KR101587681B1 - Polarizing plate and optical display apparatus comprising the same - Google Patents

Abstract

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 first polarizer, a positive C plate portion, a second polarizer, and a third retardation film are laminated in order, and an optical display device including the same.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate and an optical display device including the polarizing plate.

The present invention relates to a polarizing plate and an optical display device including the same.

An organic light emitting diode (OLED) display device is a self-emission type display device that electrically excites a fluorescent organic compound to emit light. An OLED display device can be driven at a low voltage and has advantages such as thinness. In addition, the liquid crystal display device has attracted attention recently because it can solve the drawbacks pointed out as a problem in a liquid crystal display device such as a wide viewing angle and a fast response speed.

OLED display devices are self-luminous, unlike LCDs, do not require a polarizer in screen realization. However, the OLED driving panel includes a polarizing plate to compensate for the disadvantage that the brightness is lowered by reflection of external light by the Al plate. Generally, the polarizing plate is installed on one side of the OLED glass substrate.

When the OLED panel is driven in the white mode, the blue shift phenomenon that the color on the side is blue compared to the color on the front side due to the resonance structure of the OLED is a problem. However, in the case of a conventional polarizing plate using only one quarter-wave plate, there has been a limit in improving the side reflection feeling, insufficient prevention of perfect reflection of external light, and improving blue shift on the side.

In this regard, Korean Patent Publication No. 2010-0028050 discloses a polarizing plate in which a laminate of? / 2 phase difference film and? / 4 phase difference film is laminated on one surface of a polarizer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a polarizing plate which is excellent in the effect of preventing reflection of external light and capable of minimizing the blue shift phenomenon on the side of the OLED.

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

The polarizing plate which is one aspect of the present invention may be one in which a first polarizer, a positive C plate portion, a second polarizer and a first retardation film are laminated in order.

An optical display device which is another aspect of the present invention may include the polarizing plate.

The present invention provides a polarizing plate which has a good anti-reflection effect against external light and can minimize the blue shift phenomenon on the OLED side.

1 is a conceptual view of a polarizing plate of one embodiment of the present invention.
2 is a cross-sectional view of a polarizing plate of one embodiment of the present invention.
3 is a cross-sectional view of a polarizing plate of another embodiment of the present invention.
4 is a cross-sectional view of a polarizing plate of another embodiment of the present invention.
5 is a conceptual diagram of the polarization state of external light by the polarizing plate of the present invention.
6 shows the results of the side chromaticity coordinates of Examples and Comparative Examples.

In the present specification, 'upper' and 'lower' are defined for convenience on the basis of the drawings, and 'upper' may be changed to 'lower' and 'lower' may be changed to 'upper' depending on viewing time.

The polarizing plate which is one aspect of the present invention may have a structure in which a first polarizer, a positive C plate portion, a second polarizer, and a retardation film are laminated in order.

A protective film may be further laminated on the other surface of the first polarizer.

1 is a conceptual view of a polarizing plate of the present invention.

1, the polarizing plate 100 includes a first polarizer 20, a first protective film 10 stacked on the first polarizer 20, a laminated amount A second polarizer 40 laminated on the lower portion of the positive C plate portion 30; And a first retardation film (50) laminated on the lower portion of the second polarizer (40).

The first protective film 10 may protect the first polarizer 20.

A functional layer may be further formed on the first protective film 10. The functional layer may be a hard coating layer, an anti-glare coating layer, a low reflection coating layer, an antistatic coating layer, or the like, but is not limited thereto.

The first polarizer 20 can absorb linearly polarized light having a vibration plane in a specific direction of external light and transmit linearly polarized light having a vibration plane in a direction orthogonal thereto. The external light having passed through the first polarizer may be emitted in the form of linearly polarized light (linearly polarized light 1).

The positive C plate portion 30 is a film having only a retardation value in the thickness direction and can emit the linearly polarized light 1 in a linearly polarized light form.

The positive C plate portion 30 may comprise a single layer of film or multiple layers of film laminate.

The second polarizer 40 can emit linearly polarized light having passed through the positive C plate portion in the same direction as linearly polarized light (linearly polarized light 2).

The first retardation film 50 may emit linearly polarized light 2 having passed through the second polarizer in the form of circularly polarized light. The circularly polarized light is reflected by the reflection plate of the OLED panel to be converted into the circularly polarized light in the opposite direction and converted into the linearly polarized light having the opposite direction to the linearly polarized light 2 while passing through the second polarizer again,

The positive C plate portion may include at least one of a laminate of two? / 4 retardation films or a vertically aligned liquid crystal film.

A protective film may be further laminated between the first polarizer and the positive C plate portion, between the positive C plate portion and the second polarizer, or between the second polarizer and the first retardation film.

2 is a cross-sectional view of a polarizing plate of one embodiment of the present invention.

2, the polarizing plate 200 includes a first protective film 110, a first polarizer 120, a second retardation film 130, a third retardation film 140, a second polarizer 150, The protective film 160 and the first retardation film 170 may be stacked in this order.

The first retardation film may be laminated on a panel formed of a pressure sensitive adhesive or a reflective plate.

The laminate of the second retardation film and the third retardation film may be a positive C plate.

5 is a conceptual diagram showing the polarization state of external light when external light passes through the polarizer of FIG.

The first protective film 110 may protect the first polarizer 120. The functional layer may be further formed on the first protective film 110.

The first polarizer 120 may transmit linearly polarized light in a specific direction along the absorption axis of the first polarizer 120.

The second retardation film 130 and the third retardation film 140 may be? / 4 retardation films, respectively.

The angle? 1 between the slow axis of the second retardation film 130 and the absorption axis (the dotted line portion) of the first polarizer 120 becomes + 45 ° with respect to the absorption axis of the first polarizer 120, The angle 2 between the slow axis of the third retardation film 140 and the absorption axis (dotted line portion) of the first polarizer 120 may be -45 relative to the absorption axis of the first polarizer 120.

As a result, the intersection angle (inter-angle) of the slow axis between the second retardation film 130 and the third retardation film 140 is + 90 °. The in-plane retardation values in the laminate of the second retardation film 130 and the third retardation film 140 are canceled each other and only the retardation value in the thickness direction remains, so that the laminate can be used as a positive C plate film.

The linearly polarized light having passed through the first polarizer 120 may be converted into circularly polarized light while passing through the second retardation film 130 and may be changed to linearly polarized light through the third retardation film 140.

The absorption axis of the second polarizer 150 is parallel to the absorption axis of the first polarizer 120 and the absorption axis direction thereof is the same so that the angle between the absorption axis of the second polarizer 150 and the slow axis of the second retardation film is -45 [deg.]. The linearly polarized light having passed through the second polarizer 150 can be transmitted through the linearly polarized light in the same direction as the linearly polarized light having passed through the first polarizer.

The first retardation film 170 may be a? / 4 retardation film.

The angle θ3 between the slow axis of the first retardation film 170 and the absorption axis (dotted line portion) of the second polarizer 150 may be + 45 ° with respect to the absorption axis of the second polarizer 150. The linearly polarized light having passed through the second polarizer 150 can be changed into a circularly polarized light while passing through the first retardation film 170.

In the present specification, "+" means a clockwise direction with respect to a reference axis and "-" means a counterclockwise direction with respect to a reference axis.

The circularly polarized light is converted into circularly polarized light by being reflected by the reflection plate 180, reversed to circularly polarized light, and passing through the first retardation film 170 again. At this time, the polarized light passes through the second polarizer-third retardation film and is opposite to the linear polarized light.

In the polarizing plate, a protective film may be further laminated between the first polarizer 120 and the second retardation film 130, or between the third retardation film 140 and the second polarizer 150.

Figs. 3 and 4 are sectional views of a polarizing plate of another embodiment of the present invention.

3 and 4, the polarizing plate 300 includes a first protective film 210, a first polarizer 220, a second protective film 230, a vertically aligned liquid crystal film 240, a second polarizer 250, The third protective film 260, and the first retardation film 270 are stacked in this order.

The first retardation film may be laminated on a panel formed of a pressure sensitive adhesive or a reflective plate.

Details of the protective film, the first polarizer, the second polarizer, and the first retardation film are as described above.

The vertically aligned liquid crystal film has the same function as the stacked body of the first retardation film and the second retardation film, thereby preventing reflection of external light.

As shown in FIG. 4, a fourth protective film 280 may be further laminated between the vertically aligned liquid crystal film 240 and the second polarizer 250.

Details of the polarizer, the protective film, the retardation film and the vertically aligned liquid crystal film in the polarizing plate of the present invention are as follows.

Polarizer

The polarizer may mean the first polarizer and the second polarizer.

The polarizer is made of a polyvinyl alcohol-based resin and is generally used in the art.

Specifically, the polarizer is a linear polarizer having a function of absorbing linearly polarized light having a vibration plane in a specific direction by adsorbing and orienting a dichromatic dye to a polyvinyl alcohol-based resin, and transmitting linearly polarized light having a vibration plane perpendicular to the direction, Can be used. Iodine or a dichroic organic dye is used as the dichroic dye. Usually, a polarizer can be obtained by uniaxial stretching of a polyvinyl alcohol-based resin film, dyeing with a dichroic dye, and boric acid treatment after dyeing.

The thickness of the polarizer may be 5 탆 to 30 탆.

The transmittance of the polarizer may be between 40% and 50%.

The polarizer can be adhered to a protective film, a retardation film or a vertically aligned liquid crystal film by an adhesive for a polarizing plate. The adhesive may include at least one of a polyvinyl alcohol-based water-based adhesive and a pressure-sensitive adhesive.

Protective film

The protective film may mean the first, second, third, and fourth protective films.

The protective film is laminated on one side or both sides of the polarizer, and can protect the polarizer as a transparent protective layer.

The thickness of the protective film may be 20 탆 to 1,000 탆, preferably 20 탆 to 80 탆. In the above range, it can be used as a polarizing plate upon lamination to a polarizer.

The protective film is not particularly limited as long as it is conventionally used as a protective film of a polarizer, and examples thereof include cellulose-based, polyester-based, cyclic polyolefin-based, polycarbonate-based, polyether sulfone-based, and polysulfone-based films including triacetyl cellulose , Polyamide-based, polyimide-based, polyolefin-based, polyarylate-based, polyvinyl alcohol-based, polyvinyl chloride-based, and polyvinylidene chloride-based materials.

The protective film may further include a hard coating, an anti-glare coating, an antistatic coating, and a surface modification for adhering the adhesive.

Phase difference film

The retardation film may refer to the first, second, and third retardation films.

The retardation film can be a? / 4 retardation film and can change a linear polarized light to a circularly polarized light or a circularly polarized light by giving a retardation of? / 4 to the polarized light.

The retardation film may be a film having an in-plane retardation (Ro) of 0 nm-300 nm, preferably 100 nm-200 nm at a wavelength of 550 nm. Within the above range, it is possible to prevent a decrease in the side reflection feeling.

In one embodiment, Ro of the first retardation film may be 100 nm-200 nm, Ro of the second retardation film may be 100 nm-200 nm, and Ro of the third retardation film may be 100 nm-200 nm.

The retardation film is usually used in a polarizing plate, and any film having a retardation function can be used without limitation. For example, films made of an olefinic, polycarbonate, acrylic, cellulose, or mixture thereof containing a cycloolefin polymer (COP) can be used.

Preferably, the first retardation film may be an olefin-based film comprising a cycloolefin polymer (COP), and the second retardation film may be an olefin-based film.

The thickness of each of the retardation films may be 10 占 퐉 to 100 占 퐉. In this range, it is possible to provide an optical compensation effect when used in a polarizing plate, and can have a circular polarization effect. And preferably 10 占 퐉 to 60 占 퐉 thickness.

Vertically oriented liquid crystal film

The vertically aligned liquid crystal film is a film made of a material having a higher refractive index in the z axis than that in the x axis and the y axis. Generally, in the case of a retardation film, if the in-plane retardation value Re is increased, the retardation value Rth in the thickness direction also increases and the viewing angle becomes worse. However, when the vertically aligned liquid crystal film is laminated, the lateral retardation value (Rth) in the thickness direction of the retardation film becomes smaller, so that the difference in front and side characteristics becomes smaller, thereby improving the lateral viewing angle.

The vertically aligned liquid crystal film may include a film prepared by applying a liquid crystal composition to a substrate having a vertically aligning ability (e.g., cycloolefin-based) and solidifying or curing the liquid crystal composition.

The vertically aligned liquid crystal film may have a thickness retardation value in a specific range.

The vertically aligned liquid crystal film may have a retardation value (Rth) in the thickness direction represented by the following formula 1 at a wavelength of 550 nm of 0 nm to 400 nm. Within this range, an effect of improving the side viewing angle can be obtained when the polarizing plate is laminated. Preferably, Rth can be from 200 nm to 350 nm.

<Formula 1>

Rth = ((nx + ny) / 2 - nz) xd

(Where nx, ny and nz are the refractive index in the x-axis direction, the y-axis direction and the z-axis direction of the vertically aligned liquid crystal film, and d is the thickness (unit: nm) of the vertically aligned liquid crystal film) .

The x-axis direction of the vertically aligned liquid crystal film is the longitudinal direction, the y-axis direction is the width direction, and the z-axis direction is the thickness direction.

The in-plane retardation value Re of the vertically aligned liquid crystal film expressed by the following formula 2 at a wavelength of 550 nm may be 0 nm-5 nm. Preferably, Re is from 0 nm to 2 nm, more preferably from 0 nm to 1 nm.

<Formula 2>

Re = (nx - ny) xd

(Where nx and ny are the refractive indexes in the x-axis direction and the y-axis direction of the vertically aligned liquid crystal film, respectively, and d is the thickness (unit: nm) of the vertically aligned liquid crystal film).

The thickness of the vertically aligned liquid crystal film is not particularly limited, but may be 0.5 占 퐉 to 20 占 퐉 for the lamination of polarizing plates.

An adhesive layer may be formed between the protective film and the retardation film, or between the protective film and the vertically aligned liquid crystal film, and the adhesive layer may be formed of a (meth) acrylic adhesive.

The thickness of the polarizing plate may be 10 占 퐉 to 200 占 퐉. Within this range, it can be used as a polarizing plate of an organic light emitting diode display device.

The polarizing plate may be used as a polarizing plate for OLED.

An optical display device which is another aspect of the present invention may include the polarizing plate. The optical display device may include, but is not limited to, an organic light emitting diode (OLED) display device.

Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. It is to be understood, however, that the same is by way of illustration and example only and is not to be construed in a limiting sense.

Specific specifications of the components used in the following examples and comparative examples are as follows.

(1) Polarizer: A polyvinyl alcohol film (PS # 60, manufactured by Kuraray Co., Ltd., thickness 60 占 퐉, before stretching)

(2) Protective film: triacetylcellulose film

(3)? / 4 retardation film:

Cycloolefin film 1 (ZD-12, Ro: 141 nm, Xeon at a wavelength of 550 nm)

Cyclo olefin film 2 (TER-115, Ro: 115 nm, wavelength: 550 nm)

Polycarbonate film (WRS148, Ro: 148 nm, wavelength: 550 nm, Teijin)

(4) Vertically aligned liquid crystal film: NV300, Rth: 300 nm, J x energy at a wavelength of 550 nm.

Example  One

The polyvinyl alcohol film was stretched 5 times in an aqueous iodine solution at 40 占 폚 and dried at 80 占 폚 for 10 minutes to obtain a first polarizer having a transmittance of 47%. A triacetylcellulose film hard coated on one surface of the first polarizer and a cycloolefin film 1 as a? / 4 retardation film were laminated on the other surface of the polarizer using a polyvinyl alcohol adhesive.

A second polarizer was obtained in the same manner as above, and a triacetylcellulose film was laminated on one side of the obtained second polarizer and a cycloolefin film 1 as a? / 4 retardation film on the other side was laminated using a polyvinyl alcohol adhesive.

The cycloolefin film 1 attached to the first polarizer and the cycloolefin film 1 attached to the second polarizer were adhered using an acrylic adhesive.

A polycarbonate film of? / 4 retardation film was adhered to the other side of the triacetylcellulose film attached to the second polarizer using an acrylic adhesive, thereby producing a polarizer having a sectional view of FIG.

Example  2

A polarizing plate was produced in the same manner as in Example 1 except that cycloolefin film 2 was used instead of cycloolefin film 1.

Example  3

The polyvinyl alcohol film was stretched 5 times in an aqueous iodine solution at 40 占 폚 and dried at 80 占 폚 for 10 minutes to obtain a first polarizer having a transmittance of 47%. A triacetylcellulose film hard coated on one surface of the first polarizer and a triacetylcellulose film on the other surface of the first polarizer were bonded using a polyvinyl alcohol adhesive.

A second polarizer was obtained in the same manner as described above, and a triacetyl cellulose film was bonded to both sides of the second polarizer using a polyvinyl alcohol-based adhesive.

A vertically aligned liquid crystal coating film was adhered between a triacetylcellulose film adhered to the first polarizer and a triacetylcellulose film adhered to the second polarizer using an acrylic adhesive.

A polarizing plate having a cross-sectional view of FIG. 4 was prepared by adhering a polycarbonate film of? / 4 retardation film to the other surface of the triacetylcellulose film of the second polarizer using an acrylic pressure-sensitive adhesive.

Example  4

A polarizing plate was produced in the same manner as in Example 1 except that the transmittance of the second polarizer was 45%.

Example  5

A polarizing plate was produced in the same manner as in Example 1 except that the transmittance of the first polarizer was 45%.

Example  6

A polarizing plate was produced in the same manner as in Example 1 except that the transmittances of the first polarizer and the second polarizer were both 45%.

Comparative Example  One

The polyvinyl alcohol film was stretched 5 times in an aqueous iodine solution at 40 占 폚 and dried at 80 占 폚 for 10 minutes to obtain a first polarizer having a transmittance of 43%. A triacetyl cellulose film and a triacetyl cellulose film hard-coated on both sides of the first polarizer were bonded to each other using a polyvinyl alcohol-based adhesive. On one side of the triacetylcellulose film, a polarizer was produced by adhering a? / 4 retardation film, a polycarbonate film, with an acrylic pressure-sensitive adhesive.

Comparative Example  2

The polyvinyl alcohol film was stretched 5 times in an aqueous iodine solution at 40 占 폚 and dried at 80 占 폚 for 10 minutes to obtain a polarizer having a transmittance of 43%. A triacetylcellulose film antiglare coated on both surfaces of the polarizer was adhered with a polyvinyl alcohol adhesive, and a polycarbonate film as a? / 4 retardation film was adhered with an acrylic adhesive to obtain a thin polarizer.

The polarizing plates were assembled on the single polarizing plate or the OLED panel manufactured in Examples and Comparative Examples, and the following physical properties were evaluated. The results are shown in Tables 1, 2, and 6 below.

(1) Transmittance (Ts) and degree of polarization (P.E): The polarizing plate was measured using V-7100 (JASCO, Japan).

(2) Color Coordinates: The color coordinates were measured using EZContrast XL88W (ELDIM) at the front and side angle of 60 degrees. A polarizing plate was laminated on the panel and an RGB pattern was applied. Move to the coordinates you want to measure, then focus on RGB pixels and measure the luminance, x, y, and color values of each coordinate.

Transmittance (%) Polarization degree (%) Hue group cross a b Example 1 44.950 0.3047 99.248 -0.69 2.44 Example 2 43.026 0.0278 99.927 -0.68 3.42 Example 3 42.839 0.0223 99.940 -0.83 3.45 Example 4 43.894 0.0090 99.977 -0.87 3.09 Example 5 43.836 0.0078 99.977 -0.89 3.09 Example 6 43.894 0.009 99.977 -0.87 3.09 Comparative Example 1 41.817 0.0016 99.995 -1.14 3.58 Comparative Example 2 42.624 0.0019 99.995 -0.87 5.95

Front color coordinates Side (60 °) color coordinates x y x y Example 1 0.4684 0.2429 0.3186 0.2877 Example 2 0.4684 0.2429 0.3106 0.2798 Example 3 0.4683 0.2426 0.3008 0.275 Comparative Example 1 0.4685 0.2429 0.2872 0.2513

As shown in Table 1-2 and FIG. 6, the polarizer of the present invention has good transmittance and polarization degree, and it can solve the side blue shift phenomenon in the OLED according to the result of the side chromaticity coordinates. On the other hand, the polarizing plate of Comparative Example 1-2 in which only one? / 4 retardation film was laminated on the polarizer could not solve the side blue shift in the OLED as compared with Example 1. [

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (18)

A first polarizer, a positive C plate portion, a second polarizer, and a first retardation film are laminated in this order,
The absorption axes of the first polarizer and the second polarizer are parallel to each other,
The positive C plate portion is a vertically aligned liquid crystal film,
Wherein the vertically aligned liquid crystal film has a retardation value (Rth) in the thickness direction represented by the following formula (1) at a wavelength of 550 nm of -400 nm to -200 nm:
<Formula 1>
Rth = ((nx + ny) / 2 - nz) xd
(Where nx, ny and nz are the refractive index in the x-axis direction, the y-axis direction and the z-axis direction of the vertically aligned liquid crystal film, and d is the thickness (unit: nm) of the vertically aligned liquid crystal film) .
delete delete delete delete delete delete The polarizer of claim 1, wherein the first retardation film is a lambda / 4 retardation film.
The polarizer of claim 1, wherein the angle between the absorption axis of the second polarizer and the slow axis of the first retardation film is + 45 °.
The polarizing plate for organic light emitting devices according to claim 1, wherein the first retardation film has a wavelength of 550 nm and Ro has a thickness of 0 nm to 300 nm.
The polarizer of claim 1, wherein the first retardation film is a film comprising at least one of a cycloolefin polymer (COP) system, a polycarbonate system, an acrylic system, and a cellulose system.
delete The polarizer of claim 1, wherein transmittances of the first polarizer and the second polarizer are 40-50%, respectively.
The polarizing plate for an organic light emitting device according to claim 1, wherein a protective film is further laminated on one surface of the first polarizer.
The polarizing plate for an organic light emitting device according to claim 14, wherein the protective film comprises a cellulose-based film.
The liquid crystal display according to claim 1, further comprising a protective film laminated between the first polarizer and the positive C plate portion, between the positive C plate portion and the second polarizer, or between the second polarizer and the first retardation film By weight based on the total weight of the polarizing plate.
The polarizing plate for an organic light emitting device according to claim 16, wherein the protective film comprises a cellulose-based film.
An optical display device comprising the polarizing plate for an organic light emitting element according to any one of claims 1, 8 to 11, and 13 to 17.

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