JP3441143B2 - Driving method of antiferroelectric liquid crystal display - 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 display such as a liquid crystal display having a liquid crystal layer of a matrix having an antiferroelectric liquid crystal layer and liquid crystal optical shutter arrays. Is.

[0002]

2. Description of the Related Art A liquid crystal display using an antiferroelectric liquid crystal has been reported in Japanese Patent Laid-Open No. 173724/1990, which has a wide viewing angle, a high speed response, and a good multiplex characteristic. Since then, research has been done vigorously.

FIG. 4 is a block diagram showing the structure of an antiferroelectric liquid crystal display. The first polarization axis 43 of the first polarization plate 40 and the second polarization axis 44 of the second polarization plate 41 are aligned so as to be orthogonal to each other, and the first polarization plate 40 and the second polarization plate 41 are aligned.
A liquid crystal cell 42 is placed between the two so that the long axis direction 45 of the antiferroelectric liquid crystal molecules is parallel to the second polarization axis 44 of the second polarizing plate 41 when no voltage is applied, and black is applied when no voltage is applied. However, white is displayed when a voltage is applied.

FIG. 5 is a diagram showing a change in light transmittance (hereinafter referred to as transmittance) when a voltage applied to a liquid crystal pixel of an antiferroelectric liquid crystal display has a pulse having a constant time width. The operation of FIG. 5 will be described below.

First, a voltage value is applied from which a voltage value increases from 0 volt in the positive direction and the transmittance starts to increase. The voltage value is V1, a voltage value at which the increase in the transmittance is saturated is V2, and then the voltage value is reversed. The voltage value at which the transmittance starts to decrease
3. Let V4 be a voltage value at which the decrease in transmittance is saturated.

The voltage value at which the absolute value increases from 0 volt in the negative direction and the transmittance starts to increase is -V.
1. The voltage value at which the increase in the transmittance is saturated is -V2, and then the voltage value at which the absolute value of the voltage starts decreasing from that state on the contrary and the voltage value at which the transmittance starts to decrease is -V3, and the decrease in the transmittance is saturated The voltage value is -V4.

As shown in FIG. 5, the liquid crystal pixel is brought into a ferroelectric state by applying a pulse having a voltage value of V2 for a certain period of time, and is kept in the first ferroelectric state until the voltage value becomes V3.
Further, by applying a pulse having a voltage value of -V2 for a certain period of time, a ferroelectric state is established, and the second ferroelectric state is maintained until the voltage value becomes -V3.

Further, the liquid crystal pixel is brought into an antiferroelectric state by applying a pulse having a voltage value of V4 for a certain period of time, and is kept in the first antiferroelectric state until the voltage value becomes -V1. It can be seen that the application of the pulse having the voltage value of V4 causes the antiferroelectric state, and the second ferroelectric state is maintained until the voltage value becomes V1. In FIG. 5, the first antiferroelectric state and the second antiferroelectric state are collectively shown as an antiferroelectric state.

FIG. 6 is a diagram showing an example of a driving method of a conventional antiferroelectric liquid crystal display. FIG. 6A shows scan electrode-side voltage waveforms applied to the scan electrodes T1, T2, T3, ... The scan electrode-side voltage waveform includes a first scanning period and a second scanning period, and each scanning period is a selection period. And the non-selection period.

The selection period is composed of four phases of the reference clock, and consists of a reset period of three phases and a select pulse of one phase.

FIG. 6C shows a pulse example of two signal electrode side voltage waveforms for four phases in the selection period. The pulses of the two voltage waveforms on the signal electrode side are “low” and “high” in the fourth phase, and the select pulse in the first scanning period is “high” in the voltage waveform on the scanning electrode side shown in FIG. 6A. Therefore, when the voltage waveform on the signal electrode side shown in FIG. 6C is “low”, the ferroelectric state occurs, and the voltage waveform on the signal electrode side is “high”.
At the time of, it becomes an antiferroelectric state.

Since the select pulse in the second scanning period is "low" in the voltage waveform on the scanning electrode side shown in FIG. 6A, when the voltage waveform on the signal electrode side shown in FIG. 6C is "high". The ferroelectric state occurs, and the voltage waveform on the signal electrode side is "low".
At the time of, it becomes an antiferroelectric state. In FIG. 6C, the ferroelectric state is shown as “ON” and the antiferroelectric state is shown as “OFF”.

FIG. 6B shows an example when the signal electrode side voltage waveform is continuously applied, and FIG. 6D shows a combined voltage waveform of the scanning electrode side voltage waveform and the signal electrode side voltage waveform. There is.

As shown in FIG. 6A, the selection period is 4
The scanning electrode-side voltage waveforms are always of the same type and are applied while being sequentially shifted by one selection period for each scanning electrode.

[0015]

In the conventional driving method shown in FIG. 6, a method of sequentially shifting and applying the voltage for one selection period is applied to each scanning electrode. When the number of scan electrodes is increased due to a request, the screen scanning time is proportional to the number of scanning lines, the screen scanning time is increased, and there is a problem that the screen information processing speed is lowered and flicker is increased.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a method of driving an antiferroelectric liquid crystal display for reducing the screen scanning time.

[0017]

In order to achieve the above object, according to the present invention, an antiferroelectric liquid crystal is sandwiched between a pair of glass substrates each having a plurality of scanning electrodes and signal electrodes on opposite surfaces to form a matrix. An antiferroelectric liquid crystal cell having liquid crystal pixels is arranged in two polarizing plates whose polarization axes are orthogonal to each other, and the average long axis direction of the antiferroelectric liquid crystal molecules is one of the polarization axes of the polarizing plate. In the liquid crystal pixel of the anti-ferroelectric liquid crystal display that is sandwiched so as to be in substantially the same direction as, the combined voltage waveform that is the difference between the voltage waveform on the scanning electrode side applied to the scanning electrode and the signal electrode The applied voltage waveform has two periods, that is, a selection period and a non-selection period. During the selection period, a switching pulse for switching liquid crystal molecules to an arbitrary position to set a display state is 1
The existing antiferroelectric liquid crystal display driving method is
A plurality of scan electrodes are divided into several blocks, and a selection period of a certain time is provided in the same time zone in each block, and the scan electrode side voltage waveform is applied to the plurality of scan electrodes in each block during the selection period. It was marked pressure, selected in the selection period
The number of the plurality of scan electrodes plus one is equal to the selection period.
It is characterized in that it is set as the number of phases of the pulse constituted by.

The voltage waveform on the scanning electrode side in the method for driving an anti-ferroelectric liquid crystal display of the present invention comprises a first scanning period and a second scanning period, and the waveforms of the first scanning period and the second scanning period are 0 is symmetric with respect to the bolt, the first scanning period comprises a first selection period and the first non-selection period to select a plurality of scan electrode side voltage waveform, the second scanning period includes a plurality of scan electrodes consists of a second selection period and the second non-selection period to select a side voltage waveform, the first selection period has a first select pulse out of phase, the second selection period wherein the indicia pressure to each of the scanning electrodes a plurality of scan electrode side voltage waveform and a second select pulse out of phase.

Further, the voltage waveform on the scanning electrode side in the driving method for the anti-ferroelectric liquid crystal display of the present invention has a first reset period and a second reset period, and the first reset period is the first scanning period. And a second scanning period, a width of a fixed period is provided immediately before the second select pulse, and a second reset period is immediately before the first select pulse regardless of the first scanning period and the second scanning period. It is characterized in that a certain period of time is provided in the.

[0020]

The waveform of the voltage on the scan electrode side applied to the plurality of scan electrodes is composed of two scan periods. The waveforms of the scan periods are symmetrical with respect to 0 volt, and each scan period is divided into a select period and a non-select period. Has a select pulse during the select period, and also has a reset period for setting the antiferroelectric state immediately before the select pulse, and the plurality of scan electrodes are divided into several blocks, and the block is divided into several blocks. An antiferroelectric liquid crystal display with a high screen information processing speed can be provided by providing a selection period of a certain time for selection and simultaneously applying the scan electrode side voltage waveform to the scan electrodes in each block during the selection period. .

[0021]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 7 is a configuration diagram showing a cell configuration of the liquid crystal display used in the present invention. The liquid crystal display used in the present invention is composed of a pair of glass substrates 73 sandwiching an antiferroelectric liquid crystal layer 76 having a thickness of about 2 μm. Further, an electrode 74 which is a scanning electrode and a signal electrode is formed on the opposite surface of the glass substrate 73, a polymer alignment film 75 is applied on the electrode 74, and a rubbing treatment is performed.

Further, a polarizing plate 71 is provided outside the glass substrate 73.
The polarizing axis of one polarizing plate is made parallel to the long axis direction of the antiferroelectric liquid crystal molecules by rubbing treatment, and the polarizing axis of the other polarizing plate is made long by rubbing treatment. Make it perpendicular to the axial direction.

The concept of the driving method of the antiferroelectric liquid crystal display of the present invention will be described with reference to FIGS. 1, 2 and 3. FIG. 1 is a diagram showing a voltage waveform on the scan electrode side of the present invention.
FIG. 3 is a diagram showing a signal electrode side voltage waveform of the present invention, and FIG. 3 is a diagram showing a combined voltage waveform which is a difference between the scanning electrode side voltage waveform shown in FIG. 1 and the signal electrode side voltage waveform shown in FIG. .

In FIG. 1, a plurality of scan electrodes arranged in a liquid crystal display is divided into several blocks, each block having n scan electrodes, and n scan electrodes in each block. It is a figure which shows the scanning electrode side voltage waveform applied to.

The voltage waveforms on the side of the n scanning electrodes shown in FIG.
The first scanning period 10 includes a first scanning period 10 and a second scanning period 11 in which n voltage waveforms on the scanning electrode side are simultaneously scanned.
0 and the second scanning period 11 are also the first selection period 12 and the first non-selection period 13, the second selection period 16 and the second non-selection period in which n scanning electrode side voltage waveforms are simultaneously selected. 1
It consists of 7.

Further, in the first selection period 12 and the second selection period 16, the first select pulse 14 and the second select pulse 18 having n scanning electrode side voltage waveforms are applied to
Second reset period 19 immediately before the select pulse 14 of
And the first reset period 15 immediately before the second select pulse 18 is the first scanning period 10 and the second scanning period 11
Regardless of this, a fixed period will be provided.

Further, N shown in FIG. 1 is the first selection period 12
And the number of phases that form the second selection period 16 and N
Under the condition of ≧ n, N = n in the present embodiment, and R shown in FIG. 1 constitutes the first reset period 15 and the second reset period 19 for surely making the antiferroelectric state. 1 represents the number of phases to be performed, and t in FIG. 1 represents the time per phase, and the condition is that when the voltage value of V2 shown in FIG. 5 is applied for time t, switching from the antiferroelectric state to the ferroelectric state is performed. To do.

Further, the polarity of the n scanning electrode side voltage waveforms is inverted with respect to 0 volt in the first scanning period 10 and the second scanning period 11, and each scanning electrode side voltage waveform has the same shape and phase. Is a voltage waveform obtained by shifting.

The first reset period 15 and the second reset period 19 are the first scanning period 10 and the second scanning period 1 respectively.
1st select pulse 14 or 2nd
Immediately before the select pulse 18 of
The first reset period 15 of the first scanning period 10 corresponds to the R phase immediately before the second select pulse 18 of the second scanning period 11, the voltage is set to −Vc, and the second scanning period 11 Reset period 19 is the R phase immediately before the first select pulse 14 in the first scanning period 10, and its voltage is V
Set to c.

FIG. 2A shows the first scanning period 10 shown in FIG.
2 shows the voltage waveform on the signal electrode side during the first selection period 12 consisting of N phase numbers in FIG. 1, and the first select pulse 14 of the n voltage waveforms on the scan electrode side in FIG. 2 shows that when the voltage waveform on the signal electrode side is -Vd, it is in a ferroelectric state, and when the voltage waveform on the signal electrode side is Vd, it is in an antiferroelectric state.

FIG. 2B shows the second scanning period 11 shown in FIG.
2 shows the voltage waveform on the signal electrode side during the second selection period 16 consisting of N phase numbers in FIG. 1, and the second select pulse 18 of the voltage waveforms on the n scanning electrode side in FIG. FIG. 2 shows that when the voltage waveform on the signal electrode side is Vd, it is in the ferroelectric state, and when the voltage waveform on the signal electrode side is -Vd, it is in the antiferroelectric state. In Figure 2, the ferroelectric state is "O".
N "and the antiferroelectric state are shown as" OFF ".

FIG. 3 shows a composite voltage waveform which is a difference between the voltage waveform on the scan electrode side in the first selection period 12 shown in FIG. 1 and the example of the voltage waveform on the signal electrode side shown in FIG. It shows how the select pulse 31 in the electrode side voltage waveform changes to the switching pulse 33 in the combined voltage waveform by combining with the signal electrode side voltage waveform.

Va, Vb, Vc, -Va,-shown in FIG.
Vb, -Vc and Vd, -Vd shown in FIG. 2 respectively indicate voltage values, and the setting conditions of each voltage value shown in FIG. 5 are shown below by Va, Vb, Vc shown in FIG. 1 and Vd shown in FIG. Shown in.

The conditions for selecting the antiferroelectric state are as follows. Va-Vd <V1 The conditions for selecting the ferroelectric state are as follows. Va + Vd> V2

The conditions for maintaining the ferroelectric state and the antiferroelectric state selected during the selection period during the non-selection period are as follows. -V1 (V3 is more appropriate) <Vb-Vd <Vb + Vd <
V1 Further, the conditions for resetting from the ferroelectric state to the antiferroelectric state in the reset period are as follows. Vd-Vc <V4 Furthermore, the conditions for not changing from the antiferroelectric state to the ferroelectric state during the reset period are as follows. Vd + Vc <V1 It is assumed that the voltage waveform in the second scanning period has the polarity of the voltage waveform applied in the first scanning period inverted.

As is clear from the above description, it is possible to significantly improve the screen information processing speed by being able to select n select electrodes of the voltage waveform on the scan electrode side in one selection period. .

An example of a specific embodiment will be described with reference to the drawings. FIG. 8 is a waveform diagram showing a scan electrode side voltage waveform and a signal electrode side voltage waveform in the present invention. FIG. 8A shows the voltage waveform on the scan electrode side of the present embodiment. In the drive waveform used in this embodiment, the selection period is set to 2 phases, the time required for 1 phase is set to 70 μs, and the reset period is set to 10
Phase separation, two scanning lines T1 and T2, T3 and T4, T
5 and T6, T7 and T8 ... are selected in the same selection period and 100
The present invention drives an antiferroelectric liquid crystal display having two scanning lines.

FIG. 8C shows a voltage waveform on the signal electrode side during the selection period of this embodiment, and FIG. 8B shows an example when the voltage waveform on the signal electrode side is actually applied. 9 shows a combined voltage waveform of the voltage waveform on the scanning electrode side shown in FIG. 8A and the voltage waveform on the signal electrode side shown in FIG. 8B, and FIG. 10 shows the optical response. From the above, it can be seen that two scanning lines are selected in one selection period. In the conventional driving method, the one-screen writing processing speed is 28 ms, but in the present driving method, writing can be performed in 14 ms.

An example of a more specific embodiment will be described with reference to the drawings. FIG. 11 is a waveform diagram showing a scanning electrode side voltage waveform and a signal electrode side voltage waveform in the present invention. Figure 11
(A) shows the scan electrode side voltage waveform of the present embodiment.
In the drive waveform used in this embodiment, the selection period is set to three phases, the time required for one phase is set to 70 μs, and the reset period is set to 15 phases. The two scanning lines T1, T2, and T
3 and T4, T5 and T6, T7 and T8 ... Are selected in the same selection period to drive an antiferroelectric liquid crystal display having 480 scanning lines.

FIG. 11C shows the signal electrode side voltage waveform during the selection period of this embodiment, and FIG. 11B shows an example when the signal electrode side voltage waveform is actually applied. Figure 1
2 shows the voltage waveform on the scanning electrode side shown in FIG.
A combined voltage waveform with the signal electrode side voltage waveform shown in (b) is shown, and FIG. 13 shows the optical response. From the above, it can be seen that two scanning lines are selected in one selection period. In the conventional driving method, one-screen writing processing speed is about 400 ms, but in the present driving method, writing can be performed in about 200 ms.

In an antiferroelectric liquid crystal display having X scanning lines, one selection period is set to N phases, and n scanning lines are selected in one selection period in two scanning periods having opposite polarities. Set the drive voltage waveform. At this time, if the time required for one phase is t, the time T required to write one screen is given by the following equation. T = 2tNX / n Conventionally, since T = 2tNX, writing can be performed at a speed n times faster.

[0042]

As is apparent from the description of the above embodiment, the present invention provides a selection period for simultaneously selecting a plurality of scan electrode side voltage waveforms, and within the selection period, the scan electrode side voltage waveform If the driving method of the antiferroelectric liquid crystal display in which the select pulse is shifted by at least one phase is adopted, the screen information processing speed can be significantly reduced.

[Brief description of drawings]

FIG. 1 is a waveform diagram showing a structure of a scan electrode side voltage waveform of the present invention.

FIG. 2 is a waveform diagram showing the structure of a signal electrode side voltage waveform of the present invention.

FIG. 3 is a waveform diagram showing a combined voltage waveform of the scan electrode side voltage waveform and the signal electrode side voltage waveform of the present invention.

FIG. 4 is a configuration diagram showing a configuration of an antiferroelectric liquid crystal display.

FIG. 5 is a diagram showing a change in light transmittance when a pulse for changing a voltage is applied to an antiferroelectric liquid crystal pixel.

FIG. 6 is a diagram showing a driving method of a conventional antiferroelectric liquid crystal display.

FIG. 7 is a configuration diagram showing a cell configuration of the antiferroelectric liquid crystal display of the present invention.

FIG. 8 is a waveform diagram showing a scan electrode side voltage waveform and a signal electrode side voltage waveform of the present invention.

FIG. 9 is a waveform diagram showing a composite voltage waveform of the present invention.

FIG. 10 is a diagram showing an optical response of the present invention.

FIG. 11 is a waveform diagram showing a scan electrode side voltage waveform and a signal electrode side voltage waveform of the present invention.

FIG. 12 is a waveform diagram showing a composite voltage waveform of the present invention.

FIG. 13 is a diagram showing an optical response of the present invention.

[Explanation of symbols]

10 First scan period 11 Second scan period 12 First selection period 13 First non-selection period 14 First select pulse 15 First reset period 16 Second selection period 17 Second non-selection period 18 Second select pulse 19 Second reset period

Claims (3)

(57) [Claims] 1. An antiferroelectric liquid crystal cell having a pair of glass substrates, each having a plurality of scanning electrodes and signal electrodes on opposite surfaces, sandwiching the antiferroelectric liquid crystal, and having liquid crystal pixels in a matrix form. Of the antiferroelectric liquid crystal molecule sandwiched between two polarizing plates whose polarization axes are orthogonal to each other so that the average long-axis direction of the antiferroelectric liquid crystal molecules is substantially the same as either polarization axis of the polarizing plates. A composite voltage waveform, which is the difference between the scan electrode side voltage waveform and the signal electrode side voltage waveform applied to the scan electrode and the signal electrode, is applied to the liquid crystal pixel of the liquid crystal display. There are two periods, and a switching pulse for switching liquid crystal molecules to an arbitrary position to set a display state is set to 1 during the selection period.
The existing antiferroelectric liquid crystal display driving method is
A plurality of scan electrodes are divided into several blocks, and a selection period of a certain time is provided in the same time zone in each block, and the scan electrode side voltage waveform is applied to the plurality of scan electrodes in each block during the selection period. It was marked pressure, selected in the selection period
The number of the plurality of scan electrodes plus one is equal to the selection period.
A method for driving an antiferroelectric liquid crystal display, characterized in that it is set as the number of phases of the pulse constituted by . 2. The voltage waveform on the scanning electrode side of the anti-ferroelectric liquid crystal display is composed of a first scanning period and a second scanning period, and the waveforms of the first scanning period and the second scanning period are 0 volt. symmetrical, the first scanning period comprises a first selection period and the first non-selection period to select a plurality of scan electrode side voltage waveform, the second scanning period plurality of scan electrode side voltage waveform
Consists of a second selection period and the second non-selection period to select, in the first selection period has a first select pulse out of phase, the second selection period out of phase Second
Antiferroelectric driving method as claimed in claim 1, wherein the indicia pressurizing a plurality of scan electrode side voltage waveform to each of the scanning electrodes and a select pulse. 3. The scan electrode side voltage waveform of the anti-ferroelectric liquid crystal display has a first reset period and a second reset period, and the first reset period is the first scan period and the second reset period.
A fixed period width is provided immediately before the second select pulse regardless of the scanning period, and the second reset period is a constant period immediately before the first select pulse regardless of the first scanning period and the second scanning period. 2. The method for driving an anti-ferroelectric liquid crystal display according to claim 1, wherein the width is provided.