JP5493596B2 - Difluorobenzene derivatives and liquid crystal compositions containing the same. - Google Patents

Description

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

  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 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 a problem that the storage stability at a low temperature when the liquid crystal composition is obtained is not sufficient. 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.

  On the other hand, cyclohexane derivatives having no alkyl terminal chain are already known (Patent Document 3), but these compounds are ferroelectric liquid crystal materials and are described as having an effect of expanding the temperature range of the smectic C phase. . Therefore, there is a possibility that the nematic phase temperature range may be narrowed, and it has not been studied as a liquid crystal composition for a vertical alignment method or IPS driven by a nematic phase. In addition, there is no disclosure of an invention regarding a compound having a negative dielectric anisotropy such as a compound having a 2,3-difluorophenylene group.

  Moreover, in order for a liquid crystal display to display normally over a long period of time, the liquid crystal composition must be stable over a long period of time. However, there is a finding that a compound in which two ether oxygens are bonded to the same benzene ring, such as an alkoxy group at the 1-position of the benzene ring and a cyclohexylmethoxy group at the 4-position, is chemically unstable and cannot be used. (Non-Patent Document 1). Therefore, development of the compound as a liquid crystal material has not progressed.

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

Numata, “Trends in Liquid Crystal Materials”, Monthly Display, March 1998, Volume 4, Issue 3 (5 pages)

  A compound having a negative dielectric anisotropy and a good solubility in a liquid crystal composition, a negative dielectric anisotropy, no precipitation even at a low temperature, and a low viscosity liquid crystal composition It is providing a thing and a display element.

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

  The present invention relates to general formula (I)

Wherein R is a linear alkyl group having 1 to 7 carbon atoms, a linear alkoxyl group having 1 to 7 carbon atoms, a linear alkenyl group having 2 to 7 carbon atoms, or 2 to 2 carbon atoms. represents a 7 linear alkenyloxy group, X is a single _{bond, -C 2 H 4 -, -} CH 2 O -, - CF 2 O -, - C 3 H 6 O- and -C ₄ H ₈ - the And a liquid crystal composition containing one or more of them and a liquid crystal display device using the same.

  The difluorobenzene derivative of the present invention has a negative dielectric anisotropy, a good solubility in a liquid crystal composition, and a liquid crystal composition to which the difluorobenzene derivative is added has a good storage stability at a low temperature. It is useful as a component of liquid crystal compositions for systems, IPS, etc. Further, the liquid crystal composition of the present invention has a characteristic that the dielectric anisotropy is negative and its viscosity 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.

In the present invention, R in the general formula (I) is preferably a linear alkyl group having 1 to 7 carbon atoms or a linear alkoxyl group having 1 to 7 carbon atoms. Group, propyl group, butyl group and pentyl group are more preferable, and methoxy group, ethoxy group, propoxy group, butoxy group and pentyloxy group are more preferable for increasing the absolute value of dielectric anisotropy. X 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 value of the dielectric anisotropy greatly -CH ₂ to O -, - 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- is 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 the compound represented by the general formula (I) is not particularly limited as a coexisting compound, but as a component other than the liquid crystal composition containing the compound represented by the general formula (I), 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 radical 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 -, - represents OCO- or -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 3 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 3 to 12 carbon atoms, p3 represents 0 or 1 , M ^c and M ^d each independently represent a single bond, —OCO—, —COO— or —CH ₂ CH ₂ —, and G ^c represents a trans-1,4-cyclohexylene group or -1,4-phenylene. And a liquid crystal composition containing a compound represented by the formula: 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 represents 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 3 to 7 carbon atoms, X ^a represents ^a hydrogen atom or a fluorine atom, p4, p5 and p6 each independently represents 0 or 1, and p7 and p8 represent 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 are each independently a single Represents a bond, -CH ₂ CH _2- , -CH = CH-, -OCH _2- , -CH ₂ O-, -OCF _2- , -CF ₂ O-, -OCO- or -COO-, and M ⁿ is a single bond or represents -CH ₂ CH ₂ ^{-, G d, G e, G} f, G g and G ^h it Independently represent a trans-1,4-cyclohexylene group or one to two fluorine which may optionally be substituted 1,4-phenylene ^{group, G g, G h, M} m and M ⁿ there are a plurality of In this case, they may be the same or different.) A compound selected from the group consisting of compounds represented by the following formula can also be added.

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 compounds represented by the following general formulas (II-1) to (II-15) are preferable.

In the above formula, R ¹ represents a linear alkyl group having 1 to 5 carbon atoms, and R ⁷ is a linear alkyl group having 1 to 5 carbon atoms or a linear alkoxyl group having 1 to 4 carbon atoms. Represents.

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 — or —COO—.

  The general formula (III) includes a large number of compounds, but compounds represented by the following general formulas (III-1) to (III-7) are preferable.

In the above formula, R ³ represents a linear alkyl group having 1 to 7 carbon atoms, and R ⁴ is a linear alkyl group having 1 to 5 carbon atoms or a linear alkoxyl group having 1 to 4 carbon atoms. Represents.

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), 3 1-alkenyl group or a -C 4-5 2-5 carbon atoms -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.

  As the compound represented by the general formula (IV), compounds represented by the following general formula (IV-1) to general formula (IV-14) are preferable, and the general formula (IV-1), the general formula (IV- The compound represented by 2), general formula (IV-3), general formula (IV-5) or general formula (IV-6) is particularly preferred.

In the above formula, 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 to 5 carbon atoms. R ⁷ represents a linear alkyl group having 1 to 5 carbon atoms or a linear 2-alkenyl group having 3 to 4 carbon atoms, and R ⁸ is a linear alkyl group having 1 to 3 carbon atoms. A group or a 3-alkenyl group having 4 to 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 to 4 carbon atoms.

  In the liquid crystal composition of the present invention, the compound represented by the general formula (I) is preferably contained in the composition in an amount of 1% by mass (hereinafter,% in the composition represents mass%) and 50% or less. It is more preferable to contain 30% to 30%, and it is more preferable to contain 5 to 20%. 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 liquid crystal composition of the present invention, the general formula (V) ~ 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 3 to 7 carbon atoms, X ^a represents ^a hydrogen atom or a fluorine atom, p4, p5 and p6 each independently represents 0 or 1, and p7 and p8 represent each independently 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 are each independently a single Represents a bond, —CH ₂ CH ₂ —, —CH═CH—, —OCH ₂ —, —CH ₂ O—, —OCF ₂ —, —CF ₂ O—, —OCO— or —COO—, and M ⁿ represents Represents a single bond or --CH ₂ CH _2- , and G ^d , G ^e , G ^f , G ^g and G ^h are each independently trans-1,4-cyclohex Represents a silene group or a 1,4-phenylene group optionally substituted by 1 to 2 fluorines, and when there are a plurality of G ^g , G ^h , M ^m and M ⁿ , they are the same or different And may contain one or more compounds selected from the group consisting of compounds represented by:

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 70 ° C. or higher, more preferably 75 ° C. or higher, and the nematic phase lower limit temperature (T _{> N 2} ) is −20 ° C. or lower.

  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 p represents 0 or 1), in the presence of a base such as pyridine, triethylamine, 4- (N, N-dimethylamino) pyridine, diazabicyclooctane, benzenesulfonyl chloride, p-toluenesulfonyl chloride , Methanesulfonyl chloride or trifluoromethanesulfonyl chloride, etc., or hydrobromic acid, hydroiodic acid, sulfuric acid, thionyl chloride, thionyl bromide or phosphorus trichloride , Phosphorus pentachloride, phosphorus tribromide, or carbon tetrachloride, carbon tetrabromide in the presence of triphenylphosphine, and so on,

(Wherein p represents 0 or 1, Y represents a leaving group such as chlorine, bromine, iodine, benzenesulfonyl group, p-toluenesulfonyl group, methanesulfonyl group or trifluoromethanesulfonyl group). To obtain a compound. Obtained compound (X) and phenol (XI)

(Wherein R represents the same meaning as in general formula (I)) in the presence of metallic sodium, metallic potassium, metallic cesium, or a carbonate, hydroxide, hydride thereof, etc. Formula (I)

(Wherein p represents 0 or 1, and R represents the same meaning as in general formula (I)).

  (Manufacturing method 2) Alcohol (IX)

(Wherein p represents 0 or 1) and phenol (XI).

(Wherein R represents the same meaning as in general formula (I)), in the presence of azodicarboxylic acid ester and triphenylphosphine, to give a general formula (I-1)

(Wherein p represents 0 or 1, and R represents the same meaning as in general formula (I)).

  (Production method 3) Carboxylic acid derivative (XII)

(Wherein Z represents a leaving group such as chlorine, bromine and iodine) and phenol (XI) in the presence of a base to produce an ester (XIII)

(Wherein R represents the same meaning as in general 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, to give a general formula (I-2)

(Wherein, R represents the same meaning as in general formula (I)) can be obtained.

  (Production Method 4) Cyclohexanone (IX)

Grineer Reactant (X)

(In the formula, R represents the same meaning as in general formula (I).) After acting, dehydration with an acid catalyst and hydrogenation, general formula (I-3)

(Wherein, R represents the same meaning as in general formula (I)) can be obtained.

  (Production method 5) Alcohol (XI) instead of cyclohexanone (IX) in production method 4

(Wherein p represents 0 or 1), except that general formula (I-4) is used.

(Wherein p represents 0 or 1, and R represents the same meaning as in general formula (I)).

  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
Example 1 Production of 4- (3-cyclohexylpropoxy-1-ethoxy-2,3-difluorobenzene (IA)

  5-0.0 g of 3-cyclohexylpropanol and 46.4 g of triethylamine were dissolved in 200 mL of dichloromethane and then cooled to 5 ° C., and 46.3 g of methanesulfonic acid chloride was added dropwise at 10 ° C. or lower. The reaction solution was vigorously stirred for 5 hours at room temperature, water was added, and the organic layer was separated. The aqueous layer was extracted with dichloromethane, and the collected organic layer was washed with 1M hydrochloric acid, water and saturated brine in that order, and dried over anhydrous magnesium sulfate. The solvent was distilled off to give 3-cyclohexylpropyl methanesulfonate as a pale yellow liquid (73.0 g).

Next, 8.8 g of 4-ethoxy-2,3-difluorophenol and 13.9 g of potassium carbonate were dissolved in 80 mL of dimethylformamide, and stirred at 50 ° C. for 5 minutes, and 12.8 g of methanesulfonic acid-3-cyclohexylpropyl was added dropwise. did. The reaction solution was vigorously stirred at 60 ° C. for 3 hours, and 3M hydrochloric acid and toluene were added to separate the organic layer. 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. Purification using column chromatography (alumina / silica gel, toluene), distillation under reduced pressure (121-127 ° C., 20 Pa), and recrystallization (ethanol) gave 10.0 g of white crystals.
Phase transition temperature (℃) Cry 34 Iso
¹ H-NMR (400MHz, CDCl ₃ ) δ: 0.88-0.95 (m, 2H), 1.13-1.35 (m, 6H), 1.42 (t, J = 7.2Hz, 3H), 1.54-1.83 (m, 7H) , 3.95 (t, J = 6.8Hz, 2H), 4.06 (q, J = 7.1Hz, 2H), 6.61-6.65 (m, 2H)
EI-MS: 298 [M ⁺ ]
Example 2 Production of 1-butoxy-4-cyclohexylmethoxy-2,3-difluorobenzene (IB)

By using bromomethylcyclohexane in place of 3-cyclohexylpropyl methanesulfonate in Example 1 and 4-butoxy-2,3-difluorophenol in place of 4-ethoxy-2,3-difluorophenol, 1 -Butoxy-4-cyclohexylmethoxy-2,3-difluorobenzene was obtained.
Phase transition temperature (℃) <-20 Iso
¹ H-NMR (400MHz, CDCl ₃ ) δ: 0.97 (t, J = 7.4Hz, 3H), 1.02-1.05 (m, 2H), 1.18-1.32 (m, 3H), 1.50 (dd, J = 5.6 and 7.1Hz, 2H), 1.68-1.89 (m, 8H), 3.76 (d, J = 6.4Hz, 2H), 3.98 (t, J = 6.4Hz, 2H), 6.61 (m, 2H)
EI-MS: 298 [M ⁺ ]
Example 3 Production of 1-propoxy-4-cyclohexyldifluoromethoxy-2,3-difluorobenzene (IC)

2,3-difluorophenyl = cyclohexylcarboxylate and a toluene solution of Lawesson's reagent were 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 1-propoxy-4-cyclohexyldifluoromethoxy-2,3-difluorobenzene (IC).
EI-MS: 320 [M ⁺ ]
Example 4 Production of 1-propoxy-4- (2-cyclohexylethyl) -2,3-difluorobenzene (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 cyclohexylacetaldehyde 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 1-propoxy-4- (2-cyclohexylethyl) -2,3-difluorobenzene (ID).
EI-MS: 282 [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 90% of the base liquid crystal (H) and 10% of (IA) obtained in Example 1 was prepared. The physical properties of this composition are as follows.

Nematic phase upper limit temperature (T _NI ): 78.4 ℃
Dielectric anisotropy (Δε): −0.54
Refractive index anisotropy (Δn): 0.092
In the liquid crystal composition (M-1) containing the compound (IA) of the present invention, the dielectric anisotropy (Δε) was greatly reduced to a negative value as compared with the base liquid crystal (H). From this, it can be seen that the compound of the present invention (IA) has a negative dielectric anisotropy and an extremely large absolute value.

  Further, even when (M-A) was left at -20 ° C. for 1 week, a nematic phase was exhibited. 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 liquid crystallinity.

  Further, when the voltage holding ratio of (M-A) 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). As described in the background art, it has been said that a compound in which two ether oxygens are bonded to the same benzene ring is chemically unstable and cannot be used (Non-Patent Document 1), but the compound (IA) of the present invention is It can be seen that if the purity is sufficiently improved by purifying sufficiently, it 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 90% of the base liquid crystal (H) prepared in Example 5 and 10% of (IB) obtained in Example 2 was prepared. The physical properties of this composition are as follows.

Nematic phase upper limit temperature (T _NI ): 78.4 ℃
Dielectric anisotropy (Δε): −0.52
Refractive index anisotropy (Δn): 0.094
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). From this, it can be seen that the compound of the present invention (IB) has a negative dielectric anisotropy and an extremely large absolute value.

  Further, even when (M-A) was left at -20 ° C. for 1 week, a nematic phase was exhibited. 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 liquid crystallinity.

  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)
90% of base liquid crystal (H) prepared in Example 3 and the compound described in Non-Patent Document 1 (IE)

A liquid crystal composition (M-C) consisting of 10% was prepared. The physical properties of this composition are as follows.

Nematic phase upper limit temperature (T _NI ): 86.0 ℃
Dielectric anisotropy (Δε): −0.36
Refractive index anisotropy (Δn): 0.094
The liquid crystal composition (MC) containing the compound (IE) described in Non-Patent Document 1 has an absolute value of dielectric anisotropy as compared with (MA) described in Example 3 and (MB) described in Example 4. I understand that it is small.

(Comparative Example 2) Preparation of liquid crystal composition (4)
90% of the base liquid crystal (H) prepared in Example 3 and the compound described in Non-Patent Document 1 (IF)

A liquid crystal composition (M-D) comprising 10% was prepared. The physical properties of this composition are as follows.

Nematic phase upper limit temperature (T _NI ): 92.1 ℃
Dielectric anisotropy (Δε): −0.47
Refractive index anisotropy (Δn): 0.097
The liquid crystal composition (MD) containing the compound (IF) described in Non-Patent Document 1 has an absolute value of dielectric anisotropy as compared with (MA) described in Example 5 and (MB) described in Example 6. I understand that it is small. As described above, it has been found that the addition of the compound of the present invention to the liquid crystal composition can improve the dielectric anisotropy as compared with a conventional compound having a similar structure.

  Further, when (M-D) was left at -20 ° C. for 1 week, precipitation was observed. From this, the liquid crystal composition (MD) containing the compound (IF) described in Non-Patent Document 1 is more stable at low temperatures than (MA) described in Example 3 and (MB) described in Example 4. It turns out that the nature is inferior.

Claims (6)

Formula (I)

Wherein R is a linear alkyl group having 1 to 7 carbon atoms, a linear alkoxyl group having 1 to 7 carbon atoms, a linear alkenyl group having 2 to 7 carbon atoms, or 2 to 2 carbon atoms. represents a 7 linear alkenyloxy group, X is a single _{bond, -C 2 H 4 -, -} CH 2 O -, - CF 2 O -, - C 3 H 6 O- or -C ₄ H ₈ - the A difluorobenzene derivative represented by: 2. The difluorobenzene derivative according to claim 1, wherein, in the general formula (I), R represents a linear alkyl group having 1 to 7 carbon atoms or a linear alkoxyl group having 1 to 7 carbon atoms. _{3. The} general formula (I), wherein X represents —C ₂ H ₄ —, —CH ₂ O—, —CF ₂ O—, —C ₃ H ₆ O— or —C ₄ H ₈ —. Difluorobenzene derivative. In the general formula (I), R represents a linear alkoxyl group having 1 to 7 carbon atoms, and X represents -CH ₂ O-, -CF ₂ O-, or -C ₃ H ₆ O-. The difluorobenzene derivative according to any one of to 3. A liquid crystal composition comprising one or more compounds represented by the general formula (I) according to any one of claims 1 to 4. 6. A liquid crystal device comprising the liquid crystal composition according to claim 5 as a constituent element.