KR101485773B1 - Retardation film and wideviewing twist nematic liquid crystal display comprising the same - Google Patents

Abstract

The present invention relates to a retardation film comprising a base layer having a specific optical property and a discotic liquid crystal coating layer, and a polarizing plate in which the retardation film is laminated, And a twisted nematic (TN) mode liquid crystal display device capable of securing a viewing angle.

A liquid crystal display, a polarizing plate, a discotic liquid crystal coating layer

Description

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a retardation film and a wide viewing angle twisted nematic mode liquid crystal display including the retardation film,

The present invention relates to a liquid crystal display device and a method of manufacturing the liquid crystal display device, which are capable of realizing a black state at all viewing angles in a state in which a voltage is applied, (Hereinafter referred to as " TN ") mode liquid crystal display device.

2. Description of the Related Art A liquid crystal display (LCD) is widely used as a popular image display device. However, despite its many excellent properties, a narrow viewing angle has been pointed out as a typical drawback. A technology for securing a wide viewing angle by applying a functional optical film such as a retardation film has appeared, and new liquid crystal modes capable of realizing a wide viewing angle technology without using a functional optical film in an initial TN (Twisted Nematic) mode Was presented.

The liquid crystal display device requires a polarizing plate for polarizing light on both sides of the liquid crystal cell. Generally, the polarizing plate has a protective film on both sides of the polarizer, and a liquid crystal cell has a functional Further films are used. In recent years, the retardation film generally serves not only as a viewing angle compensation but also as a protective film.

On the other hand, the TN mode has a form in which the liquid crystal is twisted by 90 degrees when no voltage is applied, and the liquid crystal is vertically aligned between the upper and lower substrates when a voltage is applied. However, even when a voltage is applied, liquid crystals located close to the substrate exist liquid crystals that can not be vertically aligned with respect to the liquid crystal substrate, which is the largest (lowest) image quality at the slope when displaying the BLACK in TN mode . In order to compensate for the liquid crystal located close to the substrate which is not vertically oriented when displaying the black (black), a film coated with a discotic liquid crystal on a triacetyl cellulose (TAC) used as a protective layer of a polarizer is used, The liquid crystal has a tilt angle in one direction. Although the viewing angle compensation is implemented by tilting the discotic liquid crystal, it is impossible to realize a complete black state simply by tilting the discotic liquid crystal.

DISCLOSURE OF THE INVENTION It is an object of the present invention to solve the problem that the conventional TN mode liquid crystal display device to which a film coated with a discotic liquid crystal is applied is difficult to implement in a black state completely because the discotic liquid crystal coating film is used for a TN liquid crystal cell And only the compensation is performed, and the compensation is not performed simultaneously with the TN liquid crystal cell.

Accordingly, the present invention accurately models and analyzes the liquid crystal behavior of the TN liquid crystal cell layer when a voltage is applied, and a phase difference film including a base layer having a specific optical property and a discotic liquid crystal layer is formed on one side of the polarizer (TN) mode liquid crystal display device comprising a polarizing plate to which the retardation film is applied and which comprises a polarizing plate to which the retardation film is applied as a top plate or a bottom plate, To achieve a perfect black state in all directions.

The present invention provides a retardation film comprising a base layer and a discotic liquid crystal coating layer, wherein the base layer has a front retardation of 100 to 160 nm, a refractive index ratio NZ of 1 to 1.6, and a direction of the slow axis perpendicular to the absorption axis of the adjacent polarizer ; The discotic liquid crystal coating layer has an oblique retardation (R ₄₀ ) of 7 to 13 nm and 55 to 85 nm when the frontal retardation is 30 to 50 nm and a slow axis is a rotation axis, and an oblique retardation (R ₄₀ ) is 25 To 45 nm.

Further, the present invention has another feature in the polarizing plate in which the retardation film is laminated on one plane of the TN liquid crystal cell side of the polarizer.

The present invention is further characterized in that the liquid crystal display device includes the polarizer plate as an upper plate or a lower plate polarizer.

The twisted nematic mode liquid crystal display device according to the present invention can be manufactured by applying a retardation film including a substrate layer having a specific optical property and a discotic liquid crystal layer, accurately modeling the liquid crystal behavior of the liquid crystal cell layer and performing optical analysis, It is possible to realize a perfect black state in all directions, thereby having a wide viewing angle and a high contrast ratio (CR).

The present invention relates to a retardation film for compensating for a TN liquid crystal cell and compensating for an absorption axis when applied to a twisted nematic mode liquid crystal display device, thereby enabling a dark state to be realized at a wide viewing angle. The retardation film comprises a base layer and a discotic liquid crystal coating layer, wherein the base layer has a front retardation of 100 to 160 nm, a refractive index ratio NZ of 1 to 1.6, and the orientation of the slow axis is orthogonal to the absorption axis of the adjacent polarizer, The discotic liquid crystal coating layer has an oblique retardation (R ₄₀ ) of 7 to 13 nm and 55 to 85 nm when the front phase difference is 30 to 50 nm and a slow axis is a rotation axis and an oblique retardation (R ₄₀ ) of 25 to 45 nm .

In general, when a voltage is applied to a TN mode liquid crystal display device, a wide angle of view can be secured by implementing a black in a full field of view. For this purpose, it is recommended that the precise direction of the TN liquid crystal cell is defined when a voltage is applied in the currently produced TN liquid crystal. Specifically, when the TN liquid crystal cell displays black, the liquid crystal direction can be defined by dividing the TN liquid crystal cell into a plurality of layers in the thickness direction, and expressing the liquid crystal direction of each layer in three dimensions.

In addition, in order to define the liquid crystal direction in the BLACK state of the TN liquid crystal cell, the TN liquid crystal cell can be calculated by changing the incident angle and measuring the phase difference while applying the voltage to the TN liquid crystal cell. FIGS. 3 and 4 are calculations of the directions of liquid crystals based on the result of measuring the retardation of the TN liquid crystal cell in various directions. The factors affecting the calculated values are the dielectric constant, the elastic modulus, and the viscosity. 3 is a graph showing the tilt angle of each layer when the liquid crystal is divided into 40 layers in the thickness direction in a state where a voltage is applied. In this case, the tilt angle refers to the angle formed by the long axis direction of the liquid crystal with the plane as shown in FIG. 5, and corresponds to 90-theta value in the coordinate system in which the Z axis is in the thickness direction as shown in FIG. 6 . Fig. 4 shows the direction angle of the liquid crystal in a state where the voltage is applied, and the direction angle coincides with? In Fig.

The information of the TN liquid crystal cell is inputted into the LCD optical simulation program (e.g., LCD Master, Techwiz LCD 1D) under the above-defined BLACK condition, (Phase difference film + polarizer) which can realize a wide viewing angle by perfectly implementing the black state.

In the case of the TN mode liquid crystal display device, the absorption axes of the lower plate polarizer and the upper polarizer are positioned in a diagonal direction not perpendicular or horizontal when viewed from the front. When the absorption axes of the lower polarizer and the upper polarizer are perpendicular to each other, Mode, and when they are parallel to each other, it is called NB (Normal Black) mode. In the normal case, the TN mode is the NW (Normal White) mode, and the TN mode of the present invention is also the 'NW (Normal White) mode'. When the rubbing angle of the substrate adjacent to the absorption axis of the polarizing plate in the TN mode is parallel to each other, the O-mode is referred to as an E-mode. In the present invention, the TN-LCD is limited to the 'O-mode'. That is, the TN mode in the present invention is limited to the range of 'NW (Normal Wite) mode' and 'O-mode'. However, it can be seen that the conventional NW (Normal Wite) mode and the O-mode TN mode liquid crystal display have poor image quality due to light leakage in the black state. In addition, when a polarizer is attached to a TN liquid crystal cell and the voltage is applied, as shown in the result of FIG. 8, which is the transmittance, a large amount of light leaks in the directions of?> 20 degrees and in the directions of 0 degrees, 90 degrees, 180 degrees, .

If the change of the polarization state due to the phase difference is understood and the Poincare Shpere is expressed, it is possible to design a phase difference that widens the viewing angle. This is because the optical principle of the viewing angle compensation technique do. However, the point S3 (1,0,0,1) on the Poincare Shpere in the present invention is the right circularly polarized light and the reference on the Poincare Sphere for [theta] and [phi] And the right side is turned toward the observer by &thetas;

That is, the present invention precisely models the liquid crystal behavior of the TN liquid crystal cell layer and clearly analyzes the change of the polarization state according to the retardation so that the retardation film can be applied to the retardation film .

When the base layer constituting the retardation film of the present invention has a front retardation of 100 to 160 nm and a refractive index ratio NZ of 1 to 1.6 and exhibits better optical characteristics of a right and left viewing angle expansion, 140 nm and a refractive index ratio NZ of 1.2 to 1.4, and the direction of the slow axis is orthogonal to the absorption axis of the adjacent polarizer. At this time, the base layer may be produced by a material commonly used in the art, which is imparted with a retardation by stretching, and can be used as long as it can satisfy the optical conditions as described above. Specifically, the material forming the base layer may be selected from the group consisting of triacetylcellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate Polysulfone (PSF) and polymethyl methacrylate (PMMA) can be used.

The discotic liquid crystal coating layer constituting the retardation film has a front retardation of 30 to 50 nm and an oblique retardation (R ₄₀ ) of 7 to 13 nm and 55 to 85 nm when the retardation axis is the rotation axis and an oblique retardation (R ₄₀ may be 25 to 45 nm, preferably a frontal retardation of 35 to 45 nm, an inclined phase difference (R ₄₀ ) of 8 to 12 nm and a radius of 60 to 80 nm when the slow axis is the rotation axis, It is preferable to use an inclined phase difference (R ₄₀ ) of 30 to 40 nm. At this time, the inclined phase difference (R ₄₀ ), which is generally defined in the art, represents the phase difference when tilted at ± 40 degrees. That is, when the ground shaft is the rotation axis, the inclination phase difference (R ₄₀ ) is the phase difference value when the ground shaft is tilted at ± 40 ° with the rotation axis, and when the leading axis is the rotation axis, the inclination phase difference (R ₄₀ ) Represents the phase difference value when tilted at 40 degrees.

Preferably, the thickness of the discotic liquid crystal coating layer is 0.1 to 10 占 퐉, the refractive index difference? N = ne-no of the liquid crystal is -0.5 to -0.03, and the tilt angle of the surface portion of the discotic liquid crystal coating layer is about 80 It is better to use a liquid crystal that can be coated to a wide range.

The slow axis of each of the base layer and the discotic liquid crystal coating layer constituting the retardation film is configured to be orthogonal to the absorption axis of the adjacent polarizer.

According to the present invention, a polarizing plate is constructed by including a retardation film obtained by analyzing a liquid crystal behavior of a TN liquid crystal cell layer and a change in polarization state according to a retardation. At this time, the retardation film may be laminated on the side of the liquid crystal cell of the polarizer, and triacetyl cellulose (TAC) may be laminated on the other side of the polarizer opposite to the liquid crystal cell.

Further, a TN liquid crystal display device is constructed by including a polarizing plate in which the retardation film is laminated as an upper plate or a lower plate polarizing plate.

When the polarizing plate in which the retardation film according to the present invention is laminated is included as the top plate polarizer, the polarizing plate of the lower plate preferably has a front retardation of 30 to 50 nm and a retardation value of 30 to 50 nm in a base layer having a front retardation of 10 nm or less and a thickness retardation Rth of 90 to 130 nm, A discotic liquid crystal layer-coated retardation film having an oblique retardation (R ₄₀ ) of 7 to 13 nm and 55 to 85 nm when the slow axis is a rotation axis and an oblique retardation (R ₄₀ ) of 25 to 45 nm when the fast axis is a rotation axis A laminated one can be used. When the polarizing plate in which the retardation film according to the present invention is laminated is included as a lower plate, the retardation film used as the lower plate may be used as the upper plate polarizing plate.

The optical properties of the base layer and the discotic liquid crystal coating layer constituting the retardation film and the polarizing plate are as shown in Fig. 7, when the thickness direction is the z axis, the direction in which the in-plane refractive index is large is the x axis and the vertical direction is the y axis Ny, and Nz, the refractive indexes corresponding to the directions of the retardation (Rx) and the retardation (Rth) defined by the following equation (2) and the following equation Is specified by the refractive index ratio (NZ).

R0 = (Nx - Ny) xd

(Where Nx and Ny are the refractive index of the phase difference film and d is the thickness of the film, where Nx > = Ny)

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

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

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

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

1 is a perspective view illustrating a basic structure of a TN mode liquid crystal display device according to an exemplary embodiment of the present invention. Referring to FIG.

The TN mode liquid crystal display device according to the present invention includes a lower polarizer plate 10, a liquid crystal cell 30 and a top polarizer plate 20 laminated in this order from the backlight unit side 40 to the lower polarizer plate 10 and the upper plate polarizer 20 The protective films TAC 13 and 23 are located on the opposite sides of the liquid crystal cell of the polarizers 11 and 21 of the polarizer 11 and the substrate layer 14 and the discotic liquid crystal coating layer 16 ). At this time, the retardation films 50 and 60 are laminated on the upper plate or the lower plate polarizer, and the retardation film is laminated on the substrate layer 14, the discotic liquid crystal coating layer 16 or the base layer 24 and the discotic liquid crystal coating layer 26 .

More specifically, the liquid crystal cell 30 having a twist angle of about 90 degrees with positive dielectric anisotropy (??> 0) between the lower plate polarizer 10 and the two glass substrates and the upper plate polarizer 20 And an active matrix drive electrode including an electrode pair is formed on the adjacent surface of the liquid crystal cell 30 on the glass substrate of the liquid crystal cell 30, So that the liquid crystal direction is changed in the vertical direction. The liquid crystal cell has the liquid crystal alignment direction of the backlight side liquid crystal substrate at 135 degrees with respect to the horizontal direction when viewed from the viewer side, and the liquid crystal alignment direction of the liquid crystal substrate at the viewer side is at 45 degrees.

The absorption axis 12 of the lower plate polarizer 10 and the absorption axis 22 of the upper plate polarizer 20 are orthogonal to each other and the absorption axis 12 of the lower polarizer 10 is positioned on the viewer side And the absorption axes 12 and 22 of the polarizers 10 and 20 are positioned at 135 degrees with respect to the horizontal direction of the liquid crystal substrate on the backlight side in the liquid crystal alignment direction of the adjacent liquid crystal cell, ). When the voltage is applied to the liquid crystal cell 30, the direction of the liquid crystal becomes more difficult to vertically align due to the voltage as it is closer to the substrate of the liquid crystal cell 30, which is the main reason for degrading the image quality in the black state.

The liquid crystal cell 30 has a panel retardation value (DELTA n x d) defined by Equation (4) is approximately 400 nm at a wavelength of 589 nm. This is because the linearly polarized light passing through the lower plate polarizer 10 in the direction of the viewer's front side in the state where the voltage is not applied to the TN-LCD panel is rotated 90 degrees after passing through the liquid crystal cell 30 and the polarizing plane passes through the upper polarizer plate This is because the retardation value of the liquid crystal cell 30 of the TN-LCD panel must be sufficiently large at 589 nm in order to be in the bright state in agreement with the axis.

Δn × d = (ne-no) × d

(Where ne is the extraordinary ray refraction index of the liquid crystal, no is the normal ray refraction index, d is the cell gap, note Δn, d is not a vector)

Any one of the base layers 14 and 24 constituting the retardation film may have a front retardation of 100 to 160 nm and a refractive index ratio NZ of 1 to 1.6 so that the direction of the slow axis is orthogonal to the absorption axis of the adjacent polarizer, 9, when the direction in which the film is wound on the roll is referred to as MD (Machine Direction, machine direction) as shown in FIG. 9, the refractive index (NZ), and the slow axes 15 and 25 are formed in the stretching direction. A discotic liquid crystal coating layer is added to the substrate layer by stretching at the substrate end, and the polarizing plate is bonded to a PVA polarizer and a protective film (TAC), and then cut in a diagonal direction to form a composite polarizing plate applicable to the present invention. And the present invention is not limited thereto. Such a series of processes can be manufactured in the form of a roll-to-roll (roll-to-roll) system.

The discotic liquid crystal coating layers 16 and 26 have an oblique phase difference R _{40 of} 7 to 13 nm and 55 to 85 nm when the front phase difference is 30 to 50 nm and the slow axis is the rotation axis, R ₄₀ ) of 25 to 45 nm can be used.

When the phase difference film is included in the upper plate polarizer, the lower plate polarizer has a phase retardation of 10 nm or less and a thickness retardation (Rth) of 90 to 130 nm , A front retardation of 30 to 50 nm and an oblique retardation (R ₄₀ ) of 7 to 13 nm and 55 to 85 nm when the slow axis is a rotation axis and an oblique retardation (R ₄₀ ) of 25 to 45 nm when the fast axis is a rotation axis, A layer-coated retardation film may be used. It is also possible to change the top and bottom plates.

The principle of compensating the viewing angle of the present invention can be expressed by the Poincare Sphere. In general, in the case of a liquid crystal display (IPS-LCD) or a vertical alignment liquid crystal display (VA-LCD), the liquid crystal shape is symmetrical with time when no voltage is applied, can do. However, when a black voltage is applied to the TN-LCD, the liquid crystal adjacent to the substrate of the liquid crystal cell 30 is not vertically aligned but has a low tilt angle. The shape of the liquid crystal changes asymmetrically, so that the compensation principle at a specific time can not be expanded from another viewpoint. In the case of TN-LCD, it is necessary to perform a viewing angle compensation design at each viewing angle. The present invention is applicable to all TN-LCDs using 486nm, 589nm, and 656nm polarizing state change and omnidirectional transmittance on the Poincare sphere of TN- It is possible to realize a complete black state in the direction of the arrow. The twisted nematic mode liquid crystal display device constituted by the optical conditions of the present invention satisfies the compensation relationship of the maximum visual sensitivity transmittance of 1% or less, preferably 0.5% or less.

Hereinafter, the effect of implementing the dark state at the full viewing angle when the voltage is applied according to the above configuration is summarized in the embodiment and the comparative example. The present invention can be better understood by the following examples, and the following examples are intended to illustrate the present invention and are not intended to limit the scope of protection defined by the appended claims.

Example

In Examples 1 to 6 and Comparative Examples 1 to 4, a liquid crystal cell parameter of the LTM220M1-L01 (Samsung Electronics), which is a TN-LCD panel, was applied to an LCD simulation program TECH WIZ LCD 1D (MANAGE SYSTEM, KOREA) The viewing angle effect was compared.

Example 1

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

The backlight unit 40 , the lower plate polarizer 10, the liquid crystal cell 30 and the upper plate polarizer 20 are sequentially laminated. The lower plate polarizer 10 includes a protective film 13, a PVA And a discotic liquid crystal coating layer 16. The top polarizer 20 is composed of a discotic liquid crystal coating layer 26, a base layer 24, a PVA A polarizer 21, and a protective film 23 in this order.

The polarizing plates 10 and 20 which impart the polarizer function through stretching and dyeing to the PVA 11 and 21 and the TAC 13 and 23 as protective films are placed on both sides of the TN mode liquid crystal cell 30, (12) and (22) are arranged orthogonally to each other. The alignment direction of the liquid crystal of the TN mode liquid crystal cell 30 is oriented at 31 on the backlight side substrate and 32 on the visible side substrate when viewed from the viewer side with reference to the direction shown in Fig. The absorption axis 12 (22) of the polarizing plate and the liquid crystal alignment direction are parallel. The tilt angle of the liquid crystal at the time of voltage application can be calculated by the retardation value in various directions and the normal refractive index and the extraordinary refractive index of the liquid crystal, and is divided into 40 layers in the thickness direction as shown in FIGS. 3 and 4 The direction of the liquid crystal defined in the layer of the layer is parameterized. At this time, a base layer 14 (24) and a discotic liquid crystal coating layer 16 (26) are positioned between the PVA 11 (21) and the liquid crystal cell 30 of each polarizing plate and the slow axes 15 And the slow axes 17 and 27 of the discotic liquid crystal coating layer 16 and 26 are perpendicular to the PVA absorption axis 12 and the liquid crystal cell 30 includes a color filter .

In the above embodiments, the optical films and the backlights having the following optical characteristics were used.

라고 할 때 하기 수학식 5 내지 9에 의해 정의된다.First, polarizers 11 and 21 of the lower plate polarizer 10 and the upper plate polarizer 20 impart a polarizer function by dyeing iodine to the stretched PVA. The polarization performance of the polarizer is such that the visual sensitivity The degree of polarization is not less than 99.9%, and the visible transmittance is 41% or more. The transmittance of the transmission axis according to the wavelength is denoted by TD (λ), the transmittance of the absorption axis with respect to wavelength is denoted by MD (λ), and the visibility correction value defined in JIS Z 8701: 1999

And is defined by the following equations (5) to (9).

The optical characteristics of the TAC, which is the protective layer of the polarizers 10 and 20, are Nx = Ny> Nz when the refractive indexes corresponding to the respective axes are Nx, Ny, and Nz and the thickness is d for the orthogonal coordinate system having the thickness direction as the z- Nz, and 50 nm in the case of Rth of TAC (13) (23) with respect to incident light of 589.3 nm.

A front retardation (RO) of 130 nm, a refractive index ratio NZ of 1.3, and a retardation of 0 nm and a thickness retardation Rth of 110 nm were applied to the substrate layer 14 of the lower polarizer plate through stretching in the substrate layer 24 of the upper polarizer. The discotic liquid crystal coating layer 16 of the lower plate polarizing plate has a retardation of 10 nm when the front retardation is 40 nm and a direction of -45 degrees with respect to the slow axis 17 is rotated 40 degrees to the direction of the observer, The phase difference is 70 nm when the rotation angle is 40 degrees and the phase difference is 70 nm and the direction of 45 degrees is rotated 40 degrees near the direction of the observer with the vertical direction (fast axis) of the slow axis 17 as the rotation axis and when the direction of -135 degrees is 40 degrees When turned, the slope was oriented so that the phase difference was 35 nm. The discotic liquid crystal coating layer 26 of the top plate polarizing plate has a frontal retardation of 40 nm and a phase difference of 10 nm when the slow axis 45 is rotated by 40 degrees toward the observer in the direction of 45 degrees with the rotation axis. The phase difference was 70 nm, and when the vertical direction of the slow axis 27 was rotated in different directions with respect to the rotation axis, the angle was made to be 35 nm. At this time, the retardation film 60 was composed of the substrate layer 24 of the upper plate polarizer and the discotic liquid crystal coating layer 26 of the upper plate polarizer.

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

The above optical components were laminated as shown in Fig. 1, and simulation of the time-varying omni-directional transmittance was performed. As a result, a low transmittance in all directions was calculated in the black state as shown in the right side of Fig. 14, 10 (right), 10 (right), 11 (left), and 12 (left) in FIG. 10 13 (a).

In the polarized state 1, the polarizer passes through the lower plate polarizing plate. In the polarizing state 2, the base plate passes through the base plate passing through the lower plate polarizing plate. Polarized state 3 is passed through the discotic liquid crystal coating layer of the lower plate polarizer, the liquid crystal passes through the black state in the polarized state 4, and passes through the discotic liquid crystal coating layer of the upper plate polarizer 5 and the base layer And shows the state of polarization after passing. These figures show that when the light passing through the lower plate polarizer passes through the optical system in which the light in the state of polarization 1 is sequentially stacked and finally passes through the base layer of the top plate polarizer, it converges to a point symmetric about the S2 axis on the Poincare Sphere And the degree of convergence in Example 1 (right side) is higher than the degree of convergence in Comparative Example 1 (left side). As a result of such axial compensation, the degree of light leakage in the black state when viewed from the right side, the upper side, the left side, and the lower side is significantly lower than that of Comparative Example 1.

Example 2

The top plate polarizer used in Example 1 was used as a lower plate polarizer, the upper plate polarizer was used as a top plate polarizer, and the orientation of the ground axes 15 and 25 of the base layer was arranged as shown in FIG. 1, A liquid crystal display device was manufactured.

The transmittance of the twisted nematic liquid crystal display fabricated as described above is as shown in FIG. 19, which is the ratio of the transmittance of each polarized light to the transmittance of the polarized light at the time at right (upper), left (left) Since the change in the state exhibits the same behavior as that of Embodiment 2 (right) in Fig. 15 (right), Fig. 16 (top), Fig. 17 (left), and Fig. 18 Cancellation was possible.

Example 3

The discotic liquid crystal coating layer 26 of the upper plate polarizing plate had a front retardation of 35 nm and an oblique retardation R ₄₀ of 8.6 nm and 61.2 nm when the retardation axis 27 was a rotation axis, (Twisted nematic liquid crystal display) was manufactured by oblique alignment so that the oblique phase difference (R ₄₀ ) was 30.6 nm when the vertical direction

The transmittance of the twisted nematic liquid crystal display manufactured as described above is shown in FIG. As shown in FIG. 20, it was confirmed that the dark region (blue region) having a low transmittance at the central portion is widened, so that the dark state can be realized at the full viewing angle.

Example 4

The liquid crystal display device was manufactured in the same manner as in Example 1 except that the base layer of the upper polarizer had a front retardation R0 of 120 nm and NZ of 1.3.

The transmittance of the twisted nematic liquid crystal display manufactured as described above is shown in FIG. As shown in FIG. 21, since the region (blue region) where the light leakage is lower than that of Example 1 and the transmittance is low at the central portion is wide, it is possible to realize a dark state at a viewing angle with a high probability of viewing the liquid crystal display device .

Example 5

The synthesis was carried out as Example 1, the discotic liquid crystal coating layer 26 of the upper panel polarization plate is inclined retardation (R ₄₀₎ 7.5nm, 56.3nm when the front retardation of 30nm, the slow axis 27 is the rotation axis and the slow axis ( (Twisted nematic liquid crystal display) was manufactured in such a manner that the inclined phase difference (R ₄₀ ) was 26.3 nm when the vertical direction

The transmittance of the twisted nematic liquid crystal display manufactured as described above is shown in FIG. As shown in FIG. 22, it was confirmed that the dark region (blue region) having a low transmittance was wide at the center, so that it was possible to realize the dark state at the full viewing angle.

Example 6

A liquid crystal display device was manufactured in the same manner as in Example 1 except that the base layer of the upper polarizer had a front retardation (R0) of 100 nm and NZ of 1.2.

The transmittance of the twisted nematic liquid crystal display manufactured as described above is shown in FIG. As shown in FIG. 23, since the area (blue area) of the lower light transmittance portion is larger than that of the first embodiment, but the transmittance is lower at the central portion, the dark state can be realized at a viewing angle with a high probability of viewing the liquid crystal display device. .

Comparative Example 1

A twisted nematic liquid crystal display device was manufactured in the same manner as in Example 1 except that the front phase difference RO of each of the base layers 14 and 24 was 0 nm and the thickness direction retardation Rth was 110 nm.

The transmittance of the twisted nematic liquid crystal display fabricated as described above is as shown in Fig. 14, which shows that the polarizations of the respective polarizations (right, left, 14 (left) because the change in the state shows the same behavior as that of Comparative Example 1 (left) in Fig. 10 (right), Fig. 11 (left), Fig. 12 The degree of convergence of the first embodiment is less than that of the first embodiment.

Comparative Example 2

The synthesis was carried out as Example 1, the discotic liquid crystal coating layer 26 of the upper polarizing plate is the front retardation (RO) to 56nm, the slow axis 17 is the axis of rotation one time inclined retardation (R ₄₀₎ is 14nm, 98nm and ground The twisted nematic liquid crystal display device was manufactured by obliquely aligning the oblique phase difference (R ₄₀ ) to be 49 nm when the vertical direction (fast phase axis) of the axis 17 is the rotation axis.

The twisted nematic liquid crystal display manufactured as described above has an omni-directional transmittance as shown in FIG. 24, and the region (blue) of the low transmittance portion at the center portion is narrow, which makes it impossible to realize a perfect black state on the inclined surface. Path on Poincare Sphere of Example 1 and Omnidirectional Transmittance Distribution of Comparative Example 2 It is seen from FIG. 24 that the difference in phase difference of the discotic liquid crystal in each direction is different from Example 1, Could know.

Comparative Example 3

The discotic liquid crystal coating layers 16 and 26 of the lower plate and the upper plate polarizing plate had a front retardation RO of 56 nm and an oblique retardation R ₄₀ when the slow axis 17 was a rotation axis. (Twisted nematic liquid crystal display) was produced in the same manner as in Example 1 except that the oblique retardation (R ₄₀ ) was 49 nm when the vertical axis (the fast axis) of the slow axis 17 was the rotation axis.

The twisted nematic liquid crystal display fabricated as described above has an omni-directional transmittance as shown in FIG. 25, and the region (blue) of the low transmittance portion at the center portion is narrow, and it is confirmed that it is impossible to realize a perfect black state on the inclined surface. The path on the Poincare Sphere of Example 1 and the omnidirectional transmittance distribution of Comparative Example 3 From FIG. 25, it can be seen from FIG. 25 that as the phase difference of the discotic liquid crystal along each direction differs from that of Example 1, Could know.

Comparative Example 4

The base layer 14 was set to have a frontal retardation RO of 0 nm and a thickness retardation Rth of 110 nm and the base layer 24 had a front retardation RO of 100 nm And NZ = 2.5, thereby producing a twisted nematic liquid crystal display device.

The twisted nematic liquid crystal display manufactured as described above has the omni-directional transmittance as shown in Fig. 26, and the area (blue) of the low transmittance portion at the center portion is narrow, which makes it impossible to realize a perfect black state on the inclined surface. The path on the Poincare Sphere of Example 1 and the omnidirectional transmittance distribution of Comparative Example 4 As shown in FIG. 26, it was found that the difference in phase difference between the respective base layers from Example 1 results in a worsening of the new viewing angle.

As shown above, in the examples and comparative examples, it was found through the Poincare Sphere expression that the substrate layer and the discotic liquid crystal layer had the effect of improving the viewing angle only when they had specific optical properties, It was confirmed that light leakage occurs when the characteristic range is exceeded.

As described above, the twisted nematic liquid crystal display device using the retardation film according to the present invention can provide excellent image quality for all viewing angles, and can be applied to a liquid crystal display requiring high viewing angle characteristics.

1 is a perspective view exemplarily showing the structure of a TN mode liquid crystal display device including a retardation film according to the present invention,

2 is a view showing a liquid crystal direction 31 adjacent to the substrate on the lower plate polarizing plate side, a liquid crystal direction 32 adjacent to the substrate on the upper plate polarizing plate side, an absorption axis 12 of the lower plate polarizing plate and the upper plate polarizing plate 12 ) 22, and Fig.

3 is a graph showing a tilt angle of a liquid crystal when a voltage is applied to a liquid crystal cell of a TN mode liquid crystal display device,

4 is a graph showing a direction angle of a liquid crystal when a voltage is applied to a liquid crystal cell of a TN mode liquid crystal display device,

5 is a schematic view for explaining the definition of the tilt angle of the liquid crystal,

6 is a schematic view for explaining the direction of the line of sight when the liquid crystal display device is viewed from the viewer side in the present invention by? And? In the circular coordinate system,

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

8 shows the results of the omni-directional transmittance when the liquid crystal cell 30 is applied with a voltage and only the polarizers 11 and 21 of Fig. 1 are disposed.

9 is a schematic view showing the MD direction in a manufacturing process of a roll film according to the present invention,

10 is a graph showing the viewing angle compensation according to the first embodiment of the present invention on a Poincare Sphere in the direction of? = 60 degrees and? = 0 degrees as compared with Comparative Example 1,

11 is a view on the Poincare Sphere in the direction of? = 60 degrees and? = 90 degrees as compared with Comparative Example 1 in the viewing angle compensation according to Embodiment 1 of the present invention,

12 is a view on the Poincare Sphere in the direction of? = 60 degrees and? = 180 degrees as compared with Comparative Example 1, according to Embodiment 1 of the present invention,

13 is a view on the Poincare Sphere in the direction of? = 60 degrees and? = 270 degrees as compared with Comparative Example 1 in the viewing angle compensation according to Embodiment 1 of the present invention,

Fig. 14 shows omnidirectional transmittance by comparing viewing angle compensation according to Example 1 of the present invention with Comparative Example 1,

15 is a view on the Poincare Sphere in the direction of? = 60 degrees and? = 0 degrees as compared with Comparative Example 1, according to Embodiment 2 of the present invention,

16 is a view on the Poincare Sphere in the direction of? = 60 degrees and? = 90 degrees in comparison with Comparative Example 1 in view angle compensation according to Embodiment 2 of the present invention,

17 is a view expressed on a Poincare Sphere in the direction of? = 60 degrees and? = 180 degrees, as compared with Comparative Example 1, according to Embodiment 2 of the present invention,

18 is a view on the Poincare Sphere in the direction of? = 60 degrees and? = 270 degrees as compared with Comparative Example 1 in the viewing angle compensation according to the second embodiment of the present invention,

19 is a diagram showing omnidirectional transmittance in comparison with Comparative Example 1 for viewing angle compensation according to Embodiment 2 of the present invention,

Fig. 20 shows a visual sensitivity transmittance according to Example 3 of the present invention,

Fig. 21 shows the visual sensitivity front-end transmission according to the fourth embodiment of the present invention,

22 is a diagram showing a visual sensitivity transmittance according to Example 5 of the present invention,

23 shows the visual sensitivity front-end transmission according to the sixth embodiment of the present invention,

24 shows the visibility transmittance in the forward direction according to Comparative Example 2 of the present invention,

25 shows the visual sensitivity transmittance according to Comparative Example 3 of the present invention,

26 shows the visual sensitivity transmittance according to Comparative Example 4 of the present invention.

Claims (13)

A retardation film comprising a substrate layer and a discotic liquid crystal coating layer, wherein the base layer has a front retardation of 100 to 160 nm, a refractive index ratio NZ of 1 to 1.6 and a direction of a slow axis of the polarizer And is configured to be orthogonal to the axis; When the discotic liquid crystal coating layer has a frontal retardation of 30 to 50 nm and an inclined retardation (R ₄₀ ) when the slow axis is a rotation axis, the retardation value is 7 to 13 nm when the -45 ° direction is rotated 40 degrees to the observer direction, Wherein the phase difference value is 55 to 85 nm when the direction is rotated by 40 degrees to the observer direction and the oblique phase difference (R ₄₀ ) is 25 to 45 nm when the fast axis is the rotation axis. The method of claim 1, wherein the substrate layer is selected from the group consisting of Triacetyl Cellulose (TAC), Cycloolefin Polymer (COP), Cycloolefin Copolymer (COC), Polyethylene Terephthalate (PET), Polypropylene (PP), Polycarbonate (PSF), and polymethyl methacrylate (PMMA). The retardation film according to claim 1, wherein the retardation of the base layer is given by stretching. Wherein the retardation film of claim 1 is laminated on the side of the TN liquid crystal cell of the polarizer. The polarizer according to claim 4, wherein triacetyl cellulose (TAC) is laminated on the other side of the polarizer. A liquid crystal display device comprising the polarizing plate of claim 4 as an upper plate or a lower plate polarizing plate. The liquid crystal display according to claim 6, wherein the upper plate polarizer is the polarizer of claim 4, The lower plate polarizing plate preferably has a retardation value of 30 to 50 nm and a retardation value of 30 to 50 nm in a base layer having a front retardation of 10 nm or less and a thickness retardation (Rth) of 90 to 130 nm on the basis of a wavelength of 589.3 nm R ₄₀ ) has a retardation value of 7 to 13 nm when the direction of -45 ° is rotated 40 degrees to the direction of the observer and a retardation value of 55 to 85 nm when the direction of 135 ° is rotated 40 degrees to the direction of the observer, Wherein the liquid crystal display device comprises a retardation film coated with a discotic liquid crystal layer having an oblique phase difference (R ₄₀ ) of 25 to 45 nm The liquid crystal display according to claim 6, wherein the lower plate polarizer is the polarizer of claim 4, The top plate polarizer is characterized by having a base layer having a frontal retardation of 10 nm or less and a retardation in thickness direction (Rth) of 90 to 130 nm and having a front retardation of 30 to 50 nm and an oblique retardation (R ₄₀₎ is a 45-degree phase difference value of 7 to 13nm, when a direction toward an observer's direction turned 40 degrees, and -135 degree is 55 to 85nm when the phase difference value in a direction close to the observer the direction turned 40 degrees, the fast axis rotation axis Wherein the liquid crystal layer comprises a retardation film coated with a discotic liquid crystal layer having an oblique phase difference (R ₄₀ ) of 25 to 45 nm. The liquid crystal display of claim 6, wherein the liquid crystal display device is a twisted nematic (TN) mode in a normal white mode and an O-mode. The liquid crystal display device according to claim 6, wherein the liquid crystal display device includes a TN liquid crystal cell in which the liquid crystal alignment direction of the backlight side liquid crystal substrate is 135 degrees with respect to the horizontal direction and the liquid crystal alignment direction of the visual side liquid crystal substrate is 45 degrees To the liquid crystal display device. The liquid crystal display device according to claim 6, wherein the absorption axis of the polarizer of the lower plate polarizer is positioned at 135 degrees with respect to the horizontal of the backlight-side liquid crystal substrate when viewed from the viewer side. The liquid crystal display device according to claim 6, wherein the top plate polarizer is configured to be perpendicular to the absorption axis of the polarizer and the slow axis of the discotic liquid crystal coating layer. The liquid crystal display device according to claim 6, wherein the lower plate polarizer is configured to be perpendicular to the absorption axis of the polarizer and the slow axis of the discotic liquid crystal coating layer.

Images