Pressure-sensitive adhesive composition and pressure-sensitive adhesive layer

Abstract

To provide an adhesive composition and adhesive layer with excellent heat resistance and also moist heat resistance that maintains, in addition to initial high adhesive strength and re-peelability, initial performance even after exposure to high-temperature or high-temperature high-humidity condition.SOLUTION: Used is an adhesive composition containing an acrylic polymer (A) and a cross-linking agent (B), and in which, characterized, the acrylic polymer (A) has a unit derived from a (meth)acrylic acid alkyl ester (a1), a nitrogen atom-containing (meth)acrylic monomer (a2), and a carboxyl group-containing (meth)acrylic monomer (a3), and the mass ratio (a2 / a3) between units derived from the nitrogen atom-containing (meth)acrylic monomer (a2) and units derived from the carboxyl group-containing (meth)acrylic monomer (a3) is 0.1 to 5.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive layer. [Background technology]

[0002] Acrylic adhesives have traditionally been used in a variety of fields, including double-sided tapes and printed labels. Some of these applications, such as protective tape used at construction sites and labels attached to recycled containers, require the adhesive to be attached to an adherend and then peeled off after a certain period of time. Adhesives used in these applications are required to be removably removable, meaning they can be removed cleanly without leaving any residue on the adherend surface, thereby contaminating the adherend.

[0003] Furthermore, adhesives require various adhesive strengths depending on the application, and it is necessary to design them to cover all adhesive strength ranges. Generally, adhesive strength increases over time after application to an adherend. Therefore, particularly in the above-mentioned removability applications, it is necessary to assume the increase in adhesive strength after application and control the initial adhesive strength to a certain level. Therefore, there is a need for a technology that can achieve both the desired adhesive performance at the time of initial application and the removability that allows the adhesive to be removed without contaminating the adherend after a certain period of time has passed since application to the adherend.

[0004] As such a pressure-sensitive adhesive, a pressure-sensitive adhesive containing a polymer obtained by solution polymerization of a monomer mixture containing 10 to 30% by weight of an alkyl (meth)acrylate having an alkyl group with 1 or 2 carbon atoms, and a curing agent has been proposed (see, for example, Patent Document 1). However, although this pressure-sensitive adhesive has good removability, it has a problem in that it has insufficient initial adhesive strength and cannot be used in applications requiring high adhesive strength. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-25200 A Summary of the Invention [Problem to be solved by the invention]

[0006] The problem to be solved by the present invention is to provide a pressure-sensitive adhesive composition and pressure-sensitive adhesive layer that not only have high initial adhesive strength and removability, but also have excellent heat resistance and moist heat resistance, and that maintain their initial performance even after exposure to high temperature or high-temperature, high-humidity conditions. [Means for solving the problem]

[0007] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by using a pressure-sensitive adhesive composition containing a specific acrylic polymer and a crosslinking agent, and have completed the present invention.

[0008] Specifically, the present invention relates to a pressure-sensitive adhesive composition comprising an acrylic polymer (A) and a crosslinking agent (B), wherein the acrylic polymer (A) comprises units derived from a (meth)acrylic acid alkyl ester (a1), a nitrogen-containing (meth)acrylic monomer (a2), and a carboxyl-containing (meth)acrylic monomer (a3), and wherein the mass ratio (a2 / a3) of the units derived from the nitrogen-containing (meth)acrylic monomer (a2) to the units derived from the carboxyl-containing (meth)acrylic monomer (a3) ​​is 0.1 to 5. [Effects of the Invention]

[0009] The pressure-sensitive adhesive composition of the present invention can provide an adhesive layer having high adhesive strength, removability, heat resistance, and moist heat resistance, and can therefore be suitably used as pressure-sensitive adhesive tapes or pressure-sensitive adhesive sheets for fixing nameplates, mechanical parts, electrical parts, home appliance parts, office automation equipment, labels, etc. DETAILED DESCRIPTION OF THE INVENTION

[0010] The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition comprising an acrylic polymer (A) and a crosslinking agent (B), wherein the acrylic polymer (A) has units derived from a (meth)acrylic acid alkyl ester (a1), a nitrogen-containing (meth)acrylic monomer (a2), and a carboxyl-containing (meth)acrylic monomer (a3), and the mass ratio (a2 / a3) of the units derived from the nitrogen-containing (meth)acrylic monomer (a2) to the units derived from the carboxyl-containing (meth)acrylic monomer (a3) ​​is 0.1 to 5.

[0011] The acrylic polymer (A) has units derived from a (meth)acrylic acid alkyl ester (a1), a nitrogen atom-containing (meth)acrylic monomer (a2), and a carboxyl group-containing (meth)acrylic monomer (a3).

[0012] Examples of the (meth)acrylic acid alkyl ester (a1) include (meth)acrylic acid alkyl esters in which an alkyl group is bonded to an ester bond. The number of carbon atoms in the alkyl group is preferably 1 or more, more preferably 3 or more, and even more preferably 4 or more, and is preferably 20 or less, more preferably 15 or less, even more preferably 12 or less, still more preferably 10 or less, and particularly preferably 8 or less.

[0013] Examples of the alkyl group include linear alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, and n-nonyl; and branched alkyl groups such as isopropyl, isobutyl, isopentyl, neopentyl, isohexyl, isoheptyl, isooctyl, and 2-ethylhexyl.

[0014] The (meth)acrylic acid alkyl ester (a1) is preferably an acrylic acid alkyl ester.

[0015] The (meth)acrylic acid alkyl ester (a1) may be used alone or in combination of two or more thereof, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and nonyl (meth)acrylate.

[0016] In the acrylic polymer (A), the content of units derived from the (meth)acrylic acid alkyl ester (a1) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and is preferably 99% by mass or less, more preferably 90% by mass or less.

[0017] The (meth)acrylic monomer (a2) having a nitrogen atom is a monomer having a nitrogen atom and a polymerizable double bond in the molecule, and is preferably a monomer having an amide bond and a polymerizable double bond in the molecule, and examples thereof include lactam compounds having a vinyl group; (meth)acrylamide monomers; and (meth)acrylate compounds having a nitrogen atom-containing functional group (e.g., amino group, mono-substituted amino group, di-substituted amino group, nitrile group, etc.). These (meth)acrylic monomers (a2) having a nitrogen atom can be used alone or in combination of two or more.

[0018] Examples of the lactam compound having a vinyl group include N-vinylpyrrolidone and N-vinylcaprolactam.

[0019] Examples of the (meth)acrylamide monomer include compounds in which a hydrogen atom or a hydrocarbon group (preferably an aliphatic hydrocarbon group, provided that -CH- contained in the hydrocarbon may be replaced with -CO-, and a hydrogen atom contained in the hydrocarbon group may be replaced with a hydroxyl group) is bonded to the nitrogen atom of (meth)acrylamide. When two or more groups (the hydrocarbon groups) are substituted to the nitrogen atom of (meth)acrylamide, the groups may be bonded to each other to form a ring containing the nitrogen atom.

[0020] The hydrocarbon group (preferably an aliphatic hydrocarbon group) substituting the nitrogen atom contained in the amide bond preferably has 1 or more carbon atoms, preferably 10 or less, and more preferably 6 or less carbon atoms.

[0021] The (meth)acrylamide monomer may be one or more of the following: (meth)acrylamide, an N-1 substituted (meth)acrylamide compound, or an N,N-2 substituted (meth)acrylamide compound.

[0022] The (meth)acrylamide compound may be used alone or in combination of two or more thereof. Examples of the (meth)acrylamide compound include (meth)acrylamide; N-1-substituted (meth)acrylamide compounds such as N-isopropyl(meth)acrylamide, N-(1,1-dimethyl-3-oxobutyl)acrylamide, N-methylol(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, N-(2-hydroxymethyl)acrylamide, and N-(2-hydroxyethyl)acrylamide; N- Examples of N-2 substituted (meth)acrylamide compounds include (meth)acryloylmorpholine, N-(meth)acryloylpiperidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloyl-4-piperidone, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-methylenebis(meth)acrylamide, and N,N-dimethylaminopropyl(meth)acrylamide.

[0023] Among these, the (meth)acrylamide monomer preferably contains a monomer represented by formula (1).

[0024] [ka] [In formula (1), R 1 represents a hydrogen atom or a methyl group. 2 and R 3 each independently represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, -CH2- contained in the hydrocarbon group may be replaced by -CO- or -O-, and a hydrogen atom contained in the hydrocarbon group may be replaced by a hydroxyl group; R 2 and R 3 may be bonded to each other to form a ring containing the nitrogen atom.

[0025] R 2 and R 3The hydrocarbon group represented by R may be one or more types, and examples thereof include linear or branched saturated aliphatic hydrocarbon groups; linear or branched unsaturated aliphatic hydrocarbon groups, etc. Among these, linear or branched saturated aliphatic hydrocarbon groups are preferred, and branched saturated aliphatic hydrocarbon groups are more preferred. 2 and R 3 At least one of these is preferably a hydrogen atom.

[0026] In the units derived from the nitrogen atom-containing (meth)acrylic monomer (a2), the content of units derived from a (meth)acrylamide compound is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and preferably 100% by mass or less.

[0027] In the units derived from the nitrogen atom-containing (meth)acrylic monomer (a2), the content of units derived from the monomer represented by formula (1) is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and preferably 100% by mass or less.

[0028] In the acrylic polymer (A), the content of units derived from the nitrogen atom-containing monomer (a2) is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less.

[0029] The (meth)acrylic monomer (a3) ​​having a carboxyl group may be one or more types, and examples thereof include unsaturated monocarboxylic acids such as (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, and β-carboxyethyl (meth)acrylate.

[0030] In the acrylic polymer (A), the content of units derived from the (meth)acrylic monomer (a3) ​​having a carboxyl group is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1% by mass or more, and is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less.

[0031] In the acrylic polymer (A), the mass ratio (a2 / a3) of the units derived from the nitrogen atom-containing (meth)acrylic monomer (a2) to the units derived from the carboxyl group-containing (meth)acrylic monomer (a3) ​​is 0.1 to 5, and is preferably 0.2 to 3, more preferably 0.3 to 2.2, in order to further improve the heat resistance and moist heat resistance.

[0032] The acrylic monomer (A) may have units derived from a monomer (a4) other than the (meth)acrylic acid alkyl ester (a1), the nitrogen atom-containing (meth)acrylic monomer (a2), and the carboxyl group-containing (meth)acrylic monomer (a3).

[0033] The other monomer (a4) may be one or more types, and examples thereof include (meth)acrylic monomers having a hydroxyl group; epoxy ring-containing (meth)acrylic monomers such as glycidyl (meth)acrylate; alicyclic ring-containing (meth)acrylic monomers such as cyclohexyl (meth)acrylate; aromatic vinyl monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethylvinylbenzene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and parahydroxystyrene; heterocyclic ring-containing vinyl monomers such as N-vinylpyrrolidone, N-vinylcaprolactam, and (meth)acryloylmorpholine; and monomers having two or more vinyl groups.

[0034] Examples of the (meth)acrylic monomer having a hydroxyl group include a compound in which a hydroxyl group is bonded to the alkyl group of a (meth)acrylic acid alkyl ester; a (meth)acrylic acid polyalkylene glycol ester; and the like. Of these, a compound in which a hydroxyl group is bonded to the alkyl group of a (meth)acrylic acid alkyl ester is preferred, and a compound in which a hydroxyl group is bonded to the terminal of the alkyl group of a (meth)alkyl acid alkyl ester is more preferred.

[0035] The number of hydroxyl groups contained in the (meth)acrylic monomer having a hydroxyl group is preferably 1. Furthermore, the (meth)acrylic monomer having a hydroxyl group is preferably an acrylic monomer having a hydroxyl group.

[0036] Examples of the alkyl acrylate include the same compounds as those exemplified as the alkyl (meth)acrylate (a1).

[0037] The (meth)acrylic monomer having a hydroxyl group can be used alone or in combination of two or more kinds, and examples thereof include hydroxylalkyl (meth)acrylates such as 2-hydroxylethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; polyethylene glycol (meth)acrylate; and the like.

[0038] In the acrylic polymer (A), the content of units derived from the (meth)acrylic monomer having a hydroxyl group is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, even more preferably 0.03% by mass or more, and is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less.

[0039] In the acrylic polymer (A), the content of units derived from the other monomer (a4) is preferably 0% by mass or more, and preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0040] The weight average molecular weight of the acrylic polymer (A) is preferably 100,000 or more, more preferably 200,000 or more, and even more preferably 300,000 or more, and is preferably 1,000,000 or less, more preferably 900,000 or less, and even more preferably 800,000 or less.

[0041] In this specification, the number average molecular weight and weight average molecular weight of the acrylic polymer (A) are expressed as converted values ​​measured by gel permeation chromatography (GPC) using polystyrene as a standard sample.

[0042] In the pressure-sensitive adhesive composition of the present invention, the content of the acrylic polymer (A) in the nonvolatile matter is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less.

[0043] In this specification, the non-volatile content of the PSA composition refers to the portion excluding the solvent component that may be contained as needed in the PSA composition.

[0044] The acrylic polymer (A) can be produced by copolymerizing the (meth)acrylic acid alkyl ester (a1), a nitrogen atom-containing (meth)acrylic monomer (a2), a carboxyl group-containing (meth)acrylic monomer (a3), and other monomers (a4) used as needed in the presence of a polymerization initiator.

[0045] As the polymerization initiator, for example, one or more thermal polymerization initiators can be used, and examples thereof include peroxide initiators such as benzoyl peroxide and lauroyl peroxide, and azo initiators such as azobisisobutylnitrile.

[0046] The pressure-sensitive adhesive composition of the present invention contains a crosslinking agent (B). One or more crosslinking agents can be used, and examples thereof include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, polyvalent metal salt crosslinking agents, metal chelate crosslinking agents, ketohydrazide crosslinking agents, oxazoline crosslinking agents, carbodiimide crosslinking agents, silane crosslinking agents, and glycidyl(alkoxy)epoxysilane crosslinking agents. Among these, isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, carbodiimide crosslinking agents, and glycidyl(alkoxy)epoxysilane crosslinking agents are preferred, with isocyanate crosslinking agents, epoxy crosslinking agents, and carbodiimide crosslinking agents being more preferred, and isocyanate crosslinking agents being particularly preferred.

[0047] The content of the isocyanate crosslinking agent in the crosslinking agent (B) is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and is preferably 100% by mass or less.

[0048] The content of the crosslinking agent (B) is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the acrylic polymer (A), and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 7 parts by mass or less.

[0049] The pressure-sensitive adhesive composition of the present invention preferably contains a tackifier resin (C). The tackifier resin may be one or more types, and examples thereof include rosin-based resins such as unmodified rosin, modified rosin, and rosin derivatives; terpene-based resins such as unmodified terpene, aromatic-modified terpene, hydrogenated terpene, and terpene phenol; polymerization-based resins such as petroleum resins, coumarone-indene resins, and pure monomer petroleum resins; and condensation-based resins such as phenolic resins and xylene resins. Rosin-based resins are preferred because they have excellent compatibility with the acrylic polymer (A) and can achieve both superior adhesive strength and excellent removability.

[0050] As the unmodified rosin, one or more types may be used, and examples thereof include gum rosin, wood rosin, and tall oil rosin.

[0051] The modified rosin may be one or more types, and examples thereof include disproportionated rosin, polymerized rosin, and hydrogenated rosin.

[0052] The rosin derivative may be one or more types, and examples thereof include rosin esters obtained by esterifying the unmodified rosin or the modified rosin; unsaturated fatty acid-modified rosin obtained by modifying the unmodified rosin or the modified rosin with an unsaturated fatty acid; unsaturated fatty acid-modified rosin esters obtained by modifying the rosin ester with an unsaturated fatty acid; rosin alcohols obtained by reducing the carboxyl groups contained in the unsaturated fatty acid-modified rosin or the unsaturated fatty acid-modified rosin ester; rosin metal salts such as metal salts of unmodified rosin, modified rosin, rosin ester, unsaturated fatty acid-modified rosin, unsaturated fatty acid-modified rosin ester, or rosin alcohol; and rosin phenols.

[0053] As the unmodified terpene, one or two types can be used, and examples thereof include polymers of terpene compounds such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene.

[0054] As the aromatic modified terpene, one or more types may be used, and examples thereof include phenol-modified or styrene-modified products of the unmodified terpene.

[0055] As the terpene phenol, one or more kinds can be used, and examples thereof include resins obtained by copolymerizing terpene and phenol.

[0056] As the petroleum resin, one or more types may be used, and examples thereof include aliphatic petroleum resins, aromatic petroleum resins, aliphatic / aromatic petroleum resins, and hydrogenated products thereof.

[0057] The tackifying resin (C) may be a commercially available product. Examples of the rosin-based resin include Pine Crystal KR-85, KR-612, and KR-614 (all manufactured by Arakawa Chemical Industries, Ltd.); Longis R-CH, K-25, K-80, and N-18 (all manufactured by Arakawa Chemical Industries, Ltd.); Shiragiku Rosin, Aradigm R-95, and Pine Cristel KR-140 (all manufactured by Arakawa Chemical Industries, Ltd.); Hyperol CH (all manufactured by Arakawa Chemical Industries, Ltd.); Ester Gum AA-G, AA-L, AAV, 105, AT, Pencel GA-100, AZ, and Pine Crystal KE-359 (all manufactured by Arakawa Chemical Industries, Ltd.), Harie Star TF, S, Neotol G2, Haritack 8LJA, and ER95 (all manufactured by Harima Chemical Industries, Ltd.); Ester Gum H, HP, and Pine Crystal K E-311, PE-590 (all manufactured by Arakawa Chemical Industries, Ltd.); Pine Crystal KE-100 (all manufactured by Arakawa Chemical Industries, Ltd.); Pencel C, D-125, D-135, D-160, KK, Super Ester A-100, E-650, E-788, E-865, E-865NT (all manufactured by Arakawa Chemical Industries, Ltd.), Harie Star SK-323NS, SK-508, SK-508H, SK-816E, SK-822E, Haritack PCJ (all manufactured by Harima Chemicals Co., Ltd.); Pine Crystal KE-604, KR-120 (all manufactured by Arakawa Chemical Industries, Ltd.); Tanomaru E-100, E-200, E-200NT (all manufactured by Arakawa Chemical Industries, Ltd.); Pine Crystal KM-1500, KR-50M (all manufactured by Arakawa Chemical Industries, Ltd.). Examples of the polymeric resin include FTR0100, FTR2120, FTR2140, FTR6100, FTR6110, FTR6125, FTR7100, FTR8100, FTR8120, and FMR0150 (all manufactured by Mitsui Chemicals, Inc.).

[0058] In the pressure-sensitive adhesive composition of the present invention, the content of the tackifier resin (C) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 15 parts by mass or more, relative to 100 parts by mass of the acrylic polymer (A), and is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 60 parts by mass or less.

[0059] The pressure-sensitive adhesive composition of the present invention preferably contains a solvent (D). As the solvent (D), one or more solvents can be used, and examples thereof include aromatic hydrocarbon solvents such as toluene and xylene; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone and methyl ethyl ketone; and aliphatic hydrocarbon solvents such as hexane. Among these, it is preferable to contain an ester solvent.

[0060] The content of the ester solvent in the solvent (D) is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and is preferably 100% by mass or less.

[0061] The content of the solvent (D) in the pressure-sensitive adhesive composition is preferably 10% by mass or more, more preferably 30% by mass or more, even more preferably 50% by mass or more, and is preferably 90% by mass or less, more preferably 70% by mass or less, even more preferably 65% ​​by mass or less.

[0062] The pressure-sensitive adhesive composition of the present invention may contain, as additives, bases (such as aqueous ammonia) or acids for adjusting the pH; foaming agents; plasticizers; softeners; antioxidants; fillers such as glass or plastic fibers, balloons, beads, and metal powder; colorants such as pigments and dyes; pH adjusters; film-forming aids; leveling agents; thickeners; water repellents; antifoaming agents; acid catalysts; acid generators, etc.

[0063] The pressure-sensitive adhesive composition can be applied to a support and dried to form a pressure-sensitive adhesive layer. The support may be a base material such as a release sheet or a pressure-sensitive adhesive sheet.

[0064] The coating method may be performed using a knife coater, reverse coater, die coater, lip die coater, slot die coater, gravure coater, curtain coater, or the like.

[0065] The thickness of the adhesive layer is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and is preferably 100 μm or less, more preferably 70 μm or less, even more preferably 50 μm or less.

[0066] The thickness of the substrate is preferably 0.1 μm or more and preferably 1,000 μm or less. [Example]

[0067] The present invention will be described in more detail below with reference to examples. The weight average molecular weight (Mw) was measured under the following GPC measurement conditions.

[0068] [GPC measurement conditions] Measurement equipment: High-speed GPC equipment (Tosoh Corporation "HLC-8220GPC") Column: The following columns manufactured by Tosoh Corporation were connected in series and used. "TSKgel G5000" (7.8mm I.D. x 30cm) x 1 "TSKgel G4000" (7.8mm I.D. x 30cm) x 1 "TSKgel G3000" (7.8mm I.D. x 30cm) x 1 "TSKgel G2000" (7.8mmI.D. x 30cm) x 1 Detector: RI (differential refractometer) Column temperature: 40℃ Eluent: tetrahydrofuran (THF) Flow rate: 1.0mL / min Injection volume: 100 μL (sample concentration 0.4% by mass in tetrahydrofuran solution) Standard sample: A calibration curve was prepared using the following standard polystyrene.

[0069] (standard polystyrene) Tosoh Corporation's "TSKgel Standard Polystyrene A-500" Tosoh Corporation's "TSKgel Standard Polystyrene A-1000" Tosoh Corporation's "TSKgel Standard Polystyrene A-2500" Tosoh Corporation's "TSKgel Standard Polystyrene A-5000" "TSKgel Standard Polystyrene F-1" manufactured by Tosoh Corporation Tosoh Corporation's "TSKgel Standard Polystyrene F-2" Tosoh Corporation's "TSKgel Standard Polystyrene F-4" Tosoh Corporation's "TSKgel Standard Polystyrene F-10" Tosoh Corporation's "TSKgel Standard Polystyrene F-20" Tosoh Corporation's "TSKgel Standard Polystyrene F-40" Tosoh Corporation's "TSKgel Standard Polystyrene F-80" Tosoh Corporation's "TSKgel Standard Polystyrene F-128" Tosoh Corporation's "TSKgel Standard Polystyrene F-288" Tosoh Corporation's "TSKgel Standard Polystyrene F-550"

[0070] (Synthesis Example 1: Synthesis of acrylic polymer (A-1)) A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet, and thermometer was charged with 930 parts by weight of n-butyl acrylate, 20 parts by weight of methyl acrylate, 29 parts by weight of acrylic acid, 20 parts by weight of dimethylacrylamide, 1 part by weight of 4-hydroxybutyl acrylate, and 1,000 parts by weight of ethyl acetate. The mixture was heated to 70°C while stirring and blowing in nitrogen. After 1 hour, 10 parts by weight of a 2,2'-azobis(2-methylbutyronitrile) solution (5% solids content) previously dissolved in ethyl acetate was added. The mixture was then held at 70°C for 8 hours with stirring, after which the contents were cooled and filtered through a 200-mesh wire screen to obtain a 40% by weight solution of acrylic polymer (A-1). The weight-average molecular weight of the acrylic polymer (A-1) was 560,000.

[0071] (Synthesis Example 2: Synthesis of acrylic polymer (A-2)) A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet, and thermometer was charged with 950 parts by weight of n-butyl acrylate, 29 parts by weight of acrylic acid, 20 parts by weight of dimethylacrylamide, 1 part by weight of 4-hydroxybutyl acrylate, and 1,000 parts by weight of ethyl acetate. The mixture was heated to 70°C while stirring and blowing in nitrogen. After 1 hour, 10 parts by weight of a 2,2'-azobis(2-methylbutyronitrile) solution (5% solids content) previously dissolved in ethyl acetate was added. The mixture was then held at 70°C for 8 hours with stirring, after which the contents were cooled and filtered through a 200-mesh wire screen to obtain a 40% by weight solution of acrylic polymer (A-2). The weight-average molecular weight of the acrylic polymer (A-2) was 650,000.

[0072] (Synthesis Example 3: Synthesis of acrylic polymer (A-3)) A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet, and thermometer was charged with 930 parts by weight of n-butyl acrylate, 20 parts by weight of methyl acrylate, 19 parts by weight of acrylic acid, 30 parts by weight of dimethylacrylamide, 1 part by weight of 4-hydroxybutyl acrylate, and 1,000 parts by weight of ethyl acetate. The mixture was heated to 70°C while stirring and blowing in nitrogen. After 1 hour, 10 parts by weight of a 2,2'-azobis(2-methylbutyronitrile) solution (5% solids content) previously dissolved in ethyl acetate was added. The mixture was then held at 70°C for 8 hours with stirring, after which the contents were cooled and filtered through a 200-mesh wire screen to obtain a 40% by weight solution of acrylic polymer (A-3). The weight-average molecular weight of the acrylic polymer (A-3) was 600,000.

[0073] (Synthesis Example 4: Synthesis of acrylic polymer (A-4)) A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet, and thermometer was charged with 910 parts by weight of n-butyl acrylate, 20 parts by weight of methyl acrylate, 19 parts by weight of acrylic acid, 50 parts by weight of dimethylacrylamide, 1 part by weight of 4-hydroxybutyl acrylate, and 1,000 parts by weight of ethyl acetate. The mixture was heated to 70°C while stirring and blowing in nitrogen. After 1 hour, 10 parts by weight of a 2,2'-azobis(2-methylbutyronitrile) solution (5% solids content) previously dissolved in ethyl acetate was added. The mixture was then held at 70°C for 8 hours with stirring, after which the contents were cooled and filtered through a 200-mesh wire screen to obtain a 40% by weight solution of acrylic polymer (A-4). The weight-average molecular weight of the acrylic polymer (A-4) was 600,000.

[0074] (Synthesis Example 5: Synthesis of acrylic polymer (A-5)) A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet, and thermometer was charged with 920 parts by weight of n-butyl acrylate, 20 parts by weight of methyl acrylate, 29 parts by weight of acrylic acid, 30 parts by weight of diacetone acrylamide, 1 part by weight of hydroxyethyl acrylate, and 1,000 parts by weight of ethyl acetate. The mixture was heated to 70°C while stirring and blowing in nitrogen. After 1 hour, 10 parts by weight of a 2,2'-azobis(2-methylbutyronitrile) solution (5% solids content) previously dissolved in ethyl acetate was added. The mixture was then held at 70°C for 8 hours with stirring, after which the contents were cooled and filtered through a 200-mesh wire screen to obtain a 40% by weight solution of acrylic polymer (A-5). The weight-average molecular weight of the acrylic polymer (A-5) was 550,000.

[0075] (Synthesis Example 6: Synthesis of acrylic polymer (A-6)) A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet, and thermometer was charged with 920 parts by weight of n-butyl acrylate, 20 parts by weight of methyl acrylate, 29 parts by weight of acrylic acid, 30 parts by weight of 2-(dimethylamino)ethyl methacrylate, 1 part by weight of hydroxyethyl acrylate, and 1,000 parts by weight of ethyl acetate. The mixture was heated to 70°C while stirring and blowing in nitrogen. After 1 hour, 10 parts by weight of a 2,2'-azobis(2-methylbutyronitrile) solution (5% solids content) previously dissolved in ethyl acetate was added. The mixture was then held at 70°C for 8 hours with stirring, after which the contents were cooled and filtered through a 200-mesh wire screen to obtain a 40% by weight solution of acrylic polymer (A-6). The weight-average molecular weight of the acrylic polymer (A-6) was 550,000.

[0076] (Synthesis Example 7: Synthesis of acrylic polymer (A-7)) A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet, and thermometer was charged with 630 parts by weight of n-butyl acrylate, 300 parts by weight of 2-ethylhexyl acrylate, 20 parts by weight of methyl acrylate, 29 parts by weight of acrylic acid, 20 parts by weight of dimethylacrylamide, 1 part by weight of 4-hydroxybutyl acrylate, and 1,000 parts by weight of ethyl acetate. The mixture was heated to 70°C while stirring and blowing in nitrogen. After 1 hour, 10 parts by weight of a 2,2'-azobis(2-methylbutyronitrile) solution (5% solids content) previously dissolved in ethyl acetate was added. The mixture was then held at 70°C for 8 hours with stirring, after which the contents were cooled and filtered through a 200-mesh wire screen to obtain a 40% by weight solution of acrylic polymer (A-7). The weight-average molecular weight of the acrylic polymer (A-7) was 650,000.

[0077] (Synthesis Example 8: Synthesis of acrylic polymer (RA-1)) A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet, and thermometer was charged with 950 parts by weight of n-butyl acrylate, 20 parts by weight of methyl acrylate, 29 parts by weight of acrylic acid, 1 part by weight of 4-hydroxybutyl acrylate, and 1,000 parts by weight of ethyl acetate. The mixture was heated to 70°C while stirring and blowing in nitrogen. After 1 hour, 10 parts by weight of a 2,2'-azobis(2-methylbutyronitrile) solution (5% solids content) previously dissolved in ethyl acetate was added. The mixture was then held at 70°C for 8 hours with stirring, after which the contents were cooled and filtered through a 200-mesh wire screen to obtain a 40% by weight solution of acrylic polymer (RA-1). The weight-average molecular weight of the acrylic polymer (RA-1) was 500,000.

[0078] (Synthesis Example 9: Synthesis of acrylic polymer (RA-2)) A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet, and thermometer was charged with 945 parts by weight of n-butyl acrylate, 20 parts by weight of methyl acrylate, 29 parts by weight of acrylic acid, 5 parts by weight of dimethylacrylamide, 1 part by weight of 4-hydroxybutyl acrylate, and 1,000 parts by weight of ethyl acetate. The mixture was heated to 70°C while stirring and blowing in nitrogen. After 1 hour, 10 parts by weight of a 2,2'-azobis(2-methylbutyronitrile) solution (5% solids content) previously dissolved in ethyl acetate was added. The mixture was then held at 70°C for 8 hours with stirring, after which the contents were cooled and filtered through a 200-mesh wire screen to obtain a 40% by weight solution of acrylic polymer (RA-2). The weight-average molecular weight of the acrylic polymer (RA-2) was 550,000.

[0079] (Synthesis Example 10: Synthesis of acrylic polymer (RA-3)) A reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet, and thermometer was charged with 814 parts by weight of n-butyl acrylate, 20 parts by weight of methyl acrylate, 15 parts by weight of acrylic acid, 150 parts by weight of dimethylacrylamide, 1 part by weight of 4-hydroxybutyl acrylate, and 1,000 parts by weight of ethyl acetate. The mixture was heated to 70°C while stirring and blowing in nitrogen. After 1 hour, 10 parts by weight of a 2,2'-azobis(2-methylbutyronitrile) solution (5% solids content) previously dissolved in ethyl acetate was added. The mixture was then held at 70°C for 8 hours with stirring, after which the contents were cooled and filtered through a 200-mesh wire screen to obtain a 40% by weight solution of acrylic polymer (RA-3). The weight-average molecular weight of the acrylic polymer (RA-3) was 600,000.

[0080] [Table 1]

[0081] [Table 2]

[0082] The abbreviations in the table are as follows: BA: n-butyl acrylate 2EHA: 2-ethylhexyl acrylate MA: methyl acrylate DMAA: Dimethylacrylamide DAAM: Diacetone acrylamide DM: 2-(dimethylamino)ethyl methacrylate AA: acrylic acid 4HBA: 4-hydroxybutyl acrylate HEA: Hydroxyethyl acrylate

[0083] (Example 1: Preparation of adhesive composition (1)) A tackifier resin (C-1; "Super Ester A-100" manufactured by Arakawa Chemical Industries, Ltd.) was added to 100 parts by mass of the solution of the acrylic polymer (A-1) obtained in Synthesis Example 1. 6Part by weight, tackifying resin (C-2; “Pensel D-135” manufactured by Arakawa Chemical Co., Ltd.) 2 Parts by mass, crosslinking agent (B-1; "Finetack D-40" manufactured by DIC Corporation, polyisocyanate-based crosslinking agent, solid content 40% by mass) 1. 5 The mass parts were stirred and mixed uniformly to obtain an acrylic pressure-sensitive adhesive composition (1).

[0084] (Examples 2 to 14: Preparation of Pressure-Sensitive Adhesive Compositions (2) to (14)) Acrylic pressure-sensitive adhesive compositions (2) to (14) were obtained in the same manner as in Example 1, except that the type of acrylic polymer (A-1) and the amount of crosslinking agent (B-1) were changed as shown in Tables 3 and 4.

[0085] (Comparative Examples 1 to 6: Preparation of Pressure-Sensitive Adhesive Compositions (R1) to (R6)) Acrylic pressure-sensitive adhesive compositions (R1) to (R6) were obtained in the same manner as in Example 1, except that the type of acrylic polymer (A-1) and the amount of crosslinking agent (B-1) were changed as shown in Table 5.

[0086] [Preparation of double-sided adhesive tape] The adhesive compositions obtained in the Examples and Comparative Examples were applied to the surface of a 25 μm thick polyethylene terephthalate film (release PET25) with a release-treated surface so that the film thickness after solvent drying would be 25 μm.The solvent was evaporated in an 80°C dryer for 3 minutes, and then a soft PVC substrate was attached.

[0087] [Method for measuring adhesive strength] A 25μm thick PET film was applied to one side of the double-sided adhesive tape prepared using the method described above, and the resulting test specimen was cut to a width of 25mm. The adherends were stainless steel (BASUS), ABS, and PP (polypropylene) plates, and the tape was attached to the adherends using a 2kg roll, rolling it back and forth once. One hour after application, the 180° peel strength was measured in an atmosphere of 23°C and 50% RH, and this was used as the adhesive strength.

[0088] [Method for measuring adhesive strength after humidity and heat exposure] Similar to the adhesive strength measurement method described above, a test piece was attached to an adherend. It was then left in an atmosphere of 60°C and 90% RH for 250 hours and then removed. After leaving it in an atmosphere of 23°C and 50% RH for 30 minutes, the 180-degree peel strength was measured at a peel rate of 300 mm / min, and this was taken as the adhesive strength after heat resistance.

[0089] [Method for measuring adhesive strength after heat resistance] In the same manner as in the adhesive strength measurement method described above, a test piece was attached to an adherend. It was then left in an 80°C atmosphere for 250 hours and then removed. After leaving it in an atmosphere of 23°C and 50% RH for 30 minutes, the 180° peel strength was measured at a peel rate of 300 mm / min, and this was taken as the adhesive strength after heat resistance.

[0090] [Method for evaluating removability] Similar to the adhesive strength measurement method described above, a test piece was attached to an adherend. It was then left for 250 hours in an atmosphere of 60°C and 90% RH or 80°C, and then removed. After leaving it in an atmosphere of 23°C and 50% RH for 30 minutes, the test piece was peeled off and the presence or absence of adhesive residue on the peeled adherend surface was checked to evaluate removability. 〇: No glue residue △: There is a slight amount of glue remaining ×: There is adhesive residue

[0091] The evaluation results of Examples 1 to 14 and Comparative Examples 1 to 6 are shown in Tables 3 to 5.

[0092] [Table 3]

[0093] [Table 4]

[0094] [Table 5]

[0095] It was confirmed that the pressure-sensitive adhesive compositions of the present invention in Examples 1 to 14 provided pressure-sensitive adhesive layers excellent in initial adhesive strength, heat resistance, moist heat resistance, and removability.

[0096] On the other hand, Comparative Examples 1 and 2 are examples in which the acrylic polymer (A) does not have units derived from the nitrogen-containing (meth)acrylic monomer (a2), and it was confirmed that the removability was insufficient.

[0097] Comparative Examples 3 and 4 are examples in which the mass ratio (a2 / a3) in the acrylic polymer (A) is less than 0.1, which is the lower limit of the present invention, and it was confirmed that the removability after heat resistance was insufficient.

[0098] Comparative Examples 5 and 6 are examples in which the mass ratio (a2 / a3) in the acrylic polymer (A) is greater than 5, which is the upper limit of the present invention, but it was confirmed that the initial adhesive strength was insufficient.

Claims

1. A pressure-sensitive adhesive composition comprising an acrylic polymer (A), a crosslinking agent (B), and a tackifier resin (C), wherein the acrylic polymer (A) has units derived from a (meth)acrylic acid alkyl ester (a1), a nitrogen-containing (meth)acrylic monomer (a2), and a carboxyl-containing (meth)acrylic monomer (a3), the content of the tackifier resin (C) being 10 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the acrylic polymer (A), and the mass ratio (a2 / a3) of the units derived from the nitrogen-containing (meth)acrylic monomer (a2) to the units derived from the carboxyl-containing (meth)acrylic monomer (a3) ​​is 0.3 to 5.

2. The nitrogen atom-containing (meth)acrylic monomer (a2) is a (meth)acrylamide compound. The pressure-sensitive adhesive composition according to claim 1, which comprises a material.

3. 3. The pressure-sensitive adhesive composition according to claim 1, wherein the nitrogen atom-containing (meth)acrylic monomer (a2) contains a monomer represented by formula (1): 【Chemistry 1】 [In formula (1), R １ represents a hydrogen atom or a methyl group. ２ and R ３ each independently represents a hydrocarbon group having 1 to 20 carbon atoms, and —CH ２ - may be replaced by -CO-, and a hydrogen atom contained in the hydrocarbon group may be replaced by a hydroxyl group.]

4. The pressure-sensitive adhesive composition according to any one of claims 1 to 3, further comprising a solvent (D).

5. A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 4.

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