JP7690474B2 - Adhesive Composition - Google Patents

Description

The present invention relates to an adhesive composition. More specifically, the present invention relates to an adhesive composition that can be used for bonding electronic components and the like.

2. Description of the Related Art As electronic devices become smaller and lighter, the applications for adhering electronic components and the like have become more diverse, and the demand for laminates with an adhesive layer has increased.
In addition, flexible printed circuit boards (hereinafter also referred to as FPCs), which are one type of electronic component, need to process large amounts of data at high speed, and are becoming more and more compatible with high frequencies. In order to increase the frequency of FPCs, it is necessary to reduce the dielectric constant of the components, and low-dielectric base films and low-dielectric adhesives are being developed. In particular, in order to efficiently transmit signals having frequencies in the 3.5 GHz and 28 GHz bands used in the fifth generation mobile communication system (hereinafter also referred to as 5G), it is becoming increasingly important to have base films and adhesives that have low loss even in the 28 GHz millimeter wave band.

However, because the polarity of the main molecule of low-dielectric adhesives is low, they are less likely to exhibit adhesion (bonding) to base films and other components related to electronic parts; in addition, low-dielectric base films can also exhibit poor adhesion (bonding) to adhesives, so there is a demand for improved adhesion.
In order to meet the demand for high adhesion while maintaining good electrical properties (low dielectric constant and low dielectric tangent), a laminate has been proposed that uses an adhesive composition containing a carboxyl group-containing styrene-based elastomer (A) and an epoxy resin (B) and that comprises an adhesive layer made of the adhesive composition and a substrate film (see, for example, Patent Document 1).

International Publication No. 2016/017473

However, low-dielectric adhesives have few reactive groups in the base molecules, which means they have poor reactivity with curing agents. Furthermore, when epoxy resins are used as curing agents, the dielectric tangent tends to be high. Due to these factors, it is extremely difficult to achieve both curability, which affects the adhesion, heat resistance, and chemical resistance (solvent resistance) of the adhesive composition, and low dielectric properties.

Therefore, the present invention aims to provide an adhesive composition for forming a low dielectric adhesive layer that has good electrical properties (dielectric properties) compatible with 5G, exhibits good adhesion even to low dielectric substrate films with poor adhesion, and combines heat resistance and chemical resistance (solvent resistance).

As a result of extensive research into solving the above problems, the inventors discovered that an adhesive composition containing a styrene-based elastomer and a specific epoxy-modified resin can solve the above problems, and thus completed the present invention.

（Ｒ^１とＲ^２とＲ^３とＲ^４は、それぞれ独立に水素、又は有機基を表す。ただし、Ｒ^１とＲ^２のうち少なくとも一方が有機基であり、かつ、Ｒ^３とＲ^４のうち少なくとも一方が有機基である。）
［２］前記スチレン系エラストマーが、カルボキシ基を含有するスチレン系エラストマーである、［１］に記載の接着剤組成物。
［３］前記スチレン系エラストマーが、アミノ基を含有するスチレン系エラストマーである、［１］に記載の接着剤組成物。
［４］前記エポキシ変性樹脂の含有量が、前記接着剤組成物１００質量部に対して１～５０質量部である、［１］～［３］のいずれかに記載の接着剤組成物。
［５］前記エポキシ変性樹脂のエポキシ当量が、２００ｇ／ｅｑ．以上２０，０００ｇ／ｅｑ．以下である、［１］～［４］のいずれかに記載の接着剤組成物。
［６］前記エポキシ変性樹脂が、下記式（２）で表される構造を有する、［１］～［５］のいずれかに記載の接着剤組成物。

（Ｒ^５とＲ^６とは、それぞれ独立に水素、又は炭素数が１０以下のアルキル基を表す。前記エポキシ変性樹脂中に前記式（２）で表される構造が複数存在する場合、それぞれの式（２）におけるＲ^５は、それぞれ同一であっても異なっていてもよく、それぞれの式（２）におけるＲ^６は、それぞれ同一であっても異なっていてもよい。＊は結合基を表す。）
［７］前記エポキシ変性樹脂が、芳香環以外の不飽和結合を含む、［１］～［６］のいずれかに記載の接着剤組成物。
［８］前記エポキシ変性樹脂が、下記式（３）で表される構造を有する、［７］に記載の接着剤組成物。

（Ｒ^７とＲ^８とは、それぞれ独立に水素、又は炭素数が１０以下のアルキル基を表す。前記エポキシ変性樹脂中に前記式（３）で表される構造が複数存在する場合、それぞれの式（３）におけるＲ^７は、それぞれ同一であっても異なっていてもよく、それぞれの式（３）におけるＲ^８は、それぞれ同一であっても異なっていてもよい。＊は結合基を表す。）
［９］前記エポキシ変性樹脂が、下記式（４）で表される構造と下記式（５）で表される構造のうち少なくともいずれかの構造を有する、［１］～［８］のいずれかに記載の接着剤組成物。

（Ｒ^９とＲ^１０とは、それぞれ独立に水素、又は炭素数が１０以下のアルキル基を表す。前記エポキシ変性樹脂中に前記式（４）で表される構造が複数存在する場合、それぞれの式（４）におけるＲ^９は、それぞれ同一であっても異なっていてもよく、それぞれの式（４）におけるＲ^１０は、それぞれ同一であっても異なっていてもよい。＊は結合基を表す。）

（Ｒ^１１とＲ^１２とは、それぞれ独立に水素、又は炭素数が１０以下のアルキル基を表す。
前記エポキシ変性樹脂中に前記式（５）で表される構造が複数存在する場合、それぞれの式（５）におけるＲ^１１は、それぞれ同一であっても異なっていてもよく、それぞれの式（５）におけるＲ^１２は、それぞれ同一であっても異なっていてもよい。＊は結合基を表す。）
［１０］前記式（２）中のＲ^５とＲ^６が、ともに水素である、［６］に記載の接着剤組成物。
［１１］前記式（３）中のＲ^７とＲ^８が、ともに水素である、［８］に記載の接着剤組成物。
［１２］前記式（４）中のＲ^９とＲ^１０が、ともに水素であるか、又は前記式（５）中のＲ^１１とＲ^１２が、ともに水素である、［９］に記載の接着剤組成物。
［１３］前記エポキシ変性樹脂が、不飽和結合含有エラストマーを過酸化物で変性したエポキシ変性エラストマーである、［１］～［１２］のいずれかに記載の接着剤組成物。
［１４］前記エポキシ変性樹脂が、スチレン系エラストマーである、［１］～［１３］のいずれかに記載の接着剤組成物。
［１５］前記エポキシ変性樹脂の重量平均分子量（Ｍｗ）が、３０，０００以上２００，０００以下である、［１］～［１４］のいずれかに記載の接着剤組成物。
［１６］前記接着剤組成物が、フィラーを含有する、［１］～［１５］のいずれかに記載の接着剤組成物。
［１７］前記接着剤組成物が、ラジカル重合開始剤を含有する、［１］～［１６］のいずれかに記載の接着剤組成物。
［１８］前記接着剤組成物が、有機過酸化物を含有する、［１］～［１７］のいずれかに記載の接着剤組成物。
［１９］［１］～［１８］のいずれかに記載の接着剤組成物を硬化させてなる接着剤層に対し、周波数２８ＧＨｚで測定した前記接着剤層の比誘電率が３以下であり、かつ誘電正接が０．００４以下である、接着剤層。
［２０］基材フィルムと、
［１］～［１８］のいずれかに記載の接着剤組成物からなる接着剤層、又は［１９］に記載の接着剤層と、を有する積層体。
［２１］前記基材フィルムが、ポリエーテルエーテルケトン（ＰＥＥＫ）樹脂を含有する、［２０］に記載の積層体。
［２２］［２０］又は［２１］に記載の積層体を含む接着剤層付きカバーレイフィルム。
［２３］［２０］又は［２１］に記載の積層体を含む銅張積層板。
［２４］［２０］又は［２１］に記載の積層体を含むプリント配線板。
［２５］［２０］又は［２１］に記載の積層体を含むシールドフィルム。
［２６］［２０］又は［２１］に記載の積層体を含むシールド付きプリント配線板。 The present invention includes the following aspects.
[1] An adhesive composition comprising a styrene-based elastomer and an epoxy-modified resin having a structure represented by the following formula (1):

( ^R1 , ^R2 , ^R3 , and ^R4 each independently represent hydrogen or an organic group, provided that at least one of ^R1 and ^R2 is an organic group, and at least one of ^R3 and ^R4 is an organic group.)
[2] The adhesive composition according to [1], wherein the styrene-based elastomer is a styrene-based elastomer containing a carboxy group.
[3] The adhesive composition according to [1], wherein the styrene-based elastomer is an amino group-containing styrene-based elastomer.
[4] The adhesive composition according to any one of [1] to [3], wherein the content of the epoxy-modified resin is 1 to 50 parts by mass per 100 parts by mass of the adhesive composition.
[5] The adhesive composition according to any one of [1] to [4], wherein the epoxy equivalent of the epoxy-modified resin is 200 g/eq. or more and 20,000 g/eq. or less.
[6] The adhesive composition according to any one of [1] to [5], wherein the epoxy-modified resin has a structure represented by the following formula (2):

( ^R5 and ^R6 each independently represent hydrogen or an alkyl group having 10 or less carbon atoms. When a plurality of structures represented by formula (2) are present in the epoxy-modified resin, ^R5 in each formula (2) may be the same or different, and ^R6 in each formula (2) may be the same or different. * represents a bonding group.)
[7] The adhesive composition according to any one of [1] to [6], wherein the epoxy-modified resin contains an unsaturated bond other than an aromatic ring.
[8] The adhesive composition according to [7], wherein the epoxy-modified resin has a structure represented by the following formula (3):

( ^R7 and ^R8 each independently represent hydrogen or an alkyl group having 10 or less carbon atoms. When a plurality of structures represented by formula (3) are present in the epoxy-modified resin, ^R7 in each formula (3) may be the same or different, and ^R8 in each formula (3) may be the same or different. * represents a bonding group.)
[9] The adhesive composition according to any one of [1] to [8], wherein the epoxy-modified resin has at least one of a structure represented by the following formula (4) and a structure represented by the following formula (5).

( ^R9 and ^R10 each independently represent hydrogen or an alkyl group having 10 or less carbon atoms. When a plurality of structures represented by formula (4) are present in the epoxy-modified resin, ^R9 in each formula (4) may be the same or different, and ^R10 in each formula (4) may be the same or different. * represents a bonding group.)

(R ¹¹ and R ¹² each independently represent a hydrogen atom or an alkyl group having 10 or less carbon atoms.
When a plurality of structures represented by the formula (5) are present in the epoxy-modified resin, R ¹¹ in each formula (5) may be the same or different, and R ¹² in each formula (5) may be the same or different. * represents a bonding group.
[10] The adhesive composition according to [6], wherein R ⁵ and R ⁶ in the formula (2) are both hydrogen.
[11] The adhesive composition according to [8], wherein R ⁷ and R ⁸ in the formula (3) are both hydrogen.
[12] The adhesive composition according to [9], wherein R ⁹ and R ¹⁰ in the formula (4) are both hydrogen, or R ¹¹ and R ¹² in the formula (5) are both hydrogen.
[13] The adhesive composition according to any one of [1] to [12], wherein the epoxy-modified resin is an epoxy-modified elastomer obtained by modifying an unsaturated bond-containing elastomer with a peroxide.
[14] The adhesive composition according to any one of [1] to [13], wherein the epoxy-modified resin is a styrene-based elastomer.
[15] The adhesive composition according to any one of [1] to [14], wherein the weight average molecular weight (Mw) of the epoxy modified resin is 30,000 or more and 200,000 or less.
[16] The adhesive composition according to any one of [1] to [15], wherein the adhesive composition contains a filler.
[17] The adhesive composition according to any one of [1] to [16], further comprising a radical polymerization initiator.
[18] The adhesive composition according to any one of [1] to [17], wherein the adhesive composition contains an organic peroxide.
[19] An adhesive layer obtained by curing the adhesive composition according to any one of [1] to [18], wherein the adhesive layer has a relative dielectric constant of 3 or less and a dielectric loss tangent of 0.004 or less, measured at a frequency of 28 GHz.
[20] A base film,
A laminate comprising an adhesive layer made of the adhesive composition according to any one of [1] to [18], or the adhesive layer according to [19].
[21] The laminate according to [20], wherein the base film contains a polyether ether ketone (PEEK) resin.
[22] A coverlay film with an adhesive layer comprising the laminate according to [20] or [21].
[23] A copper-clad laminate comprising the laminate according to [20] or [21].
[24] A printed wiring board comprising the laminate according to [20] or [21].
[25] A shielding film comprising the laminate according to [20] or [21].
[26] A shielded printed wiring board comprising the laminate according to [20] or [21].

According to the present invention, it is possible to provide an adhesive composition for forming a low dielectric adhesive layer that has good electrical properties (dielectric properties) compatible with 5G, exhibits good adhesion even to low dielectric substrate films with poor adhesion, and combines heat resistance and chemical resistance (solvent resistance).

The adhesive composition of the present invention, a laminate including an adhesive layer made of the adhesive composition, and electronic component-related components including the laminate are described in detail below. However, the description of the constituent elements described below is an example of one embodiment of the present invention and is not limited to these contents.

(Adhesive Composition)
The adhesive composition of the present invention contains a styrene-based elastomer and an epoxy-modified resin having a structure represented by the following formula (1).

（Ｒ^１とＲ^２とＲ^３とＲ^４は、それぞれ独立に水素、又は有機基を表す。ただし、Ｒ^１とＲ^２のうち少なくとも一方が有機基であり、かつ、Ｒ^３とＲ^４のうち少なくとも一方が有機基である。）
本発明の接着剤組成物は、必要に応じて、その他の成分を含有してもよい。
スチレン系エラストマーと上記式（１）で表される構造を有するエポキシ変性樹脂とを含有する本発明の接着剤組成物は、低誘電の接着剤組成物であっても良好な密着性を示し、耐熱性、耐薬品（耐溶剤）性にも優れた接着剤組成物となる。

( ^R1 , ^R2 , ^R3 , and ^R4 each independently represent hydrogen or an organic group, provided that at least one of ^R1 and ^R2 is an organic group, and at least one of ^R3 and ^R4 is an organic group.)
The adhesive composition of the present invention may contain other components as necessary.
The adhesive composition of the present invention, which contains a styrene-based elastomer and an epoxy-modified resin having a structure represented by the above formula (1), exhibits good adhesion even though it is a low dielectric adhesive composition, and is also excellent in heat resistance and chemical resistance (solvent resistance).

<Styrene-based elastomer>
The styrene-based elastomer is a copolymer mainly composed of a block or random structure of a conjugated diene compound and an aromatic vinyl compound, and a hydrogenated product thereof.
The molecule contains few highly polar bonding groups, which gives the composition good electrical properties (dielectric properties). In addition, compared to other types of elastomers, it has the advantage that the molecular weight can be easily controlled and the adhesive composition properties can be stably produced.
Examples of aromatic vinyl compounds include styrene, t-butylstyrene, α-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N,N-diethyl-p-aminoethylstyrene, vinyltoluene, etc. Examples of conjugated diene compounds include butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, etc.
Specific examples of styrene-based elastomers include styrene-butadiene block copolymers, styrene-ethylene propylene block copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, styrene-ethylenebutylene-styrene block copolymers, and styrene-ethylenepropylene-styrene block copolymers.

There are no particular restrictions on the styrene-based elastomer, and it may be modified or unmodified, and may be selected according to the purpose. As a component that imparts adhesion after curing, modified styrene-based elastomers such as styrene-based elastomers containing carboxy groups and styrene-based elastomers containing amino groups described below are preferred, and as a component that adjusts adhesion by lamination and elastic modulus for each temperature, unmodified styrene-based elastomers are preferred.

The styrene-based elastomer may be used alone or in combination of two or more kinds. In particular, by using a modified styrene-based elastomer having good surface adhesion to an adherend and an unmodified styrene-based elastomer capable of adjusting the elastic modulus of the adhesive composition at each temperature in combination, it becomes possible to control high adhesion and flowability.
Among the above copolymers, styrene-ethylenebutylene-styrene block copolymers and styrene-ethylenepropylene-styrene block copolymers are preferred from the viewpoints of being able to impart adhesive properties and electrical properties (dielectric properties) to the adhesive composition, and being able to relatively easily control the molecular structure and adjust the properties of the adhesive composition. The mass ratio of styrene/ethylenebutylene in the styrene-ethylenebutylene-styrene block copolymer and the mass ratio of styrene/ethylenepropylene in the styrene-ethylenepropylene-styrene block copolymer are preferably 10/90 to 50/50, and more preferably 20/80 to 40/60. If the mass ratio is within this range, an adhesive composition having excellent adhesive properties can be obtained.

<<Carboxy group-containing styrene-based elastomer>>
Carboxy group-containing styrene-based elastomers have high adhesion, can impart flexibility to the cured product, and are effective as a component that imparts good electrical properties.
By containing a styrene-based elastomer containing a carboxy group in the adhesive composition, the flexible adhesive composition can sufficiently conform to the surface of the adherend, even if the adherend has good electrical properties and low polarity, such as a base film or metal foil, and the highly polar carboxy group can exhibit adhesion, improving the adhesion of the adhesive layer. In addition, since the styrene-based elastomer containing a carboxy group is reactive, the heat resistance and chemical resistance of the adhesive layer are also improved by epoxy curing.
Furthermore, the inclusion of a carboxy group improves the dispersibility of the filler in the dispersion liquid.
The carboxyl group-containing styrene-based elastomer is a copolymer mainly consisting of block and random structures of a conjugated diene compound and an aromatic vinyl compound, or a hydrogenated product thereof modified with an unsaturated carboxylic acid.
The types of aromatic vinyl compounds and conjugated diene compounds and specific examples of styrene-based elastomers are as described above in the section "Styrene-based elastomers".

The modification of a carboxyl group-containing styrene elastomer can be carried out, for example, by copolymerizing an unsaturated carboxylic acid during polymerization of the styrene elastomer, or by heating and kneading the styrene elastomer and the unsaturated carboxylic acid in the presence of an organic peroxide.
Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, maleic anhydride, and itaconic anhydride.
The amount of modification with the unsaturated carboxylic acid is preferably 0.1 to 10% by mass.
The acid value of the carboxyl group-containing styrene-based elastomer is preferably 0.1 to 25 mgKOH/g, and more preferably 0.5 to 23 mgKOH/g. When the acid value is 0.1 mgKOH/g or more, the adhesive composition is cured sufficiently, and good adhesion and heat resistance are obtained. On the other hand, when the acid value is 30 mgKOH/g or less, the adhesive composition has a suppressed cohesive force, and therefore has excellent adhesion and electrical properties.

The weight average molecular weight of the carboxyl group-containing styrene-based elastomer is preferably 10,000 to 500,000, more preferably 30,000 to 300,000, and even more preferably 50,000 to 200,000. If the weight average molecular weight is equal to or higher than the lower limit, excellent adhesiveness can be exhibited, and the coatability when dissolved in a solvent and applied is also improved. If the weight average molecular weight is equal to or lower than the upper limit, compatibility with epoxy resins is improved.
The weight average molecular weight is a value obtained by converting the molecular weight measured by gel permeation chromatography (hereinafter also referred to as "GPC") into polystyrene equivalent.

The content of the carboxyl group-containing styrene-based elastomer is preferably 15 to 90 parts by mass per 100 parts by mass of the solid content of the adhesive composition. If the content is within this range, the adhesive composition can have excellent adhesive properties.

<<Styrene-based elastomer containing amino groups>>
By containing an amino group-containing styrene-based elastomer in the adhesive composition, the amino group exerts a strong interaction with the low dielectric substrate film, the reactivity of the adhesive composition is increased, and the adhesive layer has improved adhesion. In addition, since the amino group-containing styrene-based elastomer is reactive, the adhesive layer has improved heat resistance and chemical resistance due to epoxy curing.
The amino group improves adhesion to metals.
The amino group-containing styrene-based elastomer is a copolymer mainly composed of a block or random structure of a conjugated diene compound and an aromatic vinyl compound, or a hydrogenated product thereof, which is modified with an amine.
The types of aromatic vinyl compounds and conjugated diene compounds and specific examples of styrene-based elastomers are as described above in the section "Styrene-based elastomers".

The method for amine-modifying a styrene-based elastomer is not particularly limited, and known methods can be used. Examples of such methods include a method of amine-modifying a (hydrogenated) block copolymer by polymerizing it using a polymerization initiator having an amino group, a method of amine-modifying a (hydrogenated) copolymer by using an unsaturated monomer having an amino group as a raw material for copolymerization, and a method of amine-modifying a styrene-based elastomer containing a carboxy group by reacting it with an amine modifier having two or more amino groups to form an amide structure or an imide structure.

In addition, the weight average molecular weight of the styrene-based elastomer containing amino groups is preferably 10,000 to 500,000, more preferably 30,000 to 300,000, and even more preferably 50,000 to 200,000. If the weight average molecular weight is equal to or greater than the above lower limit, excellent adhesion can be achieved, and the coatability when dissolved in a solvent and applied is also improved. If the weight average molecular weight is equal to or less than the above upper limit, compatibility with epoxy resins is improved.

The content of the amino group-containing styrene-based elastomer is preferably 15 to 90 parts by mass per 100 parts by mass of the solid content of the adhesive composition. If the content is within this range, the adhesive composition can have excellent adhesive properties.

By mixing unmodified styrene-based elastomers with modified styrene-based elastomers, it is possible to adjust hardness, control MFR, and suppress resin flow while maintaining adhesion.

From the viewpoint of ensuring a low dielectric constant and adhesion (adhesiveness) of the adhesive composition, the total nitrogen content in the amino group-containing styrene-based elastomer is preferably 50 to 5000 ppm, more preferably 200 to 3000 ppm. When the total nitrogen content is equal to or greater than the above lower limit, excellent adhesion can be achieved. When the total nitrogen content is equal to or less than the above upper limit, excellent electrical properties can be achieved.
The total nitrogen content in the amino group-containing styrene-based elastomer can be determined in accordance with JIS-K2609 using a trace nitrogen analyzer ND-100 (manufactured by Mitsubishi Chemical Corporation).

<Epoxy modified resin>
The epoxy-modified resin having the structure represented by the above formula (1) has a higher reaction rate for the epoxy structure to react with the carboxy group in the styrenic elastomer containing the above carboxy group or the amino group in the styrenic elastomer containing the above amino group, or to self-polymerize, compared with ordinary epoxy resins, and is therefore effective as a component for imparting high adhesion to adherends and heat resistance to the cured adhesive.

A preferred embodiment of the epoxy-modified resin is an epoxy-modified resin having a structure represented by the following formula (2):

（Ｒ^５とＲ^６とは、それぞれ独立に水素、又は炭素数が１０以下のアルキル基を表す。エポキシ変性樹脂中に上記式（２）で表される構造が複数存在する場合、それぞれの式（２）におけるＲ^５は、それぞれ同一であっても異なっていてもよく、それぞれの式（２）におけるＲ^６は、それぞれ同一であっても異なっていてもよい。＊は結合基を表す。）
エポキシ基近くの立体障害が減少して、反応を十分に進行させることができる観点から、上記式（２）において、Ｒ^５とＲ^６が、ともに水素であるとより好ましい。

( ^R5 and ^R6 each independently represent hydrogen or an alkyl group having 10 or less carbon atoms. When a plurality of structures represented by the above formula (2) are present in the epoxy-modified resin, ^R5 in each formula (2) may be the same or different, and ^R6 in each formula (2) may be the same or different. * represents a bonding group.)
From the viewpoint of reducing steric hindrance near the epoxy group and allowing the reaction to proceed sufficiently, it is more preferable that R ⁵ and R ⁶ in the above formula (2) are both hydrogen.

The epoxy-modified resin preferably contains unsaturated bonds other than aromatic rings, such as an olefin skeleton or a vinyl group. Unsaturated bonds other than aromatic rings, such as an olefin skeleton or a vinyl group, can be incorporated into reactions involving epoxy groups to accelerate the reaction rate and increase the crosslinking density. As a result, even with a small amount of compounding, the heat resistance and chemical resistance can be improved. In addition, as described below, unsaturated bonds other than aromatic rings can be crosslinked by radical polymerization to increase the crosslinking density of the epoxy-modified resin, thereby improving the heat resistance and chemical resistance.

A preferred embodiment of the epoxy-modified resin is an epoxy-modified resin having a structure represented by the following formula (3):

（Ｒ^７とＲ^８とは、それぞれ独立に水素、又は炭素数が１０以下のアルキル基を表す。エポキシ変性樹脂中に上記式（３）で表される構造が複数存在する場合、それぞれの式（３）におけるＲ^７は、それぞれ同一であっても異なっていてもよく、それぞれの式（３）におけるＲ^８は、それぞれ同一であっても異なっていてもよい。＊は結合基を表す。）
上記式（３）において、Ｒ^７とＲ^８が、ともに水素であるとより好ましい。

( ^R7 and ^R8 each independently represent hydrogen or an alkyl group having 10 or less carbon atoms. When a plurality of structures represented by the above formula (3) are present in the epoxy-modified resin, ^R7 in each formula (3) may be the same or different, and ^R8 in each formula (3) may be the same or different. * represents a bonding group.)
In the above formula (3), it is more preferable that R ⁷ and R ⁸ are both hydrogen.

The epoxy-modified resin is preferably an epoxy-modified resin having a structure represented by the above formula (1) and a structure represented by the above formula (3), and more preferably an epoxy-modified resin having a structure represented by the above formula (2) and a structure represented by the above formula (3).

A preferred embodiment of the epoxy-modified resin is an epoxy-modified resin having at least one of the structures represented by the following formula (4) and the structure represented by the following formula (5). It is also preferred that the epoxy-modified resin has both the structure represented by the following formula (4) and the structure represented by the following formula (5).

（Ｒ^９とＲ^１０とは、それぞれ独立に水素、又は炭素数が１０以下のアルキル基を表す。エポキシ変性樹脂中に上記式（４）で表される構造が複数存在する場合、それぞれの式（４）におけるＲ^９は、それぞれ同一であっても異なっていてもよく、それぞれの式（４）におけるＲ^１０は、それぞれ同一であっても異なっていてもよい。＊は結合基を表す。）
上記式（４）において、Ｒ^９とＲ^１０が、ともに水素であるとより好ましい。

( ^R9 and ^R10 each independently represent hydrogen or an alkyl group having 10 or less carbon atoms. When a plurality of structures represented by the above formula (4) are present in the epoxy-modified resin, ^R9 in each formula (4) may be the same or different, and ^R10 in each formula (4) may be the same or different. * represents a bonding group.)
In the above formula (4), it is more preferable that R ⁹ and R ¹⁰ are both hydrogen.

（Ｒ^１１とＲ^１２とは、それぞれ独立に水素、又は炭素数が１０以下のアルキル基を表す。エポキシ変性樹脂中に上記式（５）で表される構造が複数存在する場合、それぞれの式（５）におけるＲ^１１は、それぞれ同一であっても異なっていてもよく、それぞれの式（５）におけるＲ^１２は、それぞれ同一であっても異なっていてもよい。＊は結合基を表す。）
上記式（５）において、Ｒ^１１とＲ^１２が、ともに水素であるとより好ましい。

(R ¹¹ and R ¹² each independently represent hydrogen or an alkyl group having 10 or less carbon atoms. When a plurality of structures represented by the above formula (5) are present in the epoxy-modified resin, R ¹¹ in each formula (5) may be the same or different, and R ¹² in each formula (5) may be the same or different. * represents a bonding group.)
In the above formula (5), it is more preferable that R ¹¹ and R ¹² are both hydrogen.

The epoxy-modified resin is preferably an epoxy-modified resin having a structure represented by the above formula (1), and at least one of the structures represented by the above formula (4) and the above formula (5), and is more preferably an epoxy-modified resin having a structure represented by the above formula (2), and at least one of the structures represented by the above formula (4) and the above formula (5).
Also preferred is an epoxy-modified resin having a structure represented by the above formula (1) or (2), a structure represented by the above formula (3), and at least one of a structure represented by the above formula (4) and a structure represented by the above formula (5).

In addition, the epoxy-modified resin is preferably an epoxy-modified organic compound obtained by modifying an organic compound containing an unsaturated bond. By modifying an organic compound containing an unsaturated bond, the structure represented by the above formula (1) and the unsaturated bond can coexist in the molecule depending on the modification rate, and the effect of the unsaturated bond other than the aromatic ring, such as an olefin skeleton or a vinyl group, can be easily imparted to the reaction of the epoxy structure.
Here, a method for modifying an organic compound containing an unsaturated bond into an epoxy-modified organic compound is effectively a reaction in which an epoxy skeleton is formed by a peroxide. Examples of the peroxide that can be used include percarboxylic acid compounds such as performic acid, peracetic acid, and perpropionic acid.
The epoxy-modified resin is preferably an epoxy-modified elastomer obtained by modifying an elastomer containing an unsaturated bond. The epoxy-modified elastomer can impart flexibility to the cured product and suppress the decrease in toughness of the cured product due to epoxy curing, thereby maintaining adhesion when the laminate is bent and preventing a decrease in heat resistance and chemical resistance.

Furthermore, the epoxy-modified resin is preferably a styrene-based elastomer.
In the epoxy modified resin having the structure represented by the above formula (1) or (2), it is also preferable that the resin has a styrene structural unit in addition to the structures represented by the above formulas (3) to (5).
Since the epoxy-modified resin is also a styrene-based elastomer, together with the styrene-based elastomer contained in the adhesive resin composition of the present invention, compatibility is improved when the two are mixed, and the reaction with the carboxy group in the carboxy-containing styrene-based elastomer or the amino group in the amino-containing styrene-based elastomer can proceed efficiently.

Examples of epoxy-modified resins include alicyclic epoxy compounds having an alicyclic epoxy group such as epoxycyclohexane, epoxidized polybutadiene, and epoxy compounds of styrene-butadiene block copolymers.
Among them, an epoxy compound of a styrene-butadiene block copolymer is more preferable. Since the styrene-butadiene block copolymer contains an unsaturated bond, the structure represented by the above formula (1) and the unsaturated bond can coexist in the molecule, and the effect of the unsaturated bond other than the aromatic ring, such as an olefin skeleton or a vinyl group, can be easily imparted to the reaction of the epoxy structure.
As the epoxy-modified resin, commercially available epoxy compounds can be used, such as CELLOXIDE 2021P, CELLOXIDE 2081, CELLOXIDE 2000 (manufactured by Daicel Corporation), Epolead GT401, Epolead PB3600, Epolead PB4700 (manufactured by Daicel Corporation), Epofriend AT501, and Epofriend CT310 (manufactured by Daicel Corporation).

The weight average molecular weight (Mw) of the epoxy modified resin is preferably 30,000 or more, and more preferably 50,000 or more. If the weight average molecular weight is 30,000 or more, the softening of the adhesive composition can be suppressed, and the resin flow during heat and pressure bonding can be prevented. If the weight average molecular weight is 50,000 or more, the flexibility of the epoxy modified resin is improved, and the toughness of the cured product is improved. In addition, the weight average molecular weight (Mw) of the epoxy modified resin is preferably 200,000 or less, and more preferably 160,000 or less. If the weight average molecular weight is 200,000 or less, the compatibility with styrene-based elastomers is further improved. If the weight average molecular weight is 160,000 or less, the elastic modulus of the adhesive composition can be reduced, and it can follow the shape of the adherend.

The content of the epoxy modified resin is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, relative to 100 parts by mass of the resin composition. If the content of the epoxy modified resin is 0.5 parts by mass or more, epoxy curing with the modified styrene-based elastomer is possible, and adhesion is improved. If the content of the epoxy modified resin is 1 part by mass or more, the adhesive composition is sufficiently cured and good heat resistance can be ensured. If the content of the epoxy modified resin is 2 parts by mass or more, the adhesive composition can further proceed with the crosslinking reaction, and good chemical resistance can be ensured. In addition, the content of the epoxy modified resin is preferably 50 parts by mass or less, more preferably 25 parts by mass or less, and even more preferably 15 parts by mass or less, relative to 100 parts by mass of the resin composition. If the content of the epoxy modified resin is 50 parts by mass or less, it is possible to achieve both low dielectric, heat resistance, and chemical resistance. If the content of the epoxy modified resin is 25 parts by mass or less, the flexibility of the adhesive composition after curing can be ensured, and adhesion is improved. If the content of the epoxy modified resin is 15 parts by mass or less, the dielectric constant can be further reduced.

The epoxy equivalent of the epoxy modified resin is preferably 200 g/eq. or more, more preferably 350 g/eq. or more, and even more preferably 900 g/eq. or more. If the epoxy equivalent of the epoxy modified resin is 200 g/eq. or more, the epoxy skeleton is not too dense in the epoxy modified resin, the reaction with the modified elastomer proceeds, and the adhesive composition forms a matrix, improving heat resistance and chemical resistance. If the epoxy equivalent of the epoxy modified resin is 350 g/eq. or more, the content of the epoxy skeleton relative to the amount of epoxy modified resin is reduced, improving electrical properties. If the epoxy equivalent of the epoxy modified resin is 900 g/eq. or more, the adhesive composition becomes flexible and the adhesion is improved. In addition, the epoxy equivalent of the epoxy modified resin is preferably 20,000 g/eq. or less, more preferably 16,000 g/eq. or less, and even more preferably 10,000 g/eq. or less. If the epoxy equivalent of the epoxy modified resin is 20,000 g/eq. or less, the adhesive composition can be epoxy cured, and the adhesiveness is improved. If the epoxy equivalent of the epoxy modified resin is 16,000 g/eq. or less, the crosslink density of the cured adhesive composition increases, and the heat resistance and chemical resistance are improved. If the epoxy equivalent of the epoxy modified resin is 10,000 g/eq. or less, even if the amount of the epoxy modified resin is small, a matrix can be formed with the modified elastomer, and the electrical properties can be improved while maintaining the heat resistance and chemical resistance.

<Other ingredients>
The adhesive composition of the present invention may contain other resin components in addition to the above-mentioned styrene-based elastomer and epoxy-modified resin. As the other resin components, for example, thermoplastic resins other than the styrene-based elastomer may be contained to an extent that does not affect the function of the adhesive composition.

Examples of the other thermoplastic resins include phenoxy resins, polyamide resins, bismaleimide resins, polyester resins, polycarbonate resins, polyphenylene oxide resins, polyurethane resins, polyacetal resins, polyethylene resins, polypropylene resins, and polyvinyl resins. These thermoplastic resins may be used alone or in combination of two or more.

In addition to other resin components, the adhesive composition of the present invention may contain fillers, radical polymerization initiators, tackifiers, flame retardants, curing agents, curing accelerators, coupling agents, heat aging inhibitors, leveling agents, defoamers, inorganic fillers, pigments, solvents, etc., to the extent that the functionality of the adhesive composition is not affected.

<<Filler>>
The adhesive composition of the present invention preferably contains a filler.
As the filler according to the present invention, for example, from the viewpoint of heat resistance and control of the mechanical properties of the adhesive composition, inorganic fillers are preferred, and as the inorganic filler, silicon-based inorganic fillers and boron nitride are preferred from the viewpoint of electrical properties. Furthermore, as the silicon-based inorganic filler, for example, mica and talc are preferred, which can control the mechanical properties of the adhesive composition even in small amounts and have excellent electrical properties.
As the filler according to the present invention, for example, from the viewpoint of dispersibility and brittleness, an organic filler is preferable, and as the organic filler, a styrene-based spherical filler is preferable, and a styrene-based hollow filler is more preferable, from the viewpoint of electrical properties.
These may be used alone or in combination of two or more.
The content of the filler contained in the adhesive composition of the present invention is preferably 0.5 to 25 parts by volume per 100 parts by volume of the resin composition, and more preferably 1 to 15 parts by volume per 100 parts by volume of the resin composition.
The shape of the filler is not particularly limited and can be appropriately selected according to the purpose. For example, the inorganic filler may be a spherical inorganic filler or a non-spherical inorganic filler, but from the viewpoint of the coefficient of thermal expansion (CTE) and film strength, a non-spherical inorganic filler is preferred. The shape of the non-spherical inorganic filler may be any three-dimensional shape other than a spherical shape (almost perfect sphere), and examples thereof include a plate-like, scaly, columnar, chain-like, and fibrous shape. Among them, from the viewpoint of the coefficient of thermal expansion (CTE) and film strength, a plate-like or scaly inorganic filler is preferred, and a plate-like inorganic filler is more preferred.

<<Radical Polymerization Initiator>>
The adhesive composition of the present invention preferably contains a radical polymerization initiator.
Unsaturated bonds other than aromatic rings, such as the above-mentioned olefin skeleton and vinyl group, can crosslink the resin components even by radical polymerization, thereby further improving the adhesion (adhesiveness), heat resistance, and chemical resistance of the adhesive layer.
The type of radical polymerization initiator is not particularly limited and can be appropriately selected depending on the purpose. Examples of the radical polymerization initiator include peroxides capable of crosslinking at a temperature equivalent to that of epoxy curing, and photopolymerization initiators capable of pre-crosslinking without promoting epoxy curing.

Among the radical polymerization initiators, a more preferred embodiment is, for example, an organic peroxide. By containing an organic peroxide, the crosslinking density of the adhesive composition can be improved without containing a highly polar functional group, and the adhesive layer can have improved adhesion (adhesiveness), heat resistance, and chemical resistance.
Examples of the organic peroxides include benzoyl peroxide, lauroyl peroxide, t-butyl peroxypivalate, t-butylperoxyethylhexanoate, 1,1'-bis-(t-butylperoxy)cyclohexane, t-amylperoxy-2-ethylhexanoate, and t-hexylperoxy-2-ethylhexanoate.

Examples of the tackifier include coumarone-indene resin, terpene resin, terpene-phenol resin, rosin resin, p-t-butylphenol-acetylene resin, phenol-formaldehyde resin, xylene-formaldehyde resin, petroleum-based hydrocarbon resin, hydrogenated hydrocarbon resin, turpentine-based resin, etc. These tackifiers may be used alone or in combination of two or more.

The flame retardant may be either an organic flame retardant or an inorganic flame retardant. Examples of organic flame retardants include phosphorus-based flame retardants such as melamine phosphate, melamine polyphosphate, guanidine phosphate, guanidine polyphosphate, ammonium phosphate, ammonium polyphosphate, ammonium amido phosphate, ammonium amido polyphosphate, carbamate phosphate, carbamate polyphosphate, aluminum trisdiethylphosphinate, aluminum trismethylethylphosphinate, aluminum trisdiphenylphosphinate, zinc bisdiethylphosphinate, zinc bismethylethylphosphinate, zinc bisdiphenylphosphinate, titanyl bisdiethylphosphinate, titanium tetrakisdiethylphosphinate, titanyl bismethylethylphosphinate, titanium tetrakismethylethylphosphinate, titanyl bisdiphenylphosphinate, and titanium tetrakisdiphenylphosphinate; nitrogen-based flame retardants such as triazine-based compounds such as melamine, melam, and melamine cyanurate, cyanuric acid compounds, isocyanuric acid compounds, triazole-based compounds, tetrazole compounds, diazo compounds, and urea; and silicon-based flame retardants such as silicone compounds and silane compounds. Examples of inorganic flame retardants include metal hydroxides such as aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, barium hydroxide, and calcium hydroxide, metal oxides such as tin oxide, aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide, molybdenum oxide, and nickel oxide, zinc carbonate, magnesium carbonate, barium carbonate, zinc borate, hydrated glass, etc. Two or more of these flame retardants can be used in combination.

The above-mentioned curing agents include, but are not limited to, amine-based curing agents and acid anhydride-based curing agents. Examples of amine-based curing agents include melamine resins such as methylated melamine resin, butylated melamine resin, and benzoguanamine resin, dicyandiamide, and 4,4'-diphenyldiaminosulfone. Examples of acid anhydrides include aromatic acid anhydrides and aliphatic acid anhydrides. These curing agents may be used alone or in combination of two or more.

The above-mentioned curing accelerators are used, for example, for the purpose of promoting the reaction between a styrene-based elastomer, particularly a modified styrene-based elastomer, and an epoxy resin, and examples of the curing accelerators that can be used include tertiary amine-based curing accelerators, tertiary amine salt-based curing accelerators, and imidazole-based curing accelerators.

Examples of tertiary amine curing accelerators include benzyldimethylamine, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, tetramethylguanidine, triethanolamine, N,N'-dimethylpiperazine, triethylenediamine, 1,8-diazabicyclo[5.4.0]undecene, etc.

Examples of tertiary amine salt curing accelerators include the formate, octylate, p-toluenesulfonate, o-phthalate, phenol salt, or phenol novolac resin salt of 1,8-diazabicyclo[5.4.0]undecene, and the formate, octylate, p-toluenesulfonate, o-phthalate, phenol salt, or phenol novolac resin salt of 1,5-diazabicyclo[4.3.0]nonene.

Imidazole-based curing accelerators include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-methyl-4-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2' 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, etc. These curing accelerators may be used alone or in combination of two or more.

Examples of the coupling agent include silane-based coupling agents such as vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatopropyltriethoxysilane, and imidazole silane; titanate-based coupling agents; aluminate-based coupling agents; and zirconium-based coupling agents. These may be used alone or in combination of two or more.

The above heat aging inhibitors include 2,6-di-tert-butyl-4-methylphenol, n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane, pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenol, triethylene glycol-bis[3 phenol-based antioxidants such as 3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate, sulfur-based antioxidants such as dilauryl-3,3'-thiodipropionate and dimyristyl-3,3'-dithiopropionate, phosphorus-based antioxidants such as trisnonylphenyl phosphite and tris(2,4-di-tert-butylphenyl)phosphite, etc. These may be used alone or in combination of two or more.

Examples of the inorganic filler include powders of titanium oxide, aluminum oxide, zinc oxide, carbon black, silica, copper, silver, etc. These may be used alone or in combination of two or more.

(adhesive layer)
The adhesive layer according to the present invention comprises the adhesive composition according to the present invention.
The adhesive composition that forms the adhesive layer is allowed to cure.
The curing method is not particularly limited and can be appropriately selected depending on the purpose. For example, heat curing can be used.
The thickness of the adhesive layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably, for example, 3 to 100 μm, more preferably 3 to 50 μm, and even more preferably 5 to 30 μm.

<Method of manufacturing adhesive layer>
The adhesive layer can be produced by forming the adhesive composition into a film.
The adhesive composition can be produced by mixing a resin composition containing a styrene-based elastomer and an epoxy-modified resin having a structure represented by the formula (1) above, and further mixing other components as necessary. The mixing method is not particularly limited as long as the adhesive composition is homogeneous. Since the adhesive composition is preferably used in the state of a solution or dispersion, a solvent is usually also used.
Examples of the solvent include alcohols such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, isobutyl alcohol, n-butyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, and diacetone alcohol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, and isophorone; aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and mesitylene; esters such as methyl acetate, ethyl acetate, butyl acetate, ethylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; and aliphatic hydrocarbons such as hexane, heptane, cyclohexane, and methylcyclohexane. These solvents may be used alone or in combination of two or more.
When the adhesive composition is a solution or dispersion containing a solvent (resin varnish), application to a base film and formation of an adhesive layer can be smoothly carried out, and an adhesive layer of the desired thickness can be easily obtained.
When the adhesive composition contains a solvent, the solid content is preferably in the range of 3 to 80% by mass, more preferably 10 to 50% by mass, from the viewpoint of workability including the formation of the adhesive layer. When the solid content is 80% by mass or less, the viscosity of the solution is appropriate and it is easy to apply uniformly.
In a more specific embodiment of the method for producing an adhesive layer, a resin varnish containing the above-mentioned adhesive composition and a solvent is applied to the surface of a substrate film to form a resin varnish layer, and then the solvent is removed from the resin varnish layer to form a B-stage adhesive layer. Here, the B-stage adhesive layer refers to an adhesive composition in an uncured state or a semi-cured state in which a portion of the adhesive composition has begun to cure, and refers to a state in which the curing of the adhesive composition progresses further by heating or the like.
Here, the method for applying the resin varnish onto the substrate film is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include spraying, spin coating, dipping, roll coating, blade coating, doctor roll, doctor blade, curtain coating, slit coating, screen printing, inkjet, and dispensing methods.
The adhesive layer in the B-stage state can be further subjected to heating or the like to form a cured adhesive layer.

<Characteristics of the adhesive layer>
The adhesive layer obtained by curing the adhesive composition of the present invention preferably has a relative dielectric constant (εr) at a frequency of 28 GHz of 3 or less, more preferably 2.7 or less. The adhesive layer preferably has a dielectric loss tangent (tan δ) at a frequency of 28 GHz of 0.004 or less, more preferably 0.0025 or less, and even more preferably 0.002 or less.
If the dielectric constant is 3 or less and the dielectric loss tangent is 0.004 or less, it can be used in high-frequency FPC-related products that require strict electrical properties. If the dielectric constant is 2.7 or less and the dielectric loss tangent is 0.0025 or less, it can satisfy the electrical properties expected of components of 5G-compatible high-frequency FPC-related products, has electrical properties equivalent to those of LCP, and can be suitably used in 5G high-frequency FPC-related products that require strict electrical properties. Furthermore, if the dielectric loss tangent is 0.002 or less, it is possible to manufacture high-frequency FPC-related products with further improved transmission properties.

[Dielectric constant and dielectric loss tangent]
The dielectric constant and dielectric tangent of the adhesive layer can be measured by the open resonator method using a network analyzer MS46122B (manufactured by Anritsu) and an open resonator Fabry-Perot DPS-03 (manufactured by KEYCOM) at a temperature of 23°C and a frequency of 28 GHz.

(Laminate)
The laminate of the present invention comprises a base film and the above-mentioned adhesive layer on at least one surface of the base film.

<Base film>
The substrate film used in the present invention can be selected depending on the application of the laminate. For example, when the laminate is used as a coverlay film or a copper-clad laminate (CCL), polyimide film, polyether ether ketone film, polyphenylene sulfide film, aramid film, polyethylene naphthalate film, liquid crystal polymer film, etc. can be mentioned. Among these, polyimide film, polyether ether ketone (PEEK) film, polyethylene naphthalate film, and liquid crystal polymer film are preferred from the viewpoint of adhesiveness and electrical properties.

Furthermore, when the laminate of the present invention is used as a bonding sheet, the base film must be a release film, such as polyethylene terephthalate film, polyethylene film, polypropylene film, silicone release treated paper, polyolefin resin coated paper, TPX (polymethylpentene) film, and fluorine-based resin film.

When the laminate of the present invention is used as a shielding film, the base film must be a film having electromagnetic wave shielding ability, such as a laminate of a protective insulating layer and a metal foil.

(Coverlay film)
A preferred embodiment of the laminate according to the present invention is a coverlay film.
When manufacturing an FPC, a laminate having an adhesive layer called a "coverlay film" is usually used to protect the wiring portion. This coverlay film includes an insulating resin layer and an adhesive layer formed on the surface of the insulating resin layer.
For example, a coverlay film is a laminate in which the adhesive layer is formed on at least one surface of the base film, and peeling of the base film and the adhesive layer is generally difficult.
The thickness of the base film included in the coverlay film is preferably 5 to 100 μm, more preferably 5 to 50 μm, and even more preferably 5 to 30 μm. If the thickness of the base film is equal to or less than the upper limit, the coverlay film can be made thinner. If the thickness of the base film is equal to or more than the lower limit, the design of the printed wiring board can be facilitated and handling is also good.
As a method for producing a coverlay film, for example, a resin varnish containing the above-mentioned adhesive composition and a solvent is applied to the surface of the above-mentioned base film to form a resin varnish layer, and then the solvent is removed from the resin varnish layer, thereby producing a coverlay film having a B-stage adhesive layer formed.
The drying temperature when removing the solvent is preferably from 40 to 250°C, and more preferably from 70 to 170°C.
Drying is carried out by passing the laminate coated with the adhesive composition through a furnace in which hot air drying, far infrared heating, high frequency induction heating, or the like is performed.
If necessary, a release film may be laminated on the surface of the adhesive layer for storage, etc. As the release film, known films such as polyethylene terephthalate film, polyethylene film, polypropylene film, silicone release treated paper, polyolefin resin coated paper, TPX film, and fluorine-based resin film can be used.
The coverlay film according to the present invention uses the low dielectric adhesive composition of the present invention, which enables high-speed transmission in electronic devices and also provides excellent adhesion stability to electronic devices.

(Bonding sheet)
A preferred embodiment of the laminate according to the present invention is a bonding sheet.
The bonding sheet is a sheet in which the adhesive layer is formed on the surface of a release film (substrate film). The bonding sheet may also be an embodiment in which the adhesive layer is provided between two release films. When using the bonding sheet, the release film is peeled off and used. The release film may be the same as that described in the above (coverlay film) section.
The thickness of the base film included in the bonding sheet is preferably 5 to 100 μm, more preferably 25 to 75 μm, and even more preferably 38 to 50 μm. If the thickness of the base film is within the above range, the bonding sheet is easy to manufacture and easy to handle.
The bonding sheet can be produced, for example, by applying a resin varnish containing the adhesive composition and a solvent to the surface of a release film, and then drying in the same manner as in the case of the coverlay film.
The bonding sheet according to the present invention uses the low dielectric adhesive composition of the present invention, which enables high-speed transmission in electronic devices and also provides excellent adhesion stability to electronic devices.

(Copper-clad laminate (CCL))
A preferred embodiment of the laminate according to the present invention is a copper-clad laminate obtained by laminating a copper foil to the adhesive layer in the laminate according to the present invention.
A copper-clad laminate is formed by laminating a copper foil to the above-mentioned laminate, and is composed of, for example, a base film, an adhesive layer, and a copper foil in that order. The adhesive layer and the copper foil may be formed on both sides of the base film.
The adhesive composition used in the present invention also has excellent adhesion to articles containing copper.
The copper-clad laminate according to the present invention uses the low-dielectric adhesive composition of the present invention, and therefore enables high-speed transmission in electronic devices and has excellent adhesive stability.

One method for producing a copper-clad laminate is, for example, to bring the adhesive layer of the laminate into surface contact with copper foil, perform thermal lamination at 80°C to 200°C, and then harden the adhesive layer by after-curing. The after-curing conditions can be, for example, 100°C to 200°C in an inert gas atmosphere for 30 minutes to 4 hours. The copper foil is not particularly limited, and electrolytic copper foil, rolled copper foil, etc. can be used.

(Printed Wiring Board)
One preferred embodiment of the laminate according to the present invention is a printed wiring board formed by laminating a copper wiring to the adhesive layer in the laminate according to the present invention.
A printed wiring board can be obtained by forming an electronic circuit on the above-mentioned copper-clad laminate.
The printed wiring board is formed by bonding a base film and a copper wiring using the laminate, and is configured in the order of the base film, the adhesive layer, and the copper wiring. The adhesive layer and the copper wiring may be formed on both sides of the base film.
For example, a printed wiring board is manufactured by attaching a coverlay film via an adhesive layer to a surface having wiring portions using a heat press or the like.
The printed wiring board according to the present invention uses the low dielectric adhesive composition of the present invention, and therefore enables high speed transmission in electronic devices and has excellent adhesion stability.
The method for producing the printed wiring board according to the present invention includes, for example, contacting the adhesive layer of the laminate with copper wiring, performing thermal lamination at 80° C. to 200° C., and further curing the adhesive layer by after-curing. The after-curing conditions can be, for example, 100° C. to 200° C. and 30 minutes to 4 hours. The shape of the copper wiring is not particularly limited, and an appropriate shape can be selected as desired.

(Shielding film)
A preferred embodiment of the laminate according to the present invention is a shielding film.
Shielding films are films used to shield various electronic devices, such as computers, mobile phones, and analytical equipment, in order to cut out electromagnetic noise that can affect these devices and cause them to malfunction. They are also called electromagnetic wave shielding films.
The electromagnetic wave shielding film is formed by laminating, for example, an insulating resin layer, a metal layer, and the adhesive layer according to the present invention in this order.
The shielding film according to the present invention uses the low dielectric adhesive composition of the present invention, which enables high-speed transmission in electronic devices and also provides excellent adhesion stability to electronic devices.

(Printed wiring board with shielding film)
A preferred embodiment of the laminate according to the present invention is a printed wiring board with a shielding film.
A printed wiring board with a shielding film is a board in which a printed circuit is provided on at least one surface of the board, and the above-mentioned electromagnetic wave shielding film is attached onto the board.
A printed wiring board with a shielding film includes, for example, a printed wiring board, an insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided, and the electromagnetic wave shielding film.
The printed wiring board with a shielding film according to the present invention uses the low dielectric adhesive composition of the present invention, and therefore enables high-speed transmission in electronic devices and has excellent adhesive stability.

The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples. In the following, parts and percentages are by weight unless otherwise specified.

(Carboxy group-containing styrene-based elastomer)
The product used was "Tuftec M1911" (maleic acid modified styrene-ethylenebutylene-styrene block copolymer) manufactured by Asahi Kasei Corporation. The acid value of this copolymer was 2 mgKOH/g, the styrene/ethylenebutylene ratio was 30/70, and the weight average molecular weight was 69,000.
(Carboxy group-containing styrene-based elastomer)
The product used was "Tuftec M1913" (maleic acid modified styrene-ethylenebutylene-styrene block copolymer) manufactured by Asahi Kasei Corporation. The acid value of this copolymer was 10 mgKOH/g, the styrene/ethylenebutylene ratio was 30/70, and the weight average molecular weight was 67,000.
(Carboxy group-containing styrene-based elastomer)
Kraton FG1901 (maleic acid modified styrene-ethylenebutylene-styrene block copolymer) manufactured by Kraton Corporation was used. The acid value of this copolymer was 19 mgKOH/g, the styrene/ethylenebutylene ratio was 30/70, and the weight average molecular weight was 81,000.
(Carboxy-free styrene-based elastomer)
The copolymer used was "Tuftec P1500" (hydrogenated styrene-based elastomer) manufactured by Asahi Kasei Corp. The acid value of this copolymer was 0 mgKOH/g, the styrene/ethylene-butylene ratio was 30/70, and the weight average molecular weight was 67,000.
(Unmodified styrene-based elastomer)
Kraton G1651 (styrene-ethylenebutylene-styrene block copolymer) manufactured by Kraton Corporation was used. The copolymer had an acid value of 0 mgKOH/g, a styrene/ethylenebutylene ratio of 33/67, and a weight average molecular weight of 136,700.
(Styrene-based elastomer containing amino groups)
The product name "Tuftec MP10" (amine-modified styrene-ethylenebutylene-styrene copolymer) manufactured by Asahi Kasei Corporation was used. The styrene/ethylenebutylene ratio of this copolymer was 30/70, and the weight average molecular weight was 78,000. The total nitrogen content of this copolymer was 430 ppm (μg/g).
(Epoxy modified resin)
The product used was "Epofriend AT501" (epoxidized styrene-butadiene block copolymer) manufactured by Daicel Corporation. The styrene/ethylene-butylene ratio of this copolymer was 40/60, the weight average molecular weight was 92,000, and the epoxy equivalent was 1055 g/eq.
(Epoxy modified resin)
The product used was "Epofriend CT310" (an epoxidized styrene-butadiene block copolymer) manufactured by Daicel Corporation. The styrene/ethylene-butylene ratio of this copolymer was 40/60, the weight average molecular weight was 93,000, and the epoxy equivalent was 2125 g/eq.
(Epoxy resin)
As the epoxy resin, a novolac type epoxy resin "YX7700" (softening point 65°C) manufactured by Mitsubishi Chemical Corporation was used. The epoxy equivalent was 270 g/eq.
(Epoxy resin)
As the epoxy resin, a novolac type epoxy resin "HP-7200" (epoxy resin, softening point 56-66°C) manufactured by DIC Corporation was used. The epoxy equivalent was 259 g/eq.
(Perbutyl E)
As the organic peroxide, a peroxyester manufactured by NOF Corporation under the trade name "Perbutyl E" was used.
(MK-100DS)
The product name "MK-100DS" was used, which is a mica having an average particle size of 3 μm manufactured by Katakura Co-op Agri Co., Ltd.
(UHP-S2)
The product used was "UHP-S2", a flake-like boron nitride having an average particle size of 0.7 μm manufactured by Showa Denko KK.
(OP935)
A flame retardant manufactured by Clariant Chemicals Co., Ltd. under the trade name "OP935" was used.
(solvent)
A mixed solvent of toluene and methyl ethyl ketone (mass ratio = 90:10) was used.
(Base film)
As the substrate film, "Shin-Etsu Sepla Film PEEK" (polyether ether ketone, thickness 50 μm) manufactured by Shin-Etsu Polymer Co., Ltd. was used.
(electrolytic copper foil)
The electrolytic copper foil used was "TQ-M7-VSP" manufactured by Mitsui Mining & Smelting Co., Ltd. (electrolytic copper foil, thickness 12 μm, glossy surface Rz 1.27 μm, glossy surface Ra 0.197 μm, glossy surface Rsm 12.95 μm). The surface roughness of the glossy surface was determined by measuring a roughness curve using a laser microscope and calculating the value from the roughness curve based on JIS B 0601:2013 (ISO 4287:1997 Amd.1:2009).
(Release film)
As the release film, NP75SA (silicone release PET film, 75 μm) manufactured by PANAC Corporation was used.

(Measurement of Nitrogen Content)
The total amount of nitrogen contained in the amino group-containing styrene elastomer used in the examples was determined by the following method.
<Measurement method>
The nitrogen concentration was measured using a trace nitrogen analyzer ND-100 (manufactured by Mitsubishi Chemical Corporation) in accordance with JIS-K2609.

Example 1
The components constituting the adhesive layer shown in Table 1 were contained in the proportions shown in Table 1, and these components were dissolved in a solvent to prepare a resin varnish with a solids concentration of 20 mass %.
The surface of the base film was subjected to a corona treatment.
The resin varnish was applied to the surface of the substrate film, dried in an oven at 110°C for 4 minutes, and toluene was volatilized to form an adhesive layer, thereby obtaining a substrate film with an adhesive. The adhesive layer of the adhesive laminate was placed in contact with the glossy surface of the electrolytic copper foil, and thermal lamination was performed at 120°C to obtain a pre-cured adhesive laminate. The pre-cured adhesive laminate was after-cured to cure the adhesive layer, thereby obtaining a post-cured adhesive laminate.
After curing, the adhesive strength (N/cm) between the electrolytic copper foil and the base film of the cured adhesive laminate of Example 1 was measured.

[Adhesion strength (N/cm)]
The adhesion was measured by cutting the cured adhesive laminate into a test specimen having a width of 25 mm, and measuring the peel strength when peeling the electrolytic copper foil from the adhesive-attached base film fixed to a support at a peel speed of 0.3 m/min and a peel angle of 180° in accordance with JIS Z0237:2009 (Test methods for adhesive tapes and adhesive sheets).

The dielectric constant and dielectric tangent at a frequency of 28 GHz were also measured for the adhesive layer in the cured adhesive laminate of Example 1.

[Dielectric constant and dielectric loss tangent]
The dielectric constant and dielectric loss tangent of the adhesive layer were measured by the open resonator method using a network analyzer MS46122B (manufactured by Anritsu) and an open resonator Fabry-Perot DPS-03 (manufactured by KEYCOM) at a temperature of 23 ° C. and a frequency of 28 GHz. The measurement sample was prepared by applying a resin varnish to a release film with a roll, and then placing the coated film in an oven and drying it at 110 ° C. for 4 minutes to form a B-stage adhesive layer (thickness 50 μm). Next, the adhesive layer was thermally laminated at 120 ° C. so that the adhesive surfaces were in contact with each other to form a pre-cured adhesive film (thickness 100 μm). The pre-cured adhesive film (thickness 100 μm) was placed in an oven and subjected to a heat curing treatment at 150 ° C. for 60 minutes to produce a post-cured adhesive film (100 mm × 100 mm). After curing, the release film was peeled off from the adhesive film, and the relative dielectric constant and dielectric loss tangent of the adhesive layer were measured.

The heat resistance of the adhesive layer in the laminate of Example 1 was evaluated by a solder heat resistance test.

[Solder heat resistance test]
For the solder heat resistance test, the cured adhesive laminate was floated in a solder bath at 288° C. for 10 seconds three times with the substrate film side facing up, and appearance abnormalities such as swelling or peeling of the adhesive layer were observed.
The heat resistance of the laminate was evaluated according to the following evaluation criteria.
◎ No abnormalities (no dissolution).
○ No abnormalities are found in the final product, but softening of the adhesive layer is observed during the test.
△: No peeling, but the adhesive layer has softened and a stain pattern has formed.
× Peeling off.

The measurement results are shown in Table 3.

(Examples 2 to 15)
Laminates of Examples 2 to 15 were prepared in the same manner as in Example 1, except that the types and amounts of the components constituting the adhesive layer in Example 1 were changed as shown in Table 1.
The laminate thus produced was evaluated in the same manner as in Example 1.
The results are shown in Table 3.

(Comparative Examples 1 to 11)
Laminates of Comparative Examples 1 to 11 were prepared in the same manner as in Example 1, except that the types and amounts of the components constituting the adhesive layer in Example 1 were changed as shown in Table 2.
The laminate thus produced was evaluated in the same manner as in Example 1.
The results are shown in Table 4.

実施例で示されるように、本発明の接着剤組成物からなる接着剤層は、５Ｇ対応可能な良好な電気特性（誘電特性）を示し、かつ密着性、耐熱性、耐溶剤性にも優れている。

As shown in the examples, the adhesive layer made of the adhesive composition of the present invention exhibits good electrical properties (dielectric properties) compatible with 5G, and also has excellent adhesion, heat resistance, and solvent resistance.

Laminates having an adhesive layer made of the adhesive composition of the present invention can be suitably used in the manufacture of FPC-related products for electronic devices such as smartphones, mobile phones, optical modules, digital cameras, game consoles, notebook computers, and medical devices.

Claims (10)

An adhesive composition comprising an amino group -containing styrene-based elastomer and an epoxy-modified resin ,
The content of the epoxy-modified resin is 0.5 to 50 parts by mass based on 100 parts by mass of the adhesive composition,
The epoxy-modified resin has a structure represented by the following formula (2) and a structure represented by the following formula (3),
the epoxy-modified resin is any one selected from the group consisting of an alicyclic epoxy compound, an epoxidized polybutadiene, and an epoxy compound of a styrene-butadiene block copolymer;
The epoxy equivalent of the epoxy-modified resin is 200 g/eq. or more and 20,000 g/eq. or less.

( R5 ^and R6 each independently represent hydrogen or an alkyl group having 10 or less carbon atoms. When a plurality of structures represented by formula (2) are present in the epoxy-modified resin, R5 in each formula (2) ^{may be} the same or different, and R6 in each formula (2) ^may be the same or different. * represents a bonding group.)

(R7 ^and R8 ^each independently represent hydrogen or an alkyl group having 10 or less carbon atoms. When a plurality of structures represented by formula (3) are present in the epoxy-modified resin, R7 in each formula (3) ^may be the same or different, and R8 in each formula (3) ^may be the same or different. * represents a bonding group.) The adhesive composition according to claim 1, wherein the content of the epoxy-modified resin is 1 to 50 parts by mass based on 100 parts by mass of the adhesive composition. The adhesive composition according to claim 1 , wherein R ⁵ and R ⁶ in formula (2) are both hydrogen. 2. The adhesive composition according to claim 1 , wherein the epoxy-modified resin is an epoxy compound of a styrene-butadiene block copolymer . The adhesive composition according to claim 1 , wherein the epoxy-modified resin further has a structure represented by the following formula (5):
(R ¹¹ and R ¹² each independently represents hydrogen or an alkyl group having 10 or less carbon atoms.
When a plurality of structures represented by the formula (5) are present in the epoxy-modified resin, R ¹¹ may be the same or different, and R in each formula (5) ¹² may be the same or different. * represents a bonding group.) The adhesive composition according to claim 1 , wherein the weight average molecular weight (Mw) of the epoxy-modified resin is 30,000 or more and 200,000 or less. The adhesive composition according to claim 1 , further comprising a radical polymerization initiator. An adhesive layer obtained by curing the adhesive composition according to any one of claims 1 to 7 , wherein the adhesive layer has a relative dielectric constant of 3 or less and a dielectric loss tangent of 0.004 or less, measured at a frequency of 28 GHz. A base film;
A laminate comprising an adhesive layer made of the adhesive composition according to any one of claims 1 to 7 , or the adhesive layer according to claim 8 . The laminate according to claim 9 , wherein the substrate film contains a polyether ether ketone (PEEK) resin.