 1 or more in formula (1) (hereinafter also referred to as "n = 1 or more component") in order to suppress an increase in the softening point due to the crystallinity of the aromatic lactone-containing resin. In the aromatic lactone-containing resin represented by formula (1), the content of n = 1 or more components is, for example, preferably 5% or more, more preferably 10% or more, particularly preferably 20% or more, particularly preferably 30% or more, and even more preferably 40% or more. Although not limited thereto, the content of n = 1 or less components in the aromatic lactone-containing resin represented by formula (1) may be 99% or less, or may be 95% or less. For example, from the viewpoint of handleability, the content of the component in which n is 0 in formula (1) (hereinafter also referred to as the "n=0 component") in the aromatic lactone-containing resin represented by formula (1) may be 0 to 90%, particularly 20 to 80%, and the content of the component in which n is 1 in formula (1) (hereinafter also referred to as the "n=1 component") in the aromatic lactone-containing resin represented by formula (1) may be 0 to 50%, particularly 10 to 40%. These numerical ranges may be satisfied alone or in any combination, and only either the upper or lower limit may be selected. In the aromatic lactone-containing resin A obtained in Example 1 below, the n=0 component in the aromatic lactone-containing resin represented by formula (1) was in the range of 20 to 80%, and the proportion of the n=1 component was in the range of 10 to 40%.

[0056] (Suitable Method for Producing Aromatic Lactone-Containing Resin) The aromatic lactone-containing resin of the present invention can be suitably synthesized, for example, by reacting an aromatic lactone monomer represented by the following general formula (3) with a crosslinking agent in the presence of an acid catalyst.

[0057]

[0058] In the formula, R represents an alkyl group having 1 to 8 carbon atoms, and d represents an integer of 0 to 3.

[0059] The alkyl group represented by R in the general formula (3) is R in the general formula (1). １ The alkyl group may be the same as the alkyl group represented by the above formula.

[0060] In terms of material availability and reactivity, d in general formula (3) is preferably an integer of 0 to 2, more preferably an integer of 0 to 1, and most preferably 0.

[0061] The crosslinking agent used in the synthesis of the aromatic lactone-containing resin of the present invention is not particularly limited, and can be arbitrarily selected from known crosslinking agents according to the structure of the desired aromatic lactone-containing resin. ２ - or is represented by the formula (γ) and R １４ When X is a hydrogen atom, examples of the crosslinking agent include aldehydes such as formaldehyde, benzaldehyde, hydroxybenzaldehyde, etc. Furthermore, when X is represented by formula (α) or formula (β), examples of the crosslinking agent include a compound in which an alkoxy group or a halogen atom (for example, Y1 described later) is bonded to each of the two bonds in formula (α) or formula (β) (the bonds on the opposite side to the benzene ring in each of the two Ls).

[0062] In the present invention, for example, a compound represented by the following general formula (4-1) or general formula (4-2) can be suitably used as the crosslinking agent, and a compound represented by general formula (4-2) is particularly preferred, and a compound represented by general formula (4A) is particularly preferred.

[0063]

[0064] In the formula R１１ , n11 is the same as in formula (α), and R １２ , R １３ , n12 and n13 are the same as in formula (β), and Y1 represents a halogen atom or an alkoxy group having 1 to 4 carbon atoms.

[0065]

[0066] In the formula, Y1 is the same as in formulas (4-1) and (4-2).

[0067] Examples of halogen atoms represented by Y1 in general formulas (4-1) and (4-2) include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. Examples of alkoxy groups having 1 to 4 carbon atoms represented by Y1 in general formulas (4-1) and (4-2) include methoxy groups, ethoxy groups, propoxy groups, and butoxy groups. In the present invention, from the standpoints of reactivity, availability, and the like, the group represented by Y1 in general formulas (4-1) and (4-2) is preferably a chlorine atom or an alkoxy group having 1 to 3 carbon atoms, more preferably a methoxy group or a chlorine atom, and even more preferably a methoxy group.

[0068] When the aromatic lactone monomer represented by formula (3) is reacted with a crosslinking agent, the amount of crosslinking agent is preferably 0.05 to 0.80 mol, more preferably 0.10 to 0.70 mol, and even more preferably 0.20 to 0.60 mol, per 1 mol of aromatic lactone monomer. By setting the molar ratio of aromatic lactone monomer to crosslinking agent within the above ranges, the softening point and melt viscosity of the aromatic lactone-containing resin of the present invention can be set within predetermined ranges.

[0069] The acid catalyst used in the synthesis of the aromatic lactone-containing resin of the present invention can be an acid catalyst, and the condensation polymerization reaction can be carried out under an acid catalyst. There are no particular limitations on the acid catalyst used in the condensation polymerization reaction, and known acid catalysts such as hydrochloric acid, oxalic acid, sulfuric acid, phosphoric acid, and paratoluenesulfonic acid can be used alone or in combination of two or more. Among these, it is preferable to use at least one acid selected from paratoluenesulfonic acid, hydrochloric acid, sulfuric acid, and oxalic acid.

[0070] In the method for producing an aromatic lactone-containing resin, a solvent may or may not be used. When a solvent is used, examples thereof include water and lower alcohols (aliphatic alcohols having 1 to 6 carbon atoms). Specific examples include methanol, ethanol, propanol, butanol, pentanol, hexanol, and cyclohexanol. When a solvent is used, the amount used is not particularly limited, but in consideration of the costs of removing and recovering the solvent, the amount used is preferably 100% by mass or less, more preferably 50% by mass or less, and even more preferably less than 30% by mass, based on the aromatic lactone monomer.

[0071] The reaction temperature for the condensation polymerization reaction is not particularly limited and is usually 50 to 200° C., preferably 70 to 180° C., and more preferably 80 to 170° C. If the reaction temperature is 50° C. or higher, the reaction can be easily progressed, and if the reaction temperature is 200° C. or lower, the reaction can be easily controlled and the desired aromatic lactone-containing resin of the present invention can be stably obtained.

[0072] The reaction time for the polycondensation reaction varies depending on the reaction temperature, but is usually about 0.1 to 20 hours. The polycondensation reaction is usually carried out under normal pressure, but may be carried out under increased or reduced pressure.

[0073] The synthesis of the aromatic lactone-containing resin may be carried out in an inert gas atmosphere such as nitrogen gas or argon gas, or in the air. In the present invention, carrying out the synthesis in an inert gas atmosphere is preferred from the viewpoint of suppressing oxidation of the product.

[0074] The aromatic lactone-containing resin of the present invention can be suitably used as a curing agent for epoxy resins. As will be shown in the examples described later, a curable resin composition containing the aromatic lactone-containing resin of the present invention and an epoxy resin can give a cured product that has high heat resistance, excellent mechanical properties such as flexural strength, a low hot elastic modulus, and / or excellent tracking resistance and water resistance.

[0075] Next, the curable resin composition of the present invention will be described. The curable resin composition of the present invention contains an epoxy resin and a curing accelerator in addition to the aromatic lactone-containing resin represented by the general formula (1) described above.

[0076] The epoxy resin contained in the curable resin composition of the present invention has two or more epoxy groups in its molecule. In the present invention, any epoxy resin used in the technical field to which the present invention pertains can be used without particular limitation. Specific examples of epoxy resins include glycidyl ether epoxy resins such as phenol novolac epoxy resins, cresol novolac epoxy resins, biphenyl epoxy resins, triphenylmethane epoxy resins, phenol aralkyl novolac epoxy resins, biphenyl aralkyl epoxy resins, phenol-biphenyl aralkyl epoxy resins, bisphenol A epoxy resins, and bisphenol F epoxy resins; glycidyl ester epoxy resins; glycidyl amine epoxy resins; and halogenated epoxy resins. These epoxy resins may be used alone or in combination of two or more. In the present invention, from the viewpoint of the heat resistance and mechanical properties of the cured product, it is preferable to use a glycidyl ether type epoxy resin as the epoxy resin, it is preferable to use an epoxy resin having a structure obtained by the reaction of an aromatic compound having a phenolic hydroxyl group with epichlorohydrin, and it is more preferable to use a biphenyl type epoxy resin or a phenol-biphenyl aralkyl type epoxy resin.

[0077] In the curable resin composition of the present invention, the aromatic lactone-containing resin represented by general formula (1) functions as a curing agent, as described above. The curable resin composition of the present invention may contain another curing agent in addition to the aromatic lactone-containing resin represented by general formula (1). The type of the other curing agent is not particularly limited, and various curing agents can be used depending on the application of the curable resin composition. Examples of the other curing agent include phenolic resins, amine-based curing agents, amide-based curing agents, and acid anhydride-based curing agents.

[0078] The proportion of the aromatic lactone-containing resin represented by general formula (1) in the curing agent (e.g., epoxy resin curing agent) in the curable resin composition of the present invention is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 70% by mass or more, particularly preferably 90% by mass or more, and most preferably 100% by mass, from the viewpoint of sufficiently increasing the heat resistance and mechanical properties of the cured product.

[0079] In the curable resin composition of the present invention, which contains an epoxy resin and an aromatic lactone-containing resin as a curing agent, the ratio of the number of equivalents of -OCO- groups in the lactone to the number of equivalents of epoxy groups in the epoxy resin (-OCO- group equivalents / epoxy group equivalents) is preferably 0.3 or more and 3.0 or less, more preferably 0.4 or more and 1.5 or less.

[0080] The curing accelerator contained in the curable resin composition of the present invention can be any known compound used as a curing accelerator in the technical field to which the present invention pertains, without any particular limitation. Specific examples of the curing accelerator include known curing accelerators for curing epoxy resins with phenolic resins. Examples include organic phosphine compounds and their boron salts, tertiary amines, quaternary ammonium salts, imidazoles, tetraphenylboron salts, cycloamidines, and quaternary phosphonium salts. One of these curing accelerators may be used alone, or two or more may be used in combination. The proportion of the curing accelerator added to the epoxy resin can be the same as that in known epoxy resin compositions. For example, it is preferably 0.1 to 25 parts by mass, and more preferably 1 to 20 parts by mass, per 100 parts by mass of the epoxy resin.

[0081] The curable resin composition of the present invention may further contain a maleimide compound from the viewpoint of the heat resistance and mechanical properties of the cured product. In the present invention, any maleimide compound used in the technical field to which the present invention pertains can be used without particular limitation.

[0082] In the present invention, the maleimide compound may contain at least two maleimide groups in one molecule. Examples of the maleimide compound containing at least two maleimide groups in one molecule include the maleimide compounds represented by the following general formula (5) and the maleimide compounds represented by the following general formula (6).

[0083]

[0084] In the formula, Y is a divalent group having one carbon-carbon double bond in the main chain, and Z is a divalent group having 2 to 40 carbon atoms.

[0085]

[0086] In the formula, Y is a divalent group having one carbon-carbon double bond as the main chain, and s is a value of 0 or greater.

[0087] In the general formulas (5) and (6), Y is —CR 1 =CR 2 - (R 1 and R 2 each independently represents a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms. ) In general formula (5), Z can be a cyclic aliphatic hydrocarbon group, a linear aliphatic hydrocarbon group, a branched aliphatic hydrocarbon group, an aromatic hydrocarbon group, a heterocyclic group, or a group combining two or more of these. In general formula (5), s is preferably a value of 0 or more and 4 or less, more preferably 0 or more and 2 or less.

[0088] As the maleimide compound containing at least two maleimide groups in one molecule, for example, an aromatic maleimide compound having two or more maleimide groups in one molecule, and an aliphatic maleimide compound having two or more maleimide groups in one molecule can be used.

[0089] The aromatic maleimide compound is a maleimide compound having one or more aromatic rings in its skeleton.Specific examples of the aromatic maleimide compound include N,N'-p-phenylene bismaleimide, N,N'-m-phenylene bismaleimide, N,N'-2,4-toluylene bismaleimide, N,N'-2,6-toluylene bismaleimide, N,N'-4,4-diphenylmethane bismaleimide, N,N'-3,3-diphenylmethane bismaleimide, N,N'-4,4-diphenylether bismaleimide, N,N'-3,3-diphenylether bismaleimide, N,N'-4,4-diphenylsulfide bismaleimide, and N,N'-3, 3-Diphenylsulfide bismaleimide, N,N'-4,4-diphenylsulfone bismaleimide, N,N'-3,3-diphenylsulfone bismaleimide, N,N'-4,4-diphenylketone bismaleimide, N,N'-3,3-diphenylketone bismaleimide, N,N'-4,4-biphenyl bismaleimide, N,N'-3,3-biphenyl bismaleimide, N,N'-4,4-diphenyl-1,1-propane bismaleimide, N,N'-3,3-diphenyl-1,1-propane bismaleimide, 3,3'-dimethyl-N,N'-4 ,4-diphenylmethane bismaleimide, 3,3'-dimethyl-N,N'-4,4'-biphenyl bismaleimide, 1,3-bis(3-maleimidophenoxy)benzene, bis[4-(3-maleimidophenoxy)phenyl]methane, 1,1-bis[4-(3-maleimidophenoxy)phenyl]ethane, 1,2-bis[4-(3-maleimidophenoxy)phenyl]ethane, 2,2-bis[4-(3-maleimidophenoxy)phenyl]propane, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, 2,2-bis[4 bis[4-(3-maleimidophenoxy)phenyl]butane, 2,2-bis[4-(3-maleimidophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 4,4'-bis(3-maleimidophenoxy)biphenyl, bis[4-(3-maleimidophenoxy)phenyl]ketone, bis[4-(3-maleimidophenoxy)phenyl]sulfoxide, bis[4-(3-maleimidophenoxy)phenyl]sulfone, bis[4-(3-maleimidophenoxy)phenyl]ether, and polyphenylmethane maleimide.

[0090] The aliphatic maleimide compound is a maleimide compound having an aliphatic structure in its skeleton. The aliphatic maleimide compound may or may not have an aliphatic cyclic structure in its skeleton. Examples of the aliphatic maleimide compound not having an aliphatic chain structure in its skeleton include 1,6-bismaleimide-(2,2,4-trimethyl)hexane, 1,6-bismaleimide-(2,4,4-trimethyl)hexane, N,N'-decamethylene bismaleimide, N,N'-octamethylene bismaleimide, N,N'-hexamethylene bismaleimide, N,N'-trimethylene bismaleimide, N,N'-ethylene bismaleimide, hexamethylenediamine bismaleimide, N,N'-1,2-ethylene bismaleimide, N,N'-1,3-propylene bismaleimide, and N,N'-1,4-tetramethylene bismaleimide. An example of an aliphatic maleimide compound having an aliphatic cyclic structure in its skeleton is bis[(2,5-dioxo-2,5-dihydropyrrol-1-yl)methyl]bicyclo[2,2,1]heptane.

[0091] In the present invention, the above maleimide compounds may be used singly or in combination of two or more.

[0092] In the present invention, it is preferable to use an aromatic maleimide compound as the maleimide compound containing at least two maleimide groups in one molecule.

[0093] The amount of the maleimide compound in the curable resin composition of the present invention may be, for example, less than 100 parts by mass or may be 50 parts by mass or less relative to 100 parts by mass of the epoxy resin. However, from the viewpoint of obtaining a cured product having higher heat resistance and even more excellent mechanical properties such as bending strength, the content of the maleimide compound is preferably 100 to 600 parts by mass, and more preferably 200 to 500 parts by mass, relative to 100 parts by mass of the epoxy resin.

[0094] The curable resin composition of the present invention preferably contains an inorganic filler from the viewpoint of the heat resistance and mechanical properties of the cured product. In the present invention, inorganic fillers used in the technical field to which the present invention pertains can be used without particular limitation. Specific examples of inorganic fillers include silica such as amorphous silica and crystalline silica, alumina, calcium silicate, calcium carbonate, talc, mica, barium sulfate, and magnesium oxide.

[0095] The content of the inorganic filler in the curable resin composition of the present invention is preferably 60 to 95 mass %, more preferably 65 to 95 mass %, from the viewpoint of the heat resistance and mechanical properties of the cured product. The content of the inorganic filler is calculated by the following formula.

[0096] Content of inorganic filler=[mass of inorganic filler in curable resin composition / mass of curable resin composition×100]

[0097] The curable resin composition of the present invention may contain solvents and other additives used in the technical field to which the present invention pertains, such as release agents, colorants, coupling agents, and flame retardants.

[0098] The shape of the curable resin composition of the present invention is not particularly limited, and may be a predetermined shape such as powder, granules, or tablet. In the present invention, the granular shape refers to an aggregate formed by solidifying powder of the powdered curable resin composition. The tablet shape refers to a shaped body formed into a predetermined shape by tableting the curable resin composition under high pressure.

[0099] The curable resin composition of the present invention can be suitably obtained by melting and mixing the aromatic lactone-containing resin represented by the general formula (1), the epoxy resin, and the curing accelerator as needed using a mixing device such as a twin-screw kneader or a twin-roll mill, etc. The obtained curable resin composition is suitably powdered using a pulverizer.

[0100] The use of the curable resin composition of the present invention is not particularly limited, and it can be suitably used, for example, as a semiconductor encapsulant. The cured product of the curable resin composition of the present invention has high heat resistance and mechanical properties. Therefore, it is particularly suitable for use as a semiconductor encapsulant for semiconductor devices manufactured using SiC or GaN, which require high heat resistance in addition to good mechanical properties.

[0101] A cured product can be obtained by heating and curing (thermal curing) the curable resin composition of the present invention. There are no particular limitations on the curing method and curing conditions for the curable resin composition, and any curing method and curing conditions employed in the technical field to which the present invention pertains can be applied. For example, the curable resin composition of the present invention can be cured by heat treatment at 100°C to 350°C for 0.01 to 20 hours. By setting the heating temperature to 100°C or higher, the curable resin composition can be easily cured, and by setting the heating temperature to 350°C or lower, performance degradation due to thermal decomposition can be prevented. Furthermore, by setting the heating time to 0.01 hours or longer, the reaction can be easily completed, and by setting the heating time to 20 hours or shorter, productivity can be improved.

[0102] The cured product of the curable resin composition of the present invention is preferably used as an encapsulant for semiconductor devices. Specifically, in a semiconductor device having a substrate, a semiconductor element mounted on the substrate, and an encapsulant for encapsulating the semiconductor element, the encapsulant is composed of the cured product of the curable resin composition of the present invention. Examples of semiconductor elements include SiC elements such as IGBTs (Insulated Gate Bipolar Transistors) and power chips such as diode chips, as well as Si elements, GaN elements, and Ga ２ O ３ The sealing material of the present invention can be used for sealing SiC elements, GaN elements, Ga ２ O ３ Even when used in high-temperature environments of 200°C or higher, or 250°C or higher, using elements, diamond elements, etc., the material has excellent temperature cycle reliability and durability for long-term use due to its heat resistance, toughness, low elastic modulus at heat, etc.

[0103] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0104] Example 1 Synthesis of Aromatic Lactone-Containing Resin The raw materials, 296 g (2.0 mol) of 3,4-dihydrocoumarin and 121 g (0.5 mol) of 4,4'-bismethoxymethylbiphenyl, were placed in a 1000 mL glass flask equipped with a thermometer, a charging / distillation outlet, a condenser, and a stirrer, and the internal temperature was raised to 50°C under a nitrogen stream to dissolve the raw materials. 5.9 g of paratoluenesulfonic acid was added as an acid catalyst to the flask, and the raw materials were reacted at an internal temperature of 130°C for 7 hours and then at 165°C for another 7 hours to obtain a reaction product. The reaction product was washed with water, then heated to 165°C and subjected to a reduced pressure treatment to obtain aromatic lactone-containing resin A. The aromatic lactone-containing resin A had a softening point of 102°C, a melt viscosity at 150°C of 1.5 Pa·s, and a content of components with n=1 or more of 50%.

[0105] [Measurement of softening point] The softening point was measured using the following equipment. Equipment used: FP83HT dropping point / softening point measurement system manufactured by Mettler Toledo K.K. Measurement conditions: Heating rate 2°C / min Measurement method: The molten sample was poured into a sample cup and allowed to cool and solidify. Cartridges were fitted onto the top and bottom of the cup filled with the sample, and the cup was then inserted into a furnace. The resin softened and flowed down the orifice, and the temperature at which the bottom passed through the light path was detected by a photocell as the softening point (°C).

[0106] [Measurement of Melt Viscosity] The melt viscosity (Pa s) at 150°C was measured using the following equipment. Equipment used: Brookfield Brookfield Type viscometer "DV2T" manufactured by Eiko Seiki Co., Ltd. Measurement temperature: 150°C Measurement method: The furnace temperature of the Brookfield Type viscometer was set to 150°C, and a predetermined amount of sample was weighed into a cup. The cup containing the weighed sample was placed into the furnace to melt the resin, and a spindle was inserted from above. The spindle was rotated, and the melt viscosity was read when the displayed viscosity value stabilized.

[0107] [Content of n=1 or more components] The molecular weight distribution of the aromatic lactone-containing resin was measured using a gel permeation chromatograph (GPC) analyzer, and the content (%) of trinuclear (n=1) or more components was calculated as the ratio of the area of ​​each component to the area of ​​the entire aromatic lactone-containing resin. The area of ​​each component was calculated by dividing the peak by the lowest point between each component peak, using the linear portion before and after the peak of the entire aromatic lactone-containing resin as the baseline. The instruments and measurement conditions used for the measurement are shown below. Equipment used: Waters Alliance 2695 Columns: SHODEX KF-804 x 1, KF-803 x 1, KF-802 x 1, KF-802.5 x 1, KF-801 x 1 Guard column: SHODEX KF-G Solvent: Tetrahydrofuran (THF) Detector: UV-Visible Detector 2489 Detection wavelength: 254 nm Flow rate: 1 mL / min Column oven temperature: 40°C Injection volume: 100 μL Sample concentration: 0.1 mg / mL Analysis software: Empower3 (Waters)

[0108] [Examples 2 to 4 and Comparative Example 1] <Preparation 1 of Curable Resin Composition> A mixture was obtained by blending the components shown in Table 1 in the ratios shown in Table 1. The resulting mixture was kneaded using two rolls at 80°C to 100°C and then pulverized to obtain the curable resin compositions of Examples 2 to 4 and Comparative Example 1. The components in Table 1 are as follows. The numerical values ​​in Table 1 represent parts by mass.

[0109] Aromatic lactone-containing resin A: Aromatic lactone-containing resin A synthesized in Example 1 Benzoxazine resin A': P-d-type benzoxazine (manufactured by Shikoku Chemical Industry Co., Ltd.) Epoxy resin B-1: Polyphenol-modified biphenyl aralkyl-type epoxy resin (manufactured by Nippon Kayaku Co., Ltd., "NC-3500", epoxy equivalent: 205 g / eq) Epoxy resin B-2: Biphenyl-type epoxy resin (manufactured by Mitsubishi Chemical Corporation, "YX-4000", epoxy equivalent: 185 g / eq) Maleimide compound C-1: Compound represented by the following formula (C-1) (manufactured by Daiwa Chemical Industry Co., Ltd., "BMI-4000") Maleimide compound C-2: Compound represented by the following formula (C-2) (manufactured by Daiwa Chemical Industry Co., Ltd., "BMI-2300") Curing accelerator D (curing catalyst): 2-methylimidazole (manufactured by Shikoku Chemical Industry Co., Ltd., "2MZ-H") Inorganic filler E: Silica ("FB-950" manufactured by Denka Co., Ltd.)

[0110]

[0111]

[0112]

[0113] <Evaluation> Tablets were prepared using the curable resin compositions obtained in the Examples and Comparative Examples. Test pieces were prepared by injecting the prepared tablets into a low-pressure transfer molding machine under conditions of a mold temperature of 175°C, an injection pressure of 6.8 MPa, and a dwell time of 600 seconds. The prepared test pieces were then post-cured at 180°C for 8 hours to prepare EMC (Epoxy Moldering Compound) test pieces. The thermal properties and mechanical properties of the prepared EMC test pieces were evaluated by the following tests.

[0114] <Mechanical Property Evaluation> An EMC test piece was cut into a shape of 2 mm thick x 25 mm wide x 40 mm long to prepare a sample. The stress, strain and elastic modulus of the sample were measured by a three-point bending test using a thermostatic bath-equipped universal testing machine (manufactured by A&D Co., Ltd.) under the following conditions. The results are shown in Table 2. (Measurement conditions) Test speed: 2 mm / min Support distance: 60 mm Temperature: 23°C

[0115] <Evaluation of Thermal Properties> The storage modulus, glass transition temperature, and linear expansion coefficient (α1, α2) of the EMC test specimen were measured by the following methods. The results are shown in Table 2.

[0116] (1) Glass transition temperature (Tg(DMA)), storage modulus An EMC test piece was cut into a size of 40 mm x 2 mm x 4 mm to serve as a measurement sample. Measurements were performed using a dynamic viscoelasticity (DMA) measuring device (TA Instruments' "RSA-G2"), measuring the storage modulus in an air atmosphere while raising the temperature from 30°C at a rate of 3°C / min, and determining the storage modulus at 30°C and 330°C. The peak temperature of Tan δ was taken as Tg(DMA).

[0117] (2) Glass transition temperature (Tg (TMA)) and linear expansion coefficient (α1, α2) The EMC test piece was cut into a size of 10 mm x 6 mm x 4 mm to serve as a measurement sample. Using a thermomechanical analyzer ("TMA-60" manufactured by Shimadzu Corporation), the glass transition temperature Tg (TMA) and linear expansion coefficient (α1, α2) of the sample were measured under a nitrogen atmosphere while the temperature was raised from 30°C at a heating rate of 3°C / min. The linear expansion coefficient from 60°C to 100°C was defined as α1, and the linear expansion coefficient from 260°C to 280°C was defined as α2.

[0118]

[0119] As is clear from Table 2, the cured products of the curable resin compositions of Examples 2 to 4 using the aromatic lactone-containing resin of the present invention had a lower linear expansion coefficient at 260-280°C than the benzoxazine-containing resin, comparable glass transition temperatures, and high heat resistance. Furthermore, the cured products of Examples 2 to 4 exhibited superior flexural strength compared to Comparative Example 1. The distortion of the cured products of Examples 2 to 4 was also as small as that of Comparative Example 1. The cured products of Examples 2 to 4 also exhibited excellent low modulus of elasticity at 330°C. From the above, it can be seen that the aromatic lactone-containing resin of the present invention can provide a semiconductor encapsulant that has excellent heat resistance, toughness, and low elasticity at high temperatures, and is highly reliable even when used at high temperatures.

[0120] [Examples 5 to 6 and Comparative Examples 2 to 3] <Preparation 2 of Curable Resin Composition> The components shown in Table 3 were blended in the ratios shown in Table 3 to obtain a mixture. The obtained mixture was kneaded using a two-roll mill at a temperature of 30°C to 80°C and then pulverized to obtain the curable resin compositions of Examples 5 to 6 and Comparative Examples 2 to 3. The components in Table 3 are as follows. The numerical values ​​in Table 3 represent parts by mass.

[0121] Aromatic lactone-containing resin A: Aromatic lactone-containing resin A synthesized in Example 1. Phenolic resin A″: Biphenylaralkyl-type phenolic resin represented by the following formula (A″) (hydroxyl group equivalent: 134 g / eq, weight average molecular weight (Mw): 1350) (In the formula, n is any number that results in the above Mw, and p', q', and r' are each independently an integer of 0 or 1.) Phenolic resin A'": a triphenylmethane-type phenolic resin represented by the following formula (A'") (hydroxyl group equivalent: 98 g / eq, weight average molecular weight (Mw): 680) (wherein n is any number that results in the above Mw.) Epoxy resin B-1: polyhydric phenol-modified biphenyl aralkyl type epoxy resin ("NC-3500" manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: 205 g / eq) Epoxy resin B-3: trisphenol methane type epoxy resin ("EPPN-501H" manufactured by Nippon Kayaku Co., Ltd., epoxy equivalent: 166 g / eq) Curing accelerator D-2: "TPP" manufactured by Hokko Chemical Industry Co., Ltd.

[0122]

[0123] <Evaluation> Tablets were prepared using the curable resin compositions obtained in the Examples and Comparative Examples. Test pieces were prepared by injecting the prepared tablets into a low-pressure transfer molding machine under conditions of a mold temperature of 175°C, an injection pressure of 6.8 MPa, and a dwell time of 120 seconds. The prepared test pieces were then post-cured at 180°C for 8 hours to prepare EMC (Epoxy Moldering Compound) test pieces. The prepared EMC test pieces were evaluated by the above-mentioned methods using the following tests.

[0124] <Evaluation of Flame Retardancy> (i) Flammability EMC test specimens of the following size were used to evaluate the flame retardancy in accordance with UL-94. Test specimen size: 127 mm x 13 mm x 1 mm

[0125] <Evaluation of Electrical Properties> (ii) Tracking Resistance Index (Comparative Tracking Index (CTI)) Measurement was performed in accordance with JIS C 2134 using EMC test specimens of the following size. Test specimen dimensions: 19 mm x 19 mm x 4 mm Test electrode: Platinum (tip edge 30°) Electrode arrangement: 4.0 mm ± 0.1 mm (opposing angle 60°) Electrolyte: Solution A (NH4Cl 0.1% ± 0.002%, resistivity: 3.95 Ω m ± 0.05 Ω m Test conditions: 50 drops confirmed (n = 5), 100 drops confirmed (n = 5) Test environment: 23°C ± 2°C, 50% RH ± 5% RH Measuring device: Tracking resistance tester HAT-112-3 (manufactured by Yamayo Test Instruments)

[0126] <Evaluation of Physical Properties> (iii) Water Resistance The water absorption rate (%) was measured using test specimens of the following size by the following method. Test specimen size: diameter 50 mm x thickness 3 mm Test conditions: The test specimen was immersed in pure water and heated at 95°C for 24 hours. The water absorption rate was calculated from the change in mass of the test specimen before and after water absorption using the following formula: Water absorption rate (%) = (W1 - W0) / W0 x 100 W0: mass (g) of the test specimen before water absorption W1: mass (g) of the test specimen after water absorption

[0127]

[0128] As is clear from Table 4, the cured products of the curable resin compositions of Examples 5 and 6, which used the aromatic lactone-containing resin of the present invention, were excellent in all of tracking resistance, water resistance, and flame retardancy. On the other hand, the cured products of Comparative Examples 2 and 3, which used the phenolic resin, were poor in tracking resistance and water resistance, and the cured product of Comparative Example 3 was also poor in flame retardancy. In particular, while it has traditionally been difficult to achieve both tracking resistance and flame retardancy in cured products using phenolic resins, the cured products of the curable resin compositions of Examples 5 and 6, which used the aromatic lactone-containing resin of the present disclosure, were excellent in tracking resistance and achieved both tracking resistance and flame retardancy without the need for special methods such as the addition of melamine cyanurate.

[0129] The aromatic lactone-containing resin of the present invention provides a curable resin composition that can give a cured product having high heat resistance and excellent mechanical properties such as toughness, or a cured product having excellent tracking resistance and water resistance. An encapsulant using the curable resin composition of the present invention has excellent temperature cycle reliability in high-temperature environments and durability for long-term use, or has excellent insulating properties and water resistance.

Claims

1. An aromatic lactone-containing resin represented by the following general formula (1): In the formula, R １ , R ２ and R ３ each independently represents an alkyl group having 1 to 8 carbon atoms, and X is —CH ２ -, or a hydrocarbon group having 8 to 24 carbon atoms containing an aromatic ring and an alkylene group, wherein a hydrogen atom of the hydrocarbon group may be substituted with a hydroxyl group; a represents an integer of 0 to 3; b represents an integer of 0 to 2; c represents an integer of 0 to 3; and n represents an integer of 0 to 10.

2. The aromatic lactone-containing resin according to claim 1, which is represented by the following formula (2): In the formula, n represents an integer of 0 to 10.

3. A curable resin composition comprising the aromatic lactone-containing resin according to claim 1, an epoxy resin, and a curing accelerator.

4. The curable resin composition according to claim 3, further comprising a maleimide compound containing at least two maleimide groups in one molecule.

5. The curable resin composition according to claim 3 or 4, further comprising an inorganic filler.

6. A semiconductor encapsulant comprising the curable resin composition according to claim 3 or 4.

7. A cured product obtained by heat-curing the curable resin composition according to claim 3 or 4.

8. A semiconductor device comprising the cured product according to claim 7.

9. A method for producing the aromatic lactone-containing resin according to claim 1, comprising the step of reacting an aromatic lactone monomer represented by the following general formula (3) with a crosslinking agent in the presence of an acid catalyst: In the formula, R represents an alkyl group having 1 to 8 carbon atoms, and d represents an integer of 0 to 3.

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