Releasable pressure-sensitive adhesive composition, releasable pressure-sensitive adhesive, releasable pressure-sensitive adhesive sheet, and pressure-sensitive adhesive composition

Abstract

To provide a peelable adhesive composition capable of forming a peelable adhesive used to bond an adhesive sheet to an adherend, the adhesive sheet intended to be peeled later, wherein the adhesive can prevent the adhesive sheet from breaking while being peeled.SOLUTION: A peelable adhesive composition contains a polyester resin, the polyester resin being a polyester resin (A) containing a methacryloyl group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a peelable pressure-sensitive adhesive composition, more particularly to a peelable pressure-sensitive adhesive composition used in a semiconductor processing sheet, and even more particularly to a peelable pressure-sensitive adhesive composition used in a backgrinding sheet that is attached to the surface of a semiconductor wafer during wafer backgrinding. [Background technology]

[0002] As information terminal devices are rapidly becoming thinner, smaller, and more multifunctional, there is a demand for the semiconductor devices mounted thereon to be similarly thinner and more dense. To achieve this, there is also a demand for thinner semiconductor wafers on which semiconductors are integrated, and for this reason, the backside of the semiconductor wafer is sometimes ground to make it thinner. In addition, the wafer surface often has bumps (electrodes) made of solder or the like formed thereon, resulting in unevenness. When such a semiconductor wafer with bumps is subjected to back grinding, a semiconductor processing sheet is attached to the wafer surface to protect the surface having the bumps. Conventionally, a pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer provided on one side of the substrate has generally been used as the semiconductor processing sheet.

[0003] The semiconductor processing sheet is required to have bump embedding properties and step conformability in order to adequately protect uneven portions such as bumps on the wafer surface. Furthermore, if the adhesive of the semiconductor processing sheet remains on the uneven portions of the semiconductor wafer, the adhesive residue can cause problems in the semiconductor device. Therefore, for example, Patent Document 1 discloses that in order to improve step conformability while suppressing adhesive residue on the uneven portions, an intermediate layer and an adhesive layer are provided on the substrate of the semiconductor processing sheet, and the intermediate layer and the adhesive layer are formed from a specific acrylic polymer. Patent Document 2 proposes a pressure-sensitive adhesive that uses a polyester resin instead of the acrylic resin that has been commonly used as the base resin for pressure-sensitive adhesives, and further includes a crosslinking agent in a resin composition that contains an unsaturated group-containing compound, and is crosslinked by irradiating with ultraviolet light. This pressure-sensitive adhesive hardens by crosslinking with ultraviolet light, reducing its adhesive strength and improving its releasability when peeled off. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2015 / 111310 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-221249 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, semiconductor devices have become increasingly fine-grained, and as a result, minute grooves and the like are being formed in the uneven parts, which has caused problems when the adhesive sheet is peeled off, as the adhesive sheet breaks and adhesive remains.

[0006] The pressure-sensitive adhesive sheet of Patent Document 1 has an intermediate layer between the substrate and the pressure-sensitive adhesive layer to improve embeddability, and there is a risk that peeling will occur between the intermediate layer and the pressure-sensitive adhesive layer when the pressure-sensitive adhesive layer is peeled off. In addition, the provision of an intermediate layer makes the preparation of the pressure-sensitive adhesive sheet complicated, so there is a need for a pressure-sensitive adhesive layer that can serve as both an intermediate layer and a pressure-sensitive adhesive layer in one layer.

[0007] Furthermore, the adhesive sheets described in Patent Documents 1 and 2 can reduce adhesive residue while improving bump embeddability, but it was difficult to adequately prevent the adhesive sheet from breaking. In other words, the adhesive sheets described in Patent Documents 1 and 2 can reduce adhesive residue when used on a flat adherend, but when used to embed bumps or the like, a situation easily occurs in which part of the adhesive layer physically gets caught on the unevenness, causing breakage and leaving adhesive residue. In particular, if the adhesive sheet has low elongation, the adhesive sheet does not stretch and is therefore easily torn, easily leaving adhesive residue.

[0008] Therefore, under such circumstances, the present invention provides a peelable adhesive that is used in applications where an adhesive sheet and an adherend are to be bonded together on the premise that they will be peeled off once bonded together, and that can prevent the adhesive sheet from breaking when the adhesive sheet is peeled off, as well as a peelable adhesive composition that can form such an adhesive, a peelable adhesive sheet, and an adhesive composition. [Means for solving the problem]

[0009] However, in view of these circumstances, the present inventors have conducted extensive research and have found that a pressure-sensitive adhesive using a peelable pressure-sensitive adhesive composition containing a polyester resin containing a (meth)acryloyl group has a suitable adhesive strength that allows for re-peelability and also has a high elongation, thereby completing the present invention.

[0010] That is, the present invention provides the following [1] to

[11] . [1] A peelable pressure-sensitive adhesive composition containing a polyester resin, wherein the polyester resin is a polyester resin (A) containing a (meth)acryloyl group. [2] The peelable pressure-sensitive adhesive composition according to [1], wherein the weight-average molecular weight of the (meth)acryloyl group-containing polyester resin (A) is 10,000 to 500,000. [3] The peelable pressure-sensitive adhesive composition according to [1] or [2], wherein the content of the polyester resin (A) containing a (meth)acryloyl group is 50% by weight or more of the entire peelable pressure-sensitive adhesive composition. [4] The polyester resin (A) containing a (meth)acryloyl group, A reaction product obtained by reacting a hydroxyl group of a polyester resin with an isocyanate group-containing (meth)acrylate and / or a carboxyl group-containing (meth)acrylate, or The peelable pressure-sensitive adhesive composition according to any one of [1] to [3], which is a reaction product of a carboxy group of a polyester resin and a glycidyl group-containing (meth)acrylate and / or a hydroxyl group-containing (meth)acrylate. [5] The peelable pressure-sensitive adhesive composition according to any one of [1] to [4], further comprising a crosslinking agent (B). [6] The peelable pressure-sensitive adhesive composition according to any one of [1] to [5], wherein the crosslinking agent (B) has an unsaturated group and a functional group that reacts with the polyester resin (A) containing a (meth)acryloyl group. [7] The peelable pressure-sensitive adhesive composition according to any one of [1] to [6], further comprising a polymerization initiator (C). [8] A peelable pressure-sensitive adhesive obtained by using the peelable pressure-sensitive adhesive composition according to any one of [1] to [7]. [9] A peelable adhesive sheet comprising a substrate and at least one adhesive layer containing the peelable adhesive according to [8] laminated thereon.

[10] The peelable adhesive sheet according to [9], wherein the adhesive strength (β) of the peelable adhesive sheet is 2 N / 25 mm or less. Adhesion strength (β): The peelable adhesive sheet was attached to a SUS-BA plate and left to stand at 23°C and 50% RH for at least 30 minutes. After that, it was irradiated with ultraviolet light (500 mJ / cm2 using a high-pressure mercury lamp). The 180-degree peel strength (N / 25 mm) after ultraviolet light irradiation was measured in accordance with JIS Z0237.

[11] A pressure-sensitive adhesive composition containing a polyester-based resin, wherein the polyester-based resin is a polyester-based resin (A) containing a (meth)acryloyl group, and the unsaturated group concentration is 0.15 mmol / g or more.

[0011] To date, many adhesive sheets have been designed using release adhesives containing acrylic resins. The release adhesives using the acrylic resins incorporate unsaturated groups or serve as reaction sites with crosslinkers by utilizing the side chain functional groups of the acrylic resin. An adhesive sheet is prepared from the release adhesive using the acrylic resin, and then irradiated with energy rays such as ultraviolet light to chemically react and integrate the network of the functional groups on the side chains of the acrylic resin, the crosslinker, and the unsaturated groups on the side chains of the acrylic resin, resulting in a removable adhesive sheet for semiconductor processing with very little residual residue. By controlling the copolymerization monomer, the acrylic resin can easily have a high concentration of functional groups on the side chains, making it very easy to react with unsaturated groups or crosslinkers.

[0012] On the other hand, when polyester resins are used as release adhesives, they usually only have functional groups at the molecular terminals, making it difficult to use those functional groups (by reacting a compound having an unsaturated group with a functional group that reacts with that functional group) to provide a high concentration of unsaturated groups. Increasing the unsaturated group content of polyester resins, as with the acrylic resins mentioned above, requires increasing the number of terminal groups, which reduces the molecular weight and raises concerns about increased adhesive residue. In other words, incorporating unsaturated groups into polyester resins or using the functional groups of polyester resins as reaction sites with crosslinkers often results in a shortage of functional groups in the polyester resin, making them unsuitable for applications such as release adhesives, where adhesive residue is a common problem.

[0013] For this reason, it was thought that designing a polyester-based peelable pressure-sensitive adhesive sheet using a polyester resin would be difficult without adding an unsaturated group-containing compound, as in Patent Document 2. However, this time, a removable pressure-sensitive adhesive for semiconductor processing with little adhesive residue was designed, which integrates a network of pressure-sensitive adhesive layers, using a polyester resin containing a (meth)acryloyl group. Surprisingly, compared to acrylic resins that have functional groups on the side chains that form the basis of crosslinking structures, a pressure-sensitive adhesive with greater elongation was obtained by using polyester resins that have functional groups at the molecular end. Although the details are unclear, this is thought to be due to the use of polyester resins, which increases the molecular weight between crosslinking points. [Effects of the Invention]

[0014] The releasable pressure-sensitive adhesive composition of the present invention, when used as a releasable pressure-sensitive adhesive, can have a releasable adhesive strength and can further increase elongation. Therefore, the releasable pressure-sensitive adhesive has a low adhesive strength after energy application, and can be easily peeled. Furthermore, because of its high elongation, even when the pressure-sensitive adhesive is physically caught on an uneven surface, the pressure-sensitive adhesive does not break and adhesive residue is less likely to remain. Furthermore, because of its high elongation, it can easily conform to uneven surfaces when applied by performing a heat and pressure treatment as necessary. That is, the releasable pressure-sensitive adhesive composition of the present invention can be a pressure-sensitive adhesive having low adhesive strength and high elongation after energy application, and is excellent in releasability, reduced adhesive residue, and conformability to uneven surfaces.

[0015] Furthermore, the pressure-sensitive adhesive composition of the present invention can be used not only as the above-mentioned peelable pressure-sensitive adhesive composition but also as a pressure-sensitive adhesive composition that is not intended for peeling. When used as a peelable pressure-sensitive adhesive composition, it can be a pressure-sensitive adhesive having low adhesive strength and high elongation after energy application, and it has excellent peelability, reduced adhesive residue, and unevenness-following properties. DETAILED DESCRIPTION OF THE INVENTION

[0016] The configuration of the present invention will be described in detail below, but these are merely examples of preferred embodiments. In the present invention, "(meth)acrylic" means acrylic or methacrylic, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate, respectively. Furthermore, in the present invention, "x and / or y (x and y are any constitutions or components)" means three combinations: x only, y only, and x and y.

[0017] <Releasable Pressure-Sensitive Adhesive Composition> A peelable pressure-sensitive adhesive composition according to one embodiment of the present invention (hereinafter referred to as "the peelable pressure-sensitive adhesive composition") will be described. The present peelable pressure-sensitive adhesive composition contains a polyester resin (A) containing a (meth)acryloyl group, and in addition to the polyester resin (A) containing a (meth)acryloyl group, it may also contain preferably a crosslinking agent (B), a polymerization initiator (C), and, if necessary, a hydrolysis inhibitor (D), an active energy ray-curable compound (E), etc.

[0018] [(Meth)acryloyl group-containing polyester resin (A)] The polyester resin (A) containing a (meth)acryloyl group (hereinafter referred to as "polyester resin (A)") used in the present peelable pressure-sensitive adhesive composition is a polyester resin containing a structural unit having a (meth)acryloyl group. The polyester resin (A) contains, in addition to a structural unit having a (meth)acryloyl group, a structural unit derived from a dicarboxylic acid and a structural unit derived from a diol, and optionally contains a structural unit derived from a trivalent or higher polycarboxylic acid and / or a structural unit derived from a trivalent or higher polyalcohol.

[0019] Such a polyester resin (A) is obtained by reacting a polyester resin with a (meth)acryloyl group-containing compound. The following explains each in order.

[0020] (Polyester resin) The polyester resin has structural units derived from dicarboxylic acids and diols, and optionally structural units derived from trivalent or higher polycarboxylic acids and / or trivalent or higher polyhydric alcohols. Such polyester resins are obtained by polymerizing polymerization components including polycarboxylic acids such as dicarboxylic acids and trivalent or higher polycarboxylic acids, and polyhydric alcohols such as diols and trivalent or higher polyhydric alcohols.

[0021] [Structural units derived from dicarboxylic acids] Examples of the structural unit derived from dicarboxylic acid in the polyester resin include aliphatic acyclic dicarboxylic acids such as succinic acid, methylsuccinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, pimelic acid, decanedicarboxylic acid, octadecanedicarboxylic acid, 1,12-dodecanoic acid, 1,14-tetradecanoic acid, and hydrogenated dimer acid; 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,2-cyclohexanediacetic acid, 1,3-cyclohexanediacetic acid, 1,4-cyclohexanediacetic acid, tetrahydrophthalic acid, tetrachlorophthalic acid, and hexachlorophthalic acid; Examples of the structural units include aromatic dicarboxylic acids such as aliphatic cyclic dicarboxylic acids such as hexahydrophthalic acid, aliphatic unsaturated dicarboxylic acids such as fumaric acid, maleic acid, itaconic acid, and dimer acid, benzene dicarboxylic acids such as terephthalic acid, isophthalic acid, and orthophthalic acid, and heterocyclic dicarboxylic acids such as 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, furandicarboxylic acid, and thiophenedicarboxylic acids (pyrrole, pyrazole, imidazole, pyridine, pyridazine, pyrimidine, pyrazine, etc.), as well as structural units derived from their acid anhydrides and lower alkyl esters. The polyester resin may contain one or more types of these structural units derived from dicarboxylic acids. Among these, it is preferable to have structural units derived from aromatic dicarboxylic acids and structural units derived from aliphatic acyclic dicarboxylic acids. In particular, from the viewpoint of achieving both durability and flexibility, it is more preferable to have both structural units derived from aromatic dicarboxylic acids and structural units derived from aliphatic acyclic dicarboxylic acids, and it is particularly preferable to have both structural units derived from isophthalic acid and structural units derived from sebacic acid.

[0022] [Diol-derived structural units] Examples of the diol-derived structural unit in the polyester resin include linear aliphatic diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and 1,18-octadecanediol; propylene glycol; neopentyl glycol; 2-methyl-1,3-propanediol; 1-methyl-1,3-propanediol; hexanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,3,5-trimethyl-1,3-pentanediol, 2-methyl-1,6-hexanediol, 2-methyl-1,8 aliphatic diols having hydrocarbon groups in the side chains such as 1-octanediol, 2-methyl-1,9-nonanediol, dimer diol, 4-methyl-1,7-heptanediol, 3-methyl-1,6-hexanediol, 1-methyl-1,6-hexanediol, 4-methyl-1,9-nonanediol, 3-methyl-1,9-nonanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,3-cyclobutanediol, hydrogenated bisphenol A and / or Examples of structural units include structural units derived from alicyclic diols such as their ethylene oxide adducts and propionate adducts, and aromatic diols such as bisphenol A, 9,9-bis(hydroxyphenyl)fluorene, 4,4'-thiodiphenol, 4,4'-methylenediphenol, 4,4'-dihydroxybiphenyl, o-, m-, and p-dihydroxybenzene, 2,5-naphthalenediol, p-xylenediol, and their ethylene oxide adducts and propylene oxide adducts. The polyester resin may contain one or more of these diol-derived structural units. Among these, from the viewpoint of being able to control the glass transition temperature so as not to cause crystallization, it is preferable to have both structural units derived from a linear aliphatic diol and structural units derived from an aliphatic diol having a hydrocarbon group in the side chain, and it is particularly preferable to have structural units derived from at least one selected from ethylene glycol, 1,4-butanediol, and 1,6-hexanediol as structural units derived from a linear aliphatic diol, and structural units derived from at least one selected from neopentyl glycol and 2-butyl-2-ethyl-1,3-propanediol as structural units derived from an aliphatic diol having a hydrocarbon group in the side chain.

[0023] Furthermore, the diol-derived structural unit may include a polyester diol-derived structural unit, a polyether diol-derived structural unit, a polycaprolactone diol-derived structural unit, a polycarbonate diol-derived structural unit, or the like, in order to easily obtain a polymer having a desired molecular weight.

[0024] Examples of the structural unit derived from the polyester diol include structural units derived from polyester diols obtained by dehydrating a diol component such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,10-decanediol, or octadecanediol with a dicarboxylic acid component such as succinic acid, methylsuccinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, 1,12-dodecanoic acid, 1,14-tetradecanedioic acid, terephthalic acid, isophthalic acid, or anhydrides or lower alkyl esters thereof, or derivatives thereof, either alone or in the form of a mixture. Commercially available polyester diols used to introduce such structural units into polyester resins include, for example, polyester diols of 3-methyl-1,5-pentanediol and adipic acid, trade names of which are "Kuraray Polyol P-510," "Kuraray Polyol P-1010," "Kuraray Polyol P-2010," "Kuraray Polyol P-3010," and "Kuraray Polyol P-5010" (all manufactured by Kuraray Co., Ltd.).

[0025] Examples of the structural units derived from the polyether diol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol obtained by ring-opening polymerization of ethylene oxide, propylene oxide, tetrahydrofuran, etc., and structural units derived from copolyethers obtained by copolymerizing these. Commercially available polyether diols used to introduce such structural units into polyester resins include polyether diols obtained by adding propylene oxide to propylene glycol, such as those under the trade names "ADEKA POLYETHER P-400," "ADEKA POLYETHER P-1000," "ADEKA POLYETHER P-2000," and "ADEKA POLYETHER P-3000" (all manufactured by Asahi Denka Kogyo Co., Ltd.).

[0026] Examples of the structural unit derived from the polycaprolactone diol include structural units derived from caprolactone-based polyester diols obtained by ring-opening polymerization of cyclic ester monomers such as ε-caprolactone, δ-valerolactone, etc. Commercially available polycaprolactone diols used to introduce such structural units into polyester resins include those under the trade names "PLACCEL L205AL," "PLACCEL L212AL," "PLACCEL L220AL," "PLACCEL L220PL," and "PLACCEL L230AL" (all manufactured by Daicel Chemical Industries, Ltd.).

[0027] Examples of the structural unit derived from the polycarbonate diol include structural units derived from carbonate diols such as propylene carbonate diol, hexamethylene carbonate diol, and 3-methylpentene carbonate diol, and polycarbonate diols obtained by dealcoholization reaction of polyhydric alcohols such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, and 1,9-nonanediol with dialkyl carbonates such as diethylene carbonate and dimethyl carbonate. Commercially available polycarbonate diols used to introduce such structural units into polyester resins include, for example, trade names "PLACCEL CD205," "PLACCEL CD210," "PLACCEL CD220," "PLACCEL CD205PL," "PLACCEL CD210PL," and "PLACCEL CD220PL" (all manufactured by Daicel Chemical Industries, Ltd.).

[0028] [Structural units derived from trivalent or higher polycarboxylic acids] Examples of structural units derived from trivalent or higher polycarboxylic acids in the polyester resin include aromatic polycarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid, aliphatic polycarboxylic acids such as 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, and 1,2,3,4-butanetetracarboxylic acid, and structural units derived from their acid anhydrides and lower alkyl esters, etc. The polyester resin may contain one or more types of structural units derived from trivalent or higher polycarboxylic acids. Among these, from the viewpoint of appropriately controlling the degree of dispersion, it is preferable to have a structural unit derived from a trivalent carboxylic acid, in particular a structural unit derived from a trivalent aromatic carboxylic acid, and in particular a structural unit derived from trimellitic acid.

[0029] [Structural units derived from trivalent or higher polyhydric alcohols] Examples of structural units derived from trihydric or higher polyhydric alcohols in the polyester resin include structural units derived from aliphatic polyhydric alcohols such as trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, etc. The polyester resin may contain one or more types of structural units derived from trihydric or higher polyhydric alcohols. Among these, from the viewpoint of appropriately controlling the degree of dispersion, it is preferable to have a structural unit derived from a trihydric aliphatic alcohol, and it is particularly preferable to have a structural unit derived from trimethylolpropane.

[0030] [Production of polyester resin] The polyester resin can be produced by polycondensation reaction of the above-mentioned polycarboxylic acid and the above-mentioned polyhydric alcohol as raw materials in the presence of a catalyst using a known method. That is, since the polyester resin is obtained by polycondensation reaction of a polycarboxylic acid and a polyhydric alcohol, it has a structural portion derived from the polycarboxylic acid and a structural portion derived from the polyhydric alcohol. In the polycondensation reaction, an esterification reaction or an ester exchange reaction is first carried out, and then the polycondensation reaction is carried out. Note that when a high molecular weight is not required, the resin may be produced by only an esterification reaction or an ester exchange reaction.

[0031] The blending ratio of the polycarboxylic acid and the polyhydric alcohol is preferably 1 to 3 equivalents of the polyhydric alcohol per equivalent of the polycarboxylic acid, particularly preferably 1.1 to 2.2 equivalents, and even more preferably 1.2 to 1.7 equivalents. If the blending ratio of the polyhydric alcohol 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.

[0032] [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.

[0033] 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.

[0034] 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 not to proceed sufficiently, while if it is too high, side reactions such as decomposition tend to occur easily. Furthermore, although the pressure during the reaction is usually normal pressure, it is also preferable to perform the reaction under pressure to increase the reaction temperature and efficiently proceed with the reaction.

[0035] 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.

[0036] In producing the polyester resin, it is also preferable to depolymerize after the condensation reaction, since this effectively allows the polyester resin to contain functional groups. For depolymerization, the aforementioned polycarboxylic acids and polyhydric alcohols can be used, and it is preferable to use trivalent or higher polycarboxylic acids and / or trivalent or higher polyhydric alcohol components, and dicarboxylic acids and diols can also be used as needed.

[0037] The polycarboxylic acid or polyhydric alcohol added during depolymerization is preferably a diol or a trihydric or higher polyhydric alcohol in that it can increase the hydroxyl group content, and more preferably a trihydric or higher polyhydric alcohol in that it can increase the hydroxyl group content more efficiently. In particular, trimethylolpropane is preferred in terms of its versatility.

[0038] The temperature for depolymerization is usually 150 to 260°C, and the reaction time is usually 10 minutes to 3 hours.

[0039] In addition, the depolymerization is preferably carried out using 20 mol% or less of the depolymerization component, more preferably 0.1 to 15 mol%, particularly preferably 0.5 to 10 mol%, and even more preferably 1 to 5 mol%, when the total polycarboxylic acids constituting the polyester resin is 100 mol%.

[0040] By carrying out the reaction according to the above method, a polyester resin can be obtained.

[0041] The number average molecular weight (Mn) of such polyester resin is preferably 5000 or more, more preferably 6000 to 100000, and particularly preferably 7000 to 80000. If the number average molecular weight is too small, the adhesive will not have sufficient cohesive strength and heat resistance and mechanical strength will tend to decrease, while if the number average molecular weight is too large, flexibility will be lost, initial adhesion will decrease, and sufficient adhesive strength will not be exerted even with pressure equivalent to finger pressure.

[0042] The weight-average molecular weight (Mw) of such polyester resins is preferably 5,000 or more, particularly preferably 10,000 or more, and even more preferably 30,000 or more. The upper limit is usually 500,000. If the weight-average molecular weight is too small, the adhesive will not have sufficient cohesive strength, and heat resistance and mechanical strength will tend to decrease, and adhesive residue will tend to be more likely to occur when peeled off. If the weight-average molecular weight is too large, flexibility will be lost, initial adhesion will decrease, and sufficient adhesive strength will not be exerted even with pressure equivalent to finger pressure.

[0043] The degree of dispersion (weight average molecular weight / number average molecular weight) of such polyester resins is preferably 20 or less, more preferably 15 or less, and particularly preferably 10 or less. If the degree of dispersion is too high, adhesive residue due to low molecular weight components tends to occur. However, there is no problem even if the degree of dispersion is low.

[0044] As an index of the degree of dispersion, Mw / Mp (weight average molecular weight / peak top molecular weight) can also be used. A smaller Mw / Mp is preferable, preferably 10 or less, particularly preferably 3 or less, and most preferably 1.5 or less. If Mw / Mp is large, there is a tendency for adhesive residue to remain due to the large amount of low molecular weight components.

[0045] Furthermore, it is preferable that the number average molecular weight, weight average molecular weight, and peak top molecular weight do not contain low molecular weight components in order to reduce adhesive residue, and it is preferable that components with a molecular weight of 1000 or less account for 10% or less, and even more preferably 5% or less.

[0046] The above-mentioned dispersity and the ratio of low-molecular-weight components can be adjusted by the content of the trivalent or higher polyhydric alcohol component and / or the trivalent or higher polycarboxylic acid component used to constitute the polyester resin, the conditions of the condensation reaction (temperature, degree of vacuum, stirring, reaction time, etc.), and the presence or absence of depolymerization and the conditions.

[0047] The number-average molecular weight and weight-average molecular weight are average molecular weights converted into standard polystyrene molecular weights. The high-performance liquid chromatograph (manufactured by Japan Waters, "Waters 2695 (separation module)" and "Waters 2414 (detector)") was equipped with a Shodex GPC KF-806L column (exclusion limit molecular weight: 2 × 10 7 Separation range: 100 to 2 × 10 7 The measurement was performed using three columns in series (theoretical plate number: 10,000 plates / column, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm).

[0048] The glass transition temperature of such polyester resins is preferably -100 to 30°C, particularly preferably -80 to 0°C, and especially preferably -70 to -20°C. If the glass transition temperature is too high, flexibility is lost, conformability to uneven surfaces is poor, initial tackiness is reduced, and sufficient adhesive strength tends to be insufficient with finger pressure, while if the glass transition temperature is too low, mechanical strength and heat resistance tend to decrease. The glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC).

[0049] Furthermore, it is more preferable that such polyester resins do not crystallize, and even if crystallization does occur, the crystallization temperature is preferably 0°C or lower, particularly -30°C or lower; if the crystallization temperature is too high, tack tends to be lost. The crystallization energy is also more preferably as low as possible, preferably 35 J / g or lower, particularly 20 J / g or lower, and even more preferably 15 J / g or lower; if the crystallization energy is too high, tack tends to be lost. The crystallization energy refers to the energy consumed when heating and melting a crystallized substance, and can be measured using a differential scanning calorimeter (DSC).

[0050] The polyester resin preferably contains substantially no acidic groups. The acid value of the polyester resin is preferably 10 mgKOH / g or less, more preferably 5 mgKOH / g or less, even more preferably 3 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 polyhydric alcohol 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. The acid value of the polyester resin can be determined by neutralization titration according to JIS K0070. The acid value in the present invention means the content of carboxy groups in the polyester resin. The carboxy groups include those in a carboxylate ion state in which the carboxy groups are neutralized with a basic compound.

[0051] The polyester resin preferably contains a hydroxyl group. The hydroxyl value of the polyester resin is usually 1 to 100 mgKOH / g, preferably 3 to 50 mgKOH / g, particularly preferably 5 to 40 mgKOH / g, and further preferably 15 to 30 mgKOH / g. If the hydroxyl value is too low, the reactivity with the (meth)acryloyl group-containing compound described below tends to decrease. Furthermore, since it is usually necessary to reduce the molecular weight in order to increase the hydroxyl value, if the hydroxyl value is too high, low molecular weight components tend to cause adhesive residue. In the present invention, the hydroxyl value (mgKOH / g) is determined by dissolving 1 g of polyester resin in 30 g of a mixed solvent of toluene / pyridine=5 / 5 (weight ratio) and subjecting it to neutralization titration in accordance with JIS K0070.

[0052] The ester group concentration of the polyester resin is preferably 1 to 12 mmol / g, more preferably 3 to 11 mmol / g, and even more preferably 5 to 10 mmol / g. If the ester group concentration is too low, the polarity and elastic modulus of the polyester resin will decrease, and initial adhesion will tend to be poor, while if the ester group concentration is too high, the polarity will increase too much, and solution stability will tend to be poor.

[0053] The ester group concentration (mmol / g) refers to the number of moles of ester groups per gram of polyester resin, and can be calculated from the amounts charged, for example. The calculation method is to divide the number of moles of the polycarboxylic acid or polyhydric alcohol charged, whichever is smaller, by the total weight of the finished product, and an example of the calculation formula is shown below. When the amounts of the polycarboxylic acid and the polyhydric alcohol charged 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 prepared from caprolactone or the like, the calculation method will be changed appropriately.

[0054] <When polycarboxylic acids are in short supply> Ester group concentration (mmol / g) = [(A1 / α1 × m1 + A2 / α2 × m2 + A3 / α3 × m3 ) / Z] × 1000 A: Amount of polycarboxylic acid (g) α: Molecular weight of polycarboxylic acid m: number of carboxyl groups per molecule of polycarboxylic acid Z: Finished weight (g)

[0055] <When there is little polyhydric alcohol> Ester group concentration (mmol / g) = [(B1 / β1×n1+B2 / β2×n2+B3 / β3×n3) / Z] × 1000 B: Amount of polyhydric alcohol (g) β: Molecular weight of polyhydric alcohol n: number of hydroxyl groups per molecule of polyhydric alcohol Z: Finished weight (g)

[0056] The ester group concentration can also be measured by a known method such as NMR. For example, the ester group concentration of polyester resin is 1 H-NMR measurement (proton nuclear magnetic resonance spectroscopy), 13 This can be done by C-NMR measurement (carbon-type nuclear magnetic resonance spectroscopy).

[0057] As mentioned above, the polyester resin (A) used in the present peelable pressure-sensitive adhesive composition is preferably a product obtained by reacting the above polyester resin with a (meth)acryloyl group-containing compound.

[0058] ((Meth)acryloyl group-containing compound) Examples of the (meth)acryloyl group-containing compound include hydroxyl group-containing (meth)acrylates, carboxy group-containing (meth)acrylates, amino group-containing (meth)acrylates, acetoacetyl group-containing (meth)acrylates, isocyanate group-containing (meth)acrylates, glycidyl group-containing (meth)acrylates, etc. These may be used alone or in combination of two or more.

[0059] Examples of the hydroxyl group-containing (meth)acrylate include ethylenically unsaturated (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate, and caprolactone-modified 2-hydroxyethyl (meth)acrylate. Examples of suitable hydroxyl group-containing (meth)acrylates include hydroxyl group-containing (meth)acrylates having one ethylenically unsaturated group, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified dipentaerythritol penta(meth)acrylate, and ethylene oxide-modified pentaerythritol tri(meth)acrylate. Among these, hydroxyl group-containing (meth)acrylates having two or more ethylenically unsaturated groups are preferred.

[0060] Examples of the carboxy group-containing monomer include (meth)acrylic acid, (meth)acrylic acid dimer, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, and anhydrides thereof. Among these, (meth)acrylic acid and (meth)acrylic acid dimer are preferred in terms of versatility.

[0061] Examples of the isocyanate group-containing (meth)acrylate include 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, 1,1-(bisacryloyloxymethyl)ethyl isocyanate, 1,1-(bismethacryloyloxymethyl)ethyl isocyanate, and alkylene oxide adducts thereof.

[0062] Furthermore, as the isocyanate group-containing (meth)acrylate, a urethane (meth)acrylate type isocyanate group-containing unsaturated oligomer, which is a reaction product of an isocyanate compound such as tolylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, or an adduct or isocyanurate thereof with the above-mentioned hydroxyl group-containing (meth)acrylate or a compound having a hydroxyl group and multiple (meth)acryloyl groups, can also be used.

[0063] The (meth)acryloyl group-containing compound is appropriately selected depending on the reactivity of the functional group of the polyester resin with the functional group of the (meth)acryloyl group-containing compound. For example, when the functional group of the polyester resin is a hydroxyl group, it is preferable to use an isocyanate group-containing (meth)acrylate or a carboxyl group-containing (meth)acrylate monomer as the (meth)acryloyl group-containing compound. Furthermore, when the functional group of the polyester resin is a carboxyl group, it is preferable to use a glycidyl group-containing (meth)acrylate or a hydroxyl group-containing (meth)acrylate.

[0064] That is, the polyester resin (A) is preferably, for example, a reaction product of the following: (i) A reaction product obtained by reacting a hydroxyl group of a polyester resin with an isocyanate group-containing (meth)acrylate and / or a carboxy group-containing (meth)acrylate. (ii) A reaction product obtained by reacting a carboxy group of a polyester resin with a glycidyl group-containing (meth)acrylate and / or a hydroxyl group-containing (meth)acrylate. Among these, the reaction product of (i) is preferred because a (meth)acryloyl group can be easily introduced and a hydroxyl group is likely to remain as a crosslinking site. The reaction product with an isocyanate group-containing (meth)acrylate is more preferred because the reaction is easy to control, and the reaction products with 2-methacryloyloxyethyl isocyanate and 1,1-(bisacryloyloxymethyl)ethyl isocyanate are particularly preferred.

[0065] Thus, the polyester resin (A) is obtained by reacting the polyester resin with the (meth)acryloyl group-containing monomer in a conventional manner.

[0066] Furthermore, when a polyester resin is reacted with an isocyanate group-containing (meth)acrylate, it is preferable to react the isocyanate group-containing (meth)acrylate so that 5 to 95 mol% of the hydroxyl groups in the polyester resin are consumed, particularly 10 to 80 mol%, further 20 to 70 mol%, and especially 30 to 60 mol%. If the amount of hydroxyl groups consumed is too small, the unsaturated group concentration tends to be low and the decrease in adhesive strength after energy application tends to be insufficient, while if it is too large, the reaction with the crosslinking agent (B) tends to be difficult to occur, and adhesive residue tends to remain.

[0067] The unsaturated group concentration of the polyester resin (A) is preferably 0.001 to 2 mmol / g, more preferably 0.01 to 1.5 mmol / g, and particularly preferably 0.05 to 0.5 mmol / g, per 1 g of the polyester resin (A). If the concentration of unsaturated groups in the polyester resin (A) is too low, the decrease in adhesive strength after application of energy tends to be insufficient, and the removability and resistance to contamination of the adherend tend to decrease, while if the concentration is too high, the elongation after application of energy tends to decrease. 1 H-NMR measurements and 13 It can be determined from the spectrum obtained by C-NMR measurement.

[0068] The unsaturated group is not particularly limited as long as it is a functional group having a carbon-carbon double bond or a carbon-carbon triple bond, but is preferably a functional group having a carbon-carbon double bond, and more preferably a (meth)acryloyl group, which can be easily used with a commonly used ultraviolet irradiator.

[0069] The polyester resin (A) preferably contains a hydroxyl group. The hydroxyl value of the polyester resin (A) is preferably 1 to 95 mgKOH / g, more preferably 2 to 40 mgKOH / g, particularly preferably 3 to 30 mgKOH / g, and especially preferably 5 to 15 mgKOH / g. If the hydroxyl value is too low, there will be insufficient hydroxyl groups to react with the crosslinking agent (B), which will reduce the reactivity with the crosslinking agent (B) and tend to make adhesive residues more likely to occur. In addition, in order to increase the hydroxyl value, the molecular weight will be reduced or the amount of unsaturated groups introduced will be reduced, so if the hydroxyl value is too high, low molecular weight components and a lack of unsaturated groups will tend to cause adhesive residues.

[0070] The polyester resin (A) preferably contains substantially no acidic groups. The acid value of the polyester resin (A) is preferably 10 mgKOH / g or less, more preferably 5 mgKOH / g or less, even more preferably 3 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 polyhydric alcohol during the esterification reaction or transesterification reaction, or by adjusting the reaction conditions.

[0071] The glass transition temperature of the polyester resin (A) is preferably -100 to 30°C, particularly preferably -80 to 0°C, and especially preferably -70 to -20°C. If the glass transition temperature is too high, flexibility will be lost, conformability to uneven surfaces will be poor, initial tackiness will be reduced, and sufficient adhesive strength will not be exerted with finger pressure, while if the glass transition temperature is too low, mechanical strength and heat resistance will tend to be reduced. The glass transition temperature (Tg) is measured using a differential scanning calorimeter (DSC).

[0072] Furthermore, it is more preferable that the polyester resin (A) does not crystallize. If crystallization does occur, the crystallization temperature is preferably 0°C or lower, particularly -30°C or lower; if the crystallization temperature is too high, tack tends to be lost. The crystallization energy is also preferably as low as possible, 35 J / g or lower, particularly 20 J / g or lower, and even more preferably 15 J / g or lower; if the crystallization energy is too high, tack tends to be lost. The crystallization energy refers to the energy consumed when heating and melting a crystallized substance, and can be measured by a differential scanning calorimeter (DSC).

[0073] The number average molecular weight (Mn) of such polyester resin (A) is preferably 5000 or more, more preferably 8000 to 100000, and particularly preferably 10000 to 80000. If the number average molecular weight is too small, the adhesive will not have sufficient cohesive strength and heat resistance and mechanical strength will tend to decrease, while if the number average molecular weight is too large, flexibility will be lost, initial adhesion will decrease, and sufficient adhesive strength will not be exerted even with pressure equivalent to finger pressure.

[0074] The weight average molecular weight (Mw) of the polyester resin (A) is preferably 10,000 to 500,000, more preferably 20,000 to 300,000, and even more preferably 30,000 to 100,000. If the weight average molecular weight is too small, the adhesive will not have sufficient cohesive strength, and heat resistance and mechanical strength will tend to decrease, and adhesive residue will tend to be more likely to occur when the adhesive is peeled off again. If the weight average molecular weight is too large, flexibility will be lost, initial adhesion will decrease, and sufficient adhesive strength will not be exerted even with pressure equivalent to finger pressure.

[0075] The polydispersity (weight average molecular weight / number average molecular weight) of the polyester resin (A) is preferably 20 or less, more preferably 15 or less, and particularly preferably 10 or less. If the polydispersity is too high, adhesive residue due to low molecular weight components tends to easily occur. However, a low polydispersity does not pose any problems.

[0076] As an index of the degree of dispersion, Mw / Mp (weight average molecular weight / peak top molecular weight) can also be used. A smaller Mw / Mp is preferable, preferably 10 or less, particularly preferably 3 or less, and most preferably 1.5 or less. If Mw / Mp is large, there is a tendency for adhesive residue to remain due to the large amount of low molecular weight components.

[0077] Furthermore, it is preferable that the above number average molecular weight and weight average molecular weight do not contain low molecular weight components in order to reduce adhesive residue, and it is preferable that components with a molecular weight of 1000 or less account for 10% or less, and even more preferably 5% or less.

[0078] The above-mentioned dispersity and the ratio of low-molecular-weight components can be adjusted by the content of the trivalent or higher polyhydric alcohol component and / or the trivalent or higher polycarboxylic acid component used to constitute the polyester resin (A), the conditions of the condensation reaction (temperature, degree of vacuum, stirring, reaction time, etc.), and the presence or absence of depolymerization and the conditions.

[0079] When the polyester resin (A) has structural units derived from aromatic dicarboxylic acids, the content thereof is preferably 5 to 75 mol %, more preferably 10 to 30 mol %, of the structural units derived from polycarboxylic acids. If the content is too low, heat resistance and mechanical strength tend to decrease, while if the content is too high, flexibility is lost, initial tackiness decreases, and sufficient adhesive strength cannot be exerted even with finger pressure.

[0080] Furthermore, when the polyester resin (A) has structural units derived from aliphatic acyclic dicarboxylic acids, the content thereof is preferably 25 to 95 mol %, more preferably 70 to 90 mol %, of the structural units derived from polycarboxylic acids. If the content is too low, flexibility is lost, initial adhesion (adhesion before energy application) decreases, and sufficient adhesive strength tends to be unable to be exerted with pressure equivalent to finger pressure, while if the content is too high, heat resistance and mechanical strength tend to decrease.

[0081] Furthermore, when the polyester resin (A) has structural units derived from an aromatic dicarboxylic acid and structural units derived from an acyclic aliphatic dicarboxylic acid, the ratio of structural units (mol %) derived from an acyclic aliphatic dicarboxylic acid to structural units (mol %) derived from an aromatic dicarboxylic acid is preferably 0.1 to 50, more preferably 1 to 25, and particularly preferably 2 to 10, from the viewpoint of the balance between adhesive properties and mechanical strength.

[0082] When the polyester resin (A) has a structural unit derived from a linear aliphatic diol, the content thereof is preferably 5 to 40 mol %, more preferably 10 to 30 mol %, of the structural unit derived from a polyhydric alcohol. If the content is too low, the cohesive strength tends to be insufficient, and if the content is too high, crystallization tends to occur, resulting in insufficient adhesive properties.

[0083] Furthermore, when the polyester resin (A) has a structural unit derived from a diol having a hydrocarbon group in the side chain, the content thereof is preferably 3 to 100 mol %, and more preferably 10 to 70 mol %, of the structural unit derived from the polyhydric alcohol. If the content is too low, crystallization occurs and tack tends to be easily lost.

[0084] When the polyester resin (A) has structural units derived from a linear aliphatic diol and structural units derived from an aliphatic diol having a hydrocarbon group in the side chain, the ratio (mol %) of the structural units (mol %) derived from an aliphatic diol having a hydrocarbon group in the side chain to the structural units (mol %) derived from aliphatic diol having a hydrocarbon group in the side chain is preferably 0.1 to 100, more preferably 0.5 to 20, and particularly preferably 1 to 5, from the viewpoint of making it difficult for crystallinity to be exhibited.

[0085] When the polyester resin (A) has a structural unit derived from a trivalent or higher polycarboxylic acid, the content of the structural unit derived from the polycarboxylic acid is preferably 0.1 to 5 mol % from the viewpoint of durability before energy application when used as an adhesive, more preferably 0.1 to 2.5 mol %, and even more preferably 0.2 to 2 mol %. If the content is too low, the durability before energy application when used as an adhesive tends to decrease, while if the content is too high, gelation tends to occur and adhesive strength tends to decrease.

[0086] When the polyester resin (A) has a structural unit derived from a trihydric or higher polyhydric alcohol, the content of the structural unit derived from the polyhydric alcohol is preferably 0.1 to 5 mol % from the viewpoint of durability before energy application when used as an adhesive, more preferably 0.1 to 2.5 mol %, and even more preferably 0.2 to 2 mol %. If the content is too low, the durability before energy application when used as an adhesive tends to decrease, while if the content is too high, gelation tends to occur and adhesive strength tends to decrease.

[0087] The composition and composition ratio of the polyester resin (A) are the same as those described above.1 H-NMR measurements and 13 It can be determined from the spectrum obtained by C-NMR measurement.

[0088] <Adhesive composition> A pressure-sensitive adhesive composition according to one embodiment of the present invention (hereinafter referred to as "the pressure-sensitive adhesive composition") contains a polyester resin, the polyester resin being polyester resin (A) and having an unsaturated group concentration of 0.15 mmol / g or more. The pressure-sensitive adhesive composition may also contain a crosslinking agent (B), a polymerization initiator (C), a hydrolysis inhibitor (D), etc., as necessary. The present pressure-sensitive adhesive composition can be used not only as a peelable pressure-sensitive adhesive composition, but also as a pressure-sensitive adhesive composition that is not intended to be peeled.

[0089] [Crosslinking agent (B)] The crosslinking agent (B) used in the present release pressure-sensitive adhesive composition may be any compound having a functional group that reacts with a functional group contained in the polyester resin (A), and examples thereof include epoxy compounds such as bisphenol A-epichlorohydrin epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, and diglycerol polyglycidyl ether; tetramethylolmethane-tri-β-aziridinyl propionate; trimethylolpropane-tri-β-aziridinyl propionate; N,N'-diglycidyl ether; Aziridine compounds such as phenylmethane-4,4'-bis(1-aziridinecarboxamide) and N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide), melamine compounds such as hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexaptoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, and melamine resins, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, hexamethylene diisocyanate, diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, tetramethylxylylene diisocyanate, 1,Examples of the polyisocyanate include 5-naphthalene diisocyanate, triphenylmethane triisocyanate, and adducts of these polyisocyanate compounds with polyol compounds such as trimethylolpropane; isocyanate compounds such as biuret compounds and isocyanurates of these polyisocyanate compounds; aldehyde compounds such as glyoxal, malondialdehyde, succindialdehyde, maleic dialdehyde, glutaric dialdehyde, formaldehyde, acetaldehyde, and benzaldehyde; amine compounds such as hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetraamine, diethylenetriamine, triethyltetraamine, isophoronediamine, amino resins, and polyamides; and metal chelate compounds such as acetylacetone and acetoacetyl ester coordination compounds of polymetals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, and zirconium. Among these, isocyanate compounds are preferably used in terms of their ability to improve adhesion to the substrate and their reactivity with the polyester resin (A). These crosslinking agents (B) may be used alone or in combination of two or more.

[0090] In addition to the above, the crosslinking agent (B) is preferably a compound containing a functional group reactive with the functional group contained in the polyester resin (A) and an unsaturated group, since this increases the unsaturated group concentration in the peelable pressure-sensitive adhesive composition. Examples of such compounds include polyisocyanates and epoxies containing (meth)acryloyl groups in the side chains, and among these, polyisocyanates containing (meth)acryloyl groups in the side chains are preferred.

[0091] The polyisocyanate containing a (meth)acryloyl group in the side chain is not particularly limited, but examples thereof include compounds obtained by reacting a polyisocyanate with a hydroxyl group-containing (meth)acrylic compound to produce a urethane (meth)acrylate that retains an isocyanate group, and then allophanating the compound, and compounds obtained by reacting one isocyanate group of a trifunctional or higher polyisocyanate with a hydroxyl group-containing (meth)acrylate compound, etc. Among these, allophanated compounds are preferred because they can stably have a (meth)acryloyl group in the side chain.

[0092] The polyisocyanate is not particularly limited, and examples thereof include aromatic, aliphatic, and alicyclic polyisocyanates. Specific examples include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, modified diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate, 1,3-bis(isopropyl methyl ether) Examples of suitable polyisocyanates include polyisocyanates such as (isocyanatomethyl)cyclohexane, phenylene diisocyanate, lysine diisocyanate, lysine triisocyanate, and naphthalene diisocyanate, as well as trimer or polymer compounds of these polyisocyanates, biuret-type polyisocyanates, water-dispersible polyisocyanates (e.g., "AQUANATE 100," "AQUANATE 110," "AQUANATE 200," and "AQUANATE 210," manufactured by Nippon Polyurethane Industry Co., Ltd.), and reaction products of these polyisocyanates with polyols. Among these, tolylene diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate are preferred due to their versatility, and hexamethylene diisocyanate is most preferred. These can be used alone or in combination of two or more.

[0093] Examples of the hydroxyl group-containing (meth)acrylic compound include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified dipentaerythritol penta(meth)acrylate, and ethylene oxide-modified pentaerythritol tri(meth)acrylate. Among these, it is preferable to use a hydroxyl group-containing (meth)acrylic compound having one hydroxyl group and one (meth)acrylate, because it has few impurities, can produce a compound containing an isocyanate group and an unsaturated group, and is less likely to leave adhesive residue.In order to further reduce impurities, it is particularly preferable to use 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.These compounds can be used alone or in combination of two or more.

[0094] Specific examples of such compounds containing an unsaturated group and a functional group reactive with the functional group contained in the polyester resin (A) include compounds represented by the following general formula (1).

[0095] [ka]

[0096] In the formula, n represents a positive integer, for example, 20 or less, preferably 1 to 5. R1 is hydrogen or a methyl group, preferably hydrogen. R2 is an organic chain containing at least one selected from C, O, N and S. Specific examples include -COO-, -CO-, -O-, alkylene chains, and oxyalkylene chains, and these may be used in combination of two or more. Among these, a combination of -COO- or -CO- with an alkylene chain is preferred, and a combination of -COO- with an alkylene chain is particularly preferred. Examples of the alkylene chain include alkylene chains having 1 to 10 carbon atoms, and alkylene chains having 1 to 5 carbon atoms are particularly preferred. Examples of the oxyalkylene chain include an oxyethylene chain, an oxypropylene chain, and an oxybutylene chain. Two or more types of oxyethylene chains may be combined, and each may be a repeating oxyalkylene chain. When repeating, the total number of repeating units is preferably 2 to 20.

[0097] The above R3 and R4 are each independently a linking chain containing at least one selected from C, O, N, and S, and are preferably, for example, a part of the backbone of the above polyisocyanates such as methyltoluene, isophorone, hexamethylene, or a combination of the backbone of such diisocyanates with -NHCO-.

[0098] The following general formula (2) shows the most preferred structure of a compound containing a functional group reactive with the functional group contained in the polyester resin (A) and an unsaturated group.

[0099] [ka]

[0100] The content of the crosslinking agent (B) can be appropriately selected depending on the amount of functional groups contained in the polyester resin (A), the molecular weight of the polyester resin (A), and the purpose of controlling the adhesive strength and elongation after irradiation with active energy rays. Generally, the content is preferably 0.1 to 20 parts by weight, more preferably 0.2 to 15 parts by weight, and particularly preferably 0.5 to 10 parts by weight, per 100 parts by weight of the polyester resin (A).

[0101] If the amount of crosslinking agent (B) is too small, the cohesive strength will be insufficient and sufficient durability will tend to be unavailable, whereas if the amount is too large, the flexibility before energy application will tend to decrease and the adhesive strength will tend to decrease.

[0102] In the present invention, if the concentration (mmol / g) of functional groups in the polyester resin (A) that react with the crosslinking agent (excluding unsaturated groups in the polyester resin (A)) is (X), and the concentration (mmol / g) of functional groups in the crosslinking agent (B) that react with the functional groups in the polyester resin (A) is (Y), then 0.1≦(Y) / (X)≦3.0 is preferred in order to integrate the pressure-sensitive adhesive network after energy application, 0.2≦(Y) / (X)≦2.0 is more preferred, and 0.5≦(Y) / (X)≦1.5 is particularly preferred. If the functional group concentration of the crosslinking agent (B) is too high, bubbles and the like tend to form when the pressure-sensitive adhesive layer is formed, resulting in poor appearance, while if it is too low, the overall network becomes loose, making adhesive residue more likely to occur.

[0103] It is also preferable to use a crosslinking agent (B) containing an unsaturated group and a crosslinking agent not containing an unsaturated group in combination in order to control the cohesive strength before and after energy application.

[0104] [Polymerization initiator (C)] The present peelable pressure-sensitive adhesive composition preferably contains a polymerization initiator (C) in that the curing reaction can be stabilized when peeled from the adherend.

[0105] As the polymerization initiator (C), various polymerization initiators such as a photopolymerization initiator (C1) and a thermal polymerization initiator (C2) can be used. In particular, the use of a photopolymerization initiator (C1) is preferred because it allows curing by applying energy such as ultraviolet light for a very short time.

[0106] The photopolymerization initiator (C1) is not particularly limited as long as it generates radicals by the action of light, and examples thereof include diethoxyacetophenone, 2-hydroxy-1-[4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl]-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyl dimethyl ketal, 4-(2-hydroxyethoxy)phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one ... acetophenones such as 2-methyl-2-morpholino(4-thiomethylphenyl)propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, and 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone oligomer; benzoins such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; benzophenone, methyl o-benzoylbenzoate, and 4-phenylbenzophenone; Benzophenones such as 4-benzoyl-4'-methyl-diphenyl sulfide, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N,N-dimethyl-N-[2-(1-oxo-2-propenyloxy)ethyl]benzenemethanaminium bromide, and (4-benzoylbenzyl)trimethylammonium chloride; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4 thioxanthones such as 1-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, and 2-(3-dimethylamino-2-hydroxy)-3,4-dimethyl-9H-thioxanthone-9-one mesochloride; and acylphosphine oxides such as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. These photopolymerization initiators (C1) may be used alone or in combination of two or more kinds.

[0107] Among these, it is preferable to use 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-1-[4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl]-2-methylpropan-1-one, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and benzyl dimethyl ketal.

[0108] Furthermore, as an auxiliary agent for the photopolymerization initiator (C1), it is also possible to use in combination triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Michler's ketone), 4,4'-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, ethyl 4-dimethylaminobenzoate, (n-butoxy)ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, and the like.

[0109] Examples of the thermal polymerization initiator (C2) include methyl ethyl ketone peroxide, cyclohexanone peroxide, methylcyclohexanone peroxide, methylacetoacetate peroxide, acetylacetate peroxide, 1,1-bis(t-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexylperoxy)-cyclohexane, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)-2-methylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, 1,1-bis(t-butylperoxy)butane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroperoxide, t-butyl hydroperoxide, α,α'-bis(t-butylperoxy) Diisopropylbenzene, dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyne-3, isobutyryl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, succinic acid peroxide, m-toluoylbenzoyl peroxide, benzoyl peroxide, di- n-Propyl peroxydicarbonate, diisopropyl peroxydicarbonate, bis(4-t-butylcyclohexyl) peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, di-2-ethoxyhexyl peroxydicarbonate, di-3-methoxybutyl peroxydicarbonate, di-s-butyl peroxydicarbonate, di(3-methyl-3-methoxybutyl) peroxydicarbonate, α,α'-bis(neodecanoylperoxy)diisopropylbenzene, cumyl peroxyneodecanoate, 1,1,3,3-Tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexanoate, 1-cyclohexyl-1-methylethylperoxy-2-ethylhexanoate t-butylperoxy-2-ethylhexanoate, t-hexylperoxyisopropyl monocarbonate, t-butylperoxyisobutyrate, t-butylperoxymalate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, t-butylperoxyisopropyl monocarbonate, t-butylperoxy-2-ethylhexyl monocarbonate, t-butylperoxyacetate, t-butylperoxy-m-tol Organic peroxides such as methyl benzoate, t-butyl peroxybenzoate, bis(t-butylperoxy)isophthalate, 2,5-dimethyl-2,5-bis(m-toluylperoxy)hexane, t-hexyl peroxybenzoate, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, t-butylperoxyallyl monocarbonate, t-butyltrimethylsilyl peroxide, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, and 2,3-dimethyl-2,3-diphenylbutane. System initiators: 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 1-[(1-cyano-1-methylethyl)azo]formamide, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis(2-methyl-N-phenylpropionamidine) dihydrochloride, 2,2'-Azobis[N-(4-chlorophenyl)-2-methylpropionamidine]dihydridochloride, 2,2'-Azobis[N-(4-hydrophenyl)-2-methylpropionamidine]dihydrochloride, 2,2'-Azobis[2-methyl-N-(phenylmethyl)propionamidine]dihydrochloride, 2,2'-Azobis[2-methyl-N-(2-propenyl)propionamidine]dihydrochloride, 2,2'-Azobis[N-(2-hydroxyethyl)-2-methylpropionamidine dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(4,5,6,7-tetrahydro-1H-1,3-diazepin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(3,4,5,6-tetrahydropyrimidin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(5 -hydroxy-3,4,5,6-tetrahydropyrimidin-2-yl)propane] dihydrochloride, 2,2'-azobis[2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane] dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis[2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide], 2,2'-azobis[2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide] Examples of the thermal polymerization initiator (C2) include azo initiators such as 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis(2-methylpropionamide), 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(2-methylpropane), dimethyl-2,2-azobis(2-methylpropionate), 4,4'-azobis(4-cyanopentanoic acid), and 2,2'-azobis[2-(hydroxymethyl)propionitrile]. These thermal polymerization initiators (C2) may be used alone or in combination of two or more.

[0110] The content of the polymerization initiator (C) is preferably 0.01 to 10 parts by weight, particularly preferably 0.1 to 5 parts by weight, and even more preferably 0.3 to 2 parts by weight, relative to 100 parts by weight of the polyester resin (A). If the blending amount is too small, curing tends to be insufficient, and if it is too large, there is a concern that the polymerization initiator (C) will become a residual adhesive.

[0111] [Hydrolysis inhibitor (D)] The hydrolysis inhibitor (D) is not particularly limited, and conventionally known compounds can be used, such as compounds that react with and bond to the carboxyl terminal groups of the polyester resin (A), specifically compounds having functional groups such as carbodiimide groups, epoxy groups, oxazoline groups, etc. Among 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.

[0112] The carbodiimide group-containing compound used in the present peelable pressure-sensitive adhesive composition can usually 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, even 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.

[0113] From the viewpoint of hydrolysis resistance, it is preferable to use the carbodiimide group-containing compound having a high weight-average molecular weight. 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.

[0114] 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.

[0115] 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 (meth)acryloyl group-containing polyester resin (A) tends to decrease.

[0116] 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.

[0117] 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.

[0118] (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 include aliphatic diisocyanates such as 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 peelable pressure-sensitive adhesive composition with excellent resistance to moist heat.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] As the epoxy group-containing compound, for example, a glycidyl ester group-containing compound or a glycidyl ether group-containing compound is preferable.

[0123] Examples of the glycidyl ester group-containing compound 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, phthalic acid diglycidyl ester, naphthalenedicarboxylic acid diglycidyl ester, methyl terephthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, cyclohexanedicarboxylic acid diglycidyl ester, adipic acid diglycidyl ester, succinic acid diglycidyl ester, sebacic acid diglycidyl ester, dodecanedioic acid diglycidyl ester, octadecanedicarboxylic acid diglycidyl ester, trimellitic acid triglycidyl ester, pyromellitic acid tetraglycidyl ester, and the like. These may be used alone or in combination of two or more.

[0124] Examples of the glycidyl ether group-containing 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.

[0125] 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 of suitable bisoxazoline compounds 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), and 2,2'-diphenylenebis(2-oxazoline). Of these, 2,2'-bis(2-oxazoline) is most preferred from the viewpoint of reactivity with polyesters. Furthermore, the above-listed bisoxazoline compounds can be used alone or in combination of two or more, as long as the object of the present invention is achieved.

[0126] The hydrolysis inhibitor (D) preferably has low volatility, and therefore it is preferable to use one with a high molecular weight.

[0127] The amount of the hydrolysis inhibitor (D) to be blended 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 resin (A). If the blending amount is too high, turbidity tends to occur due to poor compatibility with the polyester resin (A), while if the blending amount is too low, sufficient durability tends to be difficult to obtain.

[0128] The amount of hydrolysis inhibitor (D) blended is preferably optimized depending on the acid value of the polyester resin (A), and the molar ratio ((ii) / (i)) of the total number of carboxy groups (i), determined from the acid value of the polyester resin (A) in the release adhesive composition, to the total number of functional groups (ii) of the hydrolysis inhibitor (D) in the release adhesive composition is preferably 0.5≦(ii) / (i), particularly preferably 1≦(ii) / (i)≦1000, and even more preferably 1.5≦(ii) / (i)≦100. If the content ratio of (ii) to (i) is too high, the compatibility with the polyester resin (A) tends to decrease, and the adhesive strength, cohesive strength, and durability performance tend to decrease. If the content ratio of (ii) to (i) is too low, the moist heat resistance performance tends to decrease.

[0129] [Active energy ray-curable compound (E)] In the present peelable pressure-sensitive adhesive composition, an active energy ray-curable compound (E) can be used as needed to adjust the unsaturated group concentration within the desired range.

[0130] Examples of the active energy ray-curable compound (E) include urethane (meth)acrylate compounds and ethylenically unsaturated monomers having an ethylenically unsaturated group.

[0131] [Urethane (meth)acrylate compounds] The urethane (meth)acrylate compound is a (meth)acrylate compound having a urethane bond in the molecule, and can be produced by reacting a hydroxyl group-containing (meth)acrylic compound with a polyvalent isocyanate compound, and further, if necessary, with a polyol. By intentionally leaving an isocyanate group to form a urethane (meth)acrylate compound having an isocyanate group and an unsaturated bond in the molecule, crosslinking points with the polyester resin (A) are created, and when a peelable adhesive is produced, providing reactive points in the base resin is also effective in reducing adhesive strength after energy application.

[0132] Examples of the hydroxyl group-containing (meth)acrylic compound include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, Examples include pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified dipentaerythritol penta(meth)acrylate, and ethylene oxide-modified pentaerythritol tri(meth)acrylate, and among these, hydroxyl group-containing (meth)acrylic compounds having three or more acryloyl groups are preferably used. These can be used alone or in combination of two or more.

[0133] The polyisocyanate compound is not particularly limited, and examples thereof include aromatic, aliphatic, and alicyclic polyisocyanates, among which tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, modified diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, and norbornane diisocyanate. Examples include polyisocyanates such as benzene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, phenylene diisocyanate, lysine diisocyanate, lysine triisocyanate, and naphthalene diisocyanate, trimer compounds or polymer compounds of these polyisocyanates, biuret-type polyisocyanates, water-dispersible polyisocyanates (for example, "Aquanate 100," "Aquanate 110," "Aquanate 200," and "Aquanate 210," manufactured by Nippon Polyurethane Industry Co., Ltd.), and reaction products of these polyisocyanates with polyols. These can be used alone or in combination of two or more.

[0134] Such polyols are not particularly limited, and examples thereof include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, polybutylene glycol, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol, hydrogenated bisphenol A, polycaprolactone, trimethylolethane, trimethylolpropane, polytrimethylolpropane, pentaerythritol, polypentaerythritol, sorbitol, mannitol, glycerin, polyglycerin, Examples of suitable polyols include polyhydric alcohols such as polytetramethylene glycol; polyether polyols having at least one structure of polyethylene oxide, polypropylene oxide, or block or random copolymerization of ethylene oxide / propylene oxide; polyester polyols which are condensates of such polyhydric alcohols or polyether polyols with polybasic acids such as maleic anhydride, maleic acid, fumaric acid, itaconic anhydride, itaconic acid, adipic acid, and isophthalic acid; caprolactone-modified polyols such as caprolactone-modified polytetramethylene polyol; polyolefin polyols; and polybutadiene polyols such as hydrogenated polybutadiene polyols.

[0135] Further examples of such polyols include carboxyl group-containing polyols such as 2,2-bis(hydroxymethyl)butyric acid, tartaric acid, 2,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxyethyl)propionic acid, 2,2-bis(hydroxypropyl)propionic acid, dihydroxymethylacetic acid, bis(4-hydroxyphenyl)acetic acid, 4,4-bis(4-hydroxyphenyl)pentanoic acid, and homogentisic acid, as well as sulfonic acid group- or sulfonate salt-containing polyols such as 1,4-butanediol sodium sulfonate. These polyols can be used alone or in combination of two or more.

[0136] When a reaction product of a polyisocyanate and a polyol is used, it may be used as a terminal isocyanate group-containing polyisocyanate obtained by reacting the above-mentioned polyol with the above-mentioned polyisocyanate. In the reaction of such a polyisocyanate and a polyol, it is also preferable to use a metal catalyst such as dibutyltin dilaurate or an amine catalyst such as 1,8-diazabicyclo[5.4.0]undecene-7 to promote the reaction.

[0137] The method for producing the urethane (meth)acrylate compound is not particularly limited, and examples thereof include a method in which a hydroxyl group-containing (meth)acrylic compound and a polyvalent isocyanate compound are mixed in an inert gas atmosphere and reacted for 2 to 10 hours, typically at 30 to 80° C. In this reaction, it is preferable to use a urethane catalyst such as tin octenoate, di-n-butyltin dilaurate, lead octoate, potassium octoate, potassium acetate, stannous octoate, or triethylenediamine.

[0138] The weight average molecular weight of the urethane (meth)acrylate compound is preferably 300 to 4000, more preferably 1000 to 3500, and particularly preferably 1200 to 3000. The method for measuring the weight average molecular weight is as described above.

[0139] [Ethylenically unsaturated monomer having an ethylenically unsaturated group] Examples of the ethylenically unsaturated monomer having an ethylenically unsaturated group include a monofunctional monomer having one ethylenically unsaturated group in one molecule, a bifunctional monomer having two ethylenically unsaturated groups in one molecule, and a trifunctional or higher functional monomer having three or more ethylenically unsaturated groups in one molecule.

[0140] Examples of the monofunctional monomer include styrene, vinyltoluene, chlorostyrene, α-methylstyrene, methyl(meth)acrylate, ethyl(meth)acrylate, acrylonitrile, vinyl acetate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, phenoxyethyl(meth)acrylate, 2-phenoxy-2-hydroxypropyl(meth)acrylate, 2-hydroxy-3-phenoxypropyl(meth)acrylate, 3-chloro-2-hydroxypropyl(meth)acrylate, glycerin mono(meth)acrylate, glycidyl(meth)acrylate, lauryl(meth)acrylate, cyclohexyl(meth)acrylate, isobornyl(meth)acrylate, tricyclodecanyl(meth)acrylate, dicyclopentenyl(meth)acrylate, n-butyl(meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, ) acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, n-stearyl (meth)acrylate, benzyl (meth)acrylate, phenol ethylene oxide modified (meth)acrylate, nonylphenol propylene oxide modified (meth)acrylate, phthalic acid derivatives such as 2-(meth)acryloyloxy-2-hydroxypropyl phthalate Examples of the acrylates include half ester (meth)acrylate, furfuryl (meth)acrylate, carbitol (meth)acrylate, benzyl (meth)acrylate, butoxyethyl (meth)acrylate, allyl (meth)acrylate, acryloylmorpholine, 2-hydroxyethyl acrylamide, N-methylol (meth)acrylamide, N-vinylpyrrolidone, 2-vinylpyridine, and 2-(meth)acryloyloxyethyl acid phosphate monoester.

[0141] Examples of the bifunctional monomer include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide-modified bisphenol A di(meth)acrylate, propylene oxide-modified bisphenol A di(meth)acrylate, 1 ,6-hexanediol di(meth)acrylate, 1,6-hexanediol ethylene oxide modified di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, hydroxypivalic acid modified neopentyl glycol di(meth)acrylate, isocyanuric acid ethylene oxide modified diacrylate, 2-(meth)acryloyloxyethyl acid phosphate diester, etc.

[0142] Examples of the tri- or higher functional monomers include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane, and glycerin poly Examples thereof include glycidyl ether poly(meth)acrylate, isocyanuric acid ethylene oxide modified tri(meth)acrylate, ethylene oxide modified dipentaerythritol penta(meth)acrylate, ethylene oxide modified dipentaerythritol hexa(meth)acrylate, ethylene oxide modified pentaerythritol tri(meth)acrylate, ethylene oxide modified pentaerythritol tetra(meth)acrylate, and succinic acid modified pentaerythritol tri(meth)acrylate.

[0143] In addition to the above, ethylenically unsaturated monomers also include Michael adducts of acrylic acid and 2-acryloyloxyethyl dicarboxylic acid monoesters. Examples of Michael adducts of acrylic acid include acrylic acid dimer, methacrylic acid dimer, acrylic acid trimer, methacrylic acid trimer, acrylic acid tetramer, and methacrylic acid tetramer. Examples of 2-acryloyloxyethyl dicarboxylic acid monoesters, which are carboxylic acids having specific substituents, include 2-acryloyloxyethyl succinic acid monoester, 2-methacryloyloxyethyl succinic acid monoester, 2-acryloyloxyethyl phthalic acid monoester, 2-methacryloyloxyethyl phthalic acid monoester, 2-acryloyloxyethyl hexahydrophthalic acid monoester, and 2-methacryloyloxyethyl hexahydrophthalic acid monoester. Oligoester acrylates are also included.

[0144] These active energy ray-curable compounds (E), such as urethane (meth)acrylate compounds and ethylenically unsaturated monomers, may be used alone or in combination of two or more. Among these, in order to increase the crosslink density when used as a peelable adhesive, it is preferable to use a polyfunctional urethane (meth)acrylate compound or a polyfunctional ethylenically unsaturated monomer, and it is particularly preferable to use a compound having three or more unsaturated groups. Furthermore, in order to increase adhesion to a substrate or an adherend, it is also preferable to use a highly polar urethane (meth)acrylate compound or an ethylenically unsaturated monomer having a polar moiety.

[0145] The content of the active energy ray-curable compound (E) is preferably 1 to 50 parts by weight, more preferably 2 to 20 parts by weight, and even more preferably 3 to 10 parts by weight, per 100 parts by weight of the polyester resin (A). If the content is too high, the cohesive strength of the adhesive layer after application of energy tends to be too high, resulting in low elongation, whereas if the content is too low, the adhesive strength after application of energy tends not to decrease easily.

[0146] These active energy ray-curable compounds (E) usually contain a polymerization inhibitor, but it is preferable to add a polymerization inhibitor in addition to this in order to increase the stability of the pressure-sensitive adhesive sheet and to enable the sheet to withstand use in a peeling process after use under harsh conditions, such as in heat-resistant applications.

[0147] The content of the polymerization inhibitor is not limited, but is preferably usually 20 to 10,000 ppm, particularly 50 to 1,000 ppm, based on the unsaturated group-containing compound.

[0148] The polymerization inhibitor is not particularly limited, but it is preferable to use a phenol-type inhibitor, such as methoxyhydroquinone, hydroquinone, or di-tert-butylhydroxytoluene.

[0149] [Other ingredients] The present release pressure-sensitive adhesive composition may further contain other components such as antistatic agents, antioxidants, plasticizers, fillers, pigments, diluents, antioxidants, UV absorbers, UV stabilizers, and tackifying resins, as long as the effects of the present invention are not impaired. These additives may be used alone or in combination of two or more. In addition to the above-mentioned other components, the present release pressure-sensitive adhesive composition may also contain small amounts of impurities contained in the production raw materials of the components of the present release pressure-sensitive adhesive composition.

[0150] The present peelable pressure-sensitive adhesive composition can be obtained by mixing the above polyester resin (A), and, if necessary, a crosslinking agent (B), a polymerization initiator (C), a hydrolysis inhibitor (D), and other components.

[0151] The polyester resin (A) is preferably the main component of the present release pressure-sensitive adhesive composition, and the content of the main component is 50% by weight or more, preferably 60 to 99.9% by weight, more preferably 70 to 99.7% by weight, particularly preferably 80 to 99.5% by weight, and especially preferably 90 to 99% by weight, of the total release pressure-sensitive adhesive composition. The content of the crosslinking agent (B) is preferably 0.1 to 20% by weight, more preferably 0.2 to 15% by weight, and even more preferably 0.5 to 10% by weight of the entire peelable pressure-sensitive adhesive composition. The content of the polymerization initiator (C) is preferably 0.01 to 10% by weight, more preferably 0.1 to 5% by weight, and even more preferably 0.2 to 3% by weight of the entire peelable pressure-sensitive adhesive composition. The content of the hydrolysis inhibitor (D) is preferably 0.01 to 10% by weight, more preferably 0.1 to 5% by weight, and even more preferably 0.3 to 3% by weight of the entire peelable pressure-sensitive adhesive composition. The content of the active energy ray-curable compound (E) is 1 to 33% by weight, preferably 2 to 20% by weight, and more preferably 3 to 10% by weight, of the entire peelable pressure-sensitive adhesive composition.

[0152] The present peelable pressure-sensitive adhesive composition preferably has an unsaturated group concentration of 0.01 to 1.5 mmol / g, more preferably 0.03 to 1.2 mmol / g, even more preferably 0.1 to 1.0 mmol / g, and particularly preferably 0.2 to 0.8 mmol / g. Within this range, the effects of the present invention tend to be more pronounced.

[0153] The unsaturated group concentration (mmol / g) can be calculated by the following formula: However, in the following formula, calculation is made only for the active ingredient contained in the releasable pressure-sensitive adhesive composition, excluding the solvent and the like. Unsaturated group concentration (mmol / g) of releasable pressure-sensitive adhesive composition = amount (mmol) of unsaturated group-containing compound contained in releasable pressure-sensitive adhesive composition / total weight (g) of releasable pressure-sensitive adhesive composition

[0154] The unsaturated group concentration can also be determined by measurement using a known method. For example, the unsaturated group concentration of the peelable pressure-sensitive adhesive composition can be determined by measuring the unsaturated group concentration at a resonance frequency of 400 MHz. 1 H-NMR measurement (proton nuclear magnetic resonance spectroscopy), 13 It can be determined from the spectrum obtained by C-NMR measurement (carbon-type nuclear magnetic resonance spectroscopy). The measurement device is a VARIAN NMR device 400-MR, and deuterated chloroform can be used as the solvent.

[0155] In order to set the unsaturated group concentration of the present peelable pressure-sensitive adhesive composition within the desired range, methods such as (i) incorporating a large amount of polyester resin (A), (ii) introducing unsaturated groups into crosslinking agent (B), (iii) adding an unsaturated group-containing compound, or a combination thereof can be used. However, methods (i) and (ii) or a combination thereof are preferred in terms of integrating the pressure-sensitive adhesive layer after curing.

[0156] From the viewpoint of the balance between adhesive properties and various functionalities, the glass transition temperature of the present peelable pressure-sensitive adhesive composition is preferably 30°C or lower, particularly 20°C or lower, further preferably 10°C or lower, and especially preferably 0°C or lower. If the glass transition temperature is too high, flexibility is lost, initial adhesiveness decreases, and sufficient adhesive strength is not exerted even with pressure equivalent to finger pressure, which tends to reduce workability. The lower limit of the glass transition temperature is usually -90°C, preferably -50°C, and more preferably -40°C. Here, the glass transition temperature (Tg) of the peelable pressure-sensitive adhesive composition is measured using a differential scanning calorimeter.

[0157] The present peelable pressure-sensitive adhesive composition preferably contains substantially no acidic groups, and specifically, the acid value is preferably 10 mgKOH / g or less, more preferably 5 mgKOH / g or less, particularly preferably 3 mgKOH / g or less, even more preferably 1 mgKOH / g or less, and especially preferably 0.5 mgKOH / g or less. The lower limit of the acid value is usually 0 mgKOH / g. The acid value of the peelable pressure-sensitive adhesive composition is determined by neutralization titration in accordance with JIS K0070. The acid value in the present invention means the content of carboxy groups, including carboxylate ion states in which carboxy groups are neutralized with a basic compound.

[0158] The release adhesive composition is crosslinked to form a release adhesive (hereinafter referred to as "the release adhesive"), which is one embodiment of the present invention. When energy is applied to the release adhesive, the unsaturated groups in the release adhesive polymerize, causing the release adhesive to harden and resulting in a decrease in adhesive strength, thereby exhibiting releasability.

[0159] <Removable adhesive> The present release adhesive is suitably used as an adhesive layer of a release adhesive sheet, and the release adhesive sheet preferably has a release adhesive layer containing the present release adhesive on one or both sides of a supporting substrate. In addition, it is also preferable to use a substrateless double-sided adhesive sheet that does not have a supporting substrate, in view of its excellent transparency and high adhesive strength relative to its thickness. The release adhesive sheet will be described below.

[0160] In the present invention, the term "sheet" is used to include "film" and "tape."

[0161] <Removable adhesive sheet> The releasable adhesive sheet according to one embodiment of the present invention (hereinafter referred to as "the releasable adhesive sheet") can be produced according to a known method for producing a releasable adhesive sheet, for example, as follows. The present peelable pressure-sensitive adhesive composition is applied directly to the release-treated surface of a release film or a substrate sheet, either as is or after adjusting the concentration with an appropriate organic solvent. The composition is then dried, for example, by heating at 80 to 105°C for 0.5 to 10 minutes, and then attached to a substrate sheet or a release film to obtain the present peelable pressure-sensitive adhesive sheet. It is also preferable to further age the composition after drying to achieve a balanced adhesive property.

[0162] Examples of the substrate sheet include polyester-based resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate / isophthalate copolymer; polyolefin-based 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-based resins such as cellulose triacetate and cellophane; acrylic resins such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate; polystyrene; polycarbonate; polyarylate; and synthetic resin sheets such as polyimide; metal foils such as aluminum, copper, and iron; paper such as fine paper and glassine paper; and woven fabrics and nonwoven fabrics made of glass fiber, natural fiber, synthetic fiber, etc. These substrate sheets can be used as a single layer or as a multi-layered body in which two or more types are laminated. Among these, synthetic resin sheets are preferred from the viewpoint of weight reduction, and polyester-based resins and polyolefin-based resins are particularly preferred.

[0163] Furthermore, as the release film, for example, various synthetic resin sheets, paper, woven fabrics, nonwoven fabrics, etc. exemplified above as the base sheet can be used which have been subjected to a release treatment.

[0164] The method for applying the peelable pressure-sensitive adhesive composition is not particularly limited as long as it is a common coating method, and examples thereof include roll coating, die coating, gravure coating, comma coating, and screen printing.

[0165] Furthermore, when forming a thick adhesive layer, a peelable adhesive composition whose viscosity has been adjusted by the above-mentioned method can be directly applied to the release-treated surface of a release film, dried, and two or more release films with adhesive layers can be produced, and the adhesive layers of the two release films with adhesive layers can be bonded together to form a thick adhesive layer.

[0166] The thickness of the adhesive layer of the above-mentioned peelable adhesive sheet is usually preferably 10 to 200 μm, more preferably 15 to 100 μm.

[0167] In order to impart further conformability and extensibility to the present releasable pressure-sensitive adhesive sheet, a soft intermediate layer may be inserted between the substrate layer and the pressure-sensitive adhesive layer, if necessary.

[0168] The thickness of the adhesive layer is determined by subtracting the measured thickness of the components other than the adhesive layer from the measured thickness of the entire peelable adhesive sheet using a Mitutoyo ID-C112B.

[0169] The aging conditions are typically a temperature of room temperature (23°C) to 70°C, and a time of 1 to 30 days. Specifically, the aging may be performed under conditions such as 1 to 20 days at 23°C, 3 to 10 days at 23°C, or 1 to 10 days at 40°C.

[0170] The gel fraction of the adhesive layer of the present releasable adhesive sheet before energy application is preferably 10% or more, particularly preferably 15 to 90%, and even more preferably 20 to 70%, from the viewpoints of durability and adhesive strength. If the gel fraction is too low, the cohesive strength will decrease, and therefore durability will tend to decrease. However, if the gel fraction is too high, there is a concern that the adhesive strength will decrease due to the increased cohesive strength.

[0171] Furthermore, the gel fraction of the adhesive layer of the present releasable adhesive sheet after application of energy is preferably 70% or more, particularly preferably 80% or more, and even more preferably 90% or more, from the viewpoint of adhesive strength. If the gel fraction is too low, the cohesive strength decreases, which increases the adhesive strength and tends to result in poor releasability. The upper limit of the gel fraction is usually 100%.

[0172] The gel fraction is an index of the degree of crosslinking and is calculated, for example, by the following method. A release adhesive sheet (without a separator) consisting of a polymer sheet substrate (e.g., polyethylene terephthalate film) and a release adhesive layer formed on it is wrapped in a 200-mesh SUS wire netting and immersed in toluene at 23°C for 24 hours. The weight percentage of the undissolved adhesive component remaining in the wire netting is taken as the gel fraction. However, the weight of the substrate is deducted from this calculation.

[0173] The peelable adhesive sheet thus obtained exhibits high adhesive strength when applied to an adherend and can protect the surface of the adherend; by applying energy after the treatment step, the ethylenically unsaturated groups contained in the peelable adhesive layer polymerize, hardening the peelable adhesive layer and reducing the adhesive strength, so that the sheet can be easily peeled off and is less likely to leave adhesive residue when peeled off from the adherend.

[0174] The energy that can be used includes light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays, and infrared rays, electromagnetic waves such as X-rays and gamma rays, as well as electron beams, proton beams, and neutron beams, but curing by ultraviolet irradiation is advantageous in terms of curing speed, ease of availability of irradiation equipment, cost, etc. When electron beam irradiation is performed, curing is possible without using the photopolymerization initiator (C1).

[0175] The light source used for the ultraviolet irradiation includes a high-pressure mercury lamp, an electrodeless lamp, an ultra-high-pressure mercury lamp, a carbon arc lamp, a xenon lamp, a metal halide lamp, a chemical lamp, a black light, an LED lamp, etc. In the case of the high-pressure mercury lamp, for example, 5 to 3000 mJ / cm 2 , preferably 50 to 2000 mJ / cm2 In the case of the electrodeless lamp, for example, the irradiation condition is 2 to 2000 mJ / cm. 2 , preferably 10 to 1000 mJ / cm 2 The irradiation time varies depending on the type of light source, the distance between the light source and the coating surface, the coating thickness, and other conditions, but is usually several seconds to several tens of seconds, and in some cases may be a fraction of a second. On the other hand, in the case of the electron beam irradiation, it is preferable to use an electron beam having an energy in the range of 50 to 1000 Kev, and to set the irradiation dose at 2 to 50 Mrad.

[0176] The adhesive strength (α) of the releasable adhesive layer of the present releasable adhesive sheet is determined appropriately depending on the material of the adherend, etc., but when adhering to, for example, a silicon wafer, a glass substrate, a polycarbonate plate, a polymethyl methacrylate plate, a PET sheet vapor-deposited with an ITO layer, or a metal plate, the adhesive strength immediately after adhering is preferably 1 to 500 N / 25 mm, and particularly preferably 2 to 100 N / 25 mm.

[0177] The adhesive strength (α) can be measured, for example, as follows. This peelable adhesive sheet is attached to a SUS-BA plate as an adherend and left to stand at 23°C and 50% RH for 30 minutes or more, after which the 180-degree peel strength (N / 25 mm) is measured in accordance with JIS Z0237.

[0178] Furthermore, the adhesive strength (β) of the releasable adhesive layer of this releasable adhesive sheet after energy application is 2 N / 25 mm or less, preferably 1.5 N / 25 mm or less, particularly preferably 1 N / 25 mm or less, and even more preferably 0.5 N / 25 mm or less. If the adhesive strength (β) is too much greater than the above range, the removability tends to be poor, making it difficult to peel and leaving adhesive residue. The lower limit of the adhesive strength (β) is the better, but in practice it is usually 0.0001 N / 25 mm, preferably 0.001 N / 25 mm, and particularly preferably 0.01 N / 25 mm.

[0179] The adhesive strength (β) can be measured, for example, as follows. This peelable adhesive sheet was attached to a SUS-BA plate as an adherend, and left to stand at 23°C and 50% RH for 30 minutes or more, after which it was irradiated with ultraviolet light (500 mJ / cm from a high-pressure mercury lamp). 2 ) and then measure the 180-degree peel strength (N / 25 mm) in accordance with JIS Z0237.

[0180] Furthermore, the adhesive strength after application of energy is preferably 1 / 3 or less, more preferably 1 / 10 or less, of the adhesive strength before application of energy.

[0181] This peelable adhesive sheet has excellent adhesive strength to the substrate, and when irradiated with active energy rays, it can be peeled off smoothly from the substrate without leaving any adhesive residue. Therefore, it can be used, for example, as a temporary surface protection adhesive sheet to provide temporary surface protection for semiconductor wafers, circuit boards such as FPC boards, and ITO transparent electrode layers, or as a temporary fixing adhesive sheet to temporarily hold and reinforce products during the manufacturing process. [Example]

[0182] The present invention will be explained in more detail below by way of 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.

[0183] [Production of polyester resin (A)] [Production of polyester resin 1] A reactor equipped with a heater, a thermometer, a stirrer, a rectification column, a nitrogen inlet tube, and a vacuum device was charged with 9.6 parts (0.2 mol) of isophthalic acid and 46.8 parts (0.8 mol) of sebacic acid as polycarboxylic acids, 27.1 parts (0.9 mol) of neopentyl glycol, 13.0 parts (0.5 mol) of 1,4-butanediol, 3.0 parts (0.087 mol) of 1,6-hexanediol, and 0.5 parts (0.013 mol) of trimethylolpropane as polyhydric alcohols, and 0.01 part of tetrabutyl titanate as a catalyst. The internal temperature was gradually raised to 250°C, and an esterification reaction was carried out over 4 hours. The internal temperature was then raised to 260°C, 0.01 parts of tetrabutyl titanate was added as a catalyst, the pressure was reduced to 1.33 hPa, and a polymerization reaction was carried out over 3 hours.The pressure was then returned to normal pressure, and 0.75 parts of trimethylolpropane was added, and a reaction was carried out at 240°C for 3 hours to produce polyester resin 1. The resin composition (molar ratio) of the obtained polyester resin 1 was isophthalic acid / sebacic acid / neopentyl glycol / 1,4-butanediol / 1,6-hexanediol / trimethylolpropane=0.2 / 0.8 / 0.59 / 0.34 / 0.06 / 0.03. In addition, the ester group concentration of polyester resin 1 was 7.7 mmol / g, the heat of crystalline fusion was 0 J / g, the weight average molecular weight was 49,000, the number average molecular weight was 10,000, the peak top molecular weight was 38,000, the glass transition temperature (Tg) was -49°C, the acid value was 0.02 mg KOH / g, and the hydroxyl value was 24.5 mg KOH / g. The polymer composition and physical properties of the obtained polyester resin 1 are shown in Table 1. The molecular weights and glass transition temperatures were measured as described below.

[0184] [Table 1]

[0185] [Production of Polyester Resin (A-1)] The polyester resin 1 produced above was diluted with toluene to a solids content of 70%, and 3.7 parts of methacryloyloxyethyl isocyanate (55 mol% relative to the hydroxyl groups of the polyester resin 1) and 0.05 parts of Orgatix ZC-150 (urethane catalyst manufactured by Matsumoto Fine Chemical Co., Ltd.) were added to 100 parts of the solids content of the polyester resin 1, and the reaction was carried out at 50 ° C. for 48 hours to produce polyester resin (A-1). The obtained unsaturated group-containing polyester resin (A-1) was analyzed with an infrared spectrophotometer to confirm that there were no remaining isocyanate groups.

[0186] [Production of Polyester Resin (A-2)] The polyester resin 1 produced above was diluted with toluene to a solids content of 70%, and 4.9 parts of methacryloyloxyethyl isocyanate (73 mol% relative to the hydroxyl groups of polyester resin 1) and 0.05 parts of Orgatix ZC-150 (a urethane catalyst manufactured by Matsumoto Fine Chemical Co., Ltd.) were added to 100 parts of the solids content of polyester resin 1, and the reaction was carried out at 50°C for 48 hours to produce polyester resin (A-2).

[0187] [Production of Polyester Resin (A-3)] The polyester resin 1 produced above was diluted with toluene to a solids content of 70%, and 5.7 parts of 1,1-(bisacryloyloxymethyl)ethyl isocyanate (55 mol% relative to the hydroxyl groups of polyester resin 1) and 0.2 parts of Orgatix ZC-150 (a urethane catalyst manufactured by Matsumoto Fine Chemical Co., Ltd.) were added to 100 parts of the solids content of polyester resin 1, and the reaction was carried out at 50°C for 48 hours to produce unsaturated group-containing polyester resin (A-3).

[0188] The polyester resins (A-2) and (A-3) were also analyzed by infrared spectrophotometer in the same manner as the polyester resin (A-1), and it was confirmed that no residual isocyanate groups were present. The glass transition temperature, weight average molecular weight, number average molecular weight, and peak top molecular weight of the obtained polyester resins (A-1) to (A-3) were measured by the methods described below, and the unsaturated group concentration and hydroxyl value were measured by the methods described above. The measurement results are shown in Table 2 below.

[0189] [Table 2]

[0190] [Production of acrylic resin (Z-1)] 74 parts of butyl acrylate (BA), 20 parts of methyl methacrylate (MMA), and 6 parts of 2-hydroxyethyl acrylate (HEA) were added to an ethyl acetate solvent, and 1.0 part of azobisisobutyronitrile (AIBN) was added as a polymerization initiator. Solution polymerization was allowed to proceed, and after a certain period of time, an acrylic copolymer (BA / MMA / HEA = 74 / 20 / 6 (%)) was obtained. Subsequently, 4 parts of methacryloyloxyethyl isocyanate was added to the acrylic copolymer in an amount such that the number of isocyanate groups per 100 equivalents of total hydroxyl groups in the added 2-hydroxyethyl acrylate (HEA) was 50 equivalents, and the reaction was allowed to proceed, resulting in an energy beam-curable acrylic copolymer (Z-1) having methacryloyl groups in the side chains. The weight average molecular weight, number average molecular weight, and peak top molecular weight of the acrylic resin (Z-1) were measured using the methods described below, and the hydroxyl value was measured using a conventional method. The measurement results are shown in Table 3 below, along with the polymer composition of the acrylic resin (Z-1).

[0191] [Table 3]

[0192] The methods for measuring each molecular weight and glass transition temperature are as follows.

[0193] <Weight average molecular weight, number average molecular weight, peak top molecular weight> The weight-average molecular weight, number-average molecular weight, and peak-top molecular weight are average molecular weights converted into standard polystyrene molecular weights. The measurements were performed using a high-performance liquid chromatograph (manufactured by Japan Waters, "Waters 2695 (separation module)" and "Waters 2414 (detector)") with a Shodex GPC KF-806L column (exclusion limit molecular weight: 2 × 10 7 Separation range: 100 to 2 × 10 7 The theoretical number of plates: 10,000 plates / plate, filler material: styrene-divinylbenzene copolymer, filler particle size: 10 μm) were arranged in series and three plates were measured.

[0194] <Glass transition temperature (Tg)> The test piece was heated and cooled from room temperature at a rate of 10°C / min, the heat generation rate was measured using a differential scanning calorimeter, two extension lines were drawn on the endothermic curve or exothermic curve, and the temperature at the intersection of the half line between the extension lines and the endothermic curve or exothermic curve was determined as the glass transition temperature.

[0195] Prior to the examples, the following ingredients were prepared:

[0196] [Crosslinking agent (B)] Compound (B-1) containing an unsaturated group and an isocyanate group: "PR-9000" (manufactured by BASF) is a compound represented by the following general formula (2): TIFF0007800014000006.tif51133 · Isocyanate-based crosslinking agent (B-2): "Coronate L55E" (manufactured by Tosoh Corporation) [Polymerization initiator (C)] Photopolymerization initiator (C-1): "Omnirad184" (manufactured by IGM Resins B.V.) [Hydrolysis inhibitor (D)] Carbodiimide compound (D-1): "Carbodilite V-09GB" (Nisshinbo Chemical Co., Ltd.) [Urethanization catalyst] Zirconium compounds: Orgatics ZC-150 (Matsumoto Fine Chemical Co., Ltd.) diluted with acetylacetone to a solids concentration of 1% [Antioxidants] Hindered phenolic antioxidant: "IRGANOX 1010" (BASF)

[0197] [Production of active energy ray-curable compound (E-1)] A four-necked round-bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet, and a thermometer was charged with 6.6 parts of isophorone diisocyanate (IPDI), 93.4 parts of dipentaerythritol pentaacrylate, 0.03 parts of di-t-butylhydroxyphenol, and 0.02 parts of dibutyltin dilaurate, and the reaction was continued at 50°C to obtain an active energy ray-curable compound (E-1). The weight-average molecular weight of the active energy ray-curable compound (E-1) was 1,500.

[0198] <Examples 1 to 4, Comparative Examples 1 to 3> A release adhesive composition was prepared by blending the components in the amounts shown in Table 2 below and diluting with ethyl acetate and / or toluene to a viscosity (1000 to 5000 mPa·s / 25°C) that allowed coating. Using this release adhesive composition, a release adhesive sheet with a release adhesive was produced by the following method.

[0199] [Table 4]

[0200] [Preparation of Peelable Adhesive Sheet] A polyethylene terephthalate (PET) film (thickness: 38 μm) was prepared as a substrate, and the peelable pressure-sensitive adhesive composition was applied to the surface of the PET film in a state where ultraviolet light was blocked so that the thickness after drying would be 25 μm, and then dried for 2 minutes at 100° C. A release-treated PET film was then attached to the surface of the pressure-sensitive adhesive layer for protection, yielding a peelable pressure-sensitive adhesive sheet (thickness: 25 μm) with peelable PET. In addition, a release-treated polyethylene terephthalate (PET) film (thickness: 38 μm) was prepared, and the release-treated PET film surface was coated with the peelable pressure-sensitive adhesive composition to a dry thickness of 50 μm while UV rays were blocked, followed by drying for 5 minutes at 100° C. A release-treated PET film was then attached to the surface of the pressure-sensitive adhesive layer for protection, yielding a peelable pressure-sensitive adhesive sheet with peelable PET (thickness: 50 μm).

[0201] The peelable pressure-sensitive adhesive sheets of the Examples and Comparative Examples thus obtained were aged at 40°C for 7 days, and then various physical properties were evaluated according to the methods described below. The results are shown in Table 5 below. The release-treated PET sheet was peeled off when various measurement tests were carried out.

[0202] <Gel fraction> The peelable adhesive sheet (25 μm thick) obtained above was wrapped in a 200-mesh SUS wire netting and immersed in toluene at 23°C for 24 hours. The weight percentage of the undissolved adhesive component remaining in the wire netting was taken as the gel fraction. The gel fraction was also measured in the same way after UV irradiation. However, the weight of the substrate was subtracted.

[0203] <Adhesion strength before UV irradiation> The peelable adhesive sheet (thickness 25 μm) obtained above was attached to a SUS-BA plate as an adherend and left to stand at 23°C and 50% RH for 30 minutes or more, after which the 180-degree peel strength (N / 25 mm) was measured.

[0204] <Holding force (cohesive force)> The peelable adhesive sheet (25 μm thick) obtained above was attached to SUS304 as an adherend in accordance with JIS Z-0237 with an area of ​​25 mm × 25 mm, and then left to stand for 20 minutes at 40° C. A load of 1 kg was then applied, and the time until the sheet fell 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.

[0205] <Adhesive strength after UV irradiation> The peelable adhesive sheet (25 μm thick) obtained above was attached to a SUS-BA plate as an adherend, and left to stand at 23°C and 50% RH for 30 minutes or more, after which it was irradiated with ultraviolet light (500 mJ / cm using a high-pressure mercury lamp). 2 After this, the 180-degree peel strength (N / 25 mm) was measured in accordance with JIS Z0237.

[0206] [Preparation of samples for elongation and breaking stress] The peelable adhesive sheet (thickness 50 μm) obtained above was irradiated with ultraviolet light of 365 nm wavelength at an irradiation intensity of 200 mW / cm 2 , cumulative light intensity 500mJ / cm 2 The cured peelable adhesive sheet was punched out with a dumbbell to prepare a strip sample having a width of 15 cm and a length of 75 mm, and the release PET on both sides was then peeled off to prepare a sample piece for measurement.

[0207] <Elongation (%)> The measurement sample pieces obtained above were subjected to a tensile test at 23°C and 50% RH using a tensile tester "AG-X" (manufactured by Shimadzu Corporation) in accordance with JIS K 7127. The tensile speed was 10 mm / min, and the elongation at the breaking point was measured.

[0208] < Breaking stress (N / mm 2 )> The measurement sample pieces obtained above were subjected to a tensile test at a temperature of 23°C and 50% RH using a tensile tester "AG-X" (manufactured by Shimadzu Corporation) in accordance with JIS K 7127. The test was performed at a tensile speed of 10 mm / min, and the strength at the breaking point was measured.

[0209] [Table 5]

[0210] The releasable pressure-sensitive adhesive sheets of Examples 1 to 4 prepared from the releasable pressure-sensitive adhesive composition of the present invention had excellent releasability and high elongation after UV irradiation, because they had a releasable adhesive strength (low adhesive strength) and thus were releasable, which is thought to result in less adhesive residue. On the other hand, the release adhesive sheet produced from the release adhesive composition of Comparative Example 1, in which the adhesive strength after UV irradiation is reduced by blending a crosslinking agent and an active energy ray-curable compound, had too high a cohesive strength after UV irradiation and low elongation, which is expected to cause the adhesive layer to break easily and leave a large amount of adhesive residue. Furthermore, the peelable pressure-sensitive adhesive composition of Comparative Example 2, which used an acrylic resin containing a methacryloyl group, achieved sufficient adhesive strength to allow peeling after UV irradiation, but had low elongation, which is expected to cause the pressure-sensitive adhesive layer to break easily and leave a large amount of adhesive residue. Furthermore, the releasable pressure-sensitive adhesive sheet produced from the releasable pressure-sensitive adhesive composition of Comparative Example 3, in which the polyester resin did not contain a (meth)acryloyl group, had high adhesive strength and was difficult to peel off. [Industrial Applicability]

[0211] The removable adhesive composition of the present invention exhibits a reasonable adhesive strength initially and then becomes very low adhesive strength upon removal, so that it can be firmly fixed when fixed and easily peeled off when removed. Moreover, it has the property of being extremely stretchable even when cured by ultraviolet light or the like, so that it is difficult to tear even when the adhesive layer physically gets caught on an adherend with unevenness such as bumps, and is unlikely to leave adhesive residue. Therefore, it is preferable as an adhesive layer of an adhesive sheet for temporarily protecting the surface when processing workpieces such as electronic substrates, semiconductor wafers, processed glass products, metal plates, and plastic plates, and more specifically, it can be very useful as an adhesive layer for temporarily protecting the circuit pattern forming surface of an uneven semiconductor wafer having bumps or the like on the adherend.

Claims

1. A peelable pressure-sensitive adhesive composition comprising a polyester resin and a crosslinking agent (B), wherein the polyester resin is a polyester resin (A) containing a (meth)acryloyl group; the weight average molecular weight of the (meth)acryloyl group-containing polyester resin (A) is 10,000 to 500,000; the (meth)acryloyl group-containing polyester resin (A) has an unsaturated group concentration of 0.05 to 2 mmol / g and a hydroxyl value of 1 to 30 mgKOH / g; A peelable pressure-sensitive adhesive composition characterized in that, when the concentration (mmol / g) of functional groups in the (meth)acryloyl group-containing polyester resin (A) that react with a crosslinking agent (B) (excluding unsaturated groups in the polyester resin (A)) is defined as (X), and the concentration (mmol / g) of functional groups contained in the crosslinking agent (B) that react with functional groups in the polyester resin (A) is defined as (Y), the relationship satisfies 0.1≦(Y) / (X)≦3.

0.

2. 2. The peelable pressure-sensitive adhesive composition according to claim 1, wherein the content of the polyester resin (A) containing a (meth)acryloyl group is 50% by weight or more of the total peelable pressure-sensitive adhesive composition.

3. The polyester resin (A) containing a (meth)acryloyl group is 3. The peelable pressure-sensitive adhesive composition according to claim 1, which is a reaction product of a hydroxyl group of a polyester resin with an isocyanate group-containing (meth)acrylate and / or a carboxyl group-containing (meth)acrylate, or a reaction product of a carboxyl group of a polyester resin with a glycidyl group-containing (meth)acrylate and / or a hydroxyl group-containing (meth)acrylate.

4. The peelable pressure-sensitive adhesive composition according to any one of claims 1 to 3, characterized in that the crosslinking agent (B) has a functional group that reacts with the polyester resin (A) containing a (meth)acryloyl group and an unsaturated group.

5. The peelable pressure-sensitive adhesive composition according to any one of claims 1 to 4, further comprising a polymerization initiator (C).

6. A peelable pressure-sensitive adhesive comprising the peelable pressure-sensitive adhesive composition according to any one of claims 1 to 5.

7. A peelable adhesive sheet comprising at least one adhesive layer containing the peelable adhesive of claim 6 laminated on a substrate.

8. 8. The peelable adhesive sheet according to claim 7, wherein the adhesive strength (β) of the peelable adhesive sheet is 2 N / 25 mm or less. Adhesive strength (β): A peelable adhesive sheet was attached to an SUS-BA plate as an adherend, and left to stand at 23°C and 50% RH for 30 minutes or more. After that, the sheet was irradiated with ultraviolet light (500 mJ / cm2 using a high-pressure mercury lamp). The 180-degree peel strength (N / 25 mm) after ultraviolet light irradiation was measured in accordance with JIS Z0237.

9. A pressure-sensitive adhesive composition comprising a polyester resin and a crosslinking agent (B), The polyester resin is a polyester resin (A) containing a (meth)acryloyl group, and the weight average molecular weight of the (meth)acryloyl group-containing polyester resin (A) is 10,000 to 500,000; the (meth)acryloyl group-containing polyester resin (A) has an unsaturated group concentration of 0.05 to 2 mmol / g and a hydroxyl value of 1 to 30 mgKOH / g; A pressure-sensitive adhesive composition characterized in that, when the concentration (mmol / g) of functional groups in the (meth)acryloyl group-containing polyester resin (A) that react with a crosslinking agent (B) (excluding unsaturated groups in the polyester resin (A)) is defined as (X), and the concentration (mmol / g) of functional groups contained in the crosslinking agent (B) that react with functional groups in the polyester resin (A) is defined as (Y), the relationship satisfies 0.1≦(Y) / (X)≦3.0.

Images