Adhesive composition and adhesive tape

Abstract

The purpose of the present invention is to provide an adhesive composition capable of exhibiting excellent followability to a rough surface and suppressing generation of an odor. The purpose of the present invention is also to provide an adhesive tape having an adhesive layer formed using the adhesive composition. The present invention is an adhesive composition containing a (meth)acrylic copolymer having a constituent unit derived from an alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms.

Description

Adhesive composition and adhesive tape

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

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

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

[0004] Acrylic pressure-sensitive adhesives containing acrylic copolymers are widely used as pressure-sensitive adhesives with excellent adhesive strength. Examples of acrylic monomers that constitute the acrylic copolymers contained in acrylic pressure-sensitive adhesives include alkyl (meth)acrylates such as n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate. In particular, using an acrylic monomer with a low carbon number in the alkyl group, such as n-butyl (meth)acrylate, as the main component can enable the pressure-sensitive adhesive to exhibit excellent adhesive strength. However, while such pressure-sensitive adhesives have excellent adhesive strength on smooth surfaces, they are hard and have insufficient conformability to uneven (rough) surfaces. On the other hand, using an acrylic monomer with a high carbon number in the alkyl group, such as 2-ethylhexyl (meth)acrylate, as the main component can improve the conformability of the pressure-sensitive adhesive to uneven surfaces. However, acrylic monomers with a large number of carbon atoms in the alkyl group tend to have high boiling points, and even after undergoing a heat drying process when manufacturing adhesives or adhesive tapes, the acrylic monomers tend to remain in the adhesives or adhesive tapes, which poses the problem of odors being emitted from the manufactured adhesives or adhesive tapes.

[0005] An object of the present invention is to provide a pressure-sensitive adhesive composition that can exhibit excellent conformability to rough surfaces and can suppress the generation of odors, and a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition.

[0006] Disclosure 1 is a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer having structural units derived from an alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms. Disclosure 2 is the pressure-sensitive adhesive composition of Disclosure 1, wherein the linear or branched alkyl (meth)acrylate having 6 carbon atoms includes n-hexyl (meth)acrylate. Disclosure 3 is the pressure-sensitive adhesive composition of Disclosure 2, wherein the n-hexyl (meth)acrylate is synthesized from n-hexyl alcohol, which is a biological material, and (meth)acrylic acid. Disclosure 4 is the pressure-sensitive adhesive composition of Disclosure 1, 2, or 3, wherein the (meth)acrylic copolymer contains 40 mass% or more of structural units derived from the linear or branched alkyl group having 6 carbon atoms. Disclosure 5 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, or 4, wherein the (meth)acrylic copolymer contains 50 mass% or less of structural units derived from an alkyl (meth)acrylate having an alkyl group containing 7 or more carbon atoms, or contains no structural units derived from an alkyl (meth)acrylate having 7 or more carbon atoms. Disclosure 6 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, or 5, wherein the (meth)acrylic copolymer contains 35 mass% or less of structural units derived from an alkyl (meth)acrylate having 5 or less carbon atoms, or contains no structural units derived from an alkyl (meth)acrylate having 5 or less carbon atoms. Disclosure 7 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, or 6, wherein the (meth)acrylic copolymer further contains structural units derived from a monomer having a crosslinkable functional group. Disclosure 8 is the pressure-sensitive adhesive composition of Disclosure 7, wherein the monomer having a crosslinkable functional group includes at least one selected from the group consisting of a carboxy group-containing monomer and a hydroxy group-containing monomer. The present disclosure 9 is the pressure-sensitive adhesive composition of the present disclosure 7 or 8, wherein the (meth)acrylic copolymer has a content of structural units derived from the monomer having a crosslinkable functional group of 0.01% by mass or more and less than 20% by mass. The present disclosure 10 is the pressure-sensitive adhesive composition of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, or 9, further comprising a tackifier.Disclosure 11 is the pressure-sensitive adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, further comprising a crosslinking agent. Disclosure 12 is the pressure-sensitive adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, which does not contain a surfactant. Disclosure 13 is the pressure-sensitive adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, in which the pressure-sensitive adhesive composition has a content of bio-derived carbon of 10% or more. Disclosure 14 is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13. Disclosure 15 is the pressure-sensitive adhesive tape of Disclosure 14, in which the pressure-sensitive adhesive layer has a gel fraction of 10% by mass or more and 70% by mass or less. Disclosure 16 is the pressure-sensitive adhesive tape of Disclosure 14 or 15, which is used for fixing electronic equipment components or vehicle-mounted components. Hereinafter, embodiments of the present invention will be described in detail.

[0007] The present inventors have discovered that, in a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer, by using, among the various acrylic monomers that constitute the (meth)acrylic copolymer, particularly an alkyl (meth)acrylate having a linear or branched alkyl group with 6 carbon atoms, a pressure-sensitive adhesive composition can be obtained that exhibits excellent conformability to rough surfaces and suppresses odor generation, and have completed the present invention. The pressure-sensitive adhesive composition that is one embodiment of the present invention exhibits superior conformability to rough surfaces compared to acrylic monomers having an alkyl group with a small number of carbon atoms, such as n-butyl (meth)acrylate, and suppresses odor generation compared to acrylic monomers having an alkyl group with a large number of carbon atoms, such as 2-ethylhexyl (meth)acrylate. In this specification, the term "(meth)acrylic" refers to acrylic or methacrylic, and the term "(meth)acrylate" refers to acrylate or methacrylate.

[0008] In this specification, unless otherwise specified, each structural unit in the (meth)acrylic copolymer described below and each component in the pressure-sensitive adhesive composition may be of only one type or of two or more types. Furthermore, in this specification, unless otherwise specified, the terms "content ratio" and "content amount" mean, when two or more structural units that define the "content ratio" and two or more components that define the "content amount" are included, the total content ratio of all types of the structural units and the total content amount of all types of the components.

[0009] The pressure-sensitive adhesive composition of one embodiment of the present invention contains a (meth)acrylic copolymer. The (meth)acrylic copolymer has structural units derived from an alkyl(meth)acrylate having a linear or branched alkyl group having 6 carbon atoms (hereinafter also referred to as "C6 alkyl(meth)acrylate"). The (meth)acrylic copolymer has structural units derived from a C6 alkyl(meth)acrylate, allowing the pressure-sensitive adhesive composition of one embodiment of the present invention to exhibit excellent conformability to rough surfaces and suppress odor generation.

[0010] The reason why the (meth)acrylic copolymer containing structural units derived from the C6 alkyl (meth)acrylate enables the pressure-sensitive adhesive composition of one embodiment of the present invention to exhibit excellent conformability to rough surfaces is unclear. However, it is presumed that the (meth)acrylic copolymer containing structural units derived from the C6 alkyl (meth)acrylate reduces the glass transition temperature (Tg) of the (meth)acrylic copolymer and reduces the storage modulus at room temperature of the pressure-sensitive adhesive composition of one embodiment of the present invention compared to when the (meth)acrylic copolymer contains structural units derived from an acrylic monomer with a low alkyl group carbon number, such as n-butyl (meth)acrylate. This results in the pressure-sensitive adhesive composition of one embodiment of the present invention exhibiting flexibility and excellent conformability to rough surfaces. Furthermore, the C6 alkyl (meth)acrylate has a lower boiling point than acrylic monomers with a high carbon number, such as 2-ethylhexyl (meth)acrylate. Therefore, it is presumed that if a heat drying process is carried out when manufacturing an adhesive or adhesive tape, it is possible to prevent acrylic monomers from remaining in the adhesive or adhesive tape produced, and as a result, it is possible to prevent odors from being emitted from the adhesive or adhesive tape.

[0011] Examples of the C6 alkyl (meth)acrylate include n-hexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, 2-methylpentyl (meth)acrylate, and 4-methylpentyl (meth)acrylate. Among these, the C6 alkyl (meth)acrylate preferably contains n-hexyl (meth)acrylate, and more preferably consists of n-hexyl (meth)acrylate. When the (meth)acrylic copolymer contains a structural unit derived from n-hexyl (meth)acrylate, the cohesive strength exerted by the pressure-sensitive adhesive composition that is one embodiment of the present invention is further improved, and the peel resistance is further increased. Furthermore, since the (meth)acrylic copolymer has a structural unit derived from n-hexyl (meth)acrylate, the glass transition temperature (Tg) of the (meth)acrylic copolymer is further reduced and the storage modulus at room temperature of the pressure-sensitive adhesive composition according to one embodiment of the present invention is further reduced. It is therefore presumed that the pressure-sensitive adhesive composition according to one embodiment of the present invention will exhibit superior flexibility and be able to exhibit superior conformability to rough surfaces.

[0012] The C6 alkyl (meth)acrylate may be composed solely of petroleum-derived materials, but preferably contains a biologically-derived material. In recent years, the depletion of petroleum resources and carbon dioxide emissions from the combustion of petroleum-derived products have become a concern. Therefore, attempts have been made to conserve petroleum resources by using biologically-derived materials instead of petroleum-derived materials. The inclusion of a biologically-derived material in the C6 alkyl (meth)acrylate is preferable from the perspective of conserving petroleum resources. Furthermore, since biologically-derived materials are originally produced by absorbing carbon dioxide from the atmosphere, their combustion is thought to not increase the total amount of carbon dioxide in the atmosphere, which is also preferable from the perspective of reducing carbon dioxide emissions.

[0013] When the n-hexyl(meth)acrylate in the structural unit derived from n-hexyl(meth)acrylate contains a biological material, the n-hexyl(meth)acrylate is preferably synthesized from n-hexyl alcohol, which is a biological material, and (meth)acrylic acid, and more preferably synthesized by esterification of n-hexyl alcohol, which is a biological material, with (meth)acrylic acid. The biological material n-hexyl alcohol can be obtained, for example, by using a material collected from plants or animals (for example, linoleic acid derived from castor oil) as a raw material, converting it into hexanal using an enzyme, followed by hydrogenation.

[0014] The preferred lower limit of the content of the structural units derived from the C6 alkyl (meth)acrylate in the (meth)acrylic copolymer is 40% by mass. When the content of the structural units derived from the C6 alkyl (meth)acrylate is 40% by mass or more, the pressure-sensitive adhesive composition of one embodiment of the present invention can exhibit superior conformability to rough surfaces and can further suppress odor generation. The more preferred lower limit of the content of the structural units derived from the C6 alkyl (meth)acrylate is 60% by mass. The preferred upper limit of the content of the structural units derived from the C6 alkyl (meth)acrylate is 99% by mass. When the content of the structural units derived from the C6 alkyl (meth)acrylate is 99% by mass or less, the pressure-sensitive adhesive composition of one embodiment of the present invention can exhibit superior adhesive strength. The more preferred upper limit of the content of the structural units derived from the C6 alkyl (meth)acrylate is 97% by mass. The content of the structural unit derived from the C6 alkyl (meth)acrylate may be, for example, 40% by mass or more and 99% by mass or less, 40% by mass or more and 97% by mass or less, 60% by mass or more and 99% by mass or less, or 60% by mass or more and 97% by mass or less. The content of the structural unit derived from the C6 alkyl (meth)acrylate in the (meth)acrylic copolymer can be determined by mass spectrometry and nuclear magnetic resonance spectroscopy ( １ H-NMR, １３The carbon number can be calculated from the integrated intensity ratio of the hydrogen peak derived from the C6 alkyl (meth)acrylate by performing spectroscopy (e.g., C-NMR) on the carbonyl group.

[0015] The (meth)acrylic copolymer preferably further comprises a structural unit derived from a monomer having a crosslinkable functional group. When the (meth)acrylic copolymer comprises a structural unit derived from a monomer having a crosslinkable functional group, the pressure-sensitive adhesive composition according to one embodiment of the present invention can exhibit superior cohesive strength, thereby exhibiting superior adhesive strength. Furthermore, when the pressure-sensitive adhesive composition according to one embodiment of the present invention exhibits superior cohesive strength, the heat resistance is further improved, and the pressure-sensitive adhesive composition exhibits superior high-temperature retention performance.

[0016] Examples of the monomer having a crosslinkable functional group include a carboxy group-containing monomer, a hydroxy group-containing monomer, a glycidyl group-containing monomer, an amide group-containing monomer, and a nitrile group-containing monomer. Among these, the monomer having a crosslinkable functional group preferably includes at least one selected from the group consisting of a carboxy group-containing monomer and a hydroxy group-containing monomer, since this makes it easier to adjust the degree of crosslinking of the pressure-sensitive adhesive composition, which is one embodiment of the present invention. Furthermore, the monomer having a crosslinkable functional group preferably has a (meth)acryloyl group. In this specification, the term "(meth)acryloyl" refers to acryloyl or methacryloyl.

[0017] Examples of the carboxy group-containing monomer include unsaturated monocarboxylic acids such as (meth)acrylic acid, (meth)acryloylacetic acid, (meth)acryloylpropionic acid, (meth)acryloylbutyric acid, (meth)acryloylpentanoic acid, and crotonic acid, and unsaturated dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconic acid. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 1-methyl-2-hydroxyethyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1-methyl-2-hydroxypropyl (meth)acrylate, 1-methyl-3-hydroxypropyl (meth)acrylate, 1-ethyl-2-hydroxyethyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 7-hydroxyheptyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 9-hydroxynonyl (meth)acrylate, polypropylene glycol mono(meth)acrylate, etc. Examples of the glycidyl group-containing monomer include glycidyl (meth)acrylate, etc. Examples of the amide group-containing monomer include dimethyl(meth)acrylamide, isopropyl(meth)acrylamide, dimethylaminopropyl(meth)acrylamide, etc. Examples of the nitrile group-containing monomer include (meth)acrylonitrile, etc.

[0018] The content of the structural unit derived from the monomer having a crosslinkable functional group in the (meth)acrylic copolymer is preferably 0.01% by mass or more and less than 21% by mass, and more preferably 0.01% by mass or more and less than 20% by mass. When the content of the structural unit derived from the monomer having a crosslinkable functional group is 0.01% by mass or more, the pressure-sensitive adhesive composition of one embodiment of the present invention can exhibit superior cohesive strength, thereby exhibiting superior adhesive strength. Furthermore, when the pressure-sensitive adhesive composition of one embodiment of the present invention exhibits superior cohesive strength, the heat resistance is further improved and the retention performance at high temperatures can be better exhibited. When the content of the structural unit derived from the monomer having a crosslinkable functional group is less than 21% by mass (or less than 20% by mass), the pressure-sensitive adhesive composition of one embodiment of the present invention can exhibit greater flexibility, thereby exhibiting superior conformability to rough surfaces. The content of the structural unit derived from the monomer having a crosslinkable functional group is more preferably 1.0% by mass, even more preferably 3.0% by mass, even more preferably 15% by mass, even more preferably 5.0% by mass, and even more preferably 10% by mass. Examples of the content of the structural unit derived from the monomer having the crosslinkable functional group include 0.01% by mass or more and less than 21% by mass, 0.01% by mass or more and less than 20% by mass, 0.01% by mass or more and less than 15% by mass, 0.01% by mass or more and less than 10% by mass, 1.0% by mass or more and less than 21% by mass, 1.0% by mass or more and less than 20% by mass, 1.0% by mass or more and less than 15% by mass, 1.0% by mass or more and less than 10% by mass, 3.0% by mass or more and less than 21% by mass, 3.0% by mass or more and less than 20% by mass, 3.0% by mass or more and less than 15% by mass, 3.0% by mass or more and less than 10% by mass, 5.0% by mass or more and less than 21% by mass, 5.0% by mass or more and less than 20% by mass, 5.0% by mass or more and less than 15% by mass, and 5.0% by mass or more and less than 10% by mass. The content of the structural unit derived from the monomer having a crosslinkable functional group in the (meth)acrylic copolymer was determined by mass spectrometry and nuclear magnetic resonance spectroscopy ( １ H-NMR, １３The crosslinking functional group content can be calculated from the integrated intensity ratio of the hydrogen peak derived from the monomer having the crosslinkable functional group by performing spectroscopy (e.g., C-NMR) on the polymer.

[0019] The preferred lower limit of the content of the structural units derived from the hydroxyl group-containing monomer in the (meth)acrylic copolymer is 0.01% by mass, and the preferred upper limit is 2.0% by mass. When the content of the structural units derived from the hydroxyl group-containing monomer is within the above range, the pressure-sensitive adhesive layer is more likely to form a crosslinked structure and has appropriate bulk strength, thereby further improving the shear storage modulus at 80°C of the pressure-sensitive adhesive layer, and therefore further improving the heat resistance of the pressure-sensitive adhesive layer and the pressure-sensitive adhesive tape. In addition, the pressure-sensitive adhesive tape has further improved retention performance at high temperatures. The more preferred lower limit of the content of the structural units derived from the hydroxyl group-containing monomer is 0.05% by mass, the more preferred upper limit is 1.0% by mass, and the even more preferred lower limit is 0.1% by mass. The content of the structural units derived from the hydroxyl group-containing monomer in the (meth)acrylic copolymer can be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ The amount of hydrogen can be calculated from the integrated intensity ratio of the hydrogen peak derived from the hydroxyl group-containing monomer by performing spectroscopy (e.g., C-NMR) on the hydroxyl group-containing monomer.

[0020] The preferred lower limit of the content of the structural unit derived from the carboxyl group-containing monomer in the (meth)acrylic copolymer is 0.1% by mass, and the preferred upper limit is 15% by mass. When the content of the structural unit derived from the carboxyl group-containing monomer is within the above range, the pressure-sensitive adhesive layer is more likely to form a crosslinked structure and has appropriate bulk strength, thereby further improving the shear storage modulus at 80°C of the pressure-sensitive adhesive layer, thereby further improving the heat resistance of the pressure-sensitive adhesive layer and the pressure-sensitive adhesive tape. Furthermore, the pressure-sensitive adhesive tape has further improved retention performance at high temperatures. The more preferred lower limit of the content of the structural unit derived from the carboxyl group-containing monomer is 1.0% by mass, and the more preferred upper limit is 10% by mass, and even more preferred lower limit is 3.0% by mass, and even more preferred upper limit is 8.0% by mass. The range of the content of the structural unit derived from the carboxy group-containing monomer may be, for example, 0.1% by mass or more and 15% by mass or less, 0.1% by mass or more and 10% by mass or less, 0.1% by mass or more and 8.0% by mass or less, 1.0% by mass or more and 15% by mass or less, 1.0% by mass or more and 10% by mass or less, 1.0% by mass or more and 8.0% by mass or less, 3.0% by mass or more and 15% by mass or less, 3.0% by mass or more and 10% by mass or less, 3.0% by mass or more and 8.0% by mass or less. The content of the structural unit derived from the carboxy group-containing monomer in the (meth)acrylic copolymer can be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ The carbon number can be calculated from the integrated intensity ratio of the hydrogen peak derived from the carboxy group-containing monomer by performing spectroscopy (e.g., C-NMR) on the carbonyl group.

[0021] The (meth)acrylic copolymer may contain structural units derived from other monomers other than the structural units derived from the C6 alkyl(meth)acrylate and the structural units derived from the monomer having a crosslinkable functional group, provided that the object of the present invention is not impaired. Examples of the other monomers include alkyl(meth)acrylates having an alkyl group with 7 or more carbon atoms, alkyl(meth)acrylates having an alkyl group with 5 or less carbon atoms, monomers having a cyclic ether structure other than an epoxy structure or an oxetane structure, and monomers having an acyclic ether structure.

[0022] Examples of the alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms include 2-ethylhexyl (meth)acrylate, n-heptyl (meth)acrylate, 1-methylheptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, myristyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, esters of 5,7,7-trimethyl-2-(1,3,3-trimethylbutyl)-1-octanol and (meth)acrylic acid, esters of alcohols having a total of 18 carbon atoms and having 1 or 2 methyl groups in their linear main chain and (meth)acrylic acid, behenyl (meth)acrylate, arachidyl (meth)acrylate, and isobornyl (meth)acrylate. In a preferred embodiment of the present invention, the alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms includes n-heptyl (meth)acrylate.

[0023] The upper limit of the content of the structural units derived from the alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms in the (meth)acrylic copolymer is preferably 50% by mass. By having the content of the structural units derived from the alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms be 50% by mass or less, the PSA composition according to one embodiment of the present invention can further suppress odor generation. The upper limit of the content of the structural units derived from the alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms is more preferably 30% by mass, and even more preferably 10% by mass. Furthermore, when the (meth)acrylic copolymer contains structural units derived from the alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms, the lower limit of the content of the structural units derived from the alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms in the (meth)acrylic copolymer is not particularly limited as long as it is greater than 0% by mass, but a preferred lower limit is 1% by mass, and a more preferred lower limit is 2% by mass. The (meth)acrylic copolymer does not have any structural units derived from an alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms, i.e., the content of structural units derived from an alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms may be 0% by mass. In the pressure-sensitive adhesive composition that is one embodiment of the present invention, examples of the content of structural units derived from an alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms include 0% by mass to 50% by mass, 0% by mass to 30% by mass, 0% by mass to 10% by mass, more than 0% by mass to 50% by mass, more than 0% by mass to 30% by mass, more than 0% by mass to 10% by mass, 1% by mass to 50% by mass, 1% by mass to 30% by mass, 1% by mass to 10% by mass, 2% by mass to 50% by mass, 2% by mass to 30% by mass, and 2% by mass to 10% by mass. The content of the structural unit derived from the alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms was determined by mass spectrometry and nuclear magnetic resonance spectroscopy ( １ H-NMR, １３The carbon number can be calculated from the integrated intensity ratio of the peak of hydrogen derived from the alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms by performing spectroscopy (e.g., C-NMR) on the alkyl (meth)acrylate.

[0024] Examples of the alkyl(meth)acrylate having an alkyl group having 5 or less carbon atoms include methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, sec-butyl(meth)acrylate, tert-butyl(meth)acrylate, n-pentyl(meth)acrylate, and isopentyl(meth)acrylate.

[0025] The upper limit of the content of the structural units derived from the alkyl (meth)acrylate having an alkyl group containing 5 or less carbon atoms in the (meth)acrylic copolymer is preferably 35% by mass. When the content of the structural units derived from the alkyl (meth)acrylate having an alkyl group containing 5 or less carbon atoms is 35% by mass or less, the pressure-sensitive adhesive composition of one embodiment of the present invention can exhibit superior conformability to rough surfaces. The upper limit of the content of the structural units derived from the alkyl (meth)acrylate having an alkyl group containing 5 or less carbon atoms is more preferably 25% by mass, and even more preferably 10% by mass. Furthermore, when the (meth)acrylic copolymer contains structural units derived from the alkyl (meth)acrylate having an alkyl group containing 5 or less carbon atoms, the lower limit of the content of the structural units derived from the alkyl (meth)acrylate having an alkyl group containing 5 or less carbon atoms in the (meth)acrylic copolymer is not particularly limited, as long as it is greater than 0% by mass. However, the lower limit is preferably 1% by mass, and more preferably 2% by mass. The (meth)acrylic copolymer does not have any structural units derived from an alkyl (meth)acrylate having an alkyl group containing 5 or less carbon atoms, i.e., the content of structural units derived from an alkyl (meth)acrylate having an alkyl group containing 5 or less carbon atoms may be 0% by mass. In the pressure-sensitive adhesive composition that is one embodiment of the present invention, examples of the content of structural units derived from an alkyl (meth)acrylate having an alkyl group containing 5 or less carbon atoms include 0% by mass or more and 35% by mass or less, 0% by mass or more and 25% by mass or less, 0% by mass or more and 10% by mass or less, more than 0% by mass and 35% by mass or less, more than 0% by mass and 25% by mass or less, more than 0% by mass and 10% by mass or less, 1% by mass or more and 35% by mass or less, 1% by mass or more and 25% by mass or less, 1% by mass or more and 10% by mass or less, 2% by mass or more and 35% by mass or less, 2% by mass or more and 25% by mass or less, and 2% by mass or more and 10% by mass or less. The content of the structural unit derived from alkyl (meth)acrylate having an alkyl group having 5 or less carbon atoms was determined by mass spectrometry and nuclear magnetic resonance spectroscopy ( １ H-NMR, １３The carbon number can be calculated from the integrated intensity ratio of the peak of hydrogen derived from the alkyl (meth)acrylate having an alkyl group having 5 or less carbon atoms by performing spectroscopy (e.g., C-NMR) on the alkyl (meth)acrylate.

[0026] When the (meth)acrylic copolymer has at least one structural unit selected from the group consisting of structural units derived from monomers having a cyclic ether structure other than the epoxy structure and the oxetane structure, and structural units derived from monomers having a non-cyclic ether structure (hereinafter, sometimes simply referred to as "structural units derived from monomers having an ether structure"), the adhesive strength of the resulting pressure-sensitive adhesive composition is further improved, and the pressure-sensitive adhesive composition can exhibit better adhesion to adherends.

[0027] Examples of the monomer having a cyclic ether structure other than the epoxy structure and the oxetane structure include a monomer having a cyclic ether structure such as tetrahydrofurfuryl (meth)acrylate, etc. Examples of the monomer having an acyclic ether structure include a monomer having an acyclic ether structure such as 2-butoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, and ethyl carbitol (meth)acrylate.

[0028] The content of the structural units derived from the monomer having an ether structure in the (meth)acrylic copolymer is preferably 50% by mass or less. Having the content of the structural units derived from the monomer having an ether structure of 50% by mass or less can improve adhesive strength. The content of the structural units derived from the monomer having an ether structure is more preferably 30% by mass, and even more preferably 10% by mass. Furthermore, when the (meth)acrylic copolymer contains structural units derived from the monomer having an ether structure, the lower limit of the content of the structural units derived from the monomer having an ether structure in the (meth)acrylic copolymer is not particularly limited as long as it is greater than 0% by mass, with a preferred lower limit being 0.01% by mass, and a more preferred lower limit being 0.1% by mass. The (meth)acrylic copolymer may not contain structural units derived from the monomer having an ether structure, i.e., the content of the structural units derived from the monomer having an ether structure may be 0% by mass. Examples of the content of the structural unit derived from the monomer having an ether structure include 0% by mass or more and 50% by mass or less, 0% by mass or more and 30% by mass or less, 0% by mass or more and 10% by mass or less, more than 0% by mass or more and 50% by mass or less, more than 0% by mass or more and 30% by mass or less, more than 0% by mass or more and 10% by mass or less, 0.01% by mass or more and 50% by mass or less, 0.01% by mass or more and 30% by mass or less, 0.01% by mass or more and 10% by mass or less, 0.1% by mass or more and 50% by mass or less, 0.1% by mass or more and 30% by mass or less, and 0.1% by mass or more and 10% by mass or less. The content of the structural unit derived from the monomer having an ether structure can be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR measurement, １３ C-NMR, etc.) and calculation can be performed from the integrated intensity ratio of the hydrogen peak derived from the structural unit derived from the monomer having the ether structure.

[0029] Examples of the other monomers include cyclohexyl (meth)acrylate, benzyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-methoxyethyl (meth)acrylate, ethyl carbitol (meth)acrylate, etc. Furthermore, examples of the other monomers that can be used include various monomers that are commonly used as raw materials for (meth)acrylic copolymers, such as vinyl acetate and styrene.

[0030] The C6 alkyl (meth)acrylate, the monomer having a crosslinkable functional group, and the other monomers preferably contain an acrylate monomer. When the C6 alkyl (meth)acrylate, the monomer having a crosslinkable functional group, and the other monomers contain an acrylate monomer, the PSA composition according to one embodiment of the present invention has improved flexibility and can exhibit better conformability to rough surfaces, compared to when the PSA composition contains a methacrylate monomer.

[0031] The monomer having a crosslinkable functional group and the other monomers preferably contain biologically derived materials, but may also be composed solely of petroleum-derived materials. In theory, all of the acrylic monomers constituting the (meth)acrylic copolymer may be monomers containing biologically derived materials. From the standpoint of cost and productivity of the pressure-sensitive adhesive composition, a monomer containing a relatively inexpensive and easily available biologically derived material may be used, and this may be combined with a monomer consisting solely of petroleum-derived materials.

[0032] The weight-average molecular weight of the (meth)acrylic copolymer may be, for example, in the range of 30,000 to 2,000,000. The preferred lower limit of the weight-average molecular weight of the (meth)acrylic copolymer is 700,000, and the preferred upper limit is 1,500,000. When the weight-average molecular weight of the (meth)acrylic copolymer is 700,000 or more, the pressure-sensitive adhesive composition according to one embodiment of the present invention can exhibit superior cohesive strength, thereby exhibiting superior adhesive strength. Furthermore, when the pressure-sensitive adhesive composition according to one embodiment of the present invention exhibits superior cohesive strength, the heat resistance is further improved, and the pressure-sensitive adhesive composition according to one embodiment of the present invention can exhibit superior retention performance at high temperatures. When the weight-average molecular weight of the (meth)acrylic copolymer is 1,500,000 or less, the pressure-sensitive adhesive composition according to one embodiment of the present invention can exhibit superior flexibility, thereby exhibiting superior conformability to rough surfaces. The more preferred lower limit of the weight-average molecular weight of the (meth)acrylic copolymer is 800,000, and the more preferred upper limit is 1,300,000. The weight average molecular weight of the (meth)acrylic copolymer may be, for example, from 700,000 to 1,500,000, from 700,000 to 1,300,000, from 800,000 to 1,500,000, or from 800,000 to 1,300,000. In this specification, the "weight average molecular weight" refers to the weight average molecular weight in terms of standard polystyrene measured by GPC (gel permeation chromatography). Specifically, the (meth)acrylic copolymer is diluted 50 times with tetrahydrofuran (THF), and the resulting diluted solution is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare a measurement sample. Next, this measurement sample is fed to a gel permeation chromatograph, and GPC measurement is performed under conditions of a sample flow rate of 1 mL / min and a column temperature of 40 ° C. to measure the polystyrene-equivalent molecular weight of the (meth)acrylic copolymer, and this value is taken as the weight average molecular weight of the (meth)acrylic copolymer. The gel permeation chromatograph may be, for example, 2690 Separations Module (manufactured by Waters Corporation).

[0033] Examples of methods for adjusting the weight-average molecular weight of the acrylic copolymer include a method of changing the concentration of a polymerization initiator or a monomer during the polymerization reaction, a method of adding a small amount of a chain transfer agent such as dodecyl mercaptan, a method of controlling chain transfer to the solvent by changing the type of polymerization reaction solvent, and a method of changing the temperature and time during polymerization.

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

[0035] Examples of the polymerization initiator include organic peroxides and azo compounds. Examples of the organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the azo compounds include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. Furthermore, when the radical reaction is carried out by living radical polymerization, examples of the polymerization initiator include organotellurium polymerization initiators. The organotellurium polymerization initiator is not particularly limited as long as it is one that is commonly used in living radical polymerization, and examples thereof include organotellurium compounds, organotelluride compounds, etc. In addition to the organotellurium polymerization initiator, an azo compound may also be used as the polymerization initiator in the living radical polymerization in order to accelerate the polymerization rate.

[0036] The preferred lower limit of the content of the (meth)acrylic copolymer in the pressure-sensitive adhesive composition of one embodiment of the present invention is 60% by mass, and the preferred upper limit is 99.5% by mass. When the content of the (meth)acrylic copolymer is within this range, the pressure-sensitive adhesive composition of one embodiment of the present invention can exhibit better conformability to rough surfaces and can further suppress odor generation. The more preferred lower limit of the content of the (meth)acrylic copolymer is 70% by mass, and the more preferred upper limit is 90% by mass. Examples of the content of the (meth)acrylic copolymer include 60% by mass or more and 99.5% by mass or less, 60% by mass or more and 90% by mass or less, 70% by mass or more and 99.5% by mass or less, and 70% by mass or more and 90% by mass or less.

[0037] The pressure-sensitive adhesive composition of one embodiment of the present invention preferably further contains a tackifier. By containing a tackifier, the pressure-sensitive adhesive composition of one embodiment of the present invention can exhibit even better adhesive strength.

[0038] The tackifier is not particularly limited, and examples thereof include rosin ester tackifiers, terpene tackifiers, coumarone-indene tackifiers, alicyclic saturated hydrocarbon tackifiers, C5 petroleum tackifiers, C9 petroleum tackifiers, C5-C9 copolymer petroleum tackifiers, and acrylic tackifiers composed of (meth)acrylic compounds having a weight-average molecular weight of less than 30,000. These tackifiers may be used alone or in combination of two or more. Among these, it is preferable to include at least one selected from the group consisting of rosin ester tackifiers and terpene tackifiers, and it is more preferable to include a rosin ester tackifier and a terpene tackifier.

[0039] Examples of the rosin ester tackifier include rosin ester resins, polymerized rosin ester resins, and hydrogenated rosin ester resins. Examples of the terpene tackifier include terpene resins and terpene phenol resins. The rosin ester tackifier and the terpene tackifier are preferably derived from living organisms. Examples of the rosin ester tackifier derived from living organisms include rosin ester tackifiers derived from natural resins such as pine resin. Examples of the terpene tackifier derived from living organisms include terpene tackifiers derived from plant essential oils.

[0040] Specific examples of the rosin ester tackifier include Pencel D-135, Pine Crystal KE-359, Ester Gum AA-V, and Ester Gum H (all manufactured by Arakawa Chemical Industries, Ltd.). Specific examples of the terpene tackifier include YS Resin PX1250 and YS Polystar G150 (all manufactured by Yasuhara Chemical Co., Ltd.).

[0041] The acrylic tackifier comprises a (meth)acrylic compound having a weight-average molecular weight of less than 30,000. Examples of the (meth)acrylic compound having a weight-average molecular weight of less than 30,000 include an acrylic oligomer having a weight-average molecular weight of less than 30,000 and an acrylic monomer having a weight-average molecular weight of less than 30,000. Of these, an acrylic oligomer having a weight-average molecular weight of less than 30,000 is preferred.

[0042] The weight-average molecular weight of the acrylic oligomer used as the acrylic tackifier is less than 30,000. The weight-average molecular weight of the acrylic oligomer is preferably 1,000 or more and less than 30,000. When the weight-average molecular weight of the acrylic oligomer is within the above range, the adhesive strength of the resulting pressure-sensitive adhesive composition is further improved. The weight-average molecular weight of the acrylic oligomer is more preferably 1,500 or more and less than 20,000, and even more preferably 2,000 or more and less than 10,000. The weight-average molecular weight of the acrylic oligomer can be measured by the same method as the method for measuring the weight-average molecular weight of the (meth)acrylic copolymer described above.

[0043] The glass transition temperature of the acrylic oligomer used as the acrylic tackifier preferably has a lower limit of 0°C and an upper limit of 300°C. When the glass transition temperature of the acrylic oligomer is within the above range, the adhesive strength of the resulting pressure-sensitive adhesive composition is further improved. The lower limit of the glass transition temperature of the acrylic oligomer is more preferably 20°C, and even more preferably 40°C. Examples of the glass transition temperature of the acrylic oligomer include 0°C or higher and 300°C or lower, 20°C or higher and 300°C or lower, and 40°C or higher and 300°C or lower. The glass transition temperature of the acrylic oligomer can be measured, for example, by differential scanning calorimetry under a nitrogen atmosphere (nitrogen flow, flow rate 50 mL / min) according to JIS K6240:2011, at a measurement temperature of -100°C to 200°C and a heating rate of 10°C / min.

[0044] Examples of the constituent monomers of the acrylic oligomer and the acrylic monomer include the same monomers as those used in the constituent units derived from other monomers other than the constituent units derived from the C6 alkyl (meth)acrylate in the (meth)acrylic copolymer described above and the constituent units derived from the monomer having a crosslinkable functional group.

[0045] Specific examples of the constituent monomers of the acrylic oligomer and the acrylic monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, Preferred examples include alkyl (meth)acrylates such as isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates) such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; and (meth)acrylates obtained from terpene compound derivative alcohols. The acrylic oligomer preferably contains, as a monomer unit, an acrylic monomer having a relatively bulky structure, typified by alkyl (meth)acrylates in which the alkyl group is branched, such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates), such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; and (meth)acrylates having a cyclic structure, such as aryl (meth)acrylates, such as phenyl (meth)acrylate and benzyl (meth)acrylate, from the viewpoint of further improving the adhesiveness of the pressure-sensitive adhesive composition. In addition to the (meth)acrylate monomers, a monomer having a crosslinkable functional group can be used as a constituent monomer component of the acrylic oligomer.Suitable examples of the monomer having a crosslinkable functional group include monomers having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocycle) such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; amino group-containing monomers such as N,N-dimethylaminoethyl (meth)acrylate; amide group-containing monomers such as N,N-diethyl (meth)acrylamide; carboxy group-containing monomers such as acrylic acid and methacrylic acid; and hydroxy group-containing monomers such as 2-hydroxyethyl (meth)acrylate. These monomers having a crosslinkable functional group can be used alone or in combination of two or more. Among these, carboxy group-containing monomers are preferred, and acrylic acid is particularly preferred. For example, by using a carboxy group-containing monomer as the monomer having a crosslinkable functional group, the adhesive strength to highly polar adherends can be improved.

[0046] The tackifier preferably contains a tackifier having a softening temperature of 80°C or higher and 170°C or lower. By containing a tackifier having a softening temperature of 80°C or higher and 170°C or lower, it becomes easier to adjust the glass transition temperature of the pressure-sensitive adhesive layer to within the above-mentioned range, and the obtained pressure-sensitive adhesive tape has better heat resistance. The softening temperature of the tackifier is more preferably 90°C in lower limit, more preferably 160°C in upper limit, even more preferably 100°C in lower limit, and even more preferably 150°C in upper limit. Examples of the softening temperature range of the tackifier include 80°C in lower limit and 170°C in lower limit, respectively, 80°C in lower limit and 160°C in lower limit, 80°C in lower limit and 150°C in lower limit, respectively, 90°C in lower limit and 170°C in lower limit, 90°C in lower limit and 160°C in lower limit, 90°C in lower limit and 150°C in lower limit, respectively, 100°C in lower limit and 150°C in lower limit. In this specification, the term "softening temperature" refers to a softening point measured by a method in accordance with JIS K 2207 (ring and ball method).

[0047] In the pressure-sensitive adhesive composition according to one embodiment of the present invention, the preferred lower limit of the content of the tackifier relative to 100 parts by mass of the (meth)acrylic copolymer is 10 parts by mass, and the preferred upper limit is 50 parts by mass. When the content of the tackifier is 10 parts by mass or more, the pressure-sensitive adhesive composition according to one embodiment of the present invention can exhibit superior adhesive strength. When the content of the tackifier is 50 parts by mass or less, the flexibility of the pressure-sensitive adhesive composition according to one embodiment of the present invention is further improved, and the pressure-sensitive adhesive composition can exhibit superior conformability to rough surfaces. A more preferred lower limit of the content of the tackifier is 15 parts by mass, and a more preferred upper limit is 40 parts by mass. Examples of the content of the tackifier include 10 parts by mass or more and 50 parts by mass or less, 10 parts by mass or more and 40 parts by mass or less, 15 parts by mass or more and 50 parts by mass or less, and 15 parts by mass or more and 40 parts by mass or less.

[0048] The pressure-sensitive adhesive composition of one embodiment of the present invention preferably further contains a crosslinking agent, from the viewpoint of being able to appropriately adjust the degree of crosslinking. Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an aziridine-based crosslinking agent, and a metal chelate-based crosslinking agent. Among these, since the pressure-sensitive adhesive composition of one embodiment of the present invention can exhibit superior adhesion to the adherend, the crosslinking agent preferably includes at least one selected from the group consisting of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent, and more preferably includes an isocyanate-based crosslinking agent. The crosslinking agent may be used alone or in combination with two or more types. Furthermore, when two or more crosslinking agents are used in combination, two or more types of the same type of crosslinking agent may be used (e.g., using two or more types of isocyanate-based crosslinking agents), or one or more types of different crosslinking agents may be used in combination (e.g., using one or more types of isocyanate-based crosslinking agents and one or more types of epoxy-based crosslinking agents).

[0049] In the pressure-sensitive adhesive composition according to one embodiment of the present invention, the preferred lower limit of the content of the crosslinking agent relative to 100 parts by mass of the (meth)acrylic copolymer is 0.01 parts by mass, and the preferred upper limit is 10 parts by mass. By having the content of the crosslinking agent within this range, the degree of crosslinking of the pressure-sensitive adhesive composition according to one embodiment of the present invention can be appropriately adjusted, thereby enabling the pressure-sensitive adhesive composition to exhibit superior adhesive strength and superior adhesion to the adherend. A more preferred lower limit of the content of the crosslinking agent is 0.1 parts by mass, and a more preferred upper limit is 8.0 parts by mass. Examples of the content of the crosslinking agent include 0.01 parts by mass or more and 10 parts by mass or less, 0.01 parts by mass or more and 8.0 parts by mass or less, 0.1 parts by mass or more and 10 parts by mass or less, and 0.1 parts by mass or more and 8.0 parts by mass or less. In this specification, the term "content of crosslinking agent" refers to the content of the solids of the crosslinking agent.

[0050] The pressure-sensitive adhesive composition according to one embodiment of the present invention may further contain a crosslinking catalyst for accelerating crosslinking by the crosslinking agent. Examples of the crosslinking catalyst include crosslinking catalysts for the isocyanate-based crosslinking agents, such as dibutyltin dilaurate, dibutyltin diacetate, and dioctyltin dilaurate.

[0051] The pressure-sensitive adhesive composition of one embodiment of the present invention preferably does not contain a surfactant. The absence of a surfactant in the pressure-sensitive adhesive composition of one embodiment of the present invention allows the pressure-sensitive adhesive composition of one embodiment of the present invention to exhibit superior adhesive strength. Furthermore, the absence of a surfactant in the pressure-sensitive adhesive composition of one embodiment of the present invention further improves heat resistance and allows the pressure-sensitive adhesive composition of one embodiment of the present invention to exhibit better retention performance at high temperatures. For the pressure-sensitive adhesive composition of one embodiment of the present invention to be surfactant-free, it is preferable not to use the surfactant when obtaining the (meth)acrylic copolymer. For this purpose, for example, solution polymerization, UV polymerization, or the like may be employed as the polymerization method for obtaining the (meth)acrylic copolymer. The "surfactant-free" nature of the pressure-sensitive adhesive composition of one embodiment of the present invention means that the content of the surfactant in the pressure-sensitive adhesive composition of one embodiment of the present invention is 3% by mass or less, preferably 1% by mass or less, and most preferably 0% by mass.

[0052] The surfactant content can be determined, for example, by measuring the pressure-sensitive adhesive composition using a liquid chromatography mass spectrometer (such as Shimadzu Corporation's "NEXCERA" or Thermo Fisher Scientific's "Exactive"). More specifically, an ethyl acetate solution of the pressure-sensitive adhesive composition is filtered through a filter (material: polytetrafluoroethylene, pore size: 0.2 μm). Approximately 10 μL of the resulting filtrate is injected into a liquid chromatography mass spectrometer and analyzed under the following conditions. The surfactant content can be determined from the area ratio of the peak corresponding to the surfactant in the pressure-sensitive adhesive composition. Preferably, samples with known surfactant content in the pressure-sensitive adhesive composition are prepared for each surfactant type, and a calibration curve showing the relationship between the surfactant content and the peak area ratio is prepared and analyzed. <Analysis conditions> Column: Hypersil GOLD (2.1 x 150 mm) manufactured by Thermo Fisher Scientific Mobile phase: acetonitrile Column temperature: 40°C Flow rate: 1.0 mL / min Ionization method: ESI (electrospray ionization) Capillary temperature: 350°C

[0053] The pressure-sensitive adhesive composition of one embodiment of the present invention preferably further contains a colorant. By containing a colorant in the pressure-sensitive adhesive composition of one embodiment of the present invention, the pressure-sensitive adhesive composition of one embodiment of the present invention can exhibit light-blocking properties. Therefore, when a pressure-sensitive adhesive or pressure-sensitive adhesive tape formed from the pressure-sensitive adhesive composition of one embodiment of the present invention containing a colorant is adhered to a rough surface, the adhered surface of the rough surface is filled without gaps by the pressure-sensitive adhesive or pressure-sensitive adhesive tape, which has excellent conformability to the rough surface, and the light-blocking properties of the pressure-sensitive adhesive composition can further prevent light from leaking from the adhesive surface on the rough surface. Therefore, the pressure-sensitive adhesive composition of one embodiment of the present invention can be more suitably used for fixing electronic device components or vehicle-mounted components.

[0054] Examples of the colorant include pigments and dyes. Among these, pigments are preferred from the viewpoint of excellent durability.

[0055] Examples of the pigment include color pigments such as black fillers, titanium oxide, etc. Specific examples of the black filler include carbon black, titanium black, aniline black, etc. Examples of the dye include azo dyes, anthraquinone dyes, indigo dyes, etc.

[0056] The average particle size of the black filler preferably has a lower limit of 0.01 μm and an upper limit of 1.0 μm. When the average particle size of the black filler is within the above range, the pressure-sensitive adhesive composition, which is an embodiment of the present invention, can better exhibit light-blocking properties. The average particle size of the black filler is more preferably 0.1 μm in lower limit and 0.8 μm in upper limit. Examples of the average particle size of the black filler include 0.01 μm or more and 1.0 μm in lower limit, 0.01 μm or more and 0.8 μm in lower limit, 0.1 μm or more and 1.0 μm in lower limit, and 0.1 μm or more and 0.8 μm in lower limit. The average particle size can be determined, for example, by observing 50 random black fillers with an electron microscope or optical microscope and calculating the average particle size of each black filler, or by performing laser diffraction particle size distribution measurement.

[0057] In the pressure-sensitive adhesive composition according to one embodiment of the present invention, the preferred lower limit of the content of the colorant relative to 100 parts by mass of the (meth)acrylic copolymer is 0.1 parts by mass, and the preferred upper limit is 5.0 parts by mass. When the content of the colorant is within this range, the pressure-sensitive adhesive composition according to one embodiment of the present invention can exhibit better light-blocking properties. A more preferred lower limit of the content of the colorant is 0.5 parts by mass, and a more preferred upper limit is 3.0 parts by mass. Examples of the content of the colorant include 0.1 parts by mass or more and 5.0 parts by mass or less, 0.1 parts by mass or more and 3.0 parts by mass or less, 0.5 parts by mass or more and 5.0 parts by mass or less, and 0.5 parts by mass or more and 3.0 parts by mass or less.

[0058] The pressure-sensitive adhesive composition, which is one embodiment of the present invention, may contain other additives such as a silane coupling agent, a plasticizer, a softener, a filler, etc., as necessary, within the scope of not impairing the object of the present invention.

[0059] The method for producing the pressure-sensitive adhesive composition according to one embodiment of the present invention is not particularly limited, and the composition can be produced by a conventionally known production method, for example, by adding a solvent to a mixture of the (meth)acrylic copolymer and additives such as a tackifier and a crosslinking agent, which are used as needed.

[0060] A preferred lower limit for the bio-derived carbon content in the pressure-sensitive adhesive composition of one embodiment of the present invention is 10%. When the bio-derived carbon content in the pressure-sensitive adhesive composition of one embodiment of the present invention is 10% or more, the pressure-sensitive adhesive composition of one embodiment of the present invention is excellent in terms of saving petroleum resources and reducing carbon dioxide emissions, and can reduce the environmental burden. A more preferred lower limit for the bio-derived carbon content in the pressure-sensitive adhesive composition of one embodiment of the present invention is 40%, and an even more preferred lower limit is 60%. Furthermore, the upper limit for the bio-derived carbon content in the pressure-sensitive adhesive composition of one embodiment of the present invention is not particularly limited and may be 100%, but examples include 95%, 90%, etc. Examples of the content of bio-derived carbon in the PSA composition according to one embodiment of the present invention include 10% to 100%; 10% to 95%; 10% to 90%; 40% to 100%; 40% to 95%; 40% to 90%; 60% to 100%; 60% to 95%; and 60% to 90%. While bio-derived carbon contains a certain proportion of radioactive isotopes (C-14), petroleum-derived carbon contains almost no C-14. Therefore, the "biological carbon content" in this specification can be calculated by measuring the concentration of C-14 contained in the PSA composition or PSA layer. Specifically, it can be measured in accordance with ASTM D6866-24, a standard widely used in the bioplastics industry.

[0061] The content of biologically-derived carbon in the pressure-sensitive adhesive composition according to one embodiment of the present invention can be adjusted by changing each component constituting the pressure-sensitive adhesive composition according to one embodiment of the present invention to a biologically-derived material and by changing the content of the biologically-derived material.

[0062] The pressure-sensitive adhesive composition according to one embodiment of the present invention can be suitably used as a pressure-sensitive adhesive in the pressure-sensitive adhesive layer of a pressure-sensitive adhesive tape or as a liquid pressure-sensitive adhesive.

[0063] A pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition of one embodiment of the present invention is also one embodiment of the present invention. The gel fraction of the pressure-sensitive adhesive layer described below and the content of bio-derived carbon in the pressure-sensitive adhesive layer described below can be adjusted to the values ​​described below by adjusting the type and content of each component constituting the pressure-sensitive adhesive composition of one embodiment of the present invention. A method for forming a pressure-sensitive adhesive layer using the pressure-sensitive adhesive composition of one embodiment of the present invention can be, for example, a method in which the pressure-sensitive adhesive composition of one embodiment of the present invention is applied to a release film or the like, and then the pressure-sensitive adhesive composition is dried by heating. The pressure-sensitive adhesive layer may contain the uncrosslinked pressure-sensitive adhesive composition or may contain a crosslinked product of the pressure-sensitive adhesive composition.

[0064] The preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 10% by mass, more preferably 15% by mass, and the preferred upper limit is 80% by mass, more preferably 70% by mass. When the gel fraction of the pressure-sensitive adhesive layer is 10% by mass or more, the cohesive strength of the pressure-sensitive adhesive layer is further improved, thereby further improving the adhesive strength and high-temperature retention performance of the pressure-sensitive adhesive tape of one embodiment of the present invention. When the gel fraction of the pressure-sensitive adhesive layer is 70% by mass or less (or 80% by mass or less), the flexibility of the pressure-sensitive adhesive layer is further improved, thereby further improving the ability of the pressure-sensitive adhesive tape of one embodiment of the present invention to conform to a rough surface. A more preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 20% by mass, and an even more preferred upper limit is 60% by mass. The gel fraction of the pressure-sensitive adhesive layer may be, for example, 10% by mass or more and 80% by mass or less, 10% by mass or more and 70% by mass or less, 10% by mass or more and 60% by mass or less, 15% by mass or more and 80% by mass or less, 15% by mass or more and 70% by mass or less, 15% by mass or more and 60% by mass or less, 20% by mass or more and 80% by mass or less, 20% by mass or more and 70% by mass or less, or 20% by mass or more and 60% by mass or less. The gel fraction of the pressure-sensitive adhesive layer is measured by the following method, etc. That is, first, a pressure-sensitive adhesive tape having the pressure-sensitive adhesive layer is cut into a flat rectangular shape 20 mm wide and 40 mm long to prepare a test piece, and the test piece is immersed in ethyl acetate at 23°C for 24 hours, then removed from the ethyl acetate and dried at 110°C for 1 hour. The mass of the dried test piece is measured, and the gel fraction is calculated using the following formula (I). Note that a separator such as a release film for protecting the pressure-sensitive adhesive layer is not laminated on the test piece. In addition, when the pressure-sensitive adhesive tape according to one embodiment of the present invention is a non-support type tape that does not have a substrate layer, the measurement is carried out using a test piece having a substrate layer obtained by adhering the tape to a substrate and cutting the tape, or ... ０ The calculation is performed assuming that the gel fraction is 0. Gel fraction (mass%) = 100 × (W ２ -W ０ ) / (W １ -W ０ ) (I) (W ０ : Mass of the base material layer, W １ : mass of test piece before immersion, W ２ : Mass of test piece after immersion and drying)

[0065] The preferred lower limit of the bio-derived carbon content in the pressure-sensitive adhesive layer is 10%. When the bio-derived carbon content in the pressure-sensitive adhesive layer is 10% or more, the pressure-sensitive adhesive tape according to one embodiment of the present invention is excellent in terms of saving petroleum resources and reducing carbon dioxide emissions, and is capable of reducing the environmental burden. The more preferred lower limit of the bio-derived carbon content in the pressure-sensitive adhesive layer is 40%, and the even more preferred lower limit is 60%. The upper limit of the bio-derived carbon content in the pressure-sensitive adhesive layer is not particularly limited and may be 100%, but examples include 95% and 90%. Examples of the bio-derived carbon content in the pressure-sensitive adhesive layer include 10% to 100%, 10% to 95%, 10% to 90%, 40% to 100%, 40% to 95%, 40% to 90%, 60% to 100%, 60% to 95%, and 60% to 90%.

[0066] The preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 3 μm, and the preferred upper limit is 300 μm. When the thickness of the pressure-sensitive adhesive layer is 3 μm or more, the pressure-sensitive adhesive tape of one embodiment of the present invention has sufficient adhesive strength. When the thickness of the pressure-sensitive adhesive layer is 300 μm or less, the pressure-sensitive adhesive tape of one embodiment of the present invention has higher conformability to rough surfaces. The more preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 5 μm, and the more preferred upper limit is 200 μm. Examples of the thickness of the pressure-sensitive adhesive layer include 3 μm or more and 300 μm or less, 3 μm or more and 200 μm or less, 5 μm or more and 300 μm or less, and 5 μm or more and 200 μm or less.

[0067] The pressure-sensitive adhesive tape according to one embodiment of the present invention may have a layer other than the pressure-sensitive adhesive layer.

[0068] The pressure-sensitive adhesive tape of one embodiment of the present invention may be a non-support type tape that does not have a base layer, or may be a support type tape that has a base layer. In particular, the pressure-sensitive adhesive tape of one embodiment of the present invention preferably has a base layer, as this provides a pressure-sensitive adhesive tape with stiffness and excellent conformability to rough surfaces. Furthermore, when the pressure-sensitive adhesive tape of one embodiment of the present invention is a support type tape having a base layer, it may be a single-sided pressure-sensitive adhesive tape having the above-mentioned pressure-sensitive adhesive layer on one side of the base layer, or a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of the base layer.

[0069] When the pressure-sensitive adhesive tape of one embodiment of the present invention is a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of a base layer, at least one of the pressure-sensitive adhesive layers may be a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of one embodiment of the present invention. In this case, the pressure-sensitive adhesive tape may have a pressure-sensitive adhesive layer not formed from the pressure-sensitive adhesive composition, but from the viewpoint of increasing the content of bio-derived carbon in the pressure-sensitive adhesive tape as a whole, it is preferred that the pressure-sensitive adhesive layers on both sides are pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive composition of one embodiment of the present invention.

[0070] Examples of the substrate used in the substrate layer include a film, a nonwoven fabric, a foam substrate, etc. Among these, it is preferable that the substrate layer contains a foam substrate, from the viewpoint of providing a pressure-sensitive adhesive tape having excellent compression properties and high flexibility, and further improving the ability of the pressure-sensitive adhesive tape according to one embodiment of the present invention to conform to irregularities.

[0071] The substrate used for the substrate layer is preferably a substrate made of a bio-derived material, from the viewpoint of increasing the content of bio-derived carbon in the entire pressure-sensitive adhesive tape. Examples of the bio-derived material include polyesters (PES) such as polyethylene terephthalate (PET), polyethylene furanoate (PEF), polylactic acid (PLA), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polybutylene succinate (PBS), polyethylene (PE), polypropylene (PP), polyurethane (PU), triacetyl cellulose (TAC), cellulose, and polyamide (PA), which are derived from plants.

[0072] Furthermore, from the perspective of reducing the use of new petroleum resources and reducing the environmental burden by suppressing carbon dioxide emissions, substrates made from recycled resources may be used. Examples of resource recycling methods include collecting waste materials such as packaging containers, home appliances, automobiles, construction materials, and food, as well as waste generated during manufacturing processes, and then cleaning, decontaminating, or decomposing the extracted materials by heating or fermentation to reuse them as raw materials. Examples of substrates made from recycled resources include films and nonwoven fabrics made from PET, PBT, PE, PP, PA, etc., which are made from recycled plastics that have been re-resinized. Furthermore, the collected waste materials may be burned and used as thermal energy for the production of substrates and their raw materials. The oils and fats contained in the collected waste materials may be mixed with petroleum, fractionated, and purified, and then used as raw materials.

[0073] The foam substrate in the substrate used for the substrate layer is preferably a foam substrate containing at least one selected from the group consisting of PE, PP, and PU, and from the viewpoint of achieving a high degree of both flexibility and strength, a foam substrate containing PE is more preferred. Examples of the constituent of the foam substrate containing PE include PE made from sugarcane.

[0074] A preferred method for producing the foam base material is, for example, to prepare a foamable resin composition containing a PE resin containing sugarcane-derived PE and a foaming agent, and then foam the foaming agent when extruding the foamable resin composition into a sheet using an extruder, and optionally crosslink the resulting polyolefin foam.

[0075] The preferred lower limit of the thickness of the foam substrate is 50 μm, and the preferred upper limit is 5000 μm. By having the thickness of the foam substrate within this range, it is possible to exhibit high impact resistance while exhibiting high flexibility that allows it to be adhered to the shape of the adherend. The more preferred upper limit of the thickness of the foam substrate is 1000 μm, and even more preferred upper limit is 300 μm. The thickness of the foam substrate may be, for example, 50 μm or more and 5000 μm or less, 50 μm or more and 1000 μm or less, or 50 μm or more and 300 μm or less.

[0076] The substrate used for the substrate layer is preferably a film containing PES or a film containing PA from the viewpoint of substrate strength. Furthermore, a film containing PA is preferred from the viewpoint of heat resistance and oil resistance. Examples of PA include nylon 11, nylon 1010, nylon 610, nylon 510, and nylon 410, which are made from castor oil, and nylon 56, which is made from cellulose.

[0077] The preferred lower limit of the thickness of the substrate is 1 μm, and the preferred upper limit is 5000 μm. By having the thickness of the substrate within this range, it is possible to obtain a pressure-sensitive adhesive tape that has stiffness while exhibiting high flexibility, allowing it to be adhered closely to the shape of the adherend. The more preferred lower limit of the thickness of the substrate is 4 μm, the more preferred upper limit is 1000 μm, the even more preferred lower limit is 10 μm, and the even more preferred upper limit is 300 μm. Examples of the thickness of the substrate include 1 μm or more and 5000 μm or less, 1 μm or more and 1000 μm or less, 1 μm or more and 300 μm or less, 4 μm or more and 5000 μm or less, 4 μm or more and 1000 μm or less, 4 μm or more and 300 μm or less, 10 μm or more and 5000 μm or less, 10 μm or more and 1000 μm or less, and 10 μm or more and 300 μm or less.

[0078] The preferred lower limit of the total thickness of the pressure-sensitive adhesive tape of one embodiment of the present invention (for example, the thickness of the pressure-sensitive adhesive layer when the pressure-sensitive adhesive tape has only a pressure-sensitive adhesive layer, or the sum of the thickness of the pressure-sensitive adhesive layer and the thickness of the base layer when the pressure-sensitive adhesive tape has a pressure-sensitive adhesive layer and a base layer) is 3 μm, and the preferred upper limit is 6000 μm. When the total thickness of the pressure-sensitive adhesive tape of one embodiment of the present invention is within this range, the adhesive strength of the pressure-sensitive adhesive tape of one embodiment of the present invention is further increased. The more preferred upper limit of the total thickness of the pressure-sensitive adhesive tape of one embodiment of the present invention is 1200 μm, and even more preferred upper limit is 500 μm. Examples of the total thickness of the pressure-sensitive adhesive tape include 3 μm or more and 6000 μm or less, 3 μm or more and 1200 μm or less, and 3 μm or more and 500 μm or less.

[0079] The method for producing the pressure-sensitive adhesive tape according to one embodiment of the present invention is not particularly limited, and the tape can be produced by a conventionally known production method. For example, in the case of a double-sided pressure-sensitive adhesive tape having a substrate layer, the following method can be used. First, a pressure-sensitive adhesive composition A is prepared by the method described above. The obtained pressure-sensitive adhesive composition A is applied to the surface of the substrate, and the solvent in the composition is completely dried and removed by heating to form a pressure-sensitive adhesive layer A. Next, a release film is superimposed on the formed pressure-sensitive adhesive layer A with its release-treated surface facing the pressure-sensitive adhesive layer A. Next, a release film separate from the above release film is prepared, and a pressure-sensitive adhesive composition B prepared in the same manner as the pressure-sensitive adhesive composition A is applied to the release-treated surface of this release film. The solvent in the pressure-sensitive adhesive composition is completely dried and removed to produce a laminate film in which a pressure-sensitive adhesive layer B is formed on the surface of the release film. The obtained laminate film is superimposed on the back surface of the substrate on which the pressure-sensitive adhesive layer A has been formed, with the pressure-sensitive adhesive layer B facing the back surface of the substrate, to produce a laminate. Then, by pressing the laminate with a rubber roller or the like, a double-sided adhesive tape can be obtained which has adhesive layers on both sides of the base layer and in which the surfaces of the adhesive layers are covered with release films.

[0080] Alternatively, two sets of laminate films may be prepared in a similar manner, and these laminate films may be superimposed on each of both surfaces of the base layer with the pressure-sensitive adhesive layer of the laminate film facing the base material to prepare a laminate. This laminate may then be pressed with a rubber roller or the like to obtain a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both surfaces of the base layer and the surfaces of the pressure-sensitive adhesive layers covered with release films.

[0081] The use of the pressure-sensitive adhesive tape of one embodiment of the present invention is not particularly limited, but it is preferably used for fixing electronic device components or vehicle-mounted components. Specifically, the pressure-sensitive adhesive tape of one embodiment of the present invention can be suitably used for adhesively fixing electronic device components in large portable electronic devices, adhesively fixing vehicle-mounted components (for example, vehicle-mounted panels), etc.

[0082] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition that can exhibit excellent conformability to rough surfaces and can suppress the generation of odors. Also, according to the present invention, it is possible to provide a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition.

[0083] FIG. 1 is a diagram schematically illustrating a high temperature retention test.

[0084] The following examples further illustrate aspects of the present invention, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are as follows.

[0085] <n-Hexyl acrylate containing bio-derived carbon> Linoleic acid derived from castor oil was converted to linoleic acid hydroperoxide using lipoxygenase, and then a mixture containing n-hexylaldehyde was obtained using isomerase. The resulting mixture was distilled to obtain n-hexylaldehyde containing bio-derived carbon. The obtained n-hexylaldehyde containing bio-derived carbon was then hydrogenated to obtain n-hexyl alcohol containing bio-derived carbon. The obtained n-hexyl alcohol containing bio-derived carbon was esterified with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare n-hexyl acrylate containing bio-derived carbon.

[0086] <n-heptyl acrylate containing bio-derived carbon> Ricinoleic acid derived from castor oil was cracked to obtain a mixture containing undecylenic acid and n-heptyl alcohol. Next, undecylenic acid was separated from the obtained mixture by distillation to obtain n-heptyl alcohol containing bio-derived carbon. The obtained n-heptyl alcohol containing bio-derived carbon was esterified with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare n-heptyl acrylate containing bio-derived carbon.

[0087] <1-Methylheptyl acrylate containing bio-derived carbon> Ricinoleic acid derived from castor oil was alkali-fused to obtain a mixture containing sepacic acid and 1-methylheptyl alcohol. Next, sepacic acid was separated from the obtained mixture by distillation to obtain 1-methylheptyl alcohol containing bio-derived carbon. 1-Methylheptyl acrylate containing bio-derived carbon was prepared by esterifying the obtained 1-methylheptyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.).

[0088] <Isobornyl acrylate containing bio-derived carbon> Camphene containing bio-derived carbon was obtained by isomerizing pinene extracted from pine resin. Camphene containing bio-derived carbon was reacted with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare isobornyl acrylate containing bio-derived carbon.

[0089] <Isobornyl methacrylate containing bio-derived carbon> Camphene containing bio-derived carbon was obtained by isomerizing pinene extracted from pine resin. Camphene containing bio-derived carbon was reacted with methacrylic acid (manufactured by Mitsubishi Chemical Corporation) to prepare isobornyl methacrylate containing bio-derived carbon.

[0090] <2-hydroxyethyl acrylate containing bio-derived carbon> Ethanol containing bio-derived carbon was obtained by fermenting sugar contained in sugarcane. The obtained ethanol containing bio-derived carbon was dehydrated to obtain ethylene, which was then oxidized to obtain ethylene oxide, to which water was added to obtain ethylene glycol containing bio-derived carbon. The obtained ethylene glycol containing bio-derived carbon was esterified with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare 2-hydroxyethyl acrylate containing bio-derived carbon.

[0091] <Tetrahydrofurfuryl acrylate containing bio-derived carbon> Tetrahydrofurfuryl alcohol containing bio-derived carbon was obtained by hydrogenating furfural contained in sugarcane. Tetrahydrofurfuryl alcohol containing bio-derived carbon was reacted with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) to prepare tetrahydrofurfuryl acrylate containing bio-derived carbon.

[0092] <Bio-derived carbon-free constituent monomers> n-Butyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) 2-Ethylhexyl acrylate (manufactured by Nippon Shokubai Co., Ltd.) Acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) 2-Hydroxypropyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) Dimethylacrylamide (manufactured by Tokyo Chemical Industry Co., Ltd.) 2-Methoxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd.)

[0093] <Tackifiers> Tackifier A: terpene-based tackifier (terpene phenol-based resin, manufactured by Yasuhara Chemical Co., Ltd., "YS Polystar G150", softening temperature: 145°C to 155°C) Tackifier B: rosin ester-based tackifier (polymerized rosin ester-based resin, manufactured by Arakawa Chemical Industries, Ltd., "Pensel D-135", softening temperature: 130 to 140°C) Tackifier C: rosin ester-based tackifier (hydrogenated rosin ester-based resin, manufactured by Arakawa Chemical Industries, Ltd., "Pine Crystal KE359", softening temperature: 94 to 104°C)

[0094] <Crosslinking agent> Isocyanate-based crosslinking agent (manufactured by Covestro, "Desmodur L-75") Epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, Inc., "Tetrad X")

[0095] <Surfactant> Sodium polyoxyethylene nonylphenyl ether sulfate (Kao Corporation, "Levenol WZ")

[0096] <Pigment> Carbon black (Toyo Color Co., Ltd., "Multilac A903 Black")

[0097] Example 1 (1) Production of (meth)acrylic copolymer Ethyl acetate was added as a polymerization solvent to a reaction vessel, and nitrogen was bubbled through the vessel. The reaction vessel was then heated while nitrogen was flowing in to initiate reflux. Subsequently, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile as a polymerization initiator 10 times with ethyl acetate was added to the reaction vessel, and 40.0 parts by mass of n-butyl acrylate, 54.9 parts by mass of n-hexyl acrylate containing bio-derived carbon, 0.1 parts by mass of 2-hydroxyethyl acrylate containing bio-derived carbon, and 5.0 parts by mass of acrylic acid were added dropwise over a period of 2 hours. After completion of the dropwise addition, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile as a polymerization initiator 10 times with ethyl acetate was again added to the reaction vessel, and the polymerization reaction was carried out for 4 hours to obtain a (meth)acrylic copolymer-containing solution. The obtained (meth)acrylic copolymer-containing solution was diluted 50 times with tetrahydrofuran (THF), and the resulting diluted solution was filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare a measurement sample. This measurement sample was supplied to a gel permeation chromatograph (manufactured by Waters, "2690 Separations Module") and subjected to GPC measurement under conditions of a sample flow rate of 1 mL / min and a column temperature of 40 ° C. The polystyrene-equivalent molecular weight of the (meth)acrylic copolymer was measured, and the weight average molecular weight of the (meth)acrylic copolymer was determined. The results are shown in Table 1.

[0098] (2) Production of Pressure-Sensitive Adhesive Tape An isocyanate-based crosslinking agent was added to the obtained (meth)acrylic copolymer-containing solution so that its solid content was 0.5 parts by mass per 100 parts by mass of the (meth)acrylic copolymer in the (meth)acrylic copolymer-containing solution, thereby preparing a pressure-sensitive adhesive composition. The obtained pressure-sensitive adhesive composition was applied to the release-treated surface of a 75 μm-thick release PET film so that the thickness of the pressure-sensitive adhesive layer after drying would be 50 μm, and then dried at 110° C. for 5 minutes to form a pressure-sensitive adhesive layer. The obtained pressure-sensitive adhesive layer was placed on the release-treated surface of a 75 μm-thick release PET film and aged in an environment of 40° C. for 48 hours to obtain a pressure-sensitive adhesive tape (non-support type).

[0099] (3) Measurement of gel fraction of adhesive layer The release PET film on one side of the obtained adhesive tape was peeled off, and the tape was attached to a 23 μm thick base PET film (manufactured by Futamura Chemical Co., Ltd., "FE2002") and cut into a flat rectangular shape with a width of 20 mm and a length of 40 mm. The release PET film on the other side of the adhesive tape was then peeled off to prepare a test piece, and its mass was measured. The test piece was immersed in ethyl acetate at 23°C for 24 hours, then removed from the ethyl acetate and dried in an environment at 110°C for 1 hour. The mass of the test piece after drying was measured, and the gel fraction (mass%) was calculated using the following formula (I). The results are shown in Table 1. Gel fraction (mass%) = 100 × (W ２ -W ０ ) / (W １ -W ０ ) (I) (W ０ : Mass of the base material layer, W １ : mass of test piece before immersion, W ２ : Mass of test piece after immersion and drying)

[0100] (Examples 2 to 25, 27 to 29, 34 to 42, 44 to 55, Comparative Examples 1 to 5) Pressure-sensitive adhesive compositions were prepared and pressure-sensitive adhesive tapes were obtained in the same manner as in Example 1, except that the types and amounts of monomers constituting the (meth)acrylic copolymer and the types and amounts of each component of the pressure-sensitive adhesive composition were changed to those shown in Tables 1 to 6. Furthermore, the weight-average molecular weight of the (meth)acrylic copolymer and the gel fraction of the pressure-sensitive adhesive layer were measured in the same manner as in Example 1. The results are shown in Tables 1 to 6. Note that for Examples 21 to 23, in "(1) Production of (meth)acrylic copolymer", polymerization reactions were carried out using polymerization initiator solutions of different concentrations to synthesize (meth)acrylic copolymers.

[0101] Example 26 (1) Preparation of (meth)acrylic copolymer To 100 parts by mass of a mixture of acrylic monomers (constituent monomers) listed in Table 3 constituting the (meth)acrylic copolymer previously placed in a separate container, 5.8 parts by mass of polyoxyethylene nonylphenyl ether sodium sulfate and 57 parts by mass of deionized water were added and stirred to prepare an emulsion of the monomer mixture. 40 parts by mass of deionized water and 0.2 parts by mass of polyoxyethylene nonylphenyl ether sodium sulfate were added to a reaction vessel, and nitrogen was introduced, raising the internal temperature to 80°C. Subsequently, 4.0 parts by mass of a 5% aqueous solution of potassium persulfate was added to the reaction vessel. The emulsion of the monomer mixture previously prepared was added dropwise to the reaction vessel over 3 hours, and in parallel, 4.0 parts by mass of a 5% aqueous solution of potassium persulfate was added dropwise, and emulsion polymerization was carried out at an internal temperature of 80-83°C. After the dropwise addition was completed, the mixture was maintained at the same temperature for 3 hours, then cooled to room temperature, and 25% aqueous ammonia was added to adjust the pH of the reaction solution to 7.5, yielding an emulsion copolymer having an average particle size of 210 nm. To the resulting emulsion copolymer-containing solution was added an alkali-thickening acrylic thickener (Saibinol AZ-1, manufactured by Saiden Chemical Co., Ltd.), 25% aqueous ammonia, and deionized water to obtain a (meth)acrylic copolymer-containing solution with a solids concentration of 50%, a viscosity of 3500 mPa s, and a pH of 8.0.

[0102] (2) Production of Pressure-Sensitive Adhesive Tape Except for using the obtained (meth)acrylic copolymer, a pressure-sensitive adhesive composition was prepared and a pressure-sensitive adhesive tape was obtained in the same manner as in Example 1. The surfactant content was determined using the prepared pressure-sensitive adhesive composition, and the weight-average molecular weight and gel fraction of the (meth)acrylic copolymer were determined in the same manner as in Example 1. The results are shown in Table 3.

[0103] Examples 30 to 33, 43 Pressure-sensitive adhesive compositions were prepared in the same manner as in Example 1, except that the type and amount of the monomer constituting the (meth)acrylic copolymer and the type and amount of each component of the pressure-sensitive adhesive composition were changed as shown in Tables 3 to 4. The obtained pressure-sensitive adhesive composition was applied to the release-treated surface of a 75 μm-thick release PET film so that the thickness of the pressure-sensitive adhesive layer after drying would be 50 μm, and then dried at 110°C for 5 minutes. The obtained pressure-sensitive adhesive layer was bonded to one side of the substrate shown in Tables 3 to 4. Furthermore, a pressure-sensitive adhesive layer having the same composition and thickness was formed on the release-treated surface of another 75 μm-thick release PET film, which was then bonded to the other side of the substrate and aged at 40°C for 48 hours to obtain a pressure-sensitive adhesive tape (support type) having pressure-sensitive adhesive layers on both sides of the substrate layer, with the surfaces of the pressure-sensitive adhesive layers on both sides covered with release PET films. The weight-average molecular weight of the (meth)acrylic copolymer and the gel fraction of the pressure-sensitive adhesive layer were measured in the same manner as in Example 1. The gel fraction of the pressure-sensitive adhesive layer was measured using a test piece obtained by cutting the pressure-sensitive adhesive tape into a flat rectangular shape with a width of 20 mm and a length of 40 mm and then peeling off the release PET films on both sides. The results are shown in Tables 3 and 4.

[0104] The substrates used as the substrate layer in Examples 30 to 33 and 43 are as follows: PET film (manufactured by Futamura Chemical Co., Ltd., "FE2002", thickness 50 μm) PE foam (manufactured by Sekisui Chemical Co., Ltd., "WL02", thickness 150 μm) Nonwoven fabric (manufactured by Toray International Co., Ltd., "G2260-1S", thickness 610 μm)

[0105] <Evaluation> The pressure-sensitive adhesive tapes obtained in the Examples and Comparative Examples were evaluated by the following methods. The results are shown in Tables 1 to 6.

[0106] (Adhesion to Rough Surface (Follow-up Ability to Rough Surface)) In accordance with JIS Z 0237:2009, the 180° peel force of an adhesive tape against a waterproof abrasive paper having a rough surface (manufactured by Noritake Coated Abrasives, "C947H", grain size 360, surface roughness Ra = 10.8 μm) was measured. The surface roughness Ra of the waterproof abrasive paper was measured using a laser microscope (manufactured by KEYENCE, color 3D laser microscope, "VK-8710"). Specifically, first, the back surface (the surface not being polished) of the waterproof abrasive paper was attached to a SUS304 plate using an adhesive tape (manufactured by Sekisui Chemical Co., Ltd., "#560"). Next, one side (the side not being measured) of the adhesive tapes obtained in the Examples and Comparative Examples was lined with a 23 μm thick polyethylene terephthalate film ("FE2002" manufactured by Futamura Chemical Co., Ltd.), and then cut into a width of 25 mm and a length of 75 mm to prepare a test piece. This test piece was placed on the abrasive surface of a waterproof abrasive paper attached to a SUS304 plate, with the adhesive layer (the side to be measured) facing the abrasive surface, and then bonded by rolling a 2 kg rubber roller back and forth once on the test piece at a speed of 300 mm / min. Thereafter, the test piece was aged at 23 ° C. and 50% RH for 20 minutes to prepare a test sample. In accordance with JIS Z 0237:2009, the test piece of this test sample was peeled from the abrasive surface of the waterproof abrasive paper in a 180 ° direction at a pulling rate of 300 mm / min, and the peel force (N / 25 mm) was measured under conditions of 23 ° C. and 50% RH. The conformability of the adhesive tape to a rough surface (adhesive strength to a rough surface) was evaluated based on the following criteria: when the obtained peel force was 12.0 N / 25 mm or more, it was marked "◎"; when it was 10.0 N / 25 mm or more but less than 12.0 N / 25 mm, it was marked "◯"; when it was 9.0 N / 25 mm or more but less than 10.0 N / 25 mm, it was marked "△"; and when it was less than 9.0 N / 25 mm, it was marked "×".

[0107] (Level of Odor Generated from Adhesive Tape) The level of odor generated from the adhesive tape was evaluated in accordance with VDA 270. Specifically, a 5 cm wide x 10 cm long adhesive tape was placed in a 1.0 L glass bottle (size: 50 cm). ２) and sealed in the glass bottle containing the adhesive tape, and the glass bottle containing the adhesive tape was left to stand in an environment of 40°C for 24 hours. The adhesive tape was then removed from the glass bottle, and the level of odor emitted from the adhesive tape immediately after removal was rated using the following 6-point scale: 1: No odor was perceptible. 2: The odor was slightly perceptible, but not unpleasant. 3: The odor was clearly perceptible, but not very unpleasant. 4: The odor was clearly perceptible and unpleasant. 5: The odor was clearly perceptible and very unpleasant. 6: The odor was clearly perceptible and unpleasant to the point of being unbearable. Three subjects each made the rating, and the average value was calculated. The calculated average value was evaluated as follows: "○" if it was less than 3.0, "△" if it was 3.0 or more but less than 4.0, "△△" if it was 4.0 or more but less than 4.5, and "×" if it was 4.5 or more.

[0108] (High-Temperature Retention Performance) A high-temperature retention test was conducted in accordance with JIS Z 0237:2009. FIG. 1 shows a schematic diagram of the high-temperature retention test. Specifically, first, one side (the side not being measured) of the pressure-sensitive adhesive tape 2 was lined with a 23 μm-thick polyethylene terephthalate film 1 (manufactured by Futamura Chemical Co., Ltd., "FE2002"), and then cut into a width of 25 mm and a length of 75 mm to prepare a test piece. This test piece was placed so that its adhesive layer (the side being measured) faced a 2 mm-thick, 50 mm-wide, and 80 mm-long SUS304 plate 3 (SUS304 plate washed with ethanol and then wiped dry), and then a 2 kg rubber roller was reciprocated on the test piece at a speed of 300 mm / min, so that a portion of the test piece protruded from the SUS304 plate 3 (adhesion area: width 25 mm, length 25 mm). The test sample was then aged for 20 minutes in an environment of 23°C and 50% RH to prepare a test sample. The test sample was placed in an environment of 80°C and 50% RH and allowed to stand for 15 minutes. Under this environment, a 1 kg weight 4 was attached to the polyethylene terephthalate film 1 of the test sample so that a load in the shear direction (lengthwise direction) was applied in accordance with JIS Z 0237:2009. One hour after attaching the weight 4, the amount of displacement in the shear direction from the position where the pressure-sensitive adhesive layer was attached to the SUS304 plate 3 was measured. The high-temperature retention performance of the pressure-sensitive adhesive tape was evaluated as follows: a displacement of 0.5 mm or less was marked "○", a displacement of more than 0.5 mm but the test piece did not fall off was marked "△", and a test piece fell off was marked "×". Even if the evaluation was marked "×", the pressure-sensitive adhesive tape of the present invention can still be used without any problems depending on the application.

[0109] (Light-shielding property) The light-shielding property of the pressure-sensitive adhesive tapes of Examples 27 to 28 and Comparative Example 5 was evaluated. Specifically, the obtained pressure-sensitive adhesive tapes were first cut into a width of 2 mm and a length of 75 mm. Next, one adhesive layer of the cut adhesive tape was placed facing the abrasive surface of waterproof abrasive paper (manufactured by Noritake Coated Abrasives, "C947H", grit size 360, surface roughness Ra = 10.8 μm), and then bonded to the test piece by rolling a 2 kg rubber roller back and forth at a speed of 300 mm / min. Thereafter, the other adhesive layer of the adhesive tape was placed facing the abrasive surface of the same waterproof abrasive paper, and then bonded to the test piece by rolling a 2 kg rubber roller back and forth at a speed of 300 mm / min. Thereafter, the tape was aged for 20 minutes in an environment of 23°C and 50% RH to prepare a test sample. The light blocking property was evaluated by projecting a light source with a luminous intensity of 3.0 × 10 onto the surface of the test sample to which the adhesive tape was attached. ５ The light of CD was irradiated, and the presence or absence of light leakage was visually confirmed. The light-shielding property of the pressure-sensitive adhesive tape was evaluated by rating it as "○" when no light leakage was visually confirmed, and rating it as "△" when light leakage was confirmed. Note that even when the evaluation is "△", the pressure-sensitive adhesive tape of the present invention can be used without any problems depending on the application.

[0110]

[0111]

[0112]

[0113]

[0114]

[0115]

[0116] According to the present invention, it is possible to provide a pressure-sensitive adhesive composition that can exhibit excellent conformability to rough surfaces and can suppress the generation of odors. Also, according to the present invention, it is possible to provide a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition.

[0117] 1 Polyethylene terephthalate (PET) film 2 Adhesive tape 3 SUS304 plate 4 Weight (1 kg)

Claims

1. An adhesive composition characterized by containing a (meth)acrylic copolymer having structural units derived from alkyl (meth)acrylate having a linear or branched C6 alkyl group.

2. The adhesive composition according to claim 1, wherein the alkyl (meth)acrylate having a linear or branched C6 alkyl group comprises n-hexyl (meth)acrylate.

3. The adhesive composition according to claim 2, wherein the n-hexyl (meth)acrylate is synthesized from n-hexyl alcohol and (meth)acrylic acid, which are bio-derived materials.

4. The adhesive composition according to claim 1, 2, or 3, wherein the (meth)acrylic copolymer contains 40% by mass or more of constituent units derived from the linear or branched alkyl (meth)acrylate having a C6 alkyl group.

5. The adhesive composition according to claim 1, 2, or 3, wherein the (meth)acrylic copolymer contains 50% by mass or less of constituent units derived from alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms, or does not contain constituent units derived from alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms.

6. The adhesive composition according to claim 1, 2, or 3, wherein the (meth)acrylic copolymer contains 35% by mass or less of constituent units derived from alkyl (meth)acrylate having an alkyl group having 5 or fewer carbon atoms, or does not contain any constituent units derived from alkyl (meth)acrylate having an alkyl group having 5 or fewer carbon atoms.

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

8. The adhesive composition according to claim 7, wherein the monomer having the crosslinkable functional group comprises at least one selected from the group consisting of carboxyl group-containing monomers and hydroxyl group-containing monomers.

9. The adhesive composition according to claim 7, wherein the (meth)acrylic copolymer has a content of 0.01% by mass or more and less than 20% by mass of constituent units derived from the monomer having the crosslinkable functional group.

10. Furthermore, the adhesive composition according to claim 1, 2, or 3, further containing a tackifier.

11. Furthermore, the adhesive composition according to claim 1, 2, or 3, further containing a crosslinking agent.

12. The adhesive composition according to claim 1, 2, or 3, which does not contain a surfactant.

13. The adhesive composition according to claim 1, 2, or 3, wherein the content of bio-derived carbon in the adhesive composition is 10% or more.

14. An adhesive tape having an adhesive layer formed using the adhesive composition according to claim 1, 2, or 3.

15. The adhesive tape according to claim 14, wherein the gel fraction of the adhesive layer is 10% by mass or more and 70% by mass or less.

16. The adhesive tape according to claim 14, used for fixing electronic equipment components or in-vehicle components.