JP7555684B2 - Thermosetting maleimide resin composition - Google Patents

Description

The present invention relates to a thermosetting maleimide resin composition, uncured and cured resin films made from the resin composition, adhesives, sealing materials, and substrates containing a cured product of the thermosetting maleimide resin composition.

In recent years, the next-generation mobile communication system known as 5G has become popular, aiming to realize high-speed, large-capacity, low-latency communications. To achieve this, materials for high-frequency bands are required, and since reducing transmission loss is essential as a noise countermeasure, there is a demand for the development of insulating materials with excellent dielectric properties (low dielectric constant and low dielectric tangent).

In particular, insulating materials with excellent dielectric properties are required for circuit board applications. Insulating materials with excellent dielectric properties are required for boards such as rigid boards and flexible boards, and reactive polyphenylene ether resins (PPE) are being used for rigid boards, while liquid crystal polymers (LCPs) and modified polyimides (MPIs) with improved properties are becoming more popular.

When manufacturing the above FPC, an adhesive is required to attach the base film and coverlay film to the surface having the wiring portion using a heat press or the like. Traditionally, adhesives that mainly use epoxy resins have been used, but recently there has been a demand for adhesives with excellent dielectric properties.

In light of this background, adhesives with excellent dielectric properties have been reported (for example, Patent Documents 1 to 4), but most of these are combinations of epoxy resins, other thermosetting resins, and thermoplastic resins. These compositions have excellent dielectric properties in the frequency range of 10 GHz or less, but 5G requires them to have dielectric properties in the frequency range of 28 GHz or more, known as millimeter waves, and many of the adhesives that were previously said to have excellent dielectric properties do not currently have sufficient dielectric properties.

In addition, a resin composition containing a special maleimide compound and a thermoplastic resin has been disclosed as a composition that has excellent high-frequency characteristics and a high level of adhesion to conductors (Patent Document 5).

JP 2008-248141 A JP 2011-68713 A International Publication No. 2016-17473 JP 2016-79354 A International Publication No. 2018-16489

However, it has been confirmed that the resin composition described in Patent Document 5 is in a varnish state and the resins are not compatible with each other, resulting in separation of the varnish, making it impossible to obtain a resin film, or even if a resin film is obtained, it does not exhibit adhesiveness, making it unsuitable for substrate applications.
Accordingly, an object of the present invention is to provide a thermosetting maleimide resin composition which is in a varnish form and free of turbidity or separation, has excellent dielectric properties, and gives a cured product having strong adhesive strength even to organic resins such as LCP and MPI, and to copper, as well as an uncured or cured resin film, an adhesive, or a sealant made thereof, and a substrate including a cured product of the thermosetting maleimide resin composition.

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

（式（１）中、Ｒ¹はダイマー酸骨格に由来する二価の炭化水素基を示す。）
及び
（Ｃ）有機過酸化物
を含み、（Ａ）成分と（Ｂ）成分の比率（質量比（Ａ）／（Ｂ））が２～２０である熱硬化性マレイミド樹脂組成物。
＜２＞
（Ａ）成分のスチレン系エラストマーが、スチレンと、アルケン及び／又は非共役ジエンとの共重合体であって、その両末端の反応性官能基が、アミノ基、無水マレイン酸及びビニル基のうち少なくとも一種を含むものである＜１＞に記載の熱硬化性マレイミド樹脂組成物。
＜３＞
さらに（Ｄ）成分として接着助剤を含有する＜１＞または＜２＞に記載の熱硬化性マレイミド樹脂組成物。
＜４＞
＜１＞～＜３＞のいずれかに記載の熱硬化性マレイミド樹脂組成物からなる未硬化樹脂フィルム。
＜５＞
＜１＞～＜３＞のいずれかに記載の熱硬化性マレイミド樹脂組成物の硬化物からなる硬化樹脂フィルム。
＜６＞
＜１＞～＜３＞のいずれかに記載の熱硬化性マレイミド樹脂組成物からなる接着剤。
＜７＞
＜１＞～＜３＞のいずれかに記載の熱硬化性マレイミド樹脂組成物からなる封止材。
＜８＞
＜１＞～＜３＞のいずれかに記載の熱硬化性マレイミド樹脂組成物の硬化物を含有する基板。 ＜1＞
(A) a styrene-based elastomer having reactive functional groups at both ends,
(B) A maleimide compound represented by the following formula (1):

(In formula (1), ^R1 represents a divalent hydrocarbon group derived from a dimer acid skeleton.)
and (C) an organic peroxide, in which the ratio of component (A) to component (B) (mass ratio (A)/(B)) is 2 to 20.
＜2＞
The thermosetting maleimide resin composition according to <1>, wherein the styrene-based elastomer of the component (A) is a copolymer of styrene with an alkene and/or a non-conjugated diene, and reactive functional groups at both ends thereof include at least one of an amino group, maleic anhydride and a vinyl group.
＜3＞
The thermosetting maleimide resin composition according to <1> or <2>, further comprising an adhesive assistant as a component (D).
＜4＞
An uncured resin film comprising the thermosetting maleimide resin composition according to any one of <1> to <3>.
＜5＞
A cured resin film comprising a cured product of the thermosetting maleimide resin composition according to any one of <1> to <3>.
＜6＞
An adhesive comprising the thermosetting maleimide resin composition according to any one of <1> to <3>.
＜７＞
<4> An encapsulating material comprising the thermosetting maleimide resin composition according to any one of <1> to <3>.
＜8＞
A substrate comprising a cured product of the thermosetting maleimide resin composition according to any one of <1> to <3>.

The thermosetting maleimide resin composition of the present invention does not separate or become cloudy even when made into a varnish, and the cured product has excellent dielectric properties and adhesive strength, and has particularly strong adhesive strength to organic resins such as LCP and MPI, as well as to copper. Therefore, the thermosetting maleimide resin composition of the present invention is particularly useful as a material for FPCs.

The present invention will be explained in more detail below.

(A) Styrene-based elastomer having reactive functional groups at both ends The styrene-based elastomer of component (A) mainly contributes to improving the dielectric characteristics, heat resistance, and adhesiveness of the cured product of the composition at high frequencies, as well as improving the flexibility when the composition is made into a film, and is not particularly limited as long as it is a thermoplastic elastomer having a structural unit derived from a styrene-based compound and having reactive functional groups at both ends, and may be a thermoplastic elastomer having a structural unit derived from styrene.

In the present invention, the styrene-based elastomer is preferably a copolymer of styrene and an alkene and/or a non-conjugated diene, which is partially or completely hydrogenated. That is, it is a block copolymer and/or a random copolymer with styrene as the hard segment and alkene and/or a non-conjugated diene as the soft segment. Examples of styrene-based elastomers include styrene/butadiene/styrene block/random copolymer, styrene/isoprene/styrene block/random copolymer, styrene/ethylene/butylene/styrene block/random copolymer, styrene/ethylene/propylene/styrene block/random copolymer, and styrene/butadiene block/random copolymer. Block copolymers are preferred from the viewpoint of quality stability.

From the viewpoint of heat resistance, it is preferable to use styrene/ethylene/butylene/styrene block/random copolymer, styrene/ethylene/propylene/styrene block/random copolymer, styrene/butadiene block/random copolymer, etc., in which the double bonds of the conjugated diene component have been eliminated by a hydrogenation reaction (hydrogenation). The hydrogenation may be partial or complete, but complete hydrogenation or one with a high hydrogenation rate is more preferable from the viewpoint of heat resistance.

The mass ratio of styrene/conjugated diene and its double bond hydrogenated portion in the styrene copolymer is preferably 10/90 to 70/30, more preferably 20/80 to 67/33. If the mass ratio is within this range, a composition with excellent compatibility and dispersibility and stable quality can be obtained. In other words, the styrene content by mass in the styrene-based elastomer is preferably 10 to 90%, more preferably 20 to 67%.

In addition, both ends of the styrene-based elastomer of component (A) are modified with at least one reactive functional group selected from the group consisting of amino, carboxyl, and vinyl groups. As a result, component (A) reacts with component (B) described later to obtain a cured product with excellent heat resistance. The modification of the styrene-based elastomer can be performed, for example, by copolymerizing an unsaturated carboxylic acid during polymerization of the styrene-based elastomer. It can also be performed by heating and kneading the styrene-based elastomer and the unsaturated carboxylic acid in the presence of an organic peroxide. Examples of unsaturated carboxylic acids include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, maleic anhydride, itaconic anhydride, and fumaric anhydride. The method of amine-modifying the styrene-based elastomer is not particularly limited, and known methods can be used. For example, it can be performed by copolymerizing an unsaturated monomer containing an amino group with the styrene-based elastomer. It can also be performed by polymerization using a polymerization initiator containing an amino group.

The number average molecular weight (Mn) of component (A) is preferably 10,000 to 300,000, and more preferably 10,000 to 200,000. When the number average molecular weight is within the above range, the resulting composition has excellent film properties, is excellent in compatibility and dispersibility with other components such as components (B) and (C), and exhibits good adhesion.
The number average molecular weight referred to in this specification refers to the number average molecular weight measured by gel permeation chromatography (GPC) under the following conditions using polystyrene as a standard substance.

[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)

The styrene-based elastomer of component (A) may be a commercially available product. Specific examples include the Tuftec series manufactured by Asahi Kasei Corporation and the FG series manufactured by Kraton. The composition of the present invention may contain one type of styrene-based elastomer alone or a mixture of two or more types.
In the thermosetting maleimide resin composition of the present invention, the blending amount of component (A) is preferably 60 to 99 mass %, more preferably 65 to 97 mass %, and even more preferably 70 to 95 mass %.

（式（１）中、Ｒ¹はダイマー酸骨格に由来する二価の炭化水素基を示す。） (B) Maleimide Compound The (B) component used in the present invention is a maleimide compound represented by the following formula (1), and is preferably a maleimide compound which is a reaction product of dimer diamine and maleic anhydride. The (B) component is a thermosetting resin, and reacts with the (A) component, resulting in a composition with good heat resistance and mechanical properties and high reliability. In addition, the (B) component has a divalent hydrocarbon group derived from the dimer acid skeleton, and therefore has good dielectric properties. Therefore, the composition exhibits excellent dielectric properties.

(In formula (1), ^R1 represents a divalent hydrocarbon group derived from a dimer acid skeleton.)

Dimer acid is a liquid fatty acid mainly composed of a dicarboxylic acid with 36 carbon atoms, produced by dimerization of unsaturated fatty acids with 18 carbon atoms, which are derived from natural products such as vegetable oils. Dimer acids do not have a single skeleton, but have 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. Examples of the divalent hydrocarbon group derived from the dimer acid skeleton include, but are not limited to, the following structures.
Furthermore, from the viewpoint of the heat resistance and reliability of the cured product, it is more preferable that the divalent hydrocarbon group derived from the dimer acid skeleton of component (B) has a structure in which the carbon-carbon double bonds in the hydrocarbon group derived from the dimer acid skeleton are reduced by a hydrogenation reaction.

When a maleimide compound other than that of formula (1) is used as component (B), its compatibility with component (A) decreases, causing turbidity and separation when made into a varnish. This can cause unevenness in the composition, which can lead to variations in the properties of the composition.

The mass ratio ((A)/(B)) of the (A) component to the (B) component is 2 to 20, and preferably 3 to 15. If this ratio is greater than 20, the amount of liquid components will be greater, which may result in poor film properties when uncured. Conversely, if it is less than 2, the amount of thermosetting components will be less, which may result in poor heat resistance.

(C) Organic Peroxide The organic peroxide, component (C), is added mainly to initiate the crosslinking reaction of the maleimide compound, component (B), and, when the styrene-based elastomer, component (A), has a radically polymerizable functional group, to promote the reaction between the functional group and the maleimide compound, component (B). Examples of organic peroxides include dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, 1,3-bis(tert-butylperoxyisopropyl)benzene, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl-4,4-bis(tert-butylperoxy)valerate, benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, and tert-butylcumyl peroxide.

The amount of component (C) is preferably 0.01 to 5.0 parts by mass, and more preferably 0.1 to 3.0 parts by mass, per 100 parts by mass of the total amount of components (A) and (B). If the amount of component (C) is more than this range, the adhesive strength will decrease and the dielectric properties may deteriorate due to residual component (C). Conversely, if the amount of component (C) is less than the aforementioned range, there is a concern that the dielectric properties and heat resistance will decrease due to reduced curing properties.

<Other additives>
The thermosetting maleimide resin composition of the present invention may further contain various additives as necessary within the scope of not impairing the effects of the present invention. For example, as an adhesion promoter, a coupling agent such as a silane coupling agent or a titanate coupling agent, or a monomer having a (meth)acrylic group may be added.
(D) Adhesion Aid As the adhesion aid, a coupling agent such as a silane coupling agent or a titanate coupling agent, or a monomer having a (meth)acrylic group can be blended.
Examples of the silane coupling agent include epoxy-functional alkoxysilanes such as γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; mercapto-functional alkoxysilanes such as γ-mercaptopropyltrimethoxysilane; amine-functional alkoxysilanes such as γ-aminopropyltrimethoxysilane and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane; and methacryl-functional alkoxysilanes such as 3-methacryloxypropyltrimethoxysilane.
Examples of titanium coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris(dioctyl pyrophosphate) titanate, tetraisopropyl bis(dioctyl phosphite) titanate, tetraoctyl bis(ditridecyl phosphite) titanate, bis(dioctyl pyrophosphate) oxyacetate titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl isostearoyl diacryl titanate, isopropyl tri(dioctyl phosphate) titanate, isopropyl tricumyl phenyl titanate, and isopropyl tri(N-aminoethyl aminoethyl) titanate.
Examples of monomers having a (meth)acrylic group include 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, dipropylene glycol diacrylate, tricyclodecane dimethanol diacrylate, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene diacrylate, bisphenol A diacrylate, trimethylolpropane triacrylate, tris(2-acryloxymethyl)isocyanurate, ditrimethylolpropane tetraacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol methacrylate, dipropylene glycol methacrylate, tricyclodecane dimethanol methacrylate, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene methacrylate, bisphenol A dimethacrylate, trimethylolpropane trimethacrylate, tris(2-methacryloxymethyl)isocyanurate, and ditrimethylolpropane tetramethacrylate.

Other additives include inorganic fillers such as silica, alumina, and boron nitride, resin powders such as PTFE powder, metal particles such as silver, organopolysiloxanes having reactive functional groups, non-functional silicone oils, thermoplastic resins, thermoplastic elastomers other than styrene-based, organic synthetic rubbers, photosensitizers, light stabilizers, polymerization inhibitors, flame retardants, pigments, dyes, etc. In order to improve the electrical properties of the cured product of the thermosetting maleimide resin composition, other additives such as ion trapping agents may also be added.

The thermosetting maleimide resin composition of the present invention can be produced by mixing the components (A), (B), and (C) and other additives which are added as necessary.
The thermosetting maleimide resin composition of the present invention can also be dissolved in an organic solvent and treated as a varnish. The thermosetting maleimide resin composition can be easily molded into a sheet or film by forming it into a varnish. Any organic solvent can be used without limitation as long as it dissolves the components (A) and (B). As the organic solvent, for example, toluene, xylene, anisole, cyclohexanone, cyclopentanone, etc. can be suitably used. The above organic solvents may be used alone or in combination of two or more. The concentration of the thermosetting maleimide resin composition of the present invention in the varnish is preferably 5 to 80% by mass, more preferably 10 to 75% by mass.

This thermosetting maleimide resin composition can be suitably used primarily as an adhesive, a primer, a bonding film or sheet material for substrates, a sealing material, an adhesive layer for FPC coverlay films, and flexible flat cables. There are no limitations on the method or form of use. For example, it can be used as an uncured resin film or a cured resin film, or as an adhesive. Examples of use are given below, but are not limited to these.

For example, a thermosetting maleimide resin composition (varnish) dissolved in an organic solvent is applied to a support sheet, and then the sheet is heated at a temperature of usually 80°C or higher, preferably 100°C or higher, for 0.5 to 5 hours to remove the organic solvent, thereby obtaining an uncured film-like or sheet-like composition (uncured resin film). The support sheet may be one that is commonly used, 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, and the surface of these support sheets may be subjected to a release treatment. The coating method is not particularly limited, and examples include a gap coater, curtain coater, roll coater, and laminator. The thickness of the coating layer is not particularly limited, and the thickness after solvent removal is in the range of 1 to 100 μm, preferably 3 to 80 μm. A cover film may be used on the coating layer.

It can also be used as a substrate material by attaching copper foil onto the coating layer.

In addition, the organic solvent is removed by applying a varnish to the substrate and heating it at a temperature of typically 80°C or higher, preferably 100°C or higher, for 0.5 to 5 hours, and the item to be bonded to the substrate is pressed while being heated, and then heated at a temperature of 130°C or higher, preferably 150°C or higher, for 0.5 to 10 hours to bond the item.

Methods for applying the thermosetting maleimide composition solution (varnish) include ordinary coating methods and printing methods. Specifically, coating methods such as air doctor coating, bar coating, blade coating, knife coating, reverse coating, transfer roll coating, gravure roll coating, kiss coating, cast coating, spray coating, slot orifice coating, calendar coating, dam coating, dip coating, and die coating, as well as printing methods such as intaglio printing such as gravure printing and stencil printing such as screen printing can be used.

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 listed below.

(A) Styrene-based elastomer having reactive functional groups at both ends (A-1) Amine-modified styrene/ethylene/butylene/styrene block copolymer, hydrogenated, styrene content 30%, number average molecular weight 33,000 (Tuftec MP10: manufactured by Asahi Kasei Corporation)
(A-2) Carboxylic acid-modified styrene/ethylene/butylene/styrene block copolymer, styrene content 30%, number average molecular weight 90,000 (Tuftec M1913: manufactured by Asahi Kasei Corporation)
(A-3) Styrene/ethylene/butylene/styrene block copolymer, styrene content 30%, number average molecular weight 74,000 (Tuftec H1041: manufactured by Asahi Kasei Corporation, for comparison)

－Ｃ₃₆Ｈ₇₀－はダイマー酸骨格由来の炭化水素基を示す。
（Ｂ－２）：下記式で示されるビスマレイミド化合物（ＳＬＫ－３０００、信越化学工業（株）製、比較例用）

－Ｃ₃₆Ｈ₇₀－はダイマー酸骨格由来の炭化水素基を示す。
（Ｂ－３）：４，４’－ジフェニルメタンビスマレイミド（ＢＭＩ－１０００：大和化成工業（株）製、比較例用） (B) Maleimide compound (B-1): a bismaleimide compound represented by the following formula (SLK-6895, manufactured by Shin-Etsu Chemical Co., Ltd.)

--C ₃₆ H ₇₀ -- represents a hydrocarbon group derived from a dimer acid skeleton.
(B-2): Bismaleimide compound represented by the following formula (SLK-3000, manufactured by Shin-Etsu Chemical Co., Ltd., for comparative purposes)

--C ₃₆ H ₇₀ -- represents a hydrocarbon group derived from a dimer acid skeleton.
(B-3): 4,4'-diphenylmethane bismaleimide (BMI-1000: manufactured by Daiwa Chemical Industry Co., Ltd., for comparison)

(C) Organic peroxide (C-1): Dicumyl peroxide (Percumyl D: manufactured by NOF Corporation)
(C-2): 2-ethyl-4-methylimidazole (2E4MZ: manufactured by Shikoku Kasei Co., Ltd., for comparative purposes)

(D) Adhesion aid (D-1): 3-methacryloxypropyltrimethoxysilane (KBM-503: manufactured by Shin-Etsu Chemical Co., Ltd.)

<Preparation of varnish>
The components according to the formulations in Tables 1 and 2 were charged into a 500 mL four-neck flask equipped with a Dimroth condenser and a stirrer, and stirred at 50° C. for 2 hours to obtain a varnish-like resin composition.

<Appearance of varnish>
Regarding the varnish before being made into a film, when there was no residual insoluble matter or turbidity when visually observed, and when a 30 mass % xylene solution of the resin composition was placed in a quartz cell, the direct light transmittance at 740 nm with an optical path length of 1 mm was measured at 25°C using a spectrophotometer U-4100 (manufactured by Hitachi High-Tech Science Corporation), those that were 50% or more were marked as ○, and those that were less than 50% were marked as ×.

<Preparation of Uncured Film>
The varnish-like thermosetting maleimide resin composition was applied to a PET film having a thickness of 38 μm using a roller coater so that the thickness after drying would be 50 μm, and then dried at 120° C. for 10 minutes to obtain an uncured resin film.

<Handling of uncured resin film>
The uncured resin film was visually inspected for cracks or breakage when it was bent 90 degrees at 25° C. When no cracks, breaks, tackiness, or the like were observed, it was marked with an ◯, and when even a small amount of cracks, breaks, tackiness, or the like was observed, it was marked with an ×.

From the results in Tables 1 and 2, it was confirmed that the varnish compositions of Examples 1 to 8 were stable with no separation or turbidity in terms of varnish appearance. The stability of the varnish compositions of Comparative Examples 3 to 6 was also confirmed. On the other hand, the varnish of Comparative Examples 1 and 2 became turbid.

From the results in Tables 1 and 2, it was confirmed that the uncured resin film characteristics of Examples 1 to 8 were free of cracks, breaks, etc. As with the Examples, no cracks or other defects were observed in Comparative Examples 1, 3, 5 to 6. On the other hand, cracks and tack were observed in Comparative Examples 2 and 4. Further evaluation of Comparative Examples 2 and 4 was discontinued.

<Relative permittivity, dielectric loss tangent>
The uncured resin film was cured at 180° C. for 2 hours, and the resulting resin film was cut to prepare a 60 mm×60 mm test piece. The dielectric constant and dielectric loss tangent of the obtained test piece were measured at 10 GHz and 28 GHz at 25° C. using a SPDR dielectric resonator (MS46122B, manufactured by Anritsu Corporation).

<Heat resistance>
The cured resin film produced by the above process was stored at 150° C. for 500 hours, and then the dielectric properties were measured at 10 GHz at 25° C. using the above device. When the rate of change between the initial dielectric tangent value at 10 GHz and the dielectric tangent value at 10 GHz after storage was less than 100%, it was evaluated as ◯, and when it was 100% or more, it was evaluated as ×.

＜Peel strength＞

A slide glass measuring 75 mm in length, 25 mm in width, and 1.0 mm in thickness was prepared, and the resin composition side of the uncured resin film with PET film, without the PET substrate, was placed on one surface of the slide glass, and lamination was performed under conditions of 120°C, 0.3 MPa pressure, and 60 seconds. After lamination, the PET substrate was peeled off, and 18 μm thick copper foil (Mitsui Kinzoku Co., Ltd., Ra 0.6 μm), 50 μm thick LCP (Chiyoda Integre Co., Ltd.) or MPI (PIXEO SR, Kaneka Corporation) was placed on the resin composition surface, and lamination was performed under conditions of 120°C, 0.3 MPa pressure, and 60 seconds. After lamination, the adhesive test specimen was prepared by curing at 180°C for 2 hours.

To evaluate adhesion, the 90° peel strength (kN/m) was measured when peeling the copper foil, LCP, or MPI of each adhesive test piece from the glass slide at a temperature of 23°C and a tensile speed of 50 mm/min in accordance with JIS-C-6481 "Test methods for copper-clad laminates for printed wiring boards."

The above evaluation results are shown in Tables 3 and 4.

These results confirm that the thermosetting maleimide resin composition of the present invention is free of varnish separation or turbidity, has excellent dielectric properties after curing, and exhibits high adhesive strength to metals and organic resins, making it useful as an insulating material suitable for circuit board applications.

Claims (6)

(A) a styrene-based elastomer having reactive functional groups at both ends,
(B) A maleimide compound represented by the following formula (1):

(In formula (1), R ¹ represents a divalent hydrocarbon group derived from a dimer acid skeleton.)
and (C) an organic peroxide, wherein the ratio of the component (A) to the component (B) (mass ratio (A)/(B)) is 2 to 20;
The styrene-based elastomer of component (A) is a copolymer of styrene with an alkene and/or a non-conjugated diene, and reactive functional groups at both ends of the copolymer include at least one of an amino group, a carboxyl group, and a vinyl group;
A thermosetting maleimide resin composition further containing an adhesive aid as component (D) (provided that this does not include the case where the thermosetting maleimide resin composition contains an inorganic filler) . An uncured resin film comprising the thermosetting maleimide resin composition according to claim 1 . A cured resin film comprising a cured product of the thermosetting maleimide resin composition according to claim 1 . An adhesive comprising the thermosetting maleimide resin composition according to claim 1 . An encapsulant comprising the thermosetting maleimide resin composition according to claim 1 . A substrate comprising the cured product of the thermosetting maleimide resin composition according to claim 1 .