JPH0781143B2 - Liquid crystal composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid crystal composition containing a novel liquid crystal substance, and more particularly to a ferroelectric liquid crystal material.

2. Description of the Related Art In recent years, liquid crystal displays have come into wide use not only in wristwatches, calculators, etc., but also in video equipment, and liquid crystal color televisions are also on the market. At present, the mainstream of liquid crystal panels for color display are those using nematic liquid crystals. But,
The properties of the nematic liquid crystal are not ideal and include many problems. Ferroelectric liquid crystal has various characteristics that nematic liquid crystal does not have such as fast response speed and memory property, and it is considered to be applied to a display device, and research is progressing from various fields. (Opttronics, 1983, No.
9) The ferroelectric liquid crystal will be described below with reference to the drawings. FIG. 11 is a schematic diagram of a ferroelectric liquid crystal molecule. Ferroelectric liquid crystal is a liquid crystal having a layer structure usually called smectic liquid crystal, and liquid crystal molecules have a structure inclined by θ with respect to the layer normal direction. Further, the ferroelectric liquid crystal molecules are usually composed of optically active liquid crystal molecules which are not racemic.

In FIG. 11, 7 is a liquid crystal molecule, 8 is a spontaneous polarization, 9 is a C director, 10 is a cone, 11 is a layer structure, 12 is a layer normal direction, and 13 is a tilt angle θ.

As shown in FIG. 11, the ferroelectric liquid crystal molecules have spontaneous polarization, and in the chiral smectic C phase,
It is free to move outside the cone 10 (cone) shown. The direction of the molecular long axis is slightly deviated for each layer, and the structure has a twisted structure as a whole. Next, the display principle of the ferroelectric liquid crystal will be described. Figure 12 is a diagram of the operating principle of a ferroelectric liquid crystal. FIG. 12 (a) shows a state in which no voltage is applied, and FIG. 12 (b) shows a state in which no voltage is applied from the back side of the paper to the front side.
FIG. 6C is a principle diagram of the operation when a voltage is applied in the opposite direction. 14 is a liquid crystal molecule in which the long axis of the molecule is tilted by + θ degrees with respect to the layer normal, 15 is a liquid crystal molecule in which −θ degrees is tilted, 16 is a dipole moment facing the front side of the paper, and 17 is facing the back side of the paper. There is a dipole moment, 18 is the direction of the two polarizing plates.
When a ferroelectric liquid crystal is sandwiched between glass substrates having transparent electrodes and the thickness of the panel is set to a spiral pitch or less, a region where molecules are tilted by + θ degrees with respect to the unwinding layer is formed as shown in Fig. 12 (a). It is divided into regions that are inclined by θ degrees. By applying a voltage in the front direction from the back surface of the space between the upper and lower electrodes, the entire cell becomes a monodomain tilted by + θ degrees as shown in FIG. 12 (b). When a reverse voltage is applied, the entire cell is -θ as shown in Fig. 12 (c).
It becomes a mono-domain tilted. Therefore, if birefringence or dichroism due to the electro-optic effect is used, it is possible to represent light and dark by two states tilted by + θ degrees.

When applying a ferroelectric liquid crystal to a display device,
The conditions required for liquid crystal materials are as follows.

(1) It exhibits a ferroelectric liquid crystal phase (eg, chiral smectic C phase) in a wide temperature range including room temperature.

(2) The response speed τ of the ferroelectric liquid crystal to the electric field is τ = η / Ps · E where η: viscosity Ps; spontaneous polarization E; applied electric field. Therefore, it is necessary to have a large spontaneous polarization in order to realize a high-speed response on the order of several μsec.

(3) As described above, the optical response of the ferroelectric liquid crystal is
It is first realized by a stable bi-state. According to Clerk et al.
It is necessary to make the cell gap d equal to or smaller than the spiral pitch p and unwind the spiral. N. A. Clark, S. Tee. Ragaval; Apple. Fizz. Let. , 36 899 (1980)
(NAClerk, STLagerwall; Apll.Phys.Lett., 36 899
(1980)) Therefore, in order to use a cell with a thick cell gap that is easy to create, it is necessary to lengthen the helical pitch of the ferroelectric liquid crystal.

(4) The alignment state of the ferroelectric liquid crystal depends on the phase sequence of the liquid crystal material, and particularly the liquid crystal material having a smectic A phase (SmA) and a cholesteric phase (Ch) on the high temperature side of the ferroelectric liquid crystal phase has a good alignment. It is believed that status is obtained. That is, when the phase sequence of the ferroelectric liquid crystal material is, for example, a chiral smectic C phase * Iso → Ch → SmA → SmC * However, Iso; isotropic liquid Ch; cholesteric phase SmA; smectic A phase SmC *: chiral smectic C phase is desirable.

Further, among the liquid crystal materials having the above-mentioned phase series, it is considered that the one having a longer Ch phase pitch has a better alignment state.

In addition to the conditions described above, there are various requirements for the tilt angle θ of liquid crystal molecules.

Conventional ferroelectric liquid crystal materials are few practical materials even if only considering the temperature range, and it is the current situation that none of the materials satisfy all the above conditions and can be practically used.

An example of a conventional ferroelectric liquid crystal material is shown below. (+) P
-Decyloxybenzylidene p'amino 2-methylbutylcinnamate (+ DOBAMBC) However, SmG *; chiral smectic G phase Ps = 4 to 5 nC τ = several hundred μsec to several msec Problems to be solved by the invention However, the conventional ferroelectric liquid crystal material is practical even if only its temperature range is taken into consideration. At present, there is almost no liquid crystal material that satisfies all of the above four conditions and can be applied to a display device immediately. Further, in order to expand the temperature range, it is necessary to mix many kinds of ferroelectric liquid crystal materials. At this time, in order to satisfy the above-mentioned four conditions, all the left and right directions of pitch, the magnitude, and the polarity of spontaneous polarization in each of the cholesteric phase and the chiral smectic C phase of many ferroelectric liquid crystal materials are taken into consideration. However, there is a problem that it is difficult to obtain a practical ferroelectric liquid crystal composition because they must be mixed.

Means for Solving the Problems In order to solve the above problems, the present invention is a non-chiral ferroelectric liquid crystal material having a large spontaneous polarization (that is, has no twist structure and no spontaneous polarization) Smectic C. A ferroelectric liquid crystal composition having a long helical pitch is prepared by mixing a liquid crystal material exhibiting a phase or by mixing a liquid crystal material having a large spontaneous polarization with a liquid crystal material in which the twist direction is opposite first. However, a liquid crystal material exhibiting a smectic C phase that is non-chiral (that is, has no twisted structure and no spontaneous polarization) is mixed with the liquid crystal composition having a long pitch to exhibit a ferroelectric liquid crystal phase in a wide temperature range. In addition, it is possible to easily obtain a ferroelectric liquid crystal material having a good orientation and capable of high-speed response on the order of several tens of μsec.

Action Generally, in order to expand the temperature range of liquid crystals, it is necessary to mix two or more kinds of liquid crystal compounds having different molecular shapes. However, when mixing a ferroelectric liquid crystal material, it is necessary to consider the material constants such as the polarity of spontaneous polarization of the compound, the twisting direction of the ferroelectric liquid crystal phase, and the twisting direction of the cholesteric phase. . Therefore, if a non-chiral smectic C phase having no twist structure or spontaneous polarization is used for expanding the temperature range, the temperature range can be considered without considering the material constants such as the direction of twist and the polarity of spontaneous polarization. A liquid crystal composition having a wide range can be easily obtained. When a liquid crystal compound exhibiting a non-chiral smectic C phase is mixed with a ferroelectric liquid crystal compound, its spontaneous polarization decreases linearly with an increase in the non-chiral component as shown in FIG. When a liquid crystal compound is mixed with a non-chiral liquid crystal compound, the spontaneous polarization of the mixture becomes extremely small. In the case of the present invention, since a non-chiral liquid crystal compound is mixed with a ferroelectric liquid crystal compound having a very large spontaneous polarization, a decrease in the spontaneous polarization is considerably suppressed, and a ferroelectric liquid crystal composition having a relatively large spontaneous polarization is obtained. Easily obtained.
The twist direction of the helical axis is considered to be determined by the absolute configuration of the chiral part and whether the number of molecules from the benzene ring to the chiral center is even or odd. M. Tsukamoto. Tei. Otsuka, Kei. Morimoto, Yi. Murakami; Japan. Jay. Apple. Fizz. , 14 1307 (1975) (M.
Tukamoto, T.Otsuka, K.Morimoto, Y.Murakami; Japan.J.Ap
pl.Phys., 14 1307 (1975)) That is, if the absolute configuration of the chiral center is S-form and the number of atoms from the benzene ring to the chiral center is even, the direction of twist is right, and if it is odd, it is left. is there. Also, the absolute configuration of the chiral center is R
The opposite is true for the body. Generally, two methods can be considered for extending the pitch. One is a method of mixing a ferroelectric liquid crystal material with a liquid crystal material having no chiral, and a method of mixing a liquid crystal material having a twist direction opposite to that of the liquid crystal material. According to the latter method, a ferroelectric liquid crystal material having a long pitch can be easily obtained only by adding a small amount of a liquid crystal compound having a reverse twist, but the polarity of spontaneous polarization must be taken into consideration when mixing. On the other hand, according to the former method, in order to obtain a ferroelectric liquid crystal composition having a long pitch, the addition amount of the non-chiral liquid crystal compound increases, but the polarity of spontaneous polarization does not need to be taken into consideration, so that the pitch can be easily adjusted. It is possible to obtain a long ferroelectric liquid crystal composition. In addition, if a liquid crystal material having the same polarities of spontaneous polarization and opposite helical twist directions is mixed and a liquid crystal composition having a certain pitch pitch is mixed with a non-chiral liquid crystal material, a small amount of non-chiral component is obtained. With the addition of, a ferroelectric liquid crystal composition having a large spontaneous polarization, a long pitch, and a wide temperature range can be easily obtained.

Example An example of the present invention will be described with reference to the drawings. First, FIG. 6 shows the structure of a liquid crystal cell in which the response characteristics of the ferroelectric liquid crystal material were measured in this example. Here, 1 is a polarizing plate,
2 is a glass substrate, 3 is a transparent electrode, 4 is an organic polymer film which has been subjected to an alignment treatment by rubbing, 5 is a ferroelectric liquid crystal layer, 6
Indicates a spacer for keeping the cell thickness constant.
A ferroelectric liquid crystal material was enclosed in a cell having such a structure, and its response characteristics and spontaneous polarization were measured. The spontaneous polarization was measured using the triangular wave method.

Also, regarding the phase transition temperature, texture with a polarization microscope
Observation and DSC were used. The pitch of the Sc * phase was 100 μm and the orientation of the cell was 100 μm.
The compound that does not show the Ch phase was measured by a usual method using a wedge cell using a glass substrate that was subjected to an alignment treatment with a thickness of 5 mm by mixing it with a nematic liquid crystal.

Example 1 A compound having the general formula as a non-chiral compound is claimed as a compound (V) in which the configuration of the chiral moiety of the compound (I) according to claim 1 is 2S, 3S and X is an octoxy group. Phase transition temperature, spontaneous polarization, pitch for a four-component mixture system in which a liquid crystal mixture (VI) showing a smectic C phase consisting of three phenylpyrimidine compounds represented by the compound (II) And the response speed were measured. Table 1 below shows the structures and mixing ratios of non-chiral substances. FIG. 1 shows the phase diagram of the liquid crystal mixture (VI) and the compound (V), and FIG. 2 shows the spontaneous polarization at 25 ° C. and the concentration dependence of the response speed when 20 Vpp is applied. From FIG. 1, the chiral smectic C phase is shown in a wide temperature range including room temperature from around 53 ° C. to around 10 ° C. over the entire composition range. Moreover, from FIG. 2, the value of the spontaneous polarization decreases almost linearly with the increase of the non-chiral component, but
Even at 25 wt%, it has a relatively large spontaneous polarization of 10 nC or more. The response speed when a voltage of 20 Vpp was applied at 25 ° C did not slow down much even when the non-chiral component increased, and it showed a high-speed response of 33 μsec at 25 wt% chiral component. In this composition, the pitch was considerably long and the orientation was good. Good orientation was also obtained for compounds having compositions other than the above.

Example 2 A compound having the general formula as a non-chiral compound is claimed as the compound (V) in which the configuration of the chiral moiety of the compound (I) according to claim 1 is 2S, 3S and X is an octoxy group. Of the five-component mixed system in which a liquid crystal mixture (VII) showing a smectic C phase composed of four kinds of ester compounds represented by the compound (III) described in the above item 5 is mixed. The length and response speed were measured. Table 2 below shows the structures and mixing ratios of non-chiral substances. FIG. 3 shows the phase diagram of the liquid crystal mixture (VII) and the compound (V), and FIG. 4 shows the spontaneous polarization at 25 ° C. and the concentration dependence of the response speed when 20 Vpp is applied. From FIG. 2, a chiral smectic C phase is shown in a wide temperature range from around 50 ° C. to room temperature over the entire composition range. Moreover, although the value of the spontaneous polarization decreases almost linearly with the increase of the non-chiral component from FIG. 4, even if the chiral component reaches 25 wt%,
It has a relatively large spontaneous polarization of 10 nC or more. The response speed when a voltage of 20 Vpp is applied at 25 ° C tends to decrease as the non-chiral component increases, but the
It shows a high-speed response of 53 μsec at wt% and 95 μsec at 25 wt%. Further, in these compositions, the pitch was considerably long and the orientation was good. or,
Good orientation was obtained for compounds having compositions other than the above.

Example 3 In the compound (I) described in claim 1, since the configuration of the chiral part of the compound (I) is 2S, 3S and the compound (V) in which X is an octoxy group, the helical twist direction is right, the reverse twist The compound (VIII), wherein R of the compound (IV) is an octoxy group, is used as the compound having a left-handed twist, and the compound having the general formula as claimed in claim 3 is used as the non-chiral compound. 2 kinds of phenylpyrimidine compounds represented by the compound (II) and an ester compound 4 represented by the compound (III) whose general formula is Claim 4
And a liquid crystal mixture (I) showing a smectic C phase
The phase transition temperature, spontaneous polarization, pitch length, and response speed were measured for an 8-component mixed system in which X) was mixed. Table 3 below
The structure and mixing ratio of non-chiral substances are shown in Table 1. The composition of the mixed system measured was 25% by weight of the compound (VII) and 75% by weight of the mixture (IX). The alignment state of the liquid crystal panel produced by using this mixture was very good. The measurement results are shown below.

Transition temperature Melting point; 5 ℃ Spontaneous polarization; 6.5nC (33 ℃) Ch phase pitch; Infinite SmC * phase pitch; Infinite response speed; 85μsec (25 ℃, 40V) Example 4 A compound (I) according to claim 1, wherein the configuration of the chiral part of the compound (I) is 2S, 3S and X is a heptanoyloxy group, and the compound (I) is claimed as a non-chiral substance. The pitch length was measured for a four-component system using a mixture (VI) showing a smectic C phase in which three kinds of phenylpyrimidine compounds represented by the general formula (II) described in item 4 were mixed, and the liquid crystal composition was measured. The response characteristics of the liquid crystal display device using the product were measured. The measurement results are shown below. The structures and compositions of the non-chiral compounds are shown in Table 1. The composition of the mixed system measured was 25 wt% of the compound (X) and the mixture (V
I) was 75 wt%. The alignment state of the liquid crystal cell prepared by using this mixture was very good. The measurement results are shown below.

Example 5 Since the configuration of the chiral moiety of the compound (I) described in claim 1 is 2S, 3S and X is a heptanoyloxy group, the helical twist direction of the compound (X) is right. ,
Compound (IV) whose twist direction is left as a compound of reverse twist
5. The phenylpyrimidine compound 2 according to claim 4, which is used as a non-chiral substance in a liquid crystal material in which the pitch is extended by using the compound (VIII) in which the configuration of the chiral moiety is S-form and R'is an octoxy group. Phase transition temperature, pitch length, spontaneous polarization, response speed for an eight-component system using a mixture (IX) showing a smectic C phase in which four types and four types of ester compounds described in claim 5 are mixed. Was measured. The structure and composition of the non-chiral mixture used are shown in Table 3. The pitch of the compound (X) diverges when 75 wt% of the compound (VIII) is added. Therefore, as a chiral compound, 25 wt% of compound (X), compound (VIII)
Of 75 wt% of the mixture (XI) was used. The mixture (VI
The phase diagram of II) and the mixture (IX) are shown in Fig. 6 showing the spontaneous polarization at 25 ° C and the concentration dependence of the response speed when a voltage of 44 Vpp is applied. As shown in Fig. 5, chiral smectic C is observed in a wide temperature range from 55 ° C to 45 ° C to room temperature over the entire composition range.
In particular, when the mixture (IX) is 25 wt%, it exhibits a chiral smectic C phase from 53 ° C to 13 ° C, and Fig. 6 shows a high response speed of 100 µsec in this composition. Further, in this composition, the pitch was considerably long and the orientation was very good.
Further, compounds having compositions other than the above also showed good orientation.

Example 6 The helical twist direction of compound (X) and compound (V) in which the configuration of the chiral moiety of compound (I) according to claim 1 is 2S, 3S and X is a heptanoyloxy group. Is a right-handed compound, a compound (VII) in which the configuration of the chiral part of the compound (IV) with a left-handed twist direction is S-form and R'is an octoxy group as a compound with a reverse twist, and the pitch is extended. A mixture (IX) showing a smectic C phase in which two kinds of phenylpyrimidine compounds according to claim 4 and four kinds of ester compounds according to claim 5 are mixed as a non-chiral substance. The 8-component system used was measured for phase transition temperature, pitch length, spontaneous polarization, and response speed. The structure and composition of the non-chiral mixture used are shown in Table 2. The mixing ratio of the compound (V) and the compound (X) was 50 wt%, and the pitch of this mixture diverged when 75 wt% of the compound (VII) was added. Therefore,
25 compounds (V) + compounds (X) as chiral compounds
A mixture (XII) of wt% and compound (VII) of 75 wt% was used. The transition temperature, pitch, spontaneous polarization and response speed of a liquid crystal composition prepared by mixing a chiral substance of this composition with 50 wt% of a non-chiral mixture (IX) were measured. The results are shown below. Further, the alignment state of the liquid crystal panel prepared by using the liquid crystal composition having this composition was very good.

Transition temperature Melting point: 2.6 ℃ Spontaneous polarization: 15.4nC (25 ℃) Ch phase pitch: Infinite SmC * phase pitch: Infinite Response speed: 30μsec (25 ℃ 44Vpp) Example 7 The helical twist direction of the compound (XIII) in which the configuration of the chiral moiety of the compound (I) according to claim 1 is 2S, 3S and R is a nonyloxycarbonyloxy group is right. Therefore, as the compound of the reverse twist, the configuration of the chiral part of the compound (IV) whose twist direction is left is S-form and R ′ is R ′.
Wherein the compound (VII) in which is an octoxy group is used as a non-chiral substance in a liquid crystal material having a pitch extended, two kinds of phenylpyrimidine compounds as claimed in claim 4 and an ester compound as claimed in claim 5 The mixture (IX) which shows the smectic C phase which mixed four kinds of compounds of the above was used.
The structure and composition of the non-chiral mixture used are shown in Table 3. The pitch of compound (XIII) is 75 wt% of compound (VII)
Divers when put. Therefore, as the chiral compound, a mixture (XIV) containing 25 wt% of the compound (XIII) and 75 wt% of the compound (VII) was used. Figure 7 shows mixture (IX) and mixture (XI
The phase diagram of (V) shows the response speed at 25 ° C in Fig. 8. The composition of the mixture used for the measurement is Compound (XII) 12.5w
t%, compound (XIII) 37.5wt%, mixture (IX) 50wt
%Met. The measurement results of transition temperature, pitch, spontaneous polarization and response speed are shown below. Further, in this composition, the pitch was considerably long and the orientation was very good.

Further, compounds having compositions other than the above also showed good orientation.

Transition temperature Melting point; -7.5 ° C Spontaneous polarization; 9.15nC (25 ° C) Ch phase pitch; Infinite SmC * phase pitch; Infinite response speed; 45μsec (25 ° C, 40Vpp) Example 8 Claim 1 In the compound (I), the configuration of the chiral part is 2S, 3S and R is a nonyloxycarbonyloxy group, and the twist direction of the helix of the compound (V) is right. A compound (VII) in which the configuration of the chiral part of the compound (IV) whose twist direction is left is the S-form and R'is an octoxy group
Smectic C obtained by mixing two kinds of phenylpyrimidine-based compounds according to claim 4 and four kinds of ester-based compounds according to claim 5 as a non-chiral substance in a liquid crystal material whose pitch is extended by using Phase transition temperature, pitch length, spontaneous polarization, and response speed were measured for an eight-component system using a mixture (VIII) exhibiting a phase. The structure and composition of the non-chiral mixture used are shown in Table 3.
The mixing ratio of the compound (XIII) and the compound (V) was 50 wt%, and the pitch of this mixture diverged when 75 wt% of the compound (VII) was added. Therefore, the compound (XIII) is used as a chiral compound.
+ A mixture containing 25 wt% of the compound (V) and 75 wt% of the compound (VII) was used. A transition temperature of a liquid crystal composition obtained by mixing a chiral substance of this composition with 50 wt% of a non-chiral mixture (IX),
The pitch was measured. The results are shown below. Further, the alignment state of the liquid crystal panel prepared by using the liquid crystal composition having this composition was very good.

Transition temperature Ch phase pitch; infinity SmC * phase pitch; infinity Effect of the Invention As described above, according to the present invention, a ferroelectric liquid crystal material having a large spontaneous polarization is mixed with a non-chiral liquid crystal material, or a spontaneous polarization is large. Providing a ferroelectric liquid crystal material having a large spontaneous polarization and capable of high-speed response by mixing an anti-twist liquid crystal material with a ferroelectric liquid crystal material and extending the pitch to mix a non-chiral liquid crystal material Is.

[Brief description of drawings]

FIG. 1 is a phase diagram of a mixed system in Example 1 of the present invention, and FIG.
FIG. 3 is a characteristic diagram of the ferroelectric liquid crystal cell in Example 1 of the present invention, showing the response speed and concentration dependence of spontaneous polarization. FIG. 3 is a phase diagram of the mixed system in Example 2 of the present invention. 5 is a characteristic diagram of the response speed of the ferroelectric liquid crystal cell and concentration dependence of spontaneous polarization in Example 2, FIG. 5 is a phase diagram of the mixed system in Example 5 of the invention, and FIG. 6 is Example 5 of the invention. FIG. 7 is a characteristic diagram of the response speed of the ferroelectric liquid crystal cell and the concentration dependence of spontaneous polarization, and FIG. 7 is a phase diagram of the mixed system in Example 7 of the present invention.
FIG. 8 is a response characteristic diagram of a ferroelectric liquid crystal cell in Example 7 of the present invention, FIG. 9 is a concentration dependent characteristic diagram of spontaneous polarization when a non-chiral substance is mixed with a chiral substance, and FIG. FIG. 11 is a schematic diagram of the dielectric liquid crystal cell, FIG. 11 is a schematic diagram of the ferroelectric liquid crystal, and FIG. 12 is a schematic diagram showing the operation principle of the ferroelectric liquid crystal. 1 ... Polarizing plate, 2 ... Upper and lower glass substrates, 3 ... Transparent electrodes, 4 ... Aligned organic alignment film, 5 ... Ferroelectric liquid crystal phase, 6 ... Keeping cell thickness constant Spacers, 7 ... Ferroelectric liquid crystal molecules, 8 ... Spontaneous polarization, 9 ...
C director, 10 ...... cone, 11 ...... layer, 12 ...... layer normal, 13 ...... molecule tilt angle θ with respect to layer normal, 14 …… molecule major axis tilts + θ with respect to layer normal Liquid crystal molecules, 15 ... Liquid crystal molecules whose major axis is inclined by -θ with respect to the layer normal, 16 ...
Dipole moment facing the front of the paper, 17 …… Dipole moment facing the back of the paper, 18 …… Direction of two polarizing plates.

Front page continued (72) Inventor Takao Sakurai 1-1, Suzuki-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Ajinomoto Co., Inc. Central Research Laboratory (72) Inventor Ryoichi Higuchi 1-1, Suzuki-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Ajinomoto Co., Inc. Central Research Laboratory

Claims (11)

[Claims] 1. A smectic liquid crystal exhibiting ferroelectricity,
General formula (Wherein, X is any one of R-, RO-, RCOO-, and ROCOO-, and R is an alkyl group) and the liquid crystal compound in which the chiral portion does not form a racemate and a non-chiral smectic A liquid crystal composition comprising at least one liquid crystal compound exhibiting a C phase. 2. At least one kind of liquid crystal compounds exhibiting an asymmetric chiral smectic C phase is represented by the general formula: (Wherein R and R'represent an alkyl group or an alkoxy group respectively), The liquid crystal composition according to claim 1. 3. At least one type of liquid crystal compound exhibiting a non-chiral smectic C phase is represented by the general formula: (Wherein R and R'represent an alkyl group or an alkoxy group respectively), The liquid crystal composition according to claim 1. 4. A liquid crystal compound exhibiting a non-chiral smectic C phase is at least a compound represented by the general formula (II) and a compound represented by the general formula (III). Item 1. The liquid crystal composition according to any one of items 2 and 3. 5. A smectic liquid crystal exhibiting ferroelectricity,
General formula (Wherein, X is any one of R-, RO-, RCOO-, and ROCOO-, and R is an alkyl group), and the chiral part represented by the formula is a liquid crystal compound which is not racemic 2. A liquid crystal composition comprising a liquid crystal composition obtained by mixing a compound having the opposite twist direction and one or more kinds of liquid crystal compounds each exhibiting a non-chiral smectic C phase. 6. At least one liquid crystal compound exhibiting a non-chiral smectic C phase is represented by the general formula: (Wherein R and R'represent an alkyl group or an alkoxy group respectively), The liquid crystal composition according to claim 5. 7. At least one kind of liquid crystal compounds showing a non-chiral smectic C phase is represented by the general formula: (Wherein R and R'represent an alkyl group or an alkoxy group respectively), The liquid crystal composition according to claim 5. 8. A liquid crystal compound showing a non-chiral smectic C phase is at least a compound represented by the general formula (II) and a compound represented by the general formula (III). Item 5 The liquid crystal composition according to any one of items 6 and 7. 9. A liquid crystal compound having a non-chiral smectic C phase is at least one compound represented by the general formula: (Wherein R and R'represent an alkyl group or an alkoxy group, respectively), and at least one of the compound represented by the general formula (I) and the compound having the opposite helical twist direction is represented by the general formula (Wherein R represents an alkyl group or an alkoxy group in the formula) is a liquid crystal compound which does not form a racemate.
Item 4. The liquid crystal composition according to any one of items. 10. At least one kind of liquid crystal compounds showing a non-chiral smectic C phase is represented by the general formula: (Wherein R ″ and R each represent an alkyl group or an alkoxy group), and at least one of the compound represented by the general formula (I) and the compound having the opposite helical twist direction is a general formula. (Wherein R represents an alkyl group or an alkoxy group in the formula) is a liquid crystal compound which does not form a racemate, according to any one of claims 5 to 7. The liquid crystal composition described. 11. A liquid crystal compound exhibiting a non-chiral smectic C phase is at least a compound represented by the general formula (II) and a compound represented by the general formula (III). Item 9. The liquid crystal composition according to any one of item 10.