KR20190079425A - Acryl-based adhesive composition, polarizing plate and display device - Google Patents

Abstract

The present invention relates to an acrylic adhesive composition which includes an acrylic copolymer formed by polymerizing a monomer mixture containing an alkyl (meth)acrylate monomer, a (meth)acrylic monomer having a crosslinkable functional group, and a monomer represented by chemical formula 1, R^1-CH=CR^2-(C=O)-O-X-Y. In the acrylic adhesive composition, the acrylic copolymer has an average molecular weight of 300,000 to 1,000,000 and has a branched polymer structure. In chemical formula 1, R^1 is hydrogen, a C1-C6 alkyl group, or a C1-C6 alkenyl group, R^2 is hydrogen or a C1-C10 alkyl group, X is a single bond, a C1-C10 alkylene group, a C2-C10 alkenylene group, an ether, an ester, or a combination thereof and Y is a vinyl group, an allyl group, or a C3-C10 cycloalkenyl group. The acrylic adhesive composition provided by the present invention has low viscosity even when a solid content is high.

Description

TECHNICAL FIELD [0001] The present invention relates to an acrylic pressure-sensitive adhesive composition, a polarizer, and a display device,

The present invention relates to an acrylic pressure sensitive adhesive composition, a polarizing plate and a display device, and more particularly, to an acrylic pressure sensitive adhesive composition capable of realizing a low viscosity property even when a weight average molecular weight is high and a solid content is high, ≪ / RTI >

2. Description of the Related Art In general, a liquid crystal display device (LCD) includes a liquid crystal cell including a liquid crystal and a polarizing plate, and an adhesive layer is used to attach the liquid crystal cell and the polarizing plate. An acrylic resin, a rubber, a urethane resin, a silicone resin or EVA (Ethylene Vinyl Acetate) is used as a polarizer attaching pressure-sensitive adhesive for forming such a pressure-sensitive adhesive layer. Among them, an acrylic resin having transparency, oxidation resistance and yellowing resistance is used as a base Are widely used.

In the case of an acrylic pressure-sensitive adhesive for a polarizing plate, it is preferable to use an acrylic resin having a high weight-average molecular weight in order to improve durability and curing efficiency. When an acrylic resin having a low weight average molecular weight is used, not only the curing efficiency is lowered and the curing speed is slowed but also the durability of the pressure-sensitive adhesive decreases due to the cohesive force and the degree of curing under high temperature or high temperature / high humidity conditions.

However, when an acrylic resin having a high weight average molecular weight is used, there is a problem that the viscosity of the coating liquid increases and the workability is lowered. It is possible to control the viscosity of the coating liquid by lowering the solid content in the coating liquid. However, when the pressure-sensitive adhesive layer is formed using the coating liquid having a low solid content as described above, the production cost is increased and the productivity is lowered and it is difficult to precisely control the thickness of the pressure- There is a problem.

Therefore, as a method for increasing the solid content while maintaining the viscosity of the coating liquid at an appropriate level, a method of mixing a low molecular weight or increasing the content of the unreacted curing agent has been proposed. However, in the case of the method of mixing the low molecular weight materials, the pressure-sensitive adhesive layer is easily deformed, so that when the polarizer is stored in the roll form in the polarizer production process, the pressure-sensitive adhesive layer pit is likely to occur, A phenomenon occurs in which the pressure-sensitive adhesive agent protrudes from the surface of the polarizing plate, thereby causing the polarizing plate to be easily contaminated. Further, when the content of the unreacted curing agent is increased, it is difficult to re-peel off the adhesive after a certain period of time after the polarizing plate is attached to the liquid crystal panel, and the adhesive property changes with time due to the influence of the residual curing agent .

Accordingly, development of an acrylic pressure-sensitive adhesive composition for a polarizing plate capable of realizing a low viscosity property with a high weight-average molecular weight and a high solids content is desired.

Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to provide an acrylic pressure sensitive adhesive composition using an acrylic copolymer having a high weight average molecular weight and having low viscosity even when the solid content is high.

The present invention also provides a polarizing plate including a pressure-sensitive adhesive layer formed by the acrylic pressure-sensitive adhesive composition as described above, and a display device including the same.

In one aspect, the present invention relates to an acrylic copolymer (A) formed by polymerizing a monomer mixture comprising a monomer represented by the following formula (1), a (meth) acrylic monomer having a crosslinkable functional group, and an alkyl (meth) Wherein the acrylic copolymer has a weight average molecular weight of 300,000 to 1,000,000 and a branched polymer structure.

[Chemical Formula 1]

R ^{1 is} -CH = CR ² - (C = O) -OXY

Wherein R ¹ is hydrogen, a C ¹ to C 6 alkyl group or a C 1 to C 6 alkenyl group, R ² is hydrogen or a C 1 to C 10 alkyl group, X is a single bond, a C 1 to C 10 alkylene group, a C 2 to C 10 alkenylene group , An ether, an ester, or a combination thereof, and Y is a vinyl group, an allyl group, or a C3-C10 cycloalkenyl group.

In another aspect, the present invention provides a polarizing film comprising: a polarizing film; And a pressure-sensitive adhesive layer formed on one or both surfaces of the polarizing film, wherein the pressure-sensitive adhesive layer comprises a cured product of the acrylic pressure-sensitive adhesive composition according to the present invention.

In another aspect, the present invention provides a display device including the polarizer according to the present invention.

The acrylic pressure sensitive adhesive composition according to the present invention may include a branched acrylic copolymer, and may have a low viscosity even though an acrylic copolymer having a relatively high weight average molecular weight is used. Accordingly, when the acrylic pressure sensitive adhesive composition of the present invention is used, low viscosity can be realized even when the solid content in the coating liquid is as high as 30% by weight or more, so that the coating workability at the time of forming the pressure sensitive adhesive layer is excellent, , The thickness of the adhesive layer can be precisely controlled.

Further, since the acrylic pressure sensitive adhesive composition according to the present invention includes an acrylic copolymer having a branched structure having a high weight average molecular weight, it has excellent curing efficiency and cohesion, and the pressure sensitive adhesive layer produced using the acrylic copolymer has little change with time.

In addition, the polarizing plate including the pressure-sensitive adhesive layer formed using the acrylic pressure sensitive adhesive composition according to the present invention has excellent durability under high temperature and high temperature / high humidity conditions, and is excellent in re-peeling property and adhesive property.

Hereinafter, the present invention will be described in detail.

In the case where the word 'includes', 'having', 'done', etc. are used in this specification, other parts can be added unless '~ only' is used. Unless the context clearly dictates otherwise, including the plural unless the context clearly dictates otherwise.

In interpreting the constituent elements, it is construed to include the error range even if there is no separate description.

In the present specification, " (meth) acrylic " is a general term for acrylic and methacrylic. For example, (meth) acrylate includes methacrylate and acrylate, and (meth) acrylic acid includes acrylic acid and methacrylic acid.

In the present specification, " X to Y " representing the range means " X or more and Y or less ".

As used herein, the term " branched polymer structure " means a polymer structure having two or more long chains grown in different directions.

The present inventors have conducted extensive research to develop an acrylic pressure sensitive adhesive composition having excellent durability, productivity and workability. As a result, it has been found that by using specific monomers together in the production of an acrylic copolymer, an acrylic copolymer having a branched polymer structure can be produced When such an acrylic copolymer having a branched polymer structure is used, even when the weight average molecular weight of the copolymer is as high as 1,000,000, it has a low viscosity property and excellent coating property can be obtained even when the solid content in the coating liquid is increased And completed the present invention. Hereinafter, the acrylic pressure sensitive adhesive composition according to the present invention will be described in detail.

Pressure-sensitive adhesive composition

(1) Acrylic copolymer

The acrylic pressure sensitive adhesive composition according to the present invention is an acrylic pressure sensitive adhesive composition which is obtained by polymerizing a monomer mixture comprising a monomer represented by the following formula (1), a (meth) acrylic monomer having a crosslinkable functional group and an alkyl (meth) .

[Chemical Formula 1]

R ^{1 is} -CH = CR ² - (C = O) -OXY

Wherein R ¹ is hydrogen, a C ¹ to C 6 alkyl group or a C 1 to C 6 alkenyl group, R ² is hydrogen or a C 1 to C 10 alkyl group, X is a single bond, a C 1 to C 10 alkylene group, a C 2 to C 10 alkenylene group , An ether, an ester, or a combination thereof, and Y is a vinyl group, an allyl group, or a C3-C10 cycloalkenyl group.

The monomer represented by the above formula (1) is for forming an acrylic copolymer having a branched polymer structure. Conventionally, acrylic copolymers having a linear polymer structure in which monomers are polymerized in a single long chain type are mainly used as an acrylic copolymer used in a pressure sensitive adhesive for a polarizing plate. However, when such an acrylic copolymer having a linear polymer structure is used, there is a problem that the viscosity increases as the weight average molecular weight increases, resulting in poor workability.

However, studies by the present inventors have revealed that when an acrylic copolymer is formed by adding a monomer represented by the above formula (1), a copolymer having a non-linear branched polymer structure is produced. Specifically, the monomer of the above formula (1) has two or more ethylene groups and radicals can be respectively formed in the free radical polymerization and chains can be grown in different directions. Thus, the monomer having two or more chains Type polymer is formed. Since such an acrylic copolymer having a branched polymer structure has a lower viscosity than an acrylic copolymer having a linear polymer structure having the same weight average molecular weight, excellent coating properties can be achieved even if the solid content in the coating liquid is increased.

Specific examples of the monomer represented by the formula (1) include allyl methacrylate, allyl acrylate, methallyl methacrylate, methallyl acrylate, 3-butenyl acrylate, but-3-enyl-2-methylprop-2-enoate, 2-allyloxyethyl Acrylate, 2-allyloxyethyl acrylate, 2-allyloxyethyl methacrylate, 3-allyloxypropyl methacrylate, 3-allyloxypropyl acrylate, 2-allyloxyethoxyethyl methacrylate, 2-allyloxyethoxyethyl acrylate, cyclohex-2-enyl acrylate, cyclohex-2-enyl acrylate, 2-en-1-yl-2-methylprop-2-enoate (cyclo 3-vinylcyclohex-2-enyl acrylate), but may be at least one selected from the group consisting of hex-2-en-1-yl 2-methylprop- But is not limited thereto.

The monomer represented by the formula (1) may be contained in an amount of 0.01 to 1 part by weight, preferably 0.05 to 0.8 part by weight, more preferably 0.1 to 0.6 part by weight based on 100 parts by weight of the monomer mixture. When the content of the monomer represented by the general formula (1) is less than 0.01 part by weight, it is difficult to prepare a copolymer having a low viscosity. If the content is more than 1 part by weight, the crosslinking reaction proceeds during the polymerization reaction, It is difficult to control.

On the other hand, the (meth) acrylic monomer having a crosslinkable functional group is one for improving the durability, adhesion and cohesion of the pressure-sensitive adhesive, and examples thereof include a hydroxy group-containing monomer, a carboxyl group-containing monomer or a nitrogen- It is not. Specific examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (Meth) acrylate, 2-hydroxyethyleneglycol (meth) acrylate or 2-hydroxypropyleneglycol (meth) acrylate, and examples of the carboxyl group- (Meth) acryloyloxypropionic acid, 4- (meth) acryloyloxybutyric acid, acrylic acid dimer, itaconic acid, maleic acid (meth) acrylate, And maleic anhydride. Examples of the nitrogen-containing monomer include (meth) acrylamide, N-vinylpyrrolidone and N-vinylcaprolactam, but are not limited thereto.

The (meth) acrylic monomer having a crosslinkable functional group may be contained in an amount of 0.1 to 15 parts by weight, preferably 1 to 10 parts by weight, more preferably 1 to 5 parts by weight based on 100 parts by weight of the monomer mixture. When the content of the (meth) acrylic monomer having a crosslinkable functional group satisfies the above range, excellent adhesion and durability can be obtained.

On the other hand, the alkyl (meth) acrylate monomer preferably contains an alkyl group having 2 to 14 carbon atoms. If the alkyl group contained in the alkyl (meth) acrylate monomer is excessively cured, the cohesive force of the pressure-sensitive adhesive decreases, and it becomes difficult to control the glass transition temperature (Tg) and tackiness. Examples of the alkyl (meth) acrylate monomer include ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, Acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate and tetradecyl (meth) acrylate. In the present invention, Or more.

The alkyl (meth) acrylate monomer may be contained in an amount of 84 to 99.89 parts by weight, preferably 89.2 to 96.95 parts by weight, and more preferably 94.4 to 98.9 parts by weight based on 100 parts by weight of the monomer mixture. When the content of the alkyl (meth) acrylate monomer is within the above range, excellent adhesion and durability can be obtained.

According to one embodiment, the (meth) acrylic copolymer is a mixture of 84 parts by weight to 99.89 parts by weight of an alkyl (meth) acrylate monomer, 0.1 to 15 parts by weight of a crosslinkable functional group Meth) acrylic monomer and 0.01 to 1 part by weight of a monomer represented by the following formula (1).

The acrylic copolymer according to the present invention can be prepared by mixing each of the above-mentioned monomers to prepare a monomer mixture, and then polymerizing the monomer mixture. Here, the polymerization method is not particularly limited, and various polymerization methods known in the art can be used, for example, polymerization methods such as solution polymerization, photopolymerization, bulk polymerization, suspension polymerization or emulsion polymerization. In the polymerization, a polymerization initiator, molecular weight control, and the like may be further added, and the timing of introduction of each component is not particularly limited. That is, the components may be input in a batch or may be divided into several parts.

In the present invention, in particular, an acrylic resin can be produced by a solution polymerization method. In solution polymerization, an initiator, a molecular weight modifier and the like are added while uniformly mixing the respective monomers, and the solution polymerization is carried out at a polymerization temperature of 50 to 140 ° C . Examples of initiators that can be used in this process include azo based initiators such as azobisisobutyronitrile or azobiscyclohexanecarbonitrile and / or conventional initiators such as peroxides such as benzoyl peroxide or acetyl peroxide and the like, Or a mixture of two or more of them may be used, but the present invention is not limited thereto. Examples of the molecular weight regulator include mercaptans such as t-dodecyl mercaptan and n-dodecyl mercaptan, terpenes such as dipentin or t-terpene, halogenated hydrocarbons such as chloroform or carbon tetrachloride, or pentaerythritol Tetrakis-3-mercaptopropionate, and the like, but the present invention is not limited thereto.

The acrylic copolymer of the present invention prepared as described above has a weight average molecular weight of 300,000 to 1,000,000, preferably 400,000 to 1,000,000, more preferably 500,000 to 1,000,000. When the weight average molecular weight of the acrylic copolymer is less than 300,000, there is a problem that the cohesive force of the pressure-sensitive adhesive is insufficient due to the lowering of the curing efficiency and the re-peeling property is lowered and the durability under high temperature or high temperature / high humidity environment is poor. , When the solid content in the coating liquid is 30% by weight or more, the viscosity is so high that the coating property is lowered and it is difficult to produce a uniform pressure-sensitive adhesive layer.

In addition, the acrylic copolymer of the present invention has a branched polymer structure. Since the acrylic copolymer having a branched polymer structure has a lower viscosity than an acrylic copolymer having a linear polymer structure having the same weight average molecular weight, the pressure-sensitive adhesive composition containing the same has excellent coating properties even when the solid content is high .

(2) Multifunctional crosslinking agent

The pressure-sensitive adhesive composition of the present invention may further comprise a multifunctional crosslinking agent together with the acrylic copolymer.

The polyfunctional crosslinking agent reacts with the acrylic copolymer to form a crosslinked structure to further improve the durability of the adhesive layer. For example, an isocyanate crosslinking agent may be used. As the isocyanate crosslinking agent, those known in the art can be used, and examples thereof include toluene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylenediisocyanate, hydrogenated triphenyl diisocyanate, 1,4-diisocyanate, 1,3-bisisocyanatomethylcyclohexane, tetramethylxylene diisocyanate, 1, 1-xylylene diisocyanate, 1, , 5-naphthalene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, trimethylolpropane-modified toluene diisocyanate, trimethylolpropane- Diisocyanate, trilene diisocyanate adduct of trimethylol propane, trimethyl Xylene isocyanate radio air ducts, storage diphenylmethane diisocyanate storage of propane, methylene bis triisocyanate, those of the polyol (trimethylol propane), and a mixture thereof and the like.

The polyfunctional crosslinking agent may be included in an amount of 0.01 to 5 parts by weight, more preferably 0.1 to 5 parts by weight, and more preferably 0.1 to 3 parts by weight based on 100 parts by weight of the acrylic copolymer. When the content of the polyfunctional crosslinking agent is in the above range, excellent durability can be obtained without deteriorating physical properties such as adhesiveness.

(3) Other components

The pressure-sensitive adhesive composition of the present invention may further comprise other components in addition to the above-mentioned components for controlling properties, such as a solvent, a silane coupling agent, a crosslinking catalyst, a tackifier resin, an additive and the like.

The pressure-sensitive adhesive composition of the present invention may further comprise a solvent for viscosity control. The solvent may include, for example, ethyl acetate, n-pentane, isopentane, neopentane, n-hexane, n-octane, n-heptane, methyl ethyl ketone, acetone, toluene, But is not limited thereto. The solvent may be contained in an amount such that the solids content in the pressure-sensitive adhesive composition is 30% by weight or more, preferably 30 to 60% by weight.

Further, the pressure-sensitive adhesive composition of the present invention may further comprise a silane coupling agent.

Such a silane coupling agent improves the adhesion between the pressure-sensitive adhesive and the glass substrate and improves the adhesion stability, improves heat resistance and moisture resistance, and improves adhesion reliability when the pressure-sensitive adhesive is left standing for a long time under high temperature and / do. Examples of the coupling agent that can be used in the present invention include? -Glycidoxypropyltriethoxysilane,? -Glycidoxypropyltrimethoxysilane,? -Glycidoxypropylmethyldiethoxysilane,? -Glycidoxy Propyltrimethoxysilane, propyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane,? -Methacryloxypropyltrimethoxysilane,? -Methacryloxypropyltriethoxysilane, aminopropyltrimethoxysilane,? -aminopropyltrimethoxysilane,? -aminopropyltriethoxysilane, 3-isocyanatopropyltriethoxysilane,? -acetoacetate propyltrimethoxysilane,? -acetoacetate propyltriethoxysilane, ? -cyanoacetyltrimethoxysilane,? -cyanoacetyltriethoxysilane and acetoxyacetotrimethoxysilane, and mixtures of one or more of the above can be used. In the present invention, it is preferable to use a silane-based coupling agent having an acetoacetate group or a? -Cyanoacetyl group, but the present invention is not limited thereto.

For example, the silane coupling agent may be a compound represented by the following formula (2).

(2)

(R ³ ) _n Si (R ⁴ ) _{4 -n}

In the above formula (2), R ³ is a? -Cyano acetyl group, an acetoacetyl group or an acetoacetylalkyl group, R ⁴ is an alkoxy group, and n is an integer of 1 to 3. The alkyl group or the alkoxy group of Formula 2 may have 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms, and may be linear or branched.

Specific examples of the compound represented by Formula 2 include acetoacetylpropyltrimethoxysilane, acetoacetylpropyltriethoxysilane, beta-cyanoacetyltrimethoxysilane, and beta-cyanoacetyltriethoxysilane. But is not limited thereto.

The silane coupling agent in the composition of the present invention may be contained in an amount of 0.01 to 5 parts by weight, preferably 0.01 to 1 part by weight, based on 100 parts by weight of the acrylic copolymer. If the content of the coupling agent is less than 0.01 part by weight, the effect of increasing the adhesive strength is insignificant, and if it exceeds 5 parts by weight, the durability may be deteriorated.

The pressure-sensitive adhesive composition of the present invention may further comprise a crosslinking catalyst. The crosslinking catalyst is used for accelerating the curing (crosslinking) of the pressure-sensitive adhesive layer. When the crosslinking catalyst is contained in the pressure-sensitive adhesive composition, there is an advantage that it is not necessary to perform a separate aging step after coating and drying on the substrate surface. Examples of the crosslinking catalyst include bis (tri-n-butyltin) oxide, bis (tri-n-butyltin) sulfate, di-n-butyldiphenyltin, Di-n-butyl tin dilaurate, di-n-butyl tin oxide, dimethyl diphenyl tin, dimethyl n-propyl tin oxide, But are not limited to, dimethyl tin dichloride, diphenyl tin dichloride, diphenyl tin oxide, hexa n-butyl tin, hexaphenyl tin, tetra-n-butyl tin, tetraphenyl tin, tin (II) Tin (II) chloride, tin (II) iodide, tin (II) oxalate and the like can be used, but the present invention is not limited thereto.

The crosslinking catalyst may be used in an amount of 0.001 to 0.5 parts by weight, preferably 0.001 to 0.1 parts by weight based on 100 parts by weight of the acrylic copolymer. If the content of the crosslinking catalyst is less than 0.001 parts by weight, the effect of accelerating the curing is insignificant. If the amount exceeds 0.5 parts by weight, durability may be lowered.

The pressure-sensitive adhesive composition of the present invention may further comprise 1 part by weight to 100 parts by weight of a tackifying resin, based on 100 parts by weight of the acrylic copolymer, from the viewpoint of controlling the tacking performance. Examples of such a tackifier resin include, but are not limited to, (hydrogenated) hydrocarbon resin, hydrogenated rosin resin, hydrogenated rosin ester resin, hydrogenated terpene resin, hydrogenated terpene phenol resin, A polymerized rosin resin, a polymerized rosin ester resin and the like, or a mixture of two or more thereof. When the content of the tackifier resin is less than 1 part by weight, the effect of addition may be insignificant. When the content of the tackifier resin is more than 100 parts by weight, there is a fear that the effect of improving compatibility and / or cohesive strength is lowered.

The pressure-sensitive adhesive composition of the present invention may also contain one or more additives selected from the group consisting of epoxy resins, curing agents, ultraviolet stabilizers, antioxidants, colorants, reinforcing agents, fillers, defoamers, surfactants and plasticizers, . ≪ / RTI >

The pressure-sensitive adhesive composition according to the present invention containing the above-mentioned components has a lower viscosity than a conventional pressure-sensitive adhesive composition using a linear polymeric acrylic copolymer having the same level of weight average molecular weight. Thus, excellent coating properties can be achieved even when the solid content in the pressure-sensitive adhesive composition is high. Specifically, the pressure-sensitive adhesive composition according to the present invention has a viscosity of less than 2,000 cP, preferably about 500 cP to 2,000 cP, at 23, even when the solid content is at least 30% by weight, for example, from 30% appear. Here, the solid content may mean the solid content at the time when the pressure-sensitive adhesive composition of the present invention is prepared in the form of a coating solution or the like and applied to the process of manufacturing the pressure-sensitive adhesive. As described above, when the pressure-sensitive adhesive composition of the present invention is used, the solid content in the coating liquid can be increased without deteriorating the coating property, so that not only the productivity is excellent but also the thickness and the like can be precisely controlled.

In addition, the pressure-sensitive adhesive composition of the present invention has a weight average molecular weight of 300,000 to 1,000,000, and is excellent in re-peeling property of the pressure-sensitive adhesive layer using an acrylic copolymer having a branched polymer structure and has excellent durability in high temperature and high temperature / And also has a merit that the physical properties of the adhesive layer are not changed with the lapse of time.

Polarizer

Next, a polarizing plate according to the present invention will be described.

A polarizing plate according to the present invention includes: a polarizing film; And an adhesive layer formed on one or both surfaces of the polarizing film and containing a cured product of the above-described pressure-sensitive adhesive composition according to the present invention.

The kind of the polarizing film used in the present invention is not particularly limited, and a general kind known in this field can be employed. For example, the polarizing film may include a polarizer; And a protective film formed on one or both sides of the polarizer.

The kind of the polarizer included in the polarizing plate of the present invention is not particularly limited, and general types known in this field such as polyvinyl alcohol polarizers and the like can be employed without limitation.

A polarizer is a functional film or sheet capable of extracting only light vibrating in one direction from incident light while vibrating in various directions. Such a polarizer may be, for example, a form in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film. The polyvinyl alcohol-based resin constituting the polarizer can be obtained by, for example, gelling a polyvinyl acetate-based resin. In this case, the polyvinyl acetate-based resin that can be used may include not only homopolymers of vinyl acetate but also copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of the monomer copolymerizable with vinyl acetate include monomers such as unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group, or a mixture of two or more thereof. no. The degree of gelation of the polyvinyl alcohol-based resin may be generally from 85 mol% to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be further modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol-based resin may be about 1,000 to 10,000, preferably about 1,500 to 5,000.

The polyvinyl alcohol-based resin as described above can be formed and used as the original film of the polarizer. The method of forming the polyvinyl alcohol-based resin is not particularly limited, and a general method known in this field can be used.

The thickness of the original film formed of a polyvinyl alcohol-based resin is not particularly limited, and can be suitably controlled within a range of, for example, 1 m to 150 m. The thickness of the original film can be controlled to 10 mu m or more in consideration of easiness of drawing and the like.

The polarizer is formed by a process of stretching a polyvinyl alcohol-based resin film as described above (e.g., uniaxial stretching), dyeing a polyvinyl alcohol-based resin film with a dichroic dye and adsorbing the dichroic dye, A process of treating a polyvinyl alcohol resin film with a boric acid aqueous solution and a process of washing with a boric acid aqueous solution after washing. As the dichroic dye, iodine or dichroic organic dyes may be used.

The polarizing film of the present invention may further comprise a protective film formed on one side or both sides of the polarizer. The type of the protective film that can be included in the polarizing plate of the present invention is not particularly limited and includes, for example, a cellulose-based film such as triacetylcellulose; Polyester-based films such as polycarbonate film or polyethylene terephthalate film; Polyethersulfone-based films; And a protective film composed of a polyethylene film, a polypropylene film, or a polyolefin film such as a polyolefin film having a cyclo or norbornene structure or an ethylene propylene copolymer, or the like. At this time, the thickness of the protective film is also not particularly limited, and may be a conventional thickness.

On the other hand, the method for forming the pressure-sensitive adhesive layer on the polarizing film in the present invention is not particularly limited. For example, a method of applying the pressure-sensitive adhesive composition (coating liquid) to the film or element by a usual means such as a bar coater and curing A method of applying the pressure-sensitive adhesive composition to the surface of the peelable base material once and curing it, and then transferring the formed pressure-sensitive adhesive layer to the surface of the polarizing film or the element can be used.

In the present invention, the process of forming the pressure-sensitive adhesive layer is preferably carried out after sufficiently removing the bubble-inducing component such as volatile components or reaction residues in the pressure-sensitive adhesive composition (coating liquid). Accordingly, the crosslinking density or the molecular weight of the pressure-sensitive adhesive is too low to lower the elastic modulus, and bubbles existing between the glass plate and the pressure-sensitive adhesive layer at high temperature are increased to form scattering bodies therein.

Meanwhile, the method of curing the pressure-sensitive adhesive composition of the present invention at the time of manufacturing the polarizing plate is also not particularly limited, and can be performed through a conventional curing method known in the art. For example, the curing can be performed by a method of maintaining the crosslinking reaction between the crosslinkable functional group in the pressure-sensitive adhesive composition applied through heating or the like and the polyfunctional crosslinking agent at a temperature at which crosslinking reaction can be induced.

The polarizing plate of the present invention may further include at least one functional layer selected from the group consisting of a protective layer, a reflective layer, an antiglare layer, a retardation film, a wide view angle compensation film, and a brightness enhancement film.

The polarizing plate according to the present invention has a small change with time in the pressure-sensitive adhesive layer, has excellent durability even under high temperature or high temperature / high humidity conditions, and is excellent in re-workability.

Specifically, the polarizing plate has a creep change rate defined by the following formula (1): 15% or less, preferably 13% or less, more preferably 10% or less.

Equation (1): Rate of change of thrush distance (%) = (T ₀ -T ₁ / T ₀ ) × 100

In the above formula (1), T ₀ is a temperature at which the polarizing plate is attached to a glass substrate to produce a sample for measurement, which is then stored at 23 ° C. and 50% RH for 1 day, an advance distance is measured when the polarizing plate to hold the pulled, T ₁ is the measurement for a sample 23 ℃, 4 days, 50% RH storage conditions, and then, pulled into the polarizing plate of the specimen measured for 1,000 seconds with 1,000g load It is the jungle distance to be measured.

Further, the polarizing plate according to the present invention has a change rate of the adhesive force defined by the following formula (2): 30% or less, preferably 25% or less, more preferably 20% or less.

(2): Adhesive force change rate (%) = (B ₀ -B ₁ / B ₀ ) × 100

In the above formula (2), B ₀ is a temperature at which the polarizing plate is stored at 23 ° C. and 50% RH for 1 day, then the polarizing plate is attached to a glass substrate and stored at 23 ° C. and 50% RH for 4 hours , A peeling speed of 300 mm / min, and a peeling angle of 180 degrees. In the above B ₁ , the polarizing plate was stored at 23 ° C and 50% RH for 4 days, Is an adhesive force measured when the polarizing plate is pulled under the conditions of attaching to a substrate, storing at 23 DEG C and 50% RH for 4 hours, and then peeling at a peeling speed of 300 mm / min and a peeling angle of 180 degrees.

Display device

Next, a display device of the present invention will be described.

The display device of the present invention includes the above-described polarizing plate according to the present invention.

More specifically, the display device may be a liquid crystal display device including a liquid crystal panel in which the polarizing plate according to the present invention is bonded to one or both sides. At this time, the type of the liquid crystal panel is not particularly limited. For example, the present invention is not limited to the type, and various types of F passive matrixes including Twisted Neumatic (TN) type, STN (Super Twisted Neumatic) type, F (ferroelectric) type, PD system; Various active matrix systems including two-terminal and three-terminal; Any known liquid crystal panel including a horizontal mode (IPS mode) panel and a vertical mode (VA mode) panel can be applied. Further, the other types of structures included in the liquid crystal display device of the present invention and the manufacturing method thereof are not particularly limited, and general structures in this field can be employed without any limitations.

Production Example 1: Production of acrylic copolymer (A)

97.2 parts by weight of butyl acrylate (BA), 2.5 parts by weight of hydroxyethyl acrylate (HEA), 0.18 parts by weight of allyl methacrylate (AMA) , And 60 parts by weight of ethyl acetate (EAc) was added as a solvent. Nitrogen gas was then purged for 60 minutes to remove oxygen, and then the temperature was maintained at 70 占 폚. Then, 0.23 part by weight of n-dodecylmercaptan (n-DDM) as a molecular weight regulator, 0.15 part by weight of azobis (2-4-dimethylvaleronitrile (V-65, manufacturer: Wako) (A) was added thereto in an amount of 0.12 part by weight for 10 hours to prepare an acrylic copolymer (A). The allyl methacrylate was added after 3 hours of reaction time, and the molecular weight adjuster was reacted for 5 hours , And the polymerization initiator was added to the reaction mixture in 10 times until the reaction time was 7 hours while confirming the degree of heat generation.

Production Example 2: Production of acrylic copolymer (B)

97.0 parts by weight of butyl acrylate (BA), 2.5 parts by weight of hydroxyethyl acrylate (HEA), 0.3 part by weight of allyl methacrylate (AMA) , And 60 parts by weight of ethyl acetate (EAc) was added as a solvent. Nitrogen gas was then purged for 60 minutes to remove oxygen, and then the temperature was maintained at 70 占 폚. Thereafter, 0.185 part by weight of n-dodecylmercaptan (n-DDM) as a molecular weight modifier, 0.15 part by weight of azobis (2-4-dimethylvaleronitrile (V-65, manufacturer: Wako) (B) was prepared by reacting the reaction mixture for 10 hours while additionally adding 0.2 part by weight of AMA. The allyl methacrylate was added after 3 hours of reaction time, and the molecular weight adjuster was reacted for 5 hours , And the polymerization initiator was added to the reaction mixture in 10 times until the reaction time was 7 hours while confirming the degree of heat generation.

Production Example 3: Production of acrylic copolymer (C)

A monomer mixture containing 97.5 parts by weight of butyl acrylate (BA) and 2.5 parts by weight of hydroxyethyl acrylate (HEA) was added to a 3 L reactor equipped with a cooling device to easily regulate the temperature of the nitrogen gas, 60 parts by weight of ethyl acetate (EAc) were added. Nitrogen gas was then purged for 60 minutes to remove oxygen, and then the temperature was maintained at 70 占 폚. Thereafter, 0.147 part by weight of n-dodecylmercaptan (n-DDM) as a molecular weight modifier and 0.15 part by weight of azobis (2-4-dimethylvaleronitrile (V-65, manufacturer: Wako) For 10 hours to prepare an acrylic copolymer (C).

Manufacturing example  4: Production of acrylic copolymer (D)

A monomer mixture containing 97.5 parts by weight of butyl acrylate (BA) and 2.5 parts by weight of hydroxyethyl acrylate (HEA) was added to a 3 L reactor equipped with a cooling device to easily regulate the temperature of the nitrogen gas, 60 parts by weight of ethyl acetate (EAc) were added. Nitrogen gas was then purged for 60 minutes to remove oxygen, and then the temperature was maintained at 70 占 폚. Thereafter, 0.112 part by weight of n-dodecylmercaptan (n-DDM) as a molecular weight modifier and 0.15 part by weight of azobis (2-4-dimethylvaleronitrile (V-65, manufacturer: Wako) For 10 hours to prepare an acrylic copolymer (D).

The weight average molecular weight and the polymer structure of the acrylic copolymer prepared in Preparation Examples 1 to 4 were measured as follows and shown in Table 1.

(1) The weight average molecular weight was measured by GPC under the following conditions. For the calibration curve, the measurement results were converted using standard polystyrene of the Agilent system.

<Measurement Conditions>

Meter: Agilent GPC (Agulent 1200 series, USA)

Column: Two PL Mixed B connections

Column temperature: 40 ° C

Eluent: tetrahydrofuran

Flow rate: 1.0 mL / min

Concentration: ~ 1 mg / mL (100 μL injection)

(2) The polymer structure was evaluated by the following method.

First, an alkyl (meth) acrylate monomer and a (meth) acrylic monomer having the same kind of crosslinking functional group as those used in the acrylic copolymer (hereinafter referred to as "evaluation target copolymer") for evaluating the polymer structure To prepare a monomer mixture. At this time, the content of the (meth) acrylic monomer having a crosslinkable functional group in the monomer mixture was made equal to the content of the (meth) acrylic monomer having a crosslinkable functional group in the evaluation target copolymer. Then, the above-mentioned monomer mixture was polymerized to prepare an acrylic copolymer (hereinafter, referred to as a 'reference copolymer') having the same level of weight average molecular weight (error range ± 5%) as that of the copolymer to be evaluated.

Then, ethyl acetate solvent was added to each of the reference copolymer and the evaluation target copolymer to adjust the solid concentration to 30%, and the viscosity was measured. When the viscosity of the copolymer to be measured as described above had a viscosity lower than the viscosity of the reference copolymer by 30% or more, it was evaluated to have a branched polymer structure, and in other cases, it was evaluated to have a linear polymer structure .

Production Example 1 Production Example 2 Production Example 3 Production Example 4 sample A B C D Furtherance BA 97.2 97.0 97.5 97.5 HEA 2.5 2.5 2.5 2.5 AMA 0.3 0.5 0 0 n-DDM 0.23 0.185 0.147 0.112 Weight average molecular weight (Mw) 520,000 970,000 530,000 940,000 Polymer structure Branches Branches Linear Linear

Example  One

0.2 part by weight of a multifunctional crosslinking agent (coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.), 100 parts by weight of a crosslinking catalyst (di-n-butyltin dilaurate, Sigma Aldrich), 0.01 part by weight of the acrylic copolymer A And 0.2 parts by weight of a silane coupling agent (a silane coupling agent containing a beta-cyanoacetyl group, LG Chem, M812) were mixed, diluted with ethyl acetate to have a solid content of 51.3% by weight, and uniformly mixed to obtain a pressure- (Coating liquid) was prepared.

The pressure-sensitive adhesive composition thus prepared was coated on a release-treated surface of a 38 占 퐉 -thick polyethylene terephthalate film (release PET) having a thickness of 23 占 퐉 so that the thickness after drying was 23 占 퐉 and dried to form an adhesive layer. Thereafter, the pressure-sensitive adhesive layer was laminated on the polarizing plate to produce a polarizing plate including the pressure-sensitive adhesive layer.

Example 2

A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 1 except that a polyfunctional crosslinking agent (coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was blended in an amount of 0.14 parts by weight based on 100 parts by weight of the acrylic copolymer A.

Example 3

A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 1, except that the acrylic copolymer B prepared in Preparation Example 2 was used instead of the acrylic copolymer A and the solid content was diluted to 31.4% by weight.

Example 4

A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 3, except that the multifunctional crosslinking agent (coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was blended in an amount of 0.27 parts by weight based on 100 parts by weight of the acrylic copolymer B.

Comparative Example 1

A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 1, except that the acrylic copolymer C prepared in Preparation Example 3 was used instead of the acrylic copolymer A and the solid content was diluted to 30.2% by weight.

Comparative Example 2

A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Comparative Example 1, except that a multi-functional crosslinking agent (coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was blended in an amount of 0.27 parts by weight based on 100 parts by weight of the acrylic copolymer C.

Comparative Example 3

A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Comparative Example 1 except that a polyfunctional crosslinking agent (coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was blended in an amount of 0.14 parts by weight based on 100 parts by weight of the acrylic copolymer C.

Comparative Example 4

A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Example 1, except that the acrylic copolymer D prepared in Preparation Example 4 was used instead of the acrylic copolymer A and the solid content was diluted to 21.8% by weight.

Comparative Example 5

A pressure-sensitive adhesive composition and a polarizing plate were prepared in the same manner as in Comparative Example 4, except that 0.40 part by weight of a polyfunctional crosslinking agent (coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to 100 parts by weight of the acrylic resin D.

Comparative Example 6

The pressure-sensitive adhesive composition was prepared in the same manner as in Comparative Example 4, except that the solid content was diluted to 30.1% by weight. The viscosity of the produced pressure-sensitive adhesive composition was too high to coat the pressure-sensitive adhesive layer (coating viscosity: 9,600 cP).

The properties of the pressure-sensitive adhesive composition and the polarizing plate prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were measured by the following methods. The measurement results are shown in Tables 2 and 3 below.

How to measure property

1. Coating solids content (unit: % )

The coating solid content was measured by the following method.

First, the weight (A) of an aluminum dish was measured. Then, the pressure-sensitive adhesive composition prepared in Example or Comparative Example was sampled in an amount of about 0.3 to 0.5 g (weight of the sample before drying: S) The weight B (A + S) of the sample before drying including the aluminum dish was measured in an aluminum dish measured. Subsequently, a small amount of a solution of ethyl acetate in which a hydroquinone was dissolved (polymerization inhibitor concentration: 0.5% by weight) was added to the pressure-sensitive adhesive composition using a pipette, and the resultant was dried in an oven at 150 ° C for 30 minutes to remove the solvent Respectively. Thereafter, the dried sample was cooled at room temperature for 15 minutes to 30 minutes, and the weight including the weight C of the dried sample including the aluminum dish weight A was measured. The solid content of the coated sample was measured according to the following formula (3).

(3): Coating solid content (%) = {(C-A) / (B-A)} 100

In the formula (3), A represents the weight (unit: g) of the aluminum dish, C represents the weight (unit: g) of the sample after drying including the aluminum dish weight A, B represents the weight of the aluminum dish (Unit: g).

2. Coating viscosity (CP)

The coating viscosity of the pressure-sensitive adhesive composition was evaluated according to the following procedure using a Brookfield digital viscometer (RV DV2T).

Put 220 mL of the pressure-sensitive adhesive composition into a 250 mL PE bottle, close the lid so that the solvent does not volatilize, sufficiently seal it with a para-film, and then sufficiently leave it at constant temperature and humidity conditions (23 ° C, 50% RH) Respectively. Then, after the seal and the lid were removed, the spindle was connected to a viscometer so as to prevent air bubbles from forming in the pressure-sensitive adhesive composition, and the liquid level of the pressure-sensitive adhesive composition was adjusted to fit the groove of the spindle. Thereafter, the viscosity was measured at an rpm condition in which the torque was 20% (± 1%).

3. Coating property

When the pressure-sensitive adhesive composition prepared in Examples and Comparative Examples was coated on a polyethylene terephthalate film, the state of the coating layer was visually observed and evaluated according to the following criteria.

&Lt; Evaluation criteria of coating property &

○: No visible bubbles or streaks on the coating layer.

B: Bubbles and / or streaks were microscopically confirmed in the coating layer.

X: Bubbles and / or stripe patterns are visually confirmed in the coating layer.

4. Throw distance (Creep, unit: ㎛)

The polarizing plates produced according to Examples and Comparative Examples were cut into a size of 10 mm in width and 10 mm in length to prepare specimens. Then, the releasable PET film adhered to the adhesive layer was peeled off, and a polarizing plate was attached to the alkali-free glass using a roller of 2 kg in accordance with JIS Z 0237 to prepare a test piece for measurement. The test specimens were stored for 1 day and 4 days under constant temperature and humidity conditions (23 DEG C, 50% RH), and then measured with a TA instrument (Texture Analyzer, Stable Microsystems, UK) Were measured. Specifically, the above-mentioned jig distance was measured by a distance (unit: 탆) in which the polarizing plate was pulled from the glass substrate when the polarizing plate of the test sample was pulled for 1,000 seconds under a load of 1,000 g.

5. Adhesion at room temperature (unit: gf / 25mm)

The polarizing plates produced according to Examples and Comparative Examples were stored for 1 day and 4 days under constant temperature and humidity conditions (23 ° C, 50% RH), respectively, and then cut to a width of 25 mm and a length of 100 mm. Then, the release PET film adhered to the adhesive layer was peeled off, and a polarizing plate was attached to the alkali-free glass using a 2-kg roller according to JIS Z 0237 to prepare a test piece for measurement.

The test specimens were stored under constant temperature and humidity conditions (23 DEG C, 50% R.H.) for 4 hours. Then, using a TA instrument (Texture Analyzer, manufactured by Stable Microsystems, UK), the polarizing plate was pulled out at a peeling speed of 300 mm / min and a peeling angle of 180 degrees to measure a force required to completely separate the polarizing plate from the glass substrate (Unit: gf / 25 mm) at room temperature.

6. Re-peel force (unit: gf / 25 mm) and re-peelability:

The polarizing plates produced according to Examples and Comparative Examples were stored for 1 day and 4 days under constant temperature and humidity conditions (23 ° C, 50% RH), respectively, and then cut to a width of 25 mm and a length of 100 mm. Then, the release PET film adhered to the adhesive layer was peeled off, and a polarizing plate was attached to the alkali-free glass using a 2-kg roller according to JIS Z 0237 to prepare a test piece for measurement.

Then, the sample for measurement was stored at 80 for 1 hour, and then stored under constant temperature and humidity conditions (23 DEG C, 50% R.H.) for 1 hour. Then, using a TA instrument (Texture Analyzer, manufactured by Stable Microsystems, UK), the polarizing plate was pulled out at a peeling speed of 300 mm / min and a peeling angle of 180 degrees to measure a force required to completely separate the polarizing plate from the glass substrate And the re-peel force (unit: gf / 25 mm) was measured.

After re-peeling, re-peeling property was evaluated based on the following criteria.

<Evaluation Criteria>

A: When the re-peeling force is 1,500 gf / 25 mm or less and there is no adhesive layer remaining on the glass substrate after re-peeling

DELTA: Residual adhesive residue on the glass substrate was confirmed when the re-peeling force was 1,500 gf / 25 mm or more, 2,500 gf / 25 mm or less, or after re-peeling, and the residual area was 5%

X: When the re-peeling force is more than 3,000 gf / 25 mm, or after re-peeling, the residue of the adhesive layer is confirmed on the glass substrate. If the residual area exceeds 5%

7. Durability evaluation

The polarizing plate prepared in Examples and Comparative Examples was cut into a size of 180 mm x 250 mm (length x width) to prepare samples, and the samples were attached to a 19-inch commercial panel using a laminator. Thereafter, the panel was subjected to compression bonding for 20 minutes at 50 ° C and 5 atmospheres, followed by storage under constant temperature and humidity conditions (23 ° C, 50% R.H.) for 24 hours to prepare test specimens.

The durability of the manufactured test specimens was evaluated by observing the occurrence of bubbles or peeling after the specimens were left for 500 hours at a temperature of 60 ° C. and a relative humidity of 90% RH. And then allowed to stand at a temperature of 80 캜 for 500 hours, and then the occurrence of bubbles or peeling was observed and evaluated.

<Evaluation Criteria>

○: No bubbles and peeling occurred

B: Bubbles and / or slight peeling occurred

X: large amount of bubbles and / or peeling occurred

Example 1 Example 2 Example 3 Example 4 Furtherance
(Parts by weight) Acrylic copolymer A A B B 100 100 100 100 Multifunctional crosslinking agent 0.2 0.14 0.2 0.27 Crosslinking catalyst 0.01 0.01 0.01 0.01 Silane coupling agent 0.2 0.2 0.2 0.2 Solid content (%) 51.3 51.3 31.4 31.4 Coating viscosity (cP) 1870 1870 1980 1980 Coating property ○ ○ ○ ○ Creep
[um] After 1 day 343 398 321 247 After 4 days 318 352 307 233 adhesiveness
[gf / 25mm] After 1 day 405 535 334 286 After 4 days 330 413 302 260 Re-peeling force
[gf / 25mm] After 1 day 1110 1180 960 660 After 4 days 950 937 890 610 Re-peelability After 1 day ○ ○ ○ ○ After 4 days ○ ○ ○ ○ Heat resistance durability ○ ○ ○ ○ Wet heat resistance ○ ○ ○ ○

Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Furtherance
(Parts by weight) Acrylic copolymer C C C D D 100 100 100 100 100 Multifunctional crosslinking agent 0.2 0.27 0.14 0.2 0.38 Crosslinking catalyst 0.01 0.01 0.01 0.01 0.01 Silane coupling agent 0.2 0.2 0.2 0.2 0.2 Solid content (%) 30.2 30.2 30.2 21.8 21.8 Coating viscosity (cP) 1920 1920 1920 1890 1890 Coating property ○ ○ ○ ○ ○ Creep
[um] After 1 day 450 383 780 421 321 After 4 days 355 320 470 341 238 adhesiveness
[gf / 25mm] After 1 day 790 550 1020 680 272 After 4 days 410 323 660 392 240 Re-peeling force
[gf / 25mm] After 1 day 2830 2620 2770 2310 2010 After 4 days 1320 1170 2210 1190 2640 Re-peelability After 1 day × × × △ × After 4 days ○ ○ △ ○ × Heat resistance durability ○ ○ × ○ ○ Wet heat resistance ○ ○ △ ○ △

As shown in Table 2, the pressure-sensitive adhesive compositions of Examples 1 to 4 using the acrylic copolymer having a branched polymer structure of the present invention had a solid content of 30 wt% and 50 wt% Viscosity characteristics. In addition, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition has excellent re-peeling properties, has excellent durability in high temperature and high temperature / high humidity environments, and has little change with time in physical properties of the pressure-sensitive adhesive layer.

In contrast, the pressure-sensitive adhesive compositions of Comparative Examples 1 to 5 using an acrylic copolymer having a linear polymer structure were able to achieve a coating viscosity only when the solid content was lowered, as shown in Table 3 above. Specifically, in the case of Comparative Examples 1 to 3 using the linear acrylic copolymer C having a weight average molecular weight equal to that of the acrylic copolymer A used in Examples 1 and 2, the solid content was adjusted to 20 %, It was found to have viscosity characteristics similar to those of Examples 1 and 2. Further, in the case of Comparative Examples 4 to 5 using the acrylic copolymer D having a weight average molecular weight equal to that of the acrylic copolymer B used in Examples 3 to 4, it was necessary to reduce the solid content to 20% And when the solid content exceeds 30% by weight, the viscosity increased to over 9,000 cP and the coating was impossible (see Comparative Example 6).

In addition, the pressure-sensitive adhesive layers formed using the pressure-sensitive adhesive compositions of Comparative Examples 1 to 5 showed a significant change over time, and were also found to have poor releasability and / or durability.

Claims (12)

An acrylic pressure sensitive adhesive composition comprising an acrylic copolymer formed by polymerizing a monomer mixture comprising a monomer represented by the following formula (1), a (meth) acrylic monomer having a crosslinkable functional group, and an alkyl (meth) acrylate monomer ,
Wherein the acrylic copolymer has a weight average molecular weight of 300,000 to 1,000,000 and a branched polymer structure.
[Chemical Formula 1]
R ^{1 is} -CH = CR ² - (C = O) -OXY
Wherein R ¹ is hydrogen, a C ¹ to C 6 alkyl group or a C 1 to C 6 alkenyl group, R ² is hydrogen or a C 1 to C 10 alkyl group, X is a single bond, a C 1 to C 10 alkylene group, a C 2 to C 10 alkenylene group , An ether, an ester, or a combination thereof, and Y is a vinyl group, an allyl group, or a C3-C10 cycloalkenyl group.
The method according to claim 1,
The pressure-sensitive adhesive composition has a solid content of 30% by weight or more,
23 and a viscosity of 500 cP to 2,000 cP.
The method according to claim 1,
The monomer represented by the formula (1) may be at least one selected from the group consisting of allyl methacrylate, allyl acrylate, methallyl methacrylate, methallyl acrylate, Butenyl acrylate, but-3-enyl-2-methylprop-2-enoate, 2-allyloxyethyl acrylate ( 2-allyloxyethyl acrylate, 2-allyloxyethyl methacrylate, 3-allyloxypropyl methacrylate, 3-allyloxypropyl acrylate, 2-allyloxyethoxy acrylate, 2-allyloxyethoxyethyl methacrylate, 2-allyloxyethoxyethyl acrylate, cyclohex-2-enyl acrylate, cyclohex-2-enyl acrylate, Cyclohex-2-en-1-yl 2-methylp-ene- rop-2-enoate, and 3-vinylcyclohex-2-enyl acrylate.
The method according to claim 1,
Wherein the monomer mixture contains 0.01 to 1 part by weight of the monomer represented by the formula (1) based on 100 parts by weight of the monomer mixture.
The method according to claim 1,
The monomer mixture contains, per 100 parts by weight of the monomer mixture,
From 84 parts by weight to 99.89 parts by weight of the alkyl (meth) acrylate monomer;
0.1 to 15 parts by weight of a (meth) acrylic monomer having a crosslinkable functional group; And
0.01 to 1 part by weight of a monomer represented by the above formula (1).
The method according to claim 1,
Wherein the pressure-sensitive adhesive composition further comprises a polyfunctional crosslinking agent.
The method according to claim 6,
Wherein the polyfunctional crosslinking agent is an isocyanate crosslinking agent.
The method according to claim 6,
Wherein the polyfunctional crosslinking agent is contained in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the acrylic copolymer.
Polarizing film; And
And a pressure-sensitive adhesive layer formed on one or both sides of the polarizing film, wherein the pressure-sensitive adhesive layer comprises a cured product of the acrylic pressure-sensitive adhesive composition according to any one of claims 1 to 8.
10. The method of claim 9,
Wherein the polarizing plate has a rate of change of creep distance of 15% or less as defined by the following formula (1).
Equation (1): Rate of change of thrush distance (%) = (T ₀ -T ₁ / T ₀ ) × 100
In the above formula (1), T ₀ is a temperature at which the polarizing plate is attached to a glass substrate to produce a sample for measurement, which is then stored at 23 ° C. and 50% RH for 1 day, an advance distance is measured when the polarizing plate to hold the pulled, T ₁ is the measurement for a sample 23 ℃, 4 days, 50% RH storage conditions, and then, pulled into the polarizing plate of the specimen measured for 1,000 seconds with 1,000g load It is the jungle distance to be measured.
10. The method of claim 9,
Wherein the polarizing plate has a rate of change of the adhesive force defined by the following formula (2): 30% or less.
(2): Adhesive force change rate (%) = (B ₀ -B ₁ / B ₀ ) × 100
In the above formula (2), B ₀ is a value obtained by storing the polarizing plate at 23 ° C. and 50% RH for 1 day, attaching the polarizing plate to a glass substrate, storing the plate at 23 ° C. and 50% RH for 4 hours, A peeling speed of 300 mm / min, and a peeling angle of 180 degrees,
Wherein B ₁ is after the polarizer 23 ℃, 4 days, 50% RH condition storage, the polarizing plate is attached to the glass substrate, and the storage 23 ℃, at 50% RH for 4 hours, and then, a peel rate 300mm / min, Is an adhesive strength measured when the polarizer is pulled under the condition of a peeling angle of 180 degrees.
A display device comprising the polarizer of claim 9.