TWI744819B - Polarizing plate and optical display apparatus comprising the same - Google Patents

Abstract

A polarizing plate and an optical display apparatus. The polarizing plate includes a polarizer; and a first retardation layer and a second retardation layer sequentially stacked on a lower surface of the polarizer. The first retardation layer has regular wavelength dispersion characteristics and satisfies a relationship between indexes of refraction as represented by Relation 5. The second retardation layer has regular wavelength dispersion characteristics and satisfies a relationship between indexes of refraction as represented by Relation 8. The definition of Relation 5 and Relation 8 are the same as in detailed description.

Description

Polarizing plate and optical display device including the same

The invention relates to a polarizing plate and an optical display device including the polarizing plate. More specifically, the present invention relates to a polarizing plate and an optical display device including the same. The polarizing plate can achieve a significant reduction in frontal reflectance and side reflectance on its side surface, especially at 5° to The entire range of the polar angle (θ) of 60°.

[Cross reference of related applications]

This application claims the rights of Korean Patent Application No. 10-2019-0028393 filed with the Korean Intellectual Property Office on March 12, 2019, and the entire disclosure of the Korean patent application is incorporated into this case for reference.

An organic electroluminescent (EL) panel includes a metal electrode layer with high reflectivity. Therefore, the organic EL panel suffers from visibility degradation due to reflection of external light. This degradation of visibility can be improved by attaching a circular polarizer to the organic EL panel.

Generally speaking, the circular polarizer is made by attaching a quarter retarder to the polarizer. manufacture. When applied to polarizers, cyclic olefin polymer (COP) retarders have the problem of reflection color difference due to their flat wavelength dispersion characteristics. Among them, the retardation of COP retarders is substantially constant. It does not depend on the wavelength of the detected light. In order to solve this shortcoming of flat wavelength dispersion characteristics, a circular polarizing plate including a polycarbonate (PC) resin retardation film with reverse wavelength dispersion characteristics is proposed. The retardation of the PC resin retardation film is based on the investigation. The wavelength of the metering increases. However, although such a circular polarizing plate can achieve a significant improvement in the reflection of external light and the reflected color in the front direction of the display panel including the circular polarizing plate, when viewed in an oblique direction, the display panel will provide the same direction from the front. The color when viewed on top is different from the color, which leads to the problem of chromatic aberration.

The background art of the present invention is disclosed in Korean Patent Publication No. 10-2016-0107114 and others.

An object of the present invention is to provide a polarizing plate capable of achieving a significant reduction in side reflectance.

Another object of the present invention is to provide a polarizing plate capable of ensuring a reduction in thickness and an improvement in handleability.

One aspect of the present invention relates to a polarizing plate.

The polarizing plate includes a polarizer; and a first retardation layer and a second retardation layer are sequentially stacked on the lower surface of the polarizer, wherein the first retardation layer has regular wavelength dispersion characteristics and satisfies the relationship represented by relation 5. The relationship between the refractive index: nx>ny≒nz, ---(5) where nx, ny and nz are respectively the slow axis direction, the fast axis direction and the thickness of the first retardation layer at a wavelength of 550 nanometers The refractive index in the direction; wherein the second retardation layer has regular wavelength dispersion characteristics, and satisfies the relationship between the refractive index represented by the relationship 8: nx≒nz>ny, ---(8) where nx, ny And nz are the refractive indices of the second retardation layer in the slow axis direction, the fast axis direction, and the thickness direction of the second retardation layer at a wavelength of 550 nanometers, respectively; and wherein all of the first retardation layer The slow axis direction is inclined with respect to the transverse direction (TD) of the laminate of the first retardation layer and the second retardation layer, and the laminate of the first retardation layer and the second retardation layer The body has reverse wavelength dispersion characteristics, and the polarizer has a polarization degree of 99% or more and a single transmittance (Ts) of 44% or more.

The laminated body of the first retardation layer and the second retardation layer may be a monolithic film.

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

其中Re(450)、Re(550)及Re(650)分別為所述第一延遲層及所述第二延遲層的所述積層體在450奈米、550奈米及650奈米波長下的面內延遲值。 The laminate of the first retardation layer and the second retardation layer may satisfy Relation 1 and Relation 2:

Wherein Re(450), Re(550), and Re(650) are the values of the laminate of the first retardation layer and the second retardation layer at wavelengths of 450 nm, 550 nm, and 650 nm, respectively. In-plane delay value.

The slow axis direction of the first retardation layer may be inclined at an angle of 70°±10° with respect to the lateral direction of the laminate of the first retardation layer and the second retardation layer.

The slow axis direction of the second retardation layer may be 0°±20° (not including 0°) with respect to the lateral direction of the laminate of the first retardation layer and the second retardation layer The angle is tilted.

The angle defined between the absorption axis of the polarizer and the slow axis direction of the first retardation layer may be in the range of 10° to 30°.

The angle defined between the absorption axis of the polarizer and the slow axis direction of the second retardation layer may be in the range of 70° to 90°.

The first retardation layer may be a positive A retardation layer, and the second retardation layer may be a negative A retardation layer.

The first retardation layer may include a film, the film comprising selected from cycloolefin polymers, such as norbornene polymers, etc.; polyester, such as polyethylene terephthalate, polybutylene terephthalate Etc.; polyvinyl alcohol; polyvinyl chloride; polyarylene; polyolefin resin, such as polyethylene, polypropylene, etc.; polyarylate; and at least one of the group consisting of rod-shaped liquid crystal polymer.

The second retardation layer may include a coating, the coating including selected from the group consisting of styrene Homopolymers of olefin or styrene derivatives, polystyrene polymers including copolymers of styrene or styrene derivatives and comonomers, polyacrylonitrile polymers, poly(methyl methacrylate) copolymers and For example, at least one of the group consisting of cellulose copolymers such as cellulose ester.

The first retardation layer may have an in-plane retardation value of 220 nm to 280 nm at a wavelength of 550 nm, and the second retardation layer may have an in-plane retardation value of from 85 nm to 145 nm at a wavelength of 550 nm. The in-plane delay value in meters.

The polarizer may have a cross light transmittance of 0.001% to 0.7%.

The second retardation layer may be directly formed on the first retardation layer.

The polarizing plate may further include a protective layer formed on the upper surface of the polarizer.

Another aspect of the present invention relates to an optical display device including the polarizing plate according to the present invention as described above.

The present invention provides a polarizing plate capable of achieving a significant reduction in side reflectance.

The present invention provides a polarizing plate capable of ensuring a reduction in thickness and an improvement in handleability.

110: The first delay layer

210: second retardation layer

300: Polarizer

400: protective layer

A ₃₀₀ : Absorption shaft

MD: machine direction

SA ₁₁₀ , SA ₂₁₀ : Slow axis direction

TD: horizontal direction

Fig. 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 the first retardation layer and the second retardation layer of the polarizing plate shown in FIG. 1.

Fig. 3 shows the first retardation of the polarizing plate with respect to the absorption axis of the polarizer in Fig. 1 The direction of the slow axis of the second retardation layer and the second retardation layer.

Hereinafter, embodiments of the present invention will be explained in detail with reference to the accompanying drawings, so that those skilled in the art can easily implement the present invention. It should be understood that the present invention can be implemented in different ways and is not limited to the following embodiments. Although the thickness or width of various components may be exaggerated in the drawings for understanding, it should be understood that the present invention is not limited thereto. In all the drawings, the same components will be designated by the same reference numbers.

In this article, spatially relative terms such as "upper" and "lower" are defined with reference to the accompanying drawings. Therefore, it will be understood that the term "upper surface" can be used interchangeably with the term "lower surface", and when it is said that an element such as a layer or film is placed "on" another element, the element can be placed directly on the other element. On the element, or there may be intermediate elements. On the other hand, when a component is said to be placed “directly” on another component, there is no intermediate component in between.

In this article, "in-plane delay (Re)" is expressed by equation A, "out-of-plane delay Rth" is expressed by equation B, and "biaxiality NZ" is expressed by equation C: Re=(nx-ny)×d,- --(A) Rth=((nx+ny)/2-nz)×d, ---(B) NZ=(nx-nz)/(nx-ny), ---(C) where nx, ny and nz are the refractive indices of the optical device in the slow axis direction, the fast axis direction, and the thickness direction of the optical device at the measurement wavelength, and d is the thickness of the optical device (unit: nanometer).

In Equation A to Equation C, "optical device" means the first retardation layer, The second retardation layer or a laminate of the first retardation layer and the second retardation layer. In Equation A to Equation C, "measurement wavelength" can refer to a wavelength of 450 nm, 550 nm or 650 nm.

Here, "(meth)acrylic group" means acrylic group and/or methacrylic group.

且

Y)」。 As used herein, the expression "X to Y" used to indicate a specific numerical range means "greater than or equal to X and less than or equal to Y (X

and

Y)".

As used herein, "X±Y" used to indicate a specific numerical range means "X+Y" to "X-Y".

The inventors of the present invention have confirmed that when applied to an optical display device, the following first retardation layer and second retardation layer are stacked on a polarizer whose polarization degree and single transmittance are within a specific range. The polarizing plate formed on the lower surface can achieve a significant reduction in side reflectance on its side surface, especially in the entire range of the polar angle (θ) of 5° to 60°. The inventors of the present invention achieved a significant reduction in side reflectance by adjusting the retardation of the retardation layer and the polarization degree and single transmittance of the polarizer together.

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

Referring to FIG. 1, a polarizing plate according to an embodiment of the present invention 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 is stacked on the first On the second retardation layer 210, there is no adhesion layer (or adhesion layer) between the two retardation layers. With this structure, the thickness of the polarizing plate can be reduced.

[Layered body of the first retardation layer and the second retardation layer]

其中Re(450)、Re(550)及Re(650)分別為所述第一延遲層及所述第二延遲層的所述積層體在450奈米、550奈米及650奈米波長下的面內延遲值。 例如，第一延遲層及第二延遲層的積層體可具有0.8至0.99、具體而言為0.81至0.95的Re(450)/Re(550)。第一延遲層及第二延遲層的積層體可具有大於1.0至小於1.2、1.01至1.15、具體而言為1.04至1.13的Re(650)/Re(550)。在此範圍內，偏光板可達成螢幕品質的改善及側面反射率的顯著降低。 在一個實施例中，第一延遲層及第二延遲層的積層體在550奈米的波長下可具有140奈米至200奈米(例如140奈米、150奈米、160奈米、170奈米、180奈米、190奈米或200奈米)、具 體而言為140奈米至195奈米、更具體而言為140奈米至190奈米、再更具體而言為150奈米至190奈米的面內延遲值。在此範圍內，偏光板可達成側面反射率的降低。 The laminate of the first retardation layer 110 and the second retardation layer 210 exhibits a wavelength dispersion characteristic in which the in-plane retardation (Re) value gradually decreases as the wavelength decreases from a longer wavelength to a shorter wavelength. That is, the laminate of the first retardation layer and the second retardation layer exhibits reverse wavelength dispersion characteristics. As a result, when applied to an optical display device, the polarizing plate can achieve an improvement in the screen quality on its side surface. Specifically, the laminate of the first retardation layer and the second retardation layer can satisfy Relation 1 and Relation 2:

Wherein Re(450), Re(550), and Re(650) are the values of the laminate of the first retardation layer and the second retardation layer at wavelengths of 450 nm, 550 nm, and 650 nm, respectively. In-plane delay value. For example, the laminate of the first retardation layer and the second retardation layer may have Re(450)/Re(550) of 0.8 to 0.99, specifically 0.81 to 0.95. The laminate of the first retardation layer and the second retardation layer may have Re(650)/Re(550) greater than 1.0 to less than 1.2, 1.01 to 1.15, specifically 1.04 to 1.13. Within this range, the polarizing plate can achieve an improvement in screen quality and a significant reduction in side reflectivity. In one embodiment, the laminate of the first retardation layer and the second retardation layer may have a wavelength of 140 nm to 200 nm (for example, 140 nm, 150 nm, 160 nm, 170 nm) at a wavelength of 550 nm. Meters, 180 nanometers, 190 nanometers or 200 nanometers), specifically 140 nanometers to 195 nanometers, more specifically 140 nanometers to 190 nanometers, and more specifically 150 nanometers to In-plane retardation value of 190nm. Within this range, the polarizing plate can achieve a reduction in side reflectivity.

In another embodiment, the laminated body of the first retardation layer and the second retardation layer may have 130 nm to 190 nm, specifically 135 nm to 185 nm, at a wavelength of 450 nm. In terms of the in-plane retardation value from 140nm to 180nm. Within this range, the polarizing plate can exhibit the above-mentioned wavelength dispersion characteristics, thereby providing an ideal circular polarization effect while preventing the display panel from appearing blue. In an embodiment, the laminate of the first retardation layer and the second retardation layer may have a wavelength of 150 nm to 210 nm, specifically 155 nm to 205 nm, and more specifically, at a wavelength of 650 nm. It is the in-plane retardation value from 160nm to 200nm. Within this range, the polarizing plate can exhibit the aforementioned wavelength dispersion characteristics and can prevent the display panel from appearing red.

The laminate of the first retardation layer and the second retardation layer may have a thickness greater than 0 micrometers to 70 micrometers or less than 70 micrometers, specifically 5 micrometers to 60 micrometers, more specifically 10 micrometers to 60 micrometers. Within this thickness range, the laminate can be used in polarizing plates.

The second retardation layer is formed directly on the first retardation layer. Here, the expression "directly formed" means that no adhesion layer, adhesion layer or adhesion/adhesion layer is formed between the second retardation layer and the first retardation layer. The second retardation layer is formed by depositing a 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 monolithic monolayer film. With this structure, the laminate of the first retardation layer and the second retardation layer is bonded to the bias In the case of optical devices, the polarizing plate allows roll-to-roll bonding, thereby improving the handleability and production yield by reducing the defect rate. Although the first retardation layer and the second retardation layer have different retardation values, the first retardation layer is directly formed on the second retardation layer, so that the thickness can be reduced and the handleability of the polarizing plate can be improved.

Next, the first retardation layer and the second retardation layer will be explained.

[First retardation layer]

The first retardation layer 110 exhibits a wavelength dispersion characteristic in which the in-plane retardation (Re) value gradually increases as the wavelength decreases from a longer wavelength to a shorter wavelength. That is, the first retardation layer exhibits regular wavelength dispersion characteristics. In this way, the polarizing plate is manufactured by forming a first retardation layer having regular wavelength dispersion characteristics on the lower surface of the polarizer and forming a second retardation layer having regular wavelength dispersion characteristics on the lower surface of the first retardation layer. With this structure, the polarizing plate can improve the screen quality of the optical display device including the polarizing plate.

其中Re(450)、Re(550)及Re(650)分別為第一延遲層在450奈米、550奈米及650奈米波長下的面內延遲值。 Specifically, the first retardation layer can satisfy Relation 3 and Relation 4:

Among them, Re(450), Re(550) and Re(650) are the in-plane retardation values of the first retardation layer at wavelengths of 450nm, 550nm and 650nm, respectively.

In one embodiment, the first retardation layer may have Re(450)/Re(550) greater than 1.0 to 1.05 or less than 1.05. In another embodiment, the first retardation layer may have Re(650)/Re(550) of 0.95 or greater than 0.95 to less than 1.0. Within this range, the polarizing plate can achieve a significant reduction in front reflectivity and side reflectivity.

In one embodiment, the first retardation layer may have 220 nm to 280 nm at a wavelength of 550 nm, specifically 225 nm to 275 nm, more specifically 230 nm to 270 nm ( For example, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm or 280nm) in-plane delay value. Within this range, the polarizing plate can achieve a significant reduction in side reflectivity.

In one embodiment, the first retardation layer may have 220 nm to 280 nm at a wavelength of 450 nm, specifically 225 nm to 275 nm, more specifically 230 nm to 270 nm ( For example, 220nm, 230nm, 240nm, 250nm, 260nm, 270nm or 280nm) in-plane delay value. Within this range, the polarizing plate can exhibit the above-mentioned wavelength dispersion characteristics, and can reduce the front reflectivity and the side reflectivity. In one embodiment, the first retardation layer may have a wavelength of 220 nm to 280 nm at a wavelength of 650 nm, specifically 225 nm to 275 nm, more specifically 230 nm to 270 nm. In-plane delay value. Within this range, the polarizing plate can exhibit the above-mentioned wavelength dispersion characteristics, and can reduce the front reflectivity and the side reflectivity.

The first retardation layer has a relationship between the refractive indexes represented by relationship 5. With this relationship, the polarizing plate can have a better effect in reducing the side reflectivity.

nx>ny≒nz, ---(5) where nx, ny and nz are the refraction of the first retardation layer in the slow axis direction, the fast axis direction and the thickness direction of the first retardation layer at a wavelength of 550 nm, respectively Rate.

In one embodiment, the first retardation layer is a positive A retardation layer. With this structure, the polarizing plate can have a better effect in reducing the side reflectivity.

The first retardation layer includes a film formed of a composition including a resin having a positive intrinsic birefringence. Therefore, the first retardation layer can be easily formed to have a larger refractive index in the stretching direction than the refractive index in the direction orthogonal to the stretching direction.

The resin having positive intrinsic birefringence includes a polymer having positive intrinsic birefringence. The polymer having positive intrinsic birefringence may include selected from, for example, cycloolefin polymers, such as norbornene polymers, etc.; polyesters, such as polyethylene terephthalate, polybutylene terephthalate, etc. Polyvinyl alcohol; polyvinyl chloride; polyarylene; polyolefin resin, such as polyethylene, polypropylene, etc.; polyarylate; and at least one of the group consisting of rod-shaped liquid crystal polymer, but not limited thereto. Specifically, polycarbonate resins having good properties in terms of retardation and high elongation at low temperatures, polyolefin resins having good properties in terms of mechanical properties, heat resistance, transparency, and dimensional stability, and cyclic resins are preferred. Olefin copolymer. These polymers having positive intrinsic birefringence can be used alone or in the form of a mixture thereof.

In addition to the resin with positive intrinsic birefringence, the first retardation layer may further include typical additives. For example, the additives may include anti-coloring agents such as pigments and dyes, heat stabilizers, light stabilizers, ultraviolet (UV) absorbers, antistatic agents, antioxidants, fine particles, and surfactants, but are not limited thereto.

The first retardation layer has a slow axis in an oblique direction with respect to the lateral direction (TD) of the laminate of the first retardation layer and the second retardation layer. Here, the “tilt direction” is an in-plane direction of the first retardation layer, and means a direction that is not parallel and perpendicular to the TD of the laminate of the first retardation layer and the second retardation layer. So, due to the first retardation layer The slow axis direction is inclined with respect to the TD of the laminate of the first retardation layer and the second retardation layer. Therefore, the laminate can be bonded to the polarizer by a roll-to-roll method, thereby preventing yield deterioration.

In one embodiment, referring to FIG. 2, the slow axis direction (SA ₁₁₀ ) of the first retardation layer 110 may be 70°±10° relative to the TD of the laminate of the first retardation layer 110 and the second retardation layer 210. It is inclined at an angle of 70°±5°, more specifically, 70°±3°. Within this range, the polarizing plate can achieve a reduction in front reflectivity and side reflectivity.

The first retardation layer 110 may have a thickness of 5 micrometers to 100 micrometers, specifically 5 micrometers to 60 micrometers. Within this thickness range, the first retardation layer can be used in a polarizing plate.

The first retardation layer can be formed by melt molding, injection molding, or compression molding a composition containing a resin having a positive intrinsic birefringence to prepare a non-stretched film, and then stretch the non-stretched film in an oblique direction. The stretching of the non-stretched film may be performed to 1.1 times or more than 1.1 times, 4.0 times or less than 4.0 times, specifically 1.3 times to 3.0 times, of the initial length of the non-stretched film. Within this range, the slow axis direction of the first retardation layer can be controlled, and the refractive index of the first retardation layer in the stretching direction can be increased. Stretching can be performed at a temperature from the glass transition temperature (Tg) of the non-stretched film+2°C or greater than the glass transition temperature (Tg) of the non-stretched film+2°C to Tg+30°C or less than Tg+30°C. The stretching direction may be inclined at an angle smaller than the angle defined between the TD of the laminate of the first retardation layer and the second retardation layer and the slow axis direction of the first retardation layer with respect to the TD of the non-stretched film. For example, the stretching direction can be greater than 15° to less than 50° relative to the TD of the non-stretched film. Generally speaking, it is inclined at an angle of more than 17° to less than 48°.

Although the first retardation layer may be used alone in the polarizing plate, the primer layer may be further formed on the first retardation layer to improve the bonding strength between the first retardation layer and the second retardation layer. The primer layer may include at least one selected from the group consisting of acrylic resin, urethane resin, acrylic urethane resin, ester resin, and ethyleneimine resin, but is not limited thereto.

[Second retardation layer]

其中Re(450)、Re(550)及Re(650)分別為第二延遲層在450奈米、550奈米及650奈米波長下的面內延遲值。 The second retardation layer 210 exhibits a wavelength dispersion characteristic in which the in-plane retardation (Re) value gradually increases as the wavelength decreases from a longer wavelength to a shorter wavelength. That is, the second retardation layer exhibits regular wavelength dispersion characteristics. With this structure, the polarizing plate can improve the screen quality of the optical display device including the polarizing plate. Specifically, the second retardation layer can satisfy relations 6 and 7:

Among them, Re(450), Re(550) and Re(650) are the in-plane retardation values of the second retardation layer at wavelengths of 450nm, 550nm and 650nm, respectively.

In one embodiment, the second retardation layer may have a Re(450)/Re(550) of 1.05 to 1.15, more specifically 1.1 to 1.15. In one embodiment, the second retardation layer may have Re(650)/Re(550) greater than 0.9 to 0.95. Within this range, the polarizing plate can achieve a significant reduction in front reflectivity and side reflectivity.

In one embodiment, the second retardation layer may have a wavelength of 550 nanometers, specifically 90 nanometers to 140 nanometers, more specifically 95 nanometers to 135 nanometers. In-plane retardation values from 85nm to 145nm. Within this range, the polarizing plate can achieve a significant reduction in front reflectivity and side reflectivity.

In one embodiment, the second retardation layer may have a wavelength of 100 nanometers to 160 nanometers at a wavelength of 450 nanometers, specifically 105 nanometers to 155 nanometers, more specifically 110 nanometers to 150 nanometers. In-plane delay value. Within this range, the polarizing plate can exhibit the above-mentioned wavelength dispersion characteristics, and can reduce the front reflectivity and the side reflectivity. In one embodiment, the second retardation layer may have a wavelength of 80 nanometers to 140 nanometers at a wavelength of 650 nanometers, specifically 85 nanometers to 135 nanometers, more specifically 90 nanometers to 130 nanometers. In-plane delay value. Within this range, the polarizing plate can exhibit the above-mentioned wavelength dispersion characteristics, and can reduce the front reflectivity and the side reflectivity.

The second retardation layer has a relationship between the refractive indexes represented by relationship 8. With this relationship, the polarizing plate can have a better effect in reducing the side reflectivity.

nx≒nz>ny, ---(8) where nx, ny and nz are the refraction of the second retardation layer in the slow axis direction, the fast axis direction and the thickness direction of the second retardation layer at a wavelength of 550 nm, respectively Rate.

In one embodiment, the second retardation layer is a negative A retardation layer. With this structure, the polarizing plate can have a better effect in reducing the side reflectivity.

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

Resins having negative intrinsic birefringence include polymers having negative intrinsic birefringence. The polymer with negative intrinsic birefringence may include homopolymers selected from, for example, styrene or styrene derivatives, copolymers including styrene or styrene derivatives and comonomers. At least one of the group consisting of polystyrene polymer, polyacrylonitrile polymer, poly(methyl methacrylate) copolymer, and cellulose copolymer such as cellulose ester, but not limited thereto. The comonomer may include one of acrylonitrile, maleic anhydride, methyl methacrylate, and butadiene. Preferably, the second retardation layer includes at least one selected from a polystyrene polymer and a cellulose copolymer, more preferably a polystyrene polymer.

In addition to the resin with negative intrinsic birefringence, the second retardation layer may further include typical additives. For example, the additives may include plasticizers, anti-coloring agents such as pigments and dyes, heat stabilizers, light stabilizers, UV absorbers, antistatic agents, antioxidants, fine particles, and surfactants, but are not limited thereto.

The second retardation layer has a slow axis in the tilt direction with respect to the TD of the laminate of the first retardation layer and the second retardation layer. Here, the “tilt direction” is an in-plane direction of the second retardation layer, and means a direction that is not parallel and perpendicular to the TD of the laminate of the first retardation layer and the second retardation layer. In this way, since the slow axis direction of the second retardation layer is inclined with respect to the TD of the laminate of the first retardation layer and the second retardation layer, the laminate can be bonded to the polarizer by the roll-to-roll method, thereby preventing production The yield rate has deteriorated.

In one embodiment, referring to FIG. 2, the slow axis direction (SA ₂₁₀ ) of the second retardation layer 210 may be 0°±20° (not Including 0°), specifically 0°±10° (excluding 0°), more specifically 0°±5° (excluding 0°). Within this range, the polarizer can achieve a reduction in frontal reflectivity.

The second retardation layer can have a wavelength of -110nm to -50nm at a wavelength of 550nm, specifically -105nm to -60nm, more specifically -100nm to -70nm The in-plane delay value in meters. Within this range, the polarizing plate can achieve a significant reduction in front reflectivity and side reflectivity.

The second retardation layer may have a biaxiality of -1.0 to 0.5 at a wavelength of 550 nm. Within this range, the polarizing plate can achieve a reduction in front reflectivity and side reflectivity.

The second retardation layer may have a thickness of 2 micrometers to 15 micrometers, specifically 3 micrometers to 10 micrometers. Within this thickness range, the second retardation layer can be used in a polarizing plate.

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

The first retardation layer and the second retardation layer can be formed by coating the composition for the second retardation layer on the first retardation layer, drying the composition, and then simultaneously stretching both the first retardation layer and the second retardation layer. A laminate of two retardation layers. By stretching the first retardation layer and the second retardation layer, the slow axis direction of the first retardation layer can be adjusted, the slow axis direction of the second retardation layer can be expressed, and the first retardation layer and the second retardation layer can be achieved within the target range. The retardation value of the second retardation layer.

Specifically, the stretching may be performed at an angle of 0°±20°, specifically 0°±15°, and more specifically 5°±15° with respect to the TD of the first retardation layer and the coating. More preferably, the stretching may be performed at an angle of 90° with respect to the TD of the first retardation layer and the coating, that is, in the longitudinal direction. In this case, the control of the slow axis directions of the first retardation layer and the second retardation layer can be facilitated. Stretching can be performed from 1.1 times to 2.0 times, specifically 1.2 times to 1.8 times.

[Polarizer]

The polarizer 300 is stacked on the upper surface of the first retardation layer to The partial light or the light received from the first retardation layer is linearly polarized to reduce the side reflectance.

The polarizer 300 may have a polarization degree of 99% or more than 99% and a single transmittance (Ts) of 44% or more than 44%. By satisfying both the degree of polarization and the single transmittance at the same time, when stacked on the laminate of the first retardation layer and the second retardation layer, the polarizer can achieve a significant reduction in the side reflectance on its side surface, especially In the entire range of the polar angle (θ) of 5° to 60°. Herein, "single light transmittance" means the light transmittance (Ts) measured in the visible spectrum, for example, at a wavelength of 400 nm to 700 nm, and can be measured by those who are familiar with the art Typical method to measure.

The "polarization degree" can be measured by a typical method known to those skilled in the art. Specifically, the polarizer may have a degree of polarization of 99% to 99.9999% and a transmittance (Ts) of 44% to 50%.

The polarizer 300 may have a cross light transmittance (Tc) of 0.001% to 0.7%, specifically 0.01% to 0.2%, more specifically 0.05% to 0.2% at a wavelength of 380 nm to 780 nm. Within this range, the polarizer may have an anti-reflection effect on its side surface, especially in the entire range of the polar angle (θ) of 5° to 60°.

The polarizer 300 is bonded to the laminate of the first retardation layer and the second retardation layer by a roll-to-roll method. Therefore, the laminate of the first retardation layer and the second retardation layer serves as a lower protective film of the polarizer, so that a separate protective film on the lower surface of the polarizer can be eliminated, and thus the thickness of the polarizing plate can be reduced.

A slow axis direction with reference to FIG. 3, a first retardation layer 110 (SA ₁₁₀₎ and the slow axis direction ₍₂₁₀ SA) 210 intersects the second retardation layer. In addition, the angle defined between the slow axis direction (SA ₁₁₀ ) of the first retardation layer 110 and the absorption axis (A ₃₀₀ ) of the polarizer 300 may range from 10° to 30°, specifically 15° to 30°. Within the range, and the angle defined between the slow axis direction (SA ₂₁₀ ) of the second retardation layer 210 and the absorption axis (A ₃₀₀ ) of the polarizer 300 may range from 70° to 90°, specifically 80° to 90° °, more specifically, within the range of 80° to less than 90°. Within this range, the polarizer can achieve a reduction in frontal reflectivity.

The absorption axis of the polarizer corresponds to the machine direction (MD) of the polarizer, and can be changed to the stretching direction in the manufacture of the polarizer.

The polarizer 300 may have a thickness of 5 micrometers to 40 micrometers. Within this range, the polarizer can be used in the polarizing plate.

The polarizer 300 may include a polyvinyl alcohol-based polarizer formed by unidirectionally pulling a polyvinyl alcohol film, or a polyene-based polarizer formed by dehydrating a polyvinyl alcohol film.

In one embodiment, the polarizer can be manufactured by dyeing, stretching, cross-linking and color correction of the polyvinyl alcohol film. A polarizer whose degree of polarization and transmittance fall within the above-mentioned range can be obtained by appropriately adjusting the conditions of dyeing, stretching, cross-linking, and color correction.

Although not shown in FIG. 1, the following adhesion layer, adhesion layer or adhesion/adhesion layer or protective layer may be further formed between the polarizer 300 and the first retardation layer 110.

[The protective layer]

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

The protective layer 400 may include an optically transparent protective film and an optically transparent protective film. At least one of the coatings. The protective film may include cellulose ester resins including triacetylcellulose (TAC), cyclic polyolefins including amorphous cyclic olefin polymers (COP), polycarbonate resins, and polyterephthalate resins. Polyethylene terephthalate (polyethylene terephthalate, PET) polyester resin, polyether ether resin, polyether resin, polyamide resin, polyimide resin, non-cyclic polyolefin resin, including poly(methyl methacrylate) Ester) at least one of poly(meth)acrylate resin, polyvinyl alcohol resin, polyvinyl chloride resin, and polyvinylidene chloride resin, but is not limited thereto. The protective coating may be formed of an actinic radiation curable resin composition including an actinic radiation curable compound and a polymerization initiator. The actinic radiation curable compound may include at least one selected from a cationic polymerizable curable compound, a radical polymerizable curable compound, a urethane resin, and a silicone resin.

Although not shown in FIG. 1, the polarizing plate may further include a functional coating on the upper surface of the protective layer. The functional coating may include at least one selected from the group consisting of a hard coating, an anti-fingerprint layer, an anti-reflection layer, a low-reflectivity layer, and an ultra-low-reflectivity layer, but is not limited thereto.

Although not shown in FIG. 1, an adhesive layer may be further formed on the lower surface of the second retardation layer to stack the polarizing plate on the optical display device.

Next, a polarizing plate according to another embodiment will be explained.

The polarizing plate includes a protective layer, a polarizer, a first retardation layer and a second retardation layer. The protective layer is stacked on the upper surface of the polarizer, and the first retardation layer and the second retardation layer are sequentially stacked on the lower surface of the polarizer. Except for the first retardation layer and the second retardation layer according to this embodiment, the polarizing plate according to this embodiment is substantially the same as the polarizing plate according to the above-mentioned embodiment shown in FIG. 1.

The first retardation layer and the second retardation layer according to this embodiment are the same as the retardation layer explained with reference to FIG. 1.

According to this embodiment, the slow axis direction of the first retardation layer can be set at 22.5°±15°, specifically 22.5°±10°, more specifically, with respect to the TD of the laminate of the first retardation layer and the second retardation layer. The angle is inclined at 22.5°±5°. Within this range, the polarizer can achieve improved circular polarization.

According to the present embodiment, the slow axis direction of the second retardation layer can be 90°±25°, specifically 90°±20°, more specifically 90°±20°, with respect to the TD of the laminate of the first retardation layer and the second retardation layer. The angle is 90°±10°. Within this range, the polarizer can achieve improved circular polarization.

Next, the optical display device according to the present invention will be explained.

The optical display device according to the present invention may include at least one of the polarizing plates according to the present invention. In one embodiment, the optical display device may include a liquid crystal display and a light emitting diode display, preferably a light emitting diode display. The liquid crystal display may include a liquid crystal display including a liquid crystal for in-place switching (IPS). Light emitting diode displays include organic light emitting diode displays or organic/inorganic light emitting diode displays, such as light emitting diode (LED), organic light emitting diode (OLED), quantum Quantum dot light emitting diode (QLED) and luminescent materials, such as phosphors.

Next, the present invention will be explained in more detail with reference to some examples. However, it should be noted that these examples are provided for illustration only and should not be regarded as limiting in any way. 制本发明。 The present invention.

Example 1

By stretching the polyvinyl alcohol film to three times its original length at 60°C, dyeing the stretched film with iodine, and stretching the dyed film to 2.5 times in an aqueous boric acid solution at 40°C, To make a 12-micron thick polarizer. V7100 (JASCO) was used to measure the single transmittance and cross transmittance of the polarizer at a wavelength of 380nm to 780nm. The polarization degree of the polarizer was measured using V7100 (Japan Branch Co., Ltd.).

A hard-coated triacetyl cellulose (TAC) film (KA25-HC, Konica Minolta Opto, Inc., thickness: 32 microns) is bonded to the upper surface of the polarizer .

Monolithic film (reverse wavelength dispersion characteristics, Re(450)/Re(550)=0.91, Re(650)/Re(550)=1.06) is achieved by combining the first retardation layer without an adhesive layer (Regular wavelength dispersion characteristics, +A plate, polyolefin film, Re(450)=253nm, Re(550)=251nm, Re(650)=250nm) is bonded to the second retardation layer ( Regular wavelength dispersion characteristics, -A plate, polystyrene-based film, Re(450)=129nm, Re(550)=116nm, Re(650)=110nm), and the monolithic The type film is bonded to the lower surface of the polarizer, thereby preparing a polarizing plate in which a triacetyl cellulose (TAC) film with a hard coat layer, a polarizer, a first retardation layer, and a second retardation layer are sequentially stacked.

The monolithic film is obtained by diagonally stretching a polyolefin-based copolymer resin film at a specific elongation rate and coating it on one surface of the diagonally stretched polyolefin-based copolymer resin film A polystyrene copolymer is used to form a laminate, and then the laminate is stretched at a specific elongation to form a film.

Example 2 and Example 3

Each polarizing plate was prepared in the same manner as in Example 1, except that a film having the specifications listed in Table 1 was used as a monolithic film or the polarization degree and light transmittance of the polarizer were changed as listed in Table 1.

Comparative example 1

A polarizing plate was prepared in the same manner as in Example 2, except that a film having the specifications listed in Table 1 was used as a monolithic film and a polarizer with a polarization degree of 98.0% and a light transmittance of 44.5% was used.

Comparative example 2

A polarizing plate was prepared in the same manner as in Example 2, except that a film having the specifications listed in Table 1 was used as a monolithic film and a polarizer with a polarization degree of 99.0% and a light transmittance of 43.5% was used.

The details of the polarizing plates of the Examples and Comparative Examples are shown in Table 1.

The reflectance (unit: %) of each polarizing plate of the example and the comparative example was measured, And the results are shown in Table 2. The reflectance was measured using DMS803 (Instrument Systems, Germany) on the polarizing film attached to the Galaxy S7 panel (specular component excluded, SCE) reflectance data.

As shown in Table 2, the polarizing plate according to the present invention can achieve a significant reduction in side reflectance.

In contrast, although the front reflectance is not shown in Table 2, the polarizing plate of Comparative Example 1 including a polarizer with a degree of polarization of less than 99.0% has higher front reflectance and side reflectance than the polarizing plate of the example. In addition, although the front reflectance is not shown in Table 2, the polarizing plate of Comparative Example 2 including a polarizer with a degree of polarization of less than 44% has higher front reflectance and side reflectance than the polarizing plate of the example.

It should be understood that those skilled in the art can make various modifications, changes, alterations and equivalent embodiments without departing from the spirit and scope of the present invention.

110: The first delay layer

210: second retardation layer

300: Polarizer

400: protective layer

Claims (16)

A polarizing plate, comprising: a polarizer; and a first retardation layer and a second retardation layer, which are sequentially stacked on the lower surface of the polarizer, wherein the first retardation layer has regular wavelength dispersion characteristics and meets the requirements of Relation 5 represents the relationship between the refractive index: nx>ny≒nz, ---(5) where nx, ny, and nz are respectively the first retardation layer at the wavelength of 550nm in the first retardation The refractive index in the slow axis direction, the fast axis direction and the thickness direction of the layer; wherein the second retardation layer has regular wavelength dispersion characteristics, and satisfies the relationship between the refractive index represented by relationship 8: nx≒nz>ny , --- (8) where nx, ny and nz are the refractive index of the second retardation layer in the slow axis direction, the fast axis direction and the thickness direction of the second retardation layer at a wavelength of 550 nm, respectively And wherein the slow axis direction of the first retardation layer is inclined with respect to the lateral direction (TD) of the laminate of the first retardation layer and the second retardation layer, the first retardation layer and the second retardation layer The laminate of the retardation layer has reverse wavelength dispersion characteristics, and the polarizer has a degree of polarization of 99% or more and a single transmittance (Ts) of 44% or more. The polarizing plate according to claim 1, wherein the laminate of the first retardation layer and the second retardation layer is a monolithic film. The polarizing plate according to claim 1, wherein the laminate of the first retardation layer and the second retardation layer has an in-plane retardation (Re )value. The polarizing plate according to claim 1, wherein the laminate of the first retardation layer and the second retardation layer satisfies relation 1 and relation 2:

Wherein Re(450), Re(550), and Re(650) are the values of the laminate of the first retardation layer and the second retardation layer at wavelengths of 450 nm, 550 nm, and 650 nm, respectively. In-plane delay value. The polarizing plate according to claim 1, wherein the slow axis direction of the first retardation layer is set at 70°±10° with respect to the lateral direction of the laminate of the first retardation layer and the second retardation layer. The angle is tilted. The polarizing plate according to claim 5, wherein the slow axis direction of the second retardation layer is set at 0°±20° with respect to the lateral direction of the laminate of the first retardation layer and the second retardation layer. (Excluding 0°) angle of inclination. The polarizing plate according to claim 1, wherein the angle defined between the absorption axis of the polarizer and the slow axis direction of the first retardation layer is in the range of 10° to 30°. The polarizing plate according to claim 1, wherein the absorption of the polarizer The angle defined between the closing axis and the slow axis direction of the second retardation layer is in the range of 70° to 90°. The polarizing plate according to claim 1, wherein the first retardation layer is a positive A retardation layer, and the second retardation layer is a negative A retardation layer. The polarizing plate according to claim 1, wherein the first retardation layer includes a film, the film including a cycloolefin polymer, including norbornene polymer; polyester, including polyethylene terephthalate Esters and polybutylene terephthalate; polyvinyl alcohol; polyvinyl chloride; polyarylene; polyolefins, including polyethylene and polypropylene; polyarylates; and rod-shaped liquid crystal polymers At least one. The polarizing plate according to claim 1, wherein the second retardation layer includes a coating layer, and the coating layer includes homopolymers selected from styrene or styrene derivatives, including styrene or styrene derivatives, and copolymers. At least one of a polystyrene polymer, a polyacrylonitrile polymer, a poly(methyl methacrylate) copolymer, and a cellulose copolymer including a cellulose ester as a monomer copolymer. The polarizing plate according to claim 1, wherein the first retardation layer has an in-plane retardation value of 220 nm to 280 nm at a wavelength of 550 nm, and the second retardation layer has an in-plane retardation value of 550 nm. It has an in-plane retardation value of 85nm to 145nm at wavelength. The polarizing plate according to claim 1, wherein the polarizer has a cross light transmittance of 0.001% to 0.7%. The polarizing plate according to claim 1, wherein the second retardation layer is directly formed on the first retardation layer. The polarizing plate according to claim 1, further comprising: a protective layer formed on the upper surface of the polarizer. An optical display device comprising the polarizing plate according to any one of claims 1 to 15.

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