WO2015012524A1 - Adhesive composition for acryl-based film and polarizing plate containing same - Google Patents

Abstract

The present invention relates to an adhesive composition for an acryl-based film and a polarizing plate containing same and, more specifically, to an adhesive composition for an acryl-based film and a polarizing plate containing same, the adhesive composition containing: an acryl-based copolymer (A) containing 30-70 parts by weight of a methyl methacrylate monomer with respect to a total of 100 parts by weight of monomers and not containing a cross-linkable monomer and having a weight average molecular weight of 100,000-500,000; and an acryl-based copolymer (B) containing a cross-linkable monomer and having a weight average molecular weight of 800,000-1,500,000, thereby having excellent adhesive durability and reworkability under harsh conditions (high temperature or high temperature and humidity) when bonded to the acryl-based film.

Description

Adhesive composition for acrylic film and polarizing plate containing same

The present invention relates to a pressure-sensitive adhesive composition and a polarizing plate for acrylic films excellent in durability and reworkability.

The pressure-sensitive adhesive is a material that is sufficiently adhered to the adherend only by the pressure applied, and exhibits a low cohesive force, fast stress relaxation, and viscoelastic behavior in which deformation easily occurs with respect to external force.

The raw materials used in the pressure-sensitive adhesive is a thermoplastic resin such as natural rubber, synthetic rubber, acrylic, silicone, etc., and most of them have elastic properties. Thus, low-molecular-weight substances are mixed and used to give viscoelastic properties.

Among the raw materials of the pressure-sensitive adhesives, acrylic pressure-sensitive adhesives are rapidly increasing in use in place of rubber pressure-sensitive adhesives, and can be used in a wide range of forms such as solvent type, aqueous emulsion type, hot melt type, and 100% solid reactive pressure sensitive adhesives.

Acrylic pressure-sensitive adhesives have excellent weather resistance, heat resistance, cold resistance, oil resistance, and the like compared to rubber pressure-sensitive adhesives, and can be made relatively easily according to various purposes and uses. Therefore, it can be said that the adhesive product can be used for a variety of uses as is the current origin of the acrylic adhesive.

On the other hand, in accordance with the trend of lowering the cost of LCD materials in recent years, the lowering of the polarizing plate material is in progress, and in particular, the lowering of the polarizer protective film occupying more than 50% of the cost of the polarizing plate material is of interest. Accordingly, attempts are being made to use polymethyl methacrylate resins having high transmittance and low cost as polarizer protective films instead of existing cellulose and cycloolefin polymer resins.

The polarizer protective film is a method of polarizing by performing a process of saponifying (alkali treatment) the surface of the cellulose-based film to improve the bonding strength with the polarizer and the cycloolefin polymer-based film by performing a process of corona treating the surface thereof. This is proposed (Korean Patent Publication No. 2009-114928).

However, the polymethyl methacrylate-based film having excellent optical properties and price competitiveness is difficult to polarize the surface by corona treatment, and thus an additional nonpolar adhesive is required. Non-polar adhesives have been suggested in various ways (Japanese Patent Laid-Open No. Hei 1-39655, Hei 4-154512), but it is not sufficient to secure adhesion with the polymethyl methacrylate-based film, and thus the bonding strength is limited.

The present invention improves adhesion with acrylic films (particularly polymethyl methacrylate films), improves poor peeling under durability conditions (high temperature or high temperature and high humidity) and at the same time improves the remaining of the adhesive during rework. It is an object to provide an adhesive composition for an acrylic film (particularly a polymethyl methacrylate film).

In order to achieve the above object, the present invention contains an acrylic copolymer containing 30 to 70 parts by weight of methyl methacrylate monomer and 100% by weight of the total monomer, does not contain a crosslinkable monomer, the weight average molecular weight of 100,000 to 500,000 It provides the adhesive composition for acrylic films containing A and a crosslinkable monomer, and containing the acrylic copolymer B which has a weight average molecular weight of 800,000-1,500,000.

Preferably, the acrylic copolymer A may have a weight average molecular weight of 200,000 to 400,000.

Preferably, the acrylic copolymer B may have a weight average molecular weight of 1 million to 120.

The acrylic copolymer A may contain 10 to 50 parts by weight based on 100 parts by weight of the acrylic copolymer B.

The pressure-sensitive adhesive composition may further contain a crosslinking agent.

In another aspect, the present invention provides a polarizing plate in which an acrylic polarizer protective film is bonded to at least one surface of the polarizer, and the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition is formed on the polarizer protective film.

The polarizer protective film may be a polymethyl methacrylate film.

The polarizing plate was cut into a size of 90 mm x 170 mm and the specimens attached to both sides of the glass substrate so that the optical absorption axes intersect with each other were allowed to stand at a temperature of 80 ° C. for 1000 hours, and then less than five bubbles or peelings could occur. have.

The polarizing plate was cut into a size of 90 mm x 170 mm and the specimens attached to both sides of the glass substrate so that the optical absorption axes intersect with each other were allowed to stand for 1000 hours at a temperature of 60 ° C. and 90% RH, and then bubbles or peeling occurred. May be less than five.

The pressure-sensitive adhesive composition of the present invention has an advantage of improving adhesion strength and reworkability under severe conditions (high temperature or high temperature and high humidity) by improving adhesion by interacting at an interface of an acrylic film (particularly polymethyl methacrylate film). There is this.

In addition, the pressure-sensitive adhesive composition of the present invention has the advantage of suppressing the deterioration of coating uniformity due to the use of an acrylic copolymer containing a methyl methacrylate monomer.

The present invention relates to an adhesive composition and a polarizing plate excellent in durability and reworkability.

Hereinafter, the present invention will be described in detail.

In order that the adhesive composition for acrylic films of this invention may achieve the said objective, this invention contains 30-70 weight part of methyl methacrylate monomers with respect to 100 weight part of total monomers, and does not contain a crosslinkable monomer, and a weight average It contains an acrylic copolymer A having a molecular weight of 100,000 to 500,000 and a crosslinkable monomer, and contains an acrylic copolymer B having a weight average molecular weight of 700,000 to 1.50,000.

The adhesive composition of this invention mixes and uses a crosslinkable, high molecular weight acrylic copolymer, and the non-crosslinkable, low molecular weight, acrylic copolymer containing a methyl methacrylate monomer. At this time, the low molecular weight acrylic copolymer moves to the base surface of the acrylic film (particularly PMMA film), and improves adhesion to the film by strong interaction with the film surface, thereby improving adhesion durability under severe conditions (high temperature or high temperature and high humidity). Reworkability is improved at the same time.

In addition, the pressure-sensitive adhesive composition of the present invention may be reduced in uniformity during coating by the methyl methacrylate-containing acrylic copolymer used for improving the interfacial adhesion with the acrylic film. Thus, by adjusting the content of the methyl methacrylate and the molecular weight of the copolymer, the coating uniformity was improved.

The acrylic copolymers A and B each contain a (meth) acrylate monomer having an alkyl group having 1 to 12 carbon atoms as a main monomer, and the double acrylic copolymer A has a (meth) acrylate monomer having an alkyl group having 1 to 12 carbon atoms and Methyl methacrylate monomer is included as an essential monomer component.

Here, (meth) acrylate means acrylate and methacrylate, and the content of each component is based on solid content.

Examples of the (meth) acrylate monomer having an alkyl group having 1 to 12 carbon atoms include (meth) acrylates derived from aliphatic alcohols having 1 to 12 carbon atoms, for example methyl atrylate, ethyl acrylate, propyl acrylate, n -Butyl (meth) acrylate, 2-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, Nonyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, etc. are mentioned, These can be used individually or in mixture of 2 or more types. Among these, n-butyl acrylate, 2-ethylhexyl acrylate, or a mixture thereof is preferable.

The acrylic copolymer A may contain 30 to 70 parts by weight of methyl methacrylate monomer, preferably 40 to 60 parts by weight, based on 100 parts by weight of the total monomers. If the content is less than 30 parts by weight may be insufficient adhesion improvement effect with the acrylic film, if it exceeds 70 parts by weight lack of compatibility with the acrylic copolymer B, phase separation may occur.

Acrylic copolymer B contains the crosslinkable monomer which has a crosslinkable functional group.

The crosslinkable monomer has a function of imparting cohesive force or adhesive strength by chemical bonding with the following crosslinking agent, and examples thereof include a monomer having a hydroxy group, a monomer having a carboxyl group, a monomer having an amide group, and a monomer having a tertiary amine group. have. These can be used individually or in mixture of 2 or more types.

As a monomer which has a hydroxyl group, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate, 2-hydroxypropylene glycol (meth) acrylate, hydroxyalkylene glycol having 2 to 4 carbon atoms of an alkylene group ( Meta) acrylate, 4-hydroxybutyl vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, 7-hydroxyheptyl vinyl ether, 8-hydroxyoctyl vinyl ether, 9-hydroxynonyl Vinyl ether, 10-hydroxydecyl vinyl ether, etc. are mentioned, Among these, 4-hydroxybutyl vinyl ether is preferable.

As a monomer which has a carboxy group, Monovalent acids, such as (meth) acrylic acid and a crotonic acid; 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 with 2-3 carbon atoms of an alkyl group, Succinic anhydride ring opening adduct of hydroxyalkylene glycol (meth) acrylate with 2-4 carbon atoms of an alkylene group And a compound obtained by ring-opening addition of succinic anhydride to a caprolactone adduct of 2-hydroxyalkyl (meth) acrylate having 2 to 3 carbon atoms of an alkyl group, among which (meth) acrylic acid is preferred.

Examples of the monomer having an amide group include (meth) acrylamide, N-isopropylacrylamide, N-tert-butylacrylamide, 3-hydroxypropyl (meth) acrylamide, 4-hydroxybutyl (meth) acrylamide, 6 -Hydroxyhexyl (meth) acrylamide, 8-hydroxyoctyl (meth) acrylamide, 2-hydroxyethylhexyl (meth) acrylamide, etc. are mentioned, Among these, (meth) acrylamide is preferable.

Monomers having a tertiary amine group include N, N- (dimethylamino) ethyl (meth) acrylate, N, N- (diethylamino) ethyl (meth) acrylate, and N, N- (dimethylamino) propyl (meth ) Acrylates and the like.

It is preferable that the crosslinkable monomer of such an acrylic copolymer B is contained in 0.05-10 weight part with respect to 100 weight part of (meth) acrylate monomers which have a C1-C12 alkyl group, More preferably, it is 0.1-8 weight part. good. If the content is less than 0.05 parts by weight, the cohesive force of the pressure-sensitive adhesive may be reduced, the durability may be lowered. If the content is more than 10 parts by weight, the adhesive strength is lowered by a high gel fraction may cause problems in durability.

In addition, in addition to the monomers, other crosslinkable monomers may be further included in an amount of 40 parts by weight or less based on 100 parts by weight of the total monomers used in the preparation of the acrylic copolymer, such that the adhesive strength is not reduced.

The production method of the copolymer is not particularly limited, and may be prepared using a method such as bulk polymerization, solution polymerization, emulsion polymerization or suspension polymerization, which are 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 the polymerization, may be used.

The acrylic copolymer A has a weight average molecular weight (polystyrene equivalent, Mw) measured by gel permeation chromatography (GPC) of 100,000 to 500,000, preferably 200,000 to 400,000. When the weight average molecular weight is less than 100,000, the acrylic copolymer A containing methyl methacrylate, which is moved to the surface when mixed, may cause problems in adhesion durability such as bubble generation due to lack of cohesion between copolymers. If it exceeds, there is a lack of mobility to the surface may lack the effect of improving adhesion with the protective film (PMMA).

In addition, the acrylic copolymer B has a weight average molecular weight of 800,000 to 1.5 million, preferably 1 million to 1.2 million. If the weight average molecular weight is less than 800,000, cohesion may be insufficient and bubbles may be generated. If the weight average molecular weight exceeds 1.5 million, mura may be generated during coating due to an increase in viscosity.

In addition, it is preferable that the said acrylic copolymer A contains 10-50 weight part with respect to 100 weight part of acrylic copolymer B, Preferably it contains 20-45 weight part. If the content is less than 10 parts by weight may be insufficient adhesion improvement effect with the acrylic film, if it exceeds 50 parts by weight, the non-crosslinkable copolymer is present in a relatively excessive amount due to the lack of cohesion may cause bubbles.

The pressure-sensitive adhesive composition of the present invention may further contain a crosslinking agent.

A crosslinking agent can improve adhesiveness and durability, and can maintain the reliability and shape of an adhesive at high temperature.

The crosslinking agent may be an isocyanate type, an epoxy type, a melamine type, a peroxide type, a metal chelate type, an oxazoline type, or the like, and one or two or more kinds thereof may be used. Double isocyanate type or epoxy type is preferred.

The isocyanate type is tolylene diisocyanate, xylene diisocyanate, 2,4-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tetramethyl xylene diisocyanate, naphthalenedi Diisocyanate compounds such as isocyanate; Diisocyanate obtained from 2 moles of an adduct obtained by reacting 3 moles of a diisocyanate compound with 1 mole of a polyhydric alcohol compound such as trimethylolpropane, an isocyanurate obtained by self-condensing 3 moles of the diisocyanate compound, and 3 moles of the diisocyanate compound And polyfunctional isocyanate compounds containing three functional groups such as biuret, triphenylmethanetriisocyanate, and methylenebistriisocyanate, in which the remaining 1 mole of diisocyanate is condensed to urea.

The epoxy-based ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol di Glycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, di Glycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcin diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropanetriglycidyl ether, pentaerythritol poly Glycidyl ether, sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris (glycidyl) isocyanuric Tris (glycidoxyethyl) isocyanurate, 1,3-bis (N, N-glycidylaminomethyl) cyclohexane, N, N, N ', N'-tetraglycidyl-m- Xylylenediamine etc. are mentioned.

Examples of the melamine type include hexametholol melamine, hexamethoxymethyl melamine, hexabutoxymethyl melamine, and the like.

Such a crosslinking agent may be contained in an amount of 0.1 to 15 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the acrylic copolymer. If the content is less than 0.1 part by weight, the cohesive force may be reduced due to insufficient crosslinking degree, thereby impairing the adhesive durability and the cleavage property. If the content is more than 15 parts by weight, problems may occur in reducing residual stress due to excessive crosslinking reaction.

In addition, the pressure-sensitive adhesive composition of the present invention may further include a silane coupling agent.

The kind of the silane coupling agent is not particularly limited, and for example, vinylchlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxy Propyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, p-styryltrimethoxysilane, 3-metha Krilloxypropyl triethoxysilane, 3-methacryloxypropyl trimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyl diethoxysilane, 3-acryloxypropyl trimethoxysilane , N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropyl Methyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine, N-phenyl-3-aminopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyl Dimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanatepropyltriethoxysilane, and the like. These can be used individually or in mixture of 2 or more types.

The silane coupling agent may be included in an amount of 0 to 10 parts by weight based on 100 parts by weight of the copolymer based on the solid content, preferably 0.005 to 5 parts by weight. If the content is more than 10 parts by weight, durability may be reduced.

In addition to the above components, the pressure-sensitive adhesive composition is a tackifying resin, antioxidant, corrosion inhibitor, leveling agent, surface lubricant, dye, pigment in order to adjust the adhesion, cohesion, viscosity, modulus, glass transition temperature, etc. required according to the application It may further include additives such as antifoaming agent, filler, light stabilizer.

In addition, the present invention is characterized in that an acrylic polarizer protective film is bonded to at least one surface of the polarizer, and a polarizing plate on which the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition is formed on the polarizer protective film. At this time, the pressure-sensitive adhesive layer is formed on the opposite side of the bonding surface of the polarizer protective film.

The acrylic polarizer protective film may be preferably a polymethyl methacrylate film.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but the following examples are merely for exemplifying the present invention, and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention. It is natural that such variations and modifications fall within the scope of the appended claims.

Preparation Example: Acrylic Copolymer Preparation

Preparation Example 1 Acrylic Copolymer A

Preparation Example 1-1

After the nitrogen mixture was refluxed and a monomer mixture consisting of 50 parts by weight of n-butyl acrylate (BA) and 50 parts by weight of methyl methacrylate (MA) was added to a 1 L reactor equipped with a cooling device, a solvent 200 parts by weight of ethyl acetate (EAc) was added thereto. Then, after purging nitrogen gas for 1 hour to remove oxygen, it was maintained at 80 ℃. After the mixture was uniformly mixed, 0.07 parts by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator, and reacted for 8 hours to prepare an acrylic copolymer (weight average molecular weight of about 350,000).

Preparation Examples 1-2 to 1-7 and Comparative Preparation Examples 1-1 to 1-2

In the same manner as in Preparation Example 1-1, but mixed and reacted to the composition of Table 1 to prepare an acrylic copolymer.

TABLE 1

Preparation Example 2 Acrylic Copolymer B

97 parts by weight of n-butyl acrylate (BA), 1 part by weight of acrylic acid (AA), 4-hydroxybutyl acrylate (4-HBA) in a 1 L reactor equipped with a refrigeration system for easy reflux of nitrogen gas ) After adding a monomer mixture consisting of 0.5 parts by weight, 100 parts by weight of ethyl acetate (EAc) was added as a solvent. Then, after purging nitrogen gas for 1 hour to remove oxygen, it was maintained at 80 ℃. After the mixture was uniformly mixed, 0.07 parts by weight of azobisisobutyronitrile (AIBN) was added as a reaction initiator, and reacted for 8 hours to prepare an acrylic copolymer (a weight average molecular weight of about 1 million).

Preparation Examples 2-2 to 2-6 and Comparative Preparation Examples 2-1 to 2-2

In the same manner as in Preparation Example 2-1, but mixed and reacted to the composition of Table 2 to prepare an acrylic copolymer.

TABLE 2

Example 1-16 and Comparative Example 1-6

1) Adhesive Composition

The acrylic copolymer, the crosslinking agent, and the silane coupling agent of Preparation Example 1 and Preparation Example 2 were mixed in the composition of Table 3 below, and then diluted to a concentration of 20% by weight in consideration of coating properties to prepare an adhesive composition.

TABLE 3

2) polarizer with adhesive

The pressure-sensitive adhesive composition prepared in 1) was applied on a release film coated with a silicone release agent to have a thickness of 25 μm, and dried at 100 ° C. for 1 minute, 5 minutes, and 10 minutes, respectively, to form an adhesive layer.

On the pressure-sensitive adhesive layer, a polarizing plate having a polymethyl methacrylate protective film laminated on both surfaces of the polarizer was laminated to prepare a polarizing plate with pressure-sensitive adhesive. At this time, the protective film surface and the adhesive layer was laminated so as to contact. The prepared polarizing plate was stored under curing conditions at 23 ° C. and 60% RH.

Test Example

The physical properties of the pressure-sensitive adhesive polarizing plate prepared in Examples and Comparative Examples were measured by the following method, and the results are shown in Table 4 below.

1. Durability (heat and moisture resistant)

The prepared pressure-sensitive adhesive polarizing plate was cut to a size of 90 mm x 170 mm, the release film was peeled off, and the specimens were prepared by attaching the optical absorption axis perpendicular to both surfaces of the glass substrate (110 mm x 190 mm x 0.7 mm). At this time, the applied pressure was 5kg / ㎠ and the clean room work so as not to generate bubbles or foreign matter. The heat resistance characteristics were observed whether bubbles or peeling occurred after 1000 hours at 80 ℃ temperature, and the heat-resistant characteristics were bubbles or peeling after 1000 hours at 60 ℃ temperature and 90% RH conditions Was observed. At this time, it was observed after leaving for 24 hours at room temperature immediately before evaluating the state of the specimen.

<Evaluation Criteria>

Ⓞ: No bubbles or peeling.

○: bubble or peeling <5 pieces

△: 5 ≤ air bubbles or exfoliation <10

×: 10 ≤ air bubbles or peeling

××: air bubbles or peeling off the entire surface

2. Reworkability

The polarizing plate was cut out to a width of 25 mm and a length of 100 mm, the release film was peeled off, and then laminated to Corning's # 1737 glass at a pressure of 0.25 MPa, and the autoclave was treated at 5 atmospheres and 50 ° C. for 20 minutes. Evaluation samples were prepared. After putting in a 50 ℃ oven was taken out after 5 hours and left at room temperature for 120 hours, it was peeled off at a rate of 1.3 cm / s. In addition, after being put into an oven at 60 ° C. and 90 RH% of humidity conditions, it was taken out after 4 hours and left at room temperature for 120 hours, followed by peeling at a speed of 1.3 cm / s.

<Evaluation Criteria>

-In both conditions, there is no adhesive left on the glass substrate and peeling off without tearing of the polarizing plate: ○

The adhesive remains on the panel under more than one condition or the polarizer is torn during the peeling process: ×

3. Coating uniformity

The prepared pressure-sensitive adhesive polarizing plate was cut into a size of 90 mm x 170 mm, the release film was peeled off, and then adhered to one surface of a glass substrate (110 mm x 190 mm x 0.7 mm). Uniformity was confirmed.

<Evaluation Criteria>

No unevenness of the adhesive is observed by the reflected light: ○

Non-uniformity of the adhesive is observed by reflecting light but dimly observed: △

-When observed by reflecting light, orange peel-shaped nonuniformity caused by non-uniformity of adhesive is observed: ×

TABLE 4

As shown in Table 4, the pressure-sensitive adhesive composition of Examples 1 to 16 according to the present invention is excellent in adhesion durability and rework resistance, such as heat and moisture resistance when bonding to the acrylic film compared to Comparative Examples 1 to 6 at the same time, uniform It was confirmed that one coatability was shown.

Claims (9)

1. Acrylic copolymer A containing 30 to 70 parts by weight of methyl methacrylate monomer and containing no crosslinkable monomer with respect to 100 parts by weight of the total monomers, and having a weight average molecular weight of 100,000 to 500,000, and

   An adhesive composition for acrylic films containing a crosslinkable monomer and containing an acrylic copolymer B having a weight average molecular weight of 800,000 to 1.5 million.
2. The pressure-sensitive adhesive composition for acrylic film of claim 1, wherein the acrylic copolymer A has a weight average molecular weight of 200,000 to 400,000.
3. The pressure-sensitive adhesive composition for acrylic film of claim 1, wherein the acrylic copolymer B has a weight average molecular weight of 1 million to 1.2 million.
4. The pressure-sensitive adhesive composition for acrylic film according to claim 1, wherein the acrylic copolymer A contains 10 to 50 parts by weight based on 100 parts by weight of the acrylic copolymer B.
5. The pressure-sensitive adhesive composition for acrylic film according to claim 1, wherein the pressure-sensitive adhesive composition further contains a crosslinking agent.
6. An acrylic polarizer protective film is bonded to at least one surface of the polarizer, and a polarizing plate having an adhesive layer containing the pressure-sensitive adhesive composition of any one of claims 1 to 5 on the polarizer protective film.
7. The polarizer of claim 6, wherein the polarizer protective film is a polymethyl methacrylate film.
8. The method according to claim 6, wherein the polarizing plate is cut to a size of 90mm x 170mm and the specimens attached to both sides of the glass substrate so that the optical absorption axis intersect with each other, left for 1000 hours at a temperature of 80 ℃ after generation of bubbles or peeling There are less than five polarizing plates.
9. The method of claim 6, wherein the polarizing plate is cut to a size of 90mm x 170mm and the specimens attached to both sides of the glass substrate so that the optical absorption axis cross each other, and left for 1000 hours under a temperature of 60 ℃ and 90% RH conditions The polarizing plate whose generation | occurrence | production of a bubble and peeling is less than five.