JP2002091391A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the change of picture display characteristics at the input edge side and the termination side of a scanning signal in a liquid crystal display device. SOLUTION: This display device is constituted so that a counter electrode potential Vcom corresponding to the interval between a picture signal wiring S1 and a picture signal wiring S3072 has an inclination between the input edge side and the termination side of the scanning signal based on an optimum counter electrode potential to be obtained by a flicker minimum value deciding method. As a result, since the device can optimize pixel potential by changing the counter electrode potential Vcom, the device can uniformize picture display characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display, and more particularly to an active matrix liquid crystal display.

[0002]

2. Description of the Related Art An active matrix liquid crystal display device has a structure in which scanning signal wiring, image signal wiring, and switching elements (mainly TFTs) are arranged in a matrix. In such a liquid crystal display device, with the recent increase in the size of the device, the rounding of the signal waveform due to the electric resistance and the wiring capacitance of each signal wiring increases, and the TFT is turned on and off.
The change in pixel potential that occurs at the time of switching differs between the input end and the end of the signal, causing a phenomenon that the display characteristics of an image change on the display surface. For this reason, reduction in wiring resistance and wiring capacitance is required. However, enlargement of wiring width for reduction of wiring resistance takes into account reduction of pixel pitch due to high definition and improvement of aperture ratio for realizing high luminance. If not, it is not a good idea. There is a concern that a reduction in the additional capacitance among the wiring capacitances may cause a reliability problem, and a reduction in the parasitic capacitance requires a reduction in the size of the TFT, resulting in insufficient charging capability. For these reasons, it is difficult to reduce the rounding of the signal waveform in a large-sized TFT liquid crystal display device, and other solutions are required to make the image display characteristics uniform.

[0003]

The image display characteristics to be solved include flicker, burn-in (afterimage), crosstalk, and the like, which are different between the input end and the end of the signal wiring. The cause of such a phenomenon is a shift in the center of the pixel potential due to the rounding of the signal waveform. Normally, the pixel potential is applied alternately and symmetrically to the positive and negative sides with respect to the counter electrode potential, thereby driving the liquid crystal in an alternating electric field. Therefore, ideally, the pixel potential center coincides with the counter electrode potential. However, the above-described phenomenon occurs because the pixel potential center changes between the input end and the end of the scanning signal due to the rounding of the signal waveform, and the symmetry of the pixel potential with respect to the counter electrode potential is lost.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to make image display characteristics uniform even in a large TFT liquid crystal display device.

[0005]

A pixel potential is alternately and symmetrically applied to the positive and negative sides with respect to the counter electrode potential, and when the liquid crystal is driven by an alternating electric field, scanning is performed using a flicker minimum value determination method. When the optimum counter electrode potential corresponding to the terminal was determined from the input end of the signal, it was found that the optimum counter electrode potential tended to increase from the input end toward the end. This indicates that the center of the pixel potential increases from the input end to the end of the scanning signal line.

Here, the flicker minimum value determination method is known as a method for evaluating and determining symmetry. In a state where a display pattern in which flicker is most conspicuous is displayed, an optical response waveform is observed and frequency resolution (FFT) is performed. In this method, the potential of the common electrode (or other parameters such as Vsc) when the frequency component (often 30 Hz) of the signal voltage applied to the liquid crystal is minimized is determined as an optimum value.

Based on the above findings, the present invention provides a liquid crystal display device having a substrate on which scanning signal wiring, image signal wiring, and TFTs are arranged in a matrix, and a counter substrate on which a transparent electrode is formed. The voltage applied to the opposite substrate corresponding to the end and the terminal is provided with a gradient, or the image signal voltage corresponding to the center between the input terminal and the terminal of the scanning signal is provided with a gradient. Things.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display device according to a first aspect of the present invention has a substrate on which scanning signal wiring, image signal wiring, and TFTs are arranged in a matrix, and a counter substrate on which transparent electrodes are formed. In the liquid crystal display device, the voltage applied to the corresponding substrate between the input end and the end of the scanning signal has a slope corresponding to the optimum counter electrode potential determined by the flicker minimum value determination method. Things. This makes it possible to optimize the pixel potential and make the image display characteristics uniform.

The liquid crystal display device according to the second aspect is the first aspect.
In the configuration described above, the voltage applied to the counter substrate is configured to be higher on the terminal side than on the input side of the scanning signal.

According to a third aspect of the present invention, there is provided a liquid crystal display device having a substrate on which scanning signal lines, image signal lines, and TFTs are arranged in a matrix, and a counter substrate on which transparent electrodes are formed. The configuration is such that the center of the image signal voltage corresponding to between the input end and the end of the scanning signal has a slope corresponding to the optimal counter electrode potential determined by the value determination method. This makes it possible to optimize the pixel potential and make the image display characteristics uniform. In this case, it is possible that the potential of the counter electrode is constant within the display surface.

According to a fourth aspect of the present invention, there is provided a liquid crystal display device.
In the configuration described above, the image signal voltage center is configured to be lower on the terminal side than on the input side of the scanning signal.

An embodiment of the present invention will be specifically described with reference to the drawings. FIG. 1 shows a 15-inch XGA liquid crystal display device. This liquid crystal display device 1 has a structure as shown in FIG.
FIG. 1B shows a substrate 5 on which scanning signal lines 2, image signal lines 3, and TFTs 4 (shown simply) are arranged in a matrix.
And a counter substrate 7 having a transparent counter electrode 6 formed on the entire surface.

In FIG. 1A, reference numeral 8 denotes a display area, 9 denotes a scanning signal output IC for the scanning signal wiring 2, 9a denotes its control device, 10 denotes an image signal output IC for the image signal wiring 3, 10a Is a control device for the image signal wiring S1 (wiring number 1) corresponding to the input end of the scanning signal.
No.) is located at the left end, and the image signal wiring S3072 (wiring number 3072) corresponding to the end of the scanning signal is located at the right end. In FIG. 1B, reference numerals 11 and 12 denote voltage supply electrodes respectively corresponding to the input end and the end of the scanning signal.

In this liquid crystal display device, the rounding of the scanning signal waveform as shown in FIG. 2 occurs. In this liquid crystal display device, when the optimum common electrode potential (Vcom) was obtained by the flicker minimum value determination method, it was as shown in FIG. 3, which was 2.5 volts in S1 and 3.0 volts in S3072. .

Therefore, as a first embodiment, the voltage supply electrode 11 is set so that the potential of the common electrode gradually increases from 2.5 volts to 3.0 volts from S1 to S3072 in accordance with the optimum common electrode potential (Vcom). , 12 were able to suppress the change in the display characteristics of the image in the left-right direction. FIG. 4 shows the flicker level at this time in comparison with a conventional method in which a constant voltage of 2.5 volts is applied to the counter electrode 6, but other image display characteristics are similarly improved. .

Next, when the opposing electrode 6 is set to a constant voltage of 2.5 volts and the optimum image signal voltage center (Vsc) is changed to determine the flicker minimum value, the optimum image signal voltage center (Vsc) is obtained as shown in FIG. a) As shown in (b) and (c), Vsc0 is used for the image signal wiring S1, Vsc0−ΔV1 is used for the image signal wiring Sn, and Vsc0 is used for the image signal wiring S3072.
−ΔV2 (ΔV1 <ΔV2).

In the second embodiment, as shown in FIG. 6, the image signal output IC 10 controls the image signal voltage center (Vsc) to gradually decrease from 2.5 volts to 2.0 volts from S1 to S3072. When the signal voltage applied to the wiring 3 was controlled by the control device 10a, the same effect as in the first embodiment was obtained.

[0018]

As described above, according to the present invention, the voltage applied to the counter substrate between the input terminal of the scanning signal and the terminal is made to have a slope, or the input terminal of the scanning signal is connected to the terminal. By providing an inclination to the center of the image signal voltage corresponding to the above, even in a large-sized liquid crystal display device, it is possible to make the distribution of the image display characteristics in the display plane due to the rounding of the scanning signal waveform uniform.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a schematic configuration of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of scan signal waveform rounding in the liquid crystal display device.

FIG. 3 is an explanatory diagram showing an example of controlling an image signal voltage center in the liquid crystal display device.

FIG. 4 is an explanatory diagram showing a reduction in flicker level when the liquid crystal display device is controlled to an optimal counter electrode potential.

FIG. 5 is an explanatory diagram showing a change in an optimum counter electrode potential in the liquid crystal display device.

FIG. 6 is an explanatory diagram showing another control example of the image signal voltage center in the liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 1 liquid crystal display device 2 scanning signal wiring 3 image signal wiring 4 TFT 5 substrate 6 transparent electrode 7 counter substrate 9 scanning signal output IC 10 image signal output IC 11,12 voltage supply electrode S1 image signal wiring S3072 image signal wiring Vcom counter electrode potential Vsc Image signal voltage center

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09G 3/20 624 G09G 3/20 624D F term (Reference) 2H093 NA16 NB11 NC18 NC34 ND10 ND36 5C006 AC02 AC25 AF46 BB16 BC03 BC06 BC13 FA23 FA26 FA34 FA37 5C080 AA10 BB05 DD05 DD06 DD10 DD12 FF09 JJ02 JJ04 JJ05

Claims (4)

[Claims] In a liquid crystal display device having a substrate on which scanning signal wiring, image signal wiring, and TFTs are arranged in a matrix, and an opposing substrate on which a transparent electrode is formed, an optimum opposition determined by a flicker minimum value determination method. A liquid crystal display device characterized in that a voltage applied to a counter substrate corresponding to a portion between an input terminal and a terminal of a scanning signal has a slope corresponding to an electrode potential. 2. The liquid crystal display device according to claim 1, wherein a voltage applied to the opposite substrate is higher on the terminal side than on the input side of the scanning signal. 3. A liquid crystal display device having a substrate on which scanning signal lines, image signal lines, and TFTs are arranged in a matrix, and an opposing substrate on which transparent electrodes are formed. A liquid crystal display device characterized in that an image signal voltage center corresponding to a position between an input terminal and a terminal of a scanning signal has a slope corresponding to an electrode potential. 4. The liquid crystal display device according to claim 1, wherein the center of the image signal voltage is lower on the terminal side than on the input side of the scanning signal.