KR20050115041A - Liquid crystal display device and driving method thereof - Google Patents

Abstract

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

According to the present invention, a control signal for sequentially applying the R, G, B grayscale data to the data line and a control signal for sequentially applying the R, G, B light are formed by the same timing controller and synchronized with each other.

In this way, the same timing controller is well synchronized with each other, thereby preventing color mixing and enabling accurate color display.

Description

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

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

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

An LCD 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 control the amount of light transmitted to the substrate from an external light source (backlight). A display device for obtaining an image signal.

Such LCDs are typical of portable flat panel displays, and among them, TFT-LCDs using thin film transistors (TFTs) as switching devices are mainly used.

In the TFT-LCD, each pixel may be modeled as a capacitor having a liquid crystal as a dielectric, that is, a liquid crystal capacitor. The equivalent circuit of each pixel in the LCD is shown in FIG. 1.

As shown in FIG. 1, each pixel of the liquid crystal display device has a common voltage and a drain electrode of a TFT 10 and a TFT 10 having a source electrode and a gate electrode connected to a data line Dm and a scan line Sn, respectively. And a storage capacitor Cst connected to the drain electrode of the TFT.

In FIG. 1, when the TFT 10 is turned on by being a scan signal to the scan line Sn, the data voltage Vd supplied to the data line is applied to each pixel electrode (not shown) through the TFT. Then, an electric field corresponding to the difference between the pixel voltage Vp and the common voltage Vcom applied to the pixel electrode is applied to the liquid crystal (equivalently represented by the liquid crystal capacitor in FIG. 1), and thus transmittance corresponding to the intensity of the electric field. To allow light to pass through. In this case, the pixel voltage Vp should be maintained for one frame or one field. In FIG. 1, the storage capacitor Cst is used to maintain the pixel voltage Vp applied to the pixel electrode.

In general, the liquid crystal display may be divided 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. Display the desired color by adjusting. In the color filter type LCD, the light emitted 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 filter layers to synthesize R, G, and B colors. Display the desired color.

As described above, in a liquid crystal display device displaying a color 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. need. Therefore, in order to obtain a high resolution image, sophisticated manufacturing technology of a liquid crystal display panel is required.

In addition, there is a manufacturing problem that a separate color filter layer must be formed on the liquid crystal display substrate, and there is a problem that the light transmittance of the color filter itself must be improved.

In the liquid crystal display of the field sequential driving method, independent light sources of R, G, and B colors are periodically turned on sequentially, and a color signal corresponding to each pixel is applied in synchronization with the lighting cycle to produce a full color image. Get it. That is, according to the liquid crystal display of the field sequential driving method, the R, G, and B primary colors output from one of the R, G, and B backlights to one pixel are not divided into R, G, and B unit pixels. By displaying the light sequentially in time division, a color image is displayed using the afterimage effect of the eye.

The field sequential driving method can be classified into an analog method and a digital driving method.

The analog driving method sets a plurality of gray voltages corresponding to the number of gray scales to be displayed, selects one gray voltage corresponding to data among the gray voltages, and drives the liquid crystal panel with the selected gray voltage, thereby applying the applied gray voltage. Gradation display is performed at the corresponding transmission amount.

2 is a diagram illustrating a driving voltage and a transmitted light amount according to a conventional LCD driving apparatus. In FIG. 2, the driving voltage refers to a voltage applied to the liquid crystal and the optical tranmittance refers to a transmission ratio with respect to the applied light when light is applied to the liquid crystal. That is, the light transmittance refers to the degree of twist that the liquid crystal can transmit light.

Referring to FIG. 2, in the R field section Tr for displaying the R color, a driving voltage of the V11 level is applied to the liquid crystal so that light corresponding to the driving voltage of the V11 level passes through the liquid crystal. In the G field section Tg for displaying the G color, a driving voltage of the V12 level is applied so that light corresponding to the driving voltage of the V12 level passes through the liquid crystal. Then, in the B field section Tb for displaying the B color, a driving voltage of the V13 level is applied to obtain a light transmittance corresponding to the driving voltage of the V13 level. The desired color image is displayed by the sum of the lights of R, G, and B transmitted in the Tr, Tg, and Tb sections, respectively.

On the other hand, the digital driving method makes the driving voltage applied to the liquid crystal constant and controls the voltage application time to perform gradation display. According to this digital driving method, the gray scale is displayed by adjusting the accumulated amount of light transmitted through the liquid crystal by maintaining the driving voltage constant and controlling the voltage applied state and the non-applied state in a timely manner.

According to the conventional field sequential driving method, when the R, G, and B grayscale data voltages are applied, R, G, and B backlight light sources corresponding to the same need to be driven in synchronization, but are not synchronized with each other, resulting in color mixing. . That is, when the G backlight light source is overlapped and driven at the time when the R gray data voltage is applied, the color that we want cannot be expressed.

3 is a diagram illustrating a liquid crystal display device according to a conventional field sequential driving method.

As shown in FIG. 3, a conventional liquid crystal display device includes a liquid crystal display panel 10, a scan driver 20, a data driver 30, a gray voltage generator 40, a timing controller 50, and a reset voltage. The generator 600 includes light emitting diodes 60a, 60b, and 60c and a light source controller 70 for outputting R, G, and B light sources, respectively.

Here, in the conventional liquid crystal display, the timing controller 50 and the light source controller 70 do not share timings with each other, so that the timings of applying the R, G, and B grayscale data and the R, G, and B light emitting diodes 60a, 60b, There is a problem with 60c) being synchronized.

That is, the timing controller 50 receives the gray level data signals R, G, and B data, the horizontal synchronization signal Hsync, the vertical synchronization signal Vsync, the data application area signal DE, and the main clock MCLK. The necessary control signals Sg and Sd are supplied to the scan driver 20 and the data driver 30, respectively, and the gray scale data R, G, and B data are supplied to the gray voltage generator 400. Here, the data application area signal DE is a signal indicating an area where data is output, and the main clock MCLK is a clock signal which is input from a microprocessor (not shown) and becomes a reference signal.

On the other hand, the light source controller 70 receives the light source control signal Sb generated from the microprocessor and controls the lighting timing of the R, G, and B light emitting diodes 60a, 60b, and 60c.

At this time, since the light source control signal Sb for controlling the light source controller 70 is generated through the main clock MCLK independently of the control signals Sg and Sd output from the timing controller 50, the control signal Sg. , Sd) may cause problems. That is, as described above, a problem may occur in that the R, G, and B backlight light sources do not emit light in synchronization with the timing when the R, G, and B grayscale data voltages are applied to the LCD panel 10.

The technical problem to be solved by the present invention is to solve the above-mentioned problems of the prior art, the field sequential so that each R, G, B grayscale data is applied to the LCD panel and each R, G, B backlight light source emits light. It is to provide a drive type liquid crystal display device.

A method of driving a liquid crystal display according to a feature of the present invention is

A method of driving a liquid crystal display device comprising a liquid crystal formed between a first substrate on which a first electrode is disposed and a second substrate on which a second electrode is disposed, and sequentially transmitting red, green, and blue light to one pixel. To

 (a) generating a first control signal for sequentially applying red, green, and blue grayscale data to the first electrode and outputting the grayscale data to the first electrode in response to the first control signal; And

(b) generating a second control signal for sequentially applying the red, green, and blue light and outputting the light at the time when the gray scale data is output;

The first control signal and the second control signal may be generated from the same input signal and synchronized with each other. Here, the time point at which the red, green, and blue grayscale data is applied to the first first electrode and the start time point at which the light of each of the red, green, and blue are output are identical.

A driving method of a liquid crystal display according to another feature of the present invention is

And a liquid crystal formed between the first substrate on which the first electrode is disposed and the second substrate on which the second electrode is disposed, and sequentially transmitting light of the first color, the second color, and the third color to one pixel. In the driving method of a liquid crystal display device,

(a) generating a first control signal for applying gradation data corresponding to the first color to the first electrode, and applying gradation data to the first electrode in response to the first control signal;

(b) generating a second control signal synchronized with the first control signal and outputting light corresponding to the first color while the gray scale data of step (a) is applied in response to the second control signal; step;

(c) after the steps (a) and (b), generate a third control signal to apply the grayscale data corresponding to the second color to the first electrode, and generate the grayscale data in response to the third control signal. Applying to the first electrode; And

(d) generating a fourth control signal synchronized with the second control signal and outputting light corresponding to the second color while the grayscale data of step (b) is applied in response to the fourth control signal; Steps. Here, in the driving method of the liquid crystal display, after the steps (c) and (d), a fifth control signal is generated to apply the grayscale data corresponding to the third color to the first electrode, and the fifth Applying gradation data to the first electrode in response to a control signal, generating a sixth control signal synchronized with the fifth control signal, and corresponding to the sixth control signal, the gradation data of step (e) Outputting light corresponding to the third color while is applied. In this case, the first to fourth control signals are generated by the same input signal.

According to another aspect of the present invention,

In the form of a matrix having a plurality of scan lines for transmitting a scan signal, a plurality of data lines insulated from and intersecting the scan lines, a region surrounded by the scan lines and data lines, and switching elements connected to the scan lines and data lines, respectively. A liquid crystal display panel including a plurality of pixels arranged;

A light source sequentially outputting red, green, and blue light to one pixel;

A data driver for outputting grayscale data of red, green, and blue to the data lines, respectively; And

By using a plurality of input signals, a first control signal for sequentially applying the red, green, and blue light is generated and output to the light source, and the data driver transmits the red, green, and blue gray levels to the data line. And a timing controller for sequentially applying data and generating and outputting a second control signal synchronized with the first control signal to the data driver. Here, a time point at which each of the red, green, and blue grayscale data by the second control signal is applied to the first data line, and start of output of each of the red, green, and blue light by the first control signal are output. The viewpoint is the same.

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.

Hereinafter, a liquid crystal display and a driving method thereof according to an exemplary embodiment of the present invention will be described with reference to FIGS. 4 to 6.

4 is a diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention. That is, FIG. 4 is a diagram illustrating a liquid crystal display in which the R, G, and B light emitting diodes emit light in synchronization with the time points at which the R, G, and B grayscale data voltages are applied.

As shown in FIG. 4, the liquid crystal display according to the exemplary embodiment of the present invention includes a liquid crystal display panel 100, a scan driver 200, a data driver 300, a gray voltage generator 400, and a timing controller 500. And light emitting diodes 600a, 600b, and 600c respectively outputting R, G, and B light sources, and a light source controller 700.

A plurality of scan lines (not shown) are formed in the liquid crystal display panel 100 to transmit a gate-on signal, and are insulated from and intersect with the plurality of scan lines to transfer gray data voltages corresponding to gray data. Data lines (not shown) are formed. A plurality of pixels arranged in a matrix form is surrounded by a scan line and a data line, and each pixel includes a thin film transistor (not shown) and a drain of the thin film transistor having a gate electrode and a source electrode connected to the scan line and the data line, respectively. A pixel capacitor (not shown) and a storage capacitor (not shown) connected to the electrode are included.

The scan driver 200 sequentially applies a scan signal to the scan line, thereby turning on the TFT to which the gate electrode is connected to the scan line to which the scan signal is applied. At this time, according to an embodiment of the present invention, the signal Sg for controlling the scan driver 200 is a signal for sequentially emitting the R, G, and B light emitting diodes 600a, 600b, and 600c, and the grayscale data R and G, respectively. , B Data) is applied in synchronization with the start signal for applying the voltage.

The timing controller 500 is provided with the gray scale data signals R, G, and B data, the horizontal sync signal Hsync, the vertical sync signal Vsync, the data application area signal DE, and the like from an external or graphic controller (not shown). The main clock MCLK is input to supply the necessary control signals Sg, Sd, and Sb to the scan driver 200, the data driver 300, and the light source controller 800, respectively, and the gray scale data R, G, and B data. ) Is supplied to the gray voltage generator 400. Here, the data application area signal DE is a signal indicating an area where data is output, and the main clock MCLK is a clock signal that is input from a microprocessor (not shown) and becomes a reference signal.

In this case, according to an exemplary embodiment of the present invention, the timing controller 500 receives the plurality of signals and controls the scan control signals R, G, and B light emitting diodes 600a, 600b, and 600c that control the scan driver 200, respectively. Generating a light emission control signal for sequentially controlling light emission and a data control signal for controlling application of respective grayscale data voltages (voltages corresponding to R, G, and B data), and synchronizing the control signals with each other Each control signal is applied to the scan driver 200, the light source controller 700, and the data driver 300, respectively. In more detail, the timing controller 500 generates and outputs a control signal for applying a gradation data voltage (voltage corresponding to R, G, and B data) while simultaneously applying a scan signal to the first scan line. When gradation data voltages corresponding to the R, G, and B data are sequentially applied, the control signals are sequentially generated to output the R, G, and B light emitting diodes 600a, 600b, and 600c in synchronization with the gradation data voltages. In the exemplary embodiment of the present invention, the light emitting diode is used as the backlight as an example, but is not necessarily limited thereto.

The gray voltage generator 400 generates a gray voltage having a magnitude corresponding to gray data and supplies it to the data driver 300. The data driver 300 applies the gray voltage output by the gray voltage generator 400 to the data line in response to a control signal synchronized with the embodiment of the present invention.

The light emitting diodes 600a, 600b, and 600c respectively output light corresponding to R, G, and B to the LCD panel, and the light source controller 800 controls the lighting timing of the light emitting diodes 600a, 600b, and 600c. In this case, according to an exemplary embodiment of the present invention, the timing controller 500 may be configured to supply the grayscale data from the data driver 300 to the data line and to turn on the R, G, and B light emitting diodes by the light source controller 800. Synchronized by the control signal provided by the.

Meanwhile, the timing controller 500 according to the embodiment of the present invention includes a clock generator 520 and a start signal generator 540.

5 is a diagram illustrating an internal block diagram of a timing controller and a signal transmitted to a neighboring block according to an embodiment of the present invention.

The clock processor 520 processes the clock through the input vertical sync signal Vsync, the horizontal sync signal Hsync, and the main clock MCLK to process the data driver 300, the scan driver 200, and the light source controller 700. Generates and outputs a clock signal that controls

The start signal generator 540 uses various clocks processed by the clock processor 520 so that the data driver 300 sequentially applies the R, G, and B grayscale data voltages, and the scan driver 200 first. The light source controller 700 generates a clock for synchronizing the start signal for sequentially turning on the R, G, and B light emitting diodes with the start signal for applying the scan signal to the first scan line.

As such, various control signals generated by the clock processor 520 and the start signal generator 520 are input to the data driver 300, the scan driver 200, and the light source controller 700.

As shown in FIG. 5, the control signals output from the timing controller 500 to the data driver 300 are the data driver reference signal HCLK, the data latch reference signal STH, and the data output signal Load (TP). Although not shown in FIG. 5, grayscale data R, G, and B data are input from the timing controller 500 to the data driver 300. The data driver reference signal HCLK is a clock for transmitting data, and the timing controller 500 generates and transmits the main reference signal MCLK in synchronization with the gray scale data in accordance with the data driver 300. The data latch reference signal STH is a reference signal for accurately latching the grayscale data R, G, and B data to the data driver 300. The data output signal Load (TP) is a signal for outputting the gray scale data R, G, and B data latched to the data driver 300 to the LCD panel 100.

In addition, the gate clock CPV is transmitted from the timing controller 500 to the scan driver 200. The gate clock CPV is a clock that applies a scan signal to the scan line.

The light emitting diode clock LCLK is transmitted from the timing controller 500 to the light source controller 700. The light emitting diode clock LCLK is a clock for applying a signal to sequentially light the R, G, and B light emitting diodes 600a, 600b, and 600c. At this time, the timing of turning on the R, G, and B light emitting diodes is synchronized with the timing at which the data driver 300 supplies the grayscale data R, G, and B data to the data.

The data output signal Load (TP), the gate clock CPV, and the light emitting diode clock LCLK are synchronized with each other according to an embodiment of the present invention. That is, the data output signal Load (TP) for outputting the R gray scale data to the pixel corresponding to the first scan line, the gate clock CPV for applying the scan signal to the first scan line, and the R LED 600a. The LED clocks LCLK for applying the signal to be turned on are synchronized with each other, and the end timings are also synchronized with each other. In this manner, the G gray data and the B gray data are also synchronized with each other.

FIG. 6 illustrates R, G, and B light emitting diodes 600a, 600b, and 600c, driving methods corresponding to R, G, and B grayscale data R, G, and B data, and light of liquid crystals according to an exemplary embodiment of the present invention. It is a figure which shows the transmission amount.

As shown in Fig. 6, first, the start point and the end point of the light emitting diode 600a are synchronized with the start time and the end time when the R gray data is applied to the data line, respectively. Next, the time point at which the G light emitting diode 600b starts to emit light and the time point at which the G light emitting diode 600b starts emitting light are synchronized with the start time and the end time when the G gray data is applied to the data line. In addition, the time point at which the B light emitting diode 600c starts to emit light and the time point at which the light emission ends are synchronized with the start time and the end time when the B gray scale data is applied to the data line. In FIG. 6, the R field, the G field, and the B field represent periods in which scan signals are applied from the first scan line to the last scan line, respectively. The R, G, and B fields that apply scan signals to all of these scan lines are also synchronized with the timing at which the R, G, and B light emitting diodes 600a, 600b, and 600c emit light.

As such, according to the exemplary embodiment of the present invention, a signal for controlling the data driver 300, a signal for controlling the scan driver 200, and a signal for driving the light source controller 700 are generated and output from the timing controller 500, respectively. It is well synchronized with each other to prevent color mixing, so accurate color display is possible.

4 to 6, the analog field sequential driving method has been described, but it can be applied to the digital field sequential driving method in the same manner. However, the digital field sequential driving method differs in that the driving voltage is made constant and the gray scale display is performed by controlling the voltage application time.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

As described above, according to the present invention, a control signal for outputting grayscale data and a control signal for emitting the R, G, and B backlights are generated together in the timing controller, so that the control signal is well synchronized to achieve color mixing. To prevent accurate color display.

1 is a view showing a pixel of a conventional TFT-LCD.

2 is a waveform diagram illustrating a driving method of a conventional analog liquid crystal display device.

3 is a diagram illustrating a liquid crystal display device according to a conventional field sequential driving method.

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

5 is a diagram illustrating an internal block diagram of a timing controller and a signal transmitted to a neighboring block according to an embodiment of the present invention.

FIG. 6 is a diagram illustrating R, G, and B light emitting diodes, a method of driving R, G, and B grayscale data and a light transmittance of a liquid crystal according to an exemplary embodiment of the present invention.

Claims (11)

A method of driving a liquid crystal display device comprising a liquid crystal formed between a first substrate on which a first electrode is disposed and a second substrate on which a second electrode is disposed, and sequentially transmitting red, green, and blue light to one pixel. To  (a) generating a first control signal for sequentially applying red, green, and blue grayscale data to the first electrode and outputting the grayscale data to the first electrode in response to the first control signal; And (b) generating a second control signal for sequentially applying the red, green, and blue light and outputting the light at the time when the gray scale data is output; And the first control signal and the second control signal are generated from the same input signal and synchronized with each other. The method of claim 1, And a start time point at which each of the red, green, and blue grayscale data is applied to the first first electrode, and a start time point at which the red, green, and blue light is output. The method of claim 2, And a time point at which each of the red, green, and blue grayscale data is applied to the last first electrode, and an end time point at which the red, green, and blue light is output. The method according to claim 1 or 2, Generating a third control signal synchronized with the first and second synchronization signals to apply a scan signal to the second electrode, and generating the scan signal at a time point when the gray scale data is output in response to the third control signal; The driving method of the liquid crystal display further comprising the step of outputting. And a liquid crystal formed between the first substrate on which the first electrode is disposed and the second substrate on which the second electrode is disposed, and sequentially transmitting light of the first color, the second color, and the third color to one pixel. In the driving method of a liquid crystal display device, (a) generating a first control signal for applying gradation data corresponding to the first color to the first electrode, and applying gradation data to the first electrode in response to the first control signal; (b) generating a second control signal synchronized with the first control signal and outputting light corresponding to the first color while the gray scale data of step (a) is applied in response to the second control signal; step; (c) after the steps (a) and (b), generate a third control signal to apply the grayscale data corresponding to the second color to the first electrode, and generate the grayscale data in response to the third control signal. Applying to the first electrode; And (d) generating a fourth control signal synchronized with the second control signal and outputting light corresponding to the second color while the grayscale data of step (b) is applied in response to the fourth control signal; A method of driving a liquid crystal display comprising the step. The method of claim 5, (e) after the steps (c) and (d), generate a fifth control signal to apply the grayscale data corresponding to the third color to the first electrode, and generate the grayscale data in response to the fifth control signal. Applying to the first electrode; And (f) generating a sixth control signal synchronized with the fifth control signal, and outputting light corresponding to the third color while the gray scale data of step (e) is applied in response to the sixth control signal; A method of driving a liquid crystal display further comprising the step. The method of claim 5, The first to fourth control signals are generated by the same input signal. In the form of a matrix having a plurality of scan lines for transmitting a scan signal, a plurality of data lines insulated from and intersecting the scan lines, a region surrounded by the scan lines and data lines, and switching elements connected to the scan lines and data lines, respectively. A liquid crystal display panel including a plurality of pixels arranged; A light source sequentially outputting red, green, and blue light to one pixel; A data driver for outputting grayscale data of red, green, and blue to the data lines, respectively; And By using a plurality of input signals, a first control signal for sequentially applying the red, green, and blue light is generated and output to the light source, and the data driver transmits the red, green, and blue gray levels to the data line. And a timing controller configured to sequentially apply data and to generate a second control signal synchronized with the first control signal and to output the second control signal to the data driver. The method of claim 8, When the respective red, green, and blue grayscale data by the second control signal are applied to the first data line, and when the respective red, green, and blue light are output by the first control signal, The liquid crystal display device which is the same characterized by the above-mentioned. The method of claim 8, The timing controller A clock processor configured to generate a clock signal for controlling the data driver and the light source by using the plurality of input signals; And A first start signal for applying respective red, green, and blue gray level data to the data lines in order using the clock signal generated by the clock processor; and the light source in synchronization with the first start signal, respectively. And a start signal generator configured to generate a second start signal for outputting red, green, and blue light. The method according to claim 8 or 9, A scan driver for sequentially supplying scan signals to the scan lines; The timing controller generates a third control signal synchronized with the first and second synchronization signals to apply a scan signal to the scan line, and transmits the third control signal to the scan driver. .