Adhesive composition, adhesive tape, and method for producing adhesive tape

Abstract

The purpose of the present invention is to provide an adhesive composition that can exhibit excellent conformability with respect to a rough surface and that can reduce the occurrence of odors and the environmental impact. Another purpose of the present invention is to provide an adhesive tape that can exhibit excellent conformability with respect to a rough surface and that can reduce the occurrence of odors. Another purpose of the present invention is to provide a method for producing an adhesive tape using the adhesive composition. An adhesive composition according to the present invention comprises a (meth)acrylic monomer and a (meth)acrylic polymer, wherein: the (meth)acrylic monomer contains alkyl(meth)acrylate having a linear or branched C6 alkyl group; the (meth)acrylic polymer has a structural unit derived from alkyl(meth)acrylate; the adhesive composition contains an organic solvent; and the content ratio of the organic solvent in the adhesive composition is not more than 10 mass% or the adhesive composition contains no organic solvent.

Description

Adhesive composition, adhesive tape, and method for producing adhesive tape

[0001] The present invention relates to a pressure-sensitive adhesive composition. The present invention also relates to a pressure-sensitive adhesive tape. Furthermore, the present invention also relates to a method for producing a pressure-sensitive adhesive tape 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 adhesives containing acrylic copolymers are widely used as adhesives with excellent adhesive strength. Solvent coating methods and solventless coating methods are used to form adhesive layers containing acrylic adhesives. From the viewpoint of reducing the environmental impact of production and the environmental impact of volatile organic compounds (VOCs) remaining in the adhesive layer, solventless coating methods are preferred. Among the solventless coating methods, UV polymerization coating methods are widely used. Furthermore, a method of performing heating after UV irradiation is also used for the purpose of reducing the environmental impact of volatile organic compounds (VOCs) such as solvents in the adhesive after curing with ultraviolet (UV) light.

[0005] On the other hand, examples of acrylic monomers that constitute the acrylic copolymer contained in acrylic pressure-sensitive adhesives include alkyl (meth)acrylates such as n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate. In particular, by using an acrylic monomer with a low carbon number in the alkyl group, such as n-butyl (meth)acrylate, as the main component, the resulting pressure-sensitive adhesive layer has excellent adhesive strength. However, although such pressure-sensitive adhesive layers have excellent adhesive strength to smooth surfaces, they are hard and have insufficient conformability to uneven surfaces. On the other hand, by using an acrylic monomer with a high carbon number in the alkyl group, such as 2-ethylhexyl (meth)acrylate, as the main component, the pressure-sensitive adhesive layer's conformability to uneven surfaces can be improved. However, acrylic monomers with a high carbon number in the alkyl group tend to have high boiling points, and the acrylic monomers tend to remain even after a heat drying process when forming the pressure-sensitive adhesive layer, which poses a problem of odor generation from the produced pressure-sensitive adhesives and pressure-sensitive adhesive tapes.

[0006] An object of the present invention is to provide a pressure-sensitive adhesive composition that can exhibit excellent conformability to rough surfaces and can reduce odor generation and environmental impact. Another object of the present invention is to provide a pressure-sensitive adhesive tape that can exhibit excellent conformability to rough surfaces and can reduce odor generation. A further object of the present invention is to provide a method for producing a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition.

[0007] Disclosure 1 relates to a pressure-sensitive adhesive composition containing a (meth)acrylic monomer and a (meth)acrylic polymer, wherein the (meth)acrylic monomer comprises an alkyl(meth)acrylate having a linear or branched alkyl group having 6 carbon atoms, and the (meth)acrylic polymer has structural units derived from the alkyl(meth)acrylate. The pressure-sensitive adhesive composition contains an organic solvent, and the content of the organic solvent in the pressure-sensitive adhesive composition is 10 mass% or less. Alternatively, the pressure-sensitive adhesive composition is free of organic solvent. Disclosure 2 relates to the pressure-sensitive adhesive composition of Disclosure 1, wherein the alkyl(meth)acrylate having a linear or branched alkyl group having 6 carbon atoms in the (meth)acrylic monomer comprises n-hexyl(meth)acrylate. Disclosure 3 relates to the pressure-sensitive adhesive composition of Disclosure 2, wherein the n-hexyl(meth)acrylate comprises n-hexyl(meth)acrylate synthesized from n-hexyl alcohol and (meth)acrylic acid, which are biologically derived materials. Disclosure 4 is the pressure-sensitive adhesive composition of Disclosures 1, 2, or 3, wherein the content of an alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms is 50 parts by mass or less per 100 parts by mass of the total of the (meth)acrylic monomer and the (meth)acrylic polymer, or wherein the (meth)acrylic monomer does not contain an alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms. Disclosure 5 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, or 4, wherein the (meth)acrylic monomer comprises a monomer having two or more (meth)acryloyl groups per molecule. Disclosure 6 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, or 5, wherein the (meth)acrylic monomer comprises a monomer having a crosslinkable functional group. Disclosure 7 is the pressure-sensitive adhesive composition of Disclosure 6, wherein the monomer having a crosslinkable functional group comprises at least one selected from the group consisting of a carboxy group-containing monomer and a hydroxy group-containing monomer. The present disclosure 8 is a pressure-sensitive adhesive composition according to the present disclosure 1, 2, 3, 4, 5, 6, or 7, wherein the structural unit derived from the alkyl (meth)acrylate in the (meth)acrylic polymer includes a structural unit derived from an alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms.Disclosure 9 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, or 8, wherein the total content of the linear or branched alkyl (meth)acrylate having an alkyl group of 6 carbon atoms and the structural units derived from the linear or branched alkyl (meth)acrylate having an alkyl group of 6 carbon atoms in the (meth)acrylic polymer is 60 mass% or more in the total of the (meth)acrylic monomer and the (meth)acrylic polymer. Disclosure 10 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the (meth)acrylic polymer has structural units derived from a monomer having a crosslinkable functional group. Disclosure 11 is the pressure-sensitive adhesive composition of Disclosure 10, wherein the structural units derived from the monomer having a crosslinkable functional group include at least one structural unit selected from the group consisting of structural units derived from a carboxyl group-containing monomer and structural units derived from a hydroxyl group-containing monomer.

[0023] Disclosure 12 relates to the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein, in at least one of the cases where the (meth)acrylic monomer contains a monomer having a crosslinkable functional group and the (meth)acrylic polymer contains a structural unit derived from the monomer having a crosslinkable functional group, the total content of the monomer having a crosslinkable functional group and the structural unit in the (meth)acrylic polymer derived from the monomer having a crosslinkable functional group in the total of the (meth)acrylic monomer and the (meth)acrylic polymer is 0.01% by mass or more and 20% by mass or less. Disclosure 13 relates to the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, which contains a photopolymerization initiator. Disclosure 14 relates to the pressure-sensitive adhesive composition of Disclosure 13, wherein the photopolymerization initiator contains a compound having two or more photopolymerization reaction sites. Disclosure 15 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14, which contains a tackifier resin. Disclosure 16 is the pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15, which contains a crosslinking agent. Disclosure 17 is the pressure-sensitive adhesive composition of Disclosure 16, in which the crosslinking agent contains at least one selected from the group consisting of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent.Disclosure 18 is the PSA composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17, which contains a pigment. Disclosure 19 is the PSA composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, in which the PSA composition contains 10% or more of bio-derived carbon. Disclosure 20 is a PSA tape having a PSA layer containing a cured product of the PSA composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19. Disclosure 21 is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer 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 22 is a pressure-sensitive adhesive tape of Disclosure 21, wherein the (meth)acrylic copolymer contains 60 mass% or more of structural units derived from an alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms. Disclosure 23 is a pressure-sensitive adhesive tape of Disclosure 20, 21, or 22, wherein the pressure-sensitive adhesive layer does not contain an organic solvent, or wherein the pressure-sensitive adhesive layer contains an organic solvent, and the content of the organic solvent in the pressure-sensitive adhesive layer is 500 ppm or less. Disclosure 24 is a pressure-sensitive adhesive tape of Disclosure 20, 21, 22, or 23, wherein the pressure-sensitive adhesive layer has a gel fraction of 10 mass% or more and 70 mass% or less. Disclosure 25 is a pressure-sensitive adhesive tape of Disclosure 20, 21, 22, 23, or 24, having a substrate layer. Disclosure 26 relates to a pressure-sensitive adhesive tape according to Disclosures 20, 21, 22, 23, 24, or 25, which is used for fixing electronic components or in-vehicle components. Disclosure 27 relates to a method for producing a pressure-sensitive adhesive tape, comprising: a step (I) of irradiating a pressure-sensitive adhesive composition according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19 with light to cure it; and a step (II) of heating the cured product of the pressure-sensitive adhesive composition cured in step (I). The present invention will be described in detail below. Hereinafter, one or more embodiments of the present invention will be described as the "present embodiment."

[0008] The present inventors investigated the possibility of incorporating a (meth)acrylic monomer into a pressure-sensitive adhesive composition containing a (meth)acrylic polymer, thereby enabling the formation of a pressure-sensitive adhesive layer even with a small amount of solvent in the pressure-sensitive adhesive composition, thereby reducing the environmental impact. Furthermore, they investigated incorporating an alkyl (meth)acrylate having a linear or branched alkyl group with 6 carbon atoms as the (meth)acrylic monomer in such a pressure-sensitive adhesive composition. As a result, they discovered that a pressure-sensitive adhesive composition can be obtained that exhibits excellent conformability to rough surfaces, while reducing odor generation and environmental impact, and thus completed the present invention. The pressure-sensitive adhesive composition of this embodiment exhibits superior conformability to rough surfaces compared to pressure-sensitive adhesive compositions primarily containing (meth)acrylic monomers with alkyl groups having a small number of carbon atoms, such as n-butyl (meth)acrylate, and also reduces odor generation compared to pressure-sensitive adhesive compositions primarily containing (meth)acrylic monomers with alkyl groups having a large number of carbon atoms, such as 2-ethylhexyl (meth)acrylate. In this specification, the term "(meth)acrylic" means acrylic or methacrylic, and the term "(meth)acrylate" means acrylate or methacrylate. In addition, in this specification, the term "(meth)acrylic polymer" means a copolymer having a structural unit derived from (meth)acrylate contained in the pressure-sensitive adhesive composition before curing or before forming the pressure-sensitive adhesive layer or the pressure-sensitive adhesive.

[0009] The pressure-sensitive adhesive composition of the present embodiment contains a (meth)acrylic monomer. By containing the (meth)acrylic monomer in the pressure-sensitive adhesive composition of the present embodiment, curing of the pressure-sensitive adhesive composition of the present embodiment is facilitated. Furthermore, by containing the (meth)acrylic monomer in the pressure-sensitive adhesive composition of the present embodiment, the viscosity of the pressure-sensitive adhesive composition of the present embodiment is reduced, resulting in a pressure-sensitive adhesive composition that is easier to apply, and therefore the content of the solvent in the pressure-sensitive adhesive composition of the present embodiment can be reduced.

[0010] The (meth)acrylic monomer contains an alkyl(meth)acrylate having a linear or branched alkyl group having 6 carbon atoms (hereinafter also referred to as "C6 alkyl(meth)acrylate"). When the (meth)acrylic monomer contains a C6 alkyl(meth)acrylate, the pressure-sensitive adhesive and pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition of the present embodiment have excellent conformability to rough surfaces and can suppress the generation of odors.

[0011] Examples of the C6 alkyl (meth)acrylate include n-hexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, 2-methylpentyl (meth)acrylate, and 4-methyl-2-pentyl (meth)acrylate. Of these, the C6 alkyl (meth)acrylate preferably contains n-hexyl (meth)acrylate. When the (meth)acrylic monomer contains n-hexyl (meth)acrylate, the adhesive and adhesive layer obtained by curing the adhesive composition of this embodiment have superior conformability to rough surfaces and are able to further suppress odor generation.

[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 preferably contains n-hexyl(meth)acrylate synthesized from n-hexyl alcohol, a biological material, and (meth)acrylic acid. A method for synthesizing n-hexyl(meth)acrylate from n-hexyl alcohol and (meth)acrylic acid includes, for example, esterifying n-hexyl(meth)acrylate with n-hexyl alcohol. The biological material n-hexyl alcohol can be obtained, for example, by using a material collected from plants or animals (e.g., 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 C6 alkyl (meth)acrylate per 100 parts by mass of the (meth)acrylic monomer is 40 parts by mass, and the preferred upper limit is 99 parts by mass. When the content of the C6 alkyl (meth)acrylate is 40 parts by mass or more, the adhesive and adhesive layer obtained by curing the adhesive composition of this embodiment have better conformability to rough surfaces and can further suppress odor generation. When the content of the C6 alkyl (meth)acrylate is 99 parts by mass or less, the adhesive and adhesive layer obtained by curing the adhesive composition of this embodiment have better adhesive strength. The more preferred lower limit of the content of the C6 alkyl (meth)acrylate is 50 parts by mass, and the more preferred upper limit is 97 parts by mass, and even more preferred lower limit is 60 parts by mass, and even more preferred upper limit is 95 parts by mass.

[0015] The (meth)acrylic monomer preferably contains a monomer having two or more (meth)acryloyl groups in one molecule. When the (meth)acrylic monomer contains a monomer having two or more (meth)acryloyl groups in one molecule, curing of the pressure-sensitive adhesive composition of the present embodiment proceeds more easily, and the pressure-sensitive adhesive and pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition of the present embodiment have excellent cohesive strength and exhibit even better adhesive strength. Furthermore, having excellent cohesive strength further improves heat resistance and exhibits better retention performance at high temperatures. In this specification, the term "(meth)acryloyl" means acryloyl or methacryloyl.

[0016] Examples of the monomer having two or more (meth)acryloyl groups in one molecule include polyfunctional urethane (meth)acrylates, polyfunctional (meth)acrylic acid ester compounds, polyfunctional epoxy (meth)acrylates, etc. In this specification, the term "epoxy (meth)acrylate" refers to a compound in which all epoxy groups in an epoxy compound have reacted with (meth)acrylic acid.

[0017] The polyfunctional urethane (meth)acrylate can be obtained, for example, by reacting an isocyanate compound with a (meth)acrylic acid derivative having a hydroxyl group in the presence of a catalytic amount of a tin compound.

[0018] Examples of the isocyanate compound that can be used as a raw material for the polyfunctional urethane (meth)acrylate include isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), hydrogenated MDI, polymeric MDI, 1,5-naphthalene diisocyanate, norbornane diisocyanate, tolidine diisocyanate, xylylene diisocyanate (XDI), hydrogenated XDI, lysine diisocyanate, triphenylmethane triisocyanate, tris(isocyanatephenyl)thiophosphate, tetramethylxylylene diisocyanate, and 1,6,11-undecane triisocyanate.

[0019] Furthermore, as the isocyanate compound serving as a raw material for the polyfunctional urethane (meth)acrylate, a chain-extended isocyanate compound obtained by reacting a polyol with an excess of an isocyanate compound can also be used. Examples of the polyol include ethylene glycol, propylene glycol, tetraethylene glycol, glycerin, sorbitol, trimethylolpropane, carbonate diol, polyether diol, polyester diol, and polycaprolactone diol.

[0020] Examples of the (meth)acrylic acid derivatives having a hydroxyl group include hydroxyalkyl mono(meth)acrylates, mono(meth)acrylates of dihydric alcohols, and mono(meth)acrylates or di(meth)acrylates of trihydric alcohols. Examples of the hydroxyalkyl mono(meth)acrylates include 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, and 4-hydroxybutyl(meth)acrylate. Examples of the dihydric alcohols include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and polyethylene glycol. Examples of the trihydric alcohols include trimethylolethane, trimethylolpropane, and glycerin.

[0021] Examples of the polyfunctional (meth)acrylic acid ester compound include 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 2-n-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide-added bisphenol A di(meth)acrylate, propylene oxide-added bisphenol A di(meth)acrylate, ethylene oxide-added bisphenol F di(meth)acrylate, dimethylol dicyclopentadiene Di(meth)acrylate, ethylene oxide modified isocyanuric acid di(meth)acrylate, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate, carbonate diol di(meth)acrylate, polyether diol di(meth)acrylate, polyester diol di(meth)acrylate, polycaprolactone diol di(meth)acrylate, polybutadiene diol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, trimethyl Trimethylolpropane tri(meth)acrylate, ethylene oxide-added trimethylolpropane tri(meth)acrylate, propylene oxide-added trimethylolpropane tri(meth)acrylate, caprolactone-modified trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, ethylene oxide-added isocyanuric acid tri(meth)acrylate, glycerin tri(meth)acrylate, propylene oxide-added glycerin tri(meth)acrylate , pentaerythritol tri(meth)acrylate, tris(meth)acryloyloxyethyl phosphate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate.

[0022] Examples of the polyfunctional epoxy (meth)acrylate include bisphenol A type epoxy (meth)acrylate, bisphenol F type epoxy (meth)acrylate, bisphenol E type epoxy (meth)acrylate, and caprolactone-modified versions of these.

[0023] The preferred lower limit of the content of the monomer having two or more (meth)acryloyl groups per molecule per 100 parts by mass of the (meth)acrylic monomer is 0.01 parts by mass, and the preferred upper limit is 10 parts by mass. When the content of the monomer having two or more (meth)acryloyl groups per molecule is 0.01 parts by mass or more, curing of the pressure-sensitive adhesive composition of the present embodiment proceeds more easily, and the pressure-sensitive adhesive and pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition of the present embodiment have excellent cohesive strength and exhibit even better adhesive strength. In addition, the excellent cohesive strength further improves heat resistance and exhibits better retention performance at high temperatures. When the content of the monomer having two or more (meth)acryloyl groups per molecule is 10 parts by mass or less, the pressure-sensitive adhesive and pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition of the present embodiment have appropriate flexibility and exhibit better conformability to rough surfaces. The lower limit of the content of the monomer having two or more (meth)acryloyl groups in one molecule is more preferably 0.1 parts by mass, more preferably 8.0 parts by mass, even more preferably 0.5 parts by mass, even more preferably 5.0 parts by mass, even more preferably 2.0 parts by mass, and particularly preferably 1.0 parts by mass.

[0024] The (meth)acrylic monomer preferably contains a monomer having a crosslinkable functional group. When the (meth)acrylic monomer contains the monomer having a crosslinkable functional group, the pressure-sensitive adhesive and pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition of the present embodiment have excellent cohesive strength and even better adhesive strength. Furthermore, the excellent cohesive strength further improves heat resistance and retention performance at high temperatures. Note that in this specification, the above-mentioned monomer having two or more (meth)acryloyl groups in one molecule is not considered to be the monomer having the crosslinkable functional group in the (meth)acrylic monomer.

[0025] 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, a nitrile group-containing monomer, etc. Among these, it is preferable that 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, since this makes it easy to adjust the degree of crosslinking of the pressure-sensitive adhesive composition of the present embodiment.

[0026] Examples of the carboxy group-containing monomer include (meth)acrylic acid. Examples of the hydroxy 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, and 9-hydroxynonyl (meth)acrylate. Examples of the glycidyl group-containing monomer include glycidyl (meth)acrylate. 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.

[0027] The preferred lower limit of the content of the monomer having a crosslinkable functional group per 100 parts by mass of the (meth)acrylic monomer is 0.01 parts by mass, and the preferred upper limit is 20 parts by mass. When the content of the monomer having a crosslinkable functional group is 0.01 parts by mass or more, the pressure-sensitive adhesive and pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition of this embodiment have excellent cohesion and exhibit even better adhesive strength. Furthermore, the excellent cohesion further improves heat resistance and exhibits better retention performance at high temperatures. When the content of the monomer having a crosslinkable functional group is 20 parts by mass or less, the pressure-sensitive adhesive and pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition of this embodiment have appropriate flexibility and exhibit excellent conformability to rough surfaces. The more preferred lower limit of the content of the monomer having a crosslinkable functional group is 0.05 parts by mass, the more preferred upper limit is 15 parts by mass, the even more preferred lower limit is 0.1 parts by mass, the even more preferred upper limit is 10 parts by mass, the even more preferred lower limit is 1.0 part by mass, and the particularly preferred lower limit is 3.0 parts by mass.

[0028] The (meth)acrylic monomer may contain other (meth)acrylic monomers other than the C6 alkyl(meth)acrylate, the monomer having two or more (meth)acryloyl groups in one molecule, and the monomer having a crosslinkable functional group, as long as the object of the present invention is not impaired. Examples of the other (meth)acrylic monomers include alkyl(meth)acrylates having an alkyl group having 7 or more carbon atoms.

[0029] 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.

[0030] The content of the alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms in a total of 100 parts by mass of the (meth)acrylic monomer and the (meth)acrylic polymer described below is preferably 50 parts by mass or less. By ensuring that the content of the alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms is 50 parts by mass or less, the pressure-sensitive adhesive and pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition of this embodiment can further suppress odor generation. The upper limit of the content of the alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms is more preferably 40 parts by mass, even more preferably 30 parts by mass, and even more preferably 10 parts by mass, and it is most preferred that the (meth)acrylic monomer does not contain the alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms.

[0031] Furthermore, examples of the other (meth)acrylic monomers include alkyl (meth)acrylates having an alkyl group having 5 or less carbon atoms, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and polypropylene glycol mono(meth)acrylate.

[0032] The pressure-sensitive adhesive composition of the present embodiment may contain other monomers besides the (meth)acrylic monomers, such as vinyl acetate, styrene, and bismaleimide, within the scope of not interfering with the object of the present invention.

[0033] The C6 alkyl (meth)acrylate, the monomer having two or more (meth)acryloyl groups in one molecule, the monomer having a crosslinkable functional group, and the other monomers are preferably acrylate monomers. By using the C6 alkyl (meth)acrylate, the monomer having two or more (meth)acryloyl groups in one molecule, the monomer having a crosslinkable functional group, and the other monomers, the adhesive and adhesive layer obtained by curing the adhesive composition of this embodiment have improved flexibility and can exhibit better conformability to rough surfaces, compared to when a methacrylate monomer is used.

[0034] The monomer having two or more (meth)acryloyl groups per molecule, the monomer having a crosslinkable functional group, and the other monomers preferably contain biologically derived materials, but may also consist solely of petroleum-derived materials. Theoretically, it is also possible for all of the (meth)acrylic monomers to 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.

[0035] The preferred lower limit of the content of the (meth)acrylic monomer in the pressure-sensitive adhesive composition of this embodiment is 20% by mass, and the preferred upper limit is 95% by mass. When the content of the (meth)acrylic monomer is within this range, the pressure-sensitive adhesive and pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition of this embodiment have better conformability to rough surfaces and can further suppress odor generation. The more preferred lower limit of the content of the (meth)acrylic monomer is 30% by mass, and the more preferred upper limit is 80% by mass.

[0036] The pressure-sensitive adhesive composition of the present embodiment contains a (meth)acrylic polymer. The (meth)acrylic polymer has structural units derived from alkyl(meth)acrylate.

[0037] The alkyl(meth)acrylate-derived structural unit preferably includes a structural unit derived from an alkyl(meth)acrylate having a linear or branched alkyl group having 6 carbon atoms (hereinafter also referred to as a "C6 alkyl(meth)acrylate-derived structural unit"). When the (meth)acrylic polymer includes a C6 alkyl(meth)acrylate-derived structural unit, the pressure-sensitive adhesive composition of the present embodiment can exhibit better conformability to rough surfaces and can further suppress odor generation.

[0038] The reason why the (meth)acrylic polymer containing structural units derived from the C6 alkyl (meth)acrylate enables the PSA composition of the present embodiment to exhibit superior conformability to rough surfaces is unclear. However, it is presumed that the (meth)acrylic polymer containing structural units derived from the C6 alkyl (meth)acrylate reduces the glass transition temperature of the (meth)acrylic polymer and reduces the storage modulus of the PSA composition of the present embodiment at room temperature compared to when the (meth)acrylic polymer contains structural units derived from a (meth)acrylic monomer with a low alkyl group carbon number, such as n-butyl (meth)acrylate. This results in the PSA composition of the present embodiment exhibiting flexibility and superior conformability to rough surfaces. Furthermore, the C6 alkyl (meth)acrylate has a lower boiling point than a (meth)acrylic monomer with a high carbon number, such as 2-ethylhexyl (meth)acrylate. Therefore, when a PSA or PSA tape is produced through a heat drying process, residual (meth)acrylic monomer is prevented from remaining in the PSA or PSA tape, which in turn further reduces odor generation from the PSA or PSA tape.

[0039] Examples of the structural unit derived from the C6 alkyl (meth)acrylate include the structural unit derived from the C6 alkyl (meth)acrylate in the (meth)acrylic monomer described above. In particular, the structural unit derived from the C6 alkyl (meth)acrylate preferably includes a structural unit derived from n-hexyl (meth)acrylate. When the (meth)acrylic polymer contains a structural unit derived from n-hexyl (meth)acrylate, the cohesive strength and peel resistance of the pressure-sensitive adhesive composition of the present embodiment are increased. Furthermore, when the (meth)acrylic polymer contains a structural unit derived from n-hexyl (meth)acrylate, the glass transition temperature (Tg) of the (meth)acrylic polymer is further reduced, and the storage modulus of the pressure-sensitive adhesive composition of the present embodiment at room temperature is further reduced. Therefore, it is presumed that the pressure-sensitive adhesive composition of the present embodiment exhibits greater flexibility and is able to exhibit better conformability to rough surfaces.

[0040] The C6 alkyl (meth)acrylate in the structural unit derived from the C6 alkyl (meth)acrylate may consist 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. Inclusion of a biologically-derived material in the C6 alkyl (meth)acrylate in the structural unit derived from 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, and is also preferable from the perspective of reducing carbon dioxide emissions.

[0041] 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 by esterification of n-hexyl alcohol, 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 (e.g., linoleic acid derived from castor oil) as a raw material, converting it into hexanal using an enzyme, followed by hydrogenation.

[0042] The preferred lower limit of the content of the structural units derived from the C6 alkyl (meth)acrylate in the (meth)acrylic polymer is 40% by mass, and the preferred upper limit is 99% 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 the present embodiment can exhibit better conformability to rough surfaces and can further suppress the generation of odors. 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 can exhibit better adhesive strength. A more preferred lower limit of the content of the structural units derived from the C6 alkyl (meth)acrylate is 50% by mass, a more preferred upper limit is 97% by mass, an even more preferred lower limit is 60% by mass, and an even more preferred upper limit is 95% by mass. The content of the structural units derived from the C6 alkyl (meth)acrylate in the (meth)acrylic polymer can be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy measurement ( １ H-NMR, １３ C-NMR, etc., and calculation can be performed from the integrated intensity ratio of the hydrogen peak derived from the C6 alkyl (meth)acrylate.

[0043] In the pressure-sensitive adhesive composition of this embodiment, the total content of the alkyl (meth)acrylate having a linear or branched alkyl group containing 6 carbon atoms and the structural units derived from the alkyl (meth)acrylate having a linear or branched alkyl group containing 6 carbon atoms in the (meth)acrylic polymer in the total of the (meth)acrylic monomer and the (meth)acrylic polymer (hereinafter, sometimes simply referred to as the "total content of C6 alkyl (meth)acrylate components") is preferably 60% by mass. By having a total content of the C6 alkyl (meth)acrylate components of 60% by mass or more, the pressure-sensitive adhesive composition of this embodiment can exhibit superior conformability to rough surfaces and further suppress odor generation. A more preferred lower limit of the total content of the C6 alkyl (meth)acrylate components is 70% by mass, and an even more preferred lower limit is 80% by mass. The preferred upper limit of the total content of the C6 alkyl (meth)acrylate components is 99% by mass. When the total content of the C6 alkyl (meth)acrylate components is 99% by mass or less, the pressure-sensitive adhesive composition of this embodiment exhibits superior adhesive strength. A more preferred upper limit of the total content of the C6 alkyl (meth)acrylate components is 97% by mass, and an even more preferred upper limit is 95% by mass. Note that when the (meth)acrylic polymer does not have a structural unit derived from the C6 alkyl (meth)acrylate, the total content of the C6 alkyl (meth)acrylate components refers to the content of only the C6 alkyl (meth)acrylate contained in the C6 alkyl (meth)acrylate.

[0044] The (meth)acrylic polymer preferably has a structural unit derived from a monomer having a crosslinkable functional group. When the (meth)acrylic polymer has a structural unit derived from the monomer having a crosslinkable functional group, the pressure-sensitive adhesive composition of the present embodiment can exhibit excellent cohesive strength, thereby exhibiting even more excellent adhesive strength. Furthermore, the excellent cohesive strength further improves heat resistance, thereby exhibiting even better retention performance at high temperatures.

[0045] Examples of the structural unit derived from the monomer having a crosslinkable functional group include a structural unit derived from a carboxy group-containing monomer, a structural unit derived from a hydroxy group-containing monomer, a structural unit derived from a glycidyl group-containing monomer, a structural unit derived from an amide group-containing monomer, and a structural unit derived from a nitrile group-containing monomer. Among these, since this facilitates the adjustment of the degree of crosslinking of the pressure-sensitive adhesive composition of the present embodiment, it is preferred that the structural unit derived from the monomer having a crosslinkable functional group comprises at least one structural unit selected from the group consisting of a structural unit derived from a carboxy group-containing monomer and a structural unit derived from a hydroxy group-containing monomer. Furthermore, it is preferred that the monomer having a crosslinkable functional group in the structural unit derived from the monomer having a crosslinkable functional group has a (meth)acryloyl group.

[0046] Examples of the structural units derived from the carboxy group-containing monomer include structural units derived from the carboxy group-containing monomer in the (meth)acrylic monomer described above. Examples of the structural units derived from the hydroxy group-containing monomer include structural units derived from the hydroxy group-containing monomer in the (meth)acrylic monomer described above. Examples of the structural units derived from the glycidyl group-containing monomer include structural units derived from the glycidyl group-containing monomer in the (meth)acrylic monomer described above. Examples of the structural units derived from the amide group-containing monomer include structural units derived from the amide group-containing monomer in the (meth)acrylic monomer described above. Examples of the structural units derived from the nitrile group-containing monomer include structural units derived from the nitrile group-containing monomer in the (meth)acrylic monomer described above.

[0047] The content of the structural unit derived from the monomer having a crosslinkable functional group in the (meth)acrylic polymer is 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 the present embodiment can exhibit excellent cohesive strength, thereby exhibiting even better adhesive strength. Furthermore, the excellent cohesive strength further improves heat resistance, allowing the pressure-sensitive adhesive composition of the present embodiment to exhibit better retention performance at high temperatures. When the content of the structural unit derived from the monomer having a crosslinkable functional group is less than 20% by mass, the pressure-sensitive adhesive composition of the present embodiment can exhibit improved flexibility, thereby exhibiting even better conformability to rough surfaces. A more preferred lower limit of the content of the structural unit derived from the monomer having a crosslinkable functional group is 1.0% by mass, a more preferred upper limit is 10% by mass, and an even more preferred lower limit is 3.0% by mass. The content of the structural unit derived from the monomer having a crosslinkable functional group in the (meth)acrylic polymer can be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy ( １ H-NMR, １３ C-NMR, etc.) and calculation can be performed from the integrated intensity ratio of the hydrogen peak derived from the monomer having the crosslinkable functional group.

[0048] In at least one of the cases where the (meth)acrylic monomer contains a monomer having a crosslinkable functional group and the (meth)acrylic polymer contains a structural unit derived from the monomer having a crosslinkable functional group, the pressure-sensitive adhesive composition of the present embodiment has a preferred lower limit of 0.01% by mass and an upper limit of 20% by mass for the total content of the monomer having a crosslinkable functional group and the structural unit derived from the monomer having a crosslinkable functional group in the (meth)acrylic polymer in the total of the (meth)acrylic monomer and the (meth)acrylic polymer (hereinafter, sometimes simply referred to as the "total content of monomer components having a crosslinkable functional group"). When the total content of the monomer components having a crosslinkable functional group is 0.01% by mass or more, the pressure-sensitive adhesive composition of the present embodiment can exhibit excellent cohesive strength, thereby exhibiting even more excellent adhesive strength. Furthermore, the excellent cohesive strength further improves heat resistance, allowing for better retention performance at high temperatures. When the total content of the monomer components having a crosslinkable functional group is 20% by mass or less, the pressure-sensitive adhesive composition of the present embodiment can exhibit improved flexibility, thereby exhibiting even better conformability to rough surfaces. The lower limit of the total content of the monomer components having a crosslinkable functional group is more preferably 0.1% by mass, the upper limit is more preferably 15% by mass, the lower limit is still more preferably 1.0% by mass, the upper limit is still more preferably 10% by mass, and the lower limit is still more preferably 3.0% by mass. Note that when the (meth)acrylic monomer does not contain a monomer having a crosslinkable functional group, or when the (meth)acrylic polymer does not have a constituent unit derived from the monomer having a crosslinkable functional group, the total content of the monomer components having a crosslinkable functional group means only the content of one of the two.

[0049] The (meth)acrylic polymer may have a constituent unit derived from a monomer other than the constituent unit derived from the C6 alkyl (meth)acrylate and the constituent unit derived from the monomer having a crosslinkable functional group, as long as the object of the present invention is not impaired.

[0050] Examples of the structural units derived from the other monomers include structural units derived from monomers such as alkyl(meth)acrylates having a carbon number other than 6, cyclohexyl(meth)acrylate, benzyl(meth)acrylate, 2-butoxyethyl(meth)acrylate, 2-phenoxyethyl(meth)acrylate, tetrahydrofurfuryl(meth)acrylate, and polypropylene glycol mono(meth)acrylate. Further examples of the structural units derived from the other monomers include structural units derived from various monomers that are commonly used as raw materials for (meth)acrylic polymers, such as vinyl acetate and styrene.

[0051] The structural units derived from the C6 alkyl (meth)acrylate, the structural units derived from the monomer having a crosslinkable functional group, and the structural units derived from the other monomers are preferably structural units derived from acrylate monomers. When the structural units derived from the C6 alkyl (meth)acrylate, the structural units derived from the monomer having a crosslinkable functional group, and the structural units derived from the other monomers are structural units derived from acrylate monomers, the pressure-sensitive adhesive composition of the present embodiment has improved flexibility and can exhibit better conformability to rough surfaces, compared to when the structural units are derived from methacrylate monomers.

[0052] The monomer having a crosslinkable functional group and the other monomer preferably contain a biologically-derived material, but may also consist solely of petroleum-derived materials. Theoretically, all of the (meth)acrylic monomers constituting the (meth)acrylic polymer may be monomers containing a biologically-derived material. 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.

[0053] The preferred lower limit of the weight-average molecular weight of the (meth)acrylic polymer is 100,000, and the preferred upper limit is 2,000,000. When the weight-average molecular weight of the (meth)acrylic polymer is 100,000 or more, the pressure-sensitive adhesive composition of the present embodiment can exhibit excellent cohesive strength, thereby exhibiting even better adhesive strength. Furthermore, the excellent cohesive strength further improves heat resistance, thereby enabling better retention performance at high temperatures. When the weight-average molecular weight of the (meth)acrylic polymer is 2,000,000 or less, the pressure-sensitive adhesive composition of the present embodiment can exhibit improved flexibility, thereby enabling better conformability to rough surfaces. The more preferred lower limit of the weight-average molecular weight of the (meth)acrylic polymer is 300,000, the more preferred upper limit is 1,500,000, and the even more preferred upper limit is 1,000,000. In this specification, the weight-average molecular weight is the weight-average molecular weight converted into standard polystyrene by GPC (gel permeation chromatography) measurement. Specifically, a (meth)acrylic polymer is diluted 50 times with tetrahydrofuran (THF), and the resulting diluted solution is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm) to prepare a measurement sample. Next, this measurement sample is supplied to a gel permeation chromatograph, and GPC measurement is performed under conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C. The polystyrene-equivalent molecular weight of the (meth)acrylic polymer is measured, and this value is taken as the weight-average molecular weight of the (meth)acrylic polymer. Examples of the gel permeation chromatograph include the 2690 Separations Module (manufactured by Waters Corporation).

[0054] The (meth)acrylic polymer 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.

[0055] Examples of methods for adjusting the weight average molecular weight of the (meth)acrylic polymer include a method of changing the type or amount of a polymerization initiator or the monomer concentration during the polymerization reaction, a method of adding a small amount of a chain transfer agent such as dodecyl mercaptan, a method of changing the type of polymerization reaction solvent to control chain transfer to the solvent, and a method of changing the temperature and time during the reaction.

[0056] Examples of the polymerization initiator used for synthesizing the (meth)acrylic polymer 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 performed 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.

[0057] The preferred lower limit of the (meth)acrylic polymer content in the pressure-sensitive adhesive composition of this embodiment is 5.0% by mass, and the preferred upper limit is 80% by mass. By having the (meth)acrylic polymer content in this range, the pressure-sensitive adhesive composition of this embodiment can exhibit better conformability to rough surfaces and can further suppress the generation of odor. The more preferred lower limit of the (meth)acrylic polymer content is 20% by mass, and the more preferred upper limit is 70% by mass.

[0058] The pressure-sensitive adhesive composition of the present embodiment contains an organic solvent, and the upper limit of the organic solvent content in the pressure-sensitive adhesive composition of the present embodiment is 10% by mass, or the pressure-sensitive adhesive composition of the present embodiment is free of organic solvent. The pressure-sensitive adhesive composition of the present embodiment contains an organic solvent, and the ... Specifically, the organic solvent contained in the pressure-sensitive adhesive layer is identified, and then the pressure-sensitive adhesive composition is diluted with chloroform using the identified organic solvent as a standard sample with a known content, and the measurement sample is subjected to gas chromatography mass spectrometry (GC-MS), a calibration curve is created using the measured peak areas, and the content of the organic solvent is calculated using the created calibration curve. The measurement conditions for gas chromatography mass spectrometry are, for example, as follows. <GC-MS Measurement Conditions> Gas chromatograph mass spectrometer: JMS Q1500 (manufactured by JEOL Ltd.) Mobile phase: helium Helium flow rate: 1.0 mL / min Detector: quadrupole mass spectrometer Ionization method: EI method Column: SLB-5ms capillary GC column (manufactured by Sigma-Aldrich) Injection port temperature: 320°C Column temperature: 40°C to 340°C Injection volume: 1.0 μL

[0059] Methods for adjusting the content ratio of the organic solvent in the adhesive composition of this embodiment include, for example, a method of reducing the amount of solvent used in synthesizing the (meth)acrylic polymer, and a method of removing the organic solvent after synthesizing the (meth)acrylic polymer.

[0060] When the pressure-sensitive adhesive composition of the present embodiment contains a solvent, the solvent is not particularly limited, and water, an organic solvent, a mixed solvent of water and an organic solvent, etc. can be used. However, from the viewpoint of further reducing the environmental load caused by volatile organic compounds (VOCs) remaining in the pressure-sensitive adhesive and pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition of the present embodiment, it is preferable that the content of the organic solvent is as small as possible, as described above.

[0061] The pressure-sensitive adhesive composition of the present embodiment preferably contains a polymerization initiator. By containing the polymerization initiator in the pressure-sensitive adhesive composition of the present embodiment, curing of the pressure-sensitive adhesive composition of the present embodiment is more likely to proceed. From the viewpoint of storage stability, etc., the polymerization initiator may be blended into the pressure-sensitive adhesive composition of the present embodiment immediately before curing the pressure-sensitive adhesive composition.

[0062] The polymerization initiator may be a photopolymerization initiator or a thermal polymerization initiator, but from the viewpoint of reducing the energy required for curing, a photopolymerization initiator is preferred.

[0063] Examples of the photopolymerization initiator include acetophenone derivatives such as alkylphenone compounds, benzoin ether compounds, ketal derivatives, phosphine oxide derivatives such as acylphosphine oxide compounds, titanocene compounds, oxime ester compounds, thioxanthone compounds, etc. Among these, acetophenone derivatives and phosphine oxide derivatives are preferred from the viewpoints of adjusting the gel fraction of the pressure-sensitive adhesive layer described below and improving the reaction rate of the monomer to be polymerized, thereby facilitating the polymerization reaction.

[0064] Examples of the acetophenone derivatives include methoxyacetophenone, 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one, etc. Examples of the benzoin ether compounds include benzoin propyl ether and benzoin isobutyl ether, etc. Examples of the ketal derivatives include benzyl dimethyl ketal and acetophenone diethyl ketal, etc. Examples of the phosphine oxide derivatives include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, etc. Examples of the titanocene compounds include bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titanocene, etc. Examples of the oxime ester compound include 1-(O-acetyloxime)-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]ethanone and 1-[4-(phenylthio)phenyl]-2-(O-benzoyloxime)-1,2-octadione. Examples of the thioxanthone compound include 2-isopropylthioxanthone. Examples of the photopolymerization initiator include bis(η5-cyclopentadienyl)titanocene derivative compounds, benzophenone, Michler's ketone, chlorothioxanthone, dodecylthioxanthone, dimethylthioxanthone, diethylthioxanthone, α-hydroxycyclohexylphenyl ketone, and 2-hydroxymethylphenylpropane. These photopolymerization initiators may be used alone or in combination of two or more.

[0065] The photopolymerization initiator preferably contains a compound having two or more photopolymerization reaction sites. When the photopolymerization initiator contains a compound having two or more photopolymerization reaction sites, the pressure-sensitive adhesive composition of the present embodiment is more likely to cure. Examples of the compound having two or more photopolymerization reaction sites include Omnipol TP (manufactured by IGM Resins) and Omnipol 910 (manufactured by IGM Resins). In this specification, the term "photopolymerization reaction site" refers to the structure of a carbonyl group that contributes to a Norrish type I cleavage reaction or a carbonyl group that contributes to a Norrish type II hydrogen abstraction reaction.

[0066] Examples of the thermal polymerization initiator include organic peroxide-based thermal polymerization initiators, etc. Commercially available examples of the organic peroxide-based thermal polymerization initiator include Perbutyl H and Percumyl H (both manufactured by NOF Corporation).

[0067] The content of the polymerization initiator is preferably 0.01 parts by mass at its lower limit and 10 parts by mass at its upper limit, relative to 100 parts by mass of the total of the (meth)acrylic monomer and the (meth)acrylic polymer. By having the content of the polymerization initiator within this range, the curing of the pressure-sensitive adhesive composition of this embodiment proceeds more easily, and the pressure-sensitive adhesive and pressure-sensitive adhesive layer obtained by curing the pressure-sensitive adhesive composition of this embodiment have appropriate flexibility and exhibit excellent conformability to rough surfaces. The lower limit of the content of the polymerization initiator is more preferably 0.1 parts by mass, the upper limit is more preferably 5.0 parts by mass, and the upper limit is even more preferably 1.0 part by mass.

[0068] The pressure-sensitive adhesive composition of the present embodiment preferably contains a tackifier resin. When the pressure-sensitive adhesive composition of the present embodiment contains a tackifier resin, it can exhibit even better adhesive strength.

[0069] The tackifier resin is not particularly limited, and examples thereof include rosin ester tackifier resins, terpene tackifier resins, coumarone-indene tackifier resins, alicyclic saturated hydrocarbon tackifier resins, C5 petroleum tackifier resins, C9 petroleum tackifier resins, and C5-C9 copolymer petroleum tackifier resins. These tackifier resins may be used alone or in combination of two or more. Among these, it is preferable to use at least one selected from the group consisting of rosin ester tackifier resins and terpene tackifier resins.

[0070] Examples of the rosin ester-based tackifying resin include polymerized rosin ester-based resins and hydrogenated rosin ester-based resins. Examples of the terpene-based tackifying resin include terpene-based resins and terpene phenol-based resins. The rosin ester-based tackifying resins and terpene-based tackifying resins are preferably derived from living organisms. Examples of the rosin ester-based tackifying resins derived from living organisms include rosin ester-based tackifying resins derived from natural resins such as pine resin. Examples of the terpene-based tackifying resins derived from living organisms include terpene-based tackifying resins derived from plant essential oils.

[0071] Specific examples of the rosin ester-based tackifying resin 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-based tackifying resin include YS Resin PX1250 and YS Polystar G150 (all manufactured by Yasuhara Chemical Co., Ltd.).

[0072] In the pressure-sensitive adhesive composition of this embodiment, the preferred lower limit of the content of the tackifier resin relative to 100 parts by mass of the total of the (meth)acrylic monomer and the (meth)acrylic polymer is 10 parts by mass, and the preferred upper limit is 50 parts by mass. When the content of the tackifier resin is 10 parts by mass or more, the pressure-sensitive adhesive composition of this embodiment can exhibit superior adhesive strength. When the content of the tackifier resin is 50 parts by mass or less, the flexibility of the pressure-sensitive adhesive composition of this embodiment 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 resin is 15 parts by mass, and a more preferred upper limit is 40 parts by mass.

[0073] The pressure-sensitive adhesive composition of the present embodiment preferably contains a crosslinking agent from the viewpoint of being able to appropriately adjust the degree of crosslinking. From the viewpoint of storage stability, etc., the crosslinking agent may be blended into the pressure-sensitive adhesive composition of the present embodiment immediately before forming the pressure-sensitive adhesive layer. 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, the crosslinking agent preferably contains at least one selected from the group consisting of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent, and more preferably is an isocyanate-based crosslinking agent, so that the pressure-sensitive adhesive composition of the present embodiment can exhibit superior adhesion to the adherend.

[0074] In the pressure-sensitive adhesive composition of this embodiment, the preferred lower limit of the content of the crosslinking agent relative to 100 parts by mass of the total of the (meth)acrylic monomer and the (meth)acrylic polymer 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 of this embodiment can be appropriately adjusted, allowing for superior adhesive strength and superior adhesion to the adherend. The more preferred lower limit of the content of the crosslinking agent is 0.1 parts by mass, the more preferred upper limit is 8.0 parts by mass, the even more preferred lower limit is 1.0 part by mass, and the even more preferred upper limit is 5.0 parts by mass. In this specification, the "content of crosslinking agent" refers to the content of the solids of the crosslinking agent.

[0075] The pressure-sensitive adhesive composition of the present embodiment 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.

[0076] The pressure-sensitive adhesive composition of the present embodiment preferably further contains a pigment. By containing a pigment, the pressure-sensitive adhesive composition of the present embodiment can exhibit light-blocking properties. Therefore, when a pressure-sensitive adhesive or pressure-sensitive adhesive tape formed from the pressure-sensitive adhesive composition of the present embodiment containing a pigment is attached to a rough surface, the adhesive surface of the rough surface to which it is attached is filled without any gaps with the pressure-sensitive adhesive or pressure-sensitive adhesive tape having 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 can be more suitably used for fixing electronic device components or vehicle-mounted components.

[0077] Examples of the pigment include color pigments such as black fillers, etc. Specific examples of the black fillers include carbon black and titanium black.

[0078] 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 of the present embodiment can better exhibit light-blocking properties. A more preferred lower limit of the average particle size of the black filler is 0.1 μm and a more preferred upper limit is 0.8 μm. The average particle size can be determined, for example, by observing 50 arbitrary black fillers with an electron microscope or an optical microscope and calculating the average particle size of each black filler, or by performing laser diffraction particle size distribution measurement.

[0079] In the pressure-sensitive adhesive composition of this embodiment, the preferred lower limit of the pigment content relative to 100 parts by mass of the total of the (meth)acrylic monomer and the (meth)acrylic polymer is 0.1 parts by mass, and the preferred upper limit is 5.0 parts by mass. When the pigment content is within this range, the pressure-sensitive adhesive composition of this embodiment can exhibit better light-blocking properties. The more preferred lower limit of the pigment content is 0.5 parts by mass, and the more preferred upper limit is 3.0 parts by mass.

[0080] The pressure-sensitive adhesive composition of the present embodiment may contain additives such as a silane coupling agent, a plasticizer, a softener, a filler, a dye, etc., as needed, within the scope of not impairing the object of the present invention.

[0081] The method for producing the pressure-sensitive adhesive composition of the present embodiment is not particularly limited, and the composition can be produced by a conventionally known production method, for example, by adding the above-mentioned (meth)acrylic monomer and the above-mentioned (meth)acrylic polymer, and, if necessary, a polymerization initiator, a tackifier resin, a crosslinking agent, a solvent, etc.

[0082] The preferred lower limit of the content of bio-derived carbon in the PSA composition of this embodiment is 10%. By having the content of bio-derived carbon in the PSA composition of this embodiment be 10% or more, the PSA composition of this embodiment is excellent in terms of saving petroleum resources and reducing carbon dioxide emissions, and can reduce the environmental burden. A more preferred lower limit of the content of bio-derived carbon in the PSA composition of this embodiment is 40%, and an even more preferred lower limit is 60%. The upper limit of the content of bio-derived carbon in the PSA composition of this embodiment is not particularly limited and may be 100%. While bio-derived carbon contains a certain proportion of the radioactive isotope (C-14), petroleum-derived carbon contains almost no C-14. Therefore, the "content of bio-derived carbon" 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 D6866-22, a standard widely used in the bioplastics industry.

[0083] The content ratio of biologically-derived carbon in the pressure-sensitive adhesive composition of this embodiment can be adjusted by changing each component constituting the pressure-sensitive adhesive composition of this embodiment to a biologically-derived material and by changing the content of the biologically-derived material.

[0084] The present embodiment also includes a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer containing a cured product of the pressure-sensitive adhesive composition of the present embodiment. The gel fraction of the pressure-sensitive adhesive layer and the content of bio-derived carbon in the pressure-sensitive adhesive layer, which will be described later, can be adjusted to the values ​​described later by adjusting the types and contents of the components constituting the pressure-sensitive adhesive composition of the present embodiment.

[0085] The pressure-sensitive adhesive composition may be cured by light irradiation or by heating, but from the viewpoint of energy consumption, curing by light irradiation is preferred. Furthermore, in curing the pressure-sensitive adhesive composition, light irradiation and heating may be used in combination. In curing the pressure-sensitive adhesive composition, the solvent content of the resulting pressure-sensitive adhesive layer can be reduced by heating. A cured product of the pressure-sensitive adhesive composition can be obtained, for example, by using a wavelength of 365 nm and an irradiation intensity of 35 mW / cm. ２ The ultraviolet light irradiation dose is 1000 mJ / cm ２ or by heating for 60 seconds in an environment of 130° C. to polymerize the (meth)acrylic monomer, the (meth)acrylic polymer, etc. in the pressure-sensitive adhesive composition to obtain a (meth)acrylic copolymer. In this specification, the term "(meth)acrylic copolymer" refers to a cured product obtained by curing the pressure-sensitive adhesive composition, or a copolymer having a structural unit derived from (meth)acrylate contained in the pressure-sensitive adhesive layer.

[0086] The present invention also includes a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer 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. Examples of the (meth)acrylic copolymer having structural units derived from an alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms include the (meth)acrylic polymer in the pressure-sensitive adhesive composition, a copolymer obtained by copolymerizing the (meth)acrylic polymer with the (meth)acrylic monomer, and a copolymer obtained by copolymerizing the (meth)acrylic monomer.

[0087] In the (meth)acrylic copolymer, the preferred lower limit of the content of the structural units derived from the alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms is 60% by mass. When the content of the structural units derived from the alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms is 60% by mass or more, the pressure-sensitive adhesive layer can exhibit superior conformability to rough surfaces and can further suppress odor generation. A more preferred lower limit of the content of the structural units derived from the alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms is 70% by mass, and an even more preferred lower limit is 80% by mass. Furthermore, the preferred upper limit of the content of the structural units derived from the alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms is 99% by mass. When the content of the structural units derived from the alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms is 99% by mass or less, the pressure-sensitive adhesive layer can exhibit superior adhesive strength. The upper limit of the content of the structural units derived from the alkyl (meth)acrylate having a linear or branched alkyl group with 6 carbon atoms is more preferably 97% by mass, and even more preferably 95% by mass. The content of the structural units derived from the alkyl (meth)acrylate having a linear or branched alkyl group with 6 carbon atoms in the (meth)acrylic copolymer can be determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy of the (meth)acrylic copolymer ( １ H-NMR,１３ The carbon number can be calculated from the integrated intensity ratio of the hydrogen peak derived from the linear or branched alkyl (meth)acrylate having an alkyl group having 6 carbon atoms.

[0088] Preferably, the pressure-sensitive adhesive layer does not contain an organic solvent, or contains an organic solvent, but the content of the organic solvent in the pressure-sensitive adhesive layer is 500 ppm or less. By not containing an organic solvent in the pressure-sensitive adhesive layer, or by containing an organic solvent in the pressure-sensitive adhesive layer and the content of the organic solvent in the pressure-sensitive adhesive layer is 500 ppm or less, the environmental impact of the pressure-sensitive adhesive tape of this embodiment due to volatile organic compounds (VOCs) can be further reduced. If the pressure-sensitive adhesive layer contains an organic solvent, the upper limit of the content of the organic solvent in the pressure-sensitive adhesive layer is more preferably 200 ppm, even more preferably 150 ppm, even more preferably 100 ppm, and particularly preferably 50 ppm. It is most preferred that the pressure-sensitive adhesive layer does not contain an organic solvent. The content of the organic solvent can be measured by gas chromatography-mass spectrometry (GC / MS). Specifically, the organic solvent contained in the PSA layer is identified, and then the sol component of the PSA layer is diluted with chloroform using a standard sample with a known content of the organic solvent. The measurement sample is then subjected to gas chromatography-mass spectrometry (GC-MS measurement). A calibration curve is created from the measured peak areas, and the content of the organic solvent is calculated using the created calibration curve. The "sol component" refers to the component of the PSA layer excluding the gel component. The sol component of the PSA layer can be obtained, for example, by immersing the PSA layer in tetrahydrofuran at 23°C for 24 hours, filtering the insoluble matter through a 200-mesh wire mesh, and removing the gel component. The gas chromatography-mass spectrometry measurement conditions are, for example, as follows: <GC-MS measurement conditions> Gas chromatograph mass spectrometer: JMS Q1500 (manufactured by JEOL Ltd.) Mobile phase: Helium Helium flow rate: 1.0 mL / min Detector: Quadrupole mass spectrometer Ionization method: EI method Column: SLB-5ms capillary GC column (manufactured by Sigma-Aldrich) Injection port temperature: 320°C Column temperature: 40°C to 340°C Injection volume: 1.0 μL

[0089] Examples of methods for adjusting the content ratio of the organic solvent in the pressure-sensitive adhesive layer include a method of reducing the content ratio of the organic solvent in the pressure-sensitive adhesive composition that forms the pressure-sensitive adhesive layer, a method of reducing the amount of organic solvent used in the synthesis of the (meth)acrylic copolymer that is carried out when forming the pressure-sensitive adhesive layer, a method of lowering the boiling point of the solvent used in the synthesis of the (meth)acrylic copolymer that is carried out when forming the pressure-sensitive adhesive layer, a method of increasing the drying temperature in the heat-drying step that is carried out when forming the pressure-sensitive adhesive layer, and a method of extending the drying time in the heat-drying step that is carried out when forming the pressure-sensitive adhesive layer.

[0090] The preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 10% by mass, and the preferred upper limit is 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 this embodiment. When the gel fraction of the pressure-sensitive adhesive layer is 70% 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 this embodiment to conform to rough surfaces. The more preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 20% by mass, and the more preferred upper limit is 60% by mass, and even more preferred lower limit is 30% by mass, and even more preferred upper limit is 55% by mass. The gel fraction of the pressure-sensitive adhesive layer is measured by the following method. Specifically, first, the pressure-sensitive adhesive tape having the pressure-sensitive adhesive layer is cut into a flat rectangular shape with a width of 20 mm and a length of 40 mm to prepare a test specimen. The test specimen is then immersed in tetrahydrofuran at 23°C for 24 hours, removed from the tetrahydrofuran, and dried at 110°C for 1 hour. The mass of the test piece after drying is measured, and the gel fraction is calculated using the following formula (1). Note that no release film for protecting the pressure-sensitive adhesive layer is laminated on the test piece. When the pressure-sensitive adhesive tape of the present embodiment is a non-support type tape that does not have a substrate layer, the measurement is carried out using a test piece obtained by adhering to a substrate and cutting it, or the gel fraction is calculated by the W in the following formula (1) without using a substrate layer. ０ The calculation is performed assuming that the gel fraction is 0. Gel fraction (mass%) = 100 × (W ２ -W ０ ) / (W １ -W ０ ) (1) (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)

[0091] Methods for adjusting the gel fraction of the pressure-sensitive adhesive layer to fall within the above-mentioned range include, for example, a method for adjusting the type and content of each component constituting the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer as described above (for example, a method for changing the type and content of the crosslinking agent), and a method for adjusting the illuminance or irradiation time of the electron beam or ultraviolet light used when irradiating with an electron beam or ultraviolet light to form the pressure-sensitive adhesive layer, but are not limited to these methods.

[0092] A preferred lower limit for the content of bio-derived carbon in the pressure-sensitive adhesive layer is 10%. When the content of bio-derived carbon in the pressure-sensitive adhesive layer is 10% or more, the pressure-sensitive adhesive tape of the present embodiment is excellent from the viewpoints of saving petroleum resources and reducing carbon dioxide emissions, and is capable of reducing the environmental burden. A more preferred lower limit for the content of bio-derived carbon in the pressure-sensitive adhesive layer is 40%, and an even more preferred lower limit is 60%. Furthermore, the upper limit for the content of bio-derived carbon in the pressure-sensitive adhesive layer is not particularly limited, and may be 100%.

[0093] 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 this embodiment has sufficient adhesive strength. When the thickness of the pressure-sensitive adhesive layer is 300 μm or less, the pressure-sensitive adhesive tape of this embodiment 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, and the even more preferred lower limit is 10 μm, and the even more preferred upper limit is 100 μm.

[0094] The pressure-sensitive adhesive tape of this embodiment 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 this embodiment preferably has a base layer, as this provides a pressure-sensitive adhesive tape that is stiff and has excellent conformability to rough surfaces. Furthermore, when the pressure-sensitive adhesive tape of this embodiment is a support type tape that has a base layer, it may be a single-sided pressure-sensitive adhesive tape that has a pressure-sensitive adhesive layer on one side of the base layer, or a double-sided pressure-sensitive adhesive tape that has pressure-sensitive adhesive layers on both sides of the base layer.

[0095] 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 of the present embodiment to conform to irregularities.

[0096] The substrate used in the substrate layer is preferably a substrate made of a biological material, from the viewpoint of increasing the content of biological carbon in the entire pressure-sensitive adhesive tape. Examples of the biological 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.

[0097] Furthermore, from the perspective of reducing the use of new petroleum resources and reducing the environmental burden by suppressing carbon dioxide emissions, substrates made from recycled resources may be used. Examples of resource recycling methods include collecting waste materials such as packaging containers, home appliances, automobiles, construction materials, and food, as well as waste generated during manufacturing processes, and then cleaning, decontaminating, or decomposing the extracted materials by heating or fermentation to reuse them as raw materials. Examples of substrates made from recycled resources include films and nonwoven fabrics made from PET, PBT, PE, PP, PA, etc., which are made from recycled plastics that have been re-resinized. Furthermore, the collected waste materials may be burned and used as thermal energy for the production of substrates and their raw materials. The oils and fats contained in the collected waste materials may be mixed with petroleum, fractionated, and purified, and then used as raw materials.

[0098] The 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.

[0099] 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.

[0100] 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, even more preferred upper limit is 300 μm, and even more preferred upper limit is 100 μm.

[0101] The substrate used in 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.

[0102] 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 an adhesive tape that has stiffness while exhibiting high flexibility so that it can be adhered to the shape of the adherend. The more preferred lower limit of the thickness of the substrate is 4 μm, and the more preferred upper limit is 1000 μm, and even more preferred lower limit is 10 μm, and even more preferred upper limit is 300 μm.

[0103] The pressure-sensitive adhesive tape of this embodiment has a total thickness (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) of preferably 3 μm at the lower limit and 6000 μm at the upper limit. Having a total thickness within this range of the pressure-sensitive adhesive tape of this embodiment further increases the adhesive strength of the pressure-sensitive adhesive tape of this embodiment. A more preferred lower limit of the total thickness of the pressure-sensitive adhesive tape of this embodiment is 5 μm, a more preferred upper limit is 1200 μm, an even more preferred lower limit is 10 μm, an even more preferred upper limit is 500 μm, and an even more preferred upper limit is 100 μm. It should be noted that, in this specification, the "total thickness of the pressure-sensitive adhesive tape" does not include the thickness of a separator such as a release PET film that protects the outermost pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape.

[0104] The method for producing the pressure-sensitive adhesive tape of this embodiment is not particularly limited, and the tape can be produced by a conventionally known production method. For example, in the case of a double-sided pressure-sensitive adhesive tape, the following method can be used. First, a 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 a release film, and then another release film is placed on top of it with its release-treated surface facing the coated pressure-sensitive adhesive composition A to seal the pressure-sensitive adhesive composition A. UV light is irradiated onto the pressure-sensitive adhesive composition A through the release film. Then, one of the release films is peeled off, and the UV-irradiated pressure-sensitive adhesive composition A is dried by heating to form a pressure-sensitive adhesive layer A containing a cured product of the pressure-sensitive adhesive composition A. The obtained pressure-sensitive adhesive layer A is placed on a substrate and pressed with a rubber roller or the like to produce a laminate. Next, a pressure-sensitive adhesive layer B is formed in the same manner as the pressure-sensitive adhesive layer A. Then, the pressure-sensitive adhesive layer B is placed on the back surface of the substrate on which the pressure-sensitive adhesive layer A has been formed to produce a laminate. Then, by pressing the laminate with a rubber roller or the like, a double-sided adhesive tape can be obtained which has adhesive layers on both sides of the substrate and in which the surfaces of the adhesive layers are covered with release films.

[0105] Alternatively, two sets of laminate films may be prepared in a similar manner, and these laminate films may be superimposed on each of both surfaces of a substrate with the pressure-sensitive adhesive layer of the laminate film facing the substrate to prepare a laminate. This laminate may then be pressed with a rubber roller or the like to obtain a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both surfaces of the substrate and in which the surfaces of the pressure-sensitive adhesive layers are covered with release films.

[0106] The use of the pressure-sensitive adhesive tape of this embodiment is not particularly limited, but it is preferably used for fixing electronic device components or vehicle-mounted components. Specifically, the pressure-sensitive adhesive tape of this embodiment can be suitably used for adhesively fixing electronic device components in large portable electronic devices, adhesively fixing vehicle-mounted components (e.g., vehicle-mounted panels), etc.

[0107] This embodiment also includes a method for producing a pressure-sensitive adhesive tape, which includes step (I) of irradiating the pressure-sensitive adhesive composition of this embodiment with light to cure it, and step (II) of heating the cured product of the pressure-sensitive adhesive composition cured in step (I).

[0108] Examples of the step (I) include a step of applying the pressure-sensitive adhesive composition or a solution obtained by adding a photopolymerization initiator to the pressure-sensitive adhesive composition to a release-treated surface of a substrate or a release film, sealing the pressure-sensitive adhesive composition, and irradiating the pressure-sensitive adhesive composition with light. The light irradiation conditions in the step (I) include, for example, a wavelength of 365 nm and an irradiation intensity of 35 mW / cm. ２ The irradiation dose of light is 1000 mJ / cm ２ Examples of such a method include irradiating the light so that the

[0109] The heating conditions in the step (II) include, for example, heating at 130° C. for 60 seconds.

[0110] According to the present invention, a pressure-sensitive adhesive composition can be provided that can exhibit excellent conformability to rough surfaces and can reduce odor generation and environmental impact. Furthermore, according to the present invention, a pressure-sensitive adhesive tape can be provided that can exhibit excellent conformability to rough surfaces and can reduce odor generation. Furthermore, according to the present invention, a method for producing a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition can be provided.

[0111] FIG. 1 is a diagram schematically illustrating a high temperature retention test.

[0112] 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.

[0113] <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.

[0114] <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.

[0115] <1-Methylheptyl acrylate containing bio-derived carbon> Ricinoleic acid derived from castor oil was alkali-fused to obtain a mixture containing sebacic acid and 1-methylheptyl alcohol. Next, sebacic acid was separated from the obtained mixture by distillation to obtain 1-methylheptyl alcohol containing bio-derived carbon. 1-Methylheptyl acrylate containing bio-derived carbon was prepared by esterifying the obtained 1-methylheptyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.).

[0116] <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.

[0117] <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.

[0118] <Bio-derived carbon-free 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.) Dimethylacrylamide (manufactured by Tokyo Chemical Industry Co., Ltd.) 2-Methoxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Ltd.) 1,6-Hexane diacrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) Urethane diacrylate (polyether-based multifunctional urethane acrylate: "UA-160TM" manufactured by Shin-Nakamura Chemical Co., Ltd.) Bismaleimide compound (2,2-bis[4-(4-maleimidophenoxy)phenyl]propane (manufactured by Tokyo Chemical Industry Co., Ltd.))

[0119] <Photopolymerization initiator> Photopolymerization initiator A: 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (manufactured by IGM Resins, "Omnirad TPO", number of photopolymerization reaction sites: 1) Photopolymerization initiator B: Omnipol TP (manufactured by IGM Resins, number of photopolymerization reaction sites: 3)

[0120] <Tackifying Resin> Tackifying Resin A: Terpene-based tackifying resin (terpene phenol-based resin) (manufactured by Yasuhara Chemical Co., Ltd., "YS Polystar G150", softening temperature: 145°C to 155°C)

[0121] <Crosslinking agent> Isocyanate-based crosslinking agent (manufactured by Covestro, "Desmodur L-75", diluted with ethyl acetate (dilution concentration 75%)) Epoxy-based crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, Inc., "Tetrad X")

[0122] <Pigment> Carbon black (Toyo Color Co., Ltd., "Multilac A903 Black")

[0123] Example 1 (1) Production of (meth)acrylic polymer: 100 parts by mass of ethyl acetate was added as a polymerization solvent to a reaction vessel, and nitrogen was bubbled through. The reaction vessel was then heated while nitrogen was flowing in to initiate reflux. Subsequently, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile as a polymerization initiator 10 times with ethyl acetate was added to the reaction vessel, and 47.45 parts by mass of n-hexyl acrylate containing bio-derived carbon, 0.05 parts by mass of 2-hydroxyethyl acrylate containing bio-derived carbon, and 2.5 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 added again to the reaction vessel, and a polymerization reaction was carried out for 4 hours to obtain a (meth)acrylic polymer-containing solution. The resulting (meth)acrylic polymer-containing solution was then heated and dried in an oven at 110°C for 1 hour to completely remove the ethyl acetate, thereby obtaining (meth)acrylic polymer A. Regarding the weight average molecular weight of (meth)acrylic polymer A, the obtained (meth)acrylic polymer-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 Corporation, "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 polymer was measured, and the weight average molecular weight was determined. The results are shown in Table 1.

[0124] (2) Preparation of adhesive composition, production of adhesive tape An adhesive composition was prepared by adding 50.0 parts by mass of the obtained (meth)acrylic polymer A, 47.45 parts by mass of bio-derived n-hexyl acrylate, 0.05 parts by mass of bio-derived 2-hydroxyethyl acrylate, 2.5 parts by mass of acrylic acid, 0.3 parts by mass of photopolymerization initiator B, and an isocyanate-based crosslinking agent so that the solids content was 1.0 part by mass. The prepared adhesive composition was applied to the release-treated surface of a 50 μm-thick release PET film, and then a 38 μm-thick release PET film was placed on top of it so that the release-treated surface faced the coated adhesive composition, sealing the adhesive composition. A UV-LED irradiation device (manufactured by CCS Inc., "UVS01-01") was used to irradiate the adhesive tape with light at a wavelength of 365 nm and an irradiation intensity of 35 mW / cm. ２ The ultraviolet light irradiation dose is 1000 mJ / cm ２ The pressure-sensitive adhesive composition was irradiated through a release PET film so that the ultraviolet light was irradiated onto the pressure-sensitive adhesive composition. After the release film on one side was peeled off, the pressure-sensitive adhesive composition that had been irradiated with ultraviolet light was dried at 110°C for 5 minutes to form a pressure-sensitive adhesive layer containing a cured product of the pressure-sensitive adhesive composition having a thickness of 50 µm, thereby obtaining a pressure-sensitive adhesive tape.

[0125] (3) Measurement of the content ratio of organic solvent in the pressure-sensitive adhesive composition The prepared pressure-sensitive adhesive composition was diluted with chloroform to prepare a sample solution. The obtained sample solution was subjected to gas chromatography mass spectrometry (GC / MS) measurement, and the content ratio (mass %) of the organic solvent in the pressure-sensitive adhesive composition was measured from the peak area of ​​the obtained spectrum. The results are shown in Table 3. <GC-MS measurement conditions> Gas chromatograph mass spectrometer: JMS Q1500 (manufactured by JEOL Ltd.) Mobile phase: helium Helium flow rate: 1.0 mL / min Detector: quadrupole mass spectrometer Ionization method: EI method Column: SLB-5ms capillary GC column (manufactured by Sigma-Aldrich) Injection port temperature: 320°C Column temperature: 40°C to 340°C Injection amount: 1.0 μL

[0126] (4) 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 tetrahydrofuran at 23°C for 24 hours, then removed from the tetrahydrofuran and dried at 110°C for 1 hour. The mass of the dried test piece was measured, and the gel fraction (mass%) was calculated using the following formula (1). The results are shown in Table 3. Gel fraction (mass%) = 100 × (W ２ -W ０ ) / (W １ -W ０ ) (1) (W ０ : Mass of the substrate, W １ : mass of test piece before immersion, W ２ : Mass of test piece after immersion and drying)

[0127] (5) Measurement of Solvent Content in Pressure-Sensitive Adhesive Layer In the above-mentioned "(4) Measurement of Gel Fraction of Pressure-Sensitive Adhesive Layer," the gel component of the pressure-sensitive adhesive that had absorbed and swollen tetrahydrofuran was filtered, and the resulting sol component of the pressure-sensitive adhesive layer was diluted with chloroform to prepare a sample solution. The obtained sample solution was subjected to gas chromatography mass spectrometry (GC / MS), and the content (ppm) of the organic solvent in the pressure-sensitive adhesive layer was measured from the peak area of ​​the obtained spectrum. The results are shown in Table 3. <GC-MS Measurement Conditions> Gas chromatograph mass spectrometer: JMS Q1500 (manufactured by JEOL Ltd.) Mobile phase: helium Helium flow rate: 1.0 mL / min Detector: quadrupole mass spectrometer Ionization method: EI method Column: SLB-5ms capillary GC column (manufactured by Sigma-Aldrich) Injection port temperature: 320°C Column temperature: 40°C to 340°C Injection volume: 1.0 μL

[0128] (Examples 2 to 18, 21 to 31, Comparative Examples 1 to 4, 6) Pressure-sensitive adhesive tapes having pressure-sensitive adhesive layers of the same thickness as in Example 1 were obtained in the same manner as in Example 1, except that the types and amounts of each component of the pressure-sensitive adhesive composition were changed as shown in Tables 3 to 6. Furthermore, the weight-average molecular weight of the (meth)acrylic polymer, the content of the solvent in the pressure-sensitive adhesive layer, 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. The solvent in Example 24 and Comparative Example 6 was added when preparing the pressure-sensitive adhesive composition in the above-mentioned "(3) Production of pressure-sensitive adhesive tape", and is different from the solvent derived from the above-mentioned (meth)acrylic polymer-containing solution.

[0129] (Examples 19 and 20) Pressure-sensitive adhesive compositions were prepared in the same manner as in Example 1, except that the types and blending amounts of each component of the pressure-sensitive adhesive composition were as shown in Table 4. The obtained pressure-sensitive adhesive composition was coated on the release-treated surface of a 50 μm-thick release PET film, and then a 38 μm-thick release PET film was placed on top of it so that the release-treated surface faced the coated pressure-sensitive adhesive composition to seal the pressure-sensitive adhesive composition. The adhesive composition was then irradiated with UV-LED irradiation equipment (manufactured by CCS Inc., "UVS01-01") at a wavelength of 365 nm and an irradiation intensity of 35 mW / cm. ２ The ultraviolet light irradiation dose is 1000 mJ / cm ２The pressure-sensitive adhesive composition was irradiated through a release PET film so that the cured pressure-sensitive adhesive composition was irradiated. Furthermore, after peeling off the release film on one side, the cured pressure-sensitive adhesive composition was dried at 110°C for 5 minutes to form a 50 μm-thick pressure-sensitive adhesive layer containing a cured product of the pressure-sensitive adhesive composition. The resulting pressure-sensitive adhesive layer was then pressed back and forth at a speed of 300 mm / min using a 2 kg rubber roller to bond it to one side of the substrate shown in Table 4. Furthermore, a pressure-sensitive adhesive layer having the same composition and thickness was formed on the release-treated surface of another 50 μm-thick release PET film by the same method, bonded to the other side of the substrate, and laminated together by pressing back and forth at a speed of 300 mm / min using a 2 kg rubber roller to obtain a pressure-sensitive adhesive tape (support type) having a pressure-sensitive adhesive layer and a release PET film on both sides of the substrate. Furthermore, the weight-average molecular weight of the (meth)acrylic polymer, the solvent content in the pressure-sensitive adhesive layer, 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 1 and 4.

[0130] The substrates used as the substrate layers in Examples 19 and 20 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)

[0131] (Comparative Example 5) A pressure-sensitive adhesive composition was obtained by adding 100 parts by weight of (meth)acrylic polymer N, 30.0 parts by weight of tackifier resin A, 0.5 parts by weight of an isocyanate-based crosslinking agent, and 200.0 parts by weight of ethyl acetate as a solvent. After thoroughly stirring the resulting solution of the pressure-sensitive adhesive composition, it was coated with a doctor knife onto the release-treated surface of a 50 μm-thick release polyethylene terephthalate (PET) film with one side treated for release, and heated at 110 ° C for 10 minutes to dry the coating solution, thereby forming a 50 μm-thick pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition. Furthermore, a 25 μm-thick release PET film with one side treated for release was prepared, and the formed pressure-sensitive adhesive layer and the release-treated surface were overlapped, and then aged in an environment of 40 ° C for 48 hours to obtain a pressure-sensitive adhesive tape. Furthermore, the weight average molecular weight of the (meth)acrylic polymer, the content of the solvent in the pressure-sensitive adhesive composition, the gel fraction of the pressure-sensitive adhesive layer, and the content of the solvent in the pressure-sensitive adhesive layer were measured in the same manner as in Example 1. The results are shown in Tables 2 and 6.

[0132] <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 3 to 6.

[0133] (Adhesion to Rough Surface (Conformability to Rough Surface)) In accordance with JIS Z 0237:2009, the 180° peel force of an adhesive tape against a rough surface (water-resistant abrasive paper (manufactured by Noritake Coated Abrasives, "C947H", grain size 360, surface roughness Ra = 10.8 μm) was measured. The surface roughness Ra of the water-resistant abrasive paper was measured using a laser microscope (manufactured by KEYENCE, color 3D laser microscope, "VK-8710"). Specifically, first, the back surface of the water-resistant abrasive paper was bonded to a SUS (stainless steel) 304 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 (PET) 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 specimen. This test specimen 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 to the test specimen by rolling a 2 kg rubber roller back and forth once at a speed of 300 mm / min. Thereafter, the test specimen was aged at 23°C and 50% RH for 20 minutes to prepare a test sample. In accordance with JIS Z 0237:2009, this test sample was peeled in a 180° direction at a pulling rate of 300 mm / min under conditions of 23°C and 50% RH, and the peel force (N / 25 mm) was measured. The adhesive strength of the adhesive tape to the rough surface was evaluated as follows: if the obtained peel force was 12.0 N / 25 mm or more, it was rated as "A"; if it was 10.0 N / 25 mm or more but less than 12.0 N / 25 mm, it was rated as "B"; if it was 9.0 N / 25 mm or more but less than 10.0 N / 25 mm, it was rated as "C"; and if it was less than 9.0 N / 25 mm, it was rated as "D".

[0134] (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 their own judgments, and the average was calculated. The calculated average was evaluated as "A" if it was less than 3.0, "B" if it was 3.0 or more but less than 4.0, and "C" if it was 4.0 or more.

[0135] (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 at 23°C and 50% RH for 20 minutes 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 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" indicates a displacement of 0.2 mm or less; "B" indicates a displacement of more than 0.2 mm but not more than 0.5 mm; "C" indicates a displacement of more than 0.5 mm but the test piece did not fall; and "D" indicates a specimen fell. Even when the evaluation was "D," the pressure-sensitive adhesive tape of this embodiment can still be used without any problems depending on the application.

[0136] (Environmental Load Reduction Ability) Using the content of the organic solvent in the PSA composition measured in "(2) Measurement of the content of the organic solvent in the PSA composition" above, the environmental load reduction ability was evaluated according to the following criteria: A: The PSA composition did not contain an organic solvent, or the content of the organic solvent in the PSA composition was 10 mass% or less. B: The content of the organic solvent in the PSA composition was greater than 10 mass%.

[0137]

[0138]

[0139]

[0140]

[0141]

[0142]

[0143] According to the present invention, a pressure-sensitive adhesive composition can be provided that can exhibit excellent conformability to rough surfaces and can reduce odor generation and environmental impact. Furthermore, according to the present invention, a pressure-sensitive adhesive tape can be provided that can exhibit excellent conformability to rough surfaces and can reduce odor generation. Furthermore, according to the present invention, a method for producing a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition can be provided.

[0144] 1 Polyethylene terephthalate (PET) film 2 Adhesive tape 3 SUS304 plate 4 Weight (1 kg)

Claims

1. A pressure-sensitive adhesive composition comprising a (meth)acrylic monomer and a (meth)acrylic polymer, wherein the (meth)acrylic monomer comprises an alkyl(meth)acrylate having a linear or branched alkyl group having 6 carbon atoms, and the (meth)acrylic polymer has a structural unit derived from the alkyl(meth)acrylate, and the pressure-sensitive adhesive composition contains an organic solvent, and the content of the organic solvent in the pressure-sensitive adhesive composition is 10 mass% or less, or the pressure-sensitive adhesive composition does not contain an organic solvent.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms in the (meth)acrylic monomer includes n-hexyl (meth)acrylate.

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

4. A pressure-sensitive adhesive composition according to claim 1, 2 or 3, wherein the content of an alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms is 50 parts by mass or less per 100 parts by mass of the total of the (meth)acrylic monomer and the (meth)acrylic polymer, or the (meth)acrylic monomer does not contain an alkyl (meth)acrylate having an alkyl group having 7 or more carbon atoms.

5. The pressure-sensitive adhesive composition according to claim 1, 2, 3 or 4, wherein the (meth)acrylic monomer comprises a monomer having two or more (meth)acryloyl groups in one molecule.

6. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4 or 5, wherein the (meth)acrylic monomer comprises a monomer having a crosslinkable functional group.

7. The pressure-sensitive adhesive composition according to claim 6, wherein the monomer having a crosslinkable functional group comprises at least one selected from the group consisting of a carboxyl group-containing monomer and a hydroxyl group-containing monomer.

8. A pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the structural units derived from alkyl (meth)acrylate in the (meth)acrylic polymer include structural units derived from alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms.

9. A pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein the total content of the alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms and the structural units derived from the alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms in the (meth)acrylic polymer is 60 mass% or more in the total of the (meth)acrylic monomer and the (meth)acrylic polymer.

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

11. The pressure-sensitive adhesive composition according to claim 10, wherein the structural unit derived from a monomer having a crosslinkable functional group comprises at least one structural unit selected from the group consisting of a structural unit derived from a carboxyl group-containing monomer and a structural unit derived from a hydroxyl group-containing monomer.

12. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, wherein, in at least one of the cases where the (meth)acrylic monomer contains a monomer having a crosslinkable functional group, and the (meth)acrylic polymer has a structural unit derived from a monomer having a crosslinkable functional group, the total content of the monomer having a crosslinkable functional group and the structural unit in the (meth)acrylic polymer derived from the monomer having a crosslinkable functional group in the total of the (meth)acrylic monomer and the (meth)acrylic polymer is 0.01% by mass or more and 20% by mass or less.

13. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, which contains a photopolymerization initiator.

14. The pressure-sensitive adhesive composition according to claim 13, wherein the photopolymerization initiator comprises a compound having two or more photopolymerization reaction sites.

15. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, which contains a tackifying resin.

16. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15, which contains a crosslinking agent.

17. The pressure-sensitive adhesive composition according to claim 16, wherein the crosslinking agent comprises at least one selected from the group consisting of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent.

18. The pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16 or 17, which contains a pigment.

19. The adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 or 18, wherein the content of biologically derived carbon in the adhesive composition is 10% or more.

20. An adhesive tape having an adhesive layer containing a cured product of the adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 or 19.

21. An adhesive tape characterized by having an adhesive layer 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.

22. The adhesive tape according to claim 21, wherein the (meth)acrylic copolymer contains 60% by mass or more of structural units derived from alkyl (meth)acrylate having a linear or branched alkyl group having 6 carbon atoms.

23. The adhesive tape according to claim 20, 21 or 22, wherein the adhesive layer does not contain an organic solvent, or the adhesive layer contains an organic solvent and the content of the organic solvent in the adhesive layer is 500 ppm or less.

24. The adhesive tape according to claim 20, 21, 22 or 23, wherein the gel fraction of the adhesive layer is 10% by mass or more and 70% by mass or less.

25. The adhesive tape according to claim 20, 21, 22, 23 or 24, which has a substrate layer.

26. The adhesive tape according to claim 20, 21, 22, 23, 24 or 25, which is used to fasten electronic equipment parts or vehicle-mounted parts.

27. A method for producing a pressure-sensitive adhesive tape, comprising: step (I) of curing the pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, or 19 by irradiating it with light; and step (II) of heating the cured product of the pressure-sensitive adhesive composition cured in step (I).

Images