KR20050005670A - Liquid crystal display - Google Patents

Abstract

PURPOSE: An LCD(Liquid Crystal Display) is provided to improve lateral visibility by generating half tone effect through rendering driving of pixels, and to improve brightness by forming cutting patterns in pixels of which white pixels and green pixels are larger than red pixels and blue pixels in a size of the cutting pattern. CONSTITUTION: A plurality of red pixels(R), green pixels(G), blue pixels(B), and white pixels(W) are arranged in a predetermined type. Each of red pixels, green pixels, blue pixels, and white pixels have a large sized cutting pattern. Herein, the green pixels and the white pixels are larger than the red pixels and the blue pixels in a size of the cutting pattern. respective red pixels, green pixels, blue pixels, and white pixels are displayed by rendering driving.

Description

Liquid crystal display

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device in a vertical aligned mode (VA mode).

The liquid crystal display is one of the most widely used flat panel display devices. The liquid crystal display includes two display panels on which a field generating electrode is formed and a liquid crystal layer interposed therebetween. It is a display device which controls the transmittance | permeability of the light which passes through a liquid crystal layer by rearranging.

Among the liquid crystal display devices, a field generating electrode is provided in each of two display panels. Among them, a liquid crystal display device having a structure in which a plurality of pixel electrodes are arranged in a matrix form on one display panel and one common electrode covering the entire display panel on the other display panel is mainstream. The display of an image in this liquid crystal display device is performed by applying a separate voltage to each pixel electrode. To this end, a thin film transistor, which is a three-terminal element for switching a voltage applied to a pixel electrode, is connected to each pixel electrode, and a gate line for transmitting a signal for controlling the thin film transistor and a data line for transmitting a voltage to be applied to the pixel electrode are provided. Install on the display panel.

However, in the VA mode (Vertical aligned mode) liquid crystal display, the γ curves of the front and side are different from each other, so that the viewing angle and the side visibility are poor. In order to overcome these disadvantages, various methods for widening the viewing angle have been developed. Among them, liquid crystal molecules are oriented vertically with respect to the upper and lower substrates, and a method of forming a constant incision pattern or protrusion on the pixel electrode and the common electrode opposite thereto is performed. This is becoming potent. In this case, when the angle formed between the lower substrate and the long axis of the liquid crystal lying obliquely is called a tilt angle, the inclination angles of the liquid crystal molecules in the different domains divided by the incision pattern or the projection for the same applied voltage are the same. There is a problem in the side visibility due to the low compensation rate of the optical characteristics.

Accordingly, to solve this problem, a technique of dividing a pixel area into a plurality of sub pixel areas and applying a voltage differentially to each of the sub pixel areas has been developed. At this time, different VT curves, that is, relationship curves of transmittance to applied voltage, are mixed to show a continuous distribution of the inclination angles of the liquid crystal molecules when viewed from the side. The difference is reduced.

Therefore, a half tone phenomenon in which the optical characteristics of the two sub pixel regions are effectively compensated for each other occurs, thereby improving side visibility and widening the viewing angle.

In addition, a method of lowering cell retardation of a liquid crystal display device has been proposed to solve the problem of side visibility.

However, this method can improve the visibility of the side, but has the disadvantage of reducing the aperture ratio.

An object of the present invention is to provide a liquid crystal display device having improved luminance and side visibility.

1 is a diagram illustrating a pixel array structure of a liquid crystal display according to an exemplary embodiment of the present invention.

2 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a relation curve of transmittance with respect to an applied voltage,

4 is a diagram illustrating rendering a liquid crystal display according to an exemplary embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

R: red pixel G: green pixel

B: blue pixel W: white pixel

A liquid crystal display device according to the present invention is a liquid crystal display device in which red pixels, green pixels, blue pixels, and white pixels are arranged in a predetermined order, wherein dots consisting of red pixels, green pixels, blue pixels, and white pixels are successively. The green pixel and the white pixel are formed with a cutout pattern having a larger aperture ratio than the red pixel and the blue pixel, and the red pixel, the green pixel, the blue pixel, and the white pixel are preferably displayed by rendering driving. .

The liquid crystal display may further include a first substrate on which a pixel electrode and a switching element are formed, a second substrate facing the first substrate and having a common electrode formed thereon, and sealed between the first substrate and the second substrate. It is preferable that the major axis | shaft of the liquid crystal molecule containing the liquid crystal substance contained in the liquid crystal substance is oriented perpendicular to the said 1st board | substrate.

In addition, it is preferable that the cutting patterns of the green and white pixels are the same, and the cutting patterns of the red and blue pixels are the same.

In addition, it is preferable that the cutting patterns of the green and white pixels have a chevron structure.

Then, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

A liquid crystal display according to an exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a pixel array structure of a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 1, in the liquid crystal display according to the exemplary embodiment, a red pixel R, a green pixel G, a blue pixel B, and a white pixel forming a dot over two pixel rows. (W) are arranged adjacent to each other. For example, the white pixels W and the red pixels R or the blue pixels B and the green pixels G are sequentially arranged in the row direction, and the white pixels W and the blue pixels in the column direction. (B) or the red pixels R and the green pixels G are sequentially arranged.

Here, the order in which the red pixels R, the green pixels G, the blue pixels B, and the white pixels W are arranged is not limited to those described above, and the transmittance of the green pixels G is different from those of the color pixels. It is preferable that the green pixel G and the white pixel W are not disposed adjacent to each other because they are high in comparison with each other.

In the pixel array structure according to the exemplary embodiment of the present invention, red pixels R, green pixels G, blue pixels B, and white pixels W formed over two pixel rows are used to display an image. It is used as the "dot" which is the basic unit.

When an image is displayed using one dot in which white pixels W, red pixels R, green pixels G, and blue pixels B are sequentially arranged in a clockwise direction as in one embodiment of the present invention, Overall light efficiency becomes high. For example, suppose that the amount of light passing through the polarizer of the thin film transistor array panel in the liquid crystal display device is "1". In the case of displaying dots with three pixels of red pixels R, green pixels G, and blue pixels B, the area of each pixel is 1/3, and the transmittance of each pixel is 1/3 by color filters. Therefore, the total transmittance of one dot is [1/3 × 1/3 (R)] + [1/3 × 1/3 (G)] + [1/3 × 1/3 (B)] = 1 / 3 = 33.3%.

However, in one embodiment of the present invention, since the area of each pixel is 1/4 and the transmittance of the white pixel W is 1, the total transmittance of one dot is [1/4 x 1/3 (R)] + [1/4 x 1/3 (G)] + [1/4 x 1/3 (B)] + [1/4 x 1/3 (W)] = 1/2 = 50%. As described above, according to the exemplary embodiment of the present invention, the luminance is about 1.5 times higher than that of the conventional liquid crystal display.

As shown in FIG. 1, the green pixel G and the white pixel W are formed with a cutout pattern 51 having a larger aperture ratio than the red pixel R and the blue pixel B. That is, the cutout pattern 51 of the green pixel G and the white pixel W has a chevron structure, and is a cutout pattern 51 having a large aperture ratio since there are few areas to be cut, and the red pixel R and the blue The cutout pattern 52 of the pixel B is a petal-shaped structure, and since there are many areas to be cut off, the cutout pattern 52 has a small aperture ratio.

The cut patterns 51 of the green pixel G and the white pixel W are the same, and the cut patterns 52 of the red pixel R and the blue pixel B are the same.

This results in the formation of an incision pattern 51 having a large aperture ratio in the green pixel G and the white pixel W having a large influence on luminance, and an aperture ratio in the red pixel R and blue pixel B having a large influence on luminance. The small incision pattern 52 is formed to improve the overall brightness of the dots.

The cutout patterns 51 and 52 are formed to overcome disadvantages of the liquid crystal display having poor viewing angle and side visibility.

That is, a viewing pattern is secured by forming incision patterns on the pixel electrode and the common electrode, respectively, and evenly dispersing the tilting direction of the liquid crystal in four directions by using a fringe field formed by the incision patterns.

In addition, by forming projections on the pixel electrode and the common electrode formed on the upper and lower substrates, the viewing angle may be secured by adjusting the lying direction of the liquid crystal molecules using an electric field distorted by the projections.

In this case, when the angle formed between the lower substrate and the long axis of the liquid crystal lying obliquely is called a tilt angle, the inclination angles of the liquid crystal molecules in the different domains divided by the incision pattern or the projection for the same applied voltage are the same. There is a problem in the side visibility due to the low compensation rate of the optical characteristics.

Accordingly, to solve this problem, a technique of dividing a pixel area into a plurality of sub pixel areas and applying a voltage differentially to each of the sub pixel areas has been developed. At this time, different VT curves, that is, relationship curves of transmittance to applied voltage, are mixed to show a continuous distribution of the inclination angles of the liquid crystal molecules when viewed from the side, and thus the front and side? The difference is reduced.

Therefore, a half tone effect is generated in which the optical characteristics of the two sub-pixel regions are effectively compensated for each other, thereby improving side visibility and widening the viewing angle.

It will be described in detail below.

When a voltage lower than the second sub-pixel region Pb is applied to the first sub-pixel region Pa of the liquid crystal display, what happens in terms of the viewing angle is normally black vertically aligned (VA) mode. Take an example.

As illustrated in FIG. 2, in the liquid crystal display device, the common electrode substrate 210 is disposed at a predetermined interval to face the thin film transistor array panel 110, and the thin film transistor array panel 110 and the common electrode substrate 210 are disposed. The liquid crystal 3 is injected in between. In addition, the color filter 250 and the overcoat film 250 are sequentially formed on the common electrode substrate 210. A common electrode 270 that forms a liquid crystal capacitor between the pixel electrode 190 of the thin film transistor array panel 110 is formed on the bottom surface of the overcoat layer 250.

Since the applied voltage is different between the first sub pixel area Pa and the second sub pixel area Pb, the inclination angles of the liquid crystal molecules positioned between the two sub pixel areas Pa and Pb are different from each other. That is, the inclination angle β2 of the liquid crystal in the second sub pixel region Pa is smaller than the inclination angle β1 of the liquid crystal in the first sub pixel region Pa. This is because a lower voltage is applied to the first sub pixel area Pa than the second sub pixel area Pb, so that the liquid crystal, which is standing vertically without the voltage applied, is slightly laid down in the first sub pixel area Pa. This is because the second sub pixel area Pa is laid down more.

Accordingly, as shown in FIG. 3, the relationship curve of the transmittance with respect to the applied voltage, that is, the V-T curve, is different from each other. Therefore, the optical characteristics of the two regions Pa and Pb are effectively compensated for each other, thereby widening the viewing angle. The same applies to the VA mode as well as the twisted nematic (TN) mode or the optical compensated bend (OCB) mode.

In one embodiment of the present invention, such a halftone effect is implemented through four-color rendering. It will be described in detail below.

Render driving means that when a specific pixel is driven to display an image having a specific shape, the specific pixel is driven by driving peripheral pixels around the specific pixel to be driven without driving only the specific pixel, and corresponding specific image. It is said to be displayed naturally. In case of rendering driving, weight of half of the weight is given to a specific pixel.

4 illustrates one embodiment of rendering driving.

As shown in FIG. 4, the green pixel G1 corresponding to the position of a specific pixel, the red pixels R1 and R2 and the green pixel G2 around the green pixel G1 are driven during the rendering driving. When the rendering driving is performed, the pixel pixels are applied only to the red pixels R1 and R2 and the green pixels G1 and G2 because the blue pixels B1 and B2 have a small effect on the resolution. That is, since the blue pixels B1 and B2 have little effect on the resolution, the red pixels R1 and R2 or the green pixels G1 and G2 are provided under the condition that the areas of the blue pixels B1 and B2 are ignored during the driving of the rendering. The pixel voltage to be applied is set and applied.

When a voltage originally applied to a specific pixel is 100% to implement a specific gray scale, a 50% voltage is applied to the green pixel G1 corresponding to the position of the specific pixel, and two red pixels R1 and R2 are applied. 16% of the voltage is applied to each pixel and 16% of the voltage is applied to the green pixel G2 to implement a specific gray scale.

In the rendering driving as described above, since the voltages applied to the pixels of the red pixel R, the green pixel G, the blue pixel B, and the white pixel W are different from each other, the transmittance with respect to the applied voltage Voltage The relationship curve of the transmission, that is, the VT curve, is different for each of the red pixel R, the green pixel G, the blue pixel B, and the white pixel W. Therefore, the optical characteristics of each pixel are effectively compensated for each other, thereby widening the viewing angle. That is, the halftone effect is realized by driving four-color rendering.

In addition, in vertical switching modes such as VA (vertically aligned) mode, electrically controllable birefringence (ECB) mode, and twisted nematic (TN) mode, changes in transmittance due to voltage do not coincide with each other and are dispersed. There is this. Due to this characteristic, a color shift phenomenon occurs between the red pixel R, the green pixel G, the blue pixel B, and the white pixel W in the vertical switching mode liquid crystal display. This problem is solved by the drive conversion of the accuracy color compensation (ACC). In the ACC driving conversion, the problem that the blue pixel B can only secure about 80% of the luminance and the red pixel R can only secure about 60% of the luminance can be solved by introducing the white pixel W. have.

Although the present invention has been described with reference to one embodiment shown in the accompanying drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Could be. Accordingly, the true scope of protection of the invention should be defined only by the appended claims.

The liquid crystal display according to the present invention improves side visibility by rendering a red pixel, a green pixel, a blue pixel, and a white pixel to generate a halftone effect, and at the same time, a white pixel and a green pixel having a large influence on luminance have an aperture ratio. There is an advantage that the luminance can be improved by forming a large incision pattern.

Claims (4)

In a liquid crystal display device in which red pixels, green pixels, blue pixels, and white pixels are arranged in a predetermined order, Dots composed of red pixels, green pixels, blue pixels, and white pixels are continuously arranged, and the green and white pixels are formed with a cutout pattern having a larger aperture ratio than the red and blue pixels. And the red, green, blue, and white pixels are displayed by rendering driving. In claim 1, The liquid crystal display device A first substrate on which a pixel electrode and a switching element are formed; A second substrate facing the first substrate and having a common electrode formed thereon; And a liquid crystal material encapsulated between the first substrate and the second substrate, wherein the liquid crystal molecules contained in the liquid crystal material have their major axes oriented perpendicular to the first substrate. In claim 2, The cutting pattern of the green pixel and the white pixel are the same, and the cutting pattern of the red pixel and the blue pixel are the same. In claim 3, The cutout pattern of the green pixel and the white pixel has a chevron structure.