KR20150137367A - Multi Domain Vertical Alignment Liquid Crystal Display with High Transmittance and Wide Viewing Angle - Google Patents

Abstract

The present invention relates to a liquid crystal display device which improves transmittance by using a uniaxial film having different optical axis, phase retardation value and refractive index value according to a wavelength disposed between a vertically aligned liquid crystal layer and a top plate polarizer, The liquid crystal display device includes a lower plate polarizer, a vertically aligned liquid crystal layer, and a top plate polarizer. The optical axis of the liquid crystal in the liquid crystal cell is perpendicular to the substrate. A plurality of positive λ / 4 plates (positive A-plate) and negative λ / 4 plates for improving the transmittance in the bright state are provided in such a manner that the transmission axis of the lower plate polarizer is orthogonal to the transmission axis of the upper plate polarizer. A plurality of positive A-plates and a negative A-plate for viewing angle compensation in a dark state, a negative A-plate, plate are laminated between the lower plate polarizer and the upper plate polarizer with the liquid crystal layer interposed therebetween.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a multi-domain liquid crystal display (LCD)

The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display using a uniaxial film having different optical axes and phase retardation values and refractive index values according to wavelengths disposed between a vertically aligned liquid crystal layer and a top plate polarizer, And a high transmittance wide viewing angle vertical alignment liquid crystal display device capable of removing light leakage phenomenon irrespective of wavelength.

In general, a multi-domain vertical alignment (MVA) liquid crystal display device is a device in which a liquid crystal compound is driven in a state in which a director of a liquid crystal compound is perpendicular to a substrate, The viewing angle characteristics of the device are excellent.

Such a multi-domain vertically aligned liquid crystal display device includes a color filter layer array substrate having a color filter layer, a thin film transistor array substrate having thin film transistors, and a liquid crystal layer interposed between the two substrates. The color filter layer array substrate and the thin film transistor And an alignment film for determining an initial alignment direction of the liquid crystal layer is provided on an inner surface of the array substrate.

When voltage is not applied to the vertically aligned liquid crystal display element, the liquid crystal compound is vertically arranged on the substrate and the screen appears dark.

That is, when no voltage is applied to the liquid crystal, the light passing through the lower polarizer passes through the liquid crystal cell and there is no phase difference. Therefore, the upper polarizer having the transmission axis orthogonal thereto can not pass therethrough, ) State.

On the other hand, when a voltage is applied to the vertically-aligned liquid crystal display element, the liquid crystal compound is arranged in a direction 45 degrees to the transmission axis of the polarizer, and light is transmitted, thereby the screen is in a bright state.

That is, when a voltage is applied to the liquid crystal, light passing through a lower polarizer passes through a liquid crystal cell rotated by 45 ° due to an electric field, and is rotated through 90 °, passing through an upper polarizer (analyzer) Is displayed.

Multi-domain vertical alignment (MVA) liquid crystal cells have been proposed and put into practice to improve insufficient viewing angle characteristics of a single domain vertically aligned liquid crystal cell.

In the MVA liquid crystal cell, the liquid crystal molecules vertically align on the substrate when no voltage is applied, and when the voltage is applied, the liquid crystal molecules form a domain by the oblique electric field generated between the pixel electrode and the counter electrode and lie in the substrate surface direction .

In this case, one pixel region is divided into a plurality of divided regions, and the liquid crystal molecules are arranged symmetrically, so that a change in transmittance occurs symmetrically to obtain a wide viewing angle. The multi-domain is formed using a projection or a slit.

Fig. 1 is a cross-sectional view of a liquid crystal cell using a uniaxial film, and Fig. 2 is a simulation image of a front pixel in a bright state of the liquid crystal cell of Fig.

The liquid crystal cell shown in FIG. 1 schematically shows a general multidomain vertical alignment mode including a top plate, a bottom plate polarizer, and a liquid crystal layer having a phase retardation value? / 2, whose transmission axes are orthogonal to each other.

The structure of the liquid crystal cell shown in FIG. 1 has a low transmittance when a bright state is expressed by applying an electric field, thereby generating a disclination line in the domain between the domains.

FIG. 3 is a diagram showing a polarization state in a Poincare sphere as viewed from the side (θ = 70 °, φ = 45 °) of the compensation structure of the liquid crystal cell of FIG.

Where? Represents an angle of 70 degrees with respect to the z axis, and? Represents an angle of 45 degrees with respect to the x axis.

The liquid crystal cell shown in FIG. 1 uses a pair of a positive A-plate and a negative A-plate with no dispersion according to wavelength to move the polarization state of the polarizing plate positioned on the transmission axis of the lower polarizer to the absorption axis of the upper polarizer The principle of compensation structure.

The liquid crystal cell shown in FIG. 1 is designed to compensate the movement of the transmission axis of the lower plate polarizer and the absorption axis of the upper plate polarizer in the Poincare sphere according to the side viewing angle when viewed from the side.

However, since the phase retardation value is inversely proportional to the wavelength of the incident light, the designed state of the green wavelength is accurately located on the absorption axis of the polarizer of the top plate, while the polarization state of red or blue wavelength is the polarizing point of the absorption axis of the polarizer The light leakage phenomenon occurs in a dark state.

FIG. 4 is a simulation result showing the contrast ratio characteristic according to the viewing angle of the liquid crystal cell using the uniaxial film of FIG. 1, in which a contrast ratio similar to that of the front is obtained in the horizontal and vertical directions, .

Korean Patent Publication No. 10-2012-0071835 Korean Patent Publication No. 10-2005-0039587

The present invention solves the above problems of the conventional vertical alignment liquid crystal display, and it relates to a liquid crystal display device which is capable of suppressing the problems of the prior art vertical alignment liquid crystal display apparatuses in which a light axis and a phase retardation value disposed between vertically aligned liquid crystal layers and a top plate polarizer, a liquid crystal display device having a high transmittance, a wide viewing angle, and a liquid crystal display device capable of enhancing transmittance by using a uniaxial film and removing light leakage phenomenon regardless of a wavelength.

The present invention relates to a method and apparatus for enhancing the transmittance in a bright state by using seven uniaxial films and eliminating light leakage occurring at all angles in a dark state, It is an object of the present invention to provide a high transmissivity, wide viewing angle compensation method and structure of a multi-domain vertical alignment liquid crystal display device.

The present invention is based on the idea of increasing the transmittance in a bright state by using a positive λ / 4 A-plate and a negative λ / 4 A-plate, reversing a uniaxial film having a positive dispersion characteristic, In this paper, we propose a high transmissivity and wide viewing angle compensating method and structure of a multi - domain vertically aligned liquid crystal display capable of eliminating light leakage caused by the side and eliminating light leakage according to wavelength.

The objects of the present invention are not limited to the above-mentioned objects, and other objects not mentioned can be clearly understood by those skilled in the art from the following description.

According to an aspect of the present invention, there is provided a liquid crystal display device vertically aligned with a high transmittance wide viewing angle, including a lower plate polarizer, a vertically aligned liquid crystal layer, and a top plate polarizer, In the display device, a plurality of positive A-plates (positive A-plate) and negative (negative) plates for improving the transmittance in a bright state are provided, wherein the transmission axis of the lower plate polarizer is orthogonal to the transmission axis of the upper plate polarizer. a plurality of positive A-plates and a negative A-plate for compensating the viewing angle in a dark state, and a negative A-plate (negative A-plate) ) Are combined and laminated between the lower plate polarizer and the upper plate polarizer with the liquid crystal layer interposed therebetween.

Here, the polarizing plate is disposed between the upper plate polarizer and the lower plate polarizer such that the optical axis of the positive λ / 4 A-plate and the negative λ / 4 A-plate are orthogonal to each other.

A plurality of positive A-plates and negative A-plates are disposed between the upper polarizer and the lower polarizer to compensate for the viewing angle in the dark state. And the dispersion characteristics are reversibly used.

And the optical axes of two adjoiningpulsed A-plates disposed between the upper plate polarizer and the lower plate polarizer are orthogonal.

And the use of a flexible A-plate whose optical axes are orthogonal to each other is used to reduce the difference in the polarization state depending on the wavelength by rotation in the opposite direction on the Poincare sphere.

And the polarization state is aligned on the S ₁ axis irrespective of the wavelength of the light in the pouincere spherical shape by using the flexible A-plate whose optical axis is orthogonal.

And the optical axes of two adjacent negative A-plates disposed between the upper plate polarizer and the lower plate polarizer are orthogonal.

The use of a negative A-plate with orthogonal optical axes reduces the distance difference of the polarization state depending on the wavelength by rotation in the opposite direction on the Porcocare spheres.

And using a negative A-plate whose optical axes are orthogonal, the polarization state is aligned on the S ₁ axis irrespective of the wavelength of light in the Poincare sphere.

The first positive A plate, the second positive A plate, the negative? / 4 A plate, the negative C plate, the liquid crystal cell, the positive? / 4 A plate, The third negative A-plate, and the fourth negative A-plate, and the optical axes of two adjoining two positive A-plates and adjacent two negative A-plates are orthogonal to each other.

And a phase delay value of the first positive A-plate is smaller than a phase delay value of the second positive A-plate.

And the degree of the normal dispersion of the third negative A-plate is larger than the degree of the normal dispersion of the fourth negative A-plate.

And the positive A-plate has a phase phase retardation value in the range of 20 nm to 300 nm at a wavelength of 550 nm.

And the negative A-plate has a phase phase retardation value in the range of 20 nm to 300 nm at a wavelength of 550 nm.

And the negative C-plate has a negative retardation value in the thickness direction equal to the retardation value of the liquid crystal layer.

The high-transmittance wide-angle vertical alignment liquid crystal display according to the present invention has the following effects.

First, the transmittance can be improved in a bright state of a multi-domain vertical alignment liquid crystal display device by using a uniaxial film having seven normal dispersion characteristics.

Second, the light leakage phenomenon occurring in all directions in the dark state can be removed regardless of the wavelength.

Third, it is possible to eliminate the light leakage phenomenon occurring at the side in the dark state by removing the distance difference along the wavelength in the absorption axis of the polarizer of the top plate in the pouincere spherical shape, thereby improving the optical viewing angle characteristic.

Fourthly, the third negative A-plate and the fourth negative A-plate are sequentially positioned and rotated in the opposite direction on the Poincare sphere, and the polarized states corresponding to the wavelength are accurately detected by using the proper dispersion characteristics of the film. It can gather on the absorption axis.

1 is a cross-sectional view illustrating a compensation structure of a vertically aligned liquid crystal cell
Fig. 2 is a view showing a simulation image of front pixels in the bright state of the liquid crystal cell of Fig.
FIG. 3 is a diagram showing a polarization state in a Poincare sphere as viewed from the side (? = 70 °,? = 45 °) of the compensation structure of the liquid crystal cell of FIG.
FIG. 4 is a graph showing the result of a simulation showing the contrast ratio according to the viewing angle of the liquid crystal cell of FIG.
5 is a cross-sectional view illustrating a compensation structure of a liquid crystal cell aligned vertically with a high transmittance and a wide viewing angle using a compensation film according to a preferred embodiment of the present invention
Fig. 6 is a view showing a simulation image of a front pixel in the bright state of the liquid crystal cell of Fig. 5
7A is a diagram showing a polarization state in a Poincare sphere (S2-S3 plane) viewed from the side (? = 70 占,? = 45 占) of the compensation structure of the liquid crystal cell of Fig. 5
7B is a diagram showing a polarization state in a Poincare sphere (S1-S2 plane) viewed from the side (? = 70 占,? = 45 占) of the compensation structure of the liquid crystal cell of Fig. 5
7C is a diagram showing a polarization state in a Poincare sphere (S1-S2 plane) viewed from the side (? = 70 占,? = 270 占 from the compensation structure of the liquid crystal cell of Fig. 5
8 is a graph showing the contrast ratio of the liquid crystal cell according to the viewing angle of FIG.

Hereinafter, a preferred embodiment of a high transmittance wide viewing angle vertical alignment liquid crystal display device according to the present invention will be described in detail.

Features and advantages of a high transmittance wide viewing angle vertically aligned liquid crystal display according to the present invention will be apparent from the following detailed description of each embodiment.

5 is a cross-sectional view illustrating a compensation structure of a vertically aligned liquid crystal cell having a high transmittance and a wide viewing angle using a compensation film according to a preferred embodiment of the present invention.

The present invention relates to a vertically aligned liquid crystal display device including an optical compensation film, and more particularly, to a vertically aligned liquid crystal display device including an uniaxial film having a different optical axis and phase retardation value, ) 7 is used to increase the transmittance in the bright state and to remove the light leakage phenomenon occurring in all directions in the dark state regardless of the wavelength.

The high transmittance and wide viewing angle compensation structure of the vertically aligned liquid crystal display according to the present invention is characterized in that it includes an MVA liquid crystal cell, an upper plate and a lower plate polarizer provided on the upper and lower plates of the MVA liquid crystal cell, and a liquid crystal layer between the liquid crystal layer and the upper polarizer And includes seven uniaxial films having different optical axis, phase retardation value, and refractive index value according to wavelength.

The multi-domain vertically aligned liquid crystal display according to the present invention comprises a lower plate polarizer, a top plate polarizer, and a liquid crystal layer. The absorption axis of the lower plate polarizer and the absorption axis of the upper plate polarizer are orthogonal to each other. It is preferable to arrange them vertically.

More specifically, the present invention provides a liquid crystal display device comprising a lower plate polarizing plate, a vertically aligned liquid crystal cell filled with liquid crystal, and a top plate polarizing plate, wherein an absorption axis of the lower plate polarizing plate and an absorption axis of the upper plate polarizing plate are orthogonal, Plate (n _x > n _y = n _z ) and one or more negative A-plates (n _x (n _x n _y )) for viewing angle compensation in a dark state, <n _y = n _z ) between the polarizing plate and the liquid crystal cell, and one or more negative C-plates (n _x = n _y > n _z ), and the optical axes of two adjoining two positive A-plates, adjacent two negative A-plates are always orthogonal to each other.

The positive λ / 4 A-plate and the negative λ / 4 A-plate of the present invention are used as a circularly polarizing plate in combination with a polarizing plate while being disposed between a top polarizer and a bottom polarizer, the disclination line is effectively reduced to increase the transmittance.

The uniaxial films of the present invention use a positive λ / 4 A-plate and a negative λ / 4 A-plate in order to increase the transmittance in a bright state while being disposed between the upper polarizer and the lower polarizer, In order to compensate for the viewing angle in a dark state, and in this way, by rotating the positive A-plates perpendicular to each other with their optical axes in opposite directions on the Poincare sphere, and also by rotating the negative A- In the case of the Poincare design, the rotation in the opposite direction decreases the distance difference of the polarization state according to the wavelength.

In the vertically aligned liquid crystal display of the present invention, the phase retardation value of the liquid crystal cell is preferably a value between 200 nm and 450 nm at a wavelength of 550 nm.

In a bright state in a vertically aligned liquid crystal cell, light incident from a backlight is polarized in a 0 degree direction between polarizers in which transmission axes are orthogonal to each other, and linearly polarized light passing through the liquid crystal cell in a 0 degree direction is rotated 90 degrees And the transmitted light becomes linearly polarized light.

The phase retardation value of the liquid crystal cell must be a half wavelength (? / 2) of the incident light so that the linearly polarized light in the 0 占 direction becomes the linearly polarized light rotated by 90 占. The range of the phase delay value of the liquid crystal cell is determined according to the method used.

In the following description, the liquid crystal display device of the present invention includes orienting the liquid crystal in various directions or dividing into multiple regions by the applied voltage.

The liquid crystal display is distinguished by multi-domain vertical alignment (MVA), patterned vertical alignment (PVA), or super-patterned vertical alignment (SPVA) according to the mode of active matrix drive electrodes including electrode pairs do.

In the present invention, the multi-domain vertically aligned liquid crystal cell includes MVA, PVA, SPVA, and the like.

In order to improve the transmittance of the multi-domain vertically aligned liquid crystal cell, the positive λ / 4 A-plate and the negative λ / 4 A-plate are arranged so that their optical axes are orthogonal to each other.

In order to compensate the viewing angle, a uniaxial film with a positive dispersion characteristic was used. In order to compensate the viewing angle of the vertically aligned liquid crystal cell, two sheets of the holding plate Plate A-plate and the two negative A-plates are orthogonal to each other, it is possible to effectively remove the light leakage from the side irrespective of the wavelength, thereby realizing a wide viewing angle characteristic.

Looking at the refractive index of the uniaxial film to be used for the vertical alignment viewing angle compensation of the liquid crystal cell, and the surface index of refraction of x to the axial index of refraction n _x, the refractive index in the y-axis direction n _y, the thickness direction refractive index may be referred to as n _z, At this time, the characteristics of the uniaxial film are determined according to the refractive index size in each direction.

The uniaxial film is referred to as uniaxial film when the refractive index in one axial direction is different from the refractive index in the three axial directions.

(1) When n _x > n _y = n _z , this is called a positive A-plate, and the in-plane retardation value is defined by using the refractive index difference and the film thickness lying on the surface.

(2) n _x <n _y = n _z , it is called negative A-plate, and the in-plane retardation value is defined by using the refractive index difference and the film thickness lying on the surface.

(3) n _x = n _y <n _z , it is called a positive C-plate, and the retardation value in the thickness direction is defined by using the refractive index difference between the surface refractive index and the thickness direction and the thickness of the film.

(4) n _x = n _y > n _z , the negative retardation value is defined by using the refractive index difference between the surface refractive index and the thickness direction and the thickness of the film.

In order to compensate the vertically aligned liquid crystal cell, the phase retardation values of the positive A-plate and the negative A-plate used preferably have values in the range of 20 nm to 300 nm at a wavelength of 550 nm.

The wavelength dispersion characteristics of the uniaxial film can have a normal wavelength dispersion, a flat wavelength dispersion, and a reverse wavelength dispersion. In the present invention, a uniaxial film having a positive dispersion characteristic use.

The degree of dispersion of the uniaxial film used in the present invention is shown in Table 1 below.

Here, the value of the phase retardation value (DELTA) of the first positive A-plate, the second positive A-plate, the third negative A-plate and the fourth negative A-plate is a value selected for illustration, And the degree of dispersion.

If the degree of dispersion of the first positive A-plate is increased, the degree of dispersion of the second positive A-plate is increased. If the degree of dispersion of the first positive A-plate is increased, the degree of dispersion of the second positive A-

Further, as the degree of dispersion of the third negative A-plate increases, the degree of dispersion of the fourth negative A-plate increases, and it is possible to adjust to decrease as the amount decreases.

The high transmissivity and wide viewing angle compensation structure of the vertically aligned liquid crystal display according to the embodiment of the present invention will now be described in detail.

5, when a multi-domain vertical alignment (MVA) liquid crystal cell 60 is disposed between a lower polarizer 10 and an upper polarizer (analyzer) 100, And a first positive A-plate 20 and a second positive A-plate (not shown) are disposed between the multidomain vertical alignment (MVA) liquid crystal cell and the lower polarizer plate 10, a positive A-plate 30 are sequentially installed.

At this time, the first positive A-plate 20 has an optical axis of 0 degree and? N = 154 nm, and the second positive A-plate 30 has an optical axis of 90 degrees and? N = 49 nm.

On the second positive A-plate 30, a negative? / 4 A-plate 40 and a negative C-plate 50 are sequentially arranged.

At this time, as is commonly known, the negative C-plate has an optical axis perpendicular to the plate surface, and a Δnd value has a negative value equal to that of the vertically aligned liquid crystal.

The parameters of the third negative A-plate 80, the fourth negative A-plate 90 and the positive λ / 4 A-plate 70, which are present between the top polarizer and the vertically aligned liquid crystal cell, The first positive A-plate 20, the second positive A-plate 30 and the negative? / 4 A-plate 40, which are present between the first positive A-plate 10 and the negative C- And the DELTA n value has the same value which is opposite in sign.

FIG. 6 is a simulation image of frontal pixels in the bright state of the liquid crystal cell of FIG. 5;

As can be seen from the simulation results of FIG. 6, the high transmissivity and wide viewing angle compensation structure of the multi-domain vertically aligned liquid crystal cell according to the present invention confirms that a very high transmittance is obtained without a dicslination line in a bright state .

FIG. 7A is a diagram showing a polarization change according to a wavelength in a Poincare sphere (S2-S3 plane) viewed from the side (? = 70 °,? = 45 °) of the compensation structure of the liquid crystal cell of FIG.

Where? Represents an angle of 70 degrees with respect to the z axis, and? Represents an angle of 45 degrees with respect to the x axis.

7A and 5, the transmission axis of the lower polarizer plate 10 positioned at S ₁ is moved to the point T according to the side view field, and the absorption axis of the upper polarizer plate 100 is changed from S ₁ to A .

Therefore, in the structure proposed by the present invention, the starting point of the polarization state of light is point T, and finally the polarized light to be reached becomes point A.

First, the unpolarized light passes through the lower plate polarizer 10 having the transmission axis of 90 degrees, and is positioned at the point T.

A first positive A-plate 30 with an optical axis of 0 degrees and a value of DELTA d = 154 nm, a positive A-plate 30 with an optical axis of 90 degrees and a second plate A positive the polarization state of the light passing through the plate 40 is located at point F.

In this case, the two flexible A-plates rotate in opposite directions in the Poincare sphere because the optical axes are orthogonal.

Using the proper static dispersion characteristics of the film along with the rotation in the opposite direction in the Poincare design, the polarization states according to the wavelength can be aligned with the S ₁ axis in a straight line (φ = 45 °).

The polarization states of point F must be precisely gathered at point A, which is the final destination, irrespective of the wavelength, to achieve a perfect dark state, which is a function of the first positive A-plate 20 and the second positive A Plate 30 and a film of the third negative A-plate 90 and the fourth negative A-plate 80 having the same positive and negative values of DELTA nnd positive dispersion characteristics.

The third negative A-plate 80 and the fourth negative A-plate 90 are sequentially positioned and rotated in opposite directions on the Porcocare spheres, and the polarized states corresponding to the wavelengths are obtained Can be accurately collected on the absorption axis of the top plate polarizer 100.

Thus, the final polarization state reaches point A, so that the light is blocked even in the side view, thereby realizing a perfect dark state.

7B is a diagram showing the polarization change of 550 nm light in the Poincare sphere (S1-S2 plane) viewed from the side (? = 70 占,? = 45 占) of the compensation structure of the liquid crystal cell of Fig.

Where? Represents an angle of 70 degrees with respect to the z axis, and? Represents an angle of 45 degrees with respect to the x axis.

Referring to FIG. 7B and FIG. 5, unpolarized light passes through the lower plate polarizer 10 having the transmission axis of 90 degrees, and is located at point 1.

The polarization state of light passing through the first positive A-plate 20 and the second positive A-plate 30, whose optical axes are orthogonal to each other, is located at point 2.

The light passing through the negative? / 4 A-plate 40 is moved from point 2 to point 3 and the light passing through the positive? / 4 A-plate 70 is moved from point 3 to point 2 again.

Finally, the light having passed through the third negative A-plate 80 and the fourth negative A-plate 90 whose optical axes are orthogonal to each other is moved to point 4 coinciding with the absorption axis of the top plate polarizer 100 at point 2 do.

At this time, the uniaxial film having the normal dispersion characteristic is moved to the point 4 regardless of the wavelength because the optical axes are perpendicular to each other as shown in FIG. 7A.

7C is a diagram showing the polarization change of 550 nm light in the Poincare sphere (S1-S2 plane) viewed from the side (? = 70 占,? = 270 占 of the compensation structure of the liquid crystal cell of Fig.

Here, θ represents an angle of 70 ° with respect to the z axis, and φ represents an angle of 270 ° with respect to the x axis.

The first positive A plate 20, the second positive A plate 30, and the negative C plate 30, whose optical axes coincide with the polarizing plate, at the side (φ = 270 °) - There is no shift of the polarization state when passing through the plate 50, the liquid crystal cell 60, the third negative A-plate 80 and the fourth negative A-plate 90.

Therefore, when the polarized state moves from the point 1 to the point 2 when passing the negative? / 4 A-plate 40 and the polarized state passes the positive? / 4 plate 70, And moves to point 1 coinciding with the absorption axis.

8 is a simulation result showing the contrast ratio characteristic according to the viewing angle of the high transmittance and wide viewing angle compensation structure of the liquid crystal cell according to the present invention.

The high transmittance and wide viewing angle compensation structure of the vertically aligned liquid crystal cell according to the present invention can be confirmed that the contrast ratio at the front side as well as at the side is excellent as shown in the simulation result of FIG.

Thus, high transmittance of a multi-domain vertical alignment liquid crystal display device of the present invention having an optical viewing angle compensation method and structure use a uniaxial films (uniaxial film) having a positive dispersion characteristic, and the symmetry with respect to the reference axis S ₁ in ppoang curry spherical 4A-plate and the negative? / 4A-plate are orthogonal to each other so that the MVA liquid crystal cell can be used as a light source. The problem of lowering the transmittance can be solved.

As described above, it will be understood that the present invention is implemented in a modified form without departing from the essential characteristics of the present invention.

It is therefore to be understood that the specified embodiments are to be considered in an illustrative rather than a restrictive sense and that the scope of the invention is indicated by the appended claims rather than by the foregoing description and that all such differences falling within the scope of equivalents are intended to be embraced therein It should be interpreted.

10. Lower plate polarizer 20. First positive A-plate
30. Second positive A-plate 40. Negative? / 4 A-plate
50. Negative C-plate 60. Vertically aligned liquid crystal cell
70. A pervious λ / 4 A-plate 80. A third negative A-plate
90. Fourth negative A-plate 100. Top plate polarizer

Claims (15)

A liquid crystal display comprising a lower plate polarizer, a vertically aligned liquid crystal layer, and an upper plate polarizer, wherein the optical axis of the liquid crystal in the liquid crystal cell is vertically aligned with the substrate,
The transmission axis of the lower plate polarizer is orthogonal to the transmission axis of the upper plate polarizer,
A plurality of positive A-plates and negative A-plates for improving the transmittance in a bright state, a plurality of positive A-plates and negative A-
A plurality of positive A-plates and negative A-plates for compensating the viewing angle in a dark state are combined to form a liquid crystal layer between the lower plate polarizer and the upper plate polarizer Wherein the liquid crystal layer is stacked between the liquid crystal layer and the liquid crystal layer. The liquid crystal display according to claim 1, characterized in that the optical axis of the positive λ / 4 A-plate and the negative λ / 4 A-plate are disposed between the upper plate polarizer and the lower plate polarizer Device. The liquid crystal display according to claim 1, wherein a plurality of positive A-plates and negative A-plates are disposed between the top plate polarizer and the bottom plate polarizer to compensate the viewing angle in a dark state Wherein the positive dispersion of the uniaxial film is reversed. The liquid crystal display of claim 1, wherein optical axes of two adjoining pliable A-plates disposed between the upper polarizer and the lower polarizer are orthogonal. 5. The liquid crystal display according to claim 4, characterized in that the use of a flexible A-plate whose optical axes are orthogonal to each other reduces the difference in the polarization state depending on the wavelength by rotating in the opposite direction on the Poincare sphere, Device. 5. The liquid crystal display device according to claim 4, characterized in that the polarizing state is aligned on the S ₁ axis irrespective of the wavelength of light in the Porcocare spheres by using the flexible A-plate whose optical axes are orthogonal, . The liquid crystal display of claim 1, wherein the optical axes of two adjacent negative A-plates disposed between the upper plate polarizer and the lower plate polarizer are orthogonal. 9. The liquid crystal display device according to claim 7, characterized in that the use of negative A-plates whose optical axes are orthogonal to each other reduces the difference in the polarization state depending on the wavelength by rotation in the opposite direction on the Poincare sphere, . The liquid crystal display of claim 7, wherein the polarization state is aligned in the S ₁ axis irrespective of the wavelength of light in the Poincare sphere by using the negative A-plate whose optical axis is orthogonal. The liquid crystal display device according to claim 1, wherein between the lower plate polarizer and the upper plate polarizer,
Plate, a third negative A-plate, a fourth positive A-plate, a second positive A-plate, a negative? / 4 A-plate, a negative C-plate, a liquid crystal cell, Negative A-plate,
Wherein the optical axes of the two adjacent positive A-plates and the adjacent two negative A-plates are orthogonal to each other. The liquid crystal display of claim 10, wherein the phase retardation value of the first positive A-plate is smaller than the phase retardation value of the second positive A-plate. The liquid crystal display of claim 10, wherein the degree of the positive dispersion of the third negative A-plate is greater than the degree of the positive dispersion of the fourth negative A-plate. 11. The method of claim 10, wherein the positive A-plate has a wavelength of 550 nm,
And has a phase phase retardation value in the range of 20 nm to 300 nm. 11. The method of claim 10, wherein the negative A-plate has a wavelength of 550 nm,
And has a phase phase retardation value in the range of 20 nm to 300 nm. 11. The liquid crystal display of claim 10, wherein the negative C-plate has a negative retardation value in the thickness direction equal to the phase retardation value of the liquid crystal layer.

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