JPH02163725A - Ferroelectric liquid crystal display device - Google Patents

Abstract

PURPOSE:To eliminate the inclination in the display luminance over the entire part of a screen and to uniformize the luminance by scanning odd or even lines in the first half of one perpendicular scanning period and scanning the even or odd lines in order reverse from the above-mentioned order in the second half of one perpendicular scanning period. CONSTITUTION:A scanning electrode driving circuit 1 for the odd lines scans the lines in order of the scanning electrodes Y1 Y3 Y5 in the first half of one perpendicular scanning period and a scanning electrode driving circuit 2 for the even lines scans the lines in order of the scanning electrodes Y6 Y4 Y2 in the second half of the perpendicular scanning period. A control circuit 4 controls the above-mentioned operations and simultaneously supplies the display data to a signal electrode driving circuit 3. The average values of the respective display luminances of two pieces of the respective adjacent scanning lines are the same even in any adjacent lines on the screen. The apparent inclination of the display luminance over the entire part of the screen is, therefore, eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a ferroelectric liquid crystal display device that is effective for use 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 TVs, visions, video tape recorders (VTRs), and the like.

This type of display device uses liquid crystal, which is thin and
Recently, it has been attracting particular attention because it is lightweight and easy to realize a large screen.

In particular, ferroelectric liquid crystal display devices are rapidly being put into practical use because they have quick response to electric fields and can easily obtain high contrast.

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

FIG. 6 shows a block diagram of a general matrix type ferroelectric liquid crystal display device. Figure 6 is for ease of explanation.
An example of a 6×6 dot matrix panel is shown. X
I””X b is a signal electrode, Y.

-Y are scan electrodes, 61 is a scan electrode drive circuit, 62 is a signal electrode drive circuit, and 63 is a control circuit, which controls the scan electrode drive circuit 61 and the signal electrode drive circuit 62.

The operation of the conventional ferroelectric liquid crystal display device configured as described above will be described below.

FIGS. 7(a) to (1) show examples of drive voltage waveforms of conventional ferroelectric liquid crystal display devices, and scan electrodes Yl, Yl, Yx of the ferroelectric liquid crystal display device shown in FIG. ,...
Scanning electrode waveforms VY, ,VY, ,VY applied to ,Y
ff , . . . , VY, and the same signal electrodes X, , X
Signal electrode drive waveform applied to , ,X, x, ,vx
, ,vx, ,furthermore, the signal electrode Xl and the scanning electrode Y+
Voltage waveform applied to pixel (1) at the intersection with x, y, ,
Voltage waveform VXxYt applied to pixel (2) at the intersection of signal electrode X2 and scan electrode Y2; voltage waveform VXaYh applied to pixel (3) at the intersection of signal electrode x4 and scan electrode Y
It shows.

In FIGS. 7(a) to (1), the period te is a period for erasing, and during this period the amplitude is, for example, 3E and the width is L.
A pair of negative and positive erasing scan electrode drive pulses 70 of e/2 are applied to all scan electrodes Y+, Yz, Y3, . . .
・, Y, and at the same time signal electrodes X, ,X, ,・
A pair of pulses 71 having an opposite phase to the pulse 70 described above and having an amplitude of, for example, E are applied to . A pair of positive and negative pulses 7 with an amplitude of 4E
2 is added. Therefore, the direction of the liquid crystal molecules is reversed according to the positive or negative applied voltage during the period of te, but the liquid crystal molecules are aligned in one direction fixed by the polarity in the latter half of te, and the entire screen is erased as white, for example. become a state.

After this, the scanning electrodes Y, , Y, , Y3, . . . , Y.

A pair of positive and negative scanning pulses 73 with an amplitude of 3E and a width of
are added, and a signal pulse 74 corresponding to the pattern of characters, symbols, etc. to be displayed in synchronization with these scanning pulses 73 is used as a signal electrode drive pulse to generate VX in FIGS. 7(a) to (1).
, , vxz , VX, are added as shown. These signal pulses 74 have an amplitude of E, and are a pair of negative and positive pulses that are in opposite phase to the scanning pulse 73 to display black, and are pulses that are in phase to leave it white. Note that the width of the pair of pulses is the same as that of the scanning pulse. With this operation method, the voltage waveforms that make pixels (1) and (3) in the black state in FIG. 6 are changed to VX, Y, and VX in FIG.
, VX, Y, have the same voltage waveforms that cause the pixel (2) to become white (VXzYz, respectively).

In this way, conventional scanning electrodes Y+, Yz, Yl,...
, Y6 are simultaneously applied with a voltage or pulse 70, and the orientation of the liquid crystal molecules corresponding to that portion is made to be in one direction to make the white erased state, and then these scanning electrodes Y5, Y2, YY, .
, Y, are scanned in a line-sequential manner to display information signals, that is, signal electrodes Y,, Y,, Y! ,...,Y.

The direction of the liquid crystal molecules is reversed in accordance with the pulse applied to the screen, and the screen is displayed in a black state. (Japanese Unexamined Patent Publication No. 62-175714) However, in the above configuration, after the scanning pulse is applied to the scanning electrode Y1, the number of non-selection pulses applied to the pixels on the scanning electrode Y1 until the -scanning period ends. is greater than the number of non-selection pulses applied to pixels above scan electrode Y from the time the scan pulse is applied to scan electrode Y until the end of one scan period. Therefore, due to the cumulative response effect of non-selected pulses as shown in Figure 8, when the same data is displayed on the entire screen, the display brightness changes for each scanning line as shown in Figure 9. .

In FIG. 9, the solid line indicates the case where black data is displayed on the entire screen, and the dashed line indicates the case where white data is displayed on the entire screen.

Furthermore, in the above configuration, if the pause period from the end of one scanning period to the application of the erase pulse for the next scanning period is short, the display time of the pixels on each scanning electrode is as shown in FIG. The total time is the time from when data is written until the end of one scanning period and the pause period Ls,
The display time differs between pixels on each scanning electrode. For this reason,
As shown in FIG. 11, the brightness of the visible pixel changes depending on the length of the display time, and as shown in FIG. 12, the display time differs depending on the pixel on each scanning line. The visible display brightness changes for each scanning line. In FIG. 12, the solid line indicates the case where black data is displayed on the entire screen, and the dashed-dotted line indicates the case where white data is displayed on the entire screen.

Note that the trends of the scan electrode and brightness change shown in Figures 9 and 12, respectively, are in opposite directions, but if the influence of the cumulative response effect of non-selected pulses is large, the change will be displayed as shown in Figure 9. When the brightness changes and the influence of the difference in display time of pixels on each scanning line is large, the display brightness changes as shown in FIG. 12.

Problems to be Solved by the Invention Therefore, in a conventional matrix type ferroelectric liquid crystal display device as shown in FIG. 6, when the same data is displayed on the entire screen, if the cumulative response effect of non-selected pulses is large, the As shown in Figure 9, if the display brightness changes for each scanning line and the difference in display time of pixels on each scanning line has a large effect, the brightness for each scanning line changes as shown in Figure 12. Display brightness changes. Therefore, there was a problem in that a brightness gradient occurred across the entire liquid crystal panel.

Therefore, the present invention solves the above problems and provides an effective ferroelectric liquid crystal display device that achieves uniform display brightness.

Means for Solving the Problems And, the technical means for solving the above problems is to scan the odd-numbered scanning lines in the first half of one vertical scanning period, and scan the even-numbered scanning lines in the second half of one vertical scanning period. The scan is performed in the reverse order of the scan order.

action The effect of this technical means is as follows.

In other words, even if the same data is displayed on the entire screen, the display brightness of each scanning line will be different, but if you look at the entire screen from a macroscopic perspective, the brightness of each scanning line will be the average brightness of the adjacent scanning lines. appear.

In the present invention, the scanning lines scanned in the first half of one vertical scanning period and the scanning lines scanned in the second half are arranged alternately, and the scanning lines scanned in the second half of one vertical scanning period are the same as the scanning lines scanned in the first half. Since the lines are scanned in the reverse scanning order, the average value of the display brightness of each two adjacent scan lines is the same for any adjacent scan line on the screen. Therefore, a gradient in the apparent display brightness across the entire screen does not occur.

EXAMPLE Hereinafter, a ferroelectric 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 ferroelectric liquid crystal display device according to an embodiment of the present invention. In FIG. 1, the liquid crystal panel is similar to that shown in the conventional example of FIG. X, ~X are signal electrodes, Y1 to Y are scan electrodes, 1 is a scan electrode drive circuit that drives odd lines Y, , Y3, Y, of scan electrodes, 2 is an even line Y! of scan electrodes. ,Y4
, Yh, 3 is a signal electrode X,
-X.

4 is a control circuit that controls the scan electrode drive circuit 1 for odd lines, the scan electrode drive circuit 2 for even lines, and the signal electrode drive circuit 3.

The operation of the ferroelectric liquid crystal display device according to one embodiment of the present invention configured as described above will be described below with reference to the drawings.

In FIG. 1, the scanning electrode drive circuit 1 of odd-numbered lines is Y
, -Y, →Y, and the scan electrode drive circuit 2 for even lines scans in the order of Y, -+Y, →Y2. First, in the first half of one vertical scanning period, the odd-numbered line scan electrode drive circuit 1 is operated to scan the odd-numbered scan line, and in the second half of one vertical scanning period, the even-numbered line scan electrode drive circuit 2 is operated, and the even-numbered line is scanned. scan the scan line. The control circuit 4 controls the above operations and simultaneously supplies display data to the signal electrode drive circuit 3.

FIGS. 2(a) to 2(1) show driving voltage waveforms of a ferroelectric liquid crystal display device according to an embodiment of the present invention. Figure 2 (a
) In ~(1), VY, ~VY, is the scanning electrode Y
+~Y, drive voltage waveform, vx, , vx, , vx.

shows the drive voltage waveforms of the signal electrodes Xi, Xz, and X4. The structure of the liquid crystal panel is similar to that shown in FIG. As is clear from FIGS. 2(a) to (1), the odd lines of the scan electrodes are scanned in the first half of one vertical scanning period, and the even lines of the scan electrodes are scanned in the second half of the vertical scanning period. The odd lines are scanned in the reverse order. The signal voltages applied to the signal electrodes Xn (n=1 to 6) are applied while changing the order so as to correspond to each scanning line.

FIG. 3 shows the display brightness of each scanning line and the apparent display brightness of the entire screen when the influence of the cumulative response effect of non-selected pulses is large when operating a ferroelectric liquid crystal display device according to an embodiment of the present invention. It shows. The solid line represents the brightness on each scanning line when black is displayed on the entire screen, the dashed-dot line represents the brightness on each scanning line when white is displayed on the entire screen, and the dashed line represents the apparent display brightness of the entire screen. It shows. As is clear from FIG. 3, there is no gradient in the apparent display brightness across the entire screen.

FIG. 4 shows the display time of pixels in each scanning line when a ferroelectric liquid crystal display device according to an embodiment of the present invention is operated.

FIG. 5 shows the visible display brightness of each scanning line when the ferroelectric liquid crystal display device according to an embodiment of the present invention is operated and the influence of the difference in display time between pixels on each scanning line is large. , and the apparent display brightness of the entire screen.

The solid line represents the brightness on each scanning line when black is displayed on the entire screen, the dashed-dot line represents the brightness on each scanning line when white is displayed on the entire screen, and the dashed line represents the apparent display brightness of the entire screen. It shows. As is clear from FIG. 5, there is no gradient in the apparent display brightness across the entire screen.

It goes without saying that the scanning line at which scanning starts may be an even numbered scanning line, and the scanning order is not limited to this embodiment. It would be good if it were reversed.

Furthermore, the waveforms, voltage ratios, and pulse widths of the scanning pulse and signal pulse are not limited to those in this embodiment.

Further, the waveforms, voltage ratios, and pulse widths of the erasing scan electrode drive pulse and the erasing signal electrode drive pulse are not limited to those in this embodiment.

Effects of the Invention The present invention has the effect that, in a ferroelectric liquid crystal display device, it is possible to eliminate the slope of the display brightness of the entire screen and realize a display with good display uniformity.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a ferroelectric liquid crystal display device according to an embodiment of the present invention, and FIGS. 2(a) to (1) are driving diagrams of a ferroelectric liquid crystal display device according to an embodiment of the present invention. A voltage waveform diagram; FIG. 3 is a characteristic diagram showing the display brightness of each scanning line and the apparent display brightness of the entire screen when displaying a ferroelectric liquid crystal display device according to an embodiment of the present invention; FIG. 5 is a waveform diagram showing the display time of each scanning line of the ferroelectric liquid crystal display device according to an embodiment of the present invention, and FIG. A characteristic diagram showing the visible display brightness of each scanning line and the apparent display brightness of the entire screen, FIG. 6 is a block diagram showing the configuration of a conventional ferroelectric liquid crystal display device, and FIGS. 7(a)-
(+) is a drive voltage waveform diagram of a conventional ferroelectric liquid crystal display device, Figure 8 is a characteristic diagram showing the relationship between the number of non-selective pulses and display brightness, and Figure 9 is a diagram of a conventional ferroelectric liquid crystal display device. A characteristic diagram showing the display brightness of each scanning line during operation, Figure 10 is a waveform diagram showing the display time of each scanning line of a conventional ferroelectric liquid crystal display device, and Figure 11 is visually recognized as the display time. FIG. 12 is a characteristic diagram showing the visible display brightness of each scanning line when a conventional ferroelectric liquid crystal display device is operated. 1...Odd line scanning electrode drive circuit, 2...
...Even-numbered line scanning electrode drive circuit, 3...
- Signal electrode drive circuit, 4...control circuit, 20.
70...Scanning electrode drive pulse for erasing, 21.7
1... Signal electrode drive pulse for erasing, 22.72
...Erasing pulse, 23.73...Scanning pulse, 24.74...Signal pulse, 25.
75...Writing pulse, 61...Scanning electrode drive circuit, 62...Signal electrode drive circuit,
63...Control circuit. Name of agent: Patent attorney Shigetaka Awano and one other person
, Yuno-O-Kusano-hime Scanning Takumoto Kizu Diagram Diagram Tem Koma Toki Y5 Kensho Accent Turtle% Figure 10

Claims (1)

[Claims] Separate scan drive circuits are provided for odd and even lines of scan electrodes of a ferroelectric liquid crystal display device, and one of the odd and even lines among the scan lines is sequentially scanned in the first half of one vertical scan period. , in the second half of the one vertical scanning period, the other of the odd or even lines scanned in the first half of the one vertical scanning period is scanned in the reverse order of the scanning order of the odd or even lines scanned in the first half of the one vertical scanning period. A ferroelectric liquid crystal display device characterized in that it is configured to perform sequential scanning.