JPS63240531A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To decrease a difference in display luminance in respective divided regions by providing a period when a non-selection voltage is impressed and a period when no voltage is impressed to the other region during selective scanning period of one region and using the signal voltage to be impressed in the period when the non-selection voltage is impressed as a prescribed gradation signal. CONSTITUTION:Figures a-c respectively indicate the waveforms of the impressed voltages on a scanning voltage, signal voltage and liquid crystal layer on the upper side; figures d-f similarly indicate the waveforms of the respective impressed voltages on the lower side; Vs indicates a selection voltage, and Vn indicates the non-selection voltage. Ta is one scanning period, Ts is the period for impression of the selection signal, and Tf is the period of one frame. The polarity of the impressed voltage is inverted in the ensuing frames in order to convert the voltage to be impressed to the liquid crystal layer to AC. The period Tb when the non-selection voltage is impressed and the period Tn when no voltage is impressed exist in the lower region in T1 during scanning of the upper region. Conversely, the period Tb when the no-selection voltage is impressed and the period Tn when no voltage is impressed exist in the upper region in T2 during scanning of the lower region. The prescribed gradation signal is impressed to the signal electrodes in the period Ts. The difference in the display luminance in the respective upper and lower regions is thereby decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a display device that is effective for use in displays used in video and information equipment, and more particularly to a liquid crystal display device capable of displaying gradations.

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. 4 is a configuration diagram of a conventional liquid crystal display device having the most basic configuration, in which 41 is a scanning electrode, 42 is a signal electrode, 43 is a scanning driver, and 44 is a signal driver.

FIG. 5 shows an example of a drive voltage waveform of the conventional liquid crystal display device shown in FIG. 4, which is a voltage waveform applied to one pixel of the liquid crystal panel. Vs is a selection voltage, Vn is a non-selection voltage, Ta is one scanning period, and Ts is an application period of a selection voltage. By varying this Ts, gradation display is possible. Tf is a frame period, and the display of one screen ends at -frame. In order to alternating the voltage applied to the liquid crystal layer, the polarity of the voltage is reversed in subsequent frames.

FIG. 6 shows an example of a configuration diagram of a conventional liquid crystal display device divided into two areas. In FIG. 6, 61 is an upper scanning electrode, 62 is an upper signal electrode, 63 is a lower scanning electrode, 64 is a lower signal electrode, 65 is an upper scanning driver, 66 is an upper signal driver, 67 is a lower scanning driver, and 68 is a lower signal driver. FIG. 7 shows a driving voltage waveform diagram of the conventional liquid crystal display device shown in FIG.
1 each in the upper and lower areas of the liquid crystal display shown in the figure.
In the drive voltage waveform applied to the pixel, TI and T2 indicate the upper and lower selection scanning periods, respectively. During the period T1 in which the upper region is selectively scanned, no voltage is applied to the lower region. It has not been. Conversely, during the period T2 in which the lower region is selectively scanned, no voltage is applied to the upper region.

As is clear from comparing Fig. 5 and Fig. 7, when the effective value of the non-selection voltage applied to the liquid crystal layer for one frame period is as shown in Fig. 5 by applying the voltage as shown in Fig. 7, Therefore, the value of 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 (for example, Japanese Patent Laid-Open No. 59-1213
Publication No. 91).

Problems to be Solved by the Invention However, when the configuration shown in FIG. 6 is driven as shown in FIG. 7, the upper and lower regions are not driven at the same time. The voltages that are simultaneously applied to each panel are significantly different from each other, and due to the frequency dependence of the LCD panel, there is a problem in that there is a difference in display brightness between the upper and lower regions of the LCD panel. was.

In addition, due to the frequency dependence of the liquid crystal panel,
There was also the problem that display unevenness depending on the pattern of the displayed image also occurred.

Furthermore, in the configuration shown in FIG. 6 above, the period during which the non-selective voltage is applied to the liquid crystal layer is shorter than in the case of FIG. 4, 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. A non-selective voltage application period and a non-voltage application period are provided, and a predetermined gradation signal is applied to the signal electrode in the area that is not selectively scanned during the non-selective voltage application period. .

Furthermore, the gradation signals applied to the signal electrodes in the areas that are not selectively scanned are configured to include at least half of all the patterns of gradation signals that can be applied.

action The effect of this technical means is as follows.

That is, in the present invention, a non-selection voltage application period and a no-voltage application period are provided during a period in which one area is not selectively scanned, and the effective value of the non-selection voltage applied to the liquid crystal layer of the liquid crystal panel is The non-selection voltage can be simultaneously applied to the upper and lower regions while minimizing the increase in display contrast and reducing the difference in display brightness between the upper and lower regions. .

Furthermore, by configuring the grayscale signal applied during the non-selective scanning period to include at least half of all patterns of grayscale signals that can be applied, all patterns that can be applied to the signal electrodes can be configured. Since it is possible to apply a voltage having a frequency component of , it is possible to reduce the deviation of the frequency component of the applied voltage depending on the pattern of the displayed image, and to make the display uniform.

In addition, since the application period of the non-selection voltage is longer than in the conventional example shown in Figure 7, the effective value voltage applied to the liquid crystal panel also increases, and therefore the peak value of the drive voltage also decreases. 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.
It is a 4rA 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 scan driver 15.17 and each signal driver 16.18, and a control circuit 20 outputs each control signal and display data according to the display signal. are supplied to each of the above-mentioned drivers, and each scan driver 15, 17 and each signal driver 16, 18 supply 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 Figure 2 (a).

(b) and [c) are the applied voltage waveforms of the upper scanning voltage, signal voltage, and liquid crystal layer, respectively, +di, (el, (fl
respectively indicate the lower scanning voltage, signal voltage, and voltage waveforms applied to the liquid crystal layer. In FIG. 2, VO, Vl, V2.
V3°V4. (2) 5 is the driving voltage level, which is set to satisfy the following equation.

VO−V5==Vs...
・・+1) VO−V1=V1−V2−Vn−・・・・
・121V 3-V4-=V4-V5=
V n -=-f31Vs indicates a selection voltage, and Vn indicates a non-selection voltage. Ta is one scanning period, Ts is a selection signal application period, and by varying this Ts, gradation display is possible. This embodiment shows a case where the period Ta is divided into 10 equal parts and Ts is varied in 10 steps. Tf is the period of one frame, and the display of one screen ends at -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 selection scanning period for the upper region, T2 is a selection scanning period for the lower region, and Tb and Tn are a non-selection voltage application period and a no-voltage application period, respectively, in an area that is not selectively scanned. As is clear from FIG. 2, while the upper region is being scanned, there is a non-selection voltage application period Tb and a no-voltage application period Tn in the lower region. Conversely, while scanning the lower region, the non-selection voltage is applied to the upper region T.
b and a period Tn in which no voltage is applied.

It can also be seen that a predetermined gradation signal is applied to the signal electrode during the period Ts.

FIG. 3 is a driving voltage waveform diagram of a liquid crystal display device according to another embodiment of the present invention, and each symbol is the same as that shown in FIG. 2. In FIG. 3, the non-selection voltage application period Tb and the no-voltage application period Tn are different from those in the embodiment shown in FIG. 2, and the period Tb and the period Tn are repeated at a predetermined period.

Note that the drive waveforms shown in FIGS. 2 and 3 are only examples, and the polarity of the applied voltage is reversed every frame to convert it into an alternating current, but the present invention is not limited to this.

Furthermore, the length and cycle of the non-selection voltage application period and the no-voltage application period are also examples, and are not limited to these.

Furthermore, the scanning voltages and signal voltages shown in FIGS. 2 and 3 are just examples, and any voltage waveforms that can be applied to the liquid crystal layer may be used.

Effects of the Invention When performing gradation display on a liquid crystal panel divided into two regions, the present invention provides a period of application of a non-selection voltage and a period of no voltage application to the other region during a selection scan period of one region. and the signal voltage applied during the application period of the non-selection voltage,
With a simple configuration in which a predetermined gradation signal is used, it is possible to obtain the effect of reducing the difference in display brightness in each divided area of the liquid crystal panel.

Furthermore, in order to configure the grayscale signal applied during the period when no selective scanning is performed so as to include at least half of all the patterns of grayscale signals that can be applied, the display that depends on the pattern of the displayed image is configured. It is also possible to achieve the effect of reducing unevenness and realizing display with good uniformity.

Further, a ripple effect can also be obtained in that the peak value of the drive voltage can also be lowered.

[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. A driving voltage waveform diagram of the liquid crystal display device of the embodiment, FIG. 4 is a schematic diagram showing an example of the configuration of a conventional basic liquid crystal display device, and FIG. 5 is a driving voltage waveform diagram of the conventional liquid crystal display device shown in FIG. 4. Voltage waveform diagram, Figure 6 is a schematic diagram showing an example of the configuration of a conventional liquid crystal display device divided into two regions, and Figure 7 is a diagram of driving voltage waveforms of the conventional liquid crystal display device shown in Figure 6. be. 1). 61... Upper scanning electrode, 12.62.
...Upper signal electrode, 13.63...Lower scanning electrode, 14.64...Lower signal electrode, 15.65...Upper side 16. scanning driver;
66... Upper signal driver, 17.67...
...Lower scan driver, 18.68...
Lower signal driver, 19... Drive voltage generation circuit, 20... Control circuit, 41... Scanning electrode, 42... Signal electrode. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 4 Figure 6 Figure 7

Claims (2)

[Claims] (1) The signal electrode of a matrix liquid crystal panel consisting of a scanning electrode and a signal electrode is divided into two regions, and the pulse width of the signal voltage is varied to display gradation. During a period when one area is selectively scanned, the other area is driven to have a period of applying a predetermined non-select voltage and a period of no voltage application, and the signal electrode of the area that is not selectively scanned is driven. The liquid crystal display device is characterized in that it is configured to apply a predetermined gradation signal during the application period of the non-selection voltage. (2) A patent claim characterized in that the gradation signal applied to the signal electrode in the area that is not selectively scanned is configured to include at least half of all the patterns of gradation signals that can be applied. The liquid crystal display device according to the range (1).