JP5526686B2 - Difluorobenzene derivatives and liquid crystal compositions containing the same. - Google Patents

Description

  The present invention is a difluorobenzene derivative useful as an electro-optical liquid crystal display material, and a liquid crystal composition containing the same, having a negative dielectric anisotropy, a low rotational viscosity coefficient, and good storage stability at low temperatures, Further, the present invention relates to a liquid crystal display element using the same.

  Liquid crystal display elements are currently widely used because of their excellent features such as low power consumption and thin display. Conventional liquid crystal display device display methods include TN (twisted nematic), STN (super twisted nematic), or active matrix (TFT: thin film transistor) based on TN, which has a positive dielectric anisotropy value. The liquid crystal composition is used. However, one of the disadvantages of these display methods is a narrow viewing angle, and with the increasing demand for larger liquid crystal panels in recent years, the improvement has become a major issue.

  In recent years, display methods such as vertical alignment and IPS (in-plane switching) have been 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 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. Conventionally, a liquid crystal composition having a negative dielectric anisotropy has been produced as a compound having a 2,3-difluorophenylene group (Patent Document 1), and a liquid crystal composition using the compound has been developed (Patent Document 2). ). However, these compounds are not sufficiently soluble in the liquid crystal composition and have low storage stability at low temperatures, and thus have problems such as precipitation when the liquid crystal composition is at low temperatures. Moreover, although the dielectric anisotropy of the liquid crystal composition to which these compounds are added is negative, its absolute value is not sufficiently large, and further improvement has been demanded. Furthermore, when a liquid crystal display element is used for moving image display, there is a problem that sufficient moving image display quality cannot be obtained if the response speed of the liquid crystal composition is low. In order to increase the response speed, there is a strong demand for a liquid crystal composition having a small rotational viscosity coefficient. However, the rotational viscosity coefficient of a liquid crystal composition to which a conventional compound is added is not sufficiently small to meet the requirements, and further improvements are required. It was sought after.

  On the other hand, cyclohexane derivatives are already known as liquid crystal compounds having no alkyl terminal chain (Patent Document 3), but these compounds are ferroelectric liquid crystal materials, and compounds having a hetero ring such as a pyridine skeleton in the molecule. It is also described that it has the effect of expanding the temperature range of the chiral smectic C phase. In general, a compound having a heterocyclic ring has a low specific resistance value and cannot be added to a liquid crystal composition for TFT which requires a high specific resistance value. Furthermore, since the chiral smectic C phase, which is a liquid crystal phase existing at a lower temperature than the nematic phase, is stabilized, it is considered that the lower limit temperature of the nematic phase is increased and the nematic phase temperature range is narrowed. For this reason, it has not been studied as a liquid crystal composition material for a vertical alignment method driven by a nematic phase or for IPS. In addition, a compound having a 2,3-difluorophenylene group and a negative dielectric anisotropy has not been studied.

Japanese translation of PCT publication No. 2-503441 (page 8 example) JP 10-176167 A (Example of page 10) Japanese Unexamined Patent Publication No. 6-312959

  The problem to be solved by the present invention is to provide a compound having a negative dielectric anisotropy and a large absolute value, and a good compatibility with other liquid crystal compounds. An object of the present invention is to provide a liquid crystal composition and a display device that do not cause precipitation and have a small rotational viscosity coefficient.

  As a result of studying various difluorobenzene derivatives, nematic liquid crystal compositions and display elements using the same, the present inventors have completed the present invention.

  The present invention relates to general formula (I)

(In the formula, R represents an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 7 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, or an alkenyloxy group having 2 to 7 carbon atoms; Represents a cyclohexyl group or a phenyl group which may be substituted with a fluorine atom, B represents a trans-1,4-cyclohexylene group or a 1,4-phenylene group which may be substituted with a fluorine atom, X ¹ And X ² each independently represents a single bond, —C ₂ H ₄ —, —CH ₂ O—, —CF ₂ O—, —C ₃ H ₆ O—, and —C ₄ H ₈ —. The present invention provides a difluorobenzene derivative, a liquid crystal composition containing one or more thereof, and a liquid crystal display device using the same.

  The difluorobenzene derivative of the present invention has a negative dielectric anisotropy and a large absolute value, good compatibility with other liquid crystal compounds, and a liquid crystal composition containing it has storage stability at low temperatures. Therefore, it is useful as a constituent member of a liquid crystal composition for a vertical alignment method, IPS or the like. In addition, the liquid crystal composition of the present invention has a characteristic that the dielectric anisotropy is negative and its rotational viscosity coefficient is small, and a display element using the liquid crystal composition is useful as a liquid crystal display element such as a vertical alignment type or IPS is there.

In the present invention, R in the general formula (I) is preferably a linear alkyl group having 1 to 8 carbon atoms or a linear alkoxyl group having 1 to 8 carbon atoms. Group, propyl group, butyl group, pentyl group, vinyl group, 2-propenyl group and 3-butenyl group are more preferable. To increase the absolute value of dielectric anisotropy, methoxy group, ethoxy group, propoxy group, butoxy group And a pentyloxy group are more preferred. A represents a cyclohexyl group or a phenyl group which may be substituted with a fluorine atom, but a cyclohexyl group is preferable for improving the solubility, a phenyl group is preferable for increasing the refractive index anisotropy, and a different dielectric constant. In order to increase the absolute value of the isotropic property, a phenyl group in which 1 or 2 positions out of 2 or / and 3 positions on the phenyl group are substituted with a fluorine atom is preferable. B represents a trans-1,4-cyclohexylene group or a 1,4-phenylene group which may be substituted with a fluorine atom, but a cyclohexyl group is preferable for improving the solubility, and the refractive index anisotropy is increased. In order to increase the absolute value of dielectric anisotropy, a phenyl group in which one or two positions on the phenyl group are substituted with fluorine atoms is preferable. X ¹ represents a single bond, —C ₂ H ₄ —, —CH ₂ O—, —CF ₂ O—, —C ₃ H ₆ O— and —C ₄ H ₈ —, but in order to improve solubility single _{bond, -C 2 H 4 -, -} CH 2 O -, - CF 2 O- and -C ₃ H ₆ O-is preferably a single bond to lower the viscosity, -C ₂ H ₄ - and -C ₄ H ₈ -is preferable, and a single bond is more preferable. X ² is a single _{bond, -C 2 H 4 -, -} CH 2 O -, - CF 2 O -, - C 3 H 6 O- and -C ₄ H ₈ - represents a absolute dielectric anisotropy -CH ₂ O to increase the value -, - CF ₂ O- and -C ₃ H ₆ O- are preferable, in order to improve the solubility is a single _{bond, -C 2 H 4 -, -} CH 2 O- And -CF ₂ O- are preferable, and a single bond, -C ₂ H ₄ -and -C ₄ H ₈ -are preferable for decreasing the viscosity.

  The liquid crystal composition using one or two or more compounds represented by the general formula (I) is not particularly limited, but other liquid crystal compositions containing the compound represented by the general formula (I). As a component of general formula (II)

(In the formula, R ^a represents a linear alkyl group having 1 to 7 carbon atoms, R ^b represents a linear alkyl group having 1 to 7 carbon atoms, or a linear alkoxyl group having 1 to 7 carbon atoms. represents a straight-chain alkenyl group or a linear alkenyloxy group having a carbon number of 3 to 7 2-7 carbon atoms, p1 represents 0 or 1, M ^a and M ^b are each independently a single bond _{, -CH 2 CH 2 -, -} CH = CH -, - OCH 2 -, - CH 2 O -, - OCF 2 -, - CF 2 O -, - OCO- or represents COO-, G ^a trans - 1,4-cyclohexylene group or a 1,4-phenylene group optionally substituted by 1 to 2 fluorines)), a compound represented by the general formula (III)

(In the formula, R ^c represents a linear alkyl group having 1 to 7 carbon atoms, R ^d is a linear alkyl group having 1 to 7 carbon atoms, and a linear alkoxyl group having 1 to 7 carbon atoms. Represents a linear alkenyl group having 2 to 7 carbon atoms or a linear alkenyloxy group having 2 to 7 carbon atoms, p2 represents 0 or 1, and M ^c and M ^d are each independently a single bond , -CH ₂ CH _2- , -CH = CH-, -OCH _2- , -CH ₂ O-, -OCF _2- , -CF ₂ O-, -OCO- or COO-, and G ^b is trans- 1,4-cyclohexylene group or a 1,4-phenylene group optionally substituted by 1 to 2 fluorines)), a compound represented by the general formula (IV)

(In the formula, R ^e represents a linear alkyl group having 1 to 7 carbon atoms or a linear alkenyl group having 2 to 7 carbon atoms, and R ^f represents a linear alkyl group having 1 to 12 carbon atoms. Represents a linear alkenyl group having 2 to 12 carbon atoms, a linear alkoxyl group having 1 to 12 carbon atoms or a linear alkenyloxy group having 2 to 12 carbon atoms, p3 represents 0 or 1 , ^Me and M ^f each independently represents a single bond, —OCO—, —COO— or CH ₂ CH ₂ —, and G ^c represents a trans-1,4-cyclohexylene group or a 1,4-phenylene group. And a compound having a dielectric anisotropy of substantially 0. Furthermore, general formula (V), general formula (VI), general formula (VII) and general formula (VIII)

(In the formula, R ^g , R ⁱ , R ^j , R ^k and R ⁿ each independently represent a linear alkyl group having 1 to 7 carbon atoms or a linear alkenyl group having 2 to 7 carbon atoms. , R ^h , R ^l and R ^m are each independently a linear alkyl group having 1 to 7 carbon atoms, a linear alkenyl group having 2 to 7 carbon atoms, or a straight chain having 1 to 7 carbon atoms. Represents an alkoxyl group or a linear alkenyloxy group having 2 to 7 carbon atoms, X ^a represents ^a hydrogen atom or a fluorine atom, p4, p5 and p6 each independently represents 0 or 1, p7 and p8 represent Although each independently represent 0, 1 or 2, the sum of p7 and p8 is 1 or ^{2, M g, M h,} M i, M j, M k, M l and M ^m is each independently Single bond, -CH ₂ CH _2- , -CH = CH-, -OCH _2- , -CH ₂ O-, -OCF _2- , -CF ₂ O-, -OCO- or COO-, and M ⁿ represents single bond or CH ₂ CH ₂ - ^{represents, G d, G e, G} f, G g and G ^h are each independently trans-1,4 Shikurohe From cyclohexylene or 1 represents two which may be optionally 1,4-phenylene group substituted by fluorine atoms, G ^g, G ^h, if the M ^m and M ⁿ there are a plurality, even they are the same One or two or more compounds selected from the group consisting of compounds represented by the formula (1) may be added.

  Furthermore, an optically active compound, a stabilizer, a monomer, an antistatic agent and the like can be added as required.

In the liquid crystal composition of the present invention, Ra in the general formula (II) is preferably ^a methyl group, an ethyl group, a propyl group, a butyl group, or a pentyl group. R ^b is preferably a linear alkyl group having 1 to 7 carbon atoms or a linear alkoxyl group having 1 to 7 carbon atoms, methyl group, ethyl group, propyl group, butyl group, pentyl group, methoxy group, ethoxy group. Group, propoxy group, butoxy group and pentyloxy group are more preferred. p1 is preferably 0 in consideration of solubility in the liquid crystal composition, and 1 is preferable in consideration of expansion of the liquid crystal phase temperature range. M ^a and M ^b are each independently a single _{bond, -CH 2 CH 2 -, -} CH 2 O -, - CF 2 O- or -COO- are preferred. Ga is preferably ^a trans-1,4-cyclohexylene group.

  The general formula (II) includes a large number of compounds, but the following general formula (II-1) to general formula (II-15)

(In the formula, R ¹ represents a linear alkyl group having 1 to 5 carbon atoms, and R ² represents a linear alkyl group having 1 to 5 carbon atoms or a linear alkoxyl group having 1 to 4 carbon atoms. The compound represented by this is preferable.

In the liquid crystal composition of the present invention, R ^c in the general formula (III) is preferably a linear alkyl group having 2 to 7 carbon atoms. R ^d is preferably a linear alkyl group having 1 to 5 carbon atoms or a linear alkoxyl group, and a linear alkyl group having 1 to 4 carbon atoms or a linear alkoxyl group having 1 to 4 carbon atoms. Particularly preferred. One of M ^c and M ^d is preferably a single bond, and the other is preferably a single bond, —CH ₂ CH ₂ —, —CH ₂ O— or —COO—.

  The general formula (III) includes a large number of compounds, but the following general formula (III-1) to general formula (III-9)

(In the formula, R ³ represents a linear alkyl group having 1 to 7 carbon atoms, and R ⁴ represents a linear alkyl group having 1 to 5 carbon atoms or a linear alkoxyl group having 1 to 4 carbon atoms. The compound represented by this is preferable.

In the liquid crystal composition of the present invention, the general formula R ^e is a linear alkyl group having 2 to 7 carbon atoms in the (IV), from 2 to 5 carbon atoms 1 alkenyl group or 3 carbon atoms 4 or 5 -An alkenyl group is preferable, an ethyl group, a propyl group, a butyl group, or a pentyl group is more preferable as a linear alkyl group, and a vinyl group or a trans-1-propenyl group is more preferable as a 1-alkenyl group, The group is more preferably a 3-butenyl group or a trans-3-pentenyl group. R ^f is a linear alkyl group having 1 to 7 carbon atoms, a 1-alkenyl group having 2 to 5 carbon atoms, a 3-alkenyl group having 4 to 5 carbon atoms, or a linear chain having 1 to 3 carbon atoms. Alkoxyl groups are preferred. When ^Me is present, at least one of ^Me and ^Mf is preferably a single bond.

  The compounds represented by the general formula (IV) include the following general formulas (IV-1) to (IV-14)

Wherein R ⁵ and R ⁶ are each independently a linear alkyl group having 1 to 7 carbon atoms, a 1-alkenyl group having 2 to 3 carbon atoms, or a 3-alkenyl group having 4 or 5 carbon atoms. R ⁷ represents a linear alkyl group having 1 to 5 carbon atoms or a linear 2-alkenyl group having 3 or 4 carbon atoms, and R ⁸ is a linear alkyl group having 1 to 3 carbon atoms. Group or a 4-alkenyl group having 4 or 5 carbon atoms, and R ⁹ represents a linear alkyl group having 1 to 3 carbon atoms or a linear 2-alkenyl group having 3 or 4 carbon atoms.) A compound represented by general formula (IV-1), general formula (IV-2), general formula (IV-3), general formula (IV-5) or general formula (IV-6) is preferred. Are particularly preferred.

  In the liquid crystal composition of the present invention, the compound represented by the general formula (I) is preferably contained in the composition at a lower limit of 1% (hereinafter,% in the composition represents mass%) or more, and 5% It is more preferably contained, more preferably 10% or more, preferably 20% or more, preferably 35% or more, and more preferably 50% or more. The upper limit is more preferably 95% or less, preferably 90% or less, preferably 80% or less, preferably 65% or less, and more preferably 50% or less. .

  The compound represented by the general formula (II) is preferably contained in an amount of 1% to 50%, more preferably 2% to 30%. The compound represented by the general formula (III) is preferably contained in an amount of 1% to 50%, more preferably 2% to 40%.

In the general formula (V) to the general formula (VIII), R ^g , R ⁱ , R ^j , R ^k and R ⁿ are preferably linear alkyl groups having 2 to 7 carbon atoms. R ^h , R ^l and R ^m are preferably a linear alkyl group having 1 to 5 carbon atoms and a linear alkoxyl group. M ^g and M ^h , M ⁱ and M ^j , M ^k and M ^l , M ^m and M ⁿ are each independently a single bond, -CH ₂ CH _2- , -CH = CH-, -OCH ₂ -,- Represents CH ₂ O—, —OCF ₂ —, —CF ₂ O— or —COO—, preferably one is a single bond and the other is a single bond, —CH ₂ CH ₂ — or —COO—. It is preferable.

In the liquid crystal composition of the present invention thus obtained, the nematic phase upper limit temperature (T _NI ) is preferably 70 ° C. or higher, more preferably 75 ° C. or higher, and the nematic phase lower limit temperature (T _{> N} ) is −20 ° C. or lower. Preferably there is.

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

  (Production method 1) Alcohol (IX)

(Wherein A, B and X ¹ represent the same meaning as A, B and X ¹ in formula (I), p represents 0 or 1), pyridine, triethylamine, 4- (N, N In the presence of a base such as (dimethylamino) pyridine or diazabicyclooctane, benzenesulfonyl chloride, p-toluenesulfonyl chloride, methanesulfonyl chloride or trifluoromethanesulfonyl chloride is allowed to act, or hydrobromic acid under sulfuric acid acidity, Either hydroiodic acid, thionyl chloride, thionyl bromide, phosphorus trichloride, phosphorus pentachloride, phosphorus tribromide, or carbon tetrachloride in the presence of triphenylphosphine, By reacting carbon tetrabromide, the general formula (X)

(Expressed in the formula, A, B and X ¹ A in formula (I), the same meaning as B and X ^1, p represents 0 or 1, Y is chlorine, bromine, iodine, benzenesulfonyl group, p -Represents a leaving group such as a toluenesulfonyl group, a methanesulfonyl group or a trifluoromethanesulfonyl group). The compound represented by the general formula (X) and the general formula (XI)

(Wherein R represents the same meaning as R in general formula (I).) The phenol represented by metal sodium, metal potassium, metal cesium, or a carbonate, hydroxide, hydride thereof, etc. By reacting, general formula (I-1)

(Wherein A, B, X ¹ and R represent the same meaning as A, B, X ¹ and R in formula (I), and p represents 0 or 1). Can do.

  (Manufacturing method 2) General formula (IX)

(Wherein, A, B and X ¹ represents in the general formula (I) A, the same meaning as B and X ^1, p represents 0 or 1.) And a compound represented by the general formula (XI)

(Wherein R represents the same meaning as R in general formula (I)), by reacting the compound represented by general formula (I-1) in the presence of azodicarboxylic acid ester and triphenylphosphine.

(Wherein A, B, X ¹ and R represent the same meaning as A, B, X ¹ and R in formula (I), and p represents 0 or 1). Can do.

  (Production method 3) General formula (XII)

Carboxylic (wherein, A, B and X ¹ represents A in formula (I), the same meaning as B and X ^1, Z is representing. A leaving group such as chlorine, bromine and iodine) represented by An acid derivative and a phenol represented by the general formula (XI) are reacted in the presence of a base to give a general formula (XIII)

(Wherein A, B, X ¹ and R represent the same meaning as A, B, X ¹ and R in formula (I)). This is treated with Lawesson's reagent, and further fluorinated with a fluorinating agent such as hydrogen fluoride-pyridine in the presence of an oxidizing agent such as N-bromosuccinimide, and then represented by the general formula (I-2)

(Wherein, A, B, X ¹ and R have the same meaning as A, B, X ¹ and R in formula (I)) can be obtained.

  (Production method 4) General formula (XIV)

(Wherein, A and X ¹ in the general formula (I) represent the same meaning as A and X ^1.) Cyclohexanone represented by the general formula (XV)

(In the formula, R represents the same meaning as R in the general formula (I).) After acting the Grineer reagent represented by the formula (I-3)

It can be obtained (In the formulas, A, X ¹ and R A in formula (I), represents. The same meanings as X ¹ and R) a compound represented by.

  (Production Method 5) In the production method 4, instead of the cyclohexanone represented by the general formula (XIV), the general formula (XVI)

(Expressed in the formula, A, B, A in X ¹ and R are the general formula (I), B, the same meaning as X ¹ and R, p represents 0 or 1.) Using an aldehyde represented by Except for the general formula (I-4)

(Wherein A, B, X ¹ and R represent the same meaning as A, B, X ¹ and R in formula (I), and p represents 0 or 1). Can do.

  (Production method 6) General formula (XVII)

(Wherein, A and X ¹ have the same meanings as A and X ¹ in the general formula (I), W is represents optionally substituted 1,4-phenylene group with a fluorine atom, p is 0 or 1 Y represents a leaving group such as chlorine, bromine, iodine, benzenesulfonyl group, p-toluenesulfonyl group, methanesulfonyl group or trifluoromethanesulfonyl group) and a general formula (XVIII)

(Wherein R represents the same meaning as in general formula (I)), a boronic acid derivative represented by tetrakistriphenylphosphine palladium (0), palladium (II) acetate, bis (triphenylphosphine) (Fino) Palladium such as palladium (II), or by carrying out a coupling reaction under basic conditions in the presence of a nickel-based transition metal catalyst, the general formula (I-5)

(In the formulas, A, X ¹ and R are as defined A, X ¹ and R in the general formula (I), W is represents optionally substituted 1,4-phenylene group with a fluorine atom, p Represents 0 or 1.) 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 structure of the compound was confirmed by nuclear magnetic resonance spectrum (NMR), mass spectrum (MS) and the like. Further, “%” in the compositions of the following examples and comparative examples means “mass%”.

The following abbreviations are used in compound descriptions.
Me: methyl group
Et: ethyl group
Pr: Propyl group
Bu: Butyl group
Pen: pentyl group
THF: tetrahydrofuran
DMF: N, N-dimethylformamide
Example 1 Production of trans-4- (4-ethoxy-2,3-difluorophenoxymethyl) bicyclohexyl (IA)

  5-0.0 g of 4-cyclohexylcyclohexanol was dissolved in 200 mL of acetic acid and cooled to 5 ° C., and 225 mL of sodium hypochlorite (8% aqueous solution) was added dropwise at 20 ° C. or lower. The reaction solution was stirred at 5 ° C. for 4 hours, and 160 mL of water was added. The aqueous layer was extracted with toluene, and the collected organic layer was washed with water and then saturated brine, and dried over anhydrous magnesium sulfate. The solvent was distilled off to give 4-cyclohexylcyclohexanone as a slightly yellow liquid (77.25 g).

  Next, 101.3 g of (methoxymethyl) triphenylphosphonium chloride was dissolved in 350 mL of THF. The solution was cooled to 5 ° C., 34.5 g of potassium tert-butoxy was added, and the mixture was stirred at 5 ° C. for 30 minutes. 41.0 g of 4-cyclohexylcyclohexanone was dissolved in 200 mL of THF and added dropwise to the reaction solution while maintaining the temperature at 10 ° C. or lower. The reaction solution was stirred at 5 ° C. for 3 hours, and then 25 mL of water was added dropwise. After the solvent was distilled off, 150 mL of hexane was added and stirred, and then the solid was removed by suction filtration. The organic layer was separated from the filtrate, and sodium hypochlorite (8% aqueous solution) was added and stirred. The organic layer was separated and washed with a mixed solvent of water and methanol (1: 1), water and saturated brine in that order, and then the solvent was distilled off to give 1-methoxy-1 '-(4-cyclohexyl) Cyclohexylidene was obtained as a pale yellow liquid (53 g).

  Next, 200 mL of THF and hydrochloric acid (10% aqueous solution) were added to the obtained 1-methoxy-1 ′-(4-cyclohexyl) cyclohexylidene, heated to reflux for 2 hours, and then cooled to room temperature. 150 mL of water was added, and the mixture was extracted twice with hexane. The collected organic layer was washed with water, saturated aqueous sodium bicarbonate, and saturated brine in this order, and the solvent was distilled off. Methanol (200 mL) and triethylamine (0.5 mL) were added, and the mixture was stirred at 5 ° C. Sodium hydroxide (10% aqueous solution) (20 mL) was added, and the mixture was stirred at 10 ° C for 1 hr. After neutralization by adding water and hydrochloric acid (10% aqueous solution), the precipitated solid was filtered. This solid was dried under reduced pressure to obtain trans-4-cyclohexylcyclohexylaldehyde as a white solid (41.57 g).

  Next, 18.8 g of the obtained trans-4-cyclohexylcyclohexyl aldehyde was dissolved in 60 mL of THF, and 8.20 g of sodium borohydride was added. After stirring at room temperature for 5 hours, 130 mL of water and 40 mL of toluene were added, the organic layer was separated, and further extracted with toluene. The collected organic layer was washed with hydrochloric acid (10% aqueous solution) and saturated brine in this order, and the solvent was distilled off to obtain trans-4-cyclohexylcyclohexylmethyl alcohol as a white solid (18.2 g).

  Next, 8.48 g of the obtained trans-4-cyclohexylcyclohexylmethyl alcohol and 5.9 mL of triethylamine were dissolved in 35 mL of dichloromethane, cooled to 5 ° C., and 3.90 mL of methanesulfonic acid chloride was added dropwise. After stirring at room temperature for 2 hours, the reaction was stopped by adding 27 mL of water. The organic layer was separated and further extracted with dichloromethane. The collected organic layer was washed with hydrochloric acid (10% aqueous solution), water and saturated brine, and dried over magnesium sulfate. The solvent was distilled off to obtain trans-4-cyclohexylcyclohexylmethyl methanesulfonate as a pale yellow solid (11.71 g).

Next, 6.63 g of 2,3-difluoro-4-ethoxyphenol and 10.67 g of potassium carbonate were dissolved in 80 mL of DMF and stirred at 40 ° C. for 5 minutes. To this reaction solution, 11.6 g of trans-4-cyclohexylcyclohexylmethyl methanesulfonate was added dropwise and stirred at 60 ° C. for 5 hours. The reaction solution was cooled to room temperature, and 300 mL of water, hydrochloric acid (3 mol / l aqueous solution), and 150 mL of toluene were added in this order. The organic layer was separated and further extracted with toluene. The collected organic layer was washed with water and saturated brine in this order. Purification using column chromatography (alumina / silica gel, toluene), the solvent was distilled off under reduced pressure, and recrystallization (acetone / methanol) gave trans-4- (4-ethoxy-2,3-difluoro as white crystals. Phenoxymethyl) bicyclohexyl (IA) was obtained (11.58 g).
Phase transition temperature (℃) Cry 64 Iso
¹ H-NMR (400MHz, CDCl ₃ ) δ: 0.92-1.26 (m, 11H), 1.42 (t, J = 7.0Hz, 3H), 1.63-1.78 (m, 8H), 1.90-1.93 (m, 2H) , 3.76 (d, J = 6.4Hz, 2H), 4.05 (q, J = 7.1Hz, 2H), 6.58-6.64 (m, 2H)
EI-MS: 352 [M ⁺ ]
Example 2 Production of trans-4- (3- (4-ethoxy-2,3-difluorophenoxy) propyl) bicyclohexyl (IB)

  Ethyl diethylphosphonoacetate (25.44 g) was dissolved in 160 mL of THF and then cooled to −30 ° C., and 72 mL of n-butyllithium (1.65 M hexane solution) was added dropwise at −25 ° C., followed by stirring at −30 ° C. for 1 hour. . 20.0 g of trans-4-cyclohexylcyclohexyl aldehyde obtained in Example 1 was dissolved in 40 mL of THF and added dropwise to this reaction solution at −30 ° C. After stirring at −30 ° C. for 30 minutes, the reaction solution was heated to 0 ° C., and 150 mL of water was added to stop the reaction. The organic layer was separated and further extracted with hexane. The collected organic layer was washed with water and saturated brine in this order, and the solvent was distilled off to obtain ethyl 3- (trans-4-cyclohexylcyclohexyl) acrylate as a pale yellow solid (26.67 g).

  Next, the obtained ethyl 3- (trans-4-cyclohexylcyclohexyl) acrylate was dissolved in ethanol in a pressure reactor, and 1.33 g of palladium / carbon (about 50% water wet product) was suspended in 10 mL of ethanol. And then added. The reaction vessel was purged with hydrogen (0.5 MPa) and stirred at room temperature for 10 hours. The reaction solution was filtered and the solvent was distilled off to obtain ethyl 3- (trans-4-cyclohexylcyclohexyl) propionate as a pale yellow solid (26.6 g).

  Next, the obtained ethyl 3- (trans-4-cyclohexylcyclohexyl) propionate was dissolved in 90 mL of THF and cooled to 5 ° C. 32.1 g of bis (2-methoxyethoxy) aluminum hydride (70% toluene solution) was added dropwise and stirred at room temperature for 2 hours, and then the reaction was stopped by adding 6 mL of water and 130 mL of hydrochloric acid (10% aqueous solution). Extracted twice with toluene, and the collected organic layer was washed with hydrochloric acid (10% aqueous solution), water and saturated brine in that order, the solvent was distilled off, and 3- (trans-4-cyclohexylcyclohexyl) propanol was a white solid. As (23.77 g).

Next, 7.31 g of the obtained 3- (trans-4-cyclohexylcyclohexyl) propanol, 5.67 g of 2,3-difluoro-4-ethoxyphenol and 8.52 g of triphenylphosphine were dissolved in 100 mL of THF, and diisopropyl azodicarboxylate ( Dissolved in 60 mL of THF) was added dropwise at 10 ° C. After stirring at room temperature for 6 hours, 2 mL of water was added to stop the reaction. The solvent was distilled off, hexane was added and stirred for 1 hour, and the resulting solid was removed by filtration. Purification using column chromatography (alumina / silica gel, hexane), the solvent was distilled off under reduced pressure, and recrystallization (acetone / methanol) gave trans-4- (3- (4-ethoxy-2, 3-Difluorophenoxy) propyl) bicyclohexyl (IB) was obtained (9.95 g).
Phase transition temperature (℃) Cry 50 Iso
¹ H-NMR (400MHz, CDCl ₃ ) δ: 0.87-1.21 (m, 12H), 1.29-1.34 (m, 2H), 1.42 (t, J = 7.0Hz, 3H), 1.65-1.81 (m, 11H) , 3.95 (t, J = 6.6Hz, 2H), 4.05 (q, J = 6.9Hz, 2H), 6.61 (m, 2H)
EI-MS: 380 [M ⁺ ]
Example 3 Production of 1- (trans-4- (2-cyclohexylethyl) cyclohexyl) difluoromethoxy-2,3-difluoro-4-propoxybenzene (IC)

A toluene solution of trans-4- (2-cyclohexylethyl) cyclohexylcarboxylic acid, 2,3-difluoro-4-propoxyphenol and trifluoromethanesulfonic acid was heated to reflux until no water was distilled off. After completion of the reaction, the mixture was washed with water and saturated brine in that order, and dried over anhydrous magnesium sulfate. After magnesium sulfate was filtered off, the solvent was distilled off to obtain a solid. A toluene solution of this solid and Lawesson's reagent (a mixture of anisole and phosphorus sulfide was heated until all the precipitate dissolved and hydrogen sulfide was not generated, cooled to room temperature, and then the precipitated solid was recrystallized from toluene). Was put into a pressure vessel and reacted at 150 ° C. 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. 1- (trans-4- (2-cyclohexylethyl) cyclohexyl) difluoromethoxy-2,3-difluoro-4-propoxy Benzene (IC) was obtained.
EI-MS: 430 [M ⁺ ]
Example 4 Production of 2,3-difluoro-4- (2- (2,3-difluoro-4-cyclohexylphenyl) ethyl) -1-propoxybenzene (ID)

Under a nitrogen atmosphere, the Grineer reagent prepared from 1-bromo-2,3-difluoro-4-propoxybenzene was added dropwise to a THF solution of 2,3-difluoro-4-cyclohexylphenylacetaldehyde with stirring. After completion of the reaction, the mixture was extracted with toluene, washed with water and saturated brine, 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 alcohol obtained after distilling off the solvent was dissolved in toluene, p-toluenesulfonic acid was added, and the mixture was heated to reflux until no distillation of water occurred. The extract was washed with water and saturated brine, and then dried over anhydrous magnesium sulfate. After magnesium sulfate was filtered off, the solvent was distilled off. The obtained solid was dissolved in ethyl acetate, Pd / C was added, and the mixture was stirred under hydrogen pressure. After filtering off Pd / C, the solvent was distilled off, and the residue was purified by silica gel column chromatography to obtain 2,3-difluoro-4- (2- (2,3-difluoro-4-cyclohexylphenyl) ethyl)- 1-propoxybenzene (ID) was obtained.
EI-MS: 394 [M ⁺ ]
(Example 5) Preparation of liquid crystal composition (1)
Host liquid crystal composition comprising the following composition (H)

Was prepared. Here, the physical properties of (H) are as follows.

Nematic phase upper limit temperature (T _NI ): 103.2 ℃
Dielectric anisotropy (Δε): 0.03
Refractive index anisotropy (Δn): 0.099
A liquid crystal composition (MA) comprising 80% of the base liquid crystal (H) and 20% of the compound represented by the formula (IA) obtained in Example 1 was prepared. The physical properties of this composition are as follows.

Nematic phase upper limit temperature (T _NI ): 85.4 ℃
Dielectric anisotropy (Δε): −1.29
Refractive index anisotropy (Δn): 0.095
Rotational viscosity coefficient (γ1): 110
In the liquid crystal composition (M-1) containing the compound represented by the formula (IA) of the present invention, the dielectric anisotropy (Δε) is greatly reduced as compared with the base liquid crystal (H) and negative values. became. This shows that the compound represented by the formula (IA) of the present invention has a negative dielectric anisotropy and an extremely large absolute value.

  The liquid crystal composition (M-A) was allowed to stand at −20 ° C. for 1 week, but showed a nematic phase. This shows that the compound represented by the formula (I-A) of the present invention has liquid crystallinity that can be used as a liquid crystal display material.

  Further, when the voltage holding ratio of the liquid crystal composition (M-A) was measured at 80 ° C., the voltage holding ratio of the host liquid crystal composition (H) was as high as 98% or more. This shows that the compound (I-A) of the present invention can be sufficiently used as a liquid crystal display material from the viewpoint of stability.

(Example 6) Preparation of liquid crystal composition (2)
A liquid crystal composition (MB) comprising 80% of the base liquid crystal (H) prepared in Example 5 and 20% of the compound represented by the formula (IB) obtained in Example 2 was prepared. The physical properties of this composition are as follows.

Nematic phase upper limit temperature (T _NI ): 84.6 ℃
Dielectric anisotropy (Δε): −1.15
Refractive index anisotropy (Δn): 0.095
Rotational viscosity coefficient (γ1): 122
In the liquid crystal composition (MB) containing the compound represented by the formula (IB) of the present invention, the dielectric anisotropy (Δε) is greatly reduced to a negative value as compared with the base liquid crystal (H). . This shows that the compound represented by the formula (IB) of the present invention has a negative dielectric anisotropy and an extremely large absolute value.

  Further, (M-B) was allowed to stand at −20 ° C. for 1 week, but showed a nematic phase. This shows that the compound represented by the formula (I-B) of the present invention has liquid crystallinity that can be used as a liquid crystal display material.

  Further, when the voltage holding ratio of (M-B) was measured at 80 ° C., it showed a high value of 98% 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.

(Comparative Example 1) Preparation of liquid crystal composition (3)
80% of base liquid crystal (H) prepared in Example 5 and formula (IE)

A liquid crystal composition (M-C) comprising 20% of the compound represented by the formula: The physical properties of this composition are as follows.

Nematic phase upper limit temperature (T _NI ): 105.7 ℃
Dielectric anisotropy (Δε): −1.19
Refractive index anisotropy (Δn): 0.097
Rotational viscosity coefficient (γ1): 128
It can be seen that the liquid crystal composition (MC) containing the compound represented by the formula (IE) has a smaller absolute value of dielectric anisotropy than the liquid crystal composition (MA) described in Example 5. In addition, precipitation was observed when the liquid crystal composition (MC) was allowed to stand at −20 ° C. for 1 week. From this, the liquid crystal composition (MC) containing the compound represented by the formula (IE) is compared with the liquid crystal composition (MA) described in Example 5 and the liquid crystal composition (MB) described in Example 6, It can be seen that the storage stability at low temperatures is poor.

  Further, it can be seen that the liquid crystal composition (M-C) has a larger rotational viscosity coefficient than the liquid crystal composition (M-A). From this, it can be seen that when the present compound is added to the liquid crystal composition, the dielectric anisotropy can be improved without deteriorating the rotational viscosity.

(Comparative Example 2) Preparation of liquid crystal composition (4)
80% of the base liquid crystal (H) prepared in Example 3 and the formula (IF)

A liquid crystal composition (M-D) comprising 20% of the compound represented by the formula: The physical properties of this composition are as follows.

Nematic phase upper limit temperature (T _NI ): 107.7 ℃
Dielectric anisotropy (Δε): −1.02
Refractive index anisotropy (Δn): 0.097
Rotational viscosity coefficient (γ1): 141
A liquid crystal composition (MD) containing a compound represented by the formula (IF) described in Non-Patent Document 1 includes a liquid crystal composition (MA) described in Example 5 and a liquid crystal composition (MB) described in Example 6. In comparison, it can be seen that the absolute value of the dielectric anisotropy is small. As described above, it can be seen that the addition of the compound of the present application to the liquid crystal composition can improve the dielectric anisotropy as compared with a conventional compound having a similar structure.

  Further, it can be seen that the liquid crystal composition (M-D) has a larger rotational viscosity coefficient than the liquid crystal composition (M-A) and the liquid crystal composition (M-B). From this, it can be seen that when the present compound is added to the liquid crystal composition, the dielectric anisotropy can be improved without deteriorating the rotational viscosity.

Claims (8)

Formula (I)

(In the formula, R represents an alkyl group having 1 to 8 carbon atoms, an alkoxyl group having 1 to 7 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, or an alkenyloxy group having 2 to 7 carbon atoms; represents a cyclohexyl group, B is trans-1,4-cyclohexylene group or an optionally substituted 1,4-phenylene group with a fluorine atom, X ¹ and X ² are each independently a single bond, - _{C 2 H 4 -, - CH} 2 O -, - CF 2 O -, - difluorobenzene derivative represented by the representative of the) - C ₃ H ₆ O- and -C ₄ H _8.. 2. The difluorobenzene derivative according to claim 1, wherein, in the general formula (I), R represents a linear alkyl group having 1 to 8 carbon atoms or a linear alkoxyl group having 1 to 7 carbon atoms. 3. The difluorobenzene derivative according to claim ¹ , wherein, in the general formula (I), X ¹ represents a single bond or —C ₂ H ₄ —. In the general formula (I), X ² is _{-C 2 H 4 -, - CH} 2 O -, - CF 2 O -, - C 3 H 6 O- or -C ₄ H ₈ - claims 1 to 3 representing the The difluorobenzene derivative according to any one of the above. The difluorobenzene derivative according to any one of claims 1 to 4 , wherein B represents a trans-1,4-cyclohexylene group in the general formula (I). In the general formula (I), R represents a linear alkoxyl group having 1 to 7 carbon atoms , B represents a trans-1,4-cyclohexylene group, X ¹ represents a single bond, and X ² represents- _2. The difluorobenzene derivative according to claim 1, which represents CH ₂ O—, —CF ₂ O— or —C ₃ H ₆ O—. A liquid crystal composition comprising one or more compounds represented by the general formula (I) according to any one of claims 1 to 6 . 8. A liquid crystal device comprising the liquid crystal composition according to claim 7 as a constituent element.