KR20100022919A - Twist nematic liquid crystal display with wideviewing - Google Patents

Abstract

PURPOSE: A twist nematic liquid crystal display with wide view is provided to enable the implementation of vivid colors and wide view and to facilitate mass production by a roll to toll process. CONSTITUTION: A twist nematic liquid crystal display with wide view includes a first polarizer(10), a second polarizer(20), and a liquid crystal cell(30). Absorption axes(12,22) of the first polarizer cross at right angles and phase difference films(14,24) of the first polarizer are arranged to be crossed with the absorption axis of a polarizer adjacent to a ground axis. Absorption axes of the second polarizer cross at right angles and phase difference films of the second polarizer are arranged to be crossed with the absorption axis of a polarizer adjacent to a ground axis. The liquid crystal cell is composed in order than the rubbing direction of liquid crystal is parallel to the absorption axis of an adjacent polarizer.

Description

Twist nematic mode liquid crystal display with wide viewing angle {TWIST NEMATIC LIQUID CRYSTAL DISPLAY WITH WIDEVIEWING}

The present invention relates to a twist nematic mode liquid crystal display device capable of securing a wide viewing angle by preventing light leakage and having a vivid color.

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. Therefore, wide viewing angle technology using functional optical film such as retardation film has emerged, and new liquid crystal modes that can secure a certain viewing angle without using functional optical film in twisted nematic (TN) mode, which appeared in the early stage, are presented. It became.

LCDs require polarizers to polarize light on both sides of the liquid crystal cell, and polarizers generally have protective films on both sides of the polarizer, and functional films such as retardation films to compensate for viewing angles. This is used in addition. Recently, the retardation film plays a role not only of viewing angle compensation but also of protective film.

In the TN mode liquid crystal display, the liquid crystal is twisted by 90 ° when no voltage is applied. When the voltage is applied, the liquid crystal is vertically aligned between the upper and lower substrates. However, even though a voltage is applied, liquid crystals positioned near the substrate are not aligned vertically with respect to the liquid crystal substrate. Liquid crystals that are not vertically aligned are the biggest reason for degrading the image quality on the slope when displaying the black. In order to compensate for liquid crystals that are not vertically oriented close to the substrate when displaying the black (BLACK), a film coated with a discotic liquid crystal is coated on a triacetyl cellulose (TAC) used as a protective film of the polarizer. Such discotic liquid crystals have a tilt angle in one direction.

However, the TN mode liquid crystal display cannot realize a perfect black state only by tilting the discotic liquid crystal. In addition, in reality, it is difficult to uniformly manufacture the alignment angle and tilt angle of the discotic liquid crystal and the manufacturing cost is high. If the uniformity of the alignment angle and the tilt angle of the discotic liquid crystal is not maintained, it may adversely affect the front contrast ratio (CR) of the liquid crystal display.

The present invention is to design the optical characteristics of the retardation film by grasping the correct driving direction of the liquid crystal by the Poincare Sphere in a twisted nematic mode liquid crystal display including a first polarizing plate, a second polarizing plate and a liquid crystal cell, The present invention provides a twisted nematic mode liquid crystal display device having a clear viewing color at the same time as securing a wide viewing angle by constantly adjusting the slow retardation direction of the retardation film, the maximum retardation value in the thickness direction of the liquid crystal cell, and the alignment direction of the liquid crystal.

The present invention is a twisted nematic mode liquid crystal display device comprising a first polarizing plate, a second polarizing plate, and a liquid crystal cell stacked in the order of a retardation film, a polarizer, and a protective film, respectively, and absorbs each polarizer of the first polarizing plate and the second polarizing plate. The axes are orthogonal to each other, and each retardation film of the first polarizing plate and the second polarizing plate has a front retardation value R0 of 50 to 150 nm, a refractive index ratio NZ of 1 <NZ≤5, and an absorption axis of adjacent polarizers. Disposed at right angles to each other, the liquid crystal cell has a maximum retardation value of 300 nm or less from the center of the liquid crystal cell in the thickness direction of the liquid crystal cell to one substrate when the incident angle is 60 ° or less, and the rubbing direction of the liquid crystal absorbs adjacent polarizers, respectively. Provided is a twisted nematic mode liquid crystal display device configured to be parallel to one another on an axis.

Twisted nematic mode liquid crystal display device according to the present invention is capable of realizing a wide viewing angle and at the same time a vivid color and easy to mass production by a roll-to-roll process.

The present invention is to design the optical characteristics of the retardation film by grasping the correct driving direction of the liquid crystal by the Poincare Sphere in a twisted nematic mode liquid crystal display including a first polarizing plate, a second polarizing plate and a liquid crystal cell, Twist nematic mode liquid crystal display improved to ensure wide viewing angle and clear color by controlling light retardation direction, maximum retardation value of liquid crystal cell thickness direction, and alignment direction of liquid crystal constantly. It is about.

The configuration of the twisted nematic mode liquid crystal display device of the present invention will be described in detail as follows.

And a first polarizing plate, a second polarizing plate, and a liquid crystal cell, respectively, stacked in the order of retardation film, polarizer, and protective film. The absorption axes of the polarizers of the first polarizing plate and the second polarizing plate are perpendicular to each other.

Each of the retardation films of the first polarizing plate and the second polarizing plate has a front retardation value R0 of 50 to 150 nm and a refractive index ratio NZ of 1 <NZ≤5. In addition, the retardation film of the first polarizing plate and the second polarizing plate is such that the slow axis is disposed perpendicular to each other and the absorption axis of the adjacent polarizer.

The liquid crystal cell has a maximum phase difference value of 300 nm or less from the center of the thickness direction of the liquid crystal cell to one substrate when the incident angle is 60 ° or less when voltage is applied. In addition, the rubbing direction of the liquid crystal is configured to be parallel to each other and the absorption axis of the adjacent polarizer.

The first polarizing plate and the second polarizing plate may be formed by stacking various kinds of optical layers on a polarizer capable of satisfying required optical properties. As the optical layer, a hard coating layer, an antireflection layer, an anti-sticking layer, an anti-diffusion layer, an anti-glare layer alignment liquid crystal layer, or the like may be used.

The optical characteristic design of the retardation film according to the present invention should be preceded by grasping the correct driving direction of the liquid crystal. The liquid crystal direction of the TN liquid crystal cell divides the liquid crystal cell into a plurality of layers with respect to the thickness direction in a dark state and expresses the liquid crystal direction of each layer in three dimensions. In order to express the liquid crystal direction in three dimensions, a value calculated by changing an incident angle and measuring a phase difference while a voltage is applied to the TN liquid crystal cell is used.

The liquid crystal cell according to the present invention is configured such that the rubbing directions of the liquid crystals are parallel to the absorption axes of adjacent polarizers, respectively. The absorption axis of the polarizer is designed to be positioned at 0 to 180 degrees when the counterclockwise direction is made to the positive (+) direction with respect to the right horizontal direction on the viewing side.

3, 4, 5 and 6, for example, the directions of the liquid crystals are calculated based on the result of measuring the phase difference of the TN liquid crystal cell in various directions. The direction of the liquid crystal is influenced by the dielectric constant, elastic modulus and viscosity of the liquid crystal.

FIG. 3 shows a tilt angle of each layer when the liquid crystal cell is divided into 40 layers in the thickness direction while a voltage is applied. The tilt angle is an angle in which the long axis direction of the liquid crystal forms the surface of the substrate as shown in FIG. 7. The tilt angle coincides with a 90-θ value in the coordinate system in which the Z axis in FIG. 8 is in the thickness direction.

4, 5 and 6 show the direction angle of the liquid crystal in the state where a voltage is applied. The direction angle refers to a direction in which the tilt angle is positive (+), and corresponds to Φ in FIG. 7.

FIG. 4 illustrates a liquid crystal designed so that the rubbing direction of the liquid crystal on the backlight side is -45 ° and the rubbing direction of the liquid crystal on the viewer side is 45 ° when the counterclockwise direction is positive (+) based on the horizontal direction on the right side of the viewer. It shows the direction angle. The liquid crystal display device including the TN liquid crystal cell having the direction angle of the liquid crystal as shown in FIG. 4 can secure a wide viewing angle in the left and right (horizontal) directions when viewed from the viewer side. The rubbing direction of the backlight-side liquid crystal and the rubbing direction of the viewer-side liquid crystal indicate the direction of the liquid crystal closest to each substrate.

In addition, the direction of the liquid crystal is designed such that the rubbing direction of the liquid crystal at the backlight side is 45 ° and the rubbing direction of the liquid crystal at the viewing side is -45 °, or the rubbing direction of the liquid crystal at the backlight side is 135 °, and the rubbing direction of the liquid crystal at the viewing side is -135 °. A liquid crystal display including a TN liquid crystal cell designed to be °, or designed such that the rubbing direction of the backlight-side liquid crystal is -135 ° and the rubbing direction of the viewer-side liquid crystal is 135 °, is also viewed in the left-right (horizontal) direction when viewed from the viewer side. It is possible to secure a wide viewing angle.

5 is an orientation of a liquid crystal designed such that the rubbing direction of the backlight-side liquid crystal is 45 ° and the rubbing direction of the viewer-side liquid crystal is 135 ° when the counterclockwise direction is positive (+) based on the horizontal direction on the right side of the viewer. The angle is shown. 6 is a liquid crystal designed such that the rubbing direction of the liquid crystal on the backlight side is -135 ° and the rubbing direction of the liquid crystal on the viewer side is -45 ° when the counterclockwise direction is positive (+) based on the horizontal direction on the right side of the viewer. It shows the orientation angle of.

5 and 6 show a perfectly symmetrical structure in the rubbing direction of the liquid crystal. FIG. 5 shows a gray level inversion phenomenon according to the intensity of voltage application, and FIG. 6 is a gray level inversion phenomenon in accordance with the intensity of voltage application. . A liquid crystal display device including a TN liquid crystal cell having the direction angles of liquid crystals as shown in FIGS. 5 and 6 can secure a wide viewing angle in the vertical direction (vertical) when viewed from the viewer side.

Also, when the counterclockwise direction is set to the positive (+) direction based on the horizontal direction on the right side of the viewer, the rubbing direction of the backlight liquid crystal is designed to be 135 °, and the rubbing direction of the viewer liquid crystal is 45 °, or the backlight liquid crystal is Also, a liquid crystal display device including a TN liquid crystal cell designed such that the rubbing direction of the liquid crystal is -45 ° and the rubbing direction of the liquid crystal on the viewer side is -135 ° can ensure a wide viewing angle in the vertical direction when viewed from the viewer side.

The characteristics of the TN liquid crystal cell are parameterized in an LCD optical simulation program (eg, LCD Master, Techwiz LCD 1D) under the dark state defined above, and input and apply. The optical properties of the retardation film are designed in consideration of the polarization state that the parameterized liquid crystal is implemented on the Poincare Sphere.

The optical characteristics of the retardation film have a front retardation value R0 of 50 to 150 nm and a refractive index ratio NZ of 1 <NZ≤5, preferably a front retardation value RO of 50 to 120 nm and 1.4 <NZ <4.2. More preferably, the front phase retardation value RO is 60 to 90 nm and is designed to be 1.5 <NZ <2.7. Each retardation film of the first polarizing plate and the second polarizing plate may be the same or different within the optical properties of the designed retardation film when applied to the liquid crystal display device, preferably the same.

The optical properties of the retardation film are defined by the following equations (1) to (3) for the electric field in the visible light region.

In general, the optical properties of the retardation film is represented by the characteristics for 589 nm which is most easily obtained when there is no mention of the wavelength of the light source. The optical properties of such retardation film are defined by the refractive index. 9 is a schematic diagram for describing the refractive index of the retardation film, where Nx is the refractive index of the axis having the largest refractive index in the in-plane direction, Ny is the vertical direction of Nx in the in-plane direction, and Nz represents the refractive index in the thickness direction.

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 planar refractive indices Nx ≧ Ny, and d represents the thickness of the film)

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

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

Rth of Equation 1 is a thickness retardation value representing the difference in refractive index in the thickness direction with respect to the in-plane average refractive index, R0 of Equation 2 is a front phase that is a substantial phase difference when light passes through the normal direction (vertical direction) of the film Phase difference value.

In addition, NZ in Equation 3 is a refractive index ratio to distinguish the type of plate used as a retardation film accordingly.

The plate type of the retardation film may include 1) an A plate in the case where an optical axis without retardation exists in the in-plane direction of the film; 2) a C plate if the optical axis is present in the vertical direction of the film plane; And 3) when there are two optical axes, it is called a biaxial plate. Specifically, 1) when NZ is 1, the refractive index has a relationship of Nx> Ny = Nz and is called 'Positive A Plate'; 2) when 1 <NZ, the refractive index satisfies Nx> Ny> Nz and is called 'NEGATIVE BIAXIAL A PLATE'; 3) when 0 <NZ <1, the refractive index has a relationship of Nx> Nz> Ny and is called 'Z-axis oriented film'; 4) When NZ = 0, the refractive index is called 'NEGATIVE A PLATE' with the relationship Nx = Nz> Ny; 5) When NZ <0, the refractive index is called 'POSITIVE BIAXIAL A PLATE' with the relation Nz> Nx> Ny; 6) When NZ = ∞, the refractive index is called 'NEGATIVE C PLATE' with the relationship Nx = Ny> Nz; 7) In the case of NZ = -∞, the refractive index has a relationship of Nz> Nx = Ny and is called 'positive C plate'.

However, it is impossible in practice to make A and C plates that perfectly match the theoretical definition as above. In the general process, the A plate is divided into an approximate range of refractive index ratios, and the C plate is set to an arbitrary value by setting the range of the front phase difference. Nevertheless, the arbitrary numerical setting is limited to apply to all materials having different refractive index expression characteristics due to stretching. Therefore, the retardation film according to the present invention represents not the type of plate according to the form of refractive anisotropy, but NZ, RO, and Rth, which are optical properties of the plate.

Each retardation film of the first polarizing plate and the second polarizing plate according to the present invention is produced in the stretch type.

The retardation film is generally referred to as a film having a high refractive index in the stretching direction to impart retardation through stretching, and a film having a small refractive index in the stretching direction is called a negative refractive index property. do. Retardation films having positive refractive index characteristics include triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate ( PC), polysulfone (PSF) and polymethylmethacrylate (PMMA). In addition, the retardation film having negative refractive index characteristics may be made of modified polystyrene (PS) or modified polycarbonate (PC).

The stretching method of the retardation film is divided into fixed end stretching and free end stretching. Fixed-end stretching is a method of fixing the length of a direction other than the extending direction in the extending process of a film, and free end extending | stretching is a method of providing a degree of freedom to other directions other than the extending direction in the extending process of a film. Usually, when the film is stretched, other directions other than the stretching direction are contracted, but in the case of the Z-axis oriented film, a separate shrinkage process may be required in addition to the stretching.

The direction in which the film in the roll state is released during stretching is called the MD direction (machine direction) and the direction perpendicular thereto is called a TD direction (Transverse Direction). Free end drawing refers to stretching in the MD direction, and fixed end drawing refers to stretching in the TD direction.

The type of NZ and plate vary depending on the stretching method (only when the first process is applied). 1) the positive A plate stretches the free end of the film with positive refractive index characteristics; 2) the negative biaxial A plate fixed-stretches the film with positive refractive index characteristics; 3) the Z-axis alignment film contracts fixed end shrinkage after free end stretching of a film having a positive refractive index characteristic or a negative refractive index characteristic; 4) the negative A plate free-ends the film with negative refractive index characteristics; 5) The positive biaxial A plate can be prepared by fixed end stretching a film having negative refractive index characteristics.

In addition, the retardation film may control an optical property such as a direction of a slow axis, a retardation value, and a value of NZ by applying an additional process such as secondary stretching and additives in addition to the primary stretching as described above. The further process thereof is a process generally applied in the art and is not particularly limited in the present invention.

Each retardation film of the first polarizing plate and the second polarizing plate can be used without restriction on the wavelength dispersion of the refractive index ratio or the retardation value.

In addition, each retardation film of the first polarizing plate and the second polarizing plate is such that the slow axis is arranged perpendicular to each other and the absorption axis of the adjacent polarizer. The slow axis is distinguished from the optical axis, which is the light direction in which the phase difference does not occur in the slowest polarization direction at the viewing angle.

Each polarizer of the first and second flat plates is a polyvinyl alcohol (PVA) layer, which is a polarizer provided with a polarizing function through stretching and dyeing. Each absorption axis of the first polarizing plate and the second polarizing plate is arranged to be orthogonal to each other.

In each of the polyvinyl alcohol (PVA) layers of the first polarizing plate and the second polarizing plate, a protective film is positioned on the opposite side of the liquid crystal cell.

The protective film of the first polarizing plate and the second 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 first and second polarizing plate 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 poly Methyl methacrylate (PMMA) and the like prepared from the group consisting of can be used.

The first and second polarizing plates of the present invention may be manufactured by a process generally applied in the art, and specifically, the manufacturing process may be a roll to roll process, sheet to sheet, or the like. have. In general, it is preferable to apply a roll-to-roll process in consideration of yield and efficiency in the manufacturing process.

In the first and second polarizing plates of the present invention, the direction of the absorption axis of the PVA polarizer is always fixed in the MD direction, and the retardation film has a roll to roll since the slow axis is perpendicular to the absorption axis of the polarizing plate. ) Process can be applied. In order to make the absorption axis of the polarizing plate and the slow axis of the retardation film orthogonal, it is most preferable to use a roll-to-roll method to lower the production cost when integrating the polarizing plate and the retardation film.

The configuration of the TN mode liquid crystal display device according to the present invention will be described with reference to FIG.

The first polarizing plate 10, the liquid crystal cell 30, and the second polarizing plate 20 are stacked in the backlight unit side 40. The retardation films 14 and 24, the polarizers 11 and 21, and the protective films 13 and 23 are stacked from the liquid crystal cell 30 of the first polarizing plate 10 and the second polarizing plate 20, respectively.

The liquid crystal cell 30 is a TN liquid crystal cell having a structure in which a positive dielectric anisotropy (Δε> 0) material is stacked between two glass substrates. In the glass substrate, an active matrix drive electrode including an electrode pair is formed on an adjacent surface of the liquid crystal cell 30, and an electric field is formed in a vertical direction when a voltage is applied, thereby aligning the arrangement direction of the liquid crystals in a vertical direction. Change.

As viewed from the viewer's side, the absorption axis 12 of the first polarizing plate 10 and the absorption axis 22 of the second polarizing plate 20 are perpendicular to each other, and the absorption axis 12 of the polarizing plates 10 and 20 ( 22) is parallel to the rubbing direction of the adjacent liquid crystal. In general, when the voltage is applied, the TN liquid crystals are not vertically aligned as they are adjacent to the substrate, which is a major reason for degrading the image quality in the black state.

Each of the retardation films of the first polarizing plate and the second polarizing plate has a front retardation value RO of 50 to 150 nm, and a refractive index ratio NZ having 1 <NZ≤5. Each retardation film of the first polarizing plate and the second polarizing plate is such that the slow axis is disposed perpendicular to the absorption axis of the adjacent polarizer.

In general, when the absorption axes of the first polarizing plate and the second polarizing plate are perpendicular to each other, it is called NW (Normal White) mode, and when they are parallel to each other, it is called NB (Normal Black) mode. In the TN mode, when the absorption axis of the polarizer and the rubbing direction of the liquid crystal adjacent to each other are parallel to each other, it is called an O-mode, and when it is perpendicular, it is called an E-mode. The TN mode in the present invention is limited to the range of 'NW (Normal Wite) mode' and 'O-mode'.

Conventionally, TN mode liquid crystal display devices designed in NW (Normal Wite) mode and O-mode tend to leak light in a dark state and thus have poor visibility. For example, FIG. 10 shows the visibility of transmittance omnidirectionally when a polarizer is applied to a TN liquid crystal cell that is currently mass-produced, and a voltage is applied. Θ is 20 ° or more, Φ is 0 °, 90 °, 180 °, and 270 °. It can be seen that many leaks (based on the coordinates of FIG. 8). Accordingly, the present invention provides a retardation film designed to have a specific optical characteristic to reduce the visibility of the TN mode liquid crystal display device designed in the conventional NW (Normal Wite) mode and O-mode, the slow axis direction of the retardation film, the maximum thickness direction of the liquid crystal cell. It improves by adjusting a phase difference value and the orientation direction of a liquid crystal.

In the liquid crystal cell 30 of the present invention, it is preferable that the panel retardation value (Δn × d) defined by Equation 4 below is maintained at 200 to 600 nm at a 589 nm wavelength. The panel retardation value is a range that can express white when no voltage is applied, and when it is out of this range, the light efficiency may decrease. In addition, the liquid crystal has a cell gap (d) of 2 to 10 µm, and the refractive index difference (Δn = ne-no) of the liquid crystal is maintained at 0.2 or less.

This is because the light polarized by passing through the first polarizing plate 10 in the front side of the viewer side in the state where no voltage is applied to the TN-LCD panel is rotated 90 ° after passing through the liquid crystal cell 30 and the polarizing plane is the second polarizing plate. This is because the retardation value of the liquid crystal cell 30 of the TN-LCD panel must be sufficiently large at a wavelength of 589 nm of the light source in order to coincide with the transmission axis of.

Δn × d = (n _e -n _o ) × d

(Where n _e is the extraordinary refractive index of the liquid crystal, n _o is the normal ray refractive index, and d is the cell gap; Note. Δn, d is not a vector)

The liquid crystal cell maintains a maximum retardation value of 300 nm or less, preferably 50 to 300 nm, from the center of the thickness direction of the liquid crystal cell to one substrate when the incident angle is 60 ° or less when voltage is applied.

In the present invention, the principle that the viewing angle is compensated by the retardation films 14 and 24 may be expressed by Poincare Sphere. In the field switching mode liquid crystal display (IPS-LCD) or the vertical alignment mode liquid crystal display (VA-LCD), the liquid crystal maintains symmetry when the voltage in the black state is applied, and the viewing angle compensation at a specific time is extended to the entire viewing range. This is possible.

On the other hand, in the TN-LCD, when a dark voltage is applied, the liquid crystal adjacent to the liquid crystal cell substrate is not vertically aligned and has a low tilt angle. Since the liquid crystal has asymmetry, it is not possible to extend the compensation principle at a specific time from another view. Therefore, TN-LCD designs the viewing angle compensation structure at each time by dividing the time. The TN liquid crystal cell of the present invention is divided into three views to design a compensation structure.

4, 5 and 6 illustrate the direction of the liquid crystal cell in a dark state. When the direction of the liquid crystal cell is expressed three-dimensionally, the arrangement of the liquid crystal cell may be symmetric with respect to the left and right, and the upper and lower asymmetry with reference to the rubbing direction. Therefore, the TN liquid crystal cell is designed in consideration of one symmetrical direction and two asymmetrical directions to compensate for the viewing angle by using a phase difference.

The present invention defines the viewing angle 1 in the upward direction in two of the three views at θ = 60 ° and the viewing angle 2 in the right direction at Φ = 90 ° as θ = 60 ° and Φ = 0 °. We design the viewing angle compensation by retardation film at. Viewing angle compensation is designed by expressing the polarization state of light polarized by Poincare Sphere. However, the point S3 (1,0,0,1) on the Poincare Sphere of the present invention is a right circularly polarized light, and the reference for θ and Φ is Φ + 90 ° when viewed from the front of the liquid crystal display. This is when the surface in the Φ direction is rotated by θ toward the viewing side. At this time, the polarization state of the light coming to the front is expressed on the Poincare Sphere.

12 illustrates changes in polarization state according to Example 1-1 at the viewing angle 1 of the present invention, and FIG. 13 illustrates changes in polarization state according to Example 1-1 at the viewing angle 2 of FIG. In addition, FIG. 14 illustrates a change in polarization state according to Example 2-1 at a viewing angle 1 of the present invention, and FIG. 15 illustrates a change in polarization state according to Example 2-1 at a viewing angle 2 of FIG. 14 and 15 are different from those of Embodiment 1-1 (FIGS. 12 and 13) and the liquid crystals in the polarization state, but the principle is the same as that of FIGS. 12 and 13.

12 and 13, light passing through the polarizer 11 of the first polarizing plate 10 is polarized to P1 and thus the retardation film 24 of the retardation film 14, the liquid crystal layer 30, and the second polarizing plate 20. Pass sequentially. The polarization of light changes state depending on the optical characteristics of the retardation films 14 and 24 and the liquid crystal layer 30. When the polarization state immediately before the light of P1 passes through the polarizer 21 of the second polarizing plate 20 approaches P2, the change in the polarization state by the retardation film and the liquid crystal layer is compensated for.

The phase difference values of the retardation films 14 and 24 and the liquid crystal 30 are changed according to the incident wavelength in the visible light region, thereby changing the polarization state. This is indicated by the difference in the polarization path on the Poincare Sphere. In most cases, the retardation value of the retardation film is larger at shorter wavelengths than at longer wavelengths, so the change in polarization state on the Poincare Sphere also changes significantly at shorter wavelengths.

12 and 13, the polarization state change from point 2 to point 3 is caused by the liquid crystal cell 30 when a voltage is applied. Near each of points 2 and 3, the curve is formed because the liquid crystal adjacent to the substrate is not vertically aligned. The vertical alignment of the liquid crystal is confirmed by a tilt angle. The liquid crystal adjacent to the substrate increases to 4 ° and increases to the center of the liquid crystal, and is measured at 89 °. The more curved form is, the more liquid crystals that are not vertically aligned appear in the path from point 2 to point 3.

In addition, the liquid crystal cell is compensated by the retardation film having the optical characteristic of the present invention when the maximum retardation value from the center of the thickness direction of the liquid crystal cell to one substrate is 300 nm or less when the incident angle is 60 ° or less when voltage is applied. This is possible. When voltage is applied, the angle of the liquid crystals is changed by the properties of the liquid crystal and the energy of the substrate surface. Since the phase difference value of the liquid crystal layer is changed by the angle distribution, the optical characteristic of the retardation film is designed in consideration of the perfect compensation.

At this time, when the incident angle is 60 ° or less when the voltage is applied, the maximum retardation value from the center of the thickness direction of the liquid crystal cell to one substrate is 50 nm when Δnd of the liquid crystal layer is 200 nm and Δnd of 600 nm of the liquid crystal layer. The minimum value is 150 nm. The maximum value is 100 nm when Δnd of the liquid crystal layer is 200 nm, and the maximum value is 300 nm when Δnd of the liquid crystal layer is 600 nm.

division △ nd of liquid crystal cell 200 nm 600 nm Maximum phase difference value from the center to one substrate in the thickness direction of the liquid crystal cell when the incident angle is 60 ° or less when voltage is applied at least Phase difference value (X) 50 nm Phase difference value (X) 150 nm Retardation film Front phase difference value 100 nm Retardation film Front phase difference value 50 nm NZ One NZ 5 maximum Phase difference value (X) 100 nm Phase difference value (X) 300 nm Retardation film Front phase difference value 150 nm Retardation film Front phase difference value 140 nm NZ 0.5 NZ 1.8

Table 1 shows the optical properties designed in the optimum range of the retardation film for compensating the viewing angle in the liquid crystal properties of the present invention. The retardation film according to the present invention is 0.5≤NZ≤5 and is designed to have an optical characteristic of 50nm≤front phase difference value RO≤150nm. However, the roll to roll process for mass production is easy to carry out under the condition of NZ> 1, so it is recommended to design 1 <NZ≤5.

The twisted nematic liquid crystal display according to the present invention can secure a wide viewing angle by satisfying a compensating relationship of the maximum permeability of 2% or less in the left and right directions and the vertical direction at the viewer side. In addition, the color gamut is wider in the left and right direction and the up and down direction on the viewer side, thereby providing a vivid color.

Below, the wide viewing angle improvement effect by the said structure was put together in the following example and a comparative example. 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 Example 1 and Comparative Example 3, the viewing angle effects were compared by applying the exciter parameters of LTM220M1-L01 (Samsung Electronics), TN-LCD panels, to TECH WIZ LCD 1D (many system, KOREA), an LCD simulation program. It was.

Example 1 Fabrication of TN Liquid Crystal Display Device Having Wide Viewing Angle in Left and Right Directions

Example 1-1

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

The backlight unit 40, the first polarizing plate 10, the liquid crystal cell 30, and the second polarizing plate 20 are sequentially stacked. Specifically, the first polarizing plate 10 is composed of a protective film (TAC) 13, a PVA polarizer 11, and a first retardation film 14 from the backlight unit 40 side, and the second polarizing plate is a liquid crystal cell. The second phase difference film 24, the PVA polarizer 21, and the protective film (TAC) 23 are formed in order from the side.

The PVA polarizers 11 and 21 are provided with a polarizer function, and the first and second polarizing plates 10 and 20 including the TAC protective films 13 and 23 and the first and second retardation films 14 and 24 are provided. Absorption shafts 12 and 22 were arranged perpendicular to each other on both sides of the TN mode liquid crystal cell 30. At this time, when the counterclockwise direction is the positive (+) direction based on the right side of the horizontal direction when viewed from the viewer side, the absorption axis 12 of the PVA polarizer 11 of the first polarizing plate is located at -45 °, and the second polarizing plate is The absorption axis 22 of the PVA polarizer 21 of was positioned at 45 degrees.

The alignment direction of the liquid crystal of the TN mode liquid crystal cell 30 is aligned to 31 in the backlight side substrate and 32 in the viewing side substrate when viewed from the viewing side with reference to the direction shown in FIG. 2A. The absorption axes 12 and 22 of the substrate-side polarizing plates are parallel to the liquid crystal alignment direction. In the liquid crystal cell of FIG. 2 (a), when the counterclockwise direction is positive (+) direction based on the right side of the horizontal direction, the rubbing direction of the liquid crystal is -45 ° of the backlight side substrate and 45 ° of the viewer side substrate. When the voltage is applied, the tilt angle of the liquid crystal can be calculated as a phase difference value in various directions, and a value of the normal refractive index and the abnormal refractive index of the liquid crystal. The direction of the liquid crystal defined in the layer of was parameterized.

In addition, the liquid crystal cell used had a maximum retardation value of 125.7 nm from the center of the thickness direction of the liquid crystal cell to one substrate when the incident angle was 60 ° or less when voltage was applied. At this time, the retardation films 14 and 24 are positioned between the PVA polarizers 11 and 21 and the liquid crystal cell 30 of each polarizing plate, and the slow axes 15 and 25 of the retardation films are the absorption axes 12 and 22 of the PVA polarizers. Orthogonal to. The liquid crystal cell 30 does not include a color filter for the convenience of simulation.

Detailed optical characteristics of each optical film and backlight used in the above examples were defined as follows.

라고 할 때 하기 수학식 5 내지 9에 의해 정의된다.First, the PVA polarizers 11 and 21 of the first polarizing plate 10 and the second polarizing plate 20 impart a polarizer function by dyeing iodine on the stretched PVA, and the polarizing performance of the polarizer is 370 to 780 nm visible light region. The visual acuity polarization was 99.9% or more, and the visual transmittance group transmittance was 41% or more. The visibility polarization and the visibility single transmittance are the TD (λ) transmittance of the transmission axis according to the wavelength, the transmittance of the absorption axis according to the wavelength is MD (λ), and the visibility correction value defined in JIS Z 8701: 1999.

Is defined by the following equations (5) to (9).

The optical characteristics of the TACs 13 and 23, which are protective layers of the polarizing plates 10 and 20, have refractive indexes corresponding to each axis of Nx, Ny, and Nz with respect to an orthogonal coordinate system whose z-axis is the thickness direction. When d has a negative C plate refractive index characteristic of Nx NNy> Nz. The thickness direction retardation value Rth defined by Equation 1 for the incident light 589.3 nm was 50 nm for the TAC 13 and 23.

The retardation films 14 and 24 biaxially stretched Zeonor films (Optes, Japan) to realize retardation. The optical characteristic was NZ defined by Equation 3 above for an orthogonal coordinate system having the z axis in the thickness direction when the incident light was 589.3 nm, and the front phase difference value (RO) was 85 nm.

As the backlight unit 40, backlight measurement data mounted on the TN-LCD panel LTM220M1-L01 (Samsung Electronics) was used.

The optical components were stacked as shown in FIG. 1 and subjected to simulation of visibility and omnidirectional transmittance. As a result, FIG. 16 was obtained. FIG. 16 shows the visibility of an omnidirectional transmittance distribution when the arm BLACK is displayed on the screen. The range on the scale is 0% to 2% of the visibility transmittance without considering the color filter, and the portions exceeding 2% transmittance are displayed in red, and the portions having low transmittance are indicated in blue. In this case, the wider the range of blue in the center, the wider the viewing angle, and the above configuration shows that the left and right horizontal viewing angles are wider. In the result of FIG. 16, the gaze angle 2 satisfies the compensation relation of FIG. 13 in the Poincare Sphere, but the compensation of FIG. 12 does not hold in the gaze angle 1 direction.

Example 1-2

The liquid crystal having the same rubbing direction, cell gap, refractive index anisotropy, and polarizing plate configuration as in Example 1-1 was applied, but the first and second retardation films had a front phase difference value (R0) of 100 nm and a refractive index. A liquid crystal display device was manufactured using a ratio NZ of 1.8.

As a result of the simulation of the visibility of the omnidirectional transmittance, the results as shown in FIG. 17 were obtained. I could confirm that.

Example 1-3

Example 1 - 1 and the same rubbing direction, cell gap (Cell gap) and the refractive index was carried by applying the liquid crystal and the polarizing plate configuration having an anisotropy, the first and the second retardation film has a front retardation value (R0) 70nm, the refractive index A liquid crystal display device was manufactured using a ratio NZ of 2.6.

As a result of the simulation of the visibility of the omni-directional transmittance, the results as shown in FIG. 18 were obtained. I could confirm that.

Example 1-4

Example 1 - 1 and the same rubbing direction, cell gap (Cell gap) and the refractive index was carried by applying the liquid crystal and the polarizing plate configuration having an anisotropy, the first and the second retardation film has a front retardation value (R0) 120nm, a refractive index The liquid crystal display device was manufactured using a ratio NZ of 1.6.

As a result of conducting the simulation of visibility of omnidirectional transmittance, the results as shown in FIG. 19 were obtained. I could confirm that.

Example 1-5

Example 1 - 1 and the same rubbing direction, cell gap (Cell gap) and having a refractive index anisotropy was carried by applying the liquid crystal and the polarizing plate configuration, the first and second retardation films in a front retardation value (R0) is 50nm, the refractive index The liquid crystal display device was manufactured using a ratio NZ of 4.2.

As a result of the simulation of the visibility of the omni-directional transmittance, the results as shown in FIG. 20 were obtained. I could confirm that.

Example 2 Fabrication of TN Liquid Crystal Display Device Having Wide Viewing Angle in Up and Down Directions

Example 2-1

In the same manner as in Example 1-1, the liquid crystal cell has a rubbing direction of the backlight substrate and a polarizing plate when the counterclockwise direction is positive (+) direction based on the right side of the horizontal direction as shown in FIG. A liquid crystal display device having the structure of FIG. 1 (b) was manufactured using an absorption axis of 45 ° and a rubbing direction of the viewer-side substrate and an absorption axis of the polarizing plate located at 135 °.

The visibility of the omnidirectional permeability simulation was carried out to obtain the following FIG. 21. FIG. 21 illustrates the distribution of visibility of permeability in the case of displaying the arm BLACK on the screen. The range of the scale is 0% to 2% of the visibility transmittance without considering the color filter, and the portions exceeding 2% transmittance are indicated in red, and the portions having low transmittance are indicated in blue. In this case, the wider the range of blue in the center, the wider the viewing angle, and the above configuration shows that the upper and lower viewing angles are wider.

FIG. 14 shows polarization states on Poincare Spheres according to wavelengths 486 nm, 589 nm, and 656 nm at a viewing angle 1 (θ = 60 °, Φ = 90 °), and FIG. 15 shows a viewing angle 2 (θ = 60 °, Φ = 0 °) Shows the polarization states on the Poincare Sphere according to wavelengths 486nm, 589nm and 656nm, where field of view angle 1 compensates but field of view angle 2 compensates Since this is not true, the upper and lower viewing angles are clearly wide.

Example 2-2

Example 2 - 1 and the same rubbing direction, cell gap (Cell gap) and a refractive index having an anisotropic synthesis was carried out by applying the liquid crystal and the polarizing plate configuration, the first and second retardation films in a front retardation value (R0) is 100nm and the refractive index A liquid crystal display device was manufactured using a ratio NZ of 1.8.

As a result of the simulation of the visibility of the omnidirectional transmittance, the results as shown in FIG. 22 were obtained. I could confirm that.

Example 2-3

Example 2 - 1 and the same rubbing direction, cell gap (Cell gap), and synthesis was carried out by applying an index of refraction liquid crystal and a polarizing plate configuration having an anisotropy, the first and the second retardation film, the front retardation value (R0) is 70nm and a refractive index A liquid crystal display device was manufactured using a ratio NZ of 2.6.

As a result of performing the visibility omnidirectional permeability simulation, the results as shown in FIG. 23 were obtained. I could confirm that.

Example 2-4

Example 2 - 1 and the same rubbing direction, cell gap (Cell gap), and synthesis was carried out by applying an index of refraction liquid crystal and a polarizing plate configuration having an anisotropy, the first and the second retardation film, the front retardation value (R0) is 120nm and the refractive index The liquid crystal display device was manufactured using a ratio NZ of 1.6.

As a result of the simulation of the visibility permeability, the result as shown in FIG. 24 was obtained. I could confirm it.

Example 2-5

Example 2 - 1 and the same rubbing direction, cell gap (Cell gap) and a refractive index having an anisotropic synthesis was carried out by applying the liquid crystal and the polarizing plate configuration, the first and second retardation films in a front retardation value (R0) is 50nm and a refractive index The liquid crystal display device was manufactured using a ratio NZ of 4.2.

As a result of the simulation of the visibility permeability, the results as shown in FIG. 25 were obtained. I could confirm it.

Example 2-6

Example 2 - 1, and synthesis was carried out by applying the liquid crystal and the polarizing plate configuration having the same rubbing direction, cell gap (Cell gap) and a refractive index anisotropy, the rubbing direction of the liquid crystal of the liquid crystal cell is a half relative to the right in the horizontal direction clockwise In this positive (+) direction, the liquid crystal display device was manufactured by using a backlight substrate at -135 ° and a viewing substrate at -45 °.

As a result of the simulation of the visibility of the omni-directional transmittance, the result as shown in FIG. 26 was obtained, and the results were confirmed to be symmetrical with the result of Example 2-1.

Comparative Example 1 Fabrication of TN Liquid Crystal Display Device Having Wide Viewing Angle in Left and Right Directions

Comparative Example 1-1

Example 1 - 1 and the same rubbing direction, cell gap (Cell gap) and the refractive index was carried by applying the liquid crystal and the polarizing plate configuration having an anisotropy, the first and the second retardation film has a front retardation value (R0) 160nm, a refractive index The liquid crystal display device was manufactured using a ratio NZ of 1.4.

As a result of performing the visibility omnidirectional permeability simulation, the result as shown in FIG. 27 was obtained. Compared with the embodiment, it can be seen that the viewing angle is narrow due to the high transmittance of the black state on the inclined surface.

Comparative Example 1-2

Example 1 - 1 and the same rubbing direction, cell gap (Cell gap) and having a refractive index anisotropy was carried by applying the liquid crystal and the polarizing plate configuration, the first and second retardation films in a front retardation value (R0) is 50nm, the refractive index A liquid crystal display device was manufactured using a ratio NZ of 5.5.

As a result of conducting the simulation of visibility of all directions, results as shown in FIG. 28 were obtained. Compared with the embodiment, it can be seen that the viewing angle is narrow due to the high transmittance of the black state on the inclined surface.

Comparative Example 1-3

Instead of the biaxial retardation film of Example 1-1, WV-Film (Fuji Photo Film, Japan), which is a hybrid phase retardation film coated with a discotic liquid crystal on a triacetyl cellulose (TAC) substrate, was applied.

As a result of performing the visibility omnidirectional permeability simulation, the result as shown in FIG. 29 was obtained. When WV-Film was applied, it was confirmed that it had a good viewing angle in all directions.

In the dark state of the TN mode liquid crystal display manufactured in Examples 1-1 and Comparative Examples 1-3 and Comparative Examples 1-3, the transmittance according to the horizontal incidence angle was compared and the results were compared. 30 (Examples 1-1 and Comparative Examples 1-3) and FIG. 33 (Examples 2-1 and Comparative Examples 1-3) are shown below (the angle ranges indicated by negative numbers are opposite to the directions indicated by positive numbers). Means a change in the angle of incidence. Referring to FIGS. 30 and 33, the light leaking increases as the angle of incidence from the front (incident angle 0 °) in the dark state to the left and right direction (FIG. 30) and the up and down direction (FIG. 33) increases. It was found that leaks were much less in Examples 1-1 and 2-1 than in 1-3.

In addition, Examples 1-1 and 2-1, which are retardation films of a stretched form, are lower than those of Comparative Examples 1-3, which are hybrid type discotic coating types, which are difficult to manage the slow axis of the retardation film. It was confirmed that the transmittance was shown.

Accordingly, when the biaxial retardation film of the present invention is applied (Examples 1-1 and 2-1) compared to a liquid crystal display device (Comparative Examples 1-3) to which a hybrid type retardation film is applied (Examples 1-1 and 2-1), It can be seen that the horizontal viewing angle is wide and high contrast ratio can be realized.

Comparative Example 2 Fabrication of TN Liquid Crystal Display Device Having Wide Viewing Angle in Up and Down Directions

Comparative Example 2-1

The liquid crystal and polarizing plate having the same rubbing direction, cell gap and refractive index anisotropy as in Example 2-1 were applied, and the first and second retardation films had a front retardation value (R0) of 160 nm and a refractive index. The liquid crystal display device was manufactured using a ratio NZ of 1.4.

As a result of performing the visibility omnidirectional permeability simulation, the result as shown in FIG. 31 was obtained. It was confirmed that the upper and lower viewing angles are relatively narrow because the transmittance of the black state at the viewing angle 1 is higher than that of Examples 2-1 to 2-6.

Comparative Example 2-2

The liquid crystal and polarizing plate having the same rubbing direction, cell gap and refractive index anisotropy as in Example 2-1 were applied, and the first and second retardation films had a front phase difference value R0 of 50 nm and a refractive index. A liquid crystal display device was manufactured using a ratio NZ of 5.5.

As a result of performing the visibility omnidirectional permeability simulation, the result as shown in FIG. 32 was obtained. It was confirmed that the upper and lower viewing angles are relatively narrow because the transmittance of the black state at the viewing angle 1 is higher than that of Examples 2-1 to 2-6.

Comparative Example 2-3

A liquid crystal display was manufactured in the same manner as in Comparative Example 1-3, except that the retardation film was removed. It was as FIG. 34 as a result of the visibility visibility omnidirectional transmittance simulation.

In addition, FIG. 35 compares the color reproduction range at the viewing angle 1 (θ = 60 °, Φ = 90 °) using the liquid crystal display device of Example 2-1, Comparative Examples 1-3, and Comparative Example 2-3. It was confirmed that Example 2-1 according to the present invention has a wide color reproduction range on the inclined surface (main viewing angle 1).

As described above, the twisted nematic mode liquid crystal display device according to the present invention can provide good image quality with excellent color and can be applied to a liquid crystal display requiring high viewing angle characteristics.

1 (a) and 1 (b) are perspective views showing, as an example, the structure of a twisted nematic (TN) liquid crystal display device according to the present invention;

2 (a) and 2 (b) show a direction 31 of the liquid crystal adjacent to the first polarizing plate side substrate, a direction 32 of the liquid crystal adjacent to the second polarizing plate side substrate when viewed from the viewer side (opposite to the backlight unit). It is a schematic diagram which shows the absorption axis 12 of a polarizing plate, and the absorption axis 22 of a 2nd polarizing plate,

3 is a graph illustrating a distribution of tilt angles of liquid crystals when a voltage is applied to the liquid crystal cell in the TN mode liquid crystal display device.

FIG. 4 is a graph illustrating a distribution of the direction angles of liquid crystals when a voltage is applied to the liquid crystal cell when the rubbing direction of the backlight liquid crystal is designed to be 45 ° in a TN mode liquid crystal display device.

FIG. 5 is a graph illustrating a direction angle of liquid crystal when a voltage is applied to the liquid crystal cell when the rubbing direction of the backlight liquid crystal is designed to be 135 ° in a TN mode liquid crystal display device.

FIG. 6 is a graph showing the direction angle of liquid crystal when voltage is applied to the liquid crystal cell when the rubbing direction of the backlight liquid crystal is -135 ° and the rubbing direction of the liquid crystal cell is -45 °.

7 is a schematic view for explaining the definition of the tilt angle of the liquid crystal.

FIG. 8 is a schematic view for explaining the direction of the line of sight when the liquid crystal display device is viewed from the viewer's side in the present invention in terms of θ and Φ in a circular coordinate system.

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

FIG. 10 illustrates the results of visibility and omnidirectional transmittance simulation results in the case where the polarizers 11 and 21 and the TN liquid crystal cell 30 of FIG. 1 are disposed (excluding the phase difference film) and voltage is applied thereto.

11 is a schematic view showing the MD direction used in the process of producing a film of a roll state according to the present invention,

12 is a representation of a change in polarization state according to Example 1-1 of the present invention on a Poangcare sphere in a viewing angle of 1 (θ = 60 °, Φ = 90 °),

FIG. 13 illustrates changes in polarization state according to Example 1-1 of the present invention on a Poincare Sphere at a viewing angle 2 (θ = 60 °, Φ = 0 °),

FIG. 14 illustrates changes in polarization state according to Example 2-1 of the present invention on a Poincare Sphere at a viewing angle of 1 (θ = 60 ° and Φ = 90 °).

FIG. 15 illustrates changes in polarization state according to Example 2-1 of the present invention on a Poincare Sphere at a viewing angle 2 (θ = 60 °, Φ = 0 °),

FIG. 16 shows the results of the visibility omnidirectional permeability simulation according to Example 1-1 of the present invention.

FIG. 17 illustrates the results of the visibility omnidirectional permeability simulation according to Example 1-2 of the present invention.

FIG. 18 illustrates the results of the visibility omnidirectional permeability simulation according to Examples 1-3 of the present invention.

19 shows the results of the visibility omnidirectional permeability simulation according to Examples 1-4 of the present invention.

20 illustrates the results of the visibility omnidirectional permeability simulation according to Example 1-5 of the present invention.

FIG. 21 is a view illustrating a simulation result of visibility of transmittance according to Example 2-1 of the present invention;

FIG. 22 illustrates the results of visibility omnidirectional permeability simulation according to Example 2-2 of the present invention.

FIG. 23 shows the results of visibility simulation omni permeability simulation according to Example 2-3 of the present invention.

24 shows the results of the visibility omnidirectional transmittance simulation according to Example 2-4 of the present invention.

25 is a diagram showing the results of the visibility omnidirectional transmittance simulation according to Example 2-5 of the present invention;

FIG. 26 shows the results of the visibility omnidirectional permeability simulation according to Examples 2-6 of the present invention.

FIG. 27 shows the results of simulation of visibility of omnidirectional transparency according to Comparative Example 1-1 of the present invention.

28 shows the results of the visibility omnidirectional permeability simulation according to Comparative Example 1-2 of the present invention,

FIG. 29 is a view illustrating a simulation result of visibility of transmittance according to Comparative Examples 1-3 of the present invention.

30 is a comparison of the transmittance according to the change in the incident angle in the horizontal direction of the black state of Example 1-1 and Comparative Example 1-3,

31 is a view illustrating the results of visibility omnidirectional permeability simulation according to Comparative Example 2-1 of the present invention;

32 shows the results of the visibility omnidirectional permeability simulation according to Comparative Example 2-2 of the present invention,

33 shows the transmittance in the vertical direction of Example 2-1 and Comparative Example 1-3 of the present invention,

FIG. 34 shows the simulation results of visibility of omnidirectional transparency according to Comparative Example 2-3 of the present invention.

35 shows the results of measuring the respective color reproduction ranges in the viewing angle 1 (θ = 60 °, Φ = 90 °) in Example 2-1, Comparative Example 1-3 and Comparative Example 2-3 of the present invention. It is shown.

Claims (10)

A twisted nematic mode liquid crystal display device comprising a first polarizing plate, a second polarizing plate, and a liquid crystal cell stacked in the order of a retardation film, a polarizer, and a protective film, respectively, Absorption axes of the polarizers of the first and second polarizing plates are perpendicular to each other, Each of the retardation films of the first polarizing plate and the second polarizing plate has a front retardation value R0 of 50 to 150 nm, a refractive index ratio NZ of 1 <NZ ≤ 5, and a slow axis is disposed perpendicular to an absorption axis of adjacent polarizers. , The liquid crystal cell has a maximum phase difference value of 300 nm or less from the center of the thickness direction of the liquid crystal cell to one substrate when the angle of incidence is 60 ° or less when the voltage is applied. Nematic mode liquid crystal display. The twisted nematic mode liquid crystal display device according to claim 1, wherein each of the retardation films of the first polarizing plate and the second polarizing plate has a front retardation value (RO) of 50 to 120 nm and a refractive index ratio (NZ) of 1.4 <NZ <4.2. The twisted nematic mode liquid crystal display device according to claim 1, wherein each of the retardation films of the first polarizing plate and the second polarizing plate has a front phase difference value (RO) of 60 to 90 nm and a refractive index ratio (NZ) of 1.5 <NZ <2.7. The twisted nematic mode liquid crystal display device according to claim 1, wherein each of the retardation films of the first polarizing plate and the second polarizing plate is a retardation film of a stretch type. The twisted nematic mode liquid crystal display device according to claim 1, wherein the absorption axis of the polarizer is designed to be positioned at 0 to 180 degrees when the counterclockwise direction is made in the positive (+) direction with respect to the right horizontal direction on the viewing side. The liquid crystal cell of claim 1, wherein the rubbing direction of the backlight-side liquid crystal is 45 ° and the rubbing direction of the viewing liquid crystal is -45 ° when the counterclockwise direction is positive (+) relative to the right horizontal direction of the viewer side. Or a rubbing direction of the backlight-side liquid crystal is -45 °, and a rubbing direction of the viewer-side liquid crystal is 45 °. The liquid crystal cell of claim 1, wherein the rubbing direction of the backlight-side liquid crystal is 45 ° and the rubbing direction of the viewer-side liquid crystal is 135 ° when the counterclockwise direction is positive (+) with respect to the right horizontal direction of the viewer side. Or a rubbing direction of the liquid crystal on the backlight side is -135 °, and a rubbing direction of the viewing liquid crystal is -45 °. The liquid crystal cell of claim 1, wherein the rubbing direction of the backlight-side liquid crystal is 135 ° and the rubbing direction of the viewer-side liquid crystal is 45 °, Or a rubbing direction of the backlight-side liquid crystal is -45 °, and a rubbing direction of the viewer-side liquid crystal is -135 °. The liquid crystal cell of claim 1, wherein when the counterclockwise direction is positive (+) with respect to the right horizontal direction of the viewer side, the rubbing direction of the backlight-side liquid crystal is 135 °, and the rubbing direction of the viewer-side liquid crystal is -135 °. Or a rubbing direction of the backlight-side liquid crystal is -135 °, and a rubbing direction of the viewer-side liquid crystal is 135 °. The twisted nematic liquid crystal display device according to claim 1, wherein the liquid crystal cell has a cell gap of 2 to 10 μm, and a refractive index difference (Δn = n _e −n _o ) of the liquid crystal is 0.2 or less.

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