KR20200113498A - Polarizing plate and optical display apparatus comprising the same - Google Patents

Abstract

Provided are a polarizing plate and an optical display device including the same. The polarizing plate includes an absorption-type polarizer, and a first protective film and a reflective polarizing film sequentially stacked on a lower surface of the absorption-type polarizer. An axis having a low refractive index among in-plane directions of the first protective film forms an angle of -5° to +5° based on an axis having a high refractive index among the in-plane directions of the reflective polarizing film.

Description

Polarizing plate and optical display device including the same {POLARIZING PLATE AND OPTICAL DISPLAY APPARATUS COMPRISING THE 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 in which a front contrast ratio is improved in a simple and economical manner, and an optical display device including the same.

A liquid crystal display device arranges a liquid crystal panel and an electrode matrix between a pair of absorption polarizers. In a liquid crystal display device, a liquid crystal panel implements an optical state that is changed by moving a liquid crystal by an electric field generated by applying a voltage to two electrodes. This process displays an image of a'pixel' carrying information using polarization in a specific direction. For this reason, a liquid crystal display device includes a front absorption type polarizer and a rear absorption type polarizer for inducing polarization.

The absorption type polarizer used in a liquid crystal display device absorbs 50% or more of the light incident from the backlight. Therefore, it is not possible to sufficiently increase the use efficiency of light with only the absorption type polarizer. Therefore, a reflective polarizing film must be additionally disposed in order to increase the use efficiency of light. In addition, as liquid crystal displays have recently become large in area, demand for power consumption is increasing. In order to lower power consumption, there is a need to increase the front contrast ratio of the absorption type polarizer. However, even if a reflective polarizing film is additionally disposed, there is a limit to improving the front contrast ratio.

Background art of the present invention is disclosed in Japanese Laid-Open Patent No. 2006-251659.

An object of the present invention is to provide a polarizing plate that increases the front contrast ratio.

Another object of the present invention is to provide a polarizing plate that increases the front contrast ratio by lowering the luminance in the black mode.

Another object of the present invention is to provide a polarizing plate having excellent fairness and economy and having a thinning effect.

One aspect of the present invention is a polarizing plate.

1.The polarizing plate includes an absorption type polarizer and a first protective film and a reflection type polarizing film sequentially stacked on a lower surface of the absorption type polarizer, and an axis having a low refractive index among the in-plane directions of the first protective film is the reflection type polarization Among the in-plane directions of the film, an angle of -5° to +5° is formed based on an axis having a high refractive index.

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

The present invention provides a polarizing plate that increases the front contrast ratio.

The present invention provides a polarizing plate that increases the front contrast ratio by lowering the luminance in the black mode.

The present invention provides a polarizing plate having excellent fairness and economy and thinning effect.

1 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.
2 is a conceptual diagram of a reflective polarizing film among the polarizing plates of FIG. 1.
3 is a conceptual diagram showing a relationship between an axis having a low refractive index among the in-plane directions of a second protective film of the polarizing plate of FIG. 1 and an axis having a high refractive index among the in-plane directions of a reflective polarizing film.
4 is a conceptual diagram showing a relationship between an axis having a high refractive index among the in-plane directions of an absorption type polarizer according to another embodiment of the present invention and an axis having a high refractive index among the in-plane directions of a reflective polarizing film.
5 is a conceptual diagram illustrating a relationship between an axis having a high refractive index among an in-plane direction of an absorption type polarizer according to another embodiment of the present invention and an axis having a low refractive index among an in-plane direction of a second protective film.
6 is a conceptual diagram of a reflective polarizing film according to another embodiment of the present invention.

It will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement the present invention by examples. The present invention may be implemented in various different forms, and is not limited to the embodiments described herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and the same reference numerals are assigned to the same or similar components throughout the specification. The length and size of each component in the drawings are for explaining the present invention, and the present invention is not limited to the length and size of each component described in the drawings.

In the present specification, "upper part" and "lower part" are defined based on the drawings, and "upper part" may be changed to "lower part" and "lower part" may be changed to "upper part" according to a perspective view, and "on" or What is referred to as “on” may include a case where other structures are interposed not only above but also in the middle. On the other hand, what is referred to as "directly on", "directly on", or "directly formed" or "directly formed in contact" means that no other structure is interposed therebetween.

In the present specification, "(meth)acrylic" means acrylic and/or methacrylic.

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

[Equation A]

Re = (nx-ny) x d

[Equation B]

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

[Equation C]

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

(In Equations A, B, and C, nx, ny, and nz are refractive indexes in the x-axis direction, y-axis direction, and thickness direction of the optical element at a wavelength of 550 nm, respectively, and d is the thickness of the optical element. (Unit: nm)). In the present invention, the x-axis direction is defined as the slow axis direction of the optical element, and the y-axis direction is defined as the fast axis direction of the optical element. The optical element may be a first protective film, a second protective film, or the like.

The inventor of the present invention is a polarizing plate comprising an absorption type polarizer, a first protective film, and a reflective polarizing film, the axis having a low refractive index among the in-plane directions of the first protective film and the axis having a high refractive index among the in-plane directions of the reflective polarizing film. It was confirmed that the front contrast ratio can be improved by adjusting the angle of the liver, and the present invention was completed.

Specifically, in the polarizing plate of the present invention, the refractive index of the in-plane direction of the first protective film is based on the axis having a high refractive index among the in-plane directions of the reflective polarizing film (the axis having a high refractive index among the in-plane directions of the reflective polarizing film is referred to as 0°). The lower axis is arranged between -5° and +5°. According to the present invention, by simply adjusting the angle between the axis of the first protective film and the reflective polarizing film, the brightness in the black mode can be lowered, thereby improving the front contrast ratio and improving fairness and economy.

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

Referring to FIG. 1, the polarizing plate includes an absorption type polarizer 100, a first protective film 200, and a reflective polarizing film 300.

In the polarizing plate, a first protective film and a reflective polarizing film are disposed on the lower surface of the absorption type polarizer. The first protective film and the reflective polarizing film may be disposed on the light incident surface of the absorption type polarizer or the light exit surface of the absorption type polarizer. Preferably, when the first protective film and the reflective polarizing film are disposed on the light incident surface of the absorbing polarizer, the effect of improving the front contrast ratio may be more excellent.

In the polarizing plate, a first protective film and a reflective polarizing film are sequentially disposed from a lower surface of the absorption type polarizer [preferably a light incident surface]. A case in which the reflective polarizing film and the first protective film are sequentially disposed from the lower surface of the absorption type polarizer may also be included in the scope of the present invention. Preferably, as shown in FIG. 1, when the first protective film and the reflective polarizing film are sequentially disposed from the lower surface of the absorption type polarizer, the effect of improving the front contrast ratio may be more excellent when the angle between the axes of the present invention is satisfied. have.

A reflective polarizing film is disposed on the lower surface of the first protective film. Although not shown in FIG. 1, an adhesive layer, an adhesive layer, or an adhesive layer may be laminated between the first protective film and the reflective polarizing film, so that the first protective film and the reflective polarizing film may be integrated. The integration may provide a thinning effect of the polarizing plate. However, a case in which a reflective film is simply laminated on the first protective film without an adhesive layer, an adhesive layer, or an adhesive layer may be included in the scope of the present invention. Preferably, an adhesive layer, an adhesive layer or an adhesive adhesive layer may be laminated between the first protective film and the reflective polarizing film.

Reflective polarizing film

The reflective polarizing film 300 is disposed on the lower surface of the first protective film, and may include a brightness enhancing film that increases brightness by preventing loss of light incident from the lower surface.

In the in-plane direction, the reflective polarizing film includes an axis having a high refractive index and an axis having a low refractive index among the in-plane directions. Here, the "axis with a high refractive index" and the "axis with a low refractive index" are defined by relatively comparing the refractive index of the x-axis and the y-axis, which are two axes in the in-plane direction of the reflective polarizing film. Although not particularly limited, an axis having a high refractive index and an axis having a low refractive index may be determined by stretching during manufacturing the reflective polarizing film.

In one embodiment, the reflective polarizing film may include a substrate and a plurality of plate-shaped polymers dispersed in the substrate. Although not particularly limited, an axis having a high refractive index and an axis having a low refractive index in the in-plane direction may be formed by stretching during a process of manufacturing a reflective polarizing film.

In one embodiment, in the reflective polarizing film, an axis having a high refractive index may be a reflection axis, and an axis having a low refractive index may be a transmission axis. In one embodiment, the axis having a high refractive index may be a longitudinal direction (MD), which is a stretching direction of the reflective polarizing film, and an axis having a low refractive index, may be a width direction (TD) perpendicular to the stretching direction of the reflective polarizing film. have.

In one embodiment, the reflective polarizing film may include a diffusely reflective polarizing film. Hereinafter, a diffuse reflection type polarizing film will be described.

The reflective polarizing film passes the polarized light (P polarization) perpendicular to the stretching direction among the light reaching the reflective polarizing film, but reflects the polarized light (S polarized light) in the stretching direction to the lower surface of the reflective polarizing film. In this process, the S polarized light is re-reflected from the bottom of the reflective polarizing film, the polarized light is changed, and is again incident on the reflective polarizing film. Among the changed polarized light, the P polarized light passes and the remaining S polarized light is reflected again, thereby recycling the light. recycling) to increase the brightness.

In one embodiment, the reflective polarizing film includes a core layer, and the core layer may include a substrate and a plurality of plate-shaped polymers inside the substrate. The plate-shaped polymer has a refractive index different from that of the core layer in at least one axial direction, and the core layer is stretched in at least one axial direction. Each of the plate-shaped polymers is formed into a plurality of groups for reflecting transverse waves of a desired wavelength, and the average optical thicknesses of the plate-shaped polymers between the groups are different from each other. Through this, the reflective polarizing film passes only the polarized light perpendicular to the stretching direction (P polarization) out of the light incident from the light source and reaches the reflective polarizing film, and the polarized light in the remaining stretching direction (S polarized light) is reflected downward, In this process, the S-polarized light is re-reflected from the bottom, and the re-reflected S-polarized light passes through the P-polarized light and the S-polarized light is reflected, thereby obtaining a luminance improvement effect. In the case of the reflective polarizing film, since the refractive index of the plate-shaped polymer and the refractive index of the substrate are different from each other, the characteristics of transmitted light generally exhibit scattered characteristics. As the reflective polarizing film, a commercially available product may be used.

Plate-shaped polymers are polyethylene naphthalate, copolyethylene naphthalate, polyethylene terephthalate, polycarbonate, polycarbonate alloy, polystyrene, heat-resistant polystyrene, polymethyl methacrylate, polybutylene terephthalate, polypropylene, polyethylene, acrylonitrile butadiene. Styrene, polyurethane, polyimide, polyvinyl chloride, styrene acrylonitrile, ethylene vinyl acetate, polyamide, polyacetal, phenol, epoxy, urea, melanin, unsaturated polyester, silicone, cycloolefin polymer Can include. Preferably, the plate-shaped polymer may be polyethylene naphthalate or the like.

Substrates are polyethylene naphthalate, copolyethylene naphthalate, polyethylene terephthalate, polycarbonate, polycarbonate alloy, polystyrene, heat-resistant polystyrene, polymethyl methacrylate, polybutylene terephthalate, polypropylene, polyethylene, acrylonitrile butadiene styrene , Polyurethane, polyimide, polyvinyl chloride, styrene acrylonitrile, ethylene vinyl acetate, polyamide, polyacetal, phenol, epoxy, urea, melanin, unsaturated polyester, silicone, including one or more of cycloolefin polymer can do. Preferably, dimethyl-2,6-naphthalene dicarboxylate, dimethyl terephthalate, ethylene glycol, cyclohexane dimethanol, and the like may be polymerized copolyethylene naphthalate.

Referring to FIG. 2, a reflective polarizing film according to an embodiment of the present invention will be described.

Referring to FIG. 2, the reflective polarizing film includes a core layer 10. In the core layer 10, a group A and a group B are sequentially formed in the thickness direction of the core layer 10, and the group A and the group B are integrally formed. Group A includes plate-shaped polymers (11, 12), and group B includes plate-shaped polymers (13, 14). The plate-shaped polymers (11, 12) and the plate-shaped polymers (13, 14) are each impregnated into a substrate (not shown in Fig. 2). The optical thickness between the plate-shaped polymers included in Group A and the optical thicknesses between the plate-shaped polymers 13 and 14 included in Group B are different from each other. Through this, it is possible to reflect different wavelength regions of light. FIG. 2 shows a case in which two groups are formed as a group A and a group B, but the number of groups included in the core layer is not particularly limited as long as the effect of improving luminance can be obtained.

Although not shown in FIG. 2, the core layer may be protected by additionally forming a skin layer protecting the core layer on one or both sides of the core layer. In this case, the refractive index of the skin layer may be 1.4 or more and 1.8 or less, and preferably 1.5 or more and 1.7 or less. In the above range, since the refractive index of the layer in contact with the coating layer is higher than the refractive index of the coating layer, loss of brightness and loss of contrast ratio can be minimized.

The skin layer is polyethylene terephthalate, polycarbonate, polycarbonate alloy, polystyrene, heat-resistant polystyrene, polymethyl methacrylate, polybutylene terephthalate, polypropylene, polyethylene, acrylonitrile butadiene styrene, polyurethane, polyimide, poly It may contain one or more of vinyl chloride, styrene acrylonitrile, ethylene vinyl acetate, polyamide, polyacetal, phenol, epoxy, urea, melanin, unsaturated polyester, silicone, and cycloolefin polymer. Preferably, the skin layer may be polycarbonate or polycarbonate alloy.

Although not shown in FIG. 1, a low refractive index layer may be further stacked on the lower surface of the reflective polarizing film. The low refractive index layer can increase the durability of the reflective polarizing film and the polarizing plate by increasing the hardness of the reflective polarizing film. The low refractive index layer is a low reflective layer, and as described below, the effect of improving the front contrast ratio can be further increased.

The low refractive index layer may mean a layer having a lower refractive index than the outermost layer of the reflective polarizing film. For example, the low refractive index layer may have a refractive index of 1.52 or less, specifically 1.0 to 1.5, more specifically 1.10 to 1.44, and more specifically 1.18 to 1.36. In the above range, the transmittance of light incident on the polarizing plate is further increased to further increase the brightness, thereby further improving the front contrast ratio. The low refractive index layer may have a thickness of 5 μm or less, specifically more than 0 μm and 5 μm or less. The low-refractive-index layer does not have any special restrictions on the composition of the low-refractive-index layer as long as the above-described refractive index can be secured.

First protective film

The first protective film is disposed on the lower surface of the absorption type polarizer to protect the absorption type polarizer. The first protective film improves the front contrast ratio by adjusting the angle between the axes described below.

The first protective film may include a film formed of an optically transparent resin. For example, the first protective film is a cellulose ester resin including triacetylcellulose, a cyclic polyolefin resin including amorphous cyclic polyolefin, polycarbonate resin, polyethylene terephthalate, polybutylene terephthalate, Polyester resins including polyethylene naphthalate and polybutylene terephthalate, polyethersulfone resins, polysulfone resins, polyamide resins, polyimide resins, acyclic-polyolefin resins, polymethylmethacrylic A second protective film including at least one of a polyacrylate resin including a rate resin, a polyvinyl alcohol resin, a polyvinyl chloride resin, and a polyvinylidene chloride resin may be included.

Preferably, the first protective film may be a polyester resin film including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and the like.

In one embodiment, the first protective film has a moisture permeability of 80g.m ² /day or less, specifically 0g.m ² /day to 80g.m ² /day, specifically 65g.m ² /day or less, more specifically 50g It can be less than or equal to .m ² /day. In the above range, since the moisture permeability of the first protective film is low, durability of the polarizing plate is improved, and peeling between the reflective polarizing film and the polarizer can be prevented by preventing a decrease in adhesion between the reflective polarizing film and the polarizer. The "moisture permeability" can be measured by the KS T 1305 method, but is not limited thereto.

The first protective film may be a single layer, or may include a film in which a plurality of single-layered resin films are laminated or a plurality of laminates are integrally formed by coextrusion.

The first protective film may have a thickness of 10 μm to 100 μm, specifically 40 μm to 80 μm. In the above range, it can be used for a polarizing plate.

The first protective film includes an axis having a high refractive index and an axis having a low refractive index in the in-plane direction. Here, the "axis with a high refractive index" and the "axis with a low refractive index" are defined by relatively comparing the refractive index of the x-axis and the y-axis, which are two axes in the in-plane direction of the first protective film. Although not particularly limited, an axis having a high refractive index and an axis having a low refractive index in the in-plane direction of the first protective film may be formed by stretching during a process of manufacturing the first protective film. For example, an axis having a high refractive index may be a slow axis, and an axis having a low refractive index may be a slow axis.

Referring to FIG. 3, when an axis 310 having a high refractive index among the in-plane directions of the reflective polarizing film 300 is 0°, an angle formed by the axis 210 having a low refractive index of the first protective film 200 is It can be -5° to +5°. In the above range, there may be an effect of improving the front contrast ratio. In the present specification, "+" means an angle in a clockwise direction when the reference is 0°, and "-" means an angle in a counterclockwise direction when the reference is 0°.

Specifically, in FIG. 3, the angle may be -4° to +4°, -3° to +3°, -2° to +2°, -1° to +1°, and more specifically 0 Can be °. By making it possible to manufacture the polarizing plate by a roll-to-roll process within the above range, the fairness and economic efficiency of the polarizing plate can be improved.

In one embodiment, the axis having a low refractive index among the in-plane directions of the first protective film is the machine direction (MD) of the first protective film, and the axis having a high refractive index among the in-plane directions of the first protective film is the width of the first protective film It can be a transverse direction (TD).

In another embodiment, an axis having a low refractive index among the in-plane directions of the first protective film is the width direction (TD) of the first protective film, and an axis having a high refractive index among the in-plane directions of the first protective film is the width direction of the first protective film (MD ) Can be.

In another embodiment, an axis having a low refractive index among the in-plane directions of the first protective film is an inclined direction with respect to the width direction of the first protective film, and an axis having a high refractive index has an inclined direction with respect to the length direction of the first protective film. Can be.

Preferably, the axis having a low refractive index among the in-plane directions of the first protective film is the mechanical direction (MD) of the first protective film, and the axis having a high refractive index among the in-plane directions of the first protective film is the width direction (TD) of the first protective film. By doing so, in consideration of the axial relationship with the absorption type polarizer described below, processability and economy can be improved by enabling a roll-to-roll process in manufacturing a polarizing plate.

The first protective film may include a stretched film to have an axis having a low refractive index and an axis having a high refractive index described above. Specifically, the first protective film may be a uniaxially stretched or biaxially stretched film, preferably a uniaxially stretched film. For example, the first protective film may be a TD uniaxial stretch, MD uniaxial stretch, MD and TD biaxial stretch film, preferably a TD uniaxial stretch film.

During TD uniaxial stretching, the first protective film may be prepared by a method for manufacturing a first protective film comprising the step of stretching the melt-extruded first protective film resin 2 to 10 times only in the TD direction. In the stretching ratio range, the axis of the present invention having a low refractive index and an axis having a high refractive index may be provided. Specifically, the draw ratio may be 3 to 8 times.

During MD uniaxial stretching, the first protective film may be prepared by a first protective film manufacturing method comprising the step of stretching the melt-extruded resin for the first protective film 2 to 10 times only in the MD direction. In the stretching ratio range, the axis of the present invention having a low refractive index and an axis having a high refractive index may be provided. Specifically, the draw ratio may be 3 to 8 times.

During biaxial stretching, the first protective film may be prepared by stretching the melt-extruded resin for the first protective film sequentially or simultaneously by TD and MD. The MD draw ratio may be 1.0 to 3.5 times, and the TD draw ratio may be 2.5 to 6.0 times. In the stretching ratio range, the axis of the present invention having a low refractive index and an axis having a high refractive index may be provided.

Stretching may be performed by one or more of dry stretching and wet stretching, and the stretching temperature is (Tg-20) ° to (Tg + 50) °, specifically 70 °C to 150 based on the Tg of the resin for the second protective film. ℃, more specifically 80 ℃ to 130 ℃ is preferred, it may be more specifically 90 ℃ to 120 ℃. In the above range, there may be uniformly the same stretching effect.

After stretching, the first protective film may be heat treated at a predetermined temperature without a stretching process to fix the axis and phase difference of the first protective film. In particular, the first protective film manufactured by TD uniaxial stretching can stably fix the axis and the retardation by performing the above-described heat treatment. During heat treatment, the temperature and time may be appropriately adjusted according to the material of the first protective film.

The first protective film may have a retardation within a predetermined range due to the above-described axis having a low refractive index and an axis having a high refractive index. The retardation of the first protective film may vary depending on a degree of stretching of the second protective film, a refractive index of an axis having a low refractive index, and a refractive index of an axis having a high refractive index.

In one embodiment, the first protective film has an in-plane retardation (Re) of 3,000 nm or more at a wavelength of 550 nm, specifically 3,000 nm to 13,000 nm, more specifically 5,000 nm to 13,000 nm, and more specifically 5,000 nm to 10,000 nm. I can. In the above range, there may be an effect of improving the front contrast ratio and suppressing the rainbow mura.

In one embodiment, the first protective film may have a retardation (Rth) of 15,000 nm or less in a thickness direction at a wavelength of 550 nm, specifically 3,000 nm to 15,000 nm, and more specifically 6,000 nm to 12,000 nm. Within the above range, there may be an effect of controlling spots by birefringence and an effect of improving viewing angle characteristics in a liquid crystal display device.

In one embodiment, the first protective film has a degree of biaxiality (NZ) of 2.5 or less, specifically 1.0 to 2.2, specifically 1.2 to 2.0, more specifically 1.4 to 1.8, and most specifically 1.45 to 1.75 at a wavelength of 550 nm. I can. Within the above range, there may be an effect of controlling spots due to birefringence and an effect of maintaining mechanical strength of the film.

For example, the first protective film may be a TD uniaxially stretched film.

For example, at a wavelength of 550 nm, the first protective film may have one of a refractive index nx in the x-axis direction and a refractive index ny in the y-axis direction of 1.65 or more. If both nx and ny are less than 1.65 or both nx and ny are 1.65 or more, when used as the first protective film, rainbow stains may occur due to birefringence due to a change in retardation value depending on the incident angle and wavelength. In one embodiment, nx may be 1.65 or more, specifically 1.67 to 1.75, and ny may be 1.45 to 1.55. In other embodiments, ny may be 1.65 or more, specifically 1.67 to 1.75, more specifically 1.69 to 1.72, and nx may be 1.45 to 1.55. By setting the absolute value (|nx-ny|) of the difference between nx and ny to be 0.1 to 0.2, specifically 0.12 to 0.18, the viewing angle can be further improved and rainbow spots can be prevented from occurring.

In another embodiment, the first protective film may have an in-plane retardation (Re) of 500 nm or less at a wavelength of 550 nm, specifically 50 nm to 500 nm, and more specifically 100 nm to 350 nm. In the above range, there may be an effect of improving the front contrast ratio and suppressing the rainbow mura.

In other embodiments, the first protective film may have a thickness direction retardation (Rth) of 10,000 nm or less at a wavelength of 550 nm, specifically 300 nm to 900 nm, and more specifically 450 nm to 750 nm. Within the above range, there may be an effect of controlling spots by birefringence and an effect of improving viewing angle characteristics in a liquid crystal display device.

In another embodiment, the first protective film may have a degree of biaxiality (NZ) of 10 or more, specifically 10 to 100, and more specifically 20 to 80 at a wavelength of 550 nm. Within the above range, there may be an effect of controlling spots due to birefringence and an effect of maintaining mechanical strength of the film.

For example, the first protective film may be a TD and MD biaxially stretched film.

For example, at a wavelength of 550 nm, in the first protective film, any one of a refractive index nx in the x-axis direction among the in-plane directions and a refractive index ny in the y-axis direction among the in-plane directions may be 1.65 or more. If both nx and ny are less than 1.65 or both nx and ny are 1.65 or more, when used as a first protective film, rainbow stains may occur due to birefringence due to a change in retardation value according to an incident angle and wavelength. In one embodiment, nx may be 1.65 or more, specifically 1.67 to 1.75, and ny may be 1.45 to 1.55. In another embodiment, nx may be 1.45 to 1.55, ny may be 1.65 or more, specifically 1.67 to 1.75, and more specifically 1.69 to 1.72. By setting the absolute value (|nx-ny|) of the difference between nx and ny to be 0.1 to 0.2, specifically 0.12 to 0.18, the viewing angle can be further improved and rainbow spots can be prevented from occurring.

Absorption type Polarizer

The absorption type polarizer 100 has a function of separating incident light into two orthogonal polarization components to transmit one polarization component and absorb the other polarization component.

The light transmittance of the absorption type polarizer may be 40% or more, specifically 40% to 45%, and more specifically 41% to 45%. The degree of polarization of the absorption type polarizer may be 95% or more, specifically 95% to 100%, and more specifically 98% to 100%. In the above range, the front contrast ratio of one layer can be improved and durability can be improved.

The absorption type polarizer may include at least one of an absorption type polarizer containing a dichroic dye and an absorption type polarizer containing a polyene functional group. The absorption type polarizer containing a dichroic dye may include an absorption type polarizer manufactured by uniaxially stretching a base film for an absorption type polarizer and dyeing it with iodine or a dichroic dye. The absorption type polarizer containing a polyene functional group may include an absorption type polarizer manufactured by dehydrating and/or dechlorinating a base film for an absorption polarizing film. The base film for a polarizing film may include a polyvinyl alcohol-based film or a derivative thereof, but is not limited thereto. The absorption type polarizer may be manufactured according to a conventional method known to those skilled in the art.

The absorption polarizer may have a thickness of 1 μm to 40 μm, specifically 5 μm to 30 μm, and more specifically 10 μm to 25 μm. In the above range, it can be used for a polarizing plate.

Although not shown in FIG. 1, a second protective film may be further stacked on the upper surface of the absorption type polarizer 100.

The second protective film may protect the absorption type polarizer by being laminated on the upper surface of the absorption type polarizer.

The second protective film may include an optical film formed of an optically transparent resin. The optical film may be a film formed of an optically transparent resin. Resins include polyesters including polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, etc., acrylic, cyclic olefin polymer (COP), triacetylcellulose (TAC), etc. Cellulose ester, polyvinyl acetate, polyvinyl chloride (PVC), polynorbornene, polycarbonate (PC), polyamide, polyacetal, polyphenylene ether, polyphenylene sulfide, polysulfone, polyethersulfone, polyarylene It may include one or more of polyimide and polyimide. The optical film may include a film prepared after modification of the above-described resin. The modification may include copolymerization, branching, crosslinking, or modification of molecular ends. The optical film may be a stretched or non-stretched film. An additional function may be provided to the protective layer by further forming a functional coating layer on the upper surface of the second protective film. The functional coating layer may be a hard coating layer, but is not limited thereto.

In one embodiment, the second protective film may have an in-plane retardation (Re) of 10 nm or less at a wavelength of 550 nm, specifically 0 nm to 10 nm, and more specifically 0 nm to 5 nm. In the above range, there may be an effect of improving the front contrast ratio and suppressing the rainbow mura.

In one embodiment, the second protective film may have a thickness direction retardation (Rth) of 15 nm or less at a wavelength of 550 nm, specifically -10 nm to 15 nm, and more specifically -6 nm to 10 nm. Within the above range, there may be an effect of controlling spots by birefringence and an effect of improving viewing angle characteristics in a liquid crystal display device.

In one embodiment, the second protective film may have a biaxiality degree (NZ) of 50 or less, specifically 0 to 50, and more specifically 0 to 30 at a wavelength of 550 nm. Within the above range, there may be an effect of controlling spots due to birefringence and an effect of maintaining mechanical strength of the film.

In another embodiment, the second protective film may have an in-plane retardation (Re) of 65 nm or less at a wavelength of 550 nm, specifically 0 nm to 60 nm, and more specifically 10 nm to 60 nm. In the above range, there may be an effect of improving the front contrast ratio and suppressing the rainbow mura.

In other embodiments, the second protective film may have a thickness direction retardation (Rth) of 150 nm or less, specifically more than 15 nm and 150 nm or less, 100 nm to 150 nm, and more specifically 120 nm to 140 nm at a wavelength of 550 nm. Within the above range, there may be an effect of controlling spots by birefringence and an effect of improving viewing angle characteristics in a liquid crystal display device.

In another embodiment, the second protective film may have a degree of biaxiality (NZ) of 10 or less, specifically 0 to 8, more specifically 0 to 5 at a wavelength of 550 nm. Within the above range, there may be an effect of controlling spots due to birefringence and an effect of maintaining mechanical strength of the film.

Although not shown in FIG. 1, an adhesive layer, an adhesive layer, or an adhesive layer may be further laminated on the upper surface of the second protective film. An adhesive layer, an adhesive layer, or an adhesive adhesive layer can fix the polarizing plate to the adherend. The "adherent" may be a liquid crystal panel, but is not limited thereto.

Hereinafter, a polarizing plate according to another embodiment of the present invention will be described with reference to FIG. 4.

The polarizing plate includes an absorption type polarizer, a first protective film, and a reflective polarizing film, and the axis having a low refractive index among the in-plane directions of the first protective film is -5° to the axis of the in-plane direction of the reflective polarizing film. +5°.

In addition, in the polarizing plate, an axis having a high refractive index in the in-plane direction of the absorption type polarizer is -5° to +5° based on an axis having a high refractive index among the in-plane directions of the reflective polarizing film. It is substantially the same as the polarizing plate of FIG. 1 except that the axis having the high refractive index among the in-plane directions of the absorption type polarizer forms -5° to +5° based on the axis having the high refractive index among the in-plane directions of the reflective polarizing film. . Here, the "axis with a high refractive index" and the "axis with a low refractive index" are defined by relatively comparing the refractive index among the two axes in the in-plane direction of the absorption type polarizer, the x-axis and the y-axis. Although not particularly limited, an axis having a high refractive index and an axis having a low refractive index in the in-plane direction of the absorption type polarizer may be formed by stretching during a process of manufacturing the absorption type polarizer.

Referring to FIG. 4, in the polarizing plate, the axis 110 having a high refractive index among the in-plane directions of the absorption type polarizer 100 is -5° based on an axis 310 having a high refractive index among the in-plane directions of the reflective polarizing film 300. To +5°. In this angular range, the front contrast ratio can be further improved. Specifically, the angle in FIG. 4 may be -4° to +4°, -3° to +3°, -2° to +2°, -1° to +1°, and more specifically 0° Can be. By making it possible to manufacture the polarizing plate by a roll-to-roll process within the above range, the fairness and economic efficiency of the polarizing plate can be improved.

In one embodiment, an axis having a high refractive index among the in-plane directions of the absorption type polarizer may be an absorption axis of the absorption type polarizer, and an axis having a low refractive index may be a transmission axis of the absorption type polarizer.

In one embodiment, an axis having a high refractive index among the in-plane directions of the absorption type polarizer may be a longitudinal direction (MD) of the absorption type polarizer, and an axis having a low refractive index may be a width direction TD of the absorption type polarizer.

In one embodiment, the absorption-type polarizer may be an absorption-type polarizer manufactured by uniaxially stretching a base film for an absorption-type polarizer and dyeing it with iodine or a dichroic dye.

Hereinafter, a polarizing plate according to another embodiment of the present invention will be described with reference to FIG. 5.

The polarizing plate includes an absorption type polarizer, a first protective film, and a reflective polarizing film, and the axis having a low refractive index in the in-plane direction of the first protective film is from -5° to the axis with a high refractive index among the in-plane directions of the reflective polarizing film. +5°. In addition, in the polarizing plate, an axis having a high refractive index among the in-plane directions of the absorption type polarizer is -5° to +5° based on an axis having a low refractive index among the in-plane directions of the first protective film. In addition, the polarizing plate of FIG. 1 is substantially similar to the polarizing plate of FIG. 1 except that the axis having a high refractive index in the in-plane direction of the absorption type polarizer forms -5° to +5° based on the axis having a low refractive index among the in-plane directions of the first protective film. Is the same as

Referring to FIG. 5, the polarizing plate has an axis 110 having a high refractive index among the in-plane directions of the absorption type polarizer 100 based on an axis 210 having a low refractive index among the in-plane directions of the first protective film 200. To +5°. In the above angular range, the front contrast ratio of the polarizing plate may be further improved. Specifically, the angle in FIG. 5 may be -4° to +4°, -3° to +3°, -2° to +2°, -1° to +1°, and more specifically 0° Can be. By making it possible to manufacture the polarizing plate by a roll-to-roll process within the above range, the fairness and economic efficiency of the polarizing plate can be improved.

In one embodiment, an axis having a high refractive index among the in-plane directions of the absorption type polarizer may be an absorption axis of the absorption type polarizer and a longitudinal direction (MD) of the absorption type polarizer.

In one embodiment, an axis having a low refractive index among the in-plane directions of the first protective film may be the longitudinal direction (MD) of the second protective film.

Hereinafter, a polarizing plate according to another embodiment of the present invention will be described with reference to FIG. 6.

The polarizing plate includes an absorption type polarizer, a first protective film, and a reflective polarizing film, and the axis having a low refractive index among the in-plane directions of the first protective film is -5° to the axis of the in-plane direction of the reflective polarizing film. +5°. The reflective polarizing film is substantially the same as the polarizing plate of FIG. 1 except that it is a retroreflective polarizing film.

Referring to FIG. 6, the reflective polarizing film may be a multilayered film in which the first optical layers 24 and the second optical layers 22 are alternately formed. Although not shown in FIG. 6, a non-optical layer is additionally formed on one or both sides of the multilayered film constituting the luminance enhancing film to protect the multilayered optical film.

The first optical layer and the second optical layer are polyethylene naphthalate, copolyethylene naphthalate, polyethylene terephthalate, polycarbonate, polycarbonate alloy, polystyrene, heat-resistant polystyrene, polymethyl methacrylate, polybutylene terephthalate, poly Propylene, polyethylene, acrylonitrile butadiene styrene, polyurethane, polyimide, polyvinyl chloride, styrene acrylonitrile, ethylene vinyl acetate, polyamide, polyacetal, phenol, epoxy, urea, melanin, unsaturated polyester, silicone, It may contain one or more of the cycloolefin polymer. Preferably, the first optical layer and the second optical layer may be polyethylene naphthalate or the like.

The reflective polarizing film may be manufactured by stretching a multilayer extruded film in which a first optical layer and a second optical layer are sequentially stacked in one direction, but is not limited thereto.

The optical display device of the present invention may include the polarizing plate of the present invention. In one embodiment, the optical display device may include a liquid crystal display device.

The liquid crystal display device includes a liquid crystal panel, a polarizing plate (light source side polarizing plate) of the present invention laminated on a light incident surface of the liquid crystal panel, and a polarizing plate (viewing side polarizing plate) disposed on the light exit surface of the liquid crystal panel. The polarizing plate disposed on the light exit surface includes a polarizing plate commonly known to those skilled in the art. The liquid crystal display device includes a light source on a lower surface of the polarizing plate on the light source side. The light source may include a light source having a continuous emission spectrum. For example, the light source is a white LED light source, a quantum dot (QD) light source, a metal fluoride red phosphor light source, specifically KSF (K ₂ SiF ₆ :Mn ^{4 +} ) phosphor or KTF (K ₂ TiF ₆ : Mn ^{4 +} ) It may include a phosphor-containing light source. The liquid crystal panel may be in a resin alignment (VA) mode, but is not limited thereto.

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 for aiding understanding of the present invention, and the scope of the present invention is not limited to the following examples.

Example One

A polyvinyl alcohol film (KURARAY, VF-PS#6500, thickness: 60㎛) is uniaxially stretched twice at 30℃ with the MD of a polyvinyl alcohol film, adsorbed with iodine, and stretched in a boric acid aqueous solution at 60℃ to polarizer (Thickness: 20 μm) was prepared. The maximum draw ratio is 6.5 times, and the axis of the polarizer having a high refractive index is the absorption axis (MD) of the polarizer.

A triacetylcellulose (TAC) film (KONICA, KC4CT1W, thickness: 40 μm, Re: 0.10 nm, Rth: 0.30 nm, NZ: 0.8) at a wavelength of 550 nm was adhered to the upper surface (light exit surface) of the polarizer. A PET film (Toyobo, thickness: 80 μm, Re: 8,500 nm at a wavelength of 550 nm, Rth: 9,300 nm, NZ: 1.55) was adhered to the lower surface (light incident surface) of the polarizer. By attaching a reflective polarizing film (NRP300, Toray Chemical, a diffuse reflective polarizing film) to the lower surface of the PET film, the TAC film-polarizer-PET film-reflective polarizing film are sequentially laminated to each other. An integrated polarizing plate was prepared.

In the PET film, the axis of low refractive index is the fast axis and the MD of the PET film.

In the reflective polarizing film, an axis having a high refractive index is a reflection axis and an MD of the reflective polarizing film. When the axis of the polarizing plate having a high refractive index of the reflective polarizing film is 0°, the relationship between the axis having a high refractive index of the polarizer and the axis having a low refractive index of the PET film is shown in Table 1 below.

Example 2

In Example 1, a norbornene-based retardation film (Zeon, ZB12-052125-F1490, thickness 51 µm, wavelength 550 nm, Re: 52 nm, Rth: 125 nm, NZ: 2.9) was laminated in place of the TAC film in Example 1 A polarizing plate was manufactured in the same manner as in Example 1.

Example 3

A polarizing plate was manufactured in the same manner as in Example 1, except that the TAC film was not laminated in Example 1.

Example 4 to Example 5

In Example 1, when the axis having a high refractive index of the reflective polarizing film among the polarizing plates is set to 0°, the relationship between the axis having a high refractive index of the polarizer and the axis having a low refractive index of the PET film was changed as shown in Table 1 below. A polarizing plate was manufactured in the same manner as in Example 1.

Example 6

In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that a retroreflective polarizing film (QV2, 3M) was used instead of a reflective polarizing film (diffuse reflection polarizing film).

Comparative example One

A polarizing plate was manufactured in the same manner as in Example 1, except that the PET film was not laminated in Example 1.

Comparative example 2

In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that when the axis of the polarizing plate having a high refractive index of the reflective polarizing film is 0°, the axis of the PET film having a low refractive index formed 90°.

Comparative example 3

In Example 1, a triacetylcellulose (TAC) film (KONICA, KC8UAW, thickness: 80㎛, non-stretched film, no axis with a low refractive index in the in-plane direction and no axis with a high refractive index in the in-plane direction, x,y directions) The polarizing plate was manufactured in the same manner as in Example 1, except that the refractive index was the same.) was adhered.

Comparative example 4

In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that when the axis of the polarizing plate having a high refractive index of the reflective polarizing film is 0°, the axis of the PET film having a low refractive index formed +6°.

Comparative example 5

In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that when the axis of the polarizing plate having a high refractive index of the reflective polarizing film was 0°, the axis of the PET film having a low refractive index formed -6°.

The following liquid crystal panels were assembled for the polarizing plates of Examples and Comparative Examples.

Specifically, a liquid crystal display device including an edge-type LED light source by assembling an LED light source, a light guide plate, and a module for a liquid crystal display device using the polarizing plates of Examples and Comparative Examples (using the polarizing plates of the Examples and Comparative Examples as the polarizing plate on the light source side) Except, Samsung TV (55-inch, 16 years manufactured model name: UN55KS8000F) and the same configuration) was manufactured. Using EZCONTRAST X88RC (EZXL-176R-F422A4, ELDIM) for the manufactured liquid crystal display module in white mode and black mode in front of the spherical coordinate system (0°, 0°), respectively. The luminance value was measured at. Then, the front contrast ratio was calculated as (luminance in white mode/luminance in black mode). The difference in the front contrast ratio was calculated as (front contrast ratio of Example or Comparative Example-front contrast ratio of Example 1)/front contrast ratio of Example 1 x 100.

1st angle
(°) 2nd angle
(°) Front black
Mode luminance Front contrast ratio Front contrast ratio difference Example 1 0 0 0.056 6500 0 Example 2 0 0 0.056 6450 -0.77% Example 3 0 0 0.056 6470 -0.46% Example 4 -5 0 0.060 6410 -1.38% Example 5 +5 0 0.060 6410 -1.38% Example 6 0 0 0.057 6490 -0.15% Comparative Example 1 - - 0.063 5650 -13.08% Comparative Example 2 90 0 0.073 4900 -24.62% Comparative Example 3 - - 0.064 5600 -13.85% Comparative Example 4 +6 0 0.066 5700 -12.31% Comparative Example 5 -6 0 0.066 5700 -12.31%

*1st angle: When 0° is the axis with the high refractive index of the reflective polarizing film among the polarizing plates, the angle formed by the axis with the low refractive index of the PET film

*Second angle: When 0° is the axis with the high refractive index of the reflective polarizing film among the polarizing plates, the angle formed by the axis with the high refractive index of the absorption type polarizer

As shown in Table 1, the polarizing plate of the present invention can significantly improve the front contrast ratio. On the other hand, the polarizing plate of the comparative example, which does not satisfy the axial relationship of the present invention, had a significantly lower front contrast ratio compared to the example.

Simple modifications or changes of the present invention can be easily implemented 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 (23)

Including an absorption-type polarizer and a first protective film and a reflective polarizing film sequentially stacked on the lower surface of the absorption-type polarizer,
An axis having a low refractive index among the in-plane directions of the first protective film constitutes an angle of -5° to +5° based on an axis having a high refractive index among the in-plane directions of the reflective polarizing film.
The polarizing plate of claim 1, wherein the polarizing plate includes the first protective film and the reflective polarizing film sequentially disposed from a light incident surface of the absorption type polarizer.
The polarizing plate of claim 1, wherein the first protective film and the reflective polarizing film are adhered to each other by an adhesive layer, an adhesive layer or an adhesive adhesive layer.
The polarizing plate of claim 1, wherein the angle is -1° to +1°.
The polarizing plate of claim 1, wherein an axis having a high refractive index among the in-plane directions of the reflective polarizing film is a longitudinal direction (MD) of the reflective polarizing film.
The polarizing plate according to claim 1, wherein the reflective polarizing film includes at least one of a diffusely reflective polarizing film and a retroreflective polarizing film.
The polarizing plate of claim 6, wherein the diffuse reflection type polarizing film includes a core layer, and the core layer includes a substrate and a plurality of plate-shaped polymers inside the substrate.
The polarizing plate of claim 7, wherein the retroreflective polarizing film comprises a multilayered film in which first and second optical layers having different refractive indices are alternately formed.
The polarizing plate of claim 1, wherein an axis having a low refractive index among the in-plane directions of the first protective film is a longitudinal direction (MD) of the first protective film.
The polarizing plate according to claim 1, wherein the first protective film is a uniaxially stretched film.
The polarizing plate of claim 1, wherein the first protective film has an in-plane retardation (Re) of 5,000 nm or more at a wavelength of 550 nm.
The polarizing plate of claim 1, wherein the first protective film has a retardation (Rth) of 15,000 nm or less in a thickness direction at a wavelength of 550 nm.
The polarizing plate of claim 1, wherein the first protective film has a refractive index nx in an axial direction having a high refractive index in an in-plane direction and a refractive index ny in an axial direction having a low refractive index in an in-plane direction at a wavelength of 550 nm.
The polarizing plate of claim 1, wherein the first protective film has a moisture permeability of 80 g.m ² /day or less.
The polarizing plate according to claim 1, wherein the first protective film comprises at least one polyester resin film of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate.
The method of claim 1, wherein the polarizing plate comprises an axis having a high refractive index among the in-plane directions of the absorption-type polarizing film in an angle of -5° to +5° based on an axis having a high refractive index among the in-plane directions of the reflective polarizing film. , Polarizer.
The polarizing plate of claim 16, wherein the angle is -1° to +1°.
The polarizing plate of claim 16, wherein an axis having a high refractive index among the in-plane directions of the absorption type polarizer is a longitudinal direction (MD) of the absorption type polarizer.
The polarizing plate of claim 1, wherein an axis having a high refractive index among the in-plane directions of the absorption type polarizer forms -5° to +5° based on an axis having a low refractive index among the in-plane directions of the first protective film.
The method of claim 19, wherein an axis having a low refractive index among the in-plane directions of the first protective film is a longitudinal direction (MD) of the first protective film, and an axis having a high refractive index among the in-plane directions of the absorption type polarizer is a length of the absorption polarizer. The polarizing plate which is the direction (MD).
The polarizing plate according to claim 2, wherein a low refractive index layer is further laminated on the lower surface of the reflective polarizing film.
The polarizing plate of claim 1, wherein a second protective film is further laminated on an upper surface of the absorption type polarizer.
An optical display device comprising the polarizing plate of any one of claims 1 to 22.

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