TW201446814A - Acrylic copolymer, adhesive composition containing same, and polarizing plate - Google Patents

Abstract

Disclosed are an acrylic copolymer, an adhesive compositoin containing the same, and a polarizing plate. The acylic copolymer includes 35 to 84.9 parts by weight of a (meth)acrylate monomer having an alkyl group with 4-12 carbon atoms, 5 to 20 parts by weight of benzyl methacrylate, 0.1 to 5 parts by weight of 4-hydroxybutyl acrylate, 5 to 10 parts by weight of acrylic acid, and 5 to 30 parts by weight of methacrylate, wherein the acrylic copolymer has a weight average molecular weight (in terms of polystyrene, Mw) of 1,000,000 or more. The acrylic copolymer is used to increase the cross-linking density and enhance the cohesive strength, thereby providing an adhesive composition having improved adhesive durability under severe conditions (high temperature or high temperature and humidity) when being bonded to a non-polar film having a low water contact angle, a shortened curing time, and a light leakage prevention property, and a polarizing plate including the adhesive composition.

Description

An acrylic copolymer, an adhesive composition containing an acrylic copolymer, And polarizing plate

The present invention relates to an adhesive composition and a polarizing plate having good durability.

The adhesive is a material that is sufficiently adhered to an adhesive body only by application of pressure. Adhesives have lower cohesion and faster stress relaxation than glue, and have a viscoelastic behavior that can be easily converted by external forces.

The raw materials for the adhesive are thermoplastic resins such as natural rubber, synthetic rubber, acrylic resin and enamel, most of which have elastic properties, and thus are mixed with low molecular weight materials to provide viscous properties, thereby retaining their viscoelastic properties.

Among these adhesive materials, acrylate adhesives have replaced rubber-based adhesives in recent years and their usability has also increased rapidly. A wide variety of acrylate adhesives include solvent, aqueous, emulsion, hot melt, 100% solids, and the like.

Acrylate adhesives are better at weather resistance, heat resistance, cold resistance, oil resistance and the like than rubber-based adhesives, and can be easily prepared according to needs and uses. Therefore, adhesive products are currently widely used in many applications. The use may be due to the advent of acrylate adhesives.

In general, the adhesion of an adhesive can be judged by initial adhesion (viscosity), adhesion (adhesion), and cohesion (shear strength).

The initial adhesion is related to the glass transition temperature (Tg) of the polymer that makes up the adhesive, and the adhesion is related to the glass transition temperature and cohesion of the polymer. Cohesion refers to the interaction between molecules in the adhesive when the adhesive is attached to the adherend. Among them, the cohesive force between the polymers causes the interface of the adhesive to break, and the low intermolecular cohesive force causes the aggregation to fail, resulting in residues on the adherend. Therefore, it is urgent to design an adhesive which can cause interface cracking when the adhesive is detached from the adherend.

Recently, the price of materials for polarizing plates has become lower and lower as the price of LCD materials has become lower. More specifically, the price reduction of polarizer protective film, which accounts for 50% or more of the price of polarizing material, has always been the subject of concern. Therefore, attempts have been made to use a polymethyl methacrylate resin having a high transparency and a low cost as compared with an existing cellulose-based resin or a cycloolefin polymer-based resin as a polarizer protective film.

However, the film containing the polymethyl methacrylate resin has a high shrinkage rate under heat resistance conditions, and thus defects such as delamination and the like may occur due to shrinkage stress during the production of the polarizing plate.

In order to improve the adhesion durability of the high-shrinkage polarizing plate, Korean Patent No. 930,808 proposes an epoxy resin acrylate adhesive which improves initial adhesion, adhesion, and cohesion by using an ester tackifier resin. However, the adhesive composition including the tackifier resin cannot improve the cohesive force to such an extent that it can overcome the shrinkage characteristics of the polymethyl methacrylate-based polarizer protective film. In addition, since the increase The binder resin is a low molecular weight oligomer which has a risk of deterioration in durability due to overflow. Therefore, there is an urgent need to develop other technologies that can solve these problems.

Therefore, the present invention has been made to solve the problem that when a polarizing plate comprising a polymethyl methacrylate resin film and an existing cellulose resin and a cycloolefin resin film is produced, shrinkage stress which cannot withstand the polarizing plate is caused, and The problem of delamination failure under durability conditions (high temperature or high temperature and high humidity), and an object of the present invention is to provide an adhesive composition which can improve the adhesion durability of a polarizing plate.

In order to achieve the object, an acrylic copolymer comprising 35 to 84.9 parts by weight of a (meth)acrylic monomer having an alkyl group of 4 to 12 carbon atoms, 5 to 20 parts by weight of a benzyl ester, and 0.1 to 5 parts by weight is provided. 4-hydroxybutyl acrylate, 5 to 10 parts by weight of acrylic acid, and 5 to 30 parts by weight of methacrylate, wherein the weight average molecular weight (in terms of polystyrene, Mw) of the acrylic copolymer is 1,000,000 or the above.

The weight average molecular weight can range from 1,000,000 to 2,000,000.

The acrylic copolymer may comprise 47 to 76.5 parts by weight of a (meth)acrylic monomer having an alkyl group of 4 to 12 carbon atoms, 8 to 12 parts by weight of a benzyl ester, and 0.5 to 3 parts by weight of a 4-hydroxybutyl acrylate. Ester, 5 to 8 parts by weight of acrylic acid, and 10 to 30 parts by weight of methacrylate.

According to another object of the present invention, an adhesive composition comprising the acrylic copolymer is provided.

The adhesive composition may further comprise a crosslinking agent.

According to another object of the present invention, a polarizing plate is provided, wherein a bias is provided The light sheet protective film is adhered to at least one surface of a polarizer and an adhesive layer containing the adhesive composition is formed on the polarizer protective film.

The polarizer protective film may have a water contact angle of 30 to 80.

The polarizer protective film may be a polymethyl methacrylate film.

Here, when the polarizing plate is cut into a size of 90 mm × 170 mm and attached to both surfaces of the glass substrate so that the sample obtained by interlacing the light absorption axis is placed at a temperature of 80 ° C for 1000 hours, less sample is generated. For five bubbles or delamination.

Here, when the polarizing plate is cut into pieces of a size of 90 mm × 170 mm and attached to both surfaces of the glass substrate so that the light absorption axis is staggered, the sample is placed at 60 ° C and 90% RH for 1000 hours, and the sample is sampled. There will be less than five bubbles or delamination in the middle.

The present invention discloses an adhesive composition having good durability and a polarizing plate.

Next, the details of the present invention will be described below.

The adhesive composition of the present invention comprises 35 to 84.9 parts by weight of a (meth)acrylic monomer having an alkyl group of 4 to 12 carbon atoms, 5 to 20 parts by weight of a benzyl ester, and 0.1 to 5 parts by weight of a 4-acrylic acid. Hydroxybutyl ester, 5 to 10 parts by weight of acrylic acid, and 5 to 30 parts by weight of methacrylate. Here, the so-called (meth)acrylic acid means acrylate And methacrylate, and the content of individual components is based on the content of its solids.

Further, the weight average molecular weight (in terms of polystyrene, Mw) of the acrylic copolymer is 1,000,000 or more but not more than 2,000,000, and preferably 1,000,000 to 1,500,000, as measured by colloidal permeation chromatography (GPC). If the weight average molecular weight is less than 1,000,000, the cohesive force may be insufficient, resulting in delamination or bubbles under heat resistance conditions. If the weight average molecular weight exceeds 2,000,000, the viscosity may increase due to excessive entanglement between the acrylic copolymers, resulting in coating defects such as coating streaks when the adhesive is applied.

Although individual monomers in the acrylic copolymer are known in the art. However, the present invention is characterized by how to selectively use and combine and control the content range thereof to increase the crosslinking density, thereby increasing the cohesive force.

The alkyl (meth) acrylate monomer having 4 to 12 carbon atoms is a (meth) acrylate derived from a fatty alcohol having 4 to 12 carbon atoms, and examples may include n-(meth) acrylate Ester, butyl 2-(meth)acrylate, butyl t-(meth)acrylate, amyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth) acrylate, Ethyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, and the like. They may be used singly or in combination of two or more. Among them, preferred is n-(meth)acrylate butyl ester, 2-ethylhexyl (meth) acrylate, or a mixture thereof.

The content of the alkyl (meth)acrylic monomer having 4 to 12 carbon atoms is 35 to 84.9 parts by weight and preferably 47 to 76.5 parts by weight. If less than 35 parts by weight, the alkyl (meth)acrylic monomer will lack viscosity and will be mixed during the bonding process. The risk of bubble. When it exceeds 84.9 parts by weight, the alkyl (meth)acrylic monomer causes a decrease in the glass transition temperature and lacks hydrogen bonding, resulting in insufficient cohesive force, which may deteriorate heat resistance and durability.

The benzyl ester adjusts the birefringence to reduce light leakage and increase the glass transition temperature to improve heat resistance.

The content of the benzyl ester is 5 to 20 parts by weight and preferably 8 to 12 parts by weight. If the content of the benzyl ester is less than 5 parts by weight or more than 20 parts by weight, the birefringence will exceed the intended range, so that the light leakage characteristics are deteriorated.

4-Hydroxybutyl acrylate, such as the same crosslinkable monomer, reacts with a crosslinking agent to increase the cohesive force of the acrylic copolymer.

The content of 4-hydroxybutyl acrylate is 0.1 to 5 parts by weight and preferably 0.5 to 3 parts by weight. If the content of the crosslinking agent is less than 0.1 parts by weight, it will not be sufficient to increase the cohesive force, and if the content of the crosslinking agent exceeds 5 parts by weight, excessive crosslinking will be caused, resulting in deterioration of adhesion, so that under heat resistance conditions A delamination failure occurred.

Acrylic acid forms a hydrogen bond in the copolymer, reacts with the crosslinker to form a crosslink, thereby enhancing the cohesive force of the adhesive, or acts as an acidic catalyst between the 4-hydroxybutyl acrylate and the crosslinker to increase the reaction rate. Thereby reducing the curing effect. In addition, acrylic acid can use polar functional groups to increase adhesion through the polar interaction between the adhesive and the glass.

The content of acrylic acid is 5 to 10 parts by weight and preferably 5 to 8 parts by weight. If the content of the acrylic acid is less than 5 parts by weight, the effect of enhancing the cohesive force and the adhesive force will be insufficient and the curing effect will be insufficient. If the content of acrylic acid exceeds 10 parts by weight, The cohesive force will be increased too much, but the adhesion will be lowered, resulting in failure of delamination under heat resistance conditions, and liquid stability may be deteriorated due to excessive catalytic effect in the crosslinking reaction.

Methacrylate has a high glass transition temperature to increase the cohesive force of the adhesive. Further, the methacrylate has a polarity compared to butyl acrylate, so that the adhesion can be improved by the polar force with the glass.

The content of the methacrylate is 5 to 30 parts by weight and preferably 10 to 30 parts by weight. If the content of the methacrylate is less than 5 parts by weight, the effect of enhancing the cohesive force will be insufficient. If the content of the methacrylate exceeds 30 parts by weight, the fluidity of the polymer itself will be deteriorated, resulting in coating streaks or the like due to an increase in viscosity when the adhesive solution is applied.

Further, the acrylic copolymer of the present invention may further contain a crosslinkable monomer having a hydroxyl group or a carboxyl group in addition to the above monomer. Here, the crosslinkable monomer can enhance the cohesive force or adhesion of the adhesive composition by chemical bonds, thereby improving durability and cuttability.

Examples of the monomer having a hydroxyl group may include hydroxyethyl 2-(meth)acrylate, hydroxypropyl 2-(meth)acrylate, hydroxybutyl 2-(meth)acrylate, and hydroxy 6-(meth)acrylate Hexyl ester, hydroxyethylene glycol (meth) acrylate, 2-hydroxy propylene glycol (meth) acrylate, hydroxyalkylene glycol having an alkylene group of 2 to 4 carbon atoms ( Methyl)acrylic acid, 4-hydroxybutyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, 7-hydroxyheptyl vinyl ether, 8-hydroxyoctyl vinyl ether, 9 - hydroxydecyl vinyl ether, 10-hydroxydecyl vinyl ether, and the like.

Examples of the monomer having a carboxyl group may include a monovalent acid such as (meth) propylene Acid, crotonic acid, and the like; divalent acids such as maleic acid, itaconic acid, fumaric acid, and the like, and monoalkyl esters thereof; 3-(meth)acryloylpropionic acid; A succinic anhydride ring-opening adduct of a 2-hydroxyalkyl (meth) acrylate having 3 carbon atoms, a hydroxyalkylene glycol (meth) having an alkylene group having 2 to 4 carbon atoms a succinic anhydride ring-opening adduct of acrylic acid, and a caprolactone adduct of a 2-hydroxyalkyl (meth) acrylate which has passed through a succinic anhydride ring-opening adduct and an alkyl group having 2 to 3 carbon atoms. The resulting compound; and the like. Among them, (meth)acrylic acid is preferred.

The content of the crosslinkable monomer is preferably from 0.05 to 10 parts by weight, and most preferably 0.1, based on 100 parts by weight of the (meth) acrylate monomer having an alkyl group having 4 to 12 carbon atoms. Up to 8 parts by weight. If it is less than 0.05 part by weight, the adhesive cohesive force will be reduced, resulting in deterioration of durability. If it exceeds 10 parts by weight, the adhesive force of the adhesive will decrease due to a high gel fraction and cause a problem of durability.

The other polymerizable monomer other than the above monomers may be further included in the range which does not reduce the adhesive force of the adhesive, for example, based on 100 parts by weight of all the monomers used to prepare the acrylic copolymer, The content thereof may be 10 parts by weight or less.

The preparation method of the copolymer is not particularly limited. The copolymer can be prepared by conventional methods such as bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization. Among them, solution polymerization is preferred. Further, a solvent commonly used in conventional polymerization, a polymerization initiator, a chain transfer agent for controlling molecular weight, and the like can also be used.

Further, the present invention is characterized in that the adhesive composition comprises an acrylic copolymer. The adhesive composition may further comprise a crosslinking agent.

The crosslinking agent is a composition for appropriately crosslinking the copolymer to increase the cohesive force of the adhesive. Examples of the crosslinking agent may include an isocyanate compound, an epoxy resin compound, and the like, and these may be used singly or in combination of two or more.

Examples of the isocyanate may include a diisocyanate compound such as toluene diisocyanate, xylene diisocyanate, 2,4-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, and isophora. Ketone diisocyanate, tetramethyl xylene diisocyanate, and naphthalene diisocyanate; an addition obtained by reacting a 3 mol diisocyanate compound with 1 mol of a polyol compound such as trimethylolpropane An isocyanurate body obtained by self-condensation of a 3 molar diisocyanate compound, by using a diisocyanate urea obtained from a 2 molar 2 isocyanate compound in 3 moles with the remaining 1 mole a diuret body obtained by condensation of a diisocyanate compound, and a polyfunctional isocyanate compound having three functional groups such as triphenylmethane triisocyanate and methylene diisocyanate; and the like.

Examples of the epoxy resin compound may include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol Diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polybutylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, Glycerol polydiether, polyglycerol polyglycidyl ether, resorcinol diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, quarter Pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, tris (glycidyl) isocyanurate, tris (glycidyl) Oxyethyl)isocyanurate, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-inter- Xylylenediamine, and the like.

Further, the melamine-based compound may be used singly or in combination of two or more of an isocyanate compound and an epoxy resin compound.

Examples of the melamine-based compound may include hexamethylol melamine, hexamethoxymethyl melamine, hexabutoxymethyl melamine, and the like.

The content of the crosslinking agent is preferably from 0.1 to 15 parts by weight and most preferably from 0.1 to 5 parts by weight, based on 100 parts by weight of the copolymer. If the content of the crosslinking agent is less than 0.1 part by weight, the cohesive force may be lowered due to insufficient crosslinking degree, resulting in deterioration of durability such as delamination and poor cuttability. If the content of the crosslinking agent exceeds 15 parts by weight, there is a problem that the residual stress is lowered due to excessive crosslinking reaction.

Further, the adhesive composition of the present invention may further comprise a decane coupling agent.

The kind of the decane coupling agent is not particularly limited. Examples of the decane coupling agent may include vinyl chlorodecane, vinyl trimethoxy decane, vinyl triethoxy decane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxy decane, 3- Glycidoxypropyltrimethoxydecane, 3-glycidoxypropylmethyldiethoxydecane, 3-glycidoxypropylmethyldiethoxydecane, 3-epoxy Propoxypropyltriethoxydecane, p-styryltrimethoxydecane, 3-methacryloxypropyltriethoxy Baseline, 3-methacryloxypropyltrimethoxydecane, 3-methacryloyloxymethyldimethoxydecane, 3-methacryloxypropylmethyldiethoxy Decane, 3-acryloyloxypropyltrimethoxydecane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxydecane, N-2-(aminoethyl)-3- Aminopropyltrimethoxydecane, N-2-(aminoethyl)-3-aminopropyltriethoxydecane, 3-aminopropyltrimethoxydecane, 3-aminopropyltriethoxydecane, 3-triethoxycarbamido-N-(1,3-dimethyl-butylene)propylamine, N-phenyl-3-aminopropyltrimethoxydecane, 3-chloropropyltrimethoxydecane , 3-mercaptopropylmethyldimethoxydecane, 3-mercaptopropyltrimethoxydecane, bis(triethoxymethanepropylpropyl)tetrasulfide, 3-isocyanatepropyltriethoxydecane, And the like. They may be used singly or in combination of two or more.

The content of the decane coupling agent is preferably from 0 to 10 parts by weight, and preferably from 0.005 to 5 parts by weight, based on 100 parts by weight of the copolymer. If the content exceeds 10 parts by weight, the durability is deteriorated.

Further, the adhesive composition may further comprise an antistatic agent, of which an ionic antistatic agent is preferred. The ionic antistatic agent is an ionic salt composed of a negative ion and a positive ion, and the kind of the ionic antistatic agent is not particularly limited as long as it imparts ionic conductivity to the adhesive.

More specifically, the ionic antistatic agent may be an ionic salt composed of: a positive ion selected from the group consisting of alkali metal salts, ammonium salts, phosphonium salts, and phosphonium salts; and selected from fluorine-containing inorganic salts, An anion of a group consisting of a fluorine-containing organic salt and an iodide ion.

Based on 100 parts by weight of acrylic copolymer, ionic antistatic The content of the electric agent is from 0.1 to 5 parts by weight and preferably from 0.5 to 3 parts by weight. If the content of the ionic antistatic agent is less than 0.1 part by weight, the antistatic property will be insufficient, and if the content of the ionic antistatic agent exceeds 5 parts by weight, the durability will not be maintained.

The adhesive composition may further comprise, in addition to the above composition, an additive such as a tackifier resin, an antioxidant, a corrosion inhibitor, a leveling agent, a surface lubricant, a dye, a pigment, an antifoaming agent, a filler, and a light stabilizer. To adjust the adhesion, cohesion, viscosity, modulus of elasticity, glass transition temperature, and the like required for the adhesive composition.

Further, the present invention is characterized in that the polarizing plate has a polarizer protective film adhered to at least one surface of a polarizer and an adhesive layer containing the adhesive composition is formed on the polarizer protective film.

The polarizer protective film may be a film formed from cellulose, polyester, polycarbonate, acrylic, styrene, polyolefin, vinyl chloride, amide as known in the art. Resins of class, imide, polyether sulfone; sulfone resin, polyether sulfone resin; polyether resin, polyphenylene sulfide resin, vinyl alcohol resin, vinylidene chloride resin, vinyl acetate Butyraldehyde resin; allyl ester resin; polyoxymethylene resin; thermoplastic resin such as epoxy resin; such as (meth)acrylic, polyurethane, urethane acrylate, epoxy resin and organic hydrazine A thermosetting resin or an ultraviolet curable resin.

More specifically, the adhesive layer of the present invention can impart a bonding force to a non-polar film which is difficult to bond by a general acrylate adhesive, and has good adhesive durability.

The water contact angle of the non-polar film is preferably from 30 to 50, and the non-polar film may be a polymethyl methacrylate film.

The preferred embodiments are provided to aid in the understanding of the present invention, and the following examples are merely illustrative of the invention and are not intended to limit the invention. The scope of the present invention is defined by the scope of the appended claims, unless otherwise claimed.

Preparation Example: Preparation of Acrylic Copolymer

Preparation example 1

56 parts by weight of n-butyl acrylate (BA), 30 parts by weight of methacrylate (MA), 8 parts by weight of benzyl ester (BzMA), 5 parts by weight of acrylic acid (AA), and 1 part by weight The monomer of 4-hydroxybutyl acrylate (4-HBA) was mixed into a 1 liter reactor with a cooling device to promote nitrogen reflux and temperature control, and then 80 parts by weight of ethyl acetate (EAc). It is added as a solvent. After that, it was purged with nitrogen for 1 hour to remove oxygen, and the temperature was maintained at 70 °C. Stir the mixture evenly. Then, 0.07 part by weight of azobisisobutyronitrile (AIBN) was further added as a reaction initiator, followed by a reaction for 8 hours to prepare an acrylic copolymer (weight average molecular weight: about 1,400,000).

Preparation example 2

The acrylic copolymer was prepared by the same method as in Preparation Example 1, and mixed and reacted in the combination shown in Table 1 below.

[Table 1]

Examples 1 to 10 and Comparative Examples 1 to 11

1) Adhesive composition

The acrylic copolymer, the crosslinking agent, the decane coupling agent, and the antistatic agent of Preparation Example 1 were mixed according to the combination shown in Table 2 below, and then the mixture was diluted to 28% by weight to prepare an adhesive composition.

2) Adhesive polarizer

Each of the adhesive compositions prepared in the above item 1) was applied onto a release film coated with a ruthenium release agent to have a thickness of 25 μm, followed by 1 minute, 5 minutes, and 10 at 100 ° C, respectively. Drying is done in minutes to form an adhesive layer.

A polarizing plate obtained by bonding a triacetylcellulose type protective film to both faces of the polarizing plate was laminated on the adhesive layer to fabricate an adhesive polarizing plate. Here, lamination is used to allow the adhesive layer to come into contact with the surface of the protective film. The produced polarizing plate was stored under the conditions of 23 ° C and 60% RH for the next curing period.

In addition, a polarizing plate adhered to a polymethyl methacrylate type protective film (water contact angle: 47°) instead of a cellulose triacetate type protective film (water contact angle: 12°) was laminated on the adhesive layer to Create an adhesive polarizer.

Test case

The characteristics of the adhesive-attached polarizing plate manufactured from the above examples and comparative examples were measured in accordance with the following methods, and the results thereof are reported in Table 3.

During curing

The gel fraction was measured daily as described below during the 1 to 10 days of curing of the manufactured adhesive sheet at 23 ° C and 65% RH. The number of days of curing is extended until the gel fraction is no longer increased, meaning that the curing period is determined in accordance with the number of days required.

Approximately 2.5 g of the adhesive layer of the adhesive sheet was fixed to a 250-mesh wire mesh (100 mm X 100 mm), and the wire mesh was wrapped to prevent the gel from escaping therefrom. A precision balance was used to accurately measure the weight, and the wire mesh was immersed in an ethyl acetate solution for 3 days. The soaked wire mesh was taken out, then rinsed with a small amount of ethyl acetate solution, dried at 120 ° C for 24 hours, and then weighed. The measured weight is used to calculate the gel fraction by Equation 1. The curing time was determined based on the calculated time when the gel fraction fell within the range of 70% to 80% and no change with time was observed.

[Equation 1] Gel fraction (%) = (C-A) / (B-A) X 100

[In Equation 1, A is the weight of the wire mesh (g); B is the adhesive layer fixed to the gold The weight of the wire mesh (B-A: the weight of the adhesive layer, g); and C is the weight of the wire mesh after soaking and drying (C-A: weight of gel resin, g)]

2. Durability (heat resistance, heat and humidity resistance)

The prepared polarizing plate with an adhesive was cut into a size of 90 mm × 170 mm to prepare a sample, and the release layer was delaminated, and the polarizing plate was attached to both sides of the glass substrate (110 mm × 190 mm × 0.7 mm). The light absorption axes of the polarizing plates are orthogonal to each other. Here, a pressure of 5 kg/cm 2 was applied and carried out in a clean room to avoid generation of bubbles or foreign materials. In order to measure heat resistance, the sample was placed at a temperature of 80 ° C for 1000 hours, and then, whether or not foaming or delamination occurred was observed. In order to measure the heat and humidity resistance, the sample was placed at 60 ° C and 90% RH for 1000 hours, and it was observed whether foaming or delamination occurred. Here, the sample was placed at normal temperature for 24 hours before evaluation.

<Evaluation criteria>

◎: No bubbles or delamination:

○: The number of bubbles or delamination <5

△: 5 Number of bubbles or delamination <10

×:10 Number of bubbles or delamination

××: bubbles or delamination on the entire surface

3. Prevent light leakage

In order to confirm the uniform light transmittance of the same sample, a backlight was used in a dark room to observe the light leakage of the sample. For the test of uniform light transmittance, the coated polarizing plates (200 mm × 200 mm) were attached to the glass substrate at an angle of 90° to each other. Both sides (210 mm x 210 mm x 0.7 mm) were observed. Uniform light transmission was evaluated based on the following criteria.

<Evaluation criteria>

◎: Non-uniform light transmittance is difficult to observe with the naked eye.

○: A small amount of non-uniform light transmittance was observed.

△: Some non-uniform light transmittance was observed.

×: A lot of non-uniform light transmittance was observed.

As shown in Table 3, the polarizing plates of Examples 1 to 10 containing the adhesive composition of a specific composition within the preset range of the present invention were confirmed to be equal to the polarizing plates of Comparative Examples 1 to 11 in terms of curing time. Come better, and have significantly superior durability and light leakage prevention.

More specifically, even if a polymethyl methacrylate film is used as a polarizer protective film, its superior durability and light leakage prevention can be maintained.

According to the present invention, an adhesive composition comprising an acrylic copolymer can improve the glass transition temperature, control the content of acrylic acid to improve the crosslinking density by using a monomer having a high glass transition temperature, increasing the amount of hydrogen bonds in the copolymer, And increasing the molecular weight to increase the entanglement between the acrylic copolymers to improve the adhesion durability under severe conditions (high temperature or high temperature and high humidity), thereby enhancing the cohesive force of the composition.

More specifically, the adhesive composition exhibits good adhesion and adhesion durability when applied to a polarizing plate made of a polymethyl methacrylate resin film.

Furthermore, the adhesive composition comprising an acrylic copolymer according to the present invention can shorten the curing time and maintain equal or superior to the conventional adhesive composition. Anti-light leakage characteristics.

Claims (10)

An acrylic copolymer comprising 35 to 84.9 parts by weight of a (meth)acrylic monomer having an alkyl group of 4 to 12 carbon atoms, 5 to 20 parts by weight of a benzyl ester, and 0.1 to 5 parts by weight of a 4-hydroxybutyl acrylate The ester, 5 to 10 parts by weight of acrylic acid, and 5 to 30 parts by weight of methacrylate, wherein the acrylic copolymer has a weight average molecular weight (in terms of polystyrene, Mw) of 1,000,000 or more. The acrylic copolymer of claim 1, wherein the weight average molecular weight is from 1,000,000 to 2,000,000. The acrylic copolymer according to claim 1, wherein the acrylic copolymer comprises 47 to 76.5 parts by weight of a (meth)acrylic monomer having an alkyl group of 4 to 12 carbon atoms, and 8 to 12 parts by weight of a benzyl group. The base ester, 0.5 to 3 parts by weight of hydroxybutyl 4-acrylate, 5 to 8 parts by weight of acrylic acid, and 10 to 30 parts by weight of methacrylate. An adhesive composition comprising the acrylic copolymer according to any one of claims 1 to 3. The adhesive composition of claim 4, further comprising a crosslinking agent. A polarizing plate comprising a polarizer protective film adhered to at least one surface of a polarizer and an adhesive layer comprising the adhesive composition according to claim 4 of the invention is formed on the polarizer protective film. The polarizing plate of claim 6, wherein the polarizer protective film has a water contact angle of 30° to 80°. The polarizing plate of claim 7, wherein the polarizer protective film is a polymethyl methacrylate film. The polarizing plate of claim 6, wherein the polarizing plate is cut into a size of 90 mm × 170 mm and attached to both surfaces of the glass substrate so that the light absorption axis is staggered and the sample is placed at 80 ° C. At 1000 hours of temperature, less than five bubbles or delamination will be produced in the sample. The polarizing plate of claim 6, wherein the polarizing plate is cut into a size of 90 mm × 170 mm and attached to both surfaces of the glass substrate so that the sample obtained by interlacing the light absorption axis is placed at 60 ° C and Under 1000 hours of 90% RH, less than five bubbles or delamination will be produced in the sample.