Nematic liquid crystal composition

Description

TECHNICAL FIELD

The present invention relates to nematic liquid crystal compositions that exhibit a positive dielectric anisotropy (Δε) and that are useful as electro-optical liquid crystal display materials.

BACKGROUND ART

Liquid crystal display devices are used in applications such as watches, calculators, measuring instruments, automotive instrument panels, word processors, electronic organizers, printers, computers, televisions, clocks, and advertisement boards. Typical liquid crystal display modes include twisted nematic (TN), super-twisted nematic (STN), and other modes based on thin-film transistors (TFTs), such as VA, which is characterized by vertical alignment, and in-plane switching (IPS)/FFS, which is characterized by horizontal alignment. Liquid crystal compositions used in liquid crystal display devices are required to be stable to external factors such as moisture, air, heat, and light, to exhibit a liquid crystal phase over a wider temperature range centered on room temperature, and to have low viscosity and low driving voltage. In addition, liquid crystal compositions are composed of several to tens of compounds to optimize properties such as dielectric anisotropy (Δε) and refractive index anisotropy (Δn) depending on the specific display device.

Whereas liquid crystal compositions of negative Δε are used in vertical-alignment displays, liquid crystal compositions of positive Δε are used in horizontal-alignment displays such as TN, STN, and IPS displays. Recently, a driving mode has been reported in which a liquid crystal composition of positive Δε is vertically aligned when no voltage is applied and is driven by applying an IPS/FFS electric field, boosting the need for liquid crystal compositions of positive Δε. Liquid crystal compositions are also required to have low driving voltage, high response speed, and a wide operating temperature range in all driving modes. Specifically, liquid crystal compositions are required to have a positive Δε large in absolute value, a low viscosity (η), and a high nematic phase-isotropic liquid phase transition temperature (T_ni). The Δn of liquid crystal compositions also needs to be adjusted to an appropriate range depending on the cell gap by taking into account the product of Δn and the cell gap (d), i.e., Δn×d. Liquid crystal compositions used in applications such as televisions are also required to have a low γ₁since quick response is of a higher priority in these applications.

There are disclosed liquid crystal compositions containing compounds represented by formulas (A-1) and (A-2), which are liquid crystal compounds of positive Δε (PTLs 1 to 4). These liquid crystal compositions, however, fail to provide sufficiently low viscosity. Also disclosed are compounds represented by general formulas (A-3) and (A-4), which have a —CF₂O— or —OCF₂— linking group, and liquid crystal compositions containing such compounds (PTLs 5 to 21). Again, these liquid crystal compositions fail to provide sufficiently low viscosity.

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CITATION LIST
Patent Literature

PTL 1: WO96/032365

PTL 2: Japanese Unexamined Patent Application Publication No. 09-157202

PTL 3: WO98/023564

PTL 4: Japanese Unexamined Patent Application Publication No. 2003-183656

PTL 5: Japanese Unexamined Patent Application Publication N Y. 2-789529

PTL 6: Japanese Patent No. 3122199

PTL 7: WO96/011897

PTL 8: WO97/037960

PTL 9: Japanese Unexamined Patent Application Publication No 10-204016

PTL 10: Japanese Unexamined Patent Application Publication No. 2008-69153

PTL 11: US-4818431

PTL 12: DE4132006

PTL 13: U.S. Pat. No. 7,361,388

PTL 14: U.S. Pat. No. 7,674,507

PTL 15: U.S. Pat. No. 7,767,277

PTL 16: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2006-515283

PTL 17: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2008-545669

PTL 18: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2010-500980

PTL 19: EP-156554

PTL 20: Japanese Unexamined Patent Application Publication No. 2011-136998

PTL 21: U.S. Pat. No. 7,361,388

PTL 22: Japanese Unexamined Patent Application Publication No. 10-67988

PTL 23: Japanese Unexamined Patent Application Publication No. 11-29771.

PTL 24: Japanese Unexamined Patent Application Publication No. 2003-176251

PTL 25: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2003-533557

PTL 26: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2004-529214

PTL 27: Japanese Unexamined Patent Application Publication No. 2005-220355

PTL 28: Japanese Unexamined Patent Application Publication No. 2005-232455

PTL 29: Japanese Unexamined Patent Application Publication No. 2006-328400

PTL 30: Japanese Unexamined Patent Application Publication No. 2007-51291

PTL 31: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2007-501301

PTL 32: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2007-503485

PTL 33: Japanese Unexamined. Patent Application Publication No. 2009-84560

PTL 34: Japanese Unexamined Patent Application Publication No. 2009-179813

PTL 35: Japanese Unexamined Patent Application Publication No. 2009-185285

PTL 36: Japanese Unexamined Patent Application Publication No. 2010-275390

PTL 37: Japanese Unexamined Patent Application Publication No. 2012-117062

PTL 38: U.S. Pat. No. 5,976,407

PTL 39: U.S. Pat. No. 7,001,646

PTL 40: U.S. Pat. No. 7,175,891

PTL 41: TS-7250198

PTL 42: U.S. Pat. No. 7,604,851

PTL 43: U.S. Pat. No. 7,704,566

PTL 44: U.S. Pat. No. 8,168,083

PTL 45: US-2010/0308267

PTL 46: US-2011/0024682

PTL 47: US-2011/0315924.

SUMMARY OF INVENTION
Technical Problem

An object of the present invention is to provide a liquid crystal composition having a positive dielectric anisotropy (Δε) and a sufficiently low viscosity (q) while adjusting the refractive index anisotropy (Δn) to the desired level and maintaining an appropriate nematic phase temperature range without decreasing the nematic phase-isotropic liquid phase transition temperature (T_ni) or increasing the lower temperature limit of the nematic phase.

Solution to Problem

The inventors have researched various fluorobenzenes and have discovered that the foregoing object can be achieved by the use of a particular combination of compounds, which has led to the present invention.

The present invention provides a liquid crystal composition having a positive dielectric anisotropy and a liquid crystal display device including the liquid crystal composition. This liquid crystal composition contains at least one compound represented by general formula (LC0).

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In the formula, R⁰¹is an alkyl group of 1 to 15 carbon atoms, where at least one —CH₂— of the alkyl group is optionally replaced by —O—, —CH═CH—, —CO—, —OCO—, —COO—, —C≡C—, —CF₂O— or —OCF₂— such that no oxygen atoms are directly adjacent to each other, and at least one hydrogen atom of the alkyl group is optionally replaced by halogen.

A⁰¹to A⁰³are each independently any of the following structures.

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(In the structures, at least one —CH₂— of the cyclohexane ring is optionally replaced by —O— such that no oxygen atoms are directly adjacent to each other, at least one —CH═ of each benzene ring is optionally replaced by —N═ such that no nitrogen atoms are directly adjacent to each other, and X⁰³and X⁰⁴are each independently —H, —Cl, —F, —CF₃, or —OCF₃.)

In the formula, partial structural formula (LC0-Ph) may be formula (LC0-Np).

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X⁰¹, X⁰²and X⁰⁵are each independently hydrogen or fluorine.

Y⁰¹is —Cl, —F, —OCHF₂, —CF₃, —OCF₃, or a fluorinated alkyl, alkoxy, alkenyl, or alkenyloxy group of 2 to 5 carbon atoms.

Z⁰¹to Z⁰⁵are each independently a single bond, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—, where at least one of Z⁰¹to Z⁰⁵present is —OCH₂—, —OCF₂—, or —CF₂O—.

W⁰¹and W⁰²are each independently —CH₂— or —O—.

m⁰¹to m⁰³are each independently an integer of 0 to 2. m⁰¹+m⁰²+m⁰³is 0, 1, or 2. A plurality of A⁰¹, A⁰², A⁰³, Z⁰¹, Z⁰³, and/or Z⁰⁵, if present, may be the same or different.

Advantageous Effects of Invention

The liquid crystal composition according to the present invention has the advantage of exhibiting a positive Δε large in absolute value. The liquid crystal composition also has a low η and a low rotational viscosity (γ₁) and exhibits a stable liquid crystal phase over a wide temperature range because of its good liquid crystallinity. This liquid crystal composition is also chemically stable to factors such as heat, light, and moisture and has good phase stability at low temperature because of its good solubility, thereby serving as a practical and reliable liquid crystal composition requiring low driving voltage.

DESCRIPTION OF EMBODIMENTS

A liquid crystal composition according to the present invention contains at least one compound represented by general formula (LC0).

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In general formula (LC0), R⁰¹is preferably an alkyl group of 1 to 8 carbon atoms, an alkenyl group of 2 to 8 carbon atoms, or an alkoxy group of 1 to 8 carbon atoms and is preferably linear. If R⁰¹is an alkenyl group, it is preferably selected from the groups represented by formulas (R1) to (R5) (where the black dots are linkages to the ring). These are preferred if A⁰¹is trans-1,4-cyclohexylene, and formulas (R1), (R2), and (R4) are more preferred.

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A⁰¹to A⁰³are each independently trans-1,4-cyclohexylene, 1,4-phenylene, 3-fluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene, or tetrahydropyran. To achieve the object of the present invention, it is preferred that the liquid crystal composition contain at least one compound selected from the group consisting of these compounds.

General formula (LC0) has partial structure (LC0-Ph).

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Partial structure (LC0-Ph) is preferably selected from those represented by the following formulas.

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Z⁰¹-Z⁰⁵are preferably each independently a single bond, —CH═CH—, —C═C—, —CH₂CH₂—, —OCF₂—, or —CF₂O—. At least one of Z⁰¹to Z⁰⁵present is —OCH₂—, —OCF₂—, or —CF₂O—. Preferably, one of Z⁰²to Z⁰⁵is —OCF₂, —CF₂O—, or —OCH₂—, and more preferably, the remainder is a single bond, —OCF₂—, —CF₂O—, or —OCH₂—.

In the formula, partial structural formula (LC0-Ph) may be formula (LC0-Np).

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(In the formulas, X⁰¹, X⁰², and X⁰⁵are each independently hydrogen or fluorine, and Y⁰¹is —Cl, —F, —OCHF₂, —CF₃, —OCF₃, or a fluorinated alkyl, alkoxy, alkenyl, or alkenyloxy of 2 to 5 carbon atoms.)

X⁰¹to X⁰⁵are preferably F, which results in a significantly low viscosity (η) for a larger or similar dielectric anisotropy (Δε). Preferably, there are 2 to 7 F substituents in general formula (LC0), including the two already shown in general formula (LC0).

It is particularly preferred to use a combination of compounds where Y⁰¹is F, CF₃, OCF₃, —OCF═CF₂, or —OCH═CF₂, which lowers the lower temperature limit of the nematic phase and improves the low-temperature operation and storage stability of the liquid crystal composition.

m⁰¹to m⁰³may each independently be an integer of 0 to 2. It is particularly preferred to use a combination of a compound where m⁰¹+m⁰²+m⁰³is 0 and a compound where m⁰¹+m⁰²+m⁰³is 1.

The compound represented by general formula (LC0) is preferably a compound satisfying at least one of the following conditions.

a compound where Z⁰¹is present and is —OCH₂—, —OCF₂—, or —CF₂O—

a compound where Z⁰²is —OCH₂—, —OCF₂—, or —CF₂O—

a compound where Z⁰³is present and is —OCH₂—, —OCF₂—, or —CF₂O—

a compound where Z⁰⁴is —OCH₂—, —OCF₂—, or —CF₂O—

a compound where Z⁰⁵is present and is —OCH₂—, —OCF₂—, or —CF₂O—

a compound where both W⁰¹and W⁰²are —CH₂—

a compound where one of W⁰¹and W⁰²is —O—

a compound where both W⁰¹and W⁰²are —O—

a compound where m⁰¹+m⁰²+m⁰³is 0

a compound where m⁰¹is 0, m⁰²is 0, and m⁰³is 1

a compound where m⁰¹is 0, m⁰²is 1, and m⁰³is 0

a compound where m⁰¹is 1, m⁰²is 0, and m⁰³is 0

a compound where m⁰¹is 1, m⁰²is 0, and m⁰³is 1

a compound where m⁰¹is 1, m⁰²is 1, and m⁰³is 0

a compound where m⁰¹is 0, m⁰²is 1, and m⁰³is 1

a compound where m⁰¹is 2, one Z⁰¹is —OCH₂—, —OCF₂—, or —CF₂O—, and the other Z⁰¹is a single bond

a compound where m⁰²is 1 or 2, one of Z⁰²and Z⁰³is —OCH₂—, —OCF₂—, or —CF₂O—, and the remainder is a single bond

a compound where m⁰³is 1 or 2, one of Z⁰⁴and Z⁰⁵is —OCH₂—, —OCF₂—, or —CF₂O—, and the remainder is a single bond

More preferably, the liquid crystal compound represented by general formula (LC0) is a compound represented by any of general formulas (LC0-a) to (LC0-d) below (where R⁰¹, A⁰¹to A⁰³, Z⁰¹to Z⁰⁵, X⁰¹, X⁰², and Y⁰¹are as defined in general formula (LC0), and if two or more are present, each may be the same or different). The liquid crystal composition according to the present invention preferably contains, as the compound represented by general formula (LC0), at least one of compounds represented by (LC0-a) to (LC0-d).

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Even more preferably, the compound represented by general formula (LC0) is a compound represented by any of general formulas (LC0-1) to (LC0-74) below. In particular, compounds represented by general formulas (LC0-1) to (LC0-9) are preferred since they have a large dielectric anisotropy (Δε), a significantly low viscosity (η), and good general formula (LC0-10) to (LC0-67) are preferred since they have a large dielectric anisotropy (Δε), a relatively low viscosity (η), and a high nematic phase-isotropic liquid phase transition temperature (T_ni).

Still more preferably, the liquid crystal composition containing the compound represented by general formula (LC0) satisfies at least one of the following conditions.

containing a compound represented by any of general formulas (LC0-2) to (LC0-9) in an amount of at most 40% by mass

containing a compound represented by any of general formulas (LC0-10) to (LC0-18) in an amount of at most 60% by mass

containing a compound represented by any of general formulas (LC0-28) to (LC0-38) in an amount of at most 60% by mass

containing a compound represented by any of general formulas (LC0-48) to (LC0-51) in an amount of at most 30% by mass

containing a compound represented by any of general formulas (LC0-52) and (LC0-53) in an amount of at most 40% by mass

containing a compound represented by any of general formulas (LC0-56) to (LC0-59) in an amount of at most 50% by mass

containing a compound represented by any of general formulas (LC0-60) to (LC0-67) in an amount of at most 20% by mass

containing a compound represented by any of general formulas (LC0-68) to (LC0-74) in an amount of at most 15% by mass

containing at least one compound selected from the group consisting of compounds represented by general formulas (LC0-2) to (LC0-5), (LC0-7), (LC0-11) to (LC0-15), (LC0-17), (LC0-18), (LC0-20), (LC0-28) to (LC0-30), (LC0-34), (LC0-35), (LC0-39), (LC0-41), (LC0-45), (LC0-46), (LC0-56) to (LC0-61), (LC0-68), and (LC0-74)

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(In the formulas, R⁰¹, A⁰¹to A⁰³, Z⁰¹to Z⁰¹, X⁰¹to X⁰⁴, W⁰¹, W⁰², and Y⁰¹are as defined in Claim 1.)

Preferably, a compound of general formula (LC0) where R⁰¹is an alkyl group of 1 to 5 carbon atoms or an alkenyl group of 2 to 5 carbon atoms and Y⁰¹is —Cl, —F, —OCHF₂, —CF₃, —OCF₃, —CF₂CF₃, —CHFCF₃, —OCF₂CF₃, —OCHFCF₃, —OCF═CF₂, or —OCH═CF₂is present in an amount of at most 70% by mass.

The liquid crystal composition according to the present invention preferably further contains at least one compound selected from the group consisting of compounds represented by general formulas (LC1) to (LC5). Particularly preferred is a liquid crystal composition containing at least one compound represented by general formula (LC0) and satisfying at least one of the following conditions.

containing a compound represented by general formula (LC1) in an amount of at most 20% by mass

containing a compound represented by general formula (LC2) in an amount of at most 40% by mass

containing a compound represented by general formula (LC3) in an amount of at most 50% by mass

containing a compound represented by general formula (LC4) in an amount of at most 60% by mass

containing a compound represented by general formula (LC5) in an amount of at most 75% by mass

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In the formulas, R¹¹to R⁴¹are each independently an alkyl group of 1 to 15 carbon atoms, where at least one —CH₂— of the alkyl group is optionally replaced by —O—, —CH═CH—, —CO—, —OCO—, —COO—, —C≡C—, —CF₂O—, or —OCF₂— such that no oxygen atoms are directly adjacent to each other, and at least one hydrogen atom of the alkyl group is optionally replaced by halogen. R⁵¹and R⁵²are each independently an alkyl group of 1 to 15 carbon atoms, where at least one —CH₂— of the alkyl group is optionally replaced by —O—, —CH═CH—, —CO—, —OCO—, —COO—, or —C≡C— such that no oxygen atoms are directly adjacent to each other. If A⁵¹or A⁵³, described later, is a cyclohexane ring, R⁵¹or R⁵²may be —OCF₃, —CF₃, —OCF═CF₂, or —OCH═CF₂. A¹¹to A⁴²are each independently any of the following structures.

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(In the structures, at least one —CH₂— of the cyclohexane ring is optionally replaced by —O— such that no oxygen atoms are directly adjacent to each other, at least one —CH═ of each benzene ring is optionally replaced by —N═ such that no nitrogen atoms are directly adjacent to each other, and X⁶¹and X⁶²are each independently —H, —Cl, —F, —CF₃, or —OCF₃.) A⁵¹to A⁵³are each independently any of the following structures.

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(In the formulas, at least one —CH₂CH₂— of the cyclohexane ring is optionally replaced by —CH═CH—, —CF₂O—, or —OCF₂—, and at least one —CH═ of each benzene ring is optionally replaced by —N═ such that no nitrogen atoms are directly adjacent to each other). X¹¹to X⁴³are each independently —H, —Cl, —F, —CF₃, or —OCF₃. Y¹¹to Y⁴¹are —Cl, —F, —CF₃, —OCF₃, —CF₂CF₃, —CHFCF₃, —OCF₂CF₃, —OCHFCF₃, or —OCF═CF₂. Z³¹to Z⁴²are each independently a single bond, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—, where at least one of Z³¹and Z³²present is not a single bond. Z⁵¹and Z⁵²are each independently a single bond, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—. m¹¹to m⁵¹are each independently an integer of 0 to 3. m³¹+m³²and m⁴¹+m⁴²are each independently 1, 2, 3, or 4. A plurality of A²³, A³¹, A³², A⁴¹, A⁴², A⁵², Z³¹, Z³², Z⁴¹, Z⁴², and/or Z⁵², if present, may be the same or different. Compounds represented by general formula (LC0) are excluded.

In general formulas (LC1) to (LC5), R¹¹to R⁴¹are each independently an alkyl group of 1 to 15 carbon atoms, where at least one —CH₂— of the alkyl group is optionally replaced by —O—, —CH═CH—, —CO—, —OCO—, —COO—, —C≡C—, —CF₂O—, or —OCF₂— such that no oxygen atoms are directly adjacent to each other, and at least one hydrogen atom of the alkyl group is optionally replaced by halogen. R¹¹to R⁴¹are preferably an alkyl group of 1 to 8 carbon atoms, an alkenyl group of 2 to 8 carbon atoms, or an alkoxy group of 1 to 8 carbon atoms and are preferably linear. R⁵¹and R⁵²are each independently an alkyl group of 1 to 15 carbon atoms, where at least one —CH₂— of the alkyl group is optionally replaced by —O—, —CH═CH—, —CO—, —OCO—, —COO—, or —C≡C— such that no oxygen atoms are directly adjacent to each other. R⁵¹and R⁵²are preferably an alkyl group of 1 to 8 carbon atoms, an alkenyl group of 2 to 8 carbon atoms, or an alkoxy group of 1 to 8 carbon atoms and are preferably linear. If R¹¹to R⁵²are alkenyl groups, they are preferably selected from the groups represented by formulas (R1) to (R5).

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(In the formulas, the black dots are linkages to the ring.)

A¹¹to A⁴²are each independently trans-1,4-cyclohexylene, 1,4-phenylene, 3-fluoro-1,4-phenylene, 3,5-difluoro-1,4-phenylene, or tetrahydropyran. If any of A¹¹to A⁴²is tetrahydropyran, A¹¹, A²¹, or A³¹is preferably tetrahydropyran. A⁵¹to A⁵³are preferably each independently trans-1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, or 3-fluoro-1,4-phenylene.

X¹¹to X⁴³are preferably each independently hydrogen or fluorine. Y¹¹to Y⁴¹are preferably —F, —CF₃, or —OCF₃. Z³¹to Z⁴²are preferably each independently a single bond, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—, where at least one of Z³¹and Z³²present is not a single bond. If m⁴²is 0, Z⁴¹is each independently a single bond, —CH═CH—, —C≡C—, —CH₂CH₂—, or —(CH₂)₄—. Z⁵¹and Z⁵²are preferably each independently a single bond, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—, more preferably a single bond, —CH₂CH₂—, —OCF₂—, or —CF₂O—, even more preferably a single bond. m²¹is preferably an integer of 0 or 1. m³¹to m⁴are preferably each independently an integer of 0 to 2, and m³¹+m³²and m⁴¹+m⁴²are preferably each independently 1, 2, or 3. m⁵¹is preferably an integer of 1 or 2. A plurality of A²³, A³¹, A³², A⁴¹, A⁴², A⁵², Z³¹, Z³², Z⁴¹, Z⁴², and/or Z⁵², if present, may be the same or different.

The compound represented by general formula (LC1) is preferably a compound represented by any of general formulas (LC1-1) to (LC1-4).

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(In the formulas, R¹¹is an alkyl group of 1 to 15 carbon atoms, where at least one —CH₂— of the alkyl group is optionally replaced by —O—, —CH═CH—, —CO—, —OCO—, —COO—, —C≡C—, —CF₂O—, or —OCF₂— such that no oxygen atoms are directly adjacent to each other, and at least one hydrogen atom of the alkyl group is optionally replaced by halogen; X¹¹and X¹²are each independently —H, —Cl, —F, —CF₃, or —OCF₃; and Y¹is —Cl, —F, —CF₃, —OCF₃, —CF₂CF₃, —CHFCF₃, —OCF₂CF₃, —OCHFCF₃, or —OCF═CF₂.)

The compound represented by general formula (LC2) is preferably a compound represented by any of general formulas (LC2-1) to (LC2-14).

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(In the formulas, R²¹is an alkyl group of 1 to 15 carbon atoms, where at least one —CH₂— of the alkyl group is optionally replaced by —O—, —CH═CH—, —CO—, —OCO—, —COO—, —C≡C—, —CF₂O—, or —OCF₂— such that no oxygen atoms are directly adjacent to each other, and at least one hydrogen atom of the alkyl group is optionally replaced by halogen; X²²to X²⁶are each independently —H, —Cl, —F, —CF₃, or —OCF₃; and Y²¹is —Cl, —F, —CF₃, —OCF₃, —CF₂CF₃, —CHFCF₃, —OCF₂CF₃, —OCHFCF₃, or —OCF═CF₂.)

The compound represented by general formula (LC3) is preferably a compound selected from the group consisting of compounds represented by general formulas (LC3-1) to (LC3-32) and/or the group consisting of compounds represented by general formulas (LC3-0-1) to (LC3-0-97).

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(In the formulas, R is as defined for R³¹in general formula (LC3); X³³, X³⁴, X³⁵, X³⁶, X³⁷, and X³⁸are each independently H, Cl, F, CF₃, or OCF₃; X³², R³¹, and R³¹are an alkyl group of 1 to 15 carbon atoms, where at least one —CH₂— of the alkyl group is optionally replaced by —O—, —CH═CH—, —CO—, —OCO—, —COO—, —C≡C—, —CF₂O—, or —OCF₂— such that no oxygen atoms are directly adjacent to each other, and at least one hydrogen atom of the alkyl group is optionally replaced by halogen; X³²is —H, —Cl, —F, —CF₃, or —OCF₃; Y³¹is —Cl, —F, —CF₃, —OCF₃, —CF₂CF₃, —CHFCF₃, —OCF₂CF₃, —OCHFCF₃, or —OCF═CF₂; and —F, CF₃, and OCF₃are —F, —CF₃, or —OCF₃.)

The compound represented by general formula (LC4) is preferably a compound represented by any of general formulas (LC4-1) to (LC4-32).

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(In the formulas, X⁴⁴, X⁴⁵, X⁴⁶, and X⁴⁷are each independently H, Cl, F, CF₃, or OCF₃; R⁴¹is an alkyl group of 1 to 15 carbon atoms, where at least one —CH₂— of the alkyl group is optionally replaced by —O—, —CH═CH—, —CO—, —OCO—, —COO—, —C≡C—, —CF₂O—, or —OCF₂— such that no oxygen atoms are directly adjacent to each other, and at least one hydrogen atom of the alkyl group is optionally replaced by halogen; X⁴²and X⁴³are each independently —H, —Cl, —F, —CF₃, or —OCF₃; and Y⁴¹is —Cl, —F, —CF₃, —OCF₃, —CF₂CF₃, —CHFCF₃, —OCF₂CF₃, —OCHFCF₃, or —OCF═CF₂.)

The compound represented by general formula (LC5) is preferably a compound represented by any of general formulas (LC5-1) to (LC5-26).

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(In the formulas, R⁵¹and R⁵²are each independently an alkyl group of 1 to 15 carbon atoms, where at least one —CH₂— of the alkyl group is optionally replaced by —O—, —CH═CH—, —CO—, —OCO—, —COO—, or —C≡C— such that no oxygen atoms are directly adjacent to each other.) Preferably, the liquid crystal composition according to the present invention contains at least one compound represented by general formula (LC5). The compound represented by general formula (LC5) is preferably present in an amount of 20% to 80% by mass, more preferably 30% to 70% by mass.

More preferably, the liquid crystal composition according to the present invention contains, as the compound represented by general formula (LC5), at least one compound selected from the group consisting of the following compounds in an amount of at most 70% by mass.

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(In the formulas, alkyl and alkyl* are each independently an alkyl or alkoxy group of 1 to 5 carbon atoms; and alkenyl and alkenyl* are each independently an alkenyl or alkenyloxy group of 2 to 5 carbon atoms having the following formula.)

The liquid crystal composition according to the present invention preferably has a viscosity η of 20 mPa·s or less at 20° C.

The liquid crystal composition according to the present invention may contain at least one optically active compound. The optically active compound may be any optically active compound that allows liquid crystal molecules to be aligned in a twisted configuration. Since the twist generally varies depending on temperature, a plurality of optically active compounds may be used to achieve the desired temperature dependence. It is preferred to select and use optically active compounds having a strong twist effect to avoid a detrimental effect on properties such as the temperature range of the nematic liquid crystal phase and viscosity. As such optically active compounds, the liquid crystal composition according to the present invention preferably contains liquid crystals such as cholesteryl nonanoate and compounds represented by general formulas (Ch-1) to (Ch-6).

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In the formulas, R_c1, R_c2, and R* are each independently an alkyl group of 1 to 15 carbon atoms, where at least one —CH₂— of the alkyl group is optionally replaced by —O—, —CH═CH—, —CO—, —OCO—, —COO—, —C≡C—, —CF₂O—, or —OCF₂— such that no oxygen atoms are directly adjacent to each other, and at least one hydrogen atom of the alkyl group is optionally replaced by halogen, with the proviso that R* has at least one optically active branched-chain group or halogen substituent. Z_c1and Z_c2are each independently a single bond, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —COO—, —OCO—, —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—. D₁and D₂are a cyclohexane or benzene ring, where at least one —CH₂— of the cyclohexane ring is optionally replaced by —O— such that no oxygen atoms are directly adjacent to each other, at least one —CH₂CH₂— of the ring is optionally replaced by —CH═CH—, —CF₂O—, or —OCF₂—, at least one —CH═ of the benzene ring is optionally replaced by —N═ such that no nitrogen atoms are directly adjacent to each other, and at least one hydrogen atom of the ring is optionally replaced by F, Cl, or CH₃. t₁and t₂are 0, 1, 2, or 3. MG*, Q_c1, and Q_c2are any of the following structures.

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(In the formulas, D₃and D₄are a cyclohexane or benzene ring, where at least one —CH₂— of the cyclohexane ring is optionally replaced by —O— such that no oxygen atoms are directly adjacent to each other, at least one —CH₂CH₂— of the ring is optionally replaced by —CH═CH—, —CF₂O—, or —OCF₂—, at least one —CH═ of the benzene ring is optionally replaced by —N═ such that no nitrogen atoms are directly adjacent to each other, and at least one hydrogen atom of the ring is optionally replaced by F, Cl, or CH₃.)

The liquid crystal composition according to the present invention may contain at least one polymerizable compound. The polymerizable compound is preferably a discotic liquid crystal compound having a benzene derivative, triphenylene derivative, truxene derivative, phthalocyanine derivative, or cyclohexane derivative backbone in the center of the molecule and linear alkyl, linear alkoxy, or substituted benzoyloxy side chains extending radially from the backbone.

Specifically, the polymerizable compound is preferably a polymerizable compound represented by general formula (PC).

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(In the formula, P₁is a polymerizable functional group; Sp₁is a spacer group of 0 to 20 carbon atoms; Q_p1is a single bond, —O—, —NH—, —NHCOO—, —OCONH—, —CH═CH—, —CO—, —COO—, —OCO—, —OCOO—, —OOCO—, —CH═CH—, —CH═CH—COO—, —OCO—CH═CH—, or —C≡C—; p₁and p₂are each independently 1, 2, or 3; MG_pis a mesogenic group or mesogenic supporting group; and R_p1is halogen, cyano, or an alkyl group of 1 to 25 carbon atoms, where at least one CH₂moiety of the alkyl group is optionally replaced by —O—, —S—, —NH—, —N(CH₃)—, —CO—, —COO—, —OCO—, —OCOO—, —SCO—, —COS—, or —C≡C— such that no oxygen atoms are directly adjacent to each other, or R_p1may be P₂—S_p2-Q_p2-, where P₂, Sp₂, and Q_p2are each independently as defined for P₁, Sp₁, and Q_p1.)

More preferably, the polymerizable compound is a polymerizable compound of general formula (PC) where MG_pis represented by the following structure.

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(In the formula, C₀₁to C₀₃are each independently 1,4-phenylene, 1,4-cyclohexylene, 1,4-cyclohexenyl, tetrahydropyran-2,5-diyl, 1,3-dioxane-2,5-diyl, tetrahydrothiopyran-2,5-diyl, 1,4-bicyclo(2,2,2)octylene, decahydronaphthalene-2,6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl, pyrazine-2,5-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, 2,6-naphthylene, phenanthrene-2,7-diyl, 9,10-dihydrophenanthrene-2,7-diyl, 1,2,3,4,4a,9,10a-octahydrophenanthrene-2,7-diyl, or fluorene-2,7-diyl, where 1,4-phenylene, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, 2,6-naphthylene, phenanthrene-2,7-diyl, 9,10-dihydrophenanthrene-2,7-diyl, 1,2,3,4,4a,9,10a-octahydrophenanthrene-2,7-diyl, and fluorene-2,7-diyl are optionally substituted by at least one F, Cl, CF₃, OCF₃, or cyano group, at least one alkyl, alkoxy, alkanoyl, or alkanoyloxy group of 1 to 8 carbon atoms, or at least one alkenyl, alkenyloxy, alkenoyl, or alkenoyloxy group of 2 to 8 carbon atoms; Z_p1and Z_p2are each independently —COO—, —OCO—, —CH₂CH₂—, —OCH₂—, —CH₂O—, —CH═CH—, —C≡C—, —CH═CHCOO—, —OCOCH═CH—, —CH₂CH₂COO—, —CH₂CH₂OCO—, —COOCH₂CH₂—, —OCOCH₂CH₂—, —CONH—, —NHCO—, or a single bond; and p₃is 0, 1, or 2.)

If Sp₁and Sp₂are each independently an alkylene group, the alkylene group is optionally substituted by at least one halogen or CN group, where at least one CH₂of that group is optionally replaced by —O—, —S—, —NH—, —N(CH₃)—, —CO—, —COO—, —OCO—, —OCOO—, —SCO—, —COS—, or —C≡C— such that no oxygen atoms are directly adjacent to each other. P₁and P₂are preferably each independently any of the following general formulas.

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(In the formulas, R_p2to R_p6are each independently hydrogen, halogen, or an alkyl group of 1 to 5 carbon atoms.)

More specifically, the polymerizable compound of general formula (PC) is preferably a polymerizable compound represented by any of general formulas (PC0-1) to (PC0-6).

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(In the formulas, p₄are each independently 1, 2, or 3.) Even more specifically, the polymerizable compound of general formula (PC) is preferably a polymerizable compound represented by any of general formulas (PC1-1) to (PC1-9).

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(In the formulas, p₅is 0, 1, 2, 3, or 4.) In particular, Sp₁, Sp₂, Q_p1, and Q_p2are preferably a single bond; P₁and P₂are preferably formula (PC0-a), more preferably acryloyloxy or methacryloyloxy; p₁+p₄is preferably 2, 3, or 4; and R_p1is preferably H, F, CF₃, OCF₃, CH₃, or OCH₃. More preferred are compounds represented by general formulas (PC1-2), (PC1-3), (PC1-4), and (PC1-8).

Also preferred are discotic liquid crystal compounds of general formula (PC) where MG_pis represented by general formula (PC1)-9.

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(In the formulas, R₇is each independently P₁-Sp₁-Q_p1or a substituent of general formula (PC1-e), where R⁸¹and R⁸²are each independently hydrogen, halogen, or methyl, and R₈₃is an alkoxy group of 1 to 20 carbon atoms, where at least one hydrogen atom of the alkoxy group is replaced by a substituent represented by any of general formulas (PC0-a) to (PC0-d) above.)

The polymerizable compound is preferably present in an amount of 0.05% to 2.0% by mass.

The polymerizable compound present in the liquid crystal composition according to the present invention is polymerized to fabricate a liquid crystal display device. In this process, it is desirable to reduce the content of the unpolymerized component to the desired level or lower. The liquid crystal composition preferably contains a compound of general formula (LC0) having a partial structure containing biphenyl and/or terphenyl. More specifically, compounds represented by general formulas (LC0-10) to (LC0-27), (LC0-48) to (LC0-53), and (LC0-60) to (LC0-68) are preferred, and at least one of them is preferably present in an amount of 0.1% to 40% by mass. It is also preferred to use a combination of compounds selected from the group consisting of polymerizable compounds represented by general formulas (PC1-1) to (PC1-3), (PC1-8), and (PC1-9).

The liquid crystal composition may further contain at least one antioxidant and may further contain at least one UV absorber. The antioxidant is preferably selected from those represented by general formulas (E-1) and (E-2).

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(In the formulas, R_e1is an alkyl group of 1 to 15 carbon atoms, where at least one —CH₂— of the alkyl group is optionally replaced by —O—, —CH═CH—, —CO—, —OCO—, —COO—, —C≡C—, —CF₂O—, or —OCF₂— such that no oxygen atoms are directly adjacent to each other, and at least one hydrogen atom of the alkyl group is optionally replaced by halogen;

Z_e1and Z_e2are each independently a single bond, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —COO—, —OCO—, —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—;

E₁is a cyclohexane or benzene ring, where at least one —CH₂— of the cyclohexane ring is optionally replaced by —O— such that no oxygen atoms are directly adjacent to each other, at least one —CH₂CH₂— of the ring is optionally replaced by —CH═CH—, —CF₂O—, or —OCF₂—, at least one —CH═ of the benzene ring is optionally replaced by —N═ such that no nitrogen atoms are directly adjacent to each other, and at least one hydrogen atom of the ring is optionally replaced by F, Cl, or CH₃; and q₁is 0, 1, 2, or 3.)

The liquid crystal composition according to the present invention can be used for liquid crystal display devices, particularly active-matrix liquid crystal display devices such as TN, OCB, ECB, IPS, and VA-IPS liquid crystal display devices (including those with FFS electrodes). VA-IPS is a mode in which a liquid crystal material of positive dielectric anisotropy (Δε>0) is aligned perpendicular to a substrate surface when no voltage is applied and liquid crystal molecules are driven by pixel electrodes and a common electrode disposed on the same substrate surface. This mode, in which liquid crystal molecules are aligned along a curved electric field generated by the pixel electrodes and the common electrode, facilitates pixel division and the formation of multiple domains and also provides the advantage of quick response. This mode is known under various names, such as EOC and VA-IPS, as disclosed in the following non-patent literature: Proc. 13th IDW, 97 (1997), Proc. 13th IDW, 175 (1997), SID Sym. Digest, 319 (1998), SID Sym. Digest, 838 (1998), SID Sym. Digest, 1085 (1998), SID Sym. Digest, 334 (2000), and Eurodisplay Proc., 142 (2009). In the present invention, this mode is hereinafter abbreviated as “VA-IPS”.

In general, the threshold voltage (Vc) of Fréedericksz transition in TN and ECB is given by the following equation.

$\begin{matrix} Vc = \frac{Π d_{cell}}{d_{cell} + 〈 r 1 〉} \sqrt{\frac{K 11}{Δɛ}} & [Math . 1] \end{matrix}$

The threshold voltage (Vc) of Fréedericksz transition in IPS is given by the following equation.

$\begin{matrix} Vc = \frac{Π d_{gap}}{d_{cell} + 〈 r 2 〉} \sqrt{\frac{K 22}{Δɛ}} & [Math . 2] \end{matrix}$

The threshold voltage (Vc) of Fréedericksz transition in VA is given by the following equation.

$\begin{matrix} Vc = \frac{Π d_{cell}}{d_{cell} - 〈 r 3 〉} \sqrt{\frac{K 33}{\langle Δɛ \rangle}} & [Math . 3] \end{matrix}$

(In the equations, Vc is the Fréedericksz transition (V); Π is the circular constant; d_cellis the distance (μm) between first and second substrates; d_gapis the distance (μm) between pixel electrodes and a common electrode; d_ITOis the width (μm) of the pixel electrodes and/or the common electrode; <r1>, <r2>, and <r3> are extrapolation lengths (μm); K11 is the splay elastic constant (N); K22 is the twist elastic constant (N); K33 is the bend elastic constant (N); and Δε is the dielectric anisotropy.)

The inventors have found that Math. 4 below applies to VA-IPS.

$\begin{matrix} Vc \propto \frac{d_{gap} - 〈 r^{'} 〉}{d_{ITO} + 〈 r 〉} \frac{Π d_{cell}}{d_{cell} - 〈 r 3 〉} \sqrt{\frac{K 33}{\langle Δɛ \rangle}} & [Math . 4] \end{matrix}$

(In the equation, Vc is the Fréedericksz transition (V); Π is the circular constant; d_cellis the distance (μm) between first and second substrates; d_gapis the distance (μm) between pixel electrodes and a common electrode; d_ITOis the width (μm) of the pixel electrodes and/or the common electrode; <r>, <r′>, and <r3> are extrapolation lengths (μm); K33 is the bend elastic constant (N); and Δε is the dielectric anisotropy.) Math. 4 suggests that a cell configuration having a smaller d_gapand a larger d_ITOallows for a lower driving voltage and that a liquid crystal composition having a Δε larger in absolute value and a smaller K33 allows for a lower driving voltage.

A liquid crystal display device can be fabricated using the liquid crystal composition according to the present invention by aligning liquid crystal molecules along a substrate surface by rubbing using compounds such as polyimides and polyamides. A liquid crystal display device can also be fabricated by photoalignment using compounds such as chalcones, cinnamates, and cinnamoyl compounds. A new alignment technique that can be used involves incorporating a polymerizable liquid crystal compound into an alignment layer and polymerizing the polymerizable liquid crystal compound.

The properties, such as Δε, K11, and K33, of the liquid crystal composition according to the present invention can be adjusted to the preferred levels.

The product (Δn·d) of the refractive index anisotropy (Δn) of a liquid crystal composition and the distance (d) between first and second substrates of a display is closely related to viewing angle characteristics and response speed. The distance (d) therefore tends to become smaller, i.e., 3 to 4 μm. The product (Δn·d) is preferably 0.31 to 0.33 for TN, ECB, and IPS (in which liquid crystal molecules are aligned substantially parallel to a substrate surface when no voltage is applied). For VA-IPS, in which liquid crystal molecules are aligned perpendicular to both substrates, the product (Δn·d) is preferably 0.20 to 0.59, more preferably 0.30 to 0.40. The appropriate product (Δn·d) thus depends on the mode of the specific display device. The refractive index anisotropy (Δn) of liquid crystal compositions suitable for various modes ranges from 0.070 to 0.110, from 0.100 to 0.140, or from 0.130 to 0.180. Liquid crystal compositions having refractive index anisotropies (Δn) within such different ranges can be prepared.

A liquid crystal composition according to the present invention containing a polymerizable compound represented by general formula (PC) can be used to provide a polymer-stabilized TN, OCB, ECB, IPS, or VA-IPS liquid crystal display device by polymerizing the polymerizable compound present in the liquid crystal composition with or without the application of voltage. Specifically, a liquid crystal display device can be fabricated by placing the liquid crystal composition containing the polymerizable compound between two substrates and polymerizing the polymerizable compound present in the liquid crystal composition by means of energy such as UV radiation with or without the application of voltage. The polymerization of the polymerizable compound in the liquid crystal display device allows the alignment of liquid crystal molecules to be memorized, thereby improving the stability of the alignment. This also contributes to improved response speed.

EXAMPLES

The present invention is further illustrated by the following examples, although these examples are not intended to limit the present invention. In the compositions of the following Examples and Comparative Example, percentages are by mass.

The physical properties of liquid crystal compositions are denoted as follows:

T_N-I: nematic phase-isotropic liquid phase transition temperature (° C.)

T-n: lower temperature limit of nematic phase (° C.)

ε⊥: dielectric constant in direction perpendicular to long molecular axis at 25° C.

Δε: dielectric anisotropy at 25° C.

n_o: ordinary refractive index at 25° C.

Δn: refractive index anisotropy at 25° C.

Vth: applied voltage (V) in 6 μm thick cell that exhibits change in transmittance of 10% at 25° C. upon application of rectangular wave at frequency of 1 KHz

η₂₀: bulk viscosity at 20° C. (mPa·s)

γ₁: rotational viscosity (mPa·s)

Compounds are represented by the following abbreviations.

TABLE 1

n
C_nH_2n+1—
-2-
—CH₂CH₂—
—F
—F

m
—C_mH_2m+1
-d-
—CH═CH—
—Cl
—Cl

nO
C_nH_2n+1O—
-T-
—C≡C—
—CN
—C≡N

Om
—OC_mH_2m+1
-1O-
—CH₂O—
—CFFF
—CF₃

ndm-
C_nH_2n+1—CH═CH—(CH₂)_m−1—
-O1-
—OCH₂—
—CFF
—CHF₂

-ndm
—(CH₂)_n−1—CH═CH—C_mH_2m+1
-CFFO-
—CF₂O—
—OCFFF
—OCF₃

ndmO-
C_nH_2n+1—CH═CH—(CH₂)_m−1—O—
-OCFF-
—OCF₂—
—OCFF
—OCHF₂

-Ondm
—O—(CH₂)_n−1—CH═CH—C_mH_2m+1
-V-
—CO—
—OCFFCFFF
—OCF2CF₃

-VO-
—COO—
—CFFCFFF
—CF2CF₃

-OV-
—OCO—
—OCF═CFF
—OCF═CF₂

—OCH═CFF
—OCH═CF₂

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(Example 1) (Comparative Example 1)

The resulting liquid crystal compositions and the physical properties thereof are shown below.

TABLE 2

Component
Ex-1
Ref-1

3-Ph3-O1-Cy-Ph-OCFFF
10.0

3-Ph3-O1-Cy-Ph3-F
15.0

3-Ph3-OCFF-Cy-Ph3-F
5.0

3-Ph-O1-Cy-Ph-OCFFF

10.0

3-Ph3-1O-Cy-Ph3-F

15.0

3-Ph-OCFF-Cy-Ph3-F

5.0

1d1-Cy-Cy-2
10.0
10.0

0d3-Cy-Cy-3
15.0
15.0

2-Cy-Cy-Ph-1
8.0
8.0

3-Cy-Cy-Ph-1
7.0
7.0

3-Cy-Ph1-Ph3-CFFO-Ph3-F
5.0
5.0

3-Ph-Ph-Ph3-CFFO-Ph3-F
5.0
5.0

3-Cy-Cy-Ph3-OCFFF
5.0
5.0

5-Cy-Cy-Ph3-OCFFF
5.0
5.0

2-Cy-Cy-Ph3-Ph3-F
4.0
4.0

3-Cy-Cy-Ph3-Ph3-F
3.0
3.0

5-Cy-Cy-Ph3-Ph3-F
3.0
3.0

total
100.0
100.0

Tni (° C.)
73.7
71.4

T-n (° C.)
−38.0
−36.0

Vth (volt)
1.39
1.38

Δε
10.0
9.8

Δn
0.087
0.088

η20° C. (mPa · s)
14.5
20.3

Ex-1 is a liquid crystal composition containing compounds represented by general formula (LC0) in the present invention. Ref-1 is a liquid crystal composition containing no compound represented by general formula (LC0) in the present invention. The γ₁of Ex-1 was 74 mPa·s, whereas the γ₁of Ref-1 was 96 mPa·s. The results show that Ex-1 had a much lower viscosity than Ref-1, which contained compounds differing in partial structure from compounds represented by general formula (LC0), demonstrating the superiority of the combination according to the present invention.

Example 2

Liquid crystal compositions containing compounds of general formula (LC5) and the physical properties thereof are shown below.

TABLE 3

Conponent
Mix-A
Mix-B

0d1-Cy-Cy-3
10.0
10.0

od1-Cy-Cy-1d1
10.0
20.0

3-Cy-d-Cy-1d1
10.0
20.0

3-Pr-Cy-2
10.0

3-Pr-Cy-1d1
10.0
20.0

3-Pr-d-Cy-3d0
10.0
20.0

5-Ph-Ph-1
10.0

3-Cy-Cy-Ph-1
15.0
10.0

1-Ph-Ph1-Ph-3d0
15.0

total
100.0
100.0

Tni (° C.)
78.9
78.0

Δε
0.1
0.1

Δn
0.104
0.063

η20° C. (mPa · s)
9.3
7.1

Liquid crystal compositions prepared using Mix-A and Mix-B and the physical properties thereof are shown below.

TABLE 4

Mix-A
35.0

3-Cy-Cy-Ph3-OCFFF
5.0

3-Pr-Ph1-Ph3-CFFO-Ph3-F
5.0

3-Ph3-O1-Cy-Ph-OCFFF
7.0

3-Ph3-OCFF-Cy-Ph3-OCFFF
8.0

3-Ph3-OCFF-Pr-Ph3-F
5.0

3-Ph3-OCFF-Cy-Ph3-Ph3-OCFFF
8.0

3-Ph-Ph3-OCFF-Cy-Ph3-F
8.0

3-Pr-Ph3-O1-Cy-Ph3-F
7.0

3-Ph3-OCFF-Cy-Pr-Ph3-F
7.0

3-Ph3-OCFF-Cy-Ph1-Ph3-CFFO-Ph3-F
5.0

total
100.0

Tni (° C.)
89.7

T-n (° C.)
−43.0

Vth (volt)
1.09

Δε
14.8

Δn
0.108

η20° C. (mPa · s)
15.4

Example 3