JPS63243920A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display device having a good display grade by dividing a liquid crystal panel to two regions and periodically providing periods for impressing a high-frequency voltage and periods for impressing no voltages to the other region during selective scanning period of the one region. CONSTITUTION:A driving voltage generating circuit 19 supplies driving voltages of respective levels to respective scanning drivers 15, 17 and respective signal drivers 16, 18. A control circuit 20 supplies respective control signals and display data to the respective drivers according to display signals. The respective scanning drivers 15, 17 and signal drivers 16, 18 drive respective scanning electrodes 11, 13 and respective signal electrodes 12, 14. The periods for impressing the high-frequency voltage and the periods for impressing no voltages exist at the prescribed periods in the lower region during scanning of the upper region. Conversely, the periods for impressing the high-frequency voltage and the periods for impressing no voltages exist at the prescribed periods in the upper region during scanning of the lower region. The differences in the display brightness in the respective divided regions of the liquid crystal panel are decreased by periodically providing the above-mentioned periods to the above-mentioned regions in such a manner. The liquid crystal display having the good display grade is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal display device that is suitable and effective for displays used in video and information equipment.

2. Description of the Related Art In recent years, there has been an increasing demand for large-screen, thin display devices in the field of information equipment, mainly computers, and in the field of video equipment, mainly televisions, video tape recorders (VTRs), and the like.

Among this type of display devices, those using liquid crystals have recently been attracting particular attention because they are thin, lightweight, and easy to realize large screens.

A conventional liquid crystal display device will be described below with reference to the drawings.

FIG. 5 is a configuration diagram of a conventional liquid crystal display device having the most basic configuration, in which 51 is a scanning electrode, 52 is a signal electrode, 53 is a scanning driver, and 54 is a signal driver.

FIG. 6 shows an example of a drive voltage waveform of the conventional liquid crystal display device shown in FIG. 5, which is a voltage waveform applied to one pixel of the liquid crystal panel. Vs represents a selection voltage, Vn represents a non-selection voltage, and TF represents a frame period, and one frame completes the display of one screen. In order to alternating the voltage applied to the liquid crystal layer, the polarity of the voltage is reversed in subsequent frames.

FIG. 7 shows an example of a configuration diagram of a liquid crystal display device divided into two regions. In FIG. 7, 71 is an upper scanning electrode, 72 is an upper signal electrode, 73 is a lower scanning electrode, 74 is a lower signal electrode, 75 is an upper scanning driver,
76 is an upper signal driver, 77 is a lower scanning driver, and 7B is a lower signal driver. FIG. 8 shows a drive voltage waveform diagram of the conventional liquid crystal display device shown in FIG. In FIG. 8, (a) and (b) are driving voltage waveforms applied to each pixel in the upper and lower regions of the liquid crystal display device shown in FIG. ,
Indicates the lower selection scanning period, which indicates the lower selection scanning period, and indicates the period T during which the upper area is selectively scanned.
In 1, no voltage is applied to the lower region. vice versa,
During a period T2 in which the lower region is selectively scanned, no voltage is applied to the upper region.

As is clear from comparing Figures 6 and 8, when the effective value of the non-selection voltage applied to the liquid crystal layer for one frame period is as shown in Figure 6 by applying the voltage as shown in Figure 8, Therefore, the ratio of the effective values of the selection voltage and the non-selection voltage becomes large, and a display with high contrast can be obtained. (Japanese Unexamined Patent Publication No. 59-121391) Problems to be Solved by the Invention However, when the configuration shown in FIG. 7 is driven as shown in FIG. 8, the upper and lower regions are not driven at the same time. Therefore, the voltages that are simultaneously applied to the upper and lower regions differ greatly, and the display brightness differs between the upper and lower regions of the LCD panel due to the frequency dependence of the LCD panel. This has the problem that this occurs.

Furthermore, in the configuration shown in FIG. 5 above, the period during which the non-selective voltage is applied to the liquid crystal layer is shorter than in the case of FIG. 3, so the effective value voltage applied to the liquid crystal layer as a whole becomes smaller. However, in order to obtain the same display brightness, the peak value of the voltage applied to the liquid crystal panel must be increased.

Therefore, the present invention provides a liquid crystal display device with good display quality that solves the above problems.

Means for Solving the ProblemsThe technical means of the present invention for solving the above problems is to divide the liquid crystal panel into two areas, and during the selection scanning period of one area, the other area is scanned. The structure is such that a high-frequency voltage application period and a no-voltage application period are provided in terms of frequency.

Furthermore, the period during which the high frequency voltage is applied in the area that has not been selectively scanned is configured to be different for each predetermined period.

action The effect of this technical means is as follows.

In other words, in the present invention, a high-frequency voltage application period and a no-voltage application period are provided periodically during a period in which one area is not selectively scanned. Indeed, the effective value voltage applied to the liquid crystal layer decreases. Therefore, the increase in the effective value of the non-selection voltage applied to the liquid crystal layer of the liquid crystal panel is suppressed to a minimum, thereby preventing a decrease in display contrast and allowing high-frequency voltage to be simultaneously applied to each area on the upper and lower sides. , it is possible to reduce the difference in display brightness between the upper and lower regions.

Furthermore, by varying the application period of the high frequency voltage applied during the period when selective scanning is not performed, at a predetermined period,
It is also possible to reduce display unevenness and differences in display brightness caused by the regularity of the display pattern and the regularity of the high-frequency voltage application cycle.

Furthermore, since there is a period of application of the high-frequency voltage, the effective value voltage applied to the liquid crystal panel is also somewhat larger compared to the conventional example shown in FIG. It is something that can be done.

EXAMPLE Hereinafter, a liquid crystal display device according to an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a liquid crystal display device according to an embodiment of the present invention. In FIG. 1, 1) is an upper scanning electrode, 12 is an upper signal electrode, 13 is a lower scanning electrode,
14 is a lower signal electrode, 15 is an upper scan driver, 16 is an upper signal driver, 17 is a lower scan driver, 18 is a lower signal driver, 19 is a drive voltage generation circuit, and 20 is a control circuit.

The operation of a liquid crystal display device according to an embodiment of the present invention will be described below. In FIG. 1, a drive voltage generation circuit 19 supplies drive voltages of various levels to each scanning driver 15, 17 and each signal driver 16, 18, and a control circuit 20 generates each control signal and display data according to a display signal. is supplied to each of the above drivers, and each scan driver 15, 17 and each signal driver 16, 18 connect each scan electrode 1), 13 and each signal electrode 12.
・Drive 14.

FIG. 2 is a driving voltage waveform diagram of a liquid crystal display device according to an embodiment of the present invention. In FIG. 2, (a), fbl indicates the drive voltage waveforms applied to each pixel in the upper and lower regions of the liquid crystal panel, respectively. Vs is the selection voltage, Vn
indicates the non-select voltage. TF is a period of one frame, and the display of one screen ends in l frame. In order to alternating the voltage applied to the liquid crystal layer, the polarity of the applied voltage is reversed in subsequent frames. T1 is a selective scanning period for the upper region, T2 is a selective scanning period for the lower region, and Ts and Tn are a period of high frequency voltage application and a period of no voltage application, respectively, in the region not selectively scanned. As is clear from FIG. 2, while the upper region is being scanned, there are high frequency voltage application periods Ts and no voltage application periods Tn at predetermined intervals in the lower region. Conversely, while the lower region is being scanned, the upper region has a high frequency voltage application period Ts and a no voltage application period Tn at a predetermined period.

FIG. 3 is a diagram of voltage waveforms applied to each scanning electrode and each signal electrode of a liquid crystal display device according to an embodiment of the present invention, and shows scanning voltages and signals applied to realize the driving voltage waveform shown in FIG. Shows voltage. In Figure 3, ■0, ■1, ■2,
■3, ■4, and ■5 are drive voltage levels set to satisfy the following equation.

VO-V5=Vs ・・・・・・・・・・・・・・・
・・・・・・・・・・・・ (1) VO−Vl=V1−
V2=Vn..." T2) V3-V4=V
4-V4=Vn (3) In Fig. 3, (a) and (C) indicate the upper and lower scanning voltages, and the scanning electrode to be selected has VO or Vs. A voltage is applied, and voltage (1) or (4) is applied to the scan electrodes that are not selected. On the other hand, signal voltages as shown in (b) and (d) are applied to the signal electrodes.
1 shows an example of checkered pattern display data, and in the selection scanning period T1 of the upper region, the upper signal electrode has ■0 and ■5 or ■2 and ■3 corresponding to ON or OFF.
At the same time, Vl is applied to the lower signal electrode during the non-voltage application period Tn, and a high frequency voltage corresponding to ON or OFF is applied during the high frequency voltage application period Ts.

Similarly, in the selection scanning period of the lower region, as is clear from FIG. 3, the drive waveform is obtained by interchanging the upper and lower sides of the above operation.

FIG. 4 is a driving voltage waveform diagram of a liquid crystal display device according to another embodiment of the present invention, which is a voltage waveform applied to one pixel in the upper region. In Figure 4, TFI to TF4 are each 1
In the selection scanning period T2 of the lower region, the position of the high frequency voltage application period Ts is T.
It can be seen that there are differences between FI and TF3. Note that the applied voltage waveform of one pixel in the lower region is during the selection scanning period T1.
The waveform is similar to that obtained by switching the applied voltages of and T2.

Note that the drive waveform shown in FIG. 2 is an example and is not limited to this, and may be a waveform in which the pulse width of the signal during the -scanning period is changed in order to display gradations. Needless to say. Further, the length and cycle of the high frequency voltage application period and the no voltage application period are also examples, and are not limited to these.

Further, the scanning voltage and signal voltage shown in FIG. 3 are also examples, and any voltage that can obtain the driving voltage waveform shown in FIG. 2 may be used.

Furthermore, the drive voltage waveform shown in FIG. 4 is also an example, and it is sufficient that the application period of the high frequency voltage during the period in which selective scanning is not performed differs every predetermined period.

Effects of the Invention The present invention has a simple structure in which a liquid crystal panel divided into two regions is periodically provided with a high-frequency voltage application period and a no-voltage application period during a selection scanning period in one region. With this configuration, it is possible to obtain the effect of reducing the difference in display brightness between the divided regions of the liquid crystal panel.

Furthermore, since the application period of the high-frequency voltage is configured to be different for each predetermined period, differences in display brightness and display unevenness caused by the application period of the high-frequency voltage and the regularity of the display pattern can be reduced. You can also get the effect.

In addition, it is possible to obtain the ripple effect that the peak value of the driving voltage can also be made low.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a drive voltage waveform diagram in a liquid crystal display device according to an embodiment of the present invention, and FIG. 3 is a block diagram showing the configuration of a liquid crystal display device according to an embodiment of the present invention. FIG. 4 is a drive voltage waveform diagram of the scanning voltage and signal voltage of the liquid crystal display device of the embodiment. FIG. 4 is a drive voltage waveform diagram of the liquid crystal display device of another embodiment of the present invention. FIG. FIG. 6 is a schematic diagram showing an example of the configuration of a display device. FIG. 6 is a drive voltage waveform diagram of the conventional liquid crystal display device shown in FIG. 5. FIG. 7 is a diagram of a conventional liquid crystal display device divided into two regions. FIG. 8, which is a schematic diagram showing an example of the configuration, is a drive voltage waveform diagram of the conventional liquid crystal display device shown in FIG. 7. 1)・71・・・Upper scanning electrode, 12・72・
...Upper signal electrode, 13.73..Lower scanning electrode, 14.74..Lower signal electrode,
15・75・・・Upper scan driver, 16・7
6...Upper signal driver, 17/77...
... Lower scanning driver, 18, 78 ... Lower signal driver, 19 ... Drive voltage generation circuit, 20 ... Control circuit, 51 ... ...Scanning electrode, 52...Signal electrode. Name of agent: Patent attorney Toshio Nakao 1 person TF-+7
(Reim period) Monument 141 Drive vJ Kamem Figure 3 Figure 5 ◇ Figure 6 Figure 7

Claims (2)

[Claims] (1) The matrix liquid crystal panel is divided into two regions, and during the period of selective scanning of one of the above two regions, the period of application of high-frequency voltage to the other region at a predetermined period, and the period of application of no voltage to the other region. A liquid crystal display device characterized in that it is configured to have a period of . (2) The liquid crystal display device according to claim (1), characterized in that the period during which the high frequency voltage is applied in the area that is not selectively scanned is configured to differ for each predetermined period.