KR101250783B1 - Liquid crystal display device and method for fabricating the same - Google Patents

Abstract

The present invention relates to a liquid crystal display and a manufacturing method thereof, the liquid crystal display according to the present invention includes a lower substrate having a thin film transistor; An upper substrate on which a color filter layer is formed; A liquid crystal layer injected between the lower substrate and the upper substrate; A polarizing plate provided at an outer side of the lower substrate and the upper substrate; And a compensation film formed between the polarizing plate, the lower substrate, and the upper substrate, the compensation film being disposed away from the axis of the polarizing plate by a predetermined angle. The manufacturing method of the liquid crystal display according to the present invention includes: a lower portion provided with a thin film transistor Providing a substrate; Providing an upper substrate on which a color filter layer is formed; Bonding the lower substrate and the upper substrate together; Injecting a liquid crystal layer between the bonded lower substrate and the upper substrate; Forming a polarizing plate outside the lower substrate and the upper substrate; And disposing a compensation film between the polarizing plate, the lower substrate, and the upper substrate so as to deviate by a predetermined angle from the axis of the polarizing plate.

Compensation film, discotic liquid crystal axis, polarizer, contrast ratio

Description

TECHNICAL FIELD [0001] The present invention relates to a liquid crystal display device and a method of manufacturing the same,

1 is an exploded perspective view showing a part of a typical TN liquid crystal display device.

2A and 2B illustrate the operation of a typical TN liquid crystal display device.

3 is a view schematically showing a polarizing plate of a liquid crystal display according to the prior art.

4 is a view illustrating a polarizing plate axis, a discotic liquid crystal axis, and a rubbing axis in a TN liquid crystal display device according to the related art.

Figure 5 is a graph showing the vertical viewing angle characteristics when applying a polarizing plate of the TN liquid crystal display according to the prior art.

6 is a schematic cross-sectional view of a liquid crystal display device according to the present invention;

7 is a view schematically showing a polarizing plate structure of a liquid crystal display according to the present invention.

FIG. 8 is a diagram for explaining the principle of compensating for retardation in the TN liquid crystal display device according to the present invention; FIG.

9 is a graph showing the vertical viewing angle characteristics when applying a polarizing plate of the TN liquid crystal display according to the present invention.

10 is a graph showing the vertical viewing angle characteristics when applying a polarizing plate of the TN liquid crystal display according to the present invention.

-Code description of main parts of drawing-

111: lower substrate 113: gate electrode

115: gate insulating film 117: semiconductor layer

119 source electrode 121 drain electrode

123: protective film 125: pixel electrode

127: first alignment layer 131: upper substrate

133: black matrix 135: color filter layer

137: common electrode 139: second alignment layer

141: liquid crystal layer 151: first polarizing plate

153: first compensation film 161: second polarizing plate

163: second compensation film

The present invention relates to a liquid crystal display device and a method of manufacturing the same, and more particularly, by changing the axial angle of the compensation film of the TN liquid crystal display device to reduce the phase delay generated in the black mode to improve the contrast ratio (contrast ratio). The present invention relates to a liquid crystal display device and a method of manufacturing the same.

In general, the driving principle of the liquid crystal display device uses the optical anisotropy and polarization of the liquid crystal. Since the liquid crystal has a long structure, it has a directionality in the arrangement of molecules, and the direction of the molecular arrangement can be controlled by artificially applying an electric field to the liquid crystal.

Accordingly, when the molecular arrangement direction of the liquid crystal is arbitrarily adjusted, the molecular arrangement of the liquid crystal is changed, and light polarized by optical anisotropy may be arbitrarily modulated to express image information.

Such liquid crystals may be classified into positive liquid crystals having positive dielectric anisotropy and negative liquid crystals having negative dielectric anisotropy according to the electrical characteristics. The liquid crystal molecules having positive dielectric anisotropy have long axes of liquid crystal molecules in a direction in which an electric field is applied. The liquid crystal molecules arranged in parallel and having negative dielectric anisotropy are arranged perpendicularly to the direction in which the electric field is applied and the major axis of the liquid crystal molecules.

Currently, active matrix LCDs (AMLCDs) in which thin film transistors and pixel electrodes connected to the thin film transistors are arranged in a matrix manner have attracted the most attention due to their excellent resolution and video performance.

In this regard, the structure of a liquid crystal display panel constituting a general liquid crystal display device will be described with reference to FIG. 1.

1 is an exploded perspective view showing a part of a general TN liquid crystal display device.

Referring to FIG. 1, a general liquid crystal display includes a color filter 7 including a black matrix 5 and a sub-color filter (red, green, blue) 9 and a common electrode 19 transparent on the color filter 7. ) Is formed of an upper substrate (3) formed thereon, and a lower substrate (21) having an array wiring including a pixel region (P), a pixel electrode (17) formed on the pixel region, and a switching element (T). The liquid crystal 14 is filled between the substrate 3 and the lower substrate 21.

The lower substrate 21 may also be an array substrate, and the thin film transistor T, which is a switching element, is positioned in a matrix type, and the gate wiring 13 and the data wiring 15 passing through the plurality of thin film transistors cross each other. ) Is formed.

In addition, the pixel area P is a region where the gate line 13 and the data line 15 cross each other. The pixel electrode 17 formed on the pixel region P uses a transparent conductive metal having a relatively high transmittance of light such as ITO.

In the liquid crystal display device configured as described above, the liquid crystal layer 14 disposed on the pixel electrode 17 is oriented by a signal applied from the thin film transistor T, and the liquid crystal layer 14 is oriented according to the degree of alignment of the liquid crystal layer. The image may be expressed by controlling the amount of light passing through the liquid crystal layer 14.

The liquid crystal display device described above drives liquid crystal by an electric field applied up and down through the common electrode 19 and the pixel electrode 17, and has excellent characteristics such as transmittance and aperture ratio. The electrode serves as a ground to prevent destruction of the liquid crystal cell due to static electricity.

2A and 2B illustrate an operation of the liquid crystal 14 when voltage is applied to the TN liquid crystal display panel, and FIG. 2A is a view showing a liquid crystal array of the TN liquid crystal panel when no voltage is applied. Here, reference numerals 23 and 25 denote alignment layers, and reference numerals 31 and 41 denote polarizing plates.

Referring to FIG. 2A, when no voltage is applied to the pixel electrode 17 and the common electrode 19 of the liquid crystal display of the TN mode, the liquid crystal 14 has positive dielectric anisotropy and is planar from the alignment direction. As seen from above, the upper and lower liquid crystals have a horizontal arrangement in which they are twisted at 90 degrees.

2B is a diagram showing an arrangement state of liquid crystal molecules when a voltage is applied to the upper and lower substrates.

Referring to FIG. 2B, when voltage V is applied to the pixel electrode 17 and the common electrode 19 of the TN mode liquid crystal display, the liquid crystal molecules 14 twisted at 90 ° are rearranged in the direction of the electric field. The extreme value of the liquid crystal molecules is approximately 90 °.

Accordingly, there is a problem in that the contrast ratio (C / R) and the luminance change depending on the viewing angle become severe, and thus the wide viewing angle cannot be realized.

In this regard, the TN liquid crystal display according to the related art will be described with reference to FIGS. 3 to 5 as follows.

3 is a view schematically showing a polarizing plate of a liquid crystal display according to the prior art.

4 is a view illustrating a polarizing plate axis, a discotic liquid crystal axis, and a rubbing axis in a TN liquid crystal display device according to the related art.

5 is a graph showing the vertical viewing angle characteristics when applying a polarizing plate of the TN liquid crystal display according to the prior art.

Since the liquid crystal display of the TN mode according to the prior art is normally configured in the white mode, the black mode having a large influence on the contrast ratio is implemented under an electric field. do. At this time, the liquid crystal direction inside the cell is not perpendicularly perpendicular by the electric field, but is slightly inclined downward due to the influence of the surface energy and the rubbing direction of the alignment layer.

Referring to FIGS. 3 and 4, the liquid crystal display according to the related art is a state in which liquid crystals are not inclined vertically but lie slightly inclined in the cell, and have polarization plates 31 and 41 axes and discotics with respect to the upper and lower substrates. It consists of a structure in which the liquid crystal axis and the rubbing axis are matched.

Therefore, if the axes of the polarizing plates 31 and 41 and the axes of the compensation film 43 coincide with each other, retardation does not occur at the front side, thereby compensating for the retardation of the cells generated at the front side. can not do it.

As a result, the structural characteristics of the cell are shown in black luminance as it is, and as shown in "A" of FIG. 5, the highest contrast ratio appears at about 5 degrees near the lower field of view than the front.

Therefore, due to the structural problem of the cell of the conventional TN mode, there is a problem in that the luminance is increased due to phase delay in black.

Accordingly, the present invention has been made to solve the above problems of the prior art, by changing the axis of the compensation film in the polarizer to phase retardation in black caused by structural problems in the liquid crystal display of the TN mode It is an object of the present invention to provide a liquid crystal display device and a method of manufacturing the same, which can increase the contrast ratio by reducing the front phase delay.

According to an aspect of the present invention, a liquid crystal display device includes: a lower substrate having a thin film transistor; An upper substrate on which a color filter layer is formed; A liquid crystal layer injected between the lower substrate and the upper substrate; A polarizing plate provided at an outer side of the lower substrate and the upper substrate; And a compensation film formed between the polarizing plate, the lower substrate, and the upper substrate, and disposed to be offset by a predetermined angle from the axis of the polarizing plate.

According to an aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device, including: providing a lower substrate having a thin film transistor; Providing an upper substrate on which a color filter layer is formed; Bonding the lower substrate and the upper substrate together; Injecting a liquid crystal layer between the bonded lower substrate and the upper substrate; Forming a polarizing plate outside the lower substrate and the upper substrate; And arranging a compensation film between the polarizing plate, the lower substrate, and the upper substrate so as to deviate by a predetermined angle from the axis of the polarizing plate.

Hereinafter, a liquid crystal display and a manufacturing method thereof according to the present invention will be described in detail with reference to the accompanying drawings.

6 is a view schematically showing a polarizing plate of a liquid crystal display according to the present invention.

Referring to FIG. 6, the liquid crystal display of the TN mode according to the present invention includes a gate line (not shown) formed in one direction on the lower substrate 111, a gate electrode 113 protruding from the gate line, and the gate. A gate insulating film 115 formed on the entire surface of the lower substrate 111 including the electrode 113, a semiconductor layer 117 formed on the gate insulating film 115 above the gate electrode 113, and the semiconductor layer ( Source / drain electrodes 119 and 121 and data lines (not shown) formed on both sides of the 117 through an ohmic contact layer (not shown), and contact holes on the drain electrode 121 are provided on the lower portion. A passivation layer 123 formed on the substrate 111, a pixel electrode 125 formed on the passivation layer 123 to be electrically connected to the drain electrode 121 through the contact hole, and the pixel electrode 125. And a first alignment layer 127 rubbed in a horizontal or vertical direction.

The gate electrode 113, the gate insulating layer 115, the semiconductor layer 117, and the source / drain electrodes 119 and 121 form a thin film transistor.

On the other hand, the black matrix 133 to prevent light leakage to the gate line (not shown), the data line (not shown) and the thin film transistor (not shown) on the upper substrate 131 facing the lower substrate 111. And a color filter 135 for realizing R, G, and B colors on the black matrix 133, a common electrode 137 formed on the color filter 135, and a color on the common electrode 137. The second alignment layer 139 rubbed in a horizontal or vertical direction orthogonal to the rubbing direction of the first alignment layer 127 and a liquid crystal layer 141 formed between the two substrates.

In addition, first and second polarizers 151 and 161 in which first and second polarizers are formed in a rubbing direction of the first and alignment layers 127 and 139 are disposed outside the upper and lower substrates, respectively. Here, first and second compensation films 153 and 163 are disposed between the first and second polarizers 151 and 161 and the lower and upper substrates 111 and 131, respectively. In this case, each of the first and second compensation films 153 and 163 may be disposed to deviate by a predetermined angle from the axes of the first and second polarizing plates 151 and 161.

Although not shown in the drawings, a spacer formed to maintain a constant cell gap between the lower substrate 111 and the upper substrate 131, and a seal member formed at an edge of the two substrates to bond the two substrates. City).

In the liquid crystal display device according to the present invention configured as described above, the configuration of the polarizing plate and the compensation film will be described in detail with reference to the accompanying drawings. Here, the polarizing plate 151 and the compensation film 153 will be described as an example.

7 is a view schematically showing a polarizing plate structure of a liquid crystal display according to the present invention.

The liquid crystal display of the TN mode according to the present invention is normally configured in a white mode, so that a black mode having a large influence on the contrast ratio is implemented under an electric field. . At this time, the liquid crystal direction inside the liquid crystal cell is not vertically corrected by the electric field, but is slightly inclined downward due to the influence of the surface energy and the rubbing direction of the alignment layer.

6 and 7, the polarizing plate of the liquid crystal display according to the present invention is composed of a polarizer 151 and a compensation film 153. In the present invention, the phase delay that occurs due to the structural problem of the conventional TN mode. In order to eliminate the, the axis of the compensation film 153, 163 is disposed to deviate from the axis of the existing polarizing plate 151 by about 0.5 to 1.5 degrees. In particular, the axis of the compensation film 153 is disposed so as to match the axis of the liquid crystal, not to match the axis of the polarizing plate 151. At this time, the axis of the polarizing plate 151 is matched with the rubbing axis.

In this way, the retardation is formed in the compensation films 153 and 163 to compensate for the retardation generated in the liquid crystal cell.

The principle of retardation compensation as described above will be described with reference to FIGS. 8 and 9.

8 is a view illustrating an average director axis of a liquid crystal and an axis of a compensation film in the TN liquid crystal display device according to the present invention.

9 is a graph showing the vertical viewing angle characteristics when applying a polarizing plate of the TN liquid crystal display according to the present invention.

As shown in FIG. 8, the liquid crystal cell of the TN mode is slightly inclined downward when an electric field is applied. Thus, when the liquid crystal cell is standing in front of the liquid crystal cell, the overall arrangement of the liquid crystal is the axis of the polarizing plate. Does not match

In addition, the compensation film should be a symmetrical structure with the liquid crystal in the liquid crystal panel, so if the axis of the compensation film is arranged in the same direction as the direction of the liquid crystal cell, it can compensate for retardation occurring in the liquid crystal cell. have.

Therefore, when the axis of the compensation film is changed by a certain angle, as shown in the "B" of FIG. 9, the results of the simulation (simulation), the contrast ratio (C / R; In addition, it can be seen that the distribution of the contrast ratio (C / R) according to the vertical viewing angle is symmetrical.

As described above, the liquid crystal display according to the present invention and the manufacturing method thereof have the following effects.

According to the liquid crystal display device and the manufacturing method thereof according to the present invention, the phase delay in black caused by structural problems in the liquid crystal display device of the TN mode is changed by changing the axis of the compensation film in the polarizing plate. By increasing the contrast ratio can be increased.

On the other hand, while described above with reference to a preferred embodiment of the present invention, those skilled in the art various modifications of the present invention without departing from the spirit and scope of the invention described in the claims below And can be changed.

Claims (8)

A lower substrate having a thin film transistor; An upper substrate on which a color filter layer is formed; A liquid crystal layer injected between the lower substrate and the upper substrate; A polarizing plate provided at an outer side of the lower substrate and the upper substrate; And a compensation film formed between the polarizing plate, the lower substrate, and the upper substrate, and disposed to be offset by a predetermined angle from the axis of the polarizing plate; And the axis of the compensation film is aligned with an average director axis of liquid crystals in the liquid crystal layer. The liquid crystal display device according to claim 1, wherein the axis of the compensation film is disposed away from the axis of the polarizing plate by 0.5 to 1.5 degrees. delete The liquid crystal display of claim 1, wherein an axis of the polarizing plate is coincident with a rubbing axis. Providing a lower substrate having a thin film transistor; Providing an upper substrate on which a color filter layer is formed; Bonding the lower substrate and the upper substrate together; Injecting a liquid crystal layer between the bonded lower substrate and the upper substrate; Forming a polarizing plate outside the lower substrate and the upper substrate; And And disposing a compensation film between the polarizing plate, the lower substrate, and the upper substrate so as to deviate by a predetermined angle from the axis of the polarizing plate. Wherein the axis of the compensation film is aligned with an average director axis of liquid crystals in the liquid crystal layer. The method of claim 5, wherein an axis of the compensating film is disposed away from an axis of the polarizing plate by about 0.5 degrees to about 1.5 degrees. delete The method of claim 5, wherein the axis of the polarizing plate coincides with the rubbing axis.

Images