KR100948778B1 - Optically Compensated Acrylic Pressure-Sensitive Adhesive Composition, Polarizing Plate and Liquid Crystal Display Device containing the same - Google Patents

Abstract

The present invention relates to an acrylic pressure-sensitive adhesive composition, a polarizing plate and a liquid crystal display device using the same, and more specifically, an optically compensated acrylic copolymer (A) including a crosslinkable functional group, and an optically compensated acrylic copolymer not containing a crosslinkable functional group. (B), and a polyfunctional crosslinking agent (C), and relates to an acrylic pressure-sensitive adhesive composition having an optimum stress relaxation characteristics, wherein the polarizing plate comprising the pressure-sensitive adhesive composition and the liquid crystal display including the same occur under high temperature and high humidity conditions It satisfies the main characteristics such as adhesion durability and reliability, and at the same time, effectively provides optical compensation effects and stress relaxation characteristics to improve light leakage.

Polarizer, acrylic adhesive, light leakage, optical compensation, stress relaxation, birefringence

Description

Optically compensated acrylic pressure-sensitive adhesive composition, a polarizing plate and a liquid crystal display device comprising the same {Optically Compensated Acrylic Pressure-Sensitive Adhesive Composition, Polarizing Plate and Liquid Crystal Display Device containing the same}

The present invention relates to an acrylic pressure-sensitive adhesive composition for a polarizing plate, and more particularly, a pressure-sensitive adhesive composition for a polarizing plate excellent in low light leakage characteristics without changing main characteristics such as durability and workability under high temperature or high temperature and high humidity conditions. It relates to a polarizing plate manufactured by, and a liquid crystal display device to which the same is applied.

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 Will be configured. In addition, the polarizing plate may additionally include a wide viewing angle compensation film such as a phase difference film or a liquid crystal film having a unidirectional molecular array.

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, stress is concentrated in the TAC layer by the contraction or expansion of the polarizing plate under high temperature or under high temperature and high humidity conditions, whereby birefringence is generated and light leakage occurs. In this case, negative birefringence generally appears as a whole by the contracted TAC.

On the other hand, the pressure-sensitive adhesive layer requires a high temperature cohesive force in order to maintain the durability reliability for this purpose uses a partially cross-linked viscoelastic material form. When the partial crosslinked structure is introduced into the pressure sensitive adhesive layer, the pressure sensitive adhesive layer has a residual stress under a given deformation, which causes the polymer in the crosslinked structure to be oriented in a specific direction, thereby exhibiting birefringence. Under these orientations, typical alkyl acrylic pressure sensitive adhesives exhibit negative birefringence, similar to TAC.

On the other hand, the size of monitors such as computers is increasing in size, and the demand for LCD TVs using polarizers is increasing rapidly. As the panel is enlarged, the polarizer is also enlarged, and thus, the residual stress of the TAC and the pressure-sensitive adhesive layer is also increased. As a result, the negative birefringence is increased, and the light leakage becomes very severe.

As a method of minimizing light leakage occurring under residual stress as described above, the TAC layer under residual stress by adding (blending) a material exhibiting positive birefringence under residual stress to the final adhesive layer or copolymerizing an acrylic monomer having positive birefringence. The method of minimizing the overall birefringence including the adhesive and the adhesive may be considered.

Korean Laid-Open Patent Publication No. 2003-0069461 discloses an adhesive in which 0.01 to 40 parts by weight of a low molecular weight material showing birefringence of positive values under stress is incorporated into an acrylic pressure sensitive adhesive layer to correct birefringence of negative value indicated by an acrylic pressure sensitive adhesive layer under residual stress. . However, the pressure-sensitive adhesive has a modulus of the pressure-sensitive adhesive is reduced due to the low molecular weight mixed in the pressure-sensitive adhesive, there is a problem in cutting properties when working the polarizer. In addition, there is a problem of migration to the interface of the low molecular weight body and the phase separation with the acrylic pressure-sensitive adhesive during long-term storage.

There is also known a method of minimizing birefringence by copolymerizing a monomer having a negative birefringence with a monomer having a positive birefringence under residual stress (see Applied Optics (1997)). As a specific example, the degree of birefringence can be adjusted under a given stress by copolymerizing an acrylic monomer (negative birefringence) having an alkyl group and an acrylic monomer having a side group having an aromatic group (positive birefringence).

Japanese Laid-Open Patent Publication No. 2002-332468 describes a method of improving the fire resistance of an adhesive layer by introducing an acrylic monomer containing an aromatic group in a side chain. In addition, US Pat. No. 6,663,978, Japanese Laid-Open Patent No. 2002-173656 and Japanese Laid-Open Patent Publication No. 2003-013029 describe a method of controlling the refractive index of an adhesive layer by introducing an acrylic monomer containing an aromatic group in a side chain. In addition, Japanese Laid-Open Patent Publication No. 2005-053976 describes a method of introducing an acrylic monomer containing an aromatic group into a side chain to improve adhesive performance even for a low polar film. However, the above-mentioned prior documents have not disclosed technical ideas of improving light leakage by attempting optical compensation to control birefringence under residual stress when acrylic acrylic pressure-sensitive adhesives are prepared by introducing an acrylic monomer containing an aromatic group in a side chain. not.

The present invention is to solve the conventional problems as described above, an object of the present invention is an optically compensated acrylic copolymer (A) comprising a crosslinkable functional group, an optically compensated acrylic copolymer (B) not containing a crosslinkable functional group (B) ), And a polyfunctional crosslinking agent (C), using a (meth) acrylic copolymer having an optimum stress relaxation property as the pressure-sensitive adhesive layer, the adhesion durability reliability and re-peeling that can occur under high temperature or high temperature and high humidity conditions The present invention provides an acrylic pressure-sensitive adhesive composition for polarizing plates that improves light leakage by controlling birefringence under a residual stress to have a positive value without changing main characteristics such as properties.

Another object of the present invention is to provide a polarizing plate using an acrylic pressure-sensitive adhesive composition having the above characteristics.

Still another object of the present invention is to provide a liquid crystal display device including a polarizing plate manufactured from an acrylic pressure-sensitive adhesive composition having the above characteristics.

The present invention comprises i) 50 to 75 parts by weight of an alkyl (meth) acrylic acid ester monomer having 2 to 14 carbon atoms, ii) 25 to 50 parts by weight of an acrylic ester monomer comprising an aromatic group copolymerizable with the acrylic monomer, and iii) An acrylic copolymer (A) comprising 0.1 to 10 parts by weight of a vinyl or acrylic ester monomer including a crosslinkable functional group;

i) 50 to 75 parts by weight of an alkyl (meth) acrylic acid ester monomer having 2 to 14 carbon atoms of alkyl, and ii) an acrylic copolymer including 25 to 50 parts by weight of an acrylic ester monomer including an aromatic group copolymerizable with the acrylic monomer ( B); And

The iii) acrylic adhesive composition containing the polyfunctional crosslinking agent (C) which can react with the acrylic ester monomer containing a crosslinkable functional group.

In general, in order to improve light leakage, a method of adding a plasticizer or a low molecular weight to the high molecular weight copolymer or providing a stress relaxation function to the pressure-sensitive adhesive by controlling the crosslinking structure is used. However, it is difficult to completely suppress the light leakage phenomenon of the polarizing plate only through stress relaxation. This is because a partial crosslinked structure must be introduced into the pressure sensitive adhesive in order to maintain durability durability of the pressure sensitive adhesive for polarizing plates, and thus the residual stress of the pressure sensitive adhesive layer exhibited by the crosslinked structure cannot be completely removed. Therefore, there is a negative birefringence in the alkyl acrylate pressure-sensitive adhesive layer commonly used under such residual stress, which is a major cause that is difficult to further improve the light leakage with the negative birefringence present in the contracted TAC layer. In order to cancel the negative birefringence which arises in such an adhesive layer, it is possible by introduce | transducing (optical compensation) the adhesive layer which copolymerized the acrylic monomer (aromatic containing acrylic monomer) which shows positive birefringence to an adhesive layer. However, in the case of improving light leakage by simply using optical compensation as described above, a large amount of aromatic-containing acrylic monomer is required, and thus, there is a side effect in that the adhesive strength of the pressure-sensitive adhesive is greatly increased. This adversely affects re-peelability, which is a main function of the pressure-sensitive adhesive for polarizing plates. Therefore, in order to minimize the light leakage of the polarizing plate while maintaining the durability and re-peelability, which are the main functions of the pressure-sensitive adhesive for polarizing plates, it is necessary to simultaneously provide an appropriate level of optical compensation effect while maximizing the stress relaxation function of the pressure-sensitive adhesive by introducing an optimal crosslinked structure. do.

Thus, a feature of the present invention is the use of a mixture of optically compensated acrylic copolymers (A) comprising crosslinkable functional groups and optically compensated acrylic copolymers (B) free of crosslinkable functional groups to maintain the main function of the pressure sensitive adhesive. While having an optimal crosslinked structure that can minimize the light leakage phenomenon.

In order for the acrylic pressure-sensitive adhesive composition according to the present invention to have the optimum crosslinked structure as described above, the weight ratio of the acrylic copolymer (A) and the acrylic copolymer (B) is preferably 1: 9 to 4: 1.

In the present invention, when the ratio of the acrylic copolymer (A) is smaller than that of the acrylic copolymer (B), it is difficult to obtain sufficient cohesive force, so the ratio is preferably 1: 9 or more, and more preferably 1: 4 or more. Do. In addition, when the ratio of the acrylic copolymer (A) is 4: 1 or more relative to the acrylic copolymer (B), the proportion of the crosslinkable copolymer is increased, which makes it difficult to control the degree of crosslinking, and thus the stress of the pressure-sensitive adhesive in parallel with the optical compensation effect. It is difficult to improve light leakage through mitigation.

In addition, the acrylic pressure-sensitive adhesive composition according to the present invention, it is preferable that the weight average molecular weight of the acrylic copolymer (A) and the acrylic copolymer (B) are each independently 800,000 to 2 million.

If the weight average molecular weight is less than 800,000, the cohesive strength of the pressure-sensitive adhesive is insufficient, the durability is poor, and if more than 2 million, the effect of stress relaxation is insufficient and the light leakage effect is insignificant.

Hereinafter, each component of the composition will be described in detail in the present invention.

Acrylic Copolymers (A) and (B)

i) Alkyl (meth) acrylic acid ester monomer

The acrylic copolymer (A) and the acrylic copolymer (B) according to the present invention contain, as main resin, i) 50 to 75 parts by weight of an alkyl (meth) acrylic acid ester monomer having 2 to 14 carbon atoms of alkyl. I) Alkyl (meth) acrylic acid ester monomers contained in the acrylic copolymer (A) and the acrylic copolymer (B) may be the same or different.

When the content of the i) alkyl (meth) acrylic acid ester monomer exceeds 75 parts by weight, the final pressure-sensitive adhesive exhibits a large negative birefringence under residual stress, so that the effect of improving optical light leakage may be insignificant. In addition, i) if the content of the alkyl (meth) acrylic acid ester monomer is less than 50 parts by weight, the adhesive balance of the final acrylic pressure-sensitive adhesive deteriorates, and the final pressure-sensitive adhesive exhibits a positive birefringence under residual stress, thereby deteriorating the optical light leakage improvement effect. .

I) Alkyl (meth) acrylic acid ester monomers having 2 to 14 carbon atoms of alkyl include ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl (meth) acryl. Rate, t-butyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth As the acrylate, isononyl (meth) acrylate, it is preferable to use one or more selected from the group consisting of lauryl (meth) acrylate and tetradecyl (meth) acrylate. When carbon number of 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 limited to the range of 2-14.

ii) aromatic-containing (meth) acrylic monomers

The acrylic copolymer (A) and the acrylic copolymer (B) according to the present invention are characterized in that the birefringence of the negative value of the acrylic copolymer having the alkyl (meth) acrylic acid ester monomer having 2 to 14 carbon atoms as the main component under residual stress In order to compensate, a monomer exhibiting a positive birefringence under stress includes ii) 25 to 50 parts by weight of an acrylic ester monomer including an aromatic group copolymerizable with the acrylic monomer. The acrylic ester monomer containing the aromatic group ii) contained in the acrylic copolymer (A) and the acrylic copolymer (B) may be the same or different.

The content of the aromatic-containing (meth) acrylic ester monomer is appropriately 25 to 50 parts by weight of the total monomers. If the content of the aromatic-containing (meth) acrylic ester monomer in the total monomers is less than 25 parts by weight, the final pressure-sensitive adhesive exhibits negative birefringence under residual stress, so that the optical light leakage improvement is insignificant. The adhesive property balance is deteriorated, and in particular, the adhesive force is greatly increased, and the re-peelability of the polarizing plate is very poor.

It is preferable that the copolymerizable aromatic group containing (meth) acrylic acid ester monomer which concerns on this invention uses the compound of following General formula (1).

Where

R ₁ represents hydrogen or a methyl group,

R ₂ represents an alkylene group having 1 to 12 carbon atoms,

n represents an integer of 0 to 3, preferably 0 or 1,

X represents an oxygen atom, a sulfur atom or an alkylene group having 1 to 4 carbon atoms,

Ar represents an aromatic group unsubstituted or substituted with halogen, in particular bromine or chloro, or alkyl having 1 to 12 carbon atoms.

Preferred examples of the compound of Formula 1 include phenoxy ethyl (meth) acrylate, benzyl (meth) acrylate, 2-phenylthio-1-ethyl (meth) acrylate, 6- (4,6-dibromo- 2-isopropyl phenoxy) -1-hexyl (meth) acrylate, 6- (4,6-dibromo-2-sec-butyl phenoxy) -1-hexyl (meth) acrylate, 2,6- Dibromo-4-nonylphenyl (meth) acrylate, 2,6-dibromo-4-dodecyl phenyl (meth) acrylate, 2- (1-naphthyloxy) -1-ethyl (meth) acrylic Late, 2- (2-naphthyloxy) -1-ethyl (meth) acrylate, 6- (1-naphthyloxy) -1-hexyl (meth) acrylate, 6- (2-naphthyloxy)- 1-hexyl (meth) acrylate, 8- (1-naphthyloxy) -1-octyl (meth) acrylate, and 8- (2-naphthyloxy) -1-octyl (meth) acrylate This is not limited. The compound of Formula 1 may be used alone or in a mixture thereof.

Particularly preferred compounds of formula 1 are phenoxy ethyl (meth) acrylate, benzyl (meth) acrylate, 2-phenylthio-1-ethyl acrylate, 8- (2-naphthyloxy) -1-octyl acrylate , 2- (1-naphthyloxy) -ethyl acrylate and mixtures thereof, most preferably phenoxy ethyl (meth) acrylate, benzyl (meth) acrylate or mixtures thereof.

iii) crosslinkable monomers

The vinyl-based or acrylic ester monomer containing iii) a crosslinkable functional group of the acrylic copolymer (A) according to the present invention is for controlling adhesion and cohesion of the acrylic copolymer, and preferably contains an acidic or hydroxyl group in the structure. Do.

The vinyl monomer including the acidic group used in the present invention is a component that imparts cohesive force by chemical bonding so that the cohesive failure of the pressure-sensitive adhesive does not occur when the temperature reacts with the crosslinking agent.

The copolymerizable monomer including the acidic group may include one or more selected from the group consisting of a carboxyl group-containing copolymerizable monomer or an anhydride thereof, a sulfonic acid group-containing copolymerizable monomer, and a phosphoric acid group-containing copolymerizable monomer.

Wherein the carboxyl group-containing copolymerizable monomer is (meth) acrylic acid, carboxy ethyl acrylate, carboxy pentyl acrylate, itaconic acid, maleic acid, fumaric acid, or crotonic acid;

The anhydride of the carboxyl group-containing copolymerizable monomer is maleic anhydride or itaconic anhydride;

The sulfonic acid group-containing copolymerizable monomers include styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methyl propane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, and (meth) acryloyl oxy. Naphthalene sulfonic acid;

The phosphoric acid group-containing copolymerizable monomer may be selected from, for example, 2-hydroxy ethyl acryloyl phosphate, but is not limited thereto.

In addition, the vinyl or acryl-type monomer containing a hydroxyl group is 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethylene glycol It is preferable that it is 1 or more types chosen from the group which consists of (meth) acrylate and 2-hydroxypropylene glycol (meth) acrylate.

When the amount of the vinyl or acrylic monomer containing the acidic group or hydroxyl group in the acrylic copolymer (A) is too large, the adhesiveness is lowered and the peeling force is lowered, so the use of 0.01 to 10 parts by weight in the total monomer components is preferable. Do.

iv) functional monomers

Acrylic copolymers (A) and (B) according to the present invention are each independently 0 to 20 parts by weight of the total monomer weight as an optional component in order to control the glass transition temperature of the pressure-sensitive adhesive or to impart other functionalities of the formula (2) Preference is further given to functional monomers iv).

Where

R ₄ represents hydrogen or alkyl,

R ₃ represents cyano, alkyl substituted or unsubstituted phenyl, acetyloxy, or COR ₅ , wherein R ₅ represents amino or glycidyloxy unsubstituted or substituted with alkyl.

In the formula, alkyl in the definition of R ₃ to R ₅ preferably denotes lower alkyl having 1 to 6 carbon atoms, more preferably methyl or ethyl.

Examples of the compound of Formula 2 include styrene monomers such as styrene or alpha methyl styrene; Carboxylic acid vinyl esters such as vinyl acetate; Nitrogen containing vinyl, such as an acrylonitrile, (meth) acrylamide, (meth) acrylamide, N-methyl (meth) acrylamide, N-butoxy methyl (meth) acrylamide, or glycidyl (meth) acrylate Although a monomer etc. can be mentioned, It is not limited to this, The monomer etc. can be used individually or in mixture of 2 or more types.

When the content of the functional monomer (c) of the general formula (2) is too large, it is preferable to use less than 20 parts by weight of the total monomer components because the flexibility of the pressure-sensitive adhesive composition is lowered and the peeling force is lowered.

v) polymerization method

The method for producing the acrylic copolymers (A) and (B) according to the present invention is not particularly limited and can be prepared by solution polymerization, photopolymerization, bulk polymerization, suspension polymerization, or emulsion polymerization. Preferably, the acrylic copolymer is prepared using a solution polymerization method, the polymerization temperature is preferably 50 ℃ to 140 ℃, it is preferable to add the initiator in a state where the monomers are uniformly mixed.

Such a polymerization initiator can be used singly or in combination with an azo polymerization initiator such as azobisisobutyronitrile or azobiscyclohexanecarbonitrile and a peroxide such as benzoyl peroxide or acetyl peroxide.

Multifunctional Crosslinking agent  (C)

The acrylic pressure sensitive adhesive composition of the present invention may include 0.01 to 10 parts by weight of a multifunctional crosslinking agent (B) based on 100 parts by weight of the (meth) acrylic copolymer to crosslink the acrylic copolymer (A). It is possible to provide desirable physical properties according to the invention within the above range.

The multifunctional crosslinking agent (B) serves to increase the cohesive force of the pressure-sensitive adhesive by reacting with a carboxyl group or a hydroxyl group.

The polyfunctional crosslinking agent is preferably one or more selected from the group consisting of an isocyanate compound, an epoxy compound, an aziridine compound, and a metal chelate compound, and among these, it is easy to use an isocyanate compound.

In the above isocyanate compound, toluene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoform diisocyanate, tetramethyl xylene diisocyanate, naphthalene diisocyanate, and polyols thereof (such as trimethylolpropane) At least one selected from the group consisting of reactants with

The epoxy compound is composed of ethylene glycol diglycidyl ether, triglycidyl ether, trimethylol propane triglycidyl ether, N, N, N ', N'-tetraglycidyl ethylenediamine and glycerin diglycidyl ether. At least one selected from the group,

Aziridine-based compounds include N, N'-toluene-2,4-bis (1-aziridinecarboxide), N, N'-diphenylmethane-4,4'-bis (1-aziridinecarboxide) At least one selected from the group consisting of triethylenemelamine, bisisoprotaloyl-1- (2-methylaziridine), and tri-1-aziridinylphosphine oxide,

The metal chelate-based compound may be one or more selected from a compound in which a polyvalent metal selected from aluminum, iron, zinc, tin, titanium, antimony, magnesium, and vanadium is coordinated with acetylacetone or ethyl acetoacetate, but is not limited thereto.

At this time, the multifunctional crosslinking agent may be uniformly coated only when the functional group crosslinking reaction of the crosslinking agent is hardly generated in the compounding process for forming the adhesive layer. When the coating is finished and dried and aged, the crosslinked structure is formed to obtain an adhesive layer having strong elasticity and cohesive force.

additive

In addition, the composition of the present invention may further include a silane coupling agent in order to improve the adhesion stability when adhesion to the glass plate to further improve the heat and moisture resistance properties. Such a silane coupling agent serves to improve the adhesion reliability, especially when left for a long time under high temperature and high humidity, the content can be used in 0.005 ~ 5 parts by weight based on 100 parts by weight of the total acrylic copolymer. If the content is less than 0.005 parts by weight, there is no adhesion reliability improvement, and if the content is more than 5 parts by weight, the durability is poor.

Examples of the silane coupling agent compound include g-glycidoxypropyltrimethoxysilane, g-glycidoxypropylmethyldiethoxysilane, g-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, Vinyltrimethoxysilane, vinyltriethoxysilane, g-methacryloxypropyl trimethoxysilane, g-methacryloxypropyltriethoxysilane, g-aminopropyltriethoxysilane, 3-isocyanatepropyltriethoxy Silane, g-acetoacetatepropyltrimethoxysilane, and the like, and these may be used alone or in combination.

The present invention may further add a tackifying resin in order to adjust the adhesive performance, the content thereof may be used in the range of 1 to 100 parts by weight based on 100 parts by weight of the acrylic copolymer (A). When the content is less than 1 part by weight, the tackifying function is poor, while when the content is more than 100 parts by weight, the compatibility or cohesion force of the pressure-sensitive adhesive may be reduced.

Tackifying resins include (hydrogenated) hydrocarbon resins, (hydrogenated) rosin resins, (hydrogenated) rosin ester resins, (hydrogenated) terpene resins, (hydrogenated) terpene phenol resins, polymerized rosin resins, polymerized rosin ester resins, etc. It can be used, these can be used individually or in mixture of 2 or more types.

In addition, acrylic low molecular weights, epoxy resins and hardeners may be additionally mixed for specific purposes, and UV stabilizers, antioxidants, colorants 16, reinforcing agents, fillers, antifoaming agents, surfactants, and plasticizers may be appropriately used according to general purposes. It can be added and used.

In addition, the present invention is a polarizing film; And

Pressure-sensitive adhesive layer containing the acrylic pressure-sensitive adhesive composition according to the invention

It relates to a polarizing plate comprising a.

The polarizing plate of this invention contains the adhesive 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.

Examples of the polarizing film include a film made by containing a polarizing component such as iodine or a dichroic dye in a film made of polyvinyl alcohol-based resin, and the like, and the thickness of these polarizing films is not particularly limited. The thickness can be formed. In this case, the polyvinyl alcohol-based resin may be polyvinyl alcohol, polyvinyl formal, polyvinyl acetal, or saponified vinyl acetate copolymer.

Cellulose-based films such as triacetyl cellulose on both sides of the polarizing film; Polyester film such as polycarbonate or polyethylene terephthalate; Polyether based films such as polyethersulfone; Alternatively, a multilayer film in which protective films such as polyethylene, polypropylene, a polyolefin having a cyclo or norbornene structure, or a polyolefin-based film such as an ethylene propylene copolymer is laminated may be formed. At this time, the thickness of these protective films is also not particularly limited, and may form a conventional thickness.

There is no particular limitation on the method of forming the pressure-sensitive adhesive layer on the polarizing film in the present invention. After drying, the method of transferring the pressure-sensitive adhesive layer formed on the surface of the peelable base material onto the surface of the polarizing film and 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, or a brightness enhancement film, the pressure-sensitive adhesive according to the invention The layer may be attached to the functional layer.

The polarizing plate to which the pressure-sensitive adhesive of the present invention is applied can be applied to all conventional liquid crystal display devices, and the kind 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

68 parts by weight of n-butylacrylate (BA), 2.0 parts by weight of hydroxy methacrylate, as shown in Table 1, in a 1L reactor equipped with a refrigeration system to allow nitrogen gas to be refluxed and to facilitate temperature control. Part, a mixture of monomers consisting of 30 parts by weight of benzyl acrylate was added. Then, 150 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., 0.03 parts by weight of azobisisobutyronitrile (AIBN), a reaction initiator, and reacted for 8 hours. After the reaction, the mixture was diluted with ethyl acetate (EAc) to prepare an acrylic copolymer having a solid content of 20% by weight and a weight average molecular weight of 1.2 million.

Preparation Example 2-8

In Preparation Example 1, as shown in Table 1, a part of each component was not added or partially added to prepare a high molecular weight acrylic copolymer. The results are shown in Table 1.

sign Ingredient Preparation Example 1 Preparation Example 2 Preparation Example 3 Preparation Example 4 Preparation Example 5 Preparation Example 6 Preparation Example 7 Preparation Example 8  Copolymer Composition (parts by weight) i) n-BA 68 63 43 88 70 65 45 90 ii) BzA 30 55 10 30 55 10 PHEA 35 35 iii) 2-HEMA 2 2 2 AA 2 (C) AIBN 0.03 0.03 0.03 0.03 0.03 0.03 0.03 0.03 menstruum EAc 120 120 150 150 120 150 150 120 Weight average molecular weight (only) 150 150 120 160 160 155 125 160 n-BA: n-butyl acrylate, BzA: benzyl acrylate, PHEA: phenoxy ethyl acrylate, 2-HEMA: 2-hydroxyethyl methacrylate, AA: acrylic acid, AIBN: azobisisobutyronitrile, EAc: ethyl acetate

Example 1

<Mixing>

Tolylene diisocyanate adduct of isocyanate-based trimethylolpropane (TDI- 1) Add 0.1 parts by weight and γ-glycidoxypropyltrimethoxysilane, dilute to an appropriate concentration in consideration of coating properties, mix uniformly, coat on release paper, dry, and then apply 30 micron uniform adhesive layer. Got.

<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 | 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 below.

Examples 2-3

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.

Comparative Example 1-4

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.

Test Example

1. Re-peelability

The pressure-sensitive adhesive coated polarizing plate was cut into a width of 90 mm and a length of 170 mm, and then attached to a non-alkali glass plate of Corning by using a laminator. After standing, the polarizing plate was peeled off the glass. At this time, re-peelability was evaluated as follows.

○: It is re-peelable without difficulty

△: difficult to re-peel

X: Re-peeling is difficult so that a base material and glass may be destroyed

2. Endurance 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

3. Light transmission uniformity (light leakage)

In order to investigate the uniformity of light transmittance, it was observed whether the light leaked out from the dark room using the backlight. The pressure-sensitive adhesive-coated polarizing plate (310 mm × 385 mm) prepared in Example 1 was attached to the glass substrate in a state where the optical absorption axis was crossed on both sides. The specimens were stored for 500 hours at a temperature of 60 ° C., a relative humidity of 90% and a temperature of 80 ° C., and then evaluated for light transmission uniformity. Light transmission uniformity was evaluated based on the following criteria.

⊙: Unevenness of light transmittance is hard to judge

○: slight light transmittance nonuniformity

△: non-uniformity of light transmittance

X: The light non-uniformity is abundant.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Compounding composition (parts by weight) Preparation Example 1 20 5 Preparation Example 2 30 40 100 Preparation Example 3 20 Preparation Example 4 ○ 30 Preparation Example 5 80 95 Preparation Example 6 70 60 Preparation Example 7 80 Preparation Example 8 70 Crosslinking agent 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Re-peelability ○ ○ ○ X X ○ X Durability Reliability ○ ○ ○ X △ ○ ○ Light fountain ⊙ ⊙ ⊙ ⊙ ⊙ X ○

In the results of Table 2, Examples 1 to 3 of the present invention are excellent in durability, workability (repeelability), and exhibit excellent low light leakage properties. On the other hand, in Comparative Example 1, the content of the crosslinkable polymer is so small that the low light leakage characteristics are excellent, but the re-peelability and durability are poor. In Comparative Example 2, too much aromatic acrylic ester monomer is added to the low light leakage characteristics. Excellent but re-peelable and durable. In addition, in the case of Comparative Example 3, the content of the aromatic acrylic ester is too low, and the low light leakage property is poor. In the case of Comparative Example 4, the crosslinkable polymer is used alone, so the re-peelability is very poor.

The present invention relates to an acrylic pressure-sensitive adhesive composition for polarizing plates, and is excellent in low light leakage characteristics without changing main characteristics such as durability and reworkability under high temperature and high temperature and high humidity conditions. Therefore, when the adhesive composition is applied to the polarizing plate of the liquid crystal display device, the light leakage phenomenon generated after long time use can be prevented.

While the invention has been described in detail above with reference to the described embodiments, it will be apparent to those skilled in the art that various modifications and variations are possible within the scope and spirit of the invention, and such modifications and variations fall within the scope of the appended claims. It is also natural.

Claims (21)

i) 50 to 75 parts by weight of an alkyl (meth) acrylic acid ester monomer having 2 to 14 carbon atoms, ii) 25 to 50 parts by weight of an acrylic ester monomer including an aromatic group copolymerizable with the acrylic monomer, and iii) a crosslinkable functional group Acrylic copolymer (A) comprising 0.1 to 10 parts by weight of a vinyl or acrylic ester monomer comprising a; i) 50 to 75 parts by weight of an alkyl (meth) acrylic acid ester monomer having 2 to 14 carbon atoms of alkyl, and ii) an acrylic copolymer including 25 to 50 parts by weight of an acrylic ester monomer including an aromatic group copolymerizable with the acrylic monomer ( B); And Said iii) acrylic adhesive composition containing the polyfunctional crosslinking agent (C) which can react with the vinyl-type or acrylic ester monomer containing a crosslinkable functional group. The method of claim 1, The weight ratio of an acrylic copolymer (A) and an acrylic copolymer (B) is 1: 9-4: 1, The acrylic adhesive composition characterized by the above-mentioned. The method of claim 1, The acrylic pressure-sensitive adhesive composition, wherein the weight average molecular weight of the acrylic copolymer (A) and the acrylic copolymer (B) is independently 800,000 to 2 million. The method of claim 1, I) Alkyl (meth) acrylic acid ester monomers of the acrylic copolymer (A) and the acrylic copolymer (B) are each independently ethyl (meth) acrylate, n-propyl (meth) acrylate and isopropyl (meth) acrylate. , n-butyl (meth) acrylate, t-butyl (meth) acrylate, sec-butyl (meth) acrylate, pentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth Acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, at least one member selected from the group consisting of lauryl (meth) acrylate, and tetradecyl (meth) acrylate Pressure-sensitive adhesive composition. The method of claim 1, Acrylic pressure-sensitive adhesive composition, characterized in that the acrylic ester monomers containing the ii) aromatic group of the acrylic copolymer (A) and the acrylic copolymer (B) are each independently a compound represented by the following general formula (1): [Formula 1]

Where R ₁ represents hydrogen or a methyl group, R ₂ represents an alkylene group having 1 to 12 carbon atoms, n represents an integer of 0 to 3, X represents an oxygen atom, a sulfur atom, or an alkylene group having 1 to 4 carbon atoms, Ar represents an aromatic group unsubstituted or substituted with halogen or alkyl having 1 to 12 carbon atoms. The method of claim 5, wherein Compounds of formula (I) include phenoxy ethyl (meth) acrylate, benzyl (meth) acrylate, 2-phenylthio-1-ethyl (meth) acrylate, 6- (4,6-dibromo-2-isopropyl Phenoxy) -1-hexyl (meth) acrylate, 6- (4,6-dibromo-2-sec-butyl phenoxy) -1-hexyl (meth) acrylate, 2,6-dibromo- 4-nonylphenyl (meth) acrylate, 2,6-dibromo-4-dodecyl phenyl (meth) acrylate, 2- (1-naphthyloxy) -1-ethyl (meth) acrylate, 2- (2-naphthyloxy) -1-ethyl (meth) acrylate, 6- (1-naphthyloxy) -1-hexyl (meth) acrylate, 6- (2-naphthyloxy) -1-hexyl ( 1 type selected from the group consisting of meta) acrylate, 8- (1-naphthyloxy) -1-octyl (meth) acrylate, and 8- (2-naphthyloxy) -1-octyl (meth) acrylate The acrylic adhesive composition characterized by the above. The method of claim 1, Iii) The vinyl-based or acrylic ester monomer containing the crosslinkable functional group of the acrylic copolymer (A) contains an acidic group or a hydroxyl group in the structure. The method of claim 7, wherein Vinyl or acrylic monomers containing acidic groups include (meth) acrylic acid, acrylic acid duplexes, carboxy ethyl acrylate, carboxy pentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, maleic anhydride, itaconic anhydride, styrene sulfonic acid, Allyl sulfonic acid, 2- (meth) acrylamide-2-methyl propane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyl oxy naphthalene sulfonic acid, and 2-hydroxy ethyl arc Acrylic pressure-sensitive adhesive composition, characterized in that at least one member selected from the group consisting of lyoyl phosphate. The method of claim 7, wherein The vinyl or acrylic monomer containing a hydroxyl group is 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethylene glycol ( It is at least 1 type selected from the group which consists of a meta) acrylate, and 2-hydroxypropylene glycol (meth) acrylate, The acrylic adhesive composition characterized by the above-mentioned. The method of claim 1, Acrylic copolymer (A) and acrylic copolymer (B) are each independently an acrylic pressure-sensitive adhesive composition, characterized in that further comprises 0 to 20 parts by weight of the functional monomer of the formula (2) relative to the total monomer weight. [Formula 2]

Where R ₄ represents hydrogen or alkyl, R ₃ represents cyano, alkyl substituted or unsubstituted phenyl, acetyloxy, or COR ₅ , wherein R ₅ represents amino or glycidyloxy unsubstituted or substituted with alkyl. The method of claim 10, The functional monomer of formula (2) is acrylonitrile, (meth) acrylamide, (meth) acrylamide, N-methyl (meth) acrylamide, N-butoxy methyl (meth) acrylamide, styrene, methylstyrene, glycidyl Acrylic adhesive composition, characterized in that at least one member selected from the group consisting of (meth) acrylate and vinyl acetate. The method of claim 1, The polyfunctional crosslinking agent (C) is contained in an amount of 0.01 to 10 parts by weight based on the acrylic copolymer (A). The method of claim 12, The polyfunctional crosslinking agent (C) is at least one member selected from the group consisting of an isocyanate compound, an epoxy compound, an aziridine compound, and a metal chelate compound. The method of claim 13, The polyfunctional crosslinking agent (C) consists of tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoform diisocyanate, tetramethyl xylene diisocyanate, naphthalene diisocyanate, and reactants thereof with polyols. Acrylic pressure-sensitive adhesive composition, characterized in that the at least one isocyanate compound selected from the group. The method of claim 1, Acrylic pressure-sensitive adhesive composition, characterized in that it further comprises 0.005 to 5 parts by weight of a silane coupling agent based on 100 parts by weight of the total acrylic copolymer. The method of claim 15, Silane coupling agents include g-glycidoxypropyltrimethoxysilane, g-glycidoxypropylmethyldiethoxysilane, g-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, and vinyltri Methoxysilane, vinyltriethoxysilane, g-methacryloxypropyltrimethoxysilane, g-methacryloxypropyltriethoxysilane, g-aminopropyltriethoxysilane, 3-isocyanatepropyltriethoxysilane, And g-acetoacetatepropyltrimethoxysilane. 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 total acrylic copolymer. The method of claim 17, Tackifying resins include (hydrogenated) hydrocarbon resins, (hydrogenated) rosin resins, (hydrogenated) rosin ester resins, (hydrogenated) terpene resins, (hydrogenated) terpene phenol resins, polymeric rosin resins, and polymeric rosin ester resins. Acrylic pressure-sensitive adhesive composition, characterized in that at least one member selected from the group consisting of. Polarizing film; And A pressure-sensitive adhesive layer containing the acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 16. Polarizing plate comprising a. 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.