JPS63259516A - Method for driving matrix type liquid crystal display body - Google Patents

Abstract

PURPOSE:To eliminate hysteresis from a matrix type liquid crystal display body and to improve the display quality thereof by regulating a mean value of impressed voltage during two periods among three impressed voltages impressed to picture elements connected to a scanning electrode in a nonselective state to zero, regulating also the impressed voltages for two periods when an ON signal voltage is impressed to a signal electrode to a different voltage from that of the impression of an OFF signal voltage. CONSTITUTION:A scanning period is divided to a first period P1, second period P2, and a third period P3, and impressed voltages on a picture element connected to a nonselective scanning electrode is so regulated that a mean value for two periods among said three periods is zero and the voltage of the two periods are regulated to different voltages depending on whether an ON signal potential is impressed to a signal electrode or an OFF signal potential is impressed thereto. If the scanning electrode connected with the display element is in a nonselective state, a wave form 7 of voltage impressed to the displayed picture element is zero volt for the period P1, V1 volt for the period P2, and -V1 volt for the period P3 when an On voltage is impressed to the signal electrode, and no change in the optical state of the displayed picture element is observed because the voltage of the wave form 7 is below a threshold value. Thus, hysteresis is eliminated from the display body and the displayed quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device using ferroelectric liquid crystal, and particularly to a time division driving method.

[Conventional technology]

Liquid crystals having a chiral smectic C phase are known as ferroelectric liquid crystals. Ferroelectric liquid crystals have a response time of about microseconds to a sufficiently large externally applied voltage.
Its molecular arrangement changes.

When a ferroelectric liquid crystal is sandwiched between thin cells, it has a memory effect that retains the written state.

It is expected to be applied to matrix-type displays with a high number of divisions and high display quality by utilizing the memory effect.

The voltage averaging method used to drive a matrix type liquid crystal display panel using TN liquid crystal was used to drive a matrix type liquid crystal display panel using ferroelectric liquid crystal.

[Problem that the invention seeks to solve]

When a ferroelectric liquid crystal is driven by periodically selecting pixels and applying a voltage using the voltage averaging method, an interesting hysteresis phenomenon occurs in which the display brightness of the pixel depends on the display brightness before selection. , there was an inconvenience that the reliability of the display decreased.

[Means for solving problems]

SUMMARY OF THE INVENTION An object of the present invention is to provide a matrix-type liquid crystal display device which eliminates the above-mentioned conventional problems and has no hysteresis phenomenon and has high display quality.

In order to achieve this object, the present invention provides a first transparent substrate having a scanning electrode made of a transparent conductor on its surface.

A second transparent substrate having a signal electrode made of a transparent conductor on its surface is disposed so that the scanning electrode and the signal electrode are substantially perpendicular to each other, and a polarizing plate is provided outside the first and second transparent substrates. The ferroelectric liquid crystal exhibits a high light transmission state by applying a pulse voltage higher than the first voltage, and exhibits a low light transmission state by applying a pulse with a voltage more negative than a second voltage having a negative sign. It is arranged between two substrates, the intersection of the scanning electrode and the signal electrode is used as a display pixel, the scanning electrode is sequentially scanned to be in a selected state for one scanning period, and the signal electrode is synchronized with the selection of the 11 scanning electrodes. Then, the display information of the display pixel at the intersection of the selected scanning electrode and signal electrode is applied to the ferroelectric liquid crystal by applying an on signal voltage or an off signal voltage depending on whether the display information is in a high transmitted light state or a low transmitted light state. In a matrix type liquid crystal display driving method for displaying by controlling the arrangement state of
Divided into a second period and a third period, the applied voltage of the pixel connected to the scan electrode in the non-selected state is such that the average value of the applied voltage in two of the three periods is zero, and the average value of the applied voltage in two of the three periods is zero, and It is characterized in that the period is different depending on when an on signal voltage is applied to the signal electrode and when an off signal voltage is applied to the signal electrode.

〔Example〕

Embodiments according to the present invention will be described in detail below based on the drawings. FIG. 2 schematically shows scanning electrodes 5l-8N and signal electrodes DI-DN of a matrix type liquid crystal display. The intersection of the scanning electrode and the signal electrode is a display pixel. The scanning electrode and the signal electrode are each a transparent conductor provided on a transparent substrate. An alignment layer was formed on the surface on which the transparent conductor was formed, a ferroelectric liquid crystal was placed between the two substrates, and a polarizing plate was provided on the outside of each of the two substrates. We used a birefringence mode that utilizes the birefringence of ferroelectric liquid crystals. FIG. 3 shows the electro-optical characteristics of the liquid crystal display of this example. The horizontal axis is the voltage (scan electrode voltage−signal electrode voltage) applied to the display pixel. The vertical axis is the transmitted light intensity. The display pixel has an applied voltage of VI
High transmission state with high transmitted light intensity above I volts, -■,
At voltages more negative than volts, it exhibits a low transmission state in which the intensity of transmitted light is small.

FIG. 4 shows the voltage waveform of the scanning electrode and the voltage waveform of the signal electrode. Selection voltage 1 is applied to the scan electrode when the scan electrode is selected. The selection period includes a first period P1, a second period P2, and a third period P3. Period P1
was set to V3 port, period P2 was set to -v2 volts, and period P3 was set to zero volts.

Non-selection voltage 2 is when the scanning electrode is in a non-selected state.

applied to the scanning electrodes. The non-selection voltage is P as well as the selection voltage.
It has periods of 1, P2, and P3. Period P1 and period P2
was set to zero volts, and period P3 was set to -v1 volts.

On voltage 3 or off voltage 4 is applied to the signal electrode. If the display information of the display pixel at the intersection of the selected scanning electrode and signal electrode is in a high-transmission light display state where the transmitted light intensity is high, on-voltage 3 is applied to the signal electrode, and when the display information of the display pixel at the intersection of the selected scanning electrode and signal electrode is in a high-transmission light display state where the transmitted light intensity is low, a low-transmission state with low transmission light intensity is applied. In the case of a light display state, off-voltage 4 is applied.

The on-voltage 3 is zero volts during periods P1 and P3, and is zero volts during periods P2.
is -V1 volt. The off-voltage 4 is -v1 volts during period P1 and period P3, and is v1 volts during period P2.

When the above voltage is applied to the scan electrode and the signal electrode, the display pixel applied voltage applied to the display pixel has a value of (scan electrode voltage - signal electrode voltage). The voltage waveforms applied to the display pixels have four combinations of 5, 6, 7, and 8 shown in FIG. Waveform 5 has a selection voltage of 1 on the scan electrode and an on voltage of 3 on the signal electrode.
This is the voltage applied to the display pixel when .

The voltage is v3 volts during the period P1, -v1 volts during the period P2, and zero volts during the period P3. Waveform 6 shows selection voltage 1 on the scan electrode.
is the voltage applied to the display pixel when off voltage 4 is applied to the signal electrode. v1+v3 volts in period P1, V1-V2 volts in period P2, V in period P3
It is 1 volt.

The relationship between the voltage applied to the scanning electrode and the signal electrode and the threshold voltage of the ferroelectric liquid crystal is V 3 >V, 1-Vl-V21>
l-V, I, Vl(V,.

1-VL l<1-VL l. Vl, v2
, V3, V2=2XV1, V3=3XV1.

Since the voltage v3 in the period P1 of waveform 5 is larger than vH, the display pixel enters a high transmission light state in the period P1, regardless of the previous display state. During periods P2 and P3, the voltage is below the threshold value, so the optical state of the display pixel does not change, and the high transmission light state is maintained until a voltage more positive than VII or more negative than -vL is applied and written again. .

During waveform 60 period PI, the applied voltage V1+V3 is greater than vjl, so the display pixel is written into a high transmission state, but
The voltage in the next period P2 is 1-Vl-V 21 > I-
Since it is a VLI, the display pixels change to a low transmitted light state. Since the voltage V1 is below the threshold value during the period P3, the optical state of the display pixel does not change, and the low transmitted light state is maintained until a voltage more positive than vH or more negative than −vL is applied and written again.

When the scanning electrode to which the display pixel is connected is in a non-selected state, the voltage waveform applied to the display pixel is the pixel application waveform 7 when an on voltage is applied to the signal electrode and the pixel application waveform 7 when an off voltage is applied to the signal electrode. There are 802 types of pixel application waveforms. Waveform 7
is zero gelt in period PI, v1 volt in period P2, and -v1 port in period P3. Since the voltage of waveform 7 is below the threshold value, it does not change the optical state of the display pixel. Waveform 8 has v1 volts during period P1, -Vl volts during period P2, and zero volts during period P3. Waveform 8 does not change the optical state of the display pixel for the same reason as waveform 7.

By using the drive waveform of this embodiment, it is possible to perform correct display depending on the display information without depending on the display state before selecting and writing the display information.

FIG. 1 shows temporal changes in the drive waveform for obtaining the display state shown in FIG. 2. FIG. In FIG. 2, the ○ mark indicates a high transmitted light display state, and the * mark indicates a low transmitted light display state. Scanning electrodes S1, S2, S3
The voltage waveforms applied to the signal electrode DI are shown as Sl, S2, and S3 in FIG. 1, and the voltage waveform applied to the signal electrode DI is shown as dl. Period T1
The scan electrode S1 is put into a selected state, and a selection voltage waveform 1 is applied, and a non-selection voltage waveform 2 is applied to the other scan electrodes.

Corresponding to the progress of periods T2, T3......
The scanning electrodes are sequentially brought into the selected state in steps S2, S3, and so on.

The voltage applied to the display pixel formed at the intersection of the scanning electrode S1 and the signal electrode D1 is indicated by 5l-di in FIG. Period T
1, the display pixel is written to a high transmission light state, and the applied voltage in the subsequent period does not change the optical state of the display pixel, so the display pixel formed at the intersection of the scanning electrode S1 and the signal electrode DI is written to a high transmission light state. Retain state.

The voltage applied to the display pixel formed at the intersection of the scanning electrode S3 and the signal electrode D1 is indicated by 53-di in FIG. Period T
3, the display pixel is written to a low transmitted light state, and since the applied voltage in the subsequent period does not change the optical state of the display pixel, the display pixel formed at the intersection of the scan electrode S1 and the signal electrode D1 is written to a low transmitted light state. Retain state.

FIG. 5 shows the voltage waveform of the scanning electrode and the voltage waveform of the signal electrode. A selection voltage 9 is applied to the scan electrode when the scan electrode is selected. The selection period includes a first period P1, a second period P2, and a third period P3. Period P1
is v4 volts, period P2 is -v2 volts, period P3 is -
It was set to v1 Porto. The non-selection voltage 10 is applied to the scan electrode when the scan electrode is in the non-selected state. Like the selection voltage, the non-selection voltage also has periods P1, P2, and P3.

The period P1 and the period P2 were set to zero volts, and the period P3 was set to -Vl volts.

An on voltage 11 or an off voltage 12 is applied to the signal electrode. If the display information of the display pixel at the intersection of the selected scanning electrode and signal electrode is in a high-transmission light display state where the transmitted light intensity is high, on-voltage 11 is applied to the signal electrode, and when the display information of the display pixel at the intersection of the selected scanning electrode and signal electrode is in a high-transmission light display state where the transmission light intensity is high, the on-voltage 11 is applied to the signal electrode, In the case of a light display state, an off voltage 12 is applied. The on-voltage 11 is zero volts during periods P1 and P3, and -V1 volts during period M P2. The off-voltage 12 is -V1 volts during period P1 and period P3, and v during period P2.
It is 1 volt.

When the above voltage is applied to the scan electrode and the signal electrode, the display pixel applied voltage applied to the display pixel becomes (scan electrode voltage - signal electrode voltage) 9 values. The voltage waveforms applied to the display pixels are 4' combinations of 13, 14, 15, and 16 shown in FIG. A waveform 13 is the voltage applied to the display pixel when the selection voltage 9 is applied to the scanning electrode and the on voltage 11 is applied to the signal electrode. v4 volts in period P1, -V in period P2
2+VI volts, -V1 volts at P3.

A waveform 14 is the voltage applied to the display pixel when the selection voltage 9 is applied to the scanning electrode and the off voltage 12 is applied to the signal electrode. V1+V4 volts during period P1, -Vl during period P2
-V2 volts, zero port in period P3.

The relationship between the voltages applied to the scanning electrode and the signal electrode and the threshold voltage of the strong liquid crystal was the same as in the previous example except for v4 >V'H, V4. Therefore, 1-Vl-V21>
I −vL I, Vl(V,, 1−Vl l<l −V
It is L l. ■The relationship between 1 and v4 is V4=4xV1
And so. The relationship between V2 and vl is as in the previous example, V2=
It is 2XV1.

Since the voltage v4 in period P1 of waveform 16 is larger than Vil, the display pixel does not depend on the previous display state and the voltage v4 in period P1 is higher than Vil.
It becomes a state of high transmitted light. During periods P2 and P3, the voltage is below the threshold value, so the optical state of the display pixel does not change, and remains in a high transmitted light state until a voltage more positive than ■□ or more negative than ■□ is applied and writing is performed again. hold.

In the waveform 140 period P1, the applied voltage V1+V4 is larger than ■, so the display pixel is written into a high transmission state, but
The voltage in the next period P2 is l −V 1−V 2 l >
Since l Vt, I, the display pixel changes to a low transmitted light state. During period P3, the voltage is below the threshold value, so the optical state of the display pixel does not change and maintains the low transmitted light state until a more positive voltage or a more negative voltage is applied and written again. .

When the scanning electrode to which the display pixel is connected is in a non-selected state, the voltage waveform applied to the display pixel is the pixel application waveform 15 when an on voltage is applied to the signal electrode, and the pixel application waveform 15 when an off voltage is applied to the signal electrode. There are 1602 types of pixel application waveforms.

Waveform 15 has zero volts during period P1, Vl volts during period P2, and -V1 volts during period P3. Period P2 and period P
The average value of the voltages of 3 is zero. Since the voltage of waveform 15 is below the threshold value, it does not change the optical state of the display pixel.

Waveform 16 is V1 volts during period P1 and -v1 during period P2.
Porto is zero Porto in period P3. Waveform 16 differs from waveform 15 in that the average value of the voltages in period P1 and period P2 is zero. Waveform 16 does not change the optical state of the display pixel for the same reason as waveform 15.

Since the average voltage value of both waveform 15 and waveform 16 is zero, the average value of the voltage applied during the non-selection period, which occupies most of the time when voltage is applied to the display pixel, is zero.

By using the drive waveform of this embodiment, it is possible to perform correct display depending on the display information without depending on the display state before selecting and writing the display information.

FIG. 6 shows a temporal change in the driving waveform for obtaining the display state shown in FIG. 2. FIG. Scanning electrode 81. The voltage waveforms applied to S2 and S3 are shown as 51, s2, and S3 in FIG. 6, and the voltage waveform applied to the signal electrode D1 is shown as dl. Scanning electrode S during period T1
1 is put into a selected state, a selection voltage waveform 9 is applied, and a non-selection voltage waveform 10 is applied to the other scan electrodes. Period T2
, T3, etc., S2, S
3...Sequentially bring the scanning electrodes into the selected state.

The voltage applied to the display pixel formed at the intersection of the scanning electrode S1 and the signal electrode D1 is indicated by s1-d1 in FIG.

During the period T1, the display pixel is written to a high transmission light state, and since the applied voltage in the subsequent period does not change the optical state of the display pixel, the display pixel formed at the intersection of the scanning electrode S1 and the signal electrode D1 is written to a high transmission light state. Maintain light state.

The voltage applied to the display pixel formed at the intersection of the scanning electrode S3 and the signal electrode D1 is indicated by 83-di in FIG. Period T
3, the display pixel is written to a low transmitted light state, and since the applied voltage in the subsequent period does not change the optical state of the display pixel, the display pixel formed at the intersection of the scan electrode S1 and the signal electrode D1 is written to a low transmitted light state. Retain state.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a matrix-type liquid crystal display with high display quality that does not depend on the hysteresis phenomenon of the electro-optical characteristics of ferroelectric liquid crystal is obtained.

[Brief explanation of the drawing]

FIG. 1 is a waveform diagram showing an example of driving with the drive voltage waveform of Example 1 of the present invention, and FIG. 2 is a schematic diagram showing the display state of the display body when driven with the waveforms shown in FIGS. 1 and 6. Figure, 3rd
The figure shows the electro-optical properties of ferroelectric liquid crystal? FIG. 4 shows the drive waveform of the first embodiment of the present invention. FIG. 5 shows the drive waveform of the second embodiment of the present invention. FIG. 6 is an example of driving using the drive voltage waveform of the second embodiment of the present invention. FIG. Sl, S2...SN...Scanning electrode, Dl...DM...
Signal electrode, 1.9... Selection voltage waveform of scanning electrode, 2.10... Non-selection voltage waveform of scanning electrode, 3
．． 11...On voltage waveform of signal electrode, 4.12
・・・・・・Off voltage waveform of signal electrode, 5.6.7.8
．． 13.14.15.16...Display pixel applied voltage waveform. Figure 1 Figure 5

Claims (1)

[Claims] A first transparent substrate having a scanning electrode made of a transparent conductor on its surface and a second transparent substrate having a signal electrode made of a transparent conductive material on its surface are disposed so that the scanning electrode and the signal electrode are substantially perpendicular to each other. A polarizing plate is provided on the outside of the second transparent substrate, and by applying a pulse voltage greater than or equal to the first voltage with a positive sign, a highly transmitted light state is achieved, and a pulse with a voltage more negative than the second voltage with a negative sign is applied. A ferroelectric liquid crystal that exhibits a low transmittance state when
A display pixel is arranged between the two substrates, the intersection of the scanning electrode and the signal electrode is used as a display pixel, the scanning electrode is sequentially scanned to be in a selected state for one scanning period, and the signal electrode is provided with a display pixel that is synchronized with the selection of the scanning electrode. Then, an on signal voltage or an off signal voltage is applied depending on whether the display information of the display pixel at the intersection of the selected scanning electrode and the signal electrode is in a high transmitted light state or a low transmitted light state. In a matrix type liquid crystal display driving method in which display is performed by controlling the alignment state of liquid crystals, one scanning period is a first period,
Divided into a second period and a third period, the applied voltage of the pixel connected to the scan electrode in the non-selected state is such that the average value of the applied voltage in two of the three periods is zero, and the average value of the applied voltage in two of the three periods is zero, A method for driving a matrix type liquid crystal display, characterized in that a period is different depending on whether an on signal voltage is applied to a signal electrode or an off signal voltage is applied to a signal electrode.