JPH0695624A - Method for driving anti-ferroelectric liquid crystal panel - Google Patents

Abstract

PURPOSE:To drive it without prolonging a write time by providing an interval when all pixels are made an anti-ferroelectric state simultaneously at every rewrite of the pixel and making a pulse width selecting the non-ferroelectric state equal to the pulse width selecting a ferroelectric state. CONSTITUTION:When a drive waveform selecting an ON state is impressed to respective pixels, since the value of voltage of a first phase in a first frame is 0V, an OFF state (non-ferroelectric state) is reset, and since the voltage of a second phase exceeds a threshold value voltage value switching to the ferroelectric state, the ON state (ferroelectric state) is set. When the drive waveform selecting the OFF state is impressed to respective pixels, since the first phase voltage in a selection period is 0V, the OFF state is reset. Since thereafter no second phase voltage exceeds the threshold value voltage for setting to the ferroelectric state, the OFF state (anti-ferroelectric state) is maintained. At this time, respective pulse widths setting the anti-ferroelectric state, the ferroelectric state are made equal as well, drive is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antiferroelectric liquid crystal panel used for a liquid crystal display panel, a liquid crystal optical shutter array or the like, and more specifically to an antiferroelectric liquid crystal using an antiferroelectric liquid crystal and having pixels in a matrix. Liquid crystal panel driving method.

[0002]

2. Description of the Related Art An antiferroelectric liquid crystal panel is disclosed in Japanese Patent Laid-Open No. 2-1.
Since it was reported in Japanese Patent No. 73724 that the device has a wide viewing angle, that it can respond at high speed, and that it has good multiplex characteristics, it has been actively researched.

The antiferroelectric liquid crystal panel has hysteresis in the transmittance-applied voltage characteristic as shown in FIG. Therefore, when a certain voltage is applied to the antiferroelectric liquid crystal panel, the first stable state (ferroelectric state) is selected and applied when the product of the applied voltage value and its pulse width takes a value equal to or greater than the threshold value. The second stable state (ferroelectric state) is selected depending on the polarity of the voltage, and the third stable state (antiferroelectric state) when the absolute value of the product of the pulse width and the applied voltage value is lower than the threshold value. Is selected. FIG. 4 shows electrodes of an antiferroelectric liquid crystal panel having matrix-shaped pixels. In such an anti-ferroelectric liquid crystal panel, in general, a scanning voltage is sequentially and cyclically applied to the scanning electrodes Y1 to Y128 to generate signal electrodes X1 to X16.
For 0, a time-division drive is adopted in which a predetermined signal voltage is applied in parallel in synchronization with a scanning voltage and liquid crystal molecules of selected pixels are switched according to display information.

Various methods have been proposed as time-division driving methods. FIG. 5 and FIG. 6 are examples of that, in order to write one screen, two frames are written, and the voltage values of the respective waveforms in the first frame and the second frame are symmetrical with respect to the voltage value 0V. As a result, two frames are written to achieve alternating current. FIG. 5 shows the ON state and FIG. 6 shows the changes in the voltage and the pixel transmittance when the OFF state is set. The scan voltage applied to the scan electrodes is 3 as shown in FIGS.
It consists of phases, and is always reset to the OFF state (antiferroelectric state) once in the first phase, holds the state in the first phase in the second phase, and turns to the ON state (ferroelectric state) in the third phase. Select whether to set. In the case of FIG. 5, since the third phase exceeds the threshold voltage for setting the ferroelectric state, it is set to the ON state (ferroelectric state), and in the case of FIG. 6, the threshold voltage is set. The OFF state (the antiferroelectric state) is maintained because it does not exceed

[0005]

One of the problems of the antiferroelectric liquid crystal panel is that the response speed of switching from the antiferroelectric state to the ferroelectric state is higher than that of the ferroelectric state to the antiferroelectric state. The switching response speed may be nearly twice as slow. Therefore, in the conventional driving method, the selection time for setting the antiferroelectric state is set longer than the selection time for setting the ferroelectric state. However, if the number of scan electrodes is increased for this reason, there arises a problem that the writing time for all pixels becomes very long. Therefore, an object of the present invention is to provide a driving method that does not lengthen the writing time of all pixels even when the number of scanning electrodes increases.

[0006]

A method of driving an antiferroelectric liquid crystal panel according to the present invention comprises sandwiching an antiferroelectric liquid crystal between a pair of substrates each having a plurality of scanning electrodes and signal electrodes on opposite surfaces. In a method of driving an antiferroelectric liquid crystal panel having pixels in a matrix, a period is provided in which all pixels are simultaneously placed in an antiferroelectric state each time the pixels are rewritten.

[0007]

According to the present invention, all the pixels are simultaneously set to the antiferroelectric state once every time the pixels are rewritten, and thereafter, writing is performed for each line of each scanning electrode. After that, as the drive waveform sequentially applied to the pixels, a drive waveform in which the selection period for setting the antiferroelectric state and the selection period for setting the ferroelectric state were equal was used. In the driving method of the present invention, since a period for setting all the pixels in the antiferroelectric state at the same time is provided, there are a selection period for setting the antiferroelectric state and a selection period for setting the ferroelectric state. Can be completely set to the antiferroelectric state even if they have the same length. Further, since the writing time for one line of the electrode itself is shortened, the writing time for all pixels can be shortened even if the number of scanning electrodes increases.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view of an antiferroelectric liquid crystal panel used in this example. In this antiferroelectric liquid crystal panel, the antiferroelectric liquid crystal 46 is provided with a pair of substrates 4 so that the layer thickness thereof is about 2 μm.
It is sandwiched by 3. An electrode 44 is formed on the opposite surface of the substrate 43, and an alignment film 45 is provided thereon. Further, the first polarizing plate 41 is provided outside the one substrate 43 so that the polarization axis of the polarizing plate and the alignment treatment direction of the alignment film 45 are parallel to each other, and the first polarizing plate 41 is provided outside the other substrate 43. The second polarizing plate 41 is installed so as to be different from the polarizing axis of the polarizing plate 41 by 90 °.

FIG. 2 shows an example of a drive voltage waveform applied to a pixel. This time, as shown in FIG. 4, an antiferroelectric liquid crystal panel having 128 scanning electrodes and 160 signal electrodes was used. A1 and A128 in FIG. 2 correspond to the pixels A1 and A128 in FIG. In the driving method of the present invention, one selection period is composed of two pulses. Further, one scan is composed of two frames, and the first frame and the second frame have voltage values symmetrical with respect to 0V. When the ON state is displayed, the voltage value of the second phase during the selection period of the first frame is 30V, the voltage value of the second phase during the selection period of the second frame is -30V, and when the OFF state is displayed. The voltage value of the second phase in the selection period of one frame is 26V,
The voltage value of the second phase in the scanning period of the second frame is −26.
The driving was performed at a frame frequency of about 80 ms. Further, this time, two display screens are alternately displayed, and every time the two display screens are switched, a pause period is set to set the voltage value applied to all pixels to 0V as shown in FIG. It was set to 500 μs. Further, this time, the display time of this one screen was set to about 3 seconds, and for this reason, scanning was performed 40 times to display one screen.

When a drive waveform for selecting the ON state is applied to each pixel, the voltage value of the first phase of the first frame is 0V, so that the OFF state (antiferroelectric state) is first reset. , ON after the second phase exceeds the threshold voltage value for switching to the ferroelectric state
The state (ferroelectric state) is set. When a drive waveform for selecting the OFF state is applied to each pixel,
Since the first phase of the selection period is 0V, it is reset to the OFF state first, and the second phase thereafter does not exceed the threshold voltage value for setting the ferroelectric state.
The FF state (antiferroelectric state) is maintained.

In the conventional driving method, if the pulse width for setting the antiferroelectric state is made equal to the pulse width for setting the ferroelectric state, the pixel displaying the ON state is set to the OFF state. When resetting, it is not possible to sufficiently reset from the ferroelectric state to the antiferroelectric state with only the first phase of the selection pulse. However, in the driving method of the present invention, when a new display is performed, the voltage value applied to all pixels is 0.
Since the pause period of V is about 500 μs, all the pixels can be completely reset from the ferroelectric state to the antiferroelectric state during this period. Therefore, even if the pulse width for setting the antiferroelectric state and the pulse width for setting the ferroelectric state are equal, good driving can be performed.

[0012]

According to the driving method of the present invention, every time the pixel is rewritten, a period is provided in which all the pixels are simultaneously placed in the antiferroelectric state. Therefore, the pulse width for selecting the antiferroelectric state and the pulse width for selecting the ferroelectric state can be set to the same length, and even if the number of scan electrodes increases, driving can be performed without significantly increasing the writing time. It can be carried out.

[Brief description of drawings]

FIG. 1 is a sectional view of an antiferroelectric liquid crystal panel used in the present invention.

FIG. 2 is a diagram showing a signal waveform in the driving method of the present invention.

FIG. 3 is a diagram showing a transmittance-applied voltage characteristic of an antiferroelectric liquid crystal panel.

FIG. 4 is a diagram showing electrodes of an antiferroelectric liquid crystal panel.

FIG. 5 is a diagram showing a signal waveform in a conventional driving method.

FIG. 6 is a diagram showing a signal waveform in a conventional driving method.

[Explanation of symbols]

 41 Polarizing plate 43 Substrate 44 Electrode 45 Alignment film 46 Antiferroelectric liquid crystal X1 to X160 Signal electrodes Y1 to Y128 Scanning electrodes A1 and A128 Pixels

Claims (1)

[Claims] 1. A method of driving an anti-ferroelectric liquid crystal panel comprising a pair of substrates, each having a plurality of scanning electrodes and signal electrodes on opposite surfaces, sandwiching an anti-ferroelectric liquid crystal and having pixels in a matrix. 2. A method for driving an anti-ferroelectric liquid crystal panel, wherein every time the pixel is rewritten, a period in which all the pixels are simultaneously placed in the anti-ferroelectric state is provided.