KR20100085453A - Wideviewing vertical align liquid crystal display - Google Patents

Abstract

PURPOSE: A wide viewing angle vertically aligned LCD device is provided to improve an incline light leakage problem of a dark state. CONSTITUTION: An absorption axis(22) of a polarizer(21) of an upper plate polarizing plate(20) and a slow axis(25) of a negative biaxial A plate(24) are parallel. An absorption axis(12) of a polarizer(11) of an low plate polarizing plate(10) and a slow axis(15) of a negative biaxial A plate(14) cross at right angle. A front retardation value is 70-90nm in the negative biaxial A plate which the absorption axis and the slow axis of the adjacent polarizer cross at right angle. A front retardation value is 60-80nm in the negative biaxial A plate which the absorption axis and the slow axis of the adjacent polarizer are parallel.

Description

Wide viewing angle vertical alignment liquid crystal display {WIDEVIEWING VERTICAL ALIGN LIQUID CRYSTAL DISPLAY}

The present invention includes a polarizing plate laminated in the order of a negative biaxial A plate, a polarizer, and a protective film from the liquid crystal cell side in order to ensure a wide viewing angle on the inclined surface above and below the liquid crystal cell, and the negative biaxial A of the upper and lower polarizing plates. One of the plates relates to a vertically aligned liquid crystal display device configured to be disposed in parallel with an adjacent polarizer and the other is disposed perpendicularly to another adjacent polarizer.

Liquid crystal display (LCD) is widely used as a popular image display device. However, despite its many excellent features, a narrow viewing angle is pointed out as a representative disadvantage.

In the early stages of development, liquid crystal displays showed a distorted image on the inclined surface rather than the front due to the narrow viewing angle. However, the present invention can realize a certain degree of image quality even on the inclined surface by applying a phase difference film. Moreover, the development of liquid crystal mode technology has led to the emergence of a liquid crystal mode capable of realizing a wide viewing angle technology without the use of a retardation film. It's possible to achieve unparalleled image quality.

However, the phase difference of the optical elements used in the liquid crystal display device has a different phase difference value depending on the wavelength, so it is difficult to realize perfect black according to the viewing angle. There is a problem that looks like a stain. The most representative optical elements associated with this problem are liquid crystals and retardation films. These optical devices have been developed for the so-called reverse wavelength dispersion having the same phase difference (unit: wavelength) in the visible light range, but until now, the method of controlling the wavelength dispersion of such optical devices has been distributed. Orthogonal superimposition of the slow axis (Slow Axis) of the other film, or control the polymer arrangement or blending a polymer having a heterogeneous optical characteristics to implement a reverse wavelength dispersion. As described above, it is difficult to implement a target wavelength dispersion in the conventional single polymer state that is conventionally commercially available, and even if it is possible, it is a reality that there are various limitations such as technical and economic to apply to actual mass production.

On the other hand, the vertical alignment mode (VA mode) is a typical wide viewing angle liquid crystal driving mode by injecting a liquid crystal having a negative (-) dielectric anisotropy between the upper and lower substrates, by arranging it in the vertical direction in the non-electric field applied state (Black) White implements the liquid crystal having negative dielectric anisotropy by laying it down by vertically applying an electric field. In this case, since there is almost no phase difference effect due to the liquid crystal in the black state from the front side, a perfect black can be realized, and thus the front contrast ratio is the highest among existing liquid crystal displays. However, on the inclined surface, the polarization state is severely changed by the liquid crystal, so a wide viewing angle compensation film is necessary.

Therefore, it is possible to secure an excellent wide viewing angle by a method that is practically applicable to mass production other than the control of the wavelength dispersion of the optical element, and mass production by easily manufacturing a polarizing plate containing the optical element by using a roll-to-roll method of production. There is an urgent need for this possible new polarizer configuration.

The present invention not only improves the problem of inclined light leakage in the black state caused by wavelength dispersion characteristics of optical elements such as liquid crystals and retardation films having a conventional constant wavelength dispersion applied in a vertical alignment liquid crystal display, but also inversely. It is intended to improve the contrast ratio (contrast, white luminance / black luminance) at an inclination angle than an optical element such as a retardation film having wavelength dispersion.

Accordingly, the present invention by applying the wavelength dispersion characteristics of the optical elements that are difficult to improve in reality, by searching for a configuration that minimizes the influence of wavelength dispersion by adjusting the phase difference path on the Poang Carre sphere of each optical element through the optimal optical design 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 is 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 the liquid crystal cell, respectively, on and under the liquid crystal cell, the negative biaxial A plate of the upper and lower polarizing plates, respectively. Is arranged in parallel with the adjacent polarizer and the other is perpendicular to the other adjacent polarizer, and the negative biaxial A plate arranged in parallel with the adjacent polarizer has a front phase difference value of 60 to 80 nm, a refractive index ratio of 1.5 to 2.5, The negative biaxial A plate disposed perpendicular to the adjacent polarizer has a front phase difference value of 70 to 90 nm, a refractive index ratio of 3.5 to 4.5, and each polarization state at wavelengths of 380 nm and 780 nm immediately before passing through the planar polarizer of the upper polarizer. The vertical alignment liquid crystal display has an angle of 45 ° or less from the origin. The.

According to the present invention, the vertical alignment liquid crystal display according to the present invention has a lower luminance of an inclined plane (θ = 60 °, Φ = 45 °) dark state, so that a contrast ratio (white luminance / black luminance) is more than 100: 1. It is possible to have a clear viewing angle and excellent front viewing angle to secure a wide viewing angle. In addition, the conventional wavelength dispersion controllable optical element having ease of manufacturing process and economic inefficiency is not required separately, so it is easy to mass-produce by applying to an actual mass production process.

The present invention by controlling the phase difference path by the optical elements such as the liquid crystal cell and the retardation film, it is possible not only to realize the effect of equal or more than to secure the wide viewing angle by the wavelength dispersion control of the conventional optical element, but also the ease and economic efficiency of the manufacturing process An excellent vertical alignment liquid crystal display device. The vertically aligned liquid crystal display device includes a polarizing plate stacked in the order of a negative biaxial A plate, a polarizer, and a protective film from above and below the liquid crystal cell.

As used herein, the term 'negative biaxial A plate' refers to a positive biaxial optical element whose refractive index distribution satisfies Nx > Ny > Nz, and is called a 'negative B plate'. In this case, the positive biaxial optical element in the present invention refers to 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 polarizing plates are oriented parallel to each other. At this time, any one of the negative biaxial A plates of the upper and lower polarizing plates is disposed in parallel with the adjacent polarizer and the other is disposed perpendicular to the other adjacent polarizer. By vertical and parallel is meant the orientation of the absorption axis of the polarizer and the slow axis of the negative biaxial A plate. In general, since the polarizer absorption axis of the upper polarizing plate and the polarizer absorption axis of the lower polarizing plate are configured to be orthogonal to each other, the slow axis of the negative biaxial A plate is configured such that a plate parallel to the plate orthogonal to the absorption axis of the adjacent polarizer is simultaneously present.

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

In addition, the negative biaxial A plate, in which the absorption axis and the slow axis of the adjacent polarizers are orthogonal, has a front phase difference value (RO) of 70 to 90 nm, a refractive index ratio (NZ) of 3.5 to 4.5, and a range of phase differences in processing is considered. For example, the front phase difference value (RO) is preferably 75 to 85 nm, the refractive index ratio (NZ) is 3.7 to 4.3, and more preferably the front phase difference value (RO) is 78 to 82 nm. And the refractive index ratio NZ is preferably maintained at 3.9 to 4.1.

This negative biaxial A plate has a phase difference in wavelength dispersion, and a front phase difference (wavelength 380 nm, phase difference unit is nm) / front phase difference (wavelength 780 nm, phase difference unit is nm) [RO (380 nm) / RO (780 nm). )]> 1 can be used, and the present invention is not limited to the material as long as the optical properties of the present invention are satisfied. Specifically, triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and poly Methyl methacrylate (PMMA) can be used that is prepared from the one selected from the group consisting of.

Optical characteristics of each of the negative biaxial A plates constituting the upper and lower polarizing plates and the vertically aligned liquid crystal display device in a black state including the same are as shown in FIG. 3. When the x-axis and the vertical direction are y-axis, the refractive index corresponding to each direction is Nx, Ny, Nz, and the thickness direction phase difference (Rth) defined in Equation 1 below, It is specified by the front phase difference R0 and the refractive index ratio NZ defined by the following equation (3). At this time, the optical properties are determined according to the size of the refractive index. Of these, when the refractive indices in the three axial directions are different from each other, there are two optical axes in which no phase difference occurs. This is called a biaxial retardation film. Optical properties of each film to be implemented in the present invention is a physical property at a wavelength of 589.3 nm, and the wavelength range is a standard when referring to optical properties. Say

Rth = [(Nx + Ny) / 2-Nz] × d

(Where Nx and Ny are planar refractive indices Nx ≧ Ny, Nz represents the thickness direction refractive index of the film, and d represents the thickness of the film)

R0 = (Nx-Ny) × d

(Where Nx and Ny are the plane refractive indices of the retardation film, and d represents the thickness of the film, where Nx ≧ Ny)

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

Where Nx and Ny are planar refractive indices, where Nx ≥ Ny and Nz are the thickness direction refractive indices of the film, and d is the thickness of the film.

In the vertical alignment mode liquid crystal cell of the present invention, when the electric field is not applied, the long axis of the liquid crystal is arranged in the vertical alignment (thickness direction), and when the electric field is applied, the long axis of the liquid crystal lies in the in-plane direction to display an image. At this time, when the liquid crystal is negative dielectric anisotropy, the direction of the applied electric field is the vertical direction (thickness direction), and when the positive dielectric constant anisotropy, the electric field is applied in the in-plane direction.

In addition, when the electric field is not applied, the thickness direction phase difference (Rth) is maintained at -250 to -350 nm, preferably -290 to -320 nm at a wavelength of 589 nm. In the vertical alignment mode, the thickness direction phase difference (Rth) is determined by the refractive index anisotropy and the cell gap of the liquid crystal, which affects the transmittance, color, and response speed of the liquid crystal display. Although the thickness direction phase difference (Rth) of the liquid crystal cell used in the embodiment of the present invention is in the range of -314.28 nm, within this range, it is possible to use a negative biaxial A plate having optical properties according to the present invention. . The polarization state of the liquid crystal on the inclined surface of the liquid crystal display device depends on the Rth value of the liquid crystal cell, and the change of the polarization state is compensated by optimizing R0 and NZ which are optical properties of the negative biaxial A plate located on both sides of the liquid crystal cell. This is possible. Therefore, in order to perform the compensation, the optimum negative biaxial A plate R0 and NZ should also be changed at the same time according to the change of the Rth value of the liquid crystal cell. Therefore, when considering the optical characteristics of the negative biaxial A plate proposed in the present invention, the vertically aligned liquid crystal The thickness direction phase difference Rth of a cell is good to maintain the said range.

The liquid crystal display of the present invention includes aligning liquid crystals into multi-domains or dividing the liquid crystals into multiple regions by a voltage applied thereto. LCDs are classified into multi-domain vertical alignment (MVA), patterned vertical alignment (PVA), and super PVA (SPVA) according to the mode of an active matrix driving electrode including an electrode pair. Since the liquid crystal alignment states are the same, they are all included in the vertical alignment liquid crystal display device of the present invention.

In the polarizers of the lower polarizing plate and the upper polarizing plate of the liquid crystal display according to the present invention, a polyvinyl alcohol (PVA) layer, which is a polarizer imparted with stretching and dyeing, is positioned, respectively, and a polyvinyl alcohol (PVA) layer of the lower polarizing plate In the polyvinyl alcohol (PVA) layer of the upper polarizing plate, protective films are positioned on opposite sides of the liquid crystal cell. At this time, the protective film of the lower polarizing plate and the protective film of the upper polarizing plate is not particularly limited in the present invention because the optical properties according to the refractive index does not affect the viewing angle. Materials for forming the protective film of the upper and lower polarizing plates may be applied to those commonly used in the art independently of each other, specifically triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer ( COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and polymethyl methacrylate (PMMA) can be used selected from the group consisting of.

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

When the liquid crystal display according to the present invention is viewed at an inclination angle (θ = 60 °, Φ = 45 °), polarization states of 380 nm and 780 nm wavelengths are represented by two points on the surface of a Poincare Sphere. When the origin is connected at the two points and the Pangaregu, it is represented by the figure as shown in Fig. 6, which is widest just before passing through the polarizer of the top polarizer, and the image quality on the inclined plane is degraded due to the difference in polarization state for these two wavelengths. .

The polarization state for the wavelength 380nm is represented by the Cartesian coordinate system (x, y, z), the polarization state for the wavelength 780nm is represented by the Cartesian coordinate system (x ', y', z '), and the Poincare Sphere is the radius. Since 1 is half of the distance between two points representing the polarization state of wavelength 380 nm and wavelength 780 nm, and half of the angle connecting the origin and the two points of the coordinate system (1/2) is It can be expressed as, and the angle can be expressed as shown in Equation 5 below. Unless an optical device having perfect reverse wavelength dispersion is used in a vertical alignment liquid crystal display device, the angle between the wavelength dispersions becomes larger as they pass through each optical element, and the maximum angle immediately before passing through the polarizer on the upper panel is increased. do.

In addition, the present invention limits the wavelength dispersion to the angle formed by the polarization state for the wavelength 380nm and 780nm, which wavelength 380nm to 780nm is the visible light region in the visible light region showing the dispersion characteristics of the conventional optical device most clearly Known in the art. Since the angle between any two wavelengths existing between the 380 nm and 780 nm wavelengths is always smaller than the angle formed between the 380 nm and 780 nm wavelengths, the angle formed at the 380 nm and 780 nm wavelengths becomes a maximum value. Only the optical angle of the liquid crystal display device according to the present invention can be clearly presented. The angle formed between the wavelengths of 380 nm and 780 nm of the present invention as defined above is preferably maintained at 45 ° or less (0 to 45 °), preferably 40 ° or less.

At this time, in the aspect of light leakage prevention, the angle is closer to 0 ° is preferable, within the range of the front phase difference and the refractive index ratio of the retardation film of the present invention front phase difference (wavelength 380nm) / front phase difference (wavelength 780nm) [RO (380nm) ) / RO (780nm)] is larger, the angle between them is closer to 0 °. The following examples of the present invention use a cycloolefin polymer (COP) having a front phase difference (wavelength 380 nm) / front phase difference (wavelength 780 nm) [RO (380 nm) / RO (780 nm)] of 1.006. °. In addition, triacetyl cellulose (TAC), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and polymethyl methacrylate (PMMA) Films such as the front phase difference (wavelength 380 nm) / front phase difference (wavelength 780 nm) [RO (380 nm) / RO (780 nm)] has a larger value than the cycloolefin polymer (COP) film, so using a cycloolefin polymer (COP) Smaller angles than the case can be implemented (0 to 30 °).

The liquid crystal display according to the present invention satisfies the compensating relationship of the visibility transmittance of 0.05% or less, preferably 0.03% or less at an inclination angle (θ = 60 °, Φ = 45 °), and thus the contrast ratio ( Contrast, white luminance / black luminance) is maintained at 100: 1 or higher, preferably 150: 1 or higher.

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 the basic structure of a vertical alignment liquid crystal display according to the present invention.

In the vertical alignment liquid crystal display according to the present invention, the backlight unit 40, the lower flat plate 10, the liquid crystal cell 30, and the upper polarizing plate 20 are stacked, and the lower and upper polarizing plates are negative biaxial A from the liquid crystal cell. The plates 14, 24, polarizers 11 and 21, and protective films 13 and 23 are laminated.

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. Specifically, FIG. 1 shows that the absorption axis 22 of the polarizer 21 of the upper 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 polarizer 10 is parallel. The absorption axis 12 of the negative axis and the slow axis 15 of the negative biaxial A plate 14 is configured to be orthogonal, Figure 2 is a negative biaxial property of the absorption axis 22 of the polarizer 21 of the upper plate polarizing plate 20 The slow axis 25 of the A plate 24 is orthogonal, and the absorption axis 12 of the polarizer 11 of the lower plate polarizing plate 10 and the slow axis 15 of the negative biaxial A plate 14 are configured to be parallel. will be.

The negative biaxial A plate, in which the absorption axis and the slow axis of the adjacent polarizers are orthogonal, has a front phase difference value (RO) of 70 to 90 nm, a refractive index ratio (NZ) of 3.5 to 4.5, and an absorption axis and a slow axis of the adjacent polarizers. This parallel negative biaxial A plate has a front phase difference 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 polarizing plate 10 and the absorption axis 22 of the upper polarizing plate 20 are arranged perpendicular to each other.

The polyvinyl alcohol (PVA) layers 11 and 21 are positioned on the lower polarizer 10 and the upper polarizer 20, and the polyvinyl alcohol (PVA) layer 11 of the lower polarizer and the polyvinyl alcohol of the upper polarizer ( In the PVA layer 21, protective films 13 and 23 are positioned on opposite sides of the liquid crystal cell 30. At this time, the protective film 13 of the lower polarizing plate 10 and the protective film 23 of the upper polarizing plate 20 are not particularly limited in the present invention because the optical properties according to the refractive index does not affect the viewing angle. .

The upper polarizing plate and the lower polarizing plate of the present invention are manufactured by applying a roll to roll method which is easy to mass produce. Figure 4 is a schematic diagram illustrating the MD direction in the roll-to-roll manufacturing process with reference to this as follows.

The upper and lower polarizers are made of a combination of various optical films. The polarizers with polarizing function and the retardation film with the viewing angle compensation function are manufactured in the form of a composite polarizer and bonded to the liquid crystal cell to form a liquid crystal display device. do. In this case, each optical film exists in a roll state before being bonded to the composite polarizing plate. The direction in which the film is unwound or wound in the roll is called MD (Machine Direction) direction. In the polarizing plate, the protective film does not affect the optical properties, so roll-to-roll bonding is possible, and in the case of polarizers, the PVA is stretched through MD direction from the PVA fabric used as the material of the polarizer. Direction and the iodine dyeing, the direction of light absorption becomes the MD direction.

Since the direction of the slow axis varies according to the manufacturing method of the negative biaxial A plate, the film fabric of the negative biaxial A plate is manufactured in consideration of this. Specifically, the negative biaxial A plate of the present invention has a positive refractive index characteristic of increasing refractive index with respect to the stretching direction, and can be realized through two stretching in a plane perpendicular to the MD direction and the MD direction, and absorbs adjacent polarizers. When the axis and the slow axis are orthogonal, the retardation film fabric is produced by stretching more in the planar vertical direction in the MD direction than in the MD direction. On the contrary, when the absorption axis and the slow axis of adjacent polarizers are parallel, the fabric of the retardation film may be stretched more in the MD direction than in the planar vertical direction in the MD direction, and thus the retardation film may be manufactured to manufacture the polarizing plate of the present invention. The roll to roll process can be applied.

In the present invention, the absorption axis of the polarizer of the lower polarizing plate should be located in the vertical direction when viewed from the viewer side. Specifically, when the absorption axis of the lower polarizing plate close to the backlight unit is in the vertical direction, light passing through the lower polarizing plate is polarized in the horizontal direction, which passes through the liquid crystal cell to which the voltage of the panel is applied to become a bright state. In this case, the light is vertical and passes through the upper polarizing plate on the viewer's side where the absorption axis is horizontal. At this time, the person wearing the polarized sunglasses having the absorption axis in the horizontal direction (the absorption axis of the polarized sunglasses is in the horizontal direction) on the viewer's side can recognize the light emitted from the liquid crystal display. If the absorption axis of the lower polarizing plate near the backlight unit is in the horizontal direction, a problem occurs in that the image is not visible to the person wearing the polarized sunglasses. In addition, in the case of a large liquid crystal display device, in order to make the image visible from the viewer side, in consideration of the fact that the human field of view is wider in the horizontal direction than the vertical direction, the general liquid crystal display device except for special purpose liquid crystal display devices such as advertisements is used. Since the field of view is wider in the horizontal direction than in the vertical direction, it is manufactured in the form of 4: 3 or 16: 9.

The light does not leak in the negative biaxial A plate phase difference value condition of the present invention can be explained through Poincare Sphere (Poincare Sphere). Poincare Sphere is a very useful way of expressing the change of polarization state at a certain time, so the light traveling at a certain time in the liquid crystal display that displays the image using polarization passes through each optical element in the liquid crystal display. It can show the change of polarization state. In the present invention, the specific time point is an inclination angle in the range of θ = 60 ° and Φ = 45 ° in the circular coordinate system shown in FIG. The degree of wavelength dispersion can be confirmed based on three wavelengths, such as 550 nm.

In the following, the effect on the realization of the dark state at the viewing angle when the voltage is not applied by the above configuration is summarized in Examples and Comparative Examples. The invention can be better understood by the following examples, which are intended to illustrate the invention and are not intended to limit the scope of protection as defined by the appended claims.

Example

In Examples 1 to 4 and Comparative Examples 1 to 5, the effect was applied to the LCD simulation program TECH WIZ LCD 1D (man system, KOREA) to compare the wide viewing angle effect.

Example 1

Measurement data of each optical film, a liquid crystal cell, and a backlight according to the present invention were stacked on a TECH WIZ LCD 1D (man system, KOREA) with a structure as shown in FIG. 1. Referring to the structure of Figure 1 in detail.

The backlight unit 40 , the lower polarizing plate 10, the liquid crystal cell 30, and the upper polarizing plate 20 are sequentially stacked. The lower polarizing plate 10 is a negative biaxial A plate 14 and a polarizer from the liquid crystal cell side. It consists of (11) and the protective film 13, and the absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14 were orthogonal. The upper polarizing plate 20 is configured in the order of the negative biaxial A plate 24, the polarizer 21, and the protective film 23 from the liquid crystal cell side, and the absorption axis 22 and the negative biaxial A of the polarizer 21. The slow axis 25 of the plate 24 became parallel. The absorption axis 12 of the polarizer 11 of the lower plate polarizing plate 10 was positioned in the vertical direction when viewed from the viewing side.

At this time, the polarizer gives the function of the polarizer through stretching and dyeing, and the absorption axes are disposed perpendicular to each other on both sides of the 46-inch vertical alignment mode liquid crystal cell (Samsung Electronics, PAVV, LTA460HR0). The thickness direction phase difference (Rth) of the liquid crystal cell was used as -314.28nm.

On the other hand, each of the optical film and the backlight used in the embodiment of the present invention was used to have the optical properties as follows.

라고 할 때 하기 수학식 6 내지 10에 의해 정의된다.First, the upper and lower polarizers impart polarizer function by dyeing iodine on the stretched PVA, and the polarizing performance of the polarizers is at least 99.9% visibility and at least 41% visibility in the visible light region. The visibility polarization and the visibility single transmittance are the TD (λ) transmittance of the transmission axis according to the wavelength, and the transmittance correction of the absorption axis according to the wavelength of MD (λ) and the visibility correction value defined in JIS Z 8701: 1999.

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

The optical characteristics caused by the difference in the internal refractive index according to the direction of each film is the negative biaxial A plate 14 of the lower polarizing plate 10 at a wavelength of 589.3 nm, the front phase difference (R0) is 80nm, the refractive index ratio (NZ) is 4 The negative biaxial A plate 24 of the upper polarizing plate 20 has a front phase difference R0 of 70 nm and a refractive index ratio NZ of 2.

The negative biaxial A plate was made of cycloolefin polymer (COP, Zeonor, Optes, Japan) and the phase difference wavelength dispersibility was front phase difference (wavelength 380 nm) / front phase difference (wavelength 780 nm) [RO (380 nm) / RO (780 nm) ] Is 1.006 and the thing which shows the magnitude | size of the full-wavelength wavelength dispersion like FIG. 7 was used. As the outer protective film of the upper and lower polarizers, triacetyl cellulose (TAC) having an optical characteristic with a thickness direction phase difference value (Rth) of 50 nm for incident light 589.3 nm was used. As the backlight unit, backlight measurement spectrum data mounted on 46-inch LCD TV PAVV (LTA460HR0) of Samsung Electronics was used.

The optical components were laminated as shown in FIG. 1 and subjected to simulation of visibility omnidirectional transmittance. As a result, the results as shown in FIG. 8 were obtained. The change in polarization state at the reference time (θ = 60 °, Φ = 45 °) of the present invention is shown in FIG. 9, and the polarization state is 1, negative when passing through the lower polarizer 11 on the Poincare Sphere. The polarization state is 2 when passing through the biaxial A plate 14, the polarization state is 3 when passing through the liquid crystal cell, and the polarization state is 4 when passing through the negative biaxial A plate 24. Due to the liquid crystal cell and retardation film having a long wavelength on the Poincare Sphere (380nm), the shortest wavelength is expressed as 780nm.

FIG. 8 illustrates the distribution of visibility of permeability in the case of displaying the black on the screen. The scale ranges from 0% to 0.1% of the transmittance, and the area exceeding 0.1% of the transmittance when displaying the cancer is red, Low permeability areas are indicated in blue. At this time, it was confirmed that the wider the range of blue in the center, the wider the viewing angle.

This is because the polarization state of the Pohang Care sphere as shown in FIG. In the LCD, the polarization state 4 is represented by (-0.1296, -0.919, 0.3722) at a wavelength of 380 nm and (-0.1117, -0.9648, -0.2377) at a wavelength of 380 nm. Accordingly, it was confirmed that the angle formed by the polarization state 4 at the wavelength of 380 nm and the wavelength of 780 nm based on the origin of the Pangka Legu was 35.6294 °.

Example 2

In the same manner as in Example 1, the lower polarizing plate 10 is parallel to the absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14, the upper polarizing plate 20 The absorption axis 22 of the silver polarizer 21 and the slow axis 25 of the negative biaxial A plate 24 were laminated in the configuration of FIG. 2 so as to be perpendicular to each other. The absorption axis 12 of the polarizer 11 of the lower plate polarizing plate 10 was positioned in the vertical direction when viewed from the viewing side.

At a wavelength of 589.3 nm, the negative biaxial A plate 14 of the lower polarizing plate 10 has a front phase difference R0 of 70 nm, a refractive index ratio NZ of 2, and a negative biaxial A plate 24 of the upper polarizing plate 20. ) Has a front phase difference (R0) of 80 nm and a refractive index ratio (NZ) of 4 to arrange a vertically aligned liquid crystal display device.

The simulation results of the visibility of the vertical alignment liquid crystal display were obtained as shown in FIG. 10. This is because the polarization state of the Pohang Care sphere as shown in FIG. In the LCD, the polarization state 4 is represented as (-0.5434, -0.839, 0.0249) at a wavelength of 380 nm and (-0.0171, -0.9998, -0.004) at a wavelength of 780 nm in the Cartesian coordinate system on the Puan Care sphere. Therefore, it was confirmed that the angle at which the polarization state 4 at the wavelength of 380 nm and the wavelength of 780 nm is based on the origin of the Poang Care sphere is 33.92456 °.

Example 3

In the same manner as in Example 1, the lower polarizing plate 10 is the absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14 is orthogonal, and the upper polarizing plate 20 The absorption axis 22 of the silver polarizer 21 and the slow axis 25 of the negative biaxial A plate 24 were laminated in the configuration of FIG. 1 so as to be parallel. The absorption axis 12 of the polarizer 11 of the lower plate polarizing plate 10 was positioned in the vertical direction when viewed from the viewing side.

The negative biaxial A plate 14 of the lower polarizing plate 10 has a front phase difference R0 of 76 nm and a refractive index ratio NZ of 4.2 at a wavelength of 589.3 nm; In the negative biaxial A plate 24 of the upper polarizing plate 20, the front phase difference R0 was 66 nm and the refractive index ratio NZ was 2, thereby manufacturing a vertically aligned liquid crystal display device.

The simulation results of the visibility of the vertical alignment liquid crystal display were obtained as shown in FIG. 12. This is because the polarization state of the Pohang Care sphere as shown in FIG. In the liquid crystal display, the polarization state 4 is represented as (-0.1218, -0.9238, 0.3627) at a wavelength of 380 nm and (-0.0783, -0.9718, -0.2222) at a wavelength of 380 nm in the Cartesian coordinate system on the Puan Care sphere. Therefore, it was confirmed that the angle at which the polarization state 4 at the wavelength of 380 nm and the wavelength of 780 nm was made based on the origin of the Puanca Legu was 34.22371 °.

Example 4

In the same manner as in Example 1, the lower polarizing plate 10 is the absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14 is orthogonal, and the upper polarizing plate 20 The absorption axis 22 of the silver polarizer 21 and the slow axis 25 of the negative biaxial A plate 24 were laminated in the configuration of FIG. 1 so as to be parallel. The absorption axis 12 of the polarizer 11 of the lower plate polarizing plate 10 was positioned in the vertical direction when viewed from the viewing side.

The negative biaxial A plate 14 of the lower polarizing plate 10 has a front phase difference R0 of 80 nm and a refractive index ratio NZ of 3.8 at a wavelength of 589.3 nm; In the negative biaxial A plate 24 of the upper polarizing plate 20, the front phase difference R0 was 79 nm and the refractive index ratio NZ was 2, thereby manufacturing a vertically aligned liquid crystal display device.

The simulation results of the visibility of the vertical alignment liquid crystal display were obtained as shown in FIG. 14. This is because the polarization state of the Pohang Care sphere as shown in Fig. 15 is shown on the inclined surface. In the LCD, the polarization state 4 is represented as (-0.0873, -0.9302, 0.3563) at a wavelength of 380 nm and (-0.1483, -0.9529, -0.2642) at a wavelength of 780 nm. Therefore, it was confirmed that the angle at which the polarization state 4 at the wavelength of 380 nm and the wavelength of 780 nm was made based on the origin of the Puanca Legu was 38.78714 °.

Comparative Example 1

In the same manner as in Example 1, the lower polarizing plate 10 is the absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14 is orthogonal, and the upper polarizing plate 20 16 was laminated so that the absorption axis 22 of the silver polarizer 21 and the slow axis 25 of the negative biaxial A plate 24 were orthogonal to each other. The absorption axis 12 of the polarizer 11 of the lower plate polarizing plate 10 was positioned in the vertical direction when viewed from the viewing side. This configuration is the most commonly used in the vertical alignment liquid crystal display device [Samsung Electronics (Korea) and Sharp (Japan) as of 2008]. In the above configuration, the retardation film was used to show the wavelength dispersion of the wavelength shown in FIG. 17, and the front phase difference (wavelength 380 nm) / front phase difference (wavelength 780 nm) [RO (380 nm) / RO (780 nm)] was 0.862. It was.

The negative biaxial A plate 14 of the lower polarizing plate 10 has a front phase difference R0 of 50 nm and a refractive index ratio NZ of 3 at a wavelength of 589.3 nm; The negative biaxial A plate 24 of the upper polarizing plate 20 was arranged such that the front phase difference R0 was 50 nm and the refractive index ratio NZ was 3 to manufacture a vertically aligned liquid crystal display device.

As a result of performing the visibility omnidirectional transmittance simulation in the above configuration, the results as shown in FIG. 18 were obtained. The change in the polarization state at the reference time of the present invention is shown in FIG. 19 and when the polarization state passes through the lower polarizer 11 on the Poincare Sphere, the polarization state passes through 1 and the negative biaxial A plate 14. The polarization state is 2, the polarization state is 3 when passing through the liquid crystal cell, the polarization state is polarized to 4 when passing through the negative biaxial A plate 24, and the liquid crystal cell having the forward wavelength dispersion and the reverse wavelength dispersion Due to the retardation film, the longest path is 380 nm, the shortest path is 780 nm and the intermediate wavelength is 550 nm on Poincare Sphere.

In the LCD, the polarization state 4 is represented as (-0.6532, -0.6697, 0.3531) at a wavelength of 380 nm and (-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 of 780 nm based on the origin of the Poang Carregu was 47.68254 °.

In Example 1 and Comparative Example 1, the angles of the polarization state 4 at the wavelength of 380 nm and the wavelength of 780 nm based on the origins of the Pangka Legu are 35.6294 ° and 47.68254 °, respectively. It can be seen that is small. The retardation film of Comparative Example 1 was found to have a large difference in the polarization state according to the wavelength despite the retardation wavelength dispersion of the retardation wavelength.

In particular, FIG. 20 shows the transmittance at diagonal angle Φ = 45 ° in the liquid crystal display device of Example 1 and Comparative Example 1. Example 1 and Comparative Example 1 have an inclination angle because the transmittance of the white state is almost similar. It can be seen that the contrast ratio at (θ = 60 °, Φ = 45 °) can provide Example 1 with more than three times clearer image quality than Comparative Example 1. Specifically, when measuring the ratio of the inclined planes of Comparative Example 1, the ratio of the inclined planes of Example 1 is estimated to be about 240 in numerical calculation.

In addition, in Example 1 and Comparative Example 1, the omnidirectional transmittance of the black state is as shown in FIGS. 8 and 18, respectively. In general, when the blue in the central part is wide, it means that the viewing angle is wide. Since the blue range is wider than that of FIG. 18, it was confirmed that the viewing angle of Example 1 was wider than that of Comparative Example 1.

Comparative Example 2

In the same manner as in Comparative Example 1, but the wavelength dispersion of the negative biaxial A plate stacked on the upper and lower plates as shown in Figure 7 RO (wavelength 380nm, unit nm) / RO (wavelength 780nm, unit nm) is 1.006 Was used.

As a result of performing the visibility omnidirectional transmittance simulation in the above configuration, the results as shown in FIG. 21 were obtained. The change in polarization state at the reference time of the present invention is shown in FIG. 22. When the polarization state passes through the lower polarizer 11 on the Poincare Sphere, the polarization state passes through 1 and the negative biaxial A plate 14. The polarization state is 2, the polarization state is 3 when passing through the liquid crystal cell, and the polarization state is polarized at 4 when passing through the negative biaxial A plate 24. The longest path is 380nm and the shortest path is 780nm on the Poincare Sphere. In the LCD, the polarization state 4 is represented as (-0.7514, -0.5941, 0.2867) at a wavelength of 380 nm and (-0.0021, -0.9859, 0.1670) at a wavelength of 380 nm in the Cartesian coordinate system on the Puan-Care sphere. Accordingly, it was confirmed that the angle formed by the polarization state 4 at the wavelength of 380 nm and the wavelength of 780 nm based on the origin of the Pangka Legu was 50.78729 °.

In Comparative Examples 1 and 2, the angle at which the polarization state 4 at the wavelength of 380 nm and the wavelength of 780 nm is based on the origin of the Pangka Legu is 47.68254 ° and Comparative Example 2 is 50.78729 °, respectively. It was confirmed that the larger the dispersion angle. In addition, as the dispersion angle is increased, the slope transmittance also increases as shown in FIG.

Comparative Example 3

In the same manner as in Example 1, except that the positions of the negative biaxial A plates of the upper and lower polarizing plates were changed and stacked to manufacture a vertically aligned liquid crystal display device.

The simulation results of the visibility of the vertical alignment liquid crystal display were obtained as shown in FIG. 23. Since this shows the change in the polarization state of the Poang Carre sphere on the inclined surface as shown in FIG. 24, it was confirmed that the viewing angle was narrow because there was almost no blue range in the center, and the contrast ratio was inclined (θ = 60 ° and Φ = 45 °). 34.6 is shown.

In Comparative Example 3, the angle between the polarization state 4 at the wavelength of 380 nm and the wavelength of 780 nm was about 16.96536 ° as a reference to the origin of the Puanca Legu, but the inclined plane transmittance was not high to satisfy the object of the present invention. . In other words, the present invention must satisfy wavelength dispersion while simultaneously viewing angle compensation.

Comparative Example 4

In the same manner as in Example 1, the lower polarizing plate 10 is the absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14 is orthogonal, and the upper polarizing plate 20 The absorption axis 22 of the silver polarizer 21 and the slow axis 25 of the negative biaxial A plate 24 were laminated in the configuration of FIG. 1 so as to be parallel. The absorption axis 12 of the polarizer 11 of the lower plate polarizing plate 10 was positioned in the vertical direction when viewed from the viewing side.

The negative biaxial A plate 14 of the lower polarizing plate 10 at a wavelength of 589.3 nm has a front phase difference R0 of 69 nm and a refractive index ratio NZ of 3.8; The negative biaxial A plate 24 of the upper polarizing plate 20 has a front phase difference R0 of 65 nm and a refractive index ratio NZ of 2 to arrange a vertically aligned liquid crystal display device.

The simulation results of the visibility of the vertical alignment liquid crystal display were obtained as shown in FIG. 25.

This indicates the change in polarization state of the Poang Care sphere on the inclined plane as shown in FIG. 26, so that the blue range of the central part was narrow and the viewing angle was narrow. At this time, in Comparative Example 4, the angle of the polarization state 4 at the wavelength of 380 nm and the wavelength of 780 nm was about 32.51208 ° based on the origin of the Puan Carregu. I couldn't. In other words, the present invention must satisfy wavelength dispersion while simultaneously viewing angle compensation.

Comparative Example 5

In the same manner as in Example 1, the lower polarizing plate 10 is the absorption axis 12 of the polarizer 11 and the slow axis 15 of the negative biaxial A plate 14 is orthogonal, and the upper polarizing plate 20 The absorption axis 22 of the silver polarizer 21 and the slow axis 25 of the negative biaxial A plate 24 were laminated in the configuration of FIG. 1 so as to be parallel. The absorption axis 12 of the polarizer 11 of the lower plate polarizing plate 10 was positioned in the vertical direction when viewed from the viewing side.

The negative biaxial A plate 14 of the lower polarizing plate 10 has a front phase difference R0 of 100 nm and a refractive index ratio NZ of 1 at a wavelength of 589.3 nm; The negative biaxial A plate 24 of the upper polarizing plate 20 was disposed such that the front phase difference R0 was 50 nm and the refractive index ratio NZ was 1.2, thereby manufacturing a vertically aligned liquid crystal display device.

The simulation results of the visibility of the vertical alignment liquid crystal display were obtained as shown in FIG. 27.

This is because the change in the polarization state of the Pohang Care sphere as shown in Fig. 28 on the inclined plane, it was confirmed that the viewing angle is narrow due to the narrow blue range in the center. At this time, in Comparative Example 5, the angle at which the polarization state 4 at the wavelength of 380 nm and the wavelength of 780 nm was made based on the origin of the Pangka Legu was 67.06955 °.

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

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

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

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

Figure 4 is a schematic diagram 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,

5 is a schematic view for explaining what is represented by θ, Φ in the coordinate system of the present invention,

FIG. 6 is a schematic diagram for describing the difference in polarization states according to wavelengths as dispersion angles in the Pangareque sphere of the present invention.

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

8 is a simulation result of the visibility of the omnidirectional transmittance of Example 1 according to the present invention,

FIG. 9 illustrates a change in polarization state of light emitted in an inclined plane (θ = 60 ° and Φ = 45 °) in Example 1 of the present invention on a Poincare Sphere.

10 is a simulation result of the visibility of the visibility of Example 2 according to the present invention,

FIG. 11 illustrates a change in polarization state of light emitted in an inclined plane (θ = 60 ° and Φ = 45 °) in Example 2 of the present invention on a Poincare Sphere.

12 is a result of simulating the visibility omnidirectional transmittance of Example 3 according to the present invention,

FIG. 13 illustrates a change in polarization state of light emitted in an inclined plane (θ = 60 ° and Φ = 45 °) in Example 3 of the present invention on a Poincare Sphere.

14 is a simulation result of the visibility of the visibility of Example 4 according to the present invention,

FIG. 15 illustrates a change in polarization state of light emitted in an inclined plane (θ = 60 °, Φ = 45 °) in Example 4 of the present invention on a Poincare Sphere.

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

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

18 is a result of simulating the visibility omnidirectional transmittance of Comparative Example 1 according to the present invention,

FIG. 19 illustrates a change in polarization state of light emitted in an inclined plane (θ = 60 ° and Φ = 45 °) in Comparative Example 1 on a Poincare Sphere.

20 shows the transmittance at the inclined surface (Φ = 45 °) of Example 1 and Comparative Example 1 according to the present invention,

21 is a result of simulating the visibility omnidirectional transmittance of Comparative Example 2 according to the present invention,

FIG. 22 illustrates a change in polarization state of light emitted in an inclined plane (θ = 60 ° and Φ = 45 °) in Comparative Example 2 on a Poincare Sphere.

23 is a result of simulating the visibility omnidirectional transmittance of Comparative Example 3 according to the present invention,

FIG. 24 illustrates a change in polarization state of light emitted in an inclined plane (θ = 60 ° and Φ = 45 °) in Comparative Example 3 of the present invention on a Poincare Sphere.

25 is a result of simulating the visibility omnidirectional transmittance of Comparative Example 4 according to the present invention,

FIG. 26 illustrates a change in polarization state of light emitted in an inclined plane (θ = 60 ° and Φ = 45 °) in Comparative Example 4 on a Poincare Sphere.

27 is a result of simulating the visibility omnidirectional transmittance of Comparative Example 5 according to the present invention,

FIG. 28 illustrates a change in polarization state of light emitted in an inclined plane (θ = 60 °, Φ = 45 °) in Comparative Example 5 on a 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 above and below a liquid crystal cell, One of the negative biaxial A plates of the upper and lower polarizers is disposed in parallel with the adjacent polarizer and the other is disposed perpendicular to the other adjacent polarizer, Negative biaxial A plates arranged parallel to adjacent polarizers have a frontal phase difference of 60 to 80 nm, a refractive index ratio of 1.5 to 2.5, Negative biaxial A plates disposed perpendicular to adjacent polarizers have a frontal phase difference of 70 to 90 nm and a refractive index ratio of 3.5 to 4.5, A vertically oriented liquid crystal display in which the polarization states at wavelengths of 380 nm and 780 nm at the wavelength of 380 nm and 780 nm immediately before passing through the planar polarizer of the upper polarizing plate are 45 degrees or less with respect to the origin of the Pangka Legu. The liquid crystal display of claim 1, wherein the negative biaxial A plate disposed in parallel to the adjacent polarizer has a front phase difference value of 65 to 75 nm and a refractive index ratio of 1.7 to 2.3. The liquid crystal display of claim 1, wherein the negative biaxial A plate disposed perpendicular to the adjacent polarizer has a front phase difference 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 at which the polarization states at the wavelengths of 380 nm and 780 nm passing through the liquid crystal display are formed based on the origin of the Poang Karegu is 40 ° or less. The liquid crystal display device according to claim 1, wherein the negative biaxial A plate has a front phase difference (wavelength 380 nm) / front phase difference (wavelength 780 nm) [RO (380 nm) / RO (780 nm)]> 1. The liquid crystal display device according to claim 1, wherein the liquid crystal cell has a thickness direction phase difference value (Rth) of -350 to -250 nm at a wavelength of 589 nm. The liquid crystal display device according to claim 1, wherein the visibility transmittance satisfies a compensation relationship of 0.05% or less at an inclination angle (θ = 60 °, Φ = 45 °). The liquid crystal display device according to claim 1, wherein a contrast ratio (white luminance / black luminance) of an inclination angle (θ = 60 °, Φ = 45 °) is 100: 1 or more.

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