KR20090072861A - Acrylic pressure-sensitive adhesive composition, polarizing plate and liquid crystal display device comprising the same - Google Patents

Abstract

An acrylic pressure-sensitive adhesive composition is provided to prevent the degradation of adhesion endurance and reliability which can be generated in a high temperature and high humidity condition, and to improve stress relaxation property and light leakage phenomenon by controlling crosslinking rate and structure. An acrylic pressure-sensitive adhesive composition comprises (A) a high-molecular-weight acrylic copolymer with average molecular weight of 1,500,000-2,500,000; (B) a low-molecular-weight acrylic copolymer with average molecular weight of 500,000-1,000,000; and (C) a peroxide compound. The weight ratio of (B) a low molecular weight acrylic copolymer to (A) high molecular weight acrylic copolymer is 1-4.

Description

Acrylic pressure-sensitive adhesive composition, a polarizing plate and a liquid crystal display comprising the same {Acrylic pressure-sensitive adhesive composition, polarizing plate and liquid crystal display device comprising the same}

The present invention relates to an acrylic pressure-sensitive adhesive composition for polarizing plates, and more particularly, an acrylic pressure-sensitive adhesive having excellent low-light leakage characteristics and not lowering productivity and workability without imparting a stress relaxation function without causing a decrease in durability or the like. A composition, a polarizing plate manufactured therefrom, and a liquid crystal display device.

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; And 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 triacetyl cellulose (TAC) -based protective film on both sides to form a multilayer Will be constructed. In addition, the polarizing plate may additionally include a retardation film of a shape having a unidirectional molecular array, a wide viewing angle compensation film such as a liquid crystal film.

Each of the above-mentioned films has different physical properties because they are made of materials having different molecular structures and compositions. In particular, under high temperature or high temperature and high humidity conditions, dimensional stability due to shrinkage or expansion of materials having a unidirectional molecular arrangement is insufficient. Therefore, when the polarizing plate is fixed by the pressure-sensitive adhesive, the strain stress due to shrinkage or expansion of the polarizing plate under high temperature or high temperature and high humidity conditions remains. As a result, light leakage occurs in a stress concentrated part.

In order to improve the light leakage phenomenon, it is necessary to reduce the shrinkage of the polarizer under high temperature or high temperature and high humidity conditions, but it is very difficult to remove stress generated in the liquid crystal panel with polarizers composed of materials having different physical properties. It's work.

Another method for improving the light leakage phenomenon is to give an excellent stress relaxation function to the adhesive layer fixing the polarizing plate to the liquid crystal panel.

The adhesive layer has an excellent stress relaxation function by mixing a multifunctional crosslinking agent with a high molecular weight polymer including a crosslinkable functional group and a low molecular weight polymer containing or not containing a small amount of the crosslinkable functional group, thereby misaligning the external stress (Creep). There is a method to make a quantity large and to be easy to deform | transform.

Korean Patent Publication No. 1998-079266 discloses a high molecular weight acrylic copolymer having a weight average molecular weight of 1 million or more; Low molecular weight acrylic copolymers having a weight average molecular weight of 30,000 or less; And it discloses the adhesive composition for polarizing plates containing a polyfunctional crosslinking agent.

Japanese Patent Laid-Open No. 2002-47468 discloses a high molecular weight acrylic copolymer having a functional group having a weight average molecular weight of 800,000 to 2 million; Low molecular weight acrylic copolymer which has a weight average molecular weight of 50,000 or less and does not have a functional group whose dispersion degree is 1.0-2.5; Crosslinking agents; And it discloses the adhesive composition for polarizing plates containing a silane compound.

The preceding patents implement the technical idea of softening the final adhesive in order for the adhesive layer to have stress relaxation functionality. That is, low molecular weight is added to reduce the modulus of the pressure-sensitive adhesive, thereby increasing the amount of creep with respect to external stress and easily deforming, thereby reducing local stress caused by shrinkage or expansion of the polarizing plate. . However, in the case of reducing the modulus of the pressure-sensitive adhesive through the addition of low molecular weight, it is easy to cause a poor adhesive pressure when storing the polarizing plate in roll form in the polarizing plate manufacturing process, and when cutting the manufactured polarizing plate, Protruding phenomenon that the pressure-sensitive adhesive is protruding occurs, there is a problem that the polarizing plate is easily contaminated by the protruding pressure-sensitive adhesive. In addition, the added low molecular weight moves to the interfacial layer of the glass of the liquid crystal panel and the TAC, and the durability is likely to be accompanied.

Another method for imparting an excellent stress relaxation function to the pressure-sensitive adhesive layer is to lower the gel content of the pressure-sensitive adhesive containing a high molecular weight containing a crosslinkable functional group. This method has the advantage that the modulus of the pressure-sensitive adhesive does not significantly decrease, but it is very difficult to maintain a uniformly low gel content, and the time (curing period or Aging time) from the crosslinking of the pressure-sensitive adhesive composition to the point at which the polarizing plate can be cut is Long, there is a disadvantage that the durability is degraded under high temperature or high temperature and high humidity.

Accordingly, there is a need for development of a pressure-sensitive adhesive for polarizing plates that minimizes a decrease in pressure-sensitive adhesive modulus to suppress workability and improves light leakage without changing key characteristics such as durability.

An object of the present invention is to solve the problems of the prior art as described above, stress relief through the control of the crosslinking rate and crosslinking structure, without causing degradation of the adhesion durability reliability that may occur under high temperature or high temperature and high humidity conditions It is to provide an acrylic pressure-sensitive adhesive composition, a polarizing plate and the liquid crystal display device comprising the composition improved light leakage phenomenon.

The present invention provides a means for solving the above problems, (A) high molecular weight acrylic copolymer having a weight average molecular weight of 1.5 million to 2.5 million; (B) a low molecular weight acrylic copolymer having a weight average molecular weight of 500,000 to 1 million; And (C) a peroxide compound, wherein the weight ratio ((B) low molecular weight / (A) high molecular weight acrylic copolymer) of the (A) high molecular weight acrylic copolymer and (B) the low molecular weight acrylic copolymer is 1 to It provides an acrylic adhesive composition of four.

The gel content of the acrylic pressure-sensitive adhesive composition is preferably 20 to 55%.

The present invention as another means for solving the above problems, a polarizing film; And a pressure-sensitive adhesive layer formed on one or both surfaces of the polarizing film and containing an acrylic pressure-sensitive adhesive composition according to the present invention.

As another means for solving the above problems, the present invention provides a liquid crystal display including a liquid crystal panel in which a polarizing plate according to the present invention is bonded to one side or both sides of a liquid crystal cell.

Acrylic pressure-sensitive adhesive composition according to the present invention has a characteristic that the crosslinking rate and crosslinking structure is controlled by the peroxide according to the molecular weight of the acrylic copolymer. Therefore, the pressure-sensitive adhesive containing the same is effective in improving the light leakage phenomenon by relieving the stress caused by the shrinkage of the polarizing plate when used for a long time under high temperature or high temperature and high humidity conditions, the gel content of the pressure-sensitive adhesive is kept low, the modulus does not fall off The productivity and workability of the attached polarizing plate are excellent.

The present invention (A) high molecular weight acrylic copolymer having a weight average molecular weight of 1.5 million to 2.5 million; (B) a low molecular weight acrylic copolymer having a weight average molecular weight of 500,000 to 1 million; And (C) a peroxide compound, wherein the weight ratio ((B) low molecular weight / (A) high molecular weight acrylic copolymer) of the (A) high molecular weight acrylic copolymer and (B) the low molecular weight acrylic copolymer is 1 to It relates to an acrylic pressure-sensitive adhesive composition of 4.

The present invention is characterized in that the crosslinked structure of the acrylic pressure-sensitive adhesive is controlled to include a peroxide compound. Since the main chain of the acrylic copolymer is a saturated hydrocarbon, it is inefficient to form a crosslinked structure using a peroxide compound, but when the molecular weight of the acrylic copolymer is large, a loose three-dimensional crosslinked structure is formed in a relatively fast time. In addition, when the molecular weight of the acrylic copolymer is small to form a two-dimensional crosslinked structure (chain extension) occurs. As described above, the present invention is characterized by controlling the crosslinking structure of the acrylic pressure-sensitive adhesive by using a difference in crosslinking efficiency of the peroxide according to the molecular weight of the acrylic copolymer.

Commonly used crosslinking agents such as isocyanates or epoxys form very dense cross-linking networks with acrylic copolymers, which are advantageous in terms of durability and reliability of the adhesive, It is weakened and adversely affects light leakage. However, the crosslinked structure using the high molecular weight acrylic copolymer and the peroxide compound according to the present invention forms a loose cross-linking network and lower molecular weight acrylic air compared to the crosslinked structure using a crosslinking agent such as isocyanate or epoxy. The coalescence forms a two-dimensional crosslinked structure, and does not degrade the modulus of the pressure-sensitive adhesive, and maintains a low gel content, thereby providing excellent stress relaxation characteristics and low light leakage characteristics.

In the acrylic pressure-sensitive adhesive composition according to the present invention, the weight ratio ((B) low molecular weight / (A) high molecular weight acrylic copolymer) of the (A) high molecular weight acrylic copolymer and (B) low molecular weight acrylic copolymer is 1 to 4 When the weight ratio is less than 1, the stress relaxation property of the pressure-sensitive adhesive is lowered, and when it exceeds 4, the durability reliability of the pressure-sensitive adhesive is greatly reduced.

In addition, the acrylic pressure-sensitive adhesive composition according to the present invention is preferably a gel content of 20 to 55%, more preferably 25 to 45% represented by the following formula.

[Equation]

Gel Content (%) = (L ₂ ) / (L ₁ ) x 100

Where

L ₁ represents the mass of the acrylic pressure-sensitive adhesive composition, L ₂ represents the dry mass of the insoluble fraction of the acrylic pressure-sensitive adhesive composition after immersion in ethyl acetate for 48 hours at room temperature.

When the gel content is less than 20%, the durability is very poor under high temperature or high temperature and high humidity conditions, and when the gel content exceeds 55%, the stress relaxation property of the pressure-sensitive adhesive is greatly reduced.

Hereinafter, each component of the acrylic pressure-sensitive adhesive composition according to the present invention will be described in detail.

(A) High molecular weight acrylic copolymer having a weight average molecular weight of 1.5 million to 2.5 million

The high molecular weight acrylic copolymer (A) having a weight average molecular weight of 1.5 to 2.5 million according to the present invention forms a three-dimensional crosslinked structure when reacted with the (C) peroxide compound to maintain durability of the pressure-sensitive adhesive. . Since the main chain of the acrylic copolymer is a saturated hydrocarbon, it is inefficient to form a crosslinked structure using a peroxide compound. However, when the molecular weight of the acrylic copolymer is large, a loose three-dimensional crosslinked structure is formed within a relatively fast time. For this purpose, the larger the molecular weight of the acrylic copolymer is, the more advantageous it is.

The high molecular weight acrylic copolymer according to the present invention preferably has a weight average molecular weight of 1.5 million to 2.5 million. If the weight average molecular weight is less than 1.5 million, the crosslinking efficiency is reduced, and if it exceeds 2.5 million, the coating property of the pressure-sensitive adhesive is greatly reduced.

(B) Low molecular weight acrylic copolymer having a weight average molecular weight of 500,000 to 1 million

The low molecular weight acrylic copolymer (B) having a weight average molecular weight of 500,000 to 1 million according to the present invention has a poor crosslinking efficiency with a peroxide compound, thereby forming a two-dimensional crosslinked structure or reacting with a (C) peroxide compound. You will not participate in. Therefore, the gel content is kept low without dropping the modulus of the pressure-sensitive adhesive.

The low molecular weight acrylic copolymer according to the present invention preferably has a weight average molecular weight of 500,000 to 1 million. When the weight average molecular weight is less than 500,000, the durability of the pressure-sensitive adhesive is poor, and when the weight-average molecular weight is more than 1 million, the crosslinking degree of the final pressure-sensitive adhesive is greatly increased, thereby greatly reducing the stress relaxation characteristics of the pressure-sensitive adhesive.

The (A) high molecular weight acrylic copolymer and the (B) low molecular weight acrylic copolymer according to the present invention each contain 80 to 99.8 parts by weight of an alkyl (meth) acrylic acid ester monomer having 1 to 14 carbon atoms as the main component. The content of the alkyl (meth) acrylic acid ester monomer is preferably 80 to 99.8 parts by weight for controlling adhesion and cohesion. The alkyl (meth) acrylic acid ester monomers contained in the (A) high molecular weight acrylic copolymer and (B) the low molecular weight acrylic copolymer may be the same or different.

Specific examples of the alkyl (meth) acrylic acid ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate , Lauryl (meth) acrylate, tetradecyl (meth) acrylate, etc. can be mentioned, These can be used individually or in mixture of 2 or more types.

When the carbon number of the said alkyl is out of the said range, since the glass transition temperature (Tg) of an adhesive becomes high or it is difficult to adjust adhesiveness, it is preferable that it is 1-14.

In addition, the (A) high molecular weight acrylic copolymer or the (B) low molecular weight acrylic copolymer according to the present invention may each contain a crosslinkable functional group together with an alkyl (meth) acrylic acid ester monomer having 1 to 14 carbon atoms. To 5 parts by weight. When the content is less than 0.01 parts by weight, cohesive failure is likely to occur under high temperature or high humidity conditions, and there is a fear that the effect of improving adhesion is reduced, and when it is more than 5 parts by weight, the adhesion and peeling force may be reduced.

Specific examples of the crosslinkable functional group-containing monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethylene glycol ( Hydroxyl group-containing monomers such as meth) acrylate or 2-hydroxypropylene glycol (meth) acrylate; Carboxyl group-containing monomers such as (meth) acrylic acid, acrylic acid duplex, itaconic acid, or maleic acid; And nitrogen-containing monomers such as acrylamide, N-vinyl pyrrolidone, or N-vinyl caprolactam, and the like, and these may be used alone or in combination of two or more thereof.

In addition, the (A) high molecular weight acrylic copolymer or (B) low molecular weight acrylic copolymer according to the present invention may include 20 parts by weight or less of the functional monomer represented by the following formula together with the monomer. When the content exceeds 20 parts by weight, the flexibility of the pressure-sensitive adhesive composition is lowered, there is a fear that the peel force is lowered.

[Formula]

Where

R ₁ represents hydrogen or alkyl,

R ₂ represents 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.

In the formula, alkyl or alkoxy in the definition of R ₂ to R ₃ preferably denotes lower alkyl having 1 to 6 carbon atoms, more preferably methyl or ethyl.

Specific examples of the functional monomer represented by the above formula include styrene monomers such as styrene or alpha methyl styrene; Carboxylic acid vinyl esters such as vinyl acetate; Nitrogen-containing vinyl monomers, such as (meth) acrylamide or N-butoxy methyl (meth) acrylamide, etc. are mentioned, These can be used individually or in mixture of 2 or more types.

The method for preparing the high molecular weight acrylic copolymer and the low molecular weight acrylic copolymer is not particularly limited, and may be prepared by a solution polymerization method, a photopolymerization method, a bulk polymerization method, a suspension polymerization method or an emulsion polymerization method. Preferably, the acrylic copolymer is prepared by a solution polymerization method, the polymerization temperature is preferably 50 to 140 ℃, it is preferable to add a polymerization initiator in a state where the monomers are uniformly mixed.

Such polymerization initiators include azo polymerization initiators such as azobisisobutyronitrile or azobiscyclohexanecarbonitrile; And peroxides such as benzoyl peroxide or acetyl peroxide alone or in combination.

(C) peroxide compound

Peroxide compound of the acrylic pressure-sensitive adhesive composition according to the present invention is to generate a radical (Radical) by heat, it is estimated that the cross-linking reaction with the acrylic copolymer by this radical.

The peroxide compound that can be used in the present invention preferably has a half-life temperature of 70 to 170 ° C for one minute, more preferably 90 to 150 ° C. The "half-life temperature" is an index indicating the decomposition rate of the peroxide compound, and is a temperature required for 63% of the initial peroxide compound to be decomposed at a specific time. If the 1-minute half-life temperature of the peroxide compound is less than 70 ° C., the initiator is likely to decompose before coating, and if it exceeds 170 ° C., there is a possibility that the decomposition of the initiator may be too small to promote the crosslinking reaction.

Specific examples of the peroxide compound include lauryl peroxide, benzoyl peroxide, isobutyryl peroxide, bisneodecanoyl peroxy diisopropyl benzene, cumyl peroxy neodecanoate, dipropyl peroxy dicarbonate, di Isopropyl peroxy dicarbonate, bis-4-butylcyclohexyl peroxy dicarbonate, diethoxyethyl peroxy dicarbonate, diethoxyhexyl peroxy dicarbonate, hexyl peroxy dicarbonate, dimethoxybutyl peroxy dicarbonate, bis (3-methoxy-3methoxybutyl) peroxy dicarbonate, tetramethyl butyl peroxy neodecanoate, butyl peroxy neodecanoate, hexyl peroxy pivalate, butyl peroxy pivalate, trimethylhexanoyl peroxide , Dimethyl hydroxybutyl peroxy neodecanoate, amyl peroxy neodecanoate, butyl peroxy neodeca Noate, amyl peroxy pivalate, and the like, and these may be used alone or in combination of two or more thereof.

The content of the peroxide compound is preferably 0.01 to 2 parts by weight based on 100 parts by weight of the acrylic copolymer (A) and (B). If the content is less than 0.01 parts by weight, the gel content of the final pressure-sensitive adhesive is too low may cause problems in durability, if it exceeds 2 parts by weight, the gel content is too high, there is a fear that the light leakage is greatly increased.

The acrylic pressure-sensitive adhesive composition according to the present invention may further include a polyfunctional isocyanate-based crosslinking agent in addition to the above components. In the present invention, the polyfunctional isocyanate crosslinking agent serves to improve the adhesion between the adhesive layer and the triacetyl cellulose (TAC) interfacial layer of the polarizing plate.

Specific examples of the polyfunctional isocyanate-based crosslinking agent include tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoform diisocyanate, tetramethylxylene diisocyanate, naphthalene diisocyanate and one or more polyols ( And a reaction product with trimethylolpropane). These may be used alone or in combination of two or more thereof.

The content of the polyfunctional isocyanate compound is preferably 0.01 to 0.05 parts by weight based on 100 parts by weight of the acrylic copolymer (A) and (B). If the content is less than 0.01 parts by weight, the adhesion between the adhesive layer and the triacetylcellulose interfacial layer is lowered. If the content is more than 0.05 parts by weight, the crosslinking efficiency of the high molecular weight acrylic copolymer is affected, which makes it difficult to improve the light leakage phenomenon of the polarizing plate. .

In addition, the acrylic pressure-sensitive adhesive composition according to the present invention may further include a silane coupling agent. By including a silane coupling agent in an acrylic adhesive composition, when an acrylic adhesive adheres with a glass plate, adhesive stability can be improved and heat-and-moisture resistance characteristic can be improved further. In particular, the silane coupling agent serves to improve the adhesion reliability when left for a long time under high temperature and high humidity conditions. In the present invention, the content of the silane coupling agent is preferably 0.005 to 5 parts by weight based on 100 parts by weight of the acrylic copolymer (A) and (B). When the content is less than 0.005 parts by weight, there is no adhesion reliability improvement, and when the content is more than 5 parts by weight, the durability is poor.

Examples of the silane coupling agent include g-glycidoxypropyltrimethoxysilane, g-glycidoxypropylmethyldiethoxysilane, g-glycidoxypropyltriethoxysilane, 3-mercapto propyl trimethoxysilane, Vinyltrimethoxysilane, vinyltriethoxysilane, g-methacryloxypropyltrimethoxysilane, g-methacryloxypropyltriethoxysilane, g-aminopropyltrimethoxysilane, g-aminopropyltrie Methoxysilane, 3-isocyanatepropyltriethoxysilane, g-acetoacetatepropyltrimethoxysilane, and the like, and these may be used alone or in combination of two or more thereof.

In addition, the acrylic pressure-sensitive adhesive composition according to the present invention may further comprise a tackifier resin in order to adjust the adhesive performance. In the present invention, the content of the tackifying resin is preferably 1 to 100 parts by weight based on 100 parts by weight of the acrylic copolymer (A) and (B). If the content is less than 1 part by weight, the tackifying function is poor, and if it exceeds 100 parts by weight, the compatibility or cohesion of the pressure-sensitive adhesive may be reduced.

Examples of the tackifying resin include (hydrogenated) hydrocarbon resin, (hydrogenated) rosin resin, (hydrogenated) rosin ester resin, (hydrogenated) terpene resin, (hydrogenated) terpene phenol resin or polymerized rosin resin, polymerized rosin ester Resins, and these can be used alone or in combination of two or more thereof.

In addition, the present invention may further include a plasticizer, an epoxy resin, a curing agent, and the like for a specific purpose, and may be appropriately added with a UV stabilizer, an antioxidant, a colorant, a reinforcing agent, a filler, an antifoaming agent, or a surfactant according to a general purpose. Can be used.

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

The polarizing plate of this invention contains the adhesion layer formed from the said adhesive composition in one or both surfaces of a polarizing film, The polarizing film or polarizing element which comprises a polarizing plate is not specifically limited.

Preferably, examples of the polarizing film include a film obtained by adding a polarizing component such as iodine or a dichroic dye to a film made of polyvinyl alcohol-based resin and stretching the film, and the thickness of these polarizing films is also particularly limited. It is not possible to form a conventional thickness. At this time, the polyvinyl alcohol-based resin may be used polyvinyl alcohol, polyvinyl formal, polyvinyl acetal and ethylene, saponified vinyl acetate copolymer.

On both sides of the polarizing film, a cellulose-based film such as triacetyl cellulose, a polycarbonate film, a polyester-based film such as polyethylene terephthalate, a polyethersulfone-based film, a polyethylene, a polypropylene, a cyclo-based or a polyolefin-based having a norbornene structure And a multilayer film in which protective films such as polyolefins such as ethylene propylene copolymer are laminated. At this time, the thickness of these protective films is also not particularly limited, and may form a conventional thickness.

In the present invention, a method of forming an adhesive layer on the polarizing film is not particularly limited, and 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 once After drying, a method of transferring the pressure-sensitive adhesive layer formed on the surface of the peelable base material onto the polarizing film surface and then aging may be applied.

In addition, the polarizing plate of the present invention may be laminated with 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, and a brightness enhancement film.

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

The polarizing plate to which the pressure-sensitive adhesive according to the present invention is applied can be applied to all conventional liquid crystal display devices, and the type of the liquid crystal panel is not particularly limited. Preferably, the present invention may comprise a liquid crystal display device including a liquid crystal panel in which the adhesive polarizing plate is bonded to one or both surfaces of a liquid crystal cell.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, which are intended to help a specific understanding of the present invention, and the scope of the present invention is not limited by the Examples.

Preparation Example 1 : High molecular weight  Manufacture of acrylic copolymer (A1)

99.8 parts by weight of n-butylacrylate (BA), 2-hydroxy ethyl acrylate, as shown in the following Table 1 in a 1L reactor equipped with a refrigeration system to facilitate nitrogen temperature reflux and temperature control A mixture of monomers consisting of 0.2 parts by weight was added. Then, 100 parts by weight of ethylacetate (EAc) was added as a solvent. After purging nitrogen gas for 60 minutes to remove oxygen, the temperature was maintained at 60 ° C, and 0.05 parts by weight of azobisisobutyronitrile (AIBN), a reaction initiator, was added and reacted. After the reaction, the mixture was diluted with ethyl acetate (EAc) to prepare an acrylic copolymer (A1) having a solid content of 15% by weight, a weight average molecular weight of 2 million, and a molecular weight distribution of 3.8.

Preparation Example 2 -8: acrylic copolymers A2 to A3, B1 to B2, C1 , And D1  To D2  Produce

Acrylic copolymers A2 to A3, B1 to B2, C1, and D1 to D2 were prepared by adding or not adding a part of each component based on the composition of Table 1 in the same manner as in Preparation Example 1. The results are shown in Table 1 below.

A1 A2 A3 C1 B1 B2 D1 D2 Acrylic Copolymer Composition (parts by weight) n-BA 99.8 99.8 98.5 99.8 99 99 99 99 2-HEA 0.2 0.2 1.5 0.2 One One One One AIBN 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 nDDM - - - - - - - 3 EAc 100 120 120 70 170 180 400 100 Weight average molecular weight (only) 200 160 170 270 90 83 40 1.4 Molecular weight distribution 3.8 4.0 4.5 4.0 4.2 4.0 4.2 2.5 n-BA: n-butylacrylate, EHA: 2-ethylhexyl acrylate 2-HEA: 2-hydroxyethyl acrylate, n-DDM: normal dodecyl mercaptan, AIBN: azobisisobutyronitrile, EAc : Ethyl acetate

Example 1

<Mixing>

To 30 parts by weight of the high molecular weight acrylic copolymer A1 solids obtained in the above production example, the low molecular weight acrylic copolymer B1 was mixed so as to have a solid content of 70 parts by weight. (TDI-1) 0.02 parts by weight of diethoxyhexyl peroxy dicarbonate (1 minute half-life temperature 89 ° C., 10 hours half-life temperature 44 ° C.) as a peroxide compound was added 0.5 part by weight based on 100 parts by weight of the acrylic copolymer. It was coated on, dried for 3 minutes in an 110 ℃ oven to obtain a 25 micron uniform adhesive layer.

<Plywood process>

The pressure-sensitive adhesive layer prepared above was adhesively processed on an iodine-based polarizing plate having a thickness of 185 microns. The obtained polarizing plate was cut to an appropriate size and used for evaluation, and the results of evaluating the polarizing plate to which the pressure-sensitive adhesive was applied are shown in Table 2 below.

[Examples 2 to 7]

As shown in the following Table 2, the acrylic copolymer was blended and plywooded in the same manner as in Example 1 by not blending or partially blending a part of the formulation of Example 1. Thereafter, durability and light transmission uniformity were evaluated in the same manner as in Example 1, and the results are shown in Table 2 below.

[Comparative Examples 1 to 6]

As shown in the following Table 2, the acrylic copolymer was blended and plywooded in the same manner as in Example 1 by not blending or partially blending a part of the formulation of Example 1. Then, durability and light transmission uniformity were evaluated in the same manner as in Example 1, and the results are shown in Table 2 below.

[Test Example]

Durability Reliability

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. In addition, after leaving the pressure-sensitive adhesive polarizing plate prepared for 5 months or more, the reliability was evaluated by the above method. The evaluation criteria for reliability are as follows.

○: no bubbles or peeling

△: slight bubble or peeling phenomenon

X: A lot of bubble and peeling phenomenon generate | occur | produce

Light transmission  Uniformity ( Light fountain )

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 of testing the light transmittance uniformity, the coated polarizing plate (200 mm x 200 mm) was intersected 90 degrees to the glass substrate (210 mm x 210 mm x 0.7 mm) and attached to both sides. Light transmittance nonuniformity was evaluated based on the following criteria.

⊙: Unevenness is difficult to judge with the naked eye

○: slight unevenness

△: somewhat non-uniformity

×: there is a large amount of unevenness

Measurement of Adhesive Press

The pressure drop of the pressure-sensitive adhesive is smaller the higher the elastic modulus of the pressure-sensitive adhesive (the higher the storage elastic modulus of the pressure-sensitive adhesive). The elastic modulus of the pressure-sensitive adhesive was measured using Rheometrics' RMS-800. Using an 8mm diameter Parallel Plate fixture, the adhesive modulus was measured by measuring the storage modulus under pressure 1mm thickness, strain 10% and frequency 1rad / sec at 30 ℃. Depression failure of the pressure-sensitive adhesive was determined based on the measured storage modulus as follows.

3 points: Very low (storage modulus> 1.8x10 ⁴ Pa)

2 points: Has a bit (1.0x10 ⁴ Pa <Storage Modulus <1.8x10 ⁴ Pa)

1 point: very much (storage modulus <1.0 x10 ⁴ Pa)

Measurement of adhesive sticking out

After cutting the polarizing plate after the said plywood using the Thompson cutter (Thompson), the cut surface of each polarizing plate was observed under the microscope, and the grade which the adhesive of the cut surface sticked out was evaluated based on the following reference | standard.

3 points: good (less than 0.2 mm)

2 points: somewhat poor (0.2-0.5mm)

1 point: Very poor (0.5 mm or more)

Gel Fractional  Measure

The pressure-sensitive adhesive dried in the compounding process was left in a constant temperature / humidity (23 ° C., 60% RH) room for about 10 days, and about 0.3 g of pressure-sensitive adhesive was placed in a # 200 stainless steel wire and immersed in 100 ml of ethyl acetate. After storage for 48 hours, the insolubles were separated, and the insolubles were dried in an oven at 70 ° C. for 4 hours, and then mass was measured.

Example Comparative example One 2 3 4 One 2 3 4 5 6 7 8 Compounding composition (parts by weight) A1 30 40 60 70 15 40 A2 35 40 A3 100 100 100 C1 30 B1 70 60 40 30 85 B2 65 60 70 D1 60 D2 20 Isocyanate 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.05 0.03 0.05 Peroxide 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0 0 0 Acrylic copolymer weight ratio ((B) low molecular weight / (A) high molecular weight) 2.3 1.5 1.9 1.5 0.6 0.4 2.3 5.6 1.5 - - 0.2 Gel (%) 24 33 30 37 65 74 35 12 33 63 40 50 Durability Reliability ○ ○ ○ ○ ○ ○ ○ × × ○ × ○ Light fountain ⊙ ○ ⊙ ○ × × × ⊙ ⊙ × ⊙ ○ Sticking out of adhesive 3 3 3 3 3 3 3 3 2 3 2 One Pressure-sensitive adhesive (adhesive modulus) 3 3 3 3 3 3 3 3 One 3 3 One

As shown in the results of Table 2, in Examples 1 to 4 of the present invention, both durability and low light leakage characteristics were excellent, and pressure-sensitive adhesive squeeze and pressure-related pressure-related defects were low. On the other hand, in Comparative Examples 1 to 2, the ratio of the low molecular weight acrylic copolymer is low, so that the stress relaxation property of the pressure-sensitive adhesive is insufficient, so that the low light leakage characteristic is inferior. In Comparative Example 3, the molecular weight of the acrylic copolymer (C1) is too large. The low light quality is thirteen. In Comparative Example 4, the amount of the low molecular weight acrylic copolymer (B1) is too high and the durability is insufficient because of low gel content, and in Comparative Example 5, the molecular weight of the low molecular weight acrylic copolymer (D1) is too low, so This was not secured. Comparative Examples 6 to 8 were used to control the degree of crosslinking using only an isocyanate crosslinking agent and a low molecular weight added to a single acrylic copolymer, and the low light leakage property was insufficient, or the durability and workability of the polarizing plate were insufficient. .

Claims (21)

(A) a high molecular weight acrylic copolymer having a weight average molecular weight of 1.5 million to 2.5 million; (B) a low molecular weight acrylic copolymer having a weight average molecular weight of 500,000 to 1 million; And (C) containing a peroxide compound, An acrylic pressure-sensitive adhesive composition having a weight ratio ((B) low molecular weight / (A) high molecular weight acrylic copolymer) of the (A) high molecular weight acrylic copolymer and (B) low molecular weight acrylic copolymer. The method of claim 1, Acrylic pressure-sensitive adhesive composition characterized in that the gel content represented by the following formula is 20 to 55%: [Equation] Gel Content (%) = (L ₂ ) / (L ₁ ) x 100 Where L ₁ represents the mass of the acrylic pressure-sensitive adhesive composition, L ₂ represents the dry mass of the insoluble content of the acrylic pressure-sensitive adhesive composition after immersion in ethyl acetate for 48 hours at room temperature. The method of claim 1, (A) The high molecular weight acrylic copolymer and the (B) low molecular weight acrylic copolymer each contain 80 to 99.8 parts by weight of an alkyl (meth) acrylic acid ester monomer having 1 to 14 carbon atoms of alkyl. The method of claim 4, wherein Alkyl (meth) acrylic acid ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, t-butyl ( Meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl ( Acrylic pressure-sensitive adhesive composition, characterized in that at least one selected from the group consisting of meth) acrylate and tetra decyl (meth) acrylate. The method of claim 1, (A) High molecular weight acrylic copolymer or (B) Low molecular weight acrylic copolymer each independently contains 0.01-5 weight part of crosslinkable functional group containing monomers, The acrylic adhesive composition characterized by the above-mentioned. The method of claim 5, wherein The crosslinkable functional group-containing monomer is an acrylic pressure-sensitive adhesive composition, characterized in that at least one selected from the group consisting of hydroxyl group-containing monomers, carboxyl group-containing monomers and nitrogen-containing monomers. The method of claim 6, The hydroxyl group-containing monomers are 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate and 2 -Acrylic pressure-sensitive adhesive composition, characterized in that at least one selected from the group consisting of hydroxypropylene glycol (meth) acrylate. The method of claim 6, The carboxyl group-containing monomer is an acrylic pressure-sensitive adhesive composition, characterized in that at least one selected from the group consisting of (meth) acrylic acid, acrylic acid duplex, itaconic acid, and maleic acid. The method of claim 6, The nitrogen-containing monomer is an acrylic pressure-sensitive adhesive composition, characterized in that at least one selected from the group consisting of acryl amide, N-vinyl pyrrolidone, and N-vinyl caprolactam. The method of claim 1, (A) a high molecular weight acrylic copolymer or (B) a low molecular weight acrylic copolymer each independently comprises an acrylic pressure-sensitive adhesive composition further comprises 20 parts by weight or less of the functional monomer represented by the following formula: [Formula]

Where R ₁ represents hydrogen or alkyl, R ₂ represents 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. The method of claim 10, The functional monomer represented by the formula is at least one selected from the group consisting of styrene, alpha methyl styrene, vinyl acetate, (meth) acrylamide, and N-butoxy methyl (meth) acrylamide. The method of claim 1, (C) The peroxide compound is an acrylic pressure-sensitive adhesive composition, characterized in that the half-life temperature is 70 to 170 ℃ for 1 minute. The method of claim 1, (C) the peroxide compound is lauryl peroxide, benzoyl peroxide, isobutyryl peroxide, bisneodecanoyl peroxy diisopropyl benzene, cumyl peroxy neodecanoate, dipropyl peroxy dicarbonate, diiso Propyl peroxy dicarbonate, bis-4-butylcyclohexyl peroxy dicarbonate, diethoxyethyl peroxy dicarbonate, diethoxyhexyl peroxy dicarbonate, hexyl peroxy dicarbonate, dimethoxybutyl peroxy dicarbonate, bis ( 3-methoxy-3methoxybutyl) peroxy dicarbonate, tetramethyl butyl peroxyneodecanate, butyl peroxyneodecanoate, hexyl peroxy pivalate, butyl peroxy pivalate, trimethylhexanoyl peroxide, Dimethyl hydroxybutyl peroxy neodecanoate, amyl peroxy neodecanoate, butyl peroxy neodecanoate, and amyl The acrylic pressure-sensitive adhesive composition, characterized in that at least one selected from the group consisting of oxy-pivalate. The method of claim 1, The content of the (C) peroxide compound is 0.01 to 2 parts by weight based on 100 parts by weight of the acrylic copolymers (A) and (B). The method of claim 1, An acrylic pressure-sensitive adhesive composition further comprising 0.01 to 0.05 parts by weight of a polyfunctional isocyanate-based crosslinking agent based on 100 parts by weight of the acrylic copolymer (A) and (B). The method of claim 15, Isocyanate-based crosslinking agents are selected from the group consisting of tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoform diisocyanate, tetramethylxylene diisocyanate, naphthalene diisocyanate and reactants with at least one of the above polyols. Acrylic pressure-sensitive adhesive composition, characterized in that at least one selected. The method of claim 1, An acrylic 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, Acrylic adhesive composition, characterized in that it further comprises 1 to 100 parts by weight of the tackifier resin with respect to 100 parts by weight of the acrylic copolymer (A) and (B). Polarizing film; And A polarizing plate formed on one side or both sides of the polarizing film, the pressure-sensitive adhesive layer containing the acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 18. The method of claim 19, The polarizing plate further comprises at least one layer selected from the group consisting of a protective layer, a reflective layer, a retardation plate, a wide viewing angle compensation film and a brightness enhancement film. 20. A liquid crystal display device comprising a liquid crystal panel obtained by bonding the polarizing plate of claim 19 to one side or both sides of a liquid crystal cell.