KR20040062149A - Liquid crystal dispaly - Google Patents

Abstract

PURPOSE: An LCD(liquid crystal display) is provided to reduce power consumption of an in-plane switching mode LCD. CONSTITUTION: An LCD includes gate lines(G11,G12,G13,G14,G1n) and data lines(D11,D12,D13,D1m) arranged in an intersecting manner on a substrate to define pixels, the first and second electrodes formed in the pixels to apply an in-plane electric field to a liquid crystal layer, and a switching element(TFT1) that supplies image information to the first electrode or blocks the supply of image information. The LCD further includes the first common voltage lines that provide the first common voltage to the second electrodes of pixels corresponding to odd-numbered gate lines, and the second common voltage lines that provide the second common voltage to the second electrodes of pixel corresponding to even-numbered gate lines. The LCD also has a liquid crystal capacitor(Clc) and a storage capacitor(Cst). The liquid crystal capacitor is formed between the switching element and the first or second common voltage lines. The storage capacitor is formed between the switching element and the first and second common voltage lines. The storage capacitor is alternately connected to the first and second common voltage lines in adjacent pixels.

Description

Liquid crystal display {LIQUID CRYSTAL DISPALY}

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device employing an in plane switching (IPS) method.

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

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 display panel applied in recent years as the liquid crystal display device usually adopts a twisted nematic liquid crystal. Since such a twisted nematic liquid crystal has a characteristic that the light transmittance in gray scale display varies depending on the viewing angle, There is a limit to redness.

In the liquid crystal display 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 the range is generated to narrow the viewing angle.

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

The transverse electric field type liquid crystal display panel may improve viewing angle characteristics such as contrast, gray inversion, and color shift, compared to a liquid crystal display panel using a twisted nematic liquid crystal. Has an advantage.

In the transverse electric field type liquid crystal display 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.

The liquid crystal display panel of the transverse electric field system as described above will be described in detail with reference to the accompanying drawings.

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 display panel, the thin film transistor array substrate 17 and the color filter substrate 19 are spaced apart from each other to face each other, and the thin film transistor array substrate 17 is colored. Liquid crystals 15A and 15B are filled at spaced intervals of the filter 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 display 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 display panel has an advantage of a wide viewing angle. That is, the transverse electric field type liquid crystal display panel can view an image at an angle of about 70 ° in the up / down / left / right directions.

2 is a schematic plan view of a thin film transistor array substrate in a general transverse electric field type liquid crystal display 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 display 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 display panel, shapes of the pixel electrode 11 and the common electrode 13 formed on the thin film transistor array substrate may be variously modified.

3 is an exemplary view showing pixels as an equivalent circuit in FIG. 2.

Referring to FIG. 3, the pixels P include thin film transistors TFT1 having a gate electrode connected to the gate lines G1 to Gn, a source electrode connected to the data lines D1 to Dm, and the thin film transistor ( The liquid crystal capacitor Clc and the storage capacitor Cst connected in parallel between the drain electrodes of the TFTs 1 and the common voltage wirings Vcom1 to Vcomn are provided.

On the other hand, when an electric field in a constant direction is continuously applied to the liquid crystal, the liquid crystal is deteriorated, resulting in afterimages on the liquid crystal display 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 such that the voltage of the image information is repeated positively / negative based on the common voltage. This 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 display panel employing the same provides an excellent image.

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

Referring to FIG. 4, 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 display panel.

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

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems as described above, and an object of the present invention is to provide a liquid crystal display device capable of realizing dot inversion driving while reducing power consumption of a liquid crystal display panel employing a transverse electric field system. It is.

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

2 is a schematic plan view showing a thin film transistor array substrate in a general transverse electric field type liquid crystal display panel.

3 is an exemplary view showing pixels in an equivalent circuit in FIG.

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

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

FIG. 6 is an exemplary view showing pixels in an equivalent circuit in FIG. 5; FIG.

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

8A and 8B are exemplary views showing polarities of image information supplied to pixels of a liquid crystal display panel according to the present invention.

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

G11 to G1n: Gate wiring D11 to D1m: Data wiring

P11: pixel Clc: liquid crystal capacity

TFT11: Thin Film Transistor Cst: Storage Capacitor

Vcom11 to Vcom1n: Common voltage wiring

A liquid crystal display device for achieving the object of the present invention comprises: gate wirings and data wirings arranged vertically and horizontally on a first substrate to define pixels; First and second electrodes formed on the 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 pixels to supply or block image information to a first electrode; First common voltage lines supplying a first common voltage to a second electrode of pixels corresponding to the odd-numbered gate lines; Second common voltage lines supplying a second common voltage to a second electrode of pixels corresponding to the even-numbered gate lines; A liquid crystal capacitor formed between the switching element and the first or second common voltage wirings; And a storage capacitor formed between the switching element and the first or second common voltage lines, wherein the storage capacitor is alternately connected to the first common voltage lines and the second common voltage lines in adjacent pixels. It features.

The liquid crystal display according to the present invention as described above will be described in detail with reference to the accompanying drawings.

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

Referring to FIG. 5, a plurality of gate lines G11 to G1n are arranged to be laterally spaced apart, 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 display 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 the even-numbered common voltage wirings Vcom12, Vcom14, Vcom16, .... Vcom1n are patterned to be electrically connected to each other.

In some cases, the common voltage wirings Vcom11 to Vcom1n may be formed to be parallel to the data lines D11 to D1m at regular intervals.

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 display 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. do.

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.

Also, the liquid crystal display panel of the transverse electric field type liquid crystal is filled 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 are varied on the thin film transistor array substrate. Patterned to shape.

FIG. 6 is an exemplary view showing pixels in an equivalent circuit in FIG. 5.

Referring to FIG. 6, the pixels P include thin film transistors TFT11 having a gate electrode connected to the gate lines G11 to G1n, and a source electrode connected to the data lines D11 to D1m, and the thin film transistor ( And a storage capacitor Cst and a parallel-connected liquid crystal capacitor Clc connected between the drain electrodes of the TFTs 11 and the common voltage wirings Vcom11 to Vcomn.

However, the storage capacitor Cst includes the current odd-numbered common voltage wirings Vcom11, Vcom13, Vcom15,... Vcom1n-1 and the next-numbered even-numbered common voltage wirings Vcom12, Vcom14, Vcom16, .... Vcom1n) are connected alternately.

At this time, the odd-numbered common voltage wirings Vcom11, Vcom13, Vcom15, .... Vcom1n-1, as described above, transmit the first common voltage in the form of a pulse to be transferred to the common electrode 113A of the pixels. 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.

In addition, as the voltage difference between the first and second common voltages and the image information is applied to the liquid crystal and the pixels are driven, the pixels are alternately polarized to have a positive polarity (+) and a negative polarity (−). To drive.

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

Referring to FIG. 7, 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.

The image information V _DATA is applied in the form of a positive polarity (+) and a negative polarity (−) in the form of a pulse that is shifted every horizontal period.

As described above, in the liquid crystal display panel according to the present invention, the first common voltage is applied to the adjacent pixels as the storage capacitor Cst is alternately connected to the odd common voltage wiring and the even common voltage wiring of the adjacent pixels. (Vcom_odd) and voltage difference between the image data (V _DATA) voltage difference between the second common voltage (Vcom_even) and image information (V _DATA) is applied to a so alternating, the pixels are driven in a dot inversion method.

Then, the pixels include the image information (V _DATA) the voltage obtained by subtracting the first common voltage (Vcom_odd) (V _DATA -Vcom_odd) or a voltage obtained by subtracting the second common voltage from the image information _{(V DATA) (V DATA -Vcom_odd} ) in As the voltage is applied, the voltage applied to the pixels of the transverse electric field type liquid crystal display panel according to the present invention has a range twice that of the conventional art.

8A and 8B illustrate polarities of image information supplied to pixels of a liquid crystal display panel according to an exemplary embodiment of the present invention. As shown in FIG. 8A and FIG. 8B, all adjacent pixels in successive even and odd frames have a positive polarity ( +) And negative (-) are alternately driven by dot inversion.

As described above, in the transverse electric field type liquid crystal display according to the present invention, since the voltage having twice the range is applied to the pixels, the voltage for driving the pixels can be set lower than the conventional method, thereby reducing power consumption. Can be.

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

In addition, the transverse electric field type liquid crystal display panel according to the present invention can be driven by the dot inversion method, so that the screen distortion such as flicker and cross talk can be suppressed to the maximum, thereby providing an excellent image.

Claims (7)

Gate wirings and data wirings arranged vertically and horizontally on the first substrate to define pixels; First and second electrodes formed on the 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 pixels to supply or block image information to a first electrode; First common voltage lines supplying a first common voltage to a second electrode of pixels corresponding to the odd-numbered gate lines; Second common voltage lines supplying a second common voltage to a second electrode of pixels corresponding to the even-numbered gate lines; A liquid crystal capacitor formed between the switching element and the first or second common voltage wirings; And a storage capacitor formed between the switching element and the first or second common voltage lines, wherein the storage capacitor is alternately connected to the first common voltage lines and the second common voltage lines in adjacent pixels. Characterized in liquid crystal display device. The liquid crystal display of 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 liquid crystal display device according to claim 1, wherein the switching element is a thin film transistor having a gate electrode connected to the gate wiring, a source electrode connected to the data wiring, and a drain electrode connected to the first electrode. The liquid crystal display of 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. The liquid crystal display of claim 1, wherein the first common voltage lines and the second common voltage lines are arranged in parallel with the gate lines. The liquid crystal display of claim 1, wherein the first common voltage supplied through the first common voltage wires and the second common voltage supplied through the second common voltage wires are applied in an inverted pulse form. . The liquid crystal display of claim 1, wherein the storage capacitor is alternately connected to the first common voltage lines and the second common voltage lines of the next stage in adjacent pixels.