KR20050038218A - Method for setting gamma reference voltage of liquid crystal display device - Google Patents

Abstract

The present invention relates to a method of setting a gamma reference voltage of a liquid crystal display device, wherein the first voltage-transmittance curve is calculated from the liquid crystal display device from which the data driver is removed to set a white level and a black level of the gamma reference voltage. The second voltage-transmittance curve is calculated from the attached liquid crystal display to set an intermediate level of the gamma reference voltage, and then the voltage levels of the gamma voltages are adjusted through the white level, the black level, and the intermediate level of the gamma reference voltage. The voltage-transmittance curve is calculated to be substantially the same as the driving environment of the actual liquid crystal display device, thereby accurately setting the intermediate level of the gamma reference voltage.

Description

Gamma reference voltage setting method of liquid crystal display device {METHOD FOR SETTING GAMMA REFERENCE VOLTAGE OF LIQUID CRYSTAL DISPLAY DEVICE}

The present invention relates to a method for setting a gamma reference voltage of a liquid crystal display device, and more particularly, a voltage-transmission curve of a liquid crystal display device having a transmission rate characteristic according to voltage is used to drive a driving environment of an actual liquid crystal display device. It relates to the gamma reference voltage setting method of the liquid crystal display device to be set as close as possible, so as to accurately set the gamma reference voltage.

Recently, among the color display devices for displaying an image, the thin film type flat panel display device has been the subject of intensive development because of its advantages of being light and easily used anywhere. In particular, since liquid crystal displays have high resolution and fast reaction speeds sufficient to realize moving images, the most active research is being conducted.

The principle of the liquid crystal display device is to use the optical anisotropy and polarization properties of the liquid crystal. That is, by artificially adjusting the alignment direction of the liquid crystal molecules having directionality using polarization, light transmission and blocking are possible with optical anisotropy according to the alignment direction. This application is used as a color display device. Currently, an active matrix liquid crystal display in which thin film transistors and pixel electrodes connected thereto are arranged in a matrix manner is most commonly used because it provides excellent image quality.

The liquid crystal display as described above has a gamma characteristic in which gray levels of an image are nonlinearly changed due to voltage levels of an image signal because the light transmittance of the liquid crystal does not change linearly. In order to prevent this, gamma correction voltages are used to change the intervals between voltage levels of the image signal input to the liquid crystal display.

That is, the gamma correction voltages are added to the voltage levels of the image signal and applied to the liquid crystal display, thereby making the intervals between the voltage levels of the image signal not constant so as to correct the gamma characteristic of the liquid crystal display.

FIG. 1 is an exemplary view showing a general liquid crystal display, and as shown therein, a liquid crystal display includes a liquid crystal display panel 10 in which pixels are arranged in a matrix form; A gate driver 20 driving the gate lines GL1 to GLm of the liquid crystal display panel 10; A data driver 30 driving the data lines DL1 to DLn of the liquid crystal display panel 10; A gamma voltage generator 40 is provided to supply gamma voltages to the data driver 30.

The liquid crystal display panel 10 includes a thin film transistor array substrate and a color filter substrate bonded together to maintain a constant cell gap; The liquid crystal layer is formed between the thin film transistor array substrate and the color filter substrate.

The thin film transistor array substrate has a structure in which pixel electrodes are arranged at positions of pixels designed in a matrix manner. Gate lines GL1 to GLm are formed along the horizontal direction of the pixel electrodes, and data lines DL1 to DLn are formed along the vertical direction of the pixel electrodes. Thin film transistors for driving pixel electrodes are formed in one corner of the pixels. Gate electrodes of the thin film transistors are connected to the gate lines GL1 to GLm, and source electrodes of the thin film transistors are connected to the data lines DL1 to DLn.

On the color filter substrate, red, green, and blue color filters are repeatedly arranged at positions of the pixels. A black matrix is formed in a mesh shape between the color filters. A common electrode is formed on the color filter.

The gate driver 20 sequentially applies a scan signal to the gate lines GL1 to GLm so that the thin film transistors having the gate electrodes connected to the gate lines GL1 to GLm are conductive. GLm) is driven by one line.

The data driver 30 sequentially supplies image signals for one horizontal line to the data lines DL1 to DLn in synchronization with the scan signal, thereby sequentially displaying images in units of gate lines GL1 to GLm. To be. In this case, the gamma voltage generator 40 supplies the gamma voltages preset to the data driver 30.

Therefore, the data driver 30 corrects the gamma characteristics of the image by supplying the gamma voltages supplied from the gamma voltage generator 40 to the image signals in addition to the image signals.

The gamma voltages generated from the gamma voltage generator 40 have a plurality of voltage levels distributed by a resistor array in which a plurality of resistors are arranged in series, and white of a gamma reference voltage from a voltage-transmittance curve of a liquid crystal display. By setting the level, the black level and the intermediate level, the voltage levels of the gamma voltages are adjusted accordingly. As such, gamma voltages whose voltage levels are adjusted are added to the image signal and supplied to the data lines DL1 to DLn, thereby correcting the gamma characteristic of the image.

A method of setting the white level, black level, and intermediate level of the gamma reference voltage is described in detail as follows.

First, one sample is extracted from the liquid crystal display devices of the same model to which the fabrication is completed, and the data driver is removed.

The luminance of the liquid crystal display as shown in FIG. 3 is measured by sequentially applying a voltage waveform having a step shape as shown in FIG. 2 to the data lines of the liquid crystal display from which the data driver is removed. Calculate the transmittance curve.

The voltage value at the point where the transmittance is close to 100% from the voltage-transmittance curve is set to the white level (GMA5, GMA6) of the gamma reference voltage, and the voltage value at the point where the transmittance is close to 0% is black at the gamma reference voltage. Levels GMA1 and GMA10 are set, and the voltage value at the point where the transmittance becomes 21% is set to the intermediate levels GMA3 and GMA8 of the gamma reference voltage.

Finally, the voltage levels of the gamma voltages are adjusted through the white levels GMA5 and GMA6, the black levels GMA1 and GMA10, and the intermediate levels GMA3 and GMA8 of the set gamma reference voltage, and then the liquid crystal display of the same model is adjusted. Apply and commercialize.

However, in the case of measuring luminance while sequentially applying a stepped voltage waveform as shown in FIG. 2, an electric field in a predetermined direction is continuously applied to the liquid crystal to deteriorate the liquid crystal, and an afterimage is generated by a DC voltage component. The problem that the reliability of luminance measurement falls is caused.

Accordingly, luminance is gradually applied to data lines of the liquid crystal display panel from which the data driver is removed, in which voltage waveforms gradually increasing (or decreasing) alternately up and down with respect to the common voltage Vcom are sequentially applied, as shown in FIG. 4. A method of measuring is proposed.

As described above, when the luminance is measured while sequentially applying a voltage waveform gradually increasing (or decreasing) alternately up and down with respect to the common voltage Vcom, it is possible to prevent the electric field in a constant direction from being continuously applied to the liquid crystal. It is possible to prevent deterioration of the liquid crystal and to prevent afterimages from being generated by the DC voltage component.

However, the stepped voltage waveform as shown in FIG. 2 or the voltage waveform gradually increasing (or decreasing) alternately up and down with respect to the common voltage Vcom as shown in FIG. 4 is actually a liquid crystal display device. Since the waveform has different characteristics from the waveform of the image signal applied through the data driver during driving, the voltage-transmittance curve measured by the luminance has an error in the driving environment of the actual liquid crystal display device.

That is, the gamma voltage setting method of the conventional liquid crystal display device as described above extracts one sample from the liquid crystal display devices of the same model that has been manufactured and removes the data driver, and then a stepped voltage waveform or common to the data lines. The voltage-transmittance curve is calculated by sequentially applying voltage waveforms gradually increasing (or decreasing) alternately with respect to the voltage Vcom to calculate the voltage-transmittance curve. The calculated voltage-transmittance curve has an error in a driving environment of an actual liquid crystal display.

In general, the white level and the black level of the gamma reference voltage are set relatively accurately, but when the intermediate level of the gamma reference voltage is set, the error range is large, especially when an error occurs in the intermediate level setting of the gamma reference voltage. Since the intermediate voltage levels of gamma voltages are not accurately adjusted, there is a problem of deteriorating an image in a driving environment of an actual liquid crystal display.

Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to set the voltage-transmittance curve of the liquid crystal display device as close as possible to the driving environment of the actual liquid crystal display device. A gamma reference voltage setting method of a liquid crystal display device capable of accurately setting an intermediate level of a gamma reference voltage is provided.

In order to achieve the object of the present invention, a gamma reference voltage setting method of a liquid crystal display device measures a luminance while applying a plurality of voltage levels to data lines of a liquid crystal display device from which a data driver is removed, thereby measuring a first voltage-transmittance curve. Calculating; Setting a white level and a black level of a gamma reference voltage from the first voltage-transmission curve; Calculating voltage levels of gamma voltages by applying the set white level and black level of the gamma reference voltage to a liquid crystal display with a data driver; Calculating a gamma voltage-transmittance curve by measuring luminance while applying voltage levels of the gamma voltages to the liquid crystal display with the data driver; Calculating a gamma voltage-voltage curve by applying the white level and the black level of the set gamma reference voltage to the data driver; Calculating a second voltage-transmission curve from the gamma voltage-transmittance curve and the gamma voltage-voltage curve; Setting an intermediate level of a gamma reference voltage from the second voltage-transmission curve; And adjusting the voltage levels of the gamma voltages through the white level, the black level, and the intermediate level of the set gamma reference voltage.

As described above, the liquid crystal display includes a liquid crystal display panel in which pixels are arranged in a matrix form; A gate driver for driving gate lines of the liquid crystal display panel; A data driver for driving data lines of the liquid crystal display panel; And a gamma voltage generator provided in the data driver to supply gamma voltages to the data driver.

The liquid crystal display panel may include a thin film transistor array substrate and a color filter substrate bonded together to maintain a constant cell gap; The liquid crystal layer is formed between the thin film transistor array substrate and the color filter substrate.

The thin film transistor array substrate has a structure in which pixel electrodes are arranged at positions of pixels designed in a matrix manner. Gate lines are formed along the horizontal direction of the pixel electrodes, and data lines are formed along the vertical direction of the pixel electrodes. Thin film transistors for driving pixel electrodes are formed in one corner of the pixels. Gate electrodes of the thin film transistors are connected to the gate lines, and source electrodes of the thin film transistors are connected to the data lines.

On the color filter substrate, red, green, and blue color filters are repeatedly arranged at positions of the pixels. A black matrix is formed in a mesh shape between the color filters. A common electrode is formed on the color filter.

The gate driver sequentially applies a scan signal to the gate lines so that the thin film transistors having the gate electrode connected to the gate lines conduct. The gate driver drives the gate lines by one line unit.

The data driver sequentially supplies one horizontal line of image signals to the data lines in synchronization with the scan signal, thereby sequentially displaying images in units of gate lines. In this case, the gamma voltage generation unit supplies preset gamma voltages to the data driver.

Therefore, the data driver corrects the gamma characteristic of the image by supplying the gamma voltages supplied from the gamma voltage generator to the data lines in addition to the image signal.

The gamma voltages generated from the gamma voltage generator have a plurality of voltage levels distributed by a resistor array in which a plurality of resistors are arranged in series, and the white level, black, of the gamma reference voltage from the voltage-transmittance curve of the liquid crystal display. By setting the level and the intermediate level, the voltage levels of the gamma voltages are adjusted accordingly. As such, gamma voltages whose voltage levels are adjusted are added to the image signal and supplied to the data lines, thereby correcting the gamma characteristic of the image.

The gamma reference voltage setting method of the liquid crystal display according to the present invention for setting the white level, the black level, and the intermediate level of the gamma reference voltage as described above will be described in detail with reference to the accompanying drawings.

First, one sample is extracted from the liquid crystal display devices of the same model to which the fabrication is completed, and the data driver is removed.

The luminance is measured while applying a plurality of voltage levels to the data lines of the liquid crystal display from which the data driver is removed, thereby calculating a first voltage-transmittance curve as shown in FIG. 5. In this case, the plurality of voltage levels applied to the data lines of the liquid crystal display from which the data driver is removed are alternately up and down with respect to the stepped voltage waveform shown in FIG. 2 or the common voltage Vcom as shown in FIG. 4. Gradually increasing (or decreasing) the voltage waveform, and when the voltage waveform shown in FIG. 4 is applied, an electric field in a constant direction is continuously applied to the liquid crystal as compared with the case where the stepped voltage waveform shown in FIG. It can be prevented from being applied to prevent the deterioration of the liquid crystal, and to prevent the afterimage generated by the DC voltage component.

From the first voltage-transmittance curve, the voltage value at the point where the transmittance is close to 100% is set to the white level (GMA15, GMA16) of the gamma reference voltage, and the voltage value at the point where the transmittance is close to 0% is the gamma reference voltage. Black level (GMA11, GMA20).

The voltage levels of the gamma voltages are calculated by applying the set white levels GMA15 and GMA16 and the black levels GMA11 and GMA20 of the gamma reference voltage to a liquid crystal display device having a data driver. The luminance is measured while applying the voltage levels of the gamma voltages to the liquid crystal display to calculate a gamma voltage-transmittance curve indicated by solid lines in FIG. 6.

The data driver includes a gamma voltage generator including at least one resistor array in which a plurality of resistors are arranged in series. The gamma voltage generator includes a white level (GMA15, GMA16) and a black level (GMA11, When the GMA20) is applied, a plurality of voltage levels are distributed by a resistor array provided in the gamma voltage generator to generate gamma voltages.

Accordingly, when the luminance is measured while the gamma voltages generated by the gamma voltage generator are applied to the liquid crystal display panel through the data driver, the gamma voltage-transmittance curve shown in FIG. 6 can be calculated. At this time, since the gamma voltages generated by the gamma voltage generator are not set to the intermediate level of the gamma reference voltage, the gamma voltage-transmittance curve indicated by solid lines in FIG. Display) and an error.

The gamma voltage-voltage curve is calculated as shown in FIG. 7 by applying the set white levels GMA15 and GMA16 and the black levels GMA11 and GMA20 of the gamma reference voltage. In this case, the gamma voltage-voltage curve is determined according to the plurality of voltage levels applied to calculate the first voltage-transmittance curve, and the white levels GMA15 and GMA16 and the black levels GMA11 and GMA20 of the gamma reference voltage. The gamma voltage-voltage curve is calculated from the relationship with the gamma voltages generated in the gamma voltage setting unit of the data driver, and a gamma voltage-voltage curve is generally provided in a specification of the data driver.

Then, the second voltage-transmittance curve shown in FIG. 8 is calculated from the gamma voltage-transmittance curve shown in FIG. 6 and the gamma voltage-voltage curve shown in FIG. In this case, the second voltage-transmittance curve is calculated through 1: 1 matching between transmittance and voltage based on the gamma voltage-transmittance curve shown in FIG. 6 and the gamma voltage of the gamma voltage-voltage curve shown in FIG. .

The voltage value at the point where the transmittance becomes 21% from the second voltage-transmittance curve is set to intermediate levels GMA13 and GMA18 of the gamma reference voltage. In this case, the intermediate levels GMA13 and GMA18 of the gamma reference voltage may be set to four, six, or a plurality of eight or more according to a consumer's request.

Then, the voltage levels of the gamma voltages are adjusted through the white levels GMA15 and GMA16, the black levels GMA11 and GMA20, and the intermediate levels GMA13 and GMA18 of the set gamma reference voltage and then applied to the liquid crystal display of the same model. To commercialize.

The gamma reference voltage setting method of the liquid crystal display device according to the present invention as described above calculates a first voltage-transmittance curve from the liquid crystal display device from which the data driver is removed to set the white level and the black level of the gamma reference voltage. Calculating the second voltage-transmittance curve from the liquid crystal display with the driver to set the intermediate level of the gamma reference voltage, and then adjusting the voltage levels of the gamma voltages through the white, black and intermediate levels of the gamma reference voltage. Accordingly, the second voltage-transmittance curve can be calculated to be substantially the same as the driving environment of the actual liquid crystal display.

Therefore, by accurately setting the intermediate level of the gamma reference voltage, the intermediate voltage levels of the gamma voltages can be precisely adjusted, thereby preventing deterioration of an image in an actual driving environment of the liquid crystal display.

1 is an exemplary view showing a general liquid crystal display device.

FIG. 2 is an exemplary view showing a first example of voltage waveforms applied to data lines of a liquid crystal display in which a data driver is removed, according to a gamma reference voltage setting method of a conventional liquid crystal display. FIG.

3 is an exemplary view showing a voltage-transmittance curve calculated according to a gamma reference voltage setting method of a conventional liquid crystal display device.

FIG. 4 is an exemplary view showing a second example of voltage waveforms applied to data lines of a liquid crystal display device in which a data driver is removed according to a gamma reference voltage setting method of a conventional liquid crystal display device. FIG.

5 is an exemplary view showing a first voltage-transmittance curve calculated according to a gamma reference voltage setting method of a liquid crystal display according to the present invention.

6 is an exemplary view showing a gamma voltage-transmittance curve calculated according to a gamma reference voltage setting method of a liquid crystal display according to the present invention.

7 is an exemplary diagram showing a gamma voltage-voltage curve calculated according to a gamma reference voltage setting method of a liquid crystal display according to the present invention.

8 is an exemplary view showing a second voltage-transmittance curve calculated according to a gamma reference voltage setting method of a liquid crystal display according to the present invention.

*** Explanation of symbols for main parts of drawing ***

GMA11, GMA20: Black level of gamma reference voltage

GMA13, GMA18: Medium level of gamma reference voltage

GMA15, GMA16: White level of gamma reference voltage

Claims (6)

Calculating a first voltage-transmittance curve by measuring luminance while applying a plurality of voltage levels to data lines of the liquid crystal display from which the data driver is removed; Setting a white level and a black level of a gamma reference voltage from the first voltage-transmission curve; Calculating voltage levels of gamma voltages by applying the set white level and black level of the gamma reference voltage to a liquid crystal display with a data driver; Calculating a gamma voltage-transmittance curve by measuring luminance while applying voltage levels of the gamma voltages to the liquid crystal display with the data driver; Calculating a gamma voltage-voltage curve by applying the white level and the black level of the set gamma reference voltage to the data driver; Calculating a second voltage-transmission curve from the gamma voltage-transmittance curve and the gamma voltage-voltage curve; Setting an intermediate level of a gamma reference voltage from the second voltage-transmission curve; And adjusting the voltage levels of the gamma voltages through the white level, the black level, and the intermediate level of the set gamma reference voltage. The method of claim 1, wherein a plurality of voltage levels applied to data lines of the liquid crystal display from which the data driver is removed are sequentially applied with a stepped voltage waveform. . The voltage waveform of claim 1, wherein the plurality of voltage levels applied to the data lines of the liquid crystal display from which the data driver is removed are sequentially applied with voltage waveforms that gradually increase or decrease in alternation with respect to a common voltage. A gamma reference voltage setting method of a liquid crystal display device. The data driver of claim 1, wherein the gamma voltage-voltage curve includes a plurality of voltage levels applied to calculate the first voltage-transmission curve, and a white level and a black level of the gamma reference voltage. A gamma reference voltage setting method for a liquid crystal display device, characterized in that it is calculated from a relationship with voltage levels of gamma voltages calculated by applying to a liquid crystal display device. The liquid crystal of claim 1, wherein the second voltage-transmittance curve is calculated by 1: 1 matching between the transmittance and the voltage based on the gamma voltage of the gamma voltage-transmittance curve and the gamma voltage-voltage curve. How to set gamma reference voltage of display device. The method of claim 1, wherein the intermediate level of the gamma reference voltage is set to two, four, six, eight or more.