KR101540314B1 - Display device - Google Patents

Abstract

A display device having improved viewing angle is disclosed. The display device includes a display panel, a first optical unit, and a second optical unit. The liquid crystal layer includes a first substrate, a second substrate facing the first substrate, and a liquid crystal layer interposed between the two substrates and driven in the vertical alignment mode. The first optical unit includes a first polarizing plate disposed at a lower portion of the first substrate and having a first absorption axis, and a c-plate disposed between the first polarizing plate and the first substrate. The second optical unit includes a second polarizing plate disposed on the second substrate and having a second absorption axis orthogonal to the first absorption axis, a positive A-plate disposed between the second substrate and the second polarizing plate, And a negative A-plate disposed under the positive A-plate with respect to the negative A-plate. Thus, the viewing angle can be improved by minimizing dispersion of the polarization state of each color light through the negative and positive A-plates.

Positive A-plate, Negative A-plate

Description

DISPLAY APPARATUS

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a display device, and more particularly, to a liquid crystal display device that displays an image using a light transmittance of a liquid crystal.

The liquid crystal display includes a liquid crystal display panel that displays an image using light, and a backlight assembly disposed under the liquid crystal display panel and providing light to the liquid crystal display panel.

The liquid crystal display panel includes a first substrate having a thin film transistor and a pixel electrode, a second substrate having a common electrode facing the first substrate, and a liquid crystal layer interposed between the first and second substrates.

The liquid crystals in the liquid crystal layer can be operated in a vertical alignment (VA) mode by an electric field formed between the pixel electrode and the common electrode. For example, when an electric field is not formed between the pixel electrode and the common electrode, the liquid crystal display panel realizes a white image and implements a black image when an electric field is formed between the pixel electrode and the common electrode .

When an electric field is formed between the pixel electrode and the common electrode, the liquid crystals in the liquid crystal layer are arranged in a direction perpendicular to the pixel electrode or the common electrode. When the liquid crystals are arranged in the vertical direction, an image having a high contrast ratio (CR) is displayed on the front side of the liquid crystal display panel, but a low contrast ratio image is displayed on the side of the liquid crystal display panel Is displayed. This is because light traveling to the side of the liquid crystal display panel is retarded in the thickness direction by the liquid crystals.

As described above, the liquid crystal display panel operated in the vertical alignment mode has a problem of displaying an image having a low brightness contrast ratio on the side due to the thickness direction phase delay caused by the liquid crystals.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a display device capable of improving a viewing angle on a side surface in a vertical alignment mode.

The display device according to an embodiment of the present invention includes a display panel, a first optical unit, and a second optical unit.

The display panel includes a first substrate, a second substrate facing the first substrate, and a liquid crystal layer interposed between the first and second substrates and driven in a vertical alignment mode. The first optical unit includes a first polarizer disposed at a lower portion of the first substrate and having a first absorption axis, and a C-plate disposed between the first polarizer and the first substrate. The second optical unit includes a second polarizing plate disposed on the second substrate and having a second absorption axis orthogonal to the first absorption axis, a positive polarizing plate disposed between the second polarizing plate and the second polarizing plate, a positive A-plate, and a negative A-plate disposed below the positive A-plate with respect to the traveling direction of light.

The negative A-plate may be disposed between the liquid crystal layer and the second substrate. Here, the second substrate includes a plurality of color filters formed at a position facing the liquid crystal layer, and the negative A-plate is coated or dispensed on the color filters to face the liquid crystal layer . Alternatively, the negative A-plate may be disposed between the second substrate and the positive A-plate.

In the negative A-plate, an axis having a small refractive index among nx and ny is parallel to the first absorption axis, and an axis having a large refractive index among nx and ny may be parallel to the first absorption axis. Here, nx is the refractive index in the x-axis direction, and ny is the refractive index in the y-axis direction orthogonal to the x-axis direction.

Wherein the negative A-plate is a phase retardation film having nx? Ny and a thickness direction retardation value (Rth)? 0, wherein the positive A-plate has a phase in which nx? Ny and a thickness direction phase retardation value (Rth) Can be a retardation film. Here, Rth = {(nx + ny) / 2-nz} * d, nz is the refractive index in the z-axis direction orthogonal to the x- and y-axis directions, and d is the thickness of the film.

The absolute value of the negative coefficient Nz of the negative A-plate has a value between 0.9 and 1.1, and the absolute value of the negative coefficient Nz of the positive A-plate has a value between 0.9 and 1.1. have. However, Nz = (nx - nz) / (nx - ny).

The in-plane phase retardation value (Ro) at the green light wavelength has a value between 47.0 nm and 49.0 nm, and the in-plane phase retardation value (Ro) at the green light wavelength has an in- The first negative in-plane dispersion delay value having a value of a ratio Ro is a value between 1.00 and 1.20 and is a ratio of an in-plane phase retardation value Ro at the green light wavelength to an in-plane phase retardation value Ro at a red light wavelength. The second negative in-plane dispersion retardation value may have a value between 0.90 and 1.10. However, Ro = (nx - ny) * d.

Wherein the negative A-plate has a thickness direction phase retardation value (Rth) at the green light wavelength of between -23.0 and -25.0, and wherein the retardation value (Rth) at the blue light wavelength The first negative thickness dispersion delay value which is a ratio of the thickness direction phase retardation value (Rth) is substantially equal to the first negative in-plane dispersion retardation value, and the ratio of the thickness direction retardation value (Rth) The second negative thickness dispersion delay value that is the ratio of the thickness direction retardation value (Rth) of the first negative in-plane dispersion retardation value to the second negative in-plane dispersion retardation value can be substantially equal to the second negative dispersion retardation value. In this case, the red light wavelength has a value between 640 nm and 660 nm, the green light wavelength has a value between 540 nm and 560 nm, and the blue light wavelength can have a value between 440 nm and 460 nm.

The positive A-plate has an in-plane phase retardation value (Ro) at a green light wavelength of 179.5 nm to 180.5 nm, and an in-plane phase retardation value (Ro) at a blue wavelength of the green light wavelength The first positive in-plane dispersion retardation value, which is the ratio of the in-plane retardation value Ro to the in-plane retardation value Ro in the green light wavelength, is 0.880 to 0.890, The second positive in-plane dispersion delay value may have a value between 1.000 and 1.100. However, Ro = (nx - ny) * d.

The negative A-plate has a thickness retardation value (Rth) in the range of 96.0 to 98.0 at the green light wavelength and has a thickness direction retardation value (Rth) at the green light wavelength in the thickness direction The first positive thickness dispersion delay value which is a ratio of the phase retardation value Rth is substantially equal to the first positive in-plane dispersion retardation value, and the thickness at the wavelength of the red light with respect to the thickness direction phase retardation value Rth at the green light wavelength The second positive thickness dispersion delay value that is the ratio of the directional phase delay value Rth may be substantially equal to the second positive in-plane dispersion delay value. Here, the red light wavelength has a value between 640 nm and 660 nm, the green light wavelength has a value between 540 nm and 560 nm, and the blue light wavelength has a value between 440 nm and 460 nm.

The ratio of the in-plane phase retardation value Ro of the positive A-plate to the red light wavelength λ is referred to as a positive red wavelength retardation value, and the in-plane phase of the negative A- And the ratio of the retardation value Ro to the negative red wavelength retardation value, the value obtained by subtracting the negative red wavelength retardation value from the positive red wavelength retardation value may have a range of 0.20 to 0.30. However, Ro = (nx - ny) * d, and the units of Ro and lambda are all nm. Here, the red light wavelength may have a value between 640 nm and 660 nm.

Plane retardation value (Ro) of the positive A-plate relative to the green light wavelength (?) Is referred to as positive green wavelength retardation value, and the ratio of the in-plane phase retardation value (Ro) of the negative A- Ro) is a negative green wavelength delay value, a value obtained by subtracting the negative green wavelength delay value from the positive green wavelength delay value may have a range of 0.20 to 0.30. However, Ro = (nx - ny) * d, and the units of Ro and lambda are all nm. Here, the green light wavelength may have a value between 540 nm and 560 nm.

Plane retardation value Ro of the positive A-plate relative to the blue light wavelength λ is referred to as a positive blue wavelength retardation value and the ratio of the in-plane phase retardation value Ro of the negative A- Ro) is a negative blue wavelength retardation value, a value obtained by subtracting the negative blue wavelength retardation value from the positive blue wavelength retardation value may have a range of 0.20 to 0.30. However, Ro = (nx - ny) * d, and the units of Ro and lambda are all nm. Here, the blue light wavelength may have a value between 440 nm and 460 nm.

In the present invention, the seed-plate may be a negative seed-plate satisfying a formula of nx = ny> nz. Here, nx is the refractive index in the x-axis direction, ny is the refractive index in the y-axis direction orthogonal to the x-axis direction, and nz is the refractive index in the z-axis direction orthogonal to the x- and y-axis directions.

On the other hand, the positive and negative A-plates reflect the polarization states of the red light, green light and blue light dispersed by the seed-plate and the liquid crystal layer when viewed from the side of the display panel to the extinction point ). ≪ / RTI >

According to the present invention, as the negative A-plate and the positive A-plate are arranged in order along the light traveling direction, the brightness contrast ratio when the display panel is viewed from the side can be further increased. That is, the positive and negative A-plates can substantially match the polarization states of the red light, green light, and blue light dispersed by the cue-plate and liquid crystal layer as viewed from the side with the erasure point at the Porcocal Sphere. As a result, the brightness contrast ratio due to the dispersion of the polarization states of the respective color lights can be prevented from being reduced.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that this invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures are enlarged to illustrate the present invention in order to clarify the present invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. The singular expressions include plural expressions unless the context clearly dictates otherwise.

In this application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a part or a combination thereof is described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

Also, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in the general dictionary used should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and, unless explicitly defined in the present application, are interpreted in an ideal or overly formal sense It does not.

≪ Example 1 >

1 is a sectional view showing a display device according to a first embodiment of the present invention.

1, a display device according to the present embodiment includes a display panel 100, a first optical unit 200, a second optical unit 300, and a backlight unit 400.

The display panel 100 includes a first substrate 110, a second substrate 120 facing the first substrate 110, and a second substrate 120 interposed between the first substrate 110 and the second substrate 120. [ And a liquid crystal layer.

The first substrate 110 includes signal lines (not shown), thin film transistors (not shown) electrically connected to the signal lines (not shown), and pixel electrodes 112 electrically connected to the thin film transistors do. The pixel electrodes 112 are made of a transparent conductive material and receive data voltages transmitted from the signal lines through the thin film transistors.

The second substrate 120 includes color filters 122 corresponding to the pixel electrodes 112 and common electrodes (not shown) formed on the color filters 122. The color filters 122 may include red color filters, green color filters, and blue color filters. The common electrode is made of a transparent conductive material and receives a common voltage.

The liquid crystal layer 130 is interposed between the first substrate 110 and the second substrate 120 and may be driven in a vertical alignment mode. That is, if an electric field is not formed between the pixel electrode 112 and the common electrode, the liquid crystal molecules of the liquid crystal layer 130 are aligned in a horizontal direction with respect to the first substrate 110, The liquid crystal molecules of the liquid crystal layer 130 are aligned in a direction perpendicular to the first substrate 110. In this case,

The first optical unit 200 is disposed below the display panel 100. The first optical unit 200 includes a first polarizer 210 disposed below the display panel 100 and a second polarizer 210 disposed between the first polarizer 210 and the first optical unit 200, (C-plate, 220). That is, the light generated from the backlight unit 400 disposed at the lower portion of the first polarizer 210 passes through the first polarizer 210 and the cue-plate 220 and is transmitted to the display panel 100 .

The second optical unit 300 includes a second polarizing plate 310 disposed on the display panel 100 and a positive polarizing plate 310 disposed between the second polarizing plate 310 and the display panel 100. [ a positive A-plate 320, and a negative A-plate 330 disposed under the positive A-plate with respect to the traveling direction of light.

In this embodiment, the negative A-plate 330 is disposed between the liquid crystal layer 130 and the second substrate 120. For example, the negative A-plate 330 may be formed by coating or dispensing on the color filters 122 to face the liquid crystal layer. That is, the negative A-plate 330 may be formed on the color filters 122 instead of the overcoat layer that protects the color filters 122. Alternatively, the negative A-plate 330 may be formed on the overcoat layer.

The c-plate 220 is disposed below the first substrate 110. Alternatively, the c-plate 220 may be disposed between the first substrate 110 and the liquid crystal layer 130. [ That is, the seed-plate 220 may be formed on the first substrate 110 by a coating or a dispense method.

Fig. 2 is a view conceptually showing the relationship of optical members of the display device of Fig. 1;

1 and 2, the first polarizer 210 has a first absorption axis 212 parallel to the first direction DI1 and a second absorption axis 212 parallel to the first direction DI1 in a second direction orthogonal to the first direction DI1 And a first polarization axis (not shown) parallel to the first polarization axis DI2. That is, the light transmitted through the first polarizer 210 is polarized in the second direction DI2. Here, the third direction DI3 refers to a direction in which light travels in a direction orthogonal to the first and second directions DI1 and DI2.

The seed-plate 220 is disposed on the first polarizer 210 and has an optical axis 222 parallel to the third direction. The seed-plate 220 may be a negative C-plate satisfying a formula of nx = ny> nz. Herein, nx is the refractive index in the x-axis direction, ny is the refractive index in the y-axis direction orthogonal to the x-axis direction, and nz is the refractive index in the z-axis direction orthogonal to the x- Refractive index. In the present embodiment, the x-axis direction is parallel to the first direction DI1, the y-axis direction is parallel to the second direction DI2, and the z-axis direction is parallel to the third direction DI3 It is parallel.

The in-plane phase delay value Ro of the seed-plate 220 has a value of zero because nx = ny. Herein, the in-plane phase retardation value Ro of the seed-plate 220 is (nx-ny) * d, and d is the thickness of the seed-plate 220.

The phase retardation value Rth in the thickness direction of the seed-plate 220 has a positive value because nx = ny> nz. Here, the phase retardation value Rth in the thickness direction of the seed-plate 220 means {(nx + ny) / 2 - nz} * d.

The liquid crystal layer 130 is disposed on the upper portion of the seed-plate 220. The liquid crystals of the liquid crystal layer 130 are operated in the vertical alignment mode and have a refractive index substantially opposite to that of the seed-plate 220. The liquid crystal layer 130 has an optical axis 132 parallel to the third direction. On the other hand, the optical axis 132 of the liquid crystal layer 130 is formed in a direction opposite to the optical axis 222 of the seed-plate 220. For example, the liquid crystal layer 130 may have a property of satisfying a formula of nx = ny < nz.

The in-plane phase retardation value Ro of the liquid crystal layer 130 has a value of zero because nx = ny. In addition, the phase retardation value Rth in the thickness direction of the liquid crystal layer 130 has a negative value because nx = ny <nz. Here, the retardation value Rth in the thickness direction of the liquid crystal layer 130 is {(nx + ny) / 2 - nz} * d, where d is the thickness of the liquid crystal layer 130.

The negative A-plate 330 is disposed on the liquid crystal layer 130 and has an optical axis 332 parallel to the first direction DI1. That is, the optical axis 332 of the negative A-plate 330 is parallel to the first absorption axis 212 of the first polarizer 210. Here, the optical axis 332 of the negative A-plate 330 means an axis having a small refractive index among nx and ny, that is, a fast axis.

The negative A-plate 330 is a phase retardation film having nx? Ny and thickness direction retardation value (Rth)? 0. The retardation value Rth in the thickness direction of the negative A-plate 330 is {(nx + ny) / 2 - nz} * d, where d is the thickness of the negative A- do.

The color filter 122 is disposed on the negative A-plate 330, and changes the transmitted white light into color light, for example, red light, green light, and blue light. That is, the color filter transmits only one of the red light, the green light and the blue light in white light composed of red light, green light and blue light.

The positive A-plate 320 is disposed on the color filter 122 and has an optical axis 322 parallel to the first direction DI1. That is, the optical axis 322 of the positive A-plate 320 is parallel to the first absorption axis 212 of the first polarizer 210. Here, the optical axis of the positive A-plate 320 means an axis having a large refractive index, that is, a slow axis among nx and ny.

The positive A-plate 320 is a phase retardation film having nx? Ny and a thickness direction retardation value (Rth)? 0. The phase retardation value Rth in the thickness direction of the positive A-plate 320 is {(nx + ny) / 2 - nz} * d where d is the thickness of the positive plate 320 .

The second polarizing plate 310 is disposed on the positive A-plate 320 and has a second absorption axis 312 parallel to the second direction DI2. In the first direction DI1, And a second polarization axis (not shown) parallel to the first polarization axis.

Fig. 3 is a view showing a Porcocare spherical surface showing the relationship between the absorption axis and the optical axis of the optical members of Fig. 2. Fig.

2 and 3, the Porcocare spherical surface is composed of three coordinate axes, that is, a first coordinate axis S1, a second coordinate axis S2, and a third coordinate axis S3. The Poincare spherical surface means a spherical surface for three-dimensionally describing the state of polarization when viewed from the side of the display device. The side surface of the display device is, for example, a side when viewing the display device at an azimuth angle of 45 degrees and a polar angle of 60 degrees.

The optical axis of the liquid crystal layer 130 is a rotation axis formed along the second coordinate axis S2 and the optical axis of the seed-plate 220 is a rotation axis formed in a direction opposite to the second coordinate axis S2.

The first polarizing axis of the first polarizing plate 210, that is, the lower plate transmitting axis is formed on the plane by the first and second coordinate axes S1 and S2, .

The second polarizing axis of the second polarizing plate 310, that is, the upper plate transmitting axis is formed on the plane by the first and second coordinate axes S1 and S2, and the second polarizing axis of the second polarizing plate 310 is formed on the lower plate transmitting axis and the second coordinate axis S2 As shown in FIG.

The optical axis of the negative A-plate 330 is a rotation axis formed on a plane by the first and second coordinate axes S1 and S2, and is formed substantially in the same direction as the lower plate transmission axis.

The optical axis of the positive A-plate 320 is formed in a direction opposite to the optical axis of the negative A-plate 330 with a rotation axis formed on a plane by the first and second coordinate axes S1 and S2.

On the other hand, the extinction point at the Poincare spherical surface is formed in a direction opposite to the second polarization axis of the second polarizer 310, that is, the upper plate transmission axis. The erase point is a position indicating the ideal polarization state of light transmitted from the first polarizer 210 to the positive A-plate 320. That is, when the light transmitted from the first polarizer 210 to the positive A-plate 320 coincides with the erase point, a contrast ratio (CR) as viewed from the side of the display device is Can be increased to the maximum.

Fig. 4 is a plan view showing a porch curle plane showing polarization state after transmission of the seed-plate of Fig. 2; Fig.

Referring to Figs. 2, 3 and 4, the porch curle plane according to the present embodiment is a plane showing the polarization state when the porcine spherical surface is viewed from the first coordinate axis S1. That is, the percoke plane is composed of the second and third coordinate axes S2 and S3.

First, the polarized states of red light, green light, and blue light transmitted through the first polarizer 210 are formed on the second coordinate axis S2 in the Poincare plane. The polarization states of the red light, the green light, and the blue light transmitted through the first polarizer 210 are disposed at a position spaced apart from the center of the Poincare plane to the right along the second coordinate axis S2. Here, the erasure point is disposed at a position spaced to the left along the second coordinate axis S2 from the center of the Porcocare plane.

When the red light, the green light, and the blue light transmitted through the first polarizing plate 210 are transmitted through the seed-plate 210, the polarization states of the color light are shifted downward along the third coordinate axis S3 by a first distance . Here, the polarization states of the color lights can be dispersed and arranged.

Fig. 5 is a plan view showing a porch curle plane showing the polarization state after transmission of the liquid crystal layer of Fig. 2; Fig.

2 and 5, the red light, the green light, and the blue light pass through the liquid crystal layer 130 after passing through the seed-plate 220. The polarization state of the color light transmitted through the liquid crystal layer 130 is shifted along the third coordinate axis S3 by a second distance longer than the first distance. Therefore, the polarization state of the color light transmitted through the liquid crystal layer 130 is disposed at the upper end with respect to the second coordinate axis S2. Meanwhile, the polarization states of the color light beams can be arranged more than those transmitted through the seed-plate 220.

Fig. 6 is a plan view showing a porch curle plane showing the polarization state after transmission of the negative A-plate of Fig. 2; Fig.

Referring to FIG. 6, the red light, the green light, and the blue light pass through the liquid crystal layer 130 and then through the negative A-plate 330. The polarized state of the color light transmitted through the negative A-plate 330 rotates clockwise with respect to the optical axis of the negative A-plate 330 and moves by a third distance. On the other hand, the polarized states of the color lights are dispersed as compared with those transmitted through the liquid crystal layer 130.

Then, the red light, the green light, and the blue light transmitted through the negative A-plate 330 pass through the color filter 122 again. The color filter 122 selectively transmits only one of the red light, the green light, and the blue light.

Fig. 7 is a plan view showing a porch curle plane showing the polarization state after transmission of the positive A-plate of Fig. 2; Fig.

Referring to FIGS. 2 and 7, the red light, the green light, and the blue light transmitted through the negative A-plate 330 are transmitted through the positive A-plate 320 again. The polarized state of the color light transmitted through the positive A-plate 320 moves by a fourth distance in the counterclockwise direction on the basis of the positive A-plate 320, and is disposed adjacent to the erase point. Here, the fourth distance is longer than the third distance. At this time, the polarization states of the color light scattered and disposed by the negative A-plate 330 can be arranged to be centered on the erase point by the positive A-plate 320.

As described above, according to the present embodiment, as the polarization states of the color lights transmitted through the positive A-plates 320 substantially coincide with the erasure points in the Poincare spherical surface, The contrast ratio CR can be further improved.

8 shows the relationship between the difference in the retardation value in the thickness direction between the liquid crystal layer and the c-plate with respect to the wavelength of each color light and the distance between the polarization state of each color light in the pork curley plane and the clearance point Graph.

FIG. 8 is a graph showing the characteristics of the negative A-plate of FIG. 2. FIG.

The characteristics of the negative A-plate according to this embodiment will be described in detail with reference to FIG.

First, the negative coefficient A Nj of the negative A-plate may have a value between about-0.9 and about -1.1, preferably about -1.0. However, Nz = (nx - nz) / (nx - ny).

Secondly, the in-plane phase retardation value Ro at the green light wavelength can have a value between about 47.0 nm and about 49.0 nm, and preferably has a value of about 47.8 nm. Here, the green light wavelength may have a value between about 540 nm and about 560 nm, and preferably about 550 nm.

Third, the first negative in-plane dispersion retardation value, which is the ratio of the in-plane phase retardation value Ro at the blue light wavelength to the in-plane phase retardation value Ro at the green light wavelength, can have a value between about 1.00 and about 1.20 And preferably has a value of about 1.08. Here, the blue light wavelength may have a value between about 440 nm and about 460 nm, and preferably about 450 nm.

Fourth, the second negative in-plane dispersion retardation value, which is the ratio of the in-plane phase retardation value Ro at the red light wavelength to the in-plane phase retardation value Ro at the green light wavelength, can have a value between about 0.90 and about 1.10 And preferably has a value of about 0.96. Here, the wavelength of the red light may have a value between about 640 nm and about 660 nm, and preferably about 650 nm.

Fifthly, the thickness retardation value Rth at the green light wavelength may have a value between about-23.0 and about -25.0, preferably about -23.9.

Sixth, the first negative thickness dispersion delay value, which is the ratio of the thickness direction phase retardation value (Rth) at the green light wavelength to the thickness direction phase retardation value (Rth) at the blue light wavelength, is substantially equal to the first negative in- Value.

7, the second negative thickness dispersion delay value which is the ratio of the thickness direction phase retardation value (Rth) to the thickness direction phase retardation value (Rth) at the red light wavelength to the thickness direction phase retardation value (Rth) at the green light wavelength is substantially equal to the second negative in- Value.

9 is a graph showing the characteristics of the positive A-plate of Fig.

The characteristics of the negative A-plate according to this embodiment will be described in detail with reference to FIG.

Initially, the positive coefficient A (Nz) of the positive A-plate may have a value between about 0.9 and about 1.1, preferably about 1.04.

Secondly, the in-plane phase retardation value Ro at the green light wavelength can have a value between about 179.5 nm and about 180.5 nm, and preferably has a value of about 180 nm. Here, the green light wavelength may have a value between about 540 nm and about 560 nm, and preferably about 550 nm.

Thirdly, the first positive in-plane dispersion retardation value, which is the ratio of the in-plane phase retardation value Ro at the blue light wavelength to the in-plane phase retardation value Ro at the green light wavelength, can have a value between about 0.880 and about 0.890 And preferably has a value of about 0.885. Here, the blue light wavelength may have a value between about 440 nm and about 460 nm, and preferably about 450 nm.

Fourth, the second positive in-plane dispersion delay value, which is the ratio of the in-plane phase delay value Ro at the red light wavelength to the in-plane phase delay value Ro at the green light wavelength, may have a value between about 1.000 and about 1.100 And preferably has a value of about 1.038. Here, the wavelength of the red light may have a value between about 640 nm and about 660 nm, and preferably about 650 nm.

Fifthly, the thickness direction phase retardation value (Rth) at the green light wavelength may have a value between about 96.0 and about 98.0, and preferably about 96.7.

Sixth, the first positive thickness dispersion delay value which is the ratio of the thickness direction phase retardation value (Rth) at the blue light wavelength to the thickness direction phase retardation value (Rth) at the green light wavelength is substantially equal to the first positive in- Value.

In the seventh aspect, the second positive thickness dispersion delay value that is the ratio of the thickness direction phase retardation value (Rth) at the green light wavelength to the thickness direction phase retardation value (Rth) at the red light wavelength is substantially equal to the second positive in- Value.

On the other hand, in this embodiment, when the absolute value of the negative coefficient Nz of the negative and positive A-plates has a value between about 0.9 and about 1.1, the negative and positive A- the retardation condition can be satisfied.

The ratio of the in-plane phase retardation value Ro of the positive A-plate to the red light wavelength λ is defined as a positive red wavelength retardation value and the in-plane phase retardation value of the negative A- Value Ro is a negative red wavelength retardation value, the value obtained by subtracting the negative red wavelength retardation value from the positive red wavelength retardation value may range from about 0.20 to about 0.30, preferably about 0.25 Respectively. The red light wavelength may have a value between about 640 nm and about 660 nm, preferably about 650 nm.

Plane retardation value (Ro) of the positive A-plate relative to the green light wavelength (?) Is referred to as positive green wavelength retardation value, and the ratio of the in-plane phase retardation value (Ro) of the negative A- Ro) is a negative green wavelength delay value, the value obtained by subtracting the negative green wavelength delay value from the positive green wavelength delay value may have a range of about 0.20 to about 0.30, and preferably a value of about 0.25 . Here, the green light wavelength may have a value between about 540 nm and about 560 nm, and preferably about 550 nm.

Plane retardation value Ro of the positive A-plate relative to the blue light wavelength λ is referred to as a positive blue wavelength retardation value and the ratio of the in-plane phase retardation value Ro of the negative A- Ro) is a negative blue wavelength retardation value, the value obtained by subtracting the negative blue wavelength retardation value from the positive blue wavelength retardation value may have a range of about 0.20 to about 0.30, and preferably about 0.25 . Here, the blue light wavelength may have a value between about 440 nm and about 460 nm, and preferably about 450 nm.

&Lt; Example 2 >

10 is a sectional view showing a display device according to a second embodiment of the present invention.

Since the display device according to the present embodiment is substantially the same as the display device according to the first embodiment described with reference to Figs. 1 to 9 except for the position of the negative A-plate 330, the negative A- A detailed description of other components will be omitted. The same constituent elements as those of the first embodiment are denoted by the same reference numerals.

Referring to FIG. 10, a negative A-plate 330 according to this embodiment is disposed between the second substrate 120 and the positive A-plate 320. That is, the negative A-plate 330 is not formed between the liquid crystal layer 130 and the color filters 122 but may be disposed on the display panel 100. Here, the negative A-plate 330 may be attached to the upper surface of the second substrate 120 in the form of a film.

While the present invention has been described in connection with what is presently considered to be practical and exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, 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.

1 is a sectional view showing a display device according to a first embodiment of the present invention.

Fig. 2 is a view conceptually showing the relationship of optical members of the display device of Fig. 1;

Fig. 3 is a view showing a Porcocare spherical surface showing the relationship between the absorption axis and the optical axis of the optical members of Fig. 2. Fig.

Fig. 4 is a plan view showing a porch curle plane showing polarization state after transmission of the seed-plate of Fig. 2; Fig.

Fig. 5 is a plan view showing a porch curle plane showing the polarization state after transmission of the liquid crystal layer of Fig. 2; Fig.

Fig. 6 is a plan view showing a porch curle plane showing the polarization state after transmission of the negative A-plate of Fig. 2; Fig.

Fig. 7 is a plan view showing a porch curle plane showing the polarization state after transmission of the positive A-plate of Fig. 2; Fig.

FIG. 8 is a graph showing the characteristics of the negative A-plate of FIG. 2. FIG.

9 is a graph showing the characteristics of the positive A-plate of Fig.

10 is a sectional view showing a display device according to a second embodiment of the present invention.

        Description of the Related Art

100: display panel 110: first substrate

112: pixel electrode 120: second substrate

122: color filter 130: liquid crystal layer

200: first optical unit 210: first polarizing plate

212: first absorption axis 220: seed-plate

300: second optical unit 310: second polarizing plate

312: second absorption axis 320: positive A-plate

330: Negative A-plate

Claims (22)

A display panel having a first substrate, a second substrate facing the first substrate, and a liquid crystal layer interposed between the first and second substrates and driven in a vertical alignment mode; A first optical unit having a first polarizing plate disposed at a lower portion of the first substrate and having a first absorption axis, and a C-plate disposed between the first polarizing plate and the first substrate; And A second polarizing plate disposed on the second substrate and having a second absorption axis orthogonal to the first absorption axis, and a second polarizing plate disposed between the second substrate and the second polarizing plate and having an optical axis orthogonal to the second absorption axis And a second optical unit having a positive A-plate and a negative A-plate disposed under the positive A-plate with respect to a traveling direction of light. 2. The apparatus of claim 1, wherein the negative A- And the second substrate is disposed between the liquid crystal layer and the second substrate. The liquid crystal display device according to claim 2, wherein the second substrate includes a plurality of color filters formed at positions facing the liquid crystal layer, Wherein the negative A-plate is formed by a coating or dispense method on the color filters so as to face the liquid crystal layer. 2. The apparatus of claim 1, wherein the negative A- And the second substrate is disposed between the second substrate and the positive A-plate. The liquid crystal display device according to claim 1, wherein the negative A-plate has an axis with a small refractive index, nx and ny, parallel to the first absorption axis, Wherein the positive A-plate has an axis having a large refractive index, nx and ny being parallel to the first absorption axis. (Where nx is the refractive index in the x-axis direction and ny is the refractive index in the y-axis direction orthogonal to the x-axis direction). 6. The retardation film according to claim 5, wherein the negative A-plate is a phase retardation film having nx? Ny and thickness retardation value (Rth) Wherein the positive A-plate is a phase retardation film having nx? Ny and a retardation value in the thickness direction (Rth)? 0. (Where Rth = {(nx + ny) / 2-nz} * d, nz is the refractive index in the z-axis direction orthogonal to the x- and y-axis directions, and d is the thickness of the film. 7. The method according to claim 6, wherein the absolute value of the negative coefficient Nz of the negative A-plate has a value between 0.9 and 1.1, And an absolute value of the negative coefficient Nz of the positive A-plate has a value between 0.9 and 1.1. (Where Nz = (nx - nz) / (nx - ny)). 8. The apparatus of claim 7, wherein the negative A- Plane retardation value Ro at the green light wavelength has a value between 47.0 nm and 49.0 nm, The first negative in-plane dispersion delay value, which is the ratio of the in-plane phase retardation value (Ro) to the in-plane phase retardation value (Ro) at the green light wavelength at the blue light wavelength, is a value between 1.00 and 1.20, And a second negative in-plane dispersion delay value which is a ratio of an in-plane phase delay value (Ro) to a in-plane phase delay value (Ro) at the green light wavelength at a red light wavelength has a value between 0.90 and 1.10. (Where Ro = (nx - ny) * d) 9. The apparatus of claim 8, wherein the negative A- The phase retardation value (Rth) in the thickness direction at the green light wavelength has a value between-23.0 and -25.0, The first negative thickness dispersion delay value being the ratio of the thickness direction phase retardation value (Rth) at the blue light wavelength to the thickness direction phase retardation value (Rth) at the green light wavelength is equal to the first negative in- And a second negative thickness dispersion delay value which is a ratio of a thickness direction retardation value (Rth) to a thickness direction phase retardation value (Rth) at the green light wavelength at a red light wavelength is equal to the second negative dispersion retardation value Display device. The method of claim 9, wherein the red light wavelength has a value between 640 nm and 660 nm, The green light wavelength has a value between 540 nm and 560 nm, And the blue light wavelength has a value between 440 nm and 460 nm. 8. The apparatus of claim 7, wherein the positive A- Plane retardation value Ro at the green light wavelength has a value between 179.5 nm and 180.5 nm, The first positive in-plane dispersion retardation value, which is a ratio of the in-plane phase retardation value Ro to the in-plane phase retardation value Ro at the blue light wavelength, is in a range of 0.880 to 0.890, And the second positive in-plane dispersion retardation value, which is a ratio of the in-plane phase retardation value (Ro) to the in-plane phase retardation value (Ro) at the green light wavelength at a red light wavelength, has a value between 1.000 and 1.100. (Where Ro = (nx - ny) * d) 12. The apparatus of claim 11, wherein the negative A- The phase retardation value (Rth) in the thickness direction at the green light wavelength has a value between 96.0 and 98.0, Wherein a first positive thickness dispersion delay value which is a ratio of a thickness direction phase retardation value (Rth) at a blue light wavelength to a thickness direction phase retardation value (Rth) at the green light wavelength is equal to the first positive in- And a second positive thickness dispersion delay value which is a ratio of a thickness direction phase retardation value (Rth) to a thickness direction phase retardation value (Rth) at a red light wavelength with respect to the green light wavelength is equal to the second positive in- Display device. 13. The method of claim 12, wherein the red light wavelength has a value between 640 nm and 660 nm, The green light wavelength has a value between 540 nm and 560 nm, And the blue light wavelength has a value between 440 nm and 460 nm. 7. The liquid crystal display device according to claim 6, wherein the ratio of the in-plane phase retardation value (Ro) of the positive A-plate to the red light wavelength (?) Is referred to as a positive red wavelength retardation value, Plane retardation value Ro of the plate is defined as a negative red wavelength retardation value, And a value obtained by subtracting the negative red wavelength delay value from the positive red wavelength delay value has a range of 0.20 to 0.30. (Where Ro = (nx-ny) * d, and units of Ro and lambda are all nm) 15. The method of claim 14, wherein the red light wavelength And has a value between 640 nm and 660 nm. 7. The method according to claim 6, wherein the ratio of the in-plane phase retardation value (Ro) of the positive A-plate to the green light wavelength (?) Is a positive green wavelength retardation value, Plane retardation value Ro of the light-receiving element is a negative green wavelength delay value, And a value obtained by subtracting the negative green wavelength delay value from the positive green wavelength delay value has a range of 0.20 to 0.30. (Where Ro = (nx-ny) * d, and units of Ro and lambda are all nm) The method according to claim 16, wherein the green light wavelength is And has a value between 540 nm and 560 nm. 7. The liquid crystal display device according to claim 6, wherein the ratio of the in-plane phase retardation value (Ro) of the positive A-plate to the blue light wavelength (?) Is referred to as a positive blue wavelength retardation value, Plane retardation value Ro of the light-receiving surface of the light- And a value obtained by subtracting the negative blue wavelength retardation value from the positive blue wavelength retardation value has a range of 0.20 to 0.30. (Where Ro = (nx-ny) * d, and units of Ro and lambda are all nm) The method as claimed in claim 18, wherein the blue light wavelength is And has a value between 440 nm and 460 nm. The display device according to claim 1, wherein the seed-plate is a negative seed-plate satisfying a formula of nx = ny> nz. (Where nx is the refractive index in the x-axis direction, ny is the refractive index in the y-axis direction orthogonal to the x-axis direction, and nz is the refractive index in the z-axis direction orthogonal to the x- .) The method of claim 1, wherein the positive and negative A- And the polarizing states of the red light, the green light and the blue light dispersed by the seed-plate and the liquid crystal layer when viewed from the side of the display panel are made to coincide with the extinction point at the Porcocare spherical surface. . The display device according to claim 1, wherein the negative A-plate has an optical axis parallel to an optical axis of the positive A-plate.

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