WO2022005138A1 - Adhesive composition and adhesive sheet using same - Google Patents

Abstract

The present invention provides an adhesive composition containing a (meth)acrylic copolymer or a mixture of a (meth)acrylic copolymer and a photopolymerizable monomer, wherein the weight ratio of heteroatoms in the (meth)acrylic copolymer or the mixture of a (meth)acrylic copolymer and a photopolymerizable monomer is controlled, and the dielectric constant and dielectric loss tangent at 15 GHz of a 150 µm-thick adhesive layer after curing are controlled within a specific range. The adhesive composition according to the present invention can exhibit low dielectric properties suitable for application to image display devices which require a high frequency band or are thinned.

Description

Adhesive composition and adhesive sheet using same

The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet using the same, and more particularly, to a pressure-sensitive adhesive composition exhibiting low dielectric properties suitable for application to a thin image display device requiring a high frequency band or a pressure-sensitive adhesive sheet using the same.

Among adhesives, an optically clear adhesive (OCA) having high transparency is used for interlayer adhesion for stacking components in an image display device. 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 heat-and-moisture resistance.

In recent years, as represented by the spread of video transmission via optical fiber communication lines and wireless communication lines, the amount of information communication handled is rapidly increasing. Accordingly, there is a demand for higher frequency of the image display apparatus, and the antenna is mounted in the image display apparatus to transmit and receive signals in a 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 more, for example, 1 to 30 GHz, is required. For this reason, in response to the increase in frequency of the image display device, it is required to use an electrical insulating material having a low dielectric constant so as to enable faster antenna transmission/reception without lowering the antenna gain value.

Meanwhile. A touch sensor is a device that detects a touch point in response to a user's contact with an image displayed on the screen with a finger or a touch pen, and is a liquid crystal display (LCD), organic light- It is manufactured in a structure that is mounted on a flat panel display device such as an emitting diode (OLED). Recently, as the image display device is thinned, the gap between the lower display panel and the upper touch sensor is narrowed. Accordingly, the low dielectric constant electrical insulating material is not interfered with by the lower display panel and thus does not affect the driving of the touch sensor. It is necessary to use

Korean Patent Laid-Open No. 10-2013-0106368 discloses a (meth)acrylic acid ester-based monomer having a hydrocarbon group having 1 to 12 carbon atoms, a (meth)acrylic acid ester-based monomer containing a hydroxyl group, a monomer containing an amide group, and a vinyl ester-based monomer. An acrylic polymer compound obtained by copolymerizing the monomer component containing 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 sufficiently low dielectric properties to use a high frequency band of 1 GHz or more or to be applied to a thinned image display device.

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

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

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

On the other hand, the present invention is a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer, or a mixture of a (meth) acrylic copolymer and a photopolymerizable monomer,

The weight ratio of heteroatoms in the (meth)acrylic copolymer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer is 16.5% or less,

After curing, the dielectric constant at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm is less than 2.5, and the dielectric loss tangent at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm after curing is 0.015 or less.

In one embodiment of the present invention, the (meth)acrylic copolymer, or a mixture of the (meth)acrylic copolymer and the photopolymerizable monomer is a (meth)acrylic monomer having an aliphatic hydrocarbon group having 10 or more carbon atoms and an aliphatic hydrocarbon having 8 or more carbon atoms. One or more of the vinyl ether monomers having a group may be included in an amount of 20 wt% or more based on 100 wt% of the total monomers.

In one embodiment of the present invention, the pressure-sensitive adhesive composition may contain a (meth)acrylic copolymer and a thermosetting agent.

In one embodiment of the present invention, the thermosetting agent may include an isocyanate-based crosslinking agent.

In one embodiment of the present invention, the thermosetting agent may be contained in an amount of 0.04 to 1 part by weight based on 100 parts by weight of the (meth)acrylic copolymer.

In one embodiment of the present invention, the pressure-sensitive adhesive composition may contain a mixture of a (meth)acrylic copolymer and a photopolymerizable monomer, and a photoinitiator.

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 total amount of the (meth)acrylic copolymer and the photopolymerizable monomer.

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

The pressure-sensitive adhesive composition according to the present invention adjusts the weight ratio of heteroatoms in the (meth)acrylic copolymer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer so that the dielectric constant at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm after curing and By controlling the dielectric loss tangent to a specific value range, it is possible to exhibit low dielectric properties suitable for application to a thin image display device or requiring a high frequency band. Accordingly, when applied to an antenna, the antenna gain value is not lowered, enabling faster antenna transmission/reception, and even if the image display device is thinned, driving of the touch sensor is not affected.

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

One embodiment of the present invention is a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer, or a mixture of a (meth)acrylic copolymer and a photopolymerizable monomer,

The weight ratio of heteroatoms in the (meth)acrylic copolymer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer is 16.5% or less,

After curing, the dielectric constant at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm is less than 2.5, and the dielectric loss tangent at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm after curing is 0.015 or less.

The weight ratio of heteroatoms in the (meth)acrylic copolymer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer constitutes the (meth)acrylic copolymer, or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer. refers to the weight ratio of heteroatoms to the total atomic weight, and may be defined according to Equation 1 below.

[Equation 1]

Weight ratio of heteroatoms (%) =

That is, the weight ratio of heteroatoms in the (meth)acrylic copolymer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer is the (meth)acrylic copolymer, or the (meth)acrylic copolymer and the photopolymerizable monomer. It is a value expressed as a percentage by adding the value obtained by multiplying the weight ratio of heteroatoms contained in each monomer constituting the mixture by the ratio of the corresponding monomer.

Here, (meth)acrylate means acrylate and/or methacrylate.

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

The weight ratio of heteroatoms in the (meth)acrylic copolymer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer is 16.5% or less, such as 0.5 to 16.5%, preferably 3 to 16.5%, as described above; More preferably 5 to 16.5%, more preferably 7 to 16.5%, still more preferably 10 to 16.5%, still more preferably 10 to 16.0%.

If the weight ratio of heteroatoms in the (meth)acrylic copolymer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer is more than 16.5%, the dielectric constant at 15GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm after curing is 2.5 or more, or , the dielectric loss tangent at 15 GHz of the 150 μm thick pressure-sensitive adhesive layer after curing may be greater than 0.015. In addition, if the weight ratio of heteroatoms in the (meth)acrylic copolymer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer is more than 16.5%, the radio wave reception efficiency of the antenna may be reduced and the touch sensor may be thinned It can be difficult.

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

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 according to the method described in Experimental Examples to be described later with respect to a sample having a pressure-sensitive adhesive layer having a thickness of 150 μm after curing.

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

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

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 according to the method described in Experimental Examples to be described later with respect to a sample having a pressure-sensitive adhesive layer having a thickness of 150 μm after curing.

After the curing, the dielectric loss tangent at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm may be 0.015 or less as described above, for example, more than 0 and 0.015 or less. If the dielectric loss tangent at 15 GHz of the 150 μm-thick adhesive layer after curing exceeds 0.015, the antenna gain value can be lowered when applied to an antenna using a high frequency band such as 15 GHz, and when the image display device is thinned, the touch sensor is driven may affect

The (meth)acrylic copolymer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer can be prepared by appropriately selecting the monomer so that the weight ratio of heteroatoms is 16.5% or less.

For example, the (meth)acrylic copolymer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer is a (meth)acrylic monomer having an aliphatic hydrocarbon group having 10 or more carbon atoms and a vinyl ether having an aliphatic hydrocarbon group having 8 or more carbon atoms. One or more of the monomers may be included in an amount of 20% by weight or more, for example 20 to 99% by weight, preferably 20 to 90% by weight based on 100% by weight of the total monomers. If the content of at least one of the (meth)acrylic monomer having an aliphatic hydrocarbon group having 10 or more carbon atoms and the 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 the weight ratio of heteroatoms to be 16.5% or less can

As used herein, the aliphatic hydrocarbon group having 10 or more carbon atoms is a straight or branched chain having 10 or more carbon atoms, for example, 10 to 100, preferably 10 to 50, more preferably 10 to 30. It means a saturated or unsaturated hydrocarbon, and, for example C ₁₀ -C ₁₀₀ alkyl group, C ₁₀ -C ₁₀₀ alkenyl groups, may be an alkynyl 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, heptacosanyl, and the like.

As used herein, the aliphatic hydrocarbon group having 8 or more carbon atoms is a straight or branched chain consisting of 8 or more carbon atoms, for example 8 to 100, preferably 8 to 50, more preferably 8 to 30. It means a saturated or unsaturated hydrocarbon group, and for example, it may be a C ₈ -C ₁₀₀ alkyl group, C ₈ -C ₁₀₀ alkenyl group, or C ₈ -C ₁₀₀ alkynyl group. Specifically, the aliphatic hydrocarbon group having 8 or more carbon atoms includes octyl, ethylhexyl, nonyl, decyl, isodecyl, undecyl, dodecyl, tridecyl, cetyl, stearyl, isostearyl, heptacosanyl, and the like. it is not

The (meth)acryl 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.

Specifically, as the (meth)acrylic monomer having an aliphatic hydrocarbon group having 10 or more carbon atoms, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, Tridecyl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, 1-heptacosanyl (meth) acrylate, etc. may be used, and these may be used alone. It can 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, etc. may be used, and these may be used alone or in combination of two or more.

The pressure-sensitive adhesive composition according to an embodiment of the present invention may be a thermosetting pressure-sensitive adhesive composition containing a (meth)acrylic copolymer and a thermosetting agent.

The (meth)acrylic copolymer is a component that serves to control the balance of viscosity versus elasticity of the pressure-sensitive adhesive composition, and may be a (meth)acrylic copolymer having a crosslinkable functional group in a molecule.

The (meth)acryl copolymer can be prepared by appropriately selecting a monomer so that the weight ratio of heteroatoms is 16.5% or less as described above, and for example, (meth)acryl having an aliphatic hydrocarbon group having 10 or more carbon atoms. It may be formed from a monomer mixture including at least one of a monomer and a vinyl ether monomer having an aliphatic hydrocarbon group having 8 or more carbon atoms, and a monomer having a crosslinkable functional group.

The monomer having a crosslinkable functional group may be at least one of a monomer having a hydroxyl group and a monomer having a carboxy group.

As the monomer having a hydroxyl group, 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 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; a ring-opening adduct of succinic anhydride of 2-hydroxyalkyl (meth)acrylate having an alkyl group having 2-3 carbon atoms; Ring-opening adduct of succinic anhydride of hydroxyalkylene glycol (meth)acrylate having 2-4 carbon atoms in the alkylene group; and a compound obtained by ring-opening addition of succinic anhydride to a caprolactone adduct of 2-hydroxyalkyl (meth)acrylate having an alkyl group having 2-3 carbon atoms. Among them, (meth)acrylic acid and 2-carboxyethyl acrylate etc. are preferable.

The monomer having the crosslinkable functional group is preferably included 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 used in the preparation of the (meth)acrylic copolymer. When the content of the monomer having a crosslinkable functional group is less than 0.5 wt%, the cohesive force of the pressure-sensitive adhesive may be reduced to decrease durability, and if it exceeds 20 wt%, the dielectric constant may be increased.

The (meth)acrylic copolymer may be formed from a monomer mixture further including other polymerizable monomers in addition to the above monomers.

Specific examples of the other polymerizable monomer 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) acrylic a rate, nonyl (meth)acrylate, isobornyl (meth)acrylate, etc. are mentioned, Among these, 2-ethylhexyl (meth)acrylate and isobornyl (meth)acrylate are preferable. These can be used individually or in mixture of 2 or more types.

The other polymerizable monomer is included 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 monomer used in the preparation of the (meth)acrylic copolymer. can When the content of the other polymerizable monomer is more than 79.5% by weight, it may be difficult to control the weight ratio of heteroatoms to be 16.5% or less.

The method for preparing the (meth)acrylic copolymer is not particularly limited, and it can be prepared using methods such as bulk polymerization, solution polymerization, emulsion polymerization or suspension polymerization commonly used in the art, and solution polymerization is preferable. . In addition, a solvent, polymerization initiator, chain transfer agent for molecular weight control, etc. commonly used during polymerization may be used.

The (meth)acrylic copolymer has a weight average molecular weight (in terms of polystyrene, Mw) measured by gel permeation chromatography (GPC) is usually 50,000 to 2 million, preferably 400,000 to 2 million . If the weight average molecular weight is less than 50,000, the cohesive force between the copolymers may be insufficient, which may cause problems in adhesion durability, and if the weight average molecular weight is more than 2 million, a large amount of diluent solvent may be required to secure fairness during coating.

The molecular weight distribution [weight average molecular weight (Mw)/number average molecular weight (Mn)] of the acrylic copolymer may be 7 or less. If the molecular weight distribution is more than 7, it may be difficult to secure durability due to the monomolecular oligomer.

In one embodiment of the present invention, the thermosetting agent is a component capable of improving adhesion and durability, and maintaining reliability and shape of the pressure-sensitive adhesive at high temperatures, and is also referred to as a crosslinking agent. Specifically, as the thermosetting agent, an isocyanate type, an epoxy type, a peroxide type, a metal chelate type, an oxazoline type, etc. may be used, and one type or a mixture of two or more types may be used. Among these, an isocyanate type is preferable.

Specifically, the thermosetting agent is tolylene diisocyanate, xylene diisocyanate, 2,4-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tetramethylxylene di diisocyanate compounds such as isocyanate and naphthalene diisocyanate; An adduct obtained by reacting 3 moles of a diisocyanate compound with 1 mole of a polyhydric alcohol compound such as trimethylolpropane, an isocyanurate product obtained by self-condensing 3 moles of a diisocyanate compound, and a diisocyanate obtained from 2 moles of 3 moles of a diisocyanate compound A polyfunctional isocyanate compound containing three functional groups, such as a biuret body in which the remaining 1 mole of diisocyanate is condensed with urea, triphenylmethane triisocyanate, and methylenebistriisocyanate, etc. can be used. These can be used individually or in mixture of 2 or more types.

The thermosetting agent may be included in an amount of 0.04 to 1 part by weight, for example, 0.1 to 1 part by weight based on 100 parts by weight of the (meth)acrylic copolymer. If the content of the thermosetting agent is less than 0.04 parts by weight, the cohesive force may be small due to insufficient crosslinking, which may impair the physical properties of adhesion durability and cutability. have.

The pressure-sensitive adhesive composition according to an embodiment of the present invention may be a photocurable pressure-sensitive adhesive composition containing a mixture of a (meth)acrylic copolymer and a photopolymerizable monomer, and a photoinitiator.

The mixture of the (meth)acrylic copolymer and the photopolymerizable monomer may be a partial polymer obtained by partially polymerizing the photopolymerizable monomer mixture for preparing the (meth)acrylic copolymer.

This partial polymer exhibits a syrupy shape (viscous liquid) in which a (meth)acrylic copolymer formed from a part of the photopolymerizable monomer mixture and an unreacted photopolymerizable monomer are mixed. Therefore, the partial polymer of such properties is sometimes referred to as (meth)acrylic copolymer syrup.

The monomer mixture may be the same as that for preparing the (meth)acrylic copolymer used in the above-described thermosetting pressure-sensitive adhesive composition.

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

The weight ratio of the (meth)acrylic copolymer in the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer means the ratio in which the photopolymerizable monomer is converted to the (meth)acrylic copolymer due to partial polymerization, that is, the conversion rate, and syrup It corresponds to my solids content.

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 it is more than 40% by weight, the viscosity may be too high, so that it may not be easy to apply the pressure-sensitive adhesive composition.

In one embodiment of the present invention, the photoinitiator means an initiator that absorbs an active energy ray to generate a radical.

The photoinitiators include, for example, 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 phenylketone , 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-methyl anthraquinone, 2-ethyl anthraquinone, 2-t -Butyl anthraquinone, 2-amino anthraquinone, 2-methyl thioxanthone, 2-ethyl thioxanthone, 2-chloro thioxanthone, 2,4-dimethyl thioxanthone, 2,4-diethyl thioxanthone (DETX), 4-isopropylthioxanthone (ITX), benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylamino benzoic acid ester, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2-( 3,4-methylenedioxyphenyl)-4,6-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. are mentioned. These can be used individually or in mixture of 2 or more types.

The photoinitiator may be included in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the total amount of the (meth)acrylic copolymer and the photopolymerizable monomer. When the content of the photoinitiator is less than 0.01 parts by weight, photocuring does not proceed sufficiently, so it is difficult to implement mechanical properties or adhesion of the finally obtained pressure-sensitive adhesive sheet. .

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

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

The pressure-sensitive adhesive sheet may be one in which the pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive composition according to the present invention on the base film, or the 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 include 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, silica It may be a mold release treatment suitably made with powder or the like.

The thickness of the base film is preferably 30 to 80㎛. When the thickness is less than 30 μm, the base film is vulnerable to engraving defects, and when it exceeds 80 μm, handling properties may be deteriorated.

An adhesive layer can be formed by the method of coating an 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 method such as a bar coater, air knife, gravure, reverse roll, kiss roll, spray, blade, die coater, casting, spin coating, etc. can be used. . Specifically, it may be formed by coating the pressure-sensitive adhesive composition on a single base film, drying it at 30 to 150° C. for 1 second to 2 hours, preferably 5 seconds to 1 hour, and heat curing.

Alternatively, the pressure-sensitive adhesive composition is applied on one base film and dried at 30 to 150° C. for 1 second to 2 hours, preferably 5 seconds to 1 hour, and then about 100 to 2000 mJ/cm 2 , preferably 200 It can be formed by photocuring by irradiating with an ultraviolet irradiation amount of 1500mJ/cm2. After drying, you may bond another base film on the said adhesive layer.

The pressure-sensitive adhesive layer may have a thickness of 10 to 2,000 μm, preferably 25 to 1,500 μm. If the thickness of the pressure-sensitive adhesive layer is less than 10㎛, it may be difficult to buffer an impact generated from the outside, and if it exceeds 2,000㎛, transmission may be lowered and optical performance may be deteriorated.

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

The surface treatment method is not particularly limited, and for example, 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 applying an anchoring agent.

The pressure-sensitive adhesive sheet according to an embodiment of the present invention is applicable to not only a general flat panel display and a flexible display but also a foldable display. In particular, the pressure-sensitive adhesive sheet according to an embodiment of the present invention can be effectively applied to interlayer adhesion using a high frequency band or laminating components in a thin 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 of an antenna or a touch sensor.

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

Preparation Example 1: Preparation of acrylic copolymer

10 wt% of 2-ethylhexyl acrylate (2-EHA), 40 wt% of isobornyl acrylate (IBOA), and isostearyl acrylate in a 1L reactor equipped with a cooling device for refluxing nitrogen gas and easy temperature control (i-SA) 40 wt% and 2-hydroxyethyl acrylate (2-HEA) 10 wt% of a monomer mixture was added, and then ethyl acetate (EAc) was added as a solvent to 100 parts by weight based on 100 parts by weight of the monomer mixture. It was added in an amount by weight. Then, nitrogen gas was purged for 1 hour to remove oxygen, and then maintained at 80°C. After the mixture was uniformly mixed, 0.1 parts by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator and reacted for 8 hours to prepare an acrylic copolymer (weight average molecular weight: 1.56 million, PDI 4.1).

Preparation Example 2-7: Preparation of acrylic copolymer

It was carried out in the same manner as in Preparation Example 1, but an acrylic copolymer was prepared with the composition shown in Table 1 below.

Comparative Preparation Example 1-3: Preparation of acrylic copolymer

It was carried out in the same manner as in Preparation Example 1, but an acrylic copolymer was prepared with the composition shown in Table 1 below.

monomer	IBOA	IBOMA	2-EHA	2-EHVE	i-SA	1-HCA	BA	2-HEA	4-HBA	AA	2-CEA	heteroatoms (%)	Molecular Weight (万)
molecular formula	C 13 H 20 O 2	C 14 H 22 O 2	C 11 H 20 O 2	C 10 H 20 O	C 21 H 40 O 2	C 30 H 58 O 2	C 7 H 12 O 2	C 5 H 8 O 3	C 7 H 12 O 3	C 3 H 4 O 2	C 6 H 8 O 4
Molecular Weight	208.15	222.16	184.15	156.15	324.54	450.79	128.08	116.05	144.04	72.02	144.12
Preparation Example 1	40.0%		10.0%		40.0%			10.0%				16.0%	156
Preparation 2		40.0%	37.0%		20.0%					3.0%		15.5%	142
Preparation 3		40.0%	37.0%		20.0%						3.0%	15.2%	123
Preparation 4	40.0%			36.0%	20.0%				4.0%			13.1%	134
Preparation 5				30.0%	60.0%				10.0%			12.3%	105
Preparation 6				9.0%	90.0%				1.0%			10.1%	73
Preparation 7	40.0%		10.0%			40.0%		10.0%				15.1%	132
Comparative Preparation Example 1	40.0%		50.0%					10.0%				19.0%	143
Comparative Preparation Example 2	30.0%						68.0%			2.0%		22.7%	152
Comparative Preparation Example 3							98.0%			2.0%		25.4%	138

IBOA: isobornyl acrylate

IBOMA: isobornyl methacrylate

2-EHA: 2-ethylhexyl acrylate

2-EHVE: 2-ethylhexyl vinyl ether

i-SA: isostearyl acrylate

1-HCA: 1-heptacosanyl acrylate

BA: butyl acrylate

2-HEA: 2-hydroxyethyl acrylate

4-HBA: 4-hydroxybutyl acrylate

AA: acrylic acid

2-CEA: 2-carboxyethyl acrylate

Preparation 8: Preparation of acrylic copolymer syrup

2-ethylhexyl acrylate (2-EHA) 10% by weight, isobornyl acrylate (IBOA) 40% by weight, isostearylacrylate (i-SA) 40% by weight and 2-hydroxyethyl acrylate (2- HEA) 100 parts by weight of a monomer mixture consisting of 10% by weight and 0.04 parts by weight of Igacure 184 (BASF) as a photoinitiator were mixed in a glass container to prepare a mixture. After replacing the dissolved oxygen with nitrogen gas, the mixture was partially polymerized by irradiating ultraviolet rays using a low pressure lamp (Sylvania BL Lamp) for several minutes to have a viscosity of about 15,000 cPs and a viscous liquid having a solid content of 42% by weight; That is, an acrylic copolymer syrup was obtained (weight ratio of heteroatoms: 15.8%).

Examples 1 to 8 and Comparative Examples 1 to 3: Preparation of pressure-sensitive adhesive composition and pressure-sensitive adhesive sheet

A pressure-sensitive adhesive composition was prepared by mixing the acrylic copolymer of Preparation Examples and Comparative Preparation Examples, the acrylic copolymer syrup of Preparation Examples, a thermal curing agent and a photoinitiator in the composition shown in Table 2 below.

		Example								comparative example
		One	2	3	4	5	6	7	8	One	2	3
Acrylic copolymer or syrup	Kinds	Preparation Example 1	Preparation Example 2	Preparation 3	Preparation 4	Production Example 5	Preparation 6	Preparation 7	Preparation 8	Comparative Preparation Example 1	Comparative Preparation Example 2	Comparative Preparation Example 3
	content (parts by weight)	100	100	100	100	100	100	100	100	100	100	100
thermosetting agent	Kinds	crosslinking agent A	crosslinking agent B	crosslinking agent B	crosslinking agent A	crosslinking agent A	crosslinking agent A	crosslinking agent A	-	crosslinking agent A	crosslinking agent B	crosslinking agent B
	content (parts by weight)	0.5	0.5	0.5	0.5	0.5	0.5	0.5	-	0.5	0.5	0.5
Photoinitiator (parts by weight)		-	-	-	-	-	-	-	0.5	-	-	-

Crosslinking agent A: Coronate-L, TDI (toluene diisocyanate) type, Nippon Urethane

Crosslinking agent B: Coronate-HXR, HDI (hexamethylene diisocyanate) type, Nippon Urethane

Photoinitiator: Igacure 184 (BASF)

The pressure-sensitive adhesive compositions of Examples 1 to 6 and Comparative Examples 1 to 3 prepared above were dried on a 50 μm-thick release film coated with a silicone release agent so that the thickness became 150 μm, and dried at 100° C. for 5 minutes. An adhesive layer was formed, and a release film was laminated thereon to prepare an adhesive sheet.

On the other hand, the pressure-sensitive adhesive composition of Example 7 prepared above is dried on a 50 µm-thick release film coated with a silicone release agent, then applied to a thickness of 150 µm, and dried at 110° C. for 5 minutes to form an adhesive layer, A release film was laminated thereon. A pressure-sensitive adhesive sheet was prepared by irradiating both sides of the release film with ultraviolet light at a light amount of 1.5 J/cm 2 using a low pressure lamp (Sylvania BL Lamp) for about 6 minutes.

Experimental Example 1:

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

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

The results are shown in Table 3 below.

	Example								comparative example
	One	2	3	4	5	6	7	8	One	2	3
permittivity	2.47	2.42	2.37	2.33	2.35	2.29	2.31	2.43	2.53	2.60	2.63
dielectric loss tangent	0.014	0.011	0.009	0.006	0.004	0.002	0.010	0.013	0.023	0.028	0.032

As can be seen in Table 3, the pressure-sensitive adhesive sheets of Examples 1 to 7 in which the weight ratio of heteroatoms in the (meth)acrylic copolymer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer is 16.5% or less Even in the high frequency band of 15 GHz, the dielectric constant was less than 2.5 and the dielectric loss tangent was 0.015 or less, indicating excellent low dielectric properties. Accordingly, the 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 antenna transmission/reception, and touch even when the image display device is thinned. It was found that there was no effect on the operation of the sensor.

On the other hand, the pressure-sensitive adhesive sheets of Comparative Examples 1 to 3 in which the weight ratio of heteroatoms in the (meth)acrylic copolymer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer exceeds 16.5% has a dielectric constant in the high frequency band of 15GHz It is 2.5 or more, and the dielectric loss tangent is more than 0.015, indicating that it will affect the operation of the touch sensor when the antenna gain value is lowered or the image display device is thinned when applied to an antenna using a high frequency band.

As the specific part of the present invention has been described in detail above, for those of ordinary skill in the art to which the present invention pertains, it is clear that these specific techniques are only preferred embodiments, and the scope of the present invention is not limited thereto. do. Those of ordinary skill in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above contents.

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

Claims (8)

1. A pressure-sensitive adhesive composition comprising a (meth)acrylic copolymer or a mixture of a (meth)acrylic copolymer and a photopolymerizable monomer,

   The weight ratio of heteroatoms in the (meth)acrylic copolymer or the mixture of the (meth)acrylic copolymer and the photopolymerizable monomer is 16.5% or less,

   After curing, the dielectric constant at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm is less than 2.5, and the dielectric loss tangent at 15 GHz of the pressure-sensitive adhesive layer having a thickness of 150 μm after curing is 0.015 or less.
2. According to claim 1, wherein the (meth) acryl copolymer, or a mixture of the (meth) acryl copolymer and the photopolymerizable monomer is a (meth) acryl monomer having an aliphatic hydrocarbon group having 10 or more carbon atoms and an aliphatic hydrocarbon group having 8 or more carbon atoms. A pressure-sensitive adhesive composition comprising at least one of the vinyl ether monomers in an amount of 20% by weight or more based on 100% by weight of the total monomers.
3. The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition contains a (meth)acrylic copolymer and a thermosetting agent.
4. The pressure-sensitive adhesive composition according to claim 3, wherein the thermosetting agent comprises an isocyanate-based crosslinking agent.
5. The pressure-sensitive adhesive composition according to claim 3, wherein the thermosetting agent is contained in an amount of 0.04 to 1 part by weight based on 100 parts by weight of the (meth)acrylic copolymer.
6. The pressure-sensitive adhesive composition of claim 1, wherein the pressure-sensitive adhesive composition contains a mixture of a (meth)acrylic copolymer and a photopolymerizable monomer, and a photoinitiator.
7. The pressure-sensitive adhesive composition according to claim 6, wherein the photoinitiator is contained in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the total amount of the (meth)acrylic copolymer and the photopolymerizable monomer.
8. A pressure-sensitive adhesive sheet formed using the pressure-sensitive adhesive composition according to any one of claims 1 to 7.