KR20080108739A - Liquid crystal display device - Google Patents

Abstract

A liquid crystal display device is provided to prevent the deterioration of the display quality by regularizing brightness between pixels corresponding to the even number gate line. An LCD panel(150) has pixels as the matrix type which are defined by gate lines(102) and data lines(104). A gate driving unit(130) supplies the gate voltage to gate lines. A data driver(140) supplies data voltage which are inverted every two adjacent pixels to the data lines. A timing control part(160) controls the gate driving unit and data driver. The length of the channel of the thin film transistor connected to odd number gate lines among gate lines is different from the length of the channel of the thin film transistor connected to even number gate lines.

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY DEVICE}

1 is a schematic view illustrating pixels and a thin film transistor in a liquid crystal display panel of a two dot inversion method.

2A and 2B are diagrams illustrating polar patterns of data voltages of a 2-dot inversion method supplied to the liquid crystal display panel shown in FIG.

3 is a waveform diagram of data voltages supplied to a liquid crystal display panel of a two dot inversion method.

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

FIG. 5 is a diagram illustrating pixels and a thin film transistor in the liquid crystal display panel of FIG.

FIG. 6 is a waveform diagram illustrating a polarity inversion signal supplied to a data driver from a timing controller illustrated in FIG. 4.

<Description of Symbols for Main Parts of Drawings>

2, 102: gate line 4,104: data line

12, 112: drain electrode 10, 110: source electrode

14,114 semiconductor pattern C: channel

150: liquid crystal display panel 160: timing controller

L1, L2: Channel length of thin film transistor

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device of a two-dot inversion method.

The liquid crystal display device displays an image by adjusting the light transmittance of the liquid crystal using an electric field. To this end, the liquid crystal display device includes a liquid crystal display panel in which pixels are arranged in a matrix, and a driving circuit for driving the liquid crystal display panel.

In such a liquid crystal display device, an inversion driving method such as a frame inversion system, a line column inversion system, and a dot inversion system is used to drive pixels on the liquid crystal display panel. This is used. The frame inversion type liquid crystal display panel driving method inverts the polarity of the data voltage (or data signal) supplied to the pixels on the liquid crystal display panel every time the frame is changed. In the liquid crystal display panel driving method of the line inversion method, the polarities of the data signals supplied to the pixels are inverted according to a line (column) on the liquid crystal display panel. In the dot inversion method, data signals having polarities opposite to those supplied to neighboring pixels in the vertical and horizontal directions are supplied to each of the pixels on the liquid crystal display panel. Causes the polarity of the supplied data signals to be reversed. Of these inversion driving methods, the dot inversion method provides an image having excellent image quality compared to the frame and line inversion methods.

Such liquid crystal displays are generally driven by a frame frequency of 60 Hz. However, in a system requiring low power consumption such as a notebook computer, it is required to lower the frame frequency to 50 to 30 Hz. As the frame frequency is lowered, the flicker phenomenon occurs in the dot inversion method which provides excellent image quality among the inversion methods, and thus, the method of driving the liquid crystal display panel of the two dot inversion method has been proposed.

FIG. 1 schematically shows a data voltage supplied to a liquid crystal display panel and a liquid crystal display panel of a two dot inversion method.

In the liquid crystal display panel illustrated in FIG. 1, the pixels P defined by the gate line 2 and the data line 4 are arranged in a matrix form. Each pixel includes a liquid crystal cell Clc, a thin film transistor TFT that actively controls data by switching data voltages supplied to the liquid crystal cells Clc, and a liquid crystal cell Clc. A storage capacitor (Cst) for maintaining a data voltage charged in the.

The thin film transistor TFT includes a source electrode 10 connected to a data line 4, a drain electrode 12 connected to a liquid crystal cell Clc, and a storage capacitor Cst, a source electrode 10, and a drain electrode 12. The semiconductor pattern 14 located below is provided. The semiconductor pattern 14 forms a channel C between the source electrode 10 and the drain electrode 12.

The polarity of the data voltage data is inverted in units of 2 dots in the vertical direction. In FIG. 2, the positive data voltage Vdata is supplied to the n-th gate line 2 and the pixel P corresponding to the n-th gate line 2 in units of 2 dots, and the n + 1 th gate is provided. The case where the negative (-) data voltage Vdata is supplied to the pixel P corresponding to the line 2 and the n + 2 th gate line 2 in units of 2 dots is illustrated.

2A and 2B illustrate polarities of data voltages supplied to pixels of a liquid crystal display panel divided into odd frames and even frames by a method of driving a 2-dot inversion liquid crystal display panel.

In the odd and even frames shown in FIGS. 2A and 2B, the two-dot inversion scheme changes the polarity of the data voltage Vdata in the horizontal direction in pixels, that is, in units of dots, as in the conventional dot inversion scheme. It can be seen that it is driven to change in units of 2 dots in the vertical direction. That is, as the polarity of the data voltage Vdata is inverted with two neighboring gate lines 2, the polarity of the data voltage Vdata is changed in units of 2 dots in the vertical direction.

In the liquid crystal display of the two-dot inversion type, the luminance is uneven due to the difference in charging characteristics between the pixels corresponding to the odd gate line 2 and the pixels corresponding to the even gate line 2. This causes a problem that the display quality is degraded.

This will be described in more detail with reference to FIG. 3 as follows.

Referring to FIG. 3, in the conventional vertical two-dot inversion driving method, the polarity of the data voltage Vdata is inverted every two pulses. Here, the polarity of the first data voltage Vdata1 supplied to the liquid crystal cell Clc connected to the odd (or even) gate line 2 by the rising time RT or the falling time FT after the polarity is reversed. The supply period T1 becomes relatively shorter than the supply period T2 of the second data voltage Vdata2 supplied to the liquid crystal cell Clc connected to the even (or odd) gate line 2. Accordingly, a difference in charging time occurs between the pixels P supplied with the first data voltage Vdata1 and the pixels P supplied with the second data voltage Vdata2.

As a result, even if the same data voltage is supplied, a luminance difference is generated between the pixels corresponding to the odd (or even) gate line 2 and the pixels corresponding to the even (or odd) gate line 2, thereby degrading display quality. Problems arise.

Accordingly, an object of the present invention is to provide a liquid crystal display device which can prevent deterioration of display quality by uniformizing luminance between pixels corresponding to odd gate lines and pixels corresponding to even gate lines in a 2-dot inversion scheme. There is.

In order to achieve the above object, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel in which pixels defined by gate lines and data lines are arranged in a matrix form; A gate driver supplying gate voltages to the gate lines; A data driver configured to supply data voltages having polarities inverted in units of the two vertically adjacent pixels to the data lines; A thin film transistor having a timing controller for controlling the gate driver and the data driver, wherein the thin film transistor is connected to odd-numbered gate lines of the gate lines and is connected to even-numbered gate lines The length of the channel of the transistor is characterized in that different.

The length of the channel of the thin film transistor connected to the odd gate lines is shorter than the length of the channel of the thin film transistor connected to the even gate lines.

The magnitude of the current flowing through the channels of the thin film transistors connected to the odd-numbered gate lines over the same time is greater than the magnitude of the current flowing through the channels of the thin film transistors connected to the even-numbered gate lines.

The data driver supplies data voltages having different polarities to pixels adjacent to each other horizontally.

Each of the thin film transistors includes a source electrode and a drain electrode facing each other; A semiconductor pattern is disposed under the source electrode and the drain electrode, and the channel is formed. The length of the channel is equal to the distance between the source electrode and the drain electrode.

Other objects and features of the present invention in addition to the above objects will be apparent from the description of the embodiments with reference to the accompanying drawings.

A preferred embodiment of the present invention will be described with reference to FIGS. 4 to 6.

FIG. 4 is a block diagram schematically illustrating a two-dot inversion type liquid crystal display device according to the present invention, and FIG. 5 is a part of the liquid crystal display panel 150 and data supplied to the liquid crystal display panel 150 in FIG. 4. Indicates the voltage Vdata.

4 illustrates a liquid crystal display panel 150, a data driver 140 for driving the data lines 104 of the liquid crystal display panel 150, and a gate line of the liquid crystal display panel 150. And a timing controller 160 for controlling driving timings of the data and gate drivers 130 and 140.

The timing controller 160 controls the driving timing of the gate driver 130 and the data driver 140 in response to clock signals, horizontal and vertical synchronization signals Hsync and Vsync from a system (not shown). In addition, the timing controller 160 generates a data enable signal and the like in response to the input clock signal and the horizontal and vertical synchronization signals Hsync and Vsync, and supplies the data enable signal to the data driver 140 as well as the polarity inversion signal and the data enable signal. The red, green, and blue (B) video data from the system are supplied to the data driver 140 in synchronization with each other.

In addition, the timing controller 160 uses the vertical synchronization signal Vsync and the horizontal synchronization signal Hsync to drive the two dot inversion type liquid crystal display panel 150 as shown in FIG. 4. The polarity inversion signal POL of the version method is generated and a data enable signal DE for supplying a data voltage to the pixel is generated using the vertical synchronization signal Vsync and the horizontal synchronization signal Hsync. The polarity inversion signal POL generated by the timing controller 4 is inverted in polarity in units of two horizontal synchronization signals Hsync during the vertical synchronization signal Vsync.

The gate driver 130 sequentially supplies gate voltages to the gate lines 102 according to a control signal from the timing controller 160.

The data driver 140 converts the R, G, and B video data signals from the timing controller 160 into analog signals, and outputs one horizontal line of video data for each horizontal period in which the gate voltage is supplied to the gate line 102. To the data lines 104.

The data driver 140 supplies the polarity of the video data to the liquid crystal display panel 150 in a two dot inversion manner according to the polarity inversion signal POL2 from the timing controller 160.

Accordingly, the video data supplied from the data driver 140 to the liquid crystal display panel 110 has the polarity of the two dot inversion method as shown in FIGS. 2A and 2B.

In the liquid crystal display panel 150, pixels P defined by the gate line 2 and the data line 4 are arranged in a matrix form. Each pixel P includes a liquid crystal cell Clc, a thin film transistor TFT that actively controls data by switching data voltages supplied to the liquid crystal cells Clc, and a liquid crystal cell Clc. It includes a storage capacitor (Cst) for maintaining a charged data voltage.

The thin film transistor TFT supplies the video data from the data line 104 to the liquid crystal cell Clc in response to the gate voltage from the gate line 102. The liquid crystal cell Clc is composed of a common electrode facing each other with a liquid crystal interposed therebetween and a pixel electrode connected to the thin film transistor TFT, so that the liquid crystal cell Clc may be equivalently represented as a liquid crystal capacitor Clc.

Referring to FIG. 5, the thin film transistors TFT1 and TFT2 may include a source electrode 110 connected to a data line 104, a drain electrode 112 connected to a liquid crystal cell Clc, a storage capacitor Cst, and a source electrode. A semiconductor pattern 114 positioned below the drain electrode 112 and the drain electrode 112 is provided. The semiconductor pattern 114 forms a channel C between the source electrode 110 and the drain electrode 112.

In the present invention, in order to compensate for the difference in charging characteristics between the liquid crystal cell Clc connected to the odd gate line 102 and the liquid crystal cell Clc connected to the even gate line 102, an odd is used. The lengths of the channels C of the thin film transformer TFT1 connected to the gate line 102 and the thin film transistor TFT2 connected to the even gate line 102 are formed differently.

This will be described in detail with reference to FIGS. 3 and 5 as follows.

3 and the first data voltage supplied to the liquid crystal cell Clc connected to the odd (or even) gate line by the rising time RT or the falling time FT after the polarity is reversed. The supply period T1 of Vdata1 becomes relatively shorter than the supply period T2 of the second data voltage Vdata2 supplied to the liquid crystal cell Clc connected to the even (or odd) gate line 102. As a result, a difference between the charging time in the pixel P to which the first data voltage Vdata1 is supplied and the pixel P to which the data voltage Vdata2 is supplied occurs.

In order to prevent such a difference in charging time, the length of the channel C of the thin film transistor TFT1 connected to the odd (or even) gate line 102 having a relatively short data voltage supply period is formed. Alternatively, the length of the channel C of the thin film transistor TFT2 connected to the even (or odd) gate line 102 is long.

That is, the length of the channel C of the thin film transistor TFT1 in the pixel to which the first data voltage Vdata1 is supplied to compensate for the loss of the supply period of the data voltage according to the rising time RT or the falling time FT period. L1 is formed to be shorter than the length C of the channel C of the thin film transistor TFT2 in the pixel to which the second data voltage Vdata2 is supplied.

Equation 1 below shows the relationship between the length L of the channel C, the width W, the electron mobility μ, and the currents I flowing through the channel C. Where K is a constant.

As can be seen in Equation 1 above, the current I flowing through the channel C and the mobility μ of the electrons are proportional to each other. The current I flowing through the channel C is inversely proportional to the length L of the channel C and is proportional to the width W of the channel C.

Therefore, if the length L of the channel C is short, the characteristics of the thin film transistor TFT, that is, the magnitude of the current amount can be increased.

By using this principle, in the present invention, as the length L1 of the channel C of the thin film transistor TFT1 connected to the odd (or even) gate line 102 having a relatively short data voltage supply period is shortened, This allows a large amount of current to flow in a relatively short time. Accordingly, the charging characteristic between the pixels P corresponding to the odd gate line 102 and the pixels P corresponding to the even gate line 102 may be uniform. As a result, as the luminance becomes uniform among the vertically adjacent pixels P, it is possible to prevent deterioration of display quality.

As described above, the liquid crystal display according to the exemplary embodiment of the present invention can shorten the channel length of the thin film transistor to compensate for the amount of data voltage supplied reduced by the rising time RT or the falling time FT. As a result, the charging characteristics between the odd gate line 102 and the even gate line 102 can be made uniform, thereby making it possible to prevent the display quality from deteriorating as the luminance becomes uniform.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (5)

A liquid crystal display panel in which pixels defined by gate lines and data lines are arranged in a matrix; A gate driver supplying gate voltages to the gate lines; A data driver configured to supply data voltages having polarities inverted in units of the two vertically adjacent pixels to the data lines; A timing controller for controlling the gate driver and the data driver; The length of the channel of the thin film transistor connected to odd gate lines among the gate lines and the length of the channel of the thin film transistor connected to even gate lines are different from each other. . The method of claim 1, And a channel length of the thin film transistor connected to the odd gate lines is shorter than a channel length of the thin film transistor connected to the even gate lines. The method of claim 1, The magnitude of the current flowing through the channel of the thin film transistor connected to the odd-numbered gate lines over the same time is greater than the magnitude of the current flowing through the channel of the thin film transistor connected to the even-numbered gate lines. Liquid crystal display device characterized in that. The method of claim 1, And the data driver supplies data voltages having different polarities to pixels adjacent to each other horizontally. The method of claim 1, Each thin film transistor is A source electrode and a drain electrode facing each other; A semiconductor pattern disposed under the source electrode and the drain electrode, wherein the channel is formed; And the channel length is equal to a distance between the source electrode and the drain electrode.

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