JP3258110B2 - Driving method of antiferroelectric liquid crystal panel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an antiferroelectric liquid crystal panel such as a liquid crystal display panel having a matrix of pixels and a liquid crystal optical shutter array, using an antiferroelectric liquid crystal as a liquid crystal layer. is there.

[0002]

2. Description of the Related Art A liquid crystal panel using an antiferroelectric liquid crystal,
Japanese Patent Application Laid-Open No. 2 by Nippondenso Co., Ltd. and Showa Shell Sekiyu KK
173724 discloses that it has a wide viewing angle, high-speed response, good multiplex characteristics, etc., and has been vigorously studied.

FIG. 2 is a configuration diagram when an antiferroelectric liquid crystal is used as a display. The liquid crystal cell 22 is placed between the polarizing plates 21a and 21b in accordance with the crossed Nicols so that the polarization axis of one of the polarizing plates and the long axis direction of the molecule when no voltage is applied are parallel. Black and white are displayed when an electric field is applied. In such a cell configuration, when a voltage is applied to the liquid crystal cell, a change in the transmittance with respect to the voltage is plotted on a graph, whereby a hysteresis loop as shown in FIG. 1 can be drawn. The voltage value at which the transmittance starts to change is V1, the voltage value at which the change in the transmittance is saturated is V5, and the voltage value at which the transmittance starts to decrease when the voltage value is reduced is V2. When a reverse voltage is applied and its absolute value is increased, the voltage value at which the transmittance starts to change is V
3. The voltage value at which the transmittance change is saturated is V6, and the voltage value at which the transmittance starts to change when the absolute value of the voltage is reduced is V4. From FIG. 1, the first stable state (ferroelectric state) is selected when a certain pulse wave is applied to the liquid crystal molecules, and when the product of the pulse width and the voltage value exceeds a threshold value. And depending on the polarity of the applied voltage,
A second stable state (ferroelectric state) is selected, and if the absolute value of the product of the pulse width and the voltage value is lower than a certain threshold from the first state and the second state, It can be seen that the stable state (antiferroelectric state) of No. 3 is selected.

Various methods have been proposed as a method of time division driving. FIG. 3 shows an electrode configuration of a matrix type liquid crystal panel including the antiferroelectric liquid crystal. A selection voltage is sequentially and periodically applied to the scan electrodes Y1 to Y128, and a predetermined information signal is applied in parallel to the signal electrodes X1 to X160 in synchronization with the scan electrode signal to display the liquid crystal molecules of the selected pixel. A time-division drive that switches according to information is employed. FIG.
According to the driving method described in No. 724, writing is performed in two scanning periods to write one screen. In the first scanning period and the second scanning period, the voltage values of the respective waveforms are different from each other with respect to the voltage value of 0V. And symmetrical relationship,
We are aiming for exchange. FIG. 4 shows a voltage waveform and a change in transmittance of the pixel when the ON state and the OFF state of the pixel unit A1 in FIG. 3 are set. During the selection period, scan electrode Y
The signal applied to 1 has three phases. In the first phase, the signal is always reset to the OFF state (antiferroelectric state). In the second phase, the state in the first phase is maintained. Select whether to set to ON state (ferroelectric state). Third
If the phase exceeds the threshold voltage for setting the ferroelectric state, it is set to the ON state (ferroelectric state), and if it does not exceed the threshold voltage, the state is OFF (the antiferroelectric state). ) Hold.

Here, the voltage in the non-selection period in the case of the time-division driving is equal to or less than a voltage value V1 at which the transmittance starts to change when the applied voltage is increased in FIG. The voltage value is set to a voltage value V2 or more at which the transmittance changes when reduced.

[0006]

In order to perform the time-division driving satisfactorily, the voltage value on the scanning side is V _C and the voltage value on the signal side is V _{C.
When D} is set, considering the first scanning period described above, | V _C + V _D | ≧ V5 and V2
≦ │V _C −V _D │ ≦ V1. When time-division driving is performed here, since driving is generally performed at V _C > V _D , when a liquid crystal material having a large difference between V 1 and V 5 is used. The range of the value of V _D is considerably limited by the above relational expression.
Therefore, when a liquid crystal material having a large difference between V1 and V5 is used, the voltage setting range is regulated to be very narrow, and it has been difficult to perform good display. Accordingly, the present invention sets the range of the voltage value in the non-selection period wider than the conventional range, so that even a liquid crystal material having a large difference between the voltage values V1 and V5 can easily display good antiferroelectricity. It is an object of the present invention to provide a method for driving a transparent liquid crystal.

[0007]

In order to achieve the above object, according to the driving method of the present invention , the first stable operation is performed during the selection period.
When the voltage for selecting the state is applied to the pixel,
During the period, a voltage value of V2 or less and V3 or more was applied.
Then, the antiferroelectric liquid crystal is changed from the first stable state to the third stable state.
Less than the time required to switch to
Then, a voltage value between V2 and V1 is applied to the pixel again,
The ferroelectric liquid crystal switches from the first stable state to another stable state.
It is characterized in that the signal side voltage waveform is set so as not to cause switching . In the non-selection period, the scanning electrode
The scan-side voltage waveform applied to the
It is preferably constant.

[0008]

In the non-selection period, the three stable states set in the selection period in FIG. 1 must be maintained. For example, in the case of the first stable state, the voltage value applied during the non-selection period is the voltage value V2 of the hysteresis loop.
As described above, it is necessary to make the voltage value V1 or less. In the first stable state, if the voltage value of the pulse wave applied thereafter is between V2 and V3, the third stable state is obtained. If a pulse wave having a voltage value between V1 and V2 is applied within a time sufficiently shorter than the time required for the liquid crystal molecules to return to the third stable state after the pulse wave having the voltage value It has been found that the first stable state does not return to the third stable state. The normal antiferroelectric liquid crystal changes from the first stable state or the second stable state to the third stable state longer than the time required for switching from the third stable state to the first stable state or the second stable state. Since the switching time is longer, the pulse width of one pulse applied at the time of non-selection is short enough to switch from the first stable state to the third stable state.

From the above, conventionally, for example, when the first stable state is selected, the range of the voltage value applied at the time of non-selection must be not less than V2 and not more than V1. Although narrow, in the concept of the present invention, the lower limit range of the voltage value applied at the time of non-selection may be set to V2 or less and V3 or more, so that the voltage value range can be widened. For example, in FIG. 1, | V1−V2 | ≧ | V2
−V4 |, when the OFF set voltage at the time of non-selection of the scanning side voltage is set to V2, the upper limit voltage value of the pulse wave in the non-selection period can be increased to V1, and the lower limit voltage value is The value of V2− (V1−V2) can be obtained, and the width of the signal side voltage can be increased as compared with the related art.

In time-division driving, the smaller the difference between the absolute value of the selection pulse applied during the selection period of the scanning-side voltage waveform and the absolute value of the signal-side voltage waveform, the smaller the difference between the pixel and the ON state when selecting the ON state. When the OFF state is selected, the difference between the voltage of the pulse wave applied to the pixel and the voltage value of the pulse wave applied to the pixel can be increased, making it easy to drive a liquid crystal material in which the rise and fall of the hysteresis loop is not very steep. You can do it. For this reason, it is preferable that the absolute value of the signal side voltage is as large as possible to perform good driving. As described above, in the present invention, since the absolute value of the signal-side voltage can be made larger than that in the related art, good display can be easily performed on many liquid crystal materials.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 6 is a cell configuration diagram of the liquid crystal panel used in this embodiment. The liquid crystal panel used in this embodiment is a pair of glass substrates 63 having an antiferroelectric liquid crystal layer 66 having a thickness of about 2 μm.
a and 63b. Electrodes 64a and 64b are formed on the opposite surface of the glass substrate, and polymer alignment films 65a and 65b are applied thereon, and a rubbing process is performed. Further, a first polarizing plate 61a is provided outside the one glass substrate so that the polarizing axis of the polarizing plate and the rubbing axis are parallel to each other, and the first polarizing plate 61a is provided outside the other glass substrate. The second polarizing plate 61b is installed so as to be different from the polarization axis of the second polarizing plate by 90 °.

When the antiferroelectric liquid crystal used in the present invention has a hysteresis loop as shown in FIG.
V2 = 4V, V3 = -18V, V4 = -4V, V5 = 3
0V, V6 = -30V. FIG. 5 shows a driving waveform in the present invention when the antiferroelectric liquid crystal is used.
The driving waveform is composed of two scanning periods, and one selection period is composed of four pulses. The first scanning period and the second scanning period have voltage values symmetric with respect to 0V. Each pulse width is 100 μs, the first to third phases in the selection period of the first scanning period applied to the scanning electrodes are 0 V,
A voltage waveform of 30 V is applied at the phase and an OFF set voltage of 4.5 V is applied during the remaining non-selection period. The voltage values of the first to third phases during the selection period of the second scanning period are 0 V, and
In the case of the phase, a voltage waveform of −30 V is applied and the OFF set voltage of the remaining non-selection period is −4.5 V. On the signal electrode side, the first phase from the first phase in the ON state in synchronization with the scanning electrode side is 0V, the third phase is 12V, and the fourth phase is 12V.
A voltage waveform having a phase of -12 V is applied. In the OFF state, the first phase and the second phase are 0 V, and the third phase is -12.
For the V and fourth phases, a voltage waveform of 12 V is applied. Driving was performed with a frame frequency of about 60 ms. As a result, the signal-side voltage value can be set higher than in the prior art, and the OFF-set voltage value when the scanning-side voltage is not selected can be set lower, so that good display can be performed.

[0013]

In the antiferroelectric liquid crystal display,
By using the driving method of the present invention, good display can be easily performed without contributing to the characteristics of the antiferroelectric liquid crystal material used.

[Brief description of the drawings]

FIG. 1 is a diagram showing a hysteresis curve showing characteristics of an antiferroelectric liquid crystal.

FIG. 2 is a configuration diagram of an antiferroelectric liquid crystal panel and a polarizing plate according to the present invention.

FIG. 3 is a diagram showing an electrode structure of the antiferroelectric liquid crystal panel of the present invention.

FIG. 4 is a diagram showing a conventional driving method.

FIG. 5 is a diagram showing a driving method used in the present invention.

FIG. 6 is a diagram showing a cell configuration of the antiferroelectric liquid crystal panel of the present invention.

[Explanation of symbols]

 21a, 21b Polarizing plate 22 Liquid crystal cell 61a, 61b Polarizing plate 62a, 62b Sealing material 63a, 63b Glass substrate 64a, 64b Electrode 65a, 65b Polymer alignment film 66 Antiferroelectric liquid crystal X1 to X160 Signal electrode Y1 to Y128 Scanning electrode A1 to A128 pixel section

Claims (2)

(57) [Claims] 1. A method of driving an antiferroelectric liquid crystal panel having pixels by sandwiching an antiferroelectric liquid crystal between a pair of substrates having a scanning electrode and a signal electrode, wherein the antiferroelectric liquid crystal is Voltage
And a first stable state in which a ferroelectric state is
A second stable state that becomes a ferroelectric state by applying a voltage of
A third stable state that is an antiferroelectric state, wherein the pixel
V1 is the voltage value at which the transmittance of the pixel starts to increase by increasing the voltage value applied to the pixel, and V2 is the voltage value at which the transmittance is saturated and the voltage value begins to decrease by decreasing the voltage value.
Transmittance begins to increase by increasing the absolute value of the
A scanning period in which a voltage value is V3 and a voltage is applied to the pixel
Has a selection period and a non-selection period, and in the selection period
The first stable state is selected for the antiferroelectric liquid crystal.
In the non-selection period, V2 or less and V3 or more are applied to the pixel.
Anti-ferroelectric liquid crystal is in the first stable state
Less than the time required to return from state to the third stable state
Within a short time, a voltage value of V1 or less and V2 or more is applied,
The ferroelectric liquid crystal switches from the first stable state to another stable state.
The signal during the non-selection period to prevent switching.
The feature is to set the signal side voltage waveform applied to the signal electrode
Driving method of antiferroelectric liquid crystal panel. 2. The method according to claim 1, wherein the scanning electrode is marked during the non-selection period.
The applied scan-side voltage waveform is constant as the offset voltage value
The antiferroelectric liquid according to claim 1, wherein
Driving method of crystal panel.