Adhesive composition for flexible display, adhesive sheet for flexible display, optical member for flexible display, and display device

Abstract

To provide: an adhesive composition for a flexible display capable of forming an adhesive layer excellent in heat shock durability in the state of being folded; an adhesive sheet for the flexible display including the adhesive layer formed of the adhesive composition for the flexible display; an optical member for the flexible display; and a display device.SOLUTION: An adhesive composition for a flexible display comprises a (meth)acryl-based polymer (A) which contains a constitutional unit (a1) derived from a monomer having a hydroxy group and a constitutional unit (a2) derived from a (meth)acrylic acid alkyl ester monomer, of which the glass-transition temperature is less than -60°C and the weight average molecular weight is 1,000,000 or more, a (meth)acryl-based polymer (B) which contains a constitutional unit (b1) derived from a monomer having an alicyclic alkyl group, of which the glass-transition temperature is 60°C or more and the weight average molecular weight is 2,500-10,000, and a chelate-based cross-linking agent (C).SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to an adhesive composition for a flexible display, an adhesive sheet for a flexible display, an optical member for a flexible display, and a display device.

Background Art

[0002] In recent years, portable electronic devices equipped with flexible displays such as displays having a curved shape and foldable displays that can be folded have been increasingly popular. For adhesives used in such flexible displays, it is required to be able to form an adhesive layer in which phenomena such as floating, peeling, whitening, and foaming hardly occur even in a bent state. So far, various reports have been made on adhesive layers with excellent flexibility and adhesives that can form such adhesive layers.

[0003] For example, Patent Document 1 discloses an adhesive layer formed from an adhesive composition containing a (meth)acrylic polymer as an adhesive layer that does not peel even under repeated bending and has excellent flex resistance and adhesion, wherein the weight average molecular weight of the (meth)acrylic polymer is 1 million to 2.5 million, and the glass transition temperature of the adhesive layer is 0°C or lower. An adhesive layer for a flexible image display device is disclosed. Patent Document 2 discloses a pressure-sensitive adhesive that is excellent in transparency and can achieve all of the following properties: heat resistance, moist heat resistance, flexibility, and windability. The pressure-sensitive adhesive comprises an acrylic copolymer (A1) (excluding the case of an acrylic copolymer (A2)), an acrylic copolymer (A2), and a curing agent (B), wherein the acrylic copolymer (A1) is a copolymer of a monomer mixture containing a (meth)acrylic acid branched alkyl ester monomer having an alkyl group of 6 to 10 carbon atoms, a (meth)acrylic acid alkyl ester monomer having an alkyl group of 12 to 20 carbon atoms, and a monomer having one or more polar groups selected from monomers having a hydroxy group and monomers having a carboxy group; and the acrylic copolymer (A2) is a copolymer of a monomer mixture containing a (meth)acrylic acid alkyl ester monomer having a cycloalkyl group, and the pressure-sensitive adhesive satisfies all of the following requirements (1) to (7): (1) a storage modulus at -20°C and 1 Hz of 5 × 10 4 Pa~3×10 5 (2) the storage modulus at 25°C and 1 Hz is 1 × 10 4 Pa~5×10 4 (3) The storage modulus at 80°C and 1 Hz is 5 × 10 3 Pa~3×10 4 Pa, and (4) the storage modulus at 200°C and 1 Hz is 2 × 10 3 Pa~3×10 4 Pa, (5) the loss tangent at -50°C and 1 Hz is 0.5 to 3.0, (6) the loss tangent at -20°C and 1 Hz is 0.2 to 1.0, and (7) the loss tangent at 25°C, 80°C, and 200°C and 1 Hz is 0.01 to 0.5. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-27996 [Patent Document 2] Japanese Patent Publication No. 2022-181956 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, in a flexible display, the adhesive layer at the bent portion is more likely to be burdened and defects such as floating, peeling, whitening, and foaming are more likely to occur in the bent state than in the unfolded state. In particular, since a flexible display is excellent in portability, it is often carried under various temperature environments from low temperature to high temperature. For this reason, the adhesive used for a flexible display is required to be able to form an adhesive layer that is excellent not only in durability in a wide temperature range in the bent state but also in durability against a rapid change in environmental temperature (so-called heat shock durability). However, in recent years, with the emergence of slidable displays, rollable displays, etc., there has been a tendency for further high durability to be required for the adhesive layer provided in a flexible display.

[0006] In view of such circumstances, Patent Document 1 and Patent Document 2 do not focus on forming an adhesive layer excellent in heat shock durability in the bent state.

[0007] The present disclosure has been made in view of the above circumstances. An object to be solved by one embodiment of the present disclosure is to provide an adhesive composition for a flexible display capable of forming an adhesive layer excellent in heat shock durability in the bent state. Another object to be solved by other embodiments of the present disclosure is to provide an adhesive sheet for a flexible display, an optical member for a flexible display, and a display device including an adhesive layer formed of the above adhesive composition.

Means for Solving the Problems

[0008] Specific means for solving the problems include the following aspects. <1> A (meth)acrylic polymer (A) containing a structural unit (a1) derived from a monomer having a hydroxyl group and a structural unit (a2) derived from an alkyl (meth)acrylate monomer, having a glass transition temperature of less than -60°C and a weight average molecular weight of 1,000,000 or more, and A (meth)acrylic polymer (B) containing a structural unit (b1) derived from a monomer having an alicyclic alkyl group, having a glass transition temperature of 60°C or more and a weight average molecular weight of 2,500 to 10,000, and A chelate crosslinking agent (C), and An adhesive composition for a flexible display containing the same. <2> The (meth)acrylic polymer (A) according to <1>, wherein the (meth)acrylic polymer (A) contains at least one selected from the group consisting of a structural unit (a2-1) derived from an alkyl (meth)acrylate monomer having 1 to 4 carbon atoms in the alkyl moiety and a structural unit (a3) derived from an alkoxyalkyl (meth)acrylate monomer having 1 to 4 carbon atoms in the alkoxy moiety, and the total content of the structural unit (a2-1) and the structural unit (a3) is 1.0% by mass to 10.0% by mass based on all the structural units. The adhesive composition for a flexible display according to <1>. <3> The adhesive composition for a flexible display according to <1> or <2>, wherein the content of the (meth)acrylic polymer (B) is 1.0 part by mass to 20.0 parts by mass with respect to 100 parts by mass of the (meth)acrylic polymer (A). <4> The adhesive composition for a flexible display according to any one of <1> to <3>, wherein the content of the chelate crosslinking agent (C) is 0.05 part by mass to 0.50 part by mass with respect to 100 parts by mass of the (meth)acrylic polymer (A). <5> The adhesive composition for a flexible display according to any one of <1> to <4>, wherein the (meth)acrylic polymer (A) has a content of the structural unit (a1) of 1.0% by mass to 5.0% by mass based on all the structural units. <6> The (meth)acrylic polymer (B) described above does not contain a structural unit (b2) derived from a monomer having a hydroxyl group, or the content of the structural unit (b2) is in the range exceeding 0% by mass and 15.0% by mass or less with respect to all structural units, and is the pressure-sensitive adhesive composition for a flexible display according to any one of <1> to <5>. <7> When forming an adhesive layer, the shear strain at 100 °C is less than 80%, and the adhesive strength at 100 °C is 2.0 N / 25 mm or more, and is the pressure-sensitive adhesive composition for a flexible display according to any one of <1> to <6>. <8> A pressure-sensitive adhesive sheet for a flexible display including an adhesive layer formed by the pressure-sensitive adhesive composition for a flexible display according to any one of <1> to <7>. <9> An optical member for a flexible display including an adhesive layer formed by the pressure-sensitive adhesive composition for a flexible display according to any one of <1> to <7>. <10> A display device including the optical member for a flexible display according to <9>.

Advantages of the Invention

[0009] According to one embodiment of the present disclosure, there is provided a pressure-sensitive adhesive composition for a flexible display capable of forming an adhesive layer excellent in heat shock durability in a bent state. According to another embodiment of the present disclosure, there are provided a pressure-sensitive adhesive sheet for a flexible display, an optical member for a flexible display, and a display device including an adhesive layer formed by the pressure-sensitive adhesive composition.

Modes for Carrying Out the Invention

[0010] Hereinafter, the pressure-sensitive adhesive composition for flexible displays, the pressure-sensitive adhesive sheet for flexible displays, the optical member for flexible displays, and the display device according to the present disclosure will be described in detail. The description of the requirements described below may be made based on typical embodiments of the present disclosure, but the present disclosure is not limited to such embodiments, and modifications can be appropriately made and implemented within the scope of the object of the present disclosure.

[0011] In the present disclosure, the numerical range indicated by using "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value, respectively. In the numerical ranges described stepwise in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range of other stepwise descriptions. Also, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.

[0012] In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0013] In the present disclosure, the amount of each component in the pressure-sensitive adhesive composition means the total amount of the above-mentioned plurality of substances present in the pressure-sensitive adhesive composition when there are a plurality of substances corresponding to each component in the pressure-sensitive adhesive composition, unless otherwise specified.

[0014] In the present disclosure, "solid content" means components other than the solvent contained in the composition, unless otherwise specified, and "solvent" means water and organic solvents. For example, when the solvent contained in the composition is only water, the solid content means components other than water contained in the composition. When the solvent contained in the composition is only an organic solvent, the solid content means components other than the organic solvent contained in the composition. When the solvent contained in the composition is water and an organic solvent, the solid content means components other than water and the organic solvent contained in the composition.

[0015] In the present disclosure, the term “(meth)acrylic polymer” means a polymer that contains structural units derived from (meth)acrylic monomers and in which the proportion of the structural units derived from (meth)acrylic monomers is 50% by mass or more. In the present disclosure, the term “(meth)acrylic monomer” means a monomer having a (meth)acryloyl group.

[0016] In the present disclosure, “(meth)acrylic” is a term encompassing both “acrylic” and “methacrylic”, “(meth)acrylate” is a term encompassing both “acrylate” and “methacrylate”, and “(meth)acryloyl” is a term encompassing both “acryloyl” and “methacryloyl”.

[0017] In the present disclosure, “n-” means normal, “i-” means iso, “s-” means secondary, and “t-” means tertiary.

[0018] In the present disclosure, “monomer” and “single monomer” are synonymous, and “polymer”, “polymerized product” and “copolymer” are synonymous.

[0019] In the present disclosure, “% by mass” and “% by weight” are synonymous, and “parts by mass” and “parts by weight” are synonymous.

[0020] In the present disclosure, the term “process” includes not only an independent process but also a process that cannot be clearly distinguished from other processes, provided that the intended purpose of the process is achieved.

[0021] [[ID=?]]

[0022] In the present disclosure, the term “interface of the adhesive layer” means the interface between the adhesive layer and the adherend.

[0023] [Adhesive Composition for Flexible Display] It should be noted that there seems to be a missing ID in the original text for the line " ". I have left it as "?ID=?" in the translation for consistency with the original structure.The pressure-sensitive adhesive composition for a flexible display of the present disclosure (hereinafter, also simply referred to as "pressure-sensitive adhesive composition") includes a structural unit (a1) derived from a monomer having a hydroxyl group and a structural unit (a2) derived from a (meth)acrylic acid alkyl ester monomer, and has a glass transition temperature of less than -60°C and a weight average molecular weight of 1,000,000 or more (meth)acrylic polymer (A), a structural unit (b1) derived from a monomer having an alicyclic alkyl group, a glass transition temperature of 60°C or more, and a weight average molecular weight of 2,500 to 10,000 (meth)acrylic polymer (B), and a chelate crosslinking agent (C). By having the above-described configuration, the pressure-sensitive adhesive composition of the present disclosure can form a pressure-sensitive adhesive layer excellent in heat shock durability in a bent state. The reason why the pressure-sensitive adhesive composition of the present disclosure can exhibit such an effect is not clear, but the present inventors presume as follows. However, the following presumption does not limit the interpretation of the pressure-sensitive adhesive composition of the present disclosure and is described as an example.

[0024] Generally, the pressure-sensitive adhesive layer has the property of becoming harder as the temperature decreases. When exposed to a low-temperature environment in a bent state, the stress concentration generated in the pressure-sensitive adhesive layer at the bent portion increases, and defects such as lifting, peeling, whitening, and foaming tend to occur easily. Therefore, it is necessary for the pressure-sensitive adhesive layer to have a sufficiently low glass transition temperature so that it can maintain softness even in a low-temperature environment. On the other hand, generally, the pressure-sensitive adhesive layer has the property that the cohesive force weakens as the temperature increases. When exposed to a high-temperature environment in a bent state, the adhesive strength of the pressure-sensitive adhesive layer at the bent portion decreases, and the pressure-sensitive adhesive layer at the bent portion becomes excessively soft (in other words, the shear strain increases), and defects such as lifting, peeling, whitening, and foaming tend to occur easily. Therefore, it is necessary for the pressure-sensitive adhesive layer to maintain high adhesive strength and low shear strain even in a high-temperature environment. However, when the glass transition temperature is lowered to maintain softness in a low-temperature environment, the adhesive strength in a high-temperature environment tends to decrease, and defects such as peeling are likely to occur.

[0025] The pressure-sensitive adhesive composition of the present disclosure contains a (meth)acrylic polymer (B) having a relatively high glass transition temperature in addition to a (meth)acrylic polymer (A) having a sufficiently low glass transition temperature. Since the (meth)acrylic polymer (B) has a smaller weight average molecular weight than the (meth)acrylic polymer (A), it is considered that when a pressure-sensitive adhesive layer is formed, it is likely to localize at the interface of the pressure-sensitive adhesive layer. When a component having a high glass transition temperature localizes at the interface of the pressure-sensitive adhesive layer, while the cohesive force of the pressure-sensitive adhesive layer near the interface can be increased, the component having a high glass transition temperature may excessively aggregate at the interface of the pressure-sensitive adhesive layer, causing a decrease in wettability. Since the pressure-sensitive adhesive composition of the present disclosure contains a constitutional unit (b1) derived from a monomer having an alicyclic alkyl group having a bulky structure in the (meth)acrylic polymer (B), excessive aggregation at the interface of the pressure-sensitive adhesive layer between the (meth)acrylic polymers (B) hardly occurs. Therefore, according to the pressure-sensitive adhesive composition of the present disclosure, it is presumed that the cohesive force of the pressure-sensitive adhesive layer near the interface can be increased without impairing the wettability of the interface of the pressure-sensitive adhesive layer, and as a result, the pressure-sensitive adhesive layer exhibits a high high-temperature adhesive strength. In addition, in order for the pressure-sensitive adhesive layer to exhibit heat shock durability in a bent state, it is also necessary that the high-temperature shear strain of the pressure-sensitive adhesive layer is low. Generally, by increasing the gel content of the pressure-sensitive adhesive layer, the high-temperature shear strain of the pressure-sensitive adhesive layer can also be reduced. However, as the gel content of the pressure-sensitive adhesive layer increases, the wettability is impaired, so the high-temperature adhesive strength tends to decrease. Since the pressure-sensitive adhesive composition of the present disclosure contains a constitutional unit (a1) derived from a monomer having a hydroxyl group in the (meth)acrylic polymer (A) and a chelating crosslinking agent (C), a crosslinked structure is formed in the formed pressure-sensitive adhesive layer by a coordination bond between the hydroxyl group and the chelating crosslinking agent (C). This crosslinked structure is formed by a relatively weak interaction. Therefore, the formed pressure-sensitive adhesive layer tends to have a flexible property having both softness and cohesive force, and it is presumed that the high-temperature shear strain is reduced. From the above, in the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present disclosure, although the glass transition temperature is sufficiently low, a high high-temperature adhesive strength is exhibited, and both a high high-temperature adhesive strength and a low high-temperature shear strain are achieved. Therefore, it is presumed that the effect of excellent heat shock durability in a bent state is exhibited.

[0026] In the present disclosure, the "(meth)acrylic polymer (A) containing structural units (a1) derived from a monomer having a hydroxyl group and structural units (a2) derived from an alkyl (meth)acrylate monomer, having a glass transition temperature of less than -60°C and a weight average molecular weight of 1,000,000 or more" is also referred to as the "specific (meth)acrylic polymer (A)". Further, in the present disclosure, the "(meth)acrylic polymer (B) containing structural units (b1) derived from a monomer having an alicyclic alkyl group, having a glass transition temperature of 60°C or more and a weight average molecular weight of 2,500 to 10,000" is also referred to as the "specific (meth)acrylic polymer (B)". In the present disclosure, the "specific (meth)acrylic polymer (A) and the specific (meth)acrylic polymer (B)" may be collectively referred to as the "specific (meth)acrylic polymer".

[0027] 〔Specific (meth)acrylic polymer (A)〕 The pressure-sensitive adhesive composition of the present disclosure contains structural units (a1) derived from a monomer having a hydroxyl group and structural units (a2) derived from an alkyl (meth)acrylate monomer, and contains a (meth)acrylic polymer (A) [that is, the specific (meth)acrylic polymer (A)] having a glass transition temperature of less than -60°C and a weight average molecular weight of 1,000,000 or more. The pressure-sensitive adhesive composition of the present disclosure may contain only one kind of the specific (meth)acrylic polymer (A), or may contain two or more kinds.

[0028] <Structural units (a1) derived from a monomer having a hydroxyl group> The specific (meth)acrylic polymer (A) contains structural units (a1) derived from a monomer having a hydroxyl group. In the present disclosure, the "structural units derived from a monomer having a hydroxyl group" means the structural units formed by the addition polymerization of a monomer having a hydroxyl group.

[0029] The type of the monomer having a hydroxyl group is not particularly limited. Examples of the monomer having a hydroxyl group include a monomer having at least one hydroxyl group and an ethylenically unsaturated group in one molecule. The ethylenically unsaturated group is not particularly limited, and examples thereof include a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group. The monomer having a hydroxyl group may be, for example, a (meth)acrylic monomer or a monomer other than the (meth)acrylic monomer.

[0030] Specific examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1-dimethyl-3-hydroxybutyl (meth)acrylate, 1,3-dimethyl-3-hydroxybutyl (meth)acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth)acrylate, 2-ethyl-3-hydroxyhexyl (meth)acrylate, N-hydroxyethyl (meth)acrylamide, glycerin mono (meth)acrylate, polypropylene glycol mono (meth)acrylate, polyethylene glycol mono (meth)acrylate, and poly(ethylene glycol-propylene glycol) mono (meth)acrylate. The monomer having a hydroxyl group preferably contains a hydroxyalkyl (meth)acrylate, more preferably contains at least one selected from the group consisting of 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, still more preferably contains at least one selected from the group consisting of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 4-hydroxybutyl acrylate, and particularly preferably contains 2-hydroxyethyl methacrylate.

[0031] The specific (meth)acrylic polymer (A) may contain only one type of constituent unit (a1), or may contain two or more types.

[0032] The content rate of the constituent unit (a1) in the specific (meth)acrylic polymer (A) is not particularly limited. For example, it is preferably 0.1% by mass to 10.0% by mass, more preferably 0.5% by mass to 8.0% by mass, still more preferably 1.0% by mass to 5.0% by mass, and particularly preferably 2.0% by mass to 5.0% by mass with respect to all the constituent units of the specific (meth)acrylic polymer (A). When the content rate of the constituent unit (a1) in the specific (meth)acrylic polymer (A) is within the above range with respect to all the constituent units of the specific (meth)acrylic polymer (A), the formed crosslinked structure does not become excessively hard, so that high high-temperature adhesiveness can be maintained, and the heat shock durability in the bent state of the formed adhesive layer is less likely to be impaired.

[0033] <Constituent unit (a2) derived from (meth)acrylic acid alkyl ester monomer> The specific (meth)acrylic polymer (A) contains a constituent unit (a2) derived from a (meth)acrylic acid alkyl ester monomer. In the present disclosure, the "constituent unit derived from (meth)acrylic acid alkyl ester monomer" means a constituent unit formed by the addition polymerization of a (meth)acrylic acid alkyl ester monomer. It should be noted that the "(meth)acrylic acid alkyl ester monomer" in the present disclosure does not include monomers corresponding to monomers having a hydroxyl group. That is, the "(meth)acrylic acid alkyl ester monomer" in the present disclosure refers to a (meth)acrylic acid alkyl ester monomer having no hydroxyl group. In the present disclosure, for example, a (meth)acrylic acid alkyl ester monomer having a hydroxyl group is classified as the above-mentioned monomer having a hydroxyl group.

[0034] The type of the (meth)acrylic acid alkyl ester monomer is not particularly limited. (Meth)acrylic acid alkyl ester monomers may be acrylic acid alkyl ester monomers or methacrylic acid alkyl ester monomers. (Meth)acrylic acid alkyl ester monomers may have an unsubstituted alkyl group or may have a substituent (excluding hydroxyl groups), but it is preferably unsubstituted. (Meth)acrylic acid alkyl ester monomers may have a linear, branched, or cyclic alkyl group. (Meth)acrylic acid alkyl ester monomers preferably have 1 to 18 carbon atoms in the alkyl moiety, for example.

[0035] Specific examples of (meth)acrylic acid alkyl ester monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate. (Meth)acrylic acid alkyl ester monomers preferably contain 2-ethylhexyl acrylate from the viewpoint of having a low glass transition temperature when made into a homopolymer, for example.

[0036] The specific (meth)acrylic polymer (A) may contain only one type of constitutional unit (a2) or may contain two or more types.

[0037] The content rate of the constitutional unit (a2) in the specific (meth)acrylic polymer (A) is not particularly limited. For example, it is preferably 50.0 mass% or more, more preferably 50.0 mass% to 99.9 mass%, still more preferably 60.0 mass% to 99.5 mass%, and particularly preferably 70.0 mass% to 99.0 mass% based on all the constitutional units of the specific (meth)acrylic polymer (A). Here, the content rate of the constitutional unit (a2) in the specific (meth)acrylic polymer (A) being 50.0 mass% or more based on all the constitutional units of the specific (meth)acrylic polymer (A) means that the constitutional unit (a2) is contained as a main component of the constitutional units of the specific (meth)acrylic polymer (A).

[0038] <Constitutional unit (a3) derived from a (meth)acrylic acid alkoxyalkyl ester monomer having 1 to 4 carbon atoms in the alkoxy moiety> The specific (meth)acrylic polymer (A) may contain a constitutional unit (a3) derived from a (meth)acrylic acid alkoxyalkyl ester monomer having 1 to 4 carbon atoms in the alkoxy moiety. In the present disclosure, the "constitutional unit derived from a (meth)acrylic acid alkoxyalkyl ester monomer having 1 to 4 carbon atoms in the alkoxy moiety" means a constitutional unit formed by the addition polymerization of a (meth)acrylic acid alkoxyalkyl ester monomer having 1 to 4 carbon atoms in the alkoxy moiety.

[0039] Specific examples of the (meth)acrylic acid alkoxyalkyl ester monomer having 1 to 4 carbon atoms in the alkoxy moiety include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-propyloxyethyl (meth)acrylate, and 2-butoxyethyl (meth)acrylate. The (meth)acrylic acid alkoxyalkyl ester monomer having 1 to 4 carbon atoms in the alkoxy moiety preferably contains 2-methoxyethyl acrylate, and more preferably is 2-methoxyethyl acrylate.

[0040] When the specific (meth)acrylic polymer (A) contains the constitutional unit (a3), it may contain only one kind of the constitutional unit (a3), or may contain two or more kinds.

[0041] When the specific (meth)acrylic polymer (A) contains the constitutional unit (a3), the content of the constitutional unit (a3) is not particularly limited. For example, it is preferably 1.0% by mass to 40.0% by mass, more preferably 1.0% by mass to 30.0% by mass, still more preferably 1.0% by mass to 20.0% by mass, and particularly preferably 1.0% by mass to 10.0% by mass with respect to all the constitutional units of the specific (meth)acrylic polymer (A).

[0042] In one aspect, the specific (meth)acrylic polymer (A) contains at least one selected from the group consisting of the constitutional unit (a2-1) derived from a (meth)acrylic acid alkyl ester monomer having 1 to 4 carbon atoms in the alkyl moiety and the constitutional unit (a3) derived from a (meth)acrylic acid alkoxyalkyl ester monomer having 1 to 4 carbon atoms in the alkoxy moiety, and the total content of the constitutional unit (a2-1) and the constitutional unit (a3) is preferably 1.0% by mass to 40.0% by mass, more preferably 1.0% by mass to 30.0% by mass, still more preferably 1.0% by mass to 20.0% by mass, and particularly preferably 1.0% by mass to 10.0% by mass with respect to all the constitutional units of the specific (meth)acrylic polymer (A). According to the above aspect, the heat shock durability in the bent state of the formed adhesive layer tends to be further improved.

[0043] Specific examples of the (meth)acrylic acid alkyl ester monomer having 1 to 4 carbon atoms in the alkyl moiety include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate, and t-butyl (meth)acrylate.

[0044] <Constitutional unit (a4) derived from a monomer having a carboxy group> The specific (meth)acrylic polymer (A) may contain a structural unit derived from a monomer having a carboxy group. In the present disclosure, the "structural unit derived from a monomer having a carboxy group" means a structural unit formed by addition polymerization of a monomer having a carboxy group.

[0045] The type of the monomer having a carboxy group is not particularly limited. Examples of the monomer having a carboxy group include monomers having at least one carboxy group and an ethylenically unsaturated group in one molecule. The ethylenically unsaturated group is not particularly limited, and examples thereof include a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group.

[0046] Specific examples of the monomer having a carboxy group include (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone mono(meth)acrylate [for example, ω-carboxy-polycaprolactone (n≈2) monoacrylate], and succinic acid derivatives (for example, 2-acryloyloxyethyl-succinic acid). The monomer having a carboxy group preferably contains (meth)acrylic acid, more preferably contains acrylic acid, and even more preferably is acrylic acid.

[0047] When the specific (meth)acrylic polymer (A) contains the structural unit (a4), it may contain only one kind of the structural unit (a4) or may contain two or more kinds.

[0048] When the specific (meth)acrylic polymer (A) contains the structural unit (a4), the content of the structural unit (a4) may be 0.1% by mass or more, or may be 0.2% by mass or more, based on all the structural units of the specific (meth)acrylic polymer (A). On the other hand, the upper limit of the content of the constitutional unit (a4) is preferably 2.0% by mass or less, more preferably 1.0% by mass or less, and still more preferably 0.5% by mass or less, based on all the constitutional units of the specific (meth)acrylic polymer (A). When the content of the constitutional unit (a4) is 2.0% by mass or less based on all the constitutional units of the specific (meth)acrylic polymer (A), the formed pressure-sensitive adhesive layer tends to have flexible properties combining softness and cohesion. For this reason, the heat shock durability in the bent state of the formed pressure-sensitive adhesive layer tends not to be impaired. In one aspect, the content of the constitutional unit (a4) in the specific (meth)acrylic polymer (A) may be 0.1% by mass to 2.0% by mass, 0.1% by mass to 1.0% by mass, 0.1% by mass to 0.5% by mass, or 0.2% by mass to 0.5% by mass, based on all the constitutional units of the specific (meth)acrylic polymer (A).

[0049] <Constitutional unit (a5) derived from other monomers> The specific (meth)acrylic polymer (A) may contain a constitutional unit derived from a monomer that does not fall into any of a monomer having a hydroxyl group, a (meth)acrylic acid alkyl ester monomer, a (meth)acrylic acid alkoxyalkyl ester monomer, and a monomer having a carboxy group (so-called other monomers). In the present disclosure, the "constitutional unit derived from other monomers" means a constitutional unit formed by the addition polymerization of other monomers.

[0050] Examples of the structural unit (a5) include structural units derived from (meth)acrylates having an aromatic ring, such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; structural units derived from aromatic monovinyls represented by styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; structural units derived from vinyl cyanides represented by acrylonitrile and methacrylonitrile; structural units derived from vinyl esters represented by vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate; and the like.

[0051] When the specific (meth)acrylic polymer (A) contains the structural unit (a5), it may contain only one kind of the structural unit (a5) or two or more kinds thereof.

[0052] When the specific (meth)acrylic polymer (A) contains the structural unit (a5), the content of the structural unit (a5) can be appropriately set within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0053] <<Glass transition temperature of the specific (meth)acrylic polymer (A)>> The glass transition temperature (also referred to as "Tg") of the specific (meth)acrylic polymer (A) is less than -60°C. When the glass transition temperature of the specific (meth)acrylic polymer (A) is less than -60°C, the softness of the pressure-sensitive adhesive layer in a low-temperature environment is maintained. Therefore, the heat shock durability of the formed pressure-sensitive adhesive layer in a bent state tends to be excellent. The glass transition temperature of the specific (meth)acrylic polymer (A) is preferably -61°C or lower, more preferably -62°C or lower. The lower limit of the glass transition temperature of the specific (meth)acrylic polymer (A) is not particularly limited, but is preferably, for example, -70°C or higher. In one aspect, the glass transition temperature of the specific (meth)acrylic polymer (A) may be in the range of -70°C or higher and less than -60°C, may be in the range of -70°C or higher and -61°C or lower, or may be in the range of -70°C or higher and -62°C or lower.

[0054] The glass transition temperature of the specific (meth)acrylic polymer (A) is a value obtained by converting the absolute temperature (unit: K) obtained by calculation from the following formula 1 into Celsius temperature (unit: °C). 1 / Tg = m1 / Tg1 + m2 / Tg2 + ··· + m(k - 1) / Tg(k - 1) + mk / Tgk (Formula 1)

[0055] In Formula 1, Tg1, Tg2, ···, Tg(k - 1), and Tgk respectively represent the glass transition temperatures represented by absolute temperatures when each monomer constituting the specific (meth)acrylic polymer (A) is a homopolymer. m1, m2, ···, m(k - 1), and mk respectively represent the molar fractions of each monomer constituting the specific (meth)acrylic polymer (A), and m1 + m2 + ··· + m(k - 1) + mk = 1. Note that the absolute temperature can be converted to Celsius temperature by subtracting 273 from the absolute temperature, and the Celsius temperature can be converted to absolute temperature by adding 273 to the Celsius temperature.

[0056] Regarding the "glass transition temperature when it is a homopolymer" in the present disclosure, the values described in known materials or the values measured using a differential scanning calorimeter (DSC) shall be adopted. Specifically, which value to adopt is as follows.

[0057] Regarding the "glass transition temperature when it is a homopolymer" of the monomers shown below, the values in parentheses shall be adopted respectively. Methyl acrylate (10 °C), methyl methacrylate (105 °C), ethyl acrylate (-22 °C), ethyl methacrylate (65 °C), n-butyl acrylate (-54 °C), n-butyl methacrylate (20 °C), i-butyl methacrylate (53 °C), t-butyl acrylate (43 °C), t-butyl methacrylate (118 °C), 2-ethylhexyl acrylate (-70 °C), 2-ethylhexyl methacrylate (-10 °C), n-octyl acrylate (-65 °C), stearyl acrylate (30 °C), stearyl methacrylate (38 °C), lauryl acrylate (-3 °C), lauryl methacrylate (-65 °C), cyclohexyl methacrylate (104 °C), isobornyl acrylate (94 °C), benzyl acrylate (6 °C), phenoxyethyl acrylate (-22 °C), 2-methoxyethyl acrylate (-50 °C), glycidyl methacrylate (74 °C), 2-hydroxyethyl acrylate (-15 °C), 2-hydroxyethyl methacrylate (85 °C), 4-hydroxybutyl acrylate (-80 °C), acrylic acid (106 °C), methacrylic acid (228 °C), dimethylaminoethyl methacrylate (18 °C), ω-carboxy-polycaprolactone (n≒2) monoacrylate (-30 °C).

[0058] Regarding the "glass transition temperature when homopolymerized" of monomers other than the above-mentioned monomers, the values described in the Polymer Handbook (4th Edition, Wiley-Interscience; hereinafter the same) are adopted. When there is no description in the Polymer Handbook, the values of the glass transition temperature of the homopolymer obtained by the following measurement method are adopted.

[0059] Specifically, using a differential scanning calorimeter (DSC), in a nitrogen gas stream, measure under the conditions of 10 mg of the measurement sample (i.e., homopolymer) and a heating rate of 10 °C / min, and take the inflection point of the obtained DSC curve as the glass transition temperature of the homopolymer. As the differential scanning calorimeter, for example, a differential scanning calorimeter (trade name: Discovery DSC 2500) manufactured by TA Instruments Japan Co., Ltd. can be preferably used. However, the differential scanning calorimeter is not limited thereto.

[0060] The glass transition temperature of the specific (meth)acrylic polymer (A) can be set to a desired value, for example, by appropriately selecting the types and ratios of the monomers that are polymerization components of the specific (meth)acrylic polymer (A).

[0061] <<Weight-average molecular weight of the specific (meth)acrylic polymer (A)>> The weight-average molecular weight (also referred to as "Mw") of the specific (meth)acrylic polymer (A) is 1,000,000 or more. When the weight-average molecular weight of the specific (meth)acrylic polymer (A) is 1,000,000 or more, the polymer chains are sufficiently entangled, so that the high-temperature shear strain does not become excessively high. For this reason, the heat shock durability in the bent state of the formed adhesive layer tends to be excellent. The weight-average molecular weight of the specific (meth)acrylic polymer (A) is preferably 1,200,000 or more, and more preferably 1,400,000 or more. The upper limit of the weight-average molecular weight of the specific (meth)acrylic polymer (A) is not particularly limited, but is preferably 2,000,000 or less, for example, from the viewpoint of easy handling during production. In one aspect, the weight-average molecular weight of the specific (meth)acrylic polymer (A) may be 1,000,000 to 2,000,000, may be 1,200,000 to 2,000,000, or may be 1,400,000 to 2,000,000.

[0062] The weight-average molecular weight of the specific (meth)acrylic polymer (A) is a value measured by the following method. Specifically, it is measured according to the following (1) to (3). (1) After applying a solution of the specific (meth)acrylic polymer (A) to release paper, it is dried at 100°C for 1 minute to obtain a film-like specific (meth)acrylic polymer (A). (2) Using the film-like specific (meth)acrylic polymer (A) obtained in the above (1) and tetrahydrofuran, a sample solution with a solid content concentration of 0.2% by mass is obtained. Here, the "solid content concentration" means the mass ratio of the specific (meth)acrylic polymer (A) in the sample solution. (3) By gel permeation chromatography (GPC) under the following conditions, the weight average molecular weight of the specific (meth)acrylic polymer (A) is determined as a standard polystyrene equivalent value.

[0063] ~Conditions~ Measuring device: High-speed GPC [Model number: HLC-8420 GPC, manufactured by Tosoh Corporation] Detector: Differential refractive index meter (RI) [incorporated in HLC-8420, manufactured by Tosoh Corporation] Column: TSKgel GMH XL [manufactured by Tosoh Corporation] Two are used Column temperature: 40 °C Eluent: Tetrahydrofuran Injection volume of sample solution: 100 μL Flow rate: 0.8 mL / min

[0064] The weight average molecular weight of the specific (meth)acrylic polymer (A) can be adjusted to a desired value, for example, by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc. when polymerizing the monomer.

[0065] <<Content ratio of the specific (meth)acrylic polymer (A)>> The content ratio of the specific (meth)acrylic polymer (A) in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, but for example, it is preferably 80.0% by mass to 99.8% by mass, more preferably 82.0% by mass to 99.5% by mass, and still more preferably 85.0% by mass to 97.5% by mass with respect to the total solid content in the pressure-sensitive adhesive composition.

[0066] In the present disclosure, the "total solid content in the pressure-sensitive adhesive composition" means the total mass of the pressure-sensitive adhesive composition when the pressure-sensitive adhesive composition does not contain a solvent, and means the mass of the residue obtained by removing the solvent from the pressure-sensitive adhesive composition when the pressure-sensitive adhesive composition contains a solvent.

[0067] 〔Specific (meth)acrylic polymer (B)〕 The pressure-sensitive adhesive composition of the present disclosure contains a structural unit (b1) derived from a monomer having an alicyclic alkyl group, and has a glass transition temperature of 60°C or higher and a weight average molecular weight of 2,500 to 10,000 (meth)acrylic polymer (B) (that is, a specific (meth)acrylic polymer (B)). The pressure-sensitive adhesive composition of the present disclosure may contain only one kind of specific (meth)acrylic polymer (B), or may contain two or more kinds.

[0068] <Structural unit (b1) derived from a monomer having an alicyclic alkyl group> The specific (meth)acrylic polymer (B) contains a structural unit (b1) derived from a monomer having an alicyclic alkyl group. In the present disclosure, the "structural unit derived from a monomer having an alicyclic alkyl group" means a structural unit formed by the addition polymerization of a monomer having an alicyclic alkyl group.

[0069] The type of the monomer having an alicyclic alkyl group is not particularly limited. Examples of the monomer having an alicyclic alkyl group include monomers having at least one alicyclic alkyl group and an ethylenically unsaturated group in one molecule. The ethylenically unsaturated group is not particularly limited, and examples thereof include a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group.

[0070] The monomer having an alicyclic alkyl group may be, for example, a (meth)acrylic monomer or a monomer other than a (meth)acrylic monomer, but is preferably a (meth)acrylic monomer. When the monomer having an alicyclic alkyl group is a (meth)acrylic monomer, it may be an acrylic monomer or a methacrylic monomer. The alicyclic alkyl group may be unsubstituted or may have a substituent, but is preferably unsubstituted. The number of carbon atoms of the alicyclic alkyl group is not particularly limited, but for example, it is preferably 4 to 16, and more preferably 6 to 10. Specific examples of the monomer having an alicyclic alkyl group include cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and 4-t-butylcyclohexyl (meth)acrylate.

[0071] The specific (meth)acrylic polymer (B) may contain only one kind of constitutional unit (b1) or may contain two or more kinds.

[0072] The content of the constitutional unit (b1) in the specific (meth)acrylic polymer (B) is not particularly limited, but for example, it is preferably 50.0% by mass to 100.0% by mass, more preferably 60.0% by mass to 100.0% by mass, still more preferably 70.0% by mass to 99.9% by mass, and particularly preferably 80.0% by mass to 99.8% by mass with respect to all the constitutional units of the specific (meth)acrylic polymer (B). When the content of the constitutional unit (b1) in the specific (meth)acrylic polymer (B) is within the above range with respect to all the constitutional units of the specific (meth)acrylic polymer (B), the heat shock durability in the bent state of the pressure-sensitive adhesive layer formed tends to be further improved.

[0073] <Constitutional unit (b2) derived from a monomer having a hydroxyl group> The specific (meth)acrylic polymer (B) may contain a constitutional unit (b2) derived from a monomer having a hydroxyl group. Specific examples of the monomer having a hydroxyl group have the same meaning as the specific examples of the monomer having a hydroxyl group described in the specific (meth)acrylic polymer (A). When the specific (meth)acrylic polymer (B) contains the constituent unit (b2), it may contain only one kind of the constituent unit (b2), or may contain two or more kinds of the constituent unit (b2).

[0074] The specific (meth)acrylic polymer (B) preferably does not contain the constituent unit (b2), or the content of the constituent unit (b2) is in the range of more than 0% by mass and 20.0% by mass or less with respect to all the constituent units of the specific (meth)acrylic polymer (B). More preferably, it does not contain the constituent unit (b2), or the content of the constituent unit (b2) is in the range of more than 0% by mass and 15.0% by mass or less with respect to all the constituent units of the specific (meth)acrylic polymer (B). Still more preferably, it does not contain the constituent unit (b2), or the content of the constituent unit (b2) is in the range of more than 0% by mass and 10.0% by mass or less with respect to all the constituent units of the specific (meth)acrylic polymer (B). Particularly preferably, it does not contain the constituent unit (b2), or the content of the constituent unit (b2) is in the range of more than 0% by mass and 5.0% by mass or less with respect to all the constituent units of the specific (meth)acrylic polymer (B). When the specific (meth)acrylic polymer (B) does not contain the constituent unit (b2), or the content of the constituent unit (b2) in the specific (meth)acrylic polymer (B) is in the range of more than 0% by mass and 20.0% by mass or less with respect to all the constituent units of the specific (meth)acrylic polymer (B), the cohesive force near the interface of the adhesive layer increases, and the adhesive layer exhibits high hot tack. Therefore, the heat shock durability in the bent state of the formed adhesive layer tends to be hardly impaired.

[0075] <Constituent unit (b3) derived from a monomer having a carboxy group> The specific (meth)acrylic polymer (B) may contain a constituent unit (b3) derived from a monomer having a carboxy group. Specific examples of the monomer having a carboxy group have the same meaning as the specific examples of the monomer having a carboxy group described in the specific (meth)acrylic polymer (A). When the specific (meth)acrylic polymer (B) contains the structural unit (b3), it may contain only one type of the structural unit (b3) or may contain two or more types thereof.

[0076] The specific (meth)acrylic polymer (B) preferably does not contain the structural unit (b3) or has a content of the structural unit (b3) in the range of more than 0% by mass and 0.3% by mass or less based on all the structural units of the specific (meth)acrylic polymer (B). More preferably, it does not contain the structural unit (b3) or has a content of the structural unit (b3) in the range of more than 0% by mass and 0.2% by mass or less based on all the structural units of the specific (meth)acrylic polymer (B). Even more preferably, it does not contain the structural unit (b3) or has a content of the structural unit (b3) in the range of more than 0% by mass and 0.1% by mass or less based on all the structural units of the specific (meth)acrylic polymer (B). Particularly preferably, it does not contain the structural unit (b3). When the specific (meth)acrylic polymer (B) does not contain the structural unit (b3) or has a content of the structural unit (b3) in the range of more than 0% by mass and 0.3% by mass or less based on all the structural units of the specific (meth)acrylic polymer (B), it is difficult to inhibit the crosslink formation between the specific (meth)acrylic polymer (A) and the chelating crosslinking agent (C) by the specific (meth)acrylic polymer (B). Therefore, it is possible to maintain a low high-temperature shear strain, and the heat shock durability in the bent state of the formed adhesive layer tends to be hardly impaired.

[0077] <Structural unit (b4) derived from other monomers> The specific (meth)acrylic polymer (B) may contain a structural unit derived from a monomer that does not correspond to any of a monomer having an alicyclic alkyl group, a monomer having a hydroxyl group, and a monomer having a carboxyl group (so-called other monomers). In the present disclosure, the structural unit derived from other monomers contained in the specific (meth)acrylic polymer (B) is also referred to as "structural unit (b4)".

[0078] Examples of the structural unit (b4) include monomers having an aliphatic alkyl group. Examples of the monomer having an aliphatic alkyl group include monomers having at least one aliphatic alkyl group and an ethylenically unsaturated group in one molecule. The ethylenically unsaturated group is not particularly limited, and examples thereof include a vinyl group, an allyl group, a vinylphenyl group, a (meth)acrylamide group, and a (meth)acryloyl group. The monomer having an aliphatic alkyl group may be, for example, a (meth)acrylic monomer or a monomer other than a (meth)acrylic monomer, but is preferably a (meth)acrylic monomer. The (meth)acrylic monomer having an aliphatic alkyl group may be an acrylic monomer or a methacrylic monomer. The aliphatic alkyl group may be unsubstituted or may have a substituent, but is preferably unsubstituted. The aliphatic alkyl group may be linear or branched. The number of carbon atoms of the aliphatic alkyl group is not particularly limited, but is preferably, for example, 1 to 18, more preferably 1 to 12, and still more preferably 1 to 8. Specific examples of the monomer having an aliphatic alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, and lauryl (meth)acrylate.

[0079] Examples of the structural unit (b4) include structural units derived from (meth)acrylates having an aromatic ring, such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; structural units derived from alkoxyalkyl (meth)acrylates, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; structural units derived from aromatic monovinyls, such as styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; structural units derived from vinyl cyanides, such as acrylonitrile and methacrylonitrile; and structural units derived from vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate, etc.

[0080] When the specific (meth)acrylic polymer (B) contains the structural unit (b4), it may contain only one type of the structural unit (b4) or two or more types of the structural unit (b4).

[0081] When the specific (meth)acrylic polymer (B) contains the structural unit (b4), the content rate of the structural unit (b4) can be appropriately set within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0082] <<Glass transition temperature of the specific (meth)acrylic polymer (B)>> The glass transition temperature of the specific (meth)acrylic polymer (B) is 60°C or higher. When the glass transition temperature of the specific (meth)acrylic polymer (B) is 60°C or higher, the cohesive force near the interface of the pressure-sensitive adhesive layer increases, and the pressure-sensitive adhesive layer exhibits high high-temperature adhesive strength. Therefore, the heat shock durability in the bent state of the formed pressure-sensitive adhesive layer can be improved. The glass transition temperature of the specific (meth)acrylic polymer (B) is preferably 65°C or higher, more preferably 70°C or higher, still more preferably 75°C or higher, and particularly preferably 80°C or higher. The upper limit of the glass transition temperature of the specific (meth)acrylic polymer (B) is not particularly limited, but for example, it is preferably 200°C or lower. In one aspect, the glass transition temperature of the specific (meth)acrylic polymer (B) may be 60°C to 200°C, may be 65°C to 200°C, may be 70°C to 200°C, may be 75°C to 200°C, or may be 80°C to 200°C.

[0083] The glass transition temperature of the specific (meth)acrylic polymer (B) is determined by the same method as the method for determining the glass transition temperature of the aforementioned specific (meth)acrylic polymer (A).

[0084] The glass transition temperature of the specific (meth)acrylic polymer (B) can be set to a desired value, for example, by appropriately selecting the types and ratios of the monomers that are the polymerization components of the specific (meth)acrylic polymer (B).

[0085] <<Weight-average molecular weight of the specific (meth)acrylic polymer (B)>> The weight-average molecular weight of the specific (meth)acrylic polymer (B) is 2500 to 10000. When the weight-average molecular weight of the specific (meth)acrylic polymer (B) is 2500 or more, since the polymer chains have an appropriate length, the cohesive force near the interface of the adhesive layer increases, and the adhesive layer exhibits high high-temperature adhesiveness. Therefore, the heat shock durability of the formed adhesive layer in a bent state can be improved. The weight-average molecular weight of the specific (meth)acrylic polymer (B) is preferably 3000 or more, more preferably 3500 or more, and even more preferably 4000 or more. When the weight-average molecular weight of the specific (meth)acrylic polymer (B) is 10000 or less, the specific (meth)acrylic polymer (B) is likely to localize near the interface of the adhesive layer, so that the cohesive force near the interface of the adhesive layer increases, and the adhesive layer exhibits high high-temperature adhesiveness. Therefore, the heat shock durability of the formed adhesive layer in a bent state can be improved. The weight-average molecular weight of the specific (meth)acrylic polymer (B) is preferably 9000 or less, more preferably 8000 or less, and even more preferably 7000 or less. In one aspect, the weight average molecular weight of the specific (meth)acrylic polymer (B) may be 3000 to 9000, may be 3000 to 8000, may be 3500 to 8000, or may be 4000 to 7000.

[0086] The weight average molecular weight of the specific (meth)acrylic polymer (B) is measured by the same method as the measurement method of the weight average molecular weight of the aforementioned specific (meth)acrylic polymer (A).

[0087] <<Content of the specific (meth)acrylic polymer (B)>> The content of the specific (meth)acrylic polymer (B) in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited. For example, it is preferably 0.5 parts by mass to 25.0 parts by mass, more preferably 1.0 parts by mass to 20.0 parts by mass, and still more preferably 5.0 parts by mass to 15.0 parts by mass with respect to 100 parts by mass of the specific (meth)acrylic polymer (A). When the content of the specific (meth)acrylic polymer (B) in the pressure-sensitive adhesive composition of the present disclosure is 0.5 parts by mass or more with respect to 100 parts by mass of the specific (meth)acrylic polymer (A), the cohesive force near the interface of the pressure-sensitive adhesive layer can be sufficiently increased, and the pressure-sensitive adhesive layer is more likely to exhibit a high high-temperature adhesive force. Therefore, the heat shock durability of the formed pressure-sensitive adhesive layer in a bent state tends to be further improved. When the content of the specific (meth)acrylic polymer (B) in the pressure-sensitive adhesive composition of the present disclosure is 25.0 parts by mass or less with respect to 100 parts by mass of the specific (meth)acrylic polymer (A), the softness of the pressure-sensitive adhesive layer in a low-temperature environment is better maintained. Therefore, the heat shock durability of the formed pressure-sensitive adhesive layer in a bent state tends to be further improved.

[0088] 〔Method for producing the specific (meth)acrylic polymer〕 The method for producing the specific (meth)acrylic polymer (A) and the specific (meth)acrylic polymer (B) [that is, the specific (meth)acrylic polymer] is not particularly limited. The specific (meth)acrylic polymer can be produced, for example, by known polymerization methods typified by solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization, by polymerizing the monomers described above. As the polymerization method, the solution polymerization method is preferable in that the treatment process is relatively simple and can be carried out in a short time when preparing the pressure-sensitive adhesive composition of the present disclosure after production.

[0089] In the solution polymerization method, generally, a predetermined organic solvent, monomer, polymerization initiator, and a chain transfer agent used as necessary are charged into a polymerization tank, and for example, heated and reacted with stirring for several hours at the reflux temperature of the organic solvent. In this case, at least a part of the organic solvent, monomer, polymerization initiator, and a chain transfer agent used as necessary may be sequentially added. Further, the reaction may be carried out in a nitrogen stream.

[0090] Examples of the organic solvent used during the polymerization reaction include aromatic hydrocarbon compounds, aliphatic hydrocarbon compounds, alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, and alcohol compounds. As the organic solvent used during the polymerization reaction, more specifically, for example, aromatic hydrocarbon compounds typified by benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha; aliphatic or alicyclic hydrocarbon compounds typified by n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and turpentine oil; ester compounds typified by methyl acetate, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; ketone compounds typified by acetone, methyl ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohexanone; glycol ether compounds typified by ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; and alcohol compounds typified by methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol can be mentioned.

[0091] In the production of a specific (meth)acrylic polymer, it is preferable to use an organic solvent that hardly causes chain transfer during the polymerization reaction, such as an aromatic hydrocarbon compound, an ester compound, or a ketone compound. In particular, from the viewpoints of the solubility of the specific (meth)acrylic polymer and the ease of the polymerization reaction, etc., it is preferable to use methyl acetate and / or ethyl acetate.

[0092] During the polymerization reaction, only one type of organic solvent may be used, or two or more types may be used.

[0093] As the polymerization initiator, for example, organic peroxides and azo compounds used in ordinary solution polymerization methods can be mentioned. Specific examples of the organic peroxide include t-butyl peroxy-2-ethylhexanoate, t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxy pivalate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane. Specific examples of the azo compound include 2,2'-azobisisobutyronitrile [AIBN], 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN], 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), and 2,2'-azobis(isobutyric acid) dimethyl.

[0094] During the polymerization reaction, only one type of polymerization initiator may be used, or two or more types may be used.

[0095] The amount of the polymerization initiator used is not particularly limited and can be appropriately set, for example, according to the molecular weight of the target specific (meth)acrylic polymer.

[0096] When producing the specific (meth)acrylic polymer, a chain transfer agent may be used if necessary. Examples of the chain transfer agent include cyanoacetic acid, an alkyl ester compound of cyanoacetic acid having 1 to 8 carbon atoms, bromoacetic acid, an alkyl ester compound of bromoacetic acid having 1 to 8 carbon atoms, α-methylstyrene, anthracene, phenanthrene, an aromatic compound represented by fluorene and 9-phenylfluorene, an aromatic nitro compound represented by p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol and p-nitrotoluene, a benzoquinone derivative represented by benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, a borane derivative represented by tributylborane, carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane and a halogenated hydrocarbon compound represented by 3-chloro-1-propene, an aldehyde compound represented by chloral and furfuraldehyde, an alkyl mercaptan compound having 1 to 18 carbon atoms, an aromatic mercaptan compound represented by thiophenol and toluene mercaptan, mercaptoacetic acid, an alkyl ester compound of mercaptoacetic acid having 1 to 10 carbon atoms, a hydroxyalkyl mercaptan compound having 1 to 12 carbon atoms, and a terpene compound represented by pinene and terpinolene.

[0097] When a chain transfer agent is used in the production of a specific (meth)acrylic polymer, the amount of the chain transfer agent used is not particularly limited and can be appropriately set according to, for example, the molecular weight of the target specific (meth)acrylic polymer.

[0098] The polymerization temperature is not particularly limited and can be appropriately set according to, for example, the molecular weight of the target specific (meth)acrylic polymer.

[0099] [Chelating crosslinking agent (C)] The pressure-sensitive adhesive composition of the present disclosure contains a chelating crosslinking agent (C). The type of the chelating crosslinking agent is not particularly limited. Examples of the chelate crosslinking agent include metal chelate compounds such as aluminum chelate compounds, titanium chelate compounds, zirconium chelate compounds, and cobalt chelate compounds. The chelate crosslinking agent preferably contains at least one selected from the group consisting of an aluminum chelate compound and a zirconium chelate compound, and more preferably is at least one selected from the group consisting of an aluminum chelate compound and a zirconium chelate compound. Specific examples of the aluminum chelate compound include aluminum monoacetylacetonate bis(ethylacetoacetate), aluminum tris(ethylacetoacetate), and aluminum tris(acetylacetonate). Specific examples of the zirconium chelate compound include zirconium acetylacetonate.

[0100] Commercially available products can be used as the chelate crosslinking agent. Examples of commercially available products of the chelate crosslinking agent include "Alumikrate A", "Alumikrate D", and "ALCH-TR" [all manufactured by Kawaken Fine Chemicals Co., Ltd.], and "Narsem (registered trademark) Zirconium" [manufactured by Nippon Chemical Industry Co., Ltd.].

[0101] The pressure-sensitive adhesive composition of the present disclosure may contain only one kind of chelate crosslinking agent or may contain two or more kinds.

[0102] The content of the chelate crosslinking agent (C) in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited. For example, it is preferably 0.05 parts by mass to 0.50 parts by mass, more preferably 0.10 parts by mass to 0.40 parts by mass, still more preferably 0.15 parts by mass to 0.30 parts by mass, and particularly preferably 0.15 parts by mass to 0.25 parts by mass with respect to 100 parts by mass of the specific (meth)acrylic polymer (A). When the content of the chelate crosslinking agent (C) in the pressure-sensitive adhesive composition of the present disclosure is 0.05 parts by mass or more with respect to 100 parts by mass of the specific (meth)acrylic polymer (A), a sufficient crosslinked structure can be formed in the pressure-sensitive adhesive layer, so that the high-temperature shear strain of the pressure-sensitive adhesive layer does not tend to become excessively high. On the other hand, when the content of the chelate crosslinking agent (C) in the pressure-sensitive adhesive composition of the present disclosure is 0.50 parts by mass or less with respect to 100 parts by mass of the specific (meth)acrylic polymer (A), the crosslinked structure of the pressure-sensitive adhesive layer does not become too dense, so that the pressure-sensitive adhesive layer tends to exhibit a sufficiently high high-temperature adhesive force. When the content of the chelate crosslinking agent (C) in the pressure-sensitive adhesive composition of the present disclosure is within the above range with respect to 100 parts by mass of the specific (meth)acrylic polymer (A), the formed pressure-sensitive adhesive layer has a better balance between low high-temperature shear strain and high high-temperature adhesive force, and tends to be more excellent in heat shock durability in a bent state.

[0103] 〔Organic solvent〕 The pressure-sensitive adhesive composition of the present disclosure may contain an organic solvent. When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, the coatability can be improved. Examples of the organic solvent include the same ones as those used in the polymerization reaction of the above-mentioned specific (meth)acrylic polymer.

[0104] When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, it may contain only one kind of organic solvent or two or more kinds of organic solvents.

[0105] When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, the content of the organic solvent is not particularly limited and can be appropriately set according to the purpose.

[0106] 〔Other components〕 The pressure-sensitive adhesive composition of the present disclosure may contain components other than the above-described components (so-called other components) as necessary, as long as the effects thereof are not impaired. Examples of other components include polymers other than the specific (meth)acrylic polymer, crosslinking agents other than chelate crosslinking agents, crosslinking catalysts, antioxidants, colorants (e.g., dyes and pigments), light stabilizers (e.g., ultraviolet absorbers), antistatic agents, silane coupling agents, and various other additives.

[0107] When the pressure-sensitive adhesive composition of the present disclosure contains other components, the content of the other components can be appropriately set as long as the effects of the pressure-sensitive adhesive composition of the present disclosure are not impaired.

[0108] <<Physical properties>> When a pressure-sensitive adhesive layer is formed, the pressure-sensitive adhesive composition of the present disclosure preferably has a shear strain at 100°C of less than 80% and an adhesive force at 100°C of 2.0 N / 25 mm or more. More preferably, the shear strain at 100°C is less than 70% and the adhesive force at 100°C is 2.5 N / 25 mm or more. Even more preferably, the shear strain at 100°C is less than 60% and the adhesive force at 100°C is 3.0 N / 25 mm or more. A pressure-sensitive adhesive layer having the above physical properties tends to have better heat shock durability in a bent state.

[0109] The shear strain of the pressure-sensitive adhesive layer at 100°C is a value obtained by the following method. Using a dynamic viscoelasticity measuring device as the measuring apparatus, the deformation amount (unit: m) of the pressure-sensitive adhesive layer when a load of 200 Pa is applied for 3 minutes using an 8 mmφ cone in an environment with an ambient temperature of 100°C is measured for a pressure-sensitive adhesive layer with a thickness of 400 μm. Then, based on the following calculation formula, the shear strain (unit: %) is obtained. Shear strain (unit: %) = Deformation amount of the pressure-sensitive adhesive layer (unit: m) / Thickness of the pressure-sensitive adhesive layer (unit: m) × 100 The dynamic viscoelasticity measuring device is not particularly limited. For example, Physica MCR301 (trade name) manufactured by Anton Paar can be preferably used. However, the dynamic viscoelasticity measuring device is not limited to this.

[0110] The adhesive strength of the adhesive layer at 100 °C is the value measured by the following method. The pressure-sensitive adhesive composition of the present disclosure is applied to the easily peelable treatment surface of the release film to form a coating film. The coating amount of the pressure-sensitive adhesive composition is set to an amount such that the thickness of the pressure-sensitive adhesive film described later becomes 20 μm. Next, the formed coating film is dried to form a pressure-sensitive adhesive film on the release film. The exposed surface of the formed pressure-sensitive adhesive film and the polyimide film are overlapped and bonded together. The laminate obtained by the bonding is allowed to stand in an environment of an ambient temperature of 25 °C and 50% RH for 168 hours to cure the pressure-sensitive adhesive film, and a pressure-sensitive adhesive sheet having a structure of release film / pressure-sensitive adhesive layer / polyimide film is produced. The release film of the produced pressure-sensitive adhesive sheet is peeled off. The surface of the pressure-sensitive adhesive layer exposed by the peeling is pressure-bonded to one surface of a separately prepared polyimide film using a 2 kg roller to obtain a laminate having a structure of polyimide film / pressure-sensitive adhesive layer / polyimide film. The obtained laminate is autoclave-treated under the conditions of a treatment temperature of 50 °C and a treatment pressure of 5 kg / cm 2 for 20 minutes. After cutting the laminate after the autoclave treatment into a size of 25 mm × 150 mm, it is allowed to stand in an environment of an ambient temperature of 25 °C and 50% RH for 24 hours to obtain a measurement sample. The measurement sample is allowed to stand in an environment of an ambient temperature of 100 °C for 10 minutes. Using the measurement sample after this standing, in an environment of an ambient temperature of 100 °C, the adhesive strength (unit: N / 25 mm) when the pressure-sensitive adhesive layer is T-peel peeled from the polyimide film in the long side (150 mm) direction at a peeling speed of 300 mm / min is measured. As the universal material testing machine, for example, RTF-1350 (model number) manufactured by A&D Company, Limited can be preferably used. However, the universal material testing machine is not limited thereto.

[0111] <<Use>> The pressure-sensitive adhesive composition of the present disclosure can form a pressure-sensitive adhesive layer excellent in heat shock durability in a bent state, and thus is suitable as a pressure-sensitive adhesive composition used for a flexible display. Specific uses of the pressure-sensitive adhesive composition of the present disclosure include applications for bonding an optical film for a flexible display and a substrate for a flexible display, applications for bonding optical films for a flexible display to each other, and the like.

[0112] [Adhesive Sheet for Flexible Display] The pressure-sensitive adhesive sheet for a flexible display of the present disclosure (hereinafter, also simply referred to as "adhesive sheet") includes a pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition of the present disclosure. The adhesive sheet of the present disclosure also includes the sheet-shaped pressure-sensitive adhesive layer itself formed of the pressure-sensitive adhesive composition of the present disclosure.

[0113] The pressure-sensitive adhesive layer included in the pressure-sensitive adhesive sheet of the present disclosure contains a cured product of the pressure-sensitive adhesive composition of the present disclosure. The cured product includes, for example, a crosslinked product of a specific (meth)acrylic polymer (A) crosslinked and cured with a chelate-based crosslinking agent (C). Since the pressure-sensitive adhesive sheet of the present disclosure includes a pressure-sensitive adhesive layer formed of the above-described pressure-sensitive adhesive composition of the present disclosure, it is excellent in heat shock durability in a bent state. Specifically, in the pressure-sensitive adhesive sheet of the present disclosure, floating, peeling, whitening, and foaming that may occur when placed in an environment where low temperature and high temperature are repeated are likely to be well suppressed. The pressure-sensitive adhesive sheet of the present disclosure is suitable as a pressure-sensitive adhesive sheet used for a flexible display.

[0114] The thickness of the pressure-sensitive adhesive layer included in the pressure-sensitive adhesive sheet of the present disclosure is not particularly limited. Generally, the thickness of the pressure-sensitive adhesive layer is 1 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm.

[0115] In the present disclosure, the "thickness of the pressure-sensitive adhesive layer" means the average thickness of the pressure-sensitive adhesive layer. The average thickness of the pressure-sensitive adhesive layer is a value obtained by the following method. The thicknesses of 10 randomly selected locations in the thickness direction of the adhesive layer are measured using a film thickness gauge. The arithmetic mean value of the measured values is obtained, and the resulting value is taken as the average thickness of the adhesive layer.

[0116] The adhesive sheet of the present disclosure may be a substrate-free type adhesive sheet without a substrate, or may be a substrate type adhesive sheet provided with an adhesive layer on one or both sides of the substrate. When the adhesive sheet of the present disclosure is a substrate-free type adhesive sheet without a substrate, or when it is a substrate type adhesive sheet provided with an adhesive layer on one side of the substrate, in the adhesive sheet of the present disclosure, the exposed surface of the adhesive layer may be protected by a release sheet. Generally, the release sheet protects the surface of the adhesive layer until the adhesive sheet is put into practical use and is peeled off during use.

[0117] The release sheet is not particularly limited as long as it can be easily peeled off from the adhesive layer. Examples of the release sheet include a resin film, paper, synthetic paper, and a composite sheet obtained by laminating two or more of these, which are surface-treated (so-called easy-peeling treatment) with a release treatment agent on one or both sides. In the present disclosure, a release sheet in a form in which one or both sides of a resin film are surface-treated (so-called easy-peeling treatment) with a release treatment agent is also referred to as a "release film". Examples of the release treatment agent include silicone-based release treatment agents (e.g., silicone), wax-based release treatment agents (e.g., paraffin wax), and fluorine-based release treatment agents (e.g., fluorine-based resins). Examples of the resin film include polyester films typified by polyethylene terephthalate (PET) films. Examples of the paper include high-quality paper and coated paper. The thickness of the release sheet is not particularly limited and is generally 20 μm to 180 μm. <>

[0118] When the pressure-sensitive adhesive sheet of the present disclosure includes a base material, the base material is not particularly limited as long as it has flexibility applicable to a flexible display and an adhesive layer can be formed thereon. Examples of the base material include films containing resins such as polyolefin resins [e.g., polyethylene (PE) and polypropylene (PP)], polyester resins [e.g., polyethylene terephthalate (PET)], acetate resins (e.g., triacetyl cellulose), polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyurethane resins, (meth)acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene) resins, and fluorine resins.

[0119] From the viewpoint of improving the adhesion between the base material and the adhesive layer, the surface of the base material on the side where the adhesive layer is provided may be subjected to surface treatment such as corona discharge treatment and plasma discharge treatment (so-called easy adhesion treatment).

[0120] The base material may contain various additives such as plasticizers, colorants (e.g., dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, antioxidants, and fillers. The base material may be patterned in part or in whole.

[0121] When the pressure-sensitive adhesive sheet of the present disclosure includes a base material, the base material may be an optical film. Examples of the optical film include a polarizing plate, an AG (Anti-Glare) polarizing plate, a wavelength plate (e.g., a 1 / 2 wavelength plate and a 1 / 4 wavelength plate), a retardation film including the above wavelength plate, a viewing angle compensation film, an optical compensation film, a brightness enhancement film, a light guide plate, a reflective film, an antireflection film, a prism sheet, a lens sheet, a diffusion plate, and a transparent conductive film.

[0122] The thickness of the base material is not particularly limited. However, from the perspective of application to a flexible display, for example, it is preferably 10 μm to 300 μm, more preferably 10 μm to 200 μm, and even more preferably 10 μm to 100 μm.

[0123] In the present disclosure, the "thickness of the base material" means the average thickness of the base material. The average thickness of the base material is a value obtained by the following method. The thicknesses at 10 randomly selected locations in the thickness direction of the base material are measured using a film thickness gauge. The arithmetic mean value of the measured values is obtained, and the resulting value is taken as the average thickness of the base material.

[0124] [Method for producing an adhesive sheet] The method for producing the adhesive sheet of the present disclosure is not particularly limited. The adhesive sheet of the present disclosure can be produced by a known method. Examples of the method for producing the adhesive sheet of the present disclosure include the following methods.

[0125] When the adhesive sheet of the present disclosure is a non-base material type adhesive sheet, first, the adhesive composition of the present disclosure is applied to the easily peelable treatment surface of the release sheet to form a coating film on the release sheet. Next, the formed coating film is dried to form an adhesive film on the release sheet. Next, the exposed surface of the formed adhesive film is overlapped and bonded to the easily peelable treatment surface of a separately prepared release sheet, and then, if necessary, curing is performed to produce the adhesive sheet of the present disclosure having a laminated structure of release sheet / adhesive layer / release sheet.

[0126] When the pressure-sensitive adhesive sheet of the present disclosure is a pressure-sensitive adhesive sheet of the substrate type, first, a coating film is formed on the substrate by applying the pressure-sensitive adhesive composition of the present disclosure to one surface of the substrate (preferably, the easily adherable treated surface). Next, the formed coating film is dried to form a pressure-sensitive adhesive film on the substrate. Next, the exposed surface of the formed pressure-sensitive adhesive film is overlapped and bonded to the easily peelable treated surface of the release sheet, and then, if necessary, curing is performed to produce the pressure-sensitive adhesive sheet of the present disclosure having a laminated structure of substrate / pressure-sensitive adhesive layer / release sheet.

[0127] When the pressure-sensitive adhesive sheet of the present disclosure is a pressure-sensitive adhesive sheet of the substrate type, as another method, for example, the following method can also be mentioned. A coating film is formed on the release sheet by applying the pressure-sensitive adhesive composition of the present disclosure to the easily peelable treated surface of the release sheet. Next, the formed coating film is dried to form a pressure-sensitive adhesive film on the release sheet. Next, the exposed surface of the formed pressure-sensitive adhesive film is overlapped and bonded to one surface of the substrate (preferably, the easily adherable treated surface), and then, if necessary, curing is performed to produce the pressure-sensitive adhesive sheet of the present disclosure having a laminated structure of substrate / pressure-sensitive adhesive layer / release sheet.

[0128] The coating method of the pressure-sensitive adhesive composition is not particularly limited. Examples of the coating method of the pressure-sensitive adhesive composition include known methods using a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a knife coater, a spray coater, a bar coater, an applicator, etc. The coating amount of the pressure-sensitive adhesive composition is not particularly limited and is appropriately set according to, for example, the thickness of the pressure-sensitive adhesive layer to be formed.

[0129] The drying method of the coating film is not particularly limited. Examples of the drying method of the coating film include methods such as natural drying, heat drying, hot air drying, and vacuum drying. The drying temperature and drying time of the coating film are not particularly limited and are appropriately set according to the thickness of the coating film, the amount of the organic solvent in the coating film, etc. As an example of the drying conditions, there is a condition in which air at 60°C to 130°C is blown for 30 seconds to 300 seconds at a wind speed of 3 m / s to 5 m / s using a hot air circulation dryer for drying.

[0130] As a curing method, for example, there is a method of allowing it to stand for 2 days to 7 days in an environment with an ambient temperature of 20°C to 35°C and a relative humidity of 45% to 55%.

[0131] [Optical member for flexible display] The optical member for a flexible display of the present disclosure (hereinafter, also simply referred to as "optical member") includes an adhesive layer formed of the adhesive composition of the present disclosure described above. Since the optical member of the present disclosure includes an adhesive layer formed of the adhesive composition of the present disclosure described above, it is excellent in heat shock durability in a bent state. Specifically, in the optical member of the present disclosure, floating, peeling, whitening, and foaming that may occur when placed in an environment where low temperature and high temperature are repeated are favorably suppressed. The optical member of the present disclosure is suitable as an optical member used for a flexible display.

[0132] The adhesive layer in the optical member of the present disclosure has the same meaning as the adhesive layer in the adhesive sheet of the present disclosure, and since the preferred embodiments are also the same, the description is omitted here.

[0133] The optical member of the present disclosure may, for example, include a substrate, an adhesive layer formed of the adhesive composition of the present disclosure described above, and an optical film in this order. Examples of the substrate include a resin substrate and a glass substrate. Examples of the resin substrate include a resin film containing a resin such as polyimide or polyester. Examples of the glass substrate include a soda glass plate, a non-alkali glass plate, and a glass plate with an ITO (Indium Tin Oxide) film. The thickness of the substrate is not particularly limited, but for example, from the viewpoint of application to a flexible display, it is preferably 0.02 mm to 0.70 mm.

[0134] Since the optical film in the optical member of the present disclosure is the same as the optical film described in the section of the adhesive sheet of the present disclosure, the description thereof is omitted here.

[0135] The manufacturing method of the optical member of the present disclosure is not particularly limited. The optical member of the present disclosure can be manufactured, for example, by using an optical film as a base material, producing the adhesive sheet of the present disclosure by the method described above, and then bonding the adhesive layer of the adhesive sheet and a substrate together.

[0136] [Display device] The display device of the present disclosure includes the optical member of the present disclosure described above. Since the display device of the present disclosure includes the optical member of the present disclosure, it is excellent in heat shock durability in a bent state. Specifically, in the display device of the present disclosure, lifting, peeling, whitening, and foaming that may occur when placed in an environment where low temperature and high temperature are repeated are likely to be well suppressed.

[0137] Examples of the display device include, for example, a flexible display of liquid crystal or organic EL (Electro-Luminescence). [Example]

[0138] Hereinafter, the adhesive composition of the present disclosure will be described more specifically with reference to examples. The present disclosure is not limited to the following examples as long as the gist thereof is not exceeded.

[0139] [Production of (meth)acrylic polymer (A)] [Production Example A-1] Into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 90.0 parts by mass of 2-ethylhexyl acrylate [2EHA; an alkyl acrylate monomer], 6.8 parts by mass of n-butyl acrylate [n-BA; an alkyl acrylate monomer], 3.0 parts by mass of 2-hydroxyethyl acrylate [2HEA; a monomer having a hydroxyl group], 0.2 parts by mass of acrylic acid [AA; a monomer having a carboxyl group], and 70.0 parts by mass of ethyl acetate [an organic solvent] were placed and mixed to obtain a mixture. Then, the inside of the reactor was purged with nitrogen. Next, while stirring the mixture in the reactor, the temperature was raised to 70°C, and then 0.02 parts by mass of 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN; a polymerization initiator] and 120.0 parts by mass of ethyl acetate were sequentially added to the mixture in the reactor. After the addition was completed, the mixture was held for 6 hours to cause a polymerization reaction to obtain a polymerization reaction product. The obtained polymerization reaction product was diluted with ethyl acetate to a solid content concentration of 18.5% by mass, and then cooled to obtain a solution of (meth)acrylic polymer A-1.

[0140] As used herein, the "solid content concentration" means the mass ratio of the (meth)acrylic polymer A-1 in the solution of the (meth)acrylic polymer A-1. The same applies to the solutions of the (meth)acrylic polymers A-2 to A-16 produced below.

[0141] 〔Production Examples A-2 to A-12, A-14, and A-15〕 In Production Examples A-2 to A-12, A-14, and A-15, the monomer composition of the (meth)acrylic polymer (A) was changed to the monomer composition shown in Table 1, and the amount of the organic solvent used was adjusted to adjust the weight average molecular weight of the (meth)acrylic polymer (A) to the weight average molecular weight shown in Table 1. Otherwise, the same operations as in Production Example A-1 were performed to obtain solutions of the (meth)acrylic polymers A-2 to A-12, A-14, and A-15 having a solid content concentration of 18.5% by mass.

[0142] 〔Production Examples A-13 and A-16〕 In Production Examples A-13 and A-16, the same operations as in Production Example A-1 were carried out, except that at least one of the amount of the organic solvent used and the amount of the polymerization initiator used was adjusted so that the weight-average molecular weight of the (meth)acrylic polymer (A) was adjusted to the weight-average molecular weight shown in Table 1, and solutions of (meth)acrylic polymers A-13 and A-16 with a solid content concentration of 18.5% by mass were obtained.

[0143] Table 1 shows the monomer compositions [unit: mass%], glass transition temperatures (Tg) [unit: °C], and weight-average molecular weights (Mw) of the (meth)acrylic polymers A-1 to A-16.

[0144] The glass transition temperatures of the (meth)acrylic polymers A-1 to A-16 were determined by the same method as the method for determining the glass transition temperature of the specific (meth)acrylic polymer (A) described above. The weight-average molecular weights of the (meth)acrylic polymers A-1 to A-16 were measured by the same method as the method for measuring the weight-average molecular weight of the specific (meth)acrylic polymer (A) described above.

[0145] Among the (meth)acrylic polymers A-1 to A-16, the (meth)acrylic polymers A-1 to A-13 correspond to the specific (meth)acrylic polymer (A) in the present disclosure.

[0146]

Table 1

[0147] Details of each monomer described in Table 1 are as shown below. <(meth)acrylic acid alkyl ester monomer> "2EHA": 2-ethylhexyl acrylate (number of carbon atoms in the alkyl moiety: 8) "n-BA": n-butyl acrylate (number of carbon atoms in the alkyl moiety: 4) "MA": methyl acrylate (number of carbon atoms in the alkyl moiety: 1) "n-BMA": n-butyl methacrylate (number of carbon atoms in the alkyl moiety: 4) <(Meth)acrylic acid alkoxyalkyl ester monomer> "2MTA": 2-methoxyethyl acrylate (number of carbon atoms in the alkoxy moiety: 1) <Monomer having a hydroxyl group> "2HEA": 2-hydroxyethyl acrylate "2HEMA": 2-hydroxyethyl methacrylate "4HBA": 4-hydroxybutyl acrylate <Monomer having a carboxy group> "AA": acrylic acid

[0148] In Table 1, the "-" described in the column of monomer composition means that the monomer corresponding to that column is not used.

[0149] [Production of (meth)acrylic polymer (B)] [Production Example B-1] Into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 92.7 parts by mass of cyclohexyl methacrylate [CHMA; monomer having an alicyclic alkyl group], 7.0 parts by mass of 2-ethylhexyl methacrylate [2EHMA; monomer having an aliphatic alkyl group], 0.3 parts by mass of 2-hydroxyethyl methacrylate [2HEMA; monomer having a hydroxyl group], and 50.0 parts by mass of ethyl acetate [organic solvent] were placed and mixed to obtain a mixture. Then, the inside of the reactor was purged with nitrogen. Next, after heating the mixture in the reactor to 70°C with stirring, 1.0 part by mass of 2,2'-azobis(isobutyric acid) dimethyl [V-601; polymerization initiator] and 20.0 parts by mass of ethyl acetate were sequentially added to the mixture in the reactor. After completion of the addition, the mixture was held for 6 hours to cause a polymerization reaction to obtain a polymerization reaction product. The obtained polymerization reaction product was diluted with ethyl acetate to a solid content concentration of 40.0% by mass, and then cooled to obtain a solution of (meth)acrylic polymer B-1.

[0150] The "solid content concentration" referred to here means the mass ratio of (meth)acrylic polymer B-1 in the solution of (meth)acrylic polymer B-1. The same applies to each solution of (meth)acrylic polymers B-2 to B-12 produced below.

[0151] [Production Examples B-2 to B-4 and B-7 to B-11] In Production Examples B-2 to B-4 and B-7 to B-11, the same operations as in Production Example B-1 were carried out except that the monomer composition of the (meth)acrylic polymer (B) was changed to the monomer composition shown in Table 2, and solutions of the (meth)acrylic polymers B-2 to B-4 and B-7 to B-11 with a solid content concentration of 40.0 mass% were obtained.

[0152] [Production Examples B-5, B-6 and B-12] In Production Examples B-5, B-6 and B-12, the same operations as in Production Example B-1 were carried out except that at least one of the amount of the organic solvent used and the amount of the polymerization initiator used was adjusted so that the weight average molecular weight of the (meth)acrylic polymer (B) was adjusted to the weight average molecular weight shown in Table 2, and solutions of the (meth)acrylic polymers B-5, B-6 and B-12 with a solid content concentration of 40.0 mass% were obtained.

[0153] The monomer composition [unit: mass%], glass transition temperature (Tg) [unit: °C], and weight average molecular weight (Mw) of the (meth)acrylic polymers B-1 to B-12 are shown in Table 2.

[0154] The glass transition temperatures of the (meth)acrylic polymers B-1 to B-12 were determined by the same method as the method for determining the glass transition temperature of the specific (meth)acrylic polymer (A) described above. The weight average molecular weights of the (meth)acrylic polymers B-1 to B-12 were measured by the same method as the method for measuring the weight average molecular weight of the specific (meth)acrylic polymer (A) described above.

[0155] Among the (meth)acrylic polymers B-1 to B-12, the (meth)acrylic polymers B-1 to B-9 correspond to the specific (meth)acrylic polymer (B) in the present disclosure.

[0156] [Table 2]

[0157] The details of each monomer described in Table 2 are as follows. <Monomer with an alicyclic alkyl group> "CHMA": cyclohexyl methacrylate "IBXA": isobornyl acrylate <Monomer with a hydroxyl group> "2HEMA": 2-hydroxyethyl methacrylate <Monomer with a carboxy group> "MAA": methacrylic acid <Other monomers> "t-BMA": t-butyl methacrylate "2EHMA": 2-ethylhexyl methacrylate

[0158] In Table 2, "-" described in the column of monomer composition means that the corresponding monomer is not used in that column.

[0159] [Preparation of Adhesive Composition] [Example 1] 540.50 parts by mass of a solution of (meth)acrylic polymer A-1 (100 parts by mass as solid content), 24.32 parts by mass of a solution of (meth)acrylic polymer B-1 (10 parts by mass as solid content), 0.19 part by mass of aluminum chelate A [trade name, aluminum chelate compound, solid content concentration: 100% by mass, manufactured by Kawaken Fine Chemicals Co., Ltd.] as chelate crosslinking agent (C) (0.2 part by mass as solid content), and an appropriate amount of ethyl acetate [organic solvent] were thoroughly mixed to obtain the adhesive composition of Example 1.

[0160] [Examples 2 to 13] In Examples 2 to 13, the same operations as in Example 1 were carried out except that the composition of the adhesive composition was changed to the composition shown in Table 3, and the adhesive compositions of Examples 2 to 13 were obtained.

[0161] [Examples 14 to 28] In Examples 14 to 28, the same operations as in Example 1 were carried out except that the composition of the adhesive composition was changed to the composition shown in Table 4, and the adhesive compositions of Examples 14 to 28 were obtained.

[0162] [Comparative Examples 1 to 8] In Comparative Examples 1 to 8, the same operations as in Example 1 were carried out except that the composition of the pressure-sensitive adhesive composition was changed to the composition shown in Table 5, and each pressure-sensitive adhesive composition of Comparative Examples 1 to 8 was obtained.

[0163] [Preparation of Test Samples] The pressure-sensitive adhesive composition prepared above was applied to the easily peelable treatment surface of a release film (trade name: Film Bina (registered trademark) 100E-0010 No. 23, thickness: 100 μm, manufactured by Fujimori Kogyo Co., Ltd.) surface-treated with a silicone-based release treatment agent (so-called easy-release treatment) to form a coating film. The coating amount of the pressure-sensitive adhesive composition was set to an amount such that the thickness of the adhesive film described later would be 20 μm. Next, the formed coating film was dried by blowing air at 100 °C at a wind speed of 3 m / s for 60 seconds using a hot air circulation dryer to form an adhesive film with a thickness of 20 μm on the release film. Next, the exposed surface of the formed adhesive film was overlapped and bonded with a polyimide (PI) film (trade name: Kapton (registered trademark) 100H, manufactured by Toray DuPont Co., Ltd.). Next, the laminate obtained by the bonding was allowed to stand for 168 hours in an environment of an ambient temperature of 25 °C and 50% RH to cure the adhesive film. In this way, a test sample having a structure of release film / pressure-sensitive adhesive layer / PI film (hereinafter referred to as "PI with pressure-sensitive adhesive layer") was prepared.

[0164] [Measurement and Evaluation] 1. High-temperature Adhesion The release film of the PI with pressure-sensitive adhesive layer (structure: release film / pressure-sensitive adhesive layer / PI film) prepared above was peeled off. The surface of the pressure-sensitive adhesive layer exposed by the peeling was pressure-bonded to one surface of a PI film (X) (trade name: Kapton (registered trademark) 100H, manufactured by Toray DuPont Co., Ltd.) using a 2 kg roller to obtain a laminate having a structure of PI film (X) / pressure-sensitive adhesive layer / PI film. The obtained laminate was subjected to a treatment temperature of 50 °C and a treatment pressure of 5 kg / cm 2It was subjected to autoclave treatment for 20 minutes under the specified conditions. After the laminate after autoclave treatment was cut into a size of 25 mm × 150 mm, it was left standing for 24 hours in an environment with an ambient temperature of 25°C and 50% RH to obtain a sample for measuring adhesive strength. The sample for measuring adhesive strength was left standing for 10 minutes in an environment with an ambient temperature of 100°C. Using this sample for measuring adhesive strength after standing, the adhesive strength (so-called high-temperature adhesive strength) (unit: N / 25 mm) when the adhesive layer was T-peel peeled from the PI film (X) in the long-side (150 mm) direction under the condition of a peeling rate of 300 mm / min in an environment with an ambient temperature of 100°C was measured. As the measuring apparatus for the high-temperature adhesive strength, a universal material testing machine (model number: RTF-1350) manufactured by A&D Company, Limited was used. The measured values of the high-temperature adhesive strength are shown in Tables 3 to 5.

[0165] 2. High-temperature shear strain On the easily peelable treatment surface of a release film surface-treated (so-called, easy peel treatment) with a silicone-based release treatment agent [Product name: Film Bina (registered trademark) 100E-0010 No. 23, thickness: 100 μm, manufactured by Fujimori Kogyo Co., Ltd.], the adhesive composition prepared above was applied to form a coating film. The coating amount of the adhesive composition was set to an amount such that the thickness of the adhesive film described later would be 25 μm. Next, with respect to the formed coating film, using a hot air circulation dryer, air at 100 °C was blown at a wind speed of 3 m / sec for 120 seconds to dry the coating film, and an adhesive film with a thickness of 25 μm was formed on the release film. Next, the exposed surface of the formed adhesive film and the easily peelable treatment surface of a separately prepared release film [Product name: Film Bina (registered trademark) 100E-0010 No. 23, thickness: 100 μm, manufactured by Fujimori Kogyo Co., Ltd.] were overlapped and bonded. Next, the laminate obtained by the bonding was allowed to stand in an environment of an ambient temperature of 25 °C and 50% RH for 168 hours to cure the adhesive film. In this way, a non-substrate type adhesive sheet having a structure of release film / adhesive layer / release film was produced. Next, the release film of the non-substrate type adhesive sheet was peeled off, and the obtained adhesive layers were overlapped to obtain an adhesive layer with a thickness of 400 μm. With respect to this adhesive layer, using a dynamic viscoelasticity measuring device [Product name: Physica MCR301, manufactured by Anton Paar], in an environment of an ambient temperature of 100 °C, when a load of 200 Pa was applied for 3 minutes using an 8 mmφ cone, the deformation amount (unit: m) of the adhesive layer was measured. Then, based on the following calculation formula, the shear strain (unit: %) was obtained. Shear strain (unit: %) = Deformation amount of the adhesive layer (unit: m) / Thickness of the adhesive layer (unit: m) × 100 The values of the shear strain (so-called, high-temperature shear strain) of the adhesive layer at 100 °C are shown in Tables 3 to 5.

[0166] 3. Heat shock durability in the bent state The PI with an adhesive layer prepared above was cut into a size of 25 mm × 150 mm. Next, the release film of the cut PI with an adhesive layer (structure: release film / adhesive layer / PI film) was peeled off. The surface of the adhesive layer exposed by peeling was pressure-bonded to one surface of a PI film (X) [trade name: Kapton (registered trademark) 100H, manufactured by Toray DuPont Co., Ltd.] using a 2 kg roller to obtain a laminate having a structure of PI film (X) / adhesive layer / PI film. The obtained laminate was used as a sample for evaluation. The evaluation sample was bent at a radius of curvature (R) = 3 mm. Next, with respect to the evaluation sample in the bent state, using a thermal shock device [model: TSA-301L-W, manufactured by Espec Corporation], after standing in an environment with an ambient temperature of -30°C for 30 minutes, an operation of standing in an environment with an ambient temperature of 100°C for 30 minutes was defined as one cycle, and a test of repeating this operation 300 times was performed. Immediately after the test, the evaluation sample in the bent state was completely flattened and left standing in an environment with an ambient temperature of 25°C. Then, immediately after standing in an environment with an ambient temperature of 25°C (i.e., immediately after the test), 1 hour after standing, 24 hours after standing, and 72 hours after standing, the bent portion of the evaluation sample was observed using a magnifying glass, and the heat shock durability of the adhesive layer in the bent state was evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 3 to 5. If the evaluation result was "AA", "A", "B", or "C", it was determined that there was no problem in practical use. The evaluation result being "AA" was most preferred.

[0167] - Evaluation Criteria - AA: No change was confirmed before and after the test. A: Immediately after the test, at least one of the phenomena of lifting, peeling, whitening, and foaming was slightly confirmed, but the confirmed phenomena all disappeared 1 hour after standing in an environment with an ambient temperature of 25°C. B: Immediately after the test, at least one of the phenomena of lifting, peeling, whitening, and foaming was slightly confirmed, and the confirmed phenomena did not disappear 1 hour after standing in an environment with an ambient temperature of 25°C, but all disappeared 24 hours after standing. C: Immediately after the test, at least one of the phenomena of floating, peeling, whitening, and foaming was significantly confirmed, and the confirmed phenomenon had not disappeared 24 hours after being left standing in an environment with an ambient temperature of 25°C, but had all disappeared 72 hours after that. D: Immediately after the test, at least one of the phenomena of floating, peeling, whitening, and foaming was significantly confirmed, and the confirmed phenomenon had not disappeared even 72 hours after being left standing in an environment with an ambient temperature of 25°C.

[0168]

Table 3

[0169]

Table 4

[0170]

Table 5

[0171] The details of the crosslinking agents described in Tables 3 to 5 are as shown below. <Chelating crosslinking agent> "Aluminum chelate A" [trade name, aluminum chelate compound, solid content concentration: 100% by mass, manufactured by Kawaken Fine Chemicals Co., Ltd.] "Narsem zirconium" [trade name, zirconium chelate compound, solid content concentration: 100% by mass, manufactured by Nippon Chemical Industry Co., Ltd.] <Other crosslinking agents> "Desmodur N75 MPA / X" [trade name, biuret-modified hexamethylene diisocyanate compound, solid content concentration: 75% by mass, manufactured by Sumika Covestro Urethane Co., Ltd.] Both the above "Narsem" and "Desmodur" are registered trademarks.

[0172] In Tables 3 to 5, the numerical values described in the "Blending amount" column are all values converted to solid content. In Tables 3 to 5, "-" described in the column of the composition of the pressure-sensitive adhesive composition means that the component corresponding to that column is not blended.

[0173] As shown in Tables 3 and 4, it was confirmed that the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of Examples 1 to 28 were excellent in heat shock durability in the bent state. On the other hand, as shown in Table 5, it was confirmed that the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of Comparative Examples 1 to 8 were inferior in heat shock durability in the bent state compared to the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of the Examples.

Claims

1. A (meth)acrylic polymer (A) containing structural units (a1) derived from a monomer having a hydroxyl group and structural units (a2) derived from a (meth)acrylic acid alkyl ester monomer, having a glass transition temperature of less than -60°C and a weight average molecular weight of 1,000,000 or more, and a (meth)acrylic polymer (B) containing structural units (b1) derived from a monomer having an alicyclic alkyl group, having a glass transition temperature of 60°C or more and a weight average molecular weight of 2,500 to 10,000, and a chelate crosslinking agent (C), and A pressure-sensitive adhesive composition for flexible displays containing the same.

2. The (meth)acrylic polymer (A) contains at least one selected from the group consisting of structural units (a2-1) derived from a (meth)acrylic acid alkyl ester monomer having 1 to 4 carbon atoms in the alkyl moiety and structural units (a3) derived from a (meth)acrylic acid alkoxyalkyl ester monomer having 1 to 4 carbon atoms in the alkoxy moiety, and the total content of the structural units (a2-1) and the structural units (a3) is 1.0% by mass to 10.0% by mass based on all structural units. The pressure-sensitive adhesive composition for flexible displays according to Claim 1.

3. The content of the (meth)acrylic polymer (B) is 1.0 part by mass to 20.0 parts by mass with respect to 100 parts by mass of the (meth)acrylic polymer (A). The pressure-sensitive adhesive composition for flexible displays according to Claim 1.

4. The content of the chelate crosslinking agent (C) is 0.05 part by mass to 0.50 part by mass with respect to 100 parts by mass of the (meth)acrylic polymer (A). The pressure-sensitive adhesive composition for flexible displays according to Claim 1.

5. In the (meth)acrylic polymer (A), the content of the structural unit (a1) is 1.0% by mass to 5.0% by mass based on all structural units. The pressure-sensitive adhesive composition for flexible displays according to Claim 1.

6. The (meth)acrylic polymer (B) does not contain structural units (b2) derived from a monomer having a hydroxyl group, or the content of the structural units (b2) is in the range exceeding 0% by mass and 15.0% by mass or less based on all structural units. The pressure-sensitive adhesive composition for flexible displays according to Claim 1.

7. The pressure-sensitive adhesive composition for a flexible display according to claim 1, wherein when the pressure-sensitive adhesive layer is formed, the shear strain at 100°C is less than 80%, and the adhesive strength at 100°C is 2.0 N / 25 mm or more.

8. A pressure-sensitive adhesive sheet for a flexible display, comprising a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition for a flexible display according to any one of claims 1 to 7.

9. An optical member for a flexible display, comprising a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition for a flexible display according to any one of claims 1 to 7.

10. A display device, comprising the optical member for a flexible display according to claim 9.

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