JP3441096B2 - Antiferroelectric liquid crystal panel - Google Patents

Description

Description: 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 or a liquid crystal optical shutter array, and more particularly to an antiferroelectric liquid crystal. The present invention relates to a method for driving an antiferroelectric liquid crystal panel having pixels in a matrix shape. 2. Description of the Related Art An antiferroelectric liquid crystal panel is disclosed in
Since the publication of No. 73724 reports that it has a wide viewing angle, that it can respond at high speed, that it has good multiplex characteristics, etc., it has been energetically studied. An antiferroelectric liquid crystal panel has hysteresis in transmittance-applied voltage characteristics as shown in FIG. For this reason, when a certain voltage is applied to the antiferroelectric liquid crystal panel, the first stable state (ferroelectric state) is selected when the product of the applied voltage value and its pulse width takes a value equal to or greater than a threshold value. A second stable state (ferroelectric state) is selected according to the polarity of the voltage, and a 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 pixels in a matrix. In such an antiferroelectric liquid crystal panel, generally, a scanning voltage is sequentially and periodically applied to the scanning electrodes Y1 to Y128, and the signal electrodes X1 to X16 are applied.
For 0, a time-division driving is adopted in which a predetermined signal voltage is applied in parallel with the scanning voltage in parallel, and the liquid crystal molecules of the selected pixel are switched according to the display information. Various methods have been proposed as a method of time division driving. FIGS. 5 and 6 show an example of this, in which two frames are written in order to write one screen. In the first frame and the second frame, the voltage values of the respective waveforms are symmetrical with respect to the voltage value of 0 V. In this way, AC is achieved by writing two frames. FIG. 5 shows the change of the voltage and the transmittance of the pixel when the ON state is set, and FIG. 6 shows the change when the OFF state is set. The scanning voltage applied to the scanning electrode is 3 as shown in FIGS.
The first phase always resets to the OFF state (anti-ferroelectric state) once in the first phase, the second phase keeps the state in the first phase, and 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. , The OFF state (antiferroelectric state) is maintained. One of the problems of the antiferroelectric liquid crystal panel is that the switching speed from the antiferroelectric state to the ferroelectric state is lower than that of the ferroelectric state. The response speed of switching to a state may be nearly twice as slow. For this reason, in the conventional driving method, the selection time for setting the anti-ferroelectric state is longer than the selection time for setting the ferroelectric state. However, when the number of scanning electrodes is increased for this reason, there has been a problem that the writing time for all the pixels becomes extremely long. Therefore, an object of the present invention is to provide a driving method that does not increase the writing time of all pixels even when the number of scanning electrodes increases. An antiferroelectric liquid crystal panel according to the present invention comprises a pair of substrates each having an electrode on an opposing surface, wherein the antiferroelectric liquid crystal is sandwiched between a plurality of pixels. Has,
When switching frames, the antiferroelectric liquid of all pixels
A pause to simultaneously bring the crystals into the antiferroelectric state,
Processing for writing a display signal and when switching frames
In addition, the display signal whose polarity is inverted without providing a pause period
Function to display by writing the
And features. According to the present invention, every time a pixel is rewritten, all pixels are simultaneously set to the antiferroelectric state once, and thereafter, writing is performed for each scanning electrode line. Thereafter, the drive waveforms sequentially applied to the pixels used were the drive waveforms in which the selection period for setting the antiferroelectric state and the selection period for setting to the ferroelectric state were equal. In the driving method of the present invention, since a period for setting all the pixels to the antiferroelectric state at the same time is provided, a selection period for setting to the antiferroelectric state and a selection period for setting to the ferroelectric state are provided. Can be completely set in the antiferroelectric state even if they have the same length. Also, since the writing time itself for one electrode line is reduced, the writing time for all pixels can be reduced even when the number of scanning electrodes increases. The present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view of the antiferroelectric liquid crystal panel used in the present embodiment. In this antiferroelectric liquid crystal panel, the antiferroelectric liquid crystal 46 is placed on a pair of substrates 4 so that its layer thickness becomes about 2 μm.
3 and is constituted. An electrode 44 is formed on the opposite surface of the substrate 43, and an alignment film 45 is provided thereon. Further, a first polarizing plate 41 is provided outside one of the substrates 43 so that a polarization axis of the polarizing plate and an alignment processing direction of the alignment film 45 are parallel to each other. The second polarizing plate 41 is provided 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. In this case, 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 includes two pulses. One scan is composed of two frames, and the first frame and the second frame have mutually symmetric voltage values with respect to 0V. When displaying the ON state, the voltage value of the second phase in the selection period of the first frame is 30 V, the voltage value of the second phase in the selection period of the second frame is -30 V, and the voltage value of the second phase is -30 V. The voltage value of the second phase in the selection period of one frame is 26 V,
The voltage value of the second phase in the scanning period of the second frame is −26.
V and the frame frequency was about 80 ms. Also, this time, two display screens are alternately displayed, and each time the two display screens are changed, a pause period in which the voltage value applied to all the pixels is 0 V is provided as shown in FIG. 500 μs. This time, the display time of one screen was set to about 3 seconds, and for this purpose, 40 scans were performed to display one screen. When a drive waveform for selecting the ON state is applied to each pixel, the voltage is first reset to the OFF state (antiferroelectric state) because the voltage value of the first phase of the first frame is 0V. ON because the second phase exceeds the threshold voltage value for switching to the ferroelectric state.
Set to the state (ferroelectric state). When a drive waveform for selecting the OFF state is applied to each pixel,
Since the first phase in the selection period is 0 V, the first phase is reset to the OFF state. Since the second phase after that does not exceed the threshold voltage value for setting to the ferroelectric state, O
The FF state (antiferroelectric state) is maintained. In the conventional driving method, if the pulse width for setting the antiferroelectric state is equal to the pulse width for setting the ferroelectric state, the pixel displaying the ON state is turned OFF. When resetting, the ferroelectric state cannot be sufficiently reset to the antiferroelectric state only by the first phase of the selection pulse. However, according to the driving method of the present invention, when a new display is performed, the voltage value applied to all the pixels is zero.
Since there is a rest period of about 500 [mu] s, all pixels can be completely reset from the ferroelectric state to the antiferroelectric state in this period. Therefore, even if the pulse width for setting the antiferroelectric state is equal to the pulse width for setting the ferroelectric state, good driving can be performed. According to the driving method of the present invention, a period in which all the pixels are simultaneously placed in the antiferroelectric state every time the pixels are rewritten is provided. For this reason, 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 driving can be performed without significantly increasing the writing time even when the number of scanning electrodes increases. It can be carried out.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an antiferroelectric liquid crystal panel used in the present invention. FIG. 2 is a diagram showing signal waveforms in a driving method according to 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 signal waveforms in a conventional driving method. FIG. 6 is a diagram showing signal waveforms in a conventional driving method. [Description of Signs] 41 Polarizing plate 43 Substrate 44 Electrode 45 Alignment film 46 Antiferroelectric liquid crystal X1 to X160 Signal electrode Y1 to Y128 Scanning electrode A1, A128 Pixel

Claims (1)

(57) Claims 1. An antiferroelectric liquid crystal panel comprising a plurality of pixels, wherein an antiferroelectric liquid crystal is sandwiched between a pair of substrates each having an electrode on an opposing surface. , When rewriting display contents
, The time of the switching of the frame, to insert a pause period at the same time anti-ferroelectric state antiferroelectric liquid crystal to all the pixels
Write new display signal and rewrite display contents
When no writes upon switching of the frame, without providing the stop period, a display signal polarity inversion this
Antiferroelectric liquid crystal panel having a function of performing display by a.