Pressure-sensitive adhesive tape and electronic device

Abstract

A purpose of the present invention is to provide a pressure-sensitive adhesive tape that has excellent level-difference conformability and excellent bending resistance, and that is capable of maintaining adhesion reliability even in a high-temperature and high-humidity environment. Another purpose of the present invention is to provide an electronic device including said pressure-sensitive adhesive tape. The present invention pertains to a pressure-sensitive adhesive tape that has a pressure-sensitive adhesive agent layer having a foamed structure. The pressure-sensitive adhesive agent layer contains an acrylic copolymer that has structural units derived from a (meth)acrylic acid ester having a hydrocarbon group. The structural units derived from a (meth)acrylic acid ester having a hydrocarbon group are represented by formula (1), and include a structural unit derived from a (meth)acrylic acid ester that, when being formed into a homopolymer, exhibits a glass transition temperature of 120°C or more. In the formula, R1 represents a hydrogen atom or a methyl group, R2 represents a hydrogen atom or a hydrocarbon group, and R3 and R4 each independently represent a hydrocarbon group or are bonded as R3-C-R4 to form a cyclic hydrocarbon group.

Description

Adhesive tape, and electronic device

[0001] The present invention relates to an adhesive tape. The present invention also relates to an electronic device including the adhesive tape.

[0002] Conventionally, when fixing parts in various industrial applications such as electronic devices, vehicles, houses, and building materials, an adhesive tape having an adhesive layer containing an adhesive has been widely used (for example, Patent Documents 1 to 3). Specifically, for example, an adhesive tape is used to adhere a cover panel for protecting the surface of a portable electronic device to a touch panel module or a display panel module, or to adhere a touch panel module and a display panel module.

[0003] Japanese Patent Application Laid-Open No. 2015-052050, Japanese Patent Application Laid-Open No. 2015-021067, Japanese Patent Application Laid-Open No. 2015-120876

[0004] In recent years, with the thinning of electronic devices such as smartphones and wearable devices, an adhesive tape for fixing parts of an electronic device is required to have better step following performance and be strong against bending (excellent bending resistance).

[0005] Further, with the extension of the service life of electronic devices in recent years, the level of durability required in a high-temperature and high-humidity environment has been improved, and an adhesive tape for fixing parts of an electronic device is required not to deteriorate even in a high-temperature and high-humidity environment for a long time and to maintain adhesive reliability.

[0006] An object of the present invention is to provide an adhesive tape having excellent step following performance and excellent bending resistance, and capable of maintaining adhesive reliability even in a high-temperature and high-humidity environment. Another object of the present invention is to provide an electronic device including the adhesive tape.

[0007] Disclosure 1 is an adhesive tape having an adhesive layer having a foamed structure, wherein the adhesive layer contains an acrylic copolymer having constituent units derived from a (meth)acrylic acid ester having a hydrocarbon group, and the constituent units derived from the (meth)acrylic acid ester having a hydrocarbon group are represented by the following formula (1), and the constituent units derived from the (meth)acrylic acid ester have a glass transition temperature of 120°C or higher when homopolymerized. Disclosure 2 is an adhesive tape having the following formula (1) R １Disclosure 1 is an adhesive tape wherein the group is a methyl group. Disclosure 3 is an adhesive tape of Disclosure 2 in which the constituent units derived from a (meth)acrylic acid ester represented by the following formula (1) and having a glass transition temperature of 120°C or higher when homopolymerized are constituent units derived from isobornyl methacrylate. Disclosure 4 is an adhesive tape of Disclosure 3 in which the content of the constituent units derived from isobornyl methacrylate in the acrylic copolymer is 30% by mass or less. Disclosure 5 is an adhesive tape of Disclosure 1, 2, 3, or 4 in which the constituent units derived from a (meth)acrylic acid ester having a hydrocarbon group are at least one constituent unit selected from the group consisting of a constituent unit derived from n-hexyl (meth)acrylic acid, a constituent unit derived from n-heptyl (meth)acrylic acid, and a constituent unit derived from 1-methylheptyl (meth)acrylic acid. Disclosure 6 is an adhesive tape according to Disclosure 1, 2, 3, 4, or 5, wherein the acrylic copolymer has structural units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminal. Disclosure 7 is an adhesive tape according to Disclosure 6, wherein the content of structural units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminal in the acrylic copolymer is 5% by mass or more and 30% by mass or less. Disclosure 8 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, or 7, wherein the acrylic copolymer has structural units derived from a monomer having a crosslinkable functional group. Disclosure 9 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the acrylic copolymer includes a block copolymer having at least one block having structural units derived from a (meth)acrylic acid ester having a hydrocarbon group and at least one block having structural units derived from a vinyl aromatic compound. Disclosure 10 is an adhesive tape according to Disclosure 9, wherein the content of constituent units derived from the vinyl aromatic compound in the acrylic copolymer is 2.5% by mass or more and 20% by mass or less.Disclosure 11 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the adhesive layer contains an aromatic block copolymer (X) having at least two blocks having structural units derived from a vinyl aromatic compound, and at least one of a block having structural units derived from a conjugated diene compound and a hydrogenated body of a block having structural units derived from a conjugated diene compound. Disclosure 12 is an adhesive tape according to Disclosure 11, wherein the content of the aromatic block copolymer (X) is 60 parts by mass or less per 100 parts by mass of the acrylic copolymer. Disclosure 13 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the adhesive layer contains a pigment. Disclosure 14 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein the adhesive layer contains a tackifying resin. Disclosure 15 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein the adhesive layer does not contain a tackifying resin. Disclosure 16 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, wherein the adhesive layer has a structure derived from a crosslinking agent. Disclosure 17 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, wherein the adhesive layer has a gel fraction of 10% by mass or more and 70% by mass or less. Disclosure 18 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17, wherein the adhesive layer has a bio-derived carbon content of 10% or more. Disclosure 19 is an adhesive tape according to Disclosures 19, wherein the adhesive layer has a deemed density of 0.59 g / cm³. ３ 1.15g / cm or more ３The following are adhesive tapes according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18. Disclosure 20 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19, wherein the adhesive layer has an average major diameter of bubbles of 0.80 times or less the thickness of the adhesive layer. Disclosure 21 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, wherein the adhesive layer has a structure in which no bubbles are exposed on the surface in the thickness direction. Disclosure 22 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 21, which does not have a base material. Disclosure 23 is an adhesive tape according to Disclosure 22, which consists only of the adhesive layer. Disclosure 24 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 21, which has a base material and has the adhesive layer on at least one surface of the base material. Disclosure 25 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, or 24, further having a second adhesive layer without a foamed structure on at least one side of the adhesive layer. Disclosure 26 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25, wherein the adhesive tape has a 180° peel force of 10 N / 25 mm or more at 23°C on the side with the foamed adhesive layer. Disclosure 27 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, or 26, having a thickness of 60 μm or more and 300 μm or less. Disclosure 28 is an adhesive tape according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, or 27, used for fixing electronic equipment components or automotive components.The electronic device 29 of the present disclosure includes the adhesive tape of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27 or 28.

[0008] In the formula, R １ represents a hydrogen atom or a methyl group, and R ２ represents a hydrogen atom or a hydrocarbon group, and R ３ and R ４ each independently represents a hydrocarbon group, or the bond R ３ -C-R ４ forms a cyclic hydrocarbon group.

[0009] Hereinafter, the present invention will be described in detail. Hereinafter, an embodiment of the present invention or one thereof will be described as "this embodiment".

[0010] The inventors of the present invention considered that, for an adhesive tape having an adhesive layer with a foamed structure, the monomer constituting the acrylic copolymer contained in the adhesive layer has a specific structure and a glass transition temperature of a specific value or more. As a result, they found that an adhesive tape having excellent step-following properties, excellent bending resistance, and capable of maintaining adhesive reliability even in a high-temperature and high-humidity environment can be obtained, and thus completed the present invention.

[0011] The adhesive tape of this embodiment has an adhesive layer with a foamed structure. Since the adhesive tape of this embodiment has an adhesive layer with a foamed structure, the adhesive layer has excellent flexibility, and the adhesive tape of this embodiment has excellent step-following properties.

[0012] Methods for forming a foamed structure in the adhesive layer include, for example, a method in which foaming particles are incorporated into the adhesive composition that forms the adhesive layer, and then the mixture is applied to a release film or the like and heated and dried to form the foamed structure; a method in which gas is forcibly mixed and dispersed into the adhesive composition that forms the adhesive layer to form the foamed structure; and a method in which liquefied gas is mixed into the adhesive composition that forms the adhesive layer to form the foamed structure. Among these, the method in which foaming particles are incorporated into the adhesive composition, and then the mixture is applied to a release film or the like and heated and dried to form the foamed structure is preferred, from the viewpoint that the bubbles formed in the adhesive layer are easily dispersed when the adhesive composition is dried at a high temperature, and the resulting adhesive tape has better step-following ability.

[0013] Examples of the foaming particles mentioned above include those that foam when heated, and may also be thermally expanded particles. Specifically, examples include thermally decomposed foaming agents and thermally expandable microcapsules, and among these, it is preferable that the foaming particles include thermally expandable microcapsules.

[0014] The above-mentioned heat-expandable microcapsules are particles in which a volatile substance such as a low-boiling point solvent is encapsulated inside an outer resin shell. When heated, the outer resin shell softens, and the encapsulated volatile substance volatilizes or expands. As a result, the outer shell expands due to the resulting pressure, increasing the particle size. Therefore, when heated, the heat-expandable microcapsules become hollow particles with air bubbles inside the outer shell. Consequently, in the adhesive layer, the inclusion of the heat-expandable microcapsules in the foaming particles prevents the gas generated from the foaming particles from escaping to the outside of the adhesive layer, making it easier to maintain an appropriate amount of air bubbles within the adhesive layer and thus improving the foaming ratio of the adhesive layer. As a result, the flexibility of the adhesive layer is further improved, and the resulting adhesive tape has superior ability to follow uneven surfaces.

[0015] The outer shell resin of the above-mentioned heat-expandable microcapsules is preferably a thermoplastic resin. Examples of the above-mentioned thermoplastic resin include one or more resins selected from vinyl polymers and copolymers thereof such as ethylene, styrene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, butadiene, and chloroprene, polyamides such as nylon 6 and nylon 66, and polyesters such as polyethylene terephthalate. Among these, copolymers of acrylonitrile are preferred from the viewpoint that the encapsulated volatile substances do not easily permeate and the average particle size of the foamed particles, described later, can be adjusted to a suitable range.

[0016] Examples of volatile substances encapsulated inside the above-mentioned thermally expandable microcapsules include hydrocarbons with 3 to 7 carbon atoms such as propane, propylene, butene, n-butane, isobutane, isopentane, neopentane, n-pentane, hexane, and heptane; petroleum ethers; methane halogens such as methyl chloride and methylene chloride; and CCl ３ F, CCl ２ F ２ Examples include one or more low-boiling point liquids selected from chlorofluorocarbons, tetramethylsilanes, trimethylethylsilanes, and other tetraalkylsilanes. Among these, hydrocarbons having 3 to 7 carbon atoms are preferred.

[0017] Furthermore, the adhesive resin composition may already contain hollow particles as the foaming particles. By including hollow particles as foaming particles in the adhesive resin composition, it becomes easier to make the average diameter of the bubbles uniform compared to the case where an adhesive resin composition containing heat-expandable microcapsules is heated to form hollow particles in the foam layer. This improves the uniformity of the thickness of the foam layer, resulting in an adhesive tape with superior shock absorption properties.

[0018] Examples of hollow particles to be pre-included in the adhesive resin composition include particles produced by heating and expanding thermally expandable microcapsules, particles produced by the core-shell method, and particles produced by the bubble template method.

[0019] The average particle size of the foamed particles described above has a preferred lower limit of 15 μm and a preferred upper limit of 60 μm. Having the average particle size of the foamed particles within this range makes it easier to adjust the balance between the step-following ability and rebound resistance of the resulting adhesive tape. A more preferred lower limit for the average particle size of the foamed particles is 20 μm, a more preferred upper limit is 55 μm, an even more preferred lower limit is 25 μm, and an even more preferred upper limit is 50 μm. Examples of the average particle size of the foamed particles include 15 μm to 60 μm, 20 μm to 55 μm, 25 μm to 50 μm, etc. In this specification, the "average particle size of the foamed particles" refers to the average particle diameter of the foamed particles in an unfoamed state obtained by observing the adhesive composition containing the foamed particles. The average particle size of the foamed particles can also be obtained by randomly selecting particles using an optical microscope and calculating the average of 10 points.

[0020] Furthermore, the expansion initiation temperature of the foaming particles (also called the "foaming initiation temperature") is not particularly limited, but examples include a temperature range of 95°C to 150°C. The "expansion initiation temperature of foaming particles" refers to the temperature at which the foaming particles begin to expand, and can be measured using a thermomechanical analyzer (TMA) or the like.

[0021] Examples of commercially available foaming particles include Expancel 920DU40 (manufactured by Nippon Philite Co., Ltd., average particle size 40 μm), Expancel 920DU80 (manufactured by Nippon Philite Co., Ltd., average particle size 80 μm), EMC-20(B)R (manufactured by Nippon Philite Co., Ltd., average particle size 20 μm), and Advancel EML101 (manufactured by Sekisui Chemical Co., Ltd., average particle size 50 μm).

[0022] The above adhesive layer contains an acrylic copolymer having constituent units derived from a (meth)acrylic acid ester having a hydrocarbon group. In this specification, "(meth)acrylic" means acrylic or methacrylic. In this specification, "(meth)acrylic acid ester having a hydrocarbon group" means a (meth)acrylic acid ester in which a hydrocarbon group is directly bonded to the oxygen atom of the (meth)acryloyloxy group in the (meth)acrylic acid ester, and such hydrocarbon group includes not only saturated hydrocarbon groups but also unsaturated hydrocarbon groups and aromatic hydrocarbon groups.

[0023] The constituent units derived from the (meth)acrylic acid ester having the hydrocarbon group described above include constituent units derived from the (meth)acrylic acid ester represented by formula (1) above and having a glass transition temperature of 120°C or higher when used as a homopolymer (hereinafter sometimes simply referred to as "(meth)acrylic acid ester (a)"). In other words, (meth)acrylic acid ester (a) is "a (meth)acrylic acid ester represented by formula (1) above, derived from a (meth)acrylic acid ester having a glass transition temperature of 120°C or higher when used as a homopolymer." By including the constituent units derived from the (meth)acrylic acid ester having the hydrocarbon group described above in the constituent units derived from (meth)acrylic acid ester (a), the glass transition temperature of the acrylic copolymer is improved, resulting in a hardening of the adhesive layer, and consequently, the adhesive tape of this embodiment has excellent bending resistance.

[0024] Furthermore, the inclusion of the constituent units derived from the (meth)acrylic acid ester (a) in the constituent units derived from the (meth)acrylic acid ester (a) enables the adhesive tape of this embodiment to maintain adhesive reliability even when placed in a high-temperature, high-humidity environment. The reason why the inclusion of the constituent units derived from the (meth)acrylic acid ester (a) enables the adhesive tape of this embodiment to maintain adhesive reliability even in a high-temperature, high-humidity environment is not clear. However, it is presumed that the inclusion of the constituent units derived from the (meth)acrylic acid ester (a) increases the internal friction of the resulting adhesive layer, thereby increasing energy dissipation in the adhesive layer, and as a result, the adhesive tape of this embodiment can maintain adhesive reliability even in a high-temperature, high-humidity environment.

[0025] The preferred lower limit and preferred upper limit of the content of constituent units derived from the (meth)acrylic acid ester (a) in the above acrylic copolymer is 5% by mass. A content of 5% by mass or more of constituent units derived from the (meth)acrylic acid ester (a) results in superior bending resistance of the adhesive tape of this embodiment. A content of 50% by mass or less of constituent units derived from the (meth)acrylic acid ester (a) results in superior shock absorption of the adhesive tape of this embodiment. A more preferred lower limit for the content of constituent units derived from the (meth)acrylic acid ester (a) is 10% by mass, a more preferred upper limit is 40% by mass, an even more preferred lower limit is 20% by mass, and an even more preferred upper limit is 30% by mass. Examples of the content of constituent units derived from the (meth)acrylic acid ester (a) include 5% by mass or more and 50% by mass or less, 10% by mass or more and 40% by mass or less, 20% by mass or more and 50% by mass or less, etc.

[0026] In the above formula (1), R １ R represents a hydrogen atom or a methyl group. In particular, R in formula (1) above １It is preferable that the constituent unit derived from the (meth)acrylic acid ester (a) contains a methyl group, that is, a constituent unit derived from the methacrylic acid ester. By including a constituent unit derived from the methacrylic acid ester in the constituent unit derived from the (meth)acrylic acid ester (a), the (meth)acrylic acid ester (a) becomes bulkier, resulting in a harder adhesive layer and increased internal friction. Therefore, the adhesive tape of this embodiment has excellent bending resistance and is more likely to maintain adhesive reliability even in high temperature and high humidity environments.

[0027] In the above formula (1), R ２ R represents a hydrogen atom or a hydrocarbon group. In particular, from the viewpoint of making it easier to adjust the homopolymer Tg of the above (meth)acrylic acid ester (a) to a suitable range and preventing the adhesive layer from becoming too hard, in formula (1) above, ２ A hydrogen atom is preferred.

[0028] The above R ２ The hydrocarbon group in is not particularly limited and may be a linear hydrocarbon group, or a branched or cyclic hydrocarbon group. Among these, a branched or cyclic hydrocarbon group is preferred from the viewpoint of making it easier to adjust the homopolymer Tg of the (meth)acrylic acid ester (a) within a suitable range and preventing the adhesive layer from becoming too hard. ２ The hydrocarbon group in is not particularly limited and may be a saturated hydrocarbon group such as an alkyl group or cycloalkyl group, or an unsaturated hydrocarbon group such as an alkenyl group or alkynyl group. Also, the above R ２ In this context, the hydrocarbon group may be a hydrocarbon group containing an aromatic ring, such as a phenyl group or a benzyl group.

[0029] The above R ２Examples of alkyl groups include linear saturated hydrocarbon groups having 1 to 22 carbon atoms and branched saturated hydrocarbon groups having 3 to 22 carbon atoms. Examples of cycloalkyl groups include saturated hydrocarbon groups having 3 to 18 carbon atoms and having a cyclic structure. Among these, alkyl groups having 6 to 12 carbon atoms and having a cyclic structure are preferred. Examples of linear saturated hydrocarbon groups having 1 to 22 carbon atoms include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, lauryl group, and stearyl group. Examples of branched saturated hydrocarbon groups having 3 to 22 carbon atoms include isopropyl group, isobutyl group, s-butyl group, t-butyl group, isopentyl group, neopentyl group, isohexyl group, isooctyl group, 2-ethylhexyl group, isononyl group, and isostearyl group. Examples of saturated hydrocarbon groups having 3 to 18 carbon atoms and having the above-mentioned cyclic structure include cyclopropyl group, cyclopentyl group, cyclohexyl group, isoheptyl group, isobornyl group, adamantyl group, cyclododecane group, cyclohexadecane group, and cyclooctadecane group.

[0030] The above R ２ Examples of alkenyl groups in this context include vinyl groups, allyl groups, butenyl groups, and isopentenyl groups. Among these, vinyl groups are preferred.

[0031] The above R ２ Examples of alkynyl groups in this context include etyn, propyne, butyn, and pentyn groups.

[0032] The above R ２ Examples of hydrocarbon groups containing aromatic rings include phenyl, benzyl, naphthyl, and anthracenyl groups. Among these, the phenyl group is preferred.

[0033] Furthermore, the above R ２In the above-mentioned alkyl groups, cycloalkyl groups, alkenyl groups, alkynyl groups, and hydrocarbon groups containing aromatic rings may be unsubstituted, and hydrogen may be further substituted with the above-mentioned alkyl groups, cycloalkyl groups, alkenyl groups, alkynyl groups, and hydrocarbon groups containing aromatic rings.

[0034] In the above formula (1), R ３ and R ４ Each of these independently represents a hydrocarbon group having 1 to 4 carbon atoms, or a bond R ３ -CR-R ４ This forms a cyclic hydrocarbon group having 6 to 18 carbon atoms. In particular, the homopolymer Tg of the (meth)acrylic acid ester (a) can be easily adjusted to a suitable range, and from the viewpoint of further improving the shock absorption of the adhesive tape of this embodiment, the (meth)acrylic acid ester (a) in formula (1) has bond R ３ -CR-R ４ It is preferable to form a cyclic hydrocarbon group as a result.

[0035] In the above formula (1), bond R ３ -CR-R ４ When forming a cyclic hydrocarbon group having 6 to 18 carbon atoms, bond R ３ -CR-R ４ Examples of the (meth)acrylic acid ester (a) that forms a cyclic hydrocarbon group include isobornyl methacrylate (homopolymer Tg: 180°C) and dicyclopentanyl acrylate (homopolymer Tg: 120°C). In particular, from the viewpoint of making it easier to create an adhesive tape that has better bending resistance and can maintain adhesive reliability even when placed in a high-temperature, high-humidity environment, it is preferable that the constituent units derived from the (meth)acrylic acid ester (a) include constituent units derived from isobornyl methacrylate.

[0036] When the above acrylic copolymer contains constituent units derived from isobornyl methacrylate, the preferred upper limit of the content of the constituent units derived from isobornyl methacrylate in the above acrylic copolymer is 30% by mass. By having a content of 30% by mass or less of the constituent units derived from isobornyl methacrylate, the adhesive tape of this embodiment will have better shock absorption properties. A more preferred upper limit of the content of the constituent units derived from isobornyl methacrylate is 25% by mass. Furthermore, the preferred lower limit of the content of the constituent units derived from isobornyl methacrylate in the above acrylic copolymer is 10% by mass. By having a content of 10% by mass or more of the constituent units derived from isobornyl methacrylate, the adhesive tape of this embodiment will have better bending resistance. A more preferred lower limit of the content of the constituent units derived from isobornyl methacrylate is 15% by mass. Examples of the content ratio of constituent units derived from the above (meth)acrylic acid ester (a) include 10% by mass or more and 30% by mass or less, and 15% by mass or more and 25% by mass or less.

[0037] In the above formula (1), R ３ and R ４ When each of these independently represents a hydrocarbon group, the above R ３ and R ４ The hydrocarbon group in R may be a linear hydrocarbon group, or a branched or cyclic hydrocarbon group. ３ and R ４ The hydrocarbon group in is not particularly limited and may be a saturated hydrocarbon group such as an alkyl group, or an unsaturated hydrocarbon group such as an alkenyl group or an alkynyl group. Also, the above R ３ and R ４ In this context, the hydrocarbon group may be a hydrocarbon group containing an aromatic ring, such as a phenyl group or a benzyl group.

[0038] In the above formula (1), R ３ and R ４ When each of these independently represents a hydrocarbon group, the above R ３ and R ４Examples of hydrocarbon groups including alkyl groups, alkenyl groups, alkynyl groups, and aromatic rings in the above-mentioned R ２ Similar examples can be given. Also, in this case, the above R ３ and R ４ In the above-mentioned alkyl groups, alkenyl groups, alkynyl groups, and hydrocarbon groups containing aromatic rings may be unsubstituted, and hydrogen may be further substituted with the above-mentioned alkyl groups, alkenyl groups, alkynyl groups, and hydrocarbon groups containing aromatic rings.

[0039] The above (meth)acrylic acid ester (a) may have a glass transition temperature (hereinafter sometimes simply referred to as "homopolymer Tg") of 120°C or higher when it is in homopolymer form. However, from the viewpoint of the adhesive tape of this embodiment having superior bending resistance, a preferred lower limit is 140°C, and a more preferred lower limit is 160°C. Furthermore, a preferred upper limit for the homopolymer Tg of the above (meth)acrylic acid ester (a) is 250°C. By having a homopolymer Tg of the above (meth)acrylic acid ester (a) of 250°C or lower, the adhesive layer does not become too hard, and as a result, the adhesive tape of this embodiment has superior step-following ability. A more preferred upper limit for the homopolymer Tg of the above (meth)acrylic acid ester (a) is 220°C, and an even more preferred upper limit is 200°C. Examples of homopolymer Tg for the (meth)acrylic acid ester (a) include -140°C to 220°C, 160°C to 200°C, etc.

[0040] In this specification, "glass transition temperature of homopolymer" refers to the glass transition temperature of a homopolymer where the (meth)acrylic acid ester has a weight-average molecular weight of 100,000 to 2,000,000, measured by dynamic viscoelasticity measurement. More specifically, the Tg of the homopolymer can be measured by performing dynamic viscoelasticity measurement using a dynamic viscoelasticity measuring device (such as the "DVA-200" manufactured by IT Measuring Instruments Co., Ltd.) under the conditions of a measurement frequency of 1 Hz, a measurement temperature of -100°C to 200°C, and a heating rate of 10°C / min. Generally, if the weight-average molecular weight is 100,000 to 2,000,000, the Tg of the homopolymer does not depend on the weight-average molecular weight.

[0041] Specific examples of constituent units derived from the above (meth)acrylic acid ester (a) include isobornyl methacrylate (homopolymer Tg: 180°C), dicyclopentanyl acrylate (homopolymer Tg: 120°C), and dicyclopentenyl acrylate (homopolymer Tg: 120°C), which are all derived from (meth)acrylic acid esters.

[0042] The constituent units derived from the (meth)acrylic acid ester having the hydrocarbon group described above may further include constituent units other than those derived from the (meth)acrylic acid ester (a).

[0043] Other constituent units derived from the above-mentioned (meth)acrylic acid ester (a) that are included as constituent units derived from the above-mentioned (meth)acrylic acid ester having the above-mentioned hydrocarbon group include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, cyclohexyl (meth)acrylate, n-hexyl (meth)acrylate, and (meth)acrylic acid (a) Examples of constituent units derived from (meth)acrylic acid esters having hydrocarbon groups, such as soheptyl, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, 1-methylheptyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate.

[0044] The above acrylic copolymer has, as a constituent unit other than the constituent unit derived from the above (meth)acrylic acid ester (a), at least one constituent unit selected from the group consisting of constituent units derived from (meth)acrylic acid n-hexyl, constituent units derived from (meth)acrylic acid n-hexyl, and constituent units derived from (meth)acrylic acid 1-methylheptyl (hereinafter, it may also be simply referred to as "constituent unit derived from (meth)acrylic acid ester (b)"). By including the constituent unit derived from the above (meth)acrylic acid ester having a hydrocarbon group, the adhesive layer tends to have appropriate adhesive strength and appropriate flexibility, and the adhesive tape of this embodiment tends to be made into an adhesive tape with better step-following ability. The above acrylic copolymer may have only one type of constituent unit derived from the above (meth)acrylic acid ester (b), or it may have two or more types.

[0045] When the above acrylic copolymer contains constituent units derived from the above (meth)acrylic acid ester (b), the preferred lower limit of the content of the constituent units derived from the above (meth)acrylic acid ester (b) is 20% by mass, and the preferred upper limit is 70% by mass. By having the content of the constituent units derived from the above (meth)acrylic acid ester (b) within the above range, the resulting adhesive tape is more likely to have superior shock absorption properties. A more preferred lower limit for the content of the constituent units derived from the above (meth)acrylic acid ester (b) is 25% by mass, a more preferred upper limit is 65% by mass, an even more preferred lower limit is 30% by mass, an even more preferred upper limit is 60% by mass, and an even more preferred upper limit is 40% by mass. Examples of the content of the constituent units derived from the above (meth)acrylic acid ester (b) include 20% by mass or more and 70% by mass or less, 25% by mass or more and 65% by mass or less, 30% by mass or more and 60% by mass or less, 30% by mass or more and 40% by mass or less, etc.

[0046] In recent years, the depletion of petroleum resources and the emission of carbon dioxide from the combustion of petroleum-derived products have become serious concerns. Therefore, attempts are being made to conserve petroleum resources by using bio-derived materials instead of petroleum-derived materials. For this reason, the (meth)acrylic acid ester having hydrocarbon groups in the constituent units derived from the above-mentioned hydrocarbon group may consist only of petroleum-derived materials, but it is preferable that it also contains bio-derived materials that include bio-derived carbon. The inclusion of bio-derived materials in the above-mentioned hydrocarbon group-containing (meth)acrylic acid ester is preferable from the viewpoint of conserving petroleum resources, and furthermore, since bio-derived materials are originally produced by taking in carbon dioxide from the atmosphere, it is thought that burning them will not increase the total amount of carbon dioxide in the atmosphere, which is also preferable from the viewpoint of reducing carbon dioxide emissions.

[0047] When the (meth)acrylic acid ester having a hydrocarbon group in the constituent unit derived from the above-mentioned hydrocarbon group-containing (meth)acrylic acid ester contains a bio-derived material, it is preferable that the hydrocarbon group-containing (meth)acrylic acid ester is synthesized by esterification of an alcohol, which is a bio-derived material, with (meth)acrylic acid.

[0048] In the above acrylic copolymer, the preferred lower limit of the content of constituent units derived from the (meth)acrylic acid ester having the hydrocarbon group is 50% by mass, and the preferred upper limit is 95% by mass. By having the content of constituent units derived from the (meth)acrylic acid ester having the hydrocarbon group within the above range, the adhesive layer will have superior adhesive strength. A more preferred lower limit for the content of constituent units derived from the (meth)acrylic acid ester having the hydrocarbon group is 60% by mass, a more preferred upper limit is 90% by mass, an even more preferred lower limit is 65% by mass, and an even more preferred upper limit is 85% by mass. Examples of the content of constituent units derived from the (meth)acrylic acid ester (b) include 50% by mass or more and 95% by mass or less, 60% by mass or more and 90% by mass or less, 65% by mass or more and 85% by mass or less, etc.

[0049] The above acrylic copolymer preferably has structural units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals. By having structural units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals, the resulting adhesive tape exhibits improved shock absorption and high bending resistance.

[0050] When the above-mentioned acrylic copolymer has constituent units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals, the acrylic copolymer has a structure in which constituent units derived from the (meth)acrylic acid ester having the hydrocarbon group are used as the main chain, and constituent units derived from the olefin polymer having polymerizable unsaturated double bonds at its terminals are used as side chains. In this structure, the constituent units derived from the olefin polymer having polymerizable unsaturated double bonds at its terminals, located in the side chains of the acrylic copolymer, aggregate through interaction, forming a pseudo-crosslink. Therefore, when the adhesive layer is subjected to impact and the strain increases, the pseudo-crosslink breaks, and the molecules of the acrylic copolymer stretch, resulting in increased flexibility of the adhesive layer and excellent stress relaxation properties. As a result, the resulting adhesive tape has superior shock absorption properties.

[0051] Furthermore, when the acrylic copolymer has the above-mentioned structure, when the strain is small, the molecules of the acrylic copolymer become hard as if they were in a cross-linked structure due to the above-mentioned pseudo-crosslinking, so the adhesive layer has appropriate hardness. As a result, the resulting adhesive tape has better bending resistance. Also, when the strain applied to the adhesive layer is small, the cohesive force of the adhesive layer is further improved, and the adhesive tape of this embodiment is able to maintain adhesive reliability more easily even in high-temperature environments.

[0052] The olefin polymer having a polymerizable unsaturated double bond at one end may have a polymerizable unsaturated double bond at one end, or it may have polymerizable unsaturated double bonds at both ends. Among these, an olefin polymer having a polymerizable unsaturated double bond at one end is preferred because it is less prone to intramolecular chemical crosslinking, the cohesive force of the adhesive layer is increased, and it has a moderate hardness, thereby further improving the bending resistance of the resulting adhesive tape.

[0053] Examples of olefin polymers having a polymerizable unsaturated double bond at one or both ends include ethylene-butylene copolymers, ethylene-propylene copolymers, ethylene polymers, propylene polymers, and butene polymers, which have a group containing a polymerizable unsaturated carbon-carbon double bond at one or both ends. Examples of the group containing the polymerizable unsaturated carbon-carbon double bond include (meth)acryloyl groups, vinyl ether groups, and styryl groups. Among these, (meth)acryloyl groups are preferred because they exhibit excellent copolymerization with (meth)acrylic acid esters having the hydrocarbon group. In this specification, "(meth)acryloyl" means acryloyl or methacryloyl.

[0054] Examples of olefin polymers having polymerizable unsaturated double bonds at their ends include ethylene macromonomers having a (meth)acryloyl group at one end, propylene macromonomers having a (meth)acryloyl group at one end, ethylene-butylene macromonomers having a (meth)acryloyl group at one end, and ethylene-propylene macromonomers having a (meth)acryloyl group at one end. Among these, ethylene-butylene macromonomers having a (meth)acryloyl group at one end and ethylene-propylene macromonomers having a (meth)acryloyl group at one end are preferred from the viewpoint of improving the adhesive strength of the adhesive layer. These olefin polymers having polymerizable unsaturated double bonds at their ends may be used individually or in combination of two or more. In this specification, "macromonomer" refers to a monomer having polymerizable functional groups with a weight-average molecular weight of about 1,000 to 100,000.

[0055] In the above acrylic copolymer, the preferred lower limit of the content of constituent units derived from the olefin polymer having polymerizable unsaturated double bonds at its ends is 5% by mass, and the preferred upper limit is 30% by mass. When the content of constituent units derived from the olefin polymer having polymerizable unsaturated double bonds at its ends is 5% by mass or more, an appropriate number of pseudo-crosslinks are formed. As a result, the adhesive layer has an appropriate hardness, and the bending resistance of the resulting adhesive tape is further improved. In addition, the cohesive force of the adhesive layer is further improved, and the adhesive tape of this embodiment is able to maintain adhesive reliability more easily even in high-temperature environments. When the content of constituent units derived from the olefin polymer having polymerizable unsaturated double bonds at its ends is 30% by mass or less, the adhesive layer has an appropriate flexibility, and the shock absorption of the resulting adhesive tape is further improved. A more preferable lower limit for the content of constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their ends is 8% by mass, a more preferable upper limit is 25% by mass, an even more preferable lower limit is 10% by mass, and an even more preferable upper limit is 20% by mass. Examples of the content of constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their ends include 5% by mass or more and 30% by mass or less, 8% by mass or more and 25% by mass or less, 10% by mass or more and 20% by mass or less, etc.

[0056] The above acrylic copolymer preferably has structural units derived from monomers having crosslinkable functional groups. By having structural units derived from monomers having crosslinkable functional groups, the acrylic copolymer can sufficiently form a crosslinked structure through chemical crosslinking via a crosslinking agent between molecules, and the polar functional groups in the acrylic copolymer interact with each other, thereby increasing the cohesive force of the adhesive layer. As a result, the adhesive layer has a more appropriate hardness, and the bending resistance of the resulting adhesive tape is further improved. Furthermore, because the cohesive force of the adhesive layer is increased, the adhesive tape of this embodiment is more likely to maintain adhesive reliability even in high-temperature environments.

[0057] Examples of constituent units derived from monomers having the above-mentioned crosslinkable functional group include constituent units derived from carboxyl group-containing monomers, constituent units derived from hydroxyl group-containing monomers, constituent units derived from amide group-containing monomers, and constituent units derived from amino group-containing monomers. In particular, from the viewpoint of further increasing the cohesive force of the adhesive layer, it is preferable that the constituent units derived from monomers having the above-mentioned crosslinkable functional group include at least one selected from the group consisting of constituent units derived from carboxyl group-containing monomers and constituent units derived from hydroxyl group-containing monomers.

[0058] Specific examples of constituent units derived from the above-mentioned carboxyl group-containing monomers include unsaturated monocarboxylic acids such as (meth)acrylic acid, (meth)acryloylacetic acid, (meth)acryloylpropionic acid, (meth)acryloylbutyric acid, (meth)acryloylpentanoic acid, and crotonic acid, as well as constituent units derived from dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid. Specific examples of constituent units derived from the above-mentioned hydroxyl group-containing monomers include constituent units derived from 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate. Specific examples of constituent units derived from the above-mentioned amide group-containing monomers include constituent units derived from N-vinyl-2-pyrrolidone, N,N-dimethyl(meth)acrylamide, and N-isopropyl(meth)acrylamide. Specific examples of constituent units derived from the above-mentioned amino group-containing monomers include constituent units derived from (meth)acryloylmorpholine, dimethylaminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate. Furthermore, the constituent units derived from monomers having these crosslinkable functional groups may consist of only one type, or two or more types.

[0059] In the above acrylic copolymer, the preferred lower limit for the content of constituent units derived from the monomer having the crosslinkable functional group is 0.1% by mass, and the preferred upper limit is 10% by mass. When the content of constituent units derived from the monomer having the crosslinkable functional group is 0.1% by mass or more, the cohesive force of the adhesive layer is increased, and the adhesive layer has a more appropriate hardness, thereby improving the bending resistance and adhesive reliability of the resulting adhesive tape in high-temperature environments. When the content of constituent units derived from the monomer having the crosslinkable functional group is 10% by mass or less, the adhesive layer has an appropriate flexibility, thereby improving the shock absorption of the resulting adhesive tape. A more preferred lower limit for the content of constituent units derived from the monomer having the crosslinkable functional group is 0.5% by mass, a more preferred upper limit is 9.0% by mass, an even more preferred lower limit is 1.0% by mass, an even more preferred upper limit is 8.0% by mass, an even more preferred lower limit is 3.0% by mass, an even more preferred upper limit is 7.0% by mass, and a particularly preferred lower limit is 5.0% by mass. Examples of the content ratio of constituent units derived from monomers having the above-mentioned crosslinkable functional groups include 0.1% by mass or more and 10% by mass or less, 0.5% by mass or more and 9.0% by mass or less, 1.0% by mass or more and 8.0% by mass or less, 3.0% by mass or more and 7.0% by mass or less, 5.0% by mass or more and 7.0% by mass or less.

[0060] The above-mentioned acrylic copolymer preferably has structural units derived from vinyl aromatic compounds. Having structural units derived from vinyl aromatic compounds in the above-mentioned acrylic copolymer results in superior shock absorption of the adhesive tape of this embodiment.

[0061] Examples of constituent units derived from the vinyl aromatic compounds mentioned above include constituent units derived from styrene, constituent units derived from α-methylstyrene, and constituent units derived from their hydrogenated products. Among these, constituent units derived from styrene are preferred from the viewpoint of achieving both shock absorption and bending resistance in the resulting adhesive tape. Note that the constituent units derived from these vinyl aromatic compounds may consist of only one type, or two or more types may coexist.

[0062] When the above acrylic copolymer has structural units derived from a vinyl aromatic compound, the above acrylic copolymer may be a random copolymer, or it may be a block copolymer (hereinafter sometimes simply referred to as "block (A-2)") of a block having structural units derived from a (meth)acrylic acid ester having a hydrocarbon group (hereinafter sometimes simply referred to as "block (A-2)") and a block having structural units derived from a vinyl aromatic compound (hereinafter sometimes simply referred to as "block (A-1)"). In the above block copolymer (A), block (A-1) becomes a hard segment (hard block) and block (A-2) becomes a soft segment (soft block), imparting shock absorption to the adhesive tape. In particular, from the viewpoint of the resulting adhesive tape having superior shock absorption, it is preferable that the above acrylic copolymer includes block copolymer (A) when it has structural units derived from a vinyl aromatic compound.

[0063] The block copolymer (A) described above may be a diblock copolymer or a triblock copolymer. Among these, a triblock copolymer is preferred from the viewpoint of achieving both shock absorption and bending resistance of the resulting adhesive tape, and among triblock copolymers, a triblock copolymer having the hard block-soft block-hard block structure described above is more preferred.

[0064] The preferred lower limit for the content of block (A-1) in the block copolymer (A) is 3% by mass, and the preferred upper limit is 15% by mass. When the content of block (A-1) is 3% by mass or more, the adhesive tape of this embodiment has superior shock absorption properties. When the content of block (A-1) is 15% by mass or less, the adhesive tape of this embodiment has superior adhesive strength. The more preferred lower limit for the content of block (A-1) is 5% by mass, and the more preferred upper limit is 12% by mass. Examples of the content of block (A-1) include 3% by mass or more and 15% by mass or less, and 5% by mass or more and 12% by mass or less.

[0065] When the above acrylic copolymer contains the above block copolymer (A), the preferred lower limit of the content of constituent units derived from the vinyl aromatic compound in the above acrylic copolymer is 2.5% by mass, and the preferred upper limit of the content of constituent units derived from the vinyl aromatic compound is 20% by mass. By having the content of constituent units derived from the vinyl aromatic compound within the above range, the adhesive tape of this embodiment is more likely to be an adhesive tape that has better shock absorption, as well as excellent step-following ability and excellent bending resistance. A more preferred lower limit of the content of constituent units derived from the vinyl aromatic compound is 3.5% by mass, a more preferred upper limit is 18% by mass, an even more preferred lower limit is 4.5% by mass, an even more preferred upper limit is 15% by mass, an even more preferred lower limit is 6.0% by mass, and an even more preferred upper limit is 12% by mass. Examples of the content ratio of constituent units derived from the vinyl aromatic compound in the above acrylic copolymer include 2.5% by mass or more and 20% by mass or less, 3.5% by mass or more and 18% by mass or less, 4.5% by mass or more and 15% by mass or less, and 6.0% by mass or more and 12% by mass or less.

[0066] The weight-average molecular weight (Mw) of the above acrylic copolymer has a preferred lower limit of 300,000 and a preferred upper limit of 1,500,000. Having the weight-average molecular weight (Mw) of the above acrylic copolymer within this range increases the cohesive force of the adhesive layer, making it easier for the adhesive tape of this embodiment to maintain adhesive reliability even in high-temperature environments. A more preferred lower limit for the weight-average molecular weight (Mw) of the above acrylic copolymer is 500,000, a more preferred upper limit is 1,200,000, an even more preferred lower limit is 800,000, and an even more preferred upper limit is 1,000,000. Examples of weight-average molecular weight (Mw) of the above acrylic copolymer include 300,000 to 1,500,000, 500,000 to 1,200,000, and 800,000 to 1,000,000.

[0067] The polydispersity (weight-average molecular weight / number-average molecular weight, Mw / Mn) of the above acrylic copolymer has a preferred lower limit of 1.0 and a preferred upper limit of 8.0. When the polydispersity (Mw / Mn) of the above acrylic copolymer is within the above range, the cohesive force of the adhesive layer is further increased, and the adhesive tape of this embodiment is more likely to maintain adhesive reliability even in high-temperature environments. A more preferred lower limit for the polydispersity (Mw / Mn) of the above acrylic copolymer is 1.5, and a more preferred upper limit is 7.5. Examples of polydispersity (Mw / Mn) of the above acrylic copolymer include 1.0 to 8.0 and 1.5 to 7.5.

[0068] In this specification, weight-average molecular weight and number-average molecular weight are those obtained by GPC (Gel Permeation Chromatography) measurement on a standard polystyrene basis. Specifically, an acrylic copolymer is diluted 50-fold with an organic solvent such as ethyl acetate, and the resulting dilution is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare a sample for measurement. Next, this sample for measurement is supplied to a gel permeation chromatograph, and GPC measurement is performed under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C. The polystyrene-based molecular weight of the acrylic copolymer is measured, and the obtained values ​​are defined as the weight-average molecular weight and number-average molecular weight. Examples of gel permeation chromatographs include the 2690 Separations Module (manufactured by Waters), and examples of columns include the GPC KF-806L (manufactured by Showa Denko).

[0069] Methods for adjusting the weight-average molecular weight of the above-mentioned acrylic copolymer include, for example, changing the type and amount of polymerization initiator and monomer concentration during the polymerization reaction, adding a small amount of chain transfer agent such as dodecyl mercaptan, controlling chain transfer to the solvent by changing the type of polymerization reaction solvent, and changing the temperature and time during polymerization.

[0070] The preferred lower limit of the glass transition temperature (Tg) of the above acrylic copolymer is 5°C, and the preferred upper limit is 40°C. A glass transition temperature (Tg) of 5°C or higher for the above acrylic copolymer increases the cohesive force of the adhesive layer, making it easier for the adhesive tape of this embodiment to maintain adhesive reliability even in high-temperature environments. A glass transition temperature (Tg) of 40°C or lower for the above acrylic copolymer improves the step-following ability of the adhesive tape of this embodiment. A more preferred lower limit of the glass transition temperature (Tg) of the above acrylic copolymer is 10°C, a more preferred upper limit is 35°C, an even more preferred lower limit is 15°C, and an even more preferred upper limit is 30°C. Examples of glass transition temperatures (Tg) for the above acrylic copolymer include 5°C to 40°C, 10°C to 35°C, and 15°C to 30°C.

[0071] The glass transition temperature (Tg) of the above acrylic copolymer can be determined by differential scanning calorimetry. More specifically, it can be measured under a nitrogen atmosphere (nitrogen flow, flow rate 50 mL / min), in accordance with JIS K 6240:2011, with a measurement temperature of -100°C to 200°C and a heating rate of 10°C / min.

[0072] One method for adjusting the glass transition temperature (Tg) of the above-mentioned acrylic copolymer is to adjust the type and content of the constituent monomers of the acrylic copolymer.

[0073] The preferred lower limit for the content of the acrylic copolymer in the adhesive layer is 50% by mass, and the preferred upper limit is 100% by mass. By having the acrylic copolymer content within this range, it becomes easier to produce an adhesive tape that has excellent step-following ability and excellent bending resistance, and that maintains adhesive reliability even when placed in high-temperature and high-humidity environments. A more preferred lower limit for the acrylic copolymer content is 60% by mass, a more preferred upper limit is 98% by mass, an even more preferred lower limit is 70% by mass, and an even more preferred upper limit is 95% by mass. Examples of acrylic copolymer content include 50% by mass or more and 100% by mass or less, 60% by mass or more and 98% by mass or less, and 70% by mass or more and 95% by mass or less.

[0074] As polymerization methods for synthesizing the above-mentioned acrylic copolymer, conventionally known methods can be used in which a mixture of constituent monomers that serve as raw materials undergoes a radical reaction in the presence of a polymerization initiator. Examples include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, and bulk polymerization. Among these, solution polymerization is preferred because it is easy to synthesize.

[0075] When solution polymerization is used as the polymerization method described above, examples of reaction solvents include ethyl acetate, toluene, methyl ethyl ketone, methyl sulfoxide, ethanol, acetone, and diethyl ether. These reaction solvents may be used individually or in combination of two or more.

[0076] Examples of polymerization initiators include organic peroxides and azo compounds. Examples of organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of azo compounds include azobisisobutyronitrile and azobiscyclohexanecarbonilonitrile. These polymerization initiators may be used alone or in combination of two or more.

[0077] Furthermore, even when the acrylic copolymer is the block copolymer (A), the method for producing the block copolymer (A) is not particularly limited, and conventionally known methods can be used. Specifically, for example, a vinyl aromatic compound may be added to the soft block synthesized in the same manner as the acrylic copolymer described above, and copolymerized. Alternatively, the hard block and soft block synthesized in advance may be copolymerized.

[0078] Furthermore, if the block copolymer is a triblock copolymer having the structure of the hard block - soft block - hard block, the block copolymer can be obtained, for example, by living polymerization. Examples of living polymerization include living anionic polymerization and RAFT polymerization, but RAFT polymerization is particularly preferred. When producing the block copolymer (A) having the hard block - soft block - hard block by RAFT polymerization, the hard block is obtained using a chain transfer agent (RAFT agent), and then the constituent unit monomers of the soft block are polymerized or copolymerized in the presence of the obtained hard block to produce the triblock copolymer.

[0079] Preferably, the adhesive layer contains an aromatic block copolymer (X) having at least two blocks having structural units derived from vinyl aromatic compounds (hereinafter sometimes simply referred to as "vinyl aromatic polymer blocks"), and at least one of a block having structural units derived from a conjugated diene compound (hereinafter sometimes simply referred to as "conjugated diene polymer blocks") or a hydrogenated product of a block having structural units derived from a conjugated diene compound (hereinafter sometimes simply referred to as "hydrogenated product of conjugated diene polymer blocks"). By containing the aromatic block copolymer (X) in the adhesive layer, the adhesive tape of this embodiment has superior shock absorption properties.

[0080] The vinyl aromatic polymer block described above may be any block having 5% by mass or more of constituent units derived from a vinyl aromatic compound, and may also contain constituent units derived from other compounds such as ethylene and 1,3-butadiene (which is converted to an ethylene-butylene structure by hydrogenation). Examples of the vinyl aromatic compound in the vinyl aromatic polymer block include alkylstyrene, halogenated styrene, halogen-substituted alkylstyrene, alkoxystyrene, carboxyalkylstyrene, alkyl ether styrene, alkylsilyl styrene, vinyl benzyl dimethoxy phosphide, vinyl naphthalene, vinyl anthracene, N,N-diethyl-p-aminoethylstyrene, and vinylpyridine.

[0081] Examples of alkylstyrenes include styrene, methylstyrene, dimethylstyrene, and t-butylstyrene. Examples of halogenated styrenes include chlorostyrene, bromostyrene, and fluorostyrene. Examples of halogen-substituted alkylstyrenes include chloromethylstyrene. Examples of alkoxystyrenes include methoxystyrene and ethoxystyrene. Examples of carboxyalkylstyrenes include carboxymethylstyrene. Examples of alkyl ether styrenes include vinyl benzyl propyl ether. Examples of alkylsilyl styrenes include trimethylsilyl styrene. Among these, styrene, methylstyrene, and dimethylstyrene are preferred, and styrene is more preferred because it is readily available industrially. These vinyl aromatic compounds may be used individually or in combination of two or more.

[0082] The preferred lower limit for the content of constituent units derived from the vinyl aromatic compound in the vinyl aromatic polymer block is 7% by mass. A content of 7% by mass or more of constituent units derived from the vinyl aromatic compound further improves the bending rigidity of the adhesive layer, resulting in an adhesive tape with excellent shock absorption and superior bending resistance. A more preferred lower limit for the constituent units derived from the vinyl aromatic compound is 10% by mass. Furthermore, from the viewpoint of further improving the flexibility of the adhesive layer and resulting in an adhesive tape with superior shock absorption, a preferred upper limit for the constituent units derived from the vinyl aromatic compound is 35% by mass. Examples of the content of constituent units derived from the vinyl aromatic compound in the vinyl aromatic polymer block include 7% by mass or more and 35% by mass or less, and 10% by mass or more and 35% by mass or less.

[0083] Examples of the above-mentioned conjugated diene compounds include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-octadiene, 1,3-hexadiene, 1,3-cyclohexadiene, 4,5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, myrcene, and chloroprene. In addition to the above-mentioned conjugated diene compounds, other usable compounds include, for example, 2,5-dihydrofuran-2,5-dione. Among these, 1,3-butadiene and isoprene are preferred due to their high polymerization reactivity and ease of industrial availability. These conjugated diene compounds may be used individually or in combination of two or more.

[0084] The hydrogenated form of the above-mentioned conjugated diene polymer block refers to a block in which the carbon-carbon double bonds (unsaturated bonds) in the constituent units derived from the above-mentioned conjugated diene compound are converted to saturated bonds by hydrogenation. From the viewpoint of preventing degradation due to heat, ultraviolet rays, etc., it is preferable that 80% or more of the carbon-carbon double bonds (unsaturated bonds) in the constituent units derived from the above-mentioned conjugated diene compound of the aromatic block copolymer (X) are converted to saturated bonds by hydrogenation, more preferably 90% or more, even more preferably 95% or more, and even more preferably 96% or more. Furthermore, it is most preferable that 100% of the unsaturated bonds are converted to saturated bonds by hydrogenation (i.e., it is a fully hydrogenated form). That is, it is preferable that 80% to 100% of the carbon-carbon double bonds (unsaturated bonds) in the constituent units derived from the above-mentioned conjugated diene compound are converted to saturated bonds by hydrogenation, more preferably 90% to 100%, even more preferably 95% to 100%, and even more preferably 96% to 100%.

[0085] The preferred lower limit for the content of constituent units derived from the conjugated diene compound in the above-mentioned conjugated diene polymer block is 80% by mass. A content of 80% by mass or more of constituent units derived from the conjugated diene compound further improves the flexibility of the adhesive layer and the shock absorption of the resulting adhesive tape. Furthermore, the adhesive strength of the adhesive layer is also improved. A more preferred lower limit for the constituent units derived from the conjugated diene compound is 90% by mass, and an even more preferred lower limit is 95% by mass. There is no particular upper limit for the constituent units derived from the conjugated diene compound, and it may be 100% by mass. Examples of the content of constituent units derived from the conjugated diene compound in the above-mentioned conjugated diene polymer block include 90% by mass or more and 100% by mass or less, and 95% by mass or more and 100% by mass or less.

[0086] Examples of the structure of the above aromatic block copolymer (X) include, when the vinyl aromatic polymer block is B and the hydrogenated product of the block having constituent units derived from the conjugated diene polymer block and the conjugated diene compound is C, a triblock copolymer represented by formula B-C-B, a diblock copolymer represented by formula B-C, a pentablock copolymer represented by formula C-B-C-B-C, and the like.

[0087] Examples of aromatic block copolymers (X) having the structure represented by the above formula B-C-B include styrene-isoprene-styrene (SIS) block copolymer, styrene-butylene-styrene (SBS) block copolymer, styrene-ethylene-butylene-styrene (SEBS) block copolymer, styrene-ethylene-propylene-styrene (SEPS) block copolymer, styrene-ethylene-ethylene-propylene-styrene (SEEPS) block copolymer, styrene-isobutylene-styrene (SIBS), and ethylene-styrene-butylene copolymer. Among these, SIS block copolymer and SEBS block copolymer are preferred from the viewpoint of compatibility with the above acrylic copolymer.

[0088] The preferred lower limit for the weight-average molecular weight (Mw) of the aromatic block copolymer (X) is 50,000. A weight-average molecular weight (Mw) of 50,000 or more results in a more shock-absorbing adhesive tape. A more preferred lower limit for the weight-average molecular weight of the aromatic block copolymer (X) is 100,000, and an even more preferred lower limit is 150,000. While there is no particular upper limit for the weight-average molecular weight of the aromatic block copolymer (X), a preferred upper limit is 500,000 from the viewpoint of compatibility with the acrylic copolymer. Examples of weight-average molecular weights for the aromatic block copolymer (X) include 50,000 to 500,000, 100,000 to 500,000, and 150,000 to 500,000.

[0089] A preferred upper limit for the content of the aromatic block copolymer (X) per 100 parts by mass of the acrylic copolymer is 60 parts by mass. When the content of the aromatic block copolymer (X) is within this range, the shock absorption of the adhesive tape of this embodiment is further improved. Furthermore, the bending rigidity of the adhesive layer is further improved, resulting in an adhesive tape with superior bending resistance. Moreover, the adhesive strength of the adhesive layer is further improved. A more preferred upper limit for the content of the aromatic block copolymer (X) is 55 parts by mass, and an even more preferred upper limit is 50 parts by mass. Also, the content of the aromatic block copolymer (X) may be greater than 0 parts by mass, but a preferred lower limit is 10 parts by mass. When the content of the aromatic block copolymer (X) is 10 parts by mass or more, the flexibility of the adhesive layer is further improved, resulting in an adhesive tape with superior shock absorption. A more preferred lower limit for the content of the aromatic block copolymer (X) is 15 parts by mass, an even more preferred lower limit is 20 parts by mass, and an even more preferred lower limit is 30 parts by mass. Examples of the content of the aromatic block copolymer (X) include 10 parts by mass or more and 60 parts by mass or less, 15 parts by mass or more and 55 parts by mass or less, 20 parts by mass or more and 50 parts by mass or less, 30 parts by mass or more and 50 parts by mass or less, and so on.

[0090] The adhesive layer may be colored. If the adhesive layer is colored, light-shielding properties can be imparted to the adhesive layer, thereby suppressing deterioration of the adherend to the adhesive tape of this embodiment due to light and ultraviolet rays. Therefore, the adhesive tape of this embodiment can be more suitably used for fixing electronic equipment components or automotive components.

[0091] If the adhesive layer is colored, it is preferable that the adhesive layer contains a coloring agent. Examples of the coloring agent include pigments and dyes. Among these, pigments are preferred because they have excellent heat resistance and the resulting adhesive tape can be more suitably used for fixing electronic equipment components or automotive components. Examples of the pigments include carbon black, aniline black, and titanium dioxide. Among these, carbon black is preferred because it is relatively inexpensive and chemically stable. Examples of the dyes include azo dyes, anthraquinone dyes, and phthalocyanine dyes.

[0092] The preferred upper limit of the coloring agent content per 100 parts by mass of the acrylic copolymer is 5.0 parts by mass. A coloring agent content of 5.0 parts by mass or less results in more sufficient adhesive strength for the adhesive layer. A more preferred upper limit for the coloring agent content is 4.0 parts by mass, an even more preferred upper limit is 3.5 parts by mass, and an even more preferred upper limit is 2.0 parts by mass. Furthermore, if the adhesive layer contains a coloring agent, the preferred lower limit is 0.2 parts by mass. A coloring agent content of 0.2 parts by mass or more provides sufficient light-shielding properties to the adhesive layer. A more preferred lower limit for the coloring agent content is 0.5 parts by mass, an even more preferred lower limit is 0.8 parts by mass, and an even more preferred lower limit is 1.0 part by mass. Note that the adhesive layer does not necessarily have to contain a coloring agent, and from the viewpoint of further improving the shock absorption properties of the resulting adhesive tape, it is preferable that the adhesive layer does not contain a coloring agent. Examples of the coloring agent content include 0 parts by mass or more and 5.0 parts by mass or less, 0.2 parts by mass or more and 5.0 parts by mass or less, 0.5 parts by mass or more and 4.0 parts by mass or less, 0.8 parts by mass or more and 3.5 parts by mass or less, 1.0 part by mass or more and 2.0 parts by mass or less.

[0093] The adhesive layer may or may not contain a tackifying resin. By including a tackifying resin in the adhesive layer, the adhesive strength of the adhesive layer is further improved, and the step-following ability of the adhesive tape of this embodiment is further enhanced. On the other hand, by not including a tackifying resin in the adhesive layer, the adhesive tape of this embodiment can be given superior shock absorption.

[0094] Examples of the tackifying resins mentioned above include rosin resins, rosin ester resins, hydrogenated rosin resins, terpene resins, terpene phenol resins, coumarone indene resins, alicyclic saturated hydrocarbon resins, C5 petroleum resins, C9 petroleum resins, and C5-C9 copolymer petroleum resins. Among these, rosin ester resins or terpene phenol resins are preferred from the viewpoint of compatibility with the acrylic copolymer, and among these, rosin ester resins or terpene phenol resins having hydroxyl groups are more preferred. These tackifying resins may be used alone or in combination of two or more.

[0095] Examples of rosin ester resins having the hydroxyl group mentioned above include Pencel D-135 and Super Ester A-75 (both manufactured by Arakawa Chemical Industries, Ltd.). Examples of terpene phenol resins include YS Polystar G150 and YS Polystar T160 (both manufactured by Yasuhara Chemical Co., Ltd.).

[0096] If the adhesive layer contains the tackifying resin, it is preferable that the tackifying resin contains bio-derived carbon. By including a bio-derived carbon in the tackifying resin, the content of bio-derived carbon in the adhesive layer described later can be increased, and the environmental burden of the adhesive tape of this embodiment can be further reduced. Specific examples of bio-derived carbon-containing tackifying resins include Pine Crystal KE-604, Pine Crystal KR-140 (all rosin-based resins, manufactured by Arakawa Chemical Industries), Pine Crystal KE-100, Pine Crystal KE-359, Super Ester A-75 (all rosin ester-based resins, manufactured by Arakawa Chemical Industries), and Tamanol 803L (terpene phenol-based resin, manufactured by Arakawa Chemical Industries).

[0097] If the adhesive layer contains the tackifying resin, it is preferable that the tackifying resin has a softening point of 70°C or higher and 170°C or lower. By including a tackifying resin with a softening point of 70°C or higher, the adhesive tape of this embodiment is able to maintain adhesive reliability more easily even in high-temperature environments. By including a tackifying resin with a softening point of 170°C or lower, the wettability of the interface of the adhesive layer is improved, and the step-following ability of the adhesive tape of this embodiment is further improved. It is more preferable that the tackifying resin contains a tackifying resin with a softening point of 120°C or higher and 150°C or lower, and more preferably that it contains a tackifying resin with a softening point of 130°C or higher and 140°C or lower. In this specification, "softening point of tackifying resin" means the softening temperature measured by JIS K 2207 (ring-ball method).

[0098] If the adhesive layer contains the tackifying resin, it is preferable that the tackifying resin has a hydroxyl value of 25 mg KOH / g or more. By including a tackifying resin with a hydroxyl value of 25 mg KOH / g or more, the wettability of the interface of the adhesive layer is improved, and the step-following ability of the adhesive tape of this embodiment is further improved. It is more preferable that the tackifying resin includes a tackifying resin with a hydroxyl value of 30 mg KOH / g or more, and even more preferable that it includes a tackifying resin with a hydroxyl value of 35 mg KOH / g or more. Furthermore, there is no particular upper limit to the hydroxyl value of the tackifying resin, but from the viewpoint of compatibility with the aromatic block copolymer (X), a preferred upper limit is 50 mg KOH / g. Examples of the hydroxyl value of the tackifying resin include 25 mg KOH / g to 50 mg KOH / g, 30 mg KOH / g to 50 mg KOH / g, 35 mg KOH / g to 50 mg KOH / g, etc. Furthermore, in this specification, the hydroxyl value of the tackifying resin can be measured by JIS K1557 (phthalic anhydride method).

[0099] When the adhesive layer contains the tackifying resin, the preferred upper limit of the tackifying resin content is 50 parts by mass per 100 parts by mass of the acrylic copolymer. A content of 50 parts by mass or less of the tackifying resin prevents the adhesive layer from becoming too hard, further improving its adhesive strength and enhancing the step-following ability of the adhesive tape of this embodiment. Furthermore, the shock absorption of the adhesive tape of this embodiment is also improved. A more preferred upper limit for the tackifying resin content is 40 parts by mass, an even more preferred upper limit is 30 parts by mass, an even more preferred upper limit is 20 parts by mass, and a particularly preferred upper limit is 10 parts by mass. Additionally, when the adhesive layer contains the tackifying resin, the adhesive strength of the adhesive layer is further improved, and from the viewpoint of making it easier to maintain adhesive reliability even in high-temperature environments, a preferred lower limit for the tackifying resin content is 0.1 parts by mass. The adhesive layer does not necessarily have to contain a tackifying resin, and from the viewpoint of further improving the shock absorption of the resulting adhesive tape, it is preferable that the adhesive layer does not contain a tackifying resin. Examples of the tackifying resin content include 0 parts by mass or more and 50 parts by mass or less, more than 0 parts by mass and 50 parts by mass or less, 0.1 parts by mass or more and 40 parts by mass or less, 0.1 parts by mass or more and 30 parts by mass or less, 0.1 parts by mass or more and 20 parts by mass or less, 0.1 parts by mass or more and 10 parts by mass or less.

[0100] Preferably, the adhesive layer has a structure derived from a crosslinking agent. Since the adhesive layer has a structure derived from a crosslinking agent, its cohesive force is increased, making it easier for the adhesive tape of this embodiment to have better bending resistance and superior adhesive reliability in high-temperature environments. A method for providing the adhesive layer with a structure derived from a crosslinking agent includes, for example, applying an adhesive composition containing a crosslinking agent to a release film or the like, and then heating and drying it.

[0101] The above adhesive composition preferably contains a crosslinking agent. The inclusion of a crosslinking agent in the adhesive composition makes it easier for the adhesive layer to have a structure derived from the crosslinking agent. Therefore, the cohesive force of the adhesive layer is increased, making it easier for the adhesive tape of this embodiment to have better bending resistance and superior adhesive reliability in high-temperature environments. Furthermore, from the viewpoint of storage stability of the adhesive composition, the crosslinking agent may be added to the adhesive composition immediately before forming the adhesive layer.

[0102] Examples of the crosslinking agents include isocyanate-based crosslinking agents, aziridine-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-based crosslinking agents. Among these, isocyanate-based crosslinking agents are preferred from the viewpoint of further improving the cohesive strength of the adhesive layer.

[0103] The preferred lower limit of the crosslinking agent content per 100 parts by mass of the acrylic copolymer is 0.05 parts by mass, and the preferred upper limit is 5.0 parts by mass. By having the crosslinking agent content within the above range, the degree of crosslinking of the adhesive layer is appropriately adjusted, and the balance between the bending rigidity and flexibility of the adhesive layer is improved, so that the resulting adhesive tape has better shock absorption and excellent bending resistance. A more preferred lower limit for the crosslinking agent content is 0.10 parts by mass, a more preferred upper limit is 3.0 parts by mass, an even more preferred lower limit is 0.15 parts by mass, an even more preferred upper limit is 2.0 parts by mass, an even more preferred upper limit is 1.0 part by mass, and a particularly preferred upper limit is 0.5 parts by mass. Examples of the crosslinking agent content include 0.05 parts by mass or more and 5.0 parts by mass or less, 0.10 parts by mass or more and 3.0 parts by mass or less, 0.15 parts by mass or more and 2.0 parts by mass or less, 0.15 parts by mass or more and 1.0 part by mass or less, 0.15 parts by mass or more and 0.5 parts by mass or less.

[0104] The adhesive layer described above may contain conventionally known additives such as antioxidants, organic fillers, inorganic fillers, surfactants, stabilizers, and softeners, as needed.

[0105] The preferred lower limit for the gel fraction of the adhesive layer is 10% by mass, and the preferred upper limit is 70% by mass. A gel fraction of 10% by mass or more in the adhesive layer increases the cohesive force of the adhesive layer, making it easier to obtain the adhesive tape of this embodiment to have better bending resistance and superior adhesive reliability in high-temperature environments. A gel fraction of 70% by mass or less in the adhesive layer improves the flexibility of the adhesive layer, thus improving the shock absorption of the resulting adhesive tape. A more preferred lower limit for the gel fraction of the adhesive layer is 20% by mass, a more preferred upper limit is 60% by mass, an even more preferred lower limit is 30% by mass, an even more preferred upper limit is 50% by mass, and an even more preferred lower limit is 40% by mass. Examples of suitable gel fractions for the adhesive layer include 10% to 70% by mass, 20% to 60% by mass, 30% to 50% by mass, and 40% to 50% by mass.

[0106] The gel fraction of the adhesive layer described above can be measured by the following method. Specifically, first, a test piece is prepared by cutting the adhesive tape having the adhesive layer into a planar rectangular shape with a width of 20 mm and a length of 40 mm. The test piece is immersed in ethyl acetate at 23°C for 24 hours, then removed from the ethyl acetate and dried at 110°C for 1 hour. The mass of the dried test piece is measured, and the gel fraction is calculated using the following formula (I). Note that the test piece does not have a release film laminated on it to protect the adhesive layer. Furthermore, if the adhesive tape of this embodiment is a non-support type adhesive tape without a base material, the measurement can be performed using a test piece obtained by attaching it to a base material and then cutting it, or without using a base material, W in the following formula (I) can be calculated. ０ Calculate by setting to 0. Gel fraction (mass%) = 100 × (W ２ -W ０ ) / (W １ -W ０ ) (I) (W ０ : Mass of the base material, W １ : Mass of the test specimen before immersion, W ２ (Mass of the test specimen after immersion and drying)

[0107] Methods for adjusting the gel fraction of the adhesive layer include, for example, adjusting the type and content ratio of constituent units derived from monomers having crosslinkable functional groups contained in the acrylic copolymer in the adhesive layer; adjusting the type and content of crosslinking agents contained in the adhesive layer; and adjusting the irradiance and irradiation time of electron beams or ultraviolet rays used when electron beam irradiation or ultraviolet irradiation is performed to form the adhesive layer.

[0108] The preferred lower limit for the bio-derived carbon content in the adhesive layer is 10%. A bio-derived carbon content of 10% or more in the adhesive layer results in an adhesive tape that is superior in terms of conserving petroleum resources and reducing carbon dioxide emissions, thereby reducing environmental impact. A more preferred lower limit for the bio-derived carbon content in the adhesive layer is 15%, an even more preferred lower limit is 18%, and an even more preferred lower limit is 20%. Furthermore, there is no particular upper limit for the bio-derived carbon content in the adhesive layer, and it may be 100%. Examples of bio-derived carbon content in the adhesive layer include 10% to 100%, 15% to 100%, 18% to 100%, and 20% to 100%.

[0109] While bio-derived carbon contains a certain percentage of the radioactive isotope C-14, petroleum-derived carbon contains almost no C-14. Therefore, the "biologically derived carbon content" as used herein can be calculated by measuring the concentration of C-14 contained in the adhesive layer. Specifically, it can be measured in accordance with ASTM D6866-24, a standard widely used in the bioplastics industry.

[0110] The content of bio-derived carbon in the adhesive layer can be adjusted by adjusting the composition of the adhesive layer. Specifically, examples include a method of synthesizing the acrylic copolymer using a (meth)acrylic acid ester having a hydrocarbon group containing bio-derived carbon or a monomer having a crosslinkable functional group containing bio-derived carbon, or a method of incorporating a tackifying resin containing bio-derived carbon into the adhesive layer.

[0111] The adhesive layer may have an open-cell structure or an closed-cell structure, but it is preferable to have an closed-cell structure. Having a closed-cell structure in the adhesive layer improves its bending rigidity, resulting in improved bending resistance of the resulting adhesive tape. Furthermore, the increased tensile strength of the adhesive layer suppresses cohesive failure, thus improving the adhesive strength. Therefore, the step-following ability of the adhesive tape of this embodiment is further improved. In this specification, when observing a tape cross-section randomly, a structure where the air layers between cells are partially continuous is defined as an open-cell structure, and a structure where the air layers between cells are not continuous is defined as an closed-cell structure. The cell structure can be confirmed, for example, by observing it at a magnification of 150 to 200 times using an optical microscope (e.g., Keyence's "VHX-6000").

[0112] The deemed density of the above adhesive layer has a preferred lower limit of 0.59 g / cm³. ３ Therefore, a preferred upper limit is 1.15 g / cm³. ３ Therefore, by having the deemed density of the adhesive layer within the above range, the resulting adhesive tape will have better shock absorption and improved ability to follow uneven surfaces. A more preferable lower limit for the deemed density of the adhesive layer is 0.65 g / cm³. ３ A more preferable upper limit is 1.12 g / cm³. ３ A more preferable lower limit is 0.70 g / cm³. ３ A more preferable upper limit is 1.10 g / cm³. ３ A more preferable lower limit is 0.75 g / cm³. ３ A more preferable upper limit is 1.05 g / cm³. ３ A particularly preferred lower limit is 0.80 g / cm³. ３ A particularly preferred upper limit is 1.00 g / cm³. ３ A particularly preferable upper limit is 0.90 g / cm³. ３ The assumed density of the foam layer is, for example, 0.59 g / cm³. ３ 1.15g / cm or more ３ Below, 0.65g / cm ３ 1.12g / cm or more ３ Below, 0.70g / cm ３1.10g / cm or more ３ Below, 0.75g / cm ３ 1.05g / cm or more ３ Below, 0.80g / cm ３ 1.00g / cm or more ３ Below, 0.80g / cm ３ 0.90g / cm or more ３ The following are some examples.

[0113] The deemed density of the adhesive layer described above can be measured using an electronic hydrometer (for example, Mirage's "ED120T") in accordance with JIS K 7222, etc.

[0114] Methods for adjusting the deemed density of the adhesive layer include, for example, adjusting the type and content of foaming agents such as foaming particles, and changing the composition of the adhesive layer.

[0115] The average major diameter of the bubbles in the adhesive layer described above has a preferred lower limit of 10 μm and a preferred upper limit of 80 μm. When the average major diameter of the bubbles in the adhesive layer is 10 μm or more, the adhesive layer has appropriate flexibility, and the stress relaxation properties of the adhesive layer are further improved, resulting in an adhesive tape with better shock absorption. When the average major diameter of the bubbles in the adhesive layer is 80 μm or less, the bending rigidity of the adhesive layer is further improved, and the adhesive tape obtained has better bending resistance. In addition, since the fracture strength of the adhesive layer is increased, cohesive failure of the adhesive layer can be further suppressed, resulting in improved adhesive strength and thus improved step-following ability of the adhesive tape of this embodiment. The more preferable lower limit for the average major diameter of the bubbles in the adhesive layer is 15 μm, the more preferable upper limit is 70 μm, the even more preferable lower limit is 20 μm, the even more preferable upper limit is 65 μm, the even more preferable upper limit is 60 μm, the particularly preferable upper limit is 55 μm, and the very preferable upper limit is 50 μm. Examples of the average major diameter of the bubbles in the adhesive layer include 10 μm to 80 μm, 15 μm to 70 μm, 20 μm to 65 μm, 20 μm to 60 μm, 20 μm to 55 μm, 20 μm to 50 μm, and so on.

[0116] The average minor diameter of the bubbles in the adhesive layer is preferably 10 μm at the lower limit and preferably 75 μm at the upper limit. When the average minor diameter of the bubbles in the adhesive layer is 10 μm or more, the adhesive layer has appropriate flexibility, and the stress relaxation properties of the adhesive layer are further improved, resulting in an adhesive tape with better shock absorption. When the average minor diameter of the bubbles in the adhesive layer is 75 μm or less, the bending rigidity of the adhesive layer is further improved, and the adhesive tape obtained has better bending resistance. In addition, since the fracture strength of the adhesive layer is increased, cohesive failure of the adhesive layer can be further suppressed, resulting in improved adhesive strength and thus improved step-following ability of the adhesive tape of this embodiment. The more preferable lower limit for the average short diameter of the bubbles in the adhesive layer is 15 μm, the more preferable upper limit is 70 μm, the even more preferable lower limit is 20 μm, the even more preferable upper limit is 65 μm, the even more preferable upper limit is 60 μm, the particularly preferable upper limit is 55 μm, and the very preferable upper limit is 50 μm. Examples of the average short diameter of the bubbles in the adhesive layer include 10 μm to 75 μm, 15 μm to 70 μm, 20 μm to 65 μm, 20 μm to 60 μm, 20 μm to 55 μm, 20 μm to 50 μm, etc.

[0117] The aspect ratio of the air bubbles in the adhesive layer described above has a preferred lower limit of 1.00 and a preferred upper limit of 3.50. When the aspect ratio of the air bubbles in the adhesive layer is 1.00 or higher, the structure of the air bubbles in the adhesive layer becomes flattened, and the adhesive layer has appropriate flexibility. As a result, the stress relaxation properties of the adhesive layer are further improved, and the resulting adhesive tape has better shock absorption properties. When the aspect ratio of the air bubbles in the adhesive layer is 3.50 or lower, the bending rigidity of the adhesive layer is further improved, and the resulting adhesive tape has better bending resistance. In addition, since the fracture strength of the adhesive layer is increased, cohesive failure of the adhesive layer can be further suppressed, and as a result the adhesive strength of the adhesive layer is further improved, the step-following ability of the adhesive tape of this embodiment is further improved. A more preferred lower limit for the aspect ratio of the air bubbles in the adhesive layer is 1.25, a more preferred upper limit is 3.00, an even more preferred lower limit is 1.50, and an even more preferred upper limit is 2.50. Examples of aspect ratios for bubbles in the foam layer include 1.00 to 3.50, 1.25 to 3.00, 1.50 to 2.50, etc. In this specification, "aspect ratio of bubbles" means the value obtained by dividing the average major diameter of the bubbles by the average minor diameter of the bubbles (average major diameter of bubbles / average minor diameter of bubbles).

[0118] The average major diameter, average minor diameter, and aspect ratio of the bubbles in the adhesive layer can be determined, for example, as follows: Using a razor (Feather Corporation), the adhesive layer is sliced ​​with a plane parallel to the MD (Machine Direction) direction and the thickness direction to obtain an MD cut sample. The obtained MD cut sample is photographed using a digital microscope (for example, Keyence Corporation's "VHX-6000") under conditions such as a magnification of 200x and a measurement screen size of 1.8 mm × 1.3 mm. In the obtained photographed image, the bubble with the largest major diameter and the bubble with the second largest major diameter are selected, and the major and minor diameters of these bubbles are measured to calculate the aspect ratio. Perform this operation for three captured images. The average of the major axes of the six bubbles is taken as the average major axis of the bubbles in the adhesive layer, the average of the minor axes of the six bubbles is taken as the average minor axis of the bubbles in the adhesive layer, and the average of the aspect ratios of the six bubbles is taken as the aspect ratio of the bubbles in the adhesive layer. If the above MD direction is unknown, slice the adhesive layer with a plane parallel to the thickness direction to obtain a cut sample. Slice the sample so that the cutting direction is shifted by 30° from the direction from which the previous cut sample was cut, and measure the aspect ratio in the same manner as above. Repeat the above measurement until returning to the cutting direction of the first measurement. The average of the major axes of the twelve bubbles measured is taken as the average major axis of the bubbles in the adhesive layer, the average of the minor axes of the twelve bubbles is taken as the average minor axis of the bubbles in the adhesive layer, and the average of the aspect ratios of the twelve bubbles is taken as the aspect ratio of the bubbles in the adhesive layer.

[0119] Methods for adjusting the average major diameter of the bubbles in the adhesive layer, the average minor diameter of the bubbles in the adhesive layer, and the aspect ratio of the bubbles in the adhesive layer include, for example, a method of mechanically stretching and compressing the adhesive layer during its manufacture, and a method of including a surfactant or stabilizer in the adhesive composition that forms the adhesive layer.

[0120] The thickness of the adhesive layer described above has a preferred lower limit of 50 μm and a preferred upper limit of 500 μm. When the thickness of the adhesive layer is 50 μm or more, the adhesive strength of the adhesive layer is further improved. When the thickness of the adhesive layer is 500 μm or less, the adhesive layer has appropriate flexibility, so the stress relaxation properties of the adhesive layer are further improved, and the adhesive layer has better shock absorption properties. In addition, the step-following ability of the adhesive tape of this embodiment is further improved. A more preferred lower limit for the thickness of the adhesive layer is 80 μm, a more preferred upper limit is 400 μm, an even more preferred lower limit is 100 μm, an even more preferred upper limit is 300 μm, and an even more preferred upper limit is 200 μm. Examples of the thickness of the adhesive layer include 50 μm to 500 μm, 80 μm to 400 μm, 100 μm to 300 μm, 100 μm to 200 μm, etc.

[0121] In this specification, thickness can be measured using a dial thickness gauge (for example, Mitutoyo's "ABS Digimatic Indicator").

[0122] Preferably, the average major diameter of the bubbles in the adhesive layer is 0.80 times or less the thickness of the adhesive layer. By having an average major diameter of bubbles 0.80 times or less the thickness of the adhesive layer, the bending rigidity of the adhesive layer is further improved, and the adhesive tape of this embodiment has improved bending resistance. In addition, since the fracture strength of the adhesive layer is increased, cohesive failure of the adhesive layer can be further suppressed, resulting in improved adhesive strength and thus improved step-following ability of the adhesive tape of this embodiment. More preferably, the average major diameter of the bubbles is 0.70 times or less the thickness of the adhesive layer, and even more preferably 0.60 times or less. In addition, it is preferable that the average major diameter of the bubbles is 0.05 times or more the thickness of the adhesive layer. By having an average major diameter of bubbles 0.05 times or more the thickness of the adhesive layer, the adhesive layer has appropriate flexibility, and the stress relaxation ability of the adhesive layer is further improved, resulting in the adhesive tape having better shock absorption. Furthermore, the ability of the adhesive tape of this embodiment to follow steps is further improved. It is more preferable that the average major diameter of the bubbles is 0.10 times or more the thickness of the adhesive layer. That is, it is preferable that the average major diameter of the bubbles is 0.05 times or more and 0.80 times or less the thickness of the foam layer, more preferably 0.10 times or more and 0.70 times or less, and even more preferably 0.10 times or more and 0.60 times or less.

[0123] Preferably, the adhesive layer has a structure in which no air bubbles are exposed on the surface in the thickness direction. Because the adhesive layer does not have air bubbles exposed on the surface in the thickness direction, the area of ​​the adhesive interface between the adhesive layer and the adherend is increased, which in turn improves the adhesive strength of the adhesive layer and thus improves the step-following ability of the adhesive tape of this embodiment.

[0124] One method for creating a structure in which no air bubbles are exposed on the surface in the thickness direction of the adhesive layer is to use an adhesive composition containing large foaming particles, thereby suppressing the floating of foaming particles to the liquid surface during the solution coating of the adhesive composition in the adhesive layer formation process.

[0125] The adhesive tape of this embodiment may have layers other than the adhesive layer described above.

[0126] The adhesive tape of this embodiment may or may not have a base material. If the adhesive tape of this embodiment has a base material, the resulting adhesive tape can be given better reworkability. If the adhesive tape of this embodiment does not have a base material, the resulting adhesive tape will have improved shock absorption and step-following properties. In addition, since the resulting adhesive tape will be thinner, it will be more suitable for use in fixing electronic equipment components or automotive components. In particular, if the adhesive tape of this embodiment does not have a base material, it is preferable that the adhesive tape of this embodiment consists only of the adhesive layer described above.

[0127] If the adhesive tape of this embodiment has a base material, it may be a single-sided adhesive tape having the adhesive layer on one side of the base material, or it may be a double-sided adhesive tape having adhesive layers on both sides of the base material. Furthermore, if the adhesive tape of this embodiment is a double-sided adhesive tape, at least one of the adhesive layers may be the adhesive layer.

[0128] If the adhesive tape of this embodiment has a base material, examples of the types of base materials used for the base material include film, nonwoven fabric, and the like.

[0129] From the viewpoint of increasing the overall bio-derived carbon content of the adhesive tape, a substrate made from a bio-derived material is preferred for the substrate used in the above-mentioned substrate. Examples of the above-mentioned bio-derived materials include polyesters (PES) such as polyethylene terephthalate (PET), polyethylene furanoate (PEF), polylactic acid (PLA), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polybutylene succinate (PBS), as well as polyethylene (PE), polypropylene (PP), polyurethane (PU), triacetylcellulose (TAC), cellulose, and polyamide (PA), all of which are derived from plants.

[0130] Furthermore, from the perspective of reducing environmental impact by decreasing the use of new petroleum resources and suppressing carbon dioxide emissions, base materials made from recycled resources may be used. Methods for recycling resources include, for example, recovering waste from packaging containers, home appliances, automobiles, construction materials, food, etc., or waste generated in the manufacturing process, and using the extracted materials again as raw materials by washing, decontamination, or decomposition by heating or fermentation. Examples of base materials using the above recycled resources include films and nonwoven fabrics made from PET, PBT, PE, PP, PA, etc., using recovered plastics that have been re-resinated as raw materials. Alternatively, the recovered waste may be burned and used as thermal energy for the manufacture of base materials and their raw materials, or the oils and fats contained in the recovered waste may be mixed with petroleum, fractionally distilled, and refined to be used as raw materials.

[0131] The type of base material used for the above-mentioned base material is preferably a film, from the viewpoint of the base material having excellent stiffness and further improving the bending resistance of the resulting adhesive tape, and preferably a film containing PES or a film containing PA. Examples of PA include nylon 11, nylon 1010, nylon 610, nylon 510, nylon 410, etc., which are made from castor oil, and nylon 56, etc., which are made from cellulose.

[0132] The preferred lower limit for the thickness of the above-mentioned substrate is 3.5 μm, and the preferred upper limit is 1000 μm. By having the thickness of the above-mentioned substrate within the above range, the balance between the flexibility and rigidity of the substrate is improved, and the bending resistance and shock absorption of the resulting adhesive tape are further improved. A more preferred lower limit for the thickness of the above-mentioned substrate is 5 μm, a more preferred upper limit is 500 μm, an even more preferred lower limit is 6.5 μm, an even more preferred upper limit is 300 μm, an even more preferred lower limit is 10 μm, an even more preferred upper limit is 200 μm, a particularly preferred lower limit is 30 μm, and a particularly preferred upper limit is 100 μm. Examples of the thickness of the above-mentioned adhesive layer include 3.5 μm to 1000 μm, 5 μm to 500 μm, 6.5 μm to 300 μm, 10 μm to 200 μm, 30 μm to 100 μm, etc.

[0133] The adhesive tape of this embodiment may have a second adhesive layer without a foamed structure on at least one side of the adhesive layer. By having the second adhesive layer on at least one side of the adhesive layer of this embodiment, the interlayer strength of the resulting adhesive tape is further improved, and the shock absorption of the adhesive tape of this embodiment is further improved. Therefore, the adhesive tape of this embodiment may have the second adhesive layer on one side of the adhesive layer, or it may have the second adhesive layer on both sides of the adhesive layer.

[0134] The adhesive contained in the second adhesive layer described above is not particularly limited as long as it does not impair the effects of the present invention, and conventionally known adhesives can be used. Specifically, examples include acrylic adhesives, urethane adhesives, rubber adhesives, silicone adhesives, etc. Among these, acrylic adhesives are preferred from the viewpoint of the design range of the adhesive and the wide range of adherend selectivity, and acrylic adhesives containing the above-mentioned acrylic copolymer in the adhesive layer are more preferred from the viewpoint of excellent strong adhesion and further improvement of the step-following ability of the adhesive tape of this embodiment.

[0135] The thickness of the second adhesive layer described above has a preferred lower limit of 5 μm and a preferred upper limit of 100 μm. When the thickness of the second adhesive layer is 5 μm or more, the second adhesive layer has sufficient adhesive strength, and the handling of the adhesive tape is further improved. When the thickness of the second adhesive layer is 100 μm or less, the step-following ability of the adhesive tape of this embodiment is further improved. A more preferred lower limit for the thickness of the second adhesive layer is 10 μm, a more preferred upper limit is 90 μm, an even more preferred lower limit is 15 μm, and an even more preferred upper limit is 80 μm. Examples of the thickness of the second adhesive layer include 5 μm to 100 μm, 10 μm to 90 μm, 15 μm to 80 μm, etc.

[0136] The method for manufacturing the adhesive tape of this embodiment is not particularly limited, and conventionally known methods can be used. For example, the method for manufacturing an adhesive tape consisting only of the adhesive layer is as follows. First, a solvent is added to an acrylic copolymer, tackifying resin, etc., to prepare a solution of the adhesive composition. Next, the prepared adhesive composition solution is applied to the release surface of a release film, and the solvent in the solution is dried and removed to form an adhesive layer. Then, by placing the release surface of the release film on top of the formed adhesive layer, an adhesive tape can be obtained in which the surface of the adhesive layer is covered with a release film.

[0137] Furthermore, the method for manufacturing an adhesive tape having the above-mentioned substrate and having the above-mentioned adhesive layer on at least one surface of the substrate is as follows. That is, an adhesive layer formed in the same manner as the method for manufacturing an adhesive tape consisting only of the above-mentioned adhesive layer is bonded to the substrate, pressed together using a rubber roller to create a laminated and integrated structure, and then cured in a 40°C environment for 72 hours to obtain an adhesive tape having an adhesive layer on one surface of the substrate. Alternatively, the adhesive composition may be directly applied to the substrate, dried to form an adhesive layer, and then the release treatment surface of a release film may be placed on top of the formed adhesive layer. Alternatively, an adhesive tape having adhesive layers on both sides of the substrate can be obtained by placing an arbitrary adhesive layer prepared on the other surface of the substrate and then laminating and integrating it.

[0138] Furthermore, the method for manufacturing an adhesive tape having the second adhesive layer on at least one side of the adhesive layer is as follows. That is, after overlapping an adhesive layer formed in the same manner as the method for manufacturing an adhesive tape consisting only of the adhesive layer described above with an arbitrary second adhesive layer, pressing them together using a rubber roller to create a laminated and integrated layer, and then curing it in a 40°C environment for 72 hours, an adhesive tape having the second adhesive layer on one side of the adhesive layer can be manufactured. Also, by performing the same operation on the other side of the foam layer in an adhesive tape having the second adhesive layer on one side of the manufactured adhesive layer, an adhesive tape having the second adhesive layer on both sides of the adhesive layer can be manufactured.

[0139] Furthermore, adhesive tapes having the second adhesive layer on at least one side of the adhesive layer can also be manufactured using a multilayer extrusion extruder. Specifically, the adhesive tape can be manufactured by supplying the composition for forming the adhesive layer and the composition for forming the second adhesive layer to a multilayer extrusion extruder, melt-mixing them, and then extruding a sheet-like adhesive tape base roll in which the adhesive layer and the second adhesive layer are laminated.

[0140] In this embodiment, the preferred lower limit of the 180° peel force against SUS (stainless steel) at 23°C on the adhesive layer side having the foam structure described above (hereinafter simply referred to as "the 180° peel force of the adhesive tape against SUS at 23°C") is 10 N / 25 mm. By having a 180° peel force of 10 N / 25 mm or more on SUS at 23°C, the adhesive tape will have better adhesion and superior ability to follow steps. A more preferred lower limit of the 180° peel force of the adhesive tape against SUS at 23°C is 12 N / 25 mm, and an even more preferred lower limit is 15 N / 25 mm. Furthermore, there is no particular upper limit for the 180° peel force of the adhesive tape against SUS at 23°C, but approximately 50 N / 25 mm is a practical upper limit. Examples of the 180° peel force of the above adhesive tape on SUS at 23°C include 10N / 25mm to 50N / 25mm, 12N / 25mm to 50N / 25mm, and 15N / 25mm to 50N / 25mm.

[0141] The 180° peel force of the above adhesive tape against SUS at 23°C can be measured by the following method. First, one side of the adhesive tape (the side not to be measured) is backed with a 23 μm thick polyethylene terephthalate film by pressing it against the surface using a 2 kg rubber roller at a speed of 300 mm / min for one back-and-forth motion, if necessary. The film is then cut to a width of 25 mm and a length of 75 mm to prepare a test specimen. Next, the prepared test specimen is attached to a SUS304 plate (a SUS304 plate that has been cleaned with ethanol and then wiped dry), with the measurement surface of the adhesive layer of the adhesive tape pressed against it by pressing it against the surface using a 2 kg rubber roller at a speed of 300 mm / min for one back-and-forth motion. Finally, it is cured at 23°C and 50% RH for 20 minutes to prepare a test sample. The obtained test samples can be measured by peeling the adhesive tape from the SUS304 plate in accordance with JIS Z 0237:2009, under conditions of 23°C, 50% RH, a tensile speed of 300 mm / min, and a peeling angle of 180°.

[0142] Methods for adjusting the 180° peel force of the above adhesive tape against SUS at 23°C include, for example, changing the composition of the acrylic copolymer contained in the adhesive layer (for example, increasing the content of constituent units derived from monomers having crosslinkable functional groups), adjusting the weight-average molecular weight, polydispersity, etc., of the acrylic copolymer, including a tackifying resin in the adhesive layer, adjusting the thickness of the adhesive layer, adjusting the content of the crosslinking agent contained in the adhesive composition, and adjusting the type and thickness of the substrate.

[0143] The thickness of the adhesive tape in this embodiment has a preferred lower limit of 60 μm and a preferred upper limit of 300 μm. A thickness of 60 μm or more in this embodiment improves the step-following ability and shock absorption of the resulting adhesive tape. A thickness of 300 μm or less in this embodiment results in a more flexible adhesive tape, making it more suitable for fixing electronic equipment components or automotive components. A more preferred lower limit for the thickness of the adhesive tape in this embodiment is 80 μm, a more preferred upper limit is 250 μm, an even more preferred lower limit is 100 μm, and an even more preferred upper limit is 200 μm. Examples of adhesive tape thicknesses in this embodiment include 60 μm to 300 μm, 80 μm to 250 μm, and 100 μm to 200 μm. In this specification, "thickness of adhesive tape" does not include the thickness of the separator, such as a release film, that protects the outermost adhesive layer of the adhesive tape.

[0144] The adhesive tape of this embodiment has a preferred upper limit of 70% for light transmittance at a wavelength of 550 nm. By having a light transmittance of 70% or less at a wavelength of 550 nm, the adhesive tape of this embodiment can be more suitably used for fixing internal components of electrical and electronic equipment. A more preferred upper limit for the light transmittance of the adhesive tape of this embodiment at a wavelength of 550 nm is 50%, an even more preferred upper limit is 40%, a particularly preferred upper limit is 30%, and a very preferred upper limit is 10%. There is no particular lower limit for the light transmittance of the adhesive tape of this embodiment at a wavelength of 550 nm, with 0% being the most preferred. Examples of the light transmittance of the adhesive tape of this embodiment at a wavelength of 550 nm include 0% to 70%, 0% to 60%, 0% to 50%, 0% to 40%, 0% to 30%, and 0% to 10%. Furthermore, the transmittance of the adhesive tape of this embodiment at a wavelength of 550 nm can be measured using a spectrophotometer (such as the "V-670" manufactured by JASCO Corporation).

[0145] The application of the adhesive tape of this embodiment is not particularly limited, but because the adhesive tape of this embodiment has excellent step-following ability, it can be suitably used to fix parts with steps. Furthermore, because the adhesive tape of this embodiment has excellent bending resistance and can maintain adhesive reliability even in high temperature and high humidity environments, it can be more suitably used to fix electronic equipment parts or automotive parts. Examples of the electronic equipment parts include parts in electronic devices such as televisions, monitors, and portable electronic devices, and examples of automotive parts include automotive panels. Specifically, examples include fixing parts in foldable display devices such as thin-screen televisions and thin-screen monitors, and more specifically, using it to fix the surface cover panel of a display device to a housing with irregularities. When using the adhesive tape of this embodiment to fix parts, a primer treatment may be performed by applying a primer (undercoat) to the surface of the parts to be bonded, and then the parts may be bonded and fixed with the adhesive tape of this embodiment. The primer is not particularly limited, and conventionally known primers can be used, for example, epoxy primers, urethane primers, acrylic primers, etc.

[0146] Furthermore, it is preferable that the adhesive tape of this embodiment be further given shock absorption properties by various methods. Since an adhesive tape with excellent shock absorption properties can prevent damage to components due to impacts such as drops, it can be more suitably used for fixing components in portable electronic devices.

[0147] An electronic device including the adhesive tape of this embodiment is also one of these embodiments. The electronic device of this embodiment is not particularly limited as long as it includes the adhesive tape, but examples include electronic devices in which electronic components are bonded and fixed together with the adhesive tape, and specifically, for example, a display device in which a cover panel and a housing having irregularities are bonded and fixed together with the adhesive tape.

[0148] According to the present invention, it is possible to provide an adhesive tape that has excellent step-following ability and excellent bending resistance, and that can maintain adhesive reliability even in high-temperature and high-humidity environments. Furthermore, according to the present invention, it is possible to provide electronic equipment including the adhesive tape.

[0149] This is a schematic diagram illustrating the method for evaluating bending resistance. This is a schematic diagram of a test specimen used for evaluating impact absorption. This is a schematic diagram illustrating the method for evaluating impact absorption.

[0150] The embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are as follows.

[0151] <Monomers containing bio-derived carbon> (1) Linoleic acid derived from castor oil was converted to linoleic acid hydroperoxide by lipoxygenase, and then a mixture containing n-hexylaldehyde was obtained by isomerase. By distillation of the obtained mixture, bio-derived carbon-containing n-hexylaldehyde was obtained. Furthermore, by hydrogenation of the obtained bio-derived carbon-containing n-hexylaldehyde, bio-derived carbon-containing n-hexyl alcohol was obtained. By esterifying the obtained bio-derived carbon-containing n-hexyl alcohol with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), bio-derived carbon-containing n-hexyl acrylic acid was synthesized.

[0152] (2) Ricinoleic acid derived from n-heptyl acrylate castor oil was cracked to obtain a mixture containing undecylenic acid and n-heptyl alcohol. Then, undecylenic acid was separated from the obtained mixture by distillation to obtain n-heptyl alcohol containing bio-derived carbon. By esterifying the obtained n-heptyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), n-heptyl acrylate containing bio-derived carbon was prepared.

[0153] (3) Ricinoleic acid derived from 1-methylheptyl acrylate castor oil was dissolved in alkali to obtain a mixture containing sebacic acid and 1-methylheptyl alcohol. Then, sebacic acid was separated from the obtained mixture by distillation to obtain 1-methylheptyl alcohol containing bio-derived carbon. 1-methylheptyl acrylate containing bio-derived carbon was prepared by esterifying the obtained 1-methylheptyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.).

[0154] (4) Pinene extracted from pine resin was isomerized to obtain camphene containing bio-derived carbon. By reacting camphene containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), isobornyl acrylate containing bio-derived carbon was synthesized.

[0155] (5) Pinene extracted from pine resin was isomerized to obtain camphene containing bio-derived carbon. By reacting camphene containing bio-derived carbon with methacrylic acid (manufactured by Mitsubishi Chemical Corporation), isobornyl methacrylate containing bio-derived carbon was synthesized.

[0156] <Biologically derived, carbon-free monomers> ・Methyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) ・Methyl methacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) ・n-butyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) ・2-ethylhexyl acrylate (manufactured by Nippon Shokubai Co., Ltd.) ・Acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) ・2-hydroxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) ・Dicyclopentanyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) ・t-butyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) ・Ethylene-butylene macromonomer (ethylene-butylene macromonomer with an acryloyl group at one end, manufactured by Kraton Polymers, "HPVM-L1253")

[0157] <Expandable Particles> - Thermally expandable microcapsules: Expancel 920DU40 (manufactured by Nippon Philite Co., Ltd., average particle size 40 μm)

[0158] <Aromatic block copolymer (X)> ・SIS block copolymer: Quintac 3620 (manufactured by Zeon Corporation, styrene ratio 14%)

[0159] <Coloring agent> ・Carbon black: Multi-rack A903 Black (manufactured by Toyo Color Co., Ltd.)

[0160] <Tackifying Resin> ・Terpene phenol resin: YS Polystar G150 (manufactured by Yasuhara Chemical Co., Ltd.)

[0161] <Crosslinking agents> - Isocyanate-based crosslinking agent: Desmodulo L-75 (manufactured by Covestro) - Epoxy-based crosslinking agent: Tetrad E-5C (manufactured by Mitsubishi Gas Chemical Company)

[0162] (Synthesis of Acrylic Copolymers) (Acrylic Copolymers A-P) A reactor equipped with a thermometer, stirrer, and condenser was prepared. A mixture of the constituent unit monomers shown in Tables 1-2 and 80 parts by mass of ethyl acetate were added to the reactor, and the reactor was heated and reflux was started. Next, 0.01 parts by mass of 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane was added to the reactor as a polymerization initiator, and polymerization was started under reflux. Next, 0.01 parts by mass of 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane was added 1 hour and 2 hours after the start of polymerization, and then 0.05 parts by mass of t-hexylperoxypivalate was added 4 hours after the start of polymerization to continue the polymerization reaction. Eight hours after the start of polymerization, an ethyl acetate solution of the acrylic copolymer was obtained. The weight-average molecular weight of the obtained acrylic copolymer was measured using a 2690 Separations Module (Waters Inc.) as the measuring instrument, a GPC KF-806L column (Showa Denko Corporation), and ethyl acetate as the solvent, under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C. The results are shown in Tables 1 and 2.

[0163]

[0164]

[0165] (Example 1) (1) Preparation of adhesive tape To the solution of acrylic copolymer A obtained in the above-described "(synthesis of acrylic copolymer)", 0.4 parts by mass of thermally expandable microcapsules as foaming particles and 30 parts by mass of ethyl acetate as a solvent were added to 100 parts by mass of solid content of acrylic copolymer A, and the mixture was thoroughly stirred to prepare a solution containing an adhesive composition. The prepared solution containing the adhesive composition was applied to the release treatment surface of a 50 μm thick release PET film, and then heated at 115°C for 1 hour to dry the solvent and foam the layer of adhesive composition, thereby forming an adhesive layer with a thickness of 80 μm. The cross-section of the double-sided adhesive tape cut along a plane parallel to the thickness direction was observed at a magnification of 1000x using a digital microscope (Keyence Corporation, "VHX-6000"), and the surface in the thickness direction of the adhesive layer was further observed, and it was found that the obtained adhesive layer had a structure in which no air bubbles were exposed on the surface in the thickness direction. After bonding the obtained adhesive layer to the release-treated surface of a 50 μm thick release PET film, and curing it in a 40°C environment for 48 hours, an adhesive tape with a release PET film was obtained in which the surface of the adhesive layer was protected by the release PET film, in an adhesive tape having only an adhesive layer.

[0166] (2) Measurement of the gel fraction of the adhesive layer The release PET film was peeled off one side of the obtained adhesive tape and bonded to a 23 μm thick base PET film (Futamura Chemical Co., Ltd., "FE2002"), and cut into a flat rectangular shape with a width of 20 mm and a length of 40 mm. The release PET film was then peeled off the other side of the adhesive tape to prepare a test piece, and its mass was measured. The test piece was immersed in ethyl acetate at 23°C for 24 hours, then removed from the ethyl acetate and dried at 110°C for 1 hour. The mass of the dried test piece was measured, and the gel fraction (mass %) was calculated using the above formula (I). The results are shown in Table 3.

[0167] (Examples 2-18, 20-21, Comparative Examples 1-4) Except for the fact that the composition and thickness of the adhesive layer were as shown in Tables 3-5 in "(1) Preparation of adhesive tape" described above, adhesive tape was prepared and various measurements were taken in the same manner as in Example 1. The results are shown in Tables 3-5. The adhesive layers in Examples 2-18, 20-21, and Comparative Examples 2-4 had a foamed structure. The cross-section of the double-sided adhesive tape cut in a plane parallel to the thickness direction was observed at a magnification of 1000x using a digital microscope (Keyence Corporation, "VHX-6000"), and the surface in the thickness direction of the adhesive layer was further observed. The obtained adhesive layer had a structure in which no air bubbles were exposed on the surface in the thickness direction. On the other hand, the adhesive layer in Comparative Example 1 did not have a foamed structure.

[0168] (Example 19) An adhesive layer with a thickness of 75 μm was formed in the same manner as in Example 1, except that the composition of the adhesive layer was as shown in Table 4. The adhesive layer in Example 19 had a foamed structure, and the cross-section obtained by cutting the double-sided adhesive tape in a plane parallel to the thickness direction was observed at a magnification of 1000x using a digital microscope (Keyence Corporation, "VHX-6000"), and the surface in the thickness direction of the adhesive layer was further observed to confirm that the obtained adhesive layer had a structure in which no air bubbles were exposed on the surface in the thickness direction. After the obtained adhesive layer was attached to one side of the substrate described in Table 4, it was pressed down by running a 2 kg rubber roller back and forth at a speed of 300 mm / min for one pass. Furthermore, an adhesive layer with the same composition and thickness was prepared and attached to the other side of the substrate, then pressed down by running a 2 kg rubber roller back and forth at a speed of 300 mm / min for one pass and alight to laminate and integrate it, and then cured for 1 hour in an environment of 23°C to obtain an adhesive tape having adhesive layers on both sides of the substrate. In Table 4, "PET film" refers to E5200 (thickness: 50 μm) manufactured by Toyobo Co., Ltd. Regarding the various measurements, the procedure was the same as in Example 1, except that in "(2) Measurement of gel fraction of the adhesive layer," "(3) Measurement of bio-derived carbon content of the adhesive layer," and "(4) Measurement of deemed density of the adhesive layer," only the adhesive layer was removed from the obtained adhesive tape using a cutter knife, and the measurements were performed using the same method as in Example 1. The results are shown in Table 4.

[0169] <Evaluation> The adhesive tapes obtained in the examples and comparative examples were evaluated as follows. The results are shown in Tables 3 to 5.

[0170] (Step-following ability) The obtained adhesive tape was cut to a size of 20 mm in width and 20 mm in length, and attached to the stepped side of a silicon wafer with a step of approximately 10 μm under conditions of 23°C and 50% RH. The sample was then left to stand for 1 hour under the same conditions of 23°C and 50% RH to prepare a measurement sample. The stepped silicon wafer was prepared by making a cut of approximately 10 μm on the surface of a wafer (Φ8 inch, thickness 725 μm) using a dicing device (DISCO Corporation, "DFD6360"). The wafer surface of the measurement sample was observed with an optical microscope (KEYENCE Corporation, "VHX-970F", magnification 10x), and the step-following ability of the adhesive tape was evaluated according to the following criteria: ・A: No void was observed between the wafer and the adhesive tape. ・B: A void was observed between the wafer and the adhesive tape, but the size of the void between the wafer and the adhesive tape was less than 5% of the total area of ​​the adhesive surface. C: The size of the void between the wafer and the adhesive tape was 5% or more of the total surface area of ​​the adhesive surface.

[0171] (Bending resistance) Aluminum alloy plates (SHAANXI SHWEW-E STEEL PIPE, "Aluminum 6061-T6", 1.6 mm thick, 25.4 mm wide, 203.2 mm long) were attached to both sides of the obtained adhesive tape by applying a load of 1 MPa for 20 seconds at 65°C to laminate them together, and then cured by leaving them undisturbed at 23°C for 24 hours to produce laminate 1. The fabricated laminate 1 was set up in a Tensilon (A&D Company, Limited) used as a measuring instrument in accordance with JIS K 7171 as shown in Figure 1 (distance between compression jigs: 57.15 mm, distance between fixing jigs: 177.8 mm). Then, the laminate 1 was compressed at a constant speed of 0.05 mm / s in an environment of 23 ± 1°C and 50 ± 5% humidity until the load reached 50 N. In the obtained stress-deformation curve, the slope of the line (stress / deformation) was calculated from two points on the stress-deformation curve: one with a stress of 20 N and another with a stress of 50 N. Based on the obtained slope of the line, the bending resistance of the adhesive tape was evaluated according to the following criteria: A: The slope of the line was 17.0 N / mm or greater. B: The slope of the line was 15.5 N / mm or greater and less than 17.0 N / mm. C: The slope of the line was 12.0 N / mm or greater and less than 15.5 N / mm. D: The slope of the line was less than 12.0 N / mm.

[0172] (Adhesion reliability under high temperature and high humidity conditions) (1) Measurement of 180° peel force before standing in a high temperature and high humidity environment One side of the obtained adhesive tape (the side not measured) was pressed onto a 23 μm thick polyethylene terephthalate film by running a 2 kg rubber roller back and forth once at a speed of 300 mm / min to create a backing, and then cut to a width of 25 mm x length of 75 mm to prepare a test piece. Next, the adhesive layer on the other side of the prepared test piece was attached to a SUS304 plate (a SUS304 plate that had been washed with ethanol and then wiped dry), and pressed by running a 2 kg rubber roller back and forth once at a speed of 300 mm / min. After that, it was cured at 23°C and 50% RH for 20 minutes to prepare a test sample. Then, the prepared test samples were peeled from the SUS304 plate in accordance with JIS Z 0237:2009, under conditions of 23°C, 50% RH, tensile speed of 300 mm / min, and peel angle of 180°, thereby determining the 180° peel force F before standing in a high-temperature, high-humidity environment. １ (N / 25mm) was measured.

[0173] (2) Measurement of 180° peel force after standing in a high-temperature, high-humidity environment After preparing test samples in the same manner as in "(1) Measurement of 180° peel force before standing in a high-temperature, high-humidity environment" described above, the prepared test samples were placed in a constant temperature and humidity oven set to 85°C and 85%RH and left to stand in a high-temperature, high-humidity environment. Then, the test samples that had been left in the high-temperature, high-humidity environment were removed and air-cooled by standing in an environment of 23°C and 50%RH for 1 hour. For the air-cooled test samples, the 180° peel force (N / 25mm) after standing in a high-temperature, high-humidity environment was measured by peeling the adhesive tape from the SUS304 plate under the conditions of 23°C and 50%RH, tensile speed of 300 mm / min, and peel angle of 180°, in accordance with JIS Z 0237:2009.

[0174] (3) Calculation of the rate of decrease in 180° peeling force due to standing in a high temperature and high humidity environment Using the 180° peeling force before and after standing in a high temperature and high humidity environment, measured by the method described above, the rate of decrease in 180° peeling force due to standing in a high temperature and high humidity environment (%) was calculated using the following formula: Rate of decrease in 180° peeling force due to standing in a high temperature and high humidity environment (%) = 100 × [{(180° peeling force before standing in a high temperature and high humidity environment) - (180° peeling force after standing in a high temperature and high humidity environment)} / (180° peeling force before standing in a high temperature and high humidity environment)]

[0175] (4) Evaluation of adhesive reliability of adhesive tape in a high temperature and high humidity environment The 180° peel force after standing in a high temperature and high humidity environment was calculated for 500 hours, 1000 hours, and 1500 hours, as described in "(2) Measurement of 180° peel force after standing in a high temperature and high humidity environment" above, and the adhesive reliability of the adhesive tape in a high temperature and high humidity environment was evaluated according to the following criteria. A: When left standing in a high temperature and high humidity environment for 1500 hours, the decrease in 180° peel force due to standing in a high temperature and high humidity environment was 50% or less. B: When left standing in a high temperature and high humidity environment for 1000 hours, the decrease in 180° peel force due to standing in a high temperature and high humidity environment was 50% or less, but when left standing in a high temperature and high humidity environment for 1500 hours, the decrease in 180° peel force due to standing in a high temperature and high humidity environment was greater than 50%. C: When left standing in a high-temperature, high-humidity environment for 500 hours, the decrease in 180° peeling force due to standing in a high-temperature, high-humidity environment was 50% or less. However, when left standing in a high-temperature, high-humidity environment for 1000 hours, the decrease in 180° peeling force due to standing in a high-temperature, high-humidity environment was greater than 50%. D: When left standing in a high-temperature, high-humidity environment for 500 hours, the decrease in 180° peeling force due to standing in a high-temperature, high-humidity environment was greater than 50%.

[0176] (Impact Absorption) (1) Calculation of Impact Absorption Energy The obtained adhesive tape was cut to a size of 30 mm x 30 mm, and two SUS plates 5 measuring 125 mm x 50 mm and 2 mm thick were stacked on the cut adhesive tape 4 as shown in Figure 2 to create a test piece 6. The obtained test piece 6 was set up as shown in Figure 3 so that when the pendulum 7 passed its lowest point, it would collide with only one of the SUS plates 5 on the test piece. Then, a pendulum 7 with a mass of 1.0 kg was dropped from a height of 0.2 m (H in Figure 3) and collided with the test piece 6, and the highest height h reached was measured. Using the obtained height h, the impact absorption energy in the test piece before heating was calculated from the following formula. Note that the lowest point reached by the pendulum is set to 0 for height. Impact absorption energy in the test piece before heating (J) = mg(0.2 - h) (m: mass of the pendulum (kg), g: acceleration due to gravity (9.80 m / s) ２ ), h: measured height (m)

[0177] (2) Evaluation of the shock absorption performance of the adhesive tape Based on the calculated shock absorption energy, the shock absorption performance of the adhesive tape was evaluated according to the following criteria: A: The shock absorption energy was 0.50 J or more. B: The shock absorption energy was 0.30 J or more and less than 0.50 J. C: The shock absorption energy was 0.15 J or more and less than 0.30 J. D: The shock absorption energy was less than 0.15 J. Even if the evaluation is "D", the adhesive tape of this embodiment can be used without problems depending on the application.

[0178]

[0179]

[0180]

[0181] According to the present invention, it is possible to provide an adhesive tape that has excellent step-following ability and excellent bending resistance, and that can maintain adhesive reliability even in high-temperature and high-humidity environments. Furthermore, according to the present invention, it is possible to provide electronic equipment including the adhesive tape.

[0182] 1. Laminate 2. Compression jig 3. Fixing jig 4. Adhesive tape 5. SUS plate 6. Test piece 7. Pendulum

Claims

1. An adhesive tape having an adhesive layer having a foamed structure, wherein the adhesive layer contains an acrylic copolymer having constituent units derived from a (meth)acrylic acid ester having a hydrocarbon group, and the constituent units derived from the (meth)acrylic acid ester having a hydrocarbon group are represented by the following formula (1), and include constituent units derived from a (meth)acrylic acid ester having a glass transition temperature of 120°C or higher when formed as a homopolymer. In the formula, R １ R represents a hydrogen atom or a methyl group. ２ R represents a hydrogen atom or a hydrocarbon group. ３ and R ４ Each of these independently represents a hydrocarbon group or a bond R ３ -CR-R ４ This forms a cyclic hydrocarbon group.

2. R in formula (1) above １ The adhesive tape according to claim 1, wherein the group is a methyl group.

3. The adhesive tape according to claim 2, wherein the constituent unit derived from a (meth)acrylic acid ester represented by formula (1) and having a glass transition temperature of 120°C or higher when formed as a homopolymer includes a constituent unit derived from isobornyl methacrylate.

4. The adhesive tape according to claim 3, wherein the content of the constituent unit derived from isobornyl methacrylate in the acrylic copolymer is 30% by mass or less.

5. The adhesive tape according to claim 1, 2, 3, or 4, wherein the constituent unit derived from the (meth)acrylic acid ester having a hydrocarbon group comprises at least one constituent unit selected from the group consisting of a constituent unit derived from n-hexyl (meth)acrylic acid, a constituent unit derived from n-heptyl (meth)acrylic acid, and a constituent unit derived from 1-methylheptyl (meth)acrylic acid.

6. The adhesive tape according to claim 1, 2, 3, 4, or 5, wherein the acrylic copolymer has constituent units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals.

7. The adhesive tape according to claim 6, wherein the content of constituent units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminal in the acrylic copolymer is 5% by mass or more and 30% by mass or less.

8. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, or 7, wherein the acrylic copolymer has constituent units derived from monomers having crosslinkable functional groups.

9. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, or 8, wherein the acrylic copolymer comprises a block copolymer having at least one block having a structural unit derived from a (meth)acrylic acid ester having a hydrocarbon group, and at least one block having a structural unit derived from a vinyl aromatic compound.

10. The adhesive tape according to claim 9, wherein the content of constituent units derived from the vinyl aromatic compound in the acrylic copolymer is 2.5% by mass or more and 20% by mass or less.

11. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the adhesive layer contains an aromatic block copolymer (X) having at least two blocks having structural units derived from a vinyl aromatic compound, and at least one of a block having structural units derived from a conjugated diene compound and a hydrogenated form of a block having structural units derived from a conjugated diene compound.

12. The adhesive tape according to claim 11, wherein the content of the aromatic block copolymer (X) is 60 parts by mass or less per 100 parts by mass of the acrylic copolymer.

13. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the adhesive layer contains a pigment.

14. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein the adhesive layer contains a tackifying resin.

15. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein the adhesive layer does not contain a tackifying resin.

16. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, wherein the adhesive layer has a structure derived from a crosslinking agent.

17. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, wherein the adhesive layer has a gel fraction of 10% by mass or more and 70% by mass or less.

18. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17, wherein the adhesive layer has a bio-derived carbon content of 10% or more.

19. The adhesive layer has an apparent density of 0.59 g / cm ３ or more and 1.15 g / cm ３ or less. The adhesive tape according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18.

20. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19, wherein the adhesive layer has an average major diameter of air bubbles that is 0.80 times or less the thickness of the adhesive layer.

21. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, wherein the adhesive layer has a structure in which no air bubbles are exposed on the surface in the thickness direction.

22. An adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 21, which does not have a base material.

23. The adhesive tape according to claim 22, comprising only the adhesive layer.

24. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 21, comprising a base material and having the adhesive layer on at least one surface of the base material.

25. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, or 24, further comprising a second adhesive layer not having a foamed structure on at least one surface of the adhesive layer.

26. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25, wherein the adhesive tape has a 180° peel force of 10 N / 25 mm or more at 23°C on the side of the adhesive layer having the foamed structure.

27. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, or 26, wherein the thickness is 60 μm or more and 300 μm or less.

28. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, or 27, used for fixing electronic equipment components or in-vehicle components.

29. Electronic device comprising the adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, or 28.

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