JP4941801B2 - Liquid crystal composition, display element and liquid crystal compound containing trifluoronaphthalene derivative, production method and production intermediate thereof - Google Patents

Description

  The present invention relates to a liquid crystal composition containing a trifluoronaphthalene derivative having a negative dielectric anisotropy and a large absolute value useful as an electro-optical liquid crystal display material, a method for producing the same, and a production intermediate thereof. The present invention relates to a liquid crystal display element.

  The liquid crystal display element is used in various electric appliances for home use, measuring instruments, automobile panels, word processors, electronic notebooks, printers, computers, televisions, etc., including clocks and calculators. Typical liquid crystal display methods include TN (twisted nematic), STN (super twisted nematic), DS (dynamic light scattering), GH (guest / host), and IPS (in-plane switching). Type, OCB (optical compensation birefringence) type, ECB (voltage controlled birefringence) type, VA (vertical alignment) type, CSH (color super homeotropic) type, FLC (ferroelectric liquid crystal), etc. . As a driving method, multiplex driving is generally used instead of conventional static driving, and a simple matrix method and recently an active matrix (AM) method driven by a TFT (thin film transistor) or MIM has become mainstream.

  In these display methods, the IPS type, ECB type, VA type, CSH type, and the like use a so-called n-type liquid crystal material having a negative dielectric anisotropy, unlike currently used TN type and STN type. Have Among these, VA type display by AM driving is currently most expected in application to a display element that requires a high speed and a wide viewing angle, such as a television.

  As a liquid crystal material, a great variety of compounds have been synthesized so far, and they are used according to the display method, driving method or use thereof. However, they are used for the display method such as the VA type. There are not so many compounds known for the n-type liquid crystal material. In particular, considering active matrix driving, n-type liquid crystal materials that can be used are limited to compounds having a 2,3-difluoro-1,4-phenylene group in the molecule (see Patent Document 1). Is the actual situation.

  In the display method such as the VA type, a wide operating temperature range is required in addition to the low voltage driving and the high-speed response as in the normal display method. In addition, an appropriate refractive index anisotropy (Δn) that matches the cell thickness is also required.

  In order to reduce the driving voltage, it is important that the absolute value of the dielectric anisotropy (Δε) of the liquid crystal composition is as large as possible. In the VA display, the Δε is −3 or less, preferably −4 or less. Further, in order to increase the response speed, it is necessary to reduce the viscosity of the liquid crystal material as much as possible.

  Further, in order to drive the active matrix, a high voltage holding ratio is required for the liquid crystal material. Although it is difficult to say that the relationship between the chemical structure of each compound and the voltage holding ratio has been completely clarified, a compound having a very strong group such as a cyano group or an ester bond in the molecule has a high voltage holding ratio. In many cases, even an ether bond is not preferred. However, as described above, if an attempt is made to increase the absolute value of dielectric anisotropy due to the need for a low driving voltage, the presence of a polar group is necessary, which greatly restricts the molecular design of the compound. .

As the operating temperature range, the nematic phase upper limit temperature (T _N-I ) is preferably at least 70 ° C. or higher, and the nematic phase lower limit temperature (T _−N ) is preferably at least −20 ° C. or lower.

  Further, although depending on the cell configuration (cell thickness, display mode, etc.), Δn is usually required to be about 0.08 to 0.10 in many cases.

  There is no liquid crystal compound that can satisfy these required characteristics alone. Therefore, the liquid crystal material is a liquid crystal composition prepared from the above-mentioned 2,3-difluoro-1,4-phenylene derivative mainly from many liquid crystal compounds ( Currently, Patent Document 2) is used.

  However, most of the 2,3-difluoro-1,4-phenylene derivatives known so far are compounds having other trans-1,4-cyclohexylene groups and 1,4-phenylene groups as other ring structures. However, there is a problem that these are not necessarily good in compatibility with other liquid crystal compounds. For this reason, it is not easy to prepare a liquid crystal composition having a wide temperature range, particularly a liquid crystal composition that hardly causes crystal precipitation or phase separation even when stored at a low temperature for a long time. However, it was necessary to increase the solubility and to lower the melting point of the composition by mixing a very wide variety of compounds.

  It is well known that the addition of liquid crystal compounds having different skeleton structures is effective in reducing the melting point of the liquid crystal composition. Therefore, in order to facilitate the preparation of a liquid crystal composition having a wide temperature range, a skeleton structure different from that of the conventional compound, in particular, a strong negative dielectric anisotropy can be contributed to the liquid crystal compound, and 2,3-difluoro- A new skeleton structure different from the 1,4-phenylene skeleton, for example, a fluorine-substituted naphthalene structure (see Patent Documents 3, 4 and 5) or a tetrahydronaphthalene structure (see Patent Documents 6 and 7), and other liquid crystal compounds There has been a demand for a liquid crystalline compound that is excellent in compatibility and can improve the characteristics as an n-type liquid crystal and expand the temperature range of the composition.

  Cited Document 4 shows a wide range of general formulas having this fluorine-substituted naphthalene skeleton, but there is no description of specific synthesis methods, examples, physical properties, and electro-optical properties of the present invention. It is hard to say anything that suggests anything.

Published Patent Publication No. 2-503441 Published Patent Publication No. 10-176167 German Patent Application Publication No. 19522167 German Patent Application Publication No. 19522195 Japanese Patent Publication No. 2001-31597 Japanese Patent Publication No. 2001-40354 German Patent Application Publication No. 19522145 Published Patent Publication No. 2001-19648

  The problem to be solved by the present invention is a dielectric anisotropy including a 6-alkyl-3,4,5-trifluoronaphthalene structure, which is a skeleton different from that of conventional compounds, and having excellent compatibility with other liquid crystal compounds. (Δε) is a negative liquid crystal compound, a method for producing the same, and a production intermediate thereof, a liquid crystal composition having a negative Δε and a wide temperature range using the same as a key component, and a VA type using the same The liquid crystal display element is provided.

  As a result of intensive studies to solve the above problems, the present invention has a negative Δε having a large absolute value and a compound having a 6-alkyl-3,4,5-trifluoronaphthalene skeleton, Excellent compatibility with liquid crystal compounds. By using this, it was found that a liquid crystal composition capable of achieving a high voltage holding ratio can be prepared in addition to low voltage driving and high speed response in a VA type liquid crystal display element, and the present invention was completed. .

  That is, the general formula (1)

(In the formula, R ^a represents a linear alkyl group having 2 to 7 carbon atoms, and R ^b represents a linear alkyl group having 2 to 5 carbon atoms). Contains 2 or more, general formula (5)

(In the formula, R ^m represents a linear alkyl group or alkenyl group having 1 to 7 carbon atoms, and R ⁿ represents a linear alkyl group, alkenyl group, alkoxyl group or alkenyloxy group having 1 to 12 carbon atoms. M6 represents 0 or 1, Ml and Mm each independently represent a single bond, —COO— or —CH ₂ CH ₂ —, and ring G represents a trans-1,4-cyclohexylene group or 1, It represents a 4-phenylene group.) A liquid crystal composition containing one or more compounds represented by formula (II) and having a dielectric anisotropy of -3 or less is provided. Provided are a compound represented by formula (1), a production method thereof, and a production intermediate. The present invention also provides a liquid crystal display element using the liquid crystal composition.

  By the combination of the liquid crystal compounds of the present invention, a liquid crystal composition having a negative dielectric anisotropy having a large absolute value, a wide nematic temperature range, and a suitable refractive index anisotropy was obtained. By using this composition, a highly reliable liquid crystal display element capable of maintaining a high voltage holding ratio up to a high temperature range is provided. This display is an active matrix of VA type, ECB type, IPS type, etc., particularly VA type. It is very practical as a driving liquid crystal display.

The liquid crystal composition in the present invention contains a compound represented by the general formula (1). In the general formula (1), R ^a represents a linear alkyl group having 2 to 7 carbon atoms, but ethyl. Group, propyl group, butyl group or pentyl group is preferred, and propyl group is particularly preferred. R ^b represents a linear alkyl group having 2 to 5 carbon atoms, preferably an ethyl group or a propyl group, and particularly preferably a propyl group. The cyclohexane ring is in a trans configuration.

The liquid crystal composition of the present invention contains a compound represented by the general formula (5). In the general formula (5), R ^m represents a linear alkyl group or alkenyl group having 1 to 7 carbon atoms. And a linear alkyl group having 2 to 7 carbon atoms, a 1-alkenyl group having 2 to 5 carbon atoms, or a 3-alkenyl group having 4 to 5 carbon atoms is preferable. An ethyl group, a propyl group, a butyl group and a pentyl group are more preferable. As the 1-alkenyl group, a vinyl group and a trans-1-propenyl group are more preferable. As the 3-alkenyl group, a 3-butenyl group and trans-3-pentenyl group are preferable. Groups are more preferred. R ⁿ represents a linear alkyl group having 1 to 12 carbon atoms, an alkenyl group, an alkoxyl group, or an alkenyloxy group, but a linear alkyl group having 1 to 7 carbon atoms, 1 having 2 to 5 carbon atoms. An alkenyl group, a 4-alkenyl group having 4 to 5 carbon atoms, and a straight-chain alkoxyl group having 1 to 3 carbon atoms, particularly ethyl when ring C represents a trans-1,4-cyclohexylene group. Group, propyl group, butyl group, pentyl group, vinyl group, trans-1-propenyl group, 3-butenyl group, trans-3-pentenyl group, methoxy group, ethoxy group or propoxy group are preferred, and one ring C is present. In the case of a 1,4-phenylene group which may be substituted with fluorine, in addition to the above, an allyloxy group and a crotyloxy group are also preferable. m6 represents 0 or 1. Ml and Mm each independently represent a single bond, —COO— or —CH ₂ CH ₂ —, but when Ml is present, at least one of Ml and Mm is preferably a single bond. Ring G represents a trans-1,4-cyclohexylene group or a 1,4-phenylene group.

  As the compound represented by the general formula (5), compounds represented by the following general formula (5a) to general formula (5m) are preferable. The general formula (5a), the general formula (5b), and the general formula (5d) Or the compound represented by general formula (5e) is especially preferable.

In the above formula, R ⁷ and R ⁸ are each independently a linear alkyl group having 2 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 ⁹ 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 ¹⁰ represents 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 ¹¹ 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 (1) is preferably contained in the composition in an amount of 1% by mass (hereinafter,% in the composition represents% by mass) to 50% or less. It is more preferable to contain% -40%, and it is further more preferable to contain 4-30%. It is preferable to contain 1%-50% of the compound represented by General formula (2), and it is more preferable to contain 2%-40%.

  In the liquid crystal composition of the present invention, the general formula (2)

(Wherein R ^c represents an alkyl group having 1 to 7 carbon atoms, R ^d represents a linear alkyl group, alkoxyl group or alkenyloxy group having 1 to 7 carbon atoms, and m1 represents 0 or 1) And Ma and Mb each independently represent a single bond, —CH ₂ CH ₂ —, —OCF ₂ —, —CF ₂ O—, or —COO—, and ring B represents a trans-1,4-cyclohexylene group. Or a 1,4-phenylene group which may be substituted by 1 to 2 fluorines.) Containing one or more of 2,3-difluoro-1,4-phenylene derivatives represented by May be.

In the general formula (2), R ^c represents an alkyl group having 1 to 7 carbon atoms, and a linear alkyl group having 2 to 7 carbon atoms is preferable. R ^d represents a linear alkyl group having 1 to 7 carbon atoms, an alkoxyl group or an alkenyloxy group, preferably a linear alkyl group having 1 to 5 carbon atoms or a linear alkoxyl group, A linear alkyl group having 1 to 3 carbon atoms and a linear alkoxyl group having 1 to 3 carbon atoms are particularly preferable. m1 represents 0 or 1. Ma and Mb each independently represents a single bond, —CH ₂ CH ₂ —, —OCF ₂ —, —CF ₂ O—, or —COO—, and one of them is preferably a single bond, and the other is a single bond. It is preferably a bond, —CH ₂ CH ₂ — or —COO—. Ring B represents a trans-1,4-cyclohexylene group or a 1,4-phenylene group optionally substituted by 1 to 2 fluorine atoms. The refractive index anisotropy of the liquid crystal composition to be prepared ( Depending on Δn), a trans-1,4-cyclohexylene group is preferred when a small Δn is required, and a 1,4-phenylene group is preferred when a large Δn is required.

  The general formula (2) includes a large number of compounds, but compounds represented by the following general formulas (2a) to (2g) are preferable.

In the above formula, R ⁵ represents a linear alkyl group having 1 to 7 carbon atoms, and R ⁶ represents a linear alkyl group having 1 to 5 carbon atoms or a linear alkoxyl group having 1 to 3 carbon atoms. Represents.
In the liquid crystal composition of the present invention, the general formula (3a), the general formula (3b), the general formula (4a), and the general formula (4b)

(In the formula, R ^e , R ^g , R ⁱ and R ^k represent a linear alkyl group having 1 to 7 carbon atoms, and R ^f , R ^h and R ^l are linear chains having 1 to 7 carbon atoms. Represents an alkyl group, an alkoxyl group or an alkenyloxy group, R ^j represents a linear alkyl group having 1 to 7 carbon atoms, m2, m3, m4 and m5 represent 0 or 1, Mc and Md, Me And Mf, Mh and Mi, Mj and Mk each independently represents a single bond, —CH ₂ CH ₂ —, —OCF ₂ —, —CF ₂ O— or —COO—, and ring C, ring D, ring E And ring F represents a trans-1,4-cyclohexylene group or a 1,4-phenylene group optionally substituted by 1 to 2 fluorine atoms, wherein in (3a), the ring is represented by the general formula (1). And the compounds represented by 1) are also excluded. Ku may also contain two or more of them.

In General Formula (3a), General Formula (3b), General Formula (4a), and General Formula (4b), R ^e , R ^g , R ^i, and R ^k are linear alkyl groups having 1 to 7 carbon atoms. Although it represents, a C2-C7 linear alkyl group is preferable. R ^f , R ^h , and R ^l represent a linear alkyl group, alkoxyl group, or alkenyloxy group having 1 to 7 carbon atoms, but a linear alkyl group or linear alkoxyl group having 1 to 5 carbon atoms. Group is preferable, and a linear alkyl group having 1 to 3 carbon atoms and a linear alkoxyl group having 1 to 3 carbon atoms are particularly preferable. R ^j represents a linear alkyl group having 1 to 7 carbon atoms, preferably a linear alkyl group having 1 to 3 carbon atoms. m2, m3, m4 and m5 represent 0 or 1. Mc and Md, Me and Mf, Mh and Mi, Mj and Mk each independently represent a single bond, —CH ₂ CH ₂ —, —OCF ₂ —, —CF ₂ O— or —COO—, It is preferably a single bond, and the other is preferably a single bond, —CH ₂ CH ₂ — or —COO—. Ring C, ring D, ring E and ring F represent a trans-1,4-cyclohexylene group or a 1,4-phenylene group which may be substituted by 1 to 2 fluorine atoms. Depending on the refractive index anisotropy (Δn) of the product, a trans-1,4-cyclohexylene group is preferred when a small Δn is required, and a 1,4-phenylene group when a large Δn is required. Is preferred.

In the liquid crystal composition of the present invention thus obtained, the nematic phase upper limit temperature (T _N-I ) is 70 ° C. or higher, and the nematic phase lower limit temperature (T _N ) is −20 ° C. or lower. Further, the dielectric anisotropy (Δε) is −3 or less, and more preferably −4 or less.
The compound represented by the general formula (1) is represented by the general formula (6).

(Wherein R ^b represents the same meaning as in general formula (1)) and alkyl lithium (preferably n-butyl lithium or methyl lithium) to 6-alkyl-3,4,5-trifluoronaphthalene represented by formula (1) And lithiated, and the resulting organolithium compound is represented by the general formula (7)

(Wherein R ^a represents a linear alkyl group having 2 to 5 carbon atoms) and the resulting cyclohexanol derivative is dehydrated in the presence of an acid catalyst. Thus, a cyclohexene derivative can be synthesized by hydrogenating it and then isomerizing the cyclohexane ring into a trans isomer as necessary.

  The lithiation of 6-alkyl-3,4,5-trifluoronaphthalene and the reaction with cyclohexanone are carried out in a solvent under cooling. Solvents include ether solvents such as diisopropyl ether (IPE), tetrahydrofuran (THF), dimethoxyethane (DME), 1,4-dioxane, hydrocarbon solvents such as hexane, heptane, benzene, toluene, N, N-dimethyl. Aprotic polar solvents such as formamide (DMF), N, N-dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), hexamethylphosphoric triamide (HMPTA), tetramethylethylenediamine (TMEDA), or a mixed solvent thereof is suitable. It is. The reaction temperature is -10 ° C to -100 ° C, preferably -20 ° C to -80 ° C, more preferably -30 ° to -50 ° C.

  The dehydration of the cyclohexanol derivative is carried out in a solvent in the presence of an acid catalyst. The solvent is preferably a hydrocarbon solvent such as hexane, heptane, benzene, or toluene. The acid catalyst is a mineral acid such as sulfuric acid, p. -An organic acid such as toluenesulfonic acid or formic acid, or a weak base salt of a strong acid such as potassium hydrogen sulfate is preferred. The reaction is carried out by heating from room temperature to reflux of the solvent. When benzene or toluene is used as the solvent, heating to the reflux temperature facilitates removal of the purified water by azeotropy with the solvent. Therefore, it is particularly preferable.

  Hydrogenation of the cyclohexene is carried out under cooling to heating in the presence of a catalyst in a hydrogen atmosphere in a solvent. As the solvent, alcohols such as ethanol, methanol and isopropanol (IPA), ethers such as ethyl ether, IPE, DME and THF, hydrocarbons such as hexane, benzene and toluene, esters such as ethyl acetate and the like are preferable. The hydrogen pressure is carried out under normal pressure to increased pressure, and preferably normal pressure to 500 MPa. The reaction temperature is preferably 0 ° C to 100 ° C, more preferably 15 ° C to 50 ° C. The catalyst used is preferably a noble metal such as palladium, platinum or ruthenium supported on activated carbon, or a Raney catalyst such as Raney nickel, particularly preferably palladium or Raney nickel.

  In the reduced form obtained by hydrogenation, the cyclohexane ring usually has a mixture of trans and cis forms. When there are many trans isomers, it is possible to remove the cis isomer by recrystallization or the like and to isolate the trans isomer, but when the cis isomer content is high, isomerization to the trans isomer may be performed. preferable.

  Isomerization is carried out in a solvent in the presence of a strong base or a Lewis acid catalyst. Bases include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali metal alcoholates such as sodium methoxide, sodium ethoxide, and t-butoxy potassium, metal hydrides such as sodium hydride, alkyl lithium, lithium Organometallic reagents such as diisopropylamide (LDA) are preferred, and t-butoxy potassium is particularly preferred. As the Lewis acid, aluminum chloride, tin chloride, zinc chloride, zinc bromide, boron trifluoride ether complex and the like are preferable, and aluminum chloride is particularly preferable. The solvent is not particularly limited as long as it is inert to the catalyst used, but ethers such as ethyl ether, IPE, DME, and THF, aprotic polar solvents such as DMF, DMA, DMSO, HMPTA, and TMEDA, hexane , Hydrocarbons such as heptane, benzene and toluene, or a mixed solvent thereof is preferable. In the case of a Lewis acid catalyst, a chlorinated solvent such as dichloromethane and chloroform is also preferable. Although the reaction varies depending on the type of catalyst and solvent used, it is preferably under cooling to −80 ° C. to heating to the reflux temperature of the solvent.

  Here, the compound represented by the general formula (6) used as a starting material is a highly useful compound as a liquid crystal intermediate, and the present invention also provides this compound.

The compound represented by (6) is 3,4,5-trifluoronaphthalen-6-ol (this compound is obtained by fluorinating 3,4-difluoronaphthalen-6-ol and reducing it if necessary) Is converted to trifluoromethanesulfonic acid ester (triflate) with trifluoromethanesulfonic anhydride, then reacted with a terminal alkyne in the presence of a transition metal catalyst such as tetrakistriphenylphosphine palladium (0), and then the triple bond is reduced. Can be obtained. The transition metal catalyst is preferably a palladium (0) complex such as tetrakistriphenylphosphine palladium (0), a palladium (II) complex, a nickel (II) complex, or the like. The terminal alkyne varies depending on R ^b in the general formula (6). For example, propyne is used when R ^b is a propyl group, 1-butyne is used when it is a butyl group, and 1-pentyne is used when it is a pentyl group.

  Thus, although the compound represented by the general formula (1) is produced, the present invention also provides this production method.

  The compound represented by the general formula (1) has been synthesized for the first time by the present inventors, and its characteristics have been clarified. As described above, the compound (1) is included as a broad general formula. There are examples of possible reports.

  Cited Document 4 shows a wide range of general formulas having this trifluoronaphthalene skeleton, and it is also possible to derive the compound (1) by selecting a partial structure from the general formula. However, this patent originally aimed at a ferroelectric liquid crystal which is a smectic liquid crystal, and hardly mentions a nematic liquid crystal. In particular, a specific synthesis example of the compound (1) of the present invention and its There is no description of physical properties and electro-optical characteristics, and even a manufacturing method thereof is not disclosed, and it is difficult to say anything that suggests the present invention.

  On the other hand, in the cited document 5 by the present inventors, a series of compounds having a fluoronaphthalene skeleton are described together with the general formula, but like the compound represented by the general formula (1) of the present invention, 6- No compound is described which is linked directly to the cyclohexane ring at the 2-position of alkyl-3,4,5-trifluoronaphthalene. Furthermore, this publication does not describe a preparation example of a liquid crystal composition having a negative Δε using a 5,6-difluorotetrahydronaphthalene derivative, and among the 5,6-difluorotetrahydronaphthalene derivatives as in the present invention, It is not specifically mentioned which compound is particularly suitable for preparing a liquid crystal composition (n-type composition) having a wide Δε in a wide temperature range.

  Reference 6 describes a preparation example of a liquid crystal composition having a negative Δε using a compound having a fluoronaphthalene skeleton, and the compound represented by the general formula (1) of the present invention is a constituent compound thereof. Is not specifically described.

In the present invention, among the fluoronaphthalene derivatives, it has a structure of the general formula (1) directly bonded to the cyclohexane ring at the 2-position of 6-alkyl-3,4,5-trifluoronaphthalene, and (1 In which R ^a is ^a linear alkyl group having 2 to 7 carbon atoms and R ^b is a linear alkyl group having 2 to 5 carbon atoms is particularly effective for the preparation of the above liquid crystal composition. I found out. The present invention further provides a liquid crystal display device using the liquid crystal composition of the present invention, particularly a liquid crystal display device which is displayed in a VA (vertical alignment) mode suitable for a liquid crystal TV or the like.

EXAMPLES The present invention will be described in further detail with reference to examples below, but the present invention is not limited to these examples. Moreover, as above-mentioned,% in a composition represents the mass%.
Example 1 Synthesis of 6-propyl-3,4,5-trifluoronaphthalene (6-a)

  8.5 g of 5,5,6-trifluoronaphthalen-3-ol (this compound was obtained by reacting 2,3-difluorophenylacetic acid chloride with aluminum chloride and ethylene to obtain 5,6-difluorotetrahydronaphthalene-3- ON was aromatized with bromine and then added bromine was removed by catalytic reduction) was dissolved in 130 mL dichloromethane and stirred at 5 ° C. To this, 7.4 mL of trifluoromethanesulfonic anhydride and 7.4 mL of pyridine were slowly added dropwise at 5 to 10 ° C., and the mixture was further stirred at 5 ° C. for 1 hour.

  After slowly adding 15 mL of water and separating the aqueous layer, the organic layer was washed with 10% hydrochloric acid, saturated aqueous sodium hydrogen carbonate solution, water and saturated brine. After drying over anhydrous magnesium sulfate, the solvent was distilled off and the residue was purified by silica gel column chromatography (ethyl acetate / hexane = 1/20) to obtain 13.2 g of white crystals of triflate.

  The total amount was dissolved in 80 mL of DMF and 20 mL of triethylamine, 0.92 g of tetrakis (triphenylphosphine) palladium (0) and 0.3 g of copper (I) iodide were added, and the mixture was stirred at 50 ° C. for 8 hours while blowing propyne.

  After returning to room temperature, 150 mL of toluene was added, washed twice with 80 mL of water, and dried over anhydrous magnesium sulfate. The oily substance obtained by distilling off the solvent was dissolved again in 120 mL of toluene, 32 mL of aqueous sodium hypochlorite (8%) and 32 mL of water were added, and the mixture was stirred for 2 hours under ice water cooling. The precipitated crystals were filtered through celite, the aqueous layer was separated, washed twice with saturated brine, and dried over anhydrous magnesium sulfate. The solvent was distilled off to obtain 8.0 g of 3,4,5-trifluoro-6- (1-propynyl) naphthalene.

This whole amount was dissolved in 400 mL of THF, and the mixture was stirred at 20 ° C. for 4 hours under a hydrogen pressure of 5 atm (0.5 MPa) in an autoclave. After the catalyst was filtered off, the solvent was distilled off and further purified with a flash column (silica gel / hexane) to obtain 7.3 g of white crystals of 6-propyl-3,4,5-trifluoronaphthalene.
Example 2 Synthesis of 2- (trans-4-propylcyclohexyl) -3,4,5-trifluoro-6-propylbenzene (1-a)

  7.3 g of 6-propyl-3,4,5-trifluoronaphthalene obtained in Example 1 was dissolved in 60 mL of THF, cooled to −50 ° C. and stirred under a nitrogen stream. 23 mL of a hexane solution (1.6 M) of n-butyllithium was added dropwise over 0.5 hours, and the mixture was further stirred at −50 to −40 ° C. for 1 hour after the completion of the addition. To this solution, a solution of 4-propylcyclohexanone 5.0 g in THF 25 mL was added dropwise at −50 ° C. over 30 minutes. After the completion of dropping, the temperature was kept at −50 to −40 ° C. for 30 minutes, and then the temperature was raised to room temperature and further stirred for 1 hour. Water (100 mL) was added, and the mixture was extracted with ethyl acetate (150 mL). The organic layer was washed with water and then saturated brine, and dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to obtain 10.0 g of cyclohexanol derivative.

  The total amount was dissolved in 70 mL of toluene, 0.46 g of p-toluenesulfonic acid (monohydrate) was added, and the mixture was heated to reflux for 3 hours while removing azeotropic water. The mixture was allowed to cool to room temperature, washed successively with saturated aqueous sodium hydrogen carbonate solution, water and saturated brine, and dried over anhydrous magnesium sulfate. 8.7 g of cyclohexene obtained by distilling off the solvent was dissolved in 200 mL of THF and added to 0.95 g of 5% palladium carbon (containing 50% water) in an autoclave, and at room temperature for 3 hours at a hydrogen pressure of 0.5 MPa. Contact reduction. After the catalyst was filtered off, the solvent was distilled off to obtain 8.6 g of a cis / trans mixture of 2- (4-propylcyclohexyl) -3,4,5-trifluoro-6-propylnaphthalene.

The whole amount was dissolved in 60 mL of DMF, 1.12 g of potassium t-butoxy was added, and the mixture was heated and stirred at 40 ° C. for 3 hours. After allowing to cool, 100 mL of hexane and 50 mL of water were added, the aqueous layer was separated and extracted with hexane, the organic layers were combined, washed with 50 mL of saturated brine, and dried over anhydrous magnesium sulfate. The crude product obtained by distilling off the solvent was purified by silica gel column chromatography (hexane), recrystallized from ethanol, and 2- (trans-4-propylcyclohexyl) -3,4,5-tri 6.0 g of white crystals of fluoro-6-propylnaphthalene were obtained. The melting point was 68 ° C.
IR (KBr): 2956, 1623, 1450, 1357, 1157, 1062, 879 cm ⁻¹
NMR (CDCl ₃ ): δ = 0.9-2.0 (m, 21H), 2.7-2.9 (m, 3H), 7.2-7.5 (m, 3H)
(Example 3) Preparation of n-type liquid crystal composition (1)
A nonpolar standard matrix liquid crystal composition (M) comprising the following compounds was prepared.

The nematic phase upper limit temperature (T _N-I ) of (M) was 103.2 ° C. When the physical property values were measured at 20 ° C., the refractive index anisotropy (Δn) was 0.0986, and the dielectric anisotropy (Δε) was 0.03. The rotational viscosity was 15.6 (mPa · s).

Next, a liquid crystal composition (M-1) comprising 80% of the (M) and 20% of the compound represented by the formula (1-a) obtained in Example 1 was prepared.
This (M-1) showed a nematic phase at 86 ° C. or lower. _TN-I of (1-a) extrapolated from this was 17 ° C. Even when this was left at -20 ° C for 1 week, no precipitation of crystals or phase separation was observed. When the physical property values were measured at 20 ° C., Δn was 0.1023 and Δε was −0.81. From the above, it was confirmed that Δn of the compound represented by the formula (1-a) extrapolated from the above is 0.12, and Δε is −4.3, which is a relatively strong n-type compound. The composition had a viscosity of 20.7 (mPa · s) and a relatively low viscosity.
(Comparative Example 1)
On the other hand, 80% of (M) and the compound represented by the general formula (2a) are represented by the formula (2a-1)

で表される化合物２０％からなる液晶組成物（Ｒ−１）を調製した。この（Ｒ−１）のネマチック相上限温度（Ｔ_Ｎ−Ｉ）は７１℃で（Ｍ−１）と比較して約１４°も低下してしまった。さらに−２０℃で放置したところ、２４時間で相分離が観察された。２０℃において測定したその物性値は、Δｎが０．０８９８、Δεは−０．８５であった。従って式（２ａ−１）で表される化合物は本発明の式（１−ａ）で表される化合物と比較して、同程度の強い（絶対値の大きい）Δεを有するものの、高温域におけるネマチック相温度範囲において劣っていることがわかる。
（比較例２）
（Ｍ）の８０％と一般式（２ｃ）で表される化合物として式（２ｃ−１）で表される化合物２０％からなる液晶組成物（Ｒ−２）を調製した。

A liquid crystal composition (R-1) comprising 20% of the compound represented by the formula: The nematic phase upper limit temperature (T _N-I ) of (R-1) was reduced by about 14 ° compared to (M-1) at 71 ° C. Further, when left at −20 ° C., phase separation was observed in 24 hours. The physical property values measured at 20 ° C. were Δn of 0.0898 and Δε of −0.85. Therefore, although the compound represented by the formula (2a-1) has the same degree of strong (large absolute value) Δε as that of the compound represented by the formula (1-a) of the present invention, It turns out that it is inferior in the nematic phase temperature range.
(Comparative Example 2)
A liquid crystal composition (R-2) comprising 80% of (M) and 20% of the compound represented by formula (2c-1) was prepared as the compound represented by general formula (2c).

この（Ｒ−２）のネマチック相上限温度（Ｔ_Ｎ−Ｉ）は１０９．５℃であり、（Ｍ−１）と比較して約２４°も高かった。しかしながら−２０℃で放置したところ、３日以内に結晶の析出が観察された。また２０℃で測定した物性値は、Δｎが０．０９９と（Ｍ−１）よりやや小さく、Δεは−０．３７とその絶対値が（Ｍ−１）の半分以下に小さくなった。

The nematic phase upper limit temperature (T _N-I ) of (R-2) was 109.5 ° C., which was about 24 ° higher than that of (M-1). However, when left at −20 ° C., crystal precipitation was observed within 3 days. The physical properties measured at 20 ° C. were Δn of 0.099, which was slightly smaller than (M−1), and Δε was −0.37, and the absolute value thereof was smaller than half of (M−1).

From the above, although the compound represented by the formula (2c-1) is capable of a nematic phase temperature range higher than the compound represented by (1-a) of the present invention, the absolute value of Δε It can be seen that the value is smaller and the compatibility with conventional liquid crystals and the stability at low temperatures are also poor.
(Example 4) Preparation of n-type liquid crystal composition (2)
20% of (M), 20% of the compound represented by formula (1-a), 20% of the compound represented by formula (2a-1), 20% of the compound represented by formula (2c-1), and The compound represented by the general formula (2c) is represented by the formula (2c-2).

で表される化合物２０％からなる液晶組成物（Ｍ−２）を調製した。この（Ｍ−２）は７３℃以下で安定にネマチック相を示し、−２０℃で１週間放置しても結晶の析出や相分離は観察されなかった。２０℃においてその物性値を測定したところ、Δｎは０．０９８、Δεは−３．１８であった。またこの組成物の粘度は３４（ｍＰａ・ｓ）で比較的低粘性であり、実用的なｎ型の液晶材料として好適であった。
（実施例５）ｎ型液晶組成物の調製（３）
（Ｍ）の４０％、式（１−ａ）で表される化合物２０％、式（２ｃ−１）で表される化合物１０％及び一般式（３ａ）で表されるとして式（３ａ−１）

A liquid crystal composition (M-2) comprising 20% of the compound represented by the formula: This (M-2) showed a nematic phase stably at 73 ° C. or lower, and no crystal precipitation or phase separation was observed even after standing at −20 ° C. for 1 week. When the physical property values were measured at 20 ° C., Δn was 0.098 and Δε was −3.18. The composition had a viscosity of 34 (mPa · s) and a relatively low viscosity, and was suitable as a practical n-type liquid crystal material.
(Example 5) Preparation of n-type liquid crystal composition (3)
40% of (M), 20% of compound represented by formula (1-a), 10% of compound represented by formula (2c-1), and formula (3a-1) as represented by formula (3a) )

で表される化合物化合物２０％、及び（３ａ−２）で表される化合物１０％

20% of a compound represented by the formula: 10% of a compound represented by (3a-2)

からなる液晶組成物（Ｍ−３）を調製した。この（Ｍ−３）は９３℃以下で安定にネマチック相を示し、−２０℃で１週間放置しても結晶の析出や相分離は観察されなかった。２０℃においてその物性値を測定したところ、Δｎは０．１１９、Δεは−３．４３であった。またこの組成物の粘度は３５（ｍＰａ・ｓ）と実用的なｎ型の液晶材料として好適であった。

A liquid crystal composition (M-3) comprising: This (M-3) showed a nematic phase stably at 93 ° C. or lower, and no crystal precipitation or phase separation was observed even after standing at −20 ° C. for 1 week. When the physical property values were measured at 20 ° C., Δn was 0.119 and Δε was −3.43. The composition had a viscosity of 35 (mPa · s) and was suitable as a practical n-type liquid crystal material.

(Example 6) Preparation of n-type liquid crystal composition (4)
20% of (M), 20% of compound represented by formula (1-a), 10% of compound represented by formula (2a-1), 10% of compound represented by formula (2c-1), formula A liquid crystal composition (M-4) comprising 20% of the compound represented by (3a-1) and 20% of the compound represented by formula (3a-2) was prepared. This (M-4) showed a nematic phase stably at 86.5 ° C. or lower, and no crystal precipitation or phase separation was observed even after standing at −20 ° C. for 1 week. When the physical property values were measured at 20 ° C., Δn was 0.122 and Δε was −4.55. Further, the viscosity of this composition was 41 (mPa · s) and the absolute value of Δε was large, but the viscosity was relatively low, and it was suitable as a practical n-type liquid crystal material.

(Example 7) Creation of display element (1)
The liquid crystal composition (M-2) obtained in Example 4 was filled in a VA display cell having a cell thickness of 3.5 μm provided with a transparent electrode (electrodes on one side arranged in a zigzag shape) and subjected to vertical alignment treatment. A VA display element was prepared. When an electric field was applied to this device and its electro-optical characteristics at 25 ° C. were measured, the threshold voltage (Vth) from dark field to bright field was 3.2V. Next, when the response time when 5 V was applied was measured, the sum of the rise time (τr) and the fall time (τd) was 31 milliseconds. Further, the voltage holding ratio (HR) at 70 ° C. of this device was measured and found to be 89%. Since the HR of the nonpolar base liquid crystal (M) measured under the same conditions was 90%, it can be determined that this value is sufficiently high.
(Example 8) Creation of display element (2)
A VA display element was prepared in the same manner using (M-4) obtained in Example 6 and its electro-optical characteristics (25 ° C.) were measured. As a result, the threshold voltage (Vth) was 2.8 V. It was confirmed that low voltage drive was possible. The response time (the sum of the rise time (τr) and the fall time (τd)) when 5 V was applied was 34 milliseconds. Furthermore, the voltage holding ratio (HR) at 70 ° C. was as high as 87%.

Claims (12)

General formula (1)

(In the formula, R ^a represents a linear alkyl group having 2 to 7 carbon atoms, and R ^b represents a linear alkyl group having 2 to 5 carbon atoms). Contains 2 or more, general formula (5)

(In the formula, R ^m represents a linear alkyl group or alkenyl group having 1 to 7 carbon atoms, and R ⁿ represents a linear alkyl group, alkenyl group, alkoxyl group or alkenyloxy group having 1 to 12 carbon atoms. M6 represents 0 or 1, Ml and Mm each independently represent a single bond, —COO— or —CH ₂ CH ₂ —, and ring G represents a trans-1,4-cyclohexylene group or 1, A liquid crystal composition comprising one or more compounds represented by 4-phenylene group) and having a dielectric anisotropy of -3 or less. The liquid crystal composition according to claim 1, wherein the dielectric anisotropy is less than −4. General formula (2)

(Wherein R ^c represents an alkyl group having 1 to 7 carbon atoms, R ^d represents a linear alkyl group, alkoxyl group or alkenyloxy group having 1 to 7 carbon atoms, and m1 represents 0 or 1) And Ma and Mb each independently represent a single bond, —CH ₂ CH ₂ —, —OCF ₂ —, —CF ₂ O—, or —COO—, and ring B represents a trans-1,4-cyclohexylene group. Alternatively, it represents a 1,4-phenylene group which may be substituted with 1 to 2 fluorine atoms.) The liquid crystal composition according to claim 1 or 2, which contains one or more compounds represented by the following formula. Formulas (3a), (3b), (4a) and (4b)

(In the formula, R ^e , R ^g , R ⁱ and R ^k represent a linear alkyl group having 1 to 7 carbon atoms, and R ^f , R ^h and R ^l are linear chains having 1 to 7 carbon atoms. Represents an alkyl group, an alkoxyl group or an alkenyloxy group, R ^j represents a linear alkyl group having 1 to 7 carbon atoms, m2, m3, m4 and m5 represent 0 or 1, Mc and Md, Me And Mf, Mh and Mi, Mj and Mk each independently represents a single bond, —CH ₂ CH ₂ —, —OCF ₂ —, —CF ₂ O— or —COO—, and ring C, ring D, ring E And ring F represents a trans-1,4-cyclohexylene group or a 1,4-phenylene group optionally substituted by 1 to 2 fluorine atoms, wherein in (3a), the ring is represented by the general formula (1). Selected from the group of compounds represented by The liquid crystal composition according to any one of claims 1 to 3 containing more than one or two. 1 type or 2 types which contain 1 type, or 2 or more types of compounds represented by General formula (2), and are chosen from the compound group represented by General formula (3a), (3b), (4a), and (4b) The liquid crystal composition according to claim 4 containing at least seeds. The nematic phase upper limit temperature is 70 ° C or higher, the nematic phase lower limit temperature is -20 ° C or lower, and the content of the compound (1) is in the range of 1 to 50% by mass . The liquid crystal composition according to one item . General formula (1)

(Wherein, R ^a represents a linear alkyl group having 2 to 7 carbon atoms, and R ^b represents a linear alkyl group having 2 to 5 carbon atoms). It is a manufacturing method of the compound represented by General formula (1) of Claim 7, Comprising: General formula (6)

(In the formula, R ^b represents a linear alkyl group having 2 to 5 carbon atoms.) Alkyllithium is reacted with a trifluoronaphthalene derivative represented by formula (7) to obtain an organic lithium compound. )

(In the formula, R ^a represents a linear alkyl group having 2 to 5 carbon atoms.) After reacting with a 4-alkylcyclohexanone compound represented by the following formula, dehydration and hydrogenation, a cyclohexane ring is used as necessary. General formula (1) characterized in that

(In the formula, R ^a represents a linear alkyl group having 2 to 7 carbon atoms, and R ^b represents a linear alkyl group having 2 to 5 carbon atoms). General formula (6)

(Wherein, R ^b represents a linear alkyl group having 2 to 5 carbon atoms). The liquid crystal display element using the liquid-crystal composition as described in any one of Claims 1-6. The liquid crystal display element according to claim 9, which is driven in an active matrix. The liquid crystal display element according to claim 10, which is displayed in a vertical alignment mode.