WO2023080599A1 - Adhesive composition, adhesive sheet manufactured therefrom, and image display device - Google Patents

Abstract

Embodiments of the present invention provide an adhesive composition. Provided is an adhesive composition comprising an acrylic copolymer comprising a repeating unit derived from a first acrylic monomer, wherein the first acrylic monomer contains a sulfur atom and the refractive index of a homopolymer is 1.53 or higher. Since an adhesive layer formed from the adhesive composition has a low glass transition temperature and a high refractive index, a separate high-refractive-index pattern layer cannot be included in an image display device.

Description

Pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet and image display device prepared therefrom

The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet prepared therefrom, and an image display device. More specifically, the present invention relates to a pressure-sensitive adhesive composition containing an acrylic copolymer, a pressure-sensitive adhesive sheet prepared therefrom, and an image display device.

For example, an adhesive or a pressure-sensitive adhesive sheet may be used to bond a display panel of an image display device such as a liquid crystal display (LCD) device or an organic light emitting display (OLED) device to various optical structures or circuit structures. The pressure-sensitive adhesive needs to have improved transparency and excellent adhesion so as not to degrade the optical properties of the image display device.

For example, the adhesive may be provided between the display panel and/or touch panel and the optical structure to adhere the two elements.

However, since a level difference occurs due to patterning of the sensing electrode included in the display panel or touch sensor layer, an encapsulation layer is required to be disposed on the display panel or touch sensor layer.

A silicon-nitrogen material having a refractive index of about 2.0 may be used as a material for the encapsulation layer. However, in this case, the refractive index of the encapsulation layer has a large refractive index difference from that of the pressure-sensitive adhesive for polarizer having a refractive index of about 1.47, so interfacial reflectance may increase and luminance may decrease.

To solve this problem, a process of separately coating a high refractive index layer between the encapsulation layer and the pressure-sensitive adhesive for polarizing plate is widely used. However, in this case, problems such as an increase in the thickness of the image display device and complicated process conditions may occur.

Accordingly, there is a need to develop a pressure-sensitive adhesive for polarizing plates having high refractive index properties so that a separate high refractive index layer is not required.

One object of the present invention is to provide an adhesive composition capable of forming an adhesive layer having improved high refractive index properties.

One object of the present invention is to provide a pressure-sensitive adhesive sheet having high flexural properties and an image display device including the same.

1. An acrylic copolymer comprising a repeating unit derived from the first acrylic monomer,

The first acrylic monomer contains a sulfur atom, and the refractive index of the homopolymer of the first acrylic monomer is 1.53 or more, the pressure-sensitive adhesive composition.

2. The pressure-sensitive adhesive composition according to 1 above, wherein the homopolymer of the first acrylic monomer has a glass transition temperature (Tg) of less than -20 °C.

3. The pressure-sensitive adhesive composition according to 1 above, wherein the first acrylic monomer comprises a compound represented by Formula 1 below:

[Formula 1]

(In Formula 1, R ₁ and R ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 14 carbon atoms, or a substituted or unsubstituted carbon atom having 1 to 10 carbon atoms. 10 heteroalkyl group, a substituted or unsubstituted heteroaryl group having 6 to 14 carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to 18 carbon atoms, or a substituted or unsubstituted heteroarylalkyl group having 7 to 18 carbon atoms,

R ₃ is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted heteroalkyl group having 1 to 10 carbon atoms).

4. The pressure-sensitive adhesive composition according to 1 above, wherein the first acrylic monomer includes at least one of the compounds represented by Formulas 2 to 5 below:

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

5. The pressure-sensitive adhesive composition according to 1 above, wherein the first acrylic monomer is included in an amount of 5 to 60 parts by weight based on 100 parts by weight of the acrylic copolymer.

6. The pressure-sensitive adhesive composition according to 1 above, wherein the acrylic copolymer is a copolymer of the first acrylic monomer, a second acrylic monomer different from the first acrylic monomer, and a crosslinkable monomer.

7. In the above 6, the second acrylic monomer is methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, s- butyl (meth) acrylate, t- butyl (meth) ) Acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl ( meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl(meth)acrylate, 6-(1-naphthyloxy)-1-hexylacrylate, pentafluorooctylacrylate, pentabromophenyl(meth)acrylate, 2-(naphthalene-2- yloxy)ethyl (meth)acrylate, 2-(naphthalen-2-ylthio)ethyl (meth)acrylate, 1-ethoxylated phenol (meth)acrylate, biphenylmethyl (meth)acrylate and 1 - A pressure-sensitive adhesive composition containing at least one of pyrenemethyl (meth)acrylate.

8. The pressure-sensitive adhesive composition according to 1 above, further comprising a photopolymerization initiator.

9. An adhesive sheet comprising an adhesive layer formed from the adhesive composition of 1 above.

10. The adhesive sheet according to 9 above, wherein the adhesive layer has a refractive index of 1.57 or more.

11. The adhesive sheet according to 9 above, wherein the adhesive layer has a haze value of less than 2%.

12. display panel; a touch sensor layer disposed on the display panel; a polarizing plate disposed on the touch sensor layer; and an adhesive layer formed between the touch sensor layer and the polarizing plate and formed of the aforementioned adhesive composition.

13. The method of 12 above, wherein the touch sensor layer includes a base layer and touch sensing electrodes arranged on the base layer, and the adhesive layer fills a space between the touch sensing electrodes and directly contacts the polarizing plate , image display device.

The pressure-sensitive adhesive composition according to embodiments of the present invention includes an acrylic copolymer including a repeating unit derived from a first acrylic monomer, wherein the first acrylic monomer contains a sulfur atom, and a homopolymer of the first acrylic monomer The refractive index of is 1.53 or more.

For example, while reducing the elastic modulus and the glass transition temperature (Tg) of the pressure-sensitive adhesive composition by using the first acrylic monomer, high refractive properties may be maintained or increased. In this case, a separate high refractive pattern layer for correcting a difference in refractive index between a sensing electrode and an optical member (eg, a polarizing plate) in an image display device may be unnecessary. Accordingly, the process is simplified, the process cost is reduced, and the thickness of the image display device can be reduced.

In some embodiments, the glass transition temperature (Tg) of the homopolymer of the first acrylic monomer may be less than -20 °C. Accordingly, it is possible to sufficiently maintain or improve the adhesive strength and elastic modulus of the pressure-sensitive adhesive composition while implementing the above-described high refractive index properties.

1 is a schematic cross-sectional view illustrating an adhesive sheet according to exemplary embodiments.

2 is a schematic cross-sectional view for explaining an image display device according to exemplary embodiments.

Embodiments of the present invention provide a pressure-sensitive adhesive composition including a repeating unit derived from a first acrylic monomer containing a sulfur atom and having a homopolymer refractive index of 1.53 or more.

In addition, a pressure-sensitive adhesive sheet and an image display device formed from the pressure-sensitive adhesive composition are provided.

Hereinafter, the present invention will be described in detail.

<Adhesive composition>

Pressure-sensitive adhesive compositions according to embodiments of the present invention include an acrylic copolymer. For example, excellent adhesive properties and durability can be implemented through the acrylic copolymer.

For example, the glass transition temperature and refractive index of the polymer according to Comparative Example may have a linear proportional relationship. In this case, when the high refractive index polymer is formed, the glass transition temperature may increase and the adhesive properties may be deteriorated. Accordingly, a high refractive index pattern layer may be disposed separately from the adhesive layer in order to mitigate the refractive index difference between the sensing electrode and the optical member of the image display device, which will be described later.

In exemplary embodiments of the present invention, the acrylic copolymer may include repeating units derived from the first acrylic monomer.

The first acrylic monomer may contain a sulfur atom and have a refractive index of 1.53 or more as a homopolymer. In this case, high refractive properties may be implemented while maintaining or improving the adhesive properties (e.g. elastic modulus) of the pressure-sensitive adhesive composition including the acrylic copolymer. Accordingly, in an image display device to be described later, a separate high refractive index pattern layer for correcting a difference in refractive index between the sensing electrode and an optical member (eg, a polarizing plate) may not be necessary. Accordingly, the process is simplified, the process cost is reduced, and the thickness of the image display device can be reduced.

For example, the sulfur atom may be included in the first acrylic monomer in the form of sulfide or oxide of sulfide.

In some embodiments, the glass transition temperature (Tg) of the homopolymer of the first acrylic monomer may be less than -20 °C. Accordingly, it is possible to sufficiently maintain or improve the adhesive strength and elastic modulus of the pressure-sensitive adhesive composition while implementing the above-described high refractive index properties.

In some embodiments, the first acrylic monomer may include a compound represented by Chemical Formula 1 below, but is not limited thereto.

[Formula 1]

In Formula 1, R ₁ and R ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 14 carbon atoms, or a substituted or unsubstituted carbon atom having 1 to 10 carbon atoms. A heteroalkyl group, a substituted or unsubstituted heteroaryl group having 6 to 14 carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to 18 carbon atoms, or a substituted or unsubstituted heteroarylalkyl group having 7 to 18 carbon atoms, and R ₃ is It may be a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted heteroalkyl group having 1 to 10 carbon atoms.

When the first acrylic monomer contains a sulfur atom as in Formula 1, for example, the elastic modulus and glass transition temperature of the pressure-sensitive adhesive composition may be sufficiently reduced. Accordingly, the adhesive properties and flexibility of the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition may be secured. In addition, the above-described elastic modulus and glass transition temperature may be reduced while maintaining or improving the refractive index of the pressure-sensitive adhesive composition.

According to one embodiment, the first acrylic monomer may include at least one of the compounds represented by Chemical Formulas 2 to 5 below.

[Formula 2]

[Formula 3]

[Formula 4]

[Formula 5]

In some embodiments, the first acrylic monomer may be included in an amount of 5 to 60 parts by weight based on 100 parts by weight of the acrylic copolymer. In this case, the mechanical stability and reliability of the acrylic copolymer can be adequately maintained while sufficiently lowering the elastic modulus of the pressure-sensitive adhesive composition.

In some embodiments, the acrylic copolymer may be a copolymer of a first acrylic monomer, a second acrylic monomer different from the first acrylic monomer, and a crosslinkable monomer.

In some embodiments, the second acrylic monomer may be a (meth)acrylate monomer, but is not limited thereto. As used herein, the term "(meth)acrylate" is used to encompass either acrylate or methacrylate.

In some embodiments, the second acrylic monomer is pentabromophenyl(meth)acrylate, 2-(naphthalen-2-yloxy)ethyl(meth)acrylate, 2-(naphthalen-2-ylthio) At least one of ethyl (meth)acrylate, 1-ethoxylated phenol (meth)acrylate, biphenylmethyl (meth)acrylate, and 1-pyrenemethyl (meth)acrylate may be included.

In some embodiments, the acrylic copolymer may further include a repeating unit derived from a second acrylic monomer having a hydrocarbon group having 1 to 20 carbon atoms.

The second acrylic monomer having a hydrocarbon group having 1 to 20 carbon atoms may be a (meth)acrylate monomer.

The hydrocarbon group may include, for example, an aliphatic hydrocarbon group and an aromatic hydrocarbon group. The hydrogen atom contained in the hydrocarbon group may be substituted with an alkyl group, a halogen atom, an alkoxy group, a phenoxy group, etc., and -CH ₂ - contained in the hydrocarbon group is an oxygen atom, a sulfur atom, a hetero atom such as a nitrogen atom, or -(CH ₂ CH ₂ O)m-. In this case, m may be 1 to 4.

In some embodiments, the second acrylic monomer having a hydrocarbon group having 1 to 20 carbon atoms is methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) Acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acryl rate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isobornyl acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate , n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentafluoro At least one selected from the group consisting of rooctyl acrylate, 2-ethylhexyldiglycol acrylate, nonylphenol (modified with 4 moles of ethylene oxide) acrylate, and 6-(1-naphthyloxy)-1-hexyl acrylate It may include, and in terms of availability, it is preferably 2-ethylhexyl (meth) acrylate.

In some embodiments, the second acrylic monomer may be included in 30 to 90 parts by weight based on 100 parts by weight of the total monomers used in preparing the acrylic copolymer. Accordingly, it is possible to prevent durability deterioration due to a decrease in cohesive force while ensuring sufficient adhesive strength and adhesion of the pressure-sensitive adhesive composition.

In some embodiments, the acrylic copolymer may be polymerized by further including a cross-linkable monomer copolymerizable with the first and second acrylic monomers.

For example, the crosslinkable monomer may be a carboxyl group-containing monomer, a phosphoric acid group-containing monomer, a sulfonic acid group-containing monomer, a cyano group-containing monomer, a vinyl ester, an aromatic vinyl compound, an acid anhydride group-containing monomer, a hydroxy group-containing monomer, an amide group-containing monomer, An amino group-containing monomer, an imide group-containing monomer, an epoxy group-containing monomer, or an ether group-containing monomer may be included. These may be used alone or in combination of two or more.

Examples of the carboxyl group-containing monomer include monoacids such as (meth)acrylic acid, crotonic acid, isocrotonic acid, carboxyethyl (meth)acrylate, and carboxypentyl (meth)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 to 3 carbon atoms in the alkyl group, and ring-opening succinic acid anhydride adduct of hydroxyalkylene glycol (meth)acrylate having 2 to 4 carbon atoms in the alkylene group , compounds obtained by ring-opening addition of succinic anhydride to a caprolactone adduct of 2-hydroxyalkyl (meth)acrylate having 2 to 3 carbon atoms in the alkyl group, and the like, preferably (meth)acrylic acid.

Examples of the phosphoric acid group-containing monomer include 2-hydroxyethyl acryloyl phosphate and the like.

Examples of the sulfonic acid group-containing monomer include styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acrylamido-2-methylpropanesulfonic acid, ) Acryloyloxynaphthalenesulfonic acid, sodium vinylsulfonate, etc. are mentioned.

Examples of the cyano group-containing monomer include (meth)acrylonitrile and the like.

Examples of the vinyl esters include vinyl acetate, vinyl propionate, and vinyl laurate.

Examples of the aromatic vinyl compound include styrene, chlorostyrene, chloromethylstyrene, α-methylstyrene, and other substituted styrene.

Examples of the acid anhydride-containing monomer include maleic anhydride, itaconic anhydride, and acid anhydrides thereof.

Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate. , 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methylacrylate, N- methylol (meth)acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether and the like.

Examples of the amino group-containing monomer include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, (meth)acryloylmorpholine, and the like. can be heard

Examples of the imide group-containing monomer include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.

Examples of the epoxy group-containing monomer include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether.

Examples of the ether group-containing monomer include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, phenoxyethyl (meth) acrylate and acrylonitrile. ilmorpholine etc. are mentioned.

The crosslinkable monomer may be included in 0.05 to 10 parts by weight, preferably 1 to 8 parts by weight, based on 100 parts by weight of the total monomers used in the preparation of the acrylic copolymer. In the above range, the adhesive strength and cohesion of the pressure-sensitive adhesive composition may be excellent, and the adhesion durability of the cured product may be improved.

In addition to the above monomers, other polymerizable monomers known in the art may be further included in an amount that does not reduce adhesiveness, for example, 10 parts by weight or less based on 100 parts by weight of the total monomers used in the preparation of the acrylic copolymer.

The method for producing the acrylic copolymer is not particularly limited, and may be prepared using methods such as bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, or UV polymerization commonly used in the art, preferably solution polymerization. method or UV polymerization method. In addition, solvents commonly used in polymerization, polymerization initiators, chain transfer agents for molecular weight control, and the like may be further used.

In some embodiments, the acrylic copolymer may have a weight average molecular weight (in terms of polystyrene, Mw) of 50,000 to 2,000,000 as measured by gel permeation chromatography (GPC). Preferably, the weight average molecular weight may be 700,000 to 1,700,000. When the weight average molecular weight of the (meth)acrylate copolymer is less than 50,000, cohesive strength between the copolymers may be insufficient and adhesion durability may be deteriorated. If it exceeds 2,000,000, a large amount of diluting solvent may be required to ensure fairness during coating.

In some embodiments, a photopolymerization initiator or a thermal curing agent may be used to polymerize the acrylic monomer and/or the crosslinkable monomer.

The photopolymerization initiator is, for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, 1-hydroxycyclohexyl -1-phenylmethanone, hydroxydimethylacetophenone, dimethylaminoacetophenone, dimethoxy-2-phenylacetophenone, 3-methylacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2- Diethoxy-2-phenylacetophenone, 4-chlorocetophenone, 4,4-dimethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 4-hydroxycyclophenylketone , 1-hydroxycyclohexylphenylketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, oligo[2-hydroxy-2-methyl-1 -(4-(1-methylvinyl)phenyl)propanone], 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, 4 ,4-diaminobenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, anthraquinone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminoanthraquinone Quinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethylketal, diphenylketonebenzyl Dimethylketal, acetophenonedimethylketal, p-dimethylaminobenzoic acid ester, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO), fluorene, triphenylamine, carbazole, azobisisobutyronitrile (AIBN ) and the like. These can be used individually or in combination of 2 or more types.

In some embodiments, the photopolymerization initiator may be included in an amount of 0.01 to 3 parts by weight, preferably 0.2 to 2 parts by weight, based on 100 parts by weight of the acrylic copolymer.

The thermal curing agent is not particularly limited as long as it is a component that can enhance the cohesive force of the pressure-sensitive adhesive composition by appropriately crosslinking the acrylic copolymer, but is preferably an isocyanate-based crosslinking agent.

The isocyanate-based crosslinking agent is, for example, tolylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, 2,4-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, isophorone diisocyanate, tetra addition-type trimers such as methylxylene diisocyanate, naphthalene diisocyanate, and 2,4-toluene diisocyanate addition-type trimer; and isocyanurate trimers.

The heat curing agent is preferably included in an amount of 0.1 to 1 part by weight based on 100 parts by weight of the acrylic copolymer, and more preferably, it may be included in an amount of 0.1 to 0.5 parts by weight.

In some embodiments, the pressure-sensitive adhesive composition may include a crosslinking agent, a tackifying resin, an antioxidant, an anticorrosive agent, and a leveling agent in order to adjust adhesive strength, cohesion, viscosity, elastic modulus, glass transition temperature, antistatic property, etc. required according to use. It may further contain additives such as an agent, a surface lubricant, an antifoaming agent, a filler, a light stabilizer, a reaction initiator, and a solvent.

<Adhesive sheet and image display device>

Hereinafter, an adhesive sheet and an image display device including an adhesive layer formed from the above-described adhesive composition will be described.

1 is a schematic cross-sectional view illustrating an adhesive sheet according to exemplary embodiments.

Referring to FIG. 1 , the adhesive sheet includes a base film 120 and an adhesive layer 110 formed on one surface of the base film 120 . For example, the adhesive layer 110 may be formed by coating the aforementioned adhesive composition on one surface of the base film 120 .

The base film 120 is not particularly limited, and a release film commonly used for adhesive sheets may be used. For example, the base film 120 may be a polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, or polybutyrene naphthalate; polyimide resin; acrylic 　resin; styrene-based resins such as polystyrene and acrylonitrile-styrene; polycarbonate 　 resin; polylactic acid 　resin; polyurethane 　 resin; polyolefins and resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; vinyl resins such as polyvinyl chloride and polyvinylidene chloride; polyamide = resin; sulfone-based resin; polyether-ether ketone-based resins; Allylate type resin; Alternatively, it may be a release film formed of a mixture of the above resins.

The adhesive layer 110 may be formed by applying the adhesive composition of exemplary embodiments on one surface of the base film 120 and performing a drying and/or curing process. For example, the adhesive layer 110 may be formed by applying the adhesive composition on the base film 120 by a coating method such as roll coating, gravure coating, reverse coating, spray coating, air knife coating, or die coater. .

In some embodiments, the base film 120 may be formed on the upper and lower surfaces of the adhesive layer 110 , respectively. For example, the base film 120 formed on the lower surface of the adhesive layer 110 may be removed and the exposed surface of the adhesive layer 110 may be attached to the object. Thereafter, a laminate (eg, an image display device) may be formed by removing the base film 120 formed on the upper surface and attaching another object to the exposed surface of the adhesive layer 110 .

In some embodiments, the refractive index of the adhesive layer 110 may be 1.57 or higher. In this case, a high refractive index can be secured while the adhesive layer 110 has a low glass transition temperature and a low elastic modulus. Accordingly, a separate high refractive index pattern layer may not be formed while mitigating the difference in refractive index between the sensing electrode and the optical member in the image display device.

In some embodiments, the haze value of the adhesive layer 110 included in the adhesive sheet may be less than 2%. In this case, the light transmittance is improved, and it can be provided particularly suitably as an optical pressure-sensitive adhesive for display devices and the like.

The term "haze value" used in this application refers to the haze value (0.2%) of the slide glass after bonding the adhesive layer 110 to the slide glass and measuring the haze value according to the JIS K-713 measurement standard at 25 ° C. It can mean minus value.

2 is a schematic cross-sectional view for explaining an image display device according to exemplary embodiments.

Referring to FIG. 2 , the image display device includes a display panel 130, a touch sensor layer 140 disposed on the display panel, a polarizer 150 disposed on the touch sensor layer 140, and the touch sensor layer ( 140) and the polarizing plate 150, and may include the adhesive layer 110 formed of the adhesive composition according to the above-described embodiments.

In this case, the adhesive layer 110 having a high refractive index and excellent adhesive properties may be disposed between the touch sensor layer 140 and the polarizer 150 to mitigate a difference in refractive index between the two layers. Accordingly, the difference in refractive index can be alleviated only with the adhesive layer 110 without forming a separate refractive index mitigating layer. Accordingly, the thickness of the image display device can be reduced, the process can be simplified, and the process cost can be reduced.

The display panel 130 may be, for example, a liquid crystal display panel (LCD) or an organic light emitting display panel (OLED).

The polarizing plate 150 may include, for example, a polarizer and a protective film bonded to at least one surface of the polarizer. For example, the adhesive layer may be formed by bonding an adhesive sheet to a protective film, or may be directly coated on a protective film.

The protective film included in the polarizing plate 150 is not particularly limited as long as it has excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, and the like. Specifically, polyester-based films such as polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate as the protective film; cellulosic films such as diacetyl cellulose and triacetyl cellulose; polycarbonate-based film; acrylic films such as polymethyl (meth)acrylate and polyethyl (meth)acrylate; styrenic films such as polystyrene and acrylonitrile-styrene copolymer; polyolefin-based film; Vinyl chloride-based film; polyamide-based films such as nylon and aromatic polyamide; Imide-based film; sulfone-based film; polyether ketone-based film; Sulfurized polyphenylene-based film; vinyl alcohol-based film; Vinylidene chloride-based film; vinyl butyral-based film; allylate-based films; polyoxymethylene-based film; Urethane-based film; Epoxy-based film; A silicone type film etc. are mentioned.

The polarizer may be a polarizer known in the art, and may be, for example, one manufactured by swelling, dyeing, crosslinking, stretching, washing with water, and drying a polyvinyl alcohol-based film.

In some embodiments, the touch sensor layer 140 includes a base layer 142 and touch sensing electrodes 144 arranged on the base layer 142, and the adhesive layer 110 includes the touch sensing electrodes 144 ) and may directly contact the polarizer 150. In this case, the adhesion between the touch sensor layer 140 and the polarizer 150 may be improved by removing the step due to the patterning of the touch sensing electrodes 144 . Accordingly, mechanical stability of the image display device can be improved.

For example, the image display device may further include other components known in the art in addition to the above configurations. For example, a retardation film, a hard coating film, a protective film, a window film, a touch panel, and the like may be further included.

As shown in FIG. 2 , the image display device may further include, for example, a cover window 170 on the polarizer 150 . The polarizer 150 and the cover window 170 may be bonded through the upper adhesive layer 160 .

The cover window 170 may be used without limitation as long as it is employed in the art to protect the internal components of an image display device, and may be, for example, glass.

For example, the display panel 130, the touch sensor layer 140, and optical members may be laminated using the adhesive layer 110 formed from the above-described adhesive composition. In this case, since the adhesive layer 110 itself alleviates the difference in refractive index between the display panel 130 and the optical member (for example, the polarizing plate 150), it is unnecessary to form a separate high refractive index pattern layer in the image display device. can Accordingly, while the luminance of the image display device is improved, the thickness may be reduced and fairness may be improved.

Hereinafter, experimental examples including specific examples and comparative examples are presented to aid understanding of the present invention, but these are only illustrative of the present invention and do not limit the scope of the appended claims, and the scope and technology of the present invention It is obvious to those skilled in the art that various changes and modifications to the embodiments are possible within the scope of the spirit, and it is natural that these changes and modifications fall within the scope of the appended claims.

Example 1

50 parts by weight of the compound represented by Formula 2 of the present application as the first acrylic monomer, 45 parts by weight of biphenylmethyl acrylate (M1192, Miwon Special Chemical Co.) as the second acrylic monomer, and 4-hydroxybutyl as a crosslinkable monomer An acrylic copolymer was prepared by adding 5 parts by weight of acrylate.

An adhesive composition was prepared by adding 0.5 parts by weight of (1-hydroxycyclohexyl) phenyl ketone (Irgacure®-184) as an initiator to the prepared acrylic copolymer.

The pressure-sensitive adhesive composition was coated on a polyethylene terephthalate (PET) film having a thickness of 75 μm and treated with a coating liquid release using a bar coater. Thereafter, by curing by irradiating ultraviolet rays using a UV lamp for 10 minutes, a pressure-sensitive adhesive sheet having an adhesive layer having a thickness of 25 μm was prepared.

Examples 2 to 4, 6 and 7

A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 1, except that the pressure-sensitive adhesive composition was prepared with the components and contents shown in Table 1 below.

Example 5

50 parts by weight of the compound represented by Formula 4 of the present application, 20 parts by weight of 2-ethylhexyl acrylate, biphenylmethyl acrylate (M1192, After introducing a monomer mixture consisting of 25 parts by weight and 5 parts by weight of 4-hydroxybutyl acrylate, 300 parts by weight of methyl ethyl ketone was added as a solvent. Thereafter, nitrogen gas was introduced for 1 hour to remove oxygen, followed by substitution, and the temperature was maintained at 70°C. After uniformly stirring the monomer mixture, 0.07 parts by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator and reacted for 8 hours to prepare an acrylic copolymer having a weight average molecular weight of 1,530,000.

An adhesive composition was prepared by adding 0.5 parts by weight of an isocyanate-based crosslinking agent (AK75, Aekyung Chemical Co.) to the prepared acrylic copolymer.

The pressure-sensitive adhesive composition was coated on a polyethylene terephthalate (PET) film having a thickness of 75 μm and treated with a coating liquid release using a bar coater. Thereafter, after drying at 100 ° C. for 2 minutes, curing at room temperature for 7 days to prepare a pressure-sensitive adhesive sheet having an adhesive layer thickness of 25 μm.

Comparative Examples 1 to 3

A pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet were prepared in the same manner as in Example 1, except that the pressure-sensitive adhesive composition was prepared with the components and contents shown in Table 1 below.

division			Example							comparative example
			One	2	3	4	5	6	7	One	2	3
acrylic copolymer	First acrylic monomer	A1	50					4	65
		A2		50
		A3			50		50
		A4				50
	Second acrylic monomer	B1					20	91	30	90	90	60
		B2	45	45	45	45	25					30
	crosslinkable monomer	C1	5	5	5	5	5	5	5	10	10	10
photopolymerization initiator		D1	0.5	0.5	0.5	0.5		0.5	0.5	0.5	0.5	0.5
heat curing agent		E1					0.5
A1: Compound represented by Formula 2 (homopolymer refractive index: 1.531, Tg: -59 ° C) A2: Compound represented by Formula 3 (homopolymer refractive index: 1.577, Tg: -26 ° C) A3: Compound represented by Formula 4 (homopolymer refractive index: 1.577, Tg: -26 ° C) A4: Compound represented by Formula 5 (homopolymer refractive index: 1.572, Tg: -50 ° C) B1: 2-ethylhexyl acrylate (homopolymer refractive index: 1.466, Tg: -74 ° C) (BASF) B2: biphenylmethyl acrylate (homopolymer refractive index: 1.637, Tg: 23 ° C. (M1192, Miwon Specialty Chemical Co.) C1: 4-hydroxybutyl acrylate D1: (1-hydroxycyclohexyl) phenyl ketone (Irgacure®-184) E1: Isocyanate-based crosslinking agent (AK75) (Aekyung Chemical Co.)

Experimental example

(1) Transparency evaluation

In the adhesive sheets according to the above-described Examples and Comparative Examples, the adhesive layer was peeled from the PET film and bonded to slide glass (manufactured by Matsunami Glass Kogyo, model number: S1111).

The haze value (%) was measured at 25°C using a "reflection/transmittance meter HR-100 type" manufactured by Murakami Shikijutsu Genkyusho Co., Ltd. in accordance with the JIS K-713 measurement standard.

A value obtained by subtracting the haze value (0.2%) of the slide glass from the measured value was evaluated as the haze value of the adhesive layer. The evaluation results are shown in Table 2 below.

○: Haze value is less than 2%

Χ: Haze value is 2% or more

(2) refractive index measurement

Regarding the adhesive layer according to the above-described Examples and Comparative Examples, sodium D-ray was irradiated in an atmosphere at 25 ° C., and the refractive index was measured with an Abbe refractometer (manufactured by ATAGO, DMM4). The measurement results are shown in Table 2 below.

(3) Evaluation of step absorbency

The pressure-sensitive adhesive sheets according to the above-described Examples and Comparative Examples were bonded to glass having a printing step of 3 μm. At this time, the size of the glass on the inside is 5 cmХ10 cmХ0.7 cm.

Then, it was left at 85 ° C., 40 ° C., and room temperature (23 ° C.) for 24 hours, respectively, and the lifting state of the surface to which the adhesive layer was bonded was visually observed and evaluated. The evaluation results are shown in Table 3 below.

◎: No excitation at 85 ° C.

○: No lifting at 40°C.

△: No lifting at room temperature.

Χ: There is excitation at room temperature.

division	Example							comparative example
	One	2	3	4	5	6	7	One	2	3
transparency	○	○	○	○	○	○	○	○	○	Χ
refractive index	1.58	1.57	1.61	1.61	1.57	1.55	1.62	1.52	1.54	1.58
step absorption	◎	◎	○	◎	◎	◎	△	△	△	Χ

Referring to Table 2 above, the adhesive layers and adhesive sheets of Examples prepared with the adhesive composition comprising an acrylic copolymer containing a sulfur atom and a repeating unit derived from an acrylic monomer having a homopolymer refractive index of 1.53 or more have excellent Transparency, refractive index, and step absorption were realized.

Accordingly, it is possible to implement a pressure-sensitive adhesive composition, an adhesive layer, and a pressure-sensitive adhesive sheet having both excellent adhesive properties and high refractive properties.

However, the adhesive layer and the adhesive sheet according to Comparative Examples had at least one of refractive index, transparency, and step absorptivity significantly deteriorated, and thus could not function as a refractive index mitigating layer between the sensing electrode and the optical member.

Claims (13)

1. An acrylic copolymer comprising a repeating unit derived from a first acrylic monomer,

   The first acrylic monomer contains a sulfur atom, and the refractive index of the homopolymer of the first acrylic monomer is 1.53 or more, the pressure-sensitive adhesive composition.
2. The pressure-sensitive adhesive composition according to claim 1, wherein the homopolymer of the first acrylic monomer has a glass transition temperature (Tg) of less than -20 °C.
3. The pressure-sensitive adhesive composition of claim 1, wherein the first acrylic monomer comprises a compound represented by Formula 1 below:

   [Formula 1]

   

   (In Formula 1, R ₁ and R ₂ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 14 carbon atoms, or a substituted or unsubstituted carbon atom having 1 to 10 carbon atoms. 10 heteroalkyl group, a substituted or unsubstituted heteroaryl group having 6 to 14 carbon atoms, a substituted or unsubstituted arylalkyl group having 7 to 18 carbon atoms, or a substituted or unsubstituted heteroarylalkyl group having 7 to 18 carbon atoms,

   R ₃ is a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted heteroalkyl group having 1 to 10 carbon atoms).
4. The pressure-sensitive adhesive composition of claim 1, wherein the first acrylic monomer includes at least one of compounds represented by Formulas 2 to 5 below:

   [Formula 2]

   

   [Formula 3]

   

   [Formula 4]

   

   [Formula 5]

   

   .
5. The pressure-sensitive adhesive composition of claim 1, wherein the first acrylic monomer is included in an amount of 5 to 60 parts by weight based on 100 parts by weight of the acrylic copolymer.
6. The pressure-sensitive adhesive composition of claim 1, wherein the acrylic copolymer is a copolymer of the first acrylic monomer, a second acrylic monomer different from the first acrylic monomer, and a crosslinkable monomer.
7. The method according to claim 6, wherein the second acrylic monomer is methyl (meth) acrylate, ethyl (meth) acrylate, n- butyl (meth) acrylate, s- butyl (meth) acrylate, t- butyl (meth) acrylate Rate, isobutyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate Acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n- Tetradecyl(meth)acrylate, 6-(1-naphthyloxy)-1-hexylacrylate, pentafluorooctylacrylate, pentabromophenyl(meth)acrylate, 2-(naphthalen-2-yloxy) ) ethyl (meth) acrylate, 2- (naphthalen-2-ylthio) ethyl (meth) acrylate, 1-ethoxylated phenol (meth) acrylate, biphenylmethyl (meth) acrylate and 1-pi A pressure-sensitive adhesive composition comprising at least one of renemethyl (meth)acrylate.
8. The pressure-sensitive adhesive composition according to claim 1, further comprising a photopolymerization initiator.
9. An adhesive sheet comprising an adhesive layer formed from the adhesive composition of claim 1.
10. The adhesive sheet according to claim 9, wherein the adhesive layer has a refractive index of 1.57 or more.
11. The adhesive sheet according to claim 9, wherein the adhesive layer has a haze value of less than 2%.
12. display panel;

    a touch sensor layer disposed on the display panel;

    a polarizing plate disposed on the touch sensor layer; and

    An image display device comprising an adhesive layer formed between the touch sensor layer and the polarizing plate and formed of the adhesive composition of claim 1.
13. The method according to claim 12, wherein the touch sensor layer comprises a base layer, and touch sensing electrodes arranged on the base layer,

    The adhesive layer fills the space between the touch sensing electrodes and directly contacts the polarizing plate, the image display device.

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