JPH01145632A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent malfunction of a potential selecting logical circuit even if a large-sized matrix system liquid crystal display element is used by specifying the connection of one electrode of capacitors. CONSTITUTION:Only the capacitor 25 for the logical circuit is inserted and connected between power supply lines when a potential generating circuit 4 and the potential selecting logical circuit 2 have a ground line 3. The other capacitors 21-24 are connected at one end thereof to potential output lines 11-15 from the potential generating circuit 4 and are connected at the other end to the power supply line 1 of the circuit 4. The capacitors 21-24 which are connected at one electrode to the potential output lines 11-15 from the circuit 4 are not connected at the other electrode to the ground line 3 and, therefore, the flow of the large pulse current which flows at the time of the potential selection to the ground line 3 is prevented. The fluctuation in the potential at the time of the potential selection generated heretofore in the ground line 3 is thereby obviated and the malfunction of the potential selecting logical circuit is prevented as well.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device equipped with a power source suitable for accurately driving a large matrix type liquid crystal display element as desired.

[Prior art] A matrix type liquid crystal display element has a group of electrodes arranged in parallel in the horizontal direction and a group of electrodes arranged in parallel in the vertical direction, which face each other with a liquid crystal in between. If a potential difference equal to or greater than a threshold value is applied between the directional electrodes and the vertical/directional electrodes at a location where the directional electrodes intersect with the vertical/directional electrodes, the liquid crystal at that location will be in a different state from the surroundings, that is, a display state. If the potential difference applied to the liquid crystal is always in the same direction, the liquid crystal material will deteriorate.
The temporal average value (DC component) of the potential difference applied to the liquid crystal must be zero at any point on the display element.
Further, in general, a so-called half-selected location occurs in the vicinity of a location selected to be in a display state (where the same potential as the selected location is applied to one electrode), which should not necessarily be in a display state. The potential difference between the electrodes at the half-selected location must be below the threshold value, and there must be sufficient margin suitable for the duty ratio. In order to satisfy these various conditions, the matrix type liquid crystal display element is driven. Therefore, a potential generation circuit that generates multiple potentials is used. On the other hand, in order to perform the desired display, a potential selection logic circuit is required that sequentially selects electrode combinations over time between opposing horizontal and vertical electrodes and controls the voltage difference so that a potential difference greater than a threshold is generated. become. All of these have been widely used in the past, but as large-capacity display is required and the number of electrodes increases, various problems have arisen.

[Problem that the invention seeks to solve]

The potential of each potential output line generated by the potential generation circuit and the power supply line of the potential selection logic circuit must be stable.
Further, in order to enable the potential of the electrode line to rapidly change to a desired value when the potential selection logic circuit changes the selected electrode, it is preferable that there be a low impedance between each of the potential output lines and the IIS line of the potential generation circuit. As desired, a capacitor is connected between each of these lines. In reality, a shared power supply line, so-called ground line, has been conventionally provided in the drive circuit of a liquid crystal display device, just like in ordinary electrical equipment, and conventionally, one pole of each of the capacitors mentioned above was generally connected to this ground line. was connected to.

Figure 2 shows the vicinity of a potential generation circuit that generates a plurality of potentials (3 to 6) required for the so-called voltage averaging driving method of a conventional matrix type liquid crystal display device. 3 is a power supply line for the potential selection logic circuit, 3 is a common power supply line (ground line), 4 is a potential generation circuit, 11 to 16 are potential output lines, and 21 to 25 are capacitors. Further, FIG. 3 shows the inside of an example of the potential generation circuit 4, in which 31 to 37 are resistors and 41 to 44 are operational amplifiers. In the example shown in FIG. 2, one pole of each capacitor is all connected to a common power supply line (ground line) for the potential generation circuit and the potential selection logic circuit.

In recent years, as matrix type liquid crystal display elements have become larger, potential selection logic circuits have occasionally malfunctioned.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device that prevents display malfunctions even when using a large matrix type liquid crystal display element.

[Means for solving problems]

In order to solve the above problems, in the present invention, when the potential generation circuit and the potential selection logic circuit have a common power supply line, that is, a so-called ground line, this common power supply line and the other one of the potential selection logic circuits are connected to each other. Only the logic circuit capacitor is inserted and connected between the power supply lines, and each of the other capacitors, that is, one end of each capacitor is connected to multiple potential output lines from the potential generation circuit, and the other end of each capacitor is connected to the potential generation circuit. It was decided to connect it to a power supply line other than the above-mentioned common power supply line of the circuit, or to be inserted alone between it and an adjacent potential output line.

[Effect]

As a result of experimental research conducted by the present inventors, it has been found that the malfunction of the potential selection logic circuit described above is caused by fluctuations in the potential that occur on the ground line due to changes in electrode selection. As matrix type liquid crystal display elements become larger, a considerably large pulse current will flow through the potential output line when changing electrode selection, but this large pulse current is mostly supplied by the capacitor connected to the potential output line. be done. on the other hand,
In the case of a liquid crystal display device, the resistance or impedance of the so-called ground line itself is not so small that it can be ignored at all. Therefore, when a large pulse current flows through the ground line as described above, the potential fluctuation of the ground line occurs due to this. , that is, noise gets on the ground line. It was discovered that malfunctions of the potential selection logic circuit were caused by such causes. In the present invention, since the other pole of the capacitor whose one pole is connected to the potential output line from the potential generation circuit is not connected to the ground line, a large pulse current that flows when changing electrode selection flows to the ground line. That will no longer be the case. Therefore, potential fluctuations that conventionally occur in the ground line when changing electrode selection do not occur, and malfunctions of the electrode selection logic circuit also no longer occur.

〔Example〕

FIGS. 1(a) and 1(b) show the vicinity of the potential generation circuit of two embodiments of the present invention. In the embodiment shown in FIG. The other end is connected to the power supply line 1 other than the common power supply line of the potential generation circuit 4 t! It is continued. Further, in the embodiment shown in FIG.
and 12, between 12 and 13, between 13 and 14, and between 14 and 15.

Note that the capacitor may be connected through a resistor. If the capacitor is connected as in these examples, noise at the time of electrode switching will not be added to the ground Ij13, and malfunction of the electrode selection logic circuit will also be prevented. It will no longer occur.

〔Effect of the invention〕

As explained above, according to the present invention, a large matrix liquid crystal display device can be operated correctly by simply changing the connection of one pole of a capacitor.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are diagrams showing the vicinity of the potential generation circuit of two embodiments of the present invention, and FIG. 2 is a diagram showing the vicinity of the potential generation circuit of an example of a conventional matrix type liquid crystal display device. FIG. 3 is a diagram showing an example of a potential generation circuit. 1-Power supply line for liquid crystal drive, 2-Power supply line for potential selection logic circuit, 3-Common power supply line (ground line), L-Potential generation circuit, 11-16... Potential output line, 21-2
5-・Capacitor.

Claims (1)

[Claims] 1. A potential generation circuit that generates multiple potentials that are directly applied to the display electrodes of the liquid crystal display element from the drive power supply of the matrix type liquid crystal display device, and a potential that sequentially selects and sets the potential applied to each electrode of the display element for display. In a liquid crystal display device equipped with a selection logic circuit and a capacitor for potential stabilization and low power source impedance, when the potential generation circuit and the potential selection logic circuit have a common power supply line, this common power supply line and the potential selection logic Only the logic circuit capacitor is inserted and connected between the other power supply line of the circuit, and each of the other capacitors,
That is, one end of each capacitor is connected to a plurality of potential output lines from the potential generation circuit, and the other end of each capacitor is connected to a power supply line other than the above-mentioned shared power supply line of the potential generation circuit, or to an adjacent potential output line between them. A liquid crystal display device characterized in that it is connected so that it can be inserted alone.