Nematic liquid crystal composition

TECHNICAL FIELD

The present invention relates to a nematic liquid crystal composition that is useful as an electro-optical liquid crystal display material arid exhibits a positive value of dielectric anisotropy (Δε).

BACKGROUND ART

A liquid crystal display element is used for various measuring equipment, panels for an automobile, word processors, electronic notebooks, printers, computers, televisions, timepieces, advertisement display boards, and the like, as well as timepieces and electronic calculators. As a liquid crystal display mode, representative examples thereof include a Twisted Nematic (TN) mode, a Super Twisted Nematic (STN) mode, and a VA mode that is characterized in a vertical alignment or an In-Plane Switching (IPS) mode/Fringe Field Switching (FFS) mode that is characterized in a horizontal alignment, which uses a Thin Film Transistor (TFT). A liquid crystal composition used for this liquid crystal display element is required to be stable against external factors such as moisture, air, heat, and light; exhibit a liquid crystal phase in a wide temperature range as much as possible, which is around room temperature; and have low viscosity and low driving voltage. Furthermore, the liquid crystal composition is composed of several or tens of types of compounds, in order to obtain an optimal dielectric anisotropy (Δε) and/or an optimal value of refractive index anisotropy (Δn) or the like when applied to respective display elements.

In a vertical alignment mode display, a liquid crystal composition having negative Δε is used, and in a horizontal alignment mode display such as a TN mode, a STN mode or an IPS mode, a liquid crystal composition having positive Δε is used. In recent years, a driving mode has been reported, in which a liquid crystal composition having positive Δε is vertically aligned in the absence of applied voltage, and a horizontal electric field is applied similarly to an IPS mode/FFS mode. Since it is estimated that the liquid crystal display element using this driving mode will further grow later on as a small and medium-sized display such as a smart phone, necessity of the liquid crystal composition having positive Δε is further increased.

Meanwhile, in all of the driving modes, in the case where the liquid crystal display element is applied to a television, or the like, a high response speed is important and accordingly, in the liquid crystal composition for a display element, a response speed is required to be improved and a liquid crystal composition having a higher Δn and a lower viscosity, as compared with the current composition, is demanded. Also, from the viewpoint of adjusting Δn×d, which is a product of Δn and a cell gap (d), to a predetermined value, it is necessary to adjust Δn of the liquid crystal composition within an appropriate range depending on a cell gap. However, in a display such as a FFS mode, a liquid crystal composition having further higher Δn is required because of a reduction in the gap, and therefore, a high response speed is further demanded. Moreover, in particular, a wide operation temperature range is demanded for the use of a mobile phone. That is, the liquid crystal composition is required to exhibit a high refractive index anisotropy (Δn) and a high temperature for transition from a nematic phase to an isotropic liquid phase (T_ni) while having a relatively low viscosity.

In the related art, as a constituent component of the liquid crystal composition, for example, compounds represented by General Formulas (A) to (C) are used in combination to achieve an increase of Δn (PTL 1 and PTL 2).

embedded image

R represents an alkyl group or an alkenyl group.

However, the compound of General Formula (A) has a low T_ni, which is lower and higher of 0° C., the compound of General Formula (B) has a relatively high T_ni, which is lower and higher of 160° C., but insufficient compatibility, and the compound of General Formula (C) has high Δn, which is before and after 0.24, but deteriorated compatibility, and has a T_niof around 120° C. As a component configuring the liquid crystal composition having a wide nematic temperature range, the physical property values are not sufficient.

CITATION LIST

Patent Literature

[PTL 1] JP-T-2007-526931

[PTL 2] JP-A-2003-261873

SUMMARY OF INVENTION
Technical Problem

An object of the present invention is to provide a liquid crystal composition which has high refractive index anisotropy (Δn) and sufficiently low viscosity (η), achieves a wide nematic phase temperature range by suppressing a decrease in temperature for transition from a nematic phase to an isotropic liquid phase (T_ni), exhibits high compatibility, and has a high response speed and excellent reliability when the liquid crystal composition of the present invention is used in a liquid crystal display element.

Solution to Problem

The present inventors have reviewed a variety of fluorobenzene derivatives and found out that the problem can be solved by using specific compounds in combination, thereby completing the present invention.

The present invention provides a liquid crystal composition including at least one compound represented by General Formula (1), at least one compound represented by General Formula (2), and at least one compound represented by General Formula (LC1), and further provides a liquid crystal display element using the liquid crystal composition.

embedded image

In the formula, R⁰¹represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, and one —CH₂— or two or more —CH₂— in these groups may be substituted with —O—, —S—, —COO—, —OCO—, or —CO— as long as an oxygen atom is not directly adjacent to another oxygen atom, and at least one hydrogen atom present in these groups may be substituted with a fluorine atom;

R⁰²represents an alkenyl group having 2 to 15 carbon atoms, one —CH₂— or two or more —CH₂— present in the alkenyl group may be substituted with —O—, —S—, —COO—, —OCO—, or —CO— as long as an oxygen atom is not directly adjacent to another oxygen atom, and at least one hydrogen atom present in the alkenyl group may be substituted with a fluorine atom;

A¹is a group selected from the group consisting of (a) 1,4-cyclohexylene group in which one —CH₂— or two or more —CH₂— non-adjacent to each other present in this group may be substituted with —O— or —S—, (b) 1,4-phenylene group in which one —CH═ or two or more —CH═ non-adjacent to each other present in this group may be substituted with —N═ and at least one hydrogen atom present in this group may be substituted with a fluorine atom, and (c) naphthalene-2,6-diyl group in which one —CH═ or two or more —CH═ non-adjacent to each other present in this group may be substituted with —N═ and at least one hydrogen atom present in this group may be substituted with a fluorine atom;

Z¹represents —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, —COO—, —OCO—, —CH₂CH₂—, —CF₂CF₂—, —CH═CH—, —CF═CF—, —C≡C—, or a single bond;

X¹represents a hydrogen atom, a fluorine atom, or a chlorine atom; and

m represents 1 to 4, in the case where m is 2 to 4 and plural A¹'s are present, the plural A¹'s may be the same as or different from each other, and in the case where m is 2 to 4 and plural Z¹'s are present, the plural Z¹'s may be the same as or different from each other.

embedded image

In the formula, R²¹represents an alkyl group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, and one —CH₂— or two or more —CH₂— non-adjacent to each other present in these groups may be substituted with —O—, —S—, —COO—, —OCO—, or —CO—, and at least one hydrogen atom present in these groups may be substituted with a fluorine atom;

A²¹is a group selected from the group consisting of (a) 1,4-cyclohexylene group in which one —CH₂— or two or more —CH₂— non-adjacent to each other present in this group may be substituted with —O— or —S—, (b) 1,4-phenylene group in which one —CH═ or two or more —CH═ non-adjacent to each other present in this group may be substituted with —N═ and at least one hydrogen atom present in this group may be substituted with a fluorine atom, and (c) naphthalene-2,6-diyl group in which one —CH═ or two or more —CH═ non-adjacent to each other present in this group may be substituted with —N═ and at least one hydrogen atom present in this group may be substituted with a fluorine atom; and

B²¹is a compound represented by either of the following structures.

embedded image

In the structures, X²¹, X²², X²³, X²⁴, and X²⁵each independently represents a hydrogen atom, a fluorine atom, or a chlorine atom and Y²¹and Y²²each independently represents a halogen atom, a cyano group, a halogenated alkyl group having 1 to 5 carbon atoms, or a halogenated alkoxy group having 1 to 5 carbon atoms;

Z²¹represents —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, —OCO—, —OCO—, —CH₂CH₂—, —CF₂CF₂—, —CH═CH—, —CF═CF—, —C≡C—, or a single bond; and

m²¹represents 1, 2, or 3, in the case where m²¹is 2 or 3 and plural A²¹'s are present, the plural A²¹'s may be the same as or different from each other, and in the case where m²¹is 2 or 3 and plural Z²¹'s are present, the plural Z²¹'s may be the same as or different from each other.

embedded image

In the formula, R¹¹and R¹²each independently represents an alkyl group having 1 to 15 carbon atoms, and one —CH₂— or two or more —CH₂— in the alkyl group may be substituted with —O—, —CH═CH—, —CO—, —OCO—, —COO—, —C≡C—, —CF₂O—, or —OCF₂— as long as an oxygen atom is not directly adjacent to another oxygen atom, and one or more hydrogen atoms in the alkyl group may be substituted with a halogen atom;

A¹¹to A¹³each independently is a group selected from the group consisting of (a) 1,4-cyclohexylene group in which one —CH₂— or two or more —CH₂— non-adjacent to each other present in this group may be substituted with —O— or —S—, (b) 1,4-phenylene group in which one —CH═ or two or more —CH═ non-adjacent to each other present in this group may be substituted with —N═ and at least one hydrogen atom present in this group may be substituted with a fluorine atom, and (c) naphthalene-2,6-diyl group in which one —CH═ or two or more —CH═ non-adjacent to each other present in this group may be substituted with —N═ and at least one hydrogen atom present in this group may be substituted with a fluorine atom;

Z¹¹and Z¹²each independently represents a single bond, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—; and

m¹¹represents 0, 1, or 2, in the case where m¹¹is 2 and plural A¹¹'s are present, the plural A¹¹'s may be the same as or different from each other, and in the case where m¹¹is 2 and plural Z¹¹'s are present, the plural Z¹¹'s may be the same as or different from each other, with the proviso that the compound represented by General Formula (1) is excluded.

Advantageous Effects of Invention

The liquid crystal composition of the present invention has high refractive index anisotropy (Δn), low viscosity (η), low rotational viscosity (γ₁), and excellent crystallinity, and exhibits a stable liquid crystal phase in a wide temperature range. In addition, since the liquid crystal composition of the present invention is chemically stable with respect to heat, light, and water, and has satisfactory solubility, the phase at low temperature is satisfactorily stable. By using the liquid crystal composition of the present invention in a liquid crystal display element, it is possible to obtain a liquid crystal display element having a high response speed and high practical reliability.

DESCRIPTION OF EMBODIMENTS

The liquid crystal composition of the present invention includes at least one compound represented by General Formula (1), at least one compound represented by General Formula (2), and at least one compound represented by General Formula (LC1).

General Formula (1):

embedded image

In order to decrease the viscosity, R⁰¹is preferably an alkyl group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms, and particularly preferably an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms. Also, R⁰¹is preferably linear. In the case where R¹is an alkenyl group, R¹is preferably selected from the group represented by any one of Formula (R1) to Formula (R5). (A black point in each formula represents a point linking to a ring.) In the case where A¹which is linked to R¹is a trans-1,4-cyclohexylene group, R⁰¹preferably represents an alkenyl group of the trans-1,4-cyclohexylene group, and further preferably represents Formula (R1), Formula (R2), or Formula (R4).

embedded image

In order to decrease the viscosity, R ⁰²is preferably an alkenyl group having 2 to 8 carbon atoms, more preferably an alkenyl group having 2 to 6 carbon atoms, preferably an alkenyl group having 2 to 5 carbon atoms, and it is preferred that the group represented by —O—R ⁰²is selected from the groups represented by Formula (R6).

embedded image

In the formula, R⁰⁴represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, one —CH₂— or two or more —CH₂— non-adjacent to each other present in these groups may be substituted with —O—, —COO—, —OCO—, or —CO—, at least one hydrogen atom present in these groups may be substituted with a fluorine atom, and a black point in each formula represents a point linking to a ring.

The following groups where R⁰⁴is a hydrogen atom or a methyl group are more preferable.

embedded image

In order to decrease the viscosity, A¹each is independently preferably represents a trans-1,4-cyclohexylene group, an unsubstituted naphthalene-2,6-diyl group, or an unsubstituted 1,4-phenylene group, and more preferably a trans-1,4-cyclohexylene group. In order to improve the miscibility with other liquid crystal components, the following groups:

embedded image

are preferable as A¹.

In addition, in order to increase the Δn, A¹each is independently preferably a 1,4-phenylene group or a naphthalene-2,6-diyl group. In all of the ring structures in the compound, it is preferred that the abundance ratio of the 1,4-phenylene group and naphthalene-2,6-diyl group is relatively high, and it is more preferred that the abundance ratio of the 1,4-phenylene group is relatively high. In the case of putting importance on Δn, the abundance ratio of the 1,4-phenylene group and naphthalene-2,6-diyl group is preferably increased to fall within the preferable range, but is adjusted depending on a balance of viscosity and miscibility with other liquid crystal components. Specifically, in the case where m represents 1, A¹is preferably a trans-1,4-cyclohexylene group, a 1,4-phenylene group, or a naphthalene-2,6-diyl group, and in order to further increase the ratio, A¹preferably represents a 1,4-phenylene group or a naphthalene-2,6-diyl group, and more preferably represents a 1,4-phenylene group. In the case where m represents 2, at least one of A¹'s is preferably a 1,4-phenylene group or a naphthalene-2,6-diyl group, and in order to further increase the ratio, A¹each is independently preferably a 1,4-phenylene group or a naphthalene-2,6-diyl group, and more preferably a 1,4-phenylene group. In the case where m represents 3 or 4, at least one of A¹'s is preferably a 1,4-phenylene group or a naphthalene-2,6-diyl group, and in order to further increase the ratio, at least two of A¹'s are preferably a 1,4-phenylene group or a naphthalene-2,6-diyl group and more preferably a 1,4-phenylene group.

In order to decrease the viscosity, Z¹is preferably —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, —CF═CF—, —C≡C—, or a single bond, more preferably —CF₂O—, —OCF₂—, —CH₂CH₂—, or a single bond, and particularly preferably a single bond, and in order to increase the T_→i, Z¹is preferably —C≡C— or a single bond.

In the case of putting importance on viscosity, X¹is preferably a hydrogen atom, and in the case of putting importance on miscibility with other liquid crystal components, X¹is preferably a fluorine atom.

In the case of putting importance on viscosity, m is preferably 1 or 2, and in the case of putting importance on the Tni, m is preferably 3 or 4. In order to increase the miscibility with the liquid crystal composition, m is preferably 2 or 3.

As a compound having high Δn and an excellent balance of viscosity and miscibility with other liquid crystal components, the compound represented by General Formula (1) is preferably a compound represented by General Formula (1-1).

embedded image

In the formula, R⁰¹, R⁰², A¹, Z¹, and X¹have the same meaning as R⁰¹, R⁰², A¹, Z¹, and X¹in General Formula (1), respectively;

Z²represents —CH₂O—, —OCH₂—, —CF₂O—, —OCF₂—, —COO—, —OCO—, —CH₂CH₂—, —CF₂CF₂—, —CH═CH—, —CF═CF—, —C≡C—, or a single bond;

X², X³, and X⁴each independently represents a hydrogen atom, a fluorine atom, or a chlorine atom; and

m¹represents 0, 1, 2, or 3, in the case where m¹is 2 or 3 and plural A¹'s are present, the plural A¹'s may be the same as or different from each other, and in the case where m¹is 2 or 3 and plural Z¹'s are present, the plural Z¹'s may be the same as or different from each other.

Furthermore, the compound represented by General Formula (1-1) is preferably a compound represented by General Formula (1-1A).

embedded image

In the formula, R⁰¹, A¹, Z¹, X¹, X², X³, X⁴, and m¹have the same meaning as R¹, A¹, Z¹, X¹, X², X³, X⁴, and m¹in General Formula (1-1), respectively; and

R⁰³represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, one —CH₂— or two or more —CH₂— in the alkyl group may be substituted with —O—, —S—, —COO—, —OCO—, or —CO— as long as an oxygen atom is not directly adjacent to another oxygen atom, and at least one hydrogen atom present in the alkyl group may be substituted with a fluorine atom.

R⁰³more preferably represents a hydrogen atom or a methyl group.

Furthermore, the compounds represented by General Formula (1) or General Formula (1-1) are preferably a compound satisfying at least one of the following matters.

- Compound in which m is 2 and plural Z¹'s are single bonds
- Compound in which m⁰¹is 1 and Z¹is a single bond
- Compound in which Z¹is a single bond
- Compound in which Z²is a single bond
- Compound in which A¹is a 1,4-phenylene group

The liquid crystal compound represented by General Formula (1) is preferably compounds represented by the following General Formula (1-1-1) to General Formula (1-1-49), which are the compound represented by General Formula (1-1) (in the formulas, R⁰¹, R⁰², and X¹have the same meaning as R⁰¹, R⁰², and X¹in General Formula (1), respectively). The liquid crystal composition of the present invention preferably contains one or more compounds represented by General Formula (1-1-1) to General Formula (1-1-49), more preferably contains one or more compounds represented by General Formula (1-1-1) to General Formula (1-1-6), General Formula (1-1-9) to General Formula (1-1-14), General Formula (1-1-17) to General Formula (1-1-21), and General Formula (1-1-26) to General Formula (1-1-49), still more preferably contains one or more compounds represented by General Formula (1-1-1) to General Formula (1-1-6), General Formula (1-1-9) to General Formula (1-1-14), and General Formula (1-1-17) to General Formula (1-1-21), and particularly preferably contains one or more compounds represented by General Formula (1-1-9) to General Formula (1-1-12).

embedded image

In addition, the liquid crystal compound represented by General Formula (1) is preferably compounds represented by the following General Formula (1-2-1) to General Formula (1-2-7) (In the formulas, R⁰¹, R⁰², and X¹represent the same meaning as R⁰¹, R⁰², and X¹in General Formula (1), respectively). The liquid crystal composition of the present invention preferably contains one or more compounds represented by General Formula (1-2-1) to General Formula (1-2-7).

embedded image

In the liquid crystal composition of the present invention, the compound represented by General Formula (1) is preferably contained in the amount of 0.1% by mass or more as a lower limit in the composition (the following % in the composition represents % by mass), preferably contained in the amount of 0.3% or more, preferably contained in the amount of 0.5% or more, preferably contained in the amount of 0.8% or more, preferably contained in the amount of 1% or more, preferably contained in the amount of 2% or more, preferably contained in the amount of 3% or more, preferably contained in the amount of 5% or more, preferably contained in the amount of 6% or more, preferably contained in the amount of 7% or more, preferably contained in the amount of 8% or more, preferably contained in the amount of 9% or more, preferably contained in the amount of 10% or more, preferably contained in the amount of 13% or more, preferably contained in the amount of 15% or more, preferably contained in the amount of 18% or more, and preferably contained in the amount of 20% or more. In addition, if the content is large, a problem such as precipitation occurs, and accordingly, as an upper limit, the compound represented by General Formula (1) is preferably contained in the amount of 80% or less, preferably contained in the amount of 70% or less, preferably contained in the amount of 60% or less, preferably contained in the amount of 55% or less, preferably contained in the amount of 50% or less, preferably contained in the amount of 45% or less, preferably contained in the amount of 40% or less, preferably contained in the amount of 38% or less, preferably contained in the amount of 35% or less, preferably contained in the amount of 33% or less, preferably contained in the amount of 32% or less, preferably contained in the amount of 30% or less, preferably contained in the amount of 28% or less, preferably contained in the amount of 25% or less, preferably contained in the amount of 23% or less, preferably contained in the amount of 21% or less, preferably contained in the amount of 20% or less, preferably contained in the amount of 18% or less, and preferably contained in the amount of 15% or less. One type of the compound represented by General Formula (1) may be used alone or two or more types of the compound may be used at the same time.

A liquid crystal compound having an allyl ether group at the terminal has satisfactory properties as a constituent component of the liquid crystal composition, but has a problem in reliability. However, by difluorinating a specific position of a benzene ring having an allyl ether group, the compound represented by General Formula (1) improves reliability, further improves compatibility, and decreases viscosity without impairing original excellent properties of the skeleton. Furthermore, by imparting positive dielectric anisotropy, the compound represented by General Formula (1) is an extremely effective compound as a constituent component of the liquid crystal composition having positive dielectric anisotropy.

Since the compound represented by General Formula (1) has a wide nematic temperature range, large refractive index anisotropy, high solubility, and low viscosity, if the compound represented by General Formula (1) is contained in the liquid crystal composition, the liquid crystal composition is obtained, which has high refractive index anisotropy (Δn) and sufficiently low viscosity (η), achieves a wide nematic phase temperature range by suppressing a decrease in a nematic phase-isotropic liquid phase transition temperature (T_ni), exhibits high compatibility, and has a high response speed and excellent reliability when the liquid crystal composition is used in a liquid crystal display element. Therefore, in particular, the liquid crystal composition can be appropriately used in a liquid crystal composition for a FFS mode liquid crystal display for mobile phones or cars. In addition, in the case where an alkyl group substituted with a fluorine atom for R²in General Formula (1) is selected, positive dielectric anisotropy can be imparted, and the compound represented by General Formula (1) can be extremely appropriately used as a component configuring the liquid crystal composition having positive dielectric anisotropy. For example, the compound represented by General Formula (1) exhibits a liquid crystal phase in the range of 40° C. to 110° C. alone, and has Δn of about 0.26, flow viscosity of about 25 mPa·s, which is low, and dielectric anisotropy of about +4, and further has extremely satisfactory compatibility in the case of being used as a component of the liquid crystal composition.

General Formula (2):

embedded image

R²¹is preferably an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, or an alkoxy group having 1 to 8 carbon atoms, and is preferably linear. In the case where R²¹is an alkenyl group, R²¹is preferably selected from the group represented by any one of Formula (R1) to Formula (R5).

embedded image

A black point in each formula represents a point linking to a ring.

A²¹is preferably a trans-1,4-cyclohexylene group, a 1,4-phenylene group, a 3-fluoro-1,4-phenylene group, a 3,5-difluoro-1,4-phenylene group, a tetrahydropyran group, or a 1,3-dioxane-2,5-diyl group.

In order to decrease the viscosity, B²¹is preferably the following.

embedded image

In order to increase the T_→i, the following group:

embedded image

is preferable as B²¹.

X²¹, X²², X²³, X²⁴, and X²⁵each independently is preferably a hydrogen atom in order to decrease the viscosity and increase the T_→i, and is preferably a fluorine atom in order to increase the Δε.

In the case where X²¹and X²²are each independently a fluorine atom or hydrogen atom, B²¹preferably represents the following group in order to increase the Δε.

embedded image

In order to decrease the viscosity, the following group:

embedded image

is preferable as B²¹.

In the case where X²³to X²⁵each independently represents a fluorine atom or a hydrogen atom, B²¹preferably represents any of the following groups in order to increase the Δε.

embedded image

In order to decrease the viscosity, the following group:

embedded image

is preferable as B²¹.

Y²¹and Y²²preferably represent a fluorine atom, —CF₃, or —OCF₃to thereby improve lower limit temperature of a nematic phase and better operation at low temperature or storage properties of the liquid crystal composition. In order to increase the Δε, Y²¹and Y²²preferably represent a fluorine atom, a cyano group, —CF₃, or —OCF₃, and in order to decrease the viscosity, Y²¹and Y²²preferably represent a fluorine atom. In consideration of stability of the compound, Y²¹and Y²²preferably represent a fluorine atom, —CF₃, or —OCF₃.

B²¹is particularly preferably one selected from the following moiety structures.

embedded image

Z²¹is preferably a single bond, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—, and more preferably a single bond, —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—.

m²¹preferably represents 2 or 3. In the case where plural A²¹'s and/or Z²¹'s are present, these may be the same as or different from each other.

The compound represented by General Formula (2) preferably contains one or more compounds represented by General Formula (LC2-a).

embedded image

In the formula, X²⁶and X²⁷each independently represents a hydrogen atom or a fluorine atom, Z²³represents —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—, and R²¹, A²¹, Z²¹, X²¹, X²², Y²¹, and m²¹have the same meaning as R²¹, A²¹, Z²¹, X²¹, X²², Y²¹, and m²¹in General Formula (2), respectively.

X²⁶and X²⁷are preferably a fluorine atom, either X²⁶or X²⁷is preferably a fluorine atom, and both of X²⁶and X²⁷are preferably fluorine atoms.

The compound represented by General Formula (LC2-a) preferably contains at least one of the compounds represented by General Formula (LC2-a1) to General Formula (LC2-a12).

embedded image

In the formulas, R²¹, X²¹, X²², X²⁶, X²⁷, and Y²¹represent the same meaning as R²¹, X²¹, X²², X²⁶, X²⁷, and Y²¹in General Formula (2), respectively, and X³⁰, X³¹, X³², and X³³each independently represents a hydrogen atom or a fluorine atom.

The compound represented by General Formula (LC2-a) more preferably contains at least one of the compounds represented by (LC2-a4) to (LC2-a6), (LC2-a10), and (LC2-a11).

Furthermore, the compound represented by General Formula (2) preferably contains one or more compounds represented by General Formula (LC2-b).

embedded image

In the formula, A²²is a group selected from the group consisting of (a) 1,4-cyclohexylene group in which one —CH₂— or two or more —CH₂— non-adjacent to each other present in this group may be substituted with —O— or —S—, (b) 1,4-phenylene group in which one —CH═ or two or more —CH═ non-adjacent to each other present in this group may be substituted with —N═ and at least one hydrogen atom present in this group may be substituted with a fluorine atom, and (c) naphthalene-2,6-diyl group in which one —CH═ or two or more —CH═ non-adjacent to each other present in this group may be substituted with —N═ and at least one hydrogen atom present in this group may be substituted with a fluorine atom; m²³represents 1 or 2; and R²¹, A²¹, X²¹, X²², and Y²¹have the same meaning as R²¹, A²¹, X²¹, X²², and Y²¹in General Formula (2), respectively.

The compound represented by General Formula (LC2-b) preferably contains one or more compounds represented by General Formula (LC2-b1) to General Formula (LC2-b21).

embedded image

In the formulas, X³⁴, X³⁵, X³⁶, X³⁷, X³⁸, X³⁹, X⁵⁰, and X⁵¹each independently represents a hydrogen atom or a fluorine atom, and R²¹, X²¹, X²², and Y²¹have the same meaning as R²¹, X²¹, X²², and Y²¹in General Formula (LC2-b), respectively.

The compound represented by General Formula (LC2-b) more preferably contains one or more compounds represented by General Formula (LC2-b5) to General Formula (LC2-b8), General Formula (LC2-b10) to General Formula (LC2-b12), and General Formula (LC2-b18).

In addition, the compound represented by General Formula (LC2) preferably contains the following compounds other than the compounds of General Formula (LC2-a) and General Formula (LC2-b) and more preferably contains General Formula (LC2-16) and General Formula (LC2-17).

embedded image

In the formulas, X⁴⁰, X⁴¹, X⁴², X⁴³, X⁴⁴, X⁴⁵, X⁴⁶, X⁴⁷, X⁴⁸, X⁴⁹, and X⁵⁰each independently represents a hydrogen atom or a fluorine atom, and R²¹, X²¹, X²², X²³, X²⁴, X²⁵, Y²¹, and Y²²have the same meaning as R²¹, X²¹, X²², X²³, X²⁴, X²⁵, Y²¹, and Y²²in General Formula (2), respectively.

In the liquid crystal composition of the present invention, the compound represented by General Formula (2) is preferably contained, as a lower limit, in the amount of 0.5% or more, preferably contained in the amount of 1% or more, preferably contained in the amount of 2% or more, preferably contained in the amount of 4% or more, preferably contained in the amount of 5% or more, preferably contained in the amount of 8% or more, preferably contained in the amount of 10% or more, and preferably contained in the amount of 15% or more. In addition, the compound represented by General Formula (2) is preferably contained, as an upper limit, in the amount of 80% or less, preferably contained in the amount of 70% or less, preferably contained in the amount of 65% or less, preferably contained in the amount of 60% or less, preferably contained in the amount of 55% or less, preferably contained in the amount of 50% or less, preferably contained in the amount of 45% or less, preferably contained in the amount of 40% or less, preferably contained in the amount of 37% or less, preferably contained in the amount of 35% or less, preferably contained in the amount of 34% or less, preferably contained in the amount of 30% or less, preferably contained in the amount of 28% or less, preferably contained in the amount of 25% or less, and preferably contained in the amount of 20% or less. One type of the compound represented by General Formula (1) may be used alone or two or more types of the compound may be used at the same time.

In General Formula (LC1),

embedded image

R¹¹and R¹²each independently is preferably an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyloxy group having 2 to 8 carbon atoms, and preferably linear. In the case where R¹¹and R¹²represent an alkenyl group, R¹¹and R¹²are preferably selected from the group represented by any one of Formula (R1) to Formula (R5).

embedded image

A black point in each formula represents a point linking to a ring.

A combination of R¹¹and R¹²is not particularly limited, and a combination in which both represent an alkyl group, a combination in which one of the above represents an alkyl group and the other represents an alkenyl group, or a combination in which one of the above represents an alkyl group and the other represents an alkoxy group is preferable.

A¹¹to A¹³each independently is preferably any one of the following structures.

embedded image

A¹¹to A¹³each independently is more preferably any one of the following structures.

embedded image

Z¹¹and Z¹²each independently is preferably a single bond, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—, more preferably a single bond, —CH₂CH₂—, —OCF₂—, or —CF₂O—, and particularly preferably a single bond.

m¹¹preferably represents an integer of 1 or 2. In the case where plural A¹¹'s and/or Z¹¹'s are present, these may be the same as or different from each other.

The compound represented by General Formula (LC1) is more preferably compounds represented by the following General Formula (LC1-1) to General Formula (LC1-39). The liquid crystal composition of the present invention preferably contains one or more compounds represented by (LC1-1) to (LC1-26) as the compound represented by General Formula (LC1), and more preferably contains one or more compounds represented by (LC1-1) to (LC1-5), (LC1-7), (LC1-15), (LC1-16), (LC1-18), and (LC1-38).

embedded image

In the formulas, R¹¹and R¹²have the same meaning as R¹¹and R¹²in General Formula (LC1), respectively.

The compound represented by General Formula (LC1) is preferably the compounds represented by the above.

Furthermore, the liquid crystal composition still more preferably contains one or more compounds selected from the group consisting of the following compounds in the amount of 70% by mass at most, as the compound represented by General Formula (LC1).

embedded image

In the formulas, alkyl and alkyl* each independently represents an alkyl group having 1 to 5 carbon atoms or an alkoxy group, and alkenyl and alkenyl* each independently represents an alkenyl group having 2 to 5 carbon atoms or an alkenyloxy group.

In the liquid crystal composition of the present invention, the compound represented by General Formula (LC1) is preferably contained, as a lower limit, in the amount of 1% or more, preferably contained in the amount of 5% or more, preferably contained in the amount of 10% or more, preferably contained in the amount of 13% or more, preferably contained in the amount of 15% or more, preferably contained in the amount of 18% or more, preferably contained in the amount of 20% or more, preferably contained in the amount of 25% or more, preferably contained in the amount of 28% or more, preferably contained in the amount of 30% or more, preferably contained in the amount of 33% or more, preferably contained in the amount of 35% or more, preferably contained in the amount of 38% or more, preferably contained in the amount of 40% or more, preferably contained in the amount of 43% or more, preferably contained in the amount of 45% or more, preferably contained in the amount of 48% or more, preferably contained in the amount of 50% or more, preferably contained in the amount of 53% or more, preferably contained in the amount of 55% or more, preferably contained in the amount of 58% or more, and preferably contained in the amount of 60% or more. In addition, the compound represented by General Formula (LC1) is preferably contained, as an upper limit, in the amount of 99% or less, preferably contained in the amount of 98% or less, preferably contained in the amount of 95% or less, preferably contained in the amount of 93% or less, preferably contained in the amount of 90% or less, preferably contained in the amount of 87% or less, preferably contained in the amount of 85% or less, preferably contained in the amount of 83% or less, preferably contained in the amount of 80% or less, preferably contained in the amount of 88% or less, preferably contained in the amount of 85% or less, preferably contained in the amount of 83% or less, preferably contained in the amount of 80% or less, preferably contained in the amount of 78% or less, preferably contained in the amount of 75% or less, preferably contained in the amount of 73% or less, preferably contained in the amount of 70% or less, preferably contained in the amount of 68% or less, preferably contained in the amount of 65% or less, preferably contained in the amount of 63% or less, and preferably contained in the amount of 60% or less. One type of the compound represented by General Formula (1) may be used alone or two or more types of the compound may be used at the same time.

In the liquid crystal composition of the present invention, the compounds represented by General Formula (1) and General Formula (2) are preferably contained, as a lower limit, in the amount of 1% or more, preferably contained in the amount of 5% or more, preferably contained in the amount of 10% or more, preferably contained in the amount of 13% or more, preferably contained in the amount of 15% or more, preferably contained in the amount of 18% or more, preferably contained in the amount of 20% or more, preferably contained in the amount of 23% or more, preferably contained in the amount of 25% or more, preferably contained in the amount of 30% or more, preferably contained in the amount of 35% or more, preferably contained in the amount of 38% or more, and preferably contained in the amount of 40% or more. In addition, the compounds represented by General Formula (1) and General Formula (2) are preferably contained, as an upper limit, in the amount of 90% or less, preferably contained in the amount of 80% or less, preferably contained in the amount of 75% or less, preferably contained in the amount of 70% or less, preferably contained in the amount of 65% or less, preferably contained in the amount of 60% or less, preferably contained in the amount of 58% or less, preferably contained in the amount of 55% or less, preferably contained in the amount of 53% or less, preferably contained in the amount of 50% or less, preferably contained in the amount of 48% or less, preferably contained in the amount of 46% or less, preferably contained in the amount of 45% or less, preferably contained in the amount of 43% or less, preferably contained in the amount of 40% or less, preferably contained in the amount of 38% or less, preferably contained in the amount of 78% or less, preferably contained in the amount of 75% or less, preferably contained in the amount of 35% or less, preferably contained in the amount of 33% or less, and preferably contained in the amount of 30% or less.

In the liquid crystal composition of the present invention, the compounds represented by General Formula (1) and General Formula (LC1) are preferably contained, as a lower limit, in the amount of 1% or more, preferably contained in the amount of 5% or more, preferably contained in the amount of 10% or more, preferably contained in the amount of 15% or more, preferably contained in the amount of 20% or more, preferably contained in the amount of 25% or more, preferably contained in the amount of 30% or more, preferably contained in the amount of 35% or more, preferably contained in the amount of 38% or more, preferably contained in the amount of 40% or more, preferably contained in the amount of 43% or more, preferably contained in the amount of 45% or more, preferably contained in the amount of 48% or more, preferably contained in the amount of 50% or more, preferably contained in the amount of 53% or more, preferably contained in the amount of 55% or more, preferably contained in the amount of 58% or more, preferably contained in the amount of 60% or more, preferably contained in the amount of 63% or more, preferably contained in the amount of 65% or more, preferably contained in the amount of 68% or more, and preferably contained in the amount of 70% or more. In addition, the compounds represented by General Formula (1) and General Formula (LC1) are preferably contained, as an upper limit, in the amount of 99% or less, preferably contained in the amount of 98% or less, preferably contained in the amount of 96% or less, preferably contained in the amount of 95% or less, preferably contained in the amount of 93% or less, preferably contained in the amount of 90% or less, preferably contained in the amount of 87% or less, preferably contained in the amount of 85% or less, preferably contained in the amount of 83% or less, preferably contained in the amount of 80% or less, preferably contained in the amount of 88% or less, preferably contained in the amount of 85% or less, preferably contained in the amount of 83% or less, preferably contained in the amount of 80% or less, preferably contained in the amount of 78% or less, preferably contained in the amount of 75% or less, preferably contained in the amount of 73% or less, preferably contained in the amount of 70% or less, preferably contained in the amount of 68% or less, preferably contained in the amount of 65% or less, preferably contained in the amount of 63% or less, and preferably contained in the amount of 60% or less.

The liquid crystal composition of the present invention can contain one or more optically active compounds. Any optically active compound can be used as long as the compound can twist and align liquid crystal molecules. Normally, this twist is changed by the temperature and accordingly, a plurality of optically active compounds can be used in order to obtain a desired temperature dependency. In order not to have a bad influence on the temperature range or viscosity of the nematic liquid crystal phase, it is preferable to select and use the optically active compound having a strong twisting effect. As this optically active compound, liquid crystals such as cholesteric nonanoate or compounds represented by the following General Formula (Ch-1) to General Formula (Ch-6) are preferably contained.

embedded image

In the formulas, R_c1, R_c2, and R* each independently represents an alkyl group having 1 to 15 carbon atoms, one —CH₂— or two or more —CH₂— in the alkyl group may be substituted with —O—, —CH═CH—, —CO—, —OCO—, —COO—, —C≡C—, —CF₂O—, or —OCF₂— as long as an oxygen atom is not directly adjacent to another oxygen atom; one or more hydrogen atoms in the alkyl group may be arbitrarily substituted with a halogen atom; however, R* has at least one of a branched chain group having optical activity and a halogen-substituted group; Z_c1and Z_c2each independently represents a single bond, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —COO—, —OCO—, —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—; D₁and D₂represent a cyclohexane ring or a benzene ring; one —CH₂— or two or more —CH₂— in the cyclohexane ring may be substituted with —O— as long as an oxygen atom is not directly adjacent to another oxygen atom; one —CH₂CH₂— or two or more —CH₂CH₂— in the ring may be substituted with —CH═CH—, —CF₂O—, or —OCF₂—; one —CH═ or two or more —CH═ in the benzene ring may be substituted with —N═ as long as a nitrogen atom is not directly adjacent to another nitrogen atom; one or more hydrogen atoms in the ring may be substituted with F, Cl, or CH₃; t₁and t₂represent 0, 1, 2, or 3; and MG*, Q_c1, and Q_c2represent the following structures.

embedded image

In the formula, D₃and D₄represent a cyclohexane ring or a benzene ring, one —CH₂— or two or more —CH₂— in the cyclohexane ring may be substituted with —O— as long as an oxygen atom is not directly adjacent to another oxygen atom; one —CH₂CH₂— or two or more —CH₂CH₂— in the ring may be substituted with —CH═CH—, —CF₂O—, or —OCF₂—; one —CH═ or two or more —CH═ in the benzene ring may be substituted with —N═ as long as a nitrogen atom is not directly adjacent to another nitrogen atom; and one or more hydrogen atoms in the ring may be substituted with F, Cl, or CH₃.

The liquid crystal composition of the present invention may contain one or more polymerizable compounds, and the polymerizable compound is preferably a disk-shape liquid crystal compound having a structure in which a benzene derivative, a triphenylene derivative, a truxene derivative, a phthalocyanine derivative, or a cyclohexane derivative is used as a mother nucleus in the center of molecules and a linear alkyl group, a linear alkoxy group, or a substituted benzoyloxy group is radially substituted as a side chain thereof.

Specifically, the polymerizable compound is preferably a polymerizable compound represented by General Formula (PC).

embedded image

In the formula, P₁represents a polymerizable functional group; Sp₁represents a spacer group having 0 to 20 carbon atoms; Q_p1represents 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 p₂each independently represents 1, 2, or 3; MG_prepresents a mesogenic group or a mesogenity supporting group; R_p1represents a halogen atom, a cyano group, or an alkyl group having 1 to 25 carbon atoms; one CH₂group or two or more CH₂groups in the alkyl group may be substituted with —O—, —S—, —NH—, —N(CH₃)—, —CO—, —COO—, —OCO—, —OCOO—, —SCO—, —COS—, or —C≡C— as long as an O atom is not directly adjacent to another O atom; or R_p1may be P₂-Sp₂-Q_p2-; and P₂, Sp₂, and Q_p2have the same meaning as P₁, Sp₁, and Q_p1, respectively.

MG_pof the polymerizable compound represented by General Formula (PC) is more preferably a polymerizable compound represented by the following structure.

embedded image

In the formula, C₀₁to C₀₃each independently represents a 1,4-phenylene group, a 1,4-cyclohexylene group, a 1,4-cyclohexenyl group, a tetrahydropyran-2,5-diyl group, a 1,3-dioxane-2,5-diyl group, a tetrahydrothiopyran-2,5-diyl group, a 1,4-bicyclo(2,2,2)octylene group, a decahydro naphthalene-2,6-diyl group, a pyridine-2,5-diyl group, a pyrimidine-2,5-diyl group, a pyrazine-2,5-diyl group, a 1,2,3,4-tetrahydro naphthalene-2,6-diyl group, a 2,6-naphthylene group, a phenanthrene-2,7-diyl group, a 9,10-dihydrophenanthrene-2,7-diyl group, a 1,2,3,4,4a,9,10a-octahydrophenanthrene 2,7-diyl group, or a fluorene 2,7-diyl group; the 1,4-phenylene group, the 1,2,3,4-tetrahydro naphthalene-2,6-diyl group, the 2,6-naphthylene group, the phenanthrene-2,7-diyl group, the 9,10-dihydrophenanthrene-2,7-diyl group, the 1,2,3,4,4a,9,10a-octahydrophenanthrene 2,7-diyl group, and the fluorene-2,7-diyl group may have, as a substituent, one or more F, Cl, CF₃, OCF₃, cyano groups, alkyl groups having 1 to 8 carbon atoms, alkoxy groups, alkanoyl groups, alkanoyloxy groups, alkenyl groups having 2 to 8 carbon atoms, alkenyloxy groups, alkenoyl groups, or alkenoyloxy groups; Z_p1and Z_p2each independently represents —COO—, —OCO—, —CH₂CH₂—, —OCH₂—, —CH₂O—, —CH═CH—, —C≡C—, —CH═CHCOO—, —OCOCH═CH—, —CH₂CH₂COO—, —CH₂CH₂OCO—, —COOCH₂CH₂—, —OCOCH₂CH₂—, —CONH—, —NHCO—, or a single bond; and p₃represents 0, 1, or 2.

Here, Sp₁and Sp₂each independently represents an alkylene group, the alkylene group may be substituted with one or more halogen atoms or CN, and one CH₂group or two or more CH₂groups present in this group may be substituted with —O—, —S—, —NH—, —N(CH₃)—, —CO—, —COO—, —OCO—, —OCOO—, —SCO—, —COS—, or —C≡C— as long as an O atom is not directly adjacent to another O atom. Also, P₁and P₂each is independently preferably any one of the following general formulas.

embedded image

In the formulas, R_p2to R_p6each independently represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 5 carbon atoms.

More specifically, the polymerizable compound represented by General Formula (PC) is preferably polymerizable compounds represented by General Formula (PC0-1) to General Formula (PC0-6).

embedded image

In the formulas, p₄each independently represents 1, 2, or 3.

More specifically, the polymerizable compound represented by General Formula (PC) is preferably polymerizable compounds represented by General Formula (PC1-1) to General Formula (PC1-9).

embedded image

In the formulas, p₅represents 0, 1, 2, 3, or 4.

Among the above, Sp₁, Sp₂, Q_p1, and Q_p2are preferably a single bond, P₁and P₂are preferably Formula (PC0-a), more preferably an acryloyloxy group and a methacryloyloxy group, p₁+p₄is preferably 2, 3, or 4, and R_p1is preferably H, F, CF₃, OCF₃, CH₃, or OCH₃. Furthermore, the polymerizable compound represented by General Formula (PC) is preferably compounds represented by General Formula (PC1-2), General Formula (PC1-3), General Formula (PC1-4), and General Formula (PC1-8).

In addition, MG_pin General Formula (PC) is preferably a disk-shape liquid crystal compound represented by General Formula (PC1)-9.

embedded image

In the formulas, R₇each independently represents P₁-Sp₁-Q_p1or a substituent of General Formula (PC1-e); R₈₁and R₈₂each independently represents a hydrogen atom, a halogen atom, or a methyl group; R₈₃represents an alkoxy group having 1 to 20 carbon atoms; and at least one hydrogen atom in the alkoxy group may be substituted with substituents represented by General Formula (PC0-a) to (PC0-d).

The use amount of the polymerizable compound is preferably 0.05% to 2.0% by mass.

In the liquid crystal composition containing the polymerizable compound of the present invention, a liquid crystal display element is prepared by polymerizing the polymerizable compound. At this time, it is required to reduce an unpolymerized component to a desired amount or less, and a compound having a biphenyl group and/or a terphenyl group in the moiety structure of General Formula (LC0) is preferably contained in the liquid crystal composition. More specifically, compounds represented by General Formula (LC0-10) to General Formula (LC0-27), General Formula (LC0-48) to General Formula (LC0-53) and General Formula (LC0-60) to General Formula (LC0-68) are preferable, and one or more compounds are selected and preferably contained in the amount of 0.1% to 40% by mass. In addition, a compound in the group consisting of the polymerizable compounds represented by General Formula (PC1-1) to General Formula (PC1-3), General Formula (PC1-8) and General Formula (PC1-9) is preferably used in combination.

Furthermore, the liquid crystal composition can contain one or more antioxidants, and further contain one or more UV absorbing agents. The antioxidant is preferably selected from the compounds represented by following General Formula (E-1) and/or General Formula (E-2).

embedded image

In the formulas, R_e1represents an alkyl group having 1 to 15 carbon atoms, one —CH₂— or two or more —CH₂— in the alkyl group may be substituted with —O—, —CH═CH—, —CO—, —OCO—, —COO—, —C≡C—, —CF₂O—, or —OCF₂— as long as an oxygen atom is not directly adjacent to another oxygen atom, and one or more hydrogen atoms in the alkyl group may be arbitrarily substituted with a halogen atom;

Z_e1and Z_e2each independently represents a single bond, —CH═CH—, —C≡C—, —CH₂CH₂—, —(CH₂)₄—, —COO—, —OCO—, —OCH₂—, —CH₂O—, —OCF₂—, or —CF₂O—; and

E₁represents a cyclohexane ring or a benzene ring, one —CH₂— or two or more —CH₂— in the cyclohexane ring may be substituted with —O— as long as an oxygen atom is not directly adjacent to another oxygen atom, one —CH₂CH₂— or two or more —CH₂CH₂— in the ring may be substituted with —CH═CH—, —CF₂O—, or —OCF₂—, one —CH═ or two or more —CH═ in the benzene ring may be substituted with —N═ as long as a nitrogen atom is not directly adjacent to another nitrogen atom, one or more hydrogen atoms in the ring may be substituted with F, Cl, or CH₃, and q₁represents 0, 1, 2, or 3.

The liquid crystal composition of the present invention can be used as a liquid crystal display element, in particular, a liquid crystal display element for active matrix driving, for example, for a TN mode, an OCB mode, an ECB mode, an IPS (including FFS electrode) mode, or a VA-IPS mode (including FFS electrode). Here, the VA-IPS mode is a method in which in the absence of applied voltage, a liquid crystal material having positive dielectric anisotropy (Δε>0) is vertically aligned on a substrate surface to drive liquid crystal molecules by pixel electrodes and common electrodes disposed on the same substrate surface, and the method has an advantage in that since the liquid crystal molecules are arrayed in a direction of a curved electric field generated by the pixel electrodes and common electrodes, division of the pixels or formation of a multi-domain is easy and a response is excellent. According to non-patent documents 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), the method is referred to as various names such as EOC, VA-IPS, or the like, but in the present invention, hereinafter the method is referred to as “VA-IPS”.

In general, a threshold voltage (Vc) of freedericksz transition in the TN and ECB modes is represented by the following equation.

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

In the IPS mode, the threshold voltage is represented by the following equation.

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

In the VA mode, the threshold voltage is represented by the following equation.

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

In the equations, Vc represents freedericksz transition (V), π represents a ratio of the circumference of a circle to its diameter, d_cellrepresents a gap between a first substrate and a second substrate (μm), d_gaprepresents a gap between the pixel electrodes and common electrodes (μm), d_ITOrepresents a width of the pixel electrodes and/or common electrodes (μm), <r1>, <r2>, and <r3> represent an extrapolation length (μm), K11 represents an elastic constant (N) of a spray, K22 represents an elastic constant (N) of a twist, K33 represents an elastic constant (N) of a bend, and Δε represents dielectric anisotropy.

Meanwhile, in the VA-IPS mode, the following equation 4 is applied with respect to the present invention and the like.

$\begin{matrix} Vc \propto \frac{d_{gap} - 〈 r 〉}{d_{ITO} + 〈 r 〉} \frac{π d_{dell}}{d_{cell} - 〈 r 3 〉} \sqrt{\frac{K 33}{\langle Δɛ \rangle}} & [Equation 4] \end{matrix}$

In the equation, Vc represents freedericksz transition (V), π represents a ratio of the circumference of a circle to its diameter, d_cellrepresents a gap between a first substrate and second substrate (μm), d_gaprepresents a gap between the pixel electrodes and common electrodes (μm), d_ITOrepresents a width of the pixel electrodes and/or common electrodes (μm), <r>, <r′>, and <r3> represent an extrapolation length (μm), K33 represents an elastic constant (N) of a bend, and Δε represents dielectric anisotropy.

As a cell configuration from the equation 4, as d_gapis smaller and d_ITOis greater, a low driving voltage is achieved, and as a liquid crystal composition to be used, by selecting the liquid crystal composition having a greater absolute value of Δε and smaller K33, a low driving voltage is achieved.

The liquid crystal display element which is prepared by using the liquid crystal composition of the present invention can be prepared by performing a rubbing treatment while using a polyimide, a polyamide compound or the like, as a method for aligning liquid crystal molecules on a substrate surface. In addition, the liquid crystal display element can be prepared by a photo alignment technology using a chalcone, cinnamate, cinnamoyl compound or the like. Also, as a new alignment method, a method for causing a polymerizable liquid crystal compound to be incorporated into an alignment layer and polymerizing the polymerizable liquid crystal compound can be applied.

The liquid crystal composition of the present invention can be adjusted to exhibit preferable values of Δε, K11, and K33.

The product (Δn·d) of the refractive index anisotropy (Δn) of the liquid crystal composition and the gap (d) between the first substrate and the second substrate of a display device is strongly related to viewing angle characteristics and response speed. Accordingly, the gap (d) tends to be as small as 3 to 4 μm. The product (Δn·d) is particularly preferably 0.31 to 0.33 for the TN, ECB, and IPS (liquid crystal aligns substantially horizontal to the substrate surface in the absence of applied voltage) modes. For the VA-IPS mode, the product is preferably 0.20 to 0.59 and more preferably 0.30 to 0.40 in the case where the alignment is vertical with respect to the both substrates. Since the suitable value of the product (Δn·d) differs depending on the mode of various display elements, a liquid crystal composition which is applied to various modes has the refractive index anisotropy (Δn) in the range of 0.070 to 0.110, in the range of 0.100 to 0.140, or in the range of 0.130 to 0.180. It is possible to prepare liquid crystal compositions each having a refractive index anisotropy (Δn) falling within any of the different ranges.

The liquid crystal composition of the present invention containing the compound represented by General Formula (PC) as a polymerizable compound can provide a polymer-stabilized liquid crystal display element for a TN mode, an OCB mode, an ECB mode, an IPS mode, or a VA-IPS mode, which is prepared by polymerizing the polymerizable compound contained in the liquid crystal composition in the absence or presence of applied voltage. Specifically, the liquid crystal composition containing the polymerizable compound is interposed between two substrates, and the polymerizable compound in the liquid crystal composition is polymerized by energy such as ultraviolet rays in the absence or presence of applied voltage to prepare the liquid crystal display element. In the liquid crystal display element, an alignment state of liquid crystal molecules can be stored by polymerization of the polymerizable compound and accordingly stability of the alignment state can be improved. Also, it is expected that the response speed is improved.

EXAMPLES

Hereinafter, the present invention will be described in detail using Examples, but the present invention is not limited thereto. Also, hereinafter, “%” in the composition of Examples and Comparative Examples means “% by mass”.

The physical properties of the liquid crystal composition are presented as follows:

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

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

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

Δε: Dielectric anisotropy at 25° C.

no: Refractive index for ordinary rays at 25° C.

Δn: Refractive index anisotropy at 25° C.

Vth: Voltage (V) applied to a 6 μm-thick cell at which the transmittance changes by 10% when square waves are applied at a frequency of 1 KHz at 25° C.

η: Bulk viscosity (mPa·s) at 20° C.

γ1: Rotational viscosity (mPa·s)

K11/pN: Elastic constant (N) of a spray

K22/pN: Elastic constant (N) of a twist

K33/pN: Elastic constant (N) of a bend

Compounds are abbreviated as follows.

TABLE 1

n
C_nH_2n+1—
-2-
—CH₂CH₂—
—F
—F

m
—C_mH_2m+1
-d-
—CH═CH—
—Cl
—C1

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

embedded image

In addition, the results of the properties when the liquid crystal composition is stored at −20° C., −25° C., −30° C., and −40° C. are shown in the following tables. The numbers in the tables represent a storage time, “O” means that a state of liquid crystals before storage is maintained after the storage time, and “X” means that precipitation is recognized after the storage time.

Examples 1 to 6