Adhesive composition, adhesive sheet, and display containing the same

Abstract

The present invention provides an adhesive composition that can prevent degradation due to ultraviolet light due to its excellent absorption capacity against ultraviolet light, and also has excellent folding properties due to its low elastic modulus and high adhesive strength at low temperatures. The present invention also provides an adhesive sheet and a display. [Solution] An adhesive composition comprising an acrylic copolymer, a crosslinking agent, an additive, and an ultraviolet absorber, wherein the ultraviolet absorber comprises one or more compounds selected from the group consisting of compounds represented by the following chemical formulas, etc. JPEG2026057520000017.jpg64170

Description

Technical Field

[0005] ,

[0004] ,

[0001] The present invention relates to an adhesive composition, an adhesive sheet, and a display including the same.

Background Art

[0002] In the display industry, in order to mount a touch panel or a touch screen, or to obtain high brightness and high transmittance, a large number of optically transparent pressure-sensitive adhesives are used.

[0003] The adhesive used to attach a transparent film or UTG (ultra thin glass) to a touch screen or a touch panel used in the display industry is required to have adhesiveness to various substrates and durability to suppress the occurrence of curl, bubbles, etc. even when exposed to severe conditions such as low temperature or ultraviolet rays. In particular, in fields that require precise dimensional stability such as electronic materials, it is necessary to develop an adhesive composition with excellent durability that can prevent the occurrence of curl, bubbles, or peeling under severe conditions such as low temperature and ultraviolet rays.

[0004] Recently, with the development of display-related technologies, display devices that can be deformed during use, such as being folded or rolled up, have been researched and developed. Since these displays can be deformed into various forms, they can satisfy both the requirement for the enlargement of the display during use and the requirement for the miniaturization of the display for portability. A deformable display device can not only be deformed into a preset form, but also be deformed into various forms according to the user's requirements or the needs of the situation in which the display device is used. Therefore, it is necessary to recognize the deformed form of the display and control the display device corresponding to the recognized form.

[0005] On the other hand, deformable display devices have the problem that each component of the display device may be damaged as it deforms. Therefore, each component of such a display device must satisfy folding reliability and stability, and the adhesive used in the deformable display device must also satisfy the aforementioned folding reliability and stability.

[0006] In the case of Korean Published Patent Publication No. 10-2023-0113849, the adhesive composition for displays contains an ultraviolet absorber, but it has limitations in that it cannot ensure excellent durability due to the low folding reliability and stability in deformable displays. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Korean Published Patent Gazette No. 10-2023-0113849 [Overview of the project] [Problems that the invention aims to solve]

[0008] The present invention aims to improve upon the aforementioned conventional technical problems, and to provide an adhesive composition that can prevent degradation due to ultraviolet light with excellent absorption capacity for ultraviolet light, and has excellent folding properties because it has a low elastic modulus and high adhesive strength at low temperatures.

[0009] Furthermore, the present invention aims to provide an adhesive sheet and a display manufactured using the adhesive composition described above.

[0010] However, the problems that this invention aims to solve are not limited to those mentioned above, and other problems not mentioned should be clearly understood by an ordinary person from the following description. [Means for solving the problem]

[0011] To achieve the above objective, the present invention provides an adhesive composition comprising an acrylic copolymer, a crosslinking agent, an additive, and an ultraviolet absorber, wherein the ultraviolet absorber comprises one or more compounds selected from the group consisting of compounds represented by the following chemical formulas 1 and 2.

[0012] [Chemical formula 1]

[0013] [ka]

[0014] In the aforementioned chemical formula 1, R1 is independently a linear or branched alkyl group having 8 or more carbon atoms.

[0015] [Chemical formula 2]

[0016] [ka]

[0017] In the aforementioned chemical formula 2, R2 is independently a linear or branched alkyl group having 8 or more carbon atoms.

[0018] Each of the R1s may independently be a linear or branched alkyl group having 8 to 24 carbon atoms, and each of the R2s may independently be a linear or branched alkyl group having 8 to 24 carbon atoms.

[0019] The ultraviolet absorber may be included in an amount of 0.1 to 5 parts by weight per 100 parts by weight of the acrylic copolymer.

[0020] The acrylic copolymer may be polymerized by including linear or branched alkyl (meth)acrylate monomers having 8 to 30 carbon atoms.

[0021] The acrylic copolymer may be further polymerized by further including a polar group-containing (meth)acrylate monomer and a hydroxyl group-containing (meth)acrylate monomer.

[0022] The crosslinking agent may include a metal chelate-based crosslinking agent.

[0023] The crosslinking agent may include one selected from the group consisting of zirconium, aluminum, zinc, and magnesium.

[0024] The crosslinking agent may further include one or more selected from the group consisting of isocyanate-based, aziridine-based, epoxy-based, melamine-based, peroxide-based, and oxazoline-based crosslinking agents.

[0025] The additive may further include one or more selected from the group consisting of a silane coupling agent, an antistatic agent, an antioxidant, a corrosion inhibitor, a leveling agent, a surface lubricant, an antifoaming agent, a filler, a plasticizer, and a reaction initiator.

[0026] The adhesive sheet formed of the adhesive composition may have a light transmittance of 10% or less at a wavelength of 380 nm.

[0027] The adhesive sheet formed of the adhesive composition may have an elastic modulus of 40 kPa to 100 kPa at -20°C and 1 Hz.

[0028] Further, the present invention provides an adhesive sheet including the adhesive composition.

[0029] Further, the present invention provides a display including the adhesive sheet.

Advantages of the Invention

[0030] The present invention can provide an adhesive composition that has excellent absorption ability against ultraviolet rays and can prevent deterioration caused by ultraviolet rays, and has excellent folding properties because it has a low elastic modulus and a high adhesive force at low temperatures.

[0031] Furthermore, the present invention can provide an adhesive sheet manufactured using the adhesive composition and a display containing the adhesive sheet. [Modes for carrying out the invention]

[0032] The present invention relates to an adhesive composition comprising an acrylic copolymer, a crosslinking agent, an additive, and an ultraviolet absorber, wherein the ultraviolet absorber comprises one or more compounds selected from the group consisting of compounds represented by chemical formulas 1 and 2, an adhesive sheet containing the same, and a display. The present invention was completed through experimental confirmation that by including an ultraviolet absorber comprising one or more compounds selected from the group consisting of compounds represented by chemical formulas 1 and 2, it is possible to provide an adhesive composition that can prevent degradation due to ultraviolet light with excellent absorption capacity for ultraviolet light, and has excellent folding characteristics because it has a low elastic modulus and high adhesive strength at low temperatures. Specifically, the adhesive sheet formed with the adhesive composition may have a light transmittance of 10% or less at a wavelength of 380 nm, based on a thickness of 10 to 150 μm.

[0033] The following describes in detail each component constituting the adhesive composition of the present invention. However, the present invention is not limited to these components.

[0034] <Adhesive composition> The adhesive composition of the present invention contains a novel, specificly structured ultraviolet absorber, which prevents degradation due to ultraviolet light with excellent absorption capacity, and exhibits excellent folding properties due to its low elastic modulus and high adhesive strength at low temperatures. It may further contain an acrylic copolymer, a crosslinking agent, additives, and / or a solvent.

[0035] Acrylic copolymer The acrylic copolymer of the present invention is characterized by being polymerized with a linear or branched alkyl (meth)acrylate monomer having 8 to 30 carbon atoms, and preferably further copolymerized with a polar group-containing (meth)acrylate monomer and a hydroxyl group-containing (meth)acrylate monomer. The acrylic copolymer may be produced by adding the monomer to a solvent and then undergoing a thermal polymerization or photopolymerization reaction, but is not limited thereto. The solvent is not particularly limited as long as it can dissolve the monomer for the production of the acrylic copolymer of the present invention. Furthermore, a thermal polymerization initiator or a photopolymerization initiator can be used for the thermal polymerization or photopolymerization reaction.

[0036] Linear or branched alkyl (meth)acrylate monomers having 8 to 30 carbon atoms The acrylic copolymer of the present invention is polymerized by including a linear or branched alkyl (meth)acrylate monomer having 8 to 30 carbon atoms.

[0037] The aforementioned "(meth)acrylate" refers to both acrylate and methacrylate.

[0038] The linear or branched alkyl (meth)acrylate monomer having 8 to 30 carbon atoms is preferable because limiting the number of carbon atoms within this range allows it to have a low glass transition temperature, exhibit low elastic modulus properties at low temperatures, and demonstrate excellent adhesive strength and folding properties.

[0039] Specific examples of linear or branched alkyl (meth)acrylates having 8 to 30 carbon atoms include 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, 2-decyltetradecyl (meth)acrylate, 2-dodecylhexadecyl (meth)acrylate, stearyl (meth)acrylate, and 2-decyl-1-tetradecenyl (meth)acrylate, which can be used individually or in combination of two or more.

[0040] The linear or branched alkyl (meth)acrylate having 8 to 30 carbon atoms is preferably present in an amount of 60 to 91.99% by weight relative to the total weight of the monomers used in the polymerization of the acrylic copolymer. When the linear or branched alkyl (meth)acrylate having 8 to 30 carbon atoms is included within this range, the glass transition temperature is lowered, which improves the low-temperature modulus and allows for excellent low-temperature folding characteristics.

[0041] Polar group-containing (meth)acrylate monomers The acrylic copolymer of the present invention may be polymerized containing a polar group-containing (meth)acrylate monomer.

[0042] The aforementioned polar group-containing (meth)acrylate monomers are characterized by having polar groups other than hydroxyl groups. Specifically, examples include, but are not limited to, carboxyl group-containing (meth)acrylate monomers, amide group-containing (meth)acrylate monomers, amino group-containing (meth)acrylate monomers, imide group-containing (meth)acrylate monomers, epoxy group-containing (meth)acrylate monomers, ether group-containing (meth)acrylate monomers, and other functional group-containing monomers.

[0043] The acrylic copolymer can have excellent effects in that, by copolymerizing with the polar group-containing (meth)acrylate monomer, it can influence the crosslinking action between monomers and form an adhesive layer with excellent tackiness.

[0044] Examples of the carboxyl group-containing (meth)acrylate monomers include acrylic acid, methacrylic acid, 2-carboxyethylacrylic acid, 2-(meth)acryloyloxyacetic acid, 3-(meth)acryloyloxypropyl acid, 4-(meth)acryloyloxybutyric acid, acrylic acid dimer, itaconic acid, and maleic acid.

[0045] Examples of the amino group-containing (meth)acrylate monomers include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, and (meth)acryloylmorpholine.

[0046] Examples of the aforementioned imide group-containing (meth)acrylate monomers include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.

[0047] Examples of the epoxy group-containing (meth)acrylate monomers include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, and allylglycidyl ether.

[0048] Examples of the ether group-containing (meth)acrylate monomers include methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxy-diethylene glycol (meth)acrylate, methoxy-triethylene glycol (meth)acrylate, 2-ethylhexyl-diglycol (meth)acrylate, methoxy-polyethylene glycol (meth)acrylate, and methoxydipropylene glycol (meth)acrylate.

[0049] The polar group-containing (meth)acrylate monomer is preferably present in an amount of 0.01 to 3% by weight relative to the total weight of the monomers used in the polymerization of the acrylic copolymer. When the polar group-containing (meth)acrylate monomer is included within this range, the adhesive strength of the adhesive composition is high, which is preferable from the viewpoint of ensuring excellent durability.

[0050] Hydroxyl group-containing (meth)acrylate monomer The acrylic copolymer of the present invention may be polymerized containing a hydroxyl group-containing (meth)acrylate monomer.

[0051] By including the hydroxyl group-containing (meth)acrylate monomer in the acrylic copolymer, the acrylic copolymer can have a low glass transition temperature characteristic, thereby achieving the folding characteristics of the adhesive composition.

[0052] Specific examples of the hydroxyl group-containing (meth)acrylate monomers include 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, and 2-hydroxypropylene glycol (meth)acrylate, which can be used individually or in combination of two or more.

[0053] When polymerizing the acrylic copolymer with 2-hydroxyethyl (meth)acrylate as the hydroxyl group-containing (meth)acrylate monomer, it is preferable to produce the acrylic copolymer by excluding the monomer, from the viewpoint that the high glass transition temperature of 2-hydroxyethyl (meth)acrylate makes it difficult to exhibit low elastic modulus properties at low temperatures.

[0054] The hydroxyl group-containing (meth)acrylate monomer is preferably present in an amount of 8 to 30% by weight relative to the total weight of the monomers used in the polymerization of the acrylic copolymer. When the hydroxyl group-containing (meth)acrylate monomer is included within this range, it is possible to ensure a sufficient amount of the hydroxyl group-containing (meth)acrylate monomer, which is highly reactive with the crosslinking agent, to have appropriate cohesive force, which is preferable in terms of ensuring the durability of the adhesive sheet and having excellent folding characteristics.

[0055] The weight-average molecular weight (Mw) of the acrylic copolymer is 500,000 to 2,000,000, preferably 700,000 to 1,700,000, and more preferably 1,000,000 to 1,200,000, from the viewpoint of ensuring the low-temperature modulus and folding characteristics of the adhesive composition containing the acrylic copolymer. If the weight-average molecular weight of the acrylic copolymer is formed to be less than the above range, it becomes difficult to ensure adhesive properties and durability, and if it exceeds the above range, it may cause problems in ensuring processability.

[0056] Crosslinking agent The adhesive composition of the present invention may further contain a crosslinking agent to enhance the cohesive force of the adhesive.

[0057] The crosslinking agent is not particularly limited as long as it is a component that can enhance the cohesive force of the adhesive by appropriately crosslinking the acrylic copolymer.

[0058] The aforementioned crosslinking agent, for example, includes a functional group that reacts with a crosslinkable functional group derived from a crosslinkable group-containing monomer of a (meth)acrylate copolymer, thereby improving the adhesion and durability of the adhesive composition and maintaining reliability and shape of the adhesive at high temperatures.

[0059] Examples of the aforementioned crosslinking agents include metal chelating agents, isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, and aziridine crosslinking agents. From the viewpoint of being able to improve the adhesion of the adhesive by forming coordination bonds or ionic bonds with the surface of the object to be adhered, it is preferable to use a metal chelating agent.

[0060] Specifically, the metal atoms of the metal chelating crosslinking agent can form coordination bonds with the polar functional groups of the acrylic copolymer, such as hydroxyl groups or carboxyl groups, thereby further improving the cohesive force and mechanical stability of the adhesive. Furthermore, the metal chelating crosslinking agent can form coordination bonds or ionic bonds with, for example, the surface of a corona or plasma-treated adherend, allowing the adhesive to exhibit improved adhesion.

[0061] Examples of the aforementioned metal chelating crosslinking agents include compounds in which polyvalent metals such as zirconium, aluminum, zinc, and / or magnesium are coordinated to acetylacetone or ethyl acetoethyl acetate. These can be used individually or in combination of two or more.

[0062] Specific examples of the isocyanate-based crosslinking agent include polyfunctional isocyanate compounds such as toluene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tetramethylxylene diisocyanate, or naphthalene diisocyanate, or compounds obtained by reacting the aforementioned polyfunctional isocyanate compounds with polyol compounds such as trimethylolpropane. These can be used individually or in combination of two or more.

[0063] Specific examples of the epoxy crosslinking agents include diglycidylaniline, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate ester triglycidyl ether, trimethylolpropane triglycidyl ether, N,N,N',N'-tetraglycidyl-m-xylenediamine, N,N,N',N'-tetraglycidylethylenediamine, and glycerin diglycidyl ether. These can be used individually or in combination of two or more.

[0064] Specific examples of the oxazoline-based crosslinking agent include copolymers polymerized with at least one monomer containing an oxazoline group, such as 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline. These can be used individually or in combination of two or more.

[0065] Specific examples of the aziridine crosslinking agents include N,N'-toluene-2,4-bis(1-aziridinecarboxamide), N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), triethylenemelamine, bisisophthaloyl-1-(2-methylaziridine), and tri-1-aziridinylphosphine oxide. These can be used individually or in combination of two or more.

[0066] The crosslinking agent may be present in an amount of 0.1 to 1 part by weight, preferably 0.1 to 0.5 parts by weight, per 100 parts by weight of the acrylic copolymer. If the crosslinking agent content is less than 0.1 parts by weight, the cohesive force of the adhesive composition will be excessively reduced, resulting in poor durability. If it exceeds 1 part by weight, the crosslinking reaction will proceed excessively, resulting in an excessive reduction in adhesive strength.

[0067] additives The additives can be added selectively as needed and may include, for example, one or more selected from the group consisting of silane coupling agents.

[0068] The type of silane coupling agent is not particularly limited, and specific examples of usable silane coupling agents include vinyltrimethoxylane, vinyltriethoxylan, vinyltris(2-methoxyethoxy)silane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxylane, N-(2-aminoethyl)-3-aminopropyltrimethoxylane, 3-aminopropyltriethoxylan, 3-glycidoxypropyltrimethoxylane, 3-glycidoxypropylmethyldimethoxylane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxylane, 3-chloropropylmethyldimethoxylane, 3-chloropropyltrimethoxylane, 3-methacrylateoxypropyltrimethoxylane, 3-mercaptopropyltrimethoxylane, 3-isocyanatetopropyltrimethoxysilane, and 3-isocyanatetopropyltriethoxysilane.

[0069] In addition to the silane coupling agent exemplified above, the device may further contain additives known in the art, such as antistatic agents, antioxidants, corrosion inhibitors, labeling agents, surface lubricants, defoamers, fillers, plasticizers, and reaction initiators, as needed.

[0070] The additives exemplified above can be used individually or in combination of two or more. The additives may be present in an amount of 0.05 to 6 parts by weight, preferably 0.5 to 6 parts by weight, per 100 parts by weight of the acrylic copolymer.

[0071] UV absorber The adhesive composition of the present invention comprises an ultraviolet absorber, and the ultraviolet absorber is characterized by comprising one or more compounds selected from the group consisting of compounds represented by the following chemical formulas 1 and 2.

[0072] [Chemical formula 1]

[0073] [ka]

[0074] In the aforementioned chemical formula 1, R1 is independently a linear or branched alkyl group having 8 or more carbon atoms. [Chemical formula 2]

[0075] [ka]

[0076] In the aforementioned chemical formula 2, R2 is independently a linear or branched alkyl group having 8 or more carbon atoms, and the ultraviolet absorber includes one or more compounds selected from the group consisting of compounds represented by the aforementioned chemical formulas 1 and 2. This is preferable in terms of increasing solubility in an adhesive composition containing an acrylic copolymer having a low glass transition temperature, and because the ultraviolet absorber does not precipitate, it has high adhesive strength and excellent folding properties.

[0077] In the aforementioned chemical formulas 1 and 2, if R1 and R2 are linear or branched alkyl groups having fewer than 8 carbon atoms, this may cause problems such as precipitation of the ultraviolet absorber. In the aforementioned chemical formulas 1 and 2, there is no particular upper limit on the number of carbon atoms of R1 and R2, but from the viewpoint of the problems of difficulty in synthesis and increased manufacturing costs, it is preferable that R1 and R2 are each independently linear or branched alkyl groups having 8 to 24 carbon atoms, preferably linear or branched alkyl groups having 8 to 18 carbon atoms, and more preferably linear or branched alkyl groups having 8 to 16 carbon atoms.

[0078] In one embodiment of the present invention, the compound represented by chemical formula 1 may be a compound represented by any one of the following chemical formulas 1-1 to 1-2.

[0079] [Chemical formula 1-1]

[0080] [ka]

[0081] [Chemical formula 1-2]

[0082] [ka]

[0083] In one embodiment of the present invention, the compound represented by chemical formula 2 may be the compound represented by the following chemical formula 2-1.

[0084] [Chemical formula 2-1]

[0085] [ka]

[0086] The ultraviolet absorber is preferably included in an amount of less than 7 parts by weight, more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the acrylic copolymer, but is not limited thereto. When the ultraviolet absorber is included according to the above criteria, the adhesive composition has the advantage of being able to fully exhibit its ultraviolet absorption function and to control the total light transmittance and haze to achieve high transparency. Specifically, if the amount of ultraviolet absorber is 7 parts by weight or more according to the above criteria, the compatibility weakens, the ultraviolet absorber precipitates, and problems such as decreased transparency or decreased adhesive performance such as reduced adhesive strength may occur.

[0087] <Adhesive sheet> The present invention provides an adhesive sheet manufactured with the aforementioned adhesive composition. In order to provide the adhesive sheet of the present invention, aside from including the aforementioned adhesive composition, configurations and manufacturing methods commonly used in the art to manufacture adhesive layers, adhesive films, and adhesive sheets can be used.

[0088] The adhesive sheet may have an elastic modulus of 30kPa to 100kPa, preferably 40kPa to 80kPa, at -20°C and 1Hz. By satisfying this elastic modulus, the folding characteristics of the adhesive sheet can be made particularly excellent at low temperatures, as described above.

[0089] The adhesive sheet may have an adhesive strength of 15 N / 25 mm or more, preferably 20 N / 25 mm or more, to a substrate, particularly a glass substrate, at room temperature of 23°C and 50% relative humidity. By satisfying this adhesive strength, the sheet can have excellent folding characteristics because, as mentioned above, it has a low elastic modulus and high adhesive strength at low temperatures.

[0090] Furthermore, the adhesive sheet exhibits excellent folding properties not only in low-temperature regions of -30°C and high-temperature regions of 60°C, but also in harsh environments with high temperatures of 60°C and high humidity of 90% or more relative humidity.

[0091] <Display> Furthermore, the present invention provides a display comprising the aforementioned adhesive sheet, and the display of the present invention may include configurations commonly known in the art, as long as it comprises the adhesive composition and / or adhesive sheet of the present invention.

[0092] When an adhesive sheet satisfying the aforementioned modulus of elasticity is used in a foldable and / or flexible display, it is preferable in that it can significantly improve problems such as tearing, lifting, peeling, and wrinkle (stripe) formation of the adhesive sheet even when subjected to continuous folding, and can also exhibit excellent adhesion to various types of substrates.

[0093] The following describes specific examples for carrying out the present invention, but the present invention is not limited to the following and can be appropriately modified to the extent required in the ordinary art.

[0094] <Manufacturing example: Acrylic copolymer> Manufacturing Example 1 In a 1 L reactor equipped with a cooling device for easy temperature control and refluxing nitrogen gas, 70% by weight of 2-ethylhexyl acrylate (2-EHA), 20% by weight of 2-decyl-1-tetradecenyl acrylate (DTD-A), 0.2% by weight of acrylic acid (AA), and 9.8% by weight of 4-hydroxybutyl acrylate (4-HBA) were added. Then, 100 parts by weight of ethyl acetate (EA) was added as a solvent. After that, nitrogen gas was added for 1 hour to remove oxygen and replace the atmosphere, and the temperature was maintained at 62°C. After the mixture was uniformly stirred, 0.07 parts by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator and the mixture was reacted for 8 hours to produce acrylic copolymer A-1 with a weight-average molecular weight of 1.13 million or more.

[0095] Production examples 2 to 4 Acrylic copolymers A-2 to A-4 were produced in the same manner as in Production Example 1, with the compositions shown in Table 1 below.

[0096] [Table 1]

[0097] MA: Methyl acrylate, manufactured by TCI. BA: Butyl acrylate, manufactured by TCI EHA: 2-Ethylhexyl acrylate, manufactured by Sigma-Aldrich. LA: Lauryl acrylate, manufactured by Kyoeisha Co., Ltd. SA: Stearyl acrylate, manufactured by Kyoeisha Co., Ltd. DTD-A: 2-decyl-1-tetradecenylacrylate, manufactured by Kyoeisha Co., Ltd. AA: Acrylic acid, manufactured by Sigma-Aldrich. 2-CEA: 2-carboxyethyl acrylic acid, manufactured by Sigma-Aldrich. 4-HBA: 4-hydroxybutyl acrylate, manufactured by Sigma-Aldrich. 6-HHA:6-Hydroxyhexylacrylate, manufactured by Hanil Precision.

[0098] <Synthesis Example: Synthesis of UV Absorbers> Synthesis Example 1 In a reaction vessel, a mixture of 2,4,6-trichloro-1,3,5-triazine (18.4 g, 0.1 mol), 2-methylresorcinol (43.4 g, 0.35 mol), aluminum chloride (20 g, 0.15 mol), and chlorobenzene dissolved in cyclopentyl methyl ether was stirred and reacted for 2 hours. After the reaction was complete, 6N hydrochloric acid was added from 80°C, and the mixture was heated to 90°C and stirred for 1 hour. Then, 200 g of toluene was added, and after reflux dehydration for 2 hours, the mixture was filtered to obtain 2,4,6-tris(2,4-dihydroxy-3-methylphenyl)-1,3,5-triazine. The 2,4,6-tris(2,4-dihydroxy-3-methylphenyl)-1,3,5-triazine (5 g, 11.2 mmol) and N,N-dimethylformamide obtained above were placed in a reaction vessel and dissolved, after which potassium carbonate (5.4 g, 39.2 mmol) was added. Then, 2-ethylhexyl bromide (3.2 g, 16.8 mmol) was slowly added, and the reaction was carried out with stirring for more than 6 hours under a nitrogen atmosphere at 80°C. After the reaction was complete, the mixture was cooled to room temperature, distilled water was added to stop the reaction, and then extracted with ethyl acetate (x3). Using a silica column, the compound represented by chemical formula 1-1 was obtained.

[0099] [Chemical formula 1-1]

[0100] [ka]

[0101] Synthesis Example 2 In a reaction vessel, a mixture of 2,4,6-trichloro-1,3,5-triazine (18.4 g, 0.1 mol), 2-methylresorcinol (43.4 g, 0.35 mol), aluminum chloride (20 g, 0.15 mol), and chlorobenzene dissolved in cyclopentyl methyl ether was stirred and reacted for 2 hours. After the reaction was complete, 6N hydrochloric acid was added from 80°C, and the mixture was heated to 90°C and stirred for 1 hour. Then, 200 g of toluene was added, and after reflux dehydration for 2 hours, the mixture was filtered to obtain 2,4,6-tris(2,4-dihydroxy-3-methylphenyl)-1,3,5-triazine. The 2,4,6-tris(2,4-dihydroxy-3-methylphenyl)-1,3,5-triazine (5 g, 11.2 mmol) and N,N-dimethylformamide obtained above were placed in a reaction vessel and dissolved, after which potassium carbonate (5.4 g, 39.2 mmol) was added. Then, octyl bromide (3.2 g, 16.8 mmol) was slowly added, and the reaction was carried out with stirring for more than 6 hours under a nitrogen atmosphere at 80°C. After the reaction was complete, the mixture was cooled to room temperature, distilled water was added to stop the reaction, and then the mixture was extracted with ethyl acetate (x3) and the compound represented by chemical formula 1-2 was obtained using a silica column.

[0102] [Chemical formula 1-2]

[0103] [ka]

[0104] Synthesis Example 3 2,4,6-Tris(2,4-hydroxyphenyl)-1,3,5-triazine (5 g, 12.3 mmol) and N,N-dimethylformamide were added to a reaction vessel and dissolved, after which potassium carbonate (6 g, 43.1 mmol) was added. Then, 2-ethylhexyl bromide (3.6 g, 18.5 mmol) was slowly added, and the reaction was carried out with stirring for more than 6 hours under a nitrogen atmosphere while maintaining the temperature at 80°C. After the reaction was complete, the mixture was cooled to room temperature, and the reaction was stopped by adding distilled water. The mixture was then extracted with ethyl acetate (×3) and the compound represented by chemical formula 2-1 was obtained using a silica column.

[0105] [Chemical formula 2-1]

[0106] [ka]

[0107] <Examples and Comparative Examples: Manufacturing of Adhesive Compositions and Adhesive Sheets> (1) Adhesive composition The components and their respective amounts shown in Table 2 below were mixed and diluted in an organic solvent to produce an adhesive composition, taking into consideration its coating properties. The amounts expressed were in parts by weight.

[0108] (2) Adhesive sheet The manufactured adhesive composition was applied to a film coated with a silicone release agent to a thickness of 50 μm after drying, dried at 100°C for 5 minutes, and then laminated with a release film to form an adhesive sheet.

[0109] [Table 2-1]

[0110] [Table 2-2]

[0111] Experimental example The physical properties of the adhesive sheets produced in Examples 1 to 17, Comparative Examples 1 to 3, and Reference Examples 1 to 2 were measured by the following method, and the results are shown in Table 3 below.

[0112] (1) Transmittance The manufactured adhesive sheet was cut to a size of 50 mm x 50 mm, the release film was peeled off and it was bonded to Corning glass, the release film on the opposite side of the adhesive sheet was peeled off and it was bonded to 0.1t soda glass, and then the specimens were prepared by autoclaving. The transmission spectra of the prepared specimens were measured in the wavelength range of 300 to 800 nm using a spectrophotometer (Shimadzu Corporation, UV-2450).

[0113] (2) Elastic modulus In the above-mentioned examples, comparative examples, and reference examples, the storage modulus was measured for each adhesive sheet before the optical component layer was laminated.

[0114] The storage modulus was measured for each adhesive sheet using a viscoelasticity measuring device (MCR-301, manufactured by Anton Paar). More specifically, the adhesive sheet was cut to a size of 30 mm in length and 30 mm in width. After removing the release film attached to one side of the cut adhesive sheet, it was bonded to a glass substrate. Then, with the sheet attached to a measuring tip, measurements were taken in the temperature range of -30 to 100°C under conditions of a frequency of 1.0 Hz, a strain of 2%, and a heating rate of 5°C / min. The measurement value at 25°C was read, and the measurement results are shown in Table 3 below.

[0115] (3) Adhesive strength After peeling off the release layer of each adhesive sheet from the examples, comparative examples, and reference examples, they were bonded to a corona or plasma-treated 50 μm PET film and then cut to a size of 25 mm × 100 mm. The release film of the prepared specimens was peeled off, the surface of the adhesive was subjected to corona or plasma treatment, and then the specimens were laminated onto a glass substrate and autoclaved to produce the specimens. The room temperature adhesive strength was measured by leaving the prepared specimens at 23°C and 50% RH for 24 hours, and then peeling the adhesive layer using a universal tensile testing machine (UTM, Instron) at a peeling speed of 300 mm / min and a peeling angle of 180°. The measurement was performed under 23°C and 50% RH conditions.

[0116] (4) Foldability The adhesive films produced in the above examples, comparative examples, and reference examples were bonded to 50 μm PET, cut to 20 mm x 100 mm, and used as test pieces.

[0117] The specimen was fixed to a flexibility evaluation device (COVOTECH, CFT-720C) for folding evaluation, and folded to a radius of curvature of 2 mm. Folding evaluation was performed at -20°C, 60°C, and RH90% under conditions of 25 foldings per minute and holding for 0.2 seconds after each folding. When applying the folding evaluation, one folding was considered one cycle. After 30,000 folding cycles, if stripes or other patterns appeared at the folded area, or if the adhesive film broke, lifted, or peeled, it was judged as ×; if there was breakage, lifting, or peeling of 0.3 mm or less, it was judged as ○; and if there were no problems at all it was judged as ◎.

[0118] ◎: No defects occurred after more than 50,000 folding cycles. ○: Defects occurred within the folding recall range of 20,000 to less than 50,000 cycles. ×: Failure occurred with fewer than 20,000 folding cycles.

[0119] [Table 3]

[0120] Referring to the experimental results described above, Examples 1 to 17 and Reference Examples 1 to 2, which include an ultraviolet absorber containing one or more compounds selected from the group consisting of compounds represented by chemical formulas 1 and 2 according to the present invention, exhibit low light transmittance at a wavelength of 380 nm, thus demonstrating excellent ability to prevent degradation by ultraviolet light. In particular, Examples 1 to 17, which include both an acrylic copolymer polymerized with linear or branched alkyl (meth)acrylate monomers having 8 to 30 carbon atoms and an ultraviolet absorber containing a compound represented by chemical formula 1, exhibit low elastic modulus and high adhesiveness at low temperatures, thus demonstrating excellent folding properties.

Claims

1. An adhesive composition comprising an acrylic copolymer, a crosslinking agent, an additive, and an ultraviolet absorber, The adhesive composition is characterized by containing one or more ultraviolet absorbers selected from the group consisting of compounds represented by the following chemical formulas 1 and 2. [Chemical formula 1] 【Chemistry 1】 (In the above chemical formula 1, R １ Each of these is independently a linear or branched alkyl group having 8 or more carbon atoms. [Chemical formula 2] 【Chemistry 2】 (In the above chemical formula 2, R ２ Each of these is independently a linear or branched alkyl group having 8 or more carbon atoms.

2. The aforementioned R １ Each of these is independently a linear or branched alkyl group having 8 to 24 carbon atoms. The aforementioned R ２ The adhesive composition according to claim 1, wherein each of them is independently a linear or branched alkyl group having 8 to 24 carbon atoms.

3. The adhesive composition according to claim 1, wherein the ultraviolet absorber is contained in an amount of 0.1 to 5 parts by weight per 100 parts by weight of the acrylic copolymer.

4. The adhesive composition according to claim 1, wherein the acrylic copolymer is polymerized comprising a linear or branched alkyl (meth)acrylate monomer having 8 to 30 carbon atoms.

5. The adhesive composition according to claim 4, wherein the acrylic copolymer is further polymerized to include a polar group-containing (meth)acrylate monomer and a hydroxyl group-containing (meth)acrylate monomer.

6. The adhesive composition according to claim 1, wherein the crosslinking agent comprises a metal chelating crosslinking agent.

7. The adhesive composition according to claim 6, wherein the crosslinking agent comprises one selected from the group consisting of zirconium, aluminum, zinc, and magnesium.

8. The adhesive composition according to claim 6, wherein the crosslinking agent further comprises one or more selected from the group consisting of isocyanate-based, aziridine-based, epoxy-based, melamine-based, peroxide-based, and oxazoline-based crosslinking agents.

9. The adhesive composition according to claim 1, wherein the additive further comprises one or more selected from the group consisting of silane coupling agents, antistatic agents, antioxidants, corrosion inhibitors, labeling agents, surface lubricants, defoaming agents, fillers, plasticizers, and reaction initiators.

10. The adhesive composition according to claim 1, wherein the adhesive sheet formed with the adhesive composition has a light transmittance of 10% or less at a wavelength of 380 nm.

11. The adhesive composition according to claim 1, wherein the adhesive sheet formed with the adhesive composition has an elastic modulus of 40 kPa to 100 kPa at -20°C and 1 Hz.

12. An adhesive sheet comprising the adhesive composition according to any one of claims 1 to 11.

13. A display comprising the adhesive sheet described in claim 12.

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