JPH07239461A - Liquid crystal image display device - Google Patents

Abstract

(57) [Abstract] [Purpose] The drive of a constant counter potential is performed by suppressing the potential fluctuation of the counter electrode, which is the biggest problem when the drive of a constant counter potential is adopted, to a level at which there is no problem in image quality. An object of the present invention is to realize a liquid crystal image display device having excellent image quality without crosstalk while being adopted. [Structure] By adding a capacitance between the output terminal (opposite electrode 3 side) of the counter potential supply power supply 5 and the ground, the output of the counter potential supply power supply 5 can be stabilized, which causes crosstalk. A liquid crystal image display device which suppresses the potential fluctuation (rush voltage) of a certain counter electrode 3 to a level that causes a problem in image quality, and as a result employs a drive with a constant counter potential, but has excellent image quality without crosstalk. Can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a large-screen and high-definition liquid crystal image display device having high-quality image quality.

[0002]

2. Description of the Related Art Since an active matrix system in which a switching element is provided for each unit pixel and driven is proposed, the image quality of a liquid crystal image display device has been dramatically improved. 3 inch to 10 inch class products have already been commercialized, and they are receiving great expectations from various fields as the protagonists of the next generation flat displays. The current demands for liquid crystal image display devices are (1) large screen
(2) High definition (3) Cost reduction can be mentioned as three. With respect to (3), the improvement in yield and cost reduction of necessary members are important points, but regarding (1) and (2), crosstalk and A major point is how to avoid the delay or distortion of the signal potential that causes the deterioration of the display image quality such as the brightness gradient.

A conventional liquid crystal image display device driven at a constant counter potential will be described below. In the case of driving with a constant counter potential, there is an advantage that low power consumption can be realized as compared with the drive of the counter potential inversion type. FIG. 2 shows the configuration of a conventional liquid crystal image display device driven at a constant opposite potential. Here, a capacitive coupling drive method (Proceedings of S. ID 31 (1990), pages 87 to 9), which is one of the typical methods for driving with a constant counter potential, is used.
Announced on page 4 (Proceedings of SID Vol.31 (1990) P.87-9
4)) will be described as an example. In FIG. 2, reference numeral 1 is a driver IC for applying a scanning signal, which is connected to a scanning line 6 in the liquid crystal panel, and 2 is a driver IC for applying a video signal, which is connected to a signal line 7 in the liquid crystal panel. The signal line 7 is connected to the pixel electrode 9 via the switching element 8. From the power supply 5 to the counter electrode 3 through the conductive resin 4,
A constant potential that is not ground is supplied. 3 shows a signal waveform output from the driver IC1, and FIG. 4 shows a signal waveform output from the driver IC2.

[0004]

However, in the above-mentioned conventional configuration, the potential applied to the pixel electrode 9 changes its polarity all at once for each row. This fluctuation of the potential causes the counter electrode 3 having a constant potential to fluctuate as shown in FIG. 5 via the capacitance between the signal line 7 and the counter electrode 3. Here, V1 is the potential supplied from the power source to the counter electrode, and V2 is Tr is O.
The potential of the counter electrode during FF, V3 is the rush voltage of the counter electrode potential. By increasing the number of conductive resins 4 and decreasing the resistance of the counter electrode 3, the driver IC
The output of 1 becomes Low and the switching element 8 turns off.
It is sufficiently possible for the potential of the counter electrode 3 to drop to the potential V1 which should be originally, by the timing. However, since the rush voltage V3 of the potential of the counter electrode is determined by the size of the capacitance between the signal line 7 and the counter electrode 3,
It is impossible to suppress the fluctuation by the above method. Further, since the above-mentioned capacitance is determined by the signal line width and the gap of the liquid crystal panel, there is a limit point in design, and it is not easy to reduce the capacitance. Moreover, this capacitance value becomes high definition and increases as the number of wirings increases, which is a disadvantageous factor. This inrush voltage causes insufficient writing of the charging potential to the pixel electrode 9 and causes a deterioration in image display called crosstalk, which is a big problem in the liquid crystal image display device driven at a constant counter potential.

It is an object of the present invention to provide a liquid crystal image display device which solves the above-mentioned conventional problems and can be driven at a constant counter potential.

[0006]

In order to achieve this object, the liquid crystal image display device of the present invention has a capacitance for suppressing the potential fluctuation of the counter electrode as an input terminal (counter electrode side) of a power supply for the counter potential supply. It has the structure added between the ground and the ground.

[0007]

Function: A power supply is connected to the counter electrode in order to supply a constant potential, but the potential itself of the counter electrode fluctuates via the capacitance between the signal lines. Is not stable, and as a result, the potential of the counter electrode is unstable. However, by adding a capacitance between the power supply for the counter potential supply (counter electrode side) and the ground, the supply potential from the power supply can be more stabilized and the potential fluctuation of the counter electrode can be suppressed to a level where there is no problem in image quality. Becomes

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of the liquid crystal image display device of the present invention. Reference numeral 1 is a driver IC for applying a scanning signal, which is connected to a scanning line 6 in the liquid crystal panel. Reference numeral 2 is a driver IC for applying a video signal, which is connected to a signal line 7 in the liquid crystal panel. The signal line 7 is connected to the pixel electrode 9 via the switching element 8. 3 is a counter electrode, 4
Is a conductive resin, and 5 is a power supply for supplying a counter potential, and supplies a constant potential of 2.5 (V) to the counter electrode 3 through the conductive resin 4. Reference numeral 10 is a capacitor for suppressing the potential fluctuation of the counter electrode adopted in this embodiment, which is a driver IC.
It is added between the counter electrode 3 and the ground on the TAB mounting printed circuit board 2. The larger the number of points of the conductive resin 4, the lower the resistance of the counter electrode 3, and the difference V2 between the potential value of the counter electrode 3 and the potential to be originally supplied when the switching element 8 is OFF is advantageous. It is in the right direction. In the present embodiment, by increasing the power supply from the conductive resin, which was conventionally four points, to 12 points, the above-mentioned deviation 52 of the counter electrode potential is reduced from approximately 20 (mV) to 5 (mV) or less. I was able to improve.

With respect to the proper value of the capacitance 10, the appearance of the surface crosstalk with respect to the increase / decrease of the additional capacitance is evaluated. In order to make the surface crosstalk invisible, at least 4.4 (μ)
It was confirmed that the capacity of F) had to be added.
Therefore, in consideration of the capacitance variation due to the operating temperature and the power supply capability, a capacitance of 2.2 (μF) is added to 14 chips, a total of 30.8 (μF), in consideration of a margin. With the addition of this capacity, the conventional configuration is 1.5
It has become possible to suppress the potential fluctuation (rush voltage) of the counter electrode, which has been (V) or more, to 1.0 (V) or less. As a result, it was possible to realize a liquid crystal image display device capable of displaying a good image without crosstalk by suppressing the potential fluctuation of the counter electrode while adopting the drive with a constant counter potential.

The additional capacitance may be formed by forming a film in the liquid crystal panel and incorporated therein.

[0012]

As described above, the present invention suppresses the potential fluctuation (rush voltage) of the counter electrode by adding a capacitance between the output terminal (counter electrode side) of the power supply for the counter potential and the ground. It is possible to realize an excellent liquid crystal image display device capable of displaying a good image without crosstalk by driving with a constant opposing potential.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of a conventional liquid crystal image display device in driving with a constant counter potential.

FIG. 3 is a signal waveform output from a driver IC for applying a scanning signal

FIG. 4 is a signal waveform output from a driver IC for applying a video signal.

FIG. 5: Potential fluctuation waveform of the counter electrode in the case of conventional driving with a constant counter potential

[Explanation of symbols]

1 Driver IC for applying scan signal 2 Driver IC for applying video signal 3 Counter electrode 4 Conductive resin 5 Power supply for supplying potential to counter electrode 6 Scan line 7 Signal line 8 Switching element 9 Pixel electrode 10 Counter electrode Capacitance added to suppress potential fluctuations V1 Potential supplied to the counter electrode from the power source V2 Potential of the counter electrode when the switching element is off V3 Inrush voltage of the counter electrode potential

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Mine 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A first transparent insulating substrate having a plurality of scanning lines and signal lines, a switching element for each unit pixel, and a pixel electrode, and a second transparent insulating substrate having a transparent conductive counter electrode. A liquid crystal panel having a structure in which liquid crystal is injected between the liquid crystal panel, a drive circuit for supplying a scan signal electrically connected to a scan line in the liquid crystal panel, and a signal line in the liquid crystal panel electrically. A drive circuit for supplying the connected video signal,
In a liquid crystal image display device provided with a counter potential supply power source for supplying a constant potential which is not grounded and is electrically connected to the counter electrode in the liquid crystal panel, a capacitance for suppressing the fluctuation of the counter potential, A liquid crystal image display device, characterized in that the liquid crystal image display device is added between the output terminal (opposite electrode side) of the power supply for supplying the counter potential and the ground.