JP7515988B2 - Thermosetting citraconimide resin composition - Google Patents

Description

The present invention relates to a thermosetting citraconic imide resin composition and to uncured films, cured films, adhesives, semiconductor encapsulants, and substrates and their constituent materials that use the same.

Curable resins, especially thermosetting resins, are widely used as materials for adhesion, casting, coating, impregnation, lamination, and molding. However, in recent years, their applications have become more diverse, and depending on the usage environment and conditions, conventional curable resins may not be sufficient. For example, with the advancement of electronic devices, materials with low dielectric properties are required for laminates for printed wiring boards used in various electrical devices in order to improve signal transmission speed. In addition, as a component for electronic devices, there is a semiconductor package in which a semiconductor element is sealed with a resin, but as semiconductor elements have shifted from Si to SiC, which has better high-temperature operation, heat resistance has also come to be required for semiconductor encapsulation materials.

In light of this background, research into and use of maleimide compounds, which have better dielectric properties and a higher glass transition temperature (Tg) than epoxy resins, which are commonly used in thermosetting resins, has become more widespread, and many reports have already been published on semiconductor encapsulation materials (Patent Documents 1 and 2) and substrate materials (Patent Documents 3 and 4) that use low-molecular-weight bismaleimide compounds such as the long-known 4,4'-diphenylmethane bismaleimide.

On the other hand, there have been an increasing number of reports of new maleimide compounds and resin compositions using them recently. For example, there are maleimide compounds with a biphenylaralkyl skeleton that have high heat resistance (Patent Document 5), compounds that maintain a high Tg while lowering the melting point of maleimide resins by introducing an alkenyl group (Patent Document 6), and maleimide resins with special aliphatic skeletons (Patent Documents 7 and 8).

Among these, maleimide resins, which have a special aliphatic skeleton, have been found to have characteristics such as low elasticity and excellent dielectric properties due to the influence of the skeleton, and many compositions using this maleimide resin, such as adhesives, semiconductor encapsulants, and substrate materials, have been reported (Patent Documents 9 to 12).

Patent Document 9 reports that a resin film made of a resin composition containing a bismaleimide resin having a special aliphatic skeleton and a curing agent has excellent dielectric properties. In this resin composition, a low molecular weight aromatic bismaleimide is used as a curing agent, but when the amount of the aromatic bismaleimide resin added to the composition is increased, the dielectric loss tangent of the cured product of the composition tends to deteriorate. In addition, since the compatibility between the bismaleimide resins in this resin composition is poor, unevenness in properties and curing is likely to occur, and it is very difficult to achieve a high glass transition temperature (T _g ) of 100° C. or more required for substrate applications.

JP 2006-299246 A JP 2008-111111 A JP 2012-41386 A JP 2012-166515 A JP 2009-1783 A JP 2019-64926 A Special Publication No. 2006-526014 JP 2012-117070 A International Publication No. 2016/114286 International Publication No. 2016/114287 JP 2018-70668 A JP 2019-203122 A

In light of this background, the present inventors have conducted various studies on compositions containing citraconic imide compounds, and have found that citraconic imide compounds having aromatic groups at specific sites have high compatibility with aliphatic imide compounds, and that resin compositions containing these citraconic imide compounds have excellent dielectric properties and heat resistance.
Therefore, the object of this research is to provide a resin composition which has high compatibility, excellent dielectric properties, and gives a cured product having a high glass transition temperature, as well as uncured films, cured films, adhesives, semiconductor encapsulants, prepregs, substrates, etc., which use the same.

As a result of extensive research to solve the above problems, the inventors discovered that the following thermosetting citraconic imide resin composition can achieve the above objective, and thus completed the present invention.

（式（１）中、Ａは２価の有機基であり、置換または非置換の芳香族基である。）

＜３＞
式（１）中のＡが下記構造から選ばれるものである＜２＞に記載の熱硬化性シトラコンイミド樹脂組成物。

（＊はシトラコンイミド基中の窒素原子との結合を意味する。）

＜４＞
（Ｂ）成分が下記式（２）で表されるものである＜１＞～＜３＞のいずれか１項に記載の熱硬化性シトラコンイミド樹脂組成物。

（式（２）中、Ｂは炭素数６から１００の２価の脂肪族炭化水素基であり、Ｒ₁～Ｒ₄は水素原子またはメチル基を表す。）

＜５＞
（Ｂ）成分が下記式（３）で表されるものである＜１＞～＜３＞のいずれか１項に記載の熱硬化性シトラコンイミド樹脂組成物。

（式（３）中、Ｘは独立して環状構造を有する４価の有機基であり、Ｚは独立して炭素数
６～１００の２価の脂肪族炭化水素基であり、ｍは０～１０である。ただし、ｍで括られた繰り返し単位の構造は、同じであっても異なっていてもよく、Ｚの１つ以上はダイマー酸骨格由来の構造を有する。また、Ｒ₁～Ｒ₄は水素原子またはメチル基を表す。）

＜６＞
式（３）中のＸが下記構造式で示される４価の有機基のいずれかである＜５＞に記載の熱硬化性シトラコンイミド樹脂組成物。

（上記構造式中の置換基が結合していない結合手は、一般式（３）において環状イミド構造を形成するカルボニル炭素と結合するものである。）

＜７＞
（Ｄ）成分の反応促進剤が、窒素原子又は／及びリン原子含むアニオン重合開始触媒である＜１＞～＜６＞のいずれか１項に記載の熱硬化性シトラコンイミド樹脂組成物。

＜８＞
（Ａ）成分を１００質量部としたときの（Ｂ）成分の質量部数が５～９９００質量部であり、（Ｃ）成分が０．５～１００質量部であり、（Ｄ）成分が０．０５～１００質量部である＜１＞～＜７＞のいずれか１項に記載の熱硬化性シトラコンイミド樹脂組成物。

＜９＞
＜１＞～＜８＞のいずれか１項に記載の熱硬化性シトラコンイミド樹脂組成物からなる未硬化樹脂フィルム。

＜１０＞
＜１＞～＜８＞のいずれか１項に記載の熱硬化性シトラコンイミド樹脂組成物の硬化物からなる硬化樹脂フィルム。

＜１１＞
＜１＞～＜８＞のいずれか１項に記載の熱硬化性シトラコンイミド樹脂組成物と繊維基材とを有するプリプレグ。

＜１２＞
＜１＞～＜８＞のいずれか１項に記載の熱硬化性シトラコンイミド樹脂組成物を含む基板。

＜１３＞
＜１＞～＜８＞のいずれか１項に記載の熱硬化性シトラコンイミド樹脂組成物からなる接着剤。

＜１４＞
＜１＞～＜８＞のいずれか１項に記載の熱硬化性シトラコンイミド樹脂組成物からなる半導体封止材。
＜1＞
A thermosetting citracone imide resin composition comprising the following (A) to (D):
(A) a citraconimide compound having an aromatic group bonded to a nitrogen atom; (B) a cyclic imide compound having an aliphatic group bonded to a nitrogen atom; (C) an epoxy resin having two or more epoxy groups in one molecule; and (D) a reaction accelerator.

＜2＞
The thermosetting citraconimide resin composition according to <1>, wherein the citraconic acid compound of the component (A) is a biscitraconimide compound represented by the following formula (1):

(In formula (1), A is a divalent organic group and a substituted or unsubstituted aromatic group.)

＜3＞
The thermosetting citracone imide resin composition according to <2>, wherein A in formula (1) is selected from the following structures:

(* indicates a bond with the nitrogen atom in the citraconimide group.)

＜4＞
The thermosetting citracone imide resin composition according to any one of <1> to <3>, wherein the component (B) is represented by the following formula (2):

(In formula (2), B is a divalent aliphatic hydrocarbon group having 6 to 100 carbon atoms, and R ₁ to R ₄ each represent a hydrogen atom or a methyl group.)

＜5＞
The thermosetting citracone imide resin composition according to any one of <1> to <3>, wherein the component (B) is represented by the following formula (3):

(In formula (3), X is independently a tetravalent organic group having a cyclic structure, Z is independently a divalent aliphatic hydrocarbon group having 6 to 100 carbon atoms, and m is 0 to 10. However, the structures of the repeating units bracketed by m may be the same or different, and at least one of Z has a structure derived from a dimer acid skeleton. In addition, R ₁ to R ₄ represent a hydrogen atom or a methyl group.)

＜6＞
The thermosetting citracone imide resin composition according to <5>, wherein X in formula (3) is any one of tetravalent organic groups represented by the following structural formulas:

(The bond not bonded to a substituent in the above structural formula is bonded to the carbonyl carbon that forms a cyclic imide structure in general formula (3).)

＜７＞
The thermosetting citracone imide resin composition according to any one of <1> to <6>, wherein the reaction accelerator of the component (D) is an anionic polymerization initiation catalyst containing a nitrogen atom or/and a phosphorus atom.

＜8＞
The thermosetting citraconic resin composition according to any one of <1> to <7>, wherein the number of parts by mass of the (B) component is 5 to 9,900 parts by mass, the number of parts by mass of the (C) component is 0.5 to 100 parts by mass, and the number of parts by mass of the (D) component is 0.05 to 100 parts by mass, based on 100 parts by mass of the (A) component.

＜9＞
<1><8> An uncured resin film comprising the thermosetting citraconic imide resin composition according to any one of <1> to <8>.

＜10＞
<8> A cured resin film comprising a cured product of the thermosetting citraconic imide resin composition according to any one of <1> to <8>.

<11>
<1><8> A prepreg having the thermosetting citraconic imide resin composition according to any one of <1> to <8> and a fiber substrate.

＜12＞
<1><8> A substrate comprising the thermosetting citraconic imide resin composition according to any one of <1> to <8>.

＜13＞
An adhesive comprising the thermosetting citraconic imide resin composition according to any one of <1> to <8>.

＜14＞
<1><8> A semiconductor encapsulant comprising the thermosetting citraconic imide resin composition according to any one of <1> to <8>.

The thermosetting citraconic imide resin composition of the present invention is a resin composition that has high compatibility, excellent dielectric properties, and can give a cured product having a high glass transition temperature. Therefore, the thermosetting citraconic imide resin composition of the present invention is useful as an uncured film, a cured film, an adhesive, a semiconductor encapsulant, and is also useful as a material for prepregs, substrates, etc.

The present invention will be explained in more detail below.

(A) Citraconimide compound having an aromatic group bonded to a nitrogen atom The component (A) used in the present invention is a citraconimide compound having a substituted or unsubstituted aromatic group. The citraconimide group is a maleimide group in which one hydrogen atom is replaced by a methyl group. Due to the effect of this methyl group, the compound not only exhibits a low dielectric constant and a low dielectric loss tangent compared to maleimide compounds having the same skeleton, but also has a low melting point and improved compatibility with other components. In addition, the presence of an aromatic structure improves the glass transition temperature of a cured product containing the citraconimide compound.

（式（１）中、Ａは２価の有機基であり、置換または非置換の芳香族基である。） From the viewpoints of ease of procurement of the amine compound as the raw material, solubility of the citraconic acid compound in a solvent, and ease of synthesis, it is preferable that the citraconic acid compound of component (A) is a biscitraconimide compound having two citraconic acid groups in one molecule, as represented by the following formula (1).

(In formula (1), A is a divalent organic group and a substituted or unsubstituted aromatic group.)

（＊はシトラコンイミド基中の窒素原子との結合を意味する。） In order to improve the glass transition temperature after curing, the divalent organic group in the citraconic imide compound of component (A) is a substituted or unsubstituted aromatic group, and examples of the divalent organic group include those selected from aromatic hydrocarbon groups having the following structure:

(* indicates a bond with the nitrogen atom in the citraconimide group.)

The citraconic imide compound (A) may be used alone or in combination of two or more types.

From the viewpoint of dielectric properties and flexibility of the cured product, the citracone imide compound of component (A) preferably contains a structure having three or more aromatic rings, and among the above structures, structures derived from diamines such as 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,4-bis[2-(4-aminophenyl)-2-propyl)benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane are particularly preferred.

The properties and number average molecular weight (Mn) of the citraconic imide compound of component (A) are not particularly limited at room temperature, but the number average molecular weight is preferably 200 to 1000, and more preferably 400 to 1000.

(B) Cyclic imide compound having an aliphatic group bonded to a nitrogen atom The component (B) used in the present invention is a cyclic imide compound having a divalent aliphatic hydrocarbon group, and when the compound contains a tetravalent hydrocarbon group, the tetravalent hydrocarbon group has an aromatic structure or an aliphatic structure. The presence of a divalent aliphatic hydrocarbon group in the component (B) leads to improved dielectric properties when mixed with the component (A).

（式（２）中、Ｂは炭素数６から１００の２価の脂肪族炭化水素基であり、Ｒ₁～Ｒ₄は水素原子またはメチル基を表す。） From the viewpoints of ease of procurement of the amine compound as the raw material, solubility of the cyclic imide compound in a solvent, and ease of synthesis, it is preferable that the cyclic imide compound of component (B) is a biscyclic imide compound having two cyclic imide groups and represented by the following formula (2).

(In formula (2), B is a divalent aliphatic hydrocarbon group having 6 to 100 carbon atoms, and R ₁ to R ₄ each represent a hydrogen atom or a methyl group.)

（＊は環状イミド基中の窒素原子との結合を意味する。ｎは６～２０である。） In the cyclic imide compound of component (B), the divalent aliphatic hydrocarbon group is more preferably selected from saturated aliphatic hydrocarbon groups of the following structures and hydrocarbon groups derived from a dimer acid skeleton.

(* means a bond to a nitrogen atom in a cyclic imide group. n is 6 to 20.)

Dimer acid is a liquid dibasic acid mainly composed of a dicarboxylic acid having 36 carbon atoms, which is produced by dimerization of unsaturated fatty acids having 18 carbon atoms, which are derived from natural products such as vegetable oils. The dimer acid skeleton is not a single skeleton, but has multiple structures, and there are several types of isomers. Representative dimer acids are classified into linear (a), monocyclic (b), aromatic (c), and polycyclic (d).
In this specification, the dimer acid skeleton refers to a group derived from a dimer diamine having a structure in which the carboxy group of such a dimer acid is substituted with a primary aminomethyl group.
That is, as the hydrocarbon group derived from the dimer acid skeleton, in each of the dimer acids shown in (a) to (d) below, a branched divalent hydrocarbon group in which two carboxy groups are substituted with methylene groups is preferred.

（式（３）中、Ｘは独立して環状構造を有する４価の有機基であり、Ｚは独立して炭素数６～１００の２価炭化水素基であり、ｍは０～１０である。ただし、ｍで括られた繰り返し単位の構造は、同じであっても異なっていてもよく、Ｚの１つ以上はダイマー酸骨格由来の構造を有する。Ｒ₁～Ｒ₄は水素原子又はメチル基を表す。） When the component (B) has a dimer acid skeleton as a divalent aliphatic hydrocarbon group, it is preferably an aliphatic cyclic imide compound represented by the following formula (3).

(In formula (3), X is independently a tetravalent organic group having a cyclic structure, Z is independently a divalent hydrocarbon group having 6 to 100 carbon atoms, and m is 0 to 10. However, the structures of the repeating units bracketed by m may be the same or different, and at least one of Z has a structure derived from a dimer acid skeleton. R ₁ to R ₄ represent a hydrogen atom or a methyl group.)

（上記構造式中の置換基が結合していない結合手は、一般式（３）において環状イミド構造を形成するカルボニル炭素と結合するものである。） In formula (3), X independently represents a tetravalent organic group having a cyclic structure, and among these, any of the tetravalent organic groups represented by the following structural formulas is preferable.

(The bond not bonded to a substituent in the above structural formula is bonded to the carbonyl carbon that forms a cyclic imide structure in general formula (3).)

（ｎは６～２０である。） In formula (3), Z independently represents a divalent hydrocarbon group having 6 to 100 carbon atoms, preferably 6 to 50 carbon atoms, at least one of which is a divalent hydrocarbon group derived from a dimer acid skeleton. Specific examples of Z include divalent hydrocarbon groups represented by the following structural formulas:

(n is 6 to 20.)

In the above formula (3), R ₁ to R _{4 each} represent a hydrogen atom or a methyl group. From the viewpoint of the glass transition temperature of the cured product, R ₁ to R ₄ are preferably a hydrogen atom.
In the above formula (3), m is 0 to 10, and preferably 0 to 8. The structures of the repeating units bracketed by m may be the same or different, and when they are different, there are two or more kinds of repeating units, preferably two or three kinds.
The arrangement of the repeating units depends on the production method, and may be alternate, block or random, but is preferably block.

The amount of the cyclic imide compound in component (B) is preferably 5 to 9,900 parts by mass, and more preferably 10 to 2,000 parts by mass, per 100 parts by mass of component (A). If this range is met, a cured product with a high glass transition temperature can be obtained while maintaining low dielectric properties.

The cyclic imide compound (B) may be used alone or in combination of two or more types.

The properties and number average molecular weight (Mn) of the cyclic imide compound of component (B) at room temperature are not particularly limited, but the number average molecular weight is preferably 200 to 20,000, and more preferably 300 to 15,000.

In this specification, the number average molecular weight is a number average molecular weight calculated using polystyrene standards and measured by gel permeation chromatography (GPC) under the following measurement conditions.
[GPC measurement conditions]
Developing solvent: tetrahydrofuran (THF)
Flow rate: 0.35mL/min
Detector: Refractive index detector (RI)
Column: TSK Guard column Super H-L
TSKgel SuperHZ4000 (4.6mm I.D. x 15cm x 1)
TSKgel SuperHZ3000 (4.6mm I.D. x 15cm x 1)
TSKgel SuperHZ2000 (4.6mm I.D. x 15cm x 2)
(Both manufactured by Tosoh Corporation)
Column temperature: 40°C
Sample injection amount: 5 μL (THF solution with a concentration of 0.2% by mass)

(C) Epoxy resin having two or more epoxy groups in one molecule The component (C) used in the present invention is an epoxy resin having two or more epoxy groups in one molecule. Any epoxy resin having two or more epoxy groups in one molecule can be used without particular limitation, but from the viewpoint of handling, it is preferable that the epoxy resin is a solid at room temperature (25°C), and more preferably, the melting point is 40°C to 150°C or the softening point is 50°C to 160°C.

Specific examples of epoxy resins include biphenol type epoxy resins such as bisphenol A type epoxy resins, bisphenol F type epoxy resins, 3,3',5,5'-tetramethyl-4,4'-biphenol type epoxy resins and 4,4'-biphenol type epoxy resins; novolac type epoxy resins such as phenol novolac type epoxy resins, cresol novolac type epoxy resins and bisphenol A novolac type epoxy resins; naphthalene diol type epoxy resins, trisphenylol methane type epoxy resins, tetrakisphenylol ethane type epoxy resins, phenol biphenyl type epoxy resins, dicyclopentadiene type epoxy resins, biphenyl aralkyl type epoxy resins, epoxy resins in which the aromatic rings of phenol dicyclopentadiene novolac type epoxy resins are hydrogenated, triazine derivative epoxy resins and alicyclic epoxy resins. Among these, bisphenol A type epoxy resins, dicyclopentadiene type epoxy resins and biphenyl aralkyl type epoxy resins are preferably used.
These epoxy resins may be used alone or in combination of two or more kinds. If necessary, a certain amount of an epoxy resin other than the above may be used in combination depending on the purpose.

The amount of epoxy resin in component (C) is preferably 0.5 to 100 parts by mass, and more preferably 1 to 50 parts by mass, per 100 parts by mass of component (A). If it is in this range, a cured product with low dielectric properties can be obtained.

(D) Reaction Accelerator The reaction accelerator, component (D), is added to initiate and accelerate the polymerization reaction between the citraconic imide compound, component (A), the cyclic imide compound, component (B), and the epoxy resin, component (C).

The component (D) is not particularly limited as long as it promotes the polymerization reaction, and examples of the component (D) include ionic catalysts such as imidazoles, tertiary amines, quaternary ammonium salts, boron trifluoride amine complexes, organophosphines, and organophosphonium salts; organic peroxides such as diallyl peroxide, dialkyl peroxide, peroxide carbonate, and hydroperoxide; and radical polymerization initiators such as azoisobutyronitrile.
From the viewpoint of the reaction mechanism of the citraconic imide compound, it is preferable to use, as the component (D), an anionic polymerization initiator catalyst containing at least one of a nitrogen atom and a phosphorus atom.
The reaction accelerator as component (D) may be used alone or in combination of two or more kinds.

The reaction accelerator of component (D) is preferably blended in an amount of 0.05 to 100 parts by weight, and particularly 0.1 to 20 parts by weight, per 100 parts by weight of component (A).
If the amount is less than 0.05 parts by mass, the curing rate of the thermosetting citraconic imide resin composition during molding may become too slow, and the heat resistance and moisture resistance of the obtained cured product may become poorly balanced, and if the amount is more than 100 parts by mass, the curing rate of the thermosetting citraconic imide resin composition during molding may become too fast, which is also not preferred.

Other Additives Various additives may be added to the thermosetting citraconic imide resin composition of the present invention as necessary, provided that the effects of the present invention are not impaired. Examples of other additives are given below.

Inorganic filler Inorganic fillers are blended for the purpose of increasing the strength and rigidity of the cured product of the thermosetting citraconic imide resin composition of the present invention, and adjusting the thermal expansion coefficient and dimensional stability of the cured product. As the inorganic filler, those usually blended in epoxy resin compositions and silicone resin compositions can be used. For example, silicas such as spherical silica, fused silica, and crystalline silica, alumina, silicon nitride, aluminum nitride, boron nitride, barium sulfate, talc, clay, aluminum hydroxide, magnesium hydroxide, calcium carbonate, glass fiber, and glass particles can be mentioned. Furthermore, fluorine-containing resins, coating fillers, and/or hollow particles may be used to improve dielectric properties, and conductive fillers such as metal particles, metal-coated inorganic particles, carbon fibers, and carbon nanotubes may be added for the purpose of imparting conductivity. The inorganic fillers may be used alone or in combination of two or more types.

The primary particle size of the inorganic filler is not particularly limited, but is preferably 0.05 to 500 μm, more preferably 0.1 to 300 μm, and even more preferably 1 to 100 μm, as the median diameter measured by a laser diffraction particle size distribution measuring device. If it is within this range, it is easy to uniformly disperse the inorganic particles in the resin composition, and the inorganic particles do not settle, separate, or become unevenly distributed over time, which is preferable.

The amount of the inorganic filler is not particularly limited, but is preferably 5 to 50,000 parts by mass, more preferably 10 to 40,000 parts by mass, and even more preferably 50 to 30,000 parts by mass, per 100 parts by mass of component (A) in the composition of the present invention. Within this range, the inorganic particles can fully exert their functions while maintaining the strength of the resin composition.

Furthermore, in order to improve the properties of the inorganic filler, it is preferable that the inorganic filler is surface-treated with a silane coupling agent having an organic group capable of reacting with a citraconimide group. Examples of such silane coupling agents include epoxy group-containing alkoxysilane, amino group-containing alkoxysilane, (meth)acrylic group-containing alkoxysilane, and alkenyl group-containing alkoxysilane.
As the silane coupling agent, a (meth)acrylic group- and/or amino group-containing alkoxysilane is preferably used, and specific examples thereof include 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, and 3-aminopropyltrimethoxysilane.

Thermosetting resin having a reactive group capable of reacting with a citraconimide group In the present invention, in addition to the components (B) and (C), a thermosetting resin having a reactive group capable of reacting with a citraconimide group may be added.
Examples of reactive groups capable of reacting with a citraconimide group include a hydroxyl group, an amino group, an alkenyl group such as an allyl group or a vinyl group, a (meth)acrylic group, and a thiol group.
In addition, the thermosetting resin having a reactive group is not limited to a specific type, and examples thereof include various resins other than the components (A), (B), and (C), such as a phenol resin, a melamine resin, a urea resin, a silicone resin, a modified polyphenylene ether resin, a thermosetting acrylic resin, and a polyfunctional thiol.

Others In addition to the above, non-functional silicone oil, thermoplastic resin, thermoplastic elastomer, organic synthetic rubber, photosensitizer, light stabilizer, polymerization inhibitor, flame retardant, pigment, dye, adhesive aid, etc. may be blended, and ion trapping agent, etc. may be blended to improve electrical properties.
The amount of these ingredients (excluding inorganic fillers) is not particularly limited, but is preferably 0.1 to 100 parts by mass, and more preferably 0.5 to 50 parts by mass, per 100 parts by mass of component (A) in the composition of the present invention.

[Production method]
The resin composition of the present invention can be produced by adding the components (A) to (D) and, if necessary, other additives, and mixing them using, for example, a planetary mixer or a stirrer.

The thermosetting citraconic imide resin composition of the present invention can be used mainly as a prepreg, adhesive, and semiconductor encapsulant, and may be processed into a film or sheet depending on the application, or may be dissolved in an organic solvent and treated as a varnish. By making the composition into a varnish, it becomes easier to make a film, and it also becomes easier to apply and impregnate glass cloth made of E-glass, low dielectric glass, quartz glass, etc. Regarding organic solvents, any organic solvent that dissolves the thermosetting resins of components (A), (B), and (C) can be used without restriction. As organic solvents, for example, toluene, xylene, anisole, cyclohexanone, cyclopentanone, etc. can be used preferably. The above organic solvents may be used alone or in a mixture of two or more.

The thermosetting citraconic imide resin composition of the present invention can be prepared by applying the above-mentioned varnish to a substrate and removing the organic solvent to form an uncured resin sheet or an uncured resin film, or by further curing the uncured resin sheet or the cured resin film.
Examples of methods for producing sheets and films are given below, but the methods are not limited thereto.

For example, a thermosetting citraconic imide resin composition dissolved in an organic solvent is applied to a substrate, and then the substrate is heated for 0.5 to 5 hours at a temperature of usually 80° C. or higher, preferably 100° C. or higher, to remove the organic solvent. The substrate is then further heated for 0.5 to 10 hours at a temperature of 130° C. or higher, preferably 150° C. or higher, to form a strong citraconic imide resin cured coating having a flat surface.
The temperatures in the drying step for removing the organic solvent and the subsequent heat curing step may each be constant, but it is preferable to increase the temperature stepwise, which allows the organic solvent to be efficiently removed from the composition and allows the curing reaction of the resin to proceed efficiently.
The method for applying the varnish includes, but is not limited to, a spin coater, a slit coater, a spray, a dip coater, a bar coater, and the like.

The substrate may be any commonly used material, such as polyolefin resins, such as polyethylene (PE) resin, polypropylene (PP) resin, and polystyrene (PS) resin, and polyester resins, such as polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, and polycarbonate (PC) resin. The surface of the substrate may be subjected to a release treatment. The thickness of the coating layer is not particularly limited, but is in the range of 1 to 100 μm, and preferably 3 to 80 μm, after the solvent is removed. A cover film may be used on the coating layer.

Alternatively, the components can be premixed and extruded into a sheet or film using a melt kneader and used as is.

When producing a semiconductor encapsulant, the components (A) to (D) and, if necessary, other components are blended in a prescribed composition ratio, thoroughly and uniformly mixed using a mixer or the like, then melt-mixed using a hot roll, kneader, extruder, or the like, and then cooled and solidified, and pulverized to an appropriate size. The resulting resin composition can be used as an encapsulant.
The adhesive can be prepared by blending the components (A) to (D) and, if necessary, other components in a predetermined composition ratio, mixing them using a mixer such as a planetary mixer, and then kneading and mixing them using a three-roll mill to increase dispersibility if necessary. The resulting resin composition can be used as an adhesive.

Common molding methods using semiconductor encapsulants include transfer molding and compression molding. In the transfer molding, a transfer molding machine is used, and molding pressure is 5 to 20 N/mm ² , molding temperature is 120 to 190° C., molding time is 30 to 500 seconds, preferably molding temperature is 150 to 185° C., molding time is 30 to 180 seconds. In the compression molding, a compression molding machine is used, and molding temperature is 120 to 190° C., molding time is 30 to 600 seconds, preferably molding temperature is 130 to 160° C., molding time is 120 to 300 seconds. In addition, in either molding method, post-curing may be performed at 150 to 225° C. for 0.5 to 20 hours.

It can be used as an adhesive by using methods and devices that are well known in the art. Typical curing conditions are a temperature in the range of 100°C to 200°C, preferably 120°C to 180°C, and a time in the range of 1 hour to 8 hours, preferably 1.5 hours to 3 hours.

In addition, the varnished resin composition can be impregnated into glass cloth made of E-glass, low dielectric glass, quartz glass, etc., and the organic solvent can be removed to semi-cur it, allowing it to be used as a prepreg.
The prepreg of the present invention can be produced by using a conventional method, by dissolving the composition of the present invention in an organic solvent at a predetermined composition ratio, impregnating a fiber substrate with the composition, and drying by heating.

[substrate]
The prepreg may be laminated on copper foil, pressed, and heat-cured to be used as a substrate.
The method for producing the substrate is not particularly limited, but the substrate can be produced, for example, by using 1 to 20 sheets, preferably 2 to 10 sheets, of the prepreg, arranging copper foil on one or both sides of the prepreg, pressing the prepreg, and heat-curing the prepreg.
The thickness of the copper foil is not particularly limited, but is preferably 3 to 70 μm, more preferably 10 to 50 μm, and even more preferably 15 to 40 μm. Within this range, a multi-layer substrate with high reliability can be formed.
The molding conditions for the substrate are not particularly limited, but for example, the substrate can be molded using a multi-stage press, a multi-stage vacuum press, a continuous molding machine, an autoclave molding machine, etc., at a temperature of 100 to 400° C., a pressure of 1 to 100 MPa, and a heating time of 0.1 to 4 hours. The prepreg of the present invention, copper foil, and an inner layer wiring board can also be combined and molded to form a substrate.

The present invention will be specifically explained below with examples and comparative examples, but the present invention is not limited to the following examples.

The components used in the examples and comparative examples are shown below. Note that the number average molecular weight (Mn) below was measured by gel permeation chromatography (GPC) using polystyrene as the standard under the following measurement conditions.

[GPC measurement conditions]
Developing solvent: tetrahydrofuran (THF)
Flow rate: 0.35mL/min
Detector: Refractive index detector (RI)
Column: TSK Guard column Super H-L
TSKgel SuperHZ4000 (4.6mm I.D. x 15cm x 1)
TSKgel SuperHZ3000 (4.6mm I.D. x 15cm x 1)
TSKgel SuperHZ2000 (4.6mm I.D. x 15cm x 2)
(Both manufactured by Tosoh Corporation)
Column temperature: 40°C
Sample injection amount: 5 μL (THF solution with a concentration of 0.2% by mass)

(A) Citraconimide Compound Having an Aromatic Group Bonded to a Nitrogen Atom Synthesis Example 1 (Production of Citraconimide Compound, Formula (4))
A 2L glass four-neck flask equipped with a stirrer, a Dean-Stark tube, a cooling condenser and a thermometer was added with 184.7g (0.45 mol) of 2,2-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 111.0g (0.99 mol) of citraconic anhydride and 150g of toluene to prepare a reaction solution, which was then stirred at 80°C for 3 hours to synthesize an amic acid. After that, 40g of methanesulfonic acid was added to the reaction solution, which was then heated to 110°C and stirred for 16 hours while distilling off the by-product water, after which the reaction solution was washed five times with 200g of ion-exchanged water. The washed reaction solution was then poured into heptane, and the precipitate was collected by filtration, and 257.1g (yield 95%) of the target product (formula (4), (A-1), Mn600) in the form of a yellow powder was obtained.

Synthesis Example 2 (Production of Citraconimide Compound, Formula (5))
A 2L glass four-neck flask equipped with a stirrer, a Dean-Stark tube, a cooling condenser and a thermometer was added with 155.0g (0.45 mol) of bisaniline M, 111.0g (0.99 mol) of citraconic anhydride and 150g of toluene to prepare a reaction solution, which was then stirred at 80°C for 3 hours to synthesize an amic acid. After that, 40g of methanesulfonic acid was added to the reaction solution, and the temperature was raised to 110°C. After stirring for 16 hours while distilling off the by-product water, the reaction solution was washed five times with 200g of ion-exchanged water. Thereafter, the washed reaction solution was poured into heptane, and the precipitate was collected by filtration, and 229.7g (yield 96%) of the target product (formula (5), (A-2), Mn530) in the form of a yellow powder was obtained.

（式中のＣ₃₆Ｈ₇₂はダイマー酸骨格を意味する。）

（Ｂ－２）：下記式（７）で表されるビスマレイミド化合物（ＢＭＩ－３０００、Ｄｅｓｉｇｎｅｒ Ｍｏｌｅｃｕｌｅｓ Ｉｎｃ．製）

（式中のＣ₃₆Ｈ₇₂はダイマー酸骨格を意味する。）

（Ｂ－３）：下記式（８）で表されるビスマレイミド化合物（ＢＭＩ－１５００、Ｄｅｓｉｇｎｅｒ Ｍｏｌｅｃｕｌｅｓ Ｉｎｃ．製）

（式中のＣ₃₆Ｈ₇₂はダイマー酸骨格を意味する。）

（Ｂ－４）：下記式（９）で表されるビスマレイミド化合物（ＳＬＫ－２６００、信越化学工業（株）製）

（式中のＣ₃₆Ｈ₇₂はダイマー酸骨格由来の構造を示し、ｎ≒５、ｍ≒１である。）

（Ｂ－５）：下記式（１０）で示されるマレイミド化合物（ＢＭＩ－ＴＭＨ、大和化成工業（株）製）

（Ｂ－６）：下記式（１１）で示されるシトラコンイミド化合物（ＢＣＩ－７３７、Ｄｅｓｉｇｎｅｒ Ｍｏｌｅｃｕｌｅｓ Ｉｎｃ．製）

（式中のＣ₃₆Ｈ₇₂はダイマー酸骨格を意味する。） (B) Cyclic imide compound having an aliphatic group bonded to a nitrogen atom (B-1): a bismaleimide compound represented by the following formula (6) (trade name: BMI-689, manufactured by Designer Molecules Inc.)

(In the formula, C ₃₆ H ₇₂ represents a dimer acid skeleton.)

(B-2): A bismaleimide compound represented by the following formula (7) (BMI-3000, manufactured by Designer Molecules Inc.)

(In the formula, C ₃₆ H ₇₂ represents a dimer acid skeleton.)

(B-3): A bismaleimide compound represented by the following formula (8) (BMI-1500, manufactured by Designer Molecules Inc.)

(In the formula, C ₃₆ H ₇₂ represents a dimer acid skeleton.)

(B-4): A bismaleimide compound represented by the following formula (9) (SLK-2600, manufactured by Shin-Etsu Chemical Co., Ltd.)

(In the formula, C ₃₆ H ₇₂ represents a structure derived from a dimer acid skeleton, where n≈5 and m≈1.)

(B-5): A maleimide compound represented by the following formula (10) (BMI-TMH, manufactured by Daiwa Chemical Industry Co., Ltd.)

(B-6): A citraconimide compound represented by the following formula (11) (BCI-737, manufactured by Designer Molecules Inc.)

(In the formula, C ₃₆ H ₇₂ represents a dimer acid skeleton.)

(C) Epoxy resin having two or more epoxy groups in one molecule (C-1): biphenylaralkyl type epoxy resin (NC-3000: manufactured by Nippon Kayaku Co., Ltd., softening point 56° C.)

(D) Reaction accelerator (D-1): 2-ethyl-4-methylimidazole (2E4MZ: manufactured by Shikoku Chemical Industries, Ltd.)
(D-2): Triphenylphosphine (TPP: manufactured by Hokko Chemical Co., Ltd.)

（Ｅ－２）：下記式（１３）で表されるビスマレイミド化合物（商品名：ＢＭＩ－２３００、大和化成（株）製）

（ｎ≒１（平均値）） (E) Comparative maleimide compound (E-1): a bismaleimide compound represented by the following formula (12) (product name: BMI-4000, manufactured by Daiwa Kasei Co., Ltd.)

(E-2): A bismaleimide compound represented by the following formula (13) (product name: BMI-2300, manufactured by Daiwa Kasei Co., Ltd.)

(n ≒ 1 (average value))

Evaluation test <Preparation of composition>
The components were mixed in the compounding ratios shown in Table 1 using a twin-arm kneader (TK0.5, manufactured by Toshin Corp.) to prepare compositions. Components with high melting points and difficult mixing were mixed at 80° C. to prepare compositions.

<Moldability>
A frame with a diameter of 200 mm and a thickness of 200 μm was prepared, and the composition prepared above was sandwiched between a 50 μm-thick release-treated PET film (E7006, manufactured by Toyobo Co., Ltd.), and molded at 180° C. for 5 minutes using a vacuum press (manufactured by Nikko Materials Co., Ltd.) to obtain a cured product. When the cured product was removed from the PET film, a film-like sample was obtained, and an x was obtained when cracks or tearing occurred.

<Appearance>
The film sample prepared above was post-cured at 180° C. for 3 hours to prepare a cured resin film, and the appearance was visually confirmed. A film with no separation or uneven curing and a uniform color throughout was rated as ◯, and a film with separation or uneven curing and a locally different color was rated as ×.

<Dielectric tangent>
Using the cured resin film prepared above, a network analyzer (E5063-2D5 manufactured by Keysight Corporation) was connected to a strip line (manufactured by Keycom Corporation) to measure the dielectric tangent of the cured resin film at a frequency of 10 GHz. The results are shown in Table 1.

<Heat resistance>
The cured resin film prepared above was incubated in a thermostatic chamber at 180° C. for 24 hours, and then the cured resin film was used to connect a network analyzer (E5063-2D5 manufactured by Keysight Corporation) and a strip line (manufactured by Keycom Corporation) to measure the dielectric tangent of the cured resin film at a frequency of 10 GHz. The results are shown in Table 1.

<Glass transition temperature>
The storage modulus (MPa) of the cured resin film prepared above was measured in the range of -20 ° C. to 300 ° C. using a DMA-800 manufactured by TA Instruments, and the peak top temperature obtained from a graph plotting the Tan δ values derived from the obtained storage modulus and loss modulus values was taken as the glass transition temperature (Tg). The measurement conditions were a test sample (cured resin film) of 20 mm × 5 mm × 200 μm thickness, a heating rate of 5 ° C. / min, a multi-frequency mode, a tensile mode, and an amplitude of 15 μm. The results are shown in Table 1.

As shown in Table 1, the compositions of Examples 1 to 13 had good resin solubility and excellent moldability, and were uniformly cured without separation or uneven curing. The cured products (cured resin films) had high glass transition temperatures (150°C or higher) while maintaining low dielectric properties, and also had good heat resistance.
On the other hand, the compositions not containing the (A) component in Comparative Examples 1 and 2 showed low dielectric properties, but the glass transition temperature of the cured product was low, and the dielectric properties after 24 hours of incubation at 180 ° C. were deteriorated. The compositions containing the maleimide compound having an aromatic group shown in Comparative Examples 3 and 4 had poor compatibility with the cyclic imide compound having an aliphatic group of the (B) component, separation and curing unevenness occurred, and good dielectric properties could not be obtained. The composition of Comparative Example 5 containing the citraconimide compound having an aliphatic group (component (B-6)) instead of the citraconimide compound having an aromatic group (component (A)) had high compatibility with the aliphatic imide compound, but the glass transition temperature of the cured product was low. The composition of Comparative Example 6 did not contain the (C) component, so the citraconimide compound was not completely cured, and the glass transition temperature was low.

Claims (13)

A thermosetting citraconic imide resin composition comprising the following (A) to (D) :
A thermosetting citraconeimide resin composition, in which the number of parts by mass of the (B) component is 5 to 9,900 parts by mass, the number of parts by mass of the (C) component is 0.5 to 100 parts by mass, and the number of parts by mass of the (D) component is 0.05 to 100 parts by mass, based on 100 parts by mass of the (A) component .
(A) a citraconimide compound having an aromatic group bonded to a nitrogen atom; (B) a cyclic imide compound having an aliphatic group bonded to a nitrogen atom; (C) an epoxy resin having two or more epoxy groups in one molecule; and (D) a reaction accelerator. 2. The thermosetting citraconimide resin composition according to claim 1, wherein the citraconic acid compound of the component (A) is a biscitraconimide compound represented by the following formula (1):

(In formula (1), A is a divalent organic group and a substituted or unsubstituted aromatic group.) 3. The thermosetting citracone imide resin composition according to claim 2, wherein A in formula (1) is selected from the following structures:

(* indicates a bond with the nitrogen atom in the citraconimide group.) The thermosetting citracone imide resin composition according to any one of claims 1 to 3, wherein the component (B) is represented by the following formula (2):

(In formula (2), B is a divalent aliphatic hydrocarbon group having 6 to 100 carbon atoms, and R ₁ to R ₄ each represent a hydrogen atom or a methyl group.) The thermosetting citracone imide resin composition according to any one of claims 1 to 3, wherein the component (B) is represented by the following formula (3):

(In formula (3), X is independently a tetravalent organic group having a cyclic structure, Z is independently a divalent aliphatic hydrocarbon group having 6 to 100 carbon atoms, and m is 0 to 10. However, the structures of the repeating units bracketed by m may be the same or different, and at least one of Z has a structure derived from a dimer acid skeleton. In addition, R ₁ to R ₄ represent a hydrogen atom or a methyl group.) 6. The thermosetting citracone imide resin composition according to claim 5, wherein X in formula (3) is any of the tetravalent organic groups represented by the following structural formulas:

(The bond not bonded to a substituent in the above structural formula is bonded to the carbonyl carbon that forms a cyclic imide structure in general formula (3).) The thermosetting citraconic imide resin composition according to any one of claims 1 to 6, wherein the reaction accelerator of component (D) is an anionic polymerization initiator catalyst containing nitrogen atoms and/or phosphorus atoms. An uncured resin film comprising the thermosetting citraconic imide resin composition according to any one of claims 1 to 7 . A cured resin film comprising a cured product of the thermosetting citraconic imide resin composition according to any one of claims 1 to 7 . A prepreg comprising the thermosetting citracone imide resin composition according to any one of claims 1 to 7 and a fiber substrate. A substrate comprising the thermosetting citraconic imide resin composition according to any one of claims 1 to 7 . An adhesive comprising the thermosetting citracone imide resin composition according to any one of claims 1 to 7 . A semiconductor encapsulant comprising the thermosetting citraconic imide resin composition according to any one of claims 1 to 7 .