KR20220106940A - Polarizing plate and optical display apparatus comprising the same - Google Patents

Abstract

A polarizing plate and an optical display device comprising the same are provided. The polarizing plate includes: a polarizer; and a first retardation layer and a second retardation layer sequentially stacked on the lower surface of the polarizer. The first retardation layer has positive wavelength dispersion and has a refractive index relationship of equation 5. The second retardation layer has positive wavelength dispersion and has a refractive index relationship of equation 8. The direction of the slow axis of the first retardation layer is oriented in an oblique direction relative to the width direction of the laminate of the first retardation layer and the second retardation layer. The polarizer has a polarization degree of 99% or more and a single light transmittance (Ts) of 44% or more.

Description

Polarizing plate and optical display including same

The present invention relates to a polarizing plate and an optical display device including the same. More specifically, the present invention relates to a polarizing plate capable of remarkably lowering the side reflectance and the front reflectance in the entire range, particularly at a polar angle (θ) of 5° to 60°, and an optical display device including the same.

The organic EL panel includes a highly reflective metal electrode layer. Accordingly, the visibility of the organic EL panel is deteriorated due to reflection of external light. This deterioration of visibility is improved by attaching a circularly polarizing plate to an organic EL panel.

A circular polarizer is generally manufactured by laminating a quarter phase plate to a polarizer. The retardation plate of a COP (cyclic olefin polymer)-based resin has a problem in that an excellent reflection color is not obtained when applied because the retardation value has a so-called flat wavelength dispersion characteristic that does not depend on the wavelength of the measured light and is almost constant. In order to improve the shortcomings of the flat wavelength dispersion, a circularly polarizing plate including a retardation film of a PC (polycarbonate)-based resin having reverse wavelength dispersion, the retardation value of which increases according to the wavelength of the measurement light, has been proposed. However, this circular polarizing plate greatly improves external light reflection and reflection color in the front direction, but when the panel is viewed from an oblique direction, a color different from the color in the front direction is obtained, resulting in a color difference problem.

Background art of the present invention is disclosed in Korean Patent Application Laid-Open No. 10-2016-0107114 and the like.

An object of the present invention is to provide a polarizing plate that significantly lowers the side reflectance.

Another object of the present invention is to provide a polarizing plate having a thinning effect and a process improvement effect.

One aspect of the present invention is a polarizing plate.

1. The polarizer is a polarizer; and a first retardation layer and a second retardation layer sequentially stacked on the lower surface of the polarizer,

The first retardation layer has a positive wavelength dispersion, and has a refractive index relationship of Equation 5 below:

[Equation 5]

nx > ny ≒ nz

(In Equation 5, nx, ny, and nz are refractive indices in the slow axis direction, fast axis direction, and thickness direction of the first retardation layer at a wavelength of 550 nm, respectively),

The second retardation layer has a positive wavelength dispersion and has a refractive index relationship of Equation 8:

[Equation 8]

nx ≒ nz > ny

(in Equation 8, nx, ny, and nz are refractive indices in the slow axis direction, fast axis direction, and thickness direction of the second retardation layer at a wavelength of 550 nm, respectively),

In the first retardation layer, a slow axis direction of the first retardation layer is oriented in an oblique direction compared to a transverse direction (TD) of the stack of the first retardation layer and the second retardation layer, and the first retardation layer The laminate of the layer and the second retardation layer has reverse wavelength dispersion, and the polarizer has a polarization degree of 99% or more and a single light transmittance (Ts) of 44% or more.

In 2.1, the laminate of the first retardation layer and the second retardation layer may be a single-sheet film.

In 3.1-2, the laminate of the first retardation layer and the second retardation layer may have an in-plane retardation (Re) of 140 nm to 200 nm at a wavelength of 550 nm.

In 4.1-3, the laminate of the first retardation layer and the second retardation layer may satisfy Equations 1 and 2:

[Equation 1]

0.8 ≤ Re(450)/Re(550) < 1.0

[Equation 2]

1.0 < Re(650)/Re(550) ≤ 1.2

(In Equations 1 and 2, Re (450), Re (550), and Re (650) are in-plane retardation at wavelengths of 450 nm, 550 nm, and 650 nm of the stack of the first and second retardation layers, respectively).

In 5.1-4, the slow axis direction of the first retardation layer may be 70°±10° compared to the TD of the stack of the first retardation layer and the second retardation layer.

In 6.1-5, the slow axis direction of the second retardation layer may be 0° ± 20° (except 0°) compared to the TD of the stack of the first retardation layer and the second retardation layer .

In 7.1-6, the angle formed by the slow axis direction of the first retardation layer with respect to the absorption axis of the polarizer may be 10° to 30°.

In 8.1-7, the angle formed by the slow axis direction of the second retardation layer with respect to the absorption axis of the polarizer may be 70° to 90°.

In 9.1-8, the first retardation layer may be a positive A retardation layer, and the second retardation layer may be a negative A retardation layer.

In 10.1-9, the first retardation layer is a cyclic olefin polymer such as norbornene polymer; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyvinyl alcohol; polyvinyl chloride; polyarylsulfone; polyolefins such as polyethylene and polypropylene; polyarylate; and a film including at least one of rod-shaped liquid crystal polymers.

In 11.1-10, the second retardation layer is a homopolymer of styrene or a styrene derivative, a polystyrene-based polymer including a copolymer between styrene or a styrene derivative and a comonomer, a polyacrylonitrile polymer, a polymethyl methacrylate copolymer, A coating layer including at least one of cellulose-based copolymers such as cellulose esters may be included.

In 12.1-11, the first retardation layer may have an in-plane retardation of 220 nm to 280 nm at a wavelength of 550 nm, and the second retardation layer may have an in-plane retardation of 85 nm to 145 nm at a wavelength of 550 nm.

In 13.1-12, the polarizer may have an orthogonal light transmittance of 0.001% to 0.7%.

In 14.1-13, the second retardation layer may be directly formed on the first retardation layer.

In steps 15.1-14, a protective layer may be further laminated on the upper surface of the polarizer.

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

The present invention provides a polarizing plate that significantly lowers the side reflectance.

The present invention provides a polarizing plate having a thinning effect and an effect of improving fairness.

1 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.
FIG. 2 shows the slow axis directions of each of the first retardation layer and the second retardation layer in FIG. 1 .
FIG. 3 shows the slow axis directions of the first and second retardation layers with respect to the absorption axis of the polarizer in FIG. 1 .

Hereinafter, embodiments of the present application will be described in more detail with reference to the accompanying drawings. However, the technology disclosed in the present application is not limited to the embodiments described herein and may be embodied in other forms. However, the embodiments introduced herein are provided so that the disclosed content may be thorough and complete, and the spirit of the present application may be sufficiently conveyed to those skilled in the art. In order to clearly express the components of each device in the drawings, the size of the width or thickness of the component is slightly enlarged, and the size of the width or thickness of the component in the present invention is limited to the scope of the present invention. it's not going to be In a plurality of drawings, the same reference numerals refer to substantially the same components.

In this specification, "upper" and "lower" are defined based on the drawings, and depending on the perspective of the city, "upper" may be changed to "lower" and "lower" to "upper", and "on" or What is referred to as “on” may include cases in which other structures are interposed in the middle as well as immediately above. On the other hand, reference to "directly on" or "immediately on" or "directly formed" refers to no intervening other structures such as intermediates.

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

[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, "optical element" means a first retardation layer, a second retardation layer, or a laminate of a first retardation layer and a second retardation layer. In Formulas A to C, "measurement wavelength" may mean a wavelength of 450 nm, 550 nm, or 650 nm.

As used herein, “(meth)acryl” means acrylic and/or methacrylic.

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

When describing a numerical range in the present specification, "X ± Y" means "X + Y" to "X - Y".

The inventor of the present invention laminates a laminate of a first retardation layer and a second retardation layer in which a second retardation layer described below is formed on the first retardation layer described in detail below on the lower surface of the polarizer, and the polarization degree of the polarizer and the single light By setting the transmittance to a specific range, when the polarizing plate is applied to an optical display device, it was confirmed that the side reflectance was significantly lowered in the entire range of 5° to 60° at a polar angle (θ), and the present invention was completed. The inventor of the present invention was able to significantly lower the side reflectance by adjusting the polarization degree and the single light transmittance of the polarizer further in the phase difference control of the retardation layer.

Hereinafter, a polarizing plate according to an embodiment of the present invention will be described with reference to FIGS. 1, 2 and 3 .

Referring to FIG. 1 , the polarizing plate includes a protective layer 400 , a polarizer 300 , a first retardation layer 110 , and a second retardation layer 210 . The protective layer 400 is stacked on the upper surface of the polarizer 300 , and the first retardation layer 110 and the second retardation layer 210 are sequentially stacked on the lower surface of the polarizer 300 . The first retardation layer 110 and the second retardation layer 210 are laminated without an adhesive layer (or an adhesive layer). Through this, the polarizing plate can obtain a thinning effect.

[Laminate body of first retardation layer and second retardation layer]

The laminate of the first retardation layer 110 and the second retardation layer 210 exhibits wavelength dispersion in which the in-plane retardation Re decreases from a long wavelength to a short wavelength. That is, the laminate of the first retardation layer and the second retardation layer exhibits reverse wavelength dispersion. Through this, the polarizing plate can improve the screen quality in terms of application to the optical display device. Specifically, the laminate of the first retardation layer and the second retardation layer may satisfy Equation 1 and Equation 2 below:

[Equation 1]

0.8 ≤ Re(450)/Re(550) < 1.0

[Equation 2]

1.0 < Re(650)/Re(550) ≤ 1.2

(In Equations 1 and 2, Re (450), Re (550), and Re (650) are in-plane retardation at wavelengths of 450 nm, 550 nm, and 650 nm of the stack of the first and second retardation layers, respectively).

For example, in the laminate of the first retardation layer and the second retardation layer, Re(450)/Re(550) may be 0.8 to 0.99, specifically, 0.81 to 0.95. In the laminate of the first retardation layer and the second retardation layer, Re(650)/Re(550) may be greater than 1.0 and less than 1.2, 1.01 to 1.15, specifically 1.04 to 1.13. In the above range, the screen quality can be improved, and the side reflectance can be significantly reduced.

In one embodiment, the laminate of the first retardation layer and the second retardation layer has an in-plane retardation of 140 nm to 200 nm, specifically 140 nm to 195 nm, more specifically 140 nm to 190 nm, more specifically 150 nm to 190 nm at a wavelength of 550 nm. have. In the above range, it is possible to lower the side reflectance.

In one embodiment, the laminate of the first retardation layer and the second retardation layer may have an in-plane retardation of 130 nm to 190 nm, specifically 135 nm to 185 nm, more specifically 140 nm to 180 nm at a wavelength of 450 nm. In the above range, an ideal circular polarization effect can be expected by reaching the above-described wavelength dispersibility, and there can be an effect of preventing the display panel from appearing blue. In one embodiment, the laminate of the first retardation layer and the second retardation layer may have an in-plane retardation of 150 nm to 210 nm, specifically 155 nm to 205 nm, more specifically 160 nm to 200 nm at a wavelength of 650 nm. In the above range, the above-mentioned wavelength dispersion can be reached, and there can be an effect of preventing the display panel from appearing red.

The thickness of the laminate of the first retardation layer and the second retardation layer may be greater than 0 µm and less than or equal to 70 µm, specifically 5 µm to 60 µm, and more specifically 10 µm to 60 µm. Within the above range, it can be used for a polarizing plate.

The second retardation layer is formed directly on the first retardation layer. The "directly formed" means that any adhesive layer, adhesive layer, or adhesive layer is not formed on the second retardation layer and the first retardation layer. The second retardation layer is formed by coating the composition for the second retardation layer on the first retardation layer, drying and/or curing the composition, and then stretching. Therefore, the laminate of the first retardation layer and the second retardation layer is a single-layer film of one sheet type. Through this, in the polarizing plate of the present invention, roll-to-roll lamination is possible when the laminate of the first retardation layer and the second retardation layer is adhered to the polarizer, thereby improving processability and improving the yield due to reduced defects. Although the first retardation layer and the second retardation layer have different retardation from each other, they are directly formed to obtain an effect of reducing the thickness of the polarizing plate and improving processability.

Hereinafter, the first retardation layer and the second retardation layer will be described.

[First phase difference layer]

The first retardation layer 110 exhibits wavelength dispersion in which the in-plane retardation increases from a long wavelength to a short wavelength. That is, the first retardation layer exhibits positive wavelength dispersion. As described above, in the polarizing plate, a first retardation layer having positive wavelength dispersion is formed on a lower surface of the polarizer, and then a second retardation layer having positive wavelength dispersion is laminated on a lower surface of the first retardation layer. Through this, the polarizing plate may improve screen quality when applied to an optical display device.

Specifically, the first retardation layer may satisfy Equation 3 and Equation 4 below:

[Equation 3]

1.0 < Re(450)/Re(550) ≤ 1.1

[Equation 4]

0.9 ≤ Re(650)/Re(550) < 1.0

(In Equations 3 and 4, Re(450), Re(550), and Re(650) are in-plane retardation at wavelengths of 450 nm, 550 nm, and 650 nm of the first retardation layer, respectively).

In one embodiment, Re(450)/Re(550) of the first retardation layer may be greater than 1.0 and less than or equal to 1.05. In one embodiment, Re(650)/Re(550) of the first retardation layer may be 0.95 or more and less than 1.0. In the above range, the effect of reducing front and side reflectance may be excellent.

In one embodiment, the in-plane retardation of the first retardation layer at a wavelength of 550 nm may be 220 nm to 280 nm, specifically 225 nm to 275 nm, and more specifically 230 nm to 270 nm. In the above range, it is possible to lower the side reflectance.

In one embodiment, the first retardation layer may have an in-plane retardation of 220 nm to 280 nm, specifically 225 nm to 275 nm, more specifically 230 nm to 270 nm at a wavelength of 450 nm. In the above range, the above-mentioned wavelength dispersion can be reached, and the front and side reflectance can be lowered. In one embodiment, the first retardation layer may have an in-plane retardation of 220 nm to 280 nm, specifically 225 nm to 275 nm, more specifically 230 nm to 270 nm at a wavelength of 650 nm. In the above range, the above-mentioned wavelength dispersion can be reached, and the front and side reflectance can be lowered.

The first retardation layer has a refractive index relationship of the following Equation 5: Through this, the side reflectance reduction effect of the present invention can be improved:

[Equation 5]

nx > ny ≒ nz

(In Equation 5, nx, ny, and nz are refractive indices in the slow axis direction, fast axis direction, and thickness direction of the first retardation layer at a wavelength of 550 nm, respectively).

In one embodiment, the first retardation layer is a positive A retardation layer. Through this, the side reflectance reduction effect of the present invention can be improved.

The first retardation layer includes a film formed of a composition including a resin having positive intrinsic birefringence. Accordingly, it is possible to easily manufacture the first retardation layer having a refractive index in the stretching direction greater than the refractive index perpendicular to the stretching direction.

Positive intrinsic birefringence resins include polymers having positive intrinsic birefringence. Examples of the polymer having positive intrinsic birefringence include cyclic olefin polymers such as norbornene polymer; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyvinyl alcohol; polyvinyl chloride; polyarylsulfone; polyolefins such as polyethylene and polypropylene; polyarylate; It may include one or more kinds of rod-shaped liquid crystal polymers. Specifically, polycarbonate excellent in retardation expression and elongation at low temperatures, and polyolefin-based and cyclic olefin-based copolymers excellent in mechanical properties, heat resistance, transparency, and dimensional stability are preferable. Polymers having a positive intrinsic birefringence may be included alone or as a mixture of two or more.

The first retardation layer may further include a conventional additive in addition to the resin having a positive intrinsic birefringence. For example, additives may include, but are not limited to, pigments, coloring inhibitors such as dyes, heat stabilizers, light stabilizers, UV absorbers, antistatic agents, antioxidants, particulates, surfactants, and the like.

The slow axis direction of the first retardation layer is oriented in an oblique direction with respect to the transverse direction (TD) of the stack of the first retardation layer and the second retardation layer. The "slanted direction" refers to a direction in a plane of the first retardation layer, which is neither parallel nor perpendicular to the width direction of the stack of the first retardation layer and the second retardation layer. Since the slow axis direction of the first retardation layer is oriented in the oblique direction compared to the TD of the laminate of the first retardation layer and the second retardation layer, the roll-to-roll method of lamination with the polarizer is possible, so the yield may not decrease .

In one embodiment, referring to FIG. 2 , the slow axis direction SA ₁₁₀ of the first retardation layer 110 compared to the TD of the stack of the first retardation layer 110 and the second retardation layer 210 is 70° ± 10°, specifically 70° ± 5°, more specifically 70° ± 3°. In the above range, there may be an effect of reducing frontal and side reflections.

The first retardation layer 110 may have a thickness of 5 μm to 100 μm, specifically 5 μm to 60 μm. Within the above range, it can be used for a polarizing plate.

The first retardation layer may be prepared by preparing an unstretched film by melt-molding, injection-molding, or press-molding the composition containing the resin having a positive intrinsic birefringence as described above, and stretching the unstretched film in an oblique direction. The draw ratio may be 1.1 times or more, 4.0 times or less, specifically 1.3 times or more and 3.0 times or less. Within the above range, the slow axis direction of the first retardation layer can be controlled, and the refractive index in the stretching direction can be increased. The stretching temperature may be a glass transition temperature (Tg) of the unstretched film + 2°C or more, and Tg + 30°C or less. The stretching direction may be smaller than the angle formed by the slow axis direction of the first retardation layer compared to the TD of the laminate of the first retardation layer and the second retardation layer compared to the width direction of the unstretched film. For example, the stretching direction may be greater than 15° and less than 50°, specifically greater than 17° and less than 48°, compared to the TD of the unstretched film.

The first retardation layer may be included in the polarizing plate as the first retardation layer itself, but by further forming a primer layer on the first retardation layer, the adhesion between the first retardation layer and the second retardation layer may be increased. The primer layer may include at least one of an acrylic resin, a urethane resin, an acrylic urethane resin, an ester resin, and an ethylene imine resin, but is not limited thereto.

[2nd phase difference layer]

The second retardation layer 210 exhibits wavelength dispersion in which the in-plane retardation increases from a long wavelength to a short wavelength. That is, the second retardation layer exhibits positive wavelength dispersion. Through this, the polarizing plate may improve screen quality when applied to an optical display device. Specifically, the second retardation layer may satisfy Equation 6 and Equation 7 below:

[Equation 6]

1.0 < Re(450)/Re(550) ≤ 1.2

[Equation 7]

0.9 ≤ Re(650)/Re(550) < 1.0

(In Equations 6 and 7, Re(450), Re(550), and Re(650) are in-plane retardation at wavelengths of 450 nm, 550 nm, and 650 nm of the second retardation layer, respectively).

In one embodiment, Re(450)/Re(550) of the second retardation layer may be 1.05 to 1.15, more specifically, 1.1 to 1.15. In one embodiment, Re(650)/Re(550) of the second retardation layer may be greater than 0.9 and less than or equal to 0.95. In the above range, the effect of reducing front and side reflectance may be excellent.

In one embodiment, the second retardation layer may have an in-plane retardation of 85 nm to 145 nm, specifically 90 nm to 140 nm, more specifically 95 nm to 135 nm at a wavelength of 550 nm. In the above range, it is possible to significantly lower the frontal and side reflectance.

In one embodiment, the second retardation layer may have an in-plane retardation of 100 nm to 160 nm, specifically 105 nm to 155 nm, more specifically 110 nm to 150 nm at a wavelength of 450 nm. In the above range, the above-mentioned wavelength dispersion can be reached, and there can be an effect of reducing front and side reflectance. In one embodiment, the second retardation layer may have an in-plane retardation of 80 nm to 140 nm, specifically 85 nm to 135 nm, more specifically 90 nm to 130 nm at a wavelength of 650 nm. In the above range, the above-mentioned wavelength dispersion can be reached, and there can be an effect of reducing front and side reflectance.

The second retardation layer has a refractive index relationship of Equation 8: Through this, the side reflectance reduction effect of the present invention can be improved:

[Equation 8]

nx ≒ nz > ny

(In Equation 8, nx, ny, and nz are refractive indices in the slow axis direction, fast axis direction, and thickness direction of the second retardation layer, respectively, at a wavelength of 550 nm).

In one embodiment, the second retardation layer is a negative A retardation layer. Through this, the side reflectance reduction effect of the present invention can be improved.

The second retardation layer is formed of a composition including a resin having a negative intrinsic birefringence.

Resins with negative intrinsic birefringence include polymers with negative intrinsic birefringence. Polymers with negative intrinsic birefringence include, for example, homopolymers of styrene or styrene derivatives, polystyrene-based polymers including copolymers between styrene or styrene derivatives and comonomers, polyacrylonitrile polymers, polymethylmethacrylate copolymers, cellulose esters. It may include at least one of cellulosic copolymers such as, but is not limited thereto. The comonomer may include at least one of acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene. Specifically, preferably, the second retardation layer may include at least one of a polystyrene-based polymer and a cellulosic copolymer, and more preferably, a polystyrene-based polymer.

The second retardation layer may further include a conventional additive in addition to a resin having a negative intrinsic birefringence. For example, additives may include, but are not limited to, plasticizers, pigments, color inhibitors such as dyes, heat stabilizers, light stabilizers, UV absorbers, antistatic agents, antioxidants, particulates, surfactants, and the like.

The slow axis direction of the second retardation layer is oriented in an oblique direction relative to the transverse direction (TD) of the stack of the first retardation layer and the second retardation layer. The “slanted direction” refers to a direction in a plane of the second retardation layer that is neither parallel nor perpendicular to the width direction of the stack of the first retardation layer and the second retardation layer. Since the slow axis direction of the second retardation layer is oriented in the oblique direction compared to the width direction of the laminate of the first retardation layer and the second retardation layer, the roll-to-roll method of lamination with the polarizer is possible, so the yield may not decrease have.

In one embodiment, referring to FIG. 2 , the slow axis direction SA ₂₁₀ of the second retardation layer 210 compared to the TD of the stack of the first retardation layer 110 and the second retardation layer 210 is 0° ± 20° (excluding 0°), specifically 0° ± 10° (excluding 0°), more specifically 0° ± 5° (excluding 0°) have. In the above range, there may be an effect of improving the front reflectance.

The second retardation layer may have a thickness direction retardation of -110 nm to -50 nm, specifically -105 nm to -60 nm, more specifically -100 nm to -70 nm at a wavelength of 550 nm. In the above range, there may be an effect of improving the front reflectance and the side reflectance.

The second retardation layer may have a degree of biaxiality of -1.0 to 0.5 at a wavelength of 550 nm. In the above range, there may be an effect of improving the front reflectance and the side reflectance.

The second retardation layer may have a thickness of 2 μm to 15 μm, specifically 3 μm to 10 μm. Within the above range, it can be used for a polarizing plate.

The second retardation layer is a coating layer formed of a composition including a resin having a negative intrinsic birefringence.

The laminate of the first retardation layer and the second retardation layer may be manufactured by coating the composition for the second retardation layer on the first retardation layer, drying the composition, and then simultaneously stretching the first retardation layer. Through the stretching, the direction of the slow axis of the first retardation layer is adjusted, the direction of the slow axis of the second retardation layer appears, and the target retardation of the first retardation layer and the second retardation layer may be realized.

Specifically, the stretching may be 0°±20°, specifically 0°±15°, more specifically 5°±15° with respect to the TD of the first retardation layer and the coating layer. Most preferably, the first retardation layer and the coating layer may be stretched at 90° with respect to the TD, that is, in the longitudinal direction. In this case, the slow axis directions of the first retardation layer and the second retardation layer can be easily controlled. The draw ratio may be 1.1 times to 2.0 times, specifically 1.2 times to 1.8 times.

[Polarizer]

The polarizer 300 may be laminated on the upper surface of the first retardation layer to linearly polarize external light or light incident from the first retardation layer, thereby lowering the reflectance from the side.

The polarizer 300 may have a polarization degree of 99% or more and a single light transmittance Ts of 44% or more. The polarizer satisfies the polarization degree and the single light transmittance at the same time, so that when stacked on the above-described first and second retardation layer laminate, the side reflectance can be significantly lowered, especially in the entire polar angle (θ) 5° to 60° range. have. The "single light transmittance" means a single light transmittance (Ts) measured in a visible light region, for example, a wavelength of 400 nm to 700 nm, and may be measured by a conventional method known to those skilled in the art.

The "polarization degree" can be measured by a conventional method known to those skilled in the art. Specifically, the degree of polarization may be 99% to 99.9999%, and the light transmittance may be 44% to 50%.

The polarizer 300 may have an orthogonal light transmittance (Tc) of 0.001% to 0.7%, specifically 0.01% to 0.2%, and more specifically 0.05% to 0.2% at a wavelength of 380 nm to 780 nm. In the above range, there may be an anti-reflection effect in the entire range of the side, particularly the polar angle (θ) 5° to 60°.

The polarizer 300 is laminated in a roll-to-roll manner on the laminate of the first retardation layer and the second retardation layer. Accordingly, the laminate of the first retardation layer and the second retardation layer functions as a lower protective film of the polarizer, and there is no need to laminate a separate protective film on the lower surface of the polarizer, thereby reducing the thickness of the polarizing plate.

Referring to FIG. 3 , the slow axis direction SA _{110 of the first retardation layer 110} and the slow axis direction SA ₂₁₀ of the second retardation layer 210 intersect each other, and the absorption axis of the polarizer 300 ( The angle formed by the slow axis direction (SA ₁₁₀ ) of the first retardation layer 110 with respect to A ₃₀₀ is 10° to 30°, specifically 15° to 30°, and the absorption axis (A ₃₀₀ ) of the polarizer 300 ). The angle formed by the slow axis direction SA ₂₁₀ of the second retardation layer 210 with respect to may be 70° to 90°, specifically 80° to 90°, and more specifically 80° or more and less than 90°. In the above range, there may be an effect of reducing the front reflectance.

The absorption axis of the polarizer is the MD (machine direction) of the polarizer, and may be a stretching direction when the polarizer is manufactured.

The polarizer 300 may have a thickness of 5 μm to 40 μm. Within the above range, it can be used for a polarizing plate.

The polarizer 300 may include a polyvinyl alcohol-based polarizer manufactured by uniaxially stretching a polyvinyl alcohol-based film, or a polyene-based polarizer manufactured by dehydrating a polyvinyl alcohol-based film.

In one embodiment, the polarizer may be manufactured by dyeing a polyvinyl alcohol-based film, stretching, crosslinking, and color correction. A polarizer having the above-described degree of polarization and light transmittance at the same time can be achieved by appropriately changing conditions in the above-described dyeing, stretching, crosslinking, and color correction processes.

Although not shown in FIG. 1 , an adhesive layer, an adhesive layer or an adhesive layer, or a protective layer to be described in detail below may be further formed between the polarizer 300 and the first retardation layer 110 .

[protective layer]

The protective layer 400 may be laminated on the upper surface of the polarizer to protect the polarizer. The protective layer may protect the polarizing film to increase reliability of the polarizing plate and increase mechanical strength of the polarizing plate.

The protective layer 400 may include one or more of an optically transparent, protective film, or protective coating layer. The protective film is a cellulose ester-based resin containing triacetylcellulose (TAC), etc., a cyclic polyolefin-based resin containing amorphous cyclic polyolefin (COP), etc., a polycarbonate-based resin, polyethylene terephthalate (PET), etc. 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, polymethyl methacrylate resins, and the like It may include a film formed of at least one of a resin, polyvinyl alcohol-based resin, polyvinyl chloride-based resin, and polyvinylidene chloride-based resin, but is not limited thereto. The protective coating layer may be formed of an active energy ray-curable resin composition including 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 radical polymerizable curable compound, a urethane resin, and a silicone-based resin.

Although not shown in FIG. 1 , a functional coating layer may be additionally formed on the upper surface of the protective layer. The functional coating layer may include at least one of 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, but is not limited thereto.

Although not shown in FIG. 1 , an adhesive layer is further formed on the lower surface of the second retardation layer, so that the polarizing plate can be laminated on the optical display device.

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

The polarizing plate includes a protective layer, a polarizer, a first retardation layer, and a second retardation layer. A protective layer is stacked on an upper surface of the polarizer, and a first retardation layer and a second retardation layer are sequentially stacked on a lower surface of the polarizer. In the polarizing plate of FIG. 1 , it is substantially the same as the polarizing plate of the embodiment of the present invention, except that the first and second retardation layers described below are stacked instead of the first and second retardation layers.

The first retardation layer and the second retardation layer are the same as those described in FIG. 1 except for the details described below.

In one embodiment, the slow axis direction of the first retardation layer compared to the TD of the laminate of the first retardation layer and the second retardation layer 220 is 22.5°±15°, specifically 22.5°±10°, more specifically 22.5 ° ± 5°. In the above range, there may be an effect of increasing circular polarization.

In one embodiment, the slow axis direction of the second retardation layer relative to the TD of the laminate of the first retardation layer and the second retardation layer is 90°±25°, specifically 90°±20°, more specifically 90°±10 ° can be Within the above range, there may be an effect of increasing circular polarization.

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

The optical display device of the present invention may include at least one of the polarizing plates of the present invention. In an embodiment, the optical display device may include a liquid crystal display device, a light emitting device display device, preferably a light emitting device display device, and the like. The liquid crystal display may include a liquid crystal display having a liquid crystal for In Place Switching (IPS). The light-emitting device display device includes an organic or organic-inorganic light-emitting device, for example, a light emitting material such as a light emitting diode (LED), an organic light emitting diode (OLED), a quantum dot light emitting diode (QLED), or a phosphor. It may mean a light emitting device that

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, the following examples are provided to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example One

A polarizer (thickness: 12 μm) was prepared by stretching the polyvinyl alcohol film 3 times at 60° C., adsorbing iodine, and then stretching it 2.5 times in an aqueous boric acid solution at 40° C. Single light transmittance and orthogonal light transmittance of the polarizer were measured at a wavelength of 380 nm to 780 nm using a spectrophotometer V-7100 manufactured by JASCO. The degree of polarization of the polarizer was measured using JASCO's V-7100.

A triacetyl cellulose (TAC) film (KA25-HC, Konica Minolta Opto, Inc., thickness: 32 μm) having a hard coating layer was adhered to the upper surface of the polarizer.

On the lower surface of the polarizer, a first retardation layer [static wavelength dispersion, +A plate, polyolefin-based, Re(450)=253nm, Re(550)=251nm, Re(650)=250nm] and a second retardation layer [ One-sheet film [reverse wavelength dispersion, Re (450) / Re (550) = 0.91, Re (650) / Re (550) = 1.06] by adhering to a triacetyl cellulose (TAC) film with a hard coating layer - polarizer - first retardation layer - second retardation A polarizing plate in which the layers were sequentially stacked was prepared.

The one-sheet film is prepared by obliquely stretching a resin containing a polyolefin-based copolymer at a predetermined draw ratio, and coating a polystyrene-based copolymer on one side of the diagonally stretched polyolefin-based copolymer film to prepare a laminate, and the laminate is a film prepared by stretching again at a predetermined stretching ratio.

Example 2 to Example 3

In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that a film having the specifications of Table 1 below was used as the single-sheet film, or the polarization degree and light transmittance of the polarizer were changed as shown in Table 1 below. did.

comparative example One

In Example 2, in the same manner as in Example 2, except that a film having the specifications of Table 1 below was used as the single-sheet film, and a polarizer having a polarization degree of 98.0% and a light transmittance of 44.5% was used. A polarizing plate was manufactured.

comparative example 2

In Example 2, in the same manner as in Example 2, except that a film having the specifications shown in Table 1 below was used as the single-sheet film, and a polarizer having a polarization degree of 99.0% and a light transmittance of 43.5% was used. A polarizing plate was manufactured.

Specific specifications of the polarizing plates of Examples and Comparative Examples are shown in Table 1 below.

polarizer phase contrast laminate orientation angle Angle (°) between the absorption axis of the polarizer and the slow axis of the first retardation layer Angle (°) between the absorption axis of the polarizer and the slow axis of the second retardation layer Polarization degree
(%) single light
transmittance
(Ts, %) orthogonal light
transmittance
(Tc, %) Re(550)
(nm) Example 1 99.5 44.5 0.20 150 70 20 84 Example 2 99.5 44.5 0.20 170 70 20 84 Example 3 99.5 44.5 0.20 190 70 20 84 Comparative Example 1 98.0 44.5 0.35 170 70 20 84 Comparative Example 2 99.0 43.5 0.25 170 70 20 84

*Orientation angle: an angle between the slow axis direction of the first retardation layer and the width direction (TD) of the stack of the first retardation layer and the second retardation layer.

The reflectance (unit: %) according to the side angle of the polarizing plates prepared in Examples and Comparative Examples was evaluated, and the results are shown in Table 2 below. The reflectance is SCE (specular component excluded) reflectance data measured by DMS803 (Instrument Systems, Germany) equipment by attaching the polarizing film of Table 1 to the Galaxy S7 panel.

Viewing angle (°) 5 10 20 30 40 50 60 Example 1 0.36 0.36 0.39 0.47 0.60 0.81 0.99 Example 2 0.33 0.34 0.36 0.43 0.57 0.76 0.93 Example 3 0.39 0.39 0.42 0.50 0.65 0.86 1.03 Comparative Example 1 0.48 0.48 0.51 0.58 0.72 0.91 1.06 Comparative Example 2 0.45 0.45 0.50 0.56 0.70 0.91 1.06

As shown in Table 2, the polarizing plate of the present invention significantly lowered the side reflectance.

On the other hand, Comparative Example 1, in which the polarization degree of the polarizer was less than 99.0%, had a side reflectance higher than that of the Example, and although not shown in Table 2, the front reflectance was higher than that of the Example. Comparative Example 2, in which the transmittance of the polarizer was less than 44%, also had a high side reflectance compared to the Example, and although not shown in Table 2, the frontal reflectance was also high compared to the Example.

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 (16)

polarizer; and a first retardation layer and a second retardation layer sequentially stacked on the lower surface of the polarizer,
The first retardation layer has a positive wavelength dispersion, and has a refractive index relationship of Equation 5 below:
[Equation 5]
nx > ny ≒ nz
(In Equation 5, nx, ny, and nz are refractive indices in the slow axis direction, fast axis direction, and thickness direction of the first retardation layer at a wavelength of 550 nm, respectively),
The second retardation layer has a positive wavelength dispersion and has a refractive index relationship of Equation 8:
[Equation 8]
nx ≒ nz > ny
(in Equation 8, nx, ny, and nz are refractive indices in the slow axis direction, fast axis direction, and thickness direction of the second retardation layer at a wavelength of 550 nm, respectively),
In the first retardation layer, the slow axis direction of the first retardation layer is oriented in an oblique direction compared to the width direction (TD) of the stack of the first retardation layer and the second retardation layer,
The laminate of the first retardation layer and the second retardation layer has reverse wavelength dispersion,
The polarizer has a polarization degree of 99% or more, and a single light transmittance (Ts) of 44% or more, a polarizing plate.
The polarizing plate according to claim 1, wherein the laminate of the first retardation layer and the second retardation layer is a one-sheet film.
The polarizing plate of claim 1, wherein the laminate of the first retardation layer and the second retardation layer has an in-plane retardation (Re) of 140 nm to 200 nm at a wavelength of 550 nm.
The polarizing plate according to claim 1, wherein the laminate of the first retardation layer and the second retardation layer satisfies the following Equations 1 and 2:
[Equation 1]
0.8 ≤ Re(450)/Re(550) < 1.0
[Equation 2]
1.0 < Re(650)/Re(550) ≤ 1.2
(In Equations 1 and 2, Re (450), Re (550), and Re (650) are in-plane retardation at wavelengths of 450 nm, 550 nm, and 650 nm of the stack of the first and second retardation layers, respectively).
The polarizing plate of claim 1, wherein the slow axis direction of the first retardation layer is 70°±10° compared to the TD of the stack of the first retardation layer and the second retardation layer.
The method according to claim 5, wherein the slow axis direction of the second retardation layer is 0°±20° (except 0°) compared to the TD of the stack of the first retardation layer and the second retardation layer. , polarizer.
The polarizing plate according to claim 1, wherein an angle formed by the slow axis direction of the first retardation layer with respect to the absorption axis of the polarizer is 10° to 30°.
The polarizing plate according to claim 1, wherein an angle formed by the slow axis direction of the second retardation layer with respect to the absorption axis of the polarizer is 70° to 90°.
The polarizing plate of claim 1 , wherein the first retardation layer is a positive A retardation layer, and the second retardation layer is a negative A retardation layer.
According to claim 1, wherein the first retardation layer is a cyclic olefin polymer such as norbornene polymer; polyesters such as polyethylene terephthalate and polybutylene terephthalate; polyvinyl alcohol; polyvinyl chloride; polyarylsulfone; polyolefins such as polyethylene and polypropylene; polyarylate; A polarizing plate comprising a film comprising at least one of rod-shaped liquid crystal polymers.
According to claim 1, wherein the second retardation layer is a homopolymer of styrene or a styrene derivative, a polystyrene-based polymer comprising a copolymer between styrene or a styrene derivative and a comonomer, a polyacrylonitrile polymer, a polymethyl methacrylate copolymer , A polarizing plate comprising a coating layer comprising at least one of cellulose-based copolymers such as cellulose esters.
The polarizing plate of claim 1, wherein the first retardation layer has an in-plane retardation of 220 nm to 280 nm at a wavelength of 550 nm, and the second retardation layer has an in-plane retardation of 85 nm to 145 nm at a wavelength of 550 nm.
The polarizing plate of claim 1, wherein the polarizer has an orthogonal light transmittance of 0.001% to 0.7%.
The polarizing plate of claim 1 , wherein the second retardation layer is formed directly on the first retardation layer.
The polarizing plate according to claim 1, wherein a protective layer is further laminated on the upper surface of the polarizer.
An optical display device comprising the polarizing plate of any one of claims 1 to 15.

Images