KR20040062168A - drive system for liquid crystal display - Google Patents

Abstract

PURPOSE: A system for driving an LCD(liquid crystal display) is provided to realize a target transmissivity for each sub-frame. CONSTITUTION: A system for driving an LCD(180) includes a data generator(172), a data converter(174), and a transmitter(170). The data generator generates RGB data and control signals by frames. The data converter corrects data voltage information of the RGB data. The transmitter transmits the RGB data including the corrected data voltage information and the control signals to the LCD for each frame. The data converter compares the first RGB data transmitted to the LCD for a previous frame to the second RGB data to be transmitted to the LCD for the current frame to correct the data voltage information of the second RGB data.

Description

Drive system for liquid crystal display

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive system for a liquid crystal display, and more particularly, to transfer RGB data and control signals for a desired color image so that the liquid crystal display can display a color image. A drive system for a liquid crystal display device.

In recent years, as the society enters the information age, the display industry for processing and displaying a large amount of information has been rapidly developed.

Accordingly, a liquid crystal display (LCD) has been developed that can meet various demands of consumers, such as thinning, light weight, and low power consumption, and is a next-generation display device that replaces the existing cathode-ray tube (CRT). Be in the spotlight.

The liquid crystal display includes a circuit unit for processing RGB data and various control signals transmitted from an external driving system into an appropriate electrical signal, and a liquid crystal having an anisotropic dielectric constant whose molecular arrangement is changed by the electrical signal. It includes a liquid crystal panel that represents an image with a change in transmittance according to the backlight and a backlight for supplying light to the liquid crystal panel.

FIG. 1 is a cross-sectional view of a liquid crystal panel for a general liquid crystal display device and illustrates an active matrix LCD (AM-LCD) method which is most widely used because of its excellent resolution and video performance.

The liquid crystal panel 10 faces the upper substrate 20 having the common electrode 24 disposed on one surface thereof, and the lower substrate 30 having the pixel electrode 64 disposed on one surface thereof facing each other. 50 has a structure interposed.

The upper substrate 20 includes a transparent substrate 1 made of a transparent material such as glass, a color filter layer 22 disposed below the common substrate 24, and a common electrode 24 for applying a voltage to the liquid crystal 50. In this case, the color filter layer 22 may be classified into a red color filter that transmits red color, a green color filter that transmits green color, and a blue color filter that transmits blue color, and cover the gap therebetween. A black matrix 26 is included to block a portion of the light penetrating into the lower substrate 30.

In addition, the lower substrate 30 has a plurality of pixels P defined above the transparent substrate 1, and each of the pixels P is connected to the thin film transistor T as a switch and a one-to-one correspondence with the voltage to the liquid crystal 50. It includes a pixel electrode 64 for applying.

The first and second polarizers are positioned on the outer surfaces of the upper and lower substrates, respectively, and although not shown, the edges of both substrates are sealed so that the liquid crystal 50 between the upper and lower substrates 20 and 30 does not leak. The upper and lower alignment layers are interposed between the upper and lower substrates 20 and 30 and the liquid crystal 50 so as to determine the alignment direction of the liquid crystal molecules.

Since the liquid crystal panel 10 described above cannot emit light by itself, a backlight 60 including a white light source 62 is separately provided on the rear thereof to supply white light toward the front of the liquid crystal panel 10, thereby An image of sufficient brightness is displayed.

That is, the liquid crystal panel 10 adjusts the voltage difference between the common electrode 24 and the pixel electrode 64 through the thin film transistor T to change the molecular arrangement of the liquid crystal 50 therebetween, and at the same time to the backlight ( The white light supplied from 60 passes through the liquid crystal 50 and the color filter layer 22. Therefore, a color image is displayed through a combination of transmittances that vary according to the alignment direction of the liquid crystal molecules and color combinations of a plurality of red, green, and blue color filters included in the color filter layer 22.

However, there are some problems in using the general liquid crystal panel 10 and the backlight 60 described above. First, the transmittance of the color filter layer 22 stays at a maximum of 33%. 60) should have high illuminance. In addition, since the backlight 60 must always be on, power consumption is disadvantageous.

In addition, when the thickness of the color filter layer 22 is thick, the color characteristics are improved but the transmittance is decreased. In the opposite case, the transmittance is increased but the color characteristics are decreased. Therefore, a precise control process is required, and in particular, a liquid crystal is used because a very expensive material is used. There is a disadvantage in that the manufacturing cost of the display device is increased.

Accordingly, a time division liquid crystal display device capable of displaying a color image without a color filter layer has been proposed.

FIG. 2 is a cross-sectional view of a liquid crystal panel for a general time division liquid crystal display, and FIG. 3 is a block circuit diagram showing a schematic structure of the time division liquid crystal display, and the same elements as in FIG. Given.

The time division liquid crystal display device also includes a liquid crystal panel 10, a backlight 60, and a circuit unit 80 similarly to a general liquid crystal display device.

First, in the liquid crystal panel 10, a plurality of parallel data lines 34 and gate lines 36 are vertically and horizontally disposed between the upper and lower substrates 20 and 30 facing each other with the liquid crystal 50 interposed therebetween. The pixel P in a matrix form is defined.

Each of the pixels P includes a thin film transistor T and a pixel electrode 64 connected one-to-one to each other, and includes a pixel electrode 24 and a common electrode 64 that face each other with the liquid crystal 50 interposed therebetween. The liquid crystal capacitor C _LC is defined. In addition, each pixel P includes a storage capacitor C _ST connected in parallel with the liquid crystal capacitor C _{LC in} order to solve parasitic capacitance.

In this case, in the case of the time-division liquid crystal display, in particular, the color filter layer does not exist in the liquid crystal panel 10. Instead, the R light source 64 and the G light source (which emit R, G, and B color light, respectively, in the backlight 60). 66 and the B light source 68 are different.

In addition, a driving system 70 is provided outside the liquid crystal display to transfer the RGB data and various control signals to the circuit unit 80, which can be largely divided into a data generator 72 and a transmitter 74. .

The data generation unit 72 converts and generates a desired color image to be expressed as RGB data, and generates a control signal capable of expressing it. In this case, each of the RGB data includes data voltage information. In particular, in the time division method, the data generation unit 72 includes R data including R data voltage information, control signals therefor, G data including G data voltage information, and the like. A control signal for this purpose, B data including B data voltage information, and a control signal for the same are generated in parallel.

The transmission unit 74 stores these R, G, and B data and control signals for each, and sequentially transmits them to the circuit unit 80.

The circuit unit 80 also includes an interface 82, a timing controller 84, a gamma power supply unit 86, a data driver 88, and a gate driver 90, which are external drive systems 70. R, G, B data and control signals transmitted from the) is properly processed and finally delivered to the liquid crystal panel 10.

First, the interface 82 transmits R, G, and B data and control signals to the timing controller 84, respectively. The timing controller 84 also synchronizes the R, G, and B data and various control signals to generate data control signals transmitted to the data driver 88 and scan signal voltages transmitted to the gate driver 90, respectively. .

In addition, the gamma power supply unit 86 selects a data voltage for controlling the molecular arrangement of the liquid crystal through a data control signal and transfers the data voltage to the data driver 88. The data voltage indicates data of transmittance-voltage characteristics of the liquid crystal panel 10. Is set by the producer.

In addition, the data driver 88 is positioned at one edge of the liquid crystal panel 10 to connect one end of the plurality of data lines 34 to each data voltage transferred from the gamma power supply unit 86 through a timing synchronized data control signal. Is transmitted to the data line 34. In addition, the gate driver 90 is positioned at the other edge of the adjacent liquid crystal panel 10 to connect one end of the plurality of gate lines 36 to control the on / off of each of the thin film transistors T. Is sequentially output to the gate line 36.

Therefore, the thin film transistor T of the liquid crystal panel 10 serves as a switch for connecting the data voltage to the liquid crystal capacitor C _LC through the scan signal voltage.

In the time division liquid crystal display having the above structure, one frame is divided into three and divided into first to third sub frames having the same interval to express a color image.

Since one frame is about 1/60 second, each subframe may be 1/180 second apart.

In the time-division liquid crystal display, after each liquid crystal array is changed in each of these subframes, a process in which one of the R, G, and B light sources 64, 66, and 68 blinks is sequentially repeated to form one frame. The driving order of the G, B light sources 64, 66, 68 is explained on the premise of R, G, and B arbitrarily.

First, in one subframe, the transmitting unit 74 of the driving system 70 transmits R data and a control signal for the same to the circuit unit 80.

Subsequently, the timing controller 84 generates an R data control signal and an R scan signal voltage corresponding thereto, and transmits the R data control signal and the R scan signal voltage to the data driver 88 and the gate driver 90, respectively. Output to the driver 88. Accordingly, the data driver 88 outputs an R data voltage to all the data lines 34, and the gate driver 90 sets the R scan signal voltage for each gate line 36 from the Gn-th gate line to the Gm gate line. Scan output sequentially.

Accordingly, as the appropriate R data voltage is selected and charged into each liquid crystal capacitor C _LC , the liquid crystal array direction is changed, and then the R light source 64 blinks to display the R color image. This terminates the first subframe.

Subsequently, when the transmitting unit 74 of the driving system 70 transmits the G data and a control signal capable of expressing the same to the circuit unit 80, the liquid crystal capacitor C _LC positioned in each pixel P through the same process. Is charged with the appropriate G data voltage to change the liquid crystal array direction. The G light source 66 blinks to terminate the second subframe by displaying the G color image.

Finally, through the same process, the third subframe is charged with the B data voltage in the liquid crystal capacitor C _LC to change the liquid crystal array direction, and the B light source 68 blinks on and off to display the B color image. This terminates the third subframe to complete one unit frame as a whole.

In this case, since the first to third subframes are sequentially progressed with the same interval of about 1/180 seconds, the R color picture, the G color picture, and the B color picture are sequentially performed during one short frame of about 1/60 second. The visual observation of the observer recognizes one color image in which these R, G, and B color images are combined.

However, when the color image is displayed through the time division liquid crystal display device described above, the desired color image may be different from the color image implemented in the actual liquid crystal panel.

This is closely related to the response speed of the liquid crystal. In contrast to a general liquid crystal display, a time division liquid crystal display divides one frame into three subframes and changes the liquid crystal array for each subframe. Therefore, the response speed of the liquid crystal should be very fast. For this, the OSC mode, which is known to have the fastest response speed among the modes using nematic liquid crystal, is mainly used.

However, even in this OSC mode, various problems can occur because it cannot keep up with the desired response speed.

4 is a graph illustrating a change in actual transmittance in each subframe when the specific color is expressed using a general time division liquid crystal display as a dotted line. For reference, the change in the transmittance of the ideal for implementing the desired color is shown with a dashed line for comparison.

In this figure, L1 to L3 represent a delay time until the data voltage is transmitted in each subframe and then charged to the liquid crystal capacitor, and the same applies to FIG. 5.

Referring to this, it can be seen that the ideal transmittance for the desired color implementation and the actual transmittance are different from each other. In more detail, the actual transmittance is lower than the desired degree in the first subframe, and vice versa. The phenomenon appears. As a result, it is expected that the color image actually displayed lacks a red component and a large amount of blue components as compared to the intended color image.

This phenomenon is related to the response speed of the liquid crystal. The liquid crystal response speed is a rising time (Tr) when a voltage is applied to the liquid crystal to change the transmittance from black to white, and vice versa. This is the sum of Time, Tf).

In other words, how quickly the arrangement of liquid crystal molecules changes with respect to voltage, which can be confirmed through indirectly changing capacitance of liquid crystal capacitance according to voltage.

Accordingly, FIG. 5 is a dotted line showing the change in the data voltage transmitted to the liquid crystal capacitor for each subframe under the same condition as that of FIG. 4, thereby converting the capacitance change in the actual liquid crystal capacitor into a voltage as a dotted line. .

4 and 5, in the first subframe, before the capacitance of the liquid crystal capacitor reaches the desired level, the R light source blinks, and only after the second subframe, the desired capacitance appears. . On the other hand, in the third frame, the B light source flashes to display the B color image while the capacitance charged in the liquid crystal is not discharged in the second subframe of the previous step, so that the first subframe has a lower transmittance than desired. In the third subframe, the opposite phenomenon occurs.

This can not accurately represent the desired color image, which is a fatal defect for the display device.

In particular, the response speed of the liquid crystal is important because of the characteristics of the time-division liquid crystal display device in which the liquid crystal array has to be changed within a short time for each subframe. Currently, there is no way to solve the slow response speed of the liquid crystal. It has a drawback that it is impossible to accurately represent color images.

This is pointed out as a problem that greatly threatens the reliability of the liquid crystal display device.

The present invention has been made to solve the above problems, in the time division type liquid crystal display device, to provide a drive system of the improved time division type liquid crystal display device, which can implement the desired transmittance for each subframe. The purpose is.

1 is a cross-sectional view of a liquid crystal panel for a general liquid crystal display device

2 is a cross-sectional view of a liquid crystal panel for a general time division liquid crystal display device.

3 is a circuit diagram illustrating a structure of a general time division liquid crystal display device.

4 is a graph showing a change in transmittance for each subframe for displaying a specific color in a general time division liquid crystal display device;

FIG. 5 is a graph illustrating a change in capacitance of a liquid crystal capacitor according to R, G, and B data voltages for each subframe in FIG.

6 is a cross-sectional view of a liquid crystal panel for a time division liquid crystal display according to the present invention.

7 is a circuit diagram showing the structure of a time division liquid crystal display according to the present invention.

8 is a block diagram illustrating in detail the driving system according to the present invention;

9 is a graph showing a change in transmittance for each subframe for displaying a specific color in the time division liquid crystal display according to the present invention.

FIG. 10 is a graph illustrating a change in capacitance of a liquid crystal capacitor according to R, G, and B data voltages for each subframe in FIG. 9.

<Description of the symbols for the main parts of the drawings>

110: liquid crystal panel 134: data line

136: gate line 170: drive system

172: data generation unit 174: transmission unit

180: circuit portion 182: interface

184: timing controller 186: gamma power supply

188: data driver 190: gate driver

T: Thin Film Transistor C _LC : Liquid Crystal Capacitor

C _ST : Storage Capacitor P: Pixel

200: data conversion unit

In order to achieve the above object, the present invention provides a plurality of liquid crystal cells in which a circuit unit for generating a data voltage and a scan signal voltage through RGB data and control signals including data voltage information, and a liquid crystal capacitor and a storage capacitor are mounted. A liquid crystal display comprising a liquid crystal panel for displaying an RGB color image for each frame by a change in transmittance through the data voltage and the scan signal voltage, and a backlight for supplying light to the liquid crystal panel. And a driving system for transmitting a control signal to the liquid crystal display, comprising: a data generation unit generating the RGB data and the control signal in units of frames; A data converter for modifying data voltage information of the RGB data; A driving system including a transfer unit for transmitting RGB data and the control signal including the modified data voltage information to the liquid crystal display every frame.

In this case, the data converting unit compares the first RGB data transmitted to the liquid crystal display in the frame of the previous step and the second RGB data to be transmitted to the liquid crystal display in the frame of the step and compares the data of the second RGB data. Characterize the voltage information.

In particular, the data converter may include a luminance of the first color image in the first color image displayed through the first RGB data and the control signal, and in a second color image displayed through the second RGB data and the control signal. When the data voltage information of the second RGB data is modified to generate a lower data voltage when the luminance is greater than the luminance of the second color image, and the luminance of the first color image is smaller than the luminance of the second color image, The data voltage information of the second RGB data is modified to generate a higher data voltage.

In this case, the capacitance of the storage capacitor is C _ST , the capacitance of the liquid crystal capacitor is C _ST , and is generated through the first data voltage and the second RGB data and the control signal generated through the first RGB data and the control signal. When the difference between the second data voltage is V and the capacitance difference between the liquid crystal capacitor due to the first data voltage and the second data voltage is ΔC _LC , the data converter is configured to determine the second data voltage. As small or large modifications are characterized.

In particular, the data conversion unit comprises: a data comparison operation unit for comparing the first RGB data and the control signal with the second RGB data and the control signal; A first correction value for modifying second data voltage information of the RGB data so that a lower data voltage is generated when the luminance of the first color image is greater than the luminance of the second color image, and the first color image; A table for outputting a second correction value for modifying the second data voltage information so that a higher data voltage is generated when the brightness is less than the brightness of the second color image; And a data correction unit for reflecting the first or second correction value to the second RGB data and the control signal, wherein the capacitance of the storage capacitor is C _ST , the capacitance of the liquid crystal capacitor is C _ST , The difference between the first data voltage and the second data voltage generated through the first RGB data and the control signal is V, and the capacitance difference of the liquid crystal capacitor due to the first data voltage and the second data voltage is ΔC _LC . The correction value It is characterized by having a relationship of.

In the present invention, the liquid crystal panel divides each frame into first to third subframes having the same interval, and sequentially transmits the transmittance for the R color image, the transmittance for the G color image, and the transmittance for the B color image. And the backlight has a time division method of sequentially supplying R, G, and B color light to the liquid crystal panel every subframe, and the data generation unit includes R, G, and B image data each having data voltage information. A control signal is generated in parallel, and the data conversion unit modifies the data voltage information of the R, G, and B image data, respectively, and the transmission unit generates R, G, and B data each having the modified data voltage information. Provided is a driving system for sequentially supplying the liquid crystal display.

In this case, the data converter may include first R, G or B data transmitted to the liquid crystal display in the subframe of the previous step, and second R, G or B data to be transmitted to the liquid crystal display in the subframe of the step. The data voltage information included in the second R, G or B data is corrected.

In particular, the data converter may include a first color image displayed through the first R, G, or B data and a control signal, and a second color image displayed through the second R, G, or B data and a control signal. And correcting data voltage information of the second R, G, or B data so that a lower data voltage is generated when the luminance of the first color image is greater than the luminance of the second color image, and correcting the data voltage information of the second color image. The data voltage information of the second R, G or B data is modified to generate a higher data voltage when the brightness is smaller than the brightness of the second color image, wherein the capacitance of the storage capacitor is set to C _ST. The capacitance of the liquid crystal capacitor is determined through the C _ST , the first data voltage generated through the first R, G or B data and the control signal, and the second R, G or B data and the control signal. When the difference between the generated second data voltage is V, and the capacitance difference between the liquid crystal capacitor due to the first data voltage and the second data voltage is ΔC _LC , the data converter is configured to determine the second data voltage. As small or large modifications are characterized.

The data conversion unit may further include a data comparison operation unit configured to compare the first R, G or B data and the control signal with the second R, G or B data and the control signal; A first correction value for modifying second data voltage information of the second R, G or B data so that a lower data voltage is generated when the luminance of the first color image is greater than the luminance of the second color image; A table for outputting a second correction value for modifying the second data voltage information so that a higher data voltage is generated when the brightness of the first color image is less than the brightness of the second color image; And a data correction unit for reflecting the first or second correction value to the second R, G, or B data and the control signal, wherein the capacitance of the storage capacitor is C _ST , the capacitance of the liquid crystal capacitor. C _ST , the difference between the first data voltage and the second data voltage generated through the first R, G or B data and the control signal, V, and the liquid crystal capacitor according to the first data voltage and the second data voltage. When the capacitance difference of is ΔC _LC , the correction value is It provides a drive system having a relationship of.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. Particularly, the present invention can be obtained when the present invention is applied to a time division liquid crystal display device.

6 is a cross-sectional view of a liquid crystal panel for a time division liquid crystal display according to the present invention, and FIG. 7 is a block circuit diagram schematically showing a time division liquid crystal display and a driving system according to the present invention.

Similarly to the general case, the time division liquid crystal display according to the present invention is also divided into three sub-frames having the same interval by dividing one frame, and after changing the arrangement of liquid crystals in each of these sub frames. A color image is displayed by sequentially repeating a process in which one selected from among R, G, and B light sources blinks.

To this end, the time division liquid crystal display according to the present invention includes a liquid crystal panel 110, a backlight 160, and a circuit unit 180.

First, the liquid crystal panel 110 includes the upper substrate 120 having the common electrode 124 disposed on one surface thereof, and the lower substrate 130 having the pixel electrode 164 disposed on one surface thereof with the liquid crystal 150 interposed therebetween. Have opposite structures facing each other,

The upper upper substrate 120 is a transparent substrate 1 made of a transparent material such as glass, and a black matrix 126 and a liquid crystal 150 installed at a lower portion thereof to block a part of light penetrating into the lower substrate 130. It includes a common electrode 124 for applying a voltage to the.

In addition, the lower substrate 130 defines a plurality of pixels P by vertically crossing a plurality of parallel data lines 134 and gate lines 136 over the transparent substrate 1, and serves as a switch for each pixel P. The thin film transistor T and a pixel electrode 164 connected to the one-to-one correspondence to apply a voltage to the liquid crystal 150. At this time, the liquid crystal capacitor C _LC is defined including the pixel electrode 164 and the common electrode 124 facing each other with the liquid crystal 150 interposed therebetween, and the storage capacitor C _ST is used to solve the parasitic capacitance. It is connected in parallel with the liquid crystal capacitor (C _LC ) of (P).

The first and second polarizers 128 and 132 are positioned on the outer surfaces of the upper and lower substrates 120 and 130, respectively, and although not shown, the liquid crystal between the upper and lower substrates 120 and 130. The edges of both substrates are sealed with a sealing agent or the like so that 150 is not leaked, and the upper and lower substrates 120 and 130 and the boundary portions of the liquid crystal 150, respectively, provide images in the alignment direction of the liquid crystal molecules. The lower alignment film is interposed.

The liquid crystal panel 110 also includes a backlight 160 including R, G, and B light sources 164, 166, and 168 that emit light of red (R), green (G), and blue (B) colors, respectively. ) Is located.

The circuit unit 180 includes an interface 182, a timing controller 184, a gamma power supply unit 186, a data driver 188, and a gate driver 190. This is a portion for properly processing the R, G, B data and control signals sequentially transmitted from the unit frame 170 to the liquid crystal panel 110.

First, the interface 182 transfers these R, G, and B data and control signals to the timing controller 184, respectively. The timing controller 184 also synchronizes the R, G, and B data and various control signals to generate data control signals transmitted to the data driver 188 and scan signal voltages transmitted to the gate driver 190, respectively. .

The gamma power supply unit 186 selects data voltages for controlling the rotation angle of the liquid crystal through these data control signals and transfers the data voltages to the data drivers 188. The data voltages correspond to transmittance-voltage characteristics of the liquid crystal panel 110. The data is set by the producer.

The data driver 188 is positioned at one edge of the liquid crystal panel 110 so as to connect one end of the plurality of data lines 134 to each data voltage transferred from the gamma power supply unit 186 through a timing-synchronized data control signal. Transfer to data line 134. In addition, the gate driver 190 is positioned at the other edge of the adjacent liquid crystal panel 110 so as to connect one end of the plurality of gate lines 136 to control each scan signal voltage for controlling on / off of the thin film transistor T. A sequential scan is output to the gate line 136.

Therefore, the thin film transistor T of the liquid crystal panel 110 serves as a switch for connecting the data voltage to the liquid crystal capacitor C _LC through the scan signal voltage.

The driving system 170 according to the present invention sequentially transfers R, G, and B data and control signals to a circuit unit of the liquid crystal display device having such a configuration. The data generation unit 172, the transfer unit 174, and in particular, the data conversion unit. Characterized in that it comprises a portion (200).

First, the data generation unit 172 displays R data including R data voltage information and a control signal therefor, G data including G data voltage information, and a control signal therefor, and B data for each desired color image to be expressed. B data including voltage information and control signals for the same are generated in parallel.

In addition, the data conversion unit 200 included in the driving system 170 according to the present invention includes R data including R data voltage information generated in parallel, control signals therefor, and G data including G data voltage information. And a control signal for this, B data including B data voltage information, and a control signal for the same, respectively, and are transmitted to the transmitter 174.

In this case, the data converter 200 preferably transmits R, G or B data transmitted to the liquid crystal display in the subframe of the previous step, and the second R, G or B data to be transmitted to the liquid crystal display in the frame of the previous step. Compare and correct the data voltage information included in the second R, G or B data.

In more detail, the data converter 200 according to the present invention includes a first display of the liquid crystal panel 110 through first R, G, or B data and control signals transmitted to the liquid crystal display in the subframe of the previous step. The color image is compared with the second color image to be displayed by the liquid crystal panel 110 through the second R, G, or B data and the control signal in the subframe of the step. In particular, the luminance of the first color image is equal to the second. If the luminance is greater than the color image, the data voltage information of the second R, G, or B data is modified to generate a lower data voltage in the subframe of the step.

On the contrary, the data voltage information of the second R, G or B data is modified to generate a higher data voltage.

That is, when the color image is displayed through the time division liquid crystal display device, the transmittance different from the desired transmittance appears according to the response speed of the liquid crystal. In terms of voltage, it can be said that the capacitance of the liquid crystal capacitor C _LC does not change rapidly according to a given data voltage under the influence of the voltage charged in the previous subframe.

Therefore, the present invention modifies the data voltage information transferred in the sub-step in consideration of the data voltage transferred to the liquid crystal capacitor C _LC in the previous sub-step, and then transfers the data voltage information to the liquid crystal capacitor C _LC .

In this case, the corrected degree may be expressed as Equation 1 below.

Equation 1)

C _ST and C _ST are capacitances of the storage capacitor and the liquid crystal capacitor mounted on each pixel of the liquid crystal panel, respectively, and V is the first data of the first R, G or B data transferred to the liquid crystal capacitor in the subframe of the previous step. The difference between the voltage and the second data voltage of the second R, G, or B data to be transferred to the liquid crystal capacitor in the subframe of this step, ΔC _{LC is} the first data voltage and the second data voltage to show the liquid crystal capacitor. The difference in capacitance is shown.

Thus, substituting these values, Equation 1 yields a numerical value in units of voltage, where the luminance of the first color image represented by the first R, G or B data and the control signal in the subframe of the previous step is equal to that step. If the luminance is higher than the luminance of the second color image to be represented by the second R, G or B data and the control signal in the subframe of, the data voltage to be transmitted in the subframe of the step is represented as little as the value of Equation 1 above. On the contrary, the higher data voltage is generated.

8 is a block diagram illustrating the data conversion unit 200 according to the present invention in more detail. In order to perform the above-described role, the data comparison operation unit 200a, the table 200b, and the data correction unit 200c are shown. It may include.

First, the data comparison operation unit 200a includes first R, G or B data and control signals transmitted to the liquid crystal display in the subframe of the previous step, and second R, G or B data to be transferred to the liquid crystal display in this step. And control signals.

In this case, the data comparison operation unit 200a preferably includes a first color image implemented through the first R, G or B data and the control signal, and a second color to be implemented through the second R, G or B data and the control signal. Compare the images.

The table 200b further includes a first correction value for modifying second data voltage information of second R, G, or B data so that a lower data voltage is generated when the brightness of the first color image is greater than the brightness of the second color image. And a second correction value for correcting the second data voltage information so as to generate a higher data voltage.

In this case, the first to second correction values may be obtained through Equation 1, and may be stored in advance by the user through the transmittance-voltage curve of the liquid crystal panel 110.

Finally, the data correction unit 200c reflects the first or second correction value to the data voltage information included in the second R, G or B data, and transmits the data to the transmitter 174.

An example is demonstrated.

First, when the maximum transmittance represented by the liquid crystal panel 110 is 200 gray levels and the minimum transmittance is 20 gray levels, the highest transmittance is displayed on the liquid crystal panel in the previous subframe, and then the lowest transmittance is displayed on the subframe. While the above values are summarized in the following table.

200 gray levels 20 gray level C _LC 300ff 400ff V 1.8 (V) 4 (V) C _ST 200 fF ΔC _LC 130fF

Therefore, when these values are substituted into Equation 1, a value of about 0.4 can be obtained, which has a unit of voltage (V).

This means that when the black is displayed from white, the response speed of the liquid crystal is slow, and thus the transmittance is expressed higher than that of the desired black. In terms of voltage, the liquid crystal capacitor (C _LC ) represents the data voltage to express the lowest transmittance. The voltage conversion value of the capacitance is as small as 0.4V.

On the other hand, when using the same liquid crystal panel 110 to display the lowest transmittance of white, the highest transmittance of white can be obtained by the value of 1.3 (V) by Equation 1, which is similar to the case of displaying white from black, the liquid crystal As the response speed of is slow, the transmittance lower than the target white is expressed. In terms of voltage, the voltage conversion value of the capacitance represented by the liquid crystal capacitor (C _LC ) is as large as 1.3 V compared to the data voltage for expressing the highest transmittance. Indicates.

Therefore, if white is displayed as the first color image in the subframe of the previous step, and black is displayed as the second color image in the subframe of the step, the data voltage in the subframe of the step is rather 0.4V. Correct it high and transfer it to the liquid crystal panel, and in the opposite case, lower it by 1.3V and transfer it to the liquid crystal panel.

That is, in the above example, when changing from white to black, the table 200b delivers + 0.4V to the data correction unit 200c, and when changing from black to white, the table 200b receives -1.3V. Transfer to government 200c. Accordingly, the data correction unit 200c reflects this correction value in the data voltage of the R, G or B data.

In summary, the data conversion unit 200 according to the present invention may compensate for the high luminance of the color image expressed in the subframe of the previous step and the luminance of the color image to be expressed in the subframe of the previous step. It can be said that the data voltage expressing the higher luminance is transferred, and the data voltage expressing the lower luminance is transferred in the opposite case.

Accordingly, FIG. 9 is a graph showing a change in the actual transmittance shown in each subframe in a dotted line when a specific color is expressed using the time division liquid crystal display according to the present invention. For reference, the change in the transmittance of the ideal for implementing the desired color is shown with a dashed line for comparison.

Also, FIG. 10 is a dotted line showing the change in the data voltage transmitted to the liquid crystal capacitor for each subframe under the same condition as that of FIG. 9, and thus the change in capacitance caused by the actual liquid crystal capacitor is converted into voltage. .

In these graphs, the intervals represented by L1 to L3 represent the delay time until the data voltage is transferred to the liquid crystal capacitor.

Referring to these graphs, when the driving system 170 of the liquid crystal display according to the present invention is applied, the capacitance of the liquid crystal capacitor appears larger than the desired degree in the first subframe, while in the third frame, The capacitance will appear smaller than desired.

However, through this, it can be seen that the transmittance according to the arrangement change of the actual liquid crystal is close to the ideal transmittance for implementing the desired color.

In the time-division liquid crystal display device to which the driving system according to the present invention is applied, the driving order of the R, G, and B light sources is arbitrarily described as R, G, and B.

First, in one subframe, the transmitter 174 of the driving system 170 transmits R data and a control signal for the same to the circuit unit 180.

Subsequently, the timing controller 184 generates an R data control signal and an R scan signal voltage corresponding thereto, and transmits the R data control signal and the R scan signal voltage to the data driver 188 and the gate driver 190, respectively. Output to driver 188. Accordingly, the data driver 188 outputs the R data voltage to all the data lines 134, and the gate driver 190 sets the R scan signal voltage for each gate line 136 from the Gn-th gate line to the Gm gate line. Scan output sequentially.

Accordingly, as the appropriate R data voltage is selected and charged into each liquid crystal capacitor C _LC , the liquid crystal array direction is changed, and then the R light source 164 blinks to display the R color image. This terminates the first subframe.

Subsequently, the transmitting unit 174 of the driving system 170 transmits the G data and a control signal capable of expressing the same to the circuit unit 180, which is modified by comparing with the R data of the first subframe described above. Value. In the same manner, an appropriate G data voltage is charged in the liquid crystal capacitor C _LC positioned in each pixel P to change the liquid crystal array direction. Then, the G light source blinks to display the G color image, thereby terminating the second subframe.

Finally, the third subframe also drives the system 170 to correct the B data by comparing the G data in the second frame, which is a subframe of the previous step, and the B data in the third subframe, which is a subframe of the step. After outputting, the B data voltage is charged in the liquid crystal capacitor C _LC through the same process to change the liquid crystal array direction, and the B light source blinks on and off to display the B color image.

This terminates the third subframe to complete one unit frame as a whole.

In this case, since the first to third subframes are sequentially progressed with the same interval of about 1/180 seconds, the R color picture, the G color picture, and the B color picture are sequentially performed during one short frame of about 1/60 second. The visual observation of the observer recognizes one color image in which these R, G, and B color images are combined.

In this case, the present invention can be applied to a general liquid crystal display device. In the case of a general liquid crystal display device, an RGB color image is simultaneously expressed for each unit frame.

Therefore, the driving system also transfers the RGB data and the control signal only by the frame unit, and the data conversion unit according to the present invention also displays the first LCD data displayed by the first RGB data and the control signal implemented in the previous frame. The color image is compared with the second color image to be displayed by the liquid crystal panel through the second RGB data and the control signal in the frame of the step.

Therefore, when the luminance of the first color image is greater than the luminance of the second color image, the data voltage information of the second RGB data is modified to generate a lower data voltage in the frame of the step, and vice versa. The data voltage information of the second RGB data is corrected so as to be correct.

In this case, the correction value may also be the same as Equation 1, where C _ST and C _ST are capacitances of the storage capacitor and the liquid crystal capacitor mounted on each pixel of the liquid crystal panel, respectively, and V is the liquid crystal capacitor in the previous frame. The difference between the first data voltage of the first RGB data transmitted to and the second data voltage of the second RGB data to be delivered to the liquid crystal capacitor in the frame of the step, ΔC _{LC is} the first data voltage and the second data voltage. Indicates the difference in capacitance seen by the liquid crystal capacitor.

The present invention provides an improved driving system for a liquid crystal display device, which can accurately express a desired color image. In particular, the driving system for the liquid crystal display device according to the present invention can obtain an improved effect when applied to the time division method, which has the advantage that reliable image expression can be achieved even at a high speed of the liquid crystal response speed.

Claims (12)

A circuit unit for generating a data voltage and a scan signal voltage through RGB data and control signals including data voltage information, and a plurality of liquid crystal cells in which a liquid crystal capacitor and a storage capacitor are respectively mounted. A liquid crystal display including a liquid crystal panel displaying an RGB color image for each frame by a change in transmittance through the frame, and a backlight for supplying light to the liquid crystal panel, wherein the driving unit transmits the RGB data and control signals to the liquid crystal display. As a system, A data generator which generates the RGB data and the control signal in units of frames; A data converter for modifying data voltage information of the RGB data; Transmitter for transmitting the RGB data and the control signal including the modified data voltage information to the liquid crystal display every frame Drive system including The method according to claim 1, The data conversion unit, Driving to correct the data voltage information of the second RGB data by comparing the first RGB data transmitted to the liquid crystal display in the frame of the previous step and the second RGB data to be transmitted to the liquid crystal display in the frame of the step; system The method according to claim 2, The data conversion unit, In the first color image displayed through the first RGB data and the control signal, and the second color image displayed through the second RGB data and the control signal, Modifying data voltage information of the second RGB data so that a lower data voltage is generated when the luminance of the first color image is greater than the luminance of the second color image, A driving system for modifying data voltage information of the second RGB data so that a higher data voltage is generated when the brightness of the first color image is less than the brightness of the second color image The method according to claim 3, The capacitance of the storage capacitor C _ST , the capacitance of the liquid crystal capacitor C _ST , a first data voltage generated through the first RGB data and the control signal, and a second data generated through the second RGB data and the control signal. When the difference between the data voltage is V and the capacitance difference between the liquid crystal capacitor due to the first data voltage and the second data voltage is ΔC _LC , The data conversion unit, The second data voltage As small or as large as possible The method according to claim 3, The data conversion unit, A data comparison operation unit for comparing the first RGB data and the control signal with the second RGB data and the control signal; A first correction value for modifying second data voltage information of the RGB data so that a lower data voltage is generated when the luminance of the first color image is greater than the luminance of the second color image, and the first color image; A table for outputting a second correction value for modifying the second data voltage information so that a higher data voltage is generated when the brightness is less than the brightness of the second color image; Data correction unit reflecting the first or second correction value to the second RGB data and the control signal Drive system including The method according to claim 5, The capacitance of the storage capacitor is C _ST , the capacitance of the liquid crystal capacitor is C _ST , and the difference between the first data voltage and the second data voltage generated through the first RGB data and the control signal is V, the first When the capacitance difference of the liquid crystal capacitor by the data voltage and the second data voltage is ΔC _LC , The correction value is Drive system The method according to claim 1, The liquid crystal panel divides each frame into first to third subframes having the same interval, and sequentially displays transmittance for R color image, transmittance for G color image, and transmittance for B color image, respectively. The backlight has a time division method of sequentially supplying R, G, and B color light to the liquid crystal panel every subframe. The data generation unit generates R, G and B image data and control signals in parallel having data voltage information, respectively, and the data conversion unit modifies the data voltage information of the R, G and B image data, respectively, and the transmission unit A driving system for supplying R, G, and B data each having the modified data voltage information to the liquid crystal display sequentially in each frame. The method according to claim 7, The data conversion unit, Comparing the first R, G or B data transmitted to the liquid crystal display in the subframe of the previous step with the second R, G or B data to be transmitted to the liquid crystal display in the subframe of the step; 2 Drive system to modify data voltage information included in R, G or B data The method according to claim 8, The data conversion unit, In the first color image displayed through the first R, G or B data and the control signal, and the second color image displayed through the second R, G or B data and the control signal, Modifying data voltage information of the second R, G or B data so that a lower data voltage is generated when the luminance of the first color image is greater than the luminance of the second color image, A driving system for modifying data voltage information of the second R, G or B data so that a higher data voltage is generated when the luminance of the first color image is less than the luminance of the second color image The method according to claim 9, The capacitance of the storage capacitor is C _ST , the capacitance of the liquid crystal capacitor is C _ST , the first data voltage and the second R, G or B data generated through the first R, G or B data and the control signal. And when the difference between the second data voltage generated through the control signal is V and the capacitance difference between the liquid crystal capacitor due to the first data voltage and the second data voltage is ΔC _LC , The data conversion unit, The second data voltage As small or as large as possible The method according to claim 8, The data conversion unit, A data comparison operation unit for comparing the first R, G or B data and the control signal with the second R, G or B data and the control signal; A first correction value for modifying second data voltage information of the second R, G or B data so that a lower data voltage is generated when the luminance of the first color image is greater than the luminance of the second color image; A table for outputting a second correction value for modifying the second data voltage information so that a higher data voltage is generated when the brightness of the first color image is less than the brightness of the second color image; Data correction to reflect the first or second correction value to the second R, G or B data and the control signal Drive system including The method according to claim 11, The capacitance of the storage capacitor is C _ST , the capacitance of the liquid crystal capacitor is C _ST , and the difference between the first data voltage and the second data voltage generated through the first R, G or B data and the control signal is V. When the capacitance difference between the liquid crystal capacitor due to the first data voltage and the second data voltage is ΔC _LC , The correction value is Drive system