Adhesive composition for flexible adherend and product

Abstract

Provided is an adhesive composition for flexible adherends, which is used for bonding flexible adherends (excluding bonding of fiber fabrics, bonding of conductive sheets, bonding of fiber fabrics and conductive sheets, and bonding of fiber fabrics and elastomer substrates). The pressure-sensitive adhesive composition contains a (meth) acrylic polymer (A) having a weight-average molecular weight of 100,000 or more and a glass transition temperature of-80 DEG C to 10 DEG C, and the pressure-sensitive adhesive layer has a storage modulus of 1.0 MPa or less at 23 DEG C.

Description

Technical Field

[0001] [Cross - reference to Related Applications]

[0002] This application claims priority based on Japanese Patent Application No. 2023 - 131481 filed on August 10, 2023, and the entire content is incorporated herein by reference.

[0003] The present invention relates to an adhesive composition for flexible adherends and articles (the original Japanese term for "adhesion" is "stickiness"). Background Art

[0004] When manufacturing articles in a wide range of fields including clothing accessories, clothing, daily necessities, sports goods, electronic components, automotive interior parts, etc., the following process is carried out: Flexible adherends such as fabrics, resin sheets, resin films, leather, rubber sheets, rubber films, metal foils, etc. are bonded to each other by bonding processes. In addition, various techniques for bonding such flexible adherends to each other by bonding processes have been proposed. For example, as a technique for bonding fiber fabrics by bonding processes, there is a method using a urethane - based hot - melt adhesive (for example, refer to Patent Document 1 and Patent Document 2).

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2016 - 74996

[0008] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2017 - 78232 Summary of the Invention

[0009] Technical Problem to be Solved by the Invention

[0010] Since flexible adherends (hereinafter also referred to as "flexible adherends") are soft and tough, they are mostly used in parts that effectively utilize their characteristics and will be repeatedly bent or restored to their original shape. However, when bonding flexible adherends to each other using conventional urethane - based hot - melt adhesives, there are sometimes problems such as: the bonded part is hard and loses the feel and flexibility of the raw material; or when the flexible adherend is bent and stretched, the bonded part cannot follow the bending and stretching of the flexible adherend, and the flexible adherend peels off.

[0011] The present invention has been completed in view of the above circumstances, and its main object is to provide an adhesive composition for flexible adherends, which can form an adhesive layer with good adhesiveness while well maintaining the bending property and feel of the bonded part when bonding flexible adherends to each other.

[0012] Technical solutions for solving technical problems

[0013] As a means to solve the above-mentioned technical problems, the inventors focused on using (meth)acrylic polymers as the polymer component of the adhesive layer used when bonding flexible adherends together, and conducted in-depth research, resulting in the discovery that the above-mentioned technical problems could be solved. Specifically, according to the present invention, the following adhesive composition and article for flexible adherends are provided.

[0014] [1] An adhesive composition for flexible substrates, used to form an adhesive layer for bonding flexible substrates to each other (excluding bonding of fibrous fabrics to each other, bonding of conductive sheets to each other, bonding of fibrous fabrics to conductive sheets, and bonding of fibrous fabrics to elastomer substrates), wherein the adhesive composition for flexible substrates contains a (meth)acrylic polymer (A) with a weight-average molecular weight of 100,000 or more and a glass transition temperature of -80°C or more and 10°C or less, and the adhesive layer has a storage modulus of 1.0 MPa or less at 23°C.

[0015] [2] The adhesive composition for flexible adhered materials described in [1] above, wherein the (meth)acrylic polymer (A) is a block copolymer having a polymer block (C) having a glass transition temperature of 10°C or higher and 250°C or lower and a (meth)acrylic polymer block (D) having a glass transition temperature of -80°C or higher and less than 10°C.

[0016] [3] The adhesive composition for flexible adhered materials described in [2] above, wherein the glass transition temperature of the polymer block (C) is 10°C or higher and 90°C or lower.

[0017] [4] The adhesive composition for flexible adhered materials described in [2] or [3] above, wherein the polymer block (C) comprises a structural unit (U1) derived from an imide-containing vinyl monomer and a structural unit (U2) derived from a (meth)acrylic monomer, and the total proportion of the structural unit (U1) and the structural unit (U2) is 80% by mass or more relative to all the structural units of the polymer block (C).

[0018] [5] The adhesive composition for flexible adhered materials according to any one of [2] to [4] above, wherein the (meth)acrylic polymer block (D) comprises structural units derived from (meth)acrylic ester compounds having 3 or more carbon atoms, accounting for 20% by mass of all structural units of the (meth)acrylic polymer block (D).

[0019] [6] The adhesive composition for flexible adhered materials according to any one of [1] to [5] above, wherein the (meth)acrylic polymer (A) contains structural units derived from at least one selected from (meth)acrylic alkyl esters and (meth)acrylic alkoxyalkyl esters.

[0020] [7] The adhesive composition for flexible substrates according to any one of [1] to [6] above, wherein the adhesive composition for flexible substrates further comprises a vinyl polymer (B) having a glass transition temperature of 30°C or higher and 200°C or lower, and a number average molecular weight of 500 or higher and 10,000 or lower.

[0021] [8] The adhesive composition for flexible adhered materials described in [7] above, wherein the vinyl polymer (B) comprises structural units derived from aliphatic cyclic vinyl monomers.

[0022] [9] The adhesive composition for flexible adhered materials described in [7] or [8] above, wherein the content of the vinyl polymer (B) is 0.5 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the (meth)acrylic polymer (A).

[0023]

[10] The adhesive composition for flexible substrates according to any one of [1] to [9] above, wherein the adhesive composition for flexible substrates further contains a silane coupling agent.

[0024]

[11] The adhesive composition for flexible adhered materials described in

[10] above, wherein the silane coupling agent has at least one selected from epoxy group, (meth)acryloyl group, isocyanate group and end-capped isocyanate group.

[0025]

[12] The adhesive composition for flexible substrates according to any one of [1] to

[11] above, wherein the adhesive composition for flexible substrates further contains an isocyanate-based crosslinking agent.

[0026]

[13] The adhesive composition for flexible substrates according to any one of [1] to

[12] above, wherein the adhesive composition for flexible substrates further contains microparticles.

[0027]

[14] An article comprising a first adhesive, a second adhesive and an adhesive layer, wherein the first adhesive and the second adhesive are bonded together by the adhesive layer, wherein the first adhesive and the second adhesive are both flexible adhesives (excluding those that are both fiber fabrics, both that are conductive sheets, combinations of fiber fabrics and conductive sheets, and combinations of fiber fabrics and elastomer substrates), and the adhesive layer is formed of an adhesive composition for flexible adhesives as described in any one of [1] to

[13] .

[0028] Invention Effects

[0029] According to the adhesive composition for flexible substrates of the present invention, when flexible substrates are bonded together, an adhesive layer can be formed that exhibits excellent adhesion while maintaining the flexibility and feel of the bonded portions. Furthermore, by bonding flexible substrates together via the adhesive layer formed using the adhesive composition for flexible substrates of the present invention, articles with good flexibility and feel of the bonded portions and high adhesive strength can be obtained. Detailed Implementation

[0030] The present invention will now be described in detail. It should be noted that "(meth)acrylic acid" in this specification refers to acrylic acid and / or methacrylic acid. "(meth)acrylate / salt" refers to acrylate / salt and / or methacrylate / salt. "(meth)acryloyl" refers to acryloyl and / or methacryloyl.

[0031] The adhesive composition for flexible substrates of the present invention (hereinafter also referred to as "the composition") is a (meth)acrylic adhesive for forming an adhesive layer for bonding flexible substrates together. Hereinafter, flexible substrates will be described first, followed by a description of the composition.

[0032] Soft Adhesives

[0033] Examples of flexible substrates bonded using this composition include those that are flexible and do not crack or break even when bent. Specifically, for a 50mm x 100mm substrate sheet, it is preferable that the substrate sheet can be bent with its short sides in contact with each other, and that the substrate sheet does not crack or break during bending. Furthermore, the bending stiffness of the flexible substrate is preferably 0.01 N·m. 2 / m or more and 10 N·m 2 / m or less. For example, cowhide and artificial leather typically have a strength of 0.3 N·m. 2 / m~10N·m 2 The stiffness is 0.01 N·m. Additionally, the fabric typically has a stiffness of 0.01 N·m. 2 / m~0.5N·m 2The stiffness is / m. It should be noted that in this specification, the bending stiffness of the flexible substrate is a value measured using a bending testing machine (e.g., the KES-FB2 or FB2-L pure bending testing machine manufactured by KATO TECH Co., Ltd.).

[0034] The thickness of the flexible adhesive can be appropriately set according to the application. The thickness of the flexible adhesive is, for example, 0.01 mm or more and 15.0 mm or less. From the viewpoint of the high improvement effect on the flexibility and feel of the bonding part obtained by applying this composition, the thickness of the flexible adhesive is preferably 10.0 mm or less, more preferably 5.0 mm or less, further preferably 2.0 mm or less, and even more preferably 1.0 mm or less.

[0035] Examples of flexible adhesives include fibrous fabrics; leather; conductive substrates; film-like, sheet-like, or sponge-like resin substrates; and film-like, sheet-like, or sponge-like elastomer substrates. It should be noted that, hereinafter, film-like materials with a thickness of less than 200 μm are referred to as film-like, and sheet-like materials with a thickness of 200 μm or more are referred to as sheet-like. The flexible adhesive can be formed from only one of the above-mentioned materials, or from two or more of them. Furthermore, the two flexible adhesives bonded together by this composition can be of the same type or different types.

[0036] Examples of fiber fabrics include synthetic fibers such as polyester, polyamide, polyurethane, and acrylic fibers; regenerated fibers such as rayon and cupro fibers; semi-synthetic fibers such as acetate; and natural fibers such as cotton, linen, and wool.

[0037] As for leather, examples include synthetic leather, artificial leather, fur, and natural leather (cowhide, pigskin, sheepskin, etc.).

[0038] Examples of conductive substrates include metal foils (i.e., metal films), metal foil composite films, and conductive sheets. A metal foil composite film is a laminate comprising a metal foil and a film formed from a substance other than a metal. A metal foil composite film may consist solely of a metal foil and a film formed from a substance other than a metal, or it may further include other layers (e.g., an adhesive layer). Examples of metals used for forming the metal foil and the metal foil composite film include pure metals such as copper, silver, gold, aluminum, titanium, and magnesium, and their alloys. In metal foil composite films, the film formed from a substance other than a metal is preferably a resin film. Examples of resin film materials include polyester resins such as polyethylene terephthalate (PET), polyethersulfone resins, polyimide resins, acetate resins, polycarbonate resins, and polyolefin resins.

[0039] Conductive sheets are biosensors that acquire biological information such as heart rate, body temperature, and blood pressure by obtaining electrical signals from a living organism. A conductive sheet comprises an insulating layer and a conductive layer. As an example, a conductive sheet is a laminate in which a first insulating layer, a conductive layer, and a second insulating layer are sequentially stacked. The insulating layer is, for example, formed of a stretchable resin material (such as polyurethane resin). The conductive layer is, for example, formed of a conductive material such as pure metals like copper, silver, gold, aluminum, titanium, and magnesium, or their alloys. The conductive layer preferably has stretchability; for example, it can be formed by mixing conductive particles with a flexible resin and molding it into a film. A portion of the conductive layer becomes an electrode that contacts the skin of the person being measured. It should be noted that the conductive layer of a conductive sheet differs from a metal film formed entirely of metal.

[0040] Examples of film-like, sheet-like, or sponge-like resin substrates include those formed from polyester resins such as polyethylene terephthalate (PET), polyethersulfone resins, polyimide resins, acetate resins, polycarbonate resins, and polyolefin resins.

[0041] Film-like, sheet-like, or sponge-like elastomer substrates can be formed from thermoplastic elastomers or thermosetting elastomers. Additionally, materials combining thermoplastic and thermosetting elastomers can also be used. Specific examples of thermoplastic elastomers include styrene-based thermoplastic elastomers (TPS), polyolefin-based thermoplastic elastomers (TPO), polyester-based thermoplastic elastomers (TPEE), vinyl chloride-based thermoplastic elastomers (TPVC), polyurethane-based thermoplastic elastomers (TPU), and polyamide-based thermoplastic elastomers (TPA). Specific examples of thermosetting elastomers include polyurethane rubber, silicone rubber, isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), nitrile rubber (NBR), ethylene-propylene rubber (EPM), acrylic rubber (ACM), and fluororubber.

[0042] The flexible adhesive is preferably selected from at least one of fibrous fabric, resin substrate, conductive substrate, leather, and elastomer substrate, and more preferably from at least one of synthetic fibers, film-like resin substrate, sheet-like resin substrate, synthetic leather, film-like elastomer substrate, metal foil, and metal foil composite film. The flexible adhesive can be a mesh (mesh-like) having multiple holes extending in the thickness direction, or metal wiring can be formed on the surface of the flexible adhesive, or surface treatments such as embossing or water-repellent processing can be applied.

[0043] The combination of flexible adhered materials bonded by the adhesive layer formed by this composition can be any combination other than the bonding of fibrous fabrics to each other, the bonding of conductive sheets to each other, the bonding of fibrous fabrics and conductive sheets, and the bonding of fibrous fabrics and elastomer substrates. Specific examples of flexible adhered materials bonded by the adhesive layer formed by this composition include combinations of fibrous fabrics and resin substrates, combinations of metal films to each other, combinations of metal foil composite films to each other, combinations of leather and resin substrates, combinations of conductive substrates and resin substrates, combinations of resin substrates to each other, and combinations of leather and elastomer substrates.

[0044] As further specific examples of combinations of flexible adhered materials bonded by an adhesive layer formed from the present composition, examples include combinations of fibrous fabric and resin film, combinations of fibrous fabric and resin sheet, combinations of leather and resin film, combinations of leather and resin sheet, combinations of metal film and resin film, combinations of metal film and resin sheet, combinations of metal film and metal film, combinations of metal foil composite film and metal foil composite film, combinations of resin film and resin film, combinations of resin film and resin sheet, combinations of resin sheet and resin sheet, combinations of metal foil composite film and resin film, combinations of metal foil composite film and resin sheet, and combinations of leather and a film-like elastomer substrate.

[0045] Adhesive compositions for flexible substrates

[0046] This composition contains a (meth)acrylic polymer (A) with a weight-average molecular weight of 100,000 or more and a glass transition temperature of -80°C or more and 10°C or less. Furthermore, the adhesive layer formed by this composition has a storage modulus of 1.0 MPa or less at 23°C. The adhesive layer formed by this composition is easily stretchable and exhibits excellent adhesion, making it suitable for applications involving bonding flexible substrates together. Hereinafter, the (meth)acrylic polymer (A) incorporated into this composition and other components incorporated as needed will be described in detail.

[0047] <(Meth)Acrylic Polymer (A)>

[0048] The (meth)acrylic polymer (A) is a polymer with a weight-average molecular weight (Mw) of 100,000 or more. When the Mw of the (meth)acrylic polymer (A) is less than 100,000, cohesive strength and adhesiveness tend to deteriorate. From the viewpoint of obtaining a polymer exhibiting sufficient cohesive strength and good adhesiveness, the Mw of the (meth)acrylic polymer (A) is preferably 150,000 or more, more preferably 200,000 or more, and even more preferably 250,000 or more.

[0049] On the other hand, if the Mw of the (meth)acrylic polymer (A) is too large, the flexibility of the (meth)acrylic polymer (A) and the adhesive layer may decrease, or the viscosity of the adhesive composition may become too high, leading to reduced coatability and workability. Therefore, the Mw of the (meth)acrylic polymer (A) is preferably 2,000,000 or less, more preferably 1,500,000 or less, even more preferably 1,200,000 or less, and even more preferably 1,000,000 or less. The range of the Mw of the (meth)acrylic polymer (A) is preferably 100,000 or more and 2,000,000 or less, more preferably 150,000 or more and 1,500,000 or less, and even more preferably 200,000 or more and 1,200,000 or less.

[0050] From the viewpoint of exhibiting sufficient cohesion and good adhesion, the Mn of the (meth)acrylic polymer (A) is preferably 60,000 or more, more preferably 80,000 or more, and even more preferably 100,000 or more. Regarding the upper limit of the Mn of the (meth)acrylic polymer (A), from the viewpoint of ease of manufacture, it is preferably 500,000 or less, more preferably 400,000 or less, and even more preferably 300,000 or less. The range of Mn of the (meth)acrylic polymer (A) is preferably 60,000 or more and 500,000 or less, more preferably 80,000 or more and 400,000 or less.

[0051] Regarding the (meth)acrylic polymer (A), from the perspective of easily obtaining good adhesive strength and suppressing the high viscosity of the adhesive composition, the molecular weight distribution (Mw / Mn), expressed as the ratio of Mw to Mn, is preferably 10.0 or less, more preferably 8.0 or less, further preferably 6.0 or less, even more preferably 5.0 or less, and even more preferably 4.0 or less. The lower limit of the Mw / Mn of the (meth)acrylic polymer (A) is not particularly limited and can be set to 1.0 or more. In this specification, the Mw and Mn of the polymer are standard polystyrene conversion values ​​obtained using gel permeation chromatography (GPC).

[0052] The glass transition temperature (Tg) of the (meth)acrylic polymer (A) is -80°C or higher and 10°C or lower. If the Tg of the (meth)acrylic polymer (A) is lower than -80°C, the cohesive strength of the adhesive layer obtained from this composition cannot be sufficiently ensured, and there is a tendency for poor adhesion. Furthermore, if the Tg of the (meth)acrylic polymer (A) exceeds 10°C, the resulting (meth)acrylic polymer has poor adhesion, and adhesion cannot be sufficiently ensured. From these viewpoints, the Tg of the (meth)acrylic polymer (A) is preferably -70°C or higher, more preferably -60°C or higher. Regarding the upper limit of the Tg of the (meth)acrylic polymer (A), from the viewpoint of improving the adhesion of the (meth)acrylic polymer (A), it is preferably below 0°C, more preferably below -10°C, and even more preferably below -15°C. The range of the Tg of the (meth)acrylic polymer (A) is preferably above -70°C and below 0°C, and even more preferably above -60°C and below -10°C.

[0053] It should be noted that, in this specification, the glass transition temperature (Tg) of the polymer is a value determined by differential scanning calorimetry (DSC). Details of the measurement method are as described in the examples below. In this specification, when the (meth)acrylic acid polymer (A) is a block copolymer, the Tg of each polymer block is determined by synthesizing a polymer composed of monomers constituting the polymer blocks to be measured and then measuring the Tg of that polymer using DSC. The Tg of the polymer can be arbitrarily selected by changing the type and composition of the constituent monomers.

[0054] (Meth)acrylic polymer (A) is a polymer containing (meth)acrylic monomers as the main structural units. The (meth)acrylic monomers constituting (Meth)acrylic polymer (A) are any monomers having a (meth)acryloyl group as a polymerization participating group; there are no particular limitations. Examples of (meth)acrylic monomers include: unsaturated carboxylic acids, unsaturated acid anhydrides, alkyl methacrylates, aliphatic cyclic esters of (meth)acrylic acid, aromatic esters of (meth)acrylic acid, alkoxyalkyl methacrylates, hydroxyalkyl methacrylates, polyalkylene glycol mono(meth)acrylates, epoxy-containing (meth)acrylates, silyl-containing (meth)acrylates, amino-containing (meth)acrylates, (meth)acrylamide or its derivatives, nitrile-containing (meth)acrylates, and (meth)acrylimide compounds, etc.

[0055] Specific examples of unsaturated carboxylic acids include: (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, cinnamic acid, and monoalkyl esters of unsaturated dicarboxylic acids (monoalkyl esters of maleic acid, fumaric acid, itaconic acid, citraconic acid, etc.). Specific examples of unsaturated acid anhydrides include: maleic anhydride, itaconic anhydride, and citraconic anhydride.

[0056] Specific examples of alkyl methacrylates include: methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, n-nonyl methacrylate, isononyl methacrylate, n-decyl methacrylate, and lauryl methacrylate, which are alkyl methacrylates having 1 to 12 carbon atoms.

[0057] Specific examples of aliphatic cyclic esters of (meth)acrylic acid include: cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, isobornyl (meth)acrylate, adamantane (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentyl (meth)acrylate. Specific examples of aromatic esters of (meth)acrylic acid include: phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxymethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, and 3-phenoxypropyl (meth)acrylate.

[0058] Specific examples of alkoxyalkyl esters of (meth)acrylate include: methoxyethyl ester, ethoxyethyl ester, propoxyethyl ester, butoxyethyl ester, methoxypropyl ester, ethoxypropyl ester, propoxypropyl ester, butoxypropyl ester, methoxybutyl ester, ethoxybutyl ester, propoxybutyl ester, and butoxybutyl ester.

[0059] Specific examples of hydroxyalkyl methacrylates include: 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate. Specific examples of polyalkylene glycol mono(meth)acrylates include: polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, and polyethylene glycol-polypropylene glycol mono(meth)acrylate.

[0060] Specific examples of epoxy-containing (meth)acrylates include glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycidyl ether, and methyl (meth)acrylate-3,4-epoxycyclohexyl ester. Specific examples of silyl-containing (meth)acrylates include trimethoxysilylpropyl (meth)acrylate, triethoxysilylpropyl (meth)acrylate, methyldimethoxysilylpropyl (meth)acrylate, and dimethylmethoxysilylpropyl (meth)acrylate.

[0061] Specific examples of amino-containing (meth)acrylates include: dimethylaminomethyl (meth)acrylate, diethylaminomethyl (meth)acrylate, 2-dimethylaminoethyl (meth)acrylate, 2-diethylaminoethyl (meth)acrylate, 2-(di-n-propylamino)ethyl (meth)acrylate, 2-dimethylaminopropyl (meth)acrylate, 2-diethylaminopropyl (meth)acrylate, 2-(di-n-propylamino)propyl (meth)acrylate, 3-dimethylaminopropyl (meth)acrylate, 3-diethylaminopropyl (meth)acrylate, and 3-(di-n-propylamino)propyl (meth)acrylate.

[0062] Specific examples of (meth)acrylamide or its derivatives include: (meth)acrylamide, tert-butyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, and (meth)acryloylmorpholine, etc.

[0063] Specific examples of cyanoacrylates containing nitrile groups include: methyl cyanoacrylate, ethyl cyanoacrylate, ethyl cyanoacrylate, propyl cyanoacrylate, propyl cyanoacrylate, propyl cyanoacrylate, propyl cyanoacrylate, propyl cyanoacrylate, butyl cyanoacrylate, 6-cyanohexyl cyanoacrylate, 2-ethyl-6-cyanohexyl cyanoacrylate, and octyl cyanoacrylate.

[0064] Specific examples of (meth)acrylamide compounds include: N-(2-(meth)acryloxyethyl)succinimide, N-(2-(meth)acryloxyethyl)maleimide, N-(2-(meth)acryloxyethyl)phthalimide, N-(4-(meth)acryloxybutyl)succinimide, N-(4-(meth)acryloxybutyl)maleimide, N-(4-(meth)acryloxybutyl)phthalimide, etc.

[0065] The (meth)acrylic polymer (A) preferably contains structural units derived from at least one of the (meth)acrylic monomers selected from at least one of the (meth)acrylic alkyl esters and (meth)acrylic alkoxyalkyl esters. When the (meth)acrylic polymer (A) contains structural units derived from these monomers, the Tg of the (meth)acrylic polymer (A) becomes lower, and a polymer exhibiting sufficient adhesiveness can be obtained.

[0066] In the (meth)acrylate polymer (A), the proportion of structural units derived from at least one selected from alkyl (meth)acrylate and alkoxyalkyl (meth)acrylate, relative to all structural units of the (meth)acrylate polymer (A), is preferably 20% by mass or more, more preferably 30% by mass or more, further preferably 50% by mass or more, even more preferably 60% by mass or more, and even more preferably 70% by mass or more. By setting the proportion of structural units derived from at least one selected from alkyl (meth)acrylate and alkoxyalkyl (meth)acrylate within the above range, the adhesive strength and initial tack of the adhesive composition can be sufficiently improved.

[0067] In the (meth)acrylate polymer (A), the proportion of structural units derived from (meth)acrylate monomers relative to all structural units of the (meth)acrylate polymer (A) is preferably 60% by mass or more, more preferably 70% by mass or more, further preferably 80% by mass or more, and even more preferably 85% by mass or more. When manufacturing the (meth)acrylate polymer (A), one type of (meth)acrylate monomer may be used alone, or two or more may be used in combination.

[0068] Without impairing the function of the (meth)acrylate polymer (A), the (meth)acrylate polymer (A) may further comprise structural units derived from monomers (hereinafter also referred to as "other monomers") that are capable of copolymerizing with (meth)acrylate monomers and are different from (meth)acrylate monomers. Specific examples of other monomers constituting the (meth)acrylate polymer (A) include, for example, aromatic vinyl compounds and imide-containing vinyl monomers.

[0069] Examples of aromatic vinyl compounds include styrene, α-methylstyrene, β-methylstyrene, vinylxylene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, p-n-butylstyrene, p-isobutylstyrene, p-tert-butylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenylphenol, m-isopropenylphenol, o-isopropenylphenol, o-vinylbenzoic acid, m-vinylbenzoic acid, p-vinylbenzoic acid, and divinylbenzene, as well as vinylnaphthalene, etc. Styrene compounds among these are preferred aromatic vinyl compounds. One or more of these compounds may be used as aromatic vinyl compounds.

[0070] Examples of vinyl monomers containing an imide group include: maleimide compounds such as maleimide and N-substituted maleimide compounds; itconimide compounds such as N-methylitconimide, N-ethylitconimide, N-butylitconimide, N-octylitconimide, N-2-ethylhexylitconimide, N-cyclohexylitconimide, and N-laurylitconimide; and citconimide compounds such as N-methylcitronimidide, N-ethylcitronimidide, N-butylcitronimidide, N-octylcitronimidide, N-2-ethylhexylcitronimidide, N-cyclohexylcitronimidide, and N-laurylcitronimidide. Maleimide compounds are preferred among the vinyl compounds containing an imide group.

[0071] As the maleimide compound, at least one selected from maleimides and N-substituted maleimide compounds is preferred. Examples of N-substituted maleimide compounds include: N-methylmaleimide, N-ethylmaleimide, N-n-propylmaleimide, N-isopropylmaleimide, N-n-butylmaleimide, N-isobutylmaleimide, N-tert-butylmaleimide, N-pentylmaleimide, N-hexylmaleimide, N-heptylmaleimide, N-octylmaleimide, N-laurylmaleimide, and N-stearoylmaleimide, etc., which are N-alkyl-substituted maleimide compounds; N-cyclopentylmaleimide... N-cycloalkyl-substituted maleimide compounds such as imines and N-cyclohexylmaleimide; N-arylalkyl-substituted maleimide compounds such as N-benzylmaleimide; and N-aryl-substituted maleimide compounds such as N-phenylmaleimide, N-(4-hydroxyphenyl)maleimide, N-(4-acetylphenyl)maleimide, N-(4-methoxyphenyl)maleimide, N-(4-ethoxyphenyl)maleimide, N-(4-chlorophenyl)maleimide, and N-(4-bromophenyl)maleimide. It should be noted that one or more of these compounds can be used as vinyl monomers containing an imide group.

[0072] Other monomers constituting the (meth)acrylic polymer (A), besides those mentioned above, include, for example: aliphatic vinyl compounds such as ethylene and propylene; vinyl compounds containing amide groups such as N-vinylacetamide; polyfunctional alkenyl compounds such as trimethylolpropane diallyl ether, trimethylolpropane triallyl ether, and pentaerythritol diallyl ether; etc. Only one monomer or more monomers may be used as constituting the (meth)acrylic polymer (A).

[0073] Furthermore, in manufacturing the (meth)acrylic polymer (A), by using a monomer having crosslinking functional groups (hereinafter also referred to as "monomer containing crosslinking groups"), the (meth)acrylic polymer (A) can be made into a polymer with crosslinking structural units. By giving the (meth)acrylic polymer (A) crosslinking structural units, excellent adhesion can be achieved when flexible adherends are bonded together, while maintaining the flexibility of the product, which is therefore preferred.

[0074] The monomer containing crosslinking groups used in the manufacture of the (meth)acrylic polymer (A) is not particularly limited. The monomer containing crosslinking groups is preferably selected from at least one of (meth)acrylic acid, hydroxyalkyl (meth)acrylic acid ester compounds, epoxy-containing (meth)acrylic acid esters, and silyl-containing (meth)acrylic acid esters. From the viewpoint of adhesive properties, hydroxyalkyl (meth)acrylic acid esters are preferably compounds having 2 to 8 carbon atoms, and more preferably compounds having 2 to 4 carbon atoms.

[0075] The (meth)acrylic polymer (A) can be any polymer whose main chain is composed of a portion or all of a polymer chain consisting of a structural unit derived from a (meth)acrylic monomer. Examples of (meth)acrylic polymers (A) include random copolymers, block copolymers, alternating copolymers, and graft copolymers. Among these, block copolymers and / or random copolymers are preferred, considering that the (meth)acrylic polymer (A) can be synthesized relatively easily while obtaining a variety of improved properties. Specifically, block copolymers (hereinafter also referred to as "block copolymers (A)") comprising polymer blocks (C) and (meth)acrylic polymer blocks (D) comprising polymer chains consisting of a structural unit derived from a (meth)acrylic monomer are preferred. And / or, [2] random copolymers comprising polymer chains consisting of a structural unit derived from a (meth)acrylic monomer are preferred.

[0076] [1] Block copolymer (A)

[0077] The block copolymer (A) comprises polymer blocks (C) and (meth)acrylic polymer blocks (D) that are segments with different monomer compositions. Preferably, the polymer block (C) has a higher Tg than the (meth)acrylic polymer block (D), making the polymer block (C) a segment with a relatively high Tg and the (meth)acrylic polymer block (D) a segment with a relatively low Tg. It is believed that when the block copolymer (A) contains such polymer blocks (C) and (meth)acrylic polymer blocks (D), pseudo-crosslinks can be formed between or within molecules through microphase separation structures, thereby potentially increasing cohesive strength.

[0078] • Polymer block (C)

[0079] The Tg of the polymer block (C) is preferably 10°C or higher and 250°C or lower. If the Tg of the polymer block (C) is 10°C or higher, the increased cohesive force resulting from the pseudo-crosslinking formed by the microphase separation structure of the block copolymer (A) can be fully realized, thus ensuring the adhesion of the adhesive layer. From this perspective, the Tg of the polymer block (C) is preferably 15°C or higher, more preferably 20°C or higher, even more preferably 25°C or higher, and even more preferably 30°C or higher. Regarding the upper limit of the Tg of the polymer block (C), from the viewpoint of the ease of obtaining the raw materials, it is preferably 250°C or lower. From the viewpoint of fully improving the peel strength when bonding various flexible adhesives together and maintaining the flexibility and feel of the bonded portion, the Tg of the polymer block (C) is preferably 200°C or lower, more preferably 150°C or lower, even more preferably 100°C or lower, even more preferably 90°C or lower, even more preferably 85°C or lower, and even more preferably 80°C or lower. In particular, if the Tg of the polymer block (C) is below 90°C, the flexibility of the adhesive layer can be ensured even if the ratio of the polymer block (C) in the block copolymer (A) is increased or the molecular weight of the block copolymer (A) is increased in order to ensure good adhesion, and therefore this is preferred.

[0080] The polymer block (C) preferably has structural units derived from vinyl monomers. From the viewpoint of obtaining a polymer with excellent adhesive properties, the polymer block (C) preferably comprises structural units (U1) derived from imide-containing vinyl monomers and structural units (U2) derived from (meth)acrylate monomers. By giving the block copolymer (A) such polymer blocks (C), an adhesive layer exhibiting excellent adhesive properties can be formed. Specific examples of imide-containing vinyl monomers and (meth)acrylate monomers can be given as compounds that are the same as those exemplified as monomers constituting the (meth)acrylate polymer (A).

[0081] From the viewpoint of being able to make the block copolymer (A) have better adhesion, the imide-containing vinyl monomer used in the manufacture of the block copolymer (A) is preferably a compound represented by the following general formula.

[0082] [Chemistry 1]

[0083]

[0084] (where R) 4 This refers to a group consisting of a hydrogen atom, an alkyl group (1-3 carbon atoms), a cyclohexyl group, a phenyl group, or a group with a hydroxyl group, an alkyl group (1-2 carbon atoms), an alkoxy group (1-2 carbon atoms), an acetyl group, or a halogen atom bonded at any position on the cyclohexyl or phenyl group.

[0085] From the viewpoint of ensuring the flexibility and feel of the bonded portion when the soft adhesives are bonded together, the structural unit (U2) is preferably a structural unit derived from the compound shown in the following formula (1).

[0086] CH2=CR 1 -C(=O)O(R) 2 O) n -R 3 …(1)

[0087] (In equation (1), R) 1 R represents a hydrogen atom or a methyl group. 2 R represents a straight-chain or branched alkylene group having 2 to 6 carbon atoms. 3 This indicates an alkyl group with 1 to 20 hydrogen or carbon atoms. n represents an integer from 0 to 100.

[0088] In the above equation (1), from the viewpoint that it is easy to adjust the Tg of the polymer block (C) to the above range, R 1 Preferably, it contains hydrogen atoms. From the viewpoint of ease of obtaining raw materials and adhesive properties, n is preferably 0 to 50, and more preferably 0 to 20.

[0089] In the polymer block (C), the total content of structural units (U1) and (U2) is preferably 80% by mass or more relative to all structural units of the polymer block (C). By making the total content of structural units (U1) and (U2) 80% by mass or more relative to all structural units of the polymer block (C), an adhesive layer exhibiting excellent adhesion can be formed. From the viewpoint of excellent adhesion when bonding flexible adherends together, the total content of structural units (U1) and (U2) is preferably 85% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, and even more preferably 99% by mass or more relative to all structural units of the polymer block (C).

[0090] The ratio of structural units (U1) to structural units (U2) in the polymer block (C) can be appropriately selected according to the desired Tg. Regarding the ratio of structural units (U1) to structural units (U2) in the polymer block (C), from the viewpoint of preventing the Tg of the polymer block (C) from becoming too high and further improving the adhesion of the adhesive layer, the proportion of structural unit (U2) is preferably set to 20 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 40 parts by mass or more, and even more preferably 45 parts by mass or more, relative to the total amount of structural units (U1) and structural units (U2) of 100 parts by mass.

[0091] In manufacturing the polymer block (C), by using a monomer containing crosslinking groups, the polymer block (C) can be made into a structure with crosslinking structural units. By giving the polymer block (C) crosslinking structural units, excellent adhesion can be achieved when flexible adhered materials are bonded together, while maintaining the flexibility of the product, which is therefore preferred.

[0092] The monomer containing crosslinking groups used in the manufacture of the polymer block (C) is not particularly limited, but preferably at least one selected from (meth)acrylic acid, hydroxyalkyl (meth)acrylic acid ester compounds, epoxy-containing (meth)acrylic acid esters, and silyl-containing (meth)acrylic acid esters. Particularly from the viewpoint of easily controlling the Tg of the polymer block (C) within the aforementioned range, structural units derived from hydroxyalkyl (meth)acrylic acid esters are preferred. From the viewpoint of adhesive properties, hydroxyalkyl (meth)acrylic acid esters are preferably compounds having 2 to 8 hydroxyalkyl groups, and more preferably compounds having 2 to 4 hydroxyalkyl groups.

[0093] When cross-linked structural units are introduced into the polymer block (C), the proportion of cross-linked structural units in the polymer block (C) is preferably 1% by mass or more, and more preferably 2% by mass or more, relative to all structural units of the polymer block (C). Regarding the upper limit of the proportion of cross-linked structural units in the polymer block (C), from the viewpoint of ensuring the flexibility of the bonding area, it is preferably 30% by mass or less, and more preferably 20% by mass or less, relative to all structural units of the polymer block (C).

[0094] Without impairing the function of the block copolymer (A), the polymer block (C) may further comprise structural units derived from monomers that are capable of copolymerizing with at least one of the imide-containing vinyl monomers and (meth)acrylate monomers and are different from the imide-containing vinyl monomers and (meth)acrylate monomers. Examples of monomers constituting the polymer block (C) that are different from the imide-containing vinyl monomers and (meth)acrylate monomers include aromatic vinyl compounds, etc., which are exemplified as other monomers in the description of the acrylic polymer (A).

[0095] However, from the viewpoint of achieving better adhesion when bonding flexible adhesives together, the amount of structural units derived from aromatic vinyl compounds in the polymer block (C) is preferably as low as possible. Specifically, the proportion of structural units derived from aromatic vinyl compounds in the polymer block (C) relative to all structural units of the polymer block (C) is preferably 20% by mass or less, more preferably 15% by mass or less, further preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0096] The number-average molecular weight (Mn) of the polymer block (C) is preferably in the range of 1,000 to 70,000. If the Mn of the polymer block (C) is 1,000 or more, the cohesive force of the block copolymer (A) can be sufficiently ensured; if it is 70,000 or less, the peel strength to the adhered object can be sufficiently improved while maintaining the elasticity of the adhesive layer, which is therefore preferred. The Mn of the polymer block (C) is preferably 2,000 or more, more preferably 3,000 or more, further preferably 5,000 or more, and even more preferably 7,000 or more. Regarding the upper limit of the Mn of the polymer block (C), it is preferably 65,000 or less, more preferably 60,000 or less, and even more preferably 55,000 or less.

[0097] Furthermore, from the viewpoint of sufficiently ensuring the cohesive strength of the block copolymer (A), maintaining the flexibility of the adhesive layer, and simultaneously improving the peel strength to the adhered objects, the weight-average molecular weight (Mw) of the polymer block (C) is preferably in the range of 1,000 to 100,000. From the above viewpoint, the Mw of the polymer block (C) is preferably 2,000 or more, more preferably 3,000 or more, further preferably 6,000 or more, and even more preferably 9,000 or more. Regarding the upper limit of the Mw of the polymer block (C), it is preferably 90,000 or less, more preferably 85,000 or less, further preferably 80,000 or less, and even more preferably 75,000 or less.

[0098] It should be noted that when a block copolymer (A) has multiple polymer blocks (C) within one molecule, "Mn of polymer block (C)" and "Mw of polymer block (C)" refer to the total Mn and Mw of the multiple polymer blocks (C) in one molecule of block copolymer (A), respectively. For example, when the block copolymer (A) is a (CDC) type triblock copolymer composed of polymer block (C) - (meth)acrylic polymer block (D) - polymer block (C), the Mn of the polymer block (C) in the triblock copolymer is the value obtained by adding the Mn of the two polymer blocks (C).

[0099] • (Meth)acrylic acid polymer block (D)

[0100] The (meth)acrylic polymer block (D) preferably has a Tg of -80°C or higher and less than 10°C. If the Tg of the (meth)acrylic polymer block (D) is -80°C or higher, the cohesive strength of the adhesive layer obtained from this composition can be sufficiently ensured, enabling the formation of an adhesive layer exhibiting excellent adhesion. Furthermore, by ensuring that the Tg of the (meth)acrylic polymer block (D) is less than -10°C, the adhesion of the block copolymer (A) can be sufficiently ensured. From the viewpoint of improving the cohesive strength and adhesion of the adhesive layer, the Tg of the (meth)acrylic polymer block (D) is preferably -70°C or higher, more preferably -60°C or higher. Regarding the upper limit of the Tg of the (meth)acrylic polymer block (D), from the viewpoint of improving the adhesion and flexibility of the block copolymer (A), it is preferably 0°C or lower, more preferably -5°C or lower, further preferably -10°C or lower, and even more preferably -20°C or lower. The Tg range of the (meth)acrylic polymer block (D) is preferably above -70°C and below 0°C, and more preferably above -60°C and below -5°C.

[0101] The preferred ranges of the temperature gradient (Tg) of the polymer block (C) and the (meth)acrylic polymer block (D) in the block copolymer (A) can be set by appropriately combining the preferred ranges of the Tg of each block. Specifically, in the block copolymer (A), the preferred Tg of the polymer block (C) is 10°C or higher and 250°C or lower, and the preferred Tg of the (meth)acrylic polymer block (D) is -80°C or higher and less than 10°C. Furthermore, it is more preferable that the Tg of the polymer block (C) is 10°C or higher and 150°C or lower, and the Tg of the (meth)acrylic polymer block (D) is -80°C or higher and less than 10°C. More preferably, the Tg of the polymer block (C) is 10°C or higher and 90°C or lower, and the Tg of the (meth)acrylic polymer block (D) is -80°C or higher and less than 10°C. Even more preferably, the Tg of the polymer block (C) is 10°C or higher and 90°C or lower, and the Tg of the (meth)acrylic polymer block (D) is -70°C or higher and 0°C or lower.

[0102] The (meth)acrylic polymer block (D) is a polymer that contains a (meth)acrylic monomer as the main structural unit. Examples of compounds that constitute the (meth)acrylic polymer block (D) are the same as those exemplified as the (meth)acrylic monomers constituting the (meth)acrylic polymer (A).

[0103] From the viewpoint of obtaining an adhesive layer with excellent bonding strength between flexible adhered materials, the (meth)acrylate polymer block (D) preferably comprises structural units derived from (meth)acrylates having a hydrocarbon group having 3 or more carbon atoms. As the (meth)acrylate having a hydrocarbon group having 3 or more carbon atoms, alkyl (meth)acrylates, aliphatic cyclic esters of (meth)acrylate, aromatic esters of (meth)acrylate, alkoxyalkyl (meth)acrylates, or mixtures of two or more thereof are preferably used. Specific examples of alkyl (meth)acrylates, aliphatic cyclic esters of (meth)acrylate, aromatic esters of (meth)acrylate, and alkoxyalkyl (meth)acrylates include compounds having a hydrocarbon group having 3 or more carbon atoms, as illustrated in the description of the (meth)acrylate monomers constituting the (meth)acrylate polymer (A).

[0104] From the viewpoint of being able to improve the adhesive strength of flexible adherends while ensuring the adhesive properties of the (meth)acrylic polymer block (D), the compound shown in the following formula (2) is preferably used as a (meth)acrylic ester having a hydrocarbon group having 3 or more carbon atoms.

[0105] CH2=CR 5 -C (=O) OR 6 …(2)

[0106] (In equation (2), R) 5 R represents a hydrogen atom or a methyl group. 6 The alkyl group having 3 to 20 carbon atoms, the alkoxyalkyl group having 4 to 20 carbon atoms with an alkoxy group having 3 or more carbon atoms, the cycloalkyl group having 3 to 20 carbon atoms, the aryl group having 6 to 20 carbon atoms, or the aralkyl group having 6 to 20 carbon atoms.

[0107] In the above formula (2), from the viewpoint that it is easy to adjust the Tg of the (meth)acrylic polymer block (D) to the above range, R 5 Preferably, hydrogen atoms. From the viewpoint of further improving the adhesiveness of (meth)acrylic polymer blocks (D), R 6 Alkyl groups with 3 to 20 carbon atoms are preferred, and alkyl groups with 4 to 12 carbon atoms are more preferred.

[0108] In the (meth)acrylate polymer block (D), the proportion of structural units derived from (meth)acrylate with hydrocarbon groups having 3 or more carbon atoms is preferably 20% by mass or more relative to all structural units of the (meth)acrylate polymer block (D). By making the proportion of structural units derived from (meth)acrylate with hydrocarbon groups having 3 or more carbon atoms 20% by mass or more, an adhesive layer with higher bonding strength between flexible adherends can be obtained. From this point of view, the proportion of structural units derived from (meth)acrylate with hydrocarbon groups having 3 or more carbon atoms in the (meth)acrylate polymer block (D) is more preferably 25% by mass or more, further preferably 30% by mass or more, even more preferably 40% by mass or more, and even more preferably 50% by mass or more.

[0109] From the viewpoint of obtaining polymer blocks with low Tg and exhibiting sufficient adhesion, cohesion, and flexibility, the monomer constituting the (meth)acrylic polymer block (D) preferably comprises at least one selected from alkyl (meth)acrylates and alkoxyalkyl (meth)acrylates. Specific examples of alkyl (meth)acrylates and alkoxyalkyl (meth)acrylates include compounds identical to those illustrated in the description of polymer block (C).

[0110] In the (meth)acrylic polymer block (D), the proportion of structural units derived from at least one of (meth)acrylic alkyl esters and (meth)acrylic alkoxyalkyl esters is preferably 30% by mass or more, more preferably 50% by mass or more, further preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, relative to all structural units of the (meth)acrylic polymer block (D).

[0111] From the viewpoint of forming an adhesive layer that ensures flexibility and high cohesion, the (meth)acrylic polymer block (D) is particularly preferably composed of structural units derived from (meth)acrylic alkoxyalkyl esters. Specifically, the proportion of structural units derived from (meth)acrylic alkoxyalkyl esters in the (meth)acrylic polymer block (D) is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, and even more preferably 20% by mass or more. There is no particular upper limit to the proportion of structural units derived from (meth)acrylic alkoxyalkyl esters in the (meth)acrylic polymer block (D), but it is preferably 80% by mass or less, more preferably 75% by mass or less, relative to all structural units of the (meth)acrylic polymer block (D).

[0112] From the viewpoint of obtaining a soft and cohesive adhesive layer, alkoxyalkyl esters of (meth)acrylate, which constitute the (meth)acrylate polymer block (D), are preferably used as (meth)acrylate alkoxyalkyl esters having alkoxy groups having 1 or 2 carbon atoms.

[0113] In the manufacture of (meth)acrylic polymer blocks (D), cross-linking structural units can also be introduced into the (meth)acrylic polymer blocks (D) by using monomers containing cross-linking groups. By giving the (meth)acrylic polymer blocks (D) cross-linking structural units, the flexibility and feel of the bonded portion can be well maintained, and the adhesive strength can be improved.

[0114] The monomer containing crosslinking groups used in the manufacture of the (meth)acrylic polymer block (D) is not particularly limited. From the viewpoint of improving the adhesiveness of the (meth)acrylic polymer block (D), the monomer containing crosslinking groups used in the manufacture of the (meth)acrylic polymer block (D) is preferably selected from at least one of (meth)acrylic acid, hydroxyalkyl (meth)acrylic acid ester compounds, epoxy-containing (meth)acrylic acid esters, and silyl-containing (meth)acrylic acid esters. Among these, in particular, from the perspective of the tendency to have a high effect on improving the adhesiveness of the (meth)acrylic polymer block (D), at least one of (meth)acrylic acid and hydroxyalkyl (meth)acrylic acid ester compounds is preferred.

[0115] When the (meth)acrylic polymer block (D) has crosslinking structural units, the content of the crosslinking structural units is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, relative to all structural units of the (meth)acrylic polymer block (D). By making the content of crosslinking structural units in the (meth)acrylic polymer block (D) 0.1% by mass or more, a good crosslinking structure can be formed, further improving the adhesive strength. There is no particular upper limit to the content of crosslinking structural units, but from the viewpoint of improving the flexibility of the obtained adhesive layer, it is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, relative to all structural units of the (meth)acrylic polymer block (D). It should be noted that when manufacturing the (meth)acrylic polymer block (D), one monomer containing crosslinking groups can be used alone, or two or more monomers can be used in combination.

[0116] When manufacturing (meth)acrylic polymer blocks (D), in addition to the monomers mentioned above, monomers capable of copolymerizing with the monomers mentioned above may also be used, provided that the adhesive properties are not compromised. Examples of monomers constituting (meth)acrylic polymer blocks (D) besides those mentioned above include: aliphatic vinyl compounds, amino-containing vinyl compounds, amide-containing vinyl compounds, polyfunctional alkenyl compounds, and nitrile-containing unsaturated compounds.

[0117] The polymer block (C) preferably has the property of being phase-separable from the (meth)acrylic polymer block (D). This property facilitates the formation of a microphase-separated structure in the block copolymer (A), and is therefore preferred. Based on the technical knowledge available at the time of this application, those skilled in the art can readily design a polymer block (C) that is phase-separable from the (meth)acrylic polymer block (D). For example, the difference ΔSP (absolute value) when comparing the SP value of the polymer block (C) calculated using a known solubility parameter (e.g., the Fedors method) with the SP value of the (meth)acrylic polymer block (D) can be set to 0.01 or more. The difference ΔSP can be, for example, 0.05 or more, 0.1 or more, or 0.5 or more. When using the Fedors method, the SP value can be calculated using the method described in "Polymer Engineering and Science" 14(2), 147 (1974) edited by R.Fedors. In addition, the phase separation between blocks can be easily inferred by observing the structure of the desired block copolymer (A) using electron microscopy, scanning probe microscopy, or small-angle X-ray scattering.

[0118] The block copolymer (A) is not particularly limited in terms of the number or arrangement of blocks, as long as it contains polymer blocks (C) and (meth)acrylic polymer blocks (D). Specific examples of block copolymers (A) include: a (CD) type diblock copolymer composed of polymer blocks (C) and (meth)acrylic polymer blocks (D); a (CDC) type triblock copolymer composed of polymer blocks (C)-(meth)acrylic polymer blocks (D)-polymer blocks (C); and a (DCD) type triblock copolymer composed of (meth)acrylic polymer blocks (D)-polymer blocks (C)-(meth)acrylic polymer blocks (D). Furthermore, the block copolymer (A) may further contain polymer blocks other than polymer blocks (C) and (meth)acrylic polymer blocks (D). Preferably, the block copolymer (A) is a triblock copolymer containing polymer blocks (C)-(meth)acrylic polymer blocks (D)-polymer blocks (C). If this structure is present, the block copolymer (A) can easily form a pseudo-crosslinked structure through the polymer blocks (C), thereby fully achieving the effect of improving adhesive performance and bond strength. The content of triblock copolymer in the block copolymer (A) is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 80% by mass or more.

[0119] The ratio of polymer blocks (C) to (meth)acrylic polymer blocks (D) in the block copolymer (A) (hereinafter also referred to as the "block ratio"), expressed as polymer block (C) / (meth)acrylic polymer block (D), is preferably 3 / 97 to 30 / 70 by mass. If the block ratio is within the above range, an adhesive composition that forms an adhesive layer with excellent flexibility and adhesion can be obtained by having a block copolymer (A) having polymer blocks (C) that constitute hard segments and can act as pseudo-crosslinking points and (meth)acrylic polymer blocks (D) that can form soft segments. Furthermore, by lowering the Tg of the polymer blocks (C) to, for example, below 100°C, preferably below 90°C, the block copolymer (A) is less prone to hardening even when the ratio of polymer blocks (C) is high. This allows for improved adhesive strength while ensuring the flexibility and feel of the bonded portion. From this perspective, a block ratio is more preferably 6 / 94 to 30 / 70, further preferably 7 / 93 to 30 / 70, and even more preferably 8 / 92 to 30 / 70. It should be noted that the block ratio can be calculated based on the monomers and / or polymer blocks used in the polymerization, and the monomer consumption as determined by gas chromatography (GC). The details of the calculation method are consistent with those described in the examples below.

[0120] • Method for manufacturing block copolymer (A)

[0121] Regarding the block copolymer (A), as long as a polymer having polymer blocks (C) and (meth)acrylic acid polymer blocks (D) can be obtained, its manufacturing method is not particularly limited and can be obtained by known manufacturing methods. Examples of manufacturing methods for the block copolymer (A) include various controlled polymerization methods such as living radical polymerization and living anionic polymerization, and methods of coupling polymers having functional groups together. Among these methods, living radical polymerization is preferred from the viewpoint of ease of operation and applicability to a wide range of monomers.

[0122] Living radical polymerization can be performed using any of the following processes: batch process, semi-batch process, dry continuous polymerization, and continuous stirred tank polymerization (CSTR). Furthermore, regarding the polymerization method, it can be applied to various methods such as solvent-free bulk polymerization, solvent-based solution polymerization, aqueous emulsion polymerization, miniemulsion polymerization, or suspension polymerization.

[0123] There are no particular restrictions on the type of living radical polymerization method; various polymerization methods can be used, including reversible addition-fragmentation chain transfer polymerization (RAFT), nitroacyl radical polymerization (NMP), atom transfer radical polymerization (ATRP), polymerization using organotellurium compounds (TERP), polymerization using organoantimony compounds (SBRP), polymerization using organobismuth compounds (BIRP), and iodine transfer polymerization. Among these, RAFT, NMP, and ATRP are preferred from the perspective of polymerization control and ease of implementation.

[0124] In the RAFT process, polymerization controlled by a reversible chain transfer reaction occurs in the presence of a specific polymerization controller (RAFT agent) and a general free radical polymerization initiator. Various known RAFT agents, such as dithioester compounds, xanthate compounds, trithiocarbonate compounds, and dithiocarbamate compounds, can be used as RAFT agents. As RAFT agents, monofunctional compounds with only one active site or compounds with two or more functionalities can be used. From the viewpoint of easily and efficiently obtaining block copolymers with three or more blocks, difunctional RAFT agents are preferred. The amount of RAFT agent used can be appropriately adjusted according to the type of monomer and RAFT agent.

[0125] As polymerization initiators used in RAFT polymerization, known free radical polymerization initiators such as azo compounds, organic peroxides, and persulfates can be used. Among these, azo compounds are preferred from the viewpoint of safety, ease of operation, and minimal side reactions that occur during free radical polymerization. Specific examples of azo compounds include: 2,2′-azobis(isobutyronitrile), 2,2′-azobis(2,4-dimethylpentanitrile), 2,2′-azobis(4-methoxy-2,4-dimethylpentanitrile), dimethyl-2,2′-azobis(2-methylpropionate), 2,2′-azobis(2-methylbutyronitrile), 1,1′-azobis(cyclohexane-1-carboxylonitrile), 2,2′-azobis[N-(2-propenyl)-2-methylpropionamide], and 2,2′-azobis(N-butyl-2-methylpropionamide). As polymerization initiators, only one type can be used, or two or more types can be used in combination. Furthermore, there is no particular limitation on the proportion of polymerization initiator used. From the viewpoint of conducting the polymerization reaction stably and obtaining polymers with smaller molecular weight distribution, it is preferable to use 0.01 moles or more and 0.5 moles or less of polymerization initiator relative to 1 mole of RAFT agent, and more preferably 0.01 moles or more and 0.2 moles or less.

[0126] In polymerization reactions using the RAFT method, the reaction temperature is preferably 40°C or higher and 100°C or lower, more preferably 45°C or higher and 90°C or lower, and even more preferably 50°C or higher and 80°C or lower. A reaction temperature of 40°C or higher allows for smooth polymerization, and is therefore preferred. Furthermore, a reaction temperature of 100°C or lower suppresses side reactions and reduces limitations on the available polymerization initiators and solvents, and is therefore preferred.

[0127] In the NMP process, specific alkoxyamine compounds with nitroxide radicals are used as living radical polymerization initiators, and polymerization is carried out by nitroxide radicals derived from the living radical polymerization initiator. In the manufacture of the block copolymer (A), there are no particular restrictions on the type of nitroxide radical, and commercially available nitroxide-based polymerization initiators can be used. From the viewpoint of controlling the polymerization when polymerizing monomers containing acrylates, compounds represented by the following formula (3) are preferred as nitroxide compounds.

[0128] [Chemistry 2]

[0129]

[0130] (In equation (3), R) 8 R represents an alkyl group having 1 to 2 hydrogen atoms or carbon atoms. 9 R represents an alkyl or nitrile group having 1 to 2 carbon atoms. 10Represents -(CH2)r-, where r represents an integer from 0 to 2, and R 11 and R 12 Each R independently represents an alkyl group having 1 to 4 carbon atoms. Multiple Rs in the formula... 11 They can be the same or different, and the multiple Rs in the formula 12 They can be the same or different.

[0131] The nitroxy compound shown in formula (3) above undergoes a single dissociation upon heating to approximately 70–80°C, followed by an addition reaction with the vinyl monomer. At this point, by adding the nitroxy compound to a vinyl monomer having two or more vinyl groups, a multifunctional polymerization precursor can be obtained. Next, by subjecting the polymerization precursor to a secondary dissociation under heating, the vinyl monomer can be subjected to living polymerization. In this case, the polymerization precursor has two or more active sites within the molecule, thus yielding a polymer with a narrower molecular weight distribution. For easy and efficient production of block copolymers (A), a difunctional polymerization precursor having two active sites within the molecule is preferred. The amount of nitroxy compound used can be appropriately adjusted depending on the type of monomer and the type of nitroxy compound.

[0132] When using the NMP method to manufacture block copolymer (A), 0.001 to 0.2 moles of nitroxide radicals as shown in formula (4) can be added to polymerize the product relative to 1 mole of the nitroxide compound shown in formula (3) above.

[0133] [Chemistry 3]

[0134]

[0135] (In equation (4), R) 13 and R 14 Each R independently represents an alkyl group having 1 to 4 carbon atoms. Multiple Rs in the formula... 13 They can be the same or different, and the multiple Rs in the formula 14 They can be the same or different.

[0136] By adding 0.001 moles or more of the nitroxide radicals shown in formula (4) above, the time it takes for the concentration of the nitroxide radicals to reach a stable state can be shortened. This allows for more precise control of polymerization, resulting in polymers with a narrower molecular weight distribution, which is therefore preferable. On the other hand, if too much nitroxide radical is added, polymerization may not proceed. A more preferred addition amount of nitroxide radicals relative to 1 mole of the nitroxide compound is in the range of 0.01 moles to 0.5 moles, and a further preferred addition amount is in the range of 0.05 moles to 0.2 moles.

[0137] The reaction temperature in the NMP process is preferably 50°C or higher and 140°C or lower, more preferably 60°C or higher and 130°C or lower, and even more preferably 70°C or higher and 120°C or lower. Maintaining a reaction temperature of 50°C or higher allows the polymerization reaction to proceed smoothly. Furthermore, maintaining a reaction temperature of 140°C or lower tends to suppress side reactions such as free radical chain transfer.

[0138] In the ATRP process, organohalides are typically used as polymerization initiators, and transition metal complexes are used as catalysts for the polymerization reaction. The organohalides used as polymerization initiators can be monofunctional or difunctional or more. From the viewpoint of easily and efficiently obtaining block copolymers (A), difunctional compounds are preferred. Brominates and chlorides are preferred types of halogens. The reaction temperature in the ATRP process is preferably 20°C or higher and 200°C or lower, more preferably 50°C or higher and 150°C or lower. Maintaining a reaction temperature of 20°C or higher allows for smooth polymerization, and is therefore preferred.

[0139] For example, when obtaining a (CDC) type triblock copolymer composed of polymer block (C) - (meth)acrylic polymer block (D) - polymer block (C) by living radical polymerization, the target block copolymer can be obtained by sequentially polymerizing each block. In this case, firstly, as a first polymerization step, the monomers constituting polymer block (C) are polymerized to obtain polymer block (C). Next, as a second polymerization step, the monomers constituting (meth)acrylic polymer block (D) are polymerized to obtain (meth)acrylic polymer block (D). Further, as a third polymerization step, the monomers constituting polymer block (C) are polymerized. Thus, a (CDC) type triblock copolymer can be obtained. As the polymerization initiator, the aforementioned monofunctional polymerization initiator or polymerization precursor is preferably used.

[0140] Furthermore, by using a difunctional polymerization initiator or polymerization precursor and employing a two-stage polymerization process as shown below to manufacture (CDC)-type triblock copolymers, the target material can be obtained more efficiently. First, as a first polymerization step, the monomers constituting polymer block (C) are polymerized to obtain polymer block (C). Then, as a second polymerization step, the monomers constituting (meth)acrylic acid polymer block (D) are polymerized. Thus, a (CDC)-type triblock copolymer can be obtained. According to this method, the process is simplified compared to manufacturing by sequentially polymerizing each block.

[0141] The polymerization of the block copolymer (A) can be carried out in the presence of a chain transfer agent as needed. Known chain transfer agents can be used as chain transfer agents. Specifically, examples include alkyl thiols having 2 to 20 carbon atoms, such as ethanethiol, 1-propanethiol, 2-propanethiol, 1-butanethiol, 2-butanethiol, 1-hexanethiol, 2-hexanethiol, 2-butylbutane-1-thiol, 1,1-dimethyl-1-pentanethiol, 1-dodecanethiol, tert-tetradecanethiol, 1-hexadecanethiol, and 1-octadecanethiol, as well as mercaptoacetic acid, mercaptopropionic acid, and 2-mercaptoethanol. One or more of these can be used as chain transfer agents.

[0142] In manufacturing the block copolymer (A), known polymerization solvents can be used in living radical polymerization. Specifically, examples include: aromatic compounds such as benzene, toluene, xylene, and anisole; ester compounds such as methyl acetate, ethyl acetate, propyl acetate, and butyl acetate; ketone compounds such as acetone and methyl ethyl ketone; and solvents such as dimethylformamide, acetonitrile, dimethyl sulfoxide, alcohols, and water. Alternatively, polymerization can be carried out without a solvent, via bulk polymerization or other methods.

[0143] [2] Random copolymer (A)

[0144] The above description of the (meth)acrylate polymer block (D) applies to specific and preferred examples of the Tg and constituent monomers of the random copolymer (A). However, from the viewpoint of ensuring the flexibility of the adhesive layer, in the random copolymer (A), the structural units derived from (meth)acrylates having 3 or more carbon atoms are preferably 80% by mass or less, more preferably 70% by mass or less, further preferably 60% by mass or less, and even more preferably 50% by mass or less, relative to all structural units of the random copolymer (A).

[0145] Furthermore, the random copolymer (A), like the (meth)acrylic polymer block (D), preferably contains structural units derived from monomers containing crosslinking groups, from the viewpoint of improving the adhesive strength between flexible adherends. Specific examples and preferred examples of the monomers containing crosslinking groups used in the manufacture of the random copolymer (A) are the same as those in the (meth)acrylic polymer block (D).

[0146] The proportion of crosslinkable structural units in the random copolymer (A) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, relative to all structural units of the random copolymer (A). Regarding the upper limit of the proportion of crosslinkable structural units, from the viewpoint of ensuring the flexibility of the adhesive layer, it is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, relative to all structural units of the random copolymer (A).

[0147] Random copolymers (A) can be obtained, for example, by polymerizing monomers using known free radical polymerization methods such as solution polymerization. In the case of producing random copolymers (A) using solution polymerization, an organic solvent and monomers are added to a reactor, a polymerization initiator is added, and the mixture is heated to 50°C to 300°C for copolymerization, thereby obtaining the desired random copolymer (A). The method of adding the raw materials containing the monomers can be an intermittent initial one-time addition of all raw materials, a semi-continuous addition of at least a portion of the raw materials being continuously fed into the reactor, or a continuous polymerization method in which all raw materials are continuously fed while the resin is continuously removed from the reactor.

[0148] Examples of organic solvents used in solution polymerization include: cyclic ethers such as tetrahydrofuran and dioxane; aromatic hydrocarbons such as benzene, toluene, and xylene; esters such as ethyl acetate and butyl acetate; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; and alcohols such as methyl orthoformate, methyl orthoacetate, methanol, ethanol, and isopropanol. One or more of these can be used as organic solvents. The amount of organic solvent used is such that the total amount of monomers used in the polymerization is, for example, 1% to 50% by mass relative to the total amount of organic solvent and monomers.

[0149] As a polymerization initiator, any known free radical polymerization initiator, such as azo compounds, organic peroxides, or inorganic peroxides, can be used; there are no particular limitations. Additionally, known redox polymerization initiators composed of an oxidizing agent and a reducing agent can be used. Furthermore, a known chain transfer agent can be used in conjunction with the polymerization initiator.

[0150] Specific examples of polymerization initiators, such as azo compounds, include: 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylpentanitrile), 4,4'-azobis(4-cyanopentanoic acid), 2-(tert-butylazo)-2-cyanopropane, 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(2-methylpropane), dimethyl 2,2'-azobis(2-methylpropionate), etc.

[0151] Examples of organic peroxides include: cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, 1,1-bis(tert-butylperoxide)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, dicumyl peroxide, and 2,5-dimethyl-2,5-di(benzoylperoxide)hexane.

[0152] Examples of inorganic peroxides include potassium persulfate and sodium persulfate. Examples of redox polymerization initiators include those that use sodium sulfite, sodium thiosulfate, sodium formaldehyde sulfoxylate, ascorbic acid, and ferrous sulfate as reducing agents, and potassium persulfate, hydrogen peroxide, and tert-butyl hydroperoxide as oxidizing agents. In the manufacture of random copolymers (A), the amount of polymerization initiator used is, for example, 0.01 to 20 parts by mass relative to 100 parts by mass of all monomers used in the polymerization.

[0153] From the viewpoint of obtaining an adhesive layer with superior adhesion, the (meth)acrylic polymer (A) incorporated in this composition is preferably a block copolymer (A).

[0154] From the viewpoint of ensuring sufficient adhesion of the adhesive layer obtained using this composition, the content of (meth)acrylic polymer (A) in this composition is preferably 70% by mass or more relative to the total amount of polymers contained in this composition. From the above viewpoint, the content of (meth)acrylic polymer (A) is more preferably 80% by mass or more relative to the total amount of polymers contained in this composition, and even more preferably 85% by mass or more.

[0155] <Other Ingredients>

[0156] This composition may contain only (meth)acrylic polymer (A), or may further contain polymers other than (meth)acrylic polymer (A), additives, solvents, and other components (hereinafter also referred to as "other components") as needed. The following describes other components that may be incorporated into this composition.

[0157] Vinyl polymer (B)

[0158] This composition may further contain a vinyl polymer (hereinafter also referred to as "vinyl polymer (B)") with a glass transition temperature (Tg) of 30°C or higher and 200°C or lower, and a number average molecular weight (Mn) of 500 or higher and 10,000 or lower, together with the (meth)acrylic polymer (A). By forming an adhesive layer using an adhesive composition containing both such vinyl polymer (B) and (meth)acrylic polymer (A), partial segregation of the vinyl polymer (B) can occur in the surface portion of the adhesive layer. This sufficiently increases the Tg of the surface portion of the adhesive layer, thereby improving the adhesion when bonding flexible substrates together.

[0159] If the Tg of the vinyl polymer (B) is 30°C or higher, then when forming an adhesive layer using the adhesive composition, the Tg of the surface portion of the adhesive layer can be increased, thus ensuring sufficient adhesion. On the other hand, due to limitations such as the monomers in the raw materials, the Tg of the vinyl polymer (B) is generally 200°C or lower. The Tg of the vinyl polymer (B) is preferably 40°C or higher, more preferably 50°C or higher, even more preferably 60°C or higher, even more preferably 70°C or higher, and even more preferably 75°C or higher. Regarding the upper limit of the Tg of the vinyl polymer (B), from the viewpoint of ensuring the elasticity of the adhesive layer, it is preferably 150°C or lower, more preferably 130°C or lower, even more preferably 120°C or lower, and even more preferably 110°C or lower.

[0160] The preferred range of Tg for the vinyl polymer (B) can be determined by appropriately combining the upper and lower limits of Tg mentioned above. The Tg range of the vinyl polymer (B) is preferably above 40°C and below 150°C, more preferably above 40°C and below 130°C, further preferably above 50°C and below 120°C, and even more preferably above 60°C and below 110°C.

[0161] Various vinyl monomers with free radical polymerizing properties can be used as monomers constituting the vinyl polymer (B). Examples of such vinyl monomers include compounds similar to those exemplified as constituent monomers of the (meth)acrylate polymer (A). From the viewpoint of having suitable compatibility with the (meth)acrylate polymer (A), the vinyl polymer (B) preferably contains structural units derived from hydrocarbon vinyl monomers. Specific examples of hydrocarbon vinyl monomers include: alkyl esters of (meth)acrylate, aliphatic cyclic esters of (meth)acrylate, aromatic esters of (meth)acrylate, and aromatic vinyl compounds. These compounds can be used individually or in combination of two or more.

[0162] In the vinyl polymer (B), the proportion of structural units derived from hydrocarbon vinyl monomers is preferably in the range of 30% by mass or more and 100% by mass or less, relative to all structural units of the vinyl polymer (B). More preferably, the proportion of structural units derived from hydrocarbon vinyl monomers is 50% by mass or more, further preferably 70% by mass or more, and even more preferably 80% by mass or more, relative to all structural units of the vinyl polymer (B).

[0163] When manufacturing the vinyl polymer (B), from the viewpoint of improving the adhesion by achieving a higher Tg, aliphatic cyclic vinyl monomers are preferred. The aliphatic cyclic vinyl monomer is preferably an aliphatic cyclic ester of (meth)acrylic acid; as a specific example, the same compound as the aliphatic cyclic ester of (meth)acrylic acid illustrated in the description of the (meth)acrylic polymer (A) can be cited.

[0164] In the vinyl polymer (B), the proportion of structural units derived from aliphatic cyclic vinyl monomers is preferably 1% by mass or more, more preferably 5% by mass or more, further preferably 10% by mass or more, even more preferably 15% by mass or more, and even more preferably 20% by mass or more, relative to all structural units in the vinyl polymer (B). Regarding the upper limit of the proportion of structural units derived from aliphatic cyclic vinyl monomers, it is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less, relative to all structural units in the vinyl polymer (B). The range of the proportion of structural units derived from aliphatic cyclic vinyl monomers is preferably 1% by mass or more and 90% by mass or less, more preferably 10% by mass or more and 80% by mass or less, and even more preferably 15% by mass or more and 70% by mass or less.

[0165] As a monomer constituting the vinyl polymer (B), from the viewpoint that the vinyl polymer (B) can be set to a high Tg, the vinyl polymer (B) tends to segregate to the surface when forming the adhesive layer, and has good heat resistance properties, at least one selected from tert-butyl methacrylate, isobornyl methacrylate, dicyclopentyl methacrylate, cyclohexyl methacrylate, and adamantane methacrylate can be preferably used.

[0166] The Mn of the vinyl polymer (B) is preferably 500 or more and 10,000 or less. By keeping the Mn of the vinyl polymer (B) below 10,000, sufficient segregation of the vinyl polymer (B) in the adhesive layer can be achieved, resulting in a significant improvement in adhesion. Furthermore, compatibility with the (meth)acrylic polymer (A) can be adequately ensured. By keeping the Mn of the vinyl polymer (B) above 500, the amount of polymerization initiator and chain transfer agent used during polymer manufacturing can be appropriately controlled, preventing a decrease in productivity.

[0167] The Mn of the vinyl polymer (B) is more preferably 1000 or more, further preferably 1500 or more, even more preferably 2000 or more, and even more preferably 3000 or more. Regarding the upper limit of the Mn of the vinyl polymer (B), it is more preferably 9500 or less, further preferably 9000 or less, even more preferably 7000 or less, and even more preferably 5000 or less. Furthermore, the range of Mn of the vinyl polymer (B) is more preferably 1000 or more and 9500 or less, further preferably 1000 or more and 9000 or less, even more preferably 1500 or more and 7000 or less, and even more preferably 2000 or more and 5000 or less.

[0168] In the vinyl polymer (B), from the viewpoint of easily obtaining good adhesive strength, the molecular weight distribution (Mw / Mn), expressed as the ratio of Mw to Mn, is preferably 3.0 or less. Mw / Mn is more preferably 2.5 or less, and even more preferably 2.0 or less. The lower limit of the Mw / Mn of the vinyl polymer (B) is not particularly limited, but is 1.0 or more.

[0169] There are no particular limitations on the manufacturing method of vinyl polymer (B), and it can be obtained by known manufacturing methods. Vinyl polymer (B) can be obtained by polymerizing the above monomers using known free radical polymerization methods such as solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization.

[0170] When vinyl polymer (B) is incorporated into the adhesive composition, the content of vinyl polymer (B), in terms of solids content, is preferably in the range of 0.5 to 15 parts by weight relative to 100 parts by weight of (meth)acrylate polymer (A). If the content of vinyl polymer (B) is 0.5 parts by weight or more, a sufficient amount of vinyl polymer (B) is present in the surface portion of the adhesive layer, and the effect of improving adhesion can be sufficiently obtained. In addition, if the content of vinyl polymer (B) is 15 parts by weight or less, the flexibility of the adhesive layer can be maintained to a higher extent, and the adhesion can be well maintained. From this point of view, the lower limit of the content of vinyl polymer (B) relative to 100 parts by weight of (meth)acrylate polymer (A) is more preferably 1 part by weight or more, and even more preferably 1.5 parts by weight or more. The upper limit of the content of vinyl polymer (B) relative to 100 parts by weight of (meth)acrylate polymer (A) is more preferably 10 parts by weight or less, and even more preferably 5 parts by weight or less.

[0171] When this composition contains a vinyl polymer (B), the preferred range of the content of the vinyl polymer (B) can be determined by appropriately combining the upper and lower limits of the content of the vinyl polymer (B) described above. Specifically, the content of the vinyl polymer (B) is preferably 0.5 to 10 parts by weight relative to 100 parts by weight of the (meth)acrylate polymer (A), more preferably 0.5 to 5 parts by weight, and even more preferably 1 to 5 parts by weight.

[0172] Crosslinking agent

[0173] When the (meth)acrylic polymer (A) has a crosslinking functional group, a crosslinking agent capable of reacting with this crosslinking functional group can be incorporated into the adhesive composition. By incorporating a crosslinking agent into this composition, the adhesive strength of the adhesive layer can be further improved. Thus, even when various soft substrates are bonded together, the adhesive strength of the adhesive layer can be improved while fully ensuring the softness and feel of the soft substrates.

[0174] Examples of crosslinking agents (curing agents) include epoxy crosslinking agents having two or more glycidyl groups; isocyanate crosslinking agents having two or more isocyanate groups; aziridine crosslinking agents having two or more aziridine groups; oxazoline crosslinking agents having oxazoline groups; metal chelate compounds; and butylated melamine compounds. From the viewpoint of easily adjusting the cohesion and adhesion of the adhesive layer, at least one of epoxy crosslinking agents, isocyanate crosslinking agents, and aziridine crosslinking agents is preferred. From the viewpoint of being able to form an adhesive layer with excellent cohesion, isocyanate crosslinking agents are preferred.

[0175] Specific examples of crosslinking agents, such as epoxy-based crosslinking agents, include: ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, tetraglycidyl dimethyl diamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, trimethylolpropane polyglycidyl ether, and other multifunctional glycidyl compounds.

[0176] Examples of isocyanate-based crosslinking agents include: aromatic isocyanate compounds such as diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), naphthalene diisocyanate (NDI), terephthalic diisocyanate (PPDI), xylene diisocyanate (XDI), tetramethylphenyl dimethyl diisocyanate (TMXDI), and bitoluene diisocyanate (TODI); aliphatic isocyanate compounds such as hexamethylene diisocyanate (HDI) and lysine diisocyanate (LDI); alicyclic isocyanate compounds such as isophorone diisocyanate (IPDI), cyclohexyl diisocyanate (CHDI), hydrogenated XDI (H6XDI), and hydrogenated MDI (H12MDI); and modified isocyanate compounds such as urethane-modified compounds, dimers, trimers, carbodiimide-modified compounds, urea-modified compounds, isocyanurate-modified compounds, oxazolidinone-modified compounds, and isocyanate-terminated prepolymers.

[0177] Examples of aziridinium-based crosslinking agents include: 1,6-bis(1-aziridinylcarbonylamino)hexane, 1,1'-(methylene-di-p-phenylene)bis-3,3-aziridinylurea, ethylene bis-(2-aziridinylpropionate), 2,4,6-triaziridinyl-1,3,5-triazine, and trimethylolpropane-tris(2-aziridinylpropionate).

[0178] When a crosslinking agent is incorporated into this composition, the content of the crosslinking agent is not particularly limited. Relative to 100 parts by weight of the (meth)acrylic polymer (A), the content of the crosslinking agent is preferably 0.01 to 10 parts by weight, more preferably 0.03 to 5 parts by weight, and even more preferably 0.05 to 2 parts by weight. By setting the content of the crosslinking agent within the above range, the improved adhesive strength resulting from the formation of the crosslinked structure can be sufficiently obtained, and the flexibility of the adhesive layer can be ensured.

[0179] ·Silane coupling agent

[0180] This composition may further contain a silane coupling agent. By combining an adhesive composition with a (meth)acrylic polymer (A) and a silane coupling agent, an adhesive layer with superior adhesion to flexible substrates can be obtained. Examples of silane coupling agents include those having one or more functional groups such as epoxy, (meth)acryloyl, amino, vinyl, thiol, isocyanate, and terminal isocyanate groups.

[0181] Specific examples of silane coupling agents, including epoxy-containing silane coupling agents, include: 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-epoxypropoxypropylmethyldimethoxysilane, 3-epoxypropoxypropylmethyldiethoxysilane, 3-epoxypropoxypropyltriethoxysilane, and 8-epoxypropoxyoctyltriethoxysilane, etc.; and oxy-hexyl-containing silane coupling agents such as 2-(3,4-oxecyclobutylcyclohexyl)ethyltrimethoxysilane, 3-oxecyclobutylpropyltrimethoxysilane, 3-oxecyclobutylpropylmethyldiethoxysilane, 3-oxecyclobutylpropyltriethoxysilane, and 8-oxecyclobutyloctyltriethoxysilane.

[0182] Specific examples of silane coupling agents having a (meth)acrylyl group include: 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 6-(meth)acryloxyhexyltrimethoxysilane, and 8-(meth)acryloxyoctyltrimethoxysilane, etc.

[0183] Specific examples of silane coupling agents containing amino groups include: 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltriethoxysilane, N-(3-cyclohexylamino)propyltrimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, etc.

[0184] Specific examples of silane coupling agents with thiol groups include 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane.

[0185] Specific examples of vinyl silane coupling agents include: vinyltrimethoxysilane, vinyltriethoxysilane, p-styryltrimethoxysilane, vinyl(trimethoxysilyl) ether, vinyl(methyldiethoxysilyl) ether, vinyl(triethoxysilyl) ether, etc.

[0186] Specific examples of silane coupling agents having isocyanate groups or terminal isocyanate groups include: isocyanate-methyltrimethoxysilane, 3-isocyanate-propyltrimethoxysilane, 6-isocyanate-hexyltrimethoxysilane, 8-isocyanate-octyltrimethoxysilane, isocyanate-methyltriethoxysilane, 3-isocyanate-propyltriethoxysilane, 6-isocyanate-hexyltriethoxysilane, 8-isocyanate-octyltriethoxysilane, and other isocyanate-alkyltrialkoxysilane compounds; isocyanate-methylmethyldimethoxysilane, 3-isocyanate-propylmethyldimethoxysilane, 6-isocyanate-hexylmethyldimethoxysilane, 8-isocyanate-octylmethyldimethoxysilane, isocyanate-methylmethyldiethoxysilane, 3-isocyanate-propylmethyldiethoxysilane, 6-isocyanate-hexylmethyldimethoxysilane, 8-isocyanate-octylmethyldimethoxysilane, isocyanate-methyldiethoxysilane, 3-isocyanate-propylmethyldiethoxysilane, 6-isocyanate-hexylmethyldimethoxysilane, etc. Isocyanate-based alkyl monoalkyl dialkoxysilane compounds such as ethoxysilane and 8-isocyanate-based octylmethyl diethoxysilane; isocyanate-based methyl dimethyl methoxysilane, 3-isocyanate-based propyl dimethyl methoxysilane, 6-isocyanate-based hexyl dimethyl methoxysilane, 8-isocyanate-based octyl dimethyl methoxysilane, isocyanate-based methyl dimethyl ethoxysilane, 3-isocyanate-based propyl dimethyl ethoxysilane, 6-isocyanate-based hexyl dimethyl ethoxysilane, isocyanate-based octyl dimethyl ethoxysilane; end-capped isocyanate-based alkyl alkoxysilane compounds in which the isocyanate group is protected by an isocyanate-based alkyl trimalkoxysilane compound, an isocyanate-based alkyl monoalkyl dialkoxysilane compound, or an isocyanate-based alkyl dialkyl alkoxysilane compound; etc.

[0187] For isocyanate-terminated alkylalkoxysilane compounds, there are no particular limitations on the protecting agent used to protect the isocyanate group, and known compounds can be appropriately used. Examples of protecting agents include alcohols (ethanol, etc.), caprolactams, dimethylpyrazole, and methyl ethyl ketone oxime. Furthermore, commercially available products can also be used as end-terminated isocyanate-terminated alkylalkoxysilane compounds. Examples of commercially available end-terminated isocyanate-terminated alkylalkoxysilane compounds, as trade names, include Shin-Etsu Silicone X-12-1195, Shin-Etsu Silicone X-12-1293, and Shin-Etsu Silicone X-12-1308ES (all manufactured by Shin-Etsu Chemical Industry Co., Ltd.).

[0188] From the viewpoint of improving the peel strength when bonding fibrous fabric with a film-like resin material, the silane coupling agent incorporated in this composition is particularly preferably a silane coupling agent selected from at least one of epoxy group, (meth)acryloyl group, isocyanate group and end-capped isocyanate group, and more preferably a silane coupling agent selected from at least one of isocyanate group and end-capped isocyanate group.

[0189] When a silane coupling agent is incorporated into this composition, the content of the silane coupling agent in this composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the (meth)acrylic polymer (A). Furthermore, the content of the silane coupling agent is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A). By ensuring the content of the silane coupling agent is within the above-mentioned range, the addition of the silane coupling agent can sufficiently improve the adhesive strength while ensuring the elasticity of the adhesive layer.

[0190] ·particle

[0191] Microparticles can be further incorporated into this composition. By preparing an adhesive composition incorporating microparticles together with (meth)acrylic polymer (A), an adhesive layer with further enhanced adhesion to various flexible substrates can be obtained.

[0192] The microparticles are not particularly limited as long as the effects of the present invention can be achieved. The microparticles incorporated in this composition can be inorganic or organic. Examples of inorganic materials constituting inorganic microparticles include silica, calcium carbonate, aluminum hydroxide, magnesium hydroxide, titanium dioxide, talc, glass (sodium glass, float glass, etc.), or combinations of two or more thereof. Examples of organic materials constituting organic microparticles include (meth)acrylic resins, polystyrene resins, polyurethane resins, polyolefin resins (e.g., polyethylene, polypropylene, etc.), silicone resins, epoxy resins, nylon resins, or combinations of two or more thereof. For example, examples of (meth)acrylic resins include homopolymers of methyl methacrylate, copolymers of methyl methacrylate with other monomers (e.g., styrene, vinyl acetate, methyl acrylate, ethyl acrylate, etc.), and cross-linked polymers of these homopolymers or copolymers. The microparticles can be hot-melt powders.

[0193] Among these, the microparticles are preferably organic microparticles, and more preferably microparticles formed using one or more selected from (meth)acrylic resins, polyurethane resins, and nylon resins. It should be noted that when the microparticles are formed from one or more resins selected from (meth)acrylic resins, polyurethane resins, and nylon resins, the resin can be a hot-melt resin. The shape of the microparticles is not particularly limited, but spherical microparticles are preferred.

[0194] The volume average particle size can be appropriately selected based on factors such as the thickness of the adhesive layer. Specifically, the volume average particle size is preferably 5 μm to 200 μm, more preferably 5 μm to 100 μm, and even more preferably 10 μm to 70 μm. It should be noted that the volume average particle size is a value measured using a laser diffraction / scattering particle size distribution measuring device.

[0195] When microparticles are incorporated into this composition, the content of microparticles in this composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the (meth)acrylic polymer (A). Furthermore, the content of microparticles is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic polymer (A). By ensuring the content of microparticles is within the above range, the elasticity and adhesion of the adhesive layer can be ensured.

[0196] • Tackifier

[0197] This composition may include a tackifier. Examples of tackifiers include: rosin derivatives such as rosin esters, rosin gum, tall oil rosin, hydrogenated rosin esters, maleic rosin, and disproportionated rosin esters; terpene resins mainly composed of terpene phenolic resins, α-pinene, β-pinene, or limonene; coumarone-indene resins, hydrogenated aromatic copolymers, and phenolic resins. A single tackifier may be used, or two or more may be used in combination. The content of the tackifier relative to the content of the (meth)acrylic polymer (A) is preferably 0% to 20% by mass, more preferably 0% to 10% by mass, and even more preferably 0% to 5% by mass.

[0198] Plasticizers

[0199] Plasticizers may be incorporated into this composition. Examples of plasticizers include: phthalates such as di-n-butyl phthalate, di-n-octyl phthalate, bis(2-ethylhexyl) phthalate, and di-n-decyl phthalate; adipates such as bis(2-ethylhexyl) adipate and di-n-octyl adipate; sebacates; azelaate esters; paraffins such as chlorinated paraffin; diols such as polypropylene glycol; epoxidized vegetable oils such as epoxidized soybean oil and epoxidized linseed oil; phosphates such as trioctyl phosphate and triphenyl phosphate; phosphites such as triphenyl phosphite; ester oligomers such as esterifications of adipic acid and 1,3-butanediol; low molecular weight polymers such as low molecular weight polybutene, low molecular weight polyisobutylene, and low molecular weight polyisoprene; and oils such as processing oils and naphthenic oils. The content of plasticizer relative to the content of (meth)acrylic polymer (A) is preferably 0% to 20% by mass, more preferably 0% to 10% by mass, and even more preferably 0% to 5% by mass.

[0200] In addition to the vinyl polymer (B), crosslinking agent, silane coupling agent, microparticles, tackifier, and plasticizer mentioned above, additives that can be incorporated into this composition may include, for example, antioxidants, ultraviolet absorbers, anti-aging agents, flame retardants, mildew inhibitors, fillers, colorants, and antistatic agents. The content of the additives can be appropriately set according to the various additives without impairing the effects of the present invention.

[0201] Solvent

[0202] This composition can be a solution-type adhesive composition formed by dissolving a (meth)acrylic polymer (A) and other desired components in a solvent. When this composition is a solution-type adhesive composition, an organic solvent capable of dissolving the (meth)acrylic polymer (A) can be used as the solvent in its preparation. Specific examples of organic solvents include: aprotic polar solvents, phenolic solvents, alcoholic solvents, ester solvents, ketone solvents, ether solvents, and hydrocarbon solvents. The organic solvent can be one of these or a mixture of two or more solvents. For example, by dissolving the (meth)acrylic polymer (A) in one or more organic solvents selected from ethyl acetate, butyl acetate, methyl ethyl ketone, and toluene, a solvent-type adhesive composition can be obtained. Alternatively, when preparing this composition, an aqueous medium capable of dispersing the (meth)acrylic polymer (A) can be used as the solvent to disperse the (meth)acrylic polymer (A) in the aqueous medium, thereby preparing this composition as an emulsion-type adhesive composition.

[0203] This composition only needs to contain a (meth)acrylic polymer (A), and its form is not particularly limited. For example, in addition to the (meth)acrylic polymer (A), it may also contain monofunctional and / or polyfunctional (meth)acrylic monomers and photopolymerization initiators, thereby constituting a so-called syrup-type photocurable adhesive composition that is cured using active energy rays such as ultraviolet light. In the case of a photocurable adhesive composition, the composition may contain solvents such as organic solvents, but it is usually prepared and used in a solvent-free form without solvents. In addition, this composition may be a solid or semi-solid adhesive composition containing the (meth)acrylic polymer (A) and other components as needed.

[0204] In the case of solution-type adhesive compositions, the concentration of solid components in the composition (i.e., the ratio of the mass of components other than the solvent in the adhesive composition to the total mass of the adhesive composition) is not particularly limited, but is preferably 1% to 70% by mass. If the solid component concentration is 1% by mass or more, an adhesive layer with sufficient thickness can be formed. Furthermore, if the solid component concentration is 70% by mass or less, good coatability can be ensured, and an adhesive layer of uniform thickness is easily formed. The solid component concentration in the adhesive composition is more preferably 5% to 60% by mass, and even more preferably 10% to 50% by mass.

[0205] <Manufacturing of Adhesive Layer>

[0206] This composition is applied to a release layer or similar material and dried as needed to form an adhesive layer. The release layer can be a resin film formed from various resin materials. Examples of such resin materials include polyester resins such as polyethylene terephthalate, polyethersulfone resins, acetate resins, polycarbonate resins, and polyolefin resins. For example, to form an adhesive layer using a liquid adhesive composition, the adhesive composition is applied to the release layer using a known coating method, and the solvent is removed by drying treatment such as heating. It should be noted that the heating temperature and heating time during adhesive layer formation can be appropriately set according to the type of solvent, the concentration of solid components, etc., as long as the solvent is removed.

[0207] <Properties of the Adhesive Layer>

[0208] • Energy storage modulus

[0209] The adhesive layer formed using this composition has a storage modulus (G′) of 1.0 MPa or less at 23°C. If the storage modulus at 23°C exceeds 1.0 MPa, the softness and feel of the bonded portion cannot be adequately ensured when soft adhered materials are bonded together. From the viewpoint of adequately ensuring the softness and feel of the bonded portion, the storage modulus of the adhesive layer at 23°C is preferably 0.8 MPa or less, more preferably 0.6 MPa or less, further preferably 0.5 MPa or less, and even more preferably 0.4 MPa or less.

[0210] It should be noted that, in this specification, the storage modulus of the adhesive layer at 23°C is obtained by measuring the shear viscoelasticity of an 800 μm thick adhesive layer under conditions of a heating rate of 2°C / min, a strain of 0.1%, and a measurement frequency of 1 Hz. Details of the method for measuring the storage modulus are as described in the examples below. The storage modulus of the adhesive layer can be arbitrarily adjusted by adjusting the composition and degree of crosslinking of the (meth)acrylic polymer (A), the Tg of any component (e.g., the vinyl polymer (B) described below, tackifiers, etc.), the amount added, etc. For example, as a constituent monomer of the (meth)acrylic polymer (A), one or more of alkyl (meth)acrylic esters having 1 to 4 carbon atoms and alkoxy (meth)acrylic alkoxyalkyl esters having 1 to 4 carbon atoms can be used, and the type and amount of these monomers can be adjusted, thereby adjusting the storage modulus of the adhesive layer.

[0211] Gel fraction

[0212] The gel fraction of the adhesive layer comprising this composition is preferably 90% or less. By keeping the gel fraction at 90% or less, both adhesion and elasticity when bonding soft adhered materials together can be achieved. From this viewpoint, the gel fraction of the adhesive layer is more preferably 80% or less, further preferably 70% or less, and particularly preferably 60% or less. It should be noted that, in this specification, the gel fraction of the adhesive layer is the ratio of the mass (W2) of the adhesive layer residue remaining after solvent impregnation to the initial mass (W1) of the adhesive layer (=(W2 / W1)×100[%)). Details are as described in the measurement method of the examples described later.

[0213] Products

[0214] The article of the present invention uses an adhesive layer formed from the above-described composition to bond flexible adherends together (excluding combinations of entirely fibrous fabrics, entirely conductive sheets, combinations of fibrous fabrics and conductive sheets, and combinations of fibrous fabrics and elastomer substrates). Specifically, the article of the present invention comprises a first adherend, a second adherend, and an adhesive layer, wherein the first adherend and the second adherend are bonded together by the adhesive layer formed from the present composition. Both the first and second adherends are flexible adherends, and are combinations different from those consisting entirely of fibrous fabrics, entirely conductive sheets, combinations of fibrous fabrics and conductive sheets, and combinations of fibrous fabrics and elastomer substrates. Even when flexible adherends are bonded together, the adhesive layer formed from the present composition can suppress resistance to bending and stretching of the bonded portions of the adherends, and exhibits excellent adhesion while maintaining the original feel.

[0215] According to this composition, when flexible adherends are bonded together, the flexibility, flexibility, and hand feel of the adherends can be maintained, and a highly adhesive layer can be formed. There are no particular limitations on the articles manufactured using this composition. For example, this composition can be used as an adhesive in the manufacture (e.g., for decoration) of a wide range of clothing materials for everyday wear, such as suits, kimonos, ethnic clothing, underwear, outerwear, tops, bottoms, outdoor products, work clothes, uniforms, formal wear, swimwear, sportswear, socks, hats, shoes, gloves, etc.; for craft purposes; for apparel and accessories (e.g., belts, bags, school bags, etc.); for sporting goods (e.g., bats, racket handles, gloves, etc.); for electronic components; for automotive interiors (e.g., car seats, seat belts, etc.); for gaskets; tires; furniture; and various daily necessities.

[0216] To obtain the article of the present invention, firstly, the flexible substrates are bonded together in such a way that they come into contact with each other via an adhesive layer formed of the present composition. Next, pre-pressing is performed as needed to form a laminate of flexible substrate / adhesive layer / flexible substrate. Then, by heating the laminate (preferably heat pressing), an article formed by bonding the substrates together using the adhesive layer formed of the present composition can be obtained.

[0217] When bonding materials together by heating and pressing, the bonding pressure should be appropriately set to achieve the desired bond strength. Furthermore, the heating temperature is preferably set below the heat resistance temperature of the flexible materials being bonded.

[0218] Example

[0219] The present invention will now be specifically described through examples. However, the present invention is not limited to these examples. It should be noted that, unless otherwise specified, "parts" and "%" refer to "parts by mass" and "% by mass," respectively. The analytical methods for the polymers used in the examples are described below.

[0220] <Molecular weight determination>

[0221] Using a gel permeation chromatography apparatus (model name "HLC-8320", manufactured by Tosoh Corporation), the number-average molecular weight (Mn) and weight-average molecular weight (Mw) based on polystyrene were obtained under the following conditions. Furthermore, the molecular weight distribution (Mw / Mn) was calculated based on the obtained values.

[0222] ○ Measurement conditions

[0223] Columns: 4 TSKgel SuperMultiporeHZ-M units manufactured by Tosoh Corporation

[0224] Column temperature: 40℃

[0225] Eluent: Tetrahydrofuran

[0226] Detector: RI

[0227] Flow rate: 600 μL / min

[0228] <Polymer monomer composition ratio (mass %)>

[0229] The monomer composition (mass%) of the polymer was calculated from the input amount and the monomer consumption determined by gas chromatography (GC). The GC determination was performed under the following conditions.

[0230] GC: Manufactured by Agilent Technologies (7820A GC System); Detector: FID; Column: 100% dimethylsiloxane (CP-Sil 5CB), column length 30m, column inner diameter 0.32mm; Calculation method: internal standard method.

[0231] <Glass transition temperature (Tg) of polymers>

[0232] The glass transition temperature (Tg) of the polymer was determined by the intersection of the baseline of the heat flux curve obtained using differential scanning calorimetry and the tangent at the inflection point. The heat flux curve was obtained under the following conditions: approximately 10 mg of the sample was cooled to -50 °C, held for 5 minutes, then heated to 250 °C at a rate of 10 °C / min, then cooled to -50 °C, held for 5 minutes, and then heated to 250 °C at a rate of 10 °C / min.

[0233] Measurement equipment: DSC6220 manufactured by SII NanoTechnology

[0234] Measurement atmosphere: under nitrogen atmosphere

[0235] 1. Synthesis of acrylic polymers

[0236] [Synthesis Example 1] (Synthesis of Polymer A-1)

[0237] In a four-necked flask equipped with a stirrer and thermometer, 95.5 parts by mass of n-butyl acrylate (hereinafter also referred to as "BA"), 4.5 parts by mass of 2-hydroxyethyl acrylate (hereinafter also referred to as "HEA"), and 183.8 parts by mass of ethyl acetate were added. The mixture was thoroughly degassed by bubbling with nitrogen, and the internal temperature of the mixture was raised to 75°C. 0.0472 parts by mass of 2,2'-azobis(2,4-dimethylbutyronitrile) (manufactured by Fujifilm and Koko Pure Chemical Industries, Ltd., trade name "V-65", hereinafter also referred to as "V-65") was added, and polymerization was carried out for 5 hours. Ethyl acetate was added at a solids concentration of 30% to obtain a binder solution containing polymer A-1. The Mn of polymer A-1 was 87,000, Mw was 468,000, and Mw / Mn was 5.4. The Tg was -40°C. The analytical results of polymer A-1 are shown in Table 2.

[0238] [Synthesis Example 2] (Synthesis of Polymer A-2)

[0239] The types and amounts of raw materials added to the flask were changed to those described in Table 1, and the same procedures as in Synthesis Example 1 were performed to obtain a binder solution containing polymer A-2. The analytical results of the polymer are shown in Table 2.

[0240] (Synthesis of polymer block C-3 and polymer A-3)

[0241] In a four-necked flask equipped with a stirrer and thermometer, dibenzyl trithiocarbonate (hereinafter, also known as "DBTTC") (1.59 parts by mass) as a RAFT agent, 2,2'-azobis(2-methylbutyronitrile) (hereinafter, also known as "ABN-E") (0.255 parts by mass) as a polymerization initiator, styrene (hereinafter, also known as "St") (37.5 parts by mass) and N-phenylmaleimide (hereinafter, also known as "PhMI") (62.5 parts by mass) as monomers, and acetonitrile (233.0 parts by mass) as a solvent were added. The mixture was thoroughly degassed by nitrogen bubbling, and polymerization was initiated in a thermostat at 70°C. After 3 hours, the reaction was stopped by cooling to room temperature. The polymerization solution was then purified by reprecipitation from methanol and vacuum dried to obtain polymer block C-3. The obtained polymer block C-3 had a Mn of 10900, a Mw of 12700, and a Mw / Mn ratio of 1.2. The glass transition temperature (Tg) of the polymer block C-3 is 206℃.

[0242] Next, in a 1L flask equipped with a stirrer and thermometer, the obtained polymer block C-3 (7.0 parts by mass), ABN-E as a polymerization initiator (0.0267 parts by mass), BA as a monomer (17.0 parts by mass), 2-methoxyethyl acrylate (hereinafter also referred to as "MEA") (78.0 parts by mass) and HEA (5.0 parts by mass), and acetonitrile as a solvent (35.7 parts by mass) were added. The mixture was thoroughly degassed by bubbling with nitrogen, and polymerization was initiated in a thermostat at 70°C. After 6 hours, the mixture was cooled to room temperature, and ethyl acetate was added to adjust the solids concentration to 30% by mass, resulting in a binder solution containing a (CDC) type triblock copolymer A-3 having polymer block (C) and (meth)acrylic acid polymer block (D). The obtained polymer A-3 had a Mn of 160,000, a Mw of 283,000, and a Mw / Mn ratio of 1.8. The glass transition temperature (Tg) of polymer A-3 is -35℃.

[0243] In addition, in the synthesis of polymer A-3 using polymer block C-3 and monomers (BA, MEA, HEA), polymer block C-1 was replaced with an equal amount of DBTTC used in the synthesis of polymer block C-1. Otherwise, polymerization was carried out in the same manner, resulting in a polymer with a glass transition temperature Tg (which was taken as the glass transition temperature of polymer block D-3) of -35°C. The analytical results of polymer A-3 are shown in Table 2.

[0244] It should be noted that the "C / D block ratio" in Table 2 represents the ratio (mass ratio) of polymer blocks (C) to (meth)acrylic polymer blocks (D) in the acrylic polymer. The C / D block ratio is expressed as "Q1 / Σ(Q2×γ)" using the amount of polymer blocks (C), the amount of each monomer, and the GC reaction rate (= monomer consumption rate determined by GC) used in the synthesis of the acrylic polymer. Here, Q1 represents the amount (parts by mass) of polymer blocks (C) used in the synthesis of the acrylic polymer, Q2 represents the amount (parts by mass) of each monomer, and γ represents the GC reaction rate of each monomer.

[0245] [Synthetic Examples 4-8] (Synthesis of polymer blocks C-4-C-8 and polymers A-4-A-8)

[0246] The types and amounts of raw materials added to the flask were changed as described in Table 1. The reaction time for obtaining polymer blocks C-4 to C-8 was set to 6 hours. Otherwise, the same operation as in Synthesis Example 3 was performed to obtain polymer blocks C-4 to C-8, and binder solutions containing polymers A-4 to A-8 were obtained. It should be noted that the glass transition temperatures of polymer blocks D-4 to D-8 were determined in the same manner as for polymer D-3. The analytical results for each polymer are shown in Table 2.

[0247] [Table 1]

[0248]

[0249] [Table 2]

[0250]

[0251] The abbreviations for the monomers in Tables 1 and 2 are shown below.

[0252] St: Styrene

[0253] PhMI: N-Phenylonmaleimide

[0254] BA: Butyl acrylate

[0255] EA: Ethyl acrylate

[0256] HA: 2-Ethylhexyl acrylate

[0257] HEA: 2-Hydroxyethyl acrylate

[0258] MEA: 2-Methoxyethyl Acrylate

[0259] AA: Acrylic acid

[0260] 2. Synthesis of Vinyl Polymers

[0261] [Synthesis Example 9] (Synthesis of Polymer B-1)

[0262] In a four-necked flask equipped with a stirrer and a thermometer, a mixture of butyl acetate (200 parts by mass) and dimethyl-2,2'-azobis(2-methylpropionate) (manufactured by Fujifilm and Kouichi Chemical Co., Ltd., trade name "V-601", hereinafter also referred to as "V-601") (0.9 parts by mass) was added. The mixture was thoroughly degassed by bubbling with nitrogen, and the internal temperature of the mixture was raised to 90°C. Separately, a mixture of methyl methacrylate (hereinafter also referred to as "MMA") (165 parts by mass), isobornyl methacrylate (hereinafter also referred to as "IBXMA") (44 parts by mass), V-601 (17 parts by mass), and butyl acetate (90 parts by mass) was added dropwise to the flask over 5 hours via a dropping funnel, thereby initiating polymerization. After the addition was complete, the polymerization solution was added dropwise to a mixed solution of methanol (4800 parts by mass) and distilled water (1200 parts by mass), thereby separating the vinyl polymer from the polymerization solution to obtain polymer B-1. The monomer composition of the obtained polymer B-1 was calculated from the input amount and the monomer consumption determined by GC, and the result was composed of MMA 80% by mass and IBXMA 20% by mass, with Mw of 6700, Mn of 4370, and Mw / Mn of 1.53. The Tg was 108℃. The composition and analytical results of polymer B-1 are shown in Table 3.

[0263] [Synthesis Example 10] (Synthesis of Polymer B-2)

[0264] A mixture of butyl acetate (200 parts by mass) and V-601 (6.2 parts by mass) was added to a four-necked flask equipped with a stirrer and a thermometer. The mixture was thoroughly degassed by bubbling with nitrogen, and the internal temperature of the mixture was raised to 90°C. Separately, a mixture of MMA (100 parts by mass), IBXMA (109 parts by mass), V-601 (20 parts by mass), and butyl acetate (90 parts by mass) was added dropwise to the flask over 5 hours via a dropping funnel to initiate polymerization. After the addition was complete, the polymerization solution was added dropwise to a mixture of methanol (4800 parts by mass) and distilled water (1200 parts by mass) to separate the vinyl polymer from the polymerization solution, yielding polymer B-2. The monomer composition of polymer B-2 was calculated from the input amount and the monomer consumption determined by GC. The result was composed of 50% MMA and 50% IBXMA, with Mw of 3080, Mn of 5340, and Mw / Mn of 1.73. The Tg was 88℃. The composition and analytical results of polymer B-2 are shown in Table 3.

[0265] [Table 3]

[0266]

[0267] The abbreviations for the monomers in Table 3 are shown below.

[0268] MMA: Methyl methacrylate

[0269] IBXMA: Isoborneol Methacrylate

[0270] 3. Manufacturing of adhesive layer and adhesive film

[0271] [Example 1]

[0272] An adhesive solution containing polymer A-1 obtained in Synthesis Example 1 was used as an adhesive composition for flexible substrates and coated onto a 50 μm thick polyethylene terephthalate (PET) release liner with a dried thickness of 100 μm. The adhesive composition for flexible substrates was dried at 100°C for 6 minutes to remove volatile components, forming an adhesive layer. A 38 μm thick PET release liner with a different peel strength than the release liner coated with the adhesive composition for flexible substrates was bonded to the surface of the adhesive layer to obtain an adhesive film sample with release liners on both sides.

[0273] [Examples 2, 5, 7-10 and Comparative Example 1]

[0274] For Examples 2, 5, 7-10 and Comparative Example 1, adhesive compositions for flexible substrates were prepared based on the compositions shown in Tables 5 and 6, and adhesive film samples were obtained by operating in the same manner as in Example 1.

[0275] [Example 3]

[0276] In the adhesive solution containing polymer A-2 obtained in Synthesis Example 2, a polymer (B-1) solution with a solid content concentration of 30% by mass was prepared by mixing polymer B-1 (4 parts by mass) dissolved in acetonitrile, and a solution containing polymer A-2 (100 parts by mass) and polymer B-1 (4 parts by mass) with a solid content concentration of 30% by mass was prepared as an adhesive composition for flexible adhesives.

[0277] The flexible adhesive composition for adhered materials was coated onto a 50 μm thick PET release layer with a dried thickness of 100 μm. The flexible adhesive composition for adhered materials was dried at 100°C for 6 minutes to remove volatile components, forming an adhesive layer. A 38 μm thick PET release layer with a different peel strength than the release layer coated with the flexible adhesive composition for adhered materials was then bonded to the surface of the adhesive layer to obtain an adhesive film sample with release layers on both sides.

[0278] [Examples 4, 6, 11, 18]

[0279] For Examples 4, 6, 11, and 18, based on the compositions shown in Tables 5 and 6, the same procedures as in Example 3 were followed to obtain adhesive film samples with double-sided release layers. It should be noted that for Examples 4 and 18, which incorporated "TAKENATE D-110N" manufactured by Mitsui Chemicals Co., Ltd. as an isocyanate-based crosslinking agent, after laminating a 38 μm thick PET release layer, the samples were aged at 40°C for 5 days to obtain adhesive film samples with double-sided release layers. In Tables 5 and 6, the amount of isocyanate-based crosslinking agent (TAKENATE D-110N) indicates the amount of solid component.

[0280] [Example 12]

[0281] In the adhesive solution containing polymer A-4 obtained in Synthesis Example 4, a polymer (B-2) solution with a solid content concentration of 30% by mass was prepared by dissolving polymer B-2 (2 parts by mass) in acetonitrile. A solution containing polymer A-4 (100 parts by mass) and polymer B-2 (2 parts by mass) with a solid content concentration of 30% by mass was then prepared. A silane coupling agent containing isocyanate groups, "Shin-Etsu Organosilicon KBE-9007N" (1.0 part by mass), manufactured by Shin-Etsu Chemical Industry Co., Ltd., was then mixed in as an additive to obtain an adhesive composition for flexible adhered materials.

[0282] The flexible adhesive composition for adhered materials was coated onto a 50 μm thick PET release layer with a dried thickness of 100 μm. The flexible adhesive composition was dried at 100°C for 6 minutes to remove volatile components, forming an adhesive layer. A 38 μm thick PET release layer, with a different peel strength than the release layer coated with the flexible adhesive composition, was then bonded to the surface of the adhesive layer to obtain an adhesive film sample with release layers on both sides.

[0283] [Examples 13-17]

[0284] For Examples 13-17, the same procedures as in Example 12 were performed based on the compositions shown in Tables 5 and 6 to obtain adhesive film samples.

[0285] 4. Evaluation

[0286] Various measurements and evaluations were performed using adhesive film samples and commercially available urethane hot melt adhesive films (100 μm thick). The results are shown in Tables 5 and 6.

[0287] <Gel fraction>

[0288] 0.2 g of adhesive was collected from the adhesive film sample, and its initial mass was weighed. The collected adhesive was immersed in 50 g of ethyl acetate and allowed to stand at room temperature for 16 hours. Then, it was filtered through a 200-mesh metal mesh, and the residue remaining on the mesh was dried at 80°C for 3 hours and weighed. The gel fraction (%) was calculated based on the initial mass and the mass of the residue.

[0289] <Storage modulus G' at room temperature (23°C)>

[0290] A 50 μm thick adhesive film sample was laminated with an adhesive layer or a urethane hot melt adhesive film to prepare a test piece with an 800 μm thick adhesive layer. This test piece was punched into a 1 cm diameter circle. Using a Physica MCR301 shear viscoelasticity measuring device (Antonpah), the dynamic viscoelasticity was measured while simultaneously heating from -50°C to 150°C at a rate of 2°C / min, with a strain of 0.1% and a frequency of 1 Hz. The storage modulus G′ at 23°C was recorded. It should be noted that a parallel plate with a diameter of 8 mm was used in the measurement.

[0291] <Evaluation of peel strength>

[0292] The adhesive layer or urethane hot melt adhesive film of the adhesive film sample is sandwiched between the back of a woven fabric composed of nylon and polyurethane (hereinafter referred to as "nylon / polyurethane woven fabric", 150 μm thick) and a PET film (untreated, 50 μm thick), and temporarily bonded by hand roller. The temporarily bonded fabric laminate is then hot-pressed at 120°C and 3 kg / cm². 2 After pressing for 30 seconds, the nylon / polyurethane woven fabric was cut into 25mm wide pieces along the warp direction to prepare test pieces. For these test pieces, the T-peel strength was measured using an INSTRON 5566A tensile testing machine with a thermostatic bath (manufactured by Instron Japan) at a temperature of 23°C, a test piece width of 25mm, and a peel speed of 300mm / min. Additionally, the T-peel strength was measured similarly with different substrates as shown in Table 4.

[0293] [Table 4]

[0294]

[0295] <Hand-touch test: feel>

[0296] Using a laminate made in the same manner as the peel strength evaluation, the flexural stiffness when the bonded area is bent by hand is evaluated according to the following benchmarks.

[0297] ○: No difference in hardness can be felt before and after bonding.

[0298] ×: After bonding, it feels harder than before bonding.

[0299] <Bending Test: Bending Performance>

[0300] The cut size was set to 50mm × 100mm, and the test pieces were prepared in the same manner as for the peel strength evaluation. Additionally, test pieces without an adhesive layer and adhesive film were prepared, except for the adhesive film sample without overlapping the adhesive layer and urethane hot melt adhesive film, in the same manner as for the peel strength evaluation. With the short sides of the prepared test pieces in contact with each other, a 180° bend was made with the adherend 1 as the inside, and the end was pinched for 1cm by hand. The change in the radius of curvature of the bend was observed. Similarly, the change in the radius of curvature was observed with the adherend 2 as the inside. In the cases of bending with the adherend 1 as the inside and bending with the adherend 2 as the inside, the case with the largest change in radius of curvature was evaluated according to the following criteria.

[0301] ○: The radius of curvature of the bent portion is the same as that in the case without an adhesive layer and adhesive film.

[0302] △: The radius of curvature of the bent portion is slightly larger compared to the case without an adhesive layer and adhesive film.

[0303] ×: The radius of curvature of the bent portion is significantly larger compared to the case without an adhesive layer and adhesive film.

[0304] [Table 5]

[0305]

[0306] [Table 6]

[0307]

[0308] The abbreviations for the additives in Tables 5 and 6 are as follows.

[0309] KBE-9007N: A silane coupling agent containing isocyanate groups, "Shin-Etsu Organosilicon KBE-9007N", manufactured by Shin-Etsu Chemical Industry Co., Ltd.

[0310] KBM-403: Shin-Etsu Organosilicon KBM-403, an epoxy-containing silane coupling agent manufactured by Shin-Etsu Chemical Industry Co., Ltd.

[0311] KBM-503: A silane coupling agent containing (meth)acryloyl groups, "Shin-Etsu Organosilicon KBM-503", manufactured by Shin-Etsu Chemical Industry Co., Ltd.

[0312] KBM-903: An amino-containing silane coupling agent, "Shin-Etsu Organosilicon KBM-903," manufactured by Shin-Etsu Chemical Industry Co., Ltd.

[0313] PMMA microparticles: Cross-linked polymethyl methacrylate orthospherical microparticles "Techpolymer MBX-50", manufactured by Sekisui Chemicals Co., Ltd., with an average particle size of 50μm.

[0314] TAKENATE D-110N: Isocyanate-based crosslinking agent "TAKENATE D-110N", manufactured by Mitsui Chemicals Co., Ltd.

[0315] As shown in Tables 5 and 6, the adhesive compositions for flexible substrates in Examples 1 to 18 can form adhesive layers that exhibit high adhesion even when various flexible substrates are bonded together, and also provide good flexibility and a pleasant feel at the bonded areas. Particularly when using block copolymers as the acrylic polymer, the peel strength is excellent. Furthermore, in Examples 7 to 9 and 11 to 18, where block copolymers are used as the acrylic polymer and the Tg of the polymer block (C) is less than 95°C, even higher peel strength is observed, along with good flexibility and a pleasant feel at the bonded areas.

[0316] Furthermore, in Examples 12-14, which used isocyanate-containing silane coupling agents, epoxy-containing silane coupling agents, or (meth)acryloyl-containing silane coupling agents as silane coupling agents, the adhesion of nylon / polyurethane fabric to PET film was significantly improved compared to Example 15, which used an amino-containing silane coupling agent. Additionally, in Examples 16-18, which used block copolymers as acrylic polymers and incorporated microparticles or crosslinking agents, the adhesion to various flexible substrates was significantly improved. Further, as shown in the comparison between Examples 11-18 and Example 7, the adhesion to various flexible substrates was further improved by incorporating a vinyl polymer (B).

[0317] In contrast, the adhesive layer of Comparative Example 1, which has a storage modulus of 2.0 MPa at 23°C, and Comparative Example 2, which uses a urethane hot melt adhesive film, have insufficient feel and flexibility at the bonding sites.

[0318] The results above indicate that by using an adhesive composition containing a (meth)acrylic polymer (A) with a weight-average molecular weight of 100,000 or more and a glass transition temperature of -80°C or more and 10°C or less, and an adhesive layer with a storage modulus of 1.0 MPa or less at 23°C, an adhesive layer with good adhesion can be formed when flexible adherends are bonded together, while maintaining the flexibility and feel of the bonded parts well.

Claims

1. An adhesive composition for flexible substrates, characterized in that, This is used to form an adhesive layer for bonding flexible substrates together, excluding bonding of fibrous fabrics to each other, bonding of conductive sheets to each other, bonding of fibrous fabrics to conductive sheets, and bonding of fibrous fabrics to an elastomer substrate. The adhesive composition for flexible substrates contains a (meth)acrylic polymer (A) with a weight average molecular weight of 100,000 or more and a glass transition temperature of -80°C or more and 10°C or less. The energy storage modulus of the adhesive layer at 23°C is below 1.0 MPa.

2. The adhesive composition for flexible substrates according to claim 1, wherein, The (meth)acrylic polymer (A) is a block copolymer having a polymer block (C) with a glass transition temperature of 10°C or higher and 250°C or lower, and a (meth)acrylic polymer block (D) with a glass transition temperature of -80°C or higher and less than 10°C.

3. The adhesive composition for flexible substrates according to claim 2, wherein, The glass transition temperature of the polymer block (C) is above 10°C and below 90°C.

4. The adhesive composition for flexible substrates according to claim 2, wherein, The polymer block (C) comprises a structural unit (U1) derived from an imide-containing vinyl monomer and a structural unit (U2) derived from a (meth)acrylic acid monomer, and the total proportion of the structural unit (U1) and the structural unit (U2) is 80% by mass or more relative to all the structural units of the polymer block (C).

5. The adhesive composition for flexible substrates according to claim 2, wherein, The (meth)acrylate polymer block (D) comprises structural units derived from (meth)acrylate compounds having 3 or more carbon atoms, accounting for more than 20% by mass of all structural units of the (meth)acrylate polymer block (D).

6. The adhesive composition for flexible adhered materials according to claim 1, wherein, The (meth)acrylic polymer (A) comprises structural units derived from at least one selected from (meth)acrylic alkyl esters and (meth)acrylic alkoxyalkyl esters.

7. The adhesive composition for flexible substrates according to claim 1, wherein, The adhesive composition for flexible adherends further contains a vinyl polymer (B) having a glass transition temperature of 30°C or higher and 200°C or lower, and a number-average molecular weight of 500 or higher and 10,000 or lower.

8. The adhesive composition for flexible substrates according to claim 7, wherein, The vinyl polymer (B) comprises structural units derived from aliphatic cyclic vinyl monomers.

9. The adhesive composition for flexible substrates according to claim 7, wherein, The content of the vinyl polymer (B) is 0.5 parts by mass and less than 10 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer (A).

10. The adhesive composition for flexible substrates according to claim 1, wherein, The adhesive composition for flexible adherends also contains a silane coupling agent.

11. The adhesive composition for flexible substrates according to claim 10, wherein, The silane coupling agent has at least one selected from epoxy, (meth)acryloyl, isocyanate, and capped isocyanate groups.

12. The adhesive composition for flexible substrates according to claim 1, wherein, The adhesive composition for flexible substrates also contains an isocyanate-based crosslinking agent.

13. The adhesive composition for flexible substrates according to claim 1, wherein, The adhesive composition for flexible substrates also contains microparticles.

14. An article characterized in that, have: First adhered object; The second adhered object; and Adhesive layer, The first and second objects are bonded together by the adhesive layer. Both the first and second adherends are flexible adherends, excluding those that are both fiber fabrics, both that are conductive sheets, combinations of fiber fabrics and conductive sheets, and combinations of fiber fabrics and elastomer substrates. The adhesive layer is formed from the adhesive composition for flexible substrates according to any one of claims 1 to 13.

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