JP2010077351A - Ferroelectric liquid crystal composition and liquid crystal display element - Google Patents

Abstract

更に、本願発明は当該液晶組成物に光学活性化合物を含有する強誘電性液晶組成物及びこれを用いた液晶表示素子を提供する。本発明の液晶組成物及び強誘電性液晶組成物はチルト角が大きく、高い透過率を有する強誘電性液晶素子が可能である。またINAC相を示すため、配向性も良好である。
本願発明の強誘電性液晶組成物は、強誘電性液晶ディスプレイの構成部材として極めて有用である。
【選択図】 なしPROBLEM TO BE SOLVED: To provide a ferroelectric liquid crystal composition having a large tilt angle. A compound having a relatively long linear alkyl group in which R ₁ and R ₂ have 7 or more carbon atoms in the general formula (I). And a liquid crystal composition containing the compound represented by formula (II).
[Chemical 1]

Furthermore, the present invention provides a ferroelectric liquid crystal composition containing an optically active compound in the liquid crystal composition and a liquid crystal display device using the same. The liquid crystal composition and the ferroelectric liquid crystal composition of the present invention can be a ferroelectric liquid crystal device having a large tilt angle and high transmittance. In addition, since it exhibits an INAC phase, the orientation is also good.
The ferroelectric liquid crystal composition of the present invention is extremely useful as a constituent member of a ferroelectric liquid crystal display.
[Selection figure] None

Description

  The present invention relates to a ferroelectric liquid crystal composition and a liquid crystal display device using the composition. More specifically, the present invention relates to a ferroelectric liquid crystal composition exhibiting a ferroelectric liquid crystal phase in a wide temperature range including room temperature and having high transmittance and high contrast, and a ferroelectric liquid crystal device using the composition.

Surface Stabilized Ferroelectric Liquid Crystal (SSFLC for short) proposed by Clark and Lagerwall et al.
Next-generation display because it has characteristics such as (1) high-speed response, (2) memory performance, (3) wide viewing angle, and (4) passive drive capability. It is attracting attention as an element (see Non-Patent Document 1).

Since this SSFLC uses a chiral smectic C phase of a smectic liquid crystal, it behaves fundamentally differently from a nematic phase. That is, when the smectic phase is applied as a liquid crystal display element, a phenomenon in which the smectic liquid crystal has a layer structure and the major axis (direction of molecules) of liquid crystal molecules is inclined from the direction in which the layer structure is formed is used. The angle at which the liquid crystal molecules tilt from the normal direction of the layer is called the tilt angle (tilt angle θ), which is a characteristic property when using smectic liquid crystal as a liquid crystal element, and it is desirable to obtain a tilt angle suitable for the liquid crystal element. The general orientation of the liquid crystal element of SSFLC and the polarizing plate makes the alignment direction of the liquid crystal when no voltage is applied after voltage application (for example, + V) and the absorption axis direction of the polarizing plate coincide. Therefore, when no voltage is applied after + V is applied, light is blocked (black display). When no voltage is applied after applying −V, the liquid crystal is aligned in the direction corresponding to the tilt angle (θ) of the liquid crystal, and light is transmitted (white display). Therefore, the light transmittance becomes the largest when the tilt angle (θ) of the ferroelectric liquid crystal composition is about 22.5 °, and a bright screen can be obtained. SSFLC has the excellent features of (1) to (4) above, but it is difficult to display halftones because of the binary display of white and black with memory characteristics.

In recent years, a polarization-blocking smectic liquid crystal element (PSS-FLC) has been used as a ferroelectric liquid crystal display element having characteristics such as high-speed response and halftone display using a ferroelectric liquid crystal composition (Non-patent Document 2). ) And polymer-stable ferroelectric liquid crystal (polymer-stable FLC) (see Non-Patent Documents 3 and 4). These PSS-FLC and polymer-stable FLC operate by the chiral smectic C (SmC ^* ) phase of the smectic liquid crystal. In PSS-FLC and polymer stable FLC, the general liquid crystal element and the orientation of the polarizing plate are the average orientation of the liquid crystal when no voltage is applied, and one of the two polarizing plates. The absorption axis directions are the same. In a general operation using an applied voltage, light is blocked when no voltage is applied (black display), and light is transmitted (white display) when an electric field is applied (+ V or −V). Therefore, the light transmittance of these liquid crystal display elements becomes the largest when the tilt angle (θ) of the ferroelectric liquid crystal composition is about 45 °, and a bright screen can be obtained.

  Thus, in the case of PSS-FLC and polymer stable FLC, in order to obtain a bright screen, a tilt angle that is about twice as large as that of conventional SSFLC is required. Therefore, there is a demand for a tilt angle that is as large as possible.

In addition, in order to make the smectic phase liquid crystal orientation uniform, the phase change of the ferroelectric liquid crystal composition depending on the temperature isotropic liquid phase from the high temperature side—chiral nematic (N *) phase—smectic ASmA ^* ) phase— It is important to show the SmC ^* phase-crystal phase transition series (INAC phase). Furthermore, since the operating temperature of the ferroelectric liquid crystal display element is limited by the temperature range of the SmC ^* phase, it has a wide temperature range. It is important to develop the SmC ^* phase.

In a ferroelectric liquid crystal device, it is relatively easy to increase only the tilt angle, but it is possible to keep the tilt angle large while the phase change due to temperature shows the INAC phase and the SmC ^* phase in a wider temperature range. It was difficult.

  Patent Document 1 discloses a ferroelectric liquid crystal composition having a relaxed cone angle of 13 to 40 °. When expressed by a tilt angle (θ), it is about 7 to 20 ° and is sufficiently bright. Obviously, no screen is available.

Further, a ferroelectric liquid crystal composition having a large tilt angle while a phase change due to temperature shows an IAC phase and an SmC ^* phase in a wider temperature range is disclosed (Patent Document 2). The ferroelectric liquid crystal composition according to this publication achieves a wide temperature range of the chiral smectic (SmC ^* ) phase and the phase transition series of INAC. However, since the tilt angle is about 25 to 28 °, the screen is sufficiently bright. It is clear that cannot be obtained.

Japanese National Patent Publication No. 10-501019 JP 2002-363565 A Applied Physics Letters 36, 899 (1980) Mochizuki SID04, 1156 F. Furue, Japan Journal of Applied Physics, Jpn. J. Appl. Phys., 36, L1517 (1997) F. Furue, Japan Journal of Applied Physics (Jpn. J. Appl. Phys.), 40, 5790 (2001)

The problem to be solved by the present invention is a ferroelectric liquid crystal composition having a large tilt angle, a phase transition series depending on temperature, if necessary, showing an IAC phase, and an SmC ^* phase in a wider temperature range. And providing a ferroelectric liquid crystal device.

In order to solve the above problems, the present inventors have found that the tilt angle is effectively increased by using a specific liquid crystalline compound. The inventors of the present application have studied the composition of various liquid crystal compounds and have completed the present invention.
The present invention relates to the general formula (I)

(Wherein R ₁ and R ₂ each independently represents a linear alkyl group having 7 to 18 carbon atoms, and one or two non-adjacent —CH ₂ — groups in the alkyl group are -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -S-CO-, -O-CO-O-, -CH = CH-, -C≡C-, a cyclopropylene group, or -Si (CH ₃ ) _2- may be substituted, and a hydrogen atom in the alkyl group may be substituted with a fluorine atom or a CN group,
A, B and C are each independently 1,4-phenylene group, pyrazine-2,5-diyl group, pyridazine-3,6-diyl group, pyridine-2,5-diyl group, pyrimidine-2,5- Diyl group, trans-1,4-cyclohexylene group, 1,3,4-thiadiazole-2,5-diyl group, 1,3-dioxane-2,5-diyl group, 1,3-dithian-2, 5-diyl group, 1,3-thiazole-2,4-diyl, 1,3-thiazole-2,5-diyl, thiophene-2,4-diyl group, thiophene-2,5-diyl group, piperazine-1 , 4-diyl group, piperazine-2,5-diyl group or naphthalene-2,6-diyl group, the hydrogen atoms in the 1,4-phenylene group and naphthalene-2,5-diyl group are fluorine atoms. , CF ₃ group, OCF ₃ group, CN groups, H ₃ group, or may be substituted in the OCH ₃ group, a hydrogen atom in xylene group to said trans-1,4-cyclohexylene may be replaced by a CN group or a CH ₃ group,
L ₁ and L ₂ are each independently a single bond, —O—, —S—, —CO—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, —CO—. O—, —O—CO—, —CO—S—, —S—CO—, —O—CO—O—, —CH ₂ CH ₂ —, —CH═CH—, —C≡C— or —OCH. A compound represented by ₂ CH _2- ,
And general formula (II)

(Wherein R ₂₁ and R ₂₂ each independently represents a linear alkyl group having 1 to 12 carbon atoms). A liquid crystal composition comprising: Provided is a ferroelectric liquid crystal composition containing the liquid crystal composition and an optically active compound, and also provides a ferroelectric liquid crystal display device using the ferroelectric liquid crystal composition.

  Since the liquid crystal composition, the ferroelectric liquid crystal composition, and the ferroelectric liquid crystal element of the present invention have a characteristic that a large tilt angle can be obtained, high transmittance is possible and a bright screen can be displayed. . Therefore, the ferroelectric liquid crystal composition of the present invention is extremely useful as a constituent member of a ferroelectric liquid crystal element.

The liquid crystal composition of the present invention is composed of a compound represented by the general formula (I). In the general formula (I), R ₁ and R ₂ are each independently a straight chain having 7 to 18 carbon atoms. A linear alkyl group having 7 to 16 carbon atoms is preferable, and a linear alkyl group having 7 to 15 carbon atoms is more preferable.
In general formula (I), more specifically, a compound having a structure described below as a ring structure is preferable.

In the general formula (II), R _{21 and} R ₂₂ each independently represent a linear alkyl group having 1 to 12 carbon atoms, preferably a linear alkyl group having 4 to 12 carbon atoms.
The content of the compound represented by the general formula (I) is preferably 5 to 40%, more preferably 10 to 30%, and it is preferable to contain two or more compounds represented by the general formula (I).

The content of the compound represented by the general formula (II) is preferably 5 to 40%, more preferably 5 to 30%, and preferably two or more compounds represented by the general formula (II) are contained.
The ferroelectric liquid crystal composition of the present invention contains a compound represented by general formula (I) or general formula (II) and an optically active compound. As the optically active compound, a compound having an asymmetric atom or a compound having axial asymmetry can be used, and a compound having an asymmetric carbon or a compound having a carbon-carbon bond as axial asymmetry is preferably used. A compound having an asymmetric carbon atom is more preferable.

In an optically active compound having an asymmetric carbon, the asymmetric carbon may be introduced into a part of a chain structure or a part of a cyclic structure, and a fluorine atom or a methyl group may be present on the asymmetric carbon. A compound having an ethyl group or CF ₃ group introduced therein is preferred.
Specifically, the optically active compound is represented by the general formula (IV)

(In the formula, each of R ₄₁ and R ₄₂ independently represents a linear or branched alkyl group having 1 to 18 carbon atoms, and one or two non-adjacent —CH in the alkyl group. _2- groups are -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -S-CO-, -O-CO-O-, -CH. ═CH—, —C≡C—, a cyclopropylene group, or —Si (CH ₃ ) ₂ — may be substituted, and a hydrogen atom in the alkyl group may be substituted with a fluorine atom or a CN group,
A ₄ , B ₄ and C ₄ are each independently 1,4-phenylene group, pyrazine-2,5-diyl group, pyridazine-3,6-diyl group, pyridine-2,5-diyl group, pyrimidine-2. , 5-diyl group, trans-1,4-cyclohexylene group, 1,3,4-thiadiazole-2,5-diyl group, 1,3-dioxane-2,5-diyl group, 1,3-dithiane -2,5-diyl group, 1,3-thiazole-2,4-diyl, 1,3-thiazole-2,5-diyl, thiophene-2,4-diyl group, thiophene-2,5-diyl group, Represents a piperazine-1,4-diyl group, a piperazine-2,5-diyl group or a naphthalene-2,6-diyl group, but a hydrogen atom in the 1,4-phenylene group and naphthalene-2,5-diyl group a fluorine atom, CF ₃ group, OCF ₃ group, N group, a CH ₃ group, or may be substituted in the OCH ₃ group, a hydrogen atom in xylene group to said trans-1,4-cyclohexylene may be replaced by a CN group or a CH ₃ group,
a ₄ , b ₄ and c ₄ each independently represent 0 or 1, * represents an asymmetric carbon,
L ₄₁ and L ₄₂ are each independently a single bond, —O—, —S—, —CO—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, —CO—. O—, —O—CO—, —CO—S—, —S—CO—, —O—CO—O—, —CH ₂ CH ₂ —, —CH═CH—, —C≡C— or —OCH. ₂ represents CH ₂ —, and L ₄₃ represents the general formula (IV-b), the general formula (IV-c), or the general formula (IV-d).

(Wherein d ₄ , e ₄ , and f ₄ each independently represents an integer of 0 or more and 7 or less), Y represents a fluorine atom, a methyl group, an ethyl group, or Represents a CF3 group. ) Is preferred.
Furthermore, Y in the general formula (IV) is more preferably a fluorine atom or a methyl group.
Furthermore, the general formula (IV-a)

又は、一般式（IV-e）

Or general formula (IV-e)

（式中、Ｒ_４１、Ｒ_４２、Ａ_４、Ｂ_４、Ｃ_４、ａ_４、ｂ_４、ｃ_４、Ｌ_４１、Ｌ_４２、Ｌ_４３及び＊は、一般式（IV）と同じ意味を表す。）で表される化合物がより好ましい。
一般式（IV）において、より具体的には環構造として以下に記載される構造を有する化合物が好ましい。

(In the formula, R ₄₁ , R ₄₂ , A ₄ , B ₄ , C ₄ , a ₄ , b ₄ , c ₄ , L ₄₁ , L ₄₂ , L ₄₃ and * represent the same meaning as in general formula (IV)). .) Is more preferable.
In general formula (IV), more specifically, a compound having a structure described below as a ring structure is preferable.

これらの構造の中で、特に好ましい構造は、下記の構造である。

Among these structures, particularly preferred structures are the following structures.

不斉炭素原子を有する側鎖として具体的には下記構造を有する化合物がより好ましい。

Specifically, a compound having the following structure is more preferable as the side chain having an asymmetric carbon atom.

(In the formula, s represents an integer of 1 to 4, r represents an integer of 1 to 10, Q ₃ represents an alkyl group having 3 to 10 carbon atoms, and Q ₄ represents an alkyl group having 2 to 10 carbon atoms. Q ₅ represents an alkyl group having 1 to 10 carbon atoms, Q ₆ represents an alkyl group having 1 to 4 carbon atoms, and * represents an asymmetric carbon.)
More specifically, a compound having the following structure is particularly preferably used as the compound represented by the general formula (IV-a).

(In the formula, R ₁ represents an alkyl group having 1 to 10 carbon atoms, n represents the number of methylene groups having 1 to 10 carbon atoms, and * represents an asymmetric carbon.)
The liquid crystal composition of the present invention preferably undergoes a phase transition from the orientation surface to the SC * phase via the N * phase and then the SA phase during cooling from the isotropic liquid state. The SA phase is not necessarily required, but it is desirable from the viewpoint of orientation. However, in the case of half-V application, since the SmA phase is unnecessary, a liquid crystal composition exhibiting an isotropic phase, N * phase, or SmC * phase transition is preferable.

In a ferroelectric liquid crystal composition formed by adding a single optically active compound, it is preferable that the N * phase is untwisted just above the transition to the SmA phase in terms of orientation.
SC * in which the pitch of the spiral appearing in the N * phase from the phase transition temperature from the N * phase to the SmA phase (hereinafter referred to as N * -SA point) to the high temperature side of the N * -SA point is 3 μm or more A liquid crystal composition is more preferable, and a liquid crystal composition in which the pitch of the spiral is 10 μm or more and the pitch of the spiral increases as it approaches the N * -SA point is preferable.
In order to adjust the pitch of the helix, it is desirable to use a plurality of optically active compounds having the same sign of spontaneous polarization and the opposite directions of the helix appearing in the N * phase.
More preferably, it is preferable to add a single optically active compound with a spiral pitch diverging in the N * phase without adding optically active substances whose directions of spirals are opposite to each other.

  The temperature range showing the N * phase of the liquid crystal composition of the present invention is preferably in the range of 1 to less than 30 degrees. When the temperature range showing the N * phase is less than 1 degree, the phase transitions to the SmA phase as soon as the temperature is lowered, and thus liquid crystal molecules tend not to be sufficiently aligned in the N * phase. Further, when the temperature range showing the N * phase is 30 ° C. or more, the clearing point of the liquid crystal composition becomes high temperature, which tends to adversely affect the workability in the process of filling the cell with a liquid crystal material. .

As an optically active compound used in the present invention, it is necessary to induce spontaneous polarization (Ps) of a certain degree or more by adding it to a certain amount of base liquid crystal. For the ferroelectric liquid crystal composition, the addition amount of the optically active compound may be adjusted so that the value of Ps is in the range of about 1 to 100 nC / cm ² near room temperature.
However, when the addition amount of the optically active compound increases, the viscosity of the ferroelectric liquid crystal composition tends to increase, and it becomes difficult to obtain high-speed response.
Therefore, it is preferable that the optically active compound can obtain large Ps with a small addition amount.
As the optically active compound used in the present invention, a compound which induces Ps of ²⁰ nC / cm ² or more when added at 10% by weight to the ferroelectric liquid crystal SC base liquid crystal is preferable. When high-speed response is required, the value of Ps is preferably 100 nC / cm ² near room temperature.

  By putting the composition of the present invention in a liquid crystal cell, a liquid crystal display element can be produced. The two substrates of the liquid crystal cell can be made of a transparent material having flexibility such as glass or plastic, and one of them can be an opaque material such as silicon. A transparent substrate having a transparent electrode layer can be obtained, for example, by sputtering indium tin oxide (ITO) on a transparent substrate such as a glass plate.

  A liquid crystal display element using a ferroelectric liquid crystal can display a color without using a color filter by using a field sequential driving method, but even if a display method using a color filter is used. Good. The color filter can be produced by, for example, a pigment dispersion method, a printing method, an electrodeposition method, or a dyeing method. A method for producing a color filter by a pigment dispersion method will be described as an example. A curable coloring composition for a color filter is applied onto the transparent substrate, subjected to patterning treatment, and cured by heating or light irradiation. By performing this process for each of the three colors red, green, and blue, a pixel portion for a color filter can be manufactured. In addition, a pixel electrode provided with an active element such as a TFT, a thin film diode, or a metal insulator metal specific resistance element may be provided on the substrate.

  The said board | substrate is made to oppose so that a transparent electrode layer may become an inner side. In that case, you may adjust the space | interval of a board | substrate through a spacer. At this time, it is preferable to adjust so that the thickness of the light control layer obtained may be set to 1-100 micrometers. 2-10 μm is more preferable, and when a deflector is used, it is preferable to adjust the product of the refractive index anisotropy Δn of the liquid crystal and the cell thickness d so that the contrast is maximized. When there are two deflecting plates, the deflection axis of each deflecting plate can be adjusted to adjust the viewing angle and contrast. Furthermore, a retardation film for widening the viewing angle can also be used. Examples of the spacer include glass particles, plastic particles, alumina particles, and a photoresist material. Thereafter, a UV curable type and UV-heat combined type curable sealing material is printed on the substrate with a liquid crystal injection port provided, the substrates are bonded together, and the sealing material is cured.

  As a method for sandwiching the liquid crystal composition of the present invention between two substrates, a normal vacuum injection method, an ODF method, or the like can be used. When the injection speed of the liquid crystal is low, vacuum injection or ODF method can be performed while heating. The liquid crystal phase when heated is preferably N * with high fluidity.

Hereinafter, the liquid crystal composition of the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
In this example, the phase transition temperature was measured using a polarizing microscope equipped with a temperature adjustment stage and a differential scanning calorimeter (DSC). The tilt angle (θ) is the moving angle of the extinction position under crossed Nicols by applying a DC electric field of 10 V to the liquid crystal cell (alignment film: polyimide, rubbing direction: anti-parallel, cell gap: 2 μm) and further reversing the polarity. Obtained from (2θ).
Further, all “%” in the composition represents “% by weight”.
(Examples 1-3)
The liquid crystal compounds described in Table 1 were mixed in the contents shown in the table to obtain various ferroelectric liquid crystal compositions.
No. Ferroelectric liquid crystal compositions of Examples 1 to 3 were obtained by using 12% each of the compounds 10, 11, and 12.
Each ferroelectric liquid crystal composition was injected into a cell to produce a ferroelectric liquid crystal element, and then the phase transition temperature and tilt angle (θ) were measured.

The tilt angle of the ferroelectric liquid crystal element of Example 1 is 32.8 °.
The phase transition temperature was Cr-30.2 SmC * 78.5 SmA 84.2 N * 94.6 I.
The tilt angle of the ferroelectric liquid crystal element of (Example 2) is 32.0 °.
The phase transition temperature was Cr-31.5 SmC * 78.8 SmA 85.2 N * 95.0 I.
The tilt angle of the ferroelectric liquid crystal element of (Example 3) was 31.6 °.
The phase transition temperature was Cr-29.8 SmC * 78.0 SmA 84.0 N * 94.2 I.
Example 4
No. described in Table 1 The ferroelectric liquid crystal composition of Example 4 was prepared using 8% of each of the compounds 10 and 11. The tilt angle of the ferroelectric liquid crystal element of Example 4 was 31.2 °.
The phase transition temperature was Cr-32.8 SmC * 78.4 SmA 84.7 N * 96.0 I.

(Comparative Examples 1-2)
No. 1 to Example 3 in Table 1. In place of the compounds of 10, 11, 12 Ferroelectric liquid crystal compositions of Comparative Examples 1 and 2 were obtained using the same liquid crystalline compounds as in Examples 1 to 3 except that 12% of each of the compounds 5 and 7 was used. In the same manner as in the example, a ferroelectric liquid crystal element was manufactured, and the tilt angle (θ) was measured.
The tilt angle of the ferroelectric liquid crystal element of (Comparative Example 1) is 29.7 °.
The phase transition temperature was Cr-33.4 SmC * 78.8 SmA 85.8 N * 97.1 I.
The tilt angle of the ferroelectric liquid crystal element of (Comparative Example 2) was 29.2 °.
The phase transition temperature was Cr-31.3 SmC * 78.2 SmA 84.5 N * 95.3 I.
It is clear that the devices of Comparative Examples 1 and 2 using a liquid crystalline compound having a short alkyl chain have a smaller tilt angle than Examples 1 to 3.
(Comparative Example 3)
No. of Example 4 in Table 1. In place of the compounds of Nos. 10 and 11, No. 1 having a short alkyl chain length. A ferroelectric liquid crystal composition of Comparative Example 3 was obtained using the same liquid crystal compound as in Example 4 except that 8% of the compound of 5 or 6 was used. The tilt angle of the ferroelectric liquid crystal element of Comparative Example 3 was 29.5 °.
The phase transition temperature was Cr-34.1 SmC * 78.5 SmA 85.0 N * 98.3 I.
It is clear that the tilt angle is small compared to Example 4.

(Example 5)
No. described in Table 1 The ferroelectric liquid crystal composition of Example 5 was prepared using 4.75% of each of the 8, 9, 10 and 11 compounds. The tilt angle of the ferroelectric liquid crystal element of Example 5 was 33.7 °, and the largest tilt angle was obtained.
The phase transition temperature was Cr-30.1 SmC * 80.1 SmA 87.2 N * 101.7 I.

Claims (9)

Formula (I)

(Wherein R ₁ and R ₂ each independently represents a linear alkyl group having 7 to 18 carbon atoms, and one or two non-adjacent —CH ₂ — groups in the alkyl group are -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -S-CO-, -O-CO-O-, -CH = CH-, -C≡C-, a cyclopropylene group, or -Si (CH ₃ ) _2- may be substituted, and a hydrogen atom in the alkyl group may be substituted with a fluorine atom or a CN group,
A, B and C are each independently 1,4-phenylene group, pyrazine-2,5-diyl group, pyridazine-3,6-diyl group, pyridine-2,5-diyl group, pyrimidine-2,5- Diyl group, trans-1,4-cyclohexylene group, 1,3,4-thiadiazole-2,5-diyl group, 1,3-dioxane-2,5-diyl group, 1,3-dithian-2, 5-diyl group, 1,3-thiazole-2,4-diyl, 1,3-thiazole-2,5-diyl, thiophene-2,4-diyl group, thiophene-2,5-diyl group, piperazine-1 , 4-diyl group, piperazine-2,5-diyl group or naphthalene-2,6-diyl group, the hydrogen atoms in the 1,4-phenylene group and naphthalene-2,5-diyl group are fluorine atoms. , CF ₃ group, OCF ₃ group, CN groups, H ₃ group, or may be substituted in the OCH ₃ group, a hydrogen atom in xylene group to said trans-1,4-cyclohexylene may be replaced by a CN group or a CH ₃ group,
L ₁ and L ₂ are each independently a single bond, —O—, —S—, —CO—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, —CO—. O—, —O—CO—, —CO—S—, —S—CO—, —O—CO—O—, —CH ₂ CH ₂ —, —CH═CH—, —C≡C— or —OCH. A compound represented by ₂ CH _2- ,
And general formula (II)

(Wherein R ₂₁ and R ₂₂ each independently represents a linear alkyl group having 1 to 12 carbon atoms), and a liquid crystal composition containing the compound represented by the formula: General formula (III)

(In the formula, R ₃₁ represents _a linear alkyl group having 7 to 15 carbon atoms _, R ₃₂ represents _a linear alkyl group having 9 to 15 carbon atoms,

Represents. )
The liquid crystal composition of Claim 1 containing the compound represented by these. The liquid crystal composition according to claim 2, comprising two or more compounds represented by formula (I). The liquid crystal composition according to claim 2 or 3, wherein the content of the compound represented by formula (I) is 5 to 40%. The liquid crystal composition according to claim 2 or 3, wherein the content of the compound represented by formula (I) is 10 to 30%. A ferroelectric liquid crystal composition containing the liquid crystal composition according to claim 1 and an optically active compound. The optically active compound is represented by the general formula (IV)

(In the formula, each of R ₄₁ and R ₄₂ independently represents a linear or branched alkyl group having 1 to 18 carbon atoms, and one or two non-adjacent —CH in the alkyl group. _2- groups are -O-, -S-, -CO-, -CO-O-, -O-CO-, -CO-S-, -S-CO-, -O-CO-O-, -CH. ═CH—, —C≡C—, a cyclopropylene group, or —Si (CH ₃ ) ₂ — may be substituted, and a hydrogen atom in the alkyl group may be substituted with a fluorine atom or a CN group,
A ₄ , B ₄ and C ₄ are each independently 1,4-phenylene group, pyrazine-2,5-diyl group, pyridazine-3,6-diyl group, pyridine-2,5-diyl group, pyrimidine-2. , 5-diyl group, trans-1,4-cyclohexylene group, 1,3,4-thiadiazole-2,5-diyl group, 1,3-dioxane-2,5-diyl group, 1,3-dithiane -2,5-diyl group, 1,3-thiazole-2,4-diyl, 1,3-thiazole-2,5-diyl, thiophene-2,4-diyl group, thiophene-2,5-diyl group, Represents a piperazine-1,4-diyl group, piperazine-2,5-diyl group or naphthalene-2,6-diyl group, and a hydrogen atom in the 1,4-phenylene group and naphthalene-2,5-diyl group a fluorine atom, CF ₃ group, OCF ₃ group, N group, a CH ₃ group, or may be substituted in the OCH ₃ group, a hydrogen atom in xylene group to said trans-1,4-cyclohexylene may be replaced by a CN group or a CH ₃ group,
a ₄ , b ₄ and c ₄ each independently represent 0 or 1, * represents an asymmetric carbon,
L ₄₁ and L ₄₂ are each independently a single bond, —O—, —S—, —CO—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, —CO—. O—, —O—CO—, —CO—S—, —S—CO—, —O—CO—O—, —CH ₂ CH ₂ —, —CH═CH—, —C≡C— or —OCH. ₂ represents CH ₂ —, and L ₄₃ represents the general formula (IV-b), the general formula (IV-c), or the general formula (IV-d).

(Wherein d ₄ , e ₄ , and f ₄ each independently represents an integer of 0 or more and 7 or less), Y represents a fluorine atom, a methyl group, an ethyl group, or Represents a CF ₃ group. The ferroelectric liquid crystal composition according to claim 6, which represents a compound represented by: The ferroelectric liquid crystal composition according to claim 6 or 7, wherein a tilt angle at room temperature is 30 to 45 °. A ferroelectric liquid crystal display element using the ferroelectric liquid crystal composition according to claim 6, 7 or 8.