JP5365972B2 - Liquid crystal composition and ferroelectric liquid crystal composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal composition useful as a base liquid crystal of a ferroelectric liquid crystal composition which has a low melting point and achieves high-speed response, and a ferroelectric liquid crystal composition which has a low melting point and achieves high-speed response. <P>SOLUTION: The liquid crystal composition comprises a compound having a branched side chain represented by general formula (I) and a compound having a terminal ring represented by general formula (II), wherein R<SP>11</SP>, R<SP>12</SP>, R<SP>21</SP>and R<SP>22</SP>each represents an alkyl group or the like; a, b and c are each an integer of 1-2; rings A<SP>1</SP>, B<SP>1</SP>, C<SP>1</SP>, A<SP>2</SP>, B<SP>2</SP>and C<SP>2</SP>each represents a phenylene group or a cyclohexylene group; and L<SP>21</SP>and L<SP>22</SP>each represents a linking group such as a single bond. Since the liquid crystal composition and the ferroelectric liquid crystal composition have a low melting point, crystal deposition can be effectively prevented during low-temperature preservation and the ferroelectric liquid crystal composition is very useful as a component of a ferroelectric liquid crystal display. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a liquid crystal composition and a ferroelectric liquid crystal composition useful as a constituent member of a ferroelectric liquid crystal display.

  The surface-stabilized ferroelectric liquid crystal display device proposed by Clark and Lagerwall et al. Has (1) high-speed response, (2) memory property, (3) wide viewing angle, (4) Since it exhibits characteristics such as being capable of passive drive, it has attracted attention as a next-generation display element.

The liquid crystal phase that can be a ferroelectric liquid crystal is a tilted chiral smectic liquid crystal phase, but a chiral smectic C phase (hereinafter abbreviated as SmC ^* ) that is practically advantageous in terms of viscosity is most widely used. ing. The operating temperature and storage temperature of the ferroelectric liquid crystal display element are limited by the temperature range of the SmC ^* phase. In order to develop the SmC ^* phase in a wide temperature range, a method of adding an optically active substance to a base liquid crystal composed of a non-chiral compound that exhibits a smectic C phase is known as a general method.

  As the non-chiral compound used as the base liquid crystal, a phenylpyrimidine compound is useful. In particular, the compound represented by the following general formula (I) has a relatively low viscosity as a phenylpyrimidine-based compound and is suitable for high-speed response. Therefore, a composition in which several kinds of the compound are mixed (hereinafter abbreviated as PY base) .) Is widely used as a base liquid crystal.

(In the formula, R ₁ and R ₂ represent a linear alkyl group.)
A PY-based liquid crystal using a phenylpyrimidine compound has a relatively low viscosity, but has a high melting point of usually 0 ° C. or higher.

  As a technique for achieving a low melting point of a PY base liquid crystal, a method of adding a pyrimidine compound having the following branched methyl group in the side chain to the PY base liquid crystal is disclosed (see Patent Documents 1 and 2).

However, the composition described in the cited document has a problem that the substitution position of the methyl group is not optimized in the branched side chain of the pyrimidine-based compound. Therefore, the liquid crystal composition described in the cited document has a melting point as high as about 5 ° C., which is insufficient for practical use of a ferroelectric liquid crystal display. On the other hand, as a method effective for lowering the melting point, there has been reported a method of mixing a compound having a cyclopropane ring structure at the end of an alkyl chain and a compound having a dimethyl branch in the alkyl chain (see Patent Document 3). However, the reported melting point is as high as 11 ° C. or 13 ° C., which is insufficient practically, and no effect on response is described.

  Therefore, development of a liquid crystal composition useful as a base liquid crystal of a ferroelectric liquid crystal composition having a low melting point and a high-speed response and a ferroelectric liquid crystal composition having a low melting point and a high-speed response have been desired.

JP-A 64-79160 JP-A-2-204484 JP-A-5-255277

  The problem to be solved by the present invention is to provide a liquid crystal composition useful as a base liquid crystal of a ferroelectric liquid crystal composition having a low melting point and a high-speed response, and a ferroelectric liquid crystal composition having a low melting point and a high-speed response. is there.

  In order to solve the above-mentioned problems, the present inventors have studied liquid crystal compositions using compounds having various branched alkyl chains and compounds having a ring structure at the end of the molecular structure, and compounds having specific branched alkyl chains. And a compound having a specific terminal ring structure provide a liquid crystal composition useful as a base liquid crystal of a ferroelectric liquid crystal composition having a low melting point and a high-speed response, and a ferroelectric liquid crystal composition having a low melting point and a high-speed response. As a result, the present invention has been completed.

  The present invention relates to a general formula (I),

(In the formula, R ¹¹ and R ¹² each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms, provided that at least one of the alkyl groups is a branched alkyl group. And one or two non-adjacent —CH ₂ — groups in the alkyl group are —O—, —CO—, —CO—O—, —O—CO—, —O—CO—O—. , —CH═CH— or —C≡C—, wherein one or more hydrogen atoms in the alkyl group may be replaced with a fluorine atom or a CN group, and A ¹ , B ¹ and Each C ¹ is independently a 1,4-phenylene group in which one or two hydrogen atoms may be replaced by a fluorine atom, a CF ₃ group, an OCF ₃ group, or a CN group, or a plurality of these groups, or It represents 1,4-cyclohexylene group, ^{a 1} is 0, 1, or Represents, ^{b 1,} and ^{c 1} is an integer of 0 or ^1, the sum of a 1, ^{b 1} and ^{c 1} is 1 or 2.) And, the formula (II),

(R ²¹ represents a linear or branched alkyl group having 1 to 18 carbon atoms, and one or two non-adjacent —CH ₂ — groups in the alkyl group are —O— and —CO. —, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C—, may be replaced by one or more in the alkyl group The hydrogen atom of may be replaced by a fluorine atom or a CN group, and each of A ² , B ² and C ² is independently one or two hydrogen atoms are a fluorine atom, a CF ₃ group, an OCF ₃ group, or a CN 1,4-phenylene group which may be replaced by a plurality of groups, pyrazine-2,5-diyl group or pyridazine-3 in which one or two hydrogen atoms may be replaced by fluorine atoms , 6-diyl group, pyridine-2,5-diyl group, pyrimidine- , 5-diyl group, trans-1,4-cyclohexylene group in which one or two hydrogen atoms may be replaced by cyano group or methyl group or both, or 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 group, 1,3-thiazole -2,5-diyl group, thiophene-2,4-diyl group, thiophene-2,5-diyl group, piperazine-1,4-diyl group, piperazine-2,5-diyl group or naphthalene-2,5- A diyl group, L ⁴¹ and L ⁴² each independently represent a single bond, —O—, —CO—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, —CO; -O-, -O-CO-, -O-CO-O-, —CH ₂ CH ₂ —, —CH═CH— or —C≡C— is represented, a ² , b ² and c ² represent 0 or 1, and the sum of a ² , b ² and c ² is 2 or 3 and R ²² represents a single bond or a linear or branched alkylene group having 1 to 18 carbon atoms, and one or two non-adjacent —CH ₂ — groups in the alkylene group are — O—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C— may be substituted. One or more hydrogen atoms may be replaced by fluorine atoms or CN groups.), And a ferroelectric containing the liquid crystal composition and the optically active compound. Ferroelectric liquid crystal composition using the ferroelectric liquid crystal composition I will provide a.

  Since the liquid crystal composition and the ferroelectric liquid crystal composition of the present invention are characterized by a low melting point, it is possible to effectively prevent crystal precipitation during low-temperature storage. The ferroelectric liquid crystal composition of the present invention is extremely useful as a constituent member of a ferroelectric liquid crystal display.

  The liquid crystal composition of the present invention is composed of compounds represented by the general formula (I) and the general formula (II). The general formula (I) includes the following general formula (I-a)

(In the formula, R ¹³ and R ¹⁴ each independently represents a linear or branched alkyl group having 1 to 18 carbon atoms, provided that at least one of the alkyl groups is a branched alkyl group. And one or two non-adjacent —CH ₂ — groups in the alkyl group are —O—, —CO—, —CO—O—, —O—CO—, —O—CO—O—. , —CH═CH— or —C≡C—, wherein one or more hydrogen atoms in the alkyl group may be replaced with a fluorine atom or a CN group, and X ¹¹ and X ¹² are Each independently represents a hydrogen atom or a fluorine atom, and d ¹ represents 0 or an integer of 1) or the general formula (Ib)

(In the formula, R ¹³ and R ¹⁴ each independently represents a linear or branched alkyl group having 1 to 18 carbon atoms, provided that at least one of the alkyl groups is a branched alkyl group. And one or two non-adjacent —CH ₂ — groups in the alkyl group are —O—, —CO—, —CO—O—, —O—CO—, —O—CO—O—. , —CH═CH— or —C≡C—, wherein one or more hydrogen atoms in the alkyl group may be replaced with a fluorine atom or a CN group, and D ¹ is 1,4 -Represents a phenylene group or a 1,4-cyclohexylene group). 3-15 are preferable and, as for carbon number of this alkyl group, 4-12 are more preferable. Further, the alkyl group is particularly preferably a linear or branched alkyl group, an alkoxy group, an alkenyl group, or an alkenyloxy group.

  In addition, at least one of the alkyl groups needs to be a branched alkyl group, but in order to stabilize the liquid crystal phase upper limit temperature or achieve high-speed response, either one of the two alkyl groups It is preferred that one is linear and the other is branched. The number of branches is preferably 1 or 2 from the viewpoint of stability of liquid crystal, low melting point, and high-speed response, and that the branched structure is a methyl group in terms of stability of liquid crystal phase and high-speed response. To preferred.

Since compounds having different molecular structures have different crystal structures, crystallization is suppressed and the melting point is lowered. Therefore, it is preferable to use a mixture of two or more compounds having different structures as the compound of the general formula (I).
Specific examples of preferred compounds as the general formula (I) are given below.

(Wherein R ¹¹¹ represents an alkyl group having 4 to 14 carbon atoms or an alkoxy group, R ¹¹² represents a single bond or an alkylene group having 1 to 8 carbon atoms, and R ¹¹³ represents an alkyl group having 1 to 8 carbon atoms. R ¹¹⁴ represents an alkylene group having 1 to 8 carbon atoms, R ¹¹⁵ represents an alkyl group having 4 to 14 carbon atoms, and L ¹¹¹ represents a single bond, —O—, —OCO—, or —COO—. .)
As a compound of general formula (II), the following general formula (II-a)

(R ²³ represents a linear or branched alkyl group having 1 to 18 carbon atoms, and one or two non-adjacent —CH ₂ — groups in the alkyl group are —O— and —CO. —, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C—, may be replaced by one or more in the alkyl group The hydrogen atom may be replaced with a fluorine atom or a CN group, and R ²⁴ is a single bond or an alkylene group having 1 to 12 carbon atoms, and one or two of the alkylene groups are not adjacent to each other. The —CH ₂ — group may be replaced by —O—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C—. In addition, one or more hydrogen atoms of the alkylene group may be replaced by fluorine atoms or CN groups. X ²¹ and X ²² each independently represent a hydrogen atom or a fluorine atom, and d ² represents 0 or 1) or the general formula (II-b)

(R ²⁵ represents a linear or branched alkyl group having 1 to 18 carbon atoms, and one or two non-adjacent —CH ₂ — groups in the alkyl group are —O—, —CO. —, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C—, may be replaced by one or more in the alkyl group The hydrogen atom may be replaced with a fluorine atom or a CN group, and R ²⁶ is a single bond or an alkylene group having 1 to 12 carbon atoms, and one or two of the alkylene groups are not adjacent to each other. The —CH ₂ — group may be replaced by —O—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C—. In addition, one or more hydrogen atoms of the alkylene group may be replaced by fluorine atoms or CN groups. X ²³ and X ²⁴ each independently represent a hydrogen atom or a fluorine atom, and e ² represents 0 or 1).

The number of carbon atoms in R ²³ is preferably 3 to 15, 4 to 12 is more preferable. Further, the alkyl group is particularly preferably an alkyl group, an alkoxy group, an alkenyl group, or an alkenyloxy group. Similarly, R ²⁵ has preferably 3 to 15 carbon atoms, and more preferably 4 to 12 carbon atoms. Further, the alkyl group is particularly preferably an alkyl group, an alkoxy group, an alkenyl group, or an alkenyloxy group.

The compound having d ² of 0 has a structure in which an alkyl side chain is present only at the end of the molecule, and the structure of the compound represented by the general formula (I) greatly varies. The melting point is effective, and the molecular shape is linear / rigid, which is suitable for high-speed response. The case where d ² is 1 and R ²⁴ is a relatively short alkylene group having 1 to 5 carbon atoms is also preferable. Among these, the case where d ² is 0 and the case where d ² is 1 and R ²⁴ is a single bond or an alkylene group having 1 to 3 carbon atoms are particularly preferable.

  Specific examples of compounds particularly preferred as the general formula (II) are given below.

(In the formula, R ²²¹ represents an alkyl group or alkoxy group having 4 to 14 carbon atoms.)
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. A compound having a chirality or a compound having a plane asymmetry can be used, and a compound having an asymmetric carbon or a compound having a carbon-carbon bond as an axial asymmetry is preferably used, and 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. Alternatively, a compound having a CF ₃ group introduced therein or a compound having an oxirane ring structure having an asymmetric carbon is preferable.
Specifically, the optically active compound is represented by the general formula (III)

(In the formula, R ³¹ and R ³² each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms, and one or two non-adjacent —CH in the alkyl group. _{The 2-} group is replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C—. The hydrogen atom in the alkyl group may be replaced with a fluorine atom or a CN group, and A ³ , B ³ and C ³ are each independently a 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, piperazine -1,4-diyl group, piperazine-2,5-diyl group or naphthalene-2,6-diyl group, provided that the hydrogen atom in the 1,4-phenylene group and naphthalene-2,5-diyl group May be substituted by a fluorine atom, a CF ₃ group, an OCF ₃ group, a CN group, a CH ₃ group, or an OCH ₃ group, and the hydrogen atom in the trans-1,4-cyclohexylene group is a CN group or Optionally substituted with a CH ₃ group, a ³ , b ³ , and c ³ each independently represent 0 or 1, L ³¹ and L ³² each independently represent a single bond, —O—, —CO—. _{, -CH 2 O -, - OCH} 2 -, - CF 2 O -, - _{CF 2 -, - CO-O} -, - O-CO -, - O-CO-O -, - CH 2 CH 2 -, - CH = CH- or an -C≡C-, L ³³ is generally Formula (III-1), General Formula (III-2), or General Formula (III-3),

(Wherein d ³ , e ³ , and f ³ each independently represents an integer of 0 or more and 7 or less), Z ³¹ has the general formula (III-4 ) Or general formula (III-5),

(However, Z ³² represents a fluorine atom, a methyl group or a CF ₃ group, R ³³ and R ³⁴ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms, * Represents an asymmetric carbon). ) Is preferred.

Among the compounds represented by the general formula (III), in particular, Z ³¹ has the structure of the general formula (III-4) and Z ³² is a fluorine atom, or Z ³¹ is the general formula (III-5). More preferred is a compound having the following structure, and R ³³ and R ³⁴ are hydrogen atoms.
Among the compounds represented by the general formula (III), Z ³¹ has the structure of the general formula (III-4) and Z ³² is a fluorine atom. The following general formula (III-b)

Wherein R ³⁷ and R ³⁸ each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms, and one or two non-adjacent —CH in the alkyl group _{The 2-} group is replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C—. The hydrogen atom in the alkyl group may be replaced with a fluorine atom or a CN group, and L ³⁴ is a group represented by the general formula (III-b-1), or (III-b-2),

(Wherein g ³ and h ³ each independently represents an integer of 0 or more and 7 or less). Or a compound represented by the following general formula (III-c)

(In the formula, R ³⁹ and R ⁴⁰ each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms, provided that at least one of the alkyl groups is a branched alkyl group. And one or two non-adjacent —CH ₂ — groups in the alkyl group are —O—, —CO—, —CO—O—, —O—CO—, —O—CO—O—. , —CH═CH— or —C≡C—, wherein one or more hydrogen atoms in the alkyl group may be replaced with a fluorine atom or a CN group, and X ³¹ and X ³² are Each independently represents a hydrogen atom or a fluorine atom, d ³ represents an integer of 0 or 1, and L ³⁵ represents a general formula (III-c-1), a general formula (III-c-2), or a general formula ( III-c-3),

（式中、ｊ^３、ｋ^３、及びｍ^３は、各々独立に０以上７以下の整数を表す。）のいずれかで表される構造を有する。）の構造を有することが好ましい。

(Wherein j ³ , k ³ , and m ³ each independently represents an integer of 0 or more and 7 or less). ).

Among these compounds, in the case of the compound represented by the general formula (III-b), R ³⁷ and R ³⁸ are more preferably a linear or branched alkyl group, and particularly preferably a linear alkyl group. On the other hand, in the case of the compound represented by the general formula (III-c), R ³⁹ is more preferably a linear or branched alkyl group, alkoxy group, alkenyl group, alkenyloxy group, and R ⁴⁰ is linear or A branched alkyl group is preferable, and a linear alkyl group is particularly preferable.
Among the compounds represented by the general formula (III), the compound having the following structure is preferable as the compound in which Z ³¹ has the structure of the general formula (III-5) and R ³³ and R ³⁴ are hydrogen atoms.

Wherein R ³³¹ is an alkyl group or alkoxy group having 4 to 14 carbon atoms, R ³³² is an alkyl group having 1 to 8 carbon atoms, R ³³³ is an alkyl group having 4 to 14 carbon atoms, L ³³¹ , and L ³³² are Each independently represents a carbonyl group or a methylene group.)
Specific examples of particularly preferable compounds as the general formula (III) are shown below.

(Wherein R _aa is a linear or branched alkyl group or alkoxy group having 1 to 18 carbon atoms, R _bb is a linear or branched alkyl group having 1 to 18 carbon atoms, and M _aa is the number of carbon atoms. 1 to 3 methylene groups, and M _bb represents a methylene group having 1 to 2 carbon atoms.)
The liquid crystal composition of the present invention is composed of the compounds represented by the general formula (I) and the general formula (II), but the content of the compound represented by the general formula (I) is 5 to 80%. Preferably, 10 to 60% is more preferable, 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 1 to 60%, more preferably 2 to 50%, and preferably two or more compounds represented by the general formula (II) are contained. As the ferroelectric liquid crystal composition of the present invention, a chiral compound represented by the general formula (III) is used in addition to the compounds represented by the general formula (I) and the general formula (II). ) Is preferably 2 to 50%, more preferably 5 to 30%. If the content of general formula (III) exceeds 10%, use two or more compounds represented by general formula (III) so that the content of a single component does not exceed 10%. In this case, undesirable crystallization and disorder of the phase series can be suppressed, which is preferable.

These liquid crystal compositions may be subjected to a purification treatment with silica, alumina or the like for the purpose of removing impurities or the like or further increasing the specific resistance value. The specific resistance value is preferably 10 ¹² Ω · cm or more, and more preferably 10 ¹³ Ω · cm or more. Furthermore, dopants such as chiral compounds, dyes, and ion scavengers can be added to the liquid crystal composition according to the purpose.

  In addition, antioxidants, UV absorbers, non-reactive oligomers and inorganic fillers, organic fillers, polymerization inhibitors, antifoaming agents, leveling agents, plasticizers, silane coupling agents, etc. are added as necessary. You may do it.

  Furthermore, as a component of the ferroelectric liquid crystal composition, a liquid crystal compound other than the liquid crystal compounds represented by the general formula (I) and the general formula (II) can be used in combination as necessary. The compound that can be used in combination is not particularly limited, but in order to stabilize the ferroelectric liquid crystal phase, it is preferable to use a liquid crystalline compound exhibiting a smectic C phase or a chiral smectic C phase. (In this specification, the name of the liquid crystal phase includes the corresponding chiral liquid crystal phase unless otherwise specified.) In addition, the phase series of the ferroelectric liquid crystal phase or the temperature range of each liquid crystal phase is defined. In order to adjust, it is preferable to select a liquid crystal compound as appropriate. Specifically, in order to develop a nematic phase or expand the temperature range of the nematic phase, it is preferable to use a compound exhibiting a nematic phase in combination, or to develop a smectic A phase or a smectic A phase. When it is desired to expand the temperature range, it is preferable to use a compound exhibiting a smectic A phase, or a compound that does not exhibit a smectic A phase when a smectic A phase is unnecessary, such as a Half-V material. It is preferable to use together. Preferable specific examples of the compound used in combination for stabilizing the ferroelectric liquid crystal phase are given below.

Wherein R ⁶⁶¹ and R ⁶⁶² are each independently an alkyl group having 4 to 14 carbon atoms, R ⁶⁶³ and R ⁶⁶⁴ are each independently an alkyl group or alkoxy group having 4 to 14 carbon atoms, and R ⁶⁶⁵ is an alkyl group having 4 to 4 carbon atoms. 14 alkyl groups, L ⁶⁶¹ , and L ⁶⁶² are each independently a single bond, —O—, —COO—, or —OCO—, X ⁶⁶¹ , X ⁶⁶² , X ⁶⁶³ , X ⁶⁶⁴ , X ⁶⁶⁵ , and X ⁶⁶⁶ , Each independently represents a hydrogen atom or a fluorine atom.)
In order to obtain a display element with good contrast, it is necessary to adjust the tilt angle according to the display method. In order to increase the tilt angle, it is preferable to select a compound so as to increase the upper limit temperature of the smectic C phase or to narrow the temperature range of the smectic A phase. To reduce the tilt angle, the smectic C phase is preferred. It is preferable to use a compound that lowers the upper limit temperature of the phase or widens the temperature range of the smectic A phase.

  In order to stabilize the smectic layer structure, it is preferable to use a phenylbenzoate derivative in combination with the compounds of general formula (I) and general formula (II). Since these phenylbenzoate derivatives or biphenylbenzoate derivatives increase the viscosity of the composition, the layer structure can be stabilized, and it is preferable for suppressing orientation disorder. Moreover, the effect that a melting point falls by mixing with a phenylbenzoate derivative is acquired, and it is preferable. However, the use of the phenylbenzoate derivative increases the viscosity and slows the response speed. Therefore, the phenyl benzoate derivative is preferably used within a range where a desired response speed can be obtained.

Even if the compound represented by general formula (I) and the compound represented by general formula (II) are each used alone, the alkyl chain length, the structure of the alkyl chain, the structure of the bonding portion, the ring structure, the number of rings A plurality of different materials may be contained. In order to improve the stability of the liquid crystal temperature, it is preferable to use two or more compounds having different structures.

As for the chiral compound, one compound having the structure represented by the general formula (III) may be used, or a plurality of compounds having different chiral structure, alkyl chain length, alkyl chain structure, bond structure, ring structure and ring number may be used. It may be used. In order to suppress the helical structure in the liquid crystal phase generated based on the chiral effect and obtain a good alignment state, it is preferable to use a combination of a plurality of chiral compounds having different twist directions to be generated. At this time, if the combination of chiral compounds is selected so that the directions of spontaneous polarization are aligned, or if a combination of a compound that generates sufficiently large spontaneous polarization and a compound that induces a twisted structure but has a small spontaneous polarization value is selected, The value is preferred because it is not canceled. It is also preferable to introduce a plurality of chiral structures having different twist directions to be introduced into the same compound in order to suppress the generation of a helical structure that occurs in the liquid crystal phase based on the chiral effect. At this time, if a combination of chiral structures is selected so that the directions of spontaneous polarization are aligned, or if a combination of structures that induce sufficiently large spontaneous polarization and a torsional structure is induced but has a small spontaneous polarization value, The value is preferred because it is not canceled.

  By placing 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 composition can display a color without using a color filter by using a field sequential driving method, but a display method using a color filter is used. May be. The color filter can be prepared 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 on 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 created. 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. In this case, it is preferable to adjust the thickness of the obtained cell to be 1 to 100 μm. The cell thickness is more preferably 1 to 10 μm, still more preferably 1 to 4 μm. When a polarizing plate 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. In view of manufacturing the display element, it is preferable that the cell thickness is thick. In that case, it is necessary to use a liquid crystal having a small Δn. In that case, the compound of the general formula (I), the general formula (II) or the general formula (III) having a cyclohexyl or 1,3,4-thiadiazole-2,5-diyl structure, or the general formula ( It is desirable to use a compound having a structure other than I), general formula (II) or general formula (III) and having cyclohexyl or 1,3,4-thiadiazole-2,5-diyl structure. One or two cyclohexyl structures are preferably present in one molecule, and one 1,3,4-thiadiazole-2,5-diyl is preferably present in one molecule. In addition, when there are two polarizing plates, the polarizing axis of each polarizing plate can be adjusted so that the viewing angle and contrast are good. 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 sealant such as an epoxy thermosetting composition is screen-printed on the substrates with a liquid crystal inlet provided, the substrates are bonded together, and heated to thermally cure the sealant.

  As a method for sandwiching the polymer-stabilized ferroelectric liquid crystal composition between two substrates, a normal vacuum injection method, an ODF method, or the like can be used. At this time, the liquid crystal composition is preferably in a uniform isotropic state or in a (chiral) nematic phase. In the smectic phase, handling during device fabrication becomes difficult.

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 control stage and a differential scanning calorimeter (DSC). Response time is measured using a crossed Nicols polarization microscope with a liquid crystal cell (alignment film: polyimide, rubbing direction: anti-parallel, cell gap: 2 μm) so that the molecular long axis is parallel to the analyzer in the stable state of one molecular arrangement. The response time was _defined as the time taken for the amount of transmitted light to change from 10 to 90% after applying a rectangular wave of 60 Hz and 20 V _0-p at room temperature. Further, all “parts” in the composition represent “parts by mass”.
Example 1
As the compound of general formula (I), the following (I-aa), (I-bb) and (I-cc) shown below and the compound of (II-aa) shown below as general formula (II) are contained. A ferroelectric liquid crystal composition (FLC-1) was prepared by mixing the ferroelectric liquid crystal composition at a ratio shown in Table 1. The melting point of FLC-1 was very low at −38 ° C., which was preferable, and the response time was as fast as 150 μsec.

(Comparative Example 1)
A ferroelectric liquid crystal composition (FLC-C1) was produced in the same manner as in Example 1 except that the compound group represented by the general formula (II) was not included. The compounds used and their mixing ratios are shown in Table 1. The melting point of (FLC-C1) was 0 ° C., which was higher than that of the example, which was not preferable. Also, the response time was 210 μs, which was slower than the example, which was not preferable.
(Comparative Example 2)
A ferroelectric liquid crystal composition (FLC-C2) was produced in the same manner as in Example 1 except that the compound group represented by the general formula (I) was not included. The compounds used and their mixing ratios are shown in Table 1. The melting point of (FLC-C2) was as high as 10 ° C., which was not practical and not preferable.

Claims (6)

Formula (I)

(In the formula, R ¹¹ and R ¹² each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms, provided that at least one of the alkyl groups is a branched alkyl group. And one or two non-adjacent —CH ₂ — groups in the alkyl group are —O—, —CO—, —CO—O—, —O—CO—, —O—CO—O—. , —CH═CH— or —C≡C—, wherein one or more hydrogen atoms in the alkyl group may be replaced with a fluorine atom or a CN group, and A ¹ , B ¹ and Each C ¹ is independently a 1,4-phenylene group in which one or two hydrogen atoms may be replaced by a fluorine atom, a CF ₃ group, an OCF ₃ group, or a CN group, or a plurality of these groups, or It represents 1,4-cyclohexylene group, ^{a 1} is 0, 1, or Represents, ^{b 1,} and ^{c 1} is an integer of 0 or ^1, the sum of a 1, ^{b 1} and ^{c 1} is 1 or 2.) And, the formula (II),

(R ²¹ represents a linear or branched alkyl group having 1 to 18 carbon atoms, and one or two non-adjacent —CH ₂ — groups in the alkyl group are —O— and —CO. —, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C—, may be replaced by one or more in the alkyl group The hydrogen atom of may be replaced by a fluorine atom or a CN group, and each of A ² , B ² and C ² is independently one or two hydrogen atoms are a fluorine atom, a CF ₃ group, an OCF ₃ group, or a CN 1,4-phenylene group which may be replaced by a plurality of groups, pyrazine-2,5-diyl group or pyridazine-3 in which one or two hydrogen atoms may be replaced by fluorine atoms , 6-diyl group, pyridine-2,5-diyl group, pyrimidine- , 5-diyl group, trans-1,4-cyclohexylene group in which one or two hydrogen atoms may be replaced by cyano group or methyl group or both, or 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 group, 1,3-thiazole -2,5-diyl group, thiophene-2,4-diyl group, thiophene-2,5-diyl group, piperazine-1,4-diyl group, piperazine-2,5-diyl group or naphthalene-2,5- A diyl group, L ²¹ and L ²² each independently represent a single bond, —O—, —CO—, —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, —CO; -O-, -O-CO-, -O-CO-O-, —CH ₂ CH ₂ —, —CH═CH— or —C≡C— is represented, a ² , b ² and c ² represent 0 or 1, and the sum of a ² , b ² and c ² is 2 or 3 and R ²² represents a single bond or a linear or branched alkylene group having 1 to 18 carbon atoms, and one or two non-adjacent —CH ₂ — groups in the alkylene group are — O—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C— may be substituted. One or more hydrogen atoms may be replaced by fluorine atoms or CN groups.)
The liquid crystal composition containing the compound represented by these. The compound represented by the general formula (I) is represented by the following general formula (Ia)

(In the formula, R ¹³ and R ¹⁴ each independently represents a linear or branched alkyl group having 1 to 18 carbon atoms, provided that at least one of the alkyl groups is a branched alkyl group. And one or two non-adjacent —CH ₂ — groups in the alkyl group are —O—, —CO—, —CO—O—, —O—CO—, —O—CO—O—. , —CH═CH— or —C≡C—, wherein one or more hydrogen atoms in the alkyl group may be replaced with a fluorine atom or a CN group, and X ¹¹ and X ¹² are Each independently represents a hydrogen atom or a fluorine atom, d ¹ represents an integer of 0 or 1, or the following general formula (Ib)

(In the formula, R ¹³ and R ¹⁴ each independently represents a linear or branched alkyl group having 1 to 18 carbon atoms, provided that at least one of the alkyl groups is a branched alkyl group. And one or two non-adjacent —CH ₂ — groups in the alkyl group are —O—, —CO—, —CO—O—, —O—CO—, —O—CO—O—. , —CH═CH— or —C≡C—, wherein one or more hydrogen atoms in the alkyl group may be replaced with a fluorine atom or a CN group, and D ¹ is 1,4 A liquid crystal composition according to claim 1, which is a compound represented by -phenylene group or 1,4-cyclohexylene group. The compound represented by the general formula (II) is represented by the following general formula (II-a)

(R ²³ represents a linear or branched alkyl group having 1 to 18 carbon atoms, and one or two non-adjacent —CH ₂ — groups in the alkyl group are —O— and —CO. —, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C—, may be replaced by one or more in the alkyl group The hydrogen atom may be replaced with a fluorine atom or a CN group, and R ²⁴ is a single bond or an alkylene group having 1 to 12 carbon atoms, and one or two of the alkylene groups are not adjacent to each other. The —CH ₂ — group may be replaced by —O—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C—. In addition, one or more hydrogen atoms of the alkylene group may be replaced by fluorine atoms or CN groups. X ²¹ and X ²² each independently represent a hydrogen atom or a fluorine atom, and d ² represents 0 or 1) or the general formula (II-b)

(R ²⁵ represents a linear or branched alkyl group having 1 to 18 carbon atoms, and one or two non-adjacent —CH ₂ — groups in the alkyl group are —O—, —CO. —, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C—, may be replaced by one or more in the alkyl group The hydrogen atom may be replaced with a fluorine atom or a CN group, and R ²⁶ is a single bond or an alkylene group having 1 to 12 carbon atoms, and one or two of the alkylene groups are not adjacent to each other. The —CH ₂ — group may be replaced by —O—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C—. In addition, one or more hydrogen atoms of the alkylene group may be replaced by fluorine atoms or CN groups. The liquid crystal composition according to claim 1 or 2, wherein X ²³ and X ²⁴ each independently represents a hydrogen atom or a fluorine atom, and e ² represents 0 or 1. A ferroelectric liquid crystal composition comprising the liquid crystal composition according to any one of claims 1 to 3 and an optically active compound. The optically active compound is represented by the general formula (III)

(In the formula, R ³¹ and R ³² each independently represent a linear or branched alkyl group having 1 to 18 carbon atoms, and one or two non-adjacent —CH in the alkyl group. _{The 2-} group is replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C—. The hydrogen atom in the alkyl group may be replaced with a fluorine atom or a CN group, and A ³ , B ³ and C ³ are each independently a 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, piperazine -1,4-diyl group, piperazine-2,5-diyl group or naphthalene-2,6-diyl group, provided that the hydrogen atom in the 1,4-phenylene group and naphthalene-2,5-diyl group May be substituted by a fluorine atom, a CF ₃ group, an OCF ₃ group, a CN group, a CH ₃ group, or an OCH ₃ group, and the hydrogen atom in the trans-1,4-cyclohexylene group is a CN group or Optionally substituted with a CH ₃ group, a ³ , b ³ , and c ³ each independently represent 0 or 1, L ³¹ and L ³² each independently represent a single bond, —O—, —CO—. _{, -CH 2 O -, - OCH} 2 -, - CF 2 O -, - _{CF 2 -, - CO-O} -, - O-CO -, - O-CO-O -, - CH 2 CH 2 -, - CH = CH- or an -C≡C-, L ³³ is generally Formula (III-1), General Formula (III-2), or General Formula (III-3)

(Wherein d ³ , e ³ , and f ³ each independently represents an integer of 0 or more and 7 or less), Z ³¹ has the general formula (III-4 ) Or general formula (III-5),

(However, Z ³² represents a fluorine atom, a methyl group or a CF ₃ group, R ³³ and R ³⁴ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms, * Represents an asymmetric carbon). The ferroelectric liquid crystal composition according to claim 4. Ferroelectric liquid crystal display device using the claims 4 or 5 ferroelectric liquid crystal composition.