JPH0792449A - Gradation method for anti-ferroelectric liquid crystal display - Google Patents

Abstract

PURPOSE:To provide an excellent gradation display by modulating a driving voltage waveform and applying an auxiliary pulse for gradation according to the gradation display data after a select pulse. CONSTITUTION:For controlling a response time from a ferroelectric liquid crystal state to an anti-ferrorelectric liquid crystal state, the voltage value of the select pulse of a scanning side voltage waveform is fixed so that the voltage value of the select pulse in a selection pariod is changed, and the voltage value of a signal side voltage waveform is changed according to the respective gradation display data. In such a case, the changes in composite voltage waveforms and corresponding transmission light quantity when the voltage values of the select pulses of composite waveforms applied in respective selection periods are set at 49V in figure A, 43V in figure B, 39V in figure C and 36V in figure D are shown. In such a manner, by changing the absolute value of the select pulse voltage in the selection period, the transmission light quantity in a non-selection period is controlled. Further, by changing the voltage value of the auxiliary pulse for gradation in the selection period also, the transmission light quantity in the non-selection period is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of 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 having 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 is
JP-A-2 of Nippon Denso Co., Ltd. and Showa Shell Sekiyu Co., Ltd.
Since the publication of 173724 discloses that it has a wide viewing angle, that it can respond at high speed, and that it has good multiplex characteristics, it has been actively researched.

FIG. 3 is a block diagram of a liquid crystal display panel when an antiferroelectric liquid crystal is used as a display. Between the polarizing plates 21a and 21b that are matched to crossed Nicols,
The liquid crystal cell 22 is placed so that the polarization axis of either of the polarizing plates and the long axis direction of the molecules in the absence of an electric field are parallel to each other so that black can be displayed when no voltage is applied and white can be displayed when a voltage is applied. In such a cell configuration, when a voltage is applied to the liquid crystal cell, a change in transmittance is plotted in a graph, and a loop as shown in FIG. 4 can be drawn. When a voltage is applied and increased. The voltage value at which the transmittance starts to change is V1, and the voltage value at which the transmittance change is saturated is V1.
2. Conversely, the voltage value at which the transmittance starts to decrease when the voltage value is decreased is V5. Further, when a voltage having a polarity opposite to that of the voltage value is applied and the absolute value is increased, the voltage value at which the transmittance starts changing is V3, the voltage value at which the transmittance change is saturated is V4, and conversely the absolute value of the voltage. Let V6 be the voltage value at which the transmittance starts to change when is decreased. In FIG. 4, when a pulse wave is applied to the liquid crystal molecules, the second stable state (ferroelectric liquid crystal state) is selected when the product of the pulse width and the voltage value is a threshold value or more. The third stable state (ferroelectric liquid crystal state) is selected depending on the polarity of the applied voltage. From the second and third stable states,
This indicates that the first stable state (antiferroelectric liquid crystal state) is selected when the absolute value of the product of the pulse width and the voltage value is lower than a certain threshold value.

FIG. 5 shows an example of a conventional driving method for an antiferroelectric liquid crystal panel. As shown in FIG. 5, the first stable state, the second stable state, or the third stable state is selected in the selection period, and the state is held in the non-selection period until the next selection period. In other words, the amount of transmitted light selected in the selection period is held in the subsequent non-selection period for display.

[0005]

However, when the display is performed by such a method, there are only two kinds of the transmitted light amount, that is, the large amount of transmitted light (white display) or the small amount of transmitted light (black display), and hold the light in the middle. I couldn't. Therefore, only white display or black display can be performed as display, and gradation display cannot be performed. Therefore, an object of the present invention is to provide a driving method for performing gray scale display of two or more kinds of white display and black display.

[0006]

In order to achieve the above object, according to the present invention, (1) an antiferroelectric liquid crystal is sandwiched between a pair of substrates each having a plurality of scanning electrodes and signal electrodes on opposite surfaces. , An antiferroelectric liquid crystal cell having liquid crystal pixels in a matrix is formed on two polarizing plates whose polarization axes are orthogonal to each other, and the average long axis direction of the antiferroelectric liquid crystal molecules is the polarizing plate. In an antiferroelectric liquid crystal display having a configuration in which it is sandwiched so that it is almost in the same direction as either polarization axis, the response time from the ferroelectric liquid crystal state of the antiferroelectric liquid crystal to the antiferroelectric liquid crystal state is shown. , By controlling the change of the amount of transmitted light in the non-selected period in FIG.

(2) The driving voltage waveform of the anti-ferroelectric liquid crystal display is composed of at least two scanning periods, the waveforms of the respective scanning periods are symmetrical with respect to 0 V, and each scanning period is at least a selection period and a non-selection period. There are two periods of time. By modulating the drive voltage waveform applied during the selection period, the response time of the antiferroelectric liquid crystal is controlled to control the change in the amount of transmitted light during the non-selection period.

(3) In the selection period, there are a select pulse for setting a ferroelectric liquid crystal state and a gradation auxiliary pulse according to gradation display data, and the anti-ferroelectric liquid crystal is generated by the gradation auxiliary pulse. The change in the amount of transmitted light during the non-selection period is controlled by controlling the response time of.

[0009]

[Function] The ferroelectric liquid crystal state in the antiferroelectric liquid crystal is more unstable than that in the antiferroelectric liquid crystal state, and the liquid crystal molecules are always trying to return from the ferroelectric liquid crystal state to the antiferroelectric liquid crystal state. . Also, due to the voltage waveform applied to the liquid crystal cell, a force opposite to this return acts in the liquid crystal cell, and the balance of these forces causes the switching state from the ferroelectric liquid crystal state to the antiferroelectric liquid crystal state. Decided. Therefore, by modulating the voltage waveform applied to the liquid crystal cell, the ferroelectric liquid crystal state is quickly changed to the antiferroelectric liquid crystal state,
Alternatively, it is possible to control the time (response time) required for changing from the ferroelectric liquid crystal state to the antiferroelectric liquid crystal state, such as changing slowly. Further, when a pulse voltage having a polarity opposite to that of the select pulse is applied, a force for returning from the ferroelectric liquid crystal state switched by the select pulse to the antiferroelectric liquid crystal state is given by the applied voltage. The response time from the ferroelectric liquid crystal state to the antiferroelectric liquid crystal state can be controlled also by the magnitude of the applied voltage. When this antiferroelectric liquid crystal is used as a display, the amount of light transmitted through this display can be controlled by controlling the response time. Applying this phenomenon to actual driving,
As described above, by controlling the response time from the ferroelectric liquid crystal state to the antiferroelectric liquid crystal state in the non-selection period, the transmitted light amount in the non-selection period can be changed. When this change is observed with the naked eye, the change in the amount of transmitted light in this non-selection period is too fast to distinguish it from the change in the amount of transmitted light. It can be identified as a quantity and can be displayed in gradation.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 5 is a cell configuration diagram of the liquid crystal panel used in this example. The liquid crystal panel used in this embodiment has a pair of glass substrates 5 each having an antiferroelectric liquid crystal layer 56 having a thickness of about 2μ.
It is composed of 3a and 53b. Electrodes 54a and 54b are formed on the opposite surface of the glass substrate, and polymer alignment films 55a and 55b are applied thereon and subjected to rubbing treatment. Further, a first polarizing plate 51a is installed outside one glass substrate so that the polarization axis of the polarizing plate and the rubbing axis are parallel to each other, and the first polarizing plate 51a is installed outside the other glass substrate. The second polarizing plate 51b is installed so that the polarization axes thereof are different by 90 °.

(Embodiment 1) FIG. 1 is a diagram showing a drive voltage waveform of Embodiment 1 of the present invention and a change in the amount of transmitted light corresponding to the drive voltage waveform. The drive voltage waveform used in the first embodiment of the present invention has a selection period of four phases and a pulse width of 100 μs.
The time of the non-selection period is about 7.5 ms, and one frame is composed of two scanning periods. In order to control the response time from the ferroelectric liquid crystal state to the anti-ferroelectric liquid crystal state, the voltage value of the select pulse of the scanning side voltage waveform is kept constant so that the voltage value of the select pulse changes during the selection period. The voltage value of the signal side voltage waveform was changed according to each gradation display data. 1 (A), (B), (C),
(D) is the absolute value of the voltage of the select pulse of the composite waveform applied in the selection period, (A) is 49V, (B)
FIG. 4 is a diagram showing respective drive voltage waveforms when 43 V is set to 43 V, (C) is set to 39 V, and (D) is set to 36 V, and changes in the amount of transmitted light corresponding thereto. As shown in FIG. 1, by changing the absolute value of the voltage of the select pulse during the selection period,
It was possible to control the amount of transmitted light during the non-selected period. When the total transmitted light amount at each select pulse voltage is 100% of the total transmitted light amount in the non-selected period of (A), (B) is about 8
About 8% (C) was about 75% (D) was about 43%.

Since the time of the non-selection period is as short as about 7.5 ms, the change in the transmitted light amount cannot be visually discerned, and the value of the total transmitted light amount in the non-selection period causes a change in brightness. It was identified as a quantity, and gradation display could be performed.

Similar results can be obtained by changing the pulse width of the select pulse instead of changing the absolute value of the voltage of the select pulse.

(Embodiment 2) FIG. 2 is a diagram showing Embodiment 2 of the present invention in which an auxiliary pulse for gradation exists in the selection period.
The drive voltage waveform used in the second embodiment of the present invention has a selection period of 3
Phases, the pulse width was set to 100 μs, one frame was composed of two scanning periods, and the select pulse applied in the second phase of the selection period was set to 35V. The third phase of the selection period is a gradation auxiliary pulse for performing gradation display. In the second embodiment of the present invention, the ferroelectric liquid crystal state is set once in the second phase of the selection period, and the voltage of the grayscale auxiliary pulse is changed according to the grayscale display data. To control the response time to the antiferroelectric liquid crystal state, thereby realizing the gradation display by controlling the amount of transmitted light in the non-selected period. 2A,
(B), (C), (D) are absolute values of the voltage of the gradation auxiliary pulse, (A) is 0 V, (B) is 12 V, and (C) is 21.
V and (D) are diagrams showing respective drive voltage waveforms and a change in the amount of transmitted light corresponding thereto when the voltage is set to 26V,
(E) is an enlarged view in the vicinity of a selection period of the drive voltage waveform of (C). As shown in FIG. 2, it was possible to control the amount of transmitted light during the non-selection period by changing the voltage value of the gradation auxiliary pulse during the selection period. When the total transmitted light amount at the voltage value of each gradation auxiliary pulse is 100% of the total transmitted light amount in the non-selection period of (A), (B) is about 62% (C) is about 45% (D). It was about 21%, and gradation display could be performed as in Example 1.

[0015]

As described in the above embodiments, by modulating the drive voltage waveform or applying the auxiliary pulse for gradation according to the gradation display data after the select pulse,
The response time from the ferroelectric liquid crystal state to the antiferroelectric liquid crystal state can be controlled, and the change in the transmittance during the non-selection period can be controlled, and good gradation display can be performed. .

[Brief description of drawings]

FIG. 1 is a diagram showing a drive voltage waveform used in a first embodiment of the present invention and a corresponding amount of transmitted light.

FIG. 2 is a diagram showing a drive voltage waveform used in Example 2 of the present invention and a corresponding amount of transmitted light.

FIG. 3 is a panel configuration diagram of an antiferroelectric liquid crystal panel and a polarizing plate used in the present invention.

FIG. 4 is a diagram showing a hysteresis curve of an antiferroelectric liquid crystal panel.

FIG. 5 is a diagram showing a conventional driving method.

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

[Explanation of symbols]

 21a, 21b Polarizing plate 22 Liquid crystal cell 51a, 51b Polarizing plate 52a, 52b Sealing material 53a, 53b Glass substrate 54a, 54b Electrode 55a, 55b Polymer alignment film 56 Antiferroelectric liquid crystal

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[Procedure amendment]

[Submission date] December 21, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0003

[Correction method] Change

[Correction content]

FIG. 3 is a block diagram of a liquid crystal display panel when an antiferroelectric liquid crystal is used as a display. Between the polarizing plates 21a and 21b that are matched to crossed Nicols,
The polarization axis of either polarizing plate and the flatness of the molecule in the absence of an electric field
The liquid crystal cell 22 is placed so that the major axis directions are parallel to each other so that black can be displayed when no voltage is applied and white can be displayed when a voltage is applied. In such a cell configuration, when a voltage is applied to the liquid crystal cell, a change in transmittance is plotted in a graph, and a loop as shown in FIG. 4 can be drawn. When a voltage is applied and increased. Let V1 be the voltage value at which the transmittance starts to change, V2 be the voltage value at which the transmittance change saturates, and V5 be the voltage value at which the transmittance starts decreasing when the voltage value is decreasing. Further, when a voltage having a polarity opposite to that of the voltage value is applied and the absolute value is increased, the voltage value at which the transmittance starts changing is V3, the voltage value at which the transmittance change is saturated is V4, and conversely the absolute value of the voltage. Let V6 be the voltage value at which the transmittance starts to change when is decreased. This Figure 4
Is the voltage value when a pulse wave is applied to the liquid crystal molecules.
Above a certain voltage that is specific to the antiferroelectric liquid crystal used by
In addition, the second stable state (ferroelectric liquid crystal state) is selected when the product value of the pulse width and the voltage value is a threshold value or more, and the third stable state is selected depending on the polarity of the applied voltage. A stable state (ferroelectric liquid crystal 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 value from the second and third stable states, the first state is selected. It shows that the stable state (antiferroelectric liquid crystal state) is selected.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

FIG. 5 shows an example of a conventional driving method for an antiferroelectric liquid crystal panel. In Fig. 5, one frame is two
Scanning period, each scanning period is a selection period.
And non-selection period, scanning side voltage waveform, signal side
Along with the voltage waveform, the combined voltage waveform that is the difference between the two is shown.
In addition, the change in the amount of transmitted light according to the waveform is
It is shown. Here, two scans in this one frame
The waveform of the period is to prevent burn-in and deterioration of the liquid crystal composition.
In order to stop it, it is symmetrical with respect to 0V, and it is trying to make alternating current.
It In this driving method, the selection period consists of two phases,
Width is 100 μs, and the time of non-selection period is about 7.5 ms
It is set. Scan side voltage waveform in each selection period
A pulse with a constant crest value is given to the signal
The side voltage waveform determines the peak value of the combined voltage waveform,
Select the first or second or third stable state,
The state was kept in the non-selection period until the next selection period. In other words, the amount of transmitted light selected in the selection period is held in the subsequent non-selection period for display.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005]

However, when the display is performed by such a method, there are only two kinds of the transmitted light amount, that is, the large amount of transmitted light (white display) or the small amount of transmitted light (black display), and hold the light in the middle. I couldn't. Therefore, only white display or black display can be performed as display, and gradation display cannot be performed. Therefore, as a method of gradation display,
The unit gradation is displayed as a unit and the gradation is displayed by area.
It was done. However, with this method
Since it is considered as one pixel, the driving controller is complicated
And the image resolution becomes extremely poor,
The number of gradations that can be displayed is also limited.
Kick On the other hand, a ferroelectric liquid crystal display using the SmC ^* phase
As for the ray, as described in JP-A-4-34417,
There is no attempt to display gradation by modulating the pulse width.
However, this is a SmC that has only one stable state.
^* It is about the driving method of the ferroelectric liquid crystal showing the phase,
shows the mC _A ^* phase antiferroelectric liquid crystal display of the present invention
The driving method is different from the panel structure, material, and driving waveform.
ing. Therefore, in the present invention, the antiferroelectric liquid crystal display is
B, the display resolution is good and the drive controller is
It is an object of the present invention to provide a driving method for performing gradation display of two or more kinds of white display and black display without complicating the error.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

In order to achieve the above object, according to the present invention, (1) an antiferroelectric liquid crystal is sandwiched between a pair of substrates each having a plurality of scanning electrodes and signal electrodes on opposite surfaces. the antiferroelectric liquid crystal cell having a liquid crystal pixel in a matrix, the two polarizing plates such as mutual polarization axes are Cartesian, average long axis direction of the antiferroelectric liquid crystal molecules is the polarizer And a response time from the ferroelectric liquid crystal state of the antiferroelectric liquid crystal to the antiferroelectric liquid crystal state. Is controlled to control the change in the amount of transmitted light in the non-selection period which is constant in FIG .

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 6 is a cell configuration diagram of the liquid crystal panel used in this example. The liquid crystal panel used in this embodiment has a pair of glass substrates 5 each having an antiferroelectric liquid crystal layer 56 having a thickness of about 2μ.
It is composed of 3a and 53b. Electrodes 54a and 54b are formed on the opposite surface of the glass substrate, and polymer alignment films 55a and 55b are applied thereon and subjected to rubbing treatment. Further, a first polarizing plate 51a is installed outside one glass substrate so that the polarization axis of the polarizing plate and the rubbing axis are parallel to each other, and the first polarizing plate 51a is installed outside the other glass substrate. The second polarizing plate 51b is installed so that the polarization axes thereof are different by 90 °. In addition, this implementation
In the example, the value of V2 shown in FIG.
Dielectric liquid crystal was used.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

(Embodiment 1) FIG. 1 is a diagram showing a drive voltage waveform of Embodiment 1 of the present invention and a change in the amount of transmitted light corresponding to the drive voltage waveform. The driving voltage waveform used in the first embodiment of the present invention is one frame.
The system consists of two scanning periods, each scanning period being a selection period.
It consists of a period and a non-selection period, and 2 in this 1 frame
The waveforms in one scanning period are symmetrical with respect to 0V.
It In the driving method of the present embodiment, the selection period does not consist of 4 phases.
The pulse width is 100 μs, and the non-selection period is about 7.
It is set to 5 ms. In order to control the response time from the ferroelectric liquid crystal state to the anti-ferroelectric liquid crystal state, the voltage value of the select pulse of the scanning side voltage waveform is kept constant so that the voltage value of the select pulse changes during the selection period. The voltage value of the signal side voltage waveform was changed according to each gradation display data. 1, (A), (B), (C), and (D) are absolute values of the select pulse voltage of the composite waveform applied in the selection period, (A) is 49 V, and (B) is 43.
FIG. 9 is a diagram showing respective combined voltage waveforms when V, (C) are set to 39 V, and (D) is set to 36 V, and changes in the amount of transmitted light corresponding thereto. As shown in FIG. 1, it was possible to control the amount of transmitted light during the non-selection period by changing the absolute value of the voltage of the select pulse during the selection period. The total transmitted light amount at each select pulse voltage is about 88% in (B) when the total transmitted light amount in the non-selected period of (A) is 100%.
(C) was about 75% and (D) was about 43%.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

(Embodiment 2) FIG. 2 is a diagram showing Embodiment 2 of the present invention in which an auxiliary pulse for gradation exists in the selection period.
The drive voltage waveform used in the second embodiment of the present invention is one frame.
It consists of two scanning periods, each scanning period includes a selection period and a non-selection period.
It consists of a selection period, and two runs in this one frame
The waveform of the check period is symmetrical with respect to 0V. Real
In the driving method of the embodiment, the selection period consists of three phases, and the pulse
The width is 100 μs, and the time of the non-selection period is set to about 7.5 ms.
It is fixed. In this embodiment, the select pulse of the composite waveform applied in the second phase of the selection period is set to 35V. The third phase of the selection period is a gradation auxiliary pulse for performing gradation display. In the second embodiment of the present invention, the ferroelectric liquid crystal state is set once in the second phase of the selection period, and the voltage of the grayscale auxiliary pulse is changed according to the grayscale display data. To control the response time to the antiferroelectric liquid crystal state, thereby realizing the gradation display by controlling the amount of transmitted light in the non-selected period. 2A, 2B, 2C, and 2D are gradation auxiliary pulses.
The absolute value of the combined voltage is 0V for (A), 12V for (B),
(C) is a diagram showing respective drive composite voltage waveforms and changes in the amount of transmitted light when 21V and (D) are set to 26V, and (E) is a selection of the drive voltage waveform of (C). It is an enlarged view near the period. As shown in FIG. 2, it was possible to control the amount of transmitted light during the non-selection period by changing the voltage value of the gradation auxiliary pulse during the selection period. When the total transmitted light amount at the voltage value of each gradation auxiliary pulse is 100% of the total transmitted light amount in the non-selection period of (A), (B) is about 62% (C) is about 45% (D). It was about 21%, and gradation display could be performed as in Example 1.

Claims (3)

[Claims] 1. An antiferroelectric liquid crystal is sandwiched between a pair of substrates each having a plurality of scanning electrodes and signal electrodes on opposite surfaces,
An antiferroelectric liquid crystal cell having liquid crystal pixels in a matrix is formed by 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 polarizing plates. In a gray scale display method of an antiferroelectric liquid crystal display having a configuration in which the antiferroelectric liquid crystal display is sandwiched so as to be in substantially the same direction as the polarization axis of the antiferroelectric liquid crystal. A method of displaying an anti-ferroelectric liquid crystal display, which is characterized in that gradation display is performed by controlling the response time of the change to the. 2. The driving voltage waveform of the anti-ferroelectric liquid crystal display is composed of at least two scanning periods, the waveforms of the scanning periods are symmetrical with respect to 0 V, and each scanning period is at least a selection period and a non-selection period. 2. The anti-ferroelectric device according to claim 1, wherein the anti-ferroelectric liquid crystal device is constituted by two periods, and the response time of the anti-ferroelectric liquid crystal is controlled by modulating a drive voltage waveform applied during the selection period. Display method for liquid crystal display. 3. The selection period is composed of at least a select pulse for setting to a ferroelectric liquid crystal state and a gradation auxiliary pulse according to gradation display data. The gradation display is performed by controlling the response time.
A method for displaying the antiferroelectric liquid crystal display described.