JP7732185B2 - Adhesive composition, adhesive sheet - Google Patents

Description

The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet.

A typical application of adhesives is adhesive tape. Adhesive tape has a layer containing an adhesive, i.e., an adhesive layer, formed on a substrate. Adhesive tape is attached to various items, for example, to repair them or to secure them together. Double-sided adhesive tape, in which adhesive layers are formed on both sides of the substrate, is used in a wide range of applications, including transportation equipment such as automobiles, home appliances, and stationery.

A typical manufacturing method for adhesive tape involves applying a coating liquid, in which the adhesive is dissolved or dispersed in a liquid medium, to a substrate and then drying it to form an adhesive layer on the surface of the substrate. Natural rubber, synthetic rubber, acrylic, and other adhesives are widely used, with acrylic adhesives being particularly notable for their ability to impart a variety of functionality. In recent years, the use of water as a liquid medium has been widely considered.

For example, Patent Document 1 describes a wafer processing tape that is characterized by being formed by coating a substrate film with an acrylic resin emulsion adhesive blend liquid, which is an acrylic resin emulsion adhesive polymerized using a reactive surfactant and to which a volatile surfactant has been added. It also describes that the acrylic resin emulsion adhesive is obtained by polymerizing a monomer containing a carboxylic acid-containing vinyl compound. There is also an example in which tetramethylol-tri-β-aziridinyl propionate is added to the adhesive blend liquid.

Patent Document 2 describes a removable adhesive sheet in which the adhesive layer contains adhesive microparticles, a binder, a tackifier, and a crosslinking agent having a carbodiimide group. Furthermore, in the examples, acrylic acid is used as a monomer in the synthesis of the adhesive microparticles.

In Example 1 of Patent Document 3, an aqueous acrylic pressure-sensitive adhesive dispersion is described that contains a copolymer obtained by copolymerizing a monomer containing acrylic acid and an epoxy crosslinking agent. Furthermore, in Example 3 and other examples, an aqueous acrylic pressure-sensitive adhesive dispersion is described that contains a copolymer obtained by copolymerizing acrylic acid and a silane coupling agent and an oxazoline crosslinking agent.

Patent Document 4 describes a removable aqueous pressure-sensitive adhesive composition containing a crosslinking agent and an emulsion obtained by emulsion polymerization of a monomer mixture containing a (meth)acrylic acid alkyl ester, a carboxyl group-containing unsaturated monomer, a polyfunctional unsaturated monomer, and other unsaturated monomers. Furthermore, as an example of other unsaturated monomers, a monomer having an alkoxysilyl group is given. Furthermore, it also describes that the crosslinking agent is at least one selected from oxazoline compounds, carbodiimide compounds, epoxy compounds, and aziridine compounds.

Japanese Patent Application Publication No. 5-171117 Japanese Patent Application Laid-Open No. 2005-126479 JP 2013-189645 A Japanese Patent Application Laid-Open No. 2004-256789

The configurations described in Patent Documents 1 and 2 leave room for improvement in terms of adhesive strength and holding power in high-temperature environments.

When the configuration of Example 1 of Patent Document 3 is applied to an adhesive tape, there is room for improvement in terms of holding power in a high-temperature environment. Furthermore, when the configuration of Example 2 of Patent Document 3 is applied to an adhesive tape, there is room for improvement in terms of adhesive strength and holding power in a high-temperature environment.

The structure of Patent Document 4 also leaves room for improvement in terms of adhesive strength and holding power in high-temperature environments. Furthermore, the range of alkoxysilyl group content required for sufficient effectiveness is narrow, but the document does not disclose how much of the alkoxysilyl group is required to achieve the desired effect. Furthermore, the document lists a monomer having an alkoxysilyl group as merely one of many types of monomers, and makes no mention of its effects whatsoever.

An object of the present invention is to provide an adhesive composition that exhibits strong adhesive strength not only at room temperature but also at high temperatures, and that can form an adhesive layer that also has high holding power at high temperatures. Another object of the present invention is to provide an adhesive tape that exhibits strong adhesive strength not only at room temperature but also at high temperatures, and that also has high holding power at high temperatures.

That is, the present invention provides the following means.
[1] A pressure-sensitive adhesive composition comprising a copolymer (A), a crosslinking agent (B), and an aqueous medium,
The copolymer (A) has a carboxy group and an epoxy group,
the crosslinking agent (B) contains, as a crosslinking agent functional group, one or more selected from the group consisting of a carbodiimide group derived from a carbodiimide compound, an epoxy group derived from a polyepoxy compound, and an isocyanato group derived from a polyisocyanate compound;
the amount of carboxy groups contained in 100 g of the copolymer (A) is 10 mmol/100 g or more and 100 mmol/100 g or less,
the amount of epoxy groups contained in 100 g of the copolymer (A) is 0.30 mmol/100 g or more and 30 mmol/100 g or less;
A pressure-sensitive adhesive composition, wherein the content of the crosslinking functional groups in the crosslinking agent (B) relative to 1 mol of carboxy groups in the copolymer (A) is 0.10×10 ⁻² mol or more and 30×10 ⁻² mol or less.
[2] The pressure-sensitive adhesive composition according to the above-mentioned [1], wherein the copolymer (A) has hydroxy groups, and the amount of hydroxy groups contained per 100 g of the copolymer (A) is 0.50 mmol/100 g or more and 15 mmol/100 g or less.
[3] The pressure-sensitive adhesive composition according to the above [1] or [2], wherein the main chain of the copolymer (A) is formed by bonds between carbon atoms.
[4] The pressure-sensitive adhesive composition according to any one of the above [1] to [3], wherein a portion of the copolymer (A) other than the carboxy group, the epoxy group, and the hydroxy group and other than the terminals comprises one or more structures selected from the group consisting of a hydrocarbon structure, an ester bond, and a carbonyl group.
[5] The pressure-sensitive adhesive composition according to any one of the above [1] to [4], wherein the content of epoxy groups in the copolymer (A) relative to 1 mol of carboxy groups in the copolymer (A) is 0.60 × 10 ^-2 mol or more and 60 × 10 ^-2 mol or less.
[6] The pressure-sensitive adhesive composition according to any one of the above [1] to [5], wherein the content of the crosslinking agent functional group in the crosslinking agent (B) relative to 1 mol of the epoxy group in the copolymer (A) is 0.040 mol or more and 1.5 mol or less.
[7] The pressure-sensitive adhesive composition according to any one of the above [1] to [6], wherein the crosslinking agent (B) is a polycarbodiimide compound.
[8] The pressure-sensitive adhesive composition according to the above [7], wherein the carbodiimide equivalent of the crosslinking agent (B) is 150 or more and 1,000 or less.
[9] The pressure-sensitive adhesive composition according to any one of the above [1] to [6], wherein the crosslinking agent (B) is a polyepoxy compound.
[10] The pressure-sensitive adhesive composition according to the above [9], wherein the crosslinking agent (B) has an epoxy equivalent of 70 or more and 700 or less.
[11] The pressure-sensitive adhesive composition according to any one of the above [1] to [10], wherein the amount of crosslinking agent functional groups contained in the crosslinking agent (B) relative to 100 g of the copolymer (A) is 0.20 mmol/100 g or more.
[12] The pressure-sensitive adhesive composition according to any one of the above [1] to [11], wherein the total content of the copolymer (A) and the crosslinking agent (B) in the nonvolatile matter is 50 mass% or more.
[13] An adhesive tape comprising a substrate and an adhesive layer formed on the surface of the substrate,
The adhesive layer of the adhesive tape comprises a cured product of the adhesive composition according to any one of [1] to [12] above.
[14] A step of applying the pressure-sensitive adhesive composition according to any one of the above [1] to [12] to a substrate;
and removing the aqueous medium from the pressure-sensitive adhesive composition applied to the substrate to form a pressure-sensitive adhesive layer.

According to the present invention, it is possible to provide an aqueous dispersion pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer that exhibits strong adhesive strength not only at room temperature but also at high temperatures, and that has high holding power even at high temperatures. In this specification, adhesive strength is defined as "the force generated by contact between the adhesive surface of a pressure-sensitive adhesive sheet or tape and an adherend," and refers to the force required to peel off an adhered object. In this specification, holding power is defined as "the force with which the pressure-sensitive adhesive can resist slippage when a pressure-sensitive adhesive sheet or tape is attached to an adherend and a static load is applied in the longitudinal direction," and represents the strength of the cohesive power of the pressure-sensitive adhesive layer.
Furthermore, according to the present invention, it is possible to provide an adhesive tape that exhibits strong adhesive strength not only at room temperature but also at high temperatures, and that also has high holding power at high temperatures.

In the following explanation, unless otherwise specified, "surface" means "hyoumen."

"(Meth)acrylic" is a general term for acrylic and methacrylic, and "(meth)acrylate" is a general term for acrylate and methacrylate.

Epoxy groups also include structures that form part of a glycidyl group. For example, glycidyl methacrylate is also considered to have an epoxy group.

Unless otherwise specified, the term "ethylenically unsaturated bond" refers to an ethylenically unsaturated bond that is radically polymerizable.

In a polymer of a compound having an ethylenically unsaturated bond, a structural unit derived from the compound having an ethylenically unsaturated bond has the same chemical structure as the portion of the compound other than the ethylenically unsaturated bond and the same chemical structure as the portion of the polymer other than the portion corresponding to the ethylenically unsaturated bond of the structural unit. For example, a structural unit derived from acrylic acid has a structure represented by —CH ₂ CH(COOH)— in the polymer.

In the following explanation, the compound from which a certain structural unit is derived refers to a compound that has the above-mentioned relationship with that structural unit, and does not necessarily correspond to the monomer used in the actual manufacturing process.

Unless otherwise specified, structural units having an ionic functional group such as a carboxyl group are considered to be structural units derived from the same ionic compound, regardless of whether part of the functional group has been ion-exchanged or not. For example, a structural unit represented by —CH ₂ —C(CH ₃ )(COONa)— is also considered to be a structural unit derived from methacrylic acid.

Furthermore, in a compound having multiple independent ethylenically unsaturated bonds, the ethylenically unsaturated bonds may remain as structural units of the polymer. Multiple independent ethylenically unsaturated bonds refer to multiple ethylenically unsaturated bonds that do not form a conjugated diene with each other. For example, a structural unit derived from divinylbenzene may have a structure with no ethylenically unsaturated bonds (a form in which both ethylenically unsaturated bond-corresponding moieties are incorporated into the polymer chain), or a structure with one ethylenically unsaturated bond (a form in which only one ethylenically unsaturated bond-corresponding moiety is incorporated into the polymer chain).

Furthermore, if the chemical structure of the monomer does not correspond to the chemical structure of the polymer, such as when a chemical reaction occurs after polymerization on a portion other than the chain corresponding to the ethylenically unsaturated bond, the chemical structure after polymerization is used as the basis. For example, if vinyl acetate is polymerized and then saponified, the saponified structural units are considered to be structural units derived from vinyl alcohol rather than structural units derived from vinyl acetate, based on the chemical structure of the polymer.

"Non-volatile content" refers to the components remaining after weighing 1 g of the composition into a 5 cm diameter aluminum dish and drying it for 1 hour at 105°C with air circulating in a dryer at 1 atmosphere (1013 hPa). The composition may be in the form of a solution, dispersion, or slurry, but is not limited to these. "Non-volatile content concentration" refers to the mass ratio (mass %) of the non-volatile content after drying under the above conditions to the mass (1 g) of the composition before drying.

<1. Pressure-sensitive adhesive composition>
The pressure-sensitive adhesive composition according to the present embodiment includes a copolymer (A), a crosslinking agent (B), and an aqueous medium. The pressure-sensitive adhesive composition may also include other additives.

[1-1. Copolymer (A)]
The copolymer (A) has a carboxy group and an epoxy group. The main chain of the copolymer (A) is preferably composed of bonds between carbon atoms, more preferably single bonds between carbon atoms. That is, the copolymer (A) is preferably a polymer of a compound having an ethylenically unsaturated bond. The copolymer (A) preferably has a hydroxy group.

[1-1-1. Carboxy group]
The carboxyl group reacts with the epoxy group described later to form an internal crosslink, and reacts with the functional group of the crosslinking agent (B) described later to form an interparticle crosslink. These crosslinks are thought to impart cohesive strength to the adhesive layer and improve heat resistance. Some or all of the carboxyl group may form a salt, but the salt formation ratio is preferably 10% or less on a number (molar) basis.

The amount of carboxyl groups contained per 100 g of copolymer (A) is 10 mmol/100 g or more, preferably 20 mmol/100 g or more, more preferably 30 mmol/100 g or more, and even more preferably 40 mmol/100 g or more. This is to improve the cohesive strength of the adhesive layer and enhance heat resistance.

The amount of carboxyl groups contained per 100 g of copolymer (A) is 100 mmol/100 g or less, preferably 80 mmol/100 g or less, and more preferably 60 mmol/100 g or less. This is to maintain the polarity of copolymer (A) and the cohesive strength of the adhesive layer at an appropriate level, thereby obtaining an adhesive layer with sufficient adhesiveness.

Carboxy groups can be introduced into copolymer (A) by polymerizing a compound containing a carboxy group, or by converting a specific functional group into a carboxy group after polymerization. Examples of compounds containing a carboxy group include α,β-unsaturated mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, citraconic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, 2-carboxyethyl acrylate oligomer, and 2-acryloyloxyethyl succinic acid; and carboxyl group-containing vinyl compounds such as monohydroxyethyl (meth)acrylate phthalate and monohydroxypropyl (meth)acrylate oxalate.

[1-1-2. Epoxy group]

The amount of epoxy groups contained per 100 g of copolymer (A) is 0.30 mmol/100 g or more, preferably 1.0 mmol/100 g or more, more preferably 2.0 mmol/100 g or more, and even more preferably 2.5 mmol/100 g or more. This is to improve the cohesive strength of the adhesive layer and enhance heat resistance.

The amount of epoxy groups contained per 100 g of copolymer (A) is 30 mmol or less, preferably 20 mmol/100 g or less, more preferably 10 mmol/100 g or less, and even more preferably 5.0 mmol/100 g or less. This is to maintain an appropriate cohesive force of the adhesive layer and obtain an adhesive layer with sufficient adhesiveness.

The epoxy group can be introduced into copolymer (A) by polymerizing a compound having an epoxy group, or by converting a specific functional group into an epoxy group after polymerization. Examples of compounds having an epoxy group include glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, glycidyl vinyl ether, glycidyl (meth)allyl ether, and 3,4-epoxycyclohexyl (meth)acrylate.

[1-1-3. Hydroxy group]
The copolymer (A) having hydroxy groups further improves the holding power of the adhesive layer at high temperatures, presumably because the hydroxy groups react with the epoxy groups of the copolymer (A) and/or the functional groups of the crosslinking agent (B) described below, thereby assisting internal crosslinking and/or interparticle crosslinking.

The amount of hydroxy groups contained per 100 g of copolymer (A) is preferably 0.50 mmol/100 g or more, more preferably 1.0 mmol/100 g or more, and even more preferably 2.0 mmol/100 g or more. This is because the holding power of the adhesive layer in high-temperature environments is improved.

The amount of hydroxy groups contained per 100 g of copolymer (A) is preferably 15 mmol/100 g or less, more preferably 10 mmol/100 g or less, and even more preferably 5.0 mmol/100 g or less. This is to maintain the polarity of copolymer (A) and the cohesive strength of the adhesive layer at an appropriate level, thereby obtaining an adhesive layer with sufficient adhesiveness.

Methods for introducing hydroxy groups into copolymer (A) include polymerizing a compound containing a hydroxy group, or converting a specific functional group into a hydroxy group after polymerization. Examples of compounds containing hydroxy groups include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate.

[1-1-4. Other structures of copolymer (A)]
In order to adjust the content of the functional groups (here, referring to carboxyl groups, epoxy groups, and hydroxyl groups) in copolymer (A), it is conceivable to introduce a structure that does not have the functional groups to dilute the content of the functional groups within an appropriate range. The structure for this dilution preferably has little interaction with the functional groups. Preferred such structures include hydrocarbon structures such as alkylene groups and alkyl groups, ester bonds, and carbonyl groups.

The copolymer (A) may have, at its terminals, structures derived from the polymerization initiator or chain transfer agent used in its production process.

The structure of copolymer (A) other than the functional groups and terminals preferably consists of one or more selected from the group consisting of hydrocarbon structures, ester bonds, and carbonyl groups, and more preferably consists of at least one of a hydrocarbon structure and an ester bond.

[1-1-5. Glass transition temperature of copolymer (A)]
The glass transition point (Tg) of the copolymer (A) is preferably −80° C. or higher, more preferably −65° C. or higher, and even more preferably −55° C. or higher, in order to improve the cohesive strength of the pressure-sensitive adhesive and impart superior heat resistance to the pressure-sensitive adhesive layer.

The glass transition point of copolymer (A) is preferably 30°C or lower, more preferably 0°C or lower, even more preferably -20°C or lower, and particularly preferably -35°C or lower. This is to improve the wettability of the pressure-sensitive adhesive composition described below and improve the adhesion of the pressure-sensitive adhesive layer to the substrate. It is also to increase the flexibility of the pressure-sensitive adhesive layer and improve the tackiness of the pressure-sensitive adhesive layer when used dry.

Tg is a theoretical value calculated using the FOX formula below based on the monomer units that make up the polymer and their proportions.

1/T=W1/T1+W2/T2+W3/T3+...+Wn/Tn

T (K) = Tg (°C) + 273°C, where T is the glass transition point of copolymer (A) expressed in absolute temperature. Wn is the mass fraction of each structural unit (≦1), and Tn is the glass transition point (absolute temperature) of the homopolymer of the compound from which each structural unit is derived.

[1-1-6. Method for producing copolymer (A)]
The method for producing the copolymer (A) is not particularly limited, but may involve polymerizing a mixture of monomers containing a predetermined amount of a compound having a desired functional group, or may involve polymerizing other compounds for some or all of the structural units and then introducing the desired functional group to form the desired structural unit. Here, the desired functional group may be, for example, the functional group described above, but may also include other functional groups.

One example of a method for producing copolymer (A) is to emulsify the monomers in an aqueous medium and then perform emulsion polymerization using a polymerization initiator. During polymerization, a chain transfer agent may be used to control the molecular weight and molecular weight distribution of the copolymer within an appropriate range. An emulsifier may also be used to emulsify the monomers. The entire amount of monomers may be charged into the reactor in advance, or, to obtain uniform particles, a mixture containing all types of monomers for forming the structural units of copolymer (A) may be continuously or intermittently fed and charged during polymerization. The polymerization temperature is not particularly limited, but is preferably 5 to 100°C, and more preferably 50 to 90°C.

The aqueous medium is water, a hydrophilic solvent, or a mixture thereof. Examples of hydrophilic solvents include methanol, ethanol, isopropyl alcohol, and N-methylpyrrolidone. From the perspective of polymerization stability, the aqueous medium is preferably water. However, as long as polymerization stability is not impaired, water to which a hydrophilic solvent has been added may also be used as the aqueous medium.

Polymerization initiators used in emulsion polymerization include persulfate initiators such as potassium persulfate and ammonium persulfate, water-soluble azo initiators such as 2,2'-azobis(2-methylpropionamidine) dihydrochloride, organic peroxides such as t-butyl hydroperoxide and cumene hydroperoxide, and hydrogen peroxide. These polymerization initiators may be used alone or in combination. The amount of polymerization initiator used is preferably 0.1 to 2% by mass based on the total amount of monomers.

If necessary, a reducing agent can be used together with these polymerization initiators. Examples of such reducing agents include reducing organic compounds such as ascorbic acid, tartaric acid, citric acid, glucose, and formaldehyde sulfoxylate metal salts, and reducing inorganic compounds such as sodium thiosulfate, sodium sulfite, sodium bisulfite, and sodium metabisulfite.

Examples of chain transfer agents include, but are not limited to, n-dodecyl mercaptan, tert-dodecyl mercaptan, n-butyl mercaptan, 2-ethylhexyl thioglycolate, 2-mercaptoethanol, β-mercaptopropionic acid, methyl alcohol, n-propyl alcohol, isopropyl alcohol, t-butyl alcohol, and benzyl alcohol. Only one type of chain transfer agent may be used, or two or more types may be used.

When the amount of chain transfer agent used is small, the cohesive strength of the adhesive improves and heat resistance improves; when it is large, the cohesive strength of the adhesive decreases and the adhesive strength of the adhesive layer improves. The amount of chain transfer agent used is preferably 0.0010 parts by mass or more, more preferably 0.050 parts by mass or more, and even more preferably 0.080 parts by mass or more, per 100 parts by mass of the monomer for copolymer (A). This is to form an adhesive layer with strong adhesive strength.

The amount of chain transfer agent used is preferably 5.0 parts by mass or less, more preferably 2.0 parts by mass or less, even more preferably 0.50 parts by mass or less, and particularly preferably 0.30 parts by mass or less, per 100 parts by mass of the monomer for copolymer (A). This is to improve the heat resistance of the adhesive layer.

The emulsifier is not particularly limited, but specific examples include anionic surfactants such as sodium dodecylbenzenesulfonate and sodium dodecyl sulfate, nonionic surfactants such as polyoxyethylene alkyl ether and polyoxyethylene nonylphenyl ether, cationic surfactants such as ceciltrimethylammonium bromide and laurylpyridinium chloride, amphoteric surfactants such as laurylbetaine, and other reactive surfactants. These surfactants may be used alone or in combination of two or more.

[1-2. Crosslinking agent (B)]
The crosslinking agent (B) has, in one molecule, a plurality of functional groups selected from the group consisting of carbodiimide groups (structure represented by -N=C=N-), epoxy groups, and isocyanato groups. These functional groups are referred to herein as crosslinking agent functional groups. The content of the crosslinking agent (B) in the pressure-sensitive adhesive composition is adjusted based on the relationship between the amount of crosslinking agent functional groups and the amount of functional groups contained in the copolymer (A). The quantitative relationship between these functional groups in the pressure-sensitive adhesive composition will be described later.

The crosslinking agent (B) preferably contains one or more compounds selected from the group consisting of polycarbodiimide compounds (compounds having multiple carbodiimide groups), polyepoxy compounds (compounds having multiple epoxy groups), and polyisocyanate compounds (compounds having multiple isocyanato groups).

Examples of polycarbodiimide compounds include p-phenylene-bis(2,6-xylylcarbodiimide), tetramethylene-bis(t-butylcarbodiimide), cyclohexane-1,4-bis(methylene-t-butylcarbodiimide), and other compounds, as well as products manufactured by Nisshinbo Chemical Inc., such as "Carbodilite (registered trademark, the same applies hereinafter) V-02," "Carbodilite SV-02," "Carbodilite V-04," "Carbodilite V-10," "Carbodilite E-02," "Carbodilite E-03A," and "Carbodilite E-05."

The carbodiimide equivalent weight (molecular weight per carbodiimide group) of the polycarbodiimide compound is preferably 150 or more, more preferably 250 or more, even more preferably 300 or more, and particularly preferably 350 or more. This is to suppress steric hindrance in the crosslinking reaction with copolymer (A) and improve the rate and crosslinking density of the crosslinking reaction.

The carbodiimide equivalent weight (molecular weight per carbodiimide group) of the polycarbodiimide compound is preferably 1,000 or less, more preferably 750 or less, and even more preferably 6,000 or less. This is to improve the crosslink density in the crosslinking reaction with copolymer (A).

Examples of polyepoxy compounds include bisphenol A-epichlorohydrin type epoxy resins, sorbitol polyglycidyl ethers (e.g., "Denacol (registered trademark, hereinafter the same) EX-611," "Denacol EX-612," "Denacol EX-614," "Denacol EX-614B," and "Denacol EX-622," manufactured by Nagase ChemteX Corporation), polyglycerol polyglycidyl ethers (e.g., "Denacol EX-512" and "Denacol EX-521," manufactured by Nagase ChemteX Corporation), pentaerythritol polyglycidyl ethers (e.g., "Denacol EX-411," manufactured by Nagase ChemteX Corporation), and jigs. Glycerol polyglycidyl ether (for example, "Denacol EX-421" manufactured by Nagase ChemteX Corporation), glycerol polyglycidyl ether (for example, "Denacol EX-313" and "Denacol EX-314" manufactured by Nagase ChemteX Corporation), trimethylolpropane polyglycidyl ether (for example, "Denacol EX-321" manufactured by Nagase ChemteX Corporation), resorcinol diglycidyl ether (for example, "Denacol EX-201" manufactured by Nagase ChemteX Corporation), neopentyl glycol diglycidyl ether (for example, "Denacol EX-211" manufactured by Nagase ChemteX Corporation), 1,6-hexanediol ... glycidyl ether (for example, "Denacol EX-212" manufactured by Nagase ChemteX Corporation), hydrogenated bisphenol A diglycidyl ether (for example, "Denacol EX-252" manufactured by Nagase ChemteX Corporation), ethylene glycol diglycidyl ether (for example, "Denacol EX-810" and "Denacol EX-811" manufactured by Nagase ChemteX Corporation), diethylene glycol diglycidyl ether (for example, "Denacol EX-850" and "Denacol EX-851" manufactured by Nagase ChemteX Corporation), polyethylene glycol diglycidyl ether (for example, "Denacol EX-821" manufactured by Nagase ChemteX Corporation), ", "Denacol EX-830", "Denacol EX-832", "Denacol EX-841", "Denacol EX-861", etc.), propylene glycol diglycidyl ether (for example, "Denacol EX-911" manufactured by Nagase ChemteX Corporation), polypropylene glycol diglycidyl ether (for example, "Denacol EX-941", "Denacol EX-920", "Denacol EX-931" manufactured by Nagase ChemteX Corporation), diglycidyl aniline, diglycidyl amine, N,N,N',N'-tetraglycidyl m-xylylenediamine, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, etc. Among these, water-soluble types are preferred.

The epoxy equivalent weight (molecular weight per epoxy group) of the polyepoxy compound is preferably 70 or more, and more preferably 100 or more. This is to suppress steric hindrance in the crosslinking reaction with copolymer (A) and improve the rate and crosslinking density of the crosslinking reaction.

The epoxy equivalent weight (molecular weight per epoxy group) of the polyepoxy compound is preferably 700 or less, more preferably 400 or less, even more preferably 300 or less, and particularly preferably 200 or less. This is to improve the crosslinking density in the crosslinking reaction with copolymer (A).

Examples of polyisocyanate compounds include toluylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, meta-xylylene diisocyanate, 1,5-naphthalene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated toluylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and tetramethylxylene diisocyanate. Specific commercial products include biuret polyisocyanate compounds such as "Sumidur N" (manufactured by Sumitomo Bayer Urethane Co., Ltd.); polyisocyanate compounds having an isocyanurate ring such as "Desmodur IL" and "Desmodur HL" (manufactured by Bayer A.G.) and "Coronate EH" (manufactured by Nippon Urethane Co., Ltd.); adduct polyisocyanate compounds such as "Sumidur L" (manufactured by Sumitomo Bayer Urethane Co., Ltd.) and "Coronate HL" (manufactured by Nippon Polyurethane Co., Ltd.); and self-emulsifying water-dispersible polyisocyanate compounds such as "Aquanate 100," "Aquanate 110," "Aquanate 200," and "Aquanate 210" (manufactured by Nippon Polyurethane Co., Ltd.). Among these, water-dispersible polyisocyanate compounds are preferred. Blocked isocyanate compounds may also be used as polyisocyanate compounds.

The isocyanate equivalent weight (molecular weight per isocyanate group) of the polyisocyanate compound is preferably 60 or more, and more preferably 75 or more. This is to suppress steric hindrance in the crosslinking reaction with copolymer (A) and improve the rate and crosslinking density of the crosslinking reaction.

The isocyanate equivalent weight (molecular weight per isocyanate group) of the polyisocyanate compound is preferably 500 or less, more preferably 200 or less, and even more preferably 100 or less. This is to improve the crosslink density in the crosslinking reaction with copolymer (A).

The amount of crosslinking functional groups contained in the crosslinking agent (B) per 100 g of copolymer (A) is preferably 0.20 mmol/100 g or more, more preferably 0.35 mmol/g or more, even more preferably 0.70 mmol/100 g or more, and particularly preferably 1.0 mmol/100 g or more. This is because the crosslink density between particles increases, improving the cohesive force of the adhesive and increasing the strength of the adhesive layer.

The amount of crosslinking agent functional groups contained in the crosslinking agent (B) per 100 g of copolymer (A) is preferably 20 mmol/100 g or less, more preferably 5.0 mmol/100 g or less, even more preferably 3.0 mmol/g or less, and particularly preferably 2.0 mmol/100 g or less. This is because the flexibility of the adhesive layer is improved and stronger adhesive strength can be obtained.

[1-3. Quantitative relationships between functional groups]
The content of epoxy groups in copolymer (A) per 1 mol of carboxy groups in copolymer (A) is preferably 0.60× ¹⁰ mol or more, more preferably 2.0× ¹⁰ mol or more, even more preferably 4.0× ¹⁰ mol or more, and particularly preferably 5.0× ¹⁰ mol or more, because this improves the density of internal crosslinks in the particles (cured product of copolymer (A) and crosslinking agent (B), the same applies hereinafter) contained in the pressure-sensitive adhesive, thereby enhancing heat resistance.

The content of epoxy groups in copolymer (A) per 1 mol of carboxy groups in copolymer (A) is preferably 60× ¹⁰ mol or less, more preferably 40× ¹⁰ mol or less, even more preferably 20× ¹⁰ mol or less, and particularly preferably 10× ¹⁰ mol or less, because this maintains an appropriate density of internal crosslinks in the particles contained in the pressure-sensitive adhesive, thereby enabling the production of an adhesive layer with high adhesiveness.

The content of hydroxy groups in copolymer (A) per 1 mol of carboxy groups in copolymer (A) is preferably 1.0× ¹⁰ mol or more, more preferably 3.0× ¹⁰ mol or more, and even more preferably 4.5× ¹⁰ mol or more, because this improves the density of internal crosslinks and inter-particle crosslinks of the particles contained in the pressure-sensitive adhesive, thereby improving the holding power of the pressure-sensitive adhesive layer in a high-temperature environment.

The content of hydroxy groups in copolymer (A) per 1 mol of carboxy groups in copolymer (A) is preferably 15×10 mol or less, more preferably 10× ¹⁰ mol or less, and even more preferably 7.5× ¹⁰ mol or ^less , because this allows the density of internal crosslinks and inter-particle crosslinks of the particles contained in the pressure-sensitive adhesive to be maintained at an appropriate level, thereby providing an adhesive layer with high adhesiveness.

The content of crosslinking functional groups in the crosslinking agent (B) per 1 mol of carboxy groups in the copolymer (A) is 0.10× ¹⁰ mol or more, preferably 0.50× ¹⁰ mol or more, preferably 0.70×10 mol or more, more preferably 1.5× ¹⁰ mol or more, and even more preferably 2.0× ¹⁰ mol ^or more, because the crosslink density between particles increases, the cohesive force of the pressure-sensitive adhesive improves, and the strength of the pressure-sensitive adhesive layer improves.

The content of crosslinking functional groups in the crosslinking agent (B) per 1 mol of carboxy groups in the copolymer (A) is 30× ¹⁰ mol or less, preferably 10×10 mol or less, more preferably 7.0× ¹⁰ mol or less, even more preferably 5.0× ¹⁰ mol or less, and particularly preferably 3.5× ¹⁰ mol ^or less, because this improves the flexibility of the adhesive layer and provides stronger adhesive strength.

The content of crosslinking functional groups in crosslinking agent (B) per 1 mol of epoxy groups in copolymer (A) is preferably 0.040 mol or more, more preferably 0.080 mol or more, even more preferably 0.14 mol or more, and particularly preferably 0.28 mol or more. This is because by improving the crosslink density not only within the particles but also between the particles, an adhesive layer with high heat resistance can be obtained.

The content of crosslinking functional groups in crosslinking agent (B) per 1 mol of epoxy groups in copolymer (A) is preferably 1.5 mol or less, more preferably 1.0 mol or less, and even more preferably 0.60 mol or less. This is because by increasing the crosslink density not only between particles but also within the particles, an adhesive layer with high adhesion can be obtained.

[1-4. Aqueous medium]
The aqueous medium is water, a hydrophilic solvent, or a mixture thereof. Examples of hydrophilic solvents include methanol, ethanol, isopropyl alcohol, and N-methylpyrrolidone. The aqueous medium is preferably water. The aqueous medium may have the same composition as the aqueous solvent used in the polymerization of the copolymer (A), or may have a different composition.

[1-5. Other additives]
Additives can be appropriately contained in the pressure-sensitive adhesive composition as needed. The timing of adding the additives is not particularly limited. The additives can be added simultaneously with or after mixing of the copolymer (A) and the crosslinking agent (B). Alternatively, the additives may be added to a solution or dispersion of either or both of the copolymer (A) and the crosslinking agent (B) before mixing them. Examples of additives include pH adjusters and tackifiers. Furthermore, additives that can be appropriately used include plasticizers, antioxidants, fillers, pigments, colorants, wetting agents, antifoaming agents, thickeners, etc.

pH adjusters include common inorganic and organic acidic substances and their salts, as well as amphoteric salts of amino acids. Examples of organic acid pH adjusters include acetic acid, formic acid, glycolic acid, malic acid, citric acid, maleic acid, fumaric acid, malonic acid, phthalic acid, isophthalic acid, lactic acid, butyric acid, ascorbic acid, succinic acid, tartaric acid, acrylic acid, methacrylic acid, crotonic acid, adipic acid, oxalic acid, and abietic acid. Examples of inorganic acid pH adjusters include boric acid, phosphoric acid, hydrochloric acid, nitric acid, nitrous acid, sulfuric acid, and sulfurous acid. Examples of acidic salts include salts of the above organic or inorganic acids with sodium, potassium, ammonia, aminoethanol, diethanolamine, and triethanolamine. Examples of amino acid pH adjusters include glycine, glycylglycine, asparagine, aspartic acid, alanine, phenylalanine, arginine, glutamine, and glutamic acid. These pH adjusters can be used alone or in combination of two or more.

Examples of tackifiers include rosin resin, rosin ester resin, hydrogenated rosin resin, polymerized rosin resin, α-pinene resin, β-pinene resin, terpene phenol resin, C5 fraction petroleum resin, C9 fraction petroleum resin, C5 fraction/C9 fraction petroleum resin, dicyclopentadiene petroleum resin, alkylphenol resin, xylene resin, coumarone resin, and coumarone-indene resin. Tackifiers can be used alone or in combination of two or more.

[1-4. Content of each component of the pressure-sensitive adhesive composition]
The nonvolatile content of the pressure-sensitive adhesive composition is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. This is because a larger amount of pressure-sensitive adhesive layer can be formed with a smaller amount of pressure-sensitive adhesive composition applied. Also, the drying time of the applied pressure-sensitive adhesive composition is shortened, thereby improving productivity.

The nonvolatile content of the pressure-sensitive adhesive composition is preferably 75% by mass or less, and more preferably 65% by mass or less. This is to prevent gelation of copolymer (A) in the pressure-sensitive adhesive composition.

The total content of copolymer (A) and crosslinking agent (B) in the nonvolatile matter of the adhesive composition is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more. This is because the adhesive strength and holding power of the adhesive layer, particularly holding power at high temperatures, are improved.

In the pressure-sensitive adhesive composition, the total content of copolymer (A) and crosslinking agent (B) in the nonvolatile matter is preferably 90% by mass or less, and more preferably 80% by mass or less.

<2. Adhesive tape>
2-1. Structure of adhesive tape
A typical application of the pressure-sensitive adhesive composition according to the present invention is a pressure-sensitive adhesive tape. The pressure-sensitive adhesive tape according to this embodiment comprises a substrate and a pressure-sensitive adhesive layer formed on the surface of the substrate. The pressure-sensitive adhesive layer may be formed on only one surface of the substrate, or on both surfaces.

The material of the substrate is not particularly limited, but examples include paper, plastic, cloth, metal, etc. The substrate may also be a film, woven fabric, or nonwoven fabric. Although not particularly limited, nonwoven fabric is preferred. This is because the adhesive composition penetrates into the substrate, increasing the bonding strength between the adhesive layer and the substrate.

The adhesive layer contains a cured product of the adhesive composition. In addition to the adhesive, the adhesive layer may also contain additives contained in the adhesive composition. As described below, in adhesive tapes produced by applying an adhesive composition to a substrate, the adhesive layer contains the non-volatile components of the adhesive composition. The thickness of the adhesive layer is preferably 10 μm or more, more preferably 30 μm or more, and even more preferably 50 μm or more. This is because the adhesive layer can be sufficiently deformed to conform to the surface of the adherend. The thickness of the adhesive layer is preferably 200 μm or less, and more preferably 100 μm or less. This is because cohesive failure of the adhesive layer is suppressed.

2-2. Method for manufacturing adhesive tape
A method for producing a pressure-sensitive adhesive tape includes the steps of applying a pressure-sensitive adhesive composition to one or both surfaces of a substrate and removing the aqueous medium from the pressure-sensitive adhesive composition applied to the substrate to form a pressure-sensitive adhesive layer. During application, an aqueous medium or a thickener may be added to the pressure-sensitive adhesive composition as appropriate to adjust the viscosity of the pressure-sensitive adhesive composition. When applying the pressure-sensitive adhesive composition to both surfaces, the application may be performed on each surface one by one, or on both surfaces at the same time. The pressure-sensitive adhesive composition may be applied to the substrate continuously or intermittently.

The amount of the adhesive composition to be applied is not particularly limited, but is preferably 10 to 500 g/ ^m2 . The drying temperature of the adhesive composition applied to the substrate is not particularly limited, but is preferably 20 to 160°C. This is because an adhesive layer having sufficient adhesive strength and cohesive strength can be obtained.

3. Uses of the pressure-sensitive adhesive composition and pressure-sensitive adhesive tape
Here, pressure-sensitive adhesive tape has been described as one preferred application of the pressure-sensitive adhesive composition of the present invention, but the application of the pressure-sensitive adhesive composition of the present invention is not limited thereto. For example, the pressure-sensitive adhesive composition of the present invention may be directly applied to a member and then bonded to another member without using a pressure-sensitive adhesive tape. Furthermore, applications of pressure-sensitive adhesive tape include, for example, electrical appliances, automobiles, building materials, toys, etc. The adherend of the pressure-sensitive adhesive tape is not particularly limited, but it is particularly useful when the adherend is a plastic member such as polypropylene, or a metal member such as SUS or aluminum.

The following describes examples and comparative examples of the present invention. However, the present invention is not limited to these examples.

<1. Preparation of Pressure-Sensitive Adhesive Composition>
In a polymerization reactor equipped with a stirrer, thermometer, and reflux condenser, 23 parts by mass of ion-exchanged water and 0.10 parts by mass of Aqualon KH-10 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as an emulsifier were mixed and heated to 80°C under a nitrogen atmosphere. The mixture in the polymerization reactor was maintained at 80°C while stirring, and 2 parts by mass of a 5.0% by mass aqueous potassium persulfate solution was added as a polymerization initiator. A monomer emulsion containing 50 parts by mass of ion-exchanged water, 1.0 part by mass of an emulsifier, and a total of 100 parts by mass of a monomer and a chain transfer agent was added dropwise over 4 hours to the mixture to which the polymerization initiator had been added. The types of monomer and chain transfer agent added dropwise are as shown in Tables 1, 2-1, and 2-2 for each Example and Comparative Example. The content of each component relative to a total of 100 parts by mass of the monomer and chain transfer agent added dropwise is shown in the left column of each Example and Comparative Example in Tables 1, 2-1, and 2-2. Simultaneously with the start of the dropwise addition of the monomer emulsion, 20 parts by mass of a 2.5% by mass aqueous solution of potassium persulfate was added dropwise over 4 hours.

After the dropwise addition was completed, the mixture was allowed to react at 80°C for 2 hours. The mixture in the polymerization reactor was then cooled to 25°C. Ammonia water was added as a neutralizing agent to adjust the pH to 8.5. Furthermore, 25 parts by mass of Superester E-865NT (manufactured by Arakawa Chemical Industries, Ltd.) as a tackifier and 2.0 parts by mass of Primal ASE-60 (manufactured by The Dow Chemical Company) as a thickener were added. Then, the type and amount of crosslinker (crosslinker (B) or other crosslinker) shown in the left column of Tables 1, 2-1, and 2-2 for each Example and Comparative Example was added to obtain a pressure-sensitive adhesive composition.

Tables 1, 2-1, and 2-2 also show the number of moles (mmol/100g) of carboxyl groups, epoxy groups, and hydroxyl groups per 100g of copolymer (A) in each example and comparative example. Tables 1 and 2 also show the number of moles (mmol/100g) of crosslinking agent functional groups (carbodiimide groups, epoxy groups, and isocyanato groups) contained in crosslinking agent (B) or aziridine groups contained in other crosslinking agents, per 100g of copolymer (A).

<2. Preparation of adhesive tape>
The pressure-sensitive adhesive composition obtained in each Example and Comparative Example was applied to the release surface of release paper (KP-8D manufactured by Hayashi Convertec Co., Ltd.). The applied pressure-sensitive adhesive composition was dried at 100°C for 3 minutes to remove the aqueous medium from the pressure-sensitive adhesive composition, and a 60 μm thick adhesive layer was formed on the release surface. The adhesive layer on the release surface was transferred to both sides of a nonwoven fabric (substrate: made of rayon) with a basis weight of 14 g/ ^m2 . The adhesive layer transferred onto the nonwoven fabric was aged at 40°C for 3 days to obtain an adhesive tape. Note that the release paper was not removed after transfer to avoid adhesion of foreign matter to the adhesive layer.

<3. Evaluation of adhesive tape>
The pressure-sensitive adhesive tapes produced in each of the Examples and Comparative Examples were evaluated as follows. The evaluation results are shown in Tables 1, 2-1, and 2-2. In the following explanation, the procedures in each of the Examples and Comparative Examples are common unless otherwise specified.

3-1. Evaluation 1: Measurement of initial adhesive strength
The release paper on one side of the adhesive tape was peeled off, and a 25 μm thick polyethylene terephthalate (PET) film was attached. This film was cut into a 25 mm × 250 mm piece. Furthermore, half of the release paper on the opposite side of the adhesive tape was peeled off in the longitudinal direction, cut, and attached to a polypropylene (PP) plate to prepare an evaluation sample. The attachment was performed by rolling a 2 kg roller back and forth once in an atmosphere of 23 °C × 50% RH. In the evaluation sample, the bonded portion between the adhesive tape and the polypropylene plate was a rectangle measuring 25 mm × 125 mm. Neither edge of the bonded portion overlapped the edge of the polypropylene plate. That is, in this state, one half of one longitudinal end of the adhesive tape was bonded to the polypropylene plate, and the other half was bonded to the release paper.

After preparing the evaluation sample, it was left in an atmosphere at 23°C for 30 minutes. The following measurements were then carried out in an atmosphere at 23°C.

The test was a so-called 180° peel test. The adhesive tape of the evaluation sample was folded back 180°, with the boundary between the part that was attached to the polypropylene plate and the part that wasn't, as the fold line. The end of the adhesive tape that wasn't attached to the polypropylene plate (the folded end) was gripped with the upper chuck of the testing machine. The end of the polypropylene plate facing the upper chuck, across the fold line, was gripped with the lower chuck.

In this state, the adhesive tape was peeled from the polypropylene plate at a speed of 200 mm/min, and a graph of peel length (mm) vs. peel force (N) was obtained. The average peel force (N) for peel lengths of 25 to 100 mm was calculated from the graph (the area of the graph for peel lengths of 25 to 100 mm divided by the peel length), and this value was taken as the initial adhesive strength (N/25 mm). In all of the Examples and Comparative Examples, neither peeling between the adhesive layer and the substrate nor cohesive failure of the adhesive layer occurred during the test.

3-2. Evaluation 2: Measurement of adhesive strength in a high-temperature environment
After preparing an evaluation sample using the same procedure as above, it was left in a thermostatic chamber at 70° C. for 30 minutes. Thereafter, a 180° peel test was performed using the same procedure as above in an atmosphere at 70° C., and the average peel strength (mN) at peel lengths of 25 to 100 mm was taken as the adhesive strength (N/25 mm) after high-temperature storage.

3-3. Evaluation 3: Measurement of high-temperature holding power
The release paper on one side of the double-sided adhesive tape was peeled off, and a 25 μm thick polyethylene terephthalate (PET) film was attached. The release paper was peeled off 25 mm from one end in the longitudinal direction on the other side of the adhesive tape, and a SUS plate (SUS #304) was attached to cover the entire area where the release paper had been peeled off, to prepare an evaluation sample. That is, in the evaluation sample, the area where the adhesive tape and the SUS plate were attached was a 25 mm x 25 mm square. The attachment was performed by moving a 2 kg roller back and forth once in an atmosphere of 23°C. In addition, at this time, the portion of the SUS plate where the adhesive tape was not attached, which was an extension of one end of the adhesive tape attached to the SUS plate, was provided as a SUS plate-side chuck portion.

The evaluation sample was left in an 80°C thermostatic chamber for 30 minutes. Then, in the 80°C thermostatic chamber, the evaluation sample's chuck portion on the SUS plate side was gripped with a chuck, and a 500g weight was hung from one end of the adhesive tape's longitudinal direction on the side not attached to the SUS plate. The sample was then left for 24 hours. The distance (mm) by which the adhesive tape shifted vertically relative to the SUS plate was then measured.

<4. Evaluation Results>
As shown in Table 1, the adhesive tapes produced using the adhesive compositions of the Examples exhibit strong adhesive strength not only at room temperature but also at high temperatures, and it can be seen that an adhesive layer is formed that has high holding power even at high temperatures.

On the other hand, the adhesive tapes of Comparative Examples 1 to 4 and Comparative Examples 6 to 9, which were produced using adhesive compositions in which the copolymer (A) did not contain epoxy groups, exhibited insufficient high-temperature adhesive strength or high-temperature holding power.

Of these, in Comparative Example 2, the amount of crosslinker functional groups in the adhesive composition was increased, but the high-temperature adhesive strength of the adhesive tape decreased. Furthermore, in Comparative Examples 3 and 4, a crosslinker (B) having an epoxy group as the crosslinker functional group was used, but the high-temperature holding power or high-temperature adhesive strength of the adhesive tape was insufficient. These findings demonstrate that in a configuration in which copolymer (A) does not contain epoxy groups, the object of the present invention cannot be achieved even if the amount of crosslinker functional groups contained in the adhesive composition is increased or the type of crosslinker functional groups is changed.

Furthermore, among the above comparative examples, the pressure-sensitive adhesive tapes of Comparative Example 7, which was internally crosslinked using a large amount of ethylene glycol dimethacrylate instead of epoxy groups, and Comparative Example 9, which was internally crosslinked using a large amount of divinylbenzene, exhibited insufficient initial adhesive strength. Furthermore, the pressure-sensitive adhesive tapes of Comparative Example 6, which was internally crosslinked using a small amount of ethylene glycol dimethacrylate instead of epoxy groups, and Comparative Example 8, which was internally crosslinked using a small amount of divinylbenzene, exhibited significantly inferior high-temperature holding power. These findings demonstrate that, in a configuration in which copolymer (A) does not contain epoxy groups, the object of the present invention cannot be achieved even if the particles of copolymer (A) are internally crosslinked using a compound having multiple independent ethylenically unsaturated bonds instead.

The adhesive tape of Comparative Example 5, which was produced using an adhesive composition that did not contain crosslinking agent (B), exhibited significantly inferior high-temperature holding power.

In Comparative Example 10, in which a crosslinking agent containing an aziridine group was used instead of crosslinking agent (B), the high-temperature adhesive strength and high-temperature holding power were insufficient.

As described above, the present invention can provide an aqueous dispersion PSA composition capable of forming a PSA layer that exhibits strong adhesive strength not only at room temperature but also at high temperatures, and that also has high holding power at high temperatures.Furthermore, the present invention can provide a PSA tape that exhibits strong adhesive strength not only at room temperature but also at high temperatures, and that also has high holding power at high temperatures.

Claims (13)

A pressure-sensitive adhesive composition comprising a copolymer (A), a crosslinking agent (B), and water ,
The copolymer (A) is a polymer of a compound having an ethylenically unsaturated bond and having a carboxy group and an epoxy group,
the crosslinking agent (B) contains, as a crosslinking agent functional group, one or more selected from the group consisting of a carbodiimide group derived from a carbodiimide compound, an epoxy group derived from a polyepoxy compound, and an isocyanato group derived from a polyisocyanate compound;
the amount of carboxy groups contained in 100 g of the copolymer (A) is 10 mmol/100 g or more and 100 mmol/100 g or less,
the amount of epoxy groups contained in 100 g of the copolymer (A) is 0.30 mmol/100 g or more and 30 mmol/100 g or less;
the content of the crosslinking functional groups in the crosslinking agent (B) relative to 1 mol of carboxy groups in the copolymer (A) is 0.10×10 ⁻² mol or more and 30×10 ⁻² mol or less;
The nonvolatile content is 20% by mass or more and 75% by mass or less,
a total content of the copolymer (A) and the crosslinking agent (B) in the nonvolatile matter of the pressure-sensitive adhesive composition of 50% by mass or more and 90% by mass or less. The pressure-sensitive adhesive composition according to claim 1, wherein the copolymer (A) has hydroxy groups, and the amount of hydroxy groups contained per 100 g of the copolymer (A) is 0.50 mmol/100 g or more and 15 mmol/100 g or less. The pressure-sensitive adhesive composition according to claim 2 , wherein the main chain of the copolymer (A) is formed by bonds between carbon atoms. 4. The pressure-sensitive adhesive composition according to claim 2, wherein a portion of the copolymer (A) other than the carboxy group, the epoxy group, and the hydroxy group and other than the terminals comprises one or more structures selected from the group consisting of a hydrocarbon structure, an ester bond, and a carbonyl group. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the content of epoxy groups in the copolymer (A) relative to 1 mol of carboxy groups in the copolymer (A) is 0.60 × 10 ^-2 mol or more and 60 × 10 ^-2 mol or less. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the content of the crosslinking agent functional groups in the crosslinking agent (B) per 1 mol of epoxy groups in the copolymer (A) is 0.040 mol or more and 1.5 mol or less. The pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the crosslinking agent (B) is a polycarbodiimide compound. The pressure-sensitive adhesive composition according to claim 7, wherein the carbodiimide equivalent of the crosslinking agent (B) is 150 or more and 1,000 or less. The pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the crosslinking agent (B) is a polyepoxy compound. The pressure-sensitive adhesive composition according to claim 9, wherein the crosslinking agent (B) has an epoxy equivalent of 70 or more and 700 or less. The pressure-sensitive adhesive composition according to any one of claims 1 to 10, wherein the amount of crosslinking functional groups possessed by the crosslinking agent (B) relative to 100 g of the copolymer (A) is 0.20 mmol/100 g or more. An adhesive tape comprising a substrate and an adhesive layer formed on the surface of the substrate,
An adhesive tape, wherein the adhesive layer comprises a cured product of the adhesive composition according to any one of claims 1 to 11. A step of applying the pressure-sensitive adhesive composition according to any one of claims 1 to 11 to a substrate;
and removing water from the pressure-sensitive adhesive composition applied to the substrate to form a pressure-sensitive adhesive layer.