Adhesive tape and electronic device

Abstract

The purpose of the present invention is to provide an adhesive tape capable of achieving both excellent followability and excellent strong adhesiveness. The purpose of the present invention is also to provide an electronic device including the adhesive tape. The present invention is an adhesive tape having a foamed body layer, wherein the foamed body layer contains an acrylic copolymer having a constituent unit derived from a (meth)acrylic acid ester and a constituent unit derived from an olefin-based polymer having a polymerizable unsaturated double bond at a terminal.

Description

Adhesive tape, and electronic devices

[0001] This invention relates to an adhesive tape. Furthermore, this invention relates to an electronic device including the adhesive tape.

[0002] Adhesive tape is widely used for securing electronic components. Specifically, for example, it is used to secure the surface cover panel to the housing of display devices such as televisions and monitors.

[0003] In recent years, as a result of pursuing design and functionality, display devices such as televisions and monitors have become narrower in bezel size, and expectations for bezel-less display devices are also rising. In the manufacturing of conventional display devices, cover panels were sometimes fixed to the casing by snapping or screwing them in, but with display devices that have narrow bezels, snapping or screwing in is difficult, so the demand for fixing with adhesive tape is increasing, and adhesive tapes are also becoming thinner and narrower.

[0004] As an example of an adhesive tape that can be used in such a display device, Patent Documents 1 and 2 describe an impact-absorbing tape in which an acrylic adhesive layer is laminated and integrated on at least one side of a base layer, and the base layer is a crosslinked polyolefin resin foam sheet having a specific degree of crosslinking and a specific aspect ratio of bubbles.

[0005] Japanese Patent Publication No. 2009-242541 Japanese Patent Publication No. 2009-258274

[0006] Adhesive tapes used to secure panels and casings of smartphones, tablets, and other devices require the ability to conform to curved and uneven surfaces, while also possessing strong adhesive properties, as the internal environment of electronic components is often exposed to harsh conditions such as high temperatures.

[0007] For adhesive tapes to have excellent conformability to curved or uneven surfaces, they need to be flexible enough to deform to match the shape of the curved or uneven surface they are being bonded to. Conventionally, adhesive tapes using foam substrates, such as polyolefin substrates, have been used to achieve this flexibility. However, adhesive tapes using polyolefin substrates have the problem of relatively low adhesion between the adhesive layer and the substrate, making it difficult to achieve strong adhesion. On the other hand, acrylic foam and styrene-acrylic foam, which have been used as other foam substrates, have sufficient conformability but insufficient strong adhesion.

[0008] Furthermore, while single-layer adhesive tapes are sometimes used to increase the flexibility of adhesive tapes, even conventional single-layer adhesive tapes made of synthetic rubber have had the problem of low adhesive strength.

[0009] The present invention aims to provide an adhesive tape that can achieve both excellent conformability and excellent strong adhesion. Furthermore, the present invention aims to provide an electronic device containing the adhesive tape.

[0010] Disclosure 1 is an adhesive tape having a foam layer, wherein the foam layer contains an acrylic copolymer having constituent units derived from (meth)acrylic acid ester and constituent units derived from an olefin polymer having polymerizable unsaturated double bonds at its ends. Disclosure 2 is the adhesive tape of Disclosure 1, wherein the foam layer has a 180° peel force of 10 N / 25 mm or more against SUS at 23°C. Disclosure 3 is the adhesive tape of Disclosure 2, wherein the foam layer is formed using an adhesive resin composition. Disclosure 4 is the adhesive tape of Disclosure 1, 2, or 3, wherein the content of constituent units derived from the olefin polymer having polymerizable unsaturated double bonds at its ends in the acrylic copolymer is 5% by mass or more and 50% by mass or less. Disclosure 5 is an adhesive tape according to Disclosure 1, 2, 3, or 4, wherein the constituent units derived from the (meth)acrylic acid ester include constituent units derived from an alkyl (meth)acrylic acid ester having an alkyl group having 1 to 8 carbon atoms, and the content ratio of the constituent units derived from the alkyl (meth)acrylic acid ester having an alkyl group having 1 to 8 carbon atoms in the alkyl (meth)acrylic acid ester is 50% by mass or more and 100% by mass or less. Disclosure 6 is an adhesive tape according to Disclosure 1, 2, 3, 4, or 5, wherein the constituent units derived from the (meth)acrylic acid ester include constituent units derived from an aliphatic cyclic structure. Disclosure 7 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, or 6, wherein the acrylic copolymer has constituent units derived from a polar functional group-containing monomer, and the content ratio of the constituent units derived from the polar functional group-containing monomer in the acrylic copolymer is 0.1% by mass or more. Disclosure 8 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, or 7, comprising an aromatic block copolymer (X) in which the foam layer has 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 said block. Disclosure 9 is an adhesive tape according to Disclosure 8, 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 10 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the acrylic copolymer has constituent units derived from a vinyl aromatic compound, and the content ratio of the 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 Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the acrylic copolymer has a weight-average molecular weight of 300,000 or more and 1,500,000 or less. Disclosure 12 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the foam layer contains a tackifying resin. Disclosure 13 is an adhesive tape according to Disclosure 12, wherein the content of the tackifying resin per 100 parts by mass of the acrylic copolymer is 0.1 parts by mass or more and 15 parts by mass or less. 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 foam layer is colored. Disclosure 15 is an adhesive tape according to Disclosure 3, wherein the adhesive resin composition contains a crosslinking agent. Disclosure 16 is an adhesive tape according to Disclosure 16, wherein the foam 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, or 15. Disclosure 17 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, wherein the foam layer has an average major diameter of bubbles that is 0.8 times or less the thickness of the foam layer. Disclosure 18 is an adhesive tape according to Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17, wherein the foam layer has a structure in which bubbles are not exposed on the surface in the thickness direction. Disclosure 19 is an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, wherein the foam layer has a shear storage modulus of 0.50 MPa or more at 23°C, as measured by dynamic viscoelastic measurement at a measurement frequency of 1 Hz. Disclosure 20 is an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19, consisting only of the foam layer. Disclosure 21 is an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, having a base material and having the foam layer on at least one side of the base material. Disclosure 22 is an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 21 having an adhesive layer on at least one side of the foam layer. Disclosure 23 is an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, or 22 used for fixing internal components of electrical and electronic equipment. Disclosure 24 is an electronic device including an adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, or 23. The present invention is described in detail below. Hereinafter, embodiments of the present invention or one thereof will be described as "this embodiment."

[0011] The present inventors have found that by using an adhesive foam layer as the foam layer for adhesive tape, and by making the acrylic copolymer contained in the adhesive foam layer have constituent units derived from alkyl (meth)acrylate esters and constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their ends, a foam layer with strong adhesive properties and flexibility can be obtained. As a result of using this foam layer, the inventors have found that it is possible to provide an adhesive tape that can achieve both excellent conformability and excellent strong adhesive properties, thus completing the present invention.

[0012] The adhesive tape of this embodiment has a foam layer. The presence of the foam layer in the adhesive tape of this embodiment improves its stress relaxation properties and provides superior conformability.

[0013] The preferred lower limit for the 180° peel force of the foam layer against SUS (stainless steel) at 23°C is 10 N / 25 mm. Because the 180° peel force of the foam layer against SUS at 23°C is 10 N / 25 mm or higher, the foam layer becomes adhesive, and the adhesive tape can be made solely of the foam layer. Therefore, the adhesive tape of this embodiment has superior shock absorption while also possessing superior adhesive strength. A more preferred lower limit for the 180° peel force of the foam layer against SUS at 23°C is 12 N / 25 mm, an even more preferred lower limit is 15 N / 25 mm, and an even more preferred lower limit is 20 N / 25 mm. There is no particular upper limit for the 180° peel force of the foam layer against SUS at 23°C, but approximately 50 N / 25 mm is a practical upper limit. The 180° peel force of the foam layer against SUS at 23°C can be 10N / 25mm to 50N / 25mm, 12N / 25mm to 50N / 25mm, 15N / 25mm to 50N / 25mm, 20N / 25mm to 50N / 25mm, etc. The 180° peel force of the foam layer against SUS at 23°C is measured by the following method. First, one side of the obtained foam layer (the side not to be measured) is backed with a polyethylene terephthalate film with a thickness of 23 μm, and then cut to a width of 25 mm and a length of 75 mm to prepare a test piece. Next, the obtained test specimen was bonded to a SUS304 plate (a SUS304 plate that had been washed with ethanol and then wiped dry), and pressed down by passing 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. The obtained test sample could be measured by leaving it standing for 20 minutes in an environment of 23°C and 50% RH, and then peeling the foam layer from the SUS304 plate in accordance with JIS Z 0237:2009, under conditions of 23°C and 50% RH, a tensile speed of 300 mm / min, and a peel angle of 180°.

[0014] Methods for adjusting the 180° peel force of the foam layer against SUS at 23°C include, for example, changing the composition of the acrylic copolymer contained in the foam layer (for example, increasing the mass percentage of polar monomers), including a tackifying resin in the foam layer, adjusting the thickness of the foam layer, and adjusting the amount of crosslinking agent.

[0015] Methods for forming the foam layer include, for example, applying foaming particles to a resin composition that forms the foam layer and heating and drying it, forcibly mixing and dispersing a gas in the resin composition that forms the foam layer, and mixing liquefied gas in the resin composition that forms the foam layer. Among these, the method of applying foaming particles to a resin composition that forms the foam layer and heating and drying it is preferred from the viewpoint of ensuring foam dispersibility during high-temperature drying.

[0016] The foam layer described above is formed from an adhesive resin composition. Because the foam layer is formed from an adhesive resin composition, it becomes adhesive. A method for forming the foam layer from the adhesive resin composition includes, for example, applying the adhesive resin composition to a release film or the like, and then heating and drying the adhesive resin composition.

[0017] The above adhesive resin composition preferably contains foaming particles. The inclusion of foaming particles in the adhesive resin composition improves the dispersion of bubbles in the formed foam layer, resulting in superior stress relaxation properties.

[0018] The foam layer described above preferably has bubbles derived from foaming particles. The foam layer having bubbles derived from foaming particles can be formed by heating and foaming an adhesive resin composition containing foaming particles. Examples of the foaming particles include those that foam when heated. Specifically, examples include pyrolysis-type foaming agents and thermally expandable microcapsules, and among these, it is preferable that the foaming particles include thermally expandable microcapsules. Thermally expandable microcapsules become hollow particles with bubbles inside their outer shell when heated. Therefore, in this embodiment, by including thermally expandable microcapsules in the foaming particles, the gas generated from the foaming particles by heating is prevented from escaping to the outside of the foam layer, making it easier to have an appropriate amount of bubbles coexisting in the foam layer, and thus making it easier to improve the foaming ratio of the foam layer. As a result, the foam layer has appropriate flexibility, and the stress relaxation properties of the adhesive tape are further improved, so the adhesive tape of this embodiment has better shock absorption properties.

[0019] The above-mentioned heat-expandable microcapsules contain a volatile substance such as a low-boiling point solvent inside an outer resin shell. When heated, the outer resin softens, causing the contained volatile substance to volatilize or expand. This expansion of the outer shell increases the particle size due to the resulting pressure. Preferably, the outer shell of the heat-expandable microcapsule is formed from a thermoplastic resin. The thermoplastic resin can be one or more selected from vinyl polymers and copolymers thereof, such as ethylene, styrene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, butadiene, and chloroprene, as well as polyamides such as nylon 6 and nylon 66, and polyesters such as polyethylene terephthalate. Among these, acrylonitrile copolymers are preferred because they do not easily allow the contained volatile substance to permeate.

[0020] The volatile substances enclosed within 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 CCl３ F, CCl ２ F ２ One or more low-boiling point liquids selected from chlorofluorocarbons such as chlorofluorocarbons, tetramethylsilanes such as tetraalkylsilanes such as trimethylethylsilane, etc. are used. Among these, hydrocarbons having 3 to 7 carbon atoms are preferred.

[0021] 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.

[0022] 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.

[0023] The average particle size of the foamed particles described above has a preferred upper limit of 60 μm. By having an average particle size of 60 μm or less, the balance between the strength and impact resistance of the resulting adhesive tape can be further improved. A more preferred upper limit for the average particle size of the foamed particles is 55 μm, and an even more preferred upper limit is 50 μm. The average particle size of the foamed particles described above has a preferred lower limit of 15 μm. By having an average particle size of 15 μm or more, the flexibility of the resulting adhesive tape can be ensured. A more preferred lower limit for the average particle size of the foamed particles described above is 20 μm, and an even more preferred lower limit is 25 μm. Examples of the average particle size of the foamed particles described above include 15 μm to 60 μm, 20 μm to 55 μm, 25 μm to 50 μm, etc. Furthermore, in this specification, "average particle size of the foamed particles described above" refers to the average particle diameter of the unfoamed foamed particles observed from the adhesive resin composition containing the foamed particles described above. The average particle size can be determined by randomly selecting particles using an optical microscope and calculating the average of 10 points.

[0024] Furthermore, although not particularly limited, the expansion initiation temperature (also called the "expansion initiation temperature") of the above-mentioned foaming particles should be approximately 95°C to 150°C. The expansion initiation temperature of the above-mentioned foaming particles is the temperature at which the thermally expandable microcapsules begin to expand, and can be measured using a thermomechanical analyzer (TMA) or the like.

[0025] 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).

[0026] The foam layer described above contains an acrylic copolymer (hereinafter sometimes simply referred to as "acrylic copolymer") having constituent units derived from alkyl (meth)acrylate esters and constituent units derived from olefin polymers having polymerizable unsaturated double bonds at their terminals. In this specification, "(meth)acrylic" means acrylic or methacrylic.

[0027] The above-mentioned acrylic copolymer has a structure in which constituent units derived from an olefin polymer having polymerizable unsaturated double bonds at the ends of its side chains aggregate through interactions, forming pseudo-crosslinks. Because the acrylic copolymer adopts this structure, when peel stress is applied and the strain increases, the pseudo-crosslinks break, and the molecules of the acrylic copolymer stretch. As a result, the foam layer exhibits high flexibility and excellent stress relaxation properties. Therefore, the adhesive tape of this embodiment has excellent strong adhesion and superior conformability. On the other hand, when the strain is small, the molecules of the acrylic copolymer become hard like a crosslinked structure due to the pseudo-crosslinks, so the foam layer has moderate hardness. Therefore, the adhesive tape of this embodiment has even better retention properties. In other words, because the above-mentioned acrylic copolymer contains structural units derived from alkyl (meth)acrylate esters and structural units derived from olefin polymers having polymerizable unsaturated double bonds at their terminals, the adhesive tape of this embodiment, even with a foam layer, exhibits excellent strong adhesion, excellent conformability, and superior holding power.

[0028] The above acrylic copolymer has constituent units derived from (meth)acrylate alkyl ester. The (meth)acrylate alkyl ester in the constituent units derived from the above (meth)acrylate alkyl ester may consist only of petroleum-derived materials, but it is preferable that it also contains bio-derived materials. 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. The above (meth)acrylate alkyl ester containing bio-derived materials 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.

[0029] When the (meth)acrylic acid alkyl ester in the structural unit derived from the above (meth)acrylic acid alkyl ester contains a bio-derived material, the (meth)acrylic acid alkyl ester is preferably synthesized by esterification of an alcohol that is a bio-derived material and (meth)acrylic acid.

[0030] The structural unit derived from the above (meth)acrylic acid alkyl ester preferably contains a structural unit derived from a (meth)acrylic acid alkyl ester having 1 to 8 carbon atoms (hereinafter, may also be referred to as "structural unit (a-1)"). By the structural unit derived from the above (meth)acrylic acid alkyl ester containing the above structural unit (a-1), the glass transition temperature of the acrylic copolymer described later is likely to satisfy a suitable range, the adhesive strength of the above foam layer is further improved, and the adhesive tape of the present embodiment has more excellent high adhesive strength and more excellent holding properties.

[0031] Examples of the above structural unit (a-1) include structural units derived from (meth)acrylic acid alkyl esters such as 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-heptyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-methylheptyl acrylate, etc. Among them, from the viewpoint that the adhesive tape of the present embodiment is more excellent in peel strength, a structural unit derived from a (meth)acrylic acid alkyl ester having an alkyl group with 6 to 8 carbon atoms is preferable. Note that only one kind of the above structural unit (a-1) may be included, or two or more kinds may coexist.

[0032] In the structural unit derived from the above (meth)acrylic acid alkyl ester, the content ratio of the above structural unit (a-1) preferably has a lower limit of 50% by mass. When the content ratio of the above structural unit (a-1) is 50% by mass or more, the adhesive force of the above foam layer is further improved, and the adhesive tape of the present embodiment has more excellent strong adhesiveness and more excellent holding property. A more preferable lower limit of the content ratio of the above structural unit (a-1) is 60% by mass, a further preferable lower limit is 65% by mass, and an even more preferable lower limit is 70% by mass. Also, the content ratio of the above structural unit (a-1) may be 100% by mass, but from the viewpoint of bending resistance, a preferable upper limit is 90% by mass, a more preferable upper limit is 85% by mass, and a further preferable upper limit is 80% by mass. Note that examples of the content ratio of the above structural unit (a-1) include 50% by mass or more and 90% by mass or less, 60% by mass or more and 85% by mass or less, 65% by mass or more and 80% by mass or less, 70% by mass or more and 80% by mass or less, and the like.

[0033] The structural unit derived from the above (meth)acrylic acid alkyl ester preferably includes a structural unit derived from a (meth)acrylic acid alkyl ester having an alkyl group having an aliphatic cyclic structure (hereinafter, may also be referred to as "structural unit (a-2)"). When the structural unit derived from the above (meth)acrylic acid alkyl ester includes the above structural unit (a-2), the adhesive tape of the present embodiment becomes more excellent in bending resistance.

[0034] Examples of the above structural unit (a-2) include structural units derived from (meth)acrylic acid alkyl esters having an aliphatic cyclic structure such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, and the like. Note that only one kind of the above structural unit (a-2) may be included, or two or more kinds may coexist.

[0035] The preferred lower limit for the content of the above-mentioned structural unit (a-2) in the structural unit derived from the above-mentioned alkyl (meth)acrylate is 5% by mass. By having a content of 5% by mass or more of the above-mentioned structural unit (a-2), the adhesive tape of this embodiment will have superior bending resistance. A more preferred lower limit for the content of the above-mentioned structural unit (a-2) is 8% by mass, an even more preferred lower limit is 10% by mass, and an even more preferred lower limit is 20% by mass. Furthermore, from the viewpoint of ensuring adhesive strength and flexibility, a preferred upper limit for the content of the above-mentioned structural unit (a-2) is 50% by mass, and a more preferred upper limit is 40% by mass. Examples of the content of the above-mentioned structural unit (a-2) include 5% by mass or more and 50% by mass or less, 8% by mass or more and 40% by mass or less, 10% by mass or more and 40% by mass or less, 20% by mass or more and 40% by mass or less, etc.

[0036] The constituent units derived from the above alkyl (meth)acrylate may include other constituent units derived from alkyl (meth)acrylate other than the above constituent units (a-1) and (a-2) (hereinafter sometimes referred to as "constituent unit (a-3)").

[0037] Examples of the above constituent units (a-3) include constituent units derived from alkyl esters of (meth)acrylate, such as 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. Note that only one type of above constituent unit (a-3) may be included, or two or more types may coexist.

[0038] The preferred lower limit and preferred upper limit of the content of the constituent units derived from the alkyl (meth)acrylate in the above acrylic copolymer is 50% by mass. By having the content of the constituent units derived from the alkyl (meth)acrylate within the above range, the adhesive tape of this embodiment will have better adhesive strength and better retention. A more preferred lower limit for the content of the constituent units derived from the alkyl (meth)acrylate 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 the constituent units derived from the alkyl (meth)acrylate 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.

[0039] The above acrylic copolymer has constituent units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminal. The above olefin polymer having a polymerizable unsaturated double bond at its terminal may have a polymerizable unsaturated double bond at one terminal or at both terminals. Among these, an olefin polymer having a polymerizable unsaturated double bond at one terminal is preferred from the viewpoint of less intramolecular chemical crosslinking and further improving the retention of the adhesive tape of this embodiment.

[0040] 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 a 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 alkyl (meth)acrylates. Specific examples of olefin polymers having a polymerizable unsaturated double bond at one end 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. In particular, ethylene-butylene macromonomers having a (meth)acryloyl group at one end and ethylene-propylene macromonomers having a (meth)acryloyl group at the other end are preferred, from the viewpoint that the glass transition temperature of the acrylic copolymer described later is more likely to be within a suitable range and the adhesive strength of the foam layer is further improved. These olefin polymers having polymerizable unsaturated double bonds at their ends may be used alone or in combination of two or more. Furthermore, 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.

[0041] In the above acrylic copolymer, the preferred lower limit for 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 50% 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, further improving the adhesive strength and retention of the foam layer. When the content of constituent units derived from the olefin polymer having polymerizable unsaturated double bonds at its ends is 50% by mass or less, the bulk strength of the foam layer is further improved, and thus the retention of the adhesive tape of this embodiment is further improved. A more preferred lower limit for the content of constituent units derived from the olefin polymer having polymerizable unsaturated double bonds at its ends is 8% by mass, a more preferred upper limit is 45% by mass, an even more preferred lower limit is 10% by mass, an even more preferred upper limit is 40% by mass, an even more preferred lower limit is 15% by mass, and an even more preferred upper limit is 30% 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 50% by mass or less, 8% by mass or more and 45% by mass or less, 10% by mass or more and 40% by mass or less, and 15% by mass or more and 30% by mass or less.

[0042] The above acrylic copolymer preferably has structural units derived from a polar functional group-containing monomer. Because the acrylic copolymer has structural units derived from a polar functional group-containing monomer, it can sufficiently form a crosslinked structure through chemical crosslinking via a crosslinking agent between molecules, thereby improving the cohesive force of the foam layer. As a result, the retention of the adhesive tape of this embodiment is further improved. Furthermore, because the acrylic copolymer has structural units derived from the polar functional group-containing monomer, the polar functional groups in the acrylic copolymer interact with each other, further improving the cohesive force of the foam layer, and thus improving the adhesive strength and retention of the adhesive tape of this embodiment.

[0043] Examples of constituent units derived from the above polar functional group-containing monomers 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 improving the adhesiveness and retention of the foam layer, it is preferable that the constituent units derived from the above polar functional group-containing monomers 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. Specific examples of constituent units derived from the above 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 maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid. Specific examples of constituent units derived from the above hydroxyl group-containing monomers include constituent units derived from 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate. Specific examples of structural units derived from the above-mentioned amide group-containing monomers include those derived from N-vinyl-2-pyrrolidone, N,N-dimethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, etc. Specific examples of structural units derived from the above-mentioned amino group-containing monomers include those derived from (meth)acryloylmorpholine, dimethylaminoethyl(meth)acrylate, diethylaminoethyl(meth)acrylate, etc. Note that only one type of structural unit derived from these polar functional group-containing monomers may be included, or two or more types may coexist.

[0044] In the above acrylic copolymer, the preferred lower limit of the content of constituent units derived from the polar functional group-containing monomer is 0.1% by mass, and the preferred upper limit is 10% by mass. When the content of constituent units derived from the polar functional group-containing monomer is within the above range, the acrylic copolymer can sufficiently form a crosslinked structure, thereby improving the holding power of the adhesive tape of this embodiment. Furthermore, when the content of constituent units derived from the polar functional group-containing monomer is 0.1% by mass or more, the interaction between polar functional groups can be further enhanced, thereby improving the adhesive strength and holding power of the foam layer. When the content of constituent units derived from the polar functional group-containing monomer is 10% by mass or less, the foam layer does not become too hard, and the adhesive strength is further improved. A more preferred lower limit for the content of constituent units derived from the above polar functional group-containing monomer 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 of constituent units derived from the above polar functional group-containing monomer 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, 5.0% by mass or more and 7.0% by mass or less.

[0045] 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.

[0046] Examples of structural units derived from the above-mentioned vinyl aromatic compounds include structural units derived from styrene, structural units derived from α-methylstyrene, and structural units derived from their hydrogenated products. Among these, structural units derived from styrene are preferred from the viewpoint of balancing flexibility and strength. Note that only one type of structural unit derived from these vinyl aromatic compounds may be included, or two or more types may coexist.

[0047] 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 copolymer (A)") of a block having structural units derived from the above vinyl aromatic compound (hereinafter sometimes simply referred to as "block (A-1)") and a block having structural units derived from the above alkyl (meth)acrylate and structural units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminal (hereinafter sometimes simply referred to as "block (A-2)"). In the above block copolymer (A), block (A-1) becomes a hard segment and imparts shock absorption to the adhesive tape, and block (A-2) becomes a soft segment and imparts strong adhesion and conformability to the adhesive tape. In particular, from the viewpoint of achieving superior strong adhesion and conformability of the adhesive tape of this embodiment, it is preferable that the above acrylic copolymer includes block copolymer (A) when it has structural units derived from a vinyl aromatic compound.

[0048] The block copolymer (A) may be a diblock copolymer or a triblock copolymer. Among these, a triblock copolymer is preferred from the viewpoint of ensuring flexibility and retention performance, and among triblock copolymers, a triblock copolymer having the structure of block (A-1) - block (A-2) - block (A-1) is more preferred.

[0049] 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 conformability and strong adhesion properties. 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.

[0050] 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 block (A-2) synthesized in the same manner as the acrylic copolymer described above, and copolymerized. Alternatively, the pre-synthesized blocks (A-1) and (A-2) may be copolymerized.

[0051] The preferred lower limit for the content of constituent units derived from the vinyl aromatic compound in the above acrylic copolymer is 2.5% by mass. A content of 2.5% by mass or more of constituent units derived from the vinyl aromatic compound 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 vinyl aromatic compound is 3.0% by mass, an even more preferred lower limit is 3.5% by mass, an even more preferred lower limit is 4.5% by mass, and a particularly preferred lower limit is 6.0% by mass. Furthermore, the preferred upper limit for the content of constituent units derived from the vinyl aromatic compound is 20% by mass. A content of 20% by mass or less of constituent units derived from the vinyl aromatic compound results in superior conformability and strong adhesion of the adhesive tape of this embodiment. A more preferred upper limit for the content of constituent units derived from the vinyl aromatic compound is 18% by mass, an even more preferred upper limit is 15% by mass, an even more preferred upper limit is 12% by mass, a particularly preferred upper limit is 10% by mass, and a very preferred upper limit is 8.0% by mass. Examples of the content ratio of constituent units derived from the vinyl aromatic compound include 2.5% by mass or more and 20% by mass or less, 3.0% by mass or more and 18% by mass or less, 3.5% by mass or more and 15% by mass or less, 4.5% by mass or more and 12% by mass or less, 6.0% by mass or more and 10% by mass or less, and 6.0% by mass or more and 8.0% by mass or less.

[0052] 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 further improves the tackiness and retention of the foam layer. 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 600,000, an even more preferred upper limit is 1,000,000, and an even more preferred lower limit is 800,000. 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, 600,000 to 1,000,000, and 800,000 to 1,000,000.

[0053] 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. Having the polydispersity (Mw / Mn) of the above acrylic copolymer within this range further improves the tackiness and retention of the foam layer. A more preferred lower limit for the polydispersity (Mw / Mn) of the above acrylic copolymer is 1.5, a more preferred upper limit is 7.5, an even more preferred lower limit is 2.0, and an even more preferred upper limit is 7.0. Examples of polydispersity (Mw / Mn) of the above acrylic copolymer include 1.0 to 8.0, 1.5 to 7.5, 2.0 to 7.0, etc. Furthermore, in this specification, "weight-average molecular weight" and "number-average molecular weight" refer to the weight-average molecular weight measured as polystyrene-equivalent molecular weight by gel permeation chromatography (GPC). Specifically, the weight-average molecular weight, number-average molecular weight, and polydispersity of the above-mentioned acrylic copolymer can be measured using, for example, a Waters "2690 Separations Module" as the measuring instrument, a Showa Denko "GPC KF-806L" as the column, and ethyl acetate as the solvent, under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C.

[0054] The preferred lower limit for the content of the acrylic copolymer in the foam layer is 30% by mass. A content of 30% by mass or more of the acrylic copolymer further improves the adhesiveness and retention properties of the foam layer. A more preferred lower limit for the content of the acrylic copolymer is 40% by mass, and an even more preferred lower limit is 45% by mass. Furthermore, the upper limit for the content of the acrylic copolymer is not particularly limited and may be 100% by mass, but a preferred upper limit for the content of the acrylic copolymer is 99.5% by mass, a more preferred upper limit is 95% by mass, an even more preferred upper limit is 90% by mass, and an even more preferred upper limit is 85% by mass. Examples of the acrylic copolymer content include 30% by mass or more and 100% by mass or less, 40% by mass or more and 99.5% by mass or less, 45% by mass or more and 95% by mass or less, 45% by mass or more and 90% by mass or less, and 45% by mass or more and 85% by mass or less.

[0055] The polymerization method for synthesizing the above-mentioned acrylic copolymer can be a conventionally known method in which a mixture of monomer raw materials is subjected to 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.

[0056] 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.

[0057] 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.

[0058] Preferably, the foam 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") and a hydrogenated form of said block. By containing the aromatic block copolymer (X) in the foam layer, the adhesive tape of this embodiment has superior shock absorption properties.

[0059] 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 described above 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.

[0060] 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 benzylpropyl ether. Examples of alkylsilyl styrenes include trimethylsilylstyrene. These vinyl aromatic compounds may be used individually or in combination of two or more. Among these, styrene, methylstyrene, and dimethylstyrene are preferred, and styrene is more preferred because it is readily available industrially.

[0061] 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% or more of constituent units derived from the vinyl aromatic compound further improves the holding power of the adhesive tape of this embodiment. A more preferred lower limit for the constituent units derived from the vinyl aromatic compound is 10% by mass. Furthermore, from the viewpoint of flexibility and shock absorption, a preferred upper limit for the constituent units derived from the vinyl aromatic compound is 35% by mass, and a more preferred upper limit is 30% by mass. Examples of the content of constituent units derived from the vinyl aromatic compound in the vinyl aromatic polymer block include 7% to 35% by mass, 10% to 30% by mass, and so on.

[0062] 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. These conjugated diene compounds may be used individually or in combination of two or more. Among these, 1,3-butadiene and isoprene are preferred due to their high polymerization reactivity and ease of industrial availability. In addition to the above-mentioned conjugated diene compounds, other usable compounds include, for example, 2,5-dihydrofuran-2,5-dione.

[0063] The hydrogenated product 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% are converted to saturated bonds by hydrogenation (i.e., a fully hydrogenated product). 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%.

[0064] 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 adhesive strength of the adhesive tape of this embodiment. 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. Furthermore, there is no particular preferred upper limit for the constituent units derived from the conjugated diene compound, but the practical upper limit is 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.

[0065] Examples of the structure of the above aromatic block copolymer (X) include, when the vinyl aromatic polymer block is B and the conjugated diene polymer block and the hydrogenated product thereof are 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 so on.

[0066] 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 acrylic copolymers.

[0067] The preferred lower limit for the weight-average molecular weight (Mw) of the above aromatic block copolymer (X) is 50,000. A weight-average molecular weight (Mw) of 50,000 or more results in superior shock absorption. A more preferred lower limit for the weight-average molecular weight of the above aromatic block copolymer (X) is 100,000, and an even more preferred lower limit is 150,000. Furthermore, there is no particular preferred upper limit for the weight-average molecular weight of the above aromatic block copolymer (X), but from the viewpoint of compatibility with acrylic copolymers, it is practically limited to around 500,000. Examples of weight-average molecular weight (Mw) of the above aromatic block copolymer (X) include 50,000 to 500,000, 100,000 to 500,000, and 150,000 to 500,000.

[0068] 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 60 parts by mass or less, the adhesive strength of the foam layer is further improved, and the adhesive tape of this embodiment has superior strong adhesion. A more preferred upper limit for the content of the aromatic block copolymer (X) is 55 parts by mass, an even more preferred upper limit is 50 parts by mass, and an even more preferred upper limit is 45 parts by mass. Also, a preferred lower limit for the content of the aromatic block copolymer (X) is 10 parts by mass. When the content of the aromatic block copolymer (X) is 10 parts by mass or more, the adhesive strength of the foam layer is further improved, and the adhesive tape of this embodiment has 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 45 parts by mass or less.

[0069] The foam layer preferably contains a tackifying resin. The inclusion of a tackifying resin in the upper foam layer improves the adhesive strength of the foam layer, resulting in the adhesive tape of this embodiment having superior tackiness.

[0070] 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 resins or terpene resins are preferred from the viewpoint of compatibility with the acrylic copolymers mentioned above, and among these, rosin resins or terpene resins having hydroxyl groups are more preferred. These tackifying resins may be used alone or in combination of two or more types.

[0071] Examples of rosin-based 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-based resins having the hydroxyl group mentioned above include YS Polystar G150 and YS Polystar T160 (both manufactured by Yasuhara Chemical Co., Ltd.).

[0072] Preferably, the tackifying resin described above includes a tackifying resin containing bio-derived carbon. By including a tackifying resin containing bio-derived carbon, the content of bio-derived carbon in the foam layer described later can be increased, and the environmental impact of the resulting adhesive tape can be further reduced. Specific examples of tackifying resins containing bio-derived carbon include KE-100, KE-359, KE-604, KR-140, A-75, and 803L (all manufactured by Arakawa Chemical Industries, Ltd.).

[0073] The tackifying resin described above preferably includes a tackifying resin having 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 foam layer's retention is further improved. By including a tackifying resin with a softening point of 170°C or lower, the wettability of the interface of the foam layer is improved, resulting in the adhesive tape of this embodiment having superior tackiness. The tackifying resin more preferably includes a tackifying resin with a softening point of 100°C or higher and 160°C or lower, even more preferably includes a tackifying resin with a softening point of 120°C or higher and 150°C or lower, and still more preferably includes 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 K2207 (ring-ball method).

[0074] The tackifying resin described above preferably includes a tackifying resin having a hydroxyl value of 25 mgKOH / g or more. By including a tackifying resin having a hydroxyl value of 25 mgKOH / g or more, the wettability of the interface of the foam layer is improved, and the adhesive tape of this embodiment becomes more strongly tacky. The tackifying resin described above more preferably includes a tackifying resin having a hydroxyl value of 30 mgKOH / g or more, and even more preferably includes a tackifying resin having a hydroxyl value of 35 mgKOH / g or more. There is no particular upper limit to the hydroxyl value of the tackifying resin described above, but from the viewpoint of compatibility with the acrylic copolymer and the aromatic block copolymer described above, the substantial upper limit is 50 mgKOH / g. Examples of the hydroxyl value of the tackifying resin described above include 25 mgKOH / g or more and 50 mgKOH / g or less, 30 mgKOH / g or more and 50 mgKOH / g or less, 35 mgKOH / g or more and 50 mgKOH / g or less, etc. Furthermore, within this specification, the hydroxyl value of the tackifying resin can be measured by JIS K1557 (phthalic anhydride method).

[0075] The preferred upper limit of the content of the tackifying resin per 100 parts by mass of the acrylic copolymer is 50 parts by mass. By having a tackifying resin content within this range, the adhesive tape of this embodiment exhibits superior tackiness. 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. Furthermore, if the foam layer contains a tackifying resin, there is no particular preferred lower limit for the tackifying resin content; it should be greater than 0 parts by mass. A preferred lower limit for the tackifying resin content is 0.1 parts by mass, and a more preferred lower limit is 1.0 part by mass. Note that the foam layer does not necessarily have to contain a tackifying resin. Examples of the content of the tackifying resin 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, more than 1.0 part by mass and 30 parts by mass or less, more than 1.0 part by mass and 20 parts by mass or less, more than 1.0 part by mass and 10 parts by mass or less, and so on.

[0076] The above adhesive resin composition preferably contains a crosslinking agent. The inclusion of a crosslinking agent in the adhesive resin composition results in a crosslinked structure in the foam layer, thus providing the adhesive tape of this embodiment with superior holding power. From the viewpoint of storage stability, the crosslinking agent may be added to the adhesive resin composition immediately before forming the foam layer.

[0077] 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 adhesion of the foam layer to the substrate.

[0078] 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 this range, the adhesive tape of this embodiment exhibits superior adhesive strength. 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 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.

[0079] The foam layer preferably contains a coloring agent. Since the adhesive resin composition contains a coloring agent, the foam layer is colored and given light-shielding properties, making the adhesive tape of this embodiment more suitable for fixing internal components of electrical and electronic equipment.

[0080] If the foam layer is colored, it contains a coloring agent. Examples of coloring agents include pigments and dyes. Pigments are particularly preferred from the viewpoint of heat resistance, and examples of pigments include carbon black, aniline black, and titanium dioxide. Among these, carbon black is preferred because it is relatively inexpensive and chemically stable.

[0081] The preferred lower limit of the coloring agent content per 100 parts by mass of the acrylic copolymer is 0.2 parts by mass, and the preferred upper limit is 5.0 parts by mass. A coloring agent content within this range results in more sufficient adhesive strength for the resulting adhesive tape. A more preferred lower limit for the coloring agent content is 0.5 parts by mass, a more preferred upper limit is 4.0 parts by mass, an even more preferred lower limit is 0.8 parts by mass, an even more preferred upper limit is 3.5 parts by mass, an even more preferred lower limit is 1.0 part by mass, and an even more preferred upper limit is 2.0 parts by mass. Examples of coloring agent content include 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.

[0082] The foam layer described above preferably contains an antioxidant (anti-aging agent) from the viewpoint of preventing aging of the foam layer. Examples of the antioxidant (anti-aging agent) include phenolic antioxidants, amine antioxidants, benzotriazole antioxidants, benzophenone antioxidants, HALS (hindered amine light stabilizer), etc. Among these, phenolic antioxidants and amine antioxidants are preferred from the viewpoint of being able to better prevent the oxidation of polymerizable unsaturated hydrocarbons contained in the acrylic copolymer etc. in the foam layer.

[0083] The preferred lower limit of the antioxidant content per 100 parts by mass of the acrylic copolymer is 0.01 parts by mass, and the preferred upper limit is 5 parts by mass. By keeping the antioxidant content within the above range, the adhesive layer can maintain its adhesive strength without deterioration even when stored for a long period of time. A more preferred lower limit for the antioxidant content is 0.1 parts by mass, a more preferred upper limit is 3 parts by mass, an even more preferred lower limit is 0.5 parts by mass, and an even more preferred upper limit is 1 part by mass. Examples of antioxidant content include 0.01 parts by mass or more and 5 parts by mass or less, 0.1 parts by mass or more and 3 parts by mass or less, 0.5 parts by mass or more and 1 part by mass or less, etc.

[0084] The foam layer described above may contain conventionally known additives such as thickeners, softeners, organic fillers, and inorganic fillers, as needed.

[0085] The preferred lower limit for the bio-derived carbon content in the foam layer is 10%. A bio-derived carbon content of 10% or more in the foam layer makes the adhesive tape of this embodiment superior in terms of conserving petroleum resources and reducing carbon dioxide emissions, thus reducing environmental impact. A more preferred lower limit for the bio-derived carbon content in the foam layer is 15%, an even more preferred lower limit is 18%, and an even more preferred lower limit is 20%. The upper limit for the bio-derived carbon content in the foam layer is not particularly limited and may be 100%. Examples of bio-derived carbon content in the foam layer include 10% to 100%, 15% to 100%, 18% to 100%, and 20% to 100%. Furthermore, bio-derived carbon contains a certain percentage of radioactive isotopes (C-14), while petroleum-derived carbon contains almost no C-14. Therefore, the "biological carbon content" as used herein can be calculated by measuring the concentration of C-14 contained in the foam layer. Specifically, it can be measured in accordance with ASTM D6866-22, a standard widely used in the bioplastics industry.

[0086] The foam layer preferably has a structure derived from a crosslinking agent. Since the foam layer has a structure derived from a crosslinking agent, the adhesive tape of the present embodiment has better holding properties.

[0087] The foam layer may have an open-cell structure or a closed-cell structure, but preferably has a closed-cell structure. Since the foam layer has a closed-cell structure, the strength of the foam layer increases, and the adhesive tape of the present embodiment can suppress cohesive failure, so the adhesive tape of the present embodiment is excellent in strong adhesiveness. In this specification, when observing the tape cross-section randomly, a structure in which the air layer between bubbles is continuous even partially is defined as an open-cell structure, and a structure in which the air layer between bubbles is not continuous is defined as a closed-cell structure. The cell structure can be confirmed by, for example, observing with an optical microscope (for example, manufactured by Keyence Corporation, "VH-X6000", etc.) at a magnification of 150 to 200 times.

[0088] The apparent density of the foam layer preferably has a lower limit of 0.59 g / cm ３ and an upper limit of 1.15 g / cm ３ is preferable. Since the apparent density of the foam layer is 0.59 g / cm ３ or more, the strength of the foam layer increases, and cohesive failure of the foam layer can be further suppressed, so the adhesive tape of the present embodiment is excellent in strong adhesiveness. Since the apparent density of the foam layer is 1.15 g / cm ３ or less, the foam layer can have appropriate flexibility, the stress relaxation property of the adhesive tape is further improved, and it has excellent followability. A more preferable lower limit of the apparent density of the foam layer is 0.65 g / cm ３ , a more preferable upper limit is 1.12 g / cm ３ , a further preferable lower limit is 0.70 g / cm ３ , a further preferable upper limit is 1.10 g / cm ３ , a still more preferable lower limit is 0.75 g / cm ３ , a still more preferable upper limit is 1.00 g / cm ３ , a particularly preferable lower limit is 0.80 g / cm ３ , a particularly preferable upper limit is 0.90 g / cm３ 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 ３ 1.10g / cm or more ３ Below, 0.75g / cm ３ 1.00g / cm or more ３ Below, 0.80g / cm ３ 0.90g / cm or more ３ The following are some examples. Furthermore, the deemed density of the foam layer can be measured using an electronic hydrometer (for example, Mirage's "ED120T") in accordance with JIS K 7222, etc.

[0089] The thickness of the foam layer described above has a preferred lower limit of 50 μm and a preferred upper limit of 500 μm. When the thickness of the foam layer is 50 μm or more, the adhesive strength of the foam layer is further improved, and the adhesive tape of this embodiment has superior adhesive strength. When the thickness of the foam layer is 500 μm or less, the foam layer can have appropriate flexibility, the stress relaxation properties of the adhesive tape are further improved, and it has excellent conformability. A more preferred lower limit for the thickness of the foam 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, an even more preferred upper limit is 250 μm, and a particularly preferred upper limit is 200 μm. Examples of the thickness of the foam layer include 50 μm to 500 μm, 80 μm to 400 μm, 100 μm to 300 μm, 100 μm to 250 μm, and 100 μm to 200 μm. In this specification, the thickness can be measured using a dial thickness gauge (for example, Mitutoyo's "ABS Digimatic Indicator").

[0090] The average major diameter of the bubbles in the foam 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 foam layer is 10 μm or more, the foam layer can have appropriate flexibility, the stress relaxation properties of the adhesive tape are further improved, and it has excellent conformability. When the average major diameter of the bubbles in the foam layer is 80 μm or less, the strength of the foam layer is increased, which further suppresses cohesive failure of the foam layer, so the adhesive tape of this embodiment has superior adhesive strength. A more preferred lower limit for the average major diameter of the bubbles in the foam layer is 15 μm, a more preferred upper limit is 70 μm, an even more preferred lower limit is 20 μm, an even more preferred upper limit is 65 μm, an even more preferred upper limit is 60 μm, a particularly preferred upper limit is 55 μm, and a very preferred upper limit is 50 μm. The average major diameter of the bubbles in the adhesive layer can be, for example, 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, etc.

[0091] The average minor diameter of the bubbles in the foam layer has a preferred lower limit of 10 μm and a preferred upper limit of 75 μm. When the average minor diameter of the bubbles in the foam layer is 10 μm or more, the foam layer can have appropriate flexibility, the stress relaxation properties of the adhesive tape are further improved, and it has excellent conformability. When the average minor diameter of the bubbles in the foam layer is 75 μm or less, the strength of the foam layer is increased, which further suppresses cohesive failure of the foam layer, so the adhesive tape of this embodiment has superior adhesive strength. A more preferred lower limit for the average minor diameter of the bubbles in the foam layer is 15 μm, a more preferred upper limit is 70 μm, an even more preferred lower limit is 20 μm, an even more preferred upper limit is 65 μm, an even more preferred upper limit is 60 μm, a particularly preferred upper limit is 55 μm, and a very preferred upper limit is 50 μm. The average short diameter of the bubbles in the adhesive layer can be, for example, 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.

[0092] The aspect ratio of the bubbles in the foam 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 bubbles in the foam layer described above is 1.00 or higher, the structure of the bubbles in the foam layer becomes flattened, so the foam layer has appropriate flexibility. As a result, the stress relaxation properties of the adhesive tape are further improved, and it has excellent conformability. When the aspect ratio of the bubbles in the foam layer described above is 3.50 or lower, the strength of the foam layer is increased, which further suppresses cohesive failure of the foam layer, so the adhesive tape of this embodiment has superior adhesive strength. A more preferred lower limit for the aspect ratio of the bubbles in the foam layer described above 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 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).

[0093] The average major axis, average minor axis, and aspect ratio of the bubbles in the foam layer can be determined, for example, as follows: Using a razor (Feather Corporation), the foam 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 axis and the bubble with the second largest major axis are selected, and the major and minor axes 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 foam 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.

[0094] Preferably, the average major diameter of the bubbles in the foam layer is 0.8 times or less the thickness of the foam layer. By having an average major diameter of bubbles 0.8 times or less the thickness of the foam layer, the strength of the foam layer is increased, which further suppresses cohesive failure of the foam layer, and thus the adhesive tape of this embodiment has superior adhesive strength. More preferably, the average major diameter of the bubbles is 0.7 times or less the thickness of the foam layer, and even more preferably 0.6 times or less. Furthermore, it is preferable that the average major diameter of the bubbles is 0.05 times or more the thickness of the foam layer. By having an average major diameter of bubbles 0.05 times or more the thickness of the foam layer, the foam layer has appropriate flexibility, which further improves the stress relaxation properties of the adhesive tape, resulting in excellent conformability. More preferably, the average major diameter of the bubbles is 0.1 times or more the thickness of the foam layer. That is, it is preferable that the average major diameter of the bubbles is 0.05 times or more and 0.8 times or less the thickness of the foam layer, more preferably 0.1 times or more and 0.7 times or less, and even more preferably 0.1 times or more and 0.6 times or less.

[0095] The shear storage modulus of the foam layer at 23°C, measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz (hereinafter sometimes simply referred to as "shear storage modulus at 23°C and a measurement frequency of 1 Hz"), has a preferred lower limit of 0.50 MPa. A shear storage modulus of the foam layer at 23°C and a measurement frequency of 1 Hz of 0.50 MPa or higher improves the cohesive force of the bulk foam layer, thereby improving adhesion, and the adhesive tape of this embodiment exhibits superior strong adhesion. Furthermore, the bending resistance of the adhesive tape of this embodiment is also improved. A more preferred lower limit for the shear storage modulus of the foam layer at 23°C and a measurement frequency of 1 Hz is 0.75 MPa, and an even more preferred lower limit is 0.90 MPa. A preferred upper limit for the shear storage modulus of the foam layer at 23°C and a measurement frequency of 1 Hz is 5.00 MPa. The shear storage modulus of the foam layer at 23°C and a measurement frequency of 1 Hz is 5.00 MPa or less. This improves the wettability of the interface of the foam layer, resulting in superior adhesive strength for the adhesive tape of the present invention. A more preferable upper limit for the shear storage modulus of the foam layer at 23°C and a measurement frequency of 1 Hz is 4.00 MPa, an even more preferable upper limit is 3.50 MPa, an even more preferable upper limit is 2.00 MPa, and a particularly preferable upper limit is 1.30 MPa. Examples of the shear storage modulus of the foam layer at 23°C and a measurement frequency of 1 Hz include 0.50 MPa to 5.00 MPa, 0.75 MPa to 4.00 MPa, 0.90 MPa to 3.50 MPa, 0.90 MPa to 2.00 MPa, and 0.90 MPa to 1.30 MPa. Furthermore, the shear storage modulus of the foam layer at 23°C and a measurement frequency of 1 Hz can be measured using a viscoelasticity measuring device (for example, Rheometrics Dynamic Analyze RDA-700, manufactured by Rheometrics) under the conditions of shear mode, measurement temperature -40 to 200°C, heating rate of 3°C / min, measurement frequency of 1 Hz, and strain of 0.10%.

[0096] Methods for adjusting the shear storage modulus of the foam layer at 23°C and a measurement frequency of 1 Hz include, for example, adjusting the composition, weight-average molecular weight, and polydispersity (weight-average molecular weight / number-average molecular weight) of the acrylic copolymer contained in the foam layer; adjusting the type and amount of crosslinking agent and tackifying resin contained in the foam layer; and adjusting the thickness of the foam layer.

[0097] Preferably, the foam layer has a structure in which no air bubbles are exposed on its surface. Because the foam layer has no exposed air bubbles on its surface, the area of ​​the adhesive interface between the foam layer and the adherend is increased, thereby further improving the adhesive strength of the adhesive tape in this embodiment. Methods for creating a foam layer with no exposed air bubbles on its surface include, for example, increasing the weight of the foam particles to suppress their floating on the liquid surface during solution coating.

[0098] The adhesive tape of this embodiment may have other layers besides the foam layer as needed, but from the viewpoint of ensuring shock absorption, it is preferable that the adhesive tape of this embodiment has only the foam layer. When the adhesive tape of this embodiment has only the foam layer, it can have appropriate flexibility and excellent conformability. Furthermore, since the adhesive tape of this embodiment is thinner, it can be used more suitably for fixing electrical and electronic components.

[0099] From the viewpoint of ensuring re-peelability, the adhesive tape of this embodiment preferably has a base material, and the foam layer is provided on at least one side of the base material. Since the foam adhesive layer has strong adhesive properties, the adhesion between the foam layer and the base material in the adhesive tape having the foam layer and the base material is excellent, and therefore the adhesive tape has strong adhesive properties even with a base material. When the adhesive tape of this embodiment has a base material, it may be a single-sided adhesive tape having the foam 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, when the adhesive tape of this embodiment is a double-sided adhesive tape, at least one of the adhesive layers may be the foam layer, and the other adhesive layer may be any adhesive layer as long as it does not impair the effects of the present invention.

[0100] Examples of substrates used for the above-mentioned substrate include films, nonwoven fabrics, and foamed substrates. In particular, from the viewpoint of obtaining an adhesive tape with high flexibility and thus having superior conformability in the adhesive tape of this embodiment, it is preferable that the above-mentioned substrate includes a foamed substrate.

[0101] From the viewpoint of increasing the overall bio-derived carbon content of the adhesive tape, a substrate made of 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.

[0102] 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.

[0103] The foamed substrate used in the above-mentioned substrate is preferably a foamed substrate containing at least one selected from the group consisting of PE, PP, and PU, and a foamed substrate containing PE is more preferable from the viewpoint of achieving a high degree of both flexibility and strength. Examples of components of the foamed substrate containing PE include PE made from sugarcane.

[0104] As a method for producing the foamed substrate described above, it is preferable to prepare a foamed resin composition containing a PE resin containing PE made from sugarcane and a foaming agent, and to foam the foaming agent when extruding the foamed resin composition into a sheet using an extruder, and to crosslink the obtained polyolefin foam as needed.

[0105] From the viewpoint of substrate strength, the substrate used for the above-mentioned substrate is preferably a film containing PES or a film containing PA. Furthermore, from the viewpoint of heat resistance and oil resistance, a film containing PA is preferred. 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.

[0106] The preferred lower limit for the thickness of the above-mentioned substrate is 3.5 μm, and the preferred upper limit is 1000 μm. Having the substrate thickness within this range allows for high impact resistance while also providing high flexibility, enabling it to adhere closely to the shape of the substrate. A more preferred lower limit for the substrate thickness is 5.0 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 substrate thicknesses include 3.5 μm to 1000 μm, 5.0 μm to 500 μm, 6.5 μm to 300 μm, 10 μm to 200 μm, 30 μm to 100 μm, and so on.

[0107] From the viewpoint of ensuring adhesive strength and adhesion to the substrate, the adhesive tape of this embodiment may have an adhesive layer on at least one side of the foam layer. By having an adhesive layer on at least one side of the foam layer of the adhesive tape of this embodiment, the interlayer strength of the resulting adhesive tape is further improved, and therefore the adhesive tape of this embodiment becomes more adhesive. Accordingly, the adhesive tape of this embodiment may have an adhesive layer on one side of the foam layer, or it may have an adhesive layer on both sides of the foam layer.

[0108] The adhesive contained in the 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 selectivity of the adherend, and acrylic adhesives containing the acrylic copolymer described above in the foam layer are more preferred from the viewpoint of excellent adhesive strength.

[0109] The thickness of the adhesive layer described above has a preferred lower limit of 5 μm and a preferred upper limit of 100 μm. A thickness of 5 μm or more in the adhesive layer makes it less likely to break when the foam layer is pulled. A thickness of 100 μm or less in the adhesive layer suppresses a decrease in conformability to the adherend. A more preferred lower limit for the thickness of the 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 adhesive layer thicknesses include 5 μm to 100 μm, 10 μm to 90 μm, 15 μm to 80 μm, etc.

[0110] 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 foam layer is as follows. First, a solvent is added to an acrylic copolymer, a tackifying resin, etc., to prepare a solution of an adhesive resin composition. Next, the prepared solution of the adhesive resin composition is applied to the release surface of a release film, and the solvent in the solution is dried and removed to form a foam layer. Then, by placing the release surface of a release film on top of the formed foam layer, an adhesive tape can be obtained in which the surface of the foam layer is covered with a release film.

[0111] Furthermore, the method for manufacturing an adhesive tape having the above-mentioned base material and having the above-mentioned foam layer on at least one side of the base material is as follows. That is, a foam layer formed in the same manner as the method for manufacturing an adhesive tape consisting only of the above-mentioned foam layer is bonded to the base material, 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 a foam layer on one side of the base material. Alternatively, an adhesive resin composition may be directly coated onto the base material, dried to form a foam layer, and then the release treatment surface of a release film may be placed on top of the formed foam layer. Alternatively, an adhesive tape having adhesive layers on both sides of the base material can be obtained by placing an arbitrary adhesive layer prepared on the other side of the base material and then laminating and integrating it.

[0112] Furthermore, the method for manufacturing an adhesive tape having the adhesive layer on at least one side of the foam layer is as follows. Specifically, after overlapping a foam layer formed in the same manner as the method for manufacturing an adhesive tape consisting only of the foam layer described above with an arbitrary adhesive layer, pressing them together using a rubber roller to create a laminated and integrated structure, and then curing it in a 40°C environment for 72 hours, an adhesive tape having the adhesive layer on one side of the foam layer can be manufactured. In addition, by performing the same operation on the other side of the foam layer in the manufactured adhesive tape having the adhesive layer on one side of the foam layer, an adhesive tape having the adhesive layer on both sides of the foam layer can be manufactured.

[0113] Furthermore, adhesive tapes having the adhesive layer on at least one side of the foam layer can also be manufactured using a multilayer extrusion extruder. Specifically, the composition forming the foam layer and the composition forming the adhesive layer are supplied to a multilayer extrusion extruder, and after melt-mixing, a sheet-like adhesive tape base roll in which the foam layer and adhesive layer are laminated is extruded.

[0114] The overall thickness of the adhesive tape in this embodiment has a preferred lower limit of 50 μm and a preferred upper limit of 500 μm. A total thickness of 50 μm or more ensures sufficient adhesive strength and stress relaxation of the resulting tape. A total thickness of 500 μm or less ensures sufficient adhesion and fixation, as well as greater flexibility. A more preferred lower limit for the overall thickness of the adhesive tape in this embodiment is 80 μm, a more preferred upper limit is 400 μm, an even more preferred lower limit is 100 μm, and an even more preferred upper limit is 300 μm. Examples of the overall thickness of the adhesive tape in this embodiment include 50 μm to 500 μm, 80 μm to 400 μm, 100 μm to 300 μm, etc. Furthermore, in this specification, "overall thickness of the 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.

[0115] 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).

[0116] Methods for adjusting the transmittance of the adhesive tape of this embodiment at a wavelength of 550 nm include, for example, adding a pigment to the adhesive resin composition or adding a filler.

[0117] The adhesive tape of this embodiment has a preferred lower limit of 180° peel strength against SUS at 23°C of 10 N / 25 mm. Having a 180° peel strength of 10 N / 25 mm or more against SUS at 23°C makes the adhesive tape of this embodiment superior in adhesive strength, allowing it to be used without problems even in high-temperature environments. A more preferred lower limit for the 180° peel strength against SUS at 23°C of the adhesive tape of this embodiment is 12 N / 25 mm, an even more preferred lower limit is 15 N / 25 mm, and an even more preferred lower limit is 20 N / 25 mm. There is no particular upper limit for the 180° peel strength against SUS at 23°C of the adhesive tape of this embodiment, but approximately 50 N / 25 mm is a practical upper limit. The 180° peel force of the adhesive tape of this embodiment against SUS at 23°C can be, for example, 10N / 25mm to 50N / 25mm, 12N / 25mm to 50N / 25mm, 15N / 25mm to 50N / 25mm, 20N / 25mm to 50N / 25mm, etc. The 180° peel force of the adhesive tape of this embodiment against SUS at 23°C is measured by the following method. First, if necessary, one side of the obtained adhesive tape (the side not to be measured) is backed with a polyethylene terephthalate film with a thickness of 23 μm, and then it is cut to a width of 25 mm and a length of 75 mm to prepare a test piece. Next, the obtained test piece was attached to a SUS304 plate (a SUS304 plate that had been washed with ethanol and then wiped dry), and pressed down by passing 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. The obtained test sample could be measured by leaving it standing for 20 minutes in an environment of 23°C and 50% RH, and then peeling the adhesive tape from the SUS304 plate in accordance with JIS Z 0237:2009, under conditions of 23°C and 50% RH, a tensile speed of 300 mm / min, and a peel angle of 180°.

[0118] Methods for adjusting the 180° peel force of the adhesive tape of this embodiment against SUS at 23°C include, for example, changing the composition of the acrylic copolymer (for example, increasing the content (mass%) of constituent units derived from the polar functional group-containing monomer in the acrylic copolymer, or changing the type of constituent units of the polar functional group-containing monomer), adding a tackifying resin to the adhesive resin composition, adjusting the thickness of the adhesive layer, changing the amount of crosslinking agent, or adjusting the molecular weight of the copolymer.

[0119] The adhesive tape of this embodiment is not particularly limited in its use, but because it has strong adhesive properties, it can be suitably used for fixing parts, and is especially suitable for fixing internal components of electrical and electronic equipment that are exposed to high-temperature environments during use. Because the adhesive tape of this embodiment has excellent strong adhesive properties, it can fix parts without problems even when exposed to high-temperature environments. Examples of the electrical and electronic equipment include televisions, monitors, portable electronic devices, and in-vehicle electronic devices. 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, such as epoxy primers, urethane primers, acrylic primers, and acid etching primers. Furthermore, because the adhesive tape of this embodiment has excellent conformability to uneven and curved surfaces, it can be suitably used for fixing display devices such as televisions and monitors, specifically for fixing the surface cover panel of the display device to a housing with uneven surfaces.

[0120] 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.

[0121] According to the present invention, it is possible to provide an adhesive tape that can achieve both excellent conformability and excellent strong adhesion. Furthermore, according to the present invention, it is possible to provide an electronic device that includes the adhesive tape.

[0122] This is a schematic diagram illustrating the holding test. This is a schematic diagram illustrating the method for evaluating bending resistance. This is a schematic diagram of a sample used for evaluating shock absorption. This is a schematic diagram illustrating the method for evaluating shock absorption.

[0123] 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.

[0124] <N-hexyl acrylic acid containing bio-derived carbon> Linoleic acid derived from castor oil was converted to linoleic acid hydroperoxide using lipoxygenase, and then a mixture containing n-hexylaldehyde was obtained using isomerase. By distillation of the obtained mixture, n-hexylaldehyde containing bio-derived carbon was obtained. Furthermore, by hydrogenation of the obtained n-hexylaldehyde containing bio-derived carbon, n-hexyl alcohol containing bio-derived carbon was obtained. By esterifying the obtained n-hexyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), n-hexyl acrylic acid containing bio-derived carbon was prepared.

[0125] <n-heptyl acrylic acid containing bio-derived carbon> Ricinoleic acid derived from 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 acrylic acid containing bio-derived carbon was prepared.

[0126] <1-Methylheptyl Acrylate Containing Bio-Derived Carbon> Ricinoleic acid derived from castor oil was dissolved in alkali to obtain a mixture containing sebacic acid and 1-methylheptyl alcohol. Next, sebacic acid was separated from the obtained mixture by distillation to obtain 1-methylheptyl alcohol containing bio-derived carbon. By esterifying the obtained 1-methylheptyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 1-methylheptyl acrylic acid containing bio-derived carbon was prepared.

[0127] <Isobornyl Acrylate Containing Biologically Derived Carbon> Pinene extracted from pine resin was isomerized to obtain camphene containing biologically derived carbon. By reacting camphene containing biologically derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), isobornyl acrylate containing biologically derived carbon was prepared.

[0128] <Isobornyl methacrylate containing bio-derived carbon> 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 prepared.

[0129] <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.) ・Cyclohexyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) ・2-ethylhexyl acrylate (manufactured by Nippon Shokubai Co., Ltd.) ・Lauryl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) ・Ethylene-butylene macromonomer (manufactured by Kraton Polymer Japan, "HPVM-L1253") ・Acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) ・2-hydroxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.) ・Styrene (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0130] <Expandable Particles> - Expandable particle A: Expancel 920DU40 (thermal expandable microcapsule, manufactured by Nippon Philite Co., Ltd., average particle size 40 μm) - Expandable particle B: Expancel 920DU80 (thermal expandable microcapsule, manufactured by Nippon Philite Co., Ltd., average particle size 80 μm) - Expandable particle C: EMC-20 (hollow particle, manufactured by Nippon Philite Co., Ltd., average particle size 20 μm) - Expandable particle D: EMC-40 (hollow particle, manufactured by Nippon Philite Co., Ltd., average particle size 53 μm)

[0131] <Aromatic block copolymers (X)> - SIS block copolymer (manufactured by Zeon Corporation, "Quintac 3620") - SEBS block copolymer (manufactured by ENEOS Materials Corporation, "DYNARON 8600P")

[0132] <Tackifying Resin> ・Tackifying Resin A: Rosin-based tackifying resin (manufactured by Arakawa Chemical Industries, Ltd., "KE-359", softening point: 94°C to 104°C, hydroxyl value: 38 mg KOH / g to 47 mg KOH / g, tackifying resin containing bio-derived carbon)

[0133] <Pigments> - Carbon black (Toyo Color Co., Ltd., "Multi-Rack A903 Black") <Crosslinking agents> - Isocyanate-based crosslinking agent (Covestro Co., Ltd., "Desmodule L-75") - Epoxy-based crosslinking agent (Soken Chemical Co., Ltd., "E-5C")

[0134] <Antioxidants (anti-aging agents)> - Hindered phenol antioxidant (BASF, "Irganox 1010")

[0135] (Synthesis of Acrylic Copolymers) (Acrylic Copolymers A-R, X-Y, a) 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 to start reflux. Subsequently, 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 further, 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 and polydispersity of the obtained acrylic copolymers were measured using a 2690 Separations Module (Waters Co., Ltd.) as the measuring instrument, a GPC KF-806L column (Showa Denko Co., Ltd.) as the column, 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.

[0136] (Acrylic Copolymers S-U) Acrylic copolymers S-U were synthesized in the same manner as acrylic copolymers A-R and X-Y, except that the monomer mixture composition was as shown in Table 2 and the weight-average molecular weight was adjusted by adjusting the amount of polymerization initiator added. Specifically, the weight-average molecular weight was adjusted by adding 0.05 parts by mass of 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane to acrylic copolymer S, 0.005 parts by mass of 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane to acrylic copolymer T, and 0.07 parts by mass of 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane to acrylic copolymer U.

[0137] (Acrylic copolymers V, Z, b) 0.902 g of 1,6-hexanedithiol, 1.83 g of carbon disulfide, and 11 mL of dimethylformamide were placed in a two-necked flask and stirred at 25°C. 2.49 g of triethylamine was added dropwise over 15 minutes and stirred at 25°C for 3 hours. Next, 2.75 g of methyl-α-bromophenylacetic acid was added dropwise over 15 minutes and stirred at 25°C for 4 hours. Then, 100 mL of extraction solvent (n-hexane:ethyl acetate = 50:50) and 50 mL of water were added to the reaction mixture and liquid-liquid extraction was performed. The organic layers obtained from the first and second liquid-liquid extractions were mixed and washed sequentially with 50 mL of 1 M hydrochloric acid, 50 mL of water, and 50 mL of saturated brine. Sodium sulfate was added to the organic layer after washing and dried. The sodium sulfate was filtered off, and the filtrate was concentrated using an evaporator to remove the organic solvent. The obtained concentrate was purified by silica gel column chromatography to obtain the RAFT agent. 0.19 g of the RAFT agent, 0.035 g of styrene and polymerization initiator 2,2'-azobis(2-methylbutyronitrile) (ABN-E) as shown in Table 2, and 80 g of ethyl acetate as a solvent were placed in a two-necked flask, and the flask was heated to 85°C while purging the inside of the flask with nitrogen gas. The polymerization reaction was then carried out by stirring at 85°C for 6 hours (first stage reaction). After the completion of the first stage reaction, 400 g of n-hexane was added to the flask, and the reaction product was precipitated by stirring. Unreacted monomer (St) and RAFT agent were filtered off, and the reaction product was dried under reduced pressure at 70°C to obtain the copolymer (block (A)). As block copolymer (B), a mixture of monomers other than styrene from Table 2, 0.0027 g of 2,2'-azobis(2-methylbutyronitrile) (ABN-E) as a polymerization initiator, and 5 g of ethyl acetate as a solvent was placed in a two-necked flask along with the previously obtained copolymer (block (A)). The flask was heated to 85°C while purging it with nitrogen gas. The polymerization reaction was then carried out by stirring at 85°C for 6 hours (second-stage reaction) to obtain a reaction solution containing block copolymer (1) consisting of block (A) and block (B). A portion of the reaction solution was taken, 400 g of n-hexane was added, and the reaction products were precipitated by stirring. Unreacted monomers and solvent were filtered off, and the reaction products were dried under reduced pressure at 70°C to obtain the block copolymer, which was then removed from the reaction solution.Using the method described above, acrylic copolymers, which are triblock copolymers containing styrene as a constituent unit, were synthesized. Subsequently, ethyl acetate solutions of the synthesized acrylic copolymers were prepared. The weight-average molecular weight was measured using the same method as for acrylic copolymers A-R and X-Y. The results are shown in Table 2.

[0138] (Acrylic Copolymer W) Except for the monomer mixture composition shown in Table 2, acrylic copolymer W, which is a random copolymer having styrene as a constituent unit, was synthesized by the same method as the synthesis methods of acrylic copolymers A to R and X to Y described above, and the weight-average molecular weight was measured. The results are shown in Table 2.

[0139] (Preparation of adhesive V1) 52 parts by mass of ethyl acetate was placed in a reactor equipped with a thermometer, stirrer, and condenser, and after purging with nitrogen, the reactor was heated and reflux was started. 30 minutes after the ethyl acetate boiled, 0.08 parts by mass of azobisisobutyronitrile was added as a polymerization initiator. A monomer mixture consisting of 70 parts by mass of n-butyl acrylate, 27 parts by mass of 2-ethylhexyl acrylate, 3 parts by mass of acrylic acid, and 0.2 parts by mass of 2-hydroxyethyl acrylate was added dropwise and uniformly over 1 hour and 30 minutes to allow the reaction to proceed. 30 minutes after the end of the dropwise addition, 0.1 parts by mass of azobisisobutyronitrile was added, and the polymerization reaction was continued for a further 5 hours. By adding ethyl acetate to the reactor and cooling while diluting, a solution of acrylic random copolymer with a solid content of 40% by mass was obtained. The weight-average molecular weight of the obtained acrylic random copolymer was measured by GPC using a Waters "2690 Separations Module" column, and was found to be 710,000. The ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) (Mw / Mn) was 5.5. To 100 parts by mass of the solid content of the obtained acrylic random copolymer, 15 parts by mass of polymerized rosin ester with a softening point of 150°C, 10 parts by mass of terpene phenol with a softening point of 145°C, and 10 parts by mass of rosin ester with a softening point of 70°C were added. Furthermore, 30 parts by mass of ethyl acetate (manufactured by Fuji Chemical Co., Ltd.) and 3.0 parts by mass of isocyanate-based crosslinking agent (Coronate L45, manufactured by Tosoh Corporation) were added, and the mixture was stirred to obtain adhesive V1.

[0140] (Preparation of adhesive V2) 50.0% by mass of Kraton D1102 AS, 45.0% by mass of Decolyte A115, 4.5% by mass of Wingtack 10, and 0.5% by mass of the antioxidant Irganox 1010 were mixed to prepare 40% by mass of adhesive V2.

[0141]

[0142]

[0143] (Example 1) (1) Formation of Foam Layer To the solution of acrylic copolymer A obtained in "(Synthesis of Acrylic Copolymer)" described above, 0.4 parts by mass of Expancel 920DU40 (manufactured by Nippon Philite Co., Ltd.) as foam particles and 30 parts by mass of ethyl acetate as a solvent were added to 100 parts by mass of the solid content of the acrylic copolymer, and the mixture was thoroughly stirred to prepare an adhesive resin composition. The prepared adhesive resin composition was applied to the release surface of a 50 μm thick release PET film, and then dried at 155°C for 1 hour to form a foam layer with a thickness of 200 μm. Furthermore, by preparing sections at 1 μm units using a microtome (manufactured by Yamato Koki Kogyo Co., Ltd.) and taking images using a digital microscope (VHX-6000, manufactured by Keyence Corporation) at a magnification of 200x and a measurement screen size of 1.8 mm x 1.3 mm, the surface in the thickness direction of the adhesive layer was observed, and it was found that the obtained foam layer had a structure in which no air bubbles were exposed on the surface in the thickness direction.

[0144] (2) Measurement of the shear storage modulus of the foam layer at 23°C and a measurement frequency of 1 Hz Multiple foam layers obtained in "(1) Formation of the foam layer" described above were prepared and stacked to a thickness of 500 μm to create test specimens. Dynamic viscoelastic spectra were measured for the prepared test specimens using a viscoelastic spectrometer (IT Measurement Control Co., Ltd., "DVA-200") under the conditions of simple heating mode, heating rate of 10°C / min, shear direction, measurement frequency of 1 Hz, and temperature range from -50°C to 300°C. The shear storage modulus (MPa) of the foam layer at 23°C and a measurement frequency of 1 Hz was measured using this method. The results are shown in Table 3.

[0145] (3) Measurement of 180° peel force of foam layer against SUS at 23°C One side of the obtained foam layer (the side not measured) was laminated to a 23 μm thick polyethylene terephthalate film (Futamura Chemical Co., Ltd., "FE2002") and backed by running a 2 kg rubber roller back and forth once at a speed of 300 mm / min. Then it was cut to a width of 25 mm x length of 75 mm to prepare a test piece. Next, the obtained test piece was laminated to a SUS304 plate (SUS304 plate washed with ethanol and then wiped dry), pressed by running a 2 kg rubber roller back and forth once at a speed of 300 mm / min, and then cured at 23°C, 50% RH for 20 minutes to prepare a test sample. The obtained test samples were left to stand for 20 minutes at 23°C and 50% RH. Then, in accordance with JIS Z 0237:2009, the foam layer was peeled from the SUS304 plate using a tensile testing machine (A&D Corporation, "RTI") at 23°C and 50% RH, with a tensile speed of 300 mm / min and a peel angle of 180°. The 180° peel force of the foam layer against SUS at 23°C was measured. The results are shown in Table 3.

[0146] (4) Measurement of the deemed density of the foam layer In accordance with JIS K 7222, the deemed density of the foam layer (g / cm³) ３ The following was measured. The results are shown in Table 3.

[0147] (5) Ratio of average major diameter of bubbles to thickness of foam layer Using a razor (Feather Corporation), the foam layer was sliced ​​in planes parallel to the length and thickness directions to obtain MD cut samples. The obtained MD cut samples were photographed using a digital microscope (Keyence Corporation, "VHX-6000") at a magnification of 200x and a measurement screen size of 1.8 mm × 1.3 mm. From the obtained images, the bubble with the largest major diameter and the bubble with the second largest major diameter were selected, and the major diameters of these bubbles were measured. Furthermore, this operation was performed for three images, and the average of the major diameters of a total of six bubbles was taken as the average major diameter of the bubbles in the foam layer, and the ratio to the thickness of the foam layer was calculated. The results are shown in Table 3.

[0148] (6) Preparation of adhesive tape An adhesive tape was obtained by laminating a 50 μm thick release PET film to the release surface of the obtained foam layer and curing it in a 40°C environment for 72 hours.

[0149] (Examples 2-36, 39-46, Comparative Examples 1-3) Except for the composition and thickness of the foam layer as shown in Tables 3-8 in "(1) Formation of the foam layer" described above, adhesive tapes were prepared and various measurements were taken in the same manner as in Example 1. The results are shown in Tables 3-8. In Examples 2-36, 39-46, and Comparative Examples 1-3, the obtained foam layer had a structure in which no air bubbles were exposed on the surface in the thickness direction.

[0150] (Examples 37-38) The composition and thickness of the adhesive layer were as shown in Table 6, and instead of heating at 155°C for 1 hour during the drying process, heating at 110°C for 3 minutes was performed to form an adhesive layer having a foamed structure in the same manner as in Example 1. Otherwise, the adhesive tape was prepared and various measurements were performed in the same manner as in Example 1. The results are shown in Table 6.

[0151] (Example 47) A solution of acrylic copolymer A obtained in "(Synthesis of Acrylic Copolymer)" described above was applied to the release surface of a 50 μm thick release PET film, and a 25 μm thick adhesive layer was prepared by solvent drying at 110°C for 3 minutes. The foam layer formed in the same manner as in Example 1, except that the composition was as shown in Table 7 and the thickness was 175 μm, was superimposed with the prepared adhesive layer, and then pressed together by running a 2 kg rubber roller back and forth at a speed of 300 mm / min once, and cured at 40°C for 48 hours to obtain an adhesive tape having the adhesive layer on one side of the foam layer. Various measurements were performed in the same manner as in Example 1. The results are shown in Table 7. In Example 47, the obtained foam layer had a structure in which no air bubbles were exposed on the surface in the thickness direction.

[0152] (Example 48) In the same manner as in Example 46, a solution of acrylic copolymer A was applied to the release surface of a 50 μm thick release PET film and dried to prepare two 25 μm thick adhesive layers, the composition of which is shown in Table 7. The foam layer was formed in the same manner as in Example 1, except that the thickness was 150 μm. One of the prepared adhesive layers was then placed on each surface of the foam layer, and the layers were pressed together by running a 2 kg rubber roller back and forth at a speed of 300 mm / min once. The layers were then cured at 40°C for 48 hours to obtain an adhesive tape having adhesive layers on both sides of the foam layer. Various measurements were performed in the same manner as in Example 1. The results are shown in Table 7. In Example 48, the obtained foam layer had a structure in which no air bubbles were exposed on the surface in the thickness direction.

[0153] (Example 49) A foam layer was formed in the same manner as in Example 1, except that the composition was as shown in Table 7 and the thickness was 175 μm. The obtained foam layer was bonded to one side of a 50 μm thick PET film (Toyo Cloth Co., Ltd., "5100"), and then pressed down by running a 2 kg rubber roller back and forth once at a speed of 300 mm / min. After curing at 40°C for 48 hours, an adhesive tape was obtained having a base material and a foam layer on one side of the base material. Various measurements were performed in the same manner as in Example 1. The results are shown in Table 7. In Example 49, the obtained foam layer had a structure in which no air bubbles were exposed on the surface in the thickness direction.

[0154] (Comparative Example 4) Volara H03001 (polyethylene resin, manufactured by Sekisui Chemical Co., Ltd., 100 μm thick) was used as the foam layer. Adhesive V1 was applied to the release treatment surface of a 50 μm thick release PET film, and then dried at 110°C for 5 minutes to form a 50 μm thick adhesive layer. This was then bonded to one side of the Volara H03001, and pressed down by running a 2 kg rubber roller back and forth once at a speed of 300 mm / min. Furthermore, an adhesive layer of the same composition and 50 μm thickness was bonded to the opposite side of the Volara H03001 in the same manner to produce an adhesive tape with adhesive layers on both sides. The results are shown in Table 9.

[0155] (Comparative Example 5) Adhesive V2 was applied to the release surface of a 50 μm thick release PET film, and then dried at 110°C for 5 minutes to form a 200 μm thick adhesive layer. The formed adhesive layer was then bonded to the release surface of a 50 μm thick release PET film, and then cured at 40°C for 48 hours to obtain an adhesive tape without a foam layer. Various measurements were performed in the same manner as in Example 1, using the adhesive layer instead of the foam layer. Various measurements were performed in the same manner as in Example 1. The results are shown in Table 9.

[0156] <Evaluation> The adhesive tapes obtained in the examples and comparative examples were evaluated as follows. The results are shown in Tables 3 to 9.

[0157] (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 conditions of 23°C and 50% RH to prepare a measurement sample, which was then observed. Furthermore, after standing for 24 hours under conditions of 23°C and 50% RH, observation was performed again. The silicon wafer with a step 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 gap was observed between the wafer and the adhesive tape after 1 hour and 24 hours of standing. • B: No gap was observed between the wafer and the adhesive tape after 1 hour of standing, and even after 24 hours of standing, the size of the gap between the wafer and the adhesive tape was less than 5% of the total surface area of ​​the adhesive surface. • C: A gap was observed between the wafer and the adhesive tape after 1 hour of standing, and even after 24 hours of standing, the size of the gap between the wafer and the adhesive tape was less than 5% of the total surface area of ​​the adhesive surface. • D: After 24 hours of standing, the size of the gap between the wafer and the adhesive tape was 5% or more of the total surface area of ​​the adhesive surface.

[0158] (Strong Adhesion) One side of the obtained adhesive tape (the side not measured) was backed with a 23 μm thick polyethylene terephthalate film (Futamura Chemical Co., Ltd., "FE2002"), and then cut to a width of 25 mm x length of 75 mm to prepare a test piece. The obtained test piece was attached to a SUS304 plate (SUS304 plate washed with ethanol and then wiped dry), and pressed down 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. For the obtained test sample, the adhesive tape was peeled from the SUS304 plate in accordance with JIS Z 0237:2009 under conditions of 23°C and 50% RH, tensile speed of 300 mm / min, and peel angle of 180°, and the 180° peel force (N / 25 mm) was measured. Based on the measured 180° peeling force, the following criteria were used for evaluation: A: The 180° peeling force was greater than 30 N / 25 mm. B: The 180° peeling force was greater than 20 N / 25 mm and less than or equal to 30 N / 25 mm. C: The 180° peeling force was less than or equal to 20 N / 25 mm.

[0159] (Retention) A retention test was conducted in accordance with JIS Z 0237:2009. Figure 1 shows a schematic representation of the retention test. (1) Retention test at 60°C One side of the adhesive tape 2 (the side not measured) was backed with a 23 μm thick polyethylene terephthalate film 1 (Futamura Chemical Co., Ltd., "FE2002"), and then cut to a width of 25 mm x length of 75 mm to prepare a test piece. This test piece was placed so that its adhesive layer (the side being measured) faced a SUS304 plate 3 (a SUS304 plate that had been washed with ethanol and then wiped dry) with a thickness of 2 mm and a width of 50 mm and a length of 80 mm, and then bonded to the test piece by passing 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. The obtained test samples were placed in an environment of 60°C and 50% RH and left to stand for 15 minutes. Then, in this environment, a 0.5 kg weight 4 was attached to the polyethylene terephthalate film 1 of the test sample in accordance with JIS Z 0237:2009 so that a shear load was applied, and the time from the attachment of the weight 4 until the adhesive tape fell from the SUS304 plate 3 (fall time) was measured. Based on the measured fall time, the following criteria were used for evaluation: A: The adhesive tape did not fall even after 500 hours. B: The fall time was 100 hours or more and less than 500 hours. C: The fall time was 24 hours or more and 100 hours or less. D: The fall time was less than 24 hours. Even if the evaluation was "D", the adhesive tape of this embodiment can be used without problems depending on the application.

[0160] (2) Retention test at 100°C The test was evaluated using the same method and evaluation criteria as described in "(1) Retention test at 60°C" above, except that the prepared test sample was left standing in an environment of 100°C and 50% RH for 15 minutes. Even if the evaluation was "D", the adhesive tape of the present invention can be used without problems depending on the application.

[0161] (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 a laminate. The fabricated laminate was set up in a Tensilon (A&D Company, Limited) measuring instrument in accordance with JIS K 7171 as shown in Figure 2 (distance between compression jigs: 57.15 mm, distance between fixing jigs: 177.8 mm). Subsequently, the test piece 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 or higher. B: The slope of the line was 15.5 or higher and less than 17.0. C: The slope of the line was less than 15.5. Even if the evaluation was "C", the adhesive tape of this embodiment can be used without problems depending on the application.

[0162] (Impact Absorption) The obtained adhesive tape 2 was cut to a size of 30 mm x 30 mm, and two SUS plates 8 measuring 125 mm x 50 mm and 2 mm thick were stacked as shown in Figure 3 to create a test specimen. The obtained test specimen was set up as shown in Figure 4 so that when the pendulum passed its lowest point, it would collide with only one of the SUS plates on the test specimen. A pendulum with a mass of 1.0 kg was then dropped from a height of 0.2 m (H in Figure 4) and collided with the test specimen, after which the highest height h reached was measured. Using the obtained height h, the impact absorption energy was calculated from the following formula. Note that the lowest point reached by the pendulum is defined as 0. Impact absorption energy (J) = mg(0.2 - h) (m: mass of the pendulum (kg), g: acceleration due to gravity (9.80 m / s) ２(h: measured height) Based on the calculated shock absorption energy, the shock absorption performance of the adhesive tape was evaluated according to the following criteria: A: Shock absorption energy was 0.50 J or more. B: Shock absorption energy was 0.15 J or more and less than 0.50 J. C: Shock absorption energy was less than 0.15 J. Even if the evaluation is "C", the adhesive tape of this embodiment can be used without problems depending on the application.

[0163]

[0164]

[0165]

[0166]

[0167]

[0168]

[0169]

[0170] According to the present invention, it is possible to provide an adhesive tape that can achieve both excellent conformability and excellent strong adhesion. Furthermore, according to the present invention, it is possible to provide an electronic device that includes the adhesive tape.

[0171] 1. Polyethylene terephthalate (PET) film 2. Adhesive tape 3. SUS304 plate (50 mm wide, 80 mm long, 2 mm thick) 4. Weight (0.5 kg) 5. Laminate 6. Compression jig 7. Fixing jig 8. SUS plate (50 mm wide, 125 mm long, 2 mm thick) 9. Test piece 10. Pendulum

Claims

Having a foam layer, The foam layer contains an acrylic copolymer having structural units derived from (meth)acrylic acid ester and structural units derived from an olefin polymer having polymerizable unsaturated double bonds at its terminals. Adhesive tape. The adhesive tape according to claim 1, wherein the foam layer has a 180° peel force against SUS at 23°C of 10 N / 25 mm or more. The adhesive tape according to claim 2, wherein the foam layer is formed using an adhesive resin composition. The adhesive tape according to claim 1, 2, or 3, 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 50% by mass or less. The constituent unit derived from the (meth)acrylic acid ester includes a constituent unit derived from an alkyl (meth)acrylic acid ester having an alkyl group having 1 to 8 carbon atoms. The adhesive tape according to claim 1, 2, 3, or 4, wherein the content of constituent units derived from the alkyl (meth)acrylate having an alkyl group having 1 to 8 carbon atoms in the alkyl (meth)acrylate is 50% by mass or more and 100% by mass or less. The adhesive tape according to claim 1, 2, 3, 4, or 5, wherein the constituent unit derived from the (meth)acrylic acid ester includes a constituent unit derived from the (meth)acrylic acid ester having an aliphatic cyclic structure. The acrylic copolymer has constituent units derived from a monomer containing a polar functional group, The content of constituent units derived from the polar functional group-containing monomer in the acrylic copolymer is 0.1% by mass or more. The adhesive tape according to claim 1, 2, 3, 4, 5, or 6. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, or 7, wherein the foam layer comprises 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 said block. The adhesive tape according to claim 8, 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. The acrylic copolymer has constituent units derived from vinyl aromatic compounds, 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. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the acrylic copolymer has a weight-average molecular weight of 300,000 or more and 1,500,000 or less. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the foam layer contains a tackifying resin. The adhesive tape according to claim 12, wherein the content of the tackifying resin is 0.1 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the acrylic copolymer. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein the foam layer is colored. The adhesive tape according to claim 3, wherein the adhesive resin composition contains a crosslinking agent. The aforementioned foam layer has an assumed density of 0.59 g / cm³. ３ 1.15g / cm or more ３ The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15. 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 foam layer has an average major diameter of bubbles that is 0.8 times or less the thickness of the foam layer. 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 foam layer has a structure in which no air bubbles are exposed on the surface in the thickness direction. The adhesive tape according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, wherein the foam layer has a shear storage modulus at 23°C measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz, which is 0.50 MPa or more. 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, comprising only the foam layer. Having a base material, 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, having the foam layer on at least one surface of the substrate. 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, having an adhesive layer on at least one surface of the foam layer. 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, 21, or 22, used for fixing internal components of electrical and electronic equipment. Electronic device comprising the adhesive tape described in claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, or 23.

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