JP2000297051A - 2,7-disubstituted fluorene derivative and liquid crystal composition containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel compound useful as a component of a ferroelectric liquid crystal composition, and to provide a more useful liquid crystal composition and a liquid crystal element. . SOLUTION: General formula [1] In the formula, R ₁ and R ₂ are each independently a linear or branched alkyl group having 2 to 16 carbon atoms, and any one methylene group or two or more Non-adjacent methylene groups are -O-, -S-, -C
H = CH -, - C≡C - , - CF 2 - or -CHF-
In may be substituted, X is -CH ₂ - or -CO
And Y is a single bond, -O- or -S-.
(However, when Y is —O— or —S—, the methylene group at the 1-position of R ₁ and R ₂ is not substituted with —O— or —S—). , 7-disubstituted fluorene derivatives.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel liquid crystal compound, a liquid crystal composition containing the compound, and a liquid crystal composition containing the compound, which can be suitably used for a liquid crystal display device, particularly a ferroelectric liquid crystal display device. Liquid crystal display device.

[0002]

2. Description of the Related Art At present, it is difficult to realize a large screen of 20 inches or more with a TFT element. However, the ferroelectric liquid crystal display element has a possibility of realizing both a large screen of 20 inches or more and a reduction in production cost. @ Clark et al .; Applied Physics Letters (Appl. Phys. Lett.,) 36;
899 (1980)｝. This display system uses a chiral smectic phase such as a chiral smectic C phase (hereinafter, abbreviated as SC * phase) exhibiting ferroelectricity.
This is called a surface-stabilized ferroelectric liquid crystal display (hereinafter abbreviated as SSFLC) system, and attempts have been made to improve the characteristics and commercialize it by home appliance manufacturers and material manufacturers. The reason is that the ferroelectric liquid crystal display element has the following features in principle. 1. High-speed response 2. 2. Memory properties Wide viewing angle These features suggest the potential of SSFLC for large-capacity displays, making the SSFLC scheme very attractive.

In order to use a ferroelectric liquid crystal in a display device, a liquid crystal material must exhibit: an SC * phase in a wide range including room temperature; a sufficiently large spontaneous polarization; and an appropriate tilt angle. It is necessary to satisfy conditions such as low viscosity, but there is no known compound that satisfies these conditions alone. Therefore, it is necessary to prepare a composition showing a ferroelectric liquid crystal phase by mixing several kinds of compounds. As a method for preparing a ferroelectric liquid crystal composition, non-chiral smectic C, F, G, H, I
A compound or a composition exhibiting an inclined smectic phase (hereinafter abbreviated as a phase such as Sc) as a basic substance, and one or more ferroelectric liquid crystal compounds or optically active compounds are mixed with the compound or composition to obtain a ferromagnetic compound. There is a method of preparing a composition exhibiting a dielectric liquid crystal phase. Since a low-viscosity composition can be obtained by this method, it becomes possible to manufacture a display element having a high response speed. The ferroelectric liquid crystal display is usually performed using a chiral smectic C phase (hereinafter, abbreviated as SC * phase). However, even if the phase is higher than this phase, the chiral smectic F phase and the chiral smectic I phase (hereinafter referred to as SF * phase and SI * phase, respectively)
Phase), ferroelectric liquid crystal display is possible. As a mother liquid crystal which is a basic substance of a ferroelectric liquid crystal display material, a compound exhibiting an Sc phase in a room temperature range is desirable, and a compound exhibiting an Sc phase in components constituting the mother liquid crystal is desirable.

Various liquid crystal compounds containing a fluorene ring are known. For example, JP-A-6329919
81 has an optically active -7-alkoxyfluorene-2-
Carboxylic esters are disclosed in Tetrahedoron, 37
(16), pages 2815 and 2823, 1981
In the year, 2-alkanoyl-7-alkylfluorene,
J. Phys. (Paris), Suppl, 37, C3, 1, 1976, 2-alkanoyl-7-alkylfluorene, 2,2
7-Dialkanoylfluorene, Bull. Soc. Chim. Fr.,
P. 2060, 1975, 2-alkanoyl-7-
Liquid crystal compounds having substituents at positions 2 and 7 of the fluorene ring, such as alkoxyfluorene, 2-alkoxy-7-alkylfluorene, 2-alkanoyl-7-alkylfluorene, and 2,7-dialkanoylfluorene, are described. However, no specific description of the compound of the present invention described later can be found therein.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel compound useful as a component of a ferroelectric liquid crystal composition. Another object of the present invention is to provide a useful liquid crystal composition and a liquid crystal element.

[0006]

The present inventors have conducted a search for a liquid crystal compound having a fluorene ring, and as a result, have found that 2,7-disubstituted fluorene derivatives represented by a specific formula are constituents of a ferroelectric liquid crystal. As a result, the present invention has been completed.

The 2,7-disubstituted fluorene derivative of the present invention has the general formula [1]

Embedded image In the formula, R ₁ and R ₂ are each independently a linear or branched alkyl group having 2 to 16 carbon atoms, and any one methylene group or two or more Non-adjacent methylene groups are -O-, -S-, -C
H = CH -, - C≡C - , - CF 2 - or -CHF-
In may be substituted, X is -CH ₂ - or -CO
And Y is a single bond, -O- or -S- (provided that when Y is -O- or -S-, R ₁ and R ₂
Is not substituted with -O- or -S-). It is represented by｝. Preferably, in the general formula [1], R ₁ and R ₂ are each independently 2 to 2
16 is a linear or branched alkyl group having carbon atoms, X is -CH ₂ - is, Y is a single bond, -O
-Or -S-, a 2,7-disubstituted fluorene derivative, or in the general formula [1], R ₁ and R ₂ are each independently a linear alkyl group having 2 to 16 carbon atoms. X is -CO-, Y is a single bond,-
2,7-disubstituted fluorene derivatives that are O- or -S- are shown.

[0008] The liquid crystal composition of the present invention contains at least one 2,7-disubstituted fluorene derivative represented by the general formula [1].

The liquid crystal display device of the present invention comprises a liquid crystal composition containing at least one 2,7-disubstituted fluorene derivative represented by the general formula [1].

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As the 2,7-disubstituted fluorene derivative represented by the general formula [1] of the present invention, the following six general formulas (1a), (1b), (1c), (1d) ),
Compounds represented by (1e) and (1f) are preferred.

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More preferred derivatives include (1a)
In each of the formulas (1b), (1c) and (1d), R ₁
And compounds wherein R ₂ is an alkyl group having ₂ to 12 carbon atoms.

The 2,7-disubstituted fluorene derivative of the present invention is a compound represented by the general formula [1], preferably (1a), (1b), (1c), (1d), (1e) and (1e). In the above formulas, preferred linear alkyl groups for R ₁ and R ₂ include groups having 2 to 12 carbon atoms, that is, ethyl, propyl, butyl, pentyl , Hexyl, heptyl, octyl, nonyl, decyl, undecyl and dodecyl. In these formulas, preferred branched alkyl groups for R ₁ and R ₂ include isopropyl, 1-methylpropyl, 2-methylpropyl,
2-methylbutyl, 3-methylbutyl, 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2-
Propyl pentyl, isopropoxy, 5-methylheptyl, 6-methyloctyl and the like can be mentioned. The compound having a branched alkyl group is important because it can increase the tilt angle by being added to the ferroelectric liquid crystal composition. Optically active compounds are important as chiral doping agents.

In addition, any one methylene group or two or more non-adjacent methylene groups in the alkyl group is-
O -, - S -, - CH = CH -, - C≡C -, - CF 2
R ₁ or R ₂ substituted with — or —CHF— includes CH ₃ —CH ＝ CH—, CH ₂ ＣＨCH—CH
_{2 -, CH 2 = CH-} CH 2 -CH 2 -, CH 2 = CH-C
_{H 2 -CH 2 -CH 2 -,} CH 3 -CH = CH-CH = CH
—, CH ₃ —C≡C—, CH ₃ —CH ₂ —C≡C—, CH _{3
-CH 2 -CH 2 -C≡C-, CH 3} -C≡C-CH 2 -C
_{≡C-, CH 3 -O-CH 2} -, CH 3 -O-CH 2 CH 2
CH ₂ —, CH ₃ —O—CH ₂ —CH ₂ —CH ₂ —CH ₂ —,
_{CH 3 -CH 2 -O-CH 2} -CH 2 -CH 2 -, CH 3 -C
H ₂ —O—CH ₂ —CH ₂ —CH ₂ —CH ₂ —, CH ₃ —S—
_{CH 2 -, CH 3 -S-} CH 2 CH 2 CH 2 -, CH 3 -S-
_{CH 2 -CH 2 -CH 2 -CH 2} -, CH 3 -CH 2 -S-C
_{H 2 -CH 2 -CH 2 -,} CH 3 -CH 2 -S-CH 2 -CH
_{2 -CH 2 -CH 2 -, CH} 3 -CF 2 -CH 2 -, CH 3 -
CF ₂ —CH ₂ CH ₂ CH ₂ —, CH ₃ —CF ₂ —CH ₂ —C
_{H 2 -CH 2 -CH 2 -,} CH 3 -CH 2 -CF 2 -CH 2 -
_{CH 2 -CH 2 -, CH 3} -CH 2 -CF 2 -CH 2 -CH 2
_{-CH 2 -CH 2 -, CH 3} -CHF-CH 2 -, CH 3 -
_{CHF-CH 2 CH 2 CH 2} -, CH 3 -CHF-CH 2 -
_{CH 2 -CH 2 -CH 2 -,} CH 3 -CH 2 -CHF-CH 2
_{-CH 2 -CH 2 -, CH 3} -CH 2 -CHF-CH 2 -C
_{H 2 -CH 2 -CH 2 -,} CH 3 -CH 2 -CH 2 -CH 2 -
CH ₂ —CH ₂ —CHF—CH ₂ — and the like are preferred.

(Production method of the compound)
-A method for producing a di-substituted fluorene derivative will be exemplified. Among the 2,7-disubstituted fluorene derivatives represented by the general formula [1], the compound wherein Y is -O- can be produced by the following route. That is, 2-acetylfluorene (b) is obtained by a Friedel-Crafts reaction of fluorene (a).
This (b) is oxidized with peroxide to give 2-acetoxyfluorene (c), and the Friedel-Crafts reaction of this (c) gives 2-acetoxy-7-acetylfluorene (d). The 2-acetoxy-7-acetylfluorene (d) is hydrolyzed to give 2-acetyl-7-hydroxyfluorene (e), which is reacted with an alkyl halide (Q) in the presence of a base to give 2-acetyl-7-acetylfluorene (e). Acetyl-7-alkoxyfluorene (f) can be obtained. This (f) is oxidized with a peroxide to form an ester compound (g), hydrolyzed to a hydroxy form (h), and then etherified with an alkyl halide (Q) to give a compound represented by the general formula (1a). Can be produced. The compound represented by the general formula (1b) is (1a)
In a solvent such as 2-butanone and oxygen in the presence of a base such as potassium hydroxide.

[0015]

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Among the compounds represented by the general formula [1], the compound wherein Y is a single bond can be produced by the following route. That is, a carbonyl compound is obtained by a Friedel-Crafts reaction between fluorene (a) and alkanoyl chloride,
This is then reduced with hydrazine or the like to give 2-
Alkylfluorene (i) can be obtained. (I)
Can be further reduced by Friedel-Crafts reaction with alkanoyl chloride and then with hydrazine or the like.
A compound represented by the general formula (1c) having an alkyl group at the -position and the 7-position can be produced. This compound (1c)
The fluorenone compound represented by the general formula (1d) can be produced by oxidizing with oxygen in a solvent such as butanone in the presence of a base such as potassium hydroxide.

[0017]

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The sulfur-containing compound represented by the general formula (1e) or (1f) is described in Organic Synthesis, Vol. 51, 13
It can be produced by combining the reaction for converting a HO group into a corresponding HS group by the method described on page 9 with the above production steps.

[0019]

The compounds of the present invention will be described in more detail with reference to the following Examples and Comparative Examples. In Examples and Comparative Examples described later, various physical property values were measured by the following methods. Phase transition temperature: A sample placed on a slide glass covered with a cover glass was heated on a hot stage at a rate of 1 ° C./min, and observed and measured under a polarizing microscope. The observed liquid crystal phases are indicated by the following abbreviations, and the phase transition temperature (° C.) is indicated between the symbols indicating the respective phases. Here, Iso is a transparent liquid phase, N is a nematic phase, and SA is a smectic A.
Phase, Sc is a smectic C phase, SC * is a chiral smectic C phase, Sx is an unidentified smectic phase,
Cr indicates a solid phase. Melting point: 1 ° C./mi using a differential scanning calorimeter (DSC)
The temperature was raised by n. Spontaneous polarization value (Ps): Measured by the Sawyer-Tauer method. Tilt angle (θ): A helical structure is extinguished by applying an electric field sufficiently higher than the critical electric field to a homogeneously oriented cell, the first extinction position under orthogonal Nicols is obtained, and the polarity of the electric field is further inverted. The second extinction position was determined by using the moving angle (corresponding to 2θ) between the two extinction positions. Response time (τ): Transmission when a sample composition is injected into a cell incorporated at an interval of 2 μm of an oriented electrode and a rectangular wave having a peak-to-peak voltage (Vpp) of 20 V and 0.1 kHz is applied. It was measured from the change in light intensity. Viscosity (η): The half-width Tw of the peak of the polarization reversal current observed under the same conditions as when measuring the response time is expressed by the following equation: Tw = (1.76 · η) / (Ps · E) (where E
Is 10 V).

Example 1 Preparation of 2-heptyloxy-7-pentyloxyfluorene (compound 33): (First step) Preparation of 2-acetylfluorene A solution prepared by dissolving 150 g of fluorene in 1 liter of dichloromethane was dried at 0 ° C. 126 g of aluminum chloride were added little by little. Next, a solution prepared by dissolving 74 g of acetyl chloride in 400 ml of dichloromethane was added dropwise to this solution.
A stirring reaction was performed for 1 hour while maintaining the temperature. The obtained reaction solution was poured into 1 liter of 6N diluted hydrochloric acid, and the precipitated solid was separated by filtration. After drying the solid, it was recrystallized from toluene to obtain 165 g of 2-acetylfluorene. Its melting point was 129 ° C.

(Second step) Production of 2-acetoxyfluorene 165 g of 2-acetylfluorene prepared in the previous step, 320 g of formic acid and 120 g of acetic anhydride were dissolved and mixed in 1 liter of dichloromethane, and 40 ml of sulfuric acid was added to this mixture. Then, 120 ml of 30% hydrogen peroxide solution was added dropwise,
The mixture was stirred at room temperature for 30 minutes, heated to 40 ° C., and further stirred for 5 hours to perform a reaction. One liter of water was added to the reaction solution, and the dichloromethane layer obtained was separated, washed with saturated aqueous sodium carbonate, aqueous sodium hydrogen sulfite, and water in that order, dried over anhydrous magnesium sulfate, and filtered to remove the desiccant. After the separation, the obtained liquid was concentrated to obtain a solid. This solid was recrystallized from a 1: 1 mixed solvent of heptane and ethyl acetate to obtain 149 g of 2-acetoxyfluorene. Its melting point was 130 ° C.

(Third step) Production of 2-acetoxy-7-acetylfluorene To a solution of 140 g of 2-acetoxyfluorene prepared in the previous step dissolved in 1 liter of dichloromethane was added 189 g of anhydrous aluminum chloride at 0 ° C. Then, a solution of 62 g of acetyl chloride in 100 ml of dichloromethane was added dropwise thereto, and a stirring reaction was carried out for 5 hours while maintaining 0 ° C. The dichloromethane solution obtained by adding 6N diluted hydrochloric acid to the obtained reaction solution was separated, dried over anhydrous magnesium sulfate, and the drying agent was filtered off. The obtained solution was concentrated to obtain a solid. This solid was recrystallized from an 8: 2 mixed solvent of ethyl alcohol and ethyl acetate to obtain 143 g of 2-acetoxy-7-acetylfluorene. Its melting point was 134 ° C.

(Fourth step) Preparation of 2-acetyl-7-hydroxyfluorene 150 g of acetoxy-7-acetylfluorene prepared in the previous step, 30 g of potassium hydroxide, 400 ml of ethylene glycol, 1 liter of ethyl alcohol and 50 ml of water And the mixture was heated to reflux for 5 hours to carry out a reaction. Ethyl alcohol was distilled off from the reaction solution by distillation under reduced pressure, and the remaining reaction solution was poured into 1 liter of 6N diluted hydrochloric acid, and the precipitated solid was separated by filtration. The solid was dried and recrystallized from acetic acid to obtain 106 g of 2-acetyl-7-hydroxyfluorene. Its melting point was 220-222 ° C.

(Fifth step) Preparation of 2-acetyl-7-heptyloxyfluorene 20 g of 2-acetyl-7-hydroxyfluorene prepared in the previous step, 21 g of heptyl bromide, 18 g of potassium carbonate
And a solution obtained by mixing 300 ml of dimethylformamide (hereinafter abbreviated as DMF) was heated to reflux for 3 hours to carry out a reaction. An organic layer formed by adding 6N diluted hydrochloric acid to the reaction solution was extracted with toluene, and the extract was washed with water and dried over anhydrous magnesium sulfate. The liquid obtained after removing the desiccant was concentrated. The concentrate was recrystallized from a heptane solvent to obtain 23.5 g of 2-acetyl-7-heptyloxyfluorene. Its melting point was 104-105 ° C.

(Sixth step) Preparation of 2-heptyloxy-7-hydroxyfluorene To 22 g of 2-acetyl-7-heptyloxyfluorene obtained in the previous step, 50 g of formic acid, 20 g of acetic anhydride and 200 ml of dichloromethane are added. To the prepared mixed solution, 6 ml of sulfuric acid was added, and then a 30% hydrogen peroxide solution (20%) was added.
ml was added dropwise. This mixture was heated to 40 ° C., and stirred for 3 hours while maintaining the same temperature to carry out a reaction. The dichloromethane layer obtained by adding water to the reaction solution was washed successively with aqueous sodium carbonate, aqueous sodium hydrogen sulfite and water, and then dried over anhydrous magnesium sulfate. The residue obtained by evaporating the solvent from the washed and dried extract was dissolved in 150 g of ethyl alcohol, 5.6 g of potassium hydroxide and 10 ml of water were added, and the mixture was heated under reflux for 2 hours. After distilling off, 6N hydrochloric acid was added to the remaining solution. The organic phase was extracted from this solution with chloroform, and the extract was dried over anhydrous magnesium sulfate. The residue obtained by removing the solvent from the extract after filtering off the drying agent was recrystallized from an 8: 2 mixed solvent of heptane and ethyl acetate to give 7.2 g of 2
-Heptyloxy-7-hydroxyfluorene was obtained.
Its melting point was 156-157 ° C.

(Seventh step) 2-heptyloxy-7-pentyloxyfluorene To 2.2 g of 2-heptyloxy-7-hydroxyfluorene prepared in the previous step, 2.1 g of pentyl iodide, 1.5 g of potassium carbonate and A solution obtained by adding 30 ml of DMF was heated under reflux for 4 hours to carry out a reaction. Water was added to the obtained reaction solution, and extracted with toluene. The obtained extract (toluene layer) was washed with water and dried over anhydrous magnesium sulfate. The residue obtained by evaporating the solvent from the washed and dried extract was purified by silica gel column chromatography using toluene as a developing solvent, and 1.8 g of 2-
Heptyloxy-7-pentyloxyfluorene was obtained. The phase transition temperature is shown in Table 1.

[0027]

[Table 1]

Example 2 Preparation of 2-heptyloxy-7-pentyloxyfluorenone (compound 96): 3 g of 2-heptyloxy-7-pentyloxyfluorene and 2.2 g of powdered potassium hydroxide were added to 80 ml of 2-butanone. The solution dissolved in
Oxygen was bubbled into the solution for 1 hour while heating and refluxing, and further allowed to cool to room temperature, followed by stirring for 1 hour to perform a reaction. An organic layer formed by adding 6N diluted hydrochloric acid to the obtained reaction solution was extracted with chloroform, and the extract was dried over anhydrous magnesium sulfate. After removing the desiccant, the solvent was distilled off, and the obtained residue was purified by silica gel column chromatography and recrystallization to obtain 1.8 g of 2-heptyloxy-7-pentyloxyfluorenone. This phase transition temperature is shown in Table 1 similarly to the final product of Example 1.

Example 3 2-heptyl-7-pentylfluorene (compound 17
Production of 3): (First step) 50 g of fluorene was added to 300 parts of dichloromethane.
ml of anhydrous aluminum chloride at 0 ° C.
6 g was added, and then 50 g of heptanoic acid chloride was added dropwise, and the mixture was stirred for 8 hours while maintaining the internal temperature at 0 ° C. to carry out a reaction. An organic phase formed by adding 500 ml of 6N diluted hydrochloric acid to the obtained reaction solution was extracted with dichloromethane, and the extract was dried over anhydrous magnesium sulfate. After the desiccant was separated by filtration, the solvent of the obtained liquid was distilled off to obtain a solid. This solid was recrystallized from a heptane solvent to obtain 20 g of 2-heptanoylfluorene. Its melting point was 111-112 ° C.

(Second Step) Potassium hydroxide was added to 100 ml of a solution obtained by dissolving 10 g of 2-heptanoylfluorene prepared in the previous step in diethylene glycol.
1 g and then 3.7 g of hydrazine were added at 280.degree.
The mixture was heated and stirred for an hour to perform a reaction. An organic layer formed by adding water to the obtained reaction solution was extracted with diethyl ether, and the obtained ether layer was washed with water and dried over anhydrous magnesium sulfate. The residue obtained by evaporating the solvent from the washed and dried extract is recrystallized from ethyl alcohol to give 1
1 g of 2-heptylfluorene was obtained. This melting point is 58
６０60 ° C.

(Third Step) To a solution prepared by dissolving 7 g of 2-heptylfluorene in 50 ml of dichloromethane at 0 ° C. was added 7.2 g of anhydrous aluminum chloride at 0 ° C., and 3.2 g of pentanoyl chloride was added dropwise. And
The reaction was carried out by stirring for 3 hours while maintaining the internal temperature at 0 ° C.
An organic layer formed by adding 1 L of 6N diluted hydrochloric acid to the obtained reaction solution was extracted with dichloromethane, and the extract was dried over anhydrous magnesium sulfate. The solvent of the extract after removing the drying agent was distilled off to obtain a solid. The solid was recrystallized from heptane to obtain 6.4 g of 2-heptyl-7-pentanoylfluorene. The liquid crystal phase transition point of this compound was Cr 114 SA 119.6 Iso.

(Fourth step) 2.2 g of potassium hydroxide and then 2 g of hydrazine were added to 60 ml of a solution prepared by dissolving 6.4 g of 2-heptyl-7-pentanoylfluorene prepared in the previous step in diethylene glycol. For 4 hours to carry out a reaction. An organic layer formed by adding water to the obtained reaction solution is extracted with diethyl ether,
The extract (ether layer) was washed with water and dried over anhydrous magnesium sulfate. 3. The residue obtained by evaporating the solvent of the extract after washing and drying is recrystallized from ethyl alcohol.
8 g of 2-heptyl-7-pentylfluorene were obtained.
The phase transition temperature of this compound is shown in Table 1.

Example 4 2-heptyl-7-pentylfluorenone (Compound 24)
Production of 6): 80 ml of a solution prepared by adding 3.5 g of powdered potassium hydroxide and 2-butanone to 4.8 g of 2-heptyl-7-pentylfluorene was heated and refluxed while adding oxygen to the solution. Was blown for 1 hour, and further allowed to cool at room temperature for 2 hours to carry out a reaction. An organic phase formed by adding 6N diluted hydrochloric acid to the obtained reaction solution was extracted with chloroform,
Dry over anhydrous magnesium sulfate. The residue obtained by distilling off the solvent from the dried extract was purified by silica gel column chromatography and then recrystallization to give 2.1 g.
Of 2-heptyl-7-pentylfluorenone was obtained.

According to the above Examples 1 to 4, compounds represented by the following formulas 1 to 290 represented by the general formula [1] are produced.

[0035]

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[0036]

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[0037]

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[0038]

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[0039]

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[0040]

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[0041]

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[0042]

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[0043]

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[0044]

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[0045]

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[0046]

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[0047]

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[0048]

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Table 1 shows the phase transition temperatures of some of these compounds together with the phase transition temperatures of the compounds shown in the above Examples.

Example 5 The following smectic liquid crystal composition (a) was prepared.

[0051]

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The phase transition temperature of the smectic liquid crystal composition (a) was as follows. Cr 4 Sc 65 SA 79 N 90 Iso Example was applied to 90 parts by weight of the smectic liquid crystal composition (a).
10 parts by weight of the final product (compound 33) produced in 1 was mixed to prepare a smectic liquid crystal composition (b). The phase transition temperature of the smectic liquid crystal composition (b) was as follows. From room temperature Sc 45.9 SA 77.4 N 8
6.6 Iso

Example 6 Smectic liquid crystal composition (b) 95 obtained in Example 5
A ferroelectric liquid crystal composition (d) consisting of 5 parts by weight of the following optically active compound (c) was prepared.

[0054]

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The phase transition temperature of this ferroelectric liquid crystal composition (d) is from room temperature to SC * 51.3 SA 77.4 N 8
6.6 Iso, and the spontaneous polarization, tilt angle and electro-optical response of the ferroelectric composition were as shown in Table 2. The viscosity of the composition (d) at 25 ° C. was 0.19 poise.

[0056]

[Table 2]

Comparative Example 1 Preparation of 7-pentylfluoren-2-yl 4-propylcyclohexanecarboxylate (Compound R):
4.5 g of 2-hydroxy-7-pentylfluorene, 4
-Propylcyclohexylcarboxylic acid chloride 3.5
g was added to a mixed solvent consisting of 20 ml of pyridine and 50 ml of toluene, and the mixture was heated under reflux for 3 hours to perform a reaction. Water was added to the reaction solution to terminate the reaction, the formed organic layer was extracted with toluene, and the extract (toluene layer) was washed with 6N diluted hydrochloric acid, sodium carbonate aqueous solution and water in that order, and then dried over anhydrous magnesium sulfate. The residue obtained by evaporating the solvent from the extract obtained by filtering off the drying agent was purified by silica gel column chromatography and then recrystallized to obtain 5.6 g of 7-pentylfluorene 4-propylcyclohexanecarboxylate-.
2-yl (Compound R) was obtained. The structural formula and the phase transition temperature of this compound are shown below.

[0058]

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A composition was prepared using the compound thus obtained. Preparation of Smectic Liquid Crystal Composition (g): A smectic liquid crystal composition (g) comprising 90 parts by weight of the smectic liquid crystal composition (a) used in Example 5 and 10 parts by weight of the compound R was prepared. This smectic liquid crystal composition (g)
Was as follows. From room temperature Sc 56.3 SA 80.6 N 9
4.4 Preparation of Iso Ferroelectric Liquid Crystal Composition (H): Ferroelectric liquid crystal comprising 95 parts by weight of the above smectic liquid crystal composition (g) and 5 parts by weight of optically active compound (c) used in Example 5 Composition (H) was prepared. The phase transition temperature of this ferroelectric liquid crystal composition (H) was: From room temperature SC * 59.9 SA 77.8 N *
93.1 Iso The spontaneous polarization, tilt angle and electro-optical response of this ferroelectric composition were as shown in Table 3. The viscosity at 25 ° C. of the ferroelectric composition was 0.38 poise.

[0060]

[Table 3]

Ferroelectric liquid crystal composition using the 2,7-disubstituted fluorene derivative of the present invention (d) (Example 6, Table 2)
Is a ferroelectric liquid crystal composition containing compound R as a component (H)
Compared with (Comparative Example 1, Table 3), it can be seen that the tilt angle and spontaneous polarization are small, but the electro-optical response is faster due to the lower viscosity.

[0062]

The 2,7-disubstituted fluorene derivative of the present invention exhibits better compatibility and lower viscosity than conventional fluorene compounds. A liquid crystal composition containing this derivative has a lower viscosity than a liquid crystal composition containing a conventional fluorene compound, and a liquid crystal element having a fast electro-optical response can be realized by using the liquid crystal composition. The 2,7-disubstituted fluorene derivative of the present invention is extremely useful as a high-speed response liquid crystal display device material.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4H006 AA01 AB64 GP03 4H027 BA06 DE01 DF01 DF10 DM01 DM02 DM03

Claims (5)

[Claims] 1. A compound of the general formula [1] In the formula, R ₁ and R ₂ are each independently a linear or branched alkyl group having 2 to 16 carbon atoms, and any one methylene group or two or more Non-adjacent methylene groups are -O-, -S-, -C
H = CH -, - C≡C - , - CF 2 - or -CHF-
In may be substituted, X is -CH ₂ - or -CO
And Y is a single bond, -O- or -S- (provided that when Y is -O- or -S-, R ₁ and R ₂
Is not substituted with -O- or -S-). 2,7-disubstituted fluorene derivative represented by｝. 2. In the general formula [1], R ₁ and R ₂ are each independently a linear or branched alkyl group having 2 to 16 carbon atoms, and X is —CH ₂ —. The 2,7-disubstituted fluorene derivative according to claim 1, wherein Y is a single bond, -O- or -S-. 3. In the general formula [1], R ₁ and R ₂ are each independently a linear alkyl group having 2 to 16 carbon atoms, X is —CO—, and Y is 2. The compound according to claim 1, which is a single bond, -O- or -S-.
-Disubstituted fluorene derivatives. 4. A liquid crystal composition comprising at least one 2,7-disubstituted fluorene derivative according to claim 1. 5. A liquid crystal display device comprising a liquid crystal composition containing at least one 2,7-disubstituted fluorene derivative according to claim 1.