KR100637529B1 - Liquid crystal display and driving method thereof - Google Patents

Abstract

The present invention relates to a liquid crystal display device and a driving method thereof.

According to another exemplary embodiment of the present invention, a liquid crystal display includes a plurality of data lines including first and second data lines crossing one pixel region and transferring data voltages representing an image, a scan line of a first group, and a second group of second data lines. And a scan line for transmitting a scan signal, a first data driver for applying a data voltage to the first data line, and a second data driver for applying a data voltage to the second data line. In this case, the scanning lines are alternately arranged in the scanning lines for each group, and when a scanning signal is applied to the adjacent scanning lines, at least part of the periods are overlapped. The first and second data drivers respectively supply data voltages applied to the first and second data lines crossing the two adjacent scan lines to which the scan signal is applied. This shortens the scanning period in the field sequential liquid crystal display device.

Liquid crystal display, field sequential method, scanning line, scanning period, data line

Description

Liquid crystal display and driving method thereof {LIQUID CRYSTAL DISPLAY AND DRIVING METHOD THEREOF}

1 is a driving waveform diagram of a conventional liquid crystal display.

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

3 is a pixel circuit diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

4 is a layout view of a pixel circuit of a portion A shown in FIG. 3.

5 is a cross-sectional view taken along the line II ′.

FIG. 6 is a driving waveform diagram of the pixel circuit shown in FIG. 3.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display (LCD) and a driving method thereof, and more particularly to a liquid crystal display of a sequential driving method.

Recently, display devices are also required to be lighter and thinner in accordance with light weight and thickness of personal computers and televisions, and according to such demands, flat panel displays such as liquid crystal displays are being developed instead of cathode ray tubes (CRTs). .

The liquid crystal display applies an electric field to a liquid crystal material having an anisotropic dielectric constant injected between two substrates, and adjusts the intensity of the electric field to transmit the amount of light transmitted from the external light source (backlight) to the substrate. It is a display device that obtains a desired image signal by adjusting.

Such a liquid crystal display is representative of a portable flat panel display, and among these, a TFT-LCD using a thin film transistor (TFT) as a switching element is mainly used.

In general, the liquid crystal display may be classified into two methods, a color filter method and a field sequential driving method, according to a method of displaying a color image.

A color filter type liquid crystal display device forms a color filter layer consisting of three primary colors of red (R), green (G), and blue (B) on one of two substrates, and transmits the amount transmitted through the color filter layer. By adjusting, the desired image is displayed. In the color filter type liquid crystal display, light transmitted from a single light source is transmitted to the R, G, and B color filter layers by adjusting the amount of light transmitted through the R, G, and B color filter layers. A desired image is displayed by synthesizing the B colors.

As described above, in a liquid crystal display device that displays an image using a single light source and a three-color color filter layer, a corresponding unit pixel is required for each of the R, G, and B regions, so that three times as many pixels are used as for displaying black and white. It is necessary. Therefore, in order to obtain a high resolution image, sophisticated manufacturing technology of a liquid crystal display panel is required. In addition, such a liquid crystal display has manufacturing difficulties in that a separate color filter layer is formed on a substrate, and the luminance is lowered because the light transmittance of the color filter itself is low.

The liquid crystal display of the field sequential driving method periodically turns on independent light sources of R, G, and B colors, and applies a color signal corresponding to each pixel in synchronization with the lighting cycle to generate a full color image. Get That is, according to the liquid crystal display of the field sequential driving method, R, G, and B primary colors output from R, G, and B backlights are output to one pixel without dividing one pixel into R, G, and B unit pixels. By displaying light sequentially in time division, an image is displayed using the afterimage effect of the eye.

The field sequential driving type liquid crystal display includes TFTs having a source electrode and a gate electrode connected to a plurality of data lines and a plurality of scan lines, and liquid crystal capacitors connected between a drain electrode and a common voltage of the TFT, respectively. A pixel circuit is formed in the pixel region defined by the data line and the scan line. The operation of the liquid crystal display of the field sequential driving method will be described with reference to FIG. 1.

1 is a driving waveform diagram of a conventional liquid crystal display.

As shown in FIG. 1, when a scan signal is sequentially applied to the scan lines S1 to Sn by a scan driver, a scan signal is applied to the gates of the TFTs from the scan lines S1 to Sn, and the TFT is turned on. The gray voltage supplied by the data driver is applied to the data lines D1 to Dm. In FIG. 1, a data voltage is applied to the j th data line Dj among the plurality of data lines D1 to Dm. From this data line Dj, a data voltage is applied to each pixel electrode through the TFT.

According to the conventional driving method shown in FIG. 1, since the scan signal is sequentially applied to each scan line, when the scan line increases, the total scan time (hereinafter, the entire scan time is referred to as a 'scan period') is correspondingly increased. Will increase.

In particular, the field sequential driving type liquid crystal display device displays R, G, and B primary colors output from R, G, and B backlights in one pixel in a time-division manner, as described above. Applying the color signal should have a scanning period about 1/3 times shorter than that of the color filter type liquid crystal display. However, when the driving method shown in FIG. 1 is applied to the liquid crystal display of the field sequential driving method, there is a problem in that a sufficient scanning period is not secured within one frame period when the scanning line is increased.

An object of the present invention is to provide a liquid crystal display device and a driving method thereof capable of shortening a scanning period.

According to an aspect of the present invention, there is provided a liquid crystal display, including: a plurality of data lines including first and second data lines crossing one pixel area and transferring data voltages representing an image; A plurality of scan lines including scan lines of a first group and scan lines of a second group, wherein the scan lines transmit scan signals; A first data driver for applying a data voltage to the first data line; And a second data driver for applying a data voltage to the second data line.

The liquid crystal display includes: a first scan driver for sequentially applying a scan signal to the scan lines of the first group; And a second scan driver that sequentially applies a scan signal to the second group of scan lines. In this case, at least part of a first period during which the scan signal is applied to at least one scan line among the scan lines of the first group, and a second period during which the scan signal is applied to at least one scan line among the scan lines of the second group. May overlap, wherein the first group may be odd-numbered scan lines, and the second group may be divided into even-numbered scan lines.

In addition, the liquid crystal display includes a gray voltage generator which generates the data voltage; And a light source sequentially outputting red, green, and blue light in each pixel area.

According to another aspect of the present invention, a liquid crystal display includes: first and second pixel regions adjacent to each other in a first direction; First and second data lines crossing the first and second pixel areas; A first scan line crossing the first and second data lines and defining the first pixel area; And a second scan line intersecting the first and second data lines and defining the second pixel area. In this case, the first pixel region may include a first thin film transistor having a first electrode and a second electrode electrically connected to the first data line and the first scan line, respectively, and the second pixel region may include the first thin film transistor. And a second thin film transistor having a first electrode and a second electrode electrically connected to the second data line and the second scan line, respectively.

According to still another aspect of the present invention, a plurality of data lines including first and second data lines for transmitting a data voltage representing an image, a plurality of scan lines for transmitting a scan signal, the data lines and the scanning lines A driving method of a liquid crystal display device including a plurality of pixel areas defined is provided.

In this driving method, the plurality of scan lines are divided into a plurality of groups including a first group and a second group, wherein the first and second data lines cross one pixel area, and the scan lines of the first group Applying a first scan signal to at least one scan line and applying a data voltage to the first data line; And applying a second scan signal to at least one scan line of the second group of scan lines and applying a second data voltage to the second data line while the first scan signal is applied. In this case, the scan signals applied to the first and second scan lines adjacent to each other among the scan lines of the first group do not overlap each other.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like parts are designated by like reference numerals throughout the specification.

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

First, a schematic structure of a plasma display device according to an exemplary embodiment of the present invention will be described in detail with reference to FIG. 2.

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

As shown in FIG. 2, the liquid crystal display according to the exemplary embodiment may include a liquid crystal display panel 100, a first scan driver 200, a second scan driver 300, a first data driver 400, and a first liquid crystal display panel. 2 includes a data driver 500, a gray voltage generator 600, and a timing controller 700. Although not shown in FIG. 2, the liquid crystal display according to the exemplary embodiment may further include a light emitting diode (not shown) and a light source controller (not shown) for outputting R, G, and B light.

The liquid crystal display panel 100 includes a plurality of data lines D ₁ , ₁ , D _{1,2 to} D _{m, 1} , D _{m, 2} extending in the vertical direction, and a plurality of scanning lines S ₁ to extend in the horizontal direction. S _n ) and a plurality of pixel circuits 110.

The scan lines S _{1 to} S _n transmit a scan signal for selecting the pixel circuit to the pixel circuit 110. At this time, the plurality of scanning lines S _{1 to} S _n are divided into scanning lines of the first group and the second group.

The data lines D ₁ , ₁ , D _{1,2 to} D _{m , 1} , D _{m , and 2} transfer data voltages corresponding to grayscale data to the pixel circuit. The pixel circuit 110 is formed in the pixel region defined by the data lines D ₁ , ₁ , D _1,2 -D _{m , 1} , D _{m , 2} , and the scanning lines S ₁ -S _n . Each pixel area is formed by two data lines and one scanning line.

In the following, the data line positioned on the left side of the pixel region among the two data lines positioned in each pixel region is called the first data line, and the data line positioned on the right side is called the second data line.

 The first scan driver 200 sequentially applies a scan signal to the scan lines of the first group. The second scan drivers 200 and 300 sequentially apply scan signals to the scan lines of the second group. At this time, odd scan lines are included in the first group among the plurality of scan lines, and even scan lines are included in the second group. Therefore, the first and second scan drivers 200 and 300 alternately apply scan signals to each other in order to sequentially apply scan signals to the plurality of scan lines.

The first and second scan drivers 200 and 300 may overlap a period in which scan signals applied to two adjacent scan lines are at least part of each other. In the following, this is called nesting. The scan signals applied to the scan lines adjacent to each other among the scan lines of the first group do not overlap each other, and the same applies to the scan lines of the second group.

That is, while the first scan driver 200 applies the scan signal to the 2j-1 th scan line, the second scan driver 300 applies the scan signal to the 2j th scan line.

The first data driver 400 applies a data voltage to the first data line, and the second data driver 500 applies a data voltage to the second data line.

The gray voltage generator 600 generates a gray voltage having a magnitude corresponding to gray data and transmits the gray voltage to the first and second data drivers 400 and 500.

The timing controller 700 receives the gray level data signals R, G, and B data, the horizontal sync signal Hsync, and the vertical sync signal Vsync from an external or graphic controller (not shown), and then needs a control signal Sg. , Sd and Sb are transmitted to the first and second scan drivers 200 and 300, the first and second data drivers 400 and 500 and the light source controller (not shown), respectively, and the grayscale data R and G , B DATA) is transmitted to the gray voltage generator 600.

A light emitting diode (not shown) outputs light corresponding to R, G, and B to the liquid crystal display panel 100, respectively, and a light source controller (not shown) controls when the light emitting diode (not shown) is turned on. .

In the embodiment of the present invention, a light emitting diode (not shown) is used as the backlight, but the present invention is not limited thereto.

3 is a pixel circuit diagram of a liquid crystal display according to an exemplary embodiment of the present invention. In FIG. 3, only the 2j-1, 2j, 2j + 1 th scan lines S _2j-1 , S _2j , S _{2j + 1 are} shown, and the k th, k + 1 th first and second data lines D _{k , 1} , D _{k , 2} , D _{k +1,1} , D _{k +1,2} ) only.

As shown in Fig. 3, each pixel circuit 110 includes TFTs 10a and 10b and a liquid crystal capacitor C1.

In the TFT 10a, a gate electrode and a source electrode are connected to the scan lines S _2j-1 , S _{2j + 1} and the first data lines D _{k , 1} , D _{k +1 , 1 of the first group} , respectively. In the TFT 10b, a gate electrode and a source electrode are connected to the scan line S _2j and the second data line D _{k , 2} , D _{k +1 , 2} of the second group, respectively.

The TFTs 10a and 10b connected in this way are located in different directions in the pixel region formed by the scan line and the first data line of the first group and the pixel region formed by the scan line and the second data line of the second group. do.

The liquid crystal capacitor C1 is connected between the drain electrode of the TFTs 10a and 10b and the common voltage Vcom.

Next, the TFT of each pixel circuit will be described in detail with reference to FIGS. 4 and 5.

FIG. 4 is a layout view of the pixel circuit of the portion A shown in FIG. 3, and FIG. 5 is a cross-sectional view taken along the line II ′.

4 and 5, in the pixel circuit according to the exemplary embodiment of the present invention, a plurality of scan lines 121 and 122 are formed on the transparent insulating substrate 120 in one direction and are separated from each other. . 4 and 5, the scan lines S _2j-1 and S _2j shown in FIG. 3 are denoted by the scan lines 121 and 122, and the first and second data lines D _{k , 1} , D _{k , 2} . Are denoted by the first and second data lines 171 and 172, respectively.

The scanning lines 121 and 122 have a plurality of protrusions, and the protrusions are used as the gate electrodes 124a and 124b of the TFT. One end portion of the scan lines 121 and 122 is used to receive a signal transmitted from the first and second scan drivers (not shown).

The scanning lines 121 and 122 may be formed of a single layer of chromium (Cr), titanium (Ti), tantalum (Ta), molybdenum (Mo), copper (Cu), silver (Ag), aluminum (Al), or an alloy thereof. Or a plurality of layers. In this case, when silver or aluminum is included, other physical materials, particularly ITO or IZO, etc., may further include a metal layer having good physical, chemical, and electrical contact properties and strong oxidation resistance. The gate insulating film 140 is formed to cover the scan lines 121 and 122. The gate insulating layer 140 is formed of silicon nitride, silicon oxide, or the like, and the semiconductor layers 154a and 154b made of amorphous silicon without doping impurities are formed on a predetermined region of the gate insulating layer 140.

The semiconductor layers 154a and 154b meet the scan lines 121 and 122 to enhance the insulation between the scan lines 121 and 122 and the first and second data lines 171 and 172 and to increase the adhesion to the upper layer. In the width is formed enlarged.

A source ohmic contact (163a, 163b) and a drain ohmic contact (165a, 165b) including an amorphous silicon or silicide doped with an impurity on top of the semiconductor layer 154 Is formed.

The source and drain ohmic contacts 163a, 163b, 165a, and 165b include the semiconductor layers 154a and 154b thereunder, the data lines 171 and 172 thereon, and the drain electrodes 175a and 175b. It exists only between) and lowers contact resistance.

A plurality of data lines, that is, first and second data lines 171 and 172, are formed on the source ohmic contact layers 163a and 163b to cross the scan lines 121 and 122 to define a pixel area. The first and second data lines 171 and 172 are elongated in the direction crossing the scan lines across the pixel region, and at least a portion of the source electrodes 173a and 173b overlapping the semiconductor layers 154a and 154b of the TFT. ) In this case, the source electrode 173a overlaps the scan line 121 included in the first group, and the source electrode 173b overlaps the scan line 122 included in the second group.

On the drain resistive contact layers 165a and 165b, the gate electrodes 124a and 124b are centered to face the source electrodes 173a and 173b, and the gate electrodes 124a and 124b and the semiconductor layers 154a and 154b are disposed. Drain electrodes 175a and 175b overlapping with each other are formed. The drain electrode 175a overlaps the scan line 121, and the drain electrode 175b overlaps the scan line 122.

Like the scan lines 121 and 122, the first and second data lines 171 and 172 and the drain electrodes 175a and 175b also have a single layer (not shown) made of chromium, titanium, tantalum, molybdenum, silver, copper, aluminum, or an alloy thereof. Or a plurality of layers. In this case, in the case of containing aluminum or silver, it may be formed of a plurality of layers further comprising a metal film having excellent contact properties with other materials, particularly ITO, IZO, or the like.

A passivation layer 180 formed of an insulating material such as silicon oxide or silicon nitride is formed on the semiconductor layer 151 that is not covered by the drain electrodes 175a and 175b and the source electrodes 173a and 173b.

In this case, the pixel electrodes 190a and 190b are physically and electrically connected to the drain electrodes 175a and 175b through the contact holes 181 and 182 to receive a data voltage from the drain electrodes 175a and 175b. The pixel electrodes 190a and 190b to which the data voltage is applied rearrange the liquid crystal molecules between the two electrodes by generating an electric filed together with a common electrode (not shown) of another display panel.

 As described above, the TFT is formed by the source electrodes 173a and 173b and the drain electrodes 175a and 175b together with the semiconductor layers 154a and 154b formed on the gate electrodes 124a and 12b. In the present invention, the TFT includes a portion where the scan line 121 included in the first group and the first data line 171 meet and a portion where the scan line 122 and the second data line 172 included in the second group meet. Is formed. In this case, since the first data line 171 and the second data line 172 are formed to face each other in one pixel area, the scan line 121 and the first data line (included in the first group, as shown in FIG. 4). The TFT formed at the portion where the 171 meets and the TFT formed at the portion where the scan line 122 included in the second group and the second data line 172 meet are positioned in different directions.

Next, the operation of the pixel circuit constructed as described above with reference to FIGS. 3 and 6 will be described in detail.

FIG. 6 is a driving waveform diagram of the pixel circuit shown in FIG. 3.

As shown in FIG. 6, the scan signal is applied to the at least one scan line S _2j-1 included in the first group of scan lines by the first scan driver 200 at a time point t1. Then, the scanning signal is applied from the scanning line S _2j-1 to the gate of the TFT to turn on the TFT. The gray scale voltage is applied to the data line D _{k , 1} by the first data driver 400, and the data voltage from the data line D _{k , 1} is applied to each pixel electrode through the TFT.

And a first scan driver by a second scan driver 300 at the time point (t2) during which a scanning signal is applied to the scan line (S _2j-1) by 200 included in the scan line of the second group of scanning lines (S _2j Is applied to the scan signal. Then, a scanning signal is applied from the scanning line S _2j to the gate of the TFT to turn on the TFT. The grayscale voltage is applied to the data lines D _{k , 2} by the second data driver 500, and a data voltage from the data lines D _{k , 2} is applied to each pixel electrode through the TFT.

In the same manner, while the scan signal is applied to the scan line S _2j by the second scan driver 300, the scan line included in the scan group of the first group by the first scan driver 200 at the time point t3. The scan signal is applied to S _{2j + 1} ), and the corresponding gray voltage is applied to the data line D _{k , 1} by the first data driver 400 and transferred to each pixel electrode.

As such, the plurality of scan lines may be divided into scan lines of the first group and the second group, and first and second scan drivers for applying scan signals to the scan lines included in each group may be present, respectively, and thus, at least one of the first groups may be used. Since the time when the scan signal is applied to the scan line and the time when the scan signal is applied to the at least one scan line of the second group continuous with the scan line can be superimposed, the time for applying the scan signal to the plurality of scan lines is shortened. In addition, the first and second data drivers for applying the data voltage to the data lines included in the pixel areas to which the scan signals are applied in each group are respectively present, and thus the scan voltages overlap the scan lines. The data voltage can be applied to each pixel electrode.

In the embodiment of the present invention, the first and second scan drivers are separately provided to overlap scan signals applied to adjacent scan lines, but may be implemented in one scan driver.

Although the preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations are possible. For example, the present invention can be applied to not only a field sequential liquid crystal display but also a color filter liquid crystal display.

According to the present invention, a plurality of scan lines are divided into a plurality of groups including a first group and a second group, the scanning order is alternately performed in each group, and at least part of a period when a scan signal is applied to the scan lines of each group. Since they overlap each other, scanning time is shortened and display time is reduced.

Claims (10)

A liquid crystal display device comprising a plurality of scan lines formed in a row direction and a plurality of data lines formed in a column direction, A plurality of first pixel circuits intersecting the plurality of scan lines and allocated with first and second data lines in a column direction of one line, and connected to a first group of scan lines among the first data line and the plurality of scan lines, respectively; A plurality of pixel circuits including a plurality of second pixel circuits respectively connected to a second group of scan lines of the second data line and the plurality of scan lines; A first data driver transferring a first data voltage corresponding to an image signal to the first data line during a first period; and A second data driver transferring a second data voltage corresponding to the image signal to the second data line during a second period of time Including; And at least a portion of the first period and the second period overlap. The method of claim 1, A first scan driver for applying a first scan signal to one of the scan lines of the first group in the first period; and A second scan driver for applying a second scan signal to one of the scan lines of the second group in the second period Liquid crystal display further comprising. delete The method according to claim 1 or 2, The first and second groups are divided into odd-numbered and even-numbered scan lines. The method of claim 4, wherein A gray voltage generator generating the first and second data voltages; And A light source sequentially outputting red, green, and blue light to the plurality of pixel circuits, respectively Liquid crystal display further comprising. A plurality of pixel circuits formed in the column direction of one line, A first data line connected to a pixel circuit of a first group among the plurality of pixel circuits, A second data line connected to a second group of pixel circuits of the plurality of pixel circuits, A plurality of scanning lines connected to each pixel circuit, After applying a first scan signal to one of the plurality of first scan lines connected to the first group of pixel circuits among the plurality of scan lines, a first scan signal is applied to the pixel circuits of the second group of the plurality of scan lines. A scan driver for applying a second scan signal to one second scan line of the plurality of connected second scan lines, A first data driver applying a first data voltage to the first data line while the first scan signal is applied to the first scan line; and A second data driver that applies a second data voltage to the second data line while the second scan signal is applied to the second scan line Including; And at least a portion of a period in which the first scan signal is applied to the first scan line and a period in which the second scan signal is applied to the second scan line overlap. The method of claim 6,  Each pixel circuit of the first group is A first thin film transistor connected to the first data line and the first scan line, respectively; Each of the second group of pixel circuits may include A second thin film transistor connected to the second data line and the second scan line, respectively; Liquid crystal display comprising a. A driving method of a liquid crystal display device comprising a plurality of data lines for transmitting a data voltage representing an image, a plurality of scanning lines for transmitting a scanning signal, and a plurality of pixel circuits connected to the data lines and the scanning lines. Each pixel circuit formed in the column direction of one of the plurality of pixel circuits is alternately connected to the first and second data lines. Applying the scan signal to a first scan line connected to a pixel circuit to which the first data line is connected, and applying the data voltage to the first data line; and Applying the scan signal to a second scan line connected to a pixel circuit to which the second data line is connected, and applying the data voltage to the second data line Including; And a period in which the scan signal is applied to the first scan line and at least a portion of the period in which the scan signal is applied to the second scan line overlap. The method of claim 8, The first scan line connected to the pixel circuit to which the first data line is connected is an odd-numbered scan line, and the second scan line connected to the pixel circuit to which the second data line is connected is an even-numbered scan line. Method of driving. The method according to claim 8 or 9, Applying the scan signal to the first scan line, and then applying the scan signal to another first scan line connected to a pixel circuit to which the first data line is connected The driving method of the liquid crystal display device further comprising.

Images