Adhesive layer and adhesive sheet

Abstract

To provide an adhesive layer which has good adhesive force to various adherends even when being a thin film and exhibits little change in adhesive force over time.SOLUTION: The adhesive layer is obtained by crosslinking an adhesive composition containing a polyester resin (i) which has structural moieties derived from polycarboxylic acids (a) and structural moieties derived from polyol components (b). The thickness of the adhesive layer is 18 μm or less. A structural moiety derived from a C8 or lower aliphatic dicarboxylic acid (a1) out of the structural moieties derived from the polycarboxylic acids (a) is contained in an amount of 60 mol% or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive layer, and more particularly to a thin pressure-sensitive adhesive layer and pressure-sensitive adhesive sheet that are suitable for use in the housings and joining portions of components of portable electronic devices. [Background technology]

[0002] Adhesive tapes and adhesive sheets are excellent in workability because they can bond substrates and components without the need for heat or other energy, and as a joining means with high adhesive reliability, they are used for component fixing applications in various industrial fields, such as office automation equipment and home appliances. As these office automation equipment become more functional, efforts are being made to make them smaller and thinner, and there is a particularly high demand for smaller and thinner devices, such as personal computers, digital video cameras, electronic organizers, mobile phones, PHS devices, smartphones, game consoles, and e-books. For such portable electronic devices, along with the thinning of major components, there is a demand for thinner adhesive tapes used to fix these devices.

[0003] Patent Document 1, for example, proposes a double-sided adhesive tape having a transparent thin film excellent in adhesive strength and high-temperature retention, suitable for fastening components such as the above-mentioned mobile electronic terminals, such as mobile phones, and thin-film displays, or for bonding optical disk substrates and fastening polarizing plates. The double-sided adhesive tape has a total thickness of 30 μm or less, and the thickness of each of the adhesive layers on both sides is 2 to 10 μm. The double-sided adhesive tape has adhesive layers formed on both sides of a core material, the adhesive layers comprising an adhesive composition containing an acrylate copolymer containing 90% by mass or more of butyl acrylate units and having a weight-average molecular weight of 700,000 or more, and a specific amount of a tackifier.

[0004] Furthermore, for example, Patent Document 2 proposes that an adhesive containing a polyester-based resin having aromatic dicarboxylic acid, glycol having hydrocarbon in the side chain, and trivalent or higher polyhydric alcohol and / or trivalent or higher polycarboxylic acid as essential ingredients, and obtained by polycondensing a specific amount of polyhydric alcohol and / or polycarboxylic acid, has excellent adhesive properties and heat resistance, and that the polyester-based resin exerts sufficient adhesive strength with pressure equivalent to finger pressure, and has excellent adhesiveness, mechanical strength, and particularly excellent heat resistance, making it suitable for a wide range of applications. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-169327 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-99879 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technologies disclosed in Patent Documents 1 and 2 do not provide sufficient adhesive strength to various adherends in the form of a thin film, and further improvements are required. In addition, the acrylic adhesive of the technology disclosed in Patent Document 1 generally has a low elastic modulus and low cohesive strength, so when used to form a thin adhesive layer, adhesive residue tends to be left behind when peeled off, and there is room for further improvement.

[0007] Polyester-based adhesives have also been investigated as adhesives with a high modulus of elasticity and high cohesive strength (resistance to cracking and leaving residue when peeled off), but the polyester-based adhesives disclosed in the technology of Patent Document 2 above were not disclosed for use in thin films. Furthermore, when made into thin films, the adhesive strength was not sufficiently exhibited, and further improvement was required.

[0008] Traditionally, acrylic adhesives have been widely used, but in recent years, polyester adhesives have also been increasingly used. Compared to acrylic adhesives, polyester adhesives have higher heat resistance, making them ideal for use in electronic components. Furthermore, because they are compatible with ester films, such as polyethylene terephthalate (PET), polyester adhesives can often be used in applications where acrylic adhesives are difficult to use. Furthermore, given recent calls for addressing environmental impact, polyester adhesives can be depolymerized to return them to oligomers and monomers during disposal, making them more environmentally friendly than acrylic adhesives when it comes to recycling.

[0009] Therefore, in the present invention, under such a background, even if it is a thin film, SUS, polyimide, polypropylene The present invention provides a pressure-sensitive adhesive layer and a pressure-sensitive adhesive sheet that exhibit good adhesive strength to various adherends and little change in adhesive strength over time. In some cases, the present invention also provides a thin-film adhesive sheet that, when bonded with a thin-film adhesive layer, has low initial adhesive strength but increases adhesive strength over time. [Means for solving the problem]

[0010] The present inventors have noticed that the adhesive strength of polyester-based adhesives is little dependent on the thickness of the adhesive layer, and have discovered that by using a polyester-based resin as the resin constituting the adhesive composition to form a polyester-based adhesive, it is possible to reduce the thickness of the adhesive layer while maintaining adhesive strength. The reason why adhesive strength is less dependent on the thickness of the adhesive layer is not clear, but it is thought that this is because polyester-based adhesives have a high elastic modulus and are less likely to deform, so the energy required to deform the adhesive bulk is less and does not contribute much to adhesive strength, and therefore the adhesion between interfaces contributes more to adhesive strength. Furthermore, when a polyester-based adhesive is used to achieve strong adhesive strength in a thin film, high interfacial adhesion is preferable, as mentioned above. Increasing polarity is important to improve adhesion, and increasing the ester bond concentration is thought to be effective. On the other hand, since it is necessary for the adhesive to be compatible with thin films, the adhesive's softness must also be taken into consideration, and a low glass transition temperature (Tg) is preferable. Taking these factors into consideration, we designed the adhesive and found that the above-mentioned problems can be more effectively solved by introducing a certain amount of aliphatic dicarboxylic acid with a relatively short carbon difference.

[0011] That is, the present invention has the following aspects [1] to

[14] . [1] A pressure-sensitive adhesive layer obtained by crosslinking a pressure-sensitive adhesive composition containing a polyester resin (i) having a structural moiety derived from a polycarboxylic acid (a) and a structural moiety derived from a polyol component (b), The thickness of the pressure-sensitive adhesive layer is 18 μm or less, The pressure-sensitive adhesive layer contains 60 mol % or more of structural moieties derived from aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms among the structural moieties derived from the polyvalent carboxylic acids (a). [2] The pressure-sensitive adhesive layer according to [1], wherein the structural moiety derived from the polyol component (b) contains a structural moiety derived from at least one member selected from the group consisting of ethylene glycol, 2-methyl-1,3-propanediol, and neopentyl glycol. [3] The pressure-sensitive adhesive layer according to [1] or [2], wherein the structural moiety derived from the aliphatic dicarboxylic acid (a1) having 8 or less carbon atoms is a structural moiety derived from adipic acid. [4] The pressure-sensitive adhesive layer according to any one of [1] to [3], wherein the polyester resin (i) has an ester bond concentration of 9 to 12.5 mmol / g. [5] The pressure-sensitive adhesive layer according to any one of [1] to [4], wherein the glass transition temperature of the polyester resin (i) is -50 to -10°C. [6] The pressure-sensitive adhesive layer according to any one of [1] to [5], wherein the polyester resin (i) having a structural moiety derived from the polycarboxylic acid (a) and a structural moiety derived from the polyol component (b) is crosslinked with a crosslinking agent (ii). [7] The pressure-sensitive adhesive layer according to [6], wherein the crosslinking agent (ii) is an isocyanate-based crosslinking agent (ii-1). [8] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer according to any one of [1] to [7] and a substrate, wherein the substrate is laminated on one side of the pressure-sensitive adhesive layer and the other side is a release-treated sheet. [9] The pressure-sensitive adhesive sheet according to [8], wherein the substrate is a polyester resin sheet.

[10] A pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer according to any one of [1] to [7] and a release-treated sheet, wherein the release-treated sheet is laminated on both sides of the pressure-sensitive adhesive layer.

[11] The pressure-sensitive adhesive sheet according to [8] or [9], wherein the adherend is a polyimide.

[12] The adhesive sheet according to [8] or [9], which is used to fix electronic components.

[13] The pressure-sensitive adhesive sheet according to any one of [8] to

[12] , wherein X is the adhesive strength (N / 25 mm) measured under the following measurement conditions, and Y is the thickness (μm) of the pressure-sensitive adhesive layer, and X / Y≧0.5. [Adhesive strength (N / 25mm) measurement conditions] The adhesive sheet was cut to 25mm x 200mm in an environment of 23°C and 50%RH, the release film was peeled off, and the adhesive layer side was placed against a SUS-BA plate as the adherend, and a 2kg roller was used to pressurize and adhere the sheet. After leaving the sheet to stand for 30 minutes in the same atmosphere, the 180° peel strength (N / 25mm) was measured at a peel rate of 300mm / min using an autograph (Shimadzu Corporation, Autograph AGS-H 500N). This was taken as the adhesive strength.

[14] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer crosslinked with a pressure-sensitive adhesive composition containing a polyester resin (i') having a structural moiety derived from a polycarboxylic acid (a) and a structural moiety derived from a polyol component (b), The thickness of the pressure-sensitive adhesive layer is 18 μm or less, An adhesive sheet whose adhesive strength over time measured under the following conditions is 5N / 25mm or more. [Measurement conditions for adhesive strength over time (N / 25mm)] The adhesive sheet was cut to 25mm x 200mm in an environment of 23°C and 50%RH, and the adhesive layer was placed on a SUS-BA plate as an adherend, and a 2kg roller was used to pressurize and adhere the sheet. After leaving the sheet in the same atmosphere for 24 hours, the 180° peel strength (N / 25mm) was measured at a peel rate of 300mm / min using an autograph (Shimadzu Corporation, Autograph AGS-H 500N). This was taken as the adhesive strength over time. [Effects of the Invention]

[0012] The pressure-sensitive adhesive layer of the present invention may be a thin film, SUS, polyimide, polypropylene The adhesive layer of the present invention exhibits excellent adhesive strength to various adherends. Furthermore, the adhesive strength of the adhesive layer of the present invention changes little from the initial state to the time elapsed, that is, the adhesive layer of the present invention exhibits sufficient adhesive strength from the initial state. Therefore, the pressure-sensitive adhesive layer of the present invention is suitable for use as a single-sided or double-sided pressure-sensitive adhesive sheet for polyimides, a single-sided or double-sided pressure-sensitive adhesive sheet used for bonding optical components, a single-sided or double-sided pressure-sensitive adhesive sheet for fixing components of portable electronic devices, a single-sided or double-sided pressure-sensitive adhesive sheet for fixing electronic components, etc. DETAILED DESCRIPTION OF THE INVENTION

[0013] The configuration of the present invention will be described in detail below, but these are merely examples of preferred embodiments. In the present invention, the term "carboxylic acids" includes not only acids such as carboxylic acids, but also derivatives of carboxylic acids such as salts of carboxylic acids, anhydrides of carboxylic acids, halides of carboxylic acids, and esters of carboxylic acids.

[0014] A pressure-sensitive adhesive layer according to one embodiment of the present invention is a pressure-sensitive adhesive layer obtained by crosslinking a pressure-sensitive adhesive composition containing a polyester resin (i) having a structural moiety derived from a polycarboxylic acid (a) and a structural moiety derived from a polyol component (b), The thickness of the pressure-sensitive adhesive layer is 18 μm or less, The polycarboxylic acid (a) is characterized in that it contains 60 mol % or more of structural moieties derived from aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms among the structural moieties derived from the polycarboxylic acids (a). Furthermore, a pressure-sensitive adhesive sheet according to one embodiment of the present invention is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed by crosslinking a pressure-sensitive adhesive composition containing a polyester resin (i') having a structural moiety derived from a polyvalent carboxylic acid (a) and a structural moiety derived from a polyol component (b), The thickness of the pressure-sensitive adhesive layer is 18 μm or less, It is characterized by an adhesive strength over time of 5N / 25mm or more measured under specific measurement conditions. Hereinafter, each component contained in the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer of the present invention will be described in order.

[0015] <Polyester Resins (i) and (i')> The polyester resin (i) used in the present invention has structural moieties derived from polycarboxylic acids (a) and structural moieties derived from a polyol component (b), and contains 60 mol % or more, preferably 70 mol % or more, particularly preferably 75 mol % or more of structural moieties derived from aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms among the structural moieties derived from the polycarboxylic acids (a). The upper limit is usually 100 mol %, preferably 98 mol %. The pressure-sensitive adhesive layer of the present invention contains a polyester resin (i) containing a specific amount of structural moieties derived from aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms, and therefore can have excellent adhesive strength to various adherends even when it is a thin film, and can have little change in adhesive strength between the initial state and over time. The polyester resin (i') used in the present invention has a structural portion derived from the polycarboxylic acid (a) and a structural portion derived from the polyol component (b).

[0016] [Structural moiety derived from polycarboxylic acids (a)] The polyester resin (i) is characterized in that, as structural moieties derived from the polycarboxylic acids (a), structural moieties derived from aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms (including the carbon atoms of the carboxy group) account for 60 mol % or more of the total polycarboxylic acids (a).

[0017] (Structural moiety derived from aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms) Examples of structural moieties derived from the aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms include structural moieties derived from linear aliphatic dicarboxylic acids such as malonic acids, dimethylmalonic acids, succinic acids, glutaric acids, adipic acids, pimelic acids, suberic acids, and diglycolic acids having 8 or less carbon atoms; structural moieties derived from aliphatic dicarboxylic acids having an alkyl group on the side chain such as methylsuccinic acids, 2,2-dimethylglutaric acids, 1,3-dimethylglutaric acids, and dimethyladipic acids; structural moieties derived from sulfur-containing dicarboxylic acids such as thiodipropionic acids; and structural moieties derived from unsaturated group-containing aliphatic dicarboxylic acids such as fumaric acids, maleic acids, and itaconic acids. Of these, structural moieties derived from linear aliphatic dicarboxylic acids are preferred. These may be used alone or in combination of two or more. Among these, structural moieties derived from adipic acids are preferred because of their excellent adhesive strength to various adherends and little change in adhesive strength between the initial stage and over time. Furthermore, it is preferable that the structural moiety derived from the aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms is a structural moiety derived from adipic acid, since this provides excellent adhesive strength to various adherends even in the form of a thin film, and there is little change in adhesive strength between the initial state and over time.

[0018] The content of the structural moiety derived from the aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms is usually 60 mol% or more, preferably 70 mol% or more, and particularly preferably 75 mol% or more, relative to the structural moiety derived from the polycarboxylic acids (a). The upper limit of the content of the structural moiety derived from the aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms is usually 100 mol%, preferably 98 mol%. When the content of the structural moiety derived from the aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms is above the above-mentioned value, the adhesive strength to various adherends is excellent, and there tends to be little change in adhesive strength between the initial state and over time.

[0019] (Structural moieties derived from other polycarboxylic acids) The structural moiety derived from the polycarboxylic acid (a) contained in the polyester resin (i) may contain, in addition to the structural moiety derived from the aliphatic dicarboxylic acid (a1) having 8 or less carbon atoms, structural moieties derived from other polycarboxylic acids such as dicarboxylic acids having 9 or more carbon atoms, aromatic dicarboxylic acids, and trivalent or higher polycarboxylic acids. These may be contained alone or in combination of two or more kinds.

[0020] Examples of the structural moiety derived from dicarboxylic acids having 9 or more carbon atoms include structural moieties derived from aliphatic dicarboxylic acids such as trimethyladipic acids, pimelic acids, azelaic acids, thiodipropionic acids, diglycolic acids having 9 or more carbon atoms, and 1,9-nonanedicarboxylic acids; and structural moieties 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.

[0021] Examples of the structural units derived from aromatic dicarboxylic acids include structural moieties derived from aromatic dicarboxylic acids such as phthalic acids, terephthalic acids, isophthalic acids, benzylmalonic acids, diphenic acids, 4,4'-oxydibenzoic acids, and naphthalenedicarboxylic acids such as 1,8-naphthalenedicarboxylic acids, 2,3-naphthalenedicarboxylic acids, and 2,7-naphthalenedicarboxylic acids.

[0022] Examples of the structural moiety derived from trivalent or higher polyvalent carboxylic acids include structural moieties derived from trimellitic acids, pyromellitic acids, adamantanetricarboxylic acids, trimesic acids, and the like.

[0023] Among the structural moieties derived from the other polyvalent carboxylic acids, it is preferable to contain a structural moiety derived from an aromatic dicarboxylic acid, particularly a structural moiety derived from an asymmetric aromatic dicarboxylic acid, in order to reduce the crystallinity of the polyester resin (i).

[0024] Examples of the structural moiety derived from the asymmetric aromatic dicarboxylic acids include structural moieties derived from phthalic acids, isophthalic acids, 1,8-naphthalenedicarboxylic acids, and 2,3-naphthalenedicarboxylic acids. Among these, structural moieties derived from isophthalic acids are particularly preferred in terms of reactivity.

[0025] The content of the structural moiety derived from the aromatic dicarboxylic acid, particularly the structural moiety derived from an asymmetric aromatic dicarboxylic acid, is usually 1 to 40 mol %, preferably 2 to 30 mol %, particularly preferably 3 to 25 mol %, relative to the structural moiety derived from the polycarboxylic acid (a). If the content of the structural moiety derived from the aromatic dicarboxylic acid is too high, the initial adhesive strength and tackiness tend to decrease.

[0026] Furthermore, the structural units derived from the polyvalent carboxylic acids (a) contained in the polyester-based resin (i') are not particularly limited, but it is preferable that the polyester-based resin (i') has structural units derived from the polyvalent carboxylic acids (a) similar to those contained in the polyester-based resin (i).

[0027] [Structural moiety derived from polyol component (b)] Examples of the structural moiety derived from the polyol component (b) contained in the polyester resins (i) and (i') include a structural moiety derived from a dihydric alcohol (b1) and a structural moiety derived from a trihydric or higher polyol (b2). These may be contained alone or in combination of two or more. In particular, in the present invention, it is preferred that the polyester resins (i) and (i') contain a structural moiety derived from a dihydric alcohol (b1) and a structural moiety derived from a trihydric or higher polyol (b2).

[0028] (Structural moiety derived from dihydric alcohol (b1)) Examples of the structural moiety derived from the dihydric alcohol (b1) include structural moieties 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, and dimer diols derived from oleic acid, erucic acid, and the like; Structural moieties 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 moieties 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 their ethylene oxide adducts and propylene oxide adducts. Further examples include structural moieties derived from fatty acid esters derived from castor oil, glycerol monostearate, etc. Among these, structural moieties derived from aliphatic diols are preferred.

[0029] The structural moiety derived from the aliphatic diol can also be distinguished as a structural moiety derived from an aliphatic diol having a straight-chain structure, and a structural moiety derived from an aliphatic diol having a hydrocarbon group in the side chain.

[0030] In such cases, the content of the structural moiety derived from the linear aliphatic diol relative to the structural moiety derived from the polyol component (b) is 1 to 100 mol%, preferably 10 to 80 mol%, more preferably 20 to 75 mol%, and particularly preferably 40 to 70 mol%. If this content is too low, the reactivity of the polyester resins (i) and (i') during production tends to decrease. However, if this content is too high, the polyester resins (i) and (i') tend to crystallize, reducing the initial adhesive strength of the adhesive.

[0031] The structural moiety derived from the linear aliphatic diol is preferably a structural moiety derived from a linear aliphatic diol having 2 to 18 carbon atoms, and is particularly preferably a structural moiety derived from an aliphatic diol having 4 or less carbon atoms, since it is easy to increase the thin film adhesive strength by increasing the polarity through an increase in the ester bond concentration. Specifically, it is a structural moiety derived from ethylene glycol, 1,3-propanediol, or 1,4-butanediol, and is particularly preferably a structural moiety derived from ethylene glycol.

[0032] The content of the structural moiety derived from an aliphatic diol having a hydrocarbon group in the side chain is 5 to 100 mol%, preferably 20 to 90 mol%, more preferably 25 to 80 mol%, and particularly preferably 28 to 60 mol%, relative to the structural moiety derived from the polyol component (b). If this content ratio is too low, the polyester resins (i) and (i') tend to crystallize, reducing the initial adhesive strength of the adhesive. If this content ratio is too high, the reactivity of the polyester resin (i) during production tends to decrease.

[0033] Examples of structural moieties derived from aliphatic diols having a hydrocarbon group in the side chain include structural moieties derived from 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, dimer diol, etc. Among these, structural moieties derived from 2,2-dimethyl-1,3-propanediol (neopentyl glycol) and 2-methyl-1,3-propanediol are preferred.

[0034] (Structural moiety derived from trivalent or higher polyol (b2)) In the present invention, it is preferable that the structural moiety derived from the polyol component (b) contains a structural moiety derived from a trivalent or higher polyol (b2) in order to form a reactive site with the crosslinking agent (ii) described below and increase the cohesive strength.

[0035] The content of the structural moiety derived from the trihydric or higher polyol (b2) is preferably 20 mol % or less, more preferably 0.1 to 10 mol %, and particularly preferably 0.5 to 5 mol %, relative to the structural moiety derived from the polyol component (b). If the content of the trihydric or higher polyol (b2) is too high, it tends to be difficult to produce the polyester resins (i) and (i').

[0036] Examples of the structural moiety derived from the trivalent or higher polyol (b2) include structural moieties derived from 2-ethyl-2-hydroxymethyl-1,3-propanediol (trimethylolpropane), trimethylolethane, glycerin, pentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, and 1,2,6-hexanetriol. Among these, it is particularly preferable to contain a structural moiety derived from trimethylolpropane, as this is relatively less likely to cause gel formation.

[0037] In the present invention, in terms of adhesive strength to various adherends and minimal change in adhesive strength between initial and aging, the structural moiety derived from polyol component (b) preferably contains a structural moiety derived from at least one selected from the group consisting of ethylene glycol, 2-methyl-1,3-propanediol, and neopentyl glycol, and the structural moiety derived from polyol component (b) particularly preferably contains a structural moiety derived from ethylene glycol and / or neopentyl glycol. When both such structural moieties are contained, the molar ratio of ethylene glycol / neopentyl glycol is preferably 10 / 90 to 10 / 90, particularly 20 / 75 to 25 / 80, and even more preferably 40 / 60 to 70 / 30.

[0038] The content of the structural unit derived from at least one selected from the group consisting of ethylene glycol, 2-methyl-1,3-propanediol, and neopentyl glycol is usually 70 mol % or more, preferably 80 mol % or more, and particularly preferably 90 mol % or more, relative to the structural units derived from the polyol component (b), with the upper limit being 100 mol %.

[0039] In the present invention, the ratio of the structural moieties derived from each component of the polyester resins (i) and (i') (composition ratio) can be determined by a known method using NMR, for example, H-NMR measurement at a resonance frequency of 400 MHz (proton-type nuclear magnetic resonance spectroscopy), 13 It can be determined by C-NMR measurement (carbon-type nuclear magnetic resonance spectroscopy measurement) or the like.

[0040] The polyester resins (i) and (i') used in the present invention may contain, in addition to the structural moieties derived from the polyvalent carboxylic acids (a) and the structural moieties derived from the polyol component (b), structural moieties derived from a compound having both a carboxylic acid and a hydroxyl group in the molecule (e.g., lactic acid) within a range that does not impair the effects of the present invention. However, since the structural moieties derived from lactic acid are prone to hydrolysis, it is preferable that they not be contained.

[0041] [Production of Polyester Resins (i) and (i')] The polyester resins (i) and (i') of the present invention can be produced by polycondensation of the polycarboxylic acid (a) and the polyol component (b) in the presence of a catalyst using a known method. That is, the polyester resins (i) and (i') are obtained by polycondensation of the polycarboxylic acid (a) and the polyol component (b), and therefore have structural moieties derived from the polycarboxylic acid (a) and the polyol component (b). In the polycondensation reaction, an esterification reaction or an ester exchange reaction is carried out first, followed by the polycondensation reaction. When a high molecular weight is not required, the product may be produced by only the esterification reaction or the ester exchange reaction.

[0042] The blending ratio of the polycarboxylic acid (a) to the polyol component (b) is preferably 1 to 2 equivalents, particularly preferably 1.1 to 1.7 equivalents, of the polyol component (b) per equivalent of the polycarboxylic acid (a). If the blending ratio of the polyol component (b) is too low, the acid value tends to be high, making it difficult to achieve a high molecular weight, while if it is too high, the yield tends to decrease.

[0043] [Esterification reaction or transesterification reaction] In the esterification reaction or transesterification reaction, a catalyst is usually used, and specific examples 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 viewpoint of the balance between high catalytic activity and the hue of the resulting reaction product.

[0044] The amount of the catalyst to be added is preferably 1 to 10,000 ppm, particularly preferably 10 to 5,000 ppm, and further preferably 20 to 3,000 ppm, based on the total weight of the copolymerization components. If the amount is too small, the polymerization reaction tends to proceed insufficiently, whereas if the amount is too large, there is no advantage such as shortening the reaction time, and side reactions tend to occur easily.

[0045] The reaction temperature during the esterification reaction or transesterification reaction is preferably 200 to 300°C, particularly preferably 210 to 280°C, and even more preferably 220 to 260°C. If the reaction temperature is too low, the reaction tends to proceed insufficiently, while if it is too high, side reactions such as decomposition tend to occur. The pressure during the reaction is usually normal pressure.

[0046] As reaction conditions for the polycondensation reaction carried out after the above-mentioned esterification reaction or transesterification reaction, it is preferable to further add the same amount of the same catalyst as that used in the above-mentioned esterification reaction or transesterification reaction, set the reaction temperature to preferably 220 to 280°C, particularly preferably 230 to 270°C, and gradually reduce the pressure in the reaction system until the reaction is finally carried out 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.

[0047] The ester bond concentration of the polyester resins (i) and (i') obtained above is preferably 9 to 12.5 mmol / g, more preferably 9.2 to 11.5 mmol / g, and even more preferably 9.5 to 11.0 mmol / g. If the ester group concentration is too low, the polarity of the polyester resins (i) and (i') decreases, which tends to result in poor initial adhesion and thin film adhesive strength.

[0048] The ester bond concentration (mmol / g) refers to the number of moles of ester bonds per gram of polyester resin (i) or (i'), and can be calculated from the amounts charged. The calculation is performed by dividing the number of moles of the polycarboxylic acid (a) or polyol component (b), whichever is charged less frequently, by the total weight of the final product. An example of the calculation formula is shown below. When the charged amounts of the polyvalent carboxylic acid (a) and the polyol component (b) are equal in molar amount, either of the following calculation formulas may be used. Furthermore, when a monomer having both a carboxylic acid and a hydroxyl group is used, or when polyester is produced from caprolactone or the like, the calculation method will be changed appropriately.

[0049] <When the amount of polycarboxylic acids (a) is small> Ester bond concentration (mmol / g) = [(A1 / α1 × m1 + A2 / α2 × m2 + A3 / α3 × m3 ) / Z] × 1000 A: Amount of polycarboxylic acid (a) (g) α: Molecular weight of polycarboxylic acid (a) m: number of carboxyl groups per molecule of polycarboxylic acid (a) Z: Finished weight (g) <When the amount of polyol component (b) is small> Ester group concentration (mmol / g) = [(B1 / β1 × n1 + B2 / β2 × n2 + B3 / β3 × n3 ) / Z] × 1000 B: Amount of polyol component (b) charged (g) β: Molecular weight of polyol component (b) n: number of hydroxyl groups per molecule of polyol component (b) Z: Finished weight (g)

[0050] The ester bond concentrations of the polyester resins (i) and (i') can be determined by a known method using NMR or the like, for example, a method using a resonance frequency of 400 MHz. 1 H-NMR measurement (proton nuclear magnetic resonance spectroscopy), 13 It can also be determined by C-NMR measurement (carbon-type nuclear magnetic resonance spectroscopy).

[0051] Examples of methods for adjusting the ester bond concentration within a predetermined range include selecting a polyol having 4 or less carbon atoms as the polyol component (b), increasing the content of linear carboxylic acids having 8 or less carbon atoms as the polycarboxylic acids (a), or increasing the content of dicarboxylic acids having a smaller number of carbon atoms, or a combination of both.

[0052] The glass transition temperature (Tg) of the polyester resins (i) and (i') is preferably −70 to −10° C., particularly preferably −50 to −15° C., and further preferably −45 to −20° C. If the glass transition temperature (Tg) is too high, the adhesive strength of the thin film tends to decrease, and if it is too low, the heat resistance and cohesive strength tend to decrease. The glass transition temperature can be adjusted by, for example, introducing an aromatic skeleton or changing the alkyl chain length of the polycarboxylic acid (a) or the polyol component (b).

[0053] The glass transition temperature (Tg) is measured using a differential scanning calorimeter DSC Q20 manufactured by TA Instruments, Inc. The measurement temperature range is −90 to 100° C., and the temperature rise rate is 10° C. / min.

[0054] The weight-average molecular weight of the polyester resins (i) and (i') is preferably 2000 to 500000, more preferably 5000 to 200000, and particularly preferably 50000 to 100000. If the weight-average molecular weight is too large, handling properties will be reduced, requiring a large amount of solvent and the environmental load will tend to increase, whereas if the weight-average molecular weight is too small, adhesive properties will tend to decrease.

[0055] The weight-average molecular weights mentioned above are those calculated in terms of standard polystyrene molecular weights. The high-performance liquid chromatograph (Tosoh Corporation, "HLC-8320GPC") was used with a column: TSKgel SuperMultipore HZ-M (exclusion limit molecular weight: 2 × 10 6The measurement is performed using two columns in series (theoretical plate number: 16,000 / column, filler material: styrene-divinylbenzene copolymer, filler particle size: 4 μm).

[0056] The acid value of the polyester resins (i) and (i') is preferably 10 mgKOH / g or less in order to prevent hydrolysis and improve durability, more preferably 5 mgKOH / g or less, particularly preferably 2 mgKOH / g or less, particularly preferably 1 mgKOH / g or less, and most preferably 0.5 mgKOH / g or less. If the acid value is too high, durability tends to decrease. The acid value can be adjusted, for example, by increasing the proportion of the polyol component (b) during the esterification reaction or transesterification reaction, or by adjusting the reaction conditions. The lower limit of the acid value is usually 0 mgKOH / g.

[0057] The acid values ​​of the polyester resins (i) and (i') are determined by neutralization titration in accordance with JIS K0070. The acid value in the present invention refers to the content of carboxy groups in the polyester resins (i) and (i'). The carboxy groups include those in a carboxylate ion state in which the carboxy groups are neutralized with a basic compound.

[0058] The heat of crystalline fusion of the polyester resins (i) and (i') measured by a differential scanning calorimeter (DSC) is preferably 10 J / g or less, more preferably 5 J / g or less, even more preferably 2 J / g or less, and particularly preferably no heat of crystalline fusion. If the heat of crystalline fusion is too large, crystallinity will occur, and the storage stability of the resin solution will tend to be poor, and when made into a pressure-sensitive adhesive sheet, the stability at low temperatures and the adhesive strength of the thin film will tend to be poor.

[0059] Examples of methods for adjusting the heat of crystalline fusion within a predetermined range include a method of appropriately using a polycarboxylic acid (a) having an alkyl group on the side chain or a polyol component (b) having an alkyl group on the side chain, and a method of using three or more, preferably four or more, copolymerizable monomer components.

[0060] The heat of crystalline fusion is the energy consumed when a crystallized substance is heated to melt it, and can be measured by a differential scanning calorimeter (DSC).

[0061] The pressure-sensitive adhesive composition used in the present invention preferably contains, in addition to the polyester resin (i) or (i'), a crosslinking agent (ii), a hydrolysis inhibitor (iii), a urethanization catalyst (iv), and an antioxidant (v).

[0062] [Crosslinking agent (ii)] The pressure-sensitive adhesive composition used in the present invention preferably contains a crosslinking agent (ii). By containing the crosslinking agent (ii), the polyester resins (i) and (i') are crosslinked by the crosslinking agent (ii), resulting in excellent cohesive strength and improved performance as a pressure-sensitive adhesive.

[0063] Examples of such crosslinking agents (ii) include crosslinking agents having functional groups that react with at least one of the hydroxyl and carboxyl groups contained in the polyester resins (i) and (i'), such as isocyanate-based crosslinking agents (ii-1) and polyepoxy-based crosslinking agents. Furthermore, polyfunctional acrylic monomers and urethane acrylate oligomers that increase cohesive strength without reacting with the polyester resin (i) can also be used. Among these, isocyanate-based crosslinking agents (ii-1) are particularly preferred because they can achieve a good balance between initial adhesion, mechanical strength, and heat resistance.

[0064] Examples of such isocyanate-based crosslinking agents (ii-1) include polyisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, and triphenylmethane triisocyanate. Other examples include adducts of the above polyisocyanates with polyol compounds such as trimethylolpropane, and biuret and isocyanurate forms of these polyisocyanate-based compounds. The polyisocyanate-based compounds may also be used in which the isocyanate moiety is blocked with phenol, lactam, or the like. These isocyanate-based crosslinking agents (ii-1) may be used alone or in combination of two or more.

[0065] Among such isocyanate-based crosslinking agents (ii-1), aromatic polyisocyanate-based compounds are preferred, and it is more preferred to use trifunctional aromatic isocyanate-based compounds because of their good compatibility with the polyester-based resins (i) and (i').

[0066] The content of the crosslinking agent (ii) can be appropriately selected depending on the molecular weight and intended use of the polyester resins (i) and (i'), but it is usually preferable to contain the crosslinking agent (ii) in a proportion such that the reactive group contained in the crosslinking agent (ii) is 0.2 to 10 equivalents per equivalent of at least one of the hydroxyl group and the carboxyl group contained in the polyester resins (i) and (i'), particularly preferably 0.5 to 5 equivalents, even more preferably 0.8 to 4 equivalents, and especially 1.1 to 3 equivalents. If the equivalent number of the reactive group contained in the crosslinking agent (ii) is too small, the cohesive strength tends to decrease, and if it is too large, the flexibility tends to decrease.

[0067] The content of the crosslinking agent (ii) is preferably 0.01 to 10 parts by weight, particularly preferably 0.1 to 8 parts by weight, further preferably 0.5 to 6 parts by weight, and especially preferably 1 to 4 parts by weight, relative to 100 parts by weight of the polyester resins (i) and (i'). If the content of the crosslinking agent is too low, the cohesive strength tends to decrease, whereas if the content is too high, the flexibility tends to decrease and the required adhesive strength tends to be difficult to obtain.

[0068] In addition, in the reaction between the polyester resins (i) and (i') and the crosslinking agent (ii), organic solvents that do not have functional groups that react with these components, such as esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and aromatics such as toluene and xylene, can be used. These can be used alone or in combination of two or more.

[0069] <Hydrolysis inhibitor (iii)> The hydrolysis inhibitor (iii) is not particularly limited, and conventionally known compounds can be used, such as compounds that react with and bond to the carboxylic acid terminal groups of the polyester resins (i) and (i'), specifically compounds having functional groups such as carbodiimide groups, epoxy groups, and oxazoline groups. Of these, carbodiimide group-containing compounds are preferred because they are highly effective in eliminating the catalytic activity of protons derived from the carboxyl terminal groups.

[0070] The carbodiimide group-containing compound used in the present invention may generally be a known carbodiimide having one or more carbodiimide groups (-N=C=N-) in the molecule. However, in order to improve durability under high temperature and high humidity conditions, a compound having two or more carbodiimide groups in the molecule, i.e., a polyvalent carbodiimide compound, is preferred, and a compound having three or more, preferably five or more, and especially seven or more carbodiimide groups in the molecule is particularly preferred. The number of carbodiimide groups in a molecule is usually 50 or less, and if there are too many carbodiimide groups, the molecular structure becomes too large, which tends to reduce compatibility.

[0071] The carbodiimide group-containing compound used in the present invention preferably has a high weight-average molecular weight from the viewpoint of hydrolysis resistance. The weight-average molecular weight of the carbodiimide group-containing compound is preferably 1,000 or more, more preferably 2,000 or more, and even more preferably 3,000 or more. The upper limit of the weight-average molecular weight is usually 50,000.

[0072] Furthermore, the carbodiimide group-containing compound preferably has low volatility, and therefore it is preferable to use one with a high number average molecular weight, which is usually 300 to 10,000, and preferably 1,000 to 5,000.

[0073] If the molecular weight of the carbodiimide group-containing compound is too small, the hydrolysis resistance tends to decrease, whereas if the molecular weight is too large, the compatibility with the polyester resins (i) and (i') tends to decrease.

[0074] The carbodiimide equivalent of the carbodiimide group-containing compound is preferably 50 to 10,000, particularly preferably 100 to 1,000, and further preferably 150 to 500. The carbodiimide equivalent indicates the chemical formula weight per carbodiimide group.

[0075] As the carbodiimide group-containing compound, it is also preferable to use a polycarbodiimide compound produced by subjecting a diisocyanate to a decarboxylation condensation reaction in the presence of a carbodiimide catalyst.

[0076] [Polycarbodiimide Compounds] The polycarbodiimide compound can be obtained by subjecting an organic diisocyanate compound to a condensation reaction. Examples of the organic diisocyanate compound include aromatic diisocyanate compounds 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 acyclic aliphatic diisocyanates such as hexamethylene diisocyanate, and cyclic aliphatic 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 diisocyanate compounds are preferred, and tetramethylxylene diisocyanate is more preferred, in that they can provide a pressure-sensitive adhesive composition with excellent moist heat resistance.

[0077] The organic diisocyanate compound can be subjected to a decarboxylation condensation reaction in the usual manner using a known carbodiimidization catalyst to obtain a polycarbodiimide compound.

[0078] The polycarbodiimide compound is preferably an aromatic polycarbodiimide compound, since it can be used to produce a pressure-sensitive adhesive that exhibits little change in haze even under high-temperature and high-humidity conditions and has excellent resistance to moist heat.

[0079] Furthermore, the polycarbodiimide compound used in the present invention is preferably one in which at least one of the terminal isocyanate groups of the polycarbodiimide compound is substituted with a substituent derived from a hydrophilic organic compound.

[0080] [Polycarbodiimide compounds in which at least one of the terminal isocyanate groups has been substituted with a substituent derived from a hydrophilic organic compound] Next, a polycarbodiimide compound in which at least one of the terminal isocyanate groups is substituted with a substituent derived from a hydrophilic organic compound will be described. First, the hydrophilic organic compound will be described.

[0081] [Hydrophilic organic compound] The hydrophilic organic compound is a compound having a substituent with an active hydrogen that is reactive with the terminal isocyanate group of the polycarbodiimide compound, and further having one or more heteroatoms in the molecule in addition to the substituent.

[0082] Examples of the substituent having an active hydrogen atom 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 these, a hydroxyl group, a primary amino group, a secondary amino group, and an imino group are preferred. These substituents may be contained alone or in combination of two or more in the hydrophilic organic compound.

[0083] The number of the substituents having active hydrogen reactive with the isocyanate group in the hydrophilic organic compound is usually 2 or less, and preferably 1. In addition, the substituents are preferably located at the terminals of the hydrophilic organic compound.

[0084] Examples of the compound having a substituent having active hydrogen reactive with the isocyanate group and further having one or more heteroatoms in the molecule in addition to the substituent include an oxyalkylene structure-containing compound, a hydroxy polyester structure-containing compound, a hydroxyalkyl sulfonic acid structure-containing compound, a dialkyl amino alcohol structure-containing compound, a hydroxy carboxylic acid alkyl ester structure-containing compound, a dialkyl amino alkyl amine structure-containing compound, etc. Among these, an oxyalkylene structure-containing compound is preferred.

[0085] The ends of the hydrophilic organic compound are preferably blocked with an alkoxy group or a phenoxy group.

[0086] Among these, as the hydrophilic organic compound, a compound containing an oxyalkylene structure whose terminals are blocked with an alkoxy group or a phenoxy group is preferred, since it causes little change in haze even under high temperature and high humidity conditions.

[0087] The oxyalkylene structure-containing compound terminally blocked with an alkoxy group or a phenoxy group includes, for example, a compound represented by the following formula (1). R1-O-(CH2-CHR2-O)mH (1) In the above formula (1), R1 represents an alkyl group having 1 to 4 carbon atoms or a phenyl group, R2 represents a hydrogen atom or a methyl group, and m is an integer of 4 to 100.

[0088] Examples of the alkyl group having 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an s-butyl group, an isobutyl group, and a t-butyl group.

[0089] Specific examples of the compound represented by the above formula (1) include polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether, polypropylene glycol monomethyl ether, polypropylene glycol monoethyl ether, polypropylene glycol monophenyl ether, etc. Among these, polyethylene glycol monomethyl ether is preferred.

[0090] The weight-average molecular weight of the hydrophilic organic compound is preferably 200 or more, more preferably 400 or more. The upper limit of the weight-average molecular weight is usually 5000 or less, preferably 4000 or less, more preferably 2000 or less, and even more preferably 1000 or less. If the weight-average molecular weight is too small, the compatibility with the polyester resin tends to decrease, and further, the haze change under high temperature and high humidity conditions tends to increase. If the weight-average molecular weight is too large, the adhesive strength tends to decrease.

[0091] The polycarbodiimide-based compound in which at least one of the terminal isocyanate groups is substituted with a substituent derived from a hydrophilic organic compound can be obtained by reacting the polycarbodiimide-based compound with the hydrophilic organic compound.

[0092] The reaction between the polycarbodiimide compound and the hydrophilic organic compound is carried out by heating the polycarbodiimide compound usually to 50 to 200°C, preferably 100 to 180°C, adding the hydrophilic organic compound, and then further reacting at 80 to 200°C for 0.5 to 5 hours.

[0093] In this way, a polycarbodiimide compound can be obtained in which at least one of the terminal isocyanate groups is substituted with a substituent derived from a hydrophilic organic compound.

[0094] Commercially available polycarbodiimide compounds include, for example, 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, with Carbodilite V-09GB being preferred.

[0095] The epoxy group-containing compound is preferably, for example, a glycidyl ester compound or a glycidyl ether compound.

[0096] 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, terephthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, glycidyl ester of ... Examples of the diglycidyl ester include glycidyl ester, diglycidyl phthalate, diglycidyl naphthalenedicarboxylic acid, diglycidyl ester of methyl terephthalate, diglycidyl hexahydrophthalate, diglycidyl tetrahydrophthalate, diglycidyl ester of cyclohexanedicarboxylic acid, diglycidyl adipic acid, diglycidyl succinate, diglycidyl sebacic acid, diglycidyl dodecanedioate, diglycidyl octadecanedicarboxylic acid, triglycidyl trimellitate, and tetraglycidyl pyromellitic acid. These may be used alone or in combination of two or more.

[0097] 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, and these can be used alone or in combination of two or more.

[0098] The oxazoline group-containing compound is preferably a bisoxazoline compound. 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), and 2,2'-bis(4-hexyl-2-oxazoline). ), 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), 2 Examples include 2,2'-ethylenebis(4-methyl-2-oxazoline), 2,2'-tetramethylenebis(4,4-dimethyl-2-oxazoline), 2,2'-9,9'-diphenoxyethanebis(2-oxazoline), 2,2'-cyclohexylenebis(2-oxazoline), 2,2'-diphenylenebis(2-oxazoline), etc., and of these, 2,2'-bis(2-oxazoline) is most preferred from the viewpoint of reactivity with polyester. Furthermore, the above-mentioned bisoxazoline compounds can be used alone or in combination of two or more kinds, as long as the object of the present invention is achieved.

[0099] The hydrolysis inhibitor (iii) preferably has low volatility, and therefore it is preferable to use one with a high molecular weight.

[0100] The amount of the hydrolysis inhibitor (iii) to be added is preferably 0.01 to 10 parts by weight, particularly preferably 0.1 to 5 parts by weight, and even more preferably 0.2 to 3 parts by weight, relative to 100 parts by weight of the polyester resins (i) and (i'). If the amount is too high, turbidity tends to occur due to poor compatibility with the polyester resins (i) and (i'), while if the amount is too low, sufficient durability tends to be difficult to obtain.

[0101] The amount of hydrolysis inhibitor (iii) blended is preferably optimized depending on the acid values ​​of the polyester resins (i) and (i'), and the molar ratio ((β) / (α)) of the total acid value (α) of the polyester resins (i) in the pressure-sensitive adhesive composition to the total amount of functional groups (β) of the hydrolysis inhibitor (iii) in the pressure-sensitive adhesive composition is preferably 0.5≦(β) / (α), particularly preferably 1≦(β) / (α)≦1000, and even more preferably 1.5≦(β) / (α)≦100. If the content ratio of (β) to (α) is too high, the compatibility with polyester resins (i) and (i') tends to decrease, and the adhesive strength, cohesive strength, and durability performance tend to decrease. If the content ratio of (β) to (α) is low, the moist heat resistance performance tends to decrease.

[0102] [Urethanization catalyst (iv)] The pressure-sensitive adhesive composition used in the present invention preferably contains a urethanization catalyst (iv) from the viewpoint of reaction rate.

[0103] Examples of the urethanization catalyst (iv) include organometallic compounds, tertiary amine compounds, etc. These can be used alone or in combination of two or more kinds.

[0104] Examples of the organometallic compounds include zirconium compounds, iron compounds, tin compounds, titanium compounds, lead compounds, cobalt compounds, and zinc compounds.

[0105] Examples of the zirconium compound include zirconium naphthenate and zirconium acetylacetonate. Examples of the iron-based compound include iron acetylacetonate and iron 2-ethylhexanoate. Examples of the tin compounds include dibutyltin dichloride, dibutyltin oxide, and dibutyltin dilaurate. Examples of the titanium compounds include dibutyltitanium dichloride, tetrabutyltitanium, 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.

[0106] Examples of the tertiary amine compound include triethylamine, triethylenediamine, and 1,8-diazabicyclo-(5,4,0)-undecene-7.

[0107] Among these urethane catalysts (iv), organometallic compounds are preferred, and zirconium compounds are particularly preferred, in terms of reaction rate and pot life of the adhesive layer. Furthermore, the urethane catalyst (iv) is preferably used in combination with acetylacetone as a catalytic inhibitor. The inclusion of acetylacetone is preferred in that it inhibits catalytic activity at low temperatures and extends pot life.

[0108] The content of the urethanization catalyst (iv) is preferably 0.0001 to 1 part by weight, particularly 0.001 to 0.1 part by weight, and even more preferably 0.01 to 0.05 part by weight, per 100 parts by weight of the polyester resins (i) and (i'). If the content is too low, the aging time until the crosslinking reaction is completed tends to be long, while if the content is too high, the adhesive properties tend to be reduced.

[0109] [Antioxidants (v)] The pressure-sensitive adhesive composition used in the present invention preferably contains an antioxidant (v) in order to increase the stability of the resin.

[0110] Examples of the antioxidant (v) include hindered phenol-based antioxidants, amine-based antioxidants, sulfur-based antioxidants, phosphoric acid-based antioxidants, etc. Among these, at least one selected from the group consisting of hindered phenol-based antioxidants, amine-based antioxidants, and phosphoric acid-based antioxidants is preferred, and antioxidants consisting of hindered phenol-based compounds are particularly preferred.

[0111] Examples of hindered phenol-based antioxidants 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.

[0112] The content of the antioxidant (v) is preferably 0.01 to 10 parts by weight, more preferably 0.03 to 8 parts by weight, and even more preferably 0.05 to 5 parts by weight, relative to 100 parts by weight of the polyester resins (i) and (i'). If the content is too low, adhesive residue on the adherend tends to be more likely to occur, while if the content is too high, adhesive properties tend to decrease.

[0113] In addition to the polyester resin (i) or (i'), crosslinker (ii), hydrolysis inhibitor (iii), urethanization catalyst (iv), and antioxidant (v), the pressure-sensitive adhesive composition used in the present invention may contain additives such as tackifier resins, softeners, UV absorbers, stabilizers, antistatic agents, and other additives, as well as inorganic or organic fillers, powders, and particulate additives such as metal powders and pigments, within a range that does not impair the effects of the present invention (e.g., 10% by weight or less of the pressure-sensitive adhesive composition). These may be used alone or in combination of two or more. Furthermore, the pressure-sensitive adhesive composition may contain small amounts of impurities contained in the raw materials used to produce the components of the pressure-sensitive adhesive composition.

[0114] The pressure-sensitive adhesive composition can be obtained, for example, by preparing the polyester resin (i) or (i') and necessary optional components, etc., and blending and dispersing them during the production of the polyester resin (i), or by blending them with the polyester resin (i) or (i') and dispersing them using a mixing roller or the like. In this case, the components may be dispersed as a solution using a solvent, or may be dispersed without a solvent. The polyester resin is preferably the main component. The main component accounts for 50% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, and particularly preferably 90% by weight or more. A low content of the polyester resin tends to result in poor heat resistance.

[0115] <Adhesive layer> The pressure-sensitive adhesive layer of the present invention is obtained by crosslinking (curing) the pressure-sensitive adhesive composition. The pressure-sensitive adhesive layer can be obtained by coating and drying the pressure-sensitive adhesive composition, as will be described in detail later in the description of the method for producing a pressure-sensitive adhesive sheet.

[0116] The pressure-sensitive adhesive layer of the present invention has a thickness of 18 μm or less, preferably 15 μm or less, more preferably 12 μm or less, even more preferably 8 μm or less, and particularly preferably 3 μm or less. The lower limit is usually 0.1 μm. Generally, the thicker the pressure-sensitive adhesive layer, the higher the adhesive strength tends to be. However, the pressure-sensitive adhesive layer of the present invention has excellent adhesive strength to various adherends, despite its thin thickness.

[0117] The thickness of the pressure-sensitive adhesive layer is measured using a Digimatic Indicator (ID-C112B, manufactured by Mitutoyo Corporation). In the case of a pressure-sensitive adhesive sheet, which will be described later, the thickness is determined by subtracting the measured thickness of the constituent members other than the pressure-sensitive adhesive layer from the measured thickness of the entire pressure-sensitive adhesive sheet.

[0118] The gel fraction of the pressure-sensitive adhesive layer is preferably 10% by weight or more from the viewpoint of durability and adhesive strength, particularly preferably 15 to 80% by weight, even more preferably 20 to 70% by weight, especially 30 to 55% by weight, and most preferably 35 to 45% by weight. If the gel fraction is too low, the cohesive strength tends to decrease, resulting in a decrease in durability. However, if the gel fraction is too high, there is a concern that the adhesive strength will decrease due to an increase in cohesive strength.

[0119] The gel fraction is an index of the degree of crosslinking and is calculated, for example, by the following method: the pressure-sensitive adhesive layer 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 weight percentage of the insoluble pressure-sensitive adhesive component remaining in the wire netting after immersion relative to the weight of the pressure-sensitive adhesive component before immersion.

[0120] <Adhesive sheet> The pressure-sensitive adhesive sheet of the present invention has the pressure-sensitive adhesive layer. A first aspect of the pressure-sensitive adhesive sheet of the present invention is a sheet having the pressure-sensitive adhesive layer and a substrate, with the substrate laminated on one side of the pressure-sensitive adhesive layer and the other side being release-treated. A second aspect of the pressure-sensitive adhesive sheet of the present invention comprises the pressure-sensitive adhesive layer and a release-treated sheet, with the release-treated sheet laminated on both sides of the pressure-sensitive adhesive layer. That is, 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 substrateless double-sided pressure-sensitive adhesive sheet that does not have a substrate. In the present invention, the term "sheet" also includes "film" and "tape."

[0121] The pressure-sensitive adhesive sheet of the first aspect can be produced according to a known general method for producing a pressure-sensitive adhesive sheet, for example, by applying the pressure-sensitive adhesive composition to one side of a substrate, drying the composition to form a pressure-sensitive adhesive layer, laminating a release-treated sheet to the surface of the layer (the side opposite to the side that contacts the substrate), and optionally curing the layer.

[0122] Alternatively, the pressure-sensitive adhesive composition is applied to the release-treated sheet, followed by drying to form a pressure-sensitive adhesive layer, and then a substrate is attached to the surface (the surface opposite to the surface in contact with the release-treated sheet) and cured as necessary to obtain the pressure-sensitive adhesive layer.

[0123] Examples of the substrate include polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate / isophthalate copolymer; 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; vinyl polymers such as polyvinyl chloride, polyvinyl chloride / vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, and vinylon; cellulose resins such as cellulose triacetate and cellophane; acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate; polystyrene; polycarbonate; polyarylate; polyimide; synthetic resin sheets made of cycloolefin polymers, etc.; 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, etc. Of these, polyester resin sheets are preferred, with polyethylene terephthalate being more preferred.

[0124] The release-treated sheet may be, for example, the above-mentioned substrate that has been subjected to a release treatment. Among these, it is preferable to use a silicone-based release sheet.

[0125] The pressure-sensitive adhesive composition may be applied using, for example, a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, comma coater, or the like.

[0126] As for the drying conditions after coating the pressure-sensitive adhesive composition, the drying temperature is preferably 60 to 140° C., and particularly preferably 80 to 120° C. The drying time is preferably 0.5 to 30 minutes, and particularly preferably 1 to 5 minutes.

[0127] The conditions for the aging treatment are generally room temperature (23°C) to 70°C, and the time is generally 1 to 30 days. Specifically, the treatment may be carried out under conditions such as 1 to 20 days at 23°C, preferably 3 to 14 days at 23°C, or 1 to 10 days at 40°C.

[0128] The pressure-sensitive adhesive sheet of the second embodiment can also be produced according to a known method for producing a pressure-sensitive adhesive sheet. For example, the pressure-sensitive adhesive composition is applied to a release-treated sheet, followed by drying to form a pressure-sensitive adhesive layer, and a separate release-treated sheet is attached to the surface (the surface opposite to the surface in contact with the release-treated sheet) to obtain the pressure-sensitive adhesive sheet of the second embodiment. The release-treated sheet used in the second embodiment can be the same as that exemplified in the first embodiment. The coating method, drying conditions, and curing conditions may also be the same as those in the first embodiment.

[0129] When using the obtained pressure-sensitive adhesive sheet or substrate-less double-sided pressure-sensitive adhesive sheet, the release-treated sheet is peeled off from the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer is then attached to an adherend.

[0130] The adhesive sheet of the present invention preferably has an adhesive strength of 5 N / 25 mm or more, more preferably 6 N / 25 mm or more, and particularly preferably 7 N / 25 mm or more, as measured under the following conditions. The upper limit is not particularly limited, but is usually 100 N / 25 mm. [Adhesive strength (N / 25mm) measurement conditions] The adhesive sheet was cut to 25mm x 200mm in an environment of 23°C and 50%RH, the release film was peeled off, and the adhesive layer side was placed against a SUS-BA plate as the adherend, and a 2kg roller was used to pressurize and adhere the sheet. After leaving the sheet to stand for 30 minutes in the same atmosphere, the 180° peel strength (N / 25mm) was measured at a peel rate of 300mm / min using an autograph (Shimadzu Corporation, Autograph AGS-H 500N). This was taken as the adhesive strength. The SUS-BA plate is made by cold rolling SUS304 and then bright annealing (non-oxidation annealing), or by skin-pass rolling to enhance the gloss.

[0131] Furthermore, in the pressure-sensitive adhesive sheet of the present invention, when the adhesive strength (N / 25 mm) measured under the above measurement conditions is X and the thickness (μm) of the pressure-sensitive adhesive layer is Y, it is preferable that X / Y≧0.5, more preferably ≧1.0, and particularly preferably ≧1.5.

[0132] The pressure-sensitive adhesive sheet of the present invention preferably has an adhesive strength over time measured under the following conditions of 5 N / 25 mm or more, more preferably 6 N / 25 mm or more, and particularly preferably 7 N / 25 mm or more. The upper limit is not particularly limited, but is usually 100 N / 25 mm. [Measurement conditions for adhesive strength over time (N / 25mm)] The adhesive sheet was cut to 25mm x 200mm in an environment of 23°C and 50%RH, and the adhesive layer was placed on a SUS-BA plate as an adherend, and a 2kg roller was used to pressurize and adhere the sheet. After leaving the sheet in the same atmosphere for 24 hours, the 180° peel strength (N / 25mm) was measured at a peel rate of 300mm / min using an autograph (Shimadzu Corporation, Autograph AGS-H 500N). This was taken as the adhesive strength. The SUS-BA plate is made by cold rolling SUS304 and then bright annealing (non-oxidation annealing), or by skin-pass rolling to enhance the gloss.

[0133] Furthermore, when the adhesive strength over time (N / 25 mm) measured under the above measurement conditions is Z and the thickness (μm) of the adhesive layer is Y, the adhesive sheet of the present invention preferably satisfies Z / Y≧1.0, more preferably Z / Y≧2.0, and particularly preferably Z / Y≧3.0.

[0134] The pressure-sensitive adhesive sheet of the present invention can be used to bond various components, and is particularly suitable for use as a single-sided or double-sided pressure-sensitive adhesive sheet for polyimide, a single-sided or double-sided pressure-sensitive adhesive sheet used to bond optical components, a single-sided or double-sided pressure-sensitive adhesive sheet for fixing components of portable electronic devices, a single-sided or double-sided pressure-sensitive adhesive sheet for fixing electronic components, etc. [Example]

[0135] 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 weight.

[0136] In the following examples, the ester bond concentration, glass transition temperature, weight average molecular weight, acid value, heat of crystalline fusion of the polyester resin, and gel fraction of the pressure-sensitive adhesive layer were measured according to the methods described above.

[0137] A polyester resin was produced by the following method.

[0138] [Production Example 1: Production of Polyester Resin (i-1)] Thermometer, stirrer, distillation column, nitrogen inlet tube and vacuum equipment equipped reactor, polycarboxylic acids (a) as, adipic acid 46.2 parts, isophthalic acid 13.1 parts, polyol component (b) as, ethylene glycol 13.1 parts and neopentyl glycol 26.8 parts, trimethylolpropane 0.8 parts, tetrabutyl titanate 0.01 parts as a catalyst were charged, the internal temperature was gradually increased to 250 ° C., and an esterification reaction was carried out over 4 hours. Then, the internal temperature was increased to 260 ° C., and tetrabutyl titanate 0.01 parts as a catalyst was charged, the pressure was reduced to 1.33 hPa, and a polymerization reaction was carried out over 3 hours to produce polyester resin (i-1). The composition (molar ratio) of the obtained polyester resin (i-1) was adipic acid / isophthalic acid / ethylene glycol / neopentyl glycol / trimethylolpropane = 80 / 20 / 44.2 / 54.5 / 1.3, the ester bond concentration was 10.0 mmol / g, the heat of crystalline fusion was 0 J / g, the weight-average molecular weight was 78,000, the glass transition temperature (Tg) was -30°C, and the acid value was 0.1 mg KOH / g.

[0139] Production Examples 2 to 5 and Comparative Production Examples 1 and 2 were produced in the same manner as Production Example 1, except that the resin compositions shown in Table 1 below were used. The resin compositions and physical properties of the polyester resins (i-1) to (i-7) thus prepared are shown in Table 1 below.

[0140] [Table 1]

[0141] Comparative Production Example 3: Production of acrylic resin (b-1) A four-necked round-bottom flask equipped with a reflux condenser, stirrer, nitrogen gas inlet, and thermometer was charged with 5 parts acrylic acid, 65 parts butyl acrylate, 30 parts methyl acrylate, 150 parts ethyl acetate, and 45 parts acetone. After heating to reflux, 0.03 parts azobisisobutyronitrile (AIBN) was added as a polymerization initiator and the reaction was carried out at the ethyl acetate reflux temperature for 3 hours. After the reaction, the solution was diluted with ethyl acetate to obtain acrylic resin (b-1) solution (weight average molecular weight (Mw) 1.2 million, glass transition temperature calculated by Fox's equation -35°C, solids content 25%, viscosity 5,000 mPa·s (25°C)).

[0142] Next, the following components were prepared. [Crosslinking agent (ii)] Isocyanate crosslinking agent (ii-1A): "Coronate L55E" (manufactured by Tosoh Corporation) Isocyanate crosslinking agent (ii-2A): "Coronate HX" (manufactured by Tosoh Corporation) [Hydrolysis inhibitor (iii)] Carbodiimide compound (iii-1): Aromatic polycarbodiimide compound whose terminals are substituted with substituents derived from aromatic monoisocyanates, "Carbodilite V-09GB" (manufactured by Nisshinbo Chemical Co., Ltd.), weight-average molecular weight: 6000 [Urethanization catalyst (iv)] Zirconium compound (iv-1): "Orgatics ZC-150" (Matsumoto Fine Chemical Co., Ltd.) diluted with acetylacetone to a solids concentration of 1% [Antioxidants (v)] Hindered phenolic antioxidant (v-1): "IRGANOX 1010" (BASF)

[0143] Next, the polyester resins (i-1) to (i-3) obtained above were used to prepare pressure-sensitive adhesive compositions as described below, and pressure-sensitive adhesive sheets of Examples and Comparative Examples were fabricated.

[0144] [Example 1] The polyester resin (i-1) obtained above was diluted with ethyl acetate to a solid content concentration of 50%, and 1.5 parts (solid content) of an isocyanate crosslinking agent (ii-1A), 0.5 parts (solid content) of a carbodiimide compound (iii-1), 0.02 parts (solid content) of a zirconium compound (iv-1), and 0.1 parts (solid content) of a hindered phenol antioxidant (v-1) were blended with 100 parts of the diluted solid content, and the mixture was stirred and mixed to obtain a pressure-sensitive adhesive composition. The obtained pressure-sensitive adhesive composition was applied to a polyethylene terephthalate (PET) film (thickness: 38 μm) so that the thickness after drying would be approximately 5 μm, and then dried for 1 minute at 100° C. to form a pressure-sensitive adhesive layer. A release-treated PET sheet (release sheet) was then attached to the pressure-sensitive adhesive layer to protect its surface, and the layer was aged for 10 days in an atmosphere at a temperature of 40° C. to obtain a pressure-sensitive adhesive sheet.

[0145] [Examples 2 to 8, Comparative Examples 1 to 4] A pressure-sensitive adhesive composition was prepared and a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that the ingredients were blended as shown in Table 2 below.

[0146] [Table 2]

[0147] [Examples 9 and 10, Comparative Example 5] An adhesive composition was prepared and an adhesive sheet was obtained in the same manner as in Example 1, except that the ingredients were blended as shown in Table 3 below so that the thickness of the adhesive layer after drying was 10 μm.

[0148] [Table 3]

[0149] [Examples 11 and 12, Comparative Examples 6 and 7] An adhesive composition was prepared and an adhesive sheet was obtained in the same manner as in Example 1, except that the ingredients were blended as shown in Table 4 below so that the thickness of the adhesive layer after drying was 2 μm.

[0150] [Table 4]

[0151] The following evaluations were carried out using the resulting pressure-sensitive adhesive sheets of the Examples and Comparative Examples. Since adhesive strength varies depending on the thickness of the pressure-sensitive adhesive layer, evaluation criteria were set according to the thickness of the pressure-sensitive adhesive layer. The results for Examples 1 to 8 and Comparative Examples 1 to 4, in which the pressure-sensitive adhesive layer was 5 μm thick, are shown in Table 5 below. The results for Examples 9 and 10 and Comparative Example 5, in which the pressure-sensitive adhesive layer was 10 μm thick, are shown in Table 6 below. The results for Examples 11 and 12 and Comparative Examples 6 and 7, in which the pressure-sensitive adhesive layer was 2 μm thick, are shown in Table 7.

[0152] <Adhesion strength (peel strength) (to SUS)> A SUS-BA plate was prepared as the adherend. The pressure-sensitive adhesive sheet obtained above was cut to 25 mm x 200 mm in an environment of 23 °C and 50% RH, after which the release film was peeled off, and the pressure-sensitive adhesive layer side was placed against the SUS-BA plate, and a 2 kg roller was pressed back and forth to adhere it. After leaving it in the same atmosphere for 30 minutes, the 180-degree peel strength (N / 25 mm) was measured at a peel speed of 300 mm / min using an autograph (Shimadzu Corporation, Autograph AGS-H 500N) and evaluated according to the following criteria. SUS-BA sheet refers to SUS304 that has been cold-rolled and then bright annealed (non-oxidation annealed), or that has been skin-pass rolled to enhance gloss. (Evaluation criteria for adhesive layer thickness of 5 μm) 〇...7N / 25mm or more. △···5N / 25mm or more, less than 10N / 25mm. ×Less than 5N / 25mm. (Evaluation criteria: adhesive layer thickness 10 μm) 〇...12N / 25mm or more. ×Less than 12N / 25mm. (Evaluation criteria for adhesive layer thickness of 2 μm) 〇...5N / 25mm or more. ×Less than 5N / 25mm.

[0153] <Adhesive strength (peel strength) (against PI)> A polyimide (PI) adherend (100 μm thick film, manufactured by Toray DuPont Co., Ltd.) was attached to a SUS-BA board with double-sided tape to prepare a PI adherend. The pressure-sensitive adhesive sheet obtained above was cut to a 25 mm x 200 mm size at 23°C and 50% RH. The release film was then peeled off, and the adhesive layer was placed against the PI adherend. A 2 kg roller was then applied back and forth to pressurize the PI adherend. After leaving the sheet in the same atmosphere for 30 minutes, the 180° peel strength (N / 25 mm) was measured at a peel rate of 300 mm / min using an autograph (Shimadzu Corporation, Autograph AGS-H 500N) and evaluated according to the following criteria. (Evaluation criteria for adhesive layer thickness of 5 μm) 〇...13N / 25mm or more. △···10N / 25mm or more, less than 13N / 25mm. ×Less than 10N / 25mm. (Evaluation criteria: adhesive layer thickness 10 μm) 〇...15N / 25mm or more. ×Less than 15N / 25mm. (Evaluation criteria for adhesive layer thickness of 2 μm) 〇...5N / 25mm or more. ×Less than 5N / 25mm.

[0154] <Adhesive strength (peel strength) (against PP)> A polypropylene (PP) plate (Nippon Test Panel Co., Ltd., PP 2.0 × 70 × 150 mm) was prepared as the adherend. The pressure-sensitive adhesive sheet obtained above was cut to 25 mm × 200 mm in an environment of 23 ° C and 50% RH, and the release film was peeled off. The pressure-sensitive adhesive layer side was placed against a polypropylene (PP) plate, and a 2 kg roller was pressed back and forth to adhere the sheet. After leaving the sheet to stand for 30 minutes in the same atmosphere, the 180-degree peel strength (N / 25 mm) was measured at a peel speed of 300 mm / min using an autograph (Shimadzu Corporation, Autograph AGS-H 500N) and evaluated according to the following criteria. (Evaluation criteria for adhesive layer thickness of 5 μm) 〇...5N / 25mm or more. △···1N / 25mm or more, less than 5N / 25mm. ×...Less than 1N / 25mm. (Evaluation criteria: adhesive layer thickness 10 μm) 〇...5N / 25mm or more. ×Less than 5N / 25mm.

[0155] <Adhesive strength over time (peel strength after 24 hours)> A SUS304-BA plate was prepared as the adherend. The pressure-sensitive adhesive sheet obtained above was cut to 25 mm x 200 mm in an environment of 23 °C and 50% RH, after which the release film was peeled off, and the pressure-sensitive adhesive layer side was placed against the SUS-BA plate and pressure-bonded by reciprocating a 2 kg roller. After leaving the sheet in the same atmosphere for 24 hours, the 180° peel strength (N / 25 mm) was measured using an autograph (Shimadzu Corporation, Autograph AGS-H 500N) at a peel rate of 300 mm / min. Moreover, Examples 11 and 12 and Comparative Examples 6 and 7 were evaluated according to the following criteria. (Evaluation criteria) 〇...5N / 25mm or more. ×Less than 5N / 25mm.

[0156] <Initial rate> The value of "adhesion strength (peel strength) (against SUS)" measured above was taken as A, and the value of "adhesion strength over time (peel strength after 24 hours)" as B, and the ratio of A / B was calculated. The higher the initial ratio, the greater the adhesive strength is developed from the beginning, and the more significant the performance. (Evaluation criteria) 〇···More than 70%. ×Less than 70%.

[0157] <Holding force (cohesive force)> The pressure-sensitive adhesive sheets of Examples 1 to 8 and Comparative Examples 1 to 4 obtained above were attached to SUS304 substrate in accordance with JIS Z-0237 with an area of ​​25 mm × 25 mm, and then left to stand at 80°C for 20 minutes. A load of 1 kg was then applied, and the time until the sheet fell off was visually observed, or for sheets that did not fall off after 24 hours, the condition after 24 hours was visually observed, and the sheet was evaluated according to the following criteria. (Evaluation criteria) ○...It did not fall off even after being left standing for 24 hours. ×: The sample fell off after being left standing for 24 hours.

[0158] [Table 5]

[0159] [Table 6]

[0160] [Table 7]

[0161] From the above results, the adhesive layers (adhesive sheets) of Examples 1 to 10, which contain a specific amount or more of structural moieties derived from aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms as structural moieties derived from polycarboxylic acids (a), have excellent adhesive strength to various substrates even when they are thin, and also exhibit sufficient adhesive strength from the beginning. On the other hand, the adhesive layers (adhesive sheets) of Comparative Examples 1 to 5, which do not contain a structural moiety derived from aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms, had inferior adhesive strength to various substrates compared to the adhesive layers of the Examples, and furthermore, had low initial modulus and did not exhibit sufficient adhesive strength from the beginning. The pressure-sensitive adhesive layers (pressure-sensitive adhesive sheets) of Examples 11 and 12, even though they were very thin at 2 μm, exhibited excellent adhesive strength to various adherends and exhibited sufficient adhesive strength from the beginning. On the other hand, the pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) of Comparative Example 6, which did not contain a structural moiety derived from an aliphatic dicarboxylic acid (a1) having 8 or fewer carbon atoms, had a lower initial modulus than the pressure-sensitive adhesive layers of the Examples, and did not exhibit sufficient adhesive strength from the beginning. However, the use of a polyester-based pressure-sensitive adhesive layer confirmed that the adhesive strength over time was superior to that of Comparative Example 7, which used an acrylic-based pressure-sensitive adhesive layer. The Z / Y value measured using this adhesive strength over time was sufficiently high compared to that of acrylic resins. 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. [Industrial Applicability]

[0162] The pressure-sensitive adhesive of the present invention has excellent effects even when it is a thin film, and is used for single-sided or double-sided pressure-sensitive adhesive sheets for polyimides, single-sided or double-sided pressure-sensitive adhesive sheets used for bonding optical components, single-sided or double-sided pressure-sensitive adhesive sheets for fixing components of portable electronic devices, single-sided or double-sided pressure-sensitive adhesive sheets for fixing electronic components, etc.

Claims

1. A pressure-sensitive adhesive layer obtained by crosslinking a pressure-sensitive adhesive composition containing a polyester resin (i) having a structural moiety derived from a polyvalent carboxylic acid (a) and a structural moiety derived from a polyol component (b) and a crosslinking agent (ii), The thickness of the pressure-sensitive adhesive layer is 18 μm or less, the content of the polyester resin (i) is 80% by weight or more of the pressure-sensitive adhesive composition, Among the structural moieties derived from the polycarboxylic acids (a), 60 mol % or more of structural moieties derived from aliphatic dicarboxylic acids (a1) having 8 or less carbon atoms are contained, The structural moiety derived from the polyvalent carboxylic acid (a) further contains a structural moiety derived from an aromatic dicarboxylic acid, The pressure-sensitive adhesive layer, wherein the crosslinking agent (ii) is an isocyanate-based crosslinking agent (ii-1).

2. The pressure-sensitive adhesive layer according to claim 1, characterized in that the structural moiety derived from the polyol component (b) contains a structural moiety derived from at least one selected from the group consisting of ethylene glycol, 2-methyl-1,3-propanediol, and neopentyl glycol.

3. The pressure-sensitive adhesive layer according to claim 1 or 2, wherein the structural moiety derived from the aliphatic dicarboxylic acid (a1) having 8 or less carbon atoms is a structural moiety derived from adipic acid.

4. 4. The pressure-sensitive adhesive layer according to claim 1, wherein the polyester resin (i) has an ester bond concentration of 9.0 to 12.5 mmol / g.

5. The pressure-sensitive adhesive layer according to any one of claims 1 to 4, wherein the polyester resin (i) has a glass transition temperature of -50 to -10°C.

6. The pressure-sensitive adhesive layer according to any one of claims 1 to 5, characterized in that the polyester resin (i) having a structural moiety derived from the polyvalent carboxylic acid (a) and a structural moiety derived from the polyol component (b) is crosslinked with a crosslinking agent (ii).

7. A pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer according to any one of claims 1 to 6 and a substrate, wherein the substrate is laminated on one side of the pressure-sensitive adhesive layer, and the other side is a release-treated sheet.

8. 8. The pressure-sensitive adhesive sheet according to claim 7, wherein the substrate is a polyester resin sheet.

9. A pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer according to any one of claims 1 to 6 and a release-treated sheet, characterized in that the release-treated sheet is laminated on both sides of the pressure-sensitive adhesive layer.

10. 9. The pressure-sensitive adhesive sheet according to claim 7, wherein the adherend is a polyimide.

11. The pressure-sensitive adhesive sheet according to claim 7 or 8, which is used to fix electronic components.

12. The pressure-sensitive adhesive sheet according to any one of claims 7 to 11, wherein X is the adhesive strength (N / 25 mm) measured under the following measurement conditions, and Y is the thickness (µm) of the pressure-sensitive adhesive layer, and X / Y is ≥ 0.

5. [Measurement conditions for adhesive strength X (N / 25 mm)] The adhesive sheet was cut to 25 mm x 200 mm in an environment of 23°C and 50% RH, the release film was peeled off, and the adhesive layer side was placed against a SUS-BA plate as an adherend, and a 2 kg roller was used to press and adhere it. After leaving it to stand for 30 minutes in the same atmosphere, the 180-degree peel strength (N / 25 mm) was measured at a peel rate of 300 mm / min using an autograph (Shimadzu Corporation, Autograph AGS-H 500N), and the adhesive strength was defined as Adhesive Strength X.

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