Acrylic adhesive composition, acrylic adhesive, adhesive film, and flexible device

Abstract

Provided is an acrylic adhesive composition from which an acrylic adhesive, which can exhibit excellent bonding resistance and excellent flexibility to withstand repeated bending in a wide temperature range, can be formed.　This acrylic adhesive composition comprises: an acrylic polymer (P) obtained by polymerizing a monomer component (M); and a crosslinking agent, wherein the monomer component (M) includes alkyl (meth)acrylate (M1) and a polar group-containing monomer (M2), the alkyl (meth)acrylate (M1) includes alkyl (meth)acrylate (m1) having a Tg within the range of -80ºC to -60ºC, the content ratio of the alkyl (meth)acrylate (m1) in the monomer component (M) is at least 50 mass%, and when the content ratios of the polar group-containing monomer (M2) and the crosslinking agent in said acrylic adhesive composition are defined as A mass% and B mass%, respectively, A / B is 40-150.

Description

[Technical Field]

[0001] The present invention relates to an acrylic adhesive composition, an acrylic adhesive, an adhesive film, and a flexible device. [Background technology]

[0002] Adhesive films are used for reinforcing and protecting the surfaces of various shaped components.

[0003] For example, when bonding integrated circuits (ICs) or flexible printed circuit boards (FPCs) to a semiconductor substrate (e.g., a TFT substrate), thermocompression bonding is usually performed using an anisotropic conductive film (ACF). In some cases, when performing such thermocompression bonding, an adhesive film is pre-applied to the back side of the semiconductor substrate for reinforcement (for example, Patent Document 1).

[0004] Furthermore, in recent years, the manufacturing method for so-called flexible devices such as foldable devices and rollable devices, which are undergoing development, generally involves forming a release layer and a flexible film substrate on a support substrate such as glass, forming a TFT substrate on the film substrate, and then forming an organic EL layer on top of that. The support substrate is then peeled off to manufacture the flexible device, but because the flexible display layer is very thin, malfunctions can occur in the device due to handling. For this reason, an adhesive film is sometimes attached to the back side for reinforcement (for example, Patent Document 2).

[0005] Semiconductor element substrates and flexible devices may be repeatedly bent, and if the bending characteristics of the adhesive film bonded to the substrate are poor, the recovery after bending may deteriorate, or in the worst case, the film may break due to repeated bending. Specifically, when an adhesive film is bonded to a bent part (for example, the movable bending part of a folding member), when the adhesive film is bent at an angle, compressive stress acts on the inner diameter side of the bend and tensile stress acts on the outer diameter side of the bend. This causes stress strain in and around the bend, which can lead to damage to the semiconductor element substrate or flexible device.

[0006] One possible solution to the above-mentioned problems is to soften the adhesive contained in the adhesive film to alleviate the stress and strain described above.

[0007] The storage modulus G' is known as an indicator of the softness of adhesives, and techniques have been proposed to design adhesives such that the rate of change in elastic modulus (G'(-20) / G'(40)) × 100, based on the storage modulus G'(-20) at -20°C and the storage modulus G'(40) at 40°C, falls within a predetermined range (Patent Document 3), and that the degree of change in storage modulus, which is the value obtained by dividing the storage modulus G'(-20) at -20°C by the storage modulus G'(85) at 85°C, falls within a predetermined range (Patent Document 4).

[0008] In the examples of Patent Document 3, the following adhesives are reported: an adhesive obtained from 100 parts by mass of (meth)acrylic acid ester polymer (A) with a composition of BA / 2EHA / AA / 2HPA = 47.8 / 47.8 / 4 / 0.4 (by mass) and 0.9 parts by mass of a crosslinking agent (B) (Example 1); an adhesive obtained from 100 parts by mass of (meth)acrylic acid ester polymer (A) with a composition of BA / 4HBA = 99 / 1 (by mass) and 0.15 parts by mass of a crosslinking agent (B) (Example 2); and an adhesive obtained from 100 parts by mass of (meth)acrylic acid ester polymer (A) with a composition of BA / 2EHA / HEA = 47 / 48 / 5 (by mass) and 0.9 parts by mass of a crosslinking agent (B) (Example 3).

[0009] In the examples of Patent Document 4, adhesives obtained from 100 parts by mass of (meth)acrylic acid ester polymer (A) with a composition of BA / 2EHA / 4HBA = 54 / 45 / 1 (by mass) and 0.15 to 0.35 parts by mass of a crosslinking agent (B) are reported (Examples 1 to 10), adhesives obtained from 100 parts by mass of (meth)acrylic acid ester polymer (A) with a composition of BA / 2EHA / 4HBA = 52 / 45 / 3 (by mass) and 0.25 parts by mass of a crosslinking agent (B) are reported (Example 11), and adhesives obtained from 100 parts by mass of (meth)acrylic acid ester polymer (A) with a composition of BA / 2EHA / 4HBA = 50 / 45 / 5 (by mass) and 0.25 parts by mass of a crosslinking agent (B) are reported (Example 12).

[0010] However, the adhesives reported in Patent Documents 3 and 4 have not achieved sufficient flexibility to withstand repeated bending over a wide temperature range from low temperatures of -20°C to high temperatures of 200°C.

[0011] Furthermore, softening the adhesive increases the creep value, which can lead to problems such as adhesive overflow and bubble formation during thermal bonding processes like IC bonding (reduced bonding resistance). [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Patent No. 5600039 [Patent Document 2] Patent No. 6376271 [Patent Document 3] Patent No. 6697359 [Patent Document 4] Japanese Patent Publication No. 2020-139034 [Overview of the Initiative] [Problems that the invention aims to solve]

[0013] The object of the present invention is to provide an acrylic adhesive composition that can form an acrylic adhesive that exhibits excellent flexibility and excellent bonding resistance, capable of withstanding repeated bending over a wide temperature range. Furthermore, the object is to provide an acrylic adhesive formed from such an acrylic adhesive composition, an adhesive film having an adhesive layer composed of the acrylic adhesive, and a flexible device equipped with the adhesive film. [Means for solving the problem]

[0014] The acrylic adhesive composition according to an embodiment of the present invention is An acrylic adhesive composition comprising an acrylic polymer (P) and a crosslinking agent, The acrylic polymer (P) is obtained by polymerizing a monomer component (M), The monomer component (M) comprises an alkyl (meth)acrylate (M1) and a polar group-containing monomer (M2). The alkyl (meth)acrylate (M1) comprises an alkyl (meth)acrylate (m1) whose homopolymer has a glass transition temperature Tg in the range of -80°C to -60°C. The monomer component (M) contains 50% by mass or more of the alkyl (meth)acrylate (m1), When the content of the polar group-containing monomer (M2) in the acrylic adhesive composition is A by mass and the content of the crosslinking agent in the acrylic adhesive composition is B by mass, the ratio of A to B is 40 to 150.

[0015] In one embodiment, the above A / B is 40 to 140.

[0016] In one embodiment, the above A / B is 40 to 95.

[0017] In one embodiment, the content of the alkyl (meth)acrylate (m1) in the monomer component (M) is 75% by mass or more.

[0018] In one embodiment, the content ratio of the alkyl (meth)acrylate (m1) in the alkyl (meth)acrylate (M1) is 95% by mass or more.

[0019] The acrylic adhesive according to the embodiment of the present invention is formed from the acrylic adhesive composition according to the embodiment of the present invention.

[0020] In one embodiment, the ratio of the storage modulus G'(-20) at -20°C to the storage modulus G'(200) at 200°C (G'(-20) / G'(200)) is 20 or less.

[0021] In one embodiment, the above ratio (G'(-20) / G'(200)) is 10 or less.

[0022] An adhesive film according to an embodiment of the present invention has an adhesive layer composed of an acrylic adhesive according to an embodiment of the present invention.

[0023] A flexible device according to an embodiment of the present invention comprises an adhesive film according to an embodiment of the present invention. [Effects of the Invention]

[0024] According to the present invention, it is possible to provide an acrylic adhesive composition that can form an acrylic adhesive that exhibits excellent flexibility and excellent bonding resistance, capable of withstanding repeated bending over a wide temperature range. Furthermore, it is possible to provide an acrylic adhesive formed from such an acrylic adhesive composition, an adhesive film having an adhesive layer composed of the acrylic adhesive, and a flexible device equipped with the adhesive film. [Brief explanation of the drawing]

[0025] [Figure 1] Figure 1 is a schematic cross-sectional view showing one embodiment of the flexible device of the present invention, illustrating one form of use of the adhesive film according to the embodiment of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view illustrating the method of heat-pressing test specimens in a heat-pressure bonding test. [Modes for carrying out the invention]

[0026] In this specification, the expression "(meth)acrylic" means "acrylic and / or methacrylic," the expression "(meth)acrylate" means "acrylate and / or methacrylate," the expression "(meth)allyl" means "allyl and / or methallyl," and the expression "(meth)acrolein" means "acrolein and / or methcrolein." In this specification, the expression "acid (salt)" means "acid and / or its salt." Examples of salts include alkali metal salts and alkaline earth metal salts, specifically, sodium salts and potassium salts.

[0027] ≪≪Acrylic adhesive composition≫≫ The acrylic adhesive composition according to the embodiment of the present invention comprises an acrylic polymer (P) and a crosslinking agent.

[0028] ≪Acrylic polymer (P)≫ The acrylic polymer (P) may be of one type or two or more types.

[0029] The weight-average molecular weight Mw of the acrylic polymer (P) can be any suitable weight-average molecular weight Mw within a range that does not impair the effects of the present invention. Such a weight-average molecular weight Mw is preferably 500,000 to 3,000,000, more preferably 600,000 to 2,500,000, even more preferably 700,000 to 2,000,000, particularly preferably 850,000 to 1,500,000, and most preferably 900,000 to 1,350,000, in terms of being able to better express the effects of the present invention.

[0030] The content of the acrylic polymer (P) in the acrylic adhesive composition according to the embodiments of the present invention is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 97% by mass or more, in terms of solid content, in order to better express the effects of the present invention. The upper limit of the above content is preferably 99.9% by mass or less.

[0031] The acrylic polymer (P) is obtained by polymerizing the monomer component (M). The monomer component (M) referred to here does not include the crosslinking agent in the acrylic adhesive composition according to the embodiments of the present invention.

[0032] Acrylic polymers (P) can thus be defined as those obtained by polymerizing monomer components (M). This is because acrylic polymers (P) are formed when monomer components (M) undergo a polymerization reaction, and it is impossible and impractical to directly identify acrylic polymers (P) by their structure. Therefore, the definition "obtained by polymerizing monomer components (M)" appropriately identifies acrylic polymers (P) as a "substance."

[0033] The monomer component (M) includes an alkyl (meth)acrylate (M1) and a polar group-containing monomer (M2).

[0034] The alkyl (meth)acrylate (M1) may be one type or two or more types.

[0035] The alkyl group in the ester portion of alkyl (meth)acrylate (M1) (hereinafter sometimes referred to as "alkyl group in the ester portion") does not include alkyl groups containing hydroxyl groups or alkyl groups containing polar groups other than hydroxyl groups. Therefore, alkyl (meth)acrylate (M1) is clearly distinguished from polar group-containing monomer (M2).

[0036] The content of alkyl (meth)acrylate (M1) in the monomer component (M) is preferably 50% to 99% by mass, more preferably 70% to 99% by mass, even more preferably 80% to 99% by mass, particularly preferably 85% to 99% by mass, and most preferably 90% to 99% by mass, in order to better express the effects of the present invention.

[0037] The alkyl group of the ester portion is preferably an alkyl group having 1 to 20 carbon atoms, more preferably an alkyl group having 1 to 16 carbon atoms, even more preferably an alkyl group having 2 to 14 carbon atoms, particularly preferably an alkyl group having 4 to 14 carbon atoms, and most preferably an alkyl group having 4 to 12 carbon atoms, in order to better express the effects of the present invention.

[0038] The alkyl group in the ester portion is preferably a linear alkyl group, as this allows for better expression of the effects of the present invention. Here, "linear" includes both linear and branched alkyl groups.

[0039] Examples of alkyl (meth)acrylates in which the alkyl group of the ester portion is a chain alkyl group having 1 to 20 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isopropyl (meth)acrylate. Examples include ctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0040] In order to better express the effects of the present invention, the alkyl (meth)acrylate (M1) that can be contained in the monomer component (M) preferably has a glass transition temperature Tg of its homopolymer (homopolymer) of -10°C or lower, more preferably -12°C or lower, even more preferably -15°C or lower, particularly preferably -18°C or lower, and most preferably -20°C or lower. The lower limit of the above glass transition temperature Tg is preferably -80°C or higher. The glass transition temperature Tg of the homopolymer (homopolymer) of the alkyl (meth)acrylate (M1) that can be contained in the monomer component (M) may affect the adhesive properties and flexural properties of the acrylic polymer (P). By using an alkyl (meth)acrylate (M1) that has a glass transition temperature Tg of its homopolymer (homopolymer) within the above range as the alkyl (meth)acrylate (M1) that can be contained in the monomer component (M), the adhesiveness and elasticity of the acrylic polymer (P) can be appropriately adjusted, and the effects of the present invention can be better expressed.

[0041] Here, the glass transition temperature (Tg) of the homopolymer (Hypopolymer) of alkyl (meth)acrylate (M1) that may be contained in the monomer component (M) can be a value described in publicly available documents. For example, the value described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. If multiple values ​​are described in the "Polymer Handbook," the conventional value should be adopted. For alkyl (meth)acrylates not described in the "Polymer Handbook," the catalog value from the monomer manufacturer should be adopted. For homopolymers of alkyl (meth)acrylates not described in the "Polymer Handbook" and for which a catalog value from the monomer manufacturer is not provided, the value obtained by the measurement method described in Japanese Patent Publication No. 2007-51271 should be used.

[0042] Typical examples of glass transition temperatures (Tg) of homopolymers (H-polymers) of alkyl (meth)acrylate (M1) that may be contained in monomer component (M) are as follows: 2-Ethylhexyl acrylate (2EHA): -70℃ Lauryl acrylate (LA): -23℃ n-butyl acrylate (BA): -55℃

[0043] The alkyl (meth)acrylate (M1) preferably includes alkyl (meth)acrylate (m1) whose homopolymer has a glass transition temperature Tg in the range of -80°C to -60°C. The effects of the present invention can be more fully expressed by including alkyl (meth)acrylate (m1) in alkyl (meth)acrylate (M1).

[0044] Examples of alkyl (meth)acrylates (m1) include 2-ethylhexyl acrylate (2EHA) (the glass transition temperature Tg = -70°C of its homopolymer).

[0045] The content of alkyl(meth)acrylate (m1) in alkyl(meth)acrylate (M1) is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 90% by mass or more, and most preferably 95% by mass or more, in order to better express the effects of the present invention. The upper limit of the content of alkyl(meth)acrylate (m1) in alkyl(meth)acrylate (M1) is preferably 100% by mass. As described above, the effects of the present invention can be better expressed by including a large amount of alkyl(meth)acrylate (m1) in alkyl(meth)acrylate (M1). In the examples described in the aforementioned Patent Documents 3 and 4, the content of 2EHA, which corresponds to alkyl(meth)acrylate (m1) in the embodiments of the present invention, is 45% to 50% by mass. The level of alkyl(meth)acrylate (m1) content in the acrylic adhesive composition according to the embodiments of the present invention is higher than that of Patent Documents 3 and 4.

[0046] The content of alkyl (meth)acrylate (m1) in the monomer component (M) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 75% by mass or more, particularly preferably 80% by mass or more, and most preferably 85% by mass or more, in order to better express the effects of the present invention. The upper limit of the content of alkyl (meth)acrylate (m1) in the monomer component (M) is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less. As described above, the effects of the present invention can be better expressed by including a large amount of alkyl (meth)acrylate (m1) in the monomer component (M). In the examples described in the aforementioned Patent Documents 3 and 4, the content of 2EHA, which corresponds to alkyl (meth)acrylate (m1) in the embodiments of the present invention, in the total monomer components is 45% to 48% by mass. The level of alkyl (meth)acrylate (m1) content in the monomer component (M) of the acrylic adhesive composition according to the embodiments of the present invention is higher than that of Patent Documents 3 and 4.

[0047] The monomer component (M) may include an alkyl (meth)acrylate (M1) such that the glass transition temperature Tg of its homopolymer (homopolymer) is in the range of -60°C to less than -40°C.

[0048] The content ratio of alkyl(meth)acrylate (m2) in alkyl(meth)acrylate (M1) is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, particularly preferably 10% by mass or less, and most preferably 5% by mass or less, in order to better exhibit the effects of the present invention.

[0049] The content of alkyl (meth)acrylate (m2) in the monomer component (M) is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, particularly preferably 20% by mass or less, and most preferably 15% by mass or less, in order to better express the effects of the present invention.

[0050] Examples of alkyl (meth)acrylates (m2) include n-butyl acrylate (BA) (whose homopolymer has a glass transition temperature Tg = -55°C).

[0051] The monomer component (M) may include an alkyl (meth)acrylate (M1), specifically an alkyl (meth)acrylate (m3) whose homopolymer has a glass transition temperature Tg in the range of -40°C to -10°C.

[0052] The content ratio of alkyl(meth)acrylate (m3) in alkyl(meth)acrylate (M1) is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, particularly preferably 10% by mass or less, and most preferably 5% by mass or less, in order to better express the effects of the present invention.

[0053] The content of alkyl (meth)acrylate (m3) in the monomer component (M) is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, particularly preferably 20% by mass or less, and most preferably 15% by mass or less, in order to better express the effects of the present invention.

[0054] Examples of alkyl (meth)acrylates (m3) include lauryl acrylate (LA) (whose homopolymer has a glass transition temperature Tg = -23°C).

[0055] The polar group-containing monomer (M2) may be one type or two or more types.

[0056] In order to better express the effects of the present invention, the polar group-containing monomer (M2) preferably comprises at least one selected from the group consisting of hydroxyl group-containing monomer (m4) and monomer having a polar group other than a hydroxyl group (m5), and more preferably comprises both hydroxyl group-containing monomer (m4) and monomer having a polar group other than a hydroxyl group (m5).

[0057] The content of polar group-containing monomer (M2) in monomer component (M) is preferably 0.01% to 50% by mass, more preferably 0.1% to 40% by mass, even more preferably 0.3% to 30% by mass, particularly preferably 0.6% to 20% by mass, and most preferably 1% to 15% by mass, in order to better express the effects of the present invention.

[0058] The hydroxyl group-containing monomer (m4) may be one type or two or more types.

[0059] In order to better exhibit the effects of the present invention, the hydroxyl group-containing monomer (m4) preferably has a glass transition temperature Tg of its homopolymer (homopolymer) of -10°C or lower, more preferably -15°C or lower, even more preferably -20°C or lower, particularly preferably -25°C or lower, and most preferably -30°C or lower. The lower limit of the above glass transition temperature Tg is preferably -80°C or higher. The glass transition temperature Tg of the homopolymer (homopolymer) of the hydroxyl group-containing monomer (m4) can affect the tackiness and elasticity of the acrylic polymer (P). By using a hydroxyl group-containing monomer (m4) whose homopolymer (homopolymer) has a glass transition temperature Tg within the above range, the effects of the present invention can be better exhibited.

[0060] For homopolymers of hydroxyl group-containing monomers (m4), the glass transition temperature (Tg) can be determined using values ​​from publicly available sources. For example, the values ​​listed in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. If multiple values ​​are listed in the "Polymer Handbook," the conventional value should be adopted. For hydroxyl group-containing monomers (m4) not listed in the "Polymer Handbook," the catalog values ​​from monomer manufacturers should be used. For homopolymers of hydroxyl group-containing monomers (m4) not listed in the "Polymer Handbook" and for which monomer manufacturers do not provide catalog values, the Tg value obtained by the measurement method described in Japanese Patent Publication No. 2007-51271 should be used.

[0061] Typical examples of glass transition temperatures (Tg) for homopolymers of hydroxyl group-containing monomers (m4) are as follows: 2-Hydroxyethyl acrylate: -15℃ 4-Hydroxybutyl acrylate: -40℃

[0062] The content ratio of hydroxyl group-containing monomer (m4) in polar group-containing monomer (M2) is preferably 30% to 100% by mass, more preferably 35% to 95% by mass, even more preferably 40% to 90% by mass, particularly preferably 45% to 88% by mass, and most preferably 48% to 88% by mass, in order to better express the effects of the present invention.

[0063] The content of the hydroxyl group-containing monomer (m4) in the monomer component (M) is preferably 0.05% to 30% by mass, more preferably 0.1% to 20% by mass, even more preferably 0.3% to 15% by mass, particularly preferably 0.5% to 15% by mass, and most preferably 0.5% to 10% by mass, in order to better express the effects of the present invention.

[0064] Examples of hydroxyl group-containing monomers (m4) include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; polypropylene glycol mono(meth)acrylate; and N-hydroxyethyl (meth)acrylamide.

[0065] In order to better express the effects of the present invention, the hydroxyl group-containing monomer (m4) is preferably a hydroxyalkyl (meth)acrylate, more preferably a hydroxyalkyl (meth)acrylate in which the alkyl group portion of the hydroxyalkyl group is a linear alkyl group having 2 to 4 carbon atoms, even more preferably 2-hydroxyethyl acrylate (HEA) and 4-hydroxybutyl acrylate (4HBA), and particularly preferably 4-hydroxybutyl acrylate.

[0066] The monomer (m5) having a polar group other than a hydroxyl group may be one type or two or more types.

[0067] In order to better express the effects of the present invention, the monomer (m5) having polar groups other than hydroxyl groups preferably has a glass transition temperature Tg of its homopolymer (homopolymer) of 100°C or less, more preferably 95°C or less, and even more preferably 90°C or less. The lower limit of the above glass transition temperature Tg is preferably -30°C or higher, and more preferably -10°C or higher. By using a monomer (m5) having polar groups other than hydroxyl groups whose homopolymer (homopolymer) has a glass transition temperature Tg within the above range, the tackiness and elasticity of the acrylic polymer (P) can be appropriately adjusted, and the effects of the present invention can be better expressed.

[0068] As monomers (m5) having polar groups other than hydroxyl groups, those having polar groups other than hydroxyl groups and whose homopolymers have a glass transition temperature Tg of 50°C to 100°C are preferred in terms of being able to better express the effects of the present invention. The glass transition temperature Tg of the homopolymer of this monomer is preferably 60°C to 95°C, and more preferably 70°C to 90°C.

[0069] In the monomer (m5) having polar groups other than hydroxyl groups, the content of monomers having polar groups other than hydroxyl groups, in which the glass transition temperature Tg of its homopolymer (homopolymer) is 50°C to 100°C (preferably 60°C to 95°C, more preferably 70°C to 90°C), is preferably 30% to 100% by mass, more preferably 50% to 100% by mass, even more preferably 70% to 100% by mass, particularly preferably 90% to 100% by mass, and most preferably 95% to 100% by mass, in order to better express the effects of the present invention.

[0070] For homopolymers (Tg) of monomers (m5) having polar groups other than hydroxyl groups, the glass transition temperature (Tg) can be a value listed in publicly available documents. For example, the value listed in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. If multiple values ​​are listed in "Polymer Handbook," the conventional value should be adopted. For monomers (m5) having polar groups other than hydroxyl groups that are not listed in "Polymer Handbook," the catalog value from the monomer manufacturer should be adopted. For alkyl (meth)acrylate homopolymers that are not listed in "Polymer Handbook" and for which the monomer manufacturer does not provide a catalog value, the Tg should be a value obtained by the measurement method described in Japanese Patent Publication No. 2007-51271.

[0071] The content of monomers having polar groups other than hydroxyl groups (m5) in polar group-containing monomers (M2) is preferably 1% to 70% by mass, more preferably 3% to 65% by mass, even more preferably 5% to 60% by mass, particularly preferably 10% to 55% by mass, and most preferably 10% to 50% by mass, in order to better express the effects of the present invention.

[0072] The content of monomers (m5) having polar groups other than hydroxyl groups in monomer component (M) is preferably 0.1% to 10% by mass, more preferably 0.2% to 8% by mass, even more preferably 0.3% to 6% by mass, particularly preferably 0.4% to 5% by mass, and most preferably 0.4% to 3% by mass, in order to better express the effects of the present invention.

[0073] The monomer (m5) having a polar group other than a hydroxyl group preferably includes at least one selected from the group consisting of monomer (1) represented by general formula (1) and N-vinyl-2-pyrrolidone. [ka] (In general formula (1), R 1 R is an alkyl group having 1 to 10 carbon atoms. 2 (where R is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a -COOR group, and R is an alkyl group having 1 to 10 carbon atoms.)

[0074] The monomer (1) represented by general formula (1) may be one type or two or more types.

[0075] The monomer (1) represented by general formula (1) has two polymerizable double bonds at its terminals and a structure (C-CH2-O-CH2-C) that can construct a furan ring structure by cyclization polymerization, and furthermore, at least one of the carbon atoms second from the end of the two polymerizable double bonds at the terminals has an alkyl ester group (COOR 1By comprising a (group), it becomes possible to promote ring-opening polymerization and introduce an alkyl ester group into the structure constructed by ring-opening polymerization. Due to these characteristics, for the obtained acrylic adhesive, it is possible to concurrently exhibit more excellent flexibility and more excellent recovery with respect to bending motion.

[0076] In the monomer (1) represented by the general formula (1), R 1 is an alkyl group having 1 to 10 carbon atoms. In terms of being able to more effectively exhibit the effects of the present invention, R 1 is preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, still more preferably an alkyl group having 1 to 3 carbon atoms, particularly preferably a methyl group or an ethyl group, and most preferably a methyl group.

[0077] In the monomer (1) represented by the general formula (1), R 2 is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a -COOR group. When R 2 is an alkyl group having 1 to 10 carbon atoms, in terms of being able to more effectively exhibit the effects of the present invention, R 2 is preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, still more preferably an alkyl group having 1 to 3 carbon atoms. When R 2 is a -COOR group, R is an alkyl group having 1 to 10 carbon atoms. In terms of being able to more effectively exhibit the effects of the present invention, R is preferably an alkyl group having 1 to 8 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, still more preferably an alkyl group having 1 to 3 carbon atoms, particularly preferably a methyl group or an ethyl group, and most preferably a methyl group. In terms of being able to more effectively exhibit the effects of the present invention, R 2 is preferably a hydrogen atom.

[0078] The content ratio of at least one selected from the group consisting of monomer (1) represented by general formula (1) and N-vinyl-2-pyrrolidone in monomer component (M) is preferably 0.01% to 30% by mass, more preferably 0.1% to 20% by mass, even more preferably 0.2% to 15% by mass, even more preferably 0.3% to 10% by mass, particularly preferably 0.4% to 8.0% by mass, and most preferably 0.5% to 6.0% by mass, in order to better express the effects of the present invention.

[0079] When the monomer component (M) contains monomer (1) represented by general formula (1), the content of monomer (1) represented by general formula (1) in the monomer component (M) is preferably 0.01% to 20% by mass, more preferably 0.1% to 10% by mass, even more preferably 0.2% to 5.0% by mass, even more preferably 0.3% to 3.0% by mass, particularly preferably 0.4% to 2.0% by mass, and most preferably 0.5% to 1.5% by mass, in order to better exhibit the effects of the present invention.

[0080] When the monomer component (M) contains N-vinyl-2-pyrrolidone, the content of N-vinyl-2-pyrrolidone in the monomer component (M) is preferably 0.01% to 30% by mass, more preferably 0.1% to 20% by mass, even more preferably 0.2% to 15% by mass, even more preferably 0.3% to 10% by mass, particularly preferably 0.4% to 8.0% by mass, and most preferably 0.5% to 6.0% by mass, in order to better express the effects of the present invention.

[0081] Examples of monomers (m5) having polar groups other than hydroxyl groups include monomer (1) represented by general formula (1) and N-vinyl-2-pyrrolidone, as well as carboxyl group-containing monomers, nitrogen-containing monomers other than N-vinyl-2-pyrrolidone, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, acid anhydride group-containing monomers, vinyl esters (e.g., vinyl acetate (VAc), vinyl propionate, vinyl laurate), aromatic vinyl compounds, amide group-containing monomers, epoxy group-containing monomers, (meth)acryloylmorpholine, and vinyl ethers.

[0082] Examples of monomers containing a carboxyl group include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0083] Examples of nitrogen-containing monomers other than N-vinyl-2-pyrrolidone include methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, (meth)acryloylmorpholine, N-vinyl carboxylic acid amides, and N-vinylcaprolactam; as well as cyano group-containing acrylic monomers such as acrylonitrile and methacrylonitrile.

[0084] In order to further enhance the effects of the present invention, the monomer component (M) preferably comprises at least one selected from the group consisting of alkyl (meth)acrylate (m1) and hydroxyl group-containing monomer (m4) and monomer having a polar group other than a hydroxyl group (m5), and more preferably comprises alkyl (meth)acrylate (m1), hydroxyl group-containing monomer (m4), and monomer having a polar group other than a hydroxyl group (m5).

[0085] In order to further express the effects of the present invention, the monomer component (M) typically includes, preferably, at least one selected from the group consisting of 2-ethylhexyl acrylate, lauryl acrylate, and n-butyl acrylate, and at least one selected from the group consisting of hydroxyl group-containing monomers (m4) and monomers having polar groups other than hydroxyl groups (m5). More preferably, it includes 2-ethylhexyl acrylate and at least one selected from the group consisting of 4-hydroxybutyl acrylate and N-vinyl-2-pyrrolidone. Even more preferably, it includes 2-ethylhexyl acrylate, 4-hydroxybutyl acrylate, and N-vinyl-2-pyrrolidone.

[0086] In order to further express the effects of the present invention, the total amount of alkyl (meth)acrylate (m1) and at least one selected from the group consisting of hydroxyl group-containing monomers (m4) and monomers having polar groups other than hydroxyl groups (m5) in the monomer component (M) is preferably 60% to 100% by mass, more preferably 70% to 100% by mass, even more preferably 80% to 100% by mass, particularly preferably 90% to 100% by mass, and most preferably 95% to 100% by mass.

[0087] The monomer component (M) may include other monomers that do not fall under either alkyl (meth)acrylate (M1) or polar group-containing monomer (M2). These other monomers can be used, for example, to adjust the glass transition temperature (Tg) or tackiness of the acrylic polymer (P). The other monomers may consist of only one type or two or more types.

[0088] The content of other monomers in the monomer component (M) is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, particularly preferably 3% by mass or less, and most preferably 1% by mass or less.

[0089] As a method for obtaining the acrylic polymer (P), various polymerization methods known as synthesis methods for acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization, can be appropriately employed. Among these polymerization methods, solution polymerization is preferably used. As a method for supplying monomers when performing solution polymerization, a batch supply method in which the entire amount of monomer components is supplied at once, a continuous supply (dropping) method, a divided supply (dropping) method, etc., can be appropriately employed. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and is preferably 20°C or higher, more preferably 30°C or higher, even more preferably 40°C or higher, preferably 170°C or lower, more preferably 160°C or lower, and even more preferably 140°C or lower. As a method for obtaining the acrylic polymer, active energy ray irradiation polymerization such as photopolymerization (typically performed in the presence of a photopolymerization initiator) carried out by irradiation with light such as UV, or radiation polymerization carried out by irradiation with radiation such as beta rays and gamma rays may be employed.

[0090] The solvent used for solution polymerization (polymerization solvent) can be appropriately selected from any suitable organic solvent. Examples include aromatic compounds such as toluene (typically aromatic hydrocarbons), acetic acid esters such as ethyl acetate, and aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane.

[0091] The polymerization initiator used can be appropriately selected from any suitable polymerization initiator depending on the type of polymerization method. There may be only one polymerization initiator or two or more.

[0092] Examples of polymerization initiators include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid)dimethyl, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane)dihydrochloride, and 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride. Azo initiators such as drochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethylene isobutylamidine), 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (VA-057, manufactured by Wako Pure Chemical Industries, Ltd.); persulfates such as potassium persulfate and ammonium persulfate, di(2-ethylhexyl) peroxydicarbonate, di( Examples include peroxide initiators such as 4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butylhydroperoxide, and hydrogen peroxide; redox initiators combining peroxides with reducing agents, such as combinations of persulfates and sodium bisulfite, and combinations of peroxides and sodium ascorbate; substituted ethane initiators such as phenyl-substituted ethane; and aromatic carbonyl compounds.

[0093] The amount of polymerization initiator used is preferably 0.005 parts by mass to 1 part by mass, and more preferably 0.01 parts by mass to 1 part by mass, per 100 parts by mass of monomer component (M).

[0094] The polymerization may include any other suitable additives, as long as they do not impair the effects of the present invention.

[0095] Crosslinking agent The crosslinking agent may be one type or two or more types.

[0096] The use of a crosslinking agent can impart appropriate cohesive force to acrylic adhesives. The crosslinking agent can be included in acrylic adhesives in various forms, including post-crosslinking, pre-crosslinking, partially crosslinked, or intermediate or combined forms. Typically, the crosslinking agent is included in acrylic adhesives in its post-crosslinking form.

[0097] The proportion of the crosslinking agent in the acrylic adhesive composition is preferably 0.005 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, even more preferably 0.01 to 3 parts by mass, even more preferably 0.01 to 1 part by mass, particularly preferably 0.01 to 0.5 parts by mass, and most preferably 0.01 to 0.2 parts by mass, per 100 parts by mass of the acrylic polymer (P), in order to better express the effects of the present invention.

[0098] Examples of crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, silicone-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, silane-based crosslinking agents, alkyl etherified melamine-based crosslinking agents, metal chelate-based crosslinking agents, and peroxides. In terms of being able to better exhibit the effects of the present invention, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are preferred, and isocyanate-based crosslinking agents are more preferred.

[0099] Isocyanate-based crosslinking agents can be compounds having two or more isocyanate groups (including isocyanate-regenerating polar groups in which isocyanate groups are temporarily protected by a blocking agent or quantification, etc.) in one molecule. Examples of isocyanate-based crosslinking agents include aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; and aliphatic isocyanates such as hexamethylene diisocyanate.

[0100] Examples of isocyanate-based crosslinking agents include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic diisocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and polymethylene polyphenyl isocyanate; trimethylolpropane / tolylene diisocyanate trimer adduct (e.g., manufactured by Tosoh Corporation, trade name: Coronate L), trimethylolpropane / hexamethylene diisocyanate trimer adduct (e.g., manufactured by Tosoh Corporation, trade name: Coronate HL), and isocyanurate derivatives of hexamethylene diisocyanate (e.g., manufactured by Tosoh Corporation, Examples include isocyanate adducts such as Coronate HX; trimethylolpropane adducts of xylylene diisocyanate (e.g., Mitsui Chemicals, product name: Takenate D110N), trimethylolpropane adducts of xylylene diisocyanate (e.g., Mitsui Chemicals, product name: Takenate D120N), trimethylolpropane adducts of isophorone diisocyanate (e.g., Mitsui Chemicals, product name: Takenate D140N), trimethylolpropane adducts of hexamethylene diisocyanate (e.g., Mitsui Chemicals, product name: Takenate D160N); polyether polyisocyanates, polyester polyisocyanates, and adducts thereof with various polyols; and polyfunctionalized polyisocyanates with isocyanurate bonds, biuret bonds, allophanate bonds, etc. Among these, aromatic isocyanates and alicyclic isocyanates are preferred because they can achieve a good balance between deformability and cohesiveness.

[0101] As epoxy crosslinking agents, polyfunctional epoxy compounds having two or more epoxy groups in one molecule can be used. Examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylenediline, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and sorbitol polyglycidyl ether. Examples of epoxy crosslinking agents include tel, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate ester, diglycidyl o-phthalate ester, triglycidyl-tris(2-hydroxyethyl) isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule. Examples of commercially available epoxy crosslinking agents include the trade names "Tetrad C" and "Tetrad X" manufactured by Mitsubishi Gas Chemical Company.

[0102] In an acrylic adhesive composition according to an embodiment of the present invention, when the content of the polar group-containing monomer (M2) in the acrylic adhesive composition is A by mass %, and the content of the crosslinking agent in the acrylic adhesive composition is B by mass %, the ratio of A / B is preferably 40 to 150, more preferably 40 to 140, even more preferably 40 to 120, particularly preferably 40 to 100, and most preferably 40 to 95. If the ratio of A / B is within the above range, the effects of the present invention can be more fully realized.

[0103] <<Adhesion-enhancing resin>> The acrylic adhesive composition according to the embodiment of the present invention may contain a tackifying resin to adjust the adhesive properties and bending properties, etc. The tackifying resin may be one type or two or more types.

[0104] Examples of tackifying resins include rosin-based tackifying resins, terpene-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, polyamide-based tackifying resins, elastomer-based tackifying resins, phenol-based tackifying resins, and ketone-based tackifying resins.

[0105] The amount of tackifying resin used is preferably 70 parts by mass or less, more preferably 5 to 70 parts by mass, even more preferably 10 to 60 parts by mass, even more preferably 15 to 50 parts by mass, particularly preferably 20 to 45 parts by mass, and most preferably 25 to 40 parts by mass, based on 100 parts by mass of acrylic polymer (P), in order to better exhibit the effects of the present invention.

[0106] The tackifying resin preferably includes a tackifying resin TL having a softening point of less than 105°C, in order to better exhibit the effects of the present invention. The tackifying resin TL can effectively contribute to improving the deformability of the adhesive layer in the planar direction (shear direction). From the viewpoint of obtaining a higher deformability improvement effect, the softening point of the tackifying resin used as the tackifying resin TL is preferably 50°C to 103°C, more preferably 60°C to 100°C, even more preferably 65°C to 95°C, particularly preferably 70°C to 90°C, and most preferably 75°C to 85°C.

[0107] The softening point of the tackifying resin is defined as the value measured based on the softening point test method (ring-ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at the lowest possible temperature and carefully filled into a ring placed on a flat metal plate, taking care to avoid creating bubbles. After cooling, the raised portion from the plane, including the top end of the ring, is cut off with a slightly heated knife. Next, a support (ring stand) is placed in a glass container (heating bath) with a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured in to a depth of 90 mm or more. Next, a steel ball (diameter 9.5 mm, mass 3.5 g) and the ring filled with the sample are immersed in the glycerin so that they do not come into contact with each other, and the temperature of the glycerin is maintained at 20°C ± 5°C for 15 minutes. Next, the steel ball is placed in the center of the surface of the sample in the ring, and this is placed in a fixed position on the support. Next, maintain a distance of 50 mm from the top of the ring to the glycerin surface, place a thermometer, and position the center of the thermometer's mercury bulb at the same height as the center of the ring, then heat the container. The flame of the Bunsen burner used for heating should be positioned midway between the center and edge of the container's bottom to ensure even heating. After heating begins and the bath temperature reaches 40°C, the rate of increase must be 5.0 ± 0.5°C per minute. Read the temperature when the sample gradually softens, flows out of the ring, and finally contacts the bottom plate; this is defined as the softening point. Two or more softening points should be measured simultaneously, and the average value should be used.

[0108] The amount of tackifying resin TL used is preferably 50 parts by mass or less, more preferably 5 to 50 parts by mass, even more preferably 10 to 45 parts by mass, particularly preferably 15 to 40 parts by mass, and most preferably 20 to 35 parts by mass, per 100 parts by mass of acrylic polymer (P), in order to better exhibit the effects of the present invention.

[0109] As the tackifying resin TL, one or more types can be appropriately selected from the tackifying resins exemplified above that have a softening point of less than 105°C. The tackifying resin TL preferably includes a rosin-based resin.

[0110] Examples of rosin-based resins that can be preferably used as tackifying resins TL include rosin esters such as unmodified rosin esters and modified rosin esters. Examples of modified rosin esters include hydrogenated rosin esters.

[0111] The tackifying resin TL preferably contains a hydrogenated rosin ester, in that it can better exhibit the effects of the present invention. The hydrogenated rosin ester has a softening point that is preferably less than 105°C, more preferably 50°C to 100°C, even more preferably 60°C to 90°C, particularly preferably 70°C to 85°C, and most preferably 75°C to 85°C, in that it can better exhibit the effects of the present invention.

[0112] The tackifying resin TL may contain non-hydrogenated rosin esters. Here, non-hydrogenated rosin esters are a comprehensive term referring to all rosin esters other than hydrogenated rosin esters among the rosin esters mentioned above. Examples of non-hydrogenated rosin esters include unmodified rosin esters, disproportionated rosin esters, and polymerized rosin esters.

[0113] As for the non-hydrogenated rosin ester, the softening point is preferably less than 105°C, more preferably 50°C to 100°C, even more preferably 60°C to 90°C, particularly preferably 70°C to 85°C, and most preferably 75°C to 85°C, in order to better exhibit the effects of the present invention.

[0114] The tackifying resin TL may contain other tackifying resins in addition to the rosin-based resin. As the other tackifying resin, one or more types may be appropriately selected from the tackifying resins exemplified above that have a softening point of less than 105°C. For example, the tackifying resin TL may contain a rosin-based resin and a terpene resin.

[0115] The proportion of rosin-based resin in the total tackifying resin TL is preferably more than 50% by mass, more preferably 55% to 100% by mass, even more preferably 60% to 99% by mass, particularly preferably 65% ​​to 97% by mass, and most preferably 75% to 97% by mass, in order to better exhibit the effects of the present invention.

[0116] The tackifying resin may contain a combination of the tackifying resin TL and the tackifying resin TH having a softening point of 105°C or higher (preferably 105°C to 170°C), in order to better exhibit the effects of the present invention.

[0117] As the tackifying resin TH, one or more types may be appropriately selected from the tackifying resins exemplified above that have a softening point of 105°C or higher. The tackifying resin TH may include at least one selected from rosin-based tackifying resins (e.g., rosin esters) and terpene-based tackifying resins (e.g., terpene phenol resins).

[0118] ≪Oligomer≫ The acrylic adhesive composition according to the embodiment of the present invention may contain oligomers. The oligomers may be one type or two or more types. The effects of the present invention can be more fully realized by including oligomers in the acrylic adhesive composition according to the embodiment of the present invention.

[0119] The weight-average molecular weight Mw of the oligomer is preferably 1,000 to 30,000, more preferably 1,500 to 10,000, even more preferably 2,000 to 8,000, and particularly preferably 2,000 to 5,000. By using oligomers with such a weight-average molecular weight Mw, the tackiness and elasticity of the acrylic adhesive sheet can be improved.

[0120] As for the oligomer, acrylic oligomers are preferred because they readily blend with acrylic polymers.

[0121] The glass transition temperature Tg of the acrylic oligomer is preferably 20°C or higher, more preferably 40°C or higher, even more preferably 60°C or higher, particularly preferably 80°C or higher, and most preferably 100°C or higher. The upper limit of the glass transition temperature Tg of the acrylic oligomer is preferably 200°C or lower, more preferably 180°C or lower, and even more preferably 160°C or lower.

[0122] The glass transition temperature (Tg) of an acrylic oligomer is a value determined from Fox's formula based on the Tg of the homopolymers of each constituent monomer and the mass fraction (mass-based copolymerization ratio) of the monomers. Fox's formula is a relationship between the Tg of a copolymer and the glass transition temperature (Tgi) of the homopolymers obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below. 1 / Tg = Σ(Wi / Tgi)

[0123] In the Fox formula above, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the mass fraction of monomer i in the copolymer (mass-based copolymerization ratio), and Tgi represents the glass transition temperature of the monomer i homopolymer (unit: K). As the Tg of the homopolymer, values ​​listed in publicly available documents can be used, for example, the values ​​listed in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. If multiple values ​​are listed in the "Polymer Handbook," the conventional value should be adopted. For monomers not listed in the "Polymer Handbook," the catalog values ​​of the monomer manufacturers should be adopted. For monomers not listed in the "Polymer Handbook" and for which no catalog values ​​are provided by monomer manufacturers, the Tg of the homopolymer should be the value obtained by the measurement method described in Japanese Patent Publication No. 2007-51271.

[0124] Acrylic oligomers contain alicyclic alkyl (meth)acrylate as their main constituent monomer component. The alicyclic alkyl (meth)acrylate may be one type or two or more types.

[0125] Examples of alicyclic alkyl (meth)acrylates include cycloalkyl (meth)acrylates such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate; (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring, such as isobornyl (meth)acrylate; and (meth)acrylic acid esters having three or more aliphatic hydrocarbon rings, such as dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

[0126] As alicyclic alkyl (meth)acrylates, dicyclopentanyl acrylate, dicyclopentanyl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate are preferred in that they can better exhibit the effects of the present invention.

[0127] The ratio of alicyclic alkyl (meth)acrylate to the total amount of constituent monomer components of the acrylic oligomer is preferably 10% to 99% by mass, more preferably 30% to 98% by mass, even more preferably 40% to 97% by mass, and particularly preferably 50% to 96% by mass, in order to better express the effects of the present invention.

[0128] Acrylic oligomers may contain a linear alkyl (meth)acrylate having a linear alkyl group as a constituent monomer component. The linear alkyl (meth)acrylate having a linear alkyl group may be one type or two or more types. Here, "linear" includes both linear and branched structures.

[0129] Preferably, the linear alkyl (meth)acrylate is a linear alkyl (meth)acrylate having a linear alkyl group with 1 to 20 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate Examples include phosphates, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0130] As the linear alkyl (meth)acrylate, methyl methacrylate is preferred in that it can better exhibit the effects of the present invention.

[0131] The ratio of linear alkyl (meth)acrylate to the total amount of constituent monomer components of the acrylic oligomer is preferably 10% to 90% by mass, more preferably 20% to 80% by mass, and even more preferably 30% to 70% by mass, in order to better exhibit the effects of the present invention.

[0132] Acrylic oligomers may contain (meth)acrylic acid as a constituent monomer component. (Meth)acrylic acid may be one type or two or more types.

[0133] As the (meth)acrylic acid, acrylic acid is preferred in that it can better exhibit the effects of the present invention.

[0134] The content ratio of (meth)acrylic acid relative to the total amount of constituent monomer components of the acrylic oligomer is preferably 0.1% to 20% by mass, more preferably 1% to 10% by mass, and even more preferably 3% to 7% by mass, in order to better exhibit the effects of the present invention.

[0135] Oligomers are obtained by polymerizing constituent monomer components using various polymerization methods. Any suitable additives may be used during the polymerization of oligomers, provided they do not impair the effects of the present invention. Examples of such additives include polymerization initiators and chain transfer agents.

[0136] The oligomer content in the acrylic adhesive composition is preferably 6.0 parts by mass or less, more preferably 5.0 parts by mass or less, even more preferably 4.0 parts by mass or less, particularly preferably 3.0 parts by mass or less, and most preferably 2.0 parts by mass or less, per 100 parts by mass of the acrylic polymer (P), in order to better express the effects of the present invention.

[0137] <<Other ingredients>> The acrylic adhesive composition according to embodiments of the present invention may optionally contain various additives common in the field of adhesives, such as catalysts, solvents, leveling agents, crosslinking aids, plasticizers, softeners, fillers, antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, and light stabilizers. Such additives can be conventionally used by conventional methods.

[0138] <Antistatic agent> One preferred embodiment of the present invention is that the acrylic adhesive composition according to the embodiment of the present invention includes an antistatic agent as one of the other components.

[0139] The content of the antistatic agent is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, even more preferably 0.07 to 3 parts by mass, and particularly preferably 0.1 to 1 part by mass, per 100 parts by mass of acrylic polymer (P).

[0140] Examples of antistatic agents include ionic compounds. Any suitable ionic compound can be used as the ionic compound, as long as it does not impair the effects of the present invention. Preferably, the ionic compound is at least one selected from alkali metal salts and ionic liquids, as it can impart excellent antistatic properties and peeling charge characteristics.

[0141] Alkali metal salts are preferred because they exhibit excellent antistatic properties even with trace amounts due to their high ionic dissociation ability. Examples of alkali metal salts include Li + na + , and K + One of the cations selected from and Cl - , Br - , I - AlCl4 - Al2Cl7 - BF4 - PF6 - SCN - ClO4 - NO3 - CH3COO - C9H 19 COO - CF3COO - C3F7COO - CH3SO3 - CF3SO3 - , C4F9SO3 - ,C2H5OSO3 - , C6H 13 OSO3 - C8H 17 OSO3 - (CF3SO2)2N - , (C2F5SO2)2N - , (C3F7SO2)2N - (C4F9SO2)2N -(CF3SO2)3C - AsF6 - SbF6 - , NbF6 - TaF6 - F(HF)n - , (CN)2N - (CF3SO2)(CF3CO)N - (CH3)2PO4 - (C2H5)2PO4 - CH3(OC2H4)2OSO3 - C6H4(CH3)SO3 - (C2F5)3PF3 - CH3CH(OH)COO - , and (FSO2)2N - Metal salts composed of multiple anions are preferably used. More preferably, examples of alkali metal salts include lithium salts such as LiBr, LiI, LiBF4, LiPF6, LiSCN, LiClO4, LiCF3SO3, Li(CF3SO2)2N, Li(C2F5SO2)2N, Li(FSO2)2N, and Li(CF3SO2)3C, and even more preferably, LiCF3SO3, Li(CF3SO2)2N, Li(C2F5SO2)2N, Li(C3F7SO2)2N, Li(C4F9SO2)2N, Li(FSO2)2N, and Li(CF3SO2)3C. Alkali metal salts may be used alone or in mixtures of two or more types.

[0142] As the ionic liquid, an ionic liquid consisting of an organic cation component represented by formulas (A) to (D) below and an anion component is preferred. Among these ionic liquids, an ionic liquid with a melting point of 100°C or lower is more preferred because it can exhibit excellent antistatic properties.

[0143] [ka]

[0144] R in equation (A) a R represents a hydrocarbon group having 4 to 20 carbon atoms, and may be a functional group in which a portion of the hydrocarbon group is substituted with a heteroatom.b and R c R may be the same or different, representing hydrogen or a hydrocarbon group having 1 to 16 carbon atoms, and a functional group in which part of the hydrocarbon group is substituted with a heteroatom. However, if the nitrogen atom in formula (A) contains a double bond, R c There isn't one.

[0145] R in equation (B) d R represents a hydrocarbon group having 2 to 20 carbon atoms, and may be a functional group in which a portion of the hydrocarbon group is substituted with a heteroatom. e , R f , and R g These may be identical or different functional groups representing hydrogen or a hydrocarbon group having 1 to 16 carbon atoms, wherein a portion of the hydrocarbon group is substituted with a heteroatom.

[0146] R in equation (C) h R represents a hydrocarbon group having 2 to 20 carbon atoms, and may be a functional group in which a portion of the hydrocarbon group is substituted with a heteroatom. i , R j , and R k These may be identical or different functional groups representing hydrogen or a hydrocarbon group having 1 to 16 carbon atoms, wherein a portion of the hydrocarbon group is substituted with a heteroatom.

[0147] In formula (D), Z represents a nitrogen, sulfur, or phosphorus atom, and R l , R m , R n , and R o , may be the same or different, representing a hydrocarbon group having 1 to 20 carbon atoms, and a functional group in which part of the hydrocarbon group is substituted with a heteroatom. However, if Z is a sulfur atom, R o There isn't one.

[0148] Examples of cations represented by formula (A) include pyridinium cations, piperidinium cations, pyrrolidinium cations, cations having a pyrroline skeleton, cations having a pyrrole skeleton, and morpholinium cations.

[0149] Specific examples of cations represented by formula (A) include, for example, 1-ethylpyridinium cation, 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, 1-hexyl-3-methylpyridinium cation, 1-butyl-3,4-dimethylpyridinium cation, 1,1-dimethylpyrrolidinium cation, 1-ethyl-1-methylpyrrolidinium cation, 1-methyl-1-propylpyrrolidinium cation, and 1-methylpyrrolidinium cation. 1-butylpyrrolidinium cation, 1-methyl-1-pentylpyrrolidinium cation, 1-methyl-1-hexylpyrrolidinium cation, 1-methyl-1-heptylpyrrolidinium cation, 1-ethyl-1-propylpyrrolidinium cation, 1-ethyl-1-butylpyrrolidinium cation, 1-ethyl-1-pentylpyrrolidinium cation, 1-ethyl-1-hexylpyrrolidinium cation, 1-ethyl-1-heptylpyrrolidinium cation, 1,1-dipropylpyrrolidinium cation, 1-propyl- 1-Butylpyrrolidinium cation, 1,1-Dibutylpyrrolidinium cation, Pyrrolidinium-2-one cation, 1-Propylpiperidinium cation, 1-Pentylpiperidinium cation, 1,1-Dimethylpiperidinium cation, 1-Methyl-1-ethylpiperidinium cation, 1-Methyl-1-propylpiperidinium cation, 1-Methyl-1-butylpiperidinium cation, 1-Methyl-1-pentylpiperidinium cation, 1-Methyl-1-hexylpiperidinium cation, 1-Methyl-1-hexylpiperidinium cation Tylpiperidinium cation, 1-ethyl-1-propylpiperidinium cation, 1-ethyl-1-butylpiperidinium cation, 1-ethyl-1-pentylpiperidinium cation, 1-ethyl-1-hexylpiperidinium cation, 1-ethyl-1-heptylpiperidinium cation, 1,1-dipropylpiperidinium cation, 1-propyl-1-butylpiperidinium cation, 1,1-dibutylpiperidinium cation, 2-methyl-1-pyrroline cation, 1-ethyl-2-phenylindole cation, 1,Examples include 2-dimethylindole cation, 1-ethylcarbazole cation, and N-ethyl-N-methylmorpholinium cation.

[0150] Examples of cations represented by formula (B) include imidazolium cation, tetrahydropyrimidinium cation, and dihydropyrimidinium cation.

[0151] Specific examples of cations represented by formula (B) include, for example, 1,3-dimethylimidazolium cation, 1,3-diethylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-butyl-3-methylimidazolium cation, 1-hexyl-3-methylimidazolium cation, 1-octyl-3-methylimidazolium cation, 1-decyl-3-methylimidazolium cation, 1-dodecyl-3-methylimidazolium cation, 1-tetradecyl-3-methylimidazolium cation, 1,2-dimethyl-3-propylimidazolium cation, 1-ethyl-2,3-dimethylimidazolium cation, 1-butyl-2,3-dimethylimidazolium cation, 1-hexyl-2,3-dimethylimidazolium cation, and 1-(2-methoxyethyl)-3-methylimidazolium cation. Examples include zolium cation, 1,3-dimethyl-1,4,5,6-tetrahydropyrimidinium cation, 1,2,3-trimethyl-1,4,5,6-tetrahydropyrimidinium cation, 1,2,3,4-tetramethyl-1,4,5,6-tetrahydropyrimidinium cation, 1,2,3,5-tetramethyl-1,4,5,6-tetrahydropyrimidinium cation, 1,3-dimethyl-1,4-dihydropyrimidinium cation, 1,3-dimethyl-1,6-dihydropyrimidinium cation, 1,2,3-trimethyl-1,4-dihydropyrimidinium cation, 1,2,3-trimethyl-1,6-dihydropyrimidinium cation, 1,2,3,4-tetramethyl-1,4-dihydropyrimidinium cation, and 1,2,3,4-tetramethyl-1,6-dihydropyrimidinium cation.

[0152] Examples of cations represented by formula (C) include pyrazolium cations and pyrazolinium cations.

[0153] Specific examples of cations represented by formula (C) include, for example, 1-methylpyrazolium cation, 3-methylpyrazolium cation, 1-ethyl-2-methylpyrazolinium cation, 1-ethyl-2,3,5-trimethylpyrazolium cation, 1-propyl-2,3,5-trimethylpyrazolium cation, 1-butyl-2,3,5-trimethylpyrazolium cation, 1-ethyl-2,3,5-trimethylpyrazolinium cation, 1-propyl-2,3,5-trimethylpyrazolinium cation, and 1-butyl-2,3,5-trimethylpyrazolinium cation.

[0154] Examples of cations represented by formula (D) include ammonium cations, sulfonium cations, and phosphonium cations.

[0155] Specific examples of cations represented by formula (D) include, for example, tetraalkylammonium cations such as tetramethylammonium cation, tetraethylammonium cation, tetrabutylammonium cation, tetrapentylammonium cation, tetrahexylammonium cation, and tetraheptylammonium cation; triethylmethylammonium cation, tributylethylammonium cation, trimethyldecylammonium cation, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium cation, N,N-dimethyl-N-ethyl-N-propylammonium cation, N,N-dimethyl-N-ethyl-N-butylammonium cation, N,N-dimethyl-N-ethyl-N-pentylammonium cation, N,N-dimethyl-N-ethyl-N-hexylammonium cation, N,N-dimethyl-N-ethyl-N-heptylammonium cation, N,N-dimethyl-N-ethyl-N-nonylammonium cation, N,N-dimethyl-N,N-dipropylammonium cation, N,N-diethyl-N-propyl-N-butylammonium cation, N N-dimethyl-N-propyl-N-pentylammonium cation, N,N-dimethyl-N-propyl-N-hexylammonium cation, N,N-dimethyl-N-propyl-N-heptylammonium cation, N,N-dimethyl-N-butyl-N-hexylammonium cation, N,N-diethyl-N-butyl-N-heptylammonium cation, N,N-dimethyl-N-pentyl-N-hexylammonium cation, N,N-dimethyl-N,N-dihexylammonium cation, trimethylhept N,N-methyl-N-propylammonium cation, N,N-diethyl-N-methyl-N-pentylammonium cation, N,N-diethyl-N-methyl-N-heptylammonium cation, N,N-diethyl-N-propyl-N-pentylammonium cation, triethylpropylammonium cation, triethylpentylammonium cation, triethylheptylammonium cation, N,N-dipropyl-N-methyl-N-ethylammonium cation, N,N-dipropyl-N-methyl-N-pentylammonium cation, N,Asymmetric tetraalkylammonium cations such as N-dipropyl-N-butyl-N-hexylammonium cation, N,N-dipropyl-N,N-dihexylammonium cation, N,N-dibutyl-N-methyl-N-pentylammonium cation, N,N-dibutyl-N-methyl-N-hexylammonium cation, trioctylmethylammonium cation, N-methyl-N-ethyl-N-propyl-N-pentylammonium cation, glycidyltrimethylammonium cation, diallyldimethylammonium cation; trimethylsulfonium cation, triethylsulfonium cation, tributylsulfonium cation, trihexylsulfonium cation, etc. Examples include alkylsulfonium cations; asymmetric trialkylsulfonium cations such as diethylmethylsulfonium cation, dibutylethylsulfonium cation, and dimethyldecylsulfonium cation; tetraalkylphosphonium cations such as tetramethylphosphonium cation, tetraethylphosphonium cation, tetrabutylphosphonium cation, tetrahexylphosphonium cation, and tetraoctylphosphonium cation; and asymmetric tetraalkylphosphonium cations such as triethylmethylphosphonium cation, tributylethylphosphonium cation, trimethyldecylphosphonium cation, and tributyl-(2-methoxyethyl)phosphonium cation.

[0156] Any suitable anionic component can be used as the anionic component that constitutes an ionic liquid, as long as it is capable of forming an ionic liquid. For example, Cl - , Br - , I - AlCl4 - Al2Cl7 - BF4 - PF6 - SCN - ClO4 - NO3 - CH3COO - CF3COO - CH3SO3 - CF3SO3 -, C4F9SO3 - , (CF3SO2)2N - , (C2F5SO2)2N - , (C3F7SO2)2N - , (C4F9SO2)2N - , (CF3SO2)3C - , AsF6 - , SbF6 - , NbF6 - , TaF6 - , F(HF)n - , (CN)2N - , C4F9SO3 - , (C2F5SO2)2N - , C3F7COO - , (CF3SO2)(CF3CO)N - , C9H 19 COO - , (CH3)2PO4 - , (C2H5)2PO4 - , CH3OSO3 - , C2H5OSO3 - , C4H9OSO3 - , C6H 13 OSO3 - , C8H 17 OSO3 - , CH3(OC2H4)2OSO3 - , C6H4(CH3)SO3 - , (C2F5)3PF3 - , CH3CH(OH)COO - , (FSO2)2N - , B(CN)4 - , C(CN)3 - , N(CN)2 - , Examples include p-toluenesulfonate anion and 2-(2-methoxyethyl)ethyl sulfate anion.

[0157] The ionic liquid may be used alone or in combination of two or more.

[0158] ≪≪Acrylic Adhesive≫≫ The acrylic adhesive according to an embodiment of the present invention is formed from the acrylic adhesive composition according to an embodiment of the present invention.

[0159] The acrylic adhesive according to the embodiments of the present invention may be an adhesive of any shape. Typically, the acrylic adhesive according to the embodiments of the present invention is a sheet-like acrylic adhesive. The sheet-like acrylic adhesive may be, for example, an acrylic adhesive sheet that can be handled independently, or it may be recognized as one of the constituent members, such as an acrylic adhesive layer.

[0160] The acrylic adhesive according to the embodiment of the present invention can thus be defined as being formed from an acrylic adhesive composition. This is because, since an acrylic adhesive is formed when an acrylic adhesive composition undergoes a crosslinking reaction such as heating or ultraviolet irradiation, it is impossible and impractical to directly identify an acrylic adhesive by its structure. Therefore, the definition "formed from an acrylic adhesive composition" appropriately identifies the acrylic adhesive as a "substance."

[0161] As a method for forming an acrylic adhesive according to embodiments of the present invention, any suitable method can be used as long as it does not impair the effects of the present invention. For example, one method for forming an acrylic adhesive is to apply an acrylic adhesive composition onto any suitable substrate, heat and dry as necessary, and cure as necessary to form an acrylic adhesive in a sheet form on the substrate. As a means of such application, any suitable means can be used as long as it does not impair the effects of the present invention. For example, such means of application include gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, air knife coaters, spray coaters, comma coaters, direct coaters, and roll brush coaters. As a means of heating and drying the acrylic adhesive composition, any suitable means can be used as long as it does not impair the effects of the present invention. For example, such means of heating and drying include heating to about 60°C to 180°C. As a means of curing the acrylic adhesive composition, any suitable means can be used as long as it does not impair the effects of the present invention. Examples of such curing methods include ultraviolet irradiation, laser irradiation, alpha-ray irradiation, beta-ray irradiation, gamma-ray irradiation, X-ray irradiation, and electron beam irradiation.

[0162] The acrylic adhesive according to the embodiment of the present invention has an adhesive strength to polyimide film at 23°C, a peeling speed of 300 mm / min, and a peeling angle of 180 degrees, preferably 4.0 N / 25 mm or more, more preferably 5.0 N / 25 mm or more, even more preferably 6.0 N / 25 mm or more, particularly preferably 7.0 N / 25 mm or more, and most preferably 8.0 N / 25 mm or more. While a higher adhesive strength is generally preferable, considering the balance with other adhesive properties, it is preferably 30 N / 25 mm or less. By adjusting the adhesive strength within the above range, sufficient adhesion to various substrates such as flexible devices like foldable devices and rollable devices can be achieved. The measurement of the adhesive strength will be described later.

[0163] The acrylic adhesive according to the embodiment of the present invention has an adhesive strength to a polyimide film, after heating at 200°C for 15 seconds, with a peeling speed of 300 mm / min and a peeling angle of 180 degrees, preferably 0.5 N / 25 mm or more, more preferably 1.0 N / 25 mm or more, even more preferably 1.5 N / 25 mm or more, particularly preferably 1.8 N / 25 mm or more, and most preferably 2.0 N / 25 mm or more. While a higher adhesive strength is generally preferable, considering the balance with other adhesive properties, it is preferably 30 N / 25 mm or less. By adjusting the adhesive strength within the above range, sufficient adhesion to various substrates such as flexible devices like foldable devices and rollable devices can be achieved. The measurement of the adhesive strength will be described later.

[0164] The acrylic adhesive according to the embodiment of the present invention has a storage modulus G'(-20) at -20°C that is preferably 300 kPa or less, more preferably 250 kPa or less, even more preferably 200 kPa or less, particularly preferably 170 kPa or less, and most preferably 150 kPa or less. The lower limit of the storage modulus G'(-20) is preferably 50 kPa or more, and more preferably 70 kPa or more, considering the balance with other adhesive properties. By adjusting the storage modulus G'(-20) within the above range, the acrylic adhesive according to the embodiment of the present invention can exhibit even better flexibility and bonding resistance, capable of withstanding repeated bending over a wide temperature range. The measurement of the storage modulus G'(-20) will be described later.

[0165] The acrylic adhesive according to the embodiment of the present invention has a storage modulus G'(40) at 40°C that is preferably 200 kPa or less, more preferably 150 kPa or less, even more preferably 100 kPa or less, particularly preferably 50 kPa or less, and most preferably 30 kPa or less. The lower limit of the storage modulus G'(40) is preferably 5 kPa or more, and more preferably 10 kPa or more, considering the balance with other adhesive properties. By adjusting the storage modulus G'(40) within the above range, the acrylic adhesive according to the embodiment of the present invention can exhibit even better flexibility and bonding resistance, capable of withstanding repeated bending over a wide temperature range. The measurement of the storage modulus G'(40) will be described later.

[0166] The acrylic adhesive according to the embodiment of the present invention has a storage modulus G'(200) at 200°C that is preferably 150 kPa or less, more preferably 100 kPa or less, even more preferably 50 kPa or less, particularly preferably 40 kPa or less, and most preferably 30 kPa or less. The lower limit of the storage modulus G'(200) is preferably 1 kPa or more, and more preferably 5 kPa or more, considering the balance with other adhesive properties. By adjusting the storage modulus G'(200) within the above range, the acrylic adhesive according to the embodiment of the present invention can exhibit even better flexibility and bonding resistance, capable of withstanding repeated bending over a wide temperature range. The measurement of the storage modulus G'(200) will be described later.

[0167] The acrylic adhesive according to the embodiment of the present invention has a ratio (G'(-20) / G'(200)) of the storage modulus G'(-20) at -20°C to the storage modulus G'(200) at 200°C, which is preferably 20 or less, more preferably 17 or less, even more preferably 13 or less, particularly preferably 10 or less, and most preferably 8 or less. The lower limit of the above ratio (G'(-20) / G'(200)) is preferably 1. If the above ratio (G'(-20) / G'(200)) is within the above range, the acrylic adhesive according to the embodiment of the present invention can exhibit better flexibility and better bonding resistance, capable of withstanding repeated bending over a wide temperature range.

[0168] Adhesive film An adhesive film according to an embodiment of the present invention has an adhesive layer composed of an acrylic adhesive according to an embodiment of the present invention.

[0169] The adhesive film according to the embodiment of the present invention may be a substrate-less film consisting only of an adhesive layer, or a substrate-attached film having a substrate layer and an adhesive layer. In addition to the substrate layer and the adhesive layer, the adhesive film of the present invention may have any other suitable layer, as long as it does not impair the effects of the present invention.

[0170] The base layer may be one layer or two or more layers. Preferably, the base layer is one layer, as this allows for better expression of the effects of the present invention.

[0171] The adhesive layer may be one layer or two or more layers. Preferably, the adhesive layer is one layer, as this allows for better expression of the effects of the present invention.

[0172] The adhesive film according to the embodiment of the present invention may be provided with an optional suitable release liner on the surface opposite the substrate layer of the adhesive layer for protection until use, etc.

[0173] Examples of release liners include release liners in which the surface of a substrate (liner substrate) such as paper or plastic film is treated with silicone, and release liners in which the surface of a substrate (liner substrate) such as paper or plastic film is laminated with a polyolefin resin. Examples of plastic films used as liner substrates include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, and ethylene-vinyl acetate copolymer film.

[0174] The thickness of the release liner is preferably 1 μm to 500 μm, more preferably 3 μm to 450 μm, even more preferably 5 μm to 400 μm, and particularly preferably 10 μm to 300 μm.

[0175] The thickness of the adhesive film according to the embodiment of the present invention is preferably 1 μm to 500 μm, more preferably 5 μm to 200 μm, even more preferably 10 μm to 150 μm, particularly preferably 20 μm to 100 μm, and most preferably 30 μm to 80 μm. The effects of the present invention can be more fully realized when the thickness of the adhesive film according to the embodiment of the present invention is within the above range.

[0176] The adhesive film according to the embodiment of the present invention has a total light transmittance of preferably 20% or more, more preferably 30% or more, even more preferably 40% or more, particularly preferably 50% or more, and most preferably 60% or more. If the total light transmittance of the adhesive film of the present invention is within the above range, excellent transparency can be further expressed.

[0177] The adhesive film according to the embodiment of the present invention has a haze of preferably 15% or less, more preferably 13% or less, even more preferably 10% or less, particularly preferably 8% or less, and most preferably 6% or less. When the haze of the adhesive film of the present invention is within the above range, excellent transparency can be more easily achieved.

[0178] The adhesive film according to the embodiment of the present invention can achieve both excellent adhesiveness and excellent elasticity, and therefore can preferably be used in flexible devices such as foldable devices and rollable devices.

[0179] ≪Base material layer≫ The thickness of the substrate layer is preferably 1 μm to 500 μm, more preferably 5 μm to 300 μm, even more preferably 10 μm to 100 μm, particularly preferably 15 μm to 80 μm, and most preferably 20 μm to 60 μm. The effects of the present invention can be more fully realized when the thickness of the substrate layer is within the above range.

[0180] The base layer preferably has a Young's modulus of 6.0 × 10 at 23°C. 7 Pa or higher, more preferably 1.0 × 10⁻⁶ 8 Pa or higher, and more preferably 5.0 × 10⁻⁶ 8 The pressure is Pa or higher, and particularly preferably 8.0 × 10⁻⁶ 8 The Pa level is above, and most preferably 1.0 × 10⁻⁶. 9 It is Pa or higher. The upper limit of the Young's modulus of the substrate layer at 23°C is typically preferably 1.0 × 10⁻⁶. 11 It is less than or equal to Pa. The effects of the present invention can be more fully realized if the Young's modulus of the base layer at 23°C is within the above range. If the Young's modulus of the base layer at 23°C is too low, when the adhesive film is bent at an angle, the tension on the outer diameter side may not be sufficiently maintained against the compression on the inner diameter side, which may cause the thickness to change easily and may lead to lifting from the adherend. If the Young's modulus of the base layer at 23°C is too high, the adhesive film may not be easily deformable. The method for measuring Young's modulus will be described in detail later.

[0181] Any suitable material can be used as the base layer material, as long as it does not impair the effects of the present invention. Typical examples of such base layer materials include resin materials.

[0182] Examples of resin materials used as the base layer material include acrylic resins such as polyimide (PI), polyether ether ketone (PEEK), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), and polymethyl methacrylate (PMMA), as well as polycarbonate, triacetylcellulose (TAC), polysulfone, polyarylate, polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), polyamide (nylon), fully aromatic polyamide (aramid), polyvinyl chloride (PVC), polyvinyl acetate, polyphenylene sulfide (PPS), fluororesins, and cyclic olefin polymers.

[0183] ≪Adhesive layer≫ The adhesive layer of the adhesive film according to the embodiment of the present invention has a thickness of preferably 1 μm to 250 μm, more preferably 2 μm to 150 μm, even more preferably 3 μm to 100 μm, particularly preferably 5 μm to 50 μm, and most preferably 10 μm to 35 μm.

[0184] The adhesive layer is a form of acrylic adhesive. Any suitable method can be used to form the adhesive layer, provided it does not impair the effects of the present invention. For example, such a method involves applying an acrylic adhesive composition to any suitable substrate, heating and drying as necessary, and curing as necessary to form an acrylic adhesive layer on the substrate. Any suitable means can be used for such application, provided it does not impair the effects of the present invention. Examples of such application means include gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, air knife coaters, spray coaters, comma coaters, direct coaters, and roll brush coaters. Any suitable means can be used for heating and drying the acrylic adhesive composition, provided it does not impair the effects of the present invention. For example, heating to approximately 60°C to 180°C is used. Any suitable means can be used for curing the acrylic adhesive composition, provided it does not impair the effects of the present invention. Examples of such curing methods include ultraviolet irradiation, laser irradiation, alpha-ray irradiation, beta-ray irradiation, gamma-ray irradiation, X-ray irradiation, and electron beam irradiation.

[0185] Flexible Devices The adhesive film of the present invention can achieve both excellent adhesion and excellent elasticity, making it suitable for use in flexible devices such as bendable devices, foldable devices, and rollable devices that have a movable bending portion.

[0186] That is, a flexible device according to an embodiment of the present invention comprises an adhesive film according to an embodiment of the present invention. A foldable device according to the present invention may include any other suitable member, provided it comprises an adhesive film according to an embodiment of the present invention.

[0187] Figure 1 is a schematic cross-sectional view showing one embodiment of the flexible device of the present invention as a representative example of one use of the adhesive film according to an embodiment of the present invention. In Figure 1, the foldable device 1000 according to an embodiment of the present invention comprises a cover film 10, an adhesive layer 20, a polarizing plate 30, an adhesive layer 40, a touch sensor 50, an adhesive layer 60, an OLED 70, and an adhesive film 100 according to an embodiment of the present invention. In Figure 1, the adhesive film 100 according to an embodiment of the present invention is composed of an adhesive layer 80 and a base layer 90. The adhesive layers 20, 40, and 60 may be adhesive layers containing an adhesive with the same composition as the adhesive layer 80 that constitutes the adhesive film 100 according to an embodiment of the present invention, or they may be adhesive layers containing an adhesive with a different composition. [Examples]

[0188] The present invention will be described more specifically below with reference to examples and comparative examples. However, the present invention is not limited in any way to these. In the following description, "parts" and "%" refer to mass unless otherwise specified.

[0189] The abbreviations and details of the raw materials used in the following manufacturing examples, examples, and comparative examples are as follows. 2EHA: 2-ethylhexyl acrylate (glass transition temperature Tg = -70°C of its homopolymer) LA: Lauryl acrylate (glass transition temperature Tg = -23°C of its homopolymer) BA: n-butyl acrylate (glass transition temperature Tg = -55°C of its homopolymer) 4HBA: 4-hydroxybutyl acrylate (glass transition temperature Tg = -32°C of its homopolymer) NVP: N-vinyl-2-pyrrolidone (glass transition temperature Tg = approximately 80°C for its homopolymer) AOMA (registered trademark): Cyclopolymerizable monomer manufactured by Nippon Shokubai Co., Ltd. (In general formula (1), R 1 is a methyl group, R 2This is a hydrogen atom. (The glass transition temperature Tg of its homopolymer is approximately 80°C.) AIBN: 2,2'-Azobisisobutyronitrile C / HX: Coronate HX (manufactured by Tosoh Corporation, isocyanate-based crosslinking agent) Narsem Ferric: Iron Catalyst (manufactured by Nippon Chemical Industrial Co., Ltd.) Irganox 1010: Antioxidant (made by BASF)

[0190] <Creep value> The adhesive layer was extracted from the adhesive film, laminated to a thickness of approximately 1 mm, and then punched out to a diameter of φ9 mm to create cylindrical pellets, which were used as samples for measurement. A dynamic viscoelasticity measuring device (ARES, manufactured by Rheometrics) was used, and the obtained measurement samples were fixed to a jig with a diameter of 8 mm parallel plate. At 60°C, the deformation strain (%) after applying a deformation stress of 2 kPa and holding for 600 seconds was defined as value A, and the deformation strain after applying a deformation stress of 0 and holding for another 600 seconds was defined as value B, with value A being defined as the creep value at 60°C.

[0191] <Storage modulus G'> The storage modulus G' corresponds to the portion of elastic energy stored when a material deforms, and is an indicator of its degree of hardness. The adhesive layer was extracted from the adhesive film, laminated to a thickness of approximately 1 mm, and then punched out to a diameter of φ9 mm to create cylindrical pellets, which were used as samples for measurement. Using a dynamic viscoelasticity measuring device (ARES, manufactured by Rheometrics), the obtained measurement samples were fixed to a φ8 mm parallel plate jig, and the storage modulus G' was calculated. The measurement conditions were as follows. Measurement: Shear mode Temperature range: -30℃ to 210℃ Heating rate: 5°C / min Frequency: 1Hz

[0192] <Adhesion to polyimide film at 23°C> From the separators of the substrate-less adhesive film, the separator with low peeling force (MRQ50T100J) was peeled off, and a 25 μm thick polyimide substrate (product name "UPIREX 25RN", manufactured by Ube Industries, Ltd.) was laminated to it to create a polyimide substrate-attached adhesive film. The polyimide substrate-attached adhesive film was cut to a width of 25 mm x length of 100 mm, the separator (JT-50Wa) was peeled off to expose the adhesive, and it was attached to a polyimide film (product name "UPIREX 50S", manufactured by Ube Industries, Ltd.) with one pass of a 2 kg hand roller to obtain a sample for evaluation. The obtained evaluation samples were stored at room temperature (23°C) for 30 minutes and then measured using a tensile testing machine. The tensile testing machine used was the "Autograph AG-Xplus HS 6000mm / min high-speed model (AG-50NX plus)" manufactured by Shimadzu Corporation. After setting the evaluation samples in the tensile testing machine, the tensile test was started. The conditions for the tensile test were a peel angle of 180 degrees and a peel speed (tensile speed) of 300 mm / min. The load when peeling the adhesive film from the above polyimide film (UPIREX 50S) was measured, and the average load at that time was defined as the adhesive force.

[0193] <Adhesion to polyimide film after high-temperature heating> From the separators of the substrate-less adhesive film, the separator with low peeling force (MRQ50T100J) was peeled off, and a 25 μm thick polyimide substrate (product name "UPIREX 25RN", manufactured by Ube Industries, Ltd.) was laminated to it to create a polyimide substrate-attached adhesive film. The polyimide substrate-attached adhesive film was cut to a width of 25 mm x length of 100 mm, the separator (JT-50Wa) was peeled off to expose the adhesive, and it was attached to a polyimide film (product name "UPIREX 50S", manufactured by Ube Industries, Ltd.) with one pass of a 2 kg hand roller to obtain a sample for evaluation. The obtained evaluation samples were stored at room temperature (23°C) for 30 minutes, then heated at 200°C for 15 seconds, and measured using a tensile tester within 30 seconds. The tensile tester used was the Shimadzu Corporation product name "Autograph AG-Xplus HS 6000mm / min high-speed model (AG-50NX plus)". After setting the evaluation sample in the tensile tester, the tensile test was started. The conditions for the tensile test were: peel angle: 180 degrees, peel speed (tensile speed): 300 mm / min. The load when peeling the adhesive film from the above polyimide film (UPIREX 50S) was measured, and the average load at that time was defined as the adhesive force.

[0194] <Heat compression test (evaluation of bonding resistance)> The release film was peeled off one side of the substrate-less adhesive film, and a 50 μm thick polyimide film was laminated to it. The release film was peeled off the other side, and the adhesive film was laminated to a 25 μm thick polyimide film, and then pressed together with a hand roller. This laminate (a laminate of a 25 μm thick polyimide film 2, adhesive 1, and a 50 μm thick polyimide film 3) was cut to a size of 50 mm x 50 mm, and autoclaved at 35°C and 0.35 MPa for 15 minutes to obtain test piece 4. A small press was used to heat-press the test piece 4. As shown in Figure 2, a 2mm x 30mm x 0.5mm thick metal (SUS) block 5 was placed on top of the test piece 4, and a 4mm x 40mm Teflon (registered trademark) piece 6 was placed on top of that. A 125μm polyimide film 7 and a cushion sheet 8 were placed above and below it, and the machine was set up for the press. The upper and lower stages of the press machine were heated to 200°C. The heated upper stage was lowered, and the test specimen was heat-pressed onto it at a pressure of 50 MPa for 5 seconds. After the heat-sealing test, the test specimens (block installation area) were visually inspected, and the heat-sealing resistance was evaluated according to the following criteria. ○: There were no air bubbles in the crimped area or any excess glue from the edges of the test piece. × (Air bubbles): Air bubbles were present at the adhesive interface. × (Glue overflow): Glue was overflowing from the edge of the test piece.

[0195] <Repeated bending test (evaluation of flexibility)> The release film was peeled from one side of a substrate-less adhesive sheet, and a 50 μm thick polyimide film was laminated to it. The release film was peeled from the other side, and the adhesive sheet was laminated to a 25 μm thick polyimide film, and then pressed together with a hand roller. This laminate was cut to a size of 25 mm × 100 mm, and test specimens were obtained by autoclaving at 35°C and 0.35 MPa for 15 minutes. Using a planar unloaded U-shaped stretch tester (manufactured by Yuasa System Equipment), a bending jig was attached to the short side of the test specimen, and repeated bending tests were performed in a -20°C constant temperature bath with the polarizing plate side of the test specimen facing inward under the following conditions. (Test conditions) Bending radius: 3mm Bending angle: 180° Bending speed: 1 second / bend Number of bends: 200,000 After repeated bending tests (-20°C), the test specimens were visually inspected, and their bending durability was evaluated according to the following criteria. ○: There was no peeling of the polyimide film from the adhesive film, and no air bubbles were observed at the adhesive interface. ×: Air bubbles were present at the adhesive interface.

[0196] <Weight average molecular weight Mw> The weight-average molecular weight was measured by gel permeation chromatography (GPC). Specifically, an "Agilent 1260 Infinity" (manufactured by Agilent Technologies, Inc.) was used as the GPC analyzer. Considering the polymer concentration of the sample, a tetrahydrofuran solution with 0.1% by mass of amine-based components was prepared, left to stand for 20 hours, filtered through a 0.45 μm membrane filter, and the filtrate was subjected to GPC measurement. Measurements were taken under the following conditions, and the values ​​were calculated using standard polystyrene equivalents. (Molecular weight measurement conditions) • Sample concentration: 0.1% by mass (tetrahydrofuran solution with added amine components) • Sample injection volume: 100 μL • Column: Product name "TSKgel GMH-H(S)" (manufactured by Tosoh Corporation) • Eluent: Tetrahydrofuran with added amine components ·Flow rate: 0.5mL / min • Detector: Differential refractometer (RI) • Column temperature (measurement temperature): 40°C • Standard sample: Polystyrene (PS)

[0197] [Manufacturing Example 1]: Manufacturing of acrylic polymer (1) In a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser, 89.3 parts by mass of 2EHA, 8.9 parts by mass of 4HBA, 1.8 parts by mass of NVP, and 0.2 parts by mass of AIBN as a polymerization initiator were added. Ethyl acetate was then added to bring the total concentration of these components to 40% by mass. The system was purged with nitrogen over 1 hour while gently stirring, and the polymerization reaction was carried out for 6 hours while maintaining the temperature of the solution in the flask at around 60°C. After the reaction was complete, ethyl acetate was added to adjust the polymer concentration to 35% by mass, obtaining a solution of acrylic polymer (1). The weight-average molecular weight Mw of acrylic polymer (1) was 1.2 million. The results are shown in Table 1.

[0198] [Manufacturing Example 2]: Manufacturing of acrylic polymer (2) A solution of acrylic polymer (2) was obtained by following the same procedure as in Production Example 1, except that the monomer composition was changed to 2EHA: 94.6 parts by mass, 4HBA: 4.5 parts by mass, and NVP: 0.9 parts by weight. The weight-average molecular weight Mw of acrylic polymer (2) was 1.2 million. The results are shown in Table 1.

[0199] [Manufacturing Example 3]: Manufacturing of acrylic polymer (3) A solution of acrylic polymer (3) was obtained by following the same procedure as in Production Example 1, except that the monomer composition was changed to 2EHA: 70 parts by mass, LA: 8 parts by mass, BA: 20 parts by mass, 4HBA: 1 part by mass, and NVP: 1 part by weight. The weight-average molecular weight Mw of acrylic polymer (3) was 1.15 million. The results are shown in Table 1.

[0200] [Manufacturing Example 4]: Manufacturing of acrylic polymer (4) A solution of acrylic polymer (4) was obtained by following the same procedure as in Production Example 1, except that the monomer composition was changed to 2EHA: 68.0 parts by mass, LA: 19.4 parts by mass, BA: 7.8 parts by mass, 4HBA: 3.9 parts by mass, and AOMA®: 1 part by weight. The weight-average molecular weight Mw of acrylic polymer (4) was 1.15 million. The results are shown in Table 1.

[0201] [Manufacturing Example 5]: Manufacturing of acrylic polymer (5) A solution of acrylic polymer (5) was obtained by the same procedure as in Production Example 1, except that the monomer composition was changed to 2EHA: 45 parts by mass, BA: 45 parts by mass, 4HBA: 5 parts by mass, and NVP: 5 parts by weight. The weight-average molecular weight Mw of acrylic polymer (5) was 1.3 million. The results are shown in Table 1.

[0202] [Manufacturing Example 6]: Manufacturing of oligomer (1) In a reaction vessel equipped with a thermometer, stirrer, reflux condenser, and nitrogen gas inlet, 62 parts by weight of dicyclopentanyl methacrylate (DCPMA) and 38 parts by weight of methyl methacrylate (MMA) were added as monomers, 3.5 parts by weight of methyl thioglycolate as a chain transfer agent, 0.2 parts by weight of azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and 100 parts by weight of toluene as a solvent. Nitrogen gas was then introduced, and the mixture was purged with nitrogen for approximately 1 hour while stirring. Subsequently, the mixture was heated to 70°C and reacted for 2 hours, followed by reacting at 80°C for 4 hours, and then reacting at 90°C for 1 hour to obtain a solution of oligomer (1) with a weight-average molecular weight of 4000.

[0203] [Manufacturing Example 7]: Manufacturing of oligomer (2) In a reaction vessel equipped with a thermometer, stirrer, reflux condenser, and nitrogen gas inlet, 96 parts by weight of cyclohexyl methacrylate (CHMA) and 4 parts by weight of acrylic acid (AA) were added as monomers, 3 parts by weight of 2-mercaptoethanol as a chain transfer agent, 0.2 parts by weight of azobisisobutyronitrile (AIBN) as a thermal polymerization initiator, and 103.2 parts by weight of toluene as a solvent. Nitrogen gas was then introduced, and the mixture was purged with nitrogen for approximately 1 hour while stirring. Subsequently, the mixture was heated to 70°C and reacted for 3 hours, and then reacted at 75°C for another 2 hours to obtain a solution of oligomer (2) with a weight-average molecular weight of 4000.

[0204] [Example 1] Acrylic polymer (1): 100 parts by mass, C / HX: 0.1 parts by mass as a crosslinking agent, Irganox 1010: 0.3 parts by mass as an antioxidant, and Narsem ferric: 0.01 parts by mass as a catalyst were mixed and thoroughly stirred. Dilution with ethyl acetate and acetylacetone in an amount of 2% by mass of solvent was obtained so that the total solid content was 28% by mass. This yielded a coating solution of the acrylic adhesive composition (1). The obtained coating solution of the acrylic adhesive composition (1) was applied to the silicone-treated side of a release sheet made of polyester resin with a thickness of 50 μm (product name: MRV50T100J, manufactured by Mitsubishi Chemical Corporation), which had one side silicone-treated, so that the thickness after drying was 25 μm. Drying was performed at a drying temperature of 130°C for a drying time of 1 minute. Next, an adhesive film (1) was obtained by laminating a release sheet (product name: MRQ75T100J, manufactured by Mitsubishi Chemical Corporation) made of polyester resin with a thickness of 75 μm and one side treated with silicone, so that the silicone-treated side was in contact with the surface of the obtained adhesive layer. This was then aged at 50°C for one day and various evaluations were performed. The results are shown in Table 2.

[0205] [Examples 2-6] Except for changing the raw material composition as shown in Table 2, the procedure was carried out in the same manner as in Example 1 to obtain coating solutions of acrylic adhesive compositions (2) to (6) and adhesive films (2) to (6). These were aged at 50°C for 1 day and various evaluations were performed. The results are shown in Table 2.

[0206] [Example 7] Except for mixing 100 parts by mass of acrylic polymer (1), 0.15 parts by mass of C / HX as a crosslinking agent, 0.3 parts by mass of Irganox 1010 as an antioxidant, 0.01 parts by mass of Narsem ferric as a catalyst, 0.25 parts by mass (on a solid content basis) of the ionic compound "CIL-312" (1-butyl-3-methylpyridinium bis(trifluoromethanesulfonyl)imide, manufactured by Nippon Carlit Co., Ltd.) as an antistatic agent, and 3 parts by mass of oligomer (1), the procedure was carried out in the same manner as in Example 1 to obtain a coating solution of acrylic adhesive composition (7) and an adhesive film (7). These were aged at 50°C for 1 day and various evaluations were performed. The results are shown in Table 2.

[0207] [Example 8] The procedure was carried out in the same manner as in Example 7, except that oligomer (2) was used in place of oligomer (1) at 3 parts by mass, to obtain a coating solution of the acrylic adhesive composition (8) and an adhesive film (8). These were aged at 50°C for 1 day, and various evaluations were performed. The results are shown in Table 2.

[0208] [Example 9] Except for not using oligomer (1), the procedure was the same as in Example 7 to obtain a coating solution of the acrylic adhesive composition (9) and an adhesive film (9). These were aged at 50°C for 1 day and various evaluations were performed. The results are shown in Table 2.

[0209] [Example 10] Except for mixing 100 parts by mass of acrylic polymer (1) with 0.15 parts by mass of C / HX as a crosslinking agent, 0.3 parts by mass of Irganox 1010 as an antioxidant, 0.01 parts by mass of Narsem ferric as a catalyst, and 0.25 parts by mass (on a solid content basis) of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, manufactured by Mitsubishi Materials Corporation), an ionic compound, as an antistatic agent, the procedure was carried out in the same manner as in Example 1 to obtain a coating solution of acrylic adhesive composition (10) and an adhesive film (10). These were aged at 50°C for 1 day and various evaluations were performed. The results are shown in Table 2.

[0210] [Comparative Examples 1 - 3] Except for changing the raw material composition as shown in Table 2, the procedure was the same as in Example 1 to obtain coating solutions of acrylic adhesive compositions (C1) - (C3) and adhesive films (C1) - (C3). These were aged at 50°C for 1 day and various evaluations were conducted. The results are shown in Table 2.

[0211] [Table 1]

[0212] [Table 2] [Industrial Applicability]

[0213] The acrylic adhesive sheet etc. according to the embodiment of the present invention can be used for so - called flexible devices such as foldable devices and rollable devices. [Explanation of Reference Numerals]

[0214] 1000 Foldable device 100 Adhesive film 10 Cover film 20 Adhesive layer 30 Polarizing plate 40 Adhesive layer 50 Touch sensor 60 Adhesive layer 70 OLED 80 Adhesive layer 90 Base material layer 1 Adhesive 2 Polyimide film with a thickness of 25μm 3 Polyimide film with a thickness of 50μm 4 Test piece 5 Metal (SUS) block 6 Teflon (registered trademark) piece 7 Polyimide film 8 Cushion sheet

Claims

1. An acrylic adhesive composition comprising an acrylic polymer (P) and a crosslinking agent, The acrylic polymer (P) is obtained by polymerizing a monomer component (M), The monomer component (M) comprises an alkyl (meth)acrylate (M1) and a polar group-containing monomer (M2). The alkyl (meth)acrylate (M1) comprises an alkyl (meth)acrylate (m1) whose homopolymer has a glass transition temperature Tg in the range of -80°C to -60°C. The monomer component (M) contains 50% by mass or more of the alkyl (meth)acrylate (m1), The polar group-containing monomer (M2) includes a hydroxyl group-containing monomer (m4) and a monomer having a polar group other than a hydroxyl group (m5), wherein the content of the hydroxyl group-containing monomer (m4) in monomer component (M) is 0.05% to 10% by mass, and the content of the monomer having a polar group other than a hydroxyl group (m5) in monomer component (M) is 0.1% to 3% by mass. When the content of the polar group-containing monomer (M2) in the acrylic adhesive composition is A by mass %, and the content of the crosslinking agent in the acrylic adhesive composition is B by mass %, then A / B is 40 to 150. Acrylic adhesive composition.

2. The acrylic adhesive composition according to claim 1, wherein the A / B ratio is 40 to 140.

3. The acrylic adhesive composition according to claim 2, wherein the A / B ratio is 40 to 95.

4. The acrylic adhesive composition according to any one of claims 1 to 3, wherein the content ratio of the alkyl (meth)acrylate (m1) in the monomer component (M) is 75% by mass or more.

5. The acrylic adhesive composition according to any one of claims 1 to 4, wherein the content ratio of the alkyl (meth)acrylate (m1) in the alkyl (meth)acrylate (M1) is 95% by mass or more.

6. An acrylic adhesive formed from an acrylic adhesive composition according to any one of claims 1 to 5.

7. The acrylic adhesive according to claim 6, wherein the ratio of the storage modulus G'(-20) at -20°C to the storage modulus G'(200) at 200°C (G'(-20) / G'(200)) is 20 or less.

8. The acrylic adhesive according to claim 7, wherein the ratio (G'(-20) / G'(200)) is 10 or less.

9. An adhesive film having an adhesive layer composed of an acrylic adhesive according to any one of claims 6 to 8.

10. A flexible device comprising the adhesive film described in claim 9.

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