KR102229885B1 - Adhesive Composition and Adhesive Sheet Using the Same - Google Patents

Abstract

The present invention provides an adhesive composition which comprises a mixture of a urethane oligomer or a (meth)acrylic copolymer and a photopolymerizable monomer, a dilution monomer, and a photoinitiator, wherein a stress relaxation ratio at 70°C after first photocuring and a stress relaxation ratio at 70°C after second photocuring are adjusted within a specific range, and a dielectric constant and a dielectric loss tangent of an adhesive layer with a thickness of 150 μm at 15 GHz after the first photocuring are controlled within a specific range. Accordingly, the adhesive composition can provide excellent step filling properties and high adhesion while providing low dielectric properties suitable for application to an image display device requiring a high frequency band or a thin image display device.

Description

Adhesive Composition and Adhesive Sheet Using the Same

The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet using the same, and more specifically, a pressure-sensitive adhesive composition that requires a high frequency band or exhibits excellent step fillability and high adhesive strength while exhibiting low dielectric properties suitable for application to a thinned image display device, and It relates to an adhesive sheet using the same.

Among the adhesives, an optically clear adhesive (OCA) having high transparency is used for interlayer bonding for laminating components in image display devices. These optically transparent pressure-sensitive adhesives require high transmittance and low haze, and must satisfy physical properties such as adhesion to various substrates, heat resistance, and moisture resistance.

In recent years, as represented by the widespread use of transmission of moving pictures via optical fiber communication lines and wireless communication lines, the amount of information communication to be handled is rapidly increasing. Accordingly, a high frequency of the image display device is required, and the antenna is mounted in the image display device to transmit and receive signals in the high frequency band. In particular, in the case of an image display device applied to mobile communication, a high frequency band of 1 GHz or higher, for example, 1 to 30 GHz is required. For this reason, it is required to use an electrical insulating material with a low dielectric constant so as to enable faster transmission and reception of antennas without lowering the antenna gain value in response to the high frequency of the image display device.

Meanwhile. When a user touches an image displayed on the screen with a finger or a touch pen, the touch sensor responds to the touch to determine the touch point. Liquid crystal display (LCD), organic light-emitting diode (EL) It is manufactured in a structure that is mounted on a flat panel display device such as Emitting Diode, OLED). As the image display device has recently become thinner, the gap between the lower display panel and the upper touch sensor becomes narrower, and accordingly, an electrical insulating material with a low dielectric constant so that the touch sensor is not interfered by the lower display panel and does not affect the driving of the touch sensor. It is necessary to use.

Korean Patent Laid-Open Publication No. 10-2013-0106368 discloses a (meth)acrylic acid ester monomer having a hydrocarbon group having 1 to 12 carbon atoms, a hydroxyl group-containing (meth)acrylic acid ester monomer, an amide group-containing monomer, and a vinyl ester-based monomer. Acrylic polymer compound obtained by copolymerizing the contained monomer component, having a resin acid value of 0.1 mgKOH/g or less, a weight average molecular weight of 400,000 to 2 million, a Tg of -80 to 0°C, and a dielectric constant of 3 to 6 A pressure-sensitive adhesive composition comprising a crosslinking agent is disclosed. However, the pressure-sensitive adhesive composition has a problem in that it is difficult to secure a dielectric property sufficiently low to be applied to a thin image display device or using a high frequency band of 1 GHz or higher.

In addition, even when applied to various display devices, there is a need to develop a pressure-sensitive adhesive composition capable of securing level fillability and durability.

Republic of Korea Patent Publication No. 10-2013-0106368

One object of the present invention is to provide a pressure-sensitive adhesive composition that exhibits low dielectric properties even in a high frequency band and thus enables faster transmission and reception of antennas without lowering an antenna gain value.

Another object of the present invention is to provide a pressure-sensitive adhesive composition exhibiting low dielectric properties that does not affect driving of a touch sensor even when an image display device is thinned.

Another object of the present invention is to provide a pressure-sensitive adhesive composition exhibiting excellent step fillability and high adhesive strength.

Another object of the present invention is to provide a pressure-sensitive adhesive sheet formed by using the pressure-sensitive adhesive composition.

On the one hand, the present invention is a urethane oligomer, or a mixture of a (meth)acrylic copolymer and a photopolymerizable monomer; Dilute monomer; And as a pressure-sensitive adhesive composition containing a photoinitiator,

The stress relaxation ratio at 70°C after the first photocuring is 0.02 to 0.1, and the stress relaxation ratio at 70°C after the second photocuring is 0.2 or more,

A pressure-sensitive adhesive composition having a dielectric constant of less than 2.5 at 15 GHz of a 150 μm-thick pressure-sensitive adhesive layer after the first photocuring, and 0.015 or less of a dielectric loss tangent at 15 GHz of a 150 μm-thick pressure-sensitive adhesive layer after the first photo-curing is provided.

In one embodiment of the present invention, the urethane oligomer has at least one skeleton selected from the group consisting of polyethylene, polypropylene, polybutadiene, polyisoprene, hydrogenated polybutadiene, and hydrogenated polyisoprene, and a radically polymerizable functional group at at least one end. It may be to have.

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

In one embodiment of the present invention, the urethane oligomer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer may be contained in an amount of 10 to 50 parts by weight based on 100 parts by weight of the diluting monomer.

In one embodiment of the present invention, the weight ratio of heteroatoms in the diluted monomer may be 16.5% or less.

In one embodiment of the present invention, the diluting monomer may include at least one of a (meth)acrylic monomer and a vinyl monomer.

In one embodiment of the present invention, the photoinitiator may include a self-cleavage type photoinitiator and a hydrogen drawing type photoinitiator.

In one embodiment of the present invention, the hydrogen extraction type photoinitiator may be included in an amount of 1 to 5 parts by weight based on 1 part by weight of the self-cleaving photoinitiator.

On the other hand, the present invention provides a pressure-sensitive adhesive sheet formed by using the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive composition according to the present invention may require a high frequency band or exhibit a low dielectric property suitable for application to a thinned image display device, while exhibiting excellent step fillability and high adhesive strength.

Hereinafter, the present invention will be described in more detail.

One embodiment of the present invention is a urethane oligomer, or a mixture of a (meth)acrylic copolymer and a photopolymerizable monomer; Dilute monomer; And as a pressure-sensitive adhesive composition containing a photoinitiator,

The stress relaxation ratio at 70°C after the first photocuring is 0.02 to 0.1, and the stress relaxation ratio at 70°C after the second photocuring is 0.2 or more,

It relates to a pressure-sensitive adhesive composition having a dielectric constant of less than 2.5 at 15 GHz of a 150 μm-thick pressure-sensitive adhesive layer after the first photocuring, and 0.015 or less of a dielectric loss tangent at 15 GHz of a 150 μm-thick pressure-sensitive adhesive layer after the first photo-curing.

After the first photocuring, the stress relaxation ratio (S/R Ratio) at 70°C is 0.1 with a rheometer at 70°C after photocuring the pressure-sensitive adhesive composition with a light amount of 600 mJ/cm2 or less, for example, 500 mJ/cm2. After measuring the modulus of elasticity after seconds and the modulus of elasticity after 300 seconds, it can be obtained by Equation 1 below.

[Equation 1]

Stress relaxation ratio = modulus of elasticity after 300 seconds / modulus of elasticity after 0.1 seconds

In addition, the stress relaxation ratio at 70°C after the second photocuring is determined by using a rheometer at 70°C after photocuring the first photocured pressure-sensitive adhesive composition with a light amount of 2,000 mJ/cm2 or more, for example, 3,000 mJ/cm2. After measuring the modulus of elasticity after 0.1 second and the modulus of elasticity after 300 seconds, it can be obtained by Equation 1 above.

After the first photocuring of the pressure-sensitive adhesive composition, the stress relaxation ratio at 70° C. is 0.02 to 0.1 as described above. If the stress relaxation ratio at 70° C. after the first photocuring of the pressure-sensitive adhesive composition is less than 0.02, contamination of the pressure-sensitive adhesive may occur during bonding, and if it is greater than 0.1, the printing step may not be absorbed.

After the second photocuring of the pressure-sensitive adhesive composition, the stress relaxation ratio at 70° C. may be 0.2 or more, such as 0.2 or more and 0.6 or less, as described above. When the stress relaxation ratio at 70° C. after the second photocuring is less than 0.2, the reliability margin may be insufficient.

The dielectric constant is a physical unit indicating the effect of a medium between charges on an electric field when an electric field acts between charges, and can also be viewed as an amount of charge that a medium can store.

The dielectric constant of the 150 µm thick adhesive layer at 15 GHz after the first photocuring is a value measured at a frequency of 15 GHz for a sample in which the 150 µm thick adhesive layer is formed after the first photocuring according to the method described in Experimental Examples to be described later. .

The dielectric constant at 15 GHz of the 150 μm-thick pressure-sensitive adhesive layer after the first photocuring may be less than 2.5, for example, greater than 1 and less than 2.5, as described above. If the dielectric constant at 15GHz of the 150㎛-thick adhesive layer after the first photocuring is 2.5 or more, the antenna gain value can be lowered when applied to an antenna using a high frequency band such as 15GHz, and the image display device will be thinned. In this case, it may affect the driving of the touch sensor.

The dielectric tangent is a unit representing the ratio of power loss generated when an AC voltage is applied to the dielectric, and is generally expressed as a tangent delta.

The dielectric loss tangent at 15 GHz of the 150 μm-thick adhesive layer after the first photocuring is a value measured at a frequency of 15 GHz for a sample with a 150 μm-thick adhesive layer formed after the first photo-curing according to the method described in Experimental Examples to be described later. to be.

The dielectric loss tangent at 15 GHz of the 150 μm-thick pressure-sensitive adhesive layer after the first photocuring may be 0.015 or less, for example, greater than 0 and 0.015 or less, as described above. If the dielectric loss tangent at 15 GHz of the 150 μm thick adhesive layer after the first photocuring is greater than 0.015, the antenna gain value can be lowered when applied to an antenna using a high frequency band such as 15 GHz. It may affect the operation of the sensor.

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.

In order to control the weight ratio of the hetero atom, the urethane oligomer preferably has a long-chain aliphatic hydrocarbon skeleton as a main chain, and a radically polymerizable functional group is bonded to at least one end of the main chain through a urethane linking group. .

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 radically polymerizable functional group at at least one end. .

The radically polymerizable functional group may be a (meth)acryloyloxy group or a vinyl group, and in particular, may be a (meth)acryloyloxy group.

For example, the urethane oligomer may have a structure represented by the following formula (1).

[Formula 1]

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 C ₁ -C ₁₀ alkoxy group,

B ² is an acryloyloxy group or a methacryloyloxy group.

The C ₁ -C ₁₀ alkoxy group used herein refers to a straight-chain or branched alkoxy group consisting of 1 to 10 carbon atoms, and includes, but is limited to, methoxy, ethoxy, n-propanoxy, butoxy, etc. no.

Preferably, the urethane oligomer may have a structure represented by the following formula (2).

[Formula 2]

In the above formula,

A is polyethylene, polypropylene, polybutadiene, polyisoprene, hydrogenated polybutadiene or hydrogenated polyisoprene,

R ¹ is absent or is a C ₁ -C ₁₀ alkylene group,

R ² is a C ₁ -C ₁₀ alkylene group, a C ₃ -C ₁₀ cycloalkylene group or an arylene group,

R ³ is a C ₁ -C ₁₀ alkylene group or a C ₃ -C ₁₀ cycloalkylene group,

B ¹ is an acryloyloxy group, a methacryloyloxy group or a C ₁ -C ₁₀ alkoxy group,

B ² is an acryloyloxy group or a methacryloyloxy group.

_{The C 1} -C ₁₀ alkylene group used in the present specification means a straight-chain or branched hydrocarbon consisting of 1 to 10 carbon atoms, for example, methylene, ethylene, propylene, butylene, pentylene, hexylene, etc. Included, but is not limited thereto.

_{The C 3} -C ₁₀ cycloalkylene group used in the present specification means a simple or fused cyclic hydrocarbon consisting of 3 to 10 carbon atoms, for example, cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, etc. Included, but is not limited thereto.

The arylene group used in the present specification includes both an aromatic group and a heteroaromatic group, and partially reduced derivatives thereof. The aromatic group is a 5 to 15 membered simple or fused cyclic group, and the heteroaromatic group refers to an aromatic group containing at least one oxygen, sulfur, or nitrogen. Representative examples of arylene groups include tolylene, phenylene, naphthylene, and the like, but are not limited thereto.

The C ₃ -C ₁₀ cycloalkylene group and the arylene group may have one or more hydrogens substituted with a C ₁ -C ₆ alkyl group, a C ₁ -C ₆ alkoxy group and a halogen.

The urethane oligomer may be prepared by a method known in the art.

For example, the urethane oligomer may be prepared by reacting a hydroxy group-containing polyolefin with a diisocyanate compound and a hydroxy group-containing (meth)acrylate compound. In addition to the hydroxy group-containing (meth)acrylate compound, a C ₁ -C ₁₀ alcohol compound may be further used.

The hydroxy group-containing polyolefin may be obtained commercially or may be prepared and used by a method known in the art. For example, the hydroxy group-containing polyolefin may be prepared by reacting a polyolefin with an epoxy compound. Ethylene oxide, propylene oxide, etc. may be used as the epoxy compound. Examples of commercially available hydroxy group-containing polyolefins include Nippon Soda's GI-1000, GI-2000, and GI-3000.

As the diisocyanate compound, an aliphatic diisocyanate compound and/or an aromatic diisocyanate compound may be used.

Examples of the aliphatic diisocyanate compound include methyl diisocyanate, 1,2-ethanediyl diisocyanate, 1,3-propanediyl diisocyanate, 1,6-hexanediyl diisocyanate, and 3-methyl-octane-1,8-diyl diisocyanate. Isocyanate, 1,2-cyclopropanediyl diisocyanate, 1,3-cyclobutanediyl diisocyanate, 1,4-cyclohexanediyl diisocyanate, 1,3-cyclohexanediyl diisocyanate, isophorone diisocyanate, 4-methyl -Cyclohexane-1,3-diyl diisocyanate, etc. are mentioned.

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, and 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 di Isocyanate, 2-methyl-1,4-benzene diisocyanate, 3-methyl-1,4-benzene diisocyanate, 3-methoxy-1,2-benzene diisocyanate, 4-methoxy-1,2-benzene di Isocyanate, 5-methoxy-1,2-benzene diisocyanate, 2-methoxy-1,3-benzene diisocyanate, 4-methoxy-1,3-benzene diisocyanate, 5-methoxy-1,3- Benzene diisocyanate, 2-methoxy-1,4-benzene diisocyanate, 3-methoxy-1,4-benzene diisocyanate, 3,4-dimethyl-1,2-benzene diisocyanate, 4,5-dimethyl- 1,3-benzene diisocyanate, 2,3-dimethyl-1,4-benzene diisocyanate, 3-chloro-4-methyl-1,2-benzene diisocyanate, 3-methyl-4-chloro-1,2- Benzene diisocyanate, 3-methyl-5-chloro-1,2-benzene diisocyanate, 2-chloro-4-methyl-1,3-benzene diisocyanate, 4-chloro-5-methoxy-1,3-benzene Diisocyanate, 5-chloro-2-fluoro-1,3-benzene diisocyanate, 2-chloro-3-bromo-1,4-benzene diisocyanate, 3-chloro-5-isopropoxy-1,4 -Benzene diisocyanate, 2,3-diisocyanate pyridine, 2,4-diisocyanate pyridine, 2,5-diisocyanate pyridine, 2,6-diisocyanate pyridine, 2,5-di Isocyanate-3-methylpyridine, 2,5-diisocyanate-4-methylpyridine, 2,5-diisocyanate-6-methylpyridine, etc. are mentioned.

Examples of the hydroxy group-containing (meth)acrylate compound include hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxy-n-propyl (meth)acrylate, and 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, 4-hydroxycyclohexyl (meth)acrylate, and the like are exemplified.

Examples of the C ₁ -C ₁₀ alcohol compound include methanol, ethanol, n-propanol, and butanol.

In addition, the urethane oligomer may be commercially obtained and used. Examples of commercially available urethane oligomers include TEAI-1000 and TE-2000 manufactured by Nippon Soda.

The urethane oligomer may have a weight average molecular weight (in terms of polystyrene) measured by gel permeation chromatography (GPC) of 1000 to 200,000. When the weight average molecular weight of the urethane oligomer is out of the above range, it may be difficult to secure fairness.

In one embodiment of the present invention, the urethane oligomer may be contained in an amount of 10 to 50 parts by weight based on 100 parts by weight of the diluting monomer. When the urethane oligomer is included in an amount of less than 10 parts by weight, the viscosity may decrease, and when the urethane oligomer is included in an amount of more than 50 parts by weight, it may be difficult for the dielectric constant and/or the dielectric loss tangent to satisfy the above range.

In one embodiment of the present invention, the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer may be a partially polymerized product obtained by partially polymerizing a photopolymerizable monomer mixture for preparing a (meth)acrylic copolymer.

This partial polymerization product has a syrup shape (a viscous liquid phase) in which the (meth)acrylic copolymer formed from a part of the photopolymerizable monomer mixture and the unreacted photopolymerizable monomer are mixed. Accordingly, a partial polymer of such a property is sometimes referred to as a (meth)acrylic copolymer syrup.

The photopolymerizable monomer mixture for preparing the (meth)acrylic copolymer syrup is a high Tg monomer having a glass transition temperature (Tg) of 10°C to 100°C, a (meth)acrylic monomer having an alkyl group having 1-12 carbon atoms, and crosslinkable It may contain a monomer having a functional group. Here, (meth)acrylic means acrylic and methacrylic.

The high Tg monomer having a glass transition temperature (Tg) of 10°C to 100°C is a component that improves adhesion to various substrates by imparting elasticity to the acrylic copolymer, including t-butyl (meth)acrylate, methyl methacrylate , Ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, stearyl methacrylate, phenyl methacrylate, cyclohexyl methacrylate, isobornyl (meth)acrylate, Benzyl methacrylate, 3,3,5-trimethylcyclohexyl acrylate, cyclohexyl acrylate, N-octyl acrylamide, and the like may be used, and these may be used alone or in combination of two or more. The (meth)acrylate means acrylate and methacrylate.

The high Tg monomer is preferably contained in an amount of 30 to 50% by weight based on 100% by weight of the total monomer. If the content is less than 30% by weight, it may be difficult to secure durability, and if it is more than 50% by weight, it may be difficult to secure adhesion.

The (meth)acrylic monomer having an alkyl group having 1 to 12 carbon atoms is a monomer having a glass transition temperature (Tg) of less than -10°C, and specific examples include n-butyl acrylate, 2-ethylhexyl acrylate, ethyl acrylate, Methyl acrylate, n-propyl acrylate, isopropyl acrylate, pentyl acrylate, n-octyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, and the like, among which 2-ethylhexyl acrylic Rate, dodecyl acrylate, or mixtures thereof. These may be used alone or in combination of two or more.

The (meth)acrylic monomer containing an alkyl group having 1 to 12 carbon atoms is preferably contained in an amount of 40 to 60% by weight based on 100% by weight of the total monomer. If the content is less than 40% by weight, the adhesive strength may not be sufficient, and if the content is more than 60% by weight, the cohesion may be lowered.

The monomer having a crosslinkable functional group is a component for imparting durability and cutability by reinforcing the cohesive strength or adhesive strength of the pressure-sensitive adhesive composition by chemical bonding, and may be, for example, one or more of a monomer having a hydroxy group and a monomer having a carboxyl group. .

Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. , 6-hydroxyhexyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, 2-hydroxypropylene glycol (meth)acrylate, hydroxyalkylene glycol having 2-4 carbon atoms in the alkylene group (Meth)acrylate, 4-hydroxybutyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, 7-hydroxyheptyl vinyl ether, 8-hydroxyoctyl vinyl ether, 9-hydroxy Nonyl vinyl ether, 10-hydroxydecyl vinyl ether, etc. are mentioned, Among these, 4-hydroxybutyl acrylate, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl vinyl ether, etc. are preferable.

Examples of the monomer having a carboxyl group include monoacids such as (meth)acrylic acid, crotonic acid, and 2-carboxyethyl acrylate; Diacids such as maleic acid, itaconic acid and fumaric acid, and monoalkyl esters thereof; 3-(meth)acryloylpropionic acid; Succinic anhydride ring-opening adduct of 2-hydroxyalkyl (meth)acrylate having 2-3 carbon atoms in the alkyl group; Succinic anhydride ring-opening adduct of hydroxyalkylene glycol (meth)acrylate having 2-4 carbon atoms in the alkylene group; And compounds obtained by ring-opening addition of succinic anhydride to the caprolactone adduct of 2-hydroxyalkyl (meth)acrylate having 2-3 carbon atoms in the alkyl group, among which (meth)acrylic acid and 2-carboxyethyl acrylate And the like are preferred.

The monomer having a crosslinkable functional group is preferably contained in an amount of 1 to 40% by weight, preferably 1 to 10% by weight, based on 100% by weight of the total monomer. When the content of the monomer having a crosslinkable functional group is less than 1% by weight, the cohesive strength of the pressure-sensitive adhesive decreases, resulting in a decrease in durability, and when it exceeds 40% by weight, the adhesive strength may decrease due to a high gel fraction and the durability may decrease. have.

The photopolymerizable monomer mixture for preparing the (meth)acrylic copolymer syrup is a range that does not degrade physical properties such as adhesion, durability, and adhesion with other polymerizable monomers in addition to the monomers, for example, 10% by weight or less based on the total amount. It may contain more.

The method of partially polymerizing the monomer mixture is not particularly limited, and various polymerization methods can be appropriately selected and used. For example, a photopolymerization method can be used.

The weight ratio of the (meth)acrylic copolymer in the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer refers to the ratio in which the photopolymerizable monomer is converted to the (meth)acrylic copolymer due to partial polymerization, that is, the conversion rate. Corresponds to the solid content within.

The weight ratio of the (meth)acrylic copolymer in the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer may be appropriately adjusted to control the viscosity of the (meth)acrylic copolymer syrup. For example, the weight ratio of the (meth)acrylic copolymer in the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer may be included in an amount of 10 to 40% by weight. If the content is less than 10% by weight, the viscosity may be too low because there are many remaining photopolymerizable monomers, and if the content is more than 40% by weight, the viscosity may be too high, so that coating of the pressure-sensitive adhesive composition may not be easy.

In one embodiment of the present invention, the photopolymerizable monomer in the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer acts as a dispersion medium for the (meth)acrylic copolymer, and is a component that can be polymerized by the action of a photoinitiator. . The photopolymerizable monomer is polymerized during the first photocuring and substantially does not exist during the second photocuring.

In one embodiment of the present invention, the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer may be contained in an amount of 10 to 50 parts by weight based on 100 parts by weight of the diluting monomer. When the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer is included in an amount of less than 10 parts by weight, the viscosity may decrease, and when it is included in an amount of more than 50 parts by weight, the dielectric constant and/or the dielectric loss tangent satisfy the above range. It can be difficult.

In one embodiment of the present invention, the diluting monomer acts as a dispersion medium for the urethane oligomer or a mixture of a (meth)acrylic copolymer and a photopolymerizable monomer, and is a component that can be polymerized by the action of a photoinitiator. In addition, the diluting monomer may facilitate coating by diluting the pressure-sensitive adhesive composition and adjusting the viscosity. The diluting monomer is polymerized during the first photocuring and substantially does not exist during the second photocuring.

The weight ratio of heteroatoms in the diluted monomer may be 16.5% or less, for example, 0.5 to 16.5%.

The weight ratio of heteroatoms in the diluting monomer refers to a weight ratio of heteroatoms to the total atomic weight constituting the diluting monomer, and may be defined according to Equation 1 below.

[Equation 1]

Weight ratio of heteroatoms (%) =

That is, the weight ratio of heteroatoms in the diluting monomer is a value expressed as a percentage of a value obtained by multiplying the weight ratio of the heteroatoms contained in each monomer constituting the diluting monomer by the ratio of the corresponding monomer.

The heteroatom is an element other than carbon and means, for example, oxygen, sulfur or nitrogen.

If the weight ratio of heteroatoms in the diluting monomer is more than 16.5%, the dielectric constant of the 150 µm thick adhesive layer at 15 GHz after the first photocuring is 2.5 or more, or the 150 µm thick adhesive layer at 15 GHz after the first photocuring The dielectric loss tangent may be greater than 0.015. In addition, when the weight ratio of the hetero atom in the diluting monomer is more than 16.5%, the radio wave reception efficiency of the antenna may be lowered, and it may be difficult to thin the touch sensor.

The diluting monomer may include at least one of a (meth)acrylic monomer and a vinyl monomer.

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

The diluting monomer may be appropriately selected and used so that the weight ratio of the hetero atom is 16.5% or less.

For example, the diluting monomer is 20% by weight or more based on 100% by weight of the total monomer, at least one of a (meth)acrylic monomer having an aliphatic hydrocarbon group having 10 or more carbon atoms and a vinyl ether monomer having an aliphatic hydrocarbon group having 8 or more carbon atoms. For example, it may be included in an amount of 20 to 99% by weight, preferably 20 to 90% by weight. If the content of at least one of the (meth)acrylic monomer having an aliphatic hydrocarbon group having 10 or more carbon atoms and a vinyl ether monomer having an aliphatic hydrocarbon group having 8 or more carbon atoms is less than 20% by weight, it is difficult to control so that the weight ratio of heteroatoms is 16.5% or less. I can.

The aliphatic hydrocarbon group having 10 or more carbon atoms used herein refers to a linear or branched saturated or unsaturated hydrocarbon group consisting of 10 or more carbon atoms, for example 10 to 100, such as a C ₁₀ -C ₁₀₀ alkyl group, C ₁₀ alkenyl group -C _100, may alkynyl date of C ₁₀ -C _100. Specifically, the aliphatic hydrocarbon group having 10 or more carbon atoms includes, but is not limited to, decyl, isodecyl, undecyl, dodecyl, tridecyl, cetyl, stearyl, isostearyl, and the like.

The aliphatic hydrocarbon group having 8 or more carbon atoms used herein refers to a linear or branched saturated or unsaturated hydrocarbon group consisting of 8 or more carbon atoms, for example 8 to 100, such as a C ₈ -C ₁₀₀ alkyl group, C ₈ alkenyl group -C _100, may alkynyl date of C ₈ -C _100. Specifically, the aliphatic hydrocarbon group having 8 or more carbon atoms includes, but is not limited to, octyl, ethylhexyl, nonyl, decyl, isodecyl, undecyl, dodecyl, tridecyl, cetyl, stearyl, isostearyl, and the like.

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 radical polymerizable functional group.

Specifically, as the (meth)acrylic monomer having an aliphatic hydrocarbon group having 10 or more carbon atoms, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, Cetyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, and the like may be used, and these may be used alone or in combination of two or more.

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.

Specifically, as the vinyl ether monomer having an aliphatic hydrocarbon group having 8 or more carbon atoms, 2-ethylhexyl vinyl ether, dodecyl vinyl ether, and the like may be used, and these may be used alone or in combination of two or more.

The diluting monomer may further include a monomer having a crosslinkable functional group.

The monomer having a crosslinkable functional group may be at least one of a monomer having a hydroxy group and a monomer having a carboxyl group.

Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. , 6-hydroxyhexyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate, 2-hydroxypropylene glycol (meth)acrylate, hydroxyalkylene glycol having 2-4 carbon atoms in the alkylene group (Meth)acrylate, 4-hydroxybutyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, 7-hydroxyheptyl vinyl ether, 8-hydroxyoctyl vinyl ether, 9-hydroxy Nonyl vinyl ether, 10-hydroxydecyl vinyl ether, etc. are mentioned, Among these, 4-hydroxybutyl acrylate, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl vinyl ether, etc. are preferable.

Examples of the monomer having a carboxyl group include monoacids such as (meth)acrylic acid, crotonic acid, and 2-carboxyethyl acrylate; Diacids such as maleic acid, itaconic acid and fumaric acid, and monoalkyl esters thereof; 3-(meth)acryloylpropionic acid; Succinic anhydride ring-opening adduct of 2-hydroxyalkyl (meth)acrylate having 2-3 carbon atoms in the alkyl group; Succinic anhydride ring-opening adduct of hydroxyalkylene glycol (meth)acrylate having 2-4 carbon atoms in the alkylene group; And compounds obtained by ring-opening addition of succinic anhydride to the caprolactone adduct of 2-hydroxyalkyl (meth)acrylate having 2-3 carbon atoms in the alkyl group, among which (meth)acrylic acid and 2-carboxyethyl acrylate And the like are preferred.

The monomer having a crosslinkable functional group is preferably contained in an amount of 0.5 to 20% by weight, preferably 0.5 to 10% by weight, based on 100% by weight of the total monomer. When the content of the monomer having a crosslinkable functional group is less than 0.5% by weight, the cohesive strength of the pressure-sensitive adhesive may be reduced, thereby reducing durability, and when it is more than 20% by weight, the dielectric constant may be increased.

The diluting monomer may further include other polymerizable monomers in addition to the monomers.

Specific examples of the other polymerizable monomers are 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)acrylic Rate, nonyl (meth)acrylate, isobornyl (meth)acrylate, and the like, and among these, 2-ethylhexyl (meth)acrylate and isobornyl (meth)acrylate are preferred. These may be used alone or in combination of two or more.

The other polymerizable monomer may be included in an amount of 79.5% by weight or less, for example, 1 to 79.5% by weight, preferably 5 to 79.5% by weight, based on 100% by weight of the total monomer. When the content of the other polymerizable monomer is more than 79.5% by weight, it may be difficult to control so that the weight ratio of the hetero atom is 16.5% or less.

In one embodiment of the present invention, the photoinitiator refers to an initiator that absorbs active energy rays and generates radicals.

The photoinitiator may include a self-cleavage type photoinitiator and a hydrogen drawing type photoinitiator.

The self-cleaving photoinitiator is a photoinitiator capable of generating radicals by cleaving and decomposing its single bond, and is 600 mJ/cm2 or less, for example, about 100 to 500 mJ/cm2, preferably 200 to 500 mJ/cm2. It can be activated in low light conditions.

As the self-cleaving photoinitiator, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl (2,4,6-trimethylbenzoyl) phenyl phosphinate, bis(2,4,6-trimethylbenzoyl)phenylphosphine Pin oxide, 2-methyl-4'-(methylthio)-2-morpholinopropiophenone, 1-hydroxycyclohexylphenylketone, 2,2-dimethoxy-1,2-diphenylethane-1- One, 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylene Phenyl)-2-hydroxy-2-methylpropan-1-one, 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropan-1-one, 4-(2-hydroxyethoxy )-Phenyl (2-hydroxy-2-propyl) ketone, 2-methyl-1- (4- (methylthio) phenyl) -2-morpholinopropan-1-one, benzoin, benzoin methyl ether, Benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzyldimethylketal, α-acyloxime ester, acylphosphine oxide, methylphenylglyoxyrate, 4-(2-hydroxyethoxy)phenyl-( 2-hydroxy-2-propyl) ketone, 4-benzoyl-4'-methyldiphenylsulfide, and the like can be used, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide is particularly preferred.

The self-cleaving photoinitiator may be used in an amount of 0.1 to 1.0 parts by weight based on 100 parts by weight of the diluting monomer. When the self-cleaving photoinitiator is used within the above range, it may exhibit an appropriate degree of curing.

In one embodiment of the present invention, the hydrogen extraction type photoinitiator is a photoinitiator capable of forming an excitation complex between the photoexcited initiator and the hydrogen donor in the system and transferring hydrogen of the hydrogen donor, and is distinguished from the self-cleaving photoinitiator. . The hydrogen extraction type photoinitiator may be activated under conditions of high light intensity of 2,000 mJ/cm2 or more, for example, about 2,000 to 5,000 mJ/cm2, and preferably 3,000 to 4,000 mJ/cm2.

Even if the hydrogen drawing photoinitiator is excited once, the unreacted one of the initiators returns to the ground state, and thus can be used again as a reaction initiator. For this reason, compared with the self-cleaving type photoinitiator, the hydrogen extraction type photoinitiator tends to remain as an active species even after the reaction. Therefore, it is suitable for use as a reaction initiator when irradiating ultraviolet rays after bonding and crosslinking (secondary photocuring) again.

Examples of the hydrogen drawing photoinitiator include benzophenone, 2-ethyl anthraquinone, methylbenzoylporbate, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, 3,3'-dimethyl-4-methoxy Benzophenone, 2,4,6-trimethylbenzophenone, 4-methylbenzophenone, thioxanthone, 2-methyl thioxanthone, 2,4-dimethyl thioxanthone, isopropyl thioxanthone, campaquinone, 3, 3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, 9,10-phenanthrenequinone, etc. can be used.

The hydrogen extraction type photoinitiator may be used in an amount of 0.5 to 5.0 parts by weight based on 100 parts by weight of the total amount of the diluted monomer. If the hydrogen-pulling type photoinitiator is included in an amount of less than 0.5 parts by weight, the degree of secondary curing may be lowered, and if it is included in an amount of more than 5.0 parts by weight, durability may be deteriorated due to the residual photoinitiator.

The pressure-sensitive adhesive composition according to an embodiment of the present invention may include a hydrogen drawing-type photoinitiator in an amount of 1 to 5 parts by weight based on 1 part by weight of the self-cleaving photoinitiator. If the hydrogen-extracting photoinitiator is included in an amount of less than 1 part by weight based on 1 part by weight of the self-cleaving photoinitiator, the degree of secondary curing may be lowered, and when it is included in an amount exceeding 5 parts by weight, durability may be reduced by the residual photoinitiator.

In addition to the above components, the pressure-sensitive adhesive composition according to an embodiment of the present invention includes a silane coupling agent, a tackifier resin in order to control adhesive force, cohesive force, viscosity, elastic modulus, glass transition temperature, antistatic properties, etc. required according to the use. , Antioxidants, corrosion inhibitors, leveling agents, surface lubricants, dyes, pigments, antifoaming agents, fillers, light stabilizers, may further include additives such as antistatic agents.

The pressure-sensitive adhesive composition according to an embodiment of the present invention comprises a self-cleaving type photoinitiator and a hydrogen drawing type photoinitiator, and by including an excessive amount of a hydrogen drawing type photoinitiator compared to the self-cleaving type photoinitiator, the first photocuring condition is appropriately adjusted and the second Can leave room for photocuring reaction.

For example, after performing the first photocuring by activating the self-cleaving type photoinitiator mainly at a low light amount of 600 mJ/㎠ or less, the second photocuring is performed by activating the hydrogen drawing photoinitiator at a high light amount of 2,000 mJ/cm2 or more. You can do it.

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

The pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to the present invention on a base film, or a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to the present invention is interposed between two base films.

The base film may be a polyolefin-based film, a polyester-based film, an acrylic film, a styrene-based film, an amide-based film, a polyvinyl chloride film, a polyvinylidene chloride film, a polycarbonate film, and the like, and these are silicone-based, fluorine-based, and silica-based films. It may have been suitably molded out by powder or the like.

It is preferable that the thickness of the base film is 30 to 80 μm. If the thickness is less than 30 μm, the base film is vulnerable to poor imprinting, and if it exceeds 80 μm, handling properties may be deteriorated.

The pressure-sensitive adhesive layer can be formed by coating a pressure-sensitive adhesive composition on one base film. The coating method is not particularly limited as long as it is a method known in the art, and for example, a bar coater, air knife, gravure, reverse roll, kiss roll, spray, blade, die coater, casting, spin coating, or the like may be used. . Specifically, the pressure-sensitive adhesive composition may be applied on one base film to a predetermined thickness, or a pressure-sensitive adhesive composition is interposed between two base films and pressed to have a predetermined thickness, and then cured.

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 buffer an external impact, and if it exceeds 2,000 μm, transmission may decrease and optical performance may decrease.

The pressure-sensitive adhesive sheet according to an embodiment of the present invention may be a primary photo-cured material of 600 mJ/cm 2 or less, or a secondary photo-cured material of 2,000 mJ/cm 2 or less after a primary photo-curing of 600 mJ/cm 2 or less. .

Specifically, in the pressure-sensitive adhesive sheet according to an embodiment of the present invention, a pressure-sensitive adhesive composition is applied on one base film, and 600 mJ/cm 2 or less, for example, about 100 to 500 mJ/cm 2, preferably 200 to 500 It may be formed by first photocuring by irradiating light with an ultraviolet irradiation amount of mJ/cm2. In addition, the pressure-sensitive adhesive sheet according to an embodiment of the present invention is applied to a pressure-sensitive adhesive composition on one base film, and is 600 mJ/cm 2 or less, for example, about 100 to 500 mJ/cm 2, preferably 200 to 500 mJ. After light irradiation with an ultraviolet ray irradiation amount of /cm2 to perform primary photocuring, light irradiation with an ultraviolet ray irradiation amount of 2,000 mJ/cm2 or more, for example, about 2,000 to 5,000 mJ/cm2, preferably 3,000 to 4,000 mJ/cm2, was performed 2 It may be formed by secondary photocuring.

The secondary photocuring may be performed before or after being attached to the adherend.

The pressure-sensitive adhesive sheet according to an embodiment of the present invention exhibits a low stress relaxation ratio after the first photocuring, so that the filling property of the adherend with a step difference is excellent, and the step difference is to be restored after the second photocuring performed by increasing the amount of light. Durability can be improved by suppressing the force.

The pressure-sensitive adhesive sheet according to an embodiment of the present invention may improve adhesion by surface-treating the pressure-sensitive adhesive layer before bonding.

The surface treatment method is not particularly limited, and the surface of the pressure-sensitive adhesive layer may be activated by a method such as corona discharge treatment, plasma treatment, ultraviolet irradiation, electron beam irradiation, or application of an anchoring agent.

The pressure-sensitive adhesive sheet according to an embodiment of the present invention can be applied to a foldable display as well as a general flat panel display and a flexible display. In particular, the pressure-sensitive adhesive sheet according to an embodiment of the present invention can be effectively applied to interlayer adhesion in which components are stacked in a display device using a high frequency band or a thinner display device. Specifically, the adhesive sheet may be applied to bonding of various display materials such as an antenna, a display panel, a polarizer, a touch sensor, a cover window, a bezel, a polymer film, and an FPCB, and in particular, may be applied to bonding an antenna or a touch sensor.

The pressure-sensitive adhesive composition according to an embodiment of the present invention is first cured and in a state before the secondary curing, it is capable of leaving ultraviolet reactivity, that is, leaving a room for further curing, so that it is so flexible, and the surface of the adherend Even if there are irregularities or foreign substances or the like in the adhesive interface, it can sufficiently follow these irregularities, and the step filling property is excellent. Therefore, if the two display components are laminated through the pressure-sensitive adhesive sheet before the secondary curing, each display component can be suitably adhered to each other, and UV crosslinking (secondary curing) is performed by irradiating ultraviolet rays after making such contact. You can definitely bond. Therefore, the two display components are laminated through the pressure-sensitive adhesive sheet before secondary curing, and then ultraviolet rays are irradiated from the side of at least one of the display components, and the pressure-sensitive adhesive sheet is crosslinked with ultraviolet rays to secondary cure the pressure-sensitive adhesive sheet. Durability can be secured by making sure that it is crosslinked to have sufficient adhesive strength and cohesion.

Hereinafter, the present invention will be described in more detail by Examples, Comparative Examples and Experimental Examples. These Examples, Comparative Examples and Experimental Examples are for illustrative purposes only, and it is obvious to those skilled in the art that the scope of the present invention is not limited thereto.

Preparation Example 1: Preparation of urethane oligomer

2-hydroxyethyl acrylate 9 to an isocyanate polymer obtained by reacting 80 parts by weight of polybutadiene polyol (Poly bd, Idemitsu Kosan) with 500 ppm of dibutyl tin dilaurate catalyst (DBTDL) and 10 parts by weight of isophorone diisocyanate at 80°C By reacting parts by weight, a urethane oligomer having a weight average molecular weight of 110,000 was prepared.

Preparation Example 2: Preparation of urethane oligomer

Reaction of 9 parts by weight of 2-hydroxyethyl acrylate in an isocyanate polymer obtained by reacting 80 parts by weight of polyethylene (PPG2000, Hankseong) with 500 ppm of dibutyltindilaurate catalyst (DBTDL) and 10 parts by weight of isophorone diisocyanate at 80°C To prepare a urethane oligomer having a weight average molecular weight of 123,000.

Preparation Example 3: Preparation of acrylic copolymer syrup

2-ethylhexyl acrylate (2-EHA) 45% by weight, isobornyl acrylate (IBOA) 50% by weight, 2-hydroxyethyl in a 1L reactor equipped with a cooling device so that nitrogen gas is refluxed and temperature control is easy After adding a monomer mixture consisting of 5% by weight of acrylate (2-HEA), nitrogen gas was purged for 1 hour to remove oxygen, and then maintained at 80°C. After uniformly mixing the monomer mixture, 0.5 parts by weight of 1-hydroxycyclohexyl phenyl ketone was added as a photoinitiator based on 100 parts by weight of the monomer mixture. After stirring, a UV lamp (10mW) was irradiated to prepare an acrylic copolymer syrup having a conversion rate of 25% by weight.

Examples 1 to 7 and Comparative Examples 1 to 4: Preparation of pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet

The urethane oligomer, acrylic copolymer syrup, diluting monomer, and photoinitiator synthesized in Preparation Example were mixed in the composition shown in Table 1 below to prepare a pressure-sensitive adhesive composition (parts by weight).

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Oligomer/Syrup Manufacturing Example 1 20 20 20 20 40 20 20 Manufacturing Example 2 20 20 Manufacturing Example 3 20 60 Dilution
Monomer IBOA C ₁₃ H ₂₀ O ₂ 208.1 40 IBOMA C ₁₄ H ₂₂ O ₂ 222.1 30 30 30 30 30 30 30 30 30 2-EHA C ₁₁ H ₂₀ O ₂ 184.1 50 2-EHMA C ₁₂ H ₂₂ O ₂ 198.3 35 37 45 35 35 35 35 35 35 i-SA C ₂₁ H ₄₀ O ₂ 324.5 10 10 40 10 10 10 10 10 10 IDMA C ₁₄ H ₂₆ O ₂ 226.4 20 20 20 50 20 20 20 20 20 20 2-HEA C ₅ H ₈ O ₃ 116.0 10 2-HEMA C ₆ H ₁₀ O ₃ 130.1 5 10 5 5 5 5 5 5 AA C ₃ H ₄ O ₂ 72.0 3 2-CEA C ₆ H ₈ O ₄ 144.1 5 Heteroatom weight ratio (%) 15.6 15.4 16.1 14.7 15.6 15.6 15.6 19 15.6 15.6 15.6 Photoinitiator TPO 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Visiomer 6976 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 BP 2.0

IBOA: isobornyl acrylate

IBOMA: isobornyl methacrylate

2-EHA: 2-ethylhexylacrylate

2-EHMA: 2-ethylhexyl methacrylate

i-SA: isostearyl acrylate

IDMA: isodecyl methacrylate

2-HEA: 2-hydroxyethylacrylate

2-HEMA: 2-hydroxyethyl methacrylate

AA: acrylic acid

2-CEA: 2-carboxyethylacrylate

TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide

Visiomer 6976: (2-(4-benzoylphenoxy)ethyl methacrylate)

BP: Benzophenone

The pressure-sensitive adhesive compositions of Examples 1 to 7 and Comparative Examples 1 to 4 prepared above were coated on a release-treated polyethylene terephthalate film (thickness: 75 μm) as a release film using a bar coater. Thereafter, the pressure-sensitive adhesive sheet was prepared so that the thickness after curing of the pressure-sensitive adhesive composition was 150 μm after the pressure-sensitive adhesive composition was cured by first curing by irradiating ultraviolet rays at a light amount of 1.0 J/cm 2 for 5 minutes using a UV lamp.

Experimental Example 1:

The physical properties of the pressure-sensitive adhesive sheets prepared in Examples and Comparative Examples were measured by the following method, and the results are shown in Table 2 below.

(1) Permittivity and dielectric loss tangent

For the first photo-cured pressure-sensitive adhesive sheets prepared in Examples and Comparative Examples, dielectric constant and dielectric loss tangent were measured using a dielectric constant measuring device (Anritsu Corporation, product name MS46522B) at a temperature of 25° C. and a humidity of 50%.

More specifically, a 150 μm adhesive sheet from which the release film was removed was laminated between the upper and lower 40 μm COP films (Zeonor) and cut into a size of 30 mm in length × 70 mm in width. The cut adhesive sheet was put into a probe of a measuring device to measure the dielectric constant (Dk) and dielectric loss tangent (Df) values at 15 GHz.

(2) S/R Ratio

The stress relaxation ratio is the elastic modulus after 0.1 Sec and the elastic modulus after 300 Sec for each of the first photo-cured adhesive sheet prepared in Examples and Comparative Examples and the second photo-cured adhesive sheet obtained by secondary photo-curing the same under the following conditions. It was confirmed and determined by Equation 1 below. The second photocuring was performed by light irradiation (TL Lamp, UV) with an amount of light of 3,000 mJ/㎠.

[Equation 1]

S/R Ratio = modulus of elasticity after 300 seconds/modulus of elasticity after 0.1 seconds

Measuring instrument: Rheometer MCR-302, PP25 (25mmΦ)

Measurement conditions: Strain 25%, Axial force 1N, Frequency 15GHz

Thickness: 500㎛ (100㎛ 5 sheets overlap)

Temperature: 70℃ (Stabilization 10min)

(3) Step fillability

The release film on one side of the first photo-cured pressure-sensitive adhesive sheet was peeled off and bonded to a polyethylene terephthalate film (PET100) having a thickness of 100 μm to prepare a pressure-sensitive adhesive sheet to which PET100 was bonded to one side. This was cut into a length of 50 mm and a width of 40 mm to be used as a test piece. Separately, a polyethylene terephthalate film having a thickness of 25 µm, 50 µm, 60 µm, 75 µm, and 100 µm was cut to form a frame having a length of 40 mm, a width of 30 mm, and a width of 5 mm. The cut-out frame of each thickness was placed on the peeled PET100 with the release film on the remaining one side, and bonded to fit the other PET100 (PET100/adhesive sheet/PET film by thickness/PET100). This was subjected to autoclave treatment at 50° C./5 atm for 20 minutes, followed by UV curing (3,000 mJ/cm 2 based on UVA) to prepare a sample. Then, it was allowed to stand at a temperature of 80° C. for 24 hours, and the inner part of the PET film frame for each thickness was visually observed and evaluated according to the following evaluation criteria.

<Evaluation criteria>

○: No air bubbles or partial peeling

△: less than 5 bubbles or partial peeling

×: 5 or more bubbles or partial peeling

(4) Durability (heat resistance, moist heat resistance)

The first photo-cured pressure-sensitive adhesive sheet prepared in Examples and Comparative Examples was peeled off the release film on one side, corona-treated on the pressure-sensitive adhesive side, and bonded with a 40 μm cycloolefin (COP) film to obtain a 90 mm×170 After cutting to a size of mm and peeling the remaining release film, a sample was prepared by attaching it to a glass substrate (110 mm×190 mm×0.7 mm), followed by UV curing (3,000 mJ/cm 2 based on UVA). At this time, the applied pressure was 5 kg/㎠ and the clean room was performed to prevent bubbles or foreign matters from occurring.

Heat resistance is observed for occurrence of bubbles or peeling after leaving for 500 hours at a temperature of 80℃. Moisture and heat resistance is caused by bubbles or partial peeling after leaving for 500 hours under conditions of 60℃ and 93%RH. It was evaluated by the following evaluation criteria by observing whether or not.

<Evaluation criteria>

Ⓞ: No air bubbles or partial peeling

○: less than 5 bubbles or partial peeling

△: Bubbles or partial peeling 5 or more and less than 10

×: 10 or more bubbles or partial peeling

Example Comparative example One 2 3 4 5 6 7 One 2 3 4 permittivity 2.33 2.32 2.36 2.26 2.36 2.34 2.26 2.61 2.42 2.52 2.33 Genetic loss tangent 0.010 0.009 0.011 0.002 0.015 0.013 0.008 0.021 0.026 0.031 0.010 Stress relaxation rate After the first photocuring 0.03 0.04 0.05 0.05 0.06 0.08 0.03 0.07 0.06 0.02 0.07 After 2nd photocuring 0.35 0.39 0.38 0.35 0.36 0.40 0.33 0.36 0.16 0.29 0.07 Step fillability 25㎛ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ 50㎛ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ 60㎛ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ 75㎛ ○ ○ ○ ○ ○ ○ ○ ○ × ○ × 100㎛ ○ ○ ○ ○ ○ ○ ○ ○ × ○ × durability Heat resistant ○ ○ ○ Ⓞ ○ ○ ○ ○ ○ ○ × Moist heat resistance ○ ○ Ⓞ ○ ○ Ⓞ ○ ○ ○ ○ ×

As can be seen in Table 2, the adhesion of Examples 1 to 7 in which the stress relaxation ratio at 70°C after the first photocuring is 0.02 to 0.1, and the stress relaxation ratio at 70°C after the second photocuring is 0.2 or more. It was confirmed that the sheet had excellent step filling properties and durability. In addition, the pressure-sensitive adhesive sheets of Examples 1 to 7 in which the weight ratio of heteroatoms in the diluting monomer is 16.5% or less have a dielectric constant of less than 2.5 and a dielectric loss tangent of 0.015 or less even in a high frequency band of 15 GHz, indicating excellent low dielectric properties. there was. Accordingly, the pressure-sensitive adhesive sheets of Examples 1 to 7 do not lower the antenna gain value when applied to an antenna using a high frequency band, thereby enabling faster transmission and reception of antennas, and even if the image display device is thinned, touch It can be seen that it does not affect the driving of the sensor.

On the other hand, it was confirmed that the pressure-sensitive adhesive sheets of Comparative Examples 2 and 4 having a stress relaxation ratio of less than 0.2 at 70° C. after the second photocuring had poor step fillability and/or durability. In addition, the pressure-sensitive adhesive sheet of Comparative Example 1 in which the weight ratio of heteroatoms in the diluted monomer is more than 16.5%, and the pressure-sensitive adhesive sheet of Comparative Example 3 in which the urethane oligomer is contained in an amount of more than 50 parts by weight based on 100 parts by weight of the diluted monomer At 15GHz, the dielectric constant is more than 2.5 and the dielectric loss tangent is greater than 0.015, so when applied to an antenna that uses a high frequency band such as 15GHz, lowering the antenna gain value or thinning the image display device may affect the operation of the touch sensor. Appeared.

As described above, specific parts of the present invention have been described in detail, and it is obvious that these specific techniques are only preferred embodiments and are not intended to limit the scope of the present invention for those of ordinary skill in the art to which the present invention belongs. Do. Those of ordinary skill in the art to which the present invention belongs will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

Accordingly, it will be said that the substantial scope of the present invention is defined by the appended claims and their equivalents.

Claims (9)

Urethane oligomer, or a mixture of a (meth)acrylic copolymer and a photopolymerizable monomer; Dilute monomer; And as a pressure-sensitive adhesive composition containing a photoinitiator,
The weight ratio of heteroatoms in the diluted monomer is 14.7 to 16.1%,
The urethane oligomer, or a mixture of a (meth)acrylic copolymer and a photopolymerizable monomer is contained in an amount of 10 to 50 parts by weight based on 100 parts by weight of the diluting monomer,
After the first photocuring of the pressure-sensitive adhesive composition, the elastic modulus after 0.1 second and the elastic modulus after 300 seconds were measured with a rheometer at 70°C, and the stress relaxation ratio at 70°C after the first photocuring calculated by the following equation 1 0.02 to 0.1,
After secondary photocuring of the first photo-cured pressure-sensitive adhesive composition, the elastic modulus after 0.1 second and the elastic modulus after 300 seconds were measured with a rheometer at 70° C., and then at 70° C. after the second photo-curing calculated by Equation 1 below. The stress relaxation ratio of is 0.2 to 0.6,
A pressure-sensitive adhesive composition having a dielectric constant of more than 1 and less than 2.5 at 15 GHz of a 150 μm thick adhesive layer after the first photocuring, and a dielectric loss tangent of more than 0 and 0.015 or less at 15 GHz of the 150 μm thick adhesive layer after the first photo-curing:
[Equation 1]
Stress relaxation ratio = modulus of elasticity after 300 seconds/modulus of elasticity after 0.1 seconds. The method of claim 1, wherein the urethane oligomer has at least one skeleton selected from the group consisting of polyethylene, polypropylene, polybutadiene, polyisoprene, hydrogenated polybutadiene, and hydrogenated polyisoprene, and having a radically polymerizable functional group at at least one end. That the pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition according to claim 2, wherein the radically polymerizable functional group is a (meth)acryloyloxy group or a vinyl group. delete delete The pressure-sensitive adhesive composition of claim 1, wherein the diluting monomer comprises at least one of a (meth)acrylic monomer and a vinyl monomer. The pressure-sensitive adhesive composition of claim 1, wherein the photoinitiator comprises a self-cleavage type photoinitiator and a hydrogen drawing type photoinitiator. The pressure-sensitive adhesive composition according to claim 7, wherein the hydrogen extraction-type photoinitiator is included in an amount of 1 to 5 parts by weight based on 1 part by weight of the self-cleaving photoinitiator. A pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition according to any one of claims 1 to 3 and 6 to 8.