KR100923675B1 - Structure of liquid crystal dispaly panel and driving method thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a liquid crystal panel and a driving method thereof, and includes a pixel electrode and a common electrode formed on a unit pixel on a substrate to apply a horizontal electric field to a liquid crystal layer. Supplying the first common voltage in the form of a pulse to be transitioned every frame unit through the first common voltage lines to the common electrodes of the corresponding pixels, and also to the common electrode of the pixels corresponding to the even-numbered gate lines. The present invention provides a structure of a liquid crystal panel for supplying a second common voltage having a pulse shape in which the first common voltage is inverted and a driving method thereof.

Description

Structure of liquid crystal panel and its driving method {STRUCTURE OF LIQUID CRYSTAL DISPALY PANEL AND DRIVING METHOD THEREOF}

Figures 1a and 1b is an exemplary view showing the phase shift of the liquid crystal when on / off (on / off) in the transverse electric field method.

2 is a schematic plan view of a thin film transistor array substrate in a typical transverse electric field liquid crystal panel.

Figure 3 is an exemplary view showing a signal waveform applied to the liquid crystal panel in the dot inversion method.

4 is a schematic plan view showing a thin film transistor array substrate in a transverse electric field type liquid crystal panel according to an embodiment of the present invention.

5 is an exemplary view showing a signal waveform applied to a liquid crystal panel according to an embodiment of the present invention.

*** Explanation of symbols for main parts of drawing ***

G11 to G1n: gate wirings D11 to D1m: data wirings

P11: pixel 111: pixel electrode

TFT11: thin film transistor 113: common electrode

Vcom11 to Vcom1n: Common voltage wiring

The present invention relates to a structure of a liquid crystal panel and a driving method thereof, and more particularly, to a structure of a liquid crystal panel using an in plane switching (IPS) method and a driving method thereof.

In general, the liquid crystal panel is bonded so that inner surfaces of the thin film transistor array substrate and the color filter substrate face each other to have a predetermined gap (usually called a cell-gap), and the thin film transistor array substrate and the color filter substrate are bonded together. It is formed by filling the liquid crystal at spaced intervals of.

The thin film transistor array substrate and the outer surface of the color filter substrate are provided with a polarizing plate and a retardation plate, and by selectively configuring a plurality of such components, the brightness of the light is changed or the refractive index is changed to provide high brightness and contrast. A liquid crystal display device having the characteristics is constructed.

The liquid crystal panel applied as a liquid crystal display device in recent years generally adopts a twisted nematic liquid crystal, and since such a twisted nematic liquid crystal has a characteristic that the light transmittance in gradation display varies depending on the viewing angle, There is a limit.

In the liquid crystal panel to which the twisted nematic liquid crystal is applied, the light transmittance is symmetrically distributed over a wide range with respect to the viewing angle in the left and right directions, but since the light transmittance is distributed asymmetrically with respect to the viewing angle in the vertical direction, the image is reversed in the vertical direction. There was a problem that a range occurs and the viewing angle is narrowed.

In order to solve the problems described above, a transverse electric field type liquid crystal panel using a horizontal electric field has been proposed.

The lateral field type liquid crystal panel has an advantage of improving viewing angle characteristics such as contrast, gray inversion, and color shift, compared to a liquid crystal panel using a twisted nematic liquid crystal. Have

In the transverse electric field type liquid crystal panel, a pixel electrode and a common electrode are formed on the same plane of the thin film transistor array substrate, and thus the liquid crystal is driven by a horizontal electric field between the pixel electrode and the common electrode.

Referring to the attached liquid crystal panel of the transverse electric field method as described above in detail as follows.

1A and 1B are exemplary views showing phase shift of a liquid crystal when it is turned on / off in a transverse electric field system.

1A and 1B, in the transverse electric field type liquid crystal panel, the thin film transistor array substrate 17 and the color filter substrate 19 are uniformly spaced to face each other, and the thin film transistor array substrate 17 and the color filter are opposite to each other. Liquid crystals 15A and 15B are filled at spaced intervals of the substrate 19.

First and second polarizing plates 21 and 23 are provided on outer surfaces of the thin film transistor array substrate 17 and the color filter substrate 19, respectively.

The pixel electrode 11 and the common electrode 13 are patterned at a predetermined distance from the thin film transistor array substrate 17. In this case, the pixel electrode 11 and the common electrode 13 may be formed of an opaque conductive metal or indium-tin-oxide (ITO) and indium-zinc-oxide (IZO). Transparent conductive metals and the like can be applied.

FIG. 1A illustrates an off state in which no phase shift occurs in the liquid crystal 15A because no electric field is applied to the pixel electrode 11 and the common electrode 13. That is, the molecules of the liquid crystal 15A form an angle of 90 ° with respect to the horizontal direction of the pixel electrode 11 and the common electrode 13.

On the other hand, in FIG. 1B, when a voltage is applied to the pixel electrode 11 and the common electrode 13, the molecules of the liquid crystal 15B are formed in the pixel electrode 11 and the common electrode when compared to the off state of FIG. 1A. 13) are arranged parallel to the horizontal direction.

As described above, the transverse electric field type liquid crystal panel uses a parallel field because the pixel electrode 11 and the common electrode 13 are formed on the same plane. The transverse electric field type liquid crystal panel has an advantage of a wide viewing angle. That is, the transverse electric field type liquid crystal panel can see an image at an angle of about 70 ° in the up / down / left / right directions.

2 is an exemplary view showing a schematic planar configuration of a thin film transistor array substrate in a general transverse electric field liquid crystal panel.

Referring to FIG. 2, the plurality of gate lines G1 to Gn are arranged to be laterally spaced apart, and the plurality of data lines D1 to Dm are arranged to be regularly spaced apart vertically.

Therefore, the gate lines G1 to Gn and the data lines D1 to Dm vertically intersect each other, and the pixel P1 is defined at an intersection thereof.

Each pixel P1 is provided with a switching element such as a thin film transistor TFT1 to switch image information applied to the pixel electrode 11.

Gate electrodes of the thin film transistors TFT1 are respectively connected to the gate lines G1 to Gn, source electrodes are respectively connected to the data lines D1 to Dm, and drain electrodes are pixels in the pixel P1. It is connected to the electrode 11, respectively.

Therefore, when the scan signal of the liquid crystal panel is sequentially applied to the gate lines G1 to Gn, the thin film transistors TFT1 are turned on in units of the gate lines G1 to Gn.

A conductive channel is formed between the source electrode and the drain electrode of the thin film transistors TFT1 turned on in the gate lines G1 to Gn. In this case, when image information is supplied to the source electrodes of the thin film transistors TFT1 through the data lines D1 to Dm, the image information is supplied to the drain electrodes of the thin film transistors TFT1 through the conductive channel.

However, since the drain electrode is connected to the pixel electrode 11, image information is supplied to the pixel electrode 11. In this case, one or more pixel electrodes 11 are patterned in the pixel P1 in a direction parallel to the data lines D1 to Dm.

Meanwhile, in the pixel P1, the common electrode 13 formed to correspond to the pixel electrode 11 generates a horizontal electric field together with the pixel electrode 11 to drive the liquid crystal in a lateral electric field method.

That is, one or more common electrodes 13 are patterned in the pixel P1 in a direction parallel to the data lines D1 to Dm.

The common voltage is supplied to the common electrode 13 formed in the pixel P1 through the common voltage lines Vcom1 to Vcomn.

The common voltage wirings Vcom1 to Vcomn are regularly spaced apart from the gate wirings G1 to Gn and arranged in parallel with the gate wirings G1 to Gn, and one ends thereof are electrically connected to each other to be identical to all pixels. Allow common voltage to be applied.

Accordingly, the liquid crystal is driven by the voltage difference between the image information applied to the pixel electrode 11 and the common voltage applied to the common electrode 13.

Although not shown in the drawing, the pixel electrode 11 is electrically connected to a storage electrode of a storage capacitor provided for each liquid crystal cell.

Therefore, the image information applied to the pixel electrode 11 is charged in the storage capacitor during the turn-on period of the thin film transistor to which the scan signal is applied.

The image information charged in the storage capacitor is supplied to the pixel electrode 11 during the turn-off period of the thin film transistor to which the scan signal is not applied to maintain driving of the liquid crystal.

In the transverse electric field type liquid crystal panel, shapes of the pixel electrode 11 and the common electrode 13 formed on the thin film transistor array substrate may be variously modified.

On the other hand, when a constant electric field is continuously applied to the liquid crystal, the liquid crystal is deteriorated, resulting in afterimages in the liquid crystal panel due to the DC voltage component. Therefore, in order to prevent deterioration of the liquid crystal and to remove the DC voltage component, the voltage of the image information is applied to repeat the positive / negative based on the common voltage. Such a driving method is called an inversion method. .

The inversion driving method includes a frame inversion method in which the polarity of the image information is supplied in one frame unit of the image, a line inversion method in which the polarity of the image information is supplied in the unit of the gate wiring, and In addition, the polarity of the image information is divided into the liquid crystal cells adjacent to each other, and is also divided into a dot inversion scheme in which the polarity of the image information is supplied in the unit of one frame.

Among the inversion driving methods described above, the dot inversion method can suppress screen distortions such as flicker and cross talk as much as possible, so that the liquid crystal panel using the same provides excellent images.

3 is an exemplary view showing a signal waveform applied to the liquid crystal panel in the dot inversion method.

Referring to FIG. 3, the common voltage Vcom is supplied at a constant level DC voltage, and the scan signals V _G1 -V _Gn are sequentially applied to the gate wiring every frame.

On the other hand, the image information (V _DATA ) is applied to the liquid crystal cells adjacent to each other alternately positive and negative polarity with respect to the common voltage (Vcom), and also positive and negative polarity with respect to the common voltage (Vcom) in every frame unit This is applied alternately.

In the turn-on period of the thin film transistor to which the scan signals V _G1- V _Gn are applied at high potential, image information V _DATA applied to the pixel electrode is gradually charged due to the influence of the liquid crystal capacitor and the storage capacitor. And a pixel voltage (V _P ) waveform shown in FIG. The pixel voltage V _P is charged in the storage capacitor.

In addition, when the scan signals V _G1 -V _Gn transition to a low potential, the pixel voltage V _P may occur due to coupling of parasitic capacitance due to over-lap of the gate electrode and the drain electrode of the thin film transistor. A voltage drop is generated from), which is referred to as a change in pixel voltage (ΔV _P ).

Meanwhile, in the turn-off period of the thin film transistor to which the scan signals V _G1 -V _Gn are applied at low potential, the pixel voltage V _P charged to the storage capacitor is continuously supplied to the pixel electrode to maintain driving of the liquid crystal. Let's go.

Therefore, in the related art, the voltage V _DATA -Vcom obtained by subtracting the common voltage Vcom from the image information V _DATA is applied to the liquid crystal.

In order for the voltage (V _DATA -Vcom) obtained by subtracting the common voltage (Vcom) from the image information (V _DATA ) to drive the liquid crystal, the image information (V _DATA ) must be applied at a predetermined voltage level or higher than the common voltage (Vcom). do. This increases the power consumption of the liquid crystal panel.

Therefore, when applied to a portable device using a battery, the use time is shortened, there is a problem inconvenient use.

 The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a structure of a liquid crystal panel and a driving method thereof capable of reducing power consumption of a liquid crystal panel to which a transverse electric field is applied. .

First, the structure of the liquid crystal panel for achieving the object of the present invention as described above is opposed to the first and second substrates; A liquid crystal layer formed between the first and second substrates; Gate wirings and data wirings arranged vertically and horizontally on the first substrate to define pixels; First and second electrodes formed on unit pixels on the first substrate to apply a horizontal electric field to the liquid crystal layer; A switching element provided at one edge of the unit pixel to supply or block image information to the first electrode; First common voltage lines supplying a first common voltage to a second electrode of pixels corresponding to the odd-numbered gate lines; And second common voltage lines for supplying a second common voltage to second electrodes of the pixels corresponding to the even-numbered gate lines.

In addition, the driving method of the liquid crystal panel for achieving the object of the present invention as described above, the gate wirings and the data wirings are arranged horizontally and horizontally to define pixels, and apply image information and a common voltage to the unit pixel in the horizontal direction. In the transverse electric field driving method for driving a liquid crystal, the first common voltage in the form of a pulse that is transitioned every frame unit is supplied to the pixels corresponding to the odd-numbered gate lines, and the even-numbered gate lines The second common voltage in the form of a pulse in which the first common voltage is inverted is supplied to the pixels corresponding to.                     

The liquid crystal panel and the driving method thereof according to the present invention as described above will be described in detail with reference to the accompanying drawings.

4 is an exemplary view showing a schematic plan configuration of a thin film transistor array substrate in a transverse electric field type liquid crystal panel according to an embodiment of the present invention.

Referring to FIG. 4, a plurality of gate lines G11 to G1n are arranged to be uniformly spaced laterally, and a plurality of data lines D11 to D1m are arranged to be regularly spaced apart vertically. Therefore, the gate lines G11 to G1n and the data lines D11 to D1m vertically cross each other, and the pixel P11 is defined in the intersection area.

Each pixel P11 is provided with a switching element such as a thin film transistor TFT11 to switch image information applied to the pixel electrode 111.

Gate electrodes of the thin film transistors TFT11 are respectively connected to the gate lines G11 to G1n, source electrodes are respectively connected to the data lines D11 to D1m, and drain electrodes are respectively connected to the pixel P11. Is connected to the pixel electrode 111 within.

Therefore, when the scan signal of the liquid crystal panel is sequentially applied to the gate lines G11 to G1n, the thin film transistors TFT11 are turned on in units of the gate lines G11 to G1n.

A conductive channel is formed between the source electrode and the drain electrode of the thin film transistors TFT11 turned on in units of the gate lines G11 to G1n. At this time, when image information is supplied to the source electrode of the thin film transistors TFT11 through the data lines D11 to D1m, the image information is supplied to the drain electrode of the thin film transistors TFT11 through the conductive channel.

However, since the drain electrode is connected to the pixel electrode 111, image information is supplied to the pixel electrode 111.

One or more pixel electrodes 111 may be patterned in the pixel P11 in a direction parallel to the data lines D11 to D1m. In this case, when a plurality of vertical patterns are applied to the pixel electrode 111 in the pixel P11, a predetermined distance is formed to be spaced apart from each other in a direction parallel to the data lines D11 to D1m. It is preferable to allow the vertical patterns of the pixel electrode 111 to be connected to each other through one horizontal pattern parallel to the G11 to G1n.

In addition, the common electrode 113 formed to correspond to the pixel electrode 111 in the pixel P11 generates a horizontal electric field together with the pixel electrode 111 to drive the liquid crystal in a lateral electric field method. Accordingly, one or more common electrodes 113 may be patterned in the pixel P11 in a direction parallel to the data lines D11 to D1m.

When a plurality of vertical patterns are applied to the common electrode 113 in the pixel P11, they are formed to correspond to the plurality of vertical patterns of the pixel electrode 111 and the horizontal pattern of the pixel electrode 111. Likewise, the vertical patterns of the common electrode 113 may be connected to each other through one horizontal pattern parallel to the gate lines G11 to G1n.

Meanwhile, the common voltage is supplied to the common electrode 113 formed in the pixel P11 through the common voltage lines Vcom11 to Vcom1n.                     

The common voltage wirings Vcom11 to Vcom1n are arranged parallel to the gate wirings G11 to G1n at regular intervals, and the odd-numbered common voltage wirings Vcom11, Vcom13, Vcom15, .... It is formed to be electrically connected, and even-numbered common voltage wirings Vcom12, Vcom14, Vcom16, .... Vcom1n are patterned to be electrically connected to each other.

In describing the exemplary embodiment of the present invention, the common voltage wirings Vcom11 to Vcom1n are arranged parallel to the gate wirings G11 to G1n at regular intervals and are perpendicular to the data wirings D11 to D1m. Although the present invention is used as an example, the present invention is not limited thereto. In some cases, the common voltage wires according to the present invention may be arranged to be perpendicular to the gate wires and to be parallel to the data wires.

The odd-numbered common voltage wires Vcom11, Vcom13, Vcom15, .... Vcom1n-1 supply a first common voltage in the form of a pulse that is transitioned every frame unit to the common electrode 113A of the pixels.

In addition, the even-numbered common voltage wirings Vcom12, Vcom14, Vcom16,... Vcom1n supply a second common voltage in the form of a pulse in which the first common voltage is inverted to the common electrode 113B of the pixels.

Accordingly, the transverse electric field type liquid crystal panel according to the present invention is driven by the voltage difference between the image information applied to the pixel electrode 111 and the first and second common voltages applied to the common electrodes 113A and 113B, respectively. .

Although not shown in the drawing, the pixel electrode 111 is electrically connected to the storage electrode of the storage capacitor provided in the unit pixel P11.

Therefore, the image information applied to the pixel electrode 111 is charged in the storage capacitor during the turn-on period of the thin film transistor to which the scan signal is applied.                     

The image information charged in the storage capacitor is supplied to the pixel electrode 111 during the turn-off period of the thin film transistor to which the scan signal is not applied to maintain driving of the liquid crystal.

In addition, the transverse electric field type liquid crystal panel is filled with liquid crystal between the thin film transistor array substrate and the color filter substrate which are bonded to each other, and the pixel electrode 111 and the common electrode 113 have various shapes on the thin film transistor array substrate. Is patterned as:

5 is an exemplary view illustrating a signal waveform applied to a liquid crystal panel according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the first common voltage Vcom_odd is supplied to the common electrodes of the corresponding pixels through an odd-numbered common voltage wiring in the form of a pulse that transitions every frame. The second common voltage Vcom_even is supplied to the common electrodes of the corresponding pixels through an even-numbered common voltage wiring in the form of a pulse in which the first common voltage Vcom_odd is inverted.

Then, the scan signal (V _G11 ~V _G1n) is sequentially applied to the gate line in each frame.

On the other hand, the image information (V _DATA) is the turn of the thin film transistor when the scan signal (V _G11 ~V _G1n) is applied the classic Back-so gradually charged due to the influence of the liquid crystal capacitor and a storage capacitor in the on interval, shown in Fig. 5 It appears as a pixel voltage (V _P ) waveform. The pixel voltage V _P is charged in the storage capacitor.

Further, the scan signal (V _G11 ~V _G1n) when, over the gate electrode and the drain electrode and the thin film transistor to be shifted over the low-potential-voltage from the parasitic coupling with the pixel voltage (V _P) because of the capacitor according to the lab A drop occurs, which is referred to as a variation ΔV _P of the pixel voltage.

On the other hand, the scan signal (V _G11 ~V _G1n) is turned on, the thin film transistor is applied over the low-potential-off interval is the pixel voltage (V _P) charged in the storage capacitor are continuously supplied to the pixel electrode holding the drive of the liquid crystal Let's go.

The pixel voltage V _P is shown as a dotted circle C11 of FIG. 5 when the first common voltage Vcom_odd or the second common voltage Vcom_even is transitioned in the turn-off period of the thin film transistor. Although it is changed by the coupling as described above, since the voltage charged to the storage capacitor is applied to the actual pixel electrode, the driving of the liquid crystal is not affected.

Therefore, the transverse electric field type liquid crystal panel according to the present invention is driven by the line inversion method in which the polarity of the image information V _DATA is supplied opposite to each other in the gate wiring (in some cases, the data wiring).

In addition, a voltage V _DATA -Vcom_odd obtained by subtracting the first common voltage Vcom_odd from the image information V _DATA is applied to the pixels corresponding to the odd-numbered gate lines, and to pixels corresponding to the even-numbered gate lines. The voltage V _DATA- Vcom_even minus the second common voltage Vcom_even is applied to the image information V _DATA .

As the first common voltage Vcom_odd and the second common voltage Vcom_even are applied in an inverted pulse form, the voltage applied to the pixels of the transverse electric field type liquid crystal panel according to the present invention has a range of twice that of the conventional art. Will have

As described above, the structure of the transverse electric field type liquid crystal panel and the driving method thereof according to the present invention apply a voltage having a range twice as large as that of the conventional art to the pixels, so that the voltage for driving the pixels can be set lower. Power consumption can be reduced.

Therefore, when applied to a portable device using a battery, the portable time is increased and the use is convenient.

In addition, when the same voltage is applied as in the related art, the distance between the pixel electrode and the common electrode can be increased, thereby maximizing the area through which light is transmitted, thereby improving the aperture ratio.

Claims (9)

Opposing first and second substrates; A liquid crystal layer formed between the first and second substrates; Gate lines and data lines arranged vertically and horizontally on the first substrate to define pixels; At least one pair of first and second electrodes formed on the unit pixels on the first substrate to apply a horizontal electric field to the liquid crystal layer; A switching element provided at one edge of the unit pixel to supply or block image information to the first electrode; First common voltage lines supplying a first common voltage to a second electrode of pixels corresponding to odd-numbered gate lines; And Second common voltage lines supplying a second common voltage to a second electrode of pixels corresponding to even-numbered gate lines; It is configured to include, The first common voltage is in the form of pulses that are transitioned in units of frames, and the second common voltage is in the form of pulses inverted from the first common voltage. The image information supplied to the first electrode of the pixel has a polarity based on the first common voltage or the second common voltage supplied to the corresponding pixel in the unit of gate wiring, The image information supplied to the first electrode of the pixel has a form in which polarities based on the first common voltage or the second common voltage supplied to the corresponding pixel are opposite in units of frames. And wherein the first common voltage lines and the second common voltage lines are arranged perpendicular to the gate lines and parallel to the data lines. The structure of a liquid crystal panel according to claim 1, wherein the first electrode is a pixel electrode to which image information is applied, and the second electrode is a common electrode to which a common voltage is applied. The structure of a liquid crystal panel according to claim 1, wherein said switching element is a thin film transistor in which a gate electrode is connected to a gate wiring, a source electrode is connected to a data wiring, and a drain electrode is connected to a first electrode. The structure of a liquid crystal panel according to claim 1, wherein the first common voltage lines are electrically connected to each other, and the second common voltage lines are electrically connected to each other. delete delete The display apparatus of claim 1, wherein the first electrode comprises: a plurality of vertical patterns formed to be uniformly spaced apart from each other in a direction parallel to the data lines; A plurality of vertical patterns formed in at least one horizontal pattern formed in parallel with the gate lines such that the vertical patterns are connected to each other, and the second electrode is spaced apart from one another in a direction parallel to the data lines. With; And at least one horizontal pattern formed in parallel with the gate line such that the vertical patterns are connected to each other, and the plurality of vertical patterns of the first electrode and the plurality of vertical patterns of the second electrode correspond to each other. The structure of the liquid crystal panel characterized by the above-mentioned. delete delete

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