Adhesive composition, bonding sheet, cover lay film, laminate and printed wiring board

Abstract

To provide an adhesive composition having excellent adhesion to a film having low dielectric properties, solder heat resistance and low dielectric properties.SOLUTION: There is provided an adhesive composition which comprises a vinyl aromatic elastomer (A) and an epoxy resin (B) and satisfies all of the following conditions (1) to (3). (1) The vinyl aromatic elastomer (A) is a block copolymer comprising a block (X) mainly containing a structural unit derived from a vinyl aromatic compound and a block (Y) mainly containing a structural unit derived from a conjugated diene compound. (2) The main dispersion peak temperature of tanδ of the vinyl aromatic elastomer (A) is -45°C or more. (3) The vinyl aromatic elastomer (A) contains a reactive functional group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition, a bonding sheet, a coverlay film, a laminate, and a printed wiring board. [Background technology]

[0002] In recent years, the speed of transmission signals on printed wiring boards has increased, leading to an increase in the frequency of signals. Accordingly, there is an increasing demand for flexible circuit boards (FPCs) with low dielectric properties (low relative permittivity, low dielectric loss tangent) in the high-frequency range. To meet these demands, substrate films with low dielectric properties, such as liquid crystal polymer (LCP) and polyphenylene sulfide (PPS), have been proposed as alternatives to conventional polyimide (PI) and polyethylene terephthalate films for use in FPCs.

[0003] However, because substrate films with low dielectric properties have low polarity, conventional epoxy-based or acrylic-based adhesives have weak adhesive strength, making it difficult to produce FPC components such as coverlay films and laminates. Furthermore, epoxy-based and acrylic-based adhesives lack excellent low-dielectric properties and impair the dielectric properties of FPCs. On the other hand, polyolefin resins are known to have low dielectric properties. Therefore, adhesive compositions for FPCs using polyolefin resins have been proposed. For example, Patent Document 1 proposes a heat-reactive adhesive composition using a carboxyl-containing polyolefin copolymer, a block copolymer of an aromatic vinyl compound polymer block and a conjugated diene compound polymer block, and an epoxy resin. Patent Document 2 proposes an adhesive composition using a carboxyl-containing styrene elastomer and an epoxy resin, and Patent Document 3 proposes an adhesive composition using a maleic anhydride-modified styrene elastomer and an epoxy resin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent 3621351 [Patent Document 2] WO2014 / 147903A1 publication [Patent Document 3] Patent 6237944 Summary of the Invention [Problem to be solved by the invention]

[0005] However, Patent Document 1 describes the adhesion between polyimide film and SUS and solder heat resistance, but does not mention dielectric properties, nor does it mention adhesion to substrate films with low dielectric properties such as LCP. Patent Document 2 describes the dielectric properties and adhesion between polyimide film and copper foil, but does not mention adhesion to substrate films with low dielectric properties such as LCP, nor does it mention electrical properties in the high-frequency range of 10 GHz or higher. Patent Document 3 describes adhesion between polyimides, but does not mention adhesion to substrate films with low dielectric properties such as LCP, nor does it mention electrical properties in the high-frequency range of 10 GHz or higher. Generally, to improve adhesion to low-polarity substrate films such as LCP, it is necessary to increase the polarity of the adhesive composition, but it has been known that increasing the polarity makes it difficult to achieve low dielectric properties for the adhesive itself.

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide an adhesive composition, a bonding sheet, a coverlay, a laminate, and a printed wiring board that have excellent adhesion to films with low dielectric properties, solder heat resistance, and low dielectric properties. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have found that the above problems can be solved by using a specific vinyl aromatic elastomer, and have thus completed the present invention.

[0008] That is, the purpose is to [1] An adhesive composition comprising a vinyl aromatic elastomer (A) and an epoxy resin (B), which satisfies all of the following conditions (1) to (3): (1) The vinyl aromatic elastomer (A) is a block copolymer containing a block (X) mainly containing structural units derived from a vinyl aromatic compound and a block (Y) mainly containing structural units derived from a conjugated diene compound. (2) The main dispersion peak temperature of tan δ of the vinyl aromatic elastomer (A) is -45°C or higher. (3) The vinyl aromatic elastomer (A) contains a reactive functional group. [2] The adhesive composition according to [1], wherein the block (X) contains a structural unit derived from a styrene-based monomer; [3] The adhesive composition according to [1] or [2], wherein the block (Y) contains a structural unit derived from at least one selected from the group consisting of isoprene and butadiene; [4] The adhesive composition according to any one of [1] to [3], wherein the bonding form of the blocks of the vinyl aromatic elastomer (A) is represented by X-(YX)n or (XY)n (n is an integer of 1 or more); [5] The adhesive composition of any one of [1] to [4], wherein at least a portion of the carbon-carbon double bonds in the block (Y) are hydrogenated; [6] The adhesive composition according to [5], wherein the hydrogenation rate of carbon-carbon double bonds in the block (Y) is 80 mol % or more; [7] The adhesive composition of any one of [1] to [6], wherein the block (Y) has a vinyl bond content of 45 mol% or more; [8] The adhesive composition of any one of [1] to [7], wherein the reactive functional group contained in the vinyl aromatic elastomer (A) is at least one selected from the group consisting of a carboxy group, a hydroxy group, an amino group, an epoxy group, and a group derived from an acid anhydride; [9] The adhesive composition of any one of [1] to [8], wherein the amount of reactive functional groups contained in the vinyl aromatic elastomer (A) is 0.01 to 10 parts by weight per 100 parts by weight of the vinyl aromatic elastomer (A);

[10] The adhesive composition of any one of [1] to [9], further comprising a curing accelerator (C);

[11] The adhesive composition according to

[10] , wherein the curing accelerator (C) is an imidazole compound;

[12] The adhesive composition of any one of [1] to

[11] , further comprising a flame retardant (D);

[13] The adhesive composition according to

[12] , wherein the flame retardant (D) is an organic metal phosphinate;

[14] The adhesive composition of any one of [1] to

[13] , wherein the relative permittivity and the dielectric loss tangent measured at a frequency of 28 GHz are less than 2.5 and less than 0.005, respectively;

[15] The adhesive composition of any one of [1] to

[14] , wherein a test piece obtained by bonding liquid crystal polymer films together with the adhesive composition has a 90° peel strength of 0.5 N / mm or more at 25°C;

[16] The adhesive composition of any one of [1] to

[15] , wherein a test piece formed by bonding liquid crystal polymer films together with the adhesive composition is floated in a solder bath at 288°C, and no foaming is observed after 20 seconds;

[17] A bonding sheet comprising the adhesive composition of any one of [1] to

[16] ;

[18] A coverlay film comprising the adhesive composition of any one of [1] to

[16] ;

[19] A laminate comprising an adhesive layer containing the adhesive composition of any one of [1] to

[16] ;

[20] The laminate of

[19] , further comprising a substrate layer, the substrate layer comprising at least one selected from the group consisting of liquid crystal polymers and polyimides;

[21] A printed wiring board including the laminate of

[19] or

[20] This is achieved by providing either: [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an adhesive composition, a bonding sheet, a coverlay, a laminate, and a printed wiring board that are excellent in adhesion to films having low dielectric properties, solder heat resistance, and low dielectric properties. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Adhesive composition> The adhesive composition of the present invention comprises an aromatic elastomer (A) and an epoxy resin (B). The vinyl aromatic elastomer (A) is a block copolymer comprising a block (X) primarily containing structural units derived from a vinyl aromatic compound and a block (Y) primarily containing structural units derived from a conjugated diene compound. The vinyl aromatic elastomer (A) has a main dispersion peak temperature of tan δ of −45°C or higher and contains reactive functional groups. In this adhesive composition, the reactive functional groups in the vinyl aromatic elastomer (A) react with the epoxy groups in the epoxy resin (B) to form a cured product, thereby achieving high adhesion to adherends (e.g., LCP films). Furthermore, because the main dispersion peak temperature of tan δ of the vinyl aromatic elastomer (A) is within the above range, molecular motion due to frequency response is suppressed, resulting in excellent low dielectric properties despite the presence of reactive functional groups. In a preferred embodiment, the reactive functional groups in the vinyl aromatic elastomer (A) and / or the epoxy groups in the epoxy resin (B) react with the surface functional groups of the adherend, such as an LCP film, thereby further enhancing the adhesion between the adhesive composition and the adherend. A cured product obtained by the reaction of the vinyl aromatic elastomer (A) and the epoxy resin (B) in the adhesive composition is also one embodiment of the adhesive composition of the present invention.

[0011] (Vinyl aromatic elastomer (A)) The vinyl aromatic elastomer (A) contained in the adhesive composition of the present invention is a block copolymer comprising a block (X) primarily containing structural units derived from a vinyl aromatic compound and a block (Y) primarily containing structural units derived from a conjugated diene compound, and has a main dispersion peak temperature of tan δ of −45°C or higher and contains a reactive functional group. Here, “primarily containing” a specific structural unit means that the structural units constituting the block comprise 50% by mass or more of the specific structural unit. That is, at least 50% by mass of block (X) is derived from a vinyl aromatic compound, and at least 50% by mass of block (Y) is derived from a conjugated diene compound. Here, “derived from” indicates that the structural unit is a structural unit formed as a result of addition polymerization of monomers such as a vinyl aromatic compound and a conjugated diene compound. In this specification, a monomer such as a vinyl aromatic compound or a conjugated diene compound, which is a raw material for the vinyl aromatic elastomer (A), may be referred to as a "monomer", and a structural unit of the vinyl aromatic elastomer (A) derived from a "monomer" may be referred to as a "monomer unit".

[0012] Block Examples of aromatic vinyl compounds from which the structural units constituting block (X) are derived include styrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, 4-t-butylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 2,4,6-trimethylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, vinylanthracene, N,N-dimethyl-4-aminoethylstyrene, N,N-diethyl-4-aminoethylstyrene, vinylpyridine, 4-methoxystyrene, monochlorostyrene, dichlorostyrene, 3,5-diphenylstyrene, 2,6-diphenylstyrene, and divinylbenzene. These aromatic vinyl compounds may be used alone or in combination. In one embodiment, block (X) preferably contains a structural unit derived from a styrene-based monomer. The styrene-based monomer is preferably styrene or a styrene derivative having at least one hydrogen atom at the β-position, more preferably at least one selected from the group consisting of styrene, α-methylstyrene, and 4-methylstyrene, and even more preferably styrene.

[0013] The block (X) may contain structural units derived from monomers other than aromatic vinyl compounds, such as conjugated diene compounds described below, as long as the purpose and effects of the present invention are not impaired. From the viewpoint of adhesiveness, the content of structural units derived from aromatic vinyl compounds in the block (X) is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, and may be 100% by mass.

[0014] The content of block (X) in the vinyl aromatic elastomer (A) (when there are multiple blocks (X), the total content of these blocks) is, from the viewpoint of adhesiveness, preferably 25% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more. In other words, the content of block (X) in the vinyl aromatic elastomer (A) is preferably 1 to 25% by mass. The content of block (X) in the vinyl aromatic elastomer (A) is 1 It is a value determined by H-NMR measurement, and more specifically, it is a value measured according to the method described in the Examples.

[0015] From the viewpoint of adhesiveness, the weight-average molecular weight (Mw) of the block (X) is preferably 1,000 to 20,000, more preferably 2,000 to 15,000, and even more preferably 3,000 to 9,000. The weight-average molecular weight (Mw) of the block (X) can be adjusted to the above range by, for example, adjusting the amount of aromatic vinyl compound relative to the polymerization initiator used in the polymerization. Note that all "weight-average molecular weights" described in this specification are weight-average molecular weights calculated in terms of standard polystyrene as determined by gel permeation chromatography (GPC) measurement, and can be determined in detail according to the method described in the Examples.

[0016] The vinyl aromatic elastomer (A) may have at least one block (X), but preferably has two or more blocks (X). In this case, the blocks (X) may be the same or different. In this specification, "different blocks" means that the blocks differ in at least one of the monomer units constituting the blocks, the weight-average molecular weight, the stereoregularity, and, if multiple monomer units are present, the ratio of the monomer units and the copolymerization form (random, gradient, block). The vinyl aromatic elastomer (A) preferably has two blocks (X).

[0017] Block Examples of conjugated diene compounds from which the structural units constituting the block (Y) are derived include butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, etc. Among these, isoprene, butadiene, or a mixture of isoprene and butadiene is preferred, and isoprene or a mixture of isoprene and butadiene is more preferred.

[0018] When the conjugated diene compound is a butadiene-isoprene mixture, the mixing ratio [isoprene / butadiene] (mass ratio) thereof is not particularly limited as long as it does not impair the objects and effects of the present invention, but is preferably 5 / 95 to 95 / 5, more preferably 10 / 90 to 90 / 10, even more preferably 40 / 60 to 70 / 30, and particularly preferably 45 / 55 to 65 / 35. In addition, when the mixing ratio [isoprene / butadiene] is expressed as a molar ratio, it is preferably 5 / 95 to 95 / 5, more preferably 10 / 90 to 90 / 10, even more preferably 40 / 60 to 70 / 30, and particularly preferably 45 / 55 to 55 / 45.

[0019] The block (Y) may contain structural units derived from monomers other than the conjugated diene compound, such as the above-mentioned aromatic vinyl compounds, as long as the purpose and effects of the present invention are not impaired. From the viewpoints of adhesiveness and thermal stability, the content of the structural units derived from the conjugated diene compound in the block (Y) is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, and may be 100% by mass.

[0020] The content of block (Y) in the vinyl aromatic elastomer (A) (when there are multiple blocks (Y), the total content of these blocks) is, from the viewpoint of adhesiveness, preferably 99% by mass or less, more preferably 95% by mass or less, even more preferably 90% by mass or less, and is preferably 75% by mass or more, more preferably 80% by mass or more, even more preferably 85% by mass or more. In other words, the content of block (Y) in the vinyl aromatic elastomer (A) is preferably 75 to 99% by mass. The content of block (Y) in the vinyl aromatic elastomer (A) is1 It is determined by H-NMR measurement.

[0021] From the viewpoint of adhesiveness, the weight average molecular weight (Mw) of the block (Y) is preferably 15,000 to 800,000, more preferably 50,000 to 300,000, and even more preferably 100,000 to 200,000. The weight average molecular weight (Mw) of the block (Y) can be adjusted to the above range by, for example, adjusting the amount of the conjugated diene compound relative to the polymerization initiator used in the polymerization.

[0022] The vinyl aromatic elastomer (A) may have at least one block (Y). When the vinyl aromatic elastomer (A) has two or more blocks (Y), the blocks (Y) may be the same or different.

[0023] It is preferable that at least a portion of the carbon-carbon double bonds in block (Y) are hydrogenated, and from the viewpoint of adhesiveness and thermal stability, it is more preferable that 80 mol % or more of the carbon-carbon double bonds are hydrogenated. The hydrogenation rate of the carbon-carbon double bonds in block (Y) is more preferably 85 mol % or more, and even more preferably 89 mol % or more. There is no particular upper limit, but it can be, for example, 100 mol % or less, or it may be 97 mol % or less, or it may be 93 mol % or less. In other words, the hydrogenation rate of block (Y) is preferably 80 to 100 mol %. The hydrogenation rate of block (Y) can be adjusted to the above range by, for example, controlling the amount of hydrogenation catalyst added and the reaction time. The hydrogenation rate is calculated by dividing the content of carbon-carbon double bonds in the structural units derived from the conjugated diene compound in block (Y) by the amount of carbon-carbon double bonds after hydrogenation. 1 The values were determined by H-NMR measurement, and more specifically, the values were measured according to the method described in the Examples.

[0024] The vinyl bond content of block (Y) (total content of 3,4 bond units and 1,2 bond units) is preferably 45 mol% or more, more preferably 55 mol% or more, even more preferably 65 mol% or more, and even more preferably 75 mol% or more, from the viewpoints of adhesiveness and low dielectric properties. There is no particular upper limit, but it is preferably 85 mol% or less.

[0025] It is important that the main dispersion peak temperature of tan δ of the vinyl aromatic elastomer (A) is −45°C or higher, preferably 0°C or higher, and more preferably 10°C or higher. If the main dispersion peak temperature of tan δ is lower than −45°C, adhesion to LCP films will decrease. The upper limit is not particularly limited, but is usually 120°C, may be 100°C, preferably 80°C, and more preferably 50°C. When the main dispersion peak temperature of tan δ of the vinyl aromatic elastomer (A) is within the above range, molecular motion due to frequency response is suppressed, and the vinyl aromatic elastomer (A) has excellent low dielectric properties despite having reactive functional groups. If the main dispersion peak temperature of tan δ of the vinyl aromatic elastomer (A) is lower than −45°C, the resulting adhesive composition will be inferior in adhesion, solder heat resistance, and / or low dielectric properties, or it will be difficult to achieve both of these properties. The main dispersion peak temperature of tan δ of the vinyl aromatic elastomer (A) is a value determined by measurement using a strain-controlled dynamic viscoelasticity apparatus in accordance with JIS K7244-10 (2005), more specifically, a value measured according to the method described in the Examples. The main dispersion peak temperature of tan δ of the vinyl aromatic elastomer (A) can be adjusted to the above range by adjusting the type and amount of Lewis base added during polymerization.

[0026] The vinyl aromatic elastomer (A) is a block copolymer containing a block (X) mainly containing structural units derived from a vinyl aromatic compound and a block (Y) mainly containing structural units derived from a conjugated diene compound, and the bonding form is not particularly limited. The bonding form may be linear, branched, radial, or a combination of two or more of these. Specific examples include diblock copolymers represented by XY, triblock copolymers represented by XYX or YXY, tetrablock copolymers represented by XYXY, pentablock copolymers represented by XYXY or YXYXY, and (XY)nZ type copolymers (Z represents a coupling agent residue, and n represents an integer of 3 or greater). Of these, a linear form represented by X-(YX)n or (XY)n (n represents an integer of 1 or greater) is preferred. Of these, linear triblock copolymers or diblock copolymers are preferred. XYX type triblock copolymers are preferred because they can be easily produced. Specific examples of XYX triblock copolymers include styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene-propylene-styrene block copolymer (SEPS), and styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS).

[0027] From the viewpoint of adhesiveness, the weight average molecular weight (Mw) of the vinyl aromatic elastomer (A) is preferably 20,000 to 900,000, more preferably 50,000 to 330,000, and even more preferably 100,000 to 250,000. The weight average molecular weight (Mw) of the vinyl aromatic elastomer (A) can be adjusted to the above range by, for example, adjusting the amounts of the aromatic vinyl compound and the conjugated diene compound relative to the polymerization initiator used in the polymerization.

[0028] The content of the aromatic vinyl compound contained in the aromatic vinyl elastomer (A) is preferably less than 25% by mass, more preferably less than 15% by mass. Here, the "content of the aromatic vinyl compound contained in the aromatic vinyl elastomer (A)" means the ratio of structural units derived from aromatic vinyl compounds contained in the blocks (X) and (Y) to the total structural units constituting the blocks (X) and (Y).

[0029] The reactive functional groups contained in the vinyl aromatic elastomer (A) are not particularly limited as long as they react with the epoxy groups in the epoxy resin (B) and / or the functional groups on the surface of the LCP film to form chemical bonds. Specific examples include carboxy groups, hydroxy groups, amino groups, epoxy groups, and groups derived from acid anhydrides. The vinyl aromatic elastomer (A) used in the present invention can contain one or more of these groups. The vinyl aromatic elastomer (A) used in the present invention can be produced, for example, by introducing functional groups by reacting with a modifying agent, which is a compound having one or more functional groups selected from the group consisting of carboxy groups, hydroxy groups, amino groups, epoxy groups, and groups derived from acid anhydrides. Examples of the modifying agent include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, maleic anhydride, itaconic anhydride, fumaric anhydride, vinylbenzyl diethylamine, vinylbenzyl dimethylamine, 1-glycidyl-4-(2-pyridyl)piperazine, 1-glycidyl-4-phenylpiperazine, 1-glycidyl-4-methylpiperazine, 1-glycidyl-4-methylhomopiperazine, 1-glycidylhexamethyleneimine, and tetraglycidyl-1,3-bisaminomethylcyclohexane.

[0030] In the adhesive composition of the present invention, the amount of reactive functional groups in the vinyl aromatic elastomer (A) is preferably in the range of 0.01 to 10 parts by weight, more preferably 0.05 to 2 parts by weight, and even more preferably 0.1 to 1 part by weight, per 100 parts by weight of the vinyl aromatic elastomer (A). When the amount of reactive functional groups is 0.01 part by weight or more, adhesion to LCP films becomes more stable, while when it is 10 parts by weight or less, low dielectric properties become better. The amount of reactive functional groups in the vinyl aromatic elastomer (A) can be adjusted by adjusting the amount of modifier.

[0031] The vinyl aromatic elastomer used in the present invention can be produced, for example, by using an aromatic vinyl compound and a conjugated diene compound as monomers, polymerizing them to form a block copolymer having a block (X) mainly containing structural units derived from the aromatic vinyl compound and a block (Y) mainly containing structural units derived from the conjugated diene compound, hydrogenating the block copolymer, and then subjecting it to a modification reaction using a modifying agent.

[0032] The polymerization reaction can be carried out by, for example, solution polymerization, emulsion polymerization, or solid-phase polymerization. Among these, solution polymerization is preferred, and known methods such as anionic polymerization, cationic polymerization, and radical polymerization can also be used. The vinyl bond content can be increased by adding a Lewis base as a co-catalyst during the polymerization of the conjugated diene compound. Examples of Lewis bases include ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, and 2,2-di(2-tetrahydrofuryl)propane (DTHFP); glycol ethers such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether; amines such as triethylamine, N,N,N',N'-tetramethylethylenediamine, and N-methylmorpholine; and metal salts such as sodium or potassium salts of aliphatic alcohols, such as sodium t-butylate, sodium t-amylate, and sodium isopentylate, or sodium or potassium salts of alicyclic alcohols, such as sodium mentholate. Among the above Lewis bases, DTHFP is preferred because it can produce a high vinyl bond content.

[0033] The hydrogenation can be carried out, for example, by pressurizing with hydrogen in an inert organic solvent in the presence of a hydrogenation catalyst. Examples of the hydrogenation catalyst include Raney nickel, heterogeneous catalysts in which a metal such as Pt, Pd, Ru, Rh, or Ni is supported on a carrier such as carbon, alumina, or diatomaceous earth, and Ziegler catalysts (Al / Ni Ziegler catalysts) composed of a combination of a transition metal compound with an alkylaluminum compound, an alkyllithium compound, or the like.

[0034] The above modification reaction can be carried out, for example, by copolymerizing a modifier when polymerizing the block copolymer, or by heating and kneading the block copolymer and the modifier in the presence of an organic peroxide.

[0035] The content of the vinyl aromatic elastomer (A) in the adhesive composition of the present invention is preferably in the range of 2 to 95 wt%, more preferably in the range of 10 to 95 wt%, even more preferably in the range of 20 to 90 wt%, and even more preferably in the range of 30 to 85 wt%. A vinyl aromatic elastomer (A) content of 10 wt% or more can exhibit better adhesion to LCP films, while a content of 95 wt% or less is advantageous in terms of solder heat resistance and flame retardancy. For example, in adhesive compositions that do not contain a solvent, the content of the vinyl aromatic elastomer (A) in the adhesive composition is preferably in the range of 50 to 95 wt%, and in some cases, more preferably in the range of 60 to 85 wt%. For example, in adhesive compositions that contain a solvent, the content of the vinyl aromatic elastomer (A) in the adhesive composition is preferably in the range of 2 to 50 wt%, more preferably in the range of 10 to 40 wt%, and in some cases, even more preferably in the range of 20 to 30 wt%, from the viewpoint of workability including film-forming ability. When the content is within the above range, the viscosity of the solution of the adhesive composition containing a solvent becomes suitable, making it easier to apply the adhesive composition more uniformly.

[0036] (Epoxy resin (B)) The epoxy resin (B) used in the present invention is not particularly limited as long as it has an epoxy group in the molecule, but is preferably one having two or more epoxy groups in one molecule, since it can form a crosslinked structure by reacting with the reactive functional group of the vinyl aromatic elastomer (A) and exhibit high heat resistance and adhesiveness. Specific examples include bisphenol A epoxy resins, bisphenol F epoxy resins, and hydrogenated versions thereof; glycidyl ester epoxy resins such as orthophthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, p-hydroxybenzoic acid glycidyl ester, tetrahydrophthalic acid diglycidyl ester, succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid diglycidyl ester, and trimellitic acid triglycidyl ester; Glycidyl ether-based epoxy resins such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenylglycidyl ether ethane, triphenylglycidyl ether ethane, sorbitol polyglycidyl ether, and polyglycerol polyglycidyl ether; glycidyl amine-based epoxy resins such as triglycidyl isocyanurate and tetraglycidyldiaminodiphenylmethane; epoxidized Linear aliphatic epoxy resins such as polybutadiene and epoxidized soybean oil; novolac type epoxy resins such as phenol novolac epoxy resin, o-cresol novolac epoxy resin, and bisphenol A novolac epoxy resin; and further examples of epoxy resins include brominated bisphenol A type epoxy resin, phosphorus-containing epoxy resin, dicyclopentadiene skeleton-containing epoxy resin, naphthalene skeleton-containing epoxy resin, anthracene type epoxy resin, tertiary butylcatechol type epoxy resin, triphenylmethane type epoxy resin, tetraphenylethane type epoxy resin, biphenyl type epoxy resin, and bisphenol S type epoxy resin.Preferably, an epoxy resin having an alicyclic skeleton such as dicyclopentadiene is used, as this will give an adhesive composition with excellent dielectric properties.

[0037] As the epoxy resin (B), commercially available products can be used, such as "EPICLON (registered trademark) HP-7200" (manufactured by DIC Corporation), "EPICRON (registered trademark) N-655EXP" (manufactured by DIC Corporation), "EPICRON (registered trademark) HP-4032D" (manufactured by DIC Corporation), "jER (registered trademark) 828" (manufactured by Mitsubishi Chemical Corporation), and "NC3000H" (manufactured by Nippon Kayaku Co., Ltd.).

[0038] The content of the epoxy resin (B) in the adhesive composition of the present invention is preferably in the range of 1 to 20 parts by weight, more preferably 3 to 15 parts by weight, per 100 parts by weight of the vinyl aromatic elastomer (A). When the content of the epoxy resin (B) is 1 part by weight or more, the adhesiveness is further improved, and when it is 20 parts by weight or less, the low dielectric properties are further improved.

[0039] (Curing accelerator (C)) The adhesive composition of the present invention preferably contains a curing accelerator (C), which can further accelerate the reaction between the vinyl aromatic elastomer (A) and the epoxy resin (B). The curing accelerator (C) is not particularly limited, and preferred examples include imidazole curing accelerators, tertiary amine curing accelerators, and tertiary amine salt curing accelerators. These agents can be used alone or in combination of two or more.

[0040] Specific examples of 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'-methylimidazolyl-(1')]-ethyl-s-triazine, and 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine. 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, and 2-phenyl-4-methyl-5-hydroxymethylimidazole.

[0041] Specific examples of tertiary amine curing accelerators include benzyldimethylamine, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, tetramethylguanidine, triethanolamine, N,N'-dimethylpiperazine, triethylenediamine, and 1,8-diazabicyclo[5.4.0]undecene. Specific examples of the tertiary amine salt curing accelerator include formate, octylate, p-toluenesulfonate, o-phthalate, phenolate, and phenol novolac resin salt of 1,8-diazabicyclo[5.4.0]undecene; and formate, octylate, p-toluenesulfonate, o-phthalate, phenolate, and phenol novolac resin salt of 1,5-diazabicyclo[4.3.0]nonene.

[0042] Among the above-mentioned curing accelerators, imidazole-based curing agents are preferred because they are effective even when added in small amounts, and 2-undecylimidazole is particularly preferred because it is expected to achieve an appropriate heat-curing temperature and improve the pot life of the adhesive composition.

[0043] When the adhesive composition of the present invention contains a curing accelerator (C), the content of the curing accelerator (C) is preferably 0.5 to 10 parts by weight, more preferably 1 to 5 parts by weight, per 100 parts by weight of the epoxy resin (B). When the content of the curing accelerator is within the above range, the adhesive composition has better adhesion and solder heat resistance.

[0044] (Flame retardant (D)) The adhesive composition of the present invention preferably contains a flame retardant (D). The flame retardant (D) is not particularly limited, but may include inorganic and organic flame retardants. Examples of inorganic flame retardants include metal hydroxide compounds such as aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, calcium hydroxide, and barium hydroxide; metal carbonate compounds such as basic magnesium carbonate, zinc carbonate, magnesium-calcium carbonate, calcium carbonate, and barium carbonate; metal oxides such as magnesium oxide, molybdenum oxide, zirconium oxide, tin oxide, tin oxide hydrate, and antimony oxide; metal borate compounds such as zinc borate, zinc metaborate, and barium metaborate; inorganic metal compounds such as dolomite, hydrotalcite, and borax; and inorganic phosphorus compounds such as red phosphorus, ammonium phosphate, and ammonium polyphosphate. Examples of organic flame retardants include organic phosphoric acid compounds such as melamine phosphate, melamine polyphosphate, guanidine phosphate, guanidine polyphosphate, ammonium phosphate, ammonium polyphosphate, carbamate phosphate, and carbamate polyphosphate; organic metal phosphinates such as 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 compounds such as melamine, melam, and melamine cyanurate, cyanuric acid compounds, isocyanuric acid compounds, triazole compounds, tetrazole compounds, diazo compounds, and urea; and silicon-based flame retardants such as silicone compounds and silane compounds. Among these, organic phosphoric acid compounds and organic metal phosphinates are preferred, and organic metal phosphinates are more preferred.The flame retardants may be used alone or in combination of two or more.

[0045] When the adhesive composition of the present invention contains a flame retardant (D), the content of the flame retardant (D) is preferably 10 to 100 parts by weight per 100 parts by weight of the total of the vinyl aromatic elastomer (A) and the epoxy resin (B). If the content is equal to or greater than the lower limit, flame retardancy is easily obtained, while if the content is equal to or less than the upper limit, excellent adhesion, heat resistance, electrical properties, etc. are obtained.

[0046] The adhesive composition of the present invention may contain other thermoplastic resins than the vinyl aromatic elastomer (A), other thermosetting resins than the epoxy resin (B), tackifiers, coupling agents, heat aging inhibitors, inorganic fillers, leveling agents, antifoaming agents, pigments, and the like, to the extent that the functionality of the adhesive composition is not affected.

[0047] Examples of thermoplastic resins other than the vinyl aromatic elastomer (A) include phenoxy resins, polyamide resins, polyester resins, polycarbonate resins, polyphenylene oxide resins, polyurethane resins, polyacetal resins, polyethylene resins, polypropylene resins, and polyvinyl resins.

[0048] Examples of the thermosetting resin other than the epoxy resin (B) include phenol resin, xylene resin, guanamine resin, diallyl phthalate resin, vinyl ester resin, unsaturated polyester resin, furan resin, polyimide resin, polyurethane resin, cyanate resin, maleimide resin, benzocyclobutene resin, etc.

[0049] Examples of the tackifier include coumarone-indene resin, terpene resin, terpene-phenol resin, rosin resin, pt-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.

[0050] 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 imidazolesilane; 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.

[0051] Examples of the heat aging inhibitor include phenol-based antioxidants such as 2,6-di-tert-butyl-4-methylphenol, n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, and tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane; sulfur-based antioxidants such as dilauryl-3,3'-thiodipropionate and dimyristyl-3,3'-dithiopropionate; and phosphorus-based antioxidants such as trisnonylphenyl phosphite and tris(2,4-di-tert-butylphenyl)phosphite. These may be used alone or in combination of two or more.

[0052] 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.

[0053] The total content of the vinyl aromatic elastomer (A) and the epoxy resin (B) in the adhesive composition of the present invention is preferably 3 to 95 wt%, more preferably 50 to 95 wt%, even more preferably 60 to 90 wt%, and even more preferably 70 to 85 wt%. Within these ranges, better adhesion to substrate films with low dielectric properties can be achieved. For example, in adhesive compositions that do not contain a solvent, the total content of the vinyl aromatic elastomer (A) and the epoxy resin (B) in the adhesive composition is preferably in the range of 50 to 95 wt%, and more preferably in the range of 60 to 85 wt%. For example, in adhesive compositions that contain a solvent, from the viewpoint of workability, including film-forming ability, the total content of the vinyl aromatic elastomer (A) and the epoxy resin (B) in the adhesive composition is preferably in the range of 3 to 50 wt%, more preferably in the range of 10 to 50 wt%, and even more preferably in the range of 20 to 40 wt%. When the content is within the above range, the viscosity of the solution of the adhesive composition containing a solvent becomes suitable, making it easier to apply the adhesive composition more uniformly.

[0054] The adhesive composition of the present invention preferably exhibits a 90° peel strength of 0.5 N / mm or more at 25°C for a test piece obtained by bonding LCP films together using the adhesive composition. The peel strength is more preferably 0.8 N / mm or more, even more preferably 1.0 N / mm or more, and even more preferably 1.35 N / mm or more. The upper limit of the peel strength is not particularly limited, but may be 2.0 N / mm as a practical value that can be measured. Having a peel strength within the above range makes it less likely that a decrease in yield will occur in the manufacturing process of a laminate or the like produced using the adhesive composition. The above peel strength is a value measured using the measurement method described in the Examples below.

[0055] When a test piece formed by bonding LCP films together using the adhesive composition of the present invention is floated in a solder bath at 288°C, it is preferable that no bubbling is observed at 20 seconds, more preferably at 50 seconds, and even more preferably at 60 seconds. When the adhesive composition has the above properties, it is possible to further suppress a decrease in the yield of circuit boards during the solder reflow process. The above properties are measured by the method for measuring solder heat resistance in the examples described below.

[0056] The adhesive composition according to the present invention has a relative dielectric constant (ε r ) is preferably less than 2.5 and the dielectric dissipation factor is preferably less than 0.005. By having the dielectric constant and dielectric dissipation factor within the above ranges, it is possible to produce products related to flexible printed wiring boards with excellent dielectric properties. The dielectric constant and dielectric dissipation factor can be adjusted depending on the ratio of the vinyl aromatic elastomer (A) and the epoxy resin (B) in the adhesive composition, so adhesive compositions with various configurations can be designed depending on the application. The above dielectric constant and dielectric dissipation factor are values measured by the measurement methods described in the Examples below.

[0057] The adhesive composition of the present invention can be produced by a conventional method. For example, the vinyl aromatic elastomer (A) and the epoxy resin (B) (and, if the adhesive composition contains other optional components, these optional components) are mixed in a heated vacuum kneader with or without a solvent. Alternatively, the vinyl aromatic elastomer (A) and the epoxy resin (B) (and, if the adhesive composition contains other optional components, these optional components) can be dissolved in a predetermined solvent concentration to achieve the desired content ratio, and the resulting mixture is placed in a reaction vessel heated to 10 to 80°C. The mixture is mixed at normal pressure for 3 hours while rotating at 100 to 1,000 rpm, and then mixed and stirred under vacuum (maximum 1 Torr) for an additional 30 to 60 minutes.

[0058] In one embodiment, the adhesive composition of the present invention may contain a solvent. The solvent is preferably one that dissolves the vinyl aromatic elastomer (A) and the epoxy resin (B). Examples of solvents include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, heptane, octane, decane, cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane; alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, pentanol, hexanol, propanediol, benzyl alcohol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, and phenol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, pentanone, hexanone, cyclohexanone, isophorone, and acetophenone; esters such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and butyl formate; ethers such as dimethyl ether, diisopropyl ether, and tetrahydrofuran; and halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, and chloroform. These solvents can be used alone or in combination of two or more. By including a solvent in the adhesive composition, it becomes easier to apply the adhesive composition to an adherend or a release film.

[0059] <Bonding sheet> One embodiment of the present invention is a bonding sheet containing the above-mentioned adhesive composition. Such a bonding sheet can be used, for example, to bond substrates together, and substrates can be bonded to one or both sides of the bonding sheet. In addition, in the adhesive composition contained in the bonding sheet, the vinyl aromatic elastomer (A) and the epoxy resin (B) may react to form a cured product, or reactive functional groups in the vinyl aromatic elastomer (A) and / or epoxy groups in the epoxy resin (B) may react with surface functional groups of the substrate to form bonds.

[0060] The thickness of the bonding sheet is preferably 5 to 100 μm, and more preferably 10 to 60 μm.

[0061] The substrate may be, for example, a sheet- or film-shaped substrate used as a material for circuit boards such as printed wiring boards. The material of the substrate is not particularly limited, and may be a resin substrate containing a resin, a metal substrate containing a metal, or a composite material containing multiple materials, such as a substrate containing a resin and a metal. In one embodiment, the substrate is preferably a resin substrate or a metal substrate. The resin substrate is not particularly limited, but one having electrical insulation properties is preferred. Examples of resin substrates include polyimides containing polyimide and liquid crystal polymer films containing liquid crystal polymers. The polyimide film may be a film made solely of polyimide resin, and the liquid crystal polymer film may be a film made solely of liquid crystal polymer resin, or may be a film containing these resins with additives or a film containing multiple different resins. In particular, the bonding sheet of the present invention has excellent adhesion to liquid crystal polymer films. The metal substrate is not particularly limited, but copper foil is preferred, specifically, electrolytic copper foil, rolled copper foil, etc. may be used. The metal substrate may also be a substrate with circuit processing. The surface of the substrate on which the bonding sheet is laminated may be surface-treated. The thickness of the substrate is preferably 10 to 125 μm.

[0062] In one embodiment, the bonding sheet is preferably a laminate with a release film, and may have a configuration in which an adhesive layer is provided between two release films. The bonding sheet of this embodiment can be used by peeling off the release film when in use. Examples of release films include polyethylene terephthalate film, polyethylene film, polypropylene film, silicone release-treated paper, polyolefin resin-coated paper, TPX film, and fluororesin-based resin film. The thickness of the release film is preferably 20 to 100 μm.

[0063] A bonding sheet can be produced, for example, by applying a solvent-containing solution of the adhesive composition to the surface of a release film to form a coated film, and then drying the coated film to remove the solvent. The drying time is preferably 2 to 10 minutes. The heating temperature during drying is preferably 40 to 250°C, more preferably 70 to 170°C. Drying can be performed, for example, by passing the coated film through a furnace that employs hot air drying, far-infrared heating, high-frequency induction heating, or the like.

[0064] <Coverlay film> One embodiment of the present invention is a coverlay film containing the above-mentioned adhesive composition. In one embodiment, the coverlay film may be formed on the surface of a substrate. Examples of the substrate include the above-mentioned substrates, and the coverlay film of the present invention is particularly excellent in adhesion to liquid crystal polymer films. In addition, the surface of the substrate on which the coverlay is laminated may be surface-treated. In one embodiment, the vinyl aromatic elastomer (A) and the epoxy resin (B) contained in the coverlay film may react to form a cured product, or the reactive functional groups in the vinyl aromatic elastomer (A) and / or the epoxy groups in the epoxy resin (B) may react with surface functional groups of the adherend to form bonds.

[0065] The thickness of the coverlay film is preferably 5 to 45 μm, and more preferably 10 to 35 μm.

[0066] A method for producing a coverlay includes, for example, applying a solvent-containing solution-like adhesive composition to the surface of a substrate to form a substrate with a coating film, and then drying the substrate with the coating film to remove the solvent. The drying time is preferably 2 to 10 minutes. The heating temperature during drying is preferably 40 to 250°C, more preferably 70 to 170°C. Drying may be performed, for example, by passing the coated substrate through a furnace that employs hot air drying, far-infrared heating, high-frequency induction heating, or the like. If necessary, in order to protect the surface of the coverlay film, a release film such as that described above may be laminated on the side of the coverlay film on which the substrate is not laminated.

[0067] <Laminate> Another embodiment of the present invention is a laminate including at least one adhesive layer containing the adhesive composition. Such a laminate may be, for example, one in which an adhesive layer is formed on the above-described substrate, or may be one in which a substrate is further laminated on this adhesive layer to form a three-layer structure. Specific embodiments include a two-layer laminate of substrate / adhesive layer, a three-layer laminate of substrate / adhesive layer / substrate, and a multilayer laminate having multiple substrates and multiple adhesive layers.

[0068] Examples of the substrate include the substrates described above, and the substrates may be surface-treated. A preferred embodiment of the laminate includes a single-sided metal-clad laminate in which a resin substrate such as a polyimide film or a liquid crystal polymer film, an adhesive layer, and a metal substrate such as a copper foil are laminated in this order, and a double-sided metal-clad laminate in which metal substrates are laminated on both sides of a resin substrate via adhesive layers. Another embodiment includes a multilayer circuit board or the like, which includes at least one adhesive layer, and one or more resin substrate layers, metal substrate layers without circuit processing, and / or metal substrate layers with circuit processing.

[0069] One example of a method for producing a laminate, for example, in the case of the single-sided metal-clad laminate described above, is to coat the surface of a resin substrate such as a liquid crystal polymer film with a solvent-containing solution-like adhesive composition to form a coated film, which is then dried under the same conditions as in the coverlay film production method described above, and then the coating surface of the coated film is brought into face-to-face contact with copper foil, followed by thermal lamination at 80°C to 150°C, and then the coating is cured by after-cure. The after-cure conditions can be, for example, 100°C to 200°C and 30 minutes to 4 hours.

[0070] <Printed wiring board> Another embodiment of the present invention is a printed wiring board including the laminate. A preferred embodiment of such a printed wiring board includes, as a component, the laminate formed from a metal substrate and a resin substrate that form a conductor circuit. Specific examples include flexible circuit boards (FPCs), flat cables, and circuit boards for tape automated bonding (TAB). The conductor circuit can be formed, for example, by forming a photosensitive etching resist layer on the metal substrate of a laminate formed by providing a metal substrate on a resin substrate, exposing the metal substrate through a masking film having a circuit pattern, curing the exposed areas, and then removing the unexposed areas of the metal substrate by etching. The printed wiring board of the present invention can have any laminate structure that can function as a printed wiring board. For example, the printed wiring board can be composed of four layers: a resin substrate layer, a metal substrate layer, an adhesive layer, and a coverlay film layer. Furthermore, if necessary, two or more of the printed wiring boards can be stacked. [Example]

[0071] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0072] <Vinyl aromatic elastomers (A) and (A')> [Methods for measuring each physical property] The vinyl aromatic elastomers (A) and (A') obtained by the production methods described below were evaluated for various physical properties according to the following measurement methods.

[0073] (Block (X) content) Dissolve vinyl aromatic elastomer (A) or (A') in CDCl3. 1 H-NMR measurement [apparatus: "ADVANCE 400 Nano bay" (manufactured by Bruker), measurement temperature: 30°C] was performed, and the content (mass%) of block (X) was calculated from the ratio of the peak area derived from styrene to the peak area derived from isoprene and / or butadiene.

[0074] (Weight average molecular weight) The weight average molecular weight (Mw) of the vinyl aromatic elastomer was determined in terms of polystyrene by gel permeation chromatography (GPC) measurement under the following conditions. <GPC measurement equipment and measurement conditions> Apparatus: GPC apparatus "HLC-8020" (Tosoh Corporation) Separation column: Two "TSKgel G4000HX" columns manufactured by Tosoh Corporation were connected in series. Eluent: Tetrahydrofuran ·Eluent flow rate: 0.7mL / min Sample concentration: 5mg / 10mL Column temperature: 40℃ Detector: Refractive index (RI) detector Calibration curve: Created using standard polystyrene

[0075] (Hydrogenation rate in block (Y)) The vinyl aromatic elastomer (A) or (A') is dissolved in CDCl3. 1 H-NMR measurement [apparatus: "ADVANCE 400 Nano bay" (manufactured by Bruker), measurement temperature: 30°C] was performed, and the hydrogenation rate (mol%) was calculated from the ratio of the peak area derived from the residual olefin of isoprene or butadiene to the peak area derived from ethylene, propylene, and butylene.

[0076] (Amount of vinyl bonds in block (Y)) The block copolymer before hydrogenation was dissolved in CDCl3. 1 H-NMR measurement was performed [apparatus: "ADVANCE 400 Nano bay" (manufactured by Bruker), measurement temperature: 30°C]. The vinyl bond amount (total content of 3,4-bond units and 1,2-bond units) (mol%) was calculated from the ratio of the peak area corresponding to the 3,4-bond units and 1,2-bond units in the isoprene structural units and the 1,2-bond units in the butadiene structural units to the total peak area of the structural units derived from isoprene and / or butadiene.

[0077] (Amount of reactive functional groups) 5 g of vinyl aromatic elastomer (A) or (A') was dissolved in 180 ml of toluene, and then 20 ml of ethanol was added. The mixture was titrated with a 0.1 mol / L potassium hydroxide solution, and the amount of maleic anhydride modification (parts by weight) per 100 parts by weight of vinyl aromatic elastomer (A) or (A') was calculated using the following formula, and this was taken as the amount of reactive functional groups. Amount of modified maleic anhydride (parts by weight) = Titration amount (L) × 0.1 (mol / L) × 98 (g / mol) / 5 (g) × 100

[0078] (Main dispersion peak temperature of tanδ) The vinyl aromatic elastomer (A) or (A') was pressed at a temperature of 230°C and a pressure of 10 MPa for 3 minutes using a press molding machine "NF-50T" (manufactured by Shinto Metal Industry Co., Ltd.) to produce a sheet with a thickness of 1.0 mm, and the sheet was cut into a disk shape with a diameter of 8 mm to prepare a test specimen. The measurement device used was a rotational rheometer "ARES-G2" (manufactured by TA Instruments), a distortion-controlled dynamic viscoelasticity device, based on JIS K7244-10 (2005).The test was performed by clamping the test piece between flat plates with a diameter of 8 mm, applying vibrations at a distortion of 0.1% and a frequency of 1 Hz, and raising the temperature from -70°C to +120°C at a rate of 3°C / min. In the above test, the temperature at which the maximum peak intensity was obtained was taken as the main dispersion peak temperature (°C) of tan δ.

[0079] [Production of vinyl aromatic elastomers] (Production Example 1) A nitrogen-purged, dried pressure vessel was charged with 50 kg of cyclohexane (solvent) dried over molecular sieves A4 and 0.09 kg of a 10% by weight cyclohexane solution of sec-butyllithium (effective amount of sec-butyllithium added: 90 g) as an anionic polymerization initiator. After heating the pressure vessel to 50 °C, 1.0 kg of styrene (1) was added and polymerized for 30 minutes. The temperature was then lowered to 40 °C, and 0.033 kg of 2,2-di(2-tetrahydrofuryl)propane (DTHFP) was added as a Lewis base. 14.7 kg of isoprene was then added over 5 hours and polymerized for 1 hour. The temperature was then raised to 50 °C, 1.0 kg of styrene (2) was added, and the polymerization was continued for 30 minutes. Methanol was then added to terminate the reaction, yielding a reaction solution containing a polystyrene-polyisoprene-polystyrene triblock copolymer. After heating the reaction solution to 50°C, the reaction mixture was pressurized to a hydrogen pressure of 1 MPa, and a Ziegler catalyst (hydrogenation catalyst) formed from nickel octylate and trimethylaluminum was added under a hydrogen atmosphere. The reaction mixture was heated to 80°C by the heat of reaction and reacted until hydrogen absorption ceased. After allowing the reaction mixture to cool and the pressure to be released, the Ziegler catalyst was removed by washing with water and the mixture was vacuum dried to obtain a hydrogenated block copolymer of a polystyrene-polyisoprene-polystyrene triblock copolymer. Then, using a Coperion twin-screw extruder "ZSK26mc" (26 mmφ, L / D=56) under the following extrusion conditions, 10 kg of the hydrogenated block copolymer obtained above was blended and melted, and 0.01 kg of 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (Perhexa 25B-40, NOF Corporation) as a radical initiator and 0.1 kg of maleic anhydride as a modifier were blended to carry out a modification reaction, yielding vinyl aromatic elastomer A-1. The results of the physical property evaluation of the resulting A-1 are shown in Table 2. <Extrusion conditions> Twin-screw extruder temperature settings: Resin feed inlet 40°C, cylinder inlet 150°C, adapter 210°C, die 210°C Screw rotation speed: 300 rpm

[0080] (Manufacturing Examples 2 to 5) Vinyl aromatic elastomers A-2, A-3, and A'-1 were obtained through the same production method as in Production Example 1, except that the components and their amounts used were changed as shown in Table 1. A'-2 was also obtained as a hydrogenated block copolymer, an intermediate in the same production method as A-2. The results of the physical property evaluations of the resulting A-2, A-3, A'-1, and A'-2 are shown in Table 2.

[0081] <Adhesive composition> [Methods for measuring each physical property] The adhesive compositions obtained by the manufacturing methods described below were evaluated for various physical properties according to the following measurement methods.

[0082] (Adhesiveness) An adhesive composition liquid, which is an adhesive composition described below, was applied to a release PET film so that the thickness after drying would be 30 μm, and then dried at room temperature to obtain an adhesive film. The obtained adhesive film was peeled from the release PET film, sandwiched between 25 μm-thick LCP films (manufactured by Kuraray Co., Ltd., "Vecstar (registered trademark) CTQ-50"), pressurized and heated for 3 minutes at 120°C and 3 MPa, and then pressurized and heated for 60 minutes at 160°C and 3 MPa to obtain a sample for peel strength evaluation. Peel strength was measured by a 90° peel test at 25°C with a pulling speed of 50 mm / min, and the adhesiveness was evaluated according to the following evaluation criteria. A + A rating of A was considered a pass, and a rating of B was considered a fail. Evaluation Criteria A + :1.0N / mm or more A: 0.5N / mm or more and less than 1.0N / mm B: Less than 0.5N / mm

[0083] (solder heat resistance) A sample was prepared in the same manner as the above adhesiveness evaluation sample, and a 1cm x 1cm sample piece was placed in a solder bath at 288°C. The time until any changes in appearance such as swelling occurred was measured, and the sample was evaluated according to the following criteria. + A rating of A was considered a pass, and a rating of B was considered a fail. Evaluation Criteria A + : 60 seconds or more A: 20 seconds or more but less than 60 seconds B: Less than 20 seconds

[0084] (relative permittivity and dielectric loss tangent) The adhesive film obtained above was peeled off from the release PET film and cut into a 10cm x 10cm square to obtain a measurement sample. Using a device consisting of a network analyzer (Agilent Technologies, E8363B) and an open-type resonator (Keycom, DPS-03), the relative permittivity and dielectric loss tangent were measured at a measurement frequency of 28GHz, and the results were evaluated according to the following criteria. + A rating of A was considered a pass, and a rating of B was considered a fail. <Evaluation criteria for relative permittivity> A + : Less than 2.3 A: 2.3 or more and less than 2.5 B:2.5 or more <Evaluation criteria for dielectric loss tangent> A + : Less than 0.005 A: 0.005 or more and less than 0.01 B:0.01 or more

[0085] [Raw materials for adhesive composition] Vinyl aromatic elastomers (A) A-1 to A-3: as described in the above Production Examples Vinyl aromatic elastomer (A') A'-1, A'-2: As described in the above Production Examples Epoxy resin (B): "EPICLON (registered trademark) HP-7200" (DIC Corporation) Curing accelerator (C): "Curezol (registered trademark) C11Z" (manufactured by Shikoku Chemicals Corporation) Flame retardant (D): "Exolit (registered trademark) OP935" (manufactured by Clariant)

[0086] [Production of adhesive composition] Example 1 The components were weighed and blended to the blending ratio (parts by weight) shown in Table 3, and then toluene was added and mixed to obtain an adhesive composition liquid, which was an adhesive composition. The results of the physical property evaluation are shown in Table 3.

[0087] (Examples 2 to 5, Comparative Examples 1 and 2) An adhesive composition liquid was obtained in the same manner as in Example 1, except that the components and their blending ratios were changed as shown in Tables 3 and 4. The results of the physical property evaluation are shown in Tables 3 and 4.

[0088] As is clear from Tables 3 and 4, in Examples 1 to 5, the adhesive compositions had excellent peel strength between LCP films and solder heat resistance, while the electrical properties of the adhesive compositions were good, with low relative dielectric constants and dielectric dissipation factors. In contrast, in Comparative Example 1, which used a vinyl aromatic elastomer with a low main dispersion peak temperature of tanδ, the peel strength between LCP films was low. Furthermore, in Comparative Example 2, which used a vinyl aromatic elastomer without reactive functional groups, the peel strength and solder heat resistance were low.

[0089] [Table 1]

[0090] [Table 2]

[0091] [Table 3]

[0092] [Table 4] [Industrial Applicability]

[0093] The adhesive composition of the present invention has excellent adhesion to substrates such as LCP films having low dielectric properties, excellent solder heat resistance, and a low dielectric constant and dielectric loss tangent, and therefore can be suitably used for bonding sheets, coverlay films, laminates, printed wiring boards, etc. Furthermore, use of the adhesive composition of the present invention is expected to improve the yield of laminates in the production process of laminates containing films having low dielectric properties such as LCP films.

Claims

1. An adhesive composition comprising a vinyl aromatic elastomer (A) and an epoxy resin (B), and satisfying all of the following conditions (1) to (3): (1) The vinyl aromatic elastomer (A) is a block copolymer containing a block (X) mainly containing structural units derived from a vinyl aromatic compound and a block (Y) mainly containing structural units derived from a conjugated diene compound. (2) The main dispersion peak temperature of tan δ of the vinyl aromatic elastomer (A) is −45° C. or higher. (3) The vinyl aromatic elastomer (A) contains a reactive functional group

2. The adhesive composition according to claim 1 , wherein the block (X) contains a structural unit derived from a styrene-based monomer.

3. The adhesive composition according to claim 1, wherein the block (Y) contains a structural unit derived from at least one selected from the group consisting of isoprene and butadiene.

4. 2. The adhesive composition according to claim 1, wherein the bonding form of the blocks of the vinyl aromatic elastomer (A) is represented by X-(Y-X)n or (X-Y)n (n is an integer of 1 or more).

5. 2. The adhesive composition according to claim 1, wherein at least a portion of the carbon-carbon double bonds in said block (Y) are hydrogenated.

6. 6. The adhesive composition according to claim 5, wherein the hydrogenation rate of carbon-carbon double bonds in the block (Y) is 80 mol % or more.

7. The adhesive composition according to claim 1, wherein the block (Y) has a vinyl bond content of 45 mol% or more.

8. 2. The adhesive composition according to claim 1, wherein the reactive functional group contained in the vinyl aromatic elastomer (A) is at least one selected from the group consisting of a carboxy group, a hydroxy group, an amino group, an epoxy group, and a group derived from an acid anhydride.

9. 2. The adhesive composition according to claim 1, wherein the amount of the reactive functional group contained in the vinyl aromatic elastomer (A) is 0.01 to 10 parts by weight per 100 parts by weight of the vinyl aromatic elastomer (A).

10. The adhesive composition according to claim 1 , further comprising a curing accelerator (C).

11. The adhesive composition according to claim 10, wherein the curing accelerator (C) is an imidazole compound.

12. The adhesive composition according to claim 1 , further comprising a flame retardant (D).

13. The adhesive composition according to claim 12, wherein the flame retardant (D) is an organic metal phosphinate.

14. 2. The adhesive composition according to claim 1, wherein the relative dielectric constant and dielectric loss tangent measured at a frequency of 28 GHz are less than 2.5 and less than 0.005, respectively.

15. 2. The adhesive composition according to claim 1, wherein a test piece obtained by bonding two liquid crystal polymer films together with the adhesive composition has a 90° peel strength at 25°C of 0.5 N / mm or more.

16. 2. The adhesive composition according to claim 1, wherein when a test piece formed by bonding two liquid crystal polymer films with the adhesive composition is floated in a solder bath at 288°C, no foaming is observed after 20 seconds.

17. A bonding sheet comprising the adhesive composition according to any one of claims 1 to 16.

18. A coverlay film comprising the adhesive composition according to any one of claims 1 to 16.

19. A laminate comprising an adhesive layer containing the adhesive composition according to any one of claims 1 to 16.

20. The laminate according to claim 19, further comprising a substrate layer, the substrate layer comprising at least one selected from the group consisting of liquid crystal polymers and polyimides.

21. A printed wiring board comprising the laminate of claim 19.

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