KR102424459B1 - Polarizing plate and optical display comprising the same - Google Patents

Abstract

A polarizer, comprising a first retardation layer, a second retardation layer and a third retardation layer sequentially stacked on the lower surface of the polarizer, wherein the first retardation layer has an in-plane retardation (Re) of 180 nm to 220 nm at a wavelength of 550 nm, The second retardation layer has an in-plane retardation (Re) of 50 nm to 80 nm at a wavelength of 550 nm, and the third retardation layer includes a positive C layer having a thickness direction retardation (Rth) of -150 nm to -110 nm at a wavelength of 550 nm , a polarizing plate, and an optical display device including the same.

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.

The organic light emitting diode display device may have poor visibility and contrast due to the reflection of external light. can be implemented The optical compensation film used for the polarizing plate of the organic light emitting device display is mainly used in the form of two films manufactured by stretching or one film having reverse wavelength dispersion. They may implement an anti-reflection function, but have strong wavelength dependence on incident light, and thus may have an anti-reflection function in a specific wavelength region, but may have a poor anti-reflection function in another wavelength region. In addition, when the screen of the display device is viewed, the black visual effect that makes the screen appear black even from the front may be reduced, and the uniformity of the viewing angle in all directions may be deteriorated.

Background art of the present invention is disclosed in Korean Patent Publication No. 2013-0103595.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polarizing plate capable of improving color reproducibility when driving an optical display device.

Another object of the present invention is to provide a polarizing plate capable of lowering the reflectance from the side when the optical display device is not driven and making the reflectance at a short wavelength and a long wavelength uniform with each other.

Another object of the present invention is to provide a polarizing plate that improves black visual perception and reduces color shift by making a screen appear black when an optical display device is not driven.

Another object of the present invention is to provide an optical display device including the polarizing plate.

One aspect of the present invention is a polarizing plate.

1. The polarizing plate includes a polarizer and a first retardation layer, a second retardation layer and a third retardation layer sequentially stacked on a lower surface of the polarizer, wherein the first retardation layer has an in-plane retardation (Re) of 180 nm at a wavelength of 550 nm to 220 nm, the second retardation layer has an in-plane retardation (Re) of 50 nm to 80 nm at a wavelength of 550 nm, and the third retardation layer has a thickness direction retardation (Rth) of -150 nm to -110 nm at a wavelength of 550 nm. include

2. In 1, the third retardation layer may have a thickness direction retardation (Rth) of -150 nm to -120 nm at a wavelength of 550 nm.

In 3.1-2, the third retardation layer may have an in-plane retardation (Re) of 10 nm or less at a wavelength of 550 nm.

In 4.1-3, the third retardation layer may have reverse wavelength dispersion.

In 5.1-5, in the third retardation layer, Rth(450)/Rth(550) may be 0.8 to 0.9, and Rth(650)/Rth(550) may be 1.01 to 1.05.

In 6.1-5, the third retardation layer may be a positive C layer.

In 7.1-6, the thickness direction retardation of the first retardation layer may have a positive value at a wavelength of 550 nm, and the thickness direction retardation of the second retardation layer may have a negative value at a wavelength of 550 nm.

In 8.1-7, the first retardation layer may have reverse wavelength dispersion, and the second retardation layer may have forward wavelength dispersion.

In 9.1-8, when the clockwise direction is + and the counterclockwise direction is - with respect to the absorption axis of the polarizer, the angle between the absorption axis of the polarizer and the slow axis of the first retardation layer with respect to the absorption axis of the polarizer (α1) may be +40° to +50°, and an angle α2 between the absorption axis of the polarizer and the slow axis of the second retardation layer with respect to the absorption axis of the polarizer may be +40° to +50°.

In 10.1-9, the third retardation layer may have reverse wavelength dispersion, and the laminate of the first retardation layer and the second retardation layer may have reverse wavelength dispersion.

In 11.1-10, a protective film may be further laminated on the upper surface of the polarizer.

In 12.1-11, the polarizing plate may have a reflectance ratio of 0.7 to 1 according to Equation 1:

[Equation 1]

Ratio of reflectance = reflectance (@400nm) / reflectance (@700nm)

(In Equation 1 above,

The reflectance (@400nm) is the reflectance measured at a wavelength of 400nm with respect to the polarizing plate (unit:%)

The reflectance (@700nm) is the reflectance measured at a wavelength of 700nm with respect to the polarizing plate (unit:%))

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 improving color reproducibility when driving an optical display device.

The present invention provides a polarizing plate capable of lowering the reflectance at the non-driving side of an optical display device and making the reflectance uniform in short and long wavelengths.

The present invention provides a polarizing plate that improves the sense of black and reduces color shift by making the screen appear black when the optical display device is not driven.

The present invention provides an optical display device including the polarizing plate.

1 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.
2 is a diagram illustrating an arrangement relationship of an absorption axis of a polarizer, a slow axis of a first retardation layer, and a slow axis of a second retardation layer among the polarizing plates according to an embodiment of the present invention.

With reference to the accompanying drawings, it will be described in detail so that a person of ordinary skill in the art can easily carry out the present invention by way of example. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and the same names are used for the same or similar components throughout the specification. The length and size of each component in the drawings are for explaining 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 based on the drawings, and 'upper' may be changed to 'lower' and 'lower' to 'upper' depending on the viewing angle.

In the present specification, the 'in-plane retardation (Re)' is represented by the following formula A, the 'thickness direction retardation (Rth)' is represented by the following formula B, and the 'biaxiality (NZ)' can be represented by the following formula C have:

[Formula A]

Re = (nx - ny) x d

[Formula B]

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

[Formula C]

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

(In Equations A to C, nx, ny, and nz are refractive indices in the slow axis direction, fast axis direction, and thickness direction of the optical element, respectively, at the measurement wavelength, and d is the thickness of the optical element. (unit: nm)). In Equations A to C, the measurement wavelength may be 450 nm, 550 nm or 650 nm.

In the present specification, 'short wavelength dispersion' is Re(450)/Re(550), 'long wavelength dispersion' is Re(650)/Re(550), and Re(450), Re(550), and Re(650) are It means the in-plane retardation (Re) at wavelengths of 450 nm, 550 nm, and 650 nm of the retardation layer alone or the retardation layer stack, respectively.

When representing a numerical range in the present specification, 'X to Y' means X or more and Y or less (X≤ and ≤Y).

The inventor of the present invention has a first retardation layer having an in-plane retardation (Re) of 180 nm to 220 nm at a wavelength of 550 nm and a second retardation layer having an in-plane retardation (Re) of 50 nm to 80 nm at a wavelength of 550 nm sequentially stacked on the lower surface of the polarizer In the polarizing plate, a third retardation layer having a thickness direction retardation (Rth) of -150 nm to -110 nm at a wavelength of 550 nm and a positive C layer was further laminated on the lower surface of the second retardation layer. As a result, the polarizing plate of the present invention can increase the color reproducibility when driving the optical display device. In one embodiment, the polarizing plate of the present invention may have a color reproducibility of 73% or more. The polarizing plate of the present invention includes the first retardation layer, the second retardation layer, and the third retardation layer having the above-described retardation without including a dye for increasing the conventional color reproducibility in the polarizing plate, so that the color reproducibility improvement effect can be obtained.

On the other hand, the polarizing plate of the present invention lowers the reflectance from the side when the optical display device is not driven, makes the reflectance uniform in short and long wavelengths, and makes the screen appear black to improve the sense of blackness and reduce color shift. have. In particular, in the polarizing plate of the present invention, the degree of uniformity of reflectance between short and long wavelengths was remarkably improved by additionally stacking a positive C retardation layer, which is a third retardation layer, on the lower surface of the second retardation layer. The 'short wavelength' may have a wavelength of 380 nm to 420 nm, for example, a wavelength of 380 nm to 400 nm. The 'long wavelength' may have a wavelength of 680 nm to 780 nm, for example, a wavelength of 700 nm to 780 nm.

In one embodiment, the polarizing plate may have a reflectance ratio of 0.7 to 1 according to Equation 1 below. In the above range, since the reflectance according to the wavelength is very uniform and the degree of light leakage according to the wavelength is uniform, the screen quality of the display device may be excellent:

[Equation 1]

Ratio of reflectance = reflectance (@400nm) / reflectance (@700nm)

(In Equation 1 above,

The reflectance (@400nm) is the reflectance measured at a wavelength of 400nm with respect to the polarizing plate (unit:%)

The reflectance (@700nm) is the reflectance measured at a wavelength of 700nm with respect to the polarizing plate (unit:%))

Hereinafter, a polarizing plate according to an embodiment of the present invention will be described with reference to FIG. 1 .

1, the polarizing plate is a polarizer 110, a protective film 150 laminated on the upper surface of the polarizer 110, a first retardation layer 120 sequentially laminated on the lower surface of the polarizer 110, the first It includes a second retardation layer 130 and a third retardation layer 140 .

The first retardation layer 120 has an in-plane retardation (Re) of 180 nm to 220 nm at a wavelength of 550 nm, and the second retardation layer 130 has an in-plane retardation (Re) of 50 nm to 80 nm at a wavelength of 550 nm. The third retardation layer 140 is a positive C layer laminated on the lower surface of the second retardation layer 130 and having a thickness direction retardation (Rth) of -150 nm to -110 nm at a wavelength of 550 nm. Through this, the polarizing plate increases the color reproducibility when the optical display device is driven, lowers the reflectance from the side when the optical display device is not driven, makes the reflectance uniform at short and long wavelengths, and makes the screen appear black, resulting in a black visual experience. can be improved and the effect of reducing color shift can be obtained.

When the polarizing plate does not include the third retardation layer 140 , color gamut may decrease and color shift may be severe when the optical display device is driven. In the case where the third retardation layer 140 is laminated between the polarizer 110 and the first retardation layer 120 instead of being laminated on the lower surface of the second retardation layer 130 in the polarizing plate, the effect of the present invention cannot be obtained or the effect is not obtained. It is weak and cannot be used for display devices. When the third retardation layer 140 is laminated between the first retardation layer 120 and the second retardation layer 130 in the polarizing plate, the effect of the present invention cannot be obtained or the effect is weak and thus cannot be used in a display device. Even when the third retardation layer is laminated on the lower surface of the second retardation layer in the polarizing plate, when the thickness direction retardation (Rth) at a wavelength of 550 nm is out of -150 nm to -110 nm or is not the positive C layer, when driving the optical display device of the present invention The effect of improving color gamut may be reduced.

In one embodiment, the third retardation layer may have a thickness direction retardation (Rth) of -150 nm to -120 nm at a wavelength of 550 nm. Within the above range, the effect of the above-described color reproducibility of the present invention may be further improved, and when the polarizing plate is applied to a rigid display device, the reflectance at a short wavelength and a long wavelength may be uniform.

The polarizing plate of the present invention can make the reflectance uniform even if the reflectance varies depending on whether the organic light emitting diode display device to which the polarizing plate is mounted is a rigid type or a flexible type.

The third retardation layer 140 is a positive C layer having a refractive index relationship of nz > nx = ny (nx, ny, and nz are the slow axis, fast axis, and thickness direction refractive indices at a wavelength of 550 nm of the third retardation layer, respectively) can The third retardation layer becomes a positive C layer having a thickness direction retardation at a wavelength of 550 nm as described above. By realizing more vivid colors, reflective color improvement can be increased, visibility can be improved, and color gamut can be improved.

The third retardation layer 140 may have an in-plane retardation (Re) of 10 nm or less at a wavelength of 550 nm, preferably 0 nm to 5 nm.

The third retardation layer 140 may have a thickness of greater than 0 μm and less than or equal to 15 μm, preferably 0.1 μm to 5 μm. In the above range, it can be used for a polarizing plate, and a thinning effect of the polarizing plate can be obtained.

The third retardation layer 140 may have reverse wavelength dispersion. In an embodiment, in the third retardation layer, Rth(450)/Rth(550) may be 0.8 to 0.9, and Rth(650)/Rth(550) may be 1.01 to 1.05. Within the above range, the effects of the present invention can be well realized. The Rth(450), Rth(550), and Rth(650) are the thickness direction retardation of the third retardation layer at wavelengths of 450 nm, 550 nm, and 650 nm.

As a positive C layer, the third retardation layer 140 may be an optically transparent resin film or a coating layer if the thickness direction retardation at the above-described wavelength of 550 nm can be secured. Preferably, by forming the third retardation layer as a coating layer, the polarizing plate can be made thin, it can be easy to implement the retardation in the thickness direction, and processability during manufacturing can be improved.

In one embodiment, the third retardation layer may include a liquid crystal layer formed by coating a composition including liquid crystal. For the liquid crystal, DNP's Positive C film can be used.

In another embodiment, the third retardation layer may be a coating layer formed by coating a composition including a polymer. For example, the composition may be a cellulose ester-based coating layer, and may be formed from a composition for a coating layer including a cellulose ester-based compound.

The cellulose ester-based compound includes at least one of a cellulose ester-based resin, a cellulose ester-based oligomer, and a cellulose ester-based monomer.

Cellulose ester-based compounds refer to the condensation reaction product from the reaction of a hydroxyl group on cellulose with a carboxylic acid group of a carboxylic acid. The cellulose ester-based compound may be regioselectively or randomly substituted. Regioselectivity can be determined by determining the relative degree of substitution at C6, C3, C2 on the cellulose ester by carbon 13 NMR. Cellulose esters can be prepared by conventional methods by contacting a cellulose solution with one or more C1 to C20 acylating agents for a contact time sufficient to provide a cellulose ester having the desired degree of substitution and polymerization. Preferred acylating agents are one or more C1 to C20 straight or branched chain alkyl or aryl carboxylic acid 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 the acetoacetic acid ester may include methylacetoacetate, ethylacetoacetate, propylacetoacetate, butylacetoacetate, tert-butylacetoacetate. 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 the cellulose ester compound may include, but are not limited to, one or more of cellulose acetate (CA), cellulose acetate propionate (CAP), and cellulose acetate butyrate (CAB).

The composition for the coating layer further includes an additive having a fused ring in addition to the cellulose ester-based compound. The additive having the fused ring allows the thickness direction retardation (Rth) of the second protective layer to be expressed. The additive having the fused ring may include naphthalene, anthracene, phenanthrene, pyrene, Structure 1 or Structure 2 below. The additive having the fused ring may include 2-naphthyl benzoate, 2,6-naphthalene dicarboxylic acid diester of the following structure 3, naphthalene, and abietic acid ester of the following structure 4, but is limited thereto. Doesn't work:

[Structure 1]

[Structure 2]

[Structure 3]

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

[Structure 4]

(In Structure 4, R is C1 to C20 alkyl or C6 to C20 aryl)

Preferably, the additive having a fused ring is an additive having an aromatic ring, for example, naphthalene, anthracene, phenanthrene, pyrene, 2-naphthyl benzoate, 2,6-naphthalene dicarboxylic acid diester of structure 3 above. It may include one or more of

The third retardation layer may further include additives such as a plasticizer, a stabilizer, a UV absorber, an anti-blocking agent, a slip agent, a lubricant, a dye, a pigment, and a retardation improver, in addition to the additive having the fused ring described above.

The third retardation layer 140 may be directly formed on one surface of the second retardation layer 130 without an adhesive layer, an adhesive layer, or an adhesive layer. That is, the third retardation layer may be formed by coating and curing the composition for the third retardation layer on one surface of the second retardation layer 130 on which the first retardation layer 120 is not formed.

Although not shown in FIG. 1 , the third retardation layer 140 may be laminated on one surface of the second retardation layer by an adhesive layer. The pressure-sensitive adhesive layer may be formed of a conventional pressure-sensitive adhesive known to those skilled in the art.

The first retardation layer 120 has an in-plane retardation (Re) of 180 nm to 220 nm at a wavelength of 550 nm, and the second retardation layer 130 has an in-plane retardation (Re) of 50 nm to 80 nm at a wavelength of 550 nm. It can improve color gamut, enhance and/or improve a sense of black that can make the screen of the display device appear black even from the front, and has an effect of reducing a color shift value, and Almost constant reflectance can be realized regardless of the wavelength.

Specifically, in the polarizing plate according to an exemplary embodiment of the present invention, Δa*b* measured by a colorimeter may be 0 to 3, and black visibility may be improved and/or enhanced in the above range, and may be used in an organic light emitting diode display. In the polarizing plate of an embodiment of the present invention, the deviation of reflectance according to wavelength in the visible light region, for example, wavelengths of 400 nm to 700 nm, is very low as 0.02% to 0.1%, and there may be an effect of uniform viewing angles, and in the present specification, 'variation in reflectance' ' means the difference between the maximum value and the minimum value among reflectances (T=60°) measured in the visible region.

The first retardation layer 120 may be stacked with the second retardation layer 130 to convert linearly polarized light transmitted through the polarizer 110 from the outside into circularly polarized light, and may strengthen and/or improve the sense of black. Since the first retardation layer 120 has Re in a specific range at a wavelength of 550 nm, the polarizing plate may improve an anti-reflection function and a sense of black visibility, and may implement a uniform reflectance regardless of a wavelength. The first retardation layer 120 may have a Re of 180 nm to 220 nm, for example, 190 nm to 200 nm at a wavelength of 550 nm, and in the above range, convert the linearly polarized light transmitted through the polarizer into circularly polarized light and enhance the black visual sensation and / Or it can be improved.

The first retardation layer 120 may have a thickness direction retardation Rth of a different sign among + and - at a wavelength of 550 nm compared to the second retardation layer 130 . That is, when the thickness direction retardation Rth of the first retardation layer 120 has a positive value, the thickness direction retardation Rth of the second retardation layer 130 may have a negative value at a wavelength of 550 nm. When the thickness direction retardation Rth of the first retardation layer 120 has a negative value at a wavelength of 550 nm, the thickness direction retardation Rth of the second retardation layer 130 may have a positive value at a wavelength of 550 nm. As a result, the first retardation layer 120 and the second retardation layer 130 stacked body may implement an antireflection function by making the thickness direction retardation close to zero.

Preferably, since the first retardation layer 120 has a larger Re than the second retardation layer 130 , the thickness direction retardation Rth of the first retardation layer 120 may have a positive value at a wavelength of 550 nm. For example, the first retardation layer 120 may have a thickness direction retardation (Rth) of 100 nm to 120 nm, specifically 105 nm to 120 nm, for example, 105 nm to 115 nm at a wavelength of 550 nm, in the range of the second retardation layer Anti-reflection can be implemented with:

The first retardation layer 120 may have a degree of biaxiality (NZ) of 1.0 to 1.1, preferably 1.05 to 1.07 at a wavelength of 550 nm at a wavelength of 550 nm, and converts linearly polarized light transmitted through the polarizer into circularly polarized light in the above range and produces a black luminous sensation There may be an effect of strengthening and/or improving the color shift, and there may be further an effect of reducing the color shift.

The first retardation layer 120 has reverse wavelength dispersion, and may have a short wavelength dispersion of 0.8 to 0.9 and a long wavelength dispersion of 1.02 to 1.04, and an antireflection function may be implemented when used in a polarizing plate within the above range. In the first retardation layer 120 , nx at a wavelength of 550 nm may be 1.57 or more, for example, 1.57 to 1.572, and ny and nz may be less than 1.57, for example, 1.569 to 1.568.

The first retardation layer 120 may be made of a resin having a glass transition temperature of 140° C. to 160° C., and may be made of at least one of a cycloolefin polymer-based resin and a polycarbonate resin, but is not limited thereto. In an embodiment, the first retardation layer 120 may be a resin film obtained by extruding at least one of a cycloolefin polymer-based resin and a polycarbonate resin.

The first retardation layer 120 may have a thickness of 50 μm to 200 μm, specifically 80 μm to 100 μm, and may be used in a polarizing plate within the above range. In addition, the first retardation layer 120 may be well attached to the polarizer and the second retardation layer through corona treatment or the like.

The first retardation layer 120 may include a non-stretched film obtained by extruding a resin for retardation film. However, the first retardation layer 120 may include a film prepared by uniaxially stretching the unstretched film in MD (machine direction) or TD (transverse direction), preferably MD. Specifically, the first retardation layer 120 may be manufactured by stretching at a draw ratio of 1.45 to 1.7 times at 140° C. to 160° C., but is not limited thereto. Preferably, since the first retardation layer 120 has a larger Re than the second retardation layer 130, the glass transition temperature (Tg) of the second retardation layer is higher than that of the second retardation layer in consideration of elongation. As a result, the thickness direction retardation (Rth) at a wavelength of 550 nm may be a + value.

The second retardation layer 130 may be stacked with the first retardation layer 120 to convert linearly polarized light transmitted through the polarizer 110 from the outside into circularly polarized light, and may enhance and/or improve the sense of black. In addition, since the second retardation layer 130 has Re in a specific range at a wavelength of 550 nm, the polarizing plate may enhance and/or improve the anti-reflection function and the sense of black, and implement a uniform reflectance regardless of the wavelength.

The second retardation layer 130 may have an in-plane retardation (Re) of 50 nm to 80 nm, specifically 50 nm to 70 nm, for example, 50 nm to 60 nm at a wavelength of 550 nm. can be converted to polarized light and enhance and/or improve black perception.

The second retardation layer 120 may have a degree of biaxiality (NZ) of -0.1 to 0, for example, -0.05 to 0 at a wavelength of 550 nm at a wavelength of 550 nm, and converts linearly polarized light passing through the polarizer into circularly polarized light in the above range There may be an effect of strengthening and/or improving the black visual sensation, and there may be further an effect of reducing a color shift.

The second retardation layer 130 has a positive wavelength dispersion, and may have a short wavelength dispersion of 1.0 to 1.1, preferably 1.08 to 1.1, and a long wavelength dispersion of 0.97 to 1.0. can be At a wavelength of 550 nm, the second retardation layer 130 may have nx and nz of 1.49 or more, for example, 1.49 to 1.4903, and ny, less than 1.49, for example, 1.4894 to 1.489.

The second retardation layer 130 may be manufactured by extruding a resin for retardation film and then uniaxially stretching MD or TD, preferably TD. Specifically, the second retardation layer 130 may be prepared by stretching at a draw ratio of 1.05 to 1.125 times at 110°C to 120°C, but is not limited thereto. Preferably, since the second retardation layer 130 has a smaller Re than the first retardation layer 120, the resin for the retardation film having a lower glass transition temperature (Tg) compared to the first retardation layer in consideration of elongation can be manufactured. have.

For example, the second retardation layer may be made of a resin having a glass transition temperature of 110° C. to 120° C., acrylic resin, polymethyl methacrylate (PMMA) resin, polystyrene (PS) resin, SMA (styrene maleic anhydride) It may be prepared from at least one of a resin and a cycloolefin polymer (COP)-based resin. In one embodiment, the second retardation layer 130 is polymethyl methacrylate resin, polystyrene resin, SMA resin, cycloolefin polymer-based resin It can be prepared by co-extrusion of two or more of them, preferably a polystyrene resin and a cycloolefin polymer-based resin, followed by TD uniaxial stretching.

The second retardation layer 130 may have a thickness of 50 μm to 200 μm, specifically 70 μm to 90 μm, and specifically 70 μm to 80 μm, and may be used in a polarizing plate within the above range. In addition, the second retardation layer 130 may be well adhered to the polarizer and the first retardation layer through corona treatment or the like.

The laminate of the first retardation layer 120 and the second retardation layer 130 has an in-plane retardation (Re) of 125 nm to 150 nm, for example, 125 to 145 nm, and a thickness direction retardation (Rth) of -20 nm to −20 nm at a wavelength of 550 nm. +20 nm Specifically, -5 nm to +5 nm, the degree of biaxiality (NZ) may be 0.3 to 0.8, for example, 0.4 to 0.6. In the above range, the polarizing plate may further have an anti-reflection function and an effect of improving and/or reinforcing the black luminance, and reducing the color shift.

The stacked body of the first retardation layer 120 and the second retardation layer 130 may have nx and nz of 1.53 to 1.575 and ny of 1.52 to 1.57, respectively, at a wavelength of 550 nm.

In the stack of the first retardation layer 120 and the second retardation layer 130 , the slow axis of the first retardation layer and the slow axis of the second retardation layer may be arranged in the relationship of FIG. 2 .

2 shows an absorption axis 110a of the polarizer 110, a slow axis 120a of the first retardation layer 120, and a slow axis 130a of the second retardation layer 130 of the polarizing plate 100 according to an embodiment of the present invention. ) is shown. In FIG. 2 , when the clockwise direction is defined as + and the counterclockwise direction is - based on the absorption axis 110a of the polarizer, the absorption axis 110a of the polarizer and the first retardation layer are defined with respect to the absorption axis 110a of the polarizer. The angle α1 between the slow axis 120a of 120 is +40° to +50°, and the absorption axis 110a of the polarizer and the second retardation layer 130 are slow with respect to the absorption axis 110a of the polarizer. The angle α2 between the axes 130a may be +40° to +50°. An angle between the slow axis of the first retardation layer and the slow axis of the second retardation layer may be 0° to 10°, preferably 0°. In the above range, the anti-reflection function and the sense of black may be good. FIG. 2 shows that the slow axis of the first retardation layer 120 and the second retardation layer 130 are respectively arranged in a clockwise direction with respect to the absorption axis 110a of the polarizer.

In the laminate of the first retardation layer 120 and the second retardation layer 130 , the slow axis (film) of the first retardation layer 120 and the second retardation layer 130 with respect to the absorption axis of the polarizer 110 . stretching direction) may be arranged in the same direction as each other.

Since the first retardation layer 120 and the second retardation layer 130 have opposite signs of the thickness direction retardation (Rth) of + and - at a wavelength of 550 nm, the first retardation layer 120 and the second retardation layer 130 ) of the laminate has a thickness direction retardation (Rth) of about 0 at a wavelength of 550 nm. When the first retardation layer and the second retardation layer have the same sign in thickness direction retardation at a wavelength of 550 nm, the viewing angle is narrowed, and thus there may be a problem in that the color shift is increased for each angle.

In one embodiment, the thickness direction retardation of the first retardation layer at a wavelength of 550 nm is a + value, the thickness direction retardation of the second retardation layer at a wavelength of 550 nm is a - value, and the thickness direction retardation of the third retardation layer at a wavelength of 550 nm is a - value. have.

In another embodiment, the thickness direction retardation of the first retardation layer at a wavelength of 550 nm is a - value, the thickness direction retardation of the second retardation layer at a wavelength of 550 nm is a + value, and the thickness direction retardation of the third retardation layer at a wavelength of 550 nm may be a - value. have.

For example, the first retardation layer may have a thickness direction retardation of 100 nm to 120 nm at a wavelength of 550 nm, and the second retardation layer may have a thickness direction retardation of -50 nm to -20 nm at a wavelength of 550 nm. Within the above range, the effects of the present invention can be well realized.

The laminate of the first retardation layer 120 and the second retardation layer 130 has reverse wavelength dispersion, with short wavelength dispersion of 0.78 to 0.80 and long wavelength dispersion of 1.03 to 1.04, thereby implementing an anti-reflection function. Specifically, the polarizing plate of an embodiment of the present invention may have a spectral transmittance/reflectance (SCE mode) of 0.005% to 0.01% in a visible light region, for example, a wavelength of 400 nm to 700 nm, and is reflected when used in an organic light emitting diode display in the above range. It has a preventive function and can be used.

In FIG. 1 , the first retardation layer 120 and the second retardation layer 130 are shown as a single film, but the first retardation layer and/or the second retardation layer are each melted and co-extruded of two or more resins. By doing so, it may be a multilayer film of two or more layers. In an embodiment, the second retardation layer may be a two-layer or three-layer film made of a cycloolefin-based resin, a polystyrene resin, and specifically, a three-layered film made of a cycloolefin-based resin, a polystyrene resin, and a cycloolefin-based resin can be a film of

The polarizer 110 converts incident natural light or polarized light into linearly polarized light in a specific direction, and may be manufactured from a polymer film containing polyvinyl alcohol-based resin as a main component. Specifically, the polarizer 110 may be manufactured by dyeing the polymer film with iodine or a dichroic dye and stretching it in the machine direction (MD). Specifically, it may be prepared through a swelling process, a dyeing step, an stretching step, and a crosslinking step.

The polarizer 110 may have a thickness of 2 μm to 30 μm, specifically 4 μm to 27 μm, and may be used in a polarizing plate within the above range.

Although not shown in FIG. 1 , the polarizer 110 may be adhered to the first retardation layer 120 and the adhesive layer. The pressure-sensitive adhesive may be formed of, for example, at least one of a photocurable pressure-sensitive adhesive and a pressure-sensitive adhesive (PSA).

By further forming the protective film 150 , there may be further effects of protecting the polarizer from the external environment and increasing the mechanical strength of the polarizing plate.

The protective film 150 protects the polarizer from the external environment, as an optically transparent film, for example, cellulose-based, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate (PET) containing triacetyl cellulose (TAC), etc. ), polybutylene naphthalate, polyester-based, cyclic polyolefin-based, polycarbonate-based, polyethersulfone-based, polysulfone-based, polyamide-based, polyimide-based, polyolefin-based, polyarylate-based, polyvinyl alcohol The film may be made of one or more resins selected from the group consisting of polyvinyl chloride-based, polyvinyl chloride-based, and polyvinylidene chloride-based resins. Specifically, TAC or PET film may be used.

The protective film 150 may have a thickness of 5 μm to 70 μm, specifically 15 μm to 45 μm, and may be used for a polarizing plate within the above range.

Although not shown in FIG. 1, a functional coating layer is formed on the upper surface of the protective film 150 to provide additional functions to the polarizing plate. For example, the functional coating layer may be a hard coating layer, an anti-fingerprint layer, an anti-reflection layer, etc. and these may be formed alone or by stacking two or more types.

In one embodiment, the functional coating layer may be a hard coating layer, and the hard coating layer may be formed of a transparent material capable of implementing pencil hardness B or higher. By forming the organic coating material, the adhesion to the protective film can be improved. Specifically, it may be formed of at least one of urethane-(meth)acrylate-based, (meth)acrylate-based, epoxy-based, urethane-based, and silicone-based resins, but is not limited thereto.

In addition, although not shown in FIG. 1 , an adhesive layer is formed between the protective film and the polarizer, so that the protective film and the polarizer can adhere to each other. The adhesive layer may be formed of a conventional photocurable adhesive, a water-based adhesive, a pressure-sensitive adhesive (PSA), or the like.

The optical display device of the present invention may include the polarizing plate of the embodiment of the present invention, for example, an organic light emitting diode (OLED) display device and a liquid crystal display device.

In one embodiment, the organic light emitting diode display device may include an organic light emitting diode panel including a flexible substrate, and the polarizing plate of the present invention laminated on the organic light emitting diode panel.

In another embodiment, the organic light emitting diode display device may include an organic light emitting diode panel including a non-flexible substrate, and the polarizing plate of the present invention laminated on the organic light emitting diode panel.

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, these are presented as preferred examples of the present invention and cannot be construed as limiting the present invention in any sense.

Example One

A polyvinyl alcohol film (PS#60, Kuraray, Japan, thickness before stretching: 60 μm) was stretched 6 times in an aqueous iodine solution at 55° C. to prepare a polarizer having a transmittance of 45%.

The polycarbonate unstretched film (Samsung SDI) was MD uniaxially stretched 1.5 times at 140° C. to prepare a first retardation layer (static wavelength dispersibility) having the retardation shown in Table 1 below.

A film obtained by co-extruding a cycloolefin polymer (COP, Okura company) and polystyrene (PS, Okura company) into three layers of COP-PS-COP was TD uniaxially stretched at 120 ° C. A second retardation layer (reverse wavelength dispersion) was prepared.

The first retardation layer and the second retardation layer are laminated using PSA (EG-813, Toyo INK) so that the angle between the slow axis of the first retardation layer and the second retardation layer is 0°, and based on the absorption axis of the polarizer A polarizer was laminated on the upper surface of the first retardation layer using PSA (EG-813, Toyo INK) so that the slow axis of the first retardation layer and the slow axis of the second retardation layer were +45° and +45°, respectively. . A hard-coated TAC film (CHP2S, DNP) was laminated on the upper surface of the polarizer.

A Positive C liquid crystal film (DNP, reverse wavelength dispersion) was used as the third retardation layer.

A polarizing plate was manufactured by attaching the third retardation layer to the lower surface of the second retardation layer with PSA (EG-813, Toyo INK).

Example 2

In Example 1, a polarizing plate was manufactured in the same manner except that the first retardation layer, the second retardation layer, and the third retardation layer were changed as shown in Table 1 below.

comparative example One

A polarizing plate was manufactured in the same manner as in Example 1, except that in Example 1, a third retardation layer (+C layer) was not laminated on the lower surface of the second retardation layer.

comparative example 2 to comparative example 4

In Example 1, a polarizing plate was manufactured in the same manner except that the third retardation layer was changed as shown in Table 1 below.

Table 1 below shows the retardation Re and Rth of the first retardation layer and the second retardation layer, and Re and Rth of the third retardation layer, which were measured using Kobra WPR (Oji Corporation) at a wavelength of 550 nm.

first phase difference 2nd phase difference layer 3rd phase difference Re(550) Rth(550) NZ(550) Re(550) Rth(550) NZ(550) Re(550) Rth(550) Example 1 200 111.8 1.05 60 -31.6 -0.03 0.2 -125.7 Example 2 200 111.8 1.05 60 -31.6 -0.03 1.3 -148.5 Comparative Example 1 200 111.8 1.05 60 -31.6 -0.03 - - Comparative Example 2 200 111.8 1.05 60 -31.6 -0.03 0.4 -70.7 Comparative Example 3 200 111.8 1.05 60 -31.6 -0.03 0.6 -107.5 Comparative Example 4 200 111.8 1.05 60 -31.6 -0.03 0.3 -155

The following physical properties were evaluated using the polarizing plates of Examples and Comparative Examples, and are shown in Table 2 below.

(1) Color gamut (unit: %): NTSC standard [NTSC standard: x and y color coordinates were obtained by the color gamut measurement method of Red 0.67, 0.33 green 0.21, 0.71 blue 0.14, 0.08. Color gamut was measured using topcon's SR3-A, and after attaching the polarizing plates of Examples and Comparative Examples on the driven panel, RGB colors, Black, and White colors were displayed sequentially, and color measurement was performed. If the measured color value is expressed as a percentage of the NTSC color coordinate, the color gamut can be obtained.

(2) Reflectance (unit: %): The reflectance was measured using a DMS 803 from Japanese Instrument Systems (Konica Minolta group). After measuring against the white plate standard provided in DMS 803 from Instrument Systems (Konica Minolta group), luminance and contrast were measured using the Angular Scan function. The polarizing plates of Examples and Comparative Examples were attached to the panel (glass substrate) with a pressure-sensitive adhesive, and reflectance values were obtained for the front and side surfaces. Theta is measured in units of 5 degrees, and the spectral transmittance/reflectance (SCE) value is obtained at 60 degrees on the side (T=60°), and the wavelengths of 400 nm and 700 nm are taken.

(3) Color shift (Δa*b*): Color shift (Δa*b*) was measured using a DMS 803 from Instrument Systems (Konica Minolta group). Attach the polarizing plates of Examples and Comparative Examples with pressure-sensitive adhesive on the panel (Glass substrate), and obtain a* and b* values from the side (T=60°), respectively, ((a*) ² + (b*) ² ) ^{1 /2} .

color gamut SCE reflectance
(@T=60°) color shift
(@T=60°) @400nm @700nm Equation 1 a* b* △a*b* Example 1 73.74 0.0086 0.0111 0.7748 -0.58 1.95 2.03 Example 2 77.45 0.0111 0.0112 0.9911 -0.29 1.91 1.93 Comparative Example 1 72.35 0.0075 0.0132 0.5682 -3.83 4.61 5.99 Comparative Example 2 70.41 0.0102 0.0134 0.7612 -2.49 3.55 4.33 Comparative Example 3 73.51 0.0088 0.0105 0.8381 -1.18 3.00 3.22 Comparative Example 4 72.92 0.0084 0.0102 0.8235 -0.49 2.00 2.06

As shown in Table 2 above, the polarizing plate of the present invention can increase the color reproducibility and at the same time lower the reflectance from the side when not driven and make the reflectance uniform at short and long wavelengths, and when the optical display device is not driven, the screen is black. By making it visible, it was possible to improve the sense of black and reduce color shift.

On the other hand, in Comparative Example 1 in which the third retardation layer was not provided in the polarizing plate of the present invention, the reflectance was not uniform and the degree of color shift was high. In Comparative Examples 2 and 3, in which the thickness direction retardation of the third retardation layer exceeds -110 nm in the polarizing plate of the present invention, the color reproducibility was low, the reflectance uniformity was low, and the color shift was severe. In the polarizing plate of the present invention, the retardation in the thickness direction of the third retardation layer was less than -150 nm. Comparative Example 4 had a low color reproducibility.

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

Claims (13)

A polarizer, comprising a first retardation layer, a second retardation layer and a third retardation layer sequentially stacked on the lower surface of the polarizer,
The first retardation layer has an in-plane retardation (Re) of 180 nm to 220 nm at a wavelength of 550 nm, and the second retardation layer has an in-plane retardation (Re) of 50 nm to 80 nm at a wavelength of 550 nm,
The third retardation layer has an in-plane retardation (Re) greater than 0 nm and less than or equal to 10 nm at a wavelength of 550 nm, and a thickness direction retardation (Rth) of -150 nm to -110 nm at a wavelength of 550 nm.
The polarizing plate of claim 1, wherein the third retardation layer has a thickness direction retardation (Rth) of -150 nm to -120 nm at a wavelength of 550 nm.
delete The polarizing plate of claim 1 , wherein the third retardation layer has reverse wavelength dispersion.
The polarizing plate of claim 1 , wherein, in the third retardation layer, Rth (450)/Rth (550) is 0.8 to 0.9, and Rth (650)/Rth (550) is 1.01 to 1.05.
delete The polarizing plate of claim 1 , wherein the thickness direction retardation of the first retardation layer has a positive value at a wavelength of 550 nm, and the thickness direction retardation of the second retardation layer has a negative value at a wavelength of 550 nm.
The polarizing plate of claim 1, wherein the first retardation layer has reverse wavelength dispersion, and the second retardation layer has forward wavelength dispersion.
According to claim 1, When a clockwise direction is defined as + and a counterclockwise direction as - with respect to the absorption axis of the polarizer, between the absorption axis of the polarizer and the slow axis of the first retardation layer with respect to the absorption axis of the polarizer. The angle α1 is +40° to +50°, and the angle α2 between the absorption axis of the polarizer and the slow axis of the second retardation layer with respect to the absorption axis of the polarizer is +40° to +50° , polarizer.
The polarizing plate according to claim 1, wherein the third retardation layer has reverse wavelength dispersion, and the laminate of the first retardation layer and the second retardation layer has reverse wavelength dispersion.
The polarizing plate according to claim 1, wherein a protective film is further laminated on the upper surface of the polarizer.
The polarizing plate according to claim 1, wherein the polarizing plate has a reflectance ratio of 0.7 to 1 according to Equation 1:
[Equation 1]
Ratio of reflectance = reflectance (@400nm) / reflectance (@700nm)
(In Equation 1 above,
The reflectance (@400nm) is the reflectance (unit:%) measured at a wavelength of 400nm with respect to the polarizing plate
The reflectance (@700nm) is the reflectance measured at a wavelength of 700nm with respect to the polarizing plate (unit:%))
An optical display device comprising the polarizing plate of any one of claims 1 to 2, 4 to 5, and 7 to 12.

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