JPS6217733A - Static driving device for liquid crystal indicator - Google Patents

Abstract

PURPOSE:To easily display the video of an intermediate gradation by generating periodically the pulse train of one group of an interval of a pulse width portion by a pulse train generating means and applying it to a common electrode, and also executing a pulse position modulation in accordance with the output of a gradation detecting means by a pulse modulating means. CONSTITUTION:From the pulse signal generator 1 of a static driving device, a pulse train having the pulse interval of a pulse width portion is generated periodically in the interval of this pulse train portion, and applied to an LCD driver 4. Also, a variable density gradation is detected from a video signal by a gradation detector 2, and inputted to a pulse position modulator 3 for inputting a pulse rain from the generator 1. Also, the pulse train which passes through the driver 4 is applied to the common electrode of a liquid crystal indicator 5, also an output brought to a position modulation in accordance with an output from the detector 2 by the modulator 3 is provided to each electrode of the indicator 5 through the driver 4, and an intermediate gradation is displayed on a usual indicator.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a static drive device for a liquid crystal display that displays halftones.

[Conventional technology]

Conventionally, in static driving of a liquid crystal display, a pulse signal as shown in FIG. 7(a) is applied to the common electrode GOW.
In-phase and π12 phase-shifted pulse signals as shown in b) and (c) were applied to the segment electrodes.

Therefore, for example, in the electrode S1, the common electrode C0)1
When an in-phase pulse signal is applied to the display element DE
I indicates OFF, and for example, when a Norse signal whose phase is shifted by π12 with respect to the common electrode CON is applied to the electrode S2, the display element DIE2 is displayed ON.

[Problem that the invention seeks to solve]

Conventional static drive devices for liquid crystal displays are unable to obtain the required number of gray levels, and therefore, the resulting images lack expressive power.゛ [Means for solving the problems] This invention was made by focusing on such conventional problems, and its purpose is to express gray scale.
The pulse train generating means periodically generates a group of pulse trains having a pulse interval equal to the Norculus convergence at intervals of this pulse train and inputs them to the common electrode, while the pulse position modulating means performs gradation detection. The pulse position of the entire group of pulse trains is modulated in accordance with the output from the means and input to the segment electrodes.

〔Example〕

An embodiment of the present invention will be explained based on FIGS. 1 to 5. Note that the same or equivalent parts as in the conventional example are given the same reference numerals, and the description thereof will be omitted. In Figures 1 and 2, l is a pulse signal generation circuit (pulse train generation means) that periodically generates a part of the pulse train having a pulse interval equal to the pulse width at intervals other than this part of the pulses. do. 2 is a gradation detector (gradation detection means) that detects gradation from the image signal.
, 3 is a pulse position modulator (pulse position modulating means) which modulates the pulse position of a part of the pulse train from the pulse signal generator 1. 4 is an LCD driver that drives a liquid crystal display (LCII) 5. DEn(n=1.2.-
, , m) are display elements constituting the liquid crystal display 5, and FIGS. 1 and 2 show the display element IIEI-DH4.

Next, the operation will be explained based on the timing chart shown in FIG.

Now, in order to express 4 gradations of light and shade, we are using a common electrode COW.
The pulse signal shown in FIG. 3(a) is input from the pulse signal generator l to the segment electrode 5t-S4, and the signal from the pulse signal generator l is input to the gradation detector 2. The pulse position modulator 3 modulates the pulse position according to the output from the pulse position modulator 3 and inputs the resultant signal. It should be noted that the pulse signal, that is, the pulse train, output from the pulse signal generator l is as shown in FIG.
pulses.

It is assumed that a pulse train whose pulse position is modulated in the following manner is input to the segment electrodes 51 to S4 with respect to a part of the pulse train input to the common electrode COM. That is, a pulse train in which the first pulse starts in synchronization with the second pulse of the pulse train is input to the segment electrode S4 (see FIG. 3(e)), and to the segment electrode S3, In synchronization with the third pulse of the pulse train, the fourth pulse of the pulse train is also applied to the segment electrode S2.
A pulse train in which the first pulse starts in synchronization with the second pulse train is input (see Fig. 3(c) (, d)).Furthermore, the segment electrode S1 is connected to the pulse train input to the common electrode COW. A pulse train in which the first pulse starts with a delay of one pulse from the fourth pulse of this pulse train is inputted with respect to the pulse train of this pulse train (see FIG. 3(b)).

Then, the common electrode C is connected to the segment electrode 5l-S4.
Voltages having waveforms shown in FIGS. 4(a) to 4(d) are inputted to OW. From FIGS. 3 and 4, display elements DEI, DE2 . DE3. It can be seen that the effective value of the voltage input to DE4 decreases in this order.

On the other hand, the relationship between LCD drive voltage and transmittance (contrast) is as shown in Figure 5, so the larger the effective value of the drive voltage, the whiter (in the case of monochrome display) one display element will be displayed. .

In this embodiment, one display element DEI is white, and then the display elements DE2, DE3, DE4 approach black in this order.

The device of the present invention can be applied to all field effect type liquid crystal elements such as TN type or GH type liquid crystal elements.

〔Effect of the invention〕

Since the present invention has the above configuration, it has the effect of being able to display halftones.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing one embodiment of the present invention, and FIG. 2 is a diagram showing an embodiment of the present invention.
3(a) to 3(e) are waveform diagrams of pulse signals applied to the common electrode and segment electrode shown in FIG. 2, respectively. Figures 4 (a) to (d) are waveform diagrams of the voltage applied to the common electrode and the segment electrode, respectively. Figure 5 is a diagram showing the relationship between the voltage applied to the liquid crystal display and the transmittance. 6
The figure shows part of the display element in a liquid crystal display.
The figure shows the pulse signal applied to the liquid crystal display shown in Fig. 6, Fig. 7 (a) shows the pulse voltage waveform diagram applied to the common electrode, and Fig. 7 (b) and (c) show the conventional In an example, it is a voltage waveform diagram applied to a segment electrode. In the figure, COM is a common electrode, 5l-S4 are segment electrodes, 1 is a pulse signal generator, 2 is a gradation detector, 3 is a pulse position modulator, and 5 is a liquid crystal display. Figure 3(e) 54

Claims (1)

[Claims] Pulse train generating means for periodically generating a group of pulse trains having pulse intervals equal to the pulse width and inputting the pulse trains to a common electrode; and gradation detecting means for detecting gray scale from the image signal. and pulse position modulation means for pulse position modulating the entire group of pulse trains according to the output from the pulse train and inputting the pulse position modulation means to the segment electrodes.