KR101279612B1 - Polarizing plate and liquid crystal display comprising the same - Google Patents

Abstract

The present invention provides a polarizer comprising a polarizer and a polarizer protective film provided on at least one side of the polarizer, the polarizer protective film comprising: an aromatic unit having a chain and an aromatic portion having a hydroxyl group-containing portion; And a styrene-based unit including at least one styrene-based derivative, wherein the absolute value of the _in- plane retardation R _in and the thickness direction retardation R _th is 10 nm or less with or without stretching, and protects the polarizer and the polarizer. A polarizing plate and a liquid crystal display including the same are provided between the film including an adhesive layer comprising an epoxy acrylate oligomer, a radically polymerizable compound, and a UV curable adhesive including a photopolymerization initiator.

Description

POLARIZING PLATE AND LIQUID CRYSTAL DISPLAY COMPRISING THE SAME}

The present invention does not require pretreatment such as primer treatment or corona treatment, and has excellent adhesion between the polarizer protective film and the polarizer, the adhesive layer is thin and excellent in water resistance, and also has an initial optical property superior to that of a conventional water-based adhesive and a polarizing plate including the same. It relates to a liquid crystal display device.

Liquid crystal displays have low power consumption, operate at low voltage, make use of features such as light weight and thinness, and are used in various display devices. A liquid crystal display device is comprised from many materials, such as a liquid crystal cell, a polarizing plate, retardation film, a light condensing sheet, a diffusion film, a light guide plate, and a light reflection sheet. Therefore, improvements have been actively made aiming at reduction in the number of constituent films, thinning of the film or sheet, and improvement in productivity, light weight, and brightness.

Liquid crystal display devices require products that can withstand stringent durability conditions, depending on the application. Moreover, in the situation where the large screen of a liquid crystal display device advances in recent years, deterioration of the image quality by the thermal deformation of a polarizing plate is a problem, and it is calculated | required to show high thermal stability.

The polarizing plate has a structure in which a protective film is laminated | stacked on both surfaces or one side of the polarizer which consists of polyvinyl alcohol-type resin in which the dichroic dye was adsorbed-oriented normally. The polarizer is produced by a method of longitudinally uniaxial stretching and dyeing with a dichroic dye on a polyvinyl alcohol-based resin film, followed by boric acid treatment to cause a crosslinking reaction, followed by washing with water and drying. As a dichroic dye, iodine or a dichroic organic dye is used. The protective film is laminated | stacked on both surfaces or one surface of the polarizer obtained in this way, and it becomes a polarizing plate, and is inserted and used for a liquid crystal display device. As a protective film, the cellulose acetate-type resin film represented by triacetylose is used a lot. In addition, in many cases, the aqueous adhesive which consists of aqueous solution of polyvinyl alcohol-type resin is used for lamination | stacking of a protective film.

However, when the protective film is an acrylic film, the adhesive strength with the water-based adhesive is weak due to the properties of the material, which may cause problems in reworkability or cutting property. For this reason, after coating a primer on the protective film, the inconvenience of adhering with the water-based adhesive is generated.

Accordingly, in the art, development of a polarizing plate having excellent adhesion between the polarizer and the protective film and excellent water resistance is required for use in a display.

An object of the present invention is to provide a polarizing plate having excellent adhesion between the polarizer protective film and the polarizer, having a thin adhesive layer and excellent water resistance, without requiring pretreatment such as primer treatment, corona treatment, or the like, and a liquid crystal display device including the same.

This invention is a polarizing plate containing a polarizer and a polarizer protective film provided in at least one surface of the said polarizer,

The polarizer protective film is an aromatic unit having a chain having an hydroxyl group-containing portion and an aromatic portion; And a styrenic unit including one or more styrene derivatives, and having an in-plane phase difference R _in represented by Equation 1 below with or without stretching, and a thickness direction phase difference R _th as represented by Equation 2 below. ) Absolute value is 10 nm or less,

The polarizing plate is provided between the polarizer and the polarizer protective film is provided with an adhesive layer comprising a UV curable adhesive comprising an epoxy acrylate oligomer, a radical polymerizable compound and a photopolymerization initiator.

In Equations 1 and 2, n _x is the largest refractive index of the film plane direction refractive index,

n _y is the refractive index in the direction perpendicular to nx of the film surface direction refractive index,

n _z is a refractive index in the film thickness direction,

d is the thickness of the film.

In addition, the present invention provides a liquid crystal display device including the polarizing plate.

The polarizing plate according to the present invention does not require pretreatment such as primer treatment or corona treatment for adhesion between the polarizer protective film and the polarizer, and has excellent adhesive strength, thin adhesive layer, and excellent water resistance.

1 is a cross-sectional view of a polarizer according to an embodiment of the present invention.
2 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

A polarizing plate according to the present invention is a polarizing plate comprising a polarizer and a polarizer protective film provided on at least one side of the polarizer, the polarizer protective film is an aromatic unit having a chain and an aromatic portion having a hydroxyl group containing portion; And a styrenic unit including one or more styrene derivatives, and having an in-plane retardation R _in represented by Equation 1 and a thickness direction retardation R _th represented by Equation 2 with or without stretching. ) Is an absolute value of 10 nm or less, characterized in that an adhesive layer comprising a UV curable adhesive comprising an epoxy acrylate oligomer, a radically polymerizable compound and a photopolymerization initiator is provided between the polarizer and the polarizer protective film.

In the polarizing plate according to the present invention, the polarizer and the polarizer protective film are laminated by a UV curable adhesive, so that the polarizer or the polarizer protective film does not require a separate pretreatment step such as primer treatment or corona treatment, and the polarizer and the polarizer protective film It has excellent adhesive strength and excellent water resistance of polarizing plate.

The UV curable adhesive comprises an epoxy acrylate oligomer, a radical polymerizable compound and a photopolymerization initiator.

The epoxy acrylate oligomer is characterized in that it is an epoxy (meth) acrylate prepolymer which is a copolymer of (meth) acrylate with at least one epoxy compound, at least one (meth) acrylic acid compound and a polyacid.

The epoxy (meth) acrylate prepolymer has a weight average molecular weight of 5,000 to 20,000, characterized in that 8 to 20 average epoxy bonds per molecule are present. In addition, the polyacid in the epoxy (meth) acrylate prepolymer is characterized in that the weight average molecular weight of 100 to 3,000.

The polyacid is preferably polyether polyacid, polyester polyacid, polysaturated fatty acid or the like. Examples of the polyether polyacid may include an acid-substituted form by copolymerizing polyethylene glycol, 1,2-polypropylene glycol, polytetramethylene glycol, 1,2-polybutylene glycol, and the like with each polyol, and polyester poly Acids include ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, polytetramethylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentylglycol , Diols such as 1,4-cyclohexanedimethanol, 3-methyl-1,8-octanediol, phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, azelic acid, etc. Polyester polyacids or copolymers thereof in the form of an acid of may be exemplified. As the polysaturated fatty acid, a fatty acid having 10 to 50 carbon atoms in the polyacid molecule is preferable.

The epoxy (meth) acrylate prepolymer has a weight average molecular weight of 3,000 to 20,000, and the average epoxy bond per molecule is preferably present in the range of 8 to 20. If the weight average molecular weight is less than 3,000, the tensile strength and hardness of the cured coating film is too high, the elongation is poor, the adhesion is poor, and if the weight average molecular weight exceeds 20,000, the opposite result occurs, the molecular weight distribution as described above It is preferable to have.

The content of the epoxy acrylate oligomer is preferably 5 to 60% by weight, more preferably 20 to 40% by weight based on the total weight of the UV curable adhesive. If the content of the epoxy acrylate oligomer is less than 5% by weight may cause a problem that the curability of the adhesive is lowered, if it exceeds 60% by weight may cause a problem that the viscosity of the adhesive rises.

It is preferable that the said radically polymerizable compound contains the hydrophilic monomer containing a polar group and the hydrophobic monomer which does not contain a polar group.

The said hydrophilic monomer is for improving the adhesive force of a polarizer and a polarizer protective film, and it is preferable that it is a polar monomer containing a hydroxyl group. Specific examples of the hydrophilic monomers include hydroxy ethyl acrylate (HEA), hydroxy ethyl methacrylate (HEMA), hydroxy propyl acrylate (HPA), and hydroxy propyl. Methacrylate (hydroxyl propyl methacrylate (HPMA)), hydroxy butyl acrylate (HBA), acrylic acid (AA), N-vinyl pyrrolidone, diacetone (meth) Acrylamide, isobutoxy methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, octyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, hydroxy butyl vinyl ether, N- Vinyl caprolactam, mixtures thereof, and the like, but are not limited thereto.

The content of the hydrophilic monomer is preferably 10 to 70% by weight based on the total weight of the UV curable adhesive. When the content of the hydrophilic monomer is less than 10% by weight may cause a problem that the adhesive strength of the adhesive is lowered, when it exceeds 70% by weight may cause a problem of poor water resistance of the polarizing plate.

Specific examples of the hydrophobic monomer include 1,6-hexanediol diacrylate (1,6-hexanediol diacrylate, HDDA), isobornyl acrylate (IBOA), trimethylolpropane triacrylate (TMPTA) Dipropylene glycol diacrylate (DPGDA), benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, mixtures thereof, and the like. But it is not limited thereto.

The content of the hydrophobic monomer is preferably 1 to 30% by weight based on the total weight of the UV curable adhesive. When the content of the hydrophobic monomer is less than 1% by weight, a problem may occur that the water resistance of the polarizing plate is inferior, and when the content of the hydrophobic monomer is greater than 30% by weight, a problem may occur in that the adhesive strength of the adhesive is inferior.

In general, since the ultraviolet light of 365 nm or less is absorbed in the polarizer protective film for protecting the polarizer, including UV blocking agents, it is preferable to use a long wavelength initiator that absorbs light in a range of 365 nm or more. Specific examples thereof include α-hydroxyketone, phenylglyoxylate, benzildimethyl ketal, α-aminoketone, and mono acyl phosphine. , Bis acyl phosphine, a mixture thereof, and the like, but are not limited thereto.

The content of the photopolymerization initiator is preferably 1 to 5% by weight based on the total weight of the UV curable adhesive.

In the polarizing plate according to the present invention, the UV-curable adhesive may further include one or more photosensitizers, antioxidants and the like known in the art.

In the polarizing plate according to the present invention, the viscosity of the UV curable adhesive is preferably 5 to 100 cP, but is not limited thereto.

In addition, the thickness of the adhesive layer is preferably 1 μm or less, but is not limited thereto.

In the polarizing plate according to the present invention, the polarizer protective film comprises an aromatic unit having a chain having an hydroxy group containing portion and an aromatic portion; And a styrenic unit including one or more styrene derivatives, and having an in-plane retardation R _in represented by Equation 1 and a thickness direction retardation R _th represented by Equation 2 with or without stretching. Is an absolute value of 10 nm or less, preferably 5 nm or less.

In addition, the polarizer protective film preferably has an absolute value of the photoelastic coefficient of 3 × 10 ⁻¹² m ² / N or less regardless of stretching. Since the polarizer protective film has a small photoelastic coefficient, a change in retardation value due to external stress is small, thereby reducing light leakage.

The content ratio of the aromatic unit and the styrene unit is preferably 65 to 75: 100 based on mol. In addition, the content ratio of the aromatic unit and the styrene unit is preferably 45 to 55: 100 based on the weight. The composition within this range is advantageous for obtaining the above-described phase difference value and photoelastic coefficient.

The polarizer protective film according to the present invention may further include a (meth) acrylate-based unit including at least one (meth) acrylate-based derivative.

In addition, the ratio of the sum of the content of the aromatic unit and the styrene unit and the content of the (meth) acrylate unit is preferably 1:99 to 50:50 based on the weight. Compositions within this range are advantageous for obtaining the above-described retardation values and photoelastic coefficients.

A (meth) acrylate-based unit comprising the at least one (meth) acrylate-based derivative; An aromatic unit having a chain having the hydroxy group-containing portion and an aromatic portion; And styrenic units including the one or more styrene derivatives may be included in different compounds, respectively, and two or more units of the units may be included in one compound.

In the present invention, the (meth) acrylate-based unit gives a negative in-plane retardation (R _in ) and a negative thickness direction retardation (R _th ) to the film in the stretching process to a weak degree, and the chain having the hydroxyl group-containing portion and An aromatic unit having an aromatic portion gives positive in-plane retardation (R _in ) and positive thickness direction retardation (R _th ), and the styrene-based unit has a strong negative in-plane retardation (R _in ) and negative thickness direction. The phase difference R _th can be provided. Here, the negative in-plane retardation means the largest refractive index in the direction perpendicular to the stretching direction and in-plane, and the positive in-plane retardation means the largest refractive index in the stretching direction, and the negative thickness retardation is the thickness retardation It means that it is larger than surface direction average refractive index, and a positive thickness direction retardation means that an in-plane average refractive index is larger than thickness direction refractive index. By the retardation characteristics of each unit described above, the retardation characteristics of the polarizer protective film may vary depending on the composition and the stretching direction, the stretching ratio, uniaxial or biaxial stretching of each component. Therefore, in the present invention, the birefringence of each unit cancels each other even in the stretching process by properly combining the compositions of the above components. Thereby, in this invention, a film can maintain the optical refractive index isotropy, can manufacture the film whose absolute value of in-plane phase difference and thickness direction retardation is 10 nm, and can also provide the polarizer protective film which also has little residual phase difference.

In addition, the polarizer protective film according to the present invention is excellent in mechanical properties, unlike the fragile acrylic film. In addition, the (meth) acrylate-based unit can provide excellent optical physical properties, and the aromatic-based unit having a chain and an aromatic portion having the hydroxy group-containing portion has an excellent blend with the compound containing the (meth) acrylate-based unit. Can provide Mars. In addition, since the value of the photoelastic coefficient can be adjusted according to the content of the chain having the hydroxyl group-containing portion and the aromatic unit having the aromatic portion, a film having a small change in retardation value due to external stress can be provided.

The polarizer protective film according to the present invention may further include a ring-based unit having a ring portion. The ring-based unit having the cyclic moiety may be included in the compound containing at least one of the (meth) acrylate-based unit, the chain having the hydroxy group-containing part and the aromatic unit having the aromatic moiety, and the styrene-based unit, ) May be included in a compound different from a compound containing at least one of an acrylate unit, a chain having an hydroxy group-containing portion and an aromatic unit having an aromatic portion, and the styrene unit. The ring-based unit having the ring portion can provide excellent heat resistance to the film.

According to the exemplary embodiment of the present invention, a copolymer including the (meth) acrylate-based unit and the ring-based unit having the ring portion, a copolymer including the (meth) acrylate-based unit and the styrene-based unit, A copolymer comprising a styrene-based unit and a ring-based unit having the cyclic moiety, the (meth) acrylate-based unit, an aromatic unit having a chain and an aromatic moiety having the hydroxy group-containing part, and a copolymer comprising the styrene-based unit Can be used. In this case, the copolymers may include two or more types of at least one of the units.

As a specific example, a copolymer comprising a (meth) acrylate-based unit such as methyl (meth) acrylate and a ring-based unit such as N-cyclohexylmaleimide, that is, poly (N-cyclohexylmaleimide-co-methyl (Meth) acrylate) can be used. It is also possible to use copolymers comprising styrenic units such as styrene and cyclic units such as maleic anhydride. Moreover, the copolymer containing methyl methacrylate as a (meth) acrylate type unit, styrene and alphamethyl styrene as a styrene unit, and N-cyclohexyl maleimide as a ring type unit can be used. In addition, a copolymer including methyl methacrylate as the (meth) acrylate-based unit, styrene or alphamethylstyrene as the styrene-based unit, and N-cyclohexylmaleimide and maleic anhydride as the ring-based unit can be used. However, the above examples are for illustrating the present invention, and the scope of the present invention is not limited to the above examples.

The content of each unit is not particularly limited, in order to achieve the optical properties, mechanical properties, transparency, photoelastic coefficient, miscibility, etc., including the desired in-plane retardation and thickness direction retardation in consideration of the roles of the above-described components. The content of each unit can be determined. For example, the content of the (meth) acrylate-based unit, the chain having the hydroxyl group-containing portion and the aromatic-based unit having the aromatic moiety, the styrene-based unit and the ring-based unit may be selected in the range of about 0.1 to 99% by weight, respectively. Can be. Specifically, the content of the (meth) acrylate-based unit is preferably about 50 to 98% by weight, and the content of the aromatic-based unit having a chain and an aromatic portion having the hydroxy group-containing portion is preferably about 0.5 to 40% by weight. And, the content of the styrene-based unit is preferably about 0.5 to 30% by weight. The content of the ring-based unit is preferably about 0.5 to 45% by weight.

In the present invention, the compound comprising the (meth) acrylate-based unit, the chain having the hydroxy group-containing portion and the aromatic unit having an aromatic moiety, the styrene-based unit or the ring-based unit may be a homopolymer or a copolymer And an aromatic unit, a styrene-based unit and a unit other than the cyclic-based unit having the (meth) acrylate-based unit, the chain having the hydroxy group-containing portion and the aromatic moiety within the scope of not impairing the object of the present invention. can do. The copolymer may be a random or block copolymer.

In the present invention, it should be understood that the (meth) acrylate-based unit may include (meth) acrylate as well as (meth) acrylate derivatives. Specifically, the (meth) acrylate monomers include methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, benzyl methacrylate, and the like. It is not limited only to this. In particular, it is most preferable to use methyl methacrylate (MMA).

In the present invention, as the compound containing the (meth) acrylate-based unit, a copolymer including a (meth) acrylate-based unit and a ring-based unit having the ring portion can be used. The content of the (meth) acrylate-based unit in the copolymer including the (meth) acrylate-based unit and the cyclic-based unit having the cyclic moiety is about 50 to 99% by weight, preferably about 70 to 98% by weight, The content of the ring-based unit having the ring portion is about 1 to 50% by weight, preferably about 2 to 30% by weight. If the content of the ring-based unit having the ring portion is 50% by weight or less, it is advantageous to lower the haze value of the film.

The ring-based unit having the ring portion in the copolymer including the (meth) acrylate-based unit and the ring-based unit having the ring portion serves to improve the heat resistance of the film. Examples of the ring system unit having the ring portion will be described later. However, the ring-based unit having a ring portion included in the copolymer together with the (meth) acrylate-based unit is most preferably a maleimide unit including a maleimide portion. The maleimide-based unit may include a ring portion derived from N-cyclohexylmaleimide, N-phenylmaleimide, N-methylmaleimide, N-butylmaleimide, and the like, but is not limited thereto. Most preferably it comprises a ring moiety derived from cyclohexylmaleimide.

The copolymer including the (meth) acrylate-based unit and the cyclic-based unit having the cyclic moiety includes a cyclic monomer such as a (meth) acryl-based monomer and a maleimide-based monomer, and may include bulk polymerization, solution polymerization, suspension polymerization, It may be prepared by a method such as emulsion polymerization.

In the present invention, the number average molecular weight of the aromatic unit having the chain having the hydroxy group-containing portion and the aromatic moiety is preferably 1,500 to 2,000,000 g / mol. It is preferable that the said aromatic type unit contains a phenoxy clock resin. Here, the phenoxy resin includes a structure in which at least one oxygen radical is bonded to a benzene ring. For example, the aromatic unit may include one or more units represented by Formula 1 below. The aromatic unit preferably contains 5 to 10,000 units, more preferably 5 to 7,000 units, more preferably 5 to 5,000 units of the following general formula (1). When two or more units represented by the following Chemical Formula 1 are included in the aromatic unit, they may be included in the form of random, alternating or block.

[Formula 1]

In Formula 1,

X is a divalent group comprising at least one benzene ring, and R is a straight or branched chain alkylene having 1 to 6 carbon atoms.

Specifically, X is preferably a divalent radical derived from a compound represented by the following general formulas (2) to (4), but is not limited thereto.

[Formula 2]

R ¹ is a direct bond, a straight or branched alkylene having 1 to 6 carbon atoms or a cycloalkylidene having 3 to 20 carbon atoms,

R ² and R ³ are each independently hydrogen, straight or branched chain alkyl of 1 to 6 carbon atoms, or straight or branched chain alkenyl of 2 to 6 carbon atoms, and n and m are each independently an integer of 1 to 5 .

(3)

R ⁴ is hydrogen, straight or branched chain alkyl of 1 to 6 carbon atoms or straight or branched chain alkenyl of 2 to 6 carbon atoms, and p is an integer of 1 to 6;

[Formula 4]

R ⁶ and R ⁷ are each independently a direct bond, straight or branched chain alkylene having 1 to 6 carbon atoms, or cycloalkylidene having 3 to 20 carbon atoms,

R ⁵ and R ⁸ are each independently hydrogen, straight or branched chain alkyl of 1 to 6 carbon atoms or straight or branched chain alkenyl of 2 to 6 carbon atoms, and q and r each independently represent an integer of 1 to 5; .

Specific examples of the compounds represented by the formulas (2) to (4) are shown below, but the present invention is not limited thereto.

Most preferably, the aromatic unit includes 5 to 10,000 one or more phenoxy clock units represented by the following general formula (5).

[Chemical Formula 5]

In the above formula, R ⁹ is a direct bond or a straight or branched chain alkylene having 1 to 6 carbon atoms, and R ¹⁰ is a straight or branched chain alkylene having 1 to 6 carbon atoms.

The formula (5) is preferably represented by the following formula (6).

[Formula 6]

The terminal of the compound including the aromatic unit may be an OH group.

In the present invention, it should be understood that the styrene-based unit may include styrene-based derivatives as well as styrene. The styrene derivative includes a compound having at least one substituent containing an aliphatic hydrocarbon or a hetero atom in the benzene ring or vinyl group of the styrene, and specifically also includes alphamethyl styrene.

In the present invention, a copolymer including a styrene-based unit and a ring-based unit having the ring portion can be used as the compound containing the unit. The content of the styrene-based unit in the copolymer including the styrene-based unit and the cyclic-based unit having a ring portion is about 1 to 99% by weight, preferably about 30 to 99% by weight, more preferably about 40 to 95% by weight. And the content of the ring-based unit having a ring portion is about 1 to 99% by weight, preferably about 1 to 70% by weight, more preferably about 5 to 60% by weight. The adhesive and heat resistance of a film can be improved by melt-mixing the copolymer including the styrene-based unit and the cyclic-based unit having a ring portion. If the content of the ring-based unit having a ring portion is too small, the miscibility may be somewhat poor. Examples of the ring system unit having the ring portion will be described later. However, the ring-based unit having a ring portion included in the copolymer together with the ring-based unit is most preferably a maleic anhydride-based unit including maleic anhydride.

In the present invention, the ring-based unit can improve the heat resistance of the film. The content of the ring-based unit is about 0.1 to 99% by weight, preferably about 0.5 to 45% by weight. The ring portion of the ring-based unit includes maleic anhydride, maleimide, glutaric anhydride, glutalimide, lactone, lactam, and the like, but is not limited thereto.

According to one embodiment of the present invention, as components comprising the aforementioned units, 1) a copolymer comprising a (meth) acrylate-based unit and a maleimide-based unit, 2) a phenoxy-based unit 3) A copolymer including a resin and 3) a styrene-based unit and a maleic anhydride unit can be used. In this case, the content of each component is preferably 1 to 99% by weight. Specifically, the 1) copolymer is preferably about 50 to 99% by weight, more preferably about 75 to 98% by weight. 2) The resin is preferably about 0.5 to 40% by weight, more preferably about 1 to 30% by weight. 3) The copolymer is preferably about 0.5 to 30% by weight, more preferably about 1 to 20% by weight.

In particular, when the content of the maleimide monomer in the copolymer including the 1) (meth) acrylate-based unit and the maleimide-based unit is 50% by weight or less, regardless of the mixing ratio of the components 1) to 3) Miscibility with respect to the area can be exhibited, and optical films of this composition have an excellent advantage of exhibiting a single glass transition temperature (Tg).

The polarizer protective film according to the present invention has a thickness of 5 to 500 μm, more preferably 5 to 300 μm, but is not limited thereto. The optical transmittance of the optical film is 90% or more, haze (haze) characteristics may be in the range of 2.5% or less, preferably 1% or less, more preferably 0.5% or less. It is preferable that the glass transition temperature of the said polarizer protective film is 100 degreeC or more.

The polarizer protective film may control the value of the photoelastic coefficient extremely small according to the content of the aromatic-based unit and the styrene-based unit having the chain having the hydroxy group-containing portion and the aromatic portion, and in this case, the change in the phase difference value due to external stress is small. Since the light leakage phenomenon can be reduced.

Method for producing a polarizer protective film according to the present invention comprises the steps of preparing the above-mentioned resin composition; And molding the film using the resin composition. The method of manufacturing the optical film may further include uniaxially or biaxially stretching the film.

The resin composition may be prepared by melting and blending the aforementioned components. Melt mixing of the components may be performed using an extruder or the like.

The resin composition may further include a lubricant, an antioxidant, a UV stabilizer, a heat stabilizer, and the like, which are generally used.

When manufacturing the polarizer protective film according to the present invention can be used a method known in the art, specifically, an extrusion molding method can be used. For example, the resin composition is dried in vacuo to remove moisture and dissolved oxygen, and then fed from a raw material hopper to a single or twin extruder substituted with nitrogen, and melted at a high temperature to obtain raw material pellets, and vacuum drying the obtained raw material pellets, After melt | dissolving from a raw material hopper to the extruder with a nitrogen-substituted single extruder, it can pass through the coat hanger type T-die, and can manufacture a film through a chrome plating casting roll, a drying roll, etc.

When manufacturing the polarizer protective film according to the present invention may further comprise the step of uniaxially or biaxially stretching the film. The stretching step may be performed in the longitudinal direction (MD) stretching or in the transverse direction (TD) stretching, or both. When extending | stretching both a longitudinal direction and a lateral direction, after extending | stretching either one, you can extend in another direction and you may extend | stretch both directions simultaneously. The stretching can be performed in one step or in multiple steps. When stretching in the longitudinal direction, stretching can be performed by the speed difference between the rolls, and in the case of stretching in the transverse direction, tenter can be used. The time of railing of the tenter is within 10 degrees of the total, suppressing the bowing phenomenon occurring in the transverse direction drawing, and controlling the angle of the optical axis regularly. It is also possible to obtain the same bowing suppression effect by setting the transverse stretching in multiple stages.

The stretching may be performed at a temperature of (Tg-20 ° C) to (Tg + 30 ° C) when the glass transition temperature of the resin composition is Tg. The glass transition temperature refers to a range from a temperature where the storage elastic modulus of the resin composition begins to decrease and a loss elastic modulus becomes larger than a storage elastic modulus to a temperature at which the orientation of the polymer chain is relaxed and disappears. The glass transition temperature can be measured by a differential scanning calorimeter (DSC).

The drawing speed is preferably in the range of 1 to 100 mm / min in the case of a universal drawing machine (Zwick Z010) and in the range of 0.1 to 2 m / min in the case of a pilot drawing machine. It is preferable to stretch the film by applying an elongation of 5 to 300%.

The stretching may proceed as a separate step from the forming of the film, or may be carried out in one step in the same process as the forming of the film.

The composition and longitudinal stretching ratio, transverse stretching ratio, stretching temperature and stretching speed of each of the above-described units can be appropriately combined.

In addition, the stretched film can effectively compensate for the disadvantages of the brittle (meth) acrylate-based film because the toughness is increased.

In the polarizer protective film according to the present invention, the absolute value of the in-plane retardation represented by Equation 1 and the thickness direction retardation represented by Equation 2 is 10 nm or less, preferably 5 nm or less, with or without stretching. Moreover, the polarizer protective film which concerns on this invention is 3 * 10 <^-12> m <^2> / N or less of absolute values of a photoelastic coefficient with or without extending | stretching.

The polarizer protective film according to the present invention may be provided with an additional layer including at least one of an organic material and an inorganic material on at least one surface thereof to adjust the phase difference value and the compensation characteristic and / or the adhesion to the polarizer. Examples of the organic material include cellulose, polyimide, polyester, polyurethane, liquid crystal, and / or derivatives thereof, and the inorganic material includes TiO ₂ , ITO, and the like, but is not limited thereto.

The polarizer protective film according to the present invention may be provided only on one surface of the polarizer, or may be provided on both surfaces.

When the polarizer protective film according to the present invention is provided only on one surface of the polarizer, the other surface may be provided with a protective film known in the art. The known protective film includes a triacetate cellulose (TAC) film, a polynorbornene-based film made of ring opening metathesis polymerization (ROMP), and a HROMP obtained by hydrogenating a ring-opening polymerized cyclic olefin-based polymer again. (ring opening metathesis polymerization followed by hydrogenation) may be a polymer film, a polyester film, or a polynorbornene-based film prepared by addition polymerization. In addition, a protective film or the like made of a transparent polymer material may be used, but is not limited thereto.

In the polarizing plate according to the present invention, a film made of polyvinyl alcohol (PVA) containing iodine or dichroic dye may be used as the polarizer. The polarizer may be prepared by dyeing iodine or dichroic dye on the PVA film, but a method of manufacturing the same is not particularly limited. In the present specification, the polarizer means a state not including a protective film, and the polarizing plate means a state including a polarizer and a protective film.

The polarizing plate according to the present invention may be prepared using a polarizer, a polarizer protective film, and a UV curable adhesive as described above, using a method known in the art. For example, the UV curable adhesive may be applied to at least one surface of the polarizer or the polarizer protective film, and the polarizer and the polarizer protective film may be manufactured by passing through a laminator, but are not limited thereto.

In addition, the present invention provides a liquid crystal display device including the polarizing plate. For example, the liquid crystal display according to the present invention is a liquid crystal display including a liquid crystal cell and a first polarizing plate and a second polarizing plate respectively provided on both surfaces of the liquid crystal cell, wherein at least one of the first polarizing plate and the second polarizing plate is It is characterized in that the polarizing plate according to the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are intended to illustrate the invention and are not intended to limit the scope of the invention by the following examples.

<Examples>

Preparation Example 1 Preparation of Polarizer Protective Film

A raw material hopper is a resin composition obtained by uniformly mixing poly (N-cyclohexylmaleimide-co-methylmethacrylate), styrene-maleic anhydride copolymer resin and phenoxy resin in a weight ratio of 100: 2.5: 5. From the extruder to a nitrogen-substituted 24φ extruder and melted at 250 ° C. to prepare a raw material pellet.

The phenoxy resin was PKFE (Mw = 60,000, Mn = 16,000, Tg = 95 ° C) from InChemRez®, and the styrene-maleic anhydride copolymer resin was 85% by weight of styrene and 15% by weight of maleic anhydride. 332 was used, and the poly (N-cyclohexylmaleimide-co-methylmethacrylate) resin had a content of N-cyclohexylmaleimide of 6.5 wt% based on NMR analysis.

The obtained raw material pellets were vacuum-dried and melted with an extruder at 260 degreeC, passed through the T-die of a coat hanger type, and the film of 150 micrometers in thickness was produced through the chrome plating casting roll, a drying roll, etc. The film was stretched at a ratio shown in Table 1 below using the speed difference of the roll in the MD direction at 125 ° C. using a pilot stretching equipment, and then described in Table 1 using a denter at 125 ° C. in the TD direction. The film was prepared by stretching in one proportion. The plane direction retardation value and the thickness direction retardation value of the film are shown in Table 1 below.

MD draw ratio TD draw ratio Phase difference value (nm) Thickness (㎛) R _in R _th 100% 100% 0.4 +0.6 160 150% 100% 0.2 +1.0 118 150% 200% 1.0 -1.6 59 150% 250% 0.9 -1.1 47 160% 100% 0.4 +0.1 116 160% 200% 0.9 -1.5 56 160% 250% 0.8 -1.3 46 170% 100% 1.0 +1.9 114 170% 200% 0.7 -1.9 55 170% 220% 0.5 -1.5 50 170% 250% 0.5 -1.4 42

&Lt; Example 1 >

1) Preparation of Adhesive

40 parts by weight of CK0109A (weight average molecular weight 7,000 epoxy resin having a total of 15 epoxy bonds per molecule, light paint) as an epoxy acrylate oligomer, 47 parts by weight of HEA as a hydrophilic monomer, 5 parts by weight of IBOA as a hydrophobic monomer and 5 parts by weight of HDDA And 3 parts by weight of Irgacure 819 (Ciba) or Darocure TPO (Ciba) based on the total weight of the epoxy acrylate oligomer and the radical polymerizable compound as the photopolymerization initiator to prepare a UV curable adhesive. The viscosity of the prepared adhesive was about 30 cP.

2) Preparation of Polarizer

A Phenoxy-PS-PMMA film having a thickness of 60 µm prepared in Preparation Example 1 was coated on both sides of the PVA device, and the adhesive was dropped on the back of the PVA device, and then passed through a laminator to prepare a polarizing plate.

<Examples 2 to 13>

Except for using the adhesive composition shown in Table 2 was carried out in the same manner as in Example 1 to prepare a polarizing plate.

&Lt; Comparative Example 1 &

The polarizing plate was carried out in the same manner as in Example 1 except for using the water-based adhesive (Z200, Nippon Synthetic, 4.5 wt%; and KR 44 (crosslinking agent, Ajinomoto Co., Ltd.) 3 wt% in water) in preparing the polarizing plate in Example 1. Was prepared.

<Comparative Examples 2 to 3>

A polarizing plate was prepared in the same manner as in Example 1 except that TAC or COP was used as the adhesive composition and the protective film shown in Table 2 below.

Protective film Adhesive composition Epoxy acrylate oligomer Radically polymerizable
compound Photopolymerization initiator Kinds content
(Parts by weight) Kinds content
(Parts by weight) Kinds content
(Parts by weight) Example 2 Acryl CK0109A 40 HEA
HDDA 50
10 Irgacure 819 4 Example 3 Acryl CK0109A 40 HEA
HDDA 40
20 Irgacure 819 4 Example 4 Acryl CK0109A 40 HEA
DPGDA 40
20 Irgacure 819 4 Example 5 Acryl CK0109A 40 HEA
NVP 40
20 Irgacure 819 4 Example 6 Acryl CK0109A 40 HEA
ACMO 40
20 Irgacure 819 4 Example 7 Acryl CK0109A 40 HEA
IBOA 40
20 Irgacure 819 4 Example 8 Acryl CK0109A 40 HEA
HDDA
IBOA 40
10
10 Irgacure 819 4 Example 9 Acryl EB3604 40 HEA
HDDA
IBOA 50
5
5 Irgacure 819 4 Example 10 Acryl EB3605 40 HEA
HDDA
IBOA 50
5
5 Irgacure 819 4 Example 11 Acryl EB3700 40 HEA
HDDA
IBOA 50
5
5 Irgacure 819 4 Example 12 Acryl EB3701 40 HEA
HDDA
IBOA 50
5
5 Irgacure 819 4 Example 13 Acryl EB3703 40 HEA
HDDA
IBOA 50
5
5 Irgacure 819 4 Comparative Example 1 Acryl Water-based adhesive Comparative Example 2 TAC CK0109A 40 HEA
HDDA
IBOA 40
10
10 Irgacure 819 4 Comparative Example 3 COP CK0109A 40 HEA
HDDA
IBOA 40
10
10 Irgacure 819 4

Acryl: Phenoxy-PS-PMMA

CK0109A: Epoxy resin with a weight average molecular weight of 7,000 with an average of 15 epoxy bonds per molecule, dimming paint

EB3604: rubber modified epoxy acrylate, weight average molecular weight-1200, SK Cytec

EB3605: partially acrylic modified ester (acrylate, epoxide) of bisphenol A epoxy resin, weight average molecular weight-450, SK Cytec

EB3700: Diacrylate ester of bisphenol A epoxy resin, weight average molecular weight -500, SK Cytec

EB3701: modified bisphenol A epoxy acrylate oligomer, weight average molecular weight-850, SK Cytec

EB3703: amine-modified bisphenol A epoxy acrylate oligomer, weight average molecular weight-850, SK Cytec

HEA: hydroxyl ethyl acrylate

HDDA: 1,6-hexanediol diacrylate

DPGDA: dipropylene glycol diacrylate

NVP: N-vinyl pyrrolidone

ACMO: acryloyl morpholine

IBOA: isobornyl acrylate

<Experimental Example>

1) Peel force evaluation of polarizing plate

Ultraviolet rays of 600 mJ / cm ² were irradiated to both surfaces of each of the polarizing plates of Examples 2 to 13 and Comparative Examples 1 to 3 prepared above using a UV irradiation apparatus (mercury lamp). Then, the peel force at the time of peeling at a speed of 5 mm / sec and 90 degree using the polarizing plate of width 20mm and length 100mm was measured, and is shown in following Table 3.

2) Evaluation of Water Resistance of Polarizing Plate

The prepared polarizing plate was cut into a punching machine at a size of 5 × 8 cm, attached to glass using an adhesive, and then immersed in a 60 ° C. thermostatic bath to evaluate water resistance by discoloration of iodine in the polarizing plate. The results are shown in Table 3 below.

Viscosity
(cP at RT) Tg (占 폚) Peel force
(N / cm ² ) Water resistance Example 2 32.8 27.1 2.3 4.5 Example 3 32.9 30.0 1.9 5 Example 4 34.9 30.0 1.8 5 Example 5 29.3 34.2 1.8 5 Example 6 31.9 40.2 0.7 5 Example 7 32.8 30.0 1.4 2 Example 8 - 26.8 1.8 4 Example 9 - 37.0 0.4 2 Example 10 - 36.9 1.7 3 Example 11 - 60.3 0.2 4.5 Example 12 - 40.7 1.6 2 Example 13 - 34.8 1.1 2 Comparative Example 1 - - 0.3 5 Comparative Example 2 - 1.5 1.5 4 Comparative Example 3 - 2 2 4

Water resistance rating: 5 (very good), 3 (normal), 1 (bad)

From the results of Tables 2 and 3, it can be seen that the polarizing plate according to the present invention is excellent in adhesion even without pretreatment such as primer treatment, corona treatment, for adhesion between the polarizer protective film and the polarizer.

1: polarizer
2a, 2b: polarizer protective film
3: adhesive layer
P: polarizer
C: liquid crystal cell

Claims (19)

A polarizing plate comprising a polarizer and a polarizer protective film provided on at least one side of the polarizer,
The polarizer protective film is an aromatic unit having a chain having an hydroxyl group-containing portion and an aromatic portion; And a styrene-based unit including at least one styrene-based derivative, wherein the in-plane retardation Rin represented by the following equation (1) and the thickness direction phase difference (Rth) represented by the following equation (2) with or without stretching: Absolute value is 10nm or less,
Between the polarizer and the polarizer protective film is provided with an adhesive layer comprising a UV curable adhesive comprising an epoxy acrylate oligomer, a radical polymerizable compound and a photopolymerization initiator,
The epoxy acrylate oligomer is an epoxy (meth) acrylate prepolymer which is a copolymer of (meth) acrylate having at least one or more epoxy compounds, at least one (meth) acrylic acid compound and a polyacid.
[Equation 1]

&Quot; (2) &quot;

In Equations 1 and 2, nx is the largest refractive index of the film plane direction refractive index,
ny is the refractive index in the direction perpendicular to nx of the film surface direction refractive index,
nz is the refractive index in the film thickness direction,
d is the thickness of the film. delete The polarizing plate according to claim 1, wherein the epoxy (meth) acrylate prepolymer has a weight average molecular weight of 3,000 to 20,000 and 8 to 20 average epoxy bonds per molecule. The polarizing plate according to claim 1, wherein the polyacid in the epoxy (meth) acrylate prepolymer is any one of polyether polyacid, polyester polyacid and polysaturated fatty acid having a weight average molecular weight of 100 to 3,000. The polarizing plate of claim 1, wherein the content of the epoxy acrylate oligomer is 20 to 60 wt% based on the total weight of the UV curable adhesive. The polarizing plate of claim 1, wherein the radical polymerizable compound comprises a hydrophilic monomer and a hydrophobic monomer. The method of claim 6, wherein the hydrophilic monomer is hydroxy ethyl acrylate (HEA), hydroxy ethyl methacrylate (HEMA), hydroxy propyl acrylate (HPA), hydride Hydroxyl propyl methacrylate (HPMA), hydroxy butyl acrylate (HBA), acrylic acid (AA), N-vinyl pyrrolidone, diacetone ( Meth) acrylamide, isobutoxy methyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, octyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, hydroxy butyl vinyl ether and A polarizing plate comprising at least one member selected from the group consisting of N-vinyl caprolactam. The method according to claim 6, wherein the hydrophobic monomer is 1,6-hexanediol diacrylate (1,6-hexanediol diacrylate (HDDA), isobornyl acrylate (IBOA), trimethylolpropane triacrylate (trimethylolpropane triacrylate, TMPTA), dipropylene glycol diacrylate (DPGDA), benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, methyl (meth) acrylate and ethyl (meth) acrylate A polarizing plate comprising at least one selected. The method of claim 6, wherein the content of the hydrophilic monomer is 10 to 70% by weight based on the total weight of the UV-curable adhesive, the content of the hydrophobic monomer is characterized in that 1 to 30% by weight based on the total weight of the UV-curable adhesive Polarizer. The polarizing plate of claim 1, wherein the UV curable adhesive has a viscosity of 5 to 100 cP. The polarizing plate according to claim 1, wherein the adhesive layer has a thickness of 1 μm or less. The polarizing plate according to claim 1, wherein an absolute value of the photoelastic coefficient of the polarizer protective film is 3 × 10 ^-12 m ² / N or less. The polarizing plate according to claim 1, wherein the polarizer protective film further comprises a (meth) acrylate-based unit including at least one (meth) acrylate-based derivative. The polarizing plate of claim 1, wherein the polarizer protective film further includes a ring-based unit. The polarizing plate according to claim 1, wherein the aromatic unit of the polarizer protective film comprises a phenoxy clock resin. The polarizing plate according to claim 1, wherein the aromatic unit of the polarizer protective film includes 5 to 10,000 at least one unit represented by the following Chemical Formula 1.
[Formula 1]

In Chemical Formula 1,
X is a divalent group comprising at least one benzene ring, and R is a straight or branched chain alkylene having 1 to 6 carbon atoms. The method according to claim 13, wherein the (meth) acrylate-based unit is a copolymer of a (meth) acrylate derivative and maleimide, the aromatic unit comprises 5 to 10,000 units represented by the formula (6), The styrene-based unit is a copolymer of a styrene derivative and maleic anhydride, characterized in that:
[Chemical Formula 6]

The polarizing plate according to claim 1, wherein the polarizer protective film has a thickness of 5 to 500 µm. The liquid crystal display device containing the polarizing plate of any one of Claims 1 and 3-18.

Images