KR100928496B1 - LCD Display - Google Patents

Abstract

The present invention can easily adjust the amplitude and the center voltage of the voltage signal supplied to the liquid crystal display panel over the entire screen without depending on the display block, and suppress the occurrence of flicker and deterioration.

In the liquid crystal display device for performing gradation display by performing AC driving, the driver IC receives bit allocation data specifying which signal bit to allocate each bit of the video signal together with the video signal, and corresponds to the video signal. A driver IC that outputs an analog voltage signal according to a high bit number of positive and negative input signals, and a linear DAC driver that outputs an analog output signal corresponding to a high bit number of positive and negative input signals corresponding to a video signal. An gradation display voltage that has an IC, has a predetermined display characteristic, and has a lookup table for specifying bit allocation data corresponding to government data so that the balance of government is maintained for each display block, and outputs the bit allocation data to the driver IC. A correction unit is provided.

Description

Liquid crystal display device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device which suppresses occurrence of deterioration due to partial flicker of a liquid crystal display panel and residual DC components.

The liquid crystal display performs AC driving, and when the balance between the positive and negative polarities is broken, deterioration due to the residual of flicker or DC component occurs. Therefore, in order to prevent such deterioration due to the AC driving characteristics, the reference voltage of the driver IC (source driver) and the counter electrode (common) voltage of the liquid crystal are adjusted.

7 is a view for explaining a method of adjusting the reference voltage and the common voltage of a source driver in a conventional liquid crystal display. 8 is a diagram illustrating a correspondence relationship between positive and negative polarities with respect to the common voltage Vcom. In the conventional liquid crystal display device, the reference voltage supplied to the source driver by adjusting the control panel is set to, for example, positive polarity 8ch (corresponding to 8-bit gradation) and negative polarity 8ch (corresponding to 8-bit gradation). Doing.

Moreover, the common voltage Vcom is also supplied by the control board. The common voltage Vcom may be adjusted by a variable resistor (not shown). Thereby, individual nonuniformity adjustment is performed (for example, citation 1).

References 1 Japanese Patent Application Laid-Open No. 2005-250132

However, the liquid crystal display of the prior art has the following problems.

The reference voltage of the drive driver IC of the liquid crystal display device is about 20ch (corresponding to 16c in Fig. 7), and it is not possible to adjust all the gray scales individually. In addition, in the production line, the individual nonuniformity is adjusted only by the common voltage Vcom, and the current driving is common to all the pixels.

For this reason, optimum alternating current drive could not be performed and deterioration due to residual flicker or direct current component caused by the collapse of the balance between the positive and negative polarities could not be sufficiently suppressed.

Moreover, when color display is performed, there are the following problems. Fig. 9 is a partial sectional view of a liquid crystal display device provided with each pixel of RGB for color display. In each pixel of RGB when color display is performed, as shown in FIG. 9, a cell gap differs with each pixel of RGB. For this reason, an optimal AC drive setting is required for each pixel of RGB.

However, as described above, since common driving adjustment is performed for all the pixels, for example, even though the display is optimal in the G display, the balance between the positive and negative polarities in the R display and the B display collapses and flicker or deterioration occurs.

In addition, since the cell gap is different for each pixel of RGB, there arises a problem of non-uniformity of voltage luminance characteristics of each RGB. 10 is a diagram illustrating voltage luminance characteristics of each pixel of RGB. As a result of performing common driving adjustment, as shown in Fig. 10, the voltage luminance characteristic is different for each pixel of RGB.

In addition, the voltage applied to the liquid crystal display device is not uniform in impedance in the display screen due to the influence of wiring and the like, and the AC balance is partially broken down for each display block. Therefore, it is important to improve display quality by performing an optimal AC drive over the entire screen without depending on the display block.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is supplied to a liquid crystal display panel without depending on the display block, to have a constant display characteristic over the entire screen, and to have a balance between positive and negative polarities when performing AC driving. An object of the present invention is to obtain a liquid crystal display device that can easily adjust the amplitude and center voltage of a voltage signal to control flicker and deterioration.

A liquid crystal display device according to the present invention is a liquid crystal display device for performing gradation display by switching between positive and negative polarity of an analog voltage signal output from a driver IC to perform AC driving, wherein the driver IC is higher than the number of bits of the video signal. It is possible to process data of the number of bits, and receives bit allocation data specifying the signal bits to which each bit of the video signal is assigned together with the video signal, and has a high bit number of positive and negative polarities corresponding to the video signal. A driver IC that outputs an analog voltage signal in accordance with an input signal, wherein the relationship between the output signal from the driver IC and the brightness of the grayscale displayed image has a certain characteristic, and the polarity of the video signal is maintained so that the balance of the government is maintained. A lookup table specifying bit allocation data corresponding to each of the data and the negative data; A gradation display voltage for outputting the bit allocation data specified by the lookup table to the driver IC for each of the predetermined display blocks in response to the positive data and the negative data of the video signal. The correction part is provided.

According to the present invention, a display block is provided by separately providing a positive LUT and a negative LUT for each predetermined display block as a look-up table (hereinafter referred to as LUT) that performs data conversion according to a video signal that is the source of gray scale display. The amplitude and center voltage of the voltage signal supplied to the liquid crystal display panel can be easily adjusted to have a constant display characteristic over the entire screen and to have a balance between positive and negative polarity when performing AC driving, A liquid crystal display device capable of suppressing the occurrence of flicker and deterioration can be obtained.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of the liquid crystal display device of this invention is described using drawing.

First, the display characteristics of the liquid crystal display will be described in detail.

1 is a diagram showing display characteristics of a liquid crystal display device according to Embodiment 1 of the present invention. In the liquid crystal display device, the relationship between a given video signal (gradation signal) and the luminance displayed on the screen has a display characteristic as shown in Fig. 1, which is called a gamma characteristic.

More specifically, when the gradation signal is x and the luminance is y, it is expressed by the formula " (tau) of y = x ". However, the actual liquid crystal display device does not necessarily have such an ideal gamma characteristic, and there is individual difference.

In addition, in an AC driven liquid crystal display, in order to prevent flicker and deterioration, the balance between the positive and negative polarities becomes important. However, this balance also differs.

In addition, since the applied voltage to the liquid crystal is not uniform in impedance (wiring, etc.) in the display screen, the AC balance is partially broken off the display block. For this reason, even within one liquid crystal display panel, there are individual differences for each display block, and partial flicker occurs.

Therefore, in order to correct the display characteristics having such individual differences to match the predetermined gamma characteristics and to maintain the balance between the positive and negative polarities, the present invention uses a configuration in which a linear DAC source IC is combined as a LUT and a source driver IC. Doing.

FIG. 2 is a diagram showing an internal configuration of a gradation display voltage correction unit provided in the liquid crystal display device according to the first embodiment of the present invention. The gradation display voltage correction section 1 has a function of correcting the voltage level and the center voltage of the video signal which is the source of the gradation display according to the individual display characteristics of the liquid crystal display device.

In the first embodiment, however, the gradation display voltage correction unit 1 specifies which input processing bits of the linear DAC source IC 2 are to be assigned to each bit of the video signal without directly correcting the video signal.

In FIG. 2, the gradation display voltage correction unit 1 is composed of a display block identification circuit 11 and a LUT 12. As shown in FIG.

The display block identification circuit 11 receives a video signal and outputs identification information indicating which display block the video signal belongs to. The LUT 12 is configured individually for each display block. The LUT 12 specifies and outputs bit allocation data according to a predetermined display block according to the identification information from the display block identification circuit 11.

That is, in the liquid crystal display device of the present invention, a predetermined gamma characteristic is obtained according to individual display characteristics for each display block, and a LUT for converting according to a video signal is maintained for each display block so that a balance between positive and negative polarities is maintained. It is set in advance. Thus, the bit allocation data will be described next along with the function of the source driver.

The linear DAC source IC 2 corresponding to the source driver can process data of a higher number of bits than the number of bits of a video signal. Furthermore, the linear DAC source IC 2 can obtain a high bit number of input signals in accordance with the video signal by receiving bit allocation data specifying which signal bits to allocate each bit of the video signal together with the video signal.

More specifically, as an example, it is conceivable to use a linear DAC source IC 2 capable of input processing of 13 bits for a 10 bit video signal. In this case, the linear DAC source IC 2 can use 12 bits for positive polarity and 12 bits for negative polarity except for the sign bit.

In this case, the LUT 12 separately composed of positive and negative polarities for each display block has a constant display characteristic over the entire screen without depending on the display block for the 10-bit video signal, and the balance of the government is maintained. Since 10 bits of 12 bits are selected, the conversion data for specifying the bit allocation data of the government individual is stored in advance in the liquid crystal display panel according to the individual difference for each display block.

As a result, the linear DAC source IC 2 uses the 10-bit video signal input according to the bit allocation data given by each of the positive and negative polarities as an optimal coded 13-bit signal according to individual display characteristics for each display block. / A conversion processing, and an analog voltage can be output to the liquid crystal display panel.

FIG. 3 is a diagram for explaining the functions of the LUT 12 and the linear DAC source IC 2 in Embodiment 1 of the present invention. By correcting the amplitude of the voltage level by the movement of the LUT 12 and the linear DAC source IC 2, the luminance is adjusted to obtain a constant gamma characteristic, and the center voltage is corrected to maintain the balance between the positive and negative polarities. The state of performing flicker adjustment is illustrated by doing so.

Finally, the analog reference voltage supplied to the liquid crystal display panel by the linear DAC source IC 2 has a constant gamma characteristic according to the individual nonuniformity of the display block, and the balance between the positive and negative polarities is maintained (that is, the amplitude And the center voltage are corrected). As a result, it is possible to realize a liquid crystal display device which suppresses the occurrence of partial flicker and deterioration.

As described above, according to the first embodiment, by combining the LUT and the linear DAC source ICs individually configured for each display block, the function of correcting the display characteristics can be provided on the LUT side without having the driver IC side. As a result, the LUT can specify bit allocation data in order to perform optimal data conversion for display functions having individual differences for each display block, and the analog according to the 13-bit signal signaled through the linear DAC source IC. By outputting the voltage, a constant gamma characteristic can be obtained, and the display in which the balance between the positive and negative polarities is maintained can be realized.

Embodiment 2

In the second embodiment, a case where the gray scale display voltage correction and linear DAC source IC including the LUT described in the first embodiment is applied to a liquid crystal display device that performs color display by RGB pixels. In this case, it is necessary to have a LUT corresponding to the government data individually for each display block in RGB.

As shown in Figs. 8 and 9, in the conventional liquid crystal display device which performs color display, the impedance is changed by the cell thickness of each RGB pixel with the problem of flickering and deterioration, so that the voltage luminance characteristic of each RGB is changed. There is also a problem. Moreover, due to such characteristics, the optimum common voltage is different because the center voltage is different in each pixel of RGB. Therefore, in order to solve such a problem, the voltage luminance characteristics can be further improved by configuring the respective LUTs corresponding to the government data for each display block.

By using such a LUT, the center voltage and voltage level of the AC drive can be optimized in each RGB for each predetermined display block. That is, the input color video signal can be corrected with the corrected color video signal having a constant gamma characteristic over the entire screen without depending on the display block and maintaining a balance between positive and negative polarities. As a result, an optimal AC drive can be realized for each of the predetermined display blocks in RGB, and the change in impedance due to the difference in RGB cell thickness can be absorbed.

4 is an explanatory diagram for improving voltage luminance characteristics of each pixel of RGB after correction by the LUT in Embodiment 2 of the present invention. As a result, by adjusting the center voltage and the voltage level in each of the RGB using the LUT configured for each display block to realize the optimum AC drive, the voltage luminance characteristics of R and B become close to the voltage luminance characteristics of G. Can be. That is, the nonuniformity of the luminance voltage characteristic of RGB is improved by compensating for the difference in RGB cell thickness by specifying bit allocation data by the LUT configured for each predetermined display block.

As described above, according to the second embodiment, the LUT for correcting the color video signal is separately provided for each of the predetermined display blocks in correspondence with the respective government data, so that the center voltage and the voltage level of the AC drive are provided for each of the predetermined display blocks. Can be optimized for each in RGB. As a result, it is possible to easily correct individual variation of display characteristics for each display block for color image signals, absorb changes in impedance due to differences in cell thickness of RGB, and improve variation of voltage luminance characteristics of RGB. The liquid crystal display device which suppressed deterioration generation can be obtained.

Embodiment 3

In Embodiment 3 of the present invention, a case where a display block defined by a horizontal line and a source driver IC is employed as a specific example of a constant display block. FIG. 5 is a diagram showing a specific configuration of the LUT 12 in the gradation display voltage correction unit 1 according to the third embodiment of the present invention.

In Fig. 5, the LUTs 12 constitute separate tables with positive and negative polarities for each of the four source driver lines. As a result, an optimal voltage can be applied to each horizontal line (gate line), thereby improving flicker due to the impedance of the data signal line.

In addition, the DAC settings can be changed for each source driver IC, allowing optimization for each driver block. As a result, the DAC setting can be optimized for each driver along with the horizontal line, thereby improving the partial flicker of the LCD panel.

In addition, although FIG. 5 illustrates the case where LUTs are configured for each line and each source driver IC individually, a common LUT may be used for a plurality of lines or a plurality of source driver ICs for the purpose of reducing memory capacity. It is also possible to define a predetermined display block on either side without defining a predetermined display block for each of the horizontal lines and the plurality of driver ICs.

6 is an explanatory diagram in the case where the DAC setting is optimized for each source driver IC in Embodiment 3 of the present invention. The case where three source driver ICs are used for a liquid crystal display panel is illustrated. By providing LUTs to the source driver ICs individually, as shown in Fig. 6, an optimum AC drive can be realized for each driver block.

As described above, according to the third embodiment, by providing a separate LUT for each display block, the DAC setting can be optimized for each display block defined by the horizontal line and the driver block. As a result, the amplitude and center voltage of the voltage signal supplied to the liquid crystal display panel can be easily adjusted so as to have a constant display characteristic over the entire screen without depending on the display block and to have a balance between positive and negative polarities when performing AC driving. In this way, a liquid crystal display device capable of suppressing the occurrence of flicker and deterioration can be realized.

1 is a view showing display characteristics of a liquid crystal display device according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing an internal configuration of a gradation display voltage correction unit provided in the liquid crystal display device according to the first embodiment of the present invention.

3 is a diagram for explaining the functions of the LUT and the linear DAC source IC in Embodiment 1 of the present invention.

Fig. 4 is an explanatory diagram for improving the voltage luminance characteristic of each pixel of RGB after correction by the LUT in Embodiment 2 of the present invention.

FIG. 5 is a diagram showing a specific configuration of the LUT in the gradation display voltage correction unit in Embodiment 3 of the present invention.

6 is an explanatory diagram in the case where the DAC setting is optimized for each source driver IC in Embodiment 3 of the present invention.

7 is a view for explaining a method of adjusting the reference voltage and the common voltage of a source driver in a conventional liquid crystal display.

8 is a diagram illustrating a correspondence relationship between positive and negative polarities with respect to the common voltage Vcom.

Fig. 9 is a partial sectional view of a liquid crystal display device provided with each pixel of RGB for color display.

10 is a diagram illustrating voltage luminance characteristics of each pixel of RGB.

Explanation of symbols for the main parts of the drawings

1: Gradation display voltage correction 2: Linear DAC source IC (driver IC)

11: Display block identification circuit 12: Look-up table (LUT)

Claims (5)

In a liquid crystal display device for performing gradation display by switching between positive and negative polarity of an analog voltage signal output from a driver IC to perform AC driving. The driver IC is capable of processing data having a higher number of bits than the number of bits of the video signal, and receives bit allocation data specifying which signal bits to allocate each bit of the video signal together with the video signal, to the video signal. A driver IC for outputting an analog voltage signal corresponding to a corresponding high bit number of positive and negative input signals, The bit allocation data corresponding to each of the positive polarity data and the negative polarity data of the video signal so that the relationship between the output signal from the driver IC and the luminance of the image displayed in gray scale is constant, and the balance of the government is maintained. Outputting the bit allocation data specified by the lookup table for each of the predetermined display blocks to the driver IC in response to the positive data and the negative data of the video signal. And a gradation display voltage correction unit. The method of claim 1, The gradation display voltage compensator separates the color image signal for each RGB, and the relationship between the output signal from the driver IC and the brightness of the gradation displayed image for each RGB has a certain characteristic, and the balance of the government is maintained, and further, the RGB And a look-up table for each of the predetermined display blocks that specifies bit allocation data corresponding to each of the positive data and the negative data for each RGB so as to suppress the variation in voltage luminance characteristics. The method according to claim 1 or 2, And the gradation display voltage correction unit defines the predetermined display block according to the horizontal line of the liquid crystal display, and has a look-up table for each of the predetermined display blocks according to the horizontal line. The method according to claim 1 or 2, And the gradation display voltage correction unit defines the predetermined display block according to each of the plurality of driver ICs, and has a look-up table for each of the predetermined display blocks according to each of the plurality of driver ICs. The method according to claim 1 or 2, The gradation display voltage correction section defines the predetermined display block according to each of the horizontal lines of the liquid crystal display and the plurality of driver ICs, and has a look-up table for each of the predetermined display blocks according to the horizontal line and each of the plurality of driver ICs. Liquid crystal display device characterized in that.

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