KR101202532B1 - Acrylic pressure-sensitive adhesive composition - Google Patents

Abstract

The present invention relates to an acrylic pressure-sensitive adhesive composition, more specifically, an acrylic copolymer (A) containing a crosslinkable functional group-containing monomer and a copolymer (B) having no crosslinkable functional group in a ratio of 1: 9 to 5: 5. The pressure-sensitive adhesive composition which can improve the light leakage phenomenon due to warpage while providing excellent durability and cutting property due to the compact crosslinking structure by allowing the pressure of the pressure-sensitive adhesive used for the polarizing plate to be mixed at a constant load of 200 μm to 600 μm by mixing with will be.

Acrylic adhesive, pushed distance, polarizer, liquid crystal display device

Description

Acrylic pressure-sensitive adhesive composition {Acrylic pressure-sensitive adhesive composition}

The present invention relates to an acrylic pressure-sensitive adhesive composition, more specifically, an acrylic copolymer (A) containing a crosslinkable functional group-containing monomer and a copolymer (B) having no crosslinkable functional group in a ratio of 1: 9 to 5: 5. The pressure-sensitive adhesive composition which can improve the light leakage phenomenon due to warpage while providing excellent durability and cutting property due to the compact crosslinking structure by allowing the pressure of the pressure-sensitive adhesive used for the polarizing plate to be mixed at a constant load of 200 μm to 600 μm by mixing with will be.

In general, in order to manufacture a liquid crystal display device, a liquid crystal cell and a polarizing plate including a liquid crystal are basically required, and an appropriate adhesive layer or adhesive layer for bonding them should be used. In addition, in order to improve the function of the liquid crystal display, a retardation plate, a wide viewing angle compensation plate, or a brightness enhancement film may be additionally attached to the polarizing plate.

The main structure for forming the liquid crystal display device includes a liquid crystal layer that is constantly arranged; A polarizing plate having a multi-layered structure integrated with an adhesive layer or an adhesive layer based on a liquid crystal cell composed of a transparent glass plate or a plastic plate-like material including a transparent electrode layer; Retardation plate; And further functional film layers and the like.

At this time, the polarizing plate is a structure containing an iodine-based compound or a dichroic polarizing material arranged in a predetermined direction, in order to protect these polarizing devices by using a protective film such as a triacetyl cellulose (TAC) -based on both sides It is made up. In addition, the polarizing plate may additionally include a wide viewing angle compensation film such as a retardation film having a unidirectional molecular arrangement, a liquid crystal film, a brightness enhancement film, a reflective layer, or a flame retardant layer.

Each of the films has different physical properties because they are made of materials having different molecular structures and compositions. In particular, under thermal or wet heat conditions, dimensional stability due to shrinkage or expansion of materials with unidirectional molecular arrangements is lacking.

Twisted Nematic (TN) type or Super Twisted Nematic (STN) type liquid crystal display system generally attaches the optical axis of the polarizing plate at 45 ° and 135 ° on both sides of the liquid crystal panel. In the liquid crystal display method, when the polarizing plate is fixed by an adhesive, deformation stress due to a heat or wet heat environment remains. As a result, light leakage occurs in a portion where stress is concentrated.

However, liquid crystal displays such as IPS (In-Plane Switching) or VA (Vertical Alignment), which are mainly used in large-sized TVs, attach and attach optical axes of polarizing plates at both 0 ° and 90 ° to both sides of the liquid crystal panel. Such liquid crystal displays also generate light leakage due to stress concentration in a heat or moist heat environment, but the bending of the liquid crystal panel is known as an important cause of light leakage. The warpage of the liquid crystal panel is caused by a difference in shrinkage of the polarizing plate depending on the position (especially in the direction of stretching axis) under heat or wet heat conditions. That is, the TN or STN liquid crystal display device crosses and attaches the optical axis of the polarizing plate at 45 ° and 135 ° so that the stretching axis directions of the upper and lower polarizing plates are symmetrically or balanced, whereas the liquid crystal display device such as IPS or VA is Since the optical axes of the polarizing plates cross each other at 1 ° and 90 °, the direction of stretching axes of the upper and lower polarizing plates is asymmetrical. Therefore, in the liquid crystal display device such as IPS or VA, the warpage of the liquid crystal panel is generated in a direction in which the warpage is large because the warpage by the upper polarizer and the warpage by the lower polarizer are different. Due to the bending of the liquid crystal panel, the liquid crystal panel is pressed by the top case used to fix the liquid crystal panel, which causes light leakage due to non-uniformity of the liquid crystal. However, since the degree of warpage varies depending on the conditions of heat or wet heat, there are many technical difficulties in reducing the warpage of the panel itself by similarly adjusting the warpage of the upper and lower polarizers, respectively.

In Korean Patent Laid-Open Publication No. 10-2006-0060264, the upper polarizing plate and the lower polarizing plate include respective adhesive layers, and the adhesive layer of the upper polarizing plate and the adhesive layer of the lower polarizing plate have different adhesive strengths according to the bending direction of the liquid crystal panel. It has been disclosed that the warpage phenomenon can be improved by providing a liquid crystal display device. However, this method is difficult to improve by controlling the degree of warpage of the upper and lower polarizers according to the environment (heat or wet heat conditions).

Therefore, rather than adjusting the warpage of the upper and lower polarizers separately, the warpage of the upper and lower polarizers should be designed to be small under all heat or wet heat conditions, respectively. In order to solve this problem, there is a need for a method of reducing warpage by reducing stress applied to a polarizer in a heat or wet heat environment.

Japanese Patent Application Laid-Open No. 2006-58718 is for polarizing plates having a storage modulus of 10 ⁵ to 10 ⁹ Pa at 0-50 ° C. and a glass transition temperature of -20 ° C. or higher after crosslinking in order to suppress light leakage in liquid crystal display devices such as IPS and MVA methods. By providing an adhesive, it has been disclosed that this can be achieved by making the elastic modulus and glass transition temperature of the adhesive higher than before. However, this does not mention the improvement of the warpage of the liquid crystal panel of the IPS and MVA methods, and it is difficult to improve the light leakage caused by the warpage of the liquid crystal panel by this method.

As a method for reducing such stress, there is a method of imparting fluidity by adding a plasticizer or a low molecular weight body, but this may have a problem of significantly impairing the performance of the adhesive due to their surface transition characteristics.

In addition, there is a method of controlling the crosslinking density by adjusting the content of the crosslinking agent, which may result in weak durability and cutability if reducing the crosslinking density to improve the warpage.

Japanese Patent Application Laid-Open No. 60-207101 An acrylic copolymer (A) containing a crosslinkable functional group, an acrylic copolymer (B) not containing a crosslinkable functional group and a multifunctional crosslinking agent of two or more functional groups are mixed to obtain The technique which manufactures an adhesive in the area | region of a weight ratio 1 / 4-4 / 1 is disclosed. However, this patent shows the technical idea of excellent long-term storage property of the polarizing plate manufactured by adding a corresponding amount of polyfunctional crosslinking agent to the amount of crosslinkable functional groups at the time of crosslinking so as not to leave free functional groups. The technical idea of the condition for the crosslinked structure and the technical structure of the crosslinked structure is not expressed, and in particular, the technical idea of the stress relaxation property of the pressure-sensitive adhesive related to warpage is not described.

Therefore, the new polarizer pressure sensitive adhesive which can improve the light leakage phenomenon due to the bending of the liquid crystal panel with little change in the main characteristics of the polarizing plate products such as durability, cutability, etc., which can occur not only in heat or wet heat conditions but also in long-term use. The need for the development and development of polarizers using the same is urgently needed.

In order to solve the conventional problems as described above, an object of the present invention is to adjust the crosslinking density of the acrylic pressure-sensitive adhesive for polarizing plate excellent in the durability and cutting properties under high temperature and high humidity conditions, to improve the light leakage phenomenon due to bending It is to provide a composition.

Another object of the present invention is to provide a polarizing plate including a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition having the above excellent physical properties.

Still another object of the present invention is to provide a liquid crystal display device including the polarizing plate.

In order to achieve the above object,

A crosslinkable acrylic copolymer (A) having a weight average molecular weight of 1 million or more containing a (meth) acrylic acid ester monomer and a crosslinkable functional group-containing monomer; And

A non-crosslinkable acrylic copolymer (B) having a weight average molecular weight of at least 1 million containing a (meth) acrylic acid ester monomer, wherein the mixing ratio of the acrylic copolymers (A) and (B) is 1: 9 to 5: 5,

The adhesive composition which satisfy | fills the conditions of the following general formula 1 is provided.

[Formula 1]

ΔX = 200 μm to 600 μm

Where

ΔX represents the pushed distance of the pressure-sensitive adhesive when the polarizing plate having the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition is attached to the glass plate with an adhesive area of 1 cm × 1 cm, and then a 1000 gf load is applied at room temperature for 1000 seconds.

The invention also polarizing film; And a pressure-sensitive adhesive layer formed on one or both surfaces of the film and containing the pressure-sensitive adhesive composition according to the present invention.

The present invention also provides a liquid crystal display device wherein the polarizer includes a liquid crystal panel bonded to one or both surfaces of the liquid crystal cell.

In the pressure-sensitive adhesive composition of the present invention, the crosslinkable polymer of the acrylic copolymer forms a dense crosslinked structure, and the non-crosslinkable polymers are connected to each other to the crosslinked structure to satisfy durability and fluidity, thereby resulting in durability that can occur under high temperature and high humidity conditions. And it is excellent in cutting property, and can improve the light leakage phenomenon by the curvature of a liquid crystal panel.

EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention is demonstrated concretely.

The present inventors solve the shortcomings of the prior art in which durability is weakened by adding a low molecular weight to the high molecular weight or adjusting the crosslinking agent content so that the non-crosslinked portion of the pressure-sensitive adhesive is larger than the crosslinked portion in improving light leakage caused by bending. To this end, the mixing ratio is 1: 9 to 5: 5 so that the content of the acrylic copolymer (A) of the high molecular weight having a crosslinkable functional group is smaller than that of the acrylic copolymer (B) of the high molecular weight having no crosslinkable functional group. In the case of specifying the distance pushed under a certain load, the light leakage caused by the bending can be reduced, and the durability and the cutting property are excellent even though the crosslinking density is small.

Therefore,

A crosslinkable acrylic copolymer (A) having a weight average molecular weight of 1 million or more containing a (meth) acrylic acid ester monomer and a crosslinkable functional group-containing monomer; And

A non-crosslinkable acrylic copolymer (B) having a weight average molecular weight of at least 1 million containing a (meth) acrylic acid ester monomer, wherein the mixing ratio of the acrylic copolymers (A) and (B) is 1: 9 to 5: 5,

The adhesive composition which satisfy | fills the conditions of the following general formula 1 is provided.

[Formula 1]

ΔX = 200 μm to 600 μm

In the above formula, ΔX represents the pushed distance of the pressure-sensitive adhesive when the polarizing plate on which the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition is formed is attached to a glass plate with an adhesive area of 1 cm × 1 cm, and a 1000 gf load is applied at room temperature for 1000 seconds.

In the pressure-sensitive adhesive composition according to the present invention, each component is specified by the following.

a) acrylic copolymer

The acrylic copolymer is not particularly limited as long as it is commonly used as an adhesive in the art,

Crosslinkable acrylic copolymer (A) containing a (meth) acrylic acid ester monomer and a crosslinkable functional group-containing monomer; And

It is preferable that the non-crosslinkable acrylic copolymer (B) containing a (meth) acrylic acid ester monomer is included.

Each of the acrylic copolymers (A) and (B) may use an alkyl ester having 1 to 12 carbon atoms of acrylic acid (or methacrylic acid) as the (meth) acrylic acid ester monomer. When the carbon number of the alkyl is out of the above range, in particular, when the alkyl group is in a long chain form, since the cohesive force of the pressure-sensitive adhesive is lowered, it is preferable to use an alkyl ester having 2 to 8 carbon atoms of acrylic acid (or methacrylic acid) to maintain cohesive force at high temperatures. desirable.

As the (meth) acrylic acid ester monomer, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, t-butyl (meth) acrylate, n -Butyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate Or isononyl (meth) acrylate etc. can be used individually or in mixture of 2 or more types.

As for the (meth) acrylic acid ester monomer which has the said C1-C12 alkyl group, it is preferable that an acryl-type copolymer (A) is contained in 90 to 99.9 weight part with respect to 100 weight part. When the content of the (meth) acrylic acid ester monomer is less than 90 parts by weight, there is a problem that the initial adhesive strength is lowered, and when it exceeds 99.9 parts by weight, there is a problem that durability may occur due to the decrease in cohesion.

In addition, the acrylic copolymer (A) includes a crosslinkable functional group-containing monomer, and reacts with the multifunctional crosslinking agent to impart cohesive force or adhesive strength by chemical bonding so that cohesive breakage of the adhesive does not occur under high temperature or high humidity conditions. do.

As for the said crosslinkable functional group containing monomer, a hydroxyl group containing monomer, a carboxyl group containing monomer, or its anhydride is preferable. The crosslinkable functional group-containing monomer is 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acryl Latex, 3-hydroxypropylene glycol (meth) acrylate, acrylic acid, methacrylic acid, acrylic acid duplex, itaconic acid, maleic acid and maleic anhydride, and the like.

The crosslinkable functional group-containing (meth) acrylic acid ester monomer or vinyl monomer is preferably included in an amount of 0.1 to 10 parts by weight based on the acrylic copolymer (A), and when the content is less than 0.1 part by weight, high temperature or high humidity conditions. There is a problem that the cohesive failure is easy to occur under the following conditions, and the effect of improving the adhesive strength is lowered. When the content exceeds 10 parts by weight, the compatibility decreases, causing the surface migration to occur severely. There is a problem that the deterioration.

In addition, the present invention preferably includes a comonomer having a high glass transition temperature as an optional component in order to control the glass transition temperature of the pressure-sensitive adhesive or to impart other functionality when preparing the acrylic copolymer.

The comonomer is a monomer having a vinyl group which can be copolymerized in general, and is preferably a compound represented by the following Formula (1).

[Formula 1]

Where

R ₁ represents hydrogen or alkyl,

R ₂ is cyano; Phenyl unsubstituted or substituted with alkyl; Acetyloxy; Or COR ₃ , wherein R ₃ represents amino or glycidyloxy unsubstituted or substituted with alkyl or alkoxy having 1 to 4 carbon atoms.

The vinyl monomer may be used alone or in combination of two or more of acrylonitrile, (meth) acrylamide, N-methyl (meth) acrylamide, styrene, methyl styrene, glycidyl (meth) acrylate or vinyl acetate. Can be.

When the amount of the vinyl group-containing monomer in the acrylic copolymer is too large, the flexibility of the pressure-sensitive adhesive composition is lowered and the peeling force is lowered, so that it is preferably used at 20 parts by weight or less in the total monomer components.

In the pressure-sensitive adhesive composition of the present invention, the acrylic copolymers (A) and (B) may be prepared by conventional methods such as solution polymerization, photopolymerization, bulk polymerization, suspension polymerization, or emulsion polymerization, respectively. In particular, it is preferable to prepare by solution polymerization method. At this time, the polymerization temperature is 50 ~ 140 ℃, it is good to mix the initiator in a state in which monomers are uniformly mixed.

Such a polymerization initiator is preferably used alone or in combination with an azo polymerization initiator such as azobisisobutyronitrile and azobiscyclohexanecarbonitrile and peroxides such as benzoyl peroxide and acetyl peroxide.

In addition, in order to obtain a low molecular weight, a chain transfer agent such as mercaptans such as lauryl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan and alpha methyl styrene dimer may be used simultaneously with the polymerization initiator.

Moreover, it is preferable that the weight average molecular weights of the acrylic copolymers (A) and (B) of this invention are 1 million or more, respectively, More preferably, it is 1 million-2 million. If the weight average molecular weight is 1 million or less, the cohesive force may be insufficient, which may cause a problem in the durability reliability due to bubbles or peeling under high temperature and high humidity conditions, and in the case of 2 million or more, it is not possible to relax the stress concentration.

Further, in the pressure-sensitive adhesive composition of the present invention, the mixing ratio of the acrylic copolymers (A) and (B) is preferably 1: 9 to 5: 5, which improves light leakage due to warpage, and at the same time, is excellent in durability and cutability. . If the non-crosslinkable polymer is more than the crosslinkable polymer, even if the crosslinking density is low, the crosslinkable polymer forms a relatively dense crosslinked structure. Because it satisfies. When the mixing ratio of the copolymers (A) and (B) is 1: 9 or less, that is, when the content of the copolymer (A), which is a crosslinkable polymer, is small, the cohesive force decreases and the durability and breakability are weak, and the copolymer ( When the mixing ratio of A) and (B) is 5: 5 or more, that is, the content of the crosslinkable polymer is increased, the fluidity of the non-crosslinked polymer is relatively decreased, so that light leakage due to warpage cannot be improved.

b) Crosslinking agent

The adhesive composition of this invention which consists of such a component as mentioned above can use a polyfunctional crosslinking agent further as needed. The multifunctional crosslinker reacts with the functional group of the acrylic copolymer to increase the cohesion of the adhesive.

The polyfunctional crosslinking agent may be used singly or in combination of isocyanate compound, epoxy compound, aziridine compound or metal chelate compound.

The isocyanate compound is toluene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoform diisocyanate, tetramethyl xylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, methylene bis ( Reaction products with polyols, such as 4-phenylmethane) triisocyanate or these trimethylol propane, etc. can be used.

The epoxy compound is ethylene glycol diglycidyl ether, triglycidyl ether, trimethylol propane triglycidyl ether, N, N, N ', N'- tetraglycidyl ethylenediamine, or glycerin diglycidyl ether Etc. can be used.

The aziridine-based compound is N, N'-toluene-2,4-bis (1-aziridinecarboxide), N, N'-diphenylmethane-4,4'-bis (1-aziridinecarboxide) ), Triethylene melamine, or tri-1-aziridinylphosphine oxide.

The metal chelate compound may be a compound in which a polyvalent metal such as aluminum, iron, zinc, tin, titanium, antimony, magnesium, or vanadium is coordinated with acetylacetone or ethyl acetoacetate.

The multifunctional crosslinking agent may be uniformly coated only when the functional group crosslinking reaction of the crosslinking agent hardly occurs in the compounding process for forming the adhesive layer. After the coating operation is finished and the drying and aging process, a cross-linked structure is formed to obtain an elastic adhesive layer having a strong cohesive force. At this time, the adhesiveness and cutting property such as durability of the pressure-sensitive adhesive product is improved by the strong cohesive force of the pressure-sensitive adhesive.

The multifunctional crosslinking agent is preferably included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the acrylic copolymer (A) and (B), and when the content is within the above range, the cohesive force of the pressure-sensitive adhesive is excellent, and There is no problem in adhesion durability such as peeling, there is no effect such as lifting does not occur, there is an effect that the durability is excellent.

c) additives

The pressure-sensitive adhesive composition of the present invention comprising the above components may further use a silane coupling agent or a pressure-sensitive adhesive resin as necessary.

The silane coupling agent serves to improve the heat resistance and moisture resistance by improving the adhesion stability when the acrylic pressure-sensitive adhesive is bonded to the glass plate. In particular, the silane coupling agent serves to help improve adhesion reliability when left for a long time under high temperature and high humidity.

The silane coupling agent is γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyl Trimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxy Silane, 3-isocyanate propyl triethoxysilane, or gamma -acetoacetate propyl trimethoxysilane, etc. can be used individually or in mixture of 2 or more types.

The silane coupling agent is preferably included in an amount of 0.005 to 5 parts by weight with respect to 100 parts by weight of the acrylic copolymer (A) and (B), and when the content is within the above range, it is necessary to improve adhesion stability and adhesion reliability under high temperature and high humidity. It's even better.

On the other hand, the pressure-sensitive adhesive resin serves to adjust the adhesive performance of the acrylic pressure-sensitive adhesive.

The tackifying resins include (hydrogenated) hydrocarbon resins, (hydrogenated) rosin papers, (hydrogenated) rosin ester resins, (hydrogenated) terpene resins, (hydrogenated) terpene phenol resins, polymerized rosin resins, or polymerized rosin ester resins, and the like. It can be used individually or in mixture of 2 or more types.

The pressure-sensitive adhesive resin is preferably contained in an amount of 1 to 100 parts by weight with respect to 100 parts by weight of the acrylic copolymer (A) and (B), and when the content is in the above range, it is better in improving the compatibility and cohesion of the pressure-sensitive adhesive. .

In addition, the acrylic pressure-sensitive adhesive composition of the present invention may further use additives such as an acrylic low molecular weight, an epoxy resin, a curing agent, an ultraviolet stabilizer, an antioxidant, a colorant, a reinforcing agent, a filler, an antifoaming agent, a surfactant, or a plasticizer.

The acrylic pressure-sensitive adhesive composition of the present invention composed of the above components can be prepared according to a conventional method, and of course, can be produced by methods such as thermosetting or photocuring.

The invention also polarizing film; And

It is provided on one side or both sides of the film, and provides a polarizing plate comprising an adhesive layer containing the pressure-sensitive adhesive composition according to the present invention.

The polarizing film constituting the polarizing plate is not particularly limited. For example, the polarizing film may be a film made by containing a polarizing component such as iodine or dichroic dye in a polyvinyl alcohol-based resin and stretching the film. In addition, the thickness of these polarizing films is also not particularly limited, and may form a conventional thickness. At this time, the polyvinyl alcohol-based resin may be polyvinyl alcohol, polyvinyl formal, polyvinyl acetal and ethylene, or saponified vinyl acetate copolymer.

On both sides of the polarizing film, a cellulose film such as triacetal cellulose; Polyester film such as polycarbonate film or polyethylene terephthalate; Polyethersulfone-based films; Polyethylene, polypropylene, polyolefin-based films having a cyclo or norbornene structure; Or a multilayer film etc. which laminated | stacked protective films, such as a polyolefin type film like ethylene propylene copolymer, can be formed. At this time, the thickness of these protective films is also not particularly limited, and may form a conventional thickness.

The method of forming the pressure-sensitive adhesive layer on the polarizing film as described above is not particularly limited, and for example, a method of applying and drying the pressure-sensitive adhesive using a bar coater or the like directly on the surface of the polarizing film, or applying the pressure-sensitive adhesive to the surface of the peelable substrate After drying and drying, a method of transferring and aging the pressure-sensitive adhesive layer formed on the surface of the peelable substrate to the polarizing film may be applied.

In addition, in the polarizing plate of the present invention as described above, one or more layers that provide additional functions such as a protective layer, a reflective layer, an antiglare layer, a retardation plate, a wide viewing angle compensation film, or a brightness enhancement film may be stacked. The adhesive layer may also be formed on the functional layer.

The present invention also provides a liquid crystal display device comprising a liquid crystal panel in which the polarizing plate is bonded to one side or both sides of a liquid crystal cell.

The polarizing plate to which the pressure-sensitive adhesive of the present invention is applied can be applied to any conventional liquid crystal display device, and the kind of the liquid crystal panel is not particularly limited. Preferably, the liquid crystal display device may include a liquid crystal panel obtained by bonding the pressure sensitive adhesive polarizer to one side or both sides of the liquid crystal cell.

As described above, the pressure-sensitive adhesive composition of the present invention is excellent in durability and cutting properties that may occur under high temperature and high humidity conditions, and may have an effect of improving light leakage due to warpage of the liquid crystal panel.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples. It will be apparent to those skilled in the art that various modifications and variations are possible within the scope of the present disclosure, and such modifications and variations belong to the appended claims.

Preparation Example 1 Preparation of Acrylic Copolymer A-1

A monomer mixture consisting of 98.1 parts by weight of n-butyl acrylate (BA) and 1.9 parts by weight of hydroxyethyl methacrylate (2-HEMA) was added to a 1 L reactor equipped with a refrigeration system for easy reflux of nitrogen gas. Then, 100 parts by weight of ethyl acetate (EAc) was added as a solvent. Next, after purging nitrogen gas for 1 hour to remove oxygen, it was maintained at 62 ℃. After the mixture was homogeneous, 0.03 parts by weight of azobisisobutyronitrile (AIBN) diluted to 50% concentration in ethyl acetate was added as a reaction initiator, and reacted for 8 hours to prepare an acrylic copolymer.

Preparation Example 2 Manufacture of Acrylic Copolymers A-2 to B-3

The acrylic copolymer A-1 was prepared in the same manner as in the preparation of the acrylic copolymer A-1, except that the components and composition ratios of Table 1 were used. At this time, the unit of Table 1 is a weight part.

Acrylic copolymer manufacturers division A-1 A-2 A-3 B-1 B-2 B-3 Acrylic Copolymer Composition n-BA 98.1 72.3 98.0 100 74.6 100 EA 22.3 25.4 AA 5.1 0.5 2-HEMA 1.9 0.3 1.5 AIBN 0.03 0.03 0.03 0.03 0.03 0.03 n-DDM 1.5 Weight average molecular weight (only) 180 120 160 160 120 10 n-DDM: n-dodecyl mercaptan
n-BA: n-butyl acrylate
EA: ethyl acrylate
AA: acrylic acid
2-HEMA: 2-hydroxyethyl methacrylate
AIBN: azobisisobutyronitrile

≪ Example 1 >

(Mixing process)

After mixing 20 parts by weight of the acrylic copolymer A-1 prepared above and 80 parts by weight of the acrylic copolymer B-1 uniformly, 0.2 parts by weight of tolylene diisocyanate adduct (TDI-1) of isocyanate trimethylolpropane as a crosslinking agent. After mixing, diluting to a proper concentration and uniformly mixing, coating on a release paper and drying, to prepare a uniform adhesive layer of 25㎛.

 (Plywood process)

The pressure-sensitive adhesive layer prepared above was adhesively processed on the polarizing plate. The obtained polarizing plate was cut | disconnected to the appropriate magnitude | size, and was used for evaluation, The result of having performed the following evaluation about the polarizing plate to which the said adhesive was applied is shown in Table 2.

(Property evaluation)

Using the polarizing plate prepared above, the pushed distance, durability, cutting property, and light leakage of the pressure-sensitive adhesive were measured by the following method, and the results are shown in Table 2.

(Pulled distance measurement)

The distance the pressure-sensitive adhesive was pushed while the upper or lower polarizer with the pressure-sensitive adhesive prepared above was attached to a glass plate with a 25 μm adhesive surface in 1 cm × 1 cm, and then maintained at 1000 gf load for 1000 seconds after aging at room temperature for 24 hours ( Μm) was measured.

(Durability assessment)

The pressure-sensitive adhesive coated polarizing plate (90 mm × 170 mm) prepared in Example 1 was attached to a glass substrate (110 mm × 190 mm × 0.7 mm) in a state where the optical absorption axis was crossed on both sides. At this time, the applied pressure was about 5㎏ / ㎠ to clean the room so that no bubbles or foreign matter. The specimens were left for 1000 hours at 60 ° C. and 90% relative humidity to observe the heat and moisture resistance. The heat resistance was observed for 1000 hours at the temperature of 80 ℃ after the occurrence of bubbles or peeling. Immediately after evaluating the state of the specimen was performed at room temperature for 24 hours. The evaluation criteria for reliability are as follows.

○: no bubbles or peeling

△: slight bubble or peeling phenomenon

×: large amount of bubbles and peeling phenomenon

(Cutability evaluation)

The polarizing plate to which the pressure-sensitive adhesive was applied was subjected to a cleavage test using Thomson Carter. The cut section of the adhesive layer was observed and evaluated according to the following criteria.

(Circle): The adhesive residue of a cut surface and the grade which the adhesive slipped out are favorable (less than 0.2 mm)

(Triangle | delta): The grade which the adhesive residue of the cut surface and the adhesive fell out to some extent (0.2 mm-0.5 mm)

X: The extent to which the adhesive residue of an cut surface and an adhesive fell out (0.5 mm or more)

(Transmission uniformity (light leakage) evaluation)

In order to investigate the uniformity of the light transmittance using the same specimen as described above, it was observed whether the light leaked out of the dark room using the backlight. As a method for testing the light transmittance uniformity, an upper polarizing plate (400 mm x 200 mm) having an adhesive coating stretching direction of 0 ° and a lower polarizing plate (400 mm x 200 mm) having an adhesive coating stretching direction of 90 ° were used. (410 mm x 210 mm x 0.7 mm) was attached to both surfaces with the optical axis intersecting. After the specimen is left at 60 ° C, 500 hours or 40 ° C, 70% RH, 500 hours, removed from room temperature, the upper polarizer is placed upwards, and the surface of the sample is pressed (similar to the top case of the liquid crystal panel). Was adopted. The uniformity of light transmittance was evaluated based on the following criteria.

○: Unevenness of light transmittance It is difficult to judge with the naked eye

△: slight light transmittance nonuniformity

X: There is much light nonuniformity phenomenon

<Examples 2-3 and Comparative Examples 1-5>

Except that the adhesive layer shown in Table 2 was used in the same manner as in Example 1. Moreover, the light leakage by the pushed distance, durability reliability, cutting property, and curvature of the adhesive using the manufactured polarizing plate was measured, and the result is shown in Table 2.

Blend Composition and Physical Properties of Acrylic Copolymer Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Copolymer
(A)
(Parts by weight) A-1 20 100 80 20 A-2 45 A-3 25 100 Copolymer
(B)
(Parts by weight) B-1 80 75 20 B-2 55 100 B-3 80 Crosslinking agent (parts by weight) 0.2 0.2 0.2 0.2 0.01 0.1 0.1 0.2 Pushed distance (㎛) 450 200 570 200 1200 -(leaving out) 400 -(leaving out) Endurance reliability ○ ○ ○ ○ × × ○ × Cutability ○ ○ ○ ○ × × ○ × Light fountain ○ ○ ○ × ○ ○ × ○

As shown in Table 2, it can be confirmed that the polarizing plates of Examples 1 to 3 according to the present invention have excellent durability, cutting property and light leakage as compared with Comparative Examples 1 to 5.

Claims (17)

A crosslinkable acrylic copolymer (A) having a weight average molecular weight of 1 million or more containing a (meth) acrylic acid ester monomer and a crosslinkable functional group-containing monomer; And A non-crosslinkable acrylic copolymer (B) having a weight average molecular weight of at least 1 million containing a (meth) acrylic acid ester monomer, wherein the mixing ratio of the acrylic copolymers (A) and (B) is 1: 9 to 5: 5, Pressure-sensitive adhesive composition satisfying the conditions of the following general formula 1: [Formula 1] ΔX = 200 μm to 600 μm Where (DELTA) X adhere | attached the polarizing plate in which the 25-micrometer-thick adhesive layer containing the said adhesive composition after crosslinking was attached to the glass plate by 1 cm x 1 cm of adhesion area, and aged for 24 hours, and after applying 1000gf load at room temperature for 1000 second, Represents the distance pushed. The method of claim 1, (Meth) acrylic acid ester monomer is methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, t-butyl (meth) acrylate, n- Butyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate And isononyl (meth) acrylate is at least one selected from the group consisting of pressure-sensitive adhesive composition. The method of claim 1, The crosslinkable functional group-containing monomer is at least one selected from the group consisting of a hydroxy group-containing monomer, a carboxyl group-containing monomer and an anhydride thereof. The method of claim 1, The crosslinkable functional group-containing monomer is 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate , At least one selected from the group consisting of 3-hydroxypropylene glycol (meth) acrylate, acrylic acid, methacrylic acid, acrylic acid duplex, itaconic acid, maleic acid and maleic anhydride. The method of claim 1, The crosslinkable functional group containing monomer is 0.1-10 weight part with respect to 100 weight part of acrylic copolymers (A), The adhesive composition characterized by the above-mentioned. The method of claim 1, The acrylic copolymer (A) or (B) further comprises a functional monomer represented by the following general formula (1): [Formula 1]

Where R ₁ represents hydrogen or alkyl, R ₂ is cyano; Phenyl unsubstituted or substituted with alkyl; Acetyloxy; Or COR ₃ , wherein R ₃ represents amino or glycidyloxy unsubstituted or substituted with alkyl or alkoxy having 1 to 4 carbon atoms. The method of claim 6, Pressure-sensitive adhesive, characterized in that the functional monomer is at least one selected from the group consisting of acrylonitrile, (meth) acrylamide, N-methyl (meth) acrylamide, styrene, methyl styrene, glycidyl (meth) acrylate and vinyl acetate Composition. The method of claim 1, The pressure-sensitive adhesive composition further comprising 0.01 to 10 parts by weight of a multifunctional crosslinking agent based on 100 parts by weight of the acrylic copolymer (A) and (B). 9. The method of claim 8, The multifunctional crosslinking agent is at least one selected from the group consisting of an isocyanate compound, an epoxy compound, an aziridine compound and a metal chelate compound. The method of claim 1, The pressure-sensitive adhesive composition further comprising 0.005 to 5 parts by weight of a silane coupling agent based on 100 parts by weight of the acrylic copolymer (A) and (B). The method of claim 1, The adhesive composition which further contains 1-100 weight part of tackifying resin with respect to 100 weight part of acrylic copolymers (A) and (B). 12. The method of claim 11, The tackifying resin is from the group consisting of (hydrogenated) hydrocarbon resin, (hydrogenated) rosin resin, (hydrogenated) rosin ester resin, (hydrogenated) terpene resin, (hydrogenated) terpene phenol resin, polymerized rosin resin and polymerized rosin ester resin Pressure-sensitive adhesive composition, characterized in that at least one selected. The method of claim 1, Pressure-sensitive adhesive composition further comprises one or more selected from the group consisting of acrylic low molecular weight, epoxy resin, curing agent, ultraviolet stabilizer, antioxidant, colorant, reinforcing agent, filler, antifoaming agent, surfactant and plasticizer. Polarizing film; And A polarizing plate formed on one side or both sides of the film, the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition according to any one of claims 1 to 13. The method of claim 14, And at least one protective film selected from the group consisting of a cellulose film, a polyester film, a polyether sulfone film and a polyolefin film on both sides of the polarizing film. The method of claim 14, A polarizing plate further comprising at least one functional layer selected from the group consisting of a protective layer, a reflective layer, an antiglare layer, a retardation plate, a wide viewing angle compensation film, and a brightness enhancement film. The liquid crystal display of claim 14, wherein the polarizing plate comprises a liquid crystal panel bonded to one or both surfaces of the liquid crystal cell.