KR101023979B1 - Wide-viewing angle plate, method of manufacturing the same and liquid crystal display device having the same - Google Patents

Abstract

The wide viewing angle compensation plate according to the present invention includes a first protective film, a polarizing film attached to one surface of the first protective film, and a wide viewing angle compensation liquid crystal layer disposed on the polarizing film. In the liquid crystal molecules of the wide viewing angle compensation liquid crystal layer, the direction having the minimum refractive index of the liquid crystal molecules is gradually inclined in the inclination angle direction, and the direction of the minimum refractive index is twisted in the azimuthal direction. The present invention has the effect of further improving the wide viewing angle by tilting the direction having the minimum refractive index of the liquid crystal in the inclined angle direction and twisting in the azimuthal direction in the wide viewing angle compensation plate.

Description

Wide viewing angle compensation plate, manufacturing method thereof and liquid crystal display including the same {WIDE-VIEWING ANGLE PLATE, METHOD OF MANUFACTURING THE SAME AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THE SAME}

1A is a conceptual diagram for illustrating refractive indices in respective directions in nematic liquid crystals.

1B is a conceptual diagram showing an angle formed by the nematic liquid crystal on the substrate surface.

1C is a graph showing the inclination and azimuth angles of a twisted nematic liquid crystal.

FIG. 2 is a conceptual diagram for illustrating a refractive index in each direction in a discotic liquid crystal.

3 is a conceptual diagram illustrating a method of compensating a phase difference with respect to a traveling direction of light by combining nematic liquid crystals and discotic liquid crystals.

4 is a cross-sectional view schematically illustrating a structure of a wide viewing angle phase plate attached to a discotic liquid crystal attached to a twisted nematic liquid crystal cell according to a first embodiment of the present invention.

5 is a partially cutaway perspective view of the wide viewing angle compensation plate.

6 is a schematic cross-sectional view of a liquid crystal display device with a wide viewing angle compensation plate according to the present invention.

<Brief description of the main parts of the drawing>

101: nematic liquid crystal molecule 102: discotic liquid crystal molecule

201: liquid crystal layer 202: wide viewing angle compensation plate

400: adhesive

401: glass substrate 402: discotic liquid crystal layer

403: 2nd protective film 404: polarizing film

405: first protective film 700: color filter substrate

701: first glass substrate 702: color filter

703: planarization film 704: common electrode

705: second glass substrate 706: spacer

707: reflective electrode 708: organic insulating film

709: thin film transistor 710: transparent electrode

711: sealant 712: gate driving circuit

713: connection wiring 800: liquid crystal display panel

The present invention relates to a wide viewing angle compensation plate, a manufacturing method thereof, and a liquid crystal display device including the same, and to a compensation plate having improved wide viewing angle function, a manufacturing method thereof, and a liquid crystal display device including the same.

Liquid crystal displays have low power consumption due to low operating voltages of liquid crystals, relatively simple driving circuits and peripheral circuits, and are widely used as light and bulky display devices. Liquid crystal displays include light absorbing or scattering liquid crystal displays such as guest host (GH), polymer dispersed liquid crystal (PDLC) or polymer stabilized cholesteric textures (PSTC), and polarized liquid crystal display devices such as twisted nematic types. In the case of an absorption type or a scattering type liquid crystal display, the viewing angle is wide, while the contrast is small, and in the case of a polarization type liquid crystal display, the contrast is good but the viewing angle is narrow. The reason why the viewing angle of the polarizing liquid crystal display device is narrow is that the phase change of the light passing through the liquid crystal cell depends on the direction of the light, and the light obliquely entering the polarizing plate does not completely disappear when passing through the analyzer.

Therefore, as a liquid crystal display is commonly used as a desktop monitor, it is necessary to widen the viewing angle. Accordingly, in order to increase the viewing angle, multidomain technology, in plane switch (IPS) mode, and vertical alignment ( Vertical alignment mode, optical path control technology and phase compensation technology have been developed.

Multi-domain technology increases the viewing angle by dividing a pixel into several regions so that the orientation of liquid crystal molecules is changed in each region so that the characteristics of the pixels become an average of the characteristics of the various regions included therein. However, the process of making the orientation different for each region is complicated, and the alignment of the liquid crystal molecules cannot be controlled at the boundary where the two regions are in contact with each other, so light leaks to the portion, causing a black matrix (BM) or thin film transistor (Thin Film Transistor). Should be covered by wiring. When the multi-view technique is used, the viewing angle characteristic is shown as an average value in various directions, so that the viewing angle is improved in the direction in which the viewing angle characteristic is poor, but the image quality is relatively decreased in the direction in which the viewing angle characteristic is good.

In-plane switch mode increases the viewing angle by applying a horizontal electric field so that the director of the liquid crystal is twisted in a plane parallel to the alignment layer. In-plane switch mode has a wide viewing angle and is widely used as a 17-inch desktop liquid crystal display, but has disadvantages such as low aperture ratio, late response time, and relatively high driving voltage.

In the vertical alignment mode, the viewing angle is increased by using a vertical alignment agent, a negative liquid crystal, and a retardation plate. The vertical alignment mode simplifies the arrangement of discotic liquid crystals compared to 90 ° twisted nematic (TN) liquid crystal displays. In addition, in the 90 ° twisted nematic liquid crystal device, the phase plate only needs to be attached to one side of the liquid crystal layer, and thus the material cost is low. However, in order to apply the wide field of view technology to the vertical alignment mode, the aforementioned multi-domain technique must be applied.

Optical path control technology ensures a wide viewing angle by passing the light from the backlight perpendicular to the liquid crystal panel and spreading the light passing through the polarizer in various directions. In order to spread the light passing through the polarizer in various directions, an Allied signal company's Spectra view film is used. However, since light is absorbed by at least about 10% of light every time it passes through one optical component, the transmittance decreases and the price is very high because microlithography is used instead of injection molding.

In addition, the Light Control Film (LCF) manufactured by Sumitomo Chemical of Japan has a diffraction grating having a different refractive index between the polarizing plate and the liquid crystal cell to control the spread of light to widen the viewing angle.

The technique of adjusting the optical path to widen the viewing angle is ineffective and most studies have been discontinued.

Phase compensation technology is a technology for compensating the phase difference according to the change in the direction of light passing through the liquid crystal cell using a wide viewing angle compensation plate. The wide viewing angle compensation plate includes a discotic discotic liquid crystal.

However, in the conventional wide viewing angle compensation plate used in the twisted nematic liquid crystal display, normal vectors of discotic discotic liquid crystals present in the wide viewing angle compensation plate exist in the same plane. That is, the normal vectors of the conventional discotic liquid crystal rotate only based on the same inclination angle, and the azimuth angles are constant and are located on the same plane. On the other hand, since the inclination and direction angles of the twisted nematic liquid crystal are both rotated, the direction of the normal vector of the discotic liquid crystal layer having the minimum refractive index and the direction of the director of the nematic liquid crystal having the maximum refractive index do not match. There is a limit to viewing angle compensation.

 Accordingly, a first object of the present invention is to provide a wide viewing angle compensation plate having improved wide viewing angle function.

It is a second object of the present invention to provide a liquid crystal display device having the wide viewing angle compensation plate.

In order to achieve this object, the wide viewing angle compensation plate according to the present invention includes a first protective film, a polarizing film and a wide viewing angle compensation liquid crystal layer. The polarizing film is attached to one surface of the first protective film. Further, the liquid crystal molecules of the wide viewing angle compensation liquid crystal layer are gradually inclined in the direction of the inclination angle, and the direction of the minimum refractive index is twisted in the azimuth direction.

In addition, the method for manufacturing a wide viewing angle compensation plate according to the present invention includes the steps of forming a polarizing film on the first protective film, and a solvent comprising a liquid crystal molecule for wide viewing angle compensation and a dopant for twisting the liquid crystal molecules in the azimuth direction. Coating the upper portion of the polarizing film, vaporizing the solvent by heating, rubbing the liquid crystal molecules and tilting them in an inclination angle direction, and irradiating ultraviolet rays to the liquid crystal molecules.

In addition, the liquid crystal display according to the present invention includes a first substrate, a second substrate facing the first substrate, a liquid crystal layer interposed between the first substrate and the second substrate, and a wide viewing angle compensation plate. The wide viewing angle compensation plate is I) a first protective film, ii) a polarizing film attached to one surface of the first protective film, for polarizing light, and iii) a wide viewing angle compensation liquid crystal layer disposed on the polarizing film. The liquid crystal molecules of the wide viewing angle compensation liquid crystal layer include a direction in which the minimum refractive index of the liquid crystal molecules is gradually inclined in the inclination angle direction, and the direction of the minimum refractive index is twisted in the azimuth direction.

The present invention has the effect of further improving the wide viewing angle by tilting the direction having the minimum refractive index of the liquid crystal in the inclined angle direction and twisting in the azimuthal direction in the wide viewing angle compensation plate.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1A is a conceptual diagram for illustrating refractive indices in respective directions in nematic liquid crystals.

Referring to FIG. 1A, when light has a large incident angle θ with respect to the director of the nematic liquid crystal 101 of the liquid crystal display panel, the refractive index with respect to the P wave component becomes large in the liquid crystal layer (Δn _P / Δθ> 0 ). In this case, the refractive index n _x in the x direction and the refractive index n _y in the y direction are substantially the same, and this value is smaller than the refractive index n _z in the z direction (n _z > n _x, n _y ).

FIG. 1B is a conceptual diagram showing an angle formed by a nematic liquid crystal on the substrate surface, and FIG. 1C is a graph showing an inclination angle and an azimuth angle of a twisted nematic liquid crystal.

Referring to FIG. 1B, when a color filter substrate or an array substrate is present on a plane formed between the x-axis and the y-axis, the director of the nematic liquid crystal molecules 101 of the liquid crystal layer existing between the color filter substrate and the array substrate is z. The angle formed with respect to the axis is defined as the inclination angle θ, and the angle formed by the projection vector with respect to the xy plane of the director of the nematic liquid crystal molecule 101 with the x axis is defined as the azimuth angle φ.

Referring to FIG. 1C, the azimuth angle φ of the nematic liquid crystal molecules is increased in the direction of the z axis, that is, in the direction of the color filter substrate surface from the array substrate surface. That is, the nematic liquid crystal molecules are twisted gradually in the x-axis direction on the surface of the array substrate and in the y-axis direction on the surface of the color filter substrate.

In addition, the inclination angle θ of the nematic liquid crystal molecules is almost 90 degrees on the surface of the array substrate and the color filter substrate, and approaches 0 degrees toward the center between the array substrate and the color filter substrate. That is, the nematic liquid crystal molecules lie almost on the surface of the array substrate and the color filter substrate, and stand almost straight at the center between the array substrate and the color filter substrate.

In addition, when an electric field is not applied to the nematic liquid crystal molecules, the azimuth angle of the nematic liquid crystal molecules increases linearly from 0 degrees to 90 degrees, but when the electric field is applied, such linearity is broken.

In addition, when no electric field is applied to the nematic liquid crystal molecules, many nematic liquid crystal molecules are laid, but more liquid crystal molecules stand up when an electric field is applied.

However, even when the maximum electric field is applied, the inclination angle of the nematic liquid crystal molecules positioned at one fifth of the total cell gap (distance between the array substrate and the color filter substrate) at the substrate surface is less than 45 degrees, and the azimuth angle is Approximately equal to the value of the substrate surface at the surface. Therefore, in the case of the conventional wide viewing angle compensation plate without considering the azimuth angle, there is a limit to the compensation.

In the case of the wide viewing angle compensation plate according to the present invention, the azimuth angle of the discotic liquid crystal molecules changes along the director of the nematic liquid crystal in consideration of the arrangement of the discotic liquid crystal molecules in the molecular arrangement of the nematic liquid crystal. Therefore, the wide viewing angle compensation plate according to the present invention improves the wide viewing angle compensation function.

FIG. 2 is a conceptual diagram for illustrating a refractive index in each direction in a discotic liquid crystal.

Referring to FIG. 2, when the incident angle θ is increased with respect to the director of the discotic liquid crystal 102 of the wide viewing angle compensation plate, the refractive index of the P wave component is decreased in the compensation plate (Δn _P / Δθ <0). ). In this case, the refractive index n _x in the x direction and the refractive index n _y in the y direction are substantially the same, and this value is larger than the refractive index n _z in the z direction (n _z <n _x, n _y ).

3 is a conceptual diagram illustrating a method of compensating a phase difference with respect to a traveling direction of light by combining nematic liquid crystals and discotic liquid crystals.

Referring to FIG. 3, when the director (long axis direction) of the nematic liquid crystal 102 and the axis of the discotic liquid crystal 102 are parallel to each other, the phase difference with respect to the traveling direction of the light is compensated to some extent. This is the largest refractive index (n _z ) in the z direction, that is, the direction indicated by the director of the nematic liquid crystal molecules, as described in the description of FIGS. 1A and 1B, but in the compensation film, the z direction, that is, the discotic liquid crystal. This is because the refractive index n _{z in the} direction of the normal vector of the molecule is the smallest.

4 is a cross-sectional view schematically showing the structure of a wide viewing angle phase plate attached to a discotic liquid crystal attached to a 90 ° twisted nematic liquid crystal cell according to a first embodiment of the present invention.

Referring to FIG. 4, in order to compensate for the phase difference of light caused by the liquid crystal cell 201 on the upper and lower portions of the liquid crystal cell 201 of the liquid crystal display device attached to the discotic liquid crystal cell attached to the 90 ° twisted nematic liquid crystal cell. A wide viewing angle compensation plate 202 is attached. Although the wide viewing angle compensation plate 202 is composed of a multilayer film, only liquid crystal is shown in FIG. 4, and the multilayer film structure will be described with reference to FIG. 5.

Referring to FIG. 4, the nematic liquid crystal molecules 101 of the liquid crystal cell 201 of the liquid crystal display form a predetermined pre-tilt angle at upper and lower portions of the liquid crystal cell 201 and opposite directions thereof. to be. Also, in the central layer of the liquid crystal cell 201, the liquid crystal cell is substantially vertically aligned with respect to the wide viewing angle compensation plate 202.

The nematic liquid crystal molecules 101 of the liquid crystal cell 201 are arranged such that Helmholtz free energy is minimized. The arrangement of such liquid crystal cells can be obtained by the following method.

The Helmholtz free energy density of the nematic liquid crystal molecules 101 of the liquid crystal cell 201 is expressed as the sum of the elastic energy density of the liquid crystal molecules and the energy density due to the electromagnetic field applied to the liquid crystal layer. The elastic energy density due to the arrangement change of the liquid crystal is generated when the liquid crystal is spread (Spray), twisted (Twist), and bent (band). In each case, the Helmholtz free energy density is obtained by summing the generated elastic energy density and the energy density 1/2 ( D · E ) due to the electric field. In the case of an electrostatic field, a magnetic field does not occur, so it is not considered.

The Helmholtz free energy density is integrated into the entire space occupied by all liquid crystal cells to find the Helmholtz free energy. The Variantional method is used to find the Euler-Lagrange equation, which is a differential equation representing the minimum Helmholtz free energy.

According to the Euler-La Grande equation, the Helmholtz free energy is minimal when the pre-tilt angle is the same at the upper and lower portions of the liquid crystal cell 201 and symmetrically arranged about the center of the liquid crystal cell. have.

The condition of the Euler-Lagrandes equation (ie, the pre-tilt angle θ ₁ of the nematic liquid crystal molecules 101 disposed at the boundary between the liquid crystal cell 201 and the wide viewing angle compensation plate 202). Substituting <θ ₁ <90, the nematic liquid crystal molecules 101 of the liquid crystal cell 201 are arranged as shown in FIG. 2. In FIG. 4, the non-twisted state is shown. In fact, the nematic liquid crystal molecules 101 at the upper and lower sides are twisted by 90 ° due to boundary conditions. That is, the nematic liquid crystal molecules 101 are twisted from the x-axis to the y-axis direction as shown in the graph of FIG. 1C.

The wide viewing angle compensation plate 202 including the discotic liquid crystal molecules 102 is attached to the upper and lower portions of the liquid crystal layer 201 arranged as described above. The arrangement of the liquid crystals in the layers facing each other around the boundary surface of the liquid crystal layer 201 and the wide viewing angle compensating plate 202 is described in FIG. 1C as the director (long axis direction) and the discotic liquid crystal of the nematic liquid crystal 102. The axes of the molecules 102 are arranged side by side to reduce the phase difference, thereby improving the wide viewing angle. That is, the discotic liquid crystal molecules of the conventional wide viewing angle compensation plate consider the inclined cornea without considering the azimuth angle, but the discotic liquid crystal molecules according to the present invention improve the wide viewing angle by considering both the inclination angle and the azimuth angle.

5 is a partially cutaway perspective view of a wide viewing angle compensation plate.

Referring to FIG. 5, the wide viewing angle compensation plate 202 may include a first protective film including triacetyl cellulose (TAC, 405), and a polarizing film 404 including poly vinyl alcohol (PVA). ), A second protective film 403 including triacetyl cellulose (TAC) 403, and a discotic liquid crystal layer 402 formed on the second protective film 403.

The first protective film 405 and the second protective film 403 are in close contact with and protect the polarizing film 404 from the upper and lower, respectively, and support the polarizing film 404. Although a film containing triacetyl cellulose is attached to only one surface of the polarizing film 404, in this case, the surface on which the triacetyl cellulose film is not attached is damaged.

Polarizing film 404 comprising polyvinyl alcohol (PVA) polarizes light. The polarizing film 404 is produced by stretching the polyvinyl alcohol film in one direction and then adsorbing iodine (I) or dichroic dye. At this time, the direction of the shrink axis is the absorption axis of the polarizing plate.

The discotic liquid crystal layer 402 includes a liquid solvent containing a dopant for twisting the discotic liquid crystal molecules 102 and the discotic liquid crystal molecules 102 in the azimuth direction to the first protective film 405. Apply and heat to vaporize solvent. As a method of applying the liquid solvent containing the discotic liquid crystal molecules 102 to the first protective film 405, a spin coating method is suitable. In addition, the heating temperature is preferably about 130 ℃.

 Thereafter, the discotic liquid crystal molecules 102 are tilted by rubbing, and the wide viewing angle compensation plate 202 is formed by mutually linking the discotic liquid crystal molecules 102 by irradiating ultraviolet rays. When the Δnd value in the twisted nematic mode is approximately in the range of 0.36 to 0.40, the retardation value of the wide viewing angle compensation film is suitably in the range of 180 nm to 200 nm. In addition, since the retardation value of the TAC film is approximately 40 nm, considering the first protective film 405 and the second protective film 403, the retardation value Rth of the discotic liquid crystal layer is in the range of approximately 100 nm to 120 nm. Make sure

In FIG. 5, the thickness of the discotic liquid crystal layer 402 is shown to be very large compared to other films, but this is for displaying the discotic liquid crystal, and the actual thickness of the discotic liquid crystal layer 402 is very small compared to other films. The actual discotic liquid crystal layer 402 has a thickness in the range of about 2 μm to 3 μm, the thickness of the first film 403 is about 110 μm, and the thickness of the second film 404 is about 25 μm. The thickness of 3 films is a range of about 80 micrometers.

6 is a schematic cross-sectional view of a liquid crystal display device with a wide viewing angle compensation plate according to the present invention.

Referring to FIG. 6, the liquid crystal display includes a liquid crystal display panel 800 and a backlight assembly (not shown) for supplying light from the lower portion of the liquid crystal display panel.

The liquid crystal display panel 800 of the liquid crystal display device includes a color filter substrate 700, an array substrate 810, and a liquid crystal layer 410 interposed between the color filter substrate 700 and the array substrate 810.

A backlight assembly (not shown) is disposed under the liquid crystal display panel 800. The backlight assembly supplies light to the liquid crystal display panel 800.

The backlight assembly includes a light guide plate, a lamp for supplying light to the light guide plate at the bottom or the side of the light guide plate, and a light diffusion sheet for uniforming the brightness of the light exiting the light guide plate.

The color filter substrate 700 includes a first glass substrate 701, a color filter 702, a planarization film 703, and a first transparent electrode 104.

A color filter 702 including a red color filter R, a green color filter G, and a blue color filter B is formed on the first glass substrate 701. The planarization film 703 is formed on the color filter 702.

In addition, the first wide viewing angle compensation plate 202a is attached to the color filter substrate 700 by the adhesive 400. As described above, the wide viewing angle compensation plate 202 includes a first protective film 405, a polarizing film 404, a second protective film 403, and a second liquid crystal layer 402 including discotic liquid crystals. do. The thermal expansion rate / contraction rate of the first protective film 405 and the second protective film 403 is the same, even when the temperature rises due to the light generated from the backlight assembly (not shown). The protective film 403 does not bend because it is the same expansion or contraction. Therefore, the edge portion is not separated from the color filter substrate 700 and the arrangement of the discotic liquid crystal molecules of the second liquid crystal layer does not change.                     

The array substrate 810 includes a second glass substrate 705, a thin film transistor (TFT) 709, a transparent electrode 710, a gate driving circuit 712, a data driving circuit (not shown), and a reflective electrode ( 707 and a connection wiring 712.

The array substrate 810 is divided into a display area DR and a peripheral area PR. The thin film transistor 709, the transparent electrode 710, and the reflective electrode 707 are positioned in the display region DR, and the gate driving circuit 408 and the data driving circuit (not shown) are positioned in the peripheral region PR. .

The thin film transistor 709 is formed on the second glass substrate 705. The plurality of thin film transistors 709 are arranged in a matrix form on the second glass substrate 705. In addition, a transparent electrode (pixel electrode) 710 is formed on a portion of the thin film transistor 709 and the second glass substrate 705 so that the thin film transistor 709 and the second glass substrate 705 are electrically connected to each other.

An organic insulating layer 708 is formed on the connection portion between the thin film transistor 709 and the transparent electrode 710. The organic insulating layer 708 is entirely coated and then etched to expose a portion of the transparent electrode 710.

A large number of irregularities are formed on the upper surface of the organic insulating film 708. The reflective electrode 707 is formed on the upper side and the side of the organic insulating layer 708 with a uniform thickness. Therefore, the unevenness of the surface of the reflective electrode 707 is also formed by the unevenness of the organic insulating film 708.

This unevenness is to increase the reflection efficiency of the reflective electrode. The reflective electrode 707 includes aluminum (Al), silver (Ag), or chromium (Cr) having excellent reflectance. The reflective electrode 707 displays an image by reflecting light incident from the upper portion of the liquid crystal display panel 800 even when there is no light supply from the backlight assembly disposed under the liquid crystal display panel 800.

The gate driving circuit 712 and the connection wiring 713 are formed in the peripheral area PR of the array substrate 810. The gate driving circuit 712 positioned in the peripheral area PR is electrically connected to the gate electrode of the thin film transistor 709 of the display area DR through the connection line 712.

The thin film transistor 709 includes a gate electrode, a drain electrode, and a source electrode. As described above, the gate electrode is electrically connected to the connection wiring, the drain electrode is electrically connected to the transparent electrode 710, and the source electrode is electrically connected to the data driving circuit (not shown).

The second wide viewing angle compensation plate 202b is attached to the lower portion of the array substrate 810 by the adhesive 400. As described above, the wide viewing angle compensation plate 202 includes a first protective film 405, a polarizing film 404, a second protective film 403, and a second liquid crystal layer 402 including discotic liquid crystals. do.

The thermal expansion rate / contraction rate of the first protective film 405 and the second protective film 403 is the same, even when the temperature rises due to the light generated from the backlight assembly (not shown). The protective film 403 does not bend because it is the same expansion or contraction. Therefore, the edge portion is not separated from the color filter substrate 700 and the arrangement of the discotic liquid crystal molecules of the second liquid crystal layer does not change.                     

The color filter substrate 700 and the array substrate 810 are connected by a coupling member, that is, a sealant 711. The coupling member 711 is positioned in the peripheral area PR of the color filter substrate 700 and the peripheral area PR of the array substrate 810, respectively.

A cell gap holding member, that is, a spacer 706, is formed in the common electrode 704 of the color filter substrate 700 to form a space in which the liquid crystal is interposed between the color filter substrate 700 and the array substrate 810.

The first liquid crystal layer 201 is interposed in the space formed between the color filter substrate 700 and the array substrate 810. The first liquid crystal layer 201 includes the nematic liquid crystal and corresponds to the liquid crystal layer 201 of FIG. 3A.

According to the electric field change between the common electrode 704 and the reflective electrode 707 or the transparent electrode 710, the arrangement of the liquid crystal positioned between the common electrode 704 and the reflective electrode 707 or the transparent electrode 710 is changed. Accordingly, the amount of light emitted to the upper portion of the liquid crystal display panel 800 is changed.

A common voltage (generally, a ground voltage) is applied to the common electrode 704. When a gate driving signal voltage is applied to one of the plurality of thin film transistors in which the gate driving circuit 712 is arranged in a matrix form, the thin film transistor is turned on and an image signal is applied to the source electrode of the thin film transistor in the data driving circuit (not shown). When a voltage is applied, the applied voltage is applied to the transparent electrode 710 and the reflective electrode 707 through the drain electrode.

Therefore, the arrangement of the nematic liquid crystals positioned between the first transparent electrode and the reflective electrode 707 or the transparent electrode 710 is changed.

Light generated by the backlight assembly (not shown) is linearly polarized while passing through the second wide viewing angle compensation plate 202b disposed under the array substrate 810, and is disposed between the array substrate 810 and the color filter substrate 700. The transmittance is changed while passing through the nematic liquid crystal of the first liquid crystal layer 201, and only light having a specific wavelength is transmitted through the color filter 702 of the color filter substrate 700 to exhibit color. Then, the light is passed through the first wide viewing angle compensation plate 202a on the color filter substrate 700 and polarized to display an image. On the other hand, the phase difference due to the nematic liquid crystal of the first liquid crystal layer 201 is reduced by the discotic liquid crystal of the first wide viewing angle compensation plate 202a and the second wide viewing angle compensation plate 202b, so that the wide viewing angle is increased. Is displayed.

The liquid crystal display device described above has been described with an example of a semi-transmissive (reflective, transmissive) liquid crystal display employing a 90 ° twisted nematic liquid crystal. However, it is well known that the present invention can be applied to a super twisted nematic (STN) liquid crystal display device according to the present invention.

The present invention has the effect of further improving the wide viewing angle by tilting the direction having the minimum refractive index of the liquid crystal in the inclined angle direction and twisting in the azimuthal direction in the wide viewing angle compensation plate.

While the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art will be variously modified and modified within the scope of the present invention without departing from the spirit and scope of the present invention described in the claims below. It will be appreciated that it can be changed.

Claims (13)

First protective film; A polarizing film attached to one surface of the first protective film and configured to polarize light; And And a wide viewing angle compensation liquid crystal layer disposed on the polarizing film, wherein the liquid crystal molecules of the wide viewing angle compensation liquid crystal layer have an inclination angle that gradually approaches zero degrees as the direction having the minimum refractive index of each of the liquid crystal molecules toward the center portion thereof. Wide viewing angle compensation plate tilted in the direction and twisted in the azimuth direction in the direction of the minimum refractive index. The wide viewing angle compensation plate of claim 1, wherein the wide viewing angle compensation liquid crystal layer is a discotic liquid crystal layer. The wide viewing angle compensation plate of claim 1, wherein the wide viewing angle compensation plate further comprises a second protective film between the polarizing film and the wide viewing angle compensation liquid crystal layer. 4. The wide viewing angle compensation plate of claim 3, wherein the first and second protective films comprise triacetyl cellulose, and the polarizing film comprises polyvinyl alcohol. Forming a polarizing film on the first protective film; Applying a solvent on the polarizing film, the solvent including a liquid crystal molecule for wide viewing angle compensation and a dopant for twisting the liquid crystal molecules in an azimuth direction; Heating and evaporating the solvent; Rubbing the liquid crystal molecules and tilting the liquid crystal molecules in an inclination angle direction; And Method of manufacturing a wide viewing angle compensation plate comprising the step of irradiating ultraviolet light to the liquid crystal molecules. The method of claim 5, wherein the solvent is heated to 130 ° C. 7. 6. The method of claim 5, wherein the liquid crystal molecules are discotic liquid crystal molecules. The method of claim 5, wherein the second protective film is further formed on the polarizing film. The method of claim 8, wherein the first and second protective films comprise triacetyl cellulose, and the polarizing film comprises polyvinyl alcohol. A first substrate; A second substrate facing the first substrate; A liquid crystal layer interposed between the first substrate and the second substrate; And i) a first protective film, ii) a polarizing film attached to one surface of the first protective film, for polarizing light, and iii) a wide viewing angle compensation liquid crystal layer disposed on the polarizing film, wherein the wide viewing angle The liquid crystal molecules of the compensation liquid crystal layer are inclined in the inclination angle direction gradually closer to 0 degrees as the direction having the respective minimum refractive index toward the center portion, and also includes a wide viewing angle compensation plate in which the direction of the minimum refractive index is twisted in the azimuth direction. LCD display device. The liquid crystal display of claim 10, wherein the wide viewing angle compensation liquid crystal layer is a discotic liquid crystal layer. The liquid crystal display of claim 10, wherein the wide viewing angle compensation plate further comprises a second protective film between the polarizing film and the wide viewing angle compensation liquid crystal layer. The liquid crystal display of claim 12, wherein the first and second protective films comprise triacetyl cellulose, and the polarizing film comprises polyvinyl alcohol.

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