KR20160107646A - Adhesive Composition and Polarizing Plate Comprising the Same - Google Patents

Abstract

Provided are an adhesive composition, a polarizing plate comprising the same, and a liquid crystal display device. The adhesive composition comprises an acrylic copolymer, an isocyanate-based crosslinker, (meth)acrylate, and a thermal initiator. The adhesive composition of has excellent electrostatic properties, and excellent durability and reworkability.

Description

[0001] The present invention relates to a pressure-sensitive adhesive composition and a polarizing plate comprising the same. ≪

The present invention relates to a pressure-sensitive adhesive composition and a polarizing plate comprising the same, and more particularly, to a pressure-sensitive adhesive composition having excellent antistatic properties as well as excellent durability and reworkability, a polarizing plate and a liquid crystal display including the same.

2. Description of the Related Art A liquid crystal display device (LCD) includes a liquid crystal cell and a liquid crystal panel including a polarizing plate bonded to both sides of the liquid crystal cell via an adhesive layer.

The pressure-sensitive adhesive for bonding a liquid crystal cell and a polarizing plate is preferably a pressure-sensitive adhesive for bonding between a liquid crystal cell and a polarizing plate, in which a durability such as heat resistance, heat resistance, heat shock resistance, thermal shock resistance, cold resistance, And the antistatic property for preventing the static electricity generated when the release film is removed for the polarizing plate bonding must be satisfied at the same time.

Korean Patent Publication No. 2006-0046329 discloses an antistatic pressure-sensitive adhesive composition containing an ionic liquid, a polymer having a glass transition temperature (Tg) of 0 DEG C or lower as the base polymer, and an ethylene oxide group-containing compound and / or a surfactant . However, the pressure-sensitive adhesive composition has a problem that the durability of the pressure-sensitive adhesive composition deteriorates under high temperature or high temperature and high humidity conditions.

Korean Patent Publication No. 2006-0046329

It is an object of the present invention to provide a pressure-sensitive adhesive composition which not only has excellent antistatic properties but also has excellent durability and reworkability.

Another object of the present invention is to provide a polarizing plate in which a pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive composition is laminated.

It is still another object of the present invention to provide a liquid crystal display having the polarizing plate on at least one side of a liquid crystal cell.

On the other hand, the present invention provides a pressure-sensitive adhesive composition comprising an acrylic copolymer, an isocyanate-based crosslinking agent, a (meth) acrylate containing an ethylene oxide group and a thermal initiator.

In one embodiment of the present invention, the acrylic copolymer may be a copolymer of a (meth) acrylate monomer having an alkyl group of 1-12 carbon atoms and a monomer having a crosslinkable functional group.

In one embodiment of the present invention, the acrylic copolymer may further include a monomer having a carboxyl group.

In one embodiment of the present invention, the (meth) acrylate monomer containing the ethylene oxide group may include a compound represented by the following formula (1).

[Chemical Formula 1]

In this formula,

X is hydrogen or methyl,

n is an integer of 5 to 25;

In one embodiment of the present invention, the thermal initiator may be at least one selected from the group consisting of an azo-based compound, a peroxide-based compound, and a redox-based compound.

The pressure-sensitive adhesive composition according to one embodiment of the present invention may further comprise an ionic compound.

On the other hand, the present invention provides a polarizing plate in which a pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive composition is laminated.

On the other hand, the present invention provides a liquid crystal display in which the polarizing plate is provided on at least one surface of a liquid crystal cell.

The pressure-sensitive adhesive composition according to the present invention is excellent in antistatic property, durability and reworkability, and can be effectively used for bonding a polarizing plate to a liquid crystal cell.

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

One embodiment of the present invention relates to a pressure-sensitive adhesive composition comprising an acrylic copolymer, an isocyanate-based crosslinking agent, a (meth) acrylate containing an ethylene oxide group and a thermal initiator.

In one embodiment of the present invention, the acrylic copolymer may be a copolymer of a (meth) acrylate monomer having an alkyl group of 1-12 carbon atoms and a monomer having a crosslinkable functional group. Here, (meth) acrylate means acrylate and methacrylate.

Examples of the (meth) acrylate monomer having an alkyl group having 1-12 carbon atoms include n-butyl (meth) acrylate, 2-butyl (meth) acrylate, (Meth) acrylate, ethyl (meth) acrylate, methyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (Meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-octyl , And dodecyl (meth) acrylate. These may be used alone or in combination of two or more.

The (meth) acrylate monomer having an alkyl group having from 1 to 12 carbon atoms is preferably contained in an amount of from 87 to 99% by weight based on 100% by weight of the total monomers used in the production of the acrylic copolymer. When the content is less than 87% by weight, the adhesive strength is not sufficient. When the content is more than 99% by weight, the cohesive strength may be lowered.

The monomer having a crosslinkable functional group reacts with an isocyanate group of an isocyanate crosslinking agent to form a partially crosslinked structure, thereby providing a cohesive force by chemical bonding so that cohesive failure of the pressure-sensitive adhesive does not occur at the time of elevating temperature. As a monomer, a monomer having a hydroxyl group, , And tertiary amine groups. These monomers may be used alone or in combination of two or more.

Examples of the monomer having a hydroxy group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl Hydroxypropyleneglycol (meth) acrylate, hydroxyalkylene glycol having 2 to 4 carbon atoms in the alkylene group (e.g., methoxyethyl (meth) acrylate, (Meth) acrylate, etc. These may be used alone or in combination of two or more.

Examples of the monomer having an amide group include (meth) acrylamide, N-isopropylacrylamide and N-tert-butyl acrylamide.

Examples of the monomer having a tertiary amine group include N, N- (dimethylamino) ethyl (meth) acrylate, N, N- (diethylamino) ethyl (meth) ) Acrylate, and the like.

The monomer having a crosslinkable functional group is preferably contained in an amount of 1.0 to 8.0% by weight based on 100% by weight of the total monomers used in the production of the acrylic copolymer. When the content is less than 1.0% by weight, cohesive failure tends to occur at the time of heating, and when it is more than 8.0% by weight, the flow characteristics at the time of temperature rise may be lowered.

In one embodiment of the present invention, the acrylic copolymer may further include a monomer having a carboxyl group as a monomer having a crosslinkable functional group.

Examples of the monomer having a carboxyl group include monovalent acids such as (meth) acrylic acid and crotonic acid; Dicarboxylic acids such as maleic acid, itaconic acid, and fumaric acid, and monoalkyl esters thereof; 3- (meth) acryloylpropionic acid; A succinic anhydride ring-opening addition adduct of 2-hydroxyalkyl (meth) acrylate in which the alkyl group has 2 to 4 carbon atoms, anhydrous succinic ring opening adduct of a hydroxyalkylene glycol (meth) acrylate having 2 to 4 carbon atoms in the alkylene group , Compounds obtained by ring-opening addition of succinic anhydride to caprolactone adducts of 2-hydroxyalkyl (meth) acrylates whose alkyl groups have 2-3 carbon atoms, and the like.

The monomer having a carboxyl group is preferably contained in an amount of 5.0% by weight or less based on 100% by weight of the total monomers used in the production of the acrylic copolymer. If the content exceeds 5.0% by weight, the adhesive strength may be lowered.

In addition, other polymerizable monomers other than the above-mentioned monomers may be further added in such a range as not to lower the adhesive force, for example, 10% by weight or less, preferably 5% by weight or less.

The method for producing the copolymer is not particularly limited and can be produced by a method such as bulk polymerization, solution polymerization, emulsion polymerization or suspension polymerization, which is commonly used in the art, and solution polymerization is preferable. In addition, a solvent, a polymerization initiator, a chain transfer agent for molecular weight control and the like which are usually used in polymerization can be used.

The acrylic copolymer generally has a weight average molecular weight (in terms of polystyrene) measured by Gel Permeation Chromatography (GPC) of usually 500,000 to 1,700,000, preferably 600,000 to 1,700,000.

In one embodiment of the present invention, the isocyanate crosslinking agent is a component for reinforcing the cohesive force of the pressure-sensitive adhesive by appropriately crosslinking the copolymer, and specifically includes tolylene diisocyanate, xylylene diisocyanate, 2,4-diphenylmethane diisocyanate, Diisocyanate compounds such as 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tetramethyl xylene diisocyanate 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 compound in which 3 moles of a diisocyanate compound is self-condensed, a diisocyanate obtained from 2 moles of 3 moles of a diisocyanate compound And multifunctional isocyanate compounds containing three functional groups such as burette, triphenylmethane triisocyanate and methylene bistriisocyanate in which the remaining one mole of diisocyanate is condensed with urea, and these may be used alone or in combination of two or more kinds. Can be used.

In addition, a melamine-based compound such as hexamethylol melamine, hexamethoxymethyl melamine, hexabutoxymethyl melamine and the like together with an isocyanate-based cross-linking agent; Epoxy compounds such as condensates of bisphenol A and epichlorohydrin, polyglycidyl ether of polyoxyalkylene polyol, glycerin di- or triglycidyl ether, tetraglycidyl xylene diamine, etc., They can be used in combination.

The isocyanate crosslinking agent is preferably contained in an amount of 0.1 to 1.0 part by weight based on 100 parts by weight of the acrylic copolymer based on the solid content. If the content is less than 0.1 part by weight, the cohesive force becomes small due to insufficient crosslinking, resulting in deterioration of durability such as lifting and deterioration of cutability. If the content is more than 1.0 part by weight, excessive crosslinking reaction may cause a problem of relaxation of residual stress have.

In one embodiment of the present invention, the (meth) acrylate monomer containing the ethylene oxide group is hydrophilic and moves to the surface of the substrate bonded at room temperature to control the adhesive force, thereby improving the workability and improving the antistatic property As the component, there may be mentioned a compound represented by the following formula (1).

[Chemical Formula 1]

In this formula,

X is hydrogen or methyl,

n is an integer of 5 to 25;

The (meth) acrylate monomer containing the ethylene oxide group is preferably contained in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the acrylic copolymer based on the solid content. When the content is less than 0.1 part by weight, the effect of improving the workability and antistatic property is insignificant. When the content is more than 5.0 parts by weight, the durability may be lowered.

In one embodiment of the present invention, the thermal initiator is a component that generates radicals under heat-resistant conditions to improve the durability of the (meth) acrylate monomer containing the ethylene oxide group by polymerizing the same. The azo compound, the peroxide compound , And redox-based compounds. These may be used alone or in combination of two or more.

Examples of the azo-based compound include 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobis (isobutyronitrile), 2,2'-azobis Azo bis (2-methylpropionate), 2,2'-azobis (4-methoxyphenylacetate), 2,2'-azobis 2, 4-dimethylvaleronitrile), and the like.

Examples of the peroxide compound include inorganic peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide; Perocta ND, NOF), bis (4-butylcyclohexyl) peroxydicarbonate (e.g., peroyl TCP, peroxydicarbonate, peroxydicarbonate, peroxyacetate, tetramethylbutylperoxyneodecanoate, NOF), di (2-ethylhexyl) peroxycarbonate, butyl peroxyneodecanoate (eg Perbutyl ND, NOF), dipropyl peroxydicarbonate (ex Peroyl NPP, NOF) Propyl peroxydicarbonate (eg Peroyl IPP, NOF), diethoxyethyl peroxydicarbonate (eg Peroyl EEP, NOF), diethoxyhexyl peroxydicarbonate (eg Peroyl OEP, NOF), hexyl Peroxydicarbonate (ex. Perhexyl ND, NOF), dimethoxybutyl peroxydicarbonate (ex Peroyl MBP, NOF), bis (3-methoxy-3-methoxybutyl) peroxydicarbonate ex Peroyl SOP, NOF), dibutyl peroxydicarbonate, dicetyl peroxy dicarbonate, dimyristyl peroxy di Peroxypivalate, perhexyl PV (NOF), butyl peroxypivalate (e.g., perbutyl, NOF), 1,1,3,3-tetramethylbutyl peroxypivalate, , Trimethylhexanoyl peroxide (ex Peroyl 355, NOF), dimethylhydroxybutyl peroxyneodecanoate (ex Luperox 610M75, Atofina), amyl peroxyneodecanoate (ex Luperox 546M75, Atofina) , Butyl peroxyneodecanoate (ex Luperox 10M75, Atofina), t-butyl peroxyneoheptanoate, amyl peroxy pivalate (ex Luperox 546M75, Alofina), t-butyl peroxypivalate Organic peroxides such as t-amyl peroxy-2-ethylhexanoate, lauryl peroxide, dilauroyl peroxide, didecanoyl peroxide, benzoyl peroxide, dibenzoyl peroxide and the like, .

Examples of the redox-based compound include, but are not limited to, a mixture of a peroxide compound and a reducing agent in combination.

The thermal initiator is preferably contained in an amount of 0.01 to 3.0 parts by weight based on 100 parts by weight of the acrylic copolymer based on the solid content. When the content is less than 0.01 part by weight, the effect is insufficient at the time of opening, and when it is more than 3.0 parts by weight, the durability may be deteriorated.

The pressure-sensitive adhesive composition according to one embodiment of the present invention may further comprise an ionic compound.

As the ionic compound, for example, an organic cation or an alkali metal cation such as ammonium, phosphonium, or sulfonium can be used as the cation. Specific examples of the organic cations include quaternary ammonium salts substituted with four alkyl groups such as tetrabutylammonium, 1-ethylpyridinium, 1-butylpyridinium, 1-hexylpyridinium, 1-butyl- Butyl-4-methylpyridinium, 1-hexyl-3-methylpyridinium, 1-hexyl-4-methylpyridinium, Pyridinium, pyridinium salts in which the N of the pyridine is substituted with an alkyl group such as dodecylpyridinium, 1-methyl-3-butylimidazolium, 1-methyl-3-hexylimidazolium, A quaternary phosphonium salt having four alkyl groups such as tetrabutylphosphonium, and a tertiary sulfonium salt having three alkyl groups such as tributylsulfonium, and the like. . The alkali metal may be lithium, sodium, potassium or cesium, preferably lithium, sodium or potassium. These may be used alone or in combination of two or more.

Anion as OTf ^- (methanesulfonate trifluoroacetate), OTs ^- (toluene-4-sulfonate), OMs ^{- (methanesulfonate), Cl -, Br -,} I -, AlCl 4 -, Al 2 Cl 7 - _{^{, BF 4 -, PF 6 -}} , ClO 4 -, NO 3 -, CH 3 COO -, CF 3 COO -, CH 3 SO 3 -, CF 3 SO 3 -, (CF 3 SO 2) 2 N -, ( ^{_{CF 3 SO 2) 3 C -}} , AsF 6 -, SbF 6 -, NbF 6 -, TaF 6 -, F (HF) n -, (CN) 2 N -, C 4 F 9 SO 3 -, (C 2 F ₅ SO ₂ ) ₂ N ^- , C ₃ F ₇ COO ^- , (CF ₃ SO ₂ ) (CF ₃ CO) N ^- and the like.

Specific examples of the ionic compound include dodecylpyridinium hexafluorophosphate, lithium bistrifluoromethanesulfonimide, and the like.

The content of the ionic compound is not particularly limited as long as it is within the range of its function, and may be, for example, 0.3 to 4.0 parts by weight based on 100 parts by weight of the acrylic copolymer. When the amount is less than 0.3 part by weight, the effect is not exhibited in a trace amount, and when it is more than 4.0 parts by weight, a problem of causing deterioration of the adhesion durability may occur.

The pressure-sensitive adhesive composition according to one embodiment of the present invention may further contain additives such as a tackifier resin, antioxidant, antistatic agent, antistatic agent, antioxidant, antistatic agent, An antioxidant, a corrosion inhibitor, a leveling agent, a surface lubricant, a dye, a pigment, a defoaming agent, a filler, a light stabilizer, an antistatic agent and the like.

The pressure-sensitive adhesive composition of the present invention can be used not only as a pressure-sensitive adhesive for a polarizing plate for bonding with a liquid crystal cell but also as a pressure-sensitive adhesive for a surface protective film. In addition, it can be used not only as a protective film, a reflective sheet, a structural adhesive sheet, a photographic adhesive sheet, a lane marking adhesive sheet, an optical adhesive product, an electronic component adhesive, but also a general commercial adhesive sheet product or a medical patch.

One embodiment of the present invention relates to a polarizing plate in which a pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive composition is laminated.

The thickness of the pressure-sensitive adhesive layer can be adjusted according to the adhesive force, and is preferably 3 to 100 탆, more preferably 10 to 100 탆.

Such a polarizing plate can be applied to all ordinary liquid crystal display devices, and concretely, a liquid crystal display device including a liquid crystal panel in which a polarizing plate in which the pressure-sensitive adhesive layer is laminated is bonded to at least one surface of a liquid crystal cell can be constituted.

Therefore, one embodiment of the present invention relates to a liquid crystal display device provided with the polarizing plate on at least one surface of a liquid crystal cell.

Hereinafter, the present invention will be described more specifically with reference to Examples, Comparative Examples and Experimental Examples. It should be apparent to those skilled in the art that these examples, comparative examples and experimental examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Production Example 1: Preparation of acrylic copolymer

87 parts by weight of n-butyl acrylate (BA), 10 parts by weight of methyl acrylate (MA), 2 parts by weight of 2-hydroxyethyl acrylate (2 parts by weight) -HEA) and 1 part by weight of acrylic acid (AA), and then 100 parts by weight of ethyl acetate (EAc) was added as a solvent. Nitrogen gas was then purged for 1 hour to remove oxygen and then maintained at 80 ° C. After the mixture was homogeneously mixed, 0.07 part 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: about 1,460,000).

Production Examples 2 to 10: Preparation of acrylic copolymer

An acrylic copolymer was prepared in the same manner as in Preparation Example 1 except that the composition of the following Table 1 was used (unit: parts by weight).

Manufacturing example One 2 3 4 5 6 7 8 9 10 BA 87 87 87 87 87 87 87 64 87 87 MA 10 10 10 10 10 10 10 30 10 10 2-HEA 2.0 2.0 2.0 2.0 2.0 2.0 3.0 4.0 2.0 2.0 AA 1.0 1.0 1.0 1.0 1.0 1.0 - 2.0 1.0 1.0 Molecular Weight 146 million 139 million 143 million 151 million 148 million 155 million 166 million 66 million 136 million 148 million

BA: butyl acrylate

MA: methyl acrylate

2-HEA: 2-hydroxyethyl acrylate

AA: Acrylic acid

Examples 1 to 9 and Comparative Examples 1 to 3: Production of polarizer with adhesive

(1) Production of pressure-sensitive adhesive composition

(Unit: parts by weight) of the acrylic copolymer, cross-linking agent, ethylene oxide group-containing (meth) acrylate, thermal initiator and ionic compound obtained in the above Production Example were mixed in a ratio shown in Table 2 To prepare a pressure-sensitive adhesive composition.

division Example Comparative Example One 2 3 4 5 6 7 8 9 One 2 3 Acrylic
Copolymer
(100 parts by weight) Production Example 1 Production Example 2 Production Example 3 Production Example 4 Production Example 5 Production Example 6 Production Example 7 Production Example 8 Production Example 1 Production Example 9 Production Example 10 Production Example 1 Cross-linking agent A-1 0.3 0.3 0.3 0.3 0.3 0.5 0.6 0.3 0.3 0.3 A-2 0.3 A-3 0.3 Ionic
compound B-1 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 B-2 1.0 (Meth) acrylate containing an ethylene oxide group C-1 2.0 4.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 C-2 2.0 C-3 2.0 ten
tense D-1 0.2 0.6 0.2 0.2 0.2 0.2 0.2 0.2 0.2 D-2 0.2

A-1: Coronate-L (TMP adduct of TDI, Urethane Co., Japan)

A-2: D110N (an adduct of XDI, Mitsui Chemical)

A-3: YH-325 (trifunctional epoxy resin, Kukdo Chemical)

B-1: Dodecylpyridinium hexafluorophosphate (KOEI)

B-2: Lithium bistrifluoromethanesulfonimide (3M)

C-1: methoxypolyethylene glycol acrylate (EO 9.0 mol, Shin-Nakamura Chemical)

C-2: methoxypolyethylene glycol methacrylate (EO 13 mol, Shin-Nakamura Chemical)

C-3: 2,2-bis (4- (acryloxypolyethoxy) phenyl) propane (EO 3 mol, Shin-

D-1: Butyl peroxyneodecanoate (Perbutyl ND, NOF)

D-2: 2,2'-azobis (2-methylbutyronitrile) (Aldrich)

(2) Production of Polarizer with Adhesive

The pressure-sensitive adhesive composition thus prepared was coated on a release film coated with a silicone release agent to a thickness of 20 탆 and dried at 100 캜 for 1 minute to form a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer prepared above was laminated to an iodine-based polarizing plate having a thickness of 185 μm by a pressure-sensitive adhesive process to produce a polarizer with a pressure-sensitive adhesive. The prepared polarizing plate was stored for a curing period under the conditions of 23 캜 and 60% RH.

Experimental Example 1:

The physical properties of the polarizer with a pressure-sensitive adhesive prepared in the above Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 3 below.

(1) Gel fraction (%)

The prepared polarizer with a pressure-sensitive adhesive was cured at 23 DEG C and 65% RH for 7 days. Approximately 0.25 g of the pressure-sensitive adhesive layer of a polarizing plate with a pressure-sensitive adhesive was attached to a wire mesh (100 mm x 100 mm) of a 250 mesh precisely weighed, and the gel was wrapped so as not to leak. After accurately weighing with a precision balance, the wire mesh was immersed in ethyl acetate solution for 3 days. The immersed wire mesh was taken out, washed with a small amount of ethyl acetate solution, dried at 120 DEG C for 1 hour, and then weighed. Using the measured weight, the gel fraction was calculated by the following equation (1).

[Equation 1]

B is the weight of the wire netting attached to the pressure-sensitive adhesive layer (BA: weight of the pressure-sensitive adhesive, g), C is the weight of the dried wire net after immersion (CA: weight of the gelled resin, g) to be.

(2) Antistatic property

The surface resistivity of each of the three points of the pressure-sensitive adhesive layer of the polarizing plate with a pressure-sensitive adhesive was measured by using a surface resistance meter (MCP-HT450, manufactured by Mitsubishi Chemical Co., Ltd.).

(3) Durability (heat, moisture and heat)

The polarizing plate with a pressure-sensitive adhesive was cut into a size of 90 mm x 170 mm, the release film was peeled off, and the optical absorption axis was perpendicularly attached to both surfaces of a glass substrate (110 mm x 190 mm x 0.7 mm). At this time, the applied pressure was 5 kg / cm ² , and a clean room operation was performed so that bubbles or foreign matter would not be generated.

The heat resistance of the fabricated specimens was measured for the presence of bubbles or exfoliation after being left at a temperature of 90 ° C. for 1000 hours. The moisture resistance of the specimens was measured at a temperature of 70 ° C. and a relative humidity of 90% The occurrence of peeling was observed. At this time, the sample was allowed to stand at room temperature for 24 hours immediately before evaluating the state of the specimen.

<Evaluation Criteria>

Ⓞ: No bubble or peeling

○: Bubbles or peeling <5

?: 5 pieces? Bubbles or peeling <10 pieces

X: 10 pieces &lt; bubble &

(4) Thermal shock resistance

The polarizing plate with a pressure-sensitive adhesive was laminated on a glass substrate, left at -40 캜 for 30 minutes, and then left at 80 캜 for 30 minutes repeatedly for 100 times. Then, whether or not bubbles or peeling occurred in the polarizing plate was visually observed.

 <Evaluation Criteria>

Ⓞ: No bubble or peeling

○: Bubbles or peeling <5

?: 5 pieces? Bubbles or peeling <10 pieces

X: 10 pieces &lt; bubble &

(5) Re-workability

The polarizing plate with a pressure-sensitive adhesive was cut to a size of 25 mm in width and 100 mm in length, and the release film was peeled off. The glass plate (# 1737, Corning) was laminated at a pressure of 0.25 MPa under conditions of 5 atm and 50 캜 for 20 minutes The sample was autoclaved. After putting it in an oven at 80 ° C, which was a heat-resistant condition, it was taken out after 10 hours, left at room temperature for 120 hours, and peeled at a rate of 1.3 cm / s.

<Evaluation Criteria>

○: There is no adhesive residue on the glass substrate and the glass substrate is cleanly peeled off without tearing the polarizer

X: The pressure-sensitive adhesive was left on the glass substrate or the polarizer was torn in the peeling process

division Example Comparative Example One 2 3 4 5 6 7 8 9 One 2 3 Gel fraction (%) 73 79 77 72 74 75 79 71 70 69 74 72 Antistatic property
(Ω / □) 5.2E + 10 3.3E + 10 4.9E + 10 7.7E + 10 3.2E + 10 4.6E + 10 4.5E + 10 3.2E + 10 5.8E + 10 6.8E + 10 4.2E + 10 5.8E + 10 Heat resistance (90 ℃) ◎ ○ ○ ○ ○ ○ ○ ○ △ ○ X ○ Wet heat
(70 &lt; 0 &gt; C, 90%) ◎ ○ ◎ ◎ ○ ○ ○ ○ ◎ ○ ○ ○ Thermal shock resistance
(H / S) ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Re-workability ○ ○ ○ ○ ○ ○ ○ ○ ○ X ○ X

As shown in Table 3, the polarizer plate in which the pressure-sensitive adhesive layer composed of the pressure-sensitive adhesive composition of Examples 1 to 9 according to the present invention was laminated was composed of the pressure-sensitive adhesive composition of Comparative Example 1 containing no (meth) acrylate containing an ethylene oxide group Compared to a polarizing plate in which a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive composition of Comparative Example 2, which is excellent in reworkability and antistatic property and which does not contain a thermal initiator, is laminated with a pressure-sensitive adhesive layer laminated thereon, Sensitive adhesive layer of the pressure-sensitive adhesive composition of Comparative Example 3 containing an epoxy-based crosslinking agent was superior to the polarizing plate in which the pressure-sensitive adhesive layer was laminated.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Do. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Accordingly, the actual scope of the invention is defined by the appended claims and their equivalents.

Claims (12)

A pressure-sensitive adhesive composition comprising an acrylic copolymer, an isocyanate-based crosslinking agent, (meth) acrylate containing an ethylene oxide group and a thermal initiator. The pressure-sensitive adhesive composition according to claim 1, wherein the acrylic copolymer is a copolymer of a (meth) acrylate monomer having an alkyl group having 1-12 carbon atoms and a monomer having a crosslinkable functional group. The pressure-sensitive adhesive composition according to claim 2, wherein the acrylic copolymer further comprises a monomer having a carboxyl group. The pressure-sensitive adhesive composition according to claim 1, wherein the acrylic copolymer has a weight average molecular weight of 500,000 to 1,700,000. The pressure-sensitive adhesive composition according to claim 1, wherein the (meth) acrylate monomer containing an ethylene oxide group comprises a compound represented by the following formula (1):
[Chemical Formula 1]

In this formula,
X is hydrogen or methyl,
n is an integer of 5 to 25; The pressure-sensitive adhesive composition according to claim 1, wherein the (meth) acrylate monomer having an ethylene oxide group is contained in an amount of 0.1 to 5.0 parts by weight based on 100 parts by weight of the acrylic copolymer based on the solid content. The pressure-sensitive adhesive composition according to claim 1, wherein the thermal initiator is at least one selected from the group consisting of an azo-based compound, a peroxide-based compound, and a redox-based compound. The pressure-sensitive adhesive composition according to claim 1, wherein the thermal initiator is contained in an amount of 0.01 to 3.0 parts by weight based on 100 parts by weight of the acrylic copolymer based on the solid content. The pressure-sensitive adhesive composition according to claim 1, further comprising an ionic compound. The pressure-sensitive adhesive composition according to claim 9, wherein the ionic compound is dodecylpyridinium hexafluorophosphate or lithium bistrifluoromethanesulfonimide. A polarizing plate laminated with a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition according to any one of claims 1 to 10. A liquid crystal display device comprising the liquid crystal cell according to claim 11 on at least one surface thereof.