KR101512710B1 - Wideviewing vertical align liquid crystal display - Google Patents

Abstract

The present invention is characterized in that a polarizing plate laminated in the order of a negative biaxial A plate, a polarizer and a protective film is provided on and under the liquid crystal cell from the liquid crystal cell side, and any one of the negative biaxial A plates of the upper and lower polarizing plates is parallel And the other is arranged vertically with another adjacent polarizer to control the phase difference path of the optical element so as to be practically applicable to mass production rather than controlling the wavelength dispersion of the conventional optical element, The present invention relates to a vertically aligned liquid crystal display device capable of securing an excellent optical viewing angle by reducing light leakage of a liquid crystal display device and capable of mass production using a roll-to-roll production mode.

Vertical alignment, liquid crystal display, polarizer

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a vertical alignment liquid crystal display

The present invention is characterized in that a polarizing plate laminated in the order of a negative biaxial A plate, a polarizer, and a protective film is disposed on and under the liquid crystal cell from the liquid crystal cell side so that a wide viewing angle can be secured on the inclined plane, and negative biaxial A Wherein one of the plates is arranged in parallel with the adjacent polarizer and the other is arranged perpendicularly to another adjacent polarizer.

2. Description of the Related Art A liquid crystal display (LCD) is widely used as a popular image display device. However, despite its many excellent properties, a narrow viewing angle has been pointed out as a typical drawback.

In the early stage of development, liquid crystal display devices showed distorted images on oblique surfaces rather than on frontal surfaces because of narrow viewing angle. However, it is possible to implement a certain degree of image quality on a slope by applying a retardation film. Furthermore, due to the development of the liquid crystal mode technology, a liquid crystal mode which can realize a certain degree of wide viewing angle technology has appeared without using a retardation film. By combining the technique using a retardation film in the liquid crystal mode, It is possible to implement an image quality comparable to that of the comparative example.

However, since the phase difference of the optical elements used in the liquid crystal display device have different phase difference values according to wavelengths, there is a problem that it is difficult to realize a perfect black according to the viewing angle. In addition, when applied to a large- There is a problem that looks like a smudge. The most representative optical elements associated with this problem are liquid crystal and retardation films. Although optical elements having so-called inverse wavelength dispersibility having the same phase difference (unit: wavelength) in the visible light region are being developed, these methods have hitherto been the method of controlling the wavelength dispersion of such optical elements, A method in which the slow axis of the other film is orthogonally overlapped, a method of controlling the arrangement of polymers, or blending a polymer having different optical properties to realize reverse wavelength dispersion is suggested. As described above, it is difficult to realize the desired wavelength dispersion in a conventional single polymer state, which is commercially available. Even if it can be implemented, it is a reality that it has various technical and economical limitations in actual mass production.

On the other hand, the vertical alignment mode (VA mode) is a typical wide viewing angle liquid crystal driving mode in which a liquid crystal having a negative dielectric anisotropy is injected between the upper and lower substrates and arranged in a vertical direction in an electric field non- (White) is realized by laying liquid crystal with negative dielectric anisotropy by applying electric field vertically up and down. In this case, since there is almost no influence of the phase difference due to the liquid crystal in the black state at the front, it is possible to realize a full black (black), so that the front contrast ratio is the highest among the existing liquid crystal display devices. On the slope, however, the change of the polarization state due to the liquid crystal is severe, and a compensation film for wide viewing angle is necessarily required.

Therefore, it is possible to obtain an excellent optical viewing angle substantially by a method applicable to mass production other than the control of the wavelength dispersion of the optical element, and a polarizing plate including an optical element can be easily manufactured by using a roll- A new polarizing plate structure capable of achieving such a high resolution is strongly required.

The present invention not only improves the problem of inclined surface light leakage in a black state caused by the wavelength dispersion characteristics of optical elements such as liquid crystal and retardation film having a conventional constant wavelength dispersion property applied in vertically aligned liquid crystal displays, (Contrast, white luminance / black luminance) at an inclination angle as compared with an optical element such as a retardation film having wavelength dispersibility.

Accordingly, the present invention exploits a structure that minimizes the influence of wavelength dispersion by adjusting the phase difference path of each optical element on the optical element through optimal optical design, while applying the wavelength dispersion characteristics of optical elements that are difficult to improve in reality A liquid crystal display device capable of securing a wider viewing angle than a conventional vertical alignment liquid crystal display device is proposed.

The present invention relates to a liquid crystal display device comprising a polarizing plate laminated in the order of a negative biaxial A plate, a polarizer and a protective film from a liquid crystal cell side on a top plate and a bottom plate of a liquid crystal cell, The slow axis of any one negative biaxial A plate is disposed parallel to the absorption axis of the adjacent polarizer and the slow axis of the other negative biaxial A plate is disposed perpendicular to the absorption axis of another adjacent polarizer, The negative biaxial A plate in which the slow axes are arranged in parallel on the axis has a front retardation value of 65 to 75 nm and a refractive index ratio of 1.7 to 2.3 and the negative biaxial A plate in which the slow axis is vertically arranged on the absorption axis of the adjacent polarizer A front retardation value of 70 to 90 nm, a refractive index ratio of 3.5 to 4.5, and a polarizer Wherein an angle formed by the polarization states at 380 nm and 780 nm wavelengths with respect to the origin of the Poincare sphere is 45 ° or less.

The vertical alignment liquid crystal display according to the present invention can realize a contrast ratio (white luminance / black luminance) of 100: 1 or more because the luminance of the oblique plane (θ = 60 °, Φ = 45 °) It is possible to obtain a wide viewing angle because it is sharp and has excellent front view angle. In addition, since an optical element having a conventional wavelength dispersion property is not required separately, which is easy to manufacture and economically ineffective, mass production is easy by applying it to an actual mass production process.

It is possible to realize the same effect as that of securing a wide viewing angle by controlling the wavelength dispersion of a conventional optical element by controlling a phase difference path by an optical element such as a liquid crystal cell and a phase difference film, And more particularly to an excellent vertical alignment liquid crystal display device. Such a vertically aligned liquid crystal display device is configured to include a polarizing plate laminated in the order of a negative biaxial A plate, a polarizer, and a protective film in this order from the side of the liquid crystal cell to the side of the liquid crystal cell.

In this specification, 'NEGATIVE BIAXIAL A plate' refers to a positive biaxial optical element theoretically having a refractive index distribution satisfying Nx> Ny> Nz, and is referred to as a 'negative B plate'. Here, the positive (+) biaxial optical element in the present invention means a material having a large refractive index in the stretching direction.

According to the present invention, the slow axes of the negative biaxial A plates included in the upper and lower polarizers are aligned in parallel with each other. At this time, one of the negative biaxial A plates of the upper and lower polarizing plates is arranged in parallel with the adjacent polarizer and the other is arranged perpendicular to another adjacent polarizer. The vertical and parallel means that the absorption axis of the polarizer and the orientation of the slow axis of the negative biaxial A plate. In general, since the polarizer absorption axis of the upper plate polarizer and the polarizer absorption axis of the lower plate polarizer are orthogonal to each other, the slow axis of the negative biaxial A plate is configured so that a plate parallel to the plate orthogonal to the absorption axis of the adjacent polarizer is present at the same time.

The negative biaxial A plate in which the absorption axes of the adjacent polarizers are parallel to the slow axis has a front retardation value (RO) of 60 to 80 nm and a refractive index ratio (NZ) of 1.5 to 2.5. In order to exhibit excellent optical viewing angle characteristics, it is preferable that the front retardation value (RO) is 65 to 75 nm and the refractive index ratio (NZ) is 1.7 to 2.3, more preferably the front retardation value (RO) is 68 to 72 nm, The ratio (NZ) is preferably maintained between 1.9 and 2.1.

The negative biaxial A plate in which the absorption axes of the adjacent polarizers are orthogonal to the slow axis has a front retardation value (RO) of 70 to 90 nm, a refractive index ratio (NZ) of 3.5 to 4.5, (RO) of 75 to 85 nm and a refractive index ratio (NZ) of 3.7 to 4.3, and more preferably a front retardation value (RO) of 78 to 82 nm And a refractive index ratio (NZ) of 3.9 to 4.1.

This negative biaxial A plate has a retardation of a regular wavelength and has a front retardation (wavelength: 380 nm, a retardation unit is nm) / a front retardation (wavelength: 780 nm, a retardation unit is nm) [RO (380 nm) / RO )] ≫ 1, and the material is not limited to the material as long as it satisfies the optical characteristics of the present invention. Specifically, it is possible to use polyacetal such as triacetylcellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC) Methyl methacrylate (PMMA) may be used.

The optical characteristics of each of the negative biaxial A plates constituting the upper plate and the lower plate polarizer and the vertical alignment liquid crystal display of the black state including the same are shown in Fig. 3, in which the thickness direction is the z axis, the direction in which the in- (Nx, Ny, and Nz) corresponding to the respective directions when the x-axis and the vertical direction are y-axis, the thickness direction retardation (Rth) defined by the following equation The front retardation R0 and the refractive index ratio NZ defined by the following equation (3). At this time, the optical characteristics are determined according to the refractive index. Two optical axes exist in which the retardation does not occur when the refractive indices in the three axial directions are different, and this is called a biaxial retardation film. The optical characteristics of each film to be implemented by the present invention are physical properties at a wavelength of 589.3 nm, and the wavelength range is a standard when referring to optical characteristics in general. Therefore, when there is no specific description about wavelength, the value at a wavelength of 589.3 nm .

Rth = [(Nx + Ny) / 2 - Nz] xd

(Where Nx and Ny are surface refractive indices Nx > = Ny, Nz is refractive index in the thickness direction of the film, and d is the thickness of the film)

R0 = (Nx - Ny) xd

(Where Nx and Ny are the surface refractive indexes of the retardation film and d is the thickness of the film, where Nx > = Ny)

NZ = (Nx - Nz) / (Nx - Ny) = Rth / R0 + 0.5

(Where Nx and Ny are surface refractive indexes, Nx > = Ny, Nz is refractive index in the thickness direction of the film, and d is the thickness of the film)

In the vertical alignment mode liquid crystal cell of the present invention, the long axis of the liquid crystal is arranged in the vertical direction (thickness direction) when no electric field is applied, and when the electric field is applied, the long axis of the liquid crystal is laid in the in-plane direction to display an image. In this case, when the liquid crystal is negative (-) in dielectric anisotropy, the applied electric field is in the vertical direction (thickness direction), and in the case of positive (+) dielectric anisotropy, the electric field is applied in the in-plane direction.

Further, when the electric field is not applied, the thickness direction retardation (Rth) at a wavelength of 589 nm is maintained at -250 to -350 nm, preferably -290 to -320 nm. In the vertical alignment mode, the retardation in the thickness direction (Rth) is determined by the refractive index anisotropy and the cell gap of the liquid crystal, which influences the transmittance, hue and response speed of the liquid crystal display device. Though the thickness direction retardation (Rth) of the liquid crystal cell used in the embodiment of the present invention is in the range of -314.28 nm, it is possible to use the negative biaxial A plate having the optical properties according to the present invention within the above range . The polarization state of the liquid crystal on the slope of the liquid crystal display device varies depending on the Rth value of the liquid crystal cell. The change of the polarization state can be compensated by optimizing the optical properties R0 and NZ of the negative biaxial A plate disposed on both sides of the liquid crystal cell This is possible. Therefore, in order to perform the compensation, R0 and NZ of the optimal negative biaxial A plate must be changed at the same time according to the change of the Rth value of the liquid crystal cell. Therefore, in consideration of the optical characteristics of the negative biaxial A plate proposed in the present invention, It is preferable that the thickness direction retardation Rth of the cell maintains the above range.

The liquid crystal display device of the present invention includes a liquid crystal aligned in a multi-domain or divided into multiple regions by a voltage applied thereto. The liquid crystal display device is classified into Multi-domain Vertical Alignment (MVA), Patterned Vertical Alignment (PVA) and Super PVA (SPVA) according to the mode of the active matrix driving electrode including the electrode pairs. Are all included in the vertical alignment liquid crystal display device of the present invention.

The polarizer of the lower plate polarizer and the upper plate polarizer of the liquid crystal display according to the present invention is provided with a polyvinyl alcohol (PVA) layer, which is a polarizer imparted with a polarizing function through stretching and dyeing, and a polyvinyl alcohol On the opposite side of the liquid crystal cell in the polyvinyl alcohol (PVA) layer of the upper plate polarizer, protective films are respectively disposed. At this time, since the protective film of the lower plate polarizer and the protective film of the upper plate polarizer do not affect the viewing angle due to the optical characteristics due to the difference in refractive index, the refractive index characteristics are not particularly limited in the present invention. The protective film of the upper plate and the lower plate polarizer may be formed of materials commonly used in the art independently of each other. Specifically, triacetylcellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (PMC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and polymethylmethacrylate (PMMA).

As described above, the present invention can be practically applied to mass production without applying a special optical material by adjusting the optimal path in consideration of the optical characteristic of the optical element, rather than the view angle compensation concept by controlling the wavelength dispersion of the conventional optical element And a liquid crystal display device having a better viewing angle compensation effect than the conventional liquid crystal display device.

The polarized states of the wavelengths of 380 nm and 780 nm which pass through the liquid crystal display device according to the present invention when viewed at an oblique angle (? = 60 占 and? = 45 占 are represented by two points on the surface of the Poincare Sphere, When the two points are connected to the origin in the Poincare, the image is expressed as shown in FIG. 6, which is the widest before passing through the polarizer of the top plate polarizer, and the image quality on the slope is deteriorated due to the difference in polarization state between these two wavelengths .

The polarization state for a wavelength of 380 nm is represented by an orthogonal coordinate system (x, y, z), the polarization state for a wavelength of 780 nm is represented by an orthogonal coordinate system (x ', y', z '), and a Poincare Sphere is represented by a radius (1/2) of the distance between two points representing the polarization state of the wavelength of 380 nm and the wavelength of 780 nm and the half of the angle between the two points of the origin of the coordinate system are 1/2, , And the angle of intersection can be expressed by the following equation (5). Unless an optical element having a perfect reverse wavelength dispersion property is used in a vertically aligned liquid crystal display device, the angle indicating the degree of this wavelength dispersion becomes larger as it passes through each optical element, and the maximum value is obtained immediately before passing through the polarizer of the upper plate do.

In addition, the present invention limits the wavelength dispersion at an angle formed by the respective polarization states with respect to wavelengths of 380 nm and 780 nm. This is because the wavelength of 380 nm to 780 nm is the visible ray region, and the wavelength at which the dispersion characteristic of the optical element is most clearly shown ≪ / RTI > Since the angle between two arbitrary wavelengths between the 380 nm and 780 nm wavelengths is always smaller than the angle formed between the wavelengths of 380 nm and 780 nm, the angle formed between the wavelengths of 380 nm and 780 nm is the maximum value, The optical characteristics of the liquid crystal display device according to the present invention can be clearly shown. It is preferable that the angle formed at the wavelengths of 380 nm and 780 nm of the present invention defined above is maintained at 45 ° or less (0 to 45 °), preferably 40 ° or less.

In terms of preventing light leakage, the angle of incidence is preferably as close to 0 DEG as the frontal retardation (wavelength: 380 nm) / frontal retardation (wavelength: 780 nm) [RO (380 nm ) / RO (780 nm)] becomes larger, the angle of the interiors becomes closer to 0 °. The following embodiments of the present invention use a cycloolefin polymer (COP) having a frontal retardation (wavelength of 380 nm) / frontal retardation (wavelength of 780 nm) [RO Deg.]. Further, it is also possible to use polyacetal resin such as triacetyl cellulose (TAC), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) (380 nm) / RO (780 nm)] has a larger value than that of the cycloolefin polymer (COP) film, it is preferable to use a cycloolefin polymer (COP) because the film has a frontal retardation (wavelength of 380 nm) / frontal retardation It is possible to implement smaller angles (0 to 30 degrees).

The liquid crystal display according to the present invention satisfies the compensation relationship of the visibility transmittance of 0.05% or less, preferably 0.03% or less at the inclination angle (? = 60 占 and? = 45 占 and accordingly, Contrast, white luminance / black luminance) of 100: 1 or more, preferably 150: 1 or more.

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

1 and 2 are perspective views illustrating a basic structure of a vertical alignment liquid crystal display device according to the present invention.

The vertical alignment liquid crystal display device according to the present invention is stacked with the backlight unit 40, the lower plate 10, the liquid crystal cell 30 and the upper plate polarizer 20, and the lower plate and the upper plate polarizer are separated from the liquid crystal cell by negative divergence A The polarizer 11 and the polarizer 21 are laminated with the protective films 13 and 23. [

The optical properties of the negative biaxial A plate are determined by the relationship between the absorption axis of the adjacent polarizer and the slow axis of the negative biaxial A plate. More specifically, FIG. 1 shows a case where the absorption axis 22 of the polarizer 21 of the upper plate polarizer 20 and the slow axis 25 of the negative biaxial A plate 24 are parallel to each other and the polarizer 11 of the lower plate polarizer 10, 2 is a diagram showing the relationship between the absorption axis 22 of the polarizer 21 of the upper plate polarizer 20 and the absorption axis 22 of the negative biaxial A plate 14, The slow axis 25 of the A plate 24 is orthogonal and the absorption axis 12 of the polarizer 11 of the lower polarizer 10 is parallel to the slow axis 15 of the negative biaxial A plate 14 will be.

The negative biaxial A plate in which the absorption axes of the adjacent polarizers are orthogonal to the slow axis has a front retardation value (RO) of 70 to 90 nm and a refractive index ratio (NZ) of 3.5 to 4.5, and the absorption axis of the adjacent polarizer and the slow axis This parallel negative biaxial A plate has a front retardation value (RO) of 60 to 80 nm and a refractive index ratio (NZ) of 1.5 to 2.5.

The absorption axis 12 of the lower plate polarizer 10 and the absorption axis 22 of the upper plate polarizer 20 are arranged perpendicular to each other.

Polyvinyl alcohol (PVA) layers 11 and 21 are placed on the lower plate polarizer 10 and the upper plate polarizer 20 and the polyvinyl alcohol (PVA) layer 11 of the lower plate polarizer and the polyvinyl alcohol Protective films 13 and 23 are located on the opposite side of the liquid crystal cell 30 in the PVA layer 21. Since the protective film 13 of the lower polarizer 10 and the protective film 23 of the upper polarizer 20 do not affect the viewing angle due to the difference in refractive index, the refractive index characteristics of the present invention are not particularly limited .

The upper plate polarizer and the lower plate polarizer of the present invention are manufactured by applying a roll-to-roll method which is easy to mass-produce. FIG. 4 is a schematic view for explaining the MD direction of the roll-to-roll manufacturing process. Referring to FIG.

The top plate and the bottom plate polarizing plate are made of a combination of various optical films, and a polarizer having a polarizing function and a retardation film having a viewing angle compensating function are combined to form a composite polarizing plate, which is bonded to a liquid crystal cell to form a liquid crystal display do. At this time, each optical film is in a roll state before being bonded to the composite polarizing plate. The direction in which the film is unwound or wound in this roll is referred to as the MD (Machine Direction) direction. Since the protective film on the polarizing plate does not affect the optical characteristics, the PVA is stretched in the MD direction from the PVA fabric used as the material of the polarizer when the roll-to-roll bonding is possible and in the case of the polarizer, Direction and stained with iodine so that the light absorption direction becomes the MD direction.

Negative biaxial A plate is fabricated by considering the direction of the slow axis according to the manufacturing method. Specifically, the negative biaxial A plate of the present invention has a positive refractive index characteristic in which the refractive index increases with respect to the stretching direction, and can be realized through two stretching in a direction perpendicular to the plane of the MD and MD directions. Absorption of adjacent polarizers When the axis and the slow axis are orthogonal, the fabric of the retardation film is produced by drawing more in the direction perpendicular to the plane of the MD direction than in the MD direction. On the contrary, when the absorption axis of the adjacent polarizer is parallel to the slow axis, the fabric can be produced by stretching the farthest end of the retardation film in the MD direction more than the plane perpendicular direction in the MD direction. A roll-to-roll process can be applied.

In the present invention, the absorption axis of the polarizer of the lower plate polarizer should be positioned in the vertical direction when viewed from the viewer side. Specifically, when the absorption axis of the lower plate polarizer close to the backlight unit is in the vertical direction, light passing through the lower plate polarizer becomes polarized in the horizontal direction, and becomes a bright state through the liquid crystal cell to which the voltage of the panel is applied The light passes through the top plate polarizer on the side of the viewer with the absorption axis in the horizontal direction. At this time, the person wearing the polarized sunglass having the absorption axis in the horizontal direction on the viewer side (the absorption axis of the polarized sunglasses is in the horizontal direction) can recognize light emitted from the liquid crystal display device. If the absorption axis of the lower plate polarizer close to the backlight unit is in the horizontal direction, there is a problem that the image is not seen by the person wearing the polarized sunglasses. In addition, in the case of a large-sized liquid crystal display device, in order to make the image clearly visible from the viewer's view, considering that the human's field of view is wider than the vertical direction, the general liquid crystal display device except for the special- Since the main field of view is wider in the horizontal direction than in the vertical direction, it is produced in the form of 4: 3 or 16: 9.

The absence of light leakage under the negative biaxial A plate retardation value condition of the present invention can be explained through the Poincare Sphere. Since the Poincare Sphere is a very useful method for expressing the change of the polarization state at a specific time, the light traveling at a specific time in the liquid crystal display device displaying an image using the polarized light passes through each optical element in the liquid crystal display A change in the polarization state can be indicated. In the present invention, the specific time is the inclination angle in the range of? = 60 ° and? = 45 ° in the original coordinate system shown in FIG. 5, and the wavelength of 380 nm, the wavelength 780 nm and the wavelength of the brightest light The degree of wavelength dispersion can be confirmed based on three wavelengths, such as 550 nm.

Hereinafter, the effect of implementing the above-described configuration on the dark state at the full viewing angle when no voltage is applied is summarized in Examples and Comparative Examples. The present invention can be better understood by the following examples, and the following examples are intended to illustrate the present invention and are not intended to limit the scope of protection defined by the appended claims.

Example

In the following EXAMPLES 1 to 4 and COMPARATIVE EXAMPLES 1 to 5, simulation was performed by applying to an LCD simulation program TECH WIZ LCD 1D (MANAI SYSTEM, KOREA) to compare the optical viewing angle effects.

Example 1

Actual data such as each optical film, liquid crystal cell, and backlight according to the present invention were stacked on a TECH WIZ LCD 1D (MANAMA SYSTEM, KOREA) as shown in FIG. The structure of FIG. 1 will be described in detail as follows.

The back plate unit 40 , the lower plate polarizer 10, the liquid crystal cell 30 and the upper plate polarizer 20 are sequentially laminated. The lower plate polarizer 10 includes a negative biaxial A plate 14, The absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14 are perpendicular to each other. The upper plate polarizer 20 is composed of a negative biaxial A plate 24, a polarizer 21 and a protective film 23 in this order from the liquid crystal cell side. The absorption axis 22 of the polarizer 21 and the negative diastolic A The ground shaft 25 of the plate 24 becomes parallel. The absorption axis 12 of the polarizer 11 of the lower plate polarizer 10 is positioned in the vertical direction when viewed from the viewer's side.

At this time, the polarizer imparts the function of a polarizer through stretching and dyeing, and the absorption axes are arranged orthogonally to both sides of the 46-inch vertical alignment mode liquid crystal cell (Samsung Electronics, PAVV, LTA460HR0). The retardation in the thickness direction (Rth) of the liquid crystal cell was -314.28 nm.

On the other hand, each of the optical films and the backlight used in the embodiments of the present invention was made to have the following optical properties.

라고 할 때 하기 수학식 6 내지 10에 의해 정의된다.First, the upper and lower plate polarizers dye polarized iodine on the stretched PVA to give a polarizer function. The polarizing performance of the polarizer is 99.9% or more and the visible light transmittance is 41% or more in the range of visible light of 370 to 780 nm. The transmittance of the transmission axis according to the wavelength is denoted by TD (λ), the transmittance of the absorption axis with respect to wavelength is denoted by MD (λ), and the visibility correction value defined in JIS Z 8701: 1999

Is defined by the following equations (6) to (10).

The optical property due to the difference in internal refractive index according to the direction of each film is 589.3 nm and the negative biaxial A plate 14 of the lower polarizer plate 10 has a front retardation R0 of 80 nm and a refractive index ratio NZ of 4 And the negative biaxial A plate 24 of the top polarizer 20 has a front retardation R0 of 70 nm and a refractive index ratio NZ of 2.

(Wavelength: 380 nm) / front retardation (wavelength: 780 nm) [RO (380 nm) / RO (780 nm)], and the negative biaxial A plate used was a cycloolefin polymer (COP, Zeonor, Optes, ] Is 1.006, which shows the degree of wavelength dispersion of the propagation wavelength as shown in Fig. Triacetyl cellulose (TAC) having optical characteristics with a thickness direction retardation (Rth) of 50 nm with respect to incident light of 589.3 nm was used as the outer protective film of each of the upper plate and the lower plate polarizer. As the backlight unit, we used the backlight actual spectrum data on the Samsung 46-inch LCD TV PAVV (LTA460HR0).

The above optical components were laminated as shown in FIG. 1 and a visual sensitivity omni-directional transmittance simulation was performed. As a result, the results shown in FIG. 8 were obtained. The change in the polarization state at the reference time (? = 60 °,? = 45 °) of the present invention is shown in FIG. 9 and the polarization state is 1 when the light passes through the lower plate polarizer 11 on the Poincare Sphere, The polarization state when passing through the biaxial A plate 14 is 2, the polarization state when passing through the liquid crystal cell is 3, and the polarization state is 4 when the light passes through the negative biaxial A plate 24, The longest path is represented by 380 nm and the shortest path is represented by 780 nm on the Poincare Sphere due to the liquid crystal cell and the retardation film.

FIG. 8 shows the distribution of the visual sensitivity omnidirectional transmittance when the black is displayed on the screen. In the range of scale, the transmittance is 0% to 0.1%. When the cancer is displayed, Areas with low permeability are indicated in blue. At this time, as the range of the blue color in the center becomes wider, it is possible to secure a wide viewing angle by showing a wide viewing angle.

This is because the polarization state change of the pouincure spherical shape as shown in Fig. 9 is shown on the inclined plane. At this time, in the liquid crystal display device, the polarization state 4 in the orthogonal coordinate system on the Poincare sphere appears as (-0.1296, -0.919, 0.3722) at a wavelength of 380 nm and at (-0.1117, -0.9648, -0.2377) at a wavelength of 780 nm. Therefore, it was confirmed that the angle of the polarization state 4 at the wavelength of 380 nm and the wavelength 780 nm is 35.6294 degrees with respect to the origin of the Poincarele sphere.

Example 2

The absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14 are parallel to each other and the upper plate polarizer 20, 2 is stacked in the configuration of FIG. 2 such that the absorption axis 22 of the polarizer 21 and the slow axis 25 of the negative biaxial A plate 24 are orthogonal. The absorption axis 12 of the polarizer 11 of the lower plate polarizer 10 is positioned in the vertical direction when viewed from the viewer's side.

At the wavelength of 589.3 nm, the negative biaxial A plate 14 of the lower plate polarizer 10 had a front retardation R0 of 70 nm, a refractive index ratio NZ of 2, and a negative biaxial A plate 24 of the top polarizer 20 ) Had a front retardation (R0) of 80 nm and a refractive index ratio (NZ) of 4 to fabricate a vertically aligned liquid crystal display device.

As a result of the visual sensitivity transmission test of the vertical alignment liquid crystal display device, the results shown in FIG. 10 were obtained. This is because the polarization state change of the pouincure spherical shape as shown in Fig. 11 is shown on the inclined plane. At this time, in the liquid crystal display apparatus, the polarization state 4 in the quadrature coordinate system on the Poincare sphere is represented by (-0.5434, -0.839, 0.0249) at a wavelength of 380 nm and at (-0.0171, -0.9998, -0.004) at a wavelength of 780 nm. Therefore, it was confirmed that the angle formed by the polarization state 4 at the wavelength of 380 nm and the wavelength of 780 nm is 33.92456 degrees with respect to the origin of the pouch crest.

Example 3

The absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14 are orthogonal to each other and the upper plate polarizer 20, The polarizer 21 is laminated in the configuration shown in Fig. 1 such that the absorption axis 22 of the polarizer 21 and the slow axis 25 of the negative biaxial A plate 24 are parallel. The absorption axis 12 of the polarizer 11 of the lower plate polarizer 10 is positioned in the vertical direction when viewed from the viewer's side.

At the wavelength of 589.3 nm, the negative biaxial A plate 14 of the lower polarizer plate 10 had a front retardation R0 of 76 nm and a refractive index ratio NZ of 4.2; The negative biaxial A plate 24 of the top plate polarizer 20 had a front retardation R0 of 66 nm and a refractive index ratio NZ of 2 to prepare a vertically aligned liquid crystal display device.

As a result of the visual sensitivity transmission of the vertical alignment liquid crystal display device, the result as shown in FIG. 12 was obtained. This is because it shows a change in the polarization state of the pouincure spherical surface as shown in Fig. 13 on the inclined plane. At this time, in the liquid crystal display device, the polarization state 4 in the orthogonal coordinate system on the Poincare sphere appears as (-0.1218, -0.9238, 0.3627) at a wavelength of 380 nm and at (-0.0783, -0.9718, -0.2222) at a wavelength of 780 nm. Therefore, it was confirmed that the angle formed by the polarization state 4 at the wavelength of 380 nm and the wavelength 780 nm is 34.22371 ° with respect to the origin of the pouch crest.

Example 4

The absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14 are orthogonal to each other and the upper plate polarizer 20, The polarizer 21 is laminated in the configuration shown in Fig. 1 such that the absorption axis 22 of the polarizer 21 and the slow axis 25 of the negative biaxial A plate 24 are parallel. The absorption axis 12 of the polarizer 11 of the lower plate polarizer 10 is positioned in the vertical direction when viewed from the viewer's side.

At a wavelength of 589.3 nm, the negative biaxial A plate 14 of the lower polarizer plate 10 had a front retardation (R0) of 80 nm and a refractive index ratio (NZ) of 3.8; The negative biaxial A plate 24 of the top plate polarizer 20 had a front retardation R0 of 79 nm and a refractive index ratio NZ of 2 to fabricate a vertically aligned liquid crystal display device.

As a result of the visual sensitivity transmission of the vertical alignment liquid crystal display device, the result as shown in FIG. 14 was obtained. This is because on the slope, the change in the polarization state of the Poincare sphere as shown in Fig. 15 is shown. At this time, in the liquid crystal display apparatus, the polarization state 4 in the quadrature coordinate system on the Poincare sphere is represented by (-0.0873, -0.9302, 0.3563) at a wavelength of 380 nm and at (-0.1483, -0.9529, -0.2642) at a wavelength of 780 nm. Therefore, it was confirmed that the angle of the polarization state 4 at the wavelength of 380 nm and the wavelength of 780 nm is 38.78714 degrees with respect to the origin of the pouch crest.

Comparative Example 1

The absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14 are orthogonal to each other and the upper plate polarizer 20, 16, the absorption axis 22 of the polarizer 21 and the slow axis 25 of the negative biaxial A plate 24 are perpendicular to each other. The absorption axis 12 of the polarizer 11 of the lower plate polarizer 10 is positioned in the vertical direction when viewed from the viewer's side. This configuration is most commonly used in conventional vertical alignment liquid crystal display devices (Samsung Electronics (Korea) and Sharp (Japan) as of 2008). In the above-described configuration, the retardation film used was one showing the degree of wavelength dispersion of the propagation wavelength as shown in Fig. 17, and the front retardation (wavelength 380 nm) / front retardation (wavelength 780 nm) [RO (380 nm) / RO (780 nm)] was 0.862 Respectively.

At the wavelength of 589.3 nm, the negative biaxial A plate 14 of the lower polarizer plate 10 had a front retardation R0 of 50 nm and a refractive index ratio NZ of 3; The negative biaxial A plate 24 of the top plate polarizer 20 had a front retardation R0 of 50 nm and a refractive index ratio NZ of 3 to prepare a vertically aligned liquid crystal display device.

As a result of the visual sensitivity omni-directional transmittance simulation in the above configuration, the results shown in Fig. 18 were obtained. The change in the polarization state at the reference time of the present invention is represented in Fig. 19, and when the polarized state passes through the lower plate polarizer 11 on the Poincare Sphere, when the polarized state passes through the negative biaxial A plate 14 A polarized state is 2, a polarized state when passing through the liquid crystal cell is 3, a polarized state when the polarized state passes through the negative biaxial A plate 24, a liquid crystal cell having polarized wavelength dispersion, Due to the retardation film, the longest path on the Poincare Sphere is expressed as 380 nm, the shortest path is 780 nm, and the intermediate wavelength is 550 nm.

At this time, in the liquid crystal display device, the polarization state 4 in the quadrature coordinate system on the Poincare sphere is represented by (-0.6532, -0.6697, 0.3531) at a wavelength of 380 nm and at (-0.0300, -0.9970, -0.0709) at a wavelength of 780 nm. Therefore, it was confirmed that the angle formed by the polarization state 4 at the wavelength of 380 nm and the wavelength 780 nm is 47.68254 ° with respect to the origin of the pouch crest.

The angle of the polarization state 4 at the wavelength of 380 nm and the wavelength of 780 nm in Example 1 and Comparative Example 1 was 35.6294 ° and 47.68254 ° with respect to the origin of the pouch crest, Is small. It was confirmed that the retardation film of Comparative Example 1 had a large difference in polarization state depending on the wavelength even though the phase difference wavelength dispersion was inverse wavelength dispersion.

20 shows the transmittance in the diagonal direction? = 45 占 in the liquid crystal display devices of Example 1 and Comparative Example 1. In Example 1 and Comparative Example 1, since the transmissivity in the white state is almost the same, it can be seen that the contrast ratio in Example 1 can provide a sharp image quality that is three times or more higher than that in Comparative Example 1 in terms of the contrast ratio (? = 60 °,? = 45 °). Specifically, since the ratio of the slope of Comparative Example 1 is about 80, the ratio of the slope of Example 1 to the slope of the Example 1 is estimated to be about 240.

In addition, the omni-directional transmittances of the black state in Example 1 and Comparative Example 1 are as shown in Figs. 8 and 18, respectively. In general, when the blue portion of the central portion is wide, the viewing angle is wide. It is confirmed that the viewing angle of Example 1 is wider than that of Comparative Example 1 because the range of blue is wider than that of FIG.

Comparative Example 2

The wavelength dispersion of the propagation wavelength of the negative biaxial A plate deposited on the upper and lower plates was the same as in Comparative Example 1, and the dispersion wavelength was RO (wavelength 380 nm, unit nm) / RO (wavelength 780 nm, unit nm) .

As a result of the visual sensitivity omni-directional transmittance simulation in the above configuration, the results shown in Fig. 21 are obtained. The change in the polarization state at the reference time of the present invention is represented in Fig. 22, and when the polarized state passes through the lower plate polarizer 11 on the Poincare Sphere, when the polarized state passes through the negative biaxial A plate 14 The polarization state is 2, the polarized state when passing through the liquid crystal cell is 3, and the polarization state is 4 when the polarized light passes through the negative biaxial A plate 24. Due to the liquid crystal cell having the positive wavelength dispersion and the retardation film, On the Poincare Sphere, the longest path is represented by 380 nm, and the shortest path is represented by 780 nm. At this time, in the liquid crystal display apparatus, in the orthogonal coordinate system in the Poincare sphere, the polarization state 4 is represented by (-0.7514, -0.5941, 0.2867) at a wavelength of 380 nm and at (-0.0021, -0.9859, 0.1670) at a wavelength of 780 nm. Therefore, it was confirmed that the angle formed by the polarization state 4 at the wavelength of 380 nm and the wavelength 780 nm is 50.78729 degrees with respect to the origin of the pouch crystal.

In Comparative Example 1 and Comparative Example 2, the angles formed by the polarization state 4 at the wavelength of 380 nm and the wavelength 780 nm are 47.68254 ° and 50.78729 °, respectively, with reference to the origin of the Poincare Curve, and the wavelength dispersion of the retardation film is And it was confirmed that the larger the dispersion angle, the larger. Also, as the dispersion angle increases, the slope transmittance increases as shown in FIG. 21, and it is confirmed that the image quality deteriorates on the inclined plane.

Comparative Example 3

The same procedure as in Example 1 was carried out except that the position of the negative biaxial A plate of the polarizer of the upper plate and the lower plate was changed and laminated to produce a vertically aligned liquid crystal display device.

As a result of the visual sensitivity transmission of the vertical alignment liquid crystal display device, the result as shown in FIG. 23 was obtained. This indicates that the angle of view is narrow due to the small blue range of the center portion because it shows the polarization state change of the Poincare sphere spherical shape as shown in FIG. 24 on the slope. The contrast ratio in the slope (θ = 60 °, Φ = 45 °) 34.6.

In Comparative Example 3, the angle formed by the polarization state 4 at a wavelength of 380 nm and the wavelength 780 nm with respect to the origin of the Poincare curve was as small as 16.96536 °, but the slope transmittance was high, which failed to satisfy the object of the present invention . That is, the present invention must satisfy the wavelength dispersion and the viewing angle compensation.

Comparative Example 4

The absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14 are orthogonal to each other and the upper plate polarizer 20, The polarizer 21 is laminated in the configuration shown in Fig. 1 such that the absorption axis 22 of the polarizer 21 and the slow axis 25 of the negative biaxial A plate 24 are parallel. The absorption axis 12 of the polarizer 11 of the lower plate polarizer 10 is positioned in the vertical direction when viewed from the viewer's side.

At the wavelength of 589.3 nm, the negative biaxial A plate 14 of the lower polarizer plate 10 had a front retardation (R0) of 69 nm and a refractive index ratio (NZ) of 3.8; The negative biaxial A plate 24 of the top plate polarizer 20 had a front retardation R0 of 65 nm and a refractive index ratio NZ of 2 to prepare a vertically aligned liquid crystal display device.

As a result of the visual sensitivity transmission of the vertical alignment liquid crystal display device, the result as shown in FIG. 25 was obtained.

This indicates that the angle of view in the central part is narrow because the polarization state of the pouincure spherical surface is changed on the inclined plane as shown in Fig. 26, and thus the viewing angle is narrow. In this case, in Comparative Example 4, the angle formed by the polarization state 4 at a wavelength of 380 nm and the wavelength 780 nm was 32.51208 ° with respect to the origin of the pouch crest, but the slope transmittance was high, thereby satisfying the object of the present invention I did not. That is, the present invention must satisfy the wavelength dispersion and the viewing angle compensation.

Comparative Example 5

The absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14 are orthogonal to each other and the upper plate polarizer 20, The polarizer 21 is laminated in the configuration shown in Fig. 1 such that the absorption axis 22 of the polarizer 21 and the slow axis 25 of the negative biaxial A plate 24 are parallel. The absorption axis 12 of the polarizer 11 of the lower plate polarizer 10 is positioned in the vertical direction when viewed from the viewer's side.

At a wavelength of 589.3 nm, the negative biaxial A plate 14 of the lower polarizer 10 has a front retardation R0 of 100 nm and a refractive index ratio NZ of 1; The negative biaxial A plate 24 of the top plate polarizer 20 had a front retardation R0 of 50 nm and a refractive index ratio NZ of 1.2 to prepare a vertically aligned liquid crystal display device.

As shown in FIG. 27, the result of simulation of the visibility all-round transmission of the vertical alignment liquid crystal display device was obtained.

This shows that the blue range of the central portion is narrow because the polarization state of the pouincure spherical surface is changed as shown in Fig. 28 on the inclined surface, and it is confirmed that the viewing angle is narrow. At this time, in Comparative Example 5, the angle formed by the polarization state 4 at the wavelength of 380 nm and the wavelength 780 nm with reference to the origin of the pouch crest was 67.06955 °.

As described above, the vertical alignment liquid crystal display device according to the present invention can provide a wide viewing angle and can be applied to a large-screen liquid crystal display device requiring a high optical level.

1 is a perspective view showing a structure of a vertical alignment liquid crystal display device according to an exemplary embodiment of the present invention,

2 is a perspective view showing the structure of another example of the vertical alignment liquid crystal display device according to the present invention,

3 is a schematic view for explaining the refractive index of the retardation film according to the present invention,

4 is a schematic view showing the MD direction in the manufacturing process for explaining the stretching direction of the retardation film and the polarizing plate according to the present invention,

FIG. 5 is a schematic view for explaining the expression of? And? In the coordinate system of the present invention,

FIG. 6 is a schematic view for explaining a dispersion angle of a polarization state according to a wavelength in the Poincare sphere of the present invention,

7 is a graph showing the propagation wavelength dispersion of the retardation film (negative biaxial A plate) applied to Example 1 of the present invention,

FIG. 8 is a simulation result of the visual sensitivity of the first embodiment according to the present invention,

FIG. 9 shows the change in the polarization state of light coming out in the direction of the inclined plane (? = 60 占? = 45 占 in the first embodiment of the present invention on the Poincare Sphere,

10 is a simulation result of the visual sensitivity of the second embodiment according to the present invention,

11 shows the change in the polarization state of light coming out in the direction of the inclined plane (? = 60 °,? = 45 °) according to Embodiment 2 of the present invention on a Poincare Sphere,

12 is a simulation result of the visual sensitivity of the third embodiment according to the present invention,

13 shows the change in polarization state of light coming out in the direction of the inclined plane (? = 60 占? = 45 占) according to Embodiment 3 of the present invention on a Poincare Sphere,

14 is a simulation result of the visual sensitivity of the fourth embodiment according to the present invention,

Fig. 15 shows the change in polarization state of light coming out in the direction of the inclined plane ([theta] = 60 DEG, [phi] = 45 DEG) in the fourth embodiment of the present invention on the Poincare Sphere,

16 is a perspective view showing the structure of an example vertical alignment liquid crystal display device according to Comparative Example 1 of the present invention,

17 is a graph showing the propagation wavelength dispersion of the retardation film (negative biaxial A plate) applied to Comparative Example 1 of the present invention

18 is a simulation result of the visual sensitivity omnidirectional transmittance of Comparative Example 1 according to the present invention,

19 shows the change in the polarization state of light coming out in the direction of the inclined plane (? = 60 占? = 45 占 in Comparative Example 1 of the present invention on the Poincare Sphere,

20 shows the transmittance at an inclined plane (PHI = 45 DEG) of Example 1 and Comparative Example 1 according to the present invention,

21 is a simulation result of the visual sensitivity all-round transmission of Comparative Example 2 according to the present invention,

22 shows the change in polarization state of light emerging in the direction of an inclined plane (? = 60 占? = 45 占 in Comparative Example 2 of the present invention on a Poincare Sphere,

23 is a simulation result of the visual sensitivity omnidirectional transmittance of Comparative Example 3 according to the present invention,

24 shows the change in polarization state of light emerging in the direction of the inclined plane (? = 60 占? = 45 占 in Comparative Example 3 of the present invention on a Poincare Sphere,

25 is a simulation result of the visual sensitivity all-round transmission of Comparative Example 4 according to the present invention,

26 shows the change in the polarization state of light coming out in the direction of the inclined plane (? = 60 °,? = 45 °) in Comparative Example 4 of the present invention on a Poincare Sphere,

FIG. 27 is a simulation result of the visual sensitivity all-round transmission of Comparative Example 5 according to the present invention,

28 shows the change in the polarization state of light coming out in the direction of the inclined plane (? = 60 占? = 45 占 in Comparative Example 5 of the present invention on the Poincare Sphere).

Claims (8)

A liquid crystal display device comprising a polarizing plate laminated in the order of a negative biaxial A plate, a polarizer and a protective film from a liquid crystal cell side on an upper plate and a lower plate of a liquid crystal cell, The slow axis of the negative biaxial A plate of any one of the upper biaxial plate and the negative biaxial A plate of the upper plate and the lower plate polarizer is arranged parallel to the absorption axis of the adjacent polarizer and the slow axis of the other negative biaxial A plate is absorbed by another adjacent polarizer Axis, The negative biaxial A plate in which the slow axis is arranged in parallel to the absorption axis of the adjacent polarizer has a front retardation value of 65 to 75 nm, a refractive index ratio of 1.7 to 2.3, The negative biaxial A plate in which the slow axis is vertically arranged on the absorption axis of the adjacent polarizer has a front retardation value of 70 to 90 nm and a refractive index ratio of 3.5 to 4.5, Wherein an angle formed by the polarization states at 380 nm and 780 nm wavelengths with respect to the origin of the Poincare sphere immediately before passing through the polarizer of the upper plate polarizer is 45 ° or less. delete The liquid crystal display of claim 1, wherein the negative biaxial A plate in which the slow axes are vertically arranged on the absorption axis of the adjacent polarizer has a front retardation value of 75 to 85 nm and a refractive index ratio of 3.7 to 4.3. The liquid crystal display device according to claim 1, wherein an angle formed by the polarization states at 380 nm and 780 nm wavelengths passing through the liquid crystal display with respect to the origin of the Poincare sphere is 40 ° or less. The liquid crystal display device according to claim 1, wherein the negative biaxial A plate has a front retardation (wavelength: 380 nm) / front retardation (wavelength: 780 nm) [RO (380 nm) / RO (780 nm)]> 1. The liquid crystal display according to claim 1, wherein the liquid crystal cell has a retardation value (Rth) in the thickness direction at a wavelength of 589 nm of -350 to -250 nm. The liquid crystal display device according to claim 1, wherein the compensating relationship satisfies the visibility transmittance of 0.05% or less at an inclination angle (? = 60 占? = 45 占). The liquid crystal display device according to claim 1, wherein the contrast ratio (white luminance / black luminance) of the oblique angle (? = 60 占,? = 45 占) is 100: 1 or more.

Images