JP7122228B2 - Adhesive, adhesive sheet, method for producing adhesive sheet, and image display device - Google Patents

Description

The present invention relates to an adhesive, an adhesive sheet, a method for producing an adhesive sheet, and an image display device.

Adhesives and adhesive sheets using them are widely used in various industrial fields. Specific uses include, for example, a protective film that is used by being attached to the surface of glass or the like. Examples of the glass include window glass of mobile phones, smart phones, automobiles, buildings, and the like.

The adhesive includes, for example, an acrylic resin-based adhesive, a rubber-based adhesive, a urethane adhesive, and the like. Among these, urethane adhesives have properties such as the ability to be peeled off after being applied (hereinafter referred to as re-peelability) and the ability to prevent air bubbles from being caught in the interface between the adhesive layer and the adherend (hereinafter referred to as wettability). It is widely used because of its excellent properties (Patent Document 1, etc.).

JP 2016-186064 A

In recent years, pressure-sensitive adhesives used in surface-protecting pressure-sensitive adhesive sheets and the like are required to have removability, wettability, and resistance to contamination of adherends. This is because products such as plastics, glass, etc., which have adhesives attached to their surfaces, may be transported or stored for a long period of time. Here, the adherend contamination resistance means that even if the product to which the adhesive sheet is attached is placed under high temperature and high humidity conditions for a long time, the adherend will not be contaminated by the adhesive when the adhesive sheet is removed. Say something that won't happen. Since the degree of contamination differs depending on the type of material (adherend) to which the pressure-sensitive adhesive is applied and the environment in which the product is left for a long time, the required resistance to contamination of the adherend also differs. Conceivable causes of contamination include denaturation and contamination derived from the material of the adherend, in addition to adhesive residue derived from the adhesive.

Therefore, the present invention provides a pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, a method for producing the pressure-sensitive adhesive sheet, and an image display device that can satisfy removability, wettability, and resistance to contamination of adherends under high temperature and high humidity conditions. intended to

In order to achieve the above object, the adhesive of the present invention is characterized by containing a urethane prepolymer (A) having a hydroxyl group and a nonionic sulfonic acid ester (B).

The pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet having an adhesive layer formed on at least one surface of a substrate, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive of the present invention. .

The method for producing the pressure-sensitive adhesive sheet of the present invention includes a coating step of applying the pressure-sensitive adhesive of the present invention to the pressure-sensitive adhesive layer forming surface of the base material on which the pressure-sensitive adhesive layer is formed, and after the coating step, the pressure-sensitive adhesive and a heating step of heating the adhesive on the layer forming surface.

The image display device of the present invention is an image display device in which a protective sheet for the image display device is attached to the image display surface, and the protective sheet is the adhesive sheet of the present invention.

ADVANTAGE OF THE INVENTION According to the present invention, a pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, a method for producing the pressure-sensitive adhesive sheet, and an image display device that can satisfy removability, wettability, and resistance to contamination of adherends under high temperature and high humidity conditions are provided. can do.

The present invention will now be described with reference to examples. However, the invention is not limited by the following description.

In the adhesive of the present invention, for example, the urethane prepolymer (A) may be an adduct of polyol and isocyanate.

The pressure-sensitive adhesive of the present invention may, for example, further contain a cross-linking agent (C), and the cross-linking agent (C) may be a polyisocyanate.

The pressure-sensitive adhesive of the present invention may be, for example, a pressure-sensitive adhesive for forming a pressure-sensitive adhesive layer on at least one surface of a substrate to produce a pressure-sensitive adhesive sheet. Moreover, in the pressure-sensitive adhesive sheet of the present invention, the substrate may be, for example, a substrate such as polyethylene terephthalate or polyolefin.

In the present invention, the "aliphatic group" is not particularly limited, and may be, for example, saturated or unsaturated, and may or may not contain a cyclic structure. Examples of the aliphatic group include alkyl groups, alkenyl groups, alkynyl groups, cycloalkyl groups, cycloalkenyl groups, and the like.

In the present invention, "alkyl" includes, for example, linear or branched alkyl. The number of carbon atoms of the alkyl is not particularly limited, and is, for example, 1-30, preferably 1-18, 3-16 or 4-12. Examples of alkyl include, but are not limited to, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group and tert-butyl group, pentyl group, hexyl group and heptyl. group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group and the like. The same applies to groups and atomic groups (such as alkoxy groups) derived from alkyl groups. The same applies to groups containing alkyl groups in their structures (alkylamino groups, alkoxy groups, etc.) or groups derived from alkyl groups (haloalkyl groups, hydroxyalkyl groups, aminoalkyl groups, alkanoyl groups, etc.).

In the present invention, "alkenyl" includes, for example, linear or branched alkenyl. Examples of the alkenyl include those having one or more double bonds in the above alkyl. The number of carbon atoms in the alkenyl is not particularly limited, and is, for example, the same as the alkyl, preferably 2-12 or 2-8. Examples of alkenyl include vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1,3-butadienyl, 3-methyl-2-butenyl and the like.

In the present invention, "alkynyl" includes, for example, linear or branched alkynyl. Examples of the alkynyl include those having one or more triple bonds in the above alkyl. The number of carbon atoms in the alkynyl is not particularly limited, and is, for example, the same as the alkyl, preferably 2-12 or 2-8. Examples of the alkynyl include ethynyl, propynyl, butynyl and the like. Said alkynyl may, for example, additionally have one or more double bonds.

In the present invention, "aromatic ring" or "aromatic group" includes, for example, aryl, heteroaryl and arylalkyl. In addition, the "cyclic structure" includes, for example, the aromatic ring, cycloalkyl, bridged cyclic hydrocarbon group, spiro hydrocarbon group, and cycloalkenyl.

In the present invention, "aryl" includes, for example, monocyclic aromatic hydrocarbon groups and polycyclic aromatic hydrocarbon groups. Examples of the monocyclic aromatic hydrocarbon group include phenyl. The polycyclic aromatic hydrocarbon group is, for example, 1-naphthyl, 2-naphthyl, 1-anthryl, 2-anthryl, 9-anthryl, 1-phenanthryl, 2-phenanthryl, 3-phenanthryl, 4-phenanthryl, 9- phenanthryl and the like. Preferable examples include phenyl, naphthyl such as 1-naphthyl and 2-naphthyl, and the like.

In the present invention, "heteroaryl" includes, for example, monocyclic aromatic heterocyclic groups and condensed aromatic heterocyclic groups. The heteroaryl is, for example, furyl (eg: 2-furyl), thienyl (eg: 2-thienyl), pyrrolyl (eg: 1-pyrrolyl), imidazolyl (eg: 1-imidazolyl), pyrazolyl (eg: 1-pyrazolyl) ), triazolyl (eg: 1,2,4-triazol-1-yl), tetrazolyl (eg: 1-tetrazolyl), oxazolyl (eg: 2-oxazolyl), isoxazolyl (eg: 3-isoxazolyl), thiazolyl (eg: 2-thiazolyl), thiadiazolyl, isothiazolyl (e.g. 3-isothiazolyl), pyridyl (e.g. 2-pyridyl), pyridazinyl (e.g. 3-pyridazinyl), pyrimidinyl (e.g. 2-pyrimidinyl), furazanyl (e.g. 3-furazanyl) ), pyrazinyl (e.g. 2-pyrazinyl), oxadiazolyl (e.g. 1,3,4-oxadiazol-2-yl), benzofuryl (e.g. 2-benzo[b]furyl), benzothienyl (e.g. 2- benzo[b]thienyl), benzimidazolyl (e.g. 1-benzimidazolyl), dibenzofuryl, benzoxazolyl, benzothiazolyl, quinoxalyl (e.g. 2-quinoxalinyl), cinnolinyl (e.g. 3-cinnolinyl), quinazolyl (e.g. 2 -quinazolinyl), quinolyl (e.g. 2-quinolyl), phthalazinyl (e.g. 1-phthalazinyl), isoquinolyl (e.g. 1-isoquinolyl), prill, pteridinyl (e.g. 2-pteridinyl), carbazolyl, phenanthridinyl, acridinyl (eg: 1-acridinyl), indolyl (eg: 1-indolyl), isoindolyl, phenazinyl (eg: 1-phenazinyl), phenothiazinyl (eg: 1-phenothiazinyl) and the like.

In the present invention, "cycloalkyl" is, for example, a cyclic saturated hydrocarbon group with, but not limited to, 3-24 or 3-15 carbon atoms. The cycloalkyl includes, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, a bridged cyclic hydrocarbon group, a spiro hydrocarbon group and the like, preferably cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl. , a bridged cyclic hydrocarbon group, and the like.

In the present invention, the "bridged cyclic hydrocarbon group" includes, for example, bicyclo[2.1.0]pentyl, bicyclo[2.2.1]heptyl, bicyclo[2.2.2]octyl and bicyclo[3 .2.1]octyl, tricyclo[2.2.1.0]heptyl, bicyclo[3.3.1]nonane, 1-adamantyl, 2-adamantyl and the like.

In the present invention, the "spirohydrocarbon group" includes, for example, spiro[3.4]octyl.

In the present invention, "cycloalkenyl" includes, for example, cyclic unsaturated aliphatic hydrocarbon groups having, for example, 3-24 or 3-7 carbon atoms. Examples of the cyclic unsaturated aliphatic hydrocarbon group include cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl and the like, preferably cyclopropenyl, cyclobutenyl, cyclopentenyl and cyclohexenyl. Said cycloalkenyl also includes, for example, bridged cyclic hydrocarbon groups and spirohydrocarbon groups having unsaturated bonds in the ring.

In the present invention, "arylalkyl" includes, for example, benzyl, 2-phenethyl and naphthalenylmethyl, and "cycloalkylalkyl" includes, for example, cyclohexylmethyl, adamantylmethyl and the like, and "hydroxyalkyl ” includes, for example, hydroxymethyl and 2-hydroxyethyl, and the like.

In the present invention, the "substituent" or "further substituent" is not particularly limited, but examples include carboxy, halogen, halogenated alkyl (e.g. CF ₃ , CH ₂ CF ₃ , CH ₂ CCl ₃ ), 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. cyclopropyl, adamantyl) cyclohexylmethyl, adamantylmethyl), cycloalkenyl (e.g. cyclopropenyl), aryl (e.g. phenyl, naphthyl), arylalkyl (e.g. benzyl, phenethyl), heteroaryl (e.g. pyridyl, furyl), heteroarylalkyl (e.g. pyridylmethyl), heterocyclyl (e.g. piperidyl), heterocyclylalkyl (e.g. morpholylmethyl), alkoxy (e.g. methoxy, ethoxy, propoxy, butoxy), perfluoroalkyl (e.g. _CF3 ), halogenated alkoxy (e.g. CF3) OCF ₃ ), acyl, alkenyloxy (eg vinyloxy, allyloxy), aryloxy (eg phenyloxy), alkyloxycarbonyl (eg methoxycarbonyl, ethoxycarbonyl, tert-butoxycarbonyl), arylalkyloxy (eg benzyl oxy), amino[alkylamino (e.g. methylamino, ethylamino, dimethylamino), acylamino (e.g. acetylamino, benzoylamino), arylalkylamino (e.g. benzylamino, tritylamino), hydroxyamino), alkylamino Including alkyl (eg diethylaminomethyl), sulfamoyl, oxo and the like.

In the present invention, "alkoxy" includes, for example, the aforementioned alkyl-O- groups, and includes, for example, methoxy, ethoxy, n-propoxy, isopropoxy, and n-butoxy. Examples include methoxymethyl and the like, and "aminoalkyl" includes, for example, 2-aminoethyl and the like.

In the present invention, "acyl" is not particularly limited, but examples include formyl, acetyl, propionyl, isobutyryl, valeryl, isovaleryl, pivaloyl, hexanoyl, cyclohexanoyl, benzoyl, ethoxycarbonyl, and the like. The same applies to a group containing an acyl group in its structure (acyloxy group, alkanoyloxy group, etc.). In the present invention, the number of carbon atoms in the acyl group includes carbonyl carbon, and for example, an alkanoyl group (acyl group) having 1 carbon atom refers to a formyl group.

In the present invention, "halogen" refers to any halogen element, including fluorine, chlorine, bromine and iodine.

In the present invention, "perfluoroalkyl" is not particularly limited, but includes, for example, perfluoroalkyl groups derived from linear or branched alkyl groups having 1 to 30 carbon atoms. The "perfluoroalkyl" more specifically includes, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl , undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, icosyl, and other groups. The same applies to a group containing a perfluoroalkyl group in its structure (perfluoroalkylsulfonyl group, perfluoroacyl group, etc.).

In the present invention, when the various groups described above are heterocycles or contain heterocycles, the "number of carbon atoms" also includes the number of heteroatoms that constitute the heterocycles.

In addition, in the present invention, when isomers exist in substituents and the like, any isomers may be used unless otherwise specified. For example, a "naphthyl group" may be a 1-naphthyl group or a 2-naphthyl group, and a "propyl group" may be an n-propyl group or an isopropyl group.

Further, as described above, the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet in which an adhesive layer is formed on at least one surface of a substrate, and the pressure-sensitive adhesive layer is an adhesive layer formed from the pressure-sensitive adhesive of the present invention. characterized by being The pressure-sensitive adhesive sheet of the present invention is preferably a pressure-sensitive adhesive sheet that is used as a protective sheet for the image display surface of an image display device by being attached to the image display surface.

As described above, the method for producing an adhesive sheet according to the present invention includes a coating step of applying the adhesive of the present invention to the adhesive layer forming surface of the substrate on which the adhesive layer is formed, and the coating step. and a heating step of heating the adhesive on the adhesive layer forming surface. In the coating step, when the pressure-sensitive adhesive of the present invention does not contain the cross-linking agent (C), it is preferable to apply the pressure-sensitive adhesive of the present invention together with the cross-linking agent (C).

Hereinafter, embodiments of the present invention will be described more specifically. However, the present invention is not limited to the following embodiments.

[1. Adhesive]
As described above, the pressure-sensitive adhesive of the present invention comprises a urethane prepolymer (A) having a hydroxyl group (hereinafter sometimes referred to as "component (A)") and a nonionic sulfonic acid ester (B) (hereinafter referred to as "component (B)” in some cases).

[1-1. Urethane prepolymer having hydroxyl group (A)]
The urethane prepolymer (A) is, as described above, a urethane prepolymer having hydroxyl groups.

Urethane prepolymer (A) may be, for example, polyurethane polyol synthesized from polyol and polyisocyanate. In the present invention, "urethane prepolymer" refers to a polyurethane prepolymer. In the present invention, "polyurethane polyol" refers to a polyurethane prepolymer having a plurality of hydroxyl groups. In the present invention, the term "prepolymer" refers to a polymer in which polymerization or cross-linking has progressed halfway, and which is capable of further progressing polymerization or cross-linking. In the present invention, the term "polyurethane prepolymer" refers to a polyurethane that has been partially polymerized or crosslinked and that can be converted into a polyurethane that has been further polymerized or crosslinked. The above-mentioned "polyurethane prepolymer" can be converted into polyurethane, for example, by having a plurality of hydroxyl groups or isocyanate groups to further proceed with polymerization or cross-linking. In the present invention, unless otherwise specified, "polyurethane polyisocyanate" is a prepolymer of polyurethane that can be converted into polyurethane by further polymerization or cross-linking by having a plurality of isocyanate groups (for example, at both ends of the molecule). Say. However, in the present invention, the urethane prepolymer (A) is a urethane prepolymer having hydroxyl groups, as described above. In the present invention, "polyol" refers to an organic compound having a plurality (2 or 3 or more) of hydroxyl groups (preferably at least one of alcoholic hydroxyl groups and phenolic hydroxyl groups) in one molecule. "Polyisocyanate" refers to an organic compound (polyfunctional isocyanate) having a plurality (2 or 3 or more) of isocyanato groups (-N=C=O, also referred to as isocyanate groups) in one molecule.

The hydroxyl value of the urethane prepolymer (A) is not particularly limited. There may be. The hydroxyl value of the urethane prepolymer (A) may 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 urethane prepolymer (A) is within the predetermined range, for example, in the pressure-sensitive adhesive sheet, it is easy to obtain a pressure-sensitive adhesive layer with a good crosslink density, and the wettability is further improved.

Although the method for measuring the hydroxyl value of the urethane prepolymer (A) is not particularly limited, it can be measured, for example, by the following method.

[Method for measuring hydroxyl value]
The hydroxyl value (OHV) of the resin can be measured by a measuring method according to JIS K1557-1:2007. Specifically, 1 g of the resin to be measured (for example, urethane prepolymer (A)) is acetylated with acetic anhydride, and the number of mg of potassium hydroxide required for neutralization is the hydroxyl value of the resin [mgKOH/g]. and

The urethane prepolymer (A) may be, for example, an adduct of polyol and isocyanate, as described above. Said isocyanate may be, for example, a polyisocyanate. The urethane prepolymer (A) can be produced, for example, by reacting the polyol and the isocyanate. Further, the hydroxyl value of the urethane prepolymer (A) can be adjusted by, for example, a method of adjusting the molecular weight of the polyol during the reaction, a method of adjusting the functional group number of the hydroxyl groups of the polyol, and a mixing ratio of the polyol and the isocyanate. can be performed by a known method such as a method of adjusting the The types and the like of the polyol and the isocyanate will be described together with examples of the method for producing the pressure-sensitive adhesive of the present invention in "2. Production method for pressure-sensitive adhesive" below.

The number of hydroxyl functional groups in one molecule of the polyol, which is the raw material of the urethane 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, but may be, for example, 1,000 to 15,000, 1,000 to 6,000, or 2,000 to 5,000. The polyol preferably contains a polyether polyol. For example, the polyol preferably contains a trifunctional (containing three hydroxyl groups in one molecule) polyether polyol and has a hydroxyl value of 10 to 170 mgKOH/g. Incidentally, the hydroxyl value of the polyol can be measured by the same method as that for the urethane prepolymer. As a result, for example, it is easy to obtain an adhesive layer with an appropriate cross-linking density, good wettability with low adhesive strength, the adhesive strength does not increase excessively even when the adhesive sheet is heated, and the adhesive sheet can be peeled off from the adherend. It is possible to suppress the adhesive layer from remaining on the adherend when applying the adhesive layer. Further, the polyol may contain, for example, polyester polyol in addition to polyether polyol.

The NCO/OH ratio between the polyol and the isocyanate, which are raw materials of the urethane prepolymer (A), is not particularly limited, but may be, for example, 0.4 or more or 0.5 or more, for example, 0.9. Below, it may be 0.7 or less or 0.6 or less. The NCO/OH ratio is, for example, 0.4-0.9, 0.4-0.7, 0.4-0.6, 0.5-0.9, 0.5-0.7 or 0 It may be in the range of 0.5 to 0.6. The NCO/OH ratio is a value obtained by dividing the number of moles of isocyanate groups by the number of moles of hydroxyl groups in the total amount of the polyol and the isocyanate.

The content of the urethane prepolymer (A) in the total mass of the adhesive of the present invention is not particularly limited, but may be, for example, 20 to 80% by mass, 30 to 70% by mass, or 40 to 60% by mass. good.

[1-2. Nonionic sulfonic acid ester (B)]
The nonionic sulfonate (B) is not particularly limited, and may be, for example, an aromatic sulfonate or a non-aromatic sulfonate. The non-aromatic sulfonate ester may be, for example, an aliphatic sulfonate ester. Also, the nonionic sulfonate ester (B) may be used alone or in combination of multiple types.

In the present invention, "nonionic" means, for example, that it does not have an ionic functional group, or that even if it does, it does not ionize under normal conditions of use of the adhesive. Examples of the ionic functional group include a carboxy group and a phenolic hydroxyl group.

The nonionic sulfonate (B) may be, for example, a sulfonate represented by the following chemical formula (I).

In the chemical formula (I), R ¹ is an aliphatic group or an aromatic group. In R ¹ , the aliphatic group is not particularly limited, but is, for example, as described above, such as an alkyl group or an alkenyl group, such as a linear or branched alkyl group having 1 to 18 carbon atoms, or a carbon It is a linear or branched alkenyl group of number 1-18. In R ¹ , the aromatic group is not particularly limited, but is, for example, as described above, such as an aryl group, such as a phenyl group. Further, the aromatic group may or may not have, for example, one or more substituents, and the substituents may be the same or different when there is more than one.

In the chemical formula (I), ^R2 is an aliphatic group or an aromatic group. In R ² , the aliphatic group is not particularly limited, but is, for example, as described above, such as an alkyl group or an alkenyl group, such as a linear or branched alkyl group having 1 to 18 carbon atoms, or a carbon It is a linear or branched alkenyl group of number 1-18. In R ² , the aromatic group is not particularly limited, but is, for example, as described above, such as an aryl group, such as a phenyl group. In R ² , the aliphatic group or the aromatic group may or may not have further substituents. Said further substituents may be one or more and if more than one they may be the same or different. The additional substituents are not particularly limited, but may be, for example, the substituents described above or the same groups as R ¹ —SO ₃ — in the chemical formula (I).

The sulfonic acid ester represented by the chemical formula (I) may be, for example, a sulfonic acid ester represented by the following chemical formula (II).

In the chemical formula (II), Ar is an aromatic group. Although the aromatic group is not particularly limited, it is, for example, as described above, such as an aryl group. Further, the aromatic group may or may not have, for example, one or more substituents, and the substituents may be the same or different when there is more than one.

In the chemical formula (II), ^R2 is the same as in the chemical formula (I).

The sulfonic acid ester represented by the chemical formula (I) may be, for example, a sulfonic acid ester represented by the following chemical formula (III).

In the chemical formula (III), ^R2 is the same as in the chemical formula (I).

In the above chemical formula (III), R ³ is a substituent, which may or may not exist, and may be one or more when present, and may be the same or different when more than one.

Specific examples of the nonionic sulfonate (B) include methyl p-toluenesulfonate, ethyl p-toluenesulfonate, n-octyl p-toluenesulfonate, phenyl p-toluenesulfonate, and methanesulfonic acid. Examples include ethyl, 1,3-bis(tosyloxy)propane, and the like.

The content of the nonionic sulfonate (B) is not particularly limited, but is, for example, 0.1% by mass or more, 0.3% by mass or more, 0.5% by mass or more, based on the total mass of the urethane prepolymer (A). It may be at least 1% by mass, or at least 1% by mass, for example, at most 25% by mass, at most 13% by mass, at most 8% by mass, or at most 5% by mass. The "total mass of the urethane prepolymer (A)" is only the urethane prepolymer (A) excluding impurities (for example, the solvent when the urethane prepolymer (A) is used in the form of a solution, emulsion, etc.). means the total mass of From the viewpoint of adherend contamination resistance, it is preferable that the nonionic sulfonate ester (B) is not too small. In addition, from the viewpoint of suppressing the phenomenon that the hydrolysis product of the nonionic sulfonic acid ester (B) deteriorates product stability or inhibits the cross-linking reaction when processed into an adhesive sheet, nonionic It is preferred not to have too much sulfonic acid ester (B).

[1-3. Crosslinking agent (C)]
As described above, the pressure-sensitive adhesive of the present invention may further contain a cross-linking agent (C), and the cross-linking agent (C) may be a polyisocyanate. In the present invention, as described above, "polyisocyanate" is an organic compound having a plurality (2 or 3 or more) of isocyanate groups (also referred to as isocyanato groups), that is, (-N=C=O) in one molecule ( polyfunctional isocyanate).

When the pressure-sensitive adhesive of the present invention contains the polyisocyanate as the cross-linking agent (C), the content thereof is not particularly limited. It may be from 0.5 to 5 times or from 1 to 4 times the molar amount.

In the cross-linking agent (C), the polyisocyanate is not particularly limited. The polyisocyanate may be, for example, the same as the polyisocyanate used in the synthesis of the urethane prepolymer (A), which will be exemplified in "2. Production method of pressure-sensitive adhesive" described later. A biuret form reacted with , a trimer having an isocyanurate ring, or the like may be used, and one type or a plurality of types may be used in combination.

[1-4: Other components]
The adhesive of the present invention contains the components (A) and (B) as described above. The component (C) (crosslinking agent (C)) may or may not be included as described above. In addition, the adhesive of the present invention may or may not contain components other than the components (A) to (C). For example, the pressure-sensitive adhesive of the present invention further includes a solvent, a plasticizer, an antioxidant, an anti-crosslinking agent, a filler, a colorant, an ultraviolet absorber, an antifoaming agent, a light stabilizer, and a leveling agent as the other components. , an antistatic agent, etc. may or may not be included. Although the types thereof are not particularly limited, for example, they may be the same as or similar to general pressure-sensitive adhesives.

The antistatic agent is not particularly limited, but may be, for example, an ionic compound. The ionic compound is preferably other than an ionic compound that can exhibit basicity and an ionic sulfonate ester compound. Specific examples of the ionic compound include chlorides, perchlorates, acetates, nitrates, and more specifically lithium chloride, lithium perchlorate, sodium perchlorate, potassium acetate, trifluoro Examples include lithium acetate and lithium nitrate.

Examples of the plasticizer include carboxylic acid esters. The carboxylic acid ester is not particularly limited, but may be, for example, the carboxylic acid esters described in JP-A-2011-190420, JP-A-2015-151429, and JP-A-2016-186029. The carboxylic acid ester may be, for example, a carboxylic acid ester in Examples described later. The content of the plasticizer is not particularly limited, but may be, for example, 1% by mass or more, 3% by mass or more, 5% by mass or more, or 10% by mass or more, For example, it may be 150% by mass or less, 100% by mass or less, 75% by mass or less, or 60% by mass or less. As described above, the "total mass of the urethane prepolymer (A)" is the urethane prepolymer (A ) refers to the total mass of only From the viewpoint of improving the adhesiveness of the pressure-sensitive adhesive to the base material of the pressure-sensitive adhesive sheet (eg, PET film, etc.), it is preferable that the amount of the plasticizer is large. On the other hand, from the viewpoint of suppressing the phenomenon that the cohesive force of the adhesive is too low and the adhesive force is greatly increased when the adhesive sheet is peeled off from the adherend, or the adhesive remains on the adherend. It is preferred not to have too much plasticizer.

Examples of the ultraviolet absorber include, but are not particularly limited to, benzophenone-based, benzotriazole-based, and triazine-based ultraviolet absorbers. Examples of the antifoaming agent include, but are not particularly limited to, silicone antifoaming agents and mineral oil antifoaming agents. The light stabilizer is not particularly limited, but includes, for example, hindered amine-based light stabilizers. Examples of the antistatic agent include ionic compounds such as inorganic salts and organic salts, and nonionic compounds such as nonionic surfactants. The solvent, the antioxidant and the cross-linking inhibitor are not particularly limited. be.

Moreover, the pressure-sensitive adhesive of the present invention may or may not contain an acidic component, but it is preferable that the content of the acidic component is as small as possible. If the content of the acidic component in the adhesive is not too high, for example, the viscosity of the adhesive increases over time, and the crosslinking reaction of the adhesive occurs when the adhesive is applied to a substrate (such as a PET film). It is possible to suppress problems such as inhibiting the adhesion and corroding the metal when the adhesive touches the metal part of the coating machine or the like. Since the nonionic sulfonate ester (B) hydrolyzes slowly and hardly generates an acidic component, the pressure-sensitive adhesive of the present invention is less likely to cause such problems.

[2. Method for manufacturing adhesive]
The method for producing the pressure-sensitive adhesive of the present invention is not particularly limited except that the components (A) and (B) are used. Reference 1 and the like may be used as a reference. Hereinafter, mainly, the manufacturing method in the case where the urethane prepolymer (A) is a polyurethane polyol synthesized from a polyol and a polyisocyanate will be described with an example.

First, a reaction vessel is charged with a polyol, a polyisocyanate, a solvent, and, if necessary, a catalyst, and the reaction is carried out while heating and stirring. The amount of the polyol used is not particularly limited, but is, for example, 20 to 80% by mass, or 40 to 60% by mass, based on the mass of the pressure-sensitive adhesive after production. The amount of the polyisocyanate used is not particularly limited, but is, for example, 0.5 to 10% by mass, or 1 to 5% by mass, based on the mass of the pressure-sensitive adhesive after production. The amount of the solvent used is not particularly limited, but is, for example, 10 to 50% by mass, or 20 to 40% by mass, based on the mass of the pressure-sensitive adhesive after production. The catalyst may not be used, but is preferably used from the viewpoint of smooth progress of the reaction. When the catalyst is used, the amount used is not particularly limited, but is, for example, 0.001 to 0.1% by mass based on the mass of the pressure-sensitive adhesive after production. The reaction temperature for the above reaction is not particularly limited, but is, for example, 30 to 80°C or 40 to 60°C. The reaction time for the reaction is not particularly limited, but is, for example, 0.5 to 15 hours, 0.5 to 4 hours, or 1 to 3 hours. Thus, a polyurethane polyol (urethane prepolymer (A))-containing composition can be synthesized.

In addition, in the synthesis of the polyurethane polyol-containing composition, for example, (1) a method of charging a polyester polyol, a polyether polyol, a catalyst, and a polyisocyanate into a volumetric flask, and (2) a method of charging a polyester polyol, a polyether polyol, and a catalyst. A method of charging a flask and adding the polyisocyanate dropwise is also possible. (1) is simpler, but (2) is easier to control the reaction, so it is possible to use them properly according to need.

Furthermore, the component (B) is added to the synthesized polyurethane polyol-containing composition and stirred until uniform. At this time, if necessary, component (C) (crosslinking agent (C)) may be added. Further, if necessary, other components than components (A) to (C) may be added. The other component may contain, for example, a solvent, and may contain an antioxidant, an anti-crosslinking agent, a carboxylic acid ester, etc., as described above. Thus, the adhesive of the present invention can be obtained.

In the cross-linking agent (C), the polyisocyanate is not particularly limited, but may be the same as the polyisocyanate used for synthesizing the polyurethane polyol (urethane prepolymer (A))-containing composition exemplified below. . In the cross-linking agent (C), the amount of the polyisocyanate used is not particularly limited. Alternatively, the molar amount of the hydroxyl groups of the polyol is preferably 0.5 to 5 times or 1 to 4 times the molar amount of the isocyanate groups of the polyurethane polyisocyanate.

Although the solvent may not be used, it is preferable to use it from the viewpoint of smooth mixing of the components constituting the pressure-sensitive adhesive of the present invention. When the catalyst is used, the amount used is not particularly limited, but is, for example, 0.001 to 0.1% by mass, or 0.01 to 0.05% by mass, based on the mass of the pressure-sensitive adhesive after production. . Although the antioxidant may not be used, it is preferable to use it. When the antioxidant is used, the amount used is not particularly limited, but is, for example, 0.05 to 1% by mass, or 0.1 to 0.6% by mass, based on the mass of the pressure-sensitive adhesive after production. . When the fatty acid ester is used, the amount used is not particularly limited, but is, for example, 5 to 50% by mass, or 10 to 30% by mass, based on the mass of the pressure-sensitive adhesive after production.

The synthesis of the polyurethane polyol (urethane prepolymer (A))-containing composition will be described in more detail below.

The polyol, which is the raw material of the urethane prepolymer (A), is not particularly limited. However, it is preferably trifunctional or higher, and particularly preferably trifunctional. Further, the polyol may be used alone or in combination of multiple types. The polyol is not particularly limited, but may be, for example, one or both of a polyester polyol and a polyether polyol.

The polyester polyol is not particularly limited, and may be, for example, a known polyester polyol. Examples of the acid component of the polyester polyol include terephthalic acid, adipic acid, azelaic acid, sebacic acid, phthalic anhydride, isophthalic acid, and trimellitic acid. Examples of the glycol component of the polyester polyol include ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, 1,6-hexane glycol, 3-methyl-1,5-pentanediol, 3,3′-dimethylolheptane, poly oxyethylene glycol, polyoxypropylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol and the like. Examples of the polyol component of the polyester polyol include glycerin, trimethylolpropane, and pentaerythritol. Other examples include polyester polyols obtained by ring-opening polymerization of lactones such as polycaprolactone, poly(β-methyl-γ-valerolactone) and polyvalerolactone.

The molecular weight of the polyester polyol is not particularly limited, and a range from low molecular weight to high molecular weight can be used. A polyester polyol having a number average molecular weight of 500 to 5,000 is preferably used. If the number average molecular weight is 500 or more, it is easy to prevent gelation due to too high reactivity. Moreover, if the number average molecular weight is 5,000 or less, it is easy to prevent a decrease in reactivity and a decrease in the cohesive strength of the polyurethane polyol itself. The polyester polyol may or may not be used, but when used, the amount used is, for example, 10 to 90 mol%, or 10 to 50 mol% of the polyol constituting the polyurethane polyol. good too.

Moreover, the polyether polyol is not particularly limited, and may be, for example, a known polyether polyol. Specifically, the polyether polyol is, for example, water or a low-molecular-weight polyol such as propylene glycol, ethylene glycol, glycerin, trimethylolpropane, etc., as an initiator, and a It may be a polyether polyol obtained by polymerizing an oxirane compound. More specifically, the polyether polyol may have two or more functional groups, such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol. The molecular weight of the polyether polyol is not particularly limited, and can be used from low molecular weight to high molecular weight. For example, polyether polyols having number average molecular weights of 1,000 to 15,000 may be used. If the number average molecular weight is 1,000 or more, it is easy to prevent gelation due to too high reactivity. Further, when the number average molecular weight is 15,000 or less, it is easy to prevent a decrease in reactivity and a decrease in the cohesive strength of the polyurethane polyol itself. The polyether polyol may or may not be used, but when used, the amount used is, for example, 20 to 100 mol %, or 20 to 80 mol % of the polyols constituting the polyurethane polyol. may

Part of the polyether polyol, if necessary, is ethylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol, glycerin, trimethylolpropane, glycols such as pentaerythritol, ethylenediamine, N - Polyvalent amines such as aminoethylethanolamine, isophoronediamine, and xylylenediamine may be substituted and used in combination.

As described above, the polyol may be a bifunctional (having two hydroxyl groups in one molecule) polyether polyol, but is preferably trifunctional or higher (having three or more hydroxyl groups in one molecule). In particular, by using a polyol having a number average molecular weight of 1,000 to 15,000 and having a trifunctional or more function, in part or in whole, it becomes easier to balance adhesive strength and removability. When the number average molecular weight is 1,000 or more, it is easy to prevent gelation due to excessively high reactivity of the trifunctional or higher polyol. Further, when the number average molecular weight is 15,000 or less, it is easy to prevent a decrease in the reactivity of the tri- or higher functional polyol and a decrease in the cohesive strength of the polyurethane polyol itself. For example, a trifunctional or higher polyol having a number average molecular weight of 2,500 to 3,500 may be used partially or wholly.

The polyisocyanate (organic polyisocyanate compound), which is a raw material of the urethane prepolymer (A), is not particularly limited. polyisocyanate, and the like. In addition, one type of polyisocyanate may be used alone, or a plurality of types may be used in combination.

Examples of the aromatic polyisocyanate include 1,3-phenylene diisocyanate, 4,4'-diphenyldiisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanatotoluene, 1,3,5-triisocyanatobenzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4' , 4″-triphenylmethane triisocyanate and the like.

Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, and dodecamethylene diisocyanate. , 2,4,4-trimethylhexamethylene diisocyanate and the like.

Examples of the araliphatic polyisocyanate include ω,ω'-diisocyanate-1,3-dimethylbenzene, ω,ω'-diisocyanate-1,4-dimethylbenzene, ω,ω'-diisocyanate-1,4- diethylbenzene, 1,4-tetramethylxylylene diisocyanate, 1,3-tetramethylxylylene diisocyanate and the like.

Examples of the alicyclic polyisocyanate include 3-isocyanatomethyl-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′-methylenebis(cyclohexyl isocyanate), 1,4-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, etc. mentioned.

In addition, trimethylolpropane adducts of some of the above polyisocyanates, water-reacted biuret forms, trimers having an isocyanurate ring, and the like can also be used in combination.

As the polyisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate) and the like are preferable.

The catalyst is not particularly limited, and for example, a known catalyst can be used. Examples of the catalyst include tertiary amine compounds and organometallic compounds.

Examples of the tertiary amine compound include triethylamine, triethylenediamine, 1,8-diazabicyclo(5,4,0)-undecene-7 (DBU) and the like.

Examples of the organometallic compounds include tin-based compounds and non-tin-based compounds. Examples of the tin-based compound include dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate (DBTDL), dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, tributyltin acetate, triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, dioctyltin dilaurate, tributyltin chloride, tributyltin trichloroacetate, tin 2-ethylhexanoate and the like. Examples of the non-tin compounds include titanium compounds such as dibutyl titanium dichloride, tetrabutyl titanate and butoxy titanium trichloride; lead compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate and lead naphthenate; Iron-based such as iron 2-ethylhexanoate and iron acetylacetonate, cobalt-based such as cobalt benzoate and cobalt 2-ethylhexanoate, zinc-based such as zinc naphthenate and zinc 2-ethylhexanoate, zirconium naphthenate, etc. is mentioned.

When these catalysts are used, for example, in a system in which two kinds of polyols, polyester polyol and polyether polyol, exist, the difference in reactivity causes gelation or turbidity of the reaction solution in a single catalyst system. is likely to occur. In such a case, for example, by using two or more kinds of catalysts together, the reaction rate, the selectivity of the catalyst, etc. can be controlled, and these problems can be solved. Examples of the combination include tertiary amine/organometallic, tin/non-tin, tin/tin, etc., preferably tin/tin, more preferably dibutyltin dilaurate and 2- It is a combination of tin ethylhexanoate. The compounding ratio is not particularly limited, but for example, the mass ratio of tin 2-ethylhexanoate/dibutyltin dilaurate is less than 1, and may be, for example, 0.2 to 0.6. If the compounding ratio (mass ratio) is less than 1, it is easy to prevent gelation due to the balance of catalytic activity. The amount of these catalysts used is not particularly limited, but is, for example, 0.01 to 1.0% by mass or 0.01 to 0.2% by mass based on the total amount of polyol and organic polyisocyanate.

When using the catalyst, the reaction temperature for synthesizing the polyurethane polyol may be, for example, below 100°C, or between 40°C and 60°C. If the temperature is less than 100°C, it is easy to control the reaction rate and the crosslinked structure, and it is easy to obtain a polyurethane polyol having a predetermined molecular weight.

Moreover, when the catalyst is not used (no catalyst), the reaction temperature for synthesizing the polyurethane polyol may be, for example, 100° C. or higher, or 110° C. or higher. In addition, the reaction time for synthesizing the polyurethane polyol is, for example, 3 hours or more in the absence of a catalyst.

The solvent used for synthesizing the urethane prepolymer (A) is not particularly limited, and for example, known solvents can be used. Examples of the solvent 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 in view of the solubility of polyurethane polyol, the boiling point of the solvent, and the like.

Moreover, the antioxidant is not particularly limited, but examples thereof include phenol-based and sulfur-based antioxidants.

In the present invention, the molecular weight, molecular weight dispersity, etc. of the urethane prepolymer (A) are not particularly limited. The number average molecular weight of the urethane prepolymer (A) is determined by the molecular weights of the polyisocyanate and polyol used as raw materials for producing the urethane prepolymer (A), and the reaction ratio between the polyisocyanate and the polyol (NCO/OH equivalent ratio ) can be theoretically calculated (Japanese Patent Application Laid-Open No. 2017-025147).

[3. Adhesive sheet and its manufacturing method, use, etc.]
Next, the pressure-sensitive adhesive sheet of the present invention, its production method, uses, etc. will be described with reference to examples.

As described above, the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is formed on at least one surface of a substrate, and the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive of the present invention. characterized by The production method is not particularly limited, but for example, it can be produced by the production method of the present invention (the production method of the pressure-sensitive adhesive sheet of the present invention).

As described above, the method for producing the pressure-sensitive adhesive sheet of the present invention includes a coating step of applying the pressure-sensitive adhesive of the present invention to the adhesive layer forming surface of the substrate on which the adhesive layer is formed, and the coating step. and a heating step of heating the adhesive on the adhesive layer forming surface. Hereinafter, the method for producing the pressure-sensitive adhesive sheet of the present invention in which the urethane prepolymer (A) contains a polyurethane polyol synthesized from a polyol and a polyisocyanate will be mainly described with examples.

That is, first, the pressure-sensitive adhesive of the present invention is applied to the surface of the substrate on which the pressure-sensitive adhesive layer is to be formed (coating step). The base material is not particularly limited, and examples thereof include plastics, polyurethanes, papers, and metal foils, with plastics being preferred. Examples of the plastic include PET (polyethylene terephthalate), PE (polyethylene), PP (polypropylene), PC (polycarbonate), and the like.

The shape of the substrate is also not particularly limited, and examples thereof include sheets, films, foams, and the like. The substrate is preferably in the form of a long tape that can be taken up, for example, from the standpoint of ease of handling and storage of the pressure-sensitive adhesive sheet after production.

Further, the substrate may be, for example, a substrate having an adhesive layer-forming surface of the substrate subjected to an easy-adhesion treatment, if necessary. The adhesion-facilitating treatment is not particularly limited, but specific examples thereof include a method of treating corona discharge, a method of applying an anchor coating agent, and the like.

When the adhesive of the present invention does not contain the cross-linking agent (C), it is preferable to mix the cross-linking agent (C) prior to the coating step, for example. When the cross-linking agent (C) contains a polyisocyanate, the polyisocyanate is not particularly limited, but the polyisocyanate exemplified in "2. Production method of pressure-sensitive adhesive", and the trimethylolpropane adduct, reacting with water and a trimer having an isocyanurate ring. Moreover, the usage amount of the cross-linking agent (C) is, for example, as described above. Furthermore, for the purpose of facilitating mixing of the pressure-sensitive adhesive of the present invention and the cross-linking agent (C), or for the purpose of facilitating coating on the base material, a solvent may be further mixed prior to the coating step. . The type and the like of the solvent are not particularly limited, but are, for example, the same as the solvents exemplified in "2. Production method of pressure-sensitive adhesive", and may be used alone or in combination of multiple types.

The coating method in the coating step is not particularly limited, and may be a known method. Examples of the coating method include roll coater method, comma coater method, die coater method, reverse coater method, silk screen method, gravure coater method and the like.

In addition, the coating amount (coating amount) of the adhesive in the coating step is not particularly limited, but the thickness of the adhesive layer in the adhesive sheet to be produced is, for example, 1 to 50 μm, 5 to 30 μm, 7 to 20 μm. , or 10 to 15 μm.

Furthermore, after the coating step, the adhesive is heated on the adhesive layer forming surface (heating step). In addition, hereinafter, the heating process may be referred to as a "first heating process" in order to distinguish it from a second heating process described later. The heating temperature in the heating step (first heating step) is not particularly limited. Or it is 130° C. or higher. Although the upper limit of the heating temperature is not particularly limited, it is, for example, 150° C. or less.

In order to prevent the adhesive layer from protruding from the edge of the substrate during storage, handling, etc. of the adhesive sheet, it is preferable to raise the heating temperature in the heating step as high as possible. By making the heating temperature as high as possible, for example, the cross-linking (curing) reaction between the pressure-sensitive adhesive of the present invention and the cross-linking agent (C) is sufficiently facilitated, so it is presumed that the protrusion can be prevented. However, this mechanism is speculation and does not limit the present invention.

In general, if the heating temperature after applying the pressure-sensitive adhesive to the base material is too high, the adhesion of the pressure-sensitive adhesive layer to the base material may deteriorate. On the other hand, according to the pressure-sensitive adhesive of the present invention, for example, even if it is heated at a high temperature, it has good adhesion to the substrate and can prevent repelling and protrusion from the substrate.

In addition, the heating time in the heating step (first heating step) is not particularly limited. A time that does not cause damage is preferable. The specific heating time is, for example, 30 to 240 seconds or 60 to 180 seconds, depending on the types of the solvent and the base material.

Furthermore, the method for producing a pressure-sensitive adhesive sheet according to the present invention preferably includes a second heating step of heating at a temperature lower than that of the heating step after the heating step (first heating step). The second heating step may or may not be performed, but by performing this step, the protrusion of the adhesive layer from the edge of the base material can be more effectively prevented. Although the phenomenon that occurs in the second heating step is unknown, it is presumed that, for example, curing (crosslinking) of the adhesive layer further progresses. However, this guess does not limit the present invention. The heating temperature in the second heating step is not particularly limited, but is, for example, 30 to 50°C or 35 to 45°C. Moreover, the heating time in the second heating step is not particularly limited, but is, for example, 24 to 120 hours, or 48 to 96 hours.

The use of the pressure-sensitive adhesive sheet of the present invention is not particularly limited, but as described above, it is preferably used as a protective sheet for the image display surface of an image display device by being attached to the image display surface. Moreover, when using for this purpose, for example, it is more preferable that the base material is transparent.

As described above, the image display device of the present invention is an image display device in which a protective sheet for the image display device is attached to the image display surface, and the protective sheet is the pressure-sensitive adhesive sheet of the present invention. and Examples of the image display device include, but are not limited to, mobile phones, smart phones, tablet computers, and the like. However, the application of the pressure-sensitive adhesive sheet of the present invention is not limited to image display devices, and can be used, for example, as a protective sheet for window glass of automobiles, buildings, and the like. The pressure-sensitive adhesive sheet of the present invention is not limited to glass, and can be used as a protective sheet for ITO (Indium Tin Oxide) processed on a glass substrate as a transparent conductive film. Furthermore, the use of the pressure-sensitive adhesive sheet of the present invention is not limited to these, and for example, it can be widely used in the same applications as general pressure-sensitive adhesive sheets, pressure-sensitive adhesive films, pressure-sensitive adhesive tapes, and the like. The pressure-sensitive adhesive sheet of the present invention, for example, does not stain the adherend after peeling even when exposed to moist heat, has excellent wettability, and has excellent adhesion between the pressure-sensitive adhesive and the substrate. It can be used for a wide range of purposes. Further, the use of the pressure-sensitive adhesive of the present invention is not particularly limited to the pressure-sensitive adhesive sheet of the present invention, and for example, it can be widely used in the same applications as general pressure-sensitive adhesives.

The form of the pressure-sensitive adhesive sheet of the present invention is also not particularly limited. It is preferable to peel off the separator. Further, for example, the pressure-sensitive adhesive sheet of the present invention is in the form of a long tape that can be taken up, and is preferably taken up and stored. According to the pressure-sensitive adhesive tape of the present invention, it is possible to prevent the pressure-sensitive adhesive layer from protruding from the end of the pressure-sensitive adhesive tape during winding, storage, and the like.

Examples of the present invention will be described below. However, the present invention is not limited to these examples.

Raw material names (compound names), product names (trade names), and manufacturers used in the following examples and comparative examples are summarized in Table 1 below.

[Synthesis Example 1]
A urethane prepolymer (A) was synthesized and a urethane prepolymer (A) solution was prepared according to the following procedure.

Glycerin PO·EO, hexamethylene diisocyanate, toluene, and DBTDL were introduced into a separable flask equipped with a stirrer, a reflux condenser, and a thermometer, and reacted at 60° C. for 3 hours while stirring. When the NCO groups in the content after the reaction were measured using an infrared spectrophotometer (IR), no residual NCO groups could be confirmed. This confirmed that the synthesis of the urethane prepolymer (A) was completed. Then, this content was cooled to 40° C. or lower, and an antioxidant and ethyl acetate were added to obtain a urethane prepolymer (A) solution. This solution was used in the following examples and comparative examples. "Glycerin PO.EO" represents propylene oxide and ethylene oxide adducts of glycerin. "DBTDL" stands for dibutyltin dilaurate.

[Synthesis Example 2]
A urethane prepolymer (A) was synthesized in the same manner as in Synthesis Example 1 except that glycerin PO was used instead of glycerin PO.EO to prepare a urethane prepolymer (A) solution. "Glycerin PO" represents a propylene oxide adduct of glycerin.

[Synthesis Example 3]
A urethane prepolymer (A) was synthesized and a urethane prepolymer (A) solution was prepared in the same manner as in Synthesis Example 1, except that a pluronic polyol was used in addition to glycerin PO.EO as the polyol. "Pluronic-type polyol" represents an ethylene oxide adduct of polypropylene glycol.

[Synthesis Example 4]
A urethane prepolymer (A) was synthesized and a urethane prepolymer (A) solution was prepared in the same manner as in Synthesis Example 1, except that polypropylene glycol was used in addition to glycerin PO.EO as a polyol.

[Synthesis Example 5]
A urethane prepolymer (A) was synthesized in the same manner as in Synthesis Example 1 except that 4,4'-diphenylmethane diisocyanate was used instead of hexamethylene diisocyanate to prepare a urethane prepolymer (A) solution.

[Synthesis Example 6]
A urethane prepolymer (A) was synthesized in the same manner as in Synthesis Example 5 except that glycerin PO with a molecular weight of 4,000 was used as the polyol to prepare a urethane prepolymer (A) solution.

[Synthesis Example 7]
A urethane prepolymer (A) was synthesized in the same manner as in Synthesis Example 2, except that glycerin PO with a molecular weight of 10,000 was used as the polyol to prepare a urethane prepolymer (A) solution.

The amount (parts by mass) of each component used in the synthesis of the urethane prepolymer (A) and the preparation of the urethane prepolymer (A) solution in Synthesis Examples 1 to 7 is summarized in Table 2 below.

[Example 1]
To 100 parts by mass of the urethane prepolymer solution of Synthesis Example 1 (60 parts by mass as solid content), 3 parts by mass of methyl p-toluenesulfonate (nonionic sulfonic acid ester (B)) and isocyanurate of hexamethylene diisocyanate (crosslinked Agent (C), Asahi Kasei Corporation, trade name Duranate TKA-100) (6 parts by mass) were blended and thoroughly stirred to obtain the pressure-sensitive adhesive (coating liquid) of Example 1.

[Example 2]
A pressure-sensitive adhesive was produced in the same manner as in Example 1 except that the urethane prepolymer solution of Synthesis Example 2 was used in place of the urethane prepolymer solution of Synthesis Example 1.

[Example 3]
A pressure-sensitive adhesive was produced in the same manner as in Example 1 except that the urethane prepolymer solution of Synthesis Example 3 was used in place of the urethane prepolymer solution of Synthesis Example 1.

[Example 4]
A pressure-sensitive adhesive was produced in the same manner as in Example 1 except that the urethane prepolymer solution of Synthesis Example 4 was used in place of the urethane prepolymer solution of Synthesis Example 1.

[Example 5]
A pressure-sensitive adhesive was produced in the same manner as in Example 1 except that the urethane prepolymer solution of Synthesis Example 5 was used in place of the urethane prepolymer solution of Synthesis Example 1.

[Example 6]
A pressure-sensitive adhesive was produced in the same manner as in Example 1 except that the urethane prepolymer solution of Synthesis Example 6 was used in place of the urethane prepolymer solution of Synthesis Example 1.

[Example 7]
A pressure-sensitive adhesive was produced in the same manner as in Example 1 except that the urethane prepolymer solution of Synthesis Example 7 was used in place of the urethane prepolymer solution of Synthesis Example 1.

[Example 8]
A pressure-sensitive adhesive was produced in the same manner as in Example 1, except that the amount of methyl p-toluenesulfonate (nonionic sulfonate (B)) added was changed to 1 part by mass.

[Example 9]
A pressure-sensitive adhesive was produced in the same manner as in Example 1, except that ethyl p-toluenesulfonate of the same mass was used instead of methyl p-toluenesulfonate as the nonionic sulfonate ester (B).

[Example 10]
A pressure-sensitive adhesive was produced in the same manner as in Example 9, except that the amount of ethyl p-toluenesulfonate (nonionic sulfonate (B)) added was changed to 1 part by mass.

[Example 11]
A pressure-sensitive adhesive was produced in the same manner as in Example 1, except that the same mass of n-octyl p-toluenesulfonate was used as the nonionic sulfonate ester (B) instead of methyl p-toluenesulfonate.

[Example 12]
A pressure-sensitive adhesive was produced in the same manner as in Example 11, except that the amount of n-octyl p-toluenesulfonate (nonionic sulfonate (B)) added was changed to 1 part by mass.

[Example 13]
A pressure-sensitive adhesive was produced in the same manner as in Example 8, except that 1,3-bis(tosyloxy)propane of the same mass was used instead of methyl p-toluenesulfonate as the nonionic sulfonate (B). .

[Example 14]
A pressure-sensitive adhesive was produced in the same manner as in Example 8, except that 30 parts by mass of a carboxylic acid ester represented by the following chemical formula (1001) (where n is 12 on average) was added.

[Example 15]
A pressure-sensitive adhesive was produced in the same manner as in Example 14, except that the amount of methyl p-toluenesulfonate (nonionic sulfonate (B)) added was changed to 0.5 parts by mass.

[Example 16]
A pressure-sensitive adhesive was produced in the same manner as in Example 14, except that the amount of methyl p-toluenesulfonate (nonionic sulfonate (B)) added was changed to 0.25 parts by mass.

[Example 17]
A pressure-sensitive adhesive was produced in the same manner as in Example 8, except that 30 parts by mass of a carboxylic acid ester represented by the following chemical formula (1010) (where n is 10 on average) was added.

[Example 18]
In place of 6 parts by mass of isocyanurate hexamethylene diisocyanate (crosslinking agent (C), Asahi Kasei Co., Ltd., trade name Duranate TKA-100) in Example 14, hexamethylene diisocyanate biuret (Asahi Kasei Co., trade name Duranate 24A-100) A pressure-sensitive adhesive was produced in the same manner as in Example 14, except that 6 parts by mass were used.

[Example 19]
Instead of 6 parts by mass of the isocyanurate form of hexamethylene diisocyanate (crosslinking agent (C), Asahi Kasei Co., Ltd., trade name Duranate TKA-100) in Example 14, bifunctional hexamethylene diisocyanate (Asahi Kasei Co., trade name A pressure-sensitive adhesive was produced in the same manner as in Example 14, except that 7 parts by mass of Duranate D101) was used.

[Example 20]
Instead of 6 parts by mass of the isocyanurate of hexamethylene diisocyanate (crosslinking agent (C), Asahi Kasei Corporation, trade name Duranate TKA-100) in Example 14, an adduct of toluene diisocyanate (Tosoh Corporation, trade name Coronate L ) was produced in the same manner as in Example 14, except that 10 parts by mass of the compound was used.

[Example 21]
Instead of 6 parts by mass of isocyanurate hexamethylene diisocyanate (crosslinking agent (C), Asahi Kasei Corporation, product name Duranate TKA-100) in Example 14, non-yellowing type hexamethylene diisocyanate (Tosoh Corporation, product A pressure-sensitive adhesive was produced in the same manner as in Example 14, except that 11 parts by mass of Coronate HL) was used.

[Example 22]
Instead of 6 parts by mass of the isocyanurate of hexamethylene diisocyanate (crosslinking agent (C), Asahi Kasei Corporation, trade name Duranate TKA-100) in Example 14, an adduct of xylylene diisocyanate (Mitsui Chemicals, trade name A pressure-sensitive adhesive was produced in the same manner as in Example 14, except that 12 parts by mass of Takenate D-110N) was used.

[Example 23]
In place of 6 parts by mass of the isocyanurate of hexamethylene diisocyanate (crosslinking agent (C), Asahi Kasei Co., Ltd., trade name Duranate TKA-100) in Example 14, an adduct of isophorone diisocyanate (Mitsui Chemicals, trade name Takenate D-140N) A pressure-sensitive adhesive was produced in the same manner as in Example 14, except that 13 parts by mass of D-140N) was used.

[Example 24]
Instead of 6 parts by mass of the isocyanurate of hexamethylene diisocyanate (crosslinking agent (C), Asahi Kasei Corporation, trade name Duranate TKA-100) in Example 14, the isocyanurate of toluene diisocyanate (Mitsui Chemicals, trade name A pressure-sensitive adhesive was produced in the same manner as in Example 14, except that 18 parts by mass of Takenate D-262) was used.

[Comparative Example 1]
A pressure-sensitive adhesive was produced in the same manner as in Example 1, except that methyl p-toluenesulfonate (nonionic sulfonate (B)) was not blended.

[Comparative Example 2]
A pressure-sensitive adhesive was produced in the same manner as in Comparative Example 1, except that 1 part by mass of the carboxylic acid ester represented by the chemical formula (1010) (where n is 10 on average) was added.

[Comparative Example 3]
A pressure-sensitive adhesive was produced in the same manner as in Comparative Example 1, except that 30 parts by mass of the carboxylic acid ester represented by the chemical formula (1010) (where n is 10 on average) was added.

The pressure-sensitive adhesives of Examples and Comparative Examples produced as described above were evaluated for adhesive strength (peel strength), wettability, and adherend contamination resistance by the following methods. The results are summarized in Tables 3 and 4 below.

1. Adhesive strength Adhesive strength was evaluated using, as a sample, a pressure-sensitive adhesive sheet produced by coating a coating solution (adhesive) on a PET film having a thickness of 50 μm. In an environment of 23° C. and humidity of 50% RH, the sample was cut into a width of 25 mm and attached to an adherend (glass plate) under a load of 3 reciprocations of a 2 kg roller. After curing this for 1 hour, one end of the sample was peeled off at a rate of 300 mm/min in the 180° direction using an autograph, and the peel strength (N/25 mm) was taken as the adhesive strength. From the viewpoint of re-peelability, the peel strength of the adhesive sheet is preferably not excessively large, and is preferably 0.1 N/25 mm or less.

2. Wettability For the evaluation of wettability , a pressure-sensitive adhesive sheet produced by coating a PET film with a thickness of 50 μm with a coating liquid was used as a sample. The sample was cut into a size of 5 cm×10 cm, and only one side of the sample with a width of 5 cm was brought into contact with a glass plate while being tilted at 45°. Thereafter, the hand was released, and the time (seconds) required for the entire surface of the sample to come into contact with the glass plate (wet the glass plate) was evaluated as wettability. The shorter the time (seconds), the higher the wettability (adhesion) to the glass plate. The higher the wettability, the faster it can be attached to the adherend (the glass plate in this example). The wettability is preferably 10 seconds/10 cm or less.

3. Resistance to staining of adherend For evaluation of resistance to staining of adherend, a pressure-sensitive adhesive sheet produced by coating a PET film having a thickness of 50 µm with a coating liquid was used as a sample. The sample was cut into a size of 4 cm×10 cm, and an adhesive sheet was attached to a glass plate or PET film. After standing in a thermo-hygrostat of 80° C. and humidity of 80% RH for 72 hours, it was further left in an environment of 23° C. and humidity of 50% RH for 1 hour. Next, the pressure-sensitive adhesive sheet was peeled off from the glass plate or PET film, and the state of white contamination on the glass surface where the pressure-sensitive adhesive sheet was adhered was visually evaluated. The state of white contamination was evaluated by irradiating white light in a dark room.
(Evaluation result of adherend contamination resistance)
A: No white contaminants were observed on the glass surface.
◯: Spot-like white contaminants were found on part of the glass surface.
Δ: Mottled white contaminants were observed on the glass surface.
x: White contaminants were observed on the entire surface of the glass.

As shown in Tables 3 and 4, the pressure-sensitive adhesives of Examples 1 to 24 containing all of components (A) to (C) had all of adhesive strength (removability), wettability, and adherend stain resistance. was good. In other words, the pressure-sensitive adhesives of Examples 1 to 24 were able to simultaneously satisfy all of removability, wettability, and adherend contamination resistance. In contrast, the pressure-sensitive adhesives of Comparative Examples 1 to 3, which do not contain the nonionic sulfonate ester (B), had good adhesive strength (removability) and wettability, but had poor adherend contamination resistance. , were inferior compared to the examples.

As described above, according to the present invention, a pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, and a method for producing a pressure-sensitive adhesive sheet that can satisfy removability, wettability, and resistance to adherend contamination under high temperature and high humidity conditions, and an image display device. The pressure-sensitive adhesive, pressure-sensitive adhesive sheet, and method for producing the pressure-sensitive adhesive sheet of the present invention can be used, for example, as protective sheets for window glass of mobile phones, smart phones, automobiles, buildings, and the like. In addition, the present invention is not limited to this, and can be widely used in various applications. For example, it is widely applicable to fields where general adhesives, adhesive sheets, and methods for producing adhesive sheets are used. .

Claims (5)

A pressure-sensitive adhesive comprising a urethane prepolymer (A) having a hydroxyl group, a nonionic sulfonic acid ester (B), and a cross-linking agent (C) , wherein the cross-linking agent (C) is a polyisocyanate. . 2. The pressure-sensitive adhesive according to claim 1, wherein said urethane prepolymer (A) is an adduct of polyol and isocyanate. A pressure-sensitive adhesive sheet comprising a base material and an adhesive layer formed on at least one surface thereof, wherein the pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive according to claim 1 or 2 . A coating step of applying the adhesive according to claim 1 or 2 to the adhesive layer forming surface on which the adhesive layer is formed of the base material;
After the coating step, a heating step of heating the adhesive on the adhesive layer forming surface,
The method for producing the pressure-sensitive adhesive sheet according to claim 3 . An image display device in which a protective sheet for the image display device is attached to the image display surface,
4. An image display device, wherein the protective sheet is the adhesive sheet according to claim 3 .