Pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet using the same

Abstract

The present invention provides a pressure-sensitive adhesive composition containing a urethane oligomer, a diluent monomer, and a photoinitiator, wherein the weight ratio of heteroatoms in the diluent monomer is adjusted, and the dielectric constant and dielectric loss tangent at 15 GHz of a 150 μm-thick pressure-sensitive adhesive layer after curing are controlled within specific ranges. The pressure-sensitive adhesive composition of the present invention can exhibit low dielectric properties suitable for use in image display devices that require high frequency bands or are thin.

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition and an adhesive sheet using the same, and more particularly to an adhesive composition exhibiting low dielectric properties suitable for application to image display devices that require a high frequency band or are thin, and an adhesive sheet using the same. [Background technology]

[0002] Among pressure-sensitive adhesives, optically clear adhesives (OCA), which have high transparency, are used for interlayer bonding to laminate components together in image display devices. Such optically clear adhesives are required to have high transmittance and low haze, and also to satisfy physical properties such as adhesion to various substrates, heat resistance, and durability against moist heat.

[0003] In recent years, the amount of information traffic has increased dramatically, as exemplified by the widespread use of video transmission via optical fiber communication lines and wireless communication lines. This has led to a demand for higher frequency image display devices, and antennas are now being built into image display devices to transmit and receive signals in high-frequency bands. In particular, image display devices used in mobile communications require a high-frequency band of 1 GHz or higher, for example, 1 to 30 GHz. Therefore, in response to the increasing frequency of image display devices, there is a demand for the use of electrically insulating materials with low dielectric constants to enable faster antenna transmission and reception without reducing antenna gain.

[0004] Meanwhile, a touch sensor is a device that detects the touched location when a user touches an image displayed on a screen with a fingertip or a touch pen, and is manufactured in a structure that is attached to a flat panel display device such as a liquid crystal display (LCD), an organic light-emitting diode (OLED), etc. In recent years, as image display devices have become thinner, it has become necessary to use an electrically insulating material with a low dielectric constant so that the touch sensor is not interfered with by the lower display panel and does not affect the operation of the touch sensor.

[0005] Korean Patent Publication No. 10-2013-0106368 discloses an adhesive composition comprising an acrylic polymer compound and a crosslinker, the polymer compound being obtained by copolymerizing monomer components including a (meth)acrylic acid ester monomer having a hydrocarbon group with 1 to 12 carbon atoms, a hydroxyl group-containing (meth)acrylic acid ester monomer, an amide group-containing monomer, and a vinyl ester monomer, and the resin has an acid value of 0.1 mgKOH / g or less, a weight-average molecular weight of 400,000 to 2,000,000, a Tg of -80 to 0°C, and a dielectric constant of 3 to 6. However, the adhesive composition has the drawback of being difficult to ensure sufficiently low dielectric properties for use in high-frequency bands of 1 GHz or above or in thin-film image display devices. Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a pressure-sensitive adhesive composition that exhibits low dielectric properties even in high frequency bands, thereby enabling faster antenna transmission and reception without reducing antenna gain.

[0007] Another object of the present invention is to provide a pressure-sensitive adhesive composition that exhibits low dielectric properties that do not affect the driving of touch sensors even when image display devices are made thinner.

[0008] Another object of the present invention is to provide a pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition. [Means for solving the problem]

[0009] On the other hand, the present invention provides a pressure-sensitive adhesive composition containing a urethane oligomer, a diluent monomer, and a photoinitiator, The weight ratio of heteroatoms in the diluent monomer is 16.5% or less; The present invention provides an adhesive composition in which, after curing, the adhesive layer has a dielectric constant of less than 2.5 at 15 GHz when 150 μm thick, and a dielectric loss tangent of 0.015 or less at 15 GHz when 150 μm thick.

[0010] In one embodiment of the present invention, the urethane oligomer may have one or more skeletons selected from the group consisting of polyethylene, polypropylene, polybutadiene, polyisoprene, hydrogenated polybutadiene, and hydrogenated polyisoprene, and may have a radical polymerizable functional group at at least one end.

[0011] In one embodiment of the present invention, the radically polymerizable functional group may be a (meth)acryloyloxy group or a vinyl group.

[0012] In one embodiment of the present invention, the urethane oligomer may be contained in an amount of 5 to 50 parts by weight based on 100 parts by weight of the diluent monomer.

[0013] In one embodiment of the present invention, the diluent monomer may include one or more of a (meth)acrylic monomer and a vinyl monomer.

[0014] In one embodiment of the present invention, the photoinitiator may be contained in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the diluent monomer.

[0015] On the other hand, the present invention provides a pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition. [Effects of the Invention]

[0016] The adhesive composition according to the present invention can exhibit low dielectric properties suitable for application to thin image display devices requiring high frequency bands by controlling the dielectric constant and dielectric loss tangent at 15 GHz of a 150 μm thick adhesive layer after curing within specific ranges by adjusting the weight ratio of heteroatoms in the diluent monomer. This enables faster antenna transmission and reception without reducing antenna gain when applied to antennas, and does not affect the operation of touch sensors even when the image display device is thinned. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will now be described in more detail.

[0018] One embodiment of the present invention is a pressure-sensitive adhesive composition containing a urethane oligomer, a diluent monomer, and a photoinitiator, The weight ratio of heteroatoms in the diluent monomer is 16.5% or less; The present invention relates to a pressure-sensitive adhesive composition in which a 150 μm thick pressure-sensitive adhesive layer after curing has a dielectric constant of less than 2.5 at 15 GHz and a dielectric loss tangent of 0.015 or less at 15 GHz.

[0019] The weight ratio of the heteroatoms in the diluent monomer means the ratio of the weight of the heteroatoms to the total weight of the atoms constituting the diluent monomer, and can be defined by the following Equation 1:

[0020]

number

[0021] That is, the weight ratio of heteroatoms in the diluent monomer is the sum of the weight ratio of heteroatoms contained in each monomer constituting the diluent monomer multiplied by the ratio of the monomer, expressed as a percentage.

[0022] The heteroatom means an element other than carbon, such as oxygen, sulfur, or nitrogen.

[0023] As described above, the weight ratio of heteroatoms in the diluent monomer is 16.5% or less, for example, 0.5 to 16.5%, preferably 3 to 16.5%, more preferably 5 to 16.5%, even more preferably 7 to 16.5%, even more preferably 10 to 16.5%, and still more preferably 10 to 16.0%.

[0024] If the weight ratio of heteroatoms in the diluent monomer exceeds 16.5%, the dielectric constant at 15 GHz of a 150 μm thick adhesive layer after curing may be 2.5 or more, or the dielectric loss tangent at 15 GHz of a 150 μm thick adhesive layer after curing may exceed 0.015. Also, if the weight ratio of heteroatoms in the diluent monomer exceeds 16.5%, the radio wave reception efficiency of the antenna may decrease and it may become difficult to thin the touch sensor.

[0025] The dielectric constant is a physical unit that indicates the effect of a medium between charges on an electric field when the electric field acts between the charges, and can also be said to be the amount of charge that the medium can store.

[0026] The dielectric constant at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm after curing is a value measured at a frequency of 15 GHz by the method described in the experimental examples below for a sample having a pressure-sensitive adhesive layer having a thickness of 150 μm after curing.

[0027] The dielectric constant at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm after curing may be less than 2.5, for example, more than 1 and less than 2.5, as described above. If the dielectric constant at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm after curing is 2.5 or more, the antenna gain may be reduced when the pressure-sensitive adhesive layer is applied to an antenna using a high frequency band such as 15 GHz, and the driving of the touch sensor may be affected when the image display device is made thinner.

[0028] The dielectric tangent is a unit that indicates the ratio of power loss that occurs when an AC voltage is applied to a dielectric, and is generally expressed as tangent delta.

[0029] The dielectric loss tangent at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm after curing is a value measured at a frequency of 15 GHz by the method described in the experimental examples below for a sample having a pressure-sensitive adhesive layer having a thickness of 150 μm after curing.

[0030] As described above, the dielectric loss tangent at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm after curing may be 0.015 or less, for example, more than 0 and 0.015 or less. If the dielectric loss tangent at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm after curing exceeds 0.015, the antenna gain may be reduced when the pressure-sensitive adhesive layer is applied to a 5G antenna that uses a high frequency band such as 15 GHz, and the driving of the touch sensor may be affected when the image display device is made thinner.

[0031] In one embodiment of the present invention, the urethane oligomer may have a urethane bond in the molecule and a radically polymerizable functional group at at least one end.

[0032] In order to control the weight ratio of heteroatoms, the urethane oligomer may preferably have a structure in which a long-chain aliphatic hydrocarbon skeleton is used as the main chain and a radically polymerizable functional group is bonded to at least one end of the main chain via a urethane bonding group.

[0033] Specifically, the urethane oligomer may have one or more skeletons selected from the group consisting of polyethylene, polypropylene, polybutadiene, polyisoprene, hydrogenated polybutadiene, and hydrogenated polyisoprene, and may have a radical polymerizable functional group at at least one end.

[0034] The radically polymerizable functional group may be a (meth)acryloyloxy group or a vinyl group, and may particularly be a (meth)acryloyloxy group.

[0035] For example, the urethane oligomer may have a structure represented by the following Chemical Formula 1:

[0036] [ka]

[0037] In the above formula, A is polyethylene, polypropylene, polybutadiene, polyisoprene, hydrogenated polybutadiene, or hydrogenated polyisoprene; L is a linking group containing a urethane bond, B 1 is an acryloyloxy group, a methacryloyloxy group, or a C1-C 10 is an alkoxy group of the formula B 2 is an acryloyloxy group or a methacryloyloxy group.

[0038] As used herein, C1-C 10 The alkoxy group means a linear or branched alkoxy group having 1 to 10 carbon atoms, and includes, but is not limited to, methoxy, ethoxy, n-propaneoxy, butoxy, etc.

[0039] Preferably, the urethane oligomer may have a structure represented by the following Chemical Formula 2:

[0040] [ka]

[0041] In the above formula, A is polyethylene, polypropylene, polybutadiene, polyisoprene, hydrogenated polybutadiene, or hydrogenated polyisoprene; R 1 does not exist or C1-C 10 is an alkylene group of the formula R 2 is C1-C 10 Alkylene groups, C3-C 10 is a cycloalkylene group or an arylene group represented by the formula: R 3 is C1-C 10 or an alkylene group of C3-C 10 is a cycloalkylene group of the formula B 1 is an acryloyloxy group, a methacryloyloxy group or a C1-C 10is an alkoxy group of the formula B 2 is an acryloyloxy group or a methacryloyloxy group.

[0042] As used herein, C1-C 10 The alkylene group means a linear or branched hydrocarbon having 1 to 10 carbon atoms, and examples thereof include, but are not limited to, methylene, ethylene, propylene, butylene, pentylene, and hexylene.

[0043] As used herein, C3-C 10 The cycloalkylene group means a monocyclic or fused ring hydrocarbon having 3 to 10 carbon atoms, and examples thereof include, but are not limited to, cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, etc.

[0044] As used herein, the term "arylene group" includes aromatic groups, heteroaromatic groups, and their partially reduced derivatives. The aromatic group is a 5- to 15-membered monocyclic or fused ring, and the heteroaromatic group refers to an aromatic group containing one or more oxygen, sulfur, or nitrogen atoms. Representative examples of arylene groups include, but are not limited to, tolylene, phenylene, and naphthylene.

[0045] Said C3-C 10 In the cycloalkylene group and arylene group, one or more hydrogen atoms may be substituted with a C1-C6 alkyl group, a C1-C6 alkoxy group, a halogen, or the like.

[0046] The urethane oligomer may be prepared by methods known in the art.

[0047] For example, the urethane oligomer may be produced by reacting a hydroxyl group-containing polyolefin with a diisocyanate compound and a hydroxyl group-containing (meth)acrylate compound. 10The alcohol compounds may further be used.

[0048] The hydroxyl group-containing polyolefin may be commercially available or may be produced by a method known in the art. For example, the hydroxyl group-containing polyolefin may be produced by reacting a polyolefin with an epoxy compound. The epoxy compound may be ethylene oxide, propylene oxide, or the like. Commercially available hydroxyl group-containing polyolefins include GI-1000, GI-2000, and GI-3000 manufactured by Nippon Soda Co., Ltd.

[0049] The diisocyanate compound may be an aliphatic diisocyanate compound and / or an aromatic diisocyanate compound.

[0050] Examples of the aliphatic diisocyanate compound include methyl diisocyanate, 1,2-ethanediyl diisocyanate, 1,3-propanediyl diisocyanate, 1,6-hexanediyl diisocyanate, 3-methyl-octane-1,8-diyl diisocyanate, 1,2-cyclopropanediyl diisocyanate, 1,3-cyclobutanediyl diisocyanate, 1,4-cyclohexanediyl diisocyanate, 1,3-cyclohexanediyl diisocyanate, isophorone diisocyanate, and 4-methyl-cyclohexane-1,3-diyl diisocyanate.

[0051] Examples of the aromatic diisocyanate compound include 1,2-phenylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 3-chloro-1,2-benzene diisocyanate, 4-chloro-1,2-benzene diisocyanate, 5-chloro-1,2-benzene diisocyanate, 2-chloro-1,3-benzene diisocyanate, 4-chloro-1,3-benzene diisocyanate, 5-chloro-1,3-benzene diisocyanate, 2-chloro-1,4-benzene diisocyanate, 3-chloro-1,4- Benzene diisocyanate, 3-methyl-1,2-benzene diisocyanate, 4-methyl-1,2-benzene diisocyanate, 5-methyl-1,2-benzene diisocyanate, 2-methyl-1,3-benzene diisocyanate, 4-methyl-1,3-benzene diisocyanate, 5-methyl-1,3-benzene diisocyanate, 2-methyl-1,4-benzene diisocyanate, 3-methyl-1,4-benzene diisocyanate, 3-methoxy-1,2-benzene diisocyanate, 4-methoxy-1,2-benzene diisocyanate, 5- Methoxy-1,2-benzenediisocyanate, 2-methoxy-1,3-benzenediisocyanate, 4-methoxy-1,3-benzenediisocyanate, 5-methoxy-1,3-benzenediisocyanate, 2-methoxy-1,4-benzenediisocyanate, 3-methoxy-1,4-benzenediisocyanate, 3,4-dimethyl-1,2-benzenediisocyanate, 4,5-dimethyl-1,3-benzenediisocyanate, 2,3-dimethyl-1,4-benzenediisocyanate, 3-chloro-4-methyl-1,2-benzenediisocyanate , 3-methyl-4-chloro-1,2-benzenediisocyanate, 3-methyl-5-chloro-1,2-benzenediisocyanate, 2-chloro-4-methyl-1,3-benzenediisocyanate, 4-chloro-5-methoxy-1,3-benzenediisocyanate, 5-chloro-2-fluoro-1,3-benzenediisocyanate, 2-chloro-3-bromo-1,4-benzenediisocyanate, 3-chloro-5-isopropoxy-1,4-benzenediisocyanate, 2,3-diisocyanatopyridine, 2,4-diisocyanatopyridine, 2,Examples include 5-diisocyanate pyridine, 2,6-diisocyanate pyridine, 2,5-diisocyanate-3-methylpyridine, 2,5-diisocyanate-4-methylpyridine, and 2,5-diisocyanate-6-methylpyridine.

[0052] Examples of the hydroxy group-containing (meth)acrylate compound include hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxy-n-propyl (meth)acrylate, 2-hydroxy-n-propyl (meth)acrylate, 2-hydroxyisopropyl (meth)acrylate, 2-hydroxy-n-butyl (meth)acrylate, 3-hydroxy-n-butyl (meth)acrylate, 5-hydroxy-n-pentyl (meth)acrylate, 2-hydroxy-n-pentyl (meth)acrylate, 3-hydroxy-n-pentyl (meth)acrylate, 4-hydroxy-n-pentyl (meth)acrylate, 2-hydroxycyclopropyl (meth)acrylate, 3-hydroxycyclopentyl (meth)acrylate, and 4-hydroxycyclohexyl (meth)acrylate.

[0053] Said C1-C 10 Examples of the alcohol compound include methanol, ethanol, n-propanol, and butanol.

[0054] The urethane oligomer may be commercially available and used. Examples of commercially available urethane oligomers include TEAI-1000 and TE-2000 manufactured by Nippon Soda Co., Ltd.

[0055] The urethane oligomer may have a weight average molecular weight (polystyrene equivalent) of 1,000 to 200,000 as measured by gel permeation chromatography (GPC). If the weight average molecular weight of the urethane oligomer is outside this range, it may be difficult to ensure processability.

[0056] In one embodiment of the present invention, the urethane oligomer may be contained in an amount of 5 to 50 parts by weight relative to 100 parts by weight of the diluent monomer. If the urethane oligomer is contained in an amount less than 5 parts by weight, the viscosity may decrease, and if it is contained in an amount more than 50 parts by weight, it may become difficult to achieve the dielectric constant and / or dielectric loss tangent within the above range.

[0057] In one embodiment of the present invention, the diluent monomer acts as a dispersion medium for the urethane oligomer and is a component that can be polymerized by the action of a photoinitiator. The diluent monomer also dilutes the pressure-sensitive adhesive composition to adjust the viscosity, thereby facilitating application.

[0058] The diluent monomer may include one or more of a (meth)acrylic monomer and a vinyl monomer.

[0059] Here, (meth)acrylic means acrylic and / or methacrylic.

[0060] The diluent monomer may be appropriately selected so that the weight ratio of heteroatoms is 16.5% or less.

[0061] For example, the diluent monomer may contain one or more of a (meth)acrylic monomer having an aliphatic hydrocarbon group of 10 or more carbon atoms and a vinyl ether monomer having an aliphatic hydrocarbon group of 8 or more carbon atoms in an amount of 20% by weight or more, for example, 20 to 99% by weight, preferably 20 to 90% by weight, relative to 100% by weight of the total monomers. If the content of one or more of the (meth)acrylic monomer having an aliphatic hydrocarbon group of 10 or more carbon atoms and the vinyl ether monomer having an aliphatic hydrocarbon group of 8 or more carbon atoms is less than 20% by weight, it may be difficult to control the weight ratio of heteroatoms to 16.5% or less.

[0062] As used herein, the aliphatic hydrocarbon group having 10 or more carbon atoms means a linear or branched saturated or unsaturated hydrocarbon group having 10 or more carbon atoms, for example, 10 to 100, preferably 10 to 50, more preferably 10 to 30 carbon atoms, and examples thereof include C 10 -C 100 Alkyl groups of C 10 -C 100 Alkenyl groups of C 10 -C 100 Specific examples of aliphatic hydrocarbon groups having 10 or more carbon atoms include, but are not limited to, decyl, isodecyl, undecyl, dodecyl, tridecyl, cetyl, stearyl, isostearyl, and heptacosanyl.

[0063] As used herein, an aliphatic hydrocarbon group having 8 or more carbon atoms refers to a linear or branched saturated or unsaturated hydrocarbon group having 8 or more carbon atoms, for example, 8 to 100, preferably 8 to 50, more preferably 8 to 30 carbon atoms, such as a C8-C 100 Alkyl groups, C8-C 100 Alkenyl groups, C8-C 100 Specific examples of aliphatic hydrocarbon groups having 8 or more carbon atoms include, but are not limited to, octyl, ethylhexyl, nonyl, decyl, isodecyl, undecyl, dodecyl, tridecyl, cetyl, stearyl, isostearyl, and heptacosanyl.

[0064] The (meth)acrylic monomer having an aliphatic hydrocarbon group having 10 or more carbon atoms is a compound having an aliphatic hydrocarbon group having 10 or more carbon atoms and a (meth)acrylate group as a radically polymerizable functional group.

[0065] Specifically, examples of the (meth)acrylic monomer having an aliphatic hydrocarbon group having 10 or more carbon atoms include decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, and 1-heptacosanyl (meth)acrylate, and these may be used alone or in combination of two or more.

[0066] The vinyl ether monomer having an aliphatic hydrocarbon group having 8 or more carbon atoms is a compound having an aliphatic hydrocarbon group having 8 or more carbon atoms and a vinyl ether group as a radically polymerizable functional group.

[0067] Specifically, examples of the vinyl ether monomer having an aliphatic hydrocarbon group having 8 or more carbon atoms include 2-ethylhexyl vinyl ether and dodecyl vinyl ether, which may be used alone or in combination of two or more.

[0068] The diluent monomers may further include a monomer having a crosslinkable functional group.

[0069] The monomer having a crosslinkable functional group may be one or more of a monomer having a hydroxy group and a monomer having a carboxy group.

[0070] Examples of the monomer having a hydroxy group 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)acrylates having an alkylene group with 2 to 4 carbon atoms, 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. Of these, 4-hydroxybutyl acrylate, 2-hydroxyethyl (meth)acrylate, and 4-hydroxybutyl vinyl ether are preferred.

[0071] Examples of the monomer having a carboxy group include monovalent acids such as (meth)acrylic acid, crotonic acid, and 2-carboxyethyl acrylate; divalent acids such as maleic acid, itaconic acid, and fumaric acid, and monoalkyl esters thereof; 3-(meth)acryloylpropionic acid; ring-opening adducts of succinic anhydride with 2-hydroxyalkyl (meth)acrylates having an alkyl group with 2-3 carbon atoms; ring-opening adducts of succinic anhydride with hydroxyalkylene glycol (meth)acrylates having an alkylene group with 2-4 carbon atoms; and compounds obtained by ring-opening addition of succinic anhydride to caprolactone adducts of 2-hydroxyalkyl (meth)acrylates having an alkyl group with 2-3 carbon atoms. Of these, (meth)acrylic acid, 2-carboxyethyl acrylate, etc. are preferred.

[0072] The monomer having a crosslinkable functional group is preferably contained in an amount of 0.5 to 20 wt%, preferably 0.5 to 10 wt%, based on 100 wt% of the total monomers. If the content of the monomer having a crosslinkable functional group is less than 0.5 wt%, the cohesive strength of the adhesive may be reduced, resulting in reduced durability, while if it exceeds 20 wt%, the dielectric constant may be increased.

[0073] The diluent monomer may further contain other polymerizable monomers in addition to the above-mentioned monomers.

[0074] Specific examples of the other polymerizable monomers include n-butyl (meth)acrylate, 2-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ethyl (meth)acrylate, methyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, pentyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, and isobornyl (meth)acrylate. Of these, 2-ethylhexyl (meth)acrylate and isobornyl (meth)acrylate are preferred. These may be used alone or in combination of two or more.

[0075] The other polymerizable monomer may be contained in an amount of 79.5 wt% or less, for example, 1 to 79.5 wt%, preferably 5 to 79.5 wt%, based on 100 wt% of the total monomers. If the content of the other polymerizable monomer exceeds 79.5 wt%, it may be difficult to control the weight ratio of heteroatoms to 16.5% or less.

[0076] In one embodiment of the present invention, the photoinitiator refers to an initiator that absorbs active energy rays to generate radicals.

[0077] Examples of the photoinitiator include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4,4′-bis(diethylamino)benzophenone (EAB-F), dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminoanthraquinone, 2-methyl ... Quinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone (DETX), 4-isopropylthioxanthone (ITX), benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic acid ester, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2-(3,4-methylenedioxyphenyl)-4,6- Examples include bis(trichloromethyl)-1,3,5-triazine, 2,2'-bis(2-chlorophenyl)-4,4',5,5'-tetraphenylbiimidazole (HABI-101), 2,2'-bis(2-methoxyphenyl)-4,4',5,5'-tetraphenylbiimidazole (HABI-107), 2,2',4-tris(2-chlorophenyl)-5-(3,4-dimethoxyphenyl)-4',5'-diphenylbiimidazole (TCDM), etc. These may be used alone or in combination of two or more.

[0078] The photoinitiator may be included in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the diluent monomer. If the amount is less than 0.01 part by weight, photocuring may not be sufficient, making it difficult to achieve the mechanical properties and adhesive strength of the final pressure-sensitive adhesive sheet. If the amount is more than 5 parts by weight, discoloration may occur due to the remaining initiator, reducing durability.

[0079] In addition to the components described above, the pressure-sensitive adhesive composition according to one embodiment of the present invention may further contain additives such as a silane coupling agent, a tackifying resin, an antioxidant, a corrosion inhibitor, a leveling agent, a surface lubricant, a dye, a pigment, an antifoaming agent, a filler, a light stabilizer, and an antistatic agent in order to adjust adhesive strength, cohesive strength, viscosity, elastic modulus, glass transition temperature, antistatic property, etc. as required depending on the application.

[0080] One embodiment of the present invention relates to a pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition.

[0081] The pressure-sensitive adhesive sheet may be one in which a pressure-sensitive adhesive layer made from the pressure-sensitive adhesive composition according to the present invention is formed on a base film, or one in which a pressure-sensitive adhesive layer made from the pressure-sensitive adhesive composition according to the present invention is sandwiched between two base films.

[0082] Examples of the substrate film include polyolefin-based films, polyester-based films, acrylic-based films, styrene-based films, amide-based films, polyvinyl chloride films, polyvinylidene chloride films, and polycarbonate films, and these may be appropriately treated with a release agent such as a silicone-based film, a fluorine-based film, or silica powder.

[0083] The thickness of the base film is preferably 30 to 80 μm. If it is less than 30 μm, the base film is vulnerable to punctures, and if it exceeds 80 μm, the handleability may decrease.

[0084] The pressure-sensitive adhesive layer may be formed by coating a pressure-sensitive adhesive composition onto a single substrate film. The coating method is not particularly limited as long as it is a method known in the art, and may be, for example, a bar coater, an air knife, a gravure coater, a reverse roll, a kiss roll, a spray, a blade, a die coater, casting, or spin coating. Specifically, the pressure-sensitive adhesive composition is coated onto a single substrate film at a dose of about 100 to 2000 mJ / cm. 2 , preferably 200 to 1500 mJ / cm 2 The ultraviolet ray irradiation amount may be 1000 .mu.m or more and photo-cured to form the film.

[0085] The thickness of the pressure-sensitive adhesive layer may be 10 to 2,000 μm, preferably 25 to 1,500 μm. If the thickness of the pressure-sensitive adhesive layer is less than 10 μm, it may be difficult to cushion external impacts, and if it exceeds 2,000 μm, transmission may decrease, resulting in poor optical performance.

[0086] The pressure-sensitive adhesive sheet according to one embodiment of the present invention may be subjected to a surface treatment of the pressure-sensitive adhesive layer before lamination to improve adhesion.

[0087] The surface treatment method is not particularly limited, and the surface of the pressure-sensitive adhesive layer can be activated by, for example, corona discharge treatment, plasma treatment, ultraviolet irradiation, electron beam irradiation, or application of an anchoring agent.

[0088] The adhesive sheet according to an embodiment of the present invention can be applied to not only conventional flat displays and flexible displays, but also foldable displays. In particular, the adhesive sheet according to an embodiment of the present invention can be effectively applied to interlayer adhesion for laminating components in display devices using high frequency bands or having a thin structure. Specifically, the adhesive sheet can be applied to bonding various display materials such as antennas, display panels, polarizers, touch sensors, cover windows, bezels, polymer films, and FPCBs, and can particularly be applied to bonding antennas or touch sensors.

[0089] The present invention will be described in more detail below with reference to examples, comparative examples, and experimental examples. However, it will be obvious to those skilled in the art that these examples, comparative examples, and experimental examples are merely for the purpose of illustrating the present invention, and that the scope of the present invention is not limited thereto.

[0090] Production Example 1: Production of urethane oligomer A urethane oligomer having a weight-average molecular weight of 100,000 was produced by reacting an isocyanate polymer obtained by reacting 80 parts by weight of hydrogenated polybutadiene polyol (EPOL, manufactured by Idemitsu Kosan Co., Ltd.) with 500 ppm of dibutyltin dilaurate catalyst (DBTDL) and 10 parts by weight of isophorone diisocyanate at 80°C, and then reacting this with 9 parts by weight of 2-hydroxyethyl acrylate.

[0091] Production Example 2: Production of urethane oligomer A urethane oligomer having a weight-average molecular weight of 110,000 was produced by reacting an isocyanate polymer obtained by reacting 80 parts by weight of polybutadiene polyol (Poly bd, manufactured by Idemitsu Kosan Co., Ltd.) with 500 ppm of dibutyltin dilaurate catalyst (DBTDL) and 10 parts by weight of isophorone diisocyanate at 80°C, and then reacting this with 9 parts by weight of 2-hydroxyethyl acrylate.

[0092] Production Example 3: Production of urethane oligomer A urethane oligomer having a weight-average molecular weight of 123,000 was produced by reacting an isocyanate polymer obtained by reacting 80 parts by weight of polyisoprene polyol (Poly ip, manufactured by Idemitsu Kosan Co., Ltd.) with 500 ppm of dibutyltin dilaurate catalyst (DBTDL) and 10 parts by weight of isophorone diisocyanate at 80°C, and then reacting this with 9 parts by weight of 2-hydroxyethyl acrylate.

[0093] Examples 1 to 8 and Comparative Examples 1 to 3: Production of adhesive compositions and adhesive sheets The urethane oligomer synthesized in the above Preparation Example, a diluent monomer, and a photoinitiator were mixed according to the composition shown in Table 1 below to prepare a pressure-sensitive adhesive composition (parts by weight).

[0094] [Table 1]

[0095] The pressure-sensitive adhesive compositions prepared in Examples 1 to 7 and Comparative Examples 1 to 3 were coated on a polyethylene terephthalate film (thickness: 75 μm) that had been contoured as a release film using a bar coater. Then, ultraviolet light was applied using a UV lamp at 1.5 J / cm for 10 minutes. 2 The adhesive composition was cured by irradiating it with a light intensity of 150 μm, thereby producing an adhesive sheet having a thickness of 150 μm after curing.

[0096] Experimental Example 1: The dielectric constant and dielectric loss tangent of the pressure-sensitive adhesive sheets produced in the examples and comparative examples were measured at a temperature of 25°C and a humidity of 50% using a dielectric constant measuring device (manufactured by Anritsu Corporation, product name: MS46522B).

[0097] More specifically, a 150 μm adhesive sheet with the release film removed was laminated between 40 μm COP films (manufactured by Zeonor) on top and bottom, and cut into a size of 30 mm length x 70 mm width. The cut adhesive sheet was inserted into the probe of the measurement equipment, and the dielectric constant (Dk) and dielectric loss tangent (Df) values ​​at 15 GHz were measured.

[0098] The results are shown in Table 2 below.

[0099] [Table 2]

[0100] As can be seen from Table 2, the adhesive sheets of Examples 1 to 7, in which the weight ratio of heteroatoms in the diluent monomer is 16.5% or less, exhibit a dielectric constant of less than 2.5 and a dielectric loss tangent of 0.015 or less even in the high frequency band of 15 GHz, demonstrating excellent low dielectric properties. This indicates that the adhesive sheets of Examples 1 to 7 not only enable faster antenna transmission and reception without reducing antenna gain when applied to antennas using high frequency bands, but also do not affect the operation of touch sensors even when image display devices are made thinner.

[0101] On the other hand, the adhesive sheets of Comparative Examples 1 to 3, in which the weight ratio of heteroatoms in the diluted monomer exceeded 16.5%, exhibited a dielectric constant of 2.5 or more in the high frequency band of 15 GHz and a dielectric loss tangent exceeding 0.015, which may reduce antenna gain when applied to antennas using high frequency bands and may affect the operation of touch sensors when image display devices are made thinner.

[0102] Although specific aspects of the present invention have been described in detail above, it will be apparent to those skilled in the art that these specific descriptions are merely preferred embodiments and are not intended to limit the scope of the present invention. Those skilled in the art will be able to make various applications and modifications within the scope of the present invention based on the above content.

[0103] Therefore, the true scope of the invention is to be defined by the following claims and their equivalents.

Claims

1. A pressure-sensitive adhesive composition containing a urethane oligomer, a diluent monomer, and a photoinitiator, the urethane oligomer has one or more skeletons selected from the group consisting of polyethylene, polypropylene, polybutadiene, polyisoprene, hydrogenated polybutadiene, and hydrogenated polyisoprene, and has a radical polymerizable functional group at at least one end; The urethane oligomer is contained in an amount of 5 to 50 parts by weight based on 100 parts by weight of the diluent monomer, the diluting monomer contains a (meth)acrylic monomer having an aliphatic hydrocarbon group having 10 or more carbon atoms in an amount of 20 to 40% by weight based on 100% by weight of the total monomers; the weight ratio of heteroatoms in the diluent monomer is 12.2 to 16.0%, A pressure-sensitive adhesive composition in which a pressure-sensitive adhesive layer having a thickness of 150 μm after curing has a dielectric constant of less than 2.5 at 15 GHz and a dielectric loss tangent of 0.015 or less at 15 GHz.

2. The pressure-sensitive adhesive composition according to claim 1 , wherein the radically polymerizable functional group is a (meth)acryloyloxy group or a vinyl group.

3. The pressure-sensitive adhesive composition according to claim 1, wherein the photoinitiator is contained in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the diluent monomer.

4. A pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition according to any one of claims 1 to 3.

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