Adhesive composition and adhesive tape

Abstract

The purpose of the present invention is to provide an adhesive composition that can be peeled from an adherend without leaving a residue but still exhibits strong adhesion. The purpose of the present invention is also to provide an adhesive tape that has an adhesive layer that is formed using the adhesive composition. The present invention is an adhesive composition that contains a (meth)acrylic copolymer that includes structural units derived from an alkyl (meth)acrylate. The structural units derived from an alkyl (meth)acrylate include structural units derived from an alkyl (meth)acrylate that has a C6–9 alkyl group and structural units derived from an alkyl (meth)acrylate that has an at least C10 alkyl group. The (meth)acrylate copolymer has a carbon-carbon double bond at a side chain.

Description

Adhesive composition and adhesive tape

[0001] The present invention relates to a pressure-sensitive adhesive composition. The present invention also relates to a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition.

[0002] Conventionally, pressure-sensitive adhesive tapes having a pressure-sensitive adhesive layer containing a pressure-sensitive adhesive composition have been widely used to fix components in electronic components, vehicles, houses, and building materials (e.g., Patent Documents 1 to 3). Specifically, pressure-sensitive adhesive tapes have been 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, the reuse of electronic components constituting electronic devices has been considered. To reuse electronic component parts, it is necessary to peel them off from the adhesives or adhesive tapes that secure the components without leaving any adhesive residue. However, conventionally, adhesives or adhesive tapes that secure components have often had strong adhesive properties in order to firmly secure the components, and it has been difficult to peel off such adhesives or adhesive tapes without leaving any adhesive residue.

[0005] An object of the present invention is to provide a pressure-sensitive adhesive composition that exhibits strong adhesive properties when adhered and can be removed from an adherend while leaving little adhesive residue when removed, and also to provide a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition.

[0006] Disclosure 1 is a pressure-sensitive adhesive composition comprising a (meth)acrylic copolymer, the (meth)acrylic copolymer having structural units derived from an alkyl(meth)acrylate, the structural units derived from the alkyl(meth)acrylate including structural units derived from an alkyl(meth)acrylate having an alkyl group containing 6 to 9 carbon atoms and structural units derived from an alkyl(meth)acrylate having an alkyl group containing 10 or more carbon atoms, the (meth)acrylic copolymer including a carbon-carbon double bond in a side chain. Disclosure 2 is a pressure-sensitive adhesive composition according to Disclosure 1, wherein the structural units derived from the alkyl(meth)acrylate include structural units derived from an alkyl(meth)acrylate having an alkyl group containing 6 to 8 carbon atoms. Disclosure 3 is a pressure-sensitive adhesive composition according to Disclosure 2, wherein the structural units derived from the alkyl(meth)acrylate having an alkyl group containing 6 to 8 carbon atoms include structural units derived from an alkyl(meth)acrylate having a glass transition temperature of 0°C or lower when formed into a homopolymer. Disclosure 4 is the pressure-sensitive adhesive composition of Disclosure 2 or 3, wherein the structural units derived from an alkyl (meth)acrylate having an alkyl group containing 6 to 8 carbon atoms comprise structural units derived from at least one alkyl (meth)acrylate selected from the group consisting of n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, and 1-methylheptyl acrylate. Disclosure 5 is the pressure-sensitive adhesive composition of Disclosure 2, 3, or 4, wherein the content of the structural units derived from an alkyl (meth)acrylate having an alkyl group containing 6 to 8 carbon atoms in the (meth)acrylic copolymer is 8.0 mass% or more. Disclosure 6 is the pressure-sensitive adhesive composition of Disclosure 1, 2, 3, 4, or 5, wherein the structural units derived from an alkyl (meth)acrylate having an alkyl group containing 10 or more carbon atoms comprise structural units derived from an alkyl (meth)acrylate having a glass transition temperature of -10°C or higher when converted into a homopolymer.Disclosure 7 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, or 6, wherein the structural units derived from an alkyl (meth)acrylate having an alkyl group having 10 or more carbon atoms comprise structural units derived from an alkyl (meth)acrylate having an alkyl group having 10 or more carbon atoms and 10 to 17 carbon atoms. Disclosure 8 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, or 7, wherein the structural units derived from an alkyl (meth)acrylate having an alkyl group having 10 or more carbon atoms comprise structural units derived from at least one alkyl (meth)acrylate selected from the group consisting of isobornyl acrylate and lauryl acrylate. Disclosure 9 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, or 8, wherein the content of the structural units derived from an alkyl (meth)acrylate having an alkyl group having 10 or more carbon atoms in the (meth)acrylic copolymer is 8.0 mass% or more. Disclosure 10 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the (meth)acrylic copolymer contains structural units derived from polar functional group-containing monomers. Disclosure 11 is the pressure-sensitive adhesive composition of Disclosure 10, wherein the (meth)acrylic copolymer has a total content of structural units derived from polar functional group-containing monomers of 0.01% by mass or more and 30% by mass or less. Disclosure 12 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the (meth)acrylic copolymer has a carbon-carbon double bond equivalent of 0.05 meq / g or more. Disclosure 13 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the (meth)acrylic copolymer has an acid value of 15.0 mgKOH / g or less. The present disclosure 14 is the pressure-sensitive adhesive composition of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein the (meth)acrylic copolymer has a hydroxyl value of 5.0 mgKOH / g or more and 100 mgKOH / g or less. The present disclosure 15 is the pressure-sensitive adhesive composition of the present 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 200,000 or more.Disclosure 16 is the pressure-sensitive adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, further comprising a polymerization initiator. Disclosure 17 is the pressure-sensitive adhesive composition of Disclosure 16, wherein the polymerization initiator comprises a photopolymerization initiator. Disclosure 18 is the pressure-sensitive adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17, further comprising an inorganic filler. Disclosure 19 is the pressure-sensitive adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, further comprising at least one selected from the group consisting of a polyfunctional oligomer and a polyfunctional monomer. Disclosure 20 is the PSA composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19, further comprising a gas generating agent. Disclosure 21 is the PSA composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, further comprising a tackifier. Disclosure 22 is the PSA composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, or 21, further comprising a crosslinking agent. Disclosure 23 is the pressure-sensitive adhesive composition of Disclosure 22, 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 24 is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition of 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. Disclosure 25 is the pressure-sensitive adhesive tape of Disclosure 24, wherein the pressure-sensitive adhesive layer has a bio-derived carbon content of 20% or more. Disclosure 26 is the pressure-sensitive adhesive tape of Disclosure 24 or 25, wherein the pressure-sensitive adhesive layer has a glass transition temperature of -10°C or higher as measured by dynamic viscoelasticity measurement at a frequency of 10 Hz. Disclosure 27 is the pressure-sensitive adhesive tape of Disclosures 24, 25, or 26, wherein the pressure-sensitive adhesive layer has a gel fraction of 10% by mass or more and 90% by mass or less. This disclosure 28 is a method for manufacturing a film after heating at 150°C for 1 hour, or after irradiating the film with light having a wavelength in the range of 280 nm or more and 405 nm or less with an integrated light amount of 1000 mJ / cm.２ The pressure-sensitive adhesive tape of the present disclosure 24, 25, 26, or 27, wherein the pressure-sensitive adhesive layer has a gel fraction of 90 mass % or more after being irradiated with light having a wavelength in the range of 280 nm or more and 405 nm or less at an integrated light intensity of 1000 mJ / cm. ２ The pressure-sensitive adhesive tape of the present disclosure 31 is a pressure-sensitive adhesive tape that has been laminated to SUS and then left to stand at 60°C for 24 hours, and then heated at 150°C for 1 hour, or irradiated with light having a wavelength in the range of 280 nm or more and 405 nm or less until the integrated light intensity is 1000 mJ / cm. ２ The pressure-sensitive adhesive tape of Disclosure 24, 25, 26, 27, 28, 29, or 30, wherein the 180° peel strength of the pressure-sensitive adhesive tape against SUS after irradiation to a value equal to or greater than 1.5 N / 25 mm, is 1.5 N / 25 mm or less. Disclosure 32 is the pressure-sensitive adhesive tape of Disclosure 24, 25, 26, 27, 28, 29, 30, or 31, having a substrate and the pressure-sensitive adhesive layer on at least one surface of the substrate. Disclosure 33 is the pressure-sensitive adhesive tape of Disclosure 24, 25, 26, 27, 28, 29, 30, 31, or 32, used for fixing electronic device components. The present invention will be described in detail below. Hereinafter, one or more embodiments of the present invention will be described as the "present embodiment."

[0007] The present inventors have found that, in a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer, by using as the (meth)acrylic copolymer a (meth)acrylic copolymer having structural units derived from an alkyl (meth)acrylate having from 6 to 9 carbon atoms, the pressure-sensitive adhesive composition has excellent flexibility and improved releasability. Furthermore, they investigated the possibility of copolymerizing such a (meth)acrylic copolymer with an alkyl (meth)acrylate having from 10 or more carbon atoms as a structural unit monomer, thereby obtaining a pressure-sensitive adhesive composition that exhibits strong adhesion upon adhesion but suppresses further adhesion enhancement after application. Furthermore, the present inventors have noted that the adhesive strength of the pressure-sensitive adhesive composition is significantly reduced upon curing of the (meth)acrylic copolymer, allowing for easy peeling. They investigated the possibility of introducing a carbon-carbon double bond into the side chain of a (meth)acrylic copolymer containing structural units derived from an alkyl (meth)acrylate having a linear or branched alkyl group having from 6 to 9 carbon atoms, thereby giving the (meth)acrylic copolymer a structure that can be cured by irradiation with light, heating, or the like, thereby enabling the pressure-sensitive adhesive composition to be peeled from an adherend while suppressing adhesive residue upon peeling. As a result, they discovered that it is possible to obtain a pressure-sensitive adhesive composition that exhibits strong adhesive properties when adhering, while being able to be removed from the adherend with minimal adhesive residue when removing, and thus completed the present invention.

[0008] The pressure-sensitive adhesive composition of the present embodiment contains a (meth)acrylic copolymer. The (meth)acrylic copolymer has structural units derived from alkyl(meth)acrylate. In this specification, "(meth)acrylic" means acrylic or methacrylic, and "(meth)acrylate" means acrylate or methacrylate.

[0009] In the pressure-sensitive adhesive composition of this embodiment, the structural unit derived from the alkyl(meth)acrylate includes a structural unit derived from an alkyl(meth)acrylate having an alkyl group having from 6 to 9 carbon atoms (hereinafter, sometimes simply referred to as "alkyl(meth)acrylate (a-1)"). In the pressure-sensitive adhesive composition of this embodiment, since the structural unit derived from the alkyl(meth)acrylate includes a structural unit derived from the alkyl(meth)acrylate (a-1), the pressure-sensitive adhesive composition of this embodiment exhibits appropriate flexibility and can be peeled from an adherend while suppressing adhesive residue during peeling.

[0010] The preferred lower limit of the content of the structural units derived from the alkyl (meth)acrylate (a-1) in the (meth)acrylic copolymer is 8.0% by mass. When the content of the structural units derived from the alkyl (meth)acrylate (a-1) is 8.0% by mass or more, the PSA composition of the present embodiment has increased flexibility, thereby enabling peeling from an adherend while suppressing adhesive residue during peeling. A more preferred lower limit of the content of the structural units derived from the alkyl (meth)acrylate (a-1) is 14% by mass, an even more preferred lower limit is 33% by mass, and an even more preferred lower limit is 35% by mass. There are no particular restrictions on the upper limit of the content of the structural units derived from the alkyl (meth)acrylate (a-1). However, since the (meth)acrylic copolymer preferably contains structural units derived from an alkyl (meth)acrylate having an alkyl group having 10 or more carbon atoms, as described below, and also contains structural units derived from a polar functional group-containing monomer, as described below, and structural units derived from a functional group-containing unsaturated compound, as described below, the preferred upper limit is 80% by mass. The upper limit of the content of the structural units derived from the alkyl (meth)acrylate (a-1) is more preferably 70% by mass, and even more preferably 60% by mass. Examples of the content of the structural units derived from the alkyl (meth)acrylate (a-1) include 8.0% by mass or more and 80% by mass or less, 14% by mass or more and 70% by mass or less, 33% by mass or more and 60% by mass or less, and 35% by mass or more and 60% by mass or less.

[0011] In this specification, the content ratio of the structural units in the (meth)acrylic copolymer is determined by measuring the (meth)acrylic copolymer by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR measurement, １３ The content ratio can be calculated from the integrated intensity ratio of the hydrogen peaks derived from the monomers constituting the structural unit whose content is to be measured.

[0012] Examples of the structural unit derived from the alkyl (meth)acrylate (a-1) include structural units derived from alkyl (meth)acrylates such as n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 1-methylheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and n-nonyl (meth)acrylate. In particular, from the viewpoint of enabling the pressure-sensitive adhesive composition of the present embodiment to exhibit more appropriate flexibility, the structural unit derived from the alkyl (meth)acrylate (a-1) preferably includes a structural unit derived from an alkyl (meth)acrylate having an alkyl group containing 6 to 8 carbon atoms. Furthermore, from the viewpoint of polymerizability, the structural unit derived from an alkyl (meth)acrylate having an alkyl group containing 6 to 8 carbon atoms preferably includes a structural unit derived from at least one alkyl (meth)acrylate selected from the group consisting of butyl acrylate.

[0013] In the pressure-sensitive adhesive composition of the present embodiment, the structural unit derived from the alkyl(meth)acrylate preferably includes a structural unit derived from an alkyl(meth)acrylate (hereinafter, sometimes simply referred to as "alkyl(meth)acrylate (a-2)") whose glass transition temperature when made into a homopolymer is 0° C. or lower. In the pressure-sensitive adhesive composition of the present embodiment, by including a structural unit derived from the alkyl(meth)acrylate (a-2), the pressure-sensitive adhesive composition of the present embodiment exhibits appropriate flexibility and can be peeled from an adherend while suppressing adhesive residue during peeling. In particular, from the viewpoint of enabling the adhesive composition of this embodiment, n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, 1-methyl acrylate to exhibit more appropriate flexibility, it is more preferable that the structural unit derived from the alkyl (meth)acrylate (a-1) contains a structural unit derived from the alkyl (meth)acrylate (a-2), and it is even more preferable that the structural unit derived from the alkyl (meth)acrylate having an alkyl group having 6 to 8 carbon atoms contains a structural unit derived from the alkyl (meth)acrylate (a-2).

[0014] The upper limit of the glass transition temperature of the alkyl (meth)acrylate (a-2) when converted into a homopolymer (hereinafter, sometimes simply referred to as "homopolymer Tg") may be 0° C., but from the viewpoint of enabling the pressure-sensitive adhesive composition of the present embodiment to exhibit more appropriate flexibility, the upper limit of the homopolymer Tg of the alkyl (meth)acrylate (a-2) is preferably −20° C., more preferably −40° C. Furthermore, there is no particular lower limit for the homopolymer Tg of the alkyl (meth)acrylate (a-2), but a substantial lower limit is about −150° C.

[0015] The homopolymer Tg is measured by differential scanning calorimetry. More specifically, the homopolymer Tg can be measured by measuring a homopolymer having a weight average molecular weight of 100,000 to 2,000,000 in accordance with JIS K6240:2011 using a differential scanning calorimeter (e.g., "DSC6220ASD-2" manufactured by Hitachi High-Tech Science Corporation) under conditions of a measurement temperature of -100°C to 100°C and a heating rate of 10°C / min, in a nitrogen atmosphere (nitrogen flow, flow rate 150 mL / min).

[0016] Examples of the structural unit derived from the alkyl(meth)acrylate (a-2) include structural units derived from alkyl(meth)acrylates such as n-hexyl acrylate (homopolymer Tg: −60° C.), n-heptyl acrylate (homopolymer Tg: −68° C.), n-heptyl methacrylate (homopolymer Tg: −10° C.), n-octyl acrylate (homopolymer Tg: −65° C.), n-octyl methacrylate (homopolymer Tg: −18° C.), 1-methylheptyl acrylate (homopolymer Tg: −45° C.), 2-ethylhexyl acrylate (homopolymer Tg: −70° C.), 2-ethylhexyl methacrylate (homopolymer Tg: −30° C.), and n-nonyl acrylate (homopolymer Tg: −58° C.). In particular, from the viewpoint of making it easier for the homopolymer Tg to satisfy the above-mentioned preferred range and enabling the pressure-sensitive adhesive composition of the present embodiment to exhibit more appropriate flexibility, it is preferred that the structural unit derived from the alkyl(meth)acrylate (a-2) comprises a structural unit derived from an alkyl(meth)acrylate having an alkyl group containing 6 to 8 carbon atoms. Furthermore, from the viewpoint of polymerizability, it is preferred that the structural unit derived from an alkyl(meth)acrylate having an alkyl group containing 6 to 8 carbon atoms comprises a structural unit derived from at least one alkyl(meth)acrylate selected from the group consisting of n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, and 1-methylheptyl acrylate.

[0017] The preferred lower limit of the content of the structural units derived from alkyl (meth)acrylate having an alkyl group with 6 to 8 carbon atoms in the (meth)acrylic copolymer is 8.0% by mass. When the content of the structural units derived from alkyl (meth)acrylate having an alkyl group with 6 to 8 carbon atoms is 8.0% by mass or more, the pressure-sensitive adhesive composition of the present embodiment has increased flexibility, thereby enabling peeling from an adherend while suppressing adhesive residue during peeling. Furthermore, when the content of the structural units derived from alkyl (meth)acrylate having an alkyl group with 6 to 8 carbon atoms containing bio-derived carbon is 8.0% by mass or more, the content of bio-derived carbon in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape described below can be further increased. A more preferred lower limit of the content of the structural units derived from alkyl (meth)acrylate having an alkyl group with 6 to 8 carbon atoms is 14% by mass, an even more preferred lower limit is 33% by mass, and an even more preferred lower limit is 35% by mass. The upper limit of the content of the structural units derived from alkyl (meth)acrylates having an alkyl group with 6 to 8 carbon atoms is not particularly limited, but since the (meth)acrylic copolymer preferably has structural units derived from alkyl (meth)acrylates having an alkyl group with 10 or more carbon atoms, as described below, and also has structural units derived from polar functional group-containing monomers and structural units derived from functional group-containing unsaturated compounds, as described below, the preferred upper limit is 80% by mass. A more preferred upper limit of the content of the structural units derived from alkyl (meth)acrylates having an alkyl group with 6 to 8 carbon atoms is 70% by mass, and an even more preferred upper limit is 60% by mass. Examples of the content of the structural units derived from alkyl (meth)acrylates having an alkyl group with 6 to 8 carbon atoms include 8.0% by mass to 80% by mass, 14% by mass to 70% by mass, 33% by mass to 60% by mass, and 35% by mass to 60% by mass.

[0018] The structural units derived from the alkyl (meth)acrylate include structural units derived from an alkyl (meth)acrylate having an alkyl group having 10 or more carbon atoms (hereinafter, sometimes simply referred to as "alkyl (meth)acrylate (b)"). When the structural units derived from the alkyl (meth)acrylate include structural units derived from the alkyl (meth)acrylate (b), the pressure-sensitive adhesive composition of the present embodiment is able to exhibit strong adhesive properties upon adhesion. Furthermore, when the structural units derived from the alkyl (meth)acrylate include structural units derived from the alkyl (meth)acrylate (b), the pressure-sensitive adhesive composition of the present embodiment has low polarity, and therefore a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition of the present embodiment can suppress increased adhesion at high temperatures. As a result, the pressure-sensitive adhesive composition of the present embodiment can be more easily peeled while suppressing adhesive residue upon peeling.

[0019] The structural units derived from the alkyl (meth)acrylate (b) preferably include a structural unit derived from an alkyl (meth)acrylate having a homopolymer Tg of -10°C or higher. By including a structural unit derived from an alkyl (meth)acrylate having a homopolymer Tg of -10°C or higher as the structural unit derived from the alkyl (meth)acrylate (b), the pressure-sensitive adhesive composition of the present embodiment can exhibit superior strong adhesiveness at the time of adhesion. A more preferred lower limit of the homopolymer Tg for the alkyl (meth)acrylate having a homopolymer Tg of -10°C or higher is 0°C, an even more preferred lower limit is 10°C, and an even more preferred lower limit is 20°C. Furthermore, from the viewpoint of enabling the pressure-sensitive adhesive composition of the present embodiment to exhibit appropriate cohesive strength, a preferred upper limit of the homopolymer Tg for the alkyl (meth)acrylate having a homopolymer Tg of -10°C or higher is 100°C. In addition, examples of the homopolymer Tg of the alkyl (meth)acrylate having a homopolymer Tg of −10° C. or higher include −10° C. or higher and 100° C. or lower, 0° C. or higher and 100° C. or lower, 10° C. or higher and 100° C. or lower, and 20° C. or higher and 100° C. or lower.

[0020] Examples of the structural unit derived from the alkyl(meth)acrylate (b) include structural units derived from alkyl(meth)acrylates such as isobornyl acrylate (homopolymer Tg: 97°C), isobornyl methacrylate (homopolymer Tg: 180°C), lauryl acrylate (homopolymer Tg: 0°C), lauryl methacrylate (homopolymer Tg: -65°C), stearyl acrylate (homopolymer Tg: 30°C), stearyl methacrylate (homopolymer Tg: 38°C), and behenyl acrylate (homopolymer Tg: 46°C). Among these, from the viewpoints that the homopolymer Tg is likely to satisfy the above-mentioned preferred range and that the pressure-sensitive adhesive composition of the present embodiment can exhibit stronger adhesive properties at the time of adhesion, it is preferable that the structural unit derived from the alkyl(meth)acrylate (b) contains a structural unit derived from an alkyl(meth)acrylate having an alkyl group having from 10 to 17 carbon atoms. Furthermore, from the viewpoint of enabling the pressure-sensitive adhesive composition of the present embodiment to have more appropriate adhesiveness during adhesion and to be more easily peeled from the adherend while suppressing adhesive residue during peeling, it is more preferable that the structural unit derived from the alkyl (meth)acrylate (b) contains a structural unit derived from at least one alkyl (meth)acrylate selected from the group consisting of isobornyl acrylate and lauryl acrylate.

[0021] The preferred lower limit of the content of the structural units derived from the alkyl (meth)acrylate (b) in the (meth)acrylic copolymer is 8.0% by mass. When the content of the structural units derived from the alkyl (meth)acrylate (b) is 8.0% by mass or more, the pressure-sensitive adhesive composition of the present embodiment has improved cohesive strength and can exhibit superior adhesive strength during adhesion. Furthermore, when the content of the structural units derived from the alkyl (meth)acrylate (b) is 8.0% by mass or more, the pressure-sensitive adhesive composition has low polarity, which can suppress increased adhesion during heating and facilitate peeling while suppressing adhesive residue from the adherend during peeling. Furthermore, when the content of the structural units derived from the alkyl (meth)acrylate (b) containing bio-derived carbon is 8.0% by mass or more, the content of bio-derived carbon in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape described below can be further increased. The more preferred lower limit of the content of the structural units derived from the alkyl (meth)acrylate (b) is 14% by mass, an even more preferred lower limit is 33% by mass, and an even more preferred lower limit is 35% by mass. The upper limit of the content of the structural units derived from the alkyl (meth)acrylate (b) is not particularly limited, but the (meth)acrylic copolymer preferably has a structural unit derived from an alkyl (meth)acrylate having an alkyl group having 10 or more carbon atoms, as described below, and a structural unit derived from a polar functional group-containing monomer or a structural unit derived from a functional group-containing unsaturated compound, as described below, with a preferred upper limit of 80% by mass. The more preferred upper limit of the content of the structural units derived from the alkyl (meth)acrylate (b) is 70% by mass, and an even more preferred upper limit is 60% by mass. Examples of the content of the structural units derived from the alkyl (meth)acrylate (b) include 8.0% by mass or more and 80% by mass or less, 14% by mass or more and 70% by mass or less, 33% by mass or more and 60% by mass or less, and 35% by mass or more and 60% by mass or less.

[0022] The alkyl (meth)acrylate may be composed solely of petroleum-derived materials, but preferably contains a biologically-derived material. In recent years, the depletion of petroleum resources and carbon dioxide emissions from the combustion of petroleum-derived products have become a concern. Therefore, attempts have been made to conserve petroleum resources by using biologically-derived materials instead of petroleum-derived materials. When the alkyl (meth)acrylate contains a biologically-derived material, the content of biologically-derived carbon in the pressure-sensitive adhesive composition of the present embodiment, which will be described later, is increased, thereby further reducing the environmental impact of the pressure-sensitive adhesive composition of the present embodiment. In this specification, "containing biologically-derived carbon" means that the bio-based carbon content of the compound measured according to ASTM D6866-24 is 1% or more.

[0023] When the alkyl (meth)acrylate in the alkyl (meth)acrylate-derived structural unit contains a biological material, the alkyl (meth)acrylate preferably contains one synthesized by esterifying a biological alcohol with (meth)acrylic acid. Examples of methods for synthesizing the biological alkyl (meth)acrylate include a method in which a material collected from plants or animals (e.g., linoleic acid derived from castor oil) is used as a raw material, and the raw material is enzymatically converted into hexanal, followed by hydrogenation to obtain n-hexanol, which is then esterified with acrylic acid to synthesize n-hexyl acrylate.

[0024] The structural units derived from the alkyl (meth)acrylate may include structural units derived from other alkyl (meth)acrylates other than the structural units derived from the alkyl (meth)acrylate (a-1), the structural units derived from the alkyl (meth)acrylate (a-2), and the structural units derived from the alkyl (meth)acrylate (b), as long as the effects of the present invention are not impaired.

[0025] The (meth)acrylic copolymer has a carbon-carbon double bond in its side chain. The (meth)acrylic copolymer has a carbon-carbon double bond in its side chain, which allows it to be cured by heating, light irradiation, or the like, and the adhesive strength of the pressure-sensitive adhesive composition of this embodiment can be significantly reduced. This allows the pressure-sensitive adhesive composition of this embodiment to be peeled from an adherend while suppressing adhesive residue during peeling. In this specification, the term "side chain" refers to a branched structural portion extending from the main chain, where the longest chain in the (meth)acrylic copolymer is considered to be the main chain. In this specification, the term "carbon-carbon double bond" does not include carbon-carbon double bonds constituting aromatic rings.

[0026] Examples of methods for introducing a carbon-carbon double bond into the side chain of the (meth)acrylic copolymer include a method of reacting a (meth)acrylic polymer without a carbon-carbon double bond, obtained by copolymerizing the alkyl(meth)acrylate, a polar functional group-containing monomer described below, or another monomer described below, with a compound having a carbon-carbon double bond and a functional group reactive with a carboxy group, a hydroxyl group, or the like in the polymer (hereinafter also referred to as a "functional group-containing unsaturated compound"); and a method of copolymerizing and reacting a monomer having two or more identical or different carbon-carbon double bonds with the alkyl(meth)acrylate, a polar functional group-containing monomer described below, or another monomer described below.

[0027] The functional group-containing unsaturated compound is selected, for example, depending on the functional group in the (meth)acrylic polymer having no carbon-carbon double bond introduced therein, and examples thereof include the same as the polar functional group-containing monomers described below. When the functional group in the (meth)acrylic polymer having no carbon-carbon double bond introduced therein is a carboxy group, for example, an epoxy group-containing monomer or an isocyanate group-containing monomer is used. When the functional group in the (meth)acrylic polymer having no carbon-carbon double bond introduced therein is a hydroxyl group, for example, an isocyanate group-containing monomer is used. When the functional group in the (meth)acrylic polymer having no carbon-carbon double bond introduced therein is an epoxy group, for example, a carboxy group-containing monomer or an amide group-containing monomer such as acrylamide is used. When the functional group in the (meth)acrylic polymer having no carbon-carbon double bond introduced therein is an amino group, for example, an epoxy group-containing monomer is used. Specific examples of the functional group-containing unsaturated compound include 2-methacryloyloxyethyl isocyanate (MOI), 2-acryloyloxyethyl isocyanate (AOI), and 1,1-(bisacryloyloxymethyl)ethyl isocyanate (BEI).

[0028] The preferred lower limit of the content of the structural unit derived from the functional group-containing unsaturated compound in the (meth)acrylic copolymer is 0.1% by mass, and the preferred upper limit is 25% by mass. When the content of the structural unit derived from the functional group-containing unsaturated compound is 0.1% by mass or more, the pressure-sensitive adhesive composition of this embodiment can be sufficiently cured when cured, so that the pressure-sensitive adhesive composition of this embodiment can be peeled off from the adherend while suppressing adhesive residue during peeling. When the content of the structural unit derived from the functional group-containing unsaturated compound is 25% by mass or less, the pressure-sensitive adhesive composition of this embodiment can maintain appropriate flexibility even after curing, so that the pressure-sensitive adhesive composition can be peeled off from the adherend while suppressing adhesive residue during peeling. The more preferred lower limit of the content of the structural unit derived from the functional group-containing unsaturated compound is 0.5% by mass, and the more preferred upper limit is 20% by mass.

[0029] The (meth)acrylic copolymer preferably further contains a structural unit derived from a polar functional group-containing monomer. The (meth)acrylic copolymer contains a structural unit derived from a polar functional group-containing monomer, which increases the cohesive strength of the pressure-sensitive adhesive composition of the present embodiment, thereby exhibiting superior adhesive strength during adhesion and enabling peeling with reduced adhesive residue from the adherend. Furthermore, when the pressure-sensitive adhesive composition of the present embodiment contains a crosslinking agent (described below), the adhesive strength of the pressure-sensitive adhesive composition of the present embodiment can be significantly reduced by reacting the functional groups derived from the structural units derived from the polar functional group-containing monomer with the crosslinking agent during peeling by irradiation with light, heating, or the like, thereby making it easier to peel the pressure-sensitive adhesive composition from the adherend with reduced adhesive residue during peeling. Furthermore, when the pressure-sensitive adhesive composition of the present embodiment contains a crosslinking agent (described below), the adhesive strength of the pressure-sensitive adhesive composition of the present embodiment can be appropriately adjusted by reacting the polar functional groups derived from the structural units derived from the polar functional group-containing monomer with the crosslinking agent, thereby making it easier to peel the pressure-sensitive adhesive composition of the present embodiment from the adherend without leaving any adhesive residue during peeling.

[0030] The polar functional group in the polar functional group-containing monomer is not particularly limited as long as it has a polar structure and is reactive, and examples thereof include a carboxy group, a hydroxyl group, an epoxy group, an isocyanate group, an amino group, etc. Therefore, examples of the structural unit derived from the polar functional group-containing monomer include a structural unit derived from a carboxyl group-containing monomer, a structural unit derived from a hydroxyl group-containing monomer, a structural unit derived from an epoxy group-containing monomer, a structural unit derived from an isocyanate group-containing monomer, and a structural unit derived from an amino group-containing monomer. In particular, from the viewpoint of further improving the cohesive strength of the pressure-sensitive adhesive composition, it is preferable that the structural unit derived from the polar functional group-containing monomer includes at least one structural unit selected from the group consisting of a structural unit derived from a carboxyl group-containing monomer and a structural unit derived from a hydroxyl group-containing monomer. The structural units derived from the polar functional group-containing monomer may be used alone or in combination of two or more.

[0031] Examples of the carboxy group-containing monomer include acrylic acid and methacrylic acid. Examples of the hydroxy group-containing monomer include hydroxyethyl acrylate and hydroxyethyl methacrylate. Examples of the epoxy group-containing monomer include glycidyl acrylate and glycidyl methacrylate. Examples of the isocyanate group-containing monomer include isocyanate ethyl acrylate and isocyanate ethyl methacrylate. Examples of the amino group-containing monomer include aminoethyl acrylate and aminoethyl methacrylate.

[0032] The (meth)acrylic copolymer preferably has a lower limit of 0.01% by mass and an upper limit of 30% by mass for the total content of the structural units derived from the polar functional group-containing monomer. When the total content of the structural units derived from the polar functional group-containing monomer is 0.01% by mass or more, the pressure-sensitive adhesive composition of the present embodiment has a higher cohesive strength, exhibiting superior adhesive strength during adhesion and enabling peeling with reduced adhesive residue from the adherend during peeling. Furthermore, when the pressure-sensitive adhesive composition of the present embodiment contains a crosslinking agent (described below), the adhesive strength of the pressure-sensitive adhesive composition of the present embodiment can be reduced by reacting the functional groups derived from the structural units derived from the polar functional group-containing monomer with the crosslinking agent during peeling by irradiation with light, heating, or the like, thereby improving peeling performance of the pressure-sensitive adhesive composition of the present embodiment. Furthermore, when the pressure-sensitive adhesive composition of the present embodiment contains a crosslinking agent (described below), the adhesive strength of the pressure-sensitive adhesive composition of the present embodiment can be adjusted appropriately by reacting the polar functional groups derived from the structural units derived from the polar functional group-containing monomer with the crosslinking agent, thereby enabling the pressure-sensitive adhesive composition of the present embodiment to be easily peeled from the adherend without leaving any adhesive residue during peeling. When the total content of the structural units derived from the polar functional group-containing monomer is 30% by mass or less, the pressure-sensitive adhesive composition of this embodiment does not become too hard and exhibits superior adhesive strength during adhesion. The lower limit of the total content of the structural units derived from the polar functional group-containing monomer is more preferably 1.0% by mass, more preferably 28% by mass, even more preferably 1.5% by mass, even more preferably 25% by mass, still more preferably 3.0% by mass, and particularly preferably 4.5% by mass. Examples of the content of the structural units derived from the polar functional group-containing monomer include 0.01% by mass or more and 30% by mass or less, 1.0% by mass or more and 28% by mass or less, 1.5% by mass or more and 25% by mass or less, 3.0% by mass or more and 25% by mass or less, and 4.5% by mass or more and 25% by mass or less.In addition, in the case where a polar functional group-containing monomer is reacted with the functional group-containing unsaturated compound, the total content of the constituent units derived from the polar functional group-containing monomer is the total content of the constituent units derived from the polar functional group-containing monomer used as a constituent unit monomer of the (meth)acrylic polymer into which no carbon-carbon double bond has been introduced and the constituent units derived from the polar functional group-containing monomer reacted with the functional group-containing unsaturated compound.

[0033] The (meth)acrylic copolymer may have a constituent unit derived from a monomer other than the constituent unit derived from the alkyl (meth)acrylate and the constituent unit derived from the polar functional group-containing monomer.

[0034] Examples of the other monomers include benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and polypropylene glycol mono(meth)acrylate. Furthermore, examples of the other monomers that can be used include various monomers used in general (meth)acrylic polymers, such as vinyl carboxylates such as vinyl acetate, and styrene. These other monomers may be used alone or in combination of two or more.

[0035] Examples of methods for producing the (meth)acrylic copolymer include a method in which a monomer mixture containing the alkyl (meth)acrylate and the polar functional group-containing monomer or the like is copolymerized by radical reaction in the presence of a polymerization initiator, and then the resulting (meth)acrylic polymer into which no carbon-carbon double bond has been introduced is reacted with a functional group-containing unsaturated compound. The method of radically reacting the monomer mixture, i.e., the polymerization method, can be any conventionally known method, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, and bulk polymerization.

[0036] Examples of the polymerization initiator used to produce the (meth)acrylic copolymer 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 used as polymerization initiators to produce the (meth)acrylic copolymer include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more. Furthermore, when the radical reaction method is living radical polymerization, examples of the polymerization initiator include organic tellurium polymerization initiators. The organic tellurium polymerization initiator is not particularly limited as long as it is one that is generally used in living radical polymerization, and examples thereof include organic tellurium compounds, organic telluride compounds, etc. Note that, in living radical polymerization, in addition to the organic tellurium polymerization initiator, the azo compound may also be used as a polymerization initiator used to produce the (meth)acrylic copolymer in order to accelerate the polymerization rate.

[0037] The preferred lower limit of the carbon-carbon double bond equivalent of the (meth)acrylic copolymer is 0.05 meq / g. When the carbon-carbon double bond equivalent of the (meth)acrylic copolymer is 0.05 meq / g or more, the pressure-sensitive adhesive composition of this embodiment can be peeled from an adherend while suppressing adhesive residue upon peeling. A more preferred lower limit of the carbon-carbon double bond equivalent of the (meth)acrylic copolymer is 0.06 meq / g, an even more preferred lower limit is 0.075 meq / g, and an even more preferred lower limit is 0.10 meq / g. Furthermore, the preferred upper limit of the carbon-carbon double bond equivalent of the (meth)acrylic copolymer is 3.5 meq / g. When the carbon-carbon double bond equivalent of the (meth)acrylic copolymer is 3.5 meq / g or less, the pressure-sensitive adhesive composition of this embodiment can maintain appropriate flexibility even after curing, and can be peeled from an adherend while suppressing adhesive residue upon peeling. The upper limit of the carbon-carbon double bond equivalent of the (meth)acrylic copolymer is more preferably 2.0 meq / g, and even more preferably 1.5 meq / g. Examples of the carbon-carbon double bond equivalent of the (meth)acrylic copolymer include 0.05 meq / g or more and 3.5 meq / g or less, 0.06 meq / g or more and 2.0 meq / g or less, 0.075 meq / g or more and 1.5 meq / g or less, and 0.10 meq / g or more and 1.5 meq / g or less. In this specification, the term "carbon-carbon double bond equivalent of the (meth)acrylic copolymer" refers to the milliequivalent (meq / g) of carbon-carbon double bonds per 1 g of the (meth)acrylic copolymer.

[0038] The upper limit of the acid value of the (meth)acrylic copolymer is preferably 15.0 mgKOH / g. When the acid value of the (meth)acrylic copolymer is 15.0 mgKOH / g or less, the pressure-sensitive adhesive composition of the present embodiment does not become too hard and exhibits superior strong adhesiveness during adhesion. The upper limit of the acid value of the (meth)acrylic copolymer is more preferably 13.0 mgKOH / g, even more preferably 11.0 mgKOH / g, and even more preferably 9.0 mgKOH / g. The lower limit of the acid value of the (meth)acrylic copolymer is not particularly limited and may be 0 mgKOH / g. Examples of the acid value of the (meth)acrylic copolymer include 0 mgKOH / g or more and 15.0 mgKOH / g or less, 0 mgKOH / g or more and 13.0 mgKOH / g or less, 0 mgKOH / g or more and 11.0 mgKOH / g or less, and 0 mgKOH / g or more and 9.0 mgKOH / g or less.

[0039] The acid value is an index representing the content of carboxyl groups in a certain amount of sample. The hydroxyl value of the (meth)acrylic copolymer is the number of milligrams of potassium hydroxide required to neutralize the acid contained in 1 g of the (meth)acrylic copolymer, and can be calculated by measuring based on the potentiometric titration method specified in JIS K 0070:1992.

[0040] The preferred lower limit of the hydroxyl value of the (meth)acrylic copolymer is 5.0 mgKOH / g, and the preferred upper limit is 100 mgKOH / g. When the hydroxyl value of the (meth)acrylic copolymer is 5.0 mgKOH / g or more, the cohesive strength of the pressure-sensitive adhesive composition of this embodiment becomes greater, so that the pressure-sensitive adhesive composition of this embodiment exhibits superior adhesive strength during adhesion and can be peeled off from the adherend with reduced adhesive residue during peeling. Furthermore, when the pressure-sensitive adhesive composition of this embodiment contains a crosslinking agent described below, during peeling, the crosslinking agent can be reacted with the functional group derived from the structural unit derived from the polar functional group-containing monomer by irradiation with light, heating, or the like, thereby further reducing the adhesive strength of the pressure-sensitive adhesive composition of this embodiment, and the pressure-sensitive adhesive composition of this embodiment can be peeled off from the adherend with reduced adhesive residue during peeling.

[0033] Furthermore, when the pressure-sensitive adhesive composition of the present embodiment contains a crosslinking agent described below, the adhesive strength of the pressure-sensitive adhesive composition of the present embodiment is appropriately adjusted by the reaction of the polar functional group derived from the structural unit derived from the polar functional group-containing monomer with the crosslinking agent, resulting in the pressure-sensitive adhesive composition of the present embodiment being easily peeled from the adherend without leaving any adhesive residue. When the hydroxyl value of the (meth)acrylic copolymer is 100 mgKOH / g or less, the pressure-sensitive adhesive composition of the present embodiment does not become too hard and exhibits superior strong adhesiveness upon adhesion. The hydroxyl value of the (meth)acrylic copolymer is more preferably 7.0 mgKOH / g or less, more preferably 95 mgKOH / g or less, even more preferably 9.0 mgKOH / g or less, and even more preferably 90 mgKOH / g or less. The hydroxyl value of the (meth)acrylic copolymer may be, for example, from 5.0 mgKOH / g to 100 mgKOH / g, from 7.0 mgKOH / g to 95 mgKOH / g, or from 9.0 mgKOH / g to 90 mgKOH / g.

[0041] The hydroxyl value is an index representing the content of hydroxyl groups (hydroxy groups) in a certain amount of sample. The hydroxyl value of the (meth)acrylic copolymer is the number of milligrams of potassium hydroxide required to neutralize acetic acid bonded to hydroxyl groups by neutralization titration after acetylating 1 g of the (meth)acrylic copolymer, and can be calculated by measuring based on the potentiometric titration method specified in JIS K 0070:1992.

[0042] The preferred lower limit of the weight-average molecular weight (Mw) of the (meth)acrylic copolymer is 200,000. When the weight-average molecular weight (Mw) of the (meth)acrylic copolymer is 200,000 or more, the cohesive strength of the pressure-sensitive adhesive composition of this embodiment is increased, thereby exhibiting superior adhesive strength during adhesion and enabling peeling with reduced adhesive residue from the adherend during peeling. The more preferred lower limit of the weight-average molecular weight (Mw) of the (meth)acrylic copolymer is 250,000, and even more preferred is 300,000. The preferred upper limit of the weight-average molecular weight (Mw) of the (meth)acrylic copolymer is 1,000,000. When the weight-average molecular weight (Mw) of the (meth)acrylic copolymer is 1,000,000 or less, the pressure-sensitive adhesive composition of this embodiment does not become too hard and exhibits superior adhesive strength during adhesion. The more preferred upper limit of the weight-average molecular weight (Mw) of the (meth)acrylic copolymer is 800,000, and even more preferred is 500,000. The weight average molecular weight (Mw) of the (meth)acrylic copolymer may be, for example, from 200,000 to 1,000,000, from 250,000 to 800,000, or from 300,000 to 500,000.

[0043] In this specification, the weight-average molecular weight of the (meth)acrylic copolymer is a weight-average molecular weight calculated in terms of standard polystyrene by gel permeation chromatography (GPC). Specifically, the measurement can be performed using, for example, a Waters 2690 Separations Module as a measuring instrument, a Showa Denko GPC KF-806L column, ethyl acetate as a solvent, at a sample flow rate of 1 mL / min and a column temperature of 40°C.

[0044] The pressure-sensitive adhesive composition of the present embodiment preferably further contains a polymerization initiator. When the pressure-sensitive adhesive composition of the present embodiment contains a polymerization initiator, the carbon-carbon double bond in the side chain of the (meth)acrylic copolymer reacts with the polymerization initiator, which makes the pressure-sensitive adhesive composition of the present embodiment more likely to harden, and therefore the adhesive strength is more likely to decrease. As a result, the pressure-sensitive adhesive composition of the present embodiment can be peeled from an adherend without leaving any adhesive residue.

[0045] The polymerization initiator may be a photopolymerization initiator or a thermal polymerization initiator. In particular, from the viewpoint of enhancing adhesion of the pressure-sensitive adhesive composition of the present embodiment at high temperatures and suppressing outgassing, the pressure-sensitive adhesive composition of the present embodiment preferably contains a photopolymerization initiator.

[0046] Examples of the photopolymerization initiator include those that are activated by irradiation with light having a wavelength of 250 to 800 nm. Examples of such photopolymerization initiators include acetophenone derivative compounds such as methoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone, benzoin ether compounds such as benzoin propyl ether and benzoin isobutyl ether, ketal derivative compounds such as benzyl dimethyl ketal and acetophenone diethyl ketal, phosphine oxide derivative compounds such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(η5-cyclopentadienyl)titanocene derivative compounds, benzophenone, Michler's ketone, chlorothioxanthone, todecylthioxanthone, dimethylthioxanthone, diethylthioxanthone, α-hydroxycyclohexyl phenyl ketone, 2-hydroxymethylphenylpropane, and photoradical polymerization initiators such as 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone. These photopolymerization initiators may be used alone or in combination of two or more.

[0047] Examples of the thermal polymerization initiator include those that decompose when heated to generate active radicals that initiate polymerization and curing, such as dicumyl peroxide, di-t-butyl peroxide, t-butylperoxybenzoyl, t-butyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramenthane hydroperoxide, di-t-butyl peroxide, t-butylperoxy-2-ethylhexanoate, etc. These thermal polymerization initiators may be used alone or in combination of two or more.

[0048] The preferred lower limit of the content of the polymerization initiator relative to 100 parts by mass of the (meth)acrylic copolymer is 0.1 parts by mass. When the content of the polymerization initiator is 0.1 parts by mass or more, the pressure-sensitive adhesive composition of this embodiment can be sufficiently cured when cured, and therefore the pressure-sensitive adhesive composition of this embodiment can be peeled off from the adherend without leaving any adhesive residue. The lower limit of the content of the polymerization initiator is more preferably 0.5 parts by mass, even more preferably 0.8 parts by mass, and even more preferably 1.0 parts by mass. Furthermore, the upper limit of the content of the polymerization initiator is not particularly limited, but from the viewpoint of preventing poor appearance caused by precipitation of the polymerization initiator, the preferred upper limit of the content of the polymerization initiator relative to 100 parts by mass of the (meth)acrylic copolymer is 20 parts by mass. The more preferred upper limit is 15 parts by mass, even more preferably 10 parts by mass, and even more preferably 5.0 parts by mass. The content of the polymerization initiator may be, for example, 0.1 parts by mass or more and 20 parts by mass or less, 0.5 parts by mass or more and 15 parts by mass or less, 0.8 parts by mass or more and 10 parts by mass or less, or 1.0 parts by mass or more and 5.0 parts by mass or less.

[0049] The pressure-sensitive adhesive composition of this embodiment preferably further contains an inorganic filler. By including an inorganic filler in the pressure-sensitive adhesive composition of this embodiment, the cohesive strength of the pressure-sensitive adhesive composition of this embodiment is increased. Therefore, even when additives of different polarities are mixed with the (meth)acrylic copolymer, separation does not occur, and the pressure-sensitive adhesive composition of this embodiment can be made more uniform, allowing the pressure-sensitive adhesive composition of this embodiment to exhibit superior adhesive strength upon adhesion. Furthermore, since the tensile strength of the pressure-sensitive adhesive composition of this embodiment is significantly improved, the pressure-sensitive adhesive composition does not break due to stress during peeling, even after chemical treatment or high-temperature treatment, and can be peeled more easily while suppressing the generation of adhesive residue.

[0050] Examples of the inorganic filler include silica nanofillers such as fumed silica, fused silica, and colloidal silica, alumina nanofillers, zirconia fillers, carbon nanofillers, glass fillers, titania fillers, zinc oxide fillers, etc. Among these, fumed silica fine particles and fused silica fine particles are preferred, with fumed silica fine particles being more preferred, because the amount of hydroxyl groups on the surface can be easily adjusted, the moisture content can be easily controlled, and the primary particle size can be sufficiently small, making it easier to adjust the average particle size of the inorganic filler described below to an appropriate range.

[0051] The preferred lower limit of the average particle size of the inorganic filler is 0.05 μm, and the preferred upper limit is 3 μm. When the average particle size of the inorganic filler is within the above range, the inorganic filler is finely dispersed in the pressure-sensitive adhesive composition of the present embodiment, thereby making the pressure-sensitive adhesive composition of the present embodiment more uniform. The average particle size of the inorganic filler can be, for example, 0.05 μm or more and 3 μm or less.

[0052] The average particle size can be determined, for example, by observing 50 particles of any inorganic filler under an electron microscope or an optical microscope and calculating the average particle size of each inorganic filler, or by performing laser diffraction particle size distribution measurement.

[0053] The preferred lower limit of the content of the inorganic filler relative to 100 parts by mass of the (meth)acrylic copolymer is 1.0 part by mass, and the preferred upper limit is 40 parts by mass. When the content of the inorganic filler is within the above range, the cohesive strength of the pressure-sensitive adhesive composition of the present embodiment is increased, and the pressure-sensitive adhesive composition of the present embodiment can be peeled from the adherend without leaving any adhesive residue upon peeling. The more preferred lower limit of the content of the inorganic filler is 3.0 parts by mass, and the more preferred upper limit is 20 parts by mass. The content of the inorganic filler may, for example, be from 1.0 part by mass to 40 parts by mass, or from 3.0 parts by mass to 20 parts by mass.

[0054] The pressure-sensitive adhesive composition of the present embodiment preferably further contains a polyfunctional oligomer or a polyfunctional monomer. By including the polyfunctional oligomer or polyfunctional monomer in the pressure-sensitive adhesive composition of the present embodiment, three-dimensional reticulation of the pressure-sensitive adhesive composition by light irradiation or heat load occurs more efficiently, and the pressure-sensitive adhesive composition of the present embodiment can be peeled off from an adherend without leaving any adhesive residue. In this specification, the term "polyfunctional oligomer or polyfunctional monomer" refers to a compound having two or more functional groups having a carbon-carbon unsaturated bond in the molecule and having a weight-average molecular weight of 50,000 or less. In this specification, the carbon-carbon unsaturated bond in the "functional group having a carbon-carbon unsaturated bond" of the polyfunctional oligomer or polyfunctional monomer does not include a carbon-carbon double bond constituting an aromatic ring. Furthermore, the weight-average molecular weight of the polyfunctional oligomer or polyfunctional monomer can be determined using GPC measurement, similar to the weight-average molecular weight of the (meth)acrylic copolymer described above.

[0055] Examples of the functional group having a carbon-carbon unsaturated bond include a vinyl group, a (meth)acryloyl group, an allyl group, a maleimide group, etc. Among these, a vinyl group is preferred from the viewpoint of a fast reaction rate with light or heat.

[0056] Examples of the polyfunctional oligomer or polyfunctional monomer include the (meth)acrylate monomer having a functional group having a carbon-carbon unsaturated bond, and a (meth)acrylic oligomer copolymerized with a (meth)acrylate having a functional group having a carbon-carbon unsaturated bond (excluding those having a structural unit derived from the alkyl (meth)acrylate (a-1) or the alkyl (meth)acrylate (a-2) and a structural unit derived from the alkyl (meth)acrylate (b) and containing a carbon-carbon double bond in the side chain), as well as silicone compounds having a functional group having a carbon-carbon unsaturated bond, and fluorine compounds having a functional group having a carbon-carbon unsaturated bond.

[0057] The pressure-sensitive adhesive composition of the present embodiment contains the (meth)acrylate monomer having a functional group having a carbon-carbon unsaturated bond and the (meth)acrylic oligomer copolymerized with the (meth)acrylate having a functional group having a carbon-carbon unsaturated bond, so that the pressure-sensitive adhesive composition of the present embodiment has improved photocurability and thermosetting properties, and can be peeled from an adherend without leaving any adhesive residue upon peeling.

[0058] In the (meth)acrylate monomer having a functional group having a carbon-carbon unsaturated bond and the (meth)acrylic oligomer obtained by copolymerizing the (meth)acrylate monomer having a functional group having a carbon-carbon unsaturated bond, from the viewpoint of more efficiently forming a three-dimensional reticulation in the pressure-sensitive adhesive layer by heating or light irradiation, the preferred lower limit of the number of functional groups having a carbon-carbon unsaturated bond is 2 and the preferred upper limit is 20. The number of functional groups having a carbon-carbon unsaturated bond may be, for example, 2 or more and 20 or less.

[0059] Examples of the (meth)acrylate monomer having a functional group having a carbon-carbon unsaturated bond and the (meth)acrylic oligomer obtained by copolymerizing the (meth)acrylate monomer having a functional group having a carbon-carbon unsaturated bond include trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate 1,4-butyl acrylate. Examples of the acrylate monomer include ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol diacrylate, oligoester acrylates such as EBECRYL524 and EBECRYL436 (all manufactured by Daicel Allnex Corporation), urethane acrylate monomers such as UN-5500, UN-5590 (all manufactured by Negami Chemical Industrial Co., Ltd.) and UA-160TM and UA-122P (all manufactured by Shin-Nakamura Chemical Co., Ltd.), and (meth)acrylic oligomers copolymerized with these (meth)acrylate monomers. These (meth)acrylate monomers having a carbon-carbon unsaturated bond and (meth)acrylic oligomers copolymerized with (meth)acrylate monomers having a carbon-carbon unsaturated bond may be used alone or in combination of two or more.

[0060] The pressure-sensitive adhesive composition of the present embodiment contains the silicone compound having a functional group having a carbon-carbon unsaturated bond and the fluorine compound having a functional group having a carbon-carbon unsaturated bond, so that the silicone compound or the fluorine compound bleeds out to the adherend interface, thereby enabling the pressure-sensitive adhesive composition of the present embodiment to be more easily peeled while suppressing the occurrence of adhesive residue.The pressure-sensitive adhesive composition of the present embodiment may contain both the silicone compound having a functional group having a carbon-carbon unsaturated bond and the fluorine compound having a functional group having a carbon-carbon unsaturated bond.

[0061] The silicone compound having a carbon-carbon unsaturated bond or the fluorine compound having a carbon-carbon unsaturated bond preferably further has a functional group capable of crosslinking with the (meth)acrylic copolymer. The silicone compound having a functional group having a carbon-carbon unsaturated bond or the fluorine compound having a functional group having a carbon-carbon unsaturated bond has a functional group capable of crosslinking with the (meth)acrylic copolymer, thereby reacting more efficiently with the (meth)acrylic copolymer by using a crosslinking agent or by light irradiation. This makes it easier for the silicone compound or fluorine compound to be incorporated into the (meth)acrylic copolymer, further suppressing contamination of the adherend due to adhesion of the silicone compound or fluorine compound to the adherend.

[0062] The functional group capable of crosslinking with the (meth)acrylic copolymer is appropriately selected depending on the functional group contained in the (meth)acrylic copolymer, and examples thereof include a carboxy group, a hydroxyl group, an amide group, an isocyanate group, and an epoxy group.

[0063] In the silicone compound having a functional group having a carbon-carbon unsaturated bond or the fluorine compound having a functional group having a carbon-carbon unsaturated bond, the total number of the functional group having a carbon-carbon unsaturated bond and the functional group crosslinkable with the (meth)acrylic copolymer is preferably 2 in lower limit and 12 in upper limit. When the total number of the functional group having a carbon-carbon unsaturated bond and the functional group crosslinkable with the (meth)acrylic copolymer is 2 or more, contamination of the adherend due to adhesion of the silicone compound or the fluorine compound is further suppressed. When the total number of the functional group having a carbon-carbon unsaturated bond and the functional group crosslinkable with the (meth)acrylic copolymer is 12 or less, three-dimensional reticulation of the pressure-sensitive adhesive composition of the present embodiment by light irradiation or heating is more efficiently achieved. A more preferred upper limit of the total number of the functional group having a carbon-carbon unsaturated bond and the functional group crosslinkable with the (meth)acrylic copolymer is 4, and the most preferred total number of the functional group having a carbon-carbon unsaturated bond and the functional group crosslinkable with the (meth)acrylic copolymer is 2. The total number of the functional group having a carbon-carbon unsaturated bond and the functional group capable of crosslinking with the (meth)acrylic copolymer may be, for example, 2 or more and 12 or less, or 2 or more and 4 or less.

[0064] Examples of the silicone compound having a functional group with a carbon-carbon unsaturated bond include silicone (meth)acrylate monomers, silicone di(meth)acrylate monomers, and (meth)acrylic oligomers copolymerized with these (however, excluding those having a structural unit derived from the alkyl (meth)acrylate (a-1) or the alkyl (meth)acrylate (a-2), and a structural unit derived from the alkyl (meth)acrylate (b), and containing a carbon-carbon double bond in the side chain). Commercially available silicone compounds having a functional group with a carbon-carbon unsaturated bond include, for example, silicone compounds having a methacryloyl group such as X-22-164, X-22-164AS, X-22-164A, X-22-164B, X-22-164C, X-22-164E, X-22-174DX, X-22-2426, and X-22-2475 (all manufactured by Shin-Etsu Chemical Co., Ltd.), MAC-SQ TM-100, MACSQSI-20, and MAC-SQ HDM (all manufactured by Toagosei Co., Ltd.), EBECRYL350, EBECRYL1360 (all manufactured by Daicel Allnex Corporation), AC-SQ TA-100, AC-SQ Examples include silicone compounds having an acryloyl group, such as SI-20 (both manufactured by Toagosei Co., Ltd.).

[0065] Examples of the fluorine compound having a carbon-carbon unsaturated bond include (meth)acrylic oligomers having a structural unit derived from a fluoro(meth)acrylate monomer (excluding those having a structural unit derived from the alkyl(meth)acrylate (a-1) or the alkyl(meth)acrylate (a-2) and a structural unit derived from the alkyl(meth)acrylate (b) and containing a carbon-carbon double bond in the side chain). Examples of the fluoro(meth)acrylate monomer include methyl-2-fluoroacrylate and 2-(perfluorobutyl)ethyl acrylate.

[0066] The preferred lower limit of the content of the polyfunctional oligomer or polyfunctional monomer relative to 100 parts by mass of the (meth)acrylic copolymer is 0.1 parts by mass, and the preferred upper limit is 50 parts by mass. When the content of the polyfunctional oligomer or polyfunctional monomer is within the above range, the pressure-sensitive adhesive composition of the present embodiment can be easily peeled from an adherend without leaving any adhesive residue. The more preferred lower limit of the content of the polyfunctional oligomer or polyfunctional monomer is 1.0 part by mass, an even more preferred lower limit is 5.0 parts by mass, and an even more preferred upper limit is 40 parts by mass, and an even more preferred upper limit is 20 parts by mass. The content of the polyfunctional oligomer or polyfunctional monomer may, for example, be from 0.1 to 50 parts by mass, from 1.0 to 40 parts by mass, or from 5.0 to 20 parts by mass.

[0067] The pressure-sensitive adhesive composition of the present embodiment preferably further contains a gas-generating agent. By containing the gas-generating agent in the pressure-sensitive adhesive composition of the present embodiment, gas can be generated on the adhesion surface by light irradiation or heating, and the pressure-sensitive adhesive composition of the present embodiment can be more easily peeled from the adherend without leaving any adhesive residue.

[0068] The gas generating agent is not particularly limited, and is preferably a gas generating agent that generates gas by light (e.g., ultraviolet light, laser light, etc.), heat, electromagnetic waves, electron beams, etc. Among these, from the viewpoint of enhancing adhesion of the pressure-sensitive adhesive composition of the present embodiment at high temperatures and suppressing outgassing, a gas generating agent that generates gas by light is preferred. The gas generating agent is not particularly limited, and for example, an azo compound, an azide compound, a carboxylic acid compound, a tetrazole compound, etc. are suitably used.

[0069] Examples of the azo compound used as the gas generating agent include 2,2'-azobis-(N-butyl-2-methylpropionamide), 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis{2-methyl-N-[2-(1-hydroxybutyl)]propionamide}, 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2-azobis[N-(2-propenyl)-2-methylpropionamide], propionamide], 2,2'-azobis(N-butyl-2-methylpropionamide), 2,2'-azobis(N-cyclohexyl-2-methylpropionamide), 2,2'-azobis[2-(5-methyl-2-imidazoline-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(2-imidazoline-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(2-imidazoline-2-yl)propane]disulfate dihydrate, 2,2'-azobis [2-(3,4,5,6-tetrahydropyrimidin-2-yl)propane] dihydrochloride, 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazoline-2-yl]propane} dihydrochloride, 2,2'-azobis[2-(2-imidazoline-2-yl)propane], 2,2'-azobis(2-methylpropionamidine) hydrochloride, 2,2'-azobis(2-aminopropane) dihydrochloride, 2,2'-azobis[N-(2-carboxya 2,2'-azobis{2-[N-(2-carboxyethyl)amidine]propane}, 2,2'-azobis(2-methylpropionamidoxime), dimethyl 2,2'-azobis(2-methylpropionate), dimethyl 2,2'-azobisisobutyrate, 4,4'-azobis(4-cyanocarbonic acid), 4,4'-azobis(4-cyanopentanoic acid), 2,2'-azobis(2,4,4-trimethylpentane), and the like.

[0070] Examples of the azide compound used as the gas generating agent include polymers having an azide group, such as 3-azidomethyl-3-methyloxetane, terephthalazide, p-tert-butylbenzazide, and glycidyl azide polymer obtained by ring-opening polymerization of 3-azidomethyl-3-methyloxetane.

[0071] Examples of the carboxylic acid compound include phenylacetic acid, diphenylacetic acid, triphenylacetic acid, and salts thereof.

[0072] Examples of the tetrazole compound include 1H-tetrazole, 5-phenyl-1H-tetrazole, 5,5-azobis-1H-tetrazole, and salts thereof.

[0073] The preferred lower limit of the content of the gas generating agent relative to 100 parts by mass of the (meth)acrylic copolymer is 5.0 parts by mass, and the preferred upper limit is 50 parts by mass. When the content of the gas generating agent is 5.0 parts by mass or more, it is possible to generate a gas from the gas generating agent that is capable of sufficiently peeling off the pressure-sensitive adhesive composition of this embodiment. When the content of the gas generating agent is 50 parts by mass or less, the compatibility between the gas generating agent and other components in the pressure-sensitive adhesive composition of this embodiment is improved. A more preferred lower limit of the content of the gas generating agent is 10 parts by mass, and a more preferred upper limit is 30 parts by mass. Note that the content of the gas generating agent may, for example, be 5.0 parts by mass or more and 50 parts by mass or less, or 10 parts by mass or more and 30 parts by mass or less.

[0074] The pressure-sensitive adhesive composition of the present embodiment preferably further contains a tackifier. By containing a tackifier, the pressure-sensitive adhesive composition of the present embodiment has even stronger adhesive properties.

[0075] Examples of the tackifier include rosin resins, rosin ester resins, hydrogenated rosin resins, hydrogenated rosin ester resins, terpene resins, terpene phenol resins, coumarone-indene resins, alicyclic saturated hydrocarbon resins, C5 petroleum resins, C9 petroleum resins, C5-C9 copolymer petroleum resins, etc. These tackifiers may be used alone or in combination of two or more.

[0076] The tackifier preferably contains a tackifier containing bio-derived carbon. By including a tackifier containing bio-derived carbon in the tackifier, the content of bio-derived carbon in the adhesive layer described below can be increased, and the environmental impact of the resulting adhesive tape can be further reduced. Specific examples of the tackifier containing bio-derived carbon include KE-100, KE-359, KE-604, KR-140, A-75, and 803L (all manufactured by Arakawa Chemical Industries, Ltd.).

[0077] The preferred lower limit of the tackifier content relative to 100 parts by mass of the (meth)acrylic copolymer is 1.0 part by mass, and the preferred upper limit is 60 parts by mass. When the tackifier content is 1.0 part by mass or more, the PSA composition of this embodiment has even stronger adhesive properties. When the tackifier content is 60 parts by mass or less, the PSA composition of this embodiment does not have too high adhesive strength, and can be peeled from the adherend without leaving any adhesive residue upon peeling. The more preferred lower limit of the tackifier content is 5.0 parts by mass, the more preferred upper limit is 40 parts by mass, and the even more preferred upper limit is 20 parts by mass. The tackifier content may, for example, be from 1.0 part by mass to 60 parts by mass, from 5.0 parts by mass to 40 parts by mass, or from 5.0 parts by mass to 20 parts by mass.

[0078] When the (meth)acrylic copolymer contains a structural unit derived from the polar functional group-containing monomer, the pressure-sensitive adhesive composition of the present embodiment preferably contains a crosslinking agent. When the pressure-sensitive adhesive composition of the present embodiment contains a crosslinking agent, the polar functional group derived from the structural unit derived from the polar functional group-containing monomer reacts with the crosslinking agent, thereby appropriately adjusting the adhesive strength of the pressure-sensitive adhesive composition of the present embodiment. As a result, the pressure-sensitive adhesive composition of the present embodiment can be easily peeled from an adherend without leaving any adhesive residue.

[0079] Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an aziridine-based crosslinking agent, an epoxy-based crosslinking agent, and a metal chelate-based crosslinking agent. Among these, 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, and more preferably contains an isocyanate-based crosslinking agent, because this crosslinking agent has a fast reaction rate and further increases the cohesive strength of the pressure-sensitive adhesive composition of the present embodiment. From the viewpoint of storage stability, etc., the crosslinking agent may be blended into the pressure-sensitive adhesive composition of the present embodiment immediately before forming the pressure-sensitive adhesive layer.

[0080] The preferred lower limit of the content of the crosslinking agent relative to 100 parts by mass of the (meth)acrylic copolymer is 0.01 parts by mass, and the preferred upper limit is 10 parts by mass. When the content of the crosslinking agent is within the above range, the gel fraction of the pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition of this embodiment in the pressure-sensitive adhesive tape described below can be appropriately adjusted, and the pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition of this embodiment will have even stronger adhesive properties. The more preferred lower limit of the content of the crosslinking agent is 0.05 parts by mass, and the more preferred upper limit is 5.0 parts by mass. The content of the crosslinking agent may be, for example, from 0.01 parts by mass to 10 parts by mass, or from 0.05 parts by mass to 5.0 parts by mass.

[0081] The pressure-sensitive adhesive composition of the present embodiment may further contain known additives such as a plasticizer, a surfactant, a wax, etc. These additives may be used alone or in combination of two or more.

[0082] Examples of a method for producing the pressure-sensitive adhesive composition of the present embodiment include a method of mixing the (meth)acrylic copolymer and, if necessary, the polymerization initiator, the inorganic filler, the polyfunctional oligomer or polyfunctional monomer, the gas generating agent, the crosslinking agent, the known additives, and the like.

[0083] An adhesive tape having an adhesive layer formed using the adhesive composition of this embodiment also constitutes this embodiment. The gel fraction of the adhesive layer and the content of bio-derived carbon in the adhesive layer, which will be described later, can be adjusted to the values ​​described later by adjusting the type and content of each component constituting the adhesive composition of this embodiment. Examples of methods for forming an adhesive layer using the adhesive composition of this embodiment include a method in which the adhesive composition of this embodiment is applied to a release film or the like, and then the adhesive composition is dried by heating.

[0084] The preferred lower limit of the bio-derived carbon content in the pressure-sensitive adhesive layer is 20%. By having the bio-derived carbon content in the pressure-sensitive adhesive layer be 20% 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 can further reduce the environmental impact. The more preferred lower limit of the bio-derived carbon content in the pressure-sensitive adhesive layer is 35%, and even more preferred is 50%. The upper limit of the bio-derived carbon content in the pressure-sensitive adhesive layer is not particularly limited and may be 100%. Examples of the bio-derived carbon content in the pressure-sensitive adhesive layer include 20% or more and 100% or less, 35% or more and 100% or less, and 50% or more and 100% or less. While bio-derived carbon contains a certain proportion of the radioactive isotope (C-14), petroleum-derived carbon contains almost no C-14. Therefore, the bio-derived carbon content can be calculated by measuring the concentration of C-14 in the pressure-sensitive adhesive layer. Specifically, it can be measured in accordance with ASTM D6866-22, a standard used in many bioplastic industries.

[0085] The pressure-sensitive adhesive layer preferably has a lower limit of -10°C for the glass transition temperature measured by dynamic viscoelasticity measurement at a frequency of 10 Hz (hereinafter, sometimes simply referred to as "glass transition temperature of the pressure-sensitive adhesive layer"). When the pressure-sensitive adhesive layer has a glass transition temperature of -10°C or higher, the pressure-sensitive adhesive tape of this embodiment has even stronger adhesive properties. A more preferred lower limit for the glass transition temperature of the pressure-sensitive adhesive layer is 0°C, and an even more preferred lower limit is 10°C. Furthermore, when the pressure-sensitive adhesive layer has multiple glass transition temperatures, it is more preferred that all of the glass transition temperatures are -10°C or higher. Furthermore, the upper limit of the glass transition temperature of the pressure-sensitive adhesive layer is not particularly limited, but a preferred upper limit is, for example, 100°C. When the glass transition temperature of the pressure-sensitive adhesive layer is 100°C or lower, the pressure-sensitive adhesive layer has appropriate flexibility, and therefore the pressure-sensitive adhesive tape of this embodiment can be peeled off while suppressing adhesive residue during peeling. The glass transition temperature of the pressure-sensitive adhesive layer may be, for example, from -10°C to 100°C, from 0°C to 100°C, or from 10°C to 100°C.

[0086] As used herein, the "glass transition temperature of the pressure-sensitive adhesive layer" refers to the temperature at which a maximum due to micro-Brownian motion appears among the maximum loss tangents (tan δ) obtained by dynamic viscoelasticity measurement. The dynamic viscoelasticity measurement used to measure the glass transition temperature of the pressure-sensitive adhesive layer can be performed, for example, by the following method. First, the pressure-sensitive adhesive layers are stacked to prepare a laminate having a thickness of 400 μm to 1 mm, which is then cut into a width of 5 mm and a length of 10 mm to obtain a test piece. Next, the obtained test piece is subjected to dynamic viscoelasticity measurement in shear mode using a dynamic viscoelasticity measuring device under the following conditions: a measurement temperature of -50°C to 200°C, a heating rate of 10°C / min, a frequency of 10 Hz, and a strain of 0.05%. Examples of the dynamic viscoelasticity measuring device include the DVA-200 (manufactured by IT Measurement & Control Co., Ltd.).

[0087] The preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 10% by mass, and the preferred upper limit is 90% by mass. By having the gel fraction within the above range, the pressure-sensitive adhesive tape of this embodiment exhibits superior adhesive strength when adhered. The more preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 20% by mass, and the more preferred upper limit is 80% by mass, and the even more preferred lower limit is 30% by mass, and the even more preferred upper limit is 70% by mass, and the even more preferred lower limit is 40% by mass, and the even more preferred upper limit is 60% by mass. Examples of the gel fraction of the pressure-sensitive adhesive layer include 10% by mass or more and 90% by mass or less, 20% by mass or more and 80% by mass or less, 30% by mass or more and 70% by mass or less, and 40% by mass or more and 60% by mass or less.

[0088] The gel fraction of the pressure-sensitive adhesive layer can be measured by the following method. ０ (g) The sample is taken out, immersed in 50 mL of ethyl acetate, and shaken in a shaker at a temperature of 23°C and 200 rpm for 24 hours. After shaking, the sample is passed through a metal mesh (opening #200 mesh, W １ (g)), the ethyl acetate and the pressure-sensitive adhesive layer that has absorbed the ethyl acetate and swollen is separated, and the separated pressure-sensitive adhesive layer is dried for 1 hour under the condition of 110°C. The mass W of the pressure-sensitive adhesive layer including the metal mesh after drying ２ (g) and measure the gel fraction (mass%) of the pressure-sensitive adhesive layer using the following formula: Gel fraction (mass%) = 100 × (W ２ -W １ ) / W ０ (W ０ : initial mass of adhesive layer, W １ : initial mass of the metal mesh, W ２ : mass of adhesive layer including metal mesh after drying)

[0089] After heating at 150°C for 1 hour, or after irradiating the film with light having a wavelength of 280 nm or more and 405 nm or less with an integrated light intensity of 1000 mJ / cm ２The preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer after irradiation so as to be equal to or greater than 90% by mass (hereinafter sometimes referred to as the "gel fraction of the pressure-sensitive adhesive layer after curing") is 90% by mass. When the gel fraction of the pressure-sensitive adhesive layer after curing is 90% by mass or greater, the pressure-sensitive adhesive tape of this embodiment can be peeled off while suppressing adhesive residue upon peeling. A more preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer after curing is 92% by mass, and an even more preferred lower limit is 95% by mass. The upper limit of the gel fraction of the pressure-sensitive adhesive layer after curing is not particularly limited, and may be 100% by mass. Examples of the gel fraction of the pressure-sensitive adhesive layer after curing include 90% by mass or more and 100% by mass or less, 92% by mass or more and 100% by mass or less, and 95% by mass or more and 100% by mass or less.

[0090] The gel fraction of the pressure-sensitive adhesive layer after curing is determined by heating at 150°C for 1 hour or by irradiating the pressure-sensitive adhesive layer with light having a wavelength in the range of 280 nm or more and 405 nm or less with an integrated light intensity of 1000 mJ / cm ２ The pressure-sensitive adhesive layer is cured by irradiating the pressure-sensitive adhesive layer with light having a wavelength in the range of 280 nm or more and 405 nm or less at an integrated light intensity of 1000 mJ / cm. ２ The irradiation method for achieving the above values ​​is, for example, a wavelength of 405 nm and an illuminance of 100 mW / cm ２ The cumulative light intensity is 2500 mJ / cm ２ For example, irradiation for 25 seconds may be performed so that the

[0091] The method for adjusting the gel fraction of the pressure-sensitive adhesive layer and the gel fraction after curing of the pressure-sensitive adhesive layer to fall within the above range is not particularly limited, and examples include a method for adjusting the composition of the monomers constituting the (meth)acrylic copolymer (specifically, for example, the type and content ratio of structural units derived from polar functional group-containing monomers), a method for adjusting the weight average molecular weight (Mw) of the (meth)acrylic copolymer, a method for adjusting the carbon-carbon double bond equivalent of the (meth)acrylic copolymer, a method for adjusting the hydroxyl value and acid value of the (meth)acrylic copolymer, and a method for adjusting the type and content of a crosslinking agent contained in the pressure-sensitive adhesive composition.

[0092] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but a preferred lower limit is 5.0 μm and a preferred upper limit is 300 μm. When the thickness of the pressure-sensitive adhesive layer is within the above range, the pressure-sensitive adhesive layer has excellent adhesive strength, and the pressure-sensitive adhesive tape of this embodiment can firmly adhere to the adherend when adhered. A more preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 10 μm, a more preferred upper limit is 200 μm, an even more preferred lower limit is 25 μm, an even more preferred upper limit is 150 μm, an even more preferred upper limit is 100 μm, and a particularly preferred upper limit is 50 μm. Examples of the thickness of the pressure-sensitive adhesive layer include 5.0 μm to 300 μm, 10 μm to 200 μm, 25 μm to 150 μm, 25 μm to 100 μm, and 25 μm to 50 μm.

[0093] The adhesive tape of this embodiment may be a non-support type adhesive tape that does not have a substrate, or a supported type tape that has a substrate. However, from the viewpoint of preventing adhesive residue upon peeling, it is preferable that the adhesive tape of this embodiment has a substrate and an adhesive on at least one surface of the substrate.

[0094] When the pressure-sensitive adhesive tape of the present embodiment is a support-type tape having a substrate, it may be a single-sided pressure-sensitive adhesive tape having the above-mentioned pressure-sensitive adhesive layer on one side of the substrate, or a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of the substrate. Furthermore, when it is a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of the substrate, it is sufficient that the above-mentioned pressure-sensitive adhesive layer is present on at least one side of the substrate, and the pressure-sensitive adhesive layer on the other side may have any composition.

[0095] The substrate is not particularly limited, but is preferably one that transmits or passes light, and examples thereof include sheets made of transparent resins such as acrylic, olefin, polycarbonate, vinyl chloride, ABS, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), nylon, urethane, polyamide, polyether, polyketone, and polyether ether ketone; sheets having a mesh structure; and sheets with holes.

[0096] From the viewpoint of increasing the content of bio-derived carbon in the entire pressure-sensitive adhesive tape, it is preferable to use a bio-derived substrate. Examples of the bio-derived substrate include films and nonwoven fabrics containing 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). Other examples include films and nonwoven fabrics containing plant-derived polyethylene (PE), polypropylene (PP), polyurethane (PU), triacetyl cellulose (TAC), cellulose, polyamide (PA), and the like.

[0097] 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, or the oils and fats contained in the collected waste materials may be mixed with petroleum, fractionated, and purified, and then used as raw materials.

[0098] The thickness of the substrate is not particularly limited, but a preferred lower limit is 12 μm, and a preferred upper limit is 200 μm. By having the thickness of the substrate within the above range, it is possible to obtain a pressure-sensitive adhesive tape that exhibits high flexibility, allowing it to be adhered to the shape of the adherend, while also having moderate stiffness and excellent handleability. A more preferred lower limit of the thickness of the substrate is 25 μm, a more preferred upper limit is 125 μm, and an even more preferred upper limit is 75 μm. Examples of the thickness of the substrate include 12 μm or more and 200 μm or less, 25 μm or more and 125 μm or less, and 25 μm or more and 75 μm or less.

[0099] 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 having a substrate, the following method can be mentioned. First, a solution of pressure-sensitive adhesive composition A is prepared by adding a (meth)acrylic copolymer and, if necessary, a tackifier, a crosslinking agent, etc. to a solvent, and then the obtained solution of pressure-sensitive adhesive composition A is applied to one side of a substrate, and the solvent in the solution of pressure-sensitive adhesive composition A is dried and removed 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 solution of pressure-sensitive adhesive composition B prepared in the same manner as above is applied to the release-treated surface of a release film other than the above-mentioned release film, and the solvent in the solution is 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 formed on both sides of the substrate using the adhesive composition, and in which the surfaces of the adhesive layers are covered with a release film.

[0100] 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.

[0101] The preferred lower limit of the 180° peel strength of the pressure-sensitive adhesive tape of this embodiment from SUS (stainless steel) is 8.0 N / 25 mm. When the 180° peel strength of the pressure-sensitive adhesive tape of this embodiment from SUS is 8.0 N / 25 mm or more, the pressure-sensitive adhesive tape of this embodiment has strong adhesiveness. A more preferred lower limit of the 180° peel strength of the pressure-sensitive adhesive tape of this embodiment from SUS is 12.0 N / 25 mm, and an even more preferred lower limit is 15.0 N / 25 mm. Furthermore, there are no particular limitations on the upper limit of the 180° peel strength of the pressure-sensitive adhesive tape of this embodiment from SUS, but from the viewpoint of preventing the peel strength from increasing too much after curing, the upper limit is about 20.0 N / 25 mm. The 180° peel strength of the embodiment tape of this embodiment against SUS may be, for example, 8.0 N / 25 mm or more and 20.0 N / 25 mm or less, 12.0 N / 25 mm or more and 20.0 N / 25 mm or less, or 15.0 N / 25 mm or more and 20.0 N / 25 mm or less.

[0102] The 180° peel strength of the pressure-sensitive adhesive tape of this embodiment against SUS can be measured, for example, by a method in accordance with JIS Z0237, in which a tensile test is carried out under conditions of 23°C, a peel speed of 300 mm / min, and a peel angle of 180°.

[0103] The method for adjusting the 180° peel strength of the pressure-sensitive adhesive tape of the present embodiment against SUS within the above range is not particularly limited, and examples thereof include a method for adjusting the composition of the monomers constituting the (meth)acrylic copolymer (specifically, for example, the type and content ratio of the structural unit derived from the alkyl (meth)acrylate (b) and the structural unit derived from the polar functional group-containing monomer), a method for adjusting the weight average molecular weight (Mw) of the (meth)acrylic copolymer, and a method for adjusting the hydroxyl value, acid value, etc. of the (meth)acrylic copolymer.

[0104] After heating at 150°C for 1 hour, or after irradiating the film with light having a wavelength of 280 nm or more and 405 nm or less with an integrated light intensity of 1000 mJ / cm ２The preferred upper limit of the 180° peel strength of the pressure-sensitive adhesive tape from SUS after irradiation so as to be equal to or greater than 1.0 N / 25 mm (hereinafter, this may also be referred to as the "180° peel strength of the pressure-sensitive adhesive tape from SUS after the adhesive layer has cured") is 1.0 N / 25 mm. When the 180° peel strength of the pressure-sensitive adhesive tape from SUS after the adhesive layer has cured is 1.0 N / 25 mm or less, the pressure-sensitive adhesive tape of this embodiment can be easily peeled while suppressing adhesive residue during peeling. The more preferred upper limit of the 180° peel strength of the pressure-sensitive adhesive tape from SUS after the adhesive layer has cured is 0.6 N / 25 mm, even more preferred is 0.5 N / 25 mm, even more preferred is 0.3 N / 25 mm, and particularly preferred is 0.2 N / 25 mm. Furthermore, there is no particular limitation on the lower limit of the 180° peel strength of the pressure-sensitive adhesive tape from SUS after the adhesive layer has cured, but it is preferably greater than 0 N / 25 mm. The 180° peel strength of the pressure-sensitive adhesive tape of this embodiment against SUS may be, for example, more than 0 N / 25 mm and not more than 1.0 N / 25 mm, more than 0 N / 25 mm and not more than 0.5 N / 25 mm, or more than 0 N / 25 mm and not more than 0.3 N / 25 mm.

[0105] The 180° peel strength from SUS after the adhesive layer of the pressure-sensitive adhesive tape has cured can be measured by heating the pressure-sensitive adhesive tape of this embodiment to SUS for 1 hour before conducting a tensile test, or by irradiating the tape with light having a wavelength in the range of 280 nm or more and 405 nm or less at an integrated light intensity of 1000 mJ / cm. ２ The adhesive layer of the adhesive tape of the present embodiment is cured by irradiating the adhesive layer with light having a wavelength in the range of 280 nm or more and 405 nm or less at an integrated light intensity of 1000 mJ / cm. ２ The irradiation method for achieving the above values ​​is, for example, a wavelength of 405 nm and an illuminance of 100 mW / cm ２ The cumulative light intensity is 2500 mJ / cm ２ For example, irradiation for 25 seconds may be performed so that the

[0106] The adhesive tape was attached to SUS and left at 60°C for 24 hours, and then heated at 150°C for 1 hour, or irradiated with light of any wavelength within the range of 280 nm to 405 nm with an integrated light intensity of 1000 mJ / cm ２ The preferred upper limit of the 180° peel strength from SUS of the pressure-sensitive adhesive tape after irradiation so as to be equal to or greater than 1.5 N / 25 mm (hereinafter, this may also be referred to as "the 180° peel strength from SUS of the pressure-sensitive adhesive tape after being left to stand at high temperature and the pressure-sensitive adhesive layer being cured") is 1.5 N / 25 mm. When the 180° peel strength from SUS of the pressure-sensitive adhesive tape after being left to stand at high temperature and the pressure-sensitive adhesive layer being cured is 1.5 N / 25 mm or less, the pressure-sensitive adhesive tape of this embodiment can suppress increased adhesion at high temperatures, making it even easier to peel while suppressing adhesive residue during peeling. The more preferred upper limit of the 180° peel strength from SUS of the pressure-sensitive adhesive tape after being left to stand at high temperature and the pressure-sensitive adhesive layer being cured is 1.2 N / 25 mm, and even more preferred upper limit is 0.8 N / 25 mm. Furthermore, there is no particular limitation on the lower limit of the 180° peel strength from SUS of the pressure-sensitive adhesive tape after being left to stand at high temperature and the pressure-sensitive adhesive layer being cured, but it is preferably greater than 0 N / 25 mm. The 180° peel strength of the pressure-sensitive adhesive tape of this embodiment against SUS may be, for example, more than 0 N / 25 mm and not more than 1.5 N / 25 mm, more than 0 N / 25 mm and not more than 1.2 N / 25 mm, or more than 0 N / 25 mm and not more than 0.8 N / 25 mm.

[0107] The 180° peel strength from SUS after the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape has been left standing at a high temperature and then cured can be measured by performing a tensile test after curing the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of the present embodiment, which has been stuck to SUS and then left standing at 60°C for 24 hours, in the measurement of the 180° peel strength from SUS after the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape described above has been cured.

[0108] The method for adjusting the 180° peel strength from SUS after the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape has cured, and the 180° peel strength from SUS after the pressure-sensitive adhesive tape has been allowed to stand at high temperature and then the pressure-sensitive adhesive layer has cured, within the above ranges is not particularly limited, and examples include a method of adjusting the composition of the monomers constituting the (meth)acrylic copolymer (specifically, for example, the types and content ratios of the structural units derived from the alkyl (meth)acrylate (a-1), the structural units derived from the alkyl (meth)acrylate (a-2), and the structural units derived from the alkyl (meth)acrylate (b)), a method of adjusting the weight-average molecular weight (Mw) of the (meth)acrylic copolymer, and a method of adjusting the carbon-carbon double bond equivalent of the (meth)acrylic copolymer.

[0109] The pressure-sensitive adhesive tape of this embodiment has strong adhesive properties when adhered, and is therefore preferably used for fixing components, and in particular, the pressure-sensitive adhesive tape of this embodiment can be peeled off from the adherend while suppressing adhesive residue, and is therefore more preferably used for fixing components to be reused, and even more preferably for fixing electronic device components that are highly useful for reuse. Furthermore, the pressure-sensitive adhesive tape of this embodiment is also preferably used for temporarily fixing electronic device components to be manufactured, such as semiconductor wafers, when manufacturing electronic device components.

[0110] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition that exhibits strong adhesiveness when adhered and can be peeled off from an adherend while leaving little adhesive residue when peeled off. Also, according to the present invention, it is possible to provide a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition.

[0111] The following examples further illustrate aspects of the present invention, but the present invention is not limited to these examples. The constituent unit monomers of the (meth)acrylic copolymer used in the examples and comparative examples are as follows.

[0112] <Preparation of 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.

[0113] <Preparation of n-heptyl acrylate containing bio-derived carbon> Ricinoleic acid derived from castor oil was cracked to obtain a mixture containing undecylenic acid and heptyl alcohol. The undecylenic acid was then separated by distillation to obtain n-heptyl alcohol containing bio-derived carbon. The 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.

[0114] <Preparation of 1-methylheptyl acrylate containing bio-derived carbon> Ricinoleic acid derived from castor oil was alkali-fused to obtain a mixture containing sebacic acid and 1-methylheptyl alcohol. Next, sebacic acid was separated from the obtained mixture by distillation to obtain 1-methylheptyl alcohol containing bio-derived carbon. 1-methylheptyl acrylate containing bio-derived carbon was prepared by esterifying the obtained 1-methylheptyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.).

[0115] <Other structural unit monomers containing carbon of biological origin> n-Octyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd.) Isobornyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd.) Stearyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd.) Behenyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0116] <Bio-derived carbon-free structural unit monomers> n-Butyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) 2-Hydroxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd.) Acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) 2-Isocyanateethyl methacrylate (manufactured by Resonac Corporation)

[0117] Example 1 (1) Preparation of (meth)acrylic copolymer A reactor equipped with a thermometer, a stirrer, and a cooling tube was prepared, and 33.9 parts by mass of n-heptyl acrylate containing bio-derived carbon prepared by the method described above as an alkyl (meth)acrylate, 33.1 parts by mass of isobornyl acrylate containing bio-derived carbon, 16.9 parts by mass of 2-hydroxyethyl acrylate as a polar functional group-containing monomer, 0.8 parts by mass of acrylic acid, and 80 parts by mass of ethyl acetate were added to the reactor, and the reactor was heated to initiate reflux. Subsequently, 0.01 parts by mass of 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane was added as a polymerization initiator to the reactor, and polymerization was initiated under reflux. Next, 1 hour and 2 hours after the start of polymerization, 0.01 parts by mass of 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane was added, and further 4 hours after the start of polymerization, 0.05 parts by mass of t-hexylperoxypivalate was added to continue the polymerization reaction. Then, 8 hours after the start of polymerization, ethyl acetate was added to the reactor to dilute and cool, yielding an ethyl acetate solution containing a (meth)acrylic polymer without an introduced carbon-carbon double bond. 15.3 parts by mass of 2-isocyanatoethyl methacrylate was added as a functional group-containing unsaturated compound to the obtained ethyl acetate solution containing a (meth)acrylic polymer without an introduced carbon-carbon double bond, and the mixture was allowed to react to yield a solution of (meth)acrylic copolymer A (hydroxyl value 10 mgKOH / g, acid value 7.0 mgKOH / g, carbon-carbon double bond equivalent 1.4 meq / g). The hydroxyl value and acid value of (meth)acrylic copolymer A were measured in accordance with the potentiometric titration method specified in JIS K 0070: 1992. The weight average molecular weight of the obtained (meth)acrylic copolymer A was measured using a Waters "2690 Separations Module" as a measuring instrument, a Showa Denko "GPC KF-806L" column, and ethyl acetate as a solvent under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C, and was found to be 390,000.

[0118] (2) Preparation of Pressure-Sensitive Adhesive Composition and Pressure-Sensitive Adhesive Tape To the resulting solution of (meth)acrylic copolymer A, 0.2 parts by mass of an isocyanate-based crosslinking agent (manufactured by Soken Chemical & Engineering Co., Ltd., "Coronate L-45K") and 1.0 parts by mass of a photopolymerization initiator (manufactured by IGM Resins, "Omnirad 651") were added relative to 100 parts by mass of the (meth)acrylic copolymer, and then mixed to obtain an ethyl acetate solution of the pressure-sensitive adhesive composition. The resulting ethyl acetate solution of the pressure-sensitive adhesive composition was applied with a doctor knife to the release-treated surface of a 50 μm-thick release-treated polyethylene terephthalate (PET) film so that the thickness of the pressure-sensitive adhesive layer after drying would be 30 μm, and then dried at 110 ° C. for 5 minutes to form a pressure-sensitive adhesive layer. Thereafter, a 50 μm-thick polyethylene terephthalate (PET) film substrate was superimposed on the resulting pressure-sensitive adhesive layer, and the resulting adhesive layer was aged at 40 ° C. for 5 days to obtain a pressure-sensitive adhesive tape.

[0119] (3) Measurement of the content of bio-derived carbon in the pressure-sensitive adhesive layer The content of bio-derived carbon in the obtained pressure-sensitive adhesive layer was measured in accordance with ASTM D6866-22. The results are shown in Table 3.

[0120] (4) Measurement of the glass transition temperature of the adhesive layer An ethyl acetate solution of the obtained adhesive composition was applied to the release-treated surface of a 50 μm-thick release-treated polyethylene terephthalate (PET) film using a doctor knife so that the adhesive layer would have a thickness of 50 μm after drying, and then the applied adhesive was bonded to the release-treated surface of a 50 μm-thick release-treated polyethylene terephthalate (PET) film, and left to stand at 40 ° C. for 5 days for aging, to obtain an adhesive tape for measuring the glass transition temperature. A plurality of the obtained adhesive tapes for measuring the glass transition temperature were prepared, and the adhesive layers were overlapped to produce a laminate consisting only of an adhesive layer having a thickness of 400 μm to 1 mm, which was then cut into a width of 5 mm and a length of 10 mm to obtain a test piece. The obtained test pieces were subjected to dynamic viscoelasticity measurement in shear mode using a dynamic viscoelasticity measuring device (manufactured by IT Measurement & Control Co., Ltd., "DVA-200") under conditions of a measurement temperature of -50°C to 200°C, a heating rate of 10°C / min, a frequency of 10 Hz, and a strain of 0.05%, and the glass transition temperature (°C) of the pressure-sensitive adhesive layer was measured. The results are shown in Table 3.

[0121] (5) Measurement of gel fraction of adhesive layer An ethyl acetate solution of the obtained adhesive composition was applied with a doctor knife to the release-treated surface of a 50 μm-thick release-treated polyethylene terephthalate (PET) film so that the thickness of the adhesive layer after drying would be 30 μm, and then the adhesive composition was attached to the release-treated surface of a 50 μm-thick release-treated polyethylene terephthalate (PET) film, and left to stand at 40° C. for 5 days for aging, to obtain an adhesive tape for measuring the gel fraction. The obtained adhesive tape for measuring the gel fraction was cut into a shape of 5 cm long and 5 cm wide, and this was used as an evaluation sample. Only the adhesive layer was removed from the obtained evaluation sample. ０ (g) The sample was taken out, immersed in 50 mL of ethyl acetate, and shaken in a shaker at a temperature of 23°C and 200 rpm for 24 hours. After shaking, the sample was passed through a metal mesh (opening #200 mesh, W １ (g)), the ethyl acetate and the pressure-sensitive adhesive layer that had absorbed the ethyl acetate and swollen was separated. The separated pressure-sensitive adhesive layer was dried at 110°C for 1 hour. The mass W of the pressure-sensitive adhesive layer including the metal mesh after drying was ２ The gel fraction (mass%) of the pressure-sensitive adhesive layer was measured using the following formula. The results are shown in Table 3. Gel fraction (mass%) = 100 × (W ２ -W １ ) / W ０ (W ０ : initial mass of adhesive layer, W １ : initial mass of the metal mesh, W ２ : mass of adhesive layer including metal mesh after drying)

[0122] (6) Measurement of gel fraction after curing of adhesive layer The adhesive tape for gel fraction measurement obtained in the same manner as in the above "(5) Measurement of gel fraction of adhesive layer" was cut into a shape of 5 cm length and 5 cm width, and then irradiated with light of a wavelength of 405 nm and an illuminance of 100 mW / cm using an ultra-high pressure mercury lamp. ２ The cumulative light intensity is 2500 mJ / cm ２ The pressure-sensitive adhesive layer was cured by irradiating the sample for 25 seconds so that the temperature reached 100°C, thereby preparing a sample for evaluation. The gel fraction of the obtained sample for evaluation was measured using the same method as in "(5) Measurement of gel fraction of pressure-sensitive adhesive layer" above, and the gel fraction (% by mass) of the pressure-sensitive adhesive layer after curing was obtained. The results are shown in Table 3.

[0123] (7) Measurement of 180° Peel Strength of Pressure-Sensitive Adhesive Tape from SUS: The pressure-sensitive adhesive tape obtained in "(2) Production of Pressure-Sensitive Adhesive Composition and Pressure-Sensitive Adhesive Tape" above was cut into a flat rectangular shape measuring 25 mm wide x 100 mm long. The tape was then rolled back and forth with a 2 kg rubber roller at a speed of 300 mm / min, and bonded to a SUS plate (a SUS304 plate washed with ethanol and then wiped dry). This was then aged for 20 minutes at 23°C and 50% RH to prepare a test sample. A tensile test was performed on the obtained test sample in accordance with JIS Z0237 at 23°C, 50% RH, a tensile speed of 300 mm / min, and a peel angle of 180°, and the 180° peel strength (N / 25 mm) of the pressure-sensitive adhesive tape from SUS was measured. The results are shown in Table 3.

[0124] (8) Measurement of 180° peel strength from SUS after curing of adhesive layer of adhesive tape Using the same method as in the above-mentioned "(7) Measurement of 180° peel strength from SUS of adhesive tape," the adhesive tape obtained in the above-mentioned "(2) Production of adhesive composition and adhesive tape" was attached to an SUS plate (an SUS304 plate washed with ethanol and then wiped dry), and then aged for 20 minutes at 23°C and 50% RH. Further, using an ultra-high pressure mercury lamp, an illuminance of 100 mW / cm was applied. ２ , wavelength 405nm, illuminance 100mW / cm ２ The cumulative light intensity is 2500 mJ / cm ２ The adhesive tape was attached to a stainless steel plate and irradiated for 25 seconds so that the adhesive layer was cured to prepare a test sample. The obtained test sample was subjected to a tensile test in accordance with JIS Z0237 under conditions of 23°C, 50% RH, a tensile speed of 300 mm / min, and a peel angle of 180°, and the 180° peel strength (N / 25 mm) of the adhesive tape against the stainless steel after the adhesive layer of the adhesive tape had cured was measured. The results are shown in Table 3.

[0125] (9) Measurement of 180° peel strength from SUS after leaving the adhesive tape at high temperature and then curing the adhesive layer A tensile test was carried out in the same manner as in "(8) Measurement of 180° peel strength from SUS after curing of the adhesive layer of the adhesive tape" above, except that a test sample was prepared by laminating an adhesive tape to an SUS plate (a SUS304 plate that had been washed with ethanol and then wiped dry), leaving it to stand at 60°C for 24 hours, and then curing the adhesive layer. The 180° peel strength (N / 25 mm) of the adhesive tape after leaving it at high temperature and then curing the adhesive layer was measured. The results are shown in Table 3.

[0126] <Evaluation> The pressure-sensitive adhesive tapes obtained in the above "(2) Production of pressure-sensitive adhesive composition and pressure-sensitive adhesive tape" were evaluated as follows. The results are shown in Table 3.

[0127] (Adhesive residue after peeling of adhesive tape) In the above-mentioned "(9) Measurement of 180° peel strength from SUS after leaving adhesive tape at high temperature and then curing the adhesive layer," the adhesive residue of the adhesive tape on the SUS plate from which the adhesive tape had been peeled was observed using an optical microscope (Keyence Corporation, "VHX-970F," magnification 10x). Based on the results of observing the adhesive residue of the adhesive tape on the SUS plate, the adhesive residue after peeling of the adhesive tape was evaluated according to the following criteria. A: No adhesive residue was found. B: The adhesive residue was less than 1% of the total area of ​​the adhesive surface with the adhesive tape. C: The adhesive residue was 1% or more and less than 5% of the total area of ​​the adhesive surface with the adhesive tape. D: The adhesive residue was 5% or more of the total area of ​​the adhesive surface with the adhesive tape

[0128] (Examples 2 to 15, 17 to 27, Comparative Examples 1 to 6) Preparation of (meth)acrylic copolymers and production of pressure-sensitive adhesive compositions and pressure-sensitive adhesive tapes were carried out in the same manner as in Example 1, except that in the above-mentioned "(1) Preparation of (meth)acrylic copolymer", the compositions were changed to those shown in Tables 1 and 2, and in the above-mentioned "(2) Production of pressure-sensitive adhesive composition and pressure-sensitive adhesive tape", the compositions of the pressure-sensitive adhesive compositions were changed to those shown in Tables 3 to 6. Measurements and evaluations were carried out for the (meth)acrylic copolymer, the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive tape in the same manner as in Example 1. The results are shown in Tables 1 to 6. Note that, for (meth)acrylic copolymer N in Example 14, the weight-average molecular weight of the (meth)acrylic copolymer was adjusted by carrying out a polymerization reaction using 200 parts by mass of ethyl acetate.

[0129] (Example 16) In the above-mentioned "(1) Preparation of (meth)acrylic copolymer", the composition was set to that shown in Table 1, and in the above-mentioned "(2) Production of pressure-sensitive adhesive composition and pressure-sensitive adhesive tape", the composition of the pressure-sensitive adhesive composition was set to that shown in Table 4. In addition, in the above-mentioned measurements and evaluations of "(6) Measurement of gel fraction after curing of pressure-sensitive adhesive layer", "(8) Measurement of 180° peel strength from SUS after curing of pressure-sensitive adhesive layer of pressure-sensitive adhesive tape", and "(9) Measurement of 180° peel strength from SUS after leaving pressure-sensitive adhesive tape at high temperature and then curing the pressure-sensitive adhesive layer", an ultra-high pressure mercury lamp was used at an illuminance of 100 mW / cm, a wavelength of 405 nm, and an illuminance of 100 mW / cm. ２ The cumulative light intensity is 2500 mJ / cm ２ Instead of irradiating for 25 seconds so as to obtain a value of 1000 ppm, a heat treatment was carried out at 150°C for 10 minutes to cure the pressure-sensitive adhesive layer. Otherwise, the (meth)acrylic copolymer was prepared, and the pressure-sensitive adhesive composition and pressure-sensitive adhesive tape were produced in the same manner as in Example 1, and the (meth)acrylic copolymer, pressure-sensitive adhesive layer, and pressure-sensitive adhesive tape were measured and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 4.

[0130] (Example 28) To the solution of (meth)acrylic copolymer B obtained by the method described above in "(1) Preparation of (meth)acrylic copolymer", 0.2 parts by mass of an isocyanate-based crosslinking agent (manufactured by Soken Chemical & Engineering Co., Ltd., "Coronate L-45K") and 1.0 parts by mass of a photopolymerization initiator (manufactured by IGM Resins, "Omnirad 651") were added relative to 100 parts by mass of the (meth)acrylic copolymer, and then mixed to obtain an ethyl acetate solution of a pressure-sensitive adhesive composition. The ethyl acetate solution of the obtained pressure-sensitive adhesive composition was applied with a doctor knife to a release-treated surface of a 50 μm-thick polyethylene terephthalate (PET) film so that the thickness of the pressure-sensitive adhesive layer after drying would be 30 μm, and then dried at 110 ° C. for 5 minutes to form a pressure-sensitive adhesive layer. Thereafter, the release-treated surface of a 50 μm-thick release-treated polyethylene terephthalate (PET) film was superimposed on the obtained adhesive layer, and the film was left to stand at 40° C. for 5 days for aging to obtain an adhesive tape.

[0131] The measurements and evaluations of Example 28 were carried out as follows: That is, in the above-mentioned "(4) Measurement of the glass transition temperature of the pressure-sensitive adhesive layer," the release PET films on both sides of the obtained pressure-sensitive adhesive tape were peeled off to obtain a plurality of pressure-sensitive adhesive layers, which were then laminated to produce a laminate, and the measurements were carried out in the same manner as in Example 1. Furthermore, with regard to the above-mentioned "(7) Measurement of the 180° peel strength of the pressure-sensitive adhesive tape from SUS," "(8) Measurement of the 180° peel strength of the pressure-sensitive adhesive tape from SUS after the pressure-sensitive adhesive layer has cured," and "(9) Measurement of the 180° peel strength of the pressure-sensitive adhesive tape from SUS after leaving it at high temperature and then curing the pressure-sensitive adhesive layer," the release PET film on one side of the obtained pressure-sensitive adhesive tape was peeled off, the tape was lined with a 23 μm-thick PET film (manufactured by Futamura Chemical Co., Ltd., "FE2002"), and then cut into a width of 25 mm and a length of 75 mm. The other release PET film was peeled off to prepare test pieces, and the 180° peel strength of each test piece from SUS was measured using the same method as in Example 1. All other measurements and evaluations were performed in the same manner as in Example 1. The results are shown in Table 5.

[0132] The abbreviations for the structural unit monomers in Tables 1 and 2 represent the following compounds: n-HexA: n-hexyl acrylate, n-HPA: n-heptyl acrylate, 2-OA: 1-methylheptyl acrylate, n-OA: n-octyl acrylate, IBOA: isobornyl acrylate, LA: lauryl acrylate, STA: stearyl acrylate, BEA: behenyl acrylate, BA: n-butyl acrylate, HEA: 2-hydroxyethyl acrylate, AAc: acrylic acid, MOI: 2-isocyanatoethyl methacrylate

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139] The pressure-sensitive adhesive tapes of the Examples exhibited strong adhesiveness when adhered, and could be peeled off from the adherend with minimal adhesive residue when peeled off.

[0140] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition that exhibits strong adhesiveness when adhered and can be peeled off from an adherend while leaving little adhesive residue when peeled off. Also, according to the present invention, it is possible to provide a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition.

Claims

1. A pressure-sensitive adhesive composition comprising a (meth)acrylic copolymer, wherein the (meth)acrylic copolymer has structural units derived from alkyl (meth)acrylate, the structural units derived from alkyl (meth)acrylate including structural units derived from alkyl (meth)acrylate having an alkyl group with 6 to 9 carbon atoms and structural units derived from alkyl (meth)acrylate having an alkyl group with 10 or more carbon atoms, and the (meth)acrylic copolymer containing a carbon-carbon double bond in a side chain.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the structural units derived from alkyl (meth)acrylate include structural units derived from alkyl (meth)acrylate having an alkyl group having 6 to 8 carbon atoms.

3. The pressure-sensitive adhesive composition according to claim 2, wherein the structural units derived from alkyl (meth)acrylate having an alkyl group with 6 to 8 carbon atoms include structural units derived from alkyl (meth)acrylate having a glass transition temperature of 0°C or lower when made into a homopolymer.

4. The pressure-sensitive adhesive composition according to claim 2 or 3, wherein the structural unit derived from an alkyl (meth)acrylate having an alkyl group having 6 to 8 carbon atoms comprises a structural unit derived from at least one alkyl (meth)acrylate selected from the group consisting of n-hexyl acrylate, n-heptyl acrylate, n-octyl acrylate, and 1-methylheptyl acrylate.

5. A pressure-sensitive adhesive composition according to claim 2, 3 or 4, wherein the content of structural units derived from alkyl (meth)acrylate having an alkyl group having 6 or more and 8 or less carbon atoms in the (meth)acrylic copolymer is 8.0 mass% or more.

6. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4 or 5, wherein the structural units derived from an alkyl (meth)acrylate having an alkyl group with 10 or more carbon atoms include structural units derived from an alkyl (meth)acrylate having a glass transition temperature of -10°C or higher when made into a homopolymer.

7. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5 or 6, wherein the structural unit derived from an alkyl (meth)acrylate having an alkyl group with 10 or more carbon atoms comprises a structural unit derived from an alkyl (meth)acrylate having an alkyl group with 10 or more and 17 or less carbon atoms.

8. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the structural unit derived from an alkyl (meth)acrylate having an alkyl group having 10 or more carbon atoms includes a structural unit derived from at least one alkyl (meth)acrylate selected from the group consisting of isobornyl acrylate and lauryl acrylate.

9. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein the content of structural units derived from alkyl (meth)acrylate having an alkyl group with 10 or more carbon atoms in the (meth)acrylic copolymer is 8.0 mass% or more.

10. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8 or 9, wherein the (meth)acrylic copolymer contains a structural unit derived from a polar functional group-containing monomer.

11. The pressure-sensitive adhesive composition according to claim 10, wherein the total content of structural units derived from the polar functional group-containing monomer in the (meth)acrylic copolymer is 0.01% by mass or more and 30% by mass or less.

12. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, wherein the (meth)acrylic copolymer has a carbon-carbon double bond equivalent of 0.05 meq / g or more.

13. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, wherein the acid value of the (meth)acrylic copolymer is 15.0 mg KOH / g or less.

14. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13, wherein the hydroxyl value of the (meth)acrylic copolymer is 5.0 mgKOH / g or more and 100 mgKOH / g or less.

15. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, wherein the weight-average molecular weight of the (meth)acrylic copolymer is 200,000 or more.

16. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15, further comprising a polymerization initiator.

17. The pressure-sensitive adhesive composition according to claim 16, wherein the polymerization initiator includes a photopolymerization initiator.

18. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or 17, further comprising an inorganic filler.

19. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or 18, further comprising at least one member selected from the group consisting of polyfunctional oligomers and polyfunctional monomers.

20. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or 19, further comprising a gas generating agent.

21. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20, further comprising a tackifier.

22. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or 21, further comprising a crosslinking agent.

23. The pressure-sensitive adhesive composition according to claim 22, 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.

24. An adhesive tape having an adhesive layer formed using the adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 or 23.

25. The adhesive tape according to claim 24, wherein the adhesive layer contains 20% or more of carbon derived from living organisms.

26. The adhesive tape according to claim 24 or 25, wherein the adhesive layer has a glass transition temperature of -10°C or higher as measured by dynamic viscoelasticity measurement at a frequency of 10 Hz.

27. The adhesive tape according to claim 24, 25 or 26, wherein the gel fraction of the adhesive layer is 10% by mass or more and 90% by mass or less.

28. After heating at 150°C for 1 hour, or after irradiating with light of any wavelength in the range of 280 nm to 405 nm with an integrated light intensity of 1000 mJ / cm ２ The pressure-sensitive adhesive tape according to claim 24, 25, 26 or 27, wherein the pressure-sensitive adhesive layer has a gel fraction of 90 mass % or more after irradiation so as to achieve a gel fraction of 90 mass % or more.

29. The adhesive tape according to claim 24, 25, 26, 27 or 28, which has a 180° peel strength from SUS of 8.0 N / 25 mm or more.

30. After heating at 150°C for 1 hour, or after irradiating with light of any wavelength in the range of 280 nm to 405 nm with an integrated light intensity of 1000 mJ / cm ２ The pressure-sensitive adhesive tape according to claim 24, 25, 26, 27, 28 or 29, wherein the 180° peel strength from SUS after irradiation to the above value is 1.0 N / 25 mm or less.

31. After adhering to SUS, the adhesive tape is left at 60°C for 24 hours, and then heated at 150°C for 1 hour. After that, the adhesive tape is exposed to light with a wavelength of 280 nm or more and 405 nm or less with an integrated light intensity of 1000 mJ / cm. ２ The pressure-sensitive adhesive tape according to claim 24, 25, 26, 27, 28, 29 or 30, wherein the 180° peel strength of the pressure-sensitive adhesive tape from SUS after irradiation to the above value is 1.5 N / 25 mm or less.

32. The adhesive tape according to claim 24, 25, 26, 27, 28, 29, 30 or 31, which has a substrate and has the adhesive layer on at least one surface of the substrate.

33. The adhesive tape according to claim 24, 25, 26, 27, 28, 29, 30, 31 or 32, which is used to fix electronic equipment components.

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