Polyester resin composition, polyester adhesive composition, polyester adhesive, adhesive sheet, and adhesive sheet for electronic component

Abstract

To provide a polyester resin composition excellent in cross-linking rate, cross-linking stability, and pot-life, and further excellent in adhesive strength, and optical characteristics as an adhesive.SOLUTION: A polyester resin composition includes a polyester resin (A), a cross-linking agent (B) and a catalyst (C), where the cross-linking agent (B) includes a polyfunctional isocyanate compound, the catalyst (C) includes an iron element, and the content of the iron element relative to 100 pts.mass of the polyester resin (A) is 150 ppm or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a polyester-based resin composition, a polyester-based pressure-sensitive adhesive composition, a polyester-based pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, and a pressure-sensitive adhesive sheet for electronic components, and more specifically to a polyester-based resin composition, a polyester-based pressure-sensitive adhesive composition, a polyester-based pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, and a pressure-sensitive adhesive sheet for electronic components that are excellent in adhesive strength, curing speed, crosslinking stability, optical properties, and pot life. [Background technology]

[0002] Generally, adhesives (also called pressure-sensitive adhesives; the same applies below) are in a soft solid (viscoelastic) state in a temperature range near room temperature, and have the property of easily adhering to an adherend by pressure. Taking advantage of such properties, adhesives are widely used in various industrial fields, such as home appliances, automobiles, various machines, electrical appliances, and electronic devices, typically in the form of an adhesive sheet containing a layer of the adhesive, as a joining means with good workability and high adhesive reliability. Examples of adhesives used in these applications include acrylic adhesives, rubber adhesives, and polyester adhesives, and in particular, adhesives for electronic components, including portable electronic devices, are required to further improve adhesive strength and optical properties for adhesive reliability and design. Among them, polyester adhesives are adhesives with excellent adhesiveness, toughness, heat resistance, and mechanical strength, and various studies have been conducted.

[0003] The polyester-based adhesive is obtained by crosslinking a polyester-based resin with a crosslinking agent. This crosslinking reaction progresses with time, and requires a certain amount of time to stabilize, and the adhesive strength exhibited changes with the progress of the crosslinking reaction. Since polyester-based resins are usually linear and have crosslinking points only at the molecular ends, the crosslinking speed is slower than that of acrylic resins having a branched structure, and there are problems with the stability of adhesive properties and production efficiency when used as an adhesive. For this reason, a catalyst is used to quickly complete the crosslinking reaction between the polyester-based resin and the crosslinking agent.

[0004] For example, Patent Document 1 discloses a pressure-sensitive adhesive composition containing a polyester resin, an isocyanate crosslinking agent, and a zirconium compound as a catalyst.

[0005] Moreover, Patent Document 2 discloses a pressure-sensitive adhesive composition containing a polyester polymer, an isocyanate crosslinking agent, and an organotin compound as a catalyst. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2022-79443 [Patent Document 2] International Publication No. 2022 / 181141 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, from the viewpoint of environmental friendliness, legal restrictions have been imposed on the use of specific metals such as tin, and there is a demand for polyester-based pressure-sensitive adhesive compositions that have extremely high reactivity and an excellent pot life without using a tin-based compound as a catalyst. In the above Patent Document 1, a zirconium-based compound is used as a catalyst, and there is room for further improvement in terms of the crosslinking rate compared to tin-based compounds. Furthermore, in the above-mentioned Patent Document 2, the catalyst contains a large amount of a tin-based compound, which places a large burden on the global environment, and furthermore, although the catalytic activity is high, there remains an issue of short pot life.

[0008] Under such circumstances, an object of the present invention is to provide a polyester-based resin composition which is excellent in crosslinking rate, crosslinking stability, and pot life, and further has excellent adhesive strength and optical properties when used as a pressure-sensitive adhesive. [Means for solving the problem]

[0009] However, in view of these circumstances, the present inventors conducted extensive research and discovered that the above-mentioned problems could be solved by using a polyfunctional isocyanate compound as a crosslinking agent for a polyester resin and further using a specific trace amount of a catalyst containing iron element as a catalyst, thereby completing the present invention.

[0010] The amount of catalyst containing iron required for crosslinking polyester resins has not been clarified, and it has been common to use a large amount of catalyst containing iron to accelerate the crosslinking rate. This has led to problems such as a short pot life making it difficult to use industrially, and excess catalyst depositing at the adhesive interface, reducing adhesive strength. Furthermore, catalysts containing elemental iron have a strong color and significantly deteriorate optical properties, so their use in pressure-sensitive adhesive compositions that require good optical properties has been avoided. However, in the present invention, it has surprisingly been found that by limiting the amount of a catalyst containing an iron element to a specific trace amount relative to a polyester-based resin, a polyester-based resin composition can be obtained that is excellent in crosslinking rate, crosslinking stability, and pot life, and further has excellent adhesive strength and optical properties when used as a pressure-sensitive adhesive.

[0011] That is, the present invention has the following aspects. [1] A polyester-based resin composition comprising a polyester-based resin (A), a crosslinking agent (B), and a catalyst (C), wherein the crosslinking agent (B) contains a polyfunctional isocyanate compound, the catalyst (C) contains elemental iron, and the content of elemental iron per 100 parts by mass of the polyester-based resin (A) is 150 ppm or less. [2] The polyester-based resin composition according to [1], wherein the acid value of the polyester-based resin (A) is 5 mgKOH / g or less. [3] The polyester-based resin composition according to [1] or [2], wherein the content of the polyfunctional isocyanate compound per 100 parts by mass of the polyester-based resin (A) is 10 parts by mass or less. [4] The polyester resin composition according to any one of [1] to [3], wherein the polyfunctional isocyanate compound contains a structural unit derived from a cyclic structure. [5] The polyester resin composition according to any one of [1] to [4], wherein the catalyst (C) is an iron complex compound. [6] The polyester-based resin composition according to any one of [1] to [5], wherein the polyester-based resin (A) has a weight-average molecular weight of 10,000 or more. [7] A polyester-based pressure-sensitive adhesive composition comprising the polyester-based resin composition according to any one of [1] to [6]. [8] A polyester-based pressure-sensitive adhesive obtained by crosslinking the polyester-based pressure-sensitive adhesive composition according to [7]. [9] An adhesive sheet having an adhesive layer containing the polyester-based adhesive according to [8].

[10] The adhesive sheet according to [9], having an adhesive strength of 1 N / 25 mm or more.

[11] An adhesive sheet for electronic components, comprising the polyester-based adhesive according to [8]. Effect of the Invention

[0012] The polyester resin composition of the present invention is excellent in crosslinking rate, crosslinking stability and pot life, and further, when used as a pressure-sensitive adhesive, it is excellent in adhesive strength and optical properties. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be described below based on examples of the mode for carrying out the present invention. However, the present invention is not limited to the embodiment described below.

[0014] In this specification, "X and / or Y (X and Y are optional)" means at least one of X and Y, and means the following three cases: X only, Y only, and X and Y. In this specification, when expressed as "X to Y" (X and Y are any numbers), unless otherwise specified, it includes the meaning of "X or more and Y or less", as well as "preferably more than X" or "preferably less than Y". In the present specification, the upper limit or lower limit of a numerical range described in stages can be arbitrarily combined with the upper limit or lower limit of a numerical range of another stage. In addition, in the numerical range described in this specification, the upper limit or lower limit of the numerical range can be replaced with a value shown in the examples.

[0015] In this specification, the term "sheet" includes the terms "film" and "tape." In this specification, the term "major component" means a component that has a significant effect on the properties of the target object, and the content of the component in the target object is usually 50 mass % or more, preferably 55 mass % or more, more preferably 60 mass % or more, and even more preferably 70 mass % or more, and may be 100 mass %.

[0016] A polyester resin composition according to one embodiment of the present invention (hereinafter, sometimes referred to as "the resin composition") contains a polyester resin (A), a crosslinking agent (B), and a catalyst (C), the crosslinking agent (B) contains a polyfunctional isocyanate compound, the catalyst (C) contains iron element, and the content of the iron element per 100 parts by mass of the polyester resin (A) is 150 ppm or less. Each component contained in the resin composition will be described below.

[0017] <Polyester resin (A)> The polyester resin (A) is usually obtained by copolymerizing copolymerization components including a polyvalent carboxylic acid (a1) and a polyol (a2). The obtained polyester resin (A) has, as its resin composition, structural units derived from the polyvalent carboxylic acid (a1) and structural units derived from the polyol (a2). In the present invention, the term "carboxylic acids" is meant to include not only carboxylic acids but also carboxylic acid derivatives such as carboxylic acid salts, carboxylic acid anhydrides, carboxylic acid halides, and carboxylic acid esters.

[0018] [Structural units derived from polycarboxylic acids (a1)] Examples of the structural unit derived from the polyvalent carboxylic acid (a1) include a structural unit derived from a dicarboxylic acid and a structural unit derived from a trivalent or higher polyvalent carboxylic acid, and it is preferable that the structural unit derived from a dicarboxylic acid is contained in order to stably obtain the polyester resin (A). The polyester resin (A) may contain the structural unit derived from the polyvalent carboxylic acid (a1) alone or may contain two or more kinds of structural units.

[0019] Examples of the structural units derived from dicarboxylic acids include structural units derived from aliphatic dicarboxylic acids such as malonic acids, dimethylmalonic acids, succinic acids, glutaric acids, adipic acids, trimethyladipic acids, pimelic acids, 2,2-dimethylglutaric acids, azelaic acids, sebacic acids, fumaric acids, maleic acids, itaconic acids, thiodipropionic acids, diglycolic acids, 1,9-nonanedicarboxylic acids, oleic acid, linoleic acid, linolenic acid, erucic acid, and the like, and dimer acids (mainly having 36 to 44 carbon atoms); Structural units derived from aromatic dicarboxylic acids such as phthalic acids, terephthalic acids, isophthalic acids, benzylmalonic acids, diphenic acids, 4,4'-oxydibenzoic acids, and also naphthalenedicarboxylic acids such as 1,8-naphthalenedicarboxylic acids, 2,3-naphthalenedicarboxylic acids, and 2,7-naphthalenedicarboxylic acids; Examples of the structural units include those derived from alicyclic dicarboxylic acids such as 1,3-cyclopentanedicarboxylic acids, 1,2-cyclohexanedicarboxylic acids, 1,3-cyclopentanedicarboxylic acids, 1,4-cyclohexanedicarboxylic acids, 2,5-norbornanedicarboxylic acids, and adamantanedicarboxylic acids.

[0020] Examples of the structural units derived from trivalent or higher polyvalent carboxylic acids include structural units derived from trivalent or higher aromatic polyvalent carboxylic acids such as trimellitic acids, pyromellitic acids, and trimesic acids, and structural units derived from adamantanetricarboxylic acids.

[0021] Among the structural units derived from the polyvalent carboxylic acids (a1), from the viewpoints of reducing the crystallinity of the polyester resin (A) and of achieving excellent cohesive strength, it is preferable for the polyester resin (A) to contain a structural unit derived from an aromatic dicarboxylic acid, and it is particularly preferable for the polyester resin (A) to contain a structural unit derived from an asymmetric aromatic dicarboxylic acid.

[0022] Examples of the structural unit derived from the asymmetric aromatic dicarboxylic acid include structural units derived from phthalic acids, isophthalic acids, 1,8-naphthalenedicarboxylic acids, 2,3-naphthalenedicarboxylic acids, 2,7-naphthalenedicarboxylic acids, etc. Among them, in terms of reactivity, it is preferable that the polyester resin (A) contains a structural unit derived from an isophthalic acid.

[0023] The content of the structural units derived from the aromatic polycarboxylic acids, particularly the structural units derived from asymmetric aromatic dicarboxylic acids, is preferably 0.1 to 80 mol%, more preferably 1 to 60 mol%, further preferably 3 to 50 mol%, particularly preferably 5 to 40 mol%, particularly preferably 5 to 30 mol%, and most preferably 5 to 25 mol%, based on the total structural units derived from the polycarboxylic acids (a1). If the content is too low, the cohesive force decreases, the polyester resin (A) crystallizes, and sufficient adhesive performance tends to be difficult to obtain. If the content is too high, the tackiness tends to decrease.

[0024] In order to improve tackiness, the polyester resin (A) preferably contains, as a structural unit derived from a polyvalent carboxylic acid (a1), a structural unit derived from an aliphatic dicarboxylic acid, more preferably a structural unit derived from an aliphatic dicarboxylic acid having 4 or more carbon atoms (including the carbon of the carboxy group), even more preferably a structural unit derived from an aliphatic dicarboxylic acid having 6 to 12 carbon atoms (including the carbon of the carboxy group), and particularly preferably a structural unit derived from an adipic acid, a sebacic acid, or an azelaic acid.

[0025] The content of the structural units derived from the aliphatic dicarboxylic acids, preferably structural units derived from aliphatic dicarboxylic acids having 4 or more carbon atoms, is preferably 5 to 100 mol%, more preferably 20 to 99 mol%, further preferably 40 to 98 mol%, particularly preferably 50 to 95 mol%, particularly preferably 60 to 93 mol%, and most preferably 70 to 93 mol% based on the total structural units derived from the polyvalent carboxylic acids (a1). If the content is too small, the glass transition temperature of the polyester resin (A) becomes too high, and the tackiness tends to decrease, whereas if the content is too large, the cohesive force tends to decrease or the polyester resin (A) tends to crystallize, making it difficult to obtain sufficient adhesive performance.

[0026] From the viewpoint of adhesive properties, the polyester resin (A) preferably contains, as the structural units derived from polyvalent carboxylic acids (a1), structural units derived from aromatic dicarboxylic acids and structural units derived from aliphatic dicarboxylic acids, preferably structural units derived from aliphatic dicarboxylic acids having 4 or more carbon atoms. In this case, the content ratio (molar ratio) of the structural units derived from aromatic dicarboxylic acids and the structural units derived from aliphatic dicarboxylic acids, preferably structural units derived from aliphatic dicarboxylic acids having 4 or more carbon atoms, is preferably structural units derived from aromatic dicarboxylic acids / structural units derived from aliphatic dicarboxylic acids, preferably structural units derived from aliphatic dicarboxylic acids having 4 or more carbon atoms=0.1 / 99.9 to 80 / 20, more preferably 1 / 99 to 80 / 20, further preferably 3 / 97 to 80 / 20, particularly preferably 5 / 95 to 80 / 20.

[0027] In addition, in the present resin composition, a structural unit derived from a trivalent or higher polyvalent carboxylic acid may be contained in the polyester resin for the purpose of increasing the branching points. Among them, it is preferable that the polyester resin (A) contains a structural unit derived from a trimellitic acid, since gelation is relatively unlikely to occur during production.

[0028] When the polyester resin (A) contains a structural unit derived from a trivalent or higher polyvalent carboxylic acid, the content of the structural unit is usually 10 mol % or less, preferably 0.1 to 5 mol %, more preferably 0.5 to 3 mol %, based on the total structural units derived from the polyvalent carboxylic acid (a1), in order to increase the cohesive strength when used as an adhesive. If the content is too high, gelation tends to occur during the production of the polyester resin (A) or the acid value tends to increase.

[0029] [Structural unit derived from polyol (a2)] Examples of the structural unit derived from the polyol (a2) include a structural unit derived from a diol and a structural unit derived from a trivalent or higher polyol. The polyester resin (A) may contain the structural unit derived from the polyol (a2) alone or in combination of two or more kinds.

[0030] Examples of the structural unit derived from a diol include structural units derived from aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, 1,3-propanediol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,6-hexanediol, hyoleic acid, linoleic acid, linolenic acid, and dimer diol derived from erucic acid; Structural units derived from alicyclic diols such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecane dimethanol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol; Examples of structural units include those derived from aromatic diols such as 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.

[0031] Examples of the structural unit derived from a trivalent or higher polyol include structural units derived from pentaerythritol, dipentaerythritol, tripentaerythritol, glycerin, trimethylolpropane, trimethylolethane, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol, 1,3,6-hexanetriol, and adamantanetriol.

[0032] From the viewpoint of lowering the glass transition temperature and improving tackiness, the polyester resin (A) preferably contains, as a structural unit derived from a polyol (a2), a structural unit derived from a linear aliphatic diol, more preferably a structural unit derived from a linear aliphatic diol having 2 to 18 carbon atoms, and further preferably a structural unit derived from ethylene glycol, 1,3-propanediol, 1,4-butanediol, or 1,6-hexanediol.

[0033] The content of the structural units derived from the linear aliphatic diol is preferably 5 to 100 mol%, more preferably 10 to 100 mol%, further preferably 15 to 100 mol%, particularly preferably 20 to 100 mol%, and particularly preferably 30 to 100 mol%, based on the total structural units derived from the polyol (a2). If the content is too low, it tends to be difficult to form a stable resin.

[0034] In addition, from the viewpoint of breaking down the crystallinity of the polyester resin (A), the polyester resin (A) preferably contains a structural unit derived from a diol having a hydrocarbon group on the side chain among the structural units derived from the polyol (a2). Examples of such structural units derived from a diol having a hydrocarbon group on the side chain include structural units derived from an aliphatic diol having a branched structure, such as dipropylene glycol, 2,4-dimethyl-2-ethylhexane-1,3-diol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-methyl-2-ethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,6-hexanediol, oleic acid, erucic acid, and the like; Examples of structural units include those derived from alicyclic diols having a branched structure, such as 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, spiroglycol, tricyclodecane dimethanol, adamantanediol, and 2,2,4,4-tetramethyl-1,3-cyclobutanediol. In particular, the polyester resin (A) preferably contains structural units derived from an aliphatic diol having a branched structure, and more preferably contains structural units derived from 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 3-methyl-1,5-pentanediol, or dimer diol.

[0035] The content of the structural units derived from the diol having a hydrocarbon group in the side chain is preferably 5 to 95 mol%, more preferably 10 to 90 mol%, further preferably 15 to 80 mol%, particularly preferably 20 to 70 mol%, and particularly preferably 20 to 60 mol% based on the total structural units derived from the polyol (a2). If the content is too low, the resin tends to crystallize and it is difficult to obtain sufficient adhesive performance, while if the content is too high, the reaction time in the production of the polyester resin (A) tends to be long.

[0036] Furthermore, in the present resin composition, from the viewpoint of forming a reaction site with the crosslinking agent (B) described later in the polyester resin (A) and enhancing the cohesive force, it is also preferable that the polyester resin (A) contains a structural unit derived from a trivalent or higher polyol as a structural unit derived from the polyol (a2). Among them, the polyester resin (A) preferably contains a structural unit derived from trimethylolpropane, trimethylolethane, glycerin, pentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, or 1,2,6-hexanetriol as a structural unit derived from a trivalent or higher polyol, and more preferably contains a structural unit derived from trimethylolpropane in terms of being relatively unlikely to generate gel.

[0037] The content of the structural units derived from the trivalent or higher polyol is preferably 10 mol % or less, more preferably 0.1 to 5 mol %, and further preferably 0.5 to 3 mol %, based on the total structural units derived from the polyol (a2). If the content of the structural units derived from the trivalent or higher polyol is too high, production of the polyester resin (A) tends to be difficult.

[0038] Here, the proportion of structural units (compositional proportion) derived from each component of the polyester resin (A) can be determined, for example, by NMR.

[0039] The polyester resin (A) is produced by appropriately selecting the polyvalent carboxylic acids (a1) and the polyol (a2) so that their contents fall within the above-mentioned ranges, and subjecting them to a polycondensation reaction in the presence of a catalyst by a known method.

[0040] The mixing ratio of the polyvalent carboxylic acids (a1) and the polyol (a2) is preferably 1 to 2 equivalents, more preferably 1.1 to 1.7 equivalents, of the polyol (a2) per equivalent of the polyvalent carboxylic acids (a1). If the mixing ratio of the polyol (a2) is too low, the acid value tends to be high, making it difficult to increase the molecular weight, and if it is too high, the yield tends to decrease.

[0041] In the polycondensation reaction, an esterification reaction and / or an ester exchange reaction is carried out first, and then the polycondensation reaction is carried out.

[0042] In the esterification reaction or transesterification reaction, a catalyst is usually used, and specific examples thereof 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, and catalysts such as zinc acetate, manganese acetate, and dibutyltin oxide, and one or more of these are used. Among these, antimony trioxide, tetrabutyl titanate, germanium dioxide, and zinc acetate are preferred from the perspective of the balance between high catalytic activity and hue.

[0043] The amount of the catalyst is preferably 1 to 10,000 ppm, more preferably 10 to 5,000 ppm, and even more preferably 20 to 3,000 ppm by mass based on the total copolymerization components. If the amount is too small, the polymerization reaction tends not to proceed sufficiently, whereas if the amount is too large, there is no advantage such as shortening the reaction time, and side reactions tend to occur easily.

[0044] The reaction temperature during the esterification reaction and / or transesterification reaction is preferably 200 to 300° C., more preferably 210 to 280° C., and even more preferably 220 to 260° C. If the reaction temperature is too low, the reaction tends not to proceed sufficiently, and if the reaction temperature is too high, side reactions such as decomposition tend to occur easily. The pressure during the reaction is usually normal pressure.

[0045] After the esterification reaction and / or transesterification reaction, a polycondensation reaction is carried out. As reaction conditions for the polycondensation reaction, it is preferable to further compound the same amount of the catalyst as that used in the esterification reaction, set the reaction temperature at preferably 220 to 280° C., more preferably 230 to 270° C., and gradually reduce the pressure of the reaction system to finally carry out the reaction at 5 hPa or less. If the reaction temperature is too low, the reaction tends not to proceed sufficiently, and if it is too high, side reactions such as decomposition tend to occur easily.

[0046] Thus, the polyester resin (A) used in the present invention is obtained. The polyester resin (A) preferably has the following physical properties.

[0047] The glass transition temperature (Tg) of the polyester resin (A) is, from the viewpoint of adhesive properties, usually −80 to 30° C., preferably −75 to 10° C., more preferably −70 to 10° C., even more preferably −65 to 10° C., particularly preferably −60 to 10° C., especially preferably −55 to 10° C., and most preferably −50 to 10° C. If the glass transition temperature (Tg) is too high, flexibility is lost, tackiness decreases, adhesive strength is difficult to exert even with pressure of the order of finger pressure, and workability tends to decrease, whereas if the glass transition temperature is too low, cohesive strength tends to decrease.

[0048] Here, the glass transition temperature (Tg) of the polyester resin (A) is a value measured using a differential scanning calorimeter DSC Q20 manufactured by TA Instruments. The measurement temperature range is −90 to 100° C., and the temperature rise rate is 10° C. / min.

[0049] The weight average molecular weight of the polyester resin (A) is preferably 10,000 or more from the viewpoint of the cohesive strength of the adhesive, more preferably 15,000 to 150,000, further preferably 30,000 to 120,000, and particularly preferably 50,000 to 120,000. By setting the weight average molecular weight within the above range, the crosslinking rate and crosslinking stability are excellent, and the adhesive strength when used as an adhesive tends to be excellent. If the weight average molecular weight is too small, sufficient cohesive strength cannot be obtained as an adhesive, and the adhesive strength tends to decrease.

[0050] The number average molecular weight of the polyester resin (A), from the viewpoint of the cohesive strength of the adhesive, is usually 5000 to 50000, preferably 6000 to 40000, more preferably 6000 to 35000, and particularly preferably 6000 to 30000. By setting the number average molecular weight within the above range, the crosslinking rate and crosslinking stability tend to be excellent, and the adhesive strength when used as an adhesive tends to be excellent. If the weight average molecular weight is too small, sufficient cohesive strength cannot be obtained as an adhesive, and the adhesive strength tends to decrease.

[0051] The weight average molecular weight and number average molecular weight of the polyester resin (A) are weight average molecular weights calculated in terms of standard polystyrene molecular weights, and are measured using a high performance liquid chromatograph (manufactured by Waters, "ACQUITY APC System") equipped with four columns in series: one ACQUITY APC XT 450, one ACQUITY APC XT 200, and two ACQUITY APC XT 45.

[0052] The acid value of the polyester resin (A) is preferably 15 mgKOH / g or less, more preferably 10 mgKOH / g or less, even more preferably 5 mgKOH / g or less, particularly preferably 3 mgKOH / g or less, particularly preferably 1 mgKOH / g or less, and most preferably 0.3 mgKOH / g or less. By setting the acid value within the above range, the reaction between the catalyst (C) and the acid residue is suppressed, and the crosslinking rate, crosslinking stability, and pot life tend to be excellent.

[0053] The hydroxyl value of the polyester resin (A) is usually 0.1 to 50 mgKOH / g, preferably 1 to 30 mgKOH / g, more preferably 2 to 20 mgKOH / g, and particularly preferably 3 to 15 mgKOH / g. If the hydroxyl value is too high, the crosslinking efficiency with the crosslinking agent (B) tends to decrease.

[0054] Here, the acid value and hydroxyl value in the present invention are determined by neutralization titration based on JIS K 0070.

[0055] The content of the polyester resin (A) in the present resin composition is usually 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0056] <Crosslinking agent (B)> The crosslinking agent (B) is a compound having a functional group that reacts with a functional group such as a hydroxyl group or a carboxyl group contained in the polyester resin (A), and in the present invention, the crosslinking agent (B) includes a polyfunctional isocyanate compound.

[0057] Examples of the polyfunctional isocyanate compound include aliphatic diisocyanates such as trimethylene diisocyanate, 1,2-propylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, and trimethylhexamethylene diisocyanate; Aromatic aliphatic diisocyanates such as xylylene diisocyanate; alicyclic diisocyanates such as cyclohexane diisocyanate, methylcyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), methylene bis(cyclohexyl isocyanate) or dicyclohexylmethane diisocyanate, bis(isocyanatomethyl)cyclohexane, norbornane diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated xylylene diisocyanate; Examples of the diisocyanate include aromatic diisocyanates such as phenylene diisocyanate, tolylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, diphenylmethane diisocyanate, and 4,4'-toluidine diisocyanate, as well as trimer compounds or polymer compounds of these diisocyanates, biuret-type polyisocyanates, and reaction products of these diisocyanates with polyols. These may be used alone or in combination of two or more kinds.

[0058] The polyfunctional isocyanate compound preferably contains a structural unit derived from a cyclic structure, from the viewpoint of excellent crosslinking efficiency, adhesive strength, and optical properties when used as a pressure-sensitive adhesive, and is more preferably an aromatic diisocyanate, an araliphatic diisocyanate, or an alicyclic diisocyanate, still more preferably an aromatic diisocyanate, or an araliphatic diisocyanate, and particularly preferably tolylene diisocyanate or xylylene diisocyanate.

[0059] The content of the polyfunctional isocyanate compound is appropriately selected depending on the amount of functional groups contained in the polyester resin (A), the molecular weight of the polyester resin (A), and the purpose of controlling the adhesive strength, but is preferably 30 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and especially preferably 3 parts by mass or less, relative to 100 parts by mass of the polyester resin (A). The lower limit is usually 0.01 parts by mass or more. If the content of such a polyfunctional isocyanate compound is too high, the adhesive strength tends to be poor and the pot life tends to be insufficient.

[0060] As the crosslinking agent (B), a crosslinking agent other than the polyfunctional isocyanate compound can be used.

[0061] The other crosslinking agent may be any compound having a functional group that reacts with a functional group such as a hydroxyl group or a carboxyl group contained in the polyester resin (A), and examples thereof include epoxy compounds, aziridine compounds, melamine compounds, aldehyde compounds, amine compounds, metal chelate compounds, etc. These may be used alone or in combination of two or more kinds.

[0062] Examples of the epoxy compound include bisphenol A-epichlorohydrin type epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, and diglycerol polyglycidyl ether. Examples of the aziridine compound include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), and N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide). Examples of the melamine compound include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexaptoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, and melamine resins. Examples of the aldehyde compounds include glyoxal, malondialdehyde, succindialdehyde, maleic dialdehyde, glutaric dialdehyde, formaldehyde, acetaldehyde, and benzaldehyde. Examples of the amine compound include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetraamine, diethylenetriamine, triethyltetraamine, isophoronediamine, amino resins, and polyamides. Examples of the metal chelate compounds include acetylacetone and acetoacetyl ester coordination compounds of multiple metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium.

[0063] The content of the crosslinking agent (B) is appropriately selected depending on the amount of functional groups contained in the polyester resin (A), the molecular weight of the polyester resin (A), and the purpose of controlling the adhesive strength, and is usually 30 parts by mass or less, preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less, relative to 100 parts by mass of the polyester resin (A). The lower limit is usually 0.01 parts by mass or more. If the content of the crosslinking agent (B) is too high, the adhesive strength tends to be poor or the pot life tends to be insufficient.

[0064] The content of the polyfunctional isocyanate compound in the crosslinking agent (B) is usually 50% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, and further preferably 100% by mass.

[0065] <Catalyst (C)> The catalyst (C) contained in the present resin composition acts as a urethanization catalyst that promotes the reaction between the polyester resin (A) and the crosslinking agent (B). In particular, the present invention has found that use of a specific trace amount of a catalyst containing an iron element as the catalyst (C) results in excellent optical properties, crosslinking rate, crosslinking stability, and pot life. The reason why the effects of the present invention can be obtained by using a specific trace amount of a catalyst containing iron element is presumably because, while using a large amount of a catalyst containing iron element shortens the pot life and deteriorates the optical properties due to the color derived from the catalyst, by limiting the use to a specific trace amount, the pot life can be made sufficiently longer, and on the other hand, when a pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive composition containing this resin composition, the crosslinking reaction between the hydroxyl groups of the polyester resin (A) and the polyfunctional isocyanate compound proceeds more quickly and efficiently with a small amount of crosslinking agent.

[0066] As the catalyst containing an iron element, an iron complex compound is preferred in terms of excellent optical properties, crosslinking rate, crosslinking stability, and pot life. Specific examples of iron complex compounds include bis(2,4-pentanedionato)diaquairon(II), tris(2,4-pentanedionato)iron(III), and 2-ethylhexanoate iron. These may be used alone or in combination of two or more. Among these, acetylacetonate complexes such as bis(2,4-pentanedionato)diaquairon(II) and tris(2,4-pentanedionato)iron(III) are preferred, and tris(2,4-pentanedionato)iron(III) is more preferred, in terms of excellent optical properties, crosslinking speed, crosslinking stability, and pot life.

[0067] In the present invention, a catalyst other than a catalyst containing elemental iron may be used as the catalyst (C). Examples of catalysts other than the catalyst containing iron element include organometallic compounds (excluding iron as the metal), tertiary amine compounds, etc. These can be used alone or in combination of two or more kinds.

[0068] Examples of the organometallic compound include zirconium-based compounds, tin-based compounds, titanium-based compounds, lead-based compounds, cobalt-based compounds, zinc-based compounds, and aluminum compounds. Examples of the zirconium compound include zirconium naphthenate and zirconium acetylacetonate. Examples of the tin compounds include dibutyltin dichloride, dibutyltin oxide, and dibutyltin dilaurate. Examples of titanium compounds include dibutyltitanium dichloride, tetrabutyltitanium, and butoxytitanium trichloride. Examples of 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 zinc-based compounds include zinc naphthenate and zinc 2-ethylhexanoate.

[0069] Examples of the tertiary amine compound include triethylamine, triethylenediamine, and 1,8-diazabicyclo-(5,4,0)-undecene-7.

[0070] The content of the catalyst (C) is usually 0.1 parts by mass or less, preferably 0.05 parts by mass or less, more preferably 0.04 parts by mass or less, 0.03 parts by mass or less, 0.02 parts by mass or less, 0.01 parts by mass or less, 0.0075 parts by mass or less, 0.005 parts by mass or less, or 0.003 parts by mass or less, based on 100 parts by mass of the polyester resin (A). The lower limit is usually 0.0001 parts by mass or more.

[0071] The content of iron element relative to 100 parts by mass of polyester resin (A) is 150 ppm or less, preferably 100 ppm or less, more preferably 75 ppm or less, even more preferably 50 ppm or less, particularly preferably 30 ppm or less, particularly preferably 15 ppm or less, and most preferably 5 ppm or less. The lower limit is usually 0.1 ppm or more. When the content of iron element relative to polyester resin (A) is within the above range, the adhesive strength, optical properties, crosslinking speed, crosslinking stability, and pot life are excellent. The content of the iron element is derived from the catalyst containing the iron element, and can be determined by, for example, analysis using an ICP emission spectrometer or an atomic absorption spectrometer. The content of the iron element may also be calculated from the mass ratio of the iron element contained in the catalyst containing the iron element and the blending amount of the catalyst containing the iron element.

[0072] The content of the catalyst containing the iron element in the catalyst (C) is usually 50% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, and particularly preferably 100% by mass.

[0073] <Hydrolysis inhibitor (D)> The resin composition may contain a hydrolysis inhibitor (D) that bonds with the carboxy group of the polyester resin (A) to enhance the catalytic activity of the catalyst (C). The hydrolysis inhibitor (D) is not particularly limited, and may be a conventionally known one, for example, a compound that reacts with and bonds to the carboxy group of the polyester resin (A), specifically, a compound having a functional group such as a carbodiimide group, an epoxy group, an oxazoline group, etc. Among these, a compound having a carbodiimide group is preferred because it has a high effect of eliminating the catalytic activity of the proton derived from the carboxyl group terminal group.

[0074] [Compound having a carbodiimide group] As the compound having a carbodiimide group, a known carbodiimide having one or more carbodiimide groups (-N=C=N-) in the molecule can usually be used, such as a monocarbodiimide compound having one carbodiimide group in the molecule and a polycarbodiimide compound having two or more carbodiimide groups in the molecule.

[0075] The carbodiimide equivalent of the compound having a carbodiimide group is preferably 50 to 10,000, more preferably 100 to 1,000, and further preferably 150 to 500. The carbodiimide equivalent indicates the chemical formula weight per one carbodiimide group.

[0076] Examples of the monocarbodiimide compound include diphenylcarbodiimide, bis(methylphenyl)carbodiimide, bis(methoxyphenyl)carbodiimide, bis(nitrophenyl)carbodiimide, bis(dimethylphenyl)carbodiimide, bis(diisopropylphenyl)carbodiimide, bis(di-t-butylphenyl)carbodiimide, bis(triphenylsilyl)carbodiimide, etc. Among these, bis(diisopropylphenyl)carbodiimide is preferred in terms of compatibility with the polyester resin (A), excellent adhesive strength, reactivity with a carboxy group, and excellent durability to wet heat.

[0077] [Polycarbodiimide compounds] The polycarbodiimide compound has excellent catalytic activity due to the catalyst (C), and can be obtained by subjecting an organic diisocyanate compound to a decarboxylation condensation reaction in the presence of a carbodiimide catalyst.

[0078] Examples of the organic diisocyanate compound include aromatic diisocyanates such as 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, a mixture of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, xylylene diisocyanate, and tetramethylxylylene diisocyanate; Examples of the diisocyanate include aliphatic diisocyanates such as hexamethylene diisocyanate, and cycloaliphatic diisocyanates such as cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, methylcyclohexane diisocyanate, and 2,5(2,6)-bis(isocyanatomethyl)bicyclo[2.2.1]heptane. These may be used alone or in combination of two or more. Among these, aromatic diisocyanates are preferred, and tetramethylxylylene diisocyanate is more preferred, in that they can provide the present resin composition with excellent resistance to moist heat.

[0079] The organic diisocyanate compound can be subjected to a decarboxylation condensation reaction in the presence of a known carbodiimide catalyst in a conventional manner to obtain a polycarbodiimide compound.

[0080] The polycarbodiimide compound is preferably an aromatic polycarbodiimide compound, from the viewpoints of excellent reactivity with the carboxylic acid terminal groups of the polyester resin (A) and excellent catalytic activity of the catalyst (C).

[0081] Furthermore, the polycarbodiimide compound is preferably a polycarbodiimide compound in which at least one of the terminal isocyanate groups is substituted with a substituent derived from a hydrophilic organic compound (hereinafter referred to as a "substituted polycarbodiimide compound").

[0082] [Substituted polycarbodiimide compounds] The substituted polycarbodiimide compound can be obtained by reacting a polyimide compound with a hydrophilic organic compound in a conventional manner. The hydrophilic organic compound will now be described.

[0083] (hydrophilic organic compound) The hydrophilic organic compound is a compound having a substituent having an active hydrogen that is reactive with the isocyanate group at the end of the polycarbodiimide compound, and further having one or more heteroatoms in the molecule in addition to the substituent.

[0084] Examples of the substituent having active hydrogen reactive with the isocyanate group include a hydroxyl group, a primary amino group, a secondary amino group, an imino group, an isocyanate group, and a carboxyl group. Among them, a hydroxyl group, a primary amino group, a secondary amino group, and an imino group are preferred. The hydrophilic organic compound may have one or more of these substituents.

[0085] From the viewpoints of hydrolysis resistance and compatibility with the polyester resin (A), the weight-average molecular weight of the polycarbodiimide compound is preferably 1000 or more, more preferably 2000 or more, and even more preferably 3000 or more. The upper limit of the weight-average molecular weight is usually 50000 or less.

[0086] The polycarbodiimide compound preferably has low volatility, and therefore it is preferable to use one having a high number average molecular weight, which is usually 300 to 10,000, and preferably 1,000 to 5,000.

[0087] If the molecular weight of the polycarbodiimide compound is too small, the hydrolysis resistance tends to decrease, whereas if the molecular weight is too large, the compatibility with the polyester resin (A) tends to decrease, resulting in poor adhesive strength.

[0088] Examples of commercially available polycarbodiimide compounds include Carbodilite (registered trademark) V-09GB, V-02B, V-04K, V-04PF, and V-07 manufactured by Nisshinbo Chemical Inc., and Elastostab H01 manufactured by BASF, among which Carbodilite V-09GB and V-04K are preferred.

[0089] [Compound having an epoxy group] As the compound having an epoxy group, for example, a glycidyl ester compound, a glycidyl ether compound, or the like is preferable.

[0090] Examples of the glycidyl ester compound include benzoic acid glycidyl ester, t-butylbenzoic acid glycidyl ester, p-toluic acid glycidyl ester, cyclohexane carboxylic 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, terephthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, and the like. Examples of the diglycidyl ester include diglycidyl esters of cyclohexanedicarboxylic acid, diglycidyl esters of phthalic acid, diglycidyl esters of naphthalenedicarboxylic acid, diglycidyl esters of methyl terephthalic acid, diglycidyl esters of hexahydrophthalic acid, diglycidyl esters of tetrahydrophthalic acid, diglycidyl esters of cyclohexanedicarboxylic acid, diglycidyl esters of adipic acid, diglycidyl esters of succinic acid, diglycidyl esters of sebacic acid, diglycidyl esters of dodecanedioic acid, diglycidyl esters of octadecanedicarboxylic acid, triglycidyl esters of trimellitic acid, and tetraglycidyl esters of pyromellitic acid. These may be used alone or in combination of two or more.

[0091] 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-[р-(β,γ-epoxypropoxy)phenyl]propane, and bisphenols such as 2,2-bis-(4-hydroxyphenyl)propane and 2,2-bis-(4-hydroxyphenyl)methane, and bisglycidyl polyethers obtained by reacting epichlorohydrin with them, and these can be used alone or in combination of two or more kinds.

[0092] [Compounds having an oxazoline group] The compound having an oxazoline group is preferably a bisoxazoline compound from the viewpoint of reactivity with the polyester resin (A). Specifically, for example, 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-hexyl-2-oxazoline), etc. ), 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'-octamethylenebis(2-oxazoline), 2,2'-decamethylenebis(2-oxazoline), Examples of such oxazoline include 2,2'-ethylene bis(4-methyl-2-oxazoline), 2,2'-tetramethylene bis(4,4-dimethyl-2-oxazoline), 2,2'-9,9'-diphenoxyethane bis(2-oxazoline), 2,2'-cyclohexylene bis(2-oxazoline), and 2,2'-diphenylene bis(2-oxazoline). Of these, 2,2'-bis(2-oxazoline) is most preferred in terms of reactivity with polyester. Furthermore, the above-listed bisoxazoline compounds can be used alone or in combination of two or more kinds, so long as the object of the present invention is achieved.

[0093] The amount of the hydrolysis inhibitor (D) is preferably 0.01 to 10 parts by mass, particularly preferably 0.1 to 5 parts by mass, further preferably 0.2 to 4 parts by mass, particularly preferably 0.3 to 3 parts by mass, and most preferably 0.5 to 2 parts by mass, based on 100 parts by mass of the polyester resin (A). If the amount is too large, the crosslinking reaction between the polyester resin (A) and the crosslinking agent (B) tends to be delayed, and if the amount is too small, it tends to be difficult to obtain sufficient catalytic activity of the catalyst (C).

[0094] The amount of the hydrolysis inhibitor (D) is preferably optimized depending on the acid value of the polyester resin (A). The molar ratio ((β) / (α)) of the total acid value (α) of the polyester resin (A) in the resin composition to the total amount of functional groups (β) of the hydrolysis inhibitor (D) in the resin composition is preferably 0.5≦(β) / (α), more preferably 1≦(β) / (α)≦1000, even more preferably 1.5≦(β) / (α)≦500, particularly preferably 2≦(β) / (α)≦250, especially preferably 2.5≦(β) / (α)≦100, and most preferably 3≦(β) / (α)≦50. If the molar ratio (β) / (α) is too high, the compatibility with the polyester resin (A) tends to decrease, and the adhesive strength, cohesive strength, and durability tend to decrease. If the molar ratio (β) / (α) is too low, the moist heat resistance tends to decrease.

[0095] In addition to the polyester resin (A), crosslinking agent (B), catalyst (C), and hydrolysis inhibitor (D), other components may be added to the resin composition, such as antioxidants, tackifier resins, catalytic inhibitors, plasticizers, ultraviolet absorbers, antistatic agents, silane coupling agents, fluxes, flame retardants, dispersants, emulsifiers, defoamers, leveling agents, and ion trapping agents, as well as inorganic or organic fillers, powders such as metal powders, and pigments, and particulates, within the scope of the invention. These may be used alone or in combination of two or more. In addition, the resin composition may contain a small amount of impurities contained in the raw materials for producing the components of the resin composition.

[0096] When the present resin composition contains the other components, in order not to reduce the purity of the present resin composition, the content of the other components is preferably 30 mass% or less of the entire present resin composition, more preferably 20 mass% or less, even more preferably 15 mass% or less, and particularly preferably 10 mass% or less.

[0097] The resin composition can be obtained, for example, by preparing the polyester resin (A), the crosslinking agent (B), the catalyst (C) and optional components as necessary, and mixing and dispersing them when producing the polyester resin (A), or by mixing them with a solution of the polyester resin (A) dissolved in an organic solvent, and dispersing them using a mixing roller or the like.

[0098] The resin composition may contain a solvent in order to adjust the viscosity appropriately and to improve the handling and workability during application. There is no particular restriction on the amount of the solvent used.

[0099] Examples of the solvent include ketones such as acetone, methyl ethyl ketone (MEK), 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; aromatics such as toluene and xylene. The above-listed solvents may be used alone or in any combination and ratio of two or more.

[0100] The resin composition thus obtained is excellent in crosslinking rate, crosslinking stability and pot life, and further, when used as a pressure-sensitive adhesive, it is excellent in adhesive strength and optical properties, and is therefore useful as a polyester-based pressure-sensitive adhesive composition.

[0101] <Polyester-based pressure-sensitive adhesive composition> A polyester-based pressure-sensitive adhesive composition according to one embodiment of the present invention (hereinafter referred to as "the pressure-sensitive adhesive composition") comprises the resin composition.

[0102] The pressure-sensitive adhesive composition has a viscosity ratio between the viscosity 0 hours after preparation and the viscosity 4 hours after preparation (viscosity after 4 hours / viscosity after 0 hours) of usually 15 or less, preferably 10 or less, more preferably 5 or less, particularly preferably 3 or less, and especially preferably 2 or less. The lower limit is usually 1.0 or more. When the viscosity ratio is within the above range, the pot life tends to be excellent. The pot life means the maximum time during which the pressure-sensitive adhesive composition can be used after its preparation. After the pot life has elapsed, the pressure-sensitive adhesive composition may gel, or even if there is no apparent change, a chemical reaction may progress inside the composition, and the pressure-sensitive adhesive composition will no longer function as a pressure-sensitive adhesive. In the present invention, the catalyst (C) contains an iron element and the content thereof is a specific trace amount, so that the crosslinking rate, optical properties and pot life are excellent. The viscosity ratio can be determined by measuring the viscosity (mPa) of the pressure-sensitive adhesive composition 0 hours and 4 hours after preparation using a B-type viscometer (rotor: No. 3, rotation speed: 12 rpm, measurement time: 1 minute, measurement temperature: 25°C) and calculating the viscosity ratio using the following formula. Viscosity ratio = Viscosity after 4 hours / Viscosity after 0 hours

[0103] <Polyester-based adhesive> A polyester-based pressure-sensitive adhesive according to one embodiment of the present invention (hereinafter referred to as "the pressure-sensitive adhesive") is obtained by crosslinking the pressure-sensitive adhesive composition, and can be made into a pressure-sensitive adhesive having excellent adhesive strength and optical properties. In the present invention, "crosslinking" means intentionally crosslinking the pressure-sensitive adhesive composition by heat and / or light or the like, and the degree of crosslinking can be controlled depending on the desired physical properties and applications.

[0104] The degree of crosslinking can be confirmed by the gel fraction of the pressure-sensitive adhesive, which is preferably 10 to 100%, more preferably 15 to 90%, further preferably 20 to 80%, particularly preferably 25 to 70%, and especially preferably 40 to 65%. If the gel fraction is too low, the heat resistance, holding power, adhesive power, and long-term durability under a hot and humid environment tend to be insufficient, while if it is too high, the adhesive power tends to be insufficient. The gel fraction is a measure of the degree of crosslinking, and is calculated, for example, by the following method. That is, an adhesive sheet (without a release sheet) in which an adhesive layer is formed on a polymer sheet (e.g., a PET film, etc.) serving as a substrate is wrapped in a 200-mesh SUS wire netting, and immersed in toluene at 23°C for 24 hours, and the gel fraction is the mass percentage of the insoluble adhesive component remaining in the wire netting after immersion relative to the mass of the adhesive component before immersion. However, the mass of the substrate is subtracted.

[0105] The crosslinking rate of the present pressure-sensitive adhesive is usually 90 to 100%, preferably 95 to 100%, and more preferably 98 to 100%. In the present invention, the catalyst (C) contains an iron element and the content thereof is a specific trace amount, so that the catalyst is excellent in optical properties and crosslinking speed. The crosslinking rate can be determined by measuring the gel fraction after curing the pressure-sensitive adhesive for 5 days in an atmosphere at 40°C (gel fraction after 5 days) and after curing for 7 days (gel fraction after 7 days), and calculating using the following formula. Crosslinking rate (%) = gel fraction after 5 days / gel fraction after 7 days × 100

[0106] An adhesive sheet according to one embodiment of the present invention (hereinafter referred to as "the adhesive sheet") has an adhesive layer containing the adhesive. The pressure-sensitive adhesive sheet of the present invention may be a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one or both sides of a supporting substrate, or may be a substrate-less double-sided pressure-sensitive adhesive sheet having no substrate. The pressure-sensitive adhesive sheet of the present invention is particularly suitable as a pressure-sensitive adhesive sheet for electronic components used for bonding electronic components.

[0107] <Adhesive sheet> The present pressure-sensitive adhesive sheet can be manufactured according to a publicly known general pressure-sensitive adhesive sheet manufacturing method. For example, the present pressure-sensitive adhesive composition is applied to one side of a substrate, followed by drying to form a pressure-sensitive adhesive layer, and a release sheet is attached to the surface (the side opposite to the side in contact with the substrate) and cured as necessary to obtain a pressure-sensitive adhesive sheet having a substrate and a pressure-sensitive adhesive layer, with the pressure-sensitive adhesive layer provided on at least one side of the substrate.

[0108] Alternatively, the pressure-sensitive adhesive composition can be applied onto a release sheet, dried to form a pressure-sensitive adhesive layer, and then a substrate can be attached to the surface (the surface opposite to the surface in contact with the release sheet) and cured as necessary to obtain a pressure-sensitive adhesive sheet.

[0109] In addition, a substrateless double-sided pressure-sensitive adhesive sheet of the substrateless type that does not have a substrate can be produced by forming a pressure-sensitive adhesive layer on a release sheet and laminating the release sheet and another release sheet to its surface (the side opposite to the side that contacts the release sheet).

[0110] When using the resulting pressure-sensitive adhesive sheet or substrate-less double-sided pressure-sensitive adhesive sheet, the release sheet is peeled off from the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is attached to an adherend.

[0111] As the substrate, for example, a resin film, paper, cloth, a rubber sheet, a foam sheet, a metal foil, a composite of these, or the like can be used. Examples of the resin film include polyolefin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester films such as polyethylene terephthalate (PET); vinyl chloride resin films; vinyl acetate resin films; polyimide resin films; polyamide resin films; fluororesin films; polyurethane films; cellophane, and the like. Examples of the paper include Japanese paper, craft paper, glassine paper, fine paper, synthetic paper, and topcoat paper. Examples of the fabric include woven fabrics and nonwoven fabrics made of various fibrous materials, either alone or in admixture. Examples of the fibrous material include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, and polyolefin fiber. Examples of the rubber sheet include a natural rubber sheet and a butyl rubber sheet. Examples of the foam sheet include a foamed polyurethane sheet, a foamed polyacrylic sheet, and a foamed polyolefin sheet. Examples of the metal foil include aluminum foil and copper foil. These substrates can be used as a single layer or as a multi-layer structure in which two or more types are laminated.

[0112] Among these, substrates made of polyethylene terephthalate, polyimide, foamed polyurethane sheet, foamed polyacrylic sheet, or foamed polyolefin sheet are preferred, with polyethylene terephthalate being more preferred in terms of excellent adhesion to the adhesive, and having excellent adhesive strength between the substrate and the adhesive, allowing the effects of the adhesive used in the present invention to be prominently exhibited.

[0113] The release sheet may be, for example, any of the resin films exemplified above as the substrate, paper, cloth, rubber sheet, foam sheet, metal foil, composites thereof, etc., which have been subjected to a release treatment. Among these, it is preferable to use a silicone-based release sheet as the release sheet, in terms of excellent releasability from the pressure-sensitive adhesive.

[0114] When a resin film is used as the substrate, the thickness of the resin film is not particularly limited. In order to avoid the present pressure-sensitive adhesive sheet from becoming excessively thick, the thickness of the resin film can be, for example, 200 μm or less, preferably 150 μm or less, more preferably 100 μm or less. In addition, depending on the purpose and mode of use of the present pressure-sensitive adhesive sheet, the thickness of the resin film may be 70 μm or less, 50 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. By reducing the thickness of the resin film, the thickness of the pressure-sensitive adhesive layer can be made larger even if the total thickness of the present pressure-sensitive adhesive sheet is the same. This can be advantageous in terms of improving adhesion to the substrate. The lower limit of the thickness of the substrate film is not particularly limited, but from the viewpoints of the handleability (handling ability) and processability of the present pressure-sensitive adhesive sheet, it is usually 0.5 μm or more, preferably 2 μm or more, more preferably 4 μm or more.

[0115] In addition, when a foam sheet is used as the substrate, the thickness of the foam sheet is not particularly limited and can be appropriately set according to the strength, flexibility, and intended use of the pressure-sensitive adhesive sheet. From the viewpoint of thinning the joint, the thickness of the foam sheet is usually 0.70 mm or less, preferably 0.40 mm or less, more preferably 0.30 mm or less, and even more preferably 0.2 mm or less. From the viewpoint of impact resistance, the thickness of the foam sheet is preferably 0.05 mm or more, more preferably 0.06 mm or more, even more preferably 0.07 mm or more, and particularly preferably 0.10 mm or more. When the thickness of the foam sheet is large, impact resistance tends to be exhibited.

[0116] The pressure-sensitive adhesive composition may be applied using, for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, a comma coater or the like.

[0117] As for the drying conditions after coating the pressure-sensitive adhesive composition, in order to shorten the drying process, the drying temperature is preferably 60 to 140° C., and more preferably 80 to 120° C. The drying time is preferably 0.5 to 30 minutes, and more preferably 1 to 5 minutes.

[0118] Regarding the conditions of the aging treatment, in order to shorten the aging treatment step, the temperature is usually room temperature (23°C) to 70°C, and the time is usually 1 to 30 days, and specifically, for example, the aging treatment may be performed under conditions of 23°C for 1 to 20 days, preferably 23°C for 3 to 14 days, or 40°C for 1 to 10 days, etc.

[0119] The thickness of the pressure-sensitive adhesive sheet and the pressure-sensitive adhesive layer of the substrate-less double-sided pressure-sensitive adhesive sheet is not particularly limited, but is preferably 0.5 to 500 μm, more preferably 1 to 300 μm, even more preferably 5 to 200 μm, and particularly preferably 10 to 100 μm. If the pressure-sensitive adhesive layer is too thin, the adhesive strength tends to decrease, while if it is too thick, it becomes difficult to apply uniformly and problems such as air bubbles entering the coating film tend to occur.

[0120] The thickness of the adhesive layer is determined by subtracting the measured thickness of the components other than the adhesive layer from the measured thickness of the entire adhesive sheet using a digital indicator (ID-C112B, manufactured by Mitutoyo Corporation).

[0121] The adhesive strength of the present pressure-sensitive adhesive sheet is preferably 1 N / 25 mm or more, more preferably 3 N / 25 mm or more, even more preferably 5 N / 25 mm or more, and particularly preferably 10 N / 25 mm or more. The upper limit of the adhesive strength is usually 50 N / 25 mm or less, preferably 25 N / 25 mm or less. The adhesive strength is measured by the following procedure. The adhesive sheet with a thickness of about 25μm is cut to 25mm x 150mm in an environment of 23℃ and 50%RH, and then the adhesive layer is placed on a SUS-BA plate and pressed and attached by reciprocating a 2kg roller. After that, it is left to stand for 30 minutes in the same atmosphere, and then the 180 degree peel strength (N / 25mm) is measured using a peel tester at a peel speed of 300mm / min.

[0122] Furthermore, the pressure-sensitive adhesive sheet may be provided with a release sheet on the outer side of the pressure-sensitive adhesive layer, if necessary, to protect the pressure-sensitive adhesive layer. In a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is formed on one side of a substrate, the substrate may be subjected to a release treatment on the side opposite to the pressure-sensitive adhesive layer, and the release-treated surface may be used to protect the pressure-sensitive adhesive layer.

[0123] The present pressure-sensitive adhesive sheet can be used for bonding various members, and is particularly preferably used as a pressure-sensitive adhesive sheet for electronic members, for bonding electronic members. From the viewpoint of good optical properties, the pressure-sensitive adhesive sheet for electronic components preferably contains the polyester-based pressure-sensitive adhesive. EXAMPLES

[0124] 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 based on mass.

[0125] <Polyester resin (A)> First, polyester resins (A-1) to (A-5) were prepared as follows. The glass transition temperature, number average molecular weight, weight average molecular weight, and acid value of the polyester resin (A) were measured according to the methods described above. The compositions of the polyester resins (A-1) to (A-5) are shown in Table 1 below.

[0126] [Polyester resin (A-1)] A reaction vessel equipped with a heater, a thermometer, a stirrer, a rectification column, a nitrogen inlet tube, and a vacuum device was charged with 96 parts of isophthalic acid and 468 parts of sebacic acid as polyvalent carboxylic acids (a1), 271 parts of neopentyl glycol, 130 parts of 1,4-butanediol, 30 parts of 1,6-hexanediol, and 5 parts of trimethylolpropane as polyols (a2), and 0.1 part of zinc acetate as a catalyst, and the internal temperature was gradually raised to 250°C, and an esterification reaction was carried out over 4 hours. Thereafter, 0.05 parts of tetrabutyl titanate was charged as a catalyst, the internal temperature was raised to 260° C., the pressure was reduced to 1.33 hPa, and a polycondensation reaction was carried out over 3 hours to obtain a polyester resin (A-1). The resulting polyester resin (A-1) had a glass transition temperature (Tg) of -48°C, a number average molecular weight (Mn) of 11,000, a weight average molecular weight (Mw) of 77,000 and an acid value of 0.1 mgKOH / g. The final component ratios were as follows: polyvalent carboxylic acids (a1) were isophthalic acid / sebacic acid = 20.0 mol% / 80.0 mol%, and polyols (a2) were neopentyl glycol / 1,4-butanediol / 1,6-hexanediol / trimethylolpropane = 58.5 mol% / 34.0 mol% / 6.2 mol% / 1.3 mol%.

[0127] [Polyester resin (A-2)] A reaction vessel equipped with a heater, a thermometer, a stirrer, a rectification column, a nitrogen inlet tube, and a vacuum device was charged with 355 parts of isophthalic acid and 185 parts of sebacic acid as polyvalent carboxylic acids (a1), 286 parts of neopentyl glycol, 138 parts of 1,4-butanediol, 31 parts of 1,6-hexanediol, and 5 parts of trimethylolpropane as polyols (a2), and 0.1 part of zinc acetate as a catalyst, and the internal temperature was gradually raised to 250°C, and an esterification reaction was carried out over 4 hours. Thereafter, 0.05 parts of tetrabutyl titanate was charged as a catalyst, the internal temperature was raised to 260° C., the pressure was reduced to 1.33 hPa, and a polycondensation reaction was carried out over 3 hours to obtain a polyester resin (A-2). The resulting polyester resin (A-2) had a glass transition temperature (Tg) of 1° C., a number average molecular weight (Mn) of 13,000, a weight average molecular weight (Mw) of 106,000, and an acid value of 0.1 mgKOH / g. The final component ratios were isophthalic acid / sebacic acid = 70.0 mol% / 30.0 mol% as polyvalent carboxylic acids (a1), and neopentyl glycol / 1,4-butanediol / 1,6-hexanediol / trimethylolpropane = 58.6 mol% / 34.0 mol% / 6.2 mol% / 1.2 mol% as polyols (a2).

[0128] [Polyester resin (A-3)] A reaction vessel equipped with a heater, a thermometer, a stirrer, a rectification column, a nitrogen inlet tube, and a vacuum device was charged with 540 parts of adipic acid, 49 parts of isophthalic acid, and 1 part of terephthalic acid as polyvalent carboxylic acids (a1), 270 parts of neopentyl glycol, 133 parts of ethylene glycol, and 7 parts of trimethylolpropane as polyols (a2), and 0.1 part of zinc acetate as a catalyst, and the internal temperature was gradually raised to 250°C, and an esterification reaction was carried out over 4 hours. Thereafter, 0.05 parts of tetrabutyl titanate was charged as a catalyst, the internal temperature was raised to 260° C., the pressure was reduced to 1.33 hPa, and a polycondensation reaction was carried out over 3 hours to obtain a polyester resin (A-3). The resulting polyester resin (A-3) had a glass transition temperature (Tg) of -40°C, a number average molecular weight (Mn) of 8,900, a weight average molecular weight (Mw) of 52,000 and an acid value of 0.1 mgKOH / g. The final component ratios were adipic acid / isophthalic acid / terephthalic acid = 92.5 mol% / 7.4 mol% / 0.1 mol% as polyvalent carboxylic acids (a1), and neopentyl glycol / ethylene glycol / trimethylolpropane = 54.4 mol% / 44.1 mol% / 1.5 mol% as polyols (a2).

[0129] [Polyester resin (A-4)] A reaction vessel equipped with a heater, a thermometer, a stirrer, a rectification column, a nitrogen inlet tube, and a vacuum device was charged with 580 parts of succinic acid as the polyvalent carboxylic acid (a1), 295 parts of 1,3-propanediol as the polyol (a2), 118 parts of neopentyl glycol, 7 parts of trimethylolpropane, and 0.05 parts of tetrabutyl titanate as a catalyst, and the internal temperature was gradually raised to 250°C, and an esterification reaction was carried out over 4 hours. Thereafter, 0.05 parts of tetrabutyl titanate was charged as a catalyst, the internal temperature was raised to 260° C., the pressure was reduced to 1.33 hPa, and a polycondensation reaction was carried out over 3 hours to obtain a polyester resin (A-4). The resulting polyester resin (A-4) had a glass transition temperature (Tg) of -27°C, a number average molecular weight (Mn) of 6,000, a weight average molecular weight (Mw) of 99,000 and an acid value of 0.1 mgKOH / g. The final component ratio was 100.0 mol % of succinic acid as the polyvalent carboxylic acid (a1), and 76.7 mol % / 22.3 mol % / 1.0 mol % of 1,3-propanediol / neopentyl glycol / trimethylolpropane as the polyol (a2).

[0130] [Polyester resin (A-5)] A reaction vessel equipped with a heater, a thermometer, a stirrer, a rectification column, a nitrogen inlet tube, and a vacuum device was charged with 742 parts of dimer acid and 57 parts of terephthalic acid as polyvalent carboxylic acids (a1), 200 parts of ethylene glycol and 1 part of trimethylolpropane as polyols (a2), and 0.05 parts of tetrabutyl titanate as a catalyst, and the internal temperature was gradually raised to 250°C, and an esterification reaction was carried out over 4 hours. Thereafter, 0.05 parts of tetrabutyl titanate was charged as a catalyst, the internal temperature was raised to 260° C., the pressure was reduced to 1.33 hPa, and a polycondensation reaction was carried out over 3 hours to obtain a polyester resin (A-5). The resulting polyester resin (A-5) had a glass transition temperature (Tg) of -42°C, a number average molecular weight (Mn) of 14,200, a weight average molecular weight (Mw) of 81,000 and an acid value of 0.1 mgKOH / g. The final component ratio was dimer acid / terephthalic acid=75 mol % / 25 mol % as the polyvalent carboxylic acids (a1), and ethylene glycol / trimethylolpropane=99.4 mol % / 0.6 mol % as the polyol (a2).

[0131] <Crosslinking agent (B)> B-1: Isocyanate crosslinking agent "Takenate D101E" (Mitsui Chemicals) Tolylene diisocyanate-trimethylolpropane adduct

[0132] <Catalyst (C)> The following was prepared as the catalyst (C): C-1: Tris(2,4-pentanedionato)iron(III) (TCI) C-2: Orgatics ZC-150 (Matsumoto Fine Chemical Co., Ltd.) diluted with acetylacetone to a solids concentration of 1%

[0133] <Hydrolysis inhibitor (D)> (D-1): Polycarbodiimide compound "Carbodilite (registered trademark) V-09GB" (manufactured by Nisshinbo Chemical Co., Ltd.)

[0134] <Example 1> Polyester-based resin (A-1) was diluted with ethyl acetate to a solid content concentration of 40%, and 2.0 parts of crosslinking agent (B-1), 0.0200 parts of catalyst (C) (C-1) [containing 32 ppm of iron per 100 parts of polyester-based resin (A-1)], and 1.0 part of hydrolysis inhibitor (D-1) were blended with 100 parts of the solid content, and the mixture was stirred and mixed to obtain a polyester-based resin composition (polyester-based pressure-sensitive adhesive composition) of Example 1.

[0135] <Examples 2 to 9 and Comparative Examples 1 to 4> The same procedure was carried out as in Example 1, except that the composition of the polyester resin composition (polyester pressure-sensitive adhesive composition) was changed as shown in Tables 1 and 2 below, to obtain polyester resin compositions (polyester pressure-sensitive adhesive compositions) for Examples 2 to 9 and Comparative Examples 1 to 4.

[0136] The following evaluations were carried out using the obtained polyester resin compositions (polyester pressure-sensitive adhesive compositions) of Examples 1 to 9 and Comparative Examples 1 to 4. The evaluation results are shown in Tables 1 and 2 below.

[0137] [Production of Adhesive Sheet] The obtained polyester resin compositions (polyester adhesive compositions) of Examples 1 to 9 and Comparative Examples 1 to 4 were applied to a polyethylene terephthalate (PET) film (thickness 38 μm) so that the thickness after drying was about 25 μm, and then dried at 120° C. for 4 minutes to form an adhesive layer. Thereafter, a release-treated PET sheet (release sheet) was attached to the adhesive layer to protect its surface, and the layer was aged in an atmosphere at a temperature of 40° C. for 5 or 7 days to obtain the adhesive sheets of Examples 1 to 9 and Comparative Examples 1 to 4.

[0138] [Gel fraction] The pressure-sensitive adhesive sheets of Examples 1 to 9 and Comparative Examples 1 to 4 that had been aged for 7 days were each wrapped in a 200-mesh SUS wire net and immersed in toluene at 23°C for 24 hours, the mass of the pressure-sensitive adhesive component before immersion and the mass of the insoluble pressure-sensitive adhesive component remaining in the wire net after immersion were measured, and the percentage was calculated according to the following formula to obtain the gel fraction (%), where the mass of the substrate was subtracted. Gel fraction (%) = mass of insoluble adhesive component remaining in the wire mesh after immersion / mass of adhesive component before immersion × 100

[0139] [Crosslinking speed] The gel fractions of the pressure-sensitive adhesive sheets of Example 1, Comparative Examples 1 and 2 aged for 5 days (gel fraction after 5 days) and the gel fractions of the pressure-sensitive adhesive sheets of Example 1, Comparative Examples 1 and 2 aged for 7 days (gel fraction after 7 days) were measured according to the gel fraction measurement method described above, the crosslinking rate was calculated from the following formula, and evaluation was performed according to the following evaluation criteria. Crosslinking rate (%) = gel fraction after 5 days / gel fraction after 7 days × 100 (Evaluation Criteria) ◎ 98% or more ○ Less than 98%, 95% or more △ Less than 95%, 90% or more × Less than 90%

[0140] [Adhesive strength] The pressure-sensitive adhesive sheets of Examples 2 to 9 and Comparative Examples 3 and 4, which had been aged for 7 days, were cut to 25 mm x 150 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 placed against a SUS-BA plate, and a 2 kg roller was reciprocated to pressurize and attach the sheets. After leaving the sheets to stand for 30 minutes in the same atmosphere, the 180° peel strength (N / 25 mm) was measured at a peel speed of 300 mm / min using a peel tester.

[0141] [Optical properties] The adhesive layer of the adhesive sheet of Examples 2 to 9 and Comparative Examples 3 and 4 that had been aged for 7 days was transferred to an alkali-free glass plate (Corning, Eagle XG), and the release film was then peeled off to prepare a test piece having an adhesive layer / alkali-free glass structure. The obtained test piece was measured using a color difference meter (Nippon Denshoku Industries, SE6000) to obtain a color difference of 0.01 to 0.01 mm. * The values ​​were measured and evaluated according to the following criteria. (Evaluation Criteria) ○ 0.5 or less ×...greater than 0.5

[0142] [Pot life] The viscosities (mPa s) of the polyester resin compositions (polyester pressure-sensitive adhesive compositions) of Examples 2 to 9 and Comparative Examples 3 and 4 were measured 0 hours and 4 hours after preparation using a Brookfield viscometer (rotor: No. 3, rotation speed: 12 rpm, measurement time: 1 minute). The viscosity ratios were calculated using the following formula, and the compositions were evaluated according to the following evaluation criteria. Viscosity ratio = Viscosity after 4 hours / Viscosity after 0 hours (Evaluation Criteria) ◎ 3 or less ○ 3 or more and 5 or less △ 5 or more and 15 or less × Gelation

[0143] [Table 1]

[0144] [Table 2]

[0145] From the results in Tables 1 and 2, the polyester-based resin compositions (polyester-based pressure-sensitive adhesive compositions) of Examples 1 to 9, which contained iron element as catalyst (C) in a specific trace amount, were excellent in adhesive strength, crosslinking speed, crosslinking stability, optical properties, and pot life. On the other hand, the polyester resin compositions (polyester pressure-sensitive adhesive compositions) of Comparative Example 1, which did not contain catalyst (C), and Comparative Example 2, which did not contain iron element as the catalyst (C), were inferior in crosslinking rate and crosslinking stability. Furthermore, the polyester resin compositions (polyester pressure-sensitive adhesive compositions) of Comparative Examples 3 and 4, which contained iron element as the catalyst (C) but whose content was outside the range of the present invention, were inferior in optical properties and pot life. [Industrial Applicability]

[0146] Since the present resin composition has excellent adhesive strength, curing speed, crosslinking stability, optical properties, and pot life, it can be suitably used as a polyester-based adhesive or an adhesive layer of an adhesive sheet, and can be particularly suitably used as an adhesive sheet for electronic components.

Claims

1. A polyester-based resin composition comprising a polyester-based resin (A), a crosslinking agent (B), and a catalyst (C), wherein the crosslinking agent (B) contains a polyfunctional isocyanate compound, the catalyst (C) contains an iron element, and the content of the iron element per 100 parts by mass of the polyester-based resin (A) is 150 ppm or less.

2. 2. The polyester resin composition according to claim 1, wherein the acid value of the polyester resin (A) is 5 mgKOH / g or less.

3. 3. The polyester resin composition according to claim 1, wherein the content of the polyfunctional isocyanate compound is 10 parts by mass or less based on 100 parts by mass of the polyester resin (A).

4. The polyester resin composition according to claim 1 or 2, wherein the polyfunctional isocyanate compound contains a structural unit derived from a cyclic structure.

5. 3. The polyester resin composition according to claim 1, wherein the catalyst (C) is an iron complex compound.

6. 3. The polyester resin composition according to claim 1, wherein the polyester resin (A) has a weight average molecular weight of 10,000 or more.

7. A polyester-based pressure-sensitive adhesive composition comprising the polyester-based resin composition according to claim 1 or 2.

8. A polyester-based pressure-sensitive adhesive obtained by crosslinking the polyester-based pressure-sensitive adhesive composition according to claim 7.

9. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer comprising the polyester-based pressure-sensitive adhesive according to claim 8.

10. The pressure-sensitive adhesive sheet according to claim 9, having an adhesive strength of 1 N / 25 mm or more.

11. A pressure-sensitive adhesive sheet for electronic components, comprising the polyester-based pressure-sensitive adhesive according to claim 8 .

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