Liquid crystal display device and method for driving the same

A liquid crystal display (LCD) device includes: a plurality of gate lines; a plurality of data lines that cross the gate lines to define pixel regions; a plurality of thin film transistors at the crossings of the gate and data lines, the thin film transistors of vertically adjacent pixels each connected to a shared gate line of the plurality of gate lines and on opposite sides of the shared gate line; and a plurality of pixel electrodes in the pixel regions, wherein each pixel electrode of the plurality of pixel electrodes is formed in two horizontally-adjacent pixel regions.

This application claims the benefit of Korean Patent Application No. 10-2006-0045641, filed on May 22, 2006, which is hereby incorporated by reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display (LCD) device and more particularly to an LCD device and a method for driving the same.

2. Discussion of the Related Art

Among various ultra-thin flat type display devices, which include devices having a display screen thickness several centimeters or less, liquid crystal display (LCD) devices are widely used for notebook computers, monitors, and spacecraft and aircraft displays because or their advantages such as low operating voltage, low power consumption, and portability.

A typical LCD device includes a lower substrate, an upper substrate, and a liquid crystal layer formed between the substrates.

Gate lines and data lines substantially perpendicular to the gate lines are formed on the lower substrate. The data lines and gate lines cross each other to define pixel regions. A thin film transistor (TFT) is formed at crossings of the gate lines and data lines.

Light shield layers are formed on the upper substrate to prevent leakage of light from regions corresponding to the gate lines, data lines, and TFTs. Color filter layers are also formed on the upper substrate between the adjacent light-shielding layers to transmit light of particular wavelengths.

The color filter layers add significantly to the manufacturing costs for a liquid crystal display device.

In order to solve this problem, an LCD device driven using a field sequential driving system has been developed.

FIG. 1is a perspective view schematically illustrating a LCD device of the related art using a field sequential driving system.

As shown inFIG. 1, the LCD device of the related art includes a lower substrate1, an upper substrate2, and a liquid crystal layer (not shown) formed between the substrates1and2.

Gate lines10and data lines20are formed on the lower substrate1. The gate lines10and data lines20cross each other to define pixel regions30. A TFT41functioning as a switching device is formed at each crossing of the gate lines10and data lines20. A pixel electrode35is formed at each pixel region30and the pixel electrode35is connected to the TFT41. A backlight unit50is arranged at a lower surface of the lower substrate1, to irradiate light onto the lower substrate1.

The backlight unit50includes a red light source51, a green light source52, and a blue light source53.

A light shield layer70is formed on the upper substrate2, in order to prevent leakage of light from regions where the gate lines10, data lines20, and TFTs41are arranged. A common electrode80is formed on the upper substrate2including the light shield layer70.

In an LCD device using a field sequential driving method, no color filter is used in order to achieve an enhancement in the transmittance of light. To this end, the LCD device temporally reproduces color. That is, in the LCD device, various colors are displayed in a color reproduction period that is less than the temporal visual resolution to display a desired color.

By avoiding the forming of color filter layers in the LCD device, it is possible to save the costs of color filters and to achieve an improvement in color characteristics and image reproduction characteristics.

FIG. 2is a timing diagram for explaining driving of the field sequential driving type LCD device of the related art shown inFIG. 1.

As shown inFIG. 2, in the field sequential driving type LCD device, one frame is time-divided into three sub-frames. A red (R) light source may be operated during the first sub-frame. During the second sub-frame a green (G) light source may be operated. During the third sub-frame a blue (B) light source may be operated.

In the field sequential driving type LCD device, the temporal period during which color is reproduced has a value less than the temporal visual resolution because one frame is sub-divided into three sub-frames. Accordingly, full color display may be achieved without using color filters.

In the first sub-frame, red (R) data is charged to a first pixel for a data charging time corresponding to a scan pulse from the gate line10. After the response time of liquid crystal elapses the R light source is turned on.

In the second sub-frame the R light source is turned off and green (G) data is charged in a second pixel for a data charging time corresponding to a scan pulse from the gate line10. After the response time of liquid crystal elapses the G light source is turned on.

In the third sub-frame the B light source is turned off and blue (B) data is charged in a third pixel for a data charging time corresponding to a scan pulse from the gate line10. After the response time of liquid crystal elapses the B light source is turned on.

When the R light source is turned on, R light is emitted, so that an image according to the R light is displayed on a liquid crystal panel. Similarly, when the G or B light source is turned on, an image according to G or B light is displayed.

By sequentially turning on all the R, G, and B light sources during each frame, it is possible to display a desired color.

In the above-described sequential driving LCD device, however, each gate line is to be driven for a predetermined time within one frame period. Accordingly, as the number of gate lines is increased (for example to produce an LCD device of increased size) the time available for driving each gate line is shortened.

When the driving time for each gate line is shortened, the turn-on time of the TFTs connected to each gate line is shortened. As a result, for large sized LCD devices, there may be insufficient time to completely charge a data voltage into the pixels.

Although this problem may be at least partially addressed by increasing the size of the TFTs, there is a limitation in increasing the TFT size due to an associated design rule and problems associated with maintaining an aperture ratio.

SUMMARY OF THE INVENTION

An advantage of the present invention is to provide a liquid crystal display device and a method for driving the same which are capable of supplying a scan pulse from one gate line to vertically-adjacent pixels, and thus, securing a sufficient data charging time even when one frame is driven under the condition in which the frame is divided into a plurality of sub-frames.

To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a liquid crystal display device includes a plurality of gate lines; a plurality of data lines that cross the gate lines to define pixel regions; a plurality of thin film transistors at the crossings of the gate and data lines, the thin film transistors of vertically adjacent pixels each connected to a shared gate line of the plurality of gate lines and on opposite sides of the shared gate line; and a plurality of pixel electrodes in the pixel regions, wherein each pixel electrode of the plurality of pixel electrodes is formed in two horizontally-adjacent pixel regions.

In another aspect of the present invention, a liquid crystal display device includes: a plurality of first and second gate lines; a plurality of first to fourth data lines crossing the first and second gate lines to define pixel regions; a plurality of pixels, wherein each pixel includes from four horizontally-adjacent pixel regions; and a plurality of thin film transistors (TFTs) at the crossings of the first gate lines and the first and second data lines and at the crossings of the second gate lines and the third and fourth data lines.

In another aspect of the present invention, a method for driving a liquid crystal display device including a plurality of gate lines, a plurality of data lines crossing the gate lines to define pixel regions, and a plurality of pixel electrodes in the pixel regions, wherein one pixel electrode is formed in two horizontally-adjacent pixel regions, the liquid crystal display device driven in a plurality of sub-frames divided from one frame includes: supplying a scan pulse to a gate line; supplying data signals to pixels arranged to be vertically adjacent to each other at opposite sides of the gate line to charge the pixels with the data signals; and irradiating light onto the pixels charged with the data signals.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 3is a plan view schematically illustrating a liquid crystal display (LCD) device according to a first embodiment of the present invention.

As shown inFIG. 3, the LCD device according to the first embodiment of the present invention includes a liquid crystal panel400including a plurality of gate lines100and a plurality of data lines200crossing the gate lines100to define pixel regions, wherein one pixel300is formed to include two horizontally-adjacent pixel regions, and a backlight unit500for sequentially irradiating red (R), green (G), and blue (B) lights to the liquid crystal panel400. The LCD device also includes a data driver210for dividing one frame into a plurality of sub-frames and supplying data to the data lines200of the liquid crystal panel400for every sub-frame, a gate driver110for supplying scan pulses to the gate lines100of the liquid crystal panel400, and a timing controller600for controlling the gate driver110, data driver210, and backlight unit500.

The gate lines100and data lines200, which are included in the liquid crystal panel400, cross each other. In particular, each data line200overlaps with the associated pixel region. The liquid crystal panel400also includes thin film transistors (TFTs)410each formed at the crossings of the gate lines100and data lines200. A plurality of pixel electrodes350are formed in the pixels300, wherein one pixel electrode350is formed in each of two horizontally-adjacent pixel regions. The plurality of pixel electrodes350are connected to the TFTs410, respectively. Two pixels300are vertically arranged between the adjacent two gate lines100.

The TFTs410are arranged at opposite sides of the gate line100in a zigzag pattern along a gate line100and the TFTs410in pixels arranged to be vertically adjacent to each other are at opposite sides of each gate line100and are connected to the gate line100such that they simultaneously receive a scan pulse from the gate line100. Since the two pixels300positioned vertically-adjacent with respect to a single gate line are simultaneously driven by the corresponding gate line100, the number of the gate lines100for a given sized display is reduced by one-half. Accordingly, it is possible to secure a time for sufficiently charging a data voltage via the pixel electrodes350.

Furthermore, it is possible to reduce the time taken to drive all gate lines100, and thus, to secure a sufficient liquid crystal response time and a sufficient light source turn-on time.

Because the LCD display device according to the first embodiment of the present invention is configured such that the vertically-adjacent pixels300simultaneously are driven by one gate line100, as described above, the TFTs410of the vertically-adjacent pixels300are connected to different data lines, for example, data lines200aand200b, respectively.

If the TFTs410of the vertically-adjacent pixels300received data from the same data line while receiving a scan pulse from the same gate line100, the desired image would not be displayed because the same data would be supplied to the vertically-adjacent two pixels300.

As a portion the data lines200aand200b, in particular, the data lines200b, overlap with the pixel electrodes350, particular regions of the pixel electrodes350where connecting electrodes are arranged, as will be described hereinafter.

Because the data lines200overlap with the pixel electrodes350, parasitic capacitance is generated therebetween. As a result, the LCD device may exhibit a degradation in picture quality because the data supplied through the data lines200may leak, and thus be modulated by the parasitic capacitance.

In accordance with the illustrated embodiment of the present invention, each pixel electrode350includes sub-pixel electrodes350aformed in the pixel regions defined by the gate line100and data lines200, and connecting electrodes350beach formed between the horizontally-adjacent two sub-pixel electrodes305ato electrically connect the horizontally-adjacent two sub-pixel electrodes350a. Each connecting electrode350bhas a width smaller than that of the sub-pixel electrode350a.

The width of each connecting electrode350bis made smaller than the width of each sub-pixel electrode350ato minimize a region A where the connecting electrode350boverlaps with the data line200, and thus, to reduce parasitic capacitance.

If the width of the connecting electrode350bis increased, the parasitic capacitance generated between the connecting electrode350band the data line200increases and the LCD device may exhibit a degradation in picture quality because the data voltage supplied through the data line200may leak, and thus, be modulated by the increased parasitic capacitance.

The timing controller600generates a data control signal (DCS), a gate control signal (GCS), and a light source control signal (LCS), using a horizontal synchronizing signal (Hsync), a vertical synchronizing signal (Vsync), a main clock (MCLK), and a data enable signal (DE) provided from a source externally to the liquid crystal display device.

The timing controller600also re-arranges, or aligns, externally-input source data RGB in the order of R, G, and B data compatible with the field sequential driving system, and then sequentially supplies the aligned R, G, B data to the data driver210for every respective sub-frame.

The gate driver110sequentially shifts the gate control signal GCS from the timing controller600in accordance with gate shift clocks, to supply a scan pulse to each gate line for every sub-frame.

The data driver210samples the data supplied from the timing controller600in accordance with the data control signal (DCS) from the timing controller600, converts the sampled data to analog data, and supplies the resultant data to the data lines200.

In particular, the data driver210supplies R data to each data line200in the first sub-frame, supplies G data to each data line200in the second sub-frame, and supplies B data to each data line200in the third sub-frame.

The backlight unit500includes an R light source510for irradiating R light to the liquid crystal panel400, a G light source520for irradiating G light to the liquid crystal panel400, and a B light source530for irradiating B light to the liquid crystal panel400. The backlight unit500also includes a light source driving circuit540for driving the R, G, and B light sources510,520, and530.

The R, G, and B light sources510,520, and530sequentially irradiate R, G, and B lights to the liquid crystal panel400during the sub-divided portions of one frame in response to drive signals from the light source driving circuit.

Each of the light sources510,520, and530may include a fluorescent lamp or a light emitting diode.

The light source driving circuit540sequentially drives the R, G, and B light sources510,520, and530in every sub-frame in response to a light source control signal (LCS) from the timing controller600.

For example, in response to the light source control signal LCS, the light source driving circuit540may drive the R light source510in the first sub-frame after R data has been charged in first pixels and the liquid crystal has responded to the charged R data. In the second sub-frame, the light source driving circuit540may drive the G light source520after G data has been charged in second pixels and the liquid crystal has responded to the charged G data. In the third sub-frame, the light source driving circuit540may drive the B light source530after B data has been charged in third pixels and the liquid crystal has responded to the charged B data.

FIG. 4is a plan view schematically illustrating an LCD device according to a second embodiment of the present invention.

Referring toFIG. 4, the LCD device according to the second embodiment of the present invention is similar to the LCD device according to the first embodiment, except for the number of data lines200and the structure of the liquid crystal panel400.

In the LCD device according to the second embodiment of the present invention, the liquid crystal panel400is configured such that one pixel300includes four horizontally-adjacent pixel regions, and a plurality of thin film transistors (TFTs)410formed at the crossings of odd gate lines100and (4n−3)th and (4n−2)th data lines200and the crossings of even gate lines100and (4n−1)th and (4n)th data lines200, where n is a natural number. The TFTs410are arranged at opposite sides of the gate line100in a zigzag arrangement along with the gate line100. Two pixels300are vertically arranged between the adjacent two gate lines100.

The TFTs410of a first pair of pixels300vertically adjacent to each other are arranged at opposite sides of one gate line, namely, a first gate line100a, and the TFTs410of a second pair of vertically adjacent pixels300cand300dare at opposite sides of another gate line, namely, a second gate line100b. The respective TFTs of each the first and second pair of pixels are connected to different data lines200a,200b,200c, and200d, respectively.

This configuration will be described in more detail. The liquid crystal panel400of the LCD device according to the second embodiment of the present invention mainly includes a plurality of first (odd) and second (even) gate lines100aand100b. The liquid crystal panel400also includes a plurality of first (4n−3)th to fourth (4n)th data lines200a,200b,200c, and200darranged to cross the first and second gate lines100aand100b, and a plurality of pixels300in the pixel regions, wherein one pixel300is formed in horizontally-adjacent four pixel regions.

That is, the liquid crystal panel400includes a plurality of first pixels300athat receive a data signal from the first data line200athrough the corresponding TFT410in accordance with the scan pulse from the first gate line100a, a plurality of second pixels300bthat receive a data signal from the second data line200bthrough the corresponding TFT410in accordance with the scan pulse from the first gate line100a, a plurality of third pixels300cthat receive a data signal from the third data line200cthrough the corresponding TFT410in accordance with the scan pulse from the second gate line100b, and a plurality of fourth pixels300dthat receive a data signal from the fourth data line200dthrough the corresponding TFT410in accordance with the scan pulse from the second gate line100b.

Although the number of data lines200in the LCD device of the second embodiment increases to double that of the LCD device of the first embodiment, the time taken to drive all gate lines100is further reduced by half because the two gate lines100aand100bare simultaneously driven. Accordingly, it is possible to secure a time for sufficiently charging data into the pixels300even for large LCD devices.

In the LCD device according to the second embodiment of the present invention, the vertically-adjacent pixels300are connected to the gate line100arranged therebetween so that they simultaneously receive the scan pulse from the gate line100. Also, as illustrated inFIG. 5, scan pulses100aand100bare simultaneously supplied to two gate lines100in this LCD device. Accordingly, it is possible to supply scan pulses to all gate lines100within a time corresponding to one fourth of the time taken to drive all gate lines100as for the LCD device of the related art.

Because supplying the scan pulses to all of the gate lines100may be completed within a shortened period of time, it is possible to lengthen the turn-on time of the TFTs410to sufficiently charge data into the pixels without increasing the size of the TFTs410.

Although embodiments of the present invention have been described illustrating the case in which a scan pulse is simultaneously supplied to two gate lines100, it may be possible to simultaneously supply a scan pulse to three, four, or more gate lines100, as long as the number of data lines200is appropriately increased.

As apparent from the above description, the present invention may provide the following effects.

By sharing each gate line between the vertically-adjacent pixels arranged at opposite sides of the gate line, a scan pulse is simultaneously supplied to at least two gate lines so that the time taken to input scan pulses to all gate lines may be reduced. Accordingly, even when a field sequential system is used, it is possible to secure a sufficient data charging time without an increase in the size of TFTs.

In accordance with the reduction in the time taken to input scan pulses to all gate lines, it is also possible to secure a sufficient liquid crystal response time and a sufficient light source turn-on time.