KR930003669B1 - Driving method of lcd - Google Patents

Abstract

The method prevents contrast variation of characters and diagrams caused by the variation of wave form which is applied to segments of super twisted nematic liquid crystal display. The method comprises the steps: (A) dividing waveform applied to segment electrodes by 3; and (B) combining the divided waveform with waveform applied to common electrodes. Low state signal is combined with the first two sections of the divided wave form, and high state signal is combined with the last section of the divided wave form when pattern data exists. When no pattern data exists, high state signal is combined to the first two sections of the divided waveform and low state signal is combined with the last section of the divided waveform.

Description

Waveform Driving Method of LCD

1 is a view showing a conventional liquid crystal panel.

2a) is a waveform diagram of a segment signal for performing a waveform driving method according to the prior art.

2b) is a waveform diagram of a segment signal for performing a waveform driving method according to the present invention.

3a) and 3b) are state diagrams of data transmitted to the Nth segment electrode.

4a) is a waveform diagram of a common segment according to the prior art of FIG. 3a).

4b) is a waveform diagram of a common segment according to the present invention of FIG. 3a).

5a) is a waveform diagram of a common segment according to the prior art of FIG. 3b).

5b) is a waveform diagram of a common segment according to the present invention of FIG. 3b).

6a) is a combination waveform of FIG. 4a).

6b) and 4b) are combined waveforms.

FIG. 7a) is a combination waveform of FIG. 5a).

7b) and 5b) are combined waveforms.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform driving method of a liquid crystal display device, and in particular to a character displayed on a channel due to a difference in frequency of waveforms driven in a super twisted nematic liquid crystal device. A waveform driving method for preventing the contrast of a figure from fluctuating.

In general, the liquid crystal display device is driven by an alternating current to prevent deterioration and is classified into a static driving method and a multiplex driving method. The static driving method uses a frame frequency of several tens to hundreds of Hz as a basic method of obtaining display characteristics of the conventional liquid crystal panel shown in FIG.

In addition, the multiplex driving method is also called a time division or dynamic driving method in an effective way to reduce the plurality of liquid crystal composition circuits connected to the display cell.

In the multiplex driving method, when the common electrodes on the liquid crystal panel are sequentially selected, the entire segment electrodes are divided into a plurality of sets, and a time division display is performed by applying a signal indicating the presence or absence of data to the segment electrodes.

On the other hand, since the STN liquid crystal device is driven in the multiplex method, the frequency applied to the segment electrode is varied according to the pattern displayed on the liquid crystal panel of FIG. 1 composed of the STN liquid crystal device. The segment signal for performing the conventional panel driving method applied to the segment electrode has a shape as shown in FIG. 2a), and the section in which the data is loaded on the segment signal is "low" such as c, d, g, h and kl. "Keep the level. 3a) and 3b) show a state diagram of the data transferred to the Nth segment electrode. FIG. 3a) shows the data on the segment of the Nth column of the common electrodes 2, 4, 6 and 7. Shows the state when.

FIG. 3B also shows a state when data is present on the segment of the Nth column of the common electrodes 1, 2, 3, 4, 5, 6 and 7. FIG. The waveform of the common segment for performing the conventional panel driving method according to FIG. 3a) is shown in FIG. 4a), and the dotted line shows the waveform applied to the common electrode of the second row (low). The combined signal of the common segment waveform shown in FIG. 4A) is shown in FIG. 6A).

On the other hand, Fig. 5a) shows the waveform of the common segment according to the prior art of Fig. 3b), and the combined waveform of this common segment signal is shown in Fig. 7a).

Therefore, when a combination waveform signal such as FIG. 7a) is applied to the liquid crystal panel of FIG. 1 composed of STN liquid crystal elements, the displayed characters are changed as shown in FIGS. 3a) to 3b) as compared with FIG. 6a). As a result of the change of the component, the level of the threshold voltage (Vth) of the liquid crystal is changed, resulting in a problem that the contrast varies depending on the characters or graphics displayed on the liquid crystal panel.

Accordingly, the present invention has been made to solve the above problems, and as the waveform applied to the segment of the liquid crystal panel composed of STN liquid crystal elements is changed, the liquid crystal for preventing the contrast of letters or figures displayed on the liquid crystal panel from changing. It is an object of the present invention to provide a waveform driving method of a display device.

In order to achieve the above object, according to the present invention, the waveform of the signal applied to the segment electrode constituting the liquid crystal panel is divided into predetermined portions and combined with the waveform applied to the common electrode in accordance with a pattern such as a character or a figure displayed on the liquid crystal panel. It is characterized by preventing the frequency from changing.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2B) is a waveform diagram of a signal applied to a segment electrode of an STN liquid crystal panel for implementing the waveform driving method according to the present invention. In FIG. 2B), the present invention divides one pulse of the pattern signal applied to the segment electrode shown in FIG. 1 into three equal parts so that the data signal of the pattern is " low " (g, j), (h). , k) and " high " (i, l) signals, and if there is no data signal of the pattern, " high " (a, d), (b, e) signals and " low " By applying a signal and combining with a waveform applied to the common electrode, a waveform driving method is used to prevent the frequency from changing according to the pattern displayed on the STN liquid crystal panel.

Referring to the operation and effect of the present invention in more detail based on the above configuration as follows.

4b) is a waveform diagram of a common segment according to the present invention of FIG. 3a).

In FIG. 4B), the solid line waveform applied to the segment electrodes of the Nth column on the STN liquid crystal panel shown in FIG. 1 is loaded with the data signal of the pattern as shown in FIG. 3A) (2, 4, 6, 7) and the case where there is no data signal (1, 3, 5). At this time, the waveform shown by the dotted line represents the signal applied to the common electrode of the second row.

When the waveforms applied to the segment electrodes of the Nth column and the signals applied to the common electrode of the second row are combined, the waveforms are displayed as shown in FIG. 6B). On the other hand, solid waveforms as shown in FIG. 5b) appear when a data signal of a pattern exists on the N segment as shown in FIG. Are combined. According to the conventional method, as the display pattern changes from FIG. 3a) to FIG. 3b), the driving waveform changes from FIG. 6a to FIG. 7a), so that the frequency is changed. Compared to the?), There is less frequency change than the conventional method, so that the threshold voltage of the liquid crystal hardly changes, so the contrast of the pattern displayed on the liquid crystal panel is hardly changed.

As described above, the present invention has almost no variation in threshold voltage due to a frequency change when a pattern such as a character or a figure displayed on the STN liquid crystal panel is changed, thereby preventing a difference in operating voltage of the STN liquid crystal panel. There is an advantage.

Claims (2)

By dividing the waveform of the signal applied to the segment electrode constituting the liquid crystal panel with a predetermined waveform and combining the waveform with the waveform applied to the common electrode, the frequency is prevented from changing according to a pattern such as a character or a figure displayed on the liquid crystal panel. Waveform driving method of the liquid crystal display device. The method of claim 1, wherein the signal applied to the segment electrode is divided into three equal parts per pulse, and when the data signal of the pattern exists, the "low" signal is applied to the first two sections and the "high" signal is applied to the last section. On the other hand, when the data signal of the pattern does not exist, the "high" signal is applied to the first two sections, and the "low" signal is applied to the last section to reduce the contrast of the pattern appearing on the liquid crystal panel. A waveform driving method of a liquid crystal display device for preventing the display.

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