KR20060000232A - LCD and its driving method - Google Patents

Abstract

The liquid crystal display of the present invention includes a plurality of gate lines, a plurality of data lines perpendicular to the gate lines, and a plurality of common electrode lines parallel to the gate lines, and driven by inversion driving. A liquid crystal panel in which a ripple detection pattern for detecting a ripple signal from the ripple phenomenon is formed when a common voltage ripple occurs in the common electrode lines; A ripple compensator configured to generate a ripple compensation signal by inverting the ripple signal detected from the ripple detection pattern; And a common voltage supply unit supplying a common voltage reflecting the ripple compensation signal generated by the ripple compensation unit to the common electrode lines.

Accordingly, the present invention can improve the image quality by completely eliminating the ripple phenomenon by detecting the ripple phenomenon and compensating the common voltage correspondingly.

LCD, Ripple, Inversion, IPS, Ripple Detection Pattern

Description

Liquid crystal display device and method for driving the same             

1 is a view schematically showing the overall structure of a liquid crystal display device in a general IPS mode.

FIG. 2 is a plan view schematically showing an array substrate for a partial area A of the liquid crystal display shown in FIG.

FIG. 3 is a view showing a specific pattern displayed as dot inversion directions in the liquid crystal display of the IPS mode shown in FIG. 1; FIG.

FIG. 4 is a view showing a driving waveform diagram for displaying a specific pattern shown in FIG.

FIG. 5 is a diagram illustrating a ripple phenomenon of a common voltage due to the specific pattern shown in FIG. 4.

FIG. 6 schematically illustrates the overall structure of a liquid crystal display device in IPS mode according to an embodiment of the present invention. FIG.

FIG. 7 is a plan view schematically showing an array substrate for a partial region B of the liquid crystal display shown in FIG.

8 is a cross-sectional view taken along the line II ′ of the array substrate of FIG. 7;                 

9A to 9C illustrate a process of compensating for ripple of a common voltage in the liquid crystal display of FIG. 6.

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

21: ripple detection pattern 25: ripple compensation unit

26: common voltage supply unit

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a driving method thereof capable of compensating for ripple of a common voltage.

Conventional liquid crystal display devices display an image by adjusting the light transmittance of the liquid crystal using an electric field. The liquid crystal display is roughly classified into a twisted nematic (TN) mode in which a vertical electric field is applied and an in plane switching (IPS) mode in which a horizontal electric field is applied according to the direction of the electric field driving the liquid crystal.

The TN mode is a mode in which a liquid crystal is driven by a vertical electric field between a pixel electrode formed on a lower substrate and a common electrode line formed on an upper substrate. The TN mode has a large aperture ratio and a narrow viewing angle.

In contrast, the IPS mode is a mode in which a liquid crystal is driven by a horizontal electric field (or a transverse electric field) between a pixel electrode and a common electrode line disposed side by side on a lower substrate, and has a large viewing angle and a small aperture ratio.

FIG. 1 is a view schematically showing the overall structure of a liquid crystal display device in a general IPS mode, and FIG. 2 is a plan view schematically showing an array substrate for a portion A of the liquid crystal display device shown in FIG.

1 and 2, a liquid crystal display of a general IPS mode includes a gate in which a gate driver IC 1 is mounted to generate a predetermined gate signal according to an external first control signal (generally generated by a timing controller). Tape TCP (Tape Carrier Package) 2, data TCP 4 mounted with a data driver IC 3 for supplying a predetermined data signal in accordance with the second control signal, and predetermined by the gate signal and the data signal. The liquid crystal panel 5 which displays the image of is provided.

Typically, the timing controller is mounted on a printed circuit board (PCB) (not shown). The timing controller mounted on the printed circuit board generates first and second control signals for driving the gate driver IC 1 and the data driver IC 3. The first and second control signals generated in this manner are input to the gate driver IC 1 mounted on the gate TCP 2 and the data driver IC 3 mounted on the data TCP 4. To this end, gate signal lines and data signal lines (not shown) for transmitting respective signals are patterned on the gate TCP 2 and the data TCP 4. In this case, extra dummy signal lines may be additionally patterned on the gate TCP and the data TCP.

Accordingly, the first control signal generated by the timing controller is a corresponding data signal line on the data TCP 4, a panel signal line (not shown) formed on the liquid crystal panel 5, and a corresponding signal on the gate TCP 2. It is provided to the gate driver IC 1 through the gate signal line. In this case, the gate driver IC 1 generates a predetermined gate signal according to the first control signal and provides the gate signal to the liquid crystal panel 5. Further, the second control signal generated by the timing controller is provided to the data driver IC 3 via the corresponding data signal line on the data TCP 4. In this case, the gate driver IC 3 provides a predetermined data signal to the liquid crystal panel 5 according to the second control signal.

The liquid crystal panel 5 includes an array substrate in which thin film transistors are arranged in a matrix, a color filter substrate in which color filters are arranged, and a liquid crystal layer in which liquid crystals are filled between the array substrate and the color filter substrate. 2 shows an array substrate among them.

A plurality of gate lines 6 are arranged in the horizontal direction in the array substrate, and a plurality of data lines 7 are arranged in the vertical direction. In this case, a pixel area representing one pixel is defined by the gate line 6 and the data line 7.

A thin film transistor 9 having a switch function is formed on the gate line 6 and the data line 7, and a pixel electrode 14 is connected to the thin film transistor 9. In this case, the pixel electrodes 14 are arranged with a plurality of pixel electrode bars 14a in the vertical direction. In this case, the gate line 6 is connected to the gate electrode 10 of the thin film transistor 9, the data line 7 is connected to the source electrode 11, and the pixel is connected to the drain electrode 12. The electrode 14 is connected.

In the liquid crystal display of the IPS mode, the common electrode line 8 to which the common voltage is applied is formed together on the array substrate on which the pixel electrode 14 is formed. That is, a plurality of common electrode lines 8 are arranged in parallel with the plurality of gate lines 6. In FIG. 2, the common electrode line 8 is arranged along the center line of the pixel area, but the arrangement may be variously modified.

The common electrode lines 8 are connected to the common electrode bars 8a arranged alternately with the pixel electrode bars 14a on the pixel area.

Therefore, when a predetermined voltage (that is, the data signal and the common voltage) is applied, a horizontal electric field is generated by the pixel electrode bars 14a and the common electrode bars 8a which are alternately arranged. As the liquid crystal is driven by the horizontal electric field, an image having a good viewing angle is displayed.

Various inversion schemes are used to drive the IPS mode liquid crystal display. That is, the frame inversion system, the column inversion system, and the dot inversion system are the same.

FIG. 3 is a view showing a specific pattern displayed as dot inversion directions on the liquid crystal display of the IPS mode shown in FIG. 1, and FIG. 4 is a view showing a driving waveform diagram for displaying the specific pattern shown in FIG. FIG. 5 is a diagram illustrating a ripple phenomenon of the common voltage due to the specific pattern shown in FIG. 4.                         

Each of the pixels illustrated in FIG. 3 represents red (R), green (G), and blue (B) pixels, respectively. As each of the pixels R, G, and B is driven in a dot inversion method, the polarity of the data signal is inverted as it proceeds in the vertical direction, and the polarity of the data signal is inverted as it proceeds in the vertical direction.

In particular, in the normal black mode, each pixel displays a specific pattern, ie, a vertical stripe pattern, in which the middle gray (for example, 127 gray) and the black gray alternate in a column line unit.

As shown in FIG. 4, the data signal Vd supplied to the i-th horizontal line Hi is a data signal Vd_127 corresponding to 127 gray and a data signal corresponding to black gray based on the common voltage Vcom. (Vd_0) is supplied alternately with different polarities. In addition, as illustrated in FIG. 4, the data signal Vd supplied to the i + 1 th horizontal line Hi + 1 is black with the data signal Vd_127 corresponding to 127 gray based on the common voltage Vcom. The data signals Vd_0 corresponding to gray are alternately supplied with different polarities. Here, the data signal Vd supplied to the i + 1 th horizontal line Hi + 1 has a polarity opposite to that of the data signal Vd supplied to the i th horizontal line Hi.

In this case, since the average level of the data signal supplied to the i-th horizontal line Hi is greater than the negative level relative to the common voltage Vcom, the common voltage Vcom is shown in FIG. 5. Will rise with a relatively large peak in the positive direction. Subsequently, since the average level of the data signal supplied to the i + 1th horizontal line Hi + 1 is greater than the negative level relative to the common voltage Vcom, the common voltage is shown in FIG. 5. (Vcom) goes down with a relatively large peak in the negative direction. When the data signal for displaying a specific pattern is supplied in a horizontal unit as described above, the common voltage Vcom is in the positive and negative directions in the horizontal period H as shown in FIG. 5 according to the average level of the data signal. Ripple phenomenon will occur. Such a ripple phenomenon of the common voltage causes horizontal crosstalk in the horizontal direction, resulting in deterioration of image quality. In addition, such a ripple phenomenon is known to occur mainly between the data lines and the common electrode lines that cross vertically.

However, until now, no method for compensating for the ripple of the common voltage generated in this way has been proposed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display and a driving method thereof capable of improving the image quality by detecting and compensating for the ripple of the common voltage.

According to a preferred embodiment of the present invention for achieving the above object, a liquid crystal display device, a plurality of gate lines, a plurality of data lines perpendicular to the gate lines and a plurality of common in parallel to the gate lines A liquid crystal panel having electrode lines and having a ripple detection pattern for detecting a ripple signal from the ripple phenomenon when a common voltage ripple occurs in the common electrode lines by inversion driving; A ripple compensator configured to generate a ripple compensation signal by inverting the ripple signal detected from the ripple detection pattern; And a common voltage supply unit supplying a common voltage reflecting the ripple compensation signal generated by the ripple compensation unit to the common electrode lines.

The ripple detection pattern may be formed parallel to the plurality of common electrode lines.

In addition, the ripple detection pattern may be connected to the ripple compensator using redundant signal lines patterned on the data TCP.

In addition, the ripple detection pattern may be formed on the same surface of the same material as the gate lines.

According to another preferred embodiment of the present invention, the driving method of the liquid crystal display device, when the common electrode line and the ripple detection pattern is formed in the liquid crystal panel, due to the ripple phenomenon generated in the common electrode line during the inversion driving method Detecting a ripple signal in the ripple detection pattern; Inverting the detected ripple signal to generate a ripple compensation signal; And reflecting the generated ripple compensation signal to a common voltage and supplying the generated ripple compensation signal to the common electrode line.

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

FIG. 6 is a view schematically showing the overall structure of an IPS mode liquid crystal display device according to an exemplary embodiment of the present invention, and FIG. 7 is an array substrate for a partial region B of the liquid crystal display device shown in FIG. 8 is a cross-sectional view taken along the line II ′ of the array substrate of FIG. 7. In the drawings of the present invention, the same reference numerals are assigned to elements having the same function as the conventional drawings.

6 to 8, the liquid crystal display of the IPS mode of the present invention includes a gate TCP (2), a data TCP (4), a liquid crystal panel (5), a ripple compensator (25) and a common voltage supply (26). It includes.

A gate driver IC 1 for generating a gate signal supplied to the liquid crystal panel 5 is mounted on the gate TCP 2. The gate driver IC 1 generates a gate signal according to an external first control signal (generally generated by a timing controller) and supplies the gate signal to the gate line 6 of the liquid crystal panel 5. Gate signal lines (not shown) are formed on the gate TCP 2 to transmit an input / output signal of the gate driver IC 1, that is, a first control signal and a gate signal. In this case, extra dummy signal lines may be additionally patterned on the gate TCP 2.

The data TCP 4 is provided with a data driver IC 3 for supplying a data signal to the liquid crystal panel 5. The data driver IC 3 supplies the data signal to the data line 7 of the liquid crystal panel 5 according to an external second control signal. The data TCP 4 is patterned with data signal lines (not shown) for transmitting an input / output signal of the data driver IC 3, that is, a second control signal and a data signal. At this time, extra dummy signal lines may be additionally patterned on the data TCP 4.                     

In a typical line on glass (LOG) method, the first control signal includes signal lines (eg, extra signal lines) patterned on the data TCP 4, signal lines formed on the liquid crystal panel 5, and It is input to the gate driver IC 1 through the signal lines patterned to the gate TCP 2. To this end, redundant signal lines patterned on the data TCP 4 and signal lines formed on the liquid crystal panel 5 may be used to transmit the first control signal.

Typically, the timing controller is mounted on a printed circuit board (PCB) (not shown). Of course, the ripple compensation unit 25, the common voltage supply unit 26, and other driving circuits may be mounted on the printed circuit board in addition to the timing controller. The timing controller mounted on the printed circuit board generates first and second control signals for driving the gate driver IC 1 and the data driver IC 3. The first control signal is transmitted to the gate driver IC 1 via the signal lines of the data TCP 4, the signal lines of the liquid crystal panel 5, and the signal lines of the gate TCP 2, as described above. Is entered. Accordingly, the gate driver IC 1 supplies a predetermined gate signal to the gate line 6 of the liquid crystal panel 5. The second control signal is also input to the data driver IC 3 via the signal lines of the data TCP 4. Accordingly, the data driver IC 3 supplies a data signal to the data line 7 of the liquid crystal panel 5.

The liquid crystal panel 5 includes an array substrate in which thin film transistors are arranged in a matrix, a color filter substrate in which color filters are arranged, and a liquid crystal layer in which liquid crystals are filled between the array substrate and the color filter substrate.

As illustrated in FIG. 7, a plurality of gate lines 6 are arranged in the horizontal direction and a plurality of data lines 7 are arranged in the vertical direction on the array substrate. In this case, the pixel area representing one pixel is defined by the gate line 6 and the data line 7.

A thin film transistor 9 having a switch function is formed on the gate line 6 and the data line 7, and a pixel electrode 14 is connected to the thin film transistor 9. In this case, the pixel electrodes 14 are arranged with a plurality of pixel electrode bars 14a in the vertical direction. In this case, the gate line 6 is connected to the gate electrode 10 of the thin film transistor 9, the data line 7 is connected to the source electrode 11, and the pixel is connected to the drain electrode 12. The electrode 14 is connected.

In addition, a common electrode line 8 to which a common voltage is applied is arranged in parallel with the plurality of gate lines 6. In FIG. 7, the common electrode line 8 is arranged along the center line of the pixel area, but the arrangement may be variously modified. Here, the common voltage is supplied from the common voltage supply unit 26. In this case, the common voltage may have a predetermined DC voltage.

The common electrode lines 8 are connected to the common electrode lines 8 alternately alternately arranged with the pixel electrode bars 14a on the pixel area.

In the liquid crystal display having the array substrate configured as described above, the data signal is alternately inverted from the positive level and the negative level based on the common voltage in units of one horizontal line (H) to correspond to the data signal through the data line 7. It is supplied to the pixel electrode 14. At this time, the level average value in each horizontal line unit is biased with one polarity based on the common voltage. In addition, under the influence of the biased polarity, a ripple phenomenon having a relatively large peak value occurs in the common voltage.

In the past, it was confirmed experimentally that such a ripple phenomenon exists, but the peak value of the ripple could not be accurately detected and compensated accordingly.

In the present invention, a ripple detection pattern 21 for detecting the peak value of the ripple generated in the common voltage, that is, the ripple signal is formed in the liquid crystal panel 5. That is, the ripple detection pattern 21 is formed to be perpendicular to the data line 7 and parallel to the gate line 6 and the common electrode line 8. At this time, the ripple detection pattern 21 is preferably formed between the data TCP (4) and the first gate line (6a). Of course, the ripple detection pattern 21 may be formed in the center portion of the liquid crystal panel 5, but in reality, it is difficult to form the center portion of the liquid crystal panel 5. That is, the data line 7, the gator line 6, the thin film transistor 9, the pixel electrode 14, and the like are provided at the center of the liquid crystal panel 5 so that the elements do not affect each of these elements. It is difficult to form the ripple detection pattern 21. However, the ripple detection pattern 21 of the present invention is not necessarily limited to be formed between the data TCP 4 and the first gate line 6a, and is formed in the center portion of the liquid crystal panel 5 by the development of manufacturing technology. If it is possible, it can also form in the center part of the liquid crystal panel 5.

In addition, the IPS LCD of the present invention further includes a ripple compensator 25 for generating a ripple compensation signal inverting the ripple signal detected from the ripple detection pattern 21. For example, when the ripple signal having a positive peak value is detected from the ripple detection pattern 21, the ripple compensator 25 may generate a ripple compensation signal having a negative peak value having the same magnitude as the opposite one. Can be. Similarly, when the ripple signal having a negative peak value is detected from the ripple detection pattern 21, the ripple compensator 25 generates a ripple compensation signal having a positive peak value having the same magnitude as the opposite. In this case, the ripple compensation signal generated by the ripple compensation unit 25 is provided to the common voltage supply unit 26.

As shown in FIG. 6, the ripple detection pattern 21 and the ripple compensator 25 are connected by using extra signal lines of the data TCP 4. That is, the predetermined ripple detection pattern 21 is connected to the data pad 23 of the liquid crystal panel 5 by the same auxiliary ripple detection pattern 22 as the ripple gumpuff pattern 21. In this case, the auxiliary ripple detection pattern 22 and the data pad 23 are connected through a contact hole. The data pad 23 is connected to an extra signal line 24 of one of the extra signal lines of the data TCP 4, and an end of the extra signal line 24 is connected to the printed circuit board. And is connected to the ripple compensator 25 through a conductive line provided on the printed circuit board.

The common voltage supplier 26 supplies a common voltage reflecting the ripple compensation signal to the common electrode line 8 of the liquid crystal panel 5. Accordingly, the ripple of the common voltage generated by the data signal supplied to the liquid crystal panel 5 at the positive level and the negative level is compensated.

When the ripple phenomenon occurs in the common voltage as described above, the ripple is easily detected by detecting the ripple signal from the ripple phenomenon, generating a ripple compensation signal for inverting the detected ripple signal, and reflecting the ripple compensation signal in the common voltage. It is possible to prevent the deterioration of image quality due to horizontal crosstalk or the like by being removed.

The ripple detection pattern 21 may be formed of the same material in the same process as the gate line 6. That is, as shown in FIG. 8, the gate line 6 is formed on the substrate 31, and the ripple detection pattern 21 is formed together with the gate line 6. Preferably, the ripple detection pattern 21 and the gate line 6 are formed of the same metal material. As such, by forming the ripple detection pattern 21 together when the gate line 6 is formed, no additional process is required. Although not shown in FIG. 8, when the gate line 6 is formed, a gate electrode, a gate pad, and the like are further formed.

A gate insulating layer 33 is deposited on the substrate 31 on which the gate line 6 and the ripple detection pattern 21 are formed, and a data line 7 is formed thereon. In addition, when the data line 7 is formed, a source electrode, a drain electrode, a data pad, and the like are further formed.

A passivation layer 35 is formed on the substrate 31 on which the data line 7 is formed, and the pixel electrode 14 connected to the drain electrode 12 shown in FIG. 7 through a contact hole. A common electrode line 8 for supplying a common voltage is formed.                     

The operation of the liquid crystal display device of the IPS mode of the present invention configured as described above will be described.

First, a gate signal generated by the gate driver IC 1 mounted on the gate TCP 2 is supplied to each gate line 6 of the liquid crystal panel 5 to turn on the thin film transistor 9. As described above, the thin film transistor 9 is turned on and at the same time, a data signal is transferred from the data driver IC 3 mounted on the data TCP 4 via the data lines 7 of the liquid crystal panel 5. Supplied to the electrodes 14. In this case, the data signal is supplied by inverting the positive level and the negative level in units of one horizontal line (H). In this case, the common voltage supply unit 26 supplies a predetermined common voltage to the common electrode line 8 of the liquid crystal panel 5.

Accordingly, a horizontal electric field is formed between the plurality of pixel electrode bars 14a connected to the pixel electrode 14 and the common electrode bars 8a connected to the common electrode line 8 alternately alternately arranged with the pixel electrode bars 14a. Is generated, and the liquid crystals are driven by this horizontal electric field to display a predetermined image.

At this time, as described above, the level average value of the data signal is shifted to one side in units of one horizontal line (H). Accordingly, a ripple phenomenon occurs in the common voltage supplied to the common electrode line 8 as illustrated in FIG. 9A.

In this case, the ripple detection pattern 21 formed in the liquid crystal panel 5 detects the ripple signal having the peak value of the ripple from the ripple phenomenon and provides the ripple compensation unit 25 to the ripple compensator 25.

As illustrated in FIG. 9B, the ripple compensator 25 inverts the ripple signal based on the ripple signal to generate a ripple compensation signal and provide the ripple compensation signal to the common voltage supply unit 26.

The common voltage supplier 26 supplies a common voltage in which the ripple compensation signal is reflected to the common electrode line 8 of the liquid crystal panel 5. In this case, the common voltage reflecting the ripple compensation signal may not be a DC voltage but a voltage having a peak value in a direction opposite to the peak value of the ripple signal. For example, if the peak value of the ripple signal has a positive direction, the common voltage reflected with the ripple compensation signal may be a voltage having a negative direction. In addition, if the peak value of the ripple signal has a negative direction, the common voltage reflected with the ripple compensation signal may be a voltage having a positive direction.

Therefore, even if a ripple phenomenon occurs in the common voltage supplied to the common electrode line 8 of the liquid crystal panel 5, the ripple signal is detected using the ripple detection pattern 21 from the ripple phenomenon, and the detected ripple signal is detected. The ripple may be completely removed by generating a ripple compensation signal capable of compensating for and reflecting the ripple phenomenon by reflecting the common voltage. Therefore, the ripple can be eliminated to solve the defects such as horizontal crosstalk and the like, thereby improving image quality.

As described above, according to the present invention, a ripple phenomenon is detected using a liquid crystal panel ripple detection pattern, and a ripple compensation signal is generated based on the detected result and reflected and supplied to a common voltage, thereby providing a fundamental ripple phenomenon. Can be removed to improve image quality.

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 (9)

And a plurality of gate lines, a plurality of data lines perpendicular to the gate lines, and a plurality of common electrode lines parallel to the gate lines, and a common voltage to the common electrode lines by inversion driving. A liquid crystal panel in which a ripple detection pattern for detecting a ripple signal from the ripple phenomenon is formed when a ripple phenomenon occurs; A ripple compensator configured to generate a ripple compensation signal by inverting the ripple signal detected from the ripple detection pattern; And And a common voltage supply unit supplying a common voltage reflecting the ripple compensation signal generated by the ripple compensation unit to the common electrode lines. The liquid crystal display of claim 1, wherein the ripple detection pattern is formed in parallel to the plurality of common electrode lines. The liquid crystal display of claim 1, wherein the ripple detection pattern is formed between a data TCP connected to the liquid crystal panel and a first gate line of the plurality of gate lines. The liquid crystal display of claim 1, wherein the ripple detection pattern is connected to the ripple compensator by using extra signal lines patterned on the data TCP. The liquid crystal display device of claim 1, wherein the ripple detection pattern is formed on the same surface as the gate lines. The liquid crystal display of claim 1, wherein the ripple compensation signal is opposite to a polarity of the ripple signal and has the same magnitude. When the common electrode line and the ripple detection pattern are formed in the liquid crystal panel, detecting a ripple signal due to the ripple phenomenon generated in the common electrode line during the inversion driving method in the ripple detection pattern; Inverting the detected ripple signal to generate a ripple compensation signal; And Supplying the generated ripple compensation signal to the common electrode line by reflecting the common voltage; Method of driving a liquid crystal display device comprising a. 8. The method of claim 7, wherein the ripple signal is detected as one of a peak value of positive polarity or a peak value of negative polarity. 8. The method of claim 7, wherein the ripple compensation signal is opposite to the polarity of the ripple signal and has the same magnitude.

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