Adhesive, adhesive sheet, method for manufacturing adhesive sheet, and image display device

Abstract

The present application provides an adhesive with excellent easy peelability. An adhesive characterized by comprising the following components (A) and (B), (A) a polyurethane prepolymer having a hydroxyl group, having a structure synthesized from a polyol and an isocyanate, (B) a polyoxyalkylene ether compound represented by the following formula (1), RO-(AO) n -H … (1), in the formula (1), R is an aliphatic group or an aromatic group having 4 to 30 carbon atoms, A is an alkylene group having 2 to 4 carbon atoms, respectively, A can be the same or different when a plurality of A's are present, and n is a polymerization degree, which is an integer of 0 to 100.

Description

Technical Field

[0001] This disclosure relates to an adhesive, an adhesive sheet, a method for manufacturing the adhesive sheet, and an image display device. Background Technology

[0002] Adhesives and adhesive sheets using them are widely used in various industrial sectors. Specific applications include, for example, protective films used to adhere to the surface of objects. Examples of objects to be adhered to include, for example, the image display surface of image display devices such as mobile phones and smartphones, and windows of automobiles and buildings.

[0003] Adhesives include, for example, acrylic resin-based adhesives, rubber-based adhesives, and polyurethane adhesives. Among them, polyurethane adhesives are widely used due to their excellent properties, such as the ability to peel off after application (hereinafter referred to as re-peelability) and the property that it is difficult to trap air bubbles at the interface between the adhesive layer and the adhered object (hereinafter referred to as wetting properties) (Patent Document 1, etc.).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-186064 Summary of the Invention

[0007] The technical problem that the invention aims to solve

[0008] The adhesive used in surface protection adhesive sheets needs to have the property of being able to be peeled off with light force (light peelability) so that the adhesive sheet can be peeled off again.

[0009] Therefore, the purpose of this disclosure is to provide an adhesive with excellent peelability, an adhesive sheet, a method for manufacturing the adhesive sheet, and an image display device.

[0010] means of solving technical problems

[0011] To achieve the stated purpose, the adhesive disclosed herein is characterized by comprising the following components (A) and (B).

[0012] (A) A polyurethane prepolymer with hydroxyl groups, having a structure synthesized from polyols and isocyanates.

[0013] (B) Polyoxyalkylene ether compounds represented by the following chemical formula (1),

[0014] RO-(AO) n -H …(1)

[0015] In the chemical formula (1),

[0016] R is an aliphatic or aromatic group with 4 to 30 carbon atoms.

[0017] A represents alkylene groups having 2 to 4 carbon atoms. When there are multiple A's, they can be the same or different from each other.

[0018] n is the degree of aggregation, an integer from 0 to 100.

[0019] The adhesive sheet of this disclosure is characterized by having an adhesive layer formed by the adhesive of this disclosure.

[0020] The method for manufacturing the adhesive sheet disclosed herein includes: a coating step, wherein the adhesive disclosed herein is coated on the adhesive layer forming surface of the substrate to which the adhesive layer is to be formed; and a heating step, wherein the adhesive on the adhesive layer forming surface is heated after the coating step.

[0021] The image display device disclosed herein is an image display device in which a protective sheet is attached to an image display surface. The protective sheet is an adhesive sheet of the present disclosure that further comprises a substrate and has the adhesive layer formed on at least one surface of the substrate. The adhesive sheet is attached to the image display surface through the adhesive layer.

[0022] The effects of the invention

[0023] According to this disclosure, an adhesive with excellent peelability, an adhesive sheet, a method for manufacturing the adhesive sheet, and an image display device can be provided. Detailed Implementation

[0024] The following examples illustrate this disclosure. However, this disclosure is not limited to the following description.

[0025] In this disclosure, "aliphatic group" is not particularly limited; for example, it can be saturated or unsaturated, and may or may not contain a cyclic structure. Examples of aliphatic groups include alkyl, alkenyl, alkynyl, cycloalkyl, and cycloalkenyl groups.

[0026] In this disclosure, "alkyl" includes, for example, straight-chain or branched alkyl groups. The number of carbon atoms in the alkyl group is not particularly limited, and is, for example, 1 to 30, preferably 1 to 18, 3 to 16, or 4 to 12. The alkyl group is not particularly limited, and examples include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, octadecyl, nonadecanyl, eicosyl, etc. The same applies to groups or radicals derived from alkyl groups (alkoxy groups, etc.). The same applies to groups containing alkyl groups in their structure (alkylamino, alkoxy, etc.) or groups derived from alkyl groups (haloalkyl, hydroxyalkyl, aminoalkyl, alkylyl, etc.).

[0027] In this disclosure, "alkenyl" includes, for example, straight-chain or branched alkenyl groups. Examples of alkenyl groups include groups having one or more double bonds in the alkyl group. The number of carbon atoms in the alkenyl group is not particularly limited, and is preferably the same as that in the alkyl group, but 2 to 12 or 2 to 8. Examples of alkenyl groups include vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1,3-butadienyl, 3-methyl-2-butenyl, etc.

[0028] In this disclosure, "alkynyl" includes, for example, a straight-chain or branched alkynyl group. Examples of alkynyl groups include groups having one or more triple bonds in the alkyl group. The number of carbon atoms in the alkynyl group is not particularly limited, and is preferably the same as that in the alkyl group, but 2 to 12 or 2 to 8. Examples of alkynyl groups include ethynyl, propynyl, and butynyl. The alkynyl group may also have one or more double bonds.

[0029] In this disclosure, "aromatic ring" or "aromatic group" includes, for example, aryl, heteroaryl, and aralkyl. Additionally, "cyclic structure" includes, for example, the aromatic ring, cycloalkyl, bridged cyclic hydrocarbon group, spirocyclic hydrocarbon group, and cycloalkenyl.

[0030] In this disclosure, "aryl" includes, for example, monocyclic aromatic hydrocarbon groups and polycyclic aromatic hydrocarbon groups. Examples of monocyclic aromatic hydrocarbon groups include phenyl. Examples of polycyclic aromatic hydrocarbon groups include 1-naphthyl, 2-naphthyl, 1-anthrayl, 2-anthrayl, 9-anthrayl, 1-phenanthyl, 2-phenanthyl, 3-phenanthyl, 4-phenanthyl, 9-phenanthyl, etc. Preferably, examples include naphthyl groups such as phenyl, 1-naphthyl, and 2-naphthyl.

[0031] In this disclosure, "heteroaryl" includes, for example, monocyclic aromatic heterocyclic groups and fused aromatic heterocyclic groups. Examples of heteroaryl groups include furanyl (e.g., 2-furanyl), thienyl (e.g., 2-thienyl), pyrrolyl (e.g., 1-pyrrolyl), imidazolyl (e.g., 1-imidazolyl), pyrazolel (e.g., 1-pyrazolel), triazolyl (e.g., 1,2,4-triazol-1-yl), tetrazolyl (e.g., 1-tetrazolyl), oxazolyl (e.g., 2-oxazolyl), isoxazolyl (e.g., 3-isooxazolyl), thiazolyl (e.g., 2-thiazolyl), thiadiazolyl, isothiazolyl (e.g., 3-isothiazolyl), pyridinyl (e.g., 2-pyridinyl), pyrazinyl (e.g., 3-pyrazinyl), pyrimidinyl (e.g., 2-pyrimidinyl), furazolyl (e.g., 3-furazinyl), pyrazinyl (e.g., 2-pyrazinyl), and oxadiazolyl (e.g., 1,3,4-oxadiazolyl). -2-yl), benzofuranyl (e.g., 2-benzo[b]furanyl), benzothiophenyl (e.g., 2-benzo[b]thiophenyl), benzimidazolyl (e.g., 1-benzimidazolyl), dibenzofuranyl, benzooxazolyl, benzothiazolyl, quinoxalinyl (e.g., 2-quinoxalinyl), cenolinyl (e.g., 3-cenolinyl), quinazolinyl (e.g., 2-quinazolinyl), quinolinyl (e.g., 2-quinolinyl), phthalazinyl (e.g., 1-phthalazinyl), isoquinolinyl (e.g., 1-isoquinolinyl), purinyl, pteridinyl (e.g., 2-pteridinyl), carbazolyl, phenanthidyl, acridineyl (e.g., 1-acridinyl), indolyl (e.g., 1-indolyl), isoindolyl, phenazinyl (e.g., 1-phenazinyl) or phenothiazinyl (e.g., 1-phenothiazinyl), etc.

[0032] In this disclosure, "cycloalkyl" is, for example, a cyclic saturated hydrocarbon group, and the number of carbon atoms is not particularly limited, for example, 3 to 24 or 3 to 15. Examples of cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, bridged cycloalkyl, spirocycloalkyl, etc., and preferably include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, bridged cycloalkyl, etc.

[0033] In this disclosure, "bridged cyclic hydrocarbon groups" may include, for example, bicyclic [2.1.0]pentyl, bicyclic [2.2.1]heptyl, bicyclic [2.2.2]octyl and bicyclic [3.2.1]octyl, tricyclic [2.2.1.0]heptyl, bicyclic [3.3.1]nonane, 1-adamantyl, 2-adamantyl, etc.

[0034] In this disclosure, "spirocyclic hydrocarbon group" can be exemplified by spiro[3.4]octyl, etc.

[0035] In this disclosure, "cycloalkenyl" includes, for example, cyclic unsaturated aliphatic hydrocarbon groups with, for example, 3 to 24 or 3 to 7 carbon atoms. Examples of such cyclic unsaturated aliphatic hydrocarbon groups include cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, etc., preferably cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, etc. The cycloalkenyl also includes, for example, bridged cyclic hydrocarbon groups and spirocyclic hydrocarbon groups having unsaturated bonds in the ring.

[0036] In this disclosure, "aryl" can be exemplified by benzyl, 2-phenylethyl and naphthylmethyl, "cycloalkyl" can be exemplified by cyclohexylmethyl, adamantylmethyl and other examples, and "hydroxyalkyl" can be exemplified by hydroxymethyl and 2-hydroxyethyl.

[0037] Furthermore, in this disclosure, the term "substituent" or "further substituent" is not particularly limited, and includes, for example: carboxyl, halogen, haloalkyl (e.g., CF3, CH2CF3, CH2CCl3), nitro, nitroso, cyano, alkyl (e.g., methyl, ethyl, isopropyl, tert-butyl), alkenyl (e.g., vinyl), alkynyl (e.g., ethynyl), cycloalkyl (e.g., cyclopropyl, adamantyl), cycloalkylalkyl (e.g., cyclohexylmethyl, adamantylmethyl), cycloalkenyl (e.g., cyclopropenyl), aryl (e.g., phenyl, naphthyl), aralkyl (e.g., benzyl, phenethyl), heteroaryl (e.g., pyridyl, furanyl), heteroarylalkyl (e.g., pyridylmethyl), heterocyclic (e.g., piperidinyl) Heterocyclic alkyl groups (e.g., morpholinomethyl), alkoxy groups (e.g., methoxy, ethoxy, propoxy, butoxy), perfluoroalkyl groups (e.g., CF3), haloalkoxy groups (e.g., OCF3), acyl groups, alkenyloxy groups (e.g., ethyleneoxy, allyloxy), aryloxy groups (e.g., phenoxy), alkoxycarbonyl groups (e.g., methoxycarbonyl, ethoxycarbonyl, tert-butoxycarbonyl), aralkyloxy groups (e.g., benzyloxy), aminoalkylamino groups (e.g., methylamino, ethylamino, dimethylamino), acylamino groups (e.g., acetamido, benzoylamino), aralkylamino groups (e.g., benzylamino, triphenylmethylamino, hydroxyamino), alkylaminoalkyl groups (e.g., diethylaminomethyl), aminosulfonyl groups, oxo groups, etc.

[0038] In this disclosure, "alkoxy" includes, for example, the alkyl-O-yl group, such as methoxy, ethoxy, n-propoxy, isopropoxy and n-butoxy, etc.; "alkoxyalkyl" includes, for example, methoxymethyl, etc.; and "aminoalkyl" includes, for example, 2-aminoethyl, etc.

[0039] In this disclosure, "acyl" is not specifically limited, and examples include: formyl, acetyl, propionyl, isobutyryl, valeryl, isovaleryl, neovaleryl, hexanoyl, cyclohexanoyl, benzoyl, ethoxycarbonyl, etc. The same applies to groups containing an acyl group in their structure (acyloxy, alkanoyloxy, etc.). Furthermore, in this disclosure, the number of carbon atoms in the acyl group includes a carbonyl carbon; for example, an alkanoyl group (acyl) with one carbon atom is a methyl acyl group.

[0040] In this disclosure, "halogen" refers to any halogen element, such as fluorine, chlorine, bromine and iodine.

[0041] In this disclosure, "perfluoroalkyl" is not specifically limited, and examples include perfluoroalkyl groups derived from straight-chain or branched alkyl groups having 1 to 30 carbon atoms. More specifically, examples include perfluoroalkyl groups derived from groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecanyl, octadecyl, nonadecanyl, and eicosyl. The same applies to groups containing perfluoroalkyl in their structure (perfluoroalkylsulfonyl, perfluoroacyl, etc.).

[0042] In addition, in this disclosure, when the aforementioned groups are heterocycles or contain heterocycles, the "number of carbon atoms" also includes the number of heteroatoms constituting the heterocycle.

[0043] Furthermore, in this disclosure, when substituents or the like are isomers, they can be any isomers unless otherwise specified. For example, when referred to as "naphthyl," it can be 1-naphthyl or 2-naphthyl; when referred to as "propyl," it can be n-propyl or isopropyl.

[0044] The embodiments of this disclosure are described in more detail below. However, this disclosure is not limited to the embodiments described below.

[0045] [1. Adhesive]

[0046] As described above, the adhesive disclosed herein is characterized by comprising the following components (A) and (B).

[0047] (A) A polyurethane prepolymer with hydroxyl groups, having a structure synthesized from polyols and isocyanates;

[0048] (B) Polyoxyalkylene ether compounds represented by the following chemical formula (1),

[0049] RO-(AO) n -H …(1)

[0050] In the chemical formula (1),

[0051] R is an aliphatic or aromatic group with 4 to 30 carbon atoms.

[0052] A represents alkylene groups having 2 to 4 carbon atoms. When there are multiple A's, they can be the same or different from each other.

[0053] n is the degree of aggregation, an integer from 0 to 100.

[0054] [1-1. Polyurethane prepolymer with hydroxyl groups (A)]

[0055] As described above, the component (A) in the adhesive of this disclosure (hereinafter sometimes referred to as "polyurethane prepolymer (A)") is a polyurethane prepolymer having hydroxyl groups and having a structure synthesized from polyols and isocyanates.

[0056] As described above, polyurethane prepolymer (A) is a polyurethane polyol having a structure synthesized from polyols and polyisocyanates. Furthermore, in this disclosure, "polyurethane prepolymer" refers to a prepolymer of polyurethane. In this disclosure, "polyurethane polyol" is a prepolymer of polyurethane, referring to a prepolymer having multiple hydroxyl groups. Additionally, in this disclosure, "prepolymer" refers to a polymer that has undergone polymerization or crosslinking to an intermediate stage, and is a polymer from which further polymerization or crosslinking can proceed. In this disclosure, "polyurethane prepolymer" refers to a polyurethane that has undergone polymerization or crosslinking to an intermediate stage, and is a polyurethane that can be converted into a polyurethane that has undergone further polymerization or crosslinking. The "polyurethane prepolymer" can be converted into a polyurethane that has undergone further polymerization or crosslinking, for example, by having multiple hydroxyl or isocyanate groups. In this disclosure, "polyurethane polyisocyanate," unless specifically stated otherwise, refers to a polyurethane prepolymer that can be converted into a polyurethane that has undergone further polymerization or crosslinking by having multiple (e.g., at both ends of the molecule) isocyanate groups. However, in this disclosure, polyurethane prepolymer (A), as described above, is a polyurethane prepolymer having hydroxyl groups. In addition, in this disclosure, "polyol" refers to an organic compound having multiple (two or more) hydroxyl groups (preferably at least one of alcoholic hydroxyl and phenolic hydroxyl groups) in one molecule. "Polyisocyanate" refers to an organic compound (polyfunctional isocyanate) having multiple (two or more) isocyanate groups (-N=C=O, also called isocyanate groups) in one molecule.

[0057] The hydroxyl value of the polyurethane prepolymer (A) is not particularly limited; for example, it can be 1 mgKOH / g or more, or 10 mgKOH / g or more, or 50 mgKOH / g or less, 30 mgKOH / g or less, or 25 mgKOH / g or less. The hydroxyl value of the polyurethane prepolymer (A) can be, for example, 1–50 mgKOH / g, 1–30 mgKOH / g, 10–30 mgKOH / g, or 10–25 mgKOH / g. When the hydroxyl value of the polyurethane prepolymer (A) is within the specified range, for example in adhesive sheets, an adhesive layer with good crosslinking density is easily obtained, and wettability is further improved.

[0058] Furthermore, there are no particular limitations on the method for determining the hydroxyl value of polyurethane prepolymer (A), and it can be determined by, for example, the following methods.

[0059] [Method for determining hydroxyl value]

[0060] The hydroxyl value (OHV) of the resin can be determined according to the determination method of JIS K1557-1:2007. Specifically, 1 g of the resin (e.g., polyurethane prepolymer (A)) is acetylated with acetic anhydride, and the number of mg of potassium hydroxide required for neutralization is taken as the hydroxyl value of the resin [mgKOH / g].

[0061] As described above, the polyurethane prepolymer (A) can be, for example, an adduct of a polyol and an isocyanate. The isocyanate can be, for example, a polyisocyanate. The polyurethane prepolymer (A) can be manufactured, for example, by reacting the polyol with the isocyanate. Furthermore, the hydroxyl value of the polyurethane prepolymer (A) can be adjusted by known methods, such as adjusting the molecular weight of the polyol during the reaction, adjusting the number of functional groups of the hydroxyl groups in the polyol, adjusting the mixing ratio of the polyol and the isocyanate, etc. Moreover, the types of the polyol and the isocyanate will be described later in "2. Method for Manufacturing Adhesives," along with examples of the adhesive manufacturing methods of this disclosure.

[0062] The number of hydroxyl functional groups in one molecule of the polyol used as a raw material for polyurethane prepolymer (A) is not particularly limited, but is, for example, 2 to 4, and particularly preferably 3. The molecular weight (number average molecular weight) of the polyol is also not particularly limited, and can be, for example, 1000 to 15000, 1000 to 6000, or 2000 to 5000. The polyol preferably comprises a polyether polyol. For example, it is preferred that the polyol comprises a trifunctional (containing 3 hydroxyl groups per molecule) polyether polyol with a hydroxyl value of 10 to 170 mg KOH / g. Furthermore, the hydroxyl value of the polyol can be determined by the same method used for determining polyurethane prepolymers. Thus, for example, an adhesive layer with a moderate crosslinking density is easily obtained, exhibiting low adhesion and good wettability, and the adhesive strength does not increase excessively even when the adhesive sheet is heated, thus suppressing adhesive layer residue on the adhered object when peeling the adhesive sheet from the adhered object. In addition, the polyol may also include, for example, polyester polyols, besides polyether polyols.

[0063] The NCO / OH ratio of the polyol to the isocyanate in the polyurethane prepolymer (A) is not particularly limited, and may be, for example, 0.4 or more, or 0.5 or more, or, for example, 0.9 or less, 0.7 or less, or 0.6 or less. The NCO / OH ratio may be in the range of 0.4–0.9, 0.4–0.7, 0.4–0.6, 0.5–0.9, 0.5–0.7, or 0.5–0.6. Furthermore, the NCO / OH ratio is calculated by dividing the molar number of isocyanate groups in the total amount of the polyol and the isocyanate by the molar number of hydroxyl groups.

[0064] The content of polyurethane prepolymer (A) in the total mass of the adhesive disclosed herein is not particularly limited, and may be, for example, 20-80% by mass, 30-70% by mass, or 40-60% by mass. Furthermore, the content of polyurethane prepolymer (A) refers to the content of the total mass of polyurethane prepolymer (A) excluding impurities (e.g., solvents used when polyurethane prepolymer (A) is used in the form of solutions, emulsions, etc.).

[0065] [1-2. Polyoxyalkylene ether compounds (B)]

[0066] The component (B) in the adhesive of this disclosure (hereinafter sometimes referred to as "polyoxyalkylene ether compound (B)") is, as described above, a polyoxyalkylene ether compound represented by the chemical formula (1).

[0067] RO-(AO) n -H …(1)

[0068] In the chemical formula (1),

[0069] R is an aliphatic or aromatic group with 4 to 30 carbon atoms.

[0070] A represents alkylene groups having 2 to 4 carbon atoms. When there are multiple A's, they can be the same or different from each other.

[0071] n is the degree of aggregation, an integer from 0 to 100.

[0072] There are no particular limitations on the examples of "aliphatic groups" and their number of carbon atoms in R in the chemical formula (1), for example, as described above. There are no particular limitations on the "aromatic groups" in R in the chemical formula (1), for example, as described above.

[0073] R in the chemical formula (1) is preferably alkyl, alkenyl, or phenyl, more preferably alkyl or alkenyl, and particularly preferably alkyl. The number of carbon atoms in R in the chemical formula (1) is preferably 6 to 20, more preferably 8 to 18, and even more preferably 12 to 16.

[0074] As described above, A in the chemical formula (1) refers to alkylene groups having 2 to 4 carbon atoms. Therefore, AO in the chemical formula (1) refers to oxoalkylene groups having 2 to 4 carbon atoms, namely oxoethylene (oxoalkylene group having 2 carbon atoms), oxopropyleneene (oxoalkylene group having 3 carbon atoms), or oxobutylene (oxoalkylene group having 4 carbon atoms). Hereinafter, oxoethylene will sometimes be referred to as "EO", oxopropyleneene as "PO", and oxobutylene as "BO".

[0075] The structure of EO is represented by the chemical formula "EO". In this disclosure, PO can be linear or branched, but is preferably a branched structure represented by the chemical formula "PO1" or "PO2". In this disclosure, BO can be linear or branched, but is preferably a branched structure represented by the chemical formula "BO1" or "BO2".

[0076]

Eochemical EO

[0077]

[0078] [Chemical PO1]

[0079]

[0080] [Chemical PO2]

[0081]

[0082] [BO1]

[0083]

[0084] [Transform BO2]

[0085]

[0086] The AO in the chemical formula (1) is particularly preferably EO. When the AO in the chemical formula (1) includes EO, PO, and BO, the content of EO is not particularly limited, but is preferably 30 mol% or more, 50 mol% or more, 70 mol% or more, or 90 mol% or more. When the AO in the chemical formula (1) includes EO and PO, the degree of polymerization of each is not particularly limited, but the degree of polymerization of EO is preferably 5 to 30, and the degree of polymerization of PO is preferably 5 to 30.

[0087] The degree of polymerization n in the chemical formula (1) is an integer from 0 to 100 as described above, but preferably n = 3 to 50, 5 to 30, or 10 to 20. Furthermore, when the degree of polymerization n is 0, AO is not present in the polyoxyalkylene ether compound (B) represented by the chemical formula (1).

[0088] In the chemical formula (1), the carbon atom in RO bonded to O can be any of the primary, secondary, and tertiary carbon atoms, but is preferably a primary or secondary carbon atom, more preferably a secondary carbon atom. When the carbon atom is a primary carbon atom, it is preferably a branched alkyl group.

[0089] The component (B) is particularly preferred in that R is an alkyl group and AO is an EO group in the chemical formula (1). In this case, the number of carbon atoms in R (alkyl group) is particularly preferred to be 12 to 14. In addition, in this case, n (degree of polymerization of AO, also known as the number of moles of addition) in the chemical formula (1) is preferably 12 or more.

[0090] In the chemical formula (1), R is an alkyl group and AO is an EO. Specific examples of the component (B) are, for example: ADEKA TOL SO-160 (trade name of ADEKA Co., Ltd., with 15 mol of added EO), SANNONIC SS-120 (trade name of Sanyo Chemical Industries Co., Ltd., with 12 mol of added EO), SOFTANOL 200 (trade name of Nippon Shokubai Co., Ltd., with 20 mol of added EO), etc.

[0091] The content of component (B) in the adhesive disclosed herein is not particularly limited, but from the viewpoint of light peelability, it is preferable that the content of component (B) is not too low. Furthermore, for example, when the adhesive disclosed herein contains a crosslinking agent, from the viewpoint of suppressing the phenomenon that a large number of hydroxyl groups of component (B) react with the crosslinking agent and hinder the crosslinking reaction between the polyurethane prepolymer (A) and the crosslinking agent, the content of component (B) is preferably not too high. The content of component (B) is not particularly limited, but relative to the total mass of the polyurethane prepolymer (A), it can be, for example, 0.1% by mass or more, 0.5% by mass or more, 1.5% by mass or more, or 3% by mass or more, and for example, 50% by mass or less, 33% by mass or less, 25% by mass or less, or 16% by mass or less. Furthermore, the "total mass of polyurethane prepolymer (A)" refers to the total mass of polyurethane prepolymer (A) excluding impurities (e.g., solvents when using polyurethane prepolymer (A) in the form of solutions, emulsions, etc.).

[0092] [1-3. Crosslinking agent (C)]

[0093] The adhesive disclosed herein may or may not contain other components besides component (A) and component (B). These other components may include, for example, a crosslinking agent. The crosslinking agent may be, for example, a polyisocyanate crosslinking agent. Hereinafter, when the adhesive of this disclosure contains a polyisocyanate crosslinking agent, the polyisocyanate crosslinking agent will sometimes be referred to as "component (C)," "crosslinking agent (C)," or "polyisocyanate crosslinking agent (C)." Furthermore, in this disclosure, "polyisocyanate," as described above, refers to an organic compound (polyfunctional isocyanate) having a plurality of (two or more) isocyanate groups (also called isocyanate groups), i.e., (-N=C=O), in one molecule.

[0094] When the adhesive of this disclosure contains the polyisocyanate as a crosslinking agent (C), its content is not particularly limited. For example, the isocyanate groups of the polyisocyanate may be 0.5 to 5 times or 1 to 4 times the molar amount of hydroxyl groups in the adhesive, such as the polyurethane polyol or the polyoxyalkylene ether compound.

[0095] In the crosslinking agent (C), there is no particular limitation on the polyisocyanate. The polyisocyanate may be, for example, the same polyisocyanate used in the synthesis of polyurethane prepolymer (A) exemplified in "2. Method for Manufacturing Adhesive" described later. Alternatively, it may be, for example, a trimethylolpropane adduct, a biuret obtained by reacting with water, a trimer having an isocyanurate ring, etc. Only one type may be used, or multiple types may be used in combination.

[0096] [1-4: Other ingredients]

[0097] The adhesive disclosed herein, as described above, comprises components (A) and (B). As mentioned above, component (C) (crosslinking agent (C)) may or may not be included. Furthermore, the adhesive disclosed herein may or may not contain other components besides components (A) to (C). For example, the adhesive disclosed herein may also contain or exclude solvents, plasticizers, antioxidants, anti-crosslinking agents, fillers, colorants, UV absorbers, defoamers, light stabilizers, leveling agents, chain extenders, antistatic agents, etc., as other components. Their types are not particularly limited; for example, they may be the same as or similar to those in general adhesives.

[0098] The chain extender (also known as the chain extender material) is a low-molecular-weight polyol. The chain extender intervenes when the hydroxyl groups (OH groups) of the polyurethane prepolymer (A) react with the isocyanate groups (NCO groups) of the crosslinking agent (C), thereby changing the structure of the adhesive of this disclosure during gelation (film formation). The chain extender is not particularly limited, and can be, for example, a chain extender commonly used in the polyurethane industry, such as MPD (3-methyl-1,5-pentanediol), trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,8-decanediol, octadecanediol, glycerol, pentaerythritol, and hexanetriol, etc. Alternatively, for example, it can be a polyether polyol with a number average molecular weight of 500 or less, obtained by polymerizing oxocyclopropane compounds such as ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran using water or low molecular weight polyols such as propylene glycol, ethylene glycol, glycerol, and trimethylolpropane as initiators. More specifically, the polyether polyol can be, for example, a substance with two or more functional groups, such as polypropylene glycol, polyethylene glycol, or polytetramethylene glycol. By including the chain extender in the adhesive of this disclosure, for example, effects such as improved film strength and improved heat resistance (suppression of adhesive strength increase under high temperature conditions) can be obtained during the gelation (film formation) of the adhesive of this disclosure. In the adhesive of this disclosure, the content of the chain extender is not particularly limited, but in order to obtain the aforementioned effects, the content is preferably not too low. Furthermore, in the adhesive disclosed herein, to prevent the adhesive sheet from foaming during the aging process, resulting in loss of film surface smoothness, a significant increase in adhesive strength during peeling, or a cloudy appearance of the adhesive sheet, it is preferable that the content of the chain extender is not too high. The content of the chain extender is not particularly limited; for example, when the total mass of the polyurethane prepolymer (A) is set to 60 parts by mass, it is preferably 0.1 to 30 parts by mass, more preferably 1 to 15 parts by mass. Moreover, the "total mass of the polyurethane prepolymer (A)" refers to the total mass of the polyurethane prepolymer (A) excluding impurities (e.g., solvents used when the polyurethane prepolymer (A) is in the form of a solution, emulsion, etc.).

[0099] The antistatic agent is not particularly limited and can be, for example, an ionic compound. The ionic compound is preferably a substance other than ionic compounds that may exhibit alkalinity and ionic sulfonate compounds. Specifically, examples of such ionic compounds include chlorides, perchlorates, acetates, and nitrates; more specifically, examples include lithium chloride, lithium perchlorate, sodium perchlorate, potassium acetate, lithium trifluoroacetate, and lithium nitrate.

[0100] Examples of plasticizers include carboxylic acid esters. The carboxylic acid ester is not particularly limited and may include, for example, those described in Japanese Patent Application Publication Nos. 2011-190420, 2015-151429, and 2016-186029. The carboxylic acid ester may be, for example, the carboxylic acid ester described in the examples described later. The content of the plasticizer is not particularly limited, but relative to the total mass of the polyurethane prepolymer (A), it may be, for example, 1% or more by mass, 3% or more by mass, 5% or more by mass, or 10% or more by mass, and for example, 150% or less by mass, 100% or less by mass, 75% or less by mass, or 60% or less by mass. The "total mass of polyurethane prepolymer (A)" as described above refers to the total mass of the polyurethane prepolymer (A) excluding impurities (e.g., solvents used when the polyurethane prepolymer (A) is in the form of a solution, emulsion, etc.). From the viewpoint of improving the adhesion of the adhesive to the substrate of the adhesive sheet (such as PET film), a higher amount of plasticizer is preferred. On the other hand, from the viewpoint of suppressing the phenomenon that excessive reduction in the cohesive strength of the adhesive leads to a significant increase in adhesive force when peeling the adhesive sheet from the adhered object, or the adhesive residue remaining on the adhered object, a lower amount of plasticizer is preferred.

[0101] The leveling agent is not particularly limited, and examples include fluorinated, acrylic polymer, and silicone leveling agents. The leveling agent achieves its leveling effect, for example, by orienting the coating surface and reducing the surface tension of the coating surface.

[0102] There are no particular limitations on the ultraviolet absorber; examples include benzophenone-based, benzotriazole-based, and triazine-based ultraviolet absorbers. There are no particular limitations on the defoamer; examples include silicone-based and mineral oil-based defoamers. There are no particular limitations on the light stabilizer; examples include hindered amine-based light stabilizers. Examples of antistatic agents include ionic compounds such as inorganic salts and organic salts, and nonionic compounds such as nonionic surfactants. There are no particular limitations on the solvent, antioxidant, and anti-crosslinking agent; examples will be described later in "2. Method for Manufacturing Adhesives" along with examples of methods for manufacturing adhesives disclosed herein.

[0103] [2. Method for manufacturing adhesives]

[0104] The method for manufacturing the adhesive disclosed herein is not particularly limited except for the use of the aforementioned components (A) and (B). For example, general methods for manufacturing adhesives can be referred to, such as the aforementioned Patent Document 1. The following description mainly focuses on the manufacturing method when the polyurethane prepolymer (A) is a polyurethane polyol synthesized from polyol and polyisocyanate.

[0105] First, a polyol, a polyisocyanate, a solvent, and a catalyst, if necessary, are added to a reaction vessel, and the reaction is carried out while heating and stirring. The amount of polyol used is not particularly limited, but is, for example, 20–80% by mass or 40–60% by mass relative to the mass of the manufactured adhesive. The amount of polyisocyanate used is not particularly limited, but is, for example, 0.2–15% by mass, 0.5–10% by mass, or 1–5% by mass relative to the mass of the manufactured adhesive. The amount of solvent used is not particularly limited, but is, for example, 10–50% by mass or 20–40% by mass relative to the mass of the manufactured adhesive. The catalyst may be omitted, but it is preferred from the viewpoint of facilitating the reaction. When the catalyst is used, its amount is not particularly limited, but is, for example, 0.001–0.1% by mass relative to the mass of the manufactured adhesive. The reaction temperature is not particularly limited, for example, 30–80°C or 40–60°C. The reaction time is not particularly limited, for example, 0.5–15 hours, 0.5–4 hours, or 1–3 hours. Thus, compositions containing polyurethane polyols (polyurethane prepolymer (A)) can be synthesized.

[0106] Furthermore, in synthesizing the polyurethane polyol-containing composition, for example, one can use the method of (1) adding the total amount of polyester polyol, polyether polyol, catalyst, and polyisocyanate to a flask, and the method of (2) adding polyester polyol, polyether polyol, and catalyst to a flask and then adding polyisocyanate dropwise. Method (1) is simpler, but method (2) is easier to control the reaction, so they can be used separately as needed.

[0107] Then, component (B) is added to the synthesized composition containing polyurethane polyol, and the mixture is stirred until homogeneous. At this point, component (C) (crosslinking agent (C)) may be added as needed. Additionally, other components besides components (A) to (C) may be added as required. These other components may include, for example, solvents, and as mentioned above, may also include antioxidants, anti-crosslinking agents, carboxylic acid esters, chain extenders, leveling agents, etc. Thus, the adhesive of this disclosure can be obtained.

[0108] In the crosslinking agent (C), the polyisocyanate is not particularly limited, but can be the same as the polyisocyanate used to synthesize compositions containing polyurethane polyols (polyurethane prepolymers (A)) as exemplified below. Alternatively, it can be, for example, a trimethylolpropane adduct, a biuret obtained by reacting with water, a trimer having an isocyanurate ring, etc. Only one type can be used, or multiple types can be used in combination. In the crosslinking agent (C), the amount of the polyisocyanate used is not particularly limited. For example, relative to the molar amount of hydroxyl groups in the polyurethane prepolymer (A) or polyoxyalkylene ether compound (B) in the adhesive, it is preferable that the isocyanate groups of the polyisocyanate are 0.5 to 5 times or 1 to 4 times the molar amount of isocyanate groups in the polyurethane polyisocyanate, or preferably that the hydroxyl groups of the polyol are 0.5 to 5 times or 1 to 4 times the molar amount of isocyanate groups in the polyurethane polyisocyanate.

[0109] The solvent may be omitted, but its use is preferred from the viewpoint of ensuring smooth mixing of the components constituting the disclosed adhesive. When the catalyst is used, its amount is not particularly limited, but it is, for example, 0.001–0.1% by mass or 0.01–0.05% by mass relative to the mass of the manufactured adhesive. The antioxidant may be omitted, but its use is preferred. When the antioxidant is used, its amount is not particularly limited, but it is, for example, 0.05–1% by mass or 0.1–0.6% by mass relative to the mass of the manufactured adhesive. When the fatty acid ester is used, its amount is not particularly limited, but it is, for example, 5–50% by mass or 10–30% by mass relative to the mass of the manufactured adhesive. When the chain extender is used, its amount is not particularly limited, but it is, for example, preferably 0.1–30 parts by mass, more preferably 1–15 parts by mass relative to the mass of the manufactured adhesive. When using the leveling agent, there is no particular limitation on the amount used, but it is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, relative to the mass of the manufactured adhesive.

[0110] The synthesis of compositions containing polyurethane polyols (polyurethane prepolymer (A)) is described in more detail below.

[0111] The polyol used as a raw material for the polyurethane prepolymer (A) is not particularly limited. For example, it can be difunctional (having two hydroxyl groups in one molecule) or more functional (having three or more hydroxyl groups in one molecule), but is preferably more functional, and particularly preferably trifunctional. Furthermore, only one type of polyol may be used, or multiple types may be used in combination. The polyol is not particularly limited; for example, it can be one or both of polyester polyols and polyether polyols.

[0112] The polyester polyol is not particularly limited and can be any known polyester polyol. Examples of acid components in the polyester polyol include terephthalic acid, adipic acid, azelaic acid, sebacic acid, phthalic anhydride, isophthalic acid, and trimellitic acid. Examples of diol components in the polyester polyol include ethylene glycol, propylene glycol, diethylene glycol, butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 3,3'-dimethylolheptane, polyoxyethylene glycol, polyoxypropylene glycol, 1,4-butanediol, neopentyl glycol, and butylethylpentanediol. Examples of polyol components in the polyester polyol include glycerol, trimethylolpropane, and pentaerythritol. Additionally, polyester polyols obtained by ring-opening polymerization of lactones such as polycaprolactone, poly(β-methyl-γ-valerol), and polyvalerol can also be mentioned.

[0113] The molecular weight of the polyester polyol is not particularly limited, and substances ranging from low to high molecular weight can be used. A polyester polyol with a number average molecular weight of 500 to 5,000 is preferred. If the number average molecular weight is 500 or higher, it is easier to prevent gelation due to excessive reactivity. Conversely, if the number average molecular weight is below 5,000, it is easier to prevent a decrease in reactivity and a reduction in the cohesive strength of the polyurethane polyol itself. The polyester polyol may or may not be used, but when used, its amount may be, for example, 10 to 90 mol% or 10 to 50 mol% of the polyol constituting the polyurethane polyol.

[0114] Furthermore, the polyether polyol is not particularly limited and can be, for example, any known polyether polyol. Specifically, the polyether polyol can be, for example, a polyether polyol obtained by polymerizing oxocyclopropane compounds such as ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran using water, or low molecular weight polyols such as propylene glycol, ethylene glycol, glycerol, or trimethylolpropane as initiators. More specifically, the polyether polyol can be, for example, a substance with two or more functional groups, such as polypropylene glycol, polyethylene glycol, or polytetramethylene glycol. The molecular weight of the polyether polyol is not particularly limited, and substances ranging from low to high molecular weight can be used. For example, polyether polyols with a number average molecular weight of 1,000 to 15,000 can be used. If the number average molecular weight is 1,000 or higher, it is easier to prevent gelation due to excessive reactivity. Conversely, if the number average molecular weight is 15,000 or lower, it is easier to prevent a decrease in reactivity and a reduction in the cohesiveness of the polyurethane polyol itself. The polyether polyol may or may not be used, but when used, its amount may be, for example, 20 to 100 mol% or 20 to 80 mol% of the polyol constituting the polyurethane polyol.

[0115] As needed, a portion of the polyether polyol can be replaced and used in combination with diols such as ethylene glycol, 1,4-butanediol, neopentyl glycol, butyl ethyl pentanediol, glycerol, trimethylolpropane, pentaerythritol, etc., and polyamines such as ethylenediamine, N-aminoethyl ethanolamine, isophorone diamine, phenylenediamine, etc.

[0116] As described above, the polyol can be a difunctional (having two hydroxyl groups per molecule) polyether polyol, but is preferably trifunctional or higher (having three or more hydroxyl groups per molecule). In particular, by using polyols with a number average molecular weight of 1,000 to 15,000 and being trifunctional or higher, it is easier to achieve a balance between adhesive strength and re-peelability. If the number average molecular weight is 1,000 or higher, it is easier to prevent excessive reactivity of trifunctional or higher polyols from causing gelation. In addition, if the number average molecular weight is 15,000 or lower, it is easier to prevent a decrease in the reactivity of trifunctional or higher polyols and a decrease in the cohesive strength of the polyurethane polyol itself. For example, polyols with a number average molecular weight of 2,500 to 3,500 and being trifunctional or higher can be used partially or entirely.

[0117] The polyisocyanate (organic polyisocyanate compound) used as a raw material for polyurethane prepolymer (A) is not particularly limited, and examples include well-known aromatic polyisocyanates, aliphatic polyisocyanates, aromatic aliphatic polyisocyanates, alicyclic polyisocyanates, etc. In addition, only one polyisocyanate may be used, or multiple polyisocyanates may be used in combination.

[0118] Examples of aromatic polyisocyanates include, for example, 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, bianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4',4"-triphenylmethane triisocyanate, etc.

[0119] Examples of aliphatic polyisocyanates include, for example, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethyl diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0120] Examples of such aromatic aliphatic polyisocyanates include ω,ω'-diisocyanate-1,3-xylene, ω,ω'-diisocyanate-1,4-xylene, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylene diisocyanate, and 1,3-tetramethylxylene diisocyanate.

[0121] Examples of alicyclic polyisocyanates include, for example, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylene bis(cyclohexyl isocyanate), 1,4-bis(isocyanate methyl)cyclohexane, 1,4-bis(isocyanate methyl)cyclohexane, etc.

[0122] Alternatively, a portion of the above-mentioned polyisocyanates can be used in combination with trimethylolpropane adducts, biuret bodies obtained by reacting with water, trimers having isocyanurate rings, etc.

[0123] The preferred polyisocyanates are 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), etc.

[0124] There are no particular limitations on the catalyst used; for example, known catalysts can be used. Examples of catalysts include tertiary amine compounds and organometallic compounds.

[0125] Examples of such tertiary amine compounds include triethylamine, triethylenediamine, and 1,8-diazabicyclo(5,4,0)-undecene-7 (DBU).

[0126] Examples of such organometallic compounds include tin-based compounds and non-tin-based compounds. Examples of such tin-based compounds include, for instance, dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate (DBTDL), dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, tributyltin acetate, triethyltin oxide, tributyltin oxide, dioctyltin oxide, dioctyltin dilaurate, tributyltin chloride, tributyltin trichloroacetate, and 2-ethylhexanoate. Examples of non-tin compounds include, for example, titanium-based compounds such as dibutyltitanium dichloride, tetrabutyltitanate, and butoxytitanium trichloride; lead-based compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate; iron-based compounds such as iron 2-ethylhexanoate and iron acetylacetone; cobalt-based compounds such as cobalt benzoate and cobalt 2-ethylhexanoate; zinc-based compounds such as zinc naphthenate and zinc 2-ethylhexanoate; and zirconium naphthenate.

[0127] When using these catalysts, for example in a system containing both polyester polyols and polyether polyols, problems such as gelation or turbidity of the reaction solution can easily occur in a single catalyst system due to their different reactivity. In such cases, these problems can be solved by using two or more catalysts in combination, for example, by controlling the reaction rate, catalyst selectivity, etc. As a combination, for example, tertiary amine / organometallic, tin-based / non-tin-based, tin-based / tin-based, etc., can be used, but tin-based / tin-based is preferred, and more preferably a combination of dibutyltin dilaurate and tin 2-ethylhexanoate. The mixing ratio is not particularly limited, but for example, by mass ratio, (tin 2-ethylhexanoate / dibutyltin dilaurate) is less than 1, for example, it can also be 0.2 to 0.6. If the mixing ratio (mass ratio) is less than 1, it is easier to prevent gelation caused by the imbalance of catalyst activity. The amount of these catalysts used is not particularly limited, for example, it is 0.01 to 1.0% by mass or 0.01 to 0.2% by mass relative to the total amount of polyol and organic polyisocyanate.

[0128] When using the catalyst, the reaction temperature for synthesizing the polyurethane polyol can be, for example, below 100°C, or between 40°C and 60°C. Below 100°C, the reaction rate and cross-linking structure are easily controlled, making it easier to obtain polyurethane polyols with a specified molecular weight.

[0129] Furthermore, when the catalyst is not used (catalyst-free), the reaction temperature for synthesizing the polyurethane polyol can be, for example, 100°C or higher, or 110°C or higher. Additionally, the reaction time for synthesizing the polyurethane polyol without a catalyst is, for example, 3 hours or higher.

[0130] The solvent used to synthesize the polyurethane prepolymer (A) is not particularly limited, and known solvents can be used, for example. Examples of solvents include ketones such as methyl ethyl ketone, acetone, and methyl isobutyl ketone; esters such as ethyl acetate, n-butyl acetate, and isobutyl acetate; and hydrocarbons such as toluene and xylene. Toluene is particularly preferred considering the solubility of polyurethane polyols and the boiling point of the solvent.

[0131] Furthermore, the antioxidants mentioned are not particularly limited, and examples include phenolic and sulfur-based antioxidants.

[0132] Furthermore, in this disclosure, the molecular weight and molecular weight dispersion of the polyurethane prepolymer (A) are not particularly limited. If the molecular weights of the polyisocyanate and polyol used as raw materials for manufacturing the polyurethane prepolymer (A), and the reaction ratio (NCO / OH equivalent ratio) of the polyisocyanate and the polyol are determined, the number-average molecular weight of the polyurethane prepolymer (A) can be obtained by theoretical calculation (Japanese Patent Application Laid-Open No. 2017-025147).

[0133] [3. Adhesive sheets, their manufacturing methods, uses, etc.]

[0134] Next, examples will be given to illustrate the adhesive sheet disclosed herein, its manufacturing method, and its uses.

[0135] The adhesive sheet of this disclosure, as described above, is characterized by having an adhesive layer formed by the adhesive of this disclosure.

[0136] The adhesive sheet disclosed herein may, for example, have a substrate on which the adhesive layer may be formed at least one surface. The substrate is not particularly limited, for example as described below.

[0137] The method for manufacturing the adhesive sheet disclosed herein is not particularly limited; for example, it can be manufactured using the manufacturing method of this disclosure (the method for manufacturing the adhesive sheet disclosed herein).

[0138] The method for manufacturing the adhesive sheet disclosed herein, as described above, includes a coating step of applying the adhesive of the present disclosure to the adhesive layer forming surface of the substrate to which the adhesive layer is to be formed. In the coating step, when the adhesive of the present disclosure does not contain a crosslinking agent (C), it is preferable to apply the adhesive of the present disclosure together with the crosslinking agent (C). Furthermore, the method for manufacturing the adhesive sheet of the present disclosure may also include a heating step of heating the adhesive on the adhesive layer forming surface after the coating step. Hereinafter, the method for manufacturing the adhesive sheet of the present disclosure will be described primarily by way of example when the polyurethane prepolymer (A) contains a polyurethane polyol synthesized from a polyol and a polyisocyanate.

[0139] That is, firstly, the adhesive disclosed herein is applied to the adhesive layer forming surface of the substrate to which the adhesive layer is to be formed (coating step). The substrate is not particularly limited, and examples include plastics, polyurethane, paper, metal foil, etc., but plastics are preferred. Examples of plastics include PET (polyethylene terephthalate), polyolefins, PC (polycarbonate), etc. The polyolefin is not particularly limited, and examples include PE (polyethylene), PP (polypropylene), etc.

[0140] The shape of the substrate is not particularly limited; for example, it can be sheet-like, film-like, or foam-like. From the viewpoint of ease of handling and storage of the manufactured adhesive sheet, the substrate is preferably, for example, a long strip that can be rolled up.

[0141] Additionally, depending on the requirements, the substrate may be, for example, a substrate on which an easy-to-adhere treatment has been applied to the adhesive layer forming surface. The easy-to-adhere treatment is not particularly limited; specifically, examples include methods such as corona discharge treatment and applying a primer.

[0142] When the adhesive of this disclosure does not contain a crosslinking agent (C), it is preferable, for example, to mix the crosslinking agent (C) before the coating step. When the crosslinking agent (C) contains a polyisocyanate, there is no particular limitation on the polyisocyanate, and examples such as the polyisocyanate and trimethylolpropane adduct exemplified in "2. Method for Manufacturing Adhesive", biuret obtained by reacting with water, trimers having an isocyanurate ring, etc., can be used alone or in combination. In addition, the amount of crosslinking agent (C) used is as described above. Furthermore, for the purpose of easy mixing of the adhesive of this disclosure with the crosslinking agent (C), or for the purpose of easy coating onto the substrate, a solvent can be further mixed before the coating step. There is no particular limitation on the type of solvent, etc., for example, the same solvent as exemplified in "2. Method for Manufacturing Adhesive", and one can be used alone or in combination.

[0143] The coating method in the coating process is not particularly limited and can be a known method. Examples of coating methods include roller coating, comma coating, die coating, reverse roller coating, screen printing, and gravure coating.

[0144] In addition, the amount of adhesive applied in the coating process is not particularly limited, but is set such that the thickness of the adhesive layer in the manufactured adhesive sheet is, for example, 1-150 μm, 5-100 μm, 7-90 μm, 10-80 μm, or 70-80 μm.

[0145] Then, the adhesive on the adhesive layer forming surface is heated after the coating process (heating process). Hereinafter, to distinguish it from the second heating process described later, this heating process is sometimes referred to as the "first heating process". The heating temperature in the heating process (first heating process) is not particularly limited, and may be, for example, 60°C or higher, exceeding 60°C, 90°C or higher, or exceeding 90°C, or 100°C or higher, or 130°C or higher. The upper limit of the heating temperature is not particularly limited, and may be, for example, below 150°C.

[0146] To prevent the adhesive layer from overflowing from the end of the substrate during storage and handling of adhesive sheets, it is preferable to set the heating temperature in the heating process as high as possible. It is speculated that by setting the heating temperature as high as possible, for example, the crosslinking (curing) reaction between the adhesive of this disclosure and the crosslinking agent (C) can be easily and sufficiently carried out, thus preventing the overflow. However, this mechanism is merely speculative and does not limit the scope of this disclosure.

[0147] Generally, if the heating temperature after applying the adhesive to the substrate is too high, the adhesion of the adhesive layer to the substrate may decrease. On the other hand, the adhesive according to this disclosure exhibits good adhesion to the substrate even when heated at high temperatures, and can prevent pinholes and overflow from the substrate.

[0148] Furthermore, the heating time in the heating step (first heating step) is not particularly limited, but is preferably a time when the applied adhesive is sufficiently dried (solvent removed) and the substrate is not damaged by heat. The specific heating time also depends on the type of solvent and the substrate, for example, 60 to 300 seconds, or 90 to 270 seconds.

[0149] Furthermore, in the method for manufacturing the adhesive sheet disclosed herein, it is preferable to include a second heating step after the heating step (first heating step) at a temperature lower than that of the heating step. The second heating step may or may not be performed, but by performing this step, it is possible to more effectively prevent the adhesive layer from overflowing from the end of the substrate. Although the phenomena occurring in the second heating step are unclear, it is presumed that, for example, the curing (crosslinking) of the adhesive layer further occurs. However, this presumption does not limit the scope of this disclosure. The heating temperature in the second heating step is not particularly limited, for example, 30–50°C or 35–45°C. Additionally, the heating time in the second heating step is not particularly limited, for example, 24–120 hours or 48–96 hours.

[0150] The application of the adhesive sheet disclosed herein is not particularly limited; for example, it is preferably used as a protective sheet for the image display surface of an image display device by being adhered to the image display surface. Furthermore, when used for this purpose, for example, it is more preferable that the substrate is transparent.

[0151] The image display device disclosed herein, as described above, is characterized in that it is an image display device on which a protective sheet is adhered to an image display surface. The protective sheet is an adhesive sheet of this disclosure that further includes a substrate and has the adhesive layer formed on at least one surface of the substrate. The adhesive sheet is adhered to the image display surface through the adhesive layer. Examples of such image display devices include liquid crystal displays (LCDs) and organic light-emitting diode (OLEDs). The adhesive sheet of this disclosure can be used, for example, in flat panel displays or flexible panel displays of these image display devices, and in touchscreen displays formed by combining these displays with a touchscreen. The image display device is not particularly limited; examples include mobile phones, smartphones, televisions (TVs), personal computers (PCs), and tablet computers. However, the application of the adhesive sheet of this disclosure is not limited to image display devices; for example, it can also be used as a protective sheet for window glass in automobiles, buildings, etc. Furthermore, the adhesive sheet of this disclosure is not limited to glass; it can also be used as a protective sheet for ITO (Indium Tin Oxide) processed as a transparent conductive film on a glass substrate. Furthermore, the uses of the adhesive sheet disclosed herein are not limited to these; for example, it can be widely used for the same purposes as general adhesive sheets, adhesive films, adhesive tapes, etc. The adhesive sheet disclosed herein, for example, does not contaminate the adhered objects after peeling even when exposed to humid heat, exhibits excellent wetting properties, and provides excellent adhesion between the adhesive and the substrate; therefore, as described above, it can be used for a wide range of applications. In addition, the uses of the adhesive disclosed herein are not particularly limited to the adhesive sheet disclosed herein; for example, it can be widely used for the same purposes as general adhesives.

[0152] The form of the adhesive sheet disclosed herein is not particularly limited. For example, during storage, it is preferable to attach a release film to the adhesive layer to protect it, and to peel off the release film immediately before use (e.g., attaching it to an image display device). Alternatively, the adhesive sheet of this disclosure is preferably a rollable, long strip for winding and storage. According to the adhesive tape of this disclosure, the adhesive layer can be prevented from overflowing from the ends of the adhesive tape, for example, during winding and storage.

[0153]

Example

[0154] The following describes embodiments of the present disclosure. However, the present disclosure is not limited to these embodiments.

[0155] The names of the raw materials (compound names), their product names (trade names), and manufacturers used in the following examples and comparative examples are summarized in Table 1 below.

[0156] Table 1

[0157]

[0158] [Synthesis example 1]

[0159] Polyurethane prepolymer (A) was synthesized according to the following steps, and a polyurethane prepolymer (A) solution was prepared.

[0160] In a separable flask equipped with a stirrer, reflux condenser, and thermometer, glycerol PO / EO (trade name: SANNIX GL-3000), hexamethylene diisocyanate, toluene, and DBTDL were added, and the mixture was reacted at 60°C for 3 hours with stirring. The NCO groups in the contents were determined using an infrared spectrophotometer (IR), and no NCO group residues were detected. The contents were then cooled to below 40°C, and an antioxidant and ethyl acetate were added. Note that "glycerol PO / EO" refers to the propylene oxide and ethylene oxide adduct of glycerol, and "DBTDL" refers to dibutyltin dilaurate. As described above, a polyurethane prepolymer (A) was synthesized, and a solution of polyurethane prepolymer (A) was prepared.

[0161] [Synthesis example 2]

[0162] Except for converting the glycerol PO / EO of Synthesis Example 1 to glycerol PO (trade name: SANNIX GP-1000), polyurethane prepolymer (A) was synthesized in the same manner as in Synthesis Example 1, and a solution of polyurethane prepolymer (A) was prepared. Furthermore, "glycerol PO" refers to the propylene oxide adduct of glycerol.

[0163] [Synthesis example 3]

[0164] Except for changing the glycerol PO / EO of Synthesis Example 1 to glycerol PO (trade name: SANNIX GP-3000), polyurethane prepolymer (A) was synthesized in the same manner as in Synthesis Example 1, and a polyurethane prepolymer (A) solution was prepared.

[0165] [Synthesis Example 4]

[0166] Except for changing the glycerol PO / EO of Synthesis Example 1 to glycerol PO / EO (trade name: PREMINOL 7012), polyurethane prepolymer (A) was synthesized in the same manner as in Synthesis Example 1, and a polyurethane prepolymer (A) solution was prepared.

[0167] [Synthesis Example 5]

[0168] Polyurethane prepolymer (A) was synthesized in the same manner as in Synthesis Example 1, except that it was used in conjunction with glycerol PO / EO (trade name: SANNIX GL-3000) and Pluronic polyol (trade name: SANNIX PL-2100) from Synthesis Example 1. A solution of polyurethane prepolymer (A) was prepared. Furthermore, "Pluronic polyol" refers to the ethylene oxide adduct of polypropylene glycol.

[0169] [Synthesis example 6]

[0170] Except for the use of glycerol PO (trade name: SANNIX GP-3000) and polypropylene glycol (trade name: SANNIX PP-2000) in Synthesis Example 3, polyurethane prepolymer (A) was synthesized in the same manner as in Synthesis Example 1, and a polyurethane prepolymer (A) solution was prepared.

[0171] [Synthesis Example 7]

[0172] Except for converting the hexamethylene diisocyanate of Synthesis Example 1 to 4,4'-diphenylmethane diisocyanate, polyurethane prepolymer (A) was synthesized in the same manner as in Synthesis Example 1, and a polyurethane prepolymer (A) solution was prepared.

[0173] [Synthesis example 8]

[0174] Except for changing the hexamethylene diisocyanate of Synthesis Example 1 to m-phenylenedimethyl diisocyanate, polyurethane prepolymer (A) was synthesized in the same manner as in Synthesis Example 1, and a polyurethane prepolymer (A) solution was prepared.

[0175] [Synthesis Example 9]

[0176] Except for replacing the hexamethylene diisocyanate of Synthesis Example 1 with 1,3-bis(isocyanate methyl)cyclohexane, polyurethane prepolymer (A) was synthesized in the same manner as in Synthesis Example 1, and a polyurethane prepolymer (A) solution was prepared.

[0177] The amounts (parts by mass) of each component used in the synthesis of polyurethane prepolymer (A) in Synthesis Examples 1 to 9 are summarized in Table 2 below. That is, as described above and as recorded in Table 2 below, solutions containing polyurethane prepolymer (A) were obtained in Synthesis Examples 1 to 9.

[0178] Table 2

[0179]

[0180] [Example 1]

[0181] In 100 parts by weight (60 parts by weight based on solids) of the polyurethane prepolymer solution of Synthesis Example 1, 5 parts by weight of polyoxyethylene alkyl ether (trade name: SUNNIX SS-120) as a polyoxyalkylene ether compound and 11.6 parts by weight of DURANATE TSE-100 (a polyisocyanate-based crosslinking agent manufactured by Asahi Kasei Corporation) were mixed thoroughly to prepare the adhesive (coating liquid) of Example 1.

[0182] [Examples 2-24 and Comparative Examples 1-2]

[0183] Except for changing the composition of each component as shown in any of Tables 3 to 5 below, the adhesive (coating liquid) was manufactured using the same steps as in Example 1.

[0184] [Adhesive sheet: Examples 1-24 and Comparative Examples 1-2]

[0185] Using the adhesives of Examples 1-24 and Comparative Examples 1-2 respectively, adhesive sheets of the present disclosure having an adhesive layer formed by the adhesive on one side of a substrate were manufactured. Specifically, firstly, a PET film with a thickness of 75 μm was prepared as the substrate. On one side of the PET film (the adhesive layer forming side), the adhesive (coating liquid) of any one of Examples 1-24 and Comparative Examples 1-2 was coated (coating process). Then, the adhesive on the adhesive layer forming side was heated (heating process), and the target adhesive sheet was manufactured. In the coating process, the thickness (wet thickness) of the freshly coated adhesive (60% by mass of solids) was coated to reach 250 μm. Heating it in the heating process yielded an adhesive layer (film) with a thickness of 75 μm. Specifically, the heating process was performed in the following order: (1) and (2).

[0186] Step (1): Heat the adhesive that has just undergone the coating process at 100°C for 4 minutes (240 seconds).

[0187] Step (2): The adhesive and the substrate after step (1) are heated at 40°C for 3 days (72 hours) (curing).

[0188] For the adhesives and adhesive sheets of the embodiments and comparative examples manufactured as described above, the adhesive strength (light peel strength) and film transparency were evaluated by the following methods. These results are summarized in Tables 3 to 5 below. In addition, "NCO / OH" in Tables 3 to 5 indicates the molar ratio of isocyanate groups to the polyisocyanate crosslinking agent (C) relative to the total molar amount of hydroxyl groups in the adhesive.

[0189] 1. Adhesion (light peelability)

[0190] The adhesive strength was evaluated using any one of the adhesive sheets from Examples 1-24 and Comparative Examples 1-2, manufactured as described above, as the test specimen. Specifically, firstly, the specimen was cut into 25mm wide pieces at 23°C and 50%RH, and then bonded to the substrate (glass plate) with a 2kg roller under a load of 3 reciprocating strokes. After curing at the same 23°C and 50%RH environment for 1 hour, the peel force (N / 25mm) when one end of the specimen was peeled off in a 180° direction at a speed of 300mm / min using a universal testing machine (Autograph) was taken as the adhesive strength. From the viewpoint of re-peelability, a low adhesive strength (peel force) is preferred as the peel force of the adhesive sheet. The light peelability of each adhesive sheet was evaluated according to the following criteria.

[0191] (Light peelability evaluation criteria)

[0192] ○: Less than 0.02 N / 25mm

[0193] △: Above 0.02 N / 25mm, less than 0.03 N / 25mm

[0194] ×: 0.03 N / 25mm or more

[0195] 2. Film transparency

[0196] The film transparency was evaluated using any one of the adhesive sheets from Examples 1-24 and Comparative Examples 1-2, manufactured as described above, as a sample. Specifically, firstly, the haze value of the sample was measured using an NDH300A haze meter (trade name) manufactured by Nippon Denshoku Sangyo Co., Ltd., according to the method of JIS K7136. Then, a haze value of 1.5% or less was evaluated as film transparency ○, and a haze value exceeding 1.5% was evaluated as film transparency ×.

[0197] Table 3

[0198]

[0199] Table 4

[0200]

[0201] Table 5

[0202]

[0203] As shown in Tables 3-5, the adhesives of Examples 1-24, which contain both components (A) and (B) of this disclosure, exhibit good light peel properties. In contrast, the adhesives of Comparative Examples 1-2, which contain only component (A) and not component (B), exhibit inferior light peel properties compared to the examples.

[0204] The present disclosure has been described above using various implementation methods and examples, but the present disclosure is not limited to these implementation methods and examples.

[0205] This disclosure may also be described, for example, as noted in the appendix below, but is not limited thereto.

[0206] (Note 1)

[0207] An adhesive characterized by comprising the following components (A) and (B).

[0208] (A) A polyurethane prepolymer with hydroxyl groups, having a structure synthesized from polyols and isocyanates.

[0209] (B) Polyoxyalkylene ether compounds represented by the following chemical formula (1):

[0210] RO-(AO) n -H …(1)

[0211] In the chemical formula (1),

[0212] R is an aliphatic or aromatic group with 4 to 30 carbon atoms.

[0213] A represents alkylene groups having 2 to 4 carbon atoms. When there are multiple A's, they can be the same or different from each other.

[0214] n is the degree of aggregation, an integer from 0 to 100.

[0215] (Note 2)

[0216] According to the adhesive described in Appendix 1, in the chemical formula (1) of the component (B), R is an alkyl group having 10 to 18 carbon atoms.

[0217] (Note 3)

[0218] According to the adhesive described in Appendix 1 or 2, in the chemical formula (1) of the component (B), AO is EO (oxyethylidene) group and n is 5 to 50.

[0219] (Note 4)

[0220] According to any one of the appendices 1 to 3, the content of component (B) in the total mass of components (A) and (B) is 0.1 to 50% by mass.

[0221] (Note 5)

[0222] The adhesive described in any of Notes 1 to 4 also contains the following component (C):

[0223] (C) Polyisocyanate crosslinking agent.

[0224] (Note 6)

[0225] An adhesive sheet, characterized in that it has an adhesive layer formed by an adhesive described in any one of Appendices 1 to 5.

[0226] (Note 7)

[0227] According to Appendix 6, the adhesive sheet also has a substrate on which the adhesive layer is formed on at least one surface.

[0228] (Note 8)

[0229] A method for manufacturing an adhesive sheet as described in Appendix 7, comprising:

[0230] In the coating process, the adhesive is applied to the adhesive layer forming surface of the substrate to which the adhesive layer is to be formed; and

[0231] The heating process involves heating the adhesive on the adhesive layer forming surface after the coating process.

[0232] (Note 9)

[0233] An image display device, characterized in that it is an image display device with a protective sheet attached to the image display surface.

[0234] The protective sheet is the adhesive sheet described in Appendix 7, and the adhesive sheet is attached to the image display surface through the adhesive layer.

[0235] Industrial availability

[0236] As described above, according to this disclosure, an adhesive with excellent peelability, an adhesive sheet, a method for manufacturing the adhesive sheet, and an image display device can be provided. The adhesive, adhesive sheet, and method for manufacturing the adhesive sheet of this disclosure can be used, for example, as protective sheets for window glass in mobile phones, smartphones, automobiles, buildings, etc. More specifically, the adhesive sheet of this disclosure can be used, for example, in flat panel displays or flexible panel displays such as liquid crystal displays (LCDs) and organic light-emitting diode (OLEDs), and touch screen displays composed of these displays combined with touch screens. Such displays can be widely used, for example, in electronic devices such as televisions (TVs), personal computers (PCs), mobile phones, and portable information terminals. Furthermore, this disclosure is not limited to these applications and can be widely used in various fields, such as those using general adhesives, adhesive sheets, and methods for manufacturing adhesive sheets.

Claims

1. An adhesive, characterized in that, It contains the following ingredients (A) and (B). (A) A polyurethane prepolymer with hydroxyl groups, having a structure synthesized from polyols and isocyanates. (B) Polyoxyalkylene ether compounds represented by the following chemical formula (1), RO-(AO) n -H …(1) In the chemical formula (1), R is an aliphatic or aromatic group with 4 to 30 carbon atoms. A represents alkylene groups having 2 to 4 carbon atoms; when there are multiple A's, they may be the same or different from each other. n is the degree of aggregation, an integer from 0 to 100.

2. The adhesive according to claim 1, wherein, In the chemical formula (1) of the component (B), R is an alkyl group having 10 to 18 carbon atoms.

3. The adhesive according to claim 1, wherein, In the chemical formula (1) of the component (B), AO is oxyethylidene EO, and n is 5 to 50.

4. The adhesive according to claim 1, wherein, The content of component (B) is 0.1 to 50% by mass relative to the total mass of component (A).

5. The adhesive according to claim 1, further comprising the following component (C): (C) Polyisocyanate crosslinking agent.

6. An adhesive sheet, characterized in that, It has an adhesive layer formed by the adhesive according to any one of claims 1 to 5.

7. The adhesive sheet according to claim 6, further comprising a substrate on which the adhesive layer is formed on at least one surface.

8. A method for manufacturing the adhesive sheet according to claim 7, comprising: In the coating process, the adhesive is applied to the adhesive layer forming surface of the substrate to which the adhesive layer is to be formed; and The heating process involves heating the adhesive on the adhesive layer forming surface after the coating process.

9. An image display device, characterized in that, This is an image display device with a protective film attached to the image display surface. The protective sheet is the adhesive sheet as described in claim 7, and the adhesive sheet is attached to the image display surface through the adhesive layer.

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