JPH09218387A - Driving method for liquid crystal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the driving method for the liquid crystal display element which can reduce the power consumption, provides high picture quality, and enables high-speed driving. SOLUTION: When liquid crystal charged between substrates is driven, an effective voltage at nonselection time is suppressed by providing a voltage nonapplication part Td for an information signal applied to an information signal electrode group formed in matrix on the substrate. Further, this voltage nonapplication part Tb is provided between an information pulse of the information signal and averaged pulses P2 and P2 which have the opposite polarity from the information pulse P1 and reduce the voltage mean of the information signal to 0, and made wider than the pulse width Td of the information pulse P1 to shorten a one-line selection period.

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 a liquid crystal element, and more particularly to a method for driving a liquid crystal element by multiplexing driving.

[0002]

2. Description of the Related Art Conventionally, a liquid crystal device having a structure in which a chiral smectic liquid crystal which is a ferroelectric liquid crystal is filled between a pair of substrates in which an information signal electrode group and a scanning signal electrode group are formed in a matrix. There is a voltage modulation method as an example of a method of driving such a liquid crystal element.

Here, in this voltage modulation method, the scanning write pulse Pw shown in (1) of FIG. 10 is applied to the scanning signal electrode group, and the information on signal or the information off signal shown in (2) is applied to the information signal electrode group. By selectively applying to each of the pixels, the on-composite waveform or off-composite waveform shown in (3) is applied to a large number of pixels forming a display screen, and whether or not these combined waveforms exceed a threshold value is applied to each pixel. Writing or non-writing is decided.

On the other hand, FIG. 11 is a diagram showing a specific scanning waveform and the like in this voltage modulation method. The scanning signal shown in (1) of FIG. 11 is applied to each scanning signal electrode of the sequential scanning signal electrode group, By applying the information ON signal or the information OFF signal shown in (2) to the information signal electrode group in synchronization with the scanning signal, the ON or OFF combined waveform shown in (3) is applied to the pixel. When the value exceeds the threshold value, writing to the pixel is performed.

The scanning signal shown in (1) of FIG.
The erasing pulse Pe is applied prior to the scanning write pulse Pw.
After erasing in one direction, whether to write in the other direction is determined by the scan write pulse Pw. And
Multiplexing this write waveform enables nxm simple matrix drive.

[0006]

By the way, in such a conventional liquid crystal element driving method, the driving margin is determined according to the voltage ratio of the write pulse of the composite waveform. Therefore, in order to increase the drive margin, the voltage value of the information signal, specifically, the information pulse P1 indicating ON or OFF information in the information ON signal and the information OFF signal as shown in (2) of FIG. 11, for example. The voltage value of is relatively increased with respect to the scanning signal to increase the ratio of the ON waveform and the OFF waveform.

However, when the voltage value of the information signal is increased in this way, the effective value of the voltage in the non-selected state increases, so that the power consumption increases and the contrast decreases due to the fluctuation of the optical level due to the non-selected signal. There was a problem.

On the other hand, in the conventional drive waveform, (2) in FIG.
As shown in FIG. 5, an averaging pulse Pa having a polarity opposite to that of the information pulse P1 is provided to make the voltage average of the information signal zero. However, when the averaging pulse Pa is provided in this way, the pulse width of the averaging pulse Pa is the information pulse P1.
Since it is the same as the pulse width of 1), the writing time for one line is almost twice as long as the switching time, and there is a problem that high speed driving of the liquid crystal element is difficult.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide a driving method of a liquid crystal element capable of reducing power consumption, realizing high image quality, and driving at high speed. It is intended.

[0010]

SUMMARY OF THE INVENTION The present invention is a liquid crystal in which a liquid crystal filled between a pair of substrates is driven by an information signal and a scanning signal selectively applied to an information signal electrode group and a scanning signal electrode group. In the device driving method, a write pulse and a dividing pulse for dividing the write pulse are formed in the scan signal, and the information signal has an information pulse and a polarity opposite to that of the information pulse. While forming an averaging pulse having a voltage average of 0 and a voltage non-applied portion, the information pulse has the same pulse width as that of the dividing pulse, and the voltage non-applied portion,
It is characterized in that it is wider than the pulse width of the information pulse.

The present invention is also characterized in that the voltage non-applied portion is provided between the information pulse and the averaging pulse.

The present invention is also characterized in that the averaging pulse is provided before and after the information pulse.

The present invention is also characterized in that a plurality of the dividing pulses are provided.

The present invention is also characterized in that the scanning signal has an erase pulse.

Further, the present invention is characterized in that the pulse crest value of the information signal is larger than the pulse crest value of the divided pulse.

Further, the present invention is characterized in that the liquid crystal is a chiral smectic liquid crystal which is a ferroelectric liquid crystal.

Further, the present invention is characterized in that the liquid crystal is a chiral smectic liquid crystal which is an antiferroelectric liquid crystal.

Further, the present invention is characterized in that the information signal electrode group and the scanning signal electrode group are formed in a matrix on the substrate.

With this structure, when the liquid crystal filled between the substrates is driven, no voltage is applied to the information signal applied to the information signal electrode group formed in a matrix on the substrate. By providing, the effective voltage at the time of non-selection is suppressed. In addition, the non-voltage applied portion is provided between the information pulse of the information signal and the averaging pulse which has a polarity opposite to that of the information pulse and sets the voltage average of the information signal to 0. By increasing the width, one line selection time is shortened.

Further, by making the pulse width of the information pulse the same as the pulse width of the dividing pulse for dividing the writing pulse of the scanning signal, the dividing effect can be made effective. Further, the drive margin can be increased by making the pulse crest value of the information signal larger than the pulse crest value of the divided pulse.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a liquid crystal display circuit to which a method for driving a liquid crystal element according to the present invention is applied. In FIG. 1, 1 is a video RAM (VRAM) for storing image information.
2 is a graphic controller having image display data D1 from the graphic controller 1 to the drive control circuit 3 in accordance with the transfer clock CL.

On the other hand, the image display data D1 from the graphic controller 1 is input to the scanning signal control circuit 4 and the information signal circuit 5 of the drive control circuit 3 so as to be converted into address data D2 and display data D3, respectively. Has become.

Then, according to the address data D2 and the display data D3, the scanning signal driver 6 and the information signal driver 7 are formed in a matrix of the display portion 9 of the liquid crystal element 8, and the information signal electrode group 10 and the scanning signal electrode group are formed. 11, the scanning signal waveform shown in FIG. 2A and the information signal waveform shown in FIG. 2B are sequentially output. In addition, each drive voltage V is the drive voltage generation circuit 12
Generated by

By the way, in this embodiment, an element using a chiral smectic liquid crystal exhibiting ferroelectricity or antiferroelectricity is used as the display element 8. The display element 8 has, for example, as shown in FIG. 3, an information signal electrode group 10 and a scanning signal electrode group 11, and is filled with a strong force between the polarizing plate 81, the glass substrate 82, and the glass substrates 82, 82. It is composed of a chiral smectic liquid crystal 83 which is a dielectric liquid crystal, a retardation plate 84, a pixel electrode 85 and the like.

The main physical property values of an example of the liquid crystal 83 used in this ferroelectric liquid crystal panel are as follows.

Spontaneous polarization 7 nC / cm 2 (30 ° C.) Tilt angle 15 deg Phase transition temperature −10 ° C. SmC * 65 ° C. SmA 80 ° C. Ch 95 ° C. ISO Also, the liquid crystal panel specifications are 1024 × l280 pixels,
230um pitch and effective pixel area is diagonal 1
4.8 inches, the pixel configuration is 16 colors / pixel, the frame frequency is 15 Hz, and there is no interlace.

On the other hand, the ferroelectric liquid crystal 83 is switched in response to the polarity of the applied pulse, but this switching operation is promoted if the same polarity pulse continues, and the reverse polarity pulse is applied. Then it will be blocked. Therefore, when promoting switching,
For example, when switching from OFF to ON, pulses having the same polarity are continuously applied, and when blocking is to be applied, for example, when OFF is maintained, pulses of opposite polarity may be applied.

Therefore, in the present embodiment, as shown in (1) of FIG. 2, the scanning write pulse Pw is divided by the dividing pulse Ps, and the scanning write pulse Pw is thus divided.
By dividing w, it is possible to continuously apply pulses having the same polarity, such as the on-composition waveform and the off-composition waveform shown in (3), or to apply pulses of opposite polarity. .

Since the scan write pulse Pw divided in this way is sequentially applied to each scan signal electrode of the scan signal electrode group 11, in the present embodiment, the scan signal control circuit 4 is applied as shown in FIG. A write pulse generator 41 that generates the scan write pulse Pw, a divided pulse generator 42 that generates the divided pulse Ps, and a write pulse generator 41 that divides the scan write pulse Pw in the central portion.
And a control section 43 for controlling the pulse generation operation of the divided pulse generation section 42. The control unit 43 may be provided outside the scanning signal control circuit 4.

On the other hand, the information signal applied to one line 10a (see FIG. 1) of the information signal electrode group 10 in synchronization with this scanning signal is the information pulse P as shown in (2) of FIG.
1 and an averaging pulse P2 having a polarity opposite to that of the information pulse P1 provided before and after the information pulse P1. A voltage non-applied portion Tb is provided between the information pulse P1 and the averaging pulse P2.

Here, the pulse width T of this information pulse P1
d has the same size as the pulse width Ts of the division pulse Ps, and thus the division effect of the scan write pulse Pw can be effectively used. Also, the averaging pulse P
The pulse width Ta of 2 is 1/2 of the pulse width Td of the information pulse P1, and thus the voltage average during one line selection period can be made zero.

Further, the voltage-unapplied portion Tb is made wider than the pulse width Td of the information pulse P1, whereby the effective voltage in the non-selected state can be lowered. Then, by lowering the effective voltage in this way, optical fluctuations at the time of non-selection are reduced, contrast and brightness are improved, and crosstalk is reduced, so that an image can be improved.

FIG. 5 is a diagram showing drive waveforms according to the first example of the present embodiment having the scan write pulse and the information pulse having the above-mentioned configuration. (1) in the figure shows the scan signal. Shows. Note that this driving method is a method of writing information after erasing information by the erasing pulse Pe for each common line. By erasing information before writing information in this way, writing in two states becomes possible. ing.

By the way, in (1), ΔT represents the pulse width of the scanning write pulse Pw, and Vw represents the pulse crest value thereof. Here, the pulse crest value Vs (0 V in FIG. 5) of the divided pulse Pw is smaller than the pulse crest value Vw of the scan write pulse Pw,
As a result, even when the information-on signal as shown in (2) is applied, the polarity does not change in the on-synthesis waveform shown in (3).

By preventing the polarity from changing in the ON combined waveform in this way, the same polarity pulse can be continuously applied to the pixel selected (selected) for the switching operation, The switching operation can be promoted. Further, when the off-synthesis signal shown in (2) is applied, the reverse-polarity pulse Pr is included in the off-synthesis waveform, so that the switching operation of the unselected pixel is strongly hindered.

On the other hand, in the scan signal, the pulse width Ts of the dividing pulse Ps is 1/8 of the pulse width ΔT of the scan write pulse Pw. The ratio may be changed according to the characteristics of the liquid crystal. In the information-on signal and the information-off signal, the pulse width Td of the information pulse P1 is 1 with respect to the pulse width ΔT of the write pulse Pw.
/ 8, and the pulse width Ta of the averaging pulse P2 is 1/1
6. The voltage-unapplied portion Tb is 7/16 of the write pulse width.

Then, in this way, the voltage-unapplied portion Tb
Is set to 7/16 of the write pulse width, as shown in (1) of FIG. 6, a scanning signal is sequentially applied to the three lines 11a, 11b, 11c of the scanning signal electrode group 11 shown in FIG. When the information signal shown in (2) is applied to one line 10a of the information signal electrode group 10 shown in FIG. 1, the effective value of the voltage in the non-selected period becomes small in the composite waveform shown in (3).

Further, the pulse width Td of the information pulse P1 is
Since it can be made shorter than the pulse width Td ′ of the conventional information pulse P1 (see (2) of FIG. 11), the one-line selection time H can be shortened and the driving speed can be increased.

When the liquid crystal element 8 is driven by the drive signal thus configured, for example, the one-line selection period H is 60 μsec, the segment voltage is ± 6 V, and the common voltage is ± 15 V. Excellent image quality was obtained. Also, the contrast ratio of black and white at this time is 110.
Met.

On the other hand, as a comparative example, when the contrast in the case of using the waveform of FIG. 11 was measured under the same conditions such as the one-line selection period, the white and black contrast ratio at this time was 60.

In this way, the scanning write pulse Pw is divided by the dividing pulse Ps, and the dividing pulse Ps is also divided.
By making the pulse width Ts of the same and the pulse width Td of the information signal pulse P1 the same, a high image quality with high contrast can be obtained. Further, by providing the voltage non-applied portion Tb, the effective voltage value at the time of non-selection can be suppressed, power consumption can be reduced, and optical fluctuation at the time of non-selection can be reduced.

By the way, FIG. 7 shows a drive waveform according to a second example of the present embodiment, and (1) shows an erase pulse P.
The scan signal does not have e and has the scan write pulse Pw for writing the respective states of the positive polarity and the negative polarity, (2) shows the information signal of the above-described configuration, and (3) shows The composite waveform is shown.

Then, under the same conditions as those of the first embodiment described above, when the liquid crystal element 8 was driven by using such a waveform, a good image quality was obtained. The contrast ratio of white and black at this time was 100.

FIG. 8 shows a driving waveform according to the third example of the present embodiment. (1) shows a scanning waveform having an erase pulse Pe and a scanning writing pulse Pw, for example, FIG. 3 shows that the three lines 11a, 11b, 11c are simultaneously applied. Note that (2) shows the information signal having the above-described configuration, and (3) shows the composite waveform.

Then, under the same conditions as those of the first embodiment described above, when the liquid crystal element 8 was driven by using such a waveform, a good image quality was obtained.

In the case where the scanning waveform of (1) is simultaneously applied to 64 lines and the liquid crystal element 8 is driven by using such a waveform under the same conditions as those of the first embodiment described above. Also good image quality was obtained.

FIG. 9 shows a driving waveform according to the fourth example of the present embodiment, and (1) shows a scanning signal in which two dividing pulses Ps are introduced into the scanning writing pulse Pw. , (2) are the two divided pulses Ps1 and Ps.
An information signal having information pulses P1 and P1 corresponding to s2 is shown, and (3) shows a composite waveform.

Here, the pulse width T of this divided pulse Ps
s and the pulse width Td of the information pulses P1 and P1 are the same, and are set to 1/16 of the pulse width ΔT of the scan write pulse Pw.

Then, under the same conditions as those of the first embodiment described above, when the liquid crystal element 8 was driven by using such a waveform, a good image quality was obtained.

[0051]

As described above, according to the present invention, the effective voltage value at the time of non-selection is suppressed and the optical fluctuation at the time of non-selection is reduced by providing the information signal with no voltage applied portion. As a result, it is possible to reduce power consumption and achieve high image quality. Also,
Since the pulse width of the information pulse of the information signal can be shortened, the one-line selection time can be shortened and high speed driving can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram of a liquid crystal display circuit to which a driving method of a liquid crystal element according to the present invention is applied.

FIG. 2 is a diagram showing a scanning signal, an information signal, and a composite waveform thereof output from the scanning signal control circuit and the information signal control circuit of the liquid crystal display circuit.

FIG. 3 is a diagram showing a structure of the liquid crystal element.

FIG. 4 is a diagram showing a configuration of a scanning signal control circuit of the liquid crystal display circuit.

FIG. 5 is a diagram showing drive waveforms according to Example 1 of the present embodiment.

FIG. 6 is a diagram showing a scanning signal, an information signal, and a composite waveform applied to a pixel according to the first example of the embodiment.

FIG. 7 is a diagram showing drive waveforms according to a second example of the present embodiment.

FIG. 8 is a diagram showing a scanning signal, an information signal, and a composite waveform applied to a pixel according to a third example of the present embodiment.

FIG. 9 is a diagram showing drive waveforms according to a fourth example of the present embodiment.

FIG. 10 is a diagram showing a scan write pulse, an information signal, and a composite waveform in a conventional liquid crystal element driving method.

FIG. 11 is a diagram showing a scanning signal, an information signal, and a composite waveform applied to a pixel in a conventional liquid crystal element driving method.

[Explanation of symbols]

 8 liquid crystal element 10 information signal electrode group 11 scanning signal electrode group 82 glass substrate 83 chiral smectic liquid crystal Pw scanning write pulse Ps dividing pulse Pe erasing pulse P1 information pulse P2 averaging pulse Tb no voltage applied portion Td pulse width of information pulse Ts dividing Pulse width of pulse Ta Pulse width of averaging pulse Vs Pulse crest value of divided pulse Vw Pulse crest value of scan write pulse

Claims (9)

[Claims] 1. A method of driving a liquid crystal element, wherein a liquid crystal filled between a pair of substrates is driven by an information signal and a scanning signal selectively applied to the information signal electrode group and the scanning signal electrode group, A write pulse and a dividing pulse for dividing the write pulse are formed in the scanning signal, and the information pulse is an information pulse and an average having a polarity opposite to that of the information pulse and having a voltage average of the information signal of 0. The information pulse has a pulse width the same as the pulse width of the dividing pulse, and the voltage non-application portion is wider than the pulse width of the information pulse. And a method for driving a liquid crystal element. 2. The method of driving a liquid crystal element according to claim 1, wherein the non-voltage applied portion of the information signal is provided between the information pulse and the averaging pulse. 3. The method of driving a liquid crystal element according to claim 1, wherein the averaging pulse is provided before and after the information pulse. 4. The method of driving a liquid crystal element according to claim 1, wherein a plurality of the divided pulses are provided. 5. The method of driving a liquid crystal element according to claim 1, wherein the scan signal has an erase pulse. 6. The method of driving a liquid crystal element according to claim 1, wherein a pulse crest value of the information signal is larger than a pulse crest value of the divided pulse. 7. The method of driving a liquid crystal device according to claim 1, wherein the liquid crystal is a chiral smectic liquid crystal which is a ferroelectric liquid crystal. 8. The method of driving a liquid crystal device according to claim 1, wherein the liquid crystal is a chiral smectic liquid crystal which is an antiferroelectric liquid crystal. 9. The method of driving a liquid crystal element according to claim 1, wherein the information signal electrode group and the scanning signal electrode group are formed in a matrix on the substrate.