Adhesive composition and adhesive sheet

Abstract

An adhesive composition containing a crystalline polyester resin (A) having a crystal melting enthalpy of 5-55 mJ / mg and a tackifier resin (B) having a hydroxyl value of 1 mgKOH / g or more.

Description

Pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet

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

[0002] Pressure-sensitive adhesive sheets having a pressure-sensitive adhesive layer are used in various technical fields. For example, pressure-sensitive adhesive sheets having a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing a polyester resin are known (see, for example, Patent Document 1).

[0003] Patent No. 7299428

[0004] As a polyester resin that exhibits adhesive properties, a polyester resin having a low glass transition temperature (Tg) and being amorphous is usually used. However, such polyester resins are prone to blocking with each other during storage, which causes problems in handling. Therefore, in a pressure-sensitive adhesive composition containing a polyester resin, it is desirable to use a polyester resin having excellent blocking resistance as a raw material component from the viewpoint of its manufacturability.

[0005] An object of the present disclosure is to provide a polyester-based pressure-sensitive adhesive composition that can form a pressure-sensitive adhesive layer having excellent adhesive properties and that has excellent manufacturability.

[0006] One embodiment of the pressure-sensitive adhesive composition of the present disclosure contains a crystalline polyester resin (A) having a heat of crystalline fusion of 5 to 55 mJ / mg and a tackifier resin (B) having a hydroxyl value of 1 mgKOH / g or more.

[0007] The pressure-sensitive adhesive composition of the present disclosure can form a pressure-sensitive adhesive layer with excellent adhesive properties. The pressure-sensitive adhesive composition of the present disclosure also has excellent manufacturability because blocking between polyester resins, which are raw material components, is suppressed.

[0008] Generally, the terms "sheet," "film," and "tape" are sometimes used to distinguish between them based on thickness, etc., but in this specification, these terms are used without any particular distinction. In this specification, "adherend" means an object to which the PSA sheet is attached.

[0009] Each of the components described in this specification may be used alone or in combination of two or more.

[0010] In this specification, the numerical range n1 to n2 means n1 or more and n2 or less if n1<n2, and n1>n2 means n2 or more and n1 or less if n1>n2. In this specification, when multiple lower limit values ​​and multiple upper limit values ​​are given in the description of a certain element, a numerical range formed by combining a value arbitrarily selected from the given lower limit value and a value arbitrarily selected from the given upper limit value is also considered to be given.

[0011] [Adhesive Composition] The adhesive composition of the present disclosure contains a crystalline polyester resin (hereinafter also referred to as "crystalline polyester resin (A)") described below and a tackifier resin (hereinafter also referred to as "tackifier resin (B)") described below.

[0012] <Crystalline polyester resin (A)> The crystalline polyester resin (A) is, for example, a polycondensate of a monomer mixture containing a polycarboxylic acid component and a polyol component. The crystalline polyester resin (A) can be obtained, for example, by polycondensing the monomer mixture.

[0013] Examples of the polycarboxylic acid component include dicarboxylic acid components and trivalent or higher polycarboxylic acid components, among which dicarboxylic acid components are preferred. Examples of the polyol component include diol components and trivalent or higher polyhydric alcohols, among which diol components are preferred.

[0014] In this specification, the term "polycarboxylic acid component" is used to mean either a polycarboxylic acid or a polycarboxylic acid derivative. Examples of polycarboxylic acid derivatives include polycarboxylic acid esters such as polycarboxylic acid alkyl esters, polycarboxylic acid anhydrides, polycarboxylic acid salts such as sodium salts and potassium salts, and polycarboxylic acid halides such as polycarboxylic acid chlorides. The number of carbon atoms in the alkyl group in the polycarboxylic acid alkyl esters is preferably 1 to 15, more preferably 1 to 10, and even more preferably 1 to 5.

[0015] The crystalline polyester resin (A) has a structural unit derived from a polycarboxylic acid component and a structural unit derived from a polyol component, and preferably has a structural unit derived from a dicarboxylic acid component and a structural unit derived from a diol component.

[0016] The crystalline polyester resin (A) has, for example, one or more types of structural units derived from a dicarboxylic acid component. In producing the crystalline polyester resin (A), one or more types of dicarboxylic acid components may be used.

[0017] The dicarboxylic acid component may be a component obtained using a raw material derived from a fossil fuel, or may be a biomass component obtained using a raw material derived from biomass. The dicarboxylic acid component may be a biomass component from the viewpoint of carbon neutrality or reduction of environmental load.

[0018] As used herein, the term "dicarboxylic acid component" refers to both a dicarboxylic acid and a dicarboxylic acid derivative. Examples of dicarboxylic acid derivatives include dicarboxylic acid esters such as dicarboxylic acid alkyl esters, dicarboxylic acid anhydrides, dicarboxylic acid salts such as sodium salts and potassium salts, and dicarboxylic acid halides such as dicarboxylic acid chlorides. The number of carbon atoms in the alkyl group in the dicarboxylic acid alkyl ester is preferably 1 to 15, more preferably 1 to 10, and even more preferably 1 to 5. The dicarboxylic acid ester may be a dicarboxylic acid monoester or a dicarboxylic acid diester. The dicarboxylic acid alkyl ester may be a dicarboxylic acid monoalkyl ester or a dialkyl diester. The dicarboxylic acid salt may be a dicarboxylic acid monosalt or disalt. The dicarboxylic acid halide may be a dicarboxylic acid mono- or dihalide.

[0019] Specific examples of the dicarboxylic acid derivative include dimethyl dicarboxylate, diethyl dicarboxylate, dipropyl dicarboxylate, dibutyl dicarboxylate, dihexyl dicarboxylate, dioctyl dicarboxylate, and dicarboxylic acid dichloride.

[0020] Examples of the dicarboxylic acid component include an aliphatic dicarboxylic acid component (aliphatic dicarboxylic acid and / or derivative thereof), an alicyclic dicarboxylic acid component (alicyclic dicarboxylic acid and / or derivative thereof), and an aromatic dicarboxylic acid component (aromatic dicarboxylic acid and / or derivative thereof).

[0021] Examples of aliphatic dicarboxylic acids include malonic acid, succinic acid, glutaric acid, 3,3-dimethylglutaric acid, adipic acid, 2,2,4-trimethyladipic acid, pimelic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, diglycolic acid, 1,9-nonanedicarboxylic acid, and dimer acid. Dimer acid is a dibasic acid containing, as its main component, a dicarboxylic acid obtained by dimerization of an unsaturated fatty acid having 10 to 26 carbon atoms, preferably 12 to 24 carbon atoms, more preferably 14 to 22 carbon atoms, and even more preferably 18 carbon atoms. The unsaturated bond contained in the dicarboxylic acid may be hydrogenated. Examples of such unsaturated fatty acids include oleic acid, linoleic acid, linolenic acid, and erucic acid. The term "main component" refers to a component that accounts for 90% by mass or more, preferably 95% by mass or more, and more preferably 98% by mass or more of the total.

[0022] Examples of alicyclic dicarboxylic acids include 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, and adamantanedicarboxylic acid.

[0023] Examples of aromatic dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, benzylmalonic acid, diphenic acid, 4,4'-oxydibenzoic acid, naphthalenedicarboxylic acids (e.g., 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid), furandicarboxylic acid, and sulfonate-containing aromatic dicarboxylic acids.

[0024] The crystalline polyester resin (A) preferably has one or more structural units derived from an aromatic dicarboxylic acid component. The polycarboxylic acid component used in producing the crystalline polyester resin (A) preferably contains one or more aromatic dicarboxylic acid components. A pressure-sensitive adhesive composition containing such a crystalline polyester resin tends to be able to form a pressure-sensitive adhesive layer having high cohesive strength and excellent holding power, as described below.

[0025] In the crystalline polyester resin (A), the content of the structural units derived from the aromatic dicarboxylic acid component in 100 mol% of the structural units derived from the polycarboxylic acid component is preferably 10 to 80 mol%, more preferably 15 to 70 mol%, even more preferably 20 to 60 mol% or 25 to 52 mol%, still more preferably 25 to 50 mol%, particularly preferably 25 mol% or more but less than 50 mol%, or 25 mol% or more and 48 mol% or less. A pressure-sensitive adhesive composition containing such a crystalline polyester resin tends to be able to form a pressure-sensitive adhesive layer excellent in cohesion, holding power, and adhesive strength.

[0026] In the above-mentioned monomer mixture, the proportion of the aromatic dicarboxylic acid component in 100 mol% of the polycarboxylic acid component is preferably 10 to 80 mol%, more preferably 15 to 70 mol%, even more preferably 20 to 60 mol% or 25 to 52 mol%, still more preferably 25 to 50 mol%, and particularly preferably 25 mol% or more but less than 50 mol%, or 25 mol% or more but 48 mol% or less.

[0027] In the crystalline polyester resin (A), the total content of the structural units derived from an aliphatic dicarboxylic acid component and the structural units derived from an alicyclic dicarboxylic acid component, relative to 100 mol% of the structural units derived from a polycarboxylic acid component, is preferably 20 to 90 mol%, more preferably 30 to 85 mol%, even more preferably 40 to 80 mol% or 48 to 75 mol%, still more preferably 50 to 75 mol%, and particularly preferably more than 50 mol% but not more than 75 mol%, or 52 mol% or more but not more than 75 mol%.

[0028] In the above-mentioned monomer mixture, the total proportion of the aliphatic dicarboxylic acid component and the alicyclic dicarboxylic acid component in 100 mol% of the polycarboxylic acid component is preferably 20 to 90 mol%, more preferably 30 to 85 mol%, even more preferably 40 to 80 mol% or 48 to 75 mol%, still more preferably 50 to 75 mol%, and particularly preferably more than 50 mol% but not more than 75 mol%, or 52 mol% or more but not more than 75 mol%.

[0029] In this specification, the content ratio of the constituent units derived from each component (raw material monomer) in the crystalline polyester resin (A) is measured by nuclear magnetic resonance spectroscopy (NMR method), and details of the measurement conditions are described in the Examples section.

[0030] The crystalline polyester resin (A) may have one or more structural units derived from a sulfonate-containing dicarboxylic acid component. The polycarboxylic acid component used in the production of the crystalline polyester resin (A) preferably contains one or more sulfonate-containing dicarboxylic acid components. Such a crystalline polyester resin has high cohesive strength, and a pressure-sensitive adhesive composition containing the crystalline polyester resin tends to be able to form a pressure-sensitive adhesive layer having even more excellent holding power, as described below.

[0031] Examples of sulfonate-containing dicarboxylic acid components include sulfonate-containing dicarboxylic acids and their derivatives, such as mono- or diesters of dicarboxylic acids, carboxylic acid anhydrides, mono- or di-salts of dicarboxylic acids, and mono- or dihalides of dicarboxylic acids.

[0032] The sulfonate-containing dicarboxylic acid has two carboxy groups and a sulfonate (sulfonate group) in the molecule. Examples of the sulfonate group include metal salts, ammonium salts, and organic amine salts of the sulfonic acid group (—SO3H). Examples of metal atoms that form the metal salt include monovalent metal atoms such as alkali metal atoms such as lithium, sodium, and potassium; and divalent metal atoms such as calcium and magnesium. Examples of organic amine salts include alkanolamine salts such as ethanolamine salts, diethanolamine salts, and triethanolamine salts; and triethylamine salts. Examples of the sulfonate group include sodium sulfonate groups, potassium sulfonate groups, magnesium sulfonate groups, calcium sulfonate groups, and ammonium sulfonate groups, with sodium sulfonate groups being particularly preferred.

[0033] The sulfonate-containing dicarboxylic acid component is preferably a sulfonate-containing aromatic dicarboxylic acid component, more preferably an aromatic dicarboxylic acid component having a sulfonate group bonded to a benzene ring, and even more preferably a compound in which one hydrogen atom bonded to the benzene ring of phthalic acid, isophthalic acid, terephthalic acid, or a derivative thereof has been substituted with a sulfonate group.

[0034] Examples of sulfonate-containing dicarboxylic acid components include sodium 5-sulfoisophthalate, sodium dimethyl 5-sulfoisophthalate, potassium dimethyl 5-sulfoisophthalate, sodium 4-sulfoisophthalate, sodium dimethyl 4-sulfoisophthalate, potassium dimethyl 4-sulfoisophthalate, sodium 2-sulfoterephthalate, potassium 2-sulfoterephthalate, sodium dimethyl 2-sulfoterephthalate, and potassium dimethyl 2-sulfoterephthalate. Of these, sodium dimethyl 5-sulfoisophthalate is preferred.

[0035] In the crystalline polyester resin (A), the content of the structural units derived from the sulfonate-containing dicarboxylic acid component is preferably 1 to 10 mol%, more preferably 2 to 8 mol%, and even more preferably 3 to 7 mol% relative to 100 mol% of the structural units derived from the polycarboxylic acid component. In the monomer mixture, the content of the structural units derived from the sulfonate-containing dicarboxylic acid component is preferably 1 to 10 mol%, more preferably 2 to 8 mol%, and even more preferably 3 to 7 mol% relative to 100 mol% of the polycarboxylic acid component.

[0036] The crystalline polyester resin (A) may further have a structural unit derived from a trivalent or higher polycarboxylic acid component. As a raw material monomer for the crystalline polyester resin (A), a trivalent or higher polycarboxylic acid component may be further used together with the dicarboxylic acid component. Examples of the trivalent or higher polycarboxylic acid component include trivalent or higher polycarboxylic acids and derivatives thereof. Examples of the trivalent or higher polycarboxylic acid component include trimellitic acid, pyromellitic acid, adamantanetricarboxylic acid, and trimesic acid. By using a trivalent or higher polycarboxylic acid component, for example, a crystalline polyester resin (A) having a branching point can be produced.

[0037] In the crystalline polyester resin (A), the content of the structural units derived from the trivalent or higher polycarboxylic acid component is preferably 20 mol or less, more preferably 10 mol or less, even more preferably 5 mol or less, and particularly preferably 1 mol or less, per 100 mol of the structural units derived from the dicarboxylic acid component, from the viewpoint of the productivity of the crystalline polyester resin (A). In the above-mentioned monomer mixture, the amount of the trivalent or higher polycarboxylic acid component is preferably 20 mol or less, more preferably 10 mol or less, even more preferably 5 mol or less, and particularly preferably 1 mol or less, per 100 mol of the dicarboxylic acid component, from the viewpoint of the productivity of the crystalline polyester resin (A).

[0038] In one embodiment, the polycarboxylic acid component is not a dimer acid component.

[0039] The crystalline polyester resin (A) has, for example, one or more types of structural units derived from a diol component. In producing the crystalline polyester resin (A), one or more types of diol components may be used.

[0040] The diol component may be a component obtained using a raw material derived from a fossil fuel, or may be a biomass component obtained using a raw material derived from biomass. The diol component may be a biomass component from the viewpoint of carbon neutrality or reduction of environmental load.

[0041] The diol component has two hydroxy groups. Examples of the diol component include an aliphatic diol component, an alicyclic diol component, and an aromatic diol component. Other examples of the diol component include a fatty acid ester derived from castor oil, a dimer diol derived from oleic acid or erucic acid, and glycerol monostearate.

[0042] Examples of the aliphatic diol component include linear diols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, nonanediol, decanediol, dodecanediol, diethylene glycol, and triethylene glycol; propylene glycol, dipropylene glycol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, and 2-methyl-2-propyl-1,3-propanediol; Branched diols such as 2-ethyl-2-butyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,3,5-trimethyl-1,3-pentanediol, 2-methyl-1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, and 2,4-dimethyl-2-ethyl-1,3-hexanediol; and ethylene oxide or propylene oxide adducts of these diols.

[0043] Examples of the alicyclic diol component include 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecane dimethanol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; and ethylene oxide or propylene oxide adducts of these diols.

[0044] Examples of the aromatic diol component include dihydroxybenzene, naphthalenediol, xylenediol, 4,4'-methylenediphenol, and 4,4'-dihydroxybiphenyl; and ethylene oxide or propylene oxide adducts of these diols.

[0045] Among the diol components, from the viewpoints of the reactivity of the raw material monomers in the production of the crystalline polyester resin (A) and ease of crystallization, an aliphatic diol component is preferred, an aliphatic diol component having 2 to 20 carbon atoms is more preferred, and an aliphatic diol component having 2 to 10 carbon atoms is even more preferred.

[0046] In the crystalline polyester resin (A), the content of the structural units derived from the aliphatic diol component in 100 mol % of the structural units derived from the polyol component is preferably 50 mol % or more, more preferably 60 mol % or more, even more preferably 70 mol % or more, still more preferably 80 mol % or more, and particularly preferably 90 mol % or more, from the viewpoint of the manufacturability of the crystalline polyester resin (A).

[0047] In the above-mentioned monomer mixture, the proportion of the aliphatic diol component in 100 mol% of the polyol component is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, still more preferably 80 mol% or more, and particularly preferably 90 mol% or more, from the viewpoint of the productivity of the crystalline polyester resin (A).

[0048] The crystalline polyester resin (A) may have one or more structural units derived from a trihydric or higher polyhydric alcohol. A trihydric or higher polyhydric alcohol may be further used as a raw material monomer for the crystalline polyester resin (A) together with the diol component. The trihydric or higher polyhydric alcohol has three or more hydroxy groups. Examples of trihydric or higher polyhydric alcohols include pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,3,6-hexanetriol, and adamantanetriol.

[0049] In the crystalline polyester resin (A), the content of the constituent units derived from a trihydric or higher polyhydric alcohol is preferably 20 mol or less, more preferably 10 mol or less, even more preferably 5 mol or less, and particularly preferably 1 mol or less, per 100 mol of the constituent units derived from the diol component, from the viewpoint of the productivity of the crystalline polyester resin (A). In the above-mentioned monomer mixture, the amount of the trihydric or higher polyhydric alcohol is preferably 20 mol or less, more preferably 10 mol or less, even more preferably 5 mol or less, and particularly preferably 1 mol or less, per 100 mol of the diol component, from the viewpoint of the productivity of the crystalline polyester resin (A).

[0050] From the viewpoint of better exerting the effects described above and from the viewpoint of physical properties such as crystallinity described below, the crystalline polyester resin (A) preferably has structural units derived from an aromatic dicarboxylic acid component, structural units derived from an aliphatic dicarboxylic acid component and / or structural units derived from an alicyclic dicarboxylic acid component, and structural units derived from an aliphatic diol component, and more preferably consists of structural units derived from an aromatic dicarboxylic acid component, structural units derived from an aliphatic dicarboxylic acid component and / or structural units derived from an alicyclic dicarboxylic acid component, and structural units derived from an aliphatic diol component.

[0051] The crystalline polyester resin (A) is preferably a polycondensate of a monomer mixture containing an aromatic dicarboxylic acid component, an aliphatic dicarboxylic acid component and / or an alicyclic dicarboxylic acid component, and an aliphatic diol component, and more preferably a polycondensate of a monomer mixture consisting of an aromatic dicarboxylic acid component, an aliphatic dicarboxylic acid component and / or an alicyclic dicarboxylic acid component, and an aliphatic diol component.

[0052] The pressure-sensitive adhesive composition may contain one type of crystalline polyester resin (A) or two or more types thereof.

[0053] The content of the crystalline polyester resin (A) in the solid content of the PSA composition is preferably 30% by mass or more, more preferably 35 to 95% by mass, even more preferably 40 to 90% by mass, still more preferably 45 to 90% by mass, and particularly preferably 50 to 90% by mass. In this specification, the term "solid content" refers to all components other than the solvent and the dispersion medium.

[0054] Physical Properties of Crystalline Polyester Resin (A) In this specification, "crystalline polyester resin" refers to a polyester resin in which a crystalline melting peak is observed in a DSC curve obtained by differential scanning calorimetry (DSC), and "amorphous polyester resin" refers to a polyester resin in which a crystalline melting peak is not observed. "A crystalline melting peak is observed" means that a peak with a crystalline melting heat of 0.1 mJ / mg or more is observed. The crystallinity or amorphousness of the polyester resin can be adjusted, for example, by the type of raw material monomer and the content of each constituent unit.

[0055] Crystalline polyester resins tend to be less susceptible to blocking than amorphous polyester resins. Therefore, crystalline polyester resin (A) has excellent handleability, and the pressure-sensitive adhesive composition of the present disclosure obtained using the resin (A) has excellent manufacturability. For example, in the case of crystalline polyester resins, it is not necessarily necessary to incorporate a blocking inhibitor (e.g., talc) into the polyester resin or to store the polyester resin in small quantities to inhibit blocking of the polyester resin. For example, it is not necessarily necessary to provide a step for removing the blocking inhibitor from the polyester resin when using the polyester resin, and it is also not necessarily necessary to use a large amount of resources for storing the polyester resin in small quantities. However, the scope of the present disclosure does not exclude the incorporation and removal of such blocking inhibitors or the storage of the polyester resin in small quantities. In the present disclosure, the incorporation and removal of the blocking inhibitor or the storage of the polyester resin in small quantities may be performed.

[0056] The heat of crystalline fusion of the crystalline polyester resin (A) is preferably 5 mJ / mg or more, more preferably 7 mJ / mg or more, even more preferably 9 mJ / mg or more, even more preferably 11 mJ / mg or more, particularly preferably 12 mJ / mg or more, and preferably 55 mJ / mg or less, more preferably 50 mJ / mg or less, even more preferably 45 mJ / mg or less, even more preferably 40 mJ / mg or less, particularly preferably 35 mJ / mg or less. The heat of crystalline fusion is preferably 5 to 55 mJ / mg, more preferably 7 to 50 mJ / mg, even more preferably 9 to 45 mJ / mg, even more preferably 11 to 40 mJ / mg, particularly preferably 12 to 35 mJ / mg.

[0057] A pressure-sensitive adhesive composition containing a crystalline polyester resin (A) having a heat of crystalline fusion equal to or less than the upper limit and a tackifier resin (B) having a hydroxyl value (described later) can form a pressure-sensitive adhesive layer with excellent adhesive properties (e.g., adhesive strength and / or holding power). The reason for this is unclear, but the inventors speculate as follows: A resin (A) having a heat of crystalline fusion equal to or less than the upper limit has moderate crystallinity. As described later, the presence of the tackifier resin (B) is thought to moderately suppress the crystallization of the resin (A) while maintaining cohesive strength. This allows the resin (A) to exhibit good adhesive properties. In the case of a polyester resin having a heat of crystalline fusion significantly exceeding the upper limit, the presence of the tackifier resin (B) cannot adequately suppress the crystallization of the resin (A), and the resin tends not to exhibit good adhesive properties.

[0058] The melting point (Tm) of the crystalline polyester resin (A) is preferably 25° C. or higher, more preferably 30° C. or higher, and even more preferably 35° C. or higher, and from the viewpoint of achieving better holding power of the pressure-sensitive adhesive layer to be formed, may be, for example, 50° C. or higher, 60° C. or higher, or 70° C. or higher. A pressure-sensitive adhesive composition containing a crystalline polyester resin (A) having a Tm of at least the above lower limit tends to be able to form a pressure-sensitive adhesive layer having excellent holding power.

[0059] The melting point (Tm) of the crystalline polyester resin (A) is preferably 200° C. or lower, more preferably 180° C. or lower, even more preferably 160° C. or lower, still more preferably 140° C. or lower, and particularly preferably 120° C. or lower, and from the viewpoint of achieving better adhesive strength of the pressure-sensitive adhesive layer to be formed, may be, for example, 100° C. or lower, 80° C. or lower, or 60° C. or lower. A pressure-sensitive adhesive composition containing a crystalline polyester resin (A) having a Tm of the above upper limit or lower tends to be able to form a pressure-sensitive adhesive layer having excellent adhesive strength.

[0060] The melting point (Tm) of the crystalline polyester resin (A) is preferably 25 to 200° C., more preferably 30 to 180° C., even more preferably 30 to 160° C., still more preferably 30 to 140° C., and particularly preferably 35 to 120° C. The melting point (Tm) may be, for example, 50 to 120° C., 60 to 120° C., or 70 to 120° C. from the viewpoint of achieving better holding power of the pressure-sensitive adhesive layer, or may be, for example, 30 to 100° C., 30 to 80° C., or 30 to 60° C. from the viewpoint of achieving better adhesive power of the pressure-sensitive adhesive layer.

[0061] Differential scanning calorimetry (DSC) for measuring Tm and heat of fusion of crystals is performed in accordance with the method described in JIS K7121:2012 and JIS K7122:2024 (power compensation DSC). Tm is the melting peak temperature (the temperature at the top of the melting peak). In JIS K7121:2012, the heating rate of 8.6(1) is 5°C / min, and the measurement is performed under nitrogen gas flow. Details of the measurement conditions are described in the Examples section.

[0062] When the resin (A) exhibits multiple crystalline melting peaks in DSC, the melting point of the resin (A) refers to the melting peak temperature of the peak located on the highest temperature side, and the heat of crystalline fusion of the resin (A) refers to the sum of the heats of fusion of the observed crystalline melting peaks.

[0063] The Tm and heat of crystalline fusion of the crystalline polyester resin (A) can be adjusted, for example, by the type of raw material monomer and the content of each constituent unit.

[0064] The glass transition temperature (Tg) of the crystalline polyester resin (A) is preferably 0°C or lower, more preferably -60 to -5°C, even more preferably -55 to -10°C, still more preferably -50 to -20°C, and particularly preferably -45 to -30°C. A pressure-sensitive adhesive composition containing a crystalline polyester resin (A) having such a Tg tends to be able to form a pressure-sensitive adhesive layer that is excellent in adhesive properties and flexibility. The Tg of the crystalline polyester resin (A) can be adjusted, for example, by the type of raw material monomer and the content of each constituent unit.

[0065] Tg is obtained by differential scanning calorimetry (DSC). Differential scanning calorimetry of Tg is performed in accordance with the method described in JIS K7121:2012 (power compensation DSC). Tg is the midpoint glass transition temperature. In JIS K7121:2012, the heating rate of 8.6(3) is 5°C / min, and the measurement is performed under a nitrogen gas flow. Details of the measurement conditions are described in the Examples section.

[0066] The weight average molecular weight (Mw) of the crystalline polyester resin (A) is preferably 5,000 to 200,000, more preferably 10,000 to 150,000, even more preferably 20,000 to 100,000, and particularly preferably 30,000 to 70,000. The Mw may be, for example, less than 100,000. A crystalline polyester resin (A) having an Mw equal to or greater than the lower limit tends to exhibit excellent cohesive strength as a pressure-sensitive adhesive, and to exhibit excellent heat resistance and mechanical strength. A crystalline polyester resin (A) having an Mw equal to or less than the upper limit tends to suppress gelation during its production.

[0067] The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the crystalline polyester resin (A) is preferably 1.0 to 10.0, more preferably 1.3 to 8.0, and even more preferably 1.5 to 6.0.

[0068] Mw and Mn are values ​​calculated in terms of polystyrene as determined by gel permeation chromatography (GPC), and the details of the measurement conditions are described in the Examples section.

[0069] The acid value of the crystalline polyester resin (A) is preferably 10 mgKOH / g or less, more preferably 3 mgKOH / g or less, and even more preferably 1 mgKOH / g or less. Crystalline polyester resins (A) having an acid value of the upper limit or less tend to be less prone to hydrolysis. The acid value is a value determined by a method in accordance with JIS K 0070:1992 (neutralization titration method).

[0070] <<Production of Crystalline Polyester Resin (A)>> The crystalline polyester resin (A) can be produced, for example, by polycondensation of a polycarboxylic acid component and a polyol component, optionally in the presence of a catalyst, by a known method. In one embodiment, the esterification reaction is carried out, followed by the polycondensation reaction.

[0071] The blending ratio of the polycarboxylic acid component and the polyol component in the production of the crystalline polyester resin (A) is preferably 1 to 3 mol, more preferably 1.1 to 2.5 mol, of the polyol component per 1 mol of the polycarboxylic acid component.

[0072] The compounding ratio of the dicarboxylic acid component and the diol component in the production of the crystalline polyester resin (A) is preferably 1 to 3 mol, more preferably 1.1 to 2.5 mol, of the diol component per 1 mol of the dicarboxylic acid component.

[0073] A catalyst may be used in the esterification reaction. Examples of the catalyst include titanium-based catalysts such as titanium tetraisopropoxide and titanium tetrabutoxide; antimony-based catalysts such as antimony trioxide; germanium-based catalysts such as germanium dioxide; and catalysts such as zinc acetate, manganese acetate, and dibutyltin oxide. One type of catalyst may be used, or two or more types may be used. The amount of catalyst used is preferably 1.0 × 10 relative to 1 mol of the total of the raw material monomers contained in the monomer mixture. -7 ~1.0 x 10 -3 mol, more preferably 5.0 × 10 -7 ~0.5 x 10 -3 mol, more preferably 1.0 × 10 -6 ~1.0 x 10 -4 mol.

[0074] The reaction temperature in the esterification reaction is preferably 150 to 280°C, more preferably 160 to 260°C, and even more preferably 170 to 240°C.

[0075] A catalyst may be used in the polycondensation reaction. Examples of the catalyst include the catalysts exemplified in the explanation of the esterification reaction. The reaction temperature in the polycondensation reaction is preferably 200 to 300°C, more preferably 220 to 280°C. In the polycondensation reaction, the pressure of the reaction system may be gradually reduced, and the reaction may be finally carried out at 500 Pa or less.

[0076] <Tackifying resin (B)> Examples of the tackifying resin (B) include rosin-based resins, terpene-based resins, coumarone-based resins, petroleum resins, phenolic resins, and xylene resins. Among these, at least one selected from the group consisting of rosin-based resins, terpene-based resins, and coumarone-based resins is preferred.

[0077] Examples of rosin-based resins include rosin, polymerized rosin, hydrogenated rosin, disproportionated rosin, rosin ester, rosin-containing diol, acid-modified rosin (e.g., maleic acid-modified rosin, fumaric acid-modified rosin), rosin phenolic resin, and natural rosin.

[0078] Examples of terpene resins include α-pinene resins, β-pinene resins, dipentene resins, terpene phenol resins (e.g., terpene-phenol copolymers, phenol-modified terpene resins), acid-modified terpene resins, and aromatic-modified terpene resins, as well as resins obtained by hydrogenating these resins (e.g., hydrogenated terpene phenol resins).

[0079] Examples of coumarone resins include coumarone resins and coumarone-indene resins, and examples of coumarone-indene resins include coumarone-indene-styrene copolymers.

[0080] Examples of petroleum resins include aliphatic petroleum resins, alicyclic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, and hydrogenated petroleum resins. Examples of copolymerized petroleum resins include aromatic-aliphatic copolymerized petroleum resins such as copolymers of styrene monomers and aliphatic monomers.

[0081] The hydroxyl value of the tackifier resin (B) is preferably 1 mgKOH / g or more, more preferably 5 mgKOH / g or more, even more preferably 10 mgKOH / g or more, even more preferably 15 mgKOH / g or more, particularly preferably 20 mgKOH / g or more, and preferably 300 mgKOH / g or less, more preferably 250 mgKOH / g or less, even more preferably 200 mgKOH / g or less, even more preferably 170 mgKOH / g or less, particularly preferably 140 mgKOH / g or less. The hydroxyl value of the tackifier resin (B) is preferably 1 to 300 mgKOH / g, more preferably 5 to 250 mgKOH / g, even more preferably 10 to 200 mgKOH / g, even more preferably 15 to 170 mgKOH / g, particularly preferably 20 to 140 mgKOH / g. A tackifier resin (B) having a hydroxyl value equal to or greater than the above lower limit can be well mixed with the crystalline polyester resin (A). The hydroxyl value of the tackifier resin (B) is measured in accordance with the neutralization titration method described in JIS K0070:1992.

[0082] By using a pressure-sensitive adhesive composition containing the above-mentioned crystalline polyester resin (A) and tackifier resin (B), a pressure-sensitive adhesive layer with excellent adhesive properties can be formed. The reason for this is unclear, but the inventors speculate as follows: The tackifier resin (B) having the above hydroxyl value can be well mixed with the resin (A). It is believed that the presence of such a tackifier resin (B) ensures that the resin (A) has cohesive strength while adequately suppressing crystallization of the resin (A). This allows the resin (A) to exhibit good adhesive strength.

[0083] The form of the tackifier resin (B) at room temperature (23° C.) may be solid or liquid. Among these, from the viewpoint of being able to form a pressure-sensitive adhesive layer having more excellent adhesive properties, the form is preferably solid.

[0084] The softening point of the tackifier resin (B) is preferably 180°C or lower, more preferably 160°C or lower, even more preferably 140°C or lower, even more preferably 120°C or lower, particularly preferably 100°C or lower, and preferably 50°C or higher, more preferably 60°C or higher, even more preferably 70°C or higher, and particularly preferably 80°C or higher. The softening point of the tackifier resin (B) is preferably 50 to 180°C, more preferably 60 to 160°C, even more preferably 70 to 140°C, even more preferably 80 to 120°C, and particularly preferably 80 to 100°C. A tackifier resin (B) having the above softening point has excellent adhesive strength. The softening point of the tackifier resin (B) is measured in accordance with the ring and ball method described in JIS K2207:2006.

[0085] The pressure-sensitive adhesive composition may contain one or more tackifying resins (B).

[0086] The content of the tackifier resin (B) in the PSA composition is preferably 5 to 200 parts by mass, more preferably 10 to 175 parts by mass, even more preferably 10 to 150 parts by mass, even more preferably 10 to 125 parts by mass, and particularly preferably 10 to 100 parts by mass, per 100 parts by mass of the crystalline polyester resin (A). When the content of the tackifier resin (B) is equal to or less than the above-mentioned upper limit, the cohesive force of the resin (A) is well maintained, and a PSA layer with excellent adhesive strength and holding power tends to be formed. When the content of the tackifier resin (B) is equal to or greater than the above-mentioned lower limit, crystallization of the resin (A) is suitably suppressed, and the adhesive properties of the resin (A) tend to be well exhibited. The content of the tackifier resin (B) in the pressure-sensitive adhesive composition may be, for example, 10 to 60 parts by mass, 10 to 40 parts by mass, 10 to 30 parts by mass, or 10 to 20 parts by mass, relative to 100 parts by mass of the crystalline polyester resin (A), from the viewpoint of the balance between adhesive strength and holding power.

[0087] <Other Components> The pressure-sensitive adhesive composition of the present disclosure may further contain a polyester resin other than the crystalline polyester resin (A). The pressure-sensitive adhesive composition of the present disclosure may further contain an additive other than the tackifier resin (B). Examples of additives other than the tackifier resin (B) include crosslinkers, antioxidants, UV absorbers, stabilizers, softeners, antistatic agents, inorganic or organic fillers, metal powders, pigments, and dyes. The pressure-sensitive adhesive composition may contain one type of additive, or two or more types of additives.

[0088] When the pressure-sensitive adhesive composition contains additives other than the tackifier resin (B), the content of the additives is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less, per 100 parts by mass of the crystalline polyester resin (A).

[0089] The pressure-sensitive adhesive composition may further contain a crosslinking agent. Examples of crosslinking agents include isocyanate-based crosslinking agents. Isocyanate-based crosslinking agents are compounds having two or more isocyanate groups per molecule. The number of isocyanate groups per molecule of the isocyanate-based crosslinking agent is preferably 2 to 8, more preferably 2 to 6. Examples of isocyanate-based crosslinking agents include diisocyanate compounds having two isocyanate groups per molecule and isocyanate compounds having three or more isocyanate groups per molecule.

[0090] Examples of diisocyanate compounds include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Examples of aliphatic diisocyanates include aliphatic diisocyanates having 4 to 30 carbon atoms, such as ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and 2,2,4-trimethyl-1,6-hexamethylene diisocyanate. Examples of alicyclic diisocyanates include alicyclic diisocyanates having 7 to 30 carbon atoms, such as isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated tetramethylxylene diisocyanate. Examples of aromatic diisocyanates include aromatic diisocyanates having 8 to 30 carbon atoms, such as phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, naphthylene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, and diphenylpropane diisocyanate.

[0091] Examples of the isocyanate compound having three or more isocyanate groups in one molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates, and specific examples include 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, and 4,4',4"-triphenylmethane triisocyanate.

[0092] Examples of the isocyanate crosslinking agent include multimers (e.g., dimers or trimers, biurets, isocyanurates), derivatives (e.g., addition reaction products of polyhydric alcohols with two or more molecules of diisocyanate compounds), and polymers of the above-mentioned isocyanate compounds having two or more isocyanate groups. Examples of the polyhydric alcohols in the derivatives include low-molecular-weight polyhydric alcohols such as trimethylolpropane, glycerin, and pentaerythritol, as well as trivalent or higher alcohols, and high-molecular-weight polyhydric alcohols such as polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, and polyisoprene polyols. Examples of such isocyanate-based crosslinking agents include a trimer of diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate, a biuret or isocyanurate of hexamethylene diisocyanate or tolylene diisocyanate, a reaction product of trimethylolpropane and tolylene diisocyanate or xylylene diisocyanate (e.g., a trimolecular adduct of tolylene diisocyanate or xylylene diisocyanate), a reaction product of trimethylolpropane and hexamethylene diisocyanate (e.g., a trimolecular adduct of hexamethylene diisocyanate), polyether polyisocyanate, and polyester polyisocyanate.

[0093] When the pressure-sensitive adhesive composition contains a crosslinking agent, the content of the crosslinking agent is not particularly limited, but is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the crystalline polyester resin (A).

[0094] The crystalline polyester resin (A) has superior cohesive strength compared to amorphous polyester resins, and therefore the pressure-sensitive adhesive composition of the present disclosure containing the resin (A) tends to be able to form a pressure-sensitive adhesive layer that exhibits good cohesive strength even when it does not contain a crosslinking agent or contains a small amount of a crosslinking agent.

[0095] The pressure-sensitive adhesive composition may be, for example, a hot-melt pressure-sensitive adhesive composition.

[0096] The PSA composition may contain a solvent or a dispersion medium. Examples of the solvent or dispersion medium include an organic solvent (organic dispersion medium) and water. The PSA composition may be in the form of, for example, a solution containing a polyester resin and a solvent, or a dispersion containing a polyester resin and a dispersion medium. The PSA composition may be, for example, an emulsion-type PSA composition.

[0097] Examples of organic solvents (organic dispersion media) include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane, and cyclooctane; ethers such as diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl ether, and diphenyl ether; halogenated hydrocarbons such as chloroform, carbon tetrachloride, 1,2-dichloroethane, and chlorobenzene; esters such as ethyl acetate, propyl acetate, butyl acetate, and methyl propionate; ketones such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, and cyclohexanone; amides such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; nitriles such as acetonitrile and benzonitrile; and sulfoxides such as dimethyl sulfoxide and sulfolane. Examples of water include tap water, deionized water, and ion-exchanged water. The pressure-sensitive adhesive composition may contain one or more solvents or dispersion media.

[0098] When the PSA composition contains a solvent or a dispersion medium, the content of the solvent or dispersion medium in the PSA composition is preferably 20 to 90 mass %, more preferably 30 to 85 mass %, and even more preferably 40 to 80 mass %.

[0099] <Production of Pressure-Sensitive Adhesive Composition> The pressure-sensitive adhesive composition of the present disclosure can be produced, for example, by mixing a crystalline polyester resin (A), a tackifier resin (B), and, if necessary, other components. Examples of a method for mixing the crystalline polyester resin (A) and the tackifier resin (B) include a method of melt-mixing the crystalline polyester resin (A) and the tackifier resin (B).

[0100] The resin temperature during melt mixing is preferably equal to or higher than the melting point of the crystalline polyester resin (A), more preferably equal to or higher than the melting point of the resin (A) + 10°C, and even more preferably equal to or higher than the melting point of the resin (A) + 20°C. The resin temperature during melt mixing is preferably equal to or higher than the softening point of the tackifier resin (B), more preferably equal to or higher than the softening point of the resin (B) + 10°C, and even more preferably equal to or higher than the softening point of the resin (B) + 20°C. The resin temperature during melt mixing is preferably 280°C or lower, more preferably 250°C or lower, and even more preferably 200°C or lower.

[0101] In one embodiment, the pressure-sensitive adhesive composition of the present disclosure contains a crystalline polyester resin (A), a tackifier resin (B), and a solvent or dispersion medium. Examples of methods for producing such a pressure-sensitive adhesive composition include: (1) a method in which the crystalline polyester resin (A) and the tackifier resin (B) are melt-mixed, and the resulting mixture is mixed with a solvent or dispersion medium; (2) a method in which the crystalline polyester resin (A) and the tackifier resin (B) are mixed with a solvent or dispersion medium; and (3) a method in which a liquid in which the crystalline polyester resin (A) is dissolved or dispersed in a solvent or dispersion medium is mixed with a liquid in which the tackifier resin (B) is dissolved or dispersed in a solvent or dispersion medium. Among these, the method (1) is preferred from the viewpoint of ease of production.

[0102] [Adhesive Sheet] The adhesive sheet of the present disclosure has an adhesive layer (hereinafter also referred to as a "polyester-based adhesive layer") formed from the adhesive composition of the present disclosure. The adhesive sheet may be a double-sided adhesive sheet that does not have a substrate. The adhesive sheet may further have a substrate containing a resin material.

[0103] The substrate has a first surface and a second surface opposite the first surface.

[0104] The PSA sheet may be a single-sided PSA sheet having a polyester-based PSA layer on either the first or second surface of the substrate. The PSA sheet may be a double-sided PSA sheet having a first polyester-based PSA layer on the first surface of the substrate and a second polyester-based PSA layer on the second surface of the substrate, i.e., having a first polyester-based PSA layer, the substrate, and a second polyester-based PSA layer in this order in the stacking direction.

[0105] The pressure-sensitive adhesive sheet may have a release film on the outside of the polyester-based pressure-sensitive adhesive layer, if necessary. The release film protects the pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet may have, for example, a substrate, a polyester-based pressure-sensitive adhesive layer, and a release film, in this order in the stacking direction; a first release film, a first polyester-based pressure-sensitive adhesive layer, a substrate, a second polyester-based pressure-sensitive adhesive layer, and a second release film, in this order in the stacking direction; or a first release film, a polyester-based pressure-sensitive adhesive layer, and a second release film, in this order in the stacking direction. When using the pressure-sensitive adhesive sheet, for example, the release film is peeled off from the pressure-sensitive adhesive layer, and the exposed pressure-sensitive adhesive layer is attached to the surface of an adherend.

[0106] <Substrate> The substrate contains a resin material. Examples of the resin material include vinyl chloride resins such as polyvinyl chloride and vinyl chloride-vinyl acetate copolymer; other vinyl resins such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, and polyvinyl alcohol; polyester resins such as polyethylene terephthalate, polyethylene naphthate, polybutylene terephthalate, polyethylene furanoate, and polyethylene terephthalate / isophthalate copolymer; polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; cycloolefin resins; polystyrene resins; acrylonitrile-butadiene-styrene copolymers; fluoroethylene resins such as polyvinyl fluoride, polyvinylidene fluoride, and fluorinated polyethylene; polyamide resins such as nylon 6 and nylon 6,6; cellulose resins such as cellulose triacetate and cellophane; (meth)acrylic resins such as polymethyl(meth)acrylate, polyethyl(meth)acrylate, and polybutyl(meth)acrylate; polycarbonate resins; polyarylate resins; and polyimide resins. Among these, polyester resins or vinyl chloride resins are preferred, and polyethylene terephthalate or polyvinyl chloride are more preferred. The resin material may be a biomass material obtained using raw materials derived from biomass, from the viewpoint of carbon neutrality or reduction of environmental load.

[0107] The substrate may contain one type of resin material or two or more types of resin materials.

[0108] The content of the resin material in the substrate is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on 100% by mass of the substrate.

[0109] The substrate may further contain additives. Examples of additives include antioxidants, UV absorbers, stabilizers, softeners, antistatic agents, tackifying resins, plasticizers, inorganic or organic fillers, metal powders, pigments, and dyes. The substrate may contain one type of additive, or two or more types. The substrate may contain a plasticizer, for example, to improve its flexibility. A substrate containing a vinyl chloride resin preferably contains a plasticizer, for example, to improve its flexibility.

[0110] The substrate may have a single-layer structure or a multi-layer structure having two or more layers.

[0111] The surface of the substrate on which the polyester-based pressure-sensitive adhesive layer is to be formed may be subjected to a surface treatment in order to improve adhesion between the substrate and the polyester-based pressure-sensitive adhesive layer. Examples of the surface treatment include oxidation treatments by chemical or physical methods such as corona treatment, chromic acid treatment, ozone exposure, flame exposure, high-voltage shock exposure, and ionizing radiation treatment.

[0112] The thickness of the substrate is not particularly limited, but is preferably 1 to 1,000 μm, more preferably 5 to 500 μm, even more preferably 10 to 300 μm, and particularly preferably 20 to 200 μm.

[0113] <Polyester-based Pressure-Sensitive Adhesive Layer> The polyester-based pressure-sensitive adhesive layer is a layer formed from the pressure-sensitive adhesive composition of the present disclosure. The thickness of the polyester-based pressure-sensitive adhesive layer is not particularly limited, but is preferably 1 to 500 μm, more preferably 3 to 200 μm, even more preferably 5 to 100 μm, and particularly preferably 10 to 50 μm. Such a polyester-based pressure-sensitive adhesive layer tends to have excellent adhesive properties to an adherend. When the pressure-sensitive adhesive sheet has a first polyester-based pressure-sensitive adhesive layer and a second polyester-based pressure-sensitive adhesive layer, the above thickness refers to the thickness of each of the first and second polyester-based pressure-sensitive adhesive layers.

[0114] <Release Film> Examples of the release film include films obtained by subjecting a resin film formed from the resin materials exemplified as components constituting the above-mentioned substrate to a release treatment; foams such as polyurethane foam, vinyl foam, polyethylene foam, and polystyrene foam; metal foils such as aluminum foil, copper foil, stainless steel foil, iron foil, duralumin foil, tin foil, titanium foil, and gold foil; paper; woven fabric; and nonwoven fabric.

[0115] The release treatment may be, for example, a treatment in which a release agent is applied in the form of a layer. Examples of the release agent include silicone-based resins, long-chain alkyl-based resins, fluorine-based resins, and phosphate ester-based surfactants. One type of release agent may be used, or two or more types may be used.

[0116] The thickness of the release film is not particularly limited, but is preferably 1 to 1,000 μm, more preferably 5 to 500 μm, even more preferably 10 to 300 μm, and particularly preferably 20 to 200 μm. When the PSA sheet has a first release film and a second release film, the above thickness refers to the thickness of each of the first and second release films.

[0117] <Production of Pressure-Sensitive Adhesive Sheet> The pressure-sensitive adhesive sheet of the present disclosure can be produced, for example, by a conventionally known method, except that the pressure-sensitive adhesive composition of the present disclosure is used.

[0118] For example, a pressure-sensitive adhesive sheet according to the present disclosure can be produced as follows: A pressure-sensitive adhesive composition according to the present disclosure is prepared. The pressure-sensitive adhesive composition is applied to a first or second surface of a substrate and dried to form a pressure-sensitive adhesive layer, a release film is attached to the surface of the pressure-sensitive adhesive layer, and a curing treatment is performed as necessary. Alternatively, the pressure-sensitive adhesive composition is applied to the surface of a release film and dried to form a pressure-sensitive adhesive layer, a substrate is attached to the surface of the pressure-sensitive adhesive layer, and a curing treatment is performed as necessary. In this manner, a pressure-sensitive adhesive sheet having a substrate, a pressure-sensitive adhesive layer, and a release film is obtained.

[0119] For example, a pressure-sensitive adhesive sheet according to the present disclosure can be produced as follows: A pressure-sensitive adhesive composition according to the present disclosure is prepared. The pressure-sensitive adhesive composition is applied to the surface of a release film and dried to form a pressure-sensitive adhesive layer. Another release film is then laminated to the surface of the pressure-sensitive adhesive layer, and a curing treatment is performed as necessary. In this manner, a double-sided pressure-sensitive adhesive sheet without a substrate is obtained.

[0120] Examples of methods for applying the pressure-sensitive adhesive composition include spin coating, knife coating, roll coating, bar coating, blade coating, die coating, and gravure coating.

[0121] As for the drying conditions after application of the PSA composition, the drying temperature is preferably 50 to 150°C, more preferably 60 to 120°C, and the drying time is preferably 1 to 10 minutes, more preferably 2 to 7 minutes. As for the conditions for the curing treatment, the curing temperature is preferably 5 to 60°C, more preferably 15 to 40°C, and the curing time is preferably 1 to 30 days, more preferably 3 to 20 days.

[0122] <Uses of Pressure-Sensitive Adhesive Sheet> The pressure-sensitive adhesive sheet of the present disclosure can be used for various purposes. The pressure-sensitive adhesive sheet of the present disclosure can be used, for example, as a marking film for display or decoration. Examples of substrates to which the marking film can be attached include vehicles such as bicycles, motorcycles, cars, buses, and trains; household items such as furniture and home appliances; office supplies such as cabinets, desks, and personal computers; buildings such as houses; everyday items such as mobile phones and mobile phone covers; and exterior or interior parts thereof.

[0123] Examples of materials for the adherend include plastic, glass, and metals such as stainless steel and aluminum. The pressure-sensitive adhesive sheet of the present disclosure has excellent adhesive properties (e.g., adhesive strength and / or holding power) for adherends made of the above materials.

[0124] The pressure-sensitive adhesive sheet of the present disclosure can be used as, for example, a surface protection sheet.The uses of the surface protection sheet include, for example, a protection sheet for plastic film or glass plate, a protection sheet for optical components, a protection sheet for semiconductor wafer, a protection sheet for electronic components or electronic equipment such as electronic substrate, and a protection sheet for metal plates such as stainless steel and aluminum.Therefore, the adherend to which the surface protection sheet is attached includes, for example, a plastic film, a glass plate, an optical component, a semiconductor wafer, an electronic substrate, and other electronic components or electronic equipment, and a metal plate such as stainless steel and aluminum.

[0125] Examples of optical components include inorganic transparent electrode films such as indium tin oxide (ITO) electrode films, organic transparent electrode films such as polythiophene, polarizing plates, retardation plates, elliptically polarizing plates, light diffusion films, optical compensation films, brightness enhancement films, electromagnetic wave shielding films, near-infrared absorbing films, antireflection films, and antiglare films.

[0126] When the pressure-sensitive adhesive sheet of the present disclosure further comprises an optical member, it can be used, for example, as an optical sheet. The pressure-sensitive adhesive sheet of the present disclosure can also be used as a pressure-sensitive adhesive sheet for optical members used for bonding the optical member.

[0127] [Examples] The present disclosure relates to, for example, the following [1] to [9]. [1] A pressure-sensitive adhesive composition containing a crystalline polyester resin (A) having a heat of crystalline fusion of 5 to 55 mJ / mg and a tackifier resin (B) having a hydroxyl value of 1 mgKOH / g or more. [2] The pressure-sensitive adhesive composition according to [1] above, wherein the crystalline polyester resin (A) has a melting point (Tm) of 25°C or more. [3] The pressure-sensitive adhesive composition according to [1] or [2] above, wherein the crystalline polyester resin (A) has a glass transition temperature (Tg) of 0°C or less. [4] The pressure-sensitive adhesive composition according to any one of [1] to [3] above, wherein the tackifier resin (B) has a softening point of 100°C or less. [5] The pressure-sensitive adhesive composition according to any one of [1] to [4] above, wherein the tackifier resin (B) is at least one selected from the group consisting of a rosin-based resin, a terpene-based resin, a coumarone-based resin, a petroleum resin, a phenolic resin, and a xylene resin. [6] The pressure-sensitive adhesive composition according to any one of [1] to [5], wherein the content of the tackifier resin (B) per 100 parts by mass of the crystalline polyester resin (A) is 5 to 200 parts by mass. [7] The pressure-sensitive adhesive composition according to any one of [1] to [6], wherein the crystalline polyester resin (A) is a polycondensate of a monomer mixture containing a polycarboxylic acid component and a polyol component, and wherein 10 to 80 mol % of structural units derived from an aromatic dicarboxylic acid component are contained in 100 mol % of structural units derived from the polycarboxylic acid component. [8] The pressure-sensitive adhesive composition according to any one of [1] to [7], wherein the crystalline polyester resin (A) has a weight-average molecular weight (Mw) of less than 100,000. [9] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of [1] to [8].

[0128] The pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet of the present disclosure will be described in more detail below based on examples, but the pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet of the present disclosure are not limited to these examples in any way.

[0129] [Methods for measuring various physical properties, etc.] <Content of structural units in polyester resin> The content of structural units derived from each raw material monomer in the polyester resin (amount of structural units) was determined by nuclear magnetic resonance spectroscopy (NMR method) under the following conditions. Measuring device: ECZL-500G (manufactured by JEOL Ltd.) Measuring method: 1 H-NMR Accumulation number: 16 Sample concentration: 10 mg / mL Dilution solvent: dimethyl sulfoxide (DMSO)-d6

[0130] <Melting Point (Tm) and Heat of Fusion of Polyester Resin> The polyester resin was sealed in a simple hermetic pan and subjected to differential scanning calorimetry (DSC). Under a nitrogen gas flow, the temperature was lowered from 23°C to -80°C at 5°C / min, and then raised from -80°C to 200°C at 5°C / min to measure the thermal change. A DSC curve of "endothermic heat amount" versus "temperature" was drawn, and the temperature of the endothermic peak (melting peak temperature; if there are multiple endothermic peaks, the melting peak temperature of the endothermic peak located at the highest temperature) on the measured chart was determined and recorded as Tm. The heat of fusion (mJ / mg) was also determined from the endothermic peak of the DSC curve.

[0131] <Glass Transition Temperature (Tg) of Polyester Resin> The polyester resin was placed in a simple hermetic pan and subjected to differential scanning calorimetry (DSC). Under a nitrogen gas flow, the temperature was lowered from 23°C to -80°C at a rate of 5°C / min, and then raised from -80°C to 200°C at a rate of 5°C / min to measure the thermal change, and a DSC curve of "heat absorption and heat generation amount" versus "temperature" was drawn. The characteristic inflection point temperature (midpoint glass transition temperature) observed at this time was taken as the glass transition temperature (Tg) of the polyester resin.

[0132] <Weight-average molecular weight (Mw) of polyester resin> The weight-average molecular weight (Mw) of the polyester resin was determined by gel permeation chromatography (GPC) under the following conditions: Measurement device: HLC-8320GPC (manufactured by Tosoh Corporation) GPC column configuration: the following four columns in series (all manufactured by Tosoh Corporation) (1) TSKgel HxL-H (guard column) (2) TSKgel GMHxL (3) TSKgel GMHxL (4) TSKgel G2500HxL Flow rate: 1.0 mL / min Column temperature: 40°C Sample concentration: 1.5% (w / v) (diluted with tetrahydrofuran) Mobile phase solvent: tetrahydrofuran Standard polystyrene equivalent

[0133] [Production Example 1] A flask equipped with a heater, thermometer, stirrer, rectification column, nitrogen inlet tube, and vacuum device was charged with 0.24 mol of terephthalic acid (TPA), 0.20 mol of isophthalic acid (IPA), 0.56 mol of sebacic acid (SebA), 1.7 mol of 1,4-butanediol (1,4-BD), and 0.000035 mol of Orgatix TA-8 (titanium tetraisopropoxide, manufactured by Matsumoto Fine Chemicals) as a polymerization catalyst. While introducing nitrogen into the flask, the temperature inside the flask was gradually raised to 200°C, and an esterification reaction was carried out for 3 hours. Thereafter, the temperature inside the flask was raised to 250°C, and the pressure inside the flask was reduced to 100 Pa, and a polycondensation reaction was carried out for 3 hours. In this manner, polyester resin (1) was produced. The Mw of polyester resin (1) was 5.0 × 10 4 The Tg was −37° C., the Tm was 37° C., and the heat of fusion was 33 mJ / mg.

[0134] [Production Examples 2 to 5] Polyester resins (2) to (5) were produced in the same manner as in Production Example 1, except that the types and / or amounts of raw material monomers were changed as shown in Table 1.

[0135] The raw material monomers used in the production examples are listed below: TPA: terephthalic acid IPA: isophthalic acid SebA: sebacic acid CHA: 1,4-cyclohexanedicarboxylic acid SucA: succinic acid 1,4-BD: 1,4-butanediol DEG: diethylene glycol NPG: neopentyl glycol

[0136] [Blocking Resistance] The polyester resin obtained in the above Production Example was pelletized. The obtained pellets were left to stand in an environment of 35°C for 1 day, and the presence or absence of fusion between polyester resin particles was visually confirmed. AA: No fusion (no blocking) BB: Fusion (blocking)

[0137]

[0138] Example 1 100 parts by mass of polyester resin (1) and 15 parts by mass of a tackifier resin (Pine Crystal D-6011) were melt-mixed on a hot plate heated to 150°C. The resulting mixture was dissolved in ethyl acetate to prepare a pressure-sensitive adhesive composition in the form of a solution with a solids concentration of 30% by mass. The resulting solution was applied to a 50 μm thick polyethylene terephthalate (PET) film and dried in a 100°C environment for 3 minutes to remove the solvent, forming a 20 μm thick pressure-sensitive adhesive layer. A release-treated PET film was bonded to the surface of the pressure-sensitive adhesive layer opposite the surface in contact with the PET film. In this way, a pressure-sensitive adhesive sheet having a 50 μm thick PET film, a 20 μm thick pressure-sensitive adhesive layer, and a release-treated PET film was produced. In the following description, the sheet obtained by peeling the release-treated PET film from the pressure-sensitive adhesive layer may also be referred to as a pressure-sensitive adhesive sheet.

[0139] [Examples 2 to 8 and Comparative Examples 1 to 4] Pressure-sensitive adhesive compositions and pressure-sensitive adhesive sheets of Examples 2 to 8 and Comparative Examples 1 to 4 were produced in the same manner as in Example 1, except that the types and / or amounts of the components to be blended were changed as shown in Table 2.

[0140] The tackifying resins used in the examples and comparative examples are listed below. D-6011 Pine Crystal D-6011, manufactured by Arakawa Chemical Industries, rosin-containing diol, softening point: 84 to 99°C, hydroxyl value: 110 to 125 mgKOH / g G90 Knit Resin Coumarone G90, manufactured by Nippon Paint Chemical, coumarone-indene-styrene copolymer, softening point: 90°C, hydroxyl value: 20 to 40 mgKOH / g CP YS Resin CP, manufactured by Yasuhara Chemical, terpene phenol resin, liquid resin, hydroxyl value: 220 to 240 mgKOH / g G150 YS Polyster G150, manufactured by Yasuhara Chemical, terpene phenol resin, softening point: 150°C, hydroxyl value: 90 to 110 mgKOH / g FTR6100 FTR6100, manufactured by Mitsui Chemicals, Aromatic monomer / aliphatic monomer copolymer hydrocarbon resin, softening point: 95°C, hydroxyl value: 0 mgKOH / g

[0141] [Evaluation] <Adhesive strength> Under an environment of 23 ° C and 50% RH, the adhesive sheet of the example or comparative example was cut into a size of 20 mm wide x 100 mm long, and then the release-treated PET film was peeled off from the adhesive layer, and the exposed adhesive layer was attached to the adherend, and a pressure roller with a mass of 2 kg was reciprocated twice at a speed of 10 mm / s to perform a pressure bonding process, and a test piece was prepared. As the adherend, a SUS304 steel plate (polished with No. 360 waterproof abrasive paper) conforming to JIS Z0237:2000 or a float glass plate conforming to JIS R3202:2022 was used. When the adhesive strength of the adhesive sheet was insufficient and a test piece could not be prepared, it was marked "unable to apply" in the table.

[0142] After leaving the test piece in an environment of 23°C and 50% RH for 20 minutes after preparation, the adhesive strength was measured by pulling the edge of the pressure-sensitive adhesive sheet in a direction 180° relative to the surface of the adherend at a speed of 300 mm / min. After starting the adhesive strength measurement, the adhesive strength measured over a length of 25 mm was ignored, and the adhesive strength measured over a length of 50 mm thereafter peeled from the adherend was averaged to obtain the adhesive strength (N / 20 mm).

[0143] <Holding Power> In an environment of 23°C and 50% RH, the release-treated PET film was peeled off from the adhesive layer of the adhesive sheet of each Example or Comparative Example, and the exposed adhesive layer was attached to the SUS304 steel plate. A pressure-bonding treatment was performed by moving a 2 kg pressure roller back and forth twice at a speed of 10 mm / s to prepare a test specimen. The adhesion area of ​​the adhesive sheet to the SUS304 steel plate was 20 mm wide x 20 mm long. If the adhesive strength of the adhesive sheet was insufficient and a test specimen could not be prepared, this was recorded as "unable to attach" in the table.

[0144] After leaving the test piece in an environment of 23°C and 50% RH for 20 minutes after preparation, the test piece was hung vertically, and a load of 500 g was applied to the adhesive sheet in a direction parallel to the adhesive layer surface in an environment of 23°C and 50% RH. After 24 hours, the distance (mm) by which the adhesive sheet shifted from its original position was measured. The smaller the distance by which the adhesive sheet shifted from its original position, the higher the holding power of the adhesive sheet. If no shifting of the adhesive sheet was observed, this was recorded as "N.C." in the table. If the adhesive sheet fell within 24 hours, the time it took for the adhesive sheet to fall after the load was applied was recorded.

[0145] <Manufacturability> When a polyester resin rated AA for blocking resistance is used, the polyester resin has excellent handleability, and therefore the PSA composition can be said to have excellent manufacturability. Therefore, in this case, the manufacturability of the PSA composition was rated as "AA". When a polyester resin rated BB for blocking resistance is used, the polyester resin does not have sufficient handleability, and therefore the PSA composition cannot be said to have excellent manufacturability. Therefore, in this case, the manufacturability of the PSA composition was rated as "BB".

[0146]

Claims

1. A pressure-sensitive adhesive composition comprising: a crystalline polyester resin (A) having a heat of crystalline fusion of 5 to 55 mJ / mg; and a tackifier resin (B) having a hydroxyl value of 1 mgKOH / g or more.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the crystalline polyester resin (A) has a melting point (Tm) of 25°C or higher.

3. The pressure-sensitive adhesive composition according to claim 1, wherein the crystalline polyester resin (A) has a glass transition temperature (Tg) of 0°C or lower.

4. The pressure-sensitive adhesive composition according to claim 1, wherein the tackifier resin (B) has a softening point of 100°C or less.

5. The pressure-sensitive adhesive composition according to claim 1, wherein the tackifying resin (B) is at least one selected from the group consisting of rosin-based resins, terpene-based resins, coumarone-based resins, petroleum resins, phenolic resins, and xylene resins.

6. The pressure-sensitive adhesive composition according to claim 1, wherein the content of the tackifier resin (B) is 5 to 200 parts by mass per 100 parts by mass of the crystalline polyester resin (A).

7. The pressure-sensitive adhesive composition according to claim 1, wherein the crystalline polyester resin (A) is a polycondensate of a monomer mixture containing a polycarboxylic acid component and a polyol component, and contains 10 to 80 mol % of structural units derived from an aromatic dicarboxylic acid component out of 100 mol % of structural units derived from the polycarboxylic acid component.

8. The pressure-sensitive adhesive composition according to claim 1, wherein the crystalline polyester resin (A) has a weight average molecular weight (Mw) of less than 100,000.

9. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 8.

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