Adhesive composition, adhesive, and adhesive sheet

Abstract

This composition contains a (meth)acrylic copolymer A which has a number average molecular weight greater than 10000, measured by gel permeation chromatography, and a polymer X which has a number average molecular weight of 1000-10000, measured by gel permeation chromatography, wherein at least one of the (meth)acrylic copolymer A and the polymer X includes a constituent unit derived from a monomer M that generates an active species by photoexcitation and forms a crosslinked structure.

Description

[Technical Field]

[0001] The present invention relates to adhesive compositions, adhesives, and adhesive sheets. This application claims priority based on Japanese Patent Application No. 2021-126603, filed in Japan on August 2, 2021, and the contents of that application are incorporated herein by reference. [Background technology]

[0002] A known adhesive composition that can be coated onto a substrate and hardens upon irradiation with ultraviolet light includes a copolymer obtained by polymerizing an alkyl acrylate having an alkyl group having 1 to 4 carbon atoms, an unsaturated carboxylic acid such as acrylic acid, and a benzophenone derivative having a (meth)acryloyloxy group (Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2006-299017 [Overview of the project] [Problems that the invention aims to solve]

[0004] The composition described in Patent Document 1 has a high melt viscosity, which requires high temperatures during coating, and it is difficult to obtain sufficient holding power under high temperature and high humidity conditions. Furthermore, it is difficult to achieve both adhesive strength and holding power while ensuring minimal residue (resistance to substrate contamination) when the coating is re-peeled off.

[0005] The present invention aims to provide an adhesive composition, adhesive, and adhesive sheet that can achieve high retention power and excellent substrate stain resistance with minimal adhesive residue under high temperature and high humidity conditions. [Means for solving the problem]

[0006] The present invention has the following aspects. [1] (meth)acrylic copolymer A, whose number average molecular weight measured by gel permeation chromatography is greater than 10,000, A composition comprising polymer X having a number-average molecular weight of 1,000 to 10,000 as measured by gel permeation chromatography, An adhesive composition in which at least one of the (meth)acrylic copolymer A and the polymer X contains constituent units derived from monomer M that generate active species upon photoexcitation and form a crosslinked structure. [2] (meth)acrylic copolymer A, whose number average molecular weight measured by gel permeation chromatography is greater than 10,000, A composition comprising polymer X having a number-average molecular weight of 10,000 or less as measured by gel permeation chromatography, At least one of the (meth)acrylic copolymer A and the polymer X contains constituent units derived from monomer M that generate active species upon photoexcitation and form a crosslinked structure. An adhesive composition having a melt viscosity of 88 Pa·s or less, as measured at 130°C. [3] The adhesive composition according to [1] or [2], wherein the polymer X contains constituent units derived from the monomer M, and the content of the polymer X is 2.1% by mass or more with respect to 100% by mass of the total mass of the (meth)acrylic copolymer A and the polymer X. [4] The adhesive composition according to any one of [1] to [3], wherein the (meth)acrylic copolymer A comprises a constituent unit derived from the monomer M. [5] The adhesive composition according to any one of [1] to [4], wherein of the (meth)acrylic copolymer A and the polymer X, only the (meth)acrylic copolymer A contains constituent units derived from the monomer M. [6] The adhesive composition according to any one of [1] to [4], wherein the polymer X contains constituent units derived from the monomer M and does not have a radical polymerizable group at its terminal end. [7] The adhesive composition according to any one of [1] to [6], wherein the number average molecular weight of the (meth)acrylic copolymer A is 11,000 to 150,000. [8] The adhesive composition according to any one of [1] to [7], wherein the number average molecular weight of the (meth)acrylic copolymer A is 12,000 to 100,000. [9] The adhesive composition according to any one of [1] to [8], wherein the number average molecular weight of the polymer X is 1,000 to 9,000.

[10] The adhesive composition according to any one of [1] to [9], wherein the content of the (meth)acrylic copolymer A is 2% by mass or more with respect to 100% by mass of the total mass of the (meth)acrylic copolymer A and the polymer X.

[11] The adhesive composition according to any one of [1] to

[10] , wherein the glass transition temperature of the (meth)acrylic copolymer A is 0°C or lower.

[12] The adhesive composition according to any one of [1] to

[11] , wherein the active species is a radical.

[13] The adhesive composition according to any one of [1] to

[12] , wherein the monomer M has at least one structure selected from the group consisting of a benzophenone skeleton, a thioxanthone skeleton, and an anthraquinone skeleton.

[14] The adhesive composition according to any one of [1] to

[13] , wherein the monomer M is a monomer represented by the following formula (1).

[0007] [ka]

[0008] (In the formula, R A and R B Each of the following independently represents an alkyl group, alkoxy group, hydroxyl group, carboxyl group, or halogen atom; n represents an integer from 0 to 5; m represents an integer from 0 to 4; and X represents a (meth)acryloyloxy group or a (meth)acryloyloxyalkyleneoxy group.

[15] The adhesive composition according to any one of [1] to

[14] , wherein the content of constituent units derived from monomer M is 0.01% by mass or more and 50% by mass or less with respect to 100% by mass of the total mass of (meth)acrylic copolymer A and polymer X.

[16] The adhesive composition according to any one of [1] to

[15] , wherein the mass ratio of the polymer X to the (meth)acrylic copolymer A is 0.1:99.9 to 40:60.

[17] The number average molecular weight of the (meth)acrylic copolymer A is preferably greater than 10,000 and not more than 200,000, more preferably 11,000 to 150,000, still more preferably 12,000 to 100,000, further more preferably 13,000 to 50,000, particularly preferably 15,000 to 40,000, and most preferably 15,000 to 20,000. The adhesive composition according to any one of [1] to

[16] .

[18] The number average molecular weight of the polymer X is preferably 1,000 to 10,000, more preferably 1,000 to 9,000, still more preferably 1,100 to 8,000, particularly preferably 1,200 to 7,000, and most preferably 1,200 to 4,000. The adhesive composition according to any one of [1] to

[17] .

[19] The content of the structural unit derived from the monomer M is preferably 0.01% by mass or more and 50% by mass or less, more preferably 0.1% by mass or more and 40% by mass or less, still more preferably 0.2% by mass or more and 10% by mass or less, particularly preferably 0.2% by mass or more and 5% by mass or less, and most preferably 0.25% by mass or more and 3% by mass or less, based on 100% by mass of the total mass of the (meth)acrylic copolymer A and the polymer X. The adhesive composition according to any one of [1] to

[18] .

[20] The (meth)acrylic copolymer A contains a structural unit derived from the monomer M, The content of the structural unit derived from the monomer M is preferably 0.01% by mass or more and 30% by mass or less, more preferably 0.05% by mass or more and 10% by mass or less, still more preferably 0.08% by mass or more and 5% by mass or less, particularly preferably 0.1% by mass or more and 3% by mass or less, and most preferably 0.1% by mass or more and 1% by mass or less, based on 100% by mass of the (meth)acrylic copolymer A. The adhesive composition according to any one of [1] to

[19] .

[21] The polymer X contains a structural unit derived from the monomer M, and the content of the structural unit derived from the monomer M is preferably 0.01% by mass or more and 90% by mass or less, more preferably 0.1% by mass or more and 80% by mass or less, still more preferably 0.2% by mass or more and 60% by mass or less, particularly preferably 0.2% by mass or more and 50% by mass or less, and most preferably 0.5% by mass or more and 40% by mass or less, based on 100% by mass of the polymer X. The adhesive composition according to any one of [1] to [4] and [6] to

[20] .

[22] The (meth)acrylic copolymer A preferably does not have a radically polymerizable group at its terminal, more preferably does not have an ethylenically unsaturated group at its terminal, and still more preferably does not have either a (meth)acryloyl group or a vinyl group at its terminal. The adhesive composition according to any one of [1] to

[21] .

[23] The polymer X preferably does not have a radically polymerizable group at its terminal, more preferably does not have an ethylenically unsaturated group at its terminal, and particularly preferably does not have a (meth)acryloyl group or a vinyl group at its terminal. The adhesive composition according to any one of [1] to

[22] .

[24] The content ratio of the (meth)acrylic copolymer A is preferably 20% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 70% by mass or less, still more preferably 50% by mass or more and 65% by mass or less, and particularly preferably 55% by mass or more and 63% by mass or less, based on 100% by mass of the total mass of the adhesive composition. The adhesive composition according to any one of [1] to

[23] .

[25] The content ratio of the polymer X is preferably 0.01% by mass or more and 10% by mass or less, more preferably 0.05% by mass or more and 8% by mass or less, still more preferably 0.1% by mass or more and 5% by mass or less, and particularly preferably 0.5% by mass or more and 3% by mass or less, based on 100% by mass of the total mass of the adhesive composition. The adhesive composition according to any one of [1] to

[24] .

[26] Further containing a solvent, The content of the solvent is preferably 20% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 70% by mass or less, even more preferably 35% by mass or more and 60% by mass or less, and particularly preferably 38% by mass or more and 45% by mass or less, according to any one of [1] to

[25] of the total mass of the adhesive composition.

[27] The (meth)acrylic copolymer A contains constituent units derived from (meth)acrylic monomers other than the monomer M, The content of constituent units derived from (meth)acrylic monomers other than monomer M is preferably 30% by mass or more and 100% by mass or less, more preferably 50% by mass or more and less than 100% by mass, even more preferably 80% by mass or more and 99.9% by mass or less, particularly preferably 90% by mass or more and 99.5% by mass or less, and most preferably 93% by mass or more and 99.5% by mass or less, according to any one of [1] to

[26] .

[28] The polymer X contains constituent units derived from (meth)acrylic monomers other than the monomer M, The adhesive composition according to any one of [1] to

[27] , wherein the content of constituent units derived from (meth)acrylic monomers other than monomer M is preferably 10% by mass or more and 100% by mass or less, more preferably 20% by mass or more and less than 100% by mass, 40% by mass or more and 99.9% by mass or less, particularly preferably 50% by mass or more and 99.5% by mass or less, and most preferably 60% by mass or more and 99.5% by mass or less.

[29] The weight-average molecular weight of the (meth)acrylic copolymer A, as measured by gel permeation chromatography, is preferably 10,000 to 2,000,000, more preferably 11,000 to 1,000,000, even more preferably 30,000 to 800,000, particularly preferably 50,000 to 500,000, and most preferably 1,000,000 to 350,000, as described in any one of [1] to

[28] .

[30] The adhesive composition according to any one of [1] to

[29] , wherein the Mw of the polymer X is preferably 500 to 100,000, more preferably 1,000 to 50,000, even more preferably 1,500 to 25,000, particularly preferably 1,800 to 15,000, and most preferably 2,000 to 8,000.

[31] The adhesive composition according to any one of [1] to

[30] , wherein the molecular weight distribution (Mw / Mn) of the (meth)acrylic copolymer A is preferably 3 to 30, more preferably 5 to 20, and even more preferably 6 to 15.

[32] The adhesive composition according to any one of [1] to

[31] , wherein the mass ratio of polymer X to copolymer A, expressed as [mass of polymer X]:[mass of copolymer A], is preferably 0.01:99.9 to 40:60, more preferably 0.5:99.5 to 20:80, and even more preferably 1:99 to 15:85.

[33] The monomer M is 4-acryloyloxybenzophenone, 4-methacryloyloxybenzophenone, 4-[2-(acryloyloxy)ethoxy]benzophenone, 4-[2-(methacryloyloxy)ethoxy]benzophenone, 2-hydroxy-4-acryloyloxybenzophenone, 4-(((4-benzoylphenoxy)carbonyl)oxy)butyl acrylate, 4-(((4-benzoylphenoxy)carbonyl)oxy)butyl methacrylate, 2-hydroxy-4-methacryloyloxybenzophenone, 2-hydroxy-4-(2-acryloyloxy)ethoxybenzo The adhesive composition according to any one of [1] to

[32] , wherein the constituent units are preferably monomers selected from the group consisting of phenone, 2-hydroxy-4-(2-methyl-2-acryloyloxy)ethoxybenzophenone, 2-hydroxy-4-acryloyloxy-5-tert-butylbenzophenone, and 2-hydroxy-4-acryloyloxy-2',4'-dichlorobenzophenone; more preferably monomers selected from the group consisting of 4-methacryloyloxybenzophenone and 4-[2-(methacryloyloxy)ethoxy]benzophenone.

[34] The adhesive composition according to any one of [1] to

[33] , wherein the glass transition temperature (Tg) of the (meth)acrylic copolymer A is preferably -100°C or higher and 0°C or lower, more preferably -80°C or higher and -5°C or lower, even more preferably -50°C or higher and -10°C or lower, and particularly preferably -45°C or higher and -30°C or lower.

[35] The adhesive composition according to any one of [1] to

[34] , wherein the melt viscosity at 130°C before irradiation, as measured by the method described in the Examples, is preferably 5 to 1000 Pa·s, more preferably 10 to 900 Pa·s, even more preferably 15 to 880 Pa·s, particularly preferably 20 to 600 Pa·s, and most preferably 30 to 300 Pa·s.

[36] The adhesive composition according to any one of [1] to

[35] , wherein the peel strength measured by the method described in the Examples is preferably 5 to 30 N / 25 mm, more preferably 6 to 20 N / 25 mm, even more preferably 7 to 18 N / 25 mm, and particularly preferably 8 to 17 N / 25 mm.

[37] The adhesive composition according to any one of [1] to

[36] , wherein the retention time measured by the method described in the Examples is preferably 0.1 to 24 hours, more preferably 0.5 to 24 hours, and even more preferably 1 to 24 hours.

[38] The adhesive composition according to any one of [1] to

[37] , wherein the percentage of adhesive residue area measured by the method described in the Examples is preferably less than 30 area%, more preferably 10 area% or less, even more preferably 1 area% or less, and particularly preferably 0 area% with respect to 100 area% of the surface area of ​​the SUS plate.

[0009]

[39] An adhesive obtained by irradiating an adhesive composition described in any one of items [1] to

[38] with ultraviolet light.

[40] The amount of ultraviolet radiation is 20-150 mJ / cm². 2 Preferably, the concentration is 30-130 mJ / cm². 2 It is more preferable that the concentration be 35-105 mJ / cm². 2The adhesive described in

[39] is even more preferable.

[0010]

[41] An adhesive comprising the adhesive composition described in any one of items [1] to

[38] .

[0011]

[42] An adhesive sheet containing the adhesive described in any one of the items

[39] to

[41] .

[0012] The present invention also has the following embodiments. [1] An adhesive composition comprising a (meth)acrylic copolymer A having a number average molecular weight greater than 10,000 as measured by gel permeation chromatography, and a polymer X having a number average molecular weight of 10,000 or less as measured by gel permeation chromatography, wherein at least one of the (meth)acrylic copolymer A and the polymer X contains constituent units derived from monomer M that generate active species upon photoexcitation and form a crosslinked structure. [2] The adhesive composition according to [1], wherein the glass transition temperature of the (meth)acrylic copolymer A is 0°C or lower. [3] The adhesive composition according to [1] or [2], wherein the active species is a radical. [4] The adhesive composition according to any one of [1] to [3], wherein the monomer M is a monomer represented by the following formula (1).

[0013] [ka]

[0014] (In the formula, R A and R B Each of the following independently represents an alkyl group, alkoxy group, hydroxyl group, carboxyl group, or halogen atom; n represents an integer from 0 to 5; m represents an integer from 0 to 4; and X represents a (meth)acryloyloxy group or a (meth)acryloyloxyalkyleneoxy group. [5] The adhesive composition according to any one of [1] to [4], wherein the content of constituent units derived from monomer M is 0.01% by mass or more and 50% by mass or less with respect to 100% by mass of the total mass of (meth)acrylic copolymer A and polymer X. [6] The adhesive composition according to any one of [1] to [5], wherein the mass ratio of the polymer X to the (meth)acrylic copolymer A is 0.1:99.9 to 40:60. [7] The adhesive composition according to any one of [1] to [6], wherein the polymer X comprises a constituent unit derived from (meth)acrylate having an alicyclic structure. An adhesive obtained by irradiating an adhesive composition described in any of [8][1] to [7] with ultraviolet light. An adhesive comprising the adhesive composition described in any of [9][1] to [7]. An adhesive sheet containing the adhesive described in

[10] , [8], or [9]. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide an adhesive composition, adhesive, and adhesive sheet that can achieve high retention under high temperature and high humidity conditions and excellent substrate stain resistance with minimal adhesive residue. [Modes for carrying out the invention]

[0016] The following definitions of terms apply throughout this specification and the claims. "(Meth)acrylate" is a general term for acrylates and methacrylates. "(Meth)acrylic acid" is a general term for acrylic acid and methacrylic acid. "(meth)acrylic copolymer" means a copolymer in which at least a portion of the constituent units are derived from (meth)acrylic monomers. (Meth)acrylic copolymers may further contain constituent units derived from monomers other than (meth)acrylic monomers (e.g., styrene). "(meth)acrylic monomer" refers to a monomer having a (meth)acryloyl group. "(Meth)acryloyl" is a general term for acryloyl and methacryloyl. The "~" symbol indicating a numerical range means that the numbers before and after it are included as the lower and upper limits, respectively. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the polymer are determined by gel permeation chromatography (GPC) and are based on the molecular weight of polystyrene. The glass transition temperature of (meth)acrylic copolymers is a calculated value obtained using Fox's formula. For example, if a (meth)acrylic copolymer consists of constituent units p derived from monomer p, constituent units q derived from monomer q, and constituent units r derived from monomer r, the glass transition temperature (in °C) of the (meth)acrylic copolymer is defined as the Tg calculated by Fox's formula below, based on the glass transition temperature and mass fraction of each homopolymer of monomer p, monomer q, or monomer r. 1 / (273+Tg)=Σ(Wi / (273+Tgi)) (In the formula, Wi represents the mass fraction of monomer i, and Tgi represents the glass transition temperature (°C) of the homopolymer of monomer i.) Furthermore, the glass transition temperature of the homopolymer of monomer i can be the value listed in the Polymer Handbook [Polymer Handbook, J. Brandrup, Interscience, 1989]. In addition, if the (meth)acrylic copolymer contains constituent units derived from macromonomers, the glass transition temperature and mass fraction of the homopolymer of the monomer used in the production of the macromonomers should be used.

[0017] <Adhesive composition> The adhesive composition of the present invention comprises a (meth)acrylic copolymer A (hereinafter also simply referred to as "copolymer A") having a Mn of greater than 10,000 as measured by GPC, and a polymer X having a Mn of 10,000 or less as measured by GPC, wherein at least one of copolymer A and polymer X contains constituent units derived from monomer M that generate active species upon photoexcitation and form a crosslinked structure.

[0018] (Copolymer A) Copolymer A is a copolymer that contains constituent units derived from (meth)acrylic monomers as essential components, and whose Mn, as measured by GPC, is greater than 10,000. Copolymer A may be a random copolymer, a block copolymer, or a graft copolymer. If copolymer A is a graft copolymer, the constituent units derived from monomer M may be contained in either the stem polymer or the branch polymer, preferably in the stem polymer, and more preferably not in the branch polymer but only in the stem polymer.

[0019] Copolymer A may contain constituent units derived from monomer M, or it may contain constituent units derived from macromonomers. It may also contain other monomers other than (meth)acrylic monomers, monomer M, and macromonomers. One monomer may be used alone, or two or more monomers may be used in combination. Copolymer A substantially lacks radical polymerizable groups at its terminal ends. Note that radical polymerizable groups refer to groups having radically polymerizable unsaturated bonds, including ethylenically unsaturated groups such as (meth)acryloyl groups and vinyl groups.

[0020] Examples of (meth)acrylic monomers include hydrocarbon group-containing (meth)acrylates, hydroxyl group-containing (meth)acrylates, carboxyl group-containing (meth)acrylic monomers, amino group-containing (meth)acrylates, epoxy group-containing (meth)acrylates, and polyfunctional (meth)acrylates. As for the (meth)acrylic monomer, one type may be used alone, or two or more types may be used in combination.

[0021] Examples of hydrocarbon group-containing (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate. Examples of hydroxyl group-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate.

[0022] Examples of carboxyl group-containing (meth)acrylic monomers include (meth)acrylic acid, 2-(meth)acryloyloxyethylhexahydrophthalic acid, 2-(meth)acryloyloxypropylhexahydrophthalic acid, and 2-(meth)acryloyloxyethylphthalic acid. Examples of amino group-containing (meth)acrylates include dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate. An example of an epoxy group-containing (meth)acrylate is glycidyl (meth)acrylate. Examples of polyfunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, and polyethylene glycol di(meth)acrylate.

[0023] Copolymer A preferably contains constituent units derived from hydrocarbon group-containing (meth)acrylate, specifically alkyl (meth)acrylate having a linear or branched alkyl group with 1 to 10 carbon atoms. The number of carbon atoms in the linear or branched alkyl group with 1 to 10 carbon atoms is preferably 2 to 8, more preferably 3 to 6, and even more preferably 4. The content of alkyl (meth)acrylate-derived structural units in copolymer A is preferably 30 to 100% by mass, more preferably 50 to 98% by mass, and even more preferably 80 to 95% by mass, based on the total mass of copolymer A.

[0024] Copolymer A preferably contains constituent units derived from (meth)acrylic acid as constituent units derived from carboxyl group-containing (meth)acrylic monomers. The content of (meth)acrylic acid-derived constituent units in copolymer A is preferably 0.5 to 10% by mass, more preferably 1 to 8% by mass, and even more preferably 3 to 5% by mass, relative to the total mass of copolymer A.

[0025] From the standpoint of lowering the melt viscosity of the adhesive composition, improving its coatability, heat resistance, and moisture resistance, copolymer A preferably contains constituent units derived from hydrocarbon group-containing (meth)acrylate, specifically those derived from (meth)acrylate having an alicyclic structure. An alicyclic structure refers to an organic group containing an alicyclic group, which may be monocyclic or polycyclic. Examples of monocyclic alicyclic groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Examples of polycyclic alicyclic groups include norbornyl, isobornyl, tricyclononyl, tricyclodecyl, and tetracyclododecyl groups. Furthermore, the hydrogen atoms of these alicyclic groups may be substituted with alkyl groups, alkoxy groups, hydroxyl groups, etc. Isobornyl (meth)acrylate and cyclohexyl (meth)acrylate are particularly preferred as (meth)acrylates having an alicyclic structure. The content of constituent units derived from (meth)acrylate having an alicyclic structure in copolymer A is preferably 0.5 to 70% by mass, more preferably 1 to 60% by mass, and even more preferably 3 to 50% by mass, based on the total mass of copolymer A. Furthermore, the total content of the constituent units that make up copolymer A shall not exceed 100% by mass.

[0026] Monomer M generates active species by photoexcitation such as ultraviolet rays or electron beams, and forms a crosslinked structure. Examples of the active species include radicals, cations, and anions, and radicals are preferred from the viewpoint of reactivity. Examples of the monomer that generates radicals by photoexcitation include monomers having a benzophenone skeleton, a thioxanthone skeleton, an anthraquinone skeleton, etc. Since these skeletons include a benzophenone skeleton, an excited triplet state of the benzophenone skeleton is generated by photoexcitation, and a carbon radical A having a secondary hydroxyl group is formed by hydrogen abstraction from a hydrocarbon group. It is considered that this carbon radical A combines with the carbon radical B generated by hydrogen abstraction to form a crosslinked structure having a tertiary hydroxyl group and two phenyl groups at the crosslinking point. The crosslinked structure preferably contains, for example, a diphenylhydroxymethyl group. The phenyl group in the crosslinked structure may or may not have a substituent. As monomer M, a benzophenone derivative represented by the following formula (1) is preferred from the viewpoint of reactivity.

[0027]

Chemical formula

[0028] In formula (1), R A and R B each independently represent an alkyl group, an alkoxy group, a hydroxyl group, a carboxy group, or a halogen atom. As the alkyl group, a linear or branched alkyl group having 1 to 10 carbon atoms is preferred, and a linear or branched alkyl group having 1 to 5 carbon atoms is more preferred. As the alkoxy group, a linear or branched alkoxy group having 1 to 10 carbon atoms is preferred, and a linear or branched alkoxy group having 1 to 5 carbon atoms is more preferred. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. n is an integer of 0 to 5, preferably an integer of 0 to 3, and more preferably 0. m is an integer of 0 to 4, preferably an integer of 0 to 3, and more preferably 0. X represents a (meth)acryloyloxy group or a (meth)acryloyloxyalkyleneoxy group. The alkylene group in the (meth)acryloyloxyalkyleneoxy group is preferably a C2-C10 alkylene group, and more preferably a C2-C6 alkylene group. Examples of the (meth)acryloyloxyalkyleneoxy group include a 2-(meth)acryloyloxyethoxy group and a 2-(meth)acryloyloxypropoxy group.

[0029] Examples of monomers represented by formula (1) include 4-acryloyloxybenzophenone, 4-methacryloyloxybenzophenone, 4-[2-(acryloyloxy)ethoxy]benzophenone, 4-[2-(methacryloyloxy)ethoxy]benzophenone, 2-hydroxy-4-acryloyloxybenzophenone, 2-hydroxy-4-methacryloyloxybenzophenone, 2-hydroxy-4-(2-acryloyloxy)ethoxybenzophenone, 2-hydroxy-4-(2-methyl-2-acryloyloxy)ethoxybenzophenone, 2-hydroxy-4-acryloyloxy-5-tert-butylbenzophenone, and 2-hydroxy-4-acryloyloxy-2',4'-dichlorobenzophenone. Among these, 4-methacryloyloxybenzophenone and 4-[2-(methacryloyloxy)ethoxy]benzophenone are preferred. Monomer M may be used alone or in combination of two or more types.

[0030] As the macromonomer, the macromonomer represented by the following formula (2) is preferred.

[0031] [ka]

[0032] In formula (2) above, R represents a hydrogen atom, an alkyl group, an alicyclic group, an aryl group, or a heterocyclic group. These groups may have substituents. Examples of alkyl groups in R include branched or linear alkyl groups having 1 to 20 carbon atoms. Alicyclic groups can be monocyclic or polycyclic, for example, alicyclic groups having 3 to 20 carbon atoms. Examples of aryl groups include aryl groups having 6 to 18 carbon atoms. Examples of heterocyclic groups include heterocyclic groups having 5 to 18 carbon atoms. Examples of substituents include alkyl groups, aryl groups, carboxyl groups, alkoxycarbonyl groups, cyano groups, hydroxyl groups, alkoxy groups, amino groups, monomethylamino groups, dimethylamino groups, carbamoyl groups, N-methylcarbamoyl groups, N,N-dimethylcarbamoyl groups, halogen atoms, allyl groups, epoxy groups, siloxy groups, alkali salts of carboxyl groups, alkali salts of sulfoxy groups, polyethylene oxide groups, polypropylene oxide groups, and quaternary ammonium bases.

[0033] For R, alkyl groups or saturated alicyclic groups are preferred, with alkyl groups, saturated alicyclic groups, and saturated alicyclic groups having alkyl groups as substituents being preferred. Among these, methyl groups, ethyl groups, n-propyl groups, i-propyl groups, n-butyl groups, t-butyl groups, pentyl groups, hexyl groups, heptyl groups, octyl groups, cyclopropyl groups, cyclobutyl groups, isobornyl groups, and adamantyl groups are more preferred due to their availability, and methyl groups, ethyl groups, n-propyl groups, i-propyl groups, n-butyl groups, t-butyl groups, cyclopropyl groups, cyclobutyl groups, isobornyl groups, and adamantyl groups are even more preferred.

[0034] In formula (2), Z is a terminal group, and like the terminal groups of polymers obtained by known radical polymerization, it may be a hydrogen atom or a group derived from a radical polymerization initiator. R 21 This is either a hydrogen atom or a methyl group. R 22These are unsubstituted or substituted alkyl groups, unsubstituted or substituted alicyclic groups, unsubstituted or substituted aryl groups, unsubstituted or substituted heteroaryl groups, unsubstituted or substituted aralkyl groups, unsubstituted or substituted alkaryl groups, unsubstituted or substituted organosilyl groups, or unsubstituted or substituted (poly)organosiloxane groups. The substituents in these groups are at least one selected from the group consisting of alkyl groups, aryl groups, heteroaryl groups, non-aromatic heterocyclic groups, aralkyl groups, alkaryl groups, carboxylic acid groups, carboxylic acid ester groups, epoxy groups, hydroxyl groups, alkoxy groups, primary amino groups, secondary amino groups, tertiary amino groups, isocyanate groups, sulfonic acid groups, and halogen atoms. a is a natural number greater than or equal to 2. a is within the range where the weight-average molecular weight (Mw) of the macromonomer is between 500 and 100,000. a individual R 21 They may all be the same, or some may be different. a number of R 22 They may all be the same, or some may be different. As macromonomers, one type may be used alone, or two or more types may be used in combination.

[0035] The Mw of the macromonomer is preferably 500 to 100,000, more preferably 600 to 50,000, and even more preferably 1,000 to 20,000. When the Mw of the macromonomer is within the above range, a good balance between adhesiveness and handling properties (compatibility with other components, coating properties, hot-melt processability, etc.) tends to be achieved.

[0036] Macromonomers may be those produced by known methods or commercially available ones. Examples of methods for producing macromonomers include methods using a cobalt chain transfer agent, methods using α-substituted unsaturated compounds such as α-methylstyrene dimer as chain transfer agents, methods using initiators, methods chemically bonding radical polymerizable groups to polymers, and methods by thermal decomposition. In the production of macromonomers, for example, the various (meth)acrylic monomers and monomer M mentioned above can be used as monomers. One monomer may be used alone, or two or more monomers may be used in combination.

[0037] Other monomers are not limited to, but include styrene, crotonic acid, fumaric acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride, (meth)acrylamide, styrene, (meth)acrylonitrile, vinyl chloride, vinyl acetate, vinyl fluoride, and vinylidene fluoride. Other monomers may be used individually or in combination of two or more.

[0038] The content of constituent units derived from (meth)acrylic monomers in copolymer A is preferably 10 to 100% by mass, and more preferably 20 to 100% by mass, relative to the total mass of copolymer A. It is preferable that the (meth)acrylic monomers include carboxyl group-containing (meth)acrylic monomers, as this improves adhesion. The content of constituent units derived from carboxyl group-containing (meth)acrylic monomers in copolymer A is preferably 0.1 to 20% by mass, relative to the total mass of copolymer A. When copolymer A contains structural units derived from macromonomers, it exhibits good retention and resistance to substrate contamination. Therefore, the content of structural units derived from macromonomers is preferably 0.1 to 40% by mass, and more preferably 0.5 to 30% by mass, relative to the total mass of copolymer A. The content of each constituent unit can be calculated from the amount of monomers that make up the constituent unit (the same applies hereafter).

[0039] The Mw of copolymer A is preferably 10,000 to 2,000,000, more preferably 11,000 to 1,000,000, and even more preferably 30,000 to 350,000. When the Mw of copolymer A is above the lower limit, the adhesive layer has excellent durability. When the Mw of copolymer A is below the upper limit, the handling properties (compatibility with other components, coating properties, hot melt processability, etc.) are excellent. For the same reasons as for Mw, the Mn of copolymer A is preferably 10,000 to 1,000,000, more preferably 11,000 to 500,000, and even more preferably 12,000 to 100,000.

[0040] The glass transition temperature (Tg) of copolymer A is preferably 0°C or lower, and more preferably -5°C or lower, from the viewpoint of tackiness. The lower limit of the Tg of copolymer A is not particularly limited, but it may be, for example, -100°C or higher.

[0041] Copolymer A can be produced by known methods using known polymerization initiators. Examples of polymerization methods include known polymerization methods such as solution polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization, with solution polymerization being preferred. Radical polymerization initiators are preferred as the polymerization initiator. Examples of solvents used in solution polymerization include organic solvents such as acetone, toluene, xylene, and ethyl acetate.

[0042] (Polymer X) Polymer X is a polymer whose Mn value, as measured by GPC, is 10,000 or less. Polymer X may or may not contain constituent units derived from monomer M. Examples of monomers used in polymer X include the (meth)acrylic monomers exemplified in copolymer A, and other monomers, with the inclusion of (meth)acrylic monomers being preferable. One monomer may be used alone, or two or more monomers may be used in combination. The content of constituent units derived from (meth)acrylic monomers in polymer X is preferably 10 to 100% by mass, and more preferably 20 to 100% by mass, relative to the total mass of polymer X.

[0043] Polymer X preferably contains a constituent unit derived from alkyl (meth)acrylate having a linear or branched alkyl group having 1 to 10 carbon atoms, as a constituent unit derived from hydrocarbon group-containing (meth)acrylate. The number of carbon atoms in the linear or branched alkyl group having 1 to 10 carbon atoms is preferably 1 to 6, more preferably 1 to 4, even more preferably 1 to 3, and particularly preferably 1. The content of alkyl (meth)acrylate-derived structural units in polymer X is preferably 30 to 100% by mass, more preferably 40 to 90% by mass, and even more preferably 50 to 80% by mass, based on the total mass of polymer X.

[0044] It is preferable that polymer X contains constituent units derived from (meth)acrylate having an alicyclic structure, as this reduces the melt viscosity of the adhesive composition, improves its coatability, and enhances its heat resistance and moisture resistance. An alicyclic structure refers to an organic group containing an alicyclic group, which may be monocyclic or polycyclic. Examples of monocyclic alicyclic groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups. Examples of polycyclic alicyclic groups include norbornyl, isobornyl, tricyclononyl, tricyclodecyl, and tetracyclododecyl groups. Furthermore, the hydrogen atoms of these alicyclic groups may be substituted with alkyl groups, alkoxy groups, hydroxyl groups, etc. Isobornyl (meth)acrylate is particularly preferred as the (meth)acrylate having an alicyclic structure. The content of alicyclic structured (meth)acrylate-derived constituent units in polymer X is preferably 0.1 to 100% by mass, more preferably 10 to 90% by mass, even more preferably 20 to 80% by mass, particularly preferably 30 to 60% by mass, and most preferably 40 to 55% by mass, relative to the total mass of polymer X. Furthermore, the total content of the constituent units that make up polymer X shall not exceed 100% by mass.

[0045] Polymer X may have radical polymerizable groups at its terminals, or it may not substantially have radical polymerizable groups at its terminals. Preferred radical polymerizable groups are those having an ethylenically unsaturated bond. Examples of groups having an ethylenically unsaturated bond include CH2=C(COOR)-CH2- (where R is the same as R in formula (2) above), (meth)acryloyl group, 2-(hydroxymethyl)acryloyl group, and vinyl group. An example of polymer X having a radical polymerizable group at its terminus is the polymer represented by formula (2), which was exemplified as a macromonomer in copolymer A. In formula (2), the CH2=C portion at the left end corresponds to the terminal radical polymerizable group.

[0046] The manganese (Mn) of polymer X is preferably between 100 and 10000, and more preferably between 1000 and 9000. If the Mn of polymer X is below the upper limit, it is easier to balance the adhesive performance. If the Mn of polymer X is above the lower limit, the holding power and substrate stain resistance are improved. For the same reasons as with Mn, the Mw of polymer X is preferably 500 to 100,000, and more preferably 1,000 to 50,000.

[0047] Polymer X can be produced using known polymerization initiators and known methods. Known polymerization methods can be applied, with solution polymerization and suspension polymerization being preferred.

[0048] (composition) In the adhesive composition of the present invention, copolymer A alone may contain constituent units derived from monomer M, polymer X alone may contain constituent units derived from monomer M, or both copolymer A and polymer X may contain constituent units derived from monomer M.

[0049] The content of constituent units derived from monomer M in the adhesive composition of the present invention is preferably 0.01% by mass or more and 50% by mass or less, relative to the total mass of copolymer A and polymer X. A higher content of constituent units derived from monomer M is preferable from the viewpoint of improving holding power, and a lower content is preferable from the viewpoint of compatibility with other components. From the viewpoint of balancing performance, the content of constituent units derived from monomer M in the adhesive composition is more preferably 0.1% by mass or more and 40% by mass or less.

[0050] The mass ratio of polymer X to copolymer A in the adhesive composition of the present invention is preferably 0.1:99.9 to 40:60, more preferably 0.5:99.5 to 20:80, and even more preferably 1:99 to 15:85. When the mass ratio is within the above range, an adhesive composition with high holding power under high temperature and high humidity conditions, and excellent resistance to substrate contamination with minimal adhesive residue can be easily obtained.

[0051] The adhesive composition of the present invention may contain other components besides copolymer A and polymer X. These other components are not particularly limited and include, for example, solvents, fillers, crosslinking agents, tackifying resins, antioxidants, light stabilizers, metal deactivators, anti-aging agents, hygroscopic agents, rust inhibitors, hydrolysis inhibitors, and reaction catalysts. The adhesive composition of the present invention may be in the form of a liquid adhesive composition containing a solvent, or in the form of a hot-melt type adhesive composition that does not contain a solvent.

[0052] The adhesive composition of the present invention described above combines copolymer A, which contains at least one constituent unit derived from monomer M, with polymer X, thereby achieving high holding power under high temperature and high humidity conditions, as well as excellent substrate stain resistance with minimal adhesive residue.

[0053] <Adhesives, adhesive sheets> The adhesive of the present invention is an adhesive comprising the adhesive composition of the present invention. The adhesive of the present invention may be used in an uncured state, or it may be cured by irradiation with an active energy ray. From the viewpoint of versatility, ultraviolet light is preferred as the active energy ray.

[0054] The adhesive sheet of the present invention is an adhesive sheet containing the adhesive of the present invention and has an adhesive layer formed using the adhesive composition of the present invention. The adhesive layer may consist of the adhesive composition, or it may consist of a cured product obtained by irradiating the adhesive composition with ultraviolet light. In terms of the handling of the adhesive sheet, an adhesive layer consisting of a cured product obtained by curing the adhesive composition with ultraviolet light is preferred. The amount of ultraviolet light irradiated is 20 to 150 mJ / cm². 2 Preferably, the concentration is 30-130 mJ / cm².2 It is more preferable that the concentration be 35-105 mJ / cm². 2 It is even more preferable that this be the case.

[0055] The adhesive sheet of the present invention may consist only of an adhesive layer formed from the adhesive composition of the present invention into a sheet, or it may be a laminate in which a release substrate is laminated on one or both sides of an adhesive layer formed from the adhesive composition of the present invention into a sheet.

[0056] The thickness of the adhesive layer can be set appropriately depending on the application, with 10 to 500 μm being preferred and 20 to 100 μm being more preferred.

[0057] The applications of the adhesive sheet of the present invention are not particularly limited. For example, it can be used for bonding window films for vehicles, buildings, etc., bonding labels in label displays, bonding various panels in display displays such as liquid crystal panels, and bonding transparent plate materials such as glass. [Examples]

[0058] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following description. In the following description, "parts" means "parts by mass".

[0059] <Abbreviation> The abbreviations for the raw materials used in this example are shown below. MMA: Methyl methacrylate IBXMA: Isobornyl methacrylate IBMA: Isobutyl methacrylate SLMA: Alkyl methacrylate (Acryester SL, manufactured by Mitsubishi Chemical Corporation) ETMA: 2-Ethoxyethyl methacrylate EHA: 2-ethylhexyl acrylate CHMA: Cyclohexyl methacrylate 4-MBP:4-methacryloyloxybenzophenone BPOEMA: 4-[2-(methacryloyloxy)ethoxy]benzophenone IPA: Isopropyl alcohol n-BA:n-butyl acrylate AA: Acrylic acid Perbutyl O: Perbutyl (registered trademark) O (t-butylperoxy-2-ethylhexanoate, manufactured by NOF Corporation) Perocta-O: Perocta® O (1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, manufactured by NOF Corporation)

[0060] <Molecular weight of polymer X> Measurements were performed using a gel permeation chromatography (GPC) apparatus (HLC-8320, manufactured by Tosoh Corporation). A 0.2% by mass solution of polymer X in tetrahydrofuran (THF) was prepared, and 10 μL of this solution was injected into the apparatus equipped with a Tosoh column (TSKgel SuperHZM-M×HZM-M×HZ2000, TSKguardcolumn SuperHZ-L). Measurements were performed under the following conditions: flow rate: 0.35 mL / min, eluent: THF (stabilizer: butylhydroxytoluene (BHT)), column temperature: 40°C. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were calculated on a polystyrene basis.

[0061] <Molecular weight of copolymer A> Measurements were performed using a GPC instrument (HLC-8120, manufactured by Tosoh Corporation). A 0.3% by mass THF solution of copolymer A was prepared, and 20 μL of this solution was injected into the instrument equipped with Tosoh columns (TSKgel SuperHM-H x 4, TSKguardcolumn SuperH-H). Measurements were performed under the following conditions: flow rate: 0.6 mL / min, eluent: THF (stabilizer: BHT), column temperature: 40°C. The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were calculated on a polystyrene basis.

[0062] <Melting viscosity> The adhesive compositions obtained in each example were diluted with ethyl acetate to a solid content of 33.3% by mass, and the absence of undissolved polymer was visually confirmed to obtain a liquid adhesive composition at room temperature (23°C). The adhesive composition was applied to a release-treated PET film using an applicator and dried at 90°C for 1 hour to form an adhesive layer with a thickness of 50 μm. The melt viscosity of the adhesive layer was measured using a viscoelasticity measuring device HAAKE MARS. The viscosity (η) was measured using a 35 mm diameter cone plate at 130°C and a frequency of 0.02 Hz. * The value was taken as the melt viscosity at 130°C before irradiation.

[0063] <Preparation of test specimens> The adhesive compositions obtained in each example were diluted with ethyl acetate to a solid content of 33.3% by mass, and it was visually confirmed that there were no undissolved polymers to obtain a liquid adhesive composition at room temperature (23°C). The adhesive composition was applied to a PET film with a thickness of 38 μm using an applicator, and dried at 90°C for 1 hour to form an adhesive layer. A PET film (PET) with an adhesive layer formed on it was irradiated with ultraviolet (UV-C) light in air using a 90mW high-pressure mercury lamp to cure the adhesive layer. The UV-C irradiation dose was 35mJ / cm². 2 or 105 mJ / cm² 2 (Measured values ​​obtained using an integrated light meter UV POWER PUCK II (S / N 13685) (manufactured by EIT, USA)). A release-treated PET film (release PET) was placed on top of it to obtain a laminate with a release PET-adhesive layer-PET structure. The adhesive layer thickness was set to 50 μm. The cured laminate was cut into strips 25 mm wide and 250 mm long to create test specimens.

[0064] <Adhesive strength> The release PET from the test specimen was peeled off to expose the adhesive layer, and it was bonded to a 30mm x 110mm stainless steel (SUS) plate using a 3kg hand roller so that the bonding surface was 25mm x 70mm. The peel strength (N / 25mm) against the SUS plate was measured at a peeling angle of 180° and a tensile speed of 300mm / min, and this was defined as the adhesive strength.

[0065] <Holding power> At one end of the test specimen, the release PET was peeled off to expose the adhesive layer, and it was horizontally bonded to a 30mm x 110mm SUS plate using a 3kg hand roller so that the bonding surface was 25mm x 25mm. It was left in a constant temperature and humidity chamber at 80°C and 85% humidity for 15 minutes. Immediately afterward, the SUS plate was placed so that a shear force was applied to the bonding surface, and a 1.0kg load was applied with the other end of the test specimen facing downwards. The holding time was measured and defined as the holding force. The holding time was measured up to a maximum of 24 hours. In the table, examples where the holding time reached the maximum limit are indicated as "24<".

[0066] <Stain resistance of substrates> The release PET from the test specimen was peeled off to expose the adhesive layer, and it was bonded to a 30mm x 110mm SUS plate using a 3kg hand roller so that the bonding surface was 25mm x 70mm. After that, the test specimen was peeled off under the same conditions as the adhesive strength evaluation method, and the SUS surface was visually observed to determine the substrate stain resistance according to the following criteria. A: No adhesive residue (the ratio of the area of ​​adhesive residue to the surface area of ​​the SUS plate is 0%). B: The percentage of adhesive residue is greater than 0% but less than 30%. C: The percentage of adhesive residue is 30% or more. Furthermore, the presence or absence of adhesive residue was visually checked.

[0067] <Manufacturing Example 1> In a polymerization apparatus equipped with a stirrer, condenser, thermometer, and nitrogen gas inlet, 900 parts of deionized water, 60 parts of 2-sulfoethyl sodium methacrylate, 10 parts of potassium methacrylate, and 12 parts of MMA were added and stirred, and the temperature was raised to 50°C while purging nitrogen into the polymerization apparatus. Furthermore, 0.08 parts of 2,2'-azobis(2-methylpropionamidine) dihydrochloride were added as a polymerization initiator, and the temperature was raised to 60°C. After raising the temperature, MMA was continuously added dropwise at a rate of 0.24 parts / min for 75 minutes using a dropping pump. After holding the mixture at 60°C for 6 hours, it was cooled to room temperature to obtain dispersant 1 with a solid content of 10% by mass.

[0068] <Manufacturing Example 2> In a synthesis apparatus equipped with a stirring device, 1.00 g of cobalt(II) acetate tetrahydrate, 1.93 g of diphenylglyoxime, and 80 mL of diethyl ether, which had been deoxygenated beforehand by nitrogen bubbling, were added under a nitrogen atmosphere and stirred at room temperature for 30 minutes. Furthermore, 10 mL of boron trifluoride diethyl ether complex was added and stirred for 6 hours. The mixture was filtered, the solid was washed with diethyl ether, and vacuum-dried for 15 hours to obtain 2.12 g of chain transfer agent 1, which was a reddish-brown solid.

[0069] <Manufacturing Example 3> In a reaction vessel equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, 53 parts of ethyl acetate and 7 parts of IPA were added, and the mixture was pressurized to 350 kPa / G under nitrogen gas aeration, raising the ambient temperature to 105°C. After the ambient temperature reached 105°C and the ambient temperature stabilized, a mixture consisting of 25 parts ethyl acetate, 40 parts MMA, 49.99 parts IBXMA, 0.01 parts IBMA, 10 parts 4-MBP, and 6 parts perbutyl O was added dropwise over 3 hours. After holding for 1 hour following the completion of dropwise addition, a mixture consisting of 0.3 parts perbutyl O and 5 parts ethyl acetate was added over 30 minutes. After holding for another hour, 0.5 parts of an antioxidant (BASF, trade name "Irganox® 1010") was added, and ethyl acetate was added so that the solid content (the ratio of monomer charge amount to (monomer + solvent charge amount)) was 50% by mass. The mixture was then cooled to room temperature to obtain polymer solution X-1 containing polymer X-1.

[0070] <Manufacturing Example 4> Polymer solution X-2 (solid content 52.0% by mass) containing polymer X-2 was prepared in the same manner as in Production Example 3, except that the formulation was changed as shown in Table 1.

[0071] <Manufacturing Example 5> In a polymerization apparatus equipped with a stirrer, condenser, thermometer, and nitrogen gas inlet, 145 parts of deionized water, 0.1 parts of sodium sulfate, and 0.25 parts of dispersant 1 (10% solids by mass) were added and stirred to obtain a homogeneous aqueous solution. Furthermore, 50 parts of MMA, 49.99 parts of IBXMA, 0.01 parts of IBMA, 0.0020 parts of chain transfer agent 1, and 0.5 parts of Perocta® O as a polymerization initiator were added to obtain an aqueous suspension. Furthermore, the polymerization apparatus was purged with nitrogen, the temperature was raised to 80°C and stirred for 3.5 hours, and then the temperature was raised to 90°C and held for 1 hour to further increase the polymerization rate. After that, it was cooled to 40°C, the resulting aqueous suspension was filtered, the residue remaining on the filter was washed with deionized water, dehydrated, and dried at 40°C for 16 hours to obtain polymer X-3.

[0072] <Manufacturing Examples 6, 7> Compounds X-4 and X-5 were prepared in the same manner as in Production Example 5, except that the composition was changed as shown in Table 1. Table 1 shows the molecular weight measurements for polymers X-1 to X-5.

[0073] [Table 1]

[0074] <Manufacturing Examples 8-12> Compounds X-6 to X-10 were prepared in the same manner as in Production Example 5, except that the composition was changed as shown in Table 2. Table 2 shows the molecular weight measurements for polymers X-6 to X-10.

[0075] [Table 2]

[0076] <Manufacturing Example 13> In a four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, 40 parts of ethyl acetate and 7.7 parts of IPA were added, and the ambient temperature was raised to 85°C under nitrogen gas aeration. After the ambient temperature reached 85°C and the ambient temperature stabilized, a mixture consisting of 25 parts of ethyl acetate, 5 parts of polymer X-4, 91.9 parts of n-BA, 3 parts of AA, 0.1 parts of 4-MBP, and 0.13 parts of Niper® BMT-K40 (manufactured by NOF Corporation, trade name) was added dropwise over 4 hours. After holding for 1 hour following the completion of the dropwise addition, a mixture consisting of 0.5 parts of perocta-O and 10 parts of ethyl acetate was added over 30 minutes. After holding for 2 hours, 0.5 parts of an antioxidant (BASF, trade name "Irganox® 1010") were added, and ethyl acetate was added so that the solid content (the ratio of monomer amount to (monomer + solvent amount)) was 53% by mass. The mixture was then cooled to room temperature to obtain copolymer solution A-1 containing copolymer A-1.

[0077] <Manufacturing Examples 14, 15> Copolymer solution A-2 (53% by mass solids) containing copolymer A-2 and copolymer solution A-3 (53% by mass solids) containing copolymer A-3 were obtained in the same manner as in Production Example 13, except that the composition was changed as shown in Table 3. The properties of copolymers A-1 to A-3 are shown in Table 3.

[0078] [Table 3]

[0079] <Manufacturing Examples 16-21> Copolymer solution A-4 (53% by mass solids) containing copolymer A-4, copolymer solution A-5 (53% by mass solids) containing copolymer A-5, copolymer solution A-6 (53% by mass solids) containing copolymer A-6, copolymer solution A-7 (53% by mass solids) containing copolymer A-7, copolymer solution A-8 (53% by mass solids) containing copolymer A-8, and copolymer solution A-9 (53% by mass solids) containing copolymer A-9 were obtained in the same manner as in Production Example 13, except that the composition was changed as shown in Table 4. The properties of copolymers A-4 to A-9 are shown in Table 4.

[0080] [Table 4]

[0081] <Examples 1-8> Using polymer solution X, polymer X, and copolymer solution A obtained in each manufacturing example, adhesive compositions were prepared by blending them so that the types and masses of polymer X and copolymer A were as shown in Table 5. The obtained adhesive compositions were used to evaluate their melt viscosity, tackiness, holding power, and substrate stain resistance using the method described above. The evaluation results are shown in Table 5.

[0082] [Table 5]

[0083] <Examples 9-14> Using polymer solution X, polymer X, and copolymer solution A obtained in each manufacturing example, adhesive compositions were prepared by blending them so that the types and masses of polymer X and copolymer A were as shown in Table 6. The obtained adhesive compositions were used to evaluate their melt viscosity, tackiness, holding power, and substrate stain resistance using the method described above. The evaluation results are shown in Table 6.

[0084] [Table 6]

[0085] <Examples 15, 16, Comparative Examples 1-3> Using polymer solution X, polymer X, and copolymer solution A obtained in each manufacturing example, an adhesive composition was prepared by blending them so that the types and masses of polymer X and copolymer A were as shown in Table 7. The obtained adhesive compositions were used to evaluate their melt viscosity, tackiness, holding power, and substrate stain resistance using the method described above. The evaluation results are shown in Table 7.

[0086] [Table 7]

[0087] As shown in Tables 5-7, the adhesive compositions of Examples 1-16, in which at least one of copolymer A and polymer X contains a constituent unit derived from monomer M, exhibited low melt viscosity and excellent adhesive strength, holding power, and substrate stain resistance. The adhesive composition of Comparative Example 1, which used copolymer A-2 that does not contain constituent units derived from monomer M and does not contain polymer X, exhibited insufficient holding power and substrate stain resistance. Comparative Example 2, an adhesive composition containing copolymer A-1 with constituent units derived from monomer M but without polymer X, exhibited insufficient holding power. Comparative Example 3, which used polymer X-10 containing copolymer A-9 with constituent units derived from monomer M but with a number-average molecular weight greater than 10,000, exhibited insufficient adhesion and retention. [Industrial applicability]

[0088] According to the present invention, it is possible to provide an adhesive composition, adhesive, and adhesive sheet that can achieve high retention under high temperature and high humidity conditions and excellent substrate stain resistance with minimal adhesive residue.

Claims

1. (Meth)acrylic copolymer A, whose number-average molecular weight measured by gel permeation chromatography is 11,000 to 150,000, A composition comprising a (meth)acrylic polymer X having a number average molecular weight of 1,000 to 10,000 as measured by gel permeation chromatography, An adhesive composition wherein at least one of the (meth)acrylic copolymer A and the (meth)acrylic polymer X contains constituent units derived from monomer M that generate active species upon photoexcitation and form a crosslinked structure.

2. (Meth)acrylic copolymer A, whose number-average molecular weight measured by gel permeation chromatography is 11,000 to 150,000, A composition comprising a (meth)acrylic polymer X having a number average molecular weight of 10,000 or less as measured by gel permeation chromatography, At least one of the (meth)acrylic copolymer A and the (meth)acrylic polymer X contains a constituent unit derived from monomer M that generates active species upon photoexcitation and forms a crosslinked structure. An adhesive composition having a melt viscosity of 88 Pa·s or less, measured at 130°C.

3. The adhesive composition according to claim 1 or 2, wherein the (meth)acrylic polymer X contains constituent units derived from the monomer M, and the content of the (meth)acrylic polymer X is 2.1% by mass or more with respect to 100% by mass of the total mass of the (meth)acrylic copolymer A and the (meth)acrylic polymer X.

4. The adhesive composition according to claim 1 or 2, wherein the (meth)acrylic copolymer A contains constituent units derived from the monomer M.

5. The adhesive composition according to claim 1 or 2, wherein of the (meth)acrylic copolymer A and the (meth)acrylic polymer X, only the (meth)acrylic copolymer A contains constituent units derived from the monomer M.

6. The adhesive composition according to claim 1 or 2, wherein the (meth)acrylic polymer X contains constituent units derived from the monomer M and does not have radical polymerizable groups at its terminals.

7. The adhesive composition according to claim 1 or 2, wherein the number average molecular weight of the (meth)acrylic copolymer A is 12,000 to 100,000.

8. The adhesive composition according to claim 1 or 2, wherein the number average molecular weight of the (meth)acrylic polymer X is 1,000 to 9,000.

9. The adhesive composition according to claim 1 or 2, wherein the content of the (meth)acrylic copolymer A is 2% by mass or more, based on 100% by mass of the total mass of the (meth)acrylic copolymer A and the (meth)acrylic polymer X.

10. The adhesive composition according to claim 1 or 2, wherein the glass transition temperature of the (meth)acrylic copolymer A is 0°C or lower.

11. The adhesive composition according to claim 1 or 2, wherein the active species is a radical.

12. The adhesive composition according to claim 1 or 2, wherein the monomer M has at least one structure selected from the group consisting of a benzophenone skeleton, a thioxanthone skeleton, and an anthraquinone skeleton.

13. The adhesive composition according to claim 1 or 2, wherein the monomer M is a monomer represented by the following formula (1). 【Chemistry 1】 (In the formula, R Ａ and R Ｂ Each of the following independently represents an alkyl group, alkoxy group, hydroxyl group, carboxyl group, or halogen atom; n represents an integer from 0 to 5; m represents an integer from 0 to 4; and X represents a (meth)acryloyloxy group or a (meth)acryloyloxyalkyleneoxy group.

14. The adhesive composition according to claim 1 or 2, wherein the content of the constituent units derived from the monomer M is 0.01% by mass or more and 50% by mass or less with respect to 100% by mass of the total mass of the (meth)acrylic copolymer A and the (meth)acrylic polymer X.

15. The adhesive composition according to claim 1 or 2, wherein the mass ratio of the (meth)acrylic polymer X to the (meth)acrylic copolymer A is 0.1:99.9 to 40:

60.

16. An adhesive obtained by irradiating the adhesive composition according to claim 1 or 2 with ultraviolet light.

17. An adhesive comprising the adhesive composition according to claim 1 or 2.

18. An adhesive sheet comprising the adhesive described in claim 16.

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