KR20060129811A - Liquid crystal display - Google Patents

Abstract

An LCD is provided to use a lateral field between pixel electrodes like a fringe field, thereby improving the transmittance and enhancing the brightness, by arranging pixel electrodes such that a boundary between neighboring pixel electrodes forms a predetermined angle with respect to a gate line. Gate lines(120) and data lines(160) are arranged in row and column directions, respectively, above a first substrate. Pixel electrodes(180) are formed above the first substrate, wherein each of the pixel electrodes has first opening patterns(190a). A second substrate is opposite to the first substrate. Liquid crystal molecules are injected between the first substrate and the second substrate. A common electrode is formed above the second substrate. The common electrode has second opening patterns(200a) for division-aligning the liquid crystal molecules together with the first opening patterns. The pixel electrodes are divided in the row direction by the data lines. Each boundary for dividing the pixel electrodes in the column direction forms a predetermined angle with respect to the gate lines.

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY}

1 is a plan view of a liquid crystal display according to an exemplary embodiment of the present invention;

FIG. 2 is an enlarged view of only one pixel electrode of FIG. 1; FIG.

3 is a plan view of a liquid crystal display according to another exemplary embodiment of the present invention.

♧ explanation of the reference numerals for the main parts of the drawing.

100: thin film transistor substrate 120: gate line (first gate line)

130: second gate line 140: common line

160: data line 180: pixel electrode

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly to a liquid crystal display (LCD) having a high transmittance vertical alignment (VA).

In general, a liquid crystal display device injects a liquid crystal material between an upper substrate on which a common electrode, a color filter, and the like are formed, and a lower substrate on which a thin film transistor and a pixel electrode are formed. By applying a different potential to form an electric field to change the arrangement of the liquid crystal molecules, and through this to control the light transmittance is a device that represents the image.

The LCD has a narrow viewing angle, and various methods for improving the LCD have been proposed. There is a method of aligning the liquid crystal molecules perpendicular to the upper and lower substrates and forming a predetermined opening pattern or forming projections on the pixel electrode and the common electrode which is the opposite electrode. In the case of the patterned vertical alignment (PVA) mode in which an opening pattern is formed and using the same, an opening pattern is formed in each of the pixel electrode and the common electrode, and the lying direction of the liquid crystal molecules is determined by using a fringe field formed by the opening patterns. It is a way to widen the viewing angle by adjusting.

In the PVA mode, the number of aperture patterns is determined by the size of each pixel suitable for the resolution. This is the optimum spacing between the opening patterns is already determined according to the driving conditions, and generally 20 to 25 mu m. The opening pattern shape of the PVA mode generally has the shape of a chevron. An advantage of the opening pattern is that the number of the opening patterns can be adjusted while keeping the spacing between the opening patterns constant regardless of the pixel size.

However, despite these advantages of PVA, sufficient transmittance could not be obtained when the liquid crystal molecules were controlled only by the fringe field in the pixel electrode. That is, in the case of the conventional PVA structure, there is a problem in that the so-called lateral field direction between the pixel electrodes does not contribute to the transmittance because the long axis of the liquid crystal molecules controls the long axis of the liquid crystal molecules in the polarization axis direction or the direction perpendicular thereto.

The present invention has been proposed in consideration of the above-mentioned situation, and an object of the present invention is to provide a liquid crystal display device having improved transmittance.

In order to achieve the above object, the present invention provides a liquid crystal display device using a lateral field generated between pixel electrodes. A liquid crystal display according to an exemplary embodiment of the present invention includes a first substrate having a gate line and a data line arranged in a row direction and a column direction, a pixel electrode formed on the first substrate, and having a first opening pattern. A second substrate facing the first substrate, a liquid crystal material injected between the first substrate and the second substrate and including liquid crystal molecules, and formed on the second substrate and forming the plurality of liquid crystal molecules together with the first opening pattern; And a common electrode having a second opening pattern that is dividedly oriented into a region, wherein the pixel electrode is divided in a row direction by data lines arranged in the column direction, and a boundary separating the pixel electrode in a column direction is formed in the gate. It is characterized by forming a predetermined angle with the line.

A predetermined angle formed by a boundary that separates the pixel electrode in the column direction from the gate line may be 45 degrees, and the gate line may be formed of a low resistance metal.

Therefore, in the related art, the lateral field generated between the pixel electrodes has an undesirable effect on the pixel electrode, but in the liquid crystal display according to the exemplary embodiment of the present invention, the lateral field is defined as the pixel electrode. It can be used like a fringe field occurring within. A fringe field is formed in the aperture pattern to divide and align the liquid crystal molecules in the pixel electrode into a plurality of regions. By using the lateral field as a fringe field in this manner, the area of the liquid crystal molecules that are dividedly oriented is expanded, thereby improving transmittance and luminance.

In the present invention, the gate line passes under the pixel electrode, which may cause a problem such as a load or a signal delay on each terminal. However, in a substrate using two thin film transistors for one pixel electrode, a gate line passes under the pixel electrode, but this is not a problem. In addition, the gate line can be formed by using a low resistance metal, thereby eliminating the problem.

The pixel electrode may be an equilateral trapezoid. In this case, the equilateral trapezoidal pixel electrode is divided into a first rectangular region including a shorter side of two parallel sides and a second triangular region above and below the first region, and the first opening pattern formed in the first region It may be wing-shaped.

The wing-shaped first opening pattern may be two or more, and the first opening pattern and the second opening pattern are alternately positioned. In this case, an interval between the first opening pattern and the second opening pattern in the first region may be different from an interval between the first opening pattern and the second opening pattern in the second region. Preferably, the interval between the first opening pattern and the second opening pattern in the first region is 20 to 25 μm, but the interval between the first opening pattern and the second opening pattern in the second region is 20 to 40 μm. Can be wider.

In the first region of the pixel electrode, only the fringe field is affected. In the second region, not only the fringe field but also the lateral field is affected. The luminance may be higher than one region. In addition, in the second region affected by the lateral field, the distance between the first opening pattern and the second opening pattern may be wider than that of the first region, thereby helping to increase the aperture ratio.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed subject matter is thorough and complete, and that the spirit of the present invention to those skilled in the art will fully convey.

In the embodiments of the present specification, terms such as first and second are used to describe various regions and the like, but these regions and the like should not be limited by these terms. Also, these terms are only used to distinguish one predetermined region or the like from another region. In the drawings, the width and length of each component may be exaggerated for clarity. Furthermore, where it is mentioned that a layer (or film) is on or above another layer (or film) or substrate, it can be formed directly on another layer (or film) or substrate or between the third A layer may be interposed. The same reference numerals throughout the specification represent the same components.

1 is a plan view of a liquid crystal display according to an exemplary embodiment of the present invention, and schematically illustrates a thin film transistor substrate.

Referring to FIG. 1, a gate line 120 and a common line 140 are formed in a row direction on the thin film transistor substrate 100. The common line 140 refers to a storage capacitor wiring. The storage capacitor may be formed by extending the gate line 120 under the pixel electrode 180 without forming the common line 140. The illustration of the thin film transistor is omitted. The data line 160 is formed in the column direction. Although not shown, a shielding layer of the same component as the pixel electrode 180 may be further formed on the data line 160. The pixel electrode 180 is formed on the common line 140.

In the related art, since the pixel electrode is formed in a region separated by the intersection of the gate line 120 and the data line 160, the pixel electrode has a rectangular shape, and the pixel electrode is formed by the gate line 120 and the data line 160. This was separated.

However, the pixel electrode 180 according to the exemplary embodiment of the present invention has an equilateral trapezoid. Accordingly, the pixel electrode 180 is divided in the row direction by the data line 160, but not in the column direction by the gate line 120. This is because the gate line 120 passes under the pixel electrode 180.

The pixel electrode 180 is divided into a rectangular first region 180a including a short side of two parallel sides of an equilateral trapezoid and a triangular second region 180b disposed above and below the first region 180a. Therefore, two second regions 180b are formed with respect to one pixel electrode 180.

In one embodiment of the present invention, the pixel electrode 180 is an equilateral trapezoid, but does not necessarily have to be an equilateral trapezoid. Two pixel electrodes 180 adjacent to each other in the column direction are not separated by the gate line 120, and a boundary between the two pixel electrodes 180 may be formed at a predetermined angle with the gate line 120.

Conventionally, the pixel electrode is divided by the gate line 120, so that the alignment of liquid crystal molecules positioned on the pixel electrodes on both sides of the gate line 120 by a lateral field formed by the gate line 120. It had a very bad effect on. However, in the liquid crystal display according to the exemplary embodiment of the present invention, such a lateral field may be used as a fringe field used for preferred alignment of liquid crystal molecules, thereby improving transmittance. It looks at in detail with reference to FIG.

FIG. 2 is an enlarged view illustrating only one pixel electrode of FIG. 1.

Referring to FIG. 2, the pixel electrode 180 is divided into a rectangular first region 180a and a triangular second region 180b above and below the first region. A wing-shaped first opening pattern 190a is formed in the first region 180a. The second opening pattern 200a is formed on a common electrode (not shown) of the color filter substrate facing the first region 180a. A fringe field is formed in the first opening pattern 190a and the second opening pattern 200a positioned in the first region 180b of the pixel electrode 180 to divide and align the liquid crystal molecules into a plurality of regions. Done. That is, these opening patterns serve as a means for regulating the area of the liquid crystal molecules, and the wide viewing angle is realized by these opening patterns.

The first opening pattern 190b is also formed in the triangular second region 180b. The second opening pattern 200b is formed on a common electrode (not shown) of the color filter substrate facing the second region 180b. In the second region 180b, a fringe field is formed by the first and second opening patterns 190b and 200b like the first region 180a. In addition, unlike the first region 180a, the second region 180b is affected by a lateral field with adjacent pixel electrodes. An arrow pointing in both directions illustrated in the second area 180b is affected by the lateral field. This lateral field is formed because the adjacent pixel electrodes 180 have opposite polarities. Therefore, in the second region 180b, the distance d between the first opening pattern 190b and the second opening pattern 200b may be larger than the first region 180a. As a result, the aperture ratio also increases.

3 is a plan view of a liquid crystal display according to another exemplary embodiment, and illustrates a substrate on which two thin film transistors are formed for one pixel electrode.

Referring to FIG. 3, two gate lines, that is, the first gate line 120, the second gate line 130, and the common line 140 are formed in the horizontal direction. The positions of the first and second gate lines 120 and 130 and the common line 140 may be changed. Although not shown, there are two thin film transistors for one pixel electrode 180.

The reason why two thin film transistors are used for one pixel electrode is to secure side visibility. In the multi-domain liquid crystal display, the gradation inversion reference viewing angle defined by a contrast ratio reference viewing angle based on a contrast ratio of 1:10 or a limit angle of luminance inversion between gradations is excellent at 80 degrees or more in all directions. However, distortion of the lateral gamma curve, which does not coincide with the gamma curve of the front side and the side of the lateral gamma curve, is generated, resulting in inferior visibility from the left and right sides, even when compared to a TN (twisted nematic) mode liquid crystal display. In the PVA mode, which forms an opening pattern by domain dividing and regulating means, the screen looks brighter toward the side and the color tends to shift toward white, and in severe cases, there is no gap between bright gradations and the picture looks clumped. It also happens. Recently, as the liquid crystal display device is used for multimedia, the visibility of the picture or the video is increased, and the visibility becomes more and more important. The pixel electrode is divided into two regions using two thin film transistors for one pixel electrode. When different voltages are applied by dividing, it is possible to secure the side visibility while preventing the decrease of luminance and blurring of characters.

An equilateral trapezoidal pixel electrode as an embodiment of the present invention can be applied to such a visible structure. Therefore, not only visibility but also high transmittance can be ensured.

On the other hand, in the detailed description of the present invention has been described with respect to specific embodiments, various modifications are of course possible without departing from the scope of the invention. As in the above embodiment, the present invention can be applied not only to a PVA liquid crystal display using two thin film transistors but also to a PVA liquid crystal display having a coupling capacitor structure.

Therefore, the scope of the present invention should not be limited to the above-described embodiments, but should be defined not only by the claims below but also by the equivalents of the claims of the present invention.

According to the present invention described above, a high transmittance and luminance can be obtained by using a lateral field like a fringe field, which has a bad effect on dividing liquid crystal molecules into a plurality of regions (multi-domains). Not only that, but also the aperture ratio increases.

Claims (8)

A first substrate having a gate line and a data line arranged in a row direction and a column direction, respectively; A pixel electrode formed on the first substrate and having a first opening pattern; A second substrate facing the first substrate; A liquid crystal material injected between the first substrate and the second substrate and including liquid crystal molecules; And And a common electrode formed on the second substrate and having a second opening pattern which divides and aligns the liquid crystal molecules into a plurality of regions together with the first opening pattern. And the pixel electrode is divided in a row direction by data lines arranged in the column direction, and a boundary that divides the pixel electrode in a column direction forms a predetermined angle with the gate line. The method of claim 1, And a predetermined angle between a boundary of dividing the pixel electrode in a column direction from the gate line is 45 degrees. The method of claim 1, And the gate line is formed of a low resistance metal. The method according to any one of claims 1 to 3, The pixel electrode is an equilateral trapezoid. The method of claim 4, wherein The equilateral trapezoidal pixel electrode is divided into a rectangular first region including a shorter side of two parallel sides and a triangular second region above and below the first region, The first opening pattern formed in the first region is a wing shape. The method of claim 5, The wing-shaped first opening pattern may be two or more, and the first opening pattern and the second opening pattern are alternately positioned. The method of claim 5, The interval between the first opening pattern and the second opening pattern in the first region and the interval between the first opening pattern and the second opening pattern in the second region are different. The method of claim 7, wherein The distance between the first opening pattern and the second opening pattern in the second area is 20 to 40 μm.

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