Adhesive composition, adhesive sheet, optical film, and image display device

Abstract

To provide an adhesive composition enabling formation of an adhesive layer having improved durability, an adhesive sheet containing an adhesive layer formed with the adhesive composition, and an optical film produced from the adhesive sheet.SOLUTION: An adhesive composition according to an embodiment of the present invention comprises an acrylic copolymer, a crosslinking agent, and an ionic antistatic agent which is an ionic compound represented by Chemical Formula 1. According to an embodiment of the present invention, an adhesive sheet and an optical film including an adhesive layer formed from the adhesive composition are provided.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an adhesive composition, an adhesive sheet, an optical film, and an image display device.

Background Art

[0002] An adhesive or an adhesive sheet can be used to bond a display panel of an image display device such as a liquid crystal display (LCD) device or an organic light emitting display (OLED) device to various optical structures or circuit structures. The adhesive needs to have improved transparency and high adhesive strength so as not to deteriorate the optical properties of the image display device.

[0003] In recent years, displays having high reliability even under severe conditions of high temperature and high humidity or external physical impact have been actively studied. Accordingly, the structures coupled to the display also need to be formed so as to prevent the structures from falling off or peeling even under severe conditions or external impact.

[0004] Therefore, there is a need for an adhesive or an adhesive sheet that has high adhesive strength and durability and can bond the display structure.

Summary of the Invention

Problems to be Solved by the Invention

[0005] One problem of the present invention is to provide an adhesive composition capable of forming an adhesive layer having improved durability.

[0006] One problem of the present invention is to provide an adhesive sheet including an adhesive layer formed using the adhesive composition, and an optical film manufactured from the adhesive sheet.

Means for Solving the Problems

[0007] 1. An adhesive composition comprising an acrylic copolymer, a crosslinking agent, and an ionic antistatic agent which is an ionic compound represented by the following Chemical Formula 1.

Chemical Formula

[0008] 2. The adhesive composition according to Item 1, wherein in the Chemical Formula 1, R2 is a linear alkyl group having 12 to 18 carbon atoms.

[0009] 3. The adhesive composition according to Item 1, wherein the melting point of the ionic antistatic agent is 23°C or higher.

[0010] 4. The adhesive composition according to Item 1, wherein the melting point of the ionic antistatic agent is 25°C to 70°C.

[0011] 5. The adhesive composition according to Item 1, wherein the content of the ionic antistatic agent is 0.01 part by weight to 7 parts by weight with respect to 100 parts by weight of the acrylic copolymer.

[0012] 6. The adhesive composition according to Item 1, wherein the content of the ionic antistatic agent is 1 part by weight to 5 parts by weight with respect to 100 parts by weight of the acrylic copolymer.

[0013] 7. The adhesive composition according to Item 1, wherein the acrylic copolymer is formed from a polymerizable mixture containing an alkyl (meth)acrylate monomer, an aromatic group-containing (meth)acrylate monomer, and a polar functional group-containing crosslinkable monomer.

[0014] 8. The adhesive composition according to Item 7, wherein the alkyl (meth)acrylate monomer includes a first monomer which is an alkyl (meth)acrylate monomer having 1 to 3 carbon atoms and a second monomer which is an alkyl (meth)acrylate monomer having 4 to 12 carbon atoms.

[0015] 9. In Item 7 above, the polar functional group of the polar functional group-containing crosslinkable monomer contains at least one of a carboxy group, a hydroxy group, an amide group, and an amine group, the pressure-sensitive adhesive composition.

[0016] 10. In Item 1 above, the crosslinking agent contains a non-yellowing type isocyanate-based crosslinking agent, the pressure-sensitive adhesive composition.

[0017] 11. In Item 1 above, the content of the crosslinking agent is 0.1 part by weight to 3 parts by weight with respect to 100 parts by weight of the acrylic copolymer, the pressure-sensitive adhesive composition.

[0018] 12. In Item 1 above, further containing a silane coupling agent, the pressure-sensitive adhesive composition.

[0019] 13. In Item 12 above, the content of the silane coupling agent is 0.01 part by weight to 3 parts by weight with respect to 100 parts by weight of the acrylic copolymer, the pressure-sensitive adhesive composition.

[0020] 14. A pressure-sensitive adhesive sheet including a base film and a pressure-sensitive adhesive layer disposed on the base film and formed using the pressure-sensitive adhesive composition according to Item 1 above.

[0021] 15. In Item 14 above, the base film includes at least one selected from the group consisting of a polarizer, an antireflection layer, a hard coat layer, and a retardation layer, the pressure-sensitive adhesive sheet.

[0022] 16. In Item 14 above, the value of the surface specific resistance of the pressure-sensitive adhesive layer is 1×10 ,

[0021] , , ,

[0023] , , , , ,

[0024] , 11 , , ,

[0022] , Ω / sq or less, the pressure-sensitive adhesive sheet.

[0023] 17. An optical film including a base film, a pressure-sensitive adhesive layer disposed on the upper surface of the base film and formed using the pressure-sensitive adhesive composition according to Item 1 above, and an antireflection layer disposed on the lower surface of the base film.

[0024] 18. An image display device including the optical film according to Item 17 above.

Advantages of the Invention

[0025] From the adhesive composition according to an exemplary embodiment of the present invention, an adhesive layer having improved adhesive strength can be formed. Further, from the adhesive composition, an adhesive layer having a low surface specific resistance value can be realized.

[0026] The adhesive sheet according to an exemplary embodiment of the present invention can be firmly attached to an adherend even in a high temperature and / or high humidity environment, and can have improved adhesive strength and adhesion.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0028] The adhesive composition according to an embodiment of the present invention includes an acrylic copolymer, a crosslinking agent, and an ionic antistatic agent having a long-chain alkyl group. Further, according to an embodiment of the present invention, an adhesive sheet and an optical film having an adhesive layer formed from the adhesive composition are provided.

[0029] Hereinafter, the present disclosure will be described in detail with reference to the accompanying drawings. However, these are merely exemplary and do not limit the present disclosure to the specific embodiments illustrated.

[0030] <Adhesive Composition> The pressure-sensitive adhesive composition according to an exemplary embodiment includes an ionic antistatic agent. The ionic antistatic agent has an imidazolium-based cation and a bis(fluorosulfonyl)imide anion. The ionic antistatic agent can include an ionic compound having an imidazolium-based cation and a bis(fluorosulfonyl)imide anion. The ionic antistatic agent can impart ionic conductivity to an adhesive layer formed from the pressure-sensitive adhesive composition.

[0031] By including the ionic compound as the ionic antistatic agent, the stability over time of the pressure-sensitive adhesive composition and the durability of the adhesive layer can be improved. Also, the ionic solid has high compatibility and can maintain high transparency of the pressure-sensitive adhesive composition.

[0032] The ionic compound may be solid at room temperature. Thereby, the handling of the ionic compound and the pressure-sensitive adhesive composition containing the same can be facilitated. Also, the bleeding phenomenon of the adhesive layer formed from the pressure-sensitive adhesive composition containing the liquid ionic compound can be reduced, and contamination of the adherend can be prevented.

[0033] In an exemplary embodiment, the melting point of the ionic antistatic agent may be 23°C or higher. In some embodiments, the melting point of the ionic antistatic agent may be 25°C to 70°C. In this case, the mobility of the ionic antistatic agent in the adhesive layer in a room temperature environment can be decreased. Thereby, the ionic antistatic agent does not elute at the end of the adhesive layer, and contamination of the adherend can be prevented.

[0034] The ionic antistatic agent can include a long-chain alkyl group bonded to the cationic nitrogen of the imidazolium skeleton. Thereby, the ionic antistatic agent can be prevented from eluting from the adhesive layer as an ionic solid at room temperature.

[0035] In some embodiments, the ionic antistatic agent can include an ionic compound represented by the following Chemical Formula 1.

[0036] [Chemical formula]

[0037] In the above Chemical formula 1, R1 may be hydrogen or a methyl group. For example, R1 may be a methyl group.

[0038] In the above Chemical formula 1, R2 may be an alkyl group having 10 to 30 carbon atoms. For example, R2 may be an alkyl group having 12 to 28 carbon atoms, an alkyl group having 12 to 18 carbon atoms, or an alkyl group having 13 to 17 carbon atoms.

[0039] According to an exemplary embodiment, R2 may be a linear alkyl group having 12 to 18 carbon atoms. The ionic antistatic agent may include, for example, 1-dodecyl-3-methylimidazolium, 1-tetradecyl-3-methylimidazolium, 1-octadecyl-3-methylimidazolium, etc. as the imidazolium-based cation. These can be used alone or in combination of two or more.

[0040] In an exemplary embodiment, the content of the ionic antistatic agent may be 0.01 part by weight to 5 parts by weight based on 100 parts by weight of the acrylic copolymer. In some embodiments, the content of the ionic antistatic agent may be 0.1 part by weight to 4.5 parts by weight, 1 part by weight to 4 parts by weight, 1.5 parts by weight to 3.5 parts by weight, or 2 parts by weight to 3 parts by weight based on 100 parts by weight of the acrylic copolymer.

[0041] Within the above range, the antistatic property of the adhesive layer can be improved while maintaining excellent durability of the adhesive layer.

[0042] The adhesive composition according to an exemplary embodiment may include an acrylic copolymer. The acrylic copolymer may include an acrylic copolymer formed from a polymerizable mixture including an alkyl (meth) acrylate monomer, an aromatic group-containing (meth) acrylate monomer, and a polar functional group-containing crosslinkable monomer.

[0043] As used herein, the term "(meth)acrylate" is used to mean including acrylate or methacrylate.

[0044] The alkyl (meth)acrylate monomer may be an alkyl (meth)acrylate monomer having 1 to 12 carbon atoms. The alkyl (meth)acrylate monomer having 1 to 12 carbon atoms may include an alkyl (meth)acrylate first monomer having 1 to 3 carbon atoms and an alkyl (meth)acrylate second monomer having 4 to 12 carbon atoms. According to an exemplary embodiment, by including both the first monomer and the second monomer, the polymerizable mixture can prevent the occurrence of defects in the pressure-sensitive adhesive sheet even in a high-temperature and / or high-humidity environment while achieving improved adhesion.

[0045] The first monomer and the second monomer may each be a compound derived from an aliphatic alcohol having 1 to 12 carbon atoms.

[0046] Examples of the first monomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, etc., and for example, it may be methyl (meth)acrylate. These can be used alone or in combination of two or more.

[0047] In an exemplary embodiment, the content of the first monomer may be 15% by weight to 45% by weight based on the total weight of the polymerizable mixture. In some embodiments, the content of the first monomer may be 20% by weight to 40% by weight, or 25% by weight to 35% by weight based on the total weight of the polymerizable mixture. Within this range, the adhesion and heat resistance of the pressure-sensitive adhesive sheet can be sufficiently improved.

[0048] Examples of the second monomer include n-butyl (meth)acrylate, 2-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, and the like. The second monomer may be, for example, n-butyl (meth)acrylate or 2-ethylhexyl (meth)acrylate. These can be used alone or in combination of two or more.

[0049] In an exemplary embodiment, the content of the second monomer may be 40% by weight to 80% by weight based on the total weight of the polymerizable mixture. In some embodiments, the content of the second monomer may be 45% by weight to 70% by weight, or 55% by weight to 70% by weight based on the total weight of the polymerizable mixture. Within this range, it is possible to prevent the cohesive force of the pressure-sensitive adhesive composition from decreasing and the durability of the pressure-sensitive adhesive layer from decreasing, and it is possible to improve the crosslink density and the adhesion strength of the pressure-sensitive adhesive layer.

[0050] In an exemplary embodiment, the ratio of the content of the second monomer to the content of the first monomer in the total weight of the polymerizable mixture may be 1 to 3. In some embodiments, the ratio of the content of the second monomer to the content of the first monomer in the total weight of the polymerizable mixture may be 1.2 to 2.7.

[0051] Within this range, the content of the second monomer having an alkyl group longer than that of the first monomer becomes equal to or higher than the content of the first monomer, whereby the heat resistance of the pressure-sensitive adhesive sheet can be improved.

[0052] According to an exemplary embodiment, the polymerizable mixture may include an aromatic group-containing (meth)acrylate monomer. Thereby, the acrylic copolymer can include a bulky aromatic group with high heat resistance, and the durability of the pressure-sensitive adhesive sheet in a harsh environment can be improved. Further, the acrylic copolymer formed from the polymerizable mixture containing the aromatic group-containing (meth)acrylate monomer can improve the light leakage phenomenon by improving the refractive index of the pressure-sensitive adhesive composition.

[0053] According to an exemplary embodiment, the aromatic group of the aromatic group-containing (meth)acrylate monomer may include an aryl group having 6 to 20 carbon atoms. The aryl group is a hydrocarbon group containing at least one aromatic ring, and can include, for example, a phenyl group, a biphenyl group, a naphthalene group, and the like.

[0054] According to an exemplary embodiment, the aromatic group-containing (meth)acrylate monomer may include an aryloxy group having 6 to 20 carbon atoms. The aryloxy group can be meant as a group in which an aryl group is bonded to an oxygen atom. For example, the aryloxy group can include a phenoxy group, a biphenyloxy group, a naphthyloxy group, and the like.

[0055] According to an exemplary embodiment, the aromatic group-containing (meth)acrylate monomer may include a structure in which a (meth)acrylate group is bonded to an aryloxy group having 6 to 20 carbon atoms via an alkylene group linker.

[0056] According to some embodiments, the aromatic group-containing (meth)acrylate monomer may include a structure in which an aryl group having 6 to 20 carbon atoms and a (meth)acrylate group are bonded via a polyether segment. The "polyether segment" can mean a linker structure containing a divalent oxyalkylene repeating unit (-O-(CH2) m -).

[0057] The aromatic group-containing (meth)acrylate monomer can be represented by the following Chemical Formula 2.

[0058] [Chemical Formula]

[0059] In Chemical Formula 2, Ar may be an aryl group having 6 to 20 carbon atoms.

[0060] In Chemical Formula 2, R3 is an alkylene group having 1 to 5 carbon atoms, R4 is hydrogen or a methyl group, and m may be an integer of 1 to 10.

[0061] Examples of the aromatic group-containing (meth)acrylate monomer include phenoxymethyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, biphenyloxy methyl (meth)acrylate, biphenyloxyethyl (meth)acrylate, biphenyloxypropyl (meth)acrylate, phenoxyethoxyethyl (meth)acrylate, phenoxyethoxyethoxyethyl (meth)acrylate, and the like. The aromatic group-containing (meth)acrylate monomer may be, for example, phenoxyethyl (meth)acrylate. These can be used alone or in combination of two or more.

[0062] According to an exemplary embodiment, the content of the aromatic group-containing (meth)acrylate monomer may be 1% by weight to 15% by weight based on the total weight of the polymerizable mixture. According to some embodiments, the content of the aromatic group-containing (meth)acrylate monomer may be 5% by weight to 10% by weight based on the total weight of the polymerizable mixture. Within the above range, the refractive index can be controlled without reducing the adhesive physical properties, and a light compensation function for light leakage can be imparted.

[0063] The polar functional group-containing crosslinkable monomer can include a crosslinkable group capable of undergoing a polymerization reaction with the (meth)acrylate monomer to form a copolymer, and a polar functional group that can be contained in a form bonded to the copolymer chain.

[0064] The polar functional group-containing crosslinkable monomer can improve the crosslinking degree of the acrylic copolymer. Further, it can react with a crosslinking agent described later to prevent the cohesive force destruction of the adhesive layer under high temperature / high humidity conditions and impart adhesive strength.

[0065] The polar functional group can include a carboxy group, a hydroxy group, an amide group, an amine group, etc. In some embodiments, the polar functional group-containing crosslinkable monomer can include a carboxy group-containing crosslinkable monomer, a hydroxy group-containing crosslinkable monomer, an amide group-containing crosslinkable monomer, and / or an amine group-containing crosslinkable monomer. They can be used alone or in combination of two or more.

[0066] In one embodiment, the polar functional group-containing crosslinkable monomer can include a carboxy group-containing crosslinkable monomer and a hydroxy group-containing crosslinkable monomer.

[0067] In some embodiments, the content of the crosslinkable monomer having the polar functional group may be 0.05 wt% to 10 wt%, for example, 0.1 wt% to 3 wt% based on the total weight of the polymerizable mixture. Within this range, the cohesive force of the adhesive composition can be ensured to improve the durability of the adhesive sheet, and the adhesive force and durability can be improved by an appropriate gel fraction of the adhesive composition.

[0068] The carboxy group-containing crosslinkable monomer and the hydroxy group-containing crosslinkable monomer each include a carboxy group or a hydroxy group that can be contained in a form bonded to the copolymer chain, and can include a crosslinkable group capable of undergoing a polymerization reaction with the (meth)acrylate monomer to form a copolymer.

[0069] The carboxy group-containing crosslinkable monomer can play a role in imparting adhesiveness to the adhesive composition. For example, since the acrylic copolymer has an acidic group derived from the carboxy group-containing monomer, the adhesiveness and crosslinking degree of the adhesive composition can be improved.

[0070] Examples of the carboxy group-containing crosslinkable monomer include acrylic acid, methacrylic acid, etc. These can be used alone or in combination of two or more.

[0071] The content of the carboxy group-containing crosslinkable monomer may be 0.01% by weight to 0.5% by weight based on the total weight of the polymerizable mixture. For example, the content of the carboxy group-containing crosslinkable monomer may be 0.1% by weight to 0.5% by weight based on the total weight of the polymerizable mixture.

[0072] When the content of the carboxy group-containing crosslinkable monomer is within the above range, the adhesiveness of the adhesive sheet formed from the adhesive composition can be appropriately improved, and the migration of the ionic antistatic agent to the surface of the adhesive sheet can be prevented.

[0073] When the polymerizable mixture does not contain the carboxy group-containing crosslinkable monomer, the adhesiveness, adhesivity and durability in harsh environments of the adhesive layer may decrease.

[0074] The hydroxy group-containing crosslinkable monomer can impart a highly polar hydroxy group to the acrylic copolymer. Thereby, the adhesiveness of the acrylic copolymer to the polar base material can be enhanced.

[0075] Examples of the hydroxy group-containing crosslinkable monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, 2-hydroxypropylene glycol (meth)acrylate, hydroxyalkylene glycol (meth)acrylate having 2 to 4 carbon atoms in the alkylene group, 4-hydroxybutyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, 7-hydroxyheptyl vinyl ether, 8-hydroxyoctyl vinyl ether, 9-hydroxynonyl vinyl ether, and 10-hydroxydecyl vinyl ether. These can be used alone or in combination of two or more.

[0076] In some embodiments, the content of the hydroxy group-containing crosslinkable monomer may be 0.5% by weight to 5% by weight based on the total weight of the polymerizable mixture. For example, the content of the hydroxy group-containing crosslinkable monomer may be 0.5% by weight to 4% by weight based on the total weight of the polymerizable mixture.

[0077] Examples of the amide group-containing crosslinkable monomer include (meth)acrylamide, N-isopropylacrylamide, N-tert-butylacrylamide, 3-hydroxypropyl (meth)acrylamide, 4-hydroxybutyl (meth)acrylamide, 6-hydroxyhexyl (meth)acrylamide, 8-hydroxyoctyl (meth)acrylamide, 2-hydroxyethylhexyl (meth)acrylamide, etc. These can be used alone or in combination of two or more.

[0078] As the amine group-containing crosslinkable monomer, a tertiary amine group-containing crosslinkable monomer can be included. Examples of the tertiary amine group-containing crosslinkable monomer include N,N-(dimethylamino)ethyl (meth)acrylate, N,N-(diethylamino)ethyl (meth)acrylate, N,N-(dimethylamino)propyl (meth)acrylate, and the like. These can be used alone or in combination of two or more.

[0079] In some embodiments, in addition to the monomer, other polymerizable monomers known in the art can be further used within a range that does not reduce the adhesive strength. For example, the other polymerizable monomers can be further included in an amount of 10% by weight or less based on the total weight of the polymerizable mixture.

[0080] The method for producing the acrylic copolymer is not particularly limited, and methods such as bulk polymerization, solution polymerization, emulsion polymerization, or suspension polymerization commonly used in the art can be used. For example, the solution polymerization method can be used. Also, solvents, polymerization initiators, chain transfer agents for controlling the molecular weight, etc. that are commonly used during polymerization can be used.

[0081] In some embodiments, the adhesive composition contains a crosslinking agent. The crosslinking agent can play a role in improving the cohesive force, adhesion, and high-temperature reliability of the adhesive and maintaining the shape of the adhesive.

[0082] In some embodiments, the crosslinking agent may be a non-yellowing type isocyanate-based crosslinking agent. The "yellowing type isocyanate-based crosslinking agent" can mean a compound in which the carbon of phenyl is directly linked to the nitrogen atom of isocyanate among isocyanate-based crosslinking agents. The "non-yellowing type isocyanate-based crosslinking agent" can mean the remainder excluding the yellowing type isocyanate-based crosslinking agent among the isocyanate-based crosslinking agents.

[0083] The isocyanate compound has high reactivity with respect to polar functional groups and can have improved adhesion to a corona discharge-treated or plasma-treated substrate film.

[0084] Examples of the isocyanate compound include diisocyanate compounds such as xylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and tetramethylxylene diisocyanate; an adduct obtained by reacting 3 equivalents of a diisocyanate compound with 1 equivalent of a polyhydric alcohol compound such as trimethylolpropane, an isocyanurate formed by self-condensation of 3 equivalents of a diisocyanate compound, a biuret formed by condensing the remaining 1 equivalent of a diisocyanate with a diisocyanate urea obtained from 2 equivalents of 3 equivalents of a diisocyanate compound, and polyfunctional isocyanate compounds containing three functional groups such as triphenylmethane triisocyanate and methylene bis triisocyanate. These can be used alone or in combination of two or more.

[0085] In some embodiments, the content of the crosslinking agent may be 0.1 part by weight to 3 parts by weight, for example, 0.1 part by weight to 2 parts by weight, based on 100 parts by weight of the acrylic copolymer. Within this range, the chains of the acrylic copolymer can be appropriately crosslinked to improve the adhesion durability and cutability of the adhesive layer. Also, the adhesion of the pressure-sensitive adhesive sheet to the adherend can be improved.

[0086] The pressure-sensitive adhesive composition may further contain a silane coupling agent. The silane coupling agent can suppress the lifting and peeling of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition by forming a covalent bond or a hydrogen bond with a functional group present on the surface of the adherend, and can improve the adhesive strength.

[0087] The silane coupling agent can include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyldimethylmethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyldimethylethoxysilane, etc. These can be used alone or in combination of two or more.

[0088] In some embodiments, the content of the silane coupling agent may be 0.01 to 3 parts by weight, for example, 0.1 to 2 parts by weight, based on 100 parts by weight of the acrylic copolymer.

[0089] The pressure-sensitive adhesive composition can further contain ordinary additives known in the art in order to adjust the adhesive force, cohesive force, viscosity, elastic modulus, glass transition temperature, etc. required according to the application. For example, the pressure-sensitive adhesive composition can contain, as additives, tackifiers, antioxidants, corrosion inhibitors, leveling agents, surface lubricants, dyes, pigments, defoamers, fillers, light stabilizers, plasticizers, etc.

[0090] <Adhesive sheet> Hereinafter, embodiments of the present invention will be described more specifically with reference to the drawings. However, the drawings attached to this specification illustrate exemplary embodiments of the present invention and play a role in helping to further understand the technical idea of the present invention together with the detailed description of the invention. Therefore, the present invention is not construed as being limited only to the matters described in the drawings.

[0091] FIG. 1 is a schematic cross-sectional view showing an adhesive sheet according to an exemplary embodiment.

[0092] Referring to FIG. 1, an adhesive sheet according to an exemplary embodiment can include a base film 110, an adhesive layer 120 disposed on the upper surface of the base film 110, and a release film 130 disposed on the upper surface of the adhesive layer 120.

[0093] The adhesive layer 120 can be formed from the aforementioned adhesive composition. For example, the adhesive layer 120 can be formed by applying an adhesive composition containing an acrylic copolymer, a crosslinking agent, and an ionic antistatic agent having an imidazolium-based cation of Chemical Formula 1 and a bisfluorosulfonylimide anion onto the base film 110 and curing it.

[0094] In some embodiments, the base film 110 can include an acrylic resin, a cellulose resin, a polyolefin resin, a polyester resin, or the like. In this case, the transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. of the base film 110 can be improved.

[0095] For example, the base film 110 can include an acrylic resin such as polymethyl (meth)acrylate, polyethyl (meth)acrylate; a polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, polybutylene naphthalate; a cellulose resin such as diacetyl cellulose, triacetyl cellulose, cellulose acetate butyrate; a polyolefin resin such as polyethylene, polypropylene, cycloolefin, polyolefin having a norbornene structure, ethylene-propylene copolymer; a sulfone resin; a polyether-ether-ketone resin; an arylate resin; or a mixture of the above resins.

[0096] In some embodiments, the base film 110 can include a polarizer, an antireflection layer, a hard coat layer, a retardation layer, or the like. For example, the base film 110 can be provided as a polarizing plate, an antireflection film, a hard coat film, a window film, a retardation film, or the like.

[0097] For example, when the base film 110 includes a polarizer, the base film 110 can be provided as a polarizing plate.

[0098] In one embodiment, at least one surface of the base film 110, for example, the surface on which the adhesive layer 120 is formed, can be surface-treated. For example, corona discharge treatment, plasma treatment, blast treatment, primer treatment, etc. can be performed on one surface of the base film 110.

[0099] By the surface treatment, a carboxylic acid derivative (R-COOH) can be generated on the surface of the base film 110. The carboxyl group of the carboxylic acid derivative can react with the adhesive composition, thereby further improving the adhesion of the adhesive layer 120 to the base film 110.

[0100] In one embodiment, the surface of the base film 110 may not be saponification-treated. Since the surface of the base film 110 used for the adhesive sheet is hydrophobic, the adhesion to the adhesive and the adhesive strength may deteriorate. In this case, a pretreatment step of immersing the surface of the base film 110 in an alkaline aqueous solution for saponification can be performed, another coating layer can be formed between the base material and the adhesive, or the surface of the base film can be corona or plasma-treated, thereby improving the adhesion between the base material and the adhesive.

[0101] However, when performing the saponification step or forming another coating layer, the process may become complicated, resulting in a decrease in the yield and processability of the adhesive sheet, and contamination and quality degradation of the adhesive sheet may occur due to the additional pretreatment or coating layer forming step.

[0102] The adhesive composition according to the above-described embodiment can improve the adhesion of the adhesive layer 120 to the surface of the base film 110 by increasing the affinity between the surface of the base film 110 and the adhesive composition with an organosilicon compound having a malonyl group or an acetoacetyl group. Also, the heat and moisture resistance durability and adhesive reliability under severe conditions of high temperature and high humidity can be maintained, and improved reworkability can be realized even after being left for a long time under the severe conditions.

[0103] The surface resistivity value of the adhesive layer 120 may be 1×10 11 Ω / square or less. In an exemplary embodiment, it may be 6×10 10 Ω / square or less, or 5.5×10 10 Ω / square or less.

[0104] The adhesive layer 120 can be formed by applying the aforementioned adhesive composition onto at least one surface of the base film 110 and drying and / or curing it. For example, the adhesive layer 120 can be formed by applying the adhesive composition onto the base film 110 by a coating method such as roll coating, gravure coating, reverse coating, spray coating, air knife coating, die coater, etc.

[0105] According to an exemplary embodiment, the gel fraction of the adhesive layer 120 may be 60% - 80%, for example, it may be 65% - 75%. The gel fraction of the adhesive layer 120 can be calculated by the following formula 1.

[0106] [Formula 1] JPEG2025113221000005.jpg1077

[0107] In Formula 1, W1 may be the initial weight of the adhesive layer 120. W2 may be the weight measured after immersing the adhesive layer 120 in an ethyl acetate solution at room temperature for 3 days and drying at 120°C for 24 hours.

[0108] When the gel fraction of the adhesive layer 120 is less than 60%, the durability over time and the reworkability may decrease due to a decrease in the degree of crosslinking and cohesive force. When the gel fraction of the adhesive layer 120 exceeds 80%, the durability and adhesion of the adhesive layer 120 may decrease due to excessive crosslinking, and damage to the object may occur when the adhesive sheet is peeled off.

[0109] Referring to FIG. 1, the adhesive sheet can further include a release film 130 disposed on one surface of the adhesive layer 120. For example, the adhesive sheet can sequentially dispose a base film 110, an adhesive layer 120, and a release film 130.

[0110] In some embodiments, the adhesive sheet can be provided in a form in which the base film 110 and the release film 130 are attached to both sides. Referring to FIG. 2, when using the adhesive sheet, the release film 130 can be removed from the adhesive sheet. In this case, the release film 130 can be removed from the adhesive sheet, and the exposed adhesive layer 120 can be attached to an object to be adhered (for example, a display panel).

[0111] In some embodiments, the adhesive sheet can be provided in a form in which the release film 130 is attached to both sides of the adhesive layer 120.

[0112] For example, by removing the release film 130 attached to one surface of the adhesive sheet and attaching an optical base film 110 or a functional layer (for example, an antireflection layer) to the exposed surface of the adhesive layer 120, a laminate can be formed.

[0113] In one embodiment, the antireflection layer may be provided as an antireflection plate attached to one surface of the optical base film 110, and the adhesive layer 120 of the adhesive sheet may be attached to the other surface of the optical base film 110.

[0114] <Optical Film, Image Display Device> FIG. 3 is a schematic cross-sectional view for explaining an optical film according to an exemplary embodiment.

[0115] Referring to FIG. 3, the optical film can include a base film 110, an adhesive layer 120 disposed on one surface of the base film 110, and an optical functional layer 140 disposed on the other surface of the base film 110.

[0116] For example, an optical film can be formed by forming an optical functional layer 140 on one surface of a base film 110 and then applying and curing an adhesive composition on the other surface of the base film 110 to form an adhesive layer 120.

[0117] In some embodiments, the optical functional layer 140 can include an anti-reflection layer, a hard coat layer, a retardation layer, a polarizer, etc. For example, the optical film can be provided as an anti-reflection film, a hard coat film, a window film, a retardation film, a polarizing plate, etc., according to the optical functional layer 140.

[0118] In some embodiments, the optical film can further include a release film disposed on one surface of the adhesive layer 120. For example, the optical film can be provided in a form where the base film 110 and the release film 130 are attached to both surfaces of the adhesive layer 120. In this case, the release film 130 formed on one surface of the adhesive layer 120 can be removed, and the exposed surface of the adhesive layer 120 can be attached to an object (e.g., a display panel).

[0119] In some embodiments, when release films 130 are attached to both surfaces of the adhesive layer 120, after removing one surface's release film 130, the optical functional layer 140 can be attached to the exposed surface, and after removing the remaining release film 130 on the other surface of the adhesive layer 120, an object (e.g., a display panel) can be attached to the exposed surface.

[0120] FIG. 4 is a schematic cross-sectional view for explaining an image display device according to an exemplary embodiment.

[0121] According to an exemplary embodiment, the image display device can include a display panel 200 and an optical film disposed on the display panel 200.

[0122] In some embodiments, the image display device can include a display panel 200 and an optical film disposed on the upper surface of the display panel via an adhesive layer 120. For example, the image display device can be provided by removing the release film 130 from the optical film and attaching the exposed adhesive layer 120 to the display panel 200.

[0123] The display panel 200 may be a liquid crystal display panel (LCD), an organic light-emitting display panel (OLED), or a quantum dot light-emitting display panel (QLED).

[0124] In addition to the above configuration, the image display device can further include other configurations known in the art. For example, it can further include a retardation film, a hard coat film, a protective film, a window film, a touch panel, etc. The above configurations can be attached to each other by an adhesive composition according to an exemplary embodiment.

[0125] As described above, by improving the adhesion and bonding between the base film 110 and the adhesive layer 120, it can have improved durability and stability. Therefore, even under physical external forces such as repeated bending or harsh conditions of high temperature and high humidity, the adhesive reliability of the image display device can be maintained for a long time, and breakage, peeling, and floating phenomena of each component can be prevented.

[0126] Also, after being left for a long time under harsh conditions of high temperature and high humidity, the adhesive sheet can be peeled off without damage to the object in rework and without residue of the adhesive substance.

[0127] Hereinafter, specific examples are presented to assist in the understanding of the present invention. However, these examples are merely illustrative of the present invention and do not limit the scope of the appended claims. It is obvious to those skilled in the art that various changes and modifications to the examples are possible within the scope of the category and technical idea of the present invention, and such deformations and modifications naturally belong to the scope of the appended claims.

[0128] Production Example 1: Production of Acrylic Copolymer (A-1) Into a 1 L reactor equipped with a cooling device so that nitrogen gas is refluxed and temperature adjustment is easy, 100 parts by weight of a polymerizable mixture containing 65.8% by weight of n-butyl acrylate (BA), 25% by weight of methyl acrylate (MA), 8% by weight of phenoxyethyl acrylate (PEA), 0.2% by weight of acrylic acid (AA), and 1.0% by weight of 2-hydroxyethyl acrylate (2-HEA), and 100 parts by weight of ethyl acetate (EA) as a solvent were charged to produce a mixture. To remove oxygen, the mixture was purged with nitrogen gas for 1 hour and then the temperature was maintained at 62°C. After the mixture was uniformly stirred, 0.07 part by weight of azobisisobutyronitrile (AIBN) was added as a polymerization initiator and reacted for 8 hours to produce an acrylic copolymer (A-1) having a weight average molecular weight of 1.51 million.

[0129] Production Examples 2 to 9 An acrylic copolymer was produced in the same manner as in Production Example 1, except that the types and contents of the monomers were adjusted as shown in Table 1 below. The monomer contents were expressed as % by weight based on the total weight of the polymerizable mixture.

[0130]

Table 1

[0131] Examples 1 to 17 and Comparative Examples 1 to 3 (1) Production of the pressure-sensitive adhesive composition After producing a mixture with the components and contents as shown in Table 2 below, it was diluted with ethyl acetate to a solid content concentration of 14% by weight to produce the pressure-sensitive adhesive compositions of the examples and comparative examples. The content unit of each component in the following table is parts by weight based on 100 parts by weight of the acrylic copolymer.

[0132] (2) Manufacture of the Adhesive Sheet The manufactured adhesive composition was applied onto a release film coated with a silicone release agent, and dried at 100°C for 2 minutes to form an adhesive layer with a thickness of 20 μm. A polarizing plate was laminated as a base film onto the formed adhesive layer to manufacture an adhesive sheet. As the polarizing plate, an iodine-based polarizing plate (thickness 185 μm) in which a cycloolefin (COP) film subjected to corona discharge treatment was laminated on one surface of a polyvinyl alcohol (PVA) polarizer, and a triacetyl cellulose (TAC) film was laminated on the other surface was used. Lamination was performed such that the surface of the corona discharge-treated COP film was in contact with the adhesive layer.

[0133]

Table 2

[0134] A-1 to A-9: Acrylic copolymers of Production Examples 1 to 9 B-1: D-110N (XDI-based crosslinking agent, manufactured by Mitsui Chemicals, Inc.) B-2: Coronate-HXR (HDI-based crosslinking agent, manufactured by Nippon Polyurethane Industry Co., Ltd.) C-1: KBM-403 (3-glycidoxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.) D-1: Compound represented by the following Chemical Formula 1-1 (ImC12-FSI, melting point: 42°C) JPEG2025113221000008.jpg5043D-2: Compound represented by the following Chemical Formula 1-2 (ImC14-FSI, melting point: 66°C) JPEG2025113221000009.jpg4941D-3: Compound represented by the following Chemical Formula 1-3 (ImC18-FSI, melting point: 48°C) JPEG2025113221000010.jpg4940D-4: Compound represented by the following Chemical Formula 1-4 (H-ImC14-FSI, melting point: 40°C) JPEG2025113221000011.jpg4941D-5: Compound represented by the following Chemical Formula 1-5 (ImC10-FSI, melting point: 25°C or lower) JPEG2025113221000012.jpg4840D-6: IL-P-18-2 (1-octyl-4-methylpyridinium hexafluorophosphate, manufactured by Kyoei Chemical Co., Ltd.) D-7: Compound represented by the following Chemical Formula 4 JPEG2025113221000013.jpg5037D-8: Compound represented by the following Chemical Formula 5 (ImC8-FSI, melting point: 25°C or lower) JPEG2025113221000014.jpg4940

[0135] Experimental Example (1) Evaluation of Adhesion The adhesive sheets of the examples and comparative examples were cut into a length of 25 mm × width of 100 mm. After peeling off the release film, the exposed adhesive layer was attached to a glass substrate (#1737, manufactured by Corning), and an autoclave treatment was performed for 20 minutes under the conditions of a temperature of 50°C and a pressure of 5 atmospheres to prepare test pieces.

[0136] To measure the adhesion, the test pieces prepared above were left standing for 24 hours under the conditions of a temperature of 23°C and a humidity of 50%RH. Using a universal tensile testing machine (UTM, manufactured by Instron), the adhesive sheet was peeled from the glass substrate at a peeling speed of 300 mm / min and a peeling angle of 180° to measure the normal temperature adhesion.

[0137] (2) Evaluation of Durability (Heat Resistance, Damp Heat Resistance) The adhesive sheets of the examples and comparative examples were cut into a length of 200 mm × width of 300 mm. After peeling off the release film, the exposed adhesive layer was attached to a glass substrate (210 mm × 350 mm × 0.7 mm), and an autoclave treatment (50°C × 30 minutes, 0.5 MPa) was performed to prepare test pieces. At this time, the applied pressure was 5 kg / cm 2 and clean room work was carried out so that no bubbles or foreign substances would occur.

[0138] The heat resistance was evaluated by observing the presence or absence of bubbles and peeling after leaving the test piece at a temperature of 80 °C or 95 °C for 1000 hours. The damp heat resistance was evaluated by observing the presence or absence of bubbles and peeling after leaving the test piece under the conditions of 60 °C, 90% RH, or 65 °C, 95% RH for 1000 hours. At this time, it was observed after leaving it at room temperature for 24 hours immediately before evaluating the state of the test piece.

[0139] <Evaluation Criteria> ◎: No bubbles or peeling ○: Less than 5 bubbles or peeling △: 5 ≤ bubbles or peeling < 10 X: 10 ≤ bubbles or peeling

[0140] (3) Measurement of Adhesion The manufactured adhesive sheet was cut into a size of 25 mm in length × 50 mm in width and attached to a SUS304 plate via a double-sided adhesive tape (width: 25 mm, manufactured by SOOKWANG) on the polarizing plate surface. Then, using an elastic rubber (neoprene rubber), the surface of the adhesive layer was reciprocated 20 times in the length (25 mm) direction at a pressure of 1 MPa and a speed of 0.1 m / s. At this time, the distance that the adhesive layer was extruded on the TAC film was measured to judge the adhesion.

[0141] (4) Measurement of Antistatic Property The manufactured adhesive sheet was cut into a size of 200 mm in length × 300 mm in width. After peeling off the release film, the surface resistivity value of the exposed adhesive layer was measured to evaluate the antistatic property. The measurement method was to measure the surface resistivity under the conditions of 25 °C, 50% RH, 500 V, and 10 seconds using a resistivity meter, High Rester UP-HT450 (manufactured by Mitsubishi Chemical Analytech Co., Ltd.). The results are summarized in Table 3 below.

[0142]

Table 3

[0143] Referring to Table 3 above, the adhesive sheet of the example including an adhesive layer formed from an adhesive composition containing the ionic compound of Chemical Formula 1 had improved adhesive strength and adhesion. Also, the surface resistivity value of the adhesive sheet of the example was low, had improved antistatic properties, and maintained the adhesive quality without degradation even when left for a long time in high-temperature and high-humidity environments.

[0144] The adhesive sheet of the comparative example was formed from an adhesive composition containing an ionic antistatic agent different from the ionic compound of Chemical Formula 1. As a result, a large amount of bubbles and peeling occurred in high-temperature and high-humidity environments, and the durability decreased. Also, the surface resistivity value of the adhesive sheet of the comparative example was slightly higher than the surface resistivity value of the adhesive sheet of the example.

[0145] The foregoing description is merely an exemplification applying the principles of the present disclosure, and other configurations can be further included without departing from the scope of the present invention.

Description of Reference Numerals

[0146] 110: Substrate film 120: Adhesive layer 130: Release film 140: Optical functional layer 200: Display panel

Claims

1. An acrylic copolymer, a crosslinking agent, and an ionic antistatic agent which is an ionic compound represented by the following Chemical Formula 1. An adhesive composition containing the same. 【Chemical 1】 (In the above chemical formula 1, R １ is hydrogen or a methyl group, and R ２ is an alkyl group having 10 to 30 carbon atoms.)

2. In the above Chemical Formula 1, R ２ is a linear alkyl group having 12 to 18 carbon atoms, and the pressure-sensitive adhesive composition according to Claim 1.

3. The adhesive composition according to claim 1, wherein the melting point of the ionic antistatic agent is 23°C or higher.

4. The adhesive composition according to claim 1, wherein the melting point of the ionic antistatic agent is 25°C to 70°C.

5. The adhesive composition according to claim 1, wherein the content of the ionic antistatic agent is 0.01 part by weight to 7 parts by weight with respect to 100 parts by weight of the acrylic copolymer.

6. The adhesive composition according to claim 1, wherein the content of the ionic antistatic agent is 1 part by weight to 5 parts by weight with respect to 100 parts by weight of the acrylic copolymer.

7. The adhesive composition according to claim 1, wherein the acrylic copolymer is formed from a polymerizable mixture containing an alkyl (meth)acrylate monomer, an aromatic group-containing (meth)acrylate monomer, and a polar functional group-containing crosslinkable monomer.

8. The adhesive composition according to claim 7, wherein the alkyl (meth)acrylate monomer includes a first monomer which is an alkyl (meth)acrylate monomer having 1 to 3 carbon atoms and a second monomer which is an alkyl (meth)acrylate monomer having 4 to 12 carbon atoms.

9. The adhesive composition according to claim 7, wherein the polar functional group of the polar functional group-containing crosslinkable monomer includes at least one of a carboxy group, a hydroxy group, an amide group, and an amine group.

10. The adhesive composition according to claim 1, wherein the crosslinking agent includes a non-yellowing type isocyanate-based crosslinking agent.

11. The adhesive composition according to claim 1, wherein the content of the crosslinking agent is 0.1 part by weight to 3 parts by weight with respect to 100 parts by weight of the acrylic copolymer.

12. The adhesive composition according to claim 1, further comprising a silane coupling agent.

13. The adhesive composition according to claim 12, wherein the content of the silane coupling agent is 0.01 part by weight to 3 parts by weight with respect to 100 parts by weight of the acrylic copolymer.

14. A base film, and An adhesive sheet including an adhesive layer disposed on the base film and formed using the adhesive composition according to claim 1.

15. The adhesive sheet according to claim 14, wherein the base film includes at least one selected from the group consisting of a polarizer, an antireflection layer, a hard coat layer, and a retardation layer.

16. The surface resistivity value of the adhesive layer is 1×10 １１ Ω / sq or less. The adhesive sheet according to claim 14.

17. A base film, An adhesive layer disposed on the upper surface of the base film and formed using the adhesive composition according to claim 1, An optical film comprising an antireflection layer disposed on the lower surface of the base film.

18. An image display device comprising the optical film according to claim 17.

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