JP2925682B2 - Novel ester compound, liquid crystal composition containing the same, and optical switching element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention can take a stable thermotropic liquid crystal state, for example, for a display such as a liquid crystal television, an optical printer head, an optical Fourier transform element, a light valve, etc. The present invention relates to a novel ester compound which can be used as a liquid crystal material useful as a material for an optoelectronics device using liquid crystal or electrochemiomics, a liquid crystal composition containing this compound, and an optical switching device.

(Prior Art) At present, liquid crystal compounds are applied to various devices as display materials, and have been put to practical use in watches, calculators, small televisions, and the like.
These use cells having a nematic liquid crystal material as a main component, and adopt a display type called a TN type or STN type. Cell in this case is actuated based on a weak interaction (ΔεE ^2/2) of the dielectric anisotropy Δε and the electric field E of the liquid crystal compound, the response speed to the electric field is low and several msec is cited as disadvantages I have. Therefore, when used in a television, an active matrix system in which switching elements are arranged and added for each pixel is mainly used as a driving system, which is one of the obstacles in achieving a large screen. However, 4975 was synthesized by RBMeyer et al.
-(4-n-decyloxybenzylideneamino) cinnamic acid-2-methylbutyl ester (DOBAMBC) as a representative example of a ferroelectric liquid crystal, and a new display method proposed by NAClark et al. Phys. Lett. 1980, 3
6 , 899), it has become possible to provide a liquid crystal cell having a high-speed response on the order of μsec and a characteristic (memory property) in which the orientation of liquid crystal molecules does not change even when the electric field is cut off. Using display elements made of these materials enables a simple matrix type liquid crystal display to be driven by multiplexing without using switching elements. It will be much more advantageous in such aspects.

For this reason, many ferroelectric liquid crystal materials have been synthesized and proposed to date. In order for these ferroelectric liquid crystal materials to be used as display materials, several physical properties are required. Among them, the basic ones show a smectic C phase in a wide temperature range near room temperature, It has spontaneous polarization and is chemically stable. However, the initial ferroelectric liquid crystal has a spontaneous polarization of 10 nC / c.
It was chemically unstable because it was as small as ² m2 or less and had many Schiff bases in the molecule.

By the way, recently, a large spontaneous polarization caused by a chemically stable ester compound has been reported. For example, Is a liquid crystal of a chiral smectic C phase in a temperature range of 78.7 to 103.3 ° C. and a cholesteric phase in a temperature range of 103.3 to 120.8 ° C., and the spontaneous polarization of this liquid crystal at 83 ° C. is 89 nC / cm ² . (JP-A-61-43).

On the other hand, bicyclic compounds have been synthesized to lower the temperature at which the chiral smectic C phase is exhibited. For example, Shows a chiral smectic C phase from 44 ° C. at the time of elevating and lowering (JP-A-59-118744).

In addition, a phenylpyrimidine-based compound stably showing a chiral smectic C phase at around room temperature has been reported. For example, Is a liquid crystal having a chiral smectic C phase in a temperature range of 40.7 to 82.8 ° C. and a smectic A phase at 82.8 to 89.1 ° C. (JP-A-61-200973).

(Problems to be Solved by the Invention) However, the above ester compound has a disadvantage that the temperature range of the chiral smectic C phase is high.
The biphenyl compound is a chiral smectic C
The temperature at which the phases show is close to room temperature, but the temperature range at about 10 ° C. is not sufficiently wide. Further, the phenylpyrimidine-based compound has a response speed as slow as 1500 μsec at 43 ° C., and it is estimated that spontaneous polarization is considerably small.

That is, a liquid crystal material such as a display device that requires a high-speed response has a large spontaneous polarization, a low viscosity, or a chiral smectic C phase in a wide temperature range including near room temperature. Physical properties are required,
To date, there is no material that sufficiently satisfies these properties.

However, in recent years, compounds having fluorine on asymmetric carbon have been synthesized, and attempts have been made to solve the conventional problems. For example, the following formula having a fluorine and a methyl group on the asymmetric carbon, Has been synthesized (Japanese Patent Laid-Open Publication No. 1-501394). However, when this compound is mixed with a pyrimidine base liquid crystal, the compound has poor compatibility and has a problem that the cholesteric phase of the base liquid crystal is lost.

The present inventors have conducted intensive studies to improve the liquid crystal properties of such a compound, and as a result, by providing the compound with a phenylnaphthalene skeleton instead of a biphenylene skeleton as a core structure, a thermotropically stable liquid crystal state was obtained. And that the compound has a property that the cholesteric phase having the base liquid crystal is hard to disappear when mixed with the base liquid crystal.

The present invention has been made based on such findings, and an object of the present invention is to provide a novel ester compound useful as a liquid crystal composition and a liquid crystal composition containing the same.

Another object of the present invention is to provide a liquid crystal display device having high-speed response by using a liquid crystal composition containing such a novel ester compound.

(Means for Solving the Problems) The present invention provides the following general formula (I): (Wherein, R and R ′ are an alkyl group which may have a substituent, and the substituent is selected from a lower alkyl group, a lower alkoxy group, a halogen atom, and a trifluoromethyl group; A single bond or one of -O-, A and B is 1,
A 4-phenylene group, the other of which represents a 2,6-naphthylene group)
And a liquid crystal composition containing the ester compound, and an optical switching element having at least one of the ester compounds as a constituent.

In the above formula, when optical activity is imparted mainly to the carbon to which —CH ₃ is bonded, a good optically active material can be produced by adding this to another non-optically active compound.

Examples of typical compounds of the above formula and their physicochemical properties are as follows.

2- (6-hexyloxynaphthyl- (2)) phenyl 2-fluoro-2-methylheptanoate ¹ H-NMR spectrum (90 MHz, in CDCl ₃ , TMS standard, δ
Value): δ 0.91 6Hm δ 1.1 to 2.2 16Hm δ 1.72 3Hd (J = 22Hz) δ 4.09 2Ht (J = 7Hz) δ 7.20 2Hd (J = 9Hz) δ 7.1 to 7.32Hm δ 7.6 to 7.9 3H m δ 7.82 2H d (J = 9 Hz) δ 7.93 1H br.s IR (KBr method, cm ^-1 ): 2910,2840,1750,1625,1600,1500,1170,2-fluoro-2-methylheptanoic acid -6- (4-hexyloxyphenyl) naphthyl- (2) ¹ H-NMR spectrum (90 MHz, in CDCl ₃ , TMS standard, δ
Value): δ 0.91 6H m δ 1.1 to 2.2 16H m δ 1.75 3H d (J = 22Hz) δ 4.02 2H t (J = 7Hz) δ 7.02 2H d (J = 9Hz) δ 7.1 to 7.32H m δ 7.64 2H d (J = 9 Hz) δ 7.6 to 7.93 Hm δ 7.99 1H br.s IR (KBr method, cm ^-1 ): 2910,2840,1760,1605,1500,1240,1180 In addition, it is shown by the above-mentioned general formula (I). The chain length of the alkyl chains of R and R 'in the compound, or the presence or absence of a substituent, affects physical properties such as a temperature range in which the optically active liquid crystal material obtained by adding to the non-optically active liquid crystal material can take a liquid crystal state. It can be appropriately selected depending on the purpose.

Further, as the substituent of the alkyl group which may have a substituent in R and R ′, a lower alkyl group, a lower alkoxy group,
A halogen atom, a trifluoromethyl group and the like are preferable.

 The compound of the above formula (I) is obtained as follows.

That is, it can be obtained by esterifying phenol (1) with carboxylic acid (2) according to the above reaction formula. As a method for esterification, a dehydration condensing agent such as dicyclohexylcarbodiimide can be used. Further, the carboxylic acid (2) can be converted to an acid halide by using a halogenating agent such as thionyl chloride, and can be reacted with the phenol (1) in the presence of a base.

The phenol (1) used here can be obtained as in the following formula.

(Wherein Pro represents a protecting group) That is, aryl bromide (3) according to the above reaction formula
And (4) are obtained by metallizing one and coupling with the other, followed by deprotection.

The carboxylic acid (2) used here can be obtained as in the following formula.

That is, first, according to the above reaction formula, 2-methyl-1,2
An amine-hydrogen fluoride complex or silicon tetrafluoride is allowed to act on an epoxy alkane to give 2-fluoro-2-methyl-1-alkanol (Japanese Patent Application No. 64-56058). The carboxylic acid (2) can be obtained by oxidizing this with an oxidizing agent such as potassium permanganate.

(Examples) Next, the present invention will be specifically described with reference to examples.

Example 1 Synthesis of 4- (6-hexyloxynaphthyl- (2)) phenol 10.00 g of 6-bromo-2-naphthol, 8.02 g of hexylbromide, 2.31 g of sodium hydroxide, 100 ml of ethanol and 50 ml of distilled water were placed in a flask and heated for 10 hours. Refluxed. After the ethanol was distilled off, ether was added and the mixture was stirred, and the organic layer was separated. This organic layer was washed with a 5% aqueous sodium hydroxide solution and a saturated aqueous sodium chloride solution.
After drying over anhydrous magnesium sulfate, the solvent was distilled off, and the resulting crude crystals were recrystallized from ethanol to give 11.15 g (81% yield) of 6-hexyloxy-2-bromonaphthalene.

2.63 g of 4-bromophenol, ethyl vinyl ether 3
ml, 0.02 g of pyridinium 4-toluenesulfonate and 20 ml of dry dichloromethane were placed in a flask and added at room temperature to 1 ml.
Stirred overnight. After completion of the stirring, the mixture was washed with a saturated aqueous solution of sodium hydrogen carbonate, dried over anhydrous magnesium sulfate, and the solvent was distilled off. The resulting oil was purified by silica gel column chromatography to give 4-bromophenyl-
3.56 g (96% yield) of (1-ethoxy) ethyl ether was obtained.

Take 0.49 g of lithium dispersion in a flask,
Under a nitrogen stream, 3.56 g of 4-bromophenyl- (1-ethoxy) ethyl ether dissolved in 15 ml of dry ether was added dropwise over 20 minutes, and then the mixture was heated under reflux for 20 minutes. After returning to room temperature, 2.10 g of anhydrous zinc chloride and nickel chloride (I
I) 0.17 g of (1,2-bisdiphenylphosphinoethane)
3.07 g of the previously obtained 6-hexyloxy-2-bromonaphthalene dissolved in 20 ml of dry tetrahydrofuran was added, and 4
Heated to reflux for an hour. Next, after cooling to room temperature, 1N hydrochloric acid was added, the mixture was stirred as it was overnight, and extracted with ether.

After drying over anhydrous magnesium sulfate, the solvent was distilled off, and the resulting oil was purified by silica gel column chromatography to give 4- (6) having the following physicochemical properties.
-Hexyloxynaphthyl- (2)) phenol 1.48 g
(46% yield). ¹ H-NMR spectrum (90 MHz, in CDCl ₃ , TMS standard, δ
Value): δ 0.91 3H m δ 1.1 to 2.0 8H m δ 4.09 2H t (J = 7Hz) δ 4.80 1H br.s δ 6.9 to 7.34 H m δ 7.5 to 8.1 6H m IR (KBr method, cm ^-1 ): 3200,2910,2840,1625,1600,1500,1245,1175 Synthesis of 4- (6-hexyloxynaphthyl- (2)) phenyl 2-fluoro-2-methylheptanoate 4- (6-hexyloxynaphthyl- (2)) phenol 551.2 mg, (−)-2-fluoro-2-methylheptanoic acid 279.8 mg, dicyclohexylcarbodiimide 483.7
mg, 20.1 mg of 4-dimethylaminopyridine and 20 ml of dry dichloromethane were placed in a flask and stirred at room temperature overnight.

The resulting crystals were removed by filtration, and the solvent was distilled off. The resulting crude crystals were purified by silica gel column chromatography and recrystallization from ethanol to give 2-fluoro-2-methylheptane having the aforementioned physicochemical properties. Acid-4
-(6-hexyloxynaphthyl- (2)) phenyl 27
7.3 mg (35% yield) were obtained.

Evaluation of crystallinity The obtained target compound is a 3 μm-thick glass plate with a transparent electrode coated with polyimide and rubbed.
When the temperature was lowered at a rate of −2 ° C./min and observed with a crossed Nicol polarizing microscope, the phase changed from an isotropic liquid to a smectic A phase at 109.6 ° C., and at 80 ° C., a higher smectic phase was observed. It changed to a phase and did not crystallize to 0 ° C. or lower.

Example 2 Synthesis of 6- (4-hexyloxyphenyl) 2-naphthol 32.00 g of p-bromophenol, 33.1 g of hexyl bromide
6 g, 8.03 g of sodium hydroxide, 200 ml of ethanol and 100 ml of distilled water were placed in a flask, and heated under reflux for 10 hours. After the ethanol was distilled off, ether was added and the mixture was stirred, and the organic layer was separated. This organic layer was washed with a 5% aqueous sodium hydroxide solution and a saturated aqueous sodium chloride solution. After drying over anhydrous magnesium sulfate, the solvent was distilled off to obtain 40.4 g (yield: 85%) of 4-hexyloxybromobenzene.

6-bromo-2-naphthol 2.25 g, ethyl vinyl ether 2 ml, pyridinium 4-toluenesulfonate 0.0
2 g and 50 ml of dry dichloromethane were placed in a flask and stirred at room temperature overnight. After completion of the stirring, the mixture was washed with a saturated aqueous solution of sodium hydrogen carbonate. After drying over anhydrous magnesium sulfate,
The oily substance obtained by evaporating the solvent was purified by silica gel column chromatography to give 6-bromo-2.
2.91 g of-(1-ethoxy) ethoxynaphthalene (yield 98
%).

Take 0.28 g of lithium dispersion in a flask,
Under a nitrogen stream, 3.08 g of 4-hexyloxybromobenzene dissolved in 15 ml of dry ether was added dropwise over 15 minutes, and then the mixture was refluxed for 30 minutes. Then, the mixture was returned to room temperature, and dissolved in 1.65 g of anhydrous zinc chloride, 0.11 g of nickel (II) chloride (1,2-bisdiphenylphosphinoethane) and 15 ml of dry tetrahydrofuran to obtain the previously obtained 6-bromo-2- (1- 2.91 g of ethoxy) ethoxynaphthalene was added, and the mixture was heated under reflux for 3 hours.

After cooling to room temperature, 1N hydrochloric acid was added, the mixture was stirred for 1 hour, and extracted with ether. After drying over anhydrous magnesium sulfate, the solvent was distilled off and the resulting oil was purified by silica gel column chromatography to give 6- (4-hexyloxyphenyl) -2-naphthol 1.23 having the following physicochemical properties: g (38% yield). ¹ H-NMR spectrum (90 MHz, in CDCl ₃ , TMS standard, δ
Value): δ 0.89 3H m δ 1.1 to 2.0 8H m δ 4.01 2H t (J = 7Hz) δ 4.92 1H br.s δ 7.0 to 7.24H m δ 7.5 to 8.0 6H m IR (KBr method, cm ^-1 ): 3300,2910,2840,1625,1605,1510,1235,1180 Synthesis of 2-fluoro-2-methylheptanoic acid-6- (4-hexyloxyphenyl) naphthyl- (2) 6- (4-hexyloxyphenyl) -2-naphthol 583.9 mg, (-)-2-fluoro-2-methylheptanoic acid 295.9 mg, dicyclohexylcarbodiimide 516.2 m
g, 22.4 mg of 4-dimethylaminopyridine and 20 ml of dry dichloromethane were placed in a flask and stirred at room temperature overnight.

The resulting crystals were removed by filtration, and the solvent was distilled off. The resulting crude crystals were purified by silica gel column chromatography and recrystallization from ethanol to give 2-fluoro-2-methylheptane having the aforementioned physicochemical properties. Acid-6
-(4-hexyloxyphenyl) naphthyl- (2) 27
5.0 mg (32% yield) was obtained.

Evaluation of crystallinity The obtained target compound is a 3 μm-thick glass plate with a transparent electrode coated with polyimide and rubbed.
When the temperature was lowered at a rate of −2 ° C./min and observed with a crossed Nicol polarizing microscope, the liquid changed from an isotropic liquid to a smectic A phase at 110 ° C. and crystallized at 84 ° C. At the time of temperature rise, the crystal changed to a smectic A phase at 87.3 ° C.

Example 3 Each of the non-optically active liquid crystal compounds represented by the following formulas (5), (6), (7) and (8) was mixed at a ratio shown below to prepare a base liquid crystal mixture A.

This liquid crystal composition A exhibited the following phase transition behavior.

(Cr is a crystal phase, Sc a smectic C phase, S _A a smectic A phase, N nematic phase, I is shows the isotropic phase.) The liquid crystal composition A does not include a compound having an asymmetric carbon Therefore, it does not exhibit ferroelectric behavior.

Next, this liquid crystal composition A and the compound of Example 1 represented by the following formula were mixed at the ratio shown below to form a liquid crystal composition B.
It was created.

This liquid crystal composition B exhibited the following phase transition behavior.

(Cr LCD phase, Sc ^* is a chiral smectic C phase, S _A a smectic A phase, Ch cholesteric phase, I is shows the isotropic phase.) Further, this liquid crystal composition, rubbing treatment was applied to polyimide 2μ thick glass plate with transparent electrode
m, and the temperature was gradually lowered from the state of the isotropic liquid to align the cholesteric phase. When the temperature was further lowered to obtain a chiral smectic C phase via a smectic A phase, cells with good orientation were easily obtained. When an electric field was applied to the cell while observing the cell with a crossed Nicol polarizing microscope, a clear switching operation was observed.

When a rectangular wave of 20 Vpp was applied to the cell at 25 ° C., the amount of transmitted light was measured by a photodiode, and optical switching operation was detected. The time required for the amount of transmitted light to change from 10% to 90% was: It was a very high speed of 70 μs.

Comparative Example The liquid crystal composition A used in Example 3 and Japanese Patent Application Laid-Open No. 1-501394
The compounds of the following formula described in the publication number are mixed in the following proportions,
Liquid crystal composition C was prepared.

This liquid crystal composition C showed the following phase transition.

(Cr is a crystal phase, Sc ^* is a chiral smectic C phase, S _A is a smectic A phase, and I is an isotropic phase.) As described above, the liquid crystal composition C has no cholesteric phase. It is difficult to obtain an orientation.

(Effect of the Invention) The compound of the present invention can take a stable thermotropic liquid crystal state, and when added to a non-chiral liquid crystal, becomes a ferroelectric liquid crystal composition having a large spontaneous polarization and a high response speed. It is an extremely effective material for optoelectronics-related elements.

Therefore, the present invention can be said to be a useful liquid crystal material as a material for optoelectronics-related elements utilizing liquid crystal or electrochemiomics, for example, for displays such as liquid crystal televisions, optical printer heads, optical Fourier transform elements, light valves, and the like.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toshihiro Hirai 3-17-35 Nishinaminami, Toda City, Saitama Prefecture Within Nihon Mining Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) C07C 69 / 63 C09K 19/32 CA (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] (1) The following general formula (I): (Wherein, R and R ′ are an alkyl group which may have a substituent, and the substituent is selected from a lower alkyl group, a lower alkoxy group, a halogen atom, and a trifluoromethyl group; A single bond or one of -O-, A and B is 1,
A 4-phenylene group, the other of which represents a 2,6-naphthylene group)
A novel ester compound represented by the formula: 2. A liquid crystal composition comprising at least one ester compound represented by the general formula (I) according to claim 1. 3. An optical switching element comprising at least one of the ester compounds represented by the general formula (I) according to claim 1.