JPS63138316A - Liquid crystal display method - Google Patents

Abstract

PURPOSE:To simultaneously perform writing and erasure and to rewrite one image plane in a time which is about a half as long as usual by setting a pulse voltage which is larger in absolute value than a normal driving voltage as an erasing voltage. CONSTITUTION:Even if a larger voltage is impressed, the same stable state of storage with the impression of a saturation voltage having the same polarity is obtained and the property of no influence upon the stable state of the storage performance is utilized; and an erasure scanning signal with a voltage higher than the sum of image signal voltages of the saturation voltage is impressed to optional scanning electrodes other than a scanning electrode applied with a writing scanning signal at the same timing so as to turn off an all-picture- element display on a specific number of scanning signal forcibly regardless of an image signal impressed to the image electrode, thereby making an erasure scan simultaneously with a write scan. Consequently, deterioration in picture quality is prevented and a fast image display is made.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a liquid crystal display method using a large-sized, large-capacity, and fast-response ferroelectric liquid crystal that is highly useful as an advanced information processing terminal such as an OAI device. It is something.

(Prior art and its problems) Smectic liquid crystals, which have ferroelectricity, exhibit high-speed response and memory properties, and can be controlled by electric fields, have been proposed as liquid crystals with characteristics different from nematic liquid crystals and cholesteric liquid crystals (N ,A,C1ark S,T,La
gerwall; Appl.

Phys, Lett, 36, 899 (1980))
.

Of the smectic liquid crystals, chiral smectic C phase and chiral smectic H phase are known as this liquid crystal.

By sandwiching the liquid crystal between two polarizing plates and changing the applied electric field, the birefringence changes and light modulation occurs, the so-called DAP effect. A display device is possible using the so-called guest-host method, in which light modulation occurs by utilizing the difference in light absorption rate depending on the direction of the light.

Currently, two types of XY matrix type display driving methods for ferroelectric liquid crystal elements have been proposed.

The first method is to use a liquid crystal display (as shown in Figure 3).
2) When displaying the pattern shown in the figure above, first scan electrode χ1. X2. For scanning signals xi, x2 . x3, and Yl, Y2 . of the display electrode (6). One image signal yl, y2 . Let them each input y3. In this way, the timings of the pixel erase pulse b and the write pulse b of the scanning signal are set to xi, x2, . x3 are sequentially shifted by one pixel scanning time T, and do not overlap. Note that the voltage of the scanning signal varies between 1/2v. Here (Xl.

Looking at pixel A of Yl), the overlapping of the xi-fold signal and the y1 signal during 1 hour T is added, and the signal A becomes a composite potential pulse A, which changes from the unchanged state at O-1/2T. , it becomes black with one voltage at 1/2-3/4T, and finally becomes white with 10V between 3/4-T, and after that until T-37, it exceeds +V which is the color change voltage. Because there is no color, it remains white forever without changing from white.

This becomes white when a saturation potential of +V or more is applied.

This is because the color changes to black below -■, and during that time, the color does not change and the previous state is maintained.

The second method is to first scan the scanning electrode
I, X2. For scanning signals xi, x2 . x3 erase signals are simultaneously applied during one pixel scanning time T, and Yl, Y2 . For Y3, one image signal yt, y2 . A predetermined isomorphic pulse of y3 is generated to set the entire pixel to white. That is, if we look at pixel A of (Xi, Yl), the combination of the signals of Xl and yl between T is as shown in signal A.

This is because a white voltage of +V is applied between 1/2T and T.

Then, a black signal is sequentially output to only the pixel portions forming the boundary for display.

In other words, the scanning lines are grouped into several lines and all are darkened.
Apply a signal (or an ON signal that turns all bright), then apply an ON signal (or an OFF signal) to the necessary pixels for each individual scan line.
signal) is applied to turn ON10FF.

However, in the case of large-sized, high-capacity displays, the former driving method requires a long time to rewrite the scanning lines (and cannot rewrite the entire screen at high speed. Although it is possible to shorten the rewriting time by increasing the number of scan lines to be erased, many scan lines are left undisplayed, resulting in a decrease in display quality.Display quality decreases with large, high-capacity, and high-speed displays. There is a growing demand for a liquid crystal display device that uses a practical driving method that does not require the use of conventional methods.

(Object of the Invention) The present invention has been made in view of the current situation as described above, and provides a liquid crystal display method that can prevent deterioration of image quality and display high-speed images in a ferroelectric liquid crystal display device exhibiting memory properties. It is intended to provide.

(Structure of the Invention) For this purpose, the present invention provides a matrix in which a ferroelectric liquid crystal is sandwiched between two transparent electrode substrates each having a scanning electrode group on one side facing each other and a signal electrode group on the other side. In a liquid crystal display method that uses a scanning signal and an image signal to display a liquid crystal display in which cells with a pixel structure are placed between two polarizing plates, all of the signals on a predetermined number of scanning signals are An erase scan signal with a voltage higher than the sum of the saturation voltage and the image signal voltage is applied at the same timing to any scan electrode other than the scan electrode to which the write scan signal is applied, in order to forcibly set the pixel display to the OFF state. In addition, the present invention provides a liquid crystal display method characterized in that erasing scanning is performed simultaneously with writing scanning.

(Action of the Invention) The present invention utilizes the following properties of a ferroelectric liquid crystal cell exhibiting memory properties.

The direction of the electric field that becomes bright when a sufficiently large voltage is applied to the liquid crystal cell is defined as positive, and the direction that becomes dark is defined as negative. The initial state is defined as a dark state by applying a sufficiently large negative voltage to the cell for a long time. Figure 5-A and Figure 5- Shown in B. Initial state B (fifth state) immediately after voltage application
When a positive pulse is applied to Figure 8), there is a dead zone from 0 to Vc. A clear response change gradually occurs from a voltage higher than Vc, and the change reaches saturation at vth. Conversely, it does not respond to negative voltage pulses from 0 to -Vm2, but -
From V m2 to 7 V th, the light becomes darker than the initial state.

After 1 second of voltage application (FIG. 5-B), if a positive pulse is applied to the initial state, the initial state is maintained between 0 and +Vml. From +Vml to +Vm2, the light gradually becomes brighter and the change reaches saturation at +Vm2. Furthermore, there is no change at all for negative voltages.

In this way, even if a larger voltage is applied, the present invention
The stable state of memory property is the same as when a saturation voltage of the same polarity is applied, and the property of not affecting the stable state of memory property is utilized. As described later, the present invention has a saturation voltage (referred to as ■ in this specification).
This invention relates to a display method that rewrites the display using a combination of three signals: an erase signal that is sufficiently larger, a write signal that is slightly larger than the saturation voltage, and a non-selection signal that is kept low enough not to cause inversion of the memory state.

(Example) To explain in more detail based on an example, the present method includes a liquid crystal panel section (2), as shown in the block diagram of FIG.
It is executed by a device consisting of a drive circuit section (15), a control circuit section (12), and a part of image data (10). This device takes part of the image data into a control circuit, and outputs an image signal y whose phase is changed by a drive circuit according to ON/OFF of the display, and an erase scanning signal (b) according to the scanning order. This is a device that displays by applying a write scanning signal (a) to a liquid crystal panel section in synchronization with an image signal. When the electrodes on the upper and lower glass substrates, which are opposite and orthogonal to each other in the XY matrix shown in FIG.
), the following three types of signals are set.

10 A write signal (a) that changes a specific pixel from bright to dark or from dark to bright in combination with an image signal (y) sent to the display electrode (Y).

ii) large enough to return all pixels on a particular scanning electrode (X) to the desired stable initial state without being affected by the image signal (y) flowing through the 111 display electrode). erasure signal (b). The absolute value of the voltage of the erase signal (b) needs to be larger than the sum of the voltage of the image signal (y) and the absolute value of the saturation voltage (2) of the memory property of the liquid crystal.

Regardless of the image signal (y) flowing to the ij1 display electrode (Y), the non-selection signal (c) has a size that does not destroy the memory state of each pixel on the scanning electrode (X).
.

By matrix driving of the three scanning signals and the image signal (y), this display method is a driving method that allows writing, erasing, and memory holding operations for pixels on each scanning electrode at the same time if they are not on the same scanning electrode.

That is, when displaying as shown on the liquid crystal display (2), during the first one pixel scanning time T, Xl becomes an erase signal, x2 becomes a non-selection signal c, x3 becomes a write signal a pulse, A manual force is applied to each scanning electrode. In this way, the write signal and the erase signal are input simultaneously during the scanning time of one pixel.

The voltage of the erase signal according to the present invention is 3/2V, which is 1/2V higher than the saturation voltage (2).

And yl, y2. with a voltage ratio of 1/2. The image signal shown at y3 is Yl of the display electrode (6).

Y2. When input to Y3, the display of the pixel changes depending on the state of the combined voltage of the scanning signal and one image signal.

For example, regarding pixel A, the scanning signal xl and the image signal yl are input for one pixel time period of 0-T, and a composite potential pulse shown as pulse A is obtained. In other words, in O-T.

It changes to white, remains white at T-2T, and continues to be white because it does not reach the saturation potential (2) at 2T-3T. On the other hand, regarding image B, in the same way, at 0-T it is white, at T-2T it is black, and at 2T-3T it does not reach the saturation voltage +■, so black is maintained after all.

In this way, the display pattern of the liquid crystal shown in the figure can be changed.

In addition, in the non-selection signal sent to the scanning electrode (X), in order to increase the voltage ratio of (combined voltage of non-selected scanning signal and image signal) to (combined voltage of selected scanning signal and image signal), As shown in FIG. 6, it is also effective to improve image quality by setting the voltage of the selection scanning signal to a signal waveform (q) larger than the voltage of the image signal. Further, adding a low voltage signal waveform having a phase opposite to that of the selected scanning signal as the non-selected scanning signal is also effective in improving image quality.

The method of arbitrarily setting the display state between bright and dark, as explained in Fig. 5, is to set the display state between bright and dark not only by changing the voltage from Vm2 to Vml, but also by changing the pulse width of the applied pulse. It can be set arbitrarily. Therefore, the image signal (y) sent to the display electrode (Y) is not binarized into the bright signal (d) and dark signal (e) shown in Fig. 1, but continuously as shown in the image signal (y) shown in Fig. 7. It is also possible to continuously change the amount of light transmitted by changing the amount of light.

Additionally, to prevent deterioration of the liquid crystal, a bipolar signal with no direct current component is normally applied to each electrode, but this does not mean that display cannot be performed without applying a voltage of opposite polarity to convert it to alternating current. The present invention is not limited to this. For example, it is also possible to apply a signal as shown in FIG. 8 with the method of the invention.

(Effect) Utilizing the property of ferroelectric liquid crystal cells that no matter what voltage is applied above the saturation voltage and below the decomposition voltage, the display state does not change in any way from the display state when the saturation voltage is applied, the absolute By setting a pulse voltage with a large value as the erase voltage, until now it was necessary to erase and write at separate times within the -scanning time, but now it is possible to write and erase at the same time unless they are on the same scanning line. Compared to the former method, one screen can be rewritten in up to half the time, and a liquid crystal display method with high image quality can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of waveforms and a liquid crystal display showing one embodiment of the present invention, Fig. 2 is a block diagram showing an apparatus for carrying out the invention, and Figs. 3 and 4 are conventional ferroelectric An explanatory diagram showing a method of driving a liquid crystal cell, FIG. 5 is an explanatory diagram of a graph showing the relationship between applied voltage and light transmittance of a ferroelectric liquid crystal cell, and FIG. 6 is an example of a liquid crystal driving waveform according to the present invention. FIG. 7 is a schematic explanatory diagram showing an example of a liquid crystal drive waveform capable of displaying gradations according to the present invention. FIG. 8 is an example of a drive waveform including a DC component according to the present invention. FIG. (2)...Liquid crystal display (4)...Scanning electrode (6)...Display electrode (10)...Image data section (12)...Control i'i'J circuit Part (14)...
・Drive circuit section

Claims (2)

[Claims] (1) A cell with a matrix pixel structure consisting of a ferroelectric liquid crystal sandwiched between two transparent electrode substrates with a scanning electrode group on one side and a signal electrode group on the other side facing each other is polarized. In a liquid crystal display method that uses a scanning signal and an image signal to display a liquid crystal that is installed between plates, all pixel displays on a predetermined number of scanning signals are forcibly turned off regardless of the image signal being applied to the image electrode.
By applying an erase scan signal with a voltage higher than the sum of the saturation voltage and the image signal voltage to any scan electrode other than the scan electrode to which the write scan signal is being applied at the same timing to specify the state, write scan and A liquid crystal display method characterized by simultaneously performing erasure scanning. (2) The liquid crystal display method according to claim 1, wherein the write scanning signal in the liquid crystal display is applied to the scanning electrodes that have already been erased by the erasing scanning signal.