JP2016222662A - Liquid crystal compound, liquid crystal composition and liquid crystal display device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal composition exhibiting high dielectric anisotropy and low temperature stability at the same time, and to provide a liquid crystal compound and a liquid crystal display device.SOLUTION: There is provided the liquid crystal compound represented by the formula 1, where Ris H or a C1 to 15 alkyl group substituted by 1 to 3 halogen or is an alkyl group in which one or more -CH- is replaced by -C≡C-, -CFO-, -CH=CH-, -O-, -CO-O-, -O-CO- or -O-CO-O- so that O does not directly bind, Xis F, Cl, CN, NCS, C1 to 5 fluoroalkyl containing 1 to 3 F or a C1 to 5 fluoroalkyl group of which one or more -CH- is replaced with O, Yis H or F, Aand Aare any mono- to di-cyclic aromatic ring, alicyclic ring or a heterocyclic ring, Zis a single bond or any bivalent group and n is 0 or 1.SELECTED DRAWING: None

Description

  The present invention relates to a liquid crystal compound capable of providing a liquid crystal composition exhibiting high dielectric anisotropy and low temperature stability at the same time, a liquid crystal composition containing the same, and a liquid crystal display device.

  Liquid crystal display devices (LCDs) are used in various types of electrical equipment such as watches and electronic computers, measuring equipment, automobile panels, word processors, electronic notebooks, printers, computers, televisions, and the like. Typical examples of the liquid crystal display method include TN (Twist nematic), STN (Super-twisted nematic), IPS (In-plane switching), FFS (Fringe field switching), and VA (Virtual alignment).

A single liquid crystal compound used in such a liquid crystal display device has a molecular weight of about 200 to 600 g / mol and a rod-like molecular structure. In general, the molecular structure of the liquid crystal compound is divided into a core group that maintains straightness, a terminal group that has flexibility, and a linking group for a specific application. In this, the physical property of a liquid crystal compound and a composition containing this can be adjusted by adjusting the kind of substituent introduced into the terminal group. Specifically, a flexible group is introduced at one or both ends, such as an alkyl, alkoxy, or alkenyl group, to ensure flexibility, or a polar group at either one end. (F, CN, OCF ₃ etc.) can be introduced to adjust physical properties such as dielectric constant.

The liquid crystal compound used in the above-described liquid crystal display device is required to be capable of low-voltage driving and high-speed response and to be operable in a wide temperature range. Specifically, in order to stably drive in a wide temperature range, the liquid crystal material is required to exhibit stable physical properties at about −20 ° C. or less (low temperature stability) and to have a high clearing point. For low voltage driving and high speed response, the liquid crystal material has a large absolute value of dielectric anisotropy, a small rotational viscosity, and an appropriate elastic coefficient (K ₁₁ , K ₂₂ , K ₃₃ average value). Is required.

  The required physical properties of such a liquid crystal material cannot be satisfied by using one or two kinds of liquid crystal compounds, and usually 7 to 20 kinds of liquid crystal compounds are blended and satisfied.

  However, a composition in which various kinds of single liquid crystal compounds are mixed as described above is a compound having a higher melting point among the single liquid crystal compounds included in the composition when placed in a low temperature environment. It has the problem of losing its original function while being recrystallized.

Therefore, in order to avoid such recrystallization, a method for introducing a substituent having a long chain or appropriately blending a substance having a long chain was introduced. However, in the case of a single liquid crystal compound with a high refractive index anisotropy or dielectric anisotropy, a long chain shows that the elastic modulus and the rotational viscosity are poor, which increases the response time of the liquid crystal display device. showed that. Specifically, the liquid crystal compound represented by the following chemical formula Q-1 has a high melting point of 86 ° C., but the liquid crystal compound of the following chemical formula Q-2 in which a long alkyl chain is introduced by the liquid crystal compound of Q-1 is 64 ° C. Has a low melting point.

  However, the liquid crystal compound of the chemical formula Q-1 has a rotational viscosity of 387 mPa · s, whereas the liquid crystal compound of the chemical formula Q-2 has a rotational viscosity of 411 mPa · s. Accordingly, when the liquid crystal compound of the chemical formula Q-2 is used, there is a problem that the response speed is increased in the LCD panel.

  Therefore, it is the actual situation that technological development for improving the low temperature stability of the liquid crystal composition requiring high dielectric anisotropy is urgent.

  The present invention provides a liquid crystal compound capable of providing a liquid crystal composition exhibiting high dielectric anisotropy and low temperature stability at the same time.

  The present invention also provides a liquid crystal composition containing the liquid crystal compound and a liquid crystal display device.

  Hereinafter, a liquid crystal compound according to a specific embodiment of the invention, a liquid crystal composition including the same, a liquid crystal display device, and the like will be described.

According to one embodiment of the present invention, a liquid crystal compound represented by the following chemical formula 1 is provided.

In the above chemical formula 1,
R ¹ is a radical of any one of hydrogen and alkyl having 1 to 15 carbons, or 1 to 3 of the radicals are substituted with halogen, or one or more — —C≡C—, —CF ₂ O—, —CH═CH—, —O—, —CO—O—, —O—CO— or —O—CO so that CH ₂ — is not directly linked to an oxygen atom. A radical substituted with -O-
X ¹ is a radical of any one of F, Cl, CN, NCS and 1 to 5 fluoroalkyl containing 1 to 3 F, or one or more of the above radicals Each of —CH ₂ — is a radical substituted with an oxygen atom,
Y ¹ is H or F;
Rings A ¹ and A ² are each independently any one of the rings having the following structure:

Z ¹ is a single _{bond, -CH 2 CH 2 -, -} CH = CH -, - CH 2 O -, - OCH 2 -, - C≡C -, - CH 2 CF 2 -, - CHFCHF -, - CF ₂ CH ₂ —, —CH ₂ CHF—, —CHFCH ₂ —, —C ₂ F ₄ —, —COO—, —OCO—, —CF ₂ O— or —OCF ₂ —,
n is 0 or 1.

  When a phenyl group substituted with a methyl group is introduced into the liquid crystal compound as shown in Chemical Formula 1, the angle between the rings increases and the intermolecular aggregation density (packing density) increases. It has been found that it has the effect of decreasing and lowering the melting point. And it discovered that a liquid crystal compound can show the very outstanding low-temperature stability by such an effect.

  Such an effect can be manifested particularly when a methyl group is introduced at the third position of the terminal phenyl group (the phenyl group displayed on the rightmost side) as shown in Chemical Formula 1. If a substituent having 2 or more carbon atoms is introduced at position 3 of the terminal phenyl group in the chemical formula 1, the ratio of the molecular long axis to the shortening is decreased to induce a sharp decrease in the clearing point. Become. On the other hand, when F is introduced at the 3rd position of the terminal phenyl group in Chemical Formula 1, the effect of improving the low temperature stability can be exhibited, but the positive dielectric anisotropy is reduced and the desired high dielectric anisotropy is achieved. It is difficult to provide a liquid crystal composition.

  In this specification, unless otherwise specified, the following terms are defined as follows:

  Halogen can be fluorine (F), chlorine (Cl), bromine (Br) or iodo (I)).

  The alkyl radical having 1 to 15 carbon atoms can be a linear, branched or cyclic alkyl radical. Specifically, the alkyl radical having 1 to 15 carbon atoms is a linear alkyl radical having 1 to 10 carbon atoms; a linear alkyl radical having 1 to 5 carbon atoms; a branched or cyclic alkyl radical having 3 to 10 carbon atoms; Alternatively, it may be a branched or cyclic alkyl radical having 3 to 5 carbon atoms. More specifically, an alkyl radical having 1 to 15 carbon atoms is methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, tert-butyl, n-pentyl, iso-pentyl, cyclohexyl, or the like. possible.

In the alkyl radical having 1 to 15 carbon atoms, one or more —CH ₂ — of the radical is —C≡C—, —CF ₂ O—, —CH═CH—, —O—, —COO—, It can be replaced by a radical substituted with -OCO- or -OCO-O-. As an example, the methyl radical can be replaced by a vinyl radical (—CH═CH—H) in which —CH ₂ — of the methyl radical (—CH ₂ —H) is replaced by —CH═CH—. However, one or more —CH ₂ — of the radicals may be substituted with the above-described substituents so that an oxygen atom is not directly connected.

In addition, the alkyl radical having 1 to 15 carbon atoms can be replaced with a radical in which one or more Hs of the radical are substituted with a halogen. As an example, the methyl radical can be replaced by a perfluoromethyl radical (—CF ₃ ) in which all H of the methyl radical (—CH ₃ ) are replaced by F.

A single bond means the case where there is no separate atom in the portion represented by Z ¹ . As an example, in Formula 1, when Z ¹ is a single bond, n is 0, and the A ² ring is a cyclohexylene group, the cyclopentyl group can be directly linked to cyclohexylene.

In Formula 1, R ¹ is an alkyl radical having 1 to 3 carbon atoms, or a radical in which one or more —CH ₂ — of the alkyl radicals having 1 to 15 carbon atoms is substituted with —CH═CH—. possible. If R ¹ is a radical in which one or more of —C ₂ —alkyl radicals having 1 to 15 carbon atoms are substituted with —CH═CH—, the rotational viscosity decreases, the clearing point increases, and the elastic modulus. When R ¹ has an even number of carbon atoms, it is advantageous to introduce a double bond at the terminal, and when R ¹ has an odd number of carbon atoms, a double bond is introduced into the odd-numbered carbon. It is advantageous. As an example, R ¹ is —CH═CH ₂ , —CH ₂ —CH ₂ —CH═CH ₂ , —CH═CH—CH ₃ or —CH ₂ —CH ₂ for optimization of the elastic modulus and increase of the clearing point. It may be -CH ₌ CH 2 -CH _3. Further, in the liquid crystal compound of Chemical Formula 1, since the terminal group's terminal ring is a cyclopentyl group, when R ¹ is hydrogen, the rotational viscosity can be effectively reduced.

In Formula 1, X ¹ is a polar radical and may be any one of the aforementioned substituents. In particular, X ¹ can be F, Cl, CF ₃ or OCF ₃ to provide a low viscosity liquid crystal composition.

In Formula 1, the 6-position of the terminal phenyl group, that is, Y ¹ may be hydrogen or fluorine, and when a higher dielectric anisotropy is to be secured, use a compound in which Y ¹ is fluorine. Can do.

In the above chemical formula 1, the structure of Z ¹ is selected in consideration of dielectric anisotropy, rotational viscosity, refractive index anisotropy, etc., and a single bond or − CF ₂ O— or the like can be selected.

In Formula 1, the structures of the A ¹ and A ² rings may be selected in consideration of refractive index anisotropy or dielectric anisotropy. For example, when it is intended to provide a liquid crystal material having a high refractive index anisotropy, a liquid crystal compound in which the A ¹ and A ² rings are 1,4-phenylene groups is suitable, and the liquid crystal material having a high dielectric anisotropy In the case of providing a liquid crystal compound, the A ¹ and A ² rings are rings in which F or O is contained.

In one embodiment, the compound of Formula 1 may be any one of liquid crystal compounds having the following structure.
In the above formula, R ¹ is as defined in Chemical Formula 1.

In the present specification, the same symbols written in different chemical formulas do not mean the same type of substituent. For example, in the different chemical formulas 1-1 to 1-24, the same symbol “R ¹ ” does not mean the same kind of substituent, so even if “R ¹ ” is hydrogen in 1-1, 1-2 “R” ¹ 'can be methyl. In the chemical formulas in this specification, the parentheses “()” can be substituted with the substituents described in the parentheses. More specifically,-(F) means that hydrogen or fluorine can be bonded to the site.

  Meanwhile, according to another embodiment of the invention, a liquid crystal composition including the liquid crystal compound represented by Formula 1 is provided. The liquid crystal composition includes the liquid crystal compound represented by Formula 1 and exhibits excellent low temperature stability while exhibiting high dielectric anisotropy.

  The liquid crystal compound of Formula 1 may be included in an amount of 1 to 50 parts by weight with respect to 100 parts by weight of the total liquid crystal compound included in the composition, and may exhibit the above-described effects.

  Meanwhile, in the liquid crystal composition, the liquid crystal compound of Formula 1 can be combined with various liquid crystal compounds known in accordance with the characteristics of the liquid crystal panel to which the composition is applied.

As an example, the liquid crystal composition may include a low-viscosity liquid crystal compound represented by the following chemical formula 2 as a matrix first component.
In the above chemical formula 2,
R ²¹ and R ²² are each independently a radical of any one of hydrogen and alkyl having 1 to 15 carbons, or 1 to 3 of the radicals are substituted with halogen. Or —C≡C—, —CF ₂ O—, —CH═CH—, —O—, —CO—O—, —O so that one or more —CH ₂ — is not directly linked to an oxygen atom. A radical substituted with -CO- or -O-CO-O-
A ³ and A ⁴ rings are each independently a 1,4-cyclohexylene group or a 1,4-phenylene group.

Such a compound of Chemical Formula 2 is a liquid crystal compound having the following structure so that the clearing point, rotational viscosity, refractive index anisotropy and dielectric anisotropy can be adjusted advantageously while maintaining a high specific resistance. A compound selected from can be used.
In the above formula, R ²¹ and R ²² are as defined in Chemical Formula 2.

Meanwhile, the liquid crystal composition may include a high-temperature liquid crystal compound represented by the following chemical formula 3 as a base second component.
In the above chemical formula 3,
R ³¹ and R ³² are each independently one of hydrogen and alkyl having 1 to 15 carbon atoms, or 1 to 3 of the radicals are substituted with halogen. Or —C≡C—, —CF ₂ O—, —CH═CH—, —O—, —CO—O—, —O so that one or more —CH ₂ — is not directly linked to an oxygen atom. A radical substituted with -CO- or -O-CO-O-
A ⁵ and A ⁷ rings are each independently a 1,4-cyclohexylene group or a 1,4-phenylene group;
A ⁶ ring, 4-cyclohexylene group, 1,4-phenylene group, 2-fluoro-1,4-phenylene group, 3-fluoro-1,4-phenylene or 2,3-difluoro-1, A 4-phenylene group,
o is 1 or 2.

Such a compound of Formula 3 is a liquid crystal compound having the following structure so that the clearing point, rotational viscosity, refractive index anisotropy and dielectric anisotropy can be adjusted advantageously while maintaining a high specific resistance. A compound selected from can be used.
In the above formula, R ³¹ and R ³² are as defined in Chemical Formula 3.

On the other hand, the liquid crystal composition may include a high dielectric constant liquid crystal compound represented by the following chemical formula 4 as a base third component.
In the above chemical formula 4,
R ⁴¹ is a radical of any one of hydrogen and alkyl having 1 to 15 carbons, or 1 to 3 of the radicals are substituted with halogen, or one or more — —C≡C—, —CF ₂ O—, —CH═CH—, —O—, —CO—O—, —O—CO— or —O—CO so that CH ₂ — is not directly linked to an oxygen atom. A radical substituted with -O-
X ² is a radical of any one of F, Cl, CN, NCS and C 1-5 fluoroalkyl containing 1 to 3 F, or one or more of the radicals -CH 2 _- is a radical is replaced with an oxygen atom,
Y ² is H, F or a methyl group, Y ³ and Y ⁴ are each independently H or F,
Rings A ¹¹ , A ²² and A ³³ are each independently any one of the rings having the following structures:

Z ¹¹ , Z ¹² and Z ¹³ are each independently a single bond, —CH ₂ CH ₂ —, —CH═CH—, —CH ₂ O—, —OCH ₂ —, —C≡C—, — _{, - - CH 2 CF 2 CHFCHF} -, - CF 2 CH 2 -, - CH 2 CHF -, - CHFCH 2 -, - C 2 F 4 -, - COO -, - OCO -, - CF 2 O- or - OCF ₂ - a is,
f is 1, 2 or 3, g is 0, 1 or 2, h is 0 or 1, and the sum of f, g and h is 2 or 3.

Such a compound of Chemical Formula 4 is a liquid crystal compound having the following structure so that the clearing point, rotational viscosity, refractive index anisotropy, and dielectric anisotropy can be adjusted advantageously while maintaining a high specific resistance. A compound selected from can be used.
In the above formula, R ⁴¹ and X ² are as defined in Chemical Formula 4.

Meanwhile, the liquid crystal composition may include a high dielectric constant liquid crystal compound represented by the following chemical formula 5 as a matrix fourth component.
In the above chemical formula 5,
R ⁵¹ is a radical of any one of hydrogen and alkyl having 1 to 15 carbons, or 1 to 3 of the radicals are substituted with halogen, or one or more — —C≡C—, —CF ₂ O—, —CH═CH—, —O—, —CO—O—, —O—CO— or —O—CO so that CH ₂ — is not directly linked to an oxygen atom. A radical substituted with -O-
X ³ is a radical of any one of F, Cl, CN, NCS and 1 to 5 fluoroalkyl containing 1 to 3 F, or one or more of the above radicals -CH 2 _- is a radical is replaced with an oxygen atom,
Y ⁵ and Y ⁶ are each independently H or F;
A ⁵¹ , A ⁵² and A ⁵³ rings are each independently any one of the rings having the following structures:

Z ⁵¹ , Z ⁵² and Z ⁵³ are each independently a single bond, —CH ₂ CH ₂ —, —CH═CH—, —CH ₂ O—, —OCH ₂ —, —C≡C—, — _{, - - CH 2 CF 2 CHFCHF} -, - CF 2 CH 2 -, - CH 2 CHF -, - CHFCH 2 -, - C 2 F 4 -, - COO -, - OCO -, - CF 2 O- or - OCF ₂ - a is,
j is 1, 2 or 3, k is 0, 1 or 2, m is 0 or 1, and the sum of j, k and m is 2 or 3.

Such a compound of Chemical Formula 5 is a liquid crystal compound having the following structure so that the clearing point, rotational viscosity, refractive index anisotropy and dielectric anisotropy can be adjusted advantageously while maintaining a high specific resistance. A compound selected from can be used.
In the above formula, R ⁵¹ and X ³ are as defined in Chemical Formula 5.

  The liquid crystal composition includes at least one of the above-described matrix first to fourth components together with the liquid crystal compound of Formula 1, and has low temperature stability that is remarkably superior to existing ones, and has a dielectric anisotropy. A large liquid crystal material can be provided.

  On the other hand, the liquid crystal composition may additionally contain various additives usually used in the technical field to which the present invention belongs in addition to the liquid crystal compound.

Specifically, the liquid crystal composition may additionally include an antioxidant. Examples of such an antioxidant include an antioxidant selected from the group consisting of compounds represented by the following chemical formulas 6 and 7.

In the above chemical formulas 6 and 7, R ¹⁹ and R ²⁰ are each independently a radical of any one of hydrogen, an alkyl group having 1 to 15 carbon atoms and an alkoxy group having 1 to 15 carbon atoms, or -C≡C so that oxygen atoms are not linked directly - - one or more -CH ₂ of said _{radicals, - CH = CH -, -} CF 2 O -, - O -, - COO- or -OCO A radical substituted with-or one or more H of said radicals replaced by halogen,
A ¹³ is cyclohexylene, tetrahydropyranylene, or dioxanylene.

In addition, the liquid crystal composition may additionally include a UV stabilizer. As such a UV stabilizer, a Hals (Hindered amine light stabilizer) series can be used. As a non-limiting example, as the UV stabilizer, a UV stabilizer selected from the group consisting of compounds represented by the following chemical formula 8 and chemical formula 9 can be used.
In Formula 8, R ²³ and R ²⁴ are each independently one of hydrogen, alkyl having 1 to 15 carbons, and alkoxy having 1 to 15 carbons, or One or more of —CH ₂ — is substituted with —C≡C—, —CH═CH—, —CF ₂ O—, —O—, —COO— or —OCO— so that the oxygen atom is not directly linked. Or one or more H of said radicals are radicals replaced by halogen,
q is an integer from 0 to 12,
In Formula 9, R ²⁵ is any one of hydrogen, alkyl having 1 to 15 carbons, and alkoxy having 1 to 15 carbons, or one or more —CH of the radicals. ₂ - is -C≡C so that oxygen atoms are not linked directly _{-, - CH = CH -,} - CF 2 O -, - O -, - COO- or of or the radical is substituted with -OCO- Wherein one or more Hs of the radicals are substituted with halogens,
d is an integer of 0 to 12.

  The antioxidant and / or UV stabilizer may be used at about 1 to 2,000 ppm or about 200 to 500 ppm with respect to the total liquid crystal composition weight.

In addition, when the liquid crystal composition is to be used in an STN or TN mode liquid crystal display device, a compound represented by the following chemical formula 10 is further added to the liquid crystal composition in order to realize a spiral structure. be able to.

  The compound represented by the chemical formula 10 is used in an amount of about 0.01 to about 5 parts by weight with respect to 100 parts by weight of the liquid crystal composition, and can easily realize a desired pitch.

  A liquid crystal composition having a positive dielectric anisotropy can be provided using the liquid crystal compound of Formula 1 according to an embodiment of the present invention, more specifically, a dielectric anisotropy of 3 or more, 70 ° C. A liquid crystal composition having the above clearing point and a refractive index anisotropy of 0.09 or more can be easily provided.

  The liquid crystal composition can be used for AM-LCD (Active Matrix-LCD) or PM-LCD (Passive Matrix-LCD), and includes TN (Twist nematic), STN (Super-twisted nematic), IPS. (In-plane switching), FFS (Fringe field switching), PLS (Plane line switching), AH-IPS (advanced high-performance IPS), ADS (Advanced-superi s messenger IPS) It can be used for a mode liquid crystal display device.

  Meanwhile, according to another embodiment of the invention, a liquid crystal display device including the above-described liquid crystal composition is provided. The liquid crystal composition can be applied to a liquid crystal display device through various methods known in the technical field to which the present invention belongs. The liquid crystal display device can be manufactured as a liquid crystal display device in various modes as described above.

  The liquid crystal compound according to an embodiment of the invention exhibits excellent low-temperature stability and can provide a liquid crystal composition having a high dielectric constant and / or a high refractive index. In addition, a liquid crystal composition optimized for various liquid crystal display devices such as TN, STN, IPS, FFS, PLS, AH-IPS, ADS, and PSA mode is more easily provided through a high specific resistance. be able to.

  Hereinafter, the operation and effect of the invention will be described more specifically through specific embodiments of the invention. However, this is presented as an example of the invention, and this does not limit the scope of the invention in any way.

  A liquid crystal compound according to an embodiment of the present invention was manufactured by the following method, and the physical properties of the liquid crystal compound were evaluated using the method described below.

  And the liquid crystal composition containing the said liquid crystal compound was manufactured, and the physical property of the liquid crystal composition was also evaluated using the method described below.

Specifically, the physical properties of the liquid crystal compound are extrapolated by substituting the measured values of a sample prepared by mixing 10% by weight of the liquid crystal compound whose physical properties are to be measured and 90% by weight of the base liquid crystal into the following formula 1. Defined by value. At this time, the mother liquid crystal has a clearing point of 78.3 ° C., a refractive index anisotropy [Δn] of 0.1214, a dielectric anisotropy [Δε] of 5.0, and a rotation. The one having a viscosity [γ1] of 57 mPa · s was used.
[Formula 1]
Extrapolated value = [measurement value of mother liquid crystal] + [{(measurement value of sample) − (measurement value of mother liquid crystal)} / (weight% of liquid crystal compound) × 100]

(1) Clearing point A sample containing a liquid crystal compound for which the clearing point is to be measured or a liquid crystal composition was dropped on a slide glass with a dropper and then covered with a cover glass to produce a sample for measuring the clearing point. .
The manufactured sample was put in an instrument with a temperature controller (METTLER TOLEDO FP90), and the change of the sample was observed while the temperature was increased at a rate of 3 ° C./min on an FP82HT Hot stage. The temperature at the point where a hole was formed in the sample was recorded, and such an operation was repeated three times to derive an average value. This value was defined as the clearing point of the sample or liquid crystal composition.

(2) Refractive index anisotropy The refractive index anisotropy [Δn] of the sample or liquid crystal composition was measured with an Abbe refractometer using a 589 nm wavelength light at 20 ° C. and a polarizing plate attached to the eyepiece. . After rubbing the surface of the main prism in one direction, a sample to be measured or a liquid crystal composition was dropped on the main prism. Thereafter, the refractive index (n _|| ) when the direction of polarized light is parallel to the rubbing direction and the refractive index (n⊥) when the direction of polarized light is perpendicular to the rubbing direction were measured. Then, the refractive index anisotropy (Δn) was measured by substituting the refractive index value into Equation 2.
[Formula 2]
Δn = n _|| −n⊥

(3) Dielectric Anisotropy The dielectric anisotropy [Δε] of the sample or the liquid crystal composition was calculated by substituting ε _|| and ε⊥ measured as follows into Equation 3.
[Formula 3]
Δε = ε _|| −ε⊥

1. Measurement of dielectric constant ε _|| : A vertical alignment film was formed by applying a vertical alignment agent to the surfaces of the two glass substrates on which the ITO pattern was formed. Next, after applying a spacer to one of the two glass substrates so that the vertical alignment films face each other and the distance (cell gap) between the two glass substrates is 4 μm. Two glass substrates were bonded together. Then, a sample to be measured or a liquid crystal composition was injected into the device and sealed with an adhesive that was cured with ultraviolet rays. Thereafter, the dielectric constant ε _|| at 20 ° C. of this device was measured using a 4294A equipment manufactured by Agilent.

  2. Measurement of dielectric constant ε⊥: A horizontal alignment film was formed by applying a horizontal alignment agent to the surface of the two glass substrates on which the ITO pattern was formed. Next, after applying a spacer to any one of the two glass substrates so that the horizontal alignment films face each other and the distance (cell gap) between the two glass substrates is 4 μm, Two glass substrates were bonded together. Then, a sample to be measured or a liquid crystal composition was injected into the device and sealed with an adhesive that was cured with ultraviolet rays. Then, using the 4294A equipment manufactured by Agilent, the dielectric constant ε 測定 at 20 ° C. of this device was measured.

(4) Rotational viscosity A horizontal alignment film was formed by applying a horizontal alignment agent to the surface of the two glass substrates on which the ITO pattern was formed. Next, after applying a spacer to any one of the two glass substrates so that the horizontal alignment films face each other and the distance (cell gap) between the two glass substrates is 20 μm, Two glass substrates were bonded together. Then, a sample or a liquid crystal composition was injected into the device and sealed with an adhesive that was cured with ultraviolet rays. Thereafter, ESPEC Corp. The rotational viscosity at 20 ° C. of this device was measured using Model 6254 equipment manufactured by Toyo Corp. equipped with a temperature controller (Model SU-241) manufactured in (1).

(5) Melting point A sample for measuring the melting point was prepared by placing a sample or a liquid crystal composition on which a melting point is to be measured on a slide glass and covering the glass with a cover glass.
The manufactured sample was put in an instrument with a temperature controller (METTLER TOLEDO FP90), and the change of the sample was observed while the temperature was increased at a rate of 3 ° C./min by FP82HT Hot stage. The temperature at the point where the sample changed from a solid state to a liquid crystal phase exhibiting fluidity was recorded, and such an operation was repeated three times to derive an average value. This value was defined as the melting point when the sample was heated.
Then, using the same equipment, the change of the sample was observed while lowering the temperature at a rate of 3 ° C./min. The temperature at the point where the sample changed from the liquid crystal phase to the crystal phase was recorded, and such an operation was repeated three times to derive an average value. This value was defined as the melting point when the sample was cooled.

(6) Low temperature stability A 10 mL vial was prepared, and 2 mL of a sample or liquid crystal composition containing a liquid crystal compound to be measured for physical properties was injected into the vial. Then, the state of the sample or liquid crystal composition at −25 ° C. was observed for 30 days. The low temperature stability was evaluated with the period during which the state of the sample or the liquid crystal composition was stably maintained at -25 ° C. In the following, “30 days or more” is displayed when the sample or the liquid crystal composition maintains a stable state even after 30 days.

  Production Example 1: Synthesis of liquid crystal compound 1-A1

Of alcohol compound (A-1-2) (2.3 g, 14.2 mmol), potassium carbonate (3.6 g, 25.9 mmol), tetrabutylammonium bromide (0.42 g, 1.29 mmol) and DMF (50 mL) The mixture was heated at 40 ° C. while stirring the mixture under a nitrogen atmosphere. Then, the bromine compound (A-1-1) (5.8 g, 15 mmol) was dissolved in 50 mL of DMF and added dropwise to the mixture. Thereafter, the obtained mixture was heated at 90 ° C. and allowed to react for about 2 hours, and then the mixture was placed in an ice container and allowed to cool. Next, the product was extracted from the mixture with toluene and distilled under reduced pressure to obtain a brown solid. The solid was purified through silica gel column chromatography and recrystallization (using a mixed solvent of hexane and ethyl acetate) to obtain white crystals (4.76 g, 10.3 mol). (Yield 73%) Mass spectrum: 307, 468 [M ⁺ ]

  Production Example 2: Synthesis of liquid crystal compound 1-A2

Of alcohol compound (A-2-2) (4.1 g, 25.6 mmol), potassium carbonate (6.4 g, 46.6 mmol), tetrabutylammonium bromide (0.75 g, 2.3 mmol) and DMF (70 mL) The mixture was heated at 40 ° C. while stirring the mixture under a nitrogen atmosphere. Then, the bromo compound (A-2-1) (12.9 g, 27 mmol) was dissolved in 70 mL of DMF and added dropwise to the mixture. Thereafter, the obtained mixture was heated at 90 ° C. and allowed to react for about 2 hours, and then the mixture was placed in an ice container and allowed to cool. Next, the product was extracted from the mixture with toluene and distilled under reduced pressure to obtain a brown solid. The solid was purified through silica gel column chromatography and recrystallization (using a mixed solvent of hexane and ethyl acetate) to obtain white crystals (10.2 g, 18.1 mol). (Yield 71%) Mass spectrum: 372, 401, 562 [M ⁺ ]

Test Example 1: Evaluation of physical properties of liquid crystal compounds produced in Production Examples Liquid crystal compounds produced in Production Examples 1 and 2 and existing liquid crystal compounds P-1, P-2 and Q-1 having high dielectric anisotropy The physical properties were measured by the method described above, and the results are shown in Table 1.

  Looking at the melting point during temperature reduction, which is a factor affecting the low-temperature stability of the liquid crystal compound, the existing liquid crystal compounds P-1, P-2, and Q-1 are 41 ° C., 71 ° C., and 58 ° C., respectively. The melting point at the time of temperature reduction was shown. However, the liquid crystal compound according to an embodiment of the present invention has a lower melting point at 30 ° C. or lower and 38 ° C. than the existing liquid crystal compound. Therefore, it was confirmed that the liquid crystal compound according to an embodiment of the present invention showed excellent low-temperature stability as compared with existing liquid crystal compounds.

Examples and Comparative Examples: Production of Liquid Crystal Compositions Liquid crystal compounds used in Examples and Comparative Examples are indicated by codes. The code is created by describing the symbols of the rings forming the central group of the liquid crystal compound in order from the left side, describing the connecting groups connecting the rings of the central group in order, and then describing the terminal group on the right side. At this time, there is no separate division indication between the central group ring and the linked group that connects the central group ring, but the central group and the end group are classified with “-”, and both end groups are separated. Is classified by indicating “.”. The individual abbreviated symbols (codes) of the substances are summarized in Table 2 below.

Referring to Table 2 above, the following codes refer to liquid crystal compounds having the structures indicated below.

  The liquid crystal compositions of Examples 1 to 6 including the liquid crystal compound according to one embodiment of the invention and the liquid crystal compositions of Comparative Examples 1 to 4 not including the liquid crystal compound according to one embodiment of the invention were manufactured according to the composition of Table 3 below. . The physical properties of the liquid crystal composition were evaluated and shown in Table 3.

(Unit of composition in Table 3 is% by weight.)

  Referring to Table 3 above, the compositions of Comparative Examples 1 and 2 of the existing liquid crystal compositions exhibit dielectric anisotropy of about 4.5 and 5.3, but contrary to this, one embodiment of the invention The liquid crystal compositions of Examples 1 to 6 to which the liquid crystal compound of Formula 1 was added exhibited an anisotropy of dielectric constant increased from 7.3 to 11.3.

  On the other hand, the liquid crystal compositions of Comparative Examples 3 and 4 to which the existing liquid crystal compounds P1 and P2 for high dielectric anisotropy were added also exhibited a high dielectric anisotropy of about 11.0. However, the liquid crystal compositions of Comparative Examples 3 and 4 maintained their state only for about 8 to 10 days at a low temperature of −25 ° C. On the other hand, the liquid crystal compositions of Examples 5 and 6 were more stable for 30 days or more at a low temperature of −25 ° C. while exhibiting a further increased dielectric anisotropy compared to the compositions of Comparative Examples 3 and 4. Maintained.

  Accordingly, the liquid crystal compound of Formula 1 according to an embodiment of the present invention provides a liquid crystal composition exhibiting excellent low temperature stability while exhibiting high dielectric anisotropy, and more easily satisfies various display requirements. There is expected.

Claims (16)

Liquid crystal compound represented by the following chemical formula 1:
In the above chemical formula 1,
R ¹ is a radical of any one of hydrogen and alkyl having 1 to 15 carbons, or 1 to 3 of the radicals are substituted with halogen, or one or more — —C≡C—, —CF ₂ O—, —CH═CH—, —O—, —CO—O—, —O—CO— or —O—CO so that CH ₂ — is not directly linked to an oxygen atom. A radical substituted with -O-
X ¹ is a radical of any one of F, Cl, CN, NCS and 1 to 5 fluoroalkyl containing 1 to 3 F, or one or more of the above radicals Each of —CH ₂ — is a radical substituted with an oxygen atom,
Y ¹ is H or F;
Rings A ¹ and A ² are each independently any one of the rings having the following structure:

Z ¹ is a single _{bond, -CH 2 CH 2 -, -} CH = CH -, - CH 2 O -, - OCH 2 -, - C≡C -, - CH 2 CF 2 -, - CHFCHF -, - CF ₂ CH ₂ —, —CH ₂ CHF—, —CHFCH ₂ —, —C ₂ F ₄ —, —COO—, —OCO—, —CF ₂ O— or —OCF ₂ —,
n is 0 or 1. R ¹ is hydrogen, —CH═CH ₂ , —CH ₂ —CH ₂ —CH═CH ₂ , —CH═CH—CH ₃ or —CH ₂ —CH ₂ —CH═CH ₂ —CH ₃ and carbon number 1 The liquid crystal compound according to claim 1, which is a radical of any one of 1 to 3 alkyls. The liquid crystal compound according to claim 1, wherein X ¹ is F, Cl, CF ₃ or OCF ₃ . The liquid crystal compound according to any one of claims 1 to 3, wherein the compound represented by the chemical formula 1 is one of liquid crystal compounds having the following structure:
In the above formula, each R ¹ is independently a radical of any one of hydrogen and alkyl having 1 to 15 carbons, or 1 to 3 of the radicals are substituted with halogen. Or —C≡C—, —CF ₂ O—, —CH═CH—, —O—, —CO—O—, such that one or more —CH ₂ — is not directly linked to an oxygen atom. A radical substituted with O—CO— or —O—CO—O—.   The liquid crystal composition containing the liquid crystal compound represented by Chemical formula 1 as described in any one of Claims 1-4.   The liquid crystal composition according to claim 5, comprising 1 to 50 parts by weight of the liquid crystal compound represented by the chemical formula 1 with respect to 100 parts by weight of the entire liquid crystal compound. The liquid crystal composition according to claim 5 or 6, further comprising at least one liquid crystal compound selected from the group consisting of the following chemical formulas 2 to 5:
In the above chemical formulas 2 to 5,
R ²¹ , R ²² , R ³¹ , R ³² , R ⁴¹ and R ⁵¹ are each independently a radical of any one of hydrogen and alkyl having 1 to 15 carbons, or of the above radicals 1 to 3 H in the above are substituted with halogen or one or more —CH ₂ — is not directly linked to an oxygen atom —C≡C—, —CF ₂ O—, —CH═CH—, A radical substituted by -O-, -CO-O-, -O-CO- or -O-CO-O-;
X ² and X ³ are each independently a radical of any one of F, Cl, CN, NCS, and C 1-5 fluoroalkyl containing 1 to 3 F, or A radical in which one or more of the radicals —CH ₂ — is replaced by an oxygen atom;
Y ² is H, F or a methyl group, Y ^{3 to} Y ⁶ are each independently H or F,
A ³ , A ⁴ , A ⁵ and A ⁷ rings are each independently 1,4-cyclohexylene group or 1,4-phenylene group;
A ⁶ ring, 4-cyclohexylene group, 1,4-phenylene group, 2-fluoro-1,4-phenylene group, 3-fluoro-1,4-phenylene or 2,3-difluoro-1, A 4-phenylene group,
A ¹¹ , A ²² , A ³³ , A ⁵¹ , A ⁵² and A ⁵³ ring are each independently any one of the rings having the following structures:

Z ¹¹ , Z ¹² , Z ¹³ , Z ⁵¹ , Z ⁵² and Z ⁵³ are each independently a single bond, —CH ₂ CH ₂ —, —CH═CH—, —CH ₂ O—, —OCH _{2. -, - C≡C -, - CH} 2 CF 2 -, - CHFCHF -, - CF 2 CH 2 -, - CH 2 CHF -, - CHFCH 2 -, - C 2 F 4 -, - COO -, - OCO -, - _CF 2 O- or -OCF ₂ - and is,
o is 1 or 2,
f is 1, 2 or 3, g is 0, 1 or 2, h is 0 or 1, the sum of f, g and h is 2 or 3,
j is 1, 2 or 3, k is 0, 1 or 2, m is 0 or 1, and the sum of j, k and m is 2 or 3. The liquid crystal composition according to claim 7, wherein the compound represented by Chemical Formula 2 is a compound selected from liquid crystal compounds having the following structure:
In the above formula, R ²¹ and R ²² are each independently a radical of any one of hydrogen and alkyl having 1 to 15 carbons, or 1 to 3 H of the radicals. Is substituted with halogen or one or more —CH ₂ — is not directly linked to an oxygen atom —C≡C—, —CF ₂ O—, —CH═CH—, —O—, —CO— A radical substituted with O-, -O-CO- or -O-CO-O-. The liquid crystal composition according to claim 7, wherein the compound represented by Chemical Formula 3 is a compound selected from liquid crystal compounds having the following structure:
In the above formula, R ³¹ and R ³² are each independently a radical of any one of hydrogen and alkyl having 1 to 15 carbon atoms, or 1 to 3 H of the radicals. Is substituted with halogen or one or more —CH ₂ — is not directly linked to an oxygen atom —C≡C—, —CF ₂ O—, —CH═CH—, —O—, —CO— A radical substituted with O-, -O-CO- or -O-CO-O-. The liquid crystal composition according to claim 7, wherein the compound represented by Chemical Formula 4 is a compound selected from liquid crystal compounds having the following structure:
In the above formula, each R ⁴¹ is independently a radical of any one of hydrogen and alkyl having 1 to 15 carbons, or 1 to 3 of the radicals are halogen. —C≡C—, —CF ₂ O—, —CH═CH—, —O—, —CO—O—, so that one or more —CH ₂ — is not directly linked to an oxygen atom, A radical substituted with -O-CO- or -O-CO-O-;
X ² is a radical of any one of F, Cl, CN, NCS and C 1-5 fluoroalkyl containing 1 to 3 F, or one or more of the radicals —CH ₂ — is a radical substituted with an oxygen atom. The liquid crystal composition according to claim 7, wherein the compound represented by the chemical formula 5 is a compound selected from liquid crystal compounds having the following structure:
In the above formula, each R ⁵¹ is independently a radical of any one of hydrogen and alkyl having 1 to 15 carbons, or 1 to 3 of the radicals are halogen. —C≡C—, —CF ₂ O—, —CH═CH—, —O—, —CO—O—, so that one or more —CH ₂ — is not directly linked to an oxygen atom, A radical substituted with -O-CO- or -O-CO-O-;
X ³ is a radical of any one of F, Cl, CN, NCS and 1 to 5 fluoroalkyl containing 1 to 3 F, or one or more of the above radicals —CH ₂ — is a radical substituted with an oxygen atom. The liquid crystal composition according to any one of claims 5 to 7, further comprising an antioxidant selected from the group consisting of compounds represented by the following chemical formulas 6 and 7.
In the chemical formulas 6 and 7, R ¹⁹ and R ²⁰ are each independently a radical of any one of hydrogen, an alkyl group having 1 to 15 carbon atoms, and an alkoxy group having 1 to 15 carbon atoms, , - - -C≡C so that oxygen atoms are not linked directly - one or more -CH ₂ of the radical or _{CH = CH -, - CF 2} O -, - O -, - COO- or - A radical substituted with OCO- or one or more of said radicals replaced with a halogen,
A ¹³ is cyclohexylene, tetrahydropyranylene, or dioxanylene. The liquid crystal composition according to any one of claims 5 to 7, further comprising a UV stabilizer selected from the group consisting of compounds represented by the following chemical formulas 8 and 9:
In Formula 8, R ²³ and R ²⁴ are each independently one of hydrogen, alkyl having 1 to 15 carbons, and alkoxy having 1 to 15 carbons, or One or more of —CH ₂ — is substituted with —C≡C—, —CH═CH—, —CF ₂ O—, —O—, —COO— or —OCO— so that the oxygen atom is not directly linked. Or one or more H of said radicals are radicals replaced by halogen,
q is an integer from 0 to 12,
In Formula 9, R ²⁵ is any one of hydrogen, alkyl having 1 to 15 carbons, and alkoxy having 1 to 15 carbons, or one or more —CH of the radicals. ₂ - is -C≡C so that oxygen atoms are not linked directly _{-, - CH = CH -,} - CF 2 O -, - O -, - COO- or of or the radical is substituted with -OCO- Wherein one or more Hs of the radicals are substituted with halogens,
d is an integer of 0 to 12. The liquid crystal composition according to any one of claims 5 to 7, further comprising a compound represented by the following chemical formula 10:
  The liquid crystal display device containing the liquid-crystal composition as described in any one of Claims 5-14.   Liquid crystal display devices include TN (Twist nematic), STN (Super-twisted nematic), IPS (In-plane switching), FFS (Fringe field switching), PLS (Plane line switching), AH-IP The liquid crystal display device according to claim 15, wherein an ADS (Advanced-super dimensional switching) or PSA (Polymer sustained alignment) mode is employed.