KR20190017375A - Polarizing plate, polarizing set and liquid crystal display - Google Patents

Abstract

The present invention relates to a polarizing plate, a polarizing plate set, and a liquid crystal display device. According to the present invention, the polarizing plate or the polarizing plate set can provide a planar switching mode liquid crystal display device which has excellent optical characteristics such as light leakage characteristics at a viewing angle and is able to exhibit a desired luminous field. The polarizing plate set comprises an upper polarizing plate including a first polarizing element and a first protection film stacked on one surface of the first polarizing element, and a lower polarizing plate including a second polarizing element and a second protection film stacked on one surface of the second polarizing element.

Description

[0001] The present invention relates to a polarizing plate, a polarizing plate set,

The present invention relates to a polarizing plate, a polarizing plate set, and a liquid crystal display.

An IPS-LCD is an LCD in which the initial alignment of the liquid crystal is parallel to the glass substrate and oriented at an angle to the electrode, and the direction of the electric field is parallel to the glass substrate. The IPS-LCD exhibits a yellow color in the oblique direction according to the characteristics of the panel, thereby causing a large light leakage in the dark state (black state), resulting in deterioration of the sensation.

U.S. Pat. No. 6,078,731

In order to solve the above problem, it is necessary to improve luminance and color in the oblique direction. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a polarizing plate, a polarizing plate set, and a liquid crystal display device capable of realizing excellent optical characteristics and desired viewing feeling at a viewing angle.

The present invention relates to a polarizing plate set. The polarizing plate set may include an upper polarizer and a lower polarizer. The upper polarizer may include a first polarizer and a first protective film laminated on one side of the first polarizer. And a second protective film laminated on one surface of the second polarizing element and the second polarizing element. The first and second protective films may each be a retardation film.

In the present specification, the term polarizing element and the polarizing plate refer to objects that are distinguished from each other. The term polarizing element means a film, sheet or element itself having a polarizing function, and the term polarizing plate means an object including the polarizing element and other elements stacked on one or both sides of the polarizing element. The retardation layer and the polarizing element protective film may be exemplified as the other elements, but the present invention is not limited thereto.

A polarizing element is a functional element capable of extracting light that vibrates in one direction from incident light that vibrates in various directions. As the polarizing element, for example, a well-known absorption type linear polarization element can be used. As such a polarizing element, a PVA (poly (vinyl alcohol)) polarizing element can be exemplified. In one example, the polarizing element included in the polarizing plate may be a PVA film or sheet in which a dichroic dye or iodine is adsorbed and oriented. The PVA can be obtained by, for example, gelling polyvinyl acetate. Examples of the polyvinyl acetate include homopolymers of vinyl acetate; And copolymers of vinyl acetate and other monomers, and the like. As the other monomers copolymerized with vinyl acetate, there may be mentioned one kind or more of unsaturated carboxylic acid compounds, olefinic compounds, vinyl ether compounds, unsaturated sulfonic acid compounds and acrylamide compounds having an ammonium group. The degree of gelation of polyvinyl acetate is generally about 85 mol% to about 100 mol% or 98 mol% to 100 mol%. The degree of polymerization of the polyvinyl alcohol of the linear polarized light element may generally be from about 1,000 to about 10,000 or from about 1,500 to about 5,000.

In the present specification, the retardation film may mean an element capable of converting incident polarized light by controlling birefringence as an optically anisotropic layer. The x-axis means a direction parallel to the in-plane slow axis of the retardation film, and the y-axis means a direction parallel to the in-plane retardation axis of the retardation film, unless otherwise specified while describing the x-, y- and z- And the z axis indicates the thickness direction of the retardation film. The x-axis and the y-axis may be orthogonal to each other in a plane. In the present specification, when the retardation film includes rod-shaped liquid crystal molecules, the slow axis may mean the long axis direction of the rod shape, and when the retardation film includes disk-shaped liquid crystal molecules, the slow axis may mean the normal direction of the disk shape . In this specification, the optical axis of the retardation film is referred to as a ground axis unless otherwise specified. As used herein, the refractive index of a retardation film is described, and unless otherwise specified, it refers to a refractive index for light of a wavelength of about 550 nm.

When the terms such as vertical, horizontal, orthogonal, or parallel are used in defining the angles in this specification, they mean substantially vertical, horizontal, orthogonal, or parallel in the range not to impair the desired effect. For example, , Manufacturing tolerance (error) or variation, and the like. For example, each of the above cases may include an error within about +/- 15 degrees, an error within about +/- 10 degrees, or an error within about +/- 5 degrees.

In the present specification, the phase difference (Rin) and the thickness direction retardation (Rth) of the retardation film are calculated by the following equations (1) and (2), respectively.

[Equation 1]

Rin = d x (nx - ny)

[Equation 2]

Rth = dx (nz - ny)

In the equations (1) to (2), d is the thickness of the retardation film, and nx, ny and nz are the refractive indices in the x, y and z axis directions defined above. Means the refractive index for light of a wavelength of about 550 nm unless otherwise specified while describing the phase retardation of the retardation film in this specification.

In the present invention, the + B film satisfying the following expression (3), the -B film satisfying the expression (4), the + C plate satisfying the expression (5), and the -C plate satisfying the expression (6)

[Equation 3]

nz> nx> ny

[Equation 4]

nx> ny> nz

[Equation 5]

nz> nx = ny

[Equation 6]

nx = ny> nz

The present invention is advantageous in that the upper and lower balance can be maintained by disposing the first protective film on the upper polarizer and disposing the second protective film on the lower polarizer. Maintaining the balance between the upper part and the lower part can be advantageous in terms of being able to prevent warping of the liquid crystal panel that occurs after the durability evaluation of the liquid crystal panel.

The first protective film may have a phase retardation value of 0 nm to 10 nm and a thickness retardation value of 0 to 150 nm. The first retardation film may be classified as a + C plate. The phase retardation value of the first retardation film may be specifically 0 nm or more, and may be 10 nm or less, 8 nm or less, or 5 nm. The retardation value in the thickness direction of the first retardation film may be specifically 0 nm or more, 150 nm or less, 100 nm or less, or 50 nm or less.

The second protective film may have a phase retardation value of 0 nm to 10 nm and a thickness retardation value of 0 nm to 150 nm. The second retardation film may be classified as a + C plate. The phase retardation value of the second retardation film may be specifically 0 nm or more, 10 nm or less, 8 nm or less, or 5 nm. The retardation value in the thickness direction of the second retardation film may be specifically 0 nm or more, 150 nm or less, 100 nm or less, or 50 nm or less. It is possible to provide a planar switching mode liquid crystal display device in which optical characteristics and visual sensitivity characteristics are improved in the oblique direction when the phase retardation value to thickness direction retardation value of the first and second protective films are within the above range.

In one example, the absorption axis of the first polarizing element and the absorption axis of the second polarizing element may be orthogonal to each other.

In one example, the absorption axis of the first polarizing element and the in-plane optical axis of the first retardation film are parallel or orthogonal, and the absorption axis of the second polarizing element and the in-plane optical axis of the second retardation film can be parallel or orthogonal. With such an arrangement, it is possible to provide a planar switching mode liquid crystal display device having improved optical characteristics and visual sensitivity characteristics in the oblique direction.

In one example, the first protective film and the second protective film may be positioned inside the first polarizing element and the second polarizing element, respectively. The first and second protective films may be inner protective films of the first and second polarizing elements, respectively. When the upper polarizer and the lower polarizer are applied to a liquid crystal display device, the first protective film and the second protective film may be disposed adjacent to the liquid crystal panel, respectively.

In one example, each of the first and second protective films may be a single retardation film. When a laminate structure of a plurality of retardation films is applied to realize the retardation values of the first and second retardation films, there is a problem that the manufacturing cost increases and the thickness becomes thick, which is not preferable.

In one example, the first protective film and the second protective film may each be a polymer film. Examples of the polymer film include a polyolefin film such as a polyethylene film or a polypropylene film, a cycloolefin polymer film (COP) such as a polynorbornene film, a polyvinyl chloride film, a polyacrylonitrile film, a poly A cellulose ester polymer film such as a sulfone film, a polyacrylate film, a polyvinyl alcohol film or a TAC (triacetyl cellulose) film, or a copolymer film of two or more monomers among the monomers forming the polymer.

In one example, as the polymer film, a cyclic olefin polymer film or an acrylic film can be used. Examples of the cyclic olefin polymer include a ring-opening polymer of a cyclic olefin such as norbornene or a hydrogenated product thereof, an addition polymer of a cyclic olefin, a copolymer of another comonomer such as a cyclic olefin and an alpha-olefin, Or a graft polymer obtained by modifying a copolymer with an unsaturated carboxylic acid or a derivative thereof. According to an embodiment of the present invention, the polymer film may be an acrylic film. The present invention is advantageous in that the phase difference film can be provided as a single film through an acrylic film. The acrylic film may be stretched or shrunk under appropriate conditions to impart birefringence and be used as the retardation film.

In one example, the polymer film may use a resin containing a substituted or unsubstituted styrene group in the main chain and / or a blend containing the resin. More specifically, as the resin containing the substituted or unsubstituted styrene group, styrene-acrylonitrile copolymer (SAN), methyl methacrylate-styrene (MS), styrene-maleic anhydride (SMA), styrene- A resin containing a methyl methacrylate copolymer can be used. More specifically, the polymer film may include an acrylic resin including a resin containing a substituted or unsubstituted styrene group. As the acrylic resin, an acrylic resin composed of methacrylic acid ester and acrylic acid ester may be used. The acrylic resin may include an acrylic copolymer resin having a cyclic structure such as N-substituted maleimide, lactone ring, glutarimide, and maleic anhydride. The glass transition temperature of the resin included in the polymer film may be 100 占 폚 or higher, preferably 110 占 폚 or higher. The thickness of the polymer film may be 80 탆 or less. The polymer film can be produced by extruding or casting a fabric and biaxially stretching (simultaneous or sequential).

The first and second protective films may each have a retardation within 5% of the center value, and the optical axis is preferably ± 0.5 °. When the retardation deviation and the optical axis are within the above range, it is advantageous in terms of prevention of lowering of front contrast and improvement of visual field visibility.

In one example, the first and second protective films may each have a positive dispersion, a reverse dispersion or a flat dispersion characteristic. The normal dispersion characteristic means the following Equation (7), the reverse dispersion characteristic means the following Equation (8), and the flat dispersion characteristic can mean Equation (9). The first and second protective films may be further advantageous in providing a planar switching mode liquid crystal display in which optical characteristics and visual sensitivity characteristics are improved in an oblique direction when the first and second protective films have normal wavelength dispersion characteristics. The values of the dispersion characteristics R (450) / R (550) of the first and second protective films may be 1.04 to 1.08, respectively.

[Equation 7]

R (450) / R (550) > 1

[Equation 8]

R (450) / R (550) < 1

[Equation 9]

R (450) / R (550) = 1

In the formulas 7 to 9, R (?) Is the phase difference of the phase difference film with respect to the? Nm light.

In one example, the first protective film and the second protective film may satisfy Equation (10). When the first protective film and the second protective film satisfy the following expression (10), it is more advantageous to provide a liquid crystal display apparatus of a surface switching mode in which the optical characteristics and luminosity characteristics are improved in the oblique direction.

 [Equation 10]

? Re? |? Rth + 5

? Re is the absolute value of the difference between the in-plane retardation values of the first protective film and the second protective film, and? Rth denotes the difference in thickness retardation value between the first protective film and the second protective film. It means absolute value.

The retardation film and the polarizing element can be attached to each other by an appropriate adhesive or an adhesive to form an optical film, for example. The retardation film and the polarizing element may be directly attached through the adhesive layer or the pressure-sensitive adhesive layer, and may be further attached with a primer layer, if necessary.

The method of attaching the retardation film and the polarizing element is not particularly limited. For example, a polarizing element or a retardation film may be formed by coating an adhesive agent or a pressure-sensitive adhesive composition on one surface of a polarizing element or a retardation film, curing the adhesive composition after laminating, or by dropping using an adhesive or a pressure- And a method of curing the composition may be used. The curing of the composition described above can be performed, for example, by irradiating an active energy ray having an appropriate intensity with an appropriate light amount in consideration of the components contained in the composition.

The present invention relates to an upper polarizer plate. The upper polarizer is an upper polarizer including a first polarizer and a first protective film laminated on one surface of the first polarizer, and the second polarizer and a second protective film laminated on one surface of the second polarizer, May be used with the lower polarizer plate.

The first protective film may have a phase retardation value of 0 nm to 10 nm and a thickness retardation value of 0 to 150 nm.

The second protective film may have a phase retardation value of 0 nm to 10 nm and a thickness retardation value of 0 nm to 150 nm.

The present invention relates to a lower polarizer plate. Wherein the lower polarizer is a lower polarizer plate including a second polarizer and a second protective film laminated on one surface of the second polarizer, the first polarizer and the first protective film laminated on one surface of the first polarizer, May be used.

The first protective film may have a phase retardation value of 0 nm to 10 nm and a thickness retardation value of 0 to 150 nm.

The second protective film may have a phase retardation value of 0 nm to 10 nm and a thickness retardation value of 0 nm to 150 nm.

The details of the upper polarizer and the lower polarizer are the same as those described in the polarizer set.

The present invention relates to a liquid crystal display device. The liquid crystal display device may include the polarizing plate set and the liquid crystal panel. Wherein the liquid crystal display comprises: a top polarizer including a first polarizing element and a first protective film laminated on one surface of the first polarizing element; Plane switching mode liquid crystal panel; And a lower polarizing plate including a second polarizing element and a second protective film laminated on one surface of the second polarizing element.

The first protective film may have a phase retardation value of 0 nm to 10 nm and a thickness retardation value of 0 to 150 nm.

The second protective film may have a phase retardation value of 0 nm to 10 nm and a thickness retardation value of 0 nm to 150 nm.

The details of the upper polarizer and the lower polarizer including the retardation value may be the same as those described in the polarizer set.

The liquid crystal panel may be a liquid crystal panel of an in-plane switching (IPS) mode, a fringe field switching (FFS) mode, or a planar to line switching (PLS) mode. The liquid crystal panel may include an upper substrate, a liquid crystal layer, and a lower substrate. The upper and lower substrates may be a glass substrate or a plastic substrate, respectively. According to an embodiment of the present invention, the liquid crystal panel may be an IPS mode (in-plane switching mode) liquid crystal panel.

The liquid crystal layer may include liquid crystals whose dielectric anisotropy is positive or negative. The dielectric anisotropy of the liquid crystal layer can be appropriately selected in accordance with the mode of a desired liquid crystal panel. In one example, the phase retardation value of the liquid crystal layer may be 270 nm to 330 nm, and the retardation value in the thickness direction may be 0 nm to -40 nm.

In one example, the first and second protective films may be disposed adjacent to the top and bottom of the liquid crystal panel. In one example, the liquid crystal display may further include a backlight under the lower polarizer.

In one example, the alignment direction of the liquid crystal of the liquid crystal layer may be parallel to the absorption axis of the second polarizing element, or may be orthogonal to each other. An O mode liquid crystal panel can be defined when the angle is parallel, and an E mode liquid crystal panel can be defined when the angle is orthogonal.

In one example, when the liquid crystal display device includes an O mode liquid crystal panel, a backlight may be disposed on one surface of the lower polarizer plate. In another example, a backlight may be disposed on one surface of the upper polarizer when the liquid crystal display includes an E mode panel.

The upper and lower substrates of the liquid crystal panel may further include an alignment layer on the liquid crystal layer side. The alignment direction of the liquid crystal can be determined by the alignment layer. The alignment film may be a horizontal alignment film. As the alignment film, a rubbing alignment film or a photo alignment film can be used.

Fig. 1 exemplarily shows a liquid crystal display device according to the first embodiment of the present invention.

1, a liquid crystal display device includes an upper polarizing element 1, a first retardation film 2, a liquid crystal panel 3, a second retardation film 4 and a lower polarizing element 5 in sequence.

In FIG. 1, ↔ and ⊙ denote the in-plane optical axis of the retardation film, the absorption axis of the polarizing element, and the liquid crystal alignment direction of the liquid crystal panel. ⊙ means the direction perpendicular to the ground.

The surface-switched-mode liquid crystal display of the present invention can exhibit the optical characteristic and the desired luminosity in the oblique direction. In one example, the luminance at a 60-degree inclination angle and a 45-degree azimuth angle of the liquid crystal display device may be 1.5 or more and 2.25 or less.

According to the present invention, the light leakage characteristic can be improved by improving the luminance in the oblique direction. In one example, the liquid crystal display device may not exhibit the yellow visibility characteristics at the 60-degree inclination angle and the 45-degree azimuth angle, and may exhibit bluish visibility characteristics in particular. In one example, the liquid crystal display device may have a smaller x value and a smaller y value in a CIE xy color coordinate at an oblique angle of 60 degrees and an azimuth angle of 45 degrees than a liquid crystal display device that does not include the first and second protective films have. In one example, the liquid crystal display may have an x value and a y value of 0.36 or less in a CIE xy color coordinate at an oblique angle of 60 degrees and an azimuth angle of 45 degrees, respectively.

The present invention relates to a polarizing plate, a polarizing plate set, and a liquid crystal display. The polarizing plate to the polarizing plate set of the present invention can provide a liquid crystal display device of a plane switching mode which is excellent in optical characteristics such as light leakage characteristic at a viewing angle and can exhibit a desired visual feeling.

Fig. 1 exemplarily shows a liquid crystal display device of the present application.

The present application will be specifically described by way of the following examples, but the scope of the present application is not limited by the following examples.

Example  One

Using Techwiz LCD 1D, the optical characteristics and visual acuity were simulated for all of the long axis angles, especially at an oblique angle of 60 degrees and an azimuth angle of 45 degrees, for a planar switching mode liquid crystal display having the structure of FIG. The simulation conditions are as follows.

(1) Liquid crystal panel: cell spacing 2.9 탆, pretilt angle 0 캜, dielectric anisotropy Δε> 0, liquid crystal birefringence Δn = 0.1 at a wavelength of 550 nm. Rin (550): 290 nm Rth (550): 0 nm IPS mode liquid crystal panel

(2) upper and lower polarizing elements: a PVA polarizing element having a degree of polarization of 99.99% or more with respect to light having a wavelength of 380 nm to 780 nm and a transmissivity of 42.5%

(3) Protective Film of Protective Film and Lower Polarizing Element of Upper Polarizing Element: An acrylic film having a dispersion characteristic R (450) / R (550) of 1.06 was prepared, and the retardation value with respect to light having a wavelength of 550 nm was adjusted as follows Respectively.

The luminance is the value calculated by the simulation, and the luminance is predicted by the simulation. The actual color temperature is classified as Yellow, Bluish, Neutral, and Reddish as the color coordinate values at the inclination angle of 60 degrees and the azimuth angle of 45 degrees, which are the most vulnerable to the reference color coordinate.

Top protective film Lower protective film Luminance Color coordinates Rin Rth Rin Rth x y Comparative Example 1 0 0 0 0 1.75 0.3601 0.3635 Example 1 5 15 5 15 1.90 0.3319 0.3371 Example 2 5 20 5 20 1.95 0.3233 0.327 Example 3 5 25 5 25 2.00 0.3147 0.3167 Example 4 5 30 5 30 2.05 0.3064 0.3063 Example 5 5 40 5 40 2.10 0.2906 0.2858 Example 6 5 50 5 50 2.15 0.2762 0.266 Example 7 10 15 10 15 1.90 0.3321 0.3375 Example 8 10 20 10 20 1.95 0.3236 0.3276 Example 9 10 25 10 25 2.00 0.3151 0.3175 Example 10 10 30 10 30 2.05 0.3069 0.3072 Example 11 0 15 0 15 1.90 0.3318 0.3368 Example 12 0 20 0 20 1.95 0.3220 0.3249 Example 13 0 40 0 40 2.10 0.2885 0.2821 Example 14 0 60 0 60 2.25 0.2610 0.2433 Example 15 0 80 0 80 2.30 0.2412 0.2142 Example 16 0 100 0 100 2.30 0.2245 0.1876 Example 17 0 120 0 120 2.25 0.2103 0.1632 Example 18 0 140 0 140 2.10 0.2007 0.1462

1: upper polarizing element, 2: first retardation film, 3: liquid crystal panel, 4A: second retardation film, 5:

Claims (17)

A lower polarizer plate including an upper polarizer plate including a first polarizer and a first protective film laminated on one surface of the first polarizer, a second polarizer, and a second protective film laminated on one surface of the second polarizer, Including,
Wherein the first protective film has a phase retardation value of 0 nm to 10 nm and a thickness retardation value of 0 to 150 nm,
Wherein the second protective film is a second retardation film having an in-plane retardation value of 0 nm to 10 nm and a thickness retardation value of 0 nm to 150 nm. The polarizing plate set according to claim 1, wherein the absorption axis of the first polarizing element and the absorption axis of the second polarizing element are orthogonal to each other. The polarizing plate set according to claim 1, wherein the absorption axis of the first polarizing element and the in-plane optical axis of the first retardation film are parallel or orthogonal, and the absorption axis of the second polarizing element and the in-plane optical axis of the second retardation film are parallel or orthogonal. The polarizing plate set according to claim 1, wherein the first protective film and the second protective film are located inside the first polarizing element and the second polarizing element, respectively. The polarizing plate set according to claim 1, wherein each of the first and second protective films is a single retardation film. The polarizing plate set according to claim 1, wherein the first and second protective films are acrylic films, respectively. The polarizing plate set according to claim 1, wherein the first and second protective films each have a positive dispersion property. The polarizing plate set according to claim 1, wherein the first protective film and the second protective film satisfy the following formula 10:
[Equation 10]
? Re? |? Rth + 5
? Re is the absolute value of the difference between the in-plane retardation values of the first protective film and the second protective film, and? Rth denotes the difference in thickness retardation value between the first protective film and the second protective film. It means absolute value. And a second protective film laminated on one surface of the second polarizing element and the first polarizing plate including a first polarizing element and a first protective film laminated on one surface of the first polarizing element, Lt; / RTI &gt;
Wherein the first protective film has a phase retardation value of 0 nm to 10 nm and a thickness retardation value of 0 to 150 nm,
Wherein the second protective film is a second retardation film having an in-plane retardation value of 0 nm to 10 nm and a thickness retardation value of 0 nm to 150 nm. And a first protective film laminated on one surface of the first polarizing element and the first polarizing element, wherein the lower polarizing plate comprises a first polarizing element, a second polarizing element, and a second protective film laminated on one surface of the second polarizing element, Lt; / RTI &gt;
Wherein the first protective film has a phase retardation value of 0 nm to 10 nm and a thickness retardation value of 0 to 150 nm,
Wherein the second protective film is a second retardation film having an in-plane retardation value of 0 nm to 10 nm and a thickness retardation value of 0 nm to 150 nm. An upper polarizer including a first polarizing element and a first protective film laminated on one surface of the first polarizing element; Plane switching mode liquid crystal panel; And a lower polarizer plate including a second polarizer and a second protective film laminated on one surface of the second polarizer,
Wherein the first protective film has a phase retardation value of 0 nm to 10 nm and a thickness retardation value of 0 to 150 nm,
Wherein the second protective film is a second retardation film having an in-plane retardation value of 0 nm to 10 nm and a thickness retardation value of 0 nm to 150 nm. The liquid crystal display device according to claim 11, wherein the liquid crystal panel has a phase retardation value of 270 nm to 330 nm and a thickness retardation value of 0 nm to -40 nm. 12. The liquid crystal display of claim 11, wherein the first and second protective films are adjacent to the top and bottom of the liquid crystal panel. The liquid crystal display of claim 11, further comprising a backlight at a lower portion of the lower polarizer plate. The liquid crystal display according to claim 11, wherein the liquid crystal alignment direction of the liquid crystal panel is parallel to or orthogonal to the absorption axis of the second polarizing element. The liquid crystal display device according to claim 11, wherein the luminance of the liquid crystal display device at an oblique angle of 60 degrees and an azimuth angle of 45 degrees is 1.5 to 2.25. The liquid crystal display device according to claim 11, wherein the liquid crystal display device comprises a liquid crystal display device having a smaller x and y values in a CIE xy color coordinate at an oblique angle of 60 degrees and an azimuth angle of 45 degrees than a liquid crystal display device not including the first and second protective films, Display device.

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