JP2010270074A - Fluorobenzene derivative and liquid crystal composition containing the compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal compound that has a negative dielectric anisotropy with a large absolute value, shows a high liquid crystallinity and is excellent in compatibility with other liquid crystal materials, and a liquid crystal composition and a liquid crystal display element using the same. <P>SOLUTION: A fluorobenzene derivative represented by formula (I), the nematic liquid crystal composition using the same and the liquid crystal display element using the same are provided. The compound can be used to obtain the liquid crystal composition having the negative dielectric anisotropy value that is suitable for vertical alignment method, IPS, etc. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fluorobenzene derivative, a liquid crystal composition using the same, and a liquid crystal display device using the same.

  Liquid crystal display elements are currently widely used because of their excellent features such as low voltage operation and thin display. Conventional liquid crystal display elements, especially small and medium-sized displays, include TN (twisted nematic), STN (super twisted nematic), or active matrix (TFT: thin film transistor) based on TN, which have different dielectric constants. A liquid crystal composition having a positive isotropic value is used.

  However, one of the drawbacks of these display methods is the narrow viewing angle, and the improvement of the liquid crystal panel that has been increasing in recent years has become a major issue for improvement. In recent years, display methods such as vertical alignment and IPS (in-plane switching) have been newly put to practical use as a solution. The vertical alignment method is a method in which the viewing angle is improved by utilizing the vertical alignment of liquid crystal molecules, and a liquid crystal composition having a negative dielectric anisotropy value (Δε) is used. IPS is a method of improving viewing angle by switching liquid crystal molecules using a horizontal electric field in the horizontal direction with respect to a glass substrate, and a liquid crystal composition having a positive or negative dielectric anisotropy value is used. Is done. As described above, the vertical alignment method and the IPS, which are effective display methods for improving the viewing angle, require a liquid crystal compound and a liquid crystal composition having a negative dielectric anisotropy value. It has become. However, as described above, since the conventional display method mainly uses a liquid crystal composition having a positive dielectric anisotropy value, liquid crystal compounds and liquid crystal compositions having a negative dielectric anisotropy value are used. Is not fully developed.

  Formula (A-1) having a 2,3-difluorophenylene skeleton as a liquid crystal compound having a negative dielectric anisotropy value

Has been developed (see Patent Document 1). However, there is a growing demand to further increase the absolute value of dielectric anisotropy, and formula (A-2) in which four fluorine atoms are introduced into the molecule.

A liquid crystal compound having a tetrafluorobiphenyl skeleton represented by (see Patent Document 2) has been developed. However, although this compound has four fluorine atoms in the molecule, these compounds are in a form straddling two benzene rings, and the fluorine atom is shown in the above figure by the free rotation of a single bond between the benzene rings. I don't know if they face in the same direction. It is also conceivable that the positions of the fluorine atoms change depending on the surrounding substituents and environment, and the structures are opposite to each other. For this reason, even if the number of fluorine atoms in the molecule is increased, the absolute value of the dielectric anisotropy value is not necessarily increased accordingly. Further, although the structure of the compound represented by the formula (A-2) is shown, its physical property value is not shown, and the absolute value of the dielectric anisotropy value is not known.

  Formula (A-3)

The compound represented by (see Patent Document 3) was also developed as a compound having a negative dielectric anisotropy value and a large absolute value, but has a low liquid crystallinity and is extremely compatible with other liquid crystal materials. Since it is low, it was extremely difficult to use it in a liquid crystal composition.

  Under such circumstances, development of a liquid crystal material having a negative dielectric anisotropy value, a large absolute value, high liquid crystallinity, and excellent compatibility with other liquid crystal materials has been strongly desired.

JP-T-2-503441 WO 1999/21816 JP 2001-316669 A

  Disclosed is a liquid crystal compound having a negative dielectric anisotropy, a large absolute value, high liquid crystallinity, and excellent compatibility with other liquid crystal materials, and a liquid crystal composition and liquid crystal using the same It is to provide a display element.

  As a result of studying a fluorobenzene derivative and a nematic liquid crystal composition using the same, the present inventor has completed the present invention.

  The present invention relates to a general formula (1)

Wherein R ¹ and R ² are each independently an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkoxyl group having 1 to 12 carbon atoms or an alkenyloxy having 2 to 12 carbon atoms. Each of one or more hydrogen atoms may be independently substituted with a fluorine atom, and each —CH ₂ — group may independently be —O—, —CO—, —COO— or -OCO- may be substituted,
A ¹ and A ² are each independently a trans-1,4-cyclohexylene group, a trans-1,3-dioxane-2,5-diyl group, a pyridine-2,5-diyl group, or a pyrimidine-2,5. -Represents a diyl group or an unsubstituted 1,4-phenylene group in which one or more hydrogen atoms may be substituted with fluorine atoms,
X ¹ and X ² each independently represent —CH ₂ — or —CF ₂ —,
Y ¹ and Y ² are a single bond, —OCH ₂ —, —CH ₂ O—, —C ₂ H ₄ —, —C ₄ H ₈ —, —COO—, —OCO—, —CH═CH—, — CF = CF—, —CF ₂ O—, —OCF ₂ —, —CF ₂ CF ₂ — or —C≡C—, wherein an oxygen atom is directly present in R ¹ —Y ¹ — and —Y ² —R ² Never combine,
m and n represent 0, 1 or 2, m + n represents 1 or 2,
When m or n represents 2, a plurality of A ¹ , A ² , Y ¹ and Y ² may be the same or different. ), A liquid crystal composition using the same, and a liquid crystal display device using the same.

  In the liquid crystal compound of the present invention, four electron-withdrawing fluorine atoms are substituted on two phenylene groups of a biphenyl structure, and the 4-position and 4′-position of the biphenyl structure are bonded to a carbon atom via an oxygen atom. And having a structure. Therefore, the liquid crystal compound having this skeleton has a large polarization in the minor axis direction of the molecule, and as a result, exhibits a negative dielectric anisotropy having a large absolute value, high liquid crystallinity, and good compatibility with other liquid crystal materials. Has compatibility.

  The fluorobenzene derivative of the present invention is characterized by having a negative dielectric anisotropy and a large absolute value. Since it has a biphenyl skeleton, it exhibits a large value of refractive index anisotropy (Δn). It also has excellent liquid crystallinity and exhibits a stable liquid crystal phase over a wide temperature range. In addition, it is chemically stable against heat, light, water, etc., and has excellent compatibility with currently used liquid crystal compounds or liquid crystal compositions, so that it can be driven at low voltage and is practical and reliable. It is suitable as a component of a highly liquid crystal composition.

  Although the compound represented by general formula (I) includes many compounds, the following compounds are preferred.

In the general formula (I), R ¹ and R ² are each independently an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkoxyl group having 1 to 12 carbon atoms, or a group having 2 to 12 carbon atoms. Represents an alkenyloxy group, wherein each one or more hydrogen atoms may be independently substituted with fluorine atoms, and each —CH ₂ — group independently represents —O—, —CO—, —COO; An alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxyl group having 1 to 7 carbon atoms, or an alkenyloxy group having 2 to 7 carbon atoms, which may be substituted by-or -OCO- A linear alkyl group having 2 to 5 carbon atoms, vinyl group, 3-butenyl group, 3-butenyloxy group, trans-1-propen-1-yl group, 4-pentenyloxy group or trans-3- A penten-1-yl group is more preferred.

A ¹ and A ² are each independently a trans-1,4-cyclohexylene group, a trans-1,3-dioxane-2,5-diyl group, a pyridine-2,5-diyl group, or a pyrimidine-2,5. -Represents a diyl group or an unsubstituted 1,4-phenylene group in which one or more hydrogen atoms may be substituted by a fluorine atom, a trans-1,4-cyclohexylene group or one or more fluorine atoms An optionally substituted 1,4-phenylene group is preferable, and a trans-1,4-cyclohexylene group or an unsubstituted 1,4-phenylene group is more preferable.

X ¹ and X ² each independently represent —CH ₂ — or —CF ₂ —,
Y ¹ and Y ² are a single bond, —OCH ₂ —, —CH ₂ O—, —C ₂ H ₄ —, —C ₄ H ₈ —, —COO—, —OCO—, —CH═CH—, — CF = CF—, —CF ₂ O—, —OCF ₂ —, —CF ₂ CF ₂ — or —C≡C—, wherein an oxygen atom is directly present in R ¹ —Y ¹ — and —Y ² —R ² Without bonding, and each independently a single bond, —OCH ₂ —, —CH ₂ O—, —C ₂ H ₄ —, —CF═CF—, —CF ₂ O—, —OCF ₂ —, or — CF ₂ CF ₂ — is preferable, and a single bond or —C ₂ H ₄ — is more preferable.

m and n represent 0, 1 or 2, and m + n represents 1 or 2, but m + n is preferably 1 for improving the dielectric anisotropy, and the liquid crystal phase temperature range is expanded. m + n is preferably 2, and when m or n represents 2, a plurality of A ¹ , A ² , Y ¹ and Y ² may be the same or different.

As described above, the compound of the general formula (I) can include various compounds depending on the selection of R ¹ , R ² , A ¹ , A ² , X ¹ , X ² , Y ¹ , Y ² , m and n. However, among these, the compounds represented by the following general formulas (I-1) to (I-31) are preferable.

Wherein R ₁ and R ₂ are each independently an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxyl group having 1 to 7 carbon atoms or an alkenyloxy having 2 to 7 carbon atoms. A cyclohexyl group in the formula represents a trans form.)
Further, in the above formula, in order to improve compatibility with other liquid crystal materials, dielectric anisotropy, response speed and liquid crystallinity, the compounds of general formula (I-1) to general formula (I-16) are Preferably, in order to improve the compatibility with other liquid crystal materials, the dielectric anisotropy and the response speed, the compounds of the general formulas (I-1), (I-6), (I-9) and (I-14) Each compound is more preferable, and for improving liquid crystallinity, the compounds represented by the general formulas (I-2), (I-4), (I-5), (I-7), (I-8), (I-12) And (I-15) are more preferred.

  In the present invention, production examples of the compound of the general formula (I) are shown below. Of course, the gist and scope of the present invention are not limited by these production examples.

  (Production method 1) General formula (II)

(Wherein R ¹ , A ¹ , X ¹ , Y ¹ and m each independently represent the same meaning as in general formula (I)), and a boronic acid derivative represented by general formula (III)

(Wherein R ² , A ² , X ² , Y ² and n each independently represent the same meaning as in general formula (I), Z is chlorine, bromine, iodine, benzenesulfonyloxy group, p-toluene) A sulfonyloxy group, a methanesulfonyloxy group, or a trifluoromethanesulfonyloxy group.) A compound represented by tetrakistriphenylphosphine palladium (0), palladium (II) acetate, bis (triphenylphosphino) dichloride By performing a coupling reaction under basic conditions in the presence of palladium such as palladium (II) or a nickel-based transition metal catalyst, general formula (IV)

(Wherein R ¹ , R ² , A ¹ , A ² , X ¹ , X ² , Y ¹ , Y ² , m and n each independently represent the same meaning as in general formula (I)). Can be obtained.

  Examples of preferable bases include metal hydrides, metal carbonates, metal hydroxides, and metal carboxylates. Among these, alkali metal carbonates and alkali metal hydroxides are preferable. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide, and examples of the alkali metal carbonate include sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, sodium phosphate, sodium hydrogen phosphate, potassium phosphate, Preferable examples are potassium hydrogen phosphate. In this case, Z is preferably bromine, iodine, or trifluoromethanesulfonyloxy group, but bromine or trifluoromethanesulfonyloxy group is more preferable.

  At this time, any solvent can be used as long as it allows the reaction to proceed appropriately, but ether solvents, hydrocarbon solvents, aromatic solvents, polar solvents, and the like can be preferably used. As ether solvents, 1,4-dioxane, 1,3-dioxane, tetrahydrofuran, diethyl ether, t-butyl methyl ether and the like, and as chlorine solvents, dichloromethane, 1,2-dichloroethane, carbon tetrachloride and the like, The hydrocarbon solvent is pentane, hexane, cyclohexane, heptane, octane, etc., the aromatic solvent is benzene, toluene, xylene, mesitylene, chlorobenzene, dichlorobenzene, etc., the polar solvent is N, N-dimethylformamide, Preferred examples include N, N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane and the like. Of these, tetrahydrofuran and polar solvents such as N, N-dimethylformamide and N, N-dimethylacetamide are more preferable. Each of the above solvents may be used alone, or two or more solvents may be mixed and used.

  The reaction temperature can be in the range from the freezing point of the solvent to the reflux temperature, but is preferably from -20 ° C to 120 ° C.

(Production method 2)
By using 2,3-difluorobromobenzene as a starting material instead of general formula (III), the same reaction as in production method 1 is carried out, so that general formula (V)

(Wherein R ¹ , A ¹ , X ¹ , Y ¹ and m each independently represent the same meaning as in general formula (I)).
By oxidizing the obtained compound of general formula (V), general formula (VI)

(Wherein R ¹ , A ¹ , X ¹ , Y ¹ and m each independently represent the same meaning as in general formula (I)).
A base is reacted with the obtained compound of the general formula (25) to give a general formula (VII)

(Wherein R ¹ , A ¹ , X ¹ , Y ¹ and m each independently represent the same meaning as in general formula (I)).
The compound of the general formula (VII) obtained was added to the general formula (VIII)

(Wherein R ² , A ² , X ² , Y ² and n each independently represent the same meaning as in general formula (1), Z is chlorine, bromine, iodine, benzenesulfonyloxy group, p-toluene) A sulfonyloxy group, a methanesulfonyloxy group, or a trifluoromethanesulfonyloxy group) is reacted with a compound represented by the general formula (IX)

(Wherein R ¹ , R ² , A ¹ , A ² , X ¹ , X ² , Y ¹ , Y ² , m and n each independently represent the same meaning as in general formula (I)). Can be obtained.

  EXAMPLES Hereinafter, although an Example is given and this invention is further explained in full detail, this invention is not limited to these Examples.

  The phase transition temperature was measured using a polarizing microscope equipped with a temperature control stage and a differential scanning calorimeter (DSC). The structure of the compound was confirmed by nuclear magnetic resonance spectrum (NMR), infrared resonance spectrum (IR), mass spectrum (MS) and the like.

  In the following examples and comparative examples, “%” means “mass%”.

  The following abbreviations are used in compound descriptions.

THF: tetrahydrofuran
DMF: N, N-dimethylformamide
LDA: Lithium diisopropylamide
Et: ethyl group, Pr: propyl group, Bu: butyl group (Example 1) 4- (trans-4-butylcyclohexyl) methoxy-4′-ethoxy-2,2 ′, 3,3′-tetrafluorobiphenyl ( Synthesis of Ia)

  In a nitrogen atmosphere, 14.5 g of 4-ethoxy-2,3-difluorophenylboronic acid, 4- (trans-4-butylcyclohexyl) methoxy-2,3-difluorophenyl trifluoromethanesulfonate, 31 g of potassium carbonate, 12 g of potassium carbonate, tetrakistriphenyl Phosphine palladium (1.7 g) was dissolved in THF (106 mL) and water (25 mL), and the mixture was stirred with heating under reflux for 12 hours. Hexane and water were added to the reaction mixture and stirred, and then the organic layer was separated. The organic layer was washed with saturated brine, hydrochloric acid and saturated brine in that order, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure. The obtained crystals were purified by recrystallization and column chromatography (silica gel), and 4- (trans-4-butylcyclohexyl) methoxy-4′-ethoxy-2,2 ′, 3,3′-tetrafluorobiphenyl ( 11.5 g of Ia) was obtained.

MS m / z: 438 (M ⁺ , 100)
Phase transition temperature (℃) Cr 100 N 111 I
Example 2 Synthesis of 4- (trans-4-propylcyclohexyl) methoxy-4′-pentyloxy-2,2 ′, 3,3′-tetrafluorobiphenyl (Ib)

(2-1) In a nitrogen atmosphere, 4- (trans-4-propylcyclohexyl) methoxy-2,3-difluorophenylboronic acid (potassium carbonate was added to a DMF solution of 2,3-difluorophenol, and then trans- 4-Propyl-bromomethylcyclohexane in DMF was added dropwise to obtain 4- (trans-4-propylcyclohexyl) methoxy-2,3-difluorobenzene, and the resulting difluorobenzene in THF was cooled to -78 ° C. Lithiated with a BuLi hexane solution, a THF solution of trimethyl borate was added dropwise, stirred for 1 hour, diluted hydrochloric acid was added and hydrolyzed to give 4- (trans-4-propylcyclohexyl) methoxy-2,3-difluorophenyl. Boronic acid was obtained.) 32 g, 2,3-difluorobromobenzene 20 g, 2 M aqueous potassium carbonate solution 61 mL, tetrakistriphenylphosphine palladium 2.4 g in THF Dissolved and stirred for 2 hours under reflux with heating. Hydrochloric acid was added to the reaction mixture and stirred, and then the organic layer was separated, and the aqueous layer was extracted with ethyl acetate. The organic layers were combined, washed with saturated brine, dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. Purification by recrystallization obtained gave 20 g of 4- (trans-4-propylcyclohexyl) methoxy-2,2 ′, 3,3′-tetrafluorobiphenyl.
(2-2) To 60 mL of a THF solution of 7.6 g of diisopropylamine, 42 mL of a 1.65 MBuLi hexane solution is added dropwise at a rate that maintains 0 ° C. or lower, and the mixture is stirred at −5 to 0 ° C. for 30 minutes. The reaction solution is cooled to −20 ° C. and 19 g of 4- (trans-4-propylcyclohexyl) methoxy-2,2 ′, 3,3′-tetrafluorobiphenyl and triborate triborate at a rate that keeps the temperature below −15 ° C. 60 mL of THF solution of 13 g of isopropyl is added dropwise and stirred at -20 ° C. for 1 hour. Add 10% hydrochloric acid, allow to cool to room temperature, and extract twice with ethyl acetate. Combine all organic layers and wash with 10% brine. The solvent is distilled off to obtain 23 g of the crude product thus obtained. To a solution of this crude product in 125 mL of toluene and 50 mL of THF, 8 mL of 30% aqueous hydrogen peroxide is added dropwise, and then the temperature is raised and the mixture is stirred at room temperature for 3 hours. After confirming the completion of the reaction, the mixture is allowed to cool to room temperature, water is added, and the organic layer is separated. The obtained organic layer is washed with 10% aqueous sodium bisulfite solution, water and saturated brine, and dried over sodium sulfate. The solvent is distilled off to obtain 19.0 g of white crystalline 4′-hydroxy-4- (trans-4-propylcyclohexyl) methoxy-2,2 ′, 3,3′-tetrafluorobiphenyl.
(2-3) Under nitrogen substitution, dissolve 9.5 g of 4'-hydroxy-4- (trans-4-propylcyclohexyl) methoxy-2,2 ', 3,3'-tetrafluorobiphenyl in 50 mL of DMF, Potassium 4.7 g and pentyl iodide 6.7 g were added and stirred at 85 ° C. for 1 hour. After adding water and toluene and stirring for a while, the organic layer was separated, and the aqueous layer was extracted with toluene. The organic layers were combined, washed successively with water and saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure. The resulting yellow crystals were purified by column chromatography (silica gel, hexane) and then recrystallized to give 4- (trans-4-propylcyclohexyl) methoxy-4'-pentyloxy-2,2 ', 3,3 4.1 g of '-tetrafluorobiphenyl (Ib) was obtained.

¹ H-NMR (400 MHz, CDCl ₃ ): 0.87-1.94 (m, 26H), 3.87 (d, J = 4.8Hz, 2H), 4.16 (dd, J = 10.5, 5.4Hz, 2H), 6.75-6.81 (m, 2H), 6.98-7.02 (m, 2H).
MS m / z: 466 (M ⁺ , 100)
Phase transition temperature (℃) Cr 73 N 99 I
Example 3 Synthesis of 4- (trans, trans-4-propylbicyclohexyl-4-yl) methoxy-4′-ethoxy-2,2 ′, 3,3′-tetrafluorobiphenyl (Ic)

  Under nitrogen atmosphere, 4- (trans, trans-4-propylbicyclohexyl-4-yl) methoxy-2,3-difluorophenylboronic acid 22 g, 4-ethoxy-2,3-difluorobromobenzene 14 g, 2 mol / 55 mL of an aqueous potassium carbonate solution and 1.3 g of tetrakistriphenylphosphine palladium were dissolved in 120 mL of THF and stirred for 17.5 hours while heating under reflux. On the way, tetrakistriphenylphosphine palladium was added. Toluene and hydrochloric acid were added to the reaction mixture and stirred, and then the organic layer was separated, and the aqueous layer was extracted with toluene. The organic layers were combined, washed successively with water and saturated brine, and dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The obtained crystals were purified by column chromatography (silica gel) and recrystallization, and 4- (trans, trans-4′-propylbicyclohexyl-4-yl) methoxy-4′-ethoxy-2,2 ′, 3 Thus, 12.3 g of 3′-tetrafluorobiphenyl (Ic) was obtained.

¹ H-NMR (400 MHz, CDCl ₃ ): 0.85-1.95 (m, 30H), 3.86 (d, J = 4.8Hz, 2H), 4.16 (dd, J = 10.7, 5.3Hz, 2H), 6.77-6.79 (m, 2H), 6.98-7.01 (m, 2H).
MS m / z: 506 (M ⁺ , 100)
Phase transition temperature (℃) Cr 104 N 229 I
Comparative Example 1 Synthesis of 4- {2- (trans-4-propylcyclohexyl) ethyl} -4′-ethoxy-2,2 ′, 3,3′-tetrafluorobiphenyl (A-3)

  Under nitrogen atmosphere, 4- {2- (trans-4-propylcyclohexyl) ethyl} -2,3-difluorophenylboronic acid 40 g, 4-ethoxy-2,3-difluorobromobenzene 32 g, 2 mol / L carbonic acid 77 mL of an aqueous potassium solution and 3 g of tetrakistriphenylphosphine palladium were dissolved in 200 mL of THF, and the mixture was stirred for 5.5 hours under reflux with heating. On the way, tetrakistriphenylphosphine palladium was added. Hydrochloric acid was added to the reaction mixture and stirred, and then the organic layer was separated, and the aqueous layer was extracted with ethyl acetate. The organic layers were combined, washed in order with saturated brine, dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The obtained crystals were purified by column chromatography (silica gel) and recrystallization, and 4- {2- (trans-4-propylcyclohexyl) ethyl} -4'-ethoxy-2,2 ', 3,3'- 12.4 g of tetrafluorobiphenyl (Id) was obtained.

MS m / z: 422 (M ⁺ , 100)
Phase transition temperature (℃) Cr 63 N 109 I
(Example 4) Preparation of liquid crystal composition (1)
Host liquid crystal composition comprising the following composition (H)

Was prepared. Here, the physical properties of the host liquid crystal composition (H) are as follows.

Nematic phase upper limit temperature (T _NI ): 103.2 ℃
Dielectric anisotropy (Δε): 0.04
Refractive index anisotropy (Δn): 0.098
A liquid crystal composition (Mb) comprising 80% of the host liquid crystal (H) and 20% of (Ib) obtained in Example 2 was prepared. The physical properties of this composition are as follows.

Nematic phase upper limit temperature (TN-I): 100.7 ℃
Dielectric anisotropy (Δε): −1.63
Refractive index anisotropy (Δn): 0.106
In the liquid crystal composition (Mb) containing the compound (Ib) of the present invention, the dielectric anisotropy (Δε) was greatly reduced to a negative value as compared with the base liquid crystal (H). This shows that the compound (Ib) of the present invention has a negative dielectric anisotropy and an extremely large absolute value.

Further, when the voltage holding ratio of (Mb) was measured at 80 ° C., it showed a high value of 99% or more with respect to the voltage holding ratio of the host liquid crystal composition (H). This shows that the compound (Ib) of the present invention can be sufficiently used as a liquid crystal display material from the viewpoint of stability. In addition, the liquid crystal composition (Mb) contains 20% of the compound (Ib), but since the liquid crystal composition showed a stable liquid crystal phase without causing precipitation, the present compound was superior to other liquid crystal compositions. It has also been shown to be compatible and compatible.
(Example 5) Preparation of liquid crystal composition (2)
A liquid crystal composition (Mc) comprising 90% of the host liquid crystal (H) prepared in Example 4 and 10% of (Ic) obtained in Example 3 was prepared. The physical properties of this composition are as follows.

Nematic phase upper limit temperature (TN-I): 114.6 ℃
Dielectric anisotropy (Δε): −0.63
Refractive index anisotropy (Δn): 0.104
In the liquid crystal composition (Mc) containing the compound (Ic) of the present invention, the dielectric anisotropy (Δε) was greatly reduced to a negative value as compared with the base liquid crystal (H). This shows that the compound (Ib) of the present invention has a negative dielectric anisotropy and an extremely large absolute value.

Further, when the voltage holding ratio of (Mc) was measured at 80 ° C., it showed a high value of 99% or more with respect to the voltage holding ratio of the host liquid crystal composition (H). This shows that the compound (Ic) of the present invention can be sufficiently used as a liquid crystal display material from the viewpoint of stability.
(Comparative Example 2) Preparation of liquid crystal composition (3)
Compound (A-3) having 80% host liquid crystal (H) prepared in Example 4 and compound (Ib) having a structure relatively similar to that of ether oxygen but replaced with carbon

A liquid crystal composition (M-A3) comprising 20% was prepared. The physical properties of this composition are as follows.

Nematic phase upper limit temperature (TN-I): 102.4 ℃
Dielectric anisotropy (Δε): −1.27
Refractive index anisotropy (Δn): 0.109
It can be seen that the liquid crystal composition (M-A3) containing the compound (A-3) has an absolute value as small as 0.36 compared to the dielectric anisotropy of -1.63 of the liquid crystal composition (Mb) described in Example 4. . This shows that the introduction of oxygen atoms greatly affects the electronic state and molecular structure in the molecule, and the dielectric anisotropy is improved extremely efficiently.
Comparative Example 3 Preparation of Liquid Crystal Composition (4)
90% of the host liquid crystal (H) prepared in Example 4 and a compound having only two ring structures in the molecule (A-4)

An attempt was made to prepare a liquid crystal composition comprising 10%, but the compound (A-4) was not completely dissolved, and the physical property values could not be measured.

As mentioned above, it turns out that this-application compound is excellent in compatibility with other liquid crystal materials.
Example 6 Synthesis of 2,3-difluoro-4- (4-ethoxy-2,3-difluorophenyl) phenyloxy- (4- (trans-4-propylcyclohexyl) phenyl) difluoromethane (Id)

  To a solution of magnesium suspended in THF, a THF solution of 4- (trans-4-propylcyclohexyl) phenyl bromide was added dropwise with stirring, followed by further stirring to prepare a Grignard reagent. Carbon disulfide was added dropwise to this solution. After further stirring, the reaction was stopped by adding dilute hydrochloric acid, extracted with toluene, and dried over anhydrous magnesium sulfate. The solvent was distilled off to obtain 4- (trans-4-propylcyclohexyl) phenyldithiocarboxylic acid.

  To a THF suspension of sodium hydride, a THF solution of 4- (trans-4-propylcyclohexyl) phenyldithiocarboxylic acid was added dropwise and further stirred. To this reaction solution, a solution of 2,3-difluorophenyloxy-phenylmethane in 10 mL of THF was added dropwise and further stirred. To this reaction solution, a THF solution of iodine was added dropwise and further stirred, then returned to room temperature and stirred overnight at the same temperature. The reaction solution was poured into dilute hydrochloric acid, extracted with toluene, and dried over anhydrous magnesium sulfate. After magnesium sulfate was filtered off, the filtrate was concentrated under reduced pressure, and the residue was purified by silica gel column chromatography. 2,3-difluoro-4- (trans-4-propylcyclohexyl) phenyl = 4- (trans-4-propylcyclohexyl) ) Obtained thiobenzoate.

A dichloromethane suspension of N-bromosuccinimide was cooled to −78 ° C., and hydrogen fluoride-pyridine was added dropwise and stirred. The dichloromethane solution of 2,3-difluoro-4- (trans-4-propylcyclohexyl) phenyl = 4- (trans-4-propylcyclohexyl) thiobenzoate was added dropwise to the reaction solution and further stirred. The reaction solution was poured into a saturated aqueous sodium carbonate solution to terminate the reaction, and the methylene chloride phase was separated, washed successively with an aqueous sodium hydrogensulfite solution and water, and dried over anhydrous magnesium sulfate. After magnesium sulfate was filtered off, the solvent was distilled off, the residue was purified by silica gel column chromatography, the solvent was distilled off to make an ethyl acetate solvent, Pd / C was added, and the mixture was pressurized with hydrogen gas and stirred. did. The obtained phenol was reacted with trifluoromethanesulfonic anhydride to obtain a trifluoromethanesulfonic acid derivative. In the same manner as in Example 1, 2,3-difluoro-4- (4-ethoxy-2,3-difluorophenyl) phenyloxy- (4- (trans-4-propylcyclohexyl) phenyl) difluoromethane (Id) was obtained. Obtained.
Example 7 Synthesis of 2,3-difluoro-4- (2,3-difluoro-4-ethoxyphenyl) phenyloxy-trans-4-propylcyclohexyldifluoromethane (Ie)

A toluene solution of 2,3-difluorophenyl = trans-4-propylcyclohexylcarboxylate and Lawesson's reagent was reacted at 150 ° C. in a pressure vessel. After completion of the reaction, the mixture was extracted with toluene and dried over anhydrous magnesium sulfate. After magnesium sulfate was filtered off, the solvent was distilled off and the residue was purified by silica gel column chromatography. The solid obtained after distilling off the solvent was converted into a dichloromethane solution, and then added dropwise to a reaction solution prepared by adding hydrogen fluoride-pyridine dropwise at -78 ° C to a dichloromethane suspension of N-bromosuccinimide. After further stirring, the reaction was terminated by pouring into a saturated aqueous sodium carbonate solution, and the organic layer was washed successively with an aqueous sodium hydrogen sulfite solution and water and dried over anhydrous magnesium sulfate. After magnesium sulfate was filtered off, the solvent was distilled off, and the residue was purified by silica gel column chromatography to obtain 2,3-difluorophenyloxy-trans-4-propylcyclohexyldifluoromethane. A phenolic hydroxyl group was introduced into the obtained 2,3-difluorophenyloxy-trans-4-propylcyclohexyldifluoromethane by the same method as in Example 2, and a trifluoromethanesulfonic acid derivative was obtained by the same method as in Example 6. Then, coupling with a boric acid derivative gave 2,3-difluoro-4- (2,3-difluoro-4-ethoxyphenyl) phenyloxy-trans-4-propylcyclohexyldifluoromethane (Ie).
Example 8 Synthesis of 4,4′-bis {4- (trans-4-propylcyclohexyl) methoxy} -2,2 ′, 3,3′-tetrafluorobiphenyl (If)

Under a nitrogen atmosphere, 4- (trans-4-propylcyclohexyl) methoxy-2,3-difluorophenylboronic acid and 4- (trans-4-propylcyclohexyl) methoxy-2,3-difluorobromobenzene (4- (trans- A THF solution of 4-propylcyclohexyl) methoxy-2,3-difluorobenzene is cooled to −78 ° C., lithiated with a BuLi hexane solution, dropwise with a THF solution of bromine, stirred for 1 hour, and 4- (trans-4 -Propylcyclohexyl) methoxy-2,3-difluorobromobenzene was obtained by coupling 4,4'-bis {4- (trans-4-propylcyclohexyl) methoxy} -2 in the presence of a palladium catalyst. 2,2 ′, 3,3′-tetrafluorobiphenyl (If) was obtained.
Example 9 Synthesis of 4- (trans, trans-4-propylbicyclohexyl-4-yl) methoxy-4′-ethoxy-2,2 ′, 3,3′-tetrafluorobiphenyl (Ig)

Under nitrogen substitution, 10 g of 4′-hydroxy-4- (trans-4-propylcyclohexyl) methoxy-2,2 ′, 3,3′-tetrafluorobiphenyl was dissolved in DMF, and 4.9 g of potassium carbonate, 4- 6.7 g of (trans-4-ethylcyclohexyl) methyl bromide was added and stirred at 90 ° C. for 6 hours. After adding water and toluene and stirring for a while, the organic layer was separated, and the aqueous layer was extracted with toluene. The organic layers were combined, washed with saturated brine, dried over anhydrous sodium sulfate, and the solvent was evaporated under reduced pressure. The residue was purified by column chromatography (silica gel) and then recrystallized to produce 4- (trans-4-ethylcyclohexyl) methoxy-4 '-(trans-4-propylcyclohexyl) methoxy-2,2', 3, 9.3 g of 3′-tetrafluorobiphenyl (Ig) was obtained.
MS m / z: 520 (M ⁺ , 100)
Phase transition temperature (℃) Cr 119 N 171 I

Claims (7)

Formula (I)

Wherein R ¹ and R ² are each independently an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, an alkoxyl group having 1 to 12 carbon atoms or an alkenyloxy having 2 to 12 carbon atoms. Each of one or more hydrogen atoms may be independently substituted with a fluorine atom, and each —CH ₂ — group may independently be —O—, —CO—, —COO— or -OCO- may be substituted,
A ¹ and A ² are each independently a trans-1,4-cyclohexylene group, a trans-1,3-dioxane-2,5-diyl group, a pyridine-2,5-diyl group, or a pyrimidine-2,5. -Represents a diyl group or an unsubstituted 1,4-phenylene group in which one or more hydrogen atoms may be substituted with fluorine atoms,
X ¹ and X ² each independently represent —CH ₂ — or —CF ₂ —,
Y ¹ and Y ² are a single bond, —OCH ₂ —, —CH ₂ O—, —C ₂ H ₄ —, —C ₄ H ₈ —, —COO—, —OCO—, —CH═CH—, — CF = CF—, —CF ₂ O—, —OCF ₂ —, —CF ₂ CF ₂ — or —C≡C—, wherein an oxygen atom is directly present in R ¹ —Y ¹ — and —Y ² —R ² Never combine,
m and n represent 0, 1 or 2, m + n represents 1 or 2,
When m or n represents 2, a plurality of A ¹ , A ² , Y ¹ and Y ² may be the same or different. ) A fluorobenzene derivative represented by In the general formula (I), A ¹ and A ² are each independently a trans-1,4-cyclohexylene group or unsubstituted or one or more hydrogen atoms may be substituted with fluorine atoms, The fluorobenzene derivative according to claim 1, which represents a 4-phenylene group. In the general formula (I), ^{Y 1} and ^{Y 2} is a single _{bond, -OCH 2 -, - CH 2} O -, - C 2 H 4 -, - CF 2 O- or -OCF ₂ - Claim 1 representing the Or the fluorobenzene derivative of 2. The fluorobenzene derivative according to any one of claims 1 to 3, wherein m + n represents 1 in the general formula (I). R ¹ and R ² each independently represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, an alkoxyl group having 1 to 8 carbon atoms or an alkenyloxy group having 2 to 8 carbon atoms. Item 5. The fluorobenzene derivative according to any one of Items 1 to 4. A liquid crystal composition comprising one or more compounds represented by formula (I) according to claim 1. A liquid crystal device comprising the liquid crystal composition according to claim 6 as a constituent element.