Pressure-sensitive adhesive composition, pressure-sensitive adhesive tape, and method for producing pressure-sensitive adhesive tape

Abstract

A purpose of the present invention is to provide a pressure-sensitive adhesive composition which has a satisfactory pot life and can exhibit excellent adhesive force. Another purpose is to provide a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition. Still another purpose is to provide a method for producing a pressure-sensitive adhesive tape using the pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition comprises an alkyl (meth)acrylate in which the alkyl group has 4-20 carbon atoms, a (meth)acrylic copolymer, and one or more crosslinking agents, wherein the (meth)acrylic copolymer includes a constituent unit derived from a monomer containing an active-hydrogen-containing functional group and the crosslinking agents include a crosslinking agent (a), which is a monomer having both a functional group that reacts with the active-hydrogen-containing functional group contained in the (meth)acrylic copolymer and a functional group including a carbon-carbon unsaturated double bond. The pressure-sensitive adhesive composition contains no solvent, or the pressure-sensitive adhesive composition contains a solvent and the content of the solvent in the pressure-sensitive adhesive composition is 10 mass%.

Description

Adhesive composition, adhesive tape, method for manufacturing adhesive tape

[0001] The present invention relates to an adhesive composition. Furthermore, the present invention relates to an adhesive tape having an adhesive layer formed using the adhesive composition. Moreover, the present invention relates to a method for manufacturing an adhesive tape using the adhesive composition.

[0002] Conventionally, adhesive tapes having an adhesive layer containing an adhesive composition have been widely used to fix components in electronic devices, vehicles, houses, and building materials (for example, Patent Documents 1 to 3). Specifically, for example, 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] Japanese Patent Publication No. 2015-052050, Japanese Patent Publication No. 2015-021067, Japanese Patent Publication No. 2015-120876

[0004] In recent years, CO ２ From a reduction perspective, the trend in the adhesive sector is to reduce waste loss and use biomass raw materials. In this trend, using plant-derived raw materials will lead to CO2 emissions. ２ Because it can reduce emissions, active development is underway to create bio-based raw materials for adhesives.

[0005] On the other hand, conventional adhesives contain solvents in the adhesive coating liquid, and CO2 is produced from these solvents during the manufacturing process of adhesive tapes. ２ CO2 is emitted. Therefore, by reducing the amount of solvent contained in the adhesive, CO2 emissions during the manufacturing process can be reduced. ２ Although it can reduce CO2 from solvents, ２ Currently, sufficient consideration has not been given to reducing emissions. CO2 emissions from solvents. ２As a method to reduce emissions, production using UV polymerization coating, a solvent-free manufacturing process, is being considered. However, there is a problem in that adding crosslinking agents such as isocyanate-based crosslinking agents to achieve the desired adhesive performance shortens the pot life. On the other hand, reducing the amount of isocyanate-based crosslinking agents to improve pot life makes it difficult to achieve sufficient adhesive strength.

[0006] The present invention aims to provide an adhesive composition that has a good pot life and can exhibit excellent adhesive strength. Furthermore, the present invention aims to provide an adhesive tape having an adhesive layer formed using the adhesive composition. Moreover, the present invention aims to provide a method for manufacturing an adhesive tape using the adhesive composition.

[0007] Disclosure 1 is an adhesive composition comprising an alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms, a (meth)acrylic copolymer, and a crosslinking agent, wherein the (meth)acrylic copolymer has constituent units derived from a monomer containing a functional group having active hydrogen, and the crosslinking agent comprises a crosslinking agent (a) which is a monomer having a functional group that reacts with the functional group having active hydrogen in the (meth)acrylic copolymer, and a functional group containing a carbon-carbon unsaturated double bond, and the adhesive composition does not contain a solvent, or the adhesive composition contains a solvent, wherein the content of the solvent in the adhesive composition is 10% by mass or less. Disclosure 2 is the adhesive composition of Disclosure 1 comprising a photopolymerization initiator. Disclosure 3 is the adhesive composition of Disclosure 1 or 2 comprising a tackifying resin. Disclosure 4 is the adhesive composition of Disclosure 3 comprising at least one tackifying resin selected from the group consisting of rosin ester-based tackifying resins and terpene phenol-based tackifying resins. Disclosure 5 is an adhesive composition of Disclosure 3 or 4, wherein the content of the tackifying resin is 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms and the (meth)acrylic copolymer. Disclosure 6 is an adhesive composition of Disclosure 1, 2, 3, 4 or 5, wherein the crosslinking agent further comprises an isocyanate-based crosslinking agent. Disclosure 7 is an adhesive composition of Disclosure 6, wherein the content of isocyanate groups in the isocyanate-based crosslinking agent is 0.3 parts by mass or less per 100 parts by mass of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms and the (meth)acrylic copolymer. Disclosure 8 is an adhesive composition of Disclosure 1, 2, 3, 4, 5, 6 or 7, wherein the alkyl (meth)acrylate having an alkyl group having 6 to 8 carbon atoms is also an alkyl (meth)acrylate having an alkyl group having 6 to 8 carbon atoms.Disclosure 9 is an adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, or 8, wherein the content of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms is 40 to 95 parts by mass per 100 parts by mass of the total of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms and the (meth)acrylic copolymer. Disclosure 10 is an adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the (meth)acrylic copolymer has structural units derived from alkyl (meth)acrylate, and the structural units derived from alkyl (meth)acrylate include structural units derived from alkyl (meth)acrylate having an alkyl group having 6 to 8 carbon atoms. Disclosure 11 is an adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the (meth)acrylic copolymer has a weight-average molecular weight of 2 million or less. Disclosure 12 is an adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the content of the (meth)acrylic copolymer is 5.0 parts by mass or more per 100 parts by mass of the total of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms and the (meth)acrylic copolymer. Disclosure 13 is an adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the functional group in the crosslinking agent (a) that reacts with the functional group having the active hydrogen in the (meth)acrylic copolymer is an isocyanate group. Disclosure 14 is an adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein the content of the crosslinking agent (a) is 0.01 parts by mass or more and 5.0 parts by mass or less, based on a total of 100 parts by mass of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms and the (meth)acrylic copolymer. Disclosure 15 is an adhesive tape having an adhesive layer formed using the adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14. Disclosure 16 is an adhesive tape of Disclosure 15, wherein the gel fraction of the adhesive layer is 30% by mass or more and 70% by mass or less.Disclosure 17 is a method for manufacturing an adhesive tape, comprising the step of photocuring an adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14. The present invention will be described in detail below. Hereinafter, embodiments of the present invention or one thereof will be described as "this embodiment".

[0008] The present inventors have found that adhesive compositions containing alkyl (meth)acrylates having an alkyl group with 4 to 20 carbon atoms at the ester terminus, (meth)acrylic copolymers containing a functional group having active hydrogen, and monomers having a functional group that reacts with active hydrogen and a carbon-carbon unsaturated double bond have a good pot life. Furthermore, they have found that adhesives and adhesive layers formed by irradiation of such adhesive compositions with light have excellent adhesive strength. As a result of these findings, they have found that it is possible to obtain an adhesive composition that has a good pot life and exhibits excellent adhesive strength, thus completing the present invention. In this specification, "(meth)acrylic" means acrylic or methacrylic, and "(meth)acrylate" means acrylate or methacrylate. In this specification, "active hydrogen" means a hydrogen atom bonded to a nitrogen atom, oxygen atom, sulfur atom, or silicon atom.

[0009] The adhesive composition of this embodiment contains an alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms. The inclusion of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms in the adhesive composition of this embodiment facilitates curing by light irradiation. Furthermore, the inclusion of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms in the adhesive composition of this embodiment reduces its viscosity, making it easier to coat, thus allowing for a reduction in the solvent content in the adhesive composition of this embodiment.

[0010] Examples of alkyl (meth)acrylates having an alkyl group with 4 to 20 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl acrylate, n-hexyl acrylate, n-heptyl acrylate, 1-methylheptyl acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, iso Examples include octyl (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)octanol-1 and (meth)acrylic acid, esters of (meth)acrylic acid with an alcohol having 1 or 2 methyl groups in a linear main chain and a total of 18 carbon atoms, and arachidyl (meth)acrylate. Among these, alkyl (meth)acrylate having an alkyl group with 6 to 8 carbon atoms is preferred from the viewpoint of the adhesive properties exhibited when used as an adhesive layer. Note that alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms may be used alone or in combination of two or more.

[0011] The alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms may consist solely of petroleum-derived materials, but it is preferable that it also contains bio-derived materials. Including bio-derived materials in the alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms is preferable from the viewpoint of conserving petroleum resources. Furthermore, since bio-derived materials are originally produced by taking in carbon dioxide from the atmosphere, it is considered that burning them will not increase the total amount of carbon dioxide in the atmosphere, which is also preferable from the viewpoint of reducing carbon dioxide emissions.

[0012] When the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms contains a bio-derived material, it is preferable that the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms is synthesized by esterification of an alcohol, which is a bio-derived material, with (meth)acrylic acid.

[0013] The preferred lower limit of the content of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms in a total of 100 parts by mass of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms and the (meth)acrylic copolymer is 40 parts by mass, and the preferred upper limit is 95 parts by mass. A content of 40 parts by mass or more of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms allows the adhesive composition of this embodiment to cure more easily upon light irradiation. Furthermore, the solvent content of the adhesive composition of this embodiment can be reduced. A content of 95 parts by mass or less of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms ensures the coatability of the adhesive composition. A more preferred lower limit of the content of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms is 45 parts by mass, a more preferred upper limit is 90 parts by mass, an even more preferred lower limit is 50 parts by mass, an even more preferred upper limit is 80 parts by mass, and an even more preferred lower limit is 60 parts by mass.

[0014] The preferred lower limit for the content of alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms in the adhesive composition of this embodiment is 40% by mass, and the preferred upper limit is 95% by mass. By having the content of alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms in the adhesive composition of this embodiment within this range, the adhesive composition of this embodiment will undergo moderate curing by light irradiation, resulting in superior adhesive strength. A more preferred lower limit for the content of alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms in the adhesive composition of this embodiment is 45% by mass, and a more preferred upper limit is 80% by mass.

[0015] The adhesive composition of this embodiment contains a (meth)acrylic copolymer having structural units derived from monomers containing functional groups having active hydrogen. Because the (meth)acrylic copolymer has structural units derived from monomers containing functional groups having active hydrogen, it becomes possible to form a crosslinked structure in the (meth)acrylic copolymer using the crosslinking agent, and the adhesive composition of this embodiment can exhibit superior adhesive strength.

[0016] Examples of constituent units derived from monomers containing the above-mentioned functional group having active hydrogen include constituent units derived from carboxyl group-containing monomers, constituent units derived from hydroxyl group-containing monomers, constituent units derived from glycidyl group-containing monomers, constituent units derived from amide group-containing monomers, and constituent units derived from nitrile group-containing monomers. In particular, from the viewpoint of the adhesive properties exhibited when used as an adhesive layer, it is preferable that the constituent units derived from monomers containing the above-mentioned functional group having active hydrogen include at least one constituent unit selected from the group consisting of constituent units derived from carboxyl group-containing monomers and constituent units derived from hydroxyl group-containing monomers. Furthermore, it is preferable that the monomer having a crosslinkable functional group in the constituent units derived from monomers containing the above-mentioned functional group having active hydrogen has a (meth)acryloyl group.

[0017] Examples of the above carboxyl group-containing monomers include (meth)acrylic acid. Examples of the above hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 1-methyl-2-hydroxyethyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1-methyl-2-hydroxypropyl (meth)acrylate, 1-methyl-3-hydroxypropyl (meth)acrylate, 1-ethyl-2-hydroxyethyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 7-hydroxyheptyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 9-hydroxynonyl (meth)acrylate. Examples of the above glycidyl group-containing monomers include glycidyl (meth)acrylate. Examples of the above amide group-containing monomers include dimethyl(meth)acrylamide, isopropyl(meth)acrylamide, and dimethylaminopropyl(meth)acrylamide. Examples of the above nitrile group-containing monomers include (meth)acrylonitrile.

[0018] The monomer containing the functional group having active hydrogen in the constituent unit derived from the monomer containing the functional group having active hydrogen preferably contains biologically derived materials, but may consist only of petroleum-derived materials.

[0019] The preferred lower limit and preferred upper limit of the content of constituent units derived from monomers containing the functional group having the active hydrogen in the above (meth)acrylic copolymer is 0.05% by mass. By having a content of 0.05% by mass or more of constituent units derived from monomers containing the functional group having the active hydrogen, it becomes possible to form an appropriate crosslinked structure in the above (meth)acrylic copolymer using the above crosslinking agent, and the adhesive composition of this embodiment can exhibit better adhesive strength. By having a content of 10% by mass or less of constituent units derived from monomers containing the functional group having the active hydrogen, it becomes possible to suppress excessive reaction of the above (meth)acrylic copolymer with the above crosslinking agent and the crosslinking agent described later, and the adhesive composition of this embodiment can have a better pot life. A more preferred lower limit for the content of constituent units derived from monomers containing the functional group having the active hydrogen is 0.1% by mass, a more preferred upper limit is 5.0% by mass, an even more preferred lower limit is 1.0% by mass, and an even more preferred lower limit is 3.0% by mass. Furthermore, the content of constituent units derived from monomers containing the functional group having the active hydrogen in the above (meth)acrylic copolymer is determined by mass spectrometry and / or nuclear magnetic resonance spectroscopy of the above (meth)acrylic copolymer. １ H-NMR, １３ This can be calculated by performing 1C-NMR (or similar) and determining the integral intensity ratio of the hydrogen peaks originating from the monomer containing the functional group having the active hydrogen.

[0020] The above (meth)acrylic copolymer preferably has structural units derived from alkyl (meth)acrylate. By having structural units derived from alkyl (meth)acrylate in the above (meth)acrylic copolymer, the adhesive composition of this embodiment can exhibit superior adhesive strength.

[0021] Examples of structural units derived from the alkyl (meth)acrylate include structural units derived from alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms. Examples of structural units derived from alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms include the structural units derived from alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms as described above. In particular, from the viewpoint of the adhesive properties exhibited when used as an adhesive layer, structural units derived from alkyl (meth)acrylate having an alkyl group having 6 to 8 carbon atoms are preferred.

[0022] The alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms in the constituent unit derived from the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms may consist only of petroleum-derived materials, but it is preferable that it also contains bio-derived materials. Including bio-derived materials in the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms in the constituent unit derived from the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms is preferable from the viewpoint of conserving petroleum resources, and furthermore, since bio-derived materials are originally produced by taking in carbon dioxide from the atmosphere, it is considered that burning them will not increase the total amount of carbon dioxide in the atmosphere, which is also preferable from the viewpoint of reducing carbon dioxide emissions.

[0023] When the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms in the constituent unit derived from the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms contains a bio-derived material, it is preferable that the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms is synthesized by esterification of an alcohol, which is a bio-derived material, with (meth)acrylic acid.

[0024] The preferred lower limit of the content ratio of the structural unit derived from the alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms in the above (meth)acrylic copolymer is 90% by mass, and the preferred upper limit is 99.5% by mass. When the content ratio of the structural unit derived from the alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms is 90% by mass or more, the adhesive composition of the present embodiment can exhibit more excellent adhesive strength. When the content ratio of the structural unit derived from the alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms is 99.5% by mass or less, it becomes possible to form a suitable crosslinked structure in the above (meth)acrylic copolymer, and the adhesive composition of the present embodiment can exhibit more excellent adhesive strength. The more preferred lower limit of the content ratio of the structural unit derived from the alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms is 92% by mass, and the more preferred upper limit is 97% by mass. The content ratio of the structural unit derived from the alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms in the above (meth)acrylic copolymer can be calculated from the integrated intensity ratio of the peaks of hydrogen derived from the alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms, etc., by performing mass spectrometry and / or nuclear magnetic resonance spectroscopy measurement ( １ H-NMR, １３ C-NMR, etc.) of the above (meth)acrylic copolymer.

[0025] The above (meth)acrylic copolymer may have a structural unit derived from a monomer containing a functional group having the above active hydrogen and a structural unit derived from other monomers other than the structural unit derived from the alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms, as long as the effects of the present invention are not inhibited.

[0026] Other constituent units derived from the above-mentioned monomers include, for example, constituent units derived from monomers such as benzyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and polypropylene glycol mono(meth)acrylate. Furthermore, other constituent units derived from the above-mentioned monomers include, for example, constituent units derived from various monomers commonly used as raw materials for (meth)acrylic copolymers such as vinyl acetate and styrene.

[0027] The above-mentioned other monomers preferably include bio-derived materials, but may consist solely of petroleum-derived materials. Theoretically, it is also possible to use monomers that consist entirely of bio-derived materials as the acrylic monomers constituting the above (meth)acrylic copolymer. From the viewpoint of cost and productivity of the adhesive composition, monomers containing relatively inexpensive and readily available bio-derived materials may be used, and these may be combined with monomers consisting solely of petroleum-derived materials.

[0028] The preferable upper limit of the weight-average molecular weight of the above (meth)acrylic copolymer is 2,000,000. When the weight-average molecular weight of the above (meth)acrylic copolymer is 2,000,000 or less, the viscosity of the adhesive composition can be adjusted to a range suitable for coating. The more preferable upper limit of the weight-average molecular weight of the above (meth)acrylic copolymer is 1,900,000, the further preferable upper limit is 1,800,000, the still more preferable upper limit is 1,500,000, and the particularly preferable upper limit is 1,000,000. Also, the preferable lower limit of the weight-average molecular weight of the above (meth)acrylic copolymer is 100,000. When the weight-average molecular weight of the above (meth)acrylic copolymer is 100,000 or more, the viscosity of the adhesive composition can be adjusted to a range suitable for coating. The more preferable lower limit of the weight-average molecular weight of the above (meth)acrylic copolymer is 150,000, the further preferable lower limit is 200,000, and the still more preferable lower limit is 400,000. In this specification, the above weight-average molecular weight is the weight-average molecular weight in terms of standard polystyrene measured by GPC (Gel Permeation Chromatography). Specifically, the (meth)acrylic copolymer is diluted 50-fold with tetrahydrofuran (THF), and the obtained dilution is filtered with 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 the conditions of a sample flow rate of 1 mL / min and a column temperature of 40°C. The polystyrene-equivalent molecular weight of the (meth)acrylic copolymer is measured, and this value is taken as the weight-average molecular weight of the (meth)acrylic copolymer. Examples of the above gel permeation chromatograph include 2690 Separations Module (manufactured by Waters) and the like.

[0029] As a method for adjusting the weight-average molecular weight of the above (meth)acrylic copolymer, for example, methods such as changing the type and amount of the polymerization initiator, monomer concentration during the polymerization reaction, adding a small amount of a chain transfer agent such as dodecyl mercaptan, changing the type of the polymerization reaction solvent to control chain transfer to the solvent, and changing the temperature and time during the reaction can be mentioned.

[0030] The above (meth)acrylic copolymer can be obtained by polymerizing a mixture of constituent monomers in the presence of a polymerization initiator through a radical reaction. Examples of radical reaction methods include living radical polymerization and free radical polymerization. Living radical polymerization yields a copolymer with a more uniform molecular weight and composition compared to free radical polymerization, and suppresses the generation of low molecular weight components, resulting in an adhesive composition that exhibits superior tackiness. Polymerization of the above (meth)acrylic copolymer may be carried out by photopolymerization using light irradiation or by thermal polymerization using heating, but thermal polymerization is preferred from the viewpoint of easily increasing the molecular weight. Specific methods for polymerizing the above monomer mixture can be conventionally known methods, such as solution polymerization (boiling point polymerization or constant temperature polymerization), UV polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. When solution polymerization is used as the method for polymerizing the above monomer mixture, examples of reaction solvents include ethyl acetate, toluene, methyl ethyl ketone, dimethyl sulfoxide, ethanol, acetone, and diethyl ether.

[0031] Examples of polymerization initiators used for the synthesis of the (meth)acrylic copolymer include organic peroxides and azo compounds. Examples of 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 azo compounds used for the synthesis of the (meth)acrylic copolymer include azobisisobutyronitrile and azobiscyclohexanecarbonilonitrile. Furthermore, if the radical reaction method is living radical polymerization, examples of polymerization initiators include organic tellurium polymerization initiators. The organic tellurium polymerization initiator is not particularly limited as long as it is commonly used in living radical polymerization, and examples include organic tellurium compounds and organic telluride compounds. In addition, in living radical polymerization, an azo compound may be used as a polymerization initiator in addition to the organic tellurium polymerization initiator to accelerate the polymerization rate.

[0032] The preferable lower limit of the content of the alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms and the above (meth)acrylic copolymer in a total of 100 parts by mass is 5.0 parts by mass, and the preferable upper limit is 60 parts by mass. When the content of the above (meth)acrylic copolymer is 5.0 parts by mass or more,the adhesive composition of the present embodiment can exhibit more excellent adhesive force. When the content of the above (meth)acrylic copolymer is 60 parts by mass or less, the above (meth)acrylic copolymer can suppress an excessive reaction with the above crosslinking agent and a crosslinking agent described later, and the adhesive composition of the present embodiment has a better pot life. The more preferable lower limit of the content of the above (meth)acrylic copolymer is 7.5 parts by mass, the more preferable upper limit is 55 parts by mass, the further preferable lower limit is 10 parts by mass, the further preferable upper limit is 50 parts by mass, the still more preferable lower limit is 20 parts by mass, and the still more preferable upper limit is 40 parts by mass.

[0033] The preferable lower limit of the content ratio of the above (meth)acrylic copolymer in the adhesive composition of the present embodiment is 5.0% by mass, and the preferable upper limit is 60% by mass. When the content ratio of the above (meth)acrylic copolymer is within this range, the adhesive composition of the present embodiment has a good pot life and can exhibit excellent adhesive force. The more preferable lower limit of the content ratio of the above (meth)acrylic copolymer is 7.5% by mass, and the more preferable upper limit is 55% by mass. Further, from the viewpoint of making it easier to adjust the viscosity of the adhesive composition of the present embodiment, the preferable lower limit is 5% by mass, the preferable upper limit is 70% by mass, the more preferable lower limit is 10% by mass, the more preferable upper limit is 55% by mass, the further preferable lower limit is 15% by mass, and the further preferable upper limit is 40% by mass.

[0034] The adhesive composition of this embodiment contains a crosslinking agent. The crosslinking agent includes a monomer having a functional group that reacts with the functional group having active hydrogen in the (meth)acrylic copolymer, and a functional group containing a carbon-carbon unsaturated double bond (hereinafter sometimes simply referred to as "crosslinking agent (a)"). The crosslinking agent (a), having a carbon-carbon unsaturated double bond, reacts with the alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms upon irradiation with light, and also reacts with the functional group having active hydrogen in the (meth)acrylic copolymer through the functional group that reacts with the functional group having active hydrogen, thereby forming a crosslinked structure in the cured product. As a result, it is included in the cured product of the adhesive composition of this embodiment. Therefore, by including the crosslinking agent (a), the adhesive composition obtained using the adhesive composition of this embodiment has a crosslinked structure, and the adhesive composition of this embodiment can exhibit superior adhesive strength. Furthermore, since the crosslinking agent (a) is relatively less reactive than crosslinking agents such as isocyanate-based crosslinking agents, even if the adhesive composition of this embodiment contains the crosslinking agent (a), it can suppress reactions with other components in the adhesive composition of this embodiment, resulting in a good pot life. Moreover, by including the crosslinking agent (a) as a monomer rather than as a constituent unit of the (meth)acrylic copolymer, the viscosity of the adhesive composition of this embodiment is reduced, resulting in an adhesive composition that is easy to coat, and thus the proportion of solvent in the adhesive composition of this embodiment can be reduced.

[0035] The functional group in the crosslinking agent (a) that reacts with the functional group having active hydrogen in the (meth)acrylic copolymer is appropriately selected from the functional groups having active hydrogen in the (meth)acrylic copolymer, but examples include carboxyl groups, hydroxyl groups, amide groups, isocyanate groups, epoxy groups, etc. Among these, isocyanate groups are preferred from the viewpoint of the adhesive properties that are exhibited when it is used as an adhesive layer. Note that the functional group that reacts with the functional group having active hydrogen may be just one type or two or more types.

[0036] Examples of functional groups containing the carbon-carbon unsaturated double bond in the crosslinking agent (a) above include vinyl groups and (meth)acryloyl groups. In particular, from the viewpoint of facilitating curing by light irradiation, it is preferable that the functional group containing the carbon-carbon unsaturated double bond includes a vinyl group. In this specification, "carbon-carbon unsaturated double bond" does not include carbon-carbon double bonds that constitute an aromatic ring.

[0037] Examples of the crosslinking agent (a) include 2-acryloyloxyethyl isocyanate and 2-methacryloyloxyethyl isocyanate.

[0038] The preferred lower limit of the content of the crosslinking agent (a) in a total of 100 parts by mass of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms and the (meth)acrylic copolymer is 0.01 parts by mass, and the preferred upper limit is 5.0 parts by mass. By having a content of 0.01 parts by mass or more of the crosslinking agent (a), the adhesive composition of this embodiment can exhibit superior adhesive strength. By having a content of 5.0 parts by mass or less of the crosslinking agent (a), excessive reaction with components in the adhesive composition can be suppressed, so the adhesive composition of this embodiment has a good pot life. The more preferred lower limit of the content of the crosslinking agent (a) is 0.03 parts by mass, the more preferred upper limit is 3.0 parts by mass, the even more preferred lower limit is 0.05 parts by mass, the even more preferred upper limit is 1.0 part by mass, the even more preferred upper limit is 0.50 parts by mass, the particularly preferred upper limit is 0.45 parts by mass, and the very preferred upper limit is 0.40 parts by mass.

[0039] In the adhesive composition of this embodiment, the crosslinking agent may further contain other crosslinking agents other than the crosslinking agent (a) above, from the viewpoint of appropriately adjusting the degree of crosslinking. Examples of the other crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, metal chelate-based crosslinking agents, etc. Among these, from the viewpoint of the adhesive properties exhibited when it is used as an adhesive layer, it is preferable that the other crosslinking agent includes at least one selected from the group consisting of isocyanate-based crosslinking agents and epoxy-based crosslinking agents, and it is more preferable that it is an isocyanate-based crosslinking agent. In this specification, among the crosslinking agents (a) above, those having an isocyanate group (i.e., those having an isocyanate group and a functional group including a carbon-carbon unsaturated double bond) will not be treated as the "isocyanate-based crosslinking agent".

[0040] The preferred upper limit for the content of isocyanate groups in the isocyanate-based crosslinking agent per 100 parts by mass of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms, and the (meth)acrylic copolymer is 0.3 parts by mass. By having an isocyanate group content of 0.3 parts by mass or less in the isocyanate-based crosslinking agent, the degree of crosslinking of the adhesive composition of this embodiment is appropriately adjusted, and superior adhesive strength can be achieved. The more preferred upper limit for the content of isocyanate groups in the isocyanate-based crosslinking agent is 0.1 parts by mass, and from the viewpoint of the pot life of the adhesive composition, it is most preferable that the content of isocyanate groups in the isocyanate-based crosslinking agent is 0 parts by mass, that is, the adhesive composition of this embodiment does not contain an isocyanate-based crosslinking agent. On the other hand, from the viewpoint of being able to appropriately adjust the degree of crosslinking, the preferred lower limit for the content of isocyanate groups in the isocyanate-based crosslinking agent is 0.01 parts by mass, and the more preferred lower limit is 0.05 parts by mass. Furthermore, the isocyanate group content in an isocyanate crosslinking agent can be calculated by mixing a sample of the isocyanate crosslinking agent with an excess amount of di-n-butylamine and back-titrating with a hydrochloric acid standard solution.

[0041] In the adhesive composition of this embodiment, the preferred lower limit of the total content ratio of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms, the (meth)acrylic copolymer, and the crosslinking agent is 50% by mass, a more preferred lower limit is 60% by mass, and an even more preferred lower limit is 70% by mass. Furthermore, the upper limit of the total content ratio of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms, the (meth)acrylic copolymer, and the crosslinking agent is not particularly limited, and the total content ratio may be 100% by mass or less, 95% by mass or less, or 90% by mass or less.

[0042] The adhesive composition of this embodiment preferably contains a photopolymerization initiator. The inclusion of a photopolymerization initiator in the adhesive composition of this embodiment facilitates curing by light irradiation. However, from the viewpoint of storage stability and other factors, the photopolymerization initiator may be added to the adhesive composition of this embodiment immediately before curing.

[0043] Examples of the above-mentioned photopolymerization initiators include acetophenone derivatives, benzoin ether compounds, ketal derivatives, phosphine oxide derivatives, and oxime ester compounds. Among these, phosphine oxide derivatives are preferred from the viewpoint of the degree of curing progress by light irradiation of the adhesive composition.

[0044] Examples of the above acetophenone derivatives include methoxyacetophenone, 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone, and 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholinophenyl)butan-1-one. Examples of the above benzoin ether compounds include benzoin propyl ether and benzoin isobutyl ether. Examples of the above ketal derivatives include benzyldimethyl ketal and acetophenone diethyl ketal. Examples of the above phosphine oxide derivatives include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide. Examples of the above oxime ester compounds include 1-(O-acetyloxime)-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazole-3-yl]ethanone and 1-[4-(phenylthio)phenyl]-2-(O-benzoyloxime)-1,2-octadione. Examples of the above photopolymerization initiators include bis(η5-cyclopentadienyl)titanocene derivative compounds, benzophenone, Michler ketone, chlorothioxanthone, dodecylthioxanthone, dimethylthioxanthone, diethylthioxanthone, α-hydroxycyclohexylphenyl ketone, and 2-hydroxymethylphenylpropane. These photopolymerization initiators may be used individually or in combination of two or more.

[0045] The preferred lower limit of the photopolymerization initiator content per 100 parts by mass of the alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms is 0.1 parts by mass, and the preferred upper limit is 5.0 parts by mass. Having the photopolymerization initiator content within this range facilitates the curing of the adhesive composition of this embodiment by light irradiation. A more preferred lower limit for the photopolymerization initiator content is 0.5 parts by mass, a more preferred upper limit is 3.0 parts by mass, and an even more preferred upper limit is 1.0 part by mass.

[0046] The adhesive composition of this embodiment preferably contains a tackifying resin. By containing a tackifying resin, the adhesive composition of this embodiment can exhibit superior adhesive strength.

[0047] The tackifying resins mentioned above are not particularly limited and include, for example, rosin ester tackifying resins, terpene tackifying resins, terpene phenol tackifying resins, coumarone indene tackifying resins, alicyclic saturated hydrocarbon tackifying resins, C5 petroleum tackifying resins, C9 petroleum tackifying resins, and C5-C9 copolymer petroleum tackifying resins. These tackifying resins may be used alone or in combination of two or more. In particular, it is preferable to include at least one selected from the group consisting of rosin ester tackifying resins and terpene phenol tackifying resins.

[0048] Examples of the rosin ester tackifying resins mentioned above include polymerized rosin ester tackifying resins and hydrogenated rosin ester tackifying resins. The rosin ester tackifying resins and terpene tackifying resins mentioned above are preferably of biological origin. Examples of biologically derived rosin ester tackifying resins include rosin ester tackifying resins derived from natural resins such as pine resin. Examples of biologically derived terpene tackifying resins include terpene tackifying resins derived from plant essential oils, etc.

[0049] Examples of the above rosin ester-based tackifying resins include, for example, Pencel D-135, Pine Crystal KE-359, Ester Gum AA-V, and Ester Gum H (all manufactured by Arakawa Chemical Industries, Ltd.). Examples of the above terpene-based tackifying resins include, for example, YS Resin PX1250 (manufactured by Yasuhara Chemical Co., Ltd.). Examples of the above terpene phenol-based tackifying resins include, for example, YS Polystar G150 (manufactured by Yasuhara Chemical Co., Ltd.).

[0050] In the adhesive composition of this embodiment, the preferred lower limit of the content of the tackifying resin relative to 100 parts by mass of the total of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms and the (meth)acrylic copolymer is 10 parts by mass, and the preferred upper limit is 50 parts by mass. By having a content of 10 parts by mass or more of the tackifying resin, the adhesive composition of this embodiment can exhibit superior adhesive strength. By having a content of 50 parts by mass or less of the tackifying resin, it is possible to suppress the adhesive layer from becoming too hard and reducing the anchoring properties with the substrate in adhesive tapes using the adhesive composition of this embodiment. A more preferred lower limit of the content of the tackifying resin is 15 parts by mass, a more preferred upper limit is 45 parts by mass, an even more preferred lower limit is 20 parts by mass, and an even more preferred upper limit is 40 parts by mass.

[0051] The adhesive composition of this embodiment does not contain a solvent, or the adhesive composition of this embodiment contains a solvent, and the upper limit of the solvent content in the adhesive composition of this embodiment is 10% by mass. The adhesive composition of this embodiment contains a solvent, the adhesive composition of this embodiment does not contain a solvent, or the solvent content in the adhesive composition of this embodiment is 10% by mass or less, which reduces CO2 emissions during the manufacture of the adhesive composition of this embodiment. ２This can reduce emissions. Furthermore, it is possible to further reduce the environmental burden caused by volatile organic compounds (VOCs) remaining in the adhesive and adhesive layer obtained by curing the adhesive composition of this embodiment. When the adhesive composition of this embodiment contains a solvent, the preferred upper limit of the solvent content is 5.0% by mass, a more preferred upper limit is 2.5% by mass, an even more preferred upper limit is 1.0% by mass, and an even more preferred upper limit is 0.3% by mass, and it is most preferable that the adhesive composition of this embodiment does not contain a solvent. The solvent content in the adhesive composition of this embodiment can be measured by gas chromatography-mass spectrometry (GC / MS). Specifically, after identifying the solvent contained in the adhesive composition, the solvent content is used as a standard sample with a known solvent content, and gas chromatography-mass spectrometry (GC / MS) is performed on a measurement sample obtained by diluting the adhesive composition with chloroform. A calibration curve is created from the measured peak area, and the solvent content 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 (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 (Sigma-Aldrich) Injection port temperature: 320°C Column temperature: 40°C to 340°C Injection volume: 1.0 μL

[0052] Methods for adjusting the solvent content in the adhesive composition of this embodiment include, for example, reducing the amount of solvent used in the synthesis of the (meth)acrylic copolymer, removing the solvent after the synthesis of the (meth)acrylic copolymer (for example, drying the synthesized (meth)acrylic copolymer), and preparing the adhesive composition without using a solvent.

[0053] If the adhesive composition of this 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 burden caused by volatile organic compounds (VOCs) remaining in the adhesive and adhesive layer obtained by curing the adhesive composition of this embodiment, it is preferable that the organic solvent content is as low as possible.

[0054] The adhesive composition of this embodiment may further contain a crosslinking catalyst to promote crosslinking by the above-mentioned crosslinking agent. Examples of the above-mentioned crosslinking catalyst include dibutyltin dilaurate, dibutyltin diacetate, and dioctyltin dilaurate, which are used as crosslinking catalysts for the above-mentioned isocyanate-based crosslinking agent.

[0055] The adhesive composition of this embodiment may optionally contain additives such as silane coupling agents, plasticizers, softeners, fillers, and dyes, as long as they do not impair the effects of the present invention.

[0056] The method for producing the adhesive composition of this embodiment is not particularly limited and can be produced by conventionally known production methods. For example, it can be produced by adding an alkyl (meth)acrylate having an alkyl group with 4 to 20 carbon atoms, the (meth)acrylic copolymer, and the crosslinking agent (a), and optionally a photopolymerization initiator, tackifying resin, other crosslinking agents, solvents, etc.

[0057] The preferred lower limit for the bio-derived carbon content in the adhesive composition of this embodiment is 10%. A bio-derived carbon content of 10% or more in the adhesive composition of this embodiment is superior in terms of conserving petroleum resources and reducing carbon dioxide emissions, thereby reducing environmental impact. A more preferred lower limit for the bio-derived carbon content in the adhesive composition of this embodiment is 40%, and an even more preferred lower limit is 60%. Furthermore, the upper limit for the bio-derived carbon content in the adhesive composition of this embodiment is not particularly limited and may be 100%. Note that bio-derived carbon contains a certain percentage of radioactive isotope (C-14), while petroleum-derived carbon contains almost no C-14. Therefore, the "bio-derived carbon content" as used herein can be calculated by measuring the concentration of C-14 contained in the adhesive composition. Specifically, it can be measured in accordance with ASTM D6866-24, a standard widely used in the bioplastics industry.

[0058] The content of bio-derived carbon in the adhesive composition of this embodiment can be adjusted by changing each component constituting the adhesive composition of this embodiment to a bio-derived material, and by changing the content of said bio-derived material.

[0059] An adhesive tape having an adhesive layer formed using the adhesive composition of this embodiment is also one of these embodiments. The gel fraction of the adhesive layer, described later, can be adjusted to the value described later by adjusting the type and content of each component constituting the adhesive composition of this embodiment. The adhesive layer in the adhesive tape of this embodiment can be formed by coating the above adhesive composition onto a release film or the like, and then curing it by irradiation with light. Alternatively, a solution may be prepared by adding a photopolymerization initiator to the above adhesive composition, and then the adhesive layer may be formed using the prepared solution.

[0060] The preferred lower limit for the gel fraction of the adhesive layer is 30% by mass, and the preferred upper limit is 70% by mass. When the gel fraction of the adhesive layer is 30% by mass or more, the cohesive force of the adhesive layer is further improved, and the adhesive strength of the adhesive tape of this embodiment is further improved. When the gel fraction of the adhesive layer is 70% by mass or less, the wettability of the adhesive layer to the adherend is sufficient, and the adhesive strength of the adhesive tape is further improved. A more preferred lower limit for the gel fraction of the adhesive layer is 35% by mass, a more preferred upper limit is 65% by mass, and an even more preferred upper limit is 50% by mass. The gel fraction of the adhesive layer is measured by the following method. First, an adhesive tape having the adhesive layer is cut into a planar rectangular shape with a width of 20 mm and a length of 40 mm to prepare a test piece. The test piece is immersed in ethyl acetate at 23°C for 24 hours, then removed from the ethyl acetate and dried at 110°C for 1 hour. The mass of the dried test piece is measured, and the gel fraction is calculated using the following formula (1). Furthermore, the test specimen shall not have a release film laminated on it to protect the adhesive layer. Also, if the adhesive tape of this embodiment is a non-support type tape that does not have a base material, the measurement shall be performed using a test specimen obtained by attaching it to a base material and then cutting it, or without using a base material, W in formula (1) below ０ Calculate by setting to 0. Gel fraction (mass%) = 100 × (W ２ -W ０ ) / (W １ -W ０ ) (1) (W ０ : Mass of the base material, W １ : Mass of the test specimen before immersion, W ２ (Mass of the test specimen after immersion and drying)

[0061] Methods for adjusting the gel fraction of the adhesive layer to the range described above include, but are not limited to, methods such as adjusting the type and content of each component constituting the adhesive composition that forms the adhesive layer (for example, changing the type and content of the crosslinking agent), and methods for adjusting the illuminance and irradiation time of the light used when light irradiation is performed to form the adhesive layer.

[0062] The preferred lower limit for the thickness of the adhesive layer is 3 μm, and the preferred upper limit is 300 μm. A thickness of 3 μm or more ensures that the adhesive tape of this embodiment has sufficient adhesive strength. A thickness of 300 μm or less ensures that the adhesive tape has high holding power against shear loads. A more preferred lower limit for the thickness of the adhesive layer is 5 μm, and a more preferred upper limit is 200 μm. The thickness of the adhesive layer may also be, for example, 1500 μm, 1200 μm, 900 μm, or 600 μm.

[0063] The adhesive tape of this embodiment may be a non-support type tape without a base material, or a support type tape with a base material. Furthermore, if the adhesive tape of this embodiment is a support type tape with a base material, it may be a single-sided adhesive tape having an adhesive layer on one side of the base material, or a double-sided adhesive tape having adhesive layers on both sides of the base material.

[0064] Examples of substrates used for the above-mentioned substrate include films, nonwoven fabrics, and foamed substrates. In particular, from the viewpoint of obtaining an adhesive tape with excellent compression characteristics and flexibility, and further improving the ability of the adhesive tape of this embodiment to conform to uneven surfaces, it is preferable that the above-mentioned substrate includes a foamed substrate.

[0065] From the viewpoint of increasing the overall bio-derived carbon content of the adhesive tape, a substrate made of bio-derived material is preferred for the substrate used in the above-mentioned substrate. Examples of the above-mentioned bio-derived materials include polyesters (PES) such as polyethylene terephthalate (PET), polyethylene furanoate (PEF), polylactic acid (PLA), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polybutylene succinate (PBS), as well as polyethylene (PE), polypropylene (PP), polyurethane (PU), triacetylcellulose (TAC), cellulose, and polyamide (PA), all of which are derived from plants.

[0066] Furthermore, from the perspective of reducing environmental impact by decreasing the use of new petroleum resources and suppressing carbon dioxide emissions, base materials made from recycled resources may be used. Methods for recycling resources include, for example, recovering waste from packaging containers, home appliances, automobiles, construction materials, food, etc., or waste generated in the manufacturing process, and using the extracted materials again as raw materials by washing, decontamination, or decomposition by heating or fermentation. Examples of base materials using the above recycled resources include films and nonwoven fabrics made from PET, PBT, PE, PP, PA, etc., using recovered plastics that have been re-resinated as raw materials. Alternatively, the recovered waste may be burned and used as thermal energy for the manufacture of base materials and their raw materials, or the oils and fats contained in the recovered waste may be mixed with petroleum, fractionally distilled, and refined to be used as raw materials.

[0067] The foamed substrate in the above-mentioned substrate is preferably a foamed substrate containing at least one selected from the group consisting of PE, PP, and PU, and a foamed substrate containing PE is more preferable from the viewpoint of achieving a high degree of both flexibility and strength. Examples of components of the foamed substrate containing PE include PE made from sugarcane.

[0068] As a method for producing the foamed substrate described above, it is preferable to prepare a foamed resin composition containing a PE resin containing PE made from sugarcane and a foaming agent, and to foam the foaming agent when extruding the foamed resin composition into a sheet using an extruder, and to crosslink the obtained polyolefin foam as needed.

[0069] The preferred lower limit for the thickness of the foam substrate is 50 μm, and the preferred upper limit is 5000 μm. Having the thickness of the foam substrate within this range allows for appropriate flexibility and sufficient adhesion and fixation with adhesive tape. A more preferred upper limit for the thickness of the foam substrate is 1000 μm, and an even more preferred upper limit is 300 μm.

[0070] From the viewpoint of substrate strength, the substrate used for the above-mentioned substrate is preferably a film containing PES or a film containing PA. Furthermore, from the viewpoint of heat resistance and oil resistance, a film containing PA is preferred. Examples of PA include nylon 11, nylon 1010, nylon 610, nylon 510, nylon 410, etc., which are made from castor oil, and nylon 56, etc., which are made from cellulose.

[0071] The preferred lower limit for the thickness of the above-mentioned substrate is 1 μm, and the preferred upper limit is 5000 μm. By having the substrate thickness within this range, an adhesive tape can be made that exhibits high flexibility, allowing it to adhere closely to the shape of the adherend while maintaining rigidity. A more preferred lower limit for the thickness of the above-mentioned substrate is 4 μm, a more preferred upper limit is 1000 μm, an even more preferred lower limit is 10 μm, and an even more preferred upper limit is 300 μm.

[0072] The adhesive tape of this embodiment has a preferred lower limit of 3 μm and a preferred upper limit of 6000 μm for its total thickness (for example, the thickness of the adhesive layer if the adhesive tape has only an adhesive layer, or the sum of the thickness of the adhesive layer and the base layer if the adhesive tape has an adhesive layer and a base layer). Having the total thickness of the adhesive tape of this embodiment within this range results in higher adhesive strength. A more preferred lower limit for the total thickness of the 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. In this specification, "total thickness of the adhesive tape" does not include the thickness of the separator, such as a release PET film, that protects the outermost adhesive layer of the adhesive tape.

[0073] The method for manufacturing the adhesive tape of this embodiment is not particularly limited and can be manufactured by conventionally known manufacturing methods. For example, in the case of double-sided adhesive tape, the following method can be used. First, an adhesive composition A is prepared by the method described above. After applying the obtained adhesive composition A to the surface of a substrate, a release film is placed on top with its release-treated surface facing the coated adhesive composition A to seal the adhesive composition A, and light is shone onto the adhesive composition A from the release film side. Then, the light-irradiated adhesive composition A is dried by heating to form an adhesive layer A containing a cured body of adhesive composition A. Next, a separate release film is prepared, and adhesive composition B, prepared in the same manner as adhesive composition A, is applied to the release-treated surface of this release film. The release film is then placed on top with its release-treated surface facing the coated adhesive composition B to seal the adhesive composition B, and light is shone onto the adhesive composition B from the release film side. Then, the adhesive composition B that has been irradiated with light is dried by heating to form an adhesive layer B containing a cured body of adhesive composition B, and a laminated film is produced in which the adhesive layer B is formed on the surface of the release film. After peeling off one of the release films of the obtained laminated film, the adhesive layer B is placed on the back surface of the substrate on which the adhesive layer A is formed to create a laminate. Then, by pressing the laminate with a rubber roller or the like, a double-sided adhesive tape can be obtained in which adhesive layers are present on both sides of the substrate and the surface of the adhesive layer is covered with a release film.

[0074] Alternatively, two sets of laminated films may be prepared in the same manner, and these laminated films may be superimposed on each of the two sides of a substrate with the adhesive layer of the laminated film facing the substrate to create a laminate. This laminate may then be pressed with a rubber roller or the like to obtain a double-sided adhesive tape having adhesive layers on both sides of the substrate, with the surface of the adhesive layer covered by a release film.

[0075] The use of the adhesive tape of this embodiment is not particularly limited, but it is preferably used for fixing electronic equipment components or automotive components. Specifically, the adhesive tape of this embodiment can be suitably used for adhesive fixing of electronic equipment components in large portable electronic devices, and for adhesive fixing of automotive components (e.g., automotive panels).

[0076] A method for manufacturing adhesive tape that includes a step of curing the adhesive composition of this embodiment by irradiating it with light (photocuring) is also one of these embodiments.

[0077] The process of curing by irradiation with light includes, for example, a step of applying the adhesive composition or a solution obtained by adding a photopolymerization initiator to the adhesive composition to the release surface of a substrate or release film, sealing the adhesive composition, and then irradiating it with light. The irradiation conditions for the process of curing by irradiation with light include, for example, a wavelength of 365 nm and an irradiation intensity of 35 mW / cm². ２ The light irradiation dose is 1000 mJ / cm². ２ Examples include irradiating in such a manner.

[0078] According to the present invention, it is possible to provide an adhesive composition that has a good pot life and can exhibit excellent adhesive strength. Furthermore, according to the present invention, it is possible to provide an adhesive tape having an adhesive layer formed using the adhesive composition. Moreover, according to the present invention, it is possible to provide a method for manufacturing an adhesive tape using the adhesive composition.

[0079] The embodiments of the present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are as follows.

[0080] <n-hexyl acrylate containing bio-derived carbon> Linoleic acid derived from castor oil was converted to linoleic acid hydroperoxide by lipoxygenase, and then a mixture containing n-hexyl aldehyde was obtained by isomerase. By distillation of the obtained mixture, n-hexyl aldehyde containing bio-derived carbon was obtained. Furthermore, by hydrogenation of the obtained n-hexyl aldehyde containing bio-derived carbon, an n-hexyl alcohol containing bio-derived carbon was obtained. By esterifying the obtained n-hexyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), n-hexyl acrylate containing bio-derived carbon was prepared.

[0081] <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. Then, undecylenic acid was separated from the obtained mixture by distillation to obtain n-heptyl alcohol containing bio-derived carbon. By esterifying the obtained n-heptyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), n-heptyl acrylate containing bio-derived carbon was prepared.

[0082] <1-Methylhebutyl Acrylate Containing Bio-Derived Carbon> Ricinoleic acid derived from castor oil was dissolved in alkali to obtain a mixture containing sebacic acid and 1-methylhebutyl alcohol. Next, sebacic acid was separated from the obtained mixture by distillation to obtain 1-methylhebutyl alcohol containing bio-derived carbon. By esterifying the obtained 1-methylhebutyl alcohol containing bio-derived carbon with acrylic acid (manufactured by Nippon Shokubai Co., Ltd.), 1-methylhebutyl acrylate containing bio-derived carbon was prepared.

[0083] <Biologically derived, carbon-free monomers> ・n-propyl acrylate (manufactured by Fujifilm Corporation) ・n-butyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) ・stearyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.) ・arachidyl acrylate (manufactured by BASF) ・acrylic acid (manufactured by Nippon Shokubai Co., Ltd.) ・4-hydroxybutyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0084] <Other crosslinking agents> - Isocyanate-based crosslinking agent A (Covestro Corporation, "Desmodule L-75")

[0085] <Photopolymerization Initiator> • Photopolymerization Initiator A: 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (IGM Resins, "Omnirad TPO N")

[0086] <Tackifying Resin> ・Tackifying Resin A: Terpene phenol-based tackifying resin (Yasuhara Chemical Co., Ltd., "YS Polystar G150", softening temperature: 145℃~155℃)

[0087] (Example 1) (1) Production of (meth)acrylic copolymer Ethyl acetate was added as a polymerization solvent to a reaction vessel, and after bubbling with nitrogen, reflux was started by heating the reaction vessel while introducing nitrogen. Subsequently, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile 10 times with ethyl acetate was added to the reaction vessel as a polymerization initiator, and 95.0 parts by mass of n-butyl acrylate containing bio-derived carbon and 5.0 parts by mass of acrylic acid were added dropwise over 2 hours. After the dropwise addition was completed, a polymerization initiator solution prepared by diluting 0.1 parts by mass of azobisisobutyronitrile 10 times with ethyl acetate was added again to the reaction vessel as a polymerization initiator, and the polymerization reaction was carried out at 70°C for 4 hours to obtain a (meth)acrylic copolymer-containing solution. The obtained (meth)acrylic copolymer-containing solution was heated and dried in an oven at 110°C for 1 hour to completely remove the ethyl acetate, thereby obtaining (meth)acrylic copolymer A. For the weight-average molecular weight of (meth)acrylic copolymer A, the obtained (meth)acrylic copolymer-containing solution was diluted 50-fold with tetrahydrofuran (THF), and the resulting dilution 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 (Waters, "2690 Separations Module"), and GPC measurement was performed under conditions of sample flow rate of 1 mL / min and column temperature of 40°C to measure the polystyrene-equivalent molecular weight of the (meth)acrylic copolymer and determine the weight-average molecular weight. The results are shown in Table 1.

[0088] (2) Preparation of the adhesive composition An adhesive composition was prepared by adding 65.0 parts by mass of n-butyl acrylate containing bio-derived carbon as an alkyl (meth)acrylate, 35.0 parts by mass of (meth)acrylic copolymer A obtained as a (meth)acrylic copolymer, 1.0 part by mass of Karens AOI (manufactured by Resonaq) as a crosslinking agent (a), an amount of isocyanate-based crosslinking agent A as another crosslinking agent so that the isocyanate group content is 0.02 parts by mass, 0.95 parts by mass of photopolymerization initiator A as a photopolymerization initiator, and 11 parts by mass of ethyl acetate as a solvent.

[0089] (3) Measurement of the solvent content in the adhesive composition A sample solution was prepared by diluting the obtained adhesive composition with chloroform. Gas chromatography-mass spectrometry (GC / MS) was performed on the obtained sample solution, and the solvent content (mass%) in the adhesive composition was measured from the peak area of ​​the obtained spectrum. The results are shown in Table 2. <GC / MS measurement conditions> Gas chromatograph-mass spectrometer: JMS Q1500 (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 (Sigma-Aldrich) Injection port temperature: 320°C Column temperature: 40°C to 340°C Injection volume: 1.0 μL

[0090] (4) Measurement of the gel fraction of the adhesive layer After coating the release surface of a 75 μm thick release PET film with the prepared adhesive composition, a 23 μm thick release PET film is placed on top so that its release surface faces the coated adhesive composition, sealing the adhesive composition. Using a UV-LED irradiation device (CCS Corporation, "UVS01-01"), the irradiation is performed at a wavelength of 365 nm and an irradiation intensity of 35 mW / cm². ２ The light irradiation dose is 1000 mJ / cm². ２ The adhesive composition was irradiated from the side of a 50 μm thick release PET film through the release PET film. Furthermore, the irradiated adhesive composition was dried at 110°C for 5 minutes to form a 50 μm thick adhesive layer, and then cured by heating at 40°C for 48 hours to obtain an adhesive tape for gel fraction measurement. The release PET film was peeled off one side of the obtained adhesive tape for gel fraction measurement, and it was bonded to a 23 μm thick base PET film (Futamura Chemical Co., Ltd., "FE2002") and cut into a flat rectangular shape with a width of 20 mm and a length of 40 mm. Furthermore, the release PET film was peeled off the other side of the adhesive tape for gel fraction measurement to prepare a test piece, and its mass was measured. The test piece was immersed in ethyl acetate at 23°C for 24 hours, then removed from the ethyl acetate and dried at 110°C for 1 hour. The mass of the dried test piece was measured, and the gel fraction (mass %) was calculated using the following formula (1). The results are shown in Table 2. Gel fraction (mass%) = 100 × (W ２ -W０ ) / (W １ -W ０ ) (1) (W ０ : Mass of the base material, W １ : Mass of the test specimen before immersion, W ２ (Mass of the test specimen after immersion and drying)

[0091] (Examples 2-21, Comparative Examples 1-4) Except that the constituent unit monomers in "(1) Production of (meth)acrylic copolymer" were as shown in Table 1, and the types and amounts of each component of the adhesive composition in "(2) Production of adhesive composition" were as shown in Tables 2-4, an adhesive composition was obtained in the same manner as in Example 1. In addition, the solvent content ratio in the adhesive composition and the gel fraction of the adhesive layer were measured in the same manner as in Example 1. The results are shown in Tables 2-4. In Tables 2-4, parts by mass for isocyanate crosslinking agent A indicates the content of isocyanate groups in the isocyanate crosslinking agent, and in Tables 2-4, parts by mass for ethyl acetate indicates the amount of ethyl acetate added as a solvent in "(2) Production of adhesive composition" described above. Furthermore, for (meth)acrylic copolymers B and C, the polymerization reaction was carried out at polymerization temperatures of 80°C ((meth)acrylic copolymer B) and 90°C ((meth)acrylic copolymer C), respectively. Furthermore, in Comparative Example 1, the adhesive layer had completely hardened, making it impossible to measure the gel fraction of the adhesive layer.

[0092] <Evaluation> The adhesive compositions obtained in the examples and comparative examples were evaluated using the following method. The results are shown in Tables 2 to 4.

[0093] (1) Pot life of adhesive composition The viscosity change after the addition of additives and stirring was measured using the obtained adhesive composition. Using a B-type viscometer (RVDV-2+PRO, manufactured by Eiko Seiki Co., Ltd.) and spindle S04, the adhesive composition was stirred at 23°C and 12 rpm until the viscosity exceeded 10 Pa. The time until the viscosity of the adhesive composition exceeded 10 Pa was measured, with the time at which stirring began set as 0. The pot life of the adhesive composition was evaluated as follows: "A" if the time until the viscosity of the adhesive composition exceeded 10 Pa was longer than 12 hours, "B" if it did not exceed 10 Pa immediately after stirring but was longer than 10 minutes but within 12 hours, and "C" if it exceeded 10 Pa immediately after stirring (within 10 minutes).

[0094] (2) Degree of Adhesion in the Adhesive Composition (2-1) Preparation of Adhesive Tape The obtained adhesive composition was applied to the release surface of a 75 μm thick release PET film, and then a 23 μm thick release PET film was placed on top so that its release surface faced the coated adhesive composition to seal the adhesive composition. Using a UV-LED irradiation device (CCS Corporation, "UVS01-01"), the wavelength was 365 nm and the irradiation intensity was 35 mW / cm². ２ The light irradiation dose is 1000 mJ / cm². ２ After irradiating the adhesive composition through a release PET film in this manner, the irradiated adhesive composition was further dried at 110°C for 5 minutes to form an adhesive layer with a thickness of 50 μm. Then, it was cured by heating at 40°C for 48 hours to obtain an adhesive tape.

[0095] (2-2) Measurement of 180° peel force on SUS at 23°C One side (the side not measured) of the adhesive tape obtained in "(2-1) Preparation of adhesive tape" described above was backed with a 23 μm thick polyethylene terephthalate (PET) film (Futamura Chemical Co., Ltd., "FE2002"), and then cut to a width of 25 mm x length of 75 mm to prepare a test piece. The release PET film of this test piece was peeled off, and the exposed adhesive layer was attached to a SUS304 plate (a SUS (stainless steel) plate that had been washed with ethanol and then wiped dry). Then, pressure was applied to the test piece by running a 2 kg rubber roller back and forth once at a speed of 300 mm / min, and the sample was cured at 23°C and 50% RH for 20 minutes to prepare a test sample. For the prepared measurement samples, the adhesive tape was peeled in a 180° direction at a tensile speed of 300 mm / min using a tensile testing machine under conditions of 23°C and 50% RH, in accordance with JIS Z 0237:2009, and the peel force (N / cm) was measured. The degree of adhesive strength development of the adhesive composition was evaluated as follows: "A" if the obtained peel force was 7.0 N / cm or more, "B" if it was 6.5 N / cm or more and less than 7.0 N / cm, "C" if it was 4.0 N / cm or more and less than 6.5 N / cm, and "D" if it was less than 4.0 N / cm. Note that for Comparative Example 1, it was not possible to measure the peel force because it was not possible to coat the adhesive composition and thus not be able to produce an adhesive tape.

[0096]

[0097]

[0098]

[0099]

[0100] According to the present invention, it is possible to provide an adhesive composition that has a good pot life and can exhibit excellent adhesive strength. Furthermore, according to the present invention, it is possible to provide an adhesive tape having an adhesive layer formed using the adhesive composition. Moreover, according to the present invention, it is possible to provide a method for manufacturing an adhesive tape using the adhesive composition.

Claims

1. An adhesive composition comprising an alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms, a (meth)acrylic copolymer, and a crosslinking agent, wherein the (meth)acrylic copolymer has constituent units derived from monomers containing functional groups having active hydrogen, the crosslinking agent comprises a crosslinking agent (a) which is a monomer having a functional group that reacts with the functional group having active hydrogen in the (meth)acrylic copolymer and a functional group containing a carbon-carbon unsaturated double bond, and the adhesive composition does not contain a solvent, or the adhesive composition contains a solvent, wherein the content of the solvent in the adhesive composition is 10% by mass or less.

2. The adhesive composition according to claim 1, which contains a photopolymerization initiator.

3. The adhesive composition according to claim 1 or 2, which contains a tackifying resin.

4. The adhesive composition according to claim 3, wherein the tackifying resin comprises at least one selected from the group consisting of rosin ester-based tackifying resins and terpene phenol-based tackifying resins.

5. The adhesive composition according to claim 3 or 4, wherein the content of the tackifying resin is 10 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the total of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms and the (meth)acrylic copolymer.

6. The adhesive composition according to claim 1, 2, 3, 4, or 5, wherein the crosslinking agent further comprises an isocyanate-based crosslinking agent.

7. The adhesive composition according to claim 6, wherein the content of isocyanate groups in the isocyanate-based crosslinking agent is 0.3 parts by mass or less per 100 parts by mass of the total of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms and the (meth)acrylic copolymer.

8. The adhesive composition according to claim 1, 2, 3, 4, 5, 6, or 7, wherein the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms comprises an alkyl (meth)acrylate having an alkyl group having 6 to 8 carbon atoms.

9. The adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, or 8, wherein the content of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms is 40 parts by mass or more and 95 parts by mass or less, relative to 100 parts by mass of the total of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms and the (meth)acrylic copolymer.

10. The adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the (meth)acrylic copolymer has constituent units derived from alkyl (meth)acrylate, and the constituent units derived from alkyl (meth)acrylate have an alkyl group having 6 or more carbon atoms and 8 or less carbon atoms.

11. The adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the (meth)acrylic copolymer has a weight-average molecular weight of 2 million or less.

12. The adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the content of the (meth)acrylic copolymer is 5.0 parts by mass or more, based on a total of 100 parts by mass of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms and the (meth)acrylic copolymer.

13. The adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, wherein the functional group in the crosslinking agent (a) that reacts with the functional group having the active hydrogen in the (meth)acrylic copolymer is an isocyanate group.

14. The adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, wherein the content of the crosslinking agent (a) is 0.01 parts by mass or more and 5.0 parts by mass or less, based on a total of 100 parts by mass of the alkyl (meth)acrylate having an alkyl group having 4 to 20 carbon atoms and the (meth)acrylic copolymer.

15. An adhesive tape having an adhesive layer formed using the adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14.

16. The adhesive tape according to claim 15, wherein the gel fraction of the adhesive layer is 30% by mass or more and 70% by mass or less.

17. A method for producing an adhesive tape, comprising the step of photocuring the adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14.

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