KR102481465B1 - Retardation film, polarizing plate and display device comprising the same - Google Patents

Abstract

The present invention relates to a retardation film including an acrylic resin, a styrene resin, and a 2-hydroxyphenyl-s-triazine-based compound and satisfying a specific refractive index equation, and a polarizing plate and a display device including the same.

Description

Retardation film, polarizing plate and display device including the same {RETARDATION FILM, POLARIZING PLATE AND DISPLAY DEVICE COMPRISING THE SAME}

The present invention relates to a retardation film, a polarizing plate and a display device including the same.

Since liquid crystal display devices consume less power than cathode ray tube displays, have a small volume, and are light and easy to carry, their use as optical display devices is spreading. In general, a liquid crystal display device has a basic configuration in which polarizers are installed on both sides of a liquid crystal cell, and the orientation of the liquid crystal cell changes depending on whether or not an electric field is applied to the driving circuit, and accordingly, the characteristics of transmitted light emitted through the polarizer change. visualization takes place. At this time, the light path and birefringence are changed according to the incident angle of incident light. This is because liquid crystal is an anisotropic material having two different refractive indices.

Due to these characteristics, the contrast ratio, which is a measure of how clearly an image can be seen, changes depending on the viewing angle of the liquid crystal display device, and gray scale inversion occurs, resulting in poor visibility. has a downside In order to overcome the above disadvantages, an optical retardation film that expresses an optical retardation generated in a liquid crystal cell is used in a liquid crystal display device.

Meanwhile, various liquid crystal modes are being developed to secure clear picture quality and a wide viewing angle in liquid crystal displays. Representatively, Double Domain TN (Twisted Nematic), ASM (axially symmetric aligned microcell), OCB (optically compensated blend ), VA (vertical alignment), MVA (multidomain VA), SE (surrounding electrode), PVA (patterned VA), IPS (in-plane switching), FFS (fringe-field switching) modes, and the like. Each of these modes has a unique liquid crystal arrangement and has a unique optical anisotropy.

Therefore, in order to express the retardation due to the optical anisotropy of these liquid crystal modes, an optically anisotropic retardation film corresponding to each mode is required. In particular, in the case of a specific mode, for example n _x An optical film having a refractive index distribution of > n _z > n _y should be used. At this time, it is known that an optical film having such a refractive index distribution is generally difficult to implement using a uniaxially/biaxially stretched film alone.

Therefore, in order to form a retardation compensation layer that satisfies the refractive index distribution condition, a method of manufacturing a multilayer film of two or more layers has been proposed. However, in the case of manufacturing a multi-layer film, it is difficult to thin the film, and if the optical axis of the film of two or more layers is not accurately arranged, the desired retardation characteristics are not exhibited.

Therefore, studies for manufacturing an optical film having the above refractive index distribution with one film are continuously being conducted. For example, a laminate by attaching a shrinkable film to one or both surfaces of a resin film through an acrylic adhesive or the like. There has been proposed a method of forming a, stretching the laminate, and imparting contractive force in a direction orthogonal to the stretching direction.

However, in the case of manufacturing an optical film by attaching it on a shrinkable film in the form of a resin film as described above, the production process is complicated and , The manufacturing cost is high, and the thickness of the retardation film produced is thick, so there are disadvantages in not meeting the trend of thin and light weight display devices including the same. In addition, there is also a problem in that the occurrence rate of defects such as stains, cunicks, foreign matter mixing, etc. due to the use of the adhesive is high.

The present invention provides a retardation film capable of implementing a simple production process, excellent appearance characteristics, and uniform transmittance and uniform visual feeling.

In addition, the present invention provides a polarizing plate and a display device including the retardation film.

In this specification, A retardation film containing an acrylic resin, a styrene resin, and a 2-hydroxyphenyl-s-triazine-based compound and satisfying the following formula (1) is provided.

Equation (1): n _x > n _z > n _y

In the above formula (1),

n _x is the refractive index in the slow axis direction of the retardation film surface,

n _y is the refractive index in the fast axis direction of the retardation film surface,

n _z is the refractive index of the thickness direction of the retardation film.

In addition, the present specification provides a polarizing plate including the retardation film.

In addition, the present specification provides a display device including the retardation film.

Hereinafter, a retardation film according to a specific embodiment of the present invention, a polarizing plate and a display device including the same will be described in detail.

In this specification, (meth)acrylate is meant to include both acrylate and methacrylate.

According to one embodiment of the invention, A retardation film containing an acrylic resin, a styrene resin, and a 2-hydroxyphenyl-s-triazine-based compound and satisfying the following formula (1) is provided.

Equation (1): n _x > n _z > n _y

In the above formula (1),

n _x is the refractive index in the slow axis direction of the retardation film surface,

n _y is the refractive index in the fast axis direction of the retardation film surface,

n _z is the refractive index of the thickness direction of the retardation film.

The present inventors conducted research on retardation films applicable to polarizers and display devices, and acrylic resins, styrenic resins and The retardation film containing the 2-hydroxyphenyl-s-triazine-based compound may have a refractive index distribution of n _x > n _z > n _y , has excellent appearance characteristics, and realizes uniform transmittance and uniform visibility. , It was confirmed that a retardation film having a very thin thickness can be provided, and the invention was completed.

In addition, the retardation film may satisfy the above-described refractive index distribution by controlling the components included in the resin composition to a specific weight ratio, and accordingly, appearance characteristics, uniform transmittance, and visual sensation may be implemented. Specifically, the weight ratio of the styrene-based resin and the 2-hydroxyphenyl-s-triazine-based compound included in the retardation film is 100: 30 to 120, 100: 31 to 100, 100:32 to 90, 100:33 to 80, 100:34 to 70, or 100:35 to 60 can be controlled. When the content of the 2-hydroxyphenyl-s-triazine-based compound is too small compared to the styrene-based resin, the n _x , n _y and n _z values of the retardation film do not satisfy the n _x > n _z > n _y relationship, , in particular, n _z There is a problem that the value is too large, and when the content of the 2-hydroxyphenyl-s-triazine-based compound is too large, the n _x , n _y and n _z values of the retardation film satisfy the relationship n _x > n _z > n _y In particular, there is a problem that the n _z value becomes too small.

Specifically, the retardation film according to the embodiment satisfies Equation (1) below.

Equation (1): n _x > n _z > n _y

In Equation (1), n _x is the refractive index in the direction in which the refractive index in the plane direction of the retardation film is maximized (ie, the slow axis direction, Slow Axis), and n _y is the direction perpendicular to the slow axis in the plane direction of the retardation film. It is the refractive index in the direction (ie, the fast axis direction, Fast Axis), and n _z means the refractive index in the thickness direction of the retardation film.

Also, n _x , n _y , and n _z refer to values measured from light having a wavelength of 550 nm. On the other hand, the n _x , n _y , n _z can be measured by a known method well known in the art, for example, by using a prism coupler equipment (SAIRON TECHNOLOGY's SPA-3DR) and the like to determine the average refractive index Then, by measuring birefringence with Axoscan from Axomatrics, n _x , n _y , and n _z can be calculated, respectively.

As described above, the retardation film includes an acrylic resin, a styrenic resin, and a 2-hydroxyphenyl-s-triazine-based compound. Due to the inclusion of a specific content, n _x > n _z > n _y may be satisfied, and specifically, the styrene-based resin and the 2-hydroxyphenyl-s-triazine-based compound in the retardation film are 100: 30 to 120, 100: Due to being included in a weight ratio of 31 to 100, 100:32 to 90, 100:33 to 80, 100:34 to 70, or 100:35 to 60, The refractive index may satisfy n _x > n _z > n _y . When the retardation film satisfies n _x >n _z >n _y , it can be usefully used as an IPS (In-Plane Switching) mode retardation film.

Meanwhile, the retardation film may satisfy Equation (1) and Equation (2) below.

Equation (2): 40 nm ≤ R _in (550) ≤ 400 nm

In Equation (2), R _in (550) means the plane direction retardation value of the film measured at a wavelength of 550 nm, and is obtained by the plane direction retardation value R _in =(n _x -n _y )Хd. In this case, n _x and n _y are the same as described above, and d means the thickness of the retardation film. On the other hand, the R _in can be measured by a known method well known in the art, for example, it can be measured using Axoscan equipment from Axomatrics.

In addition, the R _in (550) may be 41 to 350 nm, 43 to 300 nm, 45 to 250 nm, 47 to 200 nm, or 47 to 150 nm.

In addition, the retardation film may satisfy Equations (1) and (2) and Equation (3) below.

Equation (3): 0 nm ≤ R _th (550) ≤ 200 nm

In Equation (3), R _th (550) means the thickness direction retardation value of the film measured at a wavelength of 550 nm, and is obtained by the thickness direction retardation value R _th =(n _z -n _y )Хd. In this case, n _y , n _z and d are the same as described above. On the other hand, the R _th can be measured by a known method well known in the art, for example, it can be measured using Axoscan equipment from Axomatrics.

In addition, the R _th (550) may be 0 to 150 nm, 1 to 100 nm, 2 to 80 nm, 3 to 60 nm, or 4 to 40 nm.

In addition, the retardation film may satisfy Equations (1) to (3) and Equation (4) below.

Equation (4): 0 ≤ Nz < 1

In the above formula (4) , Nz means the ratio of R _in and R _th , specifically the ratio of the difference between R _in and R _th to R _in (R _in - R _th ), more specifically, the Nz is It is obtained by Nz=(n _x -n _z )/(n _x -n _y ). At this time, n _x , n _y and n _z are the same as described above. On the other hand, the Nz can be obtained by substituting the values of n _x , n _y , and n _z described above, or can be obtained using R _in and R _th measured using the product name “AxoScan” manufactured by Axometrics. In this case, R _in and R _th may be phase difference values measured at a wavelength of 550 nm.

In addition, the Nz may be 0.1 to 0.99, 0.2 to 0.98, 0.3 to 0.97, 0.4 to 0.96, or 0.5 to 0.95.

The retardation film includes a negative birefringent material and a positive birefringent material, specifically, an acrylic resin and a styrenic resin as the negative birefringent material, and 2-hydroxyphenyl-s- as the positive birefringent material. A triazine-based compound may be included.

The negative birefringent material means a material that develops an optical axis in a direction perpendicular to the stretching direction after stretching (after orientation), and in the case of coating or film formation only (before stretching), the refractive index of n _z > n _x = n _y Means a substance that expresses distribution. The above-defined birefringent material means a material that develops an optical axis in a direction parallel to the stretching direction after stretching (after orientation), and in the case of coating only (before stretching), a refractive index distribution of n _x = n _y > n _z means the substance that is expressed.

The acrylic resin has a small amount of dimensional change due to moisture, so that the deformation of the film is small under heat and humidity conditions. can In addition, by using the acrylic resin mixed with the styrene-based resin and the 2-hydroxyphenyl-s-triazine-based compound, the above formulas (1) to (4) can be effectively satisfied by stretching.

In this case, the acrylic resin contains a (meth)acrylic monomer as a main component, and may include a copolymer resin copolymerized with other monomers in addition to the (meth)acrylic monomer as well as a homopolymer resin composed of the (meth)acrylic monomer. In addition, the (meth)acrylic monomers may include acrylates and methacrylates as well as derivatives of acrylates and methacrylates. Specifically, the (meth)acrylic monomers include methyl methacrylate and ethyl methacrylate. , propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, methoxyethyl methacrylate, ethoxyethyl methacrylate, butoxymethyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, methoxyethyl acrylate, It may be ethoxyethyl acrylate, butoxy methyl acrylate or oligomers thereof, but is not necessarily limited thereto.

Specifically, as long as the acrylic resin is a polyacrylate commonly used in the art, it can be used without particular limitation. For example, polymethyl methacrylate resin, polymethyl acrylate resin, and polyethyl methacrylate resin. And it may include at least one selected from the group consisting of polyethyl acrylate resin.

In addition, the acrylic resin has a weight average molecular weight of 50,000 to 250,000, 80,000 to 200,000 or 100,000 to 150,000, a number average molecular weight of 20,000 to 100,000, 30,000 to 90,000, or 40,000 to 80,000, and a molecular weight distribution (Mw1 / Mn) 5, 1.5 to 4, or 2 to 3, and a glass transition temperature of 100 to 140°C, 110 to 135°C, or 120 to 135°C.

Meanwhile, the styrenic resin may be included in the retardation film to impart a negative retardation and increase the glass transition temperature.

In addition, the styrene-based resin may be used without particular limitation as long as it contains a styrene-based monomer as a main component. At this time, examples of the styrenic monomer include, but are not limited to, styrene, α-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 2-methyl -4-chlorostyrene, 2,4,6-trimethylstyrene, cis-β-methylstyrene, trans-β-methylstyrene, 4-methyl-α-methylstyrene, 4-fluoro-α-methylstyrene, 4-chloro -α-methylstyrene, 4-bromo-α-methylstyrene, 4-t-butylstyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 2,4-difluorostyrene, 2, 3,4,5,6-pentafluorostyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene, octachlorostyrene, 2-bromo In the group consisting of styrene, 3-bromostyrene, 4-bromostyrene, 2,4-dibromostyrene, α-bromostyrene, β-bromostyrene, 2-hydroxystyrene and 4-hydroxystyrene There may be more than one selected.

Meanwhile, the content of the styrene monomer in the total amount of the styrene-based resin may be 50% by weight or more, 50 to 99% by weight, 55 to 95% by weight, 60 to 90% by weight, or 65 to 85% by weight. If the content of styrene monomer is too small in the total amount of the styrene-based resin, there is a problem in that n _z expression is lowered.

Specifically, the styrene-based resin is not limited thereto, but, for example, styrene-acrylonitrile copolymer resin, styrene-maleic anhydride copolymer, α-methylstyrene-acrylonitrile copolymer, N-phenyl maleate Contains at least one selected from the group consisting of mid-α-methylstyrene-acrylonitrile copolymer, N-phenyl maleimide-styrene-acrylonitrile copolymer and N-phenyl maleimide-α-methylstyrene-acrylonitrile can do.

In addition, the styrenic resin has a weight average molecular weight of 20,000 to 200,000, 50,000 to 190,000, or 70,000 to 185,000, a number average molecular weight of 10,000 to 80,000, 20,000 to 70,000, or 25,000 to 65,000, and a molecular weight distribution of 1.5 to 1.5 to 4.5, or 2 to 4, and has a glass transition temperature of 120 to 160°C, 125 to 165°C, or 135 to 165°C.

A weight ratio of the acrylic resin and the styrene-based resin, which are negatively birefringent materials included in the retardation film, may be 2:8 to 9:1, 5:5 to 9:1, or 6:4 to 9.5:0.5. When the styrenic resin is included less than the above range, a problem of deterioration in phase difference expression characteristics may occur, and when it is included more than the above range, a problem of lowering heat resistance due to a lowered glass transition temperature may occur, and phase difference expression characteristics This becomes too large, and since the film must be too thin to express the retardation characteristics of the desired level, handling may be difficult.

The retardation film according to the embodiment may include a 2-hydroxyphenyl-s-triazine-based compound. The 2-hydroxyphenyl-s-triazine-based compound may impart a positive phase difference to the retardation film due to the aromatic ring structure included therein.

Specifically, the 2-hydroxyphenyl-s-triazine-based compound may include hydroxyphenyl in which an alkoxy group is substituted, and in particular, may include one hydroxyphenyl in which the alkoxy group is substituted. If the 2-hydroxyphenyl-s-triazine-based compound includes two or more hydroxyphenyls in which an alkoxy group is substituted, the retardation film may not have a refractive index distribution of n _x > n _z > n _y In addition, the appearance characteristics are deteriorated, and it may be difficult to implement uniform transmittance and uniform visibility.

More specifically, the 2-hydroxyphenyl-s-triazine-based compound may be represented by Formula 1 below.

[Formula 1]

In Formula 1,

Ar ₁ and Ar ₂ are each independently an aryl having 6 to 60 carbon atoms;

R is an alkyl having 1 to 60 carbon atoms.

Specifically, Ar ₁ and Ar ₂ may be phenyl,

R may be a branched chain alkyl of 5 to 15 carbon atoms.

For example, the 2-hydroxyphenyl-s-triazine-based compound may be a compound represented by Formula 2 below.

[Formula 2]

In addition, as described above, the retardation film has a weight ratio of the styrene-based resin and the 2-hydroxyphenyl-s-triazine-based compound of 100: 30 to 120, 100: 31 to 100, 100:32 to 90, 100: 33 to 80, 100:34 to 70, or 100:35 to 60. Due to being included in such a weight ratio, the refractive index may satisfy n _x > n _z > n _y .

Meanwhile, the retardation film may have a thickness of 10 to 100 μm, 20 to 90 μm, 30 to 80 μm, or 40 to 70 μm. If the thickness of the retardation film is too thin, a problem of curling the film may occur, and if the thickness is too thin, it is difficult to sufficiently implement a desired retardation film.

The retardation film may have a glass transition temperature (Tg) of 100 to 150 °C, 105 to 140 °C, 110 to 135 °C, or 120 to 130 °C. A retardation film satisfying this glass transition temperature range may have excellent heat resistance. The method for measuring the glass transition temperature is not particularly limited, and for example, the glass transition temperature can be measured by a differential scanning calorimeter (DSC).

The retardation film may have a moisture permeability of 150 g/m ² ·day or less, 0.1 to 130 g/m ² ·day, or 0.1 to 110 g/m ² ·day. The retardation film that satisfies this range of moisture permeability has a small dimensional change due to moisture, so the film is not deformed under heat and moisture resistance conditions, and also effectively prevents moisture from penetrating into the polarizer without any separate treatment when used attached to a polarizing plate or the like. can do. The method for measuring the moisture permeability is not particularly limited, and may be measured, for example, by measuring the weight of moisture permeating the film during a day under conditions of a temperature of 40° C. and a relative humidity of 90%.

Meanwhile, the retardation film may be a uniaxially stretched film or a biaxially stretched film. Specifically, the film made of the composition containing the acrylic resin, the styrenic resin, and the 2-hydroxyphenyl-s-triazine compound may be a retardation film obtained by uniaxial stretching, and the film made of the composition It may be a retardation film subjected to biaxial stretching.

More specifically, the retardation film may be a retardation film subjected to biaxial stretching, and at this time, the ratio of the stretching ratio in one direction and the stretching ratio in the direction perpendicular to the one direction is 1: 1 to 3, 1: 1.5 to 2.5, or 1:1.8 to 2.2. The one direction and the direction perpendicular to the one direction may independently be the longitudinal direction (MD) and the width direction (TD), but more specifically, the one direction is the longitudinal direction (MD), and the one direction is perpendicular to the one direction. The direction may be a width direction (TD). More specifically, the stretching ratio in the machine direction (MD) may be 0.5 to 2 times or 1 to 1.5 times, and the stretching ratio in the width direction (TD) may be 2 to 3.5 times to 2.5 to 3 times. Meanwhile, since the ratio of the stretch ratio in the direction perpendicular to the one direction satisfies the aforementioned range, it may have a retardation value suitable for use as a retardation film of a display device.

Meanwhile, the manufacturing method of the retardation film of the embodiment is not particularly limited, and, for example, a resin composition is prepared by mixing the acrylic resin, the styrenic resin, and the 2-hydroxyphenyl-s-triazine-based compound. It can be manufactured by a method of forming a film and stretching it.

The resin composition may be prepared by extruding and kneading the obtained mixture after pre-blending the film raw material with an arbitrary appropriate mixer such as an omni mixer, for example. In this case, the mixer used for extrusion and kneading is not particularly limited, and any suitable mixer such as an extruder such as a single screw extruder or a twin screw extruder or a pressure kneader can be used.

As a method of forming the film, any appropriate film forming method such as a solution casting method (solution casting method), a melt extrusion method, a calender method, and a compression molding method may be used. More specifically, among these film forming methods, a solution casting method (solution casting method) and a melt extrusion method may be used.

The solvent used in the solution casting method (solution casting method) includes, for example, aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as cyclohexane and decalin; esters such as ethyl acetate and butyl acetate; ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; alcohols such as methanol, ethanol, isopropanol, butanol, isobutanol, methyl cellosolve, ethyl cellosolve, and butyl cellosolve; ethers such as tetrahydrofuran and dioxane; halogenated hydrocarbons such as dichloromethane, chloroform, and carbon tetrachloride; dimethylformamide; Dimethyl sulfoxide etc. are mentioned. These solvents may be used independently or may use 2 or more types together.

Examples of the apparatus for performing the solution casting method (solution casting method) include a drum type casting machine, a band type casting machine, and a spin coater. Meanwhile, examples of the melt extrusion method include a T die method and an inflation method, and the molding temperature may be 150 to 350°C or 200 to 300°C.

In the case of forming a film by the T-die method, a roll-shaped film can be obtained by attaching a T-die to the tip of a known single-screw extruder or twin-screw extruder and winding the extruded film into a film shape.

After the film is formed through the above process, the film may be stretched. At this time, in the stretching process, stretching in the longitudinal direction (MD) and stretching in the width direction (TD) may be performed, or both may be performed. Further, in the case of performing both the longitudinal direction stretching and the width direction stretching, either one side may be stretched first, then the other direction may be stretched, or both directions may be stretched simultaneously. In addition, the stretching may be performed in one step or may be performed in multiple steps. In the case of stretching in the longitudinal direction, stretching may be performed by a difference in speed between rolls, and in the case of stretching in the width direction, a tenter may be used. The starting angle of the rail of the tenter is usually within 10 degrees, suppressing the bowing phenomenon that occurs during widthwise stretching and regularly controlling the angle of the optical axis. The effect of suppressing bowing can be obtained even when the stretching in the width direction is performed in multiple stages.

The stretching temperature is preferably in the range of the glass transition temperature of the resin composition as a film raw material, and when the glass transition temperature of the resin composition is Tg, for example, (Tg-30 ° C.) to (Tg + 100 °C), or within the range of (Tg-20°C) to (Tg+80°C). If the stretching temperature is less than (Tg-30°C), sufficient stretching ratio may not be obtained, and if it exceeds (Tg+100°C), flow of the resin composition may occur, and stable stretching may not be performed. In addition, the stretching speed is within the range of 1 to 100 m/min in the case of a small-sized stretching machine (universal testing machine, Zwick/Roell Z010), and in the range of 0.1 to 2 m/min in the case of pilot stretching equipment. can do Furthermore, the stretching ratio in the stretching step is the same as described for the retardation film described above.

The retardation film may be subjected to heat treatment (annealing) after stretching in order to stabilize its optical isotropy or mechanical properties. Heat treatment conditions are not particularly limited and any appropriate conditions known to those skilled in the art may be employed.

A polarizing plate including the retardation film according to another embodiment of the present invention is provided.

The polarizing plate may include one layer or two or more layers of the retardation film. Specifically, the retardation film may be directly attached to one side or both sides of a polarizer, or attached to a protective film of a polarizing plate having a protective film attached to both sides of the polarizer, and used as a retardation film.

When the retardation film is directly attached to one side or both sides of the polarizer, for example, the structure may be an upper protective film/polarizer/retardation film or a retardation film/polarizer/lower protective film. The attachment method is, after coating the surface of the retardation film or polarizer with a primer using a roll coater, a gravure coater, a bar coater, a knife coater, a capillary coater, or a micro chamber doctor blade coater, etc. , It may be performed by a method of spraying an adhesive in a dropwise manner and heating and laminating a laminate including a retardation film and a polarizer with a laminating roll, a method of compressing and laminating at room temperature, or a method of UV curing.

For example, when a retardation film is directly attached to one side or both sides of a polarizer using a water-based adhesive, a polyurethanediamine-based primer is coated on the surface of the retardation film by a bar coater method, and then the retardation film and It may be performed by a method of spraying an adhesive between polarizers in a dropwise manner, heating the retardation film and the polarizer laminate with a laminating roll, or compressing and laminating at room temperature. In addition, when the retardation film is directly attached to one side or both sides of the polarizer using a UV curable adhesive, a primer is coated on the surface of the retardation film by a microchamber doctor blade coater, and then the adhesive is applied between the retardation film and the polarizer in a dropwise manner. It may be performed by a method of spraying, laminating, and then UV curing.

On the other hand, when attaching the retardation film on the protective film of the polarizing plate, for example, the structure may be an upper protective film/polarizer/lower protective film/retardation film or retardation film/upper protective film/polarizer/lower protective film. can In this case, the protective film and the retardation film may be attached through an adhesive layer and/or an adhesive layer. The attachment method includes, for example, a roll coater, a gravure coater, a bar coater, a knife coater, or a capillary coater to coat the adhesive on the surface of the retardation film or the protective film, and then the retardation film and the protective film. It may be carried out by a method of heating and lamination of the laminate to a lamination roll, or by compressing at room temperature to lamination.

On the other hand, as the adhesive, adhesives used in the art, for example, polyvinyl alcohol-based adhesives, polyurethane-based adhesives, acrylic adhesives, etc. may be used without limitation. In addition, the adhesive layer is not limited to any one as long as it is used in the art.

In addition, the polarizing plate may include one layer of retardation film or two or more layers of retardation film, but the required retardation film may be one layer according to the Nz value of the retardation film. For example, if the Nz value of the retardation film is approximately 0.5, only one layer of the retardation film can be used.

A display device including the retardation film according to another embodiment of the present invention is provided. In this case, the display device may be a liquid crystal display device, a plasma display device, an organic light emitting device, and the like, and may be particularly suitable for an IPS (In-Plane Switching) mode liquid crystal display device.

In this case, the liquid crystal display device may include a liquid crystal cell and a first polarizing plate and a second polarizing plate respectively provided on both sides of the liquid crystal cell, and the retardation film may include the liquid crystal cell and the first polarizing plate and/or the second polarizing plate. It may be provided between polarizing plates. That is, a retardation film may be provided between the first polarizing plate and the liquid crystal cell, and one or more retardation films may be provided between the second polarizing plate and the liquid crystal cell, or both between the first polarizing plate and the liquid crystal cell and between the second polarizing plate and the liquid crystal cell. Two or more may be provided.

According to the present invention, the production process is relatively simple, and since there is no need to use a separate adhesive, the rate of occurrence of defects such as stains, nicks, and contamination of foreign matter can be significantly reduced, and as a result, the appearance characteristics are excellent, and uniform transmittance and uniformity are obtained. A retardation film realizing one visual sense and having a refractive index distribution of n _x > n _z > n _y , a polarizing plate and a display device including the same may be provided.

Hereinafter, the action and effect of the invention will be described in more detail through specific examples of the invention. However, these embodiments are only presented as examples of the invention, and the scope of the invention is not determined thereby.

Example One

Styrene-maleic anhydride copolymer resin (product name: R200, manufactured by Denka) at 66% by weight of polymethyl methacrylate resin (product name: M100, manufactured by LGMMA, weight average molecular weight 110,000, number average molecular weight 54,000, molecular weight distribution 2) Hand mixing a resin composition containing 25% by weight and 9% by weight of 2-hydroxyphenyl-s-triazine-based compound (product name: T1600, manufactured by Basf), put it in an extruder, and melt-kneaded to prepare a fabric film having a thickness of 200㎛ did

This film was heated to 126° C. in a UTM (Universal Testing Machine Z010, manufactured by Zwick/Roell), and then stretched 1.3 times in the MD direction and 2.8 times in the TD direction to prepare a retardation film having a thickness of 50 μm.

Example 2, 3 and comparative example 1 to 3

Polymethyl methacrylate resin, styrene-maleic anhydride copolymer resin, and 2-hydroxyphenyl-s-triazine-based compound were used in the contents shown in Table 1 below, and the stretching temperature and stretching ratio (MD/TD) were shown in the following table. A retardation film was prepared in the same manner as in Example 1, except that the stretching conditions described in 1 were controlled.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 profit
composition
(Unit: % by weight) Polymethyl methacrylate resin 66 68 73 78 59 70 Styrene-maleic anhydride copolymer resin 25 23 18 9 32 30 2-Hydroxyphenyl-s-triazine-based compounds 9 9 9 13 9 - stretching
condition Stretching temperature (℃) 126 126 126 124 126 130 Stretch ratio (MD, times) 1.3 1.3 1.3 1.4 1.3 1.35 Stretch ratio (TD, times) 2.8 2.7 2.5 2.5 2.5 3.0

Experimental example : phase difference Film property measurement

1. Glass transition temperature ( Tg ) measurement

For the resin compositions prepared in Examples and Comparative Examples, by heating-cooling-heating at a temperature range of 25 to 160 ° C. at 10 ° C./min using a differential scanning calorimeter (DSC) DSC-2500 from TA Instrument, The glass transition temperature was obtained during the second heating, and the results are shown in Table 2 below.

2. average index of refraction , phase difference , Nz and by direction index of refraction ( n _x , n _y and n _z ) measurement

For the retardation films prepared in Examples and Comparative Examples, the average refractive index was measured using a prism coupler equipment (SAIRON TECHNOLOGY's SPA-3DR).

Then, for the retardation film, using Axoscan equipment from Axometrics, the plane direction retardation value of the film measured at a wavelength of 550 nm (Rin (550)), thickness direction retardation value (Rth (550 )), Nz value, and refractive indices for each direction (n _x , n _y and n _z ) were measured, and the results are shown in Table 2 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Glass transition temperature (℃) 121 121 121 119 121 123 average refractive index 1.55 1.55 1.54 1.54 1.55 1.53 R _in (550 nm) 47.8 55.1 62.8 187.9 23.2 119.0 R _th (550, nm) 20.0 20.8 3.2 -3.1 38.5 177.5 n _x /n _y /n _z 1.54951/
1.54903/
1.54923 1.54944/
1.54889/
1.54910 1.53861/
1.53798/
1.53801 1.53994/
1.53806/
1.53803 1.54915/
1.54892/
1.54931 1.53152/
1.53033/
1.53211 Nz 0.583 0.623 0.950 1.016 -0.659 -0.492

As shown in Table 2, the n _x , n _y and n _z values of the retardation films of Examples 1 to 3 satisfy the relationship n _x > n _z > n _y , R _in (550), R _th (550 ), and Nz satisfy Equations (2) to (4), so that it has a retardation value very suitable for use as a retardation film of a display device.

On the other hand, the n _x , n _y and n _z values of the retardation films of Comparative Examples 1 to 3 do not satisfy the n _x > n _z > n _y relationship, R _in (550), R _th (550), and/or It was confirmed that Nz is not suitable for use as a retardation film of a display device because it does not satisfy Equations (2) to (4).

Claims (16)

Including an acrylic resin, a styrenic resin and a 2-hydroxyphenyl-s-triazine-based compound,
The following formula (1) is satisfied,
The weight ratio of the styrene-based resin and the 2-hydroxyphenyl-s-triazine-based compound is 100: 30 to 120 retardation film:
Equation (1): n _x > n _z > n _y
In the above formula (1),
n _x is the refractive index in the slow axis direction of the retardation film surface,
n _y is the refractive index in the fast axis direction of the retardation film surface,
n _z is the refractive index of the thickness direction of the retardation film.
delete According to claim 1,
The retardation film satisfies the following formulas (2) and (3):
Equation (2): 40 nm ≤ R _in (550) ≤ 400 nm
In Equation (2), R _in (550) is the plane direction retardation value of the film measured at a wavelength of 550 nm,
Equation (3): 0 nm ≤ R _th (550) ≤ 200 nm
In Equation (3), R _th (550) is the thickness direction retardation value of the film measured at a wavelength of 550 nm.
According to claim 3,
The retardation film satisfies the following formula (4):
Equation (4): 0 ≤ Nz < 1
In the above formula (4),
Nz is (n _x -n _z )/(n _x -n _y );
Descriptions of n _x , n _y and n _z are as defined in claim 1.
According to claim 1,
Retardation film comprising at least one selected from the group consisting of the acrylic resin, polymethyl methacrylate resin, polymethyl acrylate resin, polyethyl methacrylate resin, and polyethyl acrylate resin.
According to claim 1,
The styrene-based resin is a styrene-acrylonitrile copolymer resin, a styrene-maleic anhydride copolymer, an α-methylstyrene-acrylonitrile copolymer, an N-phenyl maleimide-α-methylstyrene-acrylonitrile copolymer, A retardation film comprising at least one selected from the group consisting of N-phenyl maleimide-styrene-acrylonitrile copolymer and N-phenyl maleimide-α-methylstyrene-acrylonitrile.
According to claim 1,
The weight ratio of the acrylic resin and the styrene-based resin is 2:8 to 9:1 retardation film.
According to claim 1,
The content of the styrene monomer in the total amount of the styrene-based resin is 50% by weight or more of the retardation film.
According to claim 1,
The 2-hydroxyphenyl-s-triazine-based compound includes one hydroxyphenyl having an alkoxy group substituted, retardation film.
According to claim 1,
The 2-hydroxyphenyl-s-triazine-based compound is a retardation film comprising a compound represented by Formula 1 below:
[Formula 1]

In Formula 1,
Ar ₁ and Ar ₂ are each independently an aryl having 6 to 60 carbon atoms;
R is an alkyl having 1 to 60 carbon atoms.
According to claim 1,
The retardation film is a retardation film having a thickness of 10 to 100 μm.
According to claim 1,
The retardation film has a glass transition temperature (Tg) of 100 to 150 ℃ retardation film.
According to claim 1,
The retardation film is a biaxially stretched film.
According to claim 13,
The retardation film is a retardation film in which the ratio of a stretching ratio in one direction and a stretching ratio in a direction perpendicular to the one direction is 1:1 to 3
A polarizing plate comprising the retardation film according to claim 1 .
A display device comprising the retardation film according to claim 1 .