Adhesive, adhesive sheet, and laminate

Abstract

Provided is an adhesive containing an acrylic polymer (A) which is a copolymer of a monomer mixture, a rosin-based tackifier resin (B1) having a softening point of 120° or more, and a curing agent (C), wherein the content of the rosin-based tackifier resin (B1) is from 10 mass parts to less than 60 mass parts per 100 mass parts of the acrylic polymer (A), the content of a monomer (a1) is from 30 mass% to less than 95 mass%, the content of a monomer (a2) is from 1 mass% to less than 10 mass%, and the content of a monomer (a3) is from 4 mass% to 69 mass% in 100 mass% of the monomer mixture, and the monomer mixture may also contain less than 0.7 mass% of a monomer (a4). Here, (a1) 2-octyl (meth)acrylate, (a2) a monomer having a carboxy group, (a3) a monomer other than monomer (a1), monomer (a2), and monomer (a4), and (a4) a monomer having a hydroxy group.

Description

Adhesives, adhesive sheets, laminates

[0001] The present disclosure relates to a pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, and a laminate.

[0002] Due to their ease of handling, adhesive sheets with adhesive layers formed from adhesives are used in a wide range of fields, including labeling 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 display devices. Touch panels are equipped with cover panels to protect their surfaces. The components constituting these optical displays are typically bonded together via an adhesive layer. Among these, adhesives used in applications expected to be used for long periods, such as marking films, window films, automotive components, and optical displays, require high adhesion to the substrate to prevent peeling during use. For automotive and label applications, adhesive sheets must adhere to not only metal but also plastic materials. Durability (constant-load peel resistance) is required to prevent poor appearance, such as lifting or peeling, at the adhesive interface with the adhesive layer, even under conditions of continuous load due to material expansion or its own weight.

[0003] In addition to the increasing performance requirements, the depletion of petroleum resources and carbon dioxide emissions from the combustion of petroleum-derived products are becoming increasingly problematic in industries where PSA sheets are used. Therefore, efforts are being made to conserve petroleum resources by replacing petroleum-derived materials with bio-derived materials in various industries, starting with packaging, optics, and semiconductors. One method for increasing the proportion of bio-derived materials in PSAs primarily composed of acrylic polymers is to obtain an acrylic polymer by copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester monomer obtained by esterifying a linear alkyl alcohol produced by living organisms with (meth)acrylic acid. Furthermore, there are also tackifier resins made from naturally derived components, and selective use of these can lead to environmentally friendly products.

[0004] The adhesives described in Patent Documents 1, 2, and 3 use an acrylic polymer made from a biological material. The inventors have found that the adhesives described in these documents are unable to simultaneously achieve adhesive strength, constant load peel resistance, tackiness, etc., which poses a major problem.

[0005] Increasing the proportion of environmentally friendly materials can contribute to the conservation of petroleum resources, but this means that only limited environmentally friendly materials are used, and the current situation is that there are issues with the performance that was originally achieved, such as adhesive strength, constant load peel resistance, and fixation properties such as tackiness.

[0006] Special table 2009-529090 Publication Special table 2023-538015 Publication Special table 2024-110325

[0007] The problem that the present invention aims to solve is to provide an adhesive that can contribute to the conservation of petroleum resources by increasing the proportion of environmentally friendly materials, and that has high adhesive strength performance to adherends and is capable of achieving both constant load peel resistance and tack, as well as an adhesive sheet and laminate using the same.

[0008] After extensive investigations, the present inventors have found that the problems of the present invention can be solved in the following aspect, and have thus completed the present invention. Specifically, the present disclosure provides a PSA comprising an acrylic polymer (A) that is a copolymer of a monomer mixture, a rosin-based tackifier resin (B1) having a softening point of 120°C or higher, and a curing agent (C), wherein the content of the rosin-based tackifier resin (B1) per 100 parts by mass of the acrylic polymer (A) is 10 to 60 parts by mass, and the PSA contains, per 100 mass% of the monomer mixture, 30 to 95 mass% of the following monomer (a1), 1 to 10 mass% of the following monomer (a2), and 4 to 69 mass% of the following monomer (a3), and may further contain less than 0.7 mass% of the following monomer (a4). (a1) 2-octyl (meth)acrylate (a2) a monomer having a carboxy group (a3) ​​a monomer other than the monomer (a1), the monomer (a2), and the monomer (a4) (a4) a monomer having a hydroxy group

[0009] The present disclosure makes it possible to provide a pressure-sensitive adhesive that can contribute to the conservation of petroleum resources, a pressure-sensitive adhesive that has high adhesive strength performance to adherends and is capable of achieving both constant-load peel resistance and tackiness, and a pressure-sensitive adhesive sheet and laminate that use the same.

[0010] 1 is a schematic cross-sectional view partially illustrating an example of a laminate according to the present disclosure. FIG. 2 is a schematic view illustrating a test for constant-load peel resistance of a pressure-sensitive adhesive sheet.

[0011] The pressure-sensitive adhesive, pressure-sensitive adhesive sheet, and laminate according to the present disclosure have the following configurations [1] to

[17] .

[0012] [1] A pressure-sensitive adhesive comprising an acrylic polymer (A) that is a copolymer of a monomer mixture, a rosin-based tackifying resin (B1) having a softening point of 120°C or higher, and a curing agent (C), wherein the content of the rosin-based tackifying resin (B1) relative to 100 parts by mass of the acrylic polymer (A) is 10 to less than 60 parts by mass, and the pressure-sensitive adhesive contains, in 100% by mass of the monomer mixture, 30 to less than 95% by mass of the following monomer (a1), 1 to less than 10% by mass of the following monomer (a2), and 4 to 69% by mass of the following monomer (a3), and may further contain less than 0.7% by mass of the following monomer (a4). (a1) 2-octyl (meth)acrylate (a2) a monomer having a carboxy group (a3) ​​another monomer other than monomer (a1), monomer (a2), and monomer (a4) (a4) a monomer having a hydroxy group [2] The pressure-sensitive adhesive according to the above [1], wherein monomer (a3) ​​contains monomer (a3-1) (excluding monomer (a2) and monomer (a4)) having a glass transition temperature of a homopolymer of 0°C or higher. [3] The pressure-sensitive adhesive according to the above [1] or [2], wherein monomer (a3) ​​contains alkyl (meth)acrylate monomer (a3-2) (excluding monomer (a2) and monomer (a4)) having an alkyl group with 2 to 8 carbon atoms and having a glass transition temperature of a homopolymer of less than 0°C. [4] The pressure-sensitive adhesive according to any one of the above [1] to [3], wherein monomer (a4) is contained in an amount of 0.03% by mass or more and less than 0.7% by mass relative to 100% by mass of the monomer mixture. [5] The PSA according to any one of [1] to [4] above, having a biomass degree of 30% or more. [6] The PSA according to any one of [1] to [5] above, wherein the rosin-based tackifier resin (B1) has a biomass degree of 80% or more. [7] The PSA according to any one of [1] to [6] above, wherein the rosin-based tackifier resin (B1) has a hydroxyl value of 20 mgKOH / g or more. [8] The PSA according to any one of [1] to [7] above, further comprising 10 parts by mass or more but less than 60 parts by mass of a tackifier resin (B2) having a softening point of 90°C or more but less than 120°C per 100 parts by mass of the acrylic polymer (A), wherein the tackifier resin (B2) comprises at least one selected from the group consisting of rosin-based tackifier resins, aliphatic petroleum resins, aromatic petroleum resins, aliphatic / aromatic petroleum resins, and terpene-based tackifiers.[9] The pressure-sensitive adhesive according to any one of [1] to [8] above, wherein the curing agent (C) comprises at least one selected from the group consisting of an isocyanate-based curing agent, an epoxy-based curing agent, and an aluminum chelate-based curing agent.

[10] The pressure-sensitive adhesive according to any one of [1] to [9] above, wherein the gel fraction is less than 50%.

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

[10] above.

[12] The pressure-sensitive adhesive layer according to

[11] above, wherein the SUS adhesive strength is 10 N / 25 mm or more.

[13] The pressure-sensitive adhesive layer according to

[11] or

[12] above, wherein the PE adhesive strength is 5 N / 25 mm or more.

[14] A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer according to any one of

[11] to

[13] above and a release film.

[15] The pressure-sensitive adhesive sheet according to

[14] above, wherein the release film has a thickness of less than 200 μm.

[16] A laminate comprising the pressure-sensitive adhesive layer according to any one of

[11] to

[13] above and a substrate.

[17] The basis weight of the substrate is 230 g / m. ２ The laminate according to

[16] , wherein the thickness is less than 1 / 2 mm.

[0013] The composition, pressure-sensitive adhesive sheet, and laminate of the present disclosure are described below, but are not limited thereto. In this specification, (meth)acrylate includes acrylate and methacrylate, and (meth)acryloxy group includes acryloxy group and methacryloxy group. A monomer is a monomer having an ethylenically unsaturated group. In this specification, a numerical range specified using "to" includes the numerical values ​​before and after "to" as the lower and upper limits of the range. Furthermore, "film" and "sheet" are not distinguished by thickness. In other words, in this specification, "sheet" includes thin film-like objects, and "film" in this specification includes thick sheet-like objects. Furthermore, an adherend refers to a surface to which the pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet is attached. Unless otherwise noted, the various components mentioned in this specification may be used independently, either singly or in combination of two or more types.

[0014] <<Adhesive>> The adhesive of the present disclosure contains an acrylic polymer (A), a rosin-based tackifying resin (B1) having a softening point of 120°C or higher, and a curing agent (C).

[0015] <Acrylic Polymer (A)> The acrylic polymer (A) is a copolymer of a monomer mixture, and is a pressure-sensitive adhesive containing, based on 100% by mass of the monomer mixture, 30% by mass or more and less than 95% by mass of the following monomer (a1), 1% by mass or more and less than 10% by mass of the following monomer (a2), and 4% by mass or more and 69% by mass or less of the following monomer (a3), which may further contain less than 0.7% by mass of the following monomer (a4): (a1) 2-octyl(meth)acrylate (a2) a monomer having a carboxy group (a3) ​​another monomer other than the monomer (a1), the monomer (a2), and the monomer (a4), and (a4) a monomer having a hydroxy group.

[0016] [Monomer (a1)] Monomer (a1) refers to 2-octyl(meth)acrylate and is represented by the following formula (1). Monomer (a1) is a biomass monomer. (Formula 1) (R1 = H, CH ３ ) The content of (a1) is 30% by mass or more and less than 95% by mass based on 100% by mass of the monomer mixture. A content of (a1) less than 30% by mass is undesirable because it reduces adhesive strength. The lower limit of the content of (a1) is 30% by mass or more, but the desired effect can be obtained. However, the lower limit is preferably 35% by mass or more and less than 90% by mass, more preferably 40% by mass or more and less than 90% by mass, even more preferably 50% by mass or more and less than 90% by mass, and particularly preferably 55% by mass or more and less than 85% by mass. Furthermore, a higher content of (a1) is preferable because it contributes to the conservation of petroleum resources. The content of (a1) may be 30% by mass or more, 40% by mass or more, 50% by mass or more, or less than 95% by mass, less than 90% by mass, or less than 85% by mass.

[0017] [Monomer (a2)] Monomer (a2) is a monomer having a carboxy group, and the content of (a2) is 1% by mass or more and less than 10% by mass based on 100% by mass of the monomer mixture. A content of monomer (a2) less than 1% by mass is undesirable because cohesive strength decreases. A content of 10% by mass or more is undesirable because flexibility is impaired. Preferably, the content is 2% by mass or more and less than 10% by mass, more preferably 2% by mass or more and less than 7% by mass, even more preferably 2% by mass or more and less than 5% by mass, and particularly preferably 2% by mass or more and less than 4% by mass based on 100% by mass of the monomer mixture. The content of (a2) may be 1% by mass or more, 2% by mass or more, or less than 10% by mass, 7% by mass, 5% by mass, or less than 4% by mass.

[0018] The monomer having a carboxy group is not limited as long as it has a carboxy group in the molecule, and specific examples include (meth)acrylic acid, p-carboxybenzyl acrylate, β-carboxyethyl acrylate, maleic acid, monoethyl maleate, itaconic acid, citraconic acid, fumaric acid, etc. Of these, (meth)acrylic acid is preferred from the viewpoint of adhesive strength, and acrylic acid is more preferred.

[0019] [Monomer (a3)] The monomer (a3) ​​is a monomer other than the monomer (a1), the monomer (a2), and the monomer (a4), and is not particularly limited. In consideration of the environment, it is preferable to use a (meth)acrylate, which is a biomass monomer, as the monomer (a3), and it is more preferable to use a (meth)acrylate with a high biomass content.

[0020] The content of monomer (a3) ​​is 4% by mass or more and less than 69% by mass based on 100% by mass of the monomer mixture. It is preferably 4% by mass or more and less than 60% by mass. It is more preferably 5% by mass or more and less than 60% by mass, and even more preferably 10% by mass or more and less than 45% by mass. The content of (a3) ​​may be 4% by mass or more, 5% by mass or more, or 10% by mass or more, or may be less than 69% by mass, less than 60% by mass, or less than 45% by mass.

[0021] The monomer (a3) ​​preferably includes a monomer (a3-1) having a glass transition temperature of 0°C or higher when it is formed into a homopolymer (excluding monomers (a2) and (a4)), or an alkyl (meth)acrylate monomer (a3-2) having 2 to 8 carbon atoms in the alkyl group and having a glass transition temperature of less than 0°C when it is formed into a homopolymer (excluding monomers (a2) and (a4)), more preferably including monomer (a3-1), and even more preferably including both monomers (a3-1) and (a3-2). The inclusion of monomer (a3-1) can improve cohesive strength, and the inclusion of monomer (a3-2) can improve constant load peel strength. The glass transition temperature (° C.) of the homopolymer can be known from information provided by the vendor of the various monomers or from the values ​​listed in "Polymer Handbook 3rd Edition" (A Wiley-Interscience Publication, 1989).

[0022] (Monomer (a3-1)) The monomer (a3-1) is not particularly limited as long as it is a monomer having a glass transition temperature of 0°C or higher in the form of a homopolymer (excluding the monomers (a2) and (a4)). Examples of the monomer (a3-1) include acrylamide, N,N-dimethylacrylamide, methacrylonitrile, acrylonitrile, diacetone acrylamide, 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 (a3-1) is preferably at least one 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. In consideration of the environment, it is more preferable to use a (meth)acrylate, which is a biomass monomer.

[0023] The content of monomer (a3-1) is preferably 0.1% by mass or more and less than 69% by mass, more preferably 0.1% by mass or more and less than 20% by mass, and even more preferably 1% by mass or more and less than 15% by mass, based on 100% by mass of the monomer mixture. The content of (a3-2) may be 0.1% by mass or more, 1% by mass or more, or less than 69% by mass, less than 20% by mass, or less than 15% by mass.

[0024] (Monomer (a3-2)) Monomer (a3-2) is an alkyl(meth)acrylate monomer (excluding monomer (a2) and monomer (a4)) having an alkyl group with 2 to 8 carbon atoms and a homopolymer glass transition temperature of less than 0°C. Examples of monomer (a3-2) include ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, n-hexyl acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isoamyl acrylate. From the viewpoint of improving constant-load peel resistance, monomer (a3-2) preferably includes at least one selected from the group consisting of isopropyl acrylate, isobutyl acrylate, isopentyl acrylate, and isoamyl acrylate. In addition, it is more preferable to use (meth)acrylate, which is a biomass monomer, as (a3) ​​in consideration of the environment.

[0025] The content of (a3-2) is preferably 4% by mass or more and less than 69% by mass based on 100% by mass of the monomer mixture. By including 4% by mass or more and less than 69% by mass, a balance of cohesive strength, adhesive strength, and tackiness can be ensured. It is more preferably 8% by mass or more and less than 60% by mass, even more preferably 10% by mass or more and less than 50% by mass, and particularly preferably 10% by mass or more and less than 42% by mass. The content of (a3-2) may be 4% by mass or more, 8% by mass or more, or 10% by mass or more, or may be less than 69% by mass, less than 60% by mass, or less than 50% by mass.

[0026] [Monomer (a4)] The monomer mixture constituting the acrylic polymer (A) may further contain less than 0.7% by mass of a hydroxyl group-containing monomer (a4). It is more preferable that the monomer (a4) be 0.03% by mass or more but less than 0.7% by mass, even more preferable that the monomer (a4) be 0.05% by mass or more but less than 0.7% by mass, and particularly preferably 0.05% by mass or more but less than 0.3% by mass. The inclusion of monomer (a4) enhances the cohesive strength of the adhesive layer, making it easier to balance adhesive strength and constant-load peel resistance. The content of (a4) may be 0.03% by mass or more, 0.05% by mass or more, or less than 0.7% by mass or less than 0.3% by mass.

[0027] Monomer (a4) is not limited as long as it is a monomer having a hydroxy group in the molecule, and specific examples include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc. Of these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred from the viewpoint of the balance between adhesive strength and constant load peel resistance.

[0028] (Production of Acrylic Polymer (A)) The acrylic polymer (A) can be produced by polymerizing the monomer mixture. Although known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization are possible, solution polymerization is preferred. Preferred solvents used in solution polymerization include, 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.

[0029] The polymerization initiator used in the polymerization is preferably a radical polymerization initiator. Radical polymerization initiators are generally peroxides and azo compounds. 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; peroxy esters 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; Examples of the peroxyketals include 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; and peroxydicarbonates such as bis(t-butylcyclohexyl)peroxydicarbonate.

[0030] 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'-azobispropionitrile such as 2,2'-azobis(2-hydroxymethylpropionitrile); and 1,1'-azobis-1-alkanenitrile such as 1,1'-azobis(cyclohexane-1-carbonitrile).

[0031] 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.

[0032] (Weight average molecular weight (Mw)) The weight average molecular weight of the acrylic polymer (A) is not particularly limited, but is preferably 2,000,000 or less, more preferably 1,000,000 or less, and even more preferably 800,000 or less. The weight average molecular weight is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0033] <Rosin-based tackifying resin (B1) having a softening point of 120° C. or higher> The rosin-based tackifying resin (B1) is not particularly limited as long as it has a softening point of 120° C. or higher. Examples thereof include rosin ester, polymerized rosin, hydrogenated rosin, disproportionated rosin, maleic acid-modified rosin, fumaric acid-modified rosin, rosin phenolic resin, and natural rosin.

[0034] The PSA of the present disclosure contains 10 to less than 60 parts by mass of a rosin-based tackifier resin (B1) having a softening point of 120°C or higher per 100 parts by mass of the acrylic polymer (A). A content of less than 10 parts by mass is undesirable because adhesive strength decreases. A content of 60 parts by mass or more is undesirable because low-load peel strength deteriorates. The content of (B1) is preferably 15 to less than 50 parts by mass, more preferably 20 to less than 40 parts by mass, per 100 parts by mass of the acrylic polymer (A). The content of (B1) may be 10 to less than 15 parts by mass, 20 to less than 20 parts by mass, or less than 60 parts by mass, 50 parts by mass, or less than 40 parts by mass.

[0035] The rosin-based tackifier resin (B1) preferably has a hydroxyl value of 20 mgKOH / g or more. A hydroxyl value of 20 mgKOH / g or more is preferred because a good bond is formed between the polymer and the rosin-based tackifier when a curing agent is used, resulting in a suitable crosslinked structure and, as a result, excellent constant-load peel resistance.

[0036] In consideration of the environment, it is more preferable to use a tackifier resin (B1) having a biomass content of 80% or more.

[0037] <Tackifier resin (B2) having a softening point of 90°C or higher but less than 120°C> The PSA of the present disclosure preferably further contains 10 parts by mass or more but less than 60 parts by mass of a tackifier resin (B2) having a softening point of 90°C or higher but less than 120°C per 100 parts by mass of the acrylic polymer (A). A content of less than 10 parts by mass is undesirable because the adhesive strength decreases. A content of 60 parts by mass or more is undesirable because the low-load peel strength deteriorates. A content of 15% by mass or more but less than 50% by mass is preferably 100 parts by mass of the acrylic polymer (A), and more preferably 20% by mass or more but less than 45% by mass. The tackifier resin (B2) having a softening point of 90°C or higher but less than 120°C preferably contains at least one selected from the group consisting of rosin-based tackifier resins, aliphatic petroleum resins, aromatic petroleum resins, aliphatic / aromatic petroleum resins, and terpene-based tackifiers. It is more preferable that the resin composition contains at least one selected from the group consisting of rosin-based tackifying resins, aliphatic petroleum resins, aromatic petroleum resins, and aliphatic / aromatic petroleum resins.

[0038] Examples of rosin-based tackifying resins include the same materials as those described above for rosin-based tackifying resins having a softening point of 120°C or higher.

[0039] Examples of aliphatic petroleum resins include Quinton B170 manufactured by Zeon Corporation; examples of aromatic petroleum resins include Nisseki Neopolymer L-90 manufactured by ENEOS Materials Corporation; examples of aliphatic / aromatic petroleum resins include FTR6100 manufactured by Mitsui Chemicals, Inc.; and examples of rosin derivatives include SylvatacRE85 manufactured by Arizona Chemical Company and Superester A-75 manufactured by Arakawa Chemical Industries, Ltd.

[0040] 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.

[0041] The biomass degree of the tackifier resin (B2) is not particularly limited, but is preferably 50% or more, and more preferably 80% or more.

[0042] <Curing Agent (C)> The pressure-sensitive adhesive of the present disclosure includes a curing agent (C). The curing agent (C) can be any curing agent that can impart a crosslinked structure to the pressure-sensitive adhesive. The addition of the curing agent (C) improves the cohesive strength of the pressure-sensitive adhesive layer, thereby improving adhesive strength, heat resistance, and light resistance. The curing agent (C) preferably includes at least one selected from the group consisting of an isocyanate-based curing agent, an epoxy-based curing agent, and an aluminum chelate-based curing agent. The inclusion of at least one selected from the group consisting of an isocyanate-based curing agent, an epoxy-based curing agent, and an aluminum chelate-based curing agent is preferred in that it can adequately increase the cohesive strength of the pressure-sensitive adhesive and is less likely to adversely affect other physical properties. As long as the pressure-sensitive adhesive includes at least one of an isocyanate-based curing agent, an epoxy-based curing agent, and an aluminum chelate-based curing agent, known curing agents other than an isocyanate-based curing agent, an epoxy-based curing agent, and an aluminum chelate-based curing agent may be used in combination.

[0043] The isocyanate curing agent is an isocyanate having two or more isocyanate groups. Examples of the isocyanate 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] The isocyanate compound is preferably a trifunctional isocyanate compound from the viewpoint of forming a sufficient crosslinked structure. 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.

[0052] 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. Aluminum chelate curing agents are not particularly limited as long as they have a chelating ligand and are capable of forming a crosslinked structure with the crosslinkable resin. The chelating ligand may be a bidentate ligand or a multidentate ligand (e.g., tridentate or higher), and examples include β-diketonates such as acetylacetonate, benzoylacetonate, and methyl acetylacetonate; and β-ketoester anions such as methyl acetoacetate and ethyl acetoacetate.

[0053] Specific examples of aluminum chelate curing agents include aluminum (ethyl acetoacetate) diisopropylate, aluminum tris(acetylacetonate), aluminum tris(ethyl acetoacetate), aluminum bis(ethyl acetoacetate) mono(acetylacetonate), etc. These aluminum chelate curing agents can be used alone or in combination of two or more.

[0054] The curing agent (C) is preferably contained in an amount of 0.02 to 6 parts by mass, and more preferably 0.04 to 1 part by mass, per 100 parts by mass of the acrylic polymer (A). A content of 0.02 part by mass or more further improves the cohesive strength, and a content of 1 part by mass or less is preferred because it is easier to achieve both cohesive strength and flexibility.

[0055] (Optional Components) The pressure-sensitive adhesive of the present disclosure may contain various resins, chlorinated polyolefins described below, oils, softeners, dyes, pigments, antioxidants, and UV absorbers as optional components, as long as the problem can be solved.

[0056] Examples of chlorinated polyolefins include chlorinated polypropylene, acid-modified chlorinated polypropylene, acrylic-modified chlorinated polypropylene, chlorinated polyethylene, and chlorinated ethylene-vinyl acetate copolymers. Chlorinated polypropylene and chlorinated ethylene-vinyl acetate copolymers are preferred from the viewpoints of good compatibility with acrylic polymers and the like and effective reduction of polarity. Specific examples of commercially available products include Superchlor 390S (chlorinated polypropylene, chlorine content 36%) and Superchlor BX (chlorinated EVA, chlorine content 18%) (both manufactured by Nippon Paper Industries Co., Ltd.).

[0057] The pressure-sensitive adhesive of the present disclosure preferably has a gel fraction of 10% or more and less than 50%, more preferably 30% or more and less than 50%. The method for measuring the gel fraction will be described in detail in the Examples.

[0058] <<Pressure-Sensitive Adhesive Layer>> The pressure-sensitive adhesive layer is a layer obtained from the pressure-sensitive adhesive of the present disclosure. The method for forming the pressure-sensitive adhesive layer is not particularly limited, and may be the same as the coating method described below in the description of the pressure-sensitive adhesive sheet.

[0059] The pressure-sensitive adhesive sheet of the present disclosure preferably has a higher SUS adhesive strength for the purpose of product fixation, etc. Although a low adhesive strength may be used for some products, for multi-purpose use, a peel strength of 2 N / 25 mm or more is preferred, 10 N / 25 mm or more is more preferred, and 15 N / 25 mm or more is even more preferred. The measurement method is described in detail in the Examples. The pressure-sensitive adhesive sheet of the present disclosure preferably has a higher PE adhesive strength for the purpose of product fixation, etc. Although a low adhesive strength may be used for some products, for multi-purpose use, a peel strength of 2 N / 25 mm or more is preferred, 5 N / 25 mm or more is more preferred, and 10 N / 25 mm or more is even more preferred. The measurement method is described in detail in the Examples. The pressure-sensitive adhesive sheet of the present disclosure preferably has a high holding power. Although a low holding power may be used for some products, for multi-purpose use, the less slippage when a load is applied, the better. The pressure-sensitive adhesive sheet of the present disclosure preferably has a high constant-load peel resistance. Although a low constant-load peel resistance may be used for some products, for multi-purpose use, the less slippage when a load is applied, the better. The pressure-sensitive adhesive sheet of the present disclosure preferably has high ball tack. Although low ball tack may be usable depending on the product, higher tack is preferable for versatile use.

[0060] <<Adhesive Sheet>> The adhesive sheet comprises the adhesive of the present disclosure or an adhesive layer made of the adhesive, and a release film.

[0061] The pressure-sensitive adhesive sheet of the present disclosure may have a configuration in which a release film is formed on one or both sides of the pressure-sensitive adhesive layer.

[0062] <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.

[0063] As the release film, among the above-mentioned transparent plastic substrates, 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 film or sheet is particularly suitable as the transparent plastic substrate.

[0064] 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 up into a roll and allowing for comfortable use when laminating sheets or the like.

[0065] The pressure-sensitive adhesive sheet of the present disclosure 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, and 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 protective films, films having an ITO (indium tin oxide) layer, films having 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 a conductive polymer, metal plates made of SUS or the like, metal meshes, and laminates of these.

[0066] The viscosity of the adhesive or adhesive coating can be adjusted by adding a suitable 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, or other hydrocarbon solvents.However, water and alcohol must be used carefully because they may inhibit the reaction between the acrylic polymer (A) and the isocyanate curing agent (B).

[0067] 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.

[0068] <Laminate> The laminate of the present disclosure includes a substrate and a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer is formed using the pressure-sensitive adhesive sheet of the present disclosure. Specifically, for example, the laminate can be formed by peeling the release film from the pressure-sensitive adhesive sheet of the present disclosure and attaching the pressure-sensitive adhesive layer to the substrate.

[0069] <Substrate> The substrate refers to the other party to which the adhesive layer of the adhesive sheet having an adhesive layer is attached, and is not limited to a specific one. Examples include resins such as polyolefins including polyethylene and polypropylene, polycarbonate, and phenol, metals such as iron, stainless steel (SUS), aluminum, and copper, as well as cement, mortar, glass, nonwoven fabric, woven fabric, paper, rubber, foam sheets, and laminates thereof. The adhesive and adhesive of the present disclosure exhibit excellent adhesive strength to at least one type of adherend.

[0070] The basis weight of the substrate is 500 g / m ２ Preferably, it is less than 230 g / m ２ It is more preferable that it is less than 10 ...

[0071] The laminate of the present disclosure 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 also be subjected to an appropriate surface treatment, such as a physical treatment such as corona discharge treatment or plasma treatment, or a chemical treatment such as a primer treatment.

[0072] An example of a schematic cross-sectional view partially illustrating the laminate of the present disclosure is shown in Figure 1. In Figure 1, 1 is a pressure-sensitive adhesive layer, 2 is a release film, and 3 is a substrate.

[0073] <Production of Laminate> A 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 attaching the pressure-sensitive adhesive layer to a substrate such as a PET substrate, a foam sheet, etc. Alternatively, a pressure-sensitive adhesive layer can be directly formed on various substrates, and then a pressure-sensitive adhesive layer provided on the substrate or another pressure-sensitive adhesive sheet can be attached to the pressure-sensitive adhesive layer to form a laminate.

[0074] In light of the recent trend toward environmentally friendly materials, the adhesive of the present disclosure can be made partially or entirely from biologically derived materials by using a biomass monomer or a biomass tackifier as the monomer constituting the acrylic polymer (A). 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.

[0075] Hereinafter, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to these examples. In the examples, unless otherwise specified, "parts" refers to "parts by mass" and "%" refers to "% by mass". In addition, the blending amounts in the tables are parts by mass, and the amounts other than the solvent are calculated as non-volatile contents. Note that blank spaces in the tables indicate that no blending has been performed.

[0076] <Production Example of Acrylic Polymer> Acrylic Polymer (A-1) Using a reaction apparatus equipped with a stirrer, a reflux condenser, a nitrogen inlet pipe, a thermometer, and a dropping tube, 30 parts of 2-octyl acrylate (2OA) as the monomer (a1), 1 part of acrylic acid as the monomer (a2), 68.8 parts of ethyl acrylate as the monomer (a3), 0.2 parts of 2-hydroxyethyl acrylate (HEA) as the monomer (a4), and 110 parts of ethyl acetate as a solvent were charged into a reaction vessel, and polymerization was carried out at 70°C for 5 hours under a nitrogen atmosphere, with the viscosity being appropriately adjusted by dropwise addition of ethyl acetate during the polymerization. After completion of the reaction, the mixture was cooled and appropriately diluted with ethyl acetate to obtain an acrylic polymer solution (A-1).

[0077] Acrylic Polymers (A-2 to A-32) Acrylic polymers (A-2 to A-32) were synthesized in the same manner as in the production of acrylic polymer (A-1), except that the compositions and blending amounts (parts by mass) were changed to those shown in Table 1.

[0078]

[0079]

[0080] The abbreviations are as follows: Regarding biomass content, only confirmed cases are listed. [Monomer (a1)] 2OA: 2-octyl acrylate (biomass content 73%) 2OMA: 2-octyl methacrylate (biomass content 67%) [Monomer (a2)] AA: acrylic acid MAA: methacrylic acid [Monomer (a3)] MA: methyl acrylate (Tg: 8°C) MMA: methyl methacrylate (Tg: 105°C) IBXA: isobornyl acrylate (Tg: 97°C, biomass content 76%) BMA: butyl methacrylate (Tg: 20°C) EA: ethyl acrylate (Tg: -22°C) BA: n-butyl acrylate (Tg: -55°C) iBA: isobutyl acrylate (Tg: -26°C) HA: n-hexyl acrylate (Tg: -60°C, biomass content 64%) 2EHA: 2-ethylhexyl acrylate (Tg: -70°C) sBA: sec-butyl acrylate (Tg: -20°C) LA: lauryl acrylate (Tg: -23°C, biomass content 80%) [Monomer (a4)] HEA: hydroxyethyl acrylate 4HBA: 4-hydroxy-normal-butyl acrylate

[0081] Example 1 A pressure-sensitive adhesive was obtained by adding 30 parts of Pencel D-125 (Arakawa Chemical Industries, Ltd., polymerized rosin ester) as a tackifier (B1) to 100 parts of an acrylic polymer (A-1) and blending 2 parts of "Coronate L" (Tosoh Corporation, trimethylolpropane-modified toluene diisocyanate compound) as a curing agent (C). The resulting pressure-sensitive adhesive was applied to a 38 μm-thick polyethylene terephthalate release sheet (Cerapeel MF, Toray Advanced Film Co., Ltd.) using a comma coater to a dry thickness of 50 μm, and then dried at 100°C for 2 minutes to obtain a pressure-sensitive adhesive sheet. Next, one side of a 50 μm-thick polyethylene terephthalate film (hereinafter referred to as PET film, product name: A-4300, Toyobo Co., Ltd.) was bonded to the adhesive surface of the pressure-sensitive adhesive sheet to obtain a laminate having a configuration of "release sheet / adhesive layer / PET film." The resulting laminate was then aged for one week under conditions of a temperature of 25° C. and a relative humidity of 55%, to obtain a pressure-sensitive adhesive sheet.

[0082] Examples 2 to 37, Comparative Examples 1 to 13 As shown in Table 2, pressure-sensitive adhesive sheets were obtained in the same manner as in Example 1, except that the types and blending amounts of the acrylic polymer, curing agent, and tackifier resin were changed.

[0083] <Gel Fraction Measurement> The 38 μm release liner was peeled off from the obtained 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., thickness 100 μm), and the sheet was 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, and its 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 test specimen after drying was measured, and the gel fraction was calculated using the following formula (1). In Table 2, "10-50%" means that the gel fraction is 10% or more and 50% or less, and "50%<" means that the gel fraction is more than 50%. Gel fraction (wt %)=100×(W ２ -W ０ ) / (W １ -W ０ )...(1) (W０ : Weight of substrate (PET film), W １ : weight of test piece before immersion, W ２ : weight of test piece after immersion and drying)

[0084] <Calculation of Biomass Degree> The biomass degree of the PSA 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 degree = {(Aw x Ab) + (Bw x Bb) + (Cw x Cb)} / (Aw + Bw + Cw) (2) Aw: weight of monomer A, Bw: weight of monomer B, Cw: weight of tackifier Ab: biomass degree of monomer A (%), Bb: biomass degree of monomer B (%), Cb: biomass degree of monomer C (%) When the biomass degree was specified as a range, the minimum value was used for the calculation.

[0085] The materials used in the examples and comparative examples are listed below.

[0086] <Tackifying Resin (B1)> D-125: (Pensel D-125, Arakawa Chemical Industries, Ltd., polymerized rosin ester, biomass degree 89%, softening point 125°C, hydroxyl value 32-33 mgKOH / g) YS-T130: (YS Polystar T130, Yasuhara Chemical Co., Ltd., terpene phenol, biomass degree 65%, softening point 130°C, hydroxyl value 80 mgKOH / g) A-125: (Super Ester A-125, Arakawa Chemical Industries, Ltd., polymerized rosin ester, biomass degree 80-94%, softening point 125°C, hydroxyl value 15 mgKOH / g)

[0087] <Tackifying resin (B2)> A-100: (Super Ester A-100, Arakawa Chemical Industries, Ltd., polymerized rosin ester, biomass content 99%, softening point 100°C, hydroxyl value 15) YS-T115: (YS Polystar T115, Yasuhara Chemical Co., Ltd., terpene phenol, biomass content 60%, softening point 115°C, hydroxyl value 40 or more) FTR6100: (Mitsui Chemicals, Inc., aliphatic / aromatic petroleum resin, biomass content 0%, softening point 95°C, hydroxyl value 10 or less) <Curing agent (C)> Coronate L: trimethylolpropane adduct of toluene diisocyanate, manufactured by Tosoh Corporation Tetrad X: multifunctional epoxy resin, manufactured by Mitsubishi Gas Chemical Company, Inc. Aluminum Chelate A: chelate curing agent, manufactured by Kawaken Fine Chemicals Co., Ltd.

[0088] The examples and comparative examples were evaluated according to the following methods and criteria. The results are shown in Table 2.

[0089] <SUS Adhesion Strength> The 38 μm release liner was peeled off from the obtained pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive layer was attached to a SUS plate in an atmosphere of 23°C and 50% relative humidity (50% RH), followed by pressure bonding with a roll in accordance with JIS Z-0237. 24 hours after pressure bonding, the peel strength (peel angle 180°, peel speed 300 mm / min; unit N / 25 mm width) was measured using a tensile tester (Tensilon, manufactured by Orientec Co., Ltd.). [Evaluation Criteria] A: Peel strength of 15 N / 25 mm or more: Good B: Peel strength of 10 N / 25 mm or more but less than 15 N / 25 mm: Fairly good C: Peel strength of 2 N / 25 mm or more but less than 10 N / 25 mm: Usable D: Peel strength of less than 2 N / 25 mm: Unusable

[0090] <PE Adhesion Strength> Measurement was performed in the same manner as in the glass adhesion strength measurement above, except that the adherend was changed from a SUS plate to a PE plate. [Evaluation Criteria] A: Peel strength is 10 N / 25 mm or more: Good B: Peel strength is 5 N / 25 mm or more and less than 10 N / 25 mm: Fair C: Peel strength is 2 N / 25 mm or more and less than 5 N / 25 mm: Usable D: Peel strength is less than 2 N / 25 mm: Unusable

[0091] <Holding Power> The obtained pressure-sensitive adhesive sheet was prepared in a size of 25 mm wide x 150 mm long. The release sheet was peeled off from the pressure-sensitive adhesive sheet, and the exposed pressure-sensitive adhesive layer was polished and attached to a 25 mm wide x 25 mm wide portion of the lower end of a 30 mm wide x 150 mm long stainless steel plate. After one round-trip compression with a 2 kg roll, a 1 kg load was applied to the lower end of the pressure-sensitive adhesive sheet in an 80°C atmosphere and left for 70,000 seconds to measure the holding power (in accordance with JIS Z0237:2000). The evaluation was performed by measuring the length by which the upper end of the pressure-sensitive adhesive sheet adhered surface shifted downward from its original position. [Evaluation Criteria] A: Shift length less than 3 mm: Good B: Shift length 3 mm or more but less than 7 mm: Fairly good C: Shift length 7 mm or more but less than 10 mm: Usable D: Shift length 10 mm or more or dropped: Unusable

[0092] <Constant Load Peel Resistance> This will be explained with reference to Figure 2. In an atmosphere of 23°C (relative humidity 50%), an 80 mm long section of the pressure-sensitive adhesive sheet (2) cut to a length of 100 mm and a width of 25 mm was attached to a propylene plate (product name "Kobe Poly Sheet PP", manufactured by Yamaso Co., Ltd.) serving as the adherend plate (1), and then pressed back and forth twice with a 2 kg roll. The sheet was then left in an atmosphere of 23°C (relative humidity 50%) for 24 hours. Thereafter, in an atmosphere of 80°C, a 100 g weight (3) was attached to the non-adhered portion of the pressure-sensitive adhesive sheet (2), and a load was applied perpendicular to the surface of the adherend plate (1). After 24 hours, the length of peeling of the pressure-sensitive adhesive sheet from the adherend was measured. If the sheet completely peeled off and the length could not be measured, the time until it fell off was measured. The length between A and B in Figure 2 represents the peeled length. Those that did not fall off are better than those that fell off. Among those that did not fall off, those with shorter peeled lengths are better. Among those that fell, the longer the time it took to fall, the better. [Evaluation Criteria] S: Peeling length less than 10 mm: Excellent A: Peeling length 10 mm or more but less than 20 mm: Good B: Peeling length 20 mm or more but less than 40 mm: Fairly good C: Peeling length 40 mm or more but did not fall: Usable D: Fall: Unusable

[0093] <Ball Tack> Ball tack evaluation was performed in accordance with JIS Z0237. The obtained pressure-sensitive adhesive sheet was cut to a length of 100 mm to prepare a test specimen. Next, the separator film was peeled off from the test specimen, and the test specimen was placed on an inclined surface at an angle of 30° so that the exposed pressure-sensitive adhesive layer faced upward. Steel balls ranging from No. 2 (2 / 32 inch) to No. 32 (32 / 32) inch were rolled in order from a position 100 mm in front of the test specimen. The number of the steel ball with the largest diameter that stopped on the test specimen at this time was taken as the tack value. [Evaluation Criteria] A: No. 5 or higher: Good B: No. 3 or higher but less than No. 5: Fairly good C: No. 2 or higher but less than No. 3: Usable D: Less than No. 2: Unusable

[0094]

[0095]

[0096] Although the present invention has been described with reference to the above-mentioned several embodiments, the present invention is not limited to these several embodiments. Various modifications can be made to the configuration and details of the present invention within the scope of the present invention.

[0097] The disclosure of this application is related to the subject matter described in Japanese Patent Application No. 2023-144832 filed on September 6, 2023, the subject matter described in Japanese Patent Application No. 2023-181269 filed on October 20, 2023, and the subject matter described in Japanese Patent Application No. 2024-019160 filed on February 13, 2024, the entire disclosures of which are incorporated herein by reference.

[0098] The symbols in Fig. 1 are explained below: 1 adhesive layer, 2 release film, 3 substrate The symbols in Fig. 2 are explained below: (1) adherend plate, (2) adhesive sheet, (3) weight

Claims

1. An adhesive comprising an acrylic polymer (A) which is a copolymer of a monomer mixture, a rosin-based tackifier resin (B1) having a softening point of 120 degrees or higher, and a curing agent (C), wherein the content of the rosin-based tackifier resin (B1) relative to 100 parts by mass of the acrylic polymer (A) is 10 to less than 60 parts by mass, and the adhesive contains, in 100% by mass of the monomer mixture, 30 to less than 95% by mass of the following monomer (a1), 1 to less than 10% by mass of the following monomer (a2), and 4 to 69% by mass of the following monomer (a3), and may further contain less than 0.7% by mass of the following monomer (a4): (a1) 2-octyl (meth)acrylate (a2) a monomer having a carboxy group (a3) ​​another monomer other than the monomer (a1), the monomer (a2), and the monomer (a4) (a4) a monomer having a hydroxy group.

2. The pressure-sensitive adhesive according to claim 1, wherein the monomer (a3) ​​contains a monomer (a3-1) (excluding the monomers (a2) and (a4)) having a homopolymer glass transition temperature of 0°C or higher.

3. The adhesive according to claim 1, wherein the monomer (a3) ​​contains an alkyl (meth)acrylate monomer (a3-2) (excluding monomer (a2) and monomer (a4)) having an alkyl group with 2 to 8 carbon atoms and a homopolymer glass transition temperature of less than 0°C.

4. The adhesive according to claim 1, containing 0.03 mass% or more and less than 0.7 mass% of monomer (a4) per 100 mass% of the monomer mixture.

5. The adhesive according to claim 1, having a biomass content of 30% or more.

6. The pressure-sensitive adhesive according to claim 1, wherein the rosin-based tackifier resin (B1) has a biomass ratio of 80% or more.

7. The pressure-sensitive adhesive according to claim 1, wherein the rosin-based tackifier resin (B1) has a hydroxyl value of 20 mgKOH / g or more.

8. The adhesive according to claim 1, further comprising 10 parts by mass or more and less than 60 parts by mass of a tackifier resin (B2) having a softening point of 90 degrees or more and less than 120 degrees per 100 parts by mass of the acrylic polymer (A), wherein the tackifier resin (B2) comprises at least one selected from the group consisting of rosin-based tackifier resins, aliphatic petroleum resins, aromatic petroleum resins, aliphatic / aromatic petroleum resins and terpene-based tackifiers.

9. The pressure-sensitive adhesive according to claim 1, wherein the curing agent (C) comprises at least one member selected from the group consisting of isocyanate-based curing agents, epoxy-based curing agents and aluminum chelate-based curing agents.

10. The pressure-sensitive adhesive according to claim 9, which has a gel fraction of less than 50%.

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

12. The pressure-sensitive adhesive layer according to claim 11, which has an adhesive strength to SUS of 10 N / 25 mm or more.

13. The pressure-sensitive adhesive layer according to claim 11, having a PE adhesive strength of 5 N / 25 mm or more.

14. An adhesive sheet comprising the adhesive layer according to claim 11 and a release film.

15. The pressure-sensitive adhesive sheet according to claim 14, wherein the release film has a thickness of less than 200 μm.

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

17. The basis weight of the substrate is 230 g / m ２ The laminate of claim 16, wherein the thickness is less than 1 mm.

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