Adhesive tape

Abstract

The purpose of the present invention is to provide an adhesive tape excellent in high temperature holding properties and curved surface followability. The present invention is an adhesive tape having an adhesive layer formed using an adhesive composition, wherein the adhesive composition contains a (meth)acrylic copolymer, the (meth)acrylic copolymer has a constituent unit derived from an alkyl (meth)acrylate, the adhesive layer has a shear storage elastic modulus of 15000 Pa or more at 80°C as measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz in a measurement temperature range of -40°C to 200°C, the peak temperature of a loss tangent of the adhesive layer as measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz in a measurement temperature range of -40°C to 200°C falls within the range of -20°C to 0°C, and the adhesive layer has a gel fraction of 10%-45% by mass.

Description

adhesive tape

[0001] The present invention relates to an adhesive tape.

[0002] Conventionally, pressure-sensitive adhesive tapes having a pressure-sensitive adhesive layer formed using a pressure-sensitive adhesive composition have been widely used to fix components in electronic devices, vehicles, houses, and building materials (e.g., Patent Documents 1 to 3). Specifically, for example, pressure-sensitive adhesive tapes are used to adhere a cover panel for protecting the surface of a portable electronic device to a touch panel module or a display panel module, or to adhere a touch panel module to a display panel module.

[0003] JP 2015-052050 A JP 2015-021067 A JP 2015-120876 A

[0004] In recent years, flexible displays and curved displays have been attracting attention as a way to enhance the design of devices. Because curved displays are subject to a repulsive force that causes them to return to a flat state, adhesive tapes used to secure components in curved displays must have high curve-conforming properties (repulsion resistance). One way to improve the curve-conforming properties of adhesive tapes is to increase their flexibility by lowering the glass transition temperature of the adhesive layer. However, increasing the flexibility of the adhesive layer reduces the bulk strength, which can result in the adhesive tape having poor high-temperature retention.

[0005] An object of the present invention is to provide a pressure-sensitive adhesive tape that is excellent in high-temperature retention and curved surface conformability.

[0006] Disclosure 1 relates to a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed using a pressure-sensitive adhesive composition, wherein the pressure-sensitive adhesive composition contains a (meth)acrylic copolymer, and the (meth)acrylic copolymer has a structural unit derived from an alkyl(meth)acrylate, the pressure-sensitive adhesive layer has a shear storage modulus of 15,000 Pa or more at 80°C measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz and in a measurement temperature range of -40°C or more and 200°C or less, the pressure-sensitive adhesive layer has a peak temperature of loss tangent measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz and in a measurement temperature range of -40°C or more and 200°C or less, in a range of -20°C or more and 0°C or less, and the pressure-sensitive adhesive layer has a gel fraction of 10% by mass or more and 45% by mass or less. Disclosure 2 is the pressure-sensitive adhesive tape of Disclosure 1, wherein the alkyl (meth)acrylate comprises an alkyl (meth)acrylate having a glass transition temperature of −60° C. or lower when made into a homopolymer, and the (meth)acrylic copolymer contains 50 mass % or more of structural units derived from the alkyl (meth)acrylate having a glass transition temperature of −60° C. or lower when made into a homopolymer. Disclosure 3 is the pressure-sensitive adhesive tape of Disclosure 2, wherein the alkyl (meth)acrylate having a glass transition temperature of −60° C. or lower when made into a homopolymer comprises n-hexyl acrylate. Disclosure 4 is the pressure-sensitive adhesive tape of Disclosure 1, 2, or 3, wherein the (meth)acrylic copolymer does not have a crosslinkable functional group and comprises structural units derived from a monomer having a glass transition temperature of 0° C. or higher when made into a homopolymer. Disclosure 5 is the pressure-sensitive adhesive tape of Disclosure 4, wherein the (meth)acrylic copolymer does not have the crosslinkable functional group and has a content of structural units derived from a monomer having a glass transition temperature of 0°C or higher when converted into a homopolymer of 0.1% by mass or more and 70% by mass or less. Disclosure 6 is the pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, or 5, wherein the (meth)acrylic copolymer has structural units derived from n-heptyl (meth)acrylate. Disclosure 7 is the pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, or 5, wherein the (meth)acrylic copolymer does not have structural units derived from n-heptyl (meth)acrylate or has a content of structural units derived from n-heptyl (meth)acrylate of less than 90% by mass.

[0014] Disclosure 8 is the pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, or 7, wherein the (meth)acrylic copolymer further comprises structural units derived from at least one monomer having a non-crosslinkable ether structure selected from the group consisting of a monomer having a cyclic ether structure other than an epoxy group or an oxetanyl group, and a monomer having an acyclic ether structure. Disclosure 9 is the pressure-sensitive adhesive tape of Disclosure 8, wherein the (meth)acrylic copolymer contains structural units derived from the monomer having a non-crosslinkable ether structure in an amount of 0.01% by mass or more and 50% by mass or less. Disclosure 10 is the pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the (meth)acrylic copolymer further comprises structural units derived from a monomer having a crosslinkable functional group. Disclosure 11 is the pressure-sensitive adhesive tape of Disclosure 10, wherein the monomer having a crosslinkable functional group comprises at least one selected from the group consisting of a carboxy group-containing monomer and a hydroxy group-containing monomer.

[0023] Disclosure 12 is the pressure-sensitive adhesive tape of Disclosure 11, wherein the monomer having a crosslinkable functional group comprises the hydroxyl group-containing monomer. Disclosure 13 is the pressure-sensitive adhesive tape of Disclosure 11 or 12, wherein the monomer having a crosslinkable functional group comprises the carboxy group-containing monomer, and the (meth)acrylic copolymer contains structural units derived from the carboxy group-containing monomer at a content of 5% by mass or more. Disclosure 14 is the pressure-sensitive adhesive tape of Disclosure 10, 11, 12, or 13, wherein the (meth)acrylic copolymer contains structural units derived from the monomer having a crosslinkable functional group at a content of 0.01% by mass or more and less than 20% by mass. Disclosure 15 is the pressure-sensitive adhesive tape of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14, wherein the (meth)acrylic copolymer has a weight-average molecular weight of 800,000 or more.

[0023] Present Disclosure 16 is the pressure-sensitive adhesive tape of Present Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, wherein the pressure-sensitive adhesive composition further contains a tackifier.

[0024] Present Disclosure 17 is the pressure-sensitive adhesive tape of Present Disclosure 16, wherein the tackifier comprises at least one selected from the group consisting of (meth)acrylic tackifiers, rosin ester tackifiers, and terpene tackifiers.

[0033] Disclosure 18 is the pressure-sensitive adhesive tape of Disclosure 17, wherein the tackifier comprises the rosin ester-based tackifier and the terpene-based tackifier. Disclosure 19 is the pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, wherein the pressure-sensitive adhesive composition further contains a crosslinking agent. Disclosure 20 is the pressure-sensitive adhesive tape of Disclosure 19, wherein the crosslinking agent comprises at least one selected from the group consisting of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent. Disclosure 21 is the pressure-sensitive adhesive tape of Disclosure 20, wherein the crosslinking agent comprises the isocyanate-based crosslinking agent and the epoxy-based crosslinking agent. Disclosure 22 is the pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 21, wherein the pressure-sensitive adhesive layer has a half-width of a loss tangent peak of 44° C. or less, as measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz and a measurement temperature range of −40° C. or more and 200° C. or less. Disclosure 23 is the pressure-sensitive adhesive tape of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, or 22, having a base layer and the pressure-sensitive adhesive layer on at least one surface of the base layer. The present disclosure 24 is a pressure-sensitive adhesive tape according to disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, or 23, which is used for fixing electronic components or vehicle-mounted components. The present invention will be described in detail below. Hereinafter, an embodiment or one of embodiments of the present invention will be described as "the present embodiment."

[0007] The present inventors investigated the possibility of forming a pressure-sensitive adhesive layer in a pressure-sensitive adhesive tape using a pressure-sensitive adhesive composition containing a specific (meth)acrylic copolymer, adjusting the peak temperatures of the shear storage modulus and loss tangent at 80°C, as measured by dynamic viscoelasticity measurement, and adjusting the gel fraction to fall within specific ranges. As a result, they found that a pressure-sensitive adhesive tape with excellent high-temperature retention and curved surface conformability could be obtained, leading to the completion of the present invention.

[0008] The pressure-sensitive adhesive tape of the present embodiment has a pressure-sensitive adhesive layer formed using a pressure-sensitive adhesive composition. Examples of methods for forming the pressure-sensitive adhesive layer using the pressure-sensitive adhesive composition include a method in which the pressure-sensitive adhesive composition is applied to a release film or the like, and then the pressure-sensitive adhesive composition is dried by heating. The pressure-sensitive adhesive layer may contain the uncrosslinked pressure-sensitive adhesive composition, or may contain a crosslinked product of the pressure-sensitive adhesive composition.

[0009] The pressure-sensitive adhesive layer has a lower limit of a shear storage modulus at 80°C (hereinafter simply referred to as "shear storage modulus of the pressure-sensitive adhesive layer at 80°C") of 15,000 Pa, as measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz and a measurement temperature range of -40°C to 200°C. When the pressure-sensitive adhesive layer has a shear storage modulus of 15,000 Pa or more, the pressure-sensitive adhesive tape of this embodiment has excellent high-temperature retention properties. A preferred lower limit of the shear storage modulus of the pressure-sensitive adhesive layer at 80°C is 18,000 Pa, and a more preferred lower limit is 20,000 Pa. Furthermore, a preferred upper limit of the shear storage modulus of the pressure-sensitive adhesive layer at 80°C is, but is not particularly limited to, 35,000 Pa. When the pressure-sensitive adhesive layer has a shear storage modulus of 35,000 Pa or less, the resulting pressure-sensitive adhesive tape has excellent curved surface conformability. A more preferred upper limit of the shear storage modulus of the pressure-sensitive adhesive layer at 80°C is 30,000 Pa. The shear storage modulus of the pressure-sensitive adhesive layer at 80°C may be 15,000 to 35,000 Pa, 15,000 to 30,000 Pa, 18,000 to 35,000 Pa, 18,000 to 30,000 Pa, 20,000 to 35,000 Pa, or 20,000 to 30,000 Pa. The shear storage modulus of the pressure-sensitive adhesive layer at 80°C, as well as the peak temperature and half-width of the loss tangent of the pressure-sensitive adhesive layer described below, can be obtained by the following dynamic viscoelasticity measurement. That is, first, the pressure-sensitive adhesive layers are superposed to prepare a laminate having a thickness of about 1 mm, and the laminate is cut to a width of 6 mm and a length of 10 mm to obtain a test piece. Next, the obtained test piece is subjected to dynamic viscoelasticity measurement in a shear mode using a dynamic viscoelasticity measuring device under the conditions of a measurement temperature range of −40° C. to 200° C., a temperature rise rate of 5° C. / min, a frequency of 1 Hz, and a strain of 0.08% in a nitrogen atmosphere. Examples of the dynamic viscoelasticity measuring device include DVA-200 (manufactured by IT Measurement & Control Co., Ltd.).

[0010] The pressure-sensitive adhesive layer has a peak temperature of a loss tangent (hereinafter also simply referred to as "loss tangent of the pressure-sensitive adhesive layer") measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz and a measurement temperature range of -40°C to 200°C, in the range of -20°C to 0°C. When the peak temperature of the loss tangent of the pressure-sensitive adhesive layer is in this range, the pressure-sensitive adhesive tape of this embodiment has excellent curved surface conformability. When the pressure-sensitive adhesive layer has multiple loss tangent peaks, it is sufficient that the peak temperature of at least one of these peaks is in the range of -20°C to 0°C. The preferred lower limit of the peak temperature of the loss tangent of the pressure-sensitive adhesive layer is -17°C, and the preferred upper limit is -3°C, and the more preferred lower limit is -15°C, and the more preferred upper limit is -5°C. The peak temperature of the loss tangent of the pressure-sensitive adhesive layer may be in the range of -20°C or more and -3°C or less, or may be in the range of -20°C or more and -5°C or less, or may be in the range of -17°C or more and 0°C or less, or may be in the range of -17°C or more and -3°C or less, or may be in the range of -17°C or more and -5°C or less, or may be in the range of -15°C or more and 0°C or less, or may be in the range of -15°C or more and -3°C or less, or may be in the range of -15°C or more and -5°C or less.

[0011] The pressure-sensitive adhesive layer preferably has an upper limit of the half-value width of the peak of the loss tangent of the pressure-sensitive adhesive layer of 44°C. When the half-value width of the peak of the loss tangent of the pressure-sensitive adhesive layer is 44°C or less, the pressure-sensitive adhesive layer has a small loss tangent at around room temperature, making it difficult to disperse stress. As a result, the obtained pressure-sensitive adhesive tape has excellent high-speed releasability. The upper limit of the half-value width of the peak of the loss tangent of the pressure-sensitive adhesive layer is more preferably 42°C, even more preferably 40°C, and even more preferably 38°C. Furthermore, the lower limit of the half-value width of the peak of the loss tangent of the pressure-sensitive adhesive layer is preferably 20°C. When the half-value width of the loss tangent of the pressure-sensitive adhesive layer is 20°C or more, the obtained pressure-sensitive adhesive tape has excellent drop impact resistance. The lower limit of the half-value width of the loss tangent of the pressure-sensitive adhesive layer is more preferably 23°C, even more preferably 25°C, and even more preferably 26°C. The half width of the loss tangent peak of the pressure-sensitive adhesive layer may be 20° C. to 44° C., 23° C. to 44° C., 25° C. to 44° C., 26° C. to 44° C., 20° C. to 42° C., 23° C. to 42° C., 25° C. to 42° C., 26° C. to 42° C., 20° C. to 40° C., 23° C. to 40° C., 25° C. to 40° C., 26° C. to 40° C., 20° C. to 38° C., 23° C. to 38° C., 25° C. to 38° C., or 26° C. to 38° C. When the pressure-sensitive adhesive layer has a plurality of loss tangent peaks, the "half width of the peak of the pressure-sensitive adhesive layer" refers to the half width of the peak at the lowest temperature among the loss tangent peaks of the pressure-sensitive adhesive layer in the temperature range of −25° C. or more and 50° C. or less. In this specification, the term "half width" means full width at half maximum.

[0012] The lower limit of the gel fraction of the pressure-sensitive adhesive layer is 10% by mass, and the upper limit is 45% by mass. When the gel fraction of the pressure-sensitive adhesive layer is within this range, the pressure-sensitive adhesive tape of this embodiment exhibits excellent curved surface conformability. A more preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 15% by mass, a more preferred upper limit is 35% by mass, and an even more preferred lower limit is 20% by mass. The gel fraction of the pressure-sensitive adhesive layer may be 10 to 35% by mass, 15 to 45% by mass, 15 to 35% by mass, 20 to 45% by mass, or 20 to 35% by mass. The gel fraction of the pressure-sensitive adhesive layer is measured by the following method. Specifically, a pressure-sensitive adhesive tape having the pressure-sensitive adhesive layer is first cut into a planar rectangular shape measuring 20 mm in width and 40 mm in length to prepare a test specimen. The test specimen is then immersed in ethyl acetate at 23°C for 24 hours, removed from the ethyl acetate, and dried at 110°C for 1 hour. The mass of the test piece after drying is measured, and the gel fraction is calculated using the following formula (I). Note that no release film for protecting the pressure-sensitive adhesive layer is laminated on the test piece. When the pressure-sensitive adhesive tape is a non-support tape that does not have a substrate, the measurement is carried out using a test piece obtained by attaching the pressure-sensitive adhesive layer to a substrate and then cutting it, or the gel fraction is calculated using the W in the following formula (I) without using a substrate. ０ The calculation is performed assuming that the gel fraction is 0. Gel fraction (mass%) = 100 × (W ２ -W ０ ) / (W １ -W ０ ) (I) (W ０ : Mass of the substrate, W １ : mass of test piece before immersion, W ２ : Mass of test piece after immersion and drying)

[0013] The shear storage modulus at 80°C of the pressure-sensitive adhesive layer, the peak temperature of the loss tangent of the pressure-sensitive adhesive layer, and the gel fraction of the pressure-sensitive adhesive layer can be adjusted to the above-mentioned values ​​by adjusting the type and content of each component constituting the pressure-sensitive adhesive composition.

[0014] The pressure-sensitive adhesive composition contains a (meth)acrylic copolymer. The (meth)acrylic copolymer has structural units derived from alkyl(meth)acrylate. In this specification, the term "(meth)acrylic" refers to acrylic or methacrylic, and the term "(meth)acrylate" refers to acrylate or methacrylate.

[0015] The alkyl (meth)acrylate preferably contains an alkyl (meth)acrylate that has a glass transition temperature of −60° C. or lower when made into a homopolymer. That is, the (meth)acrylic copolymer preferably has a structural unit derived from an alkyl (meth)acrylate that has a glass transition temperature of −60° C. or lower when made into the homopolymer. When the (meth)acrylic copolymer has a structural unit derived from an alkyl (meth)acrylate that has a glass transition temperature of −60° C. or lower when made into the homopolymer, it becomes easier to adjust the peak temperature of the loss tangent of the pressure-sensitive adhesive layer to the above-mentioned range. The upper limit of the glass transition temperature of the alkyl (meth)acrylate that has a glass transition temperature of −60° C. or lower when made into the homopolymer is preferably −62° C., more preferably −65° C. Furthermore, there is no particular preferred lower limit of the glass transition temperature of the alkyl (meth)acrylate that has a glass transition temperature of −60° C. or lower when made into the homopolymer, but the substantial lower limit is −70° C. The glass transition temperature of the alkyl (meth)acrylate having a glass transition temperature of −60° C. or lower when made into a homopolymer may be −70° C. to −60° C., −70° C. to −62° C., or −70° C. to −65° C. In this specification, the term “glass transition temperature when made into a homopolymer” refers to the glass transition temperature measured by differential scanning calorimetry when made into a homopolymer having a weight-average molecular weight of 100,000 to 2,000,000. The glass transition temperature when made into the homopolymer can be measured, for example, by using a differential scanning calorimeter in a nitrogen atmosphere (nitrogen flow, flow rate 50 mL / min) according to JIS K 6240:2011, at a measurement temperature of −100° C. to 200° C. and a heating rate of 10° C. / min. The differential scanning calorimeter that can be used is, for example, a 220C (manufactured by Seiko Instruments Inc.).

[0016] Examples of the alkyl(meth)acrylate having a glass transition temperature of −60° C. or lower when made into a homopolymer include n-hexyl acrylate (glass transition temperature of −65° C. when made into a homopolymer), 2-ethylhexyl acrylate (glass transition temperature of −70° C. when made into a homopolymer), n-heptyl acrylate (glass transition temperature of −68° C. when made into a homopolymer), etc. Among these, the alkyl(meth)acrylate having a glass transition temperature of −60° C. or lower when made into a homopolymer preferably includes n-hexyl acrylate.

[0017] The preferred lower limit of the content of structural units derived from alkyl (meth)acrylates that have a glass transition temperature of −60° C. or lower when formed into the homopolymer in the (meth)acrylic copolymer is 50% by mass. By having the content of structural units derived from alkyl (meth)acrylates that have a glass transition temperature of −60° C. or lower when formed into the homopolymer be 50% by mass or higher, it becomes easier to adjust the peak temperature of the loss tangent of the pressure-sensitive adhesive layer to the above-mentioned range. The more preferred lower limit of the content of structural units derived from alkyl (meth)acrylates that have a glass transition temperature of −60° C. or lower when formed into the homopolymer is 75% by mass. Furthermore, the preferred upper limit of the content of structural units derived from alkyl (meth)acrylates that have a glass transition temperature of −60° C. or lower when formed into the homopolymer is 99.99% by mass, and from the viewpoint of the cohesive strength of the bulk of the pressure-sensitive adhesive layer, the more preferred upper limit is 99% by mass. The content of structural units derived from alkyl(meth)acrylates having a glass transition temperature of −60° C. or lower when the homopolymer is formed may be 50 to 99.99% by mass, 50 to 99% by mass, 75 to 99.99% by mass, or 75 to 99% by mass.

[0018] The (meth)acrylic copolymer may contain, as the structural unit derived from the alkyl (meth)acrylate, a structural unit derived from another alkyl (meth)acrylate other than the structural unit derived from the alkyl (meth)acrylate having a glass transition temperature of −60° C. or lower when made into a homopolymer, provided that the object of the present invention is not impaired. Examples of the other alkyl (meth)acrylate include n-butyl acrylate (glass transition temperature when made into a homopolymer: −55° C.), 1-methylheptyl acrylate (glass transition temperature when made into a homopolymer: −45° C.), n-hexyl methacrylate (glass transition temperature when made into a homopolymer: 0° C.), t-butyl acrylate (glass transition temperature when made into a homopolymer: 14° C.), and t-butyl methacrylate (glass transition temperature when made into a homopolymer: 107° C.).

[0019] Furthermore, the (meth)acrylic copolymer preferably has a structural unit derived from a monomer that does not have a crosslinkable functional group and has a glass transition temperature of 0°C or higher when made into a homopolymer. By having the structural unit derived from a monomer that does not have a crosslinkable functional group and has a glass transition temperature of 0°C or higher when made into a homopolymer, the resulting pressure-sensitive adhesive tape will have better high-temperature retention. The monomer that does not have a crosslinkable functional group and has a glass transition temperature of 0°C or higher when made into a homopolymer may be one of the other alkyl (meth)acrylates described above, or a monomer other than the alkyl (meth)acrylates. The monomer that does not have a crosslinkable functional group and has a glass transition temperature of 0°C or higher when made into a homopolymer may be one of the monomers having a non-crosslinkable ether structure described below. Examples of the crosslinkable functional group include a carboxy group, a hydroxyl group, a glycidyl group, an amide group, and a nitrile group.

[0020] Examples of the monomers that do not have a crosslinkable functional group and have a glass transition temperature of 0°C or higher when made into a homopolymer include methyl acrylate (glass transition temperature of 8°C when made into a homopolymer), methyl methacrylate (glass transition temperature of 105°C when made into a homopolymer), ethyl methacrylate (glass transition temperature of 65°C when made into a homopolymer), n-butyl methacrylate (glass transition temperature of 20°C when made into a homopolymer), n-hexyl methacrylate (glass transition temperature of 0°C when made into a homopolymer), t-butyl acrylate (glass transition temperature of 14°C when made into a homopolymer), and t-butyl methacrylate (glass transition temperature of 15°C when made into a homopolymer). Examples of the glass transition temperature of the homopolymer include cyclohexyl acrylate (glass transition temperature of 107°C), cyclohexyl acrylate (glass transition temperature of 15°C when made into a homopolymer), cyclohexyl methacrylate (glass transition temperature of 66°C when made into a homopolymer), 3,3,5-trimethylcyclohexyl acrylate (glass transition temperature of 52°C when made into a homopolymer), benzyl acrylate (glass transition temperature of 6°C when made into a homopolymer), benzyl methacrylate (glass transition temperature of 54°C when made into a homopolymer), isobornyl acrylate (glass transition temperature of 97°C when made into a homopolymer), and isobornyl methacrylate (glass transition temperature of 180°C when made into a homopolymer).

[0021] The preferred lower limit and upper limit of the content of the structural units derived from a monomer that does not have a crosslinkable functional group and that has a glass transition temperature of 0°C or higher when made into a homopolymer in the (meth)acrylic copolymer is 0.1% by mass, and 70% by mass, respectively. When the content of the structural units derived from a monomer that does not have a crosslinkable functional group and that has a glass transition temperature of 0°C or higher when made into a homopolymer is within this range, the resulting pressure-sensitive adhesive tape has better high-temperature retention properties. The more preferred lower limit and upper limit of the content of the structural units derived from a monomer that does not have a crosslinkable functional group and that has a glass transition temperature of 0°C or higher when made into a homopolymer are 10% by mass, and 50% by mass, respectively. The content of the structural units derived from a monomer that does not have a crosslinkable functional group and that has a glass transition temperature of 0°C or higher when made into a homopolymer may be 0.1 to 70% by mass, 0.1 to 50% by mass, 10 to 70% by mass, or 10 to 50% by mass. The content of the structural unit derived from a monomer that does not have a crosslinkable functional group and has a glass transition temperature of 0°C or higher when made into a homopolymer can be determined by measuring the (meth)acrylic copolymer by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR measurement, １３ The glass transition temperature of the polymer can be calculated from the integrated intensity ratio of the hydrogen peak derived from a monomer that does not have the crosslinkable functional group and has a glass transition temperature of 0°C or higher when made into a homopolymer.

[0022] From the viewpoint of being able to exert excellent adhesive strength on both smooth and rough surfaces, the (meth)acrylic copolymer preferably contains structural units derived from n-heptyl (meth)acrylate. On the other hand, from the viewpoint of making the resulting pressure-sensitive adhesive tape more excellent in high-temperature retention and adhesion to an adherend, the (meth)acrylic copolymer preferably does not contain structural units derived from n-heptyl (meth)acrylate, or the content of structural units derived from n-heptyl (meth)acrylate is preferably less than 90 mass%.

[0023] The (meth)acrylic copolymer preferably further contains a structural unit derived from at least one monomer having a non-crosslinkable ether structure selected from the group consisting of a monomer having a cyclic ether structure other than an epoxy group or an oxetanyl group, and a monomer having an acyclic ether structure. When the (meth)acrylic copolymer contains a structural unit derived from the monomer having a non-crosslinkable ether structure, the surface energy of the resulting pressure-sensitive adhesive composition is reduced, thereby enabling it to exhibit better adhesion to an adherend. Furthermore, the monomer having a non-crosslinkable ether structure preferably contains a (meth)acryloyl group. In this specification, the term "(meth)acryloyl" refers to acryloyl or methacryloyl.

[0024] Examples of the monomer having a cyclic ether structure other than the epoxy structure and the oxetanyl group include tetrahydrofurfuryl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate, etc. Examples of the monomer having an acyclic ether structure include 2-methoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, ethyl carbitol (meth)acrylate, 2-(2-(2-methoxyethoxy)ethoxy)ethyl (meth)acrylate, etc.

[0025] The preferred lower limit of the content of the structural units derived from the monomer having a non-crosslinkable ether structure in the (meth)acrylic copolymer is 0.01% by mass, and the preferred upper limit is 50% by mass. When the content of the structural units derived from the monomer having a non-crosslinkable ether structure is within this range, the resulting pressure-sensitive adhesive tape has better adhesion to an adherend. The more preferred lower limit of the content of the structural units derived from the monomer having a non-crosslinkable ether structure is 10% by mass, and the more preferred upper limit is 30% by mass. The content of the structural units derived from the monomer having a non-crosslinkable ether structure may be 0.01 to 50% by mass, 0.01 to 30% by mass, 10 to 50% by mass, or 10 to 30% by mass. The content of the structural units derived from the monomer having a non-crosslinkable ether structure can be determined by measuring the (meth)acrylic copolymer by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR measurement, １３ The content of the structural units derived from the monomer having a non-crosslinkable ether structure may be 0% by mass, and the content of the structural units derived from the monomer having a non-crosslinkable ether structure may be 0% by mass.

[0026] The (meth)acrylic copolymer preferably further contains a structural unit derived from a monomer having a crosslinkable functional group. When the (meth)acrylic copolymer contains a structural unit derived from the monomer having a crosslinkable functional group, the cohesive strength of the pressure-sensitive adhesive layer is improved, and the resulting pressure-sensitive adhesive tape has better adhesion to the adherend. The monomer having a crosslinkable functional group may have a glass transition temperature of 0°C or higher when made into a homopolymer.

[0027] Examples of the monomer having a crosslinkable functional group include a carboxyl group-containing monomer, a hydroxyl group-containing monomer, a glycidyl group-containing monomer, an amide group-containing monomer, and a nitrile group-containing monomer. Among these, since this facilitates the adjustment of the gel fraction of the pressure-sensitive adhesive layer described below, the monomer having a crosslinkable functional group preferably includes at least one selected from the group consisting of the carboxyl group-containing monomer and the hydroxyl group-containing monomer, and more preferably includes the hydroxyl group-containing monomer. Furthermore, the monomer having a crosslinkable functional group preferably has a (meth)acryloyl group.

[0028] Examples of the carboxy group-containing monomer include (meth)acrylic acid. Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 1-methyl-3-hydroxypropyl (meth)acrylate, 1-methyl-2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1-methyl-2-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 1-ethyl-2-hydroxyethyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 7-hydroxyheptyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, and 9-hydroxynonyl (meth)acrylate. Examples of the glycidyl group-containing monomer include glycidyl (meth)acrylate. Examples of the amide group-containing monomer include isopropyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, etc. Examples of the nitrile group-containing monomer include (meth)acrylonitrile, etc.

[0029] The preferred lower limit of the content of the structural units derived from the carboxyl group-containing monomer in the (meth)acrylic copolymer is 0.1% by mass, and the preferred upper limit is 15% by mass. When the content of the structural units derived from the carboxyl group-containing monomer is within this range, the resulting pressure-sensitive adhesive tape has better adhesion to the adherend. The more preferred lower limit of the content of the structural units derived from the carboxyl group-containing monomer is 1% by mass, and the more preferred upper limit is 10% by mass, and the even more preferred lower limit is 3.0% by mass, and the even more preferred upper limit is 8.0% by mass, and the even more preferred lower limit is 5.0% by mass. The content of the structural units derived from the carboxy group-containing monomer may be 0.1 to 15% by mass, 0.1 to 10% by mass, 0.1 to 8.0% by mass, 1.0 to 15% by mass, 1.0 to 10% by mass, 1.0 to 8.0% by mass, 3.0 to 15% by mass, 3.0 to 10% by mass, 3.0 to 8.0% by mass, 5.0 to 15% by mass, 5.0 to 10% by mass, or 5.0 to 8.0% by mass. The content of the structural units derived from the carboxy group-containing monomer in the (meth)acrylic copolymer may be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy of the (meth)acrylic copolymer ( １ H-NMR, １３ The carbon number can be calculated from the integrated intensity ratio of the hydrogen peak derived from the carboxy group-containing monomer by performing spectroscopy (e.g., C-NMR) and the like.

[0030] The preferred lower limit of the content of the structural units derived from the hydroxyl group-containing monomer in the (meth)acrylic copolymer is 0.01% by mass, and the preferred upper limit is 2.0% by mass. When the content of the structural units derived from the hydroxyl group-containing monomer is within this range, the resulting pressure-sensitive adhesive tape has superior adhesion to the adherend. The more preferred lower limit of the content of the structural units derived from the hydroxyl group-containing monomer is 0.05% by mass, the more preferred upper limit is 1.0% by mass, and the even more preferred lower limit is 0.1% by mass. The content of the structural units derived from the hydroxyl group-containing monomer may be 0.01 to 2.0% by mass, 0.01 to 1.0% by mass, 0.05 to 2.0% by mass, 0.05 to 1.0% by mass, 0.1 to 2.0% by mass, or 0.1 to 1.0% by mass. The content of the structural units derived from the hydroxyl group-containing monomer in the (meth)acrylic copolymer can be determined by measuring the (meth)acrylic copolymer by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ The amount of hydrogen can be calculated from the integrated intensity ratio of the hydrogen peak derived from the hydroxyl group-containing monomer by performing spectroscopy (e.g., C-NMR) and the like.

[0031] The preferred lower limit of the content of the structural units derived from the monomer having a crosslinkable functional group in the (meth)acrylic copolymer is 0.01% by mass, and the preferred upper limit is 20% by mass. When the content of the structural units derived from the monomer having a crosslinkable functional group is within this range, the resulting pressure-sensitive adhesive tape will have better adhesion to an adherend. The more preferred lower limit of the content of the structural units derived from the monomer having a crosslinkable functional group is 0.1% by mass, and the more preferred upper limit is 10% by mass, and the even more preferred lower limit is 1% by mass. The content of the structural units derived from the monomer having a crosslinkable functional group may be 0.01 to 20% by mass, 0.01 to 10% by mass, 0.1 to 20% by mass, 0.1 to 10% by mass, 1 to 20% by mass, or 1 to 10% by mass. The content of the structural units derived from the monomer having a crosslinkable functional group in the (meth)acrylic copolymer can be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy of the (meth)acrylic copolymer ( １ H-NMR measurement, １３ C-NMR measurement, etc., and calculation can be made from the integrated intensity ratio of the hydrogen peak derived from the monomer having the crosslinkable functional group.

[0032] Furthermore, the (meth)acrylic copolymer may contain, to the extent that the object of the present invention is not impaired, a constituent unit derived from a monomer other than the constituent unit derived from the alkyl (meth)acrylate, the constituent unit derived from a monomer that does not have a crosslinkable functional group and has a glass transition temperature of 0° C. or higher when made into a homopolymer, the constituent unit derived from the monomer having the non-crosslinkable ether structure, and the constituent unit derived from the monomer having the crosslinkable functional group. As the other monomer, for example, various monomers that are commonly used as raw materials for (meth)acrylic copolymers, such as vinyl acetate and styrene, can be used.

[0033] The weight-average molecular weight of the (meth)acrylic copolymer is not particularly limited, but can be, for example, in the range of approximately 30,000 to 2,000,000. Furthermore, a preferred lower limit of the weight-average molecular weight of the (meth)acrylic copolymer is 800,000. When the weight-average molecular weight of the (meth)acrylic copolymer is 800,000 or more, the resulting pressure-sensitive adhesive tape will have superior adhesion to the adherend and superior high-temperature retention. A more preferred lower limit of the weight-average molecular weight of the (meth)acrylic copolymer is 900,000, and an even more preferred lower limit is 1,000,000. Furthermore, since the pressure-sensitive adhesive layer will have appropriate flexibility and the resulting pressure-sensitive adhesive tape will have superior curved surface conformability, a preferred upper limit of the weight-average molecular weight of the (meth)acrylic copolymer is 1,500,000, and a more preferred upper limit is 1,200,000. The weight average molecular weight of the (meth)acrylic copolymer may be 30,000 to 2,000,000, 30,000 to 1,500,000, 30,000 to 1,200,000, 800,000 to 2,000,000, 800,000 to 1,500,000, 800,000 to 1,200,000, 900,000 to 2,000,000, 900,000 to 1,500,000, 900,000 to 1,200,000, 1,000,000 to 2,000,000, 1,000,000 to 1,500,000, or 1,000,000 to 1,200,000. Note that, in this specification, the weight average molecular weight is the weight average molecular weight in terms of standard polystyrene measured by GPC (Gel Permeation Chromatography). Specifically, a (meth)acrylic copolymer is diluted 50 times with tetrahydrofuran (THF), and the resulting diluted solution is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare a measurement sample. Next, this measurement sample is supplied to a gel permeation chromatograph, and GPC measurement is performed under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C. The polystyrene-equivalent molecular weight of the (meth)acrylic copolymer is measured, and this value is taken as the weight average molecular weight of the (meth)acrylic copolymer. Examples of the gel permeation chromatograph include the 2690 Separations Module (manufactured by Waters Corporation).Examples of methods for adjusting the weight average molecular weight of the (meth)acrylic copolymer include a method of changing the type or amount of a polymerization initiator or the monomer concentration during the polymerization reaction, a method of adding a small amount of a chain transfer agent such as dodecyl mercaptan, a method of changing the type of polymerization reaction solvent to control chain transfer to the solvent, and a method of changing the temperature during the reaction.

[0034] The (meth)acrylic copolymer can be obtained by polymerizing a raw material monomer mixture through a radical reaction in the presence of a polymerization initiator. Examples of the radical reaction include living radical polymerization and free radical polymerization. Living radical polymerization produces a copolymer with a more uniform molecular weight and composition than free radical polymerization, and can suppress the generation of low-molecular-weight components, etc., thereby increasing the cohesive strength of the resulting pressure-sensitive adhesive layer and providing the resulting pressure-sensitive adhesive tape with superior adhesion to the adherend. Conventional methods can be used to polymerize the monomer mixture, including solution polymerization (boiling point polymerization or constant temperature polymerization), UV polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. Among these, solution polymerization and UV polymerization are preferred because they provide the resulting pressure-sensitive adhesive tape with superior adhesion to the adherend. When solution polymerization is used to polymerize the monomer mixture, examples of the reaction solvent include ethyl acetate, toluene, methyl ethyl ketone, dimethyl sulfoxide, ethanol, acetone, and diethyl ether.

[0035] Examples of the polymerization initiator include organic peroxides and azo compounds. Examples of the 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 the azo compounds include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. Furthermore, when the radical reaction is carried out by living radical polymerization, examples of the polymerization initiator include organotellurium polymerization initiators. The organotellurium polymerization initiator is not particularly limited as long as it is one that is commonly used in living radical polymerization, and examples thereof include organotellurium compounds, organotelluride compounds, etc. In addition to the organotellurium polymerization initiator, an azo compound may also be used as the polymerization initiator in the living radical polymerization in order to accelerate the polymerization rate.

[0036] The preferred lower limit of the content of the (meth)acrylic copolymer in the pressure-sensitive adhesive composition is 50% by mass, and the preferred upper limit is 99.5% by mass. When the content of the (meth)acrylic copolymer is within this range, the resulting pressure-sensitive adhesive tape has better adhesion to the adherend. The more preferred lower limit of the content of the (meth)acrylic copolymer is 55% by mass, and the more preferred upper limit is 95% by mass, and the even more preferred lower limit is 65% by mass, and the even more preferred upper limit is 90% by mass, and the particularly preferred lower limit is 70% by mass, and the particularly preferred upper limit is 80% by mass. The content of the (meth)acrylic copolymer may be 50 to 99.5% by mass, 50 to 95% by mass, 50 to 90% by mass, 50 to 80% by mass, 55 to 99.5% by mass, 55 to 95% by mass, 55 to 90% by mass, 55 to 80% by mass, 65 to 99.5% by mass, 65 to 95% by mass, 65 to 90% by mass, 65 to 80% by mass, 70 to 99.5% by mass, 70 to 95% by mass, 70 to 90% by mass, or 70 to 80% by mass.

[0037] The pressure-sensitive adhesive composition preferably contains a tackifier. By containing the tackifier, the pressure-sensitive adhesive tape of the present embodiment has better adhesion to an adherend.

[0038] Examples of the tackifier include (meth)acrylic tackifiers, rosin resins, rosin ester tackifier resins, terpene tackifier resins, coumarone-indene tackifier resins, alicyclic saturated hydrocarbon tackifier resins, C5 petroleum tackifier resins, C9 petroleum tackifier resins, and C5-C9 copolymer petroleum tackifier resins. These tackifier resins may be used alone or in combination of two or more. Among these, it is preferable to include at least one selected from the group consisting of (meth)acrylic tackifiers, rosin ester tackifiers, and terpene tackifiers. By including at least one selected from the group consisting of the (meth)acrylic tackifiers, the rosin ester tackifiers, and the terpene tackifiers as the tackifier, the resulting pressure-sensitive adhesive tape will have better adhesion to the adherend. In particular, the tackifier preferably contains at least one selected from the group consisting of the rosin ester tackifier and the terpene tackifier, and more preferably contains the rosin ester tackifier and the terpene tackifier. The rosin ester tackifier refers to a tackifier made from a rosin ester resin, and the terpene tackifier refers to a tackifier made from a terpene resin. The terpene resin includes a terpene resin and a terpene phenol resin.

[0039] Examples of the rosin-based tackifier include rosin-based resins and rosin polyol-based resins. Examples of the rosin ester-based tackifier include rosin ester-based resins, polymerized rosin ester-based resins, and hydrogenated rosin ester-based resins, specifically Pencel D-135, Pine Crystal KE-359, Ester Gum AA-V, and Ester Gum H (all manufactured by Arakawa Chemical Industries, Ltd.). Examples of the terpene-based tackifier include terpene-based resins and terpene phenol-based resins, specifically YS Resin PX1250 (manufactured by Yasuhara Chemical Co., Ltd.) and YS Polystar G150 (manufactured by Yasuhara Chemical Co., Ltd.). The rosin ester-based tackifier resin and the terpene-based tackifier resin are preferably derived from biological sources. Examples of the biologically derived rosin ester-based tackifier resin include rosin ester-based tackifier resins derived from natural resins such as pine resin. Examples of biologically derived terpene tackifying resins include terpene tackifying resins derived from plant essential oils and the like.

[0040] The (meth)acrylic tackifier is composed of a (meth)acrylic compound having a weight-average molecular weight of less than 30,000. Examples of the (meth)acrylic compound having a weight-average molecular weight of less than 30,000 include an acrylic oligomer having a weight-average molecular weight of less than 30,000 and an acrylic monomer having a weight-average molecular weight of less than 30,000. Among these, an acrylic oligomer having a weight-average molecular weight of less than 30,000 is preferred.

[0041] The weight-average molecular weight of the acrylic oligomer having a weight-average molecular weight of less than 30,000 is preferably 1,000 or more and less than 30,000. When the weight-average molecular weight of the acrylic oligomer having a weight-average molecular weight of less than 30,000 is within this range, the adhesive strength of the resulting pressure-sensitive adhesive composition is further improved. The weight-average molecular weight of the acrylic oligomer having a weight-average molecular weight of less than 30,000 is more preferably 1,500 or more and less than 20,000, and even more preferably 2,000 or more and less than 10,000. The weight-average molecular weight of the acrylic oligomer having a weight-average molecular weight of less than 30,000 can be measured by the same method as the method for measuring the weight-average molecular weight of the (meth)acrylic copolymer described above.

[0042] The glass transition temperature of the acrylic oligomer having a weight-average molecular weight of less than 30,000 is preferably 0°C in lower limit and 300°C in upper limit. When the glass transition temperature of the acrylic oligomer having a weight-average molecular weight of less than 30,000 is within this range, the adhesive strength of the resulting pressure-sensitive adhesive composition is further improved. The glass transition temperature of the acrylic oligomer having a weight-average molecular weight of less than 30,000 is more preferably 20°C in lower limit and even more preferably 40°C in lower limit. The glass transition temperature of the acrylic oligomer having a weight-average molecular weight of less than 30,000 may be 0°C to 300°C, 20°C to 300°C, or 40°C to 300°C. The glass transition temperature of the acrylic oligomer having a weight-average molecular weight of less than 30,000 can be measured, for example, by differential scanning calorimetry under conditions of a measurement temperature of -100°C to 200°C and a heating rate of 10°C / min in a nitrogen atmosphere (nitrogen flow, flow rate 50 mL / min) according to JIS K 6240:2011.

[0043] Examples of the constituent monomer of the acrylic oligomer having a weight-average molecular weight of less than 30,000 and the acrylic monomer having a weight-average molecular weight of less than 30,000 include the same monomers as those from which the constituent units derived from the alkyl(meth)acrylate, the constituent units derived from the monomer having a crosslinkable functional group, and the constituent units derived from the other monomers are derived in the (meth)acrylic copolymer described above. Specific examples of the constituent monomers of the acrylic oligomer having a weight average molecular weight of less than 30,000 and the acrylic monomers having a weight average molecular weight of less than 30,000 include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, and isooctyl (meth)acrylate. alkyl (meth)acrylates such as acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates) such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; and (meth)acrylates obtained from terpene compound derivative alcohols.The acrylic oligomer having a weight-average molecular weight of less than 30,000 preferably contains, as a monomer unit, an acrylic monomer having a relatively bulky structure, such as alkyl(meth)acrylates having a branched alkyl group, such as isobutyl(meth)acrylate and t-butyl(meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates), such as cyclohexyl(meth)acrylate, isobornyl(meth)acrylate, and dicyclopentanyl(meth)acrylate; or (meth)acrylates having a cyclic structure, such as aryl(meth)acrylates, such as phenyl(meth)acrylate and benzyl(meth)acrylate. In addition to the above, functional group-containing monomers can also be used as constituent monomers of the acrylic oligomer having a weight-average molecular weight of less than 30,000. Examples of the functional group-containing monomer include monomers having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocycle), such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; amino group-containing monomers, such as N,N-dimethylaminoethyl (meth)acrylate; amide group-containing monomers, such as N,N-diethyl (meth)acrylamide; carboxy group-containing monomers, such as acrylic acid and methacrylic acid; and hydroxy group-containing monomers, such as 2-hydroxyethyl (meth)acrylate. These functional group-containing monomers may be used alone or in combination of two or more. Among these, carboxy group-containing monomers are preferred, with acrylic acid being particularly preferred. Use of a carboxy group-containing monomer as the functional group-containing monomer can improve adhesive strength to highly polar adherends. Furthermore, including a constituent unit derived from the monomer having a crosslinkable functional group as a constituent monomer of the acrylic oligomer having a weight-average molecular weight of less than 30,000 can further improve the adhesive strength of the resulting pressure-sensitive adhesive composition.

[0044] The tackifier preferably contains a tackifier having a softening temperature of 80°C or higher. By containing a tackifier having a softening temperature of 80°C or higher, the pressure-sensitive adhesive layer does not become too soft, and a decrease in the adhesive strength of the resulting pressure-sensitive adhesive tape can be suppressed. The softening temperature of the tackifier having a softening temperature of 80°C or higher is preferably 90°C or higher, and more preferably 100°C or higher. Furthermore, from the viewpoint of improving the wettability of the interface of the pressure-sensitive adhesive layer, the softening temperature of the tackifier having a softening temperature of 80°C or higher is preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 150°C or lower. The softening temperature of the tackifier having a softening temperature of 80°C or higher may be 80°C to 170°C, 80°C to 160°C, 80°C to 150°C, 90°C to 170°C, 90°C to 160°C, 90°C to 150°C, 100°C to 170°C, 100°C to 160°C, or 100°C to 150°C. In this specification, the "softening temperature" refers to the softening temperature measured by a method according to JIS K 2207 (ring and ball method).

[0045] In the pressure-sensitive adhesive composition, the preferred lower limit of the tackifier content per 100 parts by mass of the (meth)acrylic copolymer is 10 parts by mass, and the preferred upper limit is 50 parts by mass. When the tackifier content is within this range, the resulting pressure-sensitive adhesive tape will have better adhesion to the adherend and better high-temperature retention. The more preferred lower limit of the tackifier content is 15 parts by mass, the more preferred upper limit is 40 parts by mass, and the even more preferred lower limit is 20 parts by mass. The tackifier content may be 10 to 50 parts by mass, 10 to 40 parts by mass, 20 to 50 parts by mass, or 20 to 40 parts by mass.

[0046] The pressure-sensitive adhesive composition preferably further contains a crosslinking agent. Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, and a metal chelate-based crosslinking agent. Among these, since the resulting pressure-sensitive adhesive tape has superior adhesion to the adherend, the crosslinking agent preferably contains at least one selected from the group consisting of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent, more preferably the isocyanate-based crosslinking agent, and even more preferably the isocyanate-based crosslinking agent and the epoxy-based crosslinking agent. The crosslinking agents may be used alone or in combination of two or more. When two or more crosslinking agents are used in combination, two or more crosslinking agents of the same type may be used (e.g., two or more isocyanate-based crosslinking agents may be used), or one or more crosslinking agents of different types may be used in combination (e.g., one or more isocyanate-based crosslinking agents and one or more epoxy-based crosslinking agents may be used).

[0047] In the pressure-sensitive adhesive composition, the preferred lower limit of the content of the crosslinking agent relative to 100 parts by mass of the (meth)acrylic copolymer is 0.1 parts by mass, and the preferred upper limit is 10 parts by mass. When the content of the crosslinking agent is within this range, the resulting pressure-sensitive adhesive tape will have better adhesion to an adherend and better transparency. A more preferred lower limit of the content of the crosslinking agent is 0.2 parts by mass, and a more preferred upper limit is 5 parts by mass. The content of the crosslinking agent may be 0.1 to 10 parts by mass, 0.1 to 5 parts by mass, 0.2 to 10 parts by mass, or 0.2 to 5 parts by mass. In this specification, the term "content of crosslinking agent" refers to the content of the solids of the crosslinking agent.

[0048] The pressure-sensitive adhesive composition may further contain a crosslinking catalyst for accelerating crosslinking by the crosslinking agent. Examples of the crosslinking catalyst include crosslinking catalysts for the isocyanate-based crosslinking agents, such as dibutyltin dilaurate, dibutyltin diacetate, and dioctyltin dilaurate.

[0049] The pressure-sensitive adhesive composition preferably further contains a pigment. By containing the pigment, the resulting pressure-sensitive adhesive tape has excellent light-shielding properties and can be suitably used for fixing components used in devices that require prevention of light leakage.

[0050] Examples of the pigment include color pigments such as black fillers, etc. Specific examples of the black fillers include carbon black and titanium black.

[0051] The preferred lower limit of the average particle size of the black filler is 0.01 μm, and the preferred upper limit is 1.0 μm. When the average particle size of the black filler is within this range, the resulting pressure-sensitive adhesive tape has better light-blocking properties. The more preferred lower limit of the average particle size of the black filler is 0.1 μm, and the more preferred upper limit is 0.8 μm. The average particle size of the black filler may be 0.01 to 1.0 μm, 0.01 to 0.8 μm, 0.1 to 1.0 μm, or 0.1 to 0.8 μm. The average particle size of the black filler can be determined, for example, by observing 50 random black fillers with an electron microscope or optical microscope and calculating the average particle size of each black filler, or by performing laser diffraction particle size distribution measurement.

[0052] In the pressure-sensitive adhesive composition, the preferred lower limit of the pigment content relative to 100 parts by mass of the (meth)acrylic copolymer is 0.1 parts by mass, and the preferred upper limit is 5.0 parts by mass. When the pigment content is within this range, the resulting pressure-sensitive adhesive tape has better light-blocking properties. A more preferred lower limit of the pigment content is 0.5 parts by mass, and a more preferred upper limit is 3.0 parts by mass. The pigment content may be 0.1 to 5.0 parts by mass, 0.1 to 3.0 parts by mass, 0.5 to 5.0 parts by mass, or 0.5 to 3.0 parts by mass.

[0053] The pressure-sensitive adhesive composition may contain additives such as a silane coupling agent, a plasticizer, a softener, a filler, a dye, etc., as needed, within the scope of not impairing the object of the present invention.

[0054] The preferred lower limit of the bio-derived carbon content in the pressure-sensitive adhesive layer is 10%. By ensuring that the bio-derived carbon content in the pressure-sensitive adhesive layer is 10% or more, the pressure-sensitive adhesive tape of the present embodiment is excellent in terms of saving petroleum resources and reducing carbon dioxide emissions, and is capable of reducing the environmental impact. The more preferred lower limit of the bio-derived carbon content in the pressure-sensitive adhesive layer is 40%, and the even more preferred lower limit is 60%. The upper limit of the bio-derived carbon content is not particularly limited and may be 100%. Furthermore, the bio-derived carbon content may be 95% or less, or 90% or less. The bio-derived carbon content in the pressure-sensitive adhesive layer may be 10 to 100%, 40 to 100%, 60 to 100%, 10 to 95%, 40 to 95%, 60 to 95%, 10 to 90%, 40 to 90%, or 60 to 90%. Biologically derived carbon contains a certain percentage of the radioactive isotope (C-14), whereas petroleum-derived carbon contains almost no C-14. Therefore, the content of biogenic carbon can be calculated by measuring the concentration of C-14 contained in the PSA layer. Specifically, this can be measured in accordance with ASTM D6866-22, a standard widely used in the bioplastics industry.

[0055] The preferred lower limit of the thickness of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape of this embodiment is 3 μm, and the preferred upper limit is 300 μm. Having a thickness of the pressure-sensitive adhesive layer within this range allows the resulting pressure-sensitive adhesive tape to have superior adhesion to an adherend. The more preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 5 μm, and the more preferred upper limit is 200 μm. The thickness of the pressure-sensitive adhesive layer may be 3 to 300 μm, 3 to 200 μm, 5 to 300 μm, or 5 to 200 μm.

[0056] The pressure-sensitive adhesive tape of the present embodiment may be a non-support type tape that does not have a base layer, or a support type tape that has the base layer and the pressure-sensitive adhesive layer on at least one side of the base layer. When the pressure-sensitive adhesive tape of the present embodiment is a support type tape, it may be a double-sided pressure-sensitive adhesive tape that has the pressure-sensitive adhesive layers on both sides of the base layer.

[0057] Examples of substrates constituting the substrate layer include films and nonwoven fabrics. Furthermore, from the viewpoint of increasing the content of biologically derived carbon in the entire pressure-sensitive adhesive tape, substrates using biologically derived materials are preferred. Examples of biologically derived materials include plant-derived polyesters (PES) such as polyethylene terephthalate (PET), polyethylene furanoate (PEF), polylactic acid (PLA), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polybutylene succinate (PBS), polyethylene (PE), polypropylene (PP), polyurethane (PU), triacetyl cellulose (TAC), cellulose, and polyamide (PA).

[0058] From the viewpoint of substrate strength, the 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, and nylon 410, which are made from castor oil, and nylon 56, which is made from cellulose.

[0059] Furthermore, from the perspective of reducing the use of new petroleum resources and reducing the environmental burden by suppressing carbon dioxide emissions, substrates made from recycled resources may be used. Examples of resource recycling methods include collecting waste materials such as packaging containers, home appliances, automobiles, construction materials, and food, as well as waste generated during manufacturing processes, and then cleaning, decontaminating, or decomposing the extracted materials by heating or fermentation to reuse them as raw materials. Examples of substrates made from recycled resources include films and nonwoven fabrics made from PET, PBT, PE, PP, PA, etc., which are made from recycled plastics that have been re-resinized. Furthermore, the collected waste materials may be burned and used as thermal energy for the production of substrates and their raw materials. The oils and fats contained in the collected waste materials may be mixed with petroleum, fractionated, and purified, and then used as raw materials.

[0060] The substrate may be a foam substrate from the viewpoint of improving compression characteristics. The foam substrate is preferably a foam substrate containing at least one selected from the group consisting of PE, PP, and PU, and more preferably a foam substrate containing PE from the viewpoint of achieving a high degree of both flexibility and strength. Examples of the constituent of the foam substrate containing PE include PE made from sugarcane.

[0061] A preferred method for producing the foam base material is, for example, to prepare a foamable resin composition containing a PE resin containing sugarcane-derived PE and a foaming agent, and then foam the foaming agent when extruding the foamable resin composition into a sheet using an extruder, and optionally crosslink the resulting polyolefin foam.

[0062] The preferred lower limit of the thickness of the foam substrate is 50 μm, and the preferred upper limit is 5000 μm. By having the foam substrate have a thickness within this range, it is possible to exhibit high impact resistance while also exhibiting high flexibility, allowing it to be adhered closely to the shape of the adherend. The more preferred upper limit of the thickness of the foam substrate is 1000 μm, and even more preferred upper limit is 300 μm. The thickness of the foam substrate may be 50 to 5000 μm, 50 to 1000 μm, or 50 to 300 μm.

[0063] In the pressure-sensitive adhesive tape of this embodiment, the preferred lower limit of the total thickness of the pressure-sensitive adhesive tape (total thickness of the base layer and the pressure-sensitive adhesive layer) is 3 μm, and the preferred upper limit is 6000 μm. Having the total thickness of the pressure-sensitive adhesive tape in this range further increases the adhesive strength. The more preferred upper limit of the total thickness of the pressure-sensitive adhesive tape is 1200 μm, and the even more preferred upper limit is 500 μm. The total thickness of the pressure-sensitive adhesive tape may be 3 to 6000 μm, 3 to 1200 μm, or 3 to 500 μm.

[0064] The method for producing the pressure-sensitive adhesive tape of this embodiment is not particularly limited, and the tape can be produced by a conventionally known production method. For example, in the case of a double-sided pressure-sensitive adhesive tape, the following method can be used. First, a solvent is added to a (meth)acrylic copolymer and, if necessary, a tackifier, a crosslinking agent, etc. to prepare a pressure-sensitive adhesive composition A. The obtained pressure-sensitive adhesive composition A is applied to the surface of a substrate, and the solvent in the composition is completely dried and removed by heating to form a pressure-sensitive adhesive layer A. Next, a release film is superimposed on the formed pressure-sensitive adhesive layer A with its release-treated surface facing the pressure-sensitive adhesive layer A. Next, a release film separate from the above-mentioned release film is prepared, and pressure-sensitive adhesive composition B, prepared in the same manner as the pressure-sensitive adhesive composition A, is applied to the release-treated surface of this release film, and the solvent in the composition is completely dried and removed to produce a laminate film in which pressure-sensitive adhesive layer B is formed on the surface of the release film. The obtained laminate film is superimposed on the back surface of the substrate on which pressure-sensitive adhesive layer A has been formed, with the pressure-sensitive adhesive layer B facing the back surface of the substrate, to produce a laminate. Then, by pressing the laminate with a rubber roller or the like, a double-sided adhesive tape can be obtained which has adhesive layers on both sides of the substrate and in which the surfaces of the adhesive layers are covered with release films.

[0065] Alternatively, two sets of laminate films may be prepared in a similar manner, and these laminate films may be superimposed on each of both surfaces of a substrate with the pressure-sensitive adhesive layer of the laminate film facing the substrate to prepare a laminate. This laminate may then be pressed with a rubber roller or the like to obtain a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both surfaces of the substrate and in which the surfaces of the pressure-sensitive adhesive layers are covered with release films.

[0066] The adhesive tape of this embodiment is a laminate obtained by bonding an aluminum plate having a width of 25 mm, a length of 150 mm, and a thickness of 0.3 mm to a polycarbonate resin plate having a width of 25 mm, a length of 200 mm, and a thickness of 1 mm via the adhesive tape having a width of 25 mm and a length of 150 mm, which is placed in the center of the longitudinal direction of the polycarbonate resin plate. A bending stress is applied to the laminate in the longitudinal direction to deform the polycarbonate resin plate into an arc-shaped warp so that the distance between both ends of the longitudinal direction is 180 mm. After heating the laminate for 72 hours at 60 ° C and 90% RH, a repulsion resistance test was performed. The preferred upper limit of the lift height between the aluminum plate and the polycarbonate resin plate (hereinafter also referred to as the "lift height after the repulsion resistance test") is 5 mm. Having a lift height of 5 mm or less after the repulsion resistance test makes the adhesive tape of this embodiment more suitable for applications requiring curved surface conformability. A more preferred upper limit of the lift height after the repulsion resistance test is 2 mm. It is most preferable that the lift height after the repulsion resistance test is 0 mm, i.e., no lift occurs after the repulsion resistance test. The lift height after the repulsion resistance test may be 0 to 5 mm, or may be 0 to 2 mm. Specifically, the repulsion resistance test can be measured by the following method. FIG. 1 is a schematic diagram showing a method for testing the repulsion resistance of pressure-sensitive adhesive tapes. That is, first, pressure-sensitive adhesive tape 1 is cut into a flat rectangular shape 25 mm wide and 150 mm long, and an aluminum plate 2 having a width of 25 mm, a length of 150 mm, and a thickness of 0.3 mm is bonded to a polycarbonate resin plate 3 having a width of 25 mm, a length of 200 mm, and a thickness of 1 mm using the pressure-sensitive adhesive tape 1. At this time, the pressure-sensitive adhesive tape 1 is adjusted so as to be located in the center of the polycarbonate resin plate 3 in the longitudinal direction. A 2 kg rubber roller is rolled back and forth on the polycarbonate resin plate 3 at a speed of 300 mm / min to unite the polycarbonate resin plate 3 and the aluminum plate 2 via the adhesive tape 1, and the resulting mixture is left to stand at 23° C. for 24 hours to produce a laminate 4. The laminate 4 is attached to a jig 5 as shown in FIG. 1 , and bending stress is applied to the laminate 4 in the longitudinal direction, thereby deforming the laminate 4 into an arc-shaped warp so that the distance between both ends of the polycarbonate resin plate 3 in the longitudinal direction is 180 mm.In this state, the laminate 4 is placed in a constant temperature and humidity oven at 60°C and 90% RH and left to stand for 72 hours. The laminate 4 is taken out of the oven while still warped in an arc shape, and the floating height H (mm) between the aluminum plate 2 and the polycarbonate resin plate 3 is measured with a vernier caliper.

[0067] The application of the pressure-sensitive adhesive tape of this embodiment is not particularly limited, but it is preferably used for fixing electronic device components or vehicle-mounted components. Specifically, the pressure-sensitive adhesive tape of this embodiment can be suitably used for adhesively fixing electronic device components in large portable electronic devices having curved surfaces, adhesively fixing vehicle-mounted components having curved surfaces (for example, vehicle-mounted panels), etc.

[0068] According to the present invention, it is possible to provide a pressure-sensitive adhesive tape that is excellent in high-temperature retention and curved surface conformability.

[0069] 1 is a schematic diagram showing a method for testing the repulsion resistance of a pressure-sensitive adhesive tape, and FIG. 2 is a schematic diagram showing a method for a high-temperature retention test.

[0070] The following examples further illustrate aspects of the present invention, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are as follows.

[0071] <n-Hexyl acrylate 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. The resulting mixture was distilled to obtain n-hexylaldehyde containing bio-derived carbon. The obtained n-hexylaldehyde containing bio-derived carbon was then hydrogenated to obtain n-hexyl alcohol containing bio-derived carbon. The obtained n-hexyl alcohol containing bio-derived carbon was esterified with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare n-hexyl acrylate containing bio-derived carbon (glass transition temperature of -65°C when converted into a homopolymer).

[0072] <n-heptyl acrylate containing bio-derived carbon> Ricinoleic acid derived from castor oil was cracked to obtain a mixture containing undecylenic acid and n-heptyl alcohol. Next, undecylenic acid was separated from the obtained mixture by distillation to obtain n-heptyl alcohol containing bio-derived carbon. The obtained n-heptyl alcohol containing bio-derived carbon was esterified with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare n-heptyl acrylate containing bio-derived carbon (glass transition temperature of -68°C when made into a homopolymer).

[0073] <1-Methylheptyl acrylate containing bio-derived carbon> Ricinoleic acid derived from castor oil was alkali-fused to obtain a mixture containing sepacic acid and 1-methylheptyl alcohol. Next, sepacic acid was separated from the resulting mixture by distillation to obtain 1-methylheptyl alcohol containing bio-derived carbon. 1-Methylheptyl alcohol containing bio-derived carbon was esterified with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare 1-methylheptyl acrylate containing bio-derived carbon (glass transition temperature of -45°C when made into a homopolymer).

[0074] <2-hydroxyethyl acrylate containing bio-derived carbon> Ethanol containing bio-derived carbon was obtained by fermenting sugars contained in sugarcane. The obtained ethanol containing bio-derived carbon was dehydrated to obtain ethylene, which was then oxidized to obtain ethylene oxide, to which water was added to obtain ethylene glycol containing bio-derived carbon. The obtained ethylene glycol containing bio-derived carbon was esterified with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare 2-hydroxyethyl acrylate (hydroxyl group-containing monomer) containing bio-derived carbon.

[0075] <Bio-derived carbon-free monomers> n-Butyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd., glass transition temperature when made into a homopolymer of -55°C) 2-Ethylhexyl acrylate (manufactured by Nippon Shokubai Co., Ltd., glass transition temperature when made into a homopolymer of -70°C) Acrylic acid (manufactured by Nippon Shokubai Co., Ltd., carboxy group-containing monomer) Methyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd., glass transition temperature when made into a homopolymer of 8°C) 2-Methoxyethyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd., glass transition temperature when made into a homopolymer of -55°C, monomer having an acyclic ether structure)

[0076] <Tackifiers> Tackifier A: terpene-based tackifier (terpene phenol resin, manufactured by Yasuhara Chemical Co., Ltd., "YS Polystar G150", softening temperature: 145°C to 155°C) Tackifier B: rosin ester-based tackifier (manufactured by Arakawa Chemical Industries, Ltd., "Pine Crystal KE-359", softening temperature: 94°C to 104°C) Tackifier C: rosin ester-based tackifier (softening temperature: 150°C, hydroxyl value: 35 mgKOH / g)

[0077] <Crosslinking agent> Isocyanate-based crosslinking agent (manufactured by Covestro, "Desmodur L-75") Epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, Inc., "Tetrad X")

[0078] <Pigment> Carbon black (Toyo Color Co., Ltd., "Multilac A903 Black")

[0079] Example 1 (1) Production of Acrylic Copolymer Ethyl acetate was added as a polymerization solvent to a reaction vessel, and nitrogen was bubbled through. The reaction vessel was then heated while nitrogen was flowing in to initiate reflux. Subsequently, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile as a polymerization initiator 10 times with ethyl acetate was added to the reaction vessel, and 89.9 parts by mass of 2-ethylhexyl acrylate, 0.1 parts by mass of 2-hydroxyethyl acrylate containing biocarbon, and 10.0 parts by mass of acrylic acid were added dropwise over two hours. After completion of the dropwise addition, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile as a polymerization initiator 10 times with ethyl acetate was added again to the reaction vessel, and a polymerization reaction was carried out for four hours to obtain an acrylic copolymer-containing solution. The resulting acrylic copolymer was diluted 50 times with tetrahydrofuran (THF), and the resulting diluted solution was filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare a measurement sample. The measurement sample was supplied to a gel permeation chromatograph (Waters Corporation, "2690 Separations Module") and subjected to GPC measurement at a sample flow rate of 1 mL / min and a column temperature of 40° C. The polystyrene-equivalent molecular weight of the acrylic copolymer was measured to determine the weight average molecular weight. The results are shown in Table 1.

[0080] (2) Preparation of Pressure-Sensitive Adhesive Tape To the obtained acrylic copolymer-containing solution, 30.0 parts by mass of a terpene-based tackifier and an isocyanate-based crosslinking agent were added so that the solid content was 2.5 parts by mass per 100 parts by mass of the acrylic copolymer in the acrylic copolymer-containing solution, to prepare a pressure-sensitive adhesive composition. The obtained pressure-sensitive adhesive composition was applied to the release-treated surface of a 75 μm-thick release PET film so that the thickness of the pressure-sensitive adhesive layer after drying would be 50 μm, and then dried at 110 ° C. for 5 minutes to obtain a pressure-sensitive adhesive layer. The obtained pressure-sensitive adhesive layer was placed on the release-treated surface of a 75 μm-thick release PET film and aged at 40 ° C. for 48 hours to obtain a pressure-sensitive adhesive tape (non-support type).

[0081] (3) Measurement of gel fraction of adhesive layer The release PET film on one side of the obtained adhesive tape was peeled off, and the tape was attached to a 23 μm thick base PET film (manufactured by Futamura Chemical Co., Ltd., "FE2002"), and cut into a flat rectangular shape with a width of 20 mm and a length of 40 mm. The release PET film on the other side of the adhesive tape was then peeled off to prepare a test piece, and its mass was measured. The test piece was immersed in ethyl acetate at 23°C for 24 hours, then removed from the ethyl acetate and dried at 110°C for 1 hour. The mass of the dried test piece was measured, and the gel fraction was calculated using the following formula (I). The results are shown in Table 1. Gel fraction (mass%) = 100 × (W ２ -W ０ ) / (W １ -W ０ ) (I) (W ０ : Mass of the substrate, W １ : mass of test piece before immersion, W ２ : Mass of test piece after immersion and drying)

[0082] (4) Measurement of the shear storage modulus of the pressure-sensitive adhesive layer at 80°C and the peak temperature of the loss tangent of the pressure-sensitive adhesive layer. The release film of the obtained pressure-sensitive adhesive tape was peeled off, and the pressure-sensitive adhesive layers were stacked to prepare a laminate approximately 1 mm thick. This laminate was then cut into a width of 6 mm and a length of 10 mm to obtain a test specimen. The obtained test specimen was then subjected to dynamic viscoelasticity measurement in shear mode using a dynamic viscoelasticity measuring device under a nitrogen atmosphere at a measurement temperature range of -40°C to 200°C, a heating rate of 5°C / min, a frequency of 1 Hz, and a strain of 0.08%, to determine the shear storage modulus of the pressure-sensitive adhesive layer at 80°C and the peak temperature of the loss tangent of the pressure-sensitive adhesive layer. A DVA-200 (manufactured by IT Measurement & Control Co., Ltd.) was used as the dynamic viscoelasticity measuring device. The results are shown in Table 1.

[0083] (Examples 2 to 32, 35 to 47, Comparative Examples 1 to 8) Pressure-sensitive adhesive tapes were obtained in the same manner as in Example 1, except that the types and amounts of monomers constituting the acrylic copolymer and the types and amounts of each component contained in the pressure-sensitive adhesive composition were as shown in Tables 1 to 4. For Examples 28 to 30, pressure-sensitive adhesive tapes were obtained in the same manner as in Example 1, except that the types and amounts of each component of the pressure-sensitive adhesive composition were changed as shown in Table 2, and the amount of polymerization initiator added was also appropriately changed. Furthermore, the weight-average molecular weight of the acrylic copolymer, the gel fraction of the pressure-sensitive adhesive layer, the shear storage modulus at 80°C of the pressure-sensitive adhesive layer, and the peak temperature of the loss tangent of the pressure-sensitive adhesive layer were measured in the same manner as in Example 1. The results are shown in Tables 1 to 4.

[0084] Example 33 A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that the types and amounts of each component contained in the pressure-sensitive adhesive composition were as shown in Table 3. The obtained pressure-sensitive adhesive composition was applied to the release-treated surface of a 75 μm-thick release PET film so that the thickness of the pressure-sensitive adhesive layer after drying would be 19 μm, and then dried at 110°C for 5 minutes to obtain a pressure-sensitive adhesive layer. The obtained pressure-sensitive adhesive layer was bonded to one side of a 12 μm-thick base PET film (manufactured by Toyobo Co., Ltd., "FE2002"). Furthermore, a pressure-sensitive adhesive layer having the same composition and thickness was prepared on the release-treated surface of another 75 μm-thick release PET film, bonded to the other side of the base PET film, and aged at 40°C for 48 hours to obtain a pressure-sensitive adhesive tape (support type, total thickness 50 μm excluding the release PET film) having a pressure-sensitive adhesive layer and a release PET film on both sides of the substrate. The weight-average molecular weight of the acrylic copolymer and the gel fraction of the pressure-sensitive adhesive layer were measured in the same manner as in Example 1. The gel fraction of the pressure-sensitive adhesive layer was measured using a test piece obtained by cutting the pressure-sensitive adhesive tape into a flat rectangular shape 20 mm wide and 40 mm long and then peeling off the release PET films on both sides. The shear storage modulus at 80°C and the peak temperature of the loss tangent of the pressure-sensitive adhesive layer were measured for the pressure-sensitive adhesive layer before it was bonded to the base PET film. The results are shown in Table 3.

[0085] Example 34 A pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that the types and amounts of each component contained in the pressure-sensitive adhesive composition were as shown in Table 3. The resulting pressure-sensitive adhesive composition was applied to the release-treated surface of a 75 μm-thick release PET film so that the thickness of the pressure-sensitive adhesive layer after drying would be 50 μm, and then dried at 110°C for 5 minutes to obtain a pressure-sensitive adhesive layer. The resulting pressure-sensitive adhesive layer was bonded to one side of a 150 μm-thick PE foam substrate (manufactured by Sekisui Chemical Co., Ltd., "WL02"). Furthermore, a pressure-sensitive adhesive layer having the same composition and thickness was prepared on the release-treated surface of another 75 μm-thick release PET film, which was then bonded to the other side of the PE foam substrate and aged at 40°C for 48 hours to obtain a pressure-sensitive adhesive tape (support type, total thickness 250 μm excluding the release PET film) having a pressure-sensitive adhesive layer and a release PET film on both sides of the substrate. The weight-average molecular weight of the acrylic copolymer and the gel fraction of the pressure-sensitive adhesive layer were measured in the same manner as in Example 1. The gel fraction of the pressure-sensitive adhesive layer was measured using a test piece obtained by cutting the pressure-sensitive adhesive tape into a flat rectangular shape 20 mm wide and 40 mm long and then peeling off the release PET films on both sides. The shear storage modulus at 80°C and the peak temperature of the loss tangent of the pressure-sensitive adhesive layer were measured for the pressure-sensitive adhesive layer before it was bonded to the PE foam substrate. The results are shown in Table 3.

[0086] <Evaluation> The pressure-sensitive adhesive tapes obtained in the Examples and Comparative Examples were evaluated by the following methods. The results are shown in Tables 1 to 4.

[0087] (High-Temperature Retention Properties) A ​​high-temperature retention test was conducted in accordance with JIS Z 0237:2009. FIG. 2 is a schematic diagram showing the high-temperature retention test method. Specifically, first, one side (the side not being measured) of the pressure-sensitive adhesive tape 1 was lined with a 23 μm-thick PET film 6 (manufactured by Futamura Chemical Co., Ltd., "FE2002"), and then cut into a width of 25 mm and a length of 75 mm to prepare a test specimen. This test specimen was placed so that its adhesive layer (the side being measured) faced a 2 mm-thick, 50 mm-wide, and 80 mm-long SUS304 plate 7 (a SUS304 plate washed with ethanol and then wiped dry), and then bonded to the test specimen by rolling a 2 kg rubber roller back and forth once at a speed of 300 mm / min. The test specimen was then aged at 23° C. and 50% RH for 20 minutes to prepare a test sample. The obtained test sample was placed in an environment of 80°C and 50% RH and left to stand for 15 minutes. Under this environment, a 1.0 kg weight 8 was attached to the PET film 6 of the test sample in accordance with JIS Z 0237:2009 so that a load in the shear direction was applied to the PET film 6. 24 hours after the weight 8 was attached (24 hours after the start of the test), the amount of displacement in the shear direction from the position where the pressure-sensitive adhesive layer was attached to the SUS304 plate 7 was measured. The high-temperature retention properties of the pressure-sensitive adhesive tape were evaluated according to the following criteria: ○: When the amount of displacement was 0.5 mm or less △: When the amount of displacement exceeded 0.5 mm but the test piece had not fallen 24 hours after the start of the test ×: When the test piece had fallen 24 hours after the start of the test

[0088] (Curved Surface Conformability (Plane Rebound Test)) The obtained adhesive tape was cut into a flat rectangular shape with a width of 25 mm and a length of 150 mm, and an aluminum plate with a width of 25 mm, a length of 150 mm, and a thickness of 0.3 mm and a polycarbonate resin plate with a width of 25 mm, a length of 200 mm, and a thickness of 1 mm were bonded together using the adhesive tape. At this time, the adhesive tape was adjusted so that it was located in the center of the longitudinal direction of the polycarbonate resin plate. A 2 kg rubber roller was rolled back and forth on the polycarbonate resin plate at a speed of 300 mm / min to integrate the polycarbonate resin plate and the aluminum plate via the adhesive tape, and the resulting laminate was left to stand at 23°C for 24 hours to produce a laminate. The obtained laminate was attached to a jig as shown in Figure 1, and a bending stress was applied in the longitudinal direction of the laminate to deform the laminate into an arc-shaped warp so that the distance between both ends of the polycarbonate resin plate in the longitudinal direction was 180 mm. In this state, the laminate was placed in a constant temperature and humidity oven at 60°C and 90% RH and left to stand for 72 hours. The laminate was taken out of the oven while still warped into an arc, and the floating height H (mm) between the aluminum plate and the polycarbonate resin plate was measured with a vernier caliper. The curved surface conformability was evaluated according to the following criteria: ○: When the floating height H was 2 mm or less △: When the floating height H was more than 2 mm but not more than 5 mm ×: When the floating height H was more than 5 mm

[0089] (Adhesion to Adherend) The obtained adhesive tape was cut into 25 mm wide strips, and then the release PET film on one side was peeled off. The tape was then bonded to a SUS plate by rolling a 2 kg rubber roller back and forth at a speed of 300 mm / min. The tape was then left to stand in an environment of 23 ° C. and 50% RH for 20 minutes to obtain a test piece. The obtained test piece was subjected to a tensile test using a tensile tester (manufactured by A&D Co., Ltd., "RTI-1310") in accordance with JIS Z 0237:2009 at 80 ° C., a peel speed of 300 mm / min, and a peel angle of 180 °, and the 180 ° peel adhesive strength was measured. The adhesion to the adherend was evaluated according to the following criteria. ○: When the 180° peel adhesive strength was 10 N / 25 mm or more △: When the 180° peel adhesive strength was 5 N / 25 mm or more and less than 10 N / 25 mm ×: When the 180° peel adhesive strength was less than 5 N / 25 mm

[0090] (High-speed releasability) (1) Measurement of 180° peel force against SUS when adhesive tape is peeled at a peeling speed of 1500 mm / min. The obtained adhesive tape was cut to a size of 25 mm wide x 100 mm long, and then the release PET film on one side (the side not being measured) was peeled off, and the exposed adhesive layer was backed with a 50 μm thick PET film (manufactured by Toyobo Co., Ltd., "E5200 #50") to prepare a test piece. The release PET film on the other side (the side being measured) of the prepared test piece was peeled off, and the test piece was pressed against a SUS plate (SUS304 plate washed with alcohol and wiped dry) by moving a 2 kg rubber roller back and forth once at a speed of 10 mm / s in an environment of 23 ° C., and then left to stand for 5 minutes in an environment of 23 ° C. to prepare a measurement sample. For the obtained measurement sample, a peel test was performed in accordance with JIS Z 0237:2009 using a tensile tester ("Autograph AGS-X" manufactured by Shimadzu Corporation) in which the pressure-sensitive adhesive tape was peeled from the SUS plate in a direction of 180° at 23°C and a peel rate of 1500 mm / min, and the 180° peel force F1 (N / 25 mm) from SUS when the pressure-sensitive adhesive tape was peeled off at a peel rate of 1500 mm / min was measured.

[0091] (2) Measurement of 180° Peel Force from SUS When Adhesive Tape is Peeled Off at a Peeling Speed ​​of 300 mm / min The 180° peel force F2 (N / 25 mm) from SUS when the adhesive tape was peeled off at a peeling speed of 300 mm / min was measured in the same manner as in the above-mentioned "(1) Measurement of 180° Peel Force from SUS When Adhesive Tape is Peeled Off at a Peeling Speed ​​of 1500 mm / min", except that the adhesive tape was peeled off from the SUS plate at a peeling speed of 300 mm / min in the peel test.

[0092] (3) Calculation of the rate of increase in adhesive strength during high-speed peeling From F1 and F2 obtained by the above-mentioned method, the rate of increase in adhesive strength during high-speed peeling was calculated using the following formula (II): Rate of increase in adhesive strength during high-speed peeling (%) = {(F1 - F2) / F2} × 100 (II)

[0093] (4) Evaluation of high-speed releasability The high-speed releasability of the pressure-sensitive adhesive tape to the adherend was evaluated from the calculated rate of increase in adhesive strength during high-speed peeling according to the following criteria: ◎: When the rate of increase in adhesive strength during high-speed peeling was 10% or less ○: When the rate of increase in adhesive strength during high-speed peeling was more than 10% and 20% or less △: When the rate of increase in adhesive strength during high-speed peeling was more than 20% and 30% or less ×: When the rate of increase in adhesive strength during high-speed peeling was more than 30%

[0094]

[0095]

[0096]

[0097]

[0098] According to the present invention, it is possible to provide a pressure-sensitive adhesive tape that is excellent in high-temperature retention and curved surface conformability.

[0099] REFERENCE SIGNS LIST 1 adhesive tape 2 aluminum plate 3 polycarbonate resin plate 4 laminate 5 jig 6 PET film 7 SUS304 plate 8 weight (1.0 kg)

Claims

1. An adhesive tape having an adhesive layer formed using an adhesive composition, The adhesive composition contains a (meth)acrylic copolymer, The (meth)acrylic copolymer has constituent units derived from alkyl (meth)acrylate, The adhesive layer has a shear storage modulus of 15,000 Pa or more at 80°C, as measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz and a measurement temperature range of -40°C to 200°C. The aforementioned adhesive layer has a peak temperature of loss loss tangent measured by dynamic viscoelasticity measurement at a measurement frequency of 1 Hz and a measurement temperature range of -40°C to 200°C, which is within the range of -20°C to 0°C. The adhesive layer has a gel fraction of 10% by mass or more and 45% by mass or less. An adhesive tape characterized by the following features.

2. The alkyl (meth)acrylate includes an alkyl (meth)acrylate whose glass transition temperature when it is a homopolymer is -60°C or lower. The adhesive tape according to claim 1, wherein the (meth)acrylic copolymer contains 50% by mass or more of constituent units derived from alkyl (meth)acrylate, which has a glass transition temperature of -60°C or lower when used as the homopolymer.

3. The adhesive tape according to claim 2, wherein the alkyl (meth)acrylate, when used as a homopolymer, has a glass transition temperature of -60°C or lower, includes n-hexyl acrylate.

4. The adhesive tape according to claim 1, 2, or 3, wherein the (meth)acrylic copolymer does not have a crosslinkable functional group and has constituent units derived from a monomer whose glass transition temperature is 0°C or higher when it is a homopolymer.

5. The adhesive tape according to claim 4, wherein the (meth)acrylic copolymer does not have the crosslinkable functional group and the content of constituent units derived from monomers having a glass transition temperature of 0°C or higher when homopolymerized is 0.1% by mass or more and 70% by mass or less.

6. The adhesive tape according to claim 1, 2, or 3, wherein the (meth)acrylic copolymer has constituent units derived from n-heptyl (meth)acrylate.

7. The adhesive tape according to claim 1, 2, or 3, wherein the (meth)acrylic copolymer does not have constituent units derived from n-heptyl (meth)acrylate, or the content of constituent units derived from n-heptyl (meth)acrylate is less than 90% by mass.

8. The adhesive tape according to claim 1, 2, or 3, wherein the (meth)acrylic copolymer further comprises a constituent unit derived from at least one non-crosslinkable ether structure monomer selected from the group consisting of monomers having a cyclic ether structure other than epoxy groups and oxetanyl groups, and monomers having an acyclic ether structure.

9. The adhesive tape according to claim 8, wherein the (meth)acrylic copolymer has a content of 0.01% by mass or more and 50% by mass or less of constituent units derived from the monomer having the non-crosslinkable ether structure.

10. The adhesive tape according to claim 1, 2, or 3, wherein the (meth)acrylic copolymer further comprises structural units derived from monomers having crosslinkable functional groups.

11. The adhesive tape according to claim 10, wherein the monomer having the crosslinkable functional group comprises at least one selected from the group consisting of carboxyl group-containing monomers and hydroxyl group-containing monomers.

12. The adhesive tape according to claim 11, wherein the monomer having the crosslinkable functional group includes the hydroxyl group-containing monomer.

13. The adhesive tape according to claim 11, wherein the monomer having the crosslinkable functional group includes the carboxyl group-containing monomer, and the content of constituent units derived from the carboxyl group-containing monomer in the (meth)acrylic copolymer is 5% by mass or more.

14. The adhesive tape according to claim 10, wherein the (meth)acrylic copolymer has a content of 0.01% by mass or more and less than 20% by mass of constituent units derived from the monomer having the crosslinkable functional group.

15. The adhesive tape according to claim 1, 2, or 3, wherein the (meth)acrylic copolymer has a weight-average molecular weight of 800,000 or more.

16. The adhesive tape according to claim 1, 2, or 3, further comprising an adhesive composition and a tackifier.

17. The adhesive tape according to claim 16, wherein the tackifier comprises at least one selected from the group consisting of (meth)acrylic tackifiers, rosin ester tackifiers, and terpene tackifiers.

18. The adhesive tape according to claim 17, comprising the rosin ester-based tackifier and the terpene-based tackifier.

19. The adhesive tape according to claim 1, 2, or 3, further comprising a crosslinking agent in the adhesive composition.

20. The adhesive tape according to claim 19, wherein the crosslinking agent comprises at least one selected from the group consisting of isocyanate-based crosslinking agents and epoxy-based crosslinking agents.

21. The adhesive tape according to claim 20, wherein the crosslinking agent comprises the isocyanate-based crosslinking agent and the epoxy-based crosslinking agent.

22. The adhesive tape according to claim 1, 2, or 3, wherein the adhesive layer has a half-width of the peak of the loss loss tangent measured by dynamic viscoelastic measurement at a measurement frequency of 1 Hz and a measurement temperature range of -40°C to 200°C, and the half-width of the peak is 44°C or less.

23. The adhesive tape according to claim 1, 2, or 3, having a base layer and the adhesive layer on at least one surface of the base layer.

24. The adhesive tape according to claim 1, 2, or 3, used for fixing electronic equipment components or in-vehicle components.