KR20050064368A - Liquid crystal display device and driving method thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a storage on common liquid crystal display device in which storage wirings are formed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device and a method of driving the same, which can improve a problem in which luminance is uneven as the storage voltage drops in the liquid crystal display device.

In the present invention, the common voltage is composed of first and second common voltages having different voltage values, the first and second common voltages are applied through opposite sides of the display area, and the storage voltage is applied to the first common voltage. Provided are a liquid crystal display device and a driving method thereof applied through a side of the display area.

According to the present invention, by applying a common voltage having different voltage values to both sides of the liquid crystal display device, there is an effect that the voltage applied to the liquid crystal layer can be uniform and the luminance of the liquid crystal display device can be made uniform.

Description

Liquid crystal display device and driving method

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 a storage on command method in which storage wirings are formed.

In general, the CRT (Cathode Ray Tube) has been used most of the screen display devices for displaying the image information on the screen, which is inconvenient to use because it is bulky and heavy compared to the display area.

On the other hand, even though the display area is large, a thin film type flat panel display device having a small thickness and which can be easily used in any place has been developed, and is gradually replacing the CRT display device. In particular, the liquid crystal display device has superior display resolution than other flat panel display devices, and exhibits characteristics such that the quality of the liquid crystal display is faster than that of a CRT when a moving image is realized.

The liquid crystal display device is driven by using the optical anisotropy and polarization properties of the liquid crystal. Since the liquid crystal is thin and long in structure, the direction of the molecular arrangement is controlled by applying an electric field to the liquid crystal molecules having directionality and polarization. Therefore, if the alignment direction is arbitrarily adjusted, light may be transmitted or blocked according to the alignment direction of the liquid crystal molecules by optical anisotropy of the liquid crystal, thereby displaying colors and images. The liquid crystal display controls the operation of each pixel using a thin film transistor as a switching element.

On the other hand, in the liquid crystal display device having the characteristics described above, it is necessary to maintain the data voltage input through the data wiring for a predetermined time until the next frame in order to ensure uniformity of the image display. For this purpose, it forms a storage capacitor.

The liquid crystal display may be classified into a front gate method and a storage on common method according to a method of using a storage electrode constituting a storage capacitor.

The front gate method uses a part of the n−1 th gate wiring as the storage electrode of the n th pixel.

On the other hand, the storage on common method is a method of configuring the storage electrode as a separate storage wiring, it has an advantage of excellent image quality characteristics.

Hereinafter, a conventional storage on common liquid crystal display device will be described.

1A to 1C show a liquid crystal display of a conventional storage on common type. FIG. 1B shows an enlarged view of the pixel of FIG. 1A, and FIG. 1C shows the equivalent circuit of FIG. 1A.

As shown, the conventional liquid crystal display device includes a plurality of gate and data lines 120 and 130, gate and data drivers 150 and 160 for applying signals to the gate and data lines 120 and 130. The common voltage generator 170 is configured to generate the common voltage and the storage voltage V _com and V _s . In addition, the storage wiring 140 for transmitting the storage voltage V _s to the pixel P and the storage shorting bar 145 for transferring the storage voltage V _s to the storage wiring 140 are provided. Formed.

In the pixel P, a thin film transistor T and a pixel electrode 135 connected to the thin film transistor T are formed as a switching element formed at the intersection of the gate and the data lines 120 and 130. . The thin film transistor T may include a gate electrode 121 branched on the gate line 120, a semiconductor layer 123 formed on the gate electrode 121, a source electrode 131 branched on the data line 130, and The drain electrode 133 is spaced apart from the source electrode 131 by a predetermined distance and connected to the pixel electrode 135.

The storage line 140 is positioned between the neighboring gate lines 120 to form a storage capacitor C _st as a storage capacitor with the pixel electrode 135. The storage wiring 140 is formed of the same material in the same process when forming the gate wiring 120.

Storage shorting bar 145 is formed at one side of the display area (E) for displaying an image, the storage voltage from the common voltage generation unit (170), (V _s), the application receives the storage line 140, the storage voltage (V _s in ).

The common voltage generator 170 transmits the common voltage V _com at both sides of the display area E. FIG.

The common voltage V _com transmitted to both sides is transferred to a common electrode (not shown) facing each other with the pixel electrode 135 and a liquid crystal layer (not shown) interposed therebetween, and transmitted through the data wire 130. The data voltage is applied to the pixel electrode 135 to form the pixel electrode voltage, and the liquid crystal layer is driven by the voltage difference between the pixel electrode voltage and the common voltage V _com . Here, the common electrode and the pixel electrode 135 form a liquid crystal capacitor C _lc with a liquid crystal layer interposed therebetween.

The gate and data drivers 150 and 160 output data and gate voltages to the gate and data lines 120 and 130.

The liquid crystal display of the conventional storage on common type having the configuration as described above is driven by a common voltage applied to the same size on both sides of the display area.

Hereinafter, a method of driving a conventional storage on common type liquid crystal display device will be described with reference to FIGS. 1A to 1C and FIG. 2.

FIG. 2 is a diagram illustrating voltage waveforms applied to a conventional storage on common type liquid crystal display, and illustrates voltage waveforms in areas A and B of FIGS. 1A and 1C. Here, the storage voltage is shown separately below.

As shown, the same common voltage V _com is applied to areas A and B located on the left and right sides of the liquid crystal display, thereby driving the liquid crystal display.

However, the storage shorting bar 145 for transmitting the storage voltage V _s is positioned at the right side, and the storage voltage V _s is generated as the voltage drop ΔV progresses from the A area to the B area. Therefore, the storage voltage V _s decreases by ΔV in the B region far from the storage shorting bar 145 as compared to the A region.

Accordingly, a voltage drop occurs in which the pixel electrode voltages V _{1 and B in the B} region have a value smaller than ΔV compared to the pixel electrode voltages V _{1 and A} in the A region. Therefore, the pixel electrode voltages in the A and B regions are

V _{l, A} = V _{l, B} + ΔV

Has a relationship with

Meanwhile, the common voltage V _com having the same magnitude is applied to each of the A and B regions. Therefore, the pixel voltage applied to the liquid crystal layer in the A region is

V _{lc, A} = V _{l, A} -V _com

The pixel voltage applied to the liquid crystal layer in the region B is

V _{lc, B} = V _{l, B} -V _com = (V _{l, A} -ΔV)-V _com

Will have the value of. That is, the B region has a smaller pixel voltage as compared with the A region.

As the voltage drop of the pixel voltage occurs in the B region, the liquid crystal layers of the B region and the A region may not be uniformly driven, thereby causing a problem of uneven brightness of the liquid crystal display device.

An object of the present invention for solving the above problems is to provide a liquid crystal display device and a method of driving the same that can improve the problem that the luminance is uneven as the storage voltage drops in the liquid crystal display device.

In order to achieve the object as described above, the present invention comprises: a plurality of gate and data wirings orthogonal to each other on a substrate; A switching element connected to said gate and data wiring in a display area for displaying an image; A pixel electrode connected to the switching element; A plurality of common wires formed between the neighboring gate wires and transferring storage voltages; An electric field is formed in the pixel electrode and the liquid crystal layer, and includes a common electrode to which a common voltage is transmitted. The common voltage includes first and second common voltages having different voltage values, and first and second common voltages. A liquid crystal display device is applied through opposite sides of the display area, and the storage voltage is applied through a side of the display area to which a first common voltage is applied.

The display device may further include a common wire shorting bar to which the plurality of common wires are connected, and may further include a common voltage generator configured to output the common voltage and the storage voltage. The first common voltage may have a larger potential than the second common voltage.

The common electrode may be formed on an opposing substrate facing the substrate on which the pixel electrode is formed and the liquid crystal layer.

In addition, the common electrode may be formed in parallel with the pixel electrode.

In addition, the storage voltage and the first common voltage may have the same potential.

In another aspect, the present invention is a liquid crystal display device driving method for driving a liquid crystal layer by supplying a separate storage voltage to the pixels inside the image display area, the first common voltage in the direction in which the storage voltage is supplied, The present invention provides a method of driving a liquid crystal display device for driving a liquid crystal layer by supplying a second common voltage in a direction in which the storage voltage is transmitted.

Here, the first common voltage may have a potential larger than the second common voltage. The liquid crystal layer may be driven by an electric field formed between two substrates facing each other.

In addition, the liquid crystal layer may be driven by an electric field formed on the same substrate. In addition, the storage voltage and the first common voltage may have the same potential.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

3A and 3C illustrate a liquid crystal display of a storage on common type according to an exemplary embodiment of the present invention. FIG. 3B shows an enlarged view of the pixel of FIG. 3A, and FIG. 3C shows the equivalent circuit of FIG. 3A.

The liquid crystal display of the storage on common type according to the embodiment of the present invention can compensate for the drop in the storage voltage by applying a common voltage having different values. Therefore, the image quality characteristic can be improved by uniformly matching the left and right luminance of the liquid crystal display device.

As illustrated, the liquid crystal display according to the exemplary embodiment of the present invention includes a plurality of gate and data lines 220 and 230 and a gate and data driver for applying signals to the gate and data lines 220 and 230. 250 and 260 and a common voltage generator 270 for generating common voltages and storage voltages V _com1 , V _com2 and V _s are formed. A storage wiring 240 for transmitting the storage voltage V _s to the pixel P and a storage shorting bar 245 for transmitting the storage voltage V _s to the storage wiring 240 are formed.

In the pixel P, a thin film transistor T and a pixel electrode 235 connected to the thin film transistor T are formed as a switching element formed at a portion where the gate and the data lines 220 and 230 cross each other. The thin film transistor T includes a gate electrode 221 branched to the gate wiring 220, a semiconductor layer 223 formed on the gate electrode 221, a source electrode 231 branched to the data wiring 230, and The drain electrode 233 is spaced apart from the source electrode 231 by a predetermined distance and connected to the pixel electrode 235.

The storage line 240 is positioned between the neighboring gate lines 220 and forms a storage capacitor C _st as a storage capacitor with the pixel electrode 240. The storage line 240 may be formed of the same material in the same process when forming the gate line 220.

The storage wire 240 is connected to the storage shorting bar 245 to receive the storage voltage V _s . The storage shorting bar 245 is formed at one side of the display area E and receives a storage voltage V _s from the common voltage generator 270. Meanwhile, the storage shorting bar 245 is connected to the storage wire 240 in the display area E to prevent damage caused by static electricity generated in the liquid crystal display device.

The common voltage generator 270 generates the common voltage and the storage voltages V _com1 , V _com2 , and V _s using the reference voltage V _dd output from the power supply unit (not shown). The common voltage generator 270 transfers the first and second common voltages V _com1 and V _com2 having different magnitudes to both sides of the display area E. The first common voltage V _com1 is a storage device. The second common voltage V _com2 is supplied from the side of the display area E in which the shorting bar 245 is located, that is, from the right side, that is, from the left side of the display area E in which the gate driver 220 is located In particular, the storage voltage V _s may be applied with the same voltage as the first common voltage V _com1 .

Therefore, region A is driven by the first common voltage V _com1 , and region B is driven by the second common voltage V _com2 . Here, the second common voltage V _com2 has a lower voltage value than the first common voltage V _com1 .

The first and second common voltages V _com1 and V _com2 transmitted to both sides are transferred to a common electrode (not shown), and the common electrode and the pixel electrode 235 have a liquid crystal layer interposed therebetween, and the liquid crystal capacitor C _lc. ). The liquid crystal layer is driven on / off by an electric field generated by the liquid crystal capacitor C _lc formed between the common electrode and the pixel electrode 235 to display an image.

The gate and data drivers 250 and 260 output data and gate voltages to the gate and data lines 220 and 230. The gate and data drivers 220 and 230 are controlled by receiving signals from gate and data printed circuit boards.

The liquid crystal display of the storage on common type according to the embodiment of the present invention having the configuration as described above is driven by different first and second common voltages.

Hereinafter, a method of driving a storage on common type liquid crystal display device according to an exemplary embodiment of the present invention will be described with reference to FIGS. 3A to 3C and FIG. 4.

FIG. 4 is a diagram illustrating voltage waveforms applied to a storage on common liquid crystal display according to an exemplary embodiment of the present invention, and show voltage waveforms in areas A and B of FIGS. 3A and 3C. Here, the storage voltage is shown separately below.

As illustrated, the first common voltage V _com1 is applied to the A region, and the second common voltage V _com2 is applied to the B region. As the storage voltage V _s progresses from the A region to the B region, a voltage drop occurs, and the storage voltage V _s decreases by ΔV in the B region as compared with the A region.

Accordingly, a voltage drop occurs in which the pixel electrode voltages V _{1 and B in the B} region have a value smaller by ΔV than the pixel electrode voltages V _{s and A} in the A region. Therefore, the pixel electrode voltages in the A and B regions are

V _{l, A} = V _{l, B} + ΔV

Has a relationship with Here, the pixel electrode voltage is a data voltage output from the data driver 230, and when the high level gate voltage is transferred to the selected gate line 220, the pixel electrode T is turned on. 235 is applied.

On the other hand, the first common voltage V _com1 and the second common voltage V _com2 , which are common voltages having different magnitudes, are applied to each of the A and B regions. The second common voltage V _com2 has a voltage drop smaller than the storage voltage V _s in the B region, that is, ΔV, compared to the first common voltage V _com1 applied to the A region. Therefore, the first common voltage V _com1 and the second common voltage V _com2 are

V _com1 = V _com2 + ΔV

Has a relationship with

As described above, the storage voltage drop occurs in the B region, the pixel electrode voltage drops, and a second common voltage V _com2 having a magnitude equal to the voltage drop is applied.

Therefore, the pixel voltage applied to the liquid crystal layer located in the B region is

V _{lc, B} = V _{l, B} -V _com2 = (V _{l, A} -ΔV)-(V _com1 -ΔV)

= V _{l, A} -V _com1

Will have the value of. (V _{l, A} -V _com1 ) is a pixel voltage, V _{lc, A} applied to the liquid crystal layer located in the A region, and the same pixel voltage as the A region is applied to the B region.

Therefore, the liquid crystal layers of the A and B regions are driven with the same pixel voltage, so that the left and right sides of the liquid crystal display have the same luminance.

As described above, according to the exemplary embodiment of the present invention, by applying a common voltage having different voltage values to both sides of the liquid crystal display device, the voltage applied to the liquid crystal layer can be uniform to make the luminance of the liquid crystal display device uniform. have.

Meanwhile, the storage on common method according to an exemplary embodiment of the present invention may be applied to an in-plane switching mode liquid crystal display device driven by a transverse electric field between a pixel electrode and a common electrode formed on the same substrate. Here, the common wiring is connected to the common electrode to apply a common voltage, and at the same time, functions as a storage electrode. Therefore, the storage voltage has the same voltage value as the common voltage.

The above-described embodiment of the present invention is an example of the present invention, and various modifications thereof are possible. It is apparent to those skilled in the art that such modifications fall within the scope of the present invention, within the scope included in the spirit of the present invention.

As described above, according to the present invention, by applying a common voltage having different voltage values to both sides of the liquid crystal display device, it is possible to make the voltage applied to the liquid crystal layer uniform and to make the luminance of the liquid crystal display device uniform. have.

1A to 1C illustrate a conventional storage on common liquid crystal display device;

2 is a diagram showing voltage waveforms applied to a conventional storage on common type liquid crystal display device;

3A to 3C are views illustrating a storage on common liquid crystal display device according to an exemplary embodiment of the present invention.

4 is a diagram illustrating a voltage waveform applied to a storage on common liquid crystal display according to an exemplary embodiment of the present invention.

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

220: gate wiring 230: data wiring

240: storage wiring 245: storage shorting bar

250: gate driver 260: data driver

270: common voltage generator

Claims (12)

A plurality of gate and data wires orthogonal to each other on the substrate; A switching element connected to said gate and data wiring in a display area for displaying an image; A pixel electrode connected to the switching element; A plurality of common wires formed between the neighboring gate wires and transferring storage voltages; An electric field is formed on the pixel electrode and the liquid crystal layer, and includes a common electrode to which a common voltage is transmitted. The common voltage includes first and second common voltages having different voltage values, the first and second common voltages are applied through opposite sides of the display area, and the storage voltage is equal to the first common voltage. And a liquid crystal display device applied through side portions of the display area. The method of claim 1, And a common wire shorting bar to which the plurality of common wires are connected. The method of claim 1, And a common voltage generator configured to output the common voltage and the storage voltage. The method of claim 1, The first common voltage has a potential greater than the second common voltage. The method of claim 1, And the common electrode formed on an opposite substrate facing the substrate on which the pixel electrode is formed and the liquid crystal layer interposed therebetween. The method of claim 1, The common electrode is formed in parallel with the pixel electrode on the same substrate. The method of claim 1, The liquid crystal display device having the same potential as the storage voltage and the first common voltage. A liquid crystal display driving method for driving a liquid crystal layer by supplying a separate storage voltage to a pixel inside an image display area, And a first common voltage in a direction in which the storage voltage is supplied, and a second common voltage in a direction in which the storage voltage is transmitted to drive the liquid crystal layer. The method of claim 8, And the first common voltage has a potential greater than the second common voltage. The method of claim 8, And the liquid crystal layer is driven by an electric field formed between two substrates facing each other. The method of claim 8, And the liquid crystal layer is driven by an electric field formed on the same substrate. The method of claim 8, And the storage voltage and the first common voltage have the same potential.