Acrylic adhesive composition, adhesive, adhesive tape, method for producing adhesive tape, and method for producing acrylic copolymer

Abstract

The purpose of the present invention is to provide an acrylic adhesive composition that has excellent applicability and can applied without lines or streaks, and that can exhibit high adhesive force.　The present invention is an acrylic adhesive composition comprising an acrylic copolymer and a solvent, wherein: the acrylic copolymer has a structural unit that is derived from a (meth)acrylic acid alkyl ester and a structural unit that is derived from an olefin-based polymer having a polymerizable unsaturated double bond at a terminal thereof; the solvent includes at least one solvent selected from the group consisting of hydrocarbon-based solvents and solvents having an SP value of 7.2-8.6 (J / cm3)1 / 2; and the solid content ratio in the acrylic adhesive composition is 15-50 mass%.

Description

Acrylic adhesive composition, adhesive, adhesive tape, method for producing adhesive tape, and method for producing acrylic copolymer

[0001] The present invention relates to an acrylic pressure-sensitive adhesive composition. The present invention also relates to a pressure-sensitive adhesive and a pressure-sensitive adhesive tape formed from the acrylic pressure-sensitive adhesive composition. The present invention further relates to a pressure-sensitive adhesive tape. In addition, the present invention also relates to a method for producing a pressure-sensitive adhesive tape formed from the acrylic pressure-sensitive adhesive composition. In addition, the present invention also relates to a method for producing an acrylic copolymer.

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

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

[0004] Acrylic pressure-sensitive adhesives containing acrylic copolymers are widely used as pressure-sensitive adhesives with excellent adhesive strength. To further enhance adhesive strength, monomers other than acrylates may be copolymerized as constituent monomers of the acrylic copolymer. However, when using an acrylic pressure-sensitive adhesive containing an acrylic copolymer copolymerized with such a monomer other than acrylate, uniform application is difficult, making it difficult to produce a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer or to bond an adherend using a liquid pressure-sensitive adhesive. In such cases, pressure-sensitive adhesive tapes having a pressure-sensitive adhesive layer produced by applying an acrylic pressure-sensitive adhesive composition may suffer from lines or streaks in the pressure-sensitive adhesive layer, resulting in poor appearance. Therefore, it is an issue to obtain an acrylic pressure-sensitive adhesive composition that has excellent application properties and can exhibit high adhesive strength.

[0005] An object of the present invention is to provide an acrylic pressure-sensitive adhesive composition that has excellent coatability, can be applied without lines or streaks, and can exhibit high adhesive strength. Another object of the present invention is to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive tape formed from the acrylic pressure-sensitive adhesive composition. A further object of the present invention is to provide a pressure-sensitive adhesive tape that is free from lines or streaks and has a good appearance. In addition, an object of the present invention is to provide a method for producing a pressure-sensitive adhesive tape formed from the acrylic pressure-sensitive adhesive composition. Still another object of the present invention is to provide a method for producing an acrylic copolymer that can be used in an acrylic pressure-sensitive adhesive composition that has excellent coatability, can be applied without lines or streaks, and can exhibit high adhesive strength.

[0006] Disclosure 1 provides an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer and a solvent, wherein the acrylic copolymer has a structural unit derived from a (meth)acrylic acid alkyl ester and a structural unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond, and the solvent is a hydrocarbon solvent and a terpolymer having an SP value of 7.2 (J / cm ３ ) １／２ More than 8.6 (J / cm ３ ) １／２ or less, wherein the acrylic pressure-sensitive adhesive composition comprises at least one solvent selected from the group consisting of solvents having an SP value of 8.6 (J / cm or less), and wherein the solid content in the acrylic pressure-sensitive adhesive composition is 15% by mass or more and 50% by mass or less. Disclosure 2 is the acrylic pressure-sensitive adhesive composition of Disclosure 1, wherein the solvent comprises a hydrocarbon solvent, and the hydrocarbon solvent comprises an aliphatic hydrocarbon solvent. Disclosure 3 is the acrylic pressure-sensitive adhesive composition of Disclosure 2, wherein the aliphatic hydrocarbon solvent comprises an aliphatic hydrocarbon compound having 6 to 9 carbon atoms. Disclosure 4 is the acrylic pressure-sensitive adhesive composition of Disclosure 3, wherein the aliphatic hydrocarbon compound having 6 to 9 carbon atoms comprises at least one selected from the group consisting of normal hexane, cyclohexane, and methylcyclohexane. Disclosure 5 is the acrylic pressure-sensitive adhesive composition of Disclosure 5, wherein the solvent further comprises an ester solvent and an ester solvent having an SP value of 8.6 (J / cm or less). ３ ) １／２ greater than 9.0 (J / cm ３ ) １／２

[0014] The acrylic pressure-sensitive adhesive composition of Disclosure 1, 2, 3, or 4, comprising at least one solvent selected from the group consisting of solvents represented by the following formula (1):

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[0014] Disclosure 9 is the acrylic pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, or 8, wherein the acrylic copolymer contains structural units derived from the (meth)acrylic acid alkyl ester in an amount of 50% by mass or more and 99% by mass or less. Disclosure 10 is the acrylic pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, or 9, wherein the acrylic copolymer contains structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond in an amount of 5.0% by mass or more. Disclosure 11 is the acrylic pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10, wherein the acrylic copolymer contains structural units derived from a polar functional group-containing monomer. Disclosure 12 is the acrylic pressure-sensitive adhesive composition of Disclosure 11, wherein the structural units derived from the polar functional group-containing monomer include at least one selected from the group consisting of structural units derived from a carboxy group-containing monomer and structural units derived from a hydroxyl group-containing monomer. Disclosure 13 is the acrylic pressure-sensitive adhesive composition of Disclosure 11 or 12, wherein the acrylic copolymer contains 0.1 mass % or more and 20 mass % or less of structural units derived from polar functional group-containing monomers.Disclosure 14 is the acrylic pressure-sensitive adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, which contains a tackifier resin. Disclosure 15 is the acrylic pressure-sensitive adhesive composition of Disclosure 14, wherein the tackifier resin contains a high hydroxyl value tackifier resin having a hydroxyl value of 15 mgKOH / g or more. Disclosure 16 is the acrylic pressure-sensitive adhesive composition of Disclosure 14 or 15, in which the content of the tackifier resin is 40 parts by mass or less per 100 parts by mass of the acrylic copolymer. Disclosure 17 is the acrylic pressure-sensitive adhesive composition of Disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16, which contains a crosslinker. Disclosure 18 is a pressure-sensitive adhesive formed from the acrylic pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17. Disclosure 19 is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed from the acrylic pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17. Disclosure 20 is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed using an acrylic pressure-sensitive adhesive composition, wherein the acrylic pressure-sensitive adhesive composition contains an acrylic copolymer, and the acrylic copolymer has structural units derived from a (meth)acrylic acid alkyl ester and structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond, and the pressure-sensitive adhesive layer contains a solvent, and the solvent includes an aliphatic hydrocarbon solvent.

[0023] Disclosure 21 is the pressure-sensitive adhesive tape of Disclosure 20, wherein the acrylic copolymer has a structural unit derived from a polar functional group-containing monomer. Disclosure 22 is the pressure-sensitive adhesive tape of Disclosure 19, 20, or 21, wherein the pressure-sensitive adhesive layer does not contain an aromatic hydrocarbon solvent, or wherein the pressure-sensitive adhesive layer contains an aromatic hydrocarbon solvent and the content of the aromatic hydrocarbon solvent in the pressure-sensitive adhesive layer is 300 ppm or less. Disclosure 23 is the pressure-sensitive adhesive tape of Disclosure 19, 20, 21, or 22, wherein the pressure-sensitive adhesive layer has a gel fraction of 10% by mass or more and 70% by mass or less. Disclosure 24 is the pressure-sensitive adhesive tape of Disclosure 19, 20, 21, 22, or 23, which has a substrate.Disclosure 25 is a pressure-sensitive adhesive tape according to Disclosures 19, 20, 21, 22, 23, or 24, which is used to fix electronic components or on-vehicle components. Disclosure 26 is a method for producing a pressure-sensitive adhesive tape, comprising a step of applying the acrylic pressure-sensitive adhesive composition according to Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17. Disclosure 27 is a method for producing an acrylic copolymer, comprising step (i) of polymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester and an olefin polymer having a terminal polymerizable unsaturated double bond in a solvent in the presence of a polymerization initiator, wherein the solvent contains a hydrocarbon solvent. Disclosure 28 is a method for producing an acrylic copolymer according to Disclosure 27, wherein the hydrocarbon solvent contains an aliphatic hydrocarbon solvent. Disclosure 29 is a method for producing an acrylic copolymer according to Disclosure 28, wherein the aliphatic hydrocarbon solvent contains an aliphatic hydrocarbon compound having from 6 to 9 carbon atoms. Disclosure 30 is the method for producing an acrylic copolymer according to Disclosure 29, wherein the aliphatic hydrocarbon compound having 6 to 9 carbon atoms comprises at least one selected from the group consisting of normal hexane, cyclohexane, and methylcyclohexane. Disclosure 31 is the method for producing an acrylic copolymer according to Disclosure 27, 28, 29, or 30, wherein the solvent further comprises an ester solvent, the ester solvent comprising an ester compound represented by the following formula (1), and the blending ratio of the hydrocarbon solvent to the total blending amount of the hydrocarbon solvent and the ester solvent is 5.0 mass% or more and less than 100 mass%. Disclosure 32 is the method for producing an acrylic copolymer according to Disclosure 27, 28, 29, 30, or 31, wherein the polymerization initiator comprises at least one selected from the group consisting of organic peroxides and azo compounds. The present disclosure 33 is the method for producing an acrylic copolymer according to the present disclosure 27, 28, 29, 30, 31, or 32, wherein the amount of the polymerization initiator blended is 0.01 parts by mass or more and 3.0 parts by mass or less relative to 100 parts by mass of the monomer mixture. The present disclosure 34 is the method for producing an acrylic copolymer according to the present disclosure 27, 28, 29, 30, 31, 32, or 33, wherein the temperature at which the monomer mixture is polymerized in a solvent in the presence of a polymerization initiator in the step (i) is 50°C or more and 100°C or less.

[0007] In formula (1), R １ , R ２ each independently represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms.

[0008] The present invention will be described in detail below. The adhesive tape of Disclosure 19 will also be referred to as the "adhesive tape of Invention 19," and the adhesive tape of Disclosure 20 will also be referred to as the "adhesive tape of Invention 20." Furthermore, matters common to the adhesive tape of Invention 19 and the adhesive tape of Invention 20 will not be specified in particular, or will be described as the "adhesive tape of the present invention."

[0009] The present inventors have investigated the acrylic copolymers contained in acrylic pressure-sensitive adhesive compositions and found that high adhesive strength can be achieved by using one having a structural unit derived from a (meth)acrylic acid alkyl ester and a structural unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond. Furthermore, the present inventors have investigated the solvents contained in acrylic pressure-sensitive adhesive compositions and found that by using a low-polarity solvent (e.g., a hydrocarbon solvent) instead of ethyl acetate, which is typically used in acrylic pressure-sensitive adhesive compositions, excellent coatability can be achieved even for acrylic copolymers containing an acrylic copolymer copolymerized with a low-polarity monomer other than acrylate. The present inventors have also found that by preparing an acrylic pressure-sensitive adhesive composition containing the above-mentioned acrylic copolymer capable of exhibiting high adhesive strength and a low-polarity solvent, an acrylic pressure-sensitive adhesive composition can be obtained that has excellent coatability, can be applied without lines or streaks, and exhibits high adhesive strength, thereby completing the present invention.

[0010] The acrylic pressure-sensitive adhesive composition of the present invention contains an acrylic copolymer. The acrylic copolymer has structural units derived from a (meth)acrylic acid alkyl ester. In this specification, "(meth)acrylic" means acrylic or methacrylic.

[0011] The structural unit derived from the (meth)acrylic acid alkyl ester preferably includes a structural unit derived from a (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from an alcohol is 1 to 4. By including a structural unit derived from a (meth)acrylic acid alkyl ester in which the carbon number of the alkyl group derived from an alcohol is 1 to 4, the acrylic pressure-sensitive adhesive composition of the present invention can exhibit better retention performance at high temperatures. In this specification, the term "alcohol-derived alkyl group" refers to an alkyl group bonded to an oxygen atom of an ester bond in the (meth)acrylic acid alkyl ester.

[0012] Examples of the (meth)acrylic acid alkyl ester in which the alkyl group derived from the alcohol has 1 to 4 carbon atoms include (meth)acrylic acid alkyl esters obtained by dehydration condensation of (meth)acrylic acid and an alcohol having a linear or branched alkyl group having 1 to 4 carbon atoms. Specific examples include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, and isobutyl (meth)acrylate. Of these, n-butyl (meth)acrylate is preferred. These (meth)acrylic acid alkyl esters may be used alone or in combination of two or more.

[0013] The preferred lower limit of the content of structural units derived from (meth)acrylic acid alkyl esters in which the carbon number of the alkyl group derived from the alcohol is 1 to 4, among the structural units derived from the (meth)acrylic acid alkyl esters, is 50% by mass. When the content of structural units derived from (meth)acrylic acid alkyl esters in which the carbon number of the alkyl group derived from the alcohol is 1 to 4, is 50% by mass or more, the acrylic pressure-sensitive adhesive composition of the present invention can exhibit higher adhesive strength and better retention performance. A more preferred lower limit of the content of structural units derived from (meth)acrylic acid alkyl esters in which the carbon number of the alkyl group derived from the alcohol is 1 to 4, is 60% by mass, and an even more preferred lower limit is 70% by mass. Furthermore, it is most preferred that the content of structural units derived from (meth)acrylic acid alkyl esters in which the carbon number of the alkyl group derived from the alcohol is 1 to 4, is 100% by mass, i.e., the structural units derived from the (meth)acrylic acid alkyl esters consist solely of structural units derived from (meth)acrylic acid alkyl esters in which the carbon number of the alkyl group derived from the alcohol is 1 to 4.

[0014] The structural unit derived from the alkyl (meth)acrylate may have a structural unit derived from an alkyl (meth)acrylate other than the structural unit derived from the alkyl (meth)acrylate in which the number of carbon atoms in the alkyl group derived from the alcohol is 1 or more and 4 or less.

[0015] Examples of the other (meth)acrylic acid alkyl esters include n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, n-heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 1-methylheptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate. Among these, from the viewpoint of improving adhesive strength, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-heptyl (meth)acrylate, and 1-methylheptyl (meth)acrylate are preferred, and 2-ethylhexyl (meth)acrylate and n-heptyl (meth)acrylate are more preferred. These alkyl (meth)acrylates may be used alone or in combination of two or more.

[0016] The content of the structural units derived from the (meth)acrylic acid alkyl ester in the acrylic copolymer is preferably 50% by mass at the lower limit and 99% by mass at the upper limit. When the content of the structural units derived from the (meth)acrylic acid alkyl ester is 50% by mass or more, the performance as a pressure-sensitive adhesive is easily maintained, and the polymerization reaction during production can be efficiently promoted. When the content of the structural units derived from the (meth)acrylic acid alkyl ester is 99% by mass or less, the acrylic pressure-sensitive adhesive composition of the present invention is easily able to maintain its performance as a pressure-sensitive adhesive. The content of the structural units derived from the (meth)acrylic acid alkyl ester is more preferably 60% by mass at the lower limit, more preferably 95% by mass at the upper limit, even more preferably 70% by mass at the lower limit, and even more preferably 90% by mass at the upper limit.

[0017] The acrylic copolymer has structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond. Because the acrylic copolymer has structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond, when the acrylic pressure-sensitive adhesive composition of the present invention forms a pressure-sensitive adhesive or a pressure-sensitive adhesive layer, the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond in the side chain of the acrylic copolymer aggregate due to interaction, forming a structure in which pseudo-intermolecular cross-linking points are formed. When the acrylic copolymer has such a structure, the pressure-sensitive adhesive or pressure-sensitive adhesive layer formed from the acrylic pressure-sensitive adhesive composition of the present invention exhibits hard properties like a cross-linked pressure-sensitive adhesive or pressure-sensitive adhesive layer when the strain applied to the pressure-sensitive adhesive or pressure-sensitive adhesive layer is small, and the holding power is further improved. On the other hand, when the pressure-sensitive adhesive or pressure-sensitive adhesive layer is subjected to peel stress and the strain increases, the pseudo-cross-linking breaks and the molecules of the acrylic copolymer stretch, so the pressure-sensitive adhesive or pressure-sensitive adhesive layer formed from the acrylic pressure-sensitive adhesive composition of the present invention exhibits high flexibility and improved adhesive power. In other words, since the acrylic copolymer has a structural unit derived from an olefin polymer having a polymerizable unsaturated double bond at its terminal, the acrylic pressure-sensitive adhesive composition of the present invention can exhibit high adhesive strength and higher holding performance.

[0018] The olefin polymer having a terminal polymerizable unsaturated double bond may have a polymerizable unsaturated double bond at one terminal or at both terminals. Among them, an olefin polymer having a terminal polymerizable unsaturated double bond is preferred from the viewpoint of facilitating the formation of an appropriate number of pseudo-crosslinks.

[0019] Examples of the olefin polymer having a terminal polymerizable unsaturated double bond include ethylene-butylene copolymers, ethylene-propylene copolymers, ethylene polymers, propylene polymers, butylene polymers, etc., which have a group having a polymerizable unsaturated double bond at one or both terminals. These olefin polymers having a terminal polymerizable unsaturated double bond may be used alone or in combination of two or more.

[0020] Examples of the group having a polymerizable unsaturated double bond include a (meth)acryloyl group, a vinyl ether group, and a styryl group. Among these, a (meth)acryloyl group is preferred because of its excellent copolymerizability with the (meth)acrylic acid alkyl ester. In this specification, "(meth)acryloyl" means acryloyl or methacryloyl.

[0021] Examples of olefin polymers having a (meth)acryloyl group at their termini include an ethylene macromonomer having a (meth)acryloyl group at one terminus, a propylene macromonomer having a (meth)acryloyl group at one terminus, an ethylene-butylene macromonomer having a (meth)acryloyl group at one terminus, and an ethylene-propylene macromonomer having a (meth)acryloyl group at one terminus. Of these, an ethylene-butylene macromonomer having a (meth)acryloyl group at one terminus and an ethylene-propylene macromonomer having a (meth)acryloyl group at one terminus are preferred, as these make it easier for the glass transition temperature of the acrylic copolymer described below to fall within an appropriate range, thereby enabling the acrylic pressure-sensitive adhesive composition of the present invention to exhibit superior adhesive strength. In this specification, the term "macromonomer" refers to a monomer having a polymerizable functional group and a weight-average molecular weight of approximately 1,000 to 100,000.

[0022] The preferred lower limit of the content of the structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond in the acrylic copolymer is 5.0% by mass. When the content of the structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond is 5.0% by mass or more, an appropriate number of pseudo-crosslinks are formed in the acrylic copolymer, allowing the acrylic pressure-sensitive adhesive composition of the present invention to exhibit higher adhesive strength. A more preferred lower limit of the content of the structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond is 10% by mass, and an even more preferred lower limit is 20% by mass. Furthermore, a preferred upper limit of the content of the structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond is 40% by mass. When the content of the structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond is 40% by mass or less, cohesive failure of the acrylic pressure-sensitive adhesive composition of the present invention can be further suppressed. The upper limit of the content of the structural units derived from the olefin polymer having a terminal polymerizable unsaturated double bond is preferably 35% by mass, and more preferably 30% by mass.

[0023] The acrylic copolymer preferably contains a structural unit derived from a polar functional group-containing monomer. The acrylic copolymer contains a structural unit derived from a polar functional group-containing monomer, which increases the polarity of the acrylic copolymer, thereby enhancing the cohesive strength of the acrylic pressure-sensitive adhesive composition of the present invention and enabling it to exhibit superior holding performance at high temperatures. Furthermore, when the acrylic pressure-sensitive adhesive composition of the present invention contains a crosslinking agent described below, the acrylic copolymer has a structure crosslinked via the crosslinking agent, enabling the acrylic pressure-sensitive adhesive composition of the present invention to exhibit superior adhesive strength and superior holding performance.

[0024] Examples of the polar functional group-containing monomer include carboxy group-containing monomers, hydroxy group-containing monomers, amide group-containing monomers, and amino group-containing monomers. In particular, from the viewpoint of enabling the acrylic pressure-sensitive adhesive composition of the present invention to exhibit superior adhesive strength and superior retention performance, the polar functional group-containing monomer preferably comprises at least one selected from the group consisting of carboxy group-containing monomers and hydroxy group-containing monomers. That is, the structural unit derived from the polar functional group-containing monomer preferably comprises at least one selected from the group consisting of structural units derived from carboxy group-containing monomers and structural units derived from hydroxy group-containing monomers. These polar functional group-containing monomers may be used alone, or two or more may be used in combination.

[0025] Examples of the carboxy group-containing monomer include unsaturated carboxylic acids such as (meth)acrylic acid, (meth)acryloylacetic acid, (meth)acryloylpropionic acid, (meth)acryloylbutyric acid, (meth)acryloylpentanoic acid, crotonic acid, maleic acid, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, and 2-carboxyethyl (meth)acrylate.

[0026] Examples of the hydroxyl group-containing monomer include 4-hydroxybutyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate.

[0027] Examples of the amide group-containing monomer include N-vinyl-2-pyrrolidone, N-vinylcaprolactam, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, and N-isopropyl(meth)acrylamide.

[0028] Examples of the amino group-containing monomer include (meth)acryloylmorpholine, 2-dimethylaminoethyl (meth)acrylate, and 2-diethylaminoethyl (meth)acrylate.

[0029] The total content of the structural units derived from the polar functional group-containing monomer in the acrylic copolymer is preferably 0.1% by mass at the lower limit and 20% by mass at the upper limit. When the total content of the structural units derived from the polar functional group-containing monomer is 0.1% by mass or more, the polarity of the acrylic copolymer is increased, thereby enhancing the cohesive strength of the acrylic pressure-sensitive adhesive composition of the present invention and enabling it to exhibit superior retention performance at high temperatures. Furthermore, the polymerization reaction is more likely to proceed smoothly. When the total content of the structural units derived from the polar functional group-containing monomer is 20% by mass or less, the acrylic pressure-sensitive adhesive composition of the present invention does not become too hard and can exhibit sufficient initial adhesive strength. The lower limit of the total content of the structural units derived from the polar functional group-containing monomer is more preferably 1.0% by mass, more preferably 8.0% by mass, and even more preferably 3.0% by mass.

[0030] The acrylic copolymer may contain the structural unit derived from the alkyl (meth)acrylate, the structural unit derived from the olefin polymer having a terminal polymerizable unsaturated double bond, and the structural unit derived from the polar functional group-containing monomer, but may also contain structural units derived from other monomers in addition to these structural units.

[0031] The weight-average molecular weight (Mw) of the acrylic copolymer preferably has a lower limit of 500,000 and an upper limit of 2,000,000. When the weight-average molecular weight of the acrylic copolymer is 500,000 or more, the cohesive strength of the acrylic pressure-sensitive adhesive composition of the present invention is increased, allowing it to exhibit better retention performance at high temperatures. When the weight-average molecular weight of the acrylic copolymer is 2,000,000 or less, the acrylic pressure-sensitive adhesive composition of the present invention does not become too hard, and the initial adhesive strength is further improved. The weight-average molecular weight of the acrylic copolymer more preferably has a lower limit of 600,000, a more preferably upper limit of 1,500,000, an even more preferably lower limit of 800,000, and an even more preferably upper limit of 1,350,000.

[0032] The ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the acrylic copolymer (polydispersity: Mw / Mn) preferably has a lower limit of 1.0 and an upper limit of 10.0. When the polydispersity of the acrylic copolymer is within the above range, the acrylic pressure-sensitive adhesive composition of the present invention can exhibit superior adhesive strength and superior retention performance. The polydispersity of the acrylic copolymer more preferably has a lower limit of 1.5 and an upper limit of 9.0, an even more preferably a lower limit of 2.0, and an even more preferably a upper limit of 8.0.

[0033] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) refer to the weight average molecular weight measured in gel permeation chromatography (GPC) in terms of standard polystyrene. Specifically, the acrylic copolymer is diluted to 0.1% by mass with tetrahydrofuran (THF), and the diluted solution is filtered through a filter (material: polytetrafluoroethylene, pore diameter: 0.2 μm). The obtained filtrate is supplied to a gel permeation chromatograph (Waters, "2690 Separations Module", etc.), and GPC measurement is performed under conditions of a sample flow rate of 1 mL / min and a column temperature of 40 ° C., and the polystyrene-equivalent molecular weight of the acrylic copolymer is measured to determine the weight average molecular weight (Mw) and number average molecular weight (Mn). As the column, for example, a GPC KF-806L (Showa Denko KK) or the like is used, and as the detector, for example, a differential refractometer or the like can be used. Furthermore, the polydispersity (Mw / Mn) can be obtained using the weight average molecular weight (Mw) and number average molecular weight (Mn) thus obtained.

[0034] Examples of methods for adjusting the weight-average molecular weight of the acrylic copolymer include a method of changing the concentration of a polymerization initiator or a monomer during the polymerization reaction, a method of adding a small amount of a chain transfer agent such as dodecyl mercaptan, and a method of changing the type of polymerization reaction solvent to control chain transfer to the solvent.

[0035] The glass transition temperature (Tg) of the acrylic copolymer is preferably in the range of -100°C or higher and 200°C or lower, and more preferably -20°C as the upper limit. When the glass transition temperature of the acrylic copolymer is -20°C or lower, the molecules of the acrylic copolymer are more easily stretched, allowing the acrylic pressure-sensitive adhesive composition of the present invention to exhibit superior adhesive strength. A more preferable upper limit of the glass transition temperature of the acrylic copolymer is -25°C, and an even more preferable upper limit is -30°C. Note that, when the acrylic copolymer has multiple glass transition temperatures, it is more preferable that all of the glass transition temperatures are -20°C or lower. Note that, when the acrylic pressure-sensitive adhesive composition of the present invention contains multiple acrylic copolymers, it is more preferable that all of the acrylic copolymers have glass transition temperatures of -20°C or lower. Note that, in this specification, the glass transition temperature can be measured by differential scanning calorimetry. More specifically, the measurement can be performed in a nitrogen atmosphere (nitrogen flow, flow rate 50 mL / min) using a differential scanning calorimeter (manufactured by Seiko Instruments Inc., "220C" or the like) according to a method in accordance with JIS K6240:2011, under conditions of a measurement temperature of -100°C to 200°C and a temperature rise rate of 10°C / min.

[0036] The glass transition temperature of the acrylic copolymer can be adjusted by changing the type and content of the monomers that are the raw materials for the acrylic copolymer.

[0037] The preferred lower limit of the content of the acrylic copolymer in the acrylic pressure-sensitive adhesive composition of the present invention is 40% by mass. When the content of the acrylic copolymer is 40% by mass or more, the acrylic pressure-sensitive adhesive composition of the present invention can exhibit superior adhesive strength. The more preferred lower limit of the content of the acrylic copolymer is 50% by mass, and even more preferred lower limit is 55% by mass. Furthermore, from the viewpoint that it is preferable to blend components other than the acrylic copolymer to adjust adhesive strength, the preferred upper limit of the content of the acrylic copolymer is 99.5% by mass.

[0038] The polymerization method for synthesizing the acrylic copolymer may be a conventionally known method in which a raw material monomer mixture is subjected to a radical reaction in the presence of a polymerization initiator, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization, etc. Among these, solution polymerization is preferred because of its ease of synthesis.

[0039] When solution polymerization is used as the polymerization method, examples of the reaction solvent include ethyl acetate, toluene, methyl ethyl ketone, methyl sulfoxide, ethanol, acetone, diethyl ether, cyclohexane, etc. These reaction solvents may be used alone or in combination of two or more.

[0040] Examples of the polymerization initiator include organic peroxides and azo compounds. Examples of the organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the azo compounds include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more.

[0041] The acrylic pressure-sensitive adhesive composition of the present invention contains a solvent. In the acrylic pressure-sensitive adhesive composition of the present invention, the solvent is a hydrocarbon solvent and a solvent having an SP value of 7.2 (J / cm ３ ) １／２ More than 8.6 (J / cm ３ ) １／２ The solvent contains at least one solvent selected from the group consisting of hydrocarbon solvents and solvents having an SP value of 7.2 (J / cm ３ ) １／２ More than 8.6 (J / cm ３ )１／２ The coatability of the acrylic pressure-sensitive adhesive composition of the present invention is improved by including at least one solvent selected from the group consisting of the following: In this specification, the "SP value" is also called the solubility parameter, and is an index that can represent the affinity between substances, calculated using the Fedors method (R.F. Fedors, Polym. Eng. Sci., 14(2), 147-154 (1974)).

[0042] In the acrylic pressure-sensitive adhesive composition of the present invention, when the solvent contains the hydrocarbon solvent, the hydrocarbon solvent preferably contains an aliphatic hydrocarbon solvent. By containing an aliphatic hydrocarbon solvent, the content of volatile organic compounds (VOCs) in the solvent can be reduced, and the amount of volatile organic compounds (VOCs) remaining in the pressure-sensitive adhesive or pressure-sensitive adhesive layer formed from the acrylic pressure-sensitive adhesive composition of the present invention can be reduced, thereby reducing the impact on the human body.

[0043] The aliphatic hydrocarbon solvent preferably contains an aliphatic hydrocarbon compound having from 6 to 9 carbon atoms. When the aliphatic hydrocarbon solvent contains an aliphatic hydrocarbon compound having from 6 to 9 carbon atoms, the acrylic pressure-sensitive adhesive composition of the present invention can exhibit higher adhesive strength and more excellent retention performance.

[0044] Examples of the aliphatic hydrocarbon compound having 6 to 9 carbon atoms include normal hexane, cyclohexane, methylcyclohexane, normal heptane, cycloheptane, methylcycloheptane, normal octane, cyclooctane, methylcyclooctane, normal nonane, cyclononane, etc. Among these, it is preferable to contain at least one selected from the group consisting of normal hexane, cyclohexane, and methylcyclohexane, and it is more preferable to contain at least one selected from the group consisting of cyclohexane and methylcyclohexane.

[0045] In the acrylic pressure-sensitive adhesive composition of the present invention, the solvent has an SP value of 7.2 (J / cm ３ ) １／２ More than 8.6 (J / cm ３) １／２ When a solvent having an SP value of 0.01 or less is contained, the preferred lower limit of the SP value of the solvent is 7.4 (J / cm ３ ) １／２ and the preferred upper limit is 8.4 (J / cm ３ ) １／２ When the SP value of the solvent is within the above range, the acrylic pressure-sensitive adhesive composition of the present invention has excellent coatability. A more preferable lower limit of the SP value of the solvent is 7.6 (J / cm ３ ) １／２ , and a more preferable upper limit is 8.2 (J / cm ３ ) １／２ is.

[0046] The SP value is 7.2 (J / cm ３ ) １／２ More than 8.6 (J / cm ３ ) １／２ Examples of the solvent include hydrocarbon solvents and ether solvents, and specific examples thereof include normal hexane (SP value: 7.28 (J / cm ３ ) １／２ ), cyclohexane (SP value: 8.06 (J / cm ３ ) １／２ ), methylcyclohexane (SP value: 7.92 (J / cm ３ ) １／２ ), decahydronaphthalene (SP value: 8.53 (J / cm ３ ) １／２ ), diethyl ether (SP value: 7.25 (J / cm ３ ) １／２ ) etc.

[0047] In the acrylic pressure-sensitive adhesive composition of the present invention, it is preferred that the hydrocarbon solvent does not contain an aromatic hydrocarbon solvent, or that the hydrocarbon solvent contains an aromatic hydrocarbon solvent, and the content of the aromatic hydrocarbon solvent in the solvent is 1000 ppm or less. By having the content of the aromatic hydrocarbon solvent be 1000 ppm or less, the content of volatile organic compounds (VOCs) in the solvent can be reduced, thereby reducing the impact on the human body. The upper limit of the content of the aromatic hydrocarbon solvent is more preferably 700 ppm, even more preferably 200 ppm, and it is most preferred that the hydrocarbon solvent does not contain an aromatic hydrocarbon solvent.

[0048] In the acrylic pressure-sensitive adhesive composition of the present invention, the solvent further comprises an ester-based solvent and a solvent having an SP value of 8.6 (J / cm ３ ) １／２ greater than 9.0 (J / cm ３ ) １／２ The solvent may contain at least one solvent selected from the group consisting of ester-based solvents and solvents having an SP value of 8.6 (J / cm ３ ) １／２ greater than 9.0 (J / cm ３ ) １／２ By including the solvent below, the solubility of the solvent in the acrylic copolymer is further improved, and therefore the coatability of the acrylic pressure-sensitive adhesive composition of the present invention is further improved.

[0049] In the acrylic pressure-sensitive adhesive composition of the present invention, when the solvent contains an ester solvent, the ester solvent preferably contains an ester compound represented by the formula (1). When the ester solvent contains the ester compound represented by the formula (1), the coatability of the acrylic pressure-sensitive adhesive composition of the present invention is further improved.

[0050] In formula (1), R １ , R ２ The aliphatic hydrocarbon group represented by R may be a saturated hydrocarbon group or an unsaturated hydrocarbon group. １ , R ２The aliphatic hydrocarbon group represented by the formula (I) may be linear, branched, or cyclic. When the aliphatic hydrocarbon group is cyclic, it may be an unsubstituted hydrocarbon group or a hydrocarbon group in which specific hydrogen atoms have been substituted with alkyl groups.

[0051] In the acrylic pressure-sensitive adhesive composition of the present invention, the content of the hydrocarbon solvent in the total content of the hydrocarbon solvent and the ester solvent is preferably 5.0% by mass or more and less than 100% by mass. When the content of the hydrocarbon solvent is 5.0% by mass or more, the acrylic pressure-sensitive adhesive composition of the present invention can exhibit higher adhesive strength. When the content of the hydrocarbon solvent is less than 100% by mass, the coatability of the acrylic pressure-sensitive adhesive composition of the present invention is further improved. The lower limit of the content of the hydrocarbon solvent is more preferably 10% by mass, and more preferably 90% by mass, and even more preferably 20% by mass and even more preferably 80% by mass.

[0052] In the acrylic pressure-sensitive adhesive composition of the present invention, the solvent has an SP value of 8.6 (J / cm ３ ) １／２ greater than 9.0 (J / cm ３ ) １／２ When a solvent having an SP value of 8.7 (J / cm ３ ) １／２ and the preferred upper limit is 8.8 (J / cm ３ ) １／２ When the SP value of the solvent is within the above range, the coatability of the acrylic pressure-sensitive adhesive composition of the present invention is further improved.

[0053] The SP value is 8.6 (J / cm ３ ) １／２ greater than 9.0 (J / cm ３ ) １／２ Examples of the solvents that satisfy the following conditions include ester-based solvents and ketone-based solvents, and specific examples thereof include ethyl acetate (SP value: 8.74 (J / cm ３ ) １／２ ), methyl acetate (SP value: 8.77 (J / cm ３ ) １／２), methyl ethyl ketone (SP value: 8.98 (J / cm ３ ) １／２ ) etc.

[0054] The acrylic pressure-sensitive adhesive composition of the present invention may further contain a tackifier resin. By containing a tackifier resin, the acrylic pressure-sensitive adhesive composition of the present invention can exhibit even better adhesive strength.

[0055] The tackifier resin preferably contains a high-hydroxyl value tackifier resin having a hydroxyl value of 15 mgKOH / g or more. When the tackifier resin contains a high-hydroxyl value tackifier resin, the high-hydroxyl value tackifier resin has high polarity, making it less compatible with the low-polarity structural units derived from the olefin polymer having a polymerizable unsaturated double bond at its terminal. As a result, the formation of pseudo-crosslinking points due to interactions between the low-polarity structural units derived from the olefin polymer having a polymerizable unsaturated double bond at its terminal is not inhibited, allowing the acrylic pressure-sensitive adhesive composition of the present invention to exhibit superior adhesive strength. Examples of the high-hydroxyl value tackifier resin include terpene phenol resins and rosin-based resins. These high-hydroxyl value tackifier resins may be used alone or in combination of two or more.

[0056] Examples of the rosin resins include Pencel D-135, Superester A-125, and Pine Crystal KE359 (all manufactured by Arakawa Chemical Industries, Ltd.), Pentalyn C (manufactured by Eastman Chemical Company), and SYLVALITE 2115 (manufactured by Kraton). Examples of the terpene phenol resins include YS Polystar G150, YS Polystar T160, YS Polystar T145, YS Polystar TH130, YS Polystar UH115, YS Polystar K125, and YS Polystar U130 (all manufactured by Yasuhara Chemical Co., Ltd.), SYLVARES 1150, and SYLVARES TP7042 (both manufactured by Kraton).

[0057] The hydroxyl value of the high hydroxyl value tackifier resin may be 15 mgKOH / g or more, but from the viewpoint of improving the interaction with the adherend, the lower limit is preferably 20 mgKOH / g, more preferably 40 mgKOH / g. From the viewpoint of compatibility with the acrylic copolymer, the upper limit of the hydroxyl value of the high hydroxyl value tackifier resin is preferably 300 mgKOH / g, more preferably 200 mgKOH / g.

[0058] The tackifier resin may contain a low-hydroxyl value tackifier resin having a hydroxyl value of less than 15 mgKOH / g. Examples of the low-hydroxyl value tackifier resin include terpene resins, aromatic-modified terpene resins, petroleum resins, and styrene resins. These low-hydroxyl value tackifier resins may be used alone or in combination of two or more.

[0059] Examples of the terpene resins include YS Resin PX1250, YS Resin PX1150, and YS Resin PX1000 (all manufactured by Yasuhara Chemical Co., Ltd.), and SYLVARES 3125 (manufactured by Kraton). Examples of the aromatic modified terpene resins include YS Resin TO125 (manufactured by Yasuhara Chemical Co., Ltd.). Examples of the petroleum resins include Arcon P125 and Arcon P140 (both manufactured by Arakawa Chemical Industries, Ltd.), Quintone RX110 (manufactured by Nippon Zeon Co., Ltd.), Petcol 130 (manufactured by Tosoh Corporation), and Petrotack 100V (manufactured by Tosoh Corporation). Examples of the styrene resins include YS Resin SX100 (manufactured by Yasuhara Chemical Co., Ltd.).

[0060] The hydroxyl value of the low-hydroxyl value tackifier resin may be less than 15 mgKOH / g, but from the viewpoint of the adhesion of the acrylic pressure-sensitive adhesive composition of the present invention to an adherend with low polarity, the upper limit is preferably 10 mgKOH / g, more preferably 5 mgKOH / g, and most preferably 0 mgKOH / g.

[0061] The upper limit of the content of the tackifier resin relative to 100 parts by mass of the acrylic copolymer is preferably 40.0 parts by mass. When the content of the tackifier resin is 40.0 parts by mass or less, the acrylic pressure-sensitive adhesive composition of the present invention is more likely to maintain its adhesiveness. A more preferred upper limit of the content of the tackifier resin is 30.0 parts by mass. Furthermore, a preferred lower limit of the content of the tackifier resin is 5.0 parts by mass. When the content of the tackifier resin is 5.0 parts by mass or more, the acrylic pressure-sensitive adhesive composition of the present invention can exhibit higher adhesive strength. A more preferred lower limit of the content of the tackifier resin is 10.0 parts by mass.

[0062] The acrylic pressure-sensitive adhesive composition of the present invention preferably further contains a crosslinking agent. When the acrylic pressure-sensitive adhesive composition of the present invention contains a crosslinking agent, the acrylic copolymer is crosslinked via the crosslinking agent to form a crosslinked structure, which increases the gel fraction of the pressure-sensitive adhesive layer described below. This makes it easier to adjust the gel fraction within the above-mentioned range, and further improves the retention performance at high temperatures. From the viewpoint of storage stability, etc., the crosslinking agent may be added to the acrylic pressure-sensitive adhesive composition of the present invention immediately before forming the pressure-sensitive adhesive layer.

[0063] Examples of the crosslinking agent include epoxy-based crosslinking agents, isocyanate-based crosslinking agents, etc. Among these, isocyanate-based crosslinking agents are preferred from the viewpoint of making it easier to adjust the gel fraction of the pressure-sensitive adhesive layer (described later) within the above-mentioned range.

[0064] The preferred lower limit of the content of the crosslinking agent relative to 100 parts by mass of the acrylic copolymer is 0.01 parts by mass, and the preferred upper limit is 10 parts by mass. By having the content of the crosslinking agent within this range, it becomes easier to adjust the gel fraction of the pressure-sensitive adhesive layer described below within the above range, and the retention performance at high temperatures is further improved. The more preferred lower limit of the content of the crosslinking agent is 0.1 parts by mass, and the more preferred upper limit is 2.0 parts by mass.

[0065] The acrylic pressure-sensitive adhesive composition of the present invention may contain conventionally known fine particles and additives, such as inorganic fine particles, conductive fine particles, antioxidants, foaming agents, organic fillers, and inorganic fillers, as required.

[0066] The method for producing the acrylic pressure-sensitive adhesive composition of the present invention is not particularly limited, and a conventionally known method can be used. For example, first, the (meth)acrylic acid alkyl ester, the olefin polymer having a terminal polymerizable unsaturated double bond, the polar functional group-containing monomer, and, if necessary, other monomers are copolymerized by a conventional method to obtain the acrylic copolymer. Next, the obtained acrylic copolymer and a solvent are added, and, if necessary, a tackifier resin, a crosslinking agent, and other additives are added to obtain the acrylic pressure-sensitive adhesive composition.

[0067] The lower limit of the solid content of the acrylic pressure-sensitive adhesive composition of the present invention is 15% by mass, and the upper limit is 50% by mass. When the solid content of the acrylic pressure-sensitive adhesive composition of the present invention is 15% by mass or more, the acrylic pressure-sensitive adhesive composition of the present invention exhibits excellent coatability. When the solid content of the acrylic pressure-sensitive adhesive composition of the present invention is 50% by mass or less, the acrylic pressure-sensitive adhesive composition of the present invention can exhibit high adhesive strength. The lower limit of the solid content of the acrylic pressure-sensitive adhesive composition of the present invention is preferably 20% by mass, and the upper limit is preferably 45% by mass, more preferably 25% by mass, and more preferably 40% by mass. In this specification, the term "solid content of the acrylic pressure-sensitive adhesive composition" refers to the components in the acrylic pressure-sensitive adhesive composition excluding the solvent.

[0068] The acrylic pressure-sensitive adhesive composition of the present invention is used for a pressure-sensitive adhesive layer or a pressure-sensitive adhesive that constitutes a pressure-sensitive adhesive tape. A pressure-sensitive adhesive formed from the acrylic pressure-sensitive adhesive composition of the present invention and a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed from the acrylic pressure-sensitive adhesive composition of the present invention also constitute aspects of the present invention.

[0069] The pressure-sensitive adhesive of the present invention may be, for example, a liquid pressure-sensitive adhesive, a paste pressure-sensitive adhesive, etc. Among these, the pressure-sensitive adhesive of the present invention is preferably a liquid pressure-sensitive adhesive because it has excellent coating properties.

[0070] The pressure-sensitive adhesive of the present invention can be produced, for example, by heating and drying the solution of the acrylic pressure-sensitive adhesive composition obtained by the above-mentioned method. Alternatively, the pressure-sensitive adhesive of the present invention can be produced by thoroughly mixing the solution of the acrylic pressure-sensitive adhesive composition obtained by the above-mentioned method, and then irradiating it with ultraviolet light or an electron beam.

[0071] The pressure-sensitive adhesive tape of Invention 19 has a pressure-sensitive adhesive layer formed from the above acrylic pressure-sensitive adhesive composition. The pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape of Invention 19 is free from lines and streaks and has a good appearance.

[0072] The present invention also provides a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed using an acrylic pressure-sensitive adhesive composition, the acrylic pressure-sensitive adhesive composition containing an acrylic copolymer, the acrylic copolymer having structural units derived from a (meth)acrylic acid alkyl ester and structural units derived from an olefin polymer having a terminal polymerizable unsaturated double bond, the pressure-sensitive adhesive layer containing a solvent, the solvent including an aliphatic hydrocarbon solvent. The pressure-sensitive adhesive tape of invention 20 is free from lines and streaks and has a good appearance.

[0073] The acrylic pressure-sensitive adhesive composition in the pressure-sensitive adhesive tape of present invention 20 is not particularly limited as long as it contains an acrylic copolymer having a structural unit derived from a (meth)acrylic acid alkyl ester and a structural unit derived from an olefin polymer having a terminal polymerizable unsaturated double bond, and examples thereof include the acrylic pressure-sensitive adhesive composition of the present invention described above.

[0074] Examples of the acrylic copolymer in the pressure-sensitive adhesive tape of invention 20 include the acrylic copolymer in the acrylic pressure-sensitive adhesive composition of the present invention described above. In particular, from the viewpoint of improving adhesive strength, it is preferable that the acrylic copolymer in the pressure-sensitive adhesive tape of invention 20 has a structural unit derived from a polar functional group-containing monomer. Examples of the structural unit derived from the polar functional group-containing monomer in the pressure-sensitive adhesive tape of invention 20 include the structural unit derived from the polar functional group-containing monomer in the acrylic copolymer in the acrylic pressure-sensitive adhesive composition of the present invention described above.

[0075] The pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape of invention 20 contains a solvent. The solvent in the pressure-sensitive adhesive tape of invention 20 contains an aliphatic hydrocarbon solvent. When the solvent in the pressure-sensitive adhesive tape of invention 20 contains an aliphatic hydrocarbon solvent, the pressure-sensitive adhesive layer is free of lines or streaks, resulting in a good appearance. When the pressure-sensitive adhesive layer in the pressure-sensitive adhesive tape of the present invention contains a solvent, the content of the solvent in the pressure-sensitive adhesive layer is not particularly limited as long as a pressure-sensitive adhesive layer is formed, and may be a trace amount. A specific range for the content of the solvent in the pressure-sensitive adhesive layer is preferably 1.0 ppm or more and 1000 ppm or less. Examples of the aliphatic hydrocarbon solvent in the pressure-sensitive adhesive tape of invention 20 include the aliphatic hydrocarbon solvents in the acrylic pressure-sensitive adhesive composition of the present invention described above.

[0076] 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 pressure-sensitive adhesive layer has excellent cohesive strength, and the pressure-sensitive adhesive tape of the present invention has further improved retention performance at high temperatures. When the gel fraction of the pressure-sensitive adhesive layer is 70% by mass or less, the pressure-sensitive adhesive layer does not become too hard, and the pressure-sensitive adhesive tape of the present invention has sufficient initial adhesive strength. A more preferred lower limit of the gel fraction of the pressure-sensitive adhesive layer is 20% by mass, a more preferred upper limit is 60% by mass, an even more preferred lower limit is 25% by mass, and an even more preferred upper limit is 50% by mass. In this specification, the gel fraction is measured by the following method, etc. That is, when the pressure-sensitive adhesive layer is ０ (g) The sample is collected, immersed in 50 mL of tetrahydrofuran (THF), and shaken in a shaker at 23°C and 200 rpm for 24 hours. After shaking, the sample is passed through a metal mesh (opening #200 mesh, mass: W １ (g)), THF and the adhesive layer that has absorbed and swollen with THF are filtered out, and the adhesive that has absorbed and swollen with THF is dried at 110°C for 1 hour, and then the mass W of the adhesive layer including the metal mesh is measured. ２ (g) is measured, and the gel fraction is calculated using the following formula (I): Gel fraction (mass%) = 100 × (W ２ -W １ ) / W ０ (I) (W ０: initial mass of adhesive layer, W １ : mass of metal mesh, W ２ : Mass of adhesive layer after drying (including metal mesh)

[0077] Examples of methods for adjusting the gel fraction of the pressure-sensitive adhesive layer to fall within the above-mentioned range include, but are not limited to, a method of changing the type or content of a crosslinking agent contained in the acrylic pressure-sensitive adhesive composition that forms the pressure-sensitive adhesive layer, and a method of adjusting the illuminance or irradiation time of the electron beam or ultraviolet light used when electron beam irradiation or ultraviolet light irradiation is performed to form the pressure-sensitive adhesive layer.

[0078] The content of the aliphatic hydrocarbon solvent in the pressure-sensitive adhesive layer is preferably 1.0 ppm at the lower limit and 1000 ppm at the upper limit. When the content of the aliphatic hydrocarbon solvent is 1.0 ppm or more, the flexibility of the pressure-sensitive adhesive tape of the present invention is further improved. When the content of the aliphatic hydrocarbon solvent is 1000 ppm or less, the adhesive strength and holding performance of the pressure-sensitive adhesive tape of the present invention are further improved. The content of the aliphatic hydrocarbon solvent is more preferably 10 ppm at the lower limit and 800 ppm at the upper limit, and even more preferably 50 ppm at the lower limit and 500 ppm at the upper limit.

[0079] It is preferred that the pressure-sensitive adhesive layer does not contain an aromatic hydrocarbon solvent, or that the pressure-sensitive adhesive layer contains an aromatic hydrocarbon solvent, but the content of the aromatic hydrocarbon solvent in the pressure-sensitive adhesive layer is 300 ppm or less. If the content of the aromatic hydrocarbon solvent is 300 ppm or less, the content of volatile organic compounds (VOCs) in the pressure-sensitive adhesive layer is low, and the effects of the pressure-sensitive adhesive tape of the present invention on the human body can be further reduced. The upper limit of the content of the aromatic hydrocarbon solvent in the pressure-sensitive adhesive layer is more preferably 200 ppm, even more preferably 100 ppm, and it is most preferred that the pressure-sensitive adhesive layer does not contain an aromatic hydrocarbon solvent.

[0080] The content of the aliphatic hydrocarbon solvent or aromatic hydrocarbon solvent in the PSA layer can be measured by gas chromatography mass spectrometry (GC / MS). A measurement sample obtained by diluting the sol component of the PSA layer is measured using a gas chromatograph mass spectrometer, and the content can be calculated from the resulting spectrum. Specifically, after identifying the aliphatic hydrocarbon solvent or aromatic hydrocarbon solvent contained in the PSA layer, a measurement sample obtained by diluting the sol component of the PSA layer with chloroform is measured by gas chromatography mass spectrometry (GC-MS) using a pure substance of the identified aliphatic hydrocarbon solvent or aromatic hydrocarbon solvent as a known standard substance. A calibration curve is then created from the measured peak areas, and the content of the aliphatic hydrocarbon solvent or aromatic hydrocarbon solvent is calculated using the created calibration curve. The "sol component" refers to the components of the PSA layer excluding the gel component. The sol component of the pressure-sensitive adhesive layer can be obtained, for example, by immersing the pressure-sensitive adhesive layer in tetrahydrofuran (THF) at 23°C for 24 hours, filtering the insoluble matter through a 200-mesh wire mesh, and removing the gel component. 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

[0081] The preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 5 μm, and the preferred upper limit is 500 μm. When the thickness of the pressure-sensitive adhesive layer is 5 μm or more, the pressure-sensitive adhesive tape of the present invention is likely to have good adhesion to the adherend. When the thickness of the pressure-sensitive adhesive layer is 500 μm or less, high productivity is likely to be achieved during the production of the pressure-sensitive adhesive tape. A more preferred lower limit of the thickness of the pressure-sensitive adhesive layer is 10 μm, a more preferred upper limit is 300 μm, an even more preferred lower limit is 20 μm, and an even more preferred upper limit is 200 μm. In this specification, the thickness can be measured using a dial thickness meter (such as the "ABS Digimatic Indicator" manufactured by Mitutoyo Corporation).

[0082] The pressure-sensitive adhesive tape of the present invention may be a non-support type that does not have a substrate, or a supported type that has a substrate. In particular, from the viewpoint of facilitating reapplication of the pressure-sensitive adhesive tape of the present invention, it is preferable that the pressure-sensitive adhesive tape of the present invention has a substrate.

[0083] When the pressure-sensitive adhesive tape of the present invention has a substrate, it may be a single-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on one side of the substrate, or a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of the substrate.

[0084] The preferred lower limit of the thickness of the substrate is 1.0 μm, and the preferred upper limit is 1000 μm. When the thickness of the substrate is 1.0 μm or more, the adhesive tape can have good processability. When the thickness of the substrate is 1000 μm or less, the flexibility of the adhesive tape can be improved. The more preferred lower limit of the thickness of the substrate is 5.0 μm, and the more preferred upper limit is 500 μm, and the even more preferred lower limit is 10 μm, and the even more preferred upper limit is 300 μm.

[0085] The pressure-sensitive adhesive tape of the present invention may further have other layers as long as the effects of the present invention are not impaired.

[0086] The pressure-sensitive adhesive tape of the present invention can be produced, for example, by applying a solution of the acrylic pressure-sensitive adhesive composition obtained by the above-mentioned method to the release-treated surface of a release film that has been subjected to a release treatment, followed by drying to form a pressure-sensitive adhesive layer. Alternatively, a pressure-sensitive adhesive tape having a substrate can be produced by laminating the pressure-sensitive adhesive tape produced by the above-mentioned method as a pressure-sensitive adhesive layer to a substrate. The pressure-sensitive adhesive tape of the present invention can also be produced by thoroughly mixing the solution of the acrylic pressure-sensitive adhesive composition obtained by the above-mentioned method, applying it to the release-treated surface of a release film that has been subjected to a release treatment, heating, irradiating with ultraviolet rays or electron beams, or the like, and then drying to form a pressure-sensitive adhesive layer formed from the acrylic pressure-sensitive adhesive composition. The above-mentioned method for producing a pressure-sensitive adhesive tape, which includes the step of applying the acrylic pressure-sensitive adhesive composition, also constitutes one aspect of the present invention.

[0087] The preferred lower limit of the thickness of the entire pressure-sensitive adhesive tape of the present invention is 10 μm, and the preferred upper limit is 2000 μm. When the thickness of the entire pressure-sensitive adhesive tape of the present invention is 10 μm or more, the application of the pressure-sensitive adhesive tape of the present invention becomes easier. The more preferred lower limit of the thickness of the entire pressure-sensitive adhesive tape of the present invention is 20 μm, and the more preferred upper limit is 1000 μm, and the even more preferred lower limit is 30 μm, and the even more preferred upper limit is 800 μm.

[0088] The uses of the pressure-sensitive adhesive of the present invention and the pressure-sensitive adhesive tape of the present invention are not particularly limited, but can be used, for example, to fix parts in electronic devices, vehicles, houses, building materials, etc.

[0089]

[0013] The present invention also includes a method for producing an acrylic copolymer, which comprises a step of polymerizing a monomer mixture containing an alkyl (meth)acrylate ester and an olefin polymer having a terminal polymerizable unsaturated double bond in a solvent in the presence of a polymerization initiator (hereinafter sometimes simply referred to as "step (i)"), wherein the solvent contains a hydrocarbon solvent. The solution containing the acrylic copolymer obtained by the method for producing an acrylic copolymer of the present invention has excellent coatability and adhesive strength, and can be used as is as an acrylic pressure-sensitive adhesive composition.

[0090] In the method for producing an acrylic copolymer of the present invention, the (meth)acrylic acid alkyl ester and the olefin polymer having a terminal polymerizable unsaturated double bond can be the same as those that can be used in the above-mentioned acrylic pressure-sensitive adhesive composition of the present invention.

[0091] In the method for producing an acrylic copolymer of the present invention, the solvent contains a hydrocarbon solvent, which allows the olefin polymer having a terminal polymerizable unsaturated double bond to be uniformly introduced into the acrylic copolymer.

[0092] The hydrocarbon solvent preferably contains an aliphatic hydrocarbon solvent, which allows the amount of volatile organic compounds (VOCs) used in the production of the acrylic copolymer to be reduced, thereby reducing the impact on the human body.

[0093] In the method for producing an acrylic copolymer of the present invention, the aliphatic hydrocarbon solvent preferably contains an aliphatic hydrocarbon compound having from 6 to 9 carbon atoms. When the aliphatic hydrocarbon solvent contains an aliphatic hydrocarbon compound having from 6 to 9 carbon atoms, the olefin polymer having a terminal polymerizable unsaturated double bond can be more uniformly introduced into the acrylic copolymer.

[0094] In the method for producing an acrylic copolymer of the present invention, examples of the aliphatic hydrocarbon compound having 6 to 9 carbon atoms include normal hexane, cyclohexane, methylcyclohexane, normal heptane, cycloheptane, methylcycloheptane, normal octane, cyclooctane, methylcyclooctane, normal nonane, cyclononane, etc. Among these, it is preferable to contain at least one selected from the group consisting of normal hexane, cyclohexane, and methylcyclohexane.

[0095] In the method for producing an acrylic copolymer of the present invention, the content of the aromatic hydrocarbon solvent in the solvent is preferably 300 ppm or less. By keeping the content of the aromatic hydrocarbon solvent at 300 ppm or less, the amount of volatile organic compounds (VOCs) used in the production of the acrylic copolymer can be reduced, thereby reducing the impact on the human body. The upper limit of the content of the aromatic hydrocarbon solvent is more preferably 200 ppm, even more preferably 100 ppm, and most preferably the solvent does not contain the aromatic hydrocarbon solvent.

[0096] In the method for producing an acrylic copolymer of the present invention, the solvent may contain an ester solvent. When the solvent contains an ester solvent, the coatability of the solution containing the acrylic copolymer obtained by the method for producing an acrylic copolymer of the present invention is further improved, and the solution can be more suitably used as an acrylic pressure-sensitive adhesive composition.

[0097] In the method for producing an acrylic copolymer of the present invention, the ester solvent preferably contains an ester compound represented by the formula (1). When the ester solvent contains the ester compound represented by the formula (1), the coatability of the solution containing the acrylic copolymer obtained by the method for producing an acrylic copolymer of the present invention is further improved, and the solution can be more suitably used as an acrylic pressure-sensitive adhesive composition.

[0098] In the method for producing an acrylic copolymer of the present invention, the content of the hydrocarbon solvent in the total content of the hydrocarbon solvent and the ester solvent is preferably 5.0% by mass or more but less than 100% by mass. When the content of the hydrocarbon solvent is within the above range, the coatability of the solution containing the acrylic copolymer obtained by the method for producing an acrylic copolymer of the present invention is further improved, and the solution can be more suitably used as an acrylic pressure-sensitive adhesive composition. The lower limit of the content of the hydrocarbon solvent is more preferably 10% by mass, more preferably 90% by mass, even more preferably 20% by mass, and even more preferably 80% by mass.

[0099] In the step (i), examples of the polymerization initiator include organic peroxides and azo compounds. Examples of the organic peroxides include 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the azo compounds include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more.

[0100] The preferred lower limit of the amount of the polymerization initiator to be blended relative to 100 parts by mass of the monomer mixture is 0.01 parts by mass, and the preferred upper limit is 3.0 parts by mass. By blending the amount of the polymerization initiator within the above range, it becomes possible to more appropriately adjust the weight average molecular weight of the acrylic copolymer. The more preferred lower limit of the amount of the polymerization initiator to be blended is 0.03 parts by mass, and the more preferred upper limit is 2.0 parts by mass, and the even more preferred lower limit is 0.05 parts by mass, and the even more preferred upper limit is 1.0 parts by mass.

[0101] In the step (i), the temperature at which the monomer mixture is polymerized in a solvent in the presence of a polymerization initiator (hereinafter sometimes simply referred to as the "polymerization reaction temperature") is preferably 50°C in lower limit and 100°C in upper limit. When the polymerization reaction temperature is within the above range, the weight-average molecular weight of the acrylic copolymer can be more appropriately adjusted. The polymerization reaction temperature is more preferably 55°C in lower limit and 95°C in upper limit, still more preferably 60°C in lower limit and still more preferably 90°C in upper limit.

[0102] According to the present invention, it is possible to provide an acrylic pressure-sensitive adhesive composition that has excellent coatability, can be applied without lines or streaks, and can exert high adhesive strength. Furthermore, according to the present invention, it is possible to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive tape formed from the acrylic pressure-sensitive adhesive composition. Another object of the present invention is to provide a pressure-sensitive adhesive tape that is free from lines or streaks and has a good appearance. In addition, according to the present invention, it is possible to provide a method for producing a pressure-sensitive adhesive tape formed from the acrylic pressure-sensitive adhesive composition. Furthermore, according to the present invention, it is possible to provide a method for producing an acrylic copolymer that can be used for an acrylic pressure-sensitive adhesive composition that has excellent coatability, can be applied without lines or streaks, and can exert high adhesive strength.

[0103] FIG. 1 is a diagram schematically showing a method for evaluating retention performance at high temperatures.

[0104] The following examples will further illustrate aspects of the present invention, but the present invention is not limited to these examples.

[0105] (Synthesis of Acrylic Copolymer A) Cyclohexane and ethyl acetate were charged as a solvent into a reactor equipped with a thermometer, a stirrer, and a cooling tube, and the monomer mixture shown in Table 1 was added (monomer mixture concentration: 35% by mass). Nitrogen gas was then blown in to expel dissolved oxygen, and the reactor was heated to 60°C under a nitrogen gas flow. Next, 0.1 parts by mass of azobisisobutyronitrile was added as a polymerization initiator to 100 parts by mass of the monomer mixture into the reactor, and polymerization was initiated at a constant temperature of 60°C. Thereafter, 4 hours after the start of polymerization, 0.5 parts by mass of t-hexyl peroxypivalate was added to 100 parts by mass of the monomer mixture to continue the polymerization reaction. The polymerization reaction was then carried out for a total of 6 hours from the start of polymerization, yielding a solution containing acrylic copolymer A. The ethylene-butylene macromonomer in Table 1 was HPVM-L1253 (manufactured by Kraton Polymer Japan, weight average molecular weight: 7000). Furthermore, the weight average molecular weight (Mw) of the obtained acrylic copolymer A was measured using gel permeation chromatography (GPC) (Waters Corporation, "2690 Separations Module") under the following conditions, and the polydispersity of the acrylic copolymer was calculated. The results are shown in Table 1. <GPC measurement conditions> Solvent: tetrahydrofuran Sample flow rate: 1 mL / min Detector: differential refractometer RI Column: GPC KF-806L (Showa Denko KK) Column temperature (measurement temperature): 40°C Injection volume: 20 μL

[0106] (Synthesis of Acrylic Copolymers B to R) Except for using the monomer mixture shown in Table 1, synthesis was performed in the same manner as for Acrylic Copolymer A, and the weight average molecular weight and polydispersity index were measured. The results are shown in Table 1. The solvent, type and amount of polymerization initiator used in the polymerization reaction, and polymerization reaction temperature were as shown in Tables 2 to 4 for each Example and Comparative Example, and the acrylic copolymers were synthesized. Note that azobisisobutyronitrile and t-hexyl peroxypivalate were added in the same order as for Acrylic Copolymer A. The weight average molecular weights of the acrylic copolymers O to P were adjusted by adjusting the concentration of the monomer mixture in the polymerization reaction. In the synthesis of Acrylic Copolymer O (Example 16), polymerization was performed at a monomer mixture concentration of 30% by mass, and in the synthesis of Acrylic Copolymer P (Example 17), polymerization was performed at a monomer mixture concentration of 40% by mass, and the weight average molecular weight of the acrylic copolymers was adjusted.

[0107]

[0108]

[0109]

[0110]

[0111] (Example 1) (Preparation of acrylic pressure-sensitive adhesive composition) 20.0 parts by mass of YS Polystar G150 (manufactured by Yasuhara Chemical Co., Ltd.) as a tackifier resin and 1.0 part by mass of Desmodur L-75 (manufactured by Covestro) as a crosslinking agent were added to 100 parts by mass of the solid content of a solution containing acrylic copolymer A, and the solution containing acrylic copolymer A was diluted so that the amounts of cyclohexane and ethyl acetate were 150 parts by mass and 150 parts by mass, respectively, per 100 parts by mass of acrylic copolymer A, to obtain an acrylic pressure-sensitive adhesive composition.

[0112] (Preparation of adhesive tape) The obtained solution of the acrylic adhesive composition was thoroughly stirred, and then coated with a doctor knife onto the release-treated surface of a 50 μm-thick release polyethylene terephthalate (PET) film, one side of which had been release-treated, and the coating solution was dried by heating at 110° C. for 10 minutes, thereby forming a 50 μm-thick adhesive layer made of the acrylic adhesive composition. Furthermore, a 25 μm-thick release PET film, one side of which had been release-treated, was prepared, and the formed adhesive layer and the release-treated surface were overlapped, and then aged in an environment of 40° C. for 48 hours, thereby obtaining an adhesive tape with a release PET film.

[0113] (Measurement of gel fraction of adhesive layer) The adhesive layer of the obtained adhesive tape was ０ (g) The sample was collected, immersed in 50 mL of tetrahydrofuran (THF), and shaken in a shaker at 23°C and 200 rpm for 24 hours. After shaking, the sample was passed through a metal mesh (opening #200 mesh, mass: W １ (g)) was used to filter out the THF and the adhesive that had absorbed the THF and swollen, and the adhesive that had absorbed the THF and swollen was dried at 110°C for 1 hour, and then the mass W of the adhesive that included the metal mesh was measured. ２ The gel fraction (g) was measured and calculated using the following formula (I). The results are shown in Table 5. Gel fraction (mass%) = 100 × (W ２ -W １ ) / W ０ (I) (W ０ : initial mass of adhesive layer, W １ : mass of metal mesh, W ２ : Mass of adhesive layer after drying (including metal mesh)

[0114] (Measurement of the content of aliphatic hydrocarbon solvent in the pressure-sensitive adhesive layer) In the above-mentioned "(Measurement of the gel fraction of the pressure-sensitive adhesive layer)", the gel component of the pressure-sensitive adhesive that had absorbed THF and swollen 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) measurement, and the content (ppm) of the aliphatic hydrocarbon solvent in the pressure-sensitive adhesive layer was measured from the peak area of ​​the obtained spectrum. The results are shown in Table 5. <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

[0115] (Measurement of the content of aromatic hydrocarbon solvent in the pressure-sensitive adhesive layer) The content (ppm) of aromatic hydrocarbon solvent in the pressure-sensitive adhesive layer was measured by the same method as in "(Measurement of the content of aliphatic hydrocarbon solvent in the pressure-sensitive adhesive layer)" described above. The results are shown in Table 5.

[0116] (Examples 2 to 41, Comparative Examples 1 to 5) In the above-mentioned "(Preparation of acrylic pressure-sensitive adhesive composition)", acrylic pressure-sensitive adhesive compositions and pressure-sensitive adhesive tapes were obtained and measurements were carried out in the same manner as in Example 1, except that the compositions were changed to those shown in Tables 5 to 8. The results are shown in Tables 5 to 8.

[0117] Examples 42 to 44 Acrylic pressure-sensitive adhesive compositions were prepared in the same manner as in Example 1, except that the compositions were as shown in Table 7, and by the same method as in "(Preparation of Acrylic Pressure-sensitive Adhesive Composition)" above. The resulting solution of the acrylic pressure-sensitive adhesive composition was thoroughly stirred and then coated with a doctor knife onto the release-treated surface of a 50 μm-thick release polyethylene terephthalate (PET) film, one side of which had been release-treated. The coating solution was then dried by heating at 110°C for 10 minutes, thereby forming a 50 μm-thick pressure-sensitive adhesive layer made from the acrylic pressure-sensitive adhesive composition. The pressure-sensitive adhesive layer formed on one side of the substrate shown in Table 7 was then bonded. Another pressure-sensitive adhesive layer of the same composition and thickness was then formed, and this pressure-sensitive adhesive layer was bonded to the other side of the substrate to form an integrated laminate. This was then aged for 48 hours in an environment at 40°C, thereby obtaining a pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of the substrate. Various measurements were performed in the same manner as in Example 1. The results are shown in Table 7.

[0118] <Evaluation> The pressure-sensitive adhesive tapes obtained in the Examples and Comparative Examples were evaluated as follows. The results are shown in Tables 5 to 8.

[0119] (Coatability and Appearance) In the above-mentioned "(Preparation of Pressure-Sensitive Adhesive Tape)", the pressure-sensitive adhesive layer formed was visually observed, and the coatability and appearance were evaluated according to the following criteria. ○: The pressure-sensitive adhesive layer formed had no lines or streaks. △: The pressure-sensitive adhesive layer formed had some lines or streaks. ×: The pressure-sensitive adhesive layer formed had many lines or streaks.

[0120] (Adhesive strength) The release PET film on one side of the obtained adhesive tape (the adhesive layer side not being measured) was peeled off, and the exposed adhesive layer was attached to a 23 μm thick polyethylene terephthalate (PET) film so as not to allow air to enter, and then cut into a width of 25 mm x length of 100 mm to prepare a test piece. The obtained test piece was attached to a SUS plate (SUS304 plate washed with ethanol and then wiped dry) by moving a 2 kg rubber roller back and forth at a speed of 300 mm / min to prepare a measurement sample. The obtained measurement sample was subjected to a 180 ° peel test in accordance with JIS Z0237 using a tensile tester (manufactured by A & D Co., Ltd., "RTI-1310") under conditions of 23 ° C., 50% RH, and a peel speed of 300 mm / min, and the adhesive tape was peeled from the SUS plate to measure the 180 ° peel force (N / 25 mm). The adhesive strength was evaluated using the obtained 180° peel strength according to the following criteria: ⊚: The 180° peel strength was 35 N / 25 mm or more. ◯: The 180° peel strength was 30 N / 25 mm or more and less than 35 N / 25 mm. Δ: The 180° peel strength was 25 N / 25 mm or more and less than 30 N / 25 mm. ×: The 180° peel strength was less than 25 N / 25 mm.

[0121] (High-Temperature Retention Performance) 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 polyethylene terephthalate (PET) film without allowing air to enter. The tape was then cut into 25 mm-wide strips and bonded to a SUS plate (SUS304 plate washed with ethanol and then wiped dry) by rolling a 2 kg rubber roller back and forth at a speed of 300 mm / min. Next, an incision was made in the adhesive tape so that the adhesive area was 25 mm x 25 mm, and the tape was left to stand at 23°C for 20 minutes to prepare a test sample. The prepared test sample was placed in an 80°C oven and heated for a further 20 minutes. After that, a 500 g weight was hung from the tape and a load was applied in the shear direction under conditions of 80°C and 50% RH, as shown in Figure 1. The amount of displacement (movement) (mm) from the incision position one hour after the load was applied was measured with a scale magnifier. Using the obtained displacement (mm), the retention performance at high temperatures was evaluated according to the following criteria. ○: The amount of displacement was less than 0.5 mm. △: The amount of displacement was 0.5 mm or more and less than 25 mm. ×: The amount of displacement was 25 mm or more, and the adhesive tape fell off. Even if the evaluation is "×", the adhesive tape of the present invention can be used without any problems depending on the application.

[0122] (Degree of Odor) The degree of odor was evaluated in accordance with VDA 270. Specifically, a 5 cm wide x 10 cm long (size: 50 cm) sample was placed in a glass bottle with an internal volume of 1.0 L. 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 immediately after removal was rated using the following 6-point scale: 1: No odor was perceptible. 2: The odor was slightly perceptible, but not unpleasant. 3: The odor was clearly perceptible, but not very unpleasant. 4: The odor was clearly perceptible and unpleasant. 5: The odor was clearly perceptible and very unpleasant. 6: The odor was clearly perceptible and unpleasant to the point of being unbearable. Three subjects each made the rating, and the average value was calculated. The calculated average value was evaluated as "Good" if it was less than 3.0, "Average" if it was less than 4.0 and 3.0 or more, and "Poor" if it was 4.0 or more. Note that even if the rating is "Poor," the adhesive tape of the present invention can still be used without any problems depending on the application.

[0123]

[0124]

[0125]

[0126]

[0127] According to the present invention, it is possible to provide an acrylic pressure-sensitive adhesive composition that has excellent coatability, can be applied without lines or streaks, and can exert high adhesive strength. Furthermore, according to the present invention, it is possible to provide a pressure-sensitive adhesive and a pressure-sensitive adhesive tape formed from the acrylic pressure-sensitive adhesive composition. Another object of the present invention is to provide a pressure-sensitive adhesive tape that is free from lines or streaks and has a good appearance. In addition, according to the present invention, it is possible to provide a method for producing a pressure-sensitive adhesive tape formed from the acrylic pressure-sensitive adhesive composition. Furthermore, according to the present invention, it is possible to provide a method for producing an acrylic copolymer that can be used for an acrylic pressure-sensitive adhesive composition that has excellent coatability, can be applied without lines or streaks, and can exert high adhesive strength.

[0128] 1. Polyethylene terephthalate (PET) film 2. Adhesive tape 3. SUS304 plate 4. Weight (500 g)

Claims

1. An acrylic adhesive composition containing an acrylic copolymer and a solvent, The acrylic copolymer comprises structural units derived from alkyl (meth)acrylate esters and structural units derived from olefin polymers having polymerizable unsaturated double bonds at their terminal ends. The aforementioned solvent is a hydrocarbon solvent, and has an SP value of 7.2 (J / cm²). ３ ) １／２ More than 8.6 (J / cm ３ ) １／２ It comprises at least one solvent selected from the group consisting of the following solvents: The solid content of the acrylic adhesive composition is 15% by mass or more and 50% by mass or less. An acrylic adhesive composition characterized by the following features.

2. The solvent includes a hydrocarbon solvent, The acrylic adhesive composition according to claim 1, wherein the hydrocarbon solvent comprises an aliphatic hydrocarbon solvent.

3. The acrylic adhesive composition according to claim 2, wherein the aliphatic hydrocarbon solvent comprises an aliphatic hydrocarbon compound having 6 to 9 carbon atoms.

4. The acrylic adhesive composition according to claim 3, wherein the aliphatic hydrocarbon compound having 6 to 9 carbon atoms comprises at least one selected from the group consisting of n-hexane, cyclohexane, and methylcyclohexane.

5. The aforementioned solvent is further an ester-based solvent, and has an SP value of 8.6 (J / cm²). ３ ) １／２ Larger than 9.0 (J / cm) ３ ) １／２ The acrylic adhesive composition according to claim 1, 2, 3, or 4, comprising at least one solvent selected from the group consisting of the following solvents.

6. The aforementioned solvent includes an ester-based solvent. The ester solvent includes an ester compound represented by the following formula (1): The proportion of the hydrocarbon solvent in the total content of the hydrocarbon solvent and the ester solvent is 5.0% by mass or more and less than 100% by mass. The acrylic adhesive composition according to claim 5. 【Chemistry 1】 In formula (1), R １ , R ２ each independently represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms.

7. The hydrocarbon solvent does not contain an aromatic hydrocarbon solvent, or The hydrocarbon solvent includes an aromatic hydrocarbon solvent, and the content of the aromatic hydrocarbon solvent in the solvent is 1000 ppm or less. The acrylic adhesive composition according to claim 1, 2, 3, or 4.

8. The acrylic adhesive composition according to claim 1, 2, 3, or 4, wherein the constituent unit derived from the alkyl (meth)acrylate ester comprises a constituent unit derived from an alkyl (meth)acrylate ester having 1 to 4 carbon atoms in the alkyl group derived from an alcohol.

9. The acrylic adhesive composition according to claim 1, 2, 3, or 4, wherein the content of constituent units derived from the alkyl (meth)acrylate in the acrylic copolymer is 50% by mass or more and 99% by mass or less.

10. The acrylic adhesive composition according to claim 1, 2, 3, or 4, wherein the content of constituent units derived from an olefin polymer having a polymerizable unsaturated double bond at its terminus in the acrylic copolymer is 5.0% by mass or more.

11. The acrylic adhesive composition according to claim 1, 2, 3, or 4, wherein the acrylic copolymer has constituent units derived from a polar functional group-containing monomer.

12. The acrylic adhesive composition according to claim 11, wherein the constituent unit derived from the polar functional group-containing monomer comprises at least one selected from the group consisting of constituent units derived from carboxyl group-containing monomers and constituent units derived from hydroxyl group-containing monomers.

13. The acrylic adhesive composition according to claim 11, wherein the total content of constituent units derived from polar functional group-containing monomers in the acrylic copolymer is 0.1% by mass or more and 20% by mass or less.

14. An acrylic adhesive composition according to claim 1, 2, 3, or 4, comprising a tackifying resin.

15. The acrylic adhesive composition according to claim 14, wherein the tackifying resin comprises a high hydroxyl value tackifying resin having a hydroxyl value of 15 mgKOH / g or more.

16. The acrylic adhesive composition according to claim 14, wherein the content of the tackifying resin is 40 parts by mass or less per 100 parts by mass of the acrylic copolymer.

17. An acrylic adhesive composition according to claim 1, 2, 3, or 4, containing a crosslinking agent.

18. An adhesive formed from the acrylic adhesive composition according to claim 1, 2, 3, or 4.

19. An adhesive tape having an adhesive layer formed from the acrylic adhesive composition described in claim 1.

20. An adhesive tape having an adhesive layer formed using an acrylic adhesive composition, The acrylic adhesive composition contains an acrylic copolymer, The acrylic copolymer comprises structural units derived from alkyl (meth)acrylate esters and structural units derived from olefin polymers having polymerizable unsaturated double bonds at their terminal ends. The aforementioned adhesive layer contains a solvent, The aforementioned solvent includes an aliphatic hydrocarbon solvent. An adhesive tape characterized by the following features.

21. The adhesive tape according to claim 20, wherein the acrylic copolymer has constituent units derived from a polar functional group-containing monomer.

22. The adhesive layer does not contain aromatic hydrocarbon solvents, or The adhesive layer contains an aromatic hydrocarbon solvent, and the content of the aromatic hydrocarbon solvent in the adhesive layer is 300 ppm or less. The adhesive tape according to claim 19, 20, or 21.

23. The adhesive tape according to claim 19, 20, or 21, wherein the adhesive layer has a gel fraction of 10% by mass or more and 70% by mass or less.

24. The adhesive tape according to claim 19, 20, or 21, having a base material.

25. The adhesive tape according to claim 19, 20, or 21, used for fixing electronic equipment components or in-vehicle components.

26. A method for producing an adhesive tape, comprising the step of applying an acrylic adhesive composition according to claim 1, 2, 3, or 4.

27. The process includes step (i) polymerizing a monomer mixture containing an alkyl (meth)acrylate ester and an olefin polymer having a polymerizable unsaturated double bond at its terminus in a solvent in the presence of a polymerization initiator. The solvent includes a hydrocarbon solvent. A method for producing acrylic copolymers characterized by the above.

28. The method for producing an acrylic copolymer according to claim 27, wherein the hydrocarbon solvent includes an aliphatic hydrocarbon solvent.

29. The method for producing an acrylic copolymer according to claim 28, wherein the aliphatic hydrocarbon solvent comprises an aliphatic hydrocarbon compound having 6 to 9 carbon atoms.

30. The method for producing an acrylic copolymer according to claim 29, wherein the aliphatic hydrocarbon compound having 6 to 9 carbon atoms comprises at least one selected from the group consisting of n-hexane, cyclohexane, and methylcyclohexane.

31. The aforementioned solvent further includes an ester-based solvent. The ester solvent includes an ester compound represented by the following formula (1): The proportion of the hydrocarbon solvent in the total amount of the hydrocarbon solvent and the ester solvent is 5.0% by mass or more and less than 100% by mass. A method for producing an acrylic copolymer according to claim 27, 28, 29, or 30. 【Chemistry 2】 In formula (1), R １ , R ２ Each of these independently represents an aliphatic hydrocarbon group having between 1 and 5 carbon atoms.

32. The method for producing an acrylic copolymer according to claim 27, 28, 29, or 30, wherein the polymerization initiator comprises at least one selected from the group consisting of organic peroxides and azo compounds.

33. A method for producing an acrylic copolymer according to claim 27, 28, 29, or 30, wherein the amount of polymerization initiator added to 100 parts by mass of the monomer mixture is 0.01 parts by mass or more and 3.0 parts by mass or less.

34. A method for producing an acrylic copolymer according to claim 27, 28, 29, or 30, wherein the temperature at which the monomer mixture is polymerized in a solvent in the presence of a polymerization initiator in step (i) is 50°C or more and 100°C or less.

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