KR20080090885A - Liquid crystal display device - Google Patents

Abstract

An LCD(Liquid Crystal Display) is provided to supply a uniform common voltage to common electrodes regardless of locations of the common electrodes, thereby preventing the deterioration of picture quality. A plurality of gate lines(G1-Gn) and a plurality of data lines(D1-Dm) cross each other. A plurality of liquid crystal cells(Clc) are driven by difference of electric potential between pixel electrodes and common electrodes. A plurality of pixel switching elements(TFT) are formed within a pixel array including the liquid crystal cells to electrically connect between the data lines and to pixel electrodes. A common voltage supply line(58) supplies a common voltage to the common electrodes. A plurality of common voltage switching elements(60) electrically connect between the common voltage supply line and the common electrodes. A gate-driving circuit(54) supplies scan pulses to the gate lines sequentially to drive the pixel switching elements and the common voltage switching elements. A data-driving circuit(52) supplies data voltage to the data lines.

Description

Liquid crystal display {LIQUID CRYSTAL DISPLAY DEVICE}

1 is a view showing a liquid crystal display device according to an exemplary embodiment of the present invention.

2 is a diagram illustrating a supply of a common voltage according to an embodiment of the present invention.

<Brief description of symbols for the main parts of the drawings>

50 liquid crystal display panel 52 data driving circuit

54 gate driving circuit 56 common voltage supply

58: common voltage supply line 60: common voltage switching device

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of supplying a uniform common voltage to the common electrode regardless of the position of the common electrode.

Liquid crystal displays are widely used in display devices of office equipment, computer monitors, and even large-screen televisions with the recent development of process and driving technologies. Such a 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 liquid crystal cells are arranged in a matrix, and a driving circuit for driving the liquid crystal display panel.

The liquid crystal display panel is formed by bonding a thin film transistor array substrate on which a thin film transistor array is formed and a color filter array substrate on which a color filter array is formed, with the liquid crystal layer interposed therebetween.

Data lines and gate lines that are orthogonal to each other are formed on the thin film transistor array substrate, and a liquid crystal cell is formed in each region formed by the orthogonality of the data lines and the gate lines. The thin film transistor connected to the intersection of the data lines and the gate lines supplies the data voltage supplied through the data line to the pixel electrode of the liquid crystal cell in response to the scan pulse of the gate line.

In a horizontal field driving liquid crystal display device such as IPS (In Plane Switching) mode and FFS (Fringe Field Switching) mode, a common electrode is further formed on the thin film transistor array substrate, and a black matrix and a color filter are formed on the color filter array substrate. Is formed. Accordingly, the liquid crystal cell rotates a liquid crystal having dielectric anisotropy through a horizontal electric field due to a potential difference between the data voltage supplied to the pixel electrode and the common voltage supplied to the common electrode to adjust the light transmittance. In this case, the common voltage is supplied to the common electrode through the common voltage supply line of the thin film transistor array substrate.

In a vertical field driving liquid crystal display device such as twisted nematic (TN) mode and vertical alignment (VA) mode, a black matrix, a color filter, a common electrode, and the like are formed on a color filter array substrate. In the liquid crystal cell, a liquid crystal having dielectric anisotropy rotates through a vertical electric field due to a potential difference between a data voltage supplied to a pixel electrode disposed on a thin film transistor array substrate and a common voltage supplied to a common electrode disposed on a color filter array substrate, thereby increasing the strong transmittance. Adjust The common electrode of the color filter array substrate receives a common voltage through a transfer path such as a silver dot connected to the common voltage supply line of the thin film transistor array substrate.

The common voltage supply line is formed on one side or both sides of the thin film transistor array substrate to receive a common voltage from the common voltage supply unit. The common voltage supply line supplies a lower common voltage to the common electrode as the line resistance increases as the distance from the common voltage supply increases. As described above, the conventional liquid crystal display device has a problem in that the image quality is deteriorated due to luminance unevenness or flicker deviation in the display image due to the different magnitude of the common voltage supplied according to the position of the common electrode.

Accordingly, an object of the present invention is to provide a liquid crystal display device capable of supplying a uniform common voltage to a common electrode regardless of the position of the common electrode.

In order to achieve the above object, a liquid crystal display according to an embodiment of the present invention, a plurality of liquid crystal cells driven by a potential difference between a plurality of data lines and a plurality of gate lines, a pixel electrode and a common electrode intersecting each other, A plurality of pixel switching elements formed in the pixel array including the liquid crystal cells to connect the data line and the pixel electrode, a common voltage supply line for supplying a common voltage to the common electrode, and the common voltage supply line and the A liquid crystal display panel including a plurality of common voltage switching elements for conducting the common electrode; A gate driving circuit driving the pixel switching elements and the common voltage switching elements by supplying sequential scan pulses to the gate lines; And a data driving circuit for supplying data voltages to the data lines.

The liquid crystal display according to the exemplary embodiment of the present invention further includes a common voltage supply unit configured to generate the common voltage.

The common voltage supply unit increases the common voltage as the common electrode located farther from the common voltage supply unit.

The common voltage switching elements are connected between the gate driving circuit and the pixel switching element.

The common voltage switching device may include a gate electrode connected to the gate line; A source electrode connected to the common voltage supply line; And a drain electrode connected to the common electrode.

The common voltage supply line is formed outside the pixel array.

The common voltage supply line may include a first common voltage supply line formed outside one side of the pixel array; And a second common voltage supply line formed outside the other side of the pixel array.

The common voltage switching elements may include first common voltage switching elements for conducting the first common voltage supply line and the common electrode to each other; And second common voltage switching elements connecting the second common voltage supply line and the common electrode to each other.

A gate electrode of the first common voltage switching device is connected to the gate line, a source electrode is connected to the first common voltage supply line, and a drain electrode is connected to the common electrode.

A gate electrode of the second common voltage switching device is connected to the gate line, a source electrode is connected to the second common voltage supply line, and a drain electrode is connected to the common electrode.

Other objects and advantages of the present invention in addition to the above object will be apparent from the description of the preferred embodiment of the present invention with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2.

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

Referring to FIG. 1, in the liquid crystal display according to the exemplary embodiment, m × n liquid crystal cells Clc are arranged in a matrix type, m data lines D1 to Dm and n gate lines. The data voltages are supplied to the liquid crystal display panel 50 where the G1 to Gn intersect and the pixel switching element TFT is connected to the intersection thereof, and the data lines D1 to Dm of the liquid crystal display panel 50. A data driving circuit 52, a gate driving circuit 54 for supplying scan pulses to the gate lines G1 to Gn, and a common voltage supply unit 56 for supplying a common voltage to the common voltage supply line 58. It is provided.

The liquid crystal display panel 50 is formed by bonding a thin film transistor array substrate on which a thin film transistor array is formed and a color filter array substrate on which a color filter array is formed, with the liquid crystal layer interposed therebetween.

The data lines D1 to Dm and the gate lines G1 to Gn formed on the thin film transistor array substrate of the liquid crystal display panel 50 are perpendicular to each other. The pixel switching element TFT connected to the intersection of the data lines D1 to Dm and the gate lines G1 to Gn is in response to the scan pulses of the gate lines G1 to Gn. The data voltage supplied through the same is supplied to the pixel electrode Ep of the liquid crystal cell Clc.

The liquid crystal display panel 50 has a horizontal electric field driving method such as IPS (In Plane Switching) mode, FFS (Fringe Field Switching) mode, and a vertical electric field driving method such as twisted nematic (TN) mode and vertical alignment (VA) mode. It is roughly classified into a liquid crystal display panel.

When the liquid crystal display panel 50 is a horizontal electric field driving method, the common electrode Ec is further formed on the thin film transistor array substrate, and a black matrix and a color filter are formed on the color filter array substrate. In the liquid crystal cell Clc, a liquid crystal having dielectric anisotropy rotates through a horizontal electric field due to a potential difference between a data voltage supplied to the pixel electrode Ep and a common voltage supplied to the common electrode Ec, thereby controlling light transmittance. . The common voltage is supplied to the common electrode Ec through the common voltage supply line 58 formed on one side or both sides of the liquid crystal display panel 50. The common electrodes Ec are connected in a line form with adjacent common electrodes Ec.

A plurality of common voltage switching elements 60 are further formed on the thin film transistor array substrate to conduct the common voltage supply line 58 and the common electrode Ec by the control of the scan pulse. The common voltage switching device 60 is formed outside the pixel array 56 in which an image is displayed together with the common voltage supply line 58. The gate electrode G of the common voltage switching device 60 is connected to the gate lines G1 to Gn, the drain electrode D is connected to the common voltage supply line 58, and the source electrode S is the common electrode. It is connected to (Ec).

When the liquid crystal display panel 50 has a vertical electric field driving method, a black matrix, a color filter, a common electrode Ec, and the like are formed on the color filter array substrate. The liquid crystal cell Clc has a dielectric anisotropy through a vertical electric field due to a potential difference between a data voltage supplied to the pixel electrode Ep on the thin film transistor array substrate and a common voltage supplied to the common electrode Ec on the color filter array substrate. The liquid crystal having the rotation is to adjust the light transmittance. The common electrode Ec of the color filter array substrate is connected in line with the adjacent common electrodes Ec.

A plurality of common voltage switching elements 60 are further formed on the thin film transistor array substrate to conduct the common voltage supply line 58 of the thin film transistor array substrate and the common electrode Ec of the color filter array substrate to be controlled by the scan pulse. . The common voltage switching device 60 is formed outside the pixel array 56 in which an image is displayed together with the common voltage supply line 58. The gate electrode G of the common voltage switching device 60 is connected to the gate lines G1 to Gn, the drain electrode D is connected to the common voltage supply line 58, and the source electrode S is a silver dot. It is connected to the common electrode Ec of the color filter array substrate through a medium such as the like.

A polarizing plate having an orthogonal optical axis is attached to the thin film transistor array substrate and the color filter array substrate of the liquid crystal display panel 50, and an alignment layer for determining the pretilt angle of the liquid crystal is further formed on the inner surface of the liquid crystal display panel 50. In addition, a storage capacitor Cst is further formed in each of the liquid crystal cells Clc. The storage capacitor Cst is formed between the pixel electrode Ep and the front gate lines G1 to Gn, or is formed between the pixel electrode Ep and a common line (not shown) and is charged in the liquid crystal cell Clc. Keep it constant.

The data driving circuit 52 converts the input digital video data into an analog data voltage using a gamma voltage and supplies the analog data voltage to the data lines D1 to Dm.

The gate driving circuit 54 sequentially supplies scan pulses to the gate lines G1 to Gn to select a horizontal line of the liquid crystal cell Clc to which a data voltage is supplied. In other words, the gate driving circuit 54 turns on or turns on the pixel switching element TFT connected to the gate lines G1 to Gn by sequentially supplying scan pulses to the gate lines G1 to Gn. -Turn it off. The turned-on pixel switching element TFT conducts the data voltages to the pixel electrode Ep by connecting the data lines D1 to Dm and the pixel electrode Ep. In addition, the scan pulses sequentially supplied to the gate lines G1 to Gn turn on or turn off the common voltage switching device 60 connected to one or both ends of the gate lines G1 to Gn. Let's do it. The turned-on common voltage switching device 60 conducts the common voltage supply line 58 and the common electrode Ec so that the common voltage can be supplied to the common electrode Ec.

The common voltage supply unit 56 generates a common voltage and supplies it to the common voltage supply line 58. The common voltage supply unit 56 supplies a higher common voltage as the common electrode Ec is located farther from the common voltage supply unit 56. In the liquid crystal display shown in FIG. 1, since the common voltage supply unit 56 is supplied from the upper end of the liquid crystal display panel 50, the common electrode Ec moves toward the lower end, that is, toward the A direction, as shown in FIG. 2. High common voltage is supplied. The degree of increase of the common voltage according to the position of the common electrode Ec is set to be the same as that of the line resistance, so that the common voltage increased by the resistance increased even if the resistance of the common voltage supply line 58 is increased. Is supplied to line 58. Thus, the liquid crystal display according to the exemplary embodiment of the present invention can supply a common common voltage to the common electrode Ec regardless of the position of the common electrode Ec.

As described above, the liquid crystal display according to the exemplary embodiment of the present invention includes a common voltage switching element controlled by a scan pulse to conduct the common voltage supply line and the common electrode, and has a common voltage having a different value depending on the position of the common electrode. To the common voltage supply line. Accordingly, even when the common voltage at a specific position is lowered by the resistance of the common voltage supply line, a common voltage having a magnitude that can compensate for the lowered common voltage is supplied to the common voltage supply line, thereby providing a common common electrode regardless of its position. Voltage can be supplied.

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 (10)

A plurality of liquid crystal cells driven by a potential difference between the pixel electrode and the common electrode, a plurality of data lines and a plurality of gate lines crossing each other, and formed in a pixel array including the liquid crystal cells to conduct the data line and the pixel electrode. A liquid crystal display panel including a plurality of pixel switching elements for supplying a common voltage, a common voltage supply line for supplying a common voltage to the common electrode, and a plurality of common voltage switching elements for conducting the common voltage supply line and the common electrode; A gate driving circuit driving the pixel switching elements and the common voltage switching elements by supplying sequential scan pulses to the gate lines; And And a data driving circuit for supplying data voltages to the data lines. The method of claim 1, And a common voltage supply unit for generating the common voltage. The method of claim 2, The common voltage supply unit, And the common voltage of the common electrode located farther from the common voltage supplying unit to increase the common voltage. The method of claim 1, And the common voltage switching elements are connected between the gate driving circuit and the pixel switching element. The method of claim 4, wherein The common voltage switching device, A gate electrode connected to the gate line; A source electrode connected to the common voltage supply line; And And a drain electrode connected to the common electrode. The method of claim 1, And the common voltage supply line is formed outside the pixel array. The method of claim 1, The common voltage supply line, A first common voltage supply line formed outside one side of the pixel array; And And a second common voltage supply line formed outside the other side of the pixel array. The method of claim 7, wherein The common voltage switching device, First common voltage switching elements connecting the first common voltage supply line and the common electrode to each other; And And second common voltage switching elements for conducting the second common voltage supply line and the common electrode to each other. The method of claim 8, And a gate electrode of the first common voltage switching device is connected to the gate line, a source electrode is connected to the first common voltage supply line, and a drain electrode is connected to the common electrode. The method of claim 8, And a gate electrode of the second common voltage switching device is connected to the gate line, a source electrode is connected to the second common voltage supply line, and a drain electrode is connected to the common electrode.

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