WO2020138878A1 - Polarizing plate and optical display device including same - Google Patents

Abstract

Provided are a polarizing plate and an optical display device including same, the polarizing plate comprising a polarizing film, and a first phase difference layer and a second phase difference layer sequentially stacked on the lower surface of the polarizing film, wherein the first phase difference layer is a positive C phase difference layer having positive wavelength dispersability, the second phase difference layer is a positive A phase difference layer, and a stack including the first phase difference layer and the second phase difference layer satisfies formula 1.

Description

Polarizing plate and optical display device including same

The present invention relates to a polarizing plate and an optical display device including the same. More specifically, the present invention can significantly lower the difference in color value and the difference in visibility between the left and right sides of the screen when applied to an in-plane switching (IPS) liquid crystal display device, and can maintain a bluish color at an azimuth angle across the screen. The present invention relates to a polarizing plate having excellent color uniformity, excellent adhesion to a polarizer, or to secure excellent adhesion, and an optical display device including the same.

A liquid crystal display device is a device that expresses an image using optical anisotropy of liquid crystal. Of the liquid crystal display devices, the IPS liquid crystal display device may improve viewing angles of 170° or more by driving liquid crystal molecules in a horizontal direction with respect to the substrate.

In the IPS liquid crystal display, when viewed from the front, the light absorption axes of the upper polarizing plate and the lower polarizing plate are orthogonal to each other based on the liquid crystal panel. However, when viewed from the diagonal direction, the optical absorption axis of the upper polarizing plate and the lower polarizing plate exceeds 90°, and orthogonality between the optical absorption axes is broken. Due to this, in the IPS liquid crystal display device, light leakage is inevitably generated in the diagonal direction. To compensate for this, it is possible to reduce the light leakage in the diagonal direction by minimizing the light leakage in the black state by using an optical compensation film, but it is impossible to completely remove the light leakage. At this time, the light leaking from the light leakage causes a difference in bluish color and yellow color between the left and right sides of the screen due to the tilted pre-tilt angle of the IPS liquid crystal. Accordingly, there is a need for a method capable of increasing color uniformity at all azimuths by maintaining a bluish color at all azimuths between the left and right sides of the screen.

Background art of the present invention is disclosed in Japanese Patent Laid-Open No. 2009-271490 and the like.

An object of the present invention is to provide a polarizing plate capable of remarkably lowering a difference in color value and difference in visibility between the left and right sides of a screen when applied to an IPS liquid crystal display.

Another object of the present invention is to provide a polarizing plate capable of maintaining a bluish color at all azimuth angles when applied to an IPS liquid crystal display device.

Another object of the present invention is to provide a polarizing plate that is excellent in adhesion between the polarizing film and the first phase difference layer or can easily improve adhesion.

One aspect of the present invention is a polarizing plate.

In one embodiment, the polarizing plate includes a polarizing film and a first phase difference layer and a second phase difference layer sequentially stacked on a lower surface of the polarizing film, wherein the first phase difference layer is a positive C phase difference layer of constant wavelength dispersion, and the The second phase difference layer is a positive A phase difference layer, and the laminate including the first phase difference layer and the second phase difference layer satisfies Equation 1 below:

[Equation 1]

About 1.0 ≤ ｜1-(Rth/Re)｜ ≤ About 1.4

(Equation 1 above,

Rth is a phase difference (unit: nm) in the thickness direction at a wavelength of about 550 nm of the stack including the first phase difference layer and the second phase difference layer,

Re is an in-plane retardation (unit: nm) at a wavelength of about 550 nm of the stack including the first phase difference layer and the second phase difference layer.

2. In the above specific example, the second phase difference layer may be flat wavelength dispersion or reverse wavelength dispersion.

3. In the above 1-2 embodiments, the second phase difference layer may satisfy Equation 2 and Equation 3 below.

[Equation 2]

About 0.95 ≤ Re(450)/Re(550) ≤ about 1.05

[Equation 3]

About 0.95 ≤ Re(650)/Re(550) ≤ about 1.05

(In the above equation 2, equation 3,

Re(450), Re(550), and Re(650) are in-plane retardation at wavelengths of about 450nm, 550nm, and 650nm of the second phase difference layer, respectively.

4. In the above 1-3 embodiments, the second phase difference layer may satisfy Equation 4 and Equation 5 below:

[Equation 4]

About 0.8 ≤ Re(450)/Re(550) ≤ about 1.0

[Equation 5]

About 1.0 ≤ Re(650)/Re(550) ≤ about 1.1

(Equations 4 and 5 above,

Re(450), Re(550), and Re(650) are in-plane retardation at wavelengths of about 450nm, 550nm, and 650nm of the second phase difference layer, respectively.

5. In the above 1-4 embodiment, the second phase difference layer may have an in-plane retardation (Re) of about 100 nm to about 170 nm at a wavelength of about 550 nm.

6. In the above 1-5 embodiment, the second phase difference layer may have a degree of biaxiality (NZ) of about 0.8 to about 1.4 at a wavelength of about 550 nm.

7. In the above 1-6 embodiment, when the absorption axis of the polarizing film is about 0°, the angle formed by the slow axis of the second phase difference layer with the absorption axis of the polarizing film is about -5°. To about +5°.

8. In the seventh embodiment, the angle formed between the absorption axis of the polarizing film and the slow axis of the second phase difference layer may be about 0°.

9. In the above 1-8 embodiment, the first phase difference layer may satisfy the following Equation 6 and Equation 7:

[Equation 6]

About 1.0 <Rth(450)/Rth(550) <about 1.1

[Equation 7]

About 0.9 <Rth(650)/Rth(550) <about 1.0

(Equations 6 and 7 above,

Rth (450), Rth (550), Rth (650) is the first phase difference wavelength of about 450nm, 550nm, 650nm in the thickness direction phase difference, respectively).

10. In the embodiment 1-9, the first phase difference layer has a thickness direction retardation (Rth) of about -70 nm to about -130 nm at a wavelength of about 450 nm, and a thickness direction retardation (Rth) of about -60 nm to a wavelength of about 550 nm. A thickness direction retardation (Rth) at about -120 nm and a wavelength of about 650 nm may be about -50 nm to about -110 nm.

11. In the above 1-10 embodiment, the first phase difference layer may be a coating layer formed of a non-liquid crystal polymer.

12. In the above 11 embodiment, the first phase difference layer may be a coating layer comprising at least one of a cellulose ester or a polymer thereof, an aromatic polymer.

13. In the above 1-12 embodiment, the first phase difference layer may be directly formed on the second phase difference layer.

14. In the above 1-13 embodiment, at least one of a primer layer and a buffer layer may be further formed between the first phase difference layer and the second phase difference layer.

15. In the above 1-14 embodiment, the laminate including the first phase difference layer and the second phase difference layer may have a degree of biaxiality (NZ) of about 0 to about 0.5 at a wavelength of about 550 nm.

16. In the embodiment 1-15, the laminate including the first phase difference layer and the second phase difference layer may have an in-plane phase difference (Re) of about 100 nm to about 150 nm at a wavelength of about 550 nm.

17. In the embodiment 1-16, the laminate including the first phase difference layer and the second phase difference layer may have a thickness direction retardation (Rth) of about -80 nm to about 0 nm at a wavelength of about 550 nm.

18. In the 1-17 embodiment, a protective layer may be further laminated on the upper surface of the polarizing film.

19. In the above 1-18 embodiment, the polarizing plate may be used in an IPS liquid crystal display device.

The optical display device of the present invention includes the polarizing plate of the present invention.

The present invention provides a polarizing plate capable of significantly lowering a difference in color value and difference in visibility between the left and right sides of a screen when applied to an IPS liquid crystal display device.

The present invention provides a polarizing plate capable of maintaining a bluish color at all azimuth angles when applied to an IPS liquid crystal display device.

The present invention provides a polarizing plate that is excellent in adhesion between the polarizing film and the first phase difference layer or can easily improve adhesion.

1 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.

Figure 2 shows the color coordinate (x, y) values according to the polarization plate of Example 1 according to the azimuth angle 30 °, 45 °, 60 °, 120 °, 135 °, 150 ° at a polar angle of 60 °.

Figure 3 shows the color coordinate (x, y) values according to the polarization plate of Comparative Example 2 at a polar angle of 60 ° azimuth 30 °, 45 °, 60 °, 120 °, 135 °, 150 °.

Figure 4 shows the color coordinate (x, y) value according to the polarization plate of Example 2 according to the azimuth angle 30 °, 45 °, 60 °, 120 °, 135 °, 150 ° at a polar angle of 60 °.

With reference to the accompanying drawings, it will be described in detail so that those skilled in the art to which the present invention pertains can be easily implemented by the following examples. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. In order to clearly describe the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar elements throughout the specification. The length and size of each component in the drawings are for describing the present invention, and the present invention is not limited to the length and size of each component described in the drawings.

In this specification, "upper" and "lower" are defined on the basis of drawings, and "upper" can be changed to "lower" and "lower" to "upper" according to a city perspective, and "on" or What is referred to as "on" may include not only directly above, but also through other structures in the middle. On the other hand, what is referred to as “directly on”, “directly above” or “directly forming” or “directly forming” means that there is no intervening structure.

In this specification, "in-plane retardation (Re)" is represented by Equation A below, "thickness phase retardation (Rth)" is represented by Equation B below, and "degree of biaxiality (NZ)" is represented by Equation C below:

[Equation A]

Re = (nx-ny) x d

[Equation B]

Rth = ((nx + ny)/2-nz) x d

[Equation C]

NZ = (nx-nz)/(nx-ny)

(In the above formulas A to C, nx, ny, and nz are the refractive indexes of the slow axis direction, the fast axis direction, and the thickness direction of the optical element, respectively, at the measurement wavelength, and d is the thickness of the optical element (unit: nm)).

The “measurement wavelength” means a wavelength of about 450 nm, 550 nm, or 650 nm, and the “optical device” is a laminate including a first phase difference layer, a second phase difference layer, a first phase difference layer and a second phase difference layer, or Refers to a laminate of the first phase difference layer and the second phase difference layer.

In the present specification, the numerical range "X to Y" means X or more and Y or less (X≤ and ≤Y).

The inventor of the present invention is a polarizing plate in which a positive C phase difference layer as a first phase difference layer and a positive A phase difference layer as a second phase difference layer are sequentially stacked on a polarizing film and a lower surface of the polarizing film, and the wavelength dispersibility of the positive C phase difference layer By adjusting the, and the value represented by the following formula 1 of the laminate comprising the positive C retardation layer and the positive A retardation layer to a specific range of about 1.0 to about 1.4 by the second phase difference layer to the IPS liquid crystal display device It was confirmed that when applied, the difference in the color values between the left and right sides of the screen was significantly lowered, thereby significantly lowering the difference in visual field between the left and right sides, and that it was possible to maintain a bluish color at all azimuth angles when applied to the IPS liquid crystal display.

In the polarizing plate of the present invention, the positive C retardation layer, which is the first phase difference layer, has a constant wavelength dispersibility so that the phase difference expression is high in the short wavelength region, thereby further mixing the bluish color and simultaneously mixing the first phase difference layer and the second phase difference layer. The color mixing effect described above was increased by setting the value of Equation 1 below to be about 1.0 or more and about 1.4 or less in the specific range of the present invention. As a result, when the polarizing plate of the present invention is applied to an IPS liquid crystal display device, a blue color comes out from all azimuth angles of polar angles of 60° and azimuth angles of 30°, 45°, 60°, 120°, 135°, and 150°. This can improve color uniformity at all azimuth angles. For example, even if the polarizing plate of the present invention has the same second phase difference layer, the polarizing plate does not have the first phase difference layer of the present invention or a polarizing plate that does not satisfy Equation 1 below is applied to the IPS liquid crystal display device at a polar angle of 60°. Therefore, the maximum value of the distance between the color color coordinates (x, y) at each azimuth of 30°, 45°, 60°, 120°, 135°, and 150° can be significantly lowered.

Hereinafter, a polarizing plate of an embodiment of the present invention will be described.

Referring to FIG. 1, the polarizing plate includes the polarizing film 110, the first phase difference layer 120 and the second phase difference layer 130 and the polarization film 110 sequentially stacked on the lower surface of the polarization film 110. It includes a protective film 140 laminated on the surface.

The first phase difference layer 120 is a positive C phase difference layer having constant wavelength dispersion. The second phase difference layer 130 is a positive A phase difference layer. The laminate including the first phase difference layer 120 and the second phase difference layer 130 satisfies Equation 1 below:

[Equation 1]

About 1.0 ≤ ｜1-(Rth/Re)｜ ≤ About 1.4

(Equation 1 above,

Rth is a phase difference (unit: nm) in the thickness direction at a wavelength of about 550 nm of the stack including the first phase difference layer and the second phase difference layer,

Re is an in-plane retardation (unit: nm) at a wavelength of about 550 nm of the stack including the first phase difference layer and the second phase difference layer.

When the first phase difference layer 120 is a positive C phase difference layer, and the second phase difference layer 130 is a positive A phase difference layer, the first phase difference layer 120 has a constant wavelength dispersion and the first phase difference layer 120 When the laminate including the second phase difference layer 130 satisfies Equation 1, the phase difference expression according to the wavelength of the positive C phase difference layer may be controlled to maintain a bluish color at all azimuths with a diagonal compensation function. Therefore, the polarizing plate can significantly lower the difference in visual field between the left and right sides by significantly lowering the difference in color values between the left and right sides of the screen when applied to the IPS liquid crystal display.

The value of Equation 1 is such that when the positive C retardation layer of constant wavelength dispersion is stacked on the lower surface of the polarizing film to increase the color mixing of the bluish color in the short wavelength region, the color mixing effect described above is properly implemented or the color mixing effect is obtained. It is designed to enhance it. When the value of Equation 1 is satisfied, when applied to the IPS liquid crystal display device, a bluish color can be maintained at all azimuth angles. The value of Equation 1 may preferably be from about 1.1 to about 1.4, more preferably from about 1.1 to about 1.3.

When the stacking order of the first phase difference layer and the second phase difference layer is changed in the polarizing plate, that is, the positive A retardation layer as the second phase difference layer and the positive C retardation layer as the first phase difference layer are sequentially stacked on the lower surface of the polarizing film. The effect of maintaining the bluish color of the present invention is weak.

Second phase

The second phase difference layer 130 is a positive A phase difference layer with nx>ny≒nz. The positive A phase difference layer is a phase difference layer in which the refractive index ny in the y-axis direction and the refractive index nz in the z-axis direction are the same, and the refractive index nx in the x-axis direction is greater than ny and nz.

The second phase difference layer 130 may adjust the wavelength dispersion property of the second phase difference layer to improve the color sense and wavelength dispersion of the polarizer. The second phase difference layer 130 may be flat wavelength dispersion, forward wavelength dispersion, or reverse wavelength dispersion. Preferably, the second phase difference layer 130 can be easily manufactured or supplied to the second phase difference layer 130 by becoming flat wavelength dispersibility. The “flat wavelength dispersibility” means that the difference between the in-plane retardation at a wavelength of about 550 nm and the in-plane retardation at a wavelength of about 450 nm of the second phase difference layer is about 1 nm or less, for example, about 0 nm to about 1 nm, in-plane at a wavelength of about 650 nm. It means that the difference between the phase difference and the in-plane phase difference at a wavelength of about 550 nm is about 1 nm or less, for example, about 0 nm to about 1 nm.

For example, when the second phase difference layer 130 has flat wavelength dispersion or constant wavelength dispersion, the second phase difference layer 130 may satisfy Equation 2 and Equation 3:

[Equation 2]

About 0.95 ≤ Re(450)/Re(550) ≤ about 1.05

[Equation 3]

About 0.95 ≤ Re(650)/Re(550) ≤ about 1.05

(In the above equation 2, equation 3,

Re(450), Re(550), and Re(650) are in-plane retardation (unit: nm) at wavelengths of about 450 nm, 550 nm, and 650 nm of the second phase difference layer (positive A retardation layer).

In one embodiment, Re(450) ≥ Re(550) ≥ Re(650).

In one embodiment, Re(450) ≒ Re(550) ≒ Re(650).

In one embodiment, Re(450)> Re(550)> Re(650).

For example, Re(450)/Re(550) may be about 0.96 to about 1.04, about 0.97 to about 1.03, about 0.98 to about 1.03, about 0.99 to about 1.02, about 0.99 to about 1.01. For example, Re(650)/Re(550) is about 0.96 to about 1.04, about 0.97 to about 1.03, about 0.98 to about 1.03, about 0.99 to about 1.02, about 0.99 to about 1.01, about 0.99 to about 1.00 Can be. In the above range, the effect of the present invention can come out well.

For example, when the second phase difference layer 130 is inverse wavelength dispersion, the second phase difference layer 130 may satisfy Equation 4 and Equation 5 below:

[Equation 4]

About 0.8 ≤ Re(450)/Re(550) ≤ about 1.0

[Equation 5]

About 1.0 ≤ Re(650)/Re(550) ≤ about 1.1

(Equations 4 and 5 above,

Re(450), Re(550), and Re(650) are in-plane retardation at wavelengths of about 450nm, 550nm, and 650nm of the second phase difference layer (positive A retardation layer).

In one embodiment, Re(450) <Re(550) <Re(650). For example, Re(450)/Re(550) may be about 0.85 or more and less than about 1.0. For example, Re(650)/Re(550) may be greater than about 1.0 and less than or equal to about 1.05. In the above range, the effect of the present invention can come out well.

The second phase difference layer 130 has an in-plane retardation (Re) at a wavelength of 550 nm of about 100 nm to about 170 nm, for example, about 100 nm to about 155 nm, about 100 nm to about 140 nm, about 120 nm to about 155 nm, about 120 nm to about 140 nm. Can be. In the above range, it is possible to provide an effect of improving diagonal light leakage and reducing a difference in visual sensation between left and right colors along with a positive C phase difference layer that is a first phase difference layer.

The second phase difference layer 130 may have a thickness direction retardation (Rth) of about 30 nm to about 100 nm, for example, about 50 nm to about 9 5 nm, and about 50 nm to about 90 nm at a wavelength of about 550 nm. In the above range, it is possible to provide an effect of improving diagonal light leakage and reducing a difference in visual sensation between left and right colors along with a positive C phase difference layer that is a first phase difference layer.

The second phase difference layer 130 may have a degree of biaxiality (NZ) of about 0.8 to about 1.4, for example, about 0.9 to about 1.4 at a wavelength of about 550 nm. In the above range, it is possible to provide an effect of improving diagonal light leakage and reducing a difference in visual sensation between left and right colors along with a positive C phase difference layer that is a first phase difference layer.

The second phase difference layer 130 may be a polymer film. When the second phase difference layer becomes a polymer film, the formation of the first phase difference layer described below can be facilitated. The first phase difference layer may be formed by coating on one surface of the second phase difference layer.

The polymer film is a cellulose-based resin, a fluorene-based resin, a polyester crab, including a polycarbonate-based resin, a cyclic olefin polymer (COP) resin, a modified polycarbonate-based resin, an isosorbide-based resin, a triacetylcellulose-based resin, and the like. It may be a polymer film formed of one or more of the resin. Preferably, the second phase difference layer may be a film formed of a cyclic olefin polymer resin or the like.

The second phase difference layer 130 may be manufactured by uniaxially or biaxially stretching or obliquely stretching the polymer film in an unstretched state. The stretching method may be dry stretching or wet stretching, and detailed methods are known to those skilled in the art. When manufacturing the second phase difference layer, a positive A retardation layer can be realized by adjusting the stretching ratio, stretching temperature, stretching time, and the like.

In one embodiment, the second phase difference layer may be an MD uniaxially stretched film.

In another embodiment, the second phase difference layer may be a TD uniaxially stretched film.

The second phase difference layer 130, when the absorption axis of the polarization film 110 is about 0°, the angle formed by the slow axis of the second phase difference layer with the absorption axis of the polarization film 110 is approximately −5. ° to about +5°, preferably about -3° to about +3°, more preferably about 0°. In the above range, there may be an effect of improving diagonal light leakage and reducing a difference in left and right colors. When displaying the angle, "+" means clockwise around the reference, and "-" means counterclockwise around the reference.

The second phase difference layer 130 may have a thickness of about 20 μm to about 80 μm, preferably about 30 μm to about 60 μm, more preferably about 35 μm to about 50 μm. In the above range, it can be used for a polarizing plate.

Although not illustrated in FIG. 1, an adhesive layer, an adhesive layer, or a point adhesive layer is additionally stacked on the lower surface of the second phase difference layer 130, so that the polarizing plate can be stacked on the optical display device.

First phase difference

The first phase difference layer 120 has a constant wavelength dispersion. When the first phase difference layer becomes a constant wavelength dispersion, when applied to an IPS liquid crystal display, the phase difference in the short wavelength region is increased to further express the bluish color in the short wavelength region to increase color mixing, thereby reducing color difference between the left and right sides. You can keep the bluish color at all azimuth angles. The "constant wavelength dispersion" means that as the wavelength increases, the absolute value of the phase difference Rth value in the thickness direction of the first phase difference layer decreases.

In one embodiment, the constant wavelength dispersion may mean that the first phase difference layer satisfies Equations 6 and 7 below:

[Equation 6]

About 1.0 <Rth(450)/Rth(550) <about 1.1

[Equation 7]

About 0.9 <Rth(650)/Rth(550) <about 1.0

(Equations 6 and 7 above,

Rth (450), Rth (550), Rth (650) is the first phase difference layer (positive C phase difference layer) at a wavelength of about 450nm, 550nm, 650nm, respectively, the thickness direction phase difference (unit:nm)).

In one embodiment, the first phase difference layer may have a negative value of Rth 450, Rth 550, and Rth 650, respectively.

By satisfying the expressions 6 and 7, the polarizing plate can increase the color mixing to reduce the color difference between the left and right sides and maintain a bluish color at all azimuth angles. Preferably, Rth(450)/Rth(550) may be from about 1.02 to about 1.07, and Rth(650)/Rth(550) may be from about 0.95 to about 0.99.

In one embodiment, the first phase difference layer may have a thickness direction retardation (Rth) of about -70 nm to about -130 nm, preferably about -80 nm to about -110 nm at a wavelength of about 450 nm. Within the above range, Equations 6 and 7 can be easily satisfied, and there may be an effect of improving diagonal light leakage and reducing the difference in visual sensation between left and right colors.

The first phase difference layer may have a thickness direction retardation (Rth) of about -60 nm to about -120 nm at a wavelength of about 550 nm, preferably about -70 nm to about -100 nm. Within the above range, Equations 6 and 7 can be easily satisfied, and there may be an effect of improving diagonal light leakage and reducing the difference in visual sensation between left and right colors.

The first phase difference layer may have a thickness direction retardation (Rth) of about -50 nm to about -110 nm, preferably about -60 nm to about -90 nm at a wavelength of about 650 nm. Within the above range, Equations 6 and 7 can be easily satisfied, and there may be an effect of improving diagonal light leakage and reducing the difference in visual sensation between left and right colors.

The first phase difference layer 120 is a positive C phase difference layer with nz>nx≒ny. The positive C phase difference layer is a phase difference layer in which the refractive index nx in the x-axis direction and the refractive index ny in the y-axis direction are the same, and the refractive index nz in the z-axis direction is larger than nx and ny.

The first phase difference layer 120 may have an in-plane phase difference (Re) of about 0 nm to about 10 nm, for example, about 0 nm to about 6 nm, about 0 nm to about 3 nm, about 0 nm to about 2 nm at a wavelength of about 550 nm. In the above range, it is possible to increase the anti-reflection effect together with the second phase difference layer.

The first phase difference layer 120 may be directly formed on the second phase difference layer without an adhesive layer, an adhesive layer, or a point adhesive layer. A polarizing plate in which an adhesive layer, an adhesive layer, or a point adhesive layer is formed between the first phase difference layer and the second phase difference layer is difficult to use in a process requiring high pressure in manufacturing a polarizing plate, for example, it is difficult to use in the stretching lamination process and additional treatment is applied when applied to the above process Since it requires, fairness and economics may be deteriorated.

The first phase difference layer 120 may be a coating layer formed of a non-liquid crystal polymer. Therefore, an alignment layer is not present on one or both surfaces of the first phase difference layer. Also, the first phase difference layer is an unstretched layer.

The first phase difference layer 120 may be formed by coating and drying and/or curing the composition for the first phase difference layer on one surface of the second phase difference layer. Through this, the thinning effect of the laminate including the first phase difference layer and the second phase difference layer can be obtained. In addition, since the first phase difference layer is formed of a non-liquid crystal polymer, when the first phase difference layer is formed of a liquid crystal, adhesion to a polarizing film is increased or it is easy to improve adhesion to a polarizing film.

The first phase difference layer 120 may be formed of a composition for a first phase difference layer forming a positive C phase difference layer.

The composition for the first phase difference layer includes at least one of a cellulose ester, a polymer thereof, and an aromatic polymer. Among the several materials capable of forming the first phase difference layer, the inventor of the present invention was looking for a cellulose ester or a polymer thereof, or an aromatic polymer while searching for a material capable of producing the effect of Formula 1 when directly coated on the second phase difference layer. I found it. Preferably, the first phase difference layer may be formed of a cellulose ester or a polymer thereof. When the first phase difference layer is made of liquid crystal by satisfying Equation 1 above, it is possible to suppress the occurrence of mura due to heat on the side of contrast and to prevent cracks or cracks caused by bending, so that bending reliability can be excellent.

In particular, the cellulose ester or a polymer or an aromatic polymer thereof may improve adhesion between the first phase difference layer and the second phase difference layer, and lower the interfacial reflectance between the layers to increase the light transmittance of the polarizing plate. In one embodiment, the polarizing plate may have a light transmittance of 41% or more, for example, 42% to 46%.

Cellulose ester refers to the condensation reaction product from the reaction of hydroxyl groups on cellulose with carboxylic acid groups of carboxylic acids. Cellulose esters can be substituted position-wise or randomly. Position selectivity can be measured by determining the relative degree of substitution in C6, C3, C2 on cellulose esters by carbon 13 NMR. Cellulose esters can be prepared by conventional methods by contacting the cellulosic solution with one or more C1 to C20 acylating agents for a contact time sufficient to provide a cellulose ester with the desired degree of substitution and degree of polymerization. Preferred acylating agents are one or more C1 to C20 straight or branched chain alkyl or aryl carboxylic anhydrides, carboxylic acid halides, diketones, or acetoacetic acid esters. Examples of anhydrides of carboxylic acids include acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, hexanoic anhydride, 2-ethylhexanoic anhydride, nonanoic anhydride, lauric anhydride, palmitic anhydride, Stearic anhydride, benzoic anhydride, substituted benzoic anhydride, phthalic anhydride, isophthalic anhydride. Examples of carboxylic acid halides include acetyl, propionyl, butyryl, hexanoyl, 2-ethylhexanoyl, lauroyl, palmitoyl, benzoyl, substituted benzoyl, and stearoyl chloride. Examples of acetoacetic acid esters may include methyl acetoacetate, ethyl acetoacetate, propyl acetoacetate, butyl acetoacetate, tertiary butyl acetoacetate. Most preferred acylating agents are C2 to C9 straight or branched chain alkyl carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, 2-ethylhexanoic anhydride, nonanoic anhydride, stearic anhydride, and the like.

Preferred examples of cellulose esters may include, but are not limited to, one or more of cellulose acetate (CA), cellulose acetate propionate (CAP), cellulose acetate butyrate (CAB).

The composition for the first phase difference layer may further include an additive having an aromatic fused ring in addition to the cellulose ester or a polymer thereof or an aromatic polymer. The additive may serve to control the Rth expression rate and wavelength dispersion of the first phase difference layer. The aromatic fused ring may include naphthalene, anthracene, phenanthrene, pyrene, Formula 1 or Formula 2 below. Examples of the additive may include, but are not limited to, 2-naphthyl benzoate, 2,6-naphthalene dicarboxylic acid diester of Formula 3, naphthalene, abietic acid ester of Formula 4 below, and the like:

<Formula 1>

<Formula 2>

<Formula 3>

(In Formula 3, R is C1 to C20 alkyl or C6 to C20 aryl, n is an integer from 0 to 6)

<Formula 4>

(In the above formula 4, R is C1 to C20 alkyl or C6 to C20 aryl)

At least one of the cellulose ester or its polymer and aromatic polymer has a phase difference in the manufacturing process when the first phase difference layer is manufactured by linearly changing the thickness direction retardation (Rth) at a wavelength of 550 nm according to the thickness of the first phase difference layer. For high reliability.

The first phase difference layer may be formed of a composition for a first phase difference layer comprising at least one of the aforementioned cellulose ester or a polymer or aromatic polymer thereof.

The composition for the first phase difference layer may include a solvent capable of improving the coatability of the composition in addition to the aforementioned cellulose ester or a polymer or aromatic polymer thereof. The solvent may include, but is not limited to, organic solvents commonly used by those skilled in the art.

The solid content in the composition for the first phase difference layer may be included in an amount of 0.1% to 20% by weight, preferably 5% to 20% by weight, and 9% to 15% by weight. In this range, the interface between the first phase difference layer and the second phase difference layer may be uniform.

The composition for the first phase difference layer may further include additives such as plasticizers, stabilizers, UV absorbers, block inhibitors, slip agents, lubricants, dyes, pigments, and delay improvers.

The first phase difference layer 120 may have a thickness of 1 μm to 15 μm, and preferably 3 μm to 7 μm. In the above range, there may be an effect of improving the diagonal light leakage and reducing the difference in visual sensation between left and right colors.

A laminate comprising a first phase difference layer and a second phase difference layer

The laminate including the first phase difference layer and the second phase difference layer can satisfy the above Equation 1 to maintain a bluish color at all azimuth angles when applied to an IPS liquid crystal display, and the difference in color values between the left and right sides of the screen By significantly lowering, the difference in visual acuity between the left and right sides can be significantly lowered.

In one embodiment, the laminate including the first phase difference layer and the second phase difference layer may be a laminate of the first phase difference layer and the second phase difference layer. That is, the first phase difference layer is a case where the second phase difference layer is directly laminated without an adhesive layer and an adhesive layer.

In another embodiment, the laminate including the first phase difference layer and the second phase difference layer may be a laminate of the first phase difference layer, the adhesion layer, and the second phase difference layer. Even if the adhesive layer is included, a laminate including the first phase difference layer and the second phase difference layer may satisfy the value of Equation 1 above.

Preferably, the laminate including the first phase difference layer and the second phase difference layer may be a laminate of the first phase difference layer and the second phase difference layer.

In a laminate comprising a first phase difference layer and a second phase difference layer, the value of Equation 1 may be implemented by adjusting the wavelength dispersion and phase difference of the first phase difference layer resin and the wavelength dispersion and phase difference combination of the second phase difference layer resin. have.

The laminate including the first phase difference layer and the second phase difference layer may have an in-plane retardation (Re) of about 100 nm to about 150 nm, preferably about 100 nm to about 140 nm, about 120 nm to about 140 nm at a wavelength of about 550 nm. In the above range, there may be an effect of improving diagonal light leakage and reducing a difference in visual sensation between left and right colors.

The stack including the first phase difference layer and the second phase difference layer has a thickness direction retardation (Rth) of about -80 nm to about 0 nm at a wavelength of about 550 nm, preferably about -80 nm to about -10 nm, about -50 nm to about- It can be 10nm. In the above range, there may be an effect of improving diagonal light leakage and reducing a difference in visual sensation between left and right colors.

The stacked body including the first phase difference layer and the second phase difference layer may have a degree of biaxiality (NZ) of about 0 to about 0.5, preferably about 0.1 to about 0.4 at a wavelength of about 550 nm. In the above range, there may be an effect of improving diagonal light leakage and reducing a difference in visual sensation between left and right colors.

The laminate including the first phase difference layer and the second phase difference layer may have a thickness of about 30 μm to about 70 μm, preferably about 40 μm to about 60 μm. In the above range, the thickness of the protective film laminated on the upper surface of the polarizing film may be used as a polarizing plate even if an additional protective layer is not laminated on the lower surface of the polarizing film.

Polarizing film

The polarizing film 110 may include a polyvinyl alcohol-based polarizer prepared by uniaxially stretching a polyvinyl alcohol-based film, or a polyene-based polarizer produced by dehydrating a polyvinyl alcohol-based film. The polarizing film may have a thickness of about 5 μm to about 40 μm, preferably about 5 μm to about 30 μm. In the above range, it can be used for a polarizing plate.

Protective layer

The protective layer 150 is stacked on the upper surface of the polarizing film 110 to protect the polarizing film 110.

The protective layer 150 may include one or more of an optically transparent, protective film or protective coating layer. The protective film includes a cellulose ester-based resin including triacetyl cellulose (TAC), a cyclic polyolefin-based resin including amorphous cyclic polyolefin (COP), a polycarbonate-based resin, polyethylene terephthalate (PET), and the like. Poly(meth)acrylate-based resins including polyester-based resins, polyethersulfone-based resins, polysulfone-based resins, polyamide-based resins, polyimide-based resins, acyclic-polyolefin-based resins, and polymethylmethacrylate resins A film formed of at least one of a resin, a polyvinyl alcohol-based resin, a polyvinyl chloride-based resin, and a polyvinylidene chloride-based resin may be included, but is not limited thereto. Preferably, the protective film may include a cellulose ester-based resin film including triacetyl cellulose (TAC) or the like, or a film formed of a composition containing the same.

The protective coating layer may be formed of an active energy ray-curable resin composition comprising an active energy ray-curable compound and a polymerization initiator. The active energy ray-curable compound may include at least one of a cationically polymerizable curable compound, a radically polymerizable curable compound, a urethane resin, and a silicone resin.

The protective layer 150 may have an in-plane retardation (Re) of about 0 nm to about 10 nm, preferably about 0 nm to about 3 nm at a wavelength of about 550 nm. In the above range, there may be an effect of improving diagonal light leakage and reducing a difference in visual sensation between left and right colors.

The protective layer 150 may have a thickness of about 20 μm to 100 μm, preferably about 20 μm to 60 μm. In the above range, it can be used for a polarizing plate.

Preferably, as shown in FIG. 1, the protective layer 150 may be formed on the upper surface of the polarizing film 110 and the protective layer 150 may not be formed on the lower surface of the polarizing film 110.

Although not illustrated in FIG. 1, a functional coating layer may be additionally formed on the upper surface of the protective layer 150. The functional coating layer may include, but is not limited to, one or more of a primer layer, a hard coating layer, an anti-fingerprint layer, an anti-reflection layer, an anti-glare layer, a low reflection layer, and an ultra low reflection layer.

In addition, although the protective layer 150 is stacked on the upper surface of the polarizing film 110 in FIG. 1, the polarizing plate from which the protective layer 150 is removed, the protective layer 150 is removed, and the functional coating layer is polarized Polarizing plates formed directly on the film may also be included in the scope of the present invention.

In addition, although not shown in FIG. 1, a protective layer may be additionally stacked on the lower surface of the polarizing film 110. For example, a first protective layer is laminated on the upper surface of the polarizing film 110, a second protective layer on the lower surface of the polarizing film 110, a first phase difference layer that is a positive C phase difference layer, and a positive wavelength dispersibility, positive The second phase difference layer, which is the A phase difference layer, may be sequentially stacked.

Hereinafter, a polarizing plate according to another embodiment of the present invention will be described.

The polarizing plate of the present embodiment includes a polarizing film, and a first phase difference layer and a second phase difference layer sequentially stacked on a lower surface of the polarization film, and the first phase difference layer is a positive C phase difference layer having a constant wavelength dispersion and a second phase difference The layer is a positive A retardation layer, and the laminate including the first and second retardation layers satisfies Equation 1, and at least one of a primer layer and a buffer layer is provided between the first and second retardation layers. It is formed more. It is substantially the same as the polarizing plate according to an embodiment of the present invention, except that at least one of the primer layer and the buffer layer is further formed between the first phase difference layer and the second phase difference layer.

The buffer layer and the primer layer can increase reliability by preventing separation between the first and second phase difference layers by increasing the adhesion between the first and second phase difference layers.

The primer layer is formed on one surface of the second phase difference layer, that is, on the upper surface of the second phase difference layer, so as to increase the adhesion of the first phase difference layer when forming the first phase difference layer. The primer layer may be formed without particular limitation as long as it is a material that does not affect the implementation of the phase difference between the value of Formula 1 and the second phase difference layer. For example, the primer layer may be formed of a propylene, acrylic or polyester material, but is not limited thereto.

The primer layer may have a thickness of about 100 nm to about 1000 nm, preferably about 100 nm to about 500 nm. In the above range, the adhesion between the first phase difference layer and the second phase difference layer can be increased without affecting the thickness of the polarizing plate.

When the buffer layer is coated with a composition for forming a first phase difference layer on one surface of the second phase difference layer, that is, on the upper surface of the second phase difference layer, the solvent contained in the composition dissolves and/or erodes the second phase difference layer. It may be formed at the interface between the retardation layer and the first phase difference layer. Therefore, the second phase difference layer may be a solvent erosion layer.

The buffer layer may be formed by controlling the material of the second phase difference layer and the type of solvent included in the composition for forming the first phase difference layer.

For example, the second phase difference layer may have an in-plane retardation change amount according to the following Equation 8 of about 5 nm or more, for example, about 20 nm to about 200 nm, about 20 nm to about 150 nm:

[Equation 8]

In-plane phase difference change amount = ｜Re[0]-Re[1] ｜

(Equation 8 above,

Re[0] is the in-plane retardation (Re) (unit:nm) at a wavelength of about 550nm of the second phase difference layer specimen of MD x TD x thickness (3cm x 3cm x 50㎛)

Re[1] is added dropwise with 1 drop of methyl ethyl ketone to the sample of the second phase difference layer at about 25° C., and after standing for 1 hour, Re (unit: nm) at a wavelength of about 550 nm of the sample of the second phase difference layer).

The 1 drop may mean about 0.001ml to about 10ml, but is not limited thereto.

For example, the composition for forming the first phase difference layer is a ketone solvent such as methyl ethtone ketone (MEK), methyl isopropyl ketone (MIPK), acetone, propylene glycol methyl ether (PGME), methyl 3 as a solvent. Ether-based solvents such as secondary butyl ether (t-BME), and one or more solvents among propylene glycol methyl ether acetate (PGMEA) may be used, but are not limited thereto. The solvent may secure adhesion between the first phase difference layer and the second phase difference layer.

The buffer layer may have a thickness of about 10 μm or less, for example, greater than about 0 μm and about 10 μm or less. In the above range, the adhesion between the first phase difference layer and the second phase difference layer can be increased without affecting the thickness of the polarizing plate.

The buffer layer may be present in the solvent of about 1ppm to about 30,000ppm, preferably about 300ppm to about 10,000ppm. In the above range, when left at high temperature or high temperature and high humidity for a long time, deformation of the polarizing plate, the first phase difference layer, and the second phase difference layer due to solvent volatilization may be prevented, and adhesion may not be affected.

Hereinafter, the optical display device of the present invention will be described.

The optical display device of the present invention may include one or more of the polarizing plates of the present invention. In one embodiment, the optical display device may include a liquid crystal display device, preferably an IPS liquid crystal display device.

In one embodiment, the IPS liquid crystal display device may include an IPS liquid crystal panel, a polarizing plate of the present invention laminated on the light emitting surface of the IPS liquid crystal panel, and a polarizing plate laminated on the light incident surface of the IPS liquid crystal panel. The polarizing plate of the present invention may be stacked such that the first phase difference layer and the second phase difference layer are directed toward the liquid crystal panel. The polarizing plate laminated on the light incident surface includes a conventional polarizing plate known to those skilled in the art.

The IPS liquid crystal display device may include a light source, for example, a white LED light source, on the lower surface of the polarizing plate stacked on the light incident surface.

Hereinafter, the configuration and operation of the present invention through a preferred embodiment of the present invention will be described in more detail. However, the following examples are intended to help understanding of the present invention, and the scope of the present invention is not limited to the following examples.

Below, the phase difference was measured using Axoscan.

Example 1

The polyvinyl alcohol film was stretched 3 times at 60°C, adsorbed with iodine, and then stretched 2.5 times in a 40°C aqueous boric acid solution to prepare a polarizer (thickness: 12 μm).

A cyclic olefin polymer film (ZEON, thickness: 50 µm) was used as the second phase difference layer. The cyclic olefin polymer film is an MD uniaxially stretched film.

The composition for the first phase difference layer was prepared by uniformly mixing the VM (Eastman, cellulose acetate type) and the solvent MEK (methyl ethyl ketone) as the first phase difference layer.

The first phase difference layer (thickness: 5 µm) and the second phase difference layer were prepared by coating and curing the composition for the first phase difference layer on the upper surface of the second phase difference layer to a predetermined thickness.

A triacetylcellulose (TAC) film (KC2UAW, Konica Minolta Opto, Inc.) was attached to the upper surface of the polarizer. TAC film-polarizer-first phase difference layer (constant wavelength dispersibility positive C phase difference layer)-second phase difference layer (bonding the laminate of the prepared first phase difference layer and the second phase difference layer to the lower surface of the polarizer) A polarizing plate in which flat wavelength dispersibility positive A retardation layer) was sequentially stacked was prepared. At this time, the angle between the slow axis of the second phase difference layer and the absorption axis of the polarizer is 0°.

Example 2

In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that the in-plane retardation of the second phase difference layer was changed to high.

Example 3

In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that Rth increased while changing the phase difference of the second phase difference layer to the lower side by TD stretching.

Example 4

In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that the wavelength dispersion and the phase difference of the second phase difference layer were changed to higher.

Comparative Example 1

In Example 1, except that the polarizing plate stacking sequence was laminated with a TAC film-a polarizer-a first phase difference layer (flat wavelength dispersibility positive A retardation layer)-a second phase difference layer (constant wavelength dispersibility positive C retardation layer) A polarizing plate was manufactured in the same manner as in Example 1.

Comparative Example 2

In Example 1, a flat wavelength dispersibility first phase difference layer was prepared by using a flat wavelength dispersibility +C liquid crystal as the first phase difference layer. In the same manner as in Example 1, a TAC film-a polarizer-a first phase difference layer (flat wavelength dispersibility positive C retardation layer)-a second phase difference layer (flat wavelength dispersibility positive A retardation layer) was sequentially prepared. .

Comparative Example 3

In Example 1, a reverse wavelength dispersibility first phase difference layer was prepared by using a reverse wavelength dispersibility +C liquid crystal as the first phase difference layer. In the same manner as in Example 1, a polarizing plate in which a TAC film-a polarizer-a first phase difference layer (reverse wavelength dispersive positive C retardation layer)-a second phase difference layer (flat wavelength dispersibility positive A retardation layer) was sequentially stacked was prepared. .

Comparative Example 4

In Example 1, a constant wavelength dispersion first phase difference layer was prepared by using a coated non-liquid crystal type +C as the first phase difference layer. In the same manner as in Example 1, a polarizing plate in which a TAC film-a polarizer-a first phase difference layer (constant wavelength dispersive positive C retardation layer)-a second phase difference layer (flat wavelength dispersibility positive A retardation layer) was sequentially stacked was prepared. . The laminate of the first phase difference layer and the second phase difference layer has a value of Formula 1 of 0.9.

Comparative Example 5

In Example 1, a constant wavelength dispersion first phase difference layer was prepared by using a coated non-liquid crystal type +C as the first phase difference layer. In the same manner as in Example 1, a polarizing plate in which a TAC film-a polarizer-a first phase difference layer (constant wavelength dispersive positive C retardation layer)-a second phase difference layer (flat wavelength dispersibility positive A retardation layer) was sequentially stacked was prepared. . The laminate of the first phase difference layer and the second phase difference layer has a value of Equation 1 above of 1.5.

Table 1 shows the phase difference between the first phase difference layer, the second phase difference layer, and the first phase difference layer and the second phase difference layer used in Examples and Comparative Examples.

		Example				Comparative example
		One	2	3	4	One	2	3	4	5
First phase difference	Rth(450)	-95	-95	-95	-95	-	-90	-77	-74	-126
	Rth(550)	-90	-90	-90	-90	60	-90	-90	-50	-120
	Rth(650)	-86	-86	-86	-86	-	-90	-95	-48	-114
	Re(550)	0	0	0	0	120	0	0	0	0
	Wavelength dispersion	A regular wavelength	A regular wavelength	A regular wavelength	A regular wavelength	flat	flat	Reverse wavelength	A regular wavelength	A regular wavelength
	Phase difference	+C	+C	+C	+C	+A	+C	+C	+C	+C
Second phase	Re(450)	121	141	101	119	-	121	121	121	121
	Re(550)	120	140	100	140	0	120	120	120	120
	Re(650)	119	139	99	147	-	119	119	119	119
	Rth(550)	60	70	80	70	-90	60	60	60	60
	Wavelength dispersion	flat	flat	flat	Reverse wavelength	A regular wavelength	flat	flat	flat	flat
	Phase difference	+A	+A	+A	+A	+C	+A	+A	+A	+A
Laminate of the 1st phase difference layer and the 2nd phase difference layer	Equation 1	1.25	1.14	1.1	1.14	1.25	1.25	1.25	0.9	1.5
	Re(550)	120	140	100	140	120	120	120	120	120
	Rth(550)	-30	-20	-10	-20	-30	-30	-30	10	-60
	NZ(550)	0.25	0.36	0.40	0.36	0.25	0.25	0.25	0.58	0

A polarizing plate prepared in Examples and Comparative Examples was mounted on an IPS liquid crystal panel, and modules for measuring color coordinates x and y were prepared.

Specifically, a polarizing plate manufactured in Comparative Example and the above was mounted on the light exit surface of the IPS liquid crystal panel (LTM270HL02, SAMSUNG). At this time, the first phase difference layer and the second phase difference layer of the polarizing plate were directed toward the liquid crystal panel. A polarizing plate laminated in the order of TAC-polarizer-TAC was laminated on the light incident surface of the IPS liquid crystal panel. In the black state (dark state), the polar angle was equal to 60°, and the color coordinate (x, y) values were measured at azimuth angles of 30°, 45°, 60°, 120°, 135°, and 150°. The results are shown in Table 2 and FIGS. 2 to 4 below. The color coordinate (x, y) values were measured by an EZ Contrast measuring device and evaluated according to CIELAB standards.

		Example				Comparative example
		One	2	3	4	One	2	3	4	5
30°	X	0.18	0.2	0.3	0.3	0.25	0.26	0.3	0.27	0.3
	Y	0.13	0.18	0.29	0.33	0.29	0.18	0.28	0.17	0.3
45°	X	0.18	0.2	0.36	0.33	0.24	0.3	0.3	0.31	0.37
	Y	0.13	0.19	0.36	0.37	0.21	0.23	0.32	0.24	0.37
60°	X	0.18	0.2	0.38	0.31	0.23	0.35	0.3	0.37	0.39
	Y	0.13	0.15	0.39	0.29	0.21	0.32	0.28	0.32	0.39
120°	X	0.2	0.19	0.3	0.22	0.35	0.2	0.21	0.2	0.3
	Y	0.12	0.12	0.24	0.15	0.26	0.1	0.15	0.1	0.25
135°	X	0.18	0.18	0.36	0.22	0.36	0.22	0.21	0.21	0.37
	Y	0.1	0.1	0.31	0.14	0.28	0.13	0.13	0.11	0.31
150°	X	0.18	0.23	0.4	0.27	0.34	0.24	0.25	0.25	0.4
	Y	0.1	0.15	0.33	0.19	0.28	0.16	0.18	0.15	0.33
Maximum		0.18	0.23	0.4	0.37	0.36	0.35	0.32	0.37	0.4

'Maximum value' in Table 2 means the maximum value of the distance between color coordinate (x, y) values at azimuth angles of 30°, 45°, 60°, 120°, 135°, and 150° when the polar angle is equal to 60°. .

As shown in Tables 2, 2, and 4, the polarizing plate of the present invention can significantly lower the difference in color value and the difference in visibility between the left and right sides of the screen when applied to an IPS liquid crystal display device. When applied, bluish color can be maintained at all azimuth angles.

On the other hand, in Comparative Example 1 (maximum value is 0.36), in which the stacking order of the first phase difference layer and the second phase difference layer is changed compared to Example 1 (maximum value is 0.18), the wavelength dispersion of the first phase difference layer is not satisfied Comparative Example 2 (maximum value is 0.35) to Comparative Example 3 (maximum value is 0.32), and Comparative Example 4 (maximum value is 0.37) to Comparative Example 5 (maximum value is 0.4) which does not satisfy Equation 1 is compared to Example 1 When applied to the IPS liquid crystal display, the difference in color value and difference in visibility between the left and right sides of the screen were high, and the maximum value according to Table 2 was also remarkably high. Also, referring to FIG. 3, Comparative Example 2 was unable to maintain a bluish color at all azimuth angles when applied to the IPS liquid crystal display device compared to Example 1 of FIG. 2 and Example 2 of FIG. 2.

Simple modifications or changes of the present invention can be easily carried out by those skilled in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (20)

1. It includes a polarizing film and a first phase difference layer and a second phase difference layer sequentially stacked on the lower surface of the polarizing film,

   The first phase difference layer is a positive C phase difference layer having a constant wavelength dispersion, and the second phase difference layer is a positive A phase difference layer,

   A laminate comprising the first phase difference layer and the second phase difference layer satisfies Expression 1 below:

   [Equation 1]

   About 1.0 ≤ ｜1-(Rth/Re)｜ ≤ About 1.4

   (Equation 1 above,

   Rth is a phase difference (unit: nm) in the thickness direction at a wavelength of about 550 nm of the stack including the first phase difference layer and the second phase difference layer,

   Re is an in-plane retardation (unit: nm) at a wavelength of about 550 nm of the stack including the first phase difference layer and the second phase difference layer.
2. The polarizing plate of claim 1, wherein the second phase difference layer has flat wavelength dispersion or reverse wavelength dispersion.
3. The polarizing plate of claim 1, wherein the second phase difference layer satisfies Equation 2 and Equation 3:

   [Equation 2]

   About 0.95 ≤ Re(450)/Re(550) ≤ about 1.05

   [Equation 3]

   About 0.95 ≤ Re(650)/Re(550) ≤ about 1.05

   (In the above equation 2, equation 3,

   Re(450), Re(550), and Re(650) are in-plane retardation at wavelengths of about 450nm, 550nm, and 650nm of the second phase difference layer, respectively.
4. The polarizing plate of claim 1, wherein the second phase difference layer satisfies Expression 4 and Expression 5 below.

   [Equation 4]

   About 0.8 ≤ Re(450)/Re(550) ≤ about 1.0

   [Equation 5]

   About 1.0 ≤ Re(650)/Re(550) ≤ about 1.1

   (Equations 4 and 5 above,

   Re(450), Re(550), and Re(650) are in-plane retardation at wavelengths of about 450nm, 550nm, and 650nm of the second phase difference layer, respectively.
5. The polarizing plate of claim 1, wherein the second phase difference layer has an in-plane retardation (Re) of about 100 nm to about 170 nm at a wavelength of about 550 nm.
6. The polarizing plate of claim 1, wherein the second phase difference layer has a degree of biaxiality (NZ) of about 0.8 to about 1.4 at a wavelength of about 550 nm.
7. According to claim 1, When the absorption axis of the polarizing film is about 0°, the angle formed by the slow axis of the second phase difference layer with the absorption axis of the polarizing film is about -5° to about +5. That is, the polarizing plate.
8. The polarizing plate of claim 7, wherein an angle formed between the absorption axis of the polarizing film and the slow axis of the second phase difference layer is about 0°.
9. The polarizing plate according to claim 1, wherein the first phase difference layer satisfies Expression 6 and Expression 7 below:

   [Equation 6]

   About 1.0 <Rth(450)/Rth(550) <about 1.1

   [Equation 7]

   About 0.9 <Rth(650)/Rth(550) <about 1.0

   (Equations 6 and 7 above,

   Rth (450), Rth (550), Rth (650) is the first phase difference wavelength of about 450nm, 550nm, 650nm in the thickness direction phase difference, respectively.
10. The method of claim 1, wherein the first phase difference layer has a thickness direction retardation (Rth) of about -70 nm to-about 130 nm at a wavelength of about 450 nm, a thickness direction retardation (Rth) of about -60 nm to about -120 nm at a wavelength of about 550 nm, A polarizer having a thickness direction retardation (Rth) of about -50 nm to about -110 nm at a wavelength of about 650 nm.
11. The polarizing plate according to claim 1, wherein the first phase difference layer is a coating layer formed of a non-liquid crystal polymer.
12. The polarizing plate according to claim 11, wherein the first phase difference layer is a coating layer comprising at least one of a cellulose ester or a polymer thereof and an aromatic polymer.
13. The polarizing plate of claim 1, wherein the first phase difference layer is formed directly on the second phase difference layer.
14. The polarizing plate of claim 1, wherein at least one of a primer layer and a buffer layer is further formed between the first phase difference layer and the second phase difference layer.
15. The polarizing plate of claim 1, wherein the stacked body including the first phase difference layer and the second phase difference layer has a degree of biaxiality (NZ) of about 0 to about 0.5 at a wavelength of about 550 nm.
16. The polarizing plate of claim 1, wherein the laminate including the first phase difference layer and the second phase difference layer has an in-plane retardation (Re) of about 100 nm to about 150 nm at a wavelength of about 550 nm.
17. The polarizing plate of claim 1, wherein the laminate including the first phase difference layer and the second phase difference layer has a thickness direction retardation (Rth) of about -80 nm to about 0 nm at a wavelength of about 550 nm.
18. The polarizing plate of claim 1, wherein a protective layer is further laminated on the upper surface of the polarizing film.
19. The polarizing plate of claim 1, wherein the polarizing plate is used in an IPS liquid crystal display device.
20. An optical display device comprising the polarizing plate of any one of claims 1 to 19.

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