KR20130043016A - Liquid crystal display device having wide viewing angel - Google Patents

Abstract

PURPOSE: A liquid crystal display device having a wide viewing angle is provided to change the polarization characteristic of the light passing through the liquid crystal display device, by using an insulating layer having a compensation characteristic. CONSTITUTION: A first insulating layer(124) having positive C-compensation function is formed in a first substrate(120) having a thin film transistor. A second insulating layer(126) is formed on the first insulating layer having a pixel electrode(105). The second insulating layer is formed between the pixel electrode and a common electrode(107). A biaxial compensation film(150) is arranged under the first substrate. A first polarizing plate(162) is arranged in a lower part. A second polarizing plate(164) is arranged over a second substrate(130).

Description

Wide viewing angle liquid crystal display device {LIQUID CRYSTAL DISPLAY DEVICE HAVING WIDE VIEWING ANGEL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having an optical compensation layer to improve viewing angle characteristics.

2. Description of the Related Art Recently, various portable electronic devices such as a mobile phone, a PDA, and a notebook computer have been developed. Accordingly, there is a growing need for a flat panel display device for a light and small size. Such flat panel displays are being actively researched, such as LCD (Liquid Crystal Display), PDP (Plasma Display Panel), FED (Field Emission Display), VFD (Vacuum Fluorescent Display), but mass production technology, ease of driving means, Liquid crystal display devices (LCDs) are in the spotlight for reasons of implementation.

Such liquid crystal display devices have various display modes according to the arrangement of liquid crystal molecules. However, TN mode liquid crystal display devices are mainly used because of the advantages of easy monochrome display, fast response speed, and low driving voltage. In such a TN mode liquid crystal display device, liquid crystal molecules aligned horizontally with the substrate are almost perpendicular to the substrate when a voltage is applied. Therefore, there is a problem that the viewing angle is narrowed upon application of voltage due to the refractive anisotropy of the liquid crystal molecules.

In order to solve this viewing angle problem, liquid crystal display devices of various modes having wide viewing angle characteristics have recently been proposed, but among them, the liquid crystal display device of the lateral field mode (In Plane Switching Mode) is applied to actual production. It is produced. The IPS mode liquid crystal display device aligns liquid crystal molecules in a plane by forming at least one pair of electrodes arranged in parallel in a pixel to form a transverse electric field substantially parallel to the substrate.

FIG. 1 is a view showing the structure of a conventional IPS mode liquid crystal display device, in which FIG. 1 (a) is a plan view and FIG. 1 (b) is a sectional view taken along line II ′ of FIG. 1 (a). As shown in FIG. 1A, the pixels of the liquid crystal panel 1 are defined by gate lines 3 and data lines 4 arranged vertically and horizontally. Although only the (n, m) th pixels are shown in the drawing, in the liquid crystal panel 1, n and m gate lines 3 and data lines 4 are disposed, respectively, and thus the liquid crystal panel 1 is disposed. N x m pixels are formed throughout. The thin film transistor 10 is formed at the intersection of the gate line 3 and the data line 4 in the pixel. The thin film transistor 10 includes a gate electrode 11 to which a scan signal is applied from the gate line 3, and a semiconductor layer formed on the gate electrode 11 and activated as a scan signal is applied to form a channel layer. 12 and a source electrode 13 and a drain electrode 14 formed on the semiconductor layer 12 and to which an image signal is applied through the data line 4. The image signal input from the outside is applied to the liquid crystal layer. do.

In the pixel, a plurality of common electrodes 5 and a pixel electrode 7 are arranged substantially parallel to the data line 4. In addition, a common line 16 connected to the common electrode 5 is disposed in the middle of the pixel, and a pixel electrode line 18 connected to the pixel electrode 7 is disposed on the common line 16. It overlaps with the common line 16. Storage capacitance is formed in the transverse electric field mode liquid crystal display by overlapping the common line 16 and the pixel electrode line 18.

As described above, in the configured IPS mode liquid crystal display device, the liquid crystal molecules are oriented substantially in parallel with the common electrode 5 and the pixel electrode 7. When the thin film transistor 10 is operated to apply a signal to the pixel electrode 7, a transverse electric field substantially parallel to the liquid crystal panel 1 is generated between the common electrode 5 and the pixel electrode 7. Since the liquid crystal molecules rotate on the same plane along the transverse electric field, gray level inversion due to the refractive anisotropy of the liquid crystal molecules can be prevented.

The conventional IPS mode liquid crystal display device having the above structure will be described in more detail with reference to the cross-sectional view of FIG.

As shown in FIG. 1B, a gate electrode 11 is formed on the first substrate 20, and a gate insulating layer 22 is stacked over the entire first substrate 20. The semiconductor layer 12 is formed on the gate insulating layer 22, and the source electrode 13 and the drain electrode 14 are formed thereon. In addition, a passivation layer 24 is formed over the entire first substrate 20, and a first alignment layer having an alignment direction for determining liquid crystal molecules in a specific direction by a method such as rubbing on the first substrate 20. 28a) is formed.

In addition, a plurality of common electrodes 5 are formed on the first substrate 20, and a pixel electrode 7 and a data line 4 are formed on the gate insulating layer 22 to form the common electrode 5. The transverse electric field E is generated between the pixel electrodes 7.

The black matrix 32 and the color filter layer 34 are formed on the second substrate 30. The black matrix 32 is to prevent light leakage into an area where the liquid crystal molecules do not operate. As shown in the drawing, the black matrix 32 is formed between the region of the thin film transistor 10 and between the pixel and the pixel (ie, the gate line and the data line). Area). The color filter layer 34 is composed of R (Red), B (Blue), and G (Green) to realize actual colors. An overcoat layer 36 is formed on the color filter layer 34 to protect the color filter layer 34 and to improve flatness of the substrate, and a second alignment layer 28b having an alignment direction determined thereon is formed thereon. have.

The liquid crystal layer 40 is formed between the first substrate 20 and the second substrate 30 to complete the liquid crystal panel 1.

As described above, in the IPS mode liquid crystal display device, a transverse electric field is generated inside the liquid crystal layer 40 by the common electrode 5 and the pixel electrode 7 formed on the substrate 20 and the gate insulating layer 22, respectively. Since the liquid crystal molecules inside the liquid crystal layer 40 are rotated on a plane, gray level inversion due to refractive index anisotropy of the liquid crystal molecules can be prevented.

However, the IPS mode liquid crystal display device as described above has the following problems. That is, in the IPS mode liquid crystal display device, since the liquid crystal molecules rotate on the same plane along the transverse electric field, the gray scale inversion due to the refractive index anisotropy of the liquid crystal molecules can be prevented. The viewing angle characteristic in the diagonal direction did not improve.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and by forming an insulating layer having compensation characteristics in the liquid crystal panel to change the polarization characteristics of the light passing through the liquid crystal display element, the liquid crystal display element which can improve the viewing angle characteristic in the diagonal direction. The purpose is to provide.

In order to achieve the above object, the liquid crystal display device according to the first embodiment of the present invention comprises a liquid crystal layer formed between a first substrate having a thin film transistor, a second substrate having a color filter, a first substrate and a second substrate. A liquid crystal panel comprising; A first insulating layer formed on the first substrate and formed of a dielectric material having a c-compensation characteristic in which the retardation value in the thickness direction is Rth = 80 to 200 nm; First and second polarizing plates positioned above and below the liquid crystal panel to polarize incident light; And a polarization state of light that is disposed between the first polarizing plate and the liquid crystal panel below the liquid crystal panel and changes the polarization state of the light supplied to the liquid crystal panel, and has a horizontal retardation value of Re = 60 to 14 nm and a thickness retardation value of Rth = 80 to 160 nm. Biaxial compensation film, wherein Re = (n _x -n _y ) d and Rth = (n _x -n _z ) d and n _x , n _y and n _z are the refractive indexes in the x-axis direction and the y-axis direction, respectively. It is characterized by the refractive index of and the refractive index of the z-axis direction.

Absorption axes of the first polarizing plate and the second polarizing plate are perpendicular to each other, and the optical axis of the biaxial film is formed perpendicular to the light absorption axis of the first polarizing plate. In addition, the rubbing direction of the liquid crystal panel is parallel to the light absorption axis of the first polarizing plate.

In addition, the liquid crystal display device according to the second embodiment of the present invention includes a liquid crystal panel including a liquid crystal layer formed between a first substrate having a thin film transistor, a second substrate having a color filter, a first substrate and a second substrate; A first overcoat layer formed on the second substrate, the first overcoat layer being made of a dielectric material having an A-compensation characteristic having a retardation value in a horizontal direction of Re = 40 to 160 nm to change the polarization characteristic of incident light; A second overcoat formed on the first overcoat layer and made of a dielectric material having a c-compensation characteristic having a thickness retardation value of Rth = 40 to 200 nm to change the polarization characteristic of incident light and output the same to the first overcoat layer. layer; And a first polarizing plate and a second polarizing plate which are positioned above and below the liquid crystal panel to polarize the incident light, wherein Re = (n _x -n _y ) d and Rth = (n _x -n _z ) d. n _x , n _y and n _z are each characterized by a refractive index in the x-axis direction, a refractive index in the y-axis direction, and a refractive index in the z-axis direction.

The present invention changes the polarization characteristics of polarized light incident on the liquid crystal panel by forming an insulating layer having compensation characteristics in the liquid crystal panel. By such a change in polarization characteristics, the optical axis of the light incident on the second polarizing plate coincides with the absorption axis of the second polarizing plate, thereby improving the viewing angle characteristic in the diagonal direction.

In addition, the present invention improves the polarization characteristics of light by changing the materials of the insulating layer and the overcoat layer, which are the original structures of the liquid crystal display device, instead of using a separate compensation film in order to improve the viewing angle characteristic. The cost can be reduced compared to using.

1A and 1B are views showing the structure of a general IPS mode liquid crystal display device.
Figure 2 is a simplified perspective exploded view showing the structure of a conventional liquid crystal display device.
Fig. 3A is a diagram showing an absorption axis of a vertical polarizer when the liquid crystal display device is viewed from the front.
Fig. 3B is a diagram showing the absorption axis of the vertical polarizer when the liquid crystal display element is viewed in the diagonal direction.
4A and 4B are graphs showing a refractive index relationship in an x-, y-, and z-axis directions of an A-compensation film.
5A and 5B are graphs showing refractive index relationships in x, y and z axis directions of a C-compensation film.
6 is a view showing a refractive index relationship in the x, y, z axis direction of a biaxial compensation film.
7A and 7B are diagrams illustrating elliptical polarizations of light and corresponding Poincare vectors, respectively.
Fig. 8 is a diagram showing the polarization state of light in Poincare sphere when the liquid crystal display device is seen from the front.
Fig. 9 is a diagram showing the polarization state of light in Poincare sphere when the liquid crystal display element is viewed from a diagonal direction.
10 is a view showing the structure of a liquid crystal display device according to a first embodiment of the present invention.
11A is a view showing an optical axis of a liquid crystal display device according to a first embodiment of the present invention.
FIG. 11B is a view showing a Poang Karregu in which the polarization state of light in the liquid crystal display device according to the first embodiment of the present invention is displayed; FIG.
12 is a view showing the structure of a liquid crystal display device according to a second embodiment of the present invention.
13A is a view showing an optical axis of a liquid crystal display device according to a second embodiment of the present invention.
FIG. 13B is a view showing a Poang Karregu in which a polarization state of light in a liquid crystal display device according to a second embodiment of the present invention is displayed; FIG.
Fig. 14A is a diagram showing luminance viewing angle characteristics when a conventional liquid crystal display element is viewed in a diagonal direction.
14B and 14C illustrate luminance viewing angle characteristics when the liquid crystal display device according to the present invention is viewed in a diagonal direction.

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

The reason why the viewing angle characteristic is deteriorated in the diagonal viewing angle direction of the liquid crystal display device is that light leakage occurs in the diagonal direction of the liquid crystal display device. As shown in FIG. 2, in a general IPS mode LCD, first and second polarizing plates 152 and 154 are attached to upper and lower portions of the liquid crystal panel 101 to be input and output to the liquid crystal panel 101. Linearly polarize

In the normally black mode, the polarization axes of the first polarizing plate 152 and the second polarizing plate 154 attached to the upper and lower substrates are perpendicular to each other. Therefore, the light transmitted through the first polarizing plate 152 is linearly polarized in the x-axis direction and input to the liquid crystal display device. When no signal is applied to the liquid crystal panel, since the liquid crystal molecules 142 of the liquid crystal panel 101 are arranged in the x-axis direction, light incident on the liquid crystal panel 101 is linearly polarized along the x-axis direction. Through the liquid crystal panel 101. On the other hand, the polarization axis of the second polarizing plate 154 attached to the upper substrate is perpendicular to the polarization direction of the light transmitted through the liquid crystal layer, all the light is absorbed by the polarizing plate of the upper substrate to the outside of the second polarizing plate 152 Will not be displayed and the screen will be black.

However, when the liquid crystal display device as described above is viewed in a diagonal direction, the polarization directions of the first polarizing plate 152 and the second polarizing plate 154 are not substantially vertically disposed. That is, when viewed from the front of the liquid crystal display device 101, the polarization axes of the first polarizing plate 152 and the second polarizing plate 154 are disposed perpendicular to each other, but when viewed in a diagonal direction, the vertical polarization is broken.

FIG. 3A shows the arrangement of the polarization axes of the first polarizing plate 152 and the second polarizing plate 154 in the path of light transmitted perpendicularly to the screen of the liquid crystal display when viewed from the front, and FIG. 3B is a liquid crystal display. When the device is viewed diagonally, that is, the polarization axis of the first polarizing plate 152 and the second polarizing plate 154 in the path of light passing through the screen of the liquid crystal display device at a constant polar angle and azimuthal angle It is a batch. In this case, the dotted line in the drawing is the direction of the polarization axis (ie, the light absorption axis) in the first polarizing plate 152 and the solid line is the direction of the light absorption axis in the second polarizing plate 152.

As shown in FIG. 3A, the polarization axes of the first polarizing plate 152 and the second polarizing plate 154 when the liquid crystal display device is viewed from the front (that is, when light is transmitted perpendicularly to the screen of the liquid crystal display device). Are perpendicular to each other, but as shown in FIG. 3B, the first polarizing plate 152 and the second polarizing plate when the liquid crystal display device is viewed diagonally (when transmitted at a constant polar angle and azimuth angle with the screen of the liquid crystal display device). The polarization axis of 154 is disposed at a constant angle θ rather than vertical.

As described above, when the liquid crystal display device is viewed in a diagonal direction, the polarization directions of the first polarizing plate 152 and the second polarizing plate 154 are not perpendicular to each other, and thus are linearly polarized on the first polarizing plate 152 to form the liquid crystal panel 101. The transmitted light is not all absorbed by the second polarizing plate 154, and a part of the light passes through the second polarizing plate 154. Therefore, even when the liquid crystal display device is viewed diagonally even in the normally black state, part of the light leaks, and thus, the black state cannot be maintained.

As such, when viewing the liquid crystal display device in a diagonal direction, the viewing angle characteristic is lowered, since the polarization directions of the first polarizing plate 152 and the second polarizing plate 154 are not perpendicular to each other, and thus the polarized light of the first polarizing plate 152. This is because part of the second polarizing plate 154 is not completely absorbed and leaks. Therefore, in order to improve the viewing angle characteristic when viewing the liquid crystal display device in a diagonal direction, all of the light polarized by the first polarizing plate 152 must be absorbed by the second polarizing plate 154. To this end, in the present invention, a compensation layer is formed in the liquid crystal panel 10 to change the polarization direction of the light passing through the liquid crystal panel 101 so that the optical axis of the light incident on the second polarizing plate 154 is polarized by the second polarizing plate 154. To match the direction (i.e., the light absorbing layer). In particular, in the present invention, the optical axis of the light incident on the second polarizing plate 154 coincides with the polarization direction of the second polarizing plate 154 by forming a compensation layer having a uniaxial function and a compensation layer having a biaxial function. Let's do it

The compensation layer may be classified into a uniaxial compensation layer and a biaxial compensation layer. The uniaxial compensation layer is an anisotropic birefringence layer having only one optical axis and the biaxial compensation layer is an anisotropic birefringence layer having two optical axes. Among such compensation layers, the uniaxial compensation layer may be classified into an A-compensation layer and a C-compensation layer according to the direction and size of the optical axis. The refractive index characteristics of these A- and C-compensation layers are shown in FIGS. 4 and 5.

4A and 4B are diagrams showing a positive A-compensation layer and a negative A-compensation layer, respectively. As shown in FIGS. 4A and 4B, the A-compensation layer has the same refractive index n _y in the y-axis direction and the refractive index n _{z in the} z-axis direction (n _y = n _z ) and refractive index (n _x) is the refractive index (n _z) and wherein the other of the passage ratio of y-axis direction _(y n), and z-axis directions _{(n x ≠ n y = n} z). As shown in Fig. 4A, when the refractive index n _{x in the x-} axis direction is larger than the refractive index n _{y in the} y-axis direction, it is a positive A-compensation layer and the refractive index n _{x in the} x-axis direction is the refractive index in the y-axis direction. If less than (n _y ) is a negative A-compensation layer, these positive A-compensation layer and negative A-compensation layer are defined by Equation 1, respectively, as follows.

5A and 5B are diagrams showing a positive C-compensation layer and a negative C-compensation layer, respectively. As shown in FIGS. 5A and 5B, the C-compensation layer has the same refractive index n _x in the x-axis direction and the refractive index n _{y in the} y-axis direction (n _x = n _y ) and the z-axis direction. refractive index (n _z) this is the passage ratio (n _x) and refractive index (n _y) and different from one another in the y-axis direction along the x axis _{(n z ≠ n x = n} y). As shown in FIG. 5A, when the refractive index n _{x in the} x-axis direction and the refractive index n _{y in the y-} axis direction are smaller than the refractive index n _{z in the} z-axis direction, it is a positive C-compensation layer and the x-axis direction. If the refractive index (n _x ) and the refractive index (n _y ) in the _y- axis direction are larger than the refractive index (n _z ) in the z-axis direction, the negative C-compensation layer and the positive C-compensation layer and the negative C-compensation layer are respectively If defined by 2, it is as follows.

In addition, the phase difference by the compensation layer is determined by the refractive index n _x in the x-axis direction, the refractive index n _{y in the} y-axis direction, and the refractive index n _{z in the} z-axis direction. The relationship between the refractive indices (n _x , n _y , n _z ) is shown.

Here, Re is a retardation value in the horizontal direction, Rth is a retardation value in the thickness direction, and d is the thickness of the compensation layer.

The A-compensation layer and the C-compensation layer mainly use cycloolefin polymer or polycarbonate, UV curable horizontal or horizontal alignment liquid crystal, polystyrene resin, polyethylene terephthalate and the like.

The biaxial compensation layer has different values of n _x , n _x , n _x , and is classified into a positive biaxial compensation layer, a negative biaxial compensation layer, and a Z-axis stretching biaxial compensation layer. In FIG. 6, the biaxial compensation layer has a refractive index nx in the x-axis direction, a refractive index n _{y in} the y-axis direction, and a refractive index n _{z in the} z-axis direction. The biaxial compensation layer has a refractive index (n _x) of the x-axis direction and the passage rate of the y-axis (n _y) and the positive biaxial compensation layer according to the magnitude of the refractive index (n _z) in the z-axis direction, negative biaxial compensation layer, and Z The axially stretched biaxial compensation layer is classified, and these positive biaxial compensation layer, negative biaxial compensation layer and Z-axis stretching biaxial compensation layer are defined by the following equation (4), respectively.

In addition, the biaxiality (Nz) of the biaxial compensation layer is defined as in Equation 5 below.

As defined in Equation 3, Re is a retardation value in the horizontal direction, Rth is a retardation value in the thick direction, and d is the thickness of the compensation layer.

According to the definitions of Equations 4 and 5, the negative biaxial compensation layer is Nz ≧ 1, the positive biaxial compensation layer is Nz <0, and the z-axis stretching biaxial compensation layer is 0 <Nz <1.

In the present invention, by providing a compensation layer as described above, the linearly polarized light of the first polarizing plate 152 is phase-converted so that the polarization direction of the light is completely perpendicular to the polarization direction of the second polarizing plate 154. Allow all light incident on the beam to be absorbed.

The polarization state of the light can be analyzed by the Jones matrix, and the Jones matrix representing the polarization transmission characteristic of a transparent medium is a unitary matrix because the Jones operation ignores the reflection of light at the interface. Can be represented by Poincare shpere.

Since the Jones vector can represent only complete polarization, the Stokes parameter defined by Equation 6 below should be used to represent partial polarization.

의 부등식이 성립하는데, 이 부등식은 완전편광에서만 맞는다. 즉, 완전편광의 경우, S1, S2 및 S3를 빛의 밝기 S0로 나눈 규격화된 변수 s1, s2 및 s3 사이에는 다음의 수학식 7의 관계가 성립한다.Here, <> represents a time average and E _x and E _x are electric field components in the x-axis and y-axis directions, respectively. In this case, between these four variables

The inequality of is true, and this inequality is true only for complete polarization. That is, in the case of fully polarized light, the following equation (7) is established between the standardized variables s1, s2, and s3 obtained by dividing S1, S2, and S3 by the brightness S0 of light.

This is the equation of Poangcare sphere with radius 1 in three-dimensional space, where (s1, s2, s3) is the point of Cartesian coordinates.

In this case, all the points on the equator line in the Phang Nga district correspond to linearly polarized light, and the north pole corresponds to the right hand circularly polarized light and the south pole to the left hand circularly polarized light. All points in the northern hemisphere correspond to right-hand elliptical polarization, and all points in the southern hemisphere correspond to left-hand elliptical polarization.

7A and 7B are diagrams illustrating an arbitrary elliptical polarization and a corresponding poang curry vector in the rectangular coordinate system, respectively.

As shown in FIGS. 7A and 7B, the latitude angle of the Poang Cure vector P corresponding to the elliptically polarized light having the azimuthal angle of Ψ and the elliptic angle of x is 2x and the azimuth angle of the polarization ellipse is 2x. 2Ψ and the Cartesian coordinates are (cons (2Ψ) cons (2x), sin (2Ψ) cos (2x), sin (2x)). If this point is in the northern hemisphere, the direction of rotation of the electric field vector is clockwise; in the southern hemisphere, it is counterclockwise. At this time, the opposite points on the Poangaregu represent polarization states orthogonal to each other.

In addition, the Unitary Jones matrix, which describes the change in polarization state when light passes through a transparent medium, can be interpreted as a rotational transformation on the Poangkaregu.

FIG. 8 is a view showing a Poang Karregu showing the polarization states of the first polarizing plate 152 and the second polarizing plate 154 when the IPS mode liquid crystal display device is viewed from the front as shown in FIG. 3A.

In the Poangcurry District, the anti-corrosive points represent polarization states orthogonal to each other, so that point A represents the light absorption axis of the first polarizing plate 152 and light transmission axis of the second polarizing plate 154, and the point B represents the first polarizing plate 152. ) And a light absorption axis of the second polarizing plate 154. As shown in FIG. 8, when the IPS mode liquid crystal display device is viewed from the front, the light transmission axis of the first polarizing plate 152 maintains the same linear polarization state as the light absorption axis of the second polarizing plate 154. This is because the light absorption axis of the first polarization plate 152 and the light absorption axis of the second polarization axis 154 are perpendicular to each other when the IPS mode liquid crystal display is viewed from the front. This is because the light absorption axes of the polarizing plates 154 are parallel to each other.

As such, the light transmission axis of the first polarizing plate 152 and the light absorption axis of the second polarizing plate 154 are parallel to each other, so that the light transmission axis of the first polarizing plate 152 and the light of the second polarizing plate 154 are located in Puang Cure. Since the absorption axes are located at the same point, the linearly polarized light transmitted through the first polarizing plate 152 is absorbed by the second polarizing plate 154 so that light is not transmitted to the outside of the second polarizing plate 154, and as a result, is normally In the black mode, when the IPS mode liquid crystal display device is viewed from the front, it is possible to maintain a completely black state.

On the other hand, Figure 9 is a diagram showing a Poincare sphere showing the polarization state of the light when viewing the liquid crystal display device in the diagonal direction in the IPS mode liquid crystal display device, as shown in Figure 3b.

In FIG. 9, the A1 point represents the light absorption axis of the first polarizing plate 152, and the A2 point opposite thereto represents the light transmission axis of the first polarizing plate 152 orthogonal to the light absorption axis. Further, point B1 represents the light transmission axis of the second polarizing plate 154 and point B2 represents the light absorption axis of the second polarizing plate 154. As shown in FIG. 3B, when the IPS mode liquid crystal display device is viewed from a diagonal direction, the polarization directions of the first polarizing plate 152 and the second polarizing plate 154 are not perpendicular to each other but at a predetermined angle θ. Therefore, the point A2, which is the light transmission axis of the first polarizing plate 152, and the point B2, which is the light absorption axis of the second polarizing plate 154, do not coincide with each other, but are spaced apart by x. The interval of x means an angle between the light transmission axis of the first polarizing plate 152 and the light absorption axis of the second polarizing plate 154, and the light transmission axis of the first polarizing plate 152 and the second polarizing plate 154. As much as the angle corresponding to the angle between the light absorption axes of?) Is transmitted through the second polarizing plate 154. Accordingly, in order to prevent light leakage in the diagonal direction of the IPS mode liquid crystal display device, the light transmission axis of the first polarizing plate 152 and the light absorption axis of the second polarizing plate 154 are parallel to each other by matching the A2 and B2 points. Therefore, the light polarized by the first polarizing plate 152 must absorb all of the second polarizing plate 154.

In the present invention, by using a compensation layer to change the polarization state of the linearly polarized light in the first polarizing plate 152 to match the point A2 and B2 on the Poincare sphere (that is, the light transmission axis of the first polarizing plate 152 and the The light absorption axis of the second polarizing plate 154 is made in parallel) to prevent light leakage caused by light passing through the second polarizing plate 154.

Hereinafter, a specific embodiment of the present invention will be described. In this case, the polarization state of the liquid crystal display device according to the exemplary embodiment of the present invention will be described using the Poincare sphere. As described above, in the present invention, light leakage in the diagonal direction of the liquid crystal display device can be prevented by changing the polarization state of the light using the uniaxial compensation layer and the biaxial compensation layer.

10 is a diagram showing the structure of a transverse electric field mode liquid crystal display device according to a first embodiment of the present invention. As shown in FIG. 10, in the transverse electric field mode liquid crystal display device 101 according to the present invention, a thin film transistor is formed on the first substrate 120 made of a transparent material such as glass. The thin film transistor may include a gate electrode 111 formed on the first substrate 120, a gate insulating layer 22 and the gate insulating layer over the entire first substrate 120 on which the gate electrode 111 is formed. 122 and a source electrode 113 and a drain electrode 114 formed on the semiconductor layer 112.

A first insulating layer 124 having a positive C-compensation function is formed on the first substrate 120 on which the thin film transistor is formed, so that light incident from a backlight (not shown) passes through the first insulating layer 124. The polarization state is changed.

The first insulating layer 124 is made of an organic insulating material having a low dielectric constant, such as cycloolefin polymer or polycarbonate, UV curable horizontal or horizontal alignment liquid crystal, polystyrene resin, polyethylene terephthalate, and has a thickness of about 1-2 μm. Is formed. At this time, the phase difference value Rth in the thickness direction of the first insulating layer 124 having the positive C-compensation function is Rth = 80 to 200 nm.

The pixel electrode 105 is formed on the first insulating layer 124. The pixel electrode 105 is formed in a dummy shape over the entire pixel region of the liquid crystal display, and is electrically connected to the drain electrode 124 of the thin film transistor through a contact hole 117 formed in the first insulating layer 124. do.

The pixel electrode 105 includes a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO) or an opaque metal having good conductivity such as Cr, Mo, Ta, Cu, Ti, Al, or Al alloy. It may be formed by etching.

A second insulating layer 126 is formed on the first insulating layer 124 on which the pixel electrode 105 is formed, and a band-shaped common electrode 107 having a predetermined width is formed thereon. The second insulating layer 126 is made of an organic material, such as photoacryl, and the common electrode is made of a transparent conductive material such as ITO or IZO, or Cr, Mo, Ta, Cu, Ti, Al, or an Al alloy and an opaque metal. Can be.

The pixel electrode 105 and the common electrode 107 are formed with the second insulating layer 126 interposed therebetween, and the pixel electrode 105 is formed in a dummy shape over the entire pixel area on the first insulating layer 107. And the common electrode 107 is formed in a plurality of bands arranged in parallel with each other on the second insulating layer 126 so as to be parallel to the substrate 110 between the pixel electrode 105 and the common electrode 107. An electric field is formed. In this case, the common electrode 107 may be formed to be bent at least once in the pixel like the common electrode illustrated in FIG. 1.

In addition, a first alignment layer 128a formed of a material such as polyimide or polyamide is formed on the entire first substrate 120. In this case, an alignment direction for aligning the liquid crystal molecules in a specific direction is determined in the first alignment layer 128a by a method such as rubbing.

The black matrix 132 and the color filter layer 134 are formed on the second substrate 130. The black matrix 132 is to prevent light leakage into an area where the liquid crystal molecules do not operate. As shown in the drawing, the black matrix 132 is disposed between the thin film transistor region and the pixel and the pixel (ie, the gate line and the data line region). Mainly formed. The color filter layer 134 is composed of R (Red), B (Blue), and G (Green) to realize actual colors. An overcoat layer 136 is formed on the color filter layer 134 to protect the color filter layer 134 and to improve flatness of the substrate, and a second alignment layer 128b having an alignment direction determined thereon is formed thereon. have.

The liquid crystal layer 140 is formed between the first substrate 120 and the second substrate 130 to complete the liquid crystal panel 101. In this case, the liquid crystal layer 140 uses a nematic liquid crystal having a retardation value of about 250 nm to 350 nm.

The biaxial compensation film 150 is disposed on the lower surface of the liquid crystal panel 101, that is, outside the first substrate 110, and the first polarizing plate 162 is disposed below the liquid crystal panel 101. In addition, a second polarizing plate 1640 is disposed above the liquid crystal panel 101, that is, outside of the second substrate 130.

Although not shown in the drawing, the first polarizing plate includes a polarizer and a support attached to one surface of the polarizer. The polarizer is a film that can convert natural light into any polarized light. In this case, when the polarizer is divided into two orthogonal polarization components of the incident light, one having a function of passing one polarization component of the two polarization components and absorbing, reflecting or scattering the other polarization components may be used. . Although there is no restriction | limiting in particular as an optical film used for the said polarizer, For example, the polymer film which consists mainly of polyvinyl alcohol (PVA) type resin containing iodine or a dichroic dye, a dichroic substance, and liquid crystalline The O-type polarizer which orientated the liquid crystalline composition containing a compound in the fixed direction, and the E-type polarizer which orientated the lyotropic liquid crystal in the fixed direction can be used. The support is for protecting the polarizer, and mainly consists of a film. Therefore, any protective film may be used as long as the polarizer can be protected. For example, triacetylcellulose (TAC) or triacetylcellulose without phase difference (Rth) may be used as the support. At this time, it is preferable that the said triacetyl cellulose has a phase difference value of 0-200 nm.

The second polarizing plate 164 also includes a polarizer and a support attached to both surfaces of the polarizer. That is, as the polarizer, a polymer film containing polyvinyl alcohol (PVA) resin containing iodine or a dichroic dye as a main component, and a liquid crystal composition containing a dichroic material and a liquid crystal compound are oriented in a predetermined direction. E-type polarizer or the like in which the O-type polarizer and the lyotropic liquid crystal are oriented in a predetermined direction is used, and one side of the polarizer, that is, the surface in contact with the outside, has a triacetylcellulose (TAC) or a phase difference ( A triacetylcellulose (zero retardation TAC) free of Rth) is attached to the support. In addition, triacetyl cellulose (zero retardation TAC) having no phase difference (Rth) is attached to the support in contact with the liquid crystal panel 101.

The biaxial compensation film 150 has a retardation value Re in the horizontal direction of Re = 60 to 140 nm and a retardation value Rth in the thickness direction of Rth = 80 to 160 nm.

Therefore, the biaxiality Nz of the biaxial compensation film 150 is 1.1 <Nz <1.4 by Equation 5. In general, when the biaxiality (Nz) of the biaxial film is Nz> 1, the biaxial film is a negative biaxial film, and the refractive indices (n _x , n _y , n _z ) in the x, y and z axis directions are n _x > n. has a relationship of _y > n _z . In addition, when the biaxial film (Nz) of the biaxial film is Nz <0, the biaxial film is a positive biaxial film, the refractive index (n _x , n _y , n _z ) in the x, y, z axis direction is n _z > n has a relationship of _x > n _y . And, when the biaxiality (Nz) of the biaxial film is 0 <Nz <1, the biaxial film is a z-axis stretched biaxial film, the refractive index (n _x , n _y , n _z ) in the x, y, z axis direction is n _x > n _z > n _y . Accordingly, the first compensation film 242 is a negative biaxial film whose biaxiality Nz of the biaxial film is Nz> 1.

The biaxial compensation film 150, ie, the negative biaxial film, uses a UV curable liquid crystal film polycarbonate, polyethylene terephthalate or polystyrene using nematic liquid crystals, and has a normal wavelength dispersion. It may have a wavelength dispersion characteristic, a flat wavelength dispersion characteristic and a reverse wavelength dispersion characteristic.

The polarization directions of the first polarizing plate 162 and the second polarizing plate 164 are perpendicular to each other. That is, the absorption axis of the first polarizing plate 162 is disposed at an angle of 90 ° and the absorption axis of the second polarizing plate 164 is disposed at an angle of 0 °. In addition, the optical axis of the biaxial compensation film 150 is disposed at an angle of 0 ° and the rubbing direction of the liquid crystal panel 101 is 90 °, and is arranged at an angle of 0 ° of the optical axis of the second polarizing film 164. .

The liquid crystal molecules of the liquid crystal layer of the liquid crystal panel 101 are disposed along the rubbing direction of the alignment layer in the off state of the liquid crystal panel 101. Therefore, the optical axis of the liquid crystal molecules also forms 90 degrees.

As described above, the liquid crystal panel 101 forms 90 ° in the rubbing direction for the following reason.

In general, in the IPS mode liquid crystal display, since the common electrode and the pixel electrode forming the horizontal electric field are arranged along the data line, the rubbing direction of the alignment layer is formed at an angle of about 15 ° to 45 °. However, in the present invention, the common electrode and the pixel electrode of the IPS mode liquid crystal display element bend at least once within a pixel at a predetermined angle, and the rubbing of the alignment film is performed in the data line direction, that is, at an angle of 90 degrees.

The bending of the common electrode and the pixel electrode is intended to improve the viewing angle characteristics of the liquid crystal display element by forming a plurality of domains having a main viewing angle in different directions in one pixel. Since the common electrode and the pixel electrode are formed at a predetermined angle with the data line and the rubbing direction of the alignment layer is made with the data line direction, the common electrode and the pixel electrode with the rubbing direction have a predetermined angle, for example, about 15 ° to 45 °. It is made up of angles.

The polarization state of the liquid crystal display according to the present exemplary embodiment configured as described above will be described with reference to FIGS. 11A and 11B. 11A is a view showing the polarization state in each configuration in the liquid crystal display device according to the present invention, and FIG. 11B is a view showing the Poincare sphere showing the polarization state in the liquid crystal display device according to the present invention.

As shown in FIG. 11A, the negative biaxial compensation film 150 is disposed between the first polarizing plate 162 and the liquid crystal panel 101, wherein the optical axis of the negative biaxial compensation film 150 is the first polarizing plate ( 162 is perpendicular to the light absorption axis of the liquid crystal panel 101 and the rubbing direction of the liquid crystal panel 101 (that is, the optical axis forms 0 °). In addition, the second polarizing plate 164 is disposed above the liquid crystal panel 101, wherein the light absorption axis of the second polarizing plate 164 is perpendicular to the rubbing direction of the liquid crystal panel 101 (that is, the light of the second polarizing plate). Absorption is formed at an angle of 0 °).

As shown in FIG. 11B, when the non-polarized light is incident on the first polarizing plate 162 from the backlight of the liquid crystal panel 101, the light is linearly polarized. Most of the linearly polarized light is absorbed by the first polarizing plate 162. The polarization state of the light absorbed by the axis A1 and transmitted through the first polarizing plate 162 is positioned at A2. That is, the transmission axis of the first polarizing plate 162 is located at the point A2. At this time, the absorption axis of the second polarizing plate 164 is located at the point B2, and is spaced apart from the transmission axis of the first polarizing plate 162 by a predetermined distance.

When the linearly polarized light in the first polarizing plate 162 is transmitted through the negative biaxial compensation film 150, the polarization state is rotated from the point A2 to the point C1. In this case, since the negative biaxial compensation film 150 is a negative biaxial film, the optical axis is present between the n _x axis and the n _z axis. Therefore, the polarization state of the light is rotated clockwise about the optical axis between the n _x axis and the n _z axis so that the polarization state is moved from the A2 point to the C1 point. At this time, the polarization state of the light maintains an elliptical polarization state located on three quadrants of the Poincare sphere.

As described above, when the polarized light is transmitted through the first insulating layer 124 of the liquid crystal panel 101, that is, the positive C-compensation layer, the light is rotated about the S2 axis to move the polarization state from the C1 point to the C2 point. do.

When the light whose polarization state is changed as described above is transmitted through the liquid crystal layer, the polarization state is rotated about the S2 axis, and the polarization state is moved from the C2 point to the B2 point. As a result, the light transmitted through the liquid crystal panel 101 is changed into linearly polarized light having the same polarization axis as the absorption axis of the second polarizing plate 164, and all of the polarized light is absorbed by the second polarization 164. The second polarizing plate 164 does not penetrate.

12 is a view showing the structure of a transverse electric field mode liquid crystal display device according to a second embodiment of the present invention.

As illustrated in FIG. 12, in the transverse electric field mode liquid crystal display device 201, a thin film transistor is formed on the first substrate 220 made of a transparent material such as glass. The thin film transistor may include a gate electrode 211 formed on the first substrate 220, a gate insulating layer 222, and the gate insulating layer all over the first substrate 220 on which the gate electrode 211 is formed. The semiconductor layer 212 formed on the 222 and the source electrode 213 and the drain electrode 214 formed on the semiconductor layer 212.

A first insulating layer 224 and a second insulating layer 226 are formed on the first substrate 220 on which the thin film transistor is formed, and a pixel electrode 105 is formed on the first insulating layer 224. The common electrode is formed on the insulating layer 226. In this case, the pixel electrode 205 is formed in a dummy shape over the entire pixel region of the liquid crystal display, and electrically connected to the drain electrode 224 of the thin film transistor through the contact hole 217 formed in the first insulating layer 224. Is connected. A band-shaped common electrode 207 having a predetermined width is formed on the second insulating layer 226 to form a transverse electric field parallel to the substrate 210 between the pixel electrode 205 and the common electrode 207. In this case, the common electrode 207 may be formed to be bent at least once in the pixel like the common electrode illustrated in FIG. 1.

In addition, a first alignment layer 228a made of a material such as polyimide or polyamide is formed on the entire second substrate 120. Liquid crystal molecules are identified in the first alignment layer 228a by a method such as rubbing. The orientation direction for orientation in the direction is determined.

The black matrix 232 and the color filter layer 234 are formed on the second substrate 230. The black matrix 232 is mainly formed between the thin film transistor region and the pixel and the pixel (ie, the gate line and the data line region). The color filter layer 234 is composed of R (Red), B (Blue), and G (Green) to implement actual colors. The first overcoat layer 236 and the second overcoat layer 238 are formed on the color filter layer 234 to protect the color filter layer 234 and to improve the flatness of the substrate. An alignment film 228b is formed.

The first overcoat layer 236 is formed of an organic material having a positive A-compensation function. For example, a cycloolefin polymer or polycarbonate, UV curable horizontal or horizontal alignment liquid crystal, polystyrene resin, polyethylene terephthalate, or the like may be used. . In this case, the thickness of the first overcoat layer 236 is about 0.5-2 μm, and the retardation value Re in the horizontal direction is Re = 40 to 160 nm.

The second overcoat layer 238 is formed of a low dielectric constant organic insulating material having a positive C-compensation function. For example, cycloolefin polymer or polycarbonate, UV curable horizontal or horizontal alignment liquid crystal, polystyrene resin, polyethylene terephthalate And the like can be used. At this time, the thickness of the second overcoat layer 238 is about 0.5-2 μm and the phase difference value Rth in the thickness direction is Rth = 40 to 200 nm.

The liquid crystal layer 240 is formed between the first substrate 220 and the second substrate 230 to complete the liquid crystal panel 201. In this case, the liquid crystal layer 240 uses a nematic liquid crystal having a retardation value of about 250 nm to 350 nm.

First and second polarizing plates 262 and 264 are attached to both surfaces of the liquid crystal panel 201, respectively. In this case, the first polarizing plate 262 and the second polarizing plate 264 are made of a polarizer and a support attached to both surfaces of the polarizer, respectively.

The polarizer is a film that can convert natural light into any polarized light. In this case, when the polarizer is divided into two orthogonal polarization components of the incident light, one having a function of passing one polarization component of the two polarization components and absorbing, reflecting or scattering the other polarization components may be used. . Although there is no restriction | limiting in particular as an optical film used for the said polarizer, For example, the polymer film which consists mainly of polyvinyl alcohol (PVA) type resin containing iodine or a dichroic dye, a dichroic substance, and liquid crystalline The O-type polarizer which orientated the liquid crystalline composition containing a compound in the fixed direction, and the E-type polarizer which orientated the lyotropic liquid crystal in the fixed direction can be used.

The support is for protecting the polarizer, and mainly consists of a film. Therefore, any protective film may be used as long as the polarizer can be protected. For example, triacetylcellulose (TAC) or triacetylcellulose without phase difference (Rth) may be used as the support. At this time, it is preferable that the said triacetyl cellulose has a phase difference value of 0-200 nm.

In addition, triacetyl cellulose (zero retardation TAC) without phase difference (Rth) may be used as the support.

Triacetyl cellulose (TAC) is attached to the outer surface of the first polarizing plate 262, and triacetyl cellulose (zero retardation TAC) without phase difference (Rth) is formed on the surface of the first polarizing plate 262 in contact with the liquid crystal panel 201. Triacetyl cellulose (TAC) is attached to both surfaces of the second polarizing plate 264.

In this case, triacetyl cellulose (TAC) may be attached to only one surface of each of the first polarizing plate 262 and the second polarizing plate 264 (that is, a surface exposed to the outside without being in contact with the liquid crystal panel) or the second polarizing plate ( A triacetyl cellulose (zero retardation TAC) without a phase difference (Rth) may be attached to a surface of the liquid crystal panel 201 of 264.

The polarization directions of the first polarizing plate 262 and the second polarizing plate 264 are perpendicular to each other. That is, the absorption axis of the first polarizing plate 262 is disposed at an angle of 90 degrees and the absorption axis of the second polarizing plate 264 is disposed at an angle of 0 degrees.

In addition, the optical axis of the first overcoat layer 236 composed of the positive A-compensation layer is disposed at 0 °, the rubbing direction of the liquid crystal panel 201 is made at 0 °, and zero of the optical axis of the second polarizing film 264. Are placed at an angle of °. The liquid crystal molecules of the liquid crystal layer of the liquid crystal panel 201 are disposed along the rubbing direction of the alignment layer in the off state of the liquid crystal panel 201. Accordingly, the optical axis of the liquid crystal molecules also forms 0 °.

The polarization state of the liquid crystal display according to the present exemplary embodiment configured as described above will be described with reference to FIGS. 13A and 13B. 13A is a view showing polarization states in respective configurations of the liquid crystal display device according to the second embodiment of the present invention, and FIG. 13B is a view showing polarization states in the liquid crystal display device according to the second embodiment of the present invention. It is a figure which shows the Poincare sphere shown.

As shown in FIG. 13A, the positive c-compensation layer 238 (ie, the second overcoat layer) is disposed between the liquid crystal layer and the second polarizing plate 264, and the positive A-compensation layer 236 is positive c -Disposed between the compensation layer 238 and the second polarizing plate 264. In this case, the optical axis of the positive A-compensation layer 236 is perpendicular to the light absorption axis of the first polarizing plate 262 (that is, the optical axis forms 0 °). In addition, the second polarizing plate 264 is disposed above the liquid crystal panel 201, where the light absorption axis of the second polarizing plate 264 is parallel to the rubbing direction of the liquid crystal panel 201 (that is, the light of the second polarizing plate). Absorption is formed at an angle of 0 °).

As shown in FIG. 13B, when the non-polarized light is incident on the first polarizing plate 262 from the backlight of the liquid crystal panel 201, the light is linearly polarized. Most of the linearly polarized light is absorbed by the first polarizing plate 262. The polarization state of the light absorbed by the axis A1 and transmitted through the first polarizing plate 262 is positioned at A2. That is, the transmission axis of the first polarizing plate 262 is located at the point A2. At this time, the absorption axis of the second polarizing plate 264 is located at the point B2, and is spaced apart from the transmission axis of the first polarizing plate 262 by a predetermined distance.

When the linearly polarized light in the first polarizing plate 262 is transmitted through the liquid crystal layer of the liquid crystal panel 201, since the alignment layer is rubbed at an angle of 0 °, the polarization state of the linearly polarized light is rotated about the S2 axis. You will move to C1.

When the light with the changed polarization is transmitted through the positive c-compensation layer 238 of the liquid crystal panel 201, the polarization state of the linearly changed light is rotated about the S2 axis, and the polarization state is moved to the C2 point.

When the light whose polarization is changed as described above is transmitted through the first overcoat layer 236 of the liquid crystal panel 201, that is, the positive A-compensation layer, the polarization state is rotated around the A 2 O axis, and the polarization state is C3 at the point C2. You will be taken to the point.

In addition, when the polarized light is transmitted through the triacetyl cellulose (TAC) of the polarizing plate, the light is moved from the C3 point to the B2 point by the delay value by the triacetyl cellulose (TAC). As a result, the light transmitted through the liquid crystal panel 201 is changed into linearly polarized light having the same polarization axis as the absorption axis of the second polarizing plate 264, and the polarized light is absorbed by the second polarization 264. The second polarizing plate 264 does not penetrate.

FIG. 14A is a diagram illustrating a result of simulating luminance viewing angle characteristics in a normally black mode in a diagonal viewing direction of a conventional liquid crystal display device. FIGS. 14B and 14C illustrate the first and second embodiments of the present invention. It is a figure which shows the result of simulating the luminance viewing angle characteristic in normally black mode in the diagonal viewing direction of the conventional liquid crystal display element.

Here, the lower polarizing plate and the upper polarizing plate are arranged so that the light transmission axes are perpendicular to each other, and the optical axis of the liquid crystal layer is in a state parallel to the light transmission axis of the upper polarizing plate. 14A to 14C show a conventional liquid crystal display device and the first and second embodiments of the present invention at an inclination angle in the range of 0 ° to 80 ° with respect to all mirror angles (or azimuth angles) when white light is used. Accordingly, the contrast ratio characteristics of the liquid crystal display including the optical compensation film are simulated. 14A to 14C, the center of the circle is a case where the inclination angle is 0, indicating that the inclination angle increases as the radius of the circle increases, and the numerical values written along the circumference indicate the east angle.

In addition, in FIG. 14A to FIG. 14C, light leakage increases in a normally black mode from blue to yellow and red. When comparing the contrast ratio characteristics of the conventional liquid crystal display of FIG. 14A and the liquid crystal display according to the present invention of FIGS. 14B and 14C, 45 degrees and 135 degrees corresponding to diagonal directions of the liquid crystal display panel in the normally black mode. At 225 degrees and 315 degrees, the light leakage is markedly reduced. Accordingly, it can be seen that the brightness of the liquid crystal display is reduced and the contrast ratio is improved in the normally black mode in the liquid crystal display device of the present invention. It can be seen that significantly reduced compared to the display element.

Many details are set forth in the foregoing description but should be construed as illustrative of preferred embodiments rather than to limit the scope of the invention. For example, in the first embodiment of the present invention, light is input to the first substrate on which the thin film transistor is formed and output to the second substrate on which the color filter is formed, but light is input to the second substrate on which the color filter is formed. Even when the transistor is output to the first substrate on which the transistor is formed, the polarization direction change as shown in FIG. 11B is reversed, thereby obtaining the same result as in the first embodiment. In addition, in the second embodiment, the same result as in the second embodiment may be obtained even when light is transmitted through the liquid crystal panel through the second substrate.

Further, in the detailed description, a configuration is disclosed in which a pixel electrode is formed in a dummy shape on the first insulating layer and a common electrode is formed in a band shape on the second insulating layer to form a transverse electric field between the pixel electrode and the common electrode. Both the electrode and the common electrode may be formed in a band shape parallel to each other, and these band-shaped pixel electrodes and the common electrode may be formed in the first insulating layer and the second insulating layer.

 Therefore, the invention should not be construed as limited to the embodiments described, but should be determined by equivalents to the appended claims and the claims.

101: liquid crystal panel 120,130: substrate
124: insulating layer (c-compensation layer) 134: color filter layer
140: liquid crystal layer 150: biaxial compensation film
162,164 polarizer 236 first overcoat layer (A-compensation layer)
238: second overcoat layer (C-compensation layer)

Claims (22)

A liquid crystal panel including a first substrate having a thin film transistor, a second substrate having a color filter, a liquid crystal layer formed between the first substrate and the second substrate;
A first insulating layer formed on the first substrate and formed of a dielectric material having a c-compensation characteristic in which the retardation value in the thickness direction is Rth = 80 to 200 nm;
First and second polarizing plates positioned above and below the liquid crystal panel to polarize incident light; And
A biaxial axis disposed between the first polarizing plate and the liquid crystal panel below the liquid crystal panel to change the polarization state of the light supplied to the liquid crystal panel, and having a phase difference value Re = 60 to 14 nm in the horizontal direction and a phase difference value Rth = 80 to 160 nm in the thickness direction; Compensation film
Where Re = (n _x -n _y ) d and Rth = (n _x -n _z ) d and n _x , n _y and n _z are the refractive indices in the x-axis direction, the refractive indices in the y-axis direction and the z-axis direction, respectively. A liquid crystal display device characterized by the refractive index. The liquid crystal display of claim 1, wherein absorption axes of the first polarizing plate and the second polarizing plate are perpendicular to each other. The method of claim 1, wherein the first polarizing plate and the second polarizing plate, respectively,
A support; And
Liquid crystal display device, characterized in that one surface made of a polarizer attached to the support. The liquid crystal display device of claim 3, wherein the support is made of a transparent protective film. The liquid crystal display device according to claim 4, wherein the transparent protective film is made of triacetyl cellulose or triacetyl cellulose having no phase difference (Rth). The liquid crystal display device according to claim 3, wherein the polarizer is made of polyvinyl alcohol-based resin. The liquid crystal display device of claim 1, wherein the first insulating layer is formed of a material selected from the group consisting of cycloolefin polymer, polycarbonate, UV-curable horizontally oriented liquid crystal, polystyrene resin, and polyethylene terephthalate. The liquid crystal display device of claim 1, wherein the biaxial film is made of a material selected from a group consisting of UV curable liquid crystal films, polycarbonates, polyethylene terephthalates, and polystyrenes. The liquid crystal display of claim 1, wherein the optical axis of the biaxial film is perpendicular to the light absorption axis of the first polarizing plate. The liquid crystal display of claim 1, wherein the rubbing direction of the liquid crystal panel is parallel to the light absorption axis of the first polarizing plate. The liquid crystal display of claim 1, wherein unpolarized light is incident through the first polarizing plate. The liquid crystal display of claim 1, wherein unpolarized light is incident through the second polarizing plate. The liquid crystal display device of claim 1, wherein the first insulating layer has a thickness of 1-2 μm. The method of claim 1,
A thin film transistor formed on the first substrate;
A pixel electrode formed on the first insulating layer and electrically connected to the thin film transistor through a contact hole formed in the first insulating layer;
A second insulating layer formed on the first insulating layer on which the pixel electrode is formed;
A common electrode formed on the second insulating layer;
A color filter layer and a black matrix formed on the second substrate; And
And a first alignment layer and a second alignment layer formed on the first substrate and the second substrate, respectively. A liquid crystal panel including a first substrate having a thin film transistor, a second substrate having a color filter, a liquid crystal layer formed between the first substrate and the second substrate;
A first overcoat layer formed on the second substrate, the first overcoat layer being made of a dielectric material having an A-compensation characteristic having a retardation value in a horizontal direction of Re = 40 to 160 nm to change the polarization characteristic of incident light;
A second overcoat formed on the first overcoat layer and made of a dielectric material having a c-compensation characteristic having a thickness retardation value of Rth = 40 to 200 nm to change the polarization characteristic of incident light and output the same to the first overcoat layer. layer; And
Located in the upper and lower parts of the liquid crystal panel and consists of a first polarizing plate and a second polarizing plate for polarizing the incident light,
Where Re = (n _x -n _y ) d and Rth = (n _x -n _z ) d and n _x , n _y and n _z are the refractive indices in the x-axis direction, the refractive indices in the y-axis direction and the z-axis direction, respectively. A liquid crystal display device characterized by the refractive index. The method of claim 1, wherein the first polarizing plate,
Polarizers;
Triacetyl cellulose (zero retardation TAC) having no phase difference (Rth) attached to one surface of the polarizer in contact with the liquid crystal panel; And
Liquid crystal display device comprising a triacetyl cellulose (TAC) attached to the other surface of the polarizer. The method of claim 1, wherein the second polarizing plate,
Polarizers;
Liquid crystal display device comprising triacetyl cellulose (TAC) attached to both sides of the polarizer. The liquid crystal display of claim 15, wherein the absorption axes of the first polarizing plate and the second polarizing plate are perpendicular to each other. The liquid crystal display device of claim 15, wherein the optical axis of the first overcoat layer is perpendicular to the light absorption axis of the first polarizing plate. The liquid crystal display of claim 15, wherein the rubbing direction of the liquid crystal panel is perpendicular to the light absorption axis of the first polarizing plate. The liquid crystal display of claim 15, wherein unpolarized light is incident through the first polarizing plate. The liquid crystal display of claim 15, wherein unpolarized light is incident through the second polarizing plate.

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