JP2013203951A - Liquid crystal composition and liquid crystal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal composition which has a high Δn value and satisfactory compatibility, and is suitably used to obtain a liquid crystal element with high display quality in a wide temperature range.SOLUTION: A liquid crystal composition contains compounds represented by the following formulae (A), (B), (C). R-A-Z-A-Z-(A)-Z-(A)-R(A). (At least one of Z, Zand Zis -C≡C-). R-A-Z-A-Z-(A)-Z-(A)-R(B). (At least one of Z, Zand Zis -C≡C-). R-Ph-C≡C-Ph-COO-Ph-R(C).

Description

  The present invention relates to a liquid crystal composition containing a compound having a tolan structure, and a liquid crystal element including the composition.

  Liquid crystal elements include mobile devices such as mobile phones and PDAs, display devices for office automation equipment such as copiers and personal computer monitors, display devices for home appliances such as liquid crystal televisions, clocks, calculators, measuring instruments, automotive meters, It is used for applications such as cameras, and various performances such as a wide operating temperature range, a low operating voltage, high-speed response, and chemical stability are required. These liquid crystal elements include TN (twisted nematic) mode, STN (super twisted nematic) mode, ECB (electrically controlled birefringence) mode, OCB (optically compensated bent) mode, IPS (in-plane switching) mode, VA (vertical alignment). Various operation modes are known, such as the) mode.

  In such a liquid crystal element, a material exhibiting a liquid crystal phase is used, but at present, not all of these characteristics are satisfied by a single compound, and a plurality of excellent one or more characteristics are provided. Liquid crystal compounds and non-liquid crystal compounds are mixed to satisfy the required performance as a liquid crystal composition.

In particular, a compound having a tolan structure is used for a liquid crystal composition in order to increase the refractive index anisotropy (Δn) for the purpose of improving display quality such as prevention of interference fringes in an element having a thin cell thickness. (For example, Patent Document 1).
However, when a large amount of a compound having a tolan structure is added in order to obtain a higher Δn, the compatibility is lowered and crystals may be precipitated.

JP 09-194407 A

  The present invention provides a liquid crystal composition suitable for obtaining a liquid crystal element having a high Δn value, good compatibility, and high display quality in a wide temperature range, and a liquid crystal element using the liquid crystal composition The purpose is to do.

  As a result of extensive studies, the present inventor has used a compound having a specific Tran structure in combination as a solution to such a problem, thereby having a high Δn value and a good compatibility. It was found that a liquid crystal element using the liquid crystal composition satisfies various required performances such as a wide operating temperature range and high display quality, and the present invention was completed.

That is, the present invention provides the following liquid crystal composition.
R ^a1 -A ^a1 -Z ^a1 -A ^a2 -Z ^a2- (A ^a3 ) _m1 -Z ^a3- (A ^a4 ) _n1 -R ^a2 (A)
^{R b1 -A b1 -Z b1 -A b2} -Z b2 - (A b3) m2 -Z b3 - (A b4) n2 -R b2 (B)
R ^c1 -Ph-C≡C-Ph-COO-Ph-R ^c2 (C)
The symbols in the formula have the following meanings.
R ^a1 : an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms.
R ^a2 : a halogen atom, an alkyl group or an alkoxy group substituted with a fluorine atom, or a cyano group.
A ^a1 , A ^a2 , A ^a3 and A ^a4 : independently of each other, a trans-1,4-cyclohexylene group or a 1,4-phenylene group, and one or more hydrogen atoms in the group are halogen It may be substituted with an atom.
Z ^a1 , Z ^a2 and Z ^a3 : independently of each other, a single bond, —COO—, —C≡C—, —OCO—, —OCH ₂ —, —CH ₂ O— or —C ₂ H ₄ —. However, at least one of Z ^a1 , Z ^a2 and Z ^a3 is —C≡C—.
m ¹ and n ¹ : 0 or 1 independently of each other.
R ^b1 and R ^b2 : each independently an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms.
A ^b1 , A ^b2 , A ^b3 and A ^b4 : independently of each other, a trans-1,4-cyclohexylene group or a 1,4-phenylene group, and one or more hydrogen atoms in the group are halogen It may be substituted with an atom.
Z ^b1 , Z ^b2 and Z ^b3 : independently of each other, a single bond, —COO—, —C≡C—, —OCO—, —OCH ₂ —, —CH ₂ O—, —CF ₂ O— or — C ₂ H ₄ -. However, at least one of Z ^b1 , Z ^b2 and Z ^b3 is —C≡C—. At least one of A ^b1 , A ^b2 , A ^b3 and A ^b4 is a 2,3-difluoro-1,4-phenylene group, or A ^b2 is a 3-fluoro-1,4-phenylene group In this case, Z ^b2 is —C≡C—.
m ² and n ² : 0 or 1 independently of each other.
R ^c1 and R ^c2 : each independently an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms.
-Ph-: 1,4-phenylene group.

As the liquid crystal composition, the compound represented by the formula (A) is preferably a compound represented by the following formula (A-1).
R ^a1- (Cy) _q -Ph-C≡C-Ph (2F) -Cl (A-1)
The symbols in the formula have the following meanings.
-Cy-: trans-1,4-cyclohexylene group.
-Ph (2F)-: 2-fluoro-1,4-phenylene group.
q: 0 or 1.
Cl: chlorine atom.
R ^a1 , —Ph—has the same meaning as described above.

  Moreover, as said liquid crystal composition, (DELTA) n of a composition has a preferable thing of 0.25 or more.

  The present invention also provides a liquid crystal element comprising the liquid crystal composition sealed between two substrates provided with electrodes.

  The composition of the present invention can provide a liquid crystal device having a high Δn value, good compatibility, excellent stability as a composition, and high display quality in a wide temperature range.

The present invention will be described in more detail below.
In this specification, a compound represented by the formula (A) is referred to as a compound (A), and compounds represented by other formulas are also described in the same manner.
In the present specification, unless otherwise specified, the one closer to R ^a1 in formula (A) is always the first position. In the formula (B) and the formula (C), the first position is always closer to R ^b1 and R ^c1 . For example, in the formula (B), when A ^b2 is a 3-fluoro-1,4-phenylene group and Z ^b2 is —C≡C—, benzene of a 3-fluoro-1,4-phenylene group ring, ^{Z b1} to 1-position, the 4-position -C≡C- are bonded, a fluorine atom is meant to replace the 3-position.

In the compound (A) of the liquid crystal composition of the present invention, R ^a1 has the same meaning as described above. The group in R ^a1 may be either linear or branched, but is preferably linear. In the case of an alkenyl group, when the position of the double bond from the bonding site is an odd number, the liquid crystal temperature range increases, and the alkenyl configuration is preferably a trans configuration.
R ^a1 is preferably an alkyl group having 1 to 5 carbon atoms, an alkenyl group having 2 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms, because high compatibility and liquid crystallinity in a wide temperature range can be obtained.

In the compound (A) of the liquid crystal composition of the present invention, R ^a2 has the same meaning as described above. When R ^a2 is a halogen atom, a fluorine atom or a chlorine atom is preferable, and a chlorine atom is particularly preferable. When R ^a2 is an alkyl group or alkoxy group substituted with a fluorine atom, CF ₃ and OCF ₃ are preferred. R ^a2 is preferably a halogen atom, particularly preferably a chlorine atom.

In the compound (A), A ^a1 , A ^a2 , A ^a3 and A ^a4 have the same meaning as described above.

As the halogen atom for substituting the hydrogen atom in the groups A ^a1 , A ^a2 , A ^a3 and A ^a4 , a large Δε and low viscosity can be obtained, so a chlorine atom or a fluorine atom is preferable, and a fluorine atom is more preferable .

When A ^a1 , A ^a2 , A ^a3 and A ^a4 are 1,4-phenylene groups and further have a halogen atom as a substituent, the number of halogen atoms substituting for one 1,4-phenylene group is 1 There are four, but one or two is preferred. When it is a trans-1,4-cyclohexylene group and further has a halogen atom as a substituent, the number of halogen atoms is preferably 1 to 4. The halogen atom may be bonded to the 1st or 4th carbon atom of the cyclohexylene group.

As A ^a1 , A ^a2 , A ^a3, and A ^a4 , a low viscosity can be obtained. Therefore, a trans-1,4-cyclohexylene group, a 1,4-phenylene group, or one of hydrogen atoms in the group Alternatively, a 1,4-phenylene group in which two are substituted with fluorine atoms is preferable.

In the compound (A), Z ^a1 , Z ^a2 and Z ^a3 have the same meaning as described above. However, at least one of Z ^a1 , Z ^a2 and Z ^a3 is —C≡C—. In addition, when Z ^a1 is a single bond, it means that the ring groups on both sides of Z ^a1 are directly bonded. For example, when Z ^a1 is a single bond, A ^a1 and A ^a2 are directly bonded. Further, when m1 is 0, n2 is 1, and Z ^a2 and Z ^a3 are single bonds, A ^a2 and A ^a4 are directly bonded. The same applies to Z ^a2 and Z ^a3 .

Z ^a1 , Z ^a2 and Z ^a3 are preferably a single bond, —COO— or —C≡C— because large Δn can be obtained.

In the compound (A), m ¹ and n ¹ have the same meaning as described above.
n ¹ is preferably 0 from the viewpoint of compatibility. M ¹ is preferably 0 from the viewpoint of compatibility and 1 from the viewpoint of Tc of the liquid crystal composition.

The compound (A) is preferably the compound (A-1) because high Δn and good compatibility can be obtained.
In the compound (A-1), q has the same meaning as described above. q is preferably 0 from the viewpoint of compatibility and 1 from the viewpoint of Tc of the liquid crystal composition.

The content of the compound (A) in the liquid crystal composition of the present invention is preferably 5 to 30% by mass with respect to the total amount of the liquid crystal composition because high Δn and good compatibility can be obtained. The mass% is more preferable.
The liquid crystal composition of the present invention may contain two or more compounds (A). When two or more types are included, the total amount is preferably in the above range.

In the compound (B) of the liquid crystal composition of the present invention, R ^b1 and R ^b2 have the same meaning as described above. The aspect of R ^b1 and R ^b2 is the same as the aspect of R ^a1 described above.

In the compound (B), A ^b1 , A ^b2 , A ^a3 and A ^a4 have the same meaning as described above. Provided that at least one of A ^b1 , A ^b2 , A ^b3 and A ^b4 is a 2,3-difluoro-1,4-phenylene group, or A ^b2 is a 3-fluoro-1,4-phenylene group. It is.

In the compound (B), aspects of A ^b1 , A ^b2 , A ^b3 and A ^b4 are the same as the aspects of A ^a1 , A ^a2 , A ^a3 and A ^a4 described above.
Among them, as A ^b1 , A ^b2 , A ^b3, and A ^b4 , a low viscosity can be obtained while negatively increasing the dielectric anisotropy (Δε), so that a trans-1,4-cyclohexylene group can be obtained. 1,4-phenylene group or a 1,4-phenylene group in which one or two hydrogen atoms in the group are substituted with fluorine atoms.

In the compound (B), Z ^b1 , Z ^b2 and Z ^b3 have the same meaning as described above. However, at least one of Z ^b1 , Z ^b2 and Z ^b3 is —C≡C—.

In the compound (B), the embodiments of Z ^b1 , Z ^b2 and Z ^b3 are the same as the embodiments of Z ^a1 , Z ^a2 and Z ^a3 .

In the compound (B), m ² and n ² have the same meaning as described above.
n ² is preferably 0 from the viewpoint of compatibility. M ² is preferably 0 from the viewpoint of compatibility and 1 from the viewpoint of Tc of the liquid crystal composition.

As the compound (B), Δn is large and a negative Δε can be obtained. Therefore, the following compound (B-1), compound (B-2), compound (B-3) and compound (B-4) can be obtained. ) Are preferable, and compound (B-1), compound (B-2) and compound (B-3) are particularly preferable. In the formula, “—Ph (2F, 3F) —” is a 2,3-difluoro-1,4-phenylene group, and “—Ph (3F) —” is a 3-fluoro-1,4-phenylene group. The other symbols have the same meaning as described above.
R ^b1 -Ph-C≡C-Ph (2F, 3F) -R ^b2 (B-1)
R ^b1 -Cy-Ph-C≡C-Ph (2F, 3F) -R ^b2 (B-2)
^{R b1 -Cy-COO-Ph (} 2F, 3F) -C≡C-Ph-R b2 (B-3)
R ^b1 -Cy-Ph (3F) -C≡C-Ph-R ^b2 (B-4)

The content of the compound (B) in the liquid crystal composition of the present invention is preferably 5 to 30% by mass with respect to the total amount of the liquid crystal composition since high Δn and good compatibility can be obtained. The mass% is more preferable.
The liquid crystal composition of the present invention may contain two or more kinds of compounds (B). When two or more types are included, the total amount is preferably in the above range.

In the compound (C) of the liquid crystal composition of the present invention, R ^c1 and R ^c2 have the same meaning as described above. The aspect of R ^c1 and R ^c2 is the same as the aspect of R ^a1 described above.

  The content of the compound (C) in the liquid crystal composition of the present invention is preferably 5 to 30% by mass with respect to the total amount of the liquid crystal composition, because high Δn and good compatibility can be obtained. The mass% is more preferable. The liquid crystal composition of the present invention may contain two or more kinds of compounds (C). When two or more types are included, the total amount is preferably in the above range.

  The liquid crystal composition of the present invention preferably has Δn of 0.25 or more. This is because the display quality of the liquid crystal element is excellent by having a high Δn.

  In the composition of the present invention, other compounds than the compounds (A) to (C) include a component that adjusts the refractive index anisotropy value, a component that lowers viscosity, a component that exhibits liquid crystallinity at low temperatures, and a different dielectric constant. Examples include a component that improves the directivity, a component that imparts cholesteric properties, a component that exhibits dichroism, a component that imparts conductivity, and various other additives. These are appropriately selected depending on the application, required performance and the like, but usually those composed of a liquid crystal compound, a main component having a similar structure to the liquid crystal compound, and an additive component added if necessary.

In the liquid crystal composition of the present invention, examples of the other compound include those represented by the following formulae. In the following formulae, R ³ and R ⁴ represent a group such as an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, a halogen atom or a cyano group. R ³ and R ⁴ may be the same or different from each other. In the following formulae, -Phe- is a 1,4-phenylene group optionally substituted with a fluorine atom, and -Cy- has the same meaning as described above.

R ³ -Cy-Cy-R ⁴
R ³ -Cy-Phe-R ^{4
_{R 3 -Cy-CH 2 CH 2}} -Cy-R 4
R ³ -Phe-Phe-R ⁴
R ³ -Phe-C≡C-Phe-R ^{4
R 3 -Cy-COO-Phe-} R 4
R ³ -Phe-COO-Phe-R ^{4
_{R 3 -Cy-CH 2 CH 2}} -Phe-R 4
_{^{R 3 -Phe-CH 2 CH 2}} -Phe-R 4
^{R 3 -Cy-CH = CH-} Phe-R 4
R ³ -Phe-CH = CH-Phe-R ⁴
R ³ -Phe-CF = CF-Phe-R ^{4
R 3 -Cy-CF = CF-} Phe-R 4
R ³ —Cy—CF═CF—Cy—R ^{4
R 3 -Cy-Phe-CF =} CF-Phe-R 4

_{^{R 3 -Cy-Phe-CH 2}} CH 2 -Phe-R 4
_{^{R 3 -Cy-Phe-CH 2}} CH 2 -Cy-R 4
^{_{R 3 -Cy-CH 2 CH 2}} -Cy-Phe-R 4
_{^{R 3 -Cy-Cy-CH 2}} CH 2 -Phe-R 4
_{^{R 3 -Phe-Phe-CH 2}} CH 2 -Phe-R 4
_{^{R 3 -Phe-Phe-CH 2}} CH 2 -Cy-R 4
R ³ -Cy-Phe-Phe-R ⁴
R ³ -Cy-Cy-Phe-R ⁴
R ³ -Cy-Phe-C≡C-Phe-R ^{4
R 3 -Cy-Phe-C≡C-} Phe-Cy-R 4
R ³ —Cy—CH ₂ CH ₂ —Phe—C≡C—Phe—R ⁴

^{_{R 3 -Cy-CH 2 CH 2}} -Phe-C≡C-Phe-Cy-R 4
R ³ -Cy-Phe-Phe-Cy-R ⁴
R ³ -Phe-Phe-Phe-R ⁴
R ³ -Phe-Phe-C≡C-Phe-R ^{4
_{R 3 -Phe-CH 2 CH 2}} -Phe-C≡C-Phe-R 4
^{_{R 3 -Phe-CH 2 CH 2}} -Phe-C≡C-Phe-Cy-R 4
R ³ -Cy-COO-Phe-Phe-R ^{4
R 3 -Cy-Phe-COO-} Phe-R 4
^{R 3 -Cy-COO-Phe-} COO-Phe-R 4
^{R 3 -Phe-COO-Phe-} COO-Phe-R 4

These compounds are merely representative examples, and a hydrogen atom present in a ring structure or a terminal group in the compound may be substituted with a halogen atom, a cyano group, a methyl group, or the like. In addition, the cyclohexane ring or the benzene ring may be substituted with another 6-membered ring or 5-membered ring, for example, a pyrimidine ring or a dioxane ring. divalent bonding group, for example _{-CH 2 O -, - CF 2} O -, - CH = CH -, - N = N -, - CH = N -, - COOCH 2 CH 2 -, - OCOCH 2 CH 2 - Alternatively, it may be changed to —COCH ₂ — etc., and can be selected according to the desired performance.

Especially, it is preferable that the liquid crystal composition of this invention contains the following compound among the illustrated compounds as another compound.
R ³¹ -Cy-Ph-R ⁴¹
R ³¹ -Cy-Cy-R ⁴¹
However, R ³¹ in the formula is an alkyl group having 1 to 8 carbon atoms, an alkenyl group or an alkoxy group, R ⁴¹ is an alkyl group or an alkoxy group having 1 to 8 carbon atoms, -Cy- and -Ph- is as defined above Indicates meaning.

  Furthermore, the present invention provides a liquid crystal element using the liquid crystal composition as a constituent material of a liquid crystal phase. In this specification, the liquid crystal element is not limited to a display element, but various functional elements that use the electrical or optical characteristics of the liquid crystal, such as a liquid crystal display element, a dimming window, an optical shutter, a polarization conversion element, a variable element. It includes elements used for applications such as a focus lens. For example, a liquid crystal electric element having an electric element portion constituted by sandwiching a liquid crystal phase formed by injecting the liquid crystal composition of the present invention into a liquid crystal cell between two substrates provided with electrodes is provided. To do. Examples of the liquid crystal electric element include those driven in various modes such as a twisted nematic method, a guest host method, a dynamic scattering method, a phase change method, a DAP method, a dual frequency driving method, and a ferroelectric liquid crystal display method.

In the liquid crystal element, first, an undercoat layer such as SiO ₂ or Al ₂ O ₃ or a color filter layer is formed on a substrate such as plastic or glass as necessary, and In ₂ O ₃ —SnO ₂ (ITO), A film made of SnO ₂ or the like is formed, and an electrode having a required pattern is formed by photolithography or the like. Next, if necessary, an overcoat layer of polyimide, polyamide, SiO ₂ , Al ₂ O ₃ or the like is formed and subjected to vertical alignment treatment. A sealing material is printed on this, it arrange | positions so that an electrode surface may mutually oppose, a periphery is sealed, a sealing material is hardened, and an empty cell is formed.

  Furthermore, the composition of the present invention is injected into an empty cell, and the injection port is sealed with a sealant to form a liquid crystal cell. If necessary, this liquid crystal cell is laminated with a polarizing plate, a color polarizing plate, a light source, a color filter, a transflective plate, a reflecting plate, a light guide plate, an ultraviolet cut filter, etc., printing characters, figures, etc., non-glare processing, etc. Thus, a liquid crystal element can be obtained.

  Note that the above description describes the basic configuration and manufacturing method of the liquid crystal element, and other configurations can be employed. For example, a substrate using a two-layer electrode, a two-layer liquid crystal cell having a two-layer liquid crystal layer, a substrate using a reflective electrode, an active matrix device using an active matrix substrate having an active element such as a TFT or MIM, etc. Various configurations can be employed. Among these, the composition of the present invention is particularly useful for passive matrix devices.

  Furthermore, the composition of the present invention includes an in-plane switching (IPS) type liquid crystal element, a twisted nematic (TN) type liquid crystal element that drives liquid crystal molecules parallel to the substrate by a lateral electric field, and a super twist angle super twist. A nematic (STN) type liquid crystal element and a guest-host (GH) type liquid crystal element using a polychromatic dye can be used in various systems. Further, it can be used not only in a method of electrically writing but also in a method of writing by heat.

  Hereinafter, the present invention will be described more specifically with reference to examples. The following examples are intended to illustrate the present invention without limiting the present invention.

The compounds shown in Table 1 were blended in the proportions (mass%) shown in the same table to prepare the liquid crystal compositions of Examples 1 to 3. In addition, each compound used for the composition is easily obtained by a method described in an organic synthesis book such as a commercial product or a new experimental chemistry course (published by Maruzen Co., Ltd.).
The symbols in Table 1 have the same meaning as described above.

About Examples 1-3 of the said composition, compatibility, Tc, (DELTA) n, and (DELTA) (epsilon) were measured. The results are shown in Table 2.

In addition, each physical property in Table 2 was measured by the following methods.
[Measurement of compatibility]
1 g of the liquid crystal composition was sealed in a glass bottle and left in a refrigerator at −30 ° C. for 7 days. After leaving, the composition which did not precipitate was evaluated as “◯”.
[Measurement of Tc (° C)]
The liquid crystalline composition was placed on a hot plate (Mettler FP-82HT type hot stage) of a melting point measuring apparatus equipped with a polarizing microscope, and the polarizing microscope was observed while heating at a rate of 1 ° C./min. The temperature at which a part of the sample changed from a nematic phase to an isotropic liquid was defined as the temperature of Tc.
[Measurement of refractive index anisotropy (Δn)]
The measurement was performed at 25 ° C. using an Abbe refractometer using light with a wavelength of 589 nm and a polarizing plate attached to the eyepiece. After rubbing the surface of the main prism in one direction, the liquid crystalline composition was dropped onto the main prism. The refractive index (n‖) was measured when the direction of polarized light was parallel to the direction of rubbing. The refractive index (n⊥) was measured when the direction of polarized light was perpendicular to the direction of rubbing. The value of refractive index anisotropy (Δn) was calculated from the equation: Δn = n∥−n⊥.
[Measurement of dielectric anisotropy (Δε)]
The liquid crystal composition was sealed in a vertically aligned glass cell having an interval of 9 μm. A voltage of 100 mV was applied to the cell at 25 ° C., and the dielectric constant (∈‖) in the major axis direction of the liquid crystal molecules was measured.
Similarly, the liquid crystal composition was sealed in a horizontally aligned glass cell with a spacing of 9 μm, and the dielectric constant (ε⊥) in the minor axis direction was measured. The dielectric anisotropy (Δε) of the liquid crystal composition was determined from the formula Δε = ε∥−ε⊥.

  From the above results, the liquid crystal composition of the present invention has a good compatibility, is stable as a composition, and has a high Δn, so that a liquid crystal element having a high display quality can be obtained which is suitable for a thin cell thickness.

Claims (4)

A liquid crystal composition comprising a compound represented by the following formula (A), a compound represented by the following formula (B), and a compound represented by the following formula (C).
R ^a1 -A ^a1 -Z ^a1 -A ^a2 -Z ^a2- (A ^a3 ) _m1 -Z ^a3- (A ^a4 ) _n1 -R ^a2 (A)
^{R b1 -A b1 -Z b1 -A b2} -Z b2 - (A b3) m2 -Z b3 - (A b4) n2 -R b2 (B)
R ^c1 -Ph-C≡C-Ph-COO-Ph-R ^c2 (C)
(The symbols in the formula have the following meanings.
R ^a1 : an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms.
R ^a2 : a halogen atom, an alkyl group or an alkoxy group substituted with a fluorine atom, or a cyano group.
A ^a1 , A ^a2 , A ^a3 and A ^a4 : independently of each other, a trans-1,4-cyclohexylene group or a 1,4-phenylene group, and one or more hydrogen atoms in the group are halogen It may be substituted with an atom.
Z ^a1 , Z ^a2 and Z ^a3 : independently of each other, a single bond, —COO—, —C≡C—, —OCO—, —OCH ₂ —, —CH ₂ O— or —C ₂ H ₄ —. However, at least one of Z ^a1 , Z ^a2 and Z ^a3 is —C≡C—.
m ¹ and n ¹ : 0 or 1 independently of each other.
R ^b1 and R ^b2 : each independently an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms.
A ^b1 , A ^b2 , A ^b3 and A ^b4 : independently of each other, a trans-1,4-cyclohexylene group or a 1,4-phenylene group, and one or more hydrogen atoms in the group are halogen It may be substituted with an atom.
Z ^b1 , Z ^b2 and Z ^b3 : independently of each other, a single bond, —COO—, —C≡C—, —OCO—, —OCH ₂ —, —CH ₂ O—, —CF ₂ O— or — C ₂ H ₄ -. However, at least one of Z ^b1 , Z ^b2 and Z ^b3 is —C≡C—. At least one of A ^b1 , A ^b2 , A ^b3 and A ^b4 is a 2,3-difluoro-1,4-phenylene group, or A ^b2 is a 3-fluoro-1,4-phenylene group In this case, Z ^b2 is —C≡C—.
m ² and n ² : 0 or 1 independently of each other.
R ^c1 and R ^c2 : each independently an alkyl group having 1 to 10 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms.
-Ph-: 1,4-phenylene group. ) The liquid crystal composition according to claim 1, wherein the compound represented by the formula (A) is a compound represented by the following formula (A-1).
R ^a1- (Cy) _q -Ph-C≡C-Ph (2F) -Cl (A-1)
(The symbols in the formula have the following meanings.
-Cy-: trans-1,4-cyclohexylene group.
-Ph (2F)-: 2-fluoro-1,4-phenylene group.
q: 0 or 1.
Cl: chlorine atom.
R ^a1 and -Ph- have the same meaning as described above. )   The liquid crystal composition according to claim 1, wherein the refractive index anisotropy (Δn) is 0.25 or more.   A liquid crystal element formed by sealing the liquid crystal composition according to claim 1 between two substrates provided with electrodes.