KR20070002311A - Liquid crystal display and method for driving the same - Google Patents

Abstract

A liquid crystal display and a driving method thereof are provided to prevent pixels from being erroneously charged by increasing the W/L ratio of a TFT(Thin Film Transistor), which is connected to dark pixels. An LCD(Liquid Crystal Display) panel includes plural pixels, which are defined by gate and data lines. The LCD panel displays an image on respective pixels according to a scan signal from the gate line and an analog pixel signal from the data line. A gate driver(130) of an odd number group sequentially supplies scan signals to the gate lines, which are connected to odd-numbered pixels. A gate driver(140) of an even number group sequentially supplies the scan signals to the gate lines, which are connected to even-numbered pixels. A source driver converts an input video signal to the analog pixel signal, and supplies the analog pixel signal to a data line of the LCD panel. A TFT(170) is arranged on the intersection between gate and data lines, and supplies the analog pixel signal to the respective pixels. A timing controller supplies a timing control signal and the video signal to gate and source drivers. A TFT, which is connected to a first pixel of respective pixel lines, has greater current driving capability compared with other TFTs.

Description

Liquid crystal display and method for driving the same {Liquid crystal display and method for driving the same}

1 is a schematic configuration diagram of a liquid crystal display according to the related art.

2 is a waveform diagram illustrating pixel charging characteristics of a liquid crystal display according to the related art.

3 is a schematic overall configuration diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

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

5 is a waveform diagram illustrating pixel charging characteristics of a liquid crystal display according to an exemplary embodiment of the present invention.

6 is a flowchart illustrating a method of driving a liquid crystal display according to an exemplary embodiment of the present invention.

(Explanation of symbols for the main parts of the drawing)

100: liquid crystal display panel 110: source driver

120: gamma voltage generator 130, 140: gate driver

150: timing controller 160: expansion thin film transistor

170: thin film transistor

The present invention relates to a liquid crystal display device and a driving method thereof, and more particularly, to a liquid crystal display device and a driving method thereof for improving pixel charging characteristics.

In the liquid crystal display, a liquid crystal material having an anisotropic dielectric constant is injected between an upper transparent insulating substrate on which a common electrode, a color filter, a black matrix, and the like are formed, and a lower transparent insulating substrate on which a switching element and a pixel electrode are formed. By applying different potentials to the electrodes and the common electrode, the intensity of the electric field formed in the liquid crystal material is adjusted to change the molecular arrangement of the liquid crystal material, thereby controlling the amount of light transmitted through the transparent insulating substrate to express a desired image. It is a display device. In the liquid crystal display, a thin film transistor liquid crystal display (TFT LCD) using a thin film transistor (TFT) element as a switching element is mainly used.

Such a liquid crystal display includes a liquid crystal display panel in which an image is displayed. When driving the liquid crystal display panel, phosphorus is driven by inverting polarity in a predetermined unit to prevent deterioration of the internal liquid crystal and to improve display quality of the image. It is common for the version driving method to be used. The inversion driving method is classified into a frame inversion method, a line inversion method, and a dot inversion method according to a unit of polarity inversion.

FIG. 1 is a schematic configuration diagram of a liquid crystal display device according to the related art, and illustrates an example of a liquid crystal display device driven by a line inversion method.

As shown in FIG. 1, the liquid crystal display according to the related art includes a plurality of pixels P1 to P6, gate lines G ₁ to G ₆ , data lines D ₁ , and gate lines G _{1 that} cross each other. To G ₆ ) and an odd group disposed at each intersection of the data line D ₁ and sequentially applying scan signals to the thin film transistor 30 and gate lines G ₁ to G ₆ electrically connected to each pixel. And even-numbered gate drivers 10 and 20.

In the liquid crystal display as shown in FIG. 1, the gate drivers 10 and 20 are divided into two sides by being divided into odd-numbered gate drivers 10 and even-numbered gate drivers 20, and bezels surrounding the liquid crystal display panel. In the form of a double gate in panel (DGIP) included in the liquid crystal display panel rather than a portion thereof, the pixel charging characteristic is improved and the overall size of the liquid crystal display is reduced.

The data line D ₁ is disposed between two adjacent pixels P1 and P2, P3 and P4, P5 and P6, and is implemented by being electrically connected to each pixel through the thin film transistor 30. Reduce the number of (not shown) to half. Two adjacent pixels P1 and P2, P3 and P4, P5 and P6 share an analog pixel signal transmitted to the data line D ₁ , and the thin film transistor 30 alternates to two adjacent pixels. Is controlled to apply an analog pixel signal.

FIG. 2 is a waveform diagram illustrating pixel charging characteristics of a liquid crystal display according to the related art. As the analog pixel signal is applied to each pixel by the scan signals of the gate drivers 10 and 20 in the liquid crystal display of FIG. The change in the voltage charged is shown.

In the double gate-in panel method, when the gate drivers 10 and 20 are sequentially turned on, the pixels are charged in the order of P1 to P6. Since the double gate-in panel method has a pixel charging time of 1/2 compared to the general gate-in panel method, charging is not sufficiently performed.

Therefore, the gate on time is doubled to pre-charging before the pixel is charged. When precharging, the moment the pixel is charged from P2 to P3 and P4 to P5 As a result, line inversion causes the polarity of the positive polarity to change.

When the polarity of the pixel changes, the value of the voltage to be charged (V _DATA ) becomes relatively large, so that the pixel is not sufficiently charged within the pixel charge time of 1/2 level. As a result, the pixels of P1, P3, and P5 do not charge enough compared to the pixels of P2, P4, and P6, so they appear relatively bright (when twisted nematic liquid crystals operate in normally white mode), or appear dark (normally). In-plane switching liquid crystals operating in black mode).

That is, when the polarity of the pixel is changed due to the line inversion, due to the structural characteristics of the liquid crystal display of the double gate in panel type, pixel charging failure occurs and vertical dim occurs due to the pixel charging failure. will be.

Therefore, the technical problem to be achieved by the present invention is to form a vertical dim by configuring a relatively large width and length ratio (W / L) of the thin film transistor channel connected to a pixel that appears brighter or darker than other pixels due to poor charging. An object of the present invention is to provide a liquid crystal display device that can solve poor pixel charging and improve image quality.

Another object of the present invention is to provide a method of driving a liquid crystal display device capable of efficiently driving the above-described liquid crystal display device.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

According to an aspect of the present invention, a liquid crystal display device includes a plurality of pixels, each of which is divided into a gate line disposed above and below a pixel, and a data line disposed between two adjacent pixels. A liquid crystal display panel for displaying an image on each pixel according to a scan signal supplied through a gate line and an analog pixel signal supplied through the data line, and a gate line connected to an odd-numbered pixel in the liquid crystal display panel. An odd-numbered gate driver for supplying a scan signal, an even-numbered gate driver for sequentially supplying the scan signal to a gate line connected to an even-numbered pixel in the liquid crystal display panel, and an input video signal to the analog pixel signal To be supplied to the data line of the liquid crystal display panel. A source driver, a thin film transistor disposed at an intersection of a gate line and a data line of the liquid crystal display panel to supply the analog pixel signal to each pixel, a timing control signal to the gate driver and the source driver, and the source And a timing controller for supplying the video signal to a driver, wherein the thin film transistor connected to the first pixel of each pixel line in the liquid crystal display panel has a greater current driving capability than other thin film transistors.

In the liquid crystal display according to the exemplary embodiment of the present invention, the thin film transistor connected to the first pixel of each pixel line in the liquid crystal display panel is preferably an extended thin film transistor having a larger width and length ratio than the other thin film transistors. .

In the liquid crystal display according to the exemplary embodiment, it is preferable that the scan signal applied to the gate line of the liquid crystal display panel is inverted in polarity in pixel units.

In a method of driving a liquid crystal display according to an exemplary embodiment of the present invention, a timing controller supplies timing control signals to odd and even groups of gate and source drivers, and a video signal to the source driver. Supplying scan signals to the odd-numbered gate drivers, and sequentially supplying scan signals to the gate lines connected to the odd-numbered pixels, and sequentially scanning the gate-numbered gate drivers to the even-numbered pixels. Supplying the signal; and converting the video signal into an analog pixel signal and supplying the data signal to a data line disposed between two adjacent pixels, and at an intersection of the gate line and the data line of the liquid crystal display panel. A thin film transistor disposed thereon Comprising the step of alternately supplied to the two pixels adjacent to the pixel signal, a thin film transistor connected to the first pixel of the liquid crystal display panel, each pixel line is characterized in that a large current driving capability as compared with other TFTs.

In the method of driving a liquid crystal display according to an exemplary embodiment of the present invention, the thin film transistor connected to the first pixel of each pixel line in the liquid crystal display panel is an extended thin film transistor having a larger width and length ratio than the other thin film transistors. It is preferable.

In the driving method of the liquid crystal display according to the exemplary embodiment of the present invention, it is preferable that the scan signal applied to the gate line of the liquid crystal display panel is inverted in polarity on a pixel line basis.

Specific details of other embodiments are included in the detailed description and the drawings. Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. Like reference numerals refer to like elements throughout.

Hereinafter, a liquid crystal display and a driving method thereof according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a schematic overall configuration diagram of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 4 is a partial configuration diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

3 and 4, a liquid crystal display according to an exemplary embodiment may include a gate driver for driving the liquid crystal display panel 100 and the gate lines G ₁ to G _m of the liquid crystal display panel 100. Control driving timings of the source driver 110, the source driver 110, and the gate drivers 130 and 140 for driving the data lines D ₁ to D _n of the liquid crystal display panel 100 (130 and 140). And a gamma voltage generator 120 for supplying the gamma voltage to the source driver 110.

However, each component of the liquid crystal display may be implemented in various numbers according to the size in which the image is displayed, but for convenience, the following description will be simplified.

As shown in FIG. 4, the liquid crystal display panel 100 is disposed between two adjacent pixels with gate lines G ₁ and G ₂ , G ₃ and G ₄ , G _5, and G ₆ disposed up and down. data lines (D ₁₎ as formed of a plurality of pixels (P1 to P6), separated, the gate lines (G ₁ to G ₆₎ to scan signals supplied through the data line analog pixel supplied through a (D ₁₎ An image is displayed on each pixel P1 to P6 in accordance with the signal.

The source driver 110 converts the video signal input from the timing controller 150 into an analog pixel signal and supplies the converted video signal to the data line D ₁ of the liquid crystal display panel 100.

The gate drivers 130 and 140 are divided into odd-numbered gate drivers 130 and even-numbered gate drivers 140, and odd-numbered gate drivers 130 are odd-numbered pixels P1 in the liquid crystal display panel 100. Scan signals are sequentially supplied to the gate lines G ₁ , G ₃ , and G ₅ connected to the P3 and P5, and the even-numbered gate drivers 140 are even-numbered pixels P2 in the liquid crystal display panel 100. Scan signals are sequentially supplied to the gate lines G ₂ , G ₄ , and G ₆ connected to, P4 and P6.

The extended thin film transistor 160 and the thin film transistor 170 are disposed at the intersection of the gate lines G ₁ to G ₆ and the data line D ₁ of the liquid crystal display panel 100 to supply an analog pixel signal to each pixel. do.

The timing controller 150 supplies timing control signals to the gate drivers 130 and 140 and the source driver 110, and supplies a video signal to the source driver 110.

The gamma voltage generator 140 generates a gamma voltage by a resistor group in which a plurality of resistors are arranged in series, thereby supplying a gamma voltage that is accurate and always constant so that stable display quality can be maintained.

A thin film transistor connected to the first pixels P1, P3, and P5 of each pixel line PL1 to PL3 in the liquid crystal display panel 100 has a width and length ratio (W / L) of a channel compared to other thin film transistors 170. Is composed of a large expansion thin film transistor 160.

Herein, the polarities of the scan signals applied to the gate lines G ₁ to G ₆ of the liquid crystal display panel 100 are inverted in pixel line units, so that the polarities of the pixels P1, P3, and P5 are changed. Allow sufficient charge.

When the expansion thin film transistor 160 is disposed at the first stage of each pixel line PL1 to PL3 in the liquid crystal display panel 100 and the line inversion method of inverting the polarity of the liquid crystal display panel 100 in pixel lines is applied. , The following operation is made.

First, the odd and even groups of gate drivers 130 and 140 are sequentially turned on, so that the pixels are charged in the order of P1 to P6. At this time, since the analog pixel signal is alternately applied to P1, P2, P3, and P4 through one data line D ₁ , the pixel charge time is reduced to 1/2, so that the gate on time is sufficient to ensure sufficient charge. By doubling the precharge before the pixel is charged.

During precharging, as soon as the pixel being charged changes from P1 to P3 and P4 to P5, the positive (+) (-) polarity is changed by the line inversion.

Conventionally, since the value of the voltage to be charged (V _DATA ) becomes relatively large when the polarity of the pixel changes, and the thin film transistors having the same size are arranged in all the pixels, the pixel is sufficiently charged within the pixel charging time of 1/2 level. As a result, pixels with reversed polarities such as P1, P3, and P5 appear relatively bright or dark, resulting in vertical dim.

That is, in the case of the twisted nematic liquid crystal operating in the normally white mode, the pixels of P1, P3, and P5 appear brighter than the pixels of P2, P4, and P6, and the in-plane switching liquid crystal operates in the normally black mode. The pixels of P1, P3, and P5, which are insufficiently charged, appear darker than the pixels of P2, P4, and P6.

However, according to the present invention, the extended thin film transistor 160 having a larger current driving capability than the other thin film transistors 170 is disposed in the first pixels P1, P3, and P5 of each pixel line PL1 to PL3. Specifically, the expansion thin film transistor 160 has a width and length ratio (W / L) of a channel that is relatively larger than that of the other thin film transistors 170, thereby extending the current driving capability and thus eliminating the vertical dim. You can improve the picture quality.

FIG. 5 is a waveform diagram illustrating pixel charging characteristics of a liquid crystal display according to an exemplary embodiment of the present invention. In the liquid crystal display of FIGS. 3 and 4, a scan signal of the gate drivers 130 and 140 is applied to each pixel. A change in voltage charged as an analog pixel signal is applied is shown.

In the pixels of P1, P3, and P5, the expansion thin film transistor 160 having a larger width and length ratio (W / L) than the pixels of P2, P4, and P6 is disposed, and thus P1, P3, and P5 due to polarity inversion. It solves the pixel charging defect that appears in the pixel of.

The odd- and even-numbered gate drivers 130 and 140 are sequentially turned on so that the gate-on time overlaps, as shown in FIG. 2, P1, P2, P3, P4, P5, and P6. The pixels are charged in the order of.

At this time, as the liquid crystal display panel 100 is driven in a line inversion method, a common voltage V _COM having a polarity inverted on a pixel line basis is applied to each pixel, and a driving voltage V _{DATA that} becomes an analog pixel signal. The pixel is charged in turn as it is applied.

However, at the moment when the polarity of the pixel is changed, that is, at the moment when the pixel charged from P2 to P3 and P4 to P5 is changed, the polarity is changed so that the charging is not sufficiently performed. The expansion thin film transistor 160 having a large width / length ratio (W / L) is disposed to improve charging characteristics.

That is, by forming the thin film transistors electrically contacting the pixels of P1, P3, and P5 that appear relatively bright or dark due to poor pixel charge, the thin film transistors 160 having a large width / length ratio (W / L) are formed. In other words, for the pixels whose polarities are reversed, the current driving capability to the same applied voltage is improved and sufficient normal charging is performed to eliminate vertical dim and improve image quality.

6 is a flowchart illustrating a method of driving a liquid crystal display according to an exemplary embodiment of the present invention, and illustrates a driving method for efficiently implementing the liquid crystal display as shown in FIGS. 3 and 4.

First, in step S100, the timing controller 150 supplies timing control signals to the odd and even groups of the gate drivers 130 and 140 and the source driver 120, and supplies the video signals to the source driver 120. .

Next, in step S110, the odd-numbered gate drivers 130 sequentially supply scan signals to the gate lines connected to the odd-numbered pixels, and the even-numbered gate drivers 140 are connected to the even-numbered pixels. The scan signals are supplied sequentially.

Next, in step S120, the source driver 120 converts the video signal into an analog pixel signal and supplies it to a data line disposed between two adjacent pixels.

Next, in operation S130, the extended thin film transistor 160 and the thin film transistor 170 disposed at the intersection of the gate line and the data line of the liquid crystal display panel 100 alternately supply analog pixel signals to two adjacent pixels. do.

Here, the thin film transistor connected to the first pixel of each pixel line in the liquid crystal display panel 100 includes an extended thin film transistor 160 having a larger width and length ratio than the other thin film transistor 170. It is preferable that the scan signal applied to the gate line of 100 is inverted in polarity on a pixel line basis.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. Therefore, since the embodiments described above are provided to fully inform the scope of the invention to those skilled in the art, it should be understood that they are exemplary in all respects and not limited. The invention is only defined by the scope of the claims.

In the liquid crystal display according to the exemplary embodiment of the present invention, the width and length ratios (W / L) of the thin film transistor channels connected to the pixels appearing brighter or darker than the other pixels due to the charging failure are relatively high. By making it large, the pixel filling defect which causes a vertical dim can be solved and image quality can be improved.

In addition, the driving method of the liquid crystal display according to the exemplary embodiment of the present invention can efficiently drive such a liquid crystal display.

Claims (6)

Comprising a plurality of pixels divided into a gate line disposed up and down of the pixel and a data line disposed between two adjacent pixels, the scan signal supplied through the gate line and the analog pixel signal supplied through the data line A liquid crystal display panel which displays an image on each pixel according to; Odd-numbered gate drivers sequentially supplying scan signals to gate lines connected to odd-numbered pixels in the liquid crystal display panel; An even group of gate drivers sequentially supplying the scan signals to gate lines connected to even-numbered pixels in the liquid crystal display panel; A source driver for converting an input video signal into the analog pixel signal and supplying the converted video signal to a data line of the liquid crystal display panel; A thin film transistor disposed at an intersection of a gate line and a data line of the liquid crystal display panel to supply the analog pixel signal to each pixel; And A timing controller supplying a timing control signal to the gate driver and a source driver, and supplying the video signal to the source driver, The thin film transistor connected to the first pixel of each pixel line in the liquid crystal display panel has a greater current driving capability than other thin film transistors. The method of claim 1, And the thin film transistor connected to the first pixel of each pixel line in the liquid crystal display panel is an extended thin film transistor having a large width and length ratio of the channel compared to other thin film transistors. The method of claim 1, The scan signal applied to the gate line of the liquid crystal display panel is The liquid crystal display of claim 1, wherein the polarity is inverted in units of pixel lines. Supplying timing control signals to odd and even groups of gate and source drivers by a timing controller, and supplying a video signal to the source driver; Supplying scan signals sequentially to gate lines connected to odd-numbered pixels by the odd-numbered gate drivers, and sequentially supplying scan signals to gate lines connected to even-numbered pixels by even-numbered gate drivers; The source driver converting the video signal into an analog pixel signal and supplying the data signal to a data line disposed between two adjacent pixels; And A thin film transistor disposed at an intersection of a gate line and a data line of the liquid crystal display panel alternately supplying the analog pixel signal to two adjacent pixels, The thin film transistor connected to the first pixel of each pixel line in the liquid crystal display panel has a greater current driving capability than other thin film transistors. The method of claim 4, wherein And the thin film transistor connected to the first pixel of each pixel line in the liquid crystal display panel is an extended thin film transistor having a large width and length ratio of the channel compared to other thin film transistors. The method of claim 4, wherein The scan signal applied to the gate line of the liquid crystal display panel is A method of driving a liquid crystal display device, characterized in that the polarity is inverted on a pixel line basis.

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