Adhesive composition, adhesive and adhesive sheet

Abstract

Provided an adhesive composition which has adhesive properties equal to or higher than those of a solvent-type adhesive and excellent coating suitability, and can be easily crosslinked.　The adhesive composition contains a polyester (A), wherein the polyester (A) contains a structural unit derived from a polyvalent carboxylic acid (a1) and a structural unit derived from a polyhydric alcohol (a2), and the polyester (A) has an ester bond concentration of 3.0-14 mmol / g, has fluidity at 25 °C, and has a viscosity of 500-500,000 mPa·s.

Description

Pressure-sensitive adhesive composition, pressure-sensitive adhesive, and pressure-sensitive adhesive sheet

[0001] The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive, and a pressure-sensitive adhesive sheet containing a polyester as a main component. More specifically, the present invention relates to a solvent-free pressure-sensitive adhesive composition, a pressure-sensitive adhesive, and a pressure-sensitive adhesive sheet that have excellent coatability at room temperature and excellent adhesive properties such as adhesive strength and holding power.

[0002] Solvent-based adhesives in which an adhesive polymer is dissolved in a solvent have conventionally been used as adhesives for use in adhesive sheets such as adhesive labels and adhesive tapes. For example, Patent Document 1 discloses a polyester-based adhesive containing a polyester having a glass transition temperature of −10° C. or lower and a hydrolysis inhibitor.

[0003] In recent years, solvent-free pressure-sensitive adhesives that do not use organic solvents have been attracting attention in order to reduce environmental impacts such as VOC (Volatile Organic Compound) emissions and greenhouse gas emissions. Known examples of the solvent-free pressure-sensitive adhesives include aqueous pressure-sensitive adhesives in which a pressure-sensitive adhesive is dispersed or dissolved in water, and hot-melt pressure-sensitive adhesives that are applied by heating and melting.

[0004] For example, Patent Document 2 discloses a solventless polyester-based pressure-sensitive adhesive composition containing a polyester having a glass transition temperature of −70 to −20° C., which is obtained by condensation polymerization of a dicarboxylic acid and a diol in a ratio where the hydroxyl groups contained in the diol are 1.2 to 2.0 moles per 1.0 mole of carboxy groups contained in the dicarboxylic acid, a diisocyanate having a molecular weight of 150 to 2,000 as a chain extender, and a tri- or higher functional polyisocyanate as a crosslinker, in such ratios that the gel fraction after chain extension and crosslinking is 30 to 80%.

[0005] Patent Document 3 discloses a solventless adhesive containing a polyol and a polyisocyanate and satisfying the following (1) and (2): (1) the polyol contains a polyester polyol, and the content of the polyester polyol (a1) is 30% by mass or more and 70% by mass or less, based on the total mass of the polyol; and (2) the polyol contains castor seed oil or a castor seed oil derivative, and the content of the castor seed oil or castor seed oil derivative is 30% by mass or more and 70% by mass or less, based on the total mass of the polyol.

[0006] JP 2017-115149 A JP 2010-95672 A JP 2023-148008 A

[0007] The solvent-based pressure-sensitive adhesives have high viscosity because the polymer is designed to have a high molecular weight from the viewpoint of adhesive properties, and therefore need to be diluted with a solvent to improve coatability. Therefore, the polyester-based pressure-sensitive adhesive composition disclosed in Patent Document 1 has poor coatability due to the high viscosity of the polyester, and also has a large environmental impact due to the inclusion of a solvent, so further improvement is required. On the other hand, when the viscosity of the polyester is reduced to improve coatability, there is also the problem that the cohesive force is insufficient and the adhesive properties are reduced.

[0008] Furthermore, aqueous adhesives, known as solvent-free adhesives, have problems in terms of performance, such as the amount of energy required to volatilize water being greater than that of solvent-based adhesives, and poorer water resistance than solvent-based adhesives due to the influence of the emulsifier contained in the base resin. Furthermore, the hot-melt adhesives require special coating equipment to heat and melt the highly viscous polymer, and they cannot be crosslinked to ensure a long pot life, resulting in problems such as poor holding power and heat resistance.

[0009] The solvent-free polyester-based pressure-sensitive adhesive disclosed in Patent Document 2 has poor adhesive strength and compatibility with curing agents due to a low ester bond concentration of the polyester, and further requires a chain extender and a crosslinking agent, so further improvement is required in the stability of the degree of crosslinking. Also, the solvent-free adhesive disclosed in Patent Document 3 can be used as an adhesive, but has poor adhesive strength and tackiness due to the high crystallinity of the polyol and the inclusion of a large amount of polyisocyanate as a crosslinking agent, so further improvement is required for use as a pressure-sensitive adhesive sheet.

[0010] Under these circumstances, the present invention provides a pressure-sensitive adhesive composition that has adhesive properties equal to or better than those of conventional solvent-based pressure-sensitive adhesives, has excellent coating suitability, and can be easily crosslinked.

[0011] However, in light of these circumstances, the present inventors have conducted extensive research and have found that a pressure-sensitive adhesive composition containing a polyester having a specific ester bond concentration and viscosity can be applied without dilution with a solvent, has a low environmental impact, and is excellent in adhesive strength and holding power. Although the mechanism of action of the present invention has not been fully elucidated, the present inventors speculate as follows: If a polyester having a viscosity at 25°C within a specific range is selected for coatability, the polyester will have poor cohesive strength, making it difficult to develop adhesive strength, and will not have sufficient substrate adhesion, resulting in poor coatability. Therefore, by selecting a polyester having not only a viscosity but also an ester bond concentration within a specific range, the polyester will have polarity, which will strengthen the intermolecular interaction between polyester molecules. This results in excellent coatability at a low viscosity and excellent cohesive strength, thereby achieving both tackiness, adhesive strength, holding power, and other adhesive properties.

[0012] That is, the present invention has the following aspects. [1] A pressure-sensitive adhesive composition containing a polyester (A), wherein the polyester (A) has a structural unit derived from a polycarboxylic acid (a1) and a structural unit derived from a polyhydric alcohol (a2), the polyester (A) has an ester bond concentration of 3.0 to 14 mmol / g, and the polyester (A) has fluidity at 25°C and a viscosity of 500 to 500,000 mPa·s. [2] The pressure-sensitive adhesive composition according to [1], wherein the ester bond concentration of the polyester (A) is 8.7 mmol / g or less. [3] The pressure-sensitive adhesive composition according to [1] or [2], wherein the hydroxyl value of the polyester (A) is 20 mgKOH / g or more. [4] The pressure-sensitive adhesive composition according to any one of [1] to [3], wherein the hydroxyl value of the polyester (A) relative to the ester bond concentration of the polyester (A) (hydroxyl value / ester bond concentration) is 4.27 or more. [5] The pressure-sensitive adhesive composition according to any one of [1] to [4], wherein the content of the organic solvent relative to the total amount of the pressure-sensitive adhesive composition is 0% by mass or more and 10% by mass or less. [6] The pressure-sensitive adhesive composition according to any one of [1] to [5], wherein the weight-average molecular weight of the polyester (A) is 2,000 to 30,000. [7] The pressure-sensitive adhesive composition according to any one of [1] to [6], wherein the heat of crystalline fusion of the polyester (A) is 50 J / g or less. [8] The pressure-sensitive adhesive composition according to any one of [1] to [7], wherein the urethane bond concentration of the polyester (A) is 5 mmol / g or less. [9] The pressure-sensitive adhesive composition according to any one of [1] to [8], wherein the acid value of the polyester (A) is 3 mg KOH / g or less.

[10] The pressure-sensitive adhesive composition according to any one of [1] to [9], wherein the polyester (A) contains, as a structural unit derived from a polyhydric alcohol (a2), a branched aliphatic diol having 6 to 34 carbon atoms.

[11] The pressure-sensitive adhesive composition according to any one of [1] to

[10] , wherein the polyester (A) has a structural unit derived from a cyclic structure-containing compound as a structural unit derived from a polycarboxylic acid (a1) and / or a structural unit derived from a polyhydric alcohol (a2).

[12] The pressure-sensitive adhesive composition according to

[11] , wherein the content of the structural unit derived from the cyclic structure-containing compound is 0.1 to 50 mass% based on the polyester (A).

[13] The pressure-sensitive adhesive composition according to any one of [1] to

[12] , wherein the glass transition temperature of the polyester (A) is 15°C or lower.

[14] The pressure-sensitive adhesive composition according to any one of [1] to

[13] , wherein the polyester (A) contains a linear aliphatic dicarboxylic acid as a structural unit derived from the polyvalent carboxylic acid (a1).

[15] The pressure-sensitive adhesive composition according to any one of [1] to

[14] , further containing a crosslinking agent (B).

[16] The pressure-sensitive adhesive composition according to

[15] , wherein the crosslinking agent (B) is a polyisocyanate compound, and the equivalent (functional group molar ratio) of the isocyanate groups of the crosslinking agent (B) relative to the hydroxyl groups of the polyester (A) is 0.2 to 2.

[17] The pressure-sensitive adhesive composition according to any one of [1] to

[16] , further containing a hydrolysis inhibitor (C).

[18] The pressure-sensitive adhesive composition according to any one of [1] to

[17] , further containing a catalyst (D).

[19] The pressure-sensitive adhesive composition according to any one of [1] to

[18] , wherein the content of the polyester (A) is 50 mass% or more relative to the pressure-sensitive adhesive composition.

[20] A pressure-sensitive adhesive that is a cured product of the pressure-sensitive adhesive composition according to any one of [1] to

[19] .

[21] A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive according to

[20] .

[0013] The pressure-sensitive adhesive composition of the present invention has adhesive properties equivalent to or better than those of conventional solvent-based pressure-sensitive adhesives, has excellent coatability, and can be easily crosslinked. Therefore, the pressure-sensitive adhesive composition of the present invention can be suitably used as a pressure-sensitive adhesive, a pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet, particularly a pressure-sensitive adhesive sheet for electronic components, a pressure-sensitive adhesive sheet for optical components, and a pressure-sensitive adhesive label.

[0014] The present invention will be described below based on examples of embodiments for carrying out the present invention, but the present invention is not limited to the embodiments described below.

[0015] As used herein, "x and / or y (x and y are any configuration)" refers to at least one of x and y, and can mean three things: x only, y only, or x and y. In this specification, when "X to Y" (X and Y are any numbers) is used, unless otherwise specified, it also means "X or more and Y or less," as well as "preferably greater than X" or "preferably smaller than Y." In this specification, when "X or more" (X is any number) or "Y or less" (Y is any number) is used, it also means "preferably greater than X" or "preferably less than Y." For numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described herein, the upper or lower limit of the numerical range can also be replaced with the values ​​shown in the examples. In this specification, the term "main component" means a component that has a significant effect on the properties of the target object, and the content of the component is usually 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and may be 100% by mass.

[0016] In this specification, the term "sheet" also includes "film" and "tape." In addition, in this specification, the term "type" added after the name of a compound is a concept that encompasses not only the compound but also derivatives of the compound. For example, the term "carboxylic acids" includes not only carboxylic acids but also carboxylic acid derivatives such as carboxylic acid salts, carboxylic acid anhydrides, carboxylic acid halides, and carboxylic acid esters.

[0017] A pressure-sensitive adhesive composition according to one embodiment of the present invention (hereinafter, may be referred to as "the pressure-sensitive adhesive composition") contains a polyester (A), the polyester (A) has a structural unit derived from a polyvalent carboxylic acid (a1) and a structural unit derived from a polyhydric alcohol (a2), the polyester (A) has an ester bond concentration of 3.0 to 14 mmol / g, and the polyester (A) has fluidity at 25°C and a viscosity of 500 to 500,000 mPa s.

[0018] The present PSA composition is preferably a solvent-free PSA composition. The term "solvent-free" most preferably refers to the complete absence of organic solvents. However, if an organic solvent is contained, the content of the organic solvent relative to the total amount of the PSA composition is preferably 10% by mass or less, more preferably less than 10% by mass, even more preferably 5% by mass or less, even more preferably 3% by mass or less, particularly preferably 1% by mass or less, and most preferably 0.5% by mass or less. The lower limit is 0% by mass or more, and the range is, for example, 0% by mass or more to 10% by mass or less. Being solvent-free, the present PSA composition does not generate harmful VOCs, reduces energy consumption during drying, and tends to be environmentally friendly. The content of the organic solvent can be measured by headspace GC / MS. Each component contained in the present PSA composition will be described below.

[0019] <Polyester (A)> The polyester (A) has a structural unit derived from a polycarboxylic acid (a1) and a structural unit derived from a polyhydric alcohol (a2), and is obtained by an esterification reaction and / or transesterification reaction of a monomer component containing the polycarboxylic acid (a1) and the polyhydric alcohol (a2). Furthermore, the polyester (A) has an ester bond concentration within a specific range, fluidity at 25°C, and a viscosity within a specific range, and therefore has excellent coatability. Therefore, the pressure-sensitive adhesive composition can be coated without being diluted with an organic solvent.

[0020] [Polycarboxylic Acids (a1)] Examples of the polycarboxylic acids (a1) in the structural unit derived from the polycarboxylic acids (a1) include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and trivalent or higher polycarboxylic acids having 0 or 1 acid anhydride group. These polycarboxylic acids (a1) can be used alone or in combination of two or more.

[0021] [Aromatic Dicarboxylic Acids] Examples of the aromatic dicarboxylic acids include aromatic dicarboxylic acids such as benzene dicarboxylic acids such as terephthalic acids, isophthalic acids, and orthophthalic acids; polycyclic aromatic dicarboxylic acids such as 1,5-naphthalenedicarboxylic acids, 2,6-naphthalenedicarboxylic acids, and 4,4'-biphenyldicarboxylic acids; and heterocyclic dicarboxylic acids such as furandicarboxylic acids and thiophenedicarboxylic acids (pyrrole, pyrazole, imidazole, pyridine, pyridazine, pyrimidine, pyrazine, etc.); and sulfonic acid group-containing aromatic dicarboxylic acids such as sodium dimethyl 4-sulfoisophthalate, sodium 5-sulfoisophthalate, sodium dimethyl 5-sulfoisophthalate, potassium dimethyl 4-sulfoisophthalate, potassium dimethyl 5-sulfoisophthalate, sodium 2-sulfoterephthalate, potassium dimethyl 2-sulfoterephthalate, sodium dimethyl 2-sulfoterephthalate, potassium dimethyl 2-sulfoterephthalate, and sodium diethylene glycol 2-sulfoterephthalate.

[0022] [Aliphatic Dicarboxylic Acids] Examples of the aliphatic dicarboxylic acids include linear aliphatic dicarboxylic acids, branched aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, unsaturated aliphatic dicarboxylic acids, and other aliphatic dicarboxylic acids.

[0023] Examples of the straight-chain aliphatic dicarboxylic acids include malonic acids, succinic acids, glutaric acids, adipic acids, pimelic acids, azelaic acids, sebacic acids, 1,9-nonanedicarboxylic acids, and decanedicarboxylic acids.

[0024] Examples of the branched chain aliphatic dicarboxylic acids include dimethylmalonic acids, trimethyladipic acids, 2,2-dimethylglutaric acids, 1,3-diethylglutaric acids, and hydrogenated dimer acids.

[0025] The "dimer acid" is a dimer of an unsaturated fatty acid having an average of 10 to 26 carbon atoms as a main component, preferably a dimer of an unsaturated fatty acid having an average of 12 to 24 carbon atoms, and more preferably a dimer of an unsaturated fatty acid having an average of 14 to 22 carbon atoms. Specifically, it is a dimer of a dicarboxylic acid derived from an unsaturated fatty acid such as oleic acid, linoleic acid, linolenic acid, or erucic acid.

[0026] Examples of the unsaturated aliphatic dicarboxylic acid include fumaric acids, maleic acids, itaconic acids, and dimer acids.

[0027] Examples of the alicyclic dicarboxylic acids include 1,3-cyclopentanedicarboxylic acids, 1,2-cyclohexanedicarboxylic acids, 1,3-cyclopentanedicarboxylic acids, 1,4-cyclohexanedicarboxylic acids, 2,5-norbornanedicarboxylic acids, and adamantanedicarboxylic acids.

[0028] Examples of the other aliphatic dicarboxylic acids include thiodipropionic acid and diglycolic acid.

[0029] [Trivalent or higher polycarboxylic acids having 0 or 1 acid anhydride group] Examples of the trivalent or higher polycarboxylic acids having 0 or 1 acid anhydride group include trivalent or higher aromatic polycarboxylic acids such as trimellitic acids, trimesic acids, and pyromellitic acids, trivalent or higher aliphatic polycarboxylic acids such as 1,2,4-butanetricarboxylic acids, 1,2,5-hexanetricarboxylic acids, 1,2,4-cyclohexanetricarboxylic acids, and 1,2,3,4-butanetetracarboxylic acids, and acid anhydrides thereof.

[0030] Among these polyvalent carboxylic acids (a1), aromatic dicarboxylic acids are preferred, more preferably benzenedicarboxylic acids, because they have excellent adhesive strength, holding power, and shear strength when used as a pressure-sensitive adhesive. Isophthalic acids are particularly preferred, because they have reduced crystallinity and are excellent in tackiness and coatability.

[0031] Furthermore, aliphatic dicarboxylic acids are preferred, more preferably straight-chain aliphatic dicarboxylic acids, in that they lower the glass transition temperature and provide excellent tackiness and coatability. Straight-chain aliphatic dicarboxylic acids are even more preferred, and straight-chain aliphatic dicarboxylic acids having 5 to 12 carbon atoms are particularly preferred, in that they increase the ester bond concentration and provide excellent adhesive strength, and adipic acids, azelaic acids, and sebacic acids are particularly preferred.

[0032] Furthermore, in order to increase the number of branching points in the polyester (A), trivalent or higher polycarboxylic acids having 0 or 1 acid anhydride group may be used. Among these, trimellitic acids are preferred because they are relatively less likely to cause gelation during production.

[0033] [Polyhydric alcohols (a2)] Examples of the polyhydric alcohols (a2) in the structural units derived from the polyhydric alcohols (a2) include linear aliphatic diols, branched aliphatic diols, alicyclic diols, aromatic diols, polyester diols, polyether diols, polycaprolactone diols, polycarbonate diols, polybutadiene diols, polyisoprene diols, trihydric or higher polyhydric alcohols, etc. These polyhydric alcohols (a2) can be used alone or in combination of two or more.

[0034] [Straight-Chain Aliphatic Diol] Examples of the straight-chain aliphatic diol include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and 1,18-octadecanediol.

[0035] [Branched Aliphatic Diol] Examples of the branched aliphatic diol include propylene glycol, neopentyl glycol, 2-methyl-1,3-propanediol, 1-methyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, and 2,4-diethyl- Examples of the diol include 1,5-pentanediol, 1,3,5-trimethyl-1,3-pentanediol, 2-methyl-1,6-hexanediol, 2-methyl-1,8-octanediol, 2-methyl-1,9-nonanediol, dimerdiol, 4-methyl-1,7-heptanediol, 3-methyl-1,6-hexanediol, 1-methyl-1,6-hexanediol, 4-methyl-1,9-nonanediol, 3-methyl-1,9-nonanediol, dimerdiol, and hydrogenated products of dimerdiol.

[0036] [Alicyclic Diol] Examples of the alicyclic diol include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,3-cyclobutanediol, hydrogenated bisphenol A and / or its ethylene oxide adduct or propionate adduct.

[0037] [Aromatic Diol] Examples of the aromatic diol include bisphenol A, 9,9-bis(hydroxyphenyl)fluorene, 4,4′-thiodiphenol, 4,4′-methylenediphenol, 4,4′-dihydroxybiphenyl, o-, m-, and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol, and ethylene oxide adducts and propylene oxide adducts thereof.

[0038] [Polyester Diol] Examples of the polyester diol include polyester diols obtained by dehydrating a diol component such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,10-decanediol, or octadecanediol with a dicarboxylic acid component such as succinic acid, methylsuccinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 1,12-dodecanoic acid, 1,14-tetradecanedioic acid, terephthalic acid, isophthalic acid, or an acid anhydride or lower alkyl ester thereof, or a derivative thereof, either alone or in a mixture.

[0039] [Polyether Diol] Examples of the polyether diol include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol obtained by ring-opening polymerization of ethylene oxide, propylene oxide, tetrahydrofuran, etc., and copolyethers obtained by copolymerizing these.

[0040] [Polycaprolactone Diol] Examples of the polycaprolactone diol include caprolactone-based polyester diols obtained by ring-opening polymerization of cyclic ester monomers such as ε-caprolactone and δ-valerolactone.

[0041] [Polycarbonate Diol] Examples of the polycarbonate diol include carbonate diols such as propylene carbonate diol, hexamethylene carbonate diol, and 3-methylpentene carbonate diol, and polycarbonate diols obtained by dealcoholization reaction of polyhydric alcohols such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, and 1,9-nonanediol with dialkyl carbonates such as diethylene carbonate and dimethyl carbonate.

[0042] [Polybutadiene Diol] Examples of the polybutadiene diol include hydrogenated polybutadiene diols such as 1,2-polybutadiene diol and 1,4-polybutadiene diol in which the double bonds are saturated with hydrogen or halogen.

[0043] [Polyisoprene Diol] Examples of the polyisoprene diol include polyisoprene diol and hydrogenated polyisoprene diols in which the double bonds of polyisoprene diol are saturated with hydrogen, halogen, or the like.

[0044] [Trihydric or higher polyhydric alcohols] Examples of the trihydric or higher polyhydric alcohols include trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol, pentaerythritol, and dipentaerythritol.

[0045] Among these polyhydric alcohols (a2), branched-chain aliphatic diols are preferred from the viewpoint of excellent adhesive properties when used as a pressure-sensitive adhesive, more preferably branched-chain aliphatic diols having 6 to 34 carbon atoms, even more preferably branched-chain aliphatic diols having 6 to 12 carbon atoms, and most preferably 3-methyl-1,5-pentanediol and 2,4-diethyl-1,5-pentanediol. In particular, branched-chain aliphatic diols having 6 to 34 carbon atoms can increase the ester bond concentration and lower the glass transition temperature while disrupting the crystallinity of the polyester (A), and tend to have an excellent balance between adhesive properties and viscosity.

[0046] Furthermore, aromatic diols are preferred because they provide excellent adhesive strength, holding power, and shear strength when used as adhesives, and ethylene oxide adducts of bisphenol A are preferred because they provide excellent adhesive strength while reducing crystallinity.

[0047] Furthermore, trihydric or higher polyhydric alcohols are preferred in that they form reactive sites in the polyester (A) with the crosslinking agent (B) described below and have excellent crosslinking properties and cohesive strength, and more preferred are trimethylolpropane, trimethylolethane, glycerin, pentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, and 1,2,6-hexanetriol. Trimethylolpropane is particularly preferred in that it is relatively less likely to produce gel.

[0048] The polyester (A) may also contain structural units derived from an oxycarboxylic acid compound. The oxycarboxylic acid compound is a compound having a hydroxyl group and a carboxyl group in its molecular structure. Examples of the oxycarboxylic acid compound include 5-hydroxyisophthalic acid, p-hydroxybenzoic acid, p-hydroxyphenylpropionic acid, p-hydroxyphenylacetic acid, 6-hydroxy-2-naphthoic acid, 4,4-bis(p-hydroxyphenyl)valeric acid, glycolic acid, lactic acid, malic acid, tartaric acid, and glyceric acid. These may be used alone or in combination of two or more.

[0049] [Method for producing polyester (A)] The polyester (A) is produced by appropriately selecting the polyvalent carboxylic acids (a1) and the polyhydric alcohols (a2) and subjecting them to an esterification reaction and / or transesterification reaction in the presence of a catalyst by a known method.

[0050] The blending ratio of the polycarboxylic acids (a1) and the polyhydric alcohols (a2) is preferably 1 equivalent or more of the polyhydric alcohols (a2) per equivalent of the polycarboxylic acids (a1), more preferably 1.05 equivalents or more, even more preferably 1.1 equivalents or more, particularly preferably 1.15 equivalents or more, and most preferably 1.2 equivalents or more. On the other hand, it is preferably 2 equivalents or less, more preferably 1.8 equivalents or less, even more preferably 1.6 equivalents or less, particularly preferably 1.4 equivalents or less, and most preferably 1.35 equivalents or less. That is, it is preferably 1 to 2 equivalents, more preferably 1.05 to 1.8 equivalents, even more preferably 1.1 to 1.6 equivalents, particularly preferably 1.15 to 1.4 equivalents, and most preferably 1.2 to 1.35 equivalents. When the blending ratio is within the above range, a polyester (A) having a low acid value, low viscosity, and excellent coatability tends to be obtained.

[0051] Examples of the catalyst include titanium-based catalysts such as tetraisopropyl titanate and tetrabutyl titanate, antimony-based catalysts such as antimony trioxide, germanium-based catalysts such as germanium dioxide, aluminum-based catalysts such as aluminum formate, aluminum acetate, and aluminum lactate, and other catalysts such as zinc acetate, manganese acetate, and dibutyltin oxide. These may be used alone or in combination of two or more.

[0052] The amount of the catalyst blended is, on a mass basis with respect to the monomer components, usually 1 ppm or more, preferably 10 ppm or more, more preferably 20 ppm or more. On the other hand, it is usually 10,000 ppm or less, preferably 5,000 ppm or less, more preferably 3,000 ppm or less. That is, it is usually 1 to 10,000 ppm, preferably 10 to 5,000 ppm, more preferably 20 to 3,000 ppm. When the amount of the catalyst blended is within the above range, the esterification reaction and / or transesterification reaction tends to proceed sufficiently.

[0053] The reaction temperature of the esterification reaction and / or transesterification reaction is usually 200°C or higher, preferably 210°C or higher, and more preferably 220°C or higher. On the other hand, it is usually 300°C or lower, preferably 280°C or lower, and more preferably 260°C or lower. That is, it is usually 200 to 300°C, preferably 210 to 280°C, and more preferably 220 to 260°C. When the reaction temperature is within the above range, the esterification reaction and / or transesterification reaction tends to proceed sufficiently.

[0054] Thus, polyester (A) is obtained. Polyesters used for pressure-sensitive adhesives are usually those with a high molecular weight for enhanced functionality. Such high-molecular-weight polyesters are produced by esterification and / or transesterification followed by polycondensation. However, high-molecular-weight polyesters tend to have high viscosity and cannot be used as is at room temperature (25°C). Therefore, they must be diluted with an organic solvent when used as a pressure-sensitive adhesive. On the other hand, since polyester (A) is produced only by esterification and / or transesterification without polycondensation, it has a low molecular weight and can be made low-viscosity. Therefore, the pressure-sensitive adhesive composition containing polyester (A) can be applied without diluting it with an organic solvent.

[0055] [Structure of Polyester (A)] When the polyester (A) has structural units derived from aromatic dicarboxylic acids, the content of the structural units derived from the polycarboxylic acids (a1) is usually 5 mol% or more, preferably 10 mol% or more, more preferably 20 mol% or more, even more preferably 25 mol% or more, particularly preferably 30 mol% or more, and most preferably 35 mol% or more. On the other hand, it is preferably 80 mol% or less, more preferably 70 mol% or less, even more preferably 65 mol% or less, particularly preferably 60 mol% or less, and most preferably 55 mol% or less. That is, it is usually 5 mol% or more, preferably 10 to 80 mol%, more preferably 20 to 70 mol%, even more preferably 25 to 65 mol%, particularly preferably 30 to 60 mol%, and most preferably 35 to 55 mol%. When the content of structural units derived from aromatic dicarboxylic acids is within the above range, the resulting pressure-sensitive adhesive tends to have excellent adhesive strength, holding power, and shear strength.

[0056] When the polyester (A) has structural units derived from aliphatic dicarboxylic acids, the content of the structural units derived from the polycarboxylic acids (a1) is usually 10 mol% or more, preferably 20 mol% or more, more preferably 30 mol% or more, particularly preferably 40 mol% or more, and most preferably 50 mol% or more. The upper limit is usually 100 mol%, preferably 90 mol% or less, more preferably 80 mol% or less, particularly preferably 70 mol% or less, and most preferably 60 mol% or less. That is, it is usually 10 to 100 mol%, preferably 20 to 90 mol%, more preferably 30 to 80 mol%, particularly preferably 40 to 70 mol%, and most preferably 50 to 60 mol%. When the content of structural units derived from aliphatic dicarboxylic acids is within the above range, the glass transition temperature tends to be lower, and tackiness and coatability tend to be excellent.

[0057] Furthermore, when the polyester (A) has structural units derived from linear aliphatic dicarboxylic acids, the content of the structural units derived from the polycarboxylic acids (a1) is typically 10 mol% or more, preferably 20 mol% or more, more preferably 30 mol% or more, particularly preferably 40 mol% or more, and most preferably 50 mol% or more. The upper limit is typically 100 mol%, preferably 90 mol%, more preferably 80 mol%, particularly preferably 70 mol%, and most preferably 60 mol%. That is, it is typically 10 to 100 mol%, preferably 20 to 90 mol%, more preferably 30 to 80 mol%, particularly preferably 40 to 70 mol%, and most preferably 50 to 60 mol%. When the content of the structural units derived from linear aliphatic dicarboxylic acids is within the above range, the glass transition temperature tends to be lower, and tackiness and coatability tend to be excellent.

[0058] The molar ratio of the structural units derived from aromatic dicarboxylic acids to the structural units derived from aliphatic dicarboxylic acids [aromatic dicarboxylic acids:aliphatic dicarboxylic acids] is usually 5:95 to 95:5, preferably 10:90 to 80:20, more preferably 30:70 to 60:40, and particularly preferably 35:65 to 55:45. When the molar ratio of the structural units derived from aromatic dicarboxylic acids to the structural units derived from aliphatic dicarboxylic acids is within the above range, the balance between adhesive strength and coatability tends to be excellent.

[0059] When the polyester (A) has structural units derived from trivalent or higher polycarboxylic acids having 0 or 1 acid anhydride group, the content of the structural units derived from the polycarboxylic acids (a1) is usually 30 mol% or less, preferably 25 mol% or less, more preferably 20 mol% or less, and particularly preferably 15 mol% or less. On the other hand, it is preferably 0.1 mol% or more, more preferably 1 mol% or more, and particularly preferably 3 mol% or more. That is, it is usually 30 mol% or less, preferably 0.1 to 25 mol%, more preferably 1 to 20 mol%, and particularly preferably 3 to 15 mol%. When the content of structural units derived from trivalent or higher polycarboxylic acids having 0 or 1 acid anhydride group is within the above range, the resulting pressure-sensitive adhesive tends to have excellent crosslinkability and cohesive strength.

[0060] When the polyester (A) has structural units derived from a branched chain aliphatic diol, the content of the structural units derived from the polyhydric alcohol (a2) is usually 30 mol% or more, preferably 40 mol% or more, more preferably 50 mol% or more, even more preferably 60 mol% or more, even more preferably 70 mol% or more, particularly preferably 80 mol%, and most preferably 90 mol%. The upper limit is usually 100 mol%, and all of the structural units derived from the polyhydric alcohol (a2) may be structural units derived from a branched chain aliphatic diol. When the content of the structural units derived from a branched chain aliphatic diol is within the above range, the crystallinity of the polyester (A) can be decreased, the ester bond concentration can be increased, and the glass transition temperature can be lowered, and the balance between adhesive properties and viscosity tends to be excellent.

[0061] When the polyester (A) has structural units derived from aromatic diols, the content of the structural units derived from the polyhydric alcohols (a2) is usually 10 mol% or more, preferably 20 mol% or more, more preferably 30 mol% or more, and particularly preferably 40 mol% or more. On the other hand, it is usually 100 mol% or less, preferably 90 mol% or less, more preferably 80 mol% or less, and particularly preferably 70 mol% or less. That is, it is usually 10 to 100 mol%, preferably 20 to 90 mol%, more preferably 30 to 80 mol%, and particularly preferably 40 to 70 mol%. When the content of the structural units derived from aromatic diols is within the above range, the resulting pressure-sensitive adhesive tends to have excellent adhesive strength, holding power, and shear strength.

[0062] When the polyester (A) has a structural unit derived from a trihydric or higher polyhydric alcohol, the content of the structural unit derived from the polyhydric alcohol (a2) is usually 30 mol% or less, preferably 25 mol% or less, more preferably 20 mol% or less, and particularly preferably 15 mol% or less. On the other hand, it is preferably 0.1 mol% or more, more preferably 1 mol% or more, and particularly preferably 3 mol% or more. That is, it is usually 30 mol% or less, preferably 0.1 to 25 mol%, more preferably 1 to 20 mol%, and particularly preferably 3 to 15 mol%. When the structural unit derived from a trihydric or higher polyhydric alcohol is within the above range, the resulting pressure-sensitive adhesive tends to have excellent cohesive strength.

[0063] In order to obtain excellent adhesive properties when used as a pressure-sensitive adhesive, the polyester (A) preferably contains a structural unit derived from a cyclic structure-containing compound as a structural unit derived from a polyvalent carboxylic acid (a1) and / or a structural unit derived from a polyhydric alcohol (a2). Examples of the cyclic structure compound include the aromatic dicarboxylic acids, alicyclic dicarboxylic acids, alicyclic diols, and aromatic diols described above. Among these, the cyclic structure compound is preferably an aromatic dicarboxylic acid or an aromatic diol, and more preferably an aromatic dicarboxylic acid because of its excellent reactivity and the ability to reduce the acid value of the polyester (A). By containing the structural unit derived from an aromatic dicarboxylic acid or an aromatic diol, the polyester (A) tends to have excellent cohesive strength, adhesive strength, tackiness, and shear strength due to the interaction between the aromatic rings (π-π stacking).

[0064] Furthermore, when the polyester (A) has a structural unit derived from a cyclic structure-containing compound, the content thereof relative to the polyester (A) is preferably 0.1% by mass or more, more preferably 1% by mass or more, even more preferably 3% by mass or more, even more preferably 5% by mass or more, particularly preferably 10% by mass or more, and most preferably 15% by mass or more. On the other hand, the content is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, even more preferably 35% by mass or less, particularly preferably 30% by mass or less, and most preferably 25% by mass or less. That is, the content is preferably 0.1 to 50% by mass, more preferably 1 to 45% by mass, even more preferably 3 to 40% by mass, even more preferably 5 to 35% by mass, particularly preferably 10 to 30% by mass, and most preferably 15 to 25% by mass. When the structural unit derived from a cyclic structure-containing compound is within the above range, the resulting pressure-sensitive adhesive tends to have excellent adhesive strength, holding power, and shear strength.

[0065] When the polyester (A) contains a structural unit derived from an oxycarboxylic acid compound, the content thereof is preferably 50 mol % or less, more preferably 30 mol % or less, particularly preferably 15 mol % or less, even more preferably 10 mol % or less, and most preferably 5 mol % or less, based on the polyester (A).

[0066] [Physical Properties of Polyester (A)] The ester bond concentration of the polyester (A) is 3.0 to 14 mmol / g, preferably 4.0 mmol / g or more, more preferably 5.0 mmol / g or more, even more preferably 6.0 mmol / g or more, still more preferably 6.5 mmol / g or more, particularly preferably 7.0 mmol / g or more, and most preferably 7.5 mmol / g or more, while it is preferably 13 mmol / g or less, more preferably 12 mmol / g, even more preferably 11 mmol / g or less, still more preferably 10 mmol / g or less, particularly preferably 9.0 mmol / g or less, most preferably 8.7 mmol / g or less, and particularly preferably 8.5 mmol / g or less. That is, it is preferably 4.0 to 13 mmol / g, more preferably 5.0 to 12 mmol / g, even more preferably 6.0 to 11 mmol / g, still more preferably 6.5 to 10 mmol / g, particularly preferably 7.0 to 9.0 mmol / g, most preferably 7.5 to 8.7 mmol / g, and particularly preferably 7.5 to 8.5 mmol / g. When the ester bond concentration is within the above range, the polyester (A) has a low viscosity and is excellent in coatability, and further, when made into a pressure-sensitive adhesive, the pressure-sensitive adhesive has excellent adhesive strength and holding power.

[0067] The ester bond concentration (mmol / g) refers to the number of moles of ester groups in 1 g of polyester (A), and can be calculated, for example, from the amounts charged. The calculation method is to divide the number of moles of the polycarboxylic acids (a1) and the polyhydric alcohols (a2), whichever is charged less frequently, by the total weight of the finished product, and an example of the calculation formula is shown below. When the polycarboxylic acids (a1) and the polyhydric alcohols (a2) are charged in equal molar amounts, either of the following calculation formulas may be used. When polyester is produced from a monomer having both a carboxyl group and a hydroxyl group, or from caprolactone, the calculation method will be changed as appropriate.

[0068] <When the amount of polycarboxylic acids (a1) is small> Ester bond concentration (mmol / g) = [(X1 / x1 × m1 + X2 / x2 × m2 + X3 / x3 × m3 ...) / Z] × 1000, where X: amount of polycarboxylic acids (a1) charged (g), x: molecular weight of polycarboxylic acids (a1), m: number of carboxy groups per molecule of polycarboxylic acids (a1), and Z: finished weight (g).

[0069] <When the amount of polyhydric alcohols (a2) is small> Ester bond concentration (mmol / g) = [(Y1 / y1 × n1 + Y2 / y2 × n2 + Y3 / y3 × n3 ...) / Z] × 1000, where Y: amount of polyhydric alcohols (a2) charged (g), y: molecular weight of polyhydric alcohols (a2), n: number of hydroxyl groups per molecule of polyhydric alcohols (a2), and Z: finished weight (g).

[0070] To adjust the ester bond concentration within the above range, for example, a method of adjusting the component ratio of the polycarboxylic acid (a1) and the polyhydric alcohol (a2) can be mentioned. The ester bond concentration can also be measured by a known method using NMR or the like. For example, the ester bond concentration, composition and composition ratio of the polyester (A) can be determined by using a resonance frequency of 400 MHz. 1 H-NMR measurement (proton nuclear magnetic resonance spectroscopy), 13 This can be measured by C-NMR (carbon-type nuclear magnetic resonance spectroscopy).

[0071] The hydroxyl value of the polyester (A) is usually 5 mgKOH / g or more, preferably 10 mgKOH / g or more, more preferably 15 mgKOH / g or more, even more preferably 20 mgKOH / g or more, particularly preferably 25 mgKOH / g or more, and most preferably 30 mgKOH / g or more, and is usually 250 mgKOH / g or less, preferably 200 mgKOH / g or less, more preferably 150 mgKOH / g or less, even more preferably 100 mgKOH / g or less, particularly preferably 80 mgKOH / g or less, and most preferably 60 mgKOH / g or less. That is, it is usually 5 to 250 mgKOH / g, preferably 10 to 200 mgKOH / g, more preferably 15 to 150 mgKOH / g, even more preferably 20 to 100 mgKOH / g, particularly preferably 25 to 80 mgKOH / g, and most preferably 30 to 60 mgKOH / g. When the hydroxyl value is within the above range, the crosslinking agent (B) reacts with the crosslinking agent (B) to form an appropriate crosslink density, and the resulting pressure-sensitive adhesive tends to have excellent adhesive strength, holding power, and coating suitability. The hydroxyl value can be determined by neutralization titration in accordance with JIS K 0070.

[0072] The hydroxyl value of the polyester (A) relative to the ester bond concentration of the polyester (A) (hydroxyl value / ester bond concentration) is preferably 4.27 or more, more preferably 5.00 or more, even more preferably 7.00 or more, and particularly preferably 9.00 or more. The upper limit is preferably 25.00 or less, more preferably 20.00 or less, even more preferably 18.00 or less, and particularly preferably 15.00 or less, and the range is, for example, 4.27 to 25.00. When the hydroxyl value relative to the ester bond concentration is within the above range, the resulting pressure-sensitive adhesive tends to have excellent adhesive strength.

[0073] The acid value of the polyester (A) is preferably 3 mgKOH / g or less, more preferably 2 mgKOH / g or less, even more preferably 1 mgKOH / g or less, and particularly preferably 0.5 mgKOH / g or less. The lower limit of the acid value is usually 0 mgKOH / g. When the acid value is within this range, the polyester (A) tends to have excellent crosslinkability with the crosslinking agent (B) and to be able to suppress hydrolysis over time. Furthermore, when a hydrolysis inhibitor (C) described below is contained, the polyester (A) tends to be able to suppress reaction with the hydrolysis inhibitor (C) over time, which tends to improve storage stability. The acid value (mgKOH / g) can be determined by dissolving 1 g of polyester (A) in 30 g of a toluene / methanol mixed solvent (e.g., toluene / methanol = 9 / 1 by volume) and neutralization titration according to JIS K 0070. If the polyester (A) cannot be dissolved in the mixed solvent, another solvent can be used as appropriate. In this case, a blank test using only the mixed solvent is also performed. The acid value of the polyester (A) is determined by the content of carboxy groups in the polyester (A).

[0074] The polyester (A) has fluidity at 25°C, and its viscosity at 25°C is 500 to 500,000 mPa·s, preferably 1,000 mPa·s or more, more preferably 2,500 mPa·s or more, even more preferably 5,000 mPa·s or more, still more preferably 7,500 mPa·s or more, particularly preferably 10,000 mPa·s or more, and most preferably 20,000 mPa·s or more, while it is preferably 300,000 mPa·s or less, more preferably 200,000 mPa·s or less, even more preferably 150,000 mPa·s or less, still more preferably 100,000 mPa·s or less, particularly preferably 75,000 mPa·s or less, and most preferably 60,000 mPa·s or less. That is, the viscosity is preferably 1,000 to 300,000 mPa·s, more preferably 2,500 to 200,000 mPa·s, even more preferably 5,000 to 150,000 mPa·s, even more preferably 7,500 to 100,000 mPa·s, particularly preferably 10,000 to 75,000 mPa·s, and most preferably 20,000 to 60,000 mPa·s. When the viscosity is within the above range, application at room temperature is possible without dilution with an organic solvent, making it possible to produce a solventless pressure-sensitive adhesive. When the viscosity is outside the above range, streaks or orange peel tend to appear in the coating film, resulting in poor appearance and poor coating thickness accuracy. The term "having fluidity" means that the viscosity at 25°C is 500,000 mPa·s or less. Examples of methods for adjusting the viscosity within the above range include a method of producing the polyester (A) only by an esterification reaction and / or a transesterification reaction, a method of adjusting the blending ratio of the polyvalent carboxylic acids (a1) and the polyhydric alcohols (a2), a method of adjusting the glass transition temperature of the polyester (A), a method of adjusting the crystallinity of the polyester (A), etc. The viscosity at 25°C can be determined by measuring the polyester (A) adjusted to 25°C using a B-type viscometer (single-cylindrical rotational viscometer) under the following measurement conditions.[Measurement conditions] Equipment: TVB-10M (manufactured by Toki Sangyo Co., Ltd.) (Condition 1) When the viscosity at 25°C is 500 mPa·s or more and less than 4000 mPa·s, rotor model number M3, rotation speed 30 rpm (Condition 2) When the viscosity at 25°C is 4000 mPa·s or more and less than 40,000 mPa·s, rotor model number M3, rotation speed 3 rpm (Condition 3) When the viscosity at 25°C is 40,000 mPa·s or more and less than 200,000 mPa·s, rotor model number M4, rotation speed 3 rpm (Condition 4) When the viscosity at 25°C is 200,000 mPa·s or more and 1,000,000 mPa·s or less, rotor model number M4, rotation speed 0.6 rpm

[0075] The weight-average molecular weight (Mw) of the polyester (A) is preferably 2,000 or more, more preferably 3,000 or more, even more preferably 3,500 or more, even more preferably 4,000 or more, particularly preferably 4,500 or more, and most preferably 5,000 or more. On the other hand, it is preferably 30,000 or less, more preferably 25,000 or less, even more preferably 20,000 or less, even more preferably 17,500 or less, particularly preferably 15,000 or less, and most preferably 12,500 or less. That is, it is preferably 2,000 to 30,000, more preferably 3,000 to 25,000, even more preferably 350,000 to 20,000, even more preferably 4,000 to 17,500, particularly preferably 4,500 to 15,000, and most preferably 5,000 to 12,500. When the weight-average molecular weight (Mw) is within the above range, the composition tends to have excellent coating suitability at room temperature and excellent adhesive strength and holding power when used as a pressure-sensitive adhesive.

[0076] The number average molecular weight (Mn) of the polyester (A) is usually 20,000 or less, preferably 15,000 or less, more preferably 12,500 or less, even more preferably 10,000 or less, still more preferably 9,000 or less, particularly preferably 8,000 or less, most preferably 6,000 or less, and especially preferably 4,800 or less. The lower limit is usually 500 or more, preferably 1,000 or more, more preferably 1,500 or more, even more preferably 2,000 or more, still more preferably 2,500 or more, particularly preferably 3,000 or more, most preferably 3,300 or more, and especially preferably 3,500 or more. That is, it is usually 500 to 20,000, preferably 1,000 to 15,000, more preferably 1,500 to 12,500, even more preferably 2,000 to 10,000, still more preferably 2,500 to 9,000, particularly preferably 3,000 to 8,000, most preferably 3,300 to 6,000, and especially preferably 3,500 to 4,800. When the number average molecular weight (Mn) is within the above range, the coating suitability at room temperature tends to be excellent, and the adhesive strength and holding power when used as a pressure-sensitive adhesive tend to be excellent.

[0077] The polydispersity [weight average molecular weight (Mw) / number average molecular weight (Mn)] of the polyester (A) is usually 1.0 or more, preferably 1.2 or more, more preferably 1.4 or more, even more preferably 1.6 or more, particularly preferably 1.8 or more, and most preferably 2.0 or more. On the other hand, it is usually 5.0 or less, preferably 4.0 or less, more preferably 3.0 or less, even more preferably 2.8 or less, particularly preferably 2.6 or less, and most preferably 2.4 or less. That is, it is usually 1.0 to 5.0, preferably 1.2 to 4.0, more preferably 1.4 to 3.0, even more preferably 1.6 to 2.8, particularly preferably 1.8 to 2.6, and most preferably 2.0 to 2.4. When the polydispersity is within the above range, the polyester (A) tends to have excellent coatability at room temperature and excellent adhesive strength and holding power when used as a pressure-sensitive adhesive.

[0078] The weight average molecular weight (Mw) and number average molecular weight (Mn) were measured as follows: The weight average molecular weight (Mw) and number average molecular weight (Mn) were measured using a high performance liquid chromatograph (Waters 2695 (main body) and Waters 2414 (detector) manufactured by Waters Japan) equipped with a Shodex GPC KF-806L column (exclusion limit molecular weight: 2 × 10 7 Separation range: 100 to 2 x 10 7 The molecular weight of the filler can be calculated by measuring three columns in series (theoretical plate number: 10,000 columns / column, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm) and converting it into the molecular weight of standard polystyrene.

[0079] The glass transition temperature (Tg) of the polyester (A) is usually 15°C or lower, preferably 0°C or lower, more preferably -15°C or lower, even more preferably -30°C or lower, even more preferably -40°C or lower, particularly preferably -50°C or lower, and most preferably -55°C or lower. The lower limit is usually -90°C or higher, preferably -85°C or higher, more preferably -80°C or higher, even more preferably -75°C or higher, even more preferably -70°C or higher, particularly preferably -68°C or higher, and most preferably -65°C or higher. That is, it is usually -90 to 15°C, preferably -85 to 0°C, more preferably -80 to -15°C, even more preferably -75 to -30°C, even more preferably -70 to -40°C, particularly preferably -68 to -50°C, and most preferably -65 to -55°C. When the glass transition temperature (Tg) is within the above range, the adhesive properties tend to be excellent when used as a pressure-sensitive adhesive.

[0080] The heat of crystalline fusion of the polyester (A) is preferably 50 J / g or less, more preferably 30 J / g or less, even more preferably 10 J / g or less, particularly preferably 5 J / g or less, most preferably 3 J / g, and particularly preferably 0 J / g. When the heat of crystalline fusion is within the above range, the pressure-sensitive adhesive tends to have excellent adhesive strength, tackiness, and coatability when used as a pressure-sensitive adhesive.

[0081] The melting point (Tm) of the polyester (A) is usually 50° C. or lower, preferably 30° C. or lower, more preferably 10° C. or lower, even more preferably −10° C. or lower, particularly preferably −20° C. or lower, and most preferably −30° C. or lower, and it is particularly preferable that the polyester (A) does not exhibit a melting point. When the melting point is within the above range, the adhesive strength, tackiness, coatability, and storage stability when used as a pressure-sensitive adhesive tend to be excellent.

[0082] The glass transition temperature (Tg), heat of crystalline fusion, and melting point (Tm) are measured as follows. The glass transition temperature (Tg), heat of crystalline fusion, and melting point (Tm) can be determined by taking about 5 mg of polyester (A) that has been left to stand for 7 days in an environment of 23°C and 50% RH and measuring it using a differential scanning calorimeter. The measurement conditions for the differential scanning calorimeter are a measurement temperature range of -90 to 200°C and a temperature rise rate of 10°C / min.

[0083] The urethane bond concentration of the polyester (A) is preferably 5 mmol / g or less, more preferably 3 mmol / g or less, even more preferably 1 mmol / g or less, and particularly preferably 0 mmol / g. When the urethane bond concentration is within the above range, the polyester (A) tends to have excellent adhesive strength, tackiness, and coatability. The urethane bond concentration is a value calculated from the proportion of urethane bonds [—NHC(═O)O—] contained in the polyester (A).

[0084] The polyester (A) is preferably made from plant-derived raw materials and has a biomass degree in order to reduce the burden on the global environment. The biomass degree of the polyester (A) is preferably 10% or more, more preferably 20% or more, even more preferably 30% or more, particularly preferably 40% or more, most preferably 50% or more, and particularly preferably 60% or more. The upper limit is 100%. If the biomass degree is low, the reduction in the burden on the global environment tends to be insufficient.

[0085] Here, the biomass degree of the polyester (A) refers to the mass ratio of the plant-derived raw materials used in producing the polyester (A) incorporated into the resin relative to the total mass of the polyester (A), and is calculated as follows. The biomass degrees of the polycarboxylic acids (a1) and polyhydric alcohols (a2) are determined as weighted averages of their respective biomass degrees. It is sufficient for the value obtained by any of the following calculation methods to be within the above-mentioned range.

[0086] (Calculation Method) Biomass Degree (%) = [(Number of moles of carbon of plant-derived monomer calculated from the molar ratio of polycarboxylic acids (a1) and polyhydric alcohols (a2) in polyester (A)) / (Number of moles of carbon of all constituent monomers in polyester (A))] × 100. The biomass degree can also be determined by analyzing the composition ratio by NMR and calculating the number of carbon atoms in the plant-derived monomer / the total number of carbon atoms. Furthermore, the biomass degree can also be measured by the method described in "Technology for Determining the Origin of Biofuels Using Natural Radioactive Carbon C-14" published in Tokyo Metropolitan Industrial Technology Research Institute Research Report, No. 4, 2009.

[0087] The content of the polyester (A) relative to the pressure-sensitive adhesive composition is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 75% by mass or more, most preferably 80% by mass or more, and especially preferably 85% by mass or more. When the content of the polyester (A) is within the above range, the effects of the present invention tend to be more pronounced.

[0088] <Crosslinking agent (B)> The present pressure-sensitive adhesive composition preferably contains a crosslinking agent (B). By containing the crosslinking agent (B), the polyester (A) is crosslinked, resulting in excellent cohesive strength, and the performance as a pressure-sensitive adhesive tends to be improved.

[0089] The crosslinking agent (B) may be any compound containing a functional group reactive with a functional group such as a hydroxyl group or a carboxyl group contained in the polyester (A), and examples thereof include polyisocyanate compounds and epoxy compounds. These may be used alone or in combination of two or more. Among these, polyisocyanate compounds are preferred from the viewpoints of excellent adhesive properties, pot life, and crosslinking properties.

[0090] Examples of the polyisocyanate compound include aromatic isocyanate compounds such as tolylene diisocyanate compounds such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, xylylene diisocyanate compounds such as 1,3-xylylene diisocyanate, diphenylmethane-4,4-diisocyanate and polymethylene polyphenyl polyisocyanate, and naphthalene diisocyanate compounds such as 1,5-naphthalene diisocyanate; alicyclic isocyanate compounds such as isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, isopropylidenedicyclohexyl-4,4'-diisocyanate, 1,3-diisocyanatomethylcyclohexane, and norbornane diisocyanate; Aliphatic isocyanate compounds such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; adducts, biuret compounds, isocyanurates, etc. of the above isocyanate compounds. The polyisocyanate compounds may also be those in which the isocyanate moiety is blocked with phenol, lactam, etc. Among these, aromatic isocyanate compounds and aliphatic isocyanate compounds are preferred from the viewpoint of excellent adhesive properties and coating suitability, and aromatic isocyanate compounds are more preferred from the viewpoint of excellent interaction with the polyester (A).Preferred examples of the aliphatic isocyanate compound and aromatic isocyanate compound include an isocyanurate of hexamethylene diisocyanate, an adduct of 2,4-tolylene diisocyanate and / or 2,6-tolylene diisocyanate with trimethylolpropane, an isocyanurate of 2,4-tolylene diisocyanate and / or 2,6-tolylene diisocyanate, an adduct of tetramethylxylylene diisocyanate with trimethylolpropane, and polymethylene polyphenyl polyisocyanate, more preferred are an isocyanurate of hexamethylene diisocyanate, an adduct of 2,4-tolylene diisocyanate and / or 2,6-tolylene diisocyanate with trimethylolpropane, and polymethylene polyphenyl isocyanate, and particularly preferred are an adduct of 2,4-tolylene diisocyanate and / or 2,6-tolylene diisocyanate with trimethylolpropane.

[0091] The content of the crosslinking agent (B) relative to 100 parts by mass of the polyester (A) is usually 0.1 parts by mass or more, preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, even more preferably 4 parts by mass or more, particularly preferably 5 parts by mass or more, and most preferably 6 parts by mass or more, while it is usually 50 parts by mass or less, preferably 40 parts by mass or less, more preferably 35 parts by mass or less, even more preferably 30 parts by mass or less, even more preferably 25 parts by mass or less, particularly preferably 20 parts by mass or less, and most preferably 15 parts by mass or less. That is, it is usually 0.1 to 50 parts by mass, preferably 1 to 40 parts by mass, more preferably 2 to 35 parts by mass, even more preferably 3 to 30 parts by mass, even more preferably 4 to 25 parts by mass, particularly preferably 5 to 20 parts by mass, and most preferably 6 to 15 parts by mass. When the content of the crosslinking agent (B) is within the above range, the urethane bond concentration of the pressure-sensitive adhesive composition becomes appropriate, the polyester (A) can be crosslinked to an appropriate crosslinking density, and the pressure-sensitive adhesive composition tends to have excellent adhesive strength, tackiness, cohesion, and coatability, resulting in adhesive properties that are equal to or better than those of conventional solvent-based pressure-sensitive adhesives.

[0092] Furthermore, when the crosslinking agent (B) is a polyisocyanate compound, the equivalent of the isocyanate group of the crosslinking agent (B) relative to 1 equivalent of the hydroxyl group contained in the polyester (A) [functional group molar ratio (NCO / OH)] is preferably 0.01 equivalents or more, more preferably 0.1 equivalents or more, even more preferably 0.2 equivalents or more, even more preferably 0.3 equivalents or more, particularly preferably 0.4 equivalents or more, and most preferably 0.5 equivalents or more, while it is preferably 2 equivalents or less, more preferably 1.5 equivalents or less, even more preferably 1.1 equivalents or less, even more preferably 0.9 equivalents or less, particularly preferably 0.7 equivalents or less, and most preferably 0.6 equivalents or less. That is, it is preferably 0.01 to 2 equivalents, more preferably 0.1 to 1.5 equivalents, even more preferably 0.2 to 1.1 equivalents, even more preferably 0.3 to 0.9 equivalents, particularly preferably 0.4 to 0.7 equivalents, and most preferably 0.5 to 0.6 equivalents. When the functional group molar ratio of the polyester (A) to the crosslinking agent (B) is within the above range, the polyester (A) can be crosslinked to an appropriate crosslinking density, and the adhesive strength, tackiness, cohesive strength, and coatability are excellent, so that adhesive properties equivalent to or better than those of conventional solvent-based adhesives tend to be achieved.

[0093] [Hydrolysis Inhibitor (C)] The present pressure-sensitive adhesive composition preferably further contains a hydrolysis inhibitor (C) in terms of adhesive strength, substrate adhesion, and wet heat durability. The hydrolysis inhibitor (C) is not particularly limited, and conventionally known compounds can be used, for example, compounds that react with and bond to the carboxyl end group of the polyester (A), specifically compounds having functional groups such as carbodiimide groups, epoxy groups, and oxazoline groups. Among these, carbodiimide group-containing compounds are preferred in terms of their compatibility with the polyester (A), excellent adhesive strength, and excellent reactivity with the carboxyl group.

[0094] [Carbodiimide Group-Containing Compound] The carbodiimide group-containing compound may typically be a known carbodiimide having one or more carbodiimide groups (—N═C═N—) in the molecule, and examples thereof include a monomeric carbodiimide compound having one carbodiimide group in the molecule and a polymeric carbodiimide compound having at least two carbodiimide groups in the molecule. Among these, a monomeric carbodiimide compound having one carbodiimide group in the molecule is preferred in terms of excellent compatibility with the polyester (A), adhesive strength, storage stability, and wet heat durability.

[0095] The carbodiimide equivalent of the carbodiimide group-containing compound is preferably 50 or more, more preferably 100 or more, and even more preferably 150 or more, and is preferably 10,000 or less, more preferably 1,000 or less, and even more preferably 500 or less. That is, it is preferably 50 to 10,000, particularly preferably 100 to 1,000, and even more preferably 150 to 500. The carbodiimide equivalent indicates the chemical formula weight per carbodiimide group.

[0096] Examples of the monomeric carbodiimide compound include dicyclohexylcarbodiimide, diisopropylcarbodiimide, diphenylcarbodiimide, bis(methylphenyl)carbodiimide, bis(methoxyphenyl)carbodiimide, bis(nitrophenyl)carbodiimide, bis(dimethylphenyl)carbodiimide, bis(diisopropylphenyl)carbodiimide, bis(di-t-butylphenyl)carbodiimide, N-ethyl-N'-(3-dimethylaminopropyl)carbodiimide, bis(triphenylsilyl)carbodiimide, cyclic carbodiimide, etc. These may be used alone or in combination of two or more. Among these, diisopropylcarbodiimide, bis(methoxyphenyl)carbodiimide, bis(diisopropylphenyl)carbodiimide, N-ethyl-N'-(3-dimethylaminopropyl)carbodiimide, and bis(triphenylsilyl)carbodiimide are preferred, and bis(diisopropylphenyl)carbodiimide is preferred in terms of excellent reactivity with the carboxy group of the polyester (A), compatibility, storage stability, wet heat durability, and substrate adhesion.

[0097] Examples of the polymeric carbodiimide compound include those obtained by a decarboxylation condensation reaction of the following diisocyanates. Examples of such diisocyanates include 4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 3,3'-dimethyl-4,4'-diphenylether diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and tetramethylxylylene diisocyanate. These may be used alone or in combination of two or more.

[0098] [Epoxy Group-Containing Compound] Examples of the epoxy group-containing compound include glycidyl ester compounds and glycidyl ether compounds.

[0099] Examples of the glycidyl ester compounds include benzoic acid glycidyl ester, t-Bu-benzoic acid glycidyl ester, p-toluic acid glycidyl ester, cyclohexanecarboxylic acid glycidyl ester, pelargonic acid glycidyl ester, stearic acid glycidyl ester, lauric acid glycidyl ester, palmitic acid glycidyl ester, behenic acid glycidyl ester, versatic acid glycidyl ester, oleic acid glycidyl ester, linoleic acid glycidyl ester, linolenic acid glycidyl ester, behenolic acid glycidyl ester, stearolic acid glycidyl ester, and terephthalic acid diglycidyl ester. ester, isophthalic acid diglycidyl ester, phthalic acid diglycidyl ester, naphthalenedicarboxylic acid diglycidyl ester, methyl terephthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, cyclohexanedicarboxylic acid diglycidyl ester, adipic acid diglycidyl ester, succinic acid diglycidyl ester, sebacic acid diglycidyl ester, dodecanedioic acid diglycidyl ester, octadecanedicarboxylic acid diglycidyl ester, trimellitic acid triglycidyl ester, pyromellitic acid tetraglycidyl ester, etc. These may be used alone or in combination of two or more.

[0100] Examples of the glycidyl ether compound include phenyl glycidyl ether, o-phenyl glycidyl ether, 1,4-bis(β,γ-epoxypropoxy)butane, 1,6-bis(β,γ-epoxypropoxy)hexane, 1,4-bis(β,γ-epoxypropoxy)benzene, 1-(β,γ-epoxypropoxy)-2-ethoxyethane, 1-(β,γ-epoxypropoxy)-2-benzyloxyethane, 2,2-bis-[p-(β,γ-epoxypropoxy)phenyl]propane, and bisglycidyl polyethers obtained by reacting bisphenols such as 2,2-bis-(4-hydroxyphenyl)propane and 2,2-bis-(4-hydroxyphenyl)methane with epichlorohydrin. These compounds may be used alone or in combination of two or more.

[0101] [Oxazoline Group-Containing Compound] Examples of the oxazoline group-containing compound include bisoxazoline compounds. Specific examples include 2,2'-bis(2-oxazoline), 2,2'-bis(4-methyl-2-oxazoline), 2,2'-bis(4,4-dimethyl-2-oxazoline), 2,2'-bis(4-ethyl-2-oxazoline), 2,2'-bis(4,4'-diethyl-2-oxazoline), 2,2'-bis(4-propyl-2-oxazoline), 2,2'-bis(4-butyl-2-oxazoline), 2,2'-bis(4- 2,2'-bis(4-phenyl-2-oxazoline), 2,2'-bis(4-cyclohexyl-2-oxazoline), 2,2'-bis(4-benzyl-2-oxazoline), 2,2'-p-phenylenebis(2-oxazoline), 2,2'-m-phenylenebis(2-oxazoline), 2,2'-o-phenylenebis(2-oxazoline), 2,2'-p-phenylenebis(4-methyl-2 -oxazoline), 2,2'-p-phenylenebis(4,4-dimethyl-2-oxazoline), 2,2'-m-phenylenebis(4-methyl-2-oxazoline), 2,2'-m-phenylenebis(4,4-dimethyl-2-oxazoline), 2,2'-ethylenebis(2-oxazoline), 2,2'-tetramethylenebis(2-oxazoline), 2,2'-hexamethylenebis(2-oxazoline), 2,2'-octamethyl Examples of suitable oxazoline include 2,2'-dimethyl-2-oxazoline, 2,2'-tetramethylenebis(4,4-dimethyl-2-oxazoline), 2,2'-9,9'-diphenoxyethanebis(2-oxazoline), 2,2'-cyclohexylenebis(2-oxazoline), and 2,2'-diphenylenebis(2-oxazoline). These may be used alone or in combination of two or more. Of these, 2,2'-bis(2-oxazoline) is most preferred from the viewpoint of reactivity with the polyester (A).

[0102] When the present pressure-sensitive adhesive composition contains a hydrolysis inhibitor (C), the content thereof is typically 0.01 part by mass or more, preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, and even more preferably 0.3 part by mass or more, relative to 100 parts by mass of the polyester (A), and is typically 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 2 parts by mass or less. That is, the content is typically 0.01 to 10 parts by mass, preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass, and even more preferably 0.3 to 2 parts by mass. When the content of the hydrolysis inhibitor (C) is within the above range, the present pressure-sensitive adhesive composition tends to have excellent adhesive strength, moist heat durability, crosslinkability, and transparency.

[0103] The content of the hydrolysis inhibitor (C) is preferably optimized depending on the acid value of the polyester (A), and the molar ratio [(ii) / (i)] of the number of carboxy groups (i) determined by the acid value of the polyester (A) in the pressure-sensitive adhesive composition to the total amount of functional groups (ii) of the hydrolysis inhibitor (C) in the pressure-sensitive adhesive composition is preferably 0.5≦(ii) / (i), more preferably 1≦(ii) / (i)≦1000, even more preferably 2≦(ii) / (i)≦100, still more preferably 3≦(ii) / (i)≦50, particularly preferably 4≦(ii) / (i)≦30, and most preferably 5≦(ii) / (i)≦15. When the content ratio of (ii) to (i) is within the above range, the pressure-sensitive adhesive composition tends to be excellent in adhesive strength, moist heat durability, crosslinkability, and transparency.

[0104] <Catalyst (D)> The present pressure-sensitive adhesive composition preferably contains a catalyst (D) to promote the reaction between the polyester (A) and the crosslinking agent (B). In particular, when the crosslinking agent (B) is a polyisocyanate compound, it preferably contains the catalyst (D).

[0105] Examples of the catalyst (D) include organometallic compounds, tertiary amine compounds, etc. These may be used alone or in combination of two or more.

[0106] Examples of the organometallic compounds include zirconium compounds, iron compounds, tin compounds, titanium compounds, lead compounds, cobalt compounds, and zinc compounds.

[0107] Examples of the zirconium-based compounds include zirconium naphthenate and zirconium acetylacetonate. Examples of the iron-based compounds include iron acetylacetonate and iron 2-ethylhexanoate. Examples of the tin-based compounds include dibutyltin dichloride, dibutyltin oxide, and dibutyltin dilaurate. Examples of the titanium-based compounds include dibutyltitanium dichloride, tetrabutyl titanate, and butoxytitanium trichloride. Examples of the lead-based compounds include lead oleate, lead 2-ethylhexanoate, lead benzoate, and lead naphthenate. Examples of the cobalt-based compounds include cobalt 2-ethylhexanoate and cobalt benzoate. Examples of the zinc-based compounds include zinc naphthenate and zinc 2-ethylhexanoate.

[0108] Examples of the tertiary amine compound include triethylamine, triethylenediamine, and 1,8-diazabicyclo-(5,4,0)-undecene-7.

[0109] Among these catalysts (D), organometallic compounds are preferred in terms of reaction rate and pot life, more preferably iron compounds and tin compounds, and particularly preferably iron acetylacetonate and dibutyltin dilaurate.

[0110] When the pressure-sensitive adhesive composition contains catalyst (D), the content thereof is usually 0.0001 part by mass or more, preferably 0.0005 part by mass or more, more preferably 0.001 part by mass or more, and is usually 1 part by mass or less, preferably 0.5 part by mass or less, more preferably 0.01 part by mass or less, relative to 100 parts by mass of polyester (A). That is, the content is usually 0.0001 to 1 part by mass, preferably 0.0005 to 0.5 parts by mass, more preferably 0.001 to 0.01 part by mass. When the content of catalyst (D) is within the above range, the reaction rate with polyester (A) and the pot life tend to be excellent.

[0111] <Antioxidant (E)> The present pressure-sensitive adhesive composition may contain an antioxidant (E) in order to improve stability.

[0112] Examples of the antioxidant (E) include hindered phenol-based antioxidants, amine-based antioxidants, sulfur-based antioxidants, and phosphoric acid-based antioxidants. These may be used alone or in combination of two or more. Among these, hindered phenol-based antioxidants, amine-based antioxidants, and phosphoric acid-based antioxidants are preferred, and hindered phenol-based compounds are more preferred.

[0113] Examples of the hindered phenol-based antioxidant include antioxidants having a hindered phenol structure in which a group with large steric hindrance, such as a tertiary butyl group, is bonded to at least one of the carbon atoms adjacent to the carbon atom on the aromatic ring to which the phenolic hydroxyl group is bonded.

[0114] When the pressure-sensitive adhesive composition contains an antioxidant (E), the content thereof is usually 0.01 part by mass or more, preferably 0.03 part by mass or more, more preferably 0.05 part by mass or more, and particularly preferably 0.1 part by mass or more, relative to 100 parts by mass of the polyester (A), and is usually 10 parts by mass or less, preferably 7.5 parts by mass or less, more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less. That is, the content is usually 0.01 to 10 parts by mass, preferably 0.03 to 7.5 parts by mass, more preferably 0.05 to 5 parts by mass, and particularly preferably 0.1 to 3 parts by mass.

[0115] <Crosslinking Retarder> The present pressure-sensitive adhesive composition may contain a crosslinking retarder in order to extend the pot life when the polyester (A) and the crosslinking agent (B) are mixed.

[0116] The crosslinking retarder is not particularly limited, and conventionally known compounds can be used. Among these, keto-enol tautomeric compounds are preferred. Examples of the keto-enol tautomeric compounds include various β-dicarbonyl compounds. Examples of the β-dicarbonyl compounds include β-diketones such as acetylacetone and 2,4-hexanedione, acetoacetate esters such as methyl acetoacetate and ethyl acetoacetate, propionyl acetate esters such as ethyl propionyl acetate, isobutyryl acetate esters such as ethyl isobutyryl acetate, and malonate esters such as methyl malonate and ethyl malonate. These compounds may be used alone or in combination of two or more. Among these, acetylacetone and acetoacetate esters are preferred because of their excellent crosslinking retardation effect.

[0117] The content of the crosslinking retarder is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more, relative to 100 parts by mass of the polyester (A). The amount used is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, particularly preferably 15 parts by mass or less, and most preferably 10 parts by mass or less. That is, the content is preferably 0.1 to 50 parts by mass, more preferably 0.5 to 30 parts by mass, even more preferably 1 to 20 parts by mass, particularly preferably 3 to 15 parts by mass, and most preferably 5 to 10 parts by mass. A content of the crosslinking retarder within the above range is preferable in that it provides excellent coating suitability while allowing the crosslinking retarder to be volatilized by simple heat treatment.

[0118] <Tackifying Resin> The present pressure-sensitive adhesive composition may contain a tackifying resin, which can improve adhesive properties such as adhesive strength, holding power, and tackiness.

[0119] The tackifying resin is not particularly limited, and conventionally known resins can be used. Examples of the tackifying resin include hydrocarbon-based resins, terpene-based resins, phenol-based resins, rosin-based resins, xylene-based resins, epoxy-based resins, polyamide-based resins, ketone-based resins, and elastomer-based resins. These may be used alone or in combination of two or more. Among them, hydrocarbon-based resins and terpene-based resins are preferred because they have excellent compatibility with the polyester (A), adhesive strength, and substrate adhesion, and hydrocarbon-based resins are more preferred because they do not inhibit the reaction between the polyester (A) and the crosslinking agent (B) and have excellent crosslinking properties.

[0120] Examples of the hydrocarbon resin include various hydrocarbon resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic / alicyclic petroleum resins, hydrogenated aromatic hydrocarbon resins, hydrogenated aliphatic hydrocarbon resins, coumarone resins, and coumarone-indene resins. Of these, aromatic hydrocarbon resins and hydrogenated aromatic hydrocarbon resins are preferred because of their excellent tackiness and heat resistance.

[0121] Examples of the terpene resin include terpene resin, terpene phenol resin, aromatic-modified terpene resin, etc. Specific examples include α-pinene polymer, β-pinene polymer, dipentene polymer, and terpene resins obtained by phenol-modifying, aromatic-modifying, hydrogenation-modifying, or hydrocarbon-modifying these polymers. Among these, terpene phenol resin is preferred because of its excellent compatibility with the polyester (A), tackiness, and adhesive strength.

[0122] Examples of the phenolic resin that can be used include condensates of formaldehyde with various phenols such as phenol, m-cresol, 3,5-xylenol, p-alkylphenol, and resorcinol. Furthermore, resols obtained by subjecting the phenols and formaldehyde to an addition reaction in the presence of an alkali catalyst, novolaks obtained by subjecting the phenols and formaldehyde to a condensation reaction in the presence of an acid catalyst, and rosin-modified phenolic resins obtained by subjecting rosins such as unmodified or modified rosin or derivatives thereof to addition with phenol in the presence of an acid catalyst, followed by thermal polymerization.

[0123] Examples of the rosin-based resin include rosin resin, polymerized rosin resin, hydrogenated rosin resin, rosin ester resin, hydrogenated rosin ester resin, rosin phenol resin, and polymerized rosin ester. Specific examples of the rosin resin that can be used include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin, modified rosins obtained by hydrogenating, disproportionating, polymerizing, or otherwise chemically modifying these, and derivatives of these.

[0124] From the viewpoint of wet heat durability and storage stability, the acid value of the tackifier resin is usually 30 mgKOH / g or less, more preferably 15 mgKOH / g or less, even more preferably 10 mgKOH / g or less, particularly preferably 6 mgKOH / g or less, most preferably 3 mgKOH / g or less, and especially preferably 1 mgKOH / g or less. When multiple types of tackifier resins are used in combination, the average of their acid values ​​is preferably within the above range.

[0125] The softening point of the tackifier resin (measured, for example, by the ring and ball method) is preferably 20°C or higher, more preferably 30°C or higher, even more preferably 40°C or higher, even more preferably 45°C or higher, particularly preferably 50°C or higher, and most preferably 60°C or higher, while it is preferably 180°C or lower, more preferably 160°C or lower, even more preferably 140°C or lower, even more preferably 130°C or lower, particularly preferably 120°C or lower, and most preferably 110°C or lower. That is, it is preferably 20 to 180°C, more preferably 30 to 160°C, even more preferably 40 to 140°C, even more preferably 45 to 130°C, particularly preferably 50 to 120°C, and most preferably 60 to 110°C. When the softening point is within the above range, adhesive strength, holding power, tackiness, and coatability can be improved, which is preferable.

[0126] In the present invention, the tackifier resin is preferably derived from plants, as it places less strain on the global environment. Examples of plant-derived tackifier resins include terpene resins and rosin resins.

[0127] When a tackifier resin is used, its content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, particularly preferably 15 parts by mass or less, and most preferably 10 parts by mass or less, relative to 100 parts by mass of the polyester (A); on the other hand, it is more preferably 0.1 parts by mass or more, even more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, particularly preferably 3 parts by mass or more, and most preferably 4 parts by mass or more. That is, it is preferably 50 parts by mass or less, more preferably 0.1 to 40 parts by mass, even more preferably 1 to 30 parts by mass, even more preferably 2 to 20 parts by mass, particularly preferably 3 to 15 parts by mass, and most preferably 4 to 10 parts by mass. When the content is within the above range, adhesive strength, holding power, and tackiness can be improved, which is preferable; if the content is too high, adhesive strength, tackiness, and coatability tend to be poor.

[0128] <Organic Solvent> The present pressure-sensitive adhesive composition is a solvent-free type that has a small environmental impact. However, an organic solvent may be blended in the present pressure-sensitive adhesive composition to appropriately adjust the viscosity of the composition and to facilitate handling when forming a coating film.

[0129] Examples of the organic solvent include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as ethyl acetate; ethers such as ethylene glycol monomethyl ether; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; alcohols such as methanol and ethanol; alkanes such as hexane and cyclohexane; and aromatics such as toluene and xylene. Among these, ketones and esters are preferred in terms of VOC emission regulations and their low boiling points and excellent drying efficiency, with methyl ethyl ketone, cyclohexanone, and ethyl acetate being particularly preferred, and methyl ethyl ketone and ethyl acetate being even more preferred. The organic solvents listed above may be used alone, or two or more may be mixed in any combination and ratio.

[0130] When the pressure-sensitive adhesive composition contains an organic solvent, the content of the organic solvent relative to the total amount of the pressure-sensitive adhesive composition (including the organic solvent) is preferably 10% by mass or less, more preferably less than 10% by mass, even more preferably 5% by mass or less, particularly preferably 3% by mass or less, even more preferably 1% by mass or less, and most preferably 0.5% by mass or less. The lower limit is 0% by mass, and it is particularly preferable that no organic solvent is contained. The range of the content of the organic solvent is, for example, 0% by mass or more and 10% by mass or less. If the content of the organic solvent is too high, the amount of energy required to volatilize the organic solvent increases, which tends to increase the environmental load.

[0131] In addition to the polyester (A), crosslinking agent (B), hydrolysis inhibitor (C), catalyst (D), antioxidant (E), etc., the present pressure-sensitive adhesive composition may contain additives such as softeners, UV absorbers, stabilizers, antistatic agents, silane coupling agents, inorganic or organic fillers, powders or particles such as metal powders or pigments, within a range that does not impair the effects of the present invention (for example, 10 mass % or less of the present pressure-sensitive adhesive composition, preferably 5 mass % or less). These may be used alone or in combination of two or more.

[0132] In addition to the additives, the present pressure-sensitive adhesive composition may also contain small amounts of impurities contained in the raw materials for producing the components of the present pressure-sensitive adhesive composition.

[0133] The pressure-sensitive adhesive composition can be obtained, for example, by preparing the polyester (A), the crosslinking agent (B), and, if necessary, optional components such as a hydrolysis inhibitor (C), a catalyst (D), an antioxidant (E), and additives, and mixing them with the polyester (A). In this case, since the polyester (A) has a low viscosity, it is possible to mix the crosslinking agent (B) and the like without diluting it with an organic solvent.

[0134] The pressure-sensitive adhesive composition is then crosslinked (cured) to obtain a pressure-sensitive adhesive according to one embodiment of the present invention (hereinafter referred to as "the pressure-sensitive adhesive"). In other words, the pressure-sensitive adhesive is a cured product of the pressure-sensitive adhesive composition.

[0135] Furthermore, a pressure-sensitive adhesive sheet according to one embodiment of the present invention (hereinafter referred to as "the pressure-sensitive adhesive sheet") contains the pressure-sensitive adhesive, and preferably has a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive. The pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one or both sides of a substrate, or may be a substrate-less double-sided pressure-sensitive adhesive sheet that has only a pressure-sensitive adhesive layer and no substrate.

[0136] The present pressure-sensitive adhesive sheet can be produced according to a known general method for producing a pressure-sensitive adhesive sheet. For example, the present pressure-sensitive adhesive composition is applied to one side of a substrate, dried, and cured to form a pressure-sensitive adhesive layer, and a release sheet is attached to the surface (the side opposite to the side that contacts the substrate) and cured as necessary to obtain a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one side of the substrate.

[0137] In another manufacturing method, for example, the present pressure-sensitive adhesive composition is applied onto a release sheet, dried, and cured to form a pressure-sensitive adhesive layer, and a substrate is attached to the surface (the surface opposite to the surface that contacts the release sheet) and cured as necessary, thereby obtaining a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one surface of the substrate.

[0138] Furthermore, by forming pressure-sensitive adhesive layers on both sides of the substrate by the above-mentioned method, a pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of the substrate can be obtained.

[0139] When the PSA sheet is a substrateless double-sided PSA sheet of the substrateless type, it can be obtained, for example, by forming a PSA layer on a release sheet by the method described above, and then laminating the release sheet and another release sheet to the surface of the PSA layer (the surface opposite to the surface that contacts the release sheet).

[0140] When using the obtained pressure-sensitive adhesive sheet or substrate-less double-sided pressure-sensitive adhesive sheet, the release sheet may be peeled off from the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer may be attached to an adherend.

[0141] The pressure-sensitive adhesive composition can be applied by any known method, for example, a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, comma coater, etc.

[0142] After application of the pressure-sensitive adhesive composition, it may be subjected to a heat treatment to promote the crosslinking reaction. Heat treatment conditions include a temperature of preferably 60°C or higher, particularly preferably 80°C or higher, and preferably 140°C or lower, particularly preferably 120°C or lower. That is, 60 to 140°C is preferred, and 80 to 120°C is particularly preferred. Furthermore, the heat treatment time is preferably 0.5 minutes or longer, particularly preferably 1 minute or longer, and preferably 30 minutes or shorter, particularly preferably 5 minutes or shorter. That is, 0.5 to 30 minutes is preferred, and 1 to 5 minutes is particularly preferred.

[0143] The curing conditions are generally room temperature (23°C) to 70°C, and the curing time is generally 1 to 30 days. Specifically, the curing may be performed under conditions such as 23°C for 1 to 20 days, preferably 23°C for 3 to 14 days, or 40°C for 1 to 10 days.

[0144] Examples of the substrate include polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, polylactic acid, polybutylene adipate, polycaprolactone, polyethylene terephthalate / isophthalate copolymer, and hydroxybutyrate / hydroxyhexanoate polymer; polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; polyethylene fluoride resins such as polyvinyl fluoride, polyvinylidene fluoride, and polyethylene fluoride; polyamides such as nylon 6 and nylon 6,6; polyvinyl chloride, polyvinyl chloride / acetic acid Examples of the substrate include vinyl polymers such as vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, and vinylon; cellulose-based resins such as cellulose triacetate and cellophane; acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate; synthetic resin sheets made of polystyrene, polycarbonate, polyarylate, polyimide, cycloolefin polymers, and the like; metal foils such as aluminum, copper, and iron; paper such as fine paper and glassine paper; and woven and nonwoven fabrics made of glass fiber, natural fiber, synthetic fiber, and the like. These substrates can be used as a single layer or as a multilayer structure in which two or more types are laminated.

[0145] Among these, substrates made of polyethylene terephthalate and polyimide are preferred, and polyethylene terephthalate is particularly preferred because of its excellent adhesiveness to pressure-sensitive adhesives.

[0146] The release sheet may be, for example, any of the various synthetic resin sheets, paper, cloth, nonwoven fabric, etc. exemplified above as the substrate, which have been subjected to a release treatment. Among these, it is preferable to use a silicone-based release sheet as the release sheet.

[0147] The thickness of the substrate is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more, and is usually 1000 μm or less, preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less. That is, it is usually 1 to 1000 μm, preferably 3 to 500 μm, more preferably 5 to 300 μm, and even more preferably 10 to 200 μm.

[0148] The thickness of the pressure-sensitive adhesive layer is usually 2 μm or more, preferably 5 μm or more, and more preferably 10 μm or more, and is usually 500 μm or less, preferably 300 μm or less, and more preferably 200 μm or less. That is, it is usually 2 to 500 μm, preferably 5 to 300 μm, and more preferably 10 to 200 μm. When the thickness of the pressure-sensitive adhesive layer is within the above range, the adhesive properties tend to be excellent and the thickness tends to be uniform. When considering impact absorption properties, the thickness is preferably 50 μm or more.

[0149] The thickness of the adhesive layer is determined by subtracting the measured thickness of the constituent members other than the adhesive layer from the measured thickness of the entire adhesive sheet using a Digimatic indicator ("ID-C112B" manufactured by Mitutoyo Corporation).

[0150] From the viewpoint of durability and adhesive properties, the gel fraction of the pressure-sensitive adhesive layer is preferably 10% or more, more preferably 15% or more, even more preferably 20% or more, even more preferably 25% or more, particularly preferably 30% or more, and most preferably 35% or more, while it is more preferably 90% or less, even more preferably 80% or less, even more preferably 75% or less, particularly preferably 70% or less, and most preferably 65% ​​or less. That is, it is more preferably 15 to 90%, even more preferably 20 to 80%, even more preferably 25 to 75%, particularly preferably 30 to 70%, and most preferably 35 to 65%. When the gel fraction is within the above range, the cohesive strength is excellent, and therefore durability, adhesive strength, and tackiness tend to be excellent.

[0151] The gel fraction is an index of the degree of crosslinking and is calculated, for example, by the following method. That is, a pressure-sensitive adhesive sheet (without a separator) comprising a substrate polymer sheet (e.g., a PET film) on which a pressure-sensitive adhesive layer is formed is wrapped in a 200-mesh SUS wire netting and immersed in toluene at 23°C for 24 hours, and the gel fraction is calculated as the mass percentage of the insoluble pressure-sensitive adhesive component remaining in the wire netting after immersion relative to the mass of the pressure-sensitive adhesive component before immersion, excluding the mass of the substrate.

[0152] The adhesive strength of the pressure-sensitive adhesive sheet to glass is usually 2 N / 25 mm or more, preferably 3 N / 25 mm or more, more preferably 5 N / 25 mm or more, and even more preferably 10 N / 25 mm or more, with the upper limit usually being 50 N / 25 mm or less, preferably 40 N / 25 mm or less, and more preferably 30 N / 25 mm or less.

[0153] The adhesive strength of the pressure-sensitive adhesive sheet to SUS-BA plate is usually 2 N / 25 mm or more, preferably 4 N / 25 mm or more, more preferably 6 N / 25 mm or more, and even more preferably 10 N / 25 mm or more. The upper limit is usually 50 N / 25 mm or less, preferably 40 N / 25 mm or less, and more preferably 30 N / 25 mm or less.

[0154] The adhesive strength can be measured, for example, as follows: The adhesive sheet is attached to a glass or SUS-BA plate as an adherend, and after leaving it to stand at 23°C and 50% RH for 30 minutes or more, the 180-degree peel strength (N / 25 mm) is measured at a peel rate of 300 mm / min in accordance with JIS Z 0237.

[0155] The adhesive and adhesive sheet obtained by curing the adhesive composition are solvent-free and contain no organic solvents, which reduces CO2 and VOC emissions and places a low burden on the environment. Furthermore, the adhesive and adhesive sheet obtained by curing the adhesive composition have adhesive properties equal to or better than those of conventional solvent-based adhesives, and can be used to bond a variety of components.

[0156] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. In the examples, "parts" and "%" are by mass.

[0157] First, various polyesters (A) were produced as follows: The glass transition temperature, melting point, heat of crystalline fusion, acid value, hydroxyl value, ester bond concentration, urethane bond concentration, number average molecular weight, weight average molecular weight, and viscosity of the polyesters (A) were measured according to the methods described above.

[0158] <Polyester (A)> Prior to the production of polyester (A), the following polycarboxylic acids (a1) and polyhydric alcohols (a2) were prepared for use in the production. [Polycarboxylic acids (a1)] Isophthalic acid (IPA) Adipic acid (AdA) Sebacic acid (SebA) derived from biomass [Polyhydric alcohols (a2)] 3-methyl-1,5-pentanediol (3MPG) Neopentyl glycol (NPG) Polytetramethyl glycol (PTMG650) derived from biomass

[0159] [Production of Polyesters (A-1) to (A-5)] Polycarboxylic acids (a1) and polyhydric alcohols (a2) shown in Table 1 below were mixed in a reactor equipped with a thermometer, a stirrer, a distillation column, a nitrogen inlet tube, and a vacuum device, and 0.1 parts of tetrabutyl titanate per part of the polycarboxylic acids (a1) was added as a catalyst. The internal temperature was gradually raised to 240°C, and esterification and / or transesterification reactions were carried out over 4 hours to produce polyesters (A-1) to (A-5). The physical properties of the resulting polyesters (A-1) to (A-5) are shown in Table 2 below.

[0160]

[0161]

[0162] <Crosslinking Agent (B)> The following crosslinking agents (B) were prepared: B-1: an adduct of tolylene diisocyanate and trimethylolpropane B-2: an isocyanurate of hexamethylene diisocyanate ("Coronate HX" manufactured by Tosoh Corporation)

[0163] <Hydrolysis inhibitor (C)> The following was prepared as the hydrolysis inhibitor (C): C-1: bis-2,6-diisopropylphenylcarbodiimide

[0164] <Catalyst (D)> The following catalysts were prepared as catalyst (D): D-1: dibutyltin dilaurate

[0165] <Antioxidant (E)> The following antioxidants were prepared as antioxidants (E): E-1: Hindered phenol-based antioxidant ("Irganox 1010" manufactured by BASF)

[0166] Example 1 A pressure-sensitive adhesive composition of Example 1 was obtained by blending 28 parts of a crosslinking agent (B-1), 1 part of a hydrolysis inhibitor (C-1), 0.005 parts of a catalyst (D-1), and 0.1 parts of an antioxidant (E-1) with 100 parts of the polyester (A-1) obtained above, followed by stirring and mixing.

[0167] Examples 2 to 5, Comparative Examples 1 and 2 Pressure-sensitive adhesive compositions of Examples 2 to 5 and Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except that the components were blended as shown in Table 3 below.

[0168] The following evaluations were carried out using the obtained pressure-sensitive adhesive compositions of Examples 1 to 5 and Comparative Examples 1 and 2. The results are shown in Table 3 below.

[0169] [Coatability] After adjusting the temperature of the pressure-sensitive adhesive composition to 25°C, the viscosity at 25°C was measured using a Brookfield viscometer (manufactured by Toki Sangyo Co., Ltd., TVB-10, rotor model number M3, 3 rpm), and the coatability was evaluated according to the following evaluation criteria. (Evaluation criteria) ◎ (excellent): Viscosity of the pressure-sensitive adhesive composition is 2500 mPa·s or more and 200,000 mPa·s or less. ○ (very good): Viscosity of the pressure-sensitive adhesive composition is 500 mPa·s or more and less than 2500 mPa·s, or more than 200,000 mPa·s and 500,000 mPa·s or less. × (poor): Viscosity of the pressure-sensitive adhesive composition is less than 500 mPa·s, or more than 500,000 mPa·s.

[0170] [Production of Pressure-Sensitive Adhesive Sheet with Release Film] Each of the pressure-sensitive adhesive compositions of Examples 1 to 5 and Comparative Examples 1 and 2 was applied to a 38 μm-thick polyethylene terephthalate (PET) film using an applicator, and the film was heat-treated at 100°C for 3 minutes to form a pressure-sensitive adhesive layer (50 μm-thick). The surface of the resulting pressure-sensitive adhesive layer was then covered with a release-treated PET film (release film), and aging treatment was carried out at 40°C for 4 days to obtain a PET pressure-sensitive adhesive sheet with a release film.

[0171] The PET pressure-sensitive adhesive sheet with the release film was used to evaluate the gel fraction, adhesive strength, and holding power as described below.

[0172] [Gel Fraction] A PET pressure-sensitive adhesive sheet with a release film on one side was cut into a size of 4 cm x 4 cm, and the release film was peeled off. This was wrapped in a 200-mesh SUS wire mesh and immersed in toluene at 23°C for 24 hours. The mass of the undissolved pressure-sensitive adhesive component remaining in the wire mesh relative to the mass of the pressure-sensitive adhesive component before immersion, minus the mass of the PET substrate, was measured, and the mass percentage was calculated according to the following formula, which was defined as the gel fraction (%). Gel fraction (%) = mass of undissolved pressure-sensitive adhesive component remaining in the wire mesh after immersion / mass of pressure-sensitive adhesive component before immersion x 100

[0173] [Adhesive Strength] Non-alkali glass and SUS-BA plate were prepared as adherends. The PET pressure-sensitive adhesive sheet with one-sided release film obtained above was cut to 25 mm x 200 mm in an environment of 23°C and 50% RH, and the release film was then peeled off. The pressure-sensitive adhesive layer side was then pressed and attached to the non-alkali glass or SUS-BA plate by rolling a 2 kg roller back and forth twice. After leaving the sheet to stand for 30 minutes in the same atmosphere, the 180-degree peel strength (N / 25 mm) was measured using an autograph (Shimadzu Corporation, Autograph AG-X 50N) at a peel speed of 300 mm / min, and evaluated according to the following evaluation criteria. (Evaluation criteria) ◎ (excellent): Adhesive strength of 10N / 25mm or more, with no adhesive residue on the adherend ○ (very good): Adhesive strength of 5N / 25mm or more, but less than 10N / 25mm, with no adhesive residue on the adherend △ (good): Adhesive strength of 2N / 25mm or more, but less than 5N / 25mm, with no adhesive residue on the adherend × (poor): Adhesive strength less than 2N, or adhesive residue on the adherend

[0174] [Holding Power] The PET substrate pressure-sensitive adhesive sheet with one-sided release film obtained above was cut to a size of 25 mm x 50 mm in an environment of 23°C and 50% RH, and then the release film was peeled off. The sheet was pressed and attached to a stainless steel plate (SUS304) by rolling a 2 kg roller back and forth twice (attached area 25 mm x 25 mm), and the holding power was measured using a creep tester (Tester Sangyo Co., Ltd., Holding Power Tester BE-501 with Constant Temperature and Humidity Chamber) under a load of 1 kg in an atmosphere of 80°C for 24 hours. The evaluation criteria are as follows. (Evaluation Criteria) ◎ (Excellent): No slippage ○ (Very good): Slippage of 5.0 mm or less × (Poor): Slippage of more than 5.0 mm, or the sheet fell off

[0175]

[0176] The results in Table 3 above show that the pressure-sensitive adhesive compositions of Examples 1 to 5, which used polyester (A) having a specific ester bond concentration and viscosity, could be coated without dilution with an organic solvent, and furthermore, when made into pressure-sensitive adhesives, had excellent adhesive properties such as adhesive strength and holding power. On the other hand, the pressure-sensitive adhesive composition of Comparative Example 1, which used polyester (A) with a low ester bond concentration, had poor adhesive strength when made into a pressure-sensitive adhesive. Furthermore, the pressure-sensitive adhesive composition of Comparative Example 2, which used polyester (A) with a high viscosity, had too high a viscosity to be coated as is, making it difficult to use as a pressure-sensitive adhesive.

[0177] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0178] The present pressure-sensitive adhesive composition can be used as a solvent-free pressure-sensitive adhesive composition, which has a low environmental impact. Furthermore, since the composition has adhesive properties equivalent to or better than those of conventional solvent-based pressure-sensitive adhesives, it can be used for bonding electronic and optical components, and for adhesive labels for electronic devices and food products.

Claims

1. A pressure-sensitive adhesive composition containing a polyester (A), wherein the polyester (A) has a structural unit derived from a polycarboxylic acid (a1) and a structural unit derived from a polyhydric alcohol (a2), the ester bond concentration of the polyester (A) is 3.0 to 14 mmol / g, and the polyester (A) has fluidity at 25°C and a viscosity of 500 to 500,000 mPa·s.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the ester bond concentration of the polyester (A) is 8.7 mmol / g or less.

3. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the polyester (A) has a hydroxyl value of 20 mgKOH / g or more.

4. A pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the hydroxyl value of the polyester (A) relative to the ester bond concentration of the polyester (A) (hydroxyl value / ester bond concentration) is 4.27 or more.

5. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the content of the organic solvent relative to the total amount of the pressure-sensitive adhesive composition is 0 mass % or more and 10 mass % or less.

6. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the weight-average molecular weight of the polyester (A) is 2,000 to 30,000.

7. The pressure-sensitive adhesive composition according to any one of claims 1 to 6, wherein the polyester (A) has a heat of crystalline fusion of 50 J / g or less.

8. The pressure-sensitive adhesive composition according to any one of claims 1 to 7, wherein the urethane bond concentration of the polyester (A) is 5 mmol / g or less.

9. The pressure-sensitive adhesive composition according to any one of claims 1 to 8, wherein the acid value of the polyester (A) is 3 mg KOH / g or less.

10. A pressure-sensitive adhesive composition according to any one of claims 1 to 9, wherein the polyester (A) contains a branched-chain aliphatic diol having 6 to 34 carbon atoms as a structural unit derived from a polyhydric alcohol (a2).

11. A pressure-sensitive adhesive composition described in any one of claims 1 to 10, wherein the polyester (A) has a structural unit derived from a cyclic structure-containing compound as a structural unit derived from a polyvalent carboxylic acid (a1) and / or a structural unit derived from a polyhydric alcohol (a2).

12. The pressure-sensitive adhesive composition according to claim 11, wherein the content of the structural unit derived from the cyclic structure-containing compound is 0.1 to 50% by mass relative to the polyester (A).

13. The pressure-sensitive adhesive composition according to any one of claims 1 to 12, further comprising a crosslinking agent (B).

14. A pressure-sensitive adhesive, which is a cured product of the pressure-sensitive adhesive composition according to any one of claims 1 to 13.

15. A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive according to claim 14.

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