KR100640996B1 - In-Plane Switching mode Liquid Crystal Display Device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transverse electric field type liquid crystal display device capable of lowering an output range of data voltage applied to each data line. And a plurality of thin film transistors alternately formed in the upper and lower pixel regions of the plurality of thin film transistors, and a plurality of storage lines each formed in a zigzag form along each thin film transistor formed in the same linear pixel region to apply a common voltage. A display device comprising: a gate driver configured to sequentially apply a scan signal to each of the gate lines, alternately apply a high voltage and a low level common voltage to each of the storage lines, and a common voltage of the high level. The negative field data voltage to the pixel's data line, And a source driver for applying a positive field data voltage to the data line of the pixel to which the low level common voltage is applied.

IPS mode (In-Plane Switching mode), source driver, common voltage, storage line, gamma reference voltage

Description

In-Plane Switching mode Liquid Crystal Display Device

1 is a schematic cross-sectional view showing a general transverse electric field type liquid crystal display device

2 is a layout diagram illustrating a pixel structure of a conventional transverse electric field type liquid crystal display device;

3 is a cross-sectional view of a structure on the line AA ′ of FIG. 2.

4 is a structural cross-sectional view taken along the line BB ′ of FIG. 2.

5 is a simplified equivalent circuit diagram of the pixel structure of FIG.

FIG. 6 is a timing diagram illustrating pixel voltages of voltage signals applied to the gate lines and the storage lines of FIG. 2. FIG.

FIG. 7 is a diagram illustrating polarity variation of common voltages for each pixel of a conventional transverse electric field type liquid crystal display for each odd frame / even frame. FIG.

8 is a block diagram illustrating the inside of a gate driver of a conventional transverse electric field type liquid crystal display device.

9 is a block diagram showing a source driver of a conventional transverse electric field type liquid crystal display device.

FIG. 10 is a diagram illustrating a gamma reference voltage circuit for setting a gamma reference voltage Vref of FIG. 9 and a data voltage output range of a source drive using the same.

FIG. 11 is a timing diagram illustrating pixel voltages of voltage signals applied to gate lines and storage lines of a transverse field type liquid crystal display device according to an exemplary embodiment of the present invention. FIG.

12 is a block diagram showing a source driver of a transverse electric field type liquid crystal display device of the present invention.

FIG. 13 is a diagram illustrating a gamma reference voltage circuit for setting a gamma reference voltage ((+) Vref) / (-) Vref) of FIG. 12 and a data voltage output range of a source drive using the same.

14 is a block diagram showing a gate driver of the transverse electric field type liquid crystal display device of the present invention.

15 is a layout diagram illustrating a pixel structure of a transverse electric field type liquid crystal display device according to a first exemplary embodiment of the present invention.

16 is a cross-sectional view of the structure taken along the line C ~ C 'of FIG.

FIG. 17 is a structural cross-sectional view taken along the line D-D 'of FIG.

18 is a layout diagram illustrating a pixel structure of a transverse electric field type liquid crystal display device according to a second exemplary embodiment of the present invention.

FIG. 19 is a structural cross-sectional view taken along the line E-E 'of FIG. 18;

FIG. 20 is a cross-sectional view of the structure taken along the line FF ′ of FIG. 18.

21 is an equivalent circuit diagram of a transverse electric field type liquid crystal display device of the present invention.

FIG. 22 is a view illustrating polarity change of common voltage for each pixel of each transverse field type liquid crystal display device according to odd frames / even frames. FIG.

 * Description of symbols on the main parts of the drawings *

200: substrate 210: gate line

215: gate insulating film 220: data line

220c: drain electrode 225: protective film

230: pixel electrode 240: common electrode

250: storage line 310: shift register

320: level shifter 330: buffer

410: shift register 420: first latch portion

430: second latch portion 440: decoder

450: output buffer

TFT: thin film transistor

(+) Vref / (-) Vref: Reference voltage for (+) field / (-) field

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a transverse electric field type liquid crystal display device which can lower the output range of a data voltage applied to each data line even when the magnitude of the pixel voltage applied to the liquid crystal is maintained in a conventional dot inversion method. It is about.

Hereinafter, a conventional transverse electric field type liquid crystal display device will be described with reference to the accompanying drawings.

As the information society develops, the demand for display devices is increasing in various forms, and in recent years, liquid crystal display devices (LCDs), plasma display panels (PDPs), electro luminescent displays (ELD), and vacuum fluorescent (VFD) Various flat panel display devices such as displays have been studied, and some of them are already used as display devices in various devices.

Among them, LCD is the most widely used as the substitute for CRT (Cathode Ray Tube) for the use of mobile image display device because of the excellent image quality, light weight, thinness, and low power consumption. In addition to the use of the present invention has been developed in various ways such as a television and a computer monitor for receiving and displaying broadcast signals.

In order to use such a liquid crystal display as a general screen display device in various parts, it is a matter of how high quality images such as high definition, high brightness and large area can be realized while maintaining the characteristics of light weight, thinness and low power consumption. Can be.

Currently, an active matrix LCD, in which a thin film transistor and pixel electrodes connected to the thin film transistor are arranged in a matrix manner, is attracting the most attention due to its excellent resolution and ability to implement video.

Meanwhile, referring to the structure of a general liquid crystal display, it can be seen that the LCD is divided into a liquid crystal panel for displaying an image and a driver for applying a driving signal to the liquid crystal panel. The liquid crystal panel includes first and second substrates bonded to each other with a predetermined space, and a liquid crystal layer injected between the first and second substrates.

Here, the first substrate (thin film transistor array substrate) has a plurality of gate lines arranged in one direction at regular intervals, a plurality of data lines arranged at regular intervals in a direction perpendicular to the respective gate lines, A plurality of pixel electrodes formed in a matrix form in each pixel region defined by crossing a gate line and a data line, and a plurality of thin film transistors switched by signals of the gate line to transfer the signal of the data line to each pixel electrode. Is formed.

In the second substrate (color filter array substrate), a black matrix layer for blocking light in portions other than the pixel region, an R, G, and B color filter layer for expressing color colors and a common color for implementing an image An electrode is formed.

The first and second substrates are bonded by a seal material having a predetermined space by a spacer and having a liquid crystal injection hole, and a liquid crystal is injected between the two substrates.

In this case, in the liquid crystal injection method, the liquid crystal is injected between the two substrates by osmotic pressure when the liquid crystal injection hole is immersed in the liquid crystal container by maintaining the vacuum state between the two substrates bonded by the reality. When the liquid crystal is injected as described above, the liquid crystal injection hole is sealed with a sealing material.

The driver for applying a signal to the liquid crystal panel is divided into a gate driver for applying a scan signal to a gate line and a source driver for applying a signal to a data line, and each driver is controlled by a microcomputer.

On the other hand, the driving principle of the general liquid crystal display device uses the optical anisotropy and polarization properties of the liquid crystal. Since the liquid crystal is thin and long in structure, the liquid crystal has directivity in the arrangement of molecules, and the direction of the arrangement of molecules can be controlled by artificially applying an electric field to the liquid crystal.

Therefore, when light is irradiated to the liquid crystal exhibiting polarization characteristics according to the applied state of the electric field, it is possible to arbitrarily adjust the molecular alignment direction of the liquid crystal, the amount of light passing according to the alignment state of the liquid crystal can be adjusted to represent the image information have.

As described above, a general liquid crystal display device in which a pixel electrode is formed on a first substrate and a common electrode is formed on a second substrate, and a liquid crystal is driven by an electric field applied up and down has a disadvantage in that viewing angle characteristics are not excellent. In order to overcome these disadvantages, an in-plane switching mode (IPS mode) liquid crystal display device for driving a liquid crystal by forming a horizontal electric field has been proposed.

An advantage of the transverse electric field type liquid crystal display device is that a wide viewing angle is possible. That is, when the liquid crystal display device is viewed from the front, the liquid crystal display device may be visible in the about 70 ° direction in the up / down / left / right directions. In addition, the manufacturing process is simpler than the TN mode liquid crystal display device generally used, and there is an advantage that the color shift according to the viewing angle is small.

Hereinafter, a conventional transverse electric field type liquid crystal display device will be described with reference to the accompanying drawings.

1 is a schematic cross-sectional view illustrating a general transverse electric field type liquid crystal display device.

As shown in FIG. 1, a general transverse electric field type liquid crystal display device includes a first substrate 1, a second substrate 2 opposite thereto, and a liquid crystal layer 3 filled therebetween.

Here, a thin film transistor (TFT) array is formed on the substrate 10 in a matrix form on the first substrate 1, and although not shown, the drain electrode and the pixel electrode 20 of the thin film transistor are connected to each other. The common electrode 30 is formed to be spaced apart from the pixel electrode 20 by a predetermined interval.

In addition, although not shown, a black matrix layer covering a region other than the pixel and a color filter layer implementing color colors are formed on the second substrate 2 facing the first substrate 1.

As described above, in the transverse electric field type liquid crystal display, both the pixel electrode 20 and the common electrode 30 exist on the same plane, and the liquid crystal is driven by a horizontal electric field formed between the two electrodes.

Meanwhile, a driving method of such a general transverse electric field type liquid crystal display device will be described.

A general liquid crystal display device including a transverse electric field type liquid crystal display device adopts a method in which an image signal is applied to a pixel corresponding to a line when each pixel is arranged in a matrix form and a scan signal is input to one gate line.

However, since the deterioration of characteristics occurs when the DC voltage is applied for a long time, the liquid crystal injected between the first and second substrates is driven by periodically changing the polarity of the applied voltage, and this method is called a polarity inversion method. .

The polarity inversion scheme includes frame inversion, line inversion, column inversion, and dot inversion.

In the frame inversion method, the polarity of the data voltage applied to the liquid crystal with respect to the common electrode voltage is applied in the same frame unit. That is, if a data voltage of positive polarity is applied to an even frame, a data voltage of negative polarity is applied to an odd frame. However, such a frame inversion driving method has an advantage of low current consumption during switching, but is sensitive to flicker due to asymmetry of transmittance of positive and negative polarity and is effective in crosstalk due to inter-data interference. It is very vulnerable to crosstalk.

In addition, the line inversion method is a polarity inversion driving method which is generally used for low resolution (VGA, SVGA), and the data voltage is applied so that the polarity of the data voltage applied to the liquid crystal with respect to the common electrode voltage varies in units of horizontal lines. do. That is, if a positive polarity is applied to an odd gate line and a negative polarity data voltage is applied to an odd gate line, a negative data voltage is applied to an odd gate line in a next frame. In addition, a data voltage of positive polarity is applied to the even-numbered gate line. In this line inversion method, since data voltages of opposite polarities between adjacent lines are applied, the luminance variation between lines decreases the flicker phenomenon compared to the frame inversion by spatial averaging, and voltages of opposite polarities are distributed in the vertical direction. Therefore, the coupling phenomenon between the data is canceled out so that the vertical crosstalk compared to the frame inversion is small. However, in the horizontal direction, voltages of the same polarity are distributed to generate horizontal crosstalk, and the number of switching repetitions is increased compared to frame inversion, thereby increasing current consumption.

The thermal inversion scheme is a driving method in which the polarities of the data voltages applied to the liquid crystal with respect to the common electrode voltage are the same in the vertical direction and opposite polarities in the horizontal direction. Compared with the frame reversal method, the flicker phenomenon is smaller than the frame reversal method and the horizontal crosstalk is smaller than the frame reversal method. However, since a data voltage of opposite polarity between adjacent lines must be applied in a vertical direction with respect to the common electrode voltage, a high voltage column drive IC must be used.

Finally, the dot inversion method is a polarity inversion driving method that realizes the best image quality at present, and is applied to high resolutions (XGA, SXGA, and UXGA), and the polarities of data voltages between adjacent pixels are reversed in all directions. Therefore, the flicker phenomenon can be minimized by the spatial averaging method, but it has the disadvantage of using a high voltage source driver and having a large current consumption.

Hereinafter, the conventional transverse electric field type liquid crystal display device which takes a dot inversion drive system is demonstrated.

2 is a layout diagram illustrating a pixel structure of a conventional transverse electric field type liquid crystal display device, FIG. 3 is a cross-sectional view of a structure on a line A-A 'of FIG. 2, and FIG. 4 is a cross-sectional view of a structure on a line B-B' of FIG. 2. .

As shown in FIG. 2, a conventional transverse electric field type liquid crystal display device includes a plurality of gate lines 40 and a plurality of data lines 50 formed in a horizontal direction and a vertical direction to define a pixel area, and the plurality of gates ( 40) a plurality of storage lines 60 formed at predetermined intervals on each of the lines, a plurality of thin film transistors TFT formed at intersections of the plurality of gate lines 40 and the plurality of data lines 50, and A pixel electrode 20 connected to a drain of each of the plurality of thin film transistors TFT and formed in a pixel area in a '|' shape, spaced apart from the pixel electrode 20 in the pixel area by a predetermined interval, and the storage line ( And a common electrode 30 connected to the pixel 60 in the pixel area.

Hereinafter, a method of forming a conventional transverse electric field type liquid crystal display device will be described with reference to FIGS. 2 to 4.

First, the metal is entirely deposited on the substrate 10 and selectively removed, thereby horizontally separating the gate line 40 protruding from the gate electrode and a storage line spaced apart from each other in the same direction as the gate line 40. 60).

Subsequently, a gate insulating layer 25 is formed on the entire surface of the substrate 10 including the gate line 40 and the storage line 60.

Next, a semiconductor layer (not shown) is formed on the gate insulating layer 25 to correspond to the gate electrode.

Subsequently, a metal is entirely deposited on a predetermined region on the gate insulating layer 25 and selectively removed to form a data line 50 and a source / drain electrode 50c in a direction perpendicular to the gate line 40. In this case, a thin film transistor TFT formed of the gate electrode, the semiconductor layer, and the source / drain electrode 50c is formed.

Subsequently, a passivation layer 35 is formed on the entire surface of the substrate 10 including the data line 50.

Subsequently, contact holes are formed in the drain electrode 50c of the thin film transistor TFT and a predetermined portion of the storage line 60, and a metal is entirely deposited on the passivation layer 35 to be patterned, thereby forming a thin film transistor TFT. The pixel electrode 20 connected to the drain electrode 50c of FIG. 2 and the pixel electrode 20 are spaced apart from the pixel electrode 20 by a predetermined interval to form a common electrode 30 connected to the storage line 60.

As such, the common electrode 30 is in contact with the storage line 60 formed at the bottom thereof to receive power, and the pixel electrode 20 applies a data voltage by an on / off operation of the thin film transistor TFT. Receive. Here, the storage lines 60 are connected to one from the outside to apply the same common voltage Vcom signal, and the common voltage Vcom signal is in a DC state.

5 is an equivalent circuit diagram of FIG. 2, and FIG. 6 is a timing diagram illustrating pixel voltages of respective gate lines of FIG. 2.

Referring to FIG. 5, each pixel of a conventional transverse field type liquid crystal display includes a storage capacitor between a drain of a thin film transistor TFT formed between a gate line 40 and a data line 50 and a storage line 60. It can be seen that Cst) and the liquid crystal capacitor Clc are formed in parallel.

As shown in FIG. 6, the common voltage Vcom signal is maintained at a predetermined level even when the pixel, the gate line 40, or the frame is changed. At this time, the predetermined level state is an intermediate level between voltages of two levels applied to the data line. Although not shown, voltages applied to the data lines are different for each data line. Therefore, a positive polarity voltage is applied to the odd line with respect to the common voltage, and a negative polarity voltage is applied to the even line.

The voltages applied to the data lines are alternately inputted in one horizontal period in a (+) / (-) state with respect to the common voltage.

In addition, the pixel voltage applied to the liquid crystal of each pixel is inverted in one vertical period based on the common voltage Vcom.

The gate driver (not shown) applies a selection pulse through the gate line to drive the pixels corresponding to the same line, and the source driver (not shown) applies an image signal to the thin film transistor turned on through the signal line. When a data voltage is applied through the turned on thin film transistor, the liquid crystal capacitor Clc and the storage capacitor Cst connected between the drain and the storage line of the thin film transistor are charged while the thin film transistor is turned on. When is turned off (turn off), the next data voltage is applied to the thin film transistor to maintain the charge charge until turned on.

Referring to FIG. 6, the pixel voltage fluctuates by ΔVp due to parasitic capacitor Cgs formed between the gate electrode and the source electrode of the thin film transistor at the falling edge of the scan signal applied to the gate line. . In this case, the pixel voltage Vp is induced by the liquid crystal by the parasitic capacitor Cgs of the thin film transistor at the falling edge of the scan signal applied to the gate line.

FIG. 7 is a view illustrating polarity change of common voltage for each pixel of each conventional transverse electric field type liquid crystal display for each odd frame / even frame.

As illustrated in FIG. 7, a conventional transverse electric field type liquid crystal display device driven by a dot inversion method has different polarities (data voltages for common voltages) in adjacent pixels, and each time the frame is changed, the polarity of each pixel is inverted. do.

In this case, the polarities of the charges charged to the adjacent pixels are different from each other by (+), (-), ..., etc. of the polarities of the charges charged to each pixel, so that a high quality image can be obtained at high speed. have.

8 is a block diagram illustrating the inside of a gate driver of a conventional transverse electric field type liquid crystal display device.

As shown in FIG. 8, a gate driver of a conventional transverse electric field type liquid crystal display includes a gate start pulse signal (GSP), a gate shift clock signal (GSC), a left and right selection signal from a microcomputer (not shown). A shift register 61 sequentially operated by receiving L / R: Left / Right Select, a level shifter 62 sequentially shifting by receiving a gate output enable signal (GOE: Gate Output Enable) from a microcomputer, And a buffer 63 for outputting the gate line signals Gout 1, Gout 2, ..., Gout n for selectively applying one of the VGH, VGL, VCC, and VSS levels to each gate line. .

The operation of the gate driver will be described below.

First, the shift register 61 shifts the gate start pulse signal GSP by the gate shift clock signal GSC to sequentially enable the gate lines. Finally, after the enable operation of the gate lines of one frame is completed, a carry value is sent, and then the operation of the gate lines of the next frame is transferred.

Subsequently, the level shifter 62 sequentially shifts a signal applied to the gate line and outputs the signal to the buffer 63.

Therefore, the plurality of gate lines connected to the buffer 63 are sequentially enabled. At this time, the predetermined gate line maintains the VGH level in synchronization with the gate shift clock signal GSC, and then falls to the VGL level at the rising edge of the gate output enable signal GOE.

9 is a block diagram illustrating a source driver of a conventional transverse electric field type liquid crystal display device.

As shown in FIG. 9, a source driver of a conventional transverse electric field type liquid crystal display device includes a source start pulse signal (SSP), a source shift clock signal (SSC), and a left / right selection signal (L /) applied from a microcomputer. R: Shift register 81 for receiving Left / Right Select and storing for each address, and receiving load signal from Load Microcomputer and receiving and saving image data (RGB Data) for even mode / or mode according to the address. First and second latches 82 and 83, decoders (DACs) 84 for converting digital signals stored in the first and second latches 82 and 83 into analog signals, and the decoders 84, respectively. The output buffer 85 outputs a signal for each data line.

The operation of the source driver will now be described in detail.

That is, dot at a time scanning is performed by latching data of each RGB sequentially received through the shift register 81 in accordance with a dot clock from a microcomputer through the first and second latches 82 and 83. Change the timing scheme of the line to a time at line scan.

Subsequently, data stored in the first latch unit 82 is transferred to the second latch unit 83 in accordance with a transfer enable signal at every horizontal line period.

The data stored in the second latch unit 83 receives the gamma reference voltage from the operating power and is converted into an analog voltage in the DAC decoder 84 in response to a polarity out load (POL) applied from the microcomputer.

Then, it is applied to each data line via the output buffer 85 in accordance with the control signal applied from the analog power supply and the microcomputer.

FIG. 10 is a diagram illustrating a gamma reference voltage circuit for setting a gamma reference voltage ((+) Vref) / (-) Vref) of FIG. 9 and a data voltage output range of a source drive using the same.

As shown in FIG. 10, in the source driver of the conventional transverse type liquid crystal display, 256 gray voltages for the (+) field and 256 gray voltages for the (-) field are represented through one gamma voltage driving circuit to implement 256 grays. After setting the maximum reference voltage value for the (+) field and the minimum reference voltage value for the (-) field by using the R-string method, the gamma reference voltage is output therebetween.

When the source driver operates by applying the gamma reference voltage to the DAC 84, a data voltage is output from the source driver on the common voltage Vcom when the source driver is a positive field based on the common voltage Vcom. In the negative field, a data voltage is output from the source driver below the common voltage Vcom.

The conventional transverse electric field type liquid crystal display device has the following problems.

When the conventional transverse type liquid crystal display is driven by a dot inversion method, the common voltage signal is constantly applied to the DC value, and the data voltage applied to the data line has polarities (+) and (−) based on the common voltage signal. ) Alternately to apply voltage. In this case, since the pixel voltage applied to the liquid crystal has a polarity depending on the data voltage, a source driver having a high output voltage difference must be used in order to form a high voltage in the liquid crystal.

A source driver of a transverse field type liquid crystal display device which is generally applied at present has an output range using a VDD power supply of about 15V. In this case, the pixel voltage actually applied to the liquid crystal is about (−) 6V to (+) 6V.

However, since the cost is higher for the source driver of the high output range, efforts have been made to reduce the cost by inducing low power consumption to lower the output range.

On the other hand, in the transverse type liquid crystal display device, the liquid crystal is driven by a fringe field formed between the common electrode and the pixel electrode, so that the gap between the pixel electrode and the common electrode is narrowed between the two electrodes for smooth driving of the liquid crystal. The fringe field to be derived should be formed with large values.

In order to narrow the gap between the pixel electrode and the common electrode, when forming a pattern of the pixel electrode and the common electrode, a single line-type pixel electrode and a common electrode are not formed, but fingers that intersect and intersect at a predetermined interval apart from each other. The pixel electrode and the common electrode pattern having a fin form are formed. In this case, the gap between the pixel electrode and the common electrode is narrowed, but the aperture ratio of the pixel is lowered.

Of course, although the ITO or the like of the transparent material is mainly used as the pattern of the pixel electrode or the common electrode, various shapes of patterns are formed in the pixel area, thereby preventing light from being evenly transmitted.

In this case, when the distance between the pixel electrode and the common electrode is increased for the high opening ratio, the horizontal electric field formed between the two electrodes becomes small, so that a data voltage of a high output range is required to obtain the required luminance.

An object of the present invention is to provide a transverse electric field type liquid crystal display device of a dot reversal method in which power consumption is reduced to solve the above problems.

In an aspect of the present invention, a transverse electric field type liquid crystal display device includes a plurality of gate lines and data lines vertically intersecting to define a pixel region, and a plurality of gate lines and data lines alternately formed in upper and lower pixel regions of each gate line. 10. A transverse field type liquid crystal display device comprising a thin film transistor and a plurality of storage lines each formed in a zigzag shape along each thin film transistor formed in a pixel area on the same line to apply a common voltage. A gate driver for sequentially applying a scan signal to each of the storage lines and alternately applying a high voltage and a low level common voltage to each of the storage lines, and a negative (-) field in the data line of the pixel to which the common voltage of each high level is applied. The data voltage is referred to as data of a pixel to which a low-level common voltage is applied. The (+) is characterized in that yirueojim by further comprising: a source driver for applying a data voltage field.

The source driver outputs a data voltage having a larger value when the (+) field data voltage is output, using the low voltage common voltage as a reference voltage, and when the (-) field data voltage is output, the common voltage of the high level. It is preferable to output a data voltage having a smaller value as a reference voltage.

The source driver preferably outputs reference voltages of the (+) field data voltage and the (-) field data voltage using different gamma reference voltage circuits.

In addition, the source driver receives a source start pulse signal, a source shift clock signal, and a left and right selection signal received from a microcomputer and stores them for each address, and receives a load signal from a microcomputer in accordance with the address even mode / or mode. Analog video signal conversion of digital video signals stored in the first and second latches by receiving gamma reference voltages for each of the first and second latches and the (+) field / (-) field. And an output buffer for outputting each signal of the decoder for each data line.

The high voltage or low level common voltage applied to each of the storage lines is preferably inverted after being maintained for one vertical period.

The applied data voltage of each data line is preferably inverted after being maintained for one vertical period.

 Hereinafter, the transverse electric field type liquid crystal display of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 11 is a timing diagram illustrating a pixel voltage with respect to a voltage signal applied to each gate line and a storage line of the transverse field type liquid crystal display of the present invention.

The transverse electric field type liquid crystal display device of the present invention is a liquid crystal display device in which a common electrode and a pixel electrode are disposed on the same plane to form a transverse electric field, as shown in FIG. 11, a scan signal applied to a gate line and a common voltage applied to a storage line. The pixel voltage value is affected by the signal.

In this case, the common voltage signal applied to the storage line may be divided into odd-numbered and even-numbered lines, respectively, and may have different levels with the first common voltage Vcom (+) and the second common voltage Vcom (-). Is approved. Here, the first common voltage Vcom (+) has a high level and the second common voltage Vcom (−) has a low level.

In this case, the data voltage applied to the data line crossing the gate line is the pixel voltage when the common voltage applied to the storage line is high level, that is, the first common voltage Vcom (+). The data voltage is applied to have a polarity, and when the second common voltage Vcom (−) is applied, the data voltage is applied to have a positive polarity.

The voltages applied to each of the storage lines and the data lines maintain a predetermined state for one vertical period and are inverted.

In this case, the pixel voltage of each pixel is the difference between the data voltage and the common voltage, and the magnitude of the pixel voltage is the difference between the first and second common voltages Vcom (+) and Vcom (-) (Vcom (+). ) -Vcom (-)) Therefore, in order to maintain a constant polarity at all times in the related art, a data voltage has to be applied with a voltage difference greater than or equal to a predetermined value from the common voltage in order for each pixel to have a stable polarity. The common voltage may be set differently according to the polarity of the pixel to increase the margin of the applied data voltage. Therefore, the output width of the source driver applying the data voltage to the data line can be reduced.

12 is a block diagram illustrating a source driver of a transverse electric field type liquid crystal display device of the present invention.

As shown in FIG. 12, the source driver of the transverse electric field type liquid crystal display according to the present invention includes a source start pulse signal (SSP), a source shift clock signal (SSC), and a left and right selection signal L applied from a microcomputer. / R: Shift register 410 which receives Left / Right Select and stores by address, load signal is received from microcomputer, and receives and saves image signal (RGB Data) by even mode / or mode according to address. The first and second latch units 420 and 430, and the decoder (DAC) 440 and the decoder 440 for analogizing the digital signals stored in the first and second latch units 420 and 430. It consists of an output buffer (AMP) 450 for outputting each signal for each data line.

At this time, the decoder 440 is a gamma reference voltage circuit in which a gamma reference voltage (+) Vref for (+) field and a gamma reference voltage ((-) Vref) for (-) field are set through separate circuits. Use

The operation of the source driver will now be described in detail.

That is, dot at a time scanning is performed by latching data of each RGB sequentially received through the shift register 410 according to a dot clock from a microcomputer through the first and second latch units 420 and 430. Change the timing scheme of the line to a time at line scan.

Subsequently, data stored in the first latch unit 420 is transferred to the second latch unit 430 in accordance with a transfer enable signal at every horizontal line period.

The data stored in the second latch unit 430 receives an operating power and receives a gamma reference voltage and is converted into an analog voltage in the DAC decoder 440 in response to a polarity out load (POL) applied from the microcomputer.

Subsequently, it is applied to each data line via the output buffer 450 according to the control signal applied from the analog power source and the microcomputer.

FIG. 13 is a diagram illustrating a gamma reference voltage circuit for setting a gamma reference voltage ((+) Vref) / (-) Vref) of FIG. 12 and a data voltage output range of a source drive using the same.

As shown in FIG. 13, in a source driver of a conventional transverse electric field type liquid crystal display device, 256 gray voltages for the (+) field and 256 gray voltages for the (-) field are shown through separate gamma voltage driving circuits as shown in FIG. 13. .

The 256 gray voltages for the (+) field are R-strings, and the max reference voltage ((+) Vref (max)) for the (+) field and the max reference voltage ((+) Vref (min) for the (+) field. The gamma reference voltage for the positive field is output between the values.

In the same way, the 256 gray voltage for the (-) field is the R-string max reference voltage ((-) Vref (max)) value for the (+) field and the max reference voltage (-) for the (-) field. The gamma reference voltage for the negative field is output between the Vref (min)) values.

The source driver operating by applying the gamma reference voltage to the DAC 440 overlaps the output range of the data voltage. This means that the value may be lower than the gamma reference voltage set to the (-) field in any (+) field.

Since the output range of the source driver can be reduced by the overlapped area, the power consumption can be reduced as compared to the source driver having a conventional high output range.

14 is a block diagram illustrating a gate driver of the transverse electric field type liquid crystal display device of the present invention.

As shown in FIG. 14, the gate driver of the transverse electric field liquid crystal display according to the present invention receives the gate start pulse signal GSP and the right and left selection signals L / R from a microcomputer (not shown). A shift register 310 for sequentially storing scan signals Gout 1, Gout 2, ..., and Gout n to be applied to each gate line in synchronization with the signal GSC, and a gate output enable signal GOE from the micom Level shifter 320 for shifting the scan signals Gout 1, Gout 2,..., Gout n, a high level VGH, a low level VGL, and a first power supply voltage VCC. , The scan signals Gout 1, Gout 2,..., Gout n are output at a predetermined level among four levels of the second power supply voltage VSS, and the preset first and second common voltages Vcom (+) are output. , Vcom (-)) is applied to the buffer 330 to alternately output each storage line applying signal (Sout 0, Sout 1, Sout 2, ...., Sout n). It is.

The operation of the gate driver is as follows.

First, the shift register 310 shifts the gate start pulse signal GSP by the gate shift clock signal GSC to enable the gate lines sequentially. Finally, after the enable operation of the gate lines of one frame is completed, a carry signal Carry is sent, and then the operation of the gate lines of the next frame is performed.

Subsequently, the level shifter 320 sequentially level shifts a signal applied to the gate line and outputs the signal to the buffer 330.

Therefore, the plurality of gate lines connected to the buffer 330 are sequentially enabled. At this time, the predetermined gate line maintains the VGH level in synchronization with the gate shift clock signal GSC, and then falls to the VGL level at the rising edge of the gate output enable signal GOE.

As described above, the driving method of the transverse electric field type liquid crystal display device of the present invention including the configured gate driver is as follows.

First, the source driver (not shown) sequentially receives image data of one pixel from the microcomputer and stores the image data corresponding to the data lines.

The gate driver outputs the gate shift clock signal GSC, the gate start pulse signal GSC, and the gate output enable signal GOE, and sequentially applies a scan signal to the plurality of gate lines.

Accordingly, the plurality of thin film transistors connected to the selected gate line are turned on and the image data (data voltage form) stored in the shift register of the source driver is applied to the drain electrode, thereby displaying the image data on the liquid crystal panel. Thereafter, the above operation is repeated to display the image data on the liquid crystal panel.

The operation of the gate driver described above is an operation when the right selection signal R is applied, and when the left selection signal L is applied, the signals are applied to the respective gate lines and the storage lines in the reverse order as described above. do.

Hereinafter, the pixel structure of the liquid crystal panel operating by receiving signals from the gate driver and the source driver (not shown) will be described.

FIG. 15 is a layout diagram illustrating a pixel structure of a transverse electric field type liquid crystal display device according to a first exemplary embodiment of the present invention, FIG. 16 is a cross-sectional view of a structure on the line C ′ of FIG. 15, and FIG. It is a structural cross section on the D 'line.

15 to 17, a pixel structure of a transverse electric field type liquid crystal display according to an exemplary embodiment of the present invention is formed in a horizontal direction and a vertical direction, respectively, to define a plurality of gate lines 210 and a plurality of data. A plurality of thin film transistors (TFTs) alternately formed up and down the gate line 210 with respect to an adjacent pixel, and a drain electrode 220c of each of the thin film transistors TFTs. A plurality of pixel electrodes 230 formed in a region, a plurality of common electrodes 240 formed in the pixel region spaced apart from each pixel electrode 230 by a predetermined interval, and the plurality of thin film transistors TFT are formed. It includes a plurality of storage lines 250 formed in a continuous form of 'L' lying in the pixel area formed on the same line along the portion.

In this case, the common electrode 240 adjacent to the right data line 220 of the pixel area overlaps with the storage line 250 formed at the bottom, and crosses the right data line so that the storage line 250 is next to the next pixel area. Is connected. In this case, the pattern of the storage line 250 to be connected extends the storage line 250 formed along the thin film transistor TFT formed in the next pixel area toward the previous pixel area and thus the right data line 220. By overlapping with the adjacent common electrode 240, a storage line is connected between adjacent pixel areas.

FIG. 18 is a layout diagram illustrating a pixel structure of a transverse electric field type liquid crystal display according to another exemplary embodiment of the present invention, FIG. 19 is a cross-sectional view of a structure on the line E-E 'of FIG. 18, and FIG. 20 is a line F-F of FIG. 18. 'Structure cross section on line.

18 to 20, a pixel structure of a transverse electric field type liquid crystal display device according to another exemplary embodiment of the present invention is formed in a horizontal direction and a vertical direction, respectively, to define a plurality of gate lines 210 and a plurality of data. A plurality of thin film transistors (TFTs) alternately formed up and down the gate line 210 with respect to an adjacent pixel area, and a drain electrode of each of the thin film transistors TFTs, A plurality of pixel electrodes 230 formed, a plurality of common electrodes 240 formed in the pixel region by crossing the pixel electrodes 230 at predetermined intervals, and the plurality of thin film transistors TFTs are formed It includes a plurality of storage lines 250 formed in an inverted form of the 'r' type lying in the pixel areas formed on the same line along the portion.

In this case, the common electrode 240 adjacent to the left data line 220 of the pixel area overlaps with the storage line 250 formed at the bottom, and crosses the left data line 220 so that the storage line 250 Before and after are connected in the pixel region. In this case, the pattern of the storage line 250 to be connected extends the storage line formed to be parallel to the gate line 210 along the thin film transistor TFT formed in the previous pixel area. It is formed so as to overlap the common electrode 240 in the next pixel region.

The second exemplary embodiment described above has the same structure as the first exemplary embodiment except that the portion where the storage line 250 overlaps the common electrode 240 is a common electrode adjacent to the left data line of the pixel area. If so, they are given the same number.

Meanwhile, the idea of the present invention is to zigzag in pixel regions formed on the same line along a plurality of thin film transistors (TFTs) formed alternately up and down the gate lines, including the first and second embodiments described above. It can be extended in various ways of a transverse electric field type liquid crystal display device in which a storage line is formed to be connected.

 A method of forming the pixel structure of the transverse electric field type liquid crystal display device according to the present invention described above is as follows.

First, the metal is entirely deposited on the substrate 200 and selectively removed to form the storage line 250 in a horizontal direction, spaced apart from the gate line 210 where the gate electrode protrudes. In this case, the gate electrodes of the gate lines 210 are formed in different directions up and down with respect to adjacent pixel areas. In addition, the storage line 250 formed at this time is formed in a zigzag manner so as to overlap the portion where the drain electrode and the common electrode formed in a later process are spaced apart from the gate line 210 by a predetermined interval. do.

Subsequently, a gate insulating layer 215 is formed on the entire surface of the substrate 200 including the gate line 210 and the storage line 250.

Subsequently, a semiconductor layer (not shown) is formed on the gate insulating layer 215 to correspond to the gate electrode.

Subsequently, metal is entirely deposited on a predetermined region on the gate insulating layer 215 and selectively removed to form a data line 220 and a source / drain electrode 220c in a direction perpendicular to the gate line 210. In this case, a thin film transistor TFT including the gate electrode, the semiconductor layer, and the source / drain electrodes 220c is formed.

Subsequently, a passivation layer 225 is formed on the entire surface of the substrate 200 including the data line 220.

Subsequently, after the metal is entirely deposited on the passivation layer 225, the storage line is spaced apart from the pixel electrode 230 and the pixel electrode 230 which are connected to the drain electrode 220c of the thin film transistor TFT. The common electrode 240 connected to the 250 is formed.

In this case, a gate insulating film is interposed between the drain electrode 220c and the storage line 250 of the thin film transistor TFT to form a storage capacitor Cst (not shown) and a liquid crystal capacitor Clc (not shown). ).

The common electrode 240 and the storage line 250 are formed to have a contact in a predetermined region of the overlapped portion.

FIG. 21 is an equivalent circuit diagram of a pixel structure of the transverse electric field type liquid crystal display device of the present invention shown in FIG. 15 or FIG. 18.

As shown in FIG. 21, when the pixel structure of the transverse field type liquid crystal display of the present invention is represented by an equivalent circuit, each storage line may be illustrated as being positioned between adjacent gate lines.

That is, the pixel structure of the transverse field type liquid crystal display device according to the present invention includes a plurality of gate lines and a plurality of data lines that vertically intersect. And an nth storage line formed between the nth (n ≧ 1) gate line and the n + 1th gate line, a first thin film transistor connected to the nth + 1th gate line and the mth data line, A second thin film formed at an intersection of the first storage capacitor and the first liquid crystal capacitor formed in parallel between the drain electrode of the first thin film transistor and the nth storage line, and the nth gate line and the m + 1th data line And a second storage capacitor and a second liquid crystal capacitor formed in parallel between the transistor, the drain electrode of the second thin film transistor, and the storage line.

In this case, the storage line is an odd-numbered storage line and the odd-numbered storage lines are applied with a first common voltage (or a second common voltage), and the even-numbered storage line is even-numbered storage lines with a second common voltage (or first common). Voltage) is applied. In this case, pixel voltages having the same polarity are applied to pixels connected to the same storage line.

The output value of the pixel voltage applied to the liquid crystal may be adjusted by a voltage difference between the high voltage or the low level common voltage applied to the storage line and the data voltage applied to the data line.

FIG. 22 is a view illustrating polarity change of common voltage for each pixel of each transverse field type liquid crystal display according to an odd frame / even frame.

If the first and second common voltages having different levels are applied to each storage line, and each line is divided into the same storage lines as shown in FIG. 21, pixel voltages having the same polarity are generated in pixels formed on the same storage line. The adjacent storage lines have opposite polarities.

Accordingly, in the transverse electric field type liquid crystal display device of the present invention, a signal is applied to the liquid crystal panel side in a dot reversal manner from a gate driver and a general source driver applying different levels of common voltage, respectively, to maintain fast signal response characteristics, and also to store The line is driven by a line inversion method so that the distortion of the electric field of adjacent pixels is less affected. In particular, the electro-optical characteristics such as black luminance are good.

The above-described transverse electric field type liquid crystal display of the present invention has the following effects.

First, power consumption can be reduced by reducing the variation range of the source driver's output voltage. A higher pixel voltage can be applied to the liquid crystal by using a gate driver that applies different common voltages to adjacent storage lines together with a source driver having a data output signal polarity as in the dot inversion method.

Second, the pixel voltage value can be increased compared to the output voltage of the same source driver as compared with the related art, thereby enabling a high-aperture structure to increase the distance between the pixel electrode and the common electrode, and improve luminance.

Third, the output voltage of the source driver is simultaneously outputted with the opposite polarity in the same way as the general dot inversion method, whereas the pixel voltages of the same polarity are arranged in the actual gate line direction, so that electric fields of adjacent pixels are arranged. The distortion is less affected by the electro-optical properties, especially black brightness.

Fourth, by using the dot inversion driving method, it is possible to realize a high picture quality with smaller vertical and horizontal crosstalk than other driving methods.

Claims (7)

A plurality of gate lines and data lines vertically intersecting to define pixel regions, a plurality of thin film transistors alternately formed in upper and lower pixel regions of each gate line, and a plurality of thin film transistors formed in the same line pixel region to apply a common voltage In a transverse field type liquid crystal display device including a plurality of storage lines formed in a zigzag form along each thin film transistor, A gate driver sequentially applying a scan signal to each of the gate lines and alternately applying a high voltage and a low level common voltage to each of the storage lines; And a source driver for applying a (-) field data voltage to the data line of the pixel to which each of the high level common voltages is applied and a (+) field data voltage to the data line of the pixel to which the low level common voltages are applied. Transverse electric field type liquid crystal display device characterized in that. The method of claim 1, The source driver is When outputting a positive field data voltage, the low voltage common voltage is used as a reference voltage and is output as a larger data voltage. When outputting (-) field data voltage, the horizontal voltage type liquid crystal display device outputs a data voltage having a smaller value using the common voltage of the high level as a reference voltage. The method of claim 1, And the source driver outputs the reference voltages of the (+) field data voltage and the (-) field data voltage using different gamma reference voltage circuits. The method of claim 3, wherein The source driver is A shift register configured to receive a source start pulse signal, a source shift clock signal, and a left and right selection signal applied from a microcomputer for each address; First and second latch units receiving a load signal from a microcomputer and storing a digital image signal for each even mode / or mode according to the address; A decoder configured to receive a gamma reference voltage for each (+) field / (−) field and convert the digital video signal stored in the first and second latch units into an analog video signal; And an output buffer for outputting each signal of the decoder for each data line. The method of claim 4, wherein The decoder is characterized in that the gamma reference voltage for each (+) field / (-) field is applied according to the level of the polarity output signal (POL: Polarity Out Load) received from the microcomputer. The method of claim 1, And a high voltage or a low level common voltage applied to each of the storage lines is inverted after being maintained for one vertical period. The method of claim 1, The applied data voltage of each data line is maintained for one vertical period and then inverted.

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