Adhesive, adhesive sheet, and laminate

Abstract

To provide an adhesive that can contribute to saving of a petroleum resource by increasing a ratio of an environment-conscious type material, which has high adhesive force performance, and can achieve both constant load peeling resistance and tackiness.SOLUTION: An adhesive contains 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 more and a curing agent (C), wherein the content of the (B1) with respect to 100 pts.mass of the (A) is 10 or more and less than 60 pts.mass, in 100 mass% of the monomer mixture, 30 or more and less than 95 mass% of a monomer (a1), 1 or more and less than 10 mass% of a monomer (a2) and 4 or more and 69 mass% or less of a monomer (a3) are contained, and a monomer (a4) may be further contained. Here, (a1) is 2-octyl (meth)acrylate, (a2) is a monomer having a carboxy group, (a3) is a monomer other than (a1), (a2) and (a4), and (a4) is a monomer having a hydroxy group.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Due to their ease of handling, adhesive sheets with adhesive layers formed from adhesives are widely used in a wide range of applications, 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 often equipped with cover panels to protect their surfaces. The components that make up these optical displays are typically bonded together via an adhesive layer. 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. Therefore, they must be durable (constant-load peel resistance) 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 above-mentioned increasing performance requirements, the depletion of petroleum resources and carbon dioxide emissions from the combustion of petroleum-derived products are becoming issues in the industries in which PSA sheets are used. Therefore, attempts are being made to conserve petroleum resources by using bio-derived materials instead of petroleum-derived materials in various industries, starting with the packaging materials field, but also in the optical and semiconductor fields. One method for increasing the proportion of biologically derived materials in adhesives whose main component is an acrylic polymer 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 tackifying resins made from naturally occurring ingredients, and by selectively using these, it is possible to achieve environmentally friendly products.

[0004] The adhesives described in Patent Documents 1, 2, and 3 use acrylic polymers made from biological materials. The inventors' investigations revealed 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. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2009-529090 [Patent Document 2] Special Publication No. 2023-538015 [Patent Document 3] Special Publication No. 2024-110325 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[0008] 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 disclosure provides 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) per 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) Monomer having a carboxy group (a3) Other monomers other than the monomers (a1), (a2), and (a4). (a4) Monomer having a hydroxy group [Effects of the Invention]

[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. [Brief explanation of the drawings]

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

[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), the content of the rosin-based tackifying resin (B1) relative to 100 parts by mass of the acrylic polymer (A) is 10 parts by mass or more and less than 60 parts by mass, In 100% by mass of the monomer mixture, 30% by mass or more and less than 95% by mass of the following monomer (a1), The following monomer (a2) is contained in an amount of 1% by mass or more and less than 10% by mass: The copolymer contains the following monomer (a3) ​​in an amount of 4% by mass or more and 69% by mass or less: The pressure-sensitive adhesive may further contain less than 0.7% by mass of the following monomer (a4): (a1) 2-octyl (meth)acrylate (a2) Monomer having a carboxy group (a3) Other monomers other than the monomers (a1), (a2), and (a4). (a4) Monomer having a hydroxy group [2] The pressure-sensitive adhesive according to [1], wherein the monomer (a3) ​​contains a monomer (a3-1) (excluding the monomer (a2) and the monomer (a4)) whose homopolymer has a glass transition temperature of 0°C or higher. [3] The adhesive according to [1] or [2], wherein the monomer (a3) ​​contains an alkyl (meth)acrylate monomer (a3-2) (excluding the monomer (a2) and the monomer (a4)) having 2 to 8 carbon atoms in the alkyl group and a glass transition temperature of the homopolymer of the alkyl (meth)acrylate monomer (a3-2) of less than 0°C. [4] The pressure-sensitive adhesive according to any one of [1] to [3], wherein the monomer (a4) is contained in an amount of 0.03% by mass or more and less than 0.7% by mass based on 100% by mass of the monomer mixture. [5] The adhesive according to any one of [1] to [4] above, having a biomass content of 30% or more. [6] The pressure-sensitive adhesive according to any one of [1] to [5], wherein the rosin-based tackifying resin (B1) has a biomass content of 80% or more. [7] The pressure-sensitive adhesive according to any one of [1] to [6], wherein the rosin-based tackifying resin (B1) has a hydroxyl value of 20 mgKOH / g or more. [8] Further, the composition contains 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), The pressure-sensitive adhesive according to any one of [1] to [7], 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], 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], 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, which has an adhesive strength to SUS of 10 N / 25 mm or more.

[13] The pressure-sensitive adhesive layer according to

[11] or

[12] , 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] , wherein the thickness of the release film is 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] above, wherein the thickness is less than 1 / 2 mm.

[0013] The composition, pressure-sensitive adhesive sheet, and laminate of the present disclosure will be described below, but the present disclosure 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. In addition, 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" 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.

[0014] <Adhesive> The pressure-sensitive adhesive of the present disclosure comprises 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 the monomer mixture contains, in 100% by mass, 30% by mass or more and less than 95% by mass of the following monomer (a1), The following monomer (a2) is contained in an amount of 1% by mass or more and less than 10% by mass: The copolymer contains the following monomer (a3) ​​in an amount of 4% by mass or more and 69% by mass or less: Furthermore, the pressure-sensitive adhesive may contain less than 0.7 mass % of the following monomer (a4). (a1) 2-octyl (meth)acrylate (a2) Monomer having a carboxy group (a3) Other monomers other than the monomers (a1), (a2), and (a4). (a4) 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) [ka] (R1=H, CH3) 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, which can achieve the desired effect, but 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 in 100% by mass of the monomer mixture. The content of monomer (a2) is preferably 2% by mass or more but less than 10% by mass, more preferably 2% by mass or more but less than 7% by mass, even more preferably 2% by mass or more but less than 5% by mass, and particularly preferably 2% by mass or more but 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 may be 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 maleic acid, 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.

[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) ​​in 100% by mass of the monomer mixture is 4% by mass or more and less than 69% by mass. 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] Monomer (a3) ​​preferably includes monomer (a3-1), a monomer whose homopolymer has a glass transition temperature of 0°C or higher (excluding monomer (a2) and monomer (a4)), or monomer (a3-2), an alkyl (meth)acrylate monomer whose alkyl group has 2 to 8 carbon atoms and whose homopolymer has a glass transition temperature of less than 0°C (excluding monomer (a2) and monomer (a4)), more preferably includes monomer (a3-1), and even more preferably includes monomer (a3-1) and monomer (a3-2) simultaneously. By including the monomer (a3-1), the cohesive strength can be improved, and by including the monomer (a3-2), the constant load peel strength can be improved. 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).

[0022] (Monomer (a3-1)) The monomer (a3-1) is not particularly limited as long as it is a monomer whose homopolymer has a glass transition temperature of 0° C. or higher (excluding the monomer (a2) and the monomer (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. Furthermore, 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%, 20%, or 15% by mass.

[0024] (Monomer (a3-2)) The monomer (a3-2) is an alkyl(meth)acrylate monomer having an alkyl group with 2 to 8 carbon atoms and a homopolymer glass transition temperature of less than 0°C (excluding the monomers (a2) and (a4)). Examples of the 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 the constant load peel resistance, it is preferable that the monomer (a3-2) contains at least one selected from the group consisting of isopropyl acrylate, isobutyl acrylate, isopentyl acrylate, and isoamyl acrylate. In consideration of the environment, it is more preferable that (a3) ​​be a (meth)acrylate, which is a biomass monomer.

[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 containing 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, 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). The content is preferably 0.03% by mass or more but less than 0.7% by mass, even more preferably 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) increases 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.

[0027] Monomer (a4) is not limited as long as it is a monomer having a hydroxy group in the molecule, and specific examples thereof 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 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 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.

[0029] 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.

[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'-azobispropionitriles such as 2,2'-azobis(2-hydroxymethylpropionitrile); Examples include 1,1'-azobis-1-alkanenitriles 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 pressure-sensitive adhesive of the present disclosure contains 10 to less than 60 parts by mass of a rosin-based tackifying resin (B1) having a softening point of 120°C or higher per 100 parts by mass of an 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 decreases. 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 may be less than 60 parts by mass, 50 parts by mass, or less than 40 parts by mass.

[0035] The rosin-based tackifying 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 tackifying resin 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] <Tackifying resin (B2) having a softening point of 90°C or more and less than 120°C> The pressure-sensitive adhesive of the present disclosure preferably further contains 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). A content of less than 10 parts by mass is undesirable because adhesive strength is low, and a content of 60 parts by mass or more is undesirable because low-load peel strength is poor. The content is preferably 15% by mass or more but less than 50% by mass, more preferably 20% by mass or more but less than 45% by mass, based on 100 parts by mass of the acrylic polymer (A). The tackifying resin (B2) having a softening point of 90°C or more and less than 120°C preferably contains at least one selected from the group consisting of rosin-based tackifying resins, aliphatic petroleum resins, aromatic petroleum resins, aliphatic / aromatic petroleum resins, and terpene-based tackifiers, and more preferably 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 Nippon Oil 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 Sylvatac RE85 manufactured by Arizona Chemical Company and Super Ester 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, more preferably 80% or more.

[0042] <Curing agent (C)> The pressure-sensitive adhesive of the present disclosure contains a curing agent (C), and any curing agent (C) can be used without particular limitation as long as it provides a crosslinked structure to the pressure-sensitive adhesive. The incorporation of the curing agent (C) improves the cohesive strength of the pressure-sensitive adhesive layer, and improves the adhesive strength, heat resistance, and light resistance. The curing agent (C) preferably contains 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. By including 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 cohesive strength of the adhesive can be appropriately increased and other physical properties are less likely to be adversely affected, which is preferable. As long as at least one of an isocyanate-based curing agent, an epoxy-based curing agent, and an aluminum chelate-based curing agent is included, 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] 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.

[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. The aluminum chelate curing agent is not particularly limited as long as it has a chelating ligand and has the function 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 thereof 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), and aluminum bis(ethyl acetoacetate) mono(acetylacetonate). These aluminum chelate curing agents may be used either individually 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 ingredient) The pressure-sensitive adhesive of the present disclosure 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.

[0056] 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.).

[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] <Adhesive layer> The pressure-sensitive adhesive layer is a layer obtained from the pressure-sensitive adhesive of the present disclosure. There are no particular limitations 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.

[0059] The adhesive sheet of the present disclosure preferably has a higher SUS adhesive strength for the purpose of product fixation, etc. Although a lower adhesive strength may be used depending on the product, for versatile 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 adhesive sheet of the present disclosure preferably has a high PE adhesive strength 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 2 N / 25 mm or more, more preferably 5 N / 25 mm or more, and even more preferably 10 N / 25 mm or more. The measurement method is described in detail in the Examples. It is preferable that the pressure-sensitive adhesive sheet of the present disclosure has high holding power. Although it may be possible to use a pressure-sensitive adhesive sheet with low holding power depending on the product, for versatile use, it is preferable that the sheet has less slippage when a load is applied. It is preferable that the pressure-sensitive adhesive sheet of the present disclosure has high constant-load peel resistance. Depending on the product, it may be possible to use a pressure-sensitive adhesive sheet with low constant-load peel resistance, but for versatile 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 pressure-sensitive adhesive sheet comprises the pressure-sensitive adhesive of the present disclosure or a pressure-sensitive adhesive layer made of the pressure-sensitive 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] 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.

[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 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, 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 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 conductive polymers, 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 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).

[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] <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 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 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 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.

[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] <Manufacturing of laminate> The laminate can be produced, for example, by peeling off the release films 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 PET substrate, a foam sheet, etc. Alternatively, a pressure-sensitive adhesive layer can be directly formed on various substrates, and then an 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 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. [Example]

[0075] The present disclosure will be explained in more detail below using examples, but the present disclosure is not limited to these examples. In the examples, unless otherwise specified, "parts" means "parts by mass" and "%" means "% 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 reactor equipped with a stirrer, reflux condenser, nitrogen inlet pipe, thermometer, and dropping tube, 30 parts of 2-octyl acrylate (2OA) as monomer (a1), 1 part of acrylic acid as monomer (a2), 68.8 parts of ethyl acrylate as monomer (a3), 0.2 parts of 2-hydroxyethyl acrylate (HEA) as monomer (a4), and 110 parts of ethyl acetate as solvent were charged into a reaction vessel, and polymerized for 5 hours at 70 ° C. under a nitrogen atmosphere, and the viscosity was adjusted appropriately by dropping ethyl acetate during polymerization. After the reaction was completed, the mixture was cooled and diluted appropriately 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] [Table 1]

[0079] [Table 1]

[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 To 100 parts of the acrylic polymer (A-1), 30 parts of Pencel D-125 (Arakawa Chemical Industries, Ltd., polymerized rosin ester) was added as a tackifier (B1), and 2 parts of "Coronate L" (Tosoh Corporation, trimethylolpropane-modified toluene diisocyanate) was added as a curing agent (C) to obtain an 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 so that the dried thickness was 50 μm, and the sheet was dried at 100°C for 2 minutes to obtain an adhesive sheet. Next, one side of a 50 μm thick polyethylene terephthalate film (hereinafter referred to as PET film, product name: A-4300, manufactured by Toyobo Co., Ltd.) was bonded to the adhesive surface of the adhesive sheet to obtain a laminate consisting of "release sheet / adhesive layer / PET film." The resulting laminate was then aged for 1 week at a temperature of 25°C and a relative humidity of 55%, to obtain an adhesive sheet.

[0082] <Examples 2 to 37 and 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 resulting pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive layer was attached to a PET film substrate (Cosmoshine A-4360, 100 μm thick, manufactured by Toyobo Co., Ltd.), 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). 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 greater than 50%. Gel fraction (wt%) = 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)

[0084] <Biomass degree calculation> 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 tackifier 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.

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

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

[0087] <Adhesion-imparting 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 Polyster T115, Yasuhara Chemical Co., Ltd., terpene phenol, biomass content 60%, softening point 115°C, hydroxyl value 40 or more) s FTR6100: (Mitsui Chemicals, Inc., aliphatic / aromatic petroleum resin, biomass content 0%, softening point 95°C, hydroxyl value 10 or less) <Hardening agent (C)> Coronate L: Manufactured by Tosoh Corporation, trimethylolpropane adduct of toluene diisocyanate Tetrad X: Manufactured by Mitsubishi Gas Chemical Company, Inc., polyfunctional epoxy resin Aluminum chelate A: Manufactured by Kawaken Fine Chemicals Co., Ltd., chelating hardening agent

[0088] The evaluation of the examples and comparative examples was carried out according to the following methods and evaluation criteria. The results are shown in Table 2.

[0089] <SUS Adhesive Strength> The 38-μm release liner of the obtained adhesive sheet was peeled off, and the adhesive layer was attached to a SUS plate in an atmosphere of 23°C and 50% relative humidity (50% RH), and then crimped with a roll in accordance with JIS Z-0237. After 24 hours from the crimping, 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 is 15 N / 25 mm or more: Good B: Peel strength is 10 N / 25 mm or more and less than 15 N / 25 mm: Somewhat good C: Peel strength is 2 N / 25 mm or more and less than 10 N / 25 mm: Usable D: Peel strength is less than 2 N / 25 mm: Unusable

[0090] <PE Adhesive Strength> Measurement was carried out in the same manner as the above glass adhesive strength measurement, 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: Somewhat good 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] [[ID= thirty]]<Retention Force> The obtained adhesive sheet was prepared in a size of 25 mm in width and 150 mm in length. The adhesive layer exposed by peeling off the release sheet from the adhesive sheet was attached to a portion with a width of 25 mm and a length of 25 mm at the lower end of a stainless steel plate with a width of 30 mm and a length of 150 mm that had been polished. After crimping back and forth once with a 2-kg roll, a load of 1 kg was applied to the lower end of the adhesive sheet in an 80°C atmosphere, and the retention force was measured by leaving it for 70,000 seconds (in accordance with JIS Z0237:2000). The evaluation was carried out by measuring the length by which the upper end portion of the adhesive sheet attachment surface was displaced downward from the original position. [Evaluation Criteria] A: Displacement length is less than 3 mm: Good B: Displacement length is 3 mm or more and less than 7 mm: Somewhat good C: The deviation is 7mm or more and less than 10mm: Usable D: If the deviation is 10mm or more or if it falls, it cannot be used.

[0092] <Constant load peel resistance> The following description will be given with reference to Figure 2. In an atmosphere of 23°C (relative humidity 50%), an 80 mm long section of the 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), which was then pressed back and forth twice with a 2 kg roll and left for 24 hours in an atmosphere of 23°C (relative humidity 50%). Subsequently, in an atmosphere of 80°C, a 100 g weight (3) was attached to the non-adhered portion of the 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 adhesive sheet from the adherend was measured. If the adhesive 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 peeling lengths are better. Furthermore, among those that fell, the longer it took to fall, the better. [Evaluation criteria] S: Peeling length less than 10 mm: Excellent A: Peeling length is 10mm or more but less than 20mm: Good B: Peeling length is 20mm or more and less than 40mm: Fairly good C: Peeling length is 40mm or more and no drop occurs: Usable D: Fall: Unusable

[0093] <Ball tuck> Ball tack evaluation was performed in accordance with JIS Z0237. The obtained pressure-sensitive adhesive sheet was cut into 100 mm lengths to prepare test specimens. 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 recorded as the tack value. [Evaluation criteria] A: No.5 or higher: Good B: No. 3 or above but less than No. 5: Fairly good C: No.2 or more and less than No.3: Usable D: Below No. 2: Unusable

[0094] [Table 2]

[0095] [Table 2]

[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. [Explanation of symbols]

[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. A pressure-sensitive adhesive comprising an acrylic polymer (A) which 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), the content of the rosin-based tackifying resin (B1) relative to 100 parts by mass of the acrylic polymer (A) is 10 parts by mass or more and less than 60 parts by mass, In 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), The pressure-sensitive adhesive may further contain less than 0.7 mass % of the following monomer (a4): (a1) 2-octyl (meth)acrylate (a2) Monomer having a carboxy group (a3) Other monomers other than the monomers (a1), (a2), and (a4) (a4) 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 monomer (a2) and the monomer (a4)) whose homopolymer has a glass transition temperature of 0°C or higher.

3. The pressure-sensitive adhesive according to claim 1, wherein the monomer (a3) ​​contains an alkyl(meth)acrylate monomer (a3-2) (excluding the monomer (a2) and the 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 pressure-sensitive adhesive according to claim 1, comprising 0.03 mass% or more and less than 0.7 mass% of the monomer (a4) relative to 100 mass% of the monomer mixture.

5. The pressure-sensitive 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 tackifying resin (B1) has a biomass content of 80% or more.

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

8. Further, the composition contains 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), The pressure-sensitive adhesive according to claim 1, 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. 2. The pressure-sensitive adhesive according to claim 1, 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 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, having an SUS adhesive strength of 10 N / 25 mm or more.

13. The pressure-sensitive adhesive layer according to claim 11, 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 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 / 2 mm.

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