JPH1082985A - Display element and display element device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display element which has high-speed responsiveness and wide visual field angle characteristic and with which the decrease of seizure and flicker is possible. SOLUTION: A liquid crystal which is an antiferroelectric liquid crystal exhibiting an Sm CR phase having no correlation in the inclination of liquid crystal molecules and in which the intersectional angle of a director direction 21A and a second direction 21B in two ferroelectric phases is >=45 deg. is prepd. These liquid crystals are arranged between a pair of substrates. The transmission axis 23A of a polarizing plate 23 is arranged in the direction inclined 22.5 deg. with the intermediate direction 21C between the direction 21A and the direction 21B. The optical axis 24A of a polarizing plate 24 is arranged to intersect with the transmission axis 23A. This element is driven by impressing the voltage of a range where the liquid crystal do not form a ferroelectric phase and the max. and min. transmittance are obtainable between electrodes arranged across the liquid crystal layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a display device and a display device using a liquid crystal having a ferroelectric phase.

[0002]

2. Description of the Related Art Instead of a liquid crystal display device using a nematic liquid crystal, which has been widely used, a ferroelectric liquid crystal and an antiferroelectric liquid crystal, which are expected to have a high-speed response characteristic and a wide viewing angle characteristic, are used. Liquid crystal display devices have been developed. In these liquid crystal display elements, a ferroelectric liquid crystal or an antiferroelectric liquid crystal is interposed between a pair of opposing substrates having electrodes formed on opposing inner surfaces.

In the case of using a ferroelectric liquid crystal, a first alignment stable state in which liquid crystal molecules are aligned in one ferroelectric phase by applying a predetermined voltage of one polarity between opposing electrodes is obtained. By applying a predetermined voltage of the other polarity between the electrodes to drive the liquid crystal molecules utilizing the bistability with the second alignment stable state in which the liquid crystal molecules are aligned in the other ferroelectric phase, the desired state is obtained. An image is displayed.

[0004] In the case of using an antiferroelectric liquid crystal,
A first type in which liquid crystal molecules are oriented to one ferroelectric phase by applying a predetermined voltage of one polarity between opposing electrodes.
And a second alignment stable state in which liquid crystal molecules are aligned in the other ferroelectric phase by applying a predetermined voltage of the other polarity between the electrodes, and a reverse alignment state when no electric field is applied. A desired image is displayed by driving using the three stability of the third orientation stable state oriented to the ferroelectric phase.

In these liquid crystal display devices, liquid crystal molecules are
Since the ferroelectric phase or the antiferroelectric phase is oriented in a stable state and a binary display is performed by utilizing the memory effect, it is difficult to perform a gradation display with good reproducibility.

A DHF liquid crystal (Deformed Helical Ferroelectric L
Liquid crystal display devices using iquid crystal) have been proposed. In a DHF liquid crystal display device, a ferroelectric liquid crystal having a short pitch is interposed between substrates in the presence of a helix, and the helix is distorted in accordance with an opposing electric field. This is to continuously change the director of the liquid crystal molecules up to the neutral phase.

Further, recently, an antiferroelectric liquid crystal display device which performs gradation display using an intermediate alignment state of some antiferroelectric liquid crystals has been proposed.

[0008]

In the above-mentioned ferroelectric liquid crystal and antiferroelectric liquid crystal, liquid crystal molecules have a permanent dipole in a direction substantially orthogonal to the molecular long axis. Liquid crystal molecules behave due to a natural interaction. For this reason, the response speed is high, and the director changes of the liquid crystal molecules move in a plane parallel to the substrate, so that the viewing angle is widened.

However, since these liquid crystals have spontaneous polarization due to permanent dipoles of the liquid crystal molecules, charges having the opposite polarity to the spontaneous polarization are accumulated on the substrate side, and the interaction with the substrate becomes large. The display burn-in phenomenon occurs in that the liquid crystal molecules cannot behave sufficiently freely in response to the electric field and an image remains as an afterimage.

In the conventional ferroelectric liquid crystal element and antiferroelectric liquid crystal element, as a method of reducing the image sticking phenomenon, a driving method of inverting the polarity of the voltage applied to the liquid crystal for each frame or line is proposed. Have been. Also,
A driving method for applying a compensation pulse of the opposite polarity for each driving pulse has also been proposed.

However, in these methods, the bias of the electric charge cannot be sufficiently eliminated, and the burn-in cannot be eliminated. In addition, there is a problem that flicker occurs because the response of the liquid crystal to the pulse of the positive polarity and the pulse of the opposite polarity is different.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a display element and a display element device having a high-speed response and a wide viewing angle characteristic, capable of reducing a burn-in phenomenon and reducing flicker. The purpose is to provide.

[0013]

In order to achieve the above object, a display element according to a first aspect of the present invention comprises a pair of substrates, each having an electrode formed on an opposing surface, between the pair of substrates. And an S _m C _R ^* phase in which the tilt of the liquid crystal molecules has no correlation between the layers at least when no electric field is applied, and the director operates in accordance with the one-polarity first voltage applied between the electrodes. A first orientation state indicating a first ferroelectric phase oriented in a first direction and a second orientation in which a director is oriented in a second direction in response to a second voltage of the other polarity applied between the electrodes. The liquid crystal molecules change their directors in the first direction in response to the application of a second orientation state indicating a ferroelectric phase of and a third voltage intermediate between the first voltage and the second voltage. And a third orientation state oriented toward a middle direction between the second direction and the second direction. A liquid crystal exhibiting a ferroelectric phase to be oriented, and a pair of substrates interposed therebetween, and one of the optical axes is set in an angle range interposed between the first and second directions, and the other optical axis is set. And a pair of polarizing plates disposed substantially orthogonally or parallel to the one optical axis, respectively.

According to this structure, the intersection angle between the first direction and the second direction is set to be larger than 45 °, and the director of the liquid crystal molecules is arranged in the direction sandwiched by the intersection angle of one of the polarizing plates. By driving between the direction of the axis and the direction inclined at 45 ° therefrom, the maximum gradation and the minimum gradation can be displayed without aligning the liquid crystal in the ferroelectric phase. By driving the liquid crystal without aligning the liquid crystal in the ferroelectric phase, a display burn-in phenomenon can be suppressed. Further, since the display gradation is uniquely determined according to the applied voltage, flicker can be suppressed. Further, by using a liquid crystal exhibiting a ferroelectric phase, high-speed response and wide viewing angle characteristics can be ensured.

The liquid crystal is composed of, for example, a liquid crystal compound exhibiting an S _m CA ^* phase and a liquid crystal compound exhibiting an S _m C ^* phase. The liquid crystal is composed of a liquid crystal compound having an ether-bonded chiral terminal chain and a phenyl ring substituted with fluorine.

As the liquid crystal, a liquid crystal having a ferroelectric phase which is oriented at an angle formed by the first direction and the second direction at an angle larger than 45 ° is suitable. In this case, one of the pair of polarizing plates is at an angle of 45 from the intersection angle with respect to any one of the first direction and the second direction.
The direction of the optical axis is arranged in a range of angles from which ° is subtracted.

It is desirable that the liquid crystal has a ferroelectric phase in which an intersection angle between the first direction and the second direction is oriented at an angle larger than approximately 60 °.
One of the pair of polarizing plates is connected to the first direction and the second direction.
The direction of the optical axis is arranged at an angle of about 12.5 ° or more with respect to any of the directions.

It is more desirable that the liquid crystal has a ferroelectric phase in which the first direction and the second direction each have a ferroelectric phase that is oriented at an angle of more than 90 °. One of the polarizing plates has, for example, an optical axis direction substantially parallel to the normal direction of the smectic layer of the liquid crystal.

The liquid crystal has, for example, an approximately bisector of an angle formed by the director of the liquid crystal molecules between the first direction and the second direction when no voltage is applied between the opposed electrodes. And an antiferroelectric liquid crystal exhibiting an antiferroelectric phase oriented in a direction parallel to that of the liquid crystal.

In order to achieve the above object, a second aspect of the present invention is provided.
The display element device according to the aspect of the present invention is arranged between a pair of substrates each having an electrode formed on the opposing surface, and the pair of substrates, and when no electric field is applied, the inclination of liquid crystal molecules between the layers has a correlation. A first orientation state indicating a first ferroelectric phase in which a director is oriented in a first direction in response to a first voltage of one polarity applied between the electrodes; A second orientation state in which the director exhibits a second ferroelectric phase in which the director is oriented in the second direction in response to the applied second voltage having the other polarity, and a first orientation state between the first voltage and the second voltage. In response to the application of any intermediate third voltage, the liquid crystal molecules are brought into a third alignment state in which the director is oriented toward an intermediate direction between the first direction and the second direction. A liquid crystal exhibiting a ferroelectric phase to be oriented, and disposed between the pair of substrates; A pair of polarizing plates, wherein one optical axis is disposed at an angle sandwiched by the first and second directions, and the other optical axis is disposed substantially orthogonally or parallel to the one optical axis; Driving means for applying a voltage to the liquid crystal between the electrodes to change a director of liquid crystal molecules in an angle range narrower than an angle range sandwiched by the first direction and the second direction. And

According to such a configuration, the driving means drives the liquid crystal without aligning the liquid crystal in the ferroelectric phase. Therefore,
The display burn-in phenomenon can be suppressed. Further, since the display gradation is uniquely determined in accordance with the applied voltage, so-called DC driving becomes possible, and flicker can be suppressed. In addition, by using a liquid crystal that exhibits a ferroelectric phase,
High-speed response and wide viewing angle characteristics can be ensured.

The liquid crystal comprises, for example, a liquid crystal compound exhibiting an S _m CA ^* phase and a liquid crystal compound exhibiting an S _m C ^* phase. The liquid crystal is composed of a liquid crystal compound having an ether-bonded chiral terminal chain and a phenyl ring substituted with fluorine.

As the liquid crystal of the display device having the above-mentioned structure,
An intersection angle between the first direction and the second direction is 45 °
Suitable are those having a ferroelectric phase each oriented at a larger angle, and in this case, the driving means has an angle range between the first direction and the second direction that sandwiches the director of the liquid crystal molecules. Is applied within a range of approximately 45 °.

The pair of polarizing plates are arranged, for example, such that one of the optical axes is substantially parallel to a direction on one side of the angle range of the director which is changed by the driving means.

One of the pair of polarizers has, for example, an optical axis direction within a range of an angle obtained by subtracting 45 ° from the intersection angle with respect to either the first direction or the second direction. Is arranged.

The above-mentioned display element and display element device may be, for example, an active matrix type element or a simple matrix type (passive matrix type) element.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a display element of this embodiment, and FIG. 2 is a plan view of a transparent substrate on which pixel electrodes and active elements are formed. This display element is of an active matrix type, and as shown in FIG. 1, a pair of transparent substrates (for example, glass substrates) 11 and 12, a liquid crystal 21 disposed between the transparent substrates 11 and 12, and A pair of polarizing plates 23, 2 disposed with the transparent substrates 11, 12 interposed therebetween
4.

In FIG. 1, a lower transparent substrate (hereinafter, referred to as a lower substrate) 11 has a pixel electrode 13 made of a transparent conductive material such as ITO and a thin film transistor (hereinafter, TFT) having a source connected to the pixel electrode 13. 14 are formed in a matrix.

As shown in FIG. 2, a gate line (scanning line) 15 is arranged between rows of the pixel electrodes 13, and a data line (gradation signal line) 16 is arranged between columns of the pixel electrodes 13. The gate electrode of each TFT 14 is connected to a corresponding gate line 15, and the drain electrode is connected to a corresponding data line 16. Gate line 15
Are connected to a row driver 31, and the data lines 16 are connected to a column driver 32. The row driver 31 scans the gate line 15 by applying a gate voltage described later. On the other hand, the column driver 32 receives the image data (gradation signal) and applies a data signal corresponding to the image data to the data line 16.

In FIG. 1, an upper transparent substrate (hereinafter referred to as an upper substrate) 12 is opposed to each pixel electrode 13 of a lower substrate 11 and has a counter (common) electrode 1 to which a reference voltage V0 is applied.
7 are formed. The counter electrode 17 is made of, for example, ITO.
And the like. Alignment films 18 and 19 are provided on the electrode formation surfaces of the lower substrate 11 and the upper substrate 12, respectively. Each of the alignment films 18 and 19 is a horizontal alignment film made of an organic polymer compound such as polyimide.
An alignment process for rubbing each time is performed.

The lower substrate 11 and the upper substrate 12 are bonded to each other at the outer peripheral edge thereof via a frame-shaped sealing material 20 to form a liquid crystal cell 25. The spacing between the alignment films 18 and 19 is set to, for example, 1.4 by the sealing material 20 and the gap material 22.
μm to 2.4 μm at regular intervals.
1 is enclosed in a region surrounded by the substrates 11 and 12 and the sealing material 20.

The liquid crystal 21 has a spontaneous polarization PS, two ferroelectric phases and one antiferroelectric phase, and the intersection angle of the director direction of liquid crystal molecules in the two ferroelectric phases is larger than 45 °. , Which does not have a definite threshold in the optical characteristics.

According to the present invention, a chiral smectic C random phase (S _m C _R ^* ) having no correlation between the tilts of liquid crystal molecules between layers having a layer structure of the smectic phase liquid crystal is described as a liquid crystal satisfying such conditions. Using liquid crystal.

Examples of such a liquid crystal compound exhibiting a chiral smectic C random phase (S _m C _R ^* ) include, for example, an antiferroelectric liquid crystal having an ether-bonded chiral terminal chain and a fluorine-substituted phenyl ring. Compounds are used, and a liquid crystal display device using such an antiferroelectric liquid crystal compound can lower the threshold value of the electric field-induced transition of the antiferroelectric liquid crystal and make the precursor phenomenon remarkable. A liquid crystal having no clear threshold in optical characteristics can be generated. In such a liquid crystal, when no electric field is applied, the phase in which the correlation between the layers is lost, that is, the direction of spontaneous polarization in the C-director and the layers is random between the layers and within the layers. On the other hand, when a sufficiently high voltage is applied, the spontaneous polarization is aligned according to the electric field, and the direction is reversed according to the polarity of the applied voltage.

FIG. 3 shows how the liquid crystal responds at the molecular level when no electric field is applied and when an electric field is applied. FIG.
As shown in (A), when no voltage is applied, the major axis direction of liquid crystal molecules and the direction of spontaneous polarization are random between the layers, and the director of the liquid crystal is the same as that of the layer having the layer structure of the liquid crystal in the smectic phase. It almost coincides with the normal direction.

On the other hand, when a sufficiently high voltage (voltage equal to or higher than the saturation voltage Vs) is applied with one polarity, the interaction between the applied voltage and the spontaneous polarization causes the spontaneous spontaneous as shown in FIG. Polarization is uniform between layers, and almost all liquid crystal molecules are
In the direction 21A.

At the other polarity, a sufficiently high voltage (saturation voltage V
When a voltage of s or more is applied, the interaction between the applied voltage and the spontaneous polarization causes the spontaneous polarization to be aligned between the layers in the direction opposite to that in the case of FIG. 3B, as shown in FIG. 3C. Almost all liquid crystal molecules are oriented in the second direction 21B.

When an intermediate voltage is applied, the interaction between the applied voltage and the spontaneous polarization causes the interaction shown in FIG.
As shown in (E), an intermediate orientation state is obtained. Therefore, the director of the liquid crystal 21 changes the first direction according to the applied voltage.
And the second direction continuously changes.

A liquid crystal having such a structure and characteristics is as follows.
For example, it can be obtained by a liquid crystal composition in which a liquid crystal compound exhibiting an S _m C _A ^* phase and a liquid crystal compound exhibiting an S _m C ^* phase are blended. For example, liquid crystal substances I to II having a skeletal structure represented by Chemical Formula 1
It is obtained by mixing I at a ratio of 40% by weight, 40% by weight, and 20% by weight, respectively.

[0040]

Embedded image

Next, the relationship between the direction of the alignment treatment applied to the alignment films 18 and 19, the optical axis of the polarizing plates 23 and 24, and the alignment direction of the liquid crystal molecules of the liquid crystal 21 will be described with reference to FIG.

In FIG. 4, reference numeral 21C denotes an alignment film 18,
19 shows the direction of the alignment treatment performed, and the liquid crystal 21 adjusts the normal of the layer of the layer structure of the chiral smectic C phase (S _m C ^* phase) within the error range of about ± 2 °. It is oriented toward the direction 21C.

When a voltage lower than the predetermined negative voltage −VS is applied to the liquid crystal 21, the liquid crystal 21 enters the first alignment state (ferroelectric phase) shown in FIG. An appropriate orientation direction (director) is the first direction 21A.
A voltage VS higher than a predetermined positive voltage + VS is applied to the liquid crystal 21.
, The liquid crystal 21 is in the second alignment state (ferroelectric phase) shown in FIG. 3C, and the average alignment direction (director) of the liquid crystal molecules is in the second direction 21B. On the other hand, when the applied voltage is 0, the orientation direction and spontaneous polarization of the liquid crystal molecules are in a random state with no correlation between the layers and between the layers, and the average orientation direction (director) is substantially the same as that of the smectic phase layer of the liquid crystal. Linear direction, ie first and second directions 2
Almost intermediate direction between 1A and 21B (almost the direction of the alignment treatment)
21C.

The deviation angle 2θ between the first direction 21A and the second direction 21B is 45 ° or more, preferably 60 ° or more.

The optical axis (transmission axis in this embodiment) 23A of the polarizing plate 23 is composed of a first direction 21A and an alignment direction 2A.
1C, about 22.5 with respect to the alignment direction 21C.
° is set in the direction. Transmission axis 24A of polarizing plate 24
Is set in a direction substantially orthogonal to the transmission axis 23A of the polarizing plate 23.

As shown in FIG. 4, the display device in which the transmission axes 23A and 24A of the polarizing plates 23 and 24 are set, transmits light when the average alignment direction of the liquid crystal molecules is set parallel to the transmission axis 23A of the polarizing plate 23. Lowest rate (darkest display)
The average alignment direction of the liquid crystal molecules is determined by the transmission axis 23 of the polarizing plate 23.
The transmittance becomes highest (brightest) when set in a direction 21D at 45 ° to A.

That is, in a state where the average orientation direction of the liquid crystal molecules is in the direction of the transmission axis 23A, the linearly polarized light passing through the polarizing plate 23 on the incident side is hardly affected by the polarization action of the liquid crystal 21, and The light passes through the layer of the liquid crystal 21 as it is, and is absorbed by the polarizing plate 24 whose transmission axis 24A is set in the perpendicular direction, and the display becomes dark.

On the other hand, in a state where the average orientation direction of the liquid crystal molecules is oriented at 45 ° with respect to the transmission axis 23A, the linearly polarized light passing through the incident side polarizing plate 23 is
Becomes non-linearly polarized light due to the birefringent action of
The component parallel to the transmission axis 24 </ b> A is transmitted through the polarizing plate 24 and emitted. Therefore, the display becomes the brightest. In other orientation states, birefringence action according to the orientation state causes non-linear polarization according to the orientation state, and a component parallel to the transmission axis 24A of the exit side polarizing plate 24 passes through the polarizing plate 24 and exits. I do. Therefore, the display has a brightness according to the orientation state.

For this reason, when a sawtooth voltage having a relatively low frequency (about 0.1 Hz) is applied between the pixel electrode 13 and the counter electrode 17, the transmittance changes continuously as shown in FIG. And does not show a clear threshold.

Since this display element is of the active matrix type, it is possible to maintain a voltage for maintaining the liquid crystal 21 in an arbitrary alignment state even during the non-selection period.
Therefore, the display element having the above structure can perform gradation display by changing the transmittance.

The transmittance of the liquid crystal element is 45 ° minimum when the director of the liquid crystal is parallel to the transmission axis 23 A of the polarizing plate 23.
It becomes maximum when crossing at. Therefore, by using the liquid crystal element between the alignment states showing the transmittance of Tmin and Tmax, the liquid crystal 21 can be driven without being aligned in the first and second alignment states. The first and second alignment states are states in which all molecules in the liquid crystal layer exhibit a ferroelectric phase in which the molecules are completely aligned in the same direction. Charges due to spontaneous polarization are likely to be held, making it difficult for the molecules to be inverted. , Easy to burn. However, if the liquid crystal molecules are not completely aligned, the charge due to spontaneous polarization hardly accumulates.
Burn-in is reduced. That is, the drive voltages are VTmax and VTm
By changing the value in the range of in, the liquid crystal 21 can be driven without using a ferroelectric phase, and further, continuous gradation can be displayed.

Next, a method of driving the display element having the above configuration will be described with reference to FIG. FIG. 6A shows a gate signal applied by the row driver 31 to the gate line 15 in an arbitrary row.
FIG. 6B shows a data signal applied to each data line 16 by the column driver 32 in synchronization with the gate signal. The voltage of the data pulse is set to a voltage that does not align the liquid crystal 21 in the ferroelectric phase, that is, a voltage corresponding to the transmittance to be displayed between VTmax and VTmin. FIG.
FIG. 6B shows a change in transmittance when the data pulse shown in FIG.

The TFT 14 in the selected row is turned on by the gate pulse, and a data signal corresponding to the display gradation is applied between the pixel electrode 13 and the counter electrode 17 via the turned-on TFT 14. When the gate pulse is turned off, the TFT 14 is turned off, and the voltage applied between the pixel electrode 13 and the counter electrode 17 until that time is retained in the pixel capacitance formed by the pixel electrode 13 and the counter electrode 17 and the liquid crystal 21 therebetween. Is done.
Therefore, as shown in FIG. 6C, the display gradation corresponding to the holding voltage is held until the next selection period of this row. Therefore, according to this driving method, an arbitrary gradation image can be displayed by controlling the voltage of the data pulse.

When the liquid crystal 21 has a hysteresis in the electro-optical characteristics shown in FIG. 5, the driving method shown in FIG.
The display gradation with respect to the data pulse voltage is not uniquely determined. In such a case, for example, the driving method shown in FIG. 7 may be adopted. 7A shows a gate signal applied by the row driver 31 to the gate line 15 in an arbitrary row, and FIG. 7B shows a data signal applied to each data line 16 by the column driver 32 in synchronization with the gate signal. Show. FIG.
FIG. 7C shows a change in transmittance when the data signal shown in FIG. 7B is applied.

The TFT 14 in the selected row is turned on by the gate pulse, and a data pulse corresponding to the display gradation is applied between the pixel electrode 13 and the counter electrode 17 via the turned-on TFT 14. The data pulse includes a setting pulse VH for aligning liquid crystal molecules in a predetermined alignment state, a reset pulse VL for canceling a DC component of the setting pulse,
It consists of a gradation pulse VD corresponding to the display gradation. Liquid crystal 21
Are oriented in a substantially constant state by the setting pulse VH in each selection period. Therefore, even when there is hysteresis in the optical characteristics, the display gradation corresponding to the gradation pulse VD is uniquely determined.

When the gate pulse is turned off, the TFT 14 is turned off, and the voltage of the gradation pulse VD applied between the pixel electrode 13 and the counter electrode 17 is changed to the pixel electrode 13 and the counter electrode 17 and the liquid crystal 21 between them. Is held in the pixel capacitance formed by Therefore, as shown in FIG. 7C, the display gradation corresponding to the hold voltage is held until the next selection period of this row. Therefore, according to this driving method, an arbitrary gradation image can be displayed by controlling the voltage of the data pulse. In addition, since the reset pulse VL is applied, unnecessary DC components applied to the liquid crystal 21 can be canceled out, thereby reducing display burn-in.

According to the display element and the driving method thereof,
An arbitrary gradation image can be displayed by continuously changing the gradation from the minimum gradation to the maximum gradation without aligning the liquid crystal 21 in the ferroelectric phase. In the ferroelectric phase, the direction of the spontaneous polarization PS of the liquid crystal molecules is aligned, so that image burn-in easily occurs. In this embodiment, the spontaneous polarization PS is not completely aligned. Therefore, display burn-in hardly occurs, and a high-quality image can be displayed.

Since a chiral smectic phase liquid crystal having spontaneous polarization PS is used as the liquid crystal 21, a display element having a high response speed and a wide viewing angle can be obtained.
Further, as shown in FIGS. 6 and 7, so-called DC driving becomes possible, and since one voltage is applied to one gradation, flicker can be reduced unlike the case of AC driving.

In the driving method shown in FIG. 7, the reset pulse VL and the setting pulse VH have opposite polarities and the same absolute value of the voltage. However, the reset pulse VL is the same as the setting pulse VH and the gradation pulse VD. The voltage may have a polarity opposite to the sum of the voltages. Further, the setting pulse may be VL and the reset pulse may be VH.

The present invention is not limited to the above-described embodiment, and various modifications and applications are possible. For example, any configuration can be adopted as long as the director of the liquid crystal can be driven so as not to be in a ferroelectric phase within an angle range of 45 ° and the highest display gradation and the lowest display gradation can be obtained. . For example, when the shift angle 2θ of the liquid crystal is 60 ° or more,
The transmission axis 23A of the polarizing plate 23 is shifted from the first direction 21A by 1
The transmission axis 24A of the polarizing plate 24 is set to be orthogonal or parallel to the transmission axis 23A, and the director of the liquid crystal 21 is set in the direction of the transmission axis 23A of the polarizing plate 23 in this direction. The drive may be performed between the direction inclined by 45 ° with respect to the direction.

For example, a liquid crystal having a shift angle 2θ of 90 ° or more may be used. In this case, for example, the transmission axis of one polarizing plate may be set to the normal direction of the smectic layer, and the transmission axis of the other polarizing plate may be set to be orthogonal or parallel to the transmission axis of one polarizing plate.

The transmission axis 24A of the polarizing plate 24 and the transmission axis 23A of the polarizing plate 23 may be set in parallel. Further, an absorption axis may be used instead of the transmission axis. Also,
The present invention is not limited to a display element using a TFT as an active element, but is also applicable to a display element using an MIM as an active element. Further, according to the present invention, as shown in FIG. 8, a simple matrix type (passive matrix type) display in which a scanning electrode 71 and a signal electrode 72 orthogonal to the scanning electrode 71 are arranged on opposing surfaces of the opposing substrates 11 and 12 is provided. It is also applicable to devices.

[0063]

EXAMPLE Three kinds of antiferroelectric liquid crystals having the basic composition shown in Chemical Formula 1 were prepared, and a display element having the structure shown in FIGS. 1, 2 and 4 was formed and driven, and its characteristics were measured. .

In this experiment, one polarizing plate of the display element was arranged so that its transmission axis was inclined by 22.5 ° with respect to the normal line of the layer having the layer structure having the smectic phase (smectic layer), and the other polarizing plate was arranged. The polarizing plate was arranged so that its transmission axis was perpendicular to the transmission axis of one of the polarizing plates.

The measurement was performed by driving the display element as follows. 1. When the liquid crystal is driven to show a ferroelectric phase,
When driving the liquid crystal from +20 V to −20 V so that the liquid crystal does not show a ferroelectric phase, the pulse voltage is set to +20 V.
The voltage is sequentially applied from 5 V to -5 V in steps of 0.5 V for about 30 seconds (first drive). 2. After that, when driving the liquid crystal to show a ferroelectric phase, +20 V is continuously applied, and when driving the liquid crystal so as not to show a ferroelectric phase, +5 V is continuously applied for about 30 minutes. 3. The same drive as the first drive is performed again (second drive).

FIG. 9 shows a change in transmittance obtained by such a driving method. FIG. 9A shows the relationship between the driving voltage and the transmittance when an antiferroelectric liquid crystal is used and the liquid crystal is driven so as not to exhibit a ferroelectric phase. On the other hand, FIG.
(B) shows the relationship between the driving voltage and the transmittance when the same antiferroelectric liquid crystal is used and the liquid crystal is driven to exhibit a ferroelectric phase. Note that FIG. 9B shows only characteristics in the same voltage range as FIG. 9A.

As shown in FIG. 9B, when the liquid crystal 21 is driven so as to show a ferroelectric phase, the optical characteristics are different between the first drive and the second drive, and the burn-in phenomenon occurs. It can be understood that this has occurred. In contrast, FIG.
As shown in (A), when the liquid crystal 21 is driven so as not to exhibit a ferroelectric phase, the optical characteristics substantially match between the first drive and the second drive, and the burn-in phenomenon occurs. It does not occur, and it can be understood that there is an effect of the present invention.

[0068]

As described in the foregoing, according to the display device and the display device apparatus of the present invention, antiferroelectric shows a S _m CA ^* phase is a phase in which the tilt of the liquid crystal molecules has no correlation with the interlayer dielectric Since the liquid crystal is used, it is possible to obtain a liquid crystal display device whose optical characteristics continuously change according to the applied voltage. Moreover, since the liquid crystal is driven without using a ferroelectric phase, a display element with less display burn-in due to spontaneous polarization can be obtained. In addition, a wide viewing angle and high-speed response can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure of a display element according to an embodiment of the present invention.

FIG. 2 is a plan view showing a configuration of a lower substrate of the display element shown in FIG.

FIG. 3. Chiral smectic C random phase (S _m C _R
FIG. 3 is a diagram showing a state of an electric field-induced phase transition of an antiferroelectric liquid crystal showing ( ^* phase).

FIG. 4 is a diagram showing a relationship between a transmission axis of a polarizing plate and an alignment direction of liquid crystal molecules.

FIG. 5 is a diagram showing a relationship between a voltage applied to a liquid crystal and transmittance.

FIG. 6 is a timing chart showing a relationship between a waveform of a voltage applied to a pixel and a transmittance by a method of driving a display element according to an embodiment of the present invention.

7 is a timing chart showing a waveform of a voltage applied to a pixel of the display element according to the embodiment of the present invention by a driving method different from the driving method of FIG. 6;

FIG. 8 is a sectional view showing another example of the structure of the display element according to the embodiment of the present invention.

FIGS. 9A and 9B show an example using an antiferroelectric liquid crystal obtained by blending a liquid crystal compound having the basic structure shown in Chemical Formula 1, and the liquid crystal does not show a ferroelectric phase. The relationship between the applied voltage and the transmittance when the liquid crystal is driven in such a manner as described above and when the liquid crystal is driven to exhibit a ferroelectric phase is shown.

[Explanation of symbols]

11: transparent substrate (lower substrate), 12: transparent substrate (upper substrate), 13: pixel electrode, 14: active element (TF
T), 15: gate line (scan line), 16: data line (gradation signal line), 17: counter electrode, 1
8 ... alignment film, 19 ... alignment film, 20 ... sealing material, 21.
..Liquid crystal, 22 gap material, 23 polarizing plate (lower polarizing plate), 24 polarizing plate (upper polarizing plate), 25 liquid crystal cell, 31 row driver, 32 ... Column drivers

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tetsushi Yoshida 5 Casio Computer Co., Ltd. Hachioji Research Laboratory, 2951 Ishikawacho, Hachioji-shi, Tokyo

Claims (14)

[Claims] 1. A pair of substrates electrodes on opposing surfaces are formed respectively, are disposed between the pair of substrates, at least during no electric field is applied, the tilt of the liquid crystal molecules does not have a correlation between the layers S _m
C _R ^* phase, and a first polarity of one polarity applied between the electrodes.
A first orientation state in which the director is oriented in a first direction in accordance with the voltage of the first ferroelectric phase and a second voltage of the other polarity applied between the electrodes causes the director to operate in the second direction. A second orientation state indicating a second ferroelectric phase oriented in the direction of
An optional third intermediate between the first voltage and the second voltage;
Ferroelectric phases in which liquid crystal molecules are oriented in a third orientation state in which liquid crystal molecules are oriented in a direction intermediate between the first direction and the second direction in response to application of a voltage of And a liquid crystal, which is disposed with the pair of substrates interposed therebetween, and one of the optical axes is set in an angle range sandwiched by the first and second directions, and the other optical axis is connected to the one optical axis. A display element using a liquid crystal exhibiting a ferroelectric phase, comprising: a pair of polarizers each arranged substantially orthogonally or in parallel. 2. The display device according to claim 1, wherein the liquid crystal is a mixture of a liquid crystal compound exhibiting an S _m CA ^* phase and a liquid crystal compound exhibiting an S _m C ^* phase. 3. The display device according to claim 1, wherein the liquid crystal is a mixture of a liquid crystal compound having an ether-bonded chiral terminal chain and a fluorine-substituted phenyl ring. . 4. The liquid crystal has a ferroelectric phase in which an intersection angle between the first direction and the second direction is oriented at an angle larger than 45 °, and one of the pair of polarizing plates includes: The first direction and the second direction
4. The display element according to claim 1, wherein the direction of the optical axis is arranged in a range of an angle obtained by subtracting 45 ° from the intersection angle with respect to any of the directions. 5. The liquid crystal has a ferroelectric phase in which an intersection angle between the first direction and the second direction is oriented at an angle larger than approximately 60 °, and one of the pair of polarizing plates is , The first direction and the second direction
5. The display element according to claim 1, wherein the direction of the optical axis is arranged at an angle of about 12.5 [deg.] Or more with respect to any one of the above directions. 6. The liquid crystal according to claim 1, wherein when a voltage is not applied between the electrodes facing each other, an approximately bisector of an angle formed by the director of the liquid crystal molecules between the first direction and the second direction is provided. The display element according to claim 1, wherein the display element is an antiferroelectric liquid crystal exhibiting an antiferroelectric phase oriented in a direction parallel to the direction of the liquid crystal. 7. A pair of substrates having electrodes formed on opposing surfaces thereof, and a phase disposed between the pair of substrates and having no correlation between liquid crystal molecules between layers when no electric field is applied. A first ferroelectric phase in which the director is oriented in a first direction in response to a first voltage of one polarity applied between the electrodes;
And the second polarity of the other polarity applied between the electrodes.
A second orientation state indicating a second ferroelectric phase in which the director is oriented in a second direction in accordance with the voltage of any one of the above, and an arbitrary third voltage intermediate between the first voltage and the second voltage. And the liquid crystal molecules are oriented in a third alignment state in which the director is oriented in a direction intermediate between the first direction and the second direction in response to the application of the liquid crystal molecules. A liquid crystal, disposed between the pair of substrates, one of the optical axes is disposed at an angle sandwiched by the first and second directions, the other optical axis substantially with the one optical axis A pair of polarizing plates arranged orthogonally or parallel to each other, and the liquid crystal between the electrodes changes a director of liquid crystal molecules in an angle range narrower than an angle range sandwiched between the first direction and the second direction. Driving means for applying a voltage to be applied, Display element device using a liquid crystal exhibiting a conductive phase. 8. The display device according to claim 7, wherein the liquid crystal is formed by aligning a liquid crystal compound exhibiting an S _m CA ^* phase and a liquid crystal compound exhibiting an S _m C ^* phase. 9. The display device according to claim 7, wherein the liquid crystal is a mixture of a liquid crystal compound having an ether-bonded chiral terminal chain and a fluorine-substituted phenyl ring. . 10. The liquid crystal according to claim 1, wherein the liquid crystal is in the first direction and the second direction.
And the driving means has a ferroelectric phase each of which is oriented at an angle of intersection larger than 45 ° with respect to the direction of the liquid crystal molecules. The driving means includes an angle range in which the director of the liquid crystal molecules is sandwiched between the first direction and the second direction. 10. The display element device according to claim 7, wherein a voltage that changes in an angle range of approximately 45 ° is applied. 11. A pair of polarizing plates, wherein one of the optical axes is disposed substantially parallel to a direction on one side of an angle range of the director changed by the driving means. The display device according to claim 7, 8, 9, or 10. 12. An optical axis direction of one of the pair of polarizing plates is set in a range of an angle obtained by subtracting 45 ° from the intersection angle with respect to one of the first direction and the second direction. The display element device according to any one of claims 7 to 11, wherein 13. A pair of substrates, one of which has a pixel electrode and an active element connected to the pixel electrode arranged in a matrix, and the other of which has a counter electrode facing the pixel electrode. 13. The method according to claim 7, further comprising:
The display element device according to any one of the above. 14. The pair of substrates includes one substrate on which a scanning electrode is formed, and the other substrate on which a signal electrode extending in a direction perpendicular to the scanning electrode is formed. Claims 7 to 12
The display element device according to any one of the above.