Adhesive composition and adhesive tape

Abstract

To provide an adhesive composition which enables formation of an adhesive layer having excellent adhesive force and retention force under high temperature environment, and considers the environment.SOLUTION: There are provided an adhesive composition which contains a (meth)acrylic copolymer containing a constitutional unit derived from an alkyl (meth)acrylate ester monomer (A) having an alkyl moiety having at least 12 carbon atoms and a biomass degree of 70% or more in an amount of 30-89 mass% with respect to the total constitutional unit, a constitutional unit derived from an alkyl (meth)acrylate ester monomer (B) having an alkyl moiety having 1 to 10 carbon atoms and a glass transition temperature as a homopolymer of -30°C or higher in an amount of 10-50 mass% with respect to the total constitutional unit, and a constitutional unit derived from a monomer having a hydroxyl group in an amount of 1-10 mass% with respect to the total constitutional unit, a tackifier resin, and a crosslinking agent, wherein a content of the tackifier resin is 10-55 pts.mass with respect to 100 pts.mass of the (meth)acrylic copolymer; and an adhesive tape.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive tape. [Background technology]

[0002] In recent years, with growing interest in environmental issues such as global warming, products that use reusable organic resources derived from living organisms (also referred to as "biomass") as raw materials have been attracting attention. In the field of pressure-sensitive adhesives, development of products that use biomass raw materials has also been progressing, and pressure-sensitive adhesive compositions and pressure-sensitive adhesive tapes that contain a high proportion of biomass raw materials, so-called high biomass content, have also been reported.

[0003] For example, Patent Document 1 discloses a pressure-sensitive adhesive composition that includes an acrylic pressure-sensitive adhesive containing an acrylic polymer, where the acrylic polymer is a polymer of a monomer component containing more than 50% by weight of an acrylic monomer, and where 50% or more of the total carbon contained in the acrylic pressure-sensitive adhesive is biomass-derived carbon. Furthermore, Patent Document 2 discloses an adhesive tape having an adhesive layer containing a (meth)acrylic copolymer including a structural unit derived from a (meth)acrylic monomer containing bio-derived carbon, wherein the bio-derived carbon content of the adhesive tape is 30% by weight or more. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-105308 [Patent Document 2] Japanese Patent Application Publication No. 2019-218458 Summary of the Invention [Problem to be solved by the invention]

[0005] Adhesive tapes are widely used to fasten objects in electronic devices, vehicles, furniture, etc. In particular, electronic devices and vehicles are prone to high temperatures due to their own heat generation and exposure to high-temperature environments. Therefore, the adhesive layer of the adhesive tape is required to have excellent adhesive strength and holding power even in high-temperature environments. On the other hand, as mentioned above, from the viewpoint of global environmental conservation, there is a demand for the development of pressure-sensitive adhesive tapes that use biomass raw materials and reduce the amount of petroleum resources used.

[0006] An object of one embodiment of the present disclosure is to provide an environmentally friendly pressure-sensitive adhesive composition that can form a pressure-sensitive adhesive layer that has excellent adhesive strength and holding power in a high-temperature environment. Another problem to be solved by another embodiment of the present disclosure is to provide an environmentally friendly adhesive tape that includes an adhesive layer that has excellent adhesive strength and holding power in high-temperature environments. [Means for solving the problem]

[0007] Specific means for solving the problems include the following aspects. <1> a (meth)acrylic copolymer containing 30% by mass to 89% by mass of structural units derived from a (meth)acrylic acid alkyl ester monomer (A) having 12 or more carbon atoms in the alkyl moiety and having a biomass degree of 70% or more, based on all structural units; 10% by mass to 50% by mass of structural units derived from a (meth)acrylic acid alkyl ester monomer (B) having 1 to 10 carbon atoms in the alkyl moiety and having a glass transition temperature of −30° C. or higher when made into a homopolymer; and 1% by mass to 10% by mass of structural units derived from a monomer having a hydroxyl group, based on all structural units; a tackifying resin; and a cross-linking agent; Including, The pressure-sensitive adhesive composition has a content of the tackifier resin of 10 to 55 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer. <2> The number of carbon atoms in the alkyl moiety of the (meth)acrylic acid alkyl ester monomer (B) is 1 or 2. <1> The pressure-sensitive adhesive composition according to claim 1. <3> The softening point of the tackifier resin is 90°C to 160°C. <1> or <2> The pressure-sensitive adhesive composition according to claim 1. <4> The content of the tackifier resin is 20 parts by mass to 45 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer. <1> ~ <3> The pressure-sensitive adhesive composition according to any one of the above. <5> The tackifier resin is a terpene resin. <1> ~ <4> The pressure-sensitive adhesive composition according to any one of the above. <6> The content of the crosslinking agent is 0.1 to 1.0 parts by mass relative to 100 parts by mass of the (meth)acrylic copolymer. <1> ~ <5> The pressure-sensitive adhesive composition according to any one of the above. <7> a substrate; and a film provided on the substrate; <1> ~ <6> and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of the above. [Effects of the Invention]

[0008] According to one embodiment of the present disclosure, there is provided an environmentally friendly PSA composition that can form a PSA layer that has excellent adhesive strength and holding power in a high-temperature environment. According to another embodiment of the present disclosure, there is provided an environmentally friendly adhesive tape that includes an adhesive layer that has excellent adhesive strength and holding power in a high-temperature environment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The pressure-sensitive adhesive composition and pressure-sensitive adhesive tape of the present disclosure will be described in detail below. The following description of the requirements may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments and can be implemented with appropriate modifications within the scope of the object of the present disclosure.

[0010] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.

[0011] In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, when the PSA composition contains a plurality of substances corresponding to each component, the amount of each component in the PSA composition means the total amount of the plurality of substances present in the PSA composition, unless otherwise specified.

[0012] In the present disclosure, "(meth)acrylic copolymer" means a copolymer in which the content of structural units derived from monomers having a (meth)acryloyl group is 50 mass% or more of all structural units (i.e., all structural units of the (meth)acrylic copolymer).

[0013] In the present disclosure, "(meth)acrylic" is a term that encompasses both "acrylic" and "methacrylic," "(meth)acrylate" is a term that encompasses both "acrylate" and "methacrylate," and "(meth)acryloyl" is a term that encompasses both "acryloyl" and "methacryloyl."

[0014] In this disclosure, "n-" means normal, "i-" means iso, "s-" means secondary, and "t-" means tertiary.

[0015] In the present disclosure, the "glass transition temperature when converted into a homopolymer" refers to a value described in a publicly known document or a value measured using a differential scanning calorimeter (DSC). The specific value to be used is as follows:

[0016] The "glass transition temperature when made into a homopolymer" of the following monomers is determined by the value shown below. 2-Ethylhexyl acrylate: -70°C, 2-ethylhexyl methacrylate: -10°C, n-butyl acrylate: -54°C, n-butyl methacrylate: 20°C, t-butyl acrylate: 43°C, t-butyl methacrylate: 118°C, i-butyl methacrylate: 53°C, methyl acrylate: 10°C, methyl methacrylate: 105°C, ethyl acrylate: -22°C, ethyl methacrylate: 65°C, methacrylic acid: 228°C, 4-hydroxybutyl acrylate: -80°C, 2-hydroxyethyl acrylate: -15°C, 2-hydroxyethyl methacrylate: 85°C, acrylic acid: 106°C, n-octyl acrylate: -65°C, stearyl acrylate: 30°C, stearyl methacrylate: 38°C, lauryl acrylate: -3°C, lauryl methacrylate: -65°C, dimethylaminoethyl methacrylate: 18°C, ω-carboxy-polycaprolactone (n≒2) monoacrylate: -30°C.

[0017] Regarding the "glass transition temperature when made into a homopolymer" of a monomer other than the above-mentioned monomers, the value described in the Polymer Handbook (4th edition, Wiley-Interscience; the same applies hereinafter) is adopted. If there is no description in the Polymer Handbook, the value of the glass transition temperature of the homopolymer obtained by the following measurement method is adopted.

[0018] <<Measurement of the glass transition temperature of homopolymers>> Using a differential scanning calorimeter (DSC), measurements are taken in a nitrogen stream using 10 mg of a sample (i.e., homopolymer) at a heating rate of 10°C / min. The inflection point of the resulting DSC curve is taken as the glass transition temperature of the homopolymer. A suitable differential scanning calorimeter is, for example, a differential scanning calorimeter (trade name: Discovery DSC 2500) manufactured by TA Instruments Japan, Inc. However, the differential scanning calorimeter is not limited to this.

[0019] [Adhesive composition] The pressure-sensitive adhesive composition of the present disclosure comprises a (meth)acrylic copolymer (hereinafter also referred to as a "specific (meth)acrylic copolymer") containing 30% to 89% by mass of structural units derived from a (meth)acrylic acid alkyl ester monomer (A) having 12 or more carbon atoms in the alkyl moiety and a biomass content of 70% or more, 10% to 50% by mass of structural units derived from a (meth)acrylic acid alkyl ester monomer (B) having 1 to 10 carbon atoms in the alkyl moiety and having a glass transition temperature of -30°C or higher when made into a homopolymer, and 1% to 10% by mass of structural units derived from a monomer having a hydroxyl group, a tackifier resin, and a crosslinking agent, wherein the content of the tackifier resin is 10 to 55 parts by mass per 100 parts by mass of the (meth)acrylic copolymer. The pressure-sensitive adhesive composition of the present disclosure, having the above-described structure, can form a pressure-sensitive adhesive layer having excellent adhesive strength and holding power even in a high-temperature environment. The pressure-sensitive adhesive composition of the present disclosure uses a relatively large amount of (meth)acrylic acid alkyl ester monomer (A) having a biomass content of 70% or more as a raw material, and is an environmentally friendly pressure-sensitive adhesive composition.

[0020] [Specific (meth)acrylic copolymer] The pressure-sensitive adhesive composition of the present disclosure comprises a (meth)acrylic copolymer (i.e., a specific (meth)acrylic copolymer) containing 30% by mass to 89% by mass of structural units derived from a (meth)acrylic acid alkyl ester monomer (A) having 12 or more carbon atoms in the alkyl moiety and having a biomass degree of 70% or more, relative to all structural units; 10% by mass to 50% by mass of structural units derived from a (meth)acrylic acid alkyl ester monomer (B) having 1 to 10 carbon atoms in the alkyl moiety and having a glass transition temperature of −30° C. or higher when made into a homopolymer; and 1% by mass to 10% by mass of structural units derived from a monomer having a hydroxyl group, relative to all structural units. The pressure-sensitive adhesive composition of the present disclosure may contain only one type of specific (meth)acrylic copolymer, or may contain two or more types.

[0021] <Structural Unit Derived from (Meth)acrylic Acid Alkyl Ester Monomer (A)> The specific (meth)acrylic copolymer contains 30% by mass to 89% by mass of structural units derived from a (meth)acrylic acid alkyl ester monomer (A) having 12 or more carbon atoms in the alkyl moiety and a biomass degree of 70% or more, based on all structural units.

[0022] In the present disclosure, "a structural unit derived from a (meth)acrylic acid alkyl ester monomer (A) having 12 or more carbon atoms in the alkyl portion and a biomass degree of 70% or more" means a structural unit formed by addition polymerization of a (meth)acrylic acid alkyl ester monomer (A) having 12 or more carbon atoms in the alkyl portion and a biomass degree of 70% or more. The "(meth)acrylic acid alkyl ester monomer (A)" in the present disclosure does not include monomers that fall under the category of monomers having a hydroxyl group, which will be described later.

[0023] The (meth)acrylic acid alkyl ester monomer (A) may be an acrylic acid alkyl ester monomer or a methacrylic acid alkyl ester monomer. The (meth)acrylic acid alkyl ester monomer (A) is preferably an unsubstituted (meth)acrylic acid alkyl ester monomer. The alkyl group contained in the (meth)acrylic acid alkyl ester monomer (A) is preferably linear.

[0024] The number of carbon atoms in the alkyl group of the (meth)acrylic acid alkyl ester monomer (A) is not particularly limited as long as it is 12 or more. However, from the viewpoint of suitability for producing the specific (meth)acrylic copolymer, for example, it is preferably 22 or less, and more preferably 20 or less. Specific examples of alkyl groups having 12 or more carbon atoms include lauryl, myristyl, cetyl, stearyl, and eicosyl groups.

[0025] The (meth)acrylic acid alkyl ester monomer (A) has a biomass degree of 70% or more, and therefore is an environmentally friendly component with a small load on the global environment. From the viewpoint of realizing an environmentally friendly pressure-sensitive adhesive composition, the upper limit of the biomass degree of the (meth)acrylic acid alkyl ester monomer (A) is not particularly limited. The biomass degree of the (meth)acrylic acid alkyl ester monomer (A) in the present disclosure is a value measured by a method in accordance with ASTM D6866-20, and means the mass proportion of carbon derived from biomass to the total carbon contained in the (meth)acrylic acid alkyl ester monomer (A).

[0026] Specific examples of the (meth)acrylic acid alkyl ester monomer (A) include lauryl acrylate (number of carbon atoms in the alkyl group: 12, biomass degree: 76.0%), lauryl methacrylate (number of carbon atoms in the alkyl group: 12, biomass degree: 71.4%), myristyl acrylate (number of carbon atoms in the alkyl group: 14, biomass degree: 78.3%), myristyl methacrylate (number of carbon atoms in the alkyl group: 14, biomass degree: 74.1%), cetyl acrylate (number of carbon atoms in the alkyl group: 16, biomass degree: 75.5%), and the like. Biomass degree: 80.1%], cetyl methacrylate [number of carbon atoms in alkyl group: 16, biomass degree: 76.4%], stearyl acrylate [number of carbon atoms in alkyl group: 18, biomass degree: 81.7%], stearyl methacrylate [number of carbon atoms in alkyl group: 18, biomass degree: 78.3%], eicosyl acrylate [number of carbon atoms in alkyl group: 20, biomass degree: 83.1%], and eicosyl methacrylate [number of carbon atoms in alkyl group: 20, biomass degree: 79.9%]. The (meth)acrylic acid alkyl ester monomer (A) is preferably at least one selected from the group consisting of lauryl acrylate, lauryl methacrylate, and stearyl acrylate, more preferably at least one selected from lauryl acrylate and lauryl methacrylate, and even more preferably lauryl acrylate.

[0027] The specific (meth)acrylic copolymer may contain only one type of structural unit derived from the (meth)acrylic acid alkyl ester monomer (A), or may contain two or more types.

[0028] The content of the structural units derived from the (meth)acrylic acid alkyl ester monomer (A) in the specific (meth)acrylic copolymer is 30% by mass to 89% by mass based on the total structural units of the specific (meth)acrylic copolymer. When the content of structural units derived from the (meth)acrylic acid alkyl ester monomer (A) in the specific (meth)acrylic copolymer is 30% by mass or more relative to the total structural units of the specific (meth)acrylic copolymer, a pressure-sensitive adhesive layer having excellent adhesive strength in high-temperature environments can be formed. This is thought to be because the low polarity of the specific (meth)acrylic copolymer due to the low polarity of the (meth)acrylic acid alkyl ester monomer (A) improves the compatibility between the specific (meth)acrylic copolymer and the tackifier resin, allowing the tackifier resin to fully exert its effects. From this perspective, the content of structural units derived from the (meth)acrylic acid alkyl ester monomer (A) in the specific (meth)acrylic copolymer is 30% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more relative to the total structural units of the specific (meth)acrylic copolymer. The content of the structural units derived from the (meth)acrylic acid alkyl ester monomer (A) in the specific (meth)acrylic copolymer is 89 mass% or less, preferably 85 mass% or less, more preferably 83 mass% or less, and even more preferably 80 mass% or less, based on the total structural units of the specific (meth)acrylic copolymer.

[0029] <Structural Unit Derived from (Meth)acrylic Acid Alkyl Ester Monomer (B)> The specific (meth)acrylic copolymer contains 10% by mass to 50% by mass of structural units derived from a (meth)acrylic acid alkyl ester monomer (B) having 1 to 10 carbon atoms in the alkyl moiety and having a glass transition temperature of −30° C. or higher when made into a homopolymer.

[0030] In the present disclosure, "a structural unit derived from a (meth)acrylic acid alkyl ester monomer (B) having 1 to 10 carbon atoms in the alkyl moiety and having a glass transition temperature of -30°C or higher when made into a homopolymer" means a structural unit formed by addition polymerization of a (meth)acrylic acid alkyl ester monomer (B) having 1 to 10 carbon atoms in the alkyl moiety and having a glass transition temperature of -30°C or higher when made into a homopolymer. The "(meth)acrylic acid alkyl ester monomer (B)" in the present disclosure does not include monomers that fall under the category of monomers having a hydroxyl group, which will be described later.

[0031] The (meth)acrylic acid alkyl ester monomer (B) may be an acrylic acid alkyl ester monomer or a methacrylic acid alkyl ester monomer. The (meth)acrylic acid alkyl ester monomer (B) is preferably an unsubstituted (meth)acrylic acid alkyl ester monomer. The alkyl group contained in the (meth)acrylic acid alkyl ester monomer (B) may be linear, branched, or cyclic, but is preferably linear.

[0032] The alkyl group of the (meth)acrylic acid alkyl ester monomer (B) has 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2 carbon atoms. The (meth)acrylic acid alkyl ester monomer (B) tends to more easily cause entanglement of the specific (meth)acrylic copolymers with each other as the number of carbon atoms in the alkyl group decreases. When the specific (meth)acrylic copolymers become entangled with each other, cohesive force is generated in the pressure-sensitive adhesive layer. Therefore, when the number of carbon atoms in the alkyl group of the (meth)acrylic acid alkyl ester monomer (B) is 1 or 2, the adhesive strength of the pressure-sensitive adhesive layer in a high-temperature environment tends to be more easily increased.

[0033] The glass transition temperature of the (meth)acrylic acid alkyl ester monomer (B) when made into a homopolymer is -30°C or higher. If the glass transition temperature of the (meth)acrylic acid alkyl ester monomer (B) when made into a homopolymer is -30°C or higher, the pressure-sensitive adhesive layer that is formed tends to be easily imparted with cohesive strength. From this viewpoint, the glass transition temperature of the (meth)acrylic acid alkyl ester monomer (B) when made into a homopolymer is -30°C or higher, preferably -20°C or higher, more preferably -10°C or higher, and even more preferably 0°C or higher. The upper limit of the glass transition temperature of the homopolymer of the (meth)acrylic acid alkyl ester monomer (B) is not particularly limited, but is preferably, for example, 70° C. or lower.

[0034] Specific examples of the (meth)acrylic acid alkyl ester monomer (B) include methyl acrylate (number of carbon atoms in the alkyl group: 1, glass transition temperature when homopolymerized: 10°C), methyl methacrylate (number of carbon atoms in the alkyl group: 1, glass transition temperature when homopolymerized: 105°C), ethyl acrylate (number of carbon atoms in the alkyl group: 2, glass transition temperature when homopolymerized: -22°C), ethyl methacrylate (number of carbon atoms in the alkyl group: 2, glass transition temperature when homopolymerized: 65°C), n-butyl methacrylate (number of carbon atoms in the alkyl group: [number of carbon atoms in the alkyl group: 4, glass transition temperature when homopolymerized: 20°C], t-butyl acrylate [number of carbon atoms in the alkyl group: 4, glass transition temperature when homopolymerized: 43°C], t-butyl methacrylate [number of carbon atoms in the alkyl group: 4, glass transition temperature when homopolymerized: 118°C], i-butyl methacrylate [number of carbon atoms in the alkyl group: 4, glass transition temperature when homopolymerized: 53°C], and 2-ethylhexyl methacrylate [number of carbon atoms in the alkyl group: 8, glass transition temperature when homopolymerized: -10°C]. The (meth)acrylic acid alkyl ester monomer (B) is preferably at least one selected from methyl acrylate and ethyl acrylate, and more preferably methyl acrylate.

[0035] The specific (meth)acrylic copolymer may contain only one type of structural unit derived from the (meth)acrylic acid alkyl ester monomer (B), or may contain two or more types.

[0036] The content of the structural units derived from the (meth)acrylic acid alkyl ester monomer (B) in the specific (meth)acrylic copolymer is 10% by mass to 50% by mass based on the total structural units of the specific (meth)acrylic copolymer. When the content of the structural units derived from the (meth)acrylic acid alkyl ester monomer (B) in the specific (meth)acrylic copolymer is 10% by mass or more relative to the total structural units of the specific (meth)acrylic copolymer, a pressure-sensitive adhesive layer having excellent adhesive strength in a high-temperature environment can be formed. This is thought to be because the pressure-sensitive adhesive layer formed is imparted with an appropriate cohesive strength. From this perspective, the content of the structural units derived from the (meth)acrylic acid alkyl ester monomer (B) in the specific (meth)acrylic copolymer is 10% by mass or more relative to the total structural units of the specific (meth)acrylic copolymer, preferably 12% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. When the content of the structural units derived from the (meth)acrylic acid alkyl ester monomer (B) in the specific (meth)acrylic copolymer is 50% by mass or less relative to the total structural units of the specific (meth)acrylic copolymer, a pressure-sensitive adhesive layer having excellent adhesive strength in a high-temperature environment can be formed. This is thought to be because the resulting pressure-sensitive adhesive layer has improved wettability to the adherend. From this perspective, the content of the structural units derived from the (meth)acrylic acid alkyl ester monomer (B) in the specific (meth)acrylic copolymer is 50% by mass or less relative to the total structural units of the specific (meth)acrylic copolymer, preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0037] <Structural Units Derived from Monomers Having a Hydroxyl Group> The specific (meth)acrylic copolymer contains 1% by mass to 10% by mass of structural units derived from monomers having a hydroxyl group, based on the total structural units. The hydroxyl group of the structural unit derived from the monomer having a hydroxyl group can contribute to crosslinking with the crosslinking agent described below.

[0038] In the present disclosure, the term "structural unit derived from a monomer having a hydroxyl group" refers to a structural unit formed by addition polymerization of a monomer having a hydroxyl group.

[0039] The type of the hydroxyl group-containing monomer is not particularly limited. Examples of the monomer having a hydroxyl group include a monomer having at least one hydroxyl group and an ethylenically unsaturated group in one molecule. The type of ethylenically unsaturated group is not particularly limited. Specific examples of the ethylenically unsaturated group include a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group. The ethylenically unsaturated group is preferably a (meth)acryloyl group.

[0040] Specific examples of monomers having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1-dimethyl-3-hydroxybutyl (meth)acrylate, 1,3-dimethyl-3-hydroxybutyl (meth)acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth)acrylate, 2-ethyl-3-hydroxyhexyl (meth)acrylate, N-hydroxyethyl (meth)acrylamide, glycerin mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, and poly(ethylene glycol-propylene glycol) mono(meth)acrylate. The monomer having a hydroxyl group is preferably a hydroxyalkyl(meth)acrylate from the viewpoint of good copolymerizability with other monomers, more preferably a hydroxyalkyl(meth)acrylate having a hydroxyalkyl group with 1 to 5 carbon atoms, even more preferably a hydroxyalkyl(meth)acrylate having a hydroxyalkyl group with 2 to 4 carbon atoms, and particularly preferably 2-hydroxyethyl acrylate, from the viewpoint of good compatibility with other monomers and good reactivity with crosslinking agents (particularly isocyanate-based crosslinking agents).

[0041] The specific (meth)acrylic copolymer may contain only one type of structural unit derived from a monomer having a hydroxyl group, or may contain two or more types.

[0042] The content of the structural units derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer is 1% by mass to 10% by mass based on the total structural units of the specific (meth)acrylic copolymer. When the content of structural units derived from monomers having a hydroxyl group in the specific (meth)acrylic copolymer is 1% by mass or more relative to the total structural units of the specific (meth)acrylic copolymer, a pressure-sensitive adhesive layer having excellent holding power in a high-temperature environment can be formed. This is thought to be because the cohesive strength of the pressure-sensitive adhesive layer formed is sufficiently high. From this perspective, the content of structural units derived from monomers having a hydroxyl group in the specific (meth)acrylic copolymer is 1% by mass or more relative to the total structural units of the specific (meth)acrylic copolymer, preferably 1.5% by mass or more, more preferably 2% by mass or more, and even more preferably 2.5% by mass or more. When the content of structural units derived from monomers having a hydroxyl group in the specific (meth)acrylic copolymer is 10% by mass or less relative to the total structural units of the specific (meth)acrylic copolymer, a pressure-sensitive adhesive layer having excellent adhesive strength in high-temperature environments can be formed. This is thought to be because the compatibility between the specific (meth)acrylic copolymer and the tackifier resin is improved, allowing the effects of the tackifier resin to be fully exerted. From this perspective, the content of structural units derived from monomers having a hydroxyl group in the specific (meth)acrylic copolymer is 10% by mass or less relative to the total structural units of the specific (meth)acrylic copolymer, preferably 8% by mass or less, more preferably 7% by mass or less, and even more preferably 6% by mass or less.

[0043] <Other Structural Units Derived from (Meth)acrylic Acid Alkyl Ester Monomers> The specific (meth)acrylic copolymer may contain a structural unit derived from a (meth)acrylic acid alkyl ester monomer other than the (meth)acrylic acid alkyl ester monomer (A) and the (meth)acrylic acid alkyl ester monomer (B) (so-called other (meth)acrylic acid alkyl ester monomer).

[0044] In the present disclosure, the term "structural units derived from other (meth)acrylic acid alkyl ester monomers" refers to structural units formed by addition polymerization of other (meth)acrylic acid alkyl ester monomers. The "other (meth)acrylic acid alkyl ester monomers" in the present disclosure do not include monomers that fall under the category of the above-mentioned monomers having a hydroxyl group.

[0045] The other (meth)acrylic acid alkyl ester monomer may be an acrylic acid alkyl ester monomer or a methacrylic acid alkyl ester monomer. The other (meth)acrylic acid alkyl ester monomer is preferably an unsubstituted (meth)acrylic acid alkyl ester monomer. The alkyl group contained in the other (meth)acrylic acid alkyl ester monomer may be linear, branched, or cyclic, but is preferably linear.

[0046] The number of carbon atoms in the alkyl group of the other (meth)acrylic acid alkyl ester monomer is not particularly limited, but is preferably 4 to 10.

[0047] Other specific examples of the (meth)acrylic acid alkyl ester monomer include n-butyl acrylate, n-octyl acrylate, and n-nonyl acrylate. The other (meth)acrylic acid alkyl ester monomer is preferably n-butyl acrylate.

[0048] When the specific (meth)acrylic copolymer contains a structural unit derived from another (meth)acrylic acid alkyl ester monomer, the structural unit may contain only one type of structural unit derived from another (meth)acrylic acid alkyl ester monomer, or may contain two or more types of structural units derived from another (meth)acrylic acid alkyl ester monomer.

[0049] When the specific (meth)acrylic copolymer contains structural units derived from other (meth)acrylic acid alkyl ester monomers, the content of the structural units derived from other (meth)acrylic acid alkyl ester monomers is not particularly limited, but is, for example, preferably 5% by mass to 45% by mass, more preferably 8% by mass to 40% by mass, and even more preferably 10% by mass to 40% by mass, relative to the total structural units of the specific (meth)acrylic copolymer.

[0050] <Other structural units> The specific (meth)acrylic copolymer may contain structural units (so-called other structural units) other than the structural units described above, as needed, within the scope that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0051] Examples of monomers constituting other structural units include monomers having a carboxy group, such as acrylic acid and methacrylic acid, (meth)acrylates having an aromatic ring, such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate, alkoxyalkyl (meth)acrylates, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, aromatic monovinyls, such as styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene, vinyl cyanides, such as acrylonitrile and methacrylonitrile, and vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate. Also, examples of monomers constituting other structural units include various derivatives of these monomers.

[0052] When the specific (meth)acrylic copolymer contains other structural units, it may contain only one type of other structural unit, or may contain two or more types of other structural units.

[0053] When the specific (meth)acrylic copolymer contains other structural units, the content of the other structural units can be appropriately set depending on the purpose, as long as the effects of the pressure-sensitive adhesive composition of the present disclosure are not impaired.

[0054] <<Weight-average molecular weight of specific (meth)acrylic copolymer>> The weight average molecular weight (hereinafter also referred to as "Mw") of the specific (meth)acrylic copolymer is not particularly limited, but is, for example, preferably 300,000 to 2,000,000, more preferably 400,000 to 1,800,000, even more preferably 450,000 to 1,500,000, and particularly preferably 500,000 to 1,000,000. When the weight average molecular weight of the specific (meth)acrylic copolymer is 300,000 or more, the adhesive strength of the pressure-sensitive adhesive layer formed in a high-temperature environment tends to be further increased. When the weight average molecular weight of the specific (meth)acrylic copolymer is 2,000,000 or less, the viscosity of the pressure-sensitive adhesive composition does not increase excessively, and the pressure-sensitive adhesive composition tends to have better coatability.

[0055] The weight average molecular weight of the specific (meth)acrylic copolymer is a value measured by the following method, specifically, according to the following (1) to (3). (1) A solution of the specific (meth)acrylic copolymer is applied to a release paper and dried at 100° C. for 1 minute to obtain a film of the specific (meth)acrylic copolymer. (2) Using the film-like specific (meth)acrylic copolymer obtained in (1) above and tetrahydrofuran, a sample solution having a solids concentration of 0.2% by mass is obtained. Note that the "solids concentration" here refers to the mass proportion of the specific (meth)acrylic copolymer in the sample solution. (3) The weight average molecular weight of the specific (meth)acrylic copolymer is determined as a standard polystyrene equivalent value by gel permeation chromatography (GPC) under the following conditions.

[0056] ~Conditions~ Measurement equipment: High-speed GPC [Model: HLC-8220 GPC, manufactured by Tosoh Corporation] Detector: Differential refractometer (RI) [built into HLC-8220, manufactured by Tosoh Corporation] Column: TSKgel GMH XL Four Tosoh Corporation products are used. Column temperature: 40℃ Eluent: tetrahydrofuran Sample solution injection volume: 100 μL Flow rate: 0.8mL / min

[0057] The weight average molecular weight of the specific (meth)acrylic copolymer can be adjusted to a desired value by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc. when polymerizing the monomers.

[0058] <<Biomass content of specific (meth)acrylic copolymers>> The biomass degree of the specific (meth)acrylic copolymer is not particularly limited, but from the viewpoint of realizing a more environmentally friendly pressure-sensitive adhesive composition, it is preferably 25% or more, more preferably 30% or more, even more preferably 35% or more, and particularly preferably 40% or more. The upper limit of the biomass degree of the specific (meth)acrylic copolymer may be, for example, 75% or less, 70% or less, or 65% or less.

[0059] The biomass content of the specific (meth)acrylic copolymer is a value measured by a method in accordance with ASTM D6866-20, and means the mass proportion of biomass-derived carbon in the total carbon contained in the specific (meth)acrylic copolymer.

[0060] <<Specific (meth)acrylic copolymer content>> The content of the specific (meth)acrylic copolymer in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, but is, for example, preferably 64.1 mass % to 90.8 mass %, more preferably 68.8 mass % to 86.7 mass %, even more preferably 71.3 mass % to 86.7 mass %, and particularly preferably 73.9 mass % to 83.1 mass %, relative to the total solid content in the pressure-sensitive adhesive composition.

[0061] In the present disclosure, the "total solid content in the PSA composition" means the total mass of the PSA composition when the PSA composition does not contain a solvent, and means the mass of the residue remaining after removing the solvent from the PSA composition when the PSA composition contains a solvent. In this disclosure, "solvent" means water and organic solvents.

[0062] [Method for producing specific (meth)acrylic polymer] The method for producing the specific (meth)acrylic copolymer is not particularly limited. The specific (meth)acrylic copolymer can be produced by polymerizing the above-mentioned monomers by a known polymerization method typified by, for example, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, or a bulk polymerization method. As the polymerization method, a solution polymerization method is preferred in that the processing steps for preparing the pressure-sensitive adhesive composition after production are relatively simple and can be carried out in a short time.

[0063] In the solution polymerization method, a predetermined organic solvent, monomers, a polymerization initiator, and an optional chain transfer agent are generally charged into a polymerization vessel and reacted by heating for several hours with stirring, for example, at the reflux temperature of the organic solvent. In this case, at least a portion of the organic solvent, monomers, polymerization initiator, and optional chain transfer agent may be added sequentially. Alternatively, the reaction may be carried out in a nitrogen gas stream.

[0064] Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds, aliphatic hydrocarbon compounds, alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, and alcohol compounds. More specifically, examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds such as benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha; aliphatic or alicyclic hydrocarbon compounds such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and turpentine; ester compounds such as methyl acetate, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; acetone; Examples of the alcohol compounds include ketone compounds typified by ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohexanone; glycol ether compounds typified by ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; and alcohol compounds typified by methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol.

[0065] In producing the specific (meth)acrylic copolymer, it is preferable to use an organic solvent that is unlikely to cause chain transfer during the polymerization reaction, such as an aromatic hydrocarbon compound, an ester compound, or a ketone compound. In particular, it is preferable to use ethyl acetate from the viewpoints of the solubility of the specific (meth)acrylic copolymer, ease of the polymerization reaction, etc.

[0066] During the polymerization reaction, only one type of organic solvent may be used, or two or more types may be used.

[0067] Examples of the polymerization initiator include organic peroxides and azo compounds that are used in ordinary solution polymerization methods. Specific examples of organic peroxides include t-butyl peroxy-2-ethylhexanoate, t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 2,2-bis(4,4-di-t-butylperoxysilane), peroxycyclohexyl)propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane. Specific examples of azo compounds include 2,2'-azobisisobutyronitrile [AIBN], 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN], 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), and 2,2'-azobis(isobutyrate) dimethyl. In producing the specific (meth)acrylic copolymer, it is preferable to use a polymerization initiator that does not cause a graft reaction during the polymerization reaction, and it is particularly preferable to use an azo compound.

[0068] In the polymerization reaction, only one type of polymerization initiator may be used, or two or more types may be used.

[0069] The amount of the polymerization initiator used is not particularly limited, and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic copolymer.

[0070] In producing the specific (meth)acrylic copolymer, a chain transfer agent may be used as needed. Examples of the chain transfer agent include cyanoacetic acid, alkyl ester compounds of cyanoacetic acid having 1 to 8 carbon atoms, bromoacetic acid, alkyl ester compounds of bromoacetic acid having 1 to 8 carbon atoms, aromatic compounds such as α-methylstyrene, anthracene, phenanthrene, fluorene, and 9-phenylfluorene, aromatic nitro compounds such as p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene, benzoquinone derivatives such as benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives such as tributylborane, carbon tetrabromide, tetrabromide, tetrachloromethane, benzoquinone derivatives such as benzoquinone ... Examples of such compounds include halogenated hydrocarbon compounds such as carbon chloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene, aldehyde compounds such as chloral and furaldehyde, alkyl mercaptan compounds having 1 to 18 carbon atoms, aromatic mercaptan compounds such as thiophenol and toluene mercaptan, mercaptoacetic acid, alkyl ester compounds of mercaptoacetic acid having 1 to 10 carbon atoms, hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms, and terpene compounds such as pinene and terpinolene.

[0071] When a chain transfer agent is used in producing the specific (meth)acrylic copolymer, the amount of the chain transfer agent used is not particularly limited and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic copolymer.

[0072] The polymerization temperature is not particularly limited and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic copolymer.

[0073] [Tackifying resin] The pressure-sensitive adhesive composition of the present disclosure contains a tackifying resin. The content of the tackifier resin in the pressure-sensitive adhesive composition of the present disclosure is 10 to 55 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer.

[0074] In the present disclosure, the term "tackifying resin" refers to a resin that has the property of being able to impart tackiness when blended and has a molecular weight of less than 10,000 (preferably in the range of 500 or more and less than 10,000). Also, "tackiness" refers to a sticky property. The "tackifying resin" in the present disclosure does not include those that fall under the category of specific (meth)acrylic copolymers.

[0075] The molecular weight of the tackifier resin is a value measured by gel permeation chromatography (GPC). Specifically, the weight average molecular weight of the tackifier resin is determined as a standard polystyrene equivalent value by gel permeation chromatography (GPC) under the following conditions.

[0076] ~Conditions~ Measurement equipment: High-speed GPC [Model: HLC-8220 GPC, manufactured by Tosoh Corporation] Detector: Differential refractometer (RI) [built into HLC-8220, manufactured by Tosoh Corporation] Column: TSKgel GMH XL Four Tosoh Corporation products are used. Column temperature: 40℃ Eluent: tetrahydrofuran Sample solution injection volume: 100 μL Flow rate: 0.8mL / min

[0077] However, when a commercially available product is used as the tackifying resin and the molecular weight is listed in the catalog of the commercially available product, the value in the catalog of the commercially available product is used as the molecular weight of the tackifying resin.

[0078] The softening point of the tackifier resin is not particularly limited, but is preferably 90°C to 160°C, more preferably 100°C to 160°C, even more preferably 105°C to 160°C, and particularly preferably 110°C to 160°C. When the softening point of the tackifier resin is 90°C or higher, the adhesive strength and holding power of the formed adhesive layer in a high temperature environment tend to be further increased. When the softening point of the tackifier resin is 160° C. or lower, commercially available tackifier resins are readily available.

[0079] The softening point of the tackifier resin is a value measured by a method in accordance with JIS K 7234:1986 (the so-called ring and ball method). However, when a commercially available product is used as the tackifying resin and the softening point is listed in the catalog of the commercially available product, the value in the catalog of the commercially available product is used as the softening point of the tackifying resin.

[0080] The biomass degree of the tackifier resin is not particularly limited, but from the viewpoint of realizing a more environmentally friendly PSA composition, it is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more. The biomass degree of the tackifier resin may be, for example, 100%.

[0081] In the present disclosure, the "biomass content of a tackifier resin" is a value measured by a method in accordance with ASTM D6866-20, and refers to the mass proportion of biomass-derived carbon in the total carbon contained in the tackifier resin. However, when a commercially available product is used as the tackifier resin and the catalog of the commercially available product lists the biomass degree, the catalog value of the commercially available product is used as the biomass degree of the tackifier resin.

[0082] The type of tackifier resin is not particularly limited. For example, from the viewpoint of realizing a more environmentally friendly PSA composition, it is preferable that at least a part of the raw materials of the tackifier resin be plant-derived components. Examples of tackifying resins include resins having a rosin skeleton (so-called rosin-based resins), resins having a terpene skeleton (so-called terpene-based resins), and resins having a styrene skeleton (so-called styrene-based resins). The tackifying resin is preferably at least one selected from the group consisting of rosin-based resins and terpene-based resins, and is more preferably a terpene-based resin, for example, from the viewpoint that the adhesive layer formed tends to have a higher holding power in a high-temperature environment.

[0083] Specific examples of rosin-based resins include rosin, esterified rosin (so-called rosin ester resin), hydrogenated rosin, and disproportionated rosin. As the rosin-based resin, a rosin ester resin is preferred.

[0084] Specific examples of terpene resins include polyterpenes, which are homopolymers of terpene, terpene phenol resins, aromatic modified terpene resins, and hydrogenated terpene resins. The terpene resin is preferably an aromatic modified terpene resin.

[0085] As the tackifying resin, commercially available products can be used. Examples of commercially available tackifier resins include "YS Polystar (registered trademark) U115," "YS Polystar (registered trademark) U130," "YS Polystar (registered trademark) T30," "YS Polystar (registered trademark) T80," "YS Polystar (registered trademark) T100," "YS Polystar (registered trademark) T115," "YS Polystar (registered trademark) T130," "YS Polystar (registered trademark) TH130," "YS Polystar (registered trademark) T145," "YS Polystar (registered trademark) T160," "YS Polystar (registered trademark) S145," "YS Polystar (registered trademark) G125," "YS Polystar (registered trademark) G150," "YS Polystar (registered trademark) N125," and "YS Polystar (registered trademark) T160," manufactured by Yasuhara Chemical Co., Ltd. Examples of such resins include "YSter (registered trademark) K125," "YS Polyster (registered trademark) K140," "YS Resin (registered trademark) CP," "YS Resin PX800," "YS Resin PX1000," "YS Resin PX1150," "YS Resin PX1250," "YS Resin TO85," "YS Resin TO105," "YS Resin TO115," and "YS Resin TO125" manufactured by Arakawa Chemical Industries, Ltd.; "Pine Crystal (registered trademark) KE-359," "Pine Crystal (registered trademark) D-6011," "Super Ester A-100," "Tamanol (registered trademark) 803L," and "Tamanol (registered trademark) 901" manufactured by Kraton; and "SYLVALITE (registered trademark) 9000" manufactured by Kraton (all of the above are trade names).

[0086] The pressure-sensitive adhesive composition of the present disclosure may contain only one type of tackifying resin, or may contain two or more types.

[0087] The content of the tackifier resin in the pressure-sensitive adhesive composition of the present disclosure is 10 to 55 parts by mass relative to 100 parts by mass of the specific (meth)acrylic copolymer. When the content of the tackifier resin in the pressure-sensitive adhesive composition of the present disclosure is 10 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic copolymer, a pressure-sensitive adhesive layer having excellent adhesive strength in a high-temperature environment can be formed, presumably because the pressure-sensitive adhesive layer thus formed is imparted with an appropriate cohesive strength. When the content of the tackifier resin in the pressure-sensitive adhesive composition of the present disclosure is 55 parts by mass or less relative to 100 parts by mass of the specific (meth)acrylic copolymer, a pressure-sensitive adhesive layer having excellent holding power in a high-temperature environment can be formed, presumably because the cohesive strength of the pressure-sensitive adhesive layer formed does not become excessively high. From the above-mentioned viewpoints, the content of the tackifier resin in the pressure-sensitive adhesive composition of the present disclosure is preferably 10 parts by mass to 50 parts by mass, more preferably 15 parts by mass to 45 parts by mass, and even more preferably 20 parts by mass to 45 parts by mass, relative to 100 parts by mass of the specific (meth)acrylic copolymer.

[0088] [Crosslinking agent] The pressure-sensitive adhesive composition of the present disclosure contains a crosslinking agent. When the pressure-sensitive adhesive composition of the present disclosure contains a crosslinking agent, a crosslinked structure is formed, imparting cohesive strength to the pressure-sensitive adhesive layer. The type of crosslinking agent is not particularly limited. Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, and a metal chelate-based crosslinking agent.

[0089] In this disclosure, "isocyanate-based crosslinking agent" refers to a compound having two or more isocyanate groups in one molecule (so-called polyisocyanate-based compound). Also, "epoxy-based crosslinking agent" refers to a compound having two or more epoxy groups in one molecule (so-called bifunctional or higher epoxy-based compound). Also, "metal chelate-based crosslinking agent" refers to a metal chelate-based compound that functions as a crosslinking agent.

[0090] The crosslinking agent is preferably an isocyanate-based crosslinking agent. The type of isocyanate-based crosslinking agent is not particularly limited. Examples of the isocyanate crosslinking agent include aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, and aromatic polyisocyanate compounds.

[0091] The "aliphatic polyisocyanate compound" includes, for example, an aliphatic polyisocyanate compound, a polymer of an aliphatic polyisocyanate compound, an adduct of an aliphatic polyisocyanate compound and a polyol compound [e.g., trimethylolpropane (TMP); the same applies hereinafter], and a biuret of an aliphatic polyisocyanate compound. Specific examples of the aliphatic polyisocyanate compound include hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), tetramethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

[0092] The "alicyclic polyisocyanate compound" includes, for example, an alicyclic polyisocyanate compound, a polymer of an alicyclic polyisocyanate compound, an adduct of an alicyclic polyisocyanate compound and a polyol compound, and a biuret of an alicyclic polyisocyanate compound. Specific examples of the alicyclic polyisocyanate compound include isophorone diisocyanate (IPDI), hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0093] The term "aromatic polyisocyanate compound" includes, for example, aromatic polyisocyanate compounds, polymers of aromatic polyisocyanate compounds, adducts of aromatic polyisocyanate compounds and polyol compounds, and biuret compounds of aromatic polyisocyanate compounds. Specific examples of aromatic polyisocyanate compounds include tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), 4,4'-diphenylmethane diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0094] The isocyanate crosslinking agent is preferably an aromatic polyisocyanate compound, and more preferably at least one selected from a tolylene diisocyanate compound and a xylylene diisocyanate compound. The term "tolylene diisocyanate compounds" includes, for example, TDI, TDI polymers, adducts of TDI and polyol compounds, and biuret compounds of TDI. The same applies to "xylylene diisocyanate compounds." For example, from the viewpoint of tending to further enhance the holding power of the pressure-sensitive adhesive layer formed in a high-temperature environment, the isocyanate-based crosslinking agent is preferably a tolylene diisocyanate-based compound, and more preferably an adduct of TDI and TMP.

[0095] As the isocyanate-based crosslinking agent, commercially available products can be used. Examples of commercially available isocyanate crosslinking agents include "Coronate (registered trademark) HX," "Coronate (registered trademark) HL-S," "Coronate (registered trademark) L," "Coronate (registered trademark) L-45E," "Coronate (registered trademark) 2031," "Coronate (registered trademark) 2037," "Coronate (registered trademark) 2234," "Coronate (registered trademark) 2785," "Aquanate (registered trademark) 200," and "Aquanate (registered trademark) 210" (all manufactured by Tosoh Corporation), "Sumidur (registered trademark) N3300," "Desmodur (registered trademark) N3400," and "Sumidur (registered trademark) N75" (all manufactured by Sumika Covestro Urethane Co., Ltd.), "Duranate (registered trademark) D201," "Duranate (registered trademark) E405-70B," "Duranate (registered trademark) E405-80T," and "Duranate (registered trademark) AE700-100," "Duranate (registered trademark) 24A-100," and "Duranate (registered trademark) TSE-100" (all manufactured by Asahi Kasei Corporation), as well as "Takenate (registered trademark) D-110N," "Takenate (registered trademark) D-120N," "Takenate (registered trademark) D-140N," "Takenate (registered trademark) M-631N," "MT-Olestar (registered trademark) NP1200," and "STABIO (registered trademark) XD-340N" (all manufactured by Mitsui Chemicals, Inc.).

[0096] The pressure-sensitive adhesive composition of the present disclosure may contain only one type of crosslinking agent, or may contain two or more types.

[0097] The content of the crosslinking agent in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, but is, for example, preferably 0.1 to 1.0 parts by mass, more preferably 0.2 to 0.8 parts by mass, and even more preferably 0.3 to 0.6 parts by mass, relative to 100 parts by mass of the specific (meth)acrylic copolymer. When the content of the crosslinking agent in the pressure-sensitive adhesive composition of the present disclosure is 0.1 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic copolymer, the pressure-sensitive adhesive layer formed tends to have higher adhesive strength and holding power in a high-temperature environment, presumably because crosslinking between the specific (meth)acrylic copolymer and the crosslinking agent proceeds more sufficiently, resulting in a sufficiently increased cohesive strength of the pressure-sensitive adhesive layer formed. When the content of the crosslinking agent in the pressure-sensitive adhesive composition of the present disclosure is 1.0 part by mass or less relative to 100 parts by mass of the specific (meth)acrylic copolymer, the pressure-sensitive adhesive layer formed tends to have higher adhesive strength in high-temperature environments. This is thought to be because excessive crosslinking between the specific (meth)acrylic copolymer and the crosslinking agent does not occur, resulting in the pressure-sensitive adhesive layer formed having a more appropriate hardness.

[0098] [Organic solvent] The pressure-sensitive adhesive composition of the present disclosure may contain an organic solvent. When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, the coating properties can be improved. Examples of the organic solvent include the same organic solvents as those used in the polymerization reaction of the above-mentioned specific (meth)acrylic copolymer.

[0099] When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, it may contain only one type of organic solvent, or may contain two or more types of organic solvents.

[0100] When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, the content of the organic solvent is not particularly limited and can be set appropriately depending on the purpose.

[0101] [Other ingredients] The pressure-sensitive adhesive composition of the present disclosure may contain components other than the components described above (so-called other components) as needed, provided that the effects of the composition are not impaired. Examples of other components include various additives such as polymers other than the specific (meth)acrylic copolymer, crosslinking catalysts, antioxidants, colorants (e.g., dyes and pigments), light stabilizers (e.g., ultraviolet absorbers), and antistatic agents.

[0102] When the pressure-sensitive adhesive composition of the present disclosure contains other components, the content of the other components can be set appropriately within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0103] <Biomass content of pressure-sensitive adhesive composition> The biomass degree of the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, but from the viewpoint of consideration of environmental issues, it is preferably 35% or more, more preferably 40% or more, even more preferably 45% or more, and particularly preferably 50% or more. The upper limit of the biomass degree of the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, and may be, for example, 80% or less.

[0104] The biomass content of the PSA composition of the present disclosure is a value measured by a method in accordance with ASTM D6866-20, and means the mass proportion of biomass-derived carbon in the total carbon contained in the PSA composition.

[0105] <Uses of the pressure-sensitive adhesive composition> The use of the pressure-sensitive adhesive composition of the present disclosure is not particularly limited. The pressure-sensitive adhesive composition of the present disclosure can form a pressure-sensitive adhesive layer that has excellent adhesive strength and holding power in high-temperature environments, and is therefore suitable for applications such as fixing objects in high-temperature environments, specifically for fixing objects such as parts to adherends that are prone to high temperatures (e.g., electronic devices, vehicles, etc.).

[0106] [Adhesive tape] The pressure-sensitive adhesive tape of the present disclosure includes a substrate and a pressure-sensitive adhesive layer provided on the substrate and formed from the pressure-sensitive adhesive composition of the present disclosure, i.e., the pressure-sensitive adhesive tape of the present disclosure has a configuration in which the substrate and the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure are laminated together. The pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of the present disclosure contains a cured product of the pressure-sensitive adhesive composition of the present disclosure. The cured product includes, for example, a crosslinked product of a specific (meth)acrylic copolymer obtained by crosslinking and curing with a crosslinking agent. The pressure-sensitive adhesive tape of the present disclosure has a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure, and therefore exhibits excellent adhesive strength and holding power to an adherend even in high-temperature environments, and is also environmentally friendly.

[0107] The substrate is not particularly limited as long as a pressure-sensitive adhesive layer can be formed on the substrate. Examples of the substrate include films containing resins such as polyolefin resins (e.g., polyethylene (PE) and polypropylene (PP)), polyester resins (e.g., polyethylene terephthalate (PET)), acetate resins (e.g., triacetyl cellulose resin), polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyurethane resins, acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene) resins, and fluorine-based resins, paper (e.g., fine paper and coated paper), synthetic paper, and composite sheets formed by laminating two or more of these.

[0108] The surface of the substrate on which the adhesive layer is provided may be subjected to a surface treatment such as corona discharge treatment or plasma discharge treatment (so-called easy-adhesion treatment) in order to improve the adhesion between the substrate and the adhesive layer.

[0109] The substrate may contain various additives such as plasticizers, colorants (eg, dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, antioxidants, and the like. The substrate may be partially or entirely patterned.

[0110] The thickness of the substrate is not particularly limited, but is generally 10 μm to 500 μm, preferably 10 μm to 300 μm, more preferably 10 μm to 200 μm, and even more preferably 10 μm to 100 μm.

[0111] In this disclosure, "thickness of the substrate" means the average thickness of the substrate. The average thickness of the substrate is a value determined by the following method. The thickness of the substrate is measured at 10 randomly selected locations in the thickness direction using a film thickness meter. The arithmetic mean of the measured values ​​is calculated and this value is taken as the average thickness of the substrate.

[0112] The thickness of the pressure-sensitive adhesive layer is not particularly limited, but is generally 1 μm to 100 μm, preferably 5 μm to 50 μm, more preferably 10 μm to 45 μm, and even more preferably 15 μm to 40 μm.

[0113] In the present disclosure, the "thickness of the pressure-sensitive adhesive layer" refers to the average thickness of the pressure-sensitive adhesive layer. The average thickness of the pressure-sensitive adhesive layer is a value determined by the same method as for the average thickness of the substrate.

[0114] In the pressure-sensitive adhesive tape of the present disclosure, the exposed surface of the pressure-sensitive adhesive layer may be protected by a release sheet.

[0115] The release sheet is not particularly limited as long as it can be easily peeled off from the pressure-sensitive adhesive layer. Examples of release sheets include resin films, paper, synthetic paper, and composite sheets obtained by laminating two or more of these, each of which has been surface-treated with a release agent on one or both sides (so-called easy-release treatment). In the present disclosure, a release sheet in an embodiment in which a resin film has been surface-treated with a release agent on one or both sides (so-called easy-release treatment) is also referred to as a "release film." Examples of release agents include silicone-based release agents (e.g., silicone), wax-based release agents (e.g., paraffin wax), and fluorine-based release agents (e.g., fluorine-based resins). Examples of resin films include polyester films such as polyethylene terephthalate (PET) films. Examples of paper include fine paper and coated paper. The thickness of the release sheet is not particularly limited, and is generally 20 μm to 180 μm. The release sheet protects the surface of the adhesive layer until the adhesive tape is put into practical use, and is peeled off at the time of use.

[0116] The uses of the pressure-sensitive adhesive tape of the present disclosure are not particularly limited. The pressure-sensitive adhesive tape of the present disclosure has a pressure-sensitive adhesive layer that has excellent adhesive strength and holding power in high-temperature environments, and is therefore suitable for applications such as fixing objects in high-temperature environments, specifically for fixing objects such as parts to adherends that are prone to high temperatures (e.g., electronic devices, vehicles, etc.).

[0117] [How to make adhesive tape] The method for producing the pressure-sensitive adhesive tape of the present disclosure is not particularly limited. The pressure-sensitive adhesive tape of the present disclosure can be produced by a known method. The pressure-sensitive adhesive tape of the present disclosure can be produced, for example, by the following method. The pressure-sensitive adhesive composition of the present disclosure is applied to a surface of a substrate that has been treated for easy adhesion, thereby forming a coating film on the substrate. The formed coating film is then dried to form a pressure-sensitive adhesive film on the substrate. The exposed surface of the formed pressure-sensitive adhesive film is then laminated to the easy-release treated surface of a release sheet, and the resulting laminate is then cured as necessary, thereby producing a pressure-sensitive adhesive tape having a laminate structure of substrate / pressure-sensitive adhesive layer / release sheet.

[0118] Another method is, for example, the following method. The pressure-sensitive adhesive composition of the present disclosure is applied to the easy-release treated surface of a release sheet to form a coating film on the release sheet. The formed coating film is then dried to form an adhesive film on the release sheet. The exposed surface of the formed adhesive film is then laminated to the easy-adhesion treated surface of a substrate, and cured as necessary, to produce an adhesive tape having a laminated structure of substrate / adhesive layer / release sheet.

[0119] The method for applying the pressure-sensitive adhesive composition is not particularly limited. Examples of methods for applying the pressure-sensitive adhesive composition include known methods using a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, knife coater, spray coater, bar coater, applicator, etc. The amount of the pressure-sensitive adhesive composition to be applied is not particularly limited, and is set appropriately depending on, for example, the thickness of the pressure-sensitive adhesive layer to be formed.

[0120] The method for drying the coating film is not particularly limited. Examples of methods for drying the coating film include natural drying, heat drying, hot air drying, and vacuum drying. The drying temperature and drying time of the coating film are not particularly limited and are set appropriately depending on the thickness of the coating film, the amount of organic solvent in the coating film, and the like. An example of the drying conditions is drying using a hot air dryer at 70°C to 120°C for 30 to 180 seconds.

[0121] When curing is performed, the curing conditions include, for example, an environment with an ambient temperature of 20°C to 35°C and a relative humidity of 45% to 55% (ie, 45% RH to 55% RH) for 2 to 7 days. [Example]

[0122] The pressure-sensitive adhesive composition and pressure-sensitive adhesive tape of the present disclosure will be described in more detail below with reference to examples. The present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure.

[0123] [Production of (meth)acrylic copolymer] [Manufacturing example A-1] A reactor equipped with a stirrer, reflux condenser, successive dropping device, and thermometer was charged with 312 parts by mass of ethyl acetate (organic solvent for polymerization) and 0.07 parts by mass of 2,2'-azobisisobutyronitrile (AIBN; polymerization initiator). In a separate vessel, 600 parts by mass of a monomer mixture consisting of 450 parts by mass of lauryl acrylate (LA) (alkyl group carbon number: 12, biomass content: 76.0%, (meth)acrylic acid alkyl ester monomer (A)), 120 parts by mass of methyl acrylate (MA) (alkyl group carbon number: 1, biomass content: 0%, glass transition temperature when homopolymerized: 10°C, (meth)acrylic acid alkyl ester monomer (B)), and 30 parts by mass of 2-hydroxyethyl acrylate (2HEA) (biomass content: 0%, monomer having a hydroxyl group) was prepared. 150 parts by mass of this prepared monomer mixture (corresponding to 25% by mass of the monomer mixture) was charged into a reactor, and then heated to reflux at reflux temperature for 20 minutes. Next, under reflux temperature conditions, the remaining 450 parts by mass of the monomer mixture (corresponding to 75% by mass of the monomer mixture), 100 parts by mass of ethyl acetate (organic solvent for polymerization), and 0.20 parts by mass of AIBN (polymerization initiator) were successively added dropwise to the reactor over 90 minutes, and the mixture was maintained for 240 minutes after the completion of the addition to carry out a polymerization reaction. The solution after the polymerization reaction was diluted with toluene (organic solvent) to a solids concentration of 45% by mass, thereby obtaining a solution of (meth)acrylic copolymer A-1.

[0124] The term "solid content concentration" used herein means the mass proportion of the (meth)acrylic copolymer A-1 in the solution of the (meth)acrylic copolymer A-1. The same applies to the solutions of the following (meth)acrylic copolymers A-2 to A-16.

[0125] [Manufacturing examples A-2 to A-16] In Production Examples A-2 to A-16, the monomer composition of the (meth)acrylic copolymer was changed to the monomer composition shown in Table 1, and the weight average molecular weight of the (meth)acrylic copolymer was adjusted to the weight average molecular weight shown in Table 1 by adjusting at least one of the amount of organic solvent used and the amount of polymerization initiator used. Except for this, the same operation as in Production Example A-1 was performed to obtain solutions of (meth)acrylic copolymers A-2 to A-16 each having a solid content concentration of 45 mass%.

[0126] Table 1 shows the monomer compositions (unit: mass%) of (meth)acrylic copolymers A-1 to A-16, the weight average molecular weights (Mw) of (meth)acrylic copolymers A-1 to A-16, and the biomass ratios (unit: %) of (meth)acrylic copolymers A-1 to A-16.

[0127] Of the (meth)acrylic copolymers A-1 to A-16 obtained above, the (meth)acrylic copolymers A-1 to A-10 correspond to the specific (meth)acrylic copolymers of the present disclosure.

[0128] [Table 1]

[0129] Details of each monomer listed in Table 1 are as follows: <(Meth)acrylic acid alkyl ester monomer (A)> "LA": ​​Lauryl acrylate (alkyl group carbon number: 12, biomass content: 76.0%, manufactured by Kyoeisha Chemical Co., Ltd.) "LMA": Lauryl methacrylate [alkyl group carbon number: 12, biomass content: 71.4%, manufactured by Kyoeisha Chemical Co., Ltd.] "SA": stearyl acrylate (alkyl group carbon number: 18, biomass content: 81.7%, manufactured by Kyoeisha Chemical Co., Ltd.) <(Meth)acrylic acid alkyl ester monomer (B)> "MA": methyl acrylate (number of carbon atoms in alkyl group: 1, biomass content: 0%, glass transition temperature when homopolymerized: 10°C, manufactured by Mitsubishi Chemical Corporation) "EA": ethyl acrylate (number of carbon atoms in alkyl group: 2, biomass content: 0%, glass transition temperature when homopolymerized: -22°C, manufactured by Mitsubishi Chemical Corporation) <Other (meth)acrylic acid alkyl ester monomers> "n-BA": n-butyl acrylate (number of carbon atoms in alkyl group: 3, biomass content: 0%, glass transition temperature when homopolymerized: -54°C, manufactured by Mitsubishi Chemical Corporation) <Monomers having a hydroxyl group> "2HEA": 2-hydroxyethyl acrylate (biomass content: 0%, manufactured by Osaka Organic Chemical Industry Co., Ltd.) <Monomers having a carboxy group> "AA": acrylic acid (biomass content: 0%, manufactured by Osaka Organic Chemical Industry Co., Ltd.)

[0130] In Table 1, "-" in the column of monomer composition means that the monomer in that column was not used.

[0131] The biomass degrees of the (meth)acrylic acid alkyl ester monomer (A), the (meth)acrylic acid alkyl ester monomer (B), other (meth)acrylic acid alkyl ester monomers, monomers having a hydroxyl group, and monomers having a carboxy group were measured by a method in accordance with ASTM D6866-20. The weight average molecular weights of the (meth)acrylic copolymers A-1 to A-16 were measured by the same method as the method for measuring the weight average molecular weight of the specific (meth)acrylic copolymer described above. The biomass ratios of the (meth)acrylic copolymers A-1 to A-16 were measured by a method in accordance with ASTM D6866-20.

[0132] [Preparation of Pressure-Sensitive Adhesive Composition] Example 1 222.2 parts by mass (100 parts by mass as solids) of the solution of (meth)acrylic copolymer A-1, 10 parts by mass (10 parts by mass as solids) of a tackifier resin (trade name: YS Resin TO125, softening point: 125°C, terpene resin, solids concentration: 100% by mass, manufactured by Yasuhara Chemical Co., Ltd.), and 0.67 parts by mass (0.3 parts by mass as solids) of a crosslinker (trade name: Coronate (registered trademark) L-45E, isocyanate crosslinker, adduct of tolylene diisocyanate (TDI) and trimethylolpropane (TMP), solids concentration: 45% by mass, manufactured by Tosoh Corporation) were thoroughly mixed to obtain the adhesive composition of Example 1.

[0133] Examples 2 to 19 The same procedure as in Example 1 was carried out except that the formulation of the adhesive composition in Example 1 was changed to the formulation shown in Table 2, to obtain each of the adhesive compositions of Examples 2 to 19.

[0134] Comparative Examples 1 to 8 The same procedure as in Example 1 was carried out except that the formulation of the adhesive composition in Example 1 was changed to the formulation shown in Table 3, and adhesive compositions of Comparative Examples 1 to 8 were obtained.

[0135] The compositions (unit: parts by mass) and biomass ratios (unit: %) of the pressure-sensitive adhesive compositions of Examples 1 to 19 are shown in Table 2, and the compositions (unit: parts by mass) and biomass ratios (unit: %) of the pressure-sensitive adhesive compositions of Comparative Examples 1 to 8 are shown in Table 3.

[0136] The biomass ratio of the pressure-sensitive adhesive compositions of Examples 1 to 19 and Comparative Examples 1 to 8 was measured by a method in accordance with ASTM D6866-20.

[0137] [Preparation of adhesive tape for evaluation] The pressure-sensitive adhesive composition prepared above was applied to the easily peelable surface of a release film (trade name: Film Byna (registered trademark) 100E-0010 No. 23, thickness: 100 μm, manufactured by Fujimori Kogyo Co., Ltd.) that had been treated with a silicone-based release agent to facilitate peeling, so that the coating film would have a dry thickness of 25 μm. The coating film was then dried using a hot air circulation dryer at a drying temperature of 100°C for 2 minutes to form an adhesive film on the release film. The exposed surface of the adhesive film was then laminated to one side of a polyethylene terephthalate (PET) film (trade name: Toyobo Ester (registered trademark) Film E5001, thickness: 25 μm, manufactured by Toyobo Co., Ltd.) (hereinafter simply referred to as "PET") as a substrate, and the resulting film was left to stand at an ambient temperature of 23°C and 50% RH for 7 days to age, producing an adhesive tape for evaluation. The prepared pressure-sensitive adhesive tape for evaluation has a laminated structure of release film / pressure-sensitive adhesive layer / substrate (PET).

[0138] [Measurement and Evaluation] 1. Adhesive strength The adhesive tape for evaluation prepared above was cut into pieces measuring 25 mm × 150 mm to prepare adhesive tape pieces for evaluation. In addition, a stainless steel plate (SUS304 2B) polished on one side with sandpaper (roughness: #280) was prepared as an adherend. The release film was peeled from a piece of adhesive tape for evaluation (composition: release film / adhesive layer / PET). The exposed adhesive layer was then placed on the polished surface of a stainless steel plate, and a 2 kg roller was used to press the tape together. The resulting test piece had a laminate structure of adherend (stainless steel plate) / adhesive tape for evaluation (adhesive layer / substrate (PET)). The test piece was then left to stand for 30 minutes at an ambient temperature of 80°C. After this standing time, the adhesive tape for evaluation (composition: adhesive layer / substrate (PET)) was peeled 180° along the long side (150 mm) from the adherend (stainless steel plate) to measure its adhesive strength (unit: N / 25 mm) using an A&D single-column materials testing machine (model number: STA-1225) at an ambient temperature of 80°C and a peel speed of 300 mm / min. The adhesive strength of the pressure-sensitive adhesive layer in a high-temperature environment was then evaluated according to the following evaluation criteria. The results are shown in Tables 2 and 3. In the following evaluation criteria, "A," "B," and "C" are levels that are practically acceptable, with "A" being the most preferable.

[0139] -Evaluation criteria- A: The adhesive strength was 4.0 N / 25 mm or more. B: The adhesive strength was 3.0 N / 25 mm or more and less than 4.0 N / 25 mm. C: The adhesive strength was 2.0 N / 25 mm or more and less than 3.0 N / 25 mm. D: The adhesive strength was less than 2.0 N / 25 mm.

[0140] 2.Holding power The holding power of the pressure-sensitive adhesive layer to the adherend was measured by a method in accordance with JIS Z 0237: 2009. Specifically, the measurement was performed as follows. The adhesive tape for evaluation prepared above was cut into pieces measuring 25 mm × 90 mm to prepare adhesive tape pieces for evaluation. In addition, a stainless steel plate (SUS304 2B) polished on one side with sandpaper (roughness: #280) was prepared as an adherend. A portion of the release film of a piece of adhesive tape for evaluation (composition: release film / adhesive layer / PET) was peeled off, and the surface of the adhesive layer exposed by the peeling was laminated to the polished surface of a stainless steel plate with an adhesive area of ​​25 mm x 25 mm. Then, a 2 kg roller was used to press the adhesive layer onto the stainless steel plate, thereby producing a test piece X1 in which a portion of the adhesive layer of the adhesive tape for evaluation was adhered to the stainless steel plate. The prepared test piece X1 was then left to stand for 30 minutes in an environment with an ambient temperature of 23 ° C and 50% RH to produce test piece X2. A static load of 1 kg was applied to the test piece for evaluation adhered to the stainless steel plate of this test piece X2 in an environment with an ambient temperature of 80 ° C in the long side (90 mm) direction for 24 hours, and the distance of displacement of the test piece for evaluation from the stainless steel plate (i.e., the movement distance of the test piece for evaluation) was measured. The holding power of the adhesive layer in a high-temperature environment was evaluated according to the following evaluation criteria. The results are shown in Tables 2 and 3. In the following evaluation criteria, "A," "B," and "C" are levels that are practically acceptable, with "A" being the most preferable.

[0141] -Evaluation criteria- A: The moving distance of the evaluation adhesive tape piece was 0.1 mm or less. B: The distance traveled by the evaluation adhesive tape piece was more than 0.1 mm and 0.3 mm or less. C: The distance traveled by the evaluation adhesive tape piece was more than 0.3 mm and 1.0 mm or less. D: The moving distance of the evaluation adhesive tape piece exceeded 1.0 mm, or the evaluation adhesive tape piece fell off the stainless steel plate.

[0142] [Table 2]

[0143] [Table 3]

[0144] Details of the ingredients listed in Table 2 and / or Table 3 are as follows: <Tackifying resin> "TO125" [Product name: YS Resin TO125, terpene resin (aromatic modified terpene resin), softening point: 125°C, solid content: 100% by mass, manufactured by Yasuhara Chemical Co., Ltd.] "TO105" [Product name: YS Resin TO105, terpene resin (aromatic modified terpene resin), softening point: 105°C, solid content: 100% by mass, manufactured by Yasuhara Chemical Co., Ltd.] "U130" (product name: YS Polystar (registered trademark) U130, terpene resin (terpene phenol resin), softening point: 130°C, solid content: 100% by mass, manufactured by Yasuhara Chemical Co., Ltd.) "T130" (product name: YS Polyster (registered trademark) T130, terpene resin (terpene phenol resin), softening point: 130°C, solid content: 100% by mass, manufactured by Yasuhara Chemical Co., Ltd.) "S9000" [Product name: SYLVALITE (registered trademark) 9000, rosin-based resin (rosin ester resin), softening point: 102°C, solid content: 100% by mass, manufactured by Kraton]

[0145] <Crosslinking agent> "L-45E" (trade name: Coronate (registered trademark) L-45, isocyanate-based crosslinking agent, adduct of tolylene diisocyanate (TDI) and trimethylolpropane (TMP), solid content: 45% by mass, manufactured by Tosoh Corporation) "D-110N" (trade name: Takenate (registered trademark) D-110N, isocyanate-based crosslinking agent, adduct of xylylene diisocyanate (XDI) and trimethylolpropane (TMP), solid content: 75% by mass, manufactured by Mitsui Chemicals, Inc.)

[0146] In Tables 2 and 3, the values ​​shown in the "blending amount" column are all solid content converted values. In Tables 2 and 3, "-" means that the component in that column was not blended.

[0147] As shown in Table 2, it was confirmed that the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of Examples 1 to 19 had excellent adhesive strength and holding power in a high-temperature environment.

[0148] On the other hand, as shown in Table 3, it was confirmed that the adhesive layer formed from the adhesive composition of Comparative Example 1, in which the content of the tackifier resin was less than 10 parts by mass per 100 parts by mass of the specific (meth)acrylic copolymer, had lower adhesive strength in a high-temperature environment than the adhesive layers formed from the adhesive compositions of the Examples. It was confirmed that the adhesive layer formed from the adhesive composition of Comparative Example 2, in which the content of the tackifier resin exceeded 55 parts by mass per 100 parts by mass of the specific (meth)acrylic copolymer, had lower holding power in a high-temperature environment than the adhesive layers formed from the adhesive compositions of the Examples. It was confirmed that the adhesive layer formed from the adhesive composition of Comparative Example 3, in which the content of structural units derived from monomers having hydroxyl groups in the (meth)acrylic copolymer was less than 1 mass% relative to all structural units, had lower holding power in a high-temperature environment than the adhesive layers formed from the adhesive compositions of the Examples. It was confirmed that the adhesive layer formed from the adhesive composition of Comparative Example 4, in which the content of structural units derived from monomers having hydroxyl groups in the (meth)acrylic copolymer exceeded 10 mass% with respect to all structural units, had lower adhesive strength in high-temperature environments than the adhesive layers formed from the adhesive compositions of the Examples. It was confirmed that the adhesive layer formed from the adhesive composition of Comparative Example 5, in which the content of structural units derived from the (meth)acrylic acid alkyl ester monomer (B) in the (meth)acrylic copolymer was less than 10 mass% relative to all structural units, had lower adhesive strength in a high-temperature environment than the adhesive layers formed from the adhesive compositions of the Examples. It was confirmed that the adhesive layer formed from the adhesive composition of Comparative Example 6, in which the content of structural units derived from (meth)acrylic acid alkyl ester monomer (B) in the (meth)acrylic copolymer exceeds 50 mass% of all structural units, has lower adhesive strength in high-temperature environments than the adhesive layers formed from the adhesive compositions of the Examples. It was confirmed that the adhesive layer formed from the adhesive composition of Comparative Example 7, in which the content of structural units derived from the (meth)acrylic acid alkyl ester monomer (A) in the (meth)acrylic copolymer was less than 30 mass% relative to all structural units, had lower adhesive strength in a high-temperature environment than the adhesive layers formed from the adhesive compositions of the Examples. It was confirmed that the adhesive layer formed from the adhesive composition of Comparative Example 8, in which the (meth)acrylic copolymer contains a structural unit derived from a monomer having a carboxyl group instead of a structural unit derived from a monomer having a hydroxyl group, had lower holding power in a high-temperature environment than the adhesive layers formed from the adhesive compositions of the Examples.

Claims

1. a (meth)acrylic copolymer containing 30% by mass to 89% by mass, based on all structural units, of structural units derived from a (meth)acrylic acid alkyl ester monomer (A) having 12 or more carbon atoms in the alkyl moiety and having a biomass degree of 70% or more; 10% by mass to 50% by mass, based on all structural units, of structural units derived from a (meth)acrylic acid alkyl ester monomer (B) having 1 to 10 carbon atoms in the alkyl moiety and having a glass transition temperature of −30° C. or higher when made into a homopolymer; and 1.5% by mass to 10% by mass, based on all structural units, of structural units derived from a monomer having a hydroxyl group; a tackifying resin; and a cross-linking agent; Including, The pressure-sensitive adhesive composition has a content of the tackifier resin of 10 parts by mass to 55 parts by mass per 100 parts by mass of the (meth)acrylic copolymer.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the alkyl moiety of the (meth)acrylic acid alkyl ester monomer (B) has 1 or 2 carbon atoms.

3. 3. The pressure-sensitive adhesive composition according to claim 1, wherein the tackifier resin has a softening point of 90°C to 160°C.

4. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the content of the tackifier resin is 20 parts by mass to 45 parts by mass per 100 parts by mass of the (meth)acrylic copolymer.

5. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the tackifier resin is a terpene resin.

6. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the content of the crosslinking agent is 0.1 parts by mass to 1.0 parts by mass per 100 parts by mass of the (meth)acrylic copolymer.

7. A substrate; a pressure-sensitive adhesive layer provided on the substrate and formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 6; An adhesive tape comprising:

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