Pressure-sensitive adhesive, pressure-sensitive adhesive sheet, laminate, and display including the laminate

Abstract

To provide a pressure-sensitive adhesive which hardly causes floating or peeling from an adherend even after being exposed to a high-temperature environment and a high-temperature and high-humidity environment, a pressure-sensitive adhesive sheet using the same, a laminate, and a display including the laminate.SOLUTION: The pressure-sensitive adhesive comprises a curing agent (B) and an acrylic polymer (A) which is a copolymer of a monomer mixture comprising 2-octyl (meth) acrylate, a nitrogen-containing monomer, a hydroxy group-containing monomer, and a (meth) acrylate monomer whose homopolymer has a glass transition temperature of 0 °C or higher, and optionally comprising a carboxy group-containing monomer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, a laminate, and a display including the laminate. [Background technology]

[0002] Because of their ease of handling, adhesive sheets having adhesive layers formed from adhesives are used in a wide range of fields, including label applications and medical applications. They are also widely used in various optical displays, such as liquid crystal displays (LCDs) and organic electroluminescence displays (OLEDs). Optical displays are also used as input devices, such as touch panels, in addition to their use as display devices. A cover panel is attached to the touch panel for surface protection. The components constituting these optical displays are typically bonded together via an adhesive layer. Among these, liquid crystal displays are also used in in-vehicle devices such as car navigation systems, and are required to be durable enough to withstand harsh in-vehicle environments, such as high temperatures and humidity. Liquid crystal displays also use polarizing plates and retardation plates with various optical functions, which are attached to substrates, such as glass or transparent plastic liquid crystal cells, via adhesives.

[0003] The polarizing plate is generally a laminate in which a polyvinyl alcohol film is sandwiched between a triacetyl cellulose film or a cycloolefin film. These films have different mechanical properties and therefore different dimensional changes when heated. Therefore, when placed in a high-temperature atmosphere, the laminate often warps.

[0004] For example, if a liquid crystal cell component consisting of a polarizing plate / adhesive layer / glass (the glass is the surface component of the liquid crystal cell) is left in a high-temperature atmosphere, problems such as warping due to the dimensional change rate between the components of the polarizing plate, the formation of bubbles (foaming) at the bonding interface between the adhesive layer and the glass, or the polarizing plate lifting off the glass may occur. Furthermore, warping can cause uneven stress distribution in the liquid crystal cell component, which can lead to stress concentration at the peripheral edges of the liquid crystal cell component, resulting in a problem known as "light leakage," in which light leaks from the four corners or peripheral edges of the liquid crystal cell component. The above problems also occur in high-temperature, high-humidity atmospheres.

[0005] To solve these problems, Patent Document 1 discloses a technology for improving stress relaxation properties and preventing light leakage by using an acrylic copolymer using an aromatic ring-containing monomer. However, the pressure-sensitive adhesive using the aromatic ring-containing monomer disclosed in Patent Document 1 has problems such as white spots occurring in light leakage evaluations and poor optical properties.

[0006] Patent Document 2 discloses a technique for improving durability and adhesive properties under heated or humid conditions by using a block polymer containing two or more monomers. However, the adhesive described in Patent Document 2 has a problem in that its transmittance decreases under heated or humid conditions.

[0007] Patent Document 3 discloses a technology for suppressing peeling and lifting in high-temperature, high-humidity environments by constructing an interpenetrating network structure in the cured state using an acrylic copolymer containing hydroxyl groups and alkylene oxide groups and a polyfunctional isocyanate curing agent. However, the pressure-sensitive adhesive described in Patent Document 3 has the problem that when left in a high-temperature, high-humidity environment for a long period of time, the alkylene oxide groups decompose, causing peeling and lifting.

[0008] Furthermore, Patent Document 4 discloses a technology for preventing lifting and peeling of an adhesive sheet when placed in a high-temperature, high-humidity environment for a long period of time by using an acrylic copolymer containing hydroxyl and carboxyl groups, a mercapto group-containing silane compound, and an alcohol. However, because the adhesive described in Patent Document 4 uses a highly volatile silane compound, when the adhesive is coated and dried, the silane compound volatilizes, and a sufficient amount of the silane compound does not remain in the adhesive layer after coating, resulting in the problem of lifting and peeling. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-169329 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-82772 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-55299 [Patent Document 4] Japanese Patent Application Laid-Open No. 2004-59711 Summary of the Invention [Problem to be solved by the invention]

[0010] The problem to be solved by the present invention is to provide a pressure-sensitive adhesive that is resistant to lifting or peeling from an adherend even after exposure to a high-temperature environment and a high-temperature, high-humidity environment, a pressure-sensitive adhesive sheet using the same, a laminate, and a display including the laminate. [Means for solving the problem]

[0011] As a result of extensive research, the present inventors have found that the problems of the present invention can be solved by the following aspects, and have thus completed the present invention. That is, the present invention provides an acrylic polymer (A) which is a copolymer of a monomer mixture containing all of the following monomers (a1) to (a4) and optionally containing the following monomer (a5), and a curing agent (B): The adhesive comprises 0.05% by mass or more and 5% by mass or less (excluding 5% by mass) of a monomer (a2) based on 100% by mass of a monomer mixture. (a1) 2-octyl (meth)acrylate (a2) selected from the group consisting of N-vinyl lactams, amino group-containing (meth)acrylate monomers, (meth)acrylamides, N-vinylcarboxylic acid amides, and (meth)acryloylmorpholine (a3) Hydroxy group-containing monomer (a4) (meth)acrylate monomers having a homopolymer glass transition temperature of 0°C or higher (excluding nitrogen-containing monomers (a2), monomers having a hydroxy group (a3), and monomers having a carboxy group (a5)). (a5) Carboxy group-containing monomer [Effects of the Invention]

[0012] The present invention makes it possible to provide a pressure-sensitive adhesive that is resistant to lifting or peeling from an adherend even after exposure to a high-temperature environment and a high-temperature, high-humidity environment, a pressure-sensitive adhesive sheet using the same, a laminate, and a display including the laminate. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view partially illustrating a laminate of the present invention. [Figure 2] FIG. 1 is a schematic cross-sectional view partially illustrating a display, which is an example of the use of the laminate of the present invention. [Figure 3] 1 is a schematic cross-sectional view partially illustrating a pressure-sensitive adhesive sheet of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The pressure-sensitive adhesive, pressure-sensitive adhesive sheet, laminate, and display including the laminate according to the present disclosure have the following configurations [1] to

[14] .

[0015] [1] A pressure-sensitive adhesive comprising an acrylic polymer (A) which is a copolymer of a monomer mixture containing all of the following monomers (a1) to (a4) and optionally containing the following monomer (a5), and a curing agent (B), wherein the monomer mixture contains 0.05% by mass or more and 5% by mass or less (excluding 5% by mass) of the monomer (a2). (a1) 2-octyl (meth)acrylate (a2) a nitrogen-containing monomer selected from the group consisting of N-vinyl lactams, amino group-containing (meth)acrylate monomers, N-vinyl carboxylic acid amides, (meth)acrylamides, and (meth)acryloylmorpholine; (a3) Hydroxy group-containing monomer (a4) (meth)acrylate monomers having a homopolymer glass transition temperature of 0°C or higher (excluding nitrogen-containing monomers (a2), monomers having a hydroxy group (a3), and monomers having a carboxy group (a5)). (a5) Carboxy group-containing monomer [2] In 100% by mass of the monomer mixture, Monomer (a1) is 30% by mass or more and less than 99.5% by mass, The adhesive according to [1], comprising 0.1% by mass or more and less than 70% by mass of the monomer (a4). [3] The adhesive of [1] or [2], wherein the monomer (a2) comprises at least one selected from the group consisting of (meth)acrylamide, N-[3-(dimethylamino)propyl](meth)acrylamide, N-methyl(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, 2-(dimethylamino)ethyl (meth)acrylate, 2-(diethylamino)ethyl (meth)acrylate, 3-(dimethylamino)propyl (meth)acrylate, N-isopropyl(meth)acrylamide, N-vinylcaprolactam, N-vinylpyrrolidone, N-vinylformamide, N-hydroxyethyl(meth)acrylamide, and (meth)acryloylmorpholine. [4] The pressure-sensitive adhesive according to any one of [1] to [3], wherein the monomer (a2) is contained in an amount of 0.1% by mass or more and 3% by mass or less based on 100% by mass of the monomer mixture. [5] The pressure-sensitive adhesive according to any one of [1] to [4], wherein the content of the monomer (a5) in 100% by mass of the monomer mixture is less than 0.5% by mass. [6] The pressure-sensitive adhesive according to any one of [1] to [5], wherein the monomer (a3) ​​is contained in an amount of 0.1% by mass or more and 30% by mass or less based on 100% by mass of the monomer mixture. [7] The adhesive according to any one of [1] to [6], characterized in that the biomass ratio is 30% or more. [8] The pressure-sensitive adhesive according to any one of [1] to [7], further comprising a silane coupling agent (C). [9] The pressure-sensitive adhesive according to any one of [1] to [8], which has a gel fraction of 30% by mass or more.

[10] The pressure-sensitive adhesive according to any one of [1] to [9], further comprising 50 parts by mass or less of a tackifier resin (D) per 100 parts by mass of the acrylic polymer (A).

[11] A pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive according to any one of [1] to

[10] .

[12] A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer according to

[11] and a release film.

[13] A laminate comprising the pressure-sensitive adhesive layer according to

[11] and a substrate.

[14] A display comprising the laminate according to

[13] , a polarizing plate, and an optical element.

[0016] The composition, pressure-sensitive adhesive sheet, laminate and display of the present invention will be described below, but the present invention is not limited thereto. In this specification, the term "(meth)acrylate" includes acrylate and methacrylate, and the term "(meth)acryloxy group" includes acryloxy group and methacryloxy group. The term "monomer" refers to a monomer having an ethylenically unsaturated group. Furthermore, in this specification, a numerical range specified using "to" includes the numerical values ​​before and after "to" as the range of the lower and upper limits. Furthermore, "film" and "sheet" are not distinguished by thickness. In other words, in this specification, "sheet" includes thin film-like products, and "film" in this specification includes thick sheet-like products. Furthermore, the term "adherend" refers to a counterpart to which the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is attached. Unless otherwise noted, the various components appearing in this specification may be used independently either alone or in combination of two or more.

[0017] <Adhesive> The pressure-sensitive adhesive of the present invention contains an acrylic polymer (A) and a curing agent (B), and may also contain a silane coupling agent (C) and a tackifying resin (D) as needed.

[0018] <Acrylic polymer (A)> The acrylic polymer (A) is a copolymer of a monomer mixture, and contains all of the following monomers (a1) to (a4), and optionally contains the following monomer (a5): The monomer mixture is characterized in that it contains 0.05% by mass or more and 5% by mass or less (but excluding 5% by mass) of the monomer (a2) based on 100% by mass of the monomer mixture. (a1) 2-octyl (meth)acrylate (a2) selected from the group consisting of N-vinyl lactams, amino group-containing (meth)acrylate monomers, N-vinyl carboxylic acid amides, (meth)acrylamides, and (meth)acryloylmorpholine (a3) Hydroxy group-containing monomer (a4) (meth)acrylate monomers having a homopolymer glass transition temperature of 0°C or higher (excluding nitrogen-containing monomers (a2), monomers having a hydroxy group (a3), and monomers having a carboxy group (a5)). (a5) Carboxy group-containing monomer

[0019] [Monomer (a1)] Monomer (a1) is 2-octyl(meth)acrylate represented by the following formula (1): Monomer (a1) is a biomass monomer. (Formula 1) TIFF2026012075000002.tif53141(R1=H, CH3)

[0020] The content of monomer (a1) is preferably 30% by mass or more and less than 99.5% by mass, more preferably 40% by mass or more and less than 90% by mass, and most preferably 60% by mass or more and less than 80% by mass, based on 100% by mass of the monomer mixture. When the content of (a1) is within the above range, adhesion can be ensured while achieving both durability when exposed to a high-temperature atmosphere and durability when exposed to a high-temperature, high-humidity atmosphere.

[0021] [Monomer (a2)] Monomer (a2) is a monomer containing a nitrogen atom in the monomer skeleton and is selected from the group consisting of N-vinyl lactams, amino-group-containing (meth)acrylate monomers, N-vinyl carboxylic acid amides, (meth)acrylamides, and (meth)acryloylmorpholine. It accelerates the curing reaction between the acrylic polymer (A) and the curing agent (B), which will be described later. It also imparts cohesive strength through hydrogen bonding. Furthermore, because monomer (a2) is hydrophilic, copolymerization with the hydrophobic monomer (a1) results in phase separation, creating a sea-island structure, which is expected to improve resistance to aging under high humidity and heat. Even if a compound has a hydroxy group and / or a carboxy group, if it contains a nitrogen atom it is classified as a nitrogen atom-containing monomer (a2).

[0022] Examples of N-vinyl lactams include N-methylvinylpyrrolidone, N-vinylcaprolactam, N-vinylpyrrolidone, N-vinyl-2-pyrrolidone, N-(meth)acryloylpyrrolidone, and vinylmorpholine. Examples of amino group-containing (meth)acrylate monomers include 2-(dimethylamino)methyl (meth)acrylate, 2-(diethylamino)ethyl (meth)acrylate, 3-(dimethylamino)propyl (meth)acrylate, and 2-(dimethylamino)dimethylaminoethyl (meth)acrylate. Examples of N-vinylcarboxylic acid amides include N-vinylformamide and N-vinylacetamide. (Meth)acrylamides include (meth)acrylamide and substituted (meth)acrylamides; etc. Substituted (meth)acrylamides include: N-alkyl(meth)acrylamides such as N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-isopropyl(meth)acrylamide, Nn-butyl(meth)acrylamide, diacetone(meth)acrylamide, and N,N'-methylenebis(meth)acrylamide; N,N-dialkyl(meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-ethylmethyl(meth)acrylamide, and N,N-diallyl(meth)acrylamide; aminoalkyl(meth)acrylamides such as N-[3-(dimethylamino)propyl](meth)acrylamide, aminomethyl(meth)acrylamide, and aminoethyl(meth)acrylamide; hydroxyalkyl(meth)acrylamides such as N-hydroxymethyl(meth)acrylamide and N-hydroxyethyl(meth)acrylamide; alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide and N-(n-butoxymethyl)(meth)acrylamide; Examples include: Among these, from the viewpoint of ease of handling, it is preferred that the monomer (a2) contains at least one selected from the group consisting of (meth)acrylamide, N-[3-(dimethylamino)propyl](meth)acrylamide, N-methyl(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, 2-(dimethylamino)ethyl methacrylate, 2-(dimethylamino)ethyl (meth)acrylate, 2-(diethylamino)ethyl (meth)acrylate, 3-(dimethylamino)propyl (meth)acrylate, N-isopropyl(meth)acrylamide, N-vinylcaprolactam, N-vinylpyrrolidone, N-vinylformamide, N-hydroxyethyl(meth)acrylamide, and (meth)acryloylmorpholine.

[0023] The content of monomer (a2) is from 0.05 to 5% by mass (excluding 5% by mass) in 100% by mass of the monomer mixture, preferably from 0.1 to 3% by mass, and more preferably from 0.3 to 2% by mass in 100% by mass of the monomer mixture. When the content of (a2) is within the above range, the cohesive strength of the adhesive is improved, and a tough adhesive layer can be obtained.

[0024] [Monomer (a3)] The monomer (a3) ​​is a monomer having a hydroxy group.

[0025] The monomer having a hydroxy group is not limited as long as it does not have a nitrogen atom in the molecule and has a hydroxy group, and specific examples include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Of these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred from the viewpoints of adhesive strength and resistance to moist heat.

[0026] The content of (a3) ​​is preferably 0.1% by mass or more and 30% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, and most preferably 0.1% by mass or more and 5% by mass or less, based on 100% by mass of the monomer mixture. By setting the content of (a3) ​​to 0.1% by mass or more and 30% by mass or less, durability when exposed to a high-temperature, high-humidity atmosphere is more easily achieved.

[0027] [Monomer (a4)] Monomer (a4) is a (meth)acrylate monomer having a homopolymer glass transition temperature of 0° C. or higher. However, even if the (meth)acrylate monomer has a homopolymer glass transition temperature of 0° C. or higher, it does not include those containing a nitrogen atom in the monomer skeleton and those having a carboxy group or a hydroxy group. The glass transition temperature (°C) of a homopolymer can be obtained from information from the vendor of the various monomers or from the values ​​listed in "Polymer Handbook 3rd Edition" (A Wiley-Interscience Publication, 1989).

[0028] Examples of monomer (a4) include methyl (meth)acrylate, ethyl methacrylate, ter-butyl methacrylate, sec-butyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, isopropyl methacrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, and phenyl (meth)acrylate. From the viewpoint of improving cohesive strength and adhesive strength, the monomer (a4) is preferably selected from the group consisting of methyl (meth)acrylate, ethyl methacrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, and phenyl (meth)acrylate. Methyl (meth)acrylate is more preferably used.

[0029] The content of monomer (a4) is preferably 0.1% by mass or more and less than 70% by mass in 100% by mass of the monomer mixture. By including 0.1% by mass or more and less than 70% by mass, cohesive strength and adhesive strength can be ensured. It is more preferably 5% by mass or more and less than 50% by mass, and even more preferably 3% by mass or more and less than 30% by mass.

[0030] [Monomer (a5)] The monomer mixture constituting the acrylic polymer (A) may optionally contain a monomer (a5) having a carboxy group.

[0031] Monomer (a5) is not limited as long as it does not have a nitrogen atom in the molecule and has a carboxy group, and specific examples include (meth)acrylic acid, p-carboxybenzyl acrylate, β-carboxyethyl acrylate, maleic acid, monoethyl maleate, itaconic acid, citraconic acid, and fumaric acid. Of these, (meth)acrylic acid is preferred from the viewpoint of adhesive strength, and acrylic acid is more preferred.

[0032] The content of monomer (a5) is preferably less than 0.5 mass% in 100 mass% of the monomer mixture in order to prevent corrosion of the adherend by acid, and it is more preferable that no monomer (a5) is contained in order to prevent corrosion of the adherend by acid.

[0033] [Other monomers] The monomer mixture constituting the acrylic polymer (A) may contain other monomers in addition to the monomers (a1) to (a5), and the other monomers are not particularly limited.

[0034] When other monomers are contained, the content is preferably 40% by mass or less relative to 100% by mass of the monomer mixture. By setting the content within this range, warping of the laminate when placed in a high-temperature atmosphere can be suppressed. To suppress warping of the laminate, the content is preferably 20% by mass or less, and more preferably 10% by mass or less.

[0035] (Production of acrylic polymer (A)) The acrylic polymer (A) can be produced by polymerizing the above-mentioned monomer mixture. The polymerization can be carried out by known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization, but solution polymerization is preferred. Solvents used in solution polymerization are preferably, for example, acetone, methyl acetate, ethyl acetate, toluene, xylene, anisole, methyl ethyl ketone, and cyclohexanone. The polymerization temperature is preferably a boiling point reaction at 60 to 120°C. The polymerization time is preferably about 5 to 12 hours.

[0036] The polymerization initiator used for the polymerization is preferably a radical polymerization initiator, and the radical polymerization initiator is generally a peroxide or an azo compound. Examples of peroxides include dialkyl peroxides such as di-t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, and 2,5-di(t-butylperoxy)hexyne-3; Peroxyesters such as t-butyl peroxybenzoate, t-butyl peroxyacetate, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, and methylcyclohexanone peroxide; Peroxyketals such as 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, and n-butyl-4,4-bis(t-butylperoxy)valerate; Hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, and 2,5-dimethylcyclohexane-2,5-dihydroperoxide; diacyl peroxides such as benzoyl peroxide, decanoyl peroxide, lauroyl peroxide, and 2,4-dichlorobenzoyl peroxide; Examples include peroxydicarbonates such as bis(t-butylcyclohexyl) peroxydicarbonate.

[0037] Examples of the azo compound include 2,2'-azobisbutyronitrile such as 2,2'-azobisisobutyronitrile (abbreviation: AIBN) and 2,2'-azobis(2-methylbutyronitrile); 2,2'-azobisvaleronitrile such as 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) and 2,2'-azobis(2,4-dimethylvaleronitrile); 2,2'-azobispropionitriles such as 2,2'-azobis(2-hydroxymethylpropionitrile); Examples include 1,1'-azobis-1-alkanenitriles such as 1,1'-azobis(cyclohexane-1-carbonitrile).

[0038] The polymerization initiator is preferably used in an amount of 0.01 to 10 parts by mass, more preferably 0.1 to 2 parts by mass, based on 100 parts by mass of the monomer mixture.

[0039] (Weight average molecular weight (Mw)) The weight-average molecular weight of the acrylic polymer (A) is not particularly limited, but is preferably not more than 2.5 million, more preferably not more than 1.8 million. The weight-average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0040] <Curing agent (B)> The curing agent (B) is not particularly limited as long as it provides a crosslinked structure to the pressure-sensitive adhesive. The addition of a curing agent improves the cohesive strength of the pressure-sensitive adhesive layer, and improves adhesion, heat resistance, and moist heat resistance.

[0041] The curing agent (B) preferably contains at least one of an isocyanate-based curing agent, an epoxy-based curing agent, and a metal chelate-based curing agent, since it can moderately increase the cohesive strength of the adhesive and is less likely to adversely affect other physical properties. As long as it contains at least one of an isocyanate-based curing agent, an epoxy-based curing agent, and a metal chelate-based curing agent, known curing agents other than an isocyanate-based curing agent, an epoxy-based curing agent, and an aluminum chelate curing agent may be used in combination.

[0042] The isocyanate curing agent is an isocyanate compound having two or more isocyanate groups. Examples of the isocyanate compound include aromatic polyisocyanates, aliphatic polyisocyanates, araliphatic polyisocyanates, alicyclic polyisocyanates, and their biuret forms, nurate forms, and adduct forms, and from the viewpoint of yellowing resistance, aliphatic polyisocyanates, alicyclic polyisocyanates, and their biuret forms, nurate forms, and adduct forms are more preferred.

[0043] Examples of aromatic polyisocyanates include 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, and 4,4',4"-triphenylmethane triisocyanate.

[0044] Examples of aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (also known as HMDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0045] Examples of the aromatic aliphatic polyisocyanate include ω,ω'-diisocyanate-1,3-dimethylbenzene, ω,ω'-diisocyanate-1,4-dimethylbenzene, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, and 1,3-tetramethylxylylene diisocyanate.

[0046] Examples of alicyclic polyisocyanates include 3-isocyanatemethyl-3,5,5-trimethylcyclohexyl isocyanate (also known as IPDI, isophorone diisocyanate), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,4-bis(isocyanatemethyl)cyclohexane.

[0047] The biuret compound is a self-condensation product having a biuret bond formed by self-condensation of an isocyanate monomer, such as a biuret compound of hexamethylene diisocyanate.

[0048] The nurate derivative is a trimer of an isocyanate monomer, such as a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, or a trimer of tolylene diisocyanate.

[0049] The adduct is a bifunctional or higher isocyanate compound obtained by reacting an isocyanate monomer with a bifunctional or higher low-molecular-weight active hydrogen-containing compound. Examples of the adduct include a compound obtained by reacting trimethylolpropane with hexamethylene diisocyanate, a compound obtained by reacting trimethylolpropane with tolylene diisocyanate, a compound obtained by reacting trimethylolpropane with xylylene diisocyanate, a compound obtained by reacting trimethylolpropane with isophorone diisocyanate, and a compound obtained by reacting 1,6-hexanediol with hexamethylene diisocyanate.

[0050] From the viewpoint of forming a sufficient crosslinked structure, the isocyanate compound is preferably a trifunctional isocyanate compound. The isocyanate compound is more preferably an adduct or nurate, which is a reaction product of an isocyanate monomer and a trifunctional low-molecular-weight active hydrogen-containing compound. The isocyanate compound is preferably a trimethylolpropane adduct of hexamethylene diisocyanate, a nurate of hexamethylene diisocyanate, a trimethylolpropane adduct of tolylene diisocyanate, a nurate of tolylene diisocyanate, a trimethylolpropane adduct of isophorone diisocyanate, or a nurate of isophorone diisocyanate, and more preferably a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of tolylene diisocyanate, or a trimethylolpropane adduct of isophorone diisocyanate.

[0051] Examples of epoxy curing agents include glycerin diglycidyl ether, 1,6-hexanediol diglycidyl ether, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidylaminophenylmethane.

[0052] Preferred metal chelate curing agents are coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium with acetylacetone or ethyl acetoacetate. Examples of metal chelates include aluminum ethyl acetoacetate diisopropylate, aluminum trisacetylacetonate, aluminum bisethyl acetoacetate monoacetylacetonate, and aluminum alkyl acetoacetate diisopropylate.

[0053] The curing agent (B) is preferably contained in an amount of 0.02 to 4 parts by mass, and more preferably 0.04 to 1 part by mass, per 100 parts by mass of the acrylic polymer (A). When the content is 0.02 part by mass or more, the cohesive strength is further improved, and when it is 4 parts by mass or less, it becomes easier to achieve both cohesive strength and flexibility, making it easier to obtain sufficient adhesive strength, heat resistance, and moist heat resistance.

[0054] <Silane coupling agent (C)> The pressure-sensitive adhesive of the present invention preferably contains a silane coupling agent (C). By containing the silane coupling agent (C), adhesion, heat resistance, and moist heat resistance can be improved. The silane coupling agent (C) is preferably contained in an amount of 0.05 to 0.2 parts by mass per 100 parts by mass of the acrylic polymer (A). By using an amount of 0.05 to 0.2 parts by mass, it becomes easy to achieve both heat resistance and moist heat resistance.

[0055] Examples of the silane coupling agent (C) include an alkoxysilane compound having a (meth)acryloxy group, an alkoxysilane compound having a vinyl group, an alkoxysilane compound having an amino group, an alkoxysilane compound having a mercapto group, and an alkoxysilane compound having an epoxy group. Specific examples of commercially available products include KBM-403 (3-glycidoxypropyltrimethoxysilane), KBE-403 (3-glycidoxypropyltriethoxysilane), KBM-303 (2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane) (all manufactured by Shin-Etsu Chemical Co., Ltd.), and BYK-325N (polyether-modified polymethylalkylsiloxane) (manufactured by BYK Japan KK).

[0056] <Tackifying resin (D)> The pressure-sensitive adhesive of the present invention preferably further contains a tackifier resin (D). As the tackifier resin (D), any of the existing resins such as synthetic hydrocarbon resins, terpene resins, rosin resins, and acrylic resins (excluding the acrylic polymer (A)) can be used. The tackifier resin may be used alone or in combination of two or more.

[0057] Examples of synthetic hydrocarbon resins include aliphatic petroleum resins, aromatic petroleum resins, aliphatic / aromatic petroleum resins, hydrogenated petroleum resins, coumarone-indene resins, and phenolic resins.

[0058] Specific examples of commercially available products include Quinton B170 manufactured by Zeon Corporation as an aliphatic petroleum resin, Nippon Oil Neopolymer L-90 manufactured by JXTG as an aromatic petroleum resin, FTR6100 manufactured by Mitsui Chemicals, Inc. as an aliphatic / aromatic petroleum resin, and Sylvatac RE85 manufactured by Arizona Chemical Company and Super Ester A-75 manufactured by Arakawa Chemical Industries, Ltd. as rosin derivatives.

[0059] Examples of terpene resins include α-pinene resins, β-pinene resins, dipentene resins, aromatic modified terpene resins, hydrogenated terpene resins, terpene phenol resins, acid modified terpene resins, styrenated terpene resins, and styrene-aliphatic hydrocarbon copolymer resins.

[0060] Examples of rosin-based resins include rosin ester, polymerized rosin, hydrogenated rosin, disproportionated rosin, maleic acid-modified rosin, fumaric acid-modified rosin, rosin phenolic resin, and natural rosin.

[0061] The acrylic resin is not particularly limited as long as it is a copolymer of a (meth)acrylic monomer other than the acrylic polymer (A). The weight-average molecular weight of the acrylic resin is preferably 100,000 or less, more preferably 50,000 or less. When the acrylic resin has an Mw of 100,000 or less, it is compatible with the acrylic polymer (A) and can improve heat resistance. Furthermore, it is preferable that the monomer constituting the acrylic resin contains a monomer whose homopolymer has a glass transition temperature of 0°C or higher, and the content thereof is preferably 90% by mass or more and 99.5% by mass or less, based on 100% by mass of the total of the monomers constituting the acrylic resin. When the acrylic resin contains a monomer whose glass transition temperature is 0°C or higher within the above range, cohesive strength is imparted to the adhesive layer, improving heat resistance.

[0062] The content of the tackifier resin (D) is preferably 50 parts by mass or less, more preferably 5 parts by mass or more and 40 parts by mass or less, per 100 parts by mass of the acrylic polymer (A) in the PSA. By including the tackifier resin (D), the adhesive strength to the adherend can be improved.

[0063] Furthermore, among the tackifier resins (D), tackifier resins other than acrylic adhesives are preferably of a high softening point grade in order to enhance durability at high temperatures, and the softening point is preferably 90°C or higher, more preferably 120°C or higher, and even more preferably 140°C or higher.

[0064] The pressure-sensitive adhesive of the present invention may contain various resins, chlorinated polyolefins described below, oils, softeners, dyes, pigments, antioxidants, and ultraviolet absorbers as optional components, as long as the problem can be solved.

[0065] Examples of chlorinated polyolefins include chlorinated polypropylene, acid-modified chlorinated polypropylene, acrylic-modified chlorinated polypropylene, chlorinated polyethylene, and chlorinated ethylene vinyl acetate copolymer. From the viewpoints of good compatibility with acrylic polymers and the like and effective reduction of polarity, chlorinated polypropylene and chlorinated ethylene vinyl acetate copolymer are preferred. Specific examples of commercially available products include Superchlorine 390S (chlorinated polypropylene, chlorine content 36%) and Superchlorine BX (chlorinated EVA, chlorine content 18%) (both manufactured by Nippon Paper Industries Co., Ltd.).

[0066] The pressure-sensitive adhesive of the present invention preferably has a gel fraction of 30% by mass or more. There is no particular upper limit to the gel fraction, but it is preferably 90% by mass or less, and more preferably 60 to 80% by mass. When the gel fraction is 30% by mass or more, the cohesive strength of the pressure-sensitive adhesive is improved, a strong pressure-sensitive adhesive layer is obtained, and warping of the laminate can be further suppressed when placed in a high-temperature atmosphere. When the content is 30% by mass or more, the cohesive strength of the adhesive is improved and a strong adhesive layer is obtained, which can suppress lifting and peeling when exposed to a high-temperature atmosphere and also ensure the removability necessary for re-attachment to an optical component.When the content is 90% by mass or less, a flexible adhesive layer is easily obtained, and the adhesion of the adhesive layer to the substrate (hereinafter referred to as substrate adhesion) is further improved, which can further suppress lifting and peeling when exposed to a high-temperature atmosphere or a high-temperature, high-humidity atmosphere. The method for measuring the gel fraction will be described in detail in the Examples.

[0067] In view of the recent trend toward environmentally friendly materials, the adhesive of the present invention can be made partially or entirely from biologically derived materials by using a biomass monomer as the monomer constituting the acrylic polymer (A) or by using a biomass tackifier. The biomass ratio is preferably 30% or more. The higher the biomass ratio, more preferably 39% or more, and even more preferably 60% or more, the greater the usefulness as an environmentally friendly material. The method for calculating the biomass ratio is described in the Examples.

[0068] <Adhesive layer> The pressure-sensitive adhesive layer is a layer obtained from the pressure-sensitive adhesive of the present invention. There are no particular restrictions on the method for forming the pressure-sensitive adhesive layer, and it can be the same as the coating method described below in the description of the pressure-sensitive adhesive sheet.

[0069] The pressure-sensitive adhesive layer of the present invention preferably has a haze of 1.0 or less. A haze of 1.0 or less results in higher transparency, making it less noticeable during use and providing superior transmittance for optical applications. To achieve a haze of 1.0 or less, it is necessary to consider the type and ratio of monomers used in the pressure-sensitive adhesive to ensure that the adhesive's glass transition temperature is not too high. Furthermore, some monomers used exhibit crystallinity, and the development of crystallinity increases the haze. Therefore, it is necessary to similarly consider the crystallinity when determining the type and blending ratio of monomers used. The measurement method will be described in detail in the Examples.

[0070] The pressure-sensitive adhesive layer of the present invention preferably has a dielectric constant of 5.0 or less at 40 GHz. A dielectric constant of 5.0 or less at 40 GHz can improve optimal operation of touch sensors and the like. In order to achieve a dielectric constant of 5.0 or less, it is necessary to reduce the polarity of the pressure-sensitive adhesive. It is necessary to use a compound that is inherently low in polarity or to increase the number of carbon atoms contained in the compound. The measurement method will be described in detail in the Examples.

[0071] The pressure-sensitive adhesive layer of the present invention preferably has a dielectric loss tangent of 0.1 or less at 40 GHz. A dielectric constant of 0.1 or less at 40 GHz can suppress radiation loss of millimeter waves in high frequency bands such as millimeter waves. In order to achieve a dielectric loss tangent of 0.1 or less, it is necessary to reduce the polarity of the pressure-sensitive adhesive. It is necessary to use a compound with low polarity to begin with, or to increase the number of carbon atoms contained in the compound. The measurement method will be described in detail in the Examples.

[0072] The pressure-sensitive adhesive layer of the present invention preferably has a refractive index of 1.45 or more but less than 1.52. A refractive index of 1.45 or more but less than 1.52 is useful when used for bonding between layers of optical components, because it reduces the reflection of light at the interface between the pressure-sensitive adhesive layer and the optical component. In order to keep the refractive index within the above range, it is necessary to consider the balance between high-refractive index materials and low-refractive index materials. This can be adjusted by the composition of the pressure-sensitive adhesive. For example, it can be adjusted by the type of base polymer, the composition ratio of the monomer components, the presence or absence, type and amount of additives, etc. The measurement method is described in detail in the Examples.

[0073] The adhesive sheet of the present invention preferably has a high adhesive strength to glass for the purpose of product fixation, etc. Although a low adhesive strength may be used depending on the product, for versatile use, the peel strength is preferably 10 N / 25 mm or more, and more preferably 20 N / 25 mm or more. The measurement method will be described in detail in the Examples. The adhesive sheet of the present invention preferably has a high SUS adhesive strength for the purpose of product fixation, etc. Although a low adhesive strength may be used depending on the product, for versatile use, a peel strength of 5 N / 25 mm or more is preferred, and 10 N / 25 mm or more is even more preferred. The measurement method is described in detail in the Examples.

[0074] <Adhesive sheet> The pressure-sensitive adhesive sheet comprises a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive of the present invention and a release film.

[0075] The pressure-sensitive adhesive sheet of the present invention may have a structure in which a release film is formed on one or both sides of the pressure-sensitive adhesive layer.

[0076] <Release film> The release film is not particularly limited, but a transparent plastic substrate can be suitably used. Examples of materials for the transparent plastic substrate include polyesters such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), and plastic materials such as polycarbonate, triacetyl cellulose, polysulfone, polyarylate, and polycycloolefin. The plastic materials can be used alone or in combination of two or more.

[0077] Among the transparent plastic substrates described above, a transparent plastic substrate having excellent heat resistance, i.e., a transparent plastic substrate that is suppressed or prevented from deforming under severe conditions such as high temperature, high temperature and high humidity, etc. PET films or sheets are particularly suitable as the transparent plastic substrate.

[0078] The thickness of the release film is preferably less than 200 μm. The thickness should be adjusted depending on the handling of the member to be used, but by being less than 200 μm, the material itself is not too stiff, making it easy to wind into a roll and allowing for comfortable use when laminating sheets or the like.

[0079] The pressure-sensitive adhesive sheet of the present invention has excellent adhesiveness and is therefore suitable for forming optical display components such as display devices such as LCDs and OLEDs, and input devices such as touch panels, as well as for bonding these components together. Examples of optical components include, but are not limited to, PET films, polarizing plates, retardation plates, elliptically polarizing plates, optical compensation films, brightness-enhancing films, infrared / electromagnetic wave-blocking films, front-surface anti-reflection films, surface protection films, films with an ITO (indium tin oxide) layer, films with a zinc oxide (ZnO) layer, films obtained by coating or printing metal nanoparticles, films obtained by coating or printing a dispersion containing carbon nanotubes, films obtained by coating or printing a dispersion containing graphene, films obtained by coating or printing a dispersion containing conductive polymers, metal plates made of SUS or the like, metal meshes, and laminates of these.

[0080] The viscosity of the adhesive or adhesive coating can be adjusted by adding an appropriate liquid medium. Specific examples include hydrocarbon solvents such as toluene, xylene, hexane, and heptane; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone and methyl ethyl ketone; halogenated hydrocarbon solvents such as dichloromethane and chloroform; ether solvents such as diethyl ether, methoxytoluene, and dioxane; and other hydrocarbon solvents. However, water and alcohol must be used with caution because they may inhibit the reaction between the acrylic polymer (A) and the isocyanate curing agent (B).

[0081] The coating method is not particularly limited, and examples thereof include various coating methods using a Mayer bar, applicator, brush, spray, roller, gravure coater, die coater, lip coater, comma coater, knife coater, reverse coater, spin coater, etc. The drying and curing method is also not particularly limited, and examples thereof include hot air drying, infrared rays, reduced pressure methods, and methods using active energy rays, but hot air or steam heating at 60 to 180°C is preferred from the viewpoint of outgassing resistance.

[0082] The thickness of the pressure-sensitive adhesive layer is preferably 2 to 1000 μm, more preferably 5 to 500 μm. The pressure-sensitive adhesive layer may be in the form of a single layer or a laminate of two or more layers.

[0083] <Laminate> The laminate of the present invention includes a substrate and a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer can be formed using the pressure-sensitive adhesive sheet of the present invention. Specifically, for example, the release film can be peeled off from the pressure-sensitive adhesive sheet of the present invention, and the pressure-sensitive adhesive layer can be attached to the substrate to form the laminate.

[0084] <Base material> The substrate refers to the object to which the adhesive layer of the adhesive sheet having an adhesive layer is attached, and is not limited to a specific material. Examples include polyolefins such as polyethylene and polypropylene, resins such as polycarbonate and phenol, metals such as iron, stainless steel (SUS), aluminum and copper, cement, mortar, glass, nonwoven fabric, woven fabric, paper, rubber, foam sheets, and laminates thereof. The adhesive of the present invention exhibits excellent adhesive strength to at least one type of adherend. The thickness of the substrate is not particularly limited, and is, for example, preferably less than 500 μm, more preferably 10 to 200 μm, and even more preferably 25 to 150 μm.

[0085] <Light transparent base material> The laminate of the present invention can also use a light-transmitting substrate as the substrate. A transparent plastic substrate is used as the light-transmitting substrate. Examples of materials for such light-transmitting substrates include acrylic resins such as polyethylene terephthalate (PET), polyethylene naphthalate, and polymethyl methacrylate (PMMA), and plastic materials such as polycarbonate (PC), polycycloolefin, polyimide, polyphenylene ether, polysulfone, polyethersulfone, polystyrene, and polypropylene. PET film or PC is preferred, and PC is more preferred in terms of durability. The plastic materials can be used alone or in combination of two or more. The light-transmitting substrate may be subjected to an appropriate surface treatment, for example, a physical treatment such as a corona discharge treatment or a plasma treatment, or a chemical treatment such as a primer treatment.

[0086] For a laminate comprising a light-transmitting substrate, the pressure-sensitive adhesive sheet preferably has a total light transmittance of 60% or more. A laminate including a light-transmitting substrate has, for example, a structure of light-transmitting substrate / adhesive layer / polarizing plate. In this case, it is preferable to provide the light-transmitting substrate, adhesive layer, and polarizing plate in this order. This allows for a laminate with excellent transparency.

[0087] An example of a schematic cross-sectional view partially showing the laminate of the present invention is shown in Figure 1. In Figure 1, 3 is a light-transmitting substrate (cover panel), 1 is a pressure-sensitive adhesive layer, and 4 is a polarizing plate.

[0088] In the laminate shown in FIG. 1, a light-transmitting substrate (cover panel) is attached to a polarizing plate via an adhesive layer.

[0089] <Manufacturing of laminate> The laminate can be produced, for example, by peeling off the release film from a pressure-sensitive adhesive sheet having release films on both sides of the pressure-sensitive adhesive layer, and then attaching the pressure-sensitive adhesive layer to a substrate such as a light-transmitting flexible substrate or a polarizing plate, etc. Alternatively, the laminate can be produced by directly forming a pressure-sensitive adhesive layer on a light-transmitting flexible substrate, and then attaching a pressure-sensitive adhesive layer provided on a substrate or another pressure-sensitive adhesive sheet to the pressure-sensitive adhesive layer.

[0090] Display A display includes the laminate of the present invention, a polarizing plate, and an optical element, thereby providing the display with excellent visibility. The optical element is not particularly limited, and examples thereof include a liquid crystal element and an organic EL element. .

[0091] Figure 2 shows an example of a schematic cross section partially illustrating a display, which is an example of use of the pressure-sensitive adhesive sheet of the present invention. In Figure 2, 3 is a light-transmitting substrate (cover panel), 1 is pressure-sensitive adhesive layer 1, 4 is a polarizing plate, 5 is pressure-sensitive adhesive layer 2, 6 is a barrier layer such as silicon nitride, 7 is an organic EL layer, 8 is a support such as polyimide, and 9 is an organic EL cell. Note that the configuration of the display is not limited to that shown in Figure 2.

[0092] 2, a light-transmitting substrate (cover panel) is attached to a polarizing plate via the pressure-sensitive adhesive layer of the present invention (pressure-sensitive adhesive layer 1), and is further attached to an organic EL cell via a pressure-sensitive adhesive layer for polarizing plate (pressure-sensitive adhesive layer 2). In this way, the pressure-sensitive adhesive sheet of the present invention can be used in a form in which a transparent pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive is attached to a light-transmitting substrate (cover panel) and a polarizing plate, and the laminate is further attached to an organic EL cell via a pressure-sensitive adhesive layer for polarizing plate. For example, in FIG. 2, the pressure-sensitive adhesive layer of the present invention can be used as either pressure-sensitive adhesive layer 1 or pressure-sensitive adhesive layer 2. Generally, when comparing pressure-sensitive adhesive layer 1 and pressure-sensitive adhesive layer 2, the quality requirements for the pressure-sensitive adhesive layer are higher for pressure-sensitive adhesive layer 1, and the pressure-sensitive adhesive of the present invention has good adhesion and bonding properties to the substrate, so it is preferably used for pressure-sensitive adhesive layer 1. In this case, the pressure-sensitive adhesive for forming pressure-sensitive adhesive layer 2 may be the pressure-sensitive adhesive of the present invention or a conventionally known pressure-sensitive adhesive.

[0093] There are no particular limitations on the uses of the displays, but examples include OLED televisions, OLED smartphones, OLED tablets, and OLED smartwatches.

[0094] Due to their high environmental friendliness (biomass content) and excellent heat and humidity resistance, the adhesives of the present disclosure can be used in a wide range of applications, including but not limited to the display laminates described above, such as decorative sheets. For example, decorative sheets can be formed by coating a sheet containing a substrate and a decorative layer with the adhesive diluted with a solvent using knife coating, bar coating, blade coating, doctor coating, roll coating, cast coating, or other methods to form a coating film. The sheet can then be heated and dried as needed to form an adhesive layer on the sheet. Such decorative sheets can be used to decorate, for example, aircraft, automobiles, interior and exterior building materials, the nursing and medical fields, electrical appliances, electronic components, smartphones, furniture, musical instruments, and Shinkansen window frames. A suitable method for forming decorative sheets is three-dimensional surface decoration (Three-Dimensional Overlay Method (TOM)), a type of vacuum and compressed air molding. [Example]

[0095] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass." The blending amounts in the tables are in parts by mass, and all amounts other than the solvent are calculated as non-volatile content. Blank spaces in the tables indicate that no blending was performed. The method for measuring the weight average molecular weight of the acrylic polymer is as follows.

[0096] <Measurement of weight average molecular weight (Mw) and Mw classification evaluation method> The weight-average molecular weight (Mw) was measured by gel permeation chromatography (GPC). The instrument used was a GPC instrument manufactured by Shimadzu Corporation: an LC-GPC system "Prominence." The columns used were TSKgel α-M manufactured by Tosoh Corporation, with two columns connected in series. N,N-dimethylformamide (DMF) was used as the eluent, and measurements were carried out at 40°C. Mw was determined by conversion using polystyrene with a known Mw as the standard substance. When the weight average molecular weight (Mw) is 1.7 million to 2 million, the Mw classification is U; when it is 1.5 million to 1.65 million, the Mw classification is H; when it is 1.2 million to 1.4 million, the Mw classification is M; and when it is 500,000 to 800,000, the Mw classification is L, and these are the evaluation results.

[0097] (Production of acrylic polymers) <Production Example 1: Production of (A-1)> A reactor equipped with a stirrer, reflux condenser, nitrogen inlet, thermometer, and dropping tube was added to the reaction vessel as a polymerization solvent, and a monomer mixture containing 78.5 parts of 2-octyl acrylate (2-OA) as monomer (a1), 0.5 parts of acrylamide (AM) as monomer (a2), 1 part of 4-hydroxybutyl acrylate (4HBA) as monomer (a3), and 20 parts of methyl acrylate (MA) as monomer (a5), along with 0.02 parts of azobisisobutyronitrile as an initiator, was charged into the reaction vessel. Polymerization was carried out for 5 hours at approximately 80°C under a nitrogen atmosphere. Ethyl acetate was added dropwise through the dropping tube as a diluent to suppress viscosity increase during the reaction. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate to obtain an acrylic polymer solution. The resulting acrylic polymer was designated (A-1). The weight-average molecular weight (Mw) of the resulting acrylic polymer was measured (Mw classification), and the results are shown in Table 1.

[0098] <Production Examples 2 to 33, Comparative Production Examples 1 to 5: Production of (A-2 to A-33, A'-1 to A'-5)> Acrylic polymers (A-2 to A-33, A'-1 to A'-5) were produced in the same manner as in the production of the acrylic polymer (Production Example 1), except that the compositions and blending amounts (parts by mass) were changed as shown in Tables 1 to 3. The Mw classification of the obtained acrylic polymers is shown in Tables 1 to 3.

[0099] [Table 1]

[0100] [Table 2]

[0101] [Table 3]

[0102] The abbreviations are as follows: Regarding biomass content, only confirmed cases are listed. [Monomer (a1)] 2-OA: 2-octyl acrylate (biomass content 73%) 2-OMA: 2-octyl methacrylate (biomass content 67%) [Monomer (a2)] AM: Acrylamide (Tg: 153°C) DM: 2-(dimethylamino)ethyl methacrylate (Tg: 18°C) NIPAM: N-isopropylacrylamide (Tg: 134°C) NVP: N-vinylpyrrolidone (Tg: 80°C) NVF: N-vinylformamide (Tg: 147°C) ACMO: acryloylmorpholine (Tg: 145°C) HEAA: N-hydroxyethyl acrylamide (Tg: 98°C) [Monomer (a3)] HEA: Hydroxyethyl acrylate 4HBA: 4-hydroxy-normal butyl acrylate [Monomer (a4)] MA: methyl acrylate (Tg: 8°C) MMA: Methyl methacrylate (Tg: 105°C) IBXA: Isobornyl acrylate (Tg: 97°C, biomass content 76%) [Monomer (a5)] AA: acrylic acid [Other monomers] 2EHA: 2-ethylhexyl acrylate (Tg: -70°C) BA: n-butyl acrylate (Tg: -55°C) 2MTA: 2-methoxyethyl acrylate (Tg: -50°C)

[0103] Example 1 0.1 parts of "Mytec GP-105A" (manufactured by Mitsubishi Chemical Corporation, toluene disocyanate / trimethylolpropane adduct) as a curing agent (B) was blended with 100 parts of the acrylic polymer (A-1) to obtain a pressure-sensitive adhesive. The resulting adhesive was applied to a 38 μm-thick polyethylene terephthalate release sheet (Cerapeel MF, manufactured by Toray Advanced Film Co., Ltd.) using a comma coater to a dry thickness of 20 μm, and then dried at 105°C for 2 minutes to obtain an adhesive sheet. Next, a polarizing plate (layer structure: triacetyl cellulose film / polyvinyl alcohol film / polymethyl methacrylate film) was used to bond the adhesive layer to the polymethyl methacrylate film side of the polarizing plate, obtaining an adhesive-attached polarizing plate having a "release sheet / adhesive layer / polarizing plate" configuration. The resulting adhesive-attached polarizing plate was then aged for 1 week at a temperature of 25°C and a relative humidity of 55%, obtaining a laminate.

[0104] <Examples 2 to 47, Comparative Examples 1 to 5> As shown in Table 4, adhesives, adhesive sheets, and laminates were obtained in the same manner as in Example 1, except that the types and amounts of the acrylic polymer (A), curing agent (B), silane coupling agent (C), and tackifying resin (D) were changed. However, Example 27 is considered to be a reference example.

[0105] The materials used in the examples and comparative examples are listed below. <Curing agent (B)> Mytec GP-105A: Mitsubishi Chemical Corporation, toluene diisocyanate / trimethylolpropane adduct Tetrad X: Mitsubishi Gas Chemical Company, multifunctional epoxy resin Aluminum Chelate D: Chelate hardener manufactured by Kawaken Fine Chemicals Co., Ltd.

[0106] <Silane coupling agent (C)> KBM-403: (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) KBE-403: (3-glycidoxypropyltriethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) <Tackifying resin (D)> FTR6100: (Mitsui Chemicals, softening point 125°C) UH115: (YS Polyster UH115, Yasuhara Chemical Co., Ltd., softening point 115°C) T-145: (YS Polyster T-145, Yasuhara Chemical Co., Ltd., softening point 145°C)

[0107] The gel fraction of the pressure-sensitive adhesive of the present invention was measured and the biomass ratio was calculated by the following methods. The results are shown in Tables 4 and 5.

[0108] <Gel fraction measurement> The 38 μm release liner was peeled off from the resulting pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive layer was attached to a PET film substrate (Cosmoshine A-4360, manufactured by Toyobo Co., Ltd., 100 μm thick), which was then cut into a size of 30 mm wide x 100 mm long to prepare a test pressure-sensitive adhesive sheet. The release liner on the other side of the pressure-sensitive adhesive tape was then peeled off to prepare a test specimen, whose weight was measured. The test specimen was immersed in ethyl acetate at 23°C for 24 hours, then removed from the ethyl acetate and dried at 150°C for 30 minutes. The weight of the dried test specimen was measured, and the gel fraction was calculated using the following formula (1). Gel fraction (mass%) = 100 × (W2 − W0) / (W1 − W0) (1) (W0: weight of substrate (PET film), W1: weight of test piece before immersion, W2: weight of test piece after immersion and drying)

[0109] <Biomass ratio and its calculation method> The biomass ratio of the adhesive was calculated using the following formula (2). (In the case of a system consisting of two monomer components (A, B) and one tackifier component (C)) Biomass ratio = {(Aw × Ab) + (Bw × Bb) + (Cw × Cb)} / (Aw + Bw + Cw) (2) Aw: weight of monomer A, Bw: weight of monomer B, Cw: weight of tackifying resin Ab: Biomass ratio of monomer A (%), Bb: Biomass ratio of monomer B (%), Cb: Biomass ratio of monomer C (%) When the biomass degree was specified as a range, the minimum value was used in the calculation.

[0110] [Table 4]

[0111] [Table 5]

[0112] The heat resistance and moist heat resistance of the obtained laminate were evaluated by the following methods, and the results are shown in Tables 6 and 7.

[0113] <Heat resistance> The obtained laminate was cut into a size of 140 mm wide and 80 mm long. Next, the release sheet was peeled off, and the adhesive layer was attached to a glass plate using a laminator. Next, the glass plate to which this laminate was attached was kept in an autoclave at 50 ° C and 5 atmospheres for 20 minutes to adhere each component, thereby obtaining a measurement sample. The heat resistance of this measurement sample was evaluated as an evaluation of resistance in a high-temperature atmosphere. That is, the measurement sample was left at 105 ° C for 500 hours, and then the presence or absence of foaming was visually observed. [Evaluation criteria] ◎: No foaming observed (Excellent) ○: Foaming is observed, and foaming accounts for less than 5% of the unit area (Excellent) ○△: Foaming was observed, and the foaming accounted for 5% or more but less than 10% of the unit area (good). △: Foaming is observed, and the foaming occupies 10% to less than 20% of the unit area (fairly good). △×: Foaming was observed, and the foaming accounted for 20% or more but less than 30% of the unit area (usable). ×: Foaming is observed, and the foaming occupies 30% or more of the unit area (unusable).

[0114] <Moisture and heat resistance> Measurement samples were prepared in the same manner as in the heat resistance test, and moist heat resistance was evaluated as an evaluation of resistance in a high-temperature, high-humidity atmosphere. Specifically, the measurement samples were left at 60°C and 90% relative humidity for 500 hours, and then the presence or absence of peeling at the edges of the laminate was visually confirmed. For samples in which peeling was observed, the distance (longest distance) peeled from the adherend was measured. Heat resistance and moist heat resistance were both evaluated based on the following criteria. [Evaluation criteria] ◎: No peeling observed (Excellent) ○: Peeling of 1 mm or less is observed (Excellent) ○△: Peeling of more than 1 mm but not more than 5 mm is observed (good). △: Peeling of more than 5 mm and less than 10 mm is observed (fairly good). △×: Peeling of more than 10 mm but not exceeding 20 mm is observed (usable). ×: Peeling of more than 20 mm is observed (unusable)

[0115] [Table 6]

[0116] [Table 7] [Explanation of symbols]

[0117] The symbols in Figures 1, 2 and 3 are explained below. 1 Adhesive layer 1 2 Release film 3 Base material 4 Polarizing Plate 5. Adhesive layer 2 6 Barrier Layer 7 Organic EL layer 8 Support 9 Organic EL cells

Claims

1. The present invention comprises an acrylic polymer (A) which is a copolymer of a monomer mixture containing all of the following monomers (a1) to (a4) and optionally containing the following monomer (a5), and a curing agent (B), A pressure-sensitive adhesive comprising a monomer (a2) in an amount of 0.05% by mass or more and 5% by mass or less (excluding 5% by mass) based on 100% by mass of a monomer mixture. (a1) 2-octyl (meth)acrylate (a2) a nitrogen-containing monomer selected from the group consisting of N-vinyl lactams, amino group-containing (meth)acrylate monomers, N-vinyl carboxylic acid amides, (meth)acrylamides, and (meth)acryloylmorpholine (a3) Hydroxy group-containing monomer (a4) A (meth)acrylate monomer having a homopolymer glass transition temperature of 0°C or higher (excluding the nitrogen-containing monomer (a2), the monomer (a3) ​​having a hydroxy group, and the monomer (a5) having a carboxy group). (a5) Carboxy group-containing monomer

2. In 100% by mass of the monomer mixture, Monomer (a1) is 30% by mass or more and less than 99.5% by mass, The pressure-sensitive adhesive according to claim 1, characterized in that it contains 0.1 mass % or more and less than 70 mass % of the monomer (a4).

3. The pressure-sensitive adhesive according to claim 1, wherein the monomer (a2) comprises at least one selected from the group consisting of (meth)acrylamide, N-[3-(dimethylamino)propyl](meth)acrylamide, N-methyl(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, 2-(dimethylamino)ethyl (meth)acrylate, 2-(diethylamino)ethyl (meth)acrylate, 3-(dimethylamino)propyl (meth)acrylate, N-isopropyl(meth)acrylamide, N-vinylcaprolactam, N-vinylpyrrolidone, N-vinylformamide, N-hydroxyethyl(meth)acrylamide, and (meth)acryloylmorpholine.

4. The pressure-sensitive adhesive according to claim 1, wherein the monomer (a2) is contained in an amount of 0.1% by mass or more and 3% by mass or less based on 100% by mass of the monomer mixture.

5. The pressure-sensitive adhesive according to claim 1, wherein the content of the monomer (a5) in 100% by mass of the monomer mixture is less than 0.5% by mass.

6. The pressure-sensitive adhesive according to claim 1, wherein the monomer (a3) ​​is contained in an amount of 0.1% by mass or more and 30% by mass or less based on 100% by mass of the monomer mixture.

7. 2. The pressure-sensitive adhesive according to claim 1, wherein the biomass content is 30% or more.

8. The pressure-sensitive adhesive according to claim 1, further comprising a silane coupling agent (C).

9. 2. The pressure-sensitive adhesive according to claim 1, wherein the pressure-sensitive adhesive has a gel fraction of 30% by mass or more.

10. The pressure-sensitive adhesive according to claim 1, further comprising 50 parts by mass or less of a tackifier resin (D) per 100 parts by mass of the acrylic polymer (A).

11. A pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive according to any one of claims 1 to 10.

12. A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer according to claim 11 and a release film.

13. A laminate comprising the pressure-sensitive adhesive layer according to claim 11 and a substrate.

14. A display comprising the laminate according to claim 13, a polarizing plate, and an optical element.

Images