KR20080021381A - Liquid crystal display - Google Patents

Abstract

An LCD(Liquid Crystal Display) is provided to prevent gray inversion of blue pixels while using RGB pigments without affecting the luminance and response speed of the LCD. An LCD(200) includes red, green and blue sub-pixels(R,G,B), common electrodes(300) and pixel electrodes(310). The common electrodes and the pixel electrodes respectively correspond to the red, green and blue sub-pixels and drive liquid crystal. The distance between the common electrode and the pixel electrode corresponding to the blue sub-pixel is different from the difference between the common electrode and the pixel electrode corresponding to the red sub-pixel and the difference between the common electrode and the pixel electrode corresponding to the green sub-pixel.

Description

Liquid crystal display device

1 is a schematic cross-sectional view showing a conventional transverse electric field liquid crystal display device.

2A to 2B are diagrams illustrating phase transitions of liquid crystals when voltages are turned on and off in the transverse electric field mode.

3 is a view showing transmittance characteristics according to voltage of a conventional transverse electric field liquid crystal display device.

4 is a schematic cross-sectional view showing a transverse electric field liquid crystal display device of the present invention.

5 is a plan view showing a transverse electric field liquid crystal display device of the present invention.

* Description of the Signs of the Major Parts of the Drawings *

200: liquid crystal panel 230: gate line

240: data line 250: thin film transistor

260: gate electrode 270: semiconductor layer

280: source electrode 290: drain electrode

300: common electrode 310: pixel electrode

320: common line 330: pixel electrode line

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a transverse electric field liquid crystal display device capable of preventing gray inversion of a blue pixel by increasing a distance between electrodes of a blue pixel.

Recently, with the development of various portable electronic devices such as mobile phones, PDAs, and notebook computers, there is an increasing demand for flat panel display devices of small and thin sizes that can be applied thereto. Such flat panel displays are being actively researched, such as LCD (Liquid Crystal Display), PDP (Plasma Display Panel), FED (Field Emission Display), and VFD (Vacuum Fluorescent Display). Liquid crystal display devices (LCDs) are in the spotlight for their implementation.

Such liquid crystal display devices have various display modes, such as twisted nematic (TN) mode, in-plane switching (IPS) mode, and vertical alignment (VA) mode, depending on the arrangement of liquid crystal molecules. A display element is to align liquid crystal molecules in a plane by forming at least a pair of electrodes arranged in parallel in a pixel to form a transverse electric field substantially parallel to the substrate.

In the transverse electric field liquid crystal display, a pixel electrode and a common electrode are formed in parallel. An advantage of the transverse electric field liquid crystal display device is that a wide viewing angle is possible. When viewed from the front, the liquid crystal display device can be seen from about 70 ° in the up / down / left / right directions. In addition, there is an advantage that the manufacturing process is simpler and the color shift according to the viewing angle is smaller than that of the liquid crystal display device.

Hereinafter, a conventional transverse electric field liquid crystal display device will be described with reference to the accompanying drawings.

1 is a schematic cross-sectional view showing a conventional transverse electric field liquid crystal display device.

As shown in FIG. 1, the pixel electrode 12 and the common electrode 13 are formed on the lower substrate 11 on the same plane. The liquid crystal layer 14 formed between the lower substrate 11 and the upper substrate 15 bonded to each other with a predetermined space is formed by a transverse electric field between the pixel electrode 12 and the common electrode 13 on the lower substrate 11. Works.

2A to 2B are diagrams illustrating phase transitions of liquid crystals when voltages are turned on and off in the transverse electric field mode.

That is, FIG. 2A shows an off state in which no transverse electric field is applied to the pixel electrode 12 or the common electrode 13, so that the phase change of the liquid crystal layer 14 does not occur. For example, the image of the liquid crystal layer 14 layer is basically 45 ° in the horizontal direction of the pixel electrode 12 and the common electrode 13. FIG. 2B illustrates an on state in which a lateral electric field is applied to the pixel electrode 12 and the common electrode 13, and a phase shift of the liquid crystal layer 14 occurs, and is about 45 ° compared to the off state of FIG. 2A. With an angle, it can be seen that the horizontal direction of the pixel electrode 12 and the common electrode 13 coincide with the twist direction of the liquid crystal.

However, when a voltage is applied to the liquid crystal of the transverse electric field liquid crystal display device and varies, as can be seen from the characteristic graph of FIG. 3, it can be seen that the color characteristic difference in gray is large and the blue pixel is large. It can be seen that the transmittance of saturates at a lower voltage than that of the red and green pixels.

An object of the present invention is to provide a transverse electric field liquid crystal display device capable of preventing gray inversion of a blue pixel by increasing an interval between electrodes of a blue pixel.

The liquid crystal display of the present invention comprises red, green and blue subpixels; And a common electrode and a pixel electrode formed on each of the red, green, and blue sub-pixels to drive the liquid crystal, and the spacing between the common electrode and the pixel electrode of the blue sub-pixel is different from the sub-pixels of different colors.

The liquid crystal display of the present invention is characterized in that the spacing between the common electrode and the pixel electrode of the blue subpixel is larger than that of the subpixels of different colors.

In the liquid crystal display of the present invention, the spacing between the common electrode and the pixel electrode of the sub-pixels of different colors is the same.

In the liquid crystal display device of the present invention, the widths of the pixel electrodes of the sub-pixels are the same.

In the liquid crystal display of the present invention, the widths of the common electrodes of the sub-pixels are the same.

Hereinafter, the transverse electric field liquid crystal display device of the present invention will be described with reference to the accompanying drawings.

4 is a schematic cross-sectional view showing a transverse electric field liquid crystal display device of the present invention.

As illustrated in FIG. 4, the pixel electrode 120 and the common electrode 130 are formed in parallel on the lower substrate 110 of each sub-pixel, and the red, green, and blue color filter layers are formed on the upper substrate 150. 160) is formed. The liquid crystal layer 140 formed between the lower substrate 110 and the upper substrate 150 bonded to the lower substrate 110 is operated by a transverse electric field between the pixel electrode 120 and the common electrode 130 on the lower substrate 110. do.

In particular, the distance between the pixel electrode 120 and the common electrode 130 of the blue subpixel formed on the blue color filter layer 160 is larger than other colors. The interval between the pixel electrode 120 and the common electrode 130 corresponding to the red subpixel and the green subpixel in the color filter 160 layer is the same.

In the transverse electric field liquid crystal display device of the present invention, the threshold voltage driving the liquid crystal may be expressed by the following equation.

Where K is the elastic modulus, Δε is the dielectric anisotropy, I is the electrode spacing, g is the viscosity, and d is the cell gap.

As can be seen from the above expression, in the transverse electric field liquid crystal display device of the present invention, the threshold voltage V of blue increases as the distance I between the electrodes of blue increases.

Therefore, the blue of the transverse electric field liquid crystal display device of the present invention is saturated at a higher voltage, thereby preventing gray inversion without affecting color coordinate variation, brightness, and response speed.

5 is a plan view showing a transverse electric field liquid crystal display device of the present invention.

The liquid crystal panel of the transverse electric field liquid crystal display device according to the present invention comprises a lower substrate (TFT substrate) and an upper substrate (color filter substrate) bonded together with a space, and a liquid crystal layer injected between the lower substrate and the upper substrate. The lower substrate (TFT substrate) includes a gate line, a data line, a thin film transistor, a common electrode, and a pixel electrode. The upper substrate (color filter substrate) includes R, G, and B color filter layers, and a black matrix. ). More detailed configuration is as follows.

Pixels of the liquid crystal panel 200 are defined by gate lines 230 and data lines 240 arranged vertically and horizontally. Although only the (n, m) -th pixels are shown in the figure, n and m of the gate lines 230 and the data lines 240 are disposed in the liquid crystal panel 200, respectively, so that the lower substrate 200 is disposed. N x m pixels are formed throughout. The thin film transistor 250 is formed at an intersection of the gate line 230 and the data line 240 in the pixel. The thin film transistor 250 includes a gate electrode 260 to which a scan signal is applied from the gate line 230, and a semiconductor layer formed on the gate electrode 260 and activated as a scan signal is applied to form a channel layer. 270 and a source electrode 280 and a drain electrode 290 formed on the semiconductor layer 270 to which an image signal is applied through the data line 240, and apply an image signal input from the outside to the liquid crystal layer. do.

In the pixel, a plurality of common electrodes 300 and a pixel electrode 310 arranged substantially parallel to the data line 240 are disposed. In addition, a common line 320 connected to the common electrode 300 is disposed in an upper region of the pixel, and a pixel electrode line 330 connected to the pixel electrode 310 is disposed on the common line 320. It overlaps with the common line 320. Storage capacitance is formed in the transverse field liquid crystal display due to the overlap between the common line 320 and the pixel electrode line 330.

The upper substrate corresponding to the lower substrate configured as described above has a color filter layer (not shown) formed in a portion corresponding to the pixel region to implement color, and a black matrix (not shown) formed to serve as a distinction and light blocking between the color filter layers. It consists of o). In this case, the black matrix is formed in a portion corresponding to the peripheral region including the gate line 230 and the data line 240 and the TFT region.

Here, the distance between the pixel electrode 310 and the common electrode 300 of the blue subpixel formed in the color filter layer (not shown) is larger than the distance between the pixel electrode 310 and the common electrode 300 of the other subpixel. The distance between the pixel electrode 310 and the common electrode 300 of the red subpixel and the green subpixel, which are different subpixels, is the same.

The width of the pixel electrode 310 for each subpixel and the width of the common electrode 300 are the same.

In the transverse electric field liquid crystal display device configured as described above, the liquid crystal molecules are aligned substantially in parallel with the common electrode 300 and the pixel electrode 310. When the thin film transistor 250 operates to apply a signal to the pixel electrode 310, a transverse electric field substantially parallel to the liquid crystal panel 200 is generated between the common electrode 300 and the pixel electrode 310. 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.

As described above, the transverse electric field liquid crystal display according to the exemplary embodiment of the present invention configures the distance between the pixel electrode and the common electrode of the blue pixel to be larger than that of other subpixels, thereby preventing the luminance and response speed of the RGB pigment. While continuing to use, it is possible to prevent gray inversion of the blue pixel.

Claims (5)

Red, green and blue subpixels; And a common electrode and a pixel electrode formed on each of the red, green, and blue subpixels to drive a liquid crystal, wherein a distance between the common electrode and the pixel electrode of the blue subpixel is different from a subpixel of a different color. Electric liquid crystal display device. The method of claim 1, And the spacing between the common electrode and the pixel electrode of the blue subpixel is larger than that of the subpixels of different colors. The method of claim 2, And a gap between the common electrode and the pixel electrode of the sub-pixels of different colors. The method of claim 1, And the widths of the pixel electrodes of the sub-pixels are the same. The method of claim 1, And a width of the common electrode of each sub-pixel is the same.

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