JP2002161277A - Liquid crystal and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ferroelectric liquid crystal producible quickly at low cost. SOLUTION: This liquid crystal contains a molecule with flexible structure of the general formula 1 and comprises an achiral compound as a mixture of two or more compounds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal and a liquid crystal display using the same.

[0002]

BACKGROUND OF THE INVENTION The discovery of ferroelectric liquid crystals was made by Meyer of the United States in 1976. His point of view is that it is possible to express ferroelectricity by lowering the symmetry of the system. At that time, by using a constituent molecule or a chiral molecule having an asymmetric carbon in a part thereof, there were.
After that, due to its high-speed response, it has attracted attention as a material for a new display system that can replace nematic liquid crystal, and is still being studied.

[0003]

There are physical and structural aspects such as the occurrence of defects unique to a smectic having a layered structure, but chiral molecules having asymmetric carbon have two kinds of mirror symmetry with each other. Which need to be separated at the stage of synthesis. For this reason, it is said that ferroelectric liquid crystal materials are higher than ordinary nematic liquid crystals.

That is, the (anti) ferroelectric liquid crystal which is expected as a next generation flat panel display material is used in order to prevent the system from having the inversion symmetry which is a necessary condition for developing the ferroelectricity. In order to reduce symmetry), it is essential to construct or add chiral molecules. However, the synthesis of chiral molecules involves a chiral resolution step, and the time and cost involved are one of the problems. ing.

The present invention has been made in view of the above problems, and has as its object to provide a ferroelectric liquid crystal which can be manufactured quickly and at low cost, and a liquid crystal display using the same.

[0006]

The liquid crystal of the present invention contains molecules having a bent structure. The molecule having the above-mentioned bent structure is
It has the chemical structure shown in Chemical Formula 13.

Embedded image The above liquid crystal contains an achiral compound. The achiral compound described above is a mixture of two or more compounds. The above-mentioned achiral compound has the chemical structure shown in Chemical formula 14, Chemical formula 16, Chemical formula 17, Chemical formula 17, and Chemical formula 18.

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Further, the liquid crystal display of the present invention uses a liquid crystal containing molecules having a bent structure. The molecule having the above-mentioned bent structure has the chemical structure shown in Chemical formula 19.

Embedded image The above liquid crystal contains an achiral compound. The achiral compound described above is a mixture of two or more compounds. The above-mentioned achiral compound is a mixture of compounds having the chemical structures shown in Chemical formula 20, Chemical formula 22, Chemical formula 22, Chemical formula 23 and Chemical formula 24.

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According to the liquid crystal and the liquid crystal display of the present invention, since a molecule having a bent structure is contained in the achiral compound, a liquid crystal having ferroelectricity can be obtained, and a liquid crystal display using the same can be obtained. Can be.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention relating to a liquid crystal and a liquid crystal display will be described. The present invention introduces an achiral (having no asymmetric carbon) molecule having a specific molecular shape called a bent structure, thereby reducing the symmetry of the system not only by the chirality of the molecule but also by the molecular shape. It is intended to develop dielectric properties. It is thought that this simplifies the synthesis process and leads to cost reduction. In general, it has been reported that the liquid crystallinity of a molecule having a bent structure has a large tilt angle of the molecule and a fast response time of several microseconds, so it is considered to be attractive as a display material from the viewpoint of physical properties. Can be

A liquid crystal having a bent structure exhibits antiferroelectricity despite achiral molecules. This is considered to be a result of a decrease in symmetry caused by the bending direction of the molecule and the tilt direction of the molecule as in Link et al.

By the way, when a molecule having a bent structure is added to an ordinary rod-like molecule system, in many cases, molecules which are tilted in the same direction in the layer and whose bending directions are opposite to each other are present equally. The system will be achiral, but it is possible that in some systems the direction of the bends may be in some number of directions. In this case, the problem of the alignment, which has been a problem in the molecular liquid crystal phase having a bent structure, is solved, and (anti) ferroelectricity can be exhibited without performing chiral synthesis. In consideration of the above, the change in the liquid crystal phase when the liquid crystal molecules having a bent structure were added (doped) to the achiral rod-like liquid crystal molecules was examined.

That is, bent liquid crystal molecules have been synthesized on the assumption that ferroelectricity can be exhibited by the molecular shape and the accompanying polar interaction between the molecules. However, the theory is that the theory is based on the chirality generated by the bending direction of the molecule having a bent structure and the tilt direction of the molecule with respect to the layer normal. Therefore, this geometric chirality is equivalent to the right-handed and left-handed systems, but the generated domains are not only racemic (the same number of right-handed molecules and left-handed molecules are present and mixed equally), but only one exists. Homochiral domains have been observed. It is conceivable that the left and right equivalence may be slightly distorted depending on the surrounding environment, or that the chiral discrimination energy in the phase formation may be slightly changed depending on the environment.

[0013] That is, it is considered that this also suggests the possibility that geometric chirality is generated in each molecule itself depending on the system. When such molecules are mixed with a host liquid crystal composed of only ordinary achiral molecules, it is conceivable that one of the left and right molecular structures may become stable with the interaction with the host liquid crystal molecules. Then, they thought that it would not be necessary to synthesize a chiral molecule having an asymmetric carbon, and tried to develop it.

Here, a molecule having an achiral bent structure, that is, a molecule having a bent structure which itself forms liquid crystal,
It is added to the usual host achiral smectic liquid crystal.
Confirmation of ferroelectricity is made by measuring the polarization reversal current that contributes to spontaneous polarization when a triangular wave, which is normally measured, is applied,
The measurement was performed based on the measurement of change in transmittance. However, it is necessary to optimize the mixing amount in consideration of the compatibility between the host liquid crystal molecules and the molecules having the bent structure.

Next, the composition of the liquid crystal according to the present embodiment will be described. The liquid crystal according to this embodiment includes molecules having a bent structure. Here, the molecule of the bent structure is
Chemical formula 25 (chemical name: 1,3-phenylene bis)
[4- (4-n-alkoxyphenylimino
[methyl] -benzoate] (1,3-phenylenebis [4- (4-n-alkoxyphenyliminomethyl) -benzoate]).

[0016]

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Here, it is desirable that the carbon number n is in the range of 6 to 16. When n is smaller than 6, the liquid crystallinity is reduced. Further, this is because there is a disadvantage that the temperature range showing the liquid crystal phase depends on the high temperature side, etc.
If it is larger, the compatibility with other rod-shaped liquid crystals (host liquid crystals) will be reduced.

In this embodiment, the example of Chemical Formula 25 has been described as a molecule having a bent structure, but the present invention is not limited to this. In addition, a molecule having a bent structure such as Chemical Formula 26 can also achieve the object of the present invention.

[0019]

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The liquid crystal according to the present embodiment contains an achiral compound. Here, the achiral compound may be a mixture of two or more compounds as well as a single compound. As the achiral compound, an achiral compound shown in Chemical formula 27 and the like can be used in addition to the compounds used in Examples (described later).

[0021]

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The liquid crystal according to the present embodiment can be used for a liquid crystal display. Examples of usable liquid crystal displays include a ferroelectric liquid crystal display and an antiferroelectric liquid crystal display.

It should be noted that the present invention is not limited to the above-described embodiment, but can adopt various other configurations without departing from the gist of the present invention.

[0024]

Next, specific examples of the present invention will be described. However, it goes without saying that the present invention is not limited to these examples.

First, the composition of the liquid crystal used in this embodiment will be described. As a compound having a bent structure,
8-OPIMB (chemical name: 1,3-phenyl)
ene- [4- (4-n-octyloxyphenyly
liminomethyl) -benzoate]
(1,3-phenylene- [4- (4-n-octyloxyphenyliminomethyl) -benzoate])) was used. 8.5 wt% of a molecule 8-OPIMB having a bent structure was added as a dopant to a host liquid crystal described later. In addition, 8
-The phase series of OPIMB is B4 139.7B3 15
1.9 B2173.9 Iso. Specifically, the Iso (isotropic liquid) phase-B2 phase transition temperature is 173.9.
° C, B2 phase-B3 phase transition temperature is 151.9 ° C, B3 phase-
The B4 phase transition temperature is 139.7 ° C. Where B2
Each of the B3 and B4 phases is one of the liquid crystal phases. Further, the addition concentration is not limited to the above 8.5 wt%.
In addition, the addition concentration can be in the range of 3 to 50 wt%. If the addition concentration is less than 3 wt%, there is a disadvantage that the number of molecules having a bent structure is too small and no reversal is caused by an applied electric field, and if the addition concentration is more than 50 wt%, the ferroelectric phase becomes This is because a disadvantage of disappearing occurs.

[0026]

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The host liquid crystal used was “Mixt” shown below.
ure1 ″ is a mixture of five achiral phenylpyrimidine liquid crystals. That is, the achiral compound is represented by Chemical Formula 29 (chemical name: 5-nonyl-2- (4-h)
exyloxyphenyl) pyrimidine
(5-nonyl-2- (4-hexyloxyphenyl) pyrimidine), Chemical formula 30 (chemical name: 5-heptyl-2-
(4-nonyloxyphenyl) pyrimid
ine (5-heptyl-2- (4-nonyloxyphenyl) pyrimidine), Chemical formula 31 (chemical name: 5-octyl-
2- (4-octyloxyphenyl) pyrim
Idine (5-octyl-2- (4-octyloxyphenyl) pyrimidine), Chemical formula 32 (chemical name: 5-oct)
yl-2- (4-decyloxyphenyl) py
rimidine (5-octyl-2- (4-decyloxyphenyl) pyrimidine), and Chemical Formula 33 (chemical name:
5-heptyl-2- (4'-pentylbiph
(enyl-4-yl) pyrimidine (5-heptyl-2- (4'-pentylbiphenyl-4-yl) pyrimidine). The mixing ratio of each compound (the unit is a weight ratio)
Chemical formula 29: Chemical formula 30: Chemical formula 31: Chemical formula 32: Chemical formula 33 = 1: 1:
1: 1: 1.

[0028]

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[0029]

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[0030]

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[0031]

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[0032]

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The phase sequence of Mixture 1 is SmC
62SmA75N88iso. Can be represented by Specifically, i
so (isotropic liquid) phase-N (nematic) phase transition temperature is 8
8 ° C, N (nematic) phase-SmA (smectic A)
Phase transition temperature is 75 ° C, SmA (smectic A) phase-S
The mC (smectic C) phase transition temperature is 62 ° C. It should be noted that the mixing ratio of each compound is not limited to the above-described chemical formula 29: chemical formula 30: chemical formula 31: chemical formula 32: chemical formula 33 = 1: 1: 1: 1: 1. In addition, the mixing ratio is as follows:
0: Chemical formula 31: Chemical formula 32: Chemical formula 33 = 0 to 1: 0 to 1: 0
It can be in the range of 1: 0 to 1: 0 to 1:

Next, the adjustment of the sample will be described. As described above, the host liquid crystal used in this embodiment is a mixture of five kinds of achiral phenylpyrimidine liquid crystals.
As a dopant, a molecule 8-OPIMB having a bent structure is used as a dopant.
Was added at 8.5 wt%. The temperature of the liquid crystal was raised to about 160 ° C. and completely mixed in an isotropic phase to obtain a material.

The crystal is usually used by injecting it into a cell composed of two glass substrates called a cell. In this embodiment, I
Two glasses deposited with TO (Indium Tin Oxide) as a transparent electrode were used as substrates. Polyimide (trade name: SP550, manufactured by Toray) was applied thereto by spin coating, and imidization was performed at 270 ° C. Further, this is lightly rubbed with a velvet cloth attached to a rotating roller (rubbing treatment), and polyethylene terephthalate (P) having a thickness of 2 microns is sandwiched between two glass substrates.
ET) Two films were sandwiched and the side surfaces were fixed with epoxy resin to produce a horizontal alignment cell having a cell thickness of 2 microns.

While this was warmed to about 100 ° C. on a heater, it was heated to 100 ° C. from the side not coated with epoxy resin.
The crystals dissolved in the isotropic phase are injected with a spatula by capillary action. And from 100 ° C to about -0.2 ° C / mi
The liquid crystal was aligned in the cell by lowering the temperature to room temperature while gradually cooling to about n.

The change in the phase behavior of the liquid crystal will be described. The phase sequence of this mixed system was as follows. Mixture 1 / 8-OPIMB: Iso-N-S
mA-SmC

Next, it was confirmed whether or not the liquid crystal according to the present example had ferroelectricity. The ferroelectricity can be confirmed by (a) observation of the structure when an electric field is applied under a polarizing microscope,
(B) Change in transmitted light intensity and (c) polarization inversion current measurement. The temperature was set at room temperature (25 ° C.).

First, observation of the structure of the liquid crystal will be described. For tissue observation, use a polarizing microscope (trade name: OPTIPH).
OT-POL, manufactured by Nikon) was used. The axis of easy transmission between the polarizer and the analyzer of the microscope is made orthogonal (crossed Nicols), and the sample cell is set on the rotating stage between them.
When the sample is rotated, the amount of transmitted light changes in accordance with the orientation state of the molecules. By observing this, the orientation of the molecules can be seen.

FIG. 1 shows that, when the easy axes of transmission of the polarizer and the analyzer are orthogonal to each other and the direction of the molecular long axis of the SmA phase disposed between the polarizer and the analyzer is changed, FIG. 4 is a diagram illustrating a state in which a light amount changes and a bright state and a dark state occur.

The SmA phase has an arrangement in which the major axis of the molecule is parallel to the layer normal. Observation of this in a horizontal alignment cell arranged in the above-described manner shows that the easy axis of transmission of the polarizer is the optical axis of the SmA phase. In a state parallel to a certain molecular long axis direction (that is, the layer normal direction), the linearly polarized light that has passed through the polarizer passes through the liquid crystal as it is, so that it cannot pass through an analyzer that is set orthogonally, resulting in a dark state. .

When the orientation direction of the molecules is tilted from this state, the linearly polarized light becomes elliptically polarized light in the liquid crystal cell due to the effect of birefringence, and the light can partially pass through the upper analyzer. State.

FIGS. 2 and 3 show the case where the axes of easy transmission of the polarizer and the analyzer are orthogonal to each other and the direction of the molecular long axis of the SmC ^* phase disposed between the polarizer and the analyzer is changed. FIG. 7 is a diagram showing a state where a light transmission amount changes and a bright state and a dark state occur.

In the SmC ^* phase, which is a ferroelectric phase, the long axis of the molecule is inclined at an angle from the layer normal (this is referred to as the tilt angle). There are two possible states. Therefore, when the stage is rotated, the direction of the molecular long axis, which is the optical axis, and the direction of the easy axis of transmission of the polarizer coincide with each other when the layer normal and the axis of easy transmission of the polarizer are rotated by the tilt angle from the state where the layer normal and the easy axis of polarization are parallel. In this state, a dark state occurs.

Since there are two such states with respect to the layer normal, it is called a bistable state. Since these two states have a one-to-one correspondence with the polarization as shown in FIG. 4, if it can be confirmed that when the electric field is applied with the polarity changed, the states change uniformly to the respective states. This means that the molecule was inverted by the polarization inversion, which is a characteristic feature.

As described above, a polarizing microscope was used for the observation of the structure. The easy axis of the polarizer and the analyzer of the microscope are made orthogonal to each other, and the sample cell is set on the rotating stage between them.
Two types of domains are observed before the radio wave application, and when the stage is rotated, each domain becomes a dark state at about ± 6 degrees from a state where the layer normal and the transmission axis of the polarizer are parallel.

A DC electric field of +15 V and -15 V is applied to this.
Then, all regions change to one of the two states before the electric field is applied.
It turned out to be. This state change is caused by the ferroelectric liquid crystal S
mC ^*Corresponding to a stable two-state change in the
A change in the optical axis occurs symmetrically from the layer normal due to negative
As shown in Fig. 4, the characteristic of ferroelectricity is electric field and polarization.
Presumed to be molecular inversion caused by interaction
You. FIG. 4 shows an electric field when the liquid crystal of the present invention is used.
The liquid crystal molecules are inverted by reversing the
Changes, and the amount of transmitted light changes with the dark state.
Illustrates the appearance of a bright state, and further reduces the electric field
It is a figure which shows the memory effect in the case modelly. Also,
FIG. 5 shows that the liquid crystal molecules are inverted by changing the direction of the voltage.
Model of how the direction of the molecular long axis changes by rotating
FIG.

Next, the change in transmitted light intensity will be described. The definition of ferroelectricity is that the polarization can be inverted according to the direction of the applied electric field, which was also described in the observation of the structure, but it is also a major feature that it has a history depending on the direction of increase and decrease of the electric field. As one method for confirming this, an AC electric field is applied to the sample under a polarizing microscope, and the temporal change in the transmitted light intensity is measured.

FIG. 6 is a diagram showing an optical system used for measuring the change in transmitted light intensity and the polarization reversal current of the liquid crystal of this embodiment. The transmitted light intensity was measured by placing a photomultiplier tube (photomultiplier tube R955,
(Manufactured by Hamamatsu Photonics Co., Ltd.), and the sample, the polarizer, and the analyzer are arranged such that one of the SmC ^* phases is in a dark state.

In this state, when the molecules change the orientation direction by the electric field, the transmitted light intensity I can be expressed as I∝sin ² (2θ) · sin ² (π △ nd / λ). Here, θ, Δn, d, and λ are the tilt angle, the birefringence in the substrate surface, the cell thickness, and the wavelength of the incident light, respectively. Since this corresponds to the tilt direction of the molecule, the response of the molecule can be seen by observing the change in the transmitted light intensity with respect to the applied electric field. If it has ferroelectricity, the transmitted light intensity also has a history in the direction of increase and decrease of the applied electric field.

The measurement result of the transmitted light intensity change will be described. FIG. 7 is a diagram showing the electric field dependence of transmitted light intensity when a triangular wave voltage of 10 Hz ± 15 V is applied to the liquid crystal of this example. It clearly shows that it shows a single hysteresis (history). This also clearly shows that the system exhibits ferroelectric inversion.

The response speed was about 800 μsec with a change in transmittance of 10 to 90% when a rectangular wave of 10 Hz ± 15 V was applied.

Next, the measurement of the polarization reversal current will be described. As a method for directly confirming the electric field response of polarization, a polarization inversion current method was used. FIG. 6B shows an equivalent circuit.
An alternating current is applied to the liquid crystal from a waveform generator, and the current flowing therethrough is measured by measuring the potential on a resistor, which is an IV converter, with an oscilloscope.

The current flowing in this circuit can be broadly divided into a DC component Ii containing ions and the like, a capacitor component Ic when the cell is viewed as a capacitor, and a polarization reversal component Ip when the liquid crystal reverses polarization. Total current I
Can be written as I = Ii + Ic + Ip = V / R + C.dV / dt + Ip.

FIG. 8 shows a change in the total voltage I when a rectangular wave voltage is applied to the ferroelectric liquid crystal, and a capacitor component Ic, a DC component Ii, and a polarization inversion which are components of the total voltage I. It is a figure showing change of component Ip.
FIG. 9 shows the change in the total voltage I when a triangular wave voltage is applied to the ferroelectric liquid crystal, and the change in the total voltage I.
, A DC component Ii,
FIG. 6 is a diagram illustrating changes in polarization inversion component Ip.

The waveforms when a triangular wave and a rectangular wave are respectively applied as the AC electric field are as shown in FIGS. 8 and 9. Therefore, if the current component in the hatched portion is integrated over time, the polarization change 2P (+ P →
−P), and the spontaneous polarization is obtained by P / S because of the polarization per unit area. In the case of ferroelectricity, the polarization of molecules changes direction from + P to -P in a positive to negative electric field, so that a peak due to one polarization should be observed in a half cycle of AC.

In this embodiment, a carbon resistor was used for the IV conversion. Normally, 1 MΩ is used when applying a triangular wave, and 300 Ω is used when applying a rectangular wave. The applied waveform is frequency 1.
Hz, 5 Hz, and 10 Hz were measured at an amplitude of ± 15 V.

The measurement result of the polarization reversal current will be described. FIG. 10 is a diagram showing a time-change profile of the domain-inverted current when a triangular wave or rectangular wave voltage is applied to the liquid crystal of this embodiment. FIG. 10 shows a time-change profile of the polarization inversion current when a triangular wave of 10 Hz ± 15 V is applied.
FIG. 10A shows a time-change profile of the reversal current when a rectangular wave having the same frequency and amplitude is applied, and FIG.

Both the triangular wave and the rectangular wave application show profiles specific to ferroelectricity as described with reference to FIGS. 8 and 9, and the domain reversal current due to spontaneous polarization calculated therefrom is 3 to 4 nC / cm ^2. Was.

From the above three experimental facts, it was confirmed that this system certainly showed ferroelectric inversion. That is, from these results, it is understood that a ferroelectric liquid crystal material having high orientation can be formed even with an achiral system, and the cost can be reduced in synthesizing a display material.

Next, another embodiment will be described. As a host liquid crystal, TBBA (chemical name: N,
N '-[p-phenylenebis (methylidene)] bis [P
-Butylaniline]).

[0062]

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As the compound having a bent structure, 8-OPIMB represented by Chemical Formula 28 was used in the same manner as in the above-mentioned Example.
Molecular liquid crystal with a bent structure as a dopant in the host liquid crystal 8-
4.1 wt% of OPIMB was added. Other conditions are the same as in the above-described embodiment.

The change in the phase behavior of the liquid crystal will be described.
The phase sequence of this mixed system was as follows. TBBA / 8-OPIMB: Iso-N-SmA-SmC (low concentration) Iso-N-SmA- (SmC) -SmCA (high concentration) In this liquid crystal, it was confirmed that the liquid crystal was partially inverted.

As described above, according to this embodiment, since a molecule having a bent structure is included in the achiral compound, a liquid crystal having ferroelectricity can be obtained, and a liquid crystal display using the same can be obtained. be able to. This time, we found that even if an achiral molecule having a bent structure was added (doped) to an achiral host liquid crystal, ferroelectricity was exhibited, thereby eliminating the need for a chiral splitting step required in the synthesis of chiral molecules. This is expected to contribute to a reduction in required time and cost.

[0066]

The present invention has the following effects. According to the liquid crystal and the liquid crystal display of the present invention, since a molecule having a bent structure is included in the achiral compound, a liquid crystal having ferroelectricity can be obtained, and a liquid crystal display using the same can be obtained. Further, in a liquid crystal manufacturing process, required time can be reduced and cost can be reduced.

[Brief description of the drawings]

FIG. 1 shows that when the easy axes of the polarizer and the analyzer are orthogonal to each other and the direction of the molecular long axis of the SmA phase disposed between the polarizer and the analyzer is changed, the amount of transmitted light is FIG. 9 is a diagram illustrating a state in which a bright state and a dark state occur due to a change.

FIG. 2 shows the amount of light transmitted when the easy axes of transmission of the polarizer and the analyzer are orthogonal to each other and the direction of the molecular long axis of the SmC ^* phase disposed between the polarizer and the analyzer is changed. FIG. 6 is a diagram showing a state in which a light state changes and a bright state and a dark state occur.

FIG. 3 shows the amount of light transmitted when the easy axes of transmission of the polarizer and the analyzer are orthogonal to each other and the direction of the molecular long axis of the SmC ^* phase disposed between the polarizer and the analyzer is changed. FIG. 6 is a diagram showing a state in which a light state changes and a bright state and a dark state occur.

FIG. 4 In the case of using the liquid crystal of the present invention, by inverting the electric field, the liquid crystal molecules are inverted to change the direction of the long axis of the molecules. FIG. 9 is a diagram schematically illustrating a memory effect when an electric field is eliminated.

FIG. 5 is a diagram schematically showing a state in which liquid crystal molecules are inverted to change the direction of a molecular long axis by changing the direction of a voltage.

FIG. 6 is a diagram showing an apparatus used for measuring a change in transmitted light intensity and a polarization reversal current of the liquid crystal of the present invention.

FIG. 7 shows the results when a triangular wave voltage is applied to the liquid crystal of the present invention.
It is a figure which shows the electric field dependence of the transmitted light intensity.

FIG. 8 shows a change in a total voltage I when a rectangular wave voltage is applied to a ferroelectric liquid crystal, and a change in a capacitor component Ic, a DC component Ii, and a polarization inversion component Ip which are components of the total voltage I. It is a figure showing a change.

FIG. 9 shows a change in the total voltage I and a change in a capacitor component Ic, a DC component Ii, and a polarization reversal component Ip, which are components of the total voltage I, when a triangular wave voltage is applied to the ferroelectric liquid crystal. FIG.

FIG. 10 is a diagram showing a time-change profile of a domain inversion current when a triangular or rectangular wave voltage is applied to the liquid crystal of the present invention.

[Explanation of symbols]

1} smectic layer, 2} liquid crystal molecules (state a),
3 ‥‥ liquid crystal molecule (state b), 4 ‥‥ polarization Ps, 5 ‥‥ voltage, 6 ‥‥ light, 7 ‥‥ polarizer, 8 ‥‥ rotation stage, 9
{Electric furnace, 10} Liquid crystal cell, 11} Analyzer, 12
{Photomultiplier tube, 13} Waveform generator, 14I-
V converter, 15 ‥‥ oscilloscope, 16 ‥‥ personal computer

Claims (10)

[Claims] 1. A liquid crystal comprising a molecule having a bent structure. 2. The liquid crystal according to claim 1, wherein the molecule having the bent structure has a chemical structure represented by Chemical Formula 1. Embedded image 3. The liquid crystal according to claim 1, further comprising an achiral compound. 4. The liquid crystal according to claim 3, wherein the achiral compound is a mixture of two or more compounds. 5. The achiral compound is represented by Chemical Formula 2, Chemical Formula 3, Chemical Formula 4,
The liquid crystal according to claim 4, which is a mixture of compounds having the chemical structures shown in Chemical formulas (5) and (6). Embedded image Embedded image Embedded image Embedded image Embedded image 6. A liquid crystal display using a liquid crystal containing a molecule having a bent structure. 7. The liquid crystal display according to claim 6, wherein the molecule having the bent structure has a chemical structure shown in Chemical formula 7. Embedded image 8. The liquid crystal display according to claim 6, wherein the liquid crystal contains an achiral compound. 9. The liquid crystal display according to claim 8, wherein the achiral compound is a mixture of two or more compounds. 10. The achiral compound is represented by the following chemical formulas 8, 9 and 1.
10. The liquid crystal display according to claim 9, wherein the liquid crystal display is a mixture of compounds having the chemical structures shown in formulas (1), (2) and (3). Embedded image Embedded image Embedded image Embedded image Embedded image