KR20090013669A - Liquid crystal display device - Google Patents

Abstract

An LCD device is provided to control a central voltage and the amplitude of a voltage signal supplied to an LCD panel easily, so as to have balance between positive polarity and negative polarity when alternate driving is performed. An LCD device generates an image signal which becomes a source of gradation display, by separating the signal into positive polarity data and negative polarity data. With regard to voltage signals outputted from a driver IC(2) and an image whose gradation is displayed, the device has a desired property with brightness. The device has a lookup table for compensating positive polarity data and negative polarity data individually to maintain positive and negative balance. A gradation display voltage compensator(1) outputs positive and negative voltage signals to the driver IC.

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 in which generation of deterioration due to residual flicker and direct current component is suppressed.

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.

8 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. 9 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. 8), 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, optimal alternating current drive could not be performed and deterioration due to residual flicker or alternating current components 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. 10 is a partial sectional view of a liquid crystal display device provided with RGB pixels for color display. In each pixel of RGB when color display is performed, as shown in FIG. 10, 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. 11 is a diagram illustrating voltage luminance characteristics of each pixel of RGB. As a result of the common drive adjustment, as shown in Fig. 11, the voltage luminance characteristic varies with each pixel of RGB.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is easy to reduce the amplitude and center voltage of a voltage signal supplied to a liquid crystal display panel to have desired display characteristics 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 be adjusted and that can control the occurrence of flicker and deterioration.

A liquid crystal display device according to the present invention is a liquid crystal display device that performs gradation display by switching between positive polarity and negative polarity of an analog voltage signal output from a driver IC and performing gradation driving. The positive data and the negative polarity are separately generated by the data and the negative data, so that the voltage signal output from the driver IC and the image displayed in gray scale have desired characteristics in relation to luminance, and the balance of the government is maintained. And a gradation display voltage correction section for outputting the voltage signal of the government after correction by the lookup table to the driver IC.

The 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 a bit of the video signal. It is possible to process data having a higher number of bits than the number, and receives bit allocation data specifying which signal bits are allocated to each video signal together with the video signal, and the high bit number of positive polarity corresponding to the video signal. A driver IC that outputs an analog voltage in accordance with a negative video signal, wherein the output signal from the driver IC and the image displayed in gray scale have desired characteristics in relation to luminance, and the balance of the video signal is maintained. Lookup for specifying bit allocation data corresponding to each of the positive data and the negative data And a gradation display voltage correction section for outputting the bit allocation data specified by the lookup table to the driver IC in response to the positive data and the negative data of the video signal.

According to the present invention, a look-up table (hereinafter referred to as LUT) which performs data conversion according to a video signal that is the source of gradation display is separately provided with a positive LUT and a negative LUT to have desired display characteristics. In addition, the liquid crystal display device capable of easily adjusting the amplitude and the center voltage of the voltage signal for performing the AC drive and 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.

FIG. 1 is a diagram showing an internal configuration of a gradation display voltage correction unit provided in the liquid crystal display device according to Embodiment 1 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 addition, the said display characteristic is mentioned later using FIG.

In Fig. 1, the separation generation circuit 10 receives a video signal and separates and generates positive data (positive data) 20 and negative data (negative data) 30 from the received video signal. The separately generated definition data 20 is corrected by the definition lookup table (LUT) 21 and is supplied to the data combiner 11. The negatively generated negative data 30 is equally corrected by the negative lookup table (LUT) 31 and is supplied to the data combiner 11.

The data combiner 11 supplies the corrected government data to the source IC 2 corresponding to the source driver as a reference voltage.

Next, the correction using the LUT will be described in detail.

2 is a diagram showing display characteristics of the liquid crystal display device according to Embodiment 1 of the present invention. In a liquid crystal display device, a given video signal (gradation signal) and the luminance displayed on the screen have a display characteristic as shown in Fig. 2, which is called a gamma characteristic.

More specifically, if the gradation signal is x and the luminance is y, it is expressed by a formula of " 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.

Therefore, in order to correct the display characteristics having such individual differences so as to match the desired gamma characteristics and to maintain the balance between the positive and negative polarities, the present invention corrects the video signal using the LUT. That is, in the liquid crystal display device of the present invention, the desired gamma characteristic is obtained according to the individual display characteristics, and the LUT for converting the video signal into the corrected signal is set in advance so that the balance between the positive and negative polarities is maintained.

3 is an explanatory diagram of correction by LUT in Embodiment 1 of the present invention. FIG. 3A illustrates a state in which the positive data (0+ to 255+) and the negative data (0- to 255-) after correction by the LUT are balanced. 3 (b) illustrates a state in which flicker adjustment is performed by luminance correction so that the desired gamma characteristic is obtained by correcting the amplitude of the voltage level by the movement of the LUT.

For example, the LUT is set in advance as a separate table for converting an input 10-bit video signal into a 12-bit output signal corresponding to positive and negative polarities. As a result, the input video signal can be corrected with the corrected video signal having a desired gamma characteristic and maintaining a balance between positive and negative polarities.

The corrected video signal thus obtained is given to the source IC 2 as a reference voltage. Therefore, the analog reference voltage finally supplied to the liquid crystal display by the source IC 2 has a desired gamma characteristic according to individual variation, and a balance between positive and negative polarities is maintained (i.e., amplitude and center voltage are corrected). do). As a result, the liquid crystal display device which suppressed flicker and deterioration can be realized.

As described above, according to the first embodiment, the use of the LUT enables the LUT side to have the function of correcting display characteristics on the LUT side without having the driver IC side. More specifically, by providing the LUTs for correcting the video signal separately from the government data, it is possible to easily generate a reference voltage having a desired gamma characteristic and maintaining a balance between positive and negative polarities. As a result, individual nonuniformity of display characteristics can be corrected easily, and the liquid crystal display device which suppressed flicker and deterioration generation can be obtained.

Embodiment 2

In the second embodiment, the case where the gradation display voltage correction unit provided with the LUT described in the first embodiment is applied to the liquid crystal display device that performs color display by RGB pixels.

As shown in Fig. 11, in the conventional liquid crystal display device which performs color display, there is a problem of flickering and deterioration, as well as a difference in cell luminance in each RGB pixel, resulting in different voltage luminance characteristics of RGB. There is also. 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, it is considered to further improve the voltage luminance characteristic by using an individual RGB LUT corresponding to government data.

FIG. 4 is a diagram showing an internal configuration of a gradation display voltage adjusting unit included in the liquid crystal display according to the second embodiment of the present invention. The gradation display voltage correction unit 1 has a function of individually correcting voltage levels of RGB included in a color image signal. The separation generation circuit 10 receives the color image signal, separates the R data 40, the G data 50, and the B data 60, and separates each data from each other in the same manner as in the first embodiment. To generate separation. The government data of each of the separately generated RGB is corrected by a separate LUT.

In other words, separately generated R data of the government is corrected by the lookup table (LUT) 41 of the government R, and supplied to the data combiner 11. The separately generated G data of the government is corrected by the G government lookup table (LUT) 51 and supplied to the data combiner 11. The separately generated B data of the government is corrected by the lookup table (LUT) 61 of the government B and supplied to the data combiner 11.

The data combiner 11 supplies the corrected government data to the source IC 2 corresponding to the source driver as a reference voltage for each RGB.

Therefore, each of the LUT 41 of the R part, the LUT 51 of the G part, and the LUT 61 of the B part has a table having the correction functions of the positive LUT 21 and the negative LUT 31 shown in the first embodiment. Corresponds to

Next, the correction using the LUT will be described in detail.

5 is an explanatory diagram of voltage level correction of color video signals using LUTs in the second embodiment of the present invention. By using the LUT 41 of the R government, the LUT 51 of the G government, and the LUT 61 of the B government, the RGB correction can be performed in correspondence with the government data.

As a result, the center voltage and voltage level of the AC drive can be optimized in RGB, respectively. That is, the input color video signal can be corrected by the corrected color video signal having a desired gamma characteristic and maintaining a balance between positive and negative polarities. As a result, an optimal AC drive can be realized in each of the RGB, and the change in the impedance due to the difference in the cell thickness of the RGB can be absorbed.

Fig. 6 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. As a result, by adjusting the center voltage and the voltage level in each of the RGB using the LUT to realize the optimum AC drive, the voltage luminance characteristics of R and B can be made close to the voltage luminance characteristics of G. That is, by compensating for the difference in the cell thickness of RGB by the correction of the conditions by the LUT, the nonuniformity of the RGB luminance voltage characteristic is improved.

As described above, according to the second embodiment, the LUTs for correcting the color video signal are individually RGB corresponding to the respective government data, so that the center voltage and voltage level of the AC drive can be optimized for each of RGB. As a result, it is possible to easily correct individual variation of display characteristics with respect to color image signals, absorb variation in impedance due to different cell thicknesses of RGB, and improve variation of voltage luminance characteristics of RGB, thereby preventing flicker or degradation. A liquid crystal display device with suppressed generation can be obtained.

In addition, in Embodiment 2 mentioned above, data conversion by LUT is performed with respect to each RGB after separating into RGB data. Therefore, if the purpose of improving only the unevenness of the voltage luminance characteristic of RGB is not necessarily separated into government data, the object can also be achieved by performing data conversion by the LUT on the data before separation.

Embodiment 3

In the first and second embodiments, a case in which a corrected video signal is obtained in accordance with the input video signal with desired display characteristics and the balance of the government is obtained by the movement of the LUT. On the other hand, in the third embodiment, the case where the LUT is used to obtain bit allocation data specifying which input signal bits are allocated to each bit of the video signal will be described.

FIG. 7 is a diagram showing an internal configuration of a gradation display voltage correction unit provided in the liquid crystal display device according to Embodiment 3 of the present invention. The gradation display voltage correction unit 1 is the same as the first and second embodiments in that the gradation display voltage correction unit 1 has a function of correcting the voltage level and the center voltage of the video signal that is the source of the gradation display according to the individual display characteristics of the liquid crystal display device. Do.

However, in the third embodiment, the gradation display voltage correction unit 1 uses the linear DAC source IC 3 as the source driver without directly correcting the video signal, and uses the linear DAC source IC 3 to convert each bit of the video signal. It specifies which input processing bit of the

In FIG. 7, a description will be given using a linear DAC source IC as a driver IC capable of inputting bit allocation data. The linear DAC source IC 3 corresponding to the source driver can process data having a higher number of bits than the number of bits of the video signal. The linear DAC source IC 3 can obtain a high bit number of input signals in accordance with the video signal by receiving, together with the video signal, bit allocation data specifying which signal bits are assigned to each bit of the video signal.

More specifically, as an example, it is considered to use a linear DAC source IC 3 capable of inputting 13 bits for a 10 bit video signal. In this case, except for the sign bit, the linear DAC source IC 3 can use 12 bits for positive polarity and 12 bits for negative polarity. Thus, the LUT 71 of the third embodiment has a desired display characteristic for a 10-bit video signal and specifies bit allocation data for selecting 10 bits within 12 bits so that the balance of the government is maintained.

Here, the LUT 71 corresponds to a table having a correction function of the positive LUT 21 and the negative LUT 31 shown in FIG. 1 of the first embodiment. The bit allocation data supplied from the LUT 71 to the linear DAC source IC 3 can be set in advance corresponding to each of the positive and negative polarities of the video signal according to the display characteristics inherent in the liquid crystal display device.

As a result, the linear DAC source IC 3 converts the input 10-bit video signal based on the bit allocation data given in each of the positive and negative polarities of the video signal into a 13-bit signal having an optimal encoding according to individual display characteristics. And D / A conversion processing, and an analog voltage can be output to the liquid crystal display panel.

As described above, according to the third embodiment, by combining the LUT and the linear DAC source IC, it is possible to have the function to correct display characteristics on the LUT side without having the driver IC side. As a result, the LUT can specify bit allocation data in order to make optimal data changes for the display function having individual differences for each liquid crystal display device, and convert the analog voltage according to the signable 13-bit signal through the rear DAC source IC. By outputting, a desired gamma characteristic can be obtained, and a display device in which a balance between positive and negative polarities is maintained can be realized.

In addition, in the third embodiment, a color video signal can be applied as the video signal, and the same effect as in the second embodiment can be obtained. In this case, it is necessary to have LUTs corresponding to the government data individually in RGB.

In addition, when a color video signal is applied, data conversion is performed by each LUT separately for each RGB. However, if only the purpose of improving the nonuniformity of the voltage luminance characteristic of RGB is required, data need not be converted individually by government, and this object can also be achieved by performing data conversion by LUT on video signal data.

FIG. 1 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.

2 is an explanatory diagram of correction of a video signal using a LUT in Embodiment 1 of the present invention.

3 is an explanatory diagram of correction by LUT in Embodiment 1 of the present invention.

FIG. 4 is a diagram showing an internal configuration of a gradation display voltage correction unit provided in the liquid crystal display device according to the second embodiment of the present invention.

5 is an explanatory diagram of correction of a video signal using a LUT in Embodiment 2 of the present invention.

Fig. 6 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. 7 is a diagram showing an internal configuration of a gradation display voltage correction unit provided in the liquid crystal display device according to Embodiment 3 of the present invention.

8 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.

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

Fig. 10 is a partial sectional view of a liquid crystal display device having respective pixels of RGB for color display.

11 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: Source IC (driver IC)

3: linear DAC source IC (driver IC) 10: separation circuit

11: data combiner

21,31,41,51,61,71: LUT

Claims (4)

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 video signal, which is the source of the gray scale display, is separated and generated into the positive data and the negative data, and the voltage signal output from the driver IC and the image to be displayed in gray scale have desired characteristics and the balance of the government. And a look-up table for separately correcting the positive data and the negative data so that the negative data is maintained, and a gradation display voltage correction section for outputting the government voltage signal corrected by the look-up table to the driver IC. Liquid crystal display device. In the liquid crystal display device according to claim 1, The gradation display voltage compensator separates and generates a color image signal into positive data and negative data for each RGB, and the relationship between the voltage signal output from the driver IC for each RGB and the brightness of the grayscale image is desired. And a look-up table which individually corrects the positive data and the negative data for each RGB so that the balance of the government is maintained and the voltage luminance characteristics of the RGB are suppressed from variation. In a liquid crystal display device which performs gradation display by switching between positive and negative polarity of an analog voltage signal output from a driver IC and performing AC drive, The driver IC can process data having a higher number of bits than the number of bits of the video signal, and receives, together with the video signal, bit allocation data specifying which signal bit is allocated to each bit of the video signal. A driver IC that outputs an analog voltage according to a high bit number of positive and negative video signals corresponding to The bit allocation data corresponding to each of the positive data and the negative data of the video signal is specified so that the output signal from the driver IC and the image to be displayed in gray scale have desired characteristics and the balance of the government is maintained. And a gradation display voltage correction section for outputting the bit allocation data specified by the lookup table to the driver IC in response to the positive data and the negative data of the video signal. Display. In the liquid crystal display device according to claim 3, 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 luminance of the gradation displayed image for each RGB has a desired characteristic, and the balance of the government is maintained. And a look-up table for specifying bit allocation data corresponding to each of the positive data and the negative data for each RGB so as to suppress unevenness of voltage luminance characteristics of each RGB.

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